Vitamin C Alleviates Kidney Interstitial Fibrosis by Reducing TET2-Mediated SOCS3 m5C Modification

Background: Methylcytosine dimethoxygenase-2 (TET2) has recently been identified as an ‘eraser’ of 5-methylcytosine (m5C) to participate in RNA methylation and chronic kidneyn diseases. Studies have shown that Vitamin C (VC) can directly enhance the catalytic activity of TET enzyme. However, the role of TET2 in renal interstitial fibrosis remains unknown. This study we aimed to clarify whether upregulated TET2 by VC alleviates renal interstitial fibrosis and explore its underlying mechanism. Methods: ICR mice were randomly divided into 4 groups: normal control (NC), folic acid (FA, FA was peritoneally injected to mice), FA+ early VC (prophylactic VC treatment once a day and 4 days before folic acid injection for 34 days, and FA+ late VC (delayed VC treatment after AKI induction for 28 days). Serum creatinine (Scr), and blood urea nitrogen (BUN) were examined. Histological damages were evaluated. TET2, suppressor of cytokine signaling 3(SOCS3), profibrotic proteins α-smooth muscle actin (α-SMA), and fibronectin (FN) were also analyzed. The m5C level of SOCS3 mRNA was detected by MeRIP-qPCR. In vitro study, the HK2 cells were transfected with TET2 siRNA, VC and hTGF-β1 to repeat the associated tests in vivo. The m5C% of total RNA from different groups of HK2 cells was determined using the m5C ELISA kit. Results: In FA mice, Scr and BUN were increased on day 2 and returned to the baseline by day 30; tubular injuries and interstitial fibrosis were seen on PAS and Masson staining; α-SMA and FN were overproduced. Renal TET2 was decreased and SOCS3 was increased. The m5C level of SOCS3 mRNA was increased. In FA+ early VC mice and FA+ late VC mice, the level of SOCS3 and profibrotic α-SMA and FN were reverted by activating TET2. Importantly, the m5C level of SOCS3 mRNA was decreased. The same change directions to FA mice of SOCS3 and profibrotic proteins were seen in HK2 cells transfected with TET2 siRNA and cells stimulated by hTGF-β1; total m5C level in those cells was increased. Another side, the upon changes in HK2 cells by hTGF-β1 stimulation were reverted by VC treatment. Conclusion: Vitamin C agonism of TET2 can alleviate renal interstitial fibrosis by reducing SOCS3 expression through m5C methylation modification. Funding: Government Support – Non-U.S.