SO082LATENT TRANSFORMING GROWTH FACTOR BETA BINDING PROTEIN (LTBP4) CAN REGULATE RENAL FIBROSIS AND ALTER INFLAMMATION AND MITOCHONDRIAL DYSFUNCTION IN CHRONIC KIDNEY DISEASE (CKD)

Abstract

Abstract Background and Aims: Transforming growth factor beta (TGF-beta) has been well known as a key factor for fibrosis and inflammation. LTBPs regulate TGF-beta signalling in complicated ways. Disruption and loss of LTBP4 expression is associated with abnormal accumulation of extracellular matrix (ECM) and altered TGF-beta activation. However, the role of LTBP4 in chronic kidney disease remains largely unknown. We aim to explore the mechanisms of LTBP4-related regulation in kidney disease. Method: To investigate the impact of LTBP4 on tubulointeresitial fibrosis (TIF), we generated LTBP4-overexpression human renal proximal tubule cells (HK-2), treated with exogenous TGF-beta and established a fibroblasts-HK-2 co-culture system using rat fibroblasts (NRK-49F) and HK-2 cells. Moreover, to create TIF model, we performed unilateral ureteral ligation (UUO) in Ltbp4S-/- mice and wild-type (WT) mice to check ECM deposition and phenotypic alterations. In addition, we performed RNA-Sequencing analysis to understand transcriptomic changes associate with LTBP4 overexpression. Results: Up-regulation of Ltbp4 in fibrotic kidney was noted in TIF model with UUO and in renal tissue with diabetic nephropathy. LTBP4-overexpression reduced epithelial-mesenchymal transition (EMT) with showing increased epithelial-cadherin, reduced vimentin and collagen I in the co-culture system. Moreover, higher expression of fibronectin, collagen I and alpha-smooth muscle actin (alpha-SMA) were noted in fibrotic kidneys in Ltbp4S-/- mice compared with changes in WT mice, suggesting inflammation condition could be altered by the absence of Ltbp4S. The inflammatory change in renal tissue in UUO model was studied with F4/80 stain. Increased macrophage infiltration and increased monocyte chemoattractant protein-1 (MCP-1) expression were detected in Ltbp4S-/- mice compared with that in WT mice. In addition, LTBP4-overexpression reduced mitochondrial biogenesis. Conclusion: Ltbp4 acted as a regulator of fibrosis and inflammation in fibrotic kidneys. TGF-beta- induced EMT were clearly enhanced in ltbp4 deficient environments, accompanied with reduced macrophage infiltration, which could be the major mechanism related to LTBP4/TGF-beta pathways. Furthermore, altered ATP production and usage as well as mitochondria respiration could be regulated by LTBP4 in renal failure.