The Role of ERK5 in Rhinovirus Stimulated Macrophages in Relation to the Viral Exacerbation of Asthma

Abstract

Virus-induced asthma is resistant to therapy therefore knowledge concerning the cellular and physiological processes important in the development of virus-induced asthma is key to new forms of intervention. Previous studies implicate the macrophage as playing an important role in the inflammatory environment observed in rhinovirus-induced exacerbation of asthma. However, little is known about the cell signaling events that are initiated upon macrophage exposure with rhinovirus. Major and minor group rhinovirus are genetically similar although they bind to two different cellular receptors. To determine if the attachment of major (HRV16) and minor group (HRV1a) rhinovirus to the human monocyte-derived macrophages elicits different kinetics of activation for ERK5 and p38, macrophages cells were exposed to HRV16 or HRV1a at an MOI of 10 for 15,30,60,90 and 120 min. Cell lysates were separated by SDS-PAGE and immunoblotted with anti-phospho-ERK5 or p38. For MAP kinase p38, major and minor group rhinovirus stimulated phosphorylation occurred after 15 min and sustained phosphorylation up to 60 min. At the 90 and 120 min time points, there was no p38 phosphorylation for HRV16 and sustained phosphorylation stimulated by HRV1a. A similar kinetics profile holds true for the MAP kinase ERK5. Inhibitors were used to aid in the elucidation of the pathways involved. Furthermore, it was established that the elaboration of the inflammatory mediators MCP-1 and RANTES occurs in response to HRV stimulation and that the ERK5 and p38 kinase inhibitors SB203580, UO126, PD98059, each had varying effects on MCP-1 and RANTES release.