Fig. 1.

Ribociclib inhibits CDK4/6 activity and mitigates cisplatin-associated kidney injury. (a) Schematic representation of experimental treatment strategy. Age-matched male (8–12 weeks) C57BL/6 mice were administered a single oral dose of vehicle (citrate buffer) or ribociclib (150 mg/kg) followed by a single intraperitoneal injection of cisplatin (30 mg/kg) four hours later. (b) Blood urea nitrogen (c) Serum creatinine (d) Renal histological analysis (H&E) showed that ribociclib administration confers protection from cisplatin-associated AKI. Data (b-d) are presented as individual data points (n = 5 biologically independent samples), from one out of three independent experiments, all producing similar results. (e) Representative western blots showing ribociclib mediated suppression of cisplatin-associated Rb1 phosphorylation. Renal tissues were prepared 24 h post-cisplatin injection. (f) CDK4 and CDK6 proteins were immuno-precipitated from the kidneys of control and cisplatin treated mice, followed by in vitro kinase assays. The graphs represent data from a single experiment (n = 4 biologically independent samples), from one out of three independent experiments, all producing similar results. (g-h) Cellular thermal shift assay (CETSA) were carried out to identify drug engagement with target proteins in renal tissues 24 h post-cisplatin treatment. Thermal denaturation curves for CDK4 (g) and CDK6 (h) showed thermal stabilization upon ribociclib treatment in vivo. Data (g-h) are presented as mean (n = 3 biologically independent samples), from one out of three independent experiments, all producing similar results. In all the bar graphs, experimental values are presented as mean ± s.e.m. The height of error bar = 1 s.e. and p < 0.05 was indicated as statistically significant. One-way ANOVA followed by Tukey’s multiple-comparisons test was carried out and statistical significance is indicated by *p < 0.05, **p < 0.01, ***p < 0.001.