James Ziogas - Academia.edu (original) (raw)
Papers by James Ziogas
Chemical communications (Cambridge, England), Jan 28, 2011
Novel paramagnetic selective angiotensin AT(1) receptor antagonists (sartans) bearing nitroxides ... more Novel paramagnetic selective angiotensin AT(1) receptor antagonists (sartans) bearing nitroxides (3, 4) have been prepared and their pharmacology evaluated in vitro as well as in vivo. Compounds 3, 4 proved to be effective sartans with pK(B) estimates in the range 6.2-9.1. In addition, the sodium salt (11) of 4 (R = Bu) is able to protect against vascular injury in hypertensive rats as determined by its ability to attenuate the development of intimal thickening caused by balloon injury of the carotid artery.
Proceedings of the National Academy of Sciences, 2014
Eur J Pharmacol, 2014
Endothelin-1 has been identified as a potential mediator in the pathogenesis of ischaemic stroke ... more Endothelin-1 has been identified as a potential mediator in the pathogenesis of ischaemic stroke and cerebral vasospasm. The aim of this study was to analyse the role of voltage-operated calcium channels (VOCC) and non-VOCC in endothelin-1 induced vasoconstriction of rat cerebral arteries. Arterial segments were dissected from different regions of the cerebral circulation and responses assessed using wire myography. Endothelin-1 concentration-contraction curves were constructed in calcium-free medium or in the presence of nifedipine, NNC 55-0396 ((1S,2S)-2-(2-(N-[(3-benzimidazol-2-yl)propyl]-N-methylamino)ethyl)-6-fluoro-1,2,3,4-tetrahydro-1-isopropyl-2-naphtyl cyclopropanecarboxylate dihydrochloride) or SK&F 96365 (1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole) to inhibit the l-type VOCC, T-type VOCC and non-VOCC, respectively. Inhibition of the calcium channels or removal of calcium from the medium variably decreased the maximum effects (Emax) of endothelin-1, however its potency (pEC50) was unaltered. Endothelin-1 caused a small contraction (<22%) in calcium-free solution. Pre-treatment with nifedipine (1µM) did not affect responses to low concentrations of endothelin-1 but decreased Emax, while NNC 55-0396 (1µM) and SK&F 96365 (30-100µM) generally attenuated the endothelin-1-induced contraction. Combination of nifedipine with SK&F 96365 further decreased the Emax. The relaxant effect of the calcium channel antagonists was also assessed in pre-contracted arteries. Only nifedipine and SK&F 96365 relaxed the arteries pre-contracted with endothelin-1. In conclusion, VOCC and non-VOCC calcium channels are involved in different phases of the endothelin-1 contraction in rat cerebral vessels. T-type VOCC may be involved in contraction induced by low concentrations of endothelin-1, while l-type VOCC mediate the maintenance phase of contraction. VOCC and non-VOCC may work in concert in mediating contraction induced by endothelin-1.
Med. Chem. Commun., 2014
ABSTRACT Six derivatives containing mexiletine and its 2,6-dichloro analogue to which the potenti... more ABSTRACT Six derivatives containing mexiletine and its 2,6-dichloro analogue to which the potential antioxidant moiety isoindoline, its N-oxide and the N-hydroxy derivatives have been attached, have been evaluated as cardio-protective agents. Four of the derivatives at different oxidation states, NH, NO and NOH had significant cardioprotective properties in an in vitro ischaemia model. In contrast to previous reports the NH compounds were not the most active.
