Idiopathic pulmonary fibrosis (IPF) is a progressive and lethal disease of unknown etiology and uncertain pathogenic mechanisms. Recent studies indicate that the pathogenesis of the disease may involve the abnormal expression of certain developmental pathways. Here we evaluated the expression of Sonic Hedgehog (SHH), Patched-1, Smoothened, and transcription factors glioma-associated oncogene homolog (GLI)1 and GLI2 by RT-PCR, as well as their localization in IPF and normal lungs by immunohistochemistry. The effects of SHH on fibroblast proliferation, migration, collagen and fibronectin production, and apoptosis were analyzed by WST-1, Boyden chamber chemotaxis, RT-PCR, Sircol, and annexin V-propidium iodide binding assays, respectively. Our results showed that all the main components of the Sonic signaling pathway were overexpressed in IPF lungs. With the exception of Smoothened, they were also upregulated in IPF fibroblasts. SHH and GLI2 localized to epithelial cells, whereas Patched-1, Smoothened, and GLI1 were observed mainly in fibroblasts and inflammatory cells. No staining was detected in normal lungs. Recombinant SHH increased fibroblast proliferation (P < 0.05), collagen synthesis, (2.5 ± 0.2 vs. 4.5 ± 1.0 μg of collagen/ml; P < 0.05), fibronectin expression (2-3-fold over control), and migration (190.3 ± 12.4% over control, P < 0.05). No effect was observed on α-smooth muscle actin expression. SHH protected lung fibroblasts from TNF-α/IFN-γ/Fas-induced apoptosis (14.5 ± 3.2% vs. 37.3 ± 7.2%, P < 0.0001). This protection was accompanied by modifications in several apoptosis-related proteins, including increased expression of X-linked inhibitor of apoptosis. These findings indicate that the SHH pathway is activated in IPF lungs and that SHH may contribute to IPF pathogenesis by increasing the proliferation, migration, extracellular matrix production, and survival of fibroblasts.

Androgen vasorelaxing action is a subject of recent interest. We investigated the involvement of l-type voltage-operated Ca(2+) channels (L-VOCCs), K(+) channels, intracellular Ca(2+) concentration ([Ca(2+)]i), and cAMP in the vasorelaxing effect of testosterone and 5beta-dihydrotestosterone (5beta-DHT) on rat thoracic aorta. Isolated aortic rings were used to study the vasorelaxing potency of testosterone and 5beta-DHT on KCl- and noradrenaline-induced contractions. Patch-clamp was used to analyze androgen effects on Ca(2+) inward and K(+) outward currents. The fluorescence technique was used to evaluate [Ca(2+)]i in single myocytes; moreover, simultaneous measurements of [Ca(2+)]i and vascular contraction were evaluated. 5beta-DHT was more potent than testosterone to relax KCl-induced contraction, but they were equipotent to relax noradrenaline contraction. l-type Ca(2+) currents were blocked by nifedipine, both androgens, and an estrogen in a concentration-dependent manner, and the order of potency was: testosterone > nifedipine > 5beta-DHT > 17beta-estradiol. We observed that testosterone has different mechanism of action by the concentration range used: at nm concentrations it was a powerful L-VOCCs antagonist, whereas at mum concentrations it was observed that: 1) its Ca(2+) antagonist property is reverted by increasing the l-type inward Ca(2+) currents (Ca(2+) agonist property); and 2) the [Ca(2+)]i and cAMP production was increased. The total K(+) currents were unaffected by testosterone or 5beta-DHT. The data show that 5beta-DHT-induced vasorelaxation is due to its selective blockade on L-VOCCs (from nm to microm concentrations), but testosterone-induced vasorelaxation involves concentration-dependent additional mechanisms: acting as an L-VOCCs antagonist at low concentrations, and increasing [Ca(2+)]i and cAMP production at high concentrations.

