Identification and Characterization of Rat RhoA Gene Promoter

Pathogenesis of allergic diseases and implications for therapeutic interventions

Allergic diseases such as allergic rhinitis (AR), allergic asthma (AAS), atopic dermatitis (AD), food allergy (FA), and eczema are systemic diseases caused by an impaired immune system. Accompanied by high recurrence rates, the steadily rising incidence rates of these diseases are attracting increasing attention. The pathogenesis of allergic diseases is complex and involves many factors, including maternal-fetal environment, living environment, genetics, epigenetics, and the body's immune status. The pathogenesis of allergic diseases exhibits a marked heterogeneity, with phenotype and endotype defining visible features and associated molecular mechanisms, respectively. With the rapid development of immunology, molecular biology, and biotechnology, many new biological drugs have been designed for the treatment of allergic diseases, including anti-immunoglobulin E (IgE), anti-interleukin (IL)-5, and anti-thymic stromal lymphopoietin (TSLP)/IL-4, to control symptoms. For doctors and scientists, it is becoming more and more important to understand the influencing factors, pathogenesis, and treatment progress of allergic diseases. This review aimed to assess the epidemiology, pathogenesis, and therapeutic interventions of allergic diseases, including AR, AAS, AD, and FA. We hope to help doctors and scientists understand allergic diseases systematically.

Rho-kinase inhibitor attenuates airway mucus hypersecretion and inflammation partly by downregulation of IL-13 and the JNK1/2-AP1 signaling pathway

We measured the effect of Rho-kinase on inflammation and mucus hypersecretion in the airways of mouse models of asthma. Additionally, we aimed to determine if these effects were the result of JNK 1/2-AP1 pathway inhibition.We sensitized and challenged female C57BL/6 mice using house dust mites (HDM) followed by treatment with an inhibitor of Rho-kinase. Lung tissue was harvested to evaluate inflammation and mucus secretion in the airways of asthma mice. Cytokine expression in broncho-alveolar lavage fluid (BALF) was established by ELISA and airway responsiveness, and was determined by the invasive lung function test. JNK1/2, p-JNK1/2, AP-1, and p-AP-1 protein expression was determined by Western blot analysis. Asthma model mice that were treated with Rho-kinase inhibitor showed a significantly decrease in inflammation score, inflammatory cells, and airway responsiveness. Additionally, we found that IL-13 expressions in BALF and mucus secretion were decreased in HDM-challenged mice treated with Rho-kinase inhibitor. Furthermore, Rho-kinase inhibitor treatment decreased the expression of JNK1/2 and AP-1 phosphorylation. Our findings indicated that the Rho-kinase inhibitor decreased HDM-induced mucus secretion as well as airway inflammation in asthma mice through regulation of the JNK1/2-AP-1 pathway.

Transcriptional and post-transcriptional regulation of the genes encoding the small GTPases RhoA, RhoB, and RhoC: implications for the pathogenesis of human diseases

Rho GTPases are highly conserved proteins that play critical roles in many cellular processes including actin dynamics, vesicular trafficking, gene transcription, cell-cycle progression, and cell adhesion. The main mode of regulation of Rho GTPases is through guanine nucleotide binding (cycling between an active GTP-bound form and an inactive GDP-bound form), but transcriptional, post-transcriptional, and post-translational modes of Rho regulation have also been described. In the present review, we summarize recent progress on the mechanisms that control the expression of the three members of the Rho-like subfamily (RhoA, RhoB, and RhoC) at the level of gene transcription as well as their post-transcriptional regulation by microRNAs. We also discuss the progress made in deciphering the mechanisms of cross-talk between Rho proteins and the transforming growth factor β signaling pathway and their implications for the pathogenesis of human diseases such as cancer metastasis and fibrosis.

