Redox-modulated pathways in inflammatory skin diseases

Oxidative stress markers in canine atopic dermatitis

There are no data in the veterinary literature relating to oxidative stress in canine atopic dermatitis (CAD). The study aimed to determine levels of oxidative stress markers, plasma malondialdehyde (MDA), total antioxidant capacity (TAC), whole blood glutathione peroxidase (GPX) and erythrocyte superoxide dismutase (SOD), in 15 CAD patients and 17 healthy dogs. A correlation between CADESI (Canine Atopic Dermatitis Extent and Severity Index) score and MDA was also determined. Significantly higher plasma MDA levels were found in patients than in healthy dogs. The significant, highly positive correlation determined between CADESI score and MDA in the patient group indicates an association between the severity of CAD and the extent of oxidative damage to membrane lipids. There were no significant differences in TAC, GPX and SOD between patients and healthy dogs. Our findings suggest that oxidative stress with increased lipid peroxidation could be involved in the pathogenesis of atopic dermatitis in dogs.

The role of manganese superoxide dismutase in skin cancer

Recent studies have shown that antioxidant enzyme expression and activity are drastically reduced in most human skin diseases, leading to propagation of oxidative stress and continuous disease progression. However, antioxidants, an endogenous defense system against reactive oxygen species (ROS), can be induced by exogenous sources, resulting in protective effects against associated oxidative injury. Many studies have shown that the induction of antioxidants is an effective strategy to combat various disease states. In one approach, a SOD mimetic was applied topically to mouse skin in the two-stage skin carcinogenesis model. This method effectively reduced oxidative injury and proliferation without interfering with apoptosis. In another approach, Protandim, a combination of 5 well-studied medicinal plants, was given via dietary administration and significantly decreased tumor incidence and multiplicity by 33% and 57%, respectively. These studies suggest that alterations in antioxidant response may be a novel approach to chemoprevention. This paper focuses on how regulation of antioxidant expression and activity can be modulated in skin disease and the potential clinical implications of antioxidant-based therapies.

N-acetylcysteine inhibits chromium hypersensitivity in coadjuvant chromium-sensitized albino guinea pigs by suppressing the effects of reactive oxygen species

BACKGROUND

Chromium hypersensitivity is an important issue in occupational skin disease. When hexavalent chromium enters the cell, it can be reduced to trivalent chromium, resulting in the formation of reactive oxygen species (ROS). ROS are considered to play an important role in the progression of allergic contact dermatitis. N-acetylcysteine (NAC) could increase glutathione levels in the skin and act as an antioxidant.

AIMS

We attempted to demonstrate that NAC could inhibit chromium hypersensitivity in a coadjuvant chromium-sensitized albino guinea pig model by counteracting the formation of ROS.

METHODS

We utilized a coadjuvant chromium-sensitized albino guinea pig model to evaluate both the severity of the skin reaction by intradermal and epicutaneous elicitation tests and the sensitization rate of chromium hypersensitivity in NAC-treated and NAC-untreated albino guinea pigs (GP). Furthermore, three ROS parameters, including H(2)O(2,) malondialdehyde (MDA) levels in the skin and the oxygen radical absorbance capacity (ORAC) in plasma, were analyzed in NAC-treated and NAC-untreated coadjuvant chromium-sensitized albino GP.

RESULTS

The severity of the skin reaction in the intradermal and epicutaneous elicitation test significantly diminished when the albino GP were treated with a dose of 1200 mg/kg/day of NAC. This dose also significantly decreased the sensitization rate of chromium hypersensitivity. In addition, treatment with 1200 mg/kg/day of NAC significantly reduced the H(2)O(2) and MDA levels in the skin and significantly increased the ORAC in the plasma of albino GP. Therefore, NAC could be a potential chemopreventative agent to prevent the progression of chromium hypersensitivity.

Effect of oxidative damage due to excessive protein ingestion on pancreas function in mice

The present study was undertaken to evaluate the effect of oxidative damage due to excessive protein diet on pancreas function in mice. For this purpose, thirty male (C57BL/6J) mice were randomly divided into three groups and fed on different diets as follows: group 1 was fed on a normal diet, group 2 was fed on an excessive protein diet and group 3 was fed on an excessive protein diet supplemented with 0.06 g/kg cysteamine. Each group was fed for 2 weeks, and then pancreas samples were collected to examine oxidative and antioxidant parameters and pancreas function. The results showed that ingestion of an excessive protein diet markedly increased contents of malondialdehyde (MDA) and decreased T-AOC and activities of antioxidants SOD and GSH-Px, compared with a normal diet (P < 0.05). Pancreas weight and concentration of protein, DNA and RNA were significantly higher (P < 0.05), digestive enzyme activities were significantly lower and levels of somatostatin and insulin were higher in mice fed with an excessive protein diet than those fed with a normal protein diet. In the group fed with excessive protein diet supplemented with cysteamine, oxidative stress was mitigated and pancreas function was improved. These data demonstrate that excessive protein ingestion could increase oxidative damage of free radicals on pancreas function through destroying the balance of oxidants and antioxidants.

Redox imbalance in T cell-mediated skin diseases

The skin is permanently exposed to physical, chemical, and biological aggression by the environment. In addition, acute and chronic inflammatory events taking place in the skin are accompanied by abnormal release of pro-oxidative mediators. In this paper, we will briefly overview the homeostatic systems active in the skin to maintain the redox balance and also to counteract abnormal oxidative stress. We will concentrate on the evidence that a local and/or systemic redox dysregulation accompanies the chronic inflammatory disorder events associated to psoriasis, contact dermatitis, and atopic dermatitis. We will also discuss the fact that several well-established treatments for the therapy of chronic inflammatory skin disorders are based on the application of strong physical or chemical oxidants onto the skin, indicating that, in selected conditions, a further increase of the oxidative imbalance may lead to a beneficial outcome.

Sensitization effect of thimerosal is mediated in vitro via reactive oxygen species and calcium signaling

Thimerosal, a mercury derivative composed of ethyl mercury chloride (EtHgCl) and thiosalicylic acid (TSA), is widely used as a preservative in vaccines and cosmetic products and causes cutaneous reactions. Since dendritic cells (DCs) play an essential role in the immune response, the sensitization potency of chemicals was studied in vitro using U937, a human promyelomonocytic cell line that is used as a surrogate of monocytic differentiation and activation. Currently, this cell line is under ECVAM (European Center for the Validation of Alternative Methods) validation as an alternative method for discriminating chemicals. Thimerosal and mercury derivatives induced in U937 an overexpression of CD86 and interleukin (IL)-8 secretion similarly to 1-chloro-2,4-dinitrobenzene (DNCB), a sensitizer used as a positive control for DC activation. Non-sensitizers, dichloronitrobenzene (DCNB), TSA and sodium dodecyl sulfate (SDS), an irritant, had no effect. U937 activation was prevented by cell pretreatment with N-acetyl-L-cysteine (NAC) but not with thiol-independent antioxidants except vitamin E which affected CD86 expression by preventing lipid peroxidation of cell membranes. Thimerosal, EtHgCl and DNCB induced glutathione (GSH) depletion and reactive oxygen species (ROS) within 15 min; another peak was detected after 2h for mercury compounds only. MitoSOX, a specific mitochondrial fluorescent probe, confirmed that ROS were essentially produced by mitochondria in correlation with its membrane depolarization. Changes in mitochondrial membrane permeability induced by mercury were reversed by NAC but not by thiol-independent antioxidants. Thimerosal and EtHgCl also induced a calcium (Ca2+) influx with a peak at 3h, suggesting that Ca2+ influx is a secondary event following ROS induction as Ca2+ influx was suppressed after pretreatment with NAC but not with thiol-independent antioxidants. Ca2+ influx was also suppressed when culture medium was deprived of Ca2+ confirming the specificity of the measure. In conclusion, these data suggest that thimerosal induced U937 activation via oxidative stress from mitochondrial stores and mitochondrial membrane depolarization with a primordial effect of thiol groups. A cross-talk between ROS and Ca2+ influx was demonstrated.

