Redox regulation of wound healing? NF-kappaB activation in cultured human keratinocytes upon wounding and the effect of low energy HeNe irradiation

NF-κB signaling is key in the wound healing processes of silk fibroin

Silk fibroin (SF) is a well-studied biomaterial for tissue engineering applications including wound healing. However, the signaling mechanisms underlying the impact of SF on this phenomenon have not been determined. In this study, through microarray analysis, regulatory genes of NF-ĸB signaling were activated in SF-treated NIH3T3 cells along with other genes. Immunoblot analysis confirmed the activation of the NF-ĸB signaling pathway as SF induced protein expression levels of IKKα, IKKβ, p65, and the degradation of IκBα. The treatment of NIH3T3 cells with SF also increased the expression of cyclin D1, vimentin, fibronectin, and vascular endothelial growth factor (VEGF). The expression of these factors by SF treatment was abrogated when NF-ĸB was inhibited by a pharmacological inhibitor Bay 11-7082. Knockdown of NF-ĸB using siRNA of IKKα and IKKβ also inhibited the SF-induced wound healing response of the NIH3T3 cells in a wound scratch assay. Collectively, these results indicated that SF-induced wound healing through the canonical NF-κB signaling pathway via regulation of the expression of cyclin D1, vimentin, fibronectin, and VEGF by NIH3T3 cells. Using an in vivo study with a partial-thickness excision wound in rats we demonstrated that SF-induced wound healing via NF-κB regulated proteins including cyclin D1, fibronectin, and VEGF. The in vitro and in vivo data suggested that SF induced wound healing via modulation of NF-ĸB signaling regulated proteins.

STATEMENT OF SIGNIFICANCE

Silk fibroin has been effectively used as a dressing for wound treatment for more than a century. However, mechanistic insight into the basis for wound healing via silk fibroin has not been elucidated. Here we report a key mechanism involved in silk fibroin induced wound healing both in vitro and in vivo. Using genetic- and protein-level analyses, NF-κB signaling was found to regulate silk fibroin-induced wound healing by modulating target proteins. Thus, the NF-κB signaling pathway may be utilized as a therapeutic target during the formulation of silk fibroin-based biomaterials for wound healing and tissue engineering.

Photobiomodulation reduces oral mucositis by modulating NF-kB

The aim of this study was to evaluate NF-kB during 5-fluorouracil (FU)-induced oral mucositis and ascertain whether photobiomodulation (PBM), as a preventive and/or therapeutic modality, influences this transcription factor. Ninety-six male golden Syrian hamsters were allocated into four groups: control (no treatment); PBM therapeutic, PBM preventive, and PBM combined. Animals received an injection of 5-FU on days 0 and 2. On days 3 and 4, the buccal mucosa was scratched. Irradiation was carried out using a 660-nm, 40-mW diode laser at 6  J/cm(2) during 6  s/point, 0.24  J/point, for a total dose of 1.44  J/day of application. Animals were euthanized on days 0, 5, 10, and 15 (n=6). Buccal mucosa was removed for protein quantification by Western blot. Clinical analysis revealed that PBM groups exhibited less mucositis than controls on day 10. Control animals exhibited lower levels of NF-kB during mucositis development and healing. The preventive and combined protocols were associated with higher NF-kB levels at day 5; however, the therapeutic group had higher levels at days 10 and 15. These findings suggest that the preventive and/or therapeutic PBM protocols reduced the severity of oral mucositis by activating the NF-kB pathway.

Evaluation of lipoic acid topical application on rats skin wound healing

PURPOSE

To evaluate the effects of lipoic acid (thioctic acid) topical application on wound healing on rats skin, and the consequences of lipoic acid nanoencapsulation on this process.

METHODS

The model used was the healing activity on wounds induced by surgical incision on rats skin (n = 44). The parameters analyzed (11 days) were wound healing rate and histology (vascular proliferation, polymorphonuclear or mononuclear cells, and collagen synthesis or reepithelialization), after application of free lipoic acid or lipoic acid- loaded nanocapsules. The antioxidant activity of these formulations was evaluated by lipid peroxidation test.

RESULTS

It was demonstrated for the first time that the topical application of lipoic acid improves wound healing. On the seventh day after surgery, the animals treated with lipoic acid showed increased healing rate (60.7 ± 8.4%) compared to the negative control group (43.0 ± 17.4%), as so improvement of histological parameters. The nanoencapsulation reverted the pro-oxidant activity presented in vitro by lipoic acid, whereas diminished wound repair.

CONCLUSIONS

The topical application of lipoic acid produced an increase in the skin wound healing, which may be related to its pro-oxidant activity. On the other hand, the nanoencapsulation of the lipoic acid reversed the pro-oxidant activity, although presented minor healing activity.

