Mechanism Of Urotensin Ⅱ In Diabetes-induced Myocardial Fibrosis In Neonatal Cardiac Fibroblasts

Objective This study aimed to explore the effects of high glucose on the expressions of urotensin Ⅱ(UⅡ)and its receptor(UT)in cardiac fibroblasts,to observe the effects of UⅡ system on myocardial fibrosis and the effects of high glucose stimulation on myocardial fibrosis by blocking UⅡ system.And to explore the role and molecular mechanism of U Ⅱ system in the pathogenesis of diabetic cardiomyopathy.Methods Cardiac fibroblasts from neonatal Wistar rats were cultured and randomized to three groups: low glucose group(glucose 5.5mmol/L),high glucose group(glucose 25.0mmol/L)and hypertonic group(glucose 5.5mmol/L + mannitol 19.5mmol/L).The cell changes were observed by inverted phase contrast microscope.The expressions of UⅡ and UT in three groups were detected by Western blotting.To study the effects of blocking UⅡ system on cardiac fibroblasts,the groups were further divided into two subgroups: control group and UⅡ receptor antagonist treatment(urantide)group,namely high glucose group,high glucose + urantide group,low glucose group,low glucose + urantide group,hypertonic group and hypertonic + urantide group.Western blotting and real-time reverse transcription–polymerase chain reaction(RT-PCR)were used to detect the expressions of TGF-β1,type Ⅰ collagen and type Ⅲ collagen.Results After cultured for 24 hours,the neonatal cardiac fibroblasts were observed by inverted phase contrast microscope,the number of cells in the high glucose group showed more than those in the low glucose group or the hyperosmolar group.The expression of UⅡ and its receptor(UT)protein in high glucose group showed a significant increase compared with those in low glucose group or hypertonic group(P <0.05).The protein and m RNA expression of TGF-β1,type I collagen and type Ⅲ collagen in high glucose group were significantly higher than those in low glucose group or hypertonic group(P <0.05),and after culture with urantide,the high-glucose + urantide group showed the downregulated expression compared with high-glucose group(P < 0.05).Conclusion We found that UⅡ and UT were expressed in cardiac fibroblasts,and cardiac fibroblasts can proliferate faster by high glucose stimulation.UⅡ and its receptor UT could be stimulated by high glucose stimulation in cardiac fibroblasts.High glucose stimulation could promote the expression of transforming growth factor-β1,type I collagen and type ⅡI collagen in myocardium fibroblasts.The results indicated that UⅡ could accelerate diabetes-induced myocardial fibrosis through the TGF-β1 signaling pathway,UⅡ/UT system may be involved in the process of myocardial fibrosis during diabetic cardiomyopathy and become a new therapeutic target for diabetic cardiomyopathy.