Uremic toxin p‑cresyl sulfate enhances the calcification of aortic valvular interstitial cells via klotho/sirtuin‑1 signaling.

Calcific aortic valve disease (CAVD), a valvular heart disease with severe complications, is common in patients with chronic kidney disease (CKD). P‑cresyl sulfate (PCS) is a protein‑binding uremic toxin that induces chronic inflammation. Klotho and sirtuin‑1 (SIRT1) represent potential therapeutic agents for mitigating CKD‑induced vascular calcifications. We hypothesized that PCS could enhance valvular interstitial cell (VIC) calcification, which could be modulated by klotho/SIRT1 signaling. Alizarin Red S staining, western blotting and immunohistochemical analysis were performed in order to examine calcification and klotho/SIRT1 signaling in isolated porcine VICs following various 7‑day treatments. VIC treatments included incubation with PCS (10 and 100 µM), klotho (100 pM), the hypoxia‑inducible factor‑1α (HIF‑1α) inhibitor PX‑478 (0.5 µM) and the SIRT1 activator SRT1720 (1 mM). Furthermore, the present study established a PCS‑induced rat model of CKD and analyzed the effects of klotho on runt‑related transcription factor 2 (RUNX2) expression in rat aortic valves in vivo. Treatment with PCS increased VIC calcification, NF‑κB acetylation and the expression of RUNX2 and HIF‑1α expression but was shown to reduce klotho expression. Klotho supplementation attenuated the PCS‑induced enhancement of VIC calcification and mitigated PCS‑mediated increases in NF‑κB acetylation and RUNX2 expression. Additionally, the SIRT1 activator SRT1720 attenuated the PCS‑mediated enhancement of VIC calcification and was shown to upregulate klotho and downregulate RUNX2 in PCS‑treated VICs. Furthermore, the present study demonstrated that klotho supplementation mitigated CKD‑mediated RUNX2 upregulation in the aortic valves of PCS‑treated CKD model rats. The present study demonstrated that PCS induced VIC calcification by activating HIF‑1α signaling and downregulating klotho. Treatment with klotho or SRT1720 was shown to attenuate PCS‑mediated activation of the NF‑κB/RUNX2 signaling pathway, suggesting that these agents demonstrate notable therapeutic potential for targeting PCS‑induced CAVD.