Cell cycle regulators guide mitochondrial activity in radiation-induced adaptive response

SIGNIFICANCE

There are accruing concerns on potential genotoxic agents present in the environment including low-dose ionizing radiation (LDIR) that naturally exists on earth's surface and atmosphere and is frequently used in medical diagnosis and nuclear industry. Although its long-term health risk is being evaluated and remains controversial, LDIR is shown to induce temporary but significant adaptive responses in mammalian cells and animals. The mechanisms guiding the mitochondrial function in LDIR-induced adaptive response represent a unique communication between DNA damage and cellular metabolism. Elucidation of the LDIR-regulated mitochondrial activity may reveal new mechanisms adjusting cellular function to cope with hazardous environmental stress.

RECENT ADVANCES

Key cell cycle regulators, including Cyclin D1/CDK4 and Cyclin B1/cyclin-dependent kinase 1 (CDK1) complexes, are actively involved in the regulation of mitochondrial functions via phosphorylation of their mitochondrial targets. Accumulating new evidence supports a concept that the Cyclin B1/CDK1 complex acts as a mediator in the cross talk between radiation-induced DNA damage and mitochondrial functions to coordinate cellular responses to low-level genotoxic stresses.

CRITICAL ISSUES

The LDIR-mediated mitochondrial activity via Cyclin B1/CDK1 regulation is an irreplaceable network that is able to harmonize vital cellular functions with adjusted mitochondrial metabolism to enhance cellular homeostasis.

FUTURE DIRECTIONS

Further investigation of the coordinative mechanism that regulates mitochondrial activities in sublethal stress conditions, including LDIR, will reveal new insights of how cells cope with genotoxic injury and will be vital for future targeted therapeutic interventions that reduce environmental injury and cancer risk.

A Network Approach to Wound Healing

OBJECTIVE

The wound healing process is well-understood on the cellular and tissue level; however, its complex molecular mechanisms are not yet uncovered in their entirety. Viewing wounds as perturbed molecular networks provides the tools for analyzing and optimizing the healing process. It helps to answer specific questions that lead to better understanding of the complexity of the process. What are the molecular pathways involved in wound healing? How do these pathways interact with each other during the different stages of wound healing? Is it possible to grasp the entire mechanism of regulatory interactions in the healing of a wound?

APPROACH

Networks are structures composed of nodes connected by links. A network describing the state of a cell taking part in the healing process may contain nodes representing genes, proteins, microRNAs, metabolites, and drug molecules. The links connecting nodes represent interactions such as binding, regulation, co-expression, chemical reaction, and others. Both nodes and links can be weighted by numbers related to molecular concentration and the intensity of intermolecular interactions. Proceeding from data and from molecular profiling experiments, different types of networks are built to characterize the stages of the healing process. Network nodes having a higher degree of connectivity and centrality usually play more important roles for the functioning of the system they describe.

RESULTS

We describe here the algorithms and software packages for building, manipulating and analyzing networks proceeding from information available from a literature or database search or directly extracted from experimental gene expression, metabolic, and proteomic data. Network analysis identifies genes/proteins most differentiated during the healing process, and their organization in functional pathways or modules, and their distribution into gene ontology categories of biological processes, molecular functions, and cellular localization. We provide an example of how network analysis can be used to reach better understanding of regulation of key wound healing mediators and microRNAs that regulate them.

INNOVATION

Univariate statistical tests widely used in clinical studies are not enough to improve understanding and optimize the processes of wound healing. Network methods of analysis of patients "omics" data, such as transcriptoms, proteomes, and others can provide a better insight into the healing processes and help in development of better treatment practices. We review several articles that are examples of this emergent approach to the study of wound healing.

CONCLUSION

Network analysis has the potential to considerably contribute to the better understanding of the molecular mechanisms of wound healing and to the discovery of means to control and optimize that process.

Acceleration of wound repair by curcumin in the excision wound of mice exposed to different doses of fractionated γ radiation

Fractionated irradiation (IR) before or after surgery of malignant tumours causes a high frequency of wound healing complications. Our aim was to investigate the effect of curcumin (CUM) on the healing of deep excision wound of mice exposed to fractionated IR by mimicking clinical conditions. A full-thickness dermal excision wound was created on the shaved dorsum of mice that were orally administered or not with 100 mg of CUM per kilogram body weight before partial body exposure to 10, 20 or 40 Gy given as 2 Gy/day for 5, 10 or 20 days. The wound contraction was determined periodically by capturing video images of the wound from day 1 until complete healing of wounds. Fractionated IR caused a dose-dependent delay in the wound contraction and prolonged wound healing time, whereas CUM administration before fractionated IR caused a significant elevation in the wound contraction and reduced mean wound healing time. Fractionated IR reduced the synthesis of collagen, deoxyribonucleic acid (DNA) and nitric oxide (NO) at different post-IR times and treatment of mice with CUM before IR elevated the synthesis of collagen, DNA and NO significantly. Histological examination showed a reduction in the collagen deposition, fibroblast and vascular densities after fractionated IR, whereas CUM pre-treatment inhibited this decline significantly. Our study shows that CUM pre-treatment accelerated healing of irradiated wound and could be a substantial therapeutic strategy in the management of irradiated wounds.

