Down-regulation of HNF4A and MUCDHL in renal tubular epithelial cells promotes renal fibrosis of diabetic mice.

AIM: To explore the roles and associations of hepatocyte nuc lear factor 4 alpha (HNF4A) and mu-protocadherin (MUCDHL) in the kidney of diabetic mice. METHODS: (1) A cohort of six 12-week-old db/m mice and six db/db mice were selected and maintained on a standard diet until 16 weeks. The protein levels of fibronectin (FN), collagen type III (Col-III), E-cadherin, a-smooth muscle actin (a-SMA), HNF4A, Snail and MUCDHL in renal tissues were scrutinized using Western blot. Immunohistochemical staining was conducted to observe the distribution and expression of FN, HNF4A and MUCDHL. (2) Mouse renal tubular epithelial cells (mRTEC) were cultured in vitro and categorized into groups: normal glucose (NG) group, high glucose (HG) group, overexpression control groups (NG+vector and HG+vector), overexpression groups (NG+OE-MUCDHL, HG+OE-MUCDHL, NG+OE-HNF4A and HG+OE-HNF4A), knockdown control groups (NG+control and HG+control), and knockdown groups (NG+si-MUCDHL, HG+si-MUCDHL, NG+si-HNF4A and HG+si-HNF4A). The relevant protein levels were also detected by Western blot. RESULTS: (1) In db/db group, elevated body weight, blood glucose and urine albumin-to-creatinine ratio (UACR) indicated significant renal injury. Compared with db/m group, the mice in db/db group exhibited increased expression of FN, Col-III, a -SMA and Snail, and decreased expression of E-cadherin, HNF4A and MUCDHL. MUCDHL was predominantly expressed in the apical membrane of renal tubular epithelial cells, FN in the tubular mesenchyme, and HNF4A in the plasma and nucleus of renal tubular cells. (2) In HG group, there was an up-regulation in the expression of fibrosis-related proteins and a down-regulation in the expression of E-cadherin, HNF4A and MUCDHL compared with NG group. Overexpression of MUCDHL led to a decrease in the expression of FN, Col-III, a-SMA and Snail proteins, an increase in the expression of E-cadherin and MUCDHL proteins, and unaltered expression of HNF4A. Knockdown of MUCDHL resulted in a reversal of the aforementioned effects, with HNF4A expression remaining unaltered. Overexpression of HNF4A led to an increased expression of MUCDHL, and the expression changes of the remaining indicators were consistent with the overexpression of MUCDHL. Knockdown of HNF4A reversed the aforementioned effects. MUCDHL may represent a downstream target gene of HNF4A. CONCLUSION: The diminished expression of HNF4A and MUCDHL in the renal tubules of diabetic mice implies their involvement in the progression of renal fibrosis in diabetic kidney disease (DKD). HNF4A may potentially impede the progression of renal fibrosis in DKD by up-regulating the expression of MUCDHL. [ABSTRACT FROM AUTHOR]