Sadhna Sharma - Academia.edu (original) (raw)

Papers by Sadhna Sharma

Fems Microbiology Letters, 2001

The study demonstrates the in vitro effectiveness of phenothiazine compounds, i.e. chlorpromazine... more The study demonstrates the in vitro effectiveness of phenothiazine compounds, i.e. chlorpromazine and trifluoperazine against Candida albicans. Anticandidal effect of these drugs is suggested to be because of their interaction with Ca2+/calmodulin dependent protein phosphorylation. 3H-thymidine uptake studies revealed that both these compounds affect the DNA synthesis along with decrease in activities of nuclear calmodulin (CaM) and Ca2+/calmodulin dependent protein kinase (CaMPK). Failure in cell growth was due to defect in CaM mediated cell cycle arrest. Flow cytometric analysis showed that progression through G1 and mitotic phase was affected when cells after α-factor arrest were grown in the presence of chlorpromazine or trifluoperazine. These drugs also produced significant decline in the cellular lipids and phospholipids. 14C-acetate incorporation studies further substantiated these results. We suggest that chlorpromazine or trifluoperazine affect the cell cycle through DNA synthesis (S phase) and cell division phases which are governed by calmodulin and Ca2+/calmodulin dependent protein phosphorylation and lipids and phospholipids appear to be additional targets of phenothiazine compounds in C. albicans. These results will have important significance in the development of new anticandidal compounds.

Alginate microparticles were developed as oral sustained delivery carriers for antitubercular dru... more Alginate microparticles were developed as oral sustained delivery carriers for antitubercular drugs in order to improve patient compliance. In the present study, pharmacokinetics and therapeutic effects of alginate microparticle encapsulated antitubercular drugs, i.e. isoniazid, rifampicin and pyrazinamide were examined in guinea pigs. Alginate microparticles containing antitubercular drugs were evaluated for in vitro and in vivo release profiles. These microparticles exhibited sustained release of isoniazid, rifampicin and pyrazinamide for 3-5 days in plasma and up to 9 days in organs. Peak plasma concentration (C max ), T max , elimination half-life (t 1/2e ) and AUC 0-∞ of alginate drugs were significantly higher than those of free drugs. The encapsulation of drug in alginate microparticles resulted in up to a nine-fold increase in relative bioavailability compared with free drugs. Chemotherapeutic efficacy of alginate drug microspheres against experimental tuberculosis showed no detectable cfu values at 1:100 and 1:1000 dilutions of spleen and lung homogenates. Histopathological studies further substantiated these observations, thus suggesting that application of alginate-encapsulated drugs could be useful in the effective treatment of tuberculosis.

Tuberculosis, 2005

The present study was planned to evaluate the chemotherapeutic potential of oral solid lipid nano... more The present study was planned to evaluate the chemotherapeutic potential of oral solid lipid nanoparticles (SLNs) incorporating rifampicin, isoniazid and pyrazinamide against experimental tuberculosis. The SLNs were prepared by the "emulsion solvent diffusion" technique with an encapsulation efficiency of 51+/-5% for rifampicin, 45+/-4% for isoniazid and 41+/-4% for pyrazinamide. Following a single oral administration to mice, therapeutic drug concentrations were maintained in the plasma for 8 days and in the organs (lungs, liver and spleen) for 10 days whereas free drugs were cleared by 1-2 days. In M. tuberculosis H37Rv infected mice, no tubercle bacilli could be detected in the lungs/spleen after 5 oral doses of drug loaded SLNs administered at every 10th day whereas 46 daily doses of oral free drugs were required to obtain an equivalent therapeutic benefit. Thus, SLN based antitubercular drug therapy forms a sound basis for reducing dosing frequency and improving patient compliance for better management of tuberculosis.

Antimicrobial Agents and Chemotherapy, 2005

We evaluated the efficacy of nanoparticle-encapsulated antituberculosis drugs administered every ... more We evaluated the efficacy of nanoparticle-encapsulated antituberculosis drugs administered every 10 days versus that of daily nonencapsulated drugs against Mycobacterium tuberculosis aerosol infection in guinea pigs. Both treatments significantly reduced the bacterial count and lung histopathology, suggesting that the nanoparticle drug delivery system has potential in intermitted treatment of tuberculosis.

Fems Microbiology Letters, 2006

The aim of the present study was to evaluate the chemotherapeutic potential of econazole against ... more The aim of the present study was to evaluate the chemotherapeutic potential of econazole against latent tuberculosis. The activity of econazole and clotrimazole was tested against the latent bacilli (Mycobacterium tuberculosis H37Rv) developed by nutrient starvation under in vitro conditions and by drugs under in vivo conditions. The latent bacteria developed under in vitro latent conditions were acid-fast negative, nonreplicating, resistant to conventional antitubercular drugs and showed low respiration rates. Econazole as well as clotrimazole were found to have strong antimycobacterial potential against latent Mycobacterium tuberculosis under in vitro conditions as seen by reductions in colony-forming units. Further, econazole prevented the formation of drug-induced latency and significantly reduced bacterial burden from lungs and spleens of latent tuberculosis-infected mice. We conclude that azole drugs bear significant therapeutic potential against latent tuberculosis.

