Involvement of reactive oxygen species in TNF-alpha mediated activation of the transcription factor NF-kappaB in canine dermal fibroblasts

Gamma-tocopherol supplementation ameliorated hyper-inflammatory response during the early cutaneous wound healing in alloxan-induced diabetic mice

Delayed wound healing is one of the major diabetic complications. During wound healing process, the early inflammatory stage is important for better prognosis. One of antioxidant nutrient, gamma-tocopherol (GT) is considered to regulate inflammatory conditions. This study investigated the effect of GT supplementation on mechanism associated with inflammation, oxidative stress, and apoptosis during early cutaneous wound healing in diabetic mice. Diabetes was induced by alloxan injection in ICR mice. All mice were divided into three groups: non-diabetic control mice (CON), diabetic control mice (DMC), and diabetic mice supplemented with GT (GT). After two weeks of GT supplementation, excisional wounds were made by biopsy punches (4 mm). Diabetic mice showed increases in fasting blood glucose (FBG) level, hyper-inflammatory response, oxidative stress, and delayed wound closure rate compared to non-diabetic mice. However, GT supplementation reduced FBG level and accelerated wound closure rate by regulation of inflammatory response-related proteins such as nuclear factor kappa B, interleukin-1β, tumor necrosis factor-α, and c-reactive protein, and oxidative stress-related markers including nuclear factor (erythroid derived 2)-like 2, NAD(P)H dehydrogenase quinone1, heme oxygenase-1, manganese superoxide dismutase, catalase and glutathione peroxidase and apoptosis-related markers such as sirtuin-1, peroxisome proliferator-activated receptor gamma coactivator 1- α, and p53 in diabetic mice. Taken together, GT would be a potential therapeutic to prevent diabetes-induced delayed wound healing by regulation of inflammatory response, apoptosis, and oxidative stress. Impact statement Gamma tocopherol has shown ameliorative effect on diabetic wound healing by regulation of inflammation, oxidative stress, and apoptosis demonstrated by nuclear factor kappa B, nuclear factor (erythroid derived 2)-like 2, and sirtuin-1.

Activation of MEK/ERK pathways through NF-κB activation is involved in interleukin-1β-induced cyclooxygenease-2 expression in canine dermal fibroblasts

The proinflammatory cytokine interleukin-1β (IL-1β) induced cyclooxygenases-2 (COX-2) mRNA expression and lipid mediator prostaglandin E2 release and in a time- and dose-dependent manner in canine dermal fibroblasts. The MEK inhibitor U0126 and the ERK inhibitor FR180204 clearly inhibited IL-1β-induced prostaglandin E2 release and COX-2 mRNA expression. IL-1β enhanced ERK1/2 phosphorylation, which was attenuated by inhibitors of MEK and ERK. The NF-κB inhibitor BAY 11-7082 also suppressed IL-1β-induced prostaglandin E2 release and COX-2 mRNA expression. Treatment of fibroblasts with IL-1β led to the phosphorylation of p65 and degradation of IκBα occurred, indicating that IL-1β treatment activated NF-κB. MEK and ERK1/2 inhibitors had no effect on the phosphorylation of p65 subunit induced by IL-1β, whereas the NF-κB inhibitor completely blocked IL-1β-induced phosphorylation of ERK1/2. We also observed that IκBα-knockdown enhanced the phosphorylation of p65 and ERK1/2. These findings suggest that stimulation of MEK/ERK signaling pathway by NF-κB activation regulates IL-1β-induced COX-2 expression and subsequent prostaglandin E2 release in canine dermal fibroblasts.

Interplay among oxidants, antioxidants, and cytokines in skin disorders: Present status and future considerations

The pathogenicity of skin disorders involves a complexity of physiological, immunological, environmental, and genetic phenomena. This review focuses on cross-talks between two main agents, the oxidants and cytokines network, which have recently been found to play important roles in the pathophysiology of a large variety of skin disorders, including carcinogenesis, UVB irradiation damages, inflammatory processes, and a series of diseases such as, psoriasis, pyoderma gangrenosum, atopic dermatitis, irritant contact dermatitis, and bacterial skin infections. In particular the review discusses the question how an interplay between oxidants and cytokines might be beneficial in wound-healing and in therapeutic strategies in clinical settings. These involve topical applications and oral administration of antioxidant and inflammatory-cytokines-neutralizing antibodies. Monitoring cytokine expression in skin disorders (inflammatory versus anti-inflammatory, or Th1 versus Th2 types of cytokines) will definitely help to evaluate the severity of injury, its type, and its role in therapy. Furthermore, it is expected that future studies should explore the possible roles of the synergistic interactions between antioxidants and cytokines and their impact on the Th1/Th2 cytokine networks balances.

