Ultraviolet-B induction of interstitial collagenase and stromelyin-1 occurs in human dermal fibroblasts via an autocrine interleukin-6-dependent loop

UVB-mediated down-regulation of proteasome in cultured human primary pterygium fibroblasts

Background

Pterygium is a condition characterized by epithelial overgrowth of the cornea, inflammatory cell infiltration and an abnormal extracellular matrix accumulation. Chronic UV exposure is considered as a pathogenic factor of this disease. Proteasome is an intracellular multi-subunit protease complex that degrades intracellular proteins. Among proteasome subunits the β5 (PSMB5), bearing chymotrypsin-like activity. It is considered as the main proteasome subunit and its expression is mediated by Nrf2-ARE pathway in many cell types. This study investigates the expression of PSMB5 in pterygium and the effect of UVB irradiation on its expression and activity in pterygium fibroblasts.

Methods

Normal conjunctival and pterygium specimens were obtained from the bulbar conjunctiva of patients undergoing cataract surgery and from patients with pterygium undergoing surgical removal of primary tissue, respectively. Fibroblasts were isolated upon treatment of specimens with clostridium collagenase. The expression of PSMB5 and Nrf2 in tissues and cells was ascertained by RT-PCR analysis and western blotting. Cell survival was measured by the MTT method and the proteasome chymotrypsin-like activity was determined by fluorometry.

Results

RT-PCR analysis showed that the expression of PSMB5 was significantly lower in pterygium than in normal conjunctiva. The expression of PSMB5 was mediated by the Nrf2/ARE pathway as indicated by using the Nrf2 activator Oltipraz. The expression of PSMB5 and Nrf2 by pterygium fibroblasts was suppressed in a dose dependent manner following UVB radiation of 0–50 mJ/cm² doses. The expression of PSMB5, but not of Nrf2, remained at almost the control levels, when UVB exposure was performed after pre-incubation of cells with the src kinases inhibitor PP2. UVB irradiation had very low deleterious effect on fibroblasts survival, while it did not affect the proteasome chymotrypsin-like activity.

Conclusion

In pterygium fibroblasts, UVB exposure leads to down-regulation of Nrf2/ARE-mediated PSMB5 gene expression, in which src kinases may be implicated. This effect may be partially responsible for the lower expression of PSMB5 detected in pterygium as compared to normal conjunctiva.

Q-switched 1064 nm Nd-Yag nanosecond laser effects on skin barrier function and on molecular rejuvenation markers in keratinocyte-fibroblasts interaction

Skin represents an interface between internal and external environment; it protects human body by regulating the water loss and the maintenance of body temperature, defending against irritant and pathogen agents, and against physical, chemical, and UV damage. It provides to essential physiological functions, such as the important antioxidant defense capacity; its protective/defensive function is performed by a high number of proteins, and shows important functions in maintenance of skin barrier homeostasis. Keratinocytes and fibroblasts play a pivotal role to determine or prevent skin aging in response to intrinsic or extrinsic stimuli, modulating cytokines and several biochemical factors. Non-ablative technologies are playing an increasing role in the management of skin aging, inducing a dermal remodeling without a visible epidermal damage. The objective of this study was to evaluate the effect of Q-switched 1064 Nd-YAG laser (Medlite Conbio C6 Nd-YAG laser, Cynosure USA) in skin barrier function, analyzing the constituents which are strongly altered in aging skin. Particularly, we evaluated the expression of filaggrin, TGase, HSP70, and aquaporins, on HaCaT cells. The expression of proinflammatory cytokines has been investigated too.As a second step of the study, we analyzed the modulation of the rejuvenation molecular markers on human skin fibroblasts (HDFs) stimulated with keratinocytes conditioned medium (KCM).Our results demonstrated that Q-switched 1064 nm Nd:YAG laser acts on the skin barrier function, increasing the expression of aquaporins, filaggrin, TGase, and HSP70, modulating the proinflammatory cytokines. In fibroblasts stimulated with keratinocytes conditioned medium (KCM) and irradiated with Q-switched 1064 nm Nd:YAG laser, we can observe a reduction of MMP-1 and an increase in procollagen, collagen type I, and elastin. Our results highlight that Q-switched 1064 nm Nd:YAG laser treatment could represent an effective weapon to fight skin aging.

