Oxidative Stress and Inflammation in Acute and Chronic Lung Injuries.

Acute and chronic lung injuries are among the leading causes of mortality worldwide. Lung injury can affect several components of the respiratory system, including the airways, parenchyma, and pulmonary vasculature. Although acute and chronic lung injuries represent an enormous economic and clinical burden, currently available therapies primarily focus on alleviating disease symptoms rather than reversing and/or preventing lung pathology. Moreover, some supportive interventions, such as oxygen and mechanical ventilation, can lead to (further) deterioration of lung function and even the development of permanent injuries. Lastly, sepsis, which can originate extrapulmonary or in the respiratory system itself, contributes to many cases of lung-associated deaths. Considering these challenges, we aim to summarize molecular and cellular mechanisms, with a particular focus on airway inflammation and oxidative stress that lead to the characteristic pathophysiology of acute and chronic lung injuries. In addition, we will highlight the limitations of current therapeutic strategies and explore new antioxidant-based drug options that could potentially be effective in managing acute and chronic lung injuries.

Diallyl disulfide prevents cigarette smoke-induced emphysema in mice.

INTRODUCTION: Cigarette smoke (CS) is the main risk factor for the development of chronic obstructive pulmonary disease (COPD) and pulmonary emphysema. The use of antioxidants has emerged as a potential therapeutic strategy to treat airway inflammation and lung diseases. In the current study, we investigated the potential therapeutic impact of diallyl disulfide (Dads) treatment in a murine model of CS-induced emphysema. METHODS: C57BL/6 mice were exposed to CS for 60 consecutive days and treated with vehicle or Dads (30, 60 or 90 mg/kg) by oral gavage for the last 30 days, three times/week. The control group was sham-smoked and received vehicle treatment. All mice were euthanized 24 h after day 60; bronchoalveolar lavage (BAL) was performed and lungs were processed for further experimentation. Histological (HE stained sections, assessment of mean linear intercept (Lm)), biochemical (nitrite, superoxide dismutase (SOD), glutathione transferase (GST), and malondialdehyde (MDA) equivalents), and molecular biology (metalloproteinase (MMP) 12, SOD2, carbonyl reductase 1 (CBR1), nitrotyrosine (PNK), 4-hydroxynonenal (4-HNE), and CYP2E1) analyses were performed. RESULTS: Treatment with Dads dose-dependently reduced CS-induced leukocyte infiltration into the airways (based on BAL fluid counts) and improved lung histology (indicated by a reduction of Lm). Furthermore, CS exposure dramatically reduced the activity of the antioxidant enzymes SOD and GST in lung tissue and increased nitrite and MDA levels in BAL; these effects were all effectively counteracted by Dads treatment. Western blot analysis further confirmed the antioxidant potential of Dads, showing that treatment prevented the CS-induced decrease in SOD2 expression and increase in lung damage markers, such as CBR1, PNK, and 4-HNE. Furthermore, increased MMP12 (an important hallmark of CS-induced emphysema) and CYP2E1 lung protein levels were significantly reduced in mice receiving Dads treatment. CONCLUSION: Our findings demonstrate that treatment with Dads is effective in preventing multiple pathological features of CS-induced emphysema in an in vivo mouse model. In addition, we have identified several proteins/enzymes, including 4-HNE, CBR1, and CYP2E1, that are modifiable by Dads and could represent specific therapeutic targets for the treatment of COPD and emphysema.

Dimethyl Fumarate Attenuates Lung Inflammation and Oxidative Stress Induced by Chronic Exposure to Diesel Exhaust Particles in Mice.

