[Reciprocity regulation in photobiology. An overview]

According to the rule of Bunsen and Roscoe, a photochemical reaction is directly proportional to the total energy dose, irrespective of the time over which this dose is delivered. To date few studies have addressed the validity of this rule in experimental and applied photobiology. Most of these data point to the fact that the rule of reciprocity is invalid or of limited validity for many photobiological reactions. For UV-induced cell death, photocarcinogenesis, psoralen photochemistry, and the effects of low level laser radiation it has been shown that at a constant total dose, the intensity of the source is a major factor that determines quality and quantity of the response. In clinical photomedicine systematic investigations on the reciprocity of exposure time and radiation intensity are lacking. Such studies are urgently needed since it can be concluded from experimental evidence, that their results might lead to therapeutic regimens with an improved therapeutic index, i.e. maximized therapeutic efficacy with minimized adverse reactions.

Treatment of peripheral blood mononuclear cells with 8-methoxypsoralen plus ultraviolet A radiation induces a shift in cytokine expression from a Th1 to a Th2 response

Treatment with 8-methoxypsoralen plus ultraviolet A radiation and extracorporeal photochemotherapy (photopheresis) are widely used for the treatment of psoriasis and other inflammatory skin diseases, graft-versus-host disease, and mycosis fungoides. As the ratio of Th1 and Th2 cells appears to be critical for pathogenesis and progression of these disorders the effect of psoralen plus ultraviolet A on Th1 and Th2 cytokine production by CD4+ lymphocytes was investigated. Human peripheral blood lymphocytes were incubated in the presence of anti-CD3, rh-IL2, and rh-IL4 for 48 h. After subsequent stimulation with rh-IL2 and rh-IL4 for 72 h cells were treated with 8-methoxypsoralen (100, 500, 1000 ng per ml) plus ultraviolet A (2 J per cm2) and incubated for a further period of 5 h in the presence of ionomycine, phorbol-12-myristate acetate and monensin. Fluorescence-activated cell sorter analysis revealed a significant reduction of interleukin-2- and interferon-gamma-producing CD4+ cells upon psoralen plus ultraviolet A treatment depending on the concentration of 8-methoxypsoralen. In contrast, interleukin-4-producing CD4+ cells were increased, indicating a shift from Th1 to a Th2 cell cytokine profile upon psoralen plus ultraviolet A treatment. These results indicate that 8-methoxypsoralen photochemotherapy of lymphocytes is able to modulate their Th1/Th2 distribution. Inhibition of Th1 cytokine expression by psoralen plus ultraviolet A might help to explain its beneficial effects in the treatment of Th1 dominated skin diseases.

UVA and UVB radiation differentially regulate vascular endothelial growth factor expression in keratinocyte-derived cell lines and in human keratinocytes

Vascular endothelial growth factor (VEGF) is a central regulator of neoangiogenesis in inflammatory and neoplastic conditions. Ultraviolet irradiation is one of the mainstays of dermatological therapy for various inflammatory skin diseases. In the present study we have compared the effects of UV irradiation on the production of VEGF by keratinocytes (KC) and by the KC-derived cell lines A431 and HaCaT. Irradiation of A431 and HaCaT cells with both UVA (10 J/cm2 and 20 J/cm2) and UVB (8 mJ/cm2 and 16 mJ/cm2) led to strong upregulation of VEGF mRNA and protein. Induction of VEGF by UVA and UVB in these cells was mediated by different pathways, i.e. the generation of free radicals and the secretion of (a) soluble factor(s), respectively. Unlike KC-derived cell lines, no increase in VEGF production was observed in KC in primary culture after irradiation with the same UV doses. Increasing the irradiation dose in these cells of UVA to 40 J/cm2 led to a marked decrease in soluble VEGF, whereas doses as high as 32 mJ/cm2 UVB only minimally affected VEGF levels. Reduction of VEGF production by KC might contribute to the effect of UVA irradiation in inflammatory skin diseases. The differential response of primary KC and autonomously growing KC-derived cell lines to the induction of VEGF by UV light could favor neoangiogenesis in the vicinity of epidermal tumor cells in vivo, thereby endowing them with a growth advantage over normal cells.

Expression of the 72-kD heat shock protein is induced by ultraviolet A radiation in a human fibrosarcoma cell line

The 72-kD heat shock protein (hsp72) belongs to a family of stress inducible proteins (heat shock proteins, hsp) and its expression is associated with increased survival of cells in culture following exposure to ultraviolet radiation (UV). Hsp72 can be induced by a number of stresses, including heat, cold, and toxic chemicals. The purpose of this study was to evaluate whether UV is able to activate transcription of hsp72. The human fibrosarcoma cell line HT1080 was used for these experiments because hsp72 is not detectable in these cells under normal culture conditions. Cells were exposed to UVA and UVB using a solar simulating source and hsp72 was determined in whole cell extracts by immunoblotting. For inhibition of mRNA and protein synthesis cordycepin (20 microg/ml) and cycloheximide (10 microg/ml) were added to the cultures, respectively. UVA-induced lipid peroxidation was inhibited by alpha-tocopherol and butylated hydroxytoluene (BHT). UVA but not UVB induced hsp72 with maximal expression at 40 J/cm2, 8-12 h after exposure. Induction was blocked by cordycepin as well as by cycloheximide indicating that both, mRNA and protein synthesis, are required for UVA-induction of hsp72. Inhibition of cell lipid peroxidation with alpha-tocopherol and BHT had no effect on hsp72 expression. These results suggest that induction of hsp72 is part of an adaptive response mechanism in human cells to UV-related stress.