Ultraviolet- and infrared-induced 11 beta-hydroxysteroid dehydrogenase type 1 activating skin photoaging is inhibited by red ginseng extract containing high concentration of ginsenoside Rg3(S)

BACKGROUND

Sun irradiation is one of major extrinsic stressors responsible for premature skin aging through activation and expression of 11 beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts inactive cortisone to active cortisol. The aim of this study was to evaluate the inhibitory effects of red ginseng extract containing high concentrations of ginsenoside Rg3 (S) (GERg3) on 11β-HSD1-induced skin photoaging.

METHODS

To evaluate the inhibitory effects of GERg3 on ultraviolet- (UV) or infrared (IR)-induced skin photoaging, human dermal fibroblasts or a normal human 3D skin model was exposed to UV or an IR. RT-PCR, ELISA, Western blot, and H&E staining were used for evaluations. GERg3 was isolated from crude red ginseng.

RESULTS

GERg3 inhibited the increased expressions of 11β-HSD1, interleukin (IL)-6, and matrix metalloproteinase-1 (MMP-1) in UVB- or IR-exposed Hs68 cells. Additionally, the increased cortisol, IL-6, and MMP-1 expressions were effectively reduced by GERg3 in UVA-exposed 3D skin models. The photoinduced decrease in type 1 procollagen also recovered as a result of GERg3 treatment in Hs68 cells and the 3D skin model. In addition, the UVA-exposed dermal thickness was decreased in comparison with the UVA-protected 3D skin model, recovered with GERg3 treatment.

CONCLUSION

GERg3 had antiphotoaging effects in UV- or IR-exposed human dermal fibroblasts and normal human 3D skin model.

Triolein reduces MMP-1 upregulation in dermal fibroblasts generated by ROS production in UVB-irradiated keratinocytes

BACKGROUND

Cytokine production and oxidative stress generated by ultraviolet radiation B (UVB) skin exposure are main factors of skin photoaging. Interleukin-6 (IL-6) produced by irradiated keratinocytes is proposed to have a role in metalloproteinases (MMPs) expression activation in dermal fibroblasts.

OBJECTIVES

We examined the effect of triolein treatment of UVB-irradiated keratinocytes on MMP1 (interstitial collagenase) expression response of dermal fibroblasts. We assayed UVB-irradiated keratinocytes soluble signals, mainly IL-6 and reactive oxygen species (ROS).

METHODS

IL-6 expression and ROS generation were assayed in UVB-irradiated keratinocytes. MMP1 mRNA expression response was assayed in fibroblasts grown in keratinocytes conditioned medium. We evaluated the effect of treating keratinocytes with triolein on IL-6 expression and ROS generation in keratinocytes, and MMP1 expression in fibroblasts.

RESULTS

The irradiation of epidermal cells with sublethal UVB doses increased IL-6 expression and ROS generation. Conditioned culture medium collected from keratinocytes was used to culture dermal fibroblasts. MMP1 mRNA expression increase was observed in fibroblasts cultured in medium collected from UVB-irradiated keratinocytes. Triolein treatment reduced the IL-6 expression and ROS generation in keratinocytes and this effect was reflected in downregulation of MMP1 expression in fibroblasts.

CONCLUSIONS

Triolein reduces both the expression of IL-6 and ROS generation in irradiated keratinocytes. It seems to exert an anti-inflammatory and anti-oxidative stress effect on irradiated keratinocytes that in turn reduces MMP1 expression in dermal fibroblasts. Collectively, these results indicate that triolein could act as a photoprotective agent.

Phototherapy in Scleroderma

Systemic and localized scleroderma are difficult to manage diseases with no accepted gold standard of therapy to date. Phototherapeutic modalities for scleroderma show promise. A PubMed search of information on phototherapy for scleroderma was conducted. The information was classified into effects on pathogenesis and clinical outcomes. Studies on photopheresis were excluded. There were no randomized, double-blind, placebo-controlled studies, and only three controlled studies. The vast majority of identified studies evaluated ultraviolet A1 (UVA1) phototherapy. More rigorous studies are needed to evaluate phototherapy in the treatment of scleroderma. Based on the limited studies available, 20-50 J/cm² of UVA1 therapy 3-4 times a week for 30 treatments is recommended.

