Reducing agents inhibit the contractile response of isolated guinea-pig main bronchi

Pathogenesis-based preexposure prophylaxis associated with a low risk of SARS-CoV-2 infection in healthcare workers at a designated COVID-19 hospital: a pilot study

Background

At present, no agents are known to be effective at preventing COVID-19. Based on current knowledge of the pathogenesis of this disease, we suggest that SARS-CoV-2 infection might be attenuated by directly maintaining innate pulmonary redox, metabolic and dilation functions using well-tolerated medications that are known to serve these functions, specifically, a low-dose aerosolized combination of glutathione, inosine and potassium.

Methods

From June 1 to July 10, 2020, we conducted a pilot, prospective, open-label, single-arm, single-center study to evaluate the safety and efficacy of preexposure prophylaxis (PrEP) with aerosolized combination medication (ACM) on the incidence of SARS-CoV-2 positivity in 99 healthcare workers (HCWs) at a hospital designated for treating COVID-19 patients. We compared SARS-CoV-2 positivity in ACM users to retrospective data collected from 268 untreated HCWs at the same hospital. Eligible participants received an aerosolized combination of 21.3 mg/ml glutathione and 8.7 mg/ml inosine in 107 mM potassium solution for 14 days. The main outcome was the frequency of laboratory-confirmed SARS-CoV-2 cases, defined as individuals with positive genetic or immunological tests within 28 days of the study period.

Results

SARS-CoV-2 was detected in 2 ACM users (2, 95% CI: 0.3 to 7.1%), which was significantly less than the incidence in nonusers, at 24 (9, 95% CI: 5.8 to 13.0%; P = 0.02). During the PrEP period, solicited adverse events occurred in five participants; all were mild and transient reactions.

Conclusions

Our findings might be used either to prevent SARS-CoV-2 infection or to support ongoing and new research into more effective treatments for COVID-19.

Trial registration

ISRCTN, ISRCTN34160010. Registered 14 September 2020 - Retrospectively registered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06241-1.

Glutathione ethyl ester supplementation prevents airway hyper-responsiveness in mice

Background

Oxidative stress plays an important role in the pathogenesis of asthma. Glutathione (GSH) is considered to be one of the most important antioxidants. Our study systematically investigated the effect of the GSH alternative, glutathione ethyl ester (GSH-EE), on airway hyper-responsiveness (AHR) in mice.

Methods

Sixty-three male specific pathogen-free mice were used. Asthma was induced using a single dose of ovalbumin (OVA). The normal group (n=15) received vehicle only [Al(OH)3 in saline]. Then, 48 mice were divided into two groups, including a control group who received sodium phosphate buffer (pH =7.4), and the GSH-EE group who received 0.1% GSH-EE. AHR was measured 2, 6, and 12 hours after exposure to nebulized OVA (0.01%). The animals were then sacrificed, and lung tissue and the bronchi-alveolar lavage fluid (BALF) were harvested. Factors involved in the antioxidant response to asthma were then measured in these tissues, including thiol content (from GSH and protein), γ-glutamylcysteine synthetase (γ-GCS) activity and expression, and nuclear factor-erythroid-2-related factor (Nrf2) expression.

Results

The GSH-EE group showed a significant attenuation of AHR (P<0.01) 2 hours after OVA challenge, and significantly enhanced thiol contents by approximately 45% (P<0.05) at 2 and 6 hours after the last OVA challenge, compared to the control group. γ-GCS activity was also higher in the GSH-EE group compared to the control group at different time points (P<0.01). γ-GCSh and Nrf2 protein expression increased in the GSH-EE group and the control group compared with the normal group, but there was no statistically significant difference (P>0.05) between the GSH-EE group and the control group.

Conclusions

GSH-EE supplementation can prevent AHR in asthmatic mice during the early stages. It may function by serving as a precursor for GSH biosynthesis and by protecting sulfhydryl groups from oxidation.