Expression of the small heat shock protein HSP 27 in developing human skin

The 27 kDa heat shock protein (HSP 27) is expressed in keratinocytes of the upper epidermal layers, and recent evidence suggests that this protein is involved in the regulation of epidermal differentiation. The expression of HSP 27 was investigated in developing human skin by immunohistochemistry utilizing a specific monoclonal antibody. We used formalin-fixed, paraffin-embedded tissue of abdominal skin obtained from 34 human fetuses ranging between 13 and 30 weeks estimated gestational age (EGA). We found that HSP 27 is not expressed in keratinocytes until week 14 EGA. At this stage staining is observed in the periderm and the upper intermediate cells but not in hair germs. During further development, HSP 27 expression correlates with increasing epidermal differentiation, i.e. shedding of the periderm and beginning of keratinization. HSP 27 expression is confined to the upper cell layers and sparse basal cells. In hair follicles, HSP 27 can be detected in the innermost cell layer of the outer root sheath and in keratinocytes of the bulge identical to what is observed in adult skin. The hair papilla, matrix cells and sebaceous glands are negative for HSP 27 and remain so during further development. In eccrine sweat glands of the 24th week EGA, HSP 27 is confined to the superficial cell layer of the sweat ducts. In the present report we demonstrate differentiation-related expression of HSP 27 in developing human skin. Further in vitro studies will address the molecular function of HSP 27 in epidermal differentiation and development.

Flow cytometric quantification of UV-induced cell death in a human squamous cell carcinoma-derived cell line: dose and kinetic studies

Exposure to ultraviolet (UV) radiation and photochemotherapy induces apoptotic cell death in epidermal cells. In this study annexin V binding and propidium iodide (PI) uptake have been measured by flow cytometry to evaluate UV-induced cell death in the human squamous cell carcinoma-derived cell line A 431. Physiological and therapeutical relevant doses of UVA, UVA1, UVB, narrow-band UVB (311 nm) and photochemotherapy using 100 ng/ml of 8-methoxypsoralen (8-MOP) with UVA or UVA1 (PUVA or PUVA1) have been applied. Doses ranged from 8 to 96 J/cm2 for UVA1 and UVA, from 8 to 128 mJ/cm2 for UVB, from 256 to 4096 mJ/cm2 for narrow-band UVB (311 nm) and from 1 to 16J/cm2 for photochemotherapy. Results show that the amount of annexin V binding, a measure of early apoptosis, as well as PI uptake, a parameter of ultimate cell death, are strictly correlated with the applied UV dose. Peak values of annexin V-positive cells are noted 12 h after UV exposure in all protocols and are followed by an increase of PI-uptaking cells with peak values at 24 h after UVA and UVA1, and 48 h after PUVA, PUVA1, UVB and narrow-band UVB. To compare the effect of different wavelengths and light sources, dose equivalents are calculated based on the induction of 50% cell death (as determined by PI uptake). The equivalents are 96 J/cm2 for UVA and UVA1, 16 J/cm2 for PUVA and PUVA1, 256 mJ/cm2 for UVB and 2048 mJ/cm2 for narrow-band UVB. Our results establish annexin V/PI double staining as an appropriate method for the quantification of UV-induced cell death. Moreover, they provide a basis for further investigations concerning mechanisms and modifications of UV-induced apoptosis.

Modification of growth in small heat shock (hsp27) gene transfected breast carcinoma

The role of hsp27 in the regulation of cell growth has been investigated in the breast cancer cell line MDA-MB-23 1. Cells were co-transfected with an expression vector carrying the human hsp27 gene (pSG-2711) and a plasmid conferring neomycin resistance (pWlneo). Transfected cells were selected for neomycin resistance. Stable transfectants were used as a pooled population for further experiments, since single-cell colonies were not able to grow into mass culture under continuous selection pressure. Over-expression of hsp27 was analysed by immunohistochemistry and immunoblotting. Cells only transfected for neomycin were used as control cells. The growth rate of the transfected cell line was determined whether overexpression of hsp27 directly influences the growth properties of the cells. Growth analysis of transfected cell lines in vitro revealed a lower proliferation rate of the hsp27 overexpressing cells compared to controls. These data suggest that hsp27 is involved in downregulation of cell proliferation in this human breast cancer cell line.

