Isoferulic acid regulates CXCL12/CXCR4-mediated apoptosis and autophagy in podocyte and mice with STZ-induced diabetic nephropathy.

Diabetic nephropathy (DN) is the most common microvascular complication of diabetes mellitus and a major cause of end-stage renal disease. Isoferulic acid (IFA) is a phenolic compound that has strong antioxidant, anti-inflammatory, and hypoglycemic effects. Researches and our previous study showed the potential anti-diabetic capacity and anti- oxidative stress damage targeting podocytes of IFA. The purpose of this study was to investigate whether IFA protects MPC5 podocytes from high glucose damage and alleviates DN symptoms in STZ-induced mice, as well as to explore the mechanism. The findings revealed that IFA (10, 25, 50 μM) significantly reduced high glucose-mediated toxicity, abnormal motility and morphology, ROS release, Ca elevation with MPTP opening, apoptotic alterations with Caspase-3/7 activity increase and CXCL12 chemotaxis and interaction with CXCR4 in MPC5 podocytes. Furthermore, IFA increased Podocalyxin and LC3 II/I ratio. Meanwhile, IFA suppressed p53, mTOR, CASK, and p62. Furthermore, IFA has the ability to directly influence downstream mTOR, p53, and CASK apoptotic and podocyte motility regulatory targets when inhibiting the CXCL12/CXCR4 signaling pathway. In the sequent in vivo experiment, the results showed STZ-induced DN mice had higher kidney index, urination, UACR, lipid metabolism abnormalities and renal dysfunction, raised blood glucose, and podocyte damage than normal C57BL/6 mice. However, IFA treatment (50 mg/kg, 25 mg/kg, and 12.5 mg/kg) for 10 weeks restored the DN symptoms in the mice. IFA treatment elevated LC3B and LC3 II/I ratios and decreased p62 via suppressing chemokine axis CXCL12/CXCR4 with PI3K/Akt/mTOR, MMP9, and NF-κB p65 and activating podocyte markers WT1, nephrin, and Podocalyxin, thereby inducing autophagy and mitigating apoptosis in the DN mice kidneys. These findings suggest that IFA protective mechanism on kidney and podocytes simulating DN symptoms is primarily mediated by the CXCL12/CXCR4 pathways with the inactivation of apoptotic pathways and activation of autophagy.