Journal of Pharmacological and Toxicological Methods, 2012
Introduction: Radical-induced haemolysis has been employed by many investigators to determine the... more Introduction: Radical-induced haemolysis has been employed by many investigators to determine the antioxidant capacity of novel compounds. However the free radical generator 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) results in the complete depletion of intracellular reduced glutathione (GSH) in cells that can no longer synthesise macromolecules. As GSH is essential in recycling certain antioxidants back to their active form, the current study examined the effects of exogenous GSH on the antioxidant capacity of quercetin, phenol, ebselen and nitroxide detected using AAPH-induced haemolysis. Here we report a modification that increases the likelihood of detecting antioxidant activity in a radical-induced haemolysis assay. Methods: C57Bl/6 mouse erythrocyte suspensions were pre-incubated with 1, 3 or 10 μM of phenol, ebselen, nitroxide or 10, 20 or 30 μM of quercetin for 30 min in the presence or absence of 1 mM of glutathione. AAPH (150 mM) was added to each well to induce haemolysis. Absorbance of erythrocytes was measured spectrophotometrically at 690 nm over 5 h. Haemolysis in the presence of different pre-treatments was quantified by calculating the time to 50% lysis. Results: AAPH in the presence and absence of GSH resulted in a decrease in absorbance over time as cells lysed. Pre-incubating cells with ebselen or phenol (10 μM) delayed AAPH-induced haemolysis by 37 and 74 min only in the presence of exogenous GSH. Nitroxide accelerated radical-induced haemolysis by 40 min in the absence of exogenous GSH, however delayed haemolysis by 38 min in the presence of exogenous GSH. The antioxidant actions of quercetin were unaffected by the presence of exogenous GSH. Discussion: The results demonstrate that exogenous GSH is required to detect the antioxidant capacity of certain antioxidant moieties using the radical-induced haemolysis assay. This is particularly important as numerous groups use this technique as a high throughput screening assay of antioxidant activity.
Journal of Hypertension, 1987
The effects of angiotensin II and its precursors angiotensin I and tetradecapeptide renin substra... more The effects of angiotensin II and its precursors angiotensin I and tetradecapeptide renin substrate were investigated in isolated segments of the rat caudal artery. Each peptide constricted the rat caudal artery and also enhanced vasoconstrictor responses to sympathetic nerve stimulation (0.5 Hz, 10 s). The threshold concentrations for each peptide in enhancing sympathetic vasoconstrictor responses were lower than those required to produce vasoconstriction. Tetradecapeptide renin substrate was the least potent of the three peptides and had the slowest onset of action. Angiotensin II and angiotensin I each enhanced noradrenergic transmission to the same degree, whether perfused through the lumen or added to the adventitial surface of the artery. In contrast, tetradecapeptide renin substrate was more potent when applied to the adventitial surface. The effects of angiotensin I were blocked by the converting enzyme inhibitor enalaprilat, whereas the effects of tetradecapeptide renin substrate were unaltered by enalaprilat, or by the renin inhibitors pepstatin or a decapeptide renin inhibitor. These findings suggest that tetradecapeptide renin substrate and angiotensin I may be converted to angiotensin II within the rat caudal artery, with subsequent enhancement of noradrenergic neuroeffector function. However, the enzyme responsible for the conversion of tetradecapeptide renin substrate cannot be determined from the present findings.
Hypertension, 2002
Potassium ion (K ϩ ) normally causes cerebral vasodilatation by activating inwardly rectifying K ... more Potassium ion (K ϩ ) normally causes cerebral vasodilatation by activating inwardly rectifying K ϩ (K IR ) channels. We tested whether chronic hypertension affects the magnitude and/or mechanism of K ϩ -induced cerebral vasodilatation in vivo. Basilar artery responses were examined in anesthetized Wistar-Kyoto (WKY; mean arterial pressure, 114Ϯ4 mm Hg) and spontaneously hypertensive (SHR; 176Ϯ3 mm Hg) rats. In WKY, elevating cerebrospinal fluid K ϩ concentration from 3 mmol/L to 5 and 10 mmol/L caused vasodilatation (percent maximum, 12Ϯ1 and 48Ϯ7, respectively). The response to 5 mmol/L K ϩ was greater in SHR (percent maximum, 17Ϯ2 [PϽ0.05 versus WKY] and 49Ϯ4). The K IR channel inhibitor, barium ion (Ba 2ϩ , 100 mol/L) selectively inhibited dilator responses to 5 and 10 mmol/L K ϩ by Ϸ75% in WKY. In SHR, Ba 2ϩ had no effect on the response to 5 mmol/L K ϩ , and only partially inhibited (by Ϸ40%) the response to 10 mmol/L K ϩ . The nonselective NO synthase (NOS) inhibitor N-nitro-L-arginine methyl ester, the neuronal NOS (nNOS) inhibitor 1-(2-trifluromethyl-phenyl)imidazole, and the N-type calcium channel inhibitor -conotoxin GVIA, were all without effect in WKY, but markedly inhibited the response to 5 mmol/L K ϩ in SHR. When applied together with Ba 2ϩ , each of these inhibitors also profoundly reduced responses to 10 mmol/L K ϩ in SHR. Immunostaining of basilar arteries revealed that the perivascular nNOS-containing nerve plexus was denser in SHR. Thus, K ϩ dilates the normotensive basilar artery predominantly via K IR channel activation. During chronic hypertension, small physiological elevations in K ϩ dilate the basilar artery by an nNOS-dependent mechanism that appears to be upregulated in a compensatory manner. (Hypertension. 2002;39:880-885.)