Mispriming and PCR amplification of hsp27

No Abstract Available

Linear focal elastosis (elastotic striae): increased number of elastic fibres determined by a video measuring system

We present an unusual case of linear focal elastosis occurring exclusively on the legs of a 13-year-old girl. An increase of elastic fibres (EF) was demonstrated histologically, and the number of EF in lesional and normal skin was quantified using a video measuring system. EF were found to be increased by about 100% in lesional skin compared with unaffected skin. EF were elongated, thinned and split at their ends with a paintbrush formation.

Photopheresis treatment enhances CD95 (fas) expression in circulating lymphocytes of patients with systemic sclerosis and induces apoptosis

We investigated the effects of photopheresis in systemic sclerosis by analysing its influence on lymphocytes with regard to apoptosis and expression of bcl-2 and fas. Peripheral blood lymphocytes isolated immediately before and 24 h after photopheresis were investigated for apoptosis, bcl-2 and fas expression by fluorocytometry, and compared to controls. In addition, leucocytes from systemic sclerosis patients taken directly from the photopheresis system were tested for apoptosis after 24 h in culture. fas expression was similar in controls and patients with systemic sclerosis just before photopheresis, but increased 24 h after photopheresis, mainly due to an increase of CD4+CD95+ cells. bcl-2 was overexpressed in scleroderma peripheral lymphocytes, but not influenced by photopheresis. As compared to healthy controls, the percentage of apoptotic cells 24 h after photopheresis was high in cultured lymphocytes, but not ex vivo. The significant increase in fas on peripheral lymphocytes observed in this study may be a major operative mechanism of photopheresis in addition to (and possibly related to) the induction of apoptosis.

Overexpression of the small heat shock protein, hsp27, confers resistance to hyperthermia, but not to oxidative stress and UV-induced cell death, in a stably transfected squamous cell carcinoma cell line

The 27 kD heat shock protein (hsp27) is expressed in human keratinocytes in association with differentiation in vitro and in situ. This study was conducted to investigate whether the expression of hsp27 in keratinocytes is associated with increased resistance to the deleterious effects of heat and UV radiation. A transfection vector carrying the human gene for hsp27, under the control of hsp27 as well as the SV40 promoter (pSG2711, M. Jäättelä et al., EMBO J. 11 (1992) 3507-3512), was introduced together with a neomycin-resistance gene into the squamous cell carcinoma cell line A431. Cells were exposed to either UVA, UVB, head (45 degrees C, 4 h) or hydrogen peroxide (0.025-0.5 mM) and the percentage of surviving cells was determined. Overexpression of hsp27 induced increased resistance to hyperthermia, but not to hydrogen peroxide-mediated oxidative injury. When cells were exposed to increasing amounts of UVA (5-80 J cm-2) and UVB (4-64 mJ cm-2), the percentage of surviving cells was identical for clones overexpressing hsp27 and control clones. From these data, we conclude that hsp27 is a mediator of thermotolerance, but does not protect keratinocytes from UV-induced cell death.

alpha-Melanocyte stimulating hormone downregulates differentiation-driven heat shock protein 70 expression in keratinocytes

Heat shock proteins are versatile tools engaged in several cellular functions. In particular, the stress-inducible 70-kDa heat shock protein (hsp70) not only confers protection on cells but also is involved in the regulation of the production of cellular stress response mediators including cytokines. In addition to cytokines, neurohormones such as alpha-melanocyte stimulating hormone (alphaMSH) were recently found to be potent mediators of inflammatory and immune responses. Thus, the current study was performed to investigate the role of alphaMSH in the expression of hsp70 in a human keratinocyte cell line (HaCaT). Proliferation and differentiation of HaCaT cells are known to be regulated by changing extracellular Ca2+ concentrations. HaCaT cells induced to differentiate in high Ca2+ medium (1.5 mM) were found to express higher levels of hsp70 protein than cells grown under low Ca2+ conditions. Moreover, differentiated HaCaT cells were markedly more resistant to oxidative stress than undifferentiated control cells. alphaMSH significantly suppressed hsp70 expression in a concentration-dependent manner in differentiated HaCaT cells but had only a minor effect on undifferentiated cells. Upon treatment with alphaMSH, HaCaT cells grown in high Ca2+ medium were rendered more sensitive to oxidative stress, which significantly decreased their survival rate. These findings indicate that alphaMSH, which is released by keratinocytes in an autocrine fashion following injurious stimuli such as tumor promoters or ultraviolet light, is able to regulate the cells' cytoprotective protein equipment.

