An innovative targeted therapy for fluoroscopy-induced chronic radiation dermatitis

Fluoroscopy-induced chronic radiation dermatitis (FICRD) is a complication of fluoroscopy-guided intervention. Unlike acute radiation dermatitis, FICRD is different as delayed onset and usually appears without preexisting acute dermatitis. Unfortunately, the chronic and progressive pathology of FICRD makes it difficult to treat, and some patients need to receive wide excision and reconstruction surgery. Due to lack of standard treatment, investigating underlying mechanism is needed in order to develop an effective therapy. Herein, the Hippo pathway is specifically identified using an RNA-seq analysis in mild damaged skin specimens of patients with FICRD. Furthermore, specific increase of the Yes-associated protein (YAP1), an effector of the Hippo pathway, in skin region with mild damage plays a protective role for keratinocytes via positively regulating the numerous downstream genes involved in different biological processes. Interestingly, irradiated-keratinocytes inhibit activation of fibroblasts under TGF-β1 treatment via remote control by an exosome containing YAP1. More importantly, targeting one of YAP1 downstream genes, nuclear receptor subfamily 3 group C member 1 (NR3C1), which encodes glucocorticoid receptor, has revealed its therapeutic potential to treat FICRD by inhibiting fibroblasts activation in vitro and preventing formation of radiation ulcers in a mouse model and in patients with FICRD. Taken together, this translational research demonstrates the critical role of YAP1 in FICRD and identification of a feasible, effective therapy for patients with FICRD. KEY MESSAGES: • YAP1 overexpression in skin specimens of radiation dermatitis from FICRD patient. • Radiation-induced YAP1 expression plays protective roles by promoting DNA damage repair and inhibiting fibrosis via remote control of exosomal YAP1. • YAP1 positively regulates NR3C1 which encodes glucocorticoid receptor expression. • Targeting glucocorticoid receptor by prednisolone has therapeutic potential for FICRD patient.

Topical Application of Phlorotannins from Brown Seaweed Mitigates Radiation Dermatitis in a Mouse Model

Radiation dermatitis (RD) is one of the most common side effects of radiotherapy; its symptoms progress from erythema to dry and moist desquamation, leading to the deterioration of the patients’ quality of life. Active metabolites in brown seaweed, including phlorotannins (PTNs), show anti-inflammatory activities; however, their medical use is limited. Here, we investigated the effects of PTNs in a mouse model of RD in vivo. X-rays (36 Gy) were delivered in three fractions to the hind legs of BALB/c mice. Macroscopic RD scoring revealed that PTNs significantly mitigated RD compared with the vehicle control. Histopathological analyses of skin tissues revealed that PTNs decreased epidermal and dermal thickness compared with the vehicle control. Western blotting indicated that PTNs augmented nuclear factor erythroid 2-related factor 2 (NRF2)/heme oxygenase-1 (HO-1) pathway activation but attenuated radiation-induced NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) and inflammasome activation, suggesting the mitigation of acute inflammation in irradiated mouse skin. PTNs also facilitated fast recovery, as indicated by increased aquaporin 3 expression and decreased γH2AX (histone family member X) expression. Our results indicate that topical PTN application may alleviate RD symptoms by suppressing oxidative stress and inflammatory signaling and by promoting the healing process. Therefore, PTNs may show great potential as cosmeceuticals for patients with cancer suffering from radiation-induced inflammatory side effects such as RD.

The ion channel, TRPM2, contributes to the pathogenesis of radiodermatitis

Radiodermatitis is a painful side effect for cancer patients undergoing radiotherapy. Irradiation of the skin causes inflammation and breakdown of the epidermis and can lead to significant morbidity and mortality in severe cases, as seen in exposure from accidents or weapons such as "dirty bombs" and ultimately leads to tissue fibrosis. However, the pathogenesis of radiodermatitis is not fully understood. Using a mouse model of radiodermatitis, we showed that the Transient Receptor Potential Melastatin 2 (TRPM2) ion channel plays a significant role in the development of dermatitis following exposure to ionizing radiation. Irradiated TRPM2-deficient mice developed less inflammation, fewer severe skin lesions and decreased fibrosis when compared to wild type mice. The TRPM2-deficient mice also showed a faster recovery period as seen by their increased weight gain post irradiation. Finally, TRPM2-deficient mice exhibited lower systemic inflammation with a reduction in inflammatory cytokines present in the serum. These findings suggest that TRPM2 may be a potential therapeutic target for reducing the severity of radiodermatitis.

