Time course of expression of mRNA of inducible nitric oxide synthase and generation of nitric oxide by ultraviolet B in keratinocyte cell lines

Rg3-loaded P407/CS/HA hydrogel inhibits UVB-induced oxidative stress, inflammation and apoptosis in HaCaT cells

UVB radiation can damage human skin, whereas Ginsenoside Rg3, the active ingredient in red ginseng that is processed from ginseng (Panax ginseng C.A. Meyer), could inhibit UVB induced cell damage through anti-oxidation. Meanwhile, P407/CS/HA hydrogel has significant biomedical applications as carriers of drugs. However, the beneficial effects of Rg3-loaded hydrogel (Rg3-Gel) on human HaCaT keratinocytes induced by UVB have rarely been reported. In our study, Rg3 was loaded into hydrogel and the effect of Rg3-Gel against UVB‑induced Hacat cells damages was determined by measuring its ability to alleviate UVB‑induced elevation of oxidative stress, pro-inflammatory and apoptotic response. We found that the treatment with Rg3-Gel inhibited the generation of intracellular ROS and MDA and upregulated the expression of antioxidant enzymes SOD and GSH-Px which were inhibited by UVB exposure. Increased levels of pro-inflammatory cytokines TNF‑α, COX‑2, iNOS and IL‑1β following UVB irradiation were suppressed by the introduction of Rg3-Gel. Additionally, the level of Bcl-2 was decreased and the expression of Bax and Caspase3 were enhanced by Rg3-Gel treatment. In conclusion, Rg3-Gel equipped with the synergistic effect of Rg3 and hydrogel has an effective inhibitory effect on UVB-induced oxidative stress, inflammatory and apoptosis.

Anti-inflammatory effects of Derris scandens extract on narrowband-ultraviolet B exposed HaCaT human keratinocytes

Narrowband-ultraviolet B (NB-UVB) has been used to treat skin diseases such as psoriasis. Chronic use of NB-UVB might cause skin inflammation and lead to skin cancer. In Thailand, Derris Scandens (Roxb.) Benth. is used as an alternative medicine to nonsteroidal anti-inflammatory drugs (NSAIDs) for low back pain and osteoarthritis. Therefore, this study aimed to evaluate the potential anti-inflammatory effect of Derris scandens extract (DSE) on pre- and post exposed NB-UVB human keratinocytes (HaCaT). The results indicated that DSE could not protect HaCaT from cell morphology changes or DNA fragmentation and could not recover cell proliferation ability from the NB-UVB effects. DSE treatment reduced the expression of genes related to inflammation, collagen degradation, and carcinogenesis, such as IL-1α, IL-1β, IL-6, iNOS, COX-2, MMP-1, MMP-9, and Bax. These results indicated the potential use of DSE as a topical preparation against NB-UVB-induced inflammation, anti-aging, and prevention of skin cancer from phototherapy.

Nicotinamide Attenuates UV-Induced Stress Damage in Human Primary Keratinocytes from Cancerization Fields

UVB radiation directly damages DNA, increases ROS and nitric oxide (NO) release, and promotes inflammation leading to genomic instability and cell death. Nicotinamide (NAM) is the precursor of NAM adenine dinucleotide, essential for cell energy production and DNA damage repair. NAM protects HaCat cells from UV-induced impairment; however, little is known about its effects on human primary keratinocytes and those isolated from field cancerization (i.e., field cancerization human primary keratinocytes [FC-HPKs]). We examined the role of NAM against UV-induced oxidative stress damages in FC-HPKs, isolated from precancerous lesions and skin cancers, and in normal human epidermal keratinocytes. Cells were treated for 18, 24, and 48 hours with NAM (5, 25, and 50 μM, respectively) before UVB irradiation. FC-HPK showed four-fold higher basal ROS levels than normal human epidermal keratinocytes; NAM downregulated ROS production only in irradiated FC-HPKs, which showed a greater sensibility to UV rays. UV exposure increased OGG1, inducible nitric oxide synthase, and IL-1β expression, an effect counteracted by NAM pretreatment. Intracellular nitric oxide production and DNA damages were inhibited by NAM exposure before irradiation. Collectively, our findings indicate that pretreatment with 25 μM NAM 24 hours before UVB irradiation effectively prevents oxidative stress formation, DNA damage, and inflammation in both normal human epidermal keratinocytes and FC-HPKs.

Marine Fungal Cerebroside Flavuside B Protects HaCaT Keratinocytes against Staphylococcus aureus Induced Damage

Cerebrosides are glycosylated sphingolipids, and in mammals they contribute to the pro-/anti-inflammatory properties and innate antimicrobial activity of the skin and mucosal surfaces. Staphylococcus aureus infection can develop, not only from minor scratches of the skin, but this pathogen can also actively promote epithelial breach. The effect of cerebroside flavuside B from marine sediment-derived fungus Penicillium islandicum (Aniva Bay, the Sea of Okhotsk) on viability, apoptosis, total caspase activity, and cell cycle in human epidermal keratinocytes HaCaT line co-cultivated with S. aureus, as well as influence of flavuside B on LPS-treated HaCaT cells were studied. Influence of flavuside B on bacterial growth and biofilm formation of S. aureus and its effect on the enzymatic activity of sortase A was also investigated. It was found S. aureus co-cultivated with keratinocytes induces caspase-depended apoptosis and cell death, arrest cell cycle in the G0/G1 phase, and increases in cellular immune inflammation. Cerebroside flavuside B has demonstrated its antimicrobial and anti-inflammatory properties, substantially eliminating all the negative consequences caused by co-cultivation of keratinocytes with S. aureus or bacterial LPS. The dual action of flavuside B may be highly effective in the treatment of bacterial skin lesions and will be studied in the future in in vivo experiments.