Air pollution is mainly caused by burning of fossil fuels, such as diesel, and is associated with increased morbidity and mortality due to adverse health effects induced by inflammation and oxidative stress. Dimethyl fumarate (DMF) is a fumaric acid ester and acts as an antioxidant and anti-inflammatory agent. We investigated the potential therapeutic effects of DMF on pulmonary damage caused by chronic exposure to diesel exhaust particles (DEPs). Mice were challenged with DEPs (30 µg per mice) by intranasal instillation for 60 consecutive days. After the first 30 days, the animals were treated daily with 30 mg/kg of DMF by gavage for the remainder of the experimental period. We demonstrated a reduction in total inflammatory cell number in the bronchoalveolar lavage (BAL) of mice subjected to DEP + DMF as compared to those exposed to DEPs alone. Importantly, DMF treatment was able to reduce lung injury caused by DEP exposure. Intracellular total reactive oxygen species (ROS), peroxynitrite (OONO), and nitric oxide (NO) levels were significantly lower in the DEP + DMF than in the DEP group. In addition, DMF treatment reduced the protein expression of kelch-like ECH-associated protein 1 (Keap-1) in lung lysates from DEP-exposed mice, whereas total nuclear factor κB (NF-κB) p65 expression was decreased below baseline in the DEP + DMF group compared to both the control and DEP groups. Lastly, DMF markedly reduced DEP-induced expression of nitrotyrosine, glutathione peroxidase-1/2 (Gpx-1/2), and catalase in mouse lungs. In summary, DMF treatment effectively reduced lung injury, inflammation, and oxidative and nitrosative stress induced by chronic DEP exposure. Consequently, it may lead to new therapies to diminish lung injury caused by air pollutants.

Eucalyptol promotes lung repair in mice following cigarette smoke-induced emphysema.

BACKGROUND: Eucalyptol is a monoterpenoid oil present in many plants, principally the Eucalyptus species, and has been reported to have anti-inflammatory and antioxidative effects. HYPOTHESIS/PURPOSE: Since the potential effect of eucalyptol on mouse lung repair has not yet been studied, and considering that chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide, the aim of this study was to investigate eucalyptol treatment in emphysematous mice. STUDY DESIGN: Male mice (C57BL/6) were divided into the following groups: control (sham-exposed), cigarette smoke (CS) (mice exposed to 12 cigarettes a day for 60 days), CS + 1 mg/ml (CS mice treated with 1 mg/ml eucalyptol for 60 days), and CS + 10 mg/ml (CS mice treated with 10 mg/ml eucalyptol for 60 days). Mice in the CS and control groups received vehicle for 60 days. Eucalyptol (or the vehicle) was administered via inhalation (15 min/daily). Mice were sacrificed 24 h after the completion of the 120-day experimental procedure. METHODS: Histology and additional lung morphometric analyses, including analysis of mean linear intercept (Lm) and volume density of alveolar septa (Vv[alveolar septa]) were performed. Biochemical analyses were also performed using colorimetric assays for myeloperoxidase (MPO), malondialdehyde (MDA), and superoxide dismutase (SOD) activity, in addition to using ELISA kits for the determination of inflammatory marker levels (tumor necrosis factor alpha [TNF-α], interleukin-1 beta [IL-1ß], interleukin 6 [IL-6], keratinocyte chemoattractant [KC], and tumor growth factor beta 1 [TGF-ß1]). Finally, we investigated protein levels by western blotting (nuclear factor (erythroid-derived 2)-like 2 [Nrf2], nuclear factor kappa B [NF-κB], matrix metalloproteinase 12 [MMP-12], tissue inhibitor of matrix metalloproteinase 1 [TIMP-1], neutrophil elastase [NE], and elastin). RESULTS: Eucalyptol promoted lung repair at the higher dose (10 mg/ml), with de novo formation of alveoli, when compared to the CS group. This result was confirmed with Lm and Vv[alveolar septa] morphometric analyses. Moreover, collagen deposit around the peribronchiolar area was reduced with eucalyptol treatment when compared to the CS group. Eucalyptol also reduced all inflammatory (MPO, TNF-α, IL-1ß, IL-6, KC, and TGF-ß1) and redox marker levels (MDA) when compared to the CS group (at least p < 0.05). In general, 10 mg/ml eucalyptol was more effective than 1 mg/ml and, at both doses, we observed an upregulation of SOD activity when compared to the CS group (p < 0.001). Eucalyptol upregulated elastin and TIMP-1 levels, and reduced neutrophil elastase (NE) levels, when compared to the CS group. CONCLUSION: In summary, eucalyptol promoted lung repair in emphysematous mice and represents a potential therapeutic phytomedicine in the treatment of COPD.

Acute Exposure to Diesel-Biodiesel Particulate Matter Promotes Murine Lung Oxidative Stress by Nrf2/HO-1 and Inflammation Through the NF-kB/TNF-α Pathways.

