Abstract
Purpose::
Epidemic keratoconjunctivitis (EKC) is a highly infectious adenoviral ocular syndrome. Stromal keratitis in EKC is characterized by neutrophil infiltration early in the infection. Chemokine KC/CXCL1 is a paradigm chemotactic molecule responsible for neutrophil migration. In this study, we sought to examine the role of intracellular signaling in expression of this chemokine in a mouse model of adenovirus keratitis.
Methods::
One µL of the chemical Src inhibitor PP2, the ERK1/2 inhibitor U0126 (10 µM for each), or DMSO control was injected into the corneal stroma of C57BL/6J mice, followed by injection of 105 TCID of adenovirus type 37 (Ad37) or virus-free buffer. The activation of cSrc and ERK1/2 was analyzed by immunoblot at various times post-infection. The expression of KC/CXCL1 was examined with quantitative real-time PCR and ELISA at 4 and 16 hours post-infection. Histopathology of corneas at 4 days post-infection was analyzed to determine the effects of signaling inhibitors on corneal inflammation.
Results::
Ad37-infected corneas showed increased phosphorylation of cSrc and ERK1/2 when compared to buffer-injected corneas at 90 minutes and 120 minutes post-infection, respectively. Ad37-infected corneas pre-treated with PP2 or U0126 showed significantly decreased levels of chemokine KC when compared to DMSO, both at mRNA and protein levels (ANOVA, p<0.05). Pretreatment of virus-infected corneas with PP2 resulted in decreased infiltration of neutrophils when compared to DMSO.
Conclusions::
Ad37 rapidly activates c-Src and ERK1/2 kinases in the C57BL/6J mouse cornea following infection. Chemical inhibition of Src or ERK1/2 significantly reduces KC expression and subsequent neutrophil infiltration in murine Ad37 keratitis, consistent with a role for intracellular signaling in the innate immune responses to adenovirus infection of the cornea.
Keywords: adenovirus • keratitis • signal transduction