Honokiol Exhibits Anti-NLRP3 Inflammasome and Antimicrobial Properties in Neisseria gonorrhoeae-Infected Macrophages

Kuo-Feng Hua,1,2,* Hsien-Ta Hsu,3,4,* May-Shu Huang,5,6 Hsiao-Wen Chiu,1 Wei-Ting Wong,1 Chien-Hsiu Peng,1 Yu-Bei Lin,1 Ann Chen,7 Chien-Chun Wang,8,9 Chung-Hua Hsu,10,11 Chun-Hsien Wu,12 Wen-Yu Lin,1,12 Chen-Lung Ho,13 Lan-Hui Li14 1Department of Biotechnology and Animal Science, National Ilan University, Ilan, Taiwan; 2Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan; 3Division of Neurosurgery, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei City, Taiwan; 4School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan; 5Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan; 6Department of Laboratory Medicine, Mackay Memorial Hospital, Taipei, Taiwan; 7Department of Pathology, Hualien Tzu Chi Hospital, Hualien, Taiwan; 8Infectious Disease Division, Linsen, Chinese Medicine and Kunming Branch, Taipei City Hospital, Taipei, Taiwan; 9Kunming Prevention and Control Center, Taipei City Hospital, Taipei, Taiwan; 10Linsen, Chinese Medicine and Kunming Branch, Taipei City Hospital, Taipei, Taiwan; 11Institute of Traditional Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan; 12Division of Cardiology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan; 13Division of Wood Cellulose, Taiwan Forestry Research Institute, Taipei, Taiwan; 14Department of Laboratory Medicine, Linsen, Chinese Medicine and Kunming Branch, Taipei City Hospital, Taipei, Taiwan*These authors contributed equally to this workCorrespondence: Lan-Hui Li, Department of Laboratory Medicine, Linsen, Chinese Medicine and Kunming Branch, Taipei City Hospital, 100, Kunming Street, Wanhua District, Taipei City, 108203, Taiwan, Tel +886-2-23703739 # 1438, Fax +886-2-23885259, Email A1525@tpech.gov.twPurpose: The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, crucial in infectious and inflammatory diseases by regulating IL-1β, presents a target for disease management. Neisseria gonorrhoeae causes gonorrhea in over 87 million people annually, with previous research revealing NLRP3 inflammasome activation in infected macrophages. No natural products have been reported to counteract this activation. Exploring honokiol, a phenolic compound from Chinese herbal medicine, we investigated its impact on NLRP3 inflammasome activation in N. gonorrhoeae-infected macrophages.Methods: Honokiol’s impact on the protein expression of pro-inflammatory mediators was analyzed using ELISA and Western blotting. The generation of intracellular H2O2 and mitochondrial reactive oxygen species (ROS) was detected through specific fluorescent probes (CM-H2DCFDA and MitoSOX, respectively) and analyzed by flow cytometry. Mitochondrial membrane integrity was assessed using specific fluorescent probes (MitoTracker and DiOC2(3)) and analyzed by flow cytometry. Additionally, the effect of honokiol on the viability of N. gonorrhoeae was examined through an in vitro colony-forming units assay.Results: Honokiol effectively inhibits caspase-1, caspase-11 and GSDMD activation and reduces the extracellular release of IL-1β, NLRP3, and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) in N. gonorrhoeae-infected macrophages. Detailed investigations have demonstrated that honokiol lowers the production of H2O2 and the phosphorylation of ERK1/2 in N. gonorrhoeae-infected macrophages. Importantly, the phosphorylation of JNK1/2 and p38 and the activation of NF-κB remain unaffected. Moreover, honokiol reduces the N. gonorrhoeae-mediated generation of reactive oxygen species within the mitochondria, preserving their integrity. Additionally, honokiol suppresses the expression of the pro-inflammatory mediator IL-6 and inducible nitric oxide synthase induced by N. gonorrhoeae independently of NLRP3. Impressively, honokiol exhibits in vitro anti-gonococcal activity against N. gonorrhoeae.Conclusion: Honokiol inhibits the NLRP3 inflammasome in N. gonorrhoeae-infected macrophages and holds great promise for further development as an active ingredient in the prevention and treatment of symptoms associated with gonorrhea.Keywords: Neisseria gonorrhoeae, honokiol, NLRP3 inflammasome, mitochondria, bactericiide