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.

Neuropeptides and neurohormones in immune, inflammatory and cellular responses to ultraviolet radiation

Humans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.

Regulation of Anti-Oxidative, Anti-Inflammatory, and Anti-Apoptotic Activity of Advanced Cooling Composition (ACC) in UVB-Irradiated Human HaCaT Keratinocytes

We recently demonstrated that advanced cooling composition (ACC) has effective ingredients that exhibit anti-inflammatory effects in RAW 264.7 cells stimulated with lipopolysaccharide (LPS) and exhibit strong antimicrobial effects on Pseudomonas aeruginosa, Staphylococcus aureus, MRSA (methicillin-resistant Staphylococcus aureus), Candida albicans, and Streptococcus mutans. To further investigate whether ACC has beneficial effects in ultraviolet B (UVB)-irradiated human keratinocytes (HaCaT cells), HaCaT cells were pretreated with ACC prior to UVB irradiation. Our data showed that ACC, which is effective at 100 µg/mL, is nontoxic and has an antioxidative effect against UVB-induced intracellular reactive oxygen species (ROS) in HaCaT cells. In addition, ACC exerts cytoprotective effects against UVB-induced cytotoxicity in HaCaT cells by inhibiting abnormal inflammation and apoptosis through the regulation of mitogen-activated protein kinase (MAPK) signals, such as jun-amino-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK). Therefore, these results indicate that ACC is a potentially beneficial raw material that possesses antioxidative, anti-inflammatory, and antiapoptotic effects against UVB-induced keratinocytes and may have applications in skin health.

Inducible nitric oxide synthase is required for epidermal permeability barrier homeostasis in mice

Nitric oxide (NO) regulates a variety of epidermal functions, including epidermal proliferation, differentiation and cutaneous wound healing. However, whether nitric oxide (NO) and its synthetic enzymes regulate epidermal permeability barrier homeostasis is not clear. In the present study, we employed inducible nitric oxide synthase (iNOS) KO mice to explore the role of iNOS in epidermal permeability barrier homeostasis. Our results showed that iNOS mice displayed a comparable levels of basal transepidermal water loss rates, stratum corneum hydration and skin surface pH to their wild-type mice, but epidermal permeability barrier recovery was significantly delayed both 2 and 4 hours after acute barrier disruption by tape stripping. In parallel, expression levels of mRNA for epidermal differentiation-related proteins and lipid synthetic enzymes were lower in iNOS KO mice versus wild-type controls. Topical applications of two structurally unrelated NO donors to iNOS KO mice improved permeability barrier recovery kinetics and upregulated expression levels of mRNA for epidermal differentiation-related proteins and lipid synthetic enzymes. Together, these results indicate that iNOS and its product regulate epidermal permeability barrier homeostasis in mice.

Bioactivity, phytochemical profile and pro-healthy properties of Actinidia arguta: A review

Hardy kiwi (Actinidia arguta) is a climbing, perennial and dioecious vine from Actinidiaceae family, native from Asia and valued as ornamental and traditional medicine. In the last decade, the growing interest as fruit-bearing plant encourage the expanding cultivation of A. arguta mainly to fruits production, particularly in Europe and North America. A. arguta plants have an extensive range ofbioactive compoundsthat can be obtained from different botanical structures, such as fruits, leaves, flowers and stems. These bioactive molecules, with well-recognized health-promoting properties, include phenolic compounds, minerals, carbohydrates or even volatile substances, with a great potential to be used in several formulations of food products. Phytochemical studies on this plant reported hypoglycemic effects as well as antioxidant and anti-inflammatory activities, among others. The traditional uses ofA. arguta have been experimentally proved byin vitroandin vivostudies, in which its bioactivities were associated to its phytochemical composition. This review aims to assess and summarize the phytochemical and healthy properties ofthe different botanical parts of A. arguta, describing their bioactive composition and exploring it potential functional properties on foodstuffs.

6-shogaol, a active constiuents of ginger prevents UVB radiation mediated inflammation and oxidative stress through modulating NrF2 signaling in human epidermal keratinocytes (HaCaT cells)

Disclosure of ultraviolet (UV) radiation is the key feature from environment to cause redness of the skin, inflammation, photoaging and skin cancer. 6-Shogaol, a spicy compound secluded from ginger, which shows anti-inflammatory effects. Present study was demonstrated the role of 6-Shogaol on UVB induced oxidative stress and photoaging signaling in human epidermal keratinocytes (HaCaT cells). In this study, UVB-irratiation (180 mJ/cm2) significantly elevated the intracellular ROS levels, depletion of antioxidants resulted in apoptotic HaCaT cells. MAPKs signaling are concerned in oxidative stress; these signaling events are measured as differentiation. We found that 6-shogaol prevents over expression of MAPKs (ERK1, JNK1 & p38), in disclosure of UVB in HaCaT cells. Moreover, 6-shogaol infringed Bax and Bcl-2 in which 20 μg 6-shogaol influenced apoptosis in HaCaT cells by investigating augmented appearance of Bax and condensed appearance of Bcl-2 in contrast to control HaCaT cells. These results suggest that 6-shogaol could be a successful healing agent provides fortification against UVB-induced provocative and oxidative skin reimbursement.

