Khan Niamat, Pantakani D V Krishna, Binder Lutz, Qasim Muhammad, Asif Abdul R
Proteomics Group, Institute for Clinical Chemistry/UMG-Laboratories, University Medical CentreGoettingen, Germany; Department of Biotechnology and Genetic Engineering, Kohat University of Science and TechnologyKohat, Pakistan.
Proteomics Group, Institute for Clinical Chemistry/UMG-Laboratories, University Medical Centre Goettingen, Germany.
Front Physiol. 2015 Dec 22;6:381. doi: 10.3389/fphys.2015.00381. eCollection 2015.
Mycophenolic acid (MPA) is an important immunosuppressive drug (ISD) prescribed to prevent graft rejection in the organ transplanted patients, however, its use is also associated with adverse side effects like sporadic gastrointestinal (GI) disturbances. Recently, we reported the MPA induced tight junctions (TJs) deregulation which involves MLCK/MLC-2 pathway. Here, we investigated the global histone acetylation as well as gene-specific chromatin signature of several genes associated with TJs regulation in Caco-2 cells after MPA treatment.
The epigenetic analysis shows that MPA treatment increases the global histone acetylation levels as well as the enrichment for transcriptional active histone modification mark (H3K4me3) at promoter regions of p38MAPK, ATF-2, MLCK, and MLC-2. In contrast, the promoter region of occludin was enriched for transcriptional repressive histone modification mark (H3K27me3) after MPA treatment. In line with the chromatin status, MPA treatment increased the expression of p38MAPK, ATF-2, MLCK, and MLC-2 both at transcriptional and translational level, while occludin expression was negatively influenced. Interestingly, the MPA induced gene expression changes and functional properties of Caco-2 cells could be blocked by the inhibition of p38MAPK using a chemical inhibitor (SB203580).
Collectively, our results highlight that MPA disrupts the structure of TJs via p38MAPK-dependent activation of MLCK/MLC-2 pathway that results in decreased integrity of Caco-2 monolayer. These results led us to suggest that p38MAPK-mediated lose integrity of epithelial monolayer could be the possible cause of GI disturbance (barrier dysfunction) in the intestine, leading to leaky style diarrhea observed in the organ-transplanted patients treated with MPA.
霉酚酸（MPA）是一种重要的免疫抑制药物（ISD），用于预防器官移植患者的移植排斥反应，然而，其使用也与诸如偶发性胃肠道（GI）紊乱等不良副作用相关。最近，我们报道了MPA诱导紧密连接（TJ）失调，这涉及MLCK/MLC-2通路。在此，我们研究了MPA处理后Caco-2细胞中与TJ调节相关的几个基因的整体组蛋白乙酰化以及基因特异性染色质特征。
表观遗传学分析表明，MPA处理增加了整体组蛋白乙酰化水平以及p38MAPK、ATF-2、MLCK和MLC-2启动子区域转录活性组蛋白修饰标记（H3K4me3）的富集。相反，MPA处理后，闭合蛋白的启动子区域富集了转录抑制性组蛋白修饰标记（H3K27me3）。与染色质状态一致，MPA处理在转录和翻译水平上均增加了p38MAPK、ATF-2、MLCK和MLC-2的表达，而闭合蛋白的表达受到负面影响。有趣的是，使用化学抑制剂（SB203580）抑制p38MAPK可以阻断MPA诱导的Caco-2细胞基因表达变化和功能特性。
总体而言，我们的结果表明，MPA通过p38MAPK依赖的MLCK/MLC-2通路激活破坏TJ的结构，导致Caco-2单层完整性降低。这些结果使我们认为，p38MAPK介导的上皮单层完整性丧失可能是肠道中GI紊乱（屏障功能障碍）的可能原因，导致在用MPA治疗的器官移植患者中观察到渗漏性腹泻。
