Nitric oxide-peroxynitrite-poly(ADP-ribose) polymerase pathway in the skin

Dupilumab therapy reduces urinary biopyrrin levels in atopic patients: a new possible biomarker of oxidative status in atopic dermatitis

BACKGROUND

Accumulating evidence suggests that oxidative stress is involved in the inflammatory process of atopic dermatitis (AD). Biopyrrins are the end products of the oxidative reaction of bilirubin with reactive oxygen species. The aim of our study was to explore the correlation between urinary biopyrrin levels and AD severity as well as to assess the possible modification of them in AD patients during biologic therapy with human monoclonal antibody dupilumab.

METHODS

For this purpose, 25 adult patients with moderate-severe AD who were candidates for dupilumab therapy independently from the study, and 15 healthy control subjects, matched by sex and age, were enrolled. Morning urine samples were collected from all study participants. For AD patients, a collection was planned before starting therapy with dupilumab (WO), after 8, 16, 52 weeks (W8, W16, W52, respectively), and two years (Y2) of treatment. The analysis of urinary levels of biopyrrins was performed by ELISA assay.

RESULTS

Our results demonstrated that urinary biopyrrin levels were significantly augmented in AD patients, and interestingly they correlated with disease severity. Furthermore, dupilumab therapy decreased levels of urinary biopyrrins in AD patients after eight and 16 weeks, maintaining the result after 52 weeks as well as after two years of treatment. The correlation analysis showed a statistically significant positive correlation between the urinary concentration of biopyrrins and EASI Index, circulating total IgE as well as plasma C reactive protein levels.

CONCLUSIONS

Dupilumab therapy was able to ameliorate oxidative state in AD patients.

PARP2 poly(ADP-ribosyl)ates nuclear factor erythroid 2-related factor 2 (NRF2) affecting NRF2 subcellular localization

PARP2 is a member of the PARP enzyme family. Although, PARP2 plays role in DNA repair, it has regulatory roles in mitochondrial and lipid metabolism, it has pivotal role in bringing about the adverse effects of pharmacological PARP inhibitors. Previously, we showed that the ablation of PARP2 induces oxidative stress and, consequently, mitochondrial fragmentation. In attempt to identify the source of the reactive species we assessed the possible role of a central regulator of cellular antioxidant defense, nuclear factor erythroid 2-related factor 2 (NRF2). The silencing of PARP2 did not alter either the mRNA or the protein expression of NRF2, but changed its subcellular localization, decreasing the proportion of nuclear, active fraction of NRF2. Pharmacological inhibition of PARP2 partially restored the normal localization pattern of NRF2 and in line with that, we showed that NRF2 is PARylated that is absent in the cells in which PARP2 was silenced. Apparently, the PARylation of NRF2 by PARP2 has pivotal role in regulating the subcellular (nuclear) localization of NRF2. The silencing of PARP2 rearranged the expression of genes encoding proteins with antioxidant function, among these a subset of NRF2-dependent genes.

Protective effects of 1,25 dihydroxyvitamin D3 and its analogs on ultraviolet radiation-induced oxidative stress: a review

The active vitamin D compound, 1,25-dihydroxyvitamin D3 (1,25D) is produced in skin cells following exposure to ultraviolet radiation (UV) from the sun. However, there are many harmful effects of UV which include DNA damage caused by direct absorption of UV, as well as that caused indirectly via UV-induced reactive oxygen species (ROS). Interestingly, 1,25D and analogs have been shown to reduce both direct and indirect UV-induced DNA damage in skin cells. This was accompanied by reductions in ROS and in nitric oxide products with 1,25D following UV. Moreover, following acute UV exposure, 1,25D has been demonstrated to increase p53 levels in skin, which would presumably allow for repair of cells with damaged DNA, or apoptosis of cells with irreparably damaged DNA. Previous studies have also shown that p53 reduces intracellular ROS. Furthermore, 1,25D has been shown to induce metallothioneins, which are potent free radical scavengers. In addition to these protective effects, 1,25D has been demonstrated to inhibit stress-activated c-Jun N-terminal kinases following UV exposure, and to increase levels of the stress-induced protein heme oxygenase-1 in a model of oxidative stress. Herein, we discuss the protective effects of 1,25D and analogs in the context of UV, oxidative stress and skin cancer.

High-content screening identifies inhibitors of oxidative stress-induced parthanatos: cytoprotective and anti-inflammatory effects of ciclopirox

BACKGROUND AND PURPOSE

Excessive oxidative stress can induce PARP1-mediated programmed necrotic cell death, termed parthanatos. Inhibition of parthanatos may be therapeutically beneficial in a wide array of diseases associated with tissue injury and inflammation. Our goal was to identify novel molecules inhibiting parthanatos.

EXPERIMENTAL APPROACH

A small library of 774 pharmacologically active compounds was screened in a Sytox Green uptake assay, which identified 20 hits that reduced hydrogen-peroxide-induced parthanatos with an efficiency comparable to the benchmark PARP inhibitor, PJ34.

KEY RESULTS

Of these hits, two compounds, antifungal ciclopirox and dopamine receptor agonist apomorphine, inhibited PAR polymer synthesis. These two compounds prevented the binding of PARP1 to oxidatively damaged DNA but did not directly interfere with the interaction between DNA and PARP1. Both compounds inhibited mitochondrial superoxide and H₂ O₂ production and suppressed DNA breakage. Since H₂ O₂ -induced damage is dependent on Fe²⁺ -catalysed hydroxyl radical production (Fenton chemistry), we determined the iron chelation activity of the two test compounds and found that ciclopirox and, to a lesser extent, apomorphine act as iron chelators. We also show that the Fe²⁺ chelation and indirect PARP inhibitory effects of ciclopirox translate to anti-inflammatory actions as demonstrated in a mouse dermatitis model, where ciclopirox reduced ear swelling, inflammatory cell recruitment and poly(ADP-ribosyl)ation.

CONCLUSION AND IMPLICATIONS

Our findings indicate that the antimycotic drug, ciclopirox, acts as an iron chelator and thus targets an early event in hydrogen-peroxide-induced parthanatos. Ciclopirox has the potential to be repurposed as a cytoprotective and anti-inflammatory agent.

Tannic acid, a promising anti-photoaging agent: Evidences of its antioxidant and anti-wrinkle potentials, and its ability to prevent photodamage and MMP-1 expression in L929 fibroblasts exposed to UVB

Chronic and unprotect UV exposure leads to skin oxidative stress, following accumulation of damaged cellular components and downstream activation of specific signaling pathways, culminating in premature skin aging (photoaging). In this concern, polyphenols have been proposed for the prevention of skin disorders UV-generated. In the present study, we compared gallic acid (GA) and tannic acid (TA) regarding their potentials in prevent photoaging, using cell-free assays. The most promising compound was further investigated for its photoprotection abilities in UVB-irradiated L929 fibroblasts. TA was more efficient in scavenging radicals DPPH^•, superoxide anion, peroxyl, nitric oxide and peroxynitrite, and to reduce ferric ions. Although GA and TA exhibited similar inhibitory activity towards collagenase, TA was more potent in inhibit elastase. In addition, TA presented a broader UV absorption spectrum. Furthermore, TA treatment in UVB-irradiated cells attenuated redox imbalance, as observed by its ability to inhibit ROS production, NADPH oxidase activation and depletion of endogenous antioxidant defense system. Moreover, TA treatment prevented cellular photodamage and subsequently photoaging, by inhibiting lipid peroxidation, depolarization of mitochondrial transmembrane potential, DNA damage, and MMP-1 expression, a protein closely related to the structural degeneration of the dermis extracellular matrix. In conclusion, the results indicate the potential of TA in act as anti-photoaging agent, due to its potent antioxidant, anti-collagenase and anti-elastase activities, and UV-absorption effects, and its ability in prevent oxidative stress, oxidative damages and MMP-1 induction in UVB-irradiated L929 fibroblasts.

