Viral infections have more severe consequences in individuals who have been exposed to cigarette smoke (CS) than in those not exposed to CS. Acute exacerbations of COPD contributes toward rapid lung function decline. Surprisingly, the mechanisms that underlie the exaggerated virus-induced responses in CS-exposed individuals have not been adequately addressed. Our studies demonstrated that viruses cause increased levels of inflammation, tissue destruction and lung fibrosis in CS exposed mice. We first reported adverse effects of CS exposure were eliminated by null mutations of mitochondrial antiviral signaling molecule (MAVS), a key adapter molecule that is bound to the mitochondrial outer membrane and essential for antiviral signaling. To further define the mechanisms of these responses, on the premise that CS causes alteration of MAVS-mediated signaling, we have focused on the dysregulation of MAVS-mediated signaling and its regulatory mechanisms in CS-exposed and CS + virus exposed mice. Our studies highlight the following novel insights: (1) CS exposure leads to persistent macrophage inflammation and increased fibrotic lung changes after influenza virus (Flu); (2) Lung macrophages show increased MAVS levels which were associated with excessive inflammatory, injury and fibrotic responses during CS+Flu; (3) Ex vivo lung-derived fibroblasts from CS+Flu have increased proliferation, expression of alpha- smooth muscle actin stained stress fibers, growth factor expression with pro-fibrotic and pro-proliferative transcriptomic signature; (4) The prion-like multimeric aggregation of MAVS, a key event in MAVS-mediated antiviral signaling, is markedly enhanced in mouse lungs exposed to CS+Flu; (5) Lungs from COPD patients have increased MAVS aggregation; (6) Inflammasomes activation, inflammatory and tissue damage responses are exaggerated in CS+Flu lungs and involves MAVS; and (7) Phosphatase and tensin homologue (PTEN)- induced putative kinase 1 (PINK1), an important regulator of mitochondrial health, plays a critical inhibitory role in regulating MAVS-mediated inflammasomes and pathology. Based on these observations, we hypothesize that CS-induced dysregulation of MAVS homeostasis on mitochondria has a critical functional role in the exaggerated pulmonary inflammation and tissue damage responses observed in the lungs during viral infection.
In Aim 1, we will characterize the dysregulation of homeostatic regulation of MAVS on mitochondria, the MAVS prion-like aggregation and MAVS- and PINK1- mediated signaling after CS and influenza virus co-exposure.
In Aim 2, we will define the consequences of PINK1-mediated regulation of MAVS aggregation on pathological pulmonary outcomes in smoke exacerbated influenza pathology and PINK1 augmentation as a possible therapeutic approach.
In Aim 3, we will characterize MAVS aggregation pathway in patients with smoking exposure and respiratory viral infection. These proposed studies will provide new insights into how MAVS regulates macrophage-fibroblast interactions in CS exposure and virus infected lungs with the hope of developing novel, pathogenesis-based therapies to improve patient outcomes in diseases such as acute exacerbations of COPD.
Viral infections have more severe chronic consequences in individuals exposed to cigarette smoke (CS) than those who are not. We show that excessive accumulation of MAVS aggregates in mice exposed to CS and influenza virus (Flu) contributes to increased lung pathology. This grant will determine the mechanism of CS- induced dysregulation of mitochondrial antiviral signaling (MAVS) during Flu and the role of PINK1 kinase in correcting this dysregulation. We will characterize the pathways leading to excessive MAVS signaling and the mechanisms by which PINK1 limits MAVS aggregation. The downstream effects of PINK1-MAVS interactions and the effects on pathological pulmonary outcomes will be studied. We will explore the therapeutic potential of PINK1 augmentation using genetic and pharmacological approaches. Lastly, we will study the MAVS aggregation pathway in patients with smoking exposure and viral infections. A clear understanding of MAVS- PINK1 interactions can provide a new target to limit Flu-mediated pathology in CS-related lung diseases.