Sphingosylphosphorylcholine down-regulates filaggrin gene transcription through NOX5-based NADPH oxidase and cyclooxygenase-2 in human keratinocytes

Sphingosylphosphorylcholine (SPC) mediates various inflammatory and behavioral responses in atopic dermatitis. Recent studies have shown that dysfunction of the epidermal permeability barrier itself plays a primary role in the etiology of atopic dermatitis. However, the effects of SPC on major proteins essential to the development of the epidermal permeability barrier such as filaggrin, loricrin, involucrin, keratin 1, keratin 10 and small proline-rich proteins are still unclear. In this study, we demonstrated that SPC significantly reduces filaggrin gene transcription, implying that SPC plays a pivotal role in impairment of the epidermal permeability barrier in atopic dermatitis lesional skin. In cultured normal human keratinocytes (NHKs), SPC increases the intracellular level of reactive oxygen species (ROS) and up-regulates NADPH oxidase 5 (NOX5) gene transcription. SPC also stimulates prostaglandin (PG) E(2) production by increasing cyclooxygenase (COX)-2 expression in NHK. The effects of the prostanoid EP receptor agonists, limaprost, butaprost, and sulprostone on filaggrin gene expression in NHK suggest that the prostanoid EP2 receptor plays a significant role in the PGE(2)-mediated filaggrin down-regulation. In contrast, limaprost and butaprost do not affect NOX5 expression in NHK, implying that the NOX5-regulated ROS pathway stimulated by SPC may be upstream of the COX-2 pathway. We propose that the increase in SPC levels further aggravates dermatological symptoms of atopic dermatitis through SPC-induced down-regulation of filaggrin in NHK.

Dermal toxicity and environmental contamination: electron transfer, reactive oxygen species, oxidative stress, cell signaling, and protection by antioxidants

Large numbers of chemicals are known to produce diverse types of skin injury, and these substances fit into a wide variety of both organic and inorganic chemical classes. Skin contact with toxins is difficult to avoid, because they are widely distributed, e.g., in industrial substances, agricultural chemicals, household products, and plants. Although various hypotheses have been advanced, there is no universal agreement as to how dermal toxins act to produce their effects. In this review, we provide evidence and numerous literature citations to support the view that oxidative stress (OS) and electron transfer (ET) comprise a portion of a key mechanism, and perhaps unifying theme that underlie the action of dermatotoxins. We apply the concept that ET and OS are key elements in the induction of dermatotoxic effects to all of the main classes of toxins, and to other toxins, as well. We believe it is not coincidental that the vast majority of dermatotoxic substances incorporate recurrent ET chemical functionalities (i.e., quinone, metal complexes, ArNO2, or conjugated iminium), either per se or as metabolites; such entities potentially give rise to reactive oxygen species (ROS) by redox cycling. However, in some categories, wherein agents cause dermal damage, e.g., peroxides and radiation, it appears that ROS are generated by non-ET routes. As expected, if ET and oxidative process do constitute the mechanistic framework by which most dermal toxins act, then antioxidants (AOs), if present, should prevent or mitigate effects. This is exactly what has been discovered to occur. Because ET and OS either cause or contribute to dermal toxicity, and AOs may offer protection therefrom, policy makers and researchers may be better positioned to prevent human dermatotoxicity.

Effect of intrauterine ischaemia-reperfusion injury on rat skin

INTRODUCTION

It was previously demonstrated that decreased maternal blood flow might create impairment in skin development. The aim of this study was to show by means of lipid peroxidation the effect of intrauterine ischaemia-reperfusion injury on fetal rat skin.

METHODS

In total, 24 female Spraque-Dawley rats, 19 days pregnant, were used. They were separated into three groups (n = 8): a control group, a sham-operated group and an experimental group. Laparotomy was performed on all three groups. In the sham-operated and experimental groups, utero-ovarian artery dissection was performed in addition. In the experimental group, fetal ischaemia was induced by clamping the utero-ovarian artery bilaterally for 30 min, and reperfusion was achieved by removing the clamps for 60 min. At the end of the experiment, the fetuses were removed by caesarean section and skin specimens were taken from the fetuses. Lipid peroxidation in the skin tissues was determined as thiobarbituric acid reactive substance (TBARS) concentration for each fetal rat. One-way ANOVA and post hoc tests were used for statistical analysis.

RESULTS

The level of TBARS was significantly increased in the fetal rat skin after ischaemia-reperfusion injury compared with the control group.

CONCLUSION

Lipid peroxidation has an important role in intrauterine ischaemia-reperfusion-induced fetal skin damage in rats.

Effects of Antioxidant and Nitric Oxide on Chemokine Production in TNF-α-stimulated Human Dermal Microvascular Endothelial Cells

Chemokines have been implicated convincingly in the driving of leukocyte emigration in different inflammatory reactions. Multiple signaling mechanisms are reported to be involved in intracellular activation of chemokine expression in vascular endothelial cells by various stimuli. Nevertheless, redox-regulated mechanisms of chemokine expression in human dermal microvascular endothelial cells (HDMEC) remain unclear. This study examined the effects of pyrrolidine dithiocarbamate (PDTC, 0.1 mM) and spermine NONOate (Sper-NO, 1 mM) on the secretion and gene expression of chemokines, interleukin (IL)-8, monocyte chemotactic protein (MCP)-1, regulated upon activation normal T cell expressed and secreted (RANTES), and eotaxin. This study also addresses PDTC and Sper-NO effects on activation of nuclear factor kappa B (NF-kappaB) induced by TNF-alpha (10 ng/ml). Treatment with TNF-alpha for 8 h significantly increased secretion of IL-8, MCP-1, and RANTES, but not of eotaxin, in cultured HDMEC. Up-regulation of these chemokines was suppressed significantly by pretreatment with PDTC or Sper-NO for 1 h, but not by 1 mM 8-bromo-cyclic GMP. The mRNA accumulation of IL-8, MCP-1, RANTES, and eotaxin, and activation of NF-kappaB were induced by TNF-alpha for 2 h; all were suppressed significantly by the above two pretreatments. These findings indicate that both secretion and mRNA accumulation of IL-8, MCP-1, and RANTES in HDMEC induced by TNF-alpha are inhibited significantly by pretreatment with PDTC or Sper-NO, possibly via blocking redox-regulated NF-kappaB activation. These results suggest that restoration of the redox balance using antioxidant agents or nitric oxide pathway modulators may offer new opportunities for therapeutic interventions in inflammatory skin diseases.

