American journal of respiratory cell and molecular biology
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Am. J. Respir. Cell Mol. Biol. · Dec 2011
Gi-coupled γ-aminobutyric acid-B receptors cross-regulate phospholipase C and calcium in airway smooth muscle.
γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and exerts its actions via both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. Although the functional expression of GABA(B) receptors coupled to the G(i) protein was reported for airway smooth muscle, the role of GABA(B) receptors in airway responsiveness remains unclear. We investigated whether G(i)-coupled GABA(B) receptors cross-regulate phospholipase C (PLC), an enzyme classically regulated by G(q)-coupled receptors in human airway smooth muscle cells. ⋯ Moreover, baclofen potentiated the substance P-induced contraction of airway smooth muscle in isolated guinea pig tracheal rings. In conclusion, the stimulation of GABA(B) receptors in human airway smooth muscle cells rapidly mobilizes intracellular Ca(2+) stores by the synthesis of inositol phosphate via the activation of PLC-β, which is stimulated by G(βγ) protein liberated from G(i) proteins coupled to GABA(B) receptors. Furthermore, crosstalk between GABA(B) receptors and G(q)-coupled receptors potentiates the synthesis of inositol phosphate, transient increases in [Ca(2+)](i), and smooth muscle contraction through G(i) proteins.
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Am. J. Respir. Cell Mol. Biol. · Dec 2011
Multicenter Study Clinical TrialThe association of genome-wide significant spirometric loci with chronic obstructive pulmonary disease susceptibility.
Two recent metaanalyses of genome-wide association studies conducted by the CHARGE and SpiroMeta consortia identified novel loci yielding evidence of association at or near genome-wide significance (GWS) with FEV(1) and FEV(1)/FVC. We hypothesized that a subset of these markers would also be associated with chronic obstructive pulmonary disease (COPD) susceptibility. ⋯ Of the previously identified GWS spirometric genomic regions, three loci harbored SNPs associated with COPD susceptibility at a 5% false discovery rate: the 4q24 locus including FLJ20184/INTS12/GSTCD/NPNT, the 6p21 locus including AGER and PPT2, and the 5q33 locus including ADAM19. In conclusion, markers previously associated at or near GWS with spirometric measures were tested for association with COPD status in data from four COPD case-control studies, and three loci showed evidence of association with COPD susceptibility at a 5% false discovery rate.
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Am. J. Respir. Cell Mol. Biol. · Dec 2011
ReviewEverything prevents emphysema: are animal models of cigarette smoke-induced chronic obstructive pulmonary disease any use?
There is a very large number of experimental approaches that prevent cigarette smoke-induced emphysema in laboratory animals, but the few similar treatments that have been tried in humans have had minimal effects, leading to questions of whether animal models of chronic obstructive pulmonary disease (COPD) are of any use in developing treatments for human disease. We review possible reasons for this problem. First, humans usually get treated when they have severe (Global Initiative for Chronic Obstructive Lung Disease III/IV) COPD, but animal models only produce mild (Global Initiative for Chronic Obstructive Lung Disease I/II) disease that never progresses after smoking cessation, and never develops spontaneous exacerbations (i.e., animal models are not models of severe human disease, and probably can't be used to model treatment of severe disease). ⋯ Third, animal models are typically Day 1 of smoke exposure "prevention" models, but humans are always treated well along in the course of their disease; thus, any human treatment will be an intervention, and not a prevention. We propose that animal models should examine both emphysema and small airway remodeling, and that experiments should include a relatively late intervention arm. This approach, combined with the realization that human COPD probably needs early rather than late treatment, may make development of treatments based on animal models more relevant.