A Novel Mechanism of Action of Methyl-2-cyano-3,12 Dioxoolean-1,9 Diene-28-oate: Direct Permeabilization of the Inner Mitochondrial Membrane to Inhibit Electron Transport and Induce Apoptosis

Methyl-2-cyano-3,12 dioxoolean-1,9 diene-28-oate (CDDO-Me) is a synthetic oleanolic acid derivative that displays antitumorigenic and anti-inflammatory activities, and we have previously reported that this agent potently activates the intrinsic apoptotic pathway in leukemia cells. In this study, we demonstrate that mitochondrial dysfunction induced by CDDO-Me is mediated by direct permeabilization of the inner mitochondrial membrane, which results in the rapid depletion of mitochondrial glutathione (GSXm), loss of cardiolipin, and inhibition of mitochondrial respiration. More importantly, we demonstrate that in addition to activating the intrinsic apoptotic pathway, the mitochondrial effects of CDDO-Me may mediate its anti-inflammatory activity by modulating the generation of superoxide anion (O2*). It is noteworthy that CDDO-Me did not increase the generation of O2* and pretreatment of leukemia cells with CDDO-Me prevented the increase of this reactive oxygen species elicited by inhibition of complex I or III in the absence of de novo protein synthesis. CDDO-Me, but not other inhibitors of respiration, induced a time- and dose-dependent, cyclosporin A-independent permeability transition (PT) of isolated mitochondria that was sensitive to sulfhydryl antioxidants but not to EDTA. PT induced by CDDO-Me and Ca2+ was accompanied by loss of GSXm, suggesting that the increased permeability of the inner mitochondrial membrane facilitates the loss of this antioxidant. Finally, transmission electron microscopy revealed that CDDO-Me rapidly induced caspase-independent mitochondrial swelling and loss of inner membrane structure before the release of cytochrome c. Taken together, our results indicate that CDDO-Me is a novel mitochondriotoxic agent that induces apoptosis and inhibits mitochondrial electron transport via perturbations in inner mitochondrial membrane integrity.

Oxidized linoleic acid regulates expression and shedding of syndecan-4

Syndecan-4, a heparan sulfate proteoglycan that is widely expressed in the vascular wall and as a cell surface receptor, modulates events relevant to acute tissue repair, including cell migration and proliferation, cell-substrate interactions, and matrix remodeling. While syndecan-4 expression is regulated in response to acute vascular wall injury, its regulation under chronic proatherogenic conditions such as those characterized by prolonged exposure to oxidized lipids has not been defined. In this investigation, arterial smooth muscle cells were treated with 13-hydroperoxy-9,11-octadecadienoic acid (HPODE) and 13-hydroperoxy-10,12-octadecadienoic acid, oxidized products of linoleic acid, which is the major oxidizable fatty acid in LDL. Both oxidized fatty acids induced a dose-dependent, rapid upregulation of syndecan-4 mRNA expression that was not attenuated by cycloheximide. This response was inhibited by pretreatment with N-acetylcysteine, catalase, or MEK1/2 inhibitors, but not by curcumin or lactacystin, known inhibitors of NF-κB. These data suggest that oxidized linoleic acid induces syndecan-4 mRNA expression through the initial generation of intracellular hydrogen peroxide with subsequent activation of the extracellular signal-regulated kinase signaling pathway via MEK1/2. Notably, the HPODE-induced enhancement of syndecan-4 mRNA was accompanied by accelerated shedding of syndecan-4. In principle, alterations in both the cell surface expression and shedding of syndecan-4 may augment a variety of proatherogenic events that occur in response to oxidized lipids.

Antioxidant and prooxidant mechanisms in the regulation of redox(y)-sensitive transcription factors

A progressive rise of oxidative stress due to the altered reduction-oxidation (redox) homeostasis appears to be one of the hallmarks of the processes that regulate gene transcription in physiology and pathophysiology. Reactive oxygen (ROS) and nitrogen (RNS) species serve as signaling messengers for the evolution and perpetuation of the inflammatory process that is often associated with the condition of oxidative stress, which involves genetic regulation. Changes in the pattern of gene expression through ROS/RNS-sensitive regulatory transcription factors are crucial components of the machinery that determines cellular responses to oxidative/redox conditions. Transcription factors that are directly influenced by reactive species and pro-inflammatory signals include nuclear factor-kappaB (NF-kappaB) and hypoxia-inducible factor-1alpha (HIF-1alpha). Here, I describe the basic components of the intracellular oxidative/redox control machinery and its crucial regulation of oxygen- and redox-sensitive transcription factors such as NF-kappaB and HIF-1alpha.