Protective Effects and Mechanisms of N-Phenethyl Caffeamide from UVA-Induced Skin Damage in Human Epidermal Keratinocytes through Nrf2/HO-1 Regulation

The skin provides an effective barrier against physical, chemical, and microbial invasion; however, overexposure to ultraviolet (UV) radiation causes excessive cellular oxidative stress, which leads to skin damage, DNA damage, mutations, and skin cancer. This study investigated the protective effects of N-phenethyl caffeamide (K36) from UVA damage on human epidermal keratinocytes. We found that K36 reduced UVA-induced intracellular reactive oxygen species (ROS) production and induced the expression of the intrinsic antioxidant enzyme heme oxygenase-1 (HO-1) by increasing the translocation of nuclear factor erythroid 2⁻related factor 2 (Nrf2). K36 could inhibit the phosphorylation of extracellular-signal-regulated kinase (ERK) and c-Jun N-terminal kinases (JNK) and reduce UVA-induced matrix metalloproteinase (MMP)-1 and MMP-2 overexpression; it could also elevate the expression of tissue inhibitors of metalloproteinases (TIMP). In addition, K36 ameliorated 8-hydroxy-2'-deoxyguanosine (8-OHdG) induced by UVA irradiation. Furthermore, K36 could downregulate the expression of inducible nitric oxide synthase (iNOS) and interleukin-6 (IL-6) and the subsequent production of nitric oxide (NO) and prostaglandin E₂ (PGE₂). Based on our findings, K36 possessed potent antioxidant, anti-inflammatory, antiphotodamage, and even antiphotocarcinogenesis activities. Thus, K36 has the potential to be used to multifunctional skin care products and drugs.

iNOS inhibits hair regeneration in obese diabetic (ob/ob) mice

Previous studies have shown that androgenic alopecia is associated with metabolic syndrome and diabetes. However, the detailed mechanism whereby diabetes causes alopecia still remains unclear. We focused on the inflammatory response that is caused by diabetes or obesity, given that inflammation is a risk factor for hair loss. Inducible nitric oxide synthase (iNOS) is known to be upregulated under conditions of acute or chronic inflammation. To clarify the potential role of iNOS in diabetes-related alopecia, we generated obese diabetic iNOS-deficient (ob/ob; iNOS-KO mice). We observed that ob/ob; iNOS-KO mice were potentiated for the transition from telogen (rest phase) to anagen (growth phase) in the hair cycle compared with iNOS-proficient ob/ob mice. To determine the effect of nitric oxide (NO) on the hair cycle, we administered an iNOS inhibitor intraperitoneally (compound 1400 W, 10 mg/kg) or topically (10% aminoguanidine) in ob/ob mice. We observed that iNOS inhibitors promoted anagen transition in ob/ob mice. Next, we administered an NO donor (S-nitrosoglutathione, GSNO), to test whether NO has the telogen elongation effects. The NO donor was sufficient to induce telogen elongation in wild-type mice. Together, our data indicate that iNOS-derived NO plays a role in telogen elongation under the inflammatory conditions associated with diabetes in mice.

Interleukin-22 and Cyclosporine in Aggressive Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinomas (SCCs) account for up to 10,000 deaths annually in the United States. Most of the more than 700,000 SCCs diagnosed are cured by excision with clear margins; however, metastasis can occur despite seemingly adequate treatment in some cases. Immune-suppressed organ transplant recipients are 60 to 100 times more likely to develop SCC than immune-competent individuals. Transplant-associated SCCs occur more frequently and behave more aggressively, showing higher risk of recurrence and metastasis. This article identifies a potential role for interleukin-22 in driving SCC proliferation, particularly in solid organ transplant recipients taking cyclosporine.

Biochemical and Biophysical Cues in Matrix Design for Chronic and Diabetic Wound Treatment

Progress in biomaterial science and engineering and increasing knowledge in cell biology have enabled us to develop functional biomaterials providing appropriate biochemical and biophysical cues for tissue regeneration applications. Tissue regeneration is particularly important to treat chronic wounds of people with diabetes. Understanding and controlling the cellular microenvironment of the wound tissue are important to improve the wound healing process. In this study, we review different biochemical (e.g., growth factors, peptides, DNA, and RNA) and biophysical (e.g., topographical guidance, pressure, electrical stimulation, and pulsed electromagnetic field) cues providing a functional and instructive acellular matrix to heal diabetic chronic wounds. The biochemical and biophysical signals generally regulate cell-matrix interactions and cell behavior and function inducing the tissue regeneration for chronic wounds. Some technologies and devices have already been developed and used in the clinic employing biochemical and biophysical cues for wound healing applications. These technologies can be integrated with smart biomaterials to deliver therapeutic agents to the wound tissue in a precise and controllable manner. This review provides useful guidance in understanding molecular mechanisms and signals in the healing of diabetic chronic wounds and in designing instructive biomaterials to treat them.

