Coordinated role of voltage-gated sodium channels and the Na+/H+ exchanger in sustaining microglial activation during inflammation

Toxicol Appl Pharmacol. 2013 Dec 1;273(2):355-64. doi: 10.1016/j.taap.2013.09.011. Epub 2013 Sep 24.

Abstract

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.

Keywords: (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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Line, Transformed
  • Dose-Response Relationship, Drug
  • Inflammation / chemically induced
  • Inflammation / metabolism*
  • Inflammation / pathology*
  • Lipopolysaccharides / toxicity
  • Mice
  • Mice, Inbred C57BL
  • Microglia / drug effects
  • Microglia / metabolism*
  • Microglia / pathology
  • Sodium-Hydrogen Exchangers / physiology*
  • Voltage-Gated Sodium Channel Blockers / pharmacology
  • Voltage-Gated Sodium Channels / physiology*

Substances

  • Lipopolysaccharides
  • Sodium-Hydrogen Exchangers
  • Voltage-Gated Sodium Channel Blockers
  • Voltage-Gated Sodium Channels