Air pollution caused by fuel burning contributes to respiratory impairments that may lead to death. We aimed to investigate the effects of biodiesel (DB) burning in mouse lungs. DB particulate matter was collected from the exhaust pipes of a bus engine. Mice were treated with 250 µg or 1000 µg of DB particulate matter by intranasal instillation over 5 consecutive days. We demonstrated that DB particulate matter penetrated the lung in the 250-µg and 1000-µg groups. In addition, the DB particulate matter number in pulmonary parenchyma was 175-fold higher in the 250-µg group and 300-fold higher in the 1000-µg group compared to control mice. The instillation of DB particulate matter increased the macrophage number and protein levels of TNF-alpha in murine lungs. DB particulate matter enhanced ROS production in both exposed groups and the malondialdehyde levels compared to the control group. The protein expression levels of Nrf2, p-NF-kB, and HO-1 were higher in the 250-µg group and lower in the 1000-µg group than in control mice and the 250-µg group. In conclusion, DB particulate matter instillation promotes oxidative stress by activating the Nrf2/HO-1 and inflammation by p-NF-kB/TNF-alpha pathways.

Mate tea reduces high fat diet-induced liver and metabolic disorders in mice.

High-fat diet (HFD)-induced obesity is a worldwide health problem and can cause lipid accumulation in the liver. We evaluated the hepatoprotective effect of mate tea treatment in mice submitted to an HFD. C57BL/6 mice were fed an HFD for 13 weeks with and without mate tea. A separate group of mice was treated with fenofibrate as a positive control (a regular drug for lipid disorders). Histological analyses, glucose tolerance tests (GTT), and quantification of mediators related to lipid peroxidation, oxidative stress and blood biomarkers for lipid profile were performed. The weight of animals and major organs related to hepatic steatosis was determined, and proinflammatory cytokines and the participation of the Nrf2 pathway and adiponectin were evaluated. Mate tea prevented the accumulation of lipid droplets in hepatocytes as well as weight gain in animals submitted to the HFD. Mate tea treatment also prevented increases in the liver weight, heart weight and amount of visceral and subcutaneous white adipose tissue. Mate tea was able to prevent the deregulation of glucose uptake, as evaluated by GTT, and improved the indicators of oxidative stress, such as nitrite levels, catalase activity, and oxidative damage, as evaluated by protein carbonylation and the MDA levels. Mate tea had an anti-inflammatory effect, preventing the increase of IL-1ß and KC and upregulating the expression of Nrf2. Mate tea prevented insulin increase and HDL cholesterol decrease but did not affect total cholesterol or triglycerides levels. Treatment also prevented adiponectin increase. Mate tea may be a good resource to reduce hepatic steatosis in the future since it has anti-diabetic, anti-inflammatory and antioxidant effects, which prevent the accumulation of fat in the liver.

Atorvastatin dose-dependently promotes mouse lung repair after emphysema induced by elastase.

Emphysema results in a proteinase - antiproteinase imbalance, inflammation and oxidative stress. Our objective was to investigate whether atorvastatin could repair mouse lungs after elastase-induced emphysema. Vehicle (50 µL) or porcine pancreatic elastase (PPE) was administered on day 1, 3, 5 and 7 at 0.6 U intranasally. Male mice were divided into a control group (sham), PPE 32d (sacrificed 24 h after 32 days), PPE 64d (sacrificed 24 h after 64 days), and atorvastatin 1, 5 and 20 mg treated from day 33 until day 64 and sacrificed 24 h later (A1 mg, A5 mg and A20 mg, respectively). Treatment with atorvastatin was performed via inhalation for 10 min once a day. We observed that emphysema at day 32 was similar to emphysema at day 64. The mean airspace chord length (Lm) indicated a recovery of pulmonary morphology in groups A5 mg and A20 mg, as well as recovery of collagen and elastic fibers in comparison to the PPE group. Bronchoalveolar lavage fluid (BALF) leukocytes were reduced in all atorvastatin-treated groups. However, tissue macrophages were reduced only in the A20 mg group compared with the PPE group, while tissue neutrophils were reduced in the A5 mg and A20 mg groups. The redox balance was restored mainly in the A20 mg group compared with the PPE group. Finally, atorvastatin at doses of 5 and 20 mg reduced nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and matrix metalloproteinase-12 (MMP-12) compared with the PPE group. In conclusion, atorvastatin was able to induce lung tissue repair in emphysematous mice.

Propolis reversed cigarette smoke-induced emphysema through macrophage alternative activation independent of Nrf2.