Increased release of the tumour necrosis factor receptor p75 by immortalized human keratinocytes results from an activated shedding mechanism and is not related to augmented steady-state levels of p75 mRNA

The soluble tumour necrosis factor receptor I (sTNFRI, p55) is produced at similar levels by both immortalized (A431, HaCaT, KB) and primary normal human keratinocytes (HNK), whereas the soluble TNFR II (sTNFR II, p75) appears to be specifically released only by immortalized human keratinocytes. The purpose of this study was to investigate whether the increase in p75 secretion by immortalized human keratinocytes is due to an increased shedding of the receptor from the cell membrane, or is related to increased steady-state levels of p75 mRNA. FACS analysis showed that levels of membranous p75 decreased in a time-dependent manner in immortalized cells cultured for 1, 3, 6, 12 and 24 h, while remaining unchanged in HNK throughout. Northern blot analysis showed that after 12 h of culture, when p75 expression was decreased on the cell membrane of all immortalized cells, there was no significant difference in steady state levels of p75 mRNA between immortalized keratinocytes and HNK. Supernatants of immortalized cells, cultured for 24 h contained distinct levels of p75, while levels of p75 in supernatants of HNK were under the detection limit, confirming that the p75 decrease on the cell membrane results from increased p75 shedding from the cell membrane of immortalized cells. In contrast to p75, p55 was continuously expressed on the cell membrane of normal and immortalized keratinocytes without significant variation throughout the entire 24-h culture period and was similarly shed by both cell types. These results suggest that immortalized keratinocytes are specifically activated for shedding of p75 from the cell membrane. Since p75 has a high affinity for TNF, the release of this receptor may imply a direct role in the escape of malignant/transformed keratinocytes from the TNF-mediated immune response.

Stress proteins in the cellular response to ultraviolet radiation

Virtually all cells-from prokaryotes to highly differentiated mammalian tissues-respond to a sudden increase in temperature with increased production of a limited set of proteins, called heat shock proteins or stress proteins (hsp). Other stress factors such as alcohol, heavy metals, oxidants and agents leading to protein denaturation are equally able to induce a similar response. Induction of hsp is followed by a transient state of increased resistance to further stress. Many hsp function as "molecular chaperones" by binding to partially folded or misfolded proteins thus preventing their irreversible denaturation during stress exposure. The high evolutionary conservation of this reaction suggests its importance for the survival of cells and tissues under hostile environment conditions. Ultraviolet radiation (UV) exerts many potentially harmful effects on prokaryotic and eukaryotic cells and hsp may help the cell to cope with UV-induced damage. This review will focus on the role of hsp in the cellular response of mammalian skin to UV. Hsp have been detected in resting as well as stress exposed epidermal and dermal cells and experimental evidence points to the fact that these proteins mediate protection from UV induced cell death in vitro and in vivo. Experimental studies further indicate that UV itself might be able to induce the expression of specific hsp. Thus, hsp might provide an adaptive cellular response to increasing exposure to UV. Furthermore, UV-activation of hsp synthesis may provide a valuable model for investigation of the transcription regulation of UV-induced gene expression.

Modification of growth and tumorigenicity in epidermal cell lines by DNA-mediated gene transfer of M(r) 27,000 heat shock protein (hsp27)

In the present communication, the role of the M(r) 27,000 human small heat shock protein (hsp27) in tumorigenicity was examined. Stable transfectants of a melanoma cell line (A375) and an epidermal squamous carcinoma cell line (A431), isolated by cotransfection of a hsp27 expression vector (pSG-2711) and a neomycin-resistant plasmid, were obtained. Clones expressing high levels of hsp27 were analyzed using immunohistochemistry and immunoblotting. Cells transfected with only the plasmid for neomycin were used as control cells. Growth analysis of transfectants in A375 and A431 tumor cells showed in vitro a lower proliferation rate than control clones derived from both lines. To investigate the correlation of hsp27 expression and tumorigenicity, transfectants of each cell type and control cells were injected into nude mice. A delay in tumor development was detected in animals inoculated with cells overexpressing hsp27. However, after this initial delay, tumors appeared in some of these animals and no difference could be observed in their growth dynamics compared to control tumors. When tumors transfected with the hsp27 construct were analyzed using immunohistochemistry and PCR, no evidence for hsp27 expression was obtained which implicates instability of the transduced foreign DNA when maintained under nonselective conditions. The present study shows that genetic manipulation of tumor cells may provide valuable information on the role of hsp27 in tumor growth.

72-kD heat shock protein is a mediator of resistance to ultraviolet B light

We have shown previously that human epidermal keratinocytes in situ and in vitro constitutively express high levels of the 72-kD heat shock protein (hsp72) and that hsp72 expression in these cells can be further induced with heat treatment. In the present study, we continue our investigation of the ultraviolet (UV) B protective effect of hyperthermic treatment and ask whether hsp72 is a mediator of heat-shock-induced UVB resistance. The results of our experiments demonstrate that heat treatment (42 degrees C for 4 h) before UVB exposure is able to increase significantly the UVB resistance of the epidermal carcinoma cell line A431. Heat-induced UVB resistance was most pronounced if the cells were exposed to UVB immediately after heat treatment. The protective effect was not detectable beyond a recovery period of 12 h. To investigate the role of hsp72 in hyperthermia-induced UVB resistance, we inhibited the expression of this protein using either a specific antisense oligodeoxynucleotide or quercetin, a flavonoid that has been shown to down-regulate hsp expression. Treatment with the oligomer as well as with quercetin significantly increased the susceptibility of A431 to UVB-induced damage and nullified the protective effect of heat preconditioning. A noncomplementary control oligodeoxynucleotide had no significant effect. These results indicate that heat treatment is able to induce a state of increased resistance to the deleterious effects of UVB in human keratinocytes in vitro. hsp72 is a molecular mediator of this protective effect, and its constitutive expression in human epidermal keratinocytes may be an important mechanism for the protection of human epidermis from UVB-induced damage.

