ABSTRACT
Objective To investigate the expressions of spleen tyrosine kinase (Syk), c-Jun amino terminal kinase (JNK) and nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in the heart tissue in SD rat model of diabetic cardiomyopathy, and to explore the relationship between Syk, JNK and NLRP3. Methods Clean male SD rats were randomly divided into the control (Ctrl) group and diabetic cardiomyopathy model (DCM) group. Rats of DCM group were treated with a single intraperitoneal injection of streptozotocin (STZ), while rats of Ctrl group were injected with the same dose of citrate buffer. The random blood glucose level and body weight were monitored every week until 20 weeks after STZ or citrate buffer injection, then all the rats were killed and their hearts were obtained. Rat H 9c2 cardiomyocytes were randomly divided into normal glucose treatment (NG) group, high glucose treatment (HG) group, Syk inhibitor control (BAY) group and Syk inhibitor high glucose (HG+BAY) group. The Syk and JNK phosphorylations and NLRP3 protein expression were detected by Western blot assay in the heart tissue of SD rats and H9c2 cardiomyocytes. The NLRP3, cysteine-containing aspartate specific protease 1(caspase-1) and interleukin (IL)-1β expressions at mRNA level were detected by reverse transcription-polymerase chain reaction (RT-PCR). Results The random blood glucose level was significantly increased (P<0.05) and the body weight was significantly decreased (P<0.05) in DCM group compared with those of Ctrl group. The expressions of cardiac p-Syk, p-JNK and NLRP3 at protein level were significantly increased in DCM group compared with those of Ctrl group (P<0.05). Furthermore, the mRNA levels of NLRP3, caspase-1 and IL-1β were significantly up-regulated (P < 0.05). BAY treatment significantly inhibited the high glucose-induced NLRP3, caspase-1 and IL-1β mRNA expressions and p-JNK, NLRP3 protein expressions in H9c2 cardiomyocytes (P < 0.05). Conclusion JNK phosphorylation and NLRP3 inflammasome activation induced by Syk play an important role in the pathogenesis of diabetic cardiomyopathy.