Effects of 810-nm laser on murine bone-marrow-derived dendritic cells

OBJECTIVE

The purpose of this study was to investigate the effect of 810-nm low level laser therapy (LLLT) on dendritic cells (DC) in vitro.

BACKGROUND DATA

LLLT can enhance wound healing and increase cell proliferation and survival, and is used to treat inflammatory conditions. However there are reports that LLLT can stimulate leukocytes and could therefore be pro-inflammatory. Recently, DC have been found to play an important role in inflammation and immune response.

METHODS

Murine bone-marrow-derived DC were isolated, stimulated with lipopolysaccharide (LPS) or CpG oligodeoxynucleotide and treated with 810-nm laser, using fluences of 0.3, 3, and 30  J/cm(2) delivered at irradiances of 1, 10, and 100  mW/cm(2) respectively. Confocal microscopy, flow cytometry for DC markers, viability using propidium iodide, enzyme-linked immunosorbent assays (ELISA) for secreted interleukin-12 (IL-12), and bioluminescence measurements in cells transduced with a reporter for toll-like receptor (TLR)-9/nuclear factor kappa B (NF-κB) activation, were performed.

RESULTS

LLLT changed the morphology of LPS-stimulated DC, increased their viability, and altered the balance of DC activation markers (major histocompatibility complex [MHC] class 2 up and CD86 down). LLLT reduced IL-12 secretion from DC stimulated by either LPS or CpG. LLLT reduced NF-κB activation in reporter cells stimulated with CpG. There was no obvious light dose response observed.

CONCLUSIONS

Taken together, these data suggest that 810-nm LLLT has an anti-inflammatory effect on activated DC, possibly mediated by cyclic adenosine monophosphate (cAMP) and reduced NF-κB signaling.

Rac1 is required for epithelial stem cell function during dermal and oral mucosal wound healing but not for tissue homeostasis in mice

BACKGROUND

The regenerative capacity of the skin, including the continuous replacement of exfoliated cells and healing of injuries relies on the epidermal stem cells and their immediate cell descendants. The relative contribution of the hair follicle stem cells and the interfollicular stem cells to dermal wound healing is an area of active investigation. Recent studies have revealed that the small GTPase Rac1, which regulates cell migration and nuclear gene expression, is required for hair follicle stem function but not for the normal homeostasis of the interfollicular skin.

METHODOLOGY/PRINCIPAL FINDINGS

Here we explored whether Rac1 contributes to wound healing in the skin and in the oral mucosa, the latter an anatomical site that presents similar architecture to that of the skin but is devoid of any hair follicle structures, and hence lacks hair follicle stem cells. Epidermal Rac1 gene excision led to the clearly delayed closure of cutaneous wounds. Remarkably, genetic ablation of Rac1 from the oral mucosa resulted in the complete inability of oral wounds to heal. We present evidence that the lack of oral mucosal re-epithelization may result from the reduced migratory capacity of cells lacking Rac1 together with altered expression of injury-induced proliferative and cellular stress-related expression programs.

CONCLUSIONS/SIGNIFICANCE

Together, these observations support that while the normal development and homeostasis of the interfollicular skin and oral mucosa do not require Rac1 function, the interfollicular and oral epithelial stem cells may require a Rac1-dependent program to orchestrate the tissue response to injury and ultimate for wound closure. Ultimately, these findings may enable the molecular characterization of the acute tissue regenerative response of these stem cell populations, thus facilitating the identification of novel molecular-targeted strategies aimed at accelerating wound closure.

Role of nitric oxide in the reaction of arterial vessels to laser irradiation

Reactivity of arterial vessels in the small intestine mesentery to irradiation with a helium-neon laser before and after NO synthase blockade was studied by means of biomicroscopy. Blood flow velocity and vascular diameter increased under conditions of laser irradiation. During irradiation, arterial vasodilation was inversely related to the initial diameter. After treatment with NO synthase inhibitor, the dilatory response of vessels to laser irradiation was completely abolished (arteries, diameter >80 micro) or decreased by 2 times (arterioles, diameter <50 micro).