Cyclic AMP suppresses matrix metalloproteinase-1 expression through inhibition of MAPK and GSK-3beta

Expression of matrix metalloproteinase-1 (MMP-1) is stimulated by diverse stimuli and is likely to be regulated by many signaling pathways. cAMP is known to act as a second messenger for various extracellular stimuli and to be involved in the regulation of cell proliferation, apoptosis, and inflammation. Here, we investigated the effect of cAMP on tumor necrosis factor (TNF)-alpha-induced MMP-1 expression and the molecular events involved in the processes in human skin fibroblasts. We showed that cAMP suppresses TNF-alpha-induced MMP-1 expression via protein kinase A (PKA) pathway. cAMP inhibited TNF-alpha-stimulated ERK and JNK activation, which was shown to have an important role in MMP-1 expression. However, MMP-1 expression could also be inhibited by cAMP even when ERK and JNK activities were unaffected, indicating that there might be other target(s) that mediate cAMP-mediated suppression of MMP-1 expression. Further studies revealed that glycogen synthase kinase (GSK)-3beta can be inactivated by cAMP/PKA pathway and has important roles in MMP-1 expression, and showed that inactivation of GSK-3beta is critical for suppression of MMP-1 expression by cAMP elevation after TNF-alpha treatment. Taken together, our results suggest that cAMP/PKA pathway can suppress MMP-1 expression through inhibition of multiple signaling pathways, including MAPK and GSK-3beta.

Berberine inhibits TPA-induced MMP-9 and IL-6 expression in normal human keratinocytes

Berberine is a plant ingredient that has anti-inflammatory and anti-oxidative effects. Matrix metalloproteinase-9 (MMP-9) and interleukin-6 (IL-6) are known to be highly induced by ultraviolet (UV) light and may play important roles in UV-induced skin inflammation and the skin aging process. In this study, we investigated the effects of berberine on MMP-9 and IL-6 expression in normal human keratinocytes (NHK). Our results demonstrated that berberine dose-dependently inhibited basal and TPA-induced expression and activity of MMP-9, and also suppressed TPA-induced IL-6 expression. Berberine prevented TPA-induced ERK activation and AP-1 DNA binding activity. Therefore, berberine may be used as an effective ingredient for anti-skin aging products, which can prevent skin inflammation and the degradation of extracellular matrix proteins, including collagen, by MMPs.

Ultraviolet B-induced matrix metalloproteinase-1 and -3 secretions are mediated via PTEN/Akt pathway in human dermal fibroblasts

Matrix Metalloproteinases (MMPs) are crucial enzymes for ultraviolet irradiation-induced photoaging in human skin. Ultraviolet B (UVB) stimulates dermal fibroblasts to increase MMP-1 and -3 expression and extracellular matrix (ECM) degradation in photoaging. We investigated whether phosphatase and tensin homolog (PTEN)/Akt pathway is involved in secretions of MMP-1 and -3 in human dermal fibroblasts. The increase in MMP-1 and -3 expression and secretion occurred along with the increase in PTEN and Akt phosphorylation by UVB irradiation in a dose- and time-dependent manner. However, treatment with a casein kinase 2 inhibitor, 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole, inhibited their phosphorylations and MMP-1 and -3 secretions. Transfection of wild-type PTEN (Wt-PTEN) decreased basal and UVB-induced MMP-1 and -3 secretions, as well as activator protein-1 (AP-1) activity, while transfection of small interference RNA of PTEN (siRNA-PTEN), phosphatase-inactive PTEN (C124S-PTEN), or lipid phosphatase-inactive PTEN (G129E-PTEN) increased basal or UVB-induced MMP-1 and -3 secretions and AP-1 activity. Transfection of constitutively active Akt (Myr-Akt) also increased basal or UVB-induced MMP-1 and -3 secretions, as well as AP-1 activity. However, transfection of kinase-inactive Akt (K179M-Akt) decreased their secretions, but showed no significant change of AP-1 activity without UVB irradiation, and a significant increase of AP-1 activity with UVB irradiation. Treatment with the phosphatidylinositol 3-kinase inhibitors, LY294002 or wortmannin, downregulated basal and UVB-induced MMP-1 and -3 secretions. In conclusion, UVB irradiation increases PTEN and Akt phosphorylation in human dermal fibroblasts, and these inhibition of PTEN and activation of Akt by phosphorylation are involved in UVB-induced MMP-1 and -3 secretions partly through upregulation of AP-1 activity.

Heat shock-induced matrix metalloproteinase (MMP)-1 and MMP-3 are mediated through ERK and JNK activation and via an autocrine interleukin-6 loop

Although many studies have been performed to elucidate the molecular consequences of ultraviolet irradiation, little is known about the effect of infrared radiation on skin aging. In addition to photons, heat is likely to be generated as a consequence of infrared irradiation, and heat shock is widely considered to be an environmental stress. Here we investigated the effect of heat shock on the expressions of matrix metalloproteinase (MMP)-1, MMP-2, and MMP-3 in cultured human skin fibroblasts. Heat shock induced the expression of MMP-1 and MMP-3, but not MMP-2, at the mRNA and protein levels in a temperature-dependent manner, and caused the rapid activation of three distinct mitogen-activated protein kinases (MAPK), extracelluar signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. The heat shock-induced MMP-1 and MMP-3 expression was suppressed by the inhibition of ERK and JNK but not by p38 MAPK inhibition. Furthermore, heat shock increased the synthesis and release of interleukin-6 (IL-6) into culture media. The specific inhibition of IL-6 using a monoclonal antibody against IL-6 greatly reduced the expression of MMP-1 and MMP-3 induced by heat shock. Taken together, our results suggest that ERK and JNK play an important role in the induction of MMP-1 and MMP-3 by heat shock and that the heat shock-induced expression of MMP-1 and MMP-3 is mediated via an IL-6-dependent autocrine mechanism.

Keratinocyte-derived cytokines after photodynamic therapy and their paracrine induction of matrix metalloproteinases in fibroblasts

BACKGROUND

Recent studies have shown that collagen-degrading matrix metalloproteinase (MMP)-1 and MMP-3 are produced by fibroblasts in response to photodynamic therapy (PDT) with 5-aminolaevulinic acid (ALA) and are considered to be involved in the antisclerotic effects of ALA-PDT observed in the treatment of localized scleroderma.

OBJECTIVES

As the primary target of topical PDT is epidermal keratinocytes, we studied the indirect participation of keratinocytes in the production of MMPs and collagen by dermal fibroblasts.

METHODS

Keratinocytes were treated with sublethal doses of ALA (100 micromol L(-1)) and red light. The conditioned media were collected 24 h after PDT and primary human fibroblasts were exposed to these media for 6-48 h. Further, a coculture model, keratinocytes seeded on to collagen type IV-coated transwells in the upper chamber and fibroblasts in the lower chamber, was used to study paracrine effects of keratinocytes after PDT.

RESULTS

Keratinocyte supernatants after PDT showed a significant, up to 10-fold increase of interleukin (IL)-1alpha and a 2.5-fold increase of tumour necrosis factor-alpha as determined by enzyme-linked immunosorbent assay, while IL-6, MMP-1 and MMP-3 were not altered significantly. Fibroblasts treated with keratinocyte-conditioned media after PDT showed an induction of MMP-1 and MMP-3 protein levels up to threefold in both models used, suggesting that ALA-PDT modulates MMP-1 and MMP-3 production via indirect mechanisms. Collagen type I mRNA expression by fibroblasts was not altered significantly in either model. The addition of an IL-1 receptor antagonist to the keratinocyte-conditioned media completely inhibited the induction of MMP-1 and MMP-3 in stimulated fibroblasts, suggesting that IL-1 is mainly responsible for the observed paracrine effects.

CONCLUSIONS

We present evidence that PDT can trigger MMP production in dermal fibroblasts not only directly as has been already shown, but also by an indirect paracrine loop mediated by soluble factors released by epidermal keratinocytes.

