Inflammation-induced Oxidative Stress Research Articles

Graptopetalum paraguayenseAmeliorates Airway Inflammation and Allergy in Ovalbumin- (OVA-) Sensitized BALB/C Mice by Inhibiting Th2 Signal

Role of inflammation-induced oxidative stress in the pathogenesis and progression of chronic inflammatory airways diseases has received increasing attention in recent years. Nuclear factor erythroid 2-related factor 2 is the primary transcription factor that regulates the expression of antioxidant and detoxifying enzymes. Graptopetalum paraguayense E. Walther, a vegetable consumed in Taiwan, has been used in folk medicine for protection against liver injury through elevating antioxidation. Recently, we found that gallic acid is an active compound of Graptopetalum paraguayense E. Walther, which has been reported to inhibit T-helper 2 cytokines. Currently, we assumed that Graptopetalum paraguayense E. Walther may potentially protect against ovalbumin-induced allergy and airway inflammation. Results demonstrated that Graptopetalum paraguayense E. Walther ethanolic extracts (GPE) clearly inhibited airway inflammation, mucus cell hyperplasia, and eosinophilia in OVA-challenged mice. Additionally, GPE also prevented T-cell infiltration and Th2 cytokines, including interleukin- (IL-)4, IL-5, and IL-13 generations in bronchial alveolar lavage fluid. The adhesion molecules ICAM-1 and VCAM-1 were substantially reduced by GPE treatment mediated by Nrf2 activation. Moreover, GPE attenuated GATA3 expression and inhibited Th2 signals of the T cells. These findings suggested that GPE ameliorated the development of airway inflammation through immune regulation.

Relation of Protein Oxidation Parameters and Disease Activity in Patients with Behçet's Disease

Behçet's disease (BD) is a chronic inflammatory vasculitis characterized by endothelial dysfunction, elevated reactive oxygen species (ROS), and neutrophil hyperfunction production including acute attacks and remission periods. Ischemia modified albumin (IMA), advanced oxidation protein products (AOPP), prooxidants-antioxidants balance (PAB), and ferric reducing antioxidant power (FRAP) were evaluated in regard to their role in the pathogenesis of BD as well as their relation to clinical presentation, uveitis attacks and remission periods, and healthy volunteers. The study included 28 BD cases and 27 healthy volunteers as the control group. Blood samples were taken twice from each patient; first during an attack and second about three months after an attack, during remission period. AOPP, IMA and PAB levels were significantly increased in active periods of patients with BD compared with healthy control and remission periods of patients with BD (p < 0.0001, p < 0.0001, p < 0.0001, respectively). FRABP levels were found to be lower in active periods of patients with than healthy controls and remission periods of patients with BD (p < 0.001, p < 0.05, respectively). The AOPP levels were negatively correlated with the levels of FRAB in patients (r = -0.468, p = 0.012; r = -0.394, p = 0.038, respectively). The PAB levels were positively correlated with the levels of CRP in patients (r = -0.606, p = 0.001). Our results show that these parameters play a major role in the inflammatory reactions observed in BD. Increased levels of IMA and PAB are likely to be a result of inflammation-induced oxidative stress and hence its potential significance as a new marker of oxidative stress in BD.

Ankaflavin, a novel Nrf-2 activator for attenuating allergic airway inflammation

The role of inflammation-induced oxidative stress in the pathogenesis and progression of chronic inflammatory airways diseases has received increasing attention in recent years. Nuclear factor-erythroid 2 related factor 2 (Nrf-2) is the primary transcription factor that regulates the expression of antioxidant and detoxifying enzymes. In this study, yellow pigment ankaflavin (AK), derived from Monascus-fermented products, elevated nuclear Nrf-2 protein translocation in both the A549 lung cell line and the lungs of ovalbumin (OVA)-challenged mice. Furthermore, AK increased the mRNA expression of antioxidant enzymes regulated by Nrf-2, leading to a reduction in allergen-driven airway inflammation, mucus cell hyperplasia, and eosinophilia in OVA-challenged mice. Additionally, AK prevented T-cell infiltration and Th2 cytokines including interleukin (IL)-4, IL-5, and IL-13 generation in bronchial alveolar lavage fluid. The adhesion molecules ICAM-1, VCAM-1, and eotaxin were substantially reduced by AK treatment. Importantly, the inhibitory effect of AK on adhesion molecule production and immune cell infiltration was abolished by Nrf-2 small interfering RNA. This is the first study to illustrate that AK acts as a novel Nrf-2 activator for modulating the oxidative stress pathway to improve the lung injury and ameliorate the development of airway inflammation.

