Hitesh Soni

Beneficial effects of carbon monoxide-releasing molecule-2 (CORM-2) on acute doxorubicin cardiotoxicity in mice: Role of oxidative stress and apoptosis

Doxorubicin (DXR) has been used in variety of human malignancies for decades. Despite its efficacy in cancer, clinical usage is limited because of its cardiotoxicity, which has been associated with oxidative stress and apoptosis. Carbon monoxide-releasing molecules (CORMs) have been shown to reduce the oxidative damage and apoptosis. The present study investigated the effects of CORM-2, a fast CO-releaser, against DXR-induced cardiotoxicity in mice using biochemical, histopathological and gene expression approaches. CORM-2 (3, 10 and 30 mg/kg/day) was administered intraperitoneally (i.p.) for 10 days and terminated the study on day 11. DXR (20 mg/kg, i.p.) was injected before 72 h of termination. Mice treated with DXR showed cardiotoxicity as evidenced by elevation of serum creatine kinase (CK) and lactate dehydrogenase (LDH), tissue malondialdehyde (MDA), caspase-3 and decrease the level of total antioxidant status (TAS) in heart tissues. Pre- and post-treatment with CORM-2 (30 mg/kg, i.p.) elicited significant improvement in CK, LDH, MDA, caspase-3 and TAS levels. Histopathological studies showed that cardiac damage with DXR has been reversed with CORM-2+DXR treatment. There was dramatic decrease in hematological count in DXR-treated mice, which has been improved with CORM-2. Furthermore, there was also elevation of mRNA expression of heme oxygenase-1, hypoxia inducible factor-1 alpha, vascular endothelial growth factor and decrease in inducible-nitric oxide synthase expression upon treatment with CORM-2 that might be linked to cardioprotection. These data suggest that CORM-2 treatment provides cardioprotection against acute doxorubicin-induced cardiotoxicity in mice and this effect may be attributed to CORM-2-mediated antioxidant and anti-apoptotic properties.

Cardioprotective effect with carbon monoxide releasing molecule-2 (CORM-2) in isolated perfused rat heart: Role of coronary endothelium and underlying mechanism.

Although the cardioprotective role of carbon monoxide (CO) has been studied against myocardial ischemia-reperfusion (I/R) injury, the role of coronary endothelium and underlying mechanism in carbon monoxide-induced cardioprotection is not well understood in isolated heart. The present study was designed to determine the role of coronary endothelium in CORM-2-mediated cardioprotection during I/R injury in isolated rat heart. Preconditioning with 30microM/l and 50microM/l of CORM-2 for 10min markedly reduced lactate dehydrogenase (LDH) and creatinin kinase (CK) levels in coronary effluent after global ischemia. There was also a significant improvement in coronary flow rate, heart rate, cardiodynamic parameters and marked attenuation in infarct size. However, protective effect was abolished when hearts were pretreated with 100microM CORM-2. We observed that pretreatment with L-NAME (100microM/l), a nitric oxide synthase (NOS) inhibitor did not affect protection by CORM-2 (50microM/l). On the other hand pretreatment with Triton X-100 (0.05% for 20s) to denude endothelium before CORM-2 treatment followed by I/R injury showed similar cardioprotection. Moreover, pretreatment with K(ATP) channel inhibitor, glibenclamide almost completely reversed the cardioprotective effect of CORM-2 in endothelium-denuded hearts. These results indicate that cardioprotection by CORM-2 is highly concentration-dependent, independent of coronary endothelium and cardioprotective effect might be attributed to the activation of K(ATP) channel present on vascular smooth muscle cell (VSMC).

Synthesis and structure-activity relationship of potent, selective and orally active anthranilamide-based factor Xa inhibitors: application of weakly basic sulfoximine group as novel S4 binding element.

A novel series of potent and efficacious factor Xa inhibitors which possesses sulfoximine moiety as novel S4 binding element in anthranilamide chemotype has been identified. Lead optimization at this novel P4 group led to many potent factor Xa inhibitors with excellent anticoagulant activity in human plasma. Selected compounds were dosed orally in rats and checked for their ex vivo prothrombin time prolonging activity, which resulted in identification of compound 5-chloro-N-(5-chloropyridin-2-yl)-2-(4-(N-(2-(diethylamino)acetyl)-S-methylsulfonimidoyl)benzamido)benzamide (18f). The detailed pharmacokinetic evaluation and subsequent metabolism study of 18f suggested the presence of an active metabolite. The compound 18f and its active metabolite 18b demonstrated excellent in vivo efficacy in both arterial and venous thrombosis model in rats and were found to be highly selective against related serine proteases. Based on this promising profile, compound 18f was selected for further evaluation.