18β-Glycyrrhetinic acid mitigates radiation-induced skin damage via NADPH oxidase/ROS/p38MAPK and NF-κB pathways

Radiation-induced inflammation plays an important role in radiation-induced tissue injury. 18β-glycyrrhetinic acid (18β-GA) has shown an anti-inflammatory activity. This study aimed to assess the activity of 18β-GA against radiation-induced skin damage, and explore the underlying mechanisms. In vitro assay revealed 18β-GA treatment decreased the production of IL-1β, IL-6, PGE2 and decreased p38MAPK phosphorylation, DNA-binding activity of AP-1, and NF-κB activation in irradiated RAW264.7 macrophages. Additionally, 18β-GA suppressed NF-κB activation by inhibiting NF-κB/p65 and IκB-α phosphorylation and alleviated ROS overproduction in irradiated RAW264.7 macrophages. In vivo assay showed 18β-GA alleviated severity of radiation-induced skin damage, reduced inflammatory cell infiltration and TNF-α, IL-1β and IL-6 levels in cutaneous tissues. Our findings demonstrate that 18β-GA exhibits anti-inflammatory actions against radiation-induced skin damage probably by inhibiting NADPH oxidase activity, ROS production, activation of p38MAPK and NF-κB signaling, and the DNA binding activities of NF-κB and AP-1, consequently suppressing pro-inflammatory cytokine production.

A novel Nrf2 activator from microbial transformation inhibits radiation-induced dermatitis in mice

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcriptional factor that regulates many antioxidants, and we have recently succeeded in obtaining a novel Nrf2 activator, RS9, from microbial transformation. RS9 is categorized as a triterpenoid, and well-known triterpenoids such as RTA 402 (bardoxolone methyl) and RTA 408 have been tested in clinical trials. RTA 408 lotion is currently being tested in patients at risk for radiation dermatitis. This prompted us to study the profiles of RS9 in the skin. All the above triterpenoids increased the level of an Nrf2-targeted gene, NADPH:quinone oxidoreductase-1, in normal human epidermal keratinocytes. Among them, the activity of RS9 was prominent; furthermore, the cellular toxicity was less compared with RTA compounds. BALB/c mice were irradiated with 30 Gy/day on Day 0, and compounds were topically applied on the back once daily from Day 1 to Day 30. Dermatitis scores peaked on Day 18, with a score of 2.6 in vehicle-treated mice, and topical applications of 0.1% RTA 402, RTA 408 and RS9 reduced the scores to 1.8, 2.0 and 1.4, respectively. Moreover, the percentage of animals with scores ≥2 was analyzed, and 0.1% RS9 suppressed the percentage from 100% to 47%. These results imply that RS9 has potential efficacy for treating radiation dermatitis.

Protective effect of inhalation of hydrogen gas on radiation-induced dermatitis and skin injury in rats

The effect of inhalation of hydrogen-containing gas (1.3% hydrogen + 20.8% oxygen + 77.9% nitrogen) (HCG) on radiation-induced dermatitis and on the healing of healing-impaired skin wounds in rats was examined using a rat model of radiation-induced skin injury. An X-ray dose of 20 Gy was irradiated onto the lower part of the back through two holes in a lead shield. Irradiation was performed before or after inhalation of HCG for 2 h. Inhalation of HCG significantly reduced the severity of radiodermatitis and accelerated healing-impaired wound repair. Staining with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and 8-hydroxy-2(')-deoxyguanosine (8-OHdG) showed that the proportion of apoptotic keratinocytes and the level of staining in the X-irradiated skin of rats that pre-inhaled HCG were significantly lower than that of rats which did not pre-inhale HCG. Cutaneous full-thickness wounds were then created in the X-irradiated area to examine the time-course of wound healing. X-irradiation significantly increased the time required for wound healing, but the inhalation of HCG prior to the irradiation significantly decreased the delay in wound healing compared with the control and post-inhalation of HCG groups. Therefore, radiation-induced skin injury can potentially be alleviated by the pre-inhalation of HCG.

Role and mechanism of radiological protection cream in treating radiation dermatitis in rats

OBJECTIVE

To explore the role and mechanism of a radiation protection cream (Rp) in the treatment of radiation dermatitis, and to accumulate necessary technical information for a new drug report on Rp.

METHODS

High-performance liquid chromatography was used to establish the method of measuring the main effective ingredients of sovereign and adjuvant herbs of Rp drugs, and to formulate the draft quality standards of Rp. A total of 48 Sprague-Dawley male rats were randomly divided into the Model, Trolamine cream (Tc), Rp and Blank groups according to a random number table method. The skin of each rat's buttocks was irradiated using an electron linear accelerator to establish an acute radiation dermatitis model. The histological changes were observed under light microscopy and electron microscopy during wound healing and the effect of Rp on rat fibroblast Ku70/80 gene expression was detected at the transcriptional level.

