MECHANISMS OF DRUG-INDUCED TOXICITIES

今年，我们继续研究药物性变应性肝炎的分子基础，并开始调查那些可能控制这类药物毒性发生率的因素。麻醉师对麻醉诱导的过敏性肝炎的抵抗的一种可能解释是，肝脏中潜在的破坏性T细胞介导的免疫反应可能通过跨膜结合FasL （tmFasL）的分裂和随后可溶性FasL （sFasL）从这些细胞释放到血清中而下调。研究表明，sFasL通过阻断tmFasL与Fas表达细胞（如肝细胞）的相互作用，下调T细胞的凋亡活性。为了验证这一观点，我们确定了麻醉师的血清中sFasL水平是否升高。事实上，我们发现麻醉医师的血清sFasL水平明显高于对照组和麻醉肝炎患者。在另一项研究中，我们研究了肝脏中常驻T细胞在药物性过敏性肝炎发展中的潜在作用。研究发现，肝毒性药物在给药48小时后引起小鼠肝脏CD3+ T细胞的剂量依赖性下降。进一步的实验表明，表达γ / δ受体的CD8+淋巴细胞，而不是其他T细胞亚群，主要从肝脏中消失。由于携带γ / δ受体的T细胞与自身免疫性肝病（如自身免疫性肝炎、原发性胆汁性肝硬化和原发性硬化性胆管炎）有关，我们的研究结果表明，当肝细胞受损时，这些细胞可能会从肝脏中正常消失。这可能抑制随后由受损肝细胞释放的自身抗原和/或新抗原诱导的免疫病理反应。我们还研究了广泛使用的非甾体抗炎药双氯芬酸引起的溶血性贫血的分子基础。我们在此报道，20- 45%的小鼠在口服双氯芬酸后出现急性溶血。通过测量红细胞和网织红细胞计数的减少，小鼠患上了贫血。在感染小鼠的血清和尿液中发现血红蛋白。在SCID小鼠中也发生了毒性，这表明这种机制不是基于免疫的。双氯芬酸特异性抗血清对红细胞膜蛋白的免疫印迹分析显示，双氯芬酸形成了108,56和50kda的蛋白加合物。108 kDa加合物似乎对应于带3，RBC阴离子交换剂，因为它与抗血清反应对抗该蛋白。这些发现提示双氯芬酸介导的溶血性贫血可能是由于双氯芬酸反应性代谢物使一种或多种红细胞膜蛋白发生共价改变。-吸入性麻醉剂，氟烷，药物性肝炎，免疫病理，双氯芬酸，溶血性贫血，蛋白质加合物

This year we have continued our studies of the molecular basis of drug- induced allergic hepatitis and have begun investigating those factors that may control the incidence of this category of drug toxicity. One possible explanation for the resistance of anesthesiologists to anesthetic-induced allergic hepatitis is that potentially damaging T cell-mediated immune reactions in the liver may be down-regulated through the cleavage of transmembrane-bound FasL (tmFasL) and subsequent release of soluble FasL (sFasL) from these cells into the serum. sFasL has been suggested to down-regulate the apoptotic activity of T cells by blocking the interaction of tmFasL with Fas expressing cells, such as hepatocytes. To test this idea, we have determined whether anesthesiologists have elevated levels of sFasL in their sera. Indeed, we found that serum sFasL levels of anesthesiologists were significantly higher than those of control and anesthetic hepatitis patients. In another study we investigated the potential role of resident T cells in the liver in the development of drug-induced allergic hepatitis. It was found that hepatotoxic drugs caused a dose- dependent decrease in CD3+ T cells of the liver 48 hours after they were administered to mice. Further experiments showed that CD8+ lymphocytes expressing gamma/delta receptors, but not other T cell subsets were predominantly depleted from the liver. Since T cells bearing gamma/delta receptors have been associated with autoimmune liver diseases such as autoimmune hepatitis, primary biliary cirrhosis, and primary sclerosing cholangitis, our findings suggest that these cells may be normally depleted from the liver when hepatocytes are damaged. This may suppress subsequent immunopathological reactions induced by autoantigens and/or neoantigens that are released from damaged hepatocytes. We have also investigated the molecular basis of hemolytic anemia caused by diclofenac, a widely used nonsteroidal anti- inflammatory drug. We report here that acute hemolysis develops in 20- 45% of mice following oral administration of diclofenac. Mice developed anemia as measured by a reduction in red blood cell and reticulocyte counts. Hemoglobin was found in the serum and urine of the affected mice. Toxicity also occurred in SCID mice suggesting that the mechanism is not immune based. Immunoblot analysis of erythrocyte membrane proteins with diclofenac-specific antisera revealed that diclofenac formed protein adducts of 108, 56, and 50 kDa. The 108 kDa adduct appeared to correspond to band 3, the RBC anion exchanger, because it reacted with antisera against this protein. These findings suggest that diclofenac-mediated hemolytic anemia may be due to the covalent alteration of one or more erythrocyte membrane proteins by a reactive metabolite of diclofenac. - Inhalation anesthetics, halothane, drug- induced hepatitis, immunopathology, diclofenac, hemolytic anemia, protein adducts