Shreyasi Palit - Academia.edu (original) (raw)

Papers by Shreyasi Palit

Research paper thumbnail of Extracellular Matrix Interacting Proteins of Trypanosomatids: Adhesion and Invasion of Host Tissues

Research paper thumbnail of Leishmania donovani inhibits inflammasome-dependent macrophage activation by exploiting the negative regulatory proteins A20 and UCP2

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, Nov 1, 2017

In visceral leishmaniasis, we found that the antileishmanial drug Amp B produces a higher level o... more In visceral leishmaniasis, we found that the antileishmanial drug Amp B produces a higher level of IL-1β over the infected control. Moreover, administering anti-IL-1β antibody to infected Amp B-treated mice showed significantly less parasite clearance. Investigation revealed that Leishmania inhibits stimuli-induced expression of a multiprotein signaling platform, NLRP3 inflammasome, which in turn inhibits caspase-1 activation mediated maturation of IL-1β from its pro form. Attenuation of NLRP3 and pro-IL-1β in infection was found to result from decreased NF-κB activity. Transfecting infected cells with constitutively active NF-κB plasmid increased NLRP3 and pro-IL-1β expression but did not increase mature IL-1β, suggesting that IL-1β maturation requires a second signal, which was found to be reactive oxygen species (ROS). Decreased NF-κB was attributed to increased expression of A20, a negative regulator of NF-κB signaling. Silencing A20 in infected cells restored NLRP3 and pro-IL-1...

Research paper thumbnail of The role of PD-1 in regulation of macrophage apoptosis and its subversion by Leishmania donovani

Clinical & translational immunology, 2017

Programmed death-1 receptor (PD-1) expressed in many immune cells is known to trigger T-cell exha... more Programmed death-1 receptor (PD-1) expressed in many immune cells is known to trigger T-cell exhaustion but the significance of macrophage-associated PD-1 in relevance to macrophage apoptosis is not known. This study is aimed to delineate whether PD-1 pathway has any role in eliciting macrophage apoptosis and, if so, then how the intra-macrophage parasite, Leishmania donovani modulates PD-1 pathway for protecting its niche. Resting macrophages when treated with H2O2 showed increased PD-1 expression and apoptosis, which was further enhanced on PD-1 agonist treatment. The administration of either PD-1 receptor or PD-1 ligand-blocking antibodies reversed the process thus documenting the involvement of PD-1 in macrophage apoptosis. On the contrary, L. donovani-infected macrophages showed decreased PD-1 expression concurrent with inhibition of apoptosis. The activation of PD-1 pathway was found to negatively regulate the phosphorylation of pro-survival AKT, which was reversed during infe...

Research paper thumbnail of Leishmania donovani exploits myeloid cell leukemia 1 (MCL-1) protein to prevent mitochondria dependent host cell apoptosis

Journal of Biological Chemistry, 2015

Research paper thumbnail of Hesperetin induces apoptosis in breast carcinoma by triggering accumulation of ROS and activation of ASK1/JNK pathway

Journal of cellular physiology, Jan 10, 2014

Hesperetin, a flavanone glycoside predominantly found in citrus fruits, exhibits a wide array of ... more Hesperetin, a flavanone glycoside predominantly found in citrus fruits, exhibits a wide array of biological properties. In the present study hesperetin exhibited a significant cytotoxic effect in human breast carcinoma MCF-7 cells in a concentration- and time-dependent manner without affecting normal (HMEC) as well as immortalized normal mammary epithelial cells (MCF-10A). The cytotoxic effect of hesperetin was due to the induction of apoptosis as evident from the phosphatidyl-serine externalization, DNA fragmentation, caspase-7 activation and PARP cleavage. Apoptosis was associated with caspase-9 activation, mitochondrial membrane potential loss, release of cytochrome c and increase in Bax:Bcl-2 ratio. Pre-treatment with caspase-9 specific inhibitor (Z-LEHD-fmk) markedly attenuated apoptosis suggesting an involvement of intrinsic mitochondrial apoptotic cascade. Further, DCFDA flow-cytometric analysis revealed triggering of ROS in a time-dependent manner. Pre-treatment with ROS sca...

