Xia Yu,1,* Xiurong Yu,2,* Yang Yang,3,* Wei Cheng,4 Mingxiu Shi,1 Li Chen,5 Xiongle Zhang,6 Yongjun Xu7– 10 

1Department of Blood Transfusion, Fuqing City Hospital Affiliated to Fujian Medical University, Fuqing, Fujian, 350300, People’s Republic of China; 2Department of Blood Transfusion, Clinical Oncology School of Fujian Medical University, Fujian Cancer Hospital (Fujian Branch of Fudan University Shanghai Cancer Center), Fuzhou, Fujian, 350014, People’s Republic of China; 3Fuzong Teaching Hospital of Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian, 350025, People’s Republic of China; 4Endoscopy Department, Fuqing City Hospital Affiliated to Fujian Medical University, Fuqing, Fujian, 350300, People’s Republic of China; 5Department of Neurosurgery, Fuzong Clinical Medical College of Fujian Medical University, Fuzhou, Fujian, 350025, People’s Republic of China; 6Department of Infectious Diseases, Fuqing City Hospital Affiliated to Fujian Medical University, Fuqing, Fujian, 350300, People’s Republic of China; 7Laboratory of Basic Medicine, 900th Hospital of PLA Joint Logistics Support Force, Fuzhou, Fujian, 350025, People’s Republic of China; 8Fujian Provincial Key Laboratory of Transplant Biology, Fuzong Clinical Medical College of Fujian Medical University, Fuzhou, Fujian, 350025, People’s Republic of China; 9Fuzong Teaching Hospital of Fujian University of Traditional Chinese Medicine (900th Hospital), Fuzhou, Fujian, 350025, People’s Republic of China; 10Laboratory of Basic Medicine, Dongfang Hospital of Xiamen University, School of Medicine, Xiamen University, Fuzhou, Fujian, 350025, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xiongle Zhang, Department of Infectious Diseases, Fuqing City Hospital Affiliated to Fujian Medical University, Fuqing, Fujian, 350300, People’s Republic of China, Tel +86 13799722788, Email 82895285@qq.com Yongjun Xu, Laboratory of Basic Medicine, 900th Hospital of PLA Joint Logistics Support Force, Fuzhou, Fujian, 350025, People’s Republic of China, Tel +86 591 22859628, Email xuyongjun221123@126.com

Purpose: Dysregulation of the microbiota-gut-brain (MGB) axis and activation of the NOD-like receptor protein 3 (NLRP3) inflammasome are implicated in estrogen deficiency induced depression and anxiety disorders. This study aims to investigate the effects of the probiotic Bifico on neuroinflammation and behaviors in ovariectomized (OVX) rats.
Methods: After OVX rats were treated with Bifico for 6 weeks, depression- and anxiety-like behaviors were evaluated using the sucrose preference test, forced swimming test, open field test and elevated plus maze. Furthermore, 16S rRNA sequencing was used to analyze changes in gut microbiota. Hematoxylin-eosin (HE) staining was used to observe the changes in tissue structure (intestinal tissue and hippocampus). Enzyme-linked immunosorbent assay (ELISA) was used to detect inflammatory factors. Western blot was used to detect tissue protein levels.
Results: The treatment of Bifico for 6 weeks can ameliorate depression- and anxiety-like behaviors induced by estrogen deficiency. In addition, Bifico increased the abundance of gut microbiota, especially Lactobacillus sp. and Desulfovibrio, and significantly ameliorated histological injuries in the ileum, colon and hippocampus. Bifico up-regulated the expression of tight-junction proteins zona occludens 1 (ZO-1) and Occludin in the colon and hippocampus, and down-regulated the expression of NLRP3 inflammasome signaling pathway-related proteins, including NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), Caspase-1, interleukin (IL)-1β, IL-18, toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), phosphorylated (P)-P65 and P65. Meanwhile, Bifico also reduced the levels of IL-6 and tumor necrosis factor (TNF)-α in serum and hippocampus.
Conclusion: Our findings suggest that probiotics ameliorate the depression- and anxiety-like behaviors in OVX rats by alleviating gut microbiota dysbiosis and reduce gut inflammation, thereby dampening neuroinflammation via inhibition of the NLRP3 inflammasome signaling pathway in the hippocampus. Therefore, NLRP3 inflammasome activation mediated by the MGB axis may be a potential therapeutic target for estrogen deficiency-induced affective disorders.

Keywords: microbiota-gut-brain axis, NLRP3 inflammasome, depression, estrogen, hippocampus