#2685 SLC34A2 EXACERBATES TUBULAR INTERSTITIAL FIBROSIS VIA INDUCTION OF APOPTOSIS AND CELL CYCLE ARREST IN S PHASE

Abstract

Abstract Background and Aims Chronic kidney disease (CKD) is an urgent public health issue in the world. However, effective treatments for intervention of CKD remain undefined. Phosphate (Pi) is an essential element for synthesis of DNA, RNA, ATP, phospholipid membranes, and for regulation of phosphorylation/dephosphorylation, cellular signaling and metabolic pathways. Solute carrier family 34 (SLC34) is responsible for Pi absorption in the small intestine. However, the role of SLC34 in progression of CKD is still unknown. Method A membrane protein, solute carrier family 34 member 2 (SLC34A2), was discovered by using big data mining from the National Center for Biotechnology Information (NCBI). SLC34A2 was overexpressed in human proximal tubular cells, HK-2, by Lipofectamine 3000. RNA sequencing was carried out to uncover SLC34A2-mediated signaling pathways by using Illumina platform. Apoptosis was evaluated by Annexin V-PI staining and TEUNEL assay in cells and mouse kidneys, respectively. Cell cycle was measured by flow cytometry. Unilateral ureteral obstruction (UUO) and bilateral renal ischemia-reperfusion injury (bIRI) were employed to generate CKD mouse models. Results By using big data mining from the NCBI, we identified a membrane protein, SLC34A2, was upregulated in various types of nephropathies including diabetic nephropathy, focal segmental glomerulosclerosis, minimal change disease, ANCA-associated vasculitis. Overexpression of SLC34A2 suppressed viability of HK-2 cells. RNA sequencing revealed that apoptosis and cell cycle are high scored pathways modulated by SLC34A2. The results were further verified in HK-2 cells. Ectopic SLC34A2 promoted apoptosis via downregulation of BCL-2. Moreover, SLC34A2 induced cell cycle arrest in S phase via downregulation of CDK2. CKD mouse models of UUO and bIRI were carried out to confirm in vitro findings. In mice kidneys, the expression of Slc34a2 in UUO and bIRI groups was superior to that in sham groups. Enriched Bax and TUNEL-positive cells were observed in the fibrotic kidneys of mice. Moreover, increased expression of p21 and downregulated Cyclin A2 in the fibrotic kidneys further confirmed that Slc34a2 induced cell cycle arrest in S phase. Conclusion Slc34a2 induced apoptosis and halted cell cycle in S phase, resulting in subsequent tubulointerstitial fibrosis in mice. Our results suggest that targeting SLC34A2 might be a promising strategy for intervention of CKD.