Revefenacin, a Long-Acting Muscarinic Antagonist, Does Not Prolong QT Interval in Healthy Subjects: Results of a Placebo- and Positive-Controlled Thorough QT Study.

Revefenacin is a novel once-daily, lung-selective, long-acting muscarinic antagonist developed as a nebulized inhalation solution for the maintenance treatment of chronic obstructive pulmonary disease. In a randomized, 4-way crossover study, healthy subjects received a single inhaled dose of revefenacin 175 µg (therapeutic dose), revefenacin 700 µg (supratherapeutic dose), and placebo via standard jet nebulizer, and a single oral dose of moxifloxacin 400 mg (open-label) in separate treatment periods. Electrocardiograms were recorded, and pharmacokinetic samples were collected serially after dosing. The primary end point was the placebo-corrected change from baseline QT interval corrected for heart rate using Fridericia's formula, analyzed at each postdose time. Concentration-QTc modeling was also performed. Following administration of revefenacin 175  and 700 µg, placebo-corrected change from baseline QTcF (ΔΔQTcF) values were close to 0 at all times, with the largest mean ΔΔQTcF of 1.0 millisecond (95% confidence interval [CI], -1.2 to 3.1 milliseconds) 8 hours postdose and 1.0 millisecond (95%CI, -1.1 to 3.1 milliseconds) 1 hour postdose after inhalation of revefenacin 175 and 700 µg, respectively. Revefenacin did not have a clinically meaningful effect on heart rate (within ±5 beats per minute of placebo), or PR and QRS intervals (within ±3 and ±1 milliseconds of placebo, respectively). Using concentration-QTc modeling, an effect of revefenacin > 10 milliseconds can be excluded within the observed plasma concentration range of up to ≈3 ng/mL. Both doses of revefenacin were well tolerated. These results demonstrate that revefenacin does not prolong the QT interval.

Maintained therapeutic effect of revefenacin over 52 weeks in moderate to very severe Chronic Obstructive Pulmonary Disease (COPD).

BACKGROUND: Revefenacin is a long-acting muscarinic antagonist that was recently approved for the nebulized treatment of chronic obstructive pulmonary disease (COPD). Although shorter duration studies have documented the efficacy of revefenacin in COPD, longer-term efficacy has not been described. In a recent 52-week safety trial, revefenacin was well tolerated and had a favorable benefit-risk profile. Here we report exploratory efficacy and health outcomes in patients receiving revefenacin 175 µg or 88 µg daily during the 52-week trial. METHODS: In this randomized, parallel-group, 52-week trial (NCT02518139), 1055 participants with moderate to very severe COPD received revefenacin 175 µg or 88 µg in a double-blind manner, or open-label active control tiotropium. RESULTS: Over the 52-week treatment period, both doses of revefenacin, as well as tiotropium, elicited significant (all p < 0.0003) improvements from baseline in trough forced expiratory volume in 1 s (FEV1). The trough FEV1 profile (least squares mean change from baseline) for revefenacin 175 µg ranged from 52.3-124.3 mL and the trough FEV1 profile for tiotropium ranged from 79.7-112.8 mL. In subgroup comparisons, the effect of revefenacin on trough FEV1 was comparable in patients taking concomitant long-acting ß-agonists, with or without inhaled corticosteroids, with patients who were not taking these medications. There were statistically significant (p < 0.05) improvements in all measured health status outcomes (evaluated using St. George's Respiratory Questionnaire, COPD Assessment Test, Clinical COPD Questionnaire and Baseline and Transition Dyspnea Index) from 3 months onward, in all treatment arms. CONCLUSIONS: Significant sustained improvements from baseline in trough FEV1 and respiratory health outcomes were demonstrated for 175-µg revefenacin over 52 weeks, further supporting its use as a once-daily bronchodilator for the nebulized treatment of patients with COPD. TRIAL REGISTRATION: NCT02518139 ; Registered 5 August 2015.

Pharmacokinetics and safety of revefenacin in subjects with impaired renal or hepatic function.

Purpose: Revefenacin, a long-acting muscarinic antagonist for nebulization, has been shown to improve lung function in patients with chronic obstructive pulmonary disease. Here we report pharmacokinetic (PK) and safety results from two multicenter, open-label, single-dose trials evaluating revefenacin in subjects with severe renal impairment (NCT02578082) and moderate hepatic impairment (NCT02581592). Subjects and methods: The renal impairment trial enrolled subjects with normal renal function and severe renal impairment (estimated glomerular filtration rate <30 mL/min/1.73 m2). The hepatic impairment trial enrolled subjects with normal hepatic function and moderate hepatic impairment (Child-Pugh class B). Subjects received a single 175-µg dose of revefenacin through nebulization. PK plasma samples and urine collections were obtained at multiple time points for 5 days following treatment; all subjects were monitored for adverse events. Results: In the renal impairment study, the maximum observed plasma revefenacin concentration (Cmax) was up to 2.3-fold higher and area under the concentration-time curve from time 0 to infinity (AUCinf) was up to 2.4-fold higher in subjects with severe renal impairment compared with those with normal renal function. For THRX-195518, the major metabolite of revefenacin, the corresponding changes in Cmax and AUCinf were 1.8- and 2.7-fold higher, respectively. In the hepatic impairment study, revefenacin Cmax and AUCinf were 1.03- and 1.18-fold higher, respectively, in subjects with moderate hepatic impairment compared with those with normal hepatic function. The corresponding changes in THRX-195518 Cmax and AUCinf were 1.5- and 2.8-fold higher, respectively. Conclusion: Systemic exposure to revefenacin increased modestly in subjects with severe renal impairment but was similar between subjects with moderate hepatic impairment and normal hepatic function. The increase in plasma exposure to THRX-195518 in subjects with severe renal or moderate hepatic impairment is unlikely to be of clinical consequence given its low antimuscarinic potency, low systemic levels after inhaled revefenacin administration, and favorable safety profile.

Nebulized Versus Dry Powder Long-Acting Muscarinic Antagonist Bronchodilators in Patients With COPD and Suboptimal Peak Inspiratory Flow Rate.

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) and suboptimal peak inspiratory flow rate (sPIFR) may not benefit optimally from dry powder inhalers (DPI) because of inadequate inspiratory flow. Nebulized bronchodilators may provide a better alternative. We compared bronchodilation with the long-acting muscarinic antagonist (LAMA) revefenacin for nebulization versus the DPI LAMA tiotropium, in patients with COPD and sPIFR (< 60 L/min against the resistance of Diskus®). METHODS: This was a randomized, double-blind, double-dummy, 28-day Phase 3b study in patients with COPD enrolled based on sPIFR. The primary endpoint was trough forced expiratory volume in 1 second (FEV1) on Day 29 for revefenacin for nebulization versus tiotropium HandiHaler® DPI. RESULTS: We enrolled 206 patients with mean (standard deviation) age, 65 (8) years; percent predicted FEV1, 37 (16)%; PIFR, 45 (12) L/min. In the intent-to-treat (ITT) population, revefenacin improved trough FEV1 from baseline; however, the difference versus tiotropium was not significant (least squares [LS] mean difference [standard error], 17.0 [22.4] mL, P=0.4461). In a prespecified analysis of patients with FEV1 < 50% predicted, revefenacin produced an LS mean difference (95% confidence interval [CI]), 49.1 (6.3-91.9) mL in trough FEV1 and 103.5 (7.7-199.3) mL in forced vital capacity versus tiotropium. Revefenacin produced >100 mL increase in FEV1 in 41.6% versus 34.4% of patients with tiotropium in ITT and 41.4% versus 25.7% of patients in FEV1 < 50% predicted populations. CONCLUSIONS: Revefenacin did not produce significant improvements in FEV1 versus tiotropium in the ITT population, but increased trough FEV1 in patients with FEV1 < 50% predicted and sPIFR. Clinical Trial Registration (www.Clinicaltrials.gov): Study 0149 (NCT03095456).

Data on the safety and tolerability of revefenacin, in patients with moderate to very severe chronic obstructive pulmonary disease.