Fems Microbiology Letters, 2005

The antimycobacterial activity of two clinically approved antifungal azole drugs, clotrimazole an... more The antimycobacterial activity of two clinically approved antifungal azole drugs, clotrimazole and econazole, was evaluated against Mycobacterium tuberculosis H 37 Rv under in vitro and ex vivo conditions. The minimum inhibitory concentration (MIC 90 ) was 0.120 lg ml À1 , whereas the minimum bactericidal concentration and effective concentration was 0.125 lg ml À1 for both the drugs demonstrating their potent antimycobacterial activity. Further, the azole drugs exhibited a synergistic activity with either rifampicin or isoniazid as evaluated on the basis of reduction of colony forming units. The results suggest that azole compounds bear the potential to enhance the efficacy of currently prescribed antitubercular drugs.

Drug Delivery, 2006

Our objective was to evaluate the chemotherapeutic potential of oral poly lactide-co-glycolide (P... more Our objective was to evaluate the chemotherapeutic potential of oral poly lactide-co-glycolide (PLG, a synthetic polymer) nanoparticle encapsulated ethambutol in combination with PLG-nanoparticle encapsulated-(rifampicin + isoniazid + pyrazinamide) in a murine tuberculosis (TB) model. Our formulation was prepared by the multiple emulsion technique and administered orally to mice for the biodistribution, pharmacokinetic, and chemotherapeutic studies. A single oral administration of the formulation to mice could maintain sustained drug levels in the plasma for 5 days and in the organs (lungs, liver, spleen) for 7-9 days. There was a striking improvement in the pharmacokinetic parameters such as half-life and mean residence time as compared with free drugs. The relative/absolute bioavailability of the 4 antituberculosis drugs was enhanced several fold. Repeated administration of the formulation did not produce any hepatotoxicity as assessed on a biochemical basis. In M. tuberculosis H37Rv infected mice, just 3 oral doses of the 4-drug formulation administered at every 10th day resulted in undetectable bacilli in the organs replacing 28 conventional doses of free drugs. We concluded that polymeric nanoparticle based oral 4-drug combination bears significant potential to shorten the duration of TB chemotherapy, besides reducing the dosing frequency.

Fems Microbiology Letters, 2006

The present study was designed to evaluate the in vivo antimycobacterial potential of econazole a... more The present study was designed to evaluate the in vivo antimycobacterial potential of econazole alone and in combination with antitubercular drugs against tuberculosis in mice. Econazole was found to reduce bacterial burden by 90% in the lungs and spleen of mice infected with 1 × 107 cells of Mycobacterium tuberculosis and was found to be equipotent to rifampicin. Further, our results indicate that econazole can replace rifampicin/isoniazid as well as both rifampicin and isoniazid in chemotherapy of murine tuberculosis. Econazole alone or in combination with antitubercular drugs did not produce any hepatotoxicity in normal or M. tuberculosis-infected mice.

Current Pharmaceutical Design, 2004

Mycobacteria are intracellular pathogens that invade and reside inside macrophages. There has bee... more Mycobacteria are intracellular pathogens that invade and reside inside macrophages. There has been a rapid resurgence in infections caused by the genus mycobacteria. Chemotherapy of mycobacterial infections is prolonged, hepatotoxic and very often inadequate in achieving optimal drug concentrations inside the cells. Recent advances in controlled delivery systems for drugs such as liposomes have sparked a renewed interest in their potential application for the treatment of mycobacterial infections. The versatility of liposomes in incorporation of hydrophilic/hydrophobic components, non-toxic nature, biodegradability, biocompatibility and property of sustained release makes them attractive candidates for the delivery of antitubercular drugs. Liposome research in the area of mycobacterial diseases has evolved and matured through several phases; from the laboratory to the clinics. This review, thus focuses on the use of liposomes for the treatment of various types of mycobacterial diseases.

Nanomedicine-nanotechnology Biology and Medicine, 2007

The present study was designed to evaluate the chemotherapeutic potential of alginate nanoparticl... more The present study was designed to evaluate the chemotherapeutic potential of alginate nanoparticleencapsulated econazole and antitubercular drugs (ATDs) against murine tuberculosis. Alginate nanoparticles encapsulating econazole and ATDs were prepared by the cation-induced controlled gelification of alginate and were characterized. Drugs were analyzed by high-performance liquid chromatography. All the ATDs were detected above minimum inhibitory concentrations for as long as 15 days and econazole until the day 8 in organs (lungs, liver, and spleen) after administration of encapsulated drugs, whereas free drugs remained detectable for only 12 to 24 hours. Eight doses of alginate nanoparticle-encapsulated econazole or 112 doses of free econazole reduced bacterial burden by more than 90% in the lungs and spleen of mice infected with Mycobacterium tuberculosis. Econazole (free or encapsulated) could replace rifampicin and isoniazid during chemotherapy of murine tuberculosis. Alginate nanoparticles reduced the dosing frequency of azoles and ATDs by 15-fold. Alginate nanoparticles are the ideal carriers of azole and antitubercular drugs, which can reduce dosing frequency of azoles as well as ATDs for the better management of tuberculosis.

