Exogenous [H.sub.2]S protects H9c2 cardiac cells against high glucose-induced injury and inflammation by inhibiting the activation of the NF-κB and IL-1β pathways

Hyperglycemia has been reported to activate the nuclear factor-κB (NF-κB) pathway. We have previously demonstrated that exogenous hydrogen sulfide ([H.sub.2]S) protects cardiomyocytes against high glucose (HG)-induced injury by inhibiting the activity of p38 mitogen-activated protein kinase (MAPK), which can activate the NF-κB pathway and induce interleukin (IL)-1β production. In the present study, we aimed to investigate the hypothesis that exogenous [H.sub.2]S protects cardiomyocytes against HG-induced injury and inflammation through the inhibition of the NF-κB/IL-1β pathway. H9c2 cardiac cells were treated with 35 mM glucose (HG) for 24 h to establish a model of HG-induced damage. Our results demonstrated that treatment of the cells with 400 µM sodium hydrogen sulfide (NaHS, a donor of [H.sub.2]S) or 100 µM pyrrolidine dithiocarbamate (PDTC, an inhibitor of NF-κB) for 30 min prior to exposure to HG markedly attenuated the HG-induced increase in the expression levels of the phosphorylated (p)-NF-κB p65 subunit. Notably, pre-treatment of the H9c2 cardiac cells with NaHS or PDTC significantly suppressed the HG-induced injury, including cytotoxicity, apoptosis, oxidative stress and mitochondrial insults, as evidenced by an increase in cell viability, as well as a decrease in the number of apoptotic cells, the expression of cleaved caspase-3, the generation of reactive oxygen species (ROS) and the dissipation of mitochondrial membrane potential (MMP). In addition, pre-treatment of the cells with NaHS or PDTC ameliorated the HG-induced inflammatory response, leading to a decrease in the levels of IL-1β, IL-6 and tumor necrosis factor-a (TNF-α). Importantly, co-treatment of the H9c2 cells with 20 ng/ml IL-1 receptor antagonist (IL-1Ra) and HG markedly reduced the HG-induced increase in p-NF-κB p65 expression, cytotoxicity, the number of apoptotic cells, as well as the production of TNF-α. In conclusion, the present study presents novel mechanistic evidence that exogenous [H.sub.2]S protects H9c2 cardiac cells against HG-induced inflammation and injury, including cytotoxicity, apoptosis, overproduction of ROS and the dissipation of MMP, by inhibiting the NF-κB/IL-1β pathway. We also provide new data indicating that the positive interaction between the NF-κB pathway and IL-1β is critical in HG-induced injury and inflammation in H9c2 cardiac cells. Key words: hydrogen sulfide, high glucose, H9c2 cells, nuclear factor-κB, inflammation