Microglia induce neural cell death via a proximity-dependent mechanism involving nitric oxide.
Microglial cells play a major role in the pathogenesis of many neurological diseases by exacerbating neuronal and non-neuronal cell death, but the mechanisms involved are unclear. To investigate the microglial-neuronal interactions, we used the murine BV-2 microglial cell line and the human neuronal-like SK-N-SH neuroblastoma cell line in a co-culture system that enabled proximity-dependent interaction and communication, a trans-well system that allowed proximity-independent communication through diffusible molecules only, and a conditioned media system through which no proximity-dependent interactions or cell-to-cell communication is possible. Activation of BV-2 cells with lipopolysaccharide and interferon-gamma (LPS/IFN-gamma) decreased viability of the BV-2 cells alone and in co-cultures with SK-N-SH cells, but not SK-N-SH cells grown alone. In contrast, activation of BV-2 cells in the trans-well and conditioned media system did not have any effect on the viability of SK-N-SH cells, suggesting that microglia must be in close proximity to the neural cells to elicit cytotoxicity. To determine the molecules involved in proximity-dependent cell death, inhibitors of microglial activation were investigated. Only the specific inducible nitric oxide synthase (iNOS) inhibitor S-methylisothiourea, and hypothermia, which is known to suppress microglial iNOS expression, prevented cell death after LPS/IFN-gamma activation. These results suggest that activated microglia release nitric oxide that is, at least partially, responsible for proximity-dependent microglial-mediated neural toxicity.
Signal Transduction Laboratory, Department of Pharmacology and Clinical Pharmacology, The University of Auckland, Auckland, New Zealand.
Hannah M
HM
Gibbons
Mike
M
Dragunow
D000704:Analysis of Variance; D000818:Animals; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D018920:Coculture Techniques / Q000379:methods; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D007035:Hypothermia / Q000503:physiopathology; D007150:Immunohistochemistry / Q000379:methods; D007371:Interferon-gamma / Q000378:metabolism / Q000494:pharmacology; D007550:Isothiuronium / Q000031:analogs & derivatives / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000502:physiology*; D009447:Neuroblastoma; D009474:Neurons / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D011863:Radioimmunoassay / Q000379:methods; D013778:Tetrazolium Salts; D013844:Thiazoles
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D013778:Tetrazolium Salts; D013844:Thiazoles; D007550:Isothiuronium; D009569:Nitric Oxide; D007371:Interferon-gamma; C027744:S-methylisothiopseudouronium; C022616:thiazolyl blue; D015232:Dinoprostone