This article contains information on the experimental design and methods on how the safety and tolerability data concerning patients with moderate to very severe chronic obstructive pulmonary disease (COPD) were obtained. This is in addition to our original research article. [1] We have also provided information on the clinical laboratory tests that were conducted. Further interpretation and discussion of the data are demonstrated in the article "Revefenacin, a Once-daily, Lung-selective, Long-acting Muscarinic Antagonist for Nebulized Therapy: Safety and Tolerability Results of a 52-week Phase 3 Trial in Moderate to Very Severe Chronic Obstructive Pulmonary Disease." [1].

Revefenacin, a once-daily, lung-selective, long-acting muscarinic antagonist for nebulized therapy: Safety and tolerability results of a 52-week phase 3 trial in moderate to very severe chronic obstructive pulmonary disease.

BACKGROUND: Prior replicate 12-week phase 3 trials demonstrated that once-daily doses of revefenacin inhalation solution at 88 µg and 175 µg produced significant bronchodilation over 24 h post dose in patients with moderate to very severe chronic obstructive pulmonary disease (COPD). The objective was to characterize the safety profile of revefenacin 88 µg and 175 µg over 52 weeks of treatment. METHODS: In this randomized, parallel-group, 52-week trial (NCT02518139), 1055 participants with moderate to very severe COPD received revefenacin 88 µg or 175 µg in a double-blind manner, or open-label active control tiotropium. RESULTS: Treatment-emergent adverse events (AEs) were comparable across all treatment groups (n [%] patients; revefenacin 88 µg, 272 [74.7%]; 175 µg, 242 [72.2%]; tiotropium, 275 [77.2%]). Numerically fewer COPD exacerbations (n [%] patients) were observed with revefenacin 175 µg (73 [21.8%]) than with 88 µg (107 [29.4%]) or tiotropium (100 [28.1%]). Serious AEs were comparable with revefenacin 88 µg (58 [15.9%] and tiotropium (58 [16.3%]), but were lower with revefenacin 175 µg (43 [12.8%]), and mortality was low. In patients using revefenacin 88 µg or tiotropium with a concurrent long-acting ß-agonist (LABA) product, the incidence of AEs was slightly higher than without concurrent LABA. LABA did not affect the incidence of AEs for patients who received revefenacin 175 µg. CONCLUSIONS: Revefenacin was generally well tolerated over 52 weeks of treatment, and had a safety profile that supports its use as a long-term once-daily bronchodilator for the nebulized treatment of COPD.

Cardiovascular safety of revefenacin, a once-daily, lung-selective, long-acting muscarinic antagonist for nebulized therapy of chronic obstructive pulmonary disease: Evaluation in phase 3 clinical trials.

The cardiovascular safety of revefenacin, an anticholinergic indicated for the maintenance treatment of patients with chronic obstructive lung disease (COPD), was evaluated in phase 3 trials in patients with moderate to very severe COPD. No clinically meaningful changes in 12-lead electrocardiogram recordings were observed with up to 52 weeks of once-daily revefenacin 88 or 175 µg. In a pooled analysis of Studies 0126 and 0127, the incidence of prolonged QT interval corrected for heart rate using the Fridericia correction formula (QTcF; >450 msec) for revefenacin 88 µg (n = 23, 5.6%) and revefenacin 175 µg (n = 23, 5.9%) was similar to that for placebo (n = 22, 5.3%). In Study 0128, the incidence of prolonged QTcF was similar in the revefenacin 175 µg (n = 25, 7.7%) and tiotropium (n = 26, 7.3%) groups and lower in the revefenacin 88 µg (n = 15, 4.2%) group. There were four major adverse cardiac events (MACEs) in Study 0126 (one, two, and one in the placebo, revefenacin 88 µg, and revefenacin 175 µg groups, respectively), no MACEs in Study 0127 and 26 MACEs in Study 0128 (9, 10 and 7 in the revefenacin 88 µg, revefenacin 175 µg and tiotropium groups, respectively). In Study 0128, only one MACE was considered possibly/probably related to revefenacin (atrial fibrillation in the revefenacin 175 µg group). Thus, revefenacin may provide beneficial nebulized therapy for patients with COPD without further elevating their risk of cardiovascular events.

Improvements in Lung Function with Nebulized Revefenacin in the Treatment of Patients with Moderate to Very Severe COPD: Results from Two Replicate Phase III Clinical Trials.