RESULTS

Pathological examination revealed that Rp protected the cellular and subcellular structures of skin after irradiation, promoting the proliferation and restoration of collagen fibers. Ku70/80 mRNA expression levels in the Rp and Tc groups were higher than that in the model group (P < 0.05). Moreover, The majority of grade radiation dermatitis relative to the Model, Rp and Tc groups for reducing grade III and IV dermatitis efficiency were 85.7% and 69.2% (P < 0.05), respectively. The efficacy of Rp group in treating radiation dermatitis was better than the Trolamine cream group by 16.5% (P < 0.05).

CONCLUSION

Compared with Tc, Rp had certain advantages in the efficacy and performance to price ratio. Thus, Rp is considered an effective alternative formulation for the prevention and treatment of radiation dermatitis.

A synthetic superoxide dismutase/catalase mimetic EUK-207 mitigates radiation dermatitis and promotes wound healing in irradiated rat skin

In the event of a radionuclear attack or nuclear accident, the skin would be the first barrier exposed to radiation, though skin injury can progress over days to years following exposure. Chronic oxidative stress has been implicated as being a potential contributor to the progression of delayed radiation-induced injury to skin and other organs. To examine the causative role of oxidative stress in delayed radiation-induced skin injury, including impaired wound healing, we tested a synthetic superoxide dismutase (SOD)/catalase mimetic, EUK-207, in a rat model of combined skin irradiation and wound injury. Administered systemically, beginning 48 hours after irradiation, EUK-207 mitigated radiation dermatitis, suppressed indicators of tissue oxidative stress, and enhanced wound healing. Evaluation of gene expression in irradiated skin at 30 days after exposure revealed a significant upregulation of several key genes involved in detoxication of reactive oxygen and nitrogen species. This gene expression pattern was primarily reversed by EUK-207 therapy. These results demonstrate that oxidative stress has a critical role in the progression of radiation-induced skin injury, and that the injury can be mitigated by appropriate antioxidant compounds administered 48 hours after exposure.

Effect of pigmentation density upon 2.0 microm laser irradiation thermal response

Yucatan mini-pigs with predominantly dark skin have been used to determine skin safety standards for infrared (IR) wavelength irradiation due to its anatomical similarity to all human skin. It has generally been argued that water is the principle absorber in the IR-B band and melanin has relatively low absorbance. To accept dark pigmented damage thresholds for skin with various melanin densities, it is necessary to investigate the potential role of melanin in producing skin injury as characterized by an erythermal response. A Yucatan mini-pig covered with lightly pigmented pink and darkly pigmented brown skin was used in this study. The significance of skin pigmentation was investigated by comparing the transient thermal response, absorption coefficient, and the threshold damage of instant redness within 1 min and persistent redness at 48 h post exposure for dark and light skin areas at 2.0 microm wavelength. The density of melanin granules did not significantly alter the thermal and optical properties of in vivo skin exposed to 2.0 microm laser irradiation. For Gaussian shaped beam radiation at 1 s exposure duration and 4.83 mm 1/e spot diameter, the average radiant exposures at instant and persistent redness thresholds were 3.88 J cm and 5.08 J cm for dark skin, respectively, as well as 4.09 J cm and 4.09 J cm for light colored skin. Subjectively speaking, however, lightly pigmented mini-pig skin was more suitable for damage threshold estimation because of the increased contrast for visual determination of redness on light skin.

Endogenous phospholipid metabolite containing topical product inhibits ultraviolet light-induced inflammation and DNA damage in human skin

BACKGROUND

N-palmitoylethanolamine (PEA) and organic osmolytes are endogenous components of the human epidermis and are generated from phospholipids in the stratum granulosum. PEA has been shown to exert potent antioxidant and anti-inflammatory activities. The endogenous organic osmolytes such as betaine and sarcosine control skin humidity, but have also been shown to inhibit ultraviolet (UV) light-induced oxidative stress in keratinocytes.

OBJECTIVES

To investigate the effect of a PEA- and organic osmolyte-containing topical product (Physiogel AI) on the development of UV light-induced erythema, thymine dimer formation and p53 tumor suppressor gene activation, as well as intercellular adhesion molecule 1 (ICAM-1) and Ki67 expression in normal human skin.

METHODS

The UV-induced erythema was measured by a spectrofluorometric method. Thymine dimers, p53, ICAM-1 and Ki67 were detected in skin biopsies using immunohistochemistry.

RESULTS

Physiogel AI cream significantly inhibited the development of UV light-induced erythema and thymine dimer formation in normal human skin, but did not alter the number of Ki67+ proliferating keratinocytes and the expression of p53 and ICAM-1.