Overexpression of Phospholipid-hydroperoxide Glutathione Peroxidase in Human Dermal Fibroblasts Abrogates UVA Irradiation-induced Expression of Interstitial Collagenase/Matrix Metalloproteinase-1 by Suppression of Phosphatidylcholine Hydroperoxide-mediated NFκB Activation and Interleukin-6 Release

Phospholipid-hydroperoxide glutathione peroxidase (PHGPx) exhibits high specific activity in reducing phosphatidylcholine hydroperoxides (PCOOHs) and thus may play a central role in protecting the skin against UV irradiation-triggered detrimental long term effects like cancer formation and premature skin aging. Here we addressed the role of PHGPx in the protection against UV irradiation-induced expression of matrix metalloproteinase-1 (MMP-1). For this purpose, we created human dermal fibroblast cell lines overexpressing human PHGPx. Overexpression led to a significant increase in PHGPx activity. In contrast to a maximal 4.5-fold induction of specific MMP-1 mRNA levels in vector-transfected cells at 24 h after UVA irradiation, no MMP-1 induction occurred at any studied time point after UVA treatment of PHGPx-overexpressing fibroblasts. As interleukin-6 (IL-6) was earlier shown to mediate the UVA induction of MMP-1, we studied whether PHGPx overexpression might interfere with the NFkappaB-mediated IL-6 induction and downstream signaling. Using transient transfections of IL-6 promoter constructs containing NFkappaB binding sites, we observed a high induction of the reporter gene luciferase in vector-transfected control cells and a significantly lower induction in PHGPx-overexpressing fibroblasts following UVA irradiation. Consistently both UVA irradiation and treatment of fibroblasts with PCOOHs led to phosphorylation and nuclear translocation of the p65 subunit, whereas cells overexpressing PHGPx exhibited impaired NFkappaB activation, p65 phosphorylation, and nuclear translocation. In line with this, the PHGPx-overexpressing fibroblasts showed a reduced constitutive and UVA irradiation-induced IL-6 release. After incubating PHGPx-overexpressing cells with PCOOHs a reduced induction of IL-6 was observed. This together with the suppression of UVA irradiation-induced IL-6 release in the presence of Trolox, a chain breaker of PCOOH-initiated lipid peroxidation, indicates that UVA irradiation-induced PCOOHs and subsequent lipid peroxides initiate the NFkappaB-mediated induction of IL-6, which mediates the induction of MMP-1. Our finding is particularly relevant in light of the already available small molecule mimetics of PHGPx.

Matrix metalloproteinase-1 production observed after solar-simulated radiation exposure is assumed by dermal fibroblasts but involves a paracrine activation through epidermal keratinocytes

Chronic exposure of human skin to solar UV radiation leads to serious dermal damages, a hallmark of photoaging. In vivo, acute UV radiation has been shown previously to induce various matrix-degrading proteases. Among them, matrix metalloproteinase-1 (MMP-1) has been suggested to be involved in skin photodamage. The purpose of this study was to investigate the effects of solar-simulated radiation (SSR) on MMP-1 production in normal human skin cells. SSR exposure of human skin reconstructed in vitro comprising both a differentiated epidermis and a fibroblast-populated dermal equivalent led to an increase in MMP-1 production, which was abolished when epidermis was removed immediately after SSR exposure. In addition, SSR exposure of differentiated keratinocytes grown on an acellular collagen gel did not induce MMP-1 production. Experiments on cell cultures grown on plastic confirmed that keratinocytes failed, in contrast with fibroblasts, to produce MMP-1 in response to SSR exposure. However, when conditioned medium from SSR-exposed keratinocytes was added to human fibroblasts in culture, MMP-1 production was induced. Altogether, these data show that MMP-1 production observed after SSR exposure involved the release of soluble epidermal factors, which could modulate its production by dermal fibroblasts.

The Polyhydroxy Acid Gluconolactone Protects Against Ultraviolet Radiation in an In Vitro Model of Cutaneous Photoaging

BACKGROUND

Ultraviolet (UV) radiation damages skin through a variety of mechanisms, including the generation of free radicals. Gluconolactone is a polyhydroxy acid (PHA) that is capable of chelating metals and may also function by scavenging free radicals, thereby protecting skin from some of the damaging effects of UV radiation.

OBJECTIVE

This study measured the ability of gluconolactone to protect against UV radiation-induced damage.

