Background/Aim:We have demonstrated that exogenous hydrogen sulfide (H₂S) protects H9c2 cardiac cells against the doxorubicin (DOX)-induced injuries by inhibiting p38 mitogen-activated protein kinase (MAPK) pathway and that the p38 MAPK/nuclear factor-κB (NF-κB) pathway is involved in the DOX-induced inflammatory response and cytotoxicity. The present study attempts to test the hypothesis that exogenous H₂S might protect cardiomyocytes against the DOX-induced inflammation and cytotoxicity through inhibiting p38 MAPK/NF-κB pathway. Methods: H9c2 cardiac cells were exposed to 5µM DOX for 24 h to establish a model of DOX cardiotoxicity. The cells were pretreated with NaHS( a donor of H₂S) or other drugs before exposure to DOX. Cell viability was analyzed by cell counter kit 8 ( CCK-8), The expression of NF-κB p65 and inducible nitric oxide synthase (iNOS) was detected by Western blot assay. The levels of interleukin-1ß (IL-1ß), IL-6 and tumor necrosis factor-a (TNF-a) were tested by enzyme-linked immunosorbent assay (ELISA). Results: Our findings demonstrated that pretreatment of H9c2 cardiac cells with NaHS for 30 min before exposure to DOX markedly ameliorated the DOX-induced phosphorylation and nuclear translocation of NF-κB p65 subunit. Importantly, the pretreatment with NaHS significantly attenuated the p38 MAPK/NF-κB pathway-mediated inflammatory responses induced by DOX, as evidenced by decreases in the levels of IL-1ß, IL-6 and TNF-a. In addition, application of NaHS or IL-1ß receptor antagonist (IL-1Ra) or PDTC (an inhibitor of NF-κB) attenuated the DOX-induced expression of iNOS and production of nitric oxide (NO), respectively. Furthermore, IL-1Ra also dramatically reduced the DOX-induced cytotoxicity and phosphorylation of NF-κB p65. The pretreatment of H9c2 cells with N-acetyl-L-cysteine (NAC), a scavenger of reactive oxygen species (ROS) prior to exposure to DOX depressed the phosphorylation of NF-κB p65 induced by DOX. Conclusion: The present study has demonstrated the new mechanistic evidence that exogenous H₂S attenuates the DOX-induced inflammation and cytotoxicity by inhibiting p38 MAPK/NF-κB pathway in H9c2 cardiac cells. We also provide novel data that the interaction between NF-κB pathway and IL-1ß is important in the induction of DOX-induced inflammation and cytotoxicity in H9c2 cardiac cells.

Abstract. Hyperglycemia is a risk factor for the development of diabetic cardiovascular complications, which are associated with the activation of the mitogen-activated protein kinase (MAPK) signaling pathway. In this study, we demonstrate the inhibitory effects of exogenous hydrogen sulfide (H 2 S) on the activation of the MAPK pathway. The aim of the present study was to determine whether exogenous H 2 S prevents high glucose (HG)-induced injury by inhibiting the activation of the p38 MAPK and extracellular signal-regulated kinase (ERK)1/2 (members of MAPK) pathways in cardiomyoblasts (H9c2 cells). The findings of the present study demonstrated that the treatment of H9c2 cells with HG (35 mM glucose) for 24 h not only significantly induced injury, including cytotoxicity, apoptosis, overproduction of reactive oxygen species (ROS) and the loss of mitochondrial membrane potential (MMP), but also upregulated the expression levels of phosphorylated (p)-p38 MAPK and p-ERK1/2. The increased expression levels of p-p38 MAPK and p-ERK1/2 were markedly reduced by pre-treatment of the H9c2 cells with 400 µM sodium hydrogen sulfide (NaHS; a donor of H 2 S) prior to exposure to 35 mM glucose. Importantly, pre-treatment of the cells with 400 µM NaHS or 3 µM SB203580 (a selective inhibitor of p38 MAPK) or 15 µM U0126 (a selective inhibitor of ERK1/2) attenuated the HG-induced cardiomyocyte injury, leading to an increase in cell viability and a decrease in the number of apoptotic cells, preventing ROS generation, as well as the loss of MMP. In addition, pre-treatment of the cells with 1,000 µM N-acetyl-L-cysteine (a ROS scavenger) prior to exposure to HG ameliorated the HG-induced cytotoxicity. Taken together, the data from the present study demonstrate for the first time, to our knowledge, that exogenous H 2 S exerts a protective effect against HG-induced injury by inhibiting the activation of the p38 MAPK and ERK1/2 pathways and preventing oxidative stress in H9c2 cells.