Reaction ofpara-hydroxybenzoic acid esters with singlet oxygen in the presence of glutathione produces glutathione conjugates of hydroquinone, potent inducers of oxidative stress

The determination and toxicological characterization of products of the reaction between p-hydroxybenzoic acid esters (parabens) and singlet oxygen ((1)O(2)) are very important because of the frequent use of parabens in cosmetics and possible generation of (1)O(2) in the skin. We observed (1)O(2)-dependent production of mono-, di-, and tri-substituted glutathione (GSH) conjugates of hydroquinone (HQ) during visible light-irradiation of a mixture of methyl or ethyl paraben and GSH in the presence of rose bengal (RB). 1,4-Benzoquinone (BQ) and HQ were produced during the irradiation in the absence of GSH. While a mixture of BQ and GSH produced only mono-substituted conjugate, irradiation of the mixture with RB produced mono-, di-, and tri-substituted conjugates. These observations indicate that (1)O(2) is involved both in the production of BQ and HQ from parabens and in the formation of multi-substituted GSH conjugates from mono-substituted conjugate. Tri-substituted conjugate generated larger amounts of hydrogen peroxide in an aqueous solution than mono-substituted conjugates or HQ did. Detection of semiquinone radical suggests that the autoxidation of conjugates is related to the generation of hydrogen peroxide. The results obtained in this study indicate that parabens may induce oxidative stress in the skin after conversion to GSH conjugates of HQ by reacting with (1)O(2) and GSH.

Thioredoxin suppresses the contact hypersensitivity response by inhibiting leukocyte recruitment during the elicitation phase

Thioredoxin, a redox-regulating protein that scavenges reactive oxygen species, appears to show an excellent antiinflammatory effect in treating animal models of various human inflammatory diseases. The aim of this study was to clarify whether thioredoxin is useful for treating inflammatory skin diseases, such as contact dermatitis, caused by epicutaneous exposure to environmental and occupational antigens. The allergic contact hypersensitivity response was suppressed in thioredoxin-transgenic mice. This suppressive effect of thioredoxin appeared to be via the inhibition of the efferent limb of contact hypersensitivity because administration of recombinant thioredoxin suppressed the inflammatory response in the elicitation phase but not in the induction phase. Adoptive-transfer studies revealed that the host environment, but not donor leukocytes, is critical in this suppressive effect. In thioredoxin-transgenic mice, the infiltration of neutrophils in the elicitation site was diminished, whereas the migratory function of cutaneous dendritic cells and hapten-specific cell proliferation were not disturbed. Thioredoxin-transgenic mice had also an attenuated inflammatory response to croton oil. These findings suggest that thioredoxin prevents skin inflammatory responses and could be a suitable candidate for the treatment of contact dermatitis.

Osteopontin: a new emerging role in psoriasis

Osteopontin (OPN) is a phosphorylated acidic glycoprotein produced by cells of the immune system, epithelial tissue, smooth muscle cells, osteoblasts, and tumor cells. OPN interacts with integrins and CD44 to enhance Th1 and inhibit Th2 cytokine expression. The involvement of this molecule in the onset of psoriasis has not previously been studied. Here, we demonstrate that OPN is expressed in peripheral blood mononuclear cells and in skin biopsies of psoriatic patients. The study was conducted on 30 patients affected with plaque psoriasis, and on 11 healthy donors. Two blood samples and two skin samples from patients affected with atopic dermatitis were used as control for Th2 typical inflammatory skin disease. The analysis of IL-1beta, IFN-gamma, TauNuF-alpha, IL-8, and ICAM-1 showed the characteristic Th1 pattern in all the psoriatic blood and skin samples analyzed. This study offers an opportunity for understanding inflammation in psoriasis and supports the hypothesis that OPN could represent a potential target for therapeutic intervention in psoriatic patients.

Cellular metabolism of brevetoxin (PbTx-2) by a monocyte cell line (U-937)

Blooms of Karenia brevis produce brevetoxins which cause neurotoxic shellfish poisoning and respiratory symptoms in humans as well as harmful effects on sea life. To investigate potential effects of brevetoxins on immune system components, a monocyte cell line (U-937) was exposed in vitro to PbTx-2. U-937 cells metabolized PbTx-2 through cellular detoxification mechanisms, as evidenced by depletion of intracellular glutathione and formation of glutathione and cysteine conjugates. Total intracellular glutathione was significantly decreased in toxin-treated cells compared to control cells, as measured using an enzymatic recycling method. LC/MS was used to detect the following brevetoxin metabolites: a cysteine-PbTx-2 conjugate (m/z 1018) and two putative glutathione-PbTx-2 conjugates (m/z 1204 and 1222). During 3h incubation, glutathione conjugates were detectable as early as 1h and increased in concentration after 2 and 3h. A cysteine-PbTx-2 conjugate appeared after 2h and increased in concentration after 3h. Detectable levels of brevetoxin conjugates were present in response to toxin concentrations of 1muM. Depletion of intracellular glutathione and formation of brevetoxin metabolites, with changes in concentrations over time, suggest immune cells (U-937) have important cellular detoxification pathways for PbTx-2.

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.

Lipid peroxidation and antioxidant status in lichen planus

BACKGROUND

Lichen planus (LP) is an inflammatory skin disease of unknown aetiology. Recently, increased oxidative stress has been implicated in the pathogenesis of various skin diseases such as atopic dermatitis, psoriasis vulgaris and vitiligo.

AIM

To evaluate the status of the oxidative stress and antioxidant defence system in patients with LP.

METHODS

In total, 40 patients with LP (23 men, 17 women; mean +/- SD age 43.27 +/- 1.96 years) and 40 control subjects, matched for age and gender, were enrolled in this prospective study. The exclusion criteria included medication with immunosuppressive agents, history of trauma and surgery, and history of alcohol ingestion for at least 1 month prior to the study. The serum nitric oxide (NO), malondialdehyde (MDA) and superoxide dismutase (SOD) levels and the erythrocyte catalase (CAT) levels were investigated in both groups.

RESULTS

Mean +/- SD levels of serum NO (74.60 +/- 17.96 micromol/L) and MDA (18.24 +/- 5.21 micromol/L) in patients with LP were higher than those of the control group (P = 0.007 and P = 0.031, respectively). Serum SOD levels (18.19 +/- 3.71 U/mL) in patients with LP were also higher than in healthy controls (P = 0.002). In contrast, erythrocyte CAT levels (13 557.80 +/- 4134.42 U/kg haemoglobin) were significantly lower in the patient group than in the control group (P = 0.009).

CONCLUSIONS

The findings of this study suggest that increased oxidative stress, increased lipid peroxidation and an imbalance in the antioxidant defence system may be involved in the pathogenesis of LP.

