Rhein alleviates lethal renal ischemia-reperfusion injury via inhibition of NLRP3 inflammasomes by targeting PPARγ.

Rhein, an anthraquinone-derivative monomer isolated from the rhubarb plant, is the active ingredient of the drug Diacerein® (generic name: diacetylrhein), which possesses anti-inflammatory and antioxidant properties. It has been reported that rhein is effective in protecting against cerebral and retinal ischemia-reperfusion injury (IRI), but whether it can protect against renal IRI remains unknown. Here, a lethal renal IRI model was established with a 100 % mortality rate in untreated mice. Treatment with 100 mg/kg of rhein for 5 consecutive days before ischemia resulted in 100 % survival, maximal preservation of renal function, and a significant reduction in pathological damage, apoptosis and inflammation. In addition, rhein pretreatment significantly inhibited the upregulation of NLRP3, caspase-1, IL-1β and NGAL seen in the IRI control group. Through a series of experiments (including Co-Immunoprecipitation (Co-IP), pull-down, molecular dynamics simulation and surface plasmon resonance (SPR)), we confirmed that rhein has a strong binding affinity with PPARγ. By using the specific inhibitor T0070907 to block PPARγ, the protective effect of rhein on renal IRI in vivo and the protective effect on cell damage in the NLRP3 inflammasome activation model induced by (LPS + Nig) in vitro can be largely eliminated. We demonstrate here that rhein can potently protect against lethal renal IRI in mice. This protection is mainly achieved by targeting and enhancing the expression of PPARγ, thereby inhibiting the activation of the NLRP3 inflammasome. Thus, rhein may be therapeutically useful for the clinical prevention and treatment of renal IRI.