Expression of the 27-kDa heat shock protein in human epidermis and in epidermal neoplasms: an immunohistological study

The 27-kDa heat shock protein (HSP27) is a member of the small heat shock protein (HSP) family. In addition to its putative function in thermotolerance, this protein may play a part in the regulation of cell growth and differentiation. This study was conducted to assess the significance of the expression of HSP27 in human epidermis and in cutaneous neoplasms. Sixty-two biopsy samples from normal human skin and from inflammatory and neoplastic skin diseases were investigated by immunohistochemistry on formalin-fixed paraffin-embedded tissue sections, using a monoclonal antibody specific for HSP27. In normal human epidermis, HSP27 is expressed in the upper epidermal layers with a cytoplasmic staining pattern. The basal cell layer does not express detectable amounts of HSP27. In hair follicles, staining is mainly confined to the outer root sheath and to the infundibular epithelium. Melanocytes, dermal fibroblasts and endothelial cells do not express detectable amounts of HSP27. HSP27 could not be detected in fetal skin until the 20th week of gestation. Tumour cells in basal and squamous cell carcinomas do not express significant amounts of HSP27. In solar keratoses, seborrhoeic keratoses, human papillomavirus (HPV)-induced hyperproliferative lesions and inflammatory skin conditions, HSP27 expression largely resembles the pattern observed in normal human skin. HSP27 is expressed in a differentiation-related pattern in normal human epidermis and hyperproliferative disorders of the epidermis. We conclude that HSP27 may be regarded as a marker of differentiation in epidermal keratinocytes. Absence of HSP27 in the upper epidermal layers may be a marker for epidermal malignancy.

Selective release of tumor necrosis factor binding protein II by malignant human epidermal cells reveals protection from tumor necrosis factor alpha-mediated cytotoxicity

Most tumor cells produce both tumor necrosis factor (TNF) receptors, the M(r) 55,000 TNFRI and the M(r) 75,000 TNFRII, but they are mostly resistant to TNF-alpha-induced cytotoxicity. To gain further insight into the escape mechanisms of tumor cells from the harmful effect of TNF-alpha, we investigated the production of TNF-binding proteins (TNF-BPI, TNF-BPII, both M(r) 30,000) by malignant and normal epidermal cells and studied their functional role in TNF-alpha-induced cytotoxicity. Malignant human keratinocytes (A431, KB, HaCaT) and malignant human melanoma cells (KRFM) produced significant levels of both TNF-BPI and TNF-BPII on stimulation with phorbol myristate acetate. In contrast, normal human keratinocytes (HNK) and normal human melanocytes (HNM) released TNF-BPI but not TNF-BPII. The specific production of TNF-BPII in concert with TNF-BPI by the malignant cell lines revealed an inhibitory effect of supernatants on recombinant human TNF-alpha-mediated cytotoxicity of the TNF-dependent murine cell line L929, while supernatants of normal epidermal cells had no effect. Preincubation of supernatants with anti-TNF-BPI monoclonal antibody htr-9 or anti-TNF-BPII monoclonal antibody utr-1 reversed this inhibitory effect additively, indicating that the production of both TNF-BPs is necessary to protect cells from TNF-alpha-mediated cytotoxicity. A TNF-alpha scavanging effect of TNF-BPs resulting in subsequent inhibition of TNF-alpha binding to L929 cells could be demonstrated by ligand blotting and fluorescence-activated cell sorting analysis. Thus the production of TNF-BPII by epidermal tumor cells in concert with TNF-BPI appears to demonstrate a specific mechanism by which malignant epithelial cells escape from TNF-alpha-mediated cytotoxicity.

UVA- and UVB-induced changes in hairless mouse skin collagen

UVA- and UVB-induced alterations in dermal collagen were investigated in a murine animal model. Groups of hairless mice were exposed to UVA and UVB for 28 weeks at a dose of 60 J/cm2 three times weekly and 0.06 J/cm2 three times weekly, respectively. Untreated animals were used as controls. Every 4 weeks dorsal skin was examined for quantitative and qualitative changes in dermal collagen. Neither UVA nor UVB caused a significant alteration in total skin collagen content. However, after UVA treatment the ability of skin collagen to be digested by pepsin decreased dramatically (up to 65% of skin collagen remained insoluble after 4 months), whereas exposure to UVB had no significant effect. Furthermore a shift in the ratio of alpha 1(I,III) chains to alpha 2(I) chains was detected after UVA exposure. The amount of type V collagen in mouse skin, as determined by a sensitive ELISA method, was markedly decreased after UVA treatment, but not after UVB treatment.