CONCLUSIONS

Our results suggest that PEA and organic osmolytes might represent a new generation of compounds which suppress UV-induced photodamage.

Erbb2 regulates inflammation and proliferation in the skin after ultraviolet irradiation

Exposure to ultraviolet (UV) irradiation is the major cause of nonmelanoma skin cancer, the most common form of cancer in the United States. UV irradiation has a variety of effects on the skin associated with carcinogenesis, including DNA damage and effects on signal transduction. The alterations in signaling caused by UV regulate inflammation, cell proliferation, and apoptosis. UV also activates the orphan receptor tyrosine kinase and proto-oncogene Erbb2 (HER2/neu). In this study, we demonstrate that the UV-induced activation of Erbb2 regulates the response of the skin to UV. Inhibition or knockdown of Erbb2 before UV irradiation suppressed cell proliferation, cell survival, and inflammation after UV. In addition, Erbb2 was necessary for the UV-induced expression of numerous proinflammatory genes that are regulated by the transcription factors nuclear factor-kappaB and Comp1, including interleukin-1beta, prostaglandin-endoperoxidase synthase 2 (Cyclooxygenase-2), and multiple chemokines. These results reveal the influence of Erbb2 on the UV response and suggest a role for Erbb2 in UV-induced pathologies such as skin cancer.

Radiation-induced cutaneous carcinoma of the head and neck: is there an early role for p53 mutations?

BACKGROUND

Little is known about the molecular mechanisms underlying ionizing radiation-induced carcinogenesis of the skin.

AIMS

To investigate the possible role of p53 in radiodermatitis and in the development of radiation-induced cutaneous carcinomas.

METHODS

The study group comprised six patients affected by cutaneous carcinomas arising in radiodermatitis (one squamous cell carcinoma and five basal cell carcinomas), and seven patients presenting only chronic radiodermatitis. Skin specimens were evaluated for p53 immunohistochemical expression. Using laser-assisted microdissection, areas with different p53 immunoreactivity were separately submitted to DNA isolation and p53 gene analysis.

RESULTS

In the majority of cases (9/12, 75%), p53 immunoreactivity was detected in radiation-damaged epidermis. In carcinomas p53 oncoprotein was expressed by several neoplastic cells in one case (16.7%%), or by nearly all neoplastic cells in four (66.7%). SSCP band shifts were detected in 9/25 samples (36%) microdissected from irradiated epidermis and in 3/6 (50%) carcinomas. DNA sequencing demonstrated two repeatedly found mutations: a G deletion at codon 244 and an A-->G transition at codon 205, as well as hallmarks of ultraviolet mutagenic action, including a C-->T transition occurring at a dipyrimidine site and a CC-->TT tandem double-base transition.

CONCLUSION

Our data indicate that irradiation induces significant p53 alterations that may be relevant in the modification of epithelial maturation processes and may be responsible for the high risk for development of carcinomas in radiodermatitis.

Protective effect of esculentoside A on radiation-induced dermatitis and fibrosis

PURPOSE

To investigate the effect of esculentoside A (EsA) on radiation-induced cutaneous and fibrovascular toxicity and its possible molecular mechanisms, both in vivo and in vitro.

METHODS AND MATERIALS

Mice received drug intervention 18 hours before 30 Gy to the right hind leg. Alterations in several cytokines expressed in skin tissue 2 days after irradiation were determined by ELISA. Early skin toxicity was evaluated 3 to 4 weeks after irradiation by skin scoring, and both tissue contraction and expression of TGF-beta1 were determined for soft-tissue fibrosis 3 months after irradiation. In vitro, the effect of EsA on radiation-induced nitric oxide (NO) and cytokine production in different cell types was measured by application of 2, 4, and 8 Gy.

RESULTS

In vivo, EsA reduced levels of IL-1alpha, MCP-1, VEGF, and TGF-beta1 in cutaneous tissue and reduced soft-tissue toxicity. In vitro, EsA inhibited the IL-1alpha ordinarily produced after 4 Gy in A431 cells. In Raw264.7 cells, EsA reduced levels of IL-1alpha, IL-1beta, and NO production costimulated by radiation and lipopolysaccharide (LPS). In L-929 cells, EsA inhibited VEGF, TNF, and MCP-1 production at 2, 4, and 8 Gy.

CONCLUSIONS

Esculentoside A protects soft tissues against radiation toxicity through inhibiting the production of several proinflammatory cytokines and inflammatory mediators in epithelial cells, macrophages, fibroblasts, and skin tissue.