International Journal of Antimicrobial Agents, 2005

Pharmacokinetic and chemotherapeutic studies have been carried out with aerosolised alginate nano... more Pharmacokinetic and chemotherapeutic studies have been carried out with aerosolised alginate nanoparticles encapsulating isoniazid (INH), rifampicin (RIF) and pyrazinamide (PZA). The nanoparticles were prepared by cation-induced gelification of alginate and were 235.5 +/- 0 nm in size, with drug encapsulation efficiencies of 70-90% for INH and PZA and 80-90% for RIF. The majority of particles (80.5%) were in the respirable range, with mass median aerodynamic diameter of 1.1 +/- 0.4 microm and geometric standard deviation of 1.71 +/- 0.1 microm. The relative bioavailabilities of all drugs encapsulated in alginate nanoparticles were significantly higher compared with oral free drugs. All drugs were detected in organs (lungs, liver and spleen) above the minimum inhibitory concentration until 15 days post nebulisation, whilst free drugs stayed up to day 1. The chemotherapeutic efficacy of three doses of drug-loaded alginate nanoparticles nebulised 15 days apart was comparable with 45 daily doses of oral free drugs. Thus, inhalable alginate nanoparticles can serve as an ideal carrier for the controlled release of antitubercular drugs.

International Journal of Antimicrobial Agents, 2002

Co-administration of isoniazid (INH) and rifampicin (RIF) encapsulated in lung specific stealth l... more Co-administration of isoniazid (INH) and rifampicin (RIF) encapsulated in lung specific stealth liposomes at one third of their recommended doses of 12 and 10 mg/kg b.wt., respectively, exhibited a sustained release of these drugs in plasma (5 days) and lungs, liver and spleen (7 days). At these concentrations, T max and area under curve (AUC) values of liposomal drugs were more than that observed with free drugs. The elimination constant (Kel) was higher for liposomal INH ((/0.0349/0.008) and RIF ((/0.0179/0.009) compared with free INH ((/0.392) and RIF ((/0.243). Chemotherapeutic efficacy of once weekly-administered liposomal drugs for 6 weeks reduced the mycobacterial load significantly in lungs, liver and spleen of infected mice compared with untreated animals. #

Biochimica Et Biophysica Acta-general Subjects, 2000

A cyclic AMP dependent protein kinase (PKA), its regulatory (R) and catalytic (C) subunits were p... more A cyclic AMP dependent protein kinase (PKA), its regulatory (R) and catalytic (C) subunits were purified to homogeneity from soluble extract of Microsporum gypseum. Purified enzyme showed a final specific activity of 277.9 nmol phosphate transferred min 31 mg protein 31 with kemptide as substrate. The enzyme preparation showed two bands with molecular masses of 76 kDa and 45 kDa on sodium dodecyl polyacrylamide gel electrophoresis. The 76 kDa subunit was found to be the regulatory (R) subunit of PKA holoenzyme as determined by its immunoreactivity and the isoelectric point of this subunit was 3.98. The 45 kDa subunit was found to be the catalytic (C) subunit by its immunoreactivity and phosphotransferase activity. Gel filtration using Sepharose CL-6B revealed the molecular mass of PKA holoenzyme to be 240 kDa, compatible with its tetrameric structure, consisting of two regulatory subunits (76 kDa) and two catalytic subunits (45 kDa). The specificity of enzyme towards protein acceptors in decreasing order of phosphorylation was found to be kemptide, casein, syntide and histone IIs. Purified enzyme had apparent K m values of 71 WM and 25 WM for ATP and kemptide, respectively. Phosphorylation was strongly inhibited by mammalian PKA inhibitor (PKI) but not by inhibitors of other protein kinases. The PKA showed maximum activity at pH 7.0 and enzyme activity was inhibited in the presence of N-ethylmaleimide (NEM) which shows the involvement of sulfhydryl groups for the activity of PKA. PKA phosphorylated a number of endogenous proteins suggesting the multifunctional role of cAMP dependent protein kinase in M. gypseum. Further work is under progress to identify the natural substrates of this enzyme through which it may regulate the enzymes involved in phospholipid metabolism. ß 2000 Elsevier Science B.V. All rights reserved.

International Journal of Antimicrobial Agents, 2006

This study evaluated the antimycobacterial activity of econazole against multidrug-resistant (MDR... more This study evaluated the antimycobacterial activity of econazole against multidrug-resistant (MDR) strains of Mycobacterium tuberculosis. The minimum inhibitory concentration (MIC 90 ) and minimum bactericidal concentration (MBC >99.99 ) against MDR strains were found to be 0.120-0.125 g/mL and 0.125-0.150 g/mL, respectively, demonstrating the antimycobacterial potential of econazole.

Objectives: This study was carried out to explore lectin-functionalized poly (lactide-co-glycolid... more Objectives: This study was carried out to explore lectin-functionalized poly (lactide-co-glycolide) nanoparticles (PLG-NPs) as bioadhesive drug carriers against tuberculosis (TB), in order to reduce the drug dosage frequency of antitubercular drugs and thus improve patient compliance in TB chemotherapy.