Poly(ADP-ribose) polymerase-1 depletion enhances the severity of inflammation in an imiquimod-induced model of psoriasis

Poly(ADP-ribose) polymerase-1 (PARP1) is a pro-inflammatory protein, whose pro-inflammatory properties were demonstrated in human. The pro-inflammatory properties of PARP1 were shown in Th1- and Th2-mediated inflammatory pathologies, but not Th17-mediated inflammation. Thus, we studied the role of PARP1 in the imiquimod-induced model of psoriasis. To our surprise, in imiquimod-induced psoriasis, PARP1 acted as an anti-inflammatory factor and its genetic deletion exacerbated symptoms. We showed that in the absence of PARP1, the epidermis thickened and the number of TUNEL-positive cells decreased in the epidermis. These data indicate programmed cell death is decreased in keratinocytes. Changes in involucrin expression suggest that keratinocyte differentiation is hampered. Furthermore, epidermal expression of IL6 increased in the psoriasiform lesions of PARP1 knockout mice, suggesting that the inflammatory response is also derailed in the absence of PARP1. Finally, we showed that PARP1 expression is reduced in human psoriatic lesions compared with control skin samples. In imiquimod-treated HPV-KER keratinocytes, PARP inhibition recapitulated the in vivo findings, namely keratinocyte hyperproliferation; furthermore, the mRNA expression of psoriasis-associated cytokines (IL6, IL1β, IL8, IL17 and IL23A) was also induced. The inhibition of TRPV1 abrogated the effects of the combined imiquimod + PARP inhibitor treatment.

Redox Profiling Reveals Clear Differences between Molecular Patterns of Wound Fluids from Acute and Chronic Wounds

Wound healing is a complex multiphase process which can be hampered by many factors including impaired local circulation, hypoxia, infection, malnutrition, immunosuppression, and metabolic dysregulation in diabetes. Redox dysregulation is a common feature of many skin diseases demonstrated by virtually all cell types in the skin with overproduction of reactive oxygen and nitrogen species. The objective of this study was to characterize the redox environment in wound fluids and sera from patients suffering from chronic leg ulcers (n = 19) and acute wounds (bulla fluids from second degree burns; n = 11) with serum data also compared to those from healthy volunteers (n = 7). Significantly higher concentrations of TNF-α, interleukine-8, vascular endothelial growth factor, and lactate dehydrogenase (measure of cell damage) were found in fluids from chronic wounds compared to acute ones. The extent of protein carbonylation (measure of protein oxidation), lipid peroxidation, and tyrosine nitration (indicator of peroxynitrite production) was similar in acute and chronic wound fluids, while radical scavenging activity and glutathione (GSH) levels were elevated in chronic wound fluids compared to acute wounds. Sera were also assessed for the same set of parameters with no significant differences detected. Nitrotyrosine (the footprint of the potent oxidant peroxynitrite) and poly(ADP-ribose) (the product of the DNA damage sensor enzyme PARP-1) could be detected in wound biopsies. Our data identify multiple signs of redox stress in chronic wounds with notable differences. In chronic wounds, elevations in antioxidant levels/activities may indicate compensatory mechanisms against inflammation. The presence of nitrotyrosine and poly(ADP-ribose) in tissues from venous leg ulcers indicate peroxynitrite production and PARP activation in chronic wounds.

Bilirubin oxidation derived from oxidative stress is associated with disease severity of atopic dermatitis in adults

BACKGROUND

Bilirubin is an essential antioxidant. Its oxidative metabolites, biopyrrins, are sensitive urinary markers of oxidative stress. Multiple studies suggest that oxidative stress affects the pathogenesis of skin diseases such as atopic dermatitis (AD).

AIM

To examine oxidative stress-induced bilirubin oxidation and its association with AD pathogenesis in adults.

METHODS

In total, 11 patients with AD and 7 healthy controls (HCs) were enrolled. Bilirubin oxidation profiles in the combined urine of the patients and that of the HCs were examined using high-performance liquid chromatography (HPLC) and fast atom bombardment mass spectrometry. The concentrations of urinary biopyrrins and serum biomarkers for AD disease severity, such as IgE and thymus and activation-regulated chemokine (TARC)/CCL17, were measured by ELISA to determine correlations between urinary biopyrrins and serum biomarkers. Local bilirubin oxidation in AD skin lesions was assessed by immunohistochemical analyses using two antibodies against bilirubin.

RESULTS

Levels of dipyrrole-monopyrrole-aldehyde, a novel urinary biopyrrin, were higher in patients with AD than in HCs, and increased with disease severity based on the SCORing Atopic Dermatitis (SCORAD) objective scoring system. Additionally, urinary biopyrrin levels correlated significantly with serum IgE and TARC/CCL17 levels. Furthermore, immunohistochemical analyses revealed that biopyrrins were strongly expressed in both infiltrating and resident cells in AD lesions. However, bilirubin was expressed at low levels in the lesions, suggesting that bilirubin oxidation is augmented in AD lesions.

CONCLUSIONS

Bilirubin oxidation derived from oxidative stress in the skin lesions can be associated with disease severity of AD.

Poly(ADP-ribose)polymerase 1 inhibition protects against age-dependent endothelial dysfunction

Age-related endothelial dysfunction is closely associated with the local production of reactive oxygen species (ROS) within and in the vicinity of the vascular endothelium. Oxidant-induced DNA damage can activate the nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP-1), leading to endothelial dysfunction in various pathophysiological conditions. The present study aimed to investigate the role of PARP-1 in age-dependent changes in endothelial cell function and its underlying mechanism. Wild-type (WT) and PARP-1(-/-) mice were divided into young (2 months) and old (12 months) groups. Isolated aortic rings were suspended to record isometric tension to assess endothelial function. Nitric oxide (NO) production and content in plasma were detected by spectrophotometry. Superoxide (O2(-) production was detected by dihydroethidium. Expression of PARP-1, endothelial nitric oxide synthase (eNOS), induced nitric oxide synthase (iNOS), and arginase-2 (Arg2) was assessed by western blot analysis. Endothelium-dependent relaxation in response to acetylcholine was lost in old WT, but not PARP-1(-/-), mice. Endothelium-independent vasodilation was not impaired in aging mice. Production of O2(-) was greater in aging WT mice than young or aging PARP-1(-/-) mice. eNOS expression was not affected by aging in WT or PARP-1(-/-) mice, but p-eNOS expression decreased and iNOS and Arg2 levels were upregulated only in aging WT mice. In conclusion, PARP-1 inhibition may protect against age-dependent endothelial dysfunction, potentially by regulating NO bioavailability via iNOS. Inhibition of PARP-1 may help in vascular aging prevention.

Therapeutic evaluation of HIV transduction basic domain-conjugated superoxide dismutase solution on suppressive effects of the formation of peroxynitrite and expression of COX-2 in murine skin

Background

Homeostasis of reactive oxygen species (ROS) in the skin is regulated by antioxidant defenses. The inflammatory states of skin diseases which range from acute rashes to chronic conditions are related to the level of ROS. The involvement of superoxide dismutase (SOD) in restoring the antioxidant capacity can then neutralize the inflammatory response.

