Grubišić Vladimir, Gulbransen Brian D
Neuroscience Program, Department of Physiology, Michigan State University, 567 Wilson Road, East Lansing, MI, 48824, USA.
J Physiol. 2017 Jun 1;595(11):3409-3424. doi: 10.1113/JP273492. Epub 2017 Feb 22.
The role of enteric glial cell activity in the acute regulation of epithelial barrier and secretomotor functions of the intestines under physiological conditions is not clear. We used transgenic mice to modify glial activity and found that enteric glia significantly contribute to the neurogenic ion transport while glial activity does not appear to play a major role in the acute regulation of barrier function. The selective activation of glial activity evoked electrogenic ion transport primarily through neural pathways and was sufficient to drive electrogenic ion transport to an extent equal to the direct activation of neurogenic ion transport. These findings provide novel insight into the cellular mechanisms that control fluid transport homeostasis in the intestine and might provide novel therapeutic avenues for functional diarrheal diseases.
Enteric glial cells are often implicated in the regulation of epithelial barrier and secretomotor functions of the intestines. But whether glial cell activity regulates these functions acutely under physiological conditions is not clear. We addressed this issue by using transgenic animal models to modify the activity of enteric glia, either reducing glial expression of connexin 43 in Sox10::CreER /Cx43 mice or activating glial calcium responses in GFAP::hM3Dq mice, and tested the effects on colonic barrier function and electrogenic ion transport in Ussing chambers. We assessed neuronal-dependent and -independent contributions by activating or inhibiting neurogenic activity with veratridine and tetrodotoxin, respectively. Our results show that the reduction of glial Cx43 expression in Sox10::CreER /Cx43 mice significantly reduced neurogenic ion transport. The selective glial activation in tissues from GFAP::hM3Dq mice evoked electrogenic ion transport to an extent equal to the direct activation of neurogenic ion transport with veratridine and glial driven responses consisted of both tetrodotoxin-sensitive and -insensitive components. The selective glial stimulation did not affect transmural ion conductance or cell-impermeant dye flux but the baseline ion conductance was more variable in Sox10::CreER /Cx43 tissues. Together, our findings show that glial activity contributes to the regulation of electrogenic ion transport in the intestine through effects on neurons and possibly direct effects on epithelial cells. However, glial activity does not appear to play a major role in the acute regulation of barrier function. These findings provide novel insight into the cellular mechanisms that control fluid transport homeostasis in the intestine.
在生理条件下，肠道神经胶质细胞活性在肠道上皮屏障和分泌运动功能的急性调节中的作用尚不清楚。我们使用转基因小鼠来改变胶质细胞活性，发现肠道神经胶质细胞对神经源性离子转运有显著贡献，而胶质细胞活性在屏障功能的急性调节中似乎不起主要作用。胶质细胞活性的选择性激活主要通过神经通路诱发电生性离子转运，并且足以将电生性离子转运驱动到与直接激活神经源性离子转运相当的程度。这些发现为控制肠道液体运输稳态的细胞机制提供了新的见解，并可能为功能性腹泻疾病提供新的治疗途径。
肠道神经胶质细胞常被认为参与肠道上皮屏障和分泌运动功能的调节。但在生理条件下，胶质细胞活性是否能急性调节这些功能尚不清楚。我们通过使用转基因动物模型来改变肠道神经胶质细胞的活性，即降低Sox10::CreER /Cx43小鼠中连接蛋白43的胶质细胞表达，或激活GFAP::hM3Dq小鼠中的胶质细胞钙反应，并在尤斯灌流小室中测试其对结肠屏障功能和电生性离子转运的影响。我们分别用藜芦碱和河豚毒素激活或抑制神经源性活性，评估神经元依赖性和非依赖性的贡献。我们的结果表明，Sox10::CreER /Cx43小鼠中胶质细胞Cx43表达的降低显著减少了神经源性离子转运。GFAP::hM3Dq小鼠组织中的选择性胶质细胞激活诱发的电生性离子转运程度与用藜芦碱直接激活神经源性离子转运相当，且胶质细胞驱动的反应包括河豚毒素敏感和不敏感成分。选择性胶质细胞刺激不影响跨膜离子电导或细胞不可渗透染料通量，但Sox10::CreER /Cx43组织中的基线离子电导变化更大。总之，我们的研究结果表明，胶质细胞活性通过对神经元的影响以及可能对上皮细胞的直接影响，参与了肠道电生性离子转运的调节。然而，胶质细胞活性在屏障功能的急性调节中似乎不起主要作用。这些发现为控制肠道液体运输稳态的细胞机制提供了新的见解。