Interleukin 1beta (IL1B) signaling is a critical component of radiation-induced skin fibrosis

Interleukin 1 beta (IL1B), a potent pro-inflammatory cytokine, is directly up-regulated by radiation and is known to regulate other inflammation-related molecules, such as the matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs). However, the nature of the interaction of IL1B with MMPs and TIMPs in radiation-induced skin fibrosis is unknown. We examined the response of primary dermal keratinocytes, fibroblasts and endothelial cells to single-fraction radiation (10 Gy) and compared the results to a temporal sequence of histology from irradiated C57BL/6 and IL1R1 knockout mice. These studies showed that keratinocytes are the major IL1-producing cells in vitro and that radiation induces an immediate and chronic elevation in the expression of IL1B mRNA in the skin of C57BL/6 mice. This elevation was principally early and was less pronounced in the IL1R1 knockout strain, which also demonstrated reduced late radiation fibrosis. Radiation also increased expression of MMP mRNA in C57BL/6 mice. Finally, exogenous IL1B protein induced robust endogenous IL1B mRNA expression, along with a brisk increase in MMPs and collagen III, but only in the C57BL/6 mice. In conclusion, these data suggest that IL1B plays a critical role in radiation-induced fibrosis and that the increased MMPs fail to block the IL1-related collagen accumulation.

Identification of Skin injury-related genes induced by ionizing radiation in human keratinocytes using cDNA microarray

The skin is an external organ that is most frequently exposed to radiation. High-dose radiation initiates and promotes skin cancer and acute radiation injury. It is important to investigate the influence of high-dose radiation exposure on the skin at the molecular level to understand acute radiation injury. To identify genes that are associated with injury caused by high-dose radiation exposure of the skin, we used microarray technology to examine the effect of irradiation on approximately 1000 genes in normal human epidermal keratinocytes at 3 h postirradiation with a cytotoxic dose of X-ray (5 Gy). We found that 16 and 59 genes were up- and down-regulated respectively in the keratinocytes. Several apoptosis-related genes, for example, BAK and TSC-22, and anti-proliferative genes, for example, BTG-1 and BTG-3, were up-regulated. We focused on ATF3 because ATF3 is induced most strongly by X-irradiation, and its function in keratinocytes is unknown. The induction of the ATF3 mRNA and protein in keratinocytes following X-ray was confirmed by RT-PCR and western blot analysis. ATF3 was also induced and accumulated within the nuclei of keratinocytes after X-ray irradiation in vivo and in vitro. Exogenous EYFP-ATF3 also accumulated within the nuclei of keratinocytes. In the transient expression assay, EYFP-ATF3, but not EYFP, induced apoptosis in keratinocytes. Taken together, these results suggest that ATF3 plays a role in apoptosis in keratinocytes and is associated with skin injury caused by ionizing radiation.

Prolonged recovery of ultraviolet B-irradiated skin in neuropsin (KLK8)-deficient mice

BACKGROUND

Neuropsin (KLK8), a serine protease of the kallikrein family, is thought to be involved in the function of keratinocytes, i.e. migration, differentiation and desquamation. However, how neuropsin participates is still unknown.

OBJECTIVE

To observe the epidermal function of serine protease in neuropsin-deficient mice.

METHODS

We irradiated the skin of neuropsin-deficient mice with ultraviolet light to induce acute inflammation and compared the morphology with that of wild-type mice.

RESULTS

We observed a phenotypic change in the epidermis. An acute inflammatory dose of ultraviolet light induced a marked increase in neuropsin mRNA expression in the skin. The signal intensity of the mRNA expression was highest on day 2-3 after irradiation, when keratinocytes were aligned irregularly in the recovery period. Morphological comparison between neuropsin -/- and +/+ mice revealed that an irregular alignment of cells in the thickened epidermis was obvious on day 2 after irradiation in the wild-type mice, whereas it was prolonged for at least 2 days in the neuropsin-deficient mice. The stratum corneum of neuropsin-deficient mice was remarkably thicker than that of the wild-type mice at 5, 14 and 21 days after irradiation. The increase, as a response to this stimulus, in involucrin immunoreactivity, a marker for cell envelope assembly, was delayed in the mutant mice.

CONCLUSIONS

Thus, neuropsin might be involved early in the process of differentiation, such as in the assembly of the cell envelope, but not in migration and desquamation.