Results

We found that denatured Tat-SOD formulated in an aqueous medium could be delivered into mouse skin and the penetration signals of Tat-SOD were detected in the epidermis and dermis. According to immunohistochemical staining, Tat-SOD successfully suppressed inflammation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), the expression of sodium nitroferricyanide (SNP)-induced cyclooxygenase-2 (COX-2), and the production of nitrotyrosine proteins. In nerve growth factor (NGF) induced differentiated PC12 pheochromocytoma cells, we demonstrated that the denatured Tat-SOD regained its antioxidant activity and effectively protected PC12 cells from DNA fragmentation induced by paraquat. Using a luciferase reporter assay, the data was shown Tat-SOD protected PC12 cells from ROS damage, through suppression of COX-2 or nuclear factor-κB (NF-κB) activity occurred at the transcriptional level.

Conclusion

We showed that Tat-SOD inhibited SNP-induced COX-2 expression similarly to celecoxib and prevented the formation of peroxynitrite as 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. The results suggest that denatured Tat-SOD solution may perform potential protein therapy for patients suffering from disorders related to ROS.

Reactive Nitrogen Species Scavenging Capacity of Aqueous and Ethanolic Extracts from Galinsoga parviflora and G. quadriradiata Herbs

The aim of the study was to determine the scavenging capacity of aqueous and ethanolic extracts derived from the herb of two species of Galinsoga against NO and ONOO-. In both tests the aqueous extracts of both Galinsoga species were more active than the ethanolic extracts. The highest scavenging activity against NO, and also against ONOO- was shown by G. quadriradiata aqueous extract (SC50±SD=1.54±0.32, and 2.10±1.98, respectively). The study showed that the activity of the extracts from both Galinsoga species is related not only to the presence of flavonoids but also to caffeic acid derivatives and caffeic acid. The results of this study partly explain the beneficial effects of Galinsoga herb extracts in the treatment of skin diseases.

Poly(ADP) ribose polymerase-1 ablation alters eicosanoid and docosanoid signaling and metabolism in a murine model of contact hypersensitivity

Poly(ADP‑ribose) polymerase (PARP)‑1 is a pro‑inflammatory protein. The inhibition of PARP‑1 reduces the activity of numerous pro‑inflammatory transcription factors, which results in the reduced production of pro‑inflammatory cytokines, chemokines, matrix metalloproteinases and inducible nitric oxide synthase, culminating in reduced inflammation of the skin and other organs. The aim of the present study was to investigate the effects of the deletion of PARP‑1 expression on polyunsaturated fatty acids (PUFA), and PUFA metabolite composition, in mice under control conditions or undergoing an oxazolone (OXA)‑induced contact hypersensitivity reaction (CHS). CHS was elicited using OXA in both the PARP‑1+/+ and PARP‑1/ mice, and the concentration of PUFAs and PUFA metabolites in the diseased skin were assessed using lipidomics experiments. The levels of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were shown to be increased in the PARP‑1/ mice, as compared with the control, unsensitized PARP‑1+/+ mice. In addition, higher expression levels of fatty acid binding protein 7 (FABP7) were detected in the PARP‑1/ mice. FABP7 is considered to be a specific carrier of DHA and EPA. Furthermore, the levels of the metabolites of DHA and EPA (considered mainly as anti‑inflammatory or pro‑resolving factors) were higher, as compared with the metabolites of arachidonic acid (considered mainly pro‑inflammatory), both in the unsensitized control and OXA‑sensitized PARP‑1/ mice. The results of the present study suggest that the genetic deletion of PARP‑1 may affect the PUFA‑homeostasis of the skin, resulting in an anti‑inflammatory milieu, including increased DHA and EPA levels, and DHA and EPA metabolite levels. This may be an important component of the anti‑inflammatory action of PARP‑1 inhibition.

Efficacy of poly(adenosine diphosphate-ribose) polymerase inhibition in extracorporeal shock wave-induced renal injury

OBJECTIVES

Extracorporeal shock wave lithotripsy (ESW) induces renal damage by excessive production of free oxygen radicals. Free Oxygen radicals cause cellular injury by inducing nicks in DNA. The enzyme poly(adenosine diphosphate-ribose) polymerase (PARP) involved in the process of repair of DNA in damaged cells. However, its activation in damaged cells can lead to adenosine triphosphate depletion and death. Thus, we designed a study to evaluate the efficacy of 3-aminobenzamide (3-AB), a PARP inhibitor, against extracorporeal shock wave induced renal injury.

METHODS

Twenty-four Sprague-Dawley rats were divided into three groups: control, ESW, ESW + 3-AB groups. All groups except control group were subjected to ESW procedure. ESW + 3-AB group received 20 mg/kg/day 3-aminobenzamide intraperitoneally at 2 h before ESW and continued once a day for consecutive 3 days. The surviving animals were sacrificed at the 4th day and their kidneys were harvested for biochemical and histopathologic analysis. Blood samples from animals were also obtained.

RESULTS

Serum ALT and AST levels, serum neopterin and tissue oxidative stress parameters were increased in the ESW group and almost came to control values in the treatment group (p < 0.05, ESW vs. ESW + 3-AB). Histopathological injury score were significantly lower in treatment group than the ESW group (p < 0.05, ESW vs. ESW + 3-AB).

CONCLUSION

Our data showed that PARP inhibition protected renal tissue against ESW induced renal injury. These findings suggest that it would be possible to improve the outcome of ESW induced renal injury by using PARP inhibitors as a preventive therapy.

Activation of poly(ADP-ribose) polymerase-1 delays wound healing by regulating keratinocyte migration and production of inflammatory mediators

Poly(ADP-ribosyl)ation (PARylation) is a protein modification reaction regulating various diverse cellular functions ranging from metabolism, DNA repair and transcription to cell death. We set out to investigate the role of PARylation in wound healing, a highly complex process involving various cellular and humoral factors. We found that topically applied poly[ADP-ribose] polymerase (PARP) inhibitors 3-aminobenzamide and PJ-34 accelerated wound closure in a mouse model of excision wounding. Moreover, wounds also closed faster in PARP-1 knockout mice as compared with wild-type littermates. Immunofluorescent staining for poly(ADP-ribose) (PAR) indicated increased PAR synthesis in scattered cells of the wound bed. Expression of interleukin (IL)-6, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase and matrix metalloproteinase-9 was lower in the wounds of PARP-1 knockout mice as compared with control, and expression of IL-1β, cyclooxygenase-2, TIMP-1 and -2 also were affected. The level of nitrotyrosine (a marker of nitrating stress) was lower in the wounds of PARP-1 knockout animals as compared with controls. In vitro scratch assays revealed significantly faster migration of keratinocytes treated with 3-aminobenzamide or PJ34 as compared with control cells. These data suggest that PARylation by PARP-1 slows down the wound healing process by increasing the production of inflammatory mediators and nitrating stress and by slowing the migration of keratinocytes.

Tocotrienols promote apoptosis in human breast cancer cells by inducing poly(ADP-ribose) polymerase cleavage and inhibiting nuclear factor kappa-B activity

OBJECTIVES

Tocotrienols and tocopherols are members of the vitamin E family, with similar structures; however, only tocotrienols have been reported to achieve potent anti-cancer effects. The study described here has evaluated anti-cancer activity of vitamin E to elucidate mechanisms of cell death, using human breast cancer cells.