European Journal of Pharmacology, 2012
In this study we have investigated the in vitro angiotensin II receptor antagonist and antioxidan... more In this study we have investigated the in vitro angiotensin II receptor antagonist and antioxidant activity of a series of compounds in which the antioxidant pharmacophores (selenium, phenol, benzothiophene, ebselen or nitroxide) have been incorporated into the AT 1 receptor antagonist (sartan) milfasartan. Activity of these compounds was assessed in tissue-based assays. The novel molecules (30 nM), nitrasartan or phenol-milfasartan, retained AT 1 receptor antagonist potency in rat isolated right atria. Antioxidant capacity of the substituted sartans was examined in an AAPH (2,2 0 -azobis (2-amidinopropane) hydrochloride)-induced haemolysis assay (mouse C57/BL6 isolated erythrocytes).
European Journal of Pharmacology, 1984
Bioorganic & Medicinal Chemistry Letters, 2008
A series of selenophene analogues of the thiophene-containing antihypertensives milfasartan and e... more A series of selenophene analogues of the thiophene-containing antihypertensives milfasartan and eprosartan were prepared and tested for AT 1 receptor antagonist properties. All four selenophene compounds proved to be potent AT 1 receptor antagonists, with pK B estimates indicating that these selenides are at least as effective as the thiophene parent compounds at blocking AT 1 receptor mediated responses. These results reveal that replacement of sulfur with selenium in thiophene-containing sartans does not interfere with sartan activity.
Annals of the New York Academy of Sciences, 1990
Bell reported that angiotensin I1 (AII) enhanced the amplitude of excitatory junctional potential... more Bell reported that angiotensin I1 (AII) enhanced the amplitude of excitatory junctional potentials (EJPs) evoked by sympathetic nerve stimulation without affecting spontaneous excitatory junction potentials (SEJPs) in the guinea pig vas deferens,' suggesting that A11 enhanced noradrenergic transmission. However, it is now believed that EJPs in this preparation are not mediated by noradrenaline, but by the cotransmitter adenosine triphosphate (ATP).' A11 enhances noradrenaline release in a variety of
Analytical chemistry, Jan 30, 2015
The metabolic fate of a compound can often determine the success of a new drug lead. Thus, signif... more The metabolic fate of a compound can often determine the success of a new drug lead. Thus, significant effort is directed to identifying the metabolites formed from a given molecule. Here, an automated and non-targeted procedure is introduced for detecting drug metabolites without authentic metabolite standards via the use of stable isotope labelling, liquid chromatography mass spectrometry (LCMS), and high performance computing. LCMS of blood plasma extracts from rats that were administered a 1:1 mixture of acetaminophen (APAP) and 13C6-APAP resulted in mass spectra that contained "twin" ions for drug metabolites that were not detected in control spectra (i.e., no APAP administered). By developing a program (High-resolution Twin-Ion Metabolite Extraction; HiTIME) that can identify twin-ions in high resolution mass spectra without centroiding (i.e., reduction of mass spectral peaks to single data points), 9 doublets corresponding to APAP metabolites were identified, which ...