Inflammation regulates microRNA expression in cooperation with p53 and nitric oxide

microRNA (miRNA) are small non-coding RNA targeting mRNAs leading to their instability and diminished translation. Altered expression of miRNA is associated with cancer. Inflammation and nitric oxide modulates the development of lymphomas in p53 knockout mice and there exists a negative feedback loop between p53 and NOS2. Using a genetic strategy, we tested the hypothesis that inflammation-induced oxidative and nitrosative stress modulates miRNA expression in mouse model deficient in either p53 or NOS2. Mice treated with Corynebacterium parvum (C. parvum), to induce inflammation, clearly separated from controls by their miRNA profiles in wild-type, p53- and NOS2-knockout genetic backgrounds. C. parvum-induced inflammation significantly (p < 0.005) increased miR-21, miR-29b and miR-34a/b/c and decreased (p < 0.005) mir-29c and mir-181a/c expression in the spleen of C57BL mice. However, p53-knockout C57BL mice did not show a significant increase in the mir-34b/c or a decrease in mir-29c expression following C. parvum-induced inflammation. Expression of mir-21, mir-29b and mir-181a was independent of p53-status. NOS2-knockout C57BL mice showed a significant increase in miR-21 and miR-34a/b/c and decrease in miR-181a similar to the wild-type (WT) mice following C. parvum-induced inflammation. However, in contrast to the WT mice, miR-29b/c expression was not affected following C. parvum-induced inflammation in NOS2 knockout mice. N-acetyl cysteine, an anti-oxidant, reduced the expression of miR-21 and miR-29b in C. parvum-treated WT mice (p < 0.005) as compared with control C. parvum-treated mice. These data are consistent with the hypothesis that inflammation modulates miRNA expression in vivo and the alteration in specific miRNA under an inflammatory microenvironment, can be influenced by p53 (miR-34b/c) and NO(•) (29b/c).

Bacterial LPS Mediated Acute Inflammation-induced Spermatogenic Failure in Rats: Role of Stress Response Proteins and Mitochondrial Dysfunction

Bacterial Lipopolysaccharide (LPS) induced inflammation is implicated in the infection associated testicular tissue damage. Earlier, using a LPS induced acute endotoxemic rat model, we have shown the involvement of inflammation-induced oxidative stress in the impaired steroidogenesis and spermatogenesis. In the present study, we report a significant induction (more than 2-fold) of stress response proteins HSP-60, HMGB-1 and 2 in the testes, as early as 6 h after LPS injection with a later decrease. This induction of acute stress is closely followed by a significant reduction (74%) in Bcl2/Bax ratio along with leakage of cytochrome c (3 fold increase, p < 0.05) from mitochondria and increased caspase-3 activity levels (2.9 fold, p < 0.05) at 12 h and 24 h post LPS injection respectively. Further studies on PARP cleavage revealed a pattern similar to necrotic death during early periods (3 h to 24 h) and apoptosis at later periods (24 h to 72 h) after LPS treatment. In conclusion, the present study shows the involvement of stress response proteins and mitochondrial dysfunction in LPS-induced germ cell death in male rats.

