Long-term growth arrest of PUVA-treated fibroblasts in G2/M in the absence of p16(INK4a) p21(CIP1) or p53

Premature aging of the skin is a prominent side-effect of psoralen photoactivation, a therapy used for different skin disorders. Recently, we demonstrated that treatment of fibroblasts with 8-methoxypsoralen and ultraviolet A irradiation resulted in growth arrest with morphological and functional changes reminiscent of replicative senescence. To further elucidate the underlying molecular mechanisms, we analysed the cell-cycle phases of the growth-arrested fibroblasts. After PUVA treatment, fibroblasts arrested in G2/M, in contrast to spontaneously senesced fibroblasts arresting in a cell-cycle phase with many features similar to G1. To address the role of the cell-cycle controlling genes p16(INK4a), p21(CIP1) and p53, we analysed the expression of these genes. p16(INK4a), p21(CIP1) and p53 protein levels increased substantially with different time kinetics in growth-arrested fibroblasts. Because p16(INK4a), p21(CIP1) and p53 are involved in replicative senescence, we applied the PUVA regimen to fibroblasts deficient in either of these genes. p16(INK4a), p21(CIP1) and p53 null mutant fibroblast strains underwent growth arrest with a senescent phenotype similar to wild-type human fibroblasts. Based on these results, we propose that redundant or alternate pathways are involved in the response of dermal fibroblasts to PUVA treatment resulting in a phenocopy of replicative senescence in vitro.     

基质金属蛋白酶表达在皮肤光老化皱纹形成中的作用

目的 探讨皮肤光老化皱纹形成与真皮成纤维细胞基质金属蛋白酶(MMP)-1,MMP-3mRNA及其组织抑制剂(TIMP)-1表达的关系。方法 采用原位杂交和免疫组化的方法检测紫外线光化学疗法(PUVA)治疗期间及治疗后不同时间银屑病患者背部非皮损区真皮成纤维细胞MMP-1,MMP-3mRNA及TIMP-1蛋白的表达并定量分析。结果 在PUVA治疗期间、治疗后1~6个月及治疗后6个月以上的银屑病患者背部非皮损区真皮成纤维细胞均持续表达MMP-1、MMP-3mRNA,而TIMP-1蛋白仅在治疗期间一过性轻度表达。结论 PUVA治疗引起的皮肤光老化皱纹形成可能与真皮成纤维细胞基质金属蛋白酶及其组织抑制剂表达失衡密切相关。     

Heat shocks enhance procollagen type I and III expression in fibroblasts in ex vivo human skin

Background: The well‐known characteristics of aging skin are the development of fine lines and wrinkles, but changes in skin tone, skin texture, thickness and moisture content are also aspects of aging. Rejuvenation of the skin aims at reversing the signs of aging and can be established in the epidermis as well as in the dermis. Aged dermis, in fact, has a degenerated collagen matrix. To regenerate this matrix, fibroblasts need to be stimulated into synthesizing new collagen. Aims: In this study, the effects of heat shocks of different temperatures on human dermal fibroblasts in ex vivo skin on the expression of procollagen 1, procollagen 3, heat shock protein (hsp)27, hsp47, and hsp70 are investigated. Materials and methods: The heat shocks were applied on ex vivo skin samples by immersing the samples in heated phosphate‐buffered saline of 45 °C or 60 °C. Metabolic activity was measured and at similar time points propidium–iodide–calceine staining was performed to establish cell viability. Quantitative polymerase chain reaction (qPCR) was performed after the heat shock to determine gene expression levels relative to the reference temperature. Furthermore, PicroSirius Red and hematoxylin stainings were performed to visualize the collagen network and the cells. Results: The skin samples were shown to be viable and metabolically active. Histology indicated that the heat shocks did not influence the structure of the collagen network or cell appearance. qPCR results showed that in contrast to the 45 °C heat shock the 60 °C heat shock resulted in significant upregulations of procollagen type I and III, hsp70 and hsp47. Conclusion: A 60 °C, heat shock stimulates the human dermal fibroblasts in ex vivo skin to upregulate their procollagen type I and type III expression.     

The occurrence of vitiligo after psoralens and ultraviolet a therapy

The ability of photochemotherapy with 8-methoxypsoralen in conjunction with high-intensity long-wave ultraviolet light (PUVA) to stimulate melanogenesis is well known. This effect on the pigmentary system is evidenced by the diffuse tanning of clinically normal skin in PUVA-treated patients with psoriasis and other disorders, as well as by the repigmentation of lesions in vitiligo. It is now recognized that there may be additional pigmentary effects, resulting in clinical lesions such as PUVA mottling, PUVA lentigines, and localized hypopigmentation. We have documented the occurrence of yet another association with PUVA therapy--the paradoxical appearance of widespread hypopigmentation consistent with vitiligo in three PUVA-treated patients, one with psoriasis and two with mycosis fungoides. Histologic and ultrastructural findings are presented.     