Chemical communications (Cambridge, England), Jan 28, 2011
Novel paramagnetic selective angiotensin AT(1) receptor antagonists (sartans) bearing nitroxides ... more Novel paramagnetic selective angiotensin AT(1) receptor antagonists (sartans) bearing nitroxides (3, 4) have been prepared and their pharmacology evaluated in vitro as well as in vivo. Compounds 3, 4 proved to be effective sartans with pK(B) estimates in the range 6.2-9.1. In addition, the sodium salt (11) of 4 (R = Bu) is able to protect against vascular injury in hypertensive rats as determined by its ability to attenuate the development of intimal thickening caused by balloon injury of the carotid artery.
Proceedings of the National Academy of Sciences, 2014
Eur J Pharmacol, 2014
Endothelin-1 has been identified as a potential mediator in the pathogenesis of ischaemic stroke ... more Endothelin-1 has been identified as a potential mediator in the pathogenesis of ischaemic stroke and cerebral vasospasm. The aim of this study was to analyse the role of voltage-operated calcium channels (VOCC) and non-VOCC in endothelin-1 induced vasoconstriction of rat cerebral arteries. Arterial segments were dissected from different regions of the cerebral circulation and responses assessed using wire myography. Endothelin-1 concentration-contraction curves were constructed in calcium-free medium or in the presence of nifedipine, NNC 55-0396 ((1S,2S)-2-(2-(N-[(3-benzimidazol-2-yl)propyl]-N-methylamino)ethyl)-6-fluoro-1,2,3,4-tetrahydro-1-isopropyl-2-naphtyl cyclopropanecarboxylate dihydrochloride) or SK&F 96365 (1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole) to inhibit the l-type VOCC, T-type VOCC and non-VOCC, respectively. Inhibition of the calcium channels or removal of calcium from the medium variably decreased the maximum effects (Emax) of endothelin-1, however its potency (pEC50) was unaltered. Endothelin-1 caused a small contraction (<22%) in calcium-free solution. Pre-treatment with nifedipine (1µM) did not affect responses to low concentrations of endothelin-1 but decreased Emax, while NNC 55-0396 (1µM) and SK&F 96365 (30-100µM) generally attenuated the endothelin-1-induced contraction. Combination of nifedipine with SK&F 96365 further decreased the Emax. The relaxant effect of the calcium channel antagonists was also assessed in pre-contracted arteries. Only nifedipine and SK&F 96365 relaxed the arteries pre-contracted with endothelin-1. In conclusion, VOCC and non-VOCC calcium channels are involved in different phases of the endothelin-1 contraction in rat cerebral vessels. T-type VOCC may be involved in contraction induced by low concentrations of endothelin-1, while l-type VOCC mediate the maintenance phase of contraction. VOCC and non-VOCC may work in concert in mediating contraction induced by endothelin-1.
Med. Chem. Commun., 2014
ABSTRACT Six derivatives containing mexiletine and its 2,6-dichloro analogue to which the potenti... more ABSTRACT Six derivatives containing mexiletine and its 2,6-dichloro analogue to which the potential antioxidant moiety isoindoline, its N-oxide and the N-hydroxy derivatives have been attached, have been evaluated as cardio-protective agents. Four of the derivatives at different oxidation states, NH, NO and NOH had significant cardioprotective properties in an in vitro ischaemia model. In contrast to previous reports the NH compounds were not the most active.