METHODS

The ability of gluconolactone to prevent UV radiation-induced elastin promoter activation was determined in vitro using a transgenic model of cutaneous photoaging. Gluconolactone was also evaluated to determine its ability to promote the formation of sunburn cells in human skin after exposure to UV radiation.

RESULTS

Gluconolactone provided up to 50% protection against UV radiation, as measured in our in vitro system, and did not significantly increase sunburn cells in human skin.

CONCLUSIONS

These results demonstrate the ability of the PHA gluconolactone to protect against UV radiation-induced elastin promoter activation. In addition, in vivo studies demonstrated that gluconolactone treatment does not result in a significant increase in sunburn cells. Further investigation of this and other PHAs is necessary to identify their potential role in preventing and repairing cutaneous photodamage.

Induction of MMP-10 and MMP-1 in a squamous cell carcinoma cell line by ultraviolet radiation

Ultraviolet radiation may cause non-melanoma skin cancer by genetic and epigenetic events. In this study, we investigated in a squamous cell carcinoma cell line, SCL-1, whether UV irradiation modulates the expression of matrix metalloproteinases, known to be involved in tumor progression and metastasis by degradation of extracellular matrix components. UVA or UVB irradiation of SCL-1 resulted in a rapid transcriptional up-regulation and increased secretion of two members of the matrix metalloproteinase family, MMP-10 (stromelysin-2) and MMP-1 (interstitial collagenase). The increase in MMP-10 steady-state mRNA levels was detected 1 hour after UVA and 4 h after UVB irradiation, whereas MMP-1 was upregulated 4 h after UVA and 16 h after UVB irradiation of tumor cells. UV-induced phosphorylation of extracellular regulated kinases (ERK-1/2) and p38 stress kinase and increased binding of AP-1 transcription factor preceded the rapid stimulation of MMPs in SCL-1 cells. Incubation of cells with the MEK1/2 inhibitor U0126 or the p38 inhibitor SB202190 abolished the UVA and UVB mediated induction of MMP-1 and MMP-10. In conclusion, this study shows that UV irradiation of squamous cell carcinoma results in a rapid up-regulation of MMPs. Our results suggest that the time course of induction of target genes, like MMPs, differs between cell types depending on the stimulus.

Silk Fibroin-Coated Three-Dimensional Polyurethane Scaffolds for Tissue Engineering: Interactions with Normal Human Fibroblasts

Silk fibroin (SF)-based or -coated biomaterials hold structural and surface properties that render them suitable for biomedical applications. In this work, we investigated the behavior of four strains of normal human adult fibroblasts (HAFs) seeded onto polyurethane foam, uncoated (PUF) or SF coated (PUF/SF). HAF adhesion within 3 h to PUF/SF was 2-fold that of adhesion to PUF. After 30 days of incubation in vitro, 37% more HAFs had grown on PUF/SF than on PUF. Taking 10(5) cells as a basis for comparisons, HAFs on PUF/SF exhibited initially higher glucose consumption rates, but persistently lower glutamine uptake rates than on PUF, whereas the rates of lactate and interleukin 6 release and of extracellular assembly of type I collagen fibers were alike on either substrate. Moreover, HAFs on both PUF/SF and PUF never secreted any ELISA-assayable amounts of interleukin 1beta, tumor necrosis factor alpha, and transforming growth factor beta(1). Hence, PUF/SF scaffolds embody a novel class of biomaterials favoring the adhesion, proliferation, and performance of specific metabolic tasks by HAFs without eliciting any concurrent secretion of the chief proinflammatory cytokines.

Photoaging as a consequence of natural and therapeutic ultraviolet irradiation—studies on PUVA-induced senescence-like growth arrest of human dermal fibroblasts

Premature aging of the skin is a prominent side effect of psoralen photoactivation, a therapy widely and successfully 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. In this minireview we will focus on the similarities between intrinsic and extrinsic aging and PUVA-induced senescence-like growth arrest both resulting in the loss of the structural integrity of the dermal connective tissue as a hallmark of intrinsic aging and photoaging (extrinsic aging) of the skin, and we will discuss the important role of oxidative stress related telomere attrition in the PUVA-induced phenotype of dermal fibroblasts. With the PUVA-induced growth arrest of fibroblasts a new model has been added to the growing number of in vitro models with longterm growth arrest upon exposure to sublethal stressors (i.e. hyperoxia, hydrogen peroxide, ethanol), which are characterized by morphological and functional changes common for cellular senescence. This model may be particularly suited for further studies addressing mechanisms of stress-induced senescence-like growth arrest in vitro and in vivo, since many dermatological patients are treated with PUVA allowing the analysis of putative stress-induced premature senescence in vivo.

