The Mechanism Of HuR And MiR-890 Regulate The Inflammatory Factors ICAM-1 And HMGB1 At The Posttranscriptional Level

The acute respiratory distress syndrome (ARDS) is a common clinical critical disease which is lack of effective therapies. Several clinical disorders including sever infection, major trauma and etc. can increase ICAM-1 and HMGB1. the key initiation factors of ARDS, release heavily and then activate the cytokine storm. However, the regulatory mechanism of ICAM-1 and HMGB1 is still unknown. Intercellular adhesion molecule-1 (ICAM-1) plays an important role in the endothelium-neutrophil interaction and the accumulation of neutrophils in the lung, which results in the typical pathophysiology of ARDS, inclduing disruption of the endothelial-epithelial barrier and neutrophil-mediated lung tissue injury. High-mobility group box protein 1 (HMGB1), a recently identified proinflammatory cytokine, was found to be significantly higher in the serum with ARDS.RNA binding protein(RBP) and microRNA are two ways to regulate inflammatory cytokine expression at a posttranscriptional level. HuR, a typical RBP, plays an important role in a coherent set of cellular functions by influencing the processing, localization, translation, and stability of mRNAs. With three RNA recognition motifs (RRMs), HuR regulates its target mRNAs through binding ARE in the 5’and 3’untranslated regrions (UTRs).Both of ICAM-1 and HMGB1 have ARE in their 3’ untranslated regrions (UTRs).MoreoverBased on our previous. researches, we found that microRNA expression profiles significantly changed in the peripheral blood of patients who were suffering from ARDS caused by different factors. Further bioinformatics predictions and pre-experiments showed that miR-890 and HuR known as an RNA-binding protein could both bind to HMGB1 mRNA and regulate its expression, but yet the precise mechanism and effects on ARDS still remained to be studied. Considering literatures and preliminary experiment results, we propose that HuR and miR-890 compete for the binding site on HMGB1 mRNA to determine the expression level of HMGB1, and then influence the occurrence of ARDS. In the subject, we would like to use PCR, adenovirus transfection. RNA interference, immunofluorescence and other means on cell lines to illustrate the regulatory mechanism of HuR and miR-890 on the expression of ICAM-1 and HMGB1. We anticipate that it may provide a general target of prevention and treatment for ARDS caused by different inducements.Chapter 1 The mechanism of HuR regulate the inflammatory factors ICAM-1 at the posttranscriptional levelAcute respiratory distress syndrome (ARDS) usually displays a serious response to various forms of injuries or acute infection to the lung. Intercellular adhesion molecule-1 (ICAM-1) plays an important role in the endothelium-neutrophil interaction and the accumulation of neutrophils in the lung, which results in the typical pathophysiology of ARDS, inclduing disruption of the endothelial-epithelial barrier and neutrophil-mediated lung tissue injury. Previous studies have shown that the p38MAPK pathway regulates tumor necrosis factor-α (TNF-α)-induced expression of ICAM-1; however, the precise mechanism is not fully understood. Here, we report that the p38MAPK signaling pathway promotes ICAM-1 mRNA expression and stability in TNF-α-activated human pulmonary microvascular endothelial cells (HPMECs) and augments neutrophil adhesion via p38MAPK-activated protein kinase 2 (MK2)-mediated intracellular localization of human antigen R (HuR). RNA-chromatin immunoprecipitation (ChIP) and RNA-electrophoresis mobility shift assay (EMSA) assays showed that HuR bound to the AU-rich elements (AREs) of ICAM-1 mRNA in vitro and was co-immunoprecipitated with intracellular ICAM-1 mRNAs. Moreover, ectopic overexpression of HuR lead to stabilization of ICAM-1 mRNAs, and increased ICAM-1 protein levels and neutrophil adhesion following TNF-α stimulation of HPMECs. In addition, ectopic overexpression of MK2 significantly elevated the cytoplasmic accumulation of HuR but did not alter the mRNA and protein levels of HuR in HPMECs after TNF-α stimulation. Our results indicated that p38MAPK-MK2 signaling promoted the cytoplasmic accumulation of HuR, which in turn enhanced ICAM-1 expression via binding and stabilizing ICAM-1 mRNA, thereby promoting neutrophil adhesion to the endothelium. Our findings suggest that targeting the p38MAPK-MK2-HuR signaling axis might be a promising strategy for the treatment of ARDS.Chapter 2 The mechanism of miR-890 regulate the inflammatory factors HMGB1 at the posttranscriptional levelAcute respiratory distress syndrome (ARDS) usually displays a serious response to various forms of injuries or acute infection to the lung. Intercellular adhesion molecule-1 (ICAM-1) plays an important role in the endothelium-neutrophil interaction and the accumulation of neutrophils in the lung, which results in the typical pathophysiology of ARDS, inclduing disruption of the endothelial-epithelial barrier and neutrophil-mediated lung tissue injury. Based on our previous researches, we found that microRNA expression profiles significantly changed in the peripheral blood of patients who were suffering from ARDS caused by different factors. Further bioinformatics predictions and pre-experiments showed that miR-890 and HuR known as an RNA-binding protein could both bind to HMGB1 mRNA and regulate its expression, but yet the precise mechanism and effects on ARDS still remained to be studied. Considering literatures and preliminary experiment results, we propose that HuR and miR-890 compete for the binding site on HMGB1 mRNA to determine the expression level of HMGB1, and then influence the occurrence of ARDS. In the subject, we would like to use PCR, adenovirus transfection, RNA interference, immunofluorescence and other means on cell lines to illustrate the competitive regulatory mechanism of HuR and miR-890 on the expression of HMGB1. We anticipate that it may provide a general target of prevention and treatment for ARDS caused by different inducements.