Ferulic acid provides neuroprotection against oxidative stress-related apoptosis after cerebral ischemia/reperfusion injury by inhibiting ICAM-1 mRNA expression in rats

Our previous studies have shown that ferulic acid (4-hydroxy-3-methoxycinnamic acid, FA) inhibits intercellular adhesion molecule-1 (ICAM-1) expression in the ischemic striatum after 2 h of reperfusion in a transient middle cerebral artery occlusion model in rats. The purpose of this study is to further investigate the neuroprotective effects of FA during reperfusion after cerebral ischemia. Rats were subjected to 90 min of ischemia; they were then sacrificed after 2, 10, 24 and 36 h of reperfusion. ICAM-1 and macrophage-1 antigen (Mac-1) mRNA were detected using semi-quantitative RT-PCR at 2 h of reperfusion. Mac-1, 4-hydroxy-2-nonenal (4-HNE), 8-hydroxy-2′-deoxyguanosine (8-OHdG), active caspase 3, neuronal nuclei (NeuN) and TUNEL positive cells were measured at 2, 10, 24 and 36 h of reperfusion. FA (100 mg/kg, i.v.) administered immediately after MCAo inhibited ICAM-1 and Mac-1 mRNA expression in the striatum at 2 h of reperfusion, and reduced the number of Mac-1, 4-HNE and 8-OHdG positive cells in the ischemic rim and core at 10, 24 and 36 h of reperfusion. FA decreased TUNEL positive cells in the penumbra at 10 h, and in the ischemic boundary and core at 24 and 36 h of reperfusion. FA curtailed active caspase 3 expression in the penumbra at 10 h and restored NeuN-labeled neurons in the penumbra and ischemic core at 36 h of reperfusion. FA decreased the level of ICAM-1 mRNA and the number of microglia/macrophages, and subsequently down-regulated inflammation-induced oxidative stress and oxidative stress-related apoptosis, suggesting that FA provides neuroprotection against oxidative stress-related apoptosis by inhibiting ICAM-1 mRNA expression after cerebral ischemia/reperfusion injury in rats.

Bran from black or brown sorghum suppresses colon carcinogenesis

Colon cancer can be induced by inflammation-induced oxidative stress. Bran from black and brown sorghums has in vitro antioxidant activity. To determine whether sorghum bran would confer protection against colon cancer in vivo, SD rats (n = 10/diet) were provided diets containing 6% dietary fiber from cellulose, or white, black (contains anthocyanins) or brown sorghum (contains tannins) bran and injected with AOM (15 mg/kg BW, 2x, sc). Tissues were harvested and the number of aberrant crypts determined at wk 10. Antioxidant activity (ABTS) was 0.93, 11.6, 84 and 228 μmol TE/g for the cellulose, white, black and brown sorghum bran diets, respectively. A small reduction (P < 0.04) in intake of the black sorghum bran diet by 10 wk, compared to the other sorghum diets, had no effect on weight gain or feed efficiency. The black sorghum bran diet reduced epididymal and mesenteric fat weights (P < 0.05), compared to the white sorghum bran diet. There were no differences in number of aberrant crypts between the cellulose and white sorghum diets. Relative to cellulose rats, those consuming a brown sorghum (47%, P < 0.006) or black sorghum (29%, P < 0.04) bran diet had fewer aberrant crypts. The reduction in colon carcinogenesis in rats consuming either a brown or black sorghum bran diet may result from their antioxidant activity reducing the oxidative stress involved in colon cancer development. Funded by USDA 58-5430-5-339, and NIEHS P30-ES09106.

Pirfenidone inhibits inflammatory responses and ameliorates allograft injury in a rat lung transplant model