MATERIALS AND METHODS

Anti-cancer activity of a tocotrienol-rich fraction (TRF) and a tocotrienol-enriched fraction (TEF) isolated from palm oil, as well as pure vitamin E analogues (α-tocopherol, α-, δ- and γ-tocotrienols) were studied using highly aggressive triple negative MDA-MB-231 cells and oestrogen-dependent MCF-7 cells, both of human breast cancer cell lines. Cell population growth was evaluated using a Coulter particle counter. Cell death mechanism, poly(ADP-ribose) polymerase cleavage and levels of NF-κB were determined using commercial ELISA kits.

RESULTS

Tocotrienols exerted potent anti-proliferative effects on both types of cell by inducing apoptosis, the underlying mechanism of cell death being ascertained using respective IC50 concentrations of all test compounds. There was marked induction of apoptosis in both cell lines by tocotrienols compared to treatment with Paclitaxel, which was used as positive control. This activity was found to be associated with cleavage of poly(ADP-ribose) polymerase (a DNA repair protein), demonstrating involvement of the apoptotic cell death signalling pathway. Tocotrienols also inhibited expression of nuclear factor kappa-B (NF-κB), which in turn can increase sensitivity of cancer cells to apoptosis.

CONCLUSION

Tocotrienols induced anti-proliferative and apoptotic effects in association with DNA fragmentation, poly(ADP-ribose) polymerase cleavage and NF-κB inhibition in the two human breast cancer cell lines.

3-Aminobenzamide protects primary human keratinocytes from UV-induced cell death by a poly(ADP-ribosyl)ation independent mechanism

Poly(ADP-ribosyl)ation (PARylation) is a NAD(+)-dependent protein modification carried out by PARP [poly(ADP-ribose) polymerase] enzymes. Here we set out to investigate whether PARylation regulates UVB-induced cell death in primary human keratinocytes. We used the benchmark PARP inhibitor 3-aminobenzamide (3AB) and a more potent and specific inhibitor PJ34 and found that UVB (0.05-0.2J/cm(2)) induced a dose dependent loss of viability that was prevented by 3AB but not by PJ34. Similarly to PJ34, two other new generation PARP inhibitors also failed to protect keratinocytes from UVB-induced loss of viability. Moreover, silencing PARP-1 in HaCaT human keratinocytes sensitized cells to UVB toxicity but 3AB provided protection to both control HaCaT cells and to PARP-1 silenced cells indicating that the photoprotective effect of 3AB is independent of PARP inhibition. Lower UVB doses (0.0125-0.05J/cm(2)) caused inhibition of proliferation of keratinocytes which was prevented by 3AB but augmented by PJ34. UVB-induced keratinocyte death displayed the characteristics of both apoptosis (morphology, caspase activity, DNA fragmentation) and necrosis (morphology, LDH release) with all of these parameters being inhibited by 3AB and apoptotic parameters slightly enhanced by PJ34. UVA also caused apoptotic and necrotic cell death in keratinocytes with 3AB protecting and PJ34 sensitizing cells to UVA-induced toxicity. 3AB prevented UVB-induced mitochondrial membrane depolarization and generation of hydrogen peroxide. In summary, PARylation is a survival mechanism in UV-treated keratinocytes. Moreover, 3-aminobenzamide is photoprotective and acts by a PARP-independent mechanism at a premitochondrial step of phototoxicity.

Role of poly(ADP-ribose) polymerases in the regulation of inflammatory processes

PARP enzymes influence the immune system at several key points and thus modulate inflammatory diseases. PARP enzymes affect immune cell maturation and differentiation and regulate the expression of inflammatory mediators such as cytokines, chemokines, inducible nitric oxide synthase and adhesion molecules. Moreover, PARP enzymes are key regulators of cell death during inflammation-related oxidative and nitrosative stress. Here we provide an overview of the different inflammatory diseases regulated by PARP enzymes.

Increased transcript level of poly(ADP-ribose) polymerase (PARP-1) in human tricuspid compared with bicuspid aortic valves correlates with the stenosis severity

Oxidative stress may contribute to the hemodynamic progression of aortic valve stenosis, and is associated with activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) 1. The aim of the present study was to assess the transcriptional profile and the topological distribution of PARP-1 in human aortic valves, and its relation to the stenosis severity. Human stenotic aortic valves were obtained from 46 patients undergoing aortic valve replacement surgery and used for mRNA extraction followed by quantitative real-time PCR to correlate the PARP-1 expression levels with the non invasive hemodynamic parameters quantifying the stenosis severity. Primary isolated valvular interstitial cells (VICs) were used to explore the effects of cytokines and leukotriene C(4) (LTC(4)) on valvular PARP-1 expression. The thickened areas of stenotic valves with tricuspid morphology expressed significantly higher levels of PARP-1 mRNA compared with the corresponding part of bicuspid valves (0.501 vs 0.243, P=0.01). Furthermore, the quantitative gene expression levels of PARP-1 were inversely correlated with the aortic valve area (AVA) (r=-0.46, P=0.0469) and AVA indexed for body surface area (BSA) (r=-0.498; P=0.0298) only in tricuspid aortic valves. LTC(4) (1nM) significantly elevated the mRNA levels of PARP-1 by 2.38-fold in VICs. Taken together, these data suggest that valvular DNA-damage pathways may be associated with inflammation and the stenosis severity in tricuspid aortic valves.

Hyperglycemia magnifies Schwann cell dysfunction and cell death triggered by PA-induced lipotoxicity

Lipid overload resulting in lipotoxicity is prominent in a number of chronic diseases and has been associated with cellular dysfunction and cell death. This study characterizes palmitic acid-induced lipotoxicity (PA-LTx) in Schwann cell cultures grown in normal and high glucose concentrations. The study shows for the first time that Schwann cell (SC) cultures exposed to elevated levels of PA exhibit a dose- and time-dependent loss in cell viability. Hoescht and Annexin V/7AAD staining confirmed cell death through apoptosis and the lipotoxic effect was more dramatic in SC cultures grown under high glucose conditions. The first indication of cellular dysfunction in treated SC cultures was a decrease in Ca(++) levels in the endoplasmic reticulum (ER, [Ca(++)](ER)) observed five minutes following the initial challenge with PA. This decrease in [Ca(++) ](ER) was followed by a significant increase in the expression of ER stress signature genes CHOP, Xbp1 and GRP78. The early ER stress response induced by PA-LTx was followed by a strong mitochondrial membrane depolarization. Flow cytometry using 2', 7'-dichlorodihydrofluorescein diacetate (H(2)DCFDA) showed an increase in oxidative stress within three to six hours after PA treatment. Treatment of cultures undergoing PA-LTx with the calcium chelator BAPTA-AM and the anti-oxidant MCI-186 significantly reversed the lipotoxic effect by decreasing the generation of ROS and significantly increasing cell viability. We conclude that lipotoxicity in Schwann cells results in cellular dysfunction and cell death that involves a robust ER stress response, mitochondrial dysfunction and an augmented state of cellular oxidative stress (ASCOS).

