Ok Hee Chai

PPAR-gamma modulates allergic inflammation through up-regulation of PTEN

The ligand‐activated nuclear receptor peroxisome proliferator‐activated receptor γ (PPARγ) has been shown to regulate cell activation, differentiation, proliferation, and/or apoptosis. PPARγ is also associated with anti‐inflammatory responses. However, the signaling mechanism remains elusive. We have used a mouse model for asthma to determine the effect of PPARγ agonists, rosiglitazone or pioglitazone, and PPARγ on allergen‐induced bronchial inflammation and airway hyperresponsiveness. Administration of PPARγ agonists or adenovirus carrying PPARγ cDNA (AdPPARγ) reduced bronchial inflammation and airway hyperresponsiveness. Expression of PPARγ was increased by ovalbumin (OVA) inhalation, and the increase was further enhanced by the administration of the PPARγ agonists or AdPPARγ. Levels of IL‐4, IL‐5, IL‐13, and eosinophil cationic protein were increased after OVA inhalation, and the increased levels were significantly reduced by the administration of PPARγ agonists or AdPPARγ. The results also showed that the administration of PPARγ agonists or AdPPARγ up‐regulated phosphatase and tensin homologue deleted on chromosome ten (PTEN) expression in allergen‐induced asthmatic lungs. This up‐regulation correlated with decreased phosphatidylinositol 3‐kinase activity as measured by reduced phosphorylation of Akt. These findings demonstrate a protective role of PPARγ in the pathogenesis of the asthma phenotype through regulation of PTEN expression.

Mast Cells Can Mediate Vascular Permeability through Regulation of the PI3K–HIF-1α–VEGF Axis

RATIONALE Bronchial inflammation is usually accompanied by increased vascular permeability. Mast cells release a number of mediators that act directly on the vasculature, resulting in vasodilatation, increased permeability, and subsequent plasma protein extravasation. Vascular endothelial growth factor (VEGF) has been implicated to contribute to asthmatic tissue edema through its effect on vascular permeability. However, the effects of mast cells on VEGF-mediated signaling in allergic airway disease are not clearly understood. OBJECTIVES An aim of the present study was to investigate the role of mast cells on VEGF-mediated signal transduction in allergic airway disease. METHODS We used genetically mast cell-deficient WBB6F(1)-Kit(W)/Kit(W-v) (W/W(v)) mice and the congenic normal WBB6F(1)(+/+) mouse model for allergic airway disease to investigate the role of mast cells on VEGF-mediated signal transduction in allergic airway disease, more specifically in vascular permeability. MEASUREMENTS AND MAIN RESULTS Our present study, with ovalbumin (OVA)-sensitized without adjuvant and OVA-challenged mice, revealed the following typical pathophysiologic features of allergic airway diseases: increased inflammatory cells of the airways, airway hyperresponsiveness, increased vascular permeability, and increased levels of VEGF. However, levels of VEGF and plasma exudation in W/W(v) mice after OVA inhalation were significantly lower than levels in WBB6F(1)(+/+) mice. Moreover, mast cell-reconstituted W/W(v) mice restored vascular permeability and VEGF levels similar to those of the WBB6F(1)(+/+) mice. Our data also showed that VEGF expression was regulated by hypoxia-inducible factor-1alpha (HIF-1alpha) activation through the phosphatidylinositol 3-kinase (PI3K)-HIF-1alpha pathway in allergic airway disease. CONCLUSIONS These results suggest that mast cells modulate vascular permeability by the regulation of the PI3K-HIF-1alpha-VEGF axis.

Inhibitory effects of curcumin on passive cutaneous anaphylactoid response and compound 48/80-induced mast cell activation

Mast cells participate in allergies and inflammation by secreting a variety of pro-inflammatory mediators. Curcumin, the active component of turmeric, is a polyphenolic phytochemical with anti-tumor, anti-inflammatory, anti-oxidative, and anti-allergic properties. The effects of curcumin on compound 48/80-induced mast cell activation and passive cutaneous anaphylactoid reactions are unknown. In this report, we investigated the influences of curcumin on the passive cutaneous anaphylactoid response in vivo and compound 48/80-induced mast cell activation in vitro. The mechanism of action was examined by calcium uptake measurements and cAMP assays in mast cells. Curcumin significantly attenuated the mast cell-mediated passive cutaneous anaphylactoid reaction in an animal model. In agreement with this in vivo activity, curcumin suppressed compound 48/80-induced rat peritoneal mast cell (RPMC) degranulation and histamine release from RPMCs. Moreover, compound 48/80-elicited calcium uptake into RPMCs was reduced in a dose-dependent manner by curcumin. Furthermore, curcumin increased the level of intracellular cAMP and significantly inhibited the compound 48/80-induced reduction of cAMP in RPMCs. These results corroborate the finding that curcumin may have anti-allergic activity.