Glutathione modulation during sensitization as well as challenge phase regulates airway reactivity and inflammation in mouse model of allergic asthma

Glutathione, being a major intracellular redox regulator has been shown to be implicated in regulation of airway reactivity and inflammation. However, no study so far has investigated the effect of glutathione depletion/repletion during sensitization and challenge phases separately, which could provide an important insight into the pathophysiology of allergic asthma. The aim of the present study was to evaluate the role of glutathione depletion/repletion during sensitization and challenge phases separately in a mouse model of allergic asthma. Buthionine sulphoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase or N-acetyl cysteine (NAC), a thiol donor were used for depletion or repletion of glutathione levels respectively during both sensitization and challenge phases separately followed by assessment of airway reactivity, inflammation and oxidant-antioxidant balance in allergic mice. Depletion of glutathione with BSO during sensitization as well as challenge phase worsened allergen induced airway reactivity/inflammation and caused greater oxidant-antioxidant imbalance as reflected by increased NADPH oxidase expression/reactive oxygen species (ROS) generation/lipid peroxides formation and decreased total antioxidant capacity. On the other hand, repletion of glutathione pool by NAC during sensitization and challenge phases counteracted allergen induced airway reactivity/inflammation and restored oxidant-antioxidant balance through a decrease in NADPH oxidase expression/ROS generation/lipid peroxides formation and increase in total antioxidant capacity. Taken together, these findings suggest that depletion or repletion of glutathione exacerbates or ameliorates allergic asthma respectively by regulation of airway oxidant-antioxidant balance. This might have implications towards increased predisposition to allergy by glutathione depleting environmental pollutants.

Glutathione redox control of asthma: from molecular mechanisms to therapeutic opportunities

Asthma is a chronic inflammatory disorder of the airways associated with airway hyper-responsiveness and airflow limitation in response to specific triggers. Whereas inflammation is important for tissue regeneration and wound healing, the profound and sustained inflammatory response associated with asthma may result in airway remodeling that involves smooth muscle hypertrophy, epithelial goblet-cell hyperplasia, and permanent deposition of airway extracellular matrix proteins. Although the specific mechanisms responsible for asthma are still being unraveled, free radicals such as reactive oxygen species and reactive nitrogen species are important mediators of airway tissue damage that are increased in subjects with asthma. There is also a growing body of literature implicating disturbances in oxidation/reduction (redox) reactions and impaired antioxidant defenses as a risk factor for asthma development and asthma severity. Ultimately, these redox-related perturbations result in a vicious cycle of airway inflammation and injury that is not always amenable to current asthma therapy, particularly in cases of severe asthma. This review will discuss disruptions of redox signaling and control in asthma with a focus on the thiol, glutathione, and reduced (thiol) form (GSH). First, GSH synthesis, GSH distribution, and GSH function and homeostasis are discussed. We then review the literature related to GSH redox balance in health and asthma, with an emphasis on human studies. Finally, therapeutic opportunities to restore the GSH redox balance in subjects with asthma are discussed.

Rapid non-genomic effects of glucocorticoids on oxidative stress in a guinea pig model of asthma

BACKGROUND AND OBJECTIVE

Glucocorticoids (GC) may exert therapeutic effects in asthma by a rapid non-genomic mechanism. The lungs of asthmatic patients are exposed to oxidative stress, which is believed to be critical in the pathogenesis of asthma. The aim of this study was to investigate whether GC exert a rapid non-genomic effect on oxidative stress in asthmatic guinea pigs.

METHODS

The guinea pig asthma model was used to assess inhibitory effects of budesonide (BUD) on oxidative stress. BAL fluid (BALF), trolox equivalent antioxidant capacity and lung manganese superoxide dismutase (MnSOD) activity were measured by spectrophotometry. Superoxide anion production was measured by cytochrome c reduction assay.

RESULTS

Oxidative stress occurred within minutes following antigen challenge and BUD reduced the severity of oxidative stress in asthmatic guinea pigs within 15 min. BUD significantly decreased BALF trolox equivalent antioxidant capacity and lung MnSOD activity, as compared with those of vehicle-treated asthmatic guinea pigs (P < 0.05). Additionally, BUD rapidly inhibited in vitro superoxide anion production by BALF cells and bronchi harvested from sensitized animals. These rapid effects were not blocked by the GC receptor antagonist RU486 and/or the protein synthesis inhibitor cycloheximide.

CONCLUSIONS

BUD reduced oxidative stress in a guinea pig model of asthma by a rapid non-genomic mechanism. These data suggest new mechanisms whereby GC treatments may benefit asthma.

