Study on mechanism of inhibition effect of N 6-methyladenosine methyltransferase-like 3 on vascular calcification in chronic kidney disease through Bax/Bcl-2 / 中华肾脏病杂志

ABSTRACT

Objective:To investigate the role and mechanism of N 6-methyladenosine (m 6A) methyltransferase-like 3 (METTL3) in vascular calcification (VC) of chronic kidney disease (CKD) through apoptosis-associated protein. Methods:(1) Real-time fluorescence quantitative PCR was used to test METTL3 mRNA in serum of maintenance hemodialysis (MHD) patients. (2) Western blotting was used to detect the expression of METTL3 protein in high-phosphorus stimulated vascular smooth muscle cells (VSMCs), and immunofluorescence double lable was used to observe the distribution of METTL3 and Runt-related transcription factor 2 (Runx2). The METTL3 overexpressed and knockdown plasmids were constructed and transfected into VSMCs. Alizarin red staining was used to detect calcification degree. Western blotting was used to detect the expressions of osteogenic markers [Runx2, bone morphogenetic protein-2(BMP-2), collagen Ⅰ] and apoptosis- related proteins Bax and Bcl-2. (3) SD rats were randomly divided into control group, CKD-VC group and S-adenosylhomocysteine (SAH) intervention group. The calcification of thoracic aorta was evaluated by von Kossa staining, and the protein expressions of Runx2, Bax and Bcl-2 were detected by immunohistochemistry and Western blotting.Results:(1) METTL3 mRNA expression in MHD patients with VC was significantly lower than that in non-VC patients ( P<0.05), and was negatively correlated with coronary artery calcium score ( r=-0.65, P<0.001). (2) The expression of METTL3 in VSMCs stimulated by high phosphorus was decreased and showed a time dependence. Immunofluorescence double label showed that METTL3 and Runx2 were co-expressed in the nucleus. METTL3 was overexpressed in high-phosphorus induced VSMCs, and the expressions of Runx2, collagen I and BMP-2 were significantly decreased, accompanied by the decrease of calcified nodules and Bax/Bcl-2 ratio (all P<0.05). Conversely, METTL3 knockdown aggravated VSMCs calcification by inducing apoptosis. (3) Furthermore, METTL3 inhibitor SAH was administered in vivo, and it was found that inhibition of METTL3 expression significantly increased the calcification of rat thoracic aorta, and the Bax/Bcl-2 ratio and Runx2 expression were up-regulated. Conclusions:Serum METTL3 level is reduced in MHD patients with VC. In vivo and in vitro studies demonstrate that METTL3 inhibits VC in CKD by mediating the apoptosis-related protein Bax/Bcl-2.