Sodium butyrate alleviates experimental autoimmune prostatitis by inhibiting oxidative stress and NLRP3 inflammasome activation via the Nrf2/HO-1 pathway

BACKGROUND

Chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS) leads to severe discomfort in males and loss of sperm quality. Current therapeutic options have failed to achieve satisfactory results. Sodium butyrate (NaB) plays a beneficial role in reducing inflammation, increasing antioxidant capacities, and improving organ dysfunction; additionally NaB has good safety prospects and great potential for clinical application. The purpose of the current research was to study the effect of NaB on CP/CPPS and the underlying mechanisms using a mouse model of experimental autoimmune prostatitis (EAP) mice.

METHODS

The EAP mouse model was successfully established by subcutaneously injecting a mixture of prostate antigen and complete Freund's adjuvant. Then, EAP mice received daily intraperitoneal injections of NaB (100, 200, or 400 mg/kg/day) for 16 days, from Days 26 to 42. We then explored anti-inflammatory potential mechanisms of NaB by studying the effects of Nrf2 inhibitor ML385 and HO-1 inhibitor zinc protoporphyrin on prostate inflammation and pelvic pain using this model. On Day 42, hematoxylin-eosin staining and dihydroethidium staining were used to evaluate the histological changes and oxidative stress levels of prostate tissues. Chronic pelvic pain was assessed by applying Von Frey filaments to the lower abdomen. The levels of inflammation-related cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor were detected by enzyme-linked immunosorbent assay. The regulation of Nrf2/HO-1 signaling pathway and the expression of NLRP3 inflammasome-related protein in EAP mice were detected by western blot analysis assay.

RESULTS

Compared with the EAP group, chronic pain development, histological manifestations, and cytokine levels showed that NaB reduced the severity of EAP. NaB treatment could inhibit NLRP3 inflammasome activation. Mechanism studies showed that NaB intervention could alleviate oxidative stress in EAP mice through Nrf2/HO-1 signal pathway. Nrf2/HO-1 pathway inhibitors can inhibit NaB -mediated oxidative stress. The inhibitory effect of NaB on the activation of NLRP3 inflammasome and anti-inflammatory effect can also be blocked by Nrf2/HO-1 pathway.

CONCLUSIONS

NaB treatment can alleviates prostatic inflammation and pelvic pain associated with EAP by inhibiting oxidative stress and NLRP3 inflammasome activation via the Nrf2/HO-1 pathway. NaB has the potential as an effective agent in the treatment of EAP.

4-Octyl itaconate alleviates experimental autoimmune prostatitis by inhibiting the NLRP3 inflammasome-induced pyroptosis through activating Nrf2/HO-1 pathway

BACKGROUND

Chronic prostatitis demonstrates a prevalence rate of nearly 5%-10% among young and middle-aged individuals, significantly affecting their daily lives. Researchers have obtained significant outcomes investigating the anti-inflammatory properties of itaconic acid (IA) and its derivative, 4-Octyl itaconate (4-OI), against diverse chronic inflammatory disorders, such as osteoarthritis and airway inflammation. Nevertheless, whether IA can also exert anti-inflammatory effects in chronic prostatitis requires extensive research and validation.

METHODS

Human prostate tissues obtained through transurethral prostate resection (TURP) from individuals were divided into three groups based on different levels of inflammation using hematoxylin and eosin staining (H&E). Subsequently, immunohistochemistry (IHC) was employed to detect the expression of immune-responsive gene 1 (IRG-1) in these different groups. The animal experiment of this study induced experimental autoimmune prostatitis (EAP) in nonobese diabetic mice through intradermal prostate antigen injection and complete Freund's adjuvant. Then, the experimental group received intraperitoneal injections of different doses of 4-OI, while the control group received injections of saline. Western blot (WB), H&E staining, and TUNEL staining helped analyze the prostate tissues, while enzyme-linked immunosorbent assay (ELISA) helped evaluate serum inflammatory factors. Reactive oxygen species, superoxide dismutase (SOD), and malondialdehyde (MDA) were assessed for oxidative stress across experimental groups.

RESULTS

IHC analysis of human prostate tissue depicts that IRG-1 expression enhances as prostate inflammation worsens, highlighting the critical role of IA in human prostatitis. The application of 4-OI increased Nrf2/HO-1 expression while inhibited NLRP3 expression following the WB results, and its application resulted in a decrease in cell pyroptosis in prostate tissue, demonstrated by the results of TUNEL staining. Administering a Nrf2 inhibitor ML385 1 h before intraperitoneal injection of 50 mg/kg 4-OI reversed the previous conclusion, further confirming the above conclusion from another perspective. Meanwhile, the ELISA results of serum inflammatory factors (IL-1β, IL-6, and TNF-α), as well as the measurements of oxidative stress markers MDA and SOD, further confirmed the specific anti-inflammatory effects of 4-OI in EAP.

CONCLUSIONS

The present study indicates that 4-OI can alleviates EAP by inhibiting the NLRP3 inflammasome-induced pyroptosis through activating Nrf2/HO-1 pathway, which may facilitate a novel approach toward prostatitis treatment.