Smoking particles enhance endothelin A and endothelin B receptor-mediated contractions by enhancing translation in rat bronchi

BACKGROUND: Smoking is known to cause chronic inflammatory changes in the bronchi and to contribute to airway hyper-reactivity, such as in bronchial asthma. To study the effect of smoking on the endothelin system in rat airways, bronchial segments were exposed to DMSO-soluble smoking particles (DSP) from cigarette smoke, to nicotine and to DMSO, respectively. METHODS: Isolated rat bronchial segments were cultured for 24 hours in the presence or absence of DSP, nicotine or DMSO alone. Contractile responses to sarafotoxin 6c (a selective agonist for ET(B )receptors) and endothelin-1 (an ET(A )and ET(B )receptor agonist) were studied by use of a sensitive myograph. Before ET-1 was introduced, the ET(B )receptors were desensitized by use of S6c. The remaining contractility observed was considered to be the result of selective activation of the ET(A )receptors. ET(A )and ET(B )receptor mRNA expression was analyzed using real-time quantitative PCR. The location and concentration of ET(A )and ET(B )receptors were studied by means of immunohistochemistry together with confocal microscopy after overnight incubation with selective antibodies. RESULTS: After being cultured together with DSP for 24 hours the bronchial segments showed an increased contractility mediated by ET(A )and ET(B )receptors, whereas culturing them together with nicotine did not affect their contractility. The up-regulation of their contractility was blunted by cycloheximide treatment, a translational inhibitor. No significant change in the expression of ET(A )and ET(B )receptor mRNA through exposure to DMSO or to nicotine exposure alone occurred, although immunohistochemistry revealed a clear increase in ET(A )and ET(B )receptors in the smooth muscle after incubation in the presence of DSP. Taken as a whole, this is seen as the presence of a translation mechanism. CONCLUSION: The increased contractility of rat bronchi when exposed to DSP appears to be due to a translation mechanism

Down-Regulation of α 1

Smoking is a strong risk factor for cardiovascular disease that is a leading cause of death and disability in Western countries. The present study was designed to investigate the effect of lipid-soluble smoke particles (DSP) on alpha-adrenoceptor expression in organ culture of rat mesenteric arteries and human epiploon arteries. Myograph and real-time reverse transcription-polymerase chain reaction were employed to assess vascular smooth muscle contractibility and the receptor mRNA expression in the smooth muscle cells. Organ culture of the arterial segments in the presence of DSP (0.2 microl/ml) resulted in a significantly decreased contractile response to norepinephrine, compared to control (i.e. in the presence of dimethyl sulfoxide) (P < 0.05). This was in parallel with a down-regulation of alpha(1A)-adrenoceptor mRNA expression in the smooth muscle, while alpha(2)-adrenoceptor mRNA expression remained unchanged. General transcription inhibitor actinomycin D (10(-5.4 )M), but not the translational inhibitor cycloheximide (10(-5 )M), significantly abolished the DSP-induced depressed contraction to norepinephrine. IMD-0354 (10(-7.5 )M), a specific nuclear factor-kappaB (NF-kappaB) pathway inhibitor, markedly reversed the DSP-induced down-regulation of alpha(1A)-adrenoceptor expression in the smooth muscle at both functional and mRNA levels. Thus, we have demonstrated that smoking-induced down-regulation of alpha(1A)-adrenoceptor expression was via the transcriptional factor NF-kappaB pathway