CAMP-dependent activation of protein kinase A attenuates respiratory syncytial virus-induced human airway epithelial barrier disruption.

Fariba Rezaee,Debra T Linfield,Ghaith Altawallbeh,Ronald J Midura,Terri J Harford,Giovanni Piedimonte,Andrei I Ivanov

doi:10.1371/journal.pone.0181876

Fariba Rezaee, Debra T Linfield + Show 5 more

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https://doi.org/10.1371/journal.pone.0181876

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Abstract

Airway epithelium forms a barrier to the outside world and has a crucial role in susceptibility to viral infections. Cyclic adenosine monophosphate (cAMP) is an important second messenger acting via two intracellular signaling molecules: protein kinase A (PKA) and the guanidine nucleotide exchange factor, Epac. We sought to investigate effects of increased cAMP level on the disruption of model airway epithelial barrier caused by RSV infection and the molecular mechanisms underlying cAMP actions. Human bronchial epithelial cells were infected with RSV-A2 and treated with either cAMP releasing agent, forskolin, or cAMP analogs. Structure and functions of the Apical Junctional Complex (AJC) were evaluated by measuring transepithelial electrical resistance and permeability to FITC-dextran, and determining localization of AJC proteins by confocal microscopy. Increased intracellular cAMP level significantly attenuated RSV-induced disassembly of AJC. These barrier-protective effects of cAMP were due to the activation of PKA signaling and did not involve Epac activity. Increased cAMP level reduced RSV-induced reorganization of the actin cytoskeleton, including apical accumulation of an essential actin-binding protein, cortactin, and inhibited expression of the RSV F protein. These barrier-protective and antiviral-function of cAMP signaling were evident even when cAMP level was increased after the onset of RSV infection. Taken together, our study demonstrates that cAMP/PKA signaling attenuated RSV-induced disruption of structure and functions of the model airway epithelial barrier by mechanisms involving the stabilization of epithelial junctions and inhibition of viral biogenesis. Improving our understanding of the mechanisms involved in RSV-induced epithelial dysfunction and viral pathogenesis will help to develop novel anti-viral therapeutic approaches.

Highlights

The airway epithelial barrier functions as the front line of host defense against airborne threats
To test the hypothesis that increased intracellular Cyclic adenosine monophosphate (cAMP) level could protect the epithelial barrier from disruption caused by Respiratory syncytial virus (RSV) infection, polarized airway epithelial cells were infected with RSV strain A2 at a 0.5 MOI in the presence or absence of forskolin, a known activator of adenylyl cyclase, which is responsible for cAMP production
In order to examine if such forskolin-dependent preservation of the epithelial barrier is mediated by its effects on the Apical Junctional Complex (AJC), we visualized tight junctions (TJ) organization in control and RSVinfected epithelial cell monolayers

Summary

Introduction

The airway epithelial barrier functions as the front line of host defense against airborne threats. While viruses are responsible for the majority of respiratory illnesses in children [6], mounting evidence indicates that increased permeability of the airway epithelial barrier is a common manifestation of lower respiratory tract viral infections that may significantly contribute to the development of mucosal inflammation [7]. These findings highlight the importance of studying the effects of viral infections on structure and functions of the airway epithelial barrier

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