Extracts of Actinidia arguta stems inhibited LPS-induced inflammatory responses through nuclear factor-κB pathway in Raw 264.7 cells

The inflammatory response protects our body from bacteria and tumors, but chronic inflammation driven by the persistent activation of macrophages can lead to serious adverse effects including gastrointestinal problems, cardiac disorders, and a sore throat. Part of the ongoing research is focused on searching for antiinflammatory compounds from natural sources, so we investigated the effects of hardy kiwis (Actinidia arguta, Lauraceae) stems on inflammation induced by lipopolysaccharide (LPS) in Raw 264.7 cells to test the hypothesis that antiinflammatory effects of A. arguta stems were exerted through the inhibition of the nuclear factor (NF)-κB pathway. The methanol extract of A. arguta (20 μg/mL) stems lowered nitric oxide production in LPS-stimulated Raw 264.7 cells by 40%. It was then partitioned with hexane, chloroform, ethyl acetate, butanol, and water based on the polarity of each compound. Among the 5 layers, the chloroform layer had the greatest inhibitory effect on LPS-stimulated nitric oxide production and inducible nitric oxide synthase mRNA expression in Raw 264.7 cells. However, the levels of prostaglandin E2 and cyclooxygease 2 were not altered. On the other hand, treatment of cells with the chloroform layer of A. arguta before LPS stimulation also reduced them RNA expression of proinflammatory cytokines including tumor necrosis factor α and interleukin 1β. Nuclear translocation of NF-κB p50 and p65 subunits induced by LPS was also inhibited by treatment with the chloroform layer of A. arguta. This was accompanied with the reduced phosphorylation of mitogen-activated protein kinases including extracellular signal-regulated protein kinase 1/2, c-Jun N-terminal protein kinase, and p38. Taken together, these results suggest that chloroform layer of A. arguta exerted antiinflammatory effects by the inhibition of mitogen-activated protein kinase phosphorylation and nuclear translocation of NF-κB.

Ultraviolet-B-induced stomatal closure in Arabidopsis is regulated by the UV RESISTANCE LOCUS8 photoreceptor in a nitric oxide-dependent mechanism

UV RESISTANCE LOCUS8 (UVR8) signaling involves CONSTITUTIVELY PHOTOMORPHOGENIC1, the ELONGATED HYPOCOTYL5 (HY5) transcription factor, and the closely related HY5 HOMOLOG. Some UV-B responses mediated by UVR8 are also regulated by nitric oxide (NO), a bioactive molecule that orchestrates a wide range of processes in plants. In this study, we investigated the participation of the UVR8 pathway and its interaction with NO in UV-B-induced stomatal movements in Arabidopsis (Arabidopsis thaliana). Stomata in abaxial epidermal strips of Arabidopsis ecotype Landsberg erecta closed in response to increasing UV-B fluence rates, with maximal closure after 3-h exposure to 5.46 μmol m⁻² s⁻¹ UV-B. Both hydrogen peroxide (H₂O₂) and NO increased in response to UV-B, and stomatal closure was maintained by NO up to 24 h after the beginning of exposure. Stomata of plants expressing bacterial NO dioxygenase, which prevents NO accumulation, did not close in response to UV-B, although H₂O₂ still increased. When the uvr8-1 null mutant was exposed to UV-B, stomata remained open, irrespective of the fluence rate. Neither NO nor H₂O₂ increased in stomata of the uvr8-1 mutant. However, the NO donor S-nitrosoglutathione induced closure of uvr8-1 stomata to the same extent as in the wild type. Experiments with mutants in UVR8 signaling components implicated CONSTITUTIVELY PHOTOMORPHOGENIC1, HY5, and HY5 HOMOLOG in UV-B-induced stomatal closure. This research provides evidence that the UVR8 pathway regulates stomatal closure by a mechanism involving both H₂O₂ and NO generation in response to UV-B exposure.

Sargassum fulvellum Protects HaCaT Cells and BALB/c Mice from UVB-Induced Proinflammatory Responses

Ultraviolet (UV) radiation has been reported to induce cutaneous inflammation such as erythema and edema via induction of proinflammatory enzymes and mediators. Sargassum fulvellum is a brown alga of Sargassaceae family which has been demonstrated to exhibit antipyretic, analgesic, antiedema, antioxidant, antitumor, fibrinolytic, and hepatoprotective activities. The purpose of this study is to investigate anti-inflammatory effects of ethylacetate fraction of ethanol extract of Sargassum fulvellum (SFE-EtOAc) in HaCaT keratinocytes and BALB/c mice. In HaCaT cells, SFE-EtOAc effectively inhibited UVB-induced cytotoxicity (60 mJ/cm²) and the expression of proinflammatory proteins such as cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS). Furthermore, SFE-EtOAc significantly reduced UVB-induced production of proinflammatory mediators including prostaglandin E₂ (PGE₂) and nitric oxide (NO). In BALB/c mice, topical application of SFE-EtOAc prior to UVB irradiation (200 mJ/cm²) effectively suppressed the UVB-induced protein expression of COX-2, iNOS, and TNF-α and subsequently attenuated generation of PGE₂ and NO as well. In another experiment, SFE-EtOAc pretreatment suppressed UVB-induced reactive oxygen species production and exhibited an antioxidant potential by upregulation of antioxidant enzymes such as catalase and Cu/Zn-superoxide dismutase in HaCaT cells. These results suggest that SFE-EtOAc could be an effective anti-inflammatory agent protecting against UVB irradiation-induced skin damages.