Organophosphates are still widely used worldwide and cause thousands of intoxications every year. In this work we investigated the mechanisms of parathion (Pth) airway toxicity, using biochemical and functional approaches. A plethysmographic technique for unrestrained guinea pigs was used to analyze Pth-induced modifications of airway mechanics and responsiveness to acetylcholine (ACh: 0.1-3.2 mg/ml, 2-min inhalation each dose). The isolated perfused rabbit lung preparation was used to study the acute effects of Pth on airway responsiveness to ACh (10(-8)-10(-3) M), histamine (10(-8)-10(-3) M) and substance P (10(-10)-10(-6) M), pulmonary acetylcholinesterase inhibition and cytochrome P450 (P450) activity, and their modifications with previous administration of Pth (1 mg/kg s.c. daily, 7 days). We found that: (1) In guinea pigs Pth (3.2-17 mg/kg i.p.) produced a dose-dependent increase in a lung resistance index (iRL), which was greatly reverted (approximately 50%) by salbutamol (2 mg/ml, 2-min inhalation, or 10 microg/kg i.p.). This salbutamol effect was transient (5-10 min), suggesting that this bronchodilator triggered additional obstructive mechanisms. (2) Pth increased the water content in lung parenchyma samples, but not in trachea or bronchi, and augmented the respiratory secretions measured through monosaccharide content in bronchoalveolar lavage. (3) The increase in iRL was greater in female animals, probably due to a higher P450 basal activity, and completely blocked by pharmacological inhibition of P450 with piperonyl butoxide (500 mg/kg i.p.). (4) In male guinea pigs a subclinical dose of Pth (10 mg/kg i.p.) induced airway hyperresponsiveness to ACh. In isolated perfused rabbit lung Pth (10(-6) M) produced airway hyperresponsiveness to ACh and histamine, the latter prevented by atropine (10(-5) M). (5) Repetitive exposure to subclinical doses (1 mg/kg s.c.) of Pth during 1 week caused approximately 80% inhibition of P450 activity in rabbits, which was not enough, however, to prevent the functional manifestation of Pth toxicity in the airways.

Airway hyperresponsiveness is a key feature of asthma, but its mechanisms remain poorly understood. Leukotriene D(4) (LTD(4)) is one of the few molecules capable of producing airway hyperresponsiveness. In this study, LTD(4), but not leukotriene C(4) (LTC(4)), produced a leftward displacement of the concentration-response curve to histamine in bovine airway smooth muscle strips. Neither LTC(4) nor LTD(4) modified the concentration-response curve to carbachol. In simultaneous measurements of intracellular Ca(2+) ([Ca(2+)](i)) and contraction, histamine or carbachol produced a transient Ca(2+) peak followed by a plateau, along with a contraction. LTD(4) increased the histamine-induced transient Ca(2+) peak and contraction but did not modify responses to carbachol. Enhanced responses to histamine induced by LTD(4) were not modified by staurosporine or chelerythrine but were abolished by genistein. Western blot showed that carbachol, but not histamine, caused intense phosphorylation of extracellular signal-regulated kinase 1/2 and that LTD(4) significantly enhanced the phosphorylation induced by histamine, but not by carbachol. L-type Ca(2+) channel participation in the hyperresponsiveness to histamine was discarded because LTD(4) did not modify the [Ca(2+)](i) changes induced by KCl. In tracheal myocytes, LTD(4) enhanced the transient Ca(2+) peak induced by histamine (but not by carbachol) and the sarcoplasmic reticulum (SR) Ca(2+) refilling. Genistein abolished this last LTD(4) effect. Partial blockade of the SR-ATPase Ca(2+) pump with cyclopiazonic acid reduced the Ca(2+) transient peak induced by histamine but not by carbachol. These results suggested that LTD(4) induces hyperresponsiveness to histamine through activation of the tyrosine kinase pathway and an increasing SR-ATPase Ca(2+) pump activity. L-type Ca(2+) channels seemed not to be involved in this phenomenon.

Some receptors and signaling molecules, such as Rho-kinase (ROCK), localize in caveolae. We asked whether the function of histamine receptors (H(1)) and 5-hydroxytryptamine (serotonin) receptors (5-HT(2A)) in bovine tracheal smooth muscle are modified after caveolae disruption and if so, whether the altered ROCK activity plays a role in this modification. Methyl-beta-cyclodextrin (MbetaCD), used to deplete membrane cholesterol, was shown to disrupt caveolae and diminish sustained contractions to histamine (approximately 80%), 5-HT (100%), alpha-methyl-5-HT (100%), and KCl (approximately 30%). Cholesterol-loaded MbetaCD (CL-MbetaCD) restored the responses to KCl and partially restored the responses to agonists. ROCK inhibition by Y-27632 diminished contractions to histamine (approximately 85%) and 5-HT (approximately 59%). 5-HT or histamine stimulation augmented ROCK activity. These increases were reduced by MbetaCD and partially reestablished by CL-MbetaCD. The increase in intracellular Ca(2+) that was induced by both agonists was reduced by MbetaCD. The presence of caveolin-1 (Cav-1), H1, 5-HT(2A), and ROCK1 was corroborated by immunoblotting of membrane fractions from sucrose gradients and by confocal microscopy. H(1) receptors coimmunoprecipitated with Cav-1 in caveolar and noncaveolar membrane fractions, whereas 5-HT(2A) receptors appeared to be restricted to noncaveolar membrane fractions. We conclude that caveolar and cholesterol integrity are indispensable for the proper functionality of the H(1) and 5-HT(2A) receptors through their Rho/ROCK signaling.