TRPC6 channel activation promotes neonatal glomerular mesangial cell apoptosis via calcineurin/NFAT and FasL/Fas signaling pathways

Glomerular mesangial cell (GMC) proliferation and death are involved in the pathogenesis of glomerular disorders. The mechanisms that control GMC survival are poorly understood, but may include signal transduction pathways that are modulated by changes in intracellular Ca2+ ([Ca2+]i) concentration. In this study, we investigated whether activation of the canonical transient receptor potential (TRPC) 6 channels and successive [Ca2+]i elevation alter neonatal GMC survival. Hyperforin (HF)-induced TRPC6 channel activation increased [Ca2+]i concentration, inhibited proliferation, and triggered apoptotic cell death in primary neonatal pig GMCs. HF-induced neonatal GMC apoptosis was not associated with oxidative stress. However, HF-induced TRPC6 channel activation stimulated nuclear translocation of the nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1). HF also increased cell death surface receptor Fas ligand (FasL) level and caspase-8 activity in the cells; effects mitigated by [Ca2+]i chelator BAPTA, calcineurin/NFAT inhibitor VIVIT, and TRPC6 channel knockdown. Accordingly, HF-induced neonatal GMC apoptosis was attenuated by BAPTA, VIVIT, Fas blocking antibody, and a caspase-3/7 inhibitor. These findings suggest that TRPC6 channel-dependent [Ca2+]i elevation and the ensuing induction of the calcineurin/NFAT, FasL/Fas, and caspase signaling cascades promote neonatal pig GMC apoptosis.

Prolyl hydroxylase domain-2 (PHD2) inhibition may be a better therapeutic strategy in renal anemia.

Recombinant human erythropoietin (rHuEPO) has revolutionized the life of dialysis patients with anemia of chronic kidney disease (CKD). Newer erythropoietin analogues with improved profile have been introduced recently. However, there are many concerns such as safety, economy and patient compliance with these newer rHuEPo analogues. Small molecules aimed to inhibit prolyl hydroxylase domain-2 (PHD2) may prevent degradation of hypoxia inducible factor-2 (HIF2) which leads to endogenous erythropoietin production. This therapeutic intervention may not only overcome the patient compliance and economic burden but also possibly overcome the safety issues related to rHuEPO and its analogues. Moreover, PHD2 inhibitors may increase the endogenous circulating iron availability via suppression of hepcidin, a master regulator of iron homeostasis which further reduces the need for exogenous intravenous iron administration for effective erythropoiesis in renal anemia patients. In conclusion, small molecule PHD2 inhibitors may have better therapeutic efficacy and potential to address clinical concerns associated with rHuEPO and rHuEPO mimetic peptides.

Investigation into the mechanism(s) of antithrombotic effects of carbon monoxide releasing molecule-3 (CORM-3)

Carbon monoxide (CO) like nitric oxide (NO) has been recognized as activator of soluble guanylate cyclase (sGC) in many physiological functions. Studies, which demonstrate the mechanisms by which CO inhibits platelet aggregation in in vivo models, are few. Here we investigated the possible involvement of sGC, NO, plasminogen activator inhibitor (PAI-1) and p38 MAP Kinase in antithrombotic effects of CO released by a novel, water-soluble, CO releasing molecule-3 (CORM-3) using rat. The effects of CORM-3 on in vitro and ex vivo platelet aggregation induced by thrombin as well as in in vivo thrombosis models were studied. When added to rat washed platelets in in vitro study, CORM-3 (100 and 200 μM) inhibited thrombin-induced platelet aggregation. Similarly, antiplatelet effect was also observed when 3mg/kg i.v. infusion of CORM-3 administered for 10 minutes in ex vivo study using rat. Interestingly, in presence of inhibitor of sGC (ODQ, 10mg/kg,i.p.) and inhibitor of nitric oxide synthase (L-NAME, 30 mg/kg,i.p.), inhibition of thrombin-induced aggregation by CORM-3 was significantly blocked. Notably, in presence of inhibitor of K(ATP) channel (glibenclamide, 10mg/kg,i.p.) and p38 MAP Kinase (SCIO-469, 1mg/kg, i.p.), inhibition of aggregation by CORM-3 was not blocked. In in vivo studies using animal models of thrombosis, we found that CORM-3-mediated antithrombotic effect was dependent on activation of sGC, NO and suppression of PAI-1 in arterial thrombosis and Arterio-Venous (A-V) shunt models. Therefore, we concluded that antithrombotic activity of CORM-3 may be mediated by activation of sGC, NO and inhibition of PAI-1.

Mechanism(s) involved in carbon monoxide-releasing molecule-2-mediated cardioprotection during ischaemia-reperfusion injury in isolated rat heart

