Activation Of RhoA Signaling Pathways Research Articles

Epigenetic silencing of microRNA-125b-5p promotes liver fibrosis in nonalcoholic fatty liver disease via integrin α8-mediated activation of RhoA signaling pathway

BackgroundNonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases that may progress to liver fibrosis or cancer. The present study aimed to investigate the role of microRNA-125b-5p (miR-125b-5p) in NAFLD and to further explore underlying molecular mechanisms. MethodsA mouse model of NAFLD was constructed by high cholesterol diet feeding and a cell-model was developed by treating the mouse liver cell line NCTC1469 with palmitic acid. Gain- and loss-of-function experiments were performed to determine the effects of miR-125b-5p, integrin α8 (ITGA8), and the RhoA signaling pathway on liver fibrosis in NAFLD. After the expression levels of miR-125b-5p, ITGA8, and RhoA were determined, liver fibrosis was evaluated in vivo and in vitro. The binding relationship of miR-125b-5p and ITGA8 was then validated. Finally, miR-125b-5p promoter methylation in NAFLD liver tissues and cells was determined. ResultsIn NAFLD clinical samples, mouse model, and cell-model, miR-125b-5p expression was reduced, while ITGA8 expression was increased. Moreover, miR-125b-5p targeted and downregulated ITGA8, leading to inhibition of the RhoA signaling pathway. In NAFLD liver tissues and cells, the CpG island in the miR-125b-5p promoter was methylated, causing epigenetic silencing of miR-125b-5p. Both miR-125b-5p silencing and ITGA8 overexpression promoted in vitro and in vivo liver fibrosis in NAFLD via activation of the RhoA signaling pathway. ConclusionsCollectively, epigenetic silencing of miR-125b-5p upregulates ITGA8 expression to activate the RhoA signaling pathway, leading to liver fibrosis in NAFLD.

Meningitic Escherichia coli Induction of ANGPTL4 in Brain Microvascular Endothelial Cells Contributes to Blood-Brain Barrier Disruption via ARHGAP5/RhoA/MYL5 Signaling Cascade.

Bacterial meningitis is currently recognized as one of the most important life-threatening infections of the central nervous system (CNS) with high morbidity and mortality, despite the advancements in antimicrobial treatment. The disruption of blood–brain barrier (BBB) induced by meningitis bacteria is crucial for the development of bacterial meningitis. However, the complete mechanisms involving in the BBB disruption remain to be elucidated. Here, we found meningitic Escherichia coli induction of angiopoietin-like 4 (ANGPTL4) in brain microvascular endothelial cells (BMECs) contributes to BBB disruption via ARHGAP5/RhoA/MYL5 signaling cascade, by the demonstration that ANGPTL4 was significantly upregulated in meningitis E. coli infection of BMECs as well as mice, and treatment of the recombinant ANGPTL4 protein led to an increased permeability of the BBB in vitro and in vivo. Moreover, we found that ANGPTL4 did not affect the expression of tight junction proteins involved in BBB disruption, but it increased the expression of MYL5, which was found to have a negative role on the regulation of barrier function during meningitic E. coli infection, through the activation of RhoA signaling pathway. To our knowledge, this is the first report demonstrating the disruption of BBB induced by ANGPTL4 through the ARHGAP5/RhoA/MYL5 pathway, which largely supports the involvement of ANGPTL4 during meningitic E. coli invasion and further expands the theoretical basis for the mechanism of bacterial meningitis.