Functional analysis of the promoters of the small GTPases RhoA and RhoB in embryonic stem cells

Small GTPases of the Rho subfamily have been implicated in many physiological and pathological processes in various cell types including embryonic stem cells (ESCs). In the present study we performed a functional analysis of the promoters of the RhoA and the RhoB genes in order to identify regulatory elements that are important for their transcriptional control in ESCs. We show that RhoA mRNA levels were significantly higher compared with the RhoB mRNA levels in ESCs as well in various cancer cell lines and this difference could be accounted for by differences in the activities of the corresponding promoters. Deletion analysis of the RhoA and RhoB promoters in ESCs revealed that the proximal regions contain regulatory elements that are critical for their activity. Both proximal promoters contain CCAAT boxes and mutagenesis of these elements decreased significantly the activity of both promoters suggesting a coordinated regulation of the two genes by CCAAT box binding factors. Finally, we show that both genes are subjects to autoregulation in ESCs and in the case of RhoB, this autoregulation requires the GTPase activity of the Rho proteins. Understanding the mechanisms that control the transcription of Rho GTPases in ESCs may shed new light into the still unknown roles of these proteins in stem cell functions.

Rho-kinase inhibitor fasudil reduces allergic airway inflammation and mucus hypersecretion by regulating STAT6 and NFκB

BACKGROUND

Airway mucus hypersecretion is a key pathophysiological feature in asthma. Fasudil, a selective Rho-A/Rho kinase inhibitor, has been used in clinical trials to treat pulmonary hypertension. However, its function in modulating airway mucus hypersecretion in asthma remains undefined.

OBJECTIVE

We examined whether fasudil, a selective Rho-A/Rho kinase inhibitor, affects the mucus hypersecretion by suppressing MUC5AC via signal transducer and activator of transcription factor 6 (STAT6) and nuclear factor-kappa B (NFκB) in mice and cells.

METHODS

We measured mucus secretion and the expression of Rho-kinase in the airway tissue of patients with asthma. BALB/c mice were sensitized and challenged with ovalbumin (OVA) followed with fasudil treatment. The lung tissues were assessed for airway inflammation and mucus secretion. Cytokine levels and airway responsiveness were determined. STAT6 and NFκB were quantified by Western blot. 16HBE cells were stimulated with house dust mite (HDM) extracts. MUC5AC and muc5ac promoter activities were measured. Using siRNA to knockdown STAT6 in epithelial cells, we determined the impact of STAT6 on muc5ac promoter activity. NFκB nuclear translocation was observed with immunostaining.

RESULTS

Fasudil administration significantly decreased the number of inflammatory cells, inflammation index in the lung and airway responsiveness. Fasudil also reduced mucous secretion and MUC5AC expression in OVA-challenged mice. Fasudil down-regulated the levels of IL-17, IL-4 and IL-13 in the lung tissue of OVA-challenged mice. Fasudil also decreased the expression and phosphorylation of NFκB and STAT6 as well as the nuclear translocation of NFκB. In addition, human airway epithelial cells (16HBE) were challenged with HDM extracts and then treated with fasudil. Fasudil inhibited HDM extract-induced MUC5AC expression, which is associated with a reduction in STAT6 and NFκB in epithelial cells.

CONCLUSIONS AND CLINICAL RELEVANCE

These findings indicate that the Rho-A/Rho kinase inhibitor, fasudil, plays a negative regulatory role in allergen-induced mucus secretion and MUC5AC expression by regulating STAT6 and NFκB.

Janus kinase 1/3 signaling pathways are key initiators of TH2 differentiation and lung allergic responses

BACKGROUND

Janus kinases (JAKs) are regulators of signaling through cytokine receptors. The importance of JAK1/3 signaling on TH2 differentiation and development of lung allergic responses has not been investigated.

OBJECTIVE

We sought to examine a selective JAK1/3 inhibitor (R256) on differentiation of TH subsets in vitro and on development of ovalbumin (OVA)-induced airway hyperresponsiveness (AHR) and inflammation in an experimental model of asthma.

