Adenovirus infection induces microglial activation: involvement of mitogen-activated protein kinase pathways.
Non-replicating adenovirus vectors (AdV) represent effective tools for long-term gene expression in the central nervous system (CNS), but they also elicit inflammation. The cellular and molecular mechanisms of such a response are not understood. In the present study, we show that infection with AdV causes activation of microglial cells, the key cells involved in inflammatory and immune-regulatory functions in the brain. Exposure of cultured rat brain microglia to AdV resulted in an induced production of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS) and the pro-inflammatory cytokine, TNFalpha. The roles of signal transduction pathways believed to be involved in microglial activation in particular, mitogen-activated protein kinases (MAPKs) and nuclear factor kappaB (NFkappaB) were explored by determining their activation in response to AdV infection and by testing the effects of specific pharmacological inhibitors. It was found that AdV strongly activates extracellular signal-regulated kinase (ERK) and to a lesser extent, p38 MAPK but not NFkappaB. Addition of the kinase inhibitor, i.e. PD98059 (specific for the ERK pathway), inhibits and, in combination with the p38 MAPK inhibitor, SB203580, drastically suppresses AdV-induced expression of iNOS and TNFalpha. The results suggest that AdV uses cellular signal transduction machinery, in particular the MAPK pathways, to elicit microglial activation and that increased production by these cells of inflammatory mediators may primarily contribute to CNS inflammatory responses commonly seen in models of gene therapy using AdV vectors.
Bhat
Narayan R
NR
Department of Neurology, Medical University of South Carolina, 171 Ashley Avenue, Charleston, SC 29425, USA. bhatnr@musc.edu
Fan
Fan
F
D000257:Adenoviridae Infections / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005822:Genetic Vectors / Q000494:pharmacology / Q000502:physiology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D020935:MAP Kinase Signaling System / Q000502:physiology*; D046911:Macromolecular Substances; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000821:virology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases
D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D008164:Luminescent Proteins; D046911:Macromolecular Substances; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D049452:Green Fluorescent Proteins; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases