Proteinase-activated receptor-2 blockade inhibits changes seen in a chronic murine asthma model

BACKGROUND

Proteinase-Activated Receptor-2 (PAR₂ ) is a G protein-coupled receptor activated by serine proteinases. We have shown that PAR₂ activation in the airways is involved in the development of allergic inflammation and airway hyperresponsiveness (AHR) in acute murine models. We hypothesized that functional inhibition of PAR₂ prevents allergic inflammation, AHR and airway remodeling in chronic allergic airway inflammation models.

MATERIAL AND METHODS

We developed and used a 12 week model of cockroach extract (CE)-mediated AHR, airway inflammation and remodeling in BALB/c mice.

RESULTS

Mice sensitized and challenged with CE for 12 weeks exhibit AHR, increased numbers of eosinophils in bronchoalveolar lavage (BAL) and increased collagen content in the lung tissue compared to saline controls. Administration of an anti-PAR₂ antibody, SAM-11, after the initial development of airway inflammation significantly inhibited all these parameters.

CONCLUSIONS

Our data demonstrate that PAR₂ signaling plays a key role in CE-induced AHR and airway inflammation/remodeling in long term models of allergic airway inflammation. Targeting PAR₂ activation may be a successful therapeutic strategy for allergic asthma.

Functional inhibition of PAR2 alleviates allergen-induced airway hyperresponsiveness and inflammation

BACKGROUND

Proteinase-activated receptor 2 (PAR2 ) is a G protein-coupled receptor activated by trypsin-like serine proteinases. PAR2 activation has been associated with inflammation including allergic airway inflammation. We have also shown that PAR2 activation in the airways leads to allergic sensitization. The exact contribution of PAR2 in the development of eosinophilic inflammation and airway hyperresponsiveness (AHR) in sensitized individuals is not clear.

OBJECTIVE

To investigate whether functional inhibition of PAR2 during allergen challenge of allergic mice would inhibit allergen-induced AHR and inflammation in mouse models of asthma.

METHODS

Mice were sensitized and challenged with ovalbumin (OVA) or cockroach extract (CE). To investigate the role of PAR2 in the development of AHR and airway inflammation, we administered blocking anti-PAR2 antibodies, or a cell permeable peptide inhibitor of PAR2 signalling, pepducin, i.n. before allergen challenges and then assessed AHR and airway inflammation.

RESULTS

Administration of anti-PAR2 antibodies significantly inhibited OVA- and CE-induced AHR and airway inflammation. In particular, two anti-PAR2 antibodies, the monoclonal SAM-11 and polyclonal B5, inhibited AHR, airway eosinophilia, the increase of cytokines in the lung tissue and antigen-specific T cell proliferation, but had no effect on antigen-specific IgG and IgE levels. Pepducin was also effective in inhibiting AHR and airway inflammation in an OVA model of allergic airway inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE

Functional blockade of PAR2 in the airways during allergen challenge improves allergen-induced AHR and inflammation in mice. Therefore, topical PAR2 blockade in the airways, through anti-PAR2 antibodies or molecules that interrupt PAR2 signalling, has the potential to be used as a therapeutic option in allergic asthma.

Bronchial anthracofibrosis and tuberculosis in immigrants to Canada from the Indian subcontinent

BACKGROUND

Bronchial anthracofibrosis is a condition of proximal airway narrowing or obliteration and hyperpigmentation in persons with or without a history of occupational dust exposure. It is a bronchoscopic finding that is not uncommonly associated with pulmonary tuberculosis (PTB) in residents of South Korea, Iran and India. It is largely unrecognized in the Western world.

METHODS

We report the frequency of anthracofibrosis in foreign-born PTB patients who underwent bronchoscopy in two cities of Canada. We describe the composition of the pigment in the lungs of patients and speculate on the pathogenesis of anthracofibrosis-associated PTB.

RESULTS

Anthracofibrosis was present in 10/60 (16.7%) foreign-born patients who underwent bronchoscopy and had PTB between 2002 and 2006. Compared to patients from other Asian countries, patients from the Indian subcontinent were more likely to have anthracofibrosis (9/18, 50.0% vs. 1/26, 3.7%, P < 0.001). Carbonaceous particles, silica and silicates predominated in tissue specimens. Proximal airway narrowing appeared to be secondary to mixed dust- and smoke-related anthracofibrosis, PTB, or both.