BACKGROUND: Revefenacin, a novel, lung-selective, long-acting muscarinic antagonist, has been developed for nebulized therapy for chronic obstructive pulmonary disease (COPD). We present the results of replicate Phase III efficacy and safety studies of revefenacin in patients with moderate to very severe COPD. METHODS: In 2 double-blind, parallel-group studies, (Study 0126 and Study 0127), patients ≥ 40 years old were randomized to revefenacin 88 µg, revefenacin 175 µg or placebo administered once daily by standard jet nebulizer for 12 weeks. The primary endpoint was 24-hour trough forced expiratory volume in 1 second (FEV1) on day 85. Secondary efficacy endpoints included overall treatment effect (OTE) on trough FEV1 and peak FEV1 (0-2 hours after first dose). Safety assessments included treatment-emergent adverse events. RESULTS: At day 85, revefenacin 88 µg and 175 µg improved trough FEV1 versus placebo in Study 0126 (by 79 mL [p=0.0003] and 146 mL [p<0.0001]) and Study 0127 (by 160 mL and 147 mL; both p<0.0001). Compared with placebo, pooled data of revefenacin 88 µg and 175 µg increased OTE trough FEV1 by 115 mL and 142 mL (both p<0.001) and increased peak FEV1 by 127 mL and 129 mL (both p<0.0001). Revefenacin 175 µg demonstrated greater improvements in FEV1 in concomitant long-acting beta2-agonist patients and in more severe patients than revefenacin 88 µg. Adverse events were minor. CONCLUSION: Revefenacin, administered once daily for 12 weeks to patients with moderate to very severe COPD, demonstrated clinically significant improvements in trough FEV1 and OTE FEV1. Revefenacin was generally well tolerated with no major safety concerns.

Hyperoxia-induced p47phox activation and ROS generation is mediated through S1P transporter Spns2, and S1P/S1P1&2 signaling axis in lung endothelium.

Hyperoxia-induced lung injury adversely affects ICU patients and neonates on ventilator assisted breathing. The underlying culprit appears to be reactive oxygen species (ROS)-induced lung damage. The major contributor of hyperoxia-induced ROS is activation of the multiprotein enzyme complex NADPH oxidase. Sphingosine-1-phosphate (S1P) signaling is known to be involved in hyperoxia-mediated ROS generation; however, the mechanism(s) of S1P-induced NADPH oxidase activation is unclear. Here, we investigated various steps in the S1P signaling pathway mediating ROS production in response to hyperoxia in lung endothelium. Of the two closely related sphingosine kinases (SphKs)1 and 2, which synthesize S1P from sphingosine, only Sphk1(-/-) mice conferred protection against hyperoxia-induced lung injury. S1P is metabolized predominantly by S1P lyase and partial deletion of Sgpl1 (Sgpl1(+/-)) in mice accentuated lung injury. Hyperoxia stimulated S1P accumulation in human lung microvascular endothelial cells (HLMVECs), and downregulation of S1P transporter spinster homolog 2 (Spns2) or S1P receptors S1P1&2, but not S1P3, using specific siRNA attenuated hyperoxia-induced p47(phox) translocation to cell periphery and ROS generation in HLMVECs. These results suggest a role for Spns2 and S1P1&2 in hyperoxia-mediated ROS generation. In addition, p47(phox) (phox:phagocyte oxidase) activation and ROS generation was also reduced by PF543, a specific SphK1 inhibitor in HLMVECs. Our data indicate a novel role for Spns2 and S1P1&2 in the activation of p47(phox) and production of ROS involved in hyperoxia-mediated lung injury in neonatal and adult mice.

Sphingosine kinase 1 deficiency confers protection against hyperoxia-induced bronchopulmonary dysplasia in a murine model: role of S1P signaling and Nox proteins.