A critical role for IkappaB kinase beta in metallothionein-1 expression and protection against arsenic toxicity

Arsenic is a widespread environmental toxic agent that has been shown to cause diverse tissue and cell damage and at the same time to be an effective anti-cancer therapeutic agent. The objective of this study is to explore the signaling mechanisms involved in arsenic toxicity. We show that the IkappaB kinase beta (IKKbeta) plays a crucial role in protecting cells from arsenic toxicity. Ikkbeta(-)(/)(-) mouse 3T3 fibroblasts have decreased expression of antioxidant genes, such as metallothionein 1 (Mt1). In contrast to wild type and IKKbeta-reconstituted Ikkbeta(-)(/)(-) cells, IKKbeta-null cells display a marked increase in arsenic-induced reactive oxygen species (ROS) accumulation, which leads to activation of the MKK4-c-Jun NH(2)-terminal kinase (JNK) pathway, c-Jun phosphorylation, and apoptosis. Pretreatment with the antioxidant N-acetylcysteine (NAC) and expression of MT1 in the Ikkbeta(-)(/)(-) cells prevented JNK activation; moreover, NAC pretreatment, MT1 expression, MKK4 ablation, and JNK inhibition all protected cells from death induced by arsenic. Our data show that two signaling pathways appear to be important for modulating arsenic toxicity. First, the IKK-NF-kappaB pathway is crucial for maintaining cellular metallothionein-1 levels to counteract ROS accumulation, and second, when this pathway fails, excessive ROS leads to activation of the MKK4-JNK pathway, resulting in apoptosis.

Modulation of cutaneous wound healing by ozone: Differences between young and aged mice

Cutaneous tissues are frequently exposed to prooxidative environments, including UV radiation and air pollutants. Among the latter, ozone (O(3)) is of particular concern because of its high and dominating presence in photochemical smog. It is well known that O(3) depletes small molecular weight antioxidants, oxidizes proteins, induces lipid peroxidation and activates cellular responses in various tissues. Using an in vivo model (SKH-1 hairless mice), the interaction between O(3) exposure (0.5ppmx6h/day) and age was examined in relation to cutaneous wound healing. Compared to younger (8 weeks) mice, older (18 months) mice exposed to O(3) (day 0 to day 9 after wounding) exhibited delayed wound closure, increased lipid peroxidation (measured as 4-HNE protein adducts) and protein oxidation (measured as carbonyls concentration) and decreased levels of P-IkappaBalpha and TGFbeta protein. These findings support the hypothesis that oxidant pollutant exposure and age interact so as to disrupt normal wound healing processes.

Response of mouse skin to tattooing: use of SKH-1 mice as a surrogate model for human tattooing

Tattooing is a popular cosmetic practice involving more than 45 million US citizens. Since the toxicology of tattoo inks and pigments used to formulate tattoo inks has not been reported, we studied the immunological impact of tattooing and determined recovery time from this trauma. SKH-1 hairless mice were tattooed using commercial tattoo inks or suspensions of titanium dioxide, cadmium sulfide, or iron oxide, and sacrificed at 0.5, 1, 3, 4, 7, or 14 days post-tattooing. Histological evaluation revealed dermal hemorrhage at 0.5 and 1 day. Acute inflammation and epidermal necrosis were initiated at 0.5 day decreasing in incidence by day 14. Dermal necrosis and epidermal hyperplasia were prominent by day 3, reducing in severity by day 14. Chronic active inflammation persisted in all tattooed mice from day 3 to 14 post-tattooing. Inguinal and axillary lymph nodes were pigmented, the inguinal being most reactive as evidenced by lymphoid hyperplasia and polymorphonuclear infiltration. Cutaneous nuclear protein concentrations of nuclear factor-kappa B were elevated between 0.5 and 4 days. Inflammatory and proliferative biomarkers, cyclooxygenase-1, cyclooxygenase-2, and ornithine decarboxylase protein levels were elevated between 0.5 and 4 days in the skin and decreased to control levels by day 14. Interleukin-1 beta and interleukin-10 were elevated in the lymph nodes but suppressed in the tattooed skin, with maximal suppression occurring between days 0.5 and 4. These data demonstrate that mice substantially recover from the tattooing insult by 14 days, leaving behind pigment in the dermis and the regional lymph nodes. The response seen in mice is similar to acute injury seen in humans, suggesting that the murine model might be a suitable surrogate for investigating the toxicological and phototoxicological properties of ingredients used in tattooing.

Dietary supplementation of N-acetylcysteine enhances early inflammatory responses during cutaneous wound healing in protein malnourished mice

Prolonged wound healing is a complication that contributes to the morbidity and mortality of protein malnutrition (PM). The molecular mechanisms that underlie impaired wound healing in PM may begin in the early inflammatory stage of the process. We hypothesized that the impaired wound healing observed in PM occurs as a consequence of excessive reactive oxygen species (ROS) production that impairs the wound healing process by depressing nuclear factor kappa B (NFkappaB) activation and the subsequent synthesis and release of proinflammatory cytokines that are critical mediators of the inflammatory response. In this study, we showed that the time to wound closure was significantly prolonged in PM mice. During the early wound healing in PM, inhibitory kappa B alpha (IkappaBalpha), interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) expression and neutrophil infiltration were significantly decreased in PM mice. The role of excess ROS in PM was demonstrated by using transgenic mice with overexpression of copper zinc superoxide dismutase and with dietary supplementation of N-acetylcysteine (NAC). Both interventions improved the extent of wound closure in PM mice. Moreover, NAC supplementation in PM mice restored the expression of IkappaBalpha, IL-1beta and TNF-alpha and infiltration of neutrophils to levels observed in control animals. These findings support the notion that wound healing defects in PM may result from dysregulation of ROS-mediated and NFkappaB-regulated signaling pathways.

