Gastroenterology Unit, Department of Clinical and Experimental Medicine, Federico II University, Naples, Italy.
Dig Liver Dis. 2010 Aug;42(8):571-7. doi: 10.1016/j.dld.2009.11.002. Epub 2009 Dec 8.
Tissue transglutaminase contributes to liver damage in the development of hepatic fibrosis. In a model of neurodegeneration, the therapeutic benefit of cystamine has been partly attributed to its inhibition of transglutaminase activity. Garlic extract contains many compounds structurally related to cystamine. We investigated the anti-fibrotic effect of garlic extract and cystamine as specific tissue transglutaminase inhibitors.
Rat liver fibrosis was induced by intraperitoneal injection of carbon tetrachloride (CCl(4)) for 7 weeks. Cystamine or garlic extract was administrated by daily intraperitoneal injection, starting from the day after the first administration of CCl(4). Hepatic function, histology, tissue transglutaminase immunostaining and image analysis to quantify Red Sirius stained collagen deposition were examined. Reverse transcription-polymerase chain reaction to detect alpha-SMA, IL-1beta and tissue transglutaminase expression and Western blot for tissue transglutaminase protein amount were performed. Transglutaminase activity was assayed on liver homogenates by a radio-enzymatic method.
Transglutaminase activity was increased in CCl(4) group and reduced by cystamine and garlic extract (p<0.05). Treatment with cystamine and garlic extract reduced the liver fibrosis and collagen deposition, particularly in the garlic extract group (p<0.01). Moreover, the liver damage improved and serum alanine aminotransferase was decreased (p<0.05). Tissue transglutaminase immunolocalised with collagen fibres and is mainly found in the ECM of damaged liver. Alpha-SMA, IL-1beta, tissue transglutaminase mRNA and tissue transglutaminase protein were down-regulated in the cystamine and garlic extract groups compared to controls.
These findings concurrently suggest that transglutaminase may play a pivotal role in the pathogenesis of liver fibrosis and may identify garlic cystamine-like molecules as a potential therapeutic strategy in the treatment of liver injury.
组织转谷氨酰胺酶（tissue transglutaminase，tTG）参与肝纤维化发展过程中的肝损伤。在神经退行性疾病模型中，半胱胺的治疗益处部分归因于其对转谷氨酰胺酶活性的抑制。大蒜提取物含有许多与半胱胺结构相关的化合物。我们研究了大蒜提取物和半胱胺作为组织转谷氨酰胺酶特异性抑制剂的抗纤维化作用。
采用腹腔注射四氯化碳（CCl(4)）诱导大鼠肝纤维化模型，共 7 周。从第一次给予 CCl(4)后第 2 天开始，每天给予半胱胺或大蒜提取物腹腔注射。检测肝组织学、组织转谷氨酰胺酶免疫染色和天狼猩红染色胶原沉积的图像分析。采用反转录聚合酶链反应（reverse transcription-polymerase chain reaction，RT-PCR）检测α-SMA、IL-1β和组织转谷氨酰胺酶的表达，采用 Western blot 检测组织转谷氨酰胺酶蛋白量。采用放射性酶法测定肝组织匀浆中转谷氨酰胺酶活性。
CCl(4)组转谷氨酰胺酶活性增加，半胱胺和大蒜提取物组降低（p<0.05）。半胱胺和大蒜提取物治疗可减少肝纤维化和胶原沉积，尤其是大蒜提取物组（p<0.01）。此外，肝损伤改善，血清丙氨酸氨基转移酶降低（p<0.05）。组织转谷氨酰胺酶与胶原纤维免疫共定位，主要存在于受损肝脏的细胞外基质中。与对照组相比，半胱胺和大蒜提取物组的α-SMA、IL-1β、组织转谷氨酰胺酶 mRNA 和组织转谷氨酰胺酶蛋白表达下调。
这些发现提示转谷氨酰胺酶可能在肝纤维化发病机制中起关键作用，并确定大蒜半胱胺样分子可能是治疗肝损伤的潜在治疗策略。
