inhibits autophagy triggering cytosolic translocation of mtDNA which activates the pro-apoptotic caspase-1/IL-1β-nitric oxide axis in headkidney macrophages.

The molecular mechanisms underlying -pathogenesis are not well understood. Using head kidney macrophages (HKM) of , we previously reported the role of ER-stress in -induced pathogenesis. Here, we report that PI3K/PLC-induced cytosolic-Ca imbalance induces the expression of pro-apoptotic ER-stress marker, CHOP in 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 release modulators (2-APB and dantrolene) and mitochondrial-Ca uptake inhibitor, Ru360, together suggesting the role of ER-mitochondrial Ca dynamics in mtROS generation. Inhibiting mtROS production reduced HKM death implicating the pro-apoptotic role of mtROS in -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 -infected HKM. Our study suggests a novel role of ER-mitochondria cross-talk in regulating pathogenesis. Based on our observations, we conclude that 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.