Coordinated role of voltage-gated sodium channels and the Na+/H+ exchanger in sustaining microglial activation during inflammation.
Persistent neuroinflammation and microglial activation play an integral role in the pathogenesis of many neurological disorders. We investigated the role of voltage-gated sodium channels (VGSC) and Na(+)/H(+) exchangers (NHE) in the activation of immortalized microglial cells (BV-2) after lipopolysaccharide (LPS) exposure. LPS (10 and 100 ng/ml) caused a dose- and time-dependent accumulation of intracellular sodium [(Na(+))i] in BV-2 cells. Pre-treatment of cells with the VGSC antagonist tetrodotoxin (TTX, 1 μM) abolished short-term Na(+) influx, but was unable to prevent the accumulation of (Na(+))i observed at 6 and 24h after LPS exposure. The NHE inhibitor cariporide (1 μM) significantly reduced accumulation of (Na(+))i 6 and 24h after LPS exposure. Furthermore, LPS increased the mRNA expression and protein level of NHE-1 in a dose- and time-dependent manner, which was significantly reduced after co-treatment with TTX and/or cariporide. LPS increased production of TNF-α, ROS, and H2O2 and expression of gp91(phox), an active subunit of NADPH oxidase, in a dose- and time-dependent manner, which was significantly reduced by TTX or TTX+cariporide. Collectively, these data demonstrate a closely-linked temporal relationship between VGSC and NHE-1 in regulating function in activated microglia, which may provide avenues for therapeutic interventions aimed at reducing neuroinflammation.
Department of Environmental and Occupational Medicine and Environmental and Occupational Health Sciences Institute, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ, USA.
Muhammad M
MM
Hossain
Patricia K
PK
Sonsalla
Jason R
JR
Richardson
D000818:Animals; D002461:Cell Line, Transformed; D004305:Dose-Response Relationship, Drug; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology*; D008070:Lipopolysaccharides / Q000633:toxicity; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology*; D061567:Voltage-Gated Sodium Channel Blockers / Q000494:pharmacology; D061566:Voltage-Gated Sodium Channels / Q000502:physiology*
D008070:Lipopolysaccharides; D017923:Sodium-Hydrogen Exchangers; D061567:Voltage-Gated Sodium Channel Blockers; D061566:Voltage-Gated Sodium Channels
(Na(+))(i); 2,7-Dichlorofluorescin diacetate; 4′,6-Diamidino-2-phenylindole; DAPI; GAPDH; H(2)DCFDA; H(2)O(2); KRHB; Krebs–Ringer–HEPES buffer; LPS; Lipopoysaccharide; MEM; Microglia; NADPH oxidase; NHE; Na(+)/H(+) exchanger; Neurodegeneration; PBS; ROS; Sodium Channel; Sodium hydrogen exchanger; TNFα; TTBS; TTX; Tween 20 Tris buffered saline; VGSC; glyceraldehyde 3-phosphate dehydrogenase; hydrogen peroxide; intracellular sodium; lipopolysaccharide; minimum essential medium; nicotinamide adenine dinucleotide phosphate-oxidase; phosphate-buffered saline; qPCR; quantitative reverse transcriptase polymerase chain reaction; reactive oxygen species; tetrodotoxin; tumor necrosis factor-α; voltage-gated sodium channels