Buchner R R, Hugli T E, Ember J A, Morgan E L
Department of Immunology, Scripps Research Institute, La Jolla, CA 92037, USA.
J Immunol. 1995 Jul 1;155(1):308-15.
Acute inflammation is characterized by increased production of acute phase proteins in the liver. The induction of the hepatocytic response is primarily mediated through soluble cytokines such as IL-1, IL-6, TNF-alpha, and transforming growth factor beta, which bind to specific cell surface receptors and regulate gene expression of acute-phase proteins. Hepatoma cell lines, such as HepG2, represent a model system for studying acute-phase protein synthesis. HepG2 is induced to produce a variety of acute-phase proteins, including alpha 1-antitrypsin, alpha 1-antichymotrypsin, fibrinogen, alpha 1-acid glycoprotein, and haptoglobin, upon stimulation with cytokines. Analysis of HepG2 by reverse transcriptase PCR indicated that this cell line synthesized mRNA specific for the human C5a receptor (CD88). Flow cytometric analysis of HepG2 cells indicated that these cells bound anti-CD88 Ab, thus confirming our RT-PCR data by demonstrating that these cells also express the C5a receptor. Because C5a has been shown to be a potent mediator of inflammation and HepG2 cells express CD88, we assessed the possibility that C5a was capable of stimulating acute-phase protein synthesis by HepG2 cells. The results indicate that binding of human C5a to CD88 on HepG2 cells resulted in an increased production of alpha 1-antitrypsin- and alpha 1-antichymotrypsin-specific mRNA as assayed by RT-PCR. Analysis of culture supernatants derived from C5a-stimulated HepG2 cells showed an increased production of alpha 1-antitrypsin as measured by solid-phase ELISA. alpha 1-antitrypsin production by HepG2 cells was a direct result of C5a stimulation as evidenced by the fact that anti-C5a receptor Ab inhibited the response. These results suggest that C5a may be an important mediator of APP production in the regulation of the inflammatory response.
急性炎症的特征是肝脏中急性期蛋白的产生增加。肝细胞反应的诱导主要通过可溶性细胞因子介导，如白细胞介素-1、白细胞介素-6、肿瘤坏死因子-α和转化生长因子-β，这些细胞因子与特定的细胞表面受体结合并调节急性期蛋白的基因表达。肝癌细胞系，如HepG2，代表了研究急性期蛋白合成的模型系统。在用细胞因子刺激后，HepG2被诱导产生多种急性期蛋白，包括α1-抗胰蛋白酶、α1-抗糜蛋白酶、纤维蛋白原、α1-酸性糖蛋白和触珠蛋白。通过逆转录聚合酶链反应（RT-PCR）对HepG2进行分析表明，该细胞系合成了人类C5a受体（CD88）特异性的mRNA。对HepG2细胞进行流式细胞术分析表明，这些细胞结合抗CD88抗体，从而通过证明这些细胞也表达C5a受体来证实我们的RT-PCR数据。由于C5a已被证明是炎症的有效介质，且HepG2细胞表达CD88，我们评估了C5a能够刺激HepG2细胞合成急性期蛋白的可能性。结果表明，人C5a与HepG2细胞上的CD88结合导致通过RT-PCR检测的α1-抗胰蛋白酶和α1-抗糜蛋白酶特异性mRNA的产生增加。对来自C5a刺激的HepG2细胞的培养上清液进行分析表明，通过固相酶联免疫吸附测定法（ELISA）测量，α1-抗胰蛋白酶的产生增加。抗C5a受体抗体抑制反应这一事实证明，HepG2细胞产生α1-抗胰蛋白酶是C5a刺激的直接结果。这些结果表明，C5a可能是炎症反应调节中急性期蛋白产生的重要介质。
