Tumour necrosis factor alpha activates nuclear factor kappaB signalling to reduce N-type voltage-gated Ca2+ current in postganglionic sympathetic neurons

Autor(es): Motagally Mohamed A,Lukewich Mark K,Chisholm Susan P,Neshat Shadia,Lomax Alan E

Resumo: Inflammation has profound effects on the innervation of affected tissues, including altered neuronal excitability and neurotransmitter release. As Ca(2+) influx through voltage-gated Ca(2+) channels (VGCCs) is a critical determinant of excitation-secretion coupling in nerve terminals, the aim of this study was to characterize the effect of overnight incubation in the inflammatory mediator tumour necrosis factor alpha (TNFalpha; 1 nM) on VGCCs in dissociated neurons from mouse superior mesenteric ganglia (SMG). Voltage-gated Ca(2+) currents (I(Ca)) were measured using the perforated patch clamp technique and the VGCC subtypes present in SMG neurons were estimated based on inhibition by selective VGCC blockers: omega-conotoxin GVIA (300 nM; N-type), nifedipine (10 microM; L-type), and omega-conotoxin MVIIC (300 nM; N-, P/Q-type). We used intracellular Ca(2+) imaging with Fura-2 AM to compare Ca(2+) influx during depolarizations in control and TNFalpha-treated neurons. TNF receptor and VGCC mRNA expression were measured using PCR, and channel alpha subunit (CaV2.2) was localized with immunohistochemistry. Incubation in TNFalpha significantly decreased I(Ca) amplitude and depolarization-induced Ca(2+) influx. The reduction in I(Ca) was limited to omega-conotoxin GVIA-sensitive N-type Ca(2+) channels. Depletion of glial cells by incubation in cytosine arabinoside (5 microM) did not affect I(Ca) inhibition by TNFalpha. Preincubation of neurons with SC-514 (20 microM) or BAY 11-7082 (1 microM), which both inhibit nuclear factor kappaB signalling, prevented the reduction in I(Ca) by TNFalpha. Inhibition of N-type VGCCs following TNFalpha incubation was associated with a decrease in CaV2.2 mRNA and reduced membrane localization of CaV2.2 immunoreactivity. These data suggest that TNFalpha inhibits I(Ca) in SMG neurons and identify a novel role for NF-kappaB in the regulation of neurotransmitter release during inflammatory conditions with elevated circulating TNFalpha, such as Crohn's disease and Guillain-Barré syndrome.

Imprenta: The Journal of Physiology, v. 587, n. 11, p. 2623-2634, 2009

Identificador do objeto digital: 10.1113/jphysiol.2009.172312

Descritores: Guillain-Barre Syndrome - Biosynthesis ; Guillain-Barre Syndrome - Biochemistry ; Guillain-Barre Syndrome - Cell ; Guillain-Barre Syndrome - Pathogenesis ; Guillain-Barre Syndrome - Proteins ; Guillain-Barre Syndrome - RNA ; Guillain-Barre Syndrome - Cytokines ; Guillain-Barre Syndrome - Inflammation ; Guillain-Barre Syndrome - RT-PCR

Data de publicação: 2009