title: Ligustrazine disrupts lipopolysaccharide-activated NLRP3 inflammasome pathway associated with inhibition of Toll-like receptor 4 in hepatocytes.
abstract: Intestine microbial products may translocate into the liver via portal vein and trigger or exacerbate hepatocyte inflammatory responses during liver injury. The NLRP3 inflammasome pathway plays a key role in regulation of inflammatory cytokines in response to bacterial products. The present study was aimed to investigate the effects of ligustrazine, a natural alkaloid compound, on the NLRP3 inflammasome pathway activation and interleukin-1β (IL-1β) generation in hepatocytes. We cultured human LO2 hepatocytes and treated them with lipopolysaccharide (LPS), a membrane component of Gram-negative bacteria, for mimicking hepatic exposure to microbial products in vitro. The results demonstrated that LPS upregulated NLRP3 and cleaved-caspase-1, and promoted the expression and secretion of IL-1β in LO2 cells. Ligustrazine was found to reduce NLRP3 and cleaved-caspase-1, prevented IL-1β cleavage, and decreased IL-1β secretion into extracellular environment. Further examinations showed that LPS upregulated the expression of Toll-like receptor 4 (TLR4), but ligustrazine repressed TLR4 expression in LPS-treated hepatocytes. Moreover, pharmacological inhibition of TLR4 by its specific inhibitor TAK-242 downregulated NLRP3 and cleaved-caspase-1, and combination treatment with TAK-242 and ligustrazine led to more significant inhibitory effects on the NLRP3 pathway. TAK-242 also reduced cleaved-IL-1β, and this reducing effect was enhanced by ligustrazine. Collectively, the current results revealed that ligustrazine interrupted LPS-activated NLRP3 inflammasome signaling and reduced generation of IL-1β in hepatocytes, which was associated with inhibition of TLR4. This study uncovered a novel mechanism for ligustrazine as a potential hepatoprotective agent.
authors.affiliation: Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, China; Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing 210023, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, China.
authors.forename: Huanhuan
authors.initials: H
authors.lastname: Jin
authors.affiliation: Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wu
authors.affiliation: Departemt of Pharmacy, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, China.
authors.forename: Jiangjuan
authors.initials: J
authors.lastname: Shao
authors.affiliation: Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, China.
authors.forename: Xiafei
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, China; Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing 210023, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210023, China; Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing 210023, China. Electronic address: nytws@163.com.
authors.forename: Shizhong
authors.initials: S
authors.lastname: Zheng
mesh_terms: D002460:Cell Line; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D058847:Inflammasomes / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D058847:Inflammasomes; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D011719:Pyrazines; D051197:Toll-Like Receptor 4; C017953:tetramethylpyrazine
keywords: Hepatocyte; Ligustrazine; Lipopolysaccharide; Liver injury; NLRP3 inflammasome; Toll-like receptor 4