Emodin Protects Against Acute Pancreatitis-Associated Lung Injury by Inhibiting NLPR3 Inflammasome Activation via Nrf2/HO-1 Signaling

Abstract

Aim

Lung injury is a common complication of acute pancreatitis (AP), which leads to the development of acute respiratory distress syndrome and causes high mortality. In the present study, we investigated the therapeutic effect of emodin on AP-induced lung injury and explored the molecular mechanisms involved.

Materials and Methods

Thirty male Sprague-Dawley rats were randomly divided into AP (n=24) and normal (n=6) groups. Rats in the AP group received a retrograde injection of 5% sodium taurocholate into the biliary-pancreatic duct and then randomly assigned to untreated, emodin, combined emodin and ML385, and dexamethasone (DEX) groups. Pancreatic and pulmonary injury was assessed using H&E staining. In in vitro study, rat alveolar epithelial cell line L2 cells were exposed to lipopolysaccharide and treated with emodin. Nrf2 siRNA pool was applied for the knockdown of Nrf2. The contents of the pro-inflammatory cytokines in the bronchoalveolar lavage fluid and lung were determined using enzyme-linked immunosorbent assay. The expressions of related mRNAs and proteins in the lung or L2 cells were detected using real-time polymerase chain reaction, Western blot, immunohistochemistry and immunofluorescence.

Key Findings

Emodin administration alleviated pancreatic and pulmonary injury of rats with AP. Emodin administration suppressed the production of proinflammatory cytokines, downregulated NLRP3, ASC and caspase-1 expressions and inhibited NF-κB nuclear accumulation in the lung. In addition, Emodin increased Nrf2 nuclear translocation and upregulated HO-1 expression. Moreover, the anti-inflammatory effect of emodin was blocked by Nrf2 inhibitor ML385.

Conclusion

Emodin effectively protects rats against AP-associated lung injury by inhibiting NLRP3 inflammasome activation via Nrf2/HO-1 signaling.

Keywords:

• emodin
• acute pancreatitis
• lung injury
• Nrf2
• NLRP3 inflammasome

Acknowledgments

This project was supported by grants from the National Natural Science Foundation of China (No. 81773966) and the Traditional Chinese Medicine Related Foundation of Dalian (No. 17Z2014). ZG and RF conceived and designed the experiments. WQ, XD and DS performed the experiments. JS performed the statistical analysis and wrote the manuscript. All authors discussed the results and approved the final manuscript.

Disclosure

The authors report no conflicts of interest in this work.