Poly(ADP-ribose) polymerase inhibition modulates experimental acute necrotizing pancreatitis-induced oxidative stress, bacterial translocation and neopterin concentrations in rats

Various studies have been performed to find out novel treatment strategies for acute necrotizing pancreatitis (ANP). Inhibition of poly(ADP-ribose) polymerase (PARP) is shown to reduce inflammation in several pathological conditions. We aimed to evaluate the efficacy of benzamide, a PARP inhibitor, in an experimental model of ANP. Thirty Sprague-Dawley rats were divided into three groups: sham-operated, ANP and ANP + benzamide groups. All groups except the sham-operated group were subjected to the ANP procedure, induced by infusing of 1 mL/kg of 3% sodium taurocholate into the common biliopancreatic duct. The ANP + benzamide group received 100 mg/kg/day benzamide intraperitoneally for a total of three days after induction of pancreatitis. The surviving animals were killed at the fourth day and the pancreas was harvested for biochemical, microbiological and histological analysis. Blood samples were also obtained from the animals. In the ANP group, a significant increase was observed in concentrations of serum amylase and neopterin and tissue oxidative stress indices (malondialdehyde, superoxide dismutase and glutathione peroxidase). Almost all of these changes were found to be reversed to near their normal values in the ANP + benzamide group. Histological injury scores were significantly higher in the ANP group than in the sham group (P < 0.05, ANP versus sham), and were significantly lower in the ANP + benzamide group than in the ANP group (P < 0.05, ANP + benzamide versus ANP). Evaluation of bacterial translocation identified significantly fewer infected sites in the ANP + benzamide group than in the ANP animals (P < 0.01). We observed that inhibition of PARP with benzamide reduced the severity, the mortality, the bacterial translocation rates and the neopterin concentrations in an experimental ANP model in rats. These findings suggest that it may be possible to improve the outcome of ANP by using PARP inhibitors.

Ultraviolet B light-induced nitric oxide/peroxynitrite imbalance in keratinocytes--implications for apoptosis and necrosis

Elevation of nitric oxide (NO*) can either promote or inhibit ultraviolet B light (UVB)-induced apoptosis. In this study, we determined real-time concentration of NO* and peroxynitrite (ONOO(-)) and their role in regulation of membrane integrity and apoptosis. Nanosensors (diameter 300-500 nm) were used for direct in situ simultaneous measurements of NO* and ONOO(-) generated by UVB in cultured keratinocytes and mice epidermis. An exposure of keratinocytes to UVB immediately generated ONOO(-) at maximal concentration of 190 nm followed by NO(*) release with a maximal concentration of 91 nm. The kinetics of UVB-induced NO*/ONOO(-) was in contrast to cNOS agonist stimulated NO*/ONOO(-) from keratinocytes. After stimulating cNOS by calcium ionophore (CaI), NO* release from keratinocytes was followed by ONOO(-) production. The [NO*] to [ONOO(-)] ratio generated by UVB decreased below 0.5 indicating a serious imbalance between cytoprotective NO* and cytotoxic ONOO(-)-a main component of nitroxidative stress. The NO*/ONOO(-) imbalance increased membrane damage and cell apoptosis was partially reversed in the presence of free radical scavenger. The results suggest that UVB-induced and cNOS-produced NO* is rapidly scavenged by photolytically and enzymatically generated superoxide (O(2) (-)) to produce high levels of ONOO(-), which enhances oxidative injury and apoptosis of the irradiated cells.

Mechanisms mediating the vesicant actions of sulfur mustard after cutaneous exposure

Sulfur mustard (SM), a chemical weapon first employed during World War I, targets the skin, eyes, and lung. It remains a significant military and civilian threat. The characteristic response of human skin to SM involves erythema of delayed onset, followed by edema with inflammatory cell infiltration, the appearance of large blisters in the affected area, and a prolonged healing period. Several in vivo and in vitro models have been established to understand the pathology and investigate the mechanism of action of this vesicating agent in the skin. SM is a bifunctional alkylating agent which reacts with many targets including lipids, proteins, and DNA, forming both intra- and intermolecular cross-links. Despite the relatively nonselective chemical reactivity of this agent, basal keratinocytes are more sensitive, and blistering involves detachment of these cells from their basement membrane adherence zones. The sequence and manner in which these cells die and detach is still unresolved. Much has been discovered over the past two decades with respect to the mechanisms of SM-induced cytotoxicity and the intracellular and extracellular targets of this vesicant. In this review, the effects of SM exposure on the skin are described, as well as potential mechanisms mediating its actions. Successful therapy for SM poisoning will depend on following new mechanistic leads to develop drugs that target one or more of its sites of action.

The Val762Ala polymorphism in the poly(ADP-ribose) polymerase-1 gene is not associated with susceptibility in Turkish rheumatoid arthritis patients

The findings of the studies on poly(ADP-ribose) polymerase-1 (PARP-1) have suggested that the enzyme inactivation provides significant protection against systemic or tissue inflammation in animal models. It has also shown that the single-nucleotide polymorphism (Val762Ala) of the PARP-1 causes about 40% decrease of enzyme activity. The aim of this study was to analyze the association of the PARP-1 Val762Ala polymorphism in Turkish patients with rheumatoid arthritis. A total of 128 RA patients and 165 normal controls from the same geographic region were studied and polymerase chain reaction (PCR)-based restriction analysis was used to identify Val762Ala polymorphism of the PARP-1. Association analyses were performed using chi (2) tests. Our results indicated that the distribution of the PARP-1 genotypes and alleles did not differ significantly among subjects with or without RA (P > 0.05). The results of the study indicate that, for our Turkish sample, the V762A polymorphism of the PARP-1 may not be involved in susceptibility to RA, implying that the polymorphism may not function as a candidate gene marker for screening RA patients.

Photoprotective effects of glucomannan isolated from Candida utilis

Glucomannans belong to yeast and fungal cell wall polysaccharides with known immunostimulatory and radioprotective effects. However, glucomannan protective effects against pathological consequences of skin exposure to short wavelength solar light, ultraviolet (UV) radiation, are unclear. Herein, a highly branched glucomannan (GM) isolated from the cell wall of Candida utilis, a member of the alpha-(1-->6)-D-mannan group, was tested for its photoprotective effects in an in vitro model of UVB-irradiated human keratinocytes and an in vivo model of UV-induced erythema formation in human volunteers. GM suppressed the UVB-induced decrease of keratinocyte viability, which was connected with the suppression of UVB-induced keratinocyte apoptosis. GM reduced UVB-mediated caspase activation together with suppression of DNA fragment release into the cytoplasm. Furthermore, GM suppressed UVB-induced gene expression of pro-inflammatory markers including nuclear factor kappa B, inducible nitric oxide synthase, interleukins 8 and 1, together with suppression of prostaglandin E2 and interleukin 1alpha protein release. In vivo, GM decreased UV-induced skin erythema formation, which was correlated with a decrease of phosholipase A(2) activity within the stratum corneum. It could be concluded that GM isolated from C. utilis possesses significant photoprotective effects on human keratinocytes in vitro as well as in vivo.

Skin wound healing in the SKH-1 female mouse following inducible nitric oxide synthase inhibition

BACKGROUND

The inducible isoform of the nitric oxide (NO) synthase (NOS) enzyme (iNOS) is upregulated by inflammatory mediators and/or other pathological stresses, generating high, sustained levels of NO. Cumulative data suggest a role for NO in the regulation of skin wound healing, although it is not clear to what extent NO generated by iNOS, and possibly endothelial NOS (eNOS), contribute to that healing process. Because of the current lack of understanding regarding the contribution of iNOS in wound healing, as well as the lack of wound healing data available for SC-842, an iNOS inhibitor, this in vivo study was conducted to investigate the possible role of SC-842 in interfering with wound healing.

OBJECTIVES

This study evaluated whether inhibition of iNOS affects incisional skin wound healing.

