Paeoniflorin enhances tubular repair by promoting dihydroorotate dehydrogenase-dependent epithelial cell proliferation in cisplatin-induced chronic kidney disease.

Abstract

<p>ETHNOPHARMACOLOGICAL RELEVANCE: Repeated low-dose cisplatin (RLDC) impairs tubule repair and promotes chronic kidney disease (CKD). Paeoniae Radix Rubra (Chishao in Chinese) is the dried root of Paeonia lactiflora Pall. or Paeonia veitchii Lynch, which is used as an adjuvant herb in the treatment of CKD. Paeoniflorin (PF) is an active ingredient of Paeoniae Radix Rubra. However, whether PF can alleviate RLDC-induced CKD remains unclear. AIM OF THE STUDY: To investigate whether PF can alleviate RLDC-induced CKD and its underlying mechanisms. MATERIALS AND METHODS: RLDC-induced CKD models were established in mice and an immortalized human renal tubular epithelial cell line (HK-2). PF was used to study the proliferation-promoting role of tubules in these models. Changes in the expression of dihydroorotate dehydrogenase (DHODH) were observed in the tubules of the mouse model. Surface Plasmon Resonance and enzymatic activity assays were performed to investigate the interactions between PF and DHODH. The DHODH inhibitor brequinar was added to the cell model to determine whether it altered the drug's ability to proliferate cells. RESULTS: Compared with vehicle-treated CKD mice, PF improved renal function, increased Ki67-positive tubular cells by 2.2 times, reduced unrepaired tubules by 76.72&nbsp;% (from 14.54&nbsp;% to 3.45&nbsp;%), and reduced fibrosis. RLDC down-regulated DHODH expression in the renal tubules of CKD mice. Long-term PF treatment restored DHODH expression and maintained a steady state of the pyrimidine nucleotide pool in RLDC-induced CKD mice. Surface Plasmon Resonance analysis showed that PF had a moderate binding affinity for DHODH (KD&nbsp;=&nbsp;6.73&nbsp;μmol/L), and enzyme analysis showed that PF activated DHODH by approximately 11&nbsp;% (P&nbsp;&lt;&nbsp;0.01). In HK-2&nbsp;cells subjected to RLDC injury, survivor cells exhibited reduced proliferation when treated with up-stream L-hydroorotic acid compared with down-stream orotic acid, indicating that DHODH dysfunction hinders cell proliferation. Inhibition of DHODH impaired the regenerative effects of PF in both normal and survivor cells after RLDC injury. CONCLUSION: These results suggest that targeting tubular cell proliferation using PF may effectively enhance tubular repair and improve cisplatin-induced CKD by activating DHODH.</p>