CONCLUSIONS

Anthracofibrosis is not uncommon in immigrants to Canada from the Indian subcontinent with PTB. PTB may be a responsible or complicating condition in patients with anthracofibrosis.

Tryptophan catabolites regulate mucosal sensitization to ovalbumin in respiratory airways

BACKGROUND

Indoleamine 2,3 dioxygenase (IDO), the rate-limiting enzyme in tryptophan catabolism, is important in generating tolerance at the foetal-maternal interface. Studies using 1-methyl-tryptophan (1-MT), the specific inhibitor of IDO, showed that this enzyme is important in interferon-gamma (IFN-gamma)-dependent inhibition of allergic inflammation in the respiratory airway during immunotherapy.

AIMS OF STUDY

We investigated the role of IDO in the development of allergic sensitization, leading to allergic inflammation and airway hyper-responsiveness (AHR).

METHODS

We used a mouse model to generate mucosal tolerance to lipopolysaccharide-free ovalbumin (OVA) following repeated intranasal inoculation of OVA over a 3-day period. We tested the successful induction of tolerance by subsequent intraperitoneal (i.p.) sensitization followed by intranasal challenge with OVA. A slow-release pellet of 1-MT implanted into mice was used to block IDO activity prior to repeated intranasal inoculation of OVA. We measured T-cell proliferation in response to OVA, determined airway inflammation, and measured AHR to intranasal methacholine to investigate the role of IDO in sensitization to OVA.

RESULTS

Repeated intranasal administration of OVA generated tolerance and prevented a subsequent sensitization to OVA via the i.p. route. This response was inhibited in mice receiving a slow-release pellet of 1-MT. However, we successfully reconstituted tolerance in mice receiving 1-MT following intra-peritoneal injection of a mixture of kynurenine and hydroxyanthranilic acid.

CONCLUSION

Our data suggest that, in addition to their role in IFN-gamma-mediated inhibition of allergic airway inflammation, products of tryptophan catabolism play an important role in the prevention of sensitization to potential allergens in the respiratory airway.

Gene transfer and metabolic modulators as new therapies for pulmonary hypertension. Increasing expression and activity of potassium channels in rat and human models

Chronic Hypoxic Pulmonary Hypertension (CH-PHT) is characterized by pulmonary artery (PA) vasoconstriction and cell proliferation/hypertrophy. PA smooth muscle cell (PASMC) contractility and proliferation are controlled by cytosolic Ca++ levels, which are largely determined by membrane potential (E(M)). E(M) is depolarized in CH-PHT due to decreased expression and functional inhibition of several redox-regulated, 4-aminopyridine (4-AP) sensitive, voltage-gated K+ channels (Kv1.5 and Kv2.1). Humans with Pulmonary Arterial Hypertension (PAH) also have decreased PASMC expression of Kv1.5 and Kv2.1. We speculate this "K+-channelopathy" contributes to PASMC depolarization and Ca++ overload thus promoting vasoconstriction and PASMC proliferation. We hypothesized that restoration of Kv channel expression in PHT and might eventually be beneficial.

METHODS

Two strategies were used to increase Kv channel expression in PASMCs: oral administration of a metabolic modulator drug (Dichloroacetate, DCA) and direct Kv gene transfer using an adenovirus (Ad5-Kv2.1). DCA a pyruvate dehydrogenase kinase inhibitor, promotes a more oxidized redox state mimicking normoxia and previously has been noted to increase K+ current in myocytes. Rats were given DCA in the drinking water after the development of CH-PHT and hemodynamics were measured approximately 5 days later. We also tested the ability of Ad5-Kv2.1 to increase Kv2.1 channel expression and function in human PAs ex vivo.

RESULTS

The DCA-treated rats had decreased PVR, RVH and PA remodeling compared to the control CH-PHT rats (n=5/group, p<0.05). DCA restored Kv2.1 expression and PASMC Kv current density to near normoxic levels. Adenoviral gene transfer increased expression of Kv2.1 channels and enhanced 4-AP constriction in human PAs.

CONCLUSION

Increasing Kv channel function in PAs is feasible and might be beneficial.