Journal of Pharmacological and Toxicological Methods, 2012
Introduction: Radical-induced haemolysis has been employed by many investigators to determine the... more Introduction: Radical-induced haemolysis has been employed by many investigators to determine the antioxidant capacity of novel compounds. However the free radical generator 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) results in the complete depletion of intracellular reduced glutathione (GSH) in cells that can no longer synthesise macromolecules. As GSH is essential in recycling certain antioxidants back to their active form, the current study examined the effects of exogenous GSH on the antioxidant capacity of quercetin, phenol, ebselen and nitroxide detected using AAPH-induced haemolysis. Here we report a modification that increases the likelihood of detecting antioxidant activity in a radical-induced haemolysis assay. Methods: C57Bl/6 mouse erythrocyte suspensions were pre-incubated with 1, 3 or 10 μM of phenol, ebselen, nitroxide or 10, 20 or 30 μM of quercetin for 30 min in the presence or absence of 1 mM of glutathione. AAPH (150 mM) was added to each well to induce haemolysis. Absorbance of erythrocytes was measured spectrophotometrically at 690 nm over 5 h. Haemolysis in the presence of different pre-treatments was quantified by calculating the time to 50% lysis. Results: AAPH in the presence and absence of GSH resulted in a decrease in absorbance over time as cells lysed. Pre-incubating cells with ebselen or phenol (10 μM) delayed AAPH-induced haemolysis by 37 and 74 min only in the presence of exogenous GSH. Nitroxide accelerated radical-induced haemolysis by 40 min in the absence of exogenous GSH, however delayed haemolysis by 38 min in the presence of exogenous GSH. The antioxidant actions of quercetin were unaffected by the presence of exogenous GSH. Discussion: The results demonstrate that exogenous GSH is required to detect the antioxidant capacity of certain antioxidant moieties using the radical-induced haemolysis assay. This is particularly important as numerous groups use this technique as a high throughput screening assay of antioxidant activity.
Journal of Hypertension, 1987
The effects of angiotensin II and its precursors angiotensin I and tetradecapeptide renin substra... more The effects of angiotensin II and its precursors angiotensin I and tetradecapeptide renin substrate were investigated in isolated segments of the rat caudal artery. Each peptide constricted the rat caudal artery and also enhanced vasoconstrictor responses to sympathetic nerve stimulation (0.5 Hz, 10 s). The threshold concentrations for each peptide in enhancing sympathetic vasoconstrictor responses were lower than those required to produce vasoconstriction. Tetradecapeptide renin substrate was the least potent of the three peptides and had the slowest onset of action. Angiotensin II and angiotensin I each enhanced noradrenergic transmission to the same degree, whether perfused through the lumen or added to the adventitial surface of the artery. In contrast, tetradecapeptide renin substrate was more potent when applied to the adventitial surface. The effects of angiotensin I were blocked by the converting enzyme inhibitor enalaprilat, whereas the effects of tetradecapeptide renin substrate were unaltered by enalaprilat, or by the renin inhibitors pepstatin or a decapeptide renin inhibitor. These findings suggest that tetradecapeptide renin substrate and angiotensin I may be converted to angiotensin II within the rat caudal artery, with subsequent enhancement of noradrenergic neuroeffector function. However, the enzyme responsible for the conversion of tetradecapeptide renin substrate cannot be determined from the present findings.
Hypertension, 2002
Potassium ion (K ϩ ) normally causes cerebral vasodilatation by activating inwardly rectifying K ... more Potassium ion (K ϩ ) normally causes cerebral vasodilatation by activating inwardly rectifying K ϩ (K IR ) channels. We tested whether chronic hypertension affects the magnitude and/or mechanism of K ϩ -induced cerebral vasodilatation in vivo. Basilar artery responses were examined in anesthetized Wistar-Kyoto (WKY; mean arterial pressure, 114Ϯ4 mm Hg) and spontaneously hypertensive (SHR; 176Ϯ3 mm Hg) rats. In WKY, elevating cerebrospinal fluid K ϩ concentration from 3 mmol/L to 5 and 10 mmol/L caused vasodilatation (percent maximum, 12Ϯ1 and 48Ϯ7, respectively). The response to 5 mmol/L K ϩ was greater in SHR (percent maximum, 17Ϯ2 [PϽ0.05 versus WKY] and 49Ϯ4). The K IR channel inhibitor, barium ion (Ba 2ϩ , 100 mol/L) selectively inhibited dilator responses to 5 and 10 mmol/L K ϩ by Ϸ75% in WKY. In SHR, Ba 2ϩ had no effect on the response to 5 mmol/L K ϩ , and only partially inhibited (by Ϸ40%) the response to 10 mmol/L K ϩ . The nonselective NO synthase (NOS) inhibitor N-nitro-L-arginine methyl ester, the neuronal NOS (nNOS) inhibitor 1-(2-trifluromethyl-phenyl)imidazole, and the N-type calcium channel inhibitor -conotoxin GVIA, were all without effect in WKY, but markedly inhibited the response to 5 mmol/L K ϩ in SHR. When applied together with Ba 2ϩ , each of these inhibitors also profoundly reduced responses to 10 mmol/L K ϩ in SHR. Immunostaining of basilar arteries revealed that the perivascular nNOS-containing nerve plexus was denser in SHR. Thus, K ϩ dilates the normotensive basilar artery predominantly via K IR channel activation. During chronic hypertension, small physiological elevations in K ϩ dilate the basilar artery by an nNOS-dependent mechanism that appears to be upregulated in a compensatory manner. (Hypertension. 2002;39:880-885.)
