Study On The Mechanism Of Resveratrol Inhibiting The NLRP3Inflammasome Activation Induced By Radiation

With the development of science and technology, nuclear technology has been applied more and more widely. But at the same time, nuclear energy also brings serious challenges to our health and safety. In addition, about70%of cancer patients need to receive radiotherapy in the process of the treatment. Radiation can kill tumor cells, but also cause damage to normal cells. Complications from radiotherapy not only severely impact on the life quality of patients, but also limit the application and development of radiation therapy. Therefore, it is important to explore the mechanism of radiation injury and develop radiation protection drugs for national defense and civil use.Recently, it was found that ionizing radiation can increase the inflammatory cytokine IL-1β level in the body, generating oxidative stress response, which directly affects people’s health. IL-1β plays a central role in inflammatory response. Studies show that the secretion of IL-1β is relevant to the NLRP3inflammation complex in inflammatory cells. Once the NLRP3inflammation complex is activated, the complex will cut proIL-1β into mature IL-1β cytokine. However, the mechanism of regulating the NLRP3complex remains unclear, and we only knew that the transcription of NLRP3relys on NF-κB. Sirtl is a type III histone deacetylase. It regulates transcriptional silencing, DNA damage response and other important cellular activities via deacetylation. NF-κB is the target of Sirtl. Sirtl suppresses the expression of NLRP3by deacetylating NF-κB and then exerts anti-inflammatory effect. Studies have demonstrated that a natural active ingredient polyphenol extracted from grapes, resveratrol, is the activator of Sirtl. Resveratrol has showed good prospects on inflammatory disease treated by the way of Sirtl.This study was first to explore the potential effect of Sirtl on IL-1β expression induced by radiation in vitro. Our results showed that radiation significantly increased IL-1β mRNA and protein expression levels in mesenchymal stem cells. Pretreatment with resveratrol, a Sirtl activator, suppressed the radiation-induced IL-1β expression in a concentration-dependent manner. Furthermore, the knockdown or inhibition of Sirtl by siRNA or nicotinamide significantly enhanced the radiation-induced IL-1β expression level. These phenomena could likely be attributed to Sirtl-mediated inhibition of NLRP-3inflammasome activation because Sirtl inhibits the activity of NF-κB, leading to NLRP3transcription suppression. Taken together, these results demonstrated that resveratrol upregulated Sirtl and exerted anti-inflammatory effects by regulating NLRP3expression partially through the NF-κB pathway in mesenchymal stem cells.Next, we investigated the radioprotective effect of resveratrol in a murine model of radiation-induced inflammatory bowel disease.30male C57BL/6J mice were randomized into five groups:(1) control:vehicle;(2) radiation:vehicle+7.2Gy total body irradiation (TBI);(3) low dose resveratrol:50mg/kg resveratrol+7.2Gy TBI;(4) medium dose resveratrol:1OOmg/kg resveratrol+7.2Gy TBI;(5) high dose resveratrol:200mg/kg resveratrol+7.2Gy TBI. Mice were given vehicle or resveratrol by gavage every day for7days before irradiation and then14days after irradiation. The blood samples were collected to determine the levels of IL-1β; the intestinal tissues were fixed in10%neutral buffered formalin immediately for histologic and immunohistochemical analyses; and spleen and thymus were obtained for RT-PCR and Western blot analyses. Our results showed that resveratrol decreased the IL-1β level in serum samples; and histologic and immunohistochemical analyses showed radiation caused intestinal mucosal edema, immune cellular infiltration and the enhanced expression of IL-1β. Administration of resveratrol ameliorated radiation-induced intestinal injury and inhibited the IL-1β expression; resveratrol inhibited the IL-1β expression via activating Sirtl and suppressing NLRP3inflammasome activation in spleen and thymus.In conclusion, resveratrol decreased the IL-1β expression via upregulating Sirtl and suppressing NLRP3transcription in vitro. Also resveratrol activated Sirtl and exerted anti-inflammatory effects by regulating NLRP3expression in vivo. Our finding suggests that resveratrol is an effective agent in protecting against radiation injury. We have provided a theoretical basis for developing resveratrol as a drug to protect against radiation injury.