Medical versus surgical treatment of a primary tuberculous pleural peel

The role and timing of surgical decortication in the management of a primary tuberculous pleural peel remains controversial. The present report describes the case of a young man with an extensive primary tuberculous pleural peel that responded dramatically to medical therapy. A serious attempt at surgical decortication three weeks into antituberculous drug therapy may have removed some compressive aspects of the peel, facilitating lung expansion. However, it had almost no measurable impact on the size of peel and was technically very difficult. Response to treatment was measured anatomically (computed tomography scans) and physiologically (pulmonary function tests).

Cardiac surgery increases the activity of matrix metalloproteinases and nitric oxide synthase in human hearts

OBJECTIVES

Heart function is variably impaired after cardiopulmonary bypass. We hypothesized that, similar to other myocardial injury states, cardiopulmonary bypass leads to enhanced activity of nitric oxide synthase and matrix metalloproteinases.

METHODS

We obtained right atrial biopsy specimens and plasma samples at the onset and termination of cardiopulmonary bypass in 10 patients. Biopsy specimens were analyzed for nitric oxide synthase activity by using a citrulline assay, whereas plasma and tissue were analyzed for matrix metalloproteinase-9 and matrix metalloproteinase-2 activity by using zymography. Tissue inhibitor of metalloproteinase-4 was analyzed by means of Western blotting. The cellular expression of inducible nitric oxide, endothelial nitric oxide synthase, matrix metalloproteinase-2, and matrix metalloproteinase-9 was determined in right atrial biopsy samples from 3 additional patients by using the appropriate conjugated antibodies.

RESULTS

Nitric oxide synthase activity increased from the beginning to the end of bypass (4.46 +/- 1.07 vs 16.77 +/- 4.86 pmol citrulline/mg of protein per minute, respectively; P =.018). Pro-matrix metalloproteinase-9 activity increased in hearts (199 +/- 41 vs 660 +/- 177 density units/mg protein; P =.008) and plasma (14.1 +/- 4.6 vs 52.2 +/- 5.9 density units/mg protein; P =.008). Pro-matrix metalloproteinase-2 activity increased in the heart (201 +/- 23 vs 310 +/- 35 density units/mg protein, P <.05) but not in plasma. Tissue inhibitor of metalloproteinase-4 expression in the heart decreased (1574 +/- 280 vs 864 +/- 153 density units, P =.014).

CONCLUSIONS

Cardiopulmonary bypass activates enzymes mediating acute inflammation and organ injury (ie, nitric oxide synthase, matrix metalloproteinase-9, and matrix metalloproteinase-2). Decreased tissue inhibitor of metalloproteinase-4 expression allows relatively unopposed increases in matrix metalloproteinase tissue activity. We postulate that these changes play a role in the pathogenesis of heart dysfunction after bypass surgery.

Potassium channels regulate tone in rat pulmonary veins

Intrapulmonary veins (PVs) contribute to pulmonary vascular resistance, but the mechanisms controlling PV tone are poorly understood. Although smooth muscle cell (SMC) K+ channels regulate tone in most vascular beds, their role in PV tone is unknown. We show that voltage-gated (KV) and inward rectifier (Kir) K+ channels control resting PV tone in the rat. PVs have a coaxial structure, with layers of cardiomyocytes (CMs) arrayed externally around a subendothelial layer of typical SMCs, thus forming spinchterlike structures. PVCMs have both an inward current, inhibited by low-dose Ba2+, and an outward current, inhibited by 4-aminopyridine. In contrast, PVSMCs lack inward currents, and their outward current is inhibited by tetraethylammonium (5 mM) and 4-aminopyridine. Several KV, Kir, and large-conductance Ca2+-sensitive K+channels are present in PVs. Immunohistochemistry showed that Kir channels are present in PVCMs and PV endothelial cells but not in PVSMCs. We conclude that K+ channels are present and functionally important in rat PVs. PVCMs form sphincters rich in Kir channels, which may modulate venous return both physiologically and in disease states including pulmonary edema.

Cytologic evaluation of surgical irrigation fluid following resection of head and neck squamous cell carcinoma

INTRODUCTION

Historically, squamous cells exfoliated from head and neck carcinoma resection have been implicated in locoregional recurrence, but there have been few studies demonstrating the presence of these cells. This study was designed to evaluate the presence of exfoliated malignant cells in surgical irrigation fluid collected during head and neck cancer resection.