Celecoxib reduces skin damage after radiation: selective reduction of chemokine and receptor mRNA expression in irradiated skin but not in irradiated mammary tumor

Inflammatory cytokine and chemokine production is mediated, at least in part, by prostaglandin E (PGE2). Cyclooxygenases, COX-1 and COX-2, are two key enzymes in the conversion of arachidonic acid to PGE2. Radiation induces the overproduction of cytokines and chemokines, and it also increases PGE2 production, both locally and systemically. In this study, we tested the effects of a COX-2 inhibitor (celecoxib) after 50 Gy radiation of MCa-35 tumor and cutaneous tissues of C3H/He mice. Preclinical toxicity endpoints and associated alterations in chemokine production and cellular infiltrates were measured. Celecoxib was given by daily gavage (50 mg/kg for 15 days), with the first dose delivered either 2 hours before, 2 days after, or 7 days after a single dose of radiation. Celecoxib-treated animals had less inflammation of the dermis compared with saline-treated controls. Severe skin dermatitis occurred in 23.8% (5/21) of mice treated with 50 Gy, whereas only 17.6%, 5.3%, and 11.1% of mice in the 2-hour pre-, or the 2-day post-, and 7-day postirradiation groups, respectively, had severe dermatitis on day 20. The decreased skin toxicity scores were associated with a reduction of both blood vessels and focal necrosis in MCa-35 tumors. Celecoxib also significantly decreased C-C family chemokine (Rantes and MCP-1) mRNA expression in irradiated skin tissues, but not in tumor tissues, which was accompanied by a decrease in skin mRNA expression of both C-C (CCR2 and CCR5) and C-X-C (CXCR2 and CXCR4) chemokine receptors. A significant positive correlation was also found between skin damage (skin scores) and chemokine and its receptor mRNA expression in radiation-treated mice. Finally, celecoxib also decreased the infiltration of monocytes and neutrophils in locally irradiated tumor and surrounding normal tissue. The differential effects of celecoxib on inflammation help to explain the selective protection by celecoxib of irradiated cutaneous tissues without a concurrent protection of MCa-35 tumors.

Reduction of acute photodamage in skin by topical application of a novel PARP inhibitor

The ultraviolet (UV) components of sunlight induce damage to the DNA in skin cells, which is considered to be the initiating step in the harmful biological effects of UV radiation. Repair of DNA damage results in the formation of single-strand DNA breaks, which activate the nuclear poly(ADP-ribose) polymerase (PARP). Overactivation of PARP worsens the oxidative cell damage and impairs the energy metabolism, raising the possibility that moderation of PARP activation following DNA damage may protect skin cells from UV radiation. The topical effects of the novel PARP inhibitor O-(3-pyperidino-2-hydroxy-1-propyl) pyridine-3-carboxylic acid amidoxime monohydrochloride (BGP-15M) were investigated on UV-induced skin damage in a hairless mouse model. For evaluation of the UV-induced acute photodamage to the skin and the potential protective effect of BGP-15M, DNA injury was detected by measuring the formation of single-strand DNA breaks and counting the resulting sunburn (apoptotic) cells. The ADP-ribosylation of PARP was assessed by Western blot analysis and then quantified. In addition, the UV-induced immunosuppression was investigated by the immunostaining of tumor necrosis factor alpha and interleukin-10 expressions in epidermal cells. The signs of inflammation were examined clinically and histochemically. Besides its primary effect in decreasing the activity of nuclear PARP, topically applied BGP-15M proved to be protective against solar and artificial UV radiation-induced acute skin damage. The DNA injury was decreased (P<0.01). An inhibition of immunosuppression was observed by down-regulation of the epidermal production of cytokines IL-10 and TNFalpha. In the mouse skin, clinical or histological signs of UV-induced inflammation could not be observed. These data suggest that BGP-15M directly interferes with UV-induced cellular processes and modifies the activity of PARP. The effects provided by topical application of the new PARP-regulator BGP-15M indicate that it may be a novel type of agent in photoprotection of the skin.

Green tea polyphenol (-)-epigallocatechin-3-gallate treatment of human skin inhibits ultraviolet radiation-induced oxidative stress

The use of naturally occurring botanicals with substantial antioxidant activity to afford protection to human skin against UV damage is receiving increasing attention. The green tea constituent (-)-epigallocatechin-3-gallate (EGCG) is a potent antioxidant and has shown remarkable preventive effects against photocarcinogenesis and phototoxicity in mouse models. In this study we have investigated the effects of topical application of EGCG, the major polyphenol present in green tea, to human skin before UV irradiation on UV-induced markers of oxidative stress and antioxidant enzymes. Using immunohistochemistry and analytical enzyme assays, we found that application of EGCG (mg/cm(2) skin) before a single UV exposure of 4x minimal erythema dose (MED) markedly decreases UV-induced production of hydrogen peroxide (68-90%, P < 0.025-0.005) and nitric oxide (30-100%, P < 0.025-0.005) in both epidermis and dermis in a time-dependent manner. EGCG pretreatment also inhibits UV-induced infiltration of inflammatory leukocytes, particularly CD11b(+) cells (a surface marker of monocytes/macrophages and neutrophils), into the skin, which are considered to be the major producers of reactive oxygen species. EGCG treatment was also found to inhibit UV-induced epidermal lipid peroxidation at each time point studied (41-84%, P < 0.05). A single UV exposure of 4x MED to human skin was found to increase catalase activity (109-145%) and decrease glutathione peroxidase (GPx) activity (36-54%) and total glutathione (GSH) level (13-36%) at different time points studied. Pretreatment with EGCG was found to restore the UV-induced decrease in GSH level and afforded protection to the antioxidant enzyme GPx. Further studies are warranted to study the preventive effects of EGCG against multiple exposures to UV light of human skin.