Nitric oxide enhances plant ultraviolet-B protection up-regulating gene expression of the phenylpropanoid biosynthetic pathway

The link between ultraviolet (UV)-B, nitric oxide (NO) and phenylpropanoid biosynthetic pathway (PPBP) was studied in maize and Arabidopsis. The transcription factor (TF) ZmP regulates PPBP in maize. A genetic approach using P-rr (ZmP+) and P-ww (ZmP⁻) maize lines demonstrate that: (1) NO protects P-rr leaves but not P-ww from UV-B-induced reactive oxygen species (ROS) and cell damage; (2) NO increases flavonoid and anthocyanin content and prevents chlorophyll loss in P-rr but not in P-ww and (3) the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) blocks the UV-B-induced expression of ZmP and their targets CHS and CHI suggesting that NO plays a key role in the UV-B-regulated PPBP. Involvement of endogenous NO was studied in Arabidopsis nitric oxide dioxygenase (NOD) plants that express a NO dioxygenase gene under the control of a dexamethasone (DEX)-inducible promoter. Expression of HY5 and MYB12, TFs involved in PPBP regulation, was induced by UV-B, reduced by DEX in NOD plants and recovered by subsequent NO treatment. C4H regulates synapate esters synthesis and is UV-B-induced in a NO-independent pathway. Data indicate that UV-B perception increases NO concentration, which protects plant against UV-B by two ways: (1) scavenging ROS; and (2) up-regulating the expression of HY5, MYB12 and ZmP, resulting in the PPBP activation.

The roles of Akt and NOSs in regulation of VLA-4-mediated melanoma cell adhesion to endothelial VCAM-1 after UVB-irradiation

UVB-reduced avidity between M624 melanoma and HUVEC cells is dependent on the interaction of VLA-4 with its endothelial ligand VCAM-1. Our previous studies suggested that a spatial organization of α4 integrin, one of the two subunits of VLA-4, on the melanoma cell surface contributed to the changes in avidity for VCAM-1 upon UVB-irradiation. In this study, we demonstrate that Akt plays an important role in regulation of the expression and surface level of α4 integrin on melanoma cells upon UVB-irradiation. While the cell surface level of α4 integrin is not significantly affected by UVB-irradiation or Akt inhibitor alone, it is dynamically altered after UVB-irradiation when Akt is inhibited. Inhibition of Akt also reverses the reduction of avidity of cells after the irradiation. Our data also shows that UVB reduces the level of Akt. The inhibition of Akt activity correlates with a reduced amount of coupled cNOS and reduced amount of iNOS after UVB-irradiation. However, the effect of NOSs on melanoma cell adhesion appears due to their roles in regulation of apoptosis after UVB-irradiation. Base on these results, we propose that the UVB-induced reduction of avidity of melanoma cells is coordinatively regulated by NOSs and Akt through two differential mechanisms.

Differential roles of nitric oxide synthases in regulation of ultraviolet B light-induced apoptosis

Ultraviolet B light (UVB) activates nitric oxide synthase(s) (NOSs) and nitric oxide (NO()) production, which plays a role in regulation of apoptosis. However, the role of NO() in UVB-induced apoptosis remains controversial. In this study, we analyzed expression and activation of constitutive NOSs (cNOSs) and their roles in UV-induced apoptosis of HaCaT keratinocytes. Our data showed that the expression of neuronal NOS (nNOS) was increased while endothelial NOS (eNOS) was uncoupled in the early phase (0-6 h) post-UVB. The expression of both cNOSs peaked at 12h post-UVB and NO() was transiently elevated with 30 min and then steadily rose from 6 to 18 h post-UVB. The expression of iNOS was detected at 6h post-UVB and then sturdily increased. Inhibition of cNOSs with L-NAME reduced the inducibility of NO(*) in the early and late phases of irradiation. Along with the eNOS uncoupling, an increased level of peroxynitrite (ONOO(-)) was detected in the early phase, but not in the late phase post-UVB. Inhibition of cNOSs reduced the production of ONOO(-) in the early time, but led to an increase of ONOO(-) in the late time after UVB-irradiation. The results indicate that cNOSs regulate NO()/ONOO(-) imbalance after UVB-irradiation. Our data suggested that the activation of cNOSs in the early phase post-UVB leads to NO()/ONOO(-) imbalance and promotes apoptosis via a caspase 3-independent pathway. The elevation of NO() in the late phase of UVB-irradiation is mainly produced by inducible NOS (iNOS). However, cNOSs also contribute to the NO() production and to maintain a higher NO()/ONOO(-) ratio, which reduces caspase 3 activity and protects cells from UVB-induced apoptosis.

Ultraviolet radiation and skin aging: roles of reactive oxygen species, inflammation and protease activation, and strategies for prevention of inflammation-induced matrix degradation - a review

Inflammation and the resulting accumulation of reactive oxygen species (ROS) play an important role in the intrinsic and photoaging of human skin in vivo. Environmental insults such as ultraviolet (UV) rays from sun, cigarette smoke exposure and pollutants, and the natural process of aging contribute to the generation of free radicals and ROS that stimulate the inflammatory process in the skin. UV irradiation initiates and activates a complex cascade of biochemical reactions in human skin. In short, UV causes depletion of cellular antioxidants and antioxidant enzymes (SOD, catalase), initiates DNA damage leading to the formation of thymidine dimmers, activates the neuroendocrine system leading to immunosuppression and release of neuroendocrine mediators, and causes increased synthesis and release of pro-inflammatory mediators from a variety of skin cells. The pro-inflammatory mediators increase the permeability of capillaries leading to infiltration and activation of neutrophils and other phagocytic cells into the skin. The net result of all these effects is inflammation and free radical generation (both reactive oxygen and nitrogen species). Furthermore, elastsases and other proteases (cathepsin G) released from neutrophils cause further inflammation, and activation of matrix metalloproteases. The inflammation further activates the transcription of various matrixes degrading metalloproteases, leading to abnormal matrix degradation and accumulation of non-functional matrix components. In addition, the inflammation and ROS cause oxidative damage to cellular proteins, lipids and carbohydrates, which accumulates in the dermal and epidermal compartments, contributing to the aetiology of photoaging. Strategies to prevent photodamage caused by this cascade of reactions initiated by UV include: prevention of UV penetration into skin by physical and chemical sunscreens, prevention/reduction of inflammation using anti-inflammatory compounds (e.g. cyclooxygenase inhibitors, inhibitors of cytokine generation); scavenging and quenching of ROS by antioxidants; inhibition of neutrophil elastase activity to prevent extracellular matrix damage and activation of matrix metalloproteases (MMPs), and inhibition of MMP expression (e.g. by retinoids) and activity (e.g. by natural and synthetic inhibitors).

