Ashim K. Bagchi

Akt regulates IL-10 mediated suppression of TNFα-induced cardiomyocyte apoptosis by upregulating Stat3 phosphorylation.

Background We have already reported that TNF-α increases cardiomyocyte apoptosis and IL-10 treatment prevented these effects of TNF-α. Present study investigates the role of Akt and Jak/Stat pathway in the IL-10 modulation of TNF-α induced cardiomyocyte apoptosis. Methodology/Principal findings Cardiomyocytes isolated from adult Sprague Dawley rats were exposed to TNF-α (10 ng/ml), IL-10 (10 ng/ml) and TNF-α+IL-10 (ratio 1) for 4 h. Exposure to TNF-α resulted in an increase in cardiomyocyte apoptosis as measured by flow cytometry and TUNEL assay. IL-10 by itself had no effect, but it prevented TNF-α induced apoptosis. IL-10 treatment increased Akt levels within cardiomyocytes and this change was associated with an increase in Jak1 and Stat3 phosphorylation. Pre-exposure of cells to Akt inhibitor prevented IL-10 induced Stat3 phosphorylation. Furthermore, in the presence of Akt or Stat3 inhibitor, IL-10 treatment was unable to block TNF-α induced cardiomyocyte apoptosis. Conclusion It is suggested that IL-10 modulation of TNF-α induced cardiomyocyte apoptosis is mediated by Akt via Stat3 activation.

Vitamin C mitigates oxidative/nitrosative stress and inflammation in doxorubicin-induced cardiomyopathy

Increase in oxidative/nitrosative stress is one of the mechanisms associated with the development of cardiotoxicity due to doxorubicin (Dox), a potent chemotherapy drug. Previously, we reported mitigation of Dox-induced oxidative/nitrosative stress and apoptosis by vitamin C (Vit C) in isolated cardiomyocytes. In the present in vivo study in rats, we investigated the effect of prophylactic treatment with Vit C on Dox-induced apoptosis, inflammation, oxidative/nitrosative stress, cardiac dysfunction, and Vit C transporter proteins. Dox (cumulative dose: 15 mg/kg) in rats reduced systolic and diastolic cardiac function and caused structural damage. These changes were associated with a myocardial increase in reactive oxygen species, reduction in antioxidant enzyme activities, increased expression of apoptotic proteins, and inflammation. Dox also caused an increase in the expression of proapoptotic proteins Bax, Bnip-3, Bak, and caspase-3. An increase in oxidative/nitrosative stress attributable to Dox was indicated by an increase in superoxide, protein carbonyl formation, lipid peroxidation, nitric oxide (NO), NO synthase (NOS) activity, protein nitrosylation, and inducible NOS protein expression. Dox increased the levels of cardiac proinflammatory cytokines TNF-α, IL-1β, and IL-6, whereas the expression of Vit C transporter proteins (sodium-ascorbate cotransporter 2 and glucose transporter 4) was reduced. Prophylactic and concurrent treatment with Vit C prevented all these changes and improved survival in the Vit C + Dox group. Vit C also improved Dox-mediated systolic and diastolic dysfunctions and structural damage. These results suggest a cardioprotective role of Vit C in Dox-induced cardiomyopathy by reducing oxidative/nitrosative stress, inflammation, and apoptosis, as well as improving Vit C transporter proteins.NEW & NOTEWORTHY This in vivo study provides novel data that vitamin C improves cardiac structure and function in doxorubicin-induced cardiomyopathy by reducing oxidative/nitrosative stress, apoptosis, and inflammation along with upregulation of cardiac vitamin C transporter proteins. The latter may have a crucial role in improving antioxidant status in this cardiomyopathy.

Toll-like receptor 2 dominance over Toll-like receptor 4 in stressful conditions for its detrimental role in the heart

It has been suggested that Toll-like receptor (TLR)4 promotes IL-10-mediated cardiac cell survival, whereas another receptor, TLR2, from the same family, is detrimental. Here, we examined the interactive role of these two innate signaling molecules under stressful conditions, including IL-10 knockout (IL-10-/-) mice, global ischemia-reperfusion (I/R) injury in rat hearts, and in vitro short hairpin RNA experimental models in the presence or absence of IL-10 (10 ng/ml). Circulating and myocardial levels of TNF-α as well as apoptosis and fibrosis were higher in IL-10-/- mice. The increase in TLR2 in IL-10-/- hearts indicated its negative regulation by IL-10. Ex vivo I/R also caused a marked upregulation of TLR2 and TNF-α as well as apoptotic and fibrotic signals. However, a 40-min reperfusion with IL-10 triggered an increase in TLR4 expression and improved recovery of cardiac function. The increase in IL-1 receptor-associated kinase (IRAK)-M and IRAK-2 activity during I/R injury suggested their role in TLR2 signaling. In vitro inhibition of TLR4 activity as a consequence of RNA inhibition-mediated suppression of myeloid differentiation gene (MyD)88 suggested MyD88-dependent activation of TLR4. The inclusion of IL-10 during reperfusion also downregulated the expression of IRAK-2, TNF-α receptor-associated factor 1-interacting protein (TRAIP) and apoptotic signals, caspase-3, and the Bax-to-Bcl-xL ratio. IL-10 reduced the TNF-α receptor-associated increase in TRAIP-induced apoptosis during I/R injury, which led to an increase in IL-1β to mitigate transforming growth factor-β receptor type I-mediated fibrosis. The IL-10 mitigation of these changes suggests that the stimulation through TLR4 signaling promotes IRAK-4 and phosphorylates IRAK-1 instead of IRAK-2 and may be an important therapeutic approach in restoring heart health in stress.NEW & NOTEWORTHY Under stress conditions such as downregulation of the IL-10 gene or ischemia-reperfusion injury, Toll-like receptor (TLR)4 and IL-1 receptor-associated kinase (IRAK)-1 activation is suppressed, along with the upregulation of TLR-2 and IRAK-2, resulting in fibrosis and apoptosis. It is suggested that IL-10 helps to maintain heart function during stress via myeloid differentiation gene 88/IRAK-4/IRAK-1-dependent TLR4 signaling.