UVA-mediated downregulation of MMP-2 and MMP-9 in human epidermal keratinocytes

While human dermal fibroblasts increase the expression and secretion of distinct matrix metalloproteinases (MMPs) in response to ultraviolet (UV) irradiation, much less is known about regulation of MMPs with regard to normal human epidermal keratinocytes (NHEK). In this in vitro study, the effect of ultraviolet A (UVA) irradiation on gelatinase expression and secretion by NHEK was investigated. Irradiation of NHEK with non-toxic doses of UVA resulted in a dose-dependent downregulation of MMP-2 (gelatinase A) and MMP-9 (gelatinase B). A single dose of 30JUVA/cm(2) lowered MMP-2 activity to 26% and MMP-9 activity to 33% compared with mock-irradiated cells at 24h after irradiation. Downregulation of MMP-2 and MMP-9 steady-state mRNA levels was observed at 4h after UVA irradiation. The inhibitory effect of UVA on gelatinases was mediated by UVA-generated singlet oxygen (1O(2)). These findings suggest an inverse response to UVA irradiation in NHEK than in fibroblasts.

Protective and determining factors for the overall lipid peroxidation in ultraviolet A1-irradiated fibroblasts: in vitro and in vivo investigations

BACKGROUND

Lipid peroxidation (LPO) is one major effector mechanism by which ultraviolet (UV) A contributes to photoageing and the promotion of skin cancer. It is a fingerprint of photo-oxidative stress within the skin, and is initiated by several pathways, with different reactive oxygen species (ROS) and iron ions being involved.

OBJECTIVES

To elucidate factors involved in UVA1-induced LPO in human dermal fibroblasts and mouse dermis, and the role of antioxidant enzymes in protecting cells against LPO.

METHODS

Using a highly sensitive high-performance liquid chromatography procedure, we measured malondialdehyde (MDA), a specific metabolic tracer molecule for LPO, to determine the overall LPO produced by a given UVA1 dose in vitro and in vivo. By using the iron chelator desferrioxamine (DFO), the hydroxyl radical scavenger dimethylsulphoxide (DMSO) and fibroblasts that specifically overexpress single antioxidant enzymes, we further indirectly assessed the protective effect of manganese superoxide dismutase (MnSOD), catalase and phospholipid hydroperoxide glutathione peroxidase (PHGPx) as well as the relative importance of different ROS and the role of transitional iron for the total amount of LPO induced by a distinct UVA dose.

RESULTS

UVA1 irradiation resulted in a time- and dose-dependent increase in MDA levels in vitro, and the in vitro results were shown to have in vivo relevance. Fibroblasts incubated with DFO or DMSO produced lower levels of MDA than controls, as did fibroblasts overexpressing MnSOD, catalase or PHGPx.

CONCLUSIONS

The cellular iron pool and hydroxyl radicals were the most important determining factors for the total amount of MDA produced after a given UVA1 dose, and PHGPx overexpression had the greatest protective effect against LPO.

Ultraviolet-B irradiation and matrix metalloproteinases: from induction via signaling to initial events

Effects of sunlight have fascinated researchers for decades because nearly every living thing on earth is likely to be exposed to sunlight and the ultraviolet (UV) fraction of it. In addition to detrimental long-term effects such as immunosuppression and skin cancer, premature aging of the skin (photoaging) is a well-documented consequence of exposure to UVA and UVB. Photoaged skin is biochemically characterized by an overgrowth of abnormal elastic fibers in the dermis and by a dramatic decrease of distinct collagen types. Ultraviolet irradiation induces delayed UV-responsive genes, among them matrix metalloproteinases, which degrade macromolecules of the extracellular matrix, a hallmark in carcinogenesis and aging. We are interested in UVB-triggered initial events and in subsequent signaling resulting in enhanced expression of two major members of the matrix metalloproteinase family, the interstitial collagenase (MMP-1) and stromelysin-1 (MMP-3), in human dermal fibroblasts. Especially, these skin cells play a central role in connective tissue breakdown in photoaging and as stromal cells in tumor invasion and metastasis by means of their capability to produce matrix metalloproteinases. In this review, we will focus on UVB-triggered induction of matrix metalloproteinases, the so far identified components of the UVB-modulated signal transduction pathway(s), and the UVB irradiation-associated generation of reactive oxygen species (ROS). Finally, a potentially novel aspect in UVB irradiation-mediated expression of interstitial collagenase and stromelysin-1-namely, the involvement of reactive nitrogen species (RNS)-is discussed.