Induction of p53 expression in skin by radiotherapy and UV radiation: a randomized study

BACKGROUND

p53 protein plays an important role in the response to DNA damage, and radiotherapy can cause radiation dermatitis. p53 and p21 levels increase in vitro when DNA is damaged by UVA, UVB, or gamma-radiation. To determine whether this response occurs in human skin and predicts the level of radiation dermatitis, we investigated levels of p53 and p21 in skin exposed to different types of radiation as part of a randomized study of women with breast cancer to evaluate topical steroid or emollient cream treatments for radiation dermatitis of their irradiated breast.

METHODS

After surgery but before receiving tangential 5-mV photo-beam radiotherapy (2 Gy and 54 Gy) to the affected breast parenchyma, multiple areas on the backs of 50 women were irradiated with UVA and other areas were irradiated with UVB. Skin biopsy samples were taken from areas of normal unirradiated skin and all irradiated areas, and p53 and p21 were detected immunohistochemically. All statistical tests are two-sided.

RESULTS

In skin irradiated with UVA or UVB, medians of 4.4% (range = 0%-40.5%) or 45.5% (range = 5.3%-74.6%) p53-positive keratinocytes, respectively, were observed. Radiotherapy produced medians of 31.0% (range = 0%-79.3%) p53-immunoreactive cells after 2 Gy of radiation and 83.2% (range = 37.6%-95.2%) after 54 Gy of radiation. Despite large interindividual differences in p53 response, comparable increases in epidermal p53 response were independent of the type of radiation. A correlation between p53 and p21 was also evident (r(s) =.78). In breast skin, there was no association between the p53 response and the degree of erythema (a measure of radiation dermatitis) and no statistically significant difference between treatment arms and p21/p53 responses.

CONCLUSIONS

Individual responses to radiation-induced DNA damage varied widely and may be independent of the type of radiation. The epidermal p53 response does not predict the degree of radiation dermatitis.

Abnormal phenotype of cultured fibroblasts in human skin with chronic radiotherapy damage

PURPOSE

The pathophysiological aspects of radiation-induced fibrosis (RIF) have not been well characterized. We therefore cultured human fibroblasts from samples of skin with RIF to investigate the long-term effects of therapeutic irradiation.

MATERIALS AND METHODS

Biopsies of normal and RIF skin were obtained from patients previously irradiated for cancer, without recurrence. Cells were extracted from dermis samples by the outgrowth technique, seeded as monolayers and cultured at confluence. Enzyme activities and proteins were assayed, RNA was isolated and Northern blot analysis was performed on surviving cells between passages 2 and 5.

RESULTS

RIF cell cultures displayed heterogeneous fibroblasts populations. The initial outgrowth consisted of one-third small cells that floated rapidly, one-third spindle-shaped cells migrating far from the explant to form islets and one-third large pleiomorphic cells. In subsequent subcultures, surviving cells exhibited either myofibroblastic characteristics with a normal proliferative capacity or senescent morphology with a reduced proliferative capacity. These RIF cells had a brief finite lifespan, with dramatically reduced growth rate during their initial outgrowth and the following passages. Study of the antioxidant metabolism showed that Mn superoxide dismutase and catalase activities were significantly weaker in surviving RIF cells than healthy fibroblasts. These exhausted RIF cells exhibited no overexpression of transforming growth factor beta or tissue inhibitor of metalloproteinase.

CONCLUSION

Irradiation may lead to apparently contradictory effects such as fibrosis and necrosis in clinical practice. In cell culture, we observed two main cellular phenotypes which may be related to both processes, i.e. myofibroblast-like cells and fibrocyte-like cells. These two phenotypes may represent two steps in the differentiation induced as a long-term effect of therapeutic irradiation of the skin. Cell culture probably accelerates the induction of the terminal differentiation in RIF fibroblasts.

