P-24 Racanisodamine attenuates radiation-induced lung injury by activating the NRF2 pathway: In vivo studies

Racanisodamine, also known as 654-2, is an alkaloid extracted from the Solanaceae plant Scopolia tangutica in China. It is a toxic mushroom-type M receptor antagonist. Racanisodamine is used to treat diseases such as organophosphorus poisoning, septic shock, pulmonary valve stenosis, and gastric ulcers. Additionally, Racanisodamine can alleviate oxidative stress, inflammation, and cell apoptosis induced by bleomycin-induced acute lung injury in mice. It can also inhibit inflammation and alleviate acute lung injury induced by lipopolysaccharide (LPS) in a rat model. Racanisodamine has a protective effect on acute kidney injury induced by propylene glycol LPS, and rhabdomyolysis. However, there is currently no research on the protective effect of Racanisodamine on radiation-induced lung injury (RILI) and its mechanism.This study explores whether Racanisodamine has a therapeutic effect on RILI using a mouse model, providing new theories and methods for the clinical treatment of RILI. C57BL/6 mice were randomly divided into four groups: control, control+Racanisodamine, 18 Gy irradiation (model), and Racanisodamine combined with 18 Gy irradiation. The mice in the Racanisodamine +18 Gy group were intraperitoneally injected with Racanisodamine (5mg/kg) three days before irradiation and throughout the experiment. Single chest 18 Gy irradiation was performed in the model and Racanisodamine+model groups. The control+Racanisodamine and model+Racanisodamine groups were intraperitoneally injected with Racanisodamine once a day until 6 weeks after irradiation. Lung histopathology was observed by HE staining, while lung fibrosis was assessed by Masson staining. Serum and bronchoalveolar lavage fluid inflammatory cytokines, such as TNF-α, IL-1β, and IL-6, were determined by ELISA. Cell senescence was detected by SA-β-Gal staining. The expression of γH2A.X, NRF2, p-NRF2, and p62 in lung tissue were assessed by immunofluorescence, immunohistochemistry, and western blot. Compared with the model group, the combined group exhibited significantly alleviated lung histopathology and fibrosis (t=8.660, 9.859, P < 0.01). Serum levels of TNF-α, IL-1β, and IL-6 were significantly reduced in the combined group (t=8.17、4.583、6.541, P < 0.01). The DNA damage and cell senescence were significantly alleviated (t=17.41, P < 0.01) in the combined group. Additionally, the expression of NRF2 and p-NRF2 were significantly enhanced (t=4.896, 5.623, P < 0.01) in the combined group. Racanisodamine plays a protective role in radiation-induced lung injury by alleviating inflammation, mitigating lung fibrosis, and reversing cell senescence caused by irradiation. The protective effect may be associated with the activation of the NRF2-related pathway.