The effect of beta-carotene on the expression of interleukin-6 and heme oxygenase-1 in UV-irradiated human skin fibroblasts in vitro

beta-Carotene is discussed as an anti-oxidant micronutrient and singlet oxygen quencher in human skin, protecting against UV light-induced damage. However, we recently demonstrated that beta-carotene has a pro-oxidant potential in cultured human skin fibroblasts because it enhances the UVA induction of heme oxygenase-1 (HO-1). Herein, we further show that beta-carotene also strongly promotes the UVA induction of pro-inflammatory interleukin-6 (IL-6) in skin fibroblasts in vitro. Singlet oxygen quencher sodium azide abrogated up-regulation of IL-6, and likewise also of HO-1. In UVB-irradiated cells, beta-carotene did not modulate levels of IL-6 and HO-1. The observed effects might be relevant for UV-induced inflammatory processes.

Interleukin-6 treatment augments cutaneous wound healing in immunosuppressed mice

It has been postulated that the inflammatory response that occurs after cutaneous wounding is a prerequisite for healing and that inflammatory cytokines, such as interleukin-6 (IL-6) are involved in this process. We showed previously that IL-6-deficient mice display delayed wound healing, which could be reversed by administration of a murine IL-6 expression plasmid or recombinant murine IL-6 (rMuIL-6). In the present study, we observed that delayed cutaneous wound healing, which occurs as a result of glucocorticoid-induced immunosuppression, can also be reversed by rMuIL-6, as evidenced by epithelialization, granulation tissue formation, and wound closure. In vehicle control mice, rMuIL-6 did not augment healing but rather delayed the process. Immunochemical studies indicated that the expression of matrix metalloproteinase-10 (MMP-10) was increased in dexamethasone-treated mice and that rMuIL-6 treatment reduced its expression, indicating that IL-6 may influence dermal matrix formation and, specifically, collagen synthesis. These results demonstrate that IL-6 can restore abnormal wound repair that occurs in immunodeficiency and suggest its use as a potential therapy.

Induction of matrix metalloproteinases MMP-1 and MMP-2 by co-culture of breast cancer cells and bone marrow fibroblasts

Two invasive breast cancer cell lines (MDA-MB-231 and BT-549) were found to be more adherent and have greater migratory capacity on bone marrow fibroblasts than three non-invasive cell lines (MCF-7, T47D and BT-483). Antibodies to the adhesion molecules CD44, E-cadherin, ICAM- 1, and integrin chains alpha2, alpha3, alpha4, alpha5, alpha6, alpha v, beta1, beta3 and beta7 failed to inhibit breast cancer cell migration through bone marrow fibroblasts. Inhibitors of matrix metalloproteases, 1, 10-phenanthroline, Ro-9790, TIMP-1 and TIMP-2 were able to attenuate the migration of MDA-MB-231 cells through bone marrow fibroblast monolayers suggesting a role for these enzymes in the migration of breast cancer cells through bone marrow adherent layers. Co-culture of MDA-MB-231 cells and bone marrow fibroblasts resulted in augmentation of the levels of the matrix metalloproteases MMP-1 and MMP-2 in culture supernatants. Soluble factors produced by bone marrow fibroblasts were responsible for the increase in MMP-1 levels. However, maximal MMP-2 production was dependent on direct contract between the breast cancer cells and the bone marrow fibroblasts. Modulation of MMP production by cell-cell contact or soluble factors suggests a mechanism by which breast cancer cells can enhance their ability to invade the bone marrow microenvironment.