Objectives: To improve the bioavailability of antitubercular drugs (ATDs) as well as to assess th... more Objectives: To improve the bioavailability of antitubercular drugs (ATDs) as well as to assess the feasibility of administering ATDs via the respiratory route, this study reports the formulation of three frontline ATDs, i.e. rifampicin, isoniazid and pyrazinamide encapsulated in poly (DL-lactide-co-glycolide) nanoparticles suitable for nebulization.

International Journal of Antimicrobial Agents, 2004

1. Int J Antimicrob Agents. 2004 Jul;24(1):93-4. Nebulization of liposome encapsulated antituberc... more 1. Int J Antimicrob Agents. 2004 Jul;24(1):93-4. Nebulization of liposome encapsulated antitubercular drugs in guinea pigs. Pandey R, Sharma S, Khuller GK. PMID: 15225870 [PubMed - indexed for MEDLINE]. Publication Types: Letter. MeSH Terms: ...

International Journal of Antimicrobial Agents, 2006

This study was designed to evaluate the pharmacokinetics and tissue distribution of free and algi... more This study was designed to evaluate the pharmacokinetics and tissue distribution of free and alginate-encapsulated antitubercular drugs in mice at different doses. Alginate nanoparticles encapsulating isoniazid (INH), rifampicin (RIF), pyrazinamide (PZA) and ethambutol (EMB) were prepared by controlled cation-induced gelification of alginate. The formulation was orally administered to mice at two dose levels (D1 and D2). A comparison was made in mice receiving free drugs at equivalent doses. Drugs were analysed by high performance liquid chromatography (HPLC). The average size of alginate nanoparticles was found to be 235.5 ± 0.0 nm with a polydispersity index of 0.44; drug encapsulation was 70-90% for INH and PZA, 80-90% for RIF and 88-95% for EMB. In the free drug groups, plasma levels of RIF and INH were higher and PZA and EMB levels were lower in the D1 group (per body surface area of mice) compared with the D2 group (recommended human dose). The plasma drug levels of all drugs were higher in the D1 encapsulated group compared with D2, resulting in higher values of area under the plasma drug concentration-time curve (AUC 0-∞ ). The relative bioavailabilities of all drugs encapsulated in alginate nanoparticles were significantly higher compared with free drugs. Drug levels were maintained at or above the minimum inhibitory concentration (MIC 90 ) until Day 15 in organs after administration of encapsulated drugs, whilst free drugs stayed at or above the MIC 90 up to Day 1 only irrespective of dose. The levels of drugs in various organs remained above the MIC at both doses for equal periods, demonstrating their equiefficiency. Alginate nanoparticles hold great potential in reducing dosing frequency of antitubercular drugs.

Tuberculosis, 2003

Patient non-compliance is the major drawback associated with the long-duration chemotherapy of tu... more Patient non-compliance is the major drawback associated with the long-duration chemotherapy of tuberculosis (TB); hence, reduction in dosing frequency forms an important therapeutic strategy. The present study reports the formulation of three frontline antitubercular drugs (ATD), i.e. rifampicin (RIF), isoniazid (INH) and pyrazinamide (PZA) encapsulated in poly (DL-lactide-co-glycolide) (PLG) nanoparticles. Drug encapsulation efficiencies were 56.9+/-2.7% for RIF, 66.3+/-5.8% for INH and 68+/-5.6% for PZA. Following a single oral administration of these preparations to mice, the drugs could be detected in the circulation for 6 days (RIF) and 9 days (INH/PZA), whereas therapeutic concentrations in the tissues were maintained for 9-11 days. Further, on oral administration of drug-loaded nanoparticles to Mycobacterium tuberculosis-infected mice at every 10th day, no tubercle bacilli could be detected in the tissues after 5 oral doses of treatment. Therefore, nanoparticle-based ATD therapy forms a sound basis for reduction in dosing frequency for better management of TB.

Critical Reviews in Microbiology, 2003

The human fungal pathogen Candida albicans switches from a budding yeast form to a polarized hyph... more The human fungal pathogen Candida albicans switches from a budding yeast form to a polarized hyphal form in response to various external signals. This morphogenetic switching has been implicated in the development of pathogenicity. Several signaling pathways that regulate morphogenesis have been identified, including various transcription factors that either activate or repress hypha-specific genes. Two well-characterized pathways include the MAP kinase cascade and cAMP-dependent protein kinase pathway that regulate the transcription factors Cph1p and Efg1p, respectively. cAMP also appears to interplay with other second messengers: Ca2+, inositol tri-phosphates in regulating yeast-hyphal transition. Other, less-characterized pathways include two component histidine kinases, cyclin-dependent kinase pathway, and condition specific pathways such as pH and embedded growth conditions. Nrg1 and Rfg1 function as transcriptional repressors of hyphal genes via recruitment of Tup1 co-repressor complex. Different upstream signals converge into a common downstream output during hyphal switch. The levels of expression of several genes have been shown to be associated with hyphal morphogenesis rather than with a specific hypha-inducing condition. Hyphal development is also linked to the expression of a range of other virulence factors. This review explains the relative contribution of multiple pathways that could be used by Candida albican cells to sense subtle differences in the growth conditions of its native host environment.