[Physiopathology of human superficial radiation-induced fibrosis]

The radiation-induced fibrosis is a late sequela of both therapeutic and accidental irradiations, and has been described in several tissues such as skin and underlying sub-cutaneous tissues, and lung. Based on the newest findings arising from cellular and molecular radiobiology, this review synthesis different aspects of the human superficial radiation-induced fibrosis: clinical and paraclinical observations, radiobiological aspects, gross histological changes, cellular and molecular regulations, and medical management. However, the underlying mechanisms of the superficial radiation-induced fibrosis still remain to be resolved.

An immunohistochemical analysis of radiation fibroblasts

A commonly recognized feature of chronic radiation dermatitis is the presence of mesenchymal cells with large atypical nuclei known as radiation fibroblasts. Little is known about their lineage or potential for neoplastic transformation. To investigate these properties, we examined 16 biopsy specimens in which radiation fibroblasts were present with antisera to mesenchymal determinants (FXIIIa, CD34, HHF-35), a proliferation marker (Ki-67), and a tumor-suppressor protein that is overexpressed in many cancers (p53). Radiation fibroblasts were largely negative for the markers of lineage that we employed - only 2 of 16 specimens showed strong expression of FXIIIa, with weak expression in another case. Scattered radiation fibroblasts expressed CD34 in one case. HHF-35 (muscle specific actin) stained small, dendritic cells in the superficial dermis, but not radiation fibroblasts. P53 was not detected within radiation fibroblasts in any of our cases, but was overexpressed by endothelial cells in 2 cases. Ki-67 stained rare endothelial and interstitial cells but not radiation fibroblasts. Radiation fibroblasts are immunophenotypically distinct from dermal dendrocytes and myofibroblasts. They appear to be non-cycling cells, and do not express high levels of p53 despite their marked nuclear atypia. Their phenotype argues against their possible role as progenitors of atypical fibroxanthoma (AFX) and dermatofibrosarcoma protuberans (DFSP) which are associated with ionizing radiation-induced skin damage.

Expression of 72-kDa gelatinase (MMP-2), collagenase (MMP-1), and tissue metalloproteinase inhibitor (TIMP) in primary pig skin fibroblast cultures derived from radiation-induced skin fibrosis

In addition to producing matrix degradation for normal tissue remodeling and repair, matrix metalloproteinases (MMPs) are also involved in various pathologic processes. MMPs and the tissue inhibitor of MMPs (TIMP) were investigated in primary cultures of pig fibroblasts from radiation-induced dermal fibrosis and compared to normal dermal fibroblasts. The free gelatinolytic, collagenolytic, and caseinolytic activities secreted into the culture medium were evaluated against specific 3H denatured collagen type I, native helical collagen, and casein alpha, respectively. The 72- and 68-kilodalton (kDa) forms of type IV collagenase were investigated by protease zymography and quantified by semi-automated image analysis. Transcription of the interstitial collagenase (MMP-1) and TIMP genes was studied by Northern hybridization analysis. Results revealed that in fibrotic fibroblasts, the amount of MMP-1 mRNA was greatly reduced to undetectable levels whereas the amount of TIMP mRNA was increased fourfold compared to controls. Functional assays using specific 3H substrates demonstrated an overall decrease in free MMP activities. Concomitantly, catheptic collagenolytic activity decreased in fibrotic fibroblast extracts compared to controls. These results indicate that in addition to accumulating large amounts of collagen, proteoglycans, and fibronectin, pig fibroblasts from radiation-induced dermal fibrosis also promote connective tissue matrix formation by repressing MMP-1 and stimulating TIMP expression at the transcriptional level, and by reducing overall free MMP and catheptic collagenolytic activities at the post-transcriptional level. In contrast, enzymography assays and automated image analysis demonstrated no significant change in the 72-kDa type IV collagenase activity of fibrotic pig skin fibroblasts. This opposite regulation of 72-kDa collagenase type IV to that of MMP-1 seems to indicate that it has a specific role in remodeling the extracellular matrix during wound healing, fibrogenesis, and angiogenesis.

Polyvinylpyrrolidone (povidone) storage in RX-damaged skin following procaine-povidone intramuscular injections

A man, aged 67, has been treated in 1968 by X-rays for a basal-cell carcinoma of the back. The treatment was followed by an ulcerative radiodermatitis. 3 years later, the patient was treated by ten intramuscular injections of procaine-polyvinylpyrrolidone (or procaine-povidone) for sciatic neuralgia. An orange infiltration appeared progressively around the radiodermatitis. The area was excised in 1979 and polyvinylpyrrolidone (povidone) storage, responsible for the ring-shaped orange hue, could be demonstrated in the dermis and subcutaneous fat. Special stainings confirmed the presumed chemical nature of the deposits. 3 cases of povidone pseudotumours following procaine-povidone injections had been described previously. The preferential deposit of povidone in RX-damaged skin is discussed.