Aeromonas hydrophila inhibits autophagy triggering cytosolic translocation of mtDNA which activates the pro-apoptotic caspase-1/IL-1β-nitric oxide axis in headkidney macrophages. Issue 1 (31st December 2022)

• Record Type: Journal Article
• Authors: Kumar, Manmohan; Shelly, Asha; Dahiya, Priyanka; Ray, Atish; Mazumder, Shibnath
• Is Part Of: Virulence. Volume 13:Issue 1(2022)
• Page Start: 60
• Page End: 76
• Publication Date: 2022-12-31
• Subjects: Aeromonas hydrophila -- head kidney macrophage -- er-stress -- mtROS -- mtDNA -- autophagy -- apoptosis -- caspase-1 -- IL-1β; Virulence (Microbiology) -- Periodicals; Bacterial diseases -- Periodicals; Molecular microbiology -- Periodicals; 579.05
• DOI: 10.1080/21505594.2021.2018767
• Languages: English
• ISSNs: 2150-5608

Abstract

ABSTRACT: The molecular mechanisms underlying Aeromonas hydrophila -pathogenesis are not well understood. Using head kidney macrophages (HKM) of Clarias gariepinus, we previously reported the role of ER-stress in A. hydrophila -induced pathogenesis. Here, we report that PI3K/PLC-induced cytosolic-Ca 2+ imbalance induces the expression of pro-apoptotic ER-stress marker, CHOP in A. hydrophila- infected HKM. CHOP promotes HKM apoptosis by inhibiting AKT activation and enhancing JNK signaling. Elevated mitochondrial ROS (mtROS) was recorded which declined significantly by ameliorating ER-stress and in the presence of ER-Ca 2+ release modulators (2-APB and dantrolene) and mitochondrial-Ca 2+ uptake inhibitor, Ru360, together suggesting the role of ER-mitochondrial Ca 2+ dynamics in mtROS generation. Inhibiting mtROS production reduced HKM death implicating the pro-apoptotic role of mtROS in A. hydrophila -pathogenesis. The expression of autophagic proteins (LC3B, beclin-1, and atg 5) was suppressed in the infected HKM. Our results with autophagy-inducer rapamycin demonstrated that impaired autophagy favored the cytosolic accumulation of mitochondrial DNA (mtDNA) and the process depended on mtROS levels. Enhanced caspase-1 activity and IL-1β production was detected and transfection studies coupled with pharmacological inhibitors implicated mtROS/mtDNA axis to be crucial for activating the caspase-1/IL-1β cascade in infected HKM. RNAi studies further suggested the involvement of IL-1β in generating pro-apoptotic NO in A. hydrophila -infected HKM. Our study suggests a novel role of ER-mitochondria cross-talk in regulating A. hydrophila pathogenesis. Based on our observations, we conclude that A. hydrophila induces ER-stress and inhibits mitophagy resulting in mitochondrial dysfunction which leads to mtROS production and translocation of mtDNA into cytosol triggering the activation of caspase-1/IL-1β-mediated NO production, culminating in HKM apoptosis.