Fems Microbiology Letters, 2001

The study demonstrates the in vitro effectiveness of phenothiazine compounds, i.e. chlorpromazine... more The study demonstrates the in vitro effectiveness of phenothiazine compounds, i.e. chlorpromazine and trifluoperazine against Candida albicans. Anticandidal effect of these drugs is suggested to be because of their interaction with Ca2+/calmodulin dependent protein phosphorylation. 3H-thymidine uptake studies revealed that both these compounds affect the DNA synthesis along with decrease in activities of nuclear calmodulin (CaM) and Ca2+/calmodulin dependent protein kinase (CaMPK). Failure in cell growth was due to defect in CaM mediated cell cycle arrest. Flow cytometric analysis showed that progression through G1 and mitotic phase was affected when cells after α-factor arrest were grown in the presence of chlorpromazine or trifluoperazine. These drugs also produced significant decline in the cellular lipids and phospholipids. 14C-acetate incorporation studies further substantiated these results. We suggest that chlorpromazine or trifluoperazine affect the cell cycle through DNA synthesis (S phase) and cell division phases which are governed by calmodulin and Ca2+/calmodulin dependent protein phosphorylation and lipids and phospholipids appear to be additional targets of phenothiazine compounds in C. albicans. These results will have important significance in the development of new anticandidal compounds.

Alginate microparticles were developed as oral sustained delivery carriers for antitubercular dru... more Alginate microparticles were developed as oral sustained delivery carriers for antitubercular drugs in order to improve patient compliance. In the present study, pharmacokinetics and therapeutic effects of alginate microparticle encapsulated antitubercular drugs, i.e. isoniazid, rifampicin and pyrazinamide were examined in guinea pigs. Alginate microparticles containing antitubercular drugs were evaluated for in vitro and in vivo release profiles. These microparticles exhibited sustained release of isoniazid, rifampicin and pyrazinamide for 3-5 days in plasma and up to 9 days in organs. Peak plasma concentration (C max ), T max , elimination half-life (t 1/2e ) and AUC 0-∞ of alginate drugs were significantly higher than those of free drugs. The encapsulation of drug in alginate microparticles resulted in up to a nine-fold increase in relative bioavailability compared with free drugs. Chemotherapeutic efficacy of alginate drug microspheres against experimental tuberculosis showed no detectable cfu values at 1:100 and 1:1000 dilutions of spleen and lung homogenates. Histopathological studies further substantiated these observations, thus suggesting that application of alginate-encapsulated drugs could be useful in the effective treatment of tuberculosis.

Tuberculosis, 2005

The present study was planned to evaluate the chemotherapeutic potential of oral solid lipid nano... more The present study was planned to evaluate the chemotherapeutic potential of oral solid lipid nanoparticles (SLNs) incorporating rifampicin, isoniazid and pyrazinamide against experimental tuberculosis. The SLNs were prepared by the "emulsion solvent diffusion" technique with an encapsulation efficiency of 51+/-5% for rifampicin, 45+/-4% for isoniazid and 41+/-4% for pyrazinamide. Following a single oral administration to mice, therapeutic drug concentrations were maintained in the plasma for 8 days and in the organs (lungs, liver and spleen) for 10 days whereas free drugs were cleared by 1-2 days. In M. tuberculosis H37Rv infected mice, no tubercle bacilli could be detected in the lungs/spleen after 5 oral doses of drug loaded SLNs administered at every 10th day whereas 46 daily doses of oral free drugs were required to obtain an equivalent therapeutic benefit. Thus, SLN based antitubercular drug therapy forms a sound basis for reducing dosing frequency and improving patient compliance for better management of tuberculosis.

Antimicrobial Agents and Chemotherapy, 2005

We evaluated the efficacy of nanoparticle-encapsulated antituberculosis drugs administered every ... more We evaluated the efficacy of nanoparticle-encapsulated antituberculosis drugs administered every 10 days versus that of daily nonencapsulated drugs against Mycobacterium tuberculosis aerosol infection in guinea pigs. Both treatments significantly reduced the bacterial count and lung histopathology, suggesting that the nanoparticle drug delivery system has potential in intermitted treatment of tuberculosis.

Fems Microbiology Letters, 2006

The aim of the present study was to evaluate the chemotherapeutic potential of econazole against ... more The aim of the present study was to evaluate the chemotherapeutic potential of econazole against latent tuberculosis. The activity of econazole and clotrimazole was tested against the latent bacilli (Mycobacterium tuberculosis H37Rv) developed by nutrient starvation under in vitro conditions and by drugs under in vivo conditions. The latent bacteria developed under in vitro latent conditions were acid-fast negative, nonreplicating, resistant to conventional antitubercular drugs and showed low respiration rates. Econazole as well as clotrimazole were found to have strong antimycobacterial potential against latent Mycobacterium tuberculosis under in vitro conditions as seen by reductions in colony-forming units. Further, econazole prevented the formation of drug-induced latency and significantly reduced bacterial burden from lungs and spleens of latent tuberculosis-infected mice. We conclude that azole drugs bear significant therapeutic potential against latent tuberculosis.