Bronchopulmonary dysplasia of the premature newborn is characterized by lung injury, resulting in alveolar simplification and reduced pulmonary function. Exposure of neonatal mice to hyperoxia enhanced sphingosine-1-phosphate (S1P) levels in lung tissues; however, the role of increased S1P in the pathobiological characteristics of bronchopulmonary dysplasia has not been investigated. We hypothesized that an altered S1P signaling axis, in part, is responsible for neonatal lung injury leading to bronchopulmonary dysplasia. To validate this hypothesis, newborn wild-type, sphingosine kinase1(-/-) (Sphk1(-/-)), sphingosine kinase 2(-/-) (Sphk2(-/-)), and S1P lyase(+/-) (Sgpl1(+/-)) mice were exposed to hyperoxia (75%) from postnatal day 1 to 7. Sphk1(-/-), but not Sphk2(-/-) or Sgpl1(+/-), mice offered protection against hyperoxia-induced lung injury, with improved alveolarization and alveolar integrity compared with wild type. Furthermore, SphK1 deficiency attenuated hyperoxia-induced accumulation of IL-6 in bronchoalveolar lavage fluids and NADPH oxidase (NOX) 2 and NOX4 protein expression in lung tissue. In vitro experiments using human lung microvascular endothelial cells showed that exogenous S1P stimulated intracellular reactive oxygen species (ROS) generation, whereas SphK1 siRNA, or inhibitor against SphK1, attenuated hyperoxia-induced S1P generation. Knockdown of NOX2 and NOX4, using specific siRNA, reduced both basal and S1P-induced ROS formation. These results suggest an important role for SphK1-mediated S1P signaling-regulated ROS in the development of hyperoxia-induced lung injury in a murine neonatal model of bronchopulmonary dysplasia.

Coronin 1B regulates S1P-induced human lung endothelial cell chemotaxis: role of PLD2, protein kinase C and Rac1 signal transduction.

Coronins are a highly conserved family of actin binding proteins that regulate actin-dependent processes such as cell motility and endocytosis. We found that treatment of human pulmonary artery endothelial cells (HPAECs) with the bioactive lipid, sphingosine-1-phosphate (S1P) rapidly stimulates coronin 1B translocation to lamellipodia at the cell leading edge, which is required for S1P-induced chemotaxis. Further, S1P-induced chemotaxis of HPAECs was attenuated by pretreatment with small interfering RNA (siRNA) targeting coronin 1B (∼36%), PLD2 (∼45%) or Rac1 (∼50%) compared to scrambled siRNA controls. Down regulation PLD2 expression by siRNA also attenuated S1P-induced coronin 1B translocation to the leading edge of the cell periphery while PLD1 silencing had no effect. Also, S1P-induced coronin 1B redistribution to cell periphery and chemotaxis was attenuated by inhibition of Rac1 and over-expression of dominant negative PKC δ, ε and ζ isoforms in HPAECs. These results demonstrate that S1P activation of PLD2, PKC and Rac1 is part of the signaling cascade that regulates coronin 1B translocation to the cell periphery and the ensuing cell chemotaxis.

Targeting sphingosine kinase 1 attenuates bleomycin-induced pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease, wherein transforming growth factor ß (TGF-ß) and sphingosine-1-phosphate (S1P) contribute to the pathogenesis of fibrosis. However, the in vivo contribution of sphingosine kinase (SphK) in fibrotic processes has not been documented. Microarray analysis of blood mononuclear cells from patients with IPF and SphK1- or SphK2-knockdown mice and SphK inhibitor were used to assess the role of SphKs in fibrogenesis. The expression of SphK1/2 negatively correlated with lung function and survival in patients with IPF. Also, the expression of SphK1 was increased in lung tissues from patients with IPF and bleomycin-challenged mice. Knockdown of SphK1, but not SphK2, increased survival and resistance to pulmonary fibrosis in bleomycin-challenged mice. Administration of SphK inhibitor reduced bleomycin-induced mortality and pulmonary fibrosis in mice. Knockdown of SphK1 or treatment with SphK inhibitor attenuated S1P generation and TGF-ß secretion in a bleomycin-induced lung fibrosis mouse model that was accompanied by reduced phosphorylation of Smad2 and MAPKs in lung tissue. In vitro, bleomycin-induced expression of SphK1 in lung fibroblast was found to be TGF-ß dependent. Taken together, these data indicate that SphK1 plays a critical role in the pathology of lung fibrosis and is a novel therapeutic target.

Sphingosine kinase 1 is required for mesothelioma cell proliferation: role of histone acetylation.

