Amrani Y, Panettieri R A, Frossard N, Bronner C
INSERM U425, Faculté de Pharmacie, Illkirch, France.
Am J Respir Cell Mol Biol. 1996 Jul;15(1):55-63. doi: 10.1165/ajrcmb.15.1.8679222.
Evidence suggests that cytokines may modulate smooth muscle cell function in a variety of inflammatory diseases. In the present study, we characterized the specific receptor subtypes that mediate tumor necrosis factor alpha (TNF alpha) effects on myocyte proliferation and on agonist-induced calcium transients in cultured human tracheal smooth muscle cells (TSMC). Pretreatment of human TSMC with TNF alpha potentiated cytosolic calcium [(Ca2+)i] transients evoked by carbachol. In a similar manner, selective TNF alpha-p55 receptor agonists such as htr-9, an activating monoclonal antibody, or a recombinant TNF-p55 (rTNF-p55), which specifically activates the TNF alpha-p55 receptor but not the TNF alpha-p75 receptor, also augmented [Ca2+]i transients evoked by carbachol. In parallel experiments, TNF alpha, rTNF alpha-p55, and htr-9 induced human TSMC proliferation as measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Interestingly, activation of the TNF alpha-p75 receptor with a selective agonist, recombinant TNF alpha-p75 (rTNF alpha-p75), or inhibition of the TNF alpha-p75 receptor with utr-1, an inhibitory anti-TNF alpha-p75 receptor antibody, had no effect on TNF alpha-augmented calcium transients or on myocyte growth. To further confirm the receptor specificity of these findings, immunocytochemical studies were performed using receptor-specific antibodies. These studies demonstrated marked cell-surface expression of the TNF alpha-p55 receptor compared with expression of the TNF alpha-p75 receptor on human TSMC. Taken together, our results suggest that TNF alpha modulates agonist-induced calcium transients and induces human TSMC proliferation by specific activation of the TNF alpha-p55 receptor. Further studies addressing the cellular and molecular mechanisms regulating cytokine modulation of airway smooth muscle function may provide new insight into mechanisms that induce airway hyperresponsiveness in asthma.
有证据表明，细胞因子可能在多种炎症性疾病中调节平滑肌细胞功能。在本研究中，我们鉴定了介导肿瘤坏死因子α（TNFα）对培养的人气管平滑肌细胞（TSMC）中肌细胞增殖和激动剂诱导的钙瞬变作用的特定受体亚型。用TNFα预处理人TSMC可增强卡巴胆碱诱发的胞质钙[（Ca2 +）i]瞬变。同样，选择性TNFα-p55受体激动剂，如激活单克隆抗体htr-9或重组TNF-p55（rTNF-p55），它们特异性激活TNFα-p55受体而非TNFα-p75受体，也增强了卡巴胆碱诱发的[Ca2 +]i瞬变。在平行实验中，通过3-（4,5-二甲基噻唑-2-基）-2,5-二苯基溴化四氮唑（MTT）测定法，TNFα、rTNFα-p55和htr-9诱导了人TSMC增殖。有趣的是，用选择性激动剂重组TNFα-p75（rTNFα-p75）激活TNFα-p75受体或用抑制性抗TNFα-p75受体抗体utr-1抑制TNFα-p75受体，对TNFα增强的钙瞬变或肌细胞生长没有影响。为了进一步证实这些发现的受体特异性，使用受体特异性抗体进行了免疫细胞化学研究。这些研究表明，与人TSMC上的TNFα-p75受体表达相比，TNFα-p55受体在细胞表面有明显表达。综上所述，我们的结果表明，TNFα通过特异性激活TNFα-p55受体来调节激动剂诱导的钙瞬变并诱导人TSMC增殖。进一步研究调节细胞因子对气道平滑肌功能调节的细胞和分子机制，可能为哮喘中诱导气道高反应性的机制提供新的见解。
