外源性化合物修饰丙酮酸脱氢酶E2亚单位在原发性胆汁性肝硬化发病机制中的意义

A preliminary study on the role of the E2 subunit of pyruvate dehydrogenase modified by xenobiotics in the pathogenesis of primary bfliary cholangitis

目的初步探讨外源性化合物——2-辛炔酸（2-OA）修饰丙酮酸脱氢酶E2亚单位（PDC-E2）在PBC发病机制中的作用。方法选择PBC患者102例，原发性硬化性胆管炎（PSC）患者34例及健康对照组50名，采用ELISA方法检测周围血抗PDC-E2抗体、抗硫辛酸及抗2-OA抗体的水平；选择其中30例抗PDC-E2抗体阳性且抗2-OA抗体阴性的PBC患者，采用抑制ELISA（iELISA）实验方法，检测患者周围血中是否存在与2-OA修饰PDC-E2后新出现表位的抗体。计数资料间比较采用χ2检验和Fisher确切概率法；计量资料间的比较采用Welch修正的非配对t检验；相关分析采用Spearman秩相关分析法。 结果PBC患者抗PDC-E2抗体、抗硫辛酸阳性及抗2-OA抗体的阳性率分别是94.1%（96/102）、73.5%（73/102）和53.9%（55/102），显著高于健康对照组，PSC组与健康对照组间各抗体阳性率差异无统计学意义。PBC患者抗硫辛酸抗体与抗2-OA抗体间无相关性（r=-0.065，P=0.520）。iELISA结果显示：40%（12/30）PBC患者周围血中存在只识别经2-OA修饰后PDC-E2（2OA-PDC-E2）的抗体，此抗体主要存在于早期PBC患者中。 结论PBC患者血清中存在无相关性的抗硫辛酸抗体和抗2-OA抗体。经2-OA修饰后的PDC-E2可能出现新的抗原构象表位，介导部分PBC易患体质者对此产生免疫应答，从而有助于患者突破对PDC-E2的免疫耐受，最终导致PBC发病。

Objective To explore preliminarily the role of the E2 subunit of pyruvate dehydrogenase （PDC-E2） modified by xenobiotics （e.g. 2-octynic acid, 2-OA） in the pathogenesis of primary biliary cirrhosis （PBC）. Methods Patients of PBC （102 cases）, primary sclerosing eholangitis （PSC, 34 cases） and healthy controls （HC, 50 cases） were selected. The anti-PDC-E2, anti-2-OA and anti-lipoic acid （LA） antibody in the peripheral blood of the 3 groups were tested by enzyme linked immunosorbent assay （ELISA）. By inhibitive ELISA （iELISA）, 30 of the 102 PBC patients with anti-PDC-E2 antibody but without anti-2-OA antibody were selected to detect whether there was any new epitope on the PEC-E2 conjugated with 2-OA. The chi-square test and Fisher exact test were taken to analyze the enumeration data. The two-tailed unpaired t test with Welch＇s correction was used to compare the measurement data. Spearman rank correlation analysis was also employed for proper test. Results The positive rate of anti^PDC-E2, anti-LA and anti-2-OA antibody in PBC patients was 94.1% （96/102）, 73.5%（73/102） and 53.9%（55/102） respectively, all of which were statistically significantly higher than those in healthy controls group but were of no significant difference between PSC and healthy controls group. There was no significant relevance between the levels of Anti-LA and anti-2-OA antibody in the PBC group （r=-0.065, P=0.520）. The iELISA results showed that the antibody, which only identified the epitopes on 2-OA-PDC-E2 induced by the 2-OA conjugation with PDC-E2, existed in 40% （12/30） of the PBC patients, and more interestingly, this antibody was predominantly appeared in PBC patients at their early clinical stage. Conclusion There are anti-LA antibody and anti-2-OA antibody in PBC patients, which have shown no significant association with each other. It is very likely that new antigenic conformational epitopes on PDC-E2 modified by 2-OA would emerge, which might led to the immune response in the individuals who are susceptible to PBC, and thus contribute for the breaking of PDC-E2 immune tolerance, and PBC occurrence finally.