Mast cells play a key role in Th2 cytokine-dependent asthma model through production of adhesion molecules by liberation of TNF-α

Mast cells are well recognized as key cells in allergic reactions, such as asthma and allergic airway diseases. However, the effects of mast cells and TNF-α on T-helper type 2 (Th2) cytokine-dependent asthma are not clearly understood. Therefore, an aim of this study was to investigate the role of mast cells on Th2 cytokine-dependent airway hyperresponsiveness and inflammation. We used genetically mast cell-deficient WBB6F1/J-KitW/KitW-v (W/Wv), congenic normal WBB6F1/J-Kit+/Kit+ (+/+), and mast cell-reconstituted W/Wv mouse models of allergic asthma to investigate the role of mast cells in Th2 cytokine-dependent asthma induced by ovalbumin (OVA). And we investigated whether the intratracheal injection of TNF-α directly induce the expression of ICAM-1 and VCAM-1 in W/Wv mice. This study, with OVA-sensitized and OVA-challenged mice, revealed the following typical histopathologic features of allergic diseases: increased inflammatory cells of the airway, airway hyperresponsiveness, and increased levels of TNF-α, intercellular adhesion molecule (ICAM)-1, and vascular cellular adhesion molecule (VCAM)-1. However, the histopathologic features and levels of ICAM-1 and VCAM-1 proteins in W/Wv mice after OVA challenges were significantly inhibited. Moreover, mast cell-reconstituted W/Wv mice showed restoration of histopathologic features and recovery of ICAM-1 and VCAM-1 protein levels that were similar to those found in +/+ mice. Intratracheal administration of TNF-α resulted in increased ICAM-1 and VCAM-1 protein levels in W/Wv mice. These results suggest that mast cells play a key role in a Th2 cytokine-dependent asthma model through production of adhesion molecules, including ICAM-1 and VCAM-1, by liberation of TNF-α.

Mast cells decrease renal fibrosis in unilateral ureteral obstruction

Mast cells regulate both inflammatory responses and tissue repair in human diseases but there are conflicting reports on the role of these cells in the pathogenesis of various kidney diseases. Here we measured mast cell function in unilateral ureteral obstruction, a well-characterized model of renal fibrosis, using Kit(W)/Kit(W-v) mice genetically deficient in mast cells, wild-type mice, and deficient mice reconstituted by adoptive transfer with mast cells from the wild-type animals. Mast cell-deficient mice had higher levels of renal tubular damage, more stromal fibrosis, higher numbers of infiltrating ERHR3-positive macrophages and CD3-positive T cells, and higher tissue levels of profibrotic transforming growth factor-beta1 than wild-type mice or mice reconstituted by adoptive transfer of mast cells 3 weeks after ureteral obstruction. Similarly, while wild-type and adoptively transferred mice had increased alpha-smooth muscle actin and decreased E-cadherin expression, which are indicators of epithelial-mesenchymal transition, the obstructed kidneys of the mast cell-deficient mice had significant attenuation of those indicators. Thus, our study suggests that mast cells protect the kidney against fibrosis by modulation of inflammatory cell infiltration and by transforming growth factor-beta1-driven epithelial-to-mesenchymal transitions.

Overexpression of junctate induces cardiac hypertrophy and arrhythmia via altered calcium handling

Junctate-1 is a newly identified integral endoplasmic/sarcoplasmic reticulum Ca2+ binding protein. However, its functional role in the heart is unknown. In the present study, the consequences of constitutively overexpressed junctate in cardiomyocytes were investigated using transgenic (TG) mice overexpressing junctate-1. TG mice (8 weeks old) showed cardiac remodeling such as marked bi-atrial enlargement with intra-atrial thrombus and biventricular hypertrophy. The TG mice also showed bradycardia with atrial fibrillation, reduced amplitude and elongated decay time of Ca2+ transients, increased L-type Ca2+ current and prolonged action potential durations. Time-course study (2-8 weeks) showed an initially reduced SR function due to down-regulation of SERCA2 and calsequestrin followed by sarcolemmal protein expression and cardiac hypertrophy at later age. These sequential changes could well be correlated with the physiological changes. Adrenergic agonist treatment and subsequent biochemical study showed that junctate-1 TG mice (8 weeks old) were under local PKA signaling that could cause increased L-type Ca2+ current and reduced SR function. Junctate-1 in the heart is closely linked to the homeostasis of E-C coupling proteins and a sustained increase of junctate-1 expression leads to a severe cardiac remodeling and arrhythmias.