Increased expression of the M(r) 27,000 heat shock protein (hsp27) in in vitro differentiated normal human keratinocytes

The M(r) 27,000 heat shock protein (hsp27) is a member of the small heat shock protein family. Cell differentiation is a process in which a role for small heat shock proteins has been suggested. The ability to control the state of differentiation in normal human keratinocytes by modification of extracellular calcium concentration makes it an ideal in vitro system for exploration of the specific components and steps in differentiation. We have focused on the in vitro expression of hsp27 in undifferentiated and differentiated human normal keratinocytes (HNK) as a marker for differentiation. Immunological methods (immunohistochemistry and immunoblotting) as well as Northern blotting were used. Cells of the breast cancer line MCF-7 served as a positive control. We demonstrated that hsp27 was expressed at low levels in normal human keratinocytes, kept under calcium concentrations where cells formed discrete colonies of undifferentiated, noncornified cuboidal cells (0.03 mM Ca2+), and linked cuboidal cells with a noncornified appearance (0.15 mM Ca2+). Upon cultivation in high calcium (1.00 mM Ca2+) where a more morphological state of differentiation was reached, more spindle shaped with cornification of individual cells, a 2-fold increase in hsp27 expression was observed. A somewhat weaker increase in hsp27 mRNA was shown by Northern blot analysis. Our studies provide evidence that hsp27 is accumulated in a differentiation-dependent manner in human normal keratinocytes grown under conditions inducing terminal differentiation (0.03-1.00 mM Ca2+). Therefore, hsp27 can be regarded as a marker of differentiation in human normal keratinocytes.

Proopiomelanocortin-derived peptides are synthesized and released by human keratinocytes

Proopiomelanocortin (POMC), the precursor for melanotropic, corticotropic, and opioid peptides such as alpha-melanocyte-stimulating hormone (alpha MSH), ACTH, and other related peptides, was originally identified as a product of the pituitary gland. However, recent evidence shows that POMC products can also be produced by nonpituitary tissues. Because keratinocytes, the major constituent of the epidermis exhibit the capacity to release a variety of proinflammatory and immunomodulatory mediators, the present study was performed to investigate whether human keratinocytes are able to produce POMC-derived peptides. Supernatants of human normal keratinocytes and an epidermal carcinoma cell line (A431) contained significant levels of immunoreactive alpha MSH and ACTH. Upon immuneprecipitation and size-exclusion chromatography, keratinocyte-derived alpha MSH exhibited a molecular mass of approximately 1 kD and was biologically active as demonstrated in a tyrosinase bioassay. Northern blot analysis revealed the expression of POMC-specific transcripts (1.3 kb) in both normal keratinocytes and A431 cells. The production of alpha MSH and ACTH could be significantly upregulated both at the protein and mRNA level upon treatment with phorbol myristate acetate, ultraviolet light, or interleukin 1. These data provide first evidence that human keratinocytes produce POMC-derived peptides such as alpha MSH and ACTH. Because POMC-derived peptides recently have been recognized as potent immunomodulatory mediators, their presence in the epidermis may have a major impact on the skin immune system.

Pentoxifylline suppresses irritant and contact hypersensitivity reactions

Pharmacologic suppression of the effector phase of contact hypersensitivity appears to have major relevance with regard to treatment of type IV reactions like contact dermatitis. Recently, tumor necrosis factor alpha has been shown to be a critical mediator in hapten-induced irritant and contact hypersensitivity reactions, thus offering new possibilities, for therapeutic intervention. Pentoxifylline, a methylxanthine derivative used in the treatment of vascular disorders, currently has been found to suppress the production of tumor necrosis factor alpha by human and murine leukocytes. Therefore, the effect of pentoxifylline on the elicitation phase of contact hypersensitivity was studied. Intraperitoneal injection of pentoxifylline into sensitized Balb/c and C3H/HeN mice before application of the challenging hapten dose resulted in a significant reduction of the outcome of the contact hypersensitivity reaction. The suppressive effect of pentoxifylline was dose dependent and maximally pronounced upon injection 3 h before hapten application. In contrast to the effector phase of contact hypersensitivity, induction of contact hypersensitivity was not affected by pentoxifylline when injected into naive mice before performance of sensitization. In addition, irritant dermatitis induced by 1% croton oil or 5% benzalkonium chloride was suppressed by pentoxifylline as well. These data suggest a potential pharmacologic intervention, with pentoxifylline as a means to treat contact dermatitis.