Single base instability is promoted in vulvar lichen sclerosus

Single base substitution mutations in codons 248 and 273 of TP53 and codon 12 Kirsten-ras (KRAS) are commonly found in human carcinomas. To determine whether these mutations also occur in normal and inflamed tissues from which carcinomas arise, we utilized the ultra-sensitive polymerase chain reaction/restriction endonuclease/ligase chain reaction mutation assay. Ninety samples of genital skin, including lichen sclerosus (LS) affected skin, adjacent normal and non-adjacent normal, were assayed. Mutations were detected in 103 of 349 assays and consisted of KRAS G34A, G34T, G35A, and TP53 C742T, G818C, C817T, and G818A mutations. Mutant prevalence varied from 1 to 20 per 10(6) wild-type cells. Mutations occurred significantly more frequently in LS (78/224 (35%)) than adjacent normal (20/88 (23%)) and non-adjacent normal genital skin (5/38 (13%)). KRAS G34A mutation was relatively common to all classes of specimen, whereas TP53 gene C742T and G818C mutations were significantly more frequent in LS than normal genital skin. In matched samples, immunohistochemistry evaluation of p53 protein expression revealed the presence of epidermal p53 clones in LS whose presence and number significantly correlated with the presence of TP53 C742T and G818C mutations. Based on these results, it appears oncogenic point mutations occur in normal genital skin, and are selected for in LS.

Glutathione depletion inhibits dendritic cell maturation and delayed-type hypersensitivity: Implications for systemic disease and immunosenescence

BACKGROUND

Dendritic cells (DCs) play a key role as antigen-presenting cells in the immune system. There is growing evidence that the redox equilibrium of these cells influences their ability to induce T-cell activation and to regulate the polarity of the immune response. This could affect the outcome of the immune response during systemic diseases and aging.

OBJECTIVE

Our aim was to elucidate the mechanism by which the redox equilibrium of antigen-presenting DCs affects the delayed-type hypersensitivity (DTH) response during experimental modification of glutathione levels, as well as during aging.

METHODS

We looked at the effect of glutathione depletion by diethyl maleate in DCs as well as during systemic administration on the DTH response to the contact-sensitizing antigens, oxazolone, and 2,4-dinitro-1-fluorobenzene. We also determined whether glutathione repletion with N-acetyl cysteine could influence the decline of the DTH response in aged mice.

RESULTS

Glutathione depletion in bone marrow-derived DCs interfered in their ability to mount a DTH response on adoptive transfer into recipient mice. Glutathione depletion interfered in IL-12 production and costimulatory receptor expression in DCs, leading to decreased IFN-gamma production in the skin of recipient mice. Systemic diethyl maleate treatment exerted similar effects on the DTH response and IFN-gamma production, whereas N-acetyl cysteine administration reversed the decline of the DTH response in aged animals.

CONCLUSION

Glutathione depletion downregulates T(H)1 immunity through a perturbation of DC maturation and IL-12 production.

CLINICAL IMPLICATIONS

These data show that the induction of oxidative stress in the immune system, under disease conditions and aging, interferes in T(H)1 immunity.

EC-SOD suppresses contact hypersensitivity in mouse skin by impairing Langerhans cell migration

Extracellular superoxide dismutase (EC-SOD) is primarily a tissue enzyme and has been implicated in the modulation of inflammatory response. The biological role of EC-SOD in skin, however, has rarely been investigated. In this study, we aim to explore the effects of EC-SOD on the inflammatory response in skin by evaluating the contact hypersensitivity response (CHS) in EC-SOD transgenic mice. Transgenic mice with skin-specific expression of EC-SOD were sensitized and challenged with 2,4,6-trinitro-1-chlorobenzene (TNCB), followed by measurement of ear swelling. EC-SOD transgenic mice showed significantly reduced CHS responses compared with wild-type mice. Histological evaluation of the challenged ears of EC-SOD transgenic mice revealed diminished infiltration of inflammatory cells with a failure to induce expression of inflammatory cytokines, such as tumor necrosis factor-alpha and IFN-gamma, on sensitization and challenge with TNCB. Furthermore, Langerhans cell migration to lymph nodes was impaired in EC-SOD transgenic mice. These results indicate that EC-SOD downregulates CHS through inhibition of the inflammatory response, suggesting a possible therapeutic regimen in inflammatory skin diseases.

In vitro evaluation of quercetin cutaneous absorption from topical formulations and its functional stability by antioxidant activity

Recently, it was demonstrated that two different formulations containing quercetin inhibit the UVB-induced cutaneous oxidative stress and inflammation. Therefore, in the present study it was evaluated the functional stability of those formulations by the antioxidant activity, the release of quercetin from the formulations, and its skin retention using modified Franz diffusion cells. Both formulations tested ((1) non-ionic emulsion with high lipid content and (2) anionic emulsion with low lipid content) remained functionally (hydrogen-donating ability) stable during 180 days. Furthermore, quercetin was released from both formulations as determined using nitrocellulose membrane. In vitro antioxidant activity of retained quercetin into the skin was observed for both formulations as detected by the inhibition of malondialdehyde formation. The effect of quercetin retention was time-dependent for formulation 1. Concluding, this study demonstrates that quercetin remains functionally stable in formulations, and measuring the antioxidant activity is an efficient approach to evaluate quercetin skin retention with minimal interference of the tissue products. Furthermore, the present results on skin retention explain the previous study on quercetin in vivo activities, and together, these data suggest that formulations containing quercetin may be used as topical active products to control UVB-mediated oxidative damage of the skin.

Accumulation of oxidized low-density lipoprotein in psoriatic skin and changes of plasma lipid levels in psoriatic patients

Background. Psoriasis is a chronic inflammatory skin disease characterized by an accelerated turnover of epidermal cells and an incomplete differentiation in epidermis with lesion. However, the exact etiology of psoriasis is unknown. Abnormalities in essential fatty acid metabolism, free radical generation, lipid peroxidation, and release of lymphokines have been proposed. Objective. Our purpose was to evaluate the plasma lipids and oxidized low-density lipoprotein accumulation in psoriatic skin lesion in order to ascertain the possible participation of oxidative stress and oxidative modification of lipids in pathogenesis of psoriasis. Methods. The study group included 84 patients with psoriasis, and 40 sex- and age-matched healthy volunteers. Blood lipid profile was determined. Psoriatic and nonlesional skin samples of psoriatic patients were evaluated for the presence of oxidized low-density lipoprotein by using an immune-fluorescent staining method. Results. The mean levels of lipids (total cholesterol, triglyceride, and LDL cholesterol) in patients with psoriasis were found to be significantly higher than those of healthy subjects. Psoriatic skins were shown positive oxidized low-density lipoprotein staining. There was no staining in nonlesional skin samples of the same individuals. Conclusion. Lipid peroxidation mediated by free radicals is believed to be one of the important causes of cell membrane destruction and cell damage. This study shows for the first time the accumulation of oxidized low-density lipoprotein in psoriatic skin lesion. We believe that accumulation of ox-LDL in psoriatic skin may have an important role in the immune-inflammatory events that result in progressive skin damage.