Effect of long-term PUVA treatment of psoriasis on the collagen and elastin gene expression and growth of skin fibroblasts in vitro

The proliferation rate, collagen metabolism and collagen and elastin messenger-RNA levels were studied in fibroblasts derived from patients who had received many courses of either systemic 8-methoxypsoralen or topical trioxsalen PUVA treatment. The proliferation rate of fibroblasts as measured by the incorporation of 3H-thymidine or by cellular division was decreased in those obtained from patients who had PUVA treatment as compared with controls. Collagen synthesis was slightly increased in the cells from PUVA-treated patients, but the relative collagen synthesis and the ratio between types I and III collagen were unchanged. The levels of collagen and elastin mRNAs were increased in fibroblasts derived from the PUVA-treated patients. No significant differences in histology or immunochemistry could be found in the biopsies taken from topical and systemic PUVA-treated patients.     

PUVA therapy decreases HLA-DR+ CD1a+ Langerhans cells and epidermal cell antigen-presenting capacity in human skin, but flow cytometrically-sorted residual HLA-DR+ CD1a+Langerhans cells exhibit normal alloantigen-presenting function

We have investigated the effects of PUVA therapy on human Langerhans cell (LC) immunophenotype and function. Epidermal sheets were obtained from exposed, and control shielded, forearm skin at the end of a course of PUVA therapy, in patients receiving treatment routinely for a variety of dermatoses. PUVA therapy decreased the overall number of HLA-DR+CDIa+ LCs in epidermal sheets, and in epidermal cell (EC) suspensions examined using a fluorescence activated cell sorter (FACS). PUVA therapy also reduced the overall EC allostimulatory capacity in the allogeneic epidermal cell-lymphocyte reaction (ELR), and the capacity of ECs to present tetanus toxoid to, and augment concanavalin A-mediated stimulation of, lymphocytes in the autologous ELR. Depressed allostimulation by ECs from PUVA-treated skin could not be restored by indomethacin (added to block prostaglandin synthesis). The reductions in LC numbers and EC allostimulatory capacity varied according to dose, and time since cessation, of PUVA therapy, and in individual patients were of comparable degree. By contrast, the allostimulatory capacity of residual LCs from PUVA-treated skin (purified using the FACS) did not differ from that of purified control LCs. PUVA-induced suppression of cutaneous immune responses, therefore, results at least in part from an overall impairment of EC antigen-presenting capacity. Residual HLA-DR+CDIa+ LCs in PUVA-treated skin which retain their alloantigen-presenting function may represent a subgroup of PUVA-resistant LCs; alternatively, these cells may be as yet unaffected because they have only recently migrated into the epidermis.     

Osteopontin gene is expressed in the dermal papilla of pelage follicles in a hair-cycle-dependent manner

Hair follicle formation and maintenance involve intimate interactions between follicular epithelial cells and a group of specialized mesenchymal cells known as the dermal papilla. Using the random primer polymerase chain reaction, we have identified an approximately 1.4 kb osteopontin mRNA that is present in large quantities in cultured rat vibrissa dermal papilla cells but undetectable in cultured rat skin fibroblasts. In situ hybridization showed that the osteopontin gene is expressed in dermal papilla cells of pelage follicles during catagen but not in anagen or telogen. As an acidic glycosylated RGD-containing extracellular matrix protein, osteopontin can function both as a cell attachment protein and as a soluble cytokine playing roles in signaling, cell migration, tissue survival, anti-inflammation, and T-cell-mediated cellular immunity. Our results indicate that the comparison of the mRNA of cultured dermal papilla cells and fibroblasts can lead to the identification of not only anagen-specific genes (e.g., nexin 1), but also a catagen-specific gene. We have thus provided evidence that specific genes are turned on during catagen, which is therefore not simply a passive "degenerative" phase. The functional role of osteopontin in catagen is unclear but it may promote the formation of a tightly aggregated dermal papilla, and/or protect the dermal papilla cells from apoptosis induced by cytokines or hypoxia during catagen.     

Phototoxic erythema following PUVA treatment: independence of complement

The effect of PUVA treatment on normal human serum (NHS), on isolated PMN, or on C3-deficient guinea pigs and congenic (C3-competent) control animals was tested. At a concentration of 0.1 or 1 mM/l 8-MOP and UVA doses of 5-30 J/cm2, PUVA failed to induce any detectable C3-cleavage in NHS. Furthermore, when the complement (C) activation in NHS had been induced before or after PUVA treatment by various methods. PUVA did not modulate the extent of C3-cleavage. PUVA did not affect the viability of isolated PMN, nor did it induce a release of LDH or elastase. No differences between C3-deficient and C-competent guinea pig skin exposed to PUVA were observed in erythema or histologic responses. Immunohistologic examination of specimens from normal guinea pigs revealed C3b and C3d deposits on necrotic keratinocytes, findings restricted to the PUVA-treated areas. Necrosis of keratinocytes was present in skin specimens of C3-deficient animals from PUVA-treated sites to a similar extent. However, deposits of C3-related antigens were completely absent there. From these observations, we suggest that the induction of phototoxic erythema following PUVA treatment is independent of complement.     