Doxorubicin-induced nitrosative stress is mitigated by vitamin C via the modulation of nitric oxide synthases

An increase in oxidative stress is suggested to be the main cause in Doxorubicin (Dox)-induced cardiotoxicity. However, there is now evidence that activation of inducible nitric oxide synthase (iNOS) and nitrosative stress are also involved. The role of vitamin C (Vit C) in the regulation of nitric oxide synthase (NOS) and reduction of nitrosative stress in Dox-induced cardiotoxicity is unknown. The present study investigated the effects of Vit C in the mitigation of Dox-induced changes in the levels of nitric oxide (NO), NOS activity, protein expression of NOS isoforms, and nitrosative stress as well as cytokines TNF-α and IL-10 in isolated cardiomyocytes. Cardiomyocytes isolated from adult Sprague-Dawley rats were segregated into four groups: 1) control, 2) Vit C (25 µM), 3) Dox (10 µM), and 4) Vit C + Dox. Dox caused a significant increase in the generation of superoxide radical (O2·-), peroxynitrite, and NO, and these effects of Dox were blunted by Vit C. Dox increased the expression of iNOS and altered protein expression as well as activation of endothelial NOS (eNOS). These changes were prevented by Vit C. Dox induced an increase in the ratio of monomeric/dimeric eNOS, promoting the production of O2·-, which was prevented by Vit C by increasing the stability of the dimeric form of eNOS. Vit C protected against the Dox-induced increase in TNFα as well as a reduction in IL-10. These results suggest that Vit C provides cardioprotection by reducing oxidative/nitrosative stress and inflammation via a modulation of Dox-induced increase in the NO levels and NOS activity.

Excessive consumption of fructose causes cardiometabolic dysfunctions through oxidative stress and inflammation

A rapid rise in obesity, as well as physical inactivity, in industrialized countries is associated with fructose-consumption-mediated metabolic syndrome having a strong association with cardiovascular disease. Although insulin resistance is thought to be at the core, visceral obesity, hypertension, and hypertriglyceridemia are also considered important components of this metabolic disorder. In addition, various other abnormalities such as inflammation, oxidative stress, and elevated levels of uric acid are also part of this syndrome. Lifestyle changes through improved physical activity, as well as nutrition, are important approaches to minimize metabolic syndrome and its deleterious effects.

Selective Deletion of CD8+ Cells Upregulated by Caspases-1 via IL-18 in Mice Immunized with Major Outer Membrane Protein of Shigella dysenteriae 1 Following Infection

IntroductionMucosal lymphoid changes were observed in cryopreserved rectal tissues obtained from BALB/c mice infected with Shigella dysenteriae 1, immunized with 57-kDa major antigenic outer membrane protein, and infection after immunization.DiscussionOur data suggested that caspase-3 is downregulated in CD4+ cells of immunized BALB/c mice following infection with substantial increased expression of interleukin (IL)-2 and interferon (IFN)-γ, while caspase-1 is upregulated in CD8+ cells with decreased expression of IL-4 and IL-10. This indicated an involvement of Fas-mediated lytic pathway for selective deletion of CD8+ cells out of CD3+ T cells. IL-18 promotes inflammation and induces IFN-γ and tumor necrosis factor (TNF)-α as the expression of IFN-γ and TNF-α cytokines was evident in this study. It is assumed that the role of caspase-1 in inducing the CD4+ T cell activity increased with IL-18 rather than CD8+ suppressor cell activity. Bcl-2 is capable of inhibiting the Fas/Fas-L-mediated cell death for helper cells. Overall, the findings indicate that majority of the apoptotic cells were CD8+ T cells in the groups of infection following immunization, and there might be a selective deletion of T lymphocytes mediated by caspase-1 via IL-18.

Phosphorylation of AktSer473/Ask1Ser83 in Trolox-induced suppression of doxorubicin-induced changes in rat cardiomyocytes

OBjECTIvE: To examine the modulatory effects of the antioxidant Trolox in the interplay of Akt and apoptosis signal-regulating kinase (Ask) 1 in doxorubicin (Dox)-induced oxidative stress (OS). METHODS: Rat cardiomyocytes were treated with Dox (5 μM) or Trolox (20 μM) for 24 h, or were pretreated with Trolox (20 μM) for 4 h before treatment with Dox (5 μM) for 24 h, and were compared with cardiomyocytes without any treatment. For the Akt inhibition study, cardiomyocytes were pretreated overnight with the phosphoinositol 3-kinase/Akt inhibitor wortmannin (1 μM) before treatment with Dox, Trolox or Trolox + Dox. The gain and loss of Akt gene function with HA-tagged constitutively active Akt1 or dominant-negative mutant Akt1 (T308A; S473A) was also studied in the cardiomyocytes under all treatment conditions. Cells exposed to various treatment conditions were analyzed for OS, apoptotic and antiapoptotic proteins, and phosphorylation of Ask1Ser83, Ask1Thr845 and AktSer473.