Abstract: Objective To investigate the protective effect of Platycodin D (PD) on renal ischemia-reperfusion injury in rats. Methods The rats were divided into sham group, model group, low, middle and high-dose groups with 10 animals in each. The rat model of ischemia reperfusion injury was established by clamping the bilateral renal pedicles in model group, low, middle and high-dose group. The rats in sham group underwent the same modeling operation but did not clamp the renal pedicles. Before 5 minutes of modeling, the rats of low, middle and high-dose group were intra-peritoneally injected with 12.5, 25 and 50 mg/kg PD, respectively. After 24 h of modeling, the serum creatinine (Cr) and blood urea nitrogen (BUN) levels, as well as antioxidant markers[superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA)] levels in kidney tissues were measured. HE staining was used to evaluate renal tissue lesions. Immuno-histochemical staining was used to detect the expression of caspase-3 in renal tissue, the apoptosis index of renal tubular epithelial cells was evaluated by the counting of caspase-3 positive cells. RT-qPCR was used to detect the expression of interleukin-1β (IL-1β), IL-6 and IL-10 mRNA in renal tissues. Western blot was used to detect the expression of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), p65, p-p65, inhibitor of nuclear factor kappa B (NF-κB) (IκB) and p-IκB. Results Compared with sham group, the kidney lesions, serum Cr and BUN levels, apoptosis index of renal tubular epithelial cells in model group were all increased (P＜0.05). Compared with model group, the kidney lesions, serum Cr and BUN levels, apoptosis index of renal tubular epithelial cells in low, middle and high-dose group were decreased (P＜0.05). Compared with sham group, the level of MDA and mRNA of IL-1β and IL-6, the protein expression of TLR4/MyD88/NF-κB signaling pathway in kidney tissue in model group were all significantly increased while the level of SOD and GSH-Px and mRNA of IL-10 in rat kidney tissue were decreased(P＜0.05). Compared with model group, the level of MDA, mRNA of IL-1β and IL-6, the protein expression of TLR4/MyD88/NF-κB signaling pathway in kidney tissue in low, middle and high-dose group were all decreased, SOD and GSH-Px and IL-10 mRNA in rat kidney tissue were increased (P＜0.05). Conclusions Platycodin D has a protective effect on renal ischemia-reperfusion injury in rats, and the underlying mechanism may be related to the improvement of antioxidant capacity and inhibition of TLR4/MyD88/NF-κB signaling pathway.

Key words: kidney, ischemia-reperfusion injury, platycodin D, oxidative stress, TLR4/MyD88/NF-κB signaling pathway