Extremely low frequency electromagnetic fields modulate expression of inducible nitric oxide synthase, endothelial nitric oxide synthase and cyclooxygenase-2 in the human keratinocyte cell line HaCat: potential therapeutic effects in wound healing

BACKGROUND

Extremely low frequency (ELF) electromagnetic fields (EMF) are known to produce a variety of biological effects. Clinical studies are ongoing using EMF in healing of bone fractures and skin wounds. However, little is known about the mechanisms of action of ELF-EMF. Several studies have demonstrated that expression and regulation of nitric oxide synthase (NOS) and cyclooxygenase-2 (COX-2) are vital for wound healing; however, no reports have demonstrated a direct action of ELF-EMF in the modulation of these inflammatory molecules in human keratinocytes.

OBJECTIVES

The present study analysed the effect of ELF-EMF on the human keratinocyte cell line HaCaT in order to assess the mechanisms of action of ELF-EMF and to provide further support for their therapeutic use in wound healing.

METHODS

Exposed HaCaT cells were compared with unexposed control cells. At different exposure times, expression of inducible NOS (iNOS), endothelial NOS (eNOS) and COX-2 was evaluated by Western blot analysis. Modulation of iNOS and eNOS was monitored by evaluation of NOS activities, production of nitric oxide (NO) and O(2)(-) and expression of activator protein 1 (AP-1). In addition, catalase activity and prostaglandin (PG) E(2) production were determined. Effects of ELF-EMF on cell growth and viability were monitored.

RESULTS

The exposure of HaCaT cells to ELF-EMF increased iNOS and eNOS expression levels. These ELF-EMF-dependent increased expression levels were paralled by increased NOS activities, and increased NO production. In addition, higher levels of AP-1 expression as well as a higher cell proliferation rate were associated with ELF-EMF exposure. In contrast, ELF-EMF decreased COX-2 expression, PGE(2) production, catalase activity and O(2)(-) production.

CONCLUSIONS

Mediators of inflammation, such as reactive nitrogen and PGE(2), and keratinocyte proliferation are critical for the tissue regenerative processes. The ability of ELF-EMF to upmodulate NOS activities, thus nitrogen intermediates, as well as cell proliferation, and to downregulate COX-2 expression and the downstream intermediate PGE(2), highlights the potential therapeutic role of ELF-EMF in wound healing processes.

A Polypodium leucotomos extract inhibits solar-simulated radiation-induced TNF-alpha and iNOS expression, transcriptional activation and apoptosis

In this report, we have examined the molecular basis of the photoprotective effect of a hydrophilic extract of the fern Polypodium leucotomos (PL) in vitro, using a solar simulator as the source of UV radiation (SSR). We found that pretreatment of human keratinocytes with PL inhibited SSR-mediated increase of tumor necrosis factor (TNF)-alpha and also abrogated nitric oxide (NO) production. Consistent with this, PL blocked the induction of inducible nitric oxide synthase (iNOS) elicited by SSR. In addition, PL inhibited the SSR-mediated transcriptional activation of NF-kappaB and AP1. Finally, we demonstrated that pretreatment with PL exerted a cytoprotective effect against SSR-induced damage, resulting in increased cell survival. Together, these data postulate a multifactor mechanism of protection not exclusively reliant on the antioxidant capability of PL, and strengthen the basic knowledge on the photoprotective effect of this botanical agent.

Neuronal nitric oxide synthase control mechanisms in the cutaneous vasculature of humans in vivo

The physiological roles of constitutively expressed nitric oxide synthase (NOS) isoforms in humans, in vivo, are unknown. Cutaneous vasodilatation during both central nervous system-mediated, thermoregulatory reflex responses to whole-body heat stress and during peripheral axon reflex-mediated, local responses to skin warming in humans depend on nitric oxide (NO) generation by constitutively expressed NOS of uncertain isoform. We hypothesized that neuronal NOS (nNOS, NOS I) effects cutaneous vasodilatation during whole-body heat stress, but not during local skin warming. We examined the effects of the nNOS inhibitor 7-nitroindazole (7-NI) administered by intradermal microdialysis on vasodilatation induced by whole-body heat stress or local skin warming. Skin blood flow (SkBF) was monitored by laser-Doppler flowmetry (LDF). Blood pressure (MAP) was monitored and cutaneous vascular conductance calculated (CVC = LDF/MAP). In protocol 1, whole-body heat stress was induced with water-perfused suits. In protocol 2, local skin warming was induced through local warming units at LDF sites. At the end of each protocol, 56 mm sodium nitroprusside was perfused at microdialysis sites to raise SkBF to maximal levels for data normalization. 7-NI significantly attenuated CVC increases during whole-body heat stress (P < 0.05), but had no effect on CVC increases induced by local skin warming (P > 0.05). These diametrically opposite effects of 7-NI on two NO-dependent processes verify selective nNOS antagonism, thus proving that the nNOS isoform affects NO increases and hence vasodilatation during centrally mediated, reflex responses to whole-body heat stress, but not during locally mediated, axon reflex responses to local skin warming. We conclude that the constitutively expressed nNOS isoform has distinct physiological roles in cardiovascular control mechanisms in humans, in vivo.