Epidermal growth factor (EGF)-mediated DNA-binding activity of AP-1 is attenuated in senescent human epidermal keratinocytes

The proliferative responses of cells to mitogens decrease during aging, and this may result from age-related defects in signal transduction in response to mitogens. In this study, we have investigated the age-related alteration of responses to epidermal growth factor (EGF) in cultured human keratinocytes that were senesced in vitro by repeated passage. The stimulation with EGF increased the DNA-binding activity of activator protein 1 (AP-1), an important transcription factor for cell proliferation, in young keratinocytes, whereas the binding activity showed little or slight change in the senescent cells. The induced DNA-binding activity of AP-1 in young cells was inhibited by PD 98059, an inhibitor of MEK, and partially inhibited by GF 109203X, an inhibitor of protein kinase C. Western blot analysis demonstrated that EGF induced dramatic increase in the phosphorylation of EGF receptor (EGFR) and extracellular signal-regulated kinases (ERK) in young cells, while this phosphorylation was much less profound in senescent cells. Finally, the application of EGF to young cells resulted in increased phosphorylation of Fra-2, a Fos protein component of the Jun/Fos heterodimer AP-1 complex. This EGF-induced Fra-2 phosphorylation was attenuated in senescent cells. Taken together, our study suggests that the signal transduction mediated by EGF/ERK pathway is altered in senescent human keratinocytes, and this change may be attributed, in part, to the decreased AP-1 transcription activity observed in senescent keratinocytes.

Nuclear factor kappaB activation in pulmonary leukocytes from infants with hyaline membrane disease: associations with chorioamnionitis and Ureaplasma urealyticum colonization

Unresolved pulmonary inflammation in hyaline membrane disease (HMD) may be a precursor to the development of chronic lung disease of early infancy. We investigated whether nuclear factor kappaB (NF-kappaB), a transcription factor that regulates the inflammatory process, is activated in pulmonary leukocytes in tracheal aspirates from premature infants with HMD. A total of 172 samples were obtained from 59 infants, two thirds of whom showed NF-kappaB activation in lung neutrophils and macrophages on at least one occasion. Infants who had activated NF-kappaB showed elevated tumor necrosis factor-alpha concentrations in their tracheal aspirates. These infants also required a longer period of mechanical ventilation support. Almost half of the infants with HMD had antenatal exposure to chorioamnionitis on the basis of placental histopathologic examination. These infants had evidence of activated NF-kappaB and elevated cytokines and were more likely to have Ureaplasma urealyticum colonization in their airways. Together, these observations suggest that NF-kappaB activation in pulmonary leukocytes may be involved in the lung inflammatory process in infants with HMD.

Detection of apoptosis by caspase-3 activation in tracheal aspirate neutrophils from premature infants: relationship with NF-kappaB activation

In premature infants, inflammatory conditions in the lungs may result in the development of chronic lung disease. As neutrophil apoptosis is important for the resolution of inflammation and prevention of tissue injury, we set out to determine the extent of neutrophil apoptosis in tracheal aspirate samples from premature infants. Activation of the transcription factor nuclear factor (NF)-kappaB, which causes a delay in neutrophil apoptosis, was also investigated. We obtained 68 tracheal aspirate samples from 27 infants with median gestation and birthweight of 26 weeks and 860 g, respectively. Apoptosis was assessed by immunofluorescent detection of the active form of caspase-3, this assay being validated with peripheral blood neutrophils. Activation of NF-kappaB was monitored by the nuclear translocation of the p65 subunit, detected by immunofluorescence. Cleaved caspase-3 was detected in 11 of the 68 samples, and a median of 40% of the neutrophils showed activated caspase-3 (range 3-92%). A majority of the samples did not show evidence of apoptosis. Caspase activation was seen in cells with multilobed nuclear morphology, suggesting that early apoptosis was detectable. There was no significant difference in respiratory outcomes between infants with or without neutrophil apoptosis. Seventeen of the 68 samples (25%) had evidence of activated NF-kappaB, and a median of 20% (range 6-41%) of neutrophils showed activation. In all but one tracheal aspirate sample, there was a mutually exclusive relationship between activated caspase-3 and NF-kappaB activation, which supports in vitro observations that NF-kappaB activation delays neutrophil apoptosis.