TNF-alpha dependent NF-kappa B activation in cultured canine keratinocytes is partly mediated by reactive oxygen species

The cytokine TNF-alpha plays a major role in inflammatory and immunological reactions of canine skin. With respect to a possible therapeutic modulation, we investigated the role of the transcription factor NF-kappa B and the involvement of reactive oxygen species (ROS) in the TNF-alpha signalling pathway in cultured canine keratinocytes. TNF-alpha treatment resulted in activation of NF-kappa B which was partially inhibited by the antioxidant alpha-lipoic acid. Using the cytochrome c reduction test no superoxide production could be detected in the supernatant of TNF-alpha stimulated keratinocytes. However, TNF-alpha dependent intracellular hydrogen peroxide production was demonstrated spectroscopically. With electron energy loss spectroscopy (EELS) significant hydrogen peroxide formation was detected in the mitochondria, the endoplasmic reticulum, the cytosol and partially on the plasma membrane of the keratinocytes. Hence, ROS possibly play an important role in the TNF-alpha signalling pathway leading to NF-kappa B activation in canine skin. An adjunctive therapy with natural potent antioxidants modulating NF-kappa B overactivation in canine cutaneous inflammation may be of therapeutic benefit.

Redox-modulated pathways in inflammatory skin diseases

Inflammatory skin diseases account for a large proportion of all skin disorders and constitute a major health problem worldwide. Contact dermatitis, atopic dermatitis, and psoriasis represent the most prevalent inflammatory skin disorders and share a common efferent T-lymphocyte mediated response. Oxidative stress and inflammation have recently been linked to cutaneous damage in T-lymphocyte mediated skin diseases, particularly in contact dermatitis. Insights into the pathophysiology responsible for contact dermatitis can be used to better understand the mechanism of other T-lymphocyte mediated inflammatory skin diseases, and may help to develop novel therapeutic approaches. This review focuses on redox sensitive events in the inflammatory scenario of contact dermatitis, which comprise for example, several kinases, transcription factors, cytokines, adhesion molecules, dendritic cell surface markers, the T-lymphocyte receptor, and the cutaneous lymphocyte-associated antigen (CLA). In vitro and animal studies clearly point to a central role of several distinct but interconnected redox-sensitive pathways in the pathogenesis of contact dermatitis. However, clinical evidence that modulation of the skin's redox state can be used therapeutically to modulate the inflammatory response in contact dermatitis is presently not convincing. The rational for this discrepancy seems to be multi-faceted and complex and will be discussed.

Superoxide generation of phagocytes and nonphagocytic cells

Phagocytes release high amounts of reactive oxygen intermediates upon contact with appropriate stimuli into the environment as an important function in the immune defence against infectious agents. On the other hand nonphagocytic cells release low amounts upon stimulation, which have important functions in the inter- and intracellular signal transduction. Both systems represent a class of isoenzymes making a specific regulation possible. Fibroblasts, hepatocytes, and HeLa cells possess a superoxide system which shows higher activity with NADH than NADPH. The enzyme was purified to homogeneity in an active form, showed a molecular mass of 84 kDa and possessed a flavin and low-potential cytochrome b558.

Overexpression of catalase in the mitochondrial or cytosolic compartment increases sensitivity of HepG2 cells to tumor necrosis factor-alpha-induced apoptosis

The sensitivity of HepG2 cells overexpressing catalase in either the cytosolic or mitochondrial compartment to tumor necrosis factor-alpha (TNF-alpha) and cycloheximide was studied. Cells overexpressing catalase in the cytosol (C33 cells) and especially in mitochondria (mC5 cells) were more sensitive to TNF-alpha-induced apoptosis than were control cells (Hp cells). The activities of caspase-3 and -8 were increased by TNF-alpha, with the highest activities found in mC5 cells. Sodium azide, an inhibitor of catalase, reduced the increased sensitivity of mC5 and C33 cells to TNF-alpha to the level of toxicity found with control Hp cells. Azide also decreased the elevated caspase-3 activity of mC5 cells. A pan-caspase inhibitor prevented the TNF-alpha-induced apoptosis and toxicity produced by catalase overexpression. Addition of H(2)O(2) prevented TNF-alpha-induced apoptosis and caspase activation, an effect prevented by simultaneous addition of catalase. TNF-alpha plus cycloheximide increased ATP levels, with higher levels in C33 and mC5 cells compared with Hp cells. TNF-alpha did not produce apoptosis in mC5 cells maintained in a low energy state. TNF-alpha signaling was not altered by the overexpression of catalase, as activation of nuclear factor kappaB and AP-1 by TNF-alpha was similar in the three cell lines. These results suggest that catalase, overexpressed in the cytosolic or especially the mitochondrial compartment, potentiates TNF-alpha-induced apoptosis and activation of caspases by removal of H(2)O(2).