Electrical stimulation induces IL-6 in skeletal muscle through extracellular ATP by activating Ca2+ signals and an IL-6 autocrine loop
Electrical stimulation induces IL-6 in skeletal muscle through extracellular ATP by activating Ca2+ signals and an IL-6 autocrine loop
复制标题
DOI：
10.1152/ajpendo.00450.2013
复制
发表时间：
2014-04-01
影响因子：
5.1
通讯作者：
Buvinic, Sonja
中科院分区：
文献类型：
--
作者：
Bustamante, Mario;Fernandez-Verdejo, Rodrigo;Buvinic, Sonja
白细胞介素-6（IL-6）是一种重要的肌细胞因子，在运动时在骨骼肌细胞中高度表达。我们评估了IL-6的表达响应于电刺激（ES）或细胞外ATP作为一个已知的介质的骨骼肌中的兴奋转录机制。我们检查了IL-6下游的经典信号级联（IL-6/JAK 2/STAT 3）是否也响应于肌肉细胞兴奋，得出结论IL-6通过正环影响其自身的表达。无论是ES或外源性ATP（100 μ M）增加大鼠肌管中IL-6的表达和p-STAT 3水平，抑制100 μ M苏拉明和2 U/ml腺苷三磷酸双磷酸酶的过程。ATP也诱发IL-6表达在两个孤立的骨骼纤维和提取物来自整个FDB肌肉。ATP使IL-6释放增加高达10倍。JAK 2抑制剂HBC可阻断ATP诱导的STAT 3激活。用中和抗体阻断分泌的IL-6或与STAT 3抑制剂VIII预孵育可使细胞外ATP诱发的STAT 3激活减少70%。抑制剂VIII也减少了70%的由ATP诱发的IL-6表达，表明正IL-6环。此外，ATP使SOCS 3的蛋白质水平增加了60%，SOCS 3是IL-6信号通路的负调节因子。另一方面，细胞内钙螯合或阻断IP 3依赖的钙信号消除STAT 3磷酸化引起的细胞外ATP或ES。这些结果表明，在刺激的骨骼肌细胞中IL-6的表达是由细胞外ATP和核苷酸受体介导的，涉及IP 3依赖性钙信号作为触发阳性IL-6自分泌环的早期步骤。
Interleukin-6 (IL-6) is an important myokine that is highly expressed in skeletal muscle cells upon exercise. We assessed IL-6 expression in response to electrical stimulation (ES) or extracellular ATP as a known mediator of the excitation-transcription mechanism in skeletal muscle. We examined whether the canonical signaling cascade downstream of IL-6 (IL-6/JAK2/STAT3) also responds to muscle cell excitation, concluding that IL-6 influences its own expression through a positive loop. Either ES or exogenous ATP (100 mu M) increased both IL-6 expression and p-STAT3 levels in rat myotubes, a process inhibited by 100 mu M suramin and 2 U/ml apyrase. ATP also evoked IL-6 expression in both isolated skeletal fibers and extracts derived from whole FDB muscles. ATP increased IL-6 release up to 10-fold. STAT3 activation evoked by ATP was abolished by the JAK2 inhibitor HBC. Blockade of secreted IL-6 with a neutralizing antibody or preincubation with the STAT3 inhibitor VIII reduced STAT3 activation evoked by extracellular ATP by 70%. Inhibitor VIII also reduced by 70% IL-6 expression evoked by ATP, suggesting a positive IL-6 loop. In addition, ATP increased up to 60% the protein levels of SOCS3, a negative regulator of the IL-6 signaling pathway. On the other hand, intracellular calcium chelation or blockade of IP3-dependent calcium signals abolished STAT3 phosphorylation evoked by either extracellular ATP or ES. These results suggest that expression of IL-6 in stimulated skeletal muscle cells is mediated by extracellular ATP and nucleotide receptors, involving IP3-dependent calcium signals as an early step that triggers a positive IL-6 autocrine loop.