Fems Microbiology Letters, 2005

The antimycobacterial activity of two clinically approved antifungal azole drugs, clotrimazole an... more The antimycobacterial activity of two clinically approved antifungal azole drugs, clotrimazole and econazole, was evaluated against Mycobacterium tuberculosis H 37 Rv under in vitro and ex vivo conditions. The minimum inhibitory concentration (MIC 90 ) was 0.120 lg ml À1 , whereas the minimum bactericidal concentration and effective concentration was 0.125 lg ml À1 for both the drugs demonstrating their potent antimycobacterial activity. Further, the azole drugs exhibited a synergistic activity with either rifampicin or isoniazid as evaluated on the basis of reduction of colony forming units. The results suggest that azole compounds bear the potential to enhance the efficacy of currently prescribed antitubercular drugs.

Drug Delivery, 2006

Our objective was to evaluate the chemotherapeutic potential of oral poly lactide-co-glycolide (P... more Our objective was to evaluate the chemotherapeutic potential of oral poly lactide-co-glycolide (PLG, a synthetic polymer) nanoparticle encapsulated ethambutol in combination with PLG-nanoparticle encapsulated-(rifampicin + isoniazid + pyrazinamide) in a murine tuberculosis (TB) model. Our formulation was prepared by the multiple emulsion technique and administered orally to mice for the biodistribution, pharmacokinetic, and chemotherapeutic studies. A single oral administration of the formulation to mice could maintain sustained drug levels in the plasma for 5 days and in the organs (lungs, liver, spleen) for 7-9 days. There was a striking improvement in the pharmacokinetic parameters such as half-life and mean residence time as compared with free drugs. The relative/absolute bioavailability of the 4 antituberculosis drugs was enhanced several fold. Repeated administration of the formulation did not produce any hepatotoxicity as assessed on a biochemical basis. In M. tuberculosis H37Rv infected mice, just 3 oral doses of the 4-drug formulation administered at every 10th day resulted in undetectable bacilli in the organs replacing 28 conventional doses of free drugs. We concluded that polymeric nanoparticle based oral 4-drug combination bears significant potential to shorten the duration of TB chemotherapy, besides reducing the dosing frequency.

Fems Microbiology Letters, 2006

The present study was designed to evaluate the in vivo antimycobacterial potential of econazole a... more The present study was designed to evaluate the in vivo antimycobacterial potential of econazole alone and in combination with antitubercular drugs against tuberculosis in mice. Econazole was found to reduce bacterial burden by 90% in the lungs and spleen of mice infected with 1 × 107 cells of Mycobacterium tuberculosis and was found to be equipotent to rifampicin. Further, our results indicate that econazole can replace rifampicin/isoniazid as well as both rifampicin and isoniazid in chemotherapy of murine tuberculosis. Econazole alone or in combination with antitubercular drugs did not produce any hepatotoxicity in normal or M. tuberculosis-infected mice.

Current Pharmaceutical Design, 2004

Mycobacteria are intracellular pathogens that invade and reside inside macrophages. There has bee... more Mycobacteria are intracellular pathogens that invade and reside inside macrophages. There has been a rapid resurgence in infections caused by the genus mycobacteria. Chemotherapy of mycobacterial infections is prolonged, hepatotoxic and very often inadequate in achieving optimal drug concentrations inside the cells. Recent advances in controlled delivery systems for drugs such as liposomes have sparked a renewed interest in their potential application for the treatment of mycobacterial infections. The versatility of liposomes in incorporation of hydrophilic/hydrophobic components, non-toxic nature, biodegradability, biocompatibility and property of sustained release makes them attractive candidates for the delivery of antitubercular drugs. Liposome research in the area of mycobacterial diseases has evolved and matured through several phases; from the laboratory to the clinics. This review, thus focuses on the use of liposomes for the treatment of various types of mycobacterial diseases.

Nanomedicine-nanotechnology Biology and Medicine, 2007

The present study was designed to evaluate the chemotherapeutic potential of alginate nanoparticl... more The present study was designed to evaluate the chemotherapeutic potential of alginate nanoparticleencapsulated econazole and antitubercular drugs (ATDs) against murine tuberculosis. Alginate nanoparticles encapsulating econazole and ATDs were prepared by the cation-induced controlled gelification of alginate and were characterized. Drugs were analyzed by high-performance liquid chromatography. All the ATDs were detected above minimum inhibitory concentrations for as long as 15 days and econazole until the day 8 in organs (lungs, liver, and spleen) after administration of encapsulated drugs, whereas free drugs remained detectable for only 12 to 24 hours. Eight doses of alginate nanoparticle-encapsulated econazole or 112 doses of free econazole reduced bacterial burden by more than 90% in the lungs and spleen of mice infected with Mycobacterium tuberculosis. Econazole (free or encapsulated) could replace rifampicin and isoniazid during chemotherapy of murine tuberculosis. Alginate nanoparticles reduced the dosing frequency of azoles and ATDs by 15-fold. Alginate nanoparticles are the ideal carriers of azole and antitubercular drugs, which can reduce dosing frequency of azoles as well as ATDs for the better management of tuberculosis.

