Manganese potentiates lipopolysaccharide-induced expression of NOS2 in C6 glioma cells through mitochondrial-dependent activation of nuclear factor kappaB.
Neuronal injury in manganese neurotoxicity (manganism) is thought to involve activation of astroglial cells and subsequent overproduction of nitric oxide (NO) by inducible nitric oxide synthase (NOS2). Manganese (Mn) enhances the effects of proinflammatory cytokines on expression of NOS2 but the molecular basis for this effect has not been established. It was postulated in the present studies that Mn enhances expression of NOS2 through the cis-acting factor, nuclear factor kappaB (NF-kappaB). Exposure of C6 glioma cells to lipopopolysaccharide (LPS) resulted in increased expression of NOS2 and production of NO that was dramatically potentiated by Mn and was blocked through overexpression of mutant IkappaBalpha (S32/36A). LPS-induced DNA binding of p65/p50 was similarly enhanced by Mn and was decreased by mutant IkappaBalpha. Phosphorylation of IkappaBalpha was potentiated by Mn and LPS and was not blocked by U0126, a selective inhibitor of ERK1/2. Mn decreased mitochondrial membrane potential and increased matrix calcium, associated with a rise in intracellular reactive oxygen species (ROS) that was attenuated by the mitochondrial-specific antioxidant, MitoQ. Blocking mitochondrial ROS also attenuated the enhancing effect of Mn on LPS-induced phosphorylation of IkappaBalpha and expression of NOS2, suggesting a link between Mn-induced mitochondrial dysfunction and activation of NF-kappaB. Overexpression of a dominant-negative mutant of the NF-kappaB-interacting kinase (Nik) prevented enhancement of LPS-induced phosphorylation of IkappaBalpha by Mn. These data indicate that Mn augments LPS-induced expression of NOS2 in C6 cells by increasing mitochondrial ROS and activation of NF-kappaB.
Barhoumi
Rola
R
Department of Anatomy, Neuroscience Program, College of Veterinary Medicine, Texas A&M University, MS 4458 TAMU, College Station, TX 77843-4458, USA.
Faske
Jennifer
J
Liu
Xuhong
X
Tjalkens
Ronald B
RB
D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D002135:Calcium-Binding Proteins; D045744:Cell Line, Tumor; D004357:Drug Synergism; D004790:Enzyme Induction / Q000187:drug effects; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D020149:Manganese Poisoning / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000378:metabolism; D009498:Neurotoxins / Q000633:toxicity*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D050863:Synaptotagmin I; D050857:Synaptotagmins; D000097782:NF-kappaB-Inducing Kinase
D002135:Calcium-Binding Proteins; D020672:I-kappa B Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D017346:Protein Serine-Threonine Kinases; D017382:Reactive Oxygen Species; D050863:Synaptotagmin I; D050857:Synaptotagmins; D000097782:NF-kappaB-Inducing Kinase; C000606206:Nfkbia protein, rat; C496318:Nos2 protein, rat