Ginsenoside Rb1 protects against ischemia/reperfusion‐induced myocardial injury via energy metabolism regulation mediated by RhoA signaling pathway

Cardiac ischemia and reperfusion (I/R) injury remains a challenge for clinicians. Ginsenoside Rb1 (Rb1) has been reported to have the ability to attenuate I/R injury, but its effect on energy metabolism during cardiac I/R and the underlying mechanism remain unknown. In this study, we detected the effect of Rb1 on rat myocardial blood flow, myocardial infarct size, cardiac function, velocity of venule red blood cell, myocardial structure and apoptosis, energy metabolism and change in RhoA signaling pathway during cardiac I/R injury. In addition, the binding affinity of RhoA to Rb1 was detected using surface plasmon resonance (SPR). Results showed that Rb1 treatment at 5 mg/kg/h protected all the cardiac injuries induced by I/R, including damaged myocardial structure, decrease in myocardial blood flow, impaired heart function and microcirculation, cardiomyocyte apoptosis, myocardial infarction and release of myocardial cTnI. Rb1 also inhibited the activation of RhoA signaling pathway and restored the production of ATP during cardiac I/R. Moreover, SPR assay showed that Rb1 was able to bind to RhoA in a dose‐dependent manner. These results indicate that Rb1 may prevent I/R‐induced cardiac injury by regulation of RhoA signaling pathway, and may serve as a potential regime to improve percutaneous coronary intervention outcome.Support or Funding InformationAPS

Ginsenoside Rb1 protects against ischemia/reperfusion-induced myocardial injury via energy metabolism regulation mediated by RhoA signaling pathway

Cardiac ischemia and reperfusion (I/R) injury remains a challenge for clinicians. Ginsenoside Rb1 (Rb1) has been reported to have the ability to attenuate I/R injury, but its effect on energy metabolism during cardiac I/R and the underlying mechanism remain unknown. In this study, we detected the effect of Rb1 on rat myocardial blood flow, myocardial infarct size, cardiac function, velocity of venule red blood cell, myocardial structure and apoptosis, energy metabolism and change in RhoA signaling pathway during cardiac I/R injury. In addition, the binding affinity of RhoA to Rb1 was detected using surface plasmon resonance (SPR). Results showed that Rb1 treatment at 5 mg/kg/h protected all the cardiac injuries induced by I/R, including damaged myocardial structure, decrease in myocardial blood flow, impaired heart function and microcirculation, cardiomyocyte apoptosis, myocardial infarction and release of myocardial cTnI. Rb1 also inhibited the activation of RhoA signaling pathway and restored the production of ATP during cardiac I/R. Moreover, SPR assay showed that Rb1 was able to bind to RhoA in a dose-dependent manner. These results indicate that Rb1 may prevent I/R-induced cardiac injury by regulation of RhoA signaling pathway, and may serve as a potential regime to improve percutaneous coronary intervention outcome.

Dissecting the Role of Anti-ganglioside Antibodies in Guillain-Barré Syndrome: an Animal Model Approach.

Guillain-Barré syndrome (GBS) is an autoimmune polyneuropathy disease affecting the peripheral nervous system (PNS). Most of the GBS patients experienced neurological symptoms such as paresthesia, weakness, pain, and areflexia. There are also combinations of non-neurological symptoms which include upper respiratory tract infection and diarrhea. One of the major causes of GBS is due largely to the autoantibodies against gangliosides located on the peripheral nerves. Gangliosides are sialic acid-bearing glycosphingolipids consisting of a ceramide lipid anchor with one or more sialic acids attached to a neutral sugar backbone. Molecular mimicry between the outer components of oligosaccharide of gangliosides on nerve membrane and lipo-oligosaccharide of microbes is thought to trigger the autoimmunity. Intra-peritoneal implantation of monoclonal ganglioside antibodies secreting hybridoma into animals induced peripheral neuropathy. Recent studies demonstrated that injection of synthesized anti-ganglioside antibodies raised by hybridoma cells into mice initiates immune response against peripheral nerves, and eventually failure in peripheral nerve regeneration. Accumulating evidences indicate that the conjugation of anti-ganglioside monoclonal antibodies to activating FcγRIII present on the circulating macrophages inhibits axonal regeneration. The activation of RhoA signaling pathways is also involved in neurite outgrowth inhibition. However, the link between these two molecular events remains unresolved and requires further investigation. Development of anti-ganglioside antagonists can serve as targeted therapy for the treatment of GBS and will open a new approach of drug development with maximum efficacy and specificity.

