In smokers, Sonic hedgehog modulates pulmonary endothelial function through vascular endothelial growth factor

Background

Tobacco-induced pulmonary vascular disease is partly driven by endothelial dysfunction. The Sonic hedgehog (SHH) pathway is involved in vascular physiology. We sought to establish whether the SHH pathway has a role in pulmonary endothelial dysfunction in smokers.

Methods

The ex vivo endothelium-dependent relaxation of pulmonary artery rings in response to acetylcholine (Ach) was compared in 34 current or ex-smokers and 8 never-smokers. The results were expressed as a percentage of the contraction with phenylephrine. We tested the effects of SHH inhibitors (GANT61 and cyclopamine), an SHH activator (SAG) and recombinant VEGF on the Ach-induced relaxation. The level of VEGF protein in the pulmonary artery ring was measured in an ELISA. SHH pathway gene expression was quantified in reverse transcriptase–quantitative polymerase chain reactions.

Results

Ach-induced relaxation was much less intense in smokers than in never-smokers (respectively 24 ± 6% and 50 ± 7% with 10⁻⁴M Ach; p = 0.028). All SHH pathway genes were expressed in pulmonary artery rings from smokers. SHH inhibition by GANT61 reduced Ach-induced relaxation and VEGF gene expression in the pulmonary artery ring. Recombinant VEGF restored the ring’s endothelial function. VEGF gene and protein expression levels in the pulmonary artery rings were positively correlated with the degree of Ach-induced relaxation and negatively correlated with the number of pack-years.

Conclusion

SHH pathway genes and proteins are expressed in pulmonary artery rings from smokers, where they modulate endothelial function through VEGF.

Is arginase a potential drug target in tobacco-induced pulmonary endothelial dysfunction?

Background

Tobacco-induced pulmonary vascular disease is partly driven by endothelial dysfunction. The bioavailability of the potent vasodilator nitric oxide (NO) depends on competition between NO synthase-3 (NOS3) and arginases for their common substrate (L-arginine). We tested the hypothesis whereby tobacco smoking impairs pulmonary endothelial function via upregulation of the arginase pathway.

Methods

Endothelium-dependent vasodilation in response to acetylcholine (Ach) was compared ex vivo for pulmonary vascular rings from 29 smokers and 10 never-smokers. The results were expressed as a percentage of the contraction with phenylephrine. We tested the effects of L-arginine supplementation, arginase inhibition (by N(omega)-hydroxy-nor-l-arginine, NorNOHA) and NOS3 induction (by genistein) on vasodilation. Protein levels of NOS3 and arginases I and II in the pulmonary arteries were quantified by Western blotting.

Results

Overall, vasodilation was impaired in smokers (relative to controls; p < 0.01). Eleven of the 29 smokers (the ED⁺ subgroup) displayed endothelial dysfunction (defined as the absence of a relaxant response to Ach), whereas 18 (the ED⁻ subgroup) had normal vasodilation. The mean responses to 10⁻⁴ M Ach were −23 ± 10% and 31 ± 4% in the ED⁺ and ED⁻ subgroups, respectively (p < 0.01). Supplementation with L- arginine improved endothelial function in the ED⁺ subgroup (−4 ± 10% vs. -32 ± 10% in the presence and absence of L- arginine, respectively; p = 0.006), as did arginase inhibition (18 ± 9% vs. -1 ± 9%, respectively; p = 0.0002). Arginase I protein was overexpressed in ED⁺ samples, whereas ED⁺ and ED⁻ samples did not differ significantly in terms of NOS3 expression. Treatment with genistein did not significantly improve endothelial function in ED⁺ samples.

Conclusion

Overexpression and elevated activity of arginase I are involved in tobacco-induced pulmonary endothelial dysfunction.

Tobacco-associated pulmonary vascular dysfunction in smokers: role of the ET-1 pathway

Pulmonary vascular remodeling and dysfunction associated to tobacco smoking might pave the way for the subsequent development of pulmonary hypertension. Its prognosis is dreadful and its underlying mechanisms are so far largely unknown in humans. To assess the potential role of endothelin-1 and its receptors in smokers' pulmonary artery vasoactive properties. Endothelium-dependent vasodilation to ACh was assessed in pulmonary vascular rings from 34 smokers and compared with that of 10 nonsmokers. The effects of ET-A (BQ 123) or ET-B (BQ 788) blockers and that of an ET-B activator (sarafotoxin) were evaluated. Endothelin-1 was quantitated by ELISA. Expression of its receptors was quantitated by Western blotting. Smokers exhibited an impaired pulmonary endothelium-dependent vasodilation compared with nonsmokers (P < 0.01). In the former group, 8 of 34 subjects exhibited a marked endothelial dysfunction (ED(+)) whereas 26 (ED(-)) (P < 10(-4)) displayed a vasorelaxation to ACh that was comparable to that of nonsmokers. In ED(+) subjects, ET-A was overexpressed (P < 0.05) and inversely correlated (P < 10(-2)) with the response to ACh. Sarafotoxin significantly improved vasodilation in all subjects (P < 10(-2)). In conclusion, tobacco smoking is associated to an impaired pulmonary vasorelaxation at least partly mediated by an ET-1/ET-A-dependent dysfunction.