METHODS

Thirty patients undergoing surgery for biopsy-proven squamous cell carcinoma had their surgical sites irrigated with 1,000 cc of normal saline. Surgical gloves and instruments were also washed. These samples were prepared and stained using standard squamous cell cytologic stains. All cases were reviewed by one cytopathologist.

RESULTS

Eighteen patients (60%) had positive or suspicious cytology detected in at least one of the surgical samples. In patients with T0 and T1 tumours, all surgical samples were negative. Positive or suspicious cytology was detected in the primary site and glove and instrument irrigation in 40% of patients with T2 tumours, 42% of patients with T3 tumours, and 50% of patients with T4 tumours. This was statistically significant (p < .05). Positive or suspicious cytology was detected in the neck and glove and instrument irrigation in 29% of patients with an N0 neck, 31% of patients with an N1 neck, 39% of patients with an N2 neck, and 100% of patients with an N3 neck. Five of seven patients (71%) with previous radiation therapy had positive or suspicious cytology in at least one of the surgical samples.

CONCLUSIONS

Higher tumour and nodal staging and a previous history of radiation therapy are associated with an increased incidence of positive or suspicious cytology in surgical irrigation fluid. These findings have implications for surgical protocols.

Voltage-gated potassium channels in human ductus arteriosus

We studied tone in the human ductus arteriosus and show that the constriction to oxygen is due to inhibition of voltage-gated potassium channels and, in the acute phase, is independent of endothelin-1.

Subglottic stenosis secondary to extramedullary hematopoiesis in a patient with postpolycythemia myeloid metaplasia

BACKGROUND

Extramedullary hematopoiesis (EMH) is known to occur in myeloproliferative disorders and hemoglobinopathies and is usually seen in the spleen and liver.

METHODS

We report the first case of EMH causing subglottic stenosis in a woman with postpolycythemia myeloid metaplasia (PPMM). A tracheotomy was performed to maintain the airway and local radiotherapy was given.

RESULTS

Two months after the radiotherapy was completed laryngoscopy showed an unobstructed airway with no evidence of disease, and the patient was successfully decanulated. Magnetic resonance imaging 8 months after radiotherapy confirmed the absence of local disease.

CONCLUSION

Consideration should be given to EMH as a possible cause of airway obstruction in the differential diagnosis of a patient with a history of PPMM.

O2 sensing is preserved in mice lacking the gp91 phox subunit of NADPH oxidase

The rapid response to hypoxia in the pulmonary artery (PA), carotid body, and ductus arteriosus is partially mediated by O2-responsive K+ channels. K+ channels in PA smooth muscle cells (SMCs) are inhibited by hypoxia, causing membrane depolarization, increased cytosolic calcium, and hypoxic pulmonary vasoconstriction. We hypothesize that the K+ channels are not themselves "O2 sensors" but rather respond to the reduced redox state created by hypoxic inhibition of candidate O2 sensors (NADPH oxidase or the mitochondrial electron transport chain). Both pathways shuttle electrons from donors, down a redox gradient, to O2. Hypoxia inhibits these pathways, decreasing radical production and causing cytosolic accumulation of unused, reduced, freely diffusible electron donors. PASMC K+ channels are redox responsive, opening when oxidized and closing when reduced. Inhibitors of NADPH oxidase (diphenyleneiodonium) and mitochondrial complex 1 (rotenone) both inhibit PASMC whole-cell K+ current but lack the specificity to identify the O2-sensor pathway. We used mice lacking the gp91 subunit of NADPH oxidase [chronic granulomatous disease (CGD) mice] to assess the hypothesis that NADPH oxidase is a PA O2-sensor. In wild-type lungs, gp91 phox and p22 phox subunits are present (relative expression: macrophages > airways and veins > PASMCs). Deletion of gp91 phox did not alter p22 phox expression but severely inhibited activated O2 species production. Nonetheless, hypoxia caused identical inhibition of whole-cell K+ current (in PASMCs) and hypoxic pulmonary vasoconstriction (in isolated lungs) from CGD vs. wild-type mice. Rotenone vasoconstriction was preserved in CGD mice, consistent with a role for the mitochondrial electron transport chain in O2 sensing. NADPH oxidase, though a major source of lung radical production, is not the pulmonary vascular O2 sensor in mice.