Gene expression in rat skin induced by irritating chemicals

Occupational skin disease is the second most significant cause of occupational disease, after accidents. Irritation from occupational chemicals such as solvents, hydrocarbons, and surfactants are one cause of this disease. Gene expression studies provide useful information about normal processes in the skin and responses of the skin to exogenous chemicals. We exposed rats, cutaneously, to sodium lauryl sulfate (SLS, 1% and 10% aqueous solution), m-xylene (pure liquid), and d-limonene (pure liquid) for 1 h and measured transcriptional responses at the end of the exposure and 3 h later for comparison with untreated skin samples. Total skin RNA was isolated and analyzed using the Affymetrix RatTox U34 array. Using the Affymetrix software, we found that 234 of approximately 850 genes were detected as present in at least 80% of the normal skin samples. The largest number of these genes was related to metabolism, oxidative/cellular stress, and signal transduction. Limonene caused the largest change in mRNA levels with a total of 34 increased transcripts and 4 decreased transcripts. Xylene treatment resulted in 6 increased transcripts and 14 decreased transcripts, while 10% SLS caused 5 transcripts to increase and 17 to decrease. Only two transcripts were observed to change in skin following a 1% SLS exposure. Sodium lauryl sulfate transcript changes increased with dose and were maximum at 4 h. Limonene transcript changes were more numerous at 1 h than at 4 h. The observed differences may reflect different mechanisms of irritation.

Shikonins, phytocompounds from Lithospermum erythrorhizon, inhibit the transcriptional activation of human tumor necrosis factor alpha promoter in vivo

Tumor necrosis factor alpha (TNF-alpha) contributes to the pathogenesis of both acute and chronic inflammatory diseases and has been a target for the development of new anti-inflammatory drugs. Shikonins, the naphthoquinone pigments present in the root tissues of Lithospermum erythrorhizon Sieb. et Zucc. (Boraginaceae), have been reported to exert anti-inflammatory effects both in vitro and in vivo. In this study, we evaluated the effects of shikonin and its derivatives on the transcriptional activation of human TNF-alpha promoter in a gene gun-transfected mouse skin system by using a luciferase reporter gene assay. The crude plant extract of L. erythrorhizon as well as derived individual compounds shikonin, isobutyryl shikonin, acetyl shikonin, dimethylacryl shikonin and isovaleryl shikonin showed significant dose-dependent inhibition of TNF-alpha promoter activation. Among the tested compounds, shikonin and isobutyryl shikonin exhibited the highest inhibition of TNF-alpha promoter activation and also showed significant suppression of transgenic human TNF-alpha mRNA expression and protein production. We demonstrated that shikonin-inhibitory response was retained in the core TNF-alpha promoter region containing the TATA box and a 48-bp downstream sequence relative to the transcription start site. Further our results indicated that shikonin suppressed the basal transcription and activator-regulated transcription of TNF-alpha by inhibiting the binding of transcription factor IID protein complex (TATA box-binding protein) to TATA box. These in vivo results suggest that shikonins inhibit the transcriptional activation of the human TNF-alpha promoter through interference with the basal transcription machinery. Thus, shikonins may have clinical potential as anti-inflammatory therapeutics.

Immunomodulatory effects of low-intensity near-infrared laser irradiation on contact hypersensitivity reaction

BACKGROUND/PURPOSE

Contact hypersensitivity (CHS) reaction is a useful model for studying the skin immune system and inflammatory reactions in the skin. In this study, an experimental model of CHS reaction was employed to assess immunomodulatory effects of near-infrared (near-IR) low-intensity laser (LIL) irradiation, which is used as adjuvant therapy in dermatology, physical medicine, rheumatology, etc., because of its declared anti-inflammatory, biostimulative and analgesic effects.

METHODS

The effects of near-IR LIL irradiation (lambda=904 nm, irradiance 60 mW/cm2, fluence 3.6 J/cm2) on CHS reaction to 1-chloro-2,4-dinitrochlorobenzene (DNCB) in Albino Oxford rats were examined by irradiating experimental groups of animals before the induction phase of CHS reaction, while nonirradiated animals and animals that received vehicle instead of hapten served as controls. Ear-swelling assay, histopathological examination of H&E preparations of ear skin, computer-assisted image analysis of dermal infiltrate, ear skin organ culture with the determination of cutaneous production of tumour necrosis factor-alpha (by ELISA assay) and nitric oxide (by Griess' assay) were used for measuring the effects of LIL in the elicitation phase of CHS reaction. Cellularity, dendritic cell content, flow cytometry and proliferation assays (spontaneous and in the presence of IL-2 and concanavalin A) of the draining lymph node cells (DLNC) were performed for the assessment of LIL irradiation effects in the induction phase.