Myelin-associated glycoprotein modulates apoptosis of motoneurons during early postnatal development via NgR/p75(NTR) receptor-mediated activation of RhoA signaling pathways.

Myelin-associated glycoprotein (MAG) is a minor constituent of nervous system myelin, selectively expressed on the periaxonal myelin wrap. By engaging multiple axonal receptors, including Nogo-receptors (NgRs), MAG exerts a nurturing and protective effect the axons it ensheaths. Pharmacological activation of NgRs has a modulatory role on p75NTR-dependent postnatal apoptosis of motoneurons (MNs). However, it is not clear whether this reflects a physiological role of NgRs in MN development. NgRs are part of a multimeric receptor complex, which includes p75NTR, Lingo-1 and gangliosides. Upon ligand binding, this multimeric complex activates RhoA/ROCK signaling in a p75NTR-dependent manner. The aim of this study was to analyze a possible modulatory role of MAG on MN apoptosis during postnatal development. A time course study showed that Mag-null mice suffer a loss of MNs during the first postnatal week. Also, these mice exhibited increased susceptibility in an animal model of p75NTR-dependent MN apoptosis induced by nerve-crush injury, which was prevented by treatment with a soluble form of MAG (MAG-Fc). The protective role of MAG was confirmed in in vitro models of p75NTR-dependent MN apoptosis using the MN1 cell line and primary cultures. Lentiviral expression of shRNA sequences targeting NgRs on these cells abolished protection by MAG-Fc. Analysis of RhoA activity using a FRET-based RhoA biosensor showed that MAG-Fc activates RhoA. Pharmacological inhibition of p75NTR/RhoA/ROCK pathway, or overexpression of a p75NTR mutant unable to activate RhoA, completely blocked MAG-Fc protection against apoptosis. The role of RhoA/ROCK signaling was further confirmed in the nerve-crush model, where pretreatment with ROCK inhibitor Y-27632 blocked the pro-survival effect of MAG-Fc. These findings identify a new protective role of MAG as a modulator of apoptosis of MNs during postnatal development by a mechanism involving the p75NTR/RhoA/ROCK signaling pathway. Also, our results highlight the relevance of the nurture/protective effects of myelin on neurons.

The Interaction of Adrenomedullin and Macrophages Induces Ovarian Cancer Cell Migration via Activation of RhoA Signaling Pathway

Tumor-associated macrophages (TAMs) are correlated with poor prognosis in many human cancers; however, the mechanism by which TAMs facilitate ovarian cancer cell migration and invasion remains unknown. This study was aimed to examine the function of adrenomedullin (ADM) in macrophage polarization and their further effects on the migration of ovarian cancer cells. Exogenous ADM antagonist and small interfering RNA (siRNA) specific for ADM expression were treated to macrophages and EOC cell line HO8910, respectively. Then macrophages were cocultured with HO8910 cells without direct contact. Flow cytometry, Western blot and real-time PCR were used to detect macrophage phenotype and cytokine production. The migration ability and cytoskeleton rearrangement of ovarian cancer cells were determined by Transwell migration assay and phalloidin staining. Western blot was performed to evaluate the activity status of signaling molecules in the process of ovarian cancer cell migration. The results showed that ADM induced macrophage phenotype and cytokine production similar to TAMs. Macrophages polarized by ADM promoted the migration and cytoskeleton rearrangement of HO8910 cells. The expression of RhoA and its downstream effector, cofilin, were upregulated in macrophage-induced migration of HO8910 cells. In conclusion, ADM could polarize macrophages similar to TAMs, and then polarized macrophages promote the migration of ovarian cancer cells via activation of RhoA signaling pathway in vitro.