Reduction of SIRT1 Mediates Monosodium Iodoacetate-Induced Osteoarthritic Pain by Upregulating p53 Expression in Rats.

BACKGROUND: Clinically, chronic pain is the most common and disabling symptom of osteoarthritis (OA). OA pain is associated with OA lesion of the knee and the plastic changes in the peripheral and central nervous systems. However, the central mechanisms involved at the spinal cord level are not fully understood. OBJECTIVES: The aim of this study was to identify the mechanism underlying the role of spinal cord Sirtuin 1 (SIRT1) in OA pain induced by intraarticular injection of monosodium iodoacetate (MIA) in rats. STUDY DESIGN: Controlled animal study. METHODS: MIA was injected intraarticularly into the rat knee joint for the induction of OA. The OA lesion of the knee was assessed by histopathological examination. The mechanical allodynia were measured over 21 days post-injection by von Frey filaments. The messenger RNA and protein levels of SIRT1 and p53 were determined by real-time quantitative polymerase chain reaction and western blotting, respectively. Involvement of SIRT1-mediated p53 expression in the development of MIA-persistent pain was studied using intrathecal (i.t.) injection of the SIRT1-activating molecule resveratrol and intraperitoneal (i.p.) injection of the p53 inhibitor pifithrin-mu (PTF-µ). RESULTS: MIA induced mechanical allodynia, decreased the expression of SIRT1, and upregulated the expression of p53 in the spinal dorsal horn. Consecutive i.t. injection of resveratrol or i.p. injection of PTF-µ alleviated the MIA-induced mechanical allodynia. Upregulation of dorsal horn SIRT1 expression by i.t. injection of resveratrol also inhibited the increase of dorsal horn p53 induced by MIA. Moreover, silencing of dorsal horn SIRT1 expression by i.t. administration of small interfering RNA SIRT1 into normal rats induced the mechanical allodynia and upregulation of p53 expression in the dorsal horn. LIMITATIONS: More underlying mechanism(s) of the role of p53 signaling pathway in OA pain need to be explored in future research. CONCLUSIONS: These findings suggest that the reduction of dorsal horn SIRT1 mediated upregulation of p53 expression, which plays a critical role in persistent pain induced by OA. The i.t. drug delivery treatments targeting the spinal cord SIRT1/p53 pathway might be novel therapeutic options for OA-induced persistent pain.