The purpose of the present study was to determine the mechanism(s) involved in carbon monoxide-releasing molecule-2, carbon monoxide-releasing molecule-2-induced cardioprotection. We used the transition metal carbonyl compound carbon monoxide-releasing molecule-2 that can act as carbon monoxide donor in cardiac ischaemia-reperfusion injury model using isolated rat heart preparation. Langendorffs perfused rat hearts when treated with carbon monoxide-releasing molecule-2 (50 μM) for 10 min before global ischaemia exhibited significant reduction in postischaemic levels of myocardial injury markers, creatine kinase and lactate dehydrogenase in coronary effluent. Similarly, pretreatment with carbon monoxide-releasing molecule-2 showed significantly improved postischaemic recovery of heart rate, coronary flow rate, cardiodynamic parameters and reduced infarct size as compared to vehicle control hearts. Perfusion with p38 mitogen-activated protein kinase inhibitor, SB203580, a specific inhibitor of α and β isoform, before and concomitantly with carbon monoxide-releasing molecule-2 treatment abolished carbon monoxide-releasing molecule-2-induced cardioprotection. However, p38 mitogen-activated protein kinase alpha inhibitor, SCIO-469, was unable to inhibit the cardioprotective effect of carbon monoxide-releasing molecule-2. Furthermore, protective effect of carbon monoxide-releasing molecule-2 was significantly inhibited by the protein kinase C inhibitor, chelerythrine, when added before and concomitantly with carbon monoxide-releasing molecule-2. It was also observed that, perfusion with phosphatidylinositol 3-kinase inhibitor, wortmannin, before and concomitantly with carbon monoxide-releasing molecule-2 was not able to inhibit carbon monoxide-releasing molecule-2-induced cardioprotection. Interestingly, we observed that wortmannin perfusion before ischaemia and continued till reperfusion significantly inhibited carbon monoxide-releasing molecule-2-mediated cardioprotection. Our findings suggest that the carbon monoxide-releasing molecule-2 treatment may activate the p38 mitogen-activated protein kinase β and protein kinase C pathways before ischaemia and phosphatidylinositol 3-kinase pathway during reperfusion which may be responsible for the carbon monoxide-releasing molecule-2-mediated cardioprotective effect.

Lipid rafts are required for signal transduction by angiotensin II receptor type 1 in neonatal glomerular mesangial cells

Angiotensin II (ANG-II) receptors (AGTRs) contribute to renal physiology and pathophysiology, but the underlying mechanisms that regulate AGTR function in glomerular mesangium are poorly understood. Here, we show that AGTR1 is the functional AGTR subtype expressed in neonatal pig glomerular mesangial cells (GMCs). Cyclodextrin (CDX)-mediated cholesterol depletion attenuated cell surface AGTR1 protein expression and ANG-II-induced intracellular Ca(2+) ([Ca(2+)]i) elevation in the cells. The COOH-terminus of porcine AGTR1 contains a caveolin (CAV)-binding motif. However, neonatal GMCs express CAV-1, but not CAV-2 and CAV-3. Colocalization and in situ proximity ligation assay detected an association between endogenous AGTR1 and CAV-1 in the cells. A synthetic peptide corresponding to the CAV-1 scaffolding domain (CSD) sequence also reduced ANG-II-induced [Ca(2+)]i elevation in the cells. Real-time imaging of cell growth revealed that ANG-II stimulates neonatal GMC proliferation. ANG-II-induced GMC growth was attenuated by EMD 66684, an AGTR1 antagonist; BAPTA, a [Ca(2+)]i chelator; KN-93, a Ca(2+)/calmodulin-dependent protein kinase II inhibitor; CDX; and a CSD peptide, but not PD 123319, a selective AGTR2 antagonist. Collectively, our data demonstrate [Ca(2+)]i-dependent proliferative effect of ANG-II and highlight a critical role for lipid raft microdomains in AGTR1-mediated signal transduction in neonatal GMCs.

Discovery of inhibitors of plasminogen activator inhibitor-1: structure-activity study of 5-nitro-2-phenoxybenzoic acid derivatives.

Two novel series of 5-nitro-2-phenoxybenzoic acid derivatives are designed as potent PAI-1 inhibitors using hybridization and conformational restriction strategy in the tiplaxtinin and piperazine chemo types. The lead compounds 5a, 6c, and 6e exhibited potent PAI-1 inhibitory activity and favorable oral bioavailability in the rodents.

Peptide-based GLP-1/glucagon co-agonists: A double-edged sword to combat diabesity

Diabesity is a new term for obesity-dependent diabetes, which is also associated with cardiovascular and other comorbidities with rising epidemic. Traditional treatments (sulfonylureas and thiazolidinediones) of diabetes are associated with weight gain, except metformin. Newer agents such as glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and Sodium glucose co-transporter 2 inhibitors (SGLT2i) are causing a modest weight reduction, whereas dipeptidyl peptidase-4 inhibitors (DPP-4i) are weight neutral. Oxyntomodulin, a native GLP-1/glucagon receptor agonist produced a superior weight loss and antihyperglycemic effects in obese mice and humans. Recent findings with synthetic dual GLP-1/glucagon receptor agonists have shown a good weight loss and antihyperglycemic profile in diet-induced obese (DIO) mice. Targeting combinations of GLP-1 receptor and glucagon receptor simultaneously with a single peptide may be the better strategy to achieve marked weight loss and considerable glycemic control in diabesity. Cardiovascular safety is very important with new antidiabetic agents due to rosiglitazone controversy. Current on-going clinical trials will clarify the cardiovascular effects of incretin-based therapies in near future. Based on current knowledge and rapid progress in the field, there is a strong possibility that the GLP-1/glucagon receptor co-agonists will likely be the new therapeutic treatment for diabesity for decades to come.