RESULTS

In the irradiated group of animals, ear swelling was significantly diminished compared to control animals (101+/-11.5% vs. 58+/-11.6%, P<0.01). This was accompanied by a highly significant decrease in the density of dermal infiltrate (22+/-0.81 vs. 14.2+/-1.75 cells per unit area, P<0.01) and a significant decrease in nitrite levels in the medium conditioned by organ-cultured ear skin (17.63+/-1.91 vs. 3.16+/-1.69 microM NaNO2; P<0.01), while TNF-alpha concentration was not changed. Cellularity and dendritic cell content in DLNC population, as well as the expression of TCR-alpha, CD4, CD8 and CD25, were not changed between irradiated and nonirradiated animals. Proliferation rates of DLNC cultured for 72 h were significantly lower in irradiated animals (17.3+/-4.1 vs. 13.9+/-0.9 x 103 c.p.m.; P<0.01). In cultures of DLNC with added rIL-2 or 0.5 microg/ml of concanavalin A, proliferation rates were also significantly decreased in irradiated animals (34.7+/-3.5 vs. 31.2+/-2. c.p.m. in IL-2-supplemented culture, P<0.01; 70.9+/-6.4 vs. 58.3+/-9.1 x 103 c.p.m. in concanavalin A-supplemented culture, P<0.01). However, this effect was overcome in the presence of the higher concentration of concanavalin A (2.5 microg/ml) (nonirradiated 38.7+/-3.1, irradiated 123.1+/-7.3 x 103 c.p.m., P<0.01).

CONCLUSION

LIL irradiation showed a systemic immunomodulatory effect on CHS reaction to DNCB in rats. Decreased ear swelling observed in the elicitation phase was associated with diminished proliferative responses of the DLNC in the induction phase of CHS reaction. Further experimental work is needed to examine the possible mechanisms of these effects.

Inhibition of ultraviolet B-mediated activation of nuclear factor kappaB in normal human epidermal keratinocytes by green tea Constituent (-)-epigallocatechin-3-gallate

Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, possesses significant anti-inflammatory and cancer chemopreventive properties. Studies have shown the photochemopreventive effects of green tea and EGCG in cell culture, animal models, and human skin. The molecular mechanism(s) of photochemopreventive effects of EGCG are incompletely understood. We recently showed that EGCG treatment of the normal human epidermal keratinocytes (NHEK) inhibits ultraviolet (UV)B-mediated activation of the mitogen-activated protein kinase (MAPK) pathway. In this study, we evaluated the effect of EGCG on UVB-mediated modulation of the nuclear factor kappa B (NF-kappaB) pathway, which is known to play a critical role in a variety of physiological functions and is involved in inflammation and development of cancer. Immunoblot analysis demonstrated that the treatment of NHEK with EGCG (10-40 microM) for 24 h resulted in a significant inhibition of UVB (40 mJ/cm(2))-mediated degradation and phosphorylation of IkappaBalpha and activation of IKKalpha, in a dose-dependent manner. UVB-mediated degradation and phosphorylation of IkappaBalpha and activation of IKKalpha was also observed in a time-dependent protocol (15 and 30 min, 1, 2, 3, 6, 12 h post-UVB exposure). Employing immunoblot analysis, enzyme-linked immunosorbent assay, and gel shift assay, we demonstrate that EGCG treatment of the cells resulted in a significant dose- and time-dependent inhibition of UVB-mediated activation and nuclear translocation of a NF-kappaB/p65. Our data suggest that EGCG protects against the adverse effects of UV radiation via modulations in NF-kappaB pathway, and provide a molecular basis for the photochemopreventive effect of EGCG.

Transcription factor activation in response to cutaneous injury: role of AP-1 in reepithelialization

Reepithelialization is the process responsible for restoring an intact epidermis following cutaneous injury. A change in the activity of keratinocytes is required for reepithelialization to occur, and this is likely to be regulated by the altered expression of effector genes, mediated by transcription factors. The injury itself provides a stimulus for transcription factor activation either directly due to mechanical stress, or via paracrine mechanisms such as the release of growth factors from damaged cells. Members of the activator protein-1 family, in particular c-fos and c-jun, have been the most widely studied wound-induced transcription factors. The signal transduction pathways linking cellular injury to activator protein-1 stimulation appear to involve an increase in intracellular Ca2+ and activation of mitogen-activated protein kinases. Given that a number of genes involved in the reepithelialization of wounds are regulated by activator protein-1, a distinct role for this transcription factor in reepithelialization is beginning to emerge. This article reviews the evidence for activator protein-1 involvement in reepithelialization, with particular focus on the activation of this transcription factor in response to wounding, the second messenger/kinase pathways involved, and the modulation of downstream genes that have the capacity to regulate keratinocyte function.

Interferon regulatory factor 4 contributes to transformation of v-Rel-expressing fibroblasts

