Naif O. Al-Harbi

Airway and systemic oxidant-antioxidant dysregulation in asthma: a possible scenario of oxidants spill over from lung into blood.

Asthma is characterized by repeated episodes of airway obstruction and an ongoing cycle of airway inflammation. Reactive oxygen species (ROS) produced by inflammatory cells in the lung play a key role in the pathogenesis as well as amplification of inflammation in asthmatic airways. Several enzymatic and non-enzymatic antioxidants are available in the lung and systemic circulation to counteract ROS-mediated damage on various biomolecules such as lipid membranes, proteins, and DNA; however during asthmatic inflammation these defenses are overwhelmed due to excessive production of ROS thereby leading to inflammatory events in the airways/systemic circulation. ROS-mediated damage may result in increased vascular permeability, mucus hypersecretion, smooth muscle contraction, epithelial shedding and impairment in the responsiveness of β-adrenergic receptors. Strategies aimed to boost the endogenous antioxidants either through dietary or pharmacological intervention to redress oxidant-antioxidant imbalance in asthma is the current area of research in many laboratories throughout the world. This review aims at providing a comprehensive overview of the available literature on oxidative stress and antioxidants imbalance in asthma with a focus both on lung and blood components and bring forth correlations between lung/blood oxidative stress/antioxidant parameters and lung function.

Imiquimod-induced psoriasis-like skin inflammation is suppressed by BET bromodomain inhibitor in mice through RORC/IL-17A pathway modulation.

Psoriasis is one of the most common skin disorders characterized by erythematous plaques that result from hyperproliferative keratinocytes and infiltration of inflammatory leukocytes into dermis and epidermis. Recent studies suggest that IL-23/IL-17A/IL-22 cytokine axis plays an important role in the pathogenesis of psoriasis. The small molecule bromodomain and extraterminal domain (BET) inhibitors, that disrupt interaction of BET proteins with acetylated histones have recently demonstrated efficacy in various models of inflammation through suppression of several pathways, one of them being synthesis of IL-17A/IL-22 which primarily depends on transcription factor, retinoic acid receptor-related orphan receptor C (RORC). However, the efficacy and mechanistic aspect of a BET inhibitor in mouse model of skin inflammation has not been explored previously. Therefore, this study investigated the role of BET inhibitor, JQ-1 in mouse model of psoriasis-like inflammation. Mice were topically applied imiquimod (IMQ) to develop psoriasis-like inflammation on the shaved back and ear followed by assessment of skin inflammation (myeloperoxidase activity, ear thickness, and histopathology), RORC and its signature cytokines (IL-17A/IL-22). JQ-1 suppressed IMQ-induced skin inflammation as reflected by a decrease in ear thickness/myeloperoxidase activity, and RORC/IL-17A/IL-22 expression. Additionally, a RORα/γ agonist SR1078 was utilized to investigate the role of RORC in BET-mediated skin inflammation. SR1078 reversed the protective effect of JQ-1 on skin inflammation at both histological and molecular levels in the IMQ model. The current study suggests that BET bromodomains are involved in psoriasis-like inflammation through induction of RORC/IL-17A pathway. Therefore, inhibition of BET bromodomains may provide a new therapy against skin inflammation.

Proteinase activated receptor-2-mediated dual oxidase-2 up-regulation is involved in enhanced airway reactivity and inflammation in a mouse model of allergic asthma.

Airway epithelial cells (AECs) express a variety of receptors, which sense danger signals from various aeroallergens/pathogens being inhaled constantly. Proteinase‐activated receptor 2 (PAR‐2) is one such receptor and is activated by cockroach allergens, which have intrinsic serine proteinase activity. Recently, dual oxidases (DUOX), especially DUOX‐2, have been shown to be involved in airway inflammation in response to Toll‐like receptor activation. However, the association between PAR‐2 and DUOX‐2 has not been explored in airways of allergic mice. Therefore, this study investigated the contribution of DUOX‐2/reactive oxygen species (ROS) signalling in airway reactivity and inflammation after PAR‐2 activation. Mice were sensitized intraperitoneally with intact cockroach allergen extract (CE) in the presence of aluminium hydroxide followed by intranasal challenge with CE. Mice were then assessed for airway reactivity, inflammation, oxidative stress (DUOX‐2, ROS, inducible nitric oxide synthase, nitrite, nitrotyrosine and protein carbonyls) and apoptosis (Bax, Bcl‐2, caspase‐3). Challenge with CE led to up‐regulation of DUOX‐2 and ROS in AECs with concomitant increases in airway reactivity/inflammation and parameters of oxidative stress, and apoptosis. All of these changes were significantly inhibited by intranasal administration of ENMD‐1068, a small molecule antagonist of PAR‐2 in allergic mice. Administration of diphenyliodonium to allergic mice also led to improvement of allergic airway responses via inhibition of the DUOX‐2/ROS pathway; however, these effects were less pronounced than PAR‐2 antagonism. The current study suggests that PAR‐2 activation leads to up‐regulation of the DUOX‐2/ROS pathway in AECs, which is involved in regulation of airway reactivity and inflammation via oxidative stress and apoptosis.

