title: Involvement of NF-κB in regulation of Actinobacillus pleuropneumoniae exotoxin ApxI-induced proinflammatory cytokine production in porcine alveolar macrophages.
abstract: Actinobacillus pleuropneumoniae is a crucial respiratory pathogen that causes fibrinous, hemorrhagic, necrotizing pleuropneumonia in pigs. A. pleuropneumoniae exotoxins (ApxI to IV) are the major virulence factors contributing to A. pleuropneumoniae pathogenesis. Previously, we demonstrated that ApxI induces the expression of proinflammatory cytokines in porcine alveolar macrophages (PAMs) via the mitogen-activated protein kinases (MAPKs) p38 and cJun NH2-terminal kinase (JNK). Nonetheless, the role of nuclear factor (NF)-κB-a transcription factor widely implicated in immune and inflammatory responses-in ApxI-elicited cytokine production has yet to be defined. In the present study, we examined the involvement of NF-κB in ApxI-elicited production of interleukin (IL)-1β, IL-8, and tumor necrosis factor (TNF)-α in PAMs and investigated the correlation between NF-κB and MAPK (p38 and JNK) pathways in this event. The results of Western blot analysis, confocal microscopy, and a DNA binding activity assay revealed that the classical NF-κB pathway was activated by ApxI, as evidenced by the decreased levels of IκB and subsequent NF-κB translocation and activation in ApxI-stimulated PAMs. Moreover, the blocking of ApxI-induced NF-κB activation significantly attenuated the levels of mRNA and protein secretion of IL-1β, IL-8, and TNF-α in PAMs. Notably, the attenuation of JNK activation by a specific inhibitor (SP600125) reduced ApxI-induced NF-κB activation, whereas a p38 blocker (SB203580) had no effect on the NF-κB pathway. Further examination revealed that the level of phosphorylation at serine 536 on the NF-κB p65 subunit was dependent on JNK activity. Collectively, this study, for the first time, demonstrates a pivotal role of NF-κB in ApxI-induced IL-1β, IL-8, and TNF-α production; JNK, but not p38, may positively affect the activation of the classical NF-κB pathway.
authors: Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC; Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC.
authors: Chiung-Wen
authors: CW
authors: Hsu
authors: Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC; Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC.
authors: Siou-Cen
authors: SC
authors: Li
authors: Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC.
authors: Nai-Yun
authors: NY
authors: Chang
authors: Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC.
authors: Zeng-Weng
authors: ZW
authors: Chen
authors: Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC.
authors: Jiunn-Wang
authors: JW
authors: Liao
authors: Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC.
authors: Ter-Hsin
authors: TH
authors: Chen
authors: Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC.
authors: Jyh-Perng
authors: JP
authors: Wang
authors: Animal Technology Laboratories, Agricultural Technology Research Institute, No. 1, Ln. 51, Dahu Rd., Hsinchu City, 30093, Taiwan, ROC.
authors: Jiunn-Horng
authors: JH
authors: Lin
authors: Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC. Electronic address: hsuan@nchu.edu.tw.
authors: Shih-Ling
authors: SL
authors: Hsuan
mesh_terms: D016977:Actinobacillus pleuropneumoniae / Q000378:metabolism*; D000818:Animals; D018821:CD18 Antigens; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D005098:Exotoxins / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D007249:Inflammation / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000378:metabolism* / Q000382:microbiology; D016328:NF-kappa B / Q000378:metabolism*; D013552:Swine; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D018821:CD18 Antigens; D016207:Cytokines; D005098:Exotoxins; D016328:NF-kappa B; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4
keywords: Actinobacillus pleuropneumoniae; ApxI; Mitogen-activated protein kinases; NF-κB; Proinflammatory cytokines