The avian homologue of the interferon regulatory factor 4 (IRF-4) and a novel splice variant lacking exon 6, IRF-4DeltaE6, were isolated and characterized. Chicken IRF-4 is expressed in lymphoid organs, less in small intestine, and lungs. IRF-4DeltaE6 mRNA, though less abundant than full-length IRF-4, was detected in lymphoid tissues, with the highest levels observed in thymic cells. IRF-4 is highly expressed in v-Rel-transformed lymphocytes, and the expression of IRF-4 is increased in v-Rel- and c-Rel-transformed fibroblasts relative to control cells. The expression of IRF-4 from retrovirus vectors morphologically transformed primary fibroblasts, increased their saturation density, proliferation, and life span, and promoted their growth in soft agar. IRF-4 and v-Rel cooperated synergistically to transform fibroblasts. The expression of IRF-4 antisense RNA eliminated formation of soft agar colonies by v-Rel and reduced the proliferation of v-Rel-transformed cells. v-Rel-transformed fibroblasts produced interferon 1 (IFN1), which inhibits fibroblast proliferation. Infection of fibroblasts with retroviruses expressing v-Rel resulted in an increase in the mRNA levels of IFN1, the IFN receptor, STAT1, JAK1, and 2',5'-oligo(A) synthetase. The exogenous expression of IRF-4 in v-Rel-transformed fibroblasts decreased the production of IFN1 and suppressed the expression of several genes in the IFN transduction pathway. These results suggest that induction of IRF-4 expression by v-Rel likely facilitates transformation of fibroblasts by decreasing the induction of this antiproliferative pathway.

Regulation and role of interleukin 6 in wounded human epithelial keratinocytes

Dermal wounding is accompanied by inflammation and the resulting proinflammatory cytokines, including interleukin (IL)-6, are thought to play an important role in the repair process. IL-6 is produced by normal human keratinocytes to various dermatological diseases and we have recently shown it is also required for normal wound repair. However, neither the events responsible for its induction nor its role in repair have been clearly identified. Using a recently developed in vitro wounding model, we demonstrate that IL-6 mRNA is expressed and immunoreactive IL-6 is released from cultures of human epidermal keratinocytes (NHEKs) following wounding. The transcription factors, NF kappa B and NF-IL-6 (C/EBP beta), which coordinately help regulate IL-6 expression, were activated following wounding and preceded the appearance of IL-6. Addition of IL-1 alpha to NHEK cultures increased IL-6 production and activated NF kappa B and C/EBP beta. Addition of the IL-1 alpha receptor antagonist inhibited both IL-6 mRNA expression and the transcription factors following wounding. Immunoreactive IL-1 alpha was detected in the medium following wounding in the absence of new message. Furthermore, addition of IL-6 to NHEK cultures decreased the expression of keratins 1 and 10, differentiation markers of keratinocytes, while proliferation was not affected. Taken together, these data indicate that constitutive keratinocyte-derived IL-1 alpha is a stimulus for IL-6 production in wounded epidermis, the response involves NF kappa B and C/EBP beta transcription factors, and IL-6 may be associated with modulation of keratinocyte differentiation rather than proliferation.

Ozone potentiates vitamin E depletion by ultraviolet radiation in the murine stratum corneum

As the outermost layer of the skin, the stratum corneum is exposed to environmental oxidants. To investigate putative synergisms of environmental oxidative stressors in stratum corneum, hairless mice were exposed to ultraviolet radiation (UV) and ozone (O(3)) alone and in combination. Whereas a significant depletion of alpha-tocopherol was observed after individual exposure to either a 0.5 minimal erythemal dose of UV or 1 ppm O(3) for 2 h, the combination did not increase the effect of UV alone. However, a dose of 0.5 ppm O(3) x 2 h, which had no effect when used alone, significantly enhanced the UV-induced depletion of vitamin E. We conclude that concomitant exposure to low doses of UV and O(3) at levels near those that humans can be exposed to causes additive oxidative stress in the stratum corneum.

Activators and target genes of Rel/NF-kappaB transcription factors

The vertebrate transcription factor NF-kappaB is induced by over 150 different stimuli. Active NF-kappaB, in turn, participates in the control of transcription of over 150 target genes. Because a large variety of bacteria and viruses activate NF-kappaB and because the transcription factor regulates the expression of inflammatory cytokines, chemokines, immunoreceptors, and cell adhesion molecules, NF-kappaB has often been termed a 'central mediator of the human immune response'. This article contains a complete listing of all NF-kappaB inducers and target genes described to date. The collected data argue that NF-kappaB functions more generally as a central regulator of stress responses. In addition, NF-kappaB activation blocks apoptosis in several cell types. Coupling stress responsiveness and anti-apoptotic pathways through the use of a common transcription factor may result in increased cell survival following stress insults.

Activators and target genes of Rel/NF-kappaB transcription factors

The vertebrate transcription factor NF-kappaB is induced by over 150 different stimuli. Active NF-kappaB, in turn, participates in the control of transcription of over 150 target genes. Because a large variety of bacteria and viruses activate NF-kappaB and because the transcription factor regulates the expression of inflammatory cytokines, chemokines, immunoreceptors, and cell adhesion molecules, NF-kappaB has often been termed a 'central mediator of the human immune response'. This article contains a complete listing of all NF-kappaB inducers and target genes described to date. The collected data argue that NF-kappaB functions more generally as a central regulator of stress responses. In addition, NF-kappaB activation blocks apoptosis in several cell types. Coupling stress responsiveness and anti-apoptotic pathways through the use of a common transcription factor may result in increased cell survival following stress insults.