Distinct patterns of circulating endothelial cells in pulmonary hypertension

The respective abundance of circulating endothelial cells and endothelial progenitor cells may reflect the balance between vascular injury and repair. As pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) can share features of pulmonary remodelling, we postulated that the two disorders might be associated with different types of pulmonary endothelial dysfunction. We studied 25 consecutive patients undergoing cardiac catheterisation for suspected pulmonary hypertension. Nine patients had PAH, nine had CTEPH, and seven had normal pulmonary arterial pressure and served as controls. Circulating endothelial cells were isolated with CD146-coated beads. CD34(+)CD133(+) cell and endothelial progenitor cell numbers were respectively determined by flow cytometry and cell culture, in peripheral vein and pulmonary artery blood. Plasma levels of soluble vascular endothelial growth factor (VEGF), soluble E-selectin and soluble vascular cell adhesion molecule (sVCAM) were measured by ELISA. No difference in progenitor counts or VEGF levels was found across the three groups. Compared to controls, circulating endothelial cell numbers were significantly increased in PAH but not in CTEPH, in keeping with the elevated soluble E-selectin and sVCAM levels found in PAH alone. In conclusion, PAH, in contrast to CTEPH, is associated with markers of vascular injury (circulating endothelial cells, soluble E-selectin and sVCAM) but not with markers of remodelling (endothelial progenitor cells, CD34(+)CD133(+) cells and VEGF).

Role of nitric oxide synthase/arginase balance in bronchial reactivity in patients with chronic obstructive pulmonary disease

Competition between nitric oxide synthases (NOSs) and arginases for their common substrate l-arginine could be involved in the regulation of cholinergic airway reactivity and subsequent airway remodeling. The aims of this study were to evaluate the relationships between the expression of this enzymatic balance and the effects of NOS and arginase inhibition on bronchoconstrictive response to acetylcholine of patients without and with early chronic obstructive pulmonary disease (COPD). Twenty-two human bronchi [15 COPD (9 GOLD-0, 6 GOLD-1, -2-A), 7 nonsmokers] were investigated for immunohistochemistry and modulation of acetylcholine-induced airway constriction. Significantly increased expression of NOS2 in immunoblots of bronchial tissue and staining in smooth muscle cells was evidenced in patients with COPD compared with control subjects, whereas no modification of arginase expression was evidenced. Forced expiratory volume in 1 s (FEV1) and NOS2 expression were negatively correlated (rho=-0.54, P=0.027). Pharmacological experiments demonstrated that resting tension was elevated in COPD compared with control subjects (2,243+/-154 vs. 1,574+/-218 mg, P=0.03) and was positively correlated with the expression of NOS2 (rho=0.61, P=0.044), whereas constrictor response to acetylcholine was similar [active tension, sensitivity (-logEC10), and reactivity (slope)]. The sole effect of the specific arginase inhibitor Nomega-hydroxy-nor-L-arginine (1 microM) was to decrease sensitivity in COPD patients, whereas 1 mM NG-nitro-L-arginine methyl ester unexpectedly decreased resting tension because of a non-cGMP-dependent effect. In conclusion, an upregulation of NOS2 expression in COPD patients is involved in airway tone regulation and functional airflow limitation, whereas increased arginase activity is involved in airway sensitivity.

Treatment of chronic pulmonary aspergillosis by voriconazole in nonimmunocompromised patients

BACKGROUND

There is no recognized medical treatment for chronic pulmonary aspergillosis (CPA) apart from surgery in patients with simple aspergilloma. To evaluate the efficacy of voriconazole in this setting, we conducted a retrospective multicenter study over a 3-year period.

METHODS

For inclusion in the study, patients had to have received voriconazole for treatment of confirmed or probable CPA with a follow-up of at least 6 months. Clinical, radiologic, and mycologic data were collected at baseline, every 2 to 3 months, and at the end of treatment or at the date point.

RESULTS

Twenty-four patients were included in the study, among which 9 patients presented with chronic cavitary pulmonary aspergillosis and 15 presented with chronic necrotizing pulmonary aspergillosis (CNPA). Voriconazole was given as a first-line treatment to 13 patients. The median duration of treatment and follow-up were 6.5 and 10 months, respectively. Three patients had to stop treatment with voriconazole because of toxicity. Symptoms and imagery findings were improved in 16 of 24 patients and 17 of 24 patients, respectively, at the end of follow-up. Mycology, which was positive at baseline in 21 of 23 patients, was negative in 18 of 19 patients at the end of follow-up; serologic test results were also negative in 6 of 19 evaluable patients, all of whom had CNPA. Improved radioclinical findings and mycologic eradication were observed at the end of follow-up in 11 of 19 patients (58%). Patients in whom the disease was controlled had a significantly longer median duration of treatment than patients in whom it was uncontrolled (9 vs 6 months, respectively; p = 0.04).

CONCLUSION

Voriconazole provides effective treatment of CPA with an acceptable level of toxicity.