BACKGROUND: Malignant pleural mesothelioma (MPM) is a devastating disease with an overall poor prognosis. Despite the recent advances in targeted molecular therapies, there is a clear and urgent need for the identification of novel mesothelioma targets for the development of highly efficacious therapeutics. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we report that the expression of Sphingosine Kinase 1 (SphK1) protein was preferentially elevated in MPM tumor tissues (49 epithelioid and 13 sarcomatoid) compared to normal tissue (n = 13). In addition, we also observed significantly elevated levels of SphK1 and SphK2 mRNA and SphK1 protein expression in MPM cell lines such as H2691, H513 and H2461 compared to the non-malignant mesothelial Met5 cells. The underlying mechanism appears to be mediated by SphK1 induced upregulation of select gene transcription programs such as that of CBP/p300 and PCAF, two histone acetyl transferases (HAT), and the down regulation of cell cycle dependent kinase inhibitor genes such as p27Kip1 and p21Cip1. In addition, using immunoprecipitates of anti-acetylated histone antibody from SphK inhibitor, SphK-I2 treated Met5A and H2691 cell lysates, we also showed activation of other cell proliferation related genes, such as Top2A (DNA replication), AKB (chromosome remodeling and mitotic spindle formation), and suppression of p21 CIP1 and p27KIP1. The CDK2, HAT1 and MYST2 were, however, unaffected in the above study. Using SphK inhibitor and specific siRNA targeting either SphK1 or SphK2, we also unequivocally established that SphK1, but not SphK2, promotes H2691 mesothelioma cell proliferation. Using a multi-walled carbon nanotubes induced peritoneal mesothelioma mouse model, we showed that the SphK1-/- null mice exhibited significantly less inflammation and granulamatous nodules compared to their wild type counterparts. CONCLUSIONS/SIGNIFICANCE: The lipid kinase SphK1 plays a positive and essential role in the growth and development of malignant mesothelioma and is therefore a likely therapeutic target.

Novel role for non-muscle myosin light chain kinase (MLCK) in hyperoxia-induced recruitment of cytoskeletal proteins, NADPH oxidase activation, and reactive oxygen species generation in lung endothelium.

We recently demonstrated that hyperoxia (HO) activates lung endothelial cell NADPH oxidase and generates reactive oxygen species (ROS)/superoxide via Src-dependent tyrosine phosphorylation of p47(phox) and cortactin. Here, we demonstrate that the non-muscle ~214-kDa myosin light chain (MLC) kinase (nmMLCK) modulates the interaction between cortactin and p47(phox) that plays a role in the assembly and activation of endothelial NADPH oxidase. Overexpression of FLAG-tagged wild type MLCK in human pulmonary artery endothelial cells enhanced interaction and co-localization between cortactin and p47(phox) at the cell periphery and ROS production, whereas abrogation of MLCK using specific siRNA significantly inhibited the above. Furthermore, HO stimulated phosphorylation of MLC and recruitment of phosphorylated and non-phosphorylated cortactin, MLC, Src, and p47(phox) to caveolin-enriched microdomains (CEM), whereas silencing nmMLCK with siRNA blocked recruitment of these components to CEM and ROS generation. Exposure of nmMLCK(-/-) null mice to HO (72 h) reduced ROS production, lung inflammation, and pulmonary leak compared with control mice. These results suggest a novel role for nmMLCK in hyperoxia-induced recruitment of cytoskeletal proteins and NADPH oxidase components to CEM, ROS production, and lung injury.

FoxM1 mediates the progenitor function of type II epithelial cells in repairing alveolar injury induced by Pseudomonas aeruginosa.

The alveolar epithelium is composed of the flat type I cells comprising 95% of the gas-exchange surface area and cuboidal type II cells comprising the rest. Type II cells are described as facultative progenitor cells based on their ability to proliferate and trans-differentiate into type I cells. In this study, we observed that pneumonia induced by intratracheal instillation of Pseudomonas aeruginosa (PA) in mice increased the expression of the forkhead transcription factor FoxM1 in type II cells coincidentally with the induction of alveolar epithelial barrier repair. FoxM1 was preferentially expressed in the Sca-1(+) subpopulation of progenitor type II cells. In mice lacking FoxM1 specifically in type II cells, type II cells showed decreased proliferation and impaired trans-differentiation into type I cells. Lungs of these mice also displayed defective alveolar barrier repair after injury. Expression of FoxM1 in the knockout mouse lungs partially rescued the defective trans-differentiation phenotype. Thus, expression of FoxM1 in type II cells is essential for their proliferation and transition into type I cells and for restoring alveolar barrier homeostasis after PA-induced lung injury.