International Journal of Antimicrobial Agents, 2005

Pharmacokinetic and chemotherapeutic studies have been carried out with aerosolised alginate nano... more Pharmacokinetic and chemotherapeutic studies have been carried out with aerosolised alginate nanoparticles encapsulating isoniazid (INH), rifampicin (RIF) and pyrazinamide (PZA). The nanoparticles were prepared by cation-induced gelification of alginate and were 235.5 +/- 0 nm in size, with drug encapsulation efficiencies of 70-90% for INH and PZA and 80-90% for RIF. The majority of particles (80.5%) were in the respirable range, with mass median aerodynamic diameter of 1.1 +/- 0.4 microm and geometric standard deviation of 1.71 +/- 0.1 microm. The relative bioavailabilities of all drugs encapsulated in alginate nanoparticles were significantly higher compared with oral free drugs. All drugs were detected in organs (lungs, liver and spleen) above the minimum inhibitory concentration until 15 days post nebulisation, whilst free drugs stayed up to day 1. The chemotherapeutic efficacy of three doses of drug-loaded alginate nanoparticles nebulised 15 days apart was comparable with 45 daily doses of oral free drugs. Thus, inhalable alginate nanoparticles can serve as an ideal carrier for the controlled release of antitubercular drugs.

International Journal of Antimicrobial Agents, 2002

Co-administration of isoniazid (INH) and rifampicin (RIF) encapsulated in lung specific stealth l... more Co-administration of isoniazid (INH) and rifampicin (RIF) encapsulated in lung specific stealth liposomes at one third of their recommended doses of 12 and 10 mg/kg b.wt., respectively, exhibited a sustained release of these drugs in plasma (5 days) and lungs, liver and spleen (7 days). At these concentrations, T max and area under curve (AUC) values of liposomal drugs were more than that observed with free drugs. The elimination constant (Kel) was higher for liposomal INH ((/0.0349/0.008) and RIF ((/0.0179/0.009) compared with free INH ((/0.392) and RIF ((/0.243). Chemotherapeutic efficacy of once weekly-administered liposomal drugs for 6 weeks reduced the mycobacterial load significantly in lungs, liver and spleen of infected mice compared with untreated animals. #

Biochimica Et Biophysica Acta-general Subjects, 2000

A cyclic AMP dependent protein kinase (PKA), its regulatory (R) and catalytic (C) subunits were p... more A cyclic AMP dependent protein kinase (PKA), its regulatory (R) and catalytic (C) subunits were purified to homogeneity from soluble extract of Microsporum gypseum. Purified enzyme showed a final specific activity of 277.9 nmol phosphate transferred min 31 mg protein 31 with kemptide as substrate. The enzyme preparation showed two bands with molecular masses of 76 kDa and 45 kDa on sodium dodecyl polyacrylamide gel electrophoresis. The 76 kDa subunit was found to be the regulatory (R) subunit of PKA holoenzyme as determined by its immunoreactivity and the isoelectric point of this subunit was 3.98. The 45 kDa subunit was found to be the catalytic (C) subunit by its immunoreactivity and phosphotransferase activity. Gel filtration using Sepharose CL-6B revealed the molecular mass of PKA holoenzyme to be 240 kDa, compatible with its tetrameric structure, consisting of two regulatory subunits (76 kDa) and two catalytic subunits (45 kDa). The specificity of enzyme towards protein acceptors in decreasing order of phosphorylation was found to be kemptide, casein, syntide and histone IIs. Purified enzyme had apparent K m values of 71 WM and 25 WM for ATP and kemptide, respectively. Phosphorylation was strongly inhibited by mammalian PKA inhibitor (PKI) but not by inhibitors of other protein kinases. The PKA showed maximum activity at pH 7.0 and enzyme activity was inhibited in the presence of N-ethylmaleimide (NEM) which shows the involvement of sulfhydryl groups for the activity of PKA. PKA phosphorylated a number of endogenous proteins suggesting the multifunctional role of cAMP dependent protein kinase in M. gypseum. Further work is under progress to identify the natural substrates of this enzyme through which it may regulate the enzymes involved in phospholipid metabolism. ß 2000 Elsevier Science B.V. All rights reserved.

International Journal of Antimicrobial Agents, 2006

This study evaluated the antimycobacterial activity of econazole against multidrug-resistant (MDR... more This study evaluated the antimycobacterial activity of econazole against multidrug-resistant (MDR) strains of Mycobacterium tuberculosis. The minimum inhibitory concentration (MIC 90 ) and minimum bactericidal concentration (MBC >99.99 ) against MDR strains were found to be 0.120-0.125 g/mL and 0.125-0.150 g/mL, respectively, demonstrating the antimycobacterial potential of econazole.

Objectives: This study was carried out to explore lectin-functionalized poly (lactide-co-glycolid... more Objectives: This study was carried out to explore lectin-functionalized poly (lactide-co-glycolide) nanoparticles (PLG-NPs) as bioadhesive drug carriers against tuberculosis (TB), in order to reduce the drug dosage frequency of antitubercular drugs and thus improve patient compliance in TB chemotherapy.