European Journal of Pharmacology, 2012
In this study we have investigated the in vitro angiotensin II receptor antagonist and antioxidan... more In this study we have investigated the in vitro angiotensin II receptor antagonist and antioxidant activity of a series of compounds in which the antioxidant pharmacophores (selenium, phenol, benzothiophene, ebselen or nitroxide) have been incorporated into the AT 1 receptor antagonist (sartan) milfasartan. Activity of these compounds was assessed in tissue-based assays. The novel molecules (30 nM), nitrasartan or phenol-milfasartan, retained AT 1 receptor antagonist potency in rat isolated right atria. Antioxidant capacity of the substituted sartans was examined in an AAPH (2,2 0 -azobis (2-amidinopropane) hydrochloride)-induced haemolysis assay (mouse C57/BL6 isolated erythrocytes).
European Journal of Pharmacology, 1984
Bioorganic & Medicinal Chemistry Letters, 2008
A series of selenophene analogues of the thiophene-containing antihypertensives milfasartan and e... more A series of selenophene analogues of the thiophene-containing antihypertensives milfasartan and eprosartan were prepared and tested for AT 1 receptor antagonist properties. All four selenophene compounds proved to be potent AT 1 receptor antagonists, with pK B estimates indicating that these selenides are at least as effective as the thiophene parent compounds at blocking AT 1 receptor mediated responses. These results reveal that replacement of sulfur with selenium in thiophene-containing sartans does not interfere with sartan activity.
Annals of the New York Academy of Sciences, 1990
Bell reported that angiotensin I1 (AII) enhanced the amplitude of excitatory junctional potential... more Bell reported that angiotensin I1 (AII) enhanced the amplitude of excitatory junctional potentials (EJPs) evoked by sympathetic nerve stimulation without affecting spontaneous excitatory junction potentials (SEJPs) in the guinea pig vas deferens,' suggesting that A11 enhanced noradrenergic transmission. However, it is now believed that EJPs in this preparation are not mediated by noradrenaline, but by the cotransmitter adenosine triphosphate (ATP).' A11 enhances noradrenaline release in a variety of
Analytical chemistry, Jan 30, 2015
The metabolic fate of a compound can often determine the success of a new drug lead. Thus, signif... more The metabolic fate of a compound can often determine the success of a new drug lead. Thus, significant effort is directed to identifying the metabolites formed from a given molecule. Here, an automated and non-targeted procedure is introduced for detecting drug metabolites without authentic metabolite standards via the use of stable isotope labelling, liquid chromatography mass spectrometry (LCMS), and high performance computing. LCMS of blood plasma extracts from rats that were administered a 1:1 mixture of acetaminophen (APAP) and 13C6-APAP resulted in mass spectra that contained "twin" ions for drug metabolites that were not detected in control spectra (i.e., no APAP administered). By developing a program (High-resolution Twin-Ion Metabolite Extraction; HiTIME) that can identify twin-ions in high resolution mass spectra without centroiding (i.e., reduction of mass spectral peaks to single data points), 9 doublets corresponding to APAP metabolites were identified, which ...