Nrf2 regulates hyperoxia-induced Nox4 expression in human lung endothelium: identification of functional antioxidant response elements on the Nox4 promoter.

Reactive oxygen species (ROS) generated by vascular endothelial and smooth muscle cells contribute to the development and progression of vascular diseases. We have recently shown that hyperoxia enhances NADPH oxidase 4 (Nox4) expression, which regulates lung endothelial cell migration and angiogenesis. Regulation of Nox4 in the vasculature is poorly understood. The objective of this study was to identify the transcriptional factor(s) involved in regulation of endothelial Nox4. We found that hyperoxia-induced Nox4 expression was markedly reduced in Nrf2(-/-) mice, compared to Nrf2(+/+) mice. Exposure of human lung microvascular endothelial cells (HLMVECs) to hyperoxia stimulated Nrf2 translocation from the cytoplasm to the nucleus and increased Nox4 expression. Knockdown of Nrf2 expression using an siRNA approach attenuated basal Nox4 expression; however, it enhanced superoxide/ROS generation under both normoxia and hyperoxia. In silico analysis revealed the presence of at least three consensus sequences for the antioxidant response element (ARE) in the promoter region of Nox4. In transient transfections, hyperoxia stimulated Nox4 promoter activity in HLMVECs, and deletion of the -438 to -458 and -619 to -636 sequences markedly reduced hyperoxia-stimulated Nox4 promoter activation. ChIP analysis revealed an enhanced recruitment of Nrf2 to the endogenous Nox4 promoter spanning these two AREs after hyperoxic insult. Collectively, these results demonstrate, for the first time, a novel role for Nrf2 in regulating hyperoxia-induced Nox4 transcription via AREs in lung endothelium.

Protection of LPS-induced murine acute lung injury by sphingosine-1-phosphate lyase suppression.

A defining feature of acute lung injury (ALI) is the increased lung vascular permeability and alveolar flooding, which leads to associated morbidity and mortality. Specific therapies to alleviate the unremitting vascular leak in ALI are not currently clinically available; however, our prior studies indicate a protective role for sphingosine-1-phosphate (S1P) in animal models of ALI with reductions in lung edema. As S1P levels are tightly regulated by synthesis and degradation, we tested the hypothesis that inhibition of S1P lyase (S1PL), the enzyme that irreversibly degrades S1P via cleavage, could ameliorate ALI. Intratracheal instillation of LPS to mice enhanced S1PL expression, decreased S1P levels in lung tissue, and induced lung inflammation and injury. LPS challenge of wild-type mice receiving 2-acetyl-4(5)-[1(R),2(S),3(R),4-tetrahydroxybutyl]-imidazole to inhibit S1PL or S1PL(+/-) mice resulted in increased S1P levels in lung tissue and bronchoalveolar lavage fluids and reduced lung injury and inflammation. Moreover, down-regulation of S1PL expression by short interfering RNA (siRNA) in primary human lung microvascular endothelial cells increased S1P levels, and attenuated LPS-mediated phosphorylation of p38 mitogen-activated protein kinase and I-κB, IL-6 secretion, and endothelial barrier disruption via Rac1 activation. These results identify a novel role for intracellularly generated S1P in protection against ALI and suggest S1PL as a potential therapeutic target.

Redox regulation of Nox proteins.