Dexamethasone Attenuates LPS-induced Acute Lung Injury through Inhibition of NF-κB, COX-2, and Pro-inflammatory Mediators

ABSTRACT Dexamethasone (DEX) is a synthetic glucocorticoid with potent anti-inflammatory effects that is widely used to treat inflammatory diseases. The aim of the present study was to investigate the possible protective effect of DEX on the lipopolysaccharides (LPS)-induced acute lung injury (ALI) in a mouse model. Animals were pretreated with DEX (5 and 10 mg/kg, i.p.) for seven days and acute lung injury was induced by intranasal (i.n.) administration of LPS on day 7. In the present study, administration of LPS resulted in significant increase in neutrophils and lymphocytes count whereas a substantial reduction in T cell subsets (CD3+ and CD4+) and pro-inflammatory (IL-6 and TNF-α) cytokines occurred, which were reversed by DEX treatment. RT-PCR analysis revealed an increased mRNA expression of IL-6, TNF-α, COX-2, iNOS, and NF-κB p65 and decreased IL-10 in the LPS group, which were reversed by treatment with DEX in lung tissues. Western blot analysis revealed an increased expression of COX-2, iNOS and NF-κB p65 in the LPS-group, which was reduced by treatment with DEX. Compared with the LPS group, the DEX treatment also demonstrated a considerable increase in the protein expression level of IL-10 cytokine. Administration of LPS resulted in marked increase in malondialdehyde (MDA) levels and myeloperoxidase (MPO) activity whereas noticeable decrease in glutathione (GSH) content. These changes were significantly reversed by treatment with DEX. The histological examinations revealed protective effect of DEX while LPS group aggravated lung injury. The present findings demonstrate the potent anti-inflammatory action of the DEX against acute lung injury induced by LPS.

Diosmin downregulates the expression of T cell receptors, pro-inflammatory cytokines and NF-κB activation against LPS-induced acute lung injury in mice.

Diosmin, a natural flavonoid glycoside present abundantly in the pericarp of various citrus fruits. Because of its anti-inflammatory and antioxidant properties, it can be used in many diseases. In this study, we investigated the possible protective mechanisms of the diosmin on LPS-induced lung injury through inhibition of T cell receptors, pro-inflammatory cytokines and NF-κB activation. Animals were pretreated with diosmin (50 and 100mg/kg, p.o.) for seven days prior to lipopolysaccharides (LPS) treatment. LPS administration increased neutrophils, monocytes, lymphocytes, total leukocyte count (TLC) and platelets which were decreased by diosmin. We observed that mice exposed to LPS showed increased malondialdehyde level and MPO activity whereas marked decrease in glutathione content. These changes were significantly reversed by treatment with diosmin in a dose dependent manner. Diosmin treatment showed a substantial reduction in T cell (CD4(+) and CD8(+)) receptors and pro-inflammatory (IL-2(+) and IL-17(+)) cytokines in whole blood. In addition, RT-PCR analysis revealed increased mRNA expression of IL-6, IL-17, TNF-α, and NF-κB in the LPS group, while reduced by treatment with diosmin. Western blot analysis confirmed the increased protein expression of IL-1β, TNF-α and NF-κB p65 in the LPS group and treatment of animals with diosmin reversed these effects. The levels of cytoplasmic p-IκB-α and p-NF-κB p65 expression also were mitigated by diosmin. The histological examinations revealed protective effect of diosmin while LPS group aggravated lung injury. These results support the potential for diosmin to be investigated as a potential agent for the treatment of lung injury and inflammatory diseases.

Carbon tetrachloride-induced hepatotoxicity in rat is reversed by treatment with riboflavin

Liver is a vital organ for the detoxification of toxic substances present in the body and hepatic injury is associated with excessive exposure to toxicants. The present study was designed to evaluate the possible hepatoprotective effects of riboflavin against carbon tetrachloride (CCl4) induced hepatic injury in rats. Rats were divided into six groups. Hepatotoxicity was induced by the administration of a single intraperitoneal dose of CCl4 in experimental rats. Riboflavin was administered at 30 and 100mg/kg by oral gavage to test its protective effect on hepatic injury biochemically and histopathologically in the blood/liver and liver respectively. The administration of CCl4 resulted in marked alteration in serum hepatic enzymes (like AST, ALT and ALP), oxidant parameters (like GSH and MDA) and pro-inflammatory cytokine TNF-α release from blood leukocytes indicative of hepatic injury. Changes in serum hepatic enzymes, oxidant parameters and TNF-α production induced by CCl4 were reversed by riboflavin treatment in a dose dependent manner. Treatment with standard drug, silymarin also reversed CCl4 induced changes in biomarkers of liver function, oxidant parameters and inflammation. The biochemical observations were paralleled by histopathological findings in rat liver both in the case of CCl4 and treatment groups. In conclusion, riboflavin produced a protective effect against CCl4-induced liver damage. Our study suggests that riboflavin may be used as a hepato-protective agent against toxic effects caused by CCl4 and other chemical agents in the liver.