Towards a “free radical theory of graying”: melanocyte apoptosis in the aging human hair follicle is an indicator of oxidative stress induced tissue damage

Oxidative stress is generated by a multitude of environmental and endogenous challenges such as radiation, inflammation, or psychoemotional stress. It also speeds the aging process. Graying is a prominent but little understood feature of aging. Intriguingly, the continuous melanin synthesis in the growing (anagen) hair follicle generates high oxidative stress. We therefore hypothesize that hair bulb melanocytes are especially susceptible to free radical-induced aging. To test this hypothesis, we subjected human scalp skin anagen hair follicles from graying individuals to macroscopic and immunohistomorphometric analysis and organ culture. We found evidence of melanocyte apoptosis and increased oxidative stress in the pigmentary unit of graying hair follicles. The "common" deletion, a marker mitochondrial DNA-deletion for accumulating oxidative stress damage, occurred most prominently in graying hair follicles. Cultured unpigmented hair follicles grew better than pigmented follicles of the same donors. Finally, cultured pigmented hair follicles exposed to exogenous oxidative stress (hydroquinone) showed increased melanocyte apoptosis in the hair bulb. We conclude that oxidative stress is high in hair follicle melanocytes and leads to their selective premature aging and apoptosis. The graying hair follicle, therefore, offers a unique model system to study oxidative stress and aging and to test antiaging therapeutics in their ability to slow down or even stop this process.

Protective effect of topical formulations containing quercetin against UVB-induced oxidative stress in hairless mice

UV radiation-induced skin damages may result in pre-cancerous and cancerous skin lesions, and acceleration of skin aging. It involves an imbalance of the endogenous antioxidant system that leads to the increase of free radical levels and inflammation. Therefore, antioxidant supplementation might inhibit such imbalance. In this regard, quercetin is a promising drug, this plant derived lipophilic flavonoid presents the higher antioxidant activity among flavonoids and multiple antioxidant mechanisms. Thus, the present study investigated the possible beneficial effects of topical formulations containing quercetin to inhibit UVB irradiation-induced oxidative damages. Quercetin was administered on the dorsal skin of hairless mice using two formulations, formulation 1 (non-ionic emulsion with high lipid content) and formulation 2 (anionic emulsion with low lipid content). The UVB irradiation (0.31-3.69 J/cm(2)) induced a dose-dependent increase in the myeloperoxidase (MPO) activity (4-2708%) and depletion of reduced glutathione (GSH) (22-68%) in the skin of hairless mice after 6h. These results demonstrated that the UVB doses are not excessive, and additionally, they are lower than the doses used in other similar studies. Proteinases secretion/activity, detected by the qualitative sodium dodecyl sulphate polyacrylamide gel electrophoresis substrate-embedded enzymography (zymography), was also enhanced in the same manner as MPO activity using the UVB dose of 1.23J /cm(2). Formulations 1 and 2 inhibited the MPO activity increase (62% and 59%, respectively), GSH depletion (119% and 53%, respectively) and proteinases secretion/activity. To our knowledge, this is the first study to demonstrate the effectiveness of topical formulations containing quercetin to inhibit the UVB irradiation-induced skin damages. Thus, these data suggest the possible usefulness of topical formulations containing quercetin to prevent UVB radiation skin damages.

Trans fatty acids and atopic eczema/dermatitis syndrome: the relationship with a free radical cis-trans isomerization of membrane lipids

The formation of trans FA residues in membrane phospholipids may be due to a free radical-catalyzed isomerization process occurring to the cis unsaturated FA moieties. Radical stress is well documented in inflammatory processes of atopic diseases, but no data are yet available about a possible association with trans FA detected in these patients. We investigated the presence of trans lipid isomers in the erythrocyte and T-lymphocyte membranes of 26 children affected by atopic eczema/dermatitis syndrome (AEDS). Trans lipid isomers were found in both cell membranes, up to a total content of 2.7 and 4.9% of the FA composition, respectively. By using the geometrical trans lipid library derived from in vitro models of thiyl radical-catalyzed isomerization, oleic and arachidonic acid isomers were detected. The statistical significance was evaluated by comparison with an age-matched control group. These results suggest the role of an endogenous free radical isomerization path occurring to membrane unsaturated lipids, complementary to the dietary contribution, which can be involved in the lipid impairment in AEDS. This study contributes to lipidomic research regarding the double bond structure and the influence of a geometrical change of membrane lipids in physiology and diseases.

Aqueous extract of Salvia miltiorrhoza regulates adhesion molecule expression of tumor necrosis factor alpha-induced endothelial cells by blocking activation of nuclear factor kappaB

Salvia miltiorrhoza Bunge is a traditional herb medicine often used in China for the treatment of cardiovascular disorders, such as atherosclerosis. The purpose of this study was to examine the effect of aqueous extract of Salvia miltiorrhoza Bunge (ESM) on expression of adhesion molecules in tumor necrosis factor (TNF)alpha-induced endothelial cells. When preincubated with ESM (100, 200, 400 microg/mL) for 18 hours, the adhesion of HL-60 cells to TNFalpha-induced endothelial cells was significantly decreased in a concentration-dependent manner, and down-regulation of adhesion molecules, intracellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), was also observed. The inhibitory effect of ESM on TNFalpha-induced VCAM-1 expression was attenuated by inhibition of intracellular glutathione (GSH) synthesis. In addition, ESM also significantly inhibited TNFalpha-induced translocation of nuclear factor kappaB (NF-kappaB) from cytoplasm to nuclei in endothelial cells. These results demonstrated that inhibition of ESM on the expression of adhesion molecules may result from its blocking activation on NF-kappaB. It may imply one of the mechanisms by which ESM exerts its beneficial effect preventing the progress of atherosclerosis.

Mechanisms of drug-induced delayed-type hypersensitivity reactions in the skin

Cutaneous drug reactions (CDRs) are the most commonly reported adverse drug reactions. These reactions can range from mildly discomforting to life threatening. CDRs can arise either from immunological or nonimmunological mechanisms, though the preponderance of evidence suggests an important role for immunological responses. Some cutaneous eruptions appear shortly after drug intake, while others are not manifested until 7 to 10 days after initiation of therapy and are consistent with delayed-type hypersensitivity. This review discusses critical steps in the initiation of delayed-type hypersensitivity reactions in the skin, which include protein haptenation, dendritic cell activation/migration and T-cell propagation. Recently, an alternative mechanism of drug presentation has been postulated that does not require bioactivation of the parent drug or antigen processing to elicit a drug-specific T-cell response. This review also discusses the role of various immune-mediators, such as cytokines, nitric oxide, and reactive oxygen species, in the development of delayed-type drug hypersensitivity reactions in skin. As keratinocytes have been shown to play a crucial role in the initiation and propagation of cutaneous immune responses, we also discuss the means by which these cells may initiate or modulate CDRs.

