Project 1: Role of LUBAC and Na,K-ATPase in alveolar epithelial lung injury
Patients with acute lung injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) have impaired gas (oxygen and carbon dioxide) exchange due to altered alveolar epithelial function which results in accumulation of edema fluid leading to hypoxia. Alveolar hypoxia is common in patients with ALI and ARDS and contributes to alveolar epithelial dysfunction. Seasonal influenza infection affects a significant proportion of the population in the US and worldwide and while most patients infected with influenza A recover without sequelae, in some patients influenza virus may cause severe pneumonitis and ARDS. Alveolar epithelial cells are targets for influenza virus A, and thus play an important role in mounting the host immune response. Upon influenza A virus infection, alveolar epithelial cells release cytokines that contribute to the recruitment of monocytes and macrophages to the site of infection and also participate in virus clearance and thus limit the infection from spreading. However, the underlying mechanisms of these events are not completely understood. We hypothesize that, in addition of its barrier function, the alveolar epithelium plays an important effector role in protecting the lung from injury.
The first aim of this grant proposal seeks to elucidate the mechanisms that lead to the stabilization of Na,K-ATPase plasma membrane levels during hypoxia as an adaptation to severe stress thus promoting cell survival. We will study whether the degradation of PKCζ, which triggers the down-regulation of Na,K-ATPase, by the E3 ligase HOIL-1L decreases alveolar epithelial cell death and thus lung injury during chronic hypoxia. HOIL-1L is a member of the Linear Ubiquitination Assembly Complex (LUBAC); however, we propose that during hypoxia HOIL-1L acts independently of LUBAC. In studies proposed for the second specific aim we will assess whether LUBAC participates in the modulation of the inflammatory signaling intensity in the alveolar epithelium during influenza virus infection. We seek to understand the role of LUBAC in increasing the efficiency of NF-κB activation and interferon production. The third specific aim examines the mechanisms by which increased intracellular sodium concentration which occurs during inhibition of the Na,K-ATPase, prevents viral replication in alveolar epithelial cells and whether pharmacologic inhibition of the Na,K-ATPase by cardiotonic steroids such as ouabain and digoxin represents a protective mechanism by inhibiting viral replication. Understanding the mechanism(s) that lead to alveolar epithelial dysfunction caused by hypoxia and influenza virus infection will provide novel information which is of clinical relevance and has the potential for novel approaches in the treatment of patients with acute lung injury.
Specific Aims of Project 1
Faculty Associated With Project 1
Jacob I. Sznajder Project, Leader
Aaron Ciechanover, Co-Investigator
Laura Dada, Co-Investigator
Emilia Lecuona, Co-Investigator
Susanne Herold, Co-Investigator