METHODS

A selective JAK1/3 inhibitor was used to assay the importance of this pathway on induction of TH1, TH2, and TH17 differentiation in vitro. In vivo, the effects of inhibiting JAK1/3 signaling were examined by administering the inhibitor during the sensitization or allergen challenge phases in the primary challenge model or just before provocative challenge in the secondary challenge model. Airway inflammation and AHR were examined after the last airway challenge.

RESULTS

In vitro, R256 inhibited differentiation of TH2 but not TH1 or TH17 cells, which was associated with downregulation of signal transducer and activator of transcription (STAT) 6 and STAT5 phosphorylation. However, once polarized, TH2 cells were unaffected by the inhibitor. In vivo, R256 administered during the OVA sensitization phase prevented the development of AHR, airway eosinophilia, mucus hypersecretion, and TH2 cytokine production without changes in TH1 and TH17 cytokine levels, indicating that selective blockade of TH2 differentiation was critical. Inhibitor administration after OVA sensitization but during the challenge phases in the primary or secondary challenge models similarly suppressed AHR, airway eosinophilia, and mucus hypersecretion without any reduction in TH2 cytokine production, suggesting the inhibitory effects were downstream of TH2 cytokine receptor signaling pathways.

CONCLUSIONS

Targeting the TH2-dependent JAK/STAT activation pathway represents a novel therapeutic approach for the treatment of asthma.

Signal transducer and activator of transcription 6 directly regulates human ORMDL3 expression

Orosomucoid-like 3 (ORMDL3) has been associated with asthma and a series of autoimmune disorders, and is involved in endoplasmic reticulum-mediated inflammatory responses. However, its clinical significance and the molecular mechanism underlying its expression are still largely unclear. To elucidate the mechanisms of human ORMDL3 transcriptional regulation, we cloned a 1.5 kb genomic DNA fragment containing the putative promoter region and evaluated its transcriptional activity in a luciferase reporter system by deletion analysis. We identified a 68 bp region that functions as a minimal promoter. Bioinformatics analysis predicted that the -64 to -56 bp region contained a signal transducer and activator of transcription 6 (STAT6) binding site. Electrophoretic mobility shift assay and chromatin immunoprecipitation demonstrated that STAT6 bound to its binding site within the ORMDL3 promoter. STAT6 over-expression or knockdown trans-activated or trans-inhibited, respectively, the ORMDL3 promoter containing the STAT6-binding motif. Treatment with interleukins 4 or 13 increased ORMDL3 promoter activity as well as endogenous ORMDL3 expression. Immunoprecipitation and ChIP/Re-ChIP assays revealed that STAT6 and p300 exist in the same protein complex that binds to the ORMDL3 promoter. Our study confirmed that STAT6 plays important roles in regulating the expression of human ORMDL3 by directly binding to the promoter region, which may shed light on a possible role in various human diseases.

RhoA, a possible target for treatment of airway hyperresponsiveness in bronchial asthma

Airway hyperresponsiveness to nonspecific stimuli is one of the characteristic features of allergic bronchial asthma. An elevated contractility of bronchial smooth muscle has been considered as one of the causes of the airway hyperresponsiveness. The contraction of smooth muscles including airway smooth muscles is mediated by both Ca²+-dependent and Ca²+-independent pathways. The latter Ca²+-independent pathway, termed Ca²+ sensitization, is mainly regulated by a monomeric GTP-binding protein, RhoA, and its downstream target Rho-kinase. In animal models of allergic bronchial asthma, an augmented agonist-induced, RhoA-mediated contraction of bronchial smooth muscle has been suggested. The RhoA/Rho-kinase signaling is now proposed as a novel target for the treatment of airway hyperresponsiveness in asthma. Herein, we will discuss the mechanism of development of bronchial smooth muscle hyperresponsiveness, one of the causes of the airway hyperresponsiveness, based on the recent studies using animal models of allergic bronchial asthma and/or cultured airway smooth muscle cells. The possibility of RhoA as a therapeutic target in asthma, especially airway hyperresponsiveness, will also be described.