title: A novel immunomodulatory effect of ugonin U in human neutrophils via stimulation of phospholipase C.
abstract: Neutrophils have a crucial role in the immune system and are the first line of defense against pathogenic invaders. Neutrophil activation is required for their defensive function and can be induced by diverse stimuli, through either binding to cell surface receptors or direct intracellular target molecule stimulation. In this study, we found that 4″a,5″,6″,7″,8″,8″a-hexahydro-5,3',4'-trihydroxy-5″,5″,8″a-trimethyl-4H-chromeno [2″,3″:7,6]flavone (ugonin U), a flavonoid isolated from Helminthostachys zeylanica (L) Hook, significantly induced superoxide production and release in a time- and concentration-dependent manner. A series of experiments was performed to dissect the mechanism of ugonin U-induced respiratory burst in human neutrophils. Our results demonstrated that ugonin U induced a slow increase in intracellular Ca(2+), which was necessary for ugonin U-stimulated superoxide release. Use of a formyl peptide receptor (FPR) blocker, G protein inhibitor, and protein tyrosine kinase (PTK) inhibitor proved that FPR, G proteins, and PTKs were not associated with ugonin U-induced respiratory burst. Additionally, immunoblotting results revealed that ugonin U did not affect the phosphorylation of mitogen-activated protein kinases and protein tyrosine. Nevertheless, a phospholipase C (PLC) inhibitor and an inositol triphosphate (IP3) receptor antagonist considerably suppressed ugonin U-stimulated Ca(2+) mobilization and subsequent superoxide release. Ugonin U also induced an increase in intracellular IP3 formation, which could be blocked using a PLC inhibitor. In conclusion, our study reveals that ugonin U represents the first identified natural flavonoid compound to directly stimulate PLC. Moreover, ugonin U induces respiratory burst via the PLC/IP3/Ca(2+) pathway in human neutrophils.
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Medicine, College of Medicine, Chang Gung University, Kweishan 333, Taoyuan, Taiwan; Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Kweishan 333, Taoyuan, Taiwan; Department of Anesthesiology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
authors.forename: Chun-Yu
authors.initials: CY
authors.lastname: Chen
authors.affiliation: Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung 80424, Taiwan.
authors.forename: Chih-Chuang
authors.initials: CC
authors.lastname: Liaw
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Medicine, College of Medicine, Chang Gung University, Kweishan 333, Taoyuan, Taiwan.
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Chen
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Medicine, College of Medicine, Chang Gung University, Kweishan 333, Taoyuan, Taiwan; Chinese Herbal Medicine Research Team, Healthy Aging Research Center, Chang Gung University, Kweishan 333, Taoyuan, Taiwan.
authors.forename: Wen-Yi
authors.initials: WY
authors.lastname: Chang
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Medicine, College of Medicine, Chang Gung University, Kweishan 333, Taoyuan, Taiwan.
authors.forename: Pei-Jen
authors.initials: PJ
authors.lastname: Chung
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Medicine, College of Medicine, Chang Gung University, Kweishan 333, Taoyuan, Taiwan; Chinese Herbal Medicine Research Team, Healthy Aging Research Center, Chang Gung University, Kweishan 333, Taoyuan, Taiwan. Electronic address: htl@mail.cgu.edu.tw.
authors.forename: Tsong-Long
authors.initials: TL
authors.lastname: Hwang
mesh_terms: D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D015153:Blotting, Western; D004789:Enzyme Activation / Q000187:drug effects*; D004797:Enzyme-Linked Immunosorbent Assay; D005419:Flavonoids / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D018375:Neutrophil Activation / Q000187:drug effects*; D009504:Neutrophils / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology; D010946:Plants, Medicinal; D016897:Respiratory Burst / Q000187:drug effects; D027343:Rhizome; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D000893:Anti-Inflammatory Agents; D005419:Flavonoids; D010936:Plant Extracts; D010738:Type C Phospholipases
keywords: Flavonoid; Free radicals; Helminthostachys zeylanica; Neutrophils; Phospholipase C; Superoxide; Ugonin U