Down-regulation of L-type calcium channels in inflamed circular smooth muscle cells of the canine colon
Down-regulation of L-type calcium channels in inflamed circular smooth muscle cells of the canine colon
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DOI：
10.1053/gast.2001.21167
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发表时间：
2001-02-01
期刊：
影响因子：
29.4
通讯作者：
Sarna, SK
中科院分区：
文献类型：
--
作者：
Liu, XR;Rusch, NJ;Sarna, SK
背景和目标：在结肠炎症过程中，环状平滑肌的阶段性收缩和张力受到抑制，但其影响因素尚不清楚。本研究探讨了在炎症犬结肠环行肌细胞中，电压门控性长效（L型）Ca 2+通道蛋白和功能性Ca 2+通道电流的表达水平是否下调。研究方法：使用针对孔形成α 1C亚基的抗体通过Western免疫印迹比较正常和炎症平滑肌细胞之间的L型Ca 2+通道表达，并使用膜片钳方法评估Ca 2+通道电流密度。结果如下：与正常环形平滑肌细胞膜相比，炎症中L型Ca 2+通道蛋白的表达显著降低，这一发现与膜片钳细胞中Ca 2+通道电流的抑制水平相关。Bay K 8644使正常和炎症细胞L型Ca ~（2+）通道电流成比例增加，但炎症细胞L型Ca ~（2+）通道电流密度仍较低。乙酰胆碱增加L-型钙通道电流在正常的，但不是在发炎的细胞。结论：L型Ca 2+通道的表达水平在炎症结肠的环形平滑肌细胞膜中下调，这可能导致Ca 2+内流减少。通道的功能和药理学特性似乎正常。虽然一些Ca 2+通道仍然存在于发炎的细胞中，但乙酰胆碱不会激活这些通道，这可能是由受体信号级联中的额外上游缺陷引起的。L-型Ca 2+通道表达的下调可能抑制炎症结肠中的环形平滑肌收缩，并有助于在炎症性疾病期间观察到的运动和消化异常。
Background & Aims: Circular smooth muscle phasic contractions and tone are suppressed during colonic inflammation, but the contributing factors are poorly understood. This study investigated if the expression level of voltage-gated long-lasting (L-type) Ca2+ channel protein and functional Ca2+ channel current are downregulated in the circular muscle cells of the inflamed canine colon. Methods: L-type Ca2+ channel expression was compared between normal and inflamed smooth muscle cells by Western immunoblots using an antibody directed against the pore-forming alpha 1C-subunit, and patch-clamp methods were used to evaluate Ca2+ channel current density. Results: The expression of the L-type Ca2+ channel protein was significantly reduced in inflamed compared with normal circular smooth muscle cell membranes, and this finding was associated with suppressed levels of Ca2+ channel current in patch-clamped cells. The L-type Ca2+ channel current in normal and inflamed cells increased proportionately in response to Bay K 8644, but the maximal current density was still lower in the inflamed cells. Acetylcholine increased the L-type Ca2+ channel current in normal but not in inflamed cells. Conclusions: The expression level of L-type Ca2+ channels is down-regulated in the circular smooth muscle cell membranes of the inflamed colon, which may result in reduced Ca2+ influx. The functional and pharmacologic properties of the channels seem normal. Although some Ca2+ channels are still present in the inflamed cells, acetylcholine does not activate these channels, which may be caused by additional upstream defects in the receptor signaling cascade. The down-regulation of L-type Ca2+ channel expression may suppress circular smooth muscle contractions in the inflamed colon and contribute to the abnormalities in motility and digestion observed during inflammatory disorders.