Topical application of a novel immunomodulatory peptide, RDP58, reduces skin inflammation in the phorbol ester-induced dermatitis model

RDP58 is the first lead compound in a series of immunomodulating decapeptides discovered through activity-based screening and computer-aided, rational design. RDP58 disrupts cellular responses signaled through the Toll-like and tumor necrosis factor (TNF) receptor families and occludes important signal transduction pathways involved in inflammation, inhibiting the production of tumor necrosis factor alpha (TNFalpha), interferon-gamma, interleukin (IL)-2, IL-6, and IL-12. These pro-inflammatory cytokines are thought to be involved in the pathogenesis of several inflammatory and autoimmune diseases, including atopic dermatitis and psoriasis. The goal of this study was to determine the ability of RDP58 to inhibit skin inflammation following exposure to the well-characterized protein kinase C activator and tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Topical application of RDP58 to the epidermis following TPA treatment resulted in the amelioration of the phorbol ester-induced irritant contact dermatitis. Substantial reductions were observed in skin thickness and tissue weight, neutrophil-mediated myeloperoxidase activity, inflammatory cytokine production, and various histopathological indicators. We also found RDP58 to be effective in reducing the compounding inflammatory damage brought on by chronic TPA exposure, and that it is capable of targeting inflammatory mediators specifically in the keratinocyte. These results demonstrate that topically applied RDP58 is an effective anti-inflammatory treatment in the phorbol ester-induced dermatitis model, and suggest that it may have therapeutic potential in a variety of immune-related cutaneous diseases.

Antinuclear autoantibodies in prostate cancer: immunity to LEDGF/p75, a survival protein highly expressed in prostate tumors and cleaved during apoptosis

BACKGROUND

Cancer patients produce autoantibodies to self-proteins called tumor-associated antigens (TAA). These autoantibodies represent potentially valuable tools for identifying novel biomarkers and therapeutic targets. This study was designed to identify TAA in prostate cancer (PCa).

METHODS

Serum autoantibodies to the survival protein lens epithelium-derived growth factor p75 (LEDGF/p75) were detected by immunofluorescence microscopy, ELISA, and immunoblotting. Expression of LEDGF/p75 in prostate cells and tumors was evaluated by immunoblotting or immunohistochemistry. Apoptotic cleavage of LEDGF/p75 was detected by immunoblotting.

RESULTS

Anti-LEDGF/p75 autoantibodies were detected by ELISA in 18.4% of PCa patients and 5.5% of matched controls (P < 0.001) but not in patients with benign prostatic hyperplasia (BPH). LEDGF/p75 expression was detected in 93% of prostate tumors but not in normal prostate. Strong expression of the protein was observed in 61% of prostate tumors. Moderate to high expression was also detected in BPH tissue. Cleavage of LEDGF/p75 was detected in apoptotic prostate cells.

CONCLUSIONS

The high expression of LEDGF/p75 in prostate tumors and BPH could be induced by inflammation and oxidative stress. LEDGF/p75 cleavage fragments generated during prostate tumor cell death might trigger autoantibodies under inflammatory conditions in certain patients.

Effects of antioxidants and nitric oxide on TNF-α-induced adhesion molecule expression and NF-κB activation in human dermal microvascular endothelial cells

Cell adhesion molecules expressed on endothelial cells in inflamed skin appear to be controlled by the actions of cytokines and reactive oxygen species. However, molecular mechanisms of the expression of adhesion molecules during skin inflammation are currently not well understood. To evaluate the role of antioxidants and nitric oxide in modulating inflammatory processes in the skin, we examined the effects of pyrrolidine dithiocarbamate (PDTC, 0.1 mM) and spermine NONOate (Sper-NO, 1 mM) on adhesion molecule expression and nuclear factor kappa B (NF-kappaB) activation induced by TNF-alpha (10 ng/ml) in cultured human dermal microvascular endothelial cells (HDMEC). Treatment of cells with TNF-alpha for 4 h significantly induced the surface expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1). Treatment with TNF-alpha for 8 h significantly induced the surface expression of E-selectin, ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1). The up-regulation of these adhesion molecules was suppressed significantly by pretreatment with PDTC or Sper-NO for 1 h. The mRNA expression of E-selectin, ICAM-1 and VCAM-1, and activation of NF-kappaB induced by TNF-alpha for 2 h were significantly decreased by the above two pretreatments. N-acetylcysteine (10 mM) and S-nitroso-N-acetylpenicillamine (1 mM) had no significant inhibitory effects on the cell surface and mRNA expression of these adhesion molecules stimulated by TNF-alpha. These findings indicate that both cell surface and mRNA expression of adhesion molecules in HDMEC induced by TNF-alpha are inhibited significantly by pretreatment with PDTC or Sper-NO, possibly in part through blocking the activation of NF-kappaB. These results suggest a potential therapeutic approach using antioxidant agents or nitric oxide pathway modulators in the treatment of inflammatory skin diseases.

Antioxidant activity, lipid peroxidation and skin diseases. What's new

Due to its interface function between the body and the environment, the skin is chronically exposed to both endogenous and environmental pro-oxidant agents, leading to the harmful generation of reactive oxygen species (ROS). There is compelling evidence that oxidative stress is involved in the damage of cellular constituents, such as DNA, cell membrane lipids or proteins. To protect the skin against the over-load of oxidant species, it contains a well-organised system of both chemical and enzymatic antioxidant which are able to work in a synergistic manner. Skin antioxidant network protects cells against oxidative injury and prevent the production of oxidation products, such as 4-hydroxy-2-nonenal or malonaldehyde, which are able to induce protein damage, apoptosis or release of pro-inflammatory mediators, such as cytokines. When oxidative stress overwhelms the skin antioxidant capacity the subsequent modification of cellular redox apparatus leads to an alteration of cell homeostasis and a generation of degenerative processes. Topical application or oral administration of antioxidants has been recently suggested as preventive therapy for skin photoaging and UV-induced cancer. The recognition that ROS can act as second messengers in the induction of several biological responses, such as the activation of NF-kB or AP-1, the generation of cytokines, the modulation of signalling pathways, etc., has led many researchers to focus on the possible effects of antioxidants in many pathological processes. The recent demonstration that the peroxisome proliferators-activated receptors, whose natural ligands are polyunsaturated fatty acids and theirs oxidation products, have a central role in the induction of some skin diseases, such as psoriasis or acne, has indicated new links between free radicals and skin inflammation. Based on these findings, the review summarises the possible correlations between antioxidant imbalance, lipid oxidative breakage and skin diseases, from both a pathological and therapeutic points of view.

Vitamin E delivery to human skin: studies using deuterated alpha-tocopherol measured by APCI LC-MS

Enrichment of skin surface lipids with deuterium-labeled alpha-tocopherol was compared with plasma enrichment to evaluate kinetics of the delivery of vitamin E to skin surface lipids. For 7 d, subjects consumed 75 mg each of RRR-alpha-[5-(C2H3)]- (d3) and all rac-alpha-[5,7-(C2H3)2]- (d6) tocopheryl acetates with breakfast. Blood was drawn and skin lipids were collected daily for 2 weeks, then every other day for 2 weeks. A liquid chromatography-mass spectrometry atmospheric pressure chemical ionization method for quantification of deuterium labeled (d3, d6, d9-alpha-tocopherols) and unlabeled (d0-) alpha- and gamma-tocopherols was developed. Tocopherols were quantified at their m/z [M-1] using single ion recording. alpha-Tocopherol detection was linear from 1 to 100 pmol with a detection limit of 40 pg (93 fmol). Detection of gamma-tocopherol was twice as sensitive due to greater ionization efficiency. Though d3- and d6-alpha-tocopherols appeared in plasma within 24 h of the first dose, d3-alpha-tocopherol was not detected in skin surface lipids until approximately 1 week. Plasma percentage d3 peaked at day 8, while skin surface lipid percentage d3 increased on average until day 19. Apparently skin employs a mechanism to deliver alpha-tocopherol into skin via lipid secretions.

