Ca2+ Responses in Enteric Glia Are Mediated by Connexin-43 Hemichannels and Modulate Colonic Transit in Mice

Abstract

Background & Aims In the enteric nervous system, neurotransmitters initiate changes in Ca2+ (Ca2+ responses) in glia, but it is not clear how this process affects intestinal function. We investigated whether Ca2+-mediated responses in enteric glial are required to maintain gastrointestinal function. Methods We used in situ Ca2+ imaging to monitor glial Ca2+ responses, which were manipulated with pharmacologic agents or via glia-specific disruption of the gene encoding connexin-43 (Cx43) (hGFAP::creERT2+/−/Cx43f/f mice). Gastrointestinal function was assessed based on pellet output, total gut transit, colonic bead expulsion, and muscle tension recordings. Proteins were localized and quantified by immunohistochemistry, immunoblot, and reverse transcription PCR analyses. Results Ca2+ responses in enteric glia of mice were mediated by Cx43 hemichannels. Cx43 immunoreactivity was confined to enteric glia within the myenteric plexus of the mouse colon; the Cx43 inhibitors carbenoxolone and 43Gap26 inhibited the ability of enteric glia to propagate Ca2+ responses. In vivo attenuation of Ca2+ responses in the enteric glial network slowed gut transit overall and delayed colonic transit—these changes are also observed during normal aging. Altered motility with increasing age was associated with reduced glial Ca2+-mediated responses and changes in glial expression of Cx43 mRNA and protein. Conclusions Ca2+-mediated responses in enteric glia regulate gastrointestinal function in mice. Altered intercellular signaling between enteric glia and neurons might contribute to motility disorders.

Ganglionic GFAP+ glial Gq-GPCR signaling enhances heart functions in vivo

“…For example, Jain et al used hM3Dq transgenic mice to demonstrate that Gq-GPCR signaling in pancreatic β cells led to activation of ERK1/2 and IRS2 signaling; this activation led to markedly improved β cell function (55). Recent studies where Gfap-hM3Dq was used to activate enteric glia revealed novel mechanisms of glial regulation of gastrointestinal functions (15,56). In combination with pharmacological agents and by using in situ models, Gfap-hM3Dq mice serve as a useful model to study GFAP + glial functions in complex tissues and in intact animals.…”

“…Although SNA is mainly considered a product of integration by neuronal networks, recent evidence suggests that Gq G protein-coupled receptor (Gq-GPCR) activation in glial fibrillary acidic protein-expressing (GFAP + ) glia (CNS astrocytes and non-myelinating peripheral glia) also contributes to homeostatic control of blood gases (11)(12)(13) and gastrointestinal motility (14,15) via modulation of local neuronal activity. Recently, we showed that selective activation of Gq-GPCR signaling in GFAP + glia in vivo led to acute changes in autonomic functions, including increases in heart rate and blood pressure (16).…”

Optical Tools to Investigate Cellular Activity in the Intestinal Wall

“…It has been shown that enteric glial cells tune in to neuronal activity 108,109 and take part in ENS signaling that underlies colonic motility. 110,111 Also, our understanding of myogenic and other mesenchymal control elements present in the gut wall, has improved based on imaging results. For example, recent reports show that interstitial cells of Cajal can operate independently from enteric neurons to control segmentation motor activity, 112 and need the Ca 2+ -activated Cl − channel Ano1 to coordinate slow waves in the smooth muscle.…”

Targeting sympathetic glia for treating cardiovascular diseases

“…In the CNS, GFAP + astrocytes reside in close proximity to active synapses [4] , and regulate neuronal activity [5] and signal processing [6] in an activity-dependent and circuit-specific manner [7] . Recent studies on enteric glia revealed novel mechanisms of GFAP + glial regulation of gastrointestinal functions [8,9] , suggesting powerful neuromodulatory potential of GFAP + glia in the peripheral nervous system. We began by testing the role of GFAP + glia in the SNS in vivo.…”