Airway smooth muscle relaxation is impaired in mice lacking the p47phox subunit of NAD(P)H oxidase

NAD(P)H oxidase is one of the critical enzymes mediating cellular production of reactive oxygen species and has a central role in airway smooth muscle (ASM) cell proliferation. Since reactive oxygen species also affect ASM contractile response, we hypothesized a regulatory role of NAD(P)H oxidase in ASM contractility. We therefore studied ASM function in wild-type mice (C57BL/6J) and mice deficient in a component (p47phox) of NAD(P)H oxidase. In histological sections of the trachea, we found that the area occupied by ASM was 17% more in p47(phox-/-) than in wild-type mice. After correcting for the difference in ASM content, we found that force generation did not vary between the two genotypes. Similarly, their ASM shortening velocity, maximal power, and sensitivity to acetylcholine, as well as airway responsiveness to methacholine in vivo, were not significantly different. The main finding of this study was a significantly reduced ASM relaxation in p47phox-/- compared with wild-type mice both during the stimulus and after the end of stimulation. The tension relaxation attained at the 20th second of electric field stimulation was, respectively, 17.6 +/- 2.4 and 9.2 +/- 2.3% in null and wild-type mice (P <0.01 by t-test). Similar significant differences were found in the rate of tension relaxation and the time required to reduce tension by one-half. Our data suggest that NAD(P)H oxidase may have a role in the structural arrangement and mechanical properties of the airway tissue. Most importantly, we report the first evidence that the p47phox subunit of NAD(P)H oxidase plays a role in ASM relaxation.

The role of oxidative stress in an equine model of human asthma

Equine recurrent airway obstruction (RAO) is a naturally occurring respiratory disease in horses with many similarities to human asthma and, as a result, has been used as an animal model of this disease. Oxidative stress has been demonstrated to occur in a range of respiratory diseases in human beings including asthma. Quantitatively, horses have a greater non-enzymatic antioxidant capacity in the pulmonary epithelial lining fluid compared to human beings due to high ascorbic acid concentrations, which reflects their ability to synthesise ascorbic acid. Consequently, a greater oxidative load is likely to be required to induce oxidative stress in horses compared to human beings. Induction of acute neutrophilic airway inflammation in RAO horses by exposure to organic dust does not result in marked pulmonary oxidative stress. However, with a more prolonged inflammatory response, the antioxidant capacity is depleted and oxidative stress occurs. Despite the clear evidence of oxidative stress in RAO, there is currently limited data linking oxidative stress with a causal role in the development of the pathophysiological features of RAO, namely airway obstruction, airway hyper-responsiveness, airway inflammation and mucus accumulation. However, pathways do exist whereby oxidants could potentially augment the production of important mediators in RAO. Further work is required to ascertain the benefits of antioxidant supplementation in RAO and to determine the role of oxidative stress in the pathogenesis of the disease. Given the similarities with human asthma, results from RAO horses could enhance the understanding of the role of oxidative stress in human asthma.

Effect of levocetirizine on the contraction induced by histamine on isolated rabbit bronchioles from precision-cut lung slices

The present experiments were designed to study the effects of levocetirizine (a potent selective histamine H(1) antagonist) on the contraction induced by histamine on isolated rabbit bronchioles using the precision-cut lung slice technology. Histamine induced a concentration-dependent contraction of isolated rabbit bronchioles (pD(2) value of 5.6). Mepyramine (0.01-1 micromol/l) induced a shift to the right without any decrease in the concentration-response curve to histamine (pA(2) value of 8.2). Levocetirizine (0.03-0.1 micromol/l) induced both a shift to the right and a decrease in the maximal amplitude of the concentration-response curve to histamine (pA(2) and pD'(2) values of 7.9 and 7.0, respectively). The difference between both compounds could be explained in terms of the difference in the dissociation rate from the histamine H(1) receptor coupled to a putative low receptor reserve present in the rabbit bronchioles.

Effects of cysteine donor supplementation on exercise-induced bronchoconstriction

PURPOSE

Reactive oxygen/nitrogen species (ROS/RNS) in resident airway cells may be important in bronchoconstriction following exercise. Glutathione (GSH) is a major lung antioxidant and could influence pathological outcomes in individuals with exercise-induced bronchoconstriction (EIB). This study examined the effects of supplementation with undenatured whey protein (UWP) in subjects exhibiting airway narrowing following eucapnic voluntary hyperventilation (EVH), a surrogate challenge for diagnosis of EIB. UWP is a cysteine donor that augments GSH production.