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Naringin, an active flavonoid isolated from citrus fruit extracts, exhibits biological and pharmacological properties, such as antioxidant activity and antidiabetic effect. Mitogen-activated protein kinase (MAPK) signalling pathway has been shown to participate in hyperglycaemia-induced injury. The present study tested the hypothesis that naringin protects against high glucose (HG)-induced injuries by inhibiting MAPK pathway in H9c2 cardiac cells. To examine this, the cells were treated with 35 mM glucose (HG) for 24 hr to establish a HG-induced cardiomyocyte injury model. The cells were pre-treated with 80 lM naringin for 2 hr before exposure to HG. The findings of this study showed that exposure of H9c2 cells to HG for 24 hr markedly induced injuries, as evidenced by a decrease in cell viability, increases in apoptotic cells and reactive oxygen species (ROS) production, as well as dissipation of mitochondrial membrance potential (MMP). These injuries were significantly attenuated by the pre-treatment of cells with either naringin or SB203580 (a selective inhibitor of p38 MAPK) or U0126 (a selective inhibitor of extracellular signal regulated kinase 1/2, ERK1/2) or SP600125 (a selective inhibitor of c-jun N-termanal kinase, JNK) before exposure to HG, respectively. Furthermore, exposure of cells to HG increased the phosphorylation of p38 MAPK, ERK1/2 and JNK. The increased activation of MAPK pathway was ameliorated by pre-treatment with either naringin or N-acetyl-L-cysteine (NAC), a ROS scavenger, which also reduced HG-induced cytotoxicity and apoptosis, leading to increase in cell viability and decrease in apoptotic cells. In conclusion, our findings provide new evidence for the first time that naringin protects against HGinduced injuries by inhibiting the activation of MAPK (p38 MAPK, ERK1/2 and JNK) and oxidative stress in H9c2 cells.Hyperglycaemia, the most important feature of diabetes mellitus (DM), is believed to be a risk factor for the development of diabetic cardiovascular complications, such as diabetic cardiomyopathy (DCM) [1,2]. The mechanisms responsible for the deteriorative effects of hyperglycaemia on cardiomyocytes are complicated. Multiple factors, such as reactive oxygen species (ROS) production [3][4][5][6][7][8], decline of antioxidant defence systems [6-10], pro-inflammatory cytokine [11][12][13], activation of mitogen-activated protein kinase (MAPK) [14][15][16] and mitochondrial damage [17,18] have been reported to contribute to hyperglycaemia-induced injuries. Sustained hyperglycaemia has been identified as a principle mediator of ROS generation in diabetes [3,4,14,19], which leads to oxidative myocardial injury [14,20]. Furthermore, hyperglycaemia significantly increases phosphorylation of p38 MAPK and extracellular signal regulated kinase (ERK) 1/2 (members of MAPK) in left ventricle tissue of diabetic rats [14], the increased activation of MAPK is associated with the development of diabetic cardiomyopathy [14]. In streptozotocin (STZ)-induced diabetic rats, hyperglycaemia...

Abstract.Hydrogen sulfide (H 2 S) takes part in a diverse range of intracellular pathways and hss physical and pathological properties in vitro and in vivo. However, the effects of H 2 S on cancer are controversial and remain unclear. The present study investigates the effects of H 2 S on liver cancer progression via activating NF-κB pathway in PLC/PRF/5 hepatoma cells.