Research paper thumbnail of 18β-glycyrrhetinic acid induces apoptosis through modulation of Akt/FOXO3a/Bim pathway in human breast cancer MCF-7 cells

Journal of Cellular Physiology, 2012

Triterpenes found in plants display a multitude of biological activities, including anti-tumor pr... more Triterpenes found in plants display a multitude of biological activities, including anti-tumor properties. The present study investigates the effect of 18b-glycyrrhetinic acid (GRA) a pentacyclic triterpenoid of the b-amyrin type, isolated from the root of Licorice (Glycyrrhizza glabra) on human breast cancer cells, MCF-7. GRA showed potent inhibitory effects on MCF-7 proliferation in a concentration-and time-dependent manner without affecting immortalized normal mammary epithelial cell line (MCF-10A). Growth inhibition of MCF-7 cells by GRA occurred through apoptosis, as evident from phosphatidyl serine externalization and DNA fragmentation. Apoptosis was primarily mediated through mitochondrial death cascade as evidenced by loss of mitochondrial membrane potential, release of cytochrome c and activation of caspase-9. GRA induced an increase in Bax:Bcl-2 ratio along with a significant increase in the protein level of the BH3 protein Bim. SiRNA-mediated knock down of Bim markedly attenuated GRA-mediated apoptosis. Profiling of transcriptional regulators of Bim revealed a role of Forkhead box O 3a transcription factor (FOXO3a) as judged by increased expression and nuclear translocation of FOXO3a. Silencing of FOXO3a resulted in marked attenuation in the expression of Bim as well as protection against GRA-mediated apoptosis. Furthermore, GRA-induced activation and nuclear localization of FOXO3a was associated with a reduced activity of Akt kinase. These results suggest that GRA induces apoptosis in human breast carcinoma MCF-7 cells via caspase activation and modulation of Akt/FOXO3a pathway.

Research paper thumbnail of Carnosic acid modulates Akt/IKK/NF-κB signaling by PP2A and induces intrinsic and extrinsic pathway mediated apoptosis in human prostate carcinoma PC-3 cells

Apoptosis, 2012

This study investigates the efficacy of carnosic acid (CA), a polyphenolic diterpene, isolated fr... more This study investigates the efficacy of carnosic acid (CA), a polyphenolic diterpene, isolated from the plant rosemary (Rosemarinus officinalis), on androgen-independent human prostate cancer PC-3 cells. CA induced anti-proliferative effects in PC-3 cells in a concentration- and time-dependent manner, which was due to apoptotic induction as evident from flow-cytometry, DNA laddering and TUNEL assay. Apoptosis was associated with the activation of caspase-8, -9, -3 and -7, increase in Bax:Bcl-2 ratio, release of cytochrome-c and decrease in expression of inhibitor of apoptosis (IAP) family of proteins. Apoptosis was attenuated upon pretreatment with specific inhibitors of caspase-8 (Z-IETD-fmk) and caspase-9 (Z-LEHD-fmk) suggesting the involvement of both intrinsic and extrinsic apoptotic cascades. Further, apoptosis resulted from the inhibition of IKK/NF-κB pathway as evident from decreased DNA binding activity, nuclear translocation of p50 and p65 and IκBα phosphorylation. The down-regulation of IKK/NF-κB was associated with inhibition of Akt phosphorylation and its kinase activity with a concomitant increase in the serine/threonine protein phosphatase 2A (PP2A) activity. Pharmacologic inhibition of PP2A by okadaic acid and calyculin A, significantly reversed CA-mediated apoptotic events in PC-3 cells indicating that CA induced apoptosis by activation of PP2A through modulation of Akt/IKK/NF-κB pathway. In addition, CA induced apoptosis in another androgen refractory prostate cancer DU145 cells via intrinsic pathway as evidenced from the activation of caspase 3, cleavage of PARP, increase in Bax:Bcl-2 ratio and cytochrome-c release. Carnosic acid, therefore, may have the potential for use in the prevention and/or treatment of prostate cancer.

Research paper thumbnail of Extracellular Matrix Interacting Proteins of Trypanosomatids: Adhesion and Invasion of Host Tissues

Research paper thumbnail of Leishmania donovani inhibits inflammasome-dependent macrophage activation by exploiting the negative regulatory proteins A20 and UCP2

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, Nov 1, 2017

In visceral leishmaniasis, we found that the antileishmanial drug Amp B produces a higher level o... more In visceral leishmaniasis, we found that the antileishmanial drug Amp B produces a higher level of IL-1β over the infected control. Moreover, administering anti-IL-1β antibody to infected Amp B-treated mice showed significantly less parasite clearance. Investigation revealed that Leishmania inhibits stimuli-induced expression of a multiprotein signaling platform, NLRP3 inflammasome, which in turn inhibits caspase-1 activation mediated maturation of IL-1β from its pro form. Attenuation of NLRP3 and pro-IL-1β in infection was found to result from decreased NF-κB activity. Transfecting infected cells with constitutively active NF-κB plasmid increased NLRP3 and pro-IL-1β expression but did not increase mature IL-1β, suggesting that IL-1β maturation requires a second signal, which was found to be reactive oxygen species (ROS). Decreased NF-κB was attributed to increased expression of A20, a negative regulator of NF-κB signaling. Silencing A20 in infected cells restored NLRP3 and pro-IL-1...

Research paper thumbnail of The role of PD-1 in regulation of macrophage apoptosis and its subversion by Leishmania donovani

Clinical & translational immunology, 2017

Programmed death-1 receptor (PD-1) expressed in many immune cells is known to trigger T-cell exha... more Programmed death-1 receptor (PD-1) expressed in many immune cells is known to trigger T-cell exhaustion but the significance of macrophage-associated PD-1 in relevance to macrophage apoptosis is not known. This study is aimed to delineate whether PD-1 pathway has any role in eliciting macrophage apoptosis and, if so, then how the intra-macrophage parasite, Leishmania donovani modulates PD-1 pathway for protecting its niche. Resting macrophages when treated with H2O2 showed increased PD-1 expression and apoptosis, which was further enhanced on PD-1 agonist treatment. The administration of either PD-1 receptor or PD-1 ligand-blocking antibodies reversed the process thus documenting the involvement of PD-1 in macrophage apoptosis. On the contrary, L. donovani-infected macrophages showed decreased PD-1 expression concurrent with inhibition of apoptosis. The activation of PD-1 pathway was found to negatively regulate the phosphorylation of pro-survival AKT, which was reversed during infe...

Research paper thumbnail of Leishmania donovani exploits myeloid cell leukemia 1 (MCL-1) protein to prevent mitochondria dependent host cell apoptosis

Journal of Biological Chemistry, 2015

Research paper thumbnail of Hesperetin induces apoptosis in breast carcinoma by triggering accumulation of ROS and activation of ASK1/JNK pathway

Journal of cellular physiology, Jan 10, 2014

Hesperetin, a flavanone glycoside predominantly found in citrus fruits, exhibits a wide array of ... more Hesperetin, a flavanone glycoside predominantly found in citrus fruits, exhibits a wide array of biological properties. In the present study hesperetin exhibited a significant cytotoxic effect in human breast carcinoma MCF-7 cells in a concentration- and time-dependent manner without affecting normal (HMEC) as well as immortalized normal mammary epithelial cells (MCF-10A). The cytotoxic effect of hesperetin was due to the induction of apoptosis as evident from the phosphatidyl-serine externalization, DNA fragmentation, caspase-7 activation and PARP cleavage. Apoptosis was associated with caspase-9 activation, mitochondrial membrane potential loss, release of cytochrome c and increase in Bax:Bcl-2 ratio. Pre-treatment with caspase-9 specific inhibitor (Z-LEHD-fmk) markedly attenuated apoptosis suggesting an involvement of intrinsic mitochondrial apoptotic cascade. Further, DCFDA flow-cytometric analysis revealed triggering of ROS in a time-dependent manner. Pre-treatment with ROS sca...

Research paper thumbnail of 18β-glycyrrhetinic acid induces apoptosis through modulation of Akt/FOXO3a/Bim pathway in human breast cancer MCF-7 cells

Journal of Cellular Physiology, 2012

Triterpenes found in plants display a multitude of biological activities, including anti-tumor pr... more Triterpenes found in plants display a multitude of biological activities, including anti-tumor properties. The present study investigates the effect of 18b-glycyrrhetinic acid (GRA) a pentacyclic triterpenoid of the b-amyrin type, isolated from the root of Licorice (Glycyrrhizza glabra) on human breast cancer cells, MCF-7. GRA showed potent inhibitory effects on MCF-7 proliferation in a concentration-and time-dependent manner without affecting immortalized normal mammary epithelial cell line (MCF-10A). Growth inhibition of MCF-7 cells by GRA occurred through apoptosis, as evident from phosphatidyl serine externalization and DNA fragmentation. Apoptosis was primarily mediated through mitochondrial death cascade as evidenced by loss of mitochondrial membrane potential, release of cytochrome c and activation of caspase-9. GRA induced an increase in Bax:Bcl-2 ratio along with a significant increase in the protein level of the BH3 protein Bim. SiRNA-mediated knock down of Bim markedly attenuated GRA-mediated apoptosis. Profiling of transcriptional regulators of Bim revealed a role of Forkhead box O 3a transcription factor (FOXO3a) as judged by increased expression and nuclear translocation of FOXO3a. Silencing of FOXO3a resulted in marked attenuation in the expression of Bim as well as protection against GRA-mediated apoptosis. Furthermore, GRA-induced activation and nuclear localization of FOXO3a was associated with a reduced activity of Akt kinase. These results suggest that GRA induces apoptosis in human breast carcinoma MCF-7 cells via caspase activation and modulation of Akt/FOXO3a pathway.

Research paper thumbnail of Carnosic acid modulates Akt/IKK/NF-κB signaling by PP2A and induces intrinsic and extrinsic pathway mediated apoptosis in human prostate carcinoma PC-3 cells

Apoptosis, 2012

This study investigates the efficacy of carnosic acid (CA), a polyphenolic diterpene, isolated fr... more This study investigates the efficacy of carnosic acid (CA), a polyphenolic diterpene, isolated from the plant rosemary (Rosemarinus officinalis), on androgen-independent human prostate cancer PC-3 cells. CA induced anti-proliferative effects in PC-3 cells in a concentration- and time-dependent manner, which was due to apoptotic induction as evident from flow-cytometry, DNA laddering and TUNEL assay. Apoptosis was associated with the activation of caspase-8, -9, -3 and -7, increase in Bax:Bcl-2 ratio, release of cytochrome-c and decrease in expression of inhibitor of apoptosis (IAP) family of proteins. Apoptosis was attenuated upon pretreatment with specific inhibitors of caspase-8 (Z-IETD-fmk) and caspase-9 (Z-LEHD-fmk) suggesting the involvement of both intrinsic and extrinsic apoptotic cascades. Further, apoptosis resulted from the inhibition of IKK/NF-κB pathway as evident from decreased DNA binding activity, nuclear translocation of p50 and p65 and IκBα phosphorylation. The down-regulation of IKK/NF-κB was associated with inhibition of Akt phosphorylation and its kinase activity with a concomitant increase in the serine/threonine protein phosphatase 2A (PP2A) activity. Pharmacologic inhibition of PP2A by okadaic acid and calyculin A, significantly reversed CA-mediated apoptotic events in PC-3 cells indicating that CA induced apoptosis by activation of PP2A through modulation of Akt/IKK/NF-κB pathway. In addition, CA induced apoptosis in another androgen refractory prostate cancer DU145 cells via intrinsic pathway as evidenced from the activation of caspase 3, cleavage of PARP, increase in Bax:Bcl-2 ratio and cytochrome-c release. Carnosic acid, therefore, may have the potential for use in the prevention and/or treatment of prostate cancer.