Chronic obstructive pulmonary disease (COPD) is an incurable and progressive disease. Emphysema is the principal manifestation of COPD, and the main cause of this condition is cigarette smoke (CS). Natural products have shown antioxidant and anti-inflammatory properties that can prevent acute lung inflammation and emphysema, but there are few reports in the literature regarding therapeutic approaches to emphysema. We hypothesized that supplementation with natural extracts would repair lung damage in emphysema caused by CS exposure. Mice were exposed to 60days of CS and then treated or not with three different natural extracts (mate tea, grape and propolis) orally for additional 60days. Histological analysis revealed significant improvements in lung histoarchitecture, with recovery of alveolar spaces in all groups treated with natural extracts. Propolis was also able to recovery alveolar septa and elastic fibers. Propolis also increased MMP-2 and decreased MMP-12 expression, favoring the process of tissue repair. Additionally, propolis recruited leukocytes, including macrophages, without ROS release. These findings led us to investigate the profile of these macrophages, and we showed that propolis could promote macrophage alternative activation, thus increasing the number of arginase-positive cells and IL-10 levels and favoring an anti-inflammatory microenvironment. We further investigated the participation of Nrf2 in lung repair, but no Nrf2 translocation to the nucleus was observed in lung cells. Proteins and enzymes related to Nrf2 were not altered, other than NQO1, which seemed to be activated by propolis in a Nrf2-independent manner. Finally, propolis downregulated IGF1 expression. In conclusion, propolis promoted lung repair in a mouse emphysema model via macrophage polarization from M1 to M2 in parallel to the downregulation of IGF1 expression in a Nrf2-independent manner.

Pulmonary Emphysema Cross-Linking with Pulmonary Fibrosis and Vice Versa: a Non-usual Experimental Intervention with Elastase and Bleomycin.

Elastase (PPE) is usually used for emphysema models, whereas bleomycin (BLM) is used for fibrosis models. The aim of this study was to investigate the effect of BLM in PPE-induced emphysema, as well as the effect of PPE in BLM-induced fibrosis. C57BL/6 mice were divided into five groups: control, PPE, BLM, PPE + BLM, and BLM + PPE. Mice received saline, PPE (3 U/mouse), or BLM (20 U/kg) by intranasal instillation. Mice from the BLM and BLM + PPE groups received BLM on day 0 and saline or PPE on day 21, respectively. Those in the PPE and PPE + BLM groups received PPE on day 0 and saline or BLM on day 21, respectively. Mice were euthanized on day 42. We performed histology, morphometry in lung sections and ELISA, zymography and western blotting in BAL samples or lung homogenates. In the lungs of PPE + BLM and BLM + PPE groups, we observed inflammation, oxidative stress and expression of MMP-2 and MMP-9. The alveolar enlargement was reduced in the PPE + BLM group, suggesting that the BLM could participate in the alveolar remodeling process. The significance of this result supports future therapeutic approaches targeting extracellular-matrix deposition in patients with emphysema as a way to repair the enlargement of alveoli and airspaces.

Atorvastatin and Simvastatin Promoted Mouse Lung Repair After Cigarette Smoke-Induced Emphysema.

Cigarette smoke (CS) induces pulmonary emphysema by inflammation, oxidative stress, and metalloproteinase (MMP) activation. Pharmacological research studies have not focused on tissue repair after the establishment of emphysema but have instead focused on inflammatory stimulation. The aim of our study was to analyze the effects of atorvastatin and simvastatin on mouse lung repair after emphysema caused by CS. Male mice (C57BL/6, n = 45) were divided into the following groups: control (sham-exposed), CSr (mice exposed to 12 cigarettes a day for 60 days and then treated for another 60 days with the vehicle), CSr+A (CSr mice treated with atorvastatin for 60 days), and CSr+S (CSr mice treated with simvastatin for 60 days). The treatment with atorvastatin and simvastatin was administered via inhalation (15 min with 1 mg/mL once a day). Mice were sacrificed 24 h after the completion of the 120-day experimental procedure. We performed biochemical, morphological, and physiological analyses. We observed decreased levels of leukocytes and cytokines in statin-treated mice, accompanied by a reduction in oxidative stress markers. We also observed a morphological improvement confirmed by a mean linear intercept counting in statin-treated mice. Finally, statins also ameliorated lung function. We conclude that inhaled atorvastatin and simvastatin improved lung repair after cigarette smoke-induced emphysema in mice.