METHODS

Using a cutaneous full-thickness, sutured, incisional wound model in hairless SKH-1 mice, the role of iNOS in the wound healing process was evaluated by comparing in vivo effects of the iNOS inhibitor, SC-842, at various doses that result in selective inhibition of iNOS as well as nonselective NOS inhibition (as evidenced by elevated blood pressure resulting in inhibition of eNOS and/or neuronal NOS). Dexamethasone was used as a positive control.

RESULTS

There were no differences in wound healing at day 28 postwounding, as evaluated by tensile strength and histology, between SC-842- and vehicle-treated animals. A decrease in tensile strength was noted at day 14 postwounding in wounds from the mid- and high-dose-treated animals as compared with vehicle-treated animals, but this difference was slight and was not associated with histological differences from vehicle-treated controls.

CONCLUSIONS

These data indicate that iNOS inhibition does not adversely affect the healing of incisional wounds in SKH-1 mice as assessed over 28 days by wound tensile strength and histology.

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.

Poly (ADP-ribose) polymerase activation and circulatory shock

Sepsis is associated with increased production of reactive oxidant species. Oxidative and nitrosative stress can lead to activation of the nuclear enzyme poly (ADP-ribose) polymerase (PARP), with subsequent loss of cellular functions. Activation of PARP may dramatically lower the intracellular concentration of its substrate, NAD thus slowing the rate of glycolysis, electron transport and subsequently ATP formation. This process can result in cell dysfunction and cell death. In addition, PARP enhances the expression of various pro-inflammatory mediators, via activation of NF-kappaB, MAP kinase and AP-1 and other signal transduction pathways. Preclinical studies in various rodent and large animal models demonstrate that PARP inhibition or PAR deficiency exerts beneficial effects on the haemodynamic and metabolic alterations associated with septic and haemorrhagic shock. Recent human data also support the role of PARP in septic shock: In a retrospective study in 25 septic patients, an increase in plasma troponin level was related to increased mortality risk. In patients who died, significant myocardial damage was detected, and histological analysis of heart showed inflammatory infiltration, increased collagen deposition, and derangement of mitochondrial criptae. Immunohistochemical staining for poly(ADP-ribose) (PAR), the product of activated PARP was demonstrated in septic hearts. There was a positive correlation between PAR staining and troponin I; and a correlation of PAR staining and LVSSW. Thus, there is significant PARP activation in animal models subjected to circulatory shock, as well as in the hearts of septic patients. Based on the interventional studies in animals and the correlations observed in patients we propose that PARP activation may be, in part responsible for the cardiac depression and haemodynamic failure seen in humans with severe sepsis. Interestingly, recent studies reveal that the protective effects of PARP inhibitors are predominant in male animals, and are not apparent in female animals. Oestrogen, by providing a baseline inhibitory effect on PARP activation, may be partially responsible for this gender difference.

Polychromatic LED in Oval Full-Thickness Wound Healing in Non-diabetic and Diabetic Rats

OBJECTIVE

Our goal was to determine the efficacy of polychromatic light-emitting diode (LED) in the enhancement of wound healing in non-diabetic and diabetic rats.

BACKGROUND DATA

LEDs are increasingly used as an alternative light source for phototherapy.

METHODS

A cluster of 25 LED photons at 510-543, 594-599, 626-639, 640-670, and 842-872 nm wavelengths with 272-mW output power was used. Male Sprague-Dawley rats (n = 61) were randomly assigned into non-diabetic and diabetic groups and into light treatment groups, that is, control, 5, 10, 20, and 30 J/cm(2). Streptozotocin was used for diabetes induction. Wounds were created using a scalpel after 1 week of wounding. Wounds were measured daily and plotted in time, and the trendline was fitted to obtain slope values. Relative wound healing percentage was computed as follows: RWH% = [(Slope treated - Slope control)/(Slope control)] x 100. The t-test (alpha = 0.05) was used for analysis.

RESULTS

The RWH% in the non-diabetic rats was insignificant (p > 0.05) at 5, 10, 20, and 30 J/cm(2) treatments, giving 4.3 +/- 1.97%, 5.4 +/- 1.94%, 4.5 +/- 1.96%, and 1.2 +/- 2.03%, respectively. The healing of diabetic rats was significantly impaired by -11.7 +/- 3.25% (p = 0.02), which was mitigated by 5 J/cm(2) treatment (2.4 +/- 3.02%, (p) = 0.40) and 10 J/cm(2) treatment (-5.5 +/- 3.28%, p = 0.11). Diabetic wound healing using 20 J/cm(2) (-8.7 +/- 3.39%, p = 0.03) and 30 J/cm(2) (-10.90 +/- 1.97%, p = 0.01) affected significant inhibition.

CONCLUSION

The effect of polychromatic LED therapy in oval full-thickness wound-healing in the diabetic model with the use of 5 and 10 J/cm(2) is promising. Further studies to determine optimum dosimetry and efficacy of LEDs are recommended.

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.

Adenosine monophosphate-activated protein kinase and nitric oxide in rat steatotic liver transplantation

BACKGROUND/AIMS

Hepatic steatosis is a risk factor for transplantation. We examined the role of AMP-activated protein kinase (AMPK) and nitric oxide (NO) in the benefits of preconditioning in steatotic liver transplantation.

METHODS

Steatotic liver transplantation with or without preconditioning was induced in Zucker rats. The activities of AMPK and NO synthase (NOS) were measured and altered pharmacologically.

RESULTS

Preconditioning or AMPK activation with aminoimidazole-4-carboxamide ribonucleoside (AICAR) increased AMPK and constitutive NOS activities and protected against lipid peroxidation, nitrotyrosine formation and hepatic injury in both grafts. Inhibition of AMPK activity removed the benefits of preconditioning. NO synthesis inhibition abolished the benefits of preconditioning or AICAR. Therefore, preconditioning or AICAR, through AMPK activation, may induce NO synthesis, thus protecting against hepatic injury in both steatotic and non-steatotic liver transplantation. In non-steatotic grafts, NO donors simulated the benefits of preconditioning. However, in steatotic grafts, NO supplementation was ineffective.

CONCLUSIONS

These results indicate (a) a potential relationship between AMPK and NO in the benefits of preconditioning in steatotic liver transplantation, (b) AICAR as a new phamacological strategy in steatotic liver transplantation and (c) a differential effect of NO supplementation in both grafts.

The effect of L-NAME administrations after oral mucosal incision on wound NO level in rabbit

The aim of the current study was to comparatively investigate the effect of inhibition of nitric oxide (NO) production by N-nitro-L-arginine methyl ester (L-NAME), an isoform non-specific inhibitor of nitric oxide synthase (NOS), after oral mucosal incision on wound tissue NO levels. A standard incision was applied to the oral mucosa of rabbits. After oral mucosal incision, rabbits were divided into five groups as follows: (1) Untreated incisional group (control); (2) Titanium (Ti) implanted group; (3) Ti + Polyethylene glycol (PEG) 4000 implanted group; (4) Ti + PEG 4000 + L-NAME (2 x 10(-4) M) implanted group and (5) i.p. L-NAME administrated group (10 mg/kg). At 5 days after oral incision operations, wound tissue strips and plasma were obtained from rabbits. Oral wound tissue and plasma nitric oxide, plasma thiobarbituric acid reactive substances (TBARS) and total sulfhydryl group (RSH) levels were investigated. Plasma TBARS and NOx levels decreased after i.p. L-NAME administration. Total RSH group levels were not changed in all groups (p>0.05). This means that L-NAME inhibits the deteriorating effects of free radicals without affecting healing. L-NAME in PEG and titanium also has no effect on tissue and plasma NOx levels. These findings indicate that NO generation will not be affected both Ti and local nitric oxide synthase (NOS) inhibitor.