Tumor necrosis factor alpha is a proinflammatory cytokine that has been proved to play a crucial role in inducing posttransplantation lung injury. The present study was performed to determine whether pirfenidone, a new nonpeptide drug with potent anti-tumor necrosis factor alpha activity, promotes protection against acute allograft injury through inhibiting pulmonary inflammatory responses in a rat model of orthotopic lung transplantation. Three transplant groups were formed: isografts, untreated allografts, and allografts treated with pirfenidone (0.5% chow starting on day 1 after transplantation). The implants were harvested on day 21 after transplantation. Acute cellular rejection grade and degree of allograft injury were evaluated on the basis of hematoxylin-and-eosin staining. The pulmonary inflammatory response and inflammation-induced oxidative stress were assessed on the basis of neutrophil accumulation (myeloperoxidase immunoreactivity and enzymatic activity) and iron deposition (Prussian blue staining). In addition, circulating levels of tissue necrosis factor alpha in all animals were measured. The degree of allograft injury was significantly reduced in pirfenidone-treated allografts relative to untreated allografts (P < .01). The beneficial effect of pirfenidone was associated with decreased lung myeloperoxidase immunoreactivity (P < .05) and enzymatic activity (P < .01). Moreover, the untreated allografts contained a high concentration of iron, which was strikingly reduced by pirfenidone. Treatment with pirfenidone resulted in a lower level of plasma tissue necrosis factor alpha, which correlated positively with lung myeloperoxidase enzymatic activity (P < .0001). These results suggest that pirfenidone, with its anti-tissue necrosis factor alpha activity, reduced neutrophil recruitment and iron accumulation, hence limiting the acute lung allograft injury.

Role of Aldose Reductase and Oxidative Damage in Diabetes and the Consequent Potential for Therapeutic Options

Aldose reductase (AR) is widely expressed aldehyde-metabolizing enzyme. The reduction of glucose by the AR-catalyzed polyol pathway has been linked to the development of secondary diabetic complications. Although treatment with AR inhibitors has been shown to prevent tissue injury in animal models of diabetes, the clinical efficacy of these drugs remains to be established. Recent studies suggest that glucose may be an incidental substrate of AR, which appears to be more adept in catalyzing the reduction of a wide range of aldehydes generated from lipid peroxidation. Moreover, inhibition of the enzyme has been shown to increase inflammation-induced vascular oxidative stress and prevent myocardial protection associated with the late phase of ischemic preconditioning. On the basis of these studies, several investigators have ascribed an important antioxidant role to the enzyme. Additionally, ongoing work indicates that AR is a critical component of intracellular signaling, and inhibition of the enzyme prevents high glucose-, cytokine-, or growth factor-induced activation of protein kinase C and nuclear factor-kappa-binding protein. Thus, treatment with AR inhibitors prevents vascular smooth muscle cell growth and endothelial cell apoptosis in culture and inflammation and restenosis in vivo. Additional studies indicate that the antioxidant and signaling roles of AR are interlinked and that AR regulates protein kinase C and nuclear factor-kappaB via redox-sensitive mechanisms. These data underscore the need for reevaluating anti-AR interventions for the treatment of diabetic complications. Potentially, the development of newer drugs that selectively inhibit AR-mediated glucose metabolism and signaling, without affecting aldehyde detoxification, may be useful in preventing inflammation associated with the development of diabetic complications, particularly micro- and macrovascular diseases.

Bacterial Endotoxin Lipopolysaccharide and Reactive Oxygen Species Inhibit Leydig Cell Steroidogenesis via Perturbation of Mitochondria

Chronic inflammatory disease and acute infection are well known to inhibit gonadal steroidogenesis. Previous studies have demonstrated that immune activation in response to lipopolysaccharide (LPS) results in reductions in serum testosterone, and this is a direct effect on the Leydig cell. We hypothesize that during the early onset of LPS endotoxemia in vivo, testicular macrophages produce reactive oxygen species (ROS) leading to perturbation of Leydig cell mitochondria and an inhibition in steroidogenesis. To investigate the mechanism of LPS inhibition of Leydig cell steroidogenesis, alterations in mitochondria and markers of oxi-dative stress were assessed in vivo and in Leydig cell pri- mary culture. After a single injection of mice with LPS, serum testosterone was significantly decreased within 2 h. LPS injection of mice resulted in significant reductions in steroidogenic acute regulatory protein (StAR) and 3beta-hydroxysteroid dehydogenase-Delta4-Delta5 isomerase (3beta-HSD) proteins. LPS significantly increased lipid peroxidation of Leydig cell membranes, indicating that LPS results in oxidative damage in vivo. Mitochondria in Leydig cells isolated from LPS-injected mice were disrupted and showed a marked reduction in the mitochondrial membrane potential (DeltaPsim). Similar to the effects of LPS, treatment of Leydig cells with hydrogen peroxide acutely inhibited steroidogenesis, reduced StAR and 3beta-HSD protein levels, and disrupted DeltaPsim. These results suggest that LPS acutely inhibits Leydig cell function by ROS-mediated disruption of Leydig cell mitochondria. Taken together, these results demonstrate the necessity of having respiring mitochondria with an intact DeltaPsim to facilitate StAR function and Leydig cell steroidogenesis. The acute effects of LPS demonstrate how sensitive Leydig cell mitochondrial steroidogenesis is to inflammation-induced oxidative stress.

