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

Matrix Metalloproteinases on Skin Photoaging

BACKGROUND

Skin aging is characterized by an imbalance between the generation and degradation of extracellular matrix molecules (ECM). Matrix metalloproteinases (MMPs) are the primary enzymes responsible for ECM breakdown. Intrinsic and extrinsic stimuli can induce different MMPs. However, there is limited literature especially on the summary of skin MMPs and potential inhibitors.

OBJECTIVE

We aim to focus on the upregulation of MMP expression or activity in skin cells following exposure to UV radiation. We also would like to offer valuable insights into potential clinical applications of MMP inhibitors for mitigating skin aging.

METHODS

This article presents the summary of prior research, which involved an extensive literature search across diverse academic databases including Web of Science and PubMed.

RESULTS

Our findings offer a comprehensive insight into the effects of MMPs on skin aging after UV irradiation, including their substrate preferences and distinct roles in this process. Additionally, a comprehensive list of natural plant and animal extracts, proteins, polypeptides, amino acids, as well as natural and synthetic compounds that serve as inhibitors for MMPs is compiled.

CONCLUSION

Skin aging is a complex process influenced by environmental factors and MMPs. Research focuses on UV-induced skin damage and the formation of Advanced Glycosylation End Products (AGEs), leading to wrinkles and impaired functionality. Inhibiting MMPs is crucial for maintaining youthful skin. Natural sources of MMP inhibitor substances, such as extracts from plants and animals, offer a safer approach to obtain inhibitors through dietary supplements. Studying isolated active ingredients can contribute to developing targeted MMP inhibitors.

The antiaging effects of a product containing collagen and ascorbic acid: In vitro, ex vivo, and pre-post intervention clinical trial

Various substances, including collagen (Naticol®) and ascorbic acid, that inhibit and prevent skin aging have been studied. Collagen prevents skin aging, has anti-inflammatory effects, and assists in normal wound healing. Ascorbic acid is a representative antