Sathish Babu Vasamsetti

Metformin Inhibits Monocyte-to-Macrophage Differentiation via AMPK-Mediated Inhibition of STAT3 Activation: Potential Role in Atherosclerosis

Monocyte-to-macrophage differentiation is a critical event that accentuates atherosclerosis by promoting an inflammatory environment within the vessel wall. In this study, we investigated the molecular mechanisms responsible for monocyte-to-macrophage differentiation and, subsequently, the effect of metformin in regressing angiotensin II (Ang-II)-mediated atheromatous plaque formation in ApoE−/− mice. AMPK activity was dose and time dependently downregulated during phorbol myristate acetate (PMA)-induced monocyte-to-macrophage differentiation, which was accompanied by an upregulation of proinflammatory cytokine production. Of note, AMPK activators metformin and AICAR significantly attenuated PMA-induced monocyte-to-macrophage differentiation and proinflammatory cytokine production. However, inhibition of AMPK activity alone by compound C was ineffective in promoting monocyte-to-macrophage differentiation in the absence of PMA. On the other hand, inhibition of c-Jun N-terminal kinase activity inhibited PMA-induced inflammation but not differentiation, suggesting that inflammation and differentiation are independent events. In contrast, inhibition of STAT3 activity inhibited both inflammation and monocyte-to-macrophage differentiation. By decreasing STAT3 phosphorylation, metformin and AICAR through increased AMPK activation caused inhibition of monocyte-to-macrophage differentiation. Metformin attenuated Ang-II–induced atheromatous plaque formation and aortic aneurysm in ApoE−/− mice partly by reducing monocyte infiltration. We conclude that the AMPK-STAT3 axis plays a pivotal role in regulating monocyte-to-macrophage differentiation and that by decreasing STAT3 phosphorylation through increased AMPK activity, AMPK activators inhibit monocyte-to-macrophage differentiation.

Synthesis of novel 1,2,3-triazole substituted-N-alkyl/aryl nitrone derivatives, their anti-inflammatory and anticancer activity.

A series of novel 1,2,3-triazole substituted N-phenyl nitrone derivatives 5a-e were prepared in three steps starting from 1-substituted-1,2,3-triazole-4-carbaldehydes 2 via Schiffs base formation, reduction followed by oxidation. Similarly, 1,2,3-triazole substituted N-alkyl nitrone derivatives 6a-p were prepared in single step starting from compound 2 on reaction with N-alkyl hydroxylamine hydrochlorides. All the final compounds were screened for anti-inflammatory and anticancer activity against various cancer cell lines. Among the compounds tested, the compounds 5a, 5d, 6a, 6b, 6m and 6o exhibited significant inhibition of IL-1β secretion as a measure of anti-inflammatory activity. Compound 5b, 5c, 6h, 6i and 6o exhibited significant activity against all the cell lines (A549, COLO 205, MDA-MB 231 and PC-3) at IC50 values of <15 μM.

Statin‐induced inhibition of breast cancer proliferation and invasion involves attenuation of iron transport: intermediacy of nitric oxide and antioxidant defence mechanisms

Accumulating evidence from in vitro, in vivo, clinical and epidemiological studies shows promising results for the use of statins against many cancers including breast carcinoma. However, the molecular mechanisms responsible for the anti‐proliferative and anti‐invasive properties of statins still remain elusive. In this study, we investigated the involvement of nitric oxide, iron homeostasis and antioxidant defence mechanisms in mediating the anti‐proliferative and anti‐invasive properties of hydrophobic statins in MDA‐MB‐231, MDA‐MB‐453 and BT‐549 metastatic triple negative breast cancer cells. Fluvastatin and simvastatin significantly increased cytotoxicity which was reversed with mevalonate. Interestingly, fluvastatin downregulated transferrin receptor (TfR1), with a concomitant depletion of intracellular iron levels in these cells. Statin‐induced effects were mimicked by geranylgeranyl transferase inhibitor (GGTI‐298) but not farnesyl transferase inhibitor (FTI‐277). Further, it was observed that TfR1 downregulation is mediated by increased nitric oxide levels via inducible nitric oxide synthase (iNOS) expression. NOS inhibitors (asymmetric dimethylarginine and 1400W) counteracted and sepiapterin, a precursor of tetrahydrobiopterin, exacerbated statin‐induced depletion of intracellular iron levels. Notably, fluvastatin increased manganese superoxide dismutase (by repressing the transcription factor DNA damage‐binding protein 2), catalase and glutathione which, in turn, diminished H2O2 levels. Fluvastatin‐induced downregulation of TfR1, matrix metalloproteinase‐2, ‐9 and inhibition of invasion were reversed in the presence of aminotriazole, a specific inhibitor of catalase. Finally, we conclude that fluvastatin, by altering iron homeostasis, nitric oxide generation and antioxidant defence mechanisms, induces triple negative breast cancer cell death.

Mitochondria-targeted esculetin alleviates mitochondrial dysfunction by AMPK-mediated nitric oxide and SIRT3 regulation in endothelial cells: potential implications in atherosclerosis

Mitochondria-targeted compounds are emerging as a new class of drugs that can potentially alter the pathophysiology of those diseases where mitochondrial dysfunction plays a critical role. We have synthesized a novel mitochondria-targeted esculetin (Mito-Esc) with an aim to investigate its effect during oxidative stress-induced endothelial cell death and angiotensin (Ang)-II-induced atherosclerosis in ApoE−/− mice. Mito-Esc but not natural esculetin treatment significantly inhibited H2O2- and Ang-II-induced cell death in human aortic endothelial cells by enhancing NO production via AMPK-mediated eNOS phosphorylation. While L-NAME (NOS inhibitor) significantly abrogated Mito-Esc-mediated protective effects, Compound c (inhibitor of AMPK) significantly decreased Mito-Esc-mediated increase in NO production. Notably, Mito-Esc promoted mitochondrial biogenesis by enhancing SIRT3 expression through AMPK activation; and restored H2O2-induced inhibition of mitochondrial respiration. siSIRT3 treatment not only completely reversed Mito-Esc-mediated mitochondrial biogenetic marker expressions but also caused endothelial cell death. Furthermore, Mito-Esc administration to ApoE−/− mice greatly alleviated Ang-II-induced atheromatous plaque formation, monocyte infiltration and serum pro-inflammatory cytokines levels. We conclude that Mito-Esc is preferentially taken up by the mitochondria and preserves endothelial cell survival during oxidative stress by modulating NO generation via AMPK. Also, Mito-Esc-induced SIRT3 plays a pivotal role in mediating mitochondrial biogenesis and perhaps contributes to its anti-atherogenic effects.

Resveratrol attenuates monocyte-to-macrophage differentiation and associated inflammation via modulation of intracellular GSH homeostasis: Relevance in atherosclerosis

Monocyte-to-macrophage differentiation promotes an inflammatory environment within the arterial vessel wall that causes a mal-adaptive immune response, which contributes to the progression of atheromatous plaque formation. In the current study, we show that resveratrol, a well-known antioxidant, dose-dependently attenuated phorbol myristate acetate (PMA)-induced monocyte-to-macrophage differentiation, as measured by cell adhesion, increase in cell size, and scavenger receptor expression in THP-1 monocytes. Also, resveratrol significantly inhibited PMA-induced pro-inflammatory cytokine/chemokine and matrix metalloprotease (MMP-9) production. This inhibitory effect of resveratrol on monocyte differentiation results from its ability to restore intracellular glutathione (GSH) status, as resveratrol in the presence of buthionine sulfoximine (BSO) failed to affect monocyte differentiation. Furthermore, PMA-induced monocyte differentiation and inflammation was greatly inhibited when cells were co-treated with N-Acetyl-l-cysteine (NAC), a GSH precursor, while the presence of BSO aggravated these processes. These results also show that resveratrol mediated up-regulation of GSH is due to AMP-activated protein kinase (AMPK)-α activation, as compound C (AMPK inhibitor) treatment drastically depleted intracellular GSH and exacerbated PMA-induced monocyte differentiation and pro-inflammatory cytokine production. More importantly, chronic administration of resveratrol efficiently prevented monocyte infiltration and markedly diminished angiotensin (Ang)-II-induced atheromatous plaque formation in apolipoprotein-E knockout (ApoE(-/-)) mice. We conclude that, intracellular GSH status plays a critical role in regulating monocyte-to-macrophage differentiation and inflammation and resveratrol, by restoring GSH levels, inhibits these processes. Taken together, these results suggest that resveratrol can attenuate atherosclerosis, at least, in part, by inhibiting monocyte differentiation and pro-inflammatory cytokines production.

Synthesis of novel 1,2-benzothiazine 1,1-dioxide-3-ethanone oxime N-aryl acetamide ether derivatives as potent anti-inflammatory agents and inhibitors of monocyte-to-macrophage transformation.

A series of novel 1,2-benzothiazine 1,1-dioxide-3-ethanone oxime N-aryl acetamide ether derivatives 7a-h and 9a-h were synthesized starting from sodium salt of saccharin 1 in series of steps. Final compounds 7a-h and 9a-h were evaluated for the anti-inflammatory activity and their ability to inhibit monocyte-to-macrophage transformation. Compounds 7e, 9b, 9e and 9h showed impressive anti-inflammatory activities (TNF-α, IL-8 and MCP-1) at micro molar concentration which was found to be better than positive control i.e., piroxicam. Compound 9e marginally and compound 9h significantly inhibited PMA-induced MMP-9 gelatinase activity. Also compounds 9e and 9h greatly inhibited the PMA-induced monocyte-to-macrophage transformation, a pre-requisite step in the formation of atheroma.

Three-component, one-pot synthesis of benzo[6,7]cyclohepta[1,2-b]pyridine derivatives under catalyst free conditions and evaluation of their anti-inflammatory activity.

An efficient three-component protocol is described for the synthesis of benzo[6,7]cyclohepta[1,2-b]pyridine derivatives using β-chloroacroleins, 1,3-dicarbonyls and ammonium acetate under catalyst free conditions by using ethanol as reaction media. The mild reaction conditions, operational simplicity and high yields are the advantages of this protocol and the broad scope of this one-pot reaction makes this procedure promising for practical usages. All the final compounds were screened for anti-inflammatory activity. Among the compounds tested, the compounds 5a, 5b, 5c, 5d, 5f, and 5k exhibited significant inhibition of IL-1β and MCP-1 secretion as a measure of anti-inflammatory activity.

Synthesis of novel 1-substituted triazole linked 1,2-benzothiazine 1,1-dioxido propenone derivatives as potent anti-inflammatory agents and inhibitors of monocyte-to-macrophage differentiation

A series of novel 1-substituted-triazole linked 1,2-benzothiazine 1,1-dioxido propenone derivatives 8a–s & 12a–l were prepared from 1-substituted 1,2,3-triazol-4-aldehydes 6 & 11 with N-methyl-3-acetyl-4-hydroxybenzothiazine-1,1-dioxide 7 by condensation. Final compounds 8 and 12 were evaluated for their anti-inflammatory activity and ability to inhibit monocyte-to-macrophage transformation, a process pivotal during the development and progression of atherosclerosis. Among all the compounds, 12e, 12g, 12i, 12j, 12k and 12l showed impressive anti-inflammatory activity against TNF-α, IL-1β and MCP-1 cytokines released in a dose-dependent manner. The most promising compounds 12g, 12i and 12l further significantly inhibited phorbol 12-myristate 13-acetate (PMA)-induced MMP-9 activity and PMA-induced monocyte-to-macrophage differentiation.

A facile and single pot strategy for the synthesis of novel naphthyridine derivatives under microwave irradiation conditions using ZnCl2 as catalyst, evaluation of AChE inhibitory activity, and molecular modeling studies

A series of novel naphthyridine derivatives 3 and 4 was prepared from substituted pyridine 2 and ketones using ZnCl2 as catalyst under microwave irradiation conditions. All the compounds were evaluated for AChE inhibitory activity and promising compounds 3d, 3e, 4b, and 4g was identified. Representative compounds 3d and 3e were found to show insignificant THLE-2 liver cell viability/toxicity. The binding mode between X-ray crystal structure of human AChE and compounds was studied using molecular docking method and fitness scores were found to be in good correlation with the activity data.