Early and late suppression of Toll-like receptor 4 signaling induces distinct changes in a nephrotoxicant-induced mouse model of acute kidney injury

Abstract: Background: Many essential genes in different signaling pathways are significantly expressed in a stress- and time-dependent manner after acute kidney injury (AKI). Despite their traditional role in driving inflammation, TLR activation is increasingly recognized to promote renal epithelial repair by inducing the secretion of specific interleukins and growth factors. Objectives: This study explored the effects of TLR4 inhibition at early and late time points of cisplatin-mediated AKI. Methods: A mouse kidney injury model was developed using a single dose of cisplatin (10 mg/kg) and treated with the TLR4 inhibitor TAK-242 at either the initial or a later time point after cisplatin induction. Kidney tissues were analyzed for histopathological and gene expression changes by HE staining and qRT-PCR, respectively. Renal functional analysis was performed by estimating serum creatinine levels in the control and all treated groups. Results: Elevated biochemical markers and serum creatinine levels correlated with histological findings of tubular damage in all groups. Compared with the late intervention group, we observed prominent tubular cell injury in the cisplatin AKI model and the TAK242-early groups. Cisplatin significantly increased TLR4 expression in the AKI model, which was abrogated in both TAK242-treated AKI groups. Compared to the TAK242-early group, the late intervention group showed upregulation of Sod1 (p≤0.05), Hsp25 (p≤0.05), Nf-ĸb, Fzd8 and c-Met genes and downregulation of Il22 (p ≤0.001), Lcn2, and hsp70 gene expression. Other genes, such as Hgf1, Wnt4 and Lc3 II, showed no notable difference between the two intervention groups. Conclusion: The TLR4 pathway may be involved in immediate cell survival mechanisms after injury, as massive necrosis and elevated serum creatinine were observed following early inhibition of the TLR4 pathway, whereas late inhibition preserved tissue architecture and function. Understanding the optimal timing of TLR inhibition to achieve significant tissue protection can help underscore the role of this pathway in AKI repair and its associated pathological processes.