Trichloroethylene induce nitric oxide production and nitric oxide synthase mRNA expression in cultured normal human epidermal keratinocytes

Trichloroethylene (TCE), a major chemical hazard during occupational exposure, can cause obvious skin lesions, including irritant reactions and dermatitis. Nitric oxide (NO) synthesized by nitric oxide synthase (NOS) is involved in a broad array of pathogenesis of skin inflammatory and immune responses. To understand the mechanisms of TCE-induced dermatoxicity, we investigated the effects of TCE on NO production and NOS mRNA expression in cultured normal human epidermal keratinocytes (NHEK). Cells were treated with TCE (0 mM, 0.125 mM, 0.25 mM, 0.5 mM, 1.0 mM, 2.0 mM) for 4 h, and then incubated for 12 h, 24 h, 48 h and 72 h. At each given time point, NO production were evaluated indirectly by measuring nitrite plus nitrate concentration in the culture medium using Griess reaction, as well as cell viability determined by MTT test, iNOS and cNOS activities assayed with a NOS activity detecting kit. The expression of iNOS and cNOS mRNA was detected using RT-PCR. TCE decreases cell viability and enhance NO production from NHEK in concentration- and time-dependent manner. Aminoguanidine (AG), an inhibitor of NOS, can prevent NO production and cell viability decrease in NHEK by TCE induced. Change to NO production was accompanied by increased activities of both types of NOS, but the iNOS activity accounted mainly for the TCE-induced NO production. RT-PCR detection showed that NHEK expressed both iNOS and cNOS mRNA by TCE exposure. Whereas a concentration- and time-dependent up-regulation of the mRNA expression was observed for iNOS and cNOS following TCE exposure, changes to iNOS were more marked. These results suggest that TCE caused increase in NO production, attributed to activation of iNOS as well as cNOS, and expression of iNOS and cNOS mRNA. These cellular changes may contribute to the pathological and physiological features of TCE-induced erythema and skin inflammation.

Biological fate and clinical implications of arginine metabolism in tissue healing

Since its discovery in 1987, many biological roles (including wound healing) have been identified for nitric oxide (NO). The gas is produced by NO synthase using the dibasic amino acid L-arginine as a substrate. It has been established that a lack of dietary L-arginine delays experimental wound healing. Arginine can also be metabolized to urea and ornithine by arginase-1, a pathway that generates L-proline, a substrate for collagen synthesis, and polyamines, which stimulate cellular proliferation. Herein, we review subjects of interest in arginine metabolism, with emphasis on the biochemistry of wound NO production, relative NO synthase isoform activity in healing wounds, cellular contributions to NO production, and NO effects and mechanisms of action in wound healing.

Neuropeptide (Calcitonin Gene-Related Peptide) Induction of Nitric Oxide in Human Keratinocytes in vitro

Nitric oxide (NO) is an important signaling molecule in both the central nervous system and the periphery, where it is involved in neurotransmission, vascular and bronchial tone, inflammation, and cutaneous immune function. More recently, NO has been implicated in intracellular signaling and may have a role in cellular differentiation, cytokine expression, and apoptosis. The experiments described herein examined the effect of calcitonin gene-related protein (CGRP), a cutaneous nerve neuropeptide, on NO production in human keratinocytes in vitro. CGRP stimulated two distinct increases in NO production: one within 30 minutes and a second at 24 hours. CGRP stimulated a modest increase in inducible nitric oxide synthase (iNOS) at 3-6 hours. Experimental evidence suggested that CGRP stimulated both constitutive NOS activity and generation of NO via nitrosothiol degradation within the first hour. Production of NO was paralleled by a decrease in nitrosothiol levels for 2 hour, suggesting that immediate NO release may originate from pre-existing stores. Nitrosothiols are ubiquitous molecules that comprise an important NO pool and have intracellular regulatory roles, particularly linked to oxidative stress. The present data indicate that, in addition to its known cAMP signaling pathway, CGRP may act to regulate keratinocyte biology through intracellular NO by modulation of S-nitrosothiol stores and stimulation of NOS activity.

Topical application of a novel, hydrophilic gamma-tocopherol derivative reduces photo-inflammation in mice skin

We previously demonstrated that a novel hydrophilic gamma-tocopherol (gamma-Toc) derivative, gamma-tocopherol-N,N-dimethylglycinate hydrochloride (gamma-TDMG) converts to gamma-Toc in the mouse skin and has a higher bioavailability than gamma-Toc itself. In the present study, we determined whether gamma-TDMG could reduce photo-inflammation in mouse skin, and compared its effectiveness to that of alpha-Toc acetate (alpha-TA). Topical pre- or post-application of 5% gamma-TDMG significantly reduced the formation of edema and tempered the increase in cyclooxygenase-2 (COX-2)-catalyzed synthesis of prostaglandin E2 (PGE2) that were induced by a single dose of UV irradiation of 2 kJ/m2 (290-380 nm, maximum 312 nm). The pre-treatment of mouse skin with 10% alpha-TA had the same anti-inflammatory effect as did gamma-TDMG. In spite of same having the ability to reduce PGE2 levels, the effect of gamma-TDMG pre-treatment on the inhibition of COX-2 mRNA/protein expression was less than that seen with 10% alpha-TA. In contrast, the increase in COX-2 activity seen after UV exposure was reduced more by gamma-TDMG than by alpha-TA, suggesting that the reduction in PGE2 levels might have been due to the direct inhibition of COX-2 activity by gamma-TDMG-derived gamma-Toc. Both Toc derivatives strongly suppressed inducible nitric oxide synthase (iNOS) mRNA expression and nitric oxide (NO) production, both of which play important roles in UV-induced inflammation. Both derivatives also significantly reduced lipid peroxidation in response to UV exposure, though gamma-TDMG's ability in this regard was less than that seen with alpha-TA, which correlated with their abilities to suppress COX-2 expression. Thus, the gamma-TDMG-derived gamma-Toc acts as an antioxidant, suppresses iNOS expression and directly inhibits COX-2 activity, all of which likely play a role in mediating its suppressive effects on photo-inflammation. Our data further suggest that the topical application of gamma-TDMG, a novel hydrophilic gamma-Toc derivative, may be efficacious in preventing and reducing UV-induced inflammation in humans.