Human keratinocytes in vivo and in vitro constitutively express the 72-kD heat shock protein

Exposure of cells to elevated temperatures induces a physiologic response characterized by the synthesis of a specific set of proteins (heat shock or stress proteins, HSPs) mediating repair mechanisms and protection from cellular damage. In the present study upon immunohistochemistry using a specific monoclonal antibody, the constitutive and heat-induced expression of the 72-kD HSP (HSP72) in normal human skin and in human epidermal cell lines (KB, A431) was investigated. Normal (unstressed) epidermis and adnexal structures of normal human skin were found to constitutively express HSP72. In contrast, a substantial HSP72 expression could not be observed in the dermal cellular compartment. In vitro heat treatment of punch biopsies from normal skin (42 degrees C, 4 h) resulted in a further increase of epidermal HSP72 expression. In addition, dermal cells were found to be induced to express HSP72. To further evaluate the spontaneous HSP72 expression of epidermal cells two epidermoid carcinoma cell lines (A431, KB) were investigated. Upon immunohistochemistry and Western blot analysis a significant HSP72 expression could be detected in unstressed KB and A431 cells. In contrast, a human fibrosarcoma cell line (HT1080) was negative for HSP72 at 37 degrees C but upon heat treatment a strong induction was observed. Furthermore, Northern blot analysis using a cDNA probe specific for human HSP72 revealed a constitutive expression of HSP72 mRNA in both epidermal cell lines. These findings demonstrate a significant expression of the stress-inducible HSP72 in unstressed human skin as well as in epidermal cell lines, suggesting that HSP72 may inherently be involved in the protective function of normal human skin.

Granulocytes of critically ill patients spontaneously express the 72 kD heat shock protein

Polymorphonuclear neutrophils (PMN), through their ability to release oxygen-free radicals and other tissue-damaging molecules, play a major role in the pathogenesis of multiple organ failure syndrome (MOFS). There is evidence that heat shock proteins (stress proteins; HSPs) are involved in cellular repair mechanisms, and are protecting cells against oxidative injury. In this study, we analyzed the spontaneous expression of the 72 kD HSP (HSP72) in peripheral blood PMN of 20 critically ill patients (16 polytrauma victims, four patients after major surgery) admitted to an intensive care unit. The expression of HSP72 was investigated in PMN of patients and healthy donors by immunohistochemistry. We found spontaneous expression of HSP72 in PMN of 12 (60%) of 20 patients. No specific staining was detected in PMN of healthy donors (n = 10). In PMN of six of 12 patients expressing HSP72 without previous heat treatment, we found an impairment of respiratory burst activity (RBA) compared to the control population. These results demonstrate for the first time the in vivo expression of HSP72 in human leukocytes without previous heat treatment, and suggest a possible role of this protein in patients suffering from severe tissue injury.

Parenteral administration of 8-methoxypsoralen in photopheresis

BACKGROUND

Extracorporeal photochemotherapy (EP) is used for the treatment of cutaneous T-cell lymphoma (CTCL), progressive systemic sclerosis (PSS), pemphigus vulgaris, and rheumatoid arthritis. During this procedure, the oral administration of the photoactive drug 8-methoxypsoralen (8-MOP) results in an unpredictable range of serum levels and in side effects limiting its efficacy.

OBJECTIVE

To circumvent this limitation, extracorporeally administrable 8-MOP (EX-8-MOP) was developed. It is administered directly to the leukocyte/plasma concentrate in the treatment bag of the EP apparatus before irradiation with UVA light.

METHODS

Efficacy, tolerance, and side effects of EX-8-MOP were evaluated in 108 consecutive treatments of 16 patients who had previously been treated with oral 8-MOP (91 treatments).

RESULTS

With EX-8-MOP constant drug levels for UV light exposure were obtained; for equivalent levels only a small fraction of the oral dose (1/250 to 1/500) was required with none of the side effects associated with oral 8-MOP. Effective and reproducible inhibition of lymphocyte proliferation and cell viability was attained. No difference in clinical efficacy could be observed.

CONCLUSION

EX-8-MOP eliminates the need for premedication and drug level monitoring of 8-MOP and should improve the effectiveness of EP.

Extracorporeal photochemotherapy for the treatment of systemic lupus erythematosus. A pilot study

OBJECTIVE

To investigate the effectiveness and feasibility of extracorporeal photochemotherapy (ECP) in the treatment of an autoimmune disease with known cutaneous photosensitivity.

METHODS

Ten patients with systemic lupus erythematosus (SLE) were treated with ECP in an open clinical trial. The efficacy of treatment was analyzed by means of established disease activity scores.

RESULTS

Eight patients completed the trial. In 7 of the 8, there was a significant response to the treatment, with no or minor side effects. The clinical activity score in the group of 8 patients decreased from a median of 7 (range 4-9) to a median of 1 (range 0-5) (P less than 0.05). Laboratory abnormalities did not change significantly, but were mild at the outset.

CONCLUSION

ECP led to clinical improvement of SLE without side effects. The effectiveness of this method should be investigated further in controlled clinical trials.