Association between Paraoxonases Gene Expression and Oxidative Stress in Hepatotoxicity Induced by CCl4

Objectives. The purpose of the study is to evaluate the hepatoprotective effect of rutin in carbon tetrachloride- (CCl4-) induced liver injuries in rat model. Methods. Forty male Wistar albino rats were divided into four groups. Group I was the control group and received dimethyl sulphoxide (DMSO) and olive oil. Group II received rutin. Groups III was treated with CCl4. Group IV was administered rutin after 48 h of CCl4 treatment. Liver enzymes level, lipid profile, lipid peroxidation, and hydrogen peroxide were measured. The genes expression levels were monitored by real time RT-PCR and western blot techniques. Results. CCl4 group showed significant increase in alanine aminotransferase (ALT), aspartate aminotransferase (AST), thiobarbituric acid reactive substances (TBAR), hydrogen peroxide (H2O2), and lipid profile and a significant decrease in glutathione peroxidase (GPx), glutathione S transferase (GST), catalase (CAT), paraoxonase-1 (PON-1), paraoxonase-3 (PON-3), peroxisome proliferator activated receptor delta (PPAR-δ), and ATP-binding cassette transporter 1 (ABAC1) genes expression levels. Interestingly, rutin supplementation completely reversed the biochemical and gene expression levels induced by CCl4 to control values. Conclusion. CCl4 administration causes aberration of genes expression levels in oxidative stress pathway resulting in DNA damage and hepatotoxicity. Rutin causes hepatoprotective effect through enhancing the antioxidant genes.

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.

Oxidative airway inflammation leads to systemic and vascular oxidative stress in a murine model of allergic asthma

Oxidant-antioxidant imbalance plays an important role in repeated cycles of airway inflammation observed in asthma. It is when reactive oxygen species (ROS) overwhelm antioxidant defenses that a severe inflammatory state becomes apparent and may impact vasculature. Several studies have shown an association between airway inflammation and cardiovascular complications; however so far none has investigated the link between airway oxidative stress and systemic/vascular oxidative stress in a murine model of asthma. Therefore, this study investigated the contribution of oxidative stress encountered in asthmatic airways in modulation of vascular/systemic oxidant-antioxidant balance. Rats were sensitized intraperitoneally with ovalbumin (OVA) in the presence of aluminum hydroxide followed by several intranasal (i.n.) challenges with OVA. Rats were then assessed for airway and vascular inflammation, oxidative stress (ROS, lipid peroxides) and antioxidants measured as total antioxidant capacity (TAC) and thiol content. Challenge with OVA led to increased airway inflammation and oxidative stress with a concomitant increase in vascular inflammation and oxidative stress. Oxidative stress in the vasculature was significantly inhibited by antioxidant treatment, N-acetyl cysteine; whereas hydrogen peroxide (H2O2) inhalation worsened it. Therefore, our study shows that oxidative airway inflammation is associated with vascular/systemic oxidative stress which might predispose these patients to increased cardiovascular risk.

Toll-like receptor 4 signaling is associated with upregulated NADPH oxidase expression in peripheral T cells of children with autism

Autism spectrum disorders (ASD) affect millions of children worldwide, and are characterized by impairment in social interaction and communication, and specific repetitive behavioral patterns. Growing evidence highlights a role of toll-like receptors (TLRs) in the pathogenesis of ASD. Specifically, TLR-4 activation has been shown to be associated with increased pro-inflammatory cytokines as well as autistic symptoms in offspring. NADPH oxidase (NOX-2) derived reactive oxygen species (ROS) have also been shown to play pathogenic role under inflammatory conditions. However, the role of TLR-4 in the regulation of NOX-2 derived ROS has not been explored in ASD, particularly in T cells. Therefore, this study explored TLR-4 and NOX-2 related signaling in peripheral T cells of ASD patients (n=35) and age-matched typically developing children (n=30). In this study, we find that ASD individuals have increased TLR-4 expression on T cells which is associated with increased NOX-2 expression and ROS generation as compared to typically developing children. Moreover, activation of TLR-4 on T cells by lipopolysaccharide (LPS) in vitro leads to enhanced generation of NOX-2 derived ROS via nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) pathway. These data support a link between T cell TLR-4 activation and NOX-2/ROS upregulation in ASD patients. Our study has implications in the context of neuroinflammation observed in ASD patients as ROS may lead to amplification and perpetuation of inflammation both in the periphery and central nervous system. Our data also suggest that therapeutic targeting of TLR-4 signaling may lead to reduction in inflammation of ASD patients.