METHODS

In a randomized, double-blind, placebo-controlled study, 18 EIB-positive subjects (age: 25.2 +/- 9.01 yr; weight: 77.3 +/- 18.92 kg; height: 1.7 +/- 0.09 m) with post-EVH falls of > or =10% in FEV1 received 30 g UWP (TX) or casein placebo (PL)/d. Subjects performed 6-min EVH challenges before and after 4 and 8 wk of supplementation. Exhaled nitric oxide (eNO) was measured serially before spirometry and at 1-wk intervals. Spirometry was performed pre- and 5, 10, and 15 min postchallenge.

RESULTS

Subjects exhibited significant mean improvement in postchallenge falls in FEV(1) from 0 wk (-22.6 +/- 12.22%) with TX at 4 (-18.9 +/- 12.89%, P < 0.05) and 8 wk (-16.98 +/- 11.61%, P < 0.05) and significant mean reduction in post-EVH peak falls in FEF(25-75) from 0 wk (-40.6 +/- 15.28%) with TX at 4 (-33.1 +/- 17.11%, P < 0.01) and 8 (-29.7 +/- 17.42%, P < 0.05) wk. No changes in FEV(1) or FEF(25-75) were observed in the PL group at any time point. Mean eNO for PL and TX groups at 0, 4, and 8 wk (46.8 +/- 31.33, 46.5 +/- 35.73, 49.3 +/- 37.12 vs 35.2 +/- 26.87, 29.1 +/- 17.26, 34.7 +/- 21.11 ppb, respectively) was not significantly different.

CONCLUSIONS

UWP may augment pulmonary antioxidant capacity and be therapeutically beneficial in individuals exhibiting EIB, as postchallenge pulmonary function improved with supplementation. The lack of significant change in eNO suggests that the pulmonary function improvements from UWP supplementation are independent of eNO.

Sputum levels of reduced glutathione increase 24 hours after allergen challenge in isolated early, but not dual asthmatic responders

BACKGROUND

The pathogenesis of late asthmatic reactions after allergen challenge in contrast to isolated early responses is incompletely understood. Recently, the antioxidant glutathione and endogenous nitrosothiols were shown to protect against bronchoconstriction. We compared reduced (GSH) and oxidized glutathione (GSSG) and nitrosothiols in induced sputum following allergen challenge in mild asthmatics with isolated early (EAR) and dual early and late (LAR) asthmatic responses.

METHODS

Exhaled nitric oxide, sputum cells and sputum supernatant concentrations of GSH, GSSG and nitrosothiols were quantified 2-5 days prior to and 24 h after allergen challenge in 24 mild asthmatics (12 EAR, 12 LAR, only beta-agonists prn).

RESULTS

There were no differences at baseline between EAR and LAR asthmatics for any of the parameters (p > 0.1, all comparisons). Mean +/- SD fall in forced expiratory volume in 1 s, expressed as the percentage decrease compared to the baseline value, between 3 and 8 h after allergen challenge was 1 +/- 5% in the group of patients without LAR vs. 24.9 +/- 8.7% in the group of patients with LAR (p < 0.001). Sputum eosinophils increased in both groups (p < 0.05, both comparisons), whereas neutrophils only increased in LAR subjects (p = 0.06 vs. EAR). In contrast, GSH was significantly increased 24 h after challenge only in EAR asthmatics [geometric mean with 95% confidence intervals: before: 3.3 microM (1.25-7.9 microM), after: 5.9 microM (2.7-12.9 microM), p = 0.05; mean difference vs. LAR subjects: 6 microM (0.1-12 microM), p = 0.048], and the proportion of GSSG was positively correlated with postallergen eosinophils in all patients (rho = 0.4, p = 0.05). There was no change in nitrosothiols after 24 h in either EAR or LAR subjects (p > 0.23, all comparisons).

CONCLUSIONS

GSH increases 24 h after allergen challenge in isolated early responders. These data suggest that different adoptive responses to allergen may result in different physiologic phenotypes. Further studies on the role of glutathione in allergen-induced bronchoconstriction are clearly warranted.