Noninvasive diagnostic tool for inflammation-induced oxidative stress using electron spin resonance spectroscopy and an extracellular cyclic hydroxylamine

Inflammation is one of the leading causes of the many pathological states associated with oxidative stress. A crucial role in the development of inflammation-induced oxidative stress is played by reactive oxidant species (ROS), which are very difficult to detect in vivo. One of the most sensitive and definitive methods in the detection of ROS is electron spin resonance, especially as used in conjunction with spin trapping. Unfortunately, the commonly used nitrone spin traps have a very low efficacy for trapping superoxide radicals, and their radical adducts are not stable. To address this deficiency, we have developed negatively charged cyclic hydroxylamines such as 1-hydroxy-4-phosphonooxy-2,2,6,6-tetramethylpiperidine (PP-H) for the detection of reactive oxidant species as a diagnostic tool for extracellular inflammation-induced oxidative stress. We used inflammation induced by a bacterial endotoxin lipopolysaccharide (LPS) as a model. ROS formation was tested in cultured macrophages, in blood and in vivo. PP-H reacts with reactive oxidant species generating the stable nitroxide radical 4-phosphonooxy-TEMPO. It was shown that a 5-h treatment of macrophages with LPS (1 μg/ml) leads to a threefold increase in superoxide formation as demonstrated using superoxide dismutase. Formation of reactive oxidant species 5 h after LPS (1 mg/kg) treatment of Fischer rats was analyzed in arterial blood; formation of reactive oxidant species in LPS-treated animals increased by a factor of 2.2 and was dependent upon the LPS dose. Diphenyleneiodonium (0.1 mM) inhibited formation of LPS-stimulated reactive oxidant species by 80%. We suggest that this test could be used as a noninvasive diagnostic tool for inflammation-induced oxidative stress.

Persistently expressed interleukin-1β and tumor necrosis factor-α gene in accepted rat lung allografts

Tumor necrosis factor α is a proinflammatory cytokine that has been proved to play a crucial role in inducing posttransplantation lung injury. The present study was performed to determine whether pirfenidone, a new nonpeptide drug with potent anti–tumor necrosis factor α activity, promotes protection against acute allograft injury through inhibiting pulmonary inflammatory responses in a rat model of orthotopic lung transplantation.Three transplant groups were formed: isografts, untreated allografts, and allografts treated with pirfenidone (0.5% chow starting on day 1 after transplantation). The implants were harvested on day 21 after transplantation. Acute cellular rejection grade and degree of allograft injury were evaluated on the basis of hematoxylin-and-eosin staining. The pulmonary inflammatory response and inflammation-induced oxidative stress were assessed on the basis of neutrophil accumulation (myeloperoxidase immunoreactivity and enzymatic activity) and iron deposition (Prussian blue staining). In addition, circulating levels of tissue necrosis factor α in all animals were measured.The degree of allograft injury was significantly reduced in pirfenidone-treated allografts relative to untreated allografts (P < .01). The beneficial effect of pirfenidone was associated with decreased lung myeloperoxidase immunoreactivity (P < .05) and enzymatic activity (P < .01). Moreover, the untreated allografts contained a high concentration of iron, which was strikingly reduced by pirfenidone. Treatment with pirfenidone resulted in a lower level of plasma tissue necrosis factor α, which correlated positively with lung myeloperoxidase enzymatic activity (P < .0001).These results suggest that pirfenidone, with its anti–tissue necrosis factor α activity, reduced neutrophil recruitment and iron accumulation, hence limiting the acute lung allograft injury.