Determination of antioxidant efficacy of cosmetic formulations by non-invasive measurements

BACKGROUND/AIMS

Antioxidants have been proposed, over the last decade, as functional ingredients for anti aging preparations and to prevent and modulate oxidative skin damages. Up to date, beside the photo-induced oxidative skin damages model, none in vivo protocols have shown sufficient reproducibility for the validation of the antioxidant claim for a cosmetic finished product. To this aim, we have recently anticipated a new in vivo protocol based on a microinflammatory model, driven by reactive oxygen species. In the present study our model was validated by comparison with four different instrumental methods.

METHODS

The effects of a pre-treatment of two different formulations based on antioxidant functional ingredients, were investigated on forearm skin of 15 healthy volunteers, and compared to a cosmetic base and control area. The instruments considered in the study were Chromameter (CR-300 Minolta), Tewameter TM 210 (Courage-khazaka, Cologne, Germany), Laser Doppler Perfusion Imager (PIM1.0 Lisca Development AB, Sweden), in comparison to DermAnalyzer(R), an easy to use software program developed by us, using the CIE L*a*b* color space parameters.

RESULTS

The comparative measurements showed that the antioxidant formulations tested were all able to reduce, in different but statistically significant extent, the intensity of skin redness, and of cutaneous blood flow, when compared to control area (P < 0.0001).

CONCLUSIONS

The methyl nicotinate (MN) based microinflammatory model, in conjunction with objective measure- ments, resulted an effective tool for in vivo assessment of oxidative skin injuries. In view of the high level of repeatability, short time of answer and simplicity, the procedure by us developed, is proposed as a possible protocol for the evaluation of in vivo efficacy of antioxidant functional ingredients in cosmetic formulations.

Over-expression of Mn-superoxide dismutase as a marker of oxidative stress in lesional skin of chronic idiopathic urticaria

We studied the involvement of oxidative stress in chronic idiopathic urticaria (CIU), assessing the activities of superoxide dismutase (SOD) and glutathione and the levels of malondialdeyde (MDA), a marker of lipid peroxidation, in samples taken from lesional skin (n = 16) and nonlesional skin (n = 11) of CIU patients. The activity of SOD and glutathione and the levels of MDA were markedly increased in lesional skin as compared with skin of healthy subjects, whereas no differences were detected between nonlesional skin of CIU patients and control samples. Immuno-dot blot assay revealed an up-regulation of Mn-SOD expression in lesional skin. These findings show that oxidative stress is crucially involved in CIU. The evidence of lipid peroxidation and compensatory increase of Mn-SOD and glutathione activities in lesional skin, in the absence of any alteration in uninvolved skin, suggests that oxidative stress is secondary to the development of inflammation.

Evaluation of the atherogenic tendency of lipids and lipoprotein content and their relationships with oxidant-antioxidant system in patients with psoriasis

BACKGROUND

Psoriasis is a common chronic and recurrent inflammatory skin disease that can occur due to abnormalities in essential fatty acid metabolism, lymphokine secretion, free radical generation, lipid peroxidation and eicosanoid metabolism, and has been associated with increased frequency of cardiovascular events. The current study was designed to evaluate plasma lipids, susceptibility of LDL to oxidation and oxidant-antioxidant status and their relationships in patients with psoriasis.

METHODS

The study group included 35 patients with psoriasis (18 females and 17 males), and 35 sex- and age-matched healthy volunteers (16 females and 19 males). From blood samples, their lipids, lipoproteins, acute phase reactants, lipid peroxidation products [lipid hydroperoxide (LHP) and malondialdehyde (MDA)], antioxidant enzymes [glutathione peroxidase (GSH-Px), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT)], total antioxidant status (TAS) and autoantibodies against oxidized low-density lipoprotein (AuAb-oxLDL) levels were determined. Moreover, the susceptibility of copper-induced in vitro oxidation of LDL was examined.

RESULTS

The mean levels of atherogenic lipids (total cholesterol [TC], triacylglycerol [TG] and LDL cholesterol [LDL-C]), acute-phase reactants (CRP, ESR, PMNLs, ceruloplasmin and fibrinogen) and lipid peroxidation products, AuAb-oxLDL levels in patients with psoriasis were found to be significantly higher than those of healthy subjects. On the other hand, TAS and antioxidant enzyme activities (CAT, SOD and GSH-Px in erythrocyte and SOD in plasma) were significantly lower when compared to healthy subjects. The lag times [t(lag)], a measure of resistance to oxidation of LDL, were also lower. The levels of AuAb-oxLDL in patients were correlated with TC, LDL-C, plasma LHP, erythrocyte MDA, oxidized LDL-MDA (oxLDL-MDA), fibrinogen, CRP, PMNL levels and plasma SOD activities (r = 0.69, P < 0.01; r = 0.64, P < 0.01; r = 0.38, P < 0.05; r = 0.65, P < 0.01; r = 0.34, P < 0.05; r = 0.34, P < 0.05; r = 0.53, P < 0.01, r = 0.34, P < 0.05; r = -0.67, P < 0.01, respectively). On the other hand, t(lag) was correlated negatively with the levels of VLDL-TG, VLDL-TC and LDL-TG but positively correlated with the levels of TAS in psoriatics (r = -0.49, P < 0.01; r = -0.49, P < 0.01, r = -0.65, P < 0.05; r = 0.37, P < 0.05).

CONCLUSIONS

It was concluded that the psoriatic patients could be considered as a group with an increased atherosclerotic risk because of increased oxidant stress, decreased antioxidant capacity and susceptibility in lipid profile and lipoprotein content to atherogenicity.

Inhibition of collagenase and metalloproteinases by aloins and aloe gel

The effects of Aloe barbadensis gel and aloe gel constituents on the activity of microbial and human metalloproteinases have been investigated. Clostridium histolyticum collagenase (ChC) results dose-dependently inhibited by aloe gel and the activity-guided fractionation led to an active fraction enriched in phenolics and aloins. Aloins have been shown to be able to bind and to inhibit ChC reversibly and non-competitively. Aloe gel and aloins are also effective inhibitors of stimulated granulocyte matrix metalloproteinases (MMPs). The remarkable structural resemblances between aloins and the pharmacophore structure of inhibitory tetracyclines, suggest that the inhibitory effects of aloins are via an interaction between the carbonyl group at C(9) and an adjacent hydroxyl group of anthrone (C(1) or C(8)) at the secondary binding site of enzyme, destabilizing the structure of granulocyte MMPs.