Histamine Release Induced By Dendroaspis Natriuretic Peptide From Rat Mast Cells

Dendroaspis natriuretic peptide (DNP), recently isolated from the venom of the green Mamba snake Dendroaspis angusticeps, is a 38 amino acid peptide containing a 17 amino acid disulfide ring structure similar to that of the natriuretic peptide family. The natriuretic peptide family is known to induce histamine release from human and rat mast cells, but there are no published data concerning the effects of DNP on histamine release from mast cells. The purpose of this study is to investigate whether DNP induces the histamine release from rat peritoneal mast cells (RMPCs) and to determine the mechanism of DNP-induced histamine release from RPMCs. After treatment of RPMC with DNP, mast cell degranulation was observed, and calcium uptake and histamine release were measured. DNP released the histamine, induced the mast cell degranulation, and increased the calcium uptake of RPMCs, in a dose-dependent manner. The results indicate that DNP can increase Ca-uptake and induce histamine release.

Inhibitory effects of epigallocatechin gallate on compound 48/80-inducedmast cell activation and passive cutaneous anaphylaxis

Epigallocatechin gallate (EGCG) is a principle phenolic antioxidant found in a variety of plants, including green and black tea. The anti-allergic effect of EGCG is unknown. The purpose of this study is to investigate the effects of EGCG on compound 48/80-induced mast cell activation and passive cutaneous anaphylaxis. For this, the influences of EGCG on the compound 48/80-induced cutaneous reaction were measured in vivo and the effects of EGCG on the compound 48/80-induced mast cell activations were examined in vitro. Results are below: as 1) EGCG significantly inhibited compound 48/80-induced passive cutaneous anaphylaxis, 2) the compound 48/80-induced degranulation, calcium influx and histamine release of rat peritoneal mast cells (RPMCs) were significantly inhibited by the pretreatment with EGCG, and 3) the compound 48/80-mediated inhibition of cAMP level in RPMCs was significantly increased by the pretreatment with EGCG. These results suggested that EGCG, the most abundant polyphenol in green tea, inhibits the compound 48/80-induced mast cell activation and the increase of vascular permeability, and potentially serve as effective therapeutic tools for allergic diseases.

Atrial natriuretic peptide induces rat peritoneal mast cell activation by cGMP-independent and calcium uptake-dependent mechanism.

Atrial natriuretic peptide (ANP), a 28 amino acid basic polypeptide, is known to induce histamine release from human and rat mast cells in vitro and cause a wheel formation in rat skin. However, cellular events associated with histamine release are not clearly understood. In this study, we have examined the calcium flux and cGMP formation associated with histamine release in the ANP-treated mast cells. ANP, in vitro, induced mast cell degranulation and histamine release in a dose-dependent manner. ANP also induced an enhanced calcium uptake into cells and increased the cellular level of cGMP in mast cells. A high level of calcium in the media caused an inhibition of ANP-dependent histamine release but enhanced the level of intracellular cGMP of mast cells. ANP inducing a dose-dependent increase in vascular permeability of rat skin was confirmed by the extravasation of the circulating Evans blue. The results indicate ANP induced the histamine release and an increase in vascular permeability through mast cell degranulation in cGMP-independent and calcium uptake-dependent manner.

Effects of Anemarrhena asphodeloides on IgE-mediated passive cutaneous anaphylaxis, compound 48/80-induced systemic anaphylaxis and mast cell activation

BACKGROUND We investigated the effect of Anemarrhena asphodeloides Bunge (Liliaceae) water extract (AAWE) on mast cell-mediated anaphylactic reactions. Mast cell-mediated anaphylactic reaction is involved in many allergic diseases, including asthma and allergic rhinitis. In Korea, where it has been used as a traditional medicine, AAWE is known to have antioxidant and anticancer activity. However, its specific effect on mast cell-mediated anaphylactic reactions is still unknown. METHODS We examined whether or not AAWE could inhibit IgE-mediated passive cutaneous anaphylaxis (PCA), compound 48/80-induced systemic anaphylaxis, and mast cell activation. RESULTS Oral administration of AAWE inhibited compound 48/80-induced systemic anaphylaxis in mice. AAWE also inhibited the local allergic reaction, PCA, activated by anti-dinitrophenyl IgE antibody in rats. AAWE reduced compound 48/80-induced degranulation of rat peritoneal mast cells (RPMCs). Moreover, AAWE inhibited histamine release and calcium uptake of RPMCs induced by compound 48/80 in a dose-dependent manner. AAWE also significantly inhibited secretion of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 in phorbol 12-myristate 13-acetate plus calcium ionophores A23187-stimulated RPMCs. CONCLUSIONS These results suggest that AAWE suppresses compound 48/80-induced mast cell activation by inhibition of cellular mechanisms in signaling pathways, and would be beneficial for treatment of mast cell-mediated anaphylactic response.