The generation of reactive oxygen species (ROS) plays a major role in endothelial signaling and function. Of the several potential sources of ROS in the vasculature, the endothelial NADPH oxidase (Nox) family of proteins, Nox1, Nox2, Nox4 and Nox5, are major contributors of ROS. Excess generation of ROS contributes to the development and progression of vascular disease. While hyperoxia stimulates ROS production through Nox proteins, hypoxia appears to involve mitochondrial electron transport in the generation of superoxide. ROS generated from Nox proteins and mitochondria are important for oxygen sensing mechanisms. Physiological concentrations of ROS function as signaling molecule in the endothelium; however, excess ROS production leads to pathological disorders like inflammation, atherosclerosis, and lung injury. Regulation of Nox proteins is unclear; however, antioxidants, MAP Kinases, STATs, and Nrf2 regulate Nox under normal physiological and pathological conditions. Studies related to redox regulation of Nox should provide a better understanding of ROS and its role in the pathophysiology of vascular diseases.

Particulate matter disrupts human lung endothelial barrier integrity via ROS- and p38 MAPK-dependent pathways.

Epidemiologic studies have linked exposure to airborne pollutant particulate matter (PM) with increased cardiopulmonary mortality and morbidity. The mechanisms of PM-mediated lung pathophysiology, however, remain unknown. We tested the hypothesis that PM, via enhanced oxidative stress, disrupts lung endothelial cell (EC) barrier integrity, thereby enhancing organ dysfunction. Using PM collected from Ft. McHenry Tunnel (Baltimore, MD), we assessed PM-mediated changes in transendothelial electrical resistance (TER) (a highly sensitive measure of barrier function), reactive oxygen species (ROS) generation, and p38 mitogen-activated protein kinase (MAPK) activation in human pulmonary artery EC. PM induced significant dose (10-100 microg/ml)- and time (0-10 h)-dependent EC barrier disruption reflected by reduced TER values. Exposure of human lung EC to PM resulted in significant ROS generation, which was directly involved in PM-mediated EC barrier dysfunction, as N-acetyl-cysteine (NAC, 5 mM) pretreatment abolished both ROS production and barrier disruption induced by PM. Furthermore, PM induced p38 MAPK activation and HSP27 phosphorylation, events that were both attenuated by NAC. In addition, PM-induced EC barrier disruption was partially prevented by the p38 MAP kinase inhibitor SB203580 (10 microM) as well as by reduced expression of either p38 MAPK beta or HSP27 (siRNA). These results demonstrate that PM induces ROS generation in human lung endothelium, resulting in oxidative stress-mediated EC barrier disruption via p38 MAPK- and HSP27-dependent pathways. These findings support a novel mechanism for PM-induced lung dysfunction and adverse cardiopulmonary outcomes.

Role of lysophosphatidic acid receptor LPA2 in the development of allergic airway inflammation in a murine model of asthma.

BACKGROUND: Lysophosphatidic acid (LPA) plays a critical role in airway inflammation through G protein-coupled LPA receptors (LPA1-3). We have demonstrated that LPA induced cytokine and lipid mediator release in human bronchial epithelial cells. Here we provide evidence for the role of LPA and LPA receptors in Th2-dominant airway inflammation. METHODS: Wild type, LPA1 heterozygous knockout mice (LPA1+/-), and LPA2 heterozygous knockout mice (LPA2+/-) were sensitized with inactivated Schistosoma mansoni eggs and local antigenic challenge with Schistosoma mansoni soluble egg Ag (SEA) in the lungs. Bronchoalveolar larvage (BAL) fluids and lung tissues were collected for analysis of inflammatory responses. Further, tracheal epithelial cells were isolated and challenged with LPA. RESULTS: BAL fluids from Schistosoma mansoni egg-sensitized and challenged wild type mice (4 days of challenge) showed increase of LPA level (approximately 2.8 fold), compared to control mice. LPA2+/- mice, but not LPA1+/- mice, exposed to Schistosoma mansoni egg revealed significantly reduced cell numbers and eosinophils in BAL fluids, compared to challenged wild type mice. Both LPA2+/- and LPA1+/- mice showed decreases in bronchial goblet cells. LPA2+/- mice, but not LPA1+/- mice showed the decreases in prostaglandin E2 (PGE2) and LPA levels in BAL fluids after SEA challenge. The PGE2 production by LPA was reduced in isolated tracheal epithelial cells from LPA2+/- mice. These results suggest that LPA and LPA receptors are involved in Schistosoma mansoni egg-mediated inflammation and further studies are proposed to understand the role of LPA and LPA receptors in the inflammatory process.