Antibody formation against human collagen and C1q in response to a bovine collagen implant

The humoral immune response to commercially available bovine collagen implants (Zyderm, Zyplast) is characterized in a 45-year-old female patient. Circulating anti-collagen antibodies were detected after eight injections of Zyderm and after two injections of Zyplast given during a period of 3 years. The specificity of these antibodies for bovine and human collagens as well as for the collagen-like region of C1q (a subcomponent of the first component of complement), was investigated by affinity chromatography. Serum levels of anti-collagen and anti-C1q antibodies were measured using ELISA. High levels of antibodies to bovine collagens, showing a strong cross-reactivity with human collagen type III were detected in the patient's serum. Only weak cross-reactivity with human collagen type I and IV and no reactivity with type II were observed. In addition, these antibodies specifically cross-reacted with the collagen-like region of C1q. The antibody levels decreased continuously and disappeared 1 year after cessation of treatment. These results demonstrate for the first time the formation of autoantibodies upon treatment with a bovine collagen implant. Although antibodies to collagens and C1q have been found in various autoimmune diseases, neither adverse reactions to the bovine collagen implant nor any other clinical symptoms were observed in association with the described antibody response.

Increased IL-6 production by monocytes and keratinocytes in patients with psoriasis

Interleukin-6 (IL-6) is a multifunctional inflammatory cytokine that is produced by monocytes and keratinocytes upon stimulation. Because psoriasis is a skin disease characterized by a hyperproliferative activity of keratinocytes and an inflammatory infiltrate, in the present study IL-6 production of monocytes and keratinocytes of patients with psoriasis was investigated. Peripheral blood mononuclear cells (PBMC) derived from psoriatics, atopics, and healthy controls were incubated for 24 h and, subsequently, supernatant IL-6 activity was measured using an IL-6-dependent hybridoma cell line (B9). Compared to controls and atopics, PBMC of psoriatics produced significantly increased amounts of biologically active IL-6. These findings were also confirmed by Western blot analysis using a specific antiserum directed against IL-6. Moreover, when the sera of the same patients were tested for IL-6 activity, sera of psoriatics contained significantly elevated amounts of circulating IL-6 in comparison to samples from atopics and healthy controls. In contrast to normal or uninvolved skin, keratinocytes in psoriatic lesions were remarkably positive for IL-6 as detected by immunohistochemistry and in situ hybridization. In addition, IL-6 also was found to induce its own synthesis and release by monocytes. These findings indicate that keratinocytes and monocytes in psoriasis are activated to produce increased amounts of IL-6, which may be one of the mediators involved in the regulation of both local and systemic inflammatory reactions occurring in skin diseases such as psoriasis.

Respiratory burst capability of polymorphonuclear neutrophils and TNF-alpha serum levels in relationship to the development of septic syndrome in critically ill patients

Activated polymorphonuclear neutrophils (PMN) and neutrophil activating mediators such as tumor necrosis factor-alpha (TNF-alpha) are thought to be involved in the pathophysiology of sepsis and multiple organ failure syndrome (MOFS). In critically ill patients at high risk for the development of septic syndrome (n = 17) peripheral blood PMN were assayed for O2- and H2O2 production after stimulation with phorbol myristate acetate (PMA, 40 nM). Serum TNF-alpha levels were determined by ELISA. At the time of admission to the intensive care unit we found significant higher levels of TNF-alpha (P = 0.0001) in the serum of patients finally developing sepsis correlating to higher respiratory burst capability in comparison to nonseptic patients. Additionally we were able to demonstrate a significant (P = 0.0016) lower dismutation rate of O2- to H2O2 in deceased patients in comparison to survivors. These results give further evidence that elevated levels of circulating TNF-alpha and activated PMN play a significant role in the pathogenesis of septic syndrome in critically ill patients.

Treatment of cutaneous T cell lymphoma with a combination of low-dose interferon alfa-2b and retinoids

In a pilot study the therapeutic effect and side effect profile of low-dose interferon alfa-2b in combination with a retinoid for the treatment of cutaneous T cell lymphoma were evaluated. Seven patients (four women, three men) with histologically confirmed cutaneous T cell lymphoma were included. Four patients had received therapy previously. The treatment schedule consisted of 2 million U of interferon alfa-2b administered subcutaneously three times per week and oral 13-cis-retinoic acid, 1 mg/kg/day, with subsequent dose reduction in case of response. The combination therapy produced two complete and two partial remissions. Responses were maintained by continuous therapy for up to 15 months even after dose reduction of both agents by 50%. Side effects were negligible and did not result in discontinuation of treatment in any patient.

Long-term adjuvant therapy of high-risk malignant melanoma with interferon alpha 2b

Fifty-three high-risk melanoma patients in stage I and 15 patients in stage II were treated after standard surgical intervention with adjuvant therapy with recombinant interferon alpha-2b (rIFN alpha 2b) therapy for a total period of 20 months. Concomitant patients (stage I, n = 82; stage II, n = 33) with identical stages and prognostic factors without adjuvant therapy were used to evaluate the efficacy of rIFN alpha 2b therapy. No difference in 5-year relapse incidence and overall survival rates could be detected. However, it appears that patients of both stage I and stage II benefit from long-term adjuvant rIFN alpha 2b therapy, because during the treatment period (20 months), the incidence of relapses was lower in comparison to controls. After stopping treatment the incidence of relapse is equal in treated and control groups. According to the results of our study, we suggest using continuous low-dose rIFN alpha 2b therapy for adjuvant treatment of malignant melanoma.