Human adenovirus type 19 infection of corneal cells induces p38 MAPK-dependent interleukin-8 expression

Jaya Rajaiya,Raju Vs Rajala,Jingnan Xiao,James Chodosh

doi:10.1186/1743-422x-5-17

Abstract

BackgroundHuman adenovirus type 19 (HAdV-19) is a major cause of epidemic keratoconjunctivitis, the only ocular adenoviral infection associated with prolonged corneal inflammation. In this study, we investigated the role of p38 mitogen-activated protein kinase (MAPK) in HAdV-19 infection, with particular attention to the role of p38 MAPK in the transcriptional control of interleukin-8 (IL-8), a chemokine previously shown to be central to the initiation of adenovirus keratitis.ResultsWe found that infection of corneal cells with HAdV-19 led to activation of p38 MAPK and its downstream targets, HSP-27 and ATF-2, within 15 to 30 minutes post-infection. Infection also induced phosphorylation of IκB and NFκB in a p38 MAPK-dependent fashion. Furthermore, HAdV-19 induced an interaction between p38 MAPK and NFκB-p65, followed by nuclear translocation of activated NFκB-p65 and its binding to the IL-8 promoter. The interaction between p38 MAPK and NFκB-p65 was inhibited in concentration-dependent fashion by SB203580, a chemical inhibitor of p38 MAPK, but not by SP600125, an inhibitor of JNK – another MAPK implicated in chemokine expression by HAdV-19 infected cells. IL-8 gene expression in HAdV-19 infection was significantly reduced in the presence of sequence-specific p38 MAPK siRNA but not control siRNA.ConclusionThese results provide the first direct evidence for transcriptional regulation of IL-8 in HAdV-19 infected cells through the activation of the p38 MAPK signaling pathway. The p38 MAPK pathway may play a biologically important role in regulation of IL-8 gene expression in the adenovirus-infected cornea.

Highlights

Human adenovirus type 19 (HAdV-19) is a major cause of epidemic keratoconjunctivitis, the only ocular adenoviral infection associated with prolonged corneal inflammation
human adenovirus (HAdV)-19 infection activates p38 mitogen-activated protein kinase (MAPK) To determine whether adenovirus infection induced the activation of p38 MAPK, we infected keratocytes with HAdV-19 and immunoblotted for phosphorylation of p38
To further determine whether HAdV-19 infection induces the activation of p38 MAPK alone or the complete MAPK pathway, we examined two downstream effectors of p38 MAPK, HSP27 and ATF-2

Summary

Introduction

Human adenovirus type 19 (HAdV-19) is a major cause of epidemic keratoconjunctivitis, the only ocular adenoviral infection associated with prolonged corneal inflammation. Epidemic keratoconjunctivitis is an explosive and highly contagious ocular surface infection associated with prolonged corneal stromal inflammation [1], and caused by species D human adenovirus (HAdV) serotypes 8, 19, and 37 [2]. While internalization of the virus is unequivocally mediated by an intracellular signaling cascade, other consequences of intracellular signaling upon HAdV-19 infection of corneal cells were more recently reported, including PI3K/Akt-mediated promotion of cell viability during viral replication [8], and Src kinase-dependent expression of pro-inflammatory mediators [9]. The p38 MAPK signaling cascade regulates numerous cellular functions, including the cell cycle, development, differentiation, apoptosis, and inflammation, dependent on the specific cell type and extracellular stimulus [10]. Four isoforms of p38 MAPK, α, β, γ, and δ, are expressed in a cell specific manner [10], with the ubiquitously expressed α isoform most prominently implicated in cytokine production [16,17]

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