Levels of enzymatic antioxidants activities in mononuclear cells and skin reactivity to sodium dodecyl sulphate

Chemical irritants are able to produce several biological modifications of the skin, including the direct or indirect production of cytokines and reactive oxygen species leading to an inflammatory reaction. This report examines the existence of a possible correlation between the skin sensitivity to the irritant sodium dodecyl sulphate (SDS) and the activity of the enzymatic antioxidants. In twenty-three healthy subjects the evaluation of the epidermal and peripheral blood mononuclear cells (PBMCs) activities of Superoxide Dismutase (SOD) and Catalase (Cat) demonstrate a significant correlation (r= 0,85 and p< 0,005 for SOD, and r= 0,87 and p< 0,0001 for Cat). Based on this result, on a further group of normal subjects (n=13) we studied the link between the threshold dose of skin reactivity to SDS and the activities of the enzymatic antioxidants in PBMCs. The degree of skin modification induced by SDS, applied at different concentrations for 24 hrs, was determined by means of Trans Epidermal Water Loss (TEWL), Erythemal Index or by Visual Score (VS). The minimal dose of the irritant capable of inducing skin modifications, was significantly correlated with SOD (r=0,77) and Cat (r=0,81) activities in PBMCs, and the modification of TEWL or EI were inversely correlated with levels of antioxidants in PBMCs (r=-0,62 for SOD and r=-0,66 for Cat). Our results indicate that the skin reactivity to irritants can be modulated by the levels of antioxidants, and suggest a possible therapeutical approach in preventing irritant contact dermatitis.

Thimerosal stimulates focal adhesion kinase and cytoskeletal changes by redox modulation

Thimerosal is one of the most widely used preservatives and has been reported to cause chemically mediated side effects. However, the mechanism of the side effects is not clearly understood yet. In the present study, we showed that HeLa S cells treated by thimerosal generated reactive oxygen species (ROS). Thimerosal-generated ROS stimulated the tyrosine phosphorylation of focal adhesion kinase (FAK) and also induced cytoskeletal changes. Pretreatment with intracellular calcium chelator, BAPTA did not block the thimerosal-mediated FAK tyrosine phosphorylation. On the other hand, either FAK inhibitor, tyrphostin or ROS scavenger, N-acetyl-L-cysteine (NAC) suppressed the tyrosine phosphorylation and cytoskeletal changes. These results suggest that thimerosal seems to induce FAK tyrosine phosphorylation and cytoskeletal changes by ROS generation but not by intracellular calcium mobilization. We think the present finding can be an important clue to understanding the mechanism of thimerosal-mediated side effects, such as contact dermatitis, and allergy.

A paradigm for determining the relevance of short-term assays: application to oxidative mutagenesis

A simple substructure-based approach was developed to determine whether a short-term assay under development is related mechanistically to the endpoint it seeks to predict. Thus, substructures associated with mutagenicity in Salmonella are also present in carcinogens and agents active in other mutagenicity and genotoxicity assays. When applied to test results obtained with an Escherichia coli strain designed to identify oxidative mutagens, there was no significant association with either carcinogens or mutagens and genotoxicants detected by other systems. There was, however, a significant association between alerts for oxidative mutagenesis and chemicals capable of inducing allergic contact dermatitis (ACD) in humans.

Pharmaco-redox regulation of cytokine-related pathways: from receptor signaling to pharmacogenomics

Cytokines represent a multi-diverse family of polypeptide regulators; they are relatively low molecular weight (< 30 kDa), pharmacologically active proteins that are secreted by one cell for the purpose of altering either its own functions (autocrine effect) or those of adjacent cells (paracrine effect). Cytokines are small, nonenzymatic glycoproteins whose actions are both diverse and overlapping (specificity/redundancy) and may affect diverse and overlapping target cell populations. In many instances, individual cytokines have multiple biological activities. Different cytokines can also have the same activity, which provides for functional redundancy (network) within the inflammatory and immune systems. As biological cofactors that are released by specific cells, cytokines have specific effects on cell-cell interaction, communication, and behavior of other cells. As a result, it is infrequent that loss or neutralization of one cytokine will markedly interfere with either of these systems. The biological effect of one cytokine is often modified or augmented by another. Because an interdigitating, redundant network of cytokines is involved in the production of most biological effects, both under physiologic and pathologic conditions, it usually requires more than a single defect in the network to alter drastically the outcome of the process. This fact, therefore, may have crucial significance in the development of therapeutic strategies for biopharmacologic intervention in cytokine-mediated inflammatory processes and infections.

Modeling of the anticancer action for radical derivatives of nitroazoles: quantitative structure-activity relationship (QSAR) study

A QSAR analysis of the anti-tumor, anti-metastasis and anti-colony formation (for metastatic colonies) activities of eighteen nitroazoles (including metronidazole and hypoxic radiosensitizers RP-170, KU-2285 and sanazole (drug AK-2123)) and their nitro and nitroso anion radical derivatives against melanoma B16 in mice has been performed. The QSAR models were built with the use of the frontal polygon method. This approach has features of different 3D QSAR methodologies and belongs to the group of "indirect" methods. The procedure allows to build robust models with high predictive ability even in series of diverse and conformationally flexible compounds. Key atomic characteristics accompany the geometrical requirements in the analysis of local 3D molecular similarity. By variation of weight coefficients for hydrophobicity, refraction increments, and partial charge it is possible to achieve better quality of QSAR and evaluate the importance of each characteristic for biological activity under consideration. It was found that hydrophobicity, molar refraction and charge characteristics of nitro anion radical derivatives are more significant for interaction with molecular targets than those of the parent compounds and of the nitroso anion radical derivatives. Size and hydrophobic properties of substituents in nitro anion radicals play significant role for ligand-target interaction in the processes of inhibition of metastatic spreading and growth of metastatic colonies by nitroazoles. A scheme of competitive interaction of parent nitroazoles and their anion radicals with a target in organism is suggested. It can be concluded that the step of one-electron reduction of nitroazoles can be important for anticancer activity of these drugs.

Thioredoxin-(dithiol-)linked inactivation of elastase

Following inactivation by the alpha-1-antitrypsin (AAT) inhibitor, the protease elastase was reduced by thioredoxin, itself reduced by NADPH and NADP-thioredoxin reductase (NTR). Under these conditions, reduction of enzyme disulfide groups was accompanied by loss of more than 60% of the activity measured following dissociation of the enzyme-inhibitor complex with NaCl. The inhibitor was required (1) to prevent proteolysis of both reduced thioredoxin and NTR and (2) to assess the progress of the reduction reaction. At elevated temperature, elastase was also reduced by dithiols (dithiothreitol and lipoic acid) but not by monothiols (reduced glutathione, beta-mercaptoethanol). When reduced by dithiols under these conditions, the enzyme digested itself. Self-digestion was independent of the antitrypsin inhibitor and was proportional to temperature in the 37-50 degree C range. These findings open the door to a new mode of regulation of elastase and to possible new therapies for treating diseases associated with the enzyme.