Aims: Diabetes, characterized by hyperglycaemia, causes sinus node dysfunction (SND) in several rodent models. Interleukin (IL)-10, which is a potent anti-inflammatory cytokine, has been reported to decrease in obese and diabetic patients. We tested the hypothesis that administration of IL-10 inhibits the development of SND caused by hyperglycaemia in streptozotocin (STZ)-induced diabetic mice.
Methods and results: Six-week old CL57/B6 (WT) mice were divided into the following groups: control, STZ injection, and STZ injection with systemic administration of IL-10. IL-10 knockout mice were similarly treated. STZ-induced hyperglycaemia for 8 weeks significantly depressed serum levels of IL-10, but increased several proinflammatory cytokines in WT mice. STZ-induced hyperglycaemia-reduced resting heart rate (HR), and attenuated HR response to isoproterenol in WT mice. In isolated perfused heart experiments, corrected-sinus node recovery time was prolonged in WT mice with STZ injection. Sinus node tissue isolated from the WT-STZ group showed fibrosis, abundant infiltration of macrophages, increased production of reactive oxygen species (ROS), and depressed hyperpolarization activated cyclic nucleotide-gated potassium channel 4 (HCN4). However, the changes observed in the WT-STZ group were significantly attenuated by IL-10 administration and were further exaggerated in IL-10 knockout mice. In cultured cells, preincubation of IL-10 suppressed hyperglycaemia-induced apoptotic and profibrotic signals, and overproduction of ROS. IL-10 markedly inhibited the high glucose-induced p38 activation, and activated signal transducer and activator of transcription (STAT) 3 phosphorylation.
Conclusions: Our results suggest that IL-10 attenuates ROS production, inflammation and fibrosis, and plays an important role in the inhibition of hyperglycaemia-induced SND by suppression of HCN4 downregulation. In addition, IL-10-mediated inhibition of p38 is dependent on STAT3 phosphorylation.