8-MOP/UVA诱导培养真皮成纤维细胞衰老的作用

目的　探讨以 8 MOP/UVA作用于培养真皮成纤维细胞建立皮肤光老化模型的可行性。方法　采用光镜、电镜、流式细胞仪、酶组织化学、免疫组织化学等方法检测 8 MOP/UVA对培养真皮成纤维细胞多项细胞衰老相关指标的影响。结果　 8 MOP/UVA作用后 ,培养真皮成纤维细胞迅速出现细胞衰老特征性的形态学及生物学特性改变 :细胞由分裂表型转化为无分裂活性表型 ,SA β Gal表达增加、p16蛋白表达增加。结论　 8 MOP/UVA可诱导培养真皮成纤维细胞迅速出现具有细胞衰老特征性的形态学及生物学特性改变 ,以 8 MOP/UVA作用于培养真皮成纤维细胞建立皮肤光老化模型是可行的     

Biological consequences of 8-methoxypsoralen-photoinduced lesions: sequence-specificity of mutations and preponderance of T to C and T to a mutations

Psoriatic patients undergoing psoralen plus ultraviolet radiation (PUVA) therapy are susceptible for squamous cell carcinoma and melanoma of the skin. To investigate the etiological relevance of PUVA for these diseases, we performed mutation spectrometry on the cII transgene in mouse embryonic fibroblasts treated with a single or split PUVA dose (PUVA-I or PUVA-II, respectively). Both treatments were significantly mutagenic as they increased the cII mutant frequency up to 3.7-fold over background, and produced different mutational spectra from that derived spontaneously (p<0.01), but not from one another. The signature of induced mutations, i.e., T to C transitions and T to A transversions with significant site-specificities, i.e., adjacent to T bases at the 3'-neighboring side and to pyrimidines at the 5'-neighboring side, was more pronounced after PUVA-II treatment. Also, the overall mutations occurring at T bases with the same site-specificities were more prevalent after PUVA-II treatment. The characteristic PUVA-induced mutations predominate in the p53 mutational spectrum in controlled in vivo test systems or in high-dose PUVA-treated patients, and also are easily recognizable in the overall PUVA-treated patients. We conclude that PUVA-induced mutagenesis is initiated by PUVA-I treatment and subsequently, augmented by PUVA-II treatment, leaving a unique mutational signature on the cII transgene. The signature mutations of PUVA are discernible in the p53 mutational spectrum in PUVA-treated patients but complex exposure to other therapeutic/environmental carcinogens also leads to the frequent occurrence of other types of mutations in this population.     

H2O2 accumulation by catalase reduction changes MAP kinase signaling in aged human skin in vivo

To understand the molecular alterations occurring during the aging process, we compared mitogen-activated protein (MAP) kinase activities in the intrinsically aged and photoaged skins in the same individuals. Furthermore, we investigated the molecular events related to MAP kinase changes in intrinsically aged and photoaged skins. We found that extracellular-signal-regulated kinase (ERK) activity in photoaged skin was reduced, and that the activities of c-Jun N-terminal kinase (JNK) and p38 kinase were increased compared with intrinsically aged skin in the same individuals. Phospho-c-Jun levels and activator protein 1 activities in photoaged skin were also higher than in intrinsically aged skin. Moreover, catalase activity was found to be much reduced in primary dermal fibroblasts from photoaged skin, and as a result, H2O2 accumulated more in primary dermal fibroblasts in photoaged skin. In addition, treating primary dermal fibroblasts from photoaged skin with catalase reduced H2O2 levels, reversed aging-dependent MAP kinase changes, and inhibited matrix metalloproteinase (MMP)-1 expression. Our results indicate that the accumulation of reactive oxygen species due to catalase attenuation may be a critical aspect of the MAP kinase signaling changes that may lead to skin aging and photoaging in human skin in vivo. Thus, the induction and regulation of endogenous antioxidant enzymes including catalase may offer a strategy for preventing and treating skin aging.     

PUVA-induced blisters, complement deposition, and damage to the dermoepidermal junction

We followed the course of 56 patients receiving psoralen plus long-wave ultraviolet light (PUVA) therapy. Nonhemorrhagic blisters developed on clinically normal skin on the limbs of seven patients. Seeming to be related to friction and trauma, the blisters form as a result of damage to the basal and suprabasal layers. Perilesional skin specimens from all blistered patients contained granular deposits of C3 at the dermoepidermal junction, around the upper dermal blood vessels, or at both sites. The average time for initiation and complete formation of suction blisters was measured in 51 patients at different stages during the course of PUVA treatment. Blister separation was in the lamina lucida, with the pemphigoid antigen in the roof while the blister floor contained the lamina densa, laminin, and type IV collagen. This impaired dermoepidermal adhesion was a general phenomenon that occurred in all PUVA-treated patients. The mechanism remains to be determined.