Shock, inflammation and PARP

The activation of poly(ADP-ribose) polymerase (PARP) is well considered to play an important role in various patho-physiological conditions like inflammation and shock. A vast amount of circumstantial evidence implicates oxygen-derived free radicals (especially, superoxide and hydroxyl radical) and high-energy oxidants (such as peroxynitrite) as mediators of inflammation and shock. ROS (e.g., superoxide, peroxynitrite, hydroxyl radical and hydrogen peroxide) are all potential reactants capable of initiating DNA single strand breakage, with subsequent activation of the nuclear enzyme poly(ADP-ribose) synthetase (PARS), leading to eventual severe energy depletion of the cells, and necrotic-type cell death. During the last years, numerous experimental studies have clearly demonstrated the beneficial effects of PARP inhibition in cell cultures through rodent models and more recently in pre-clinical large animal models of acute and chronic inflammation. The aim of this review is to describe recent experimental evidence implicating PARP as a pathophysiological modulator of acute and chronic inflammation.

Poly(ADP-ribose) polymerase activation by reactive nitrogen species--relevance for the pathogenesis of inflammation

Oxidative and nitrosative stress triggers DNA strand breakage, which then activates the nuclear enzyme poly(ADP-ribose) polymerase (PARP). Nitrogen-derived reactive oxidant species capable of involving DNA single strand breakage and PARP activation include peroxynitrite (the reaction product of nitric oxide and superoxide), but not nitric oxide per se. Activation of PARP may dramatically lower the intracellular concentration of its substrate, nicotinamide adenine dinucleotide, thus slowing the rate of glycolysis, electron transport, and subsequently ATP formation. This process can result in cell dysfunction and cell death. Here we review the role of reactive nitrogen species in the process of PARP activation, followed by the effect of pharmacological inhibition or genetic inactivation of PARP on the course of various forms of inflammation.

Skin nitric oxide and its metabolites are increased in nonburned skin after thermal injuries

Local and systemic inflammation can lead to progression of burn wounds, converting second- to third-degree wounds or extending the burn to adjacent areas. Previous studies have suggested that the skin is an important site of production of nitric oxide (NO), synthesized by inducible nitric oxide synthase (iNOS) activation after injury. NO increases in burned wounds, but its formation in noninjured skin has not been investigated. We hypothesized that after severe burns, NO and cytotoxic peroxynitrite would increase in noninjured skin. We also tested the hypothesis that BBS-2, a specific inhibitor of iNOS, would impair NO formation after burn. Thirteen female sheep were randomized into burn injury and smoke inhalation (n = 5, group 1), burn and smoke treated with BBS-2 (n = 3, group 2), and sham (saline treatment, no injury) (n = 5, group 3). All the animals, including the sham-injury group, were mechanically ventilated for 48 h. Samples of nonburned skin and plasma were collected from each animal, and levels of NO and its metabolites were evaluated using a NO chemiluminescent detector. Nitrotyrosine and iNOS expression were determined in the skin by Immunoperoxidase staining, and scoring of masked slides (epidermis, hair follicles, vessels, glands, and stroma) was performed. Skin NO and metabolites significantly increased in the burn and smoke injury group, and this was inhibited by BBS-2. Nitrotyrosine expression also increased significantly in the skin of burned animals. BBS-2 prevented the increase of NOx but not the increase of nitrotyrosine expression in skin. Plasma levels of NO increased in burned animals when compared with sham, but this increase was not significant. The increase of NO and its metabolites after burn in noninjured skin is followed by a significant increase in peroxynitrite, a potent cytotoxic mediator.

Isoprenylhydroquinone glucoside: a new non-antioxidant inhibitor of peroxynitrite-mediated tyrosine nitration

Three hydroquinone glucosides and four caffeoylquinic esters were examined for their effect on tyrosine nitration, as well as on the oxidation of dihydrorhodamine (DHR) 123 and cytochrome c(2+) induced by peroxynitrite. All these phenolics, which had previously been characterized as the active principles of the plant Phagnalon rupestre, were fairly active in preventing the oxidation of DHR 123, though inefficient in the cytochrome c test. While their antioxidant potency is associated with the presence of a caffeoyl moiety, not so an obvious chemical character was correlated to a greater activity against nitration of tyrosine. Here, the highest potency corresponded to 2-isoprenylhydroquinone-1-glucoside. On the basis of the fact that the susceptibility to nitration of given aromatic compound confers to it inhibitory activity of tyrosine nitration, the analysis of ultraviolet and nuclear magnetic resonance spectral shifts provides valuable information for explaining the ability of natural phenolics to interfere with that reaction.

New advances on the functions of epidermal growth factor receptor and ceramides in skin cell differentiation, disorders and cancers

Recent advances in understanding of the biological functions of the epidermal growth factor and epidermal growth factor receptor (EGF-EGFR) system and ceramide production for the maintenance of skin integrity and barrier function are reported. In particular, the opposite roles of EGFR and ceramide cascades in epithelial keratinocyte proliferation, migration and terminal differentiation are described. Moreover, the functions of ceramides in the epidermal permeability barrier are reviewed. The alterations in EGFR signaling and ceramide metabolism, which might be involved in the etiopathogenesis of diverse skin disorders and cancers, are described. New progress in understanding of skin organization, which might provide the basis for the design of new transcutaneous drug delivery techniques as well as for the development of new therapies of skin disorders and cancers, are reported.

Cytoprotective effect of gallotannin in oxidatively stressed HaCaT keratinocytes: the role of poly(ADP-ribose) metabolism

Oxidative stress-induced cytotoxicity is mediated in part by accelerated poly-ADP ribosylation. Peroxynitrite and hydrogen peroxide cause DNA breakage triggering the activation of the DNA nick sensor enzyme poly(ADP-ribose) polymerase-1 (PARP-1). Overactivation of PARP-1 leads to cell dysfunction and cell death mainly due to depletion of NAD(+) (the substrate of PARP-1) and ATP. PARP-1 attaches most ADP-ribose residues onto itself, leading to downregulation of enzyme activity. Here, we have investigated the role of poly(ADP-ribose) glycohydrolase (PARG), the poly(ADP-ribose)-catabolyzing enzyme in oxidative stress-induced cytotoxicity in HaCaT cells. We have found that inhibition of PARG by gallotannin (GT) (50 microM) provided significant cytoprotection to peroxynitrite- or hydrogen peroxide-treated HaCaT cells, as assessed by lactate dehydrogenase release and propidium iodide uptake (parameters of necrotic cell death) as well as caspase activation (apoptotic parameter). GT pretreatment has also inhibited the depletion of cellular NAD(+) pools in hydrogen peroxide- or peroxynitrite-treated HaCaT cells. GT caused the accumulation of poly(ADP-ribose) and concomitant inhibition in cellular PARP activity in oxidatively stressed cells. Therefore, PARG is likely to contribute to maintaining the active state of PARP-1 by continuously removing inhibitory ADP-ribose residues from PARP-1.

UV irradiation inhibits ABC transporters via generation of ADP-ribose by concerted action of poly(ADP-ribose) polymerase-1 and glycohydrolase

ATP-binding cassette (ABC) transporters are involved in the transport of multiple substrates across cellular membranes, including metabolites, proteins, and drugs. Employing a functional fluorochrome export assay, we found that UVB irradiation strongly inhibits the activity of ABC transporters. Specific inhibitors of poly(ADP-ribose) polymerase-1 (PARP-1) restored the function of ABC transporters in UVB-irradiated cells, and PARP-1-deficient cells did not undergo UVB-induced membrane transport inhibition. These data suggest that PARP-1 activation is necessary for ABC transporter functional downregulation. The hydrolysis of poly(ADP-ribose) by poly(ADP-ribose) glycohydrolase (PARG) was also required, since specific PARG inhibitors, which limit the production of ADP-ribose molecules, restored the function of ABC transporters. Furthermore, ADP-ribose molecules potently inhibited the activity of the ABC transporter P-glycoprotein. Hence, poly(ADP-ribose) metabolism appears to play a novel role in the regulation of ABC transporters.

Solar ultraviolet radiation as a trigger of cell signal transduction

Ultraviolet light radiation in sunlight is known to cause major alterations in growth and differentiation patterns of exposed human tissues. The specific effects depend on the wavelengths and doses of the light, and the nature of the exposed tissue. Both growth inhibition and proliferation are observed, as well as inflammation and immune suppression. Whereas in the clinical setting, these responses may be beneficial, for example, in the treatment of psoriasis and atopic dermatitis, as an environmental toxicant, ultraviolet light can induce significant tissue damage. Thus, in the eye, ultraviolet light causes cataracts, while in the skin, it induces premature aging and the development of cancer. Although ultraviolet light can damage many tissue components including membrane phospholipids, proteins, and nucleic acids, it is now recognized that many of its cellular effects are due to alterations in growth factor- and cytokine-mediated signal transduction pathways leading to aberrant gene expression. It is generally thought that reactive oxygen intermediates are mediators of some of the damage induced by ultraviolet light. Generated when ultraviolet light is absorbed by endogenous photosensitizers in the presence of molecular oxygen, reactive oxygen intermediates and their metabolites induce damage by reacting with cellular electrophiles, some of which can directly initiate cell signaling processes. In an additional layer of complexity, ultraviolet light-damaged nucleic acids initiate signaling during the activation of repair processes. Thus, mechanisms by which solar ultraviolet radiation triggers cell signal transduction are multifactorial. The present review summarizes some of the mechanisms by which ultraviolet light alters signaling pathways as well as the genes important in the beneficial and toxic effects of ultraviolet light.

Polychromatic LED Therapy in Burn Healing of Non-diabetic and Diabetic Rats

OBJECTIVE

We determined the effect of polychromatic light-emitting diodes (LED) in burn healing of non-diabetic and streptozotocin-induced diabetic rats.

BACKGROUND DATA

LEDs were used as the light source for phototherapy.

MATERIALS AND METHODS

The polychromatic LED is a cluster of 25 diodes emitting photons at wavelengths of 510-543, 594-599, 626-639, 640-670, and 842-879 nm with 272-mW output power. Age-matched, male Sprague-Dawley rats (n = 30) were used. Streptozotocin (70 mg/kg) was used for diabetes induction. Rat weight, hyperglycemia, and glycosuria were monitored for the first 3 days and weekly thereafter. Rats were anesthetized and shaved after 1 week of diabetes. Burn areas of 1.5 +/-.03 cm2 were created using a metal rod pre-heated up to 600 degrees C that was applied for 2 sec. Diabetic and non-diabetic rats were randomized into the following treatment groups: control, 5, 10, 20, and 30 J/cm2. Light treatment commenced after burn infliction and was repeated three times per week. Burn areas were measured daily.

RESULTS

Burn healing was impaired significantly during diabetes by -46.17%. Polychromatic LED treatment using 5, 10, 20, and 30 J/cm2 incident doses influenced healing by 6.85%, 4.93%, -4.18%, and -5.42% in the non-diabetic rats; and 73.87%, 76.77%, 60.92%, and 48.77% in the diabetic rats, relative to their controls, respectively.

CONCLUSION

The effect of polychromatic LED in non-diabetic rats was insignificant; however, it simulated the trend of stimulation and inhibition seen using low-level lasers. Significant stimulation observed in the diabetic rats demonstrated the usefulness of polychromatic LED in diabetic burn healing.

Healing responses of skin and muscle in critical illness

OBJECTIVE

Many aspects of the care and underlying pathologies in patients suffering critical illness can detrimentally influence the normal healing processes of skin and soft tissues. Although a great diversity of pathologies exists, some aspects of the diseases and their treatments are common in critically ill patients. We aimed to identify some features, both common and specific, that could influence wound healing and the mechanisms by which they may do so.

DESIGN

In this review, we first outline the biology of normal skin and muscle healing and then explore how critical illness may influence the normal healing cascade.

FINDINGS

The healing of skin and skeletal muscle in critical illness is influenced by both underlying disease processes and the intensive care environment. Local and systemic factors can contribute to impaired healing, with the potential to prolong functional disability and increase the likelihood of wound complications. The frequency and number of soft tissue injuries derived from accidental injury, surgical intervention, and the need for invasive monitoring and therapies in the intensive care unit setting are likely to compromise the innate immunity and potentially further jeopardize the patient's ability to heal. Alterations in coagulation, tissue perfusion, inflammation, immune functioning, metabolism, nutrition, and drug therapies will influence healing responses by modifying the biological responses to tissue disruption. Locally, wound contamination, sepsis, tissue hypoxia, edema, and excessive or prolonged local pressure all have the potential to compromise soft tissue healing. One or more of these factors may be present at any time.

CONCLUSION

The skin and soft tissues are vulnerable to both injury and compromised healing when a patient is critically ill and exposed to a critical care environment. The identification of risk factors may aid in forming and modifying treatment strategies when caring for the critically ill patient with soft tissue injuries.

Role of intracellular calcium mobilization and cell-density-dependent signaling in oxidative-stress-induced cytotoxicity in HaCaT keratinocytes

Peroxynitrite is a nitric-oxide-derived cytotoxic mediator produced in a broad range of inflammatory conditions, ranging from sunburn erythema to contact hypersensitivity. Our previous work has shown that in HaCaT cells the cytotoxic activity of peroxynitrite involves both apoptotic and necrotic routes with poly(ADP-ribose) polymerase activation serving as a mol-ecular switch diverting the default apoptotic pathway toward necrosis. Nonetheless, keratinocytes are regarded as highly resistant toward environmental noxa including oxidative stress. We set out to investigate the possible role of two parameters, intracellular calcium mobilization and high cell density, in protecting HaCaT cells from peroxynitrite/oxidative-stress-induced cytotoxicity. First we characterized the effect of peroxynitrite on the calcium homeostasis of HaCaT cells and demonstrated that both authentic peroxynitrite and the peroxynitrite generating compound 3-morpholino-sydnonimine triggered an elevation in intracellular calcium levels. Moreover, we established that treatment of cells with the cell-permeable calcium chelator BAPTA-AM provided significant cytoprotection against peroxynitrite- and hydrogen-peroxide-induced cytotoxicity. Furthermore, when cells reached confluence they were highly resistant to the toxic effects of peroxynitrite, hydrogen peroxide, and superoxide. The resistance to oxidative stress provided by calcium chelation and high cell density involved inhibiting the activation of both poly(ADP-ribose) polymerase and caspases. Our data may provide an explanation for the resistance to oxidative stress of superficial, highly differentiated keratinocytes and indicate that basal proliferative keratinocytes are sensitive in vivo targets of oxidative stress injury.