Nitric oxide: a newly discovered function on wound healing

Wound healing impairment represents a particularly challenging clinical problem to which no efficacious treatment regimens currently exist. The factors ensuring appropriate intercellular communication during wound repair are not completely understood. Although protein-type mediators are well-established players in this process, emerging evidence from both animal and human studies indicates that nitric oxide (NO) plays a key role in wound repair. The beneficial effects of NO on wound repair may be attributed to its functional influences on angiogenesis, inflammation, cell proliferation, matrix deposition, and remodeling. Recent findings from in vitro and in vivo studies of NO on wound repair are summarized in this review. The unveiled novel mechanisms support the use of NO-containing agents and/or NO synthase gene therapy as new therapeutic regimens for impaired wound healing.

Identification of Nitric Oxide Metabolites in Various Honeys: Effects of Intravenous Honey on Plasma and Urinary Nitric Oxide Metabolites Concentrations

Honey has antibacterial activity, promotes healing, and enhances immunity. Its acidity, osmotic effects of its high content of sugar, and hydrogen peroxide are assumed to be responsible for its effects. In this study, various honeys were investigated for the presence of nitrite/nitrate, the stable nitric oxide (NO) metabolites, and the effects of intravenous infusion of honey on urinary and plasma NO end products were studied in healthy sheep. Seven kinds of honey, different in their origin (three from Yemen, two from the United Arab Emirates, one from Germany, and one from India), color, and duration of storage, were investigated for the presence of NO metabolites. The assessment of NO metabolites was performed before and after exposure of the honey samples to heating (80 degrees C for 1 hour) or ultraviolet light (for 24 hours). Seven healthy male sheep were used for the study. Fresh unprocessed yellow honey (2 g/kg of body weight) was infused over a period of 45 minutes to each fasting sheep. Plasma and urinary NO metabolites were measured before and after the infusion. All the honey samples examined had various concentrations of NO metabolites; the highest concentration was in the fresh dark honey collected from Yemen, and the lowest in 1-year-stored dark honey collected from India. Darker or fresh honeys contained more NO metabolites than light or stored honey. After heating, NO metabolites decreased in all the kinds of honey. After ultraviolet exposure, NO metabolites were decreased in four kinds of honey, increased in one kind, and unchanged in two kinds. The darker stored honey had more resistance to heating and ultraviolet exposure. Intravenous infusion of honey elevated urinary NO metabolites from 8.4 +/- 7.4 micromol/L to 14.9 +/- 10 micromol/L during the first 60-90 min after infusion and to 35.2 +/- 34 micromol/L during the next 150-180 min. Plasma NO metabolites were increased during 1, 2, and 3 hours after infusion by 3%, 3.6%, and 17%, respectively. No side effects were reported with the use of intravenous honey. It might be concluded that honey contains various concentrations of NO metabolites. Its intravenous infusion increased plasma and urinary NO metabolites. It is assumed that NO might be responsible, in part, for the biological and therapeutic effects of honey.

The effect of amniotic membrane extract on the expression of iNOS mRNA and generation of NO in HaCaT cell by ultraviolet B irradiation

BACKGROUND/PURPOSE

Amniotic membrane (AM) is the innermost fetal membrane, which contains several proteinase inhibitors and expresses several growth factors. Nitric oxide (NO) has been implicated in the pathogenesis of various inflammatory diseases including sunburn and ultraviolet induced erythema. The expression of inducible nitric oxide synthase (iNOS) is up regulated by UVB irradiation and inhibited by TGF-beta and EGF-beta. We evaluated the effect of AM extract on the expression of iNOS mRNA by UV irradiation in HaCaT cell (immortalized human keratinocyte cell line).

METHODS

HaCaT cells were irradiated UVB 30 mJ/cm2 and AM extract was added. The iNOS mRNA was isolated by RT-PCR and NO production was assessed by spectrophotometric method based on Griess reaction.

RESULTS

The expression of iNOS mRNA was induced by UVB irradiation in HaCaT cell and the expression of iNOS mRNA was higher at 48 h than that at 24 h. AM extract down regulated the induction of iNOS mRNA in HaCaT cell by UVB irradiation. NO generation was increased by UVB irradiation, but down regulated by AM extract treatment in HaCaT cells.

CONCLUSION

These results assured that the expression of iNOS mRNA and generation of NO are up regulated by UVB irradiation and showed that AM extract down regulated the induction of iNOS mRNA and decreased generation of NO by UVB irradiation.