Objectives: To improve the bioavailability of antitubercular drugs (ATDs) as well as to assess th... more Objectives: To improve the bioavailability of antitubercular drugs (ATDs) as well as to assess the feasibility of administering ATDs via the respiratory route, this study reports the formulation of three frontline ATDs, i.e. rifampicin, isoniazid and pyrazinamide encapsulated in poly (DL-lactide-co-glycolide) nanoparticles suitable for nebulization.

International Journal of Antimicrobial Agents, 2004

1. Int J Antimicrob Agents. 2004 Jul;24(1):93-4. Nebulization of liposome encapsulated antituberc... more 1. Int J Antimicrob Agents. 2004 Jul;24(1):93-4. Nebulization of liposome encapsulated antitubercular drugs in guinea pigs. Pandey R, Sharma S, Khuller GK. PMID: 15225870 [PubMed - indexed for MEDLINE]. Publication Types: Letter. MeSH Terms: ...

International Journal of Antimicrobial Agents, 2006

This study was designed to evaluate the pharmacokinetics and tissue distribution of free and algi... more This study was designed to evaluate the pharmacokinetics and tissue distribution of free and alginate-encapsulated antitubercular drugs in mice at different doses. Alginate nanoparticles encapsulating isoniazid (INH), rifampicin (RIF), pyrazinamide (PZA) and ethambutol (EMB) were prepared by controlled cation-induced gelification of alginate. The formulation was orally administered to mice at two dose levels (D1 and D2). A comparison was made in mice receiving free drugs at equivalent doses. Drugs were analysed by high performance liquid chromatography (HPLC). The average size of alginate nanoparticles was found to be 235.5 ± 0.0 nm with a polydispersity index of 0.44; drug encapsulation was 70-90% for INH and PZA, 80-90% for RIF and 88-95% for EMB. In the free drug groups, plasma levels of RIF and INH were higher and PZA and EMB levels were lower in the D1 group (per body surface area of mice) compared with the D2 group (recommended human dose). The plasma drug levels of all drugs were higher in the D1 encapsulated group compared with D2, resulting in higher values of area under the plasma drug concentration-time curve (AUC 0-∞ ). The relative bioavailabilities of all drugs encapsulated in alginate nanoparticles were significantly higher compared with free drugs. Drug levels were maintained at or above the minimum inhibitory concentration (MIC 90 ) until Day 15 in organs after administration of encapsulated drugs, whilst free drugs stayed at or above the MIC 90 up to Day 1 only irrespective of dose. The levels of drugs in various organs remained above the MIC at both doses for equal periods, demonstrating their equiefficiency. Alginate nanoparticles hold great potential in reducing dosing frequency of antitubercular drugs.

Tuberculosis, 2003

Patient non-compliance is the major drawback associated with the long-duration chemotherapy of tu... more Patient non-compliance is the major drawback associated with the long-duration chemotherapy of tuberculosis (TB); hence, reduction in dosing frequency forms an important therapeutic strategy. The present study reports the formulation of three frontline antitubercular drugs (ATD), i.e. rifampicin (RIF), isoniazid (INH) and pyrazinamide (PZA) encapsulated in poly (DL-lactide-co-glycolide) (PLG) nanoparticles. Drug encapsulation efficiencies were 56.9+/-2.7% for RIF, 66.3+/-5.8% for INH and 68+/-5.6% for PZA. Following a single oral administration of these preparations to mice, the drugs could be detected in the circulation for 6 days (RIF) and 9 days (INH/PZA), whereas therapeutic concentrations in the tissues were maintained for 9-11 days. Further, on oral administration of drug-loaded nanoparticles to Mycobacterium tuberculosis-infected mice at every 10th day, no tubercle bacilli could be detected in the tissues after 5 oral doses of treatment. Therefore, nanoparticle-based ATD therapy forms a sound basis for reduction in dosing frequency for better management of TB.

Critical Reviews in Microbiology, 2003

The human fungal pathogen Candida albicans switches from a budding yeast form to a polarized hyph... more The human fungal pathogen Candida albicans switches from a budding yeast form to a polarized hyphal form in response to various external signals. This morphogenetic switching has been implicated in the development of pathogenicity. Several signaling pathways that regulate morphogenesis have been identified, including various transcription factors that either activate or repress hypha-specific genes. Two well-characterized pathways include the MAP kinase cascade and cAMP-dependent protein kinase pathway that regulate the transcription factors Cph1p and Efg1p, respectively. cAMP also appears to interplay with other second messengers: Ca2+, inositol tri-phosphates in regulating yeast-hyphal transition. Other, less-characterized pathways include two component histidine kinases, cyclin-dependent kinase pathway, and condition specific pathways such as pH and embedded growth conditions. Nrg1 and Rfg1 function as transcriptional repressors of hyphal genes via recruitment of Tup1 co-repressor complex. Different upstream signals converge into a common downstream output during hyphal switch. The levels of expression of several genes have been shown to be associated with hyphal morphogenesis rather than with a specific hypha-inducing condition. Hyphal development is also linked to the expression of a range of other virulence factors. This review explains the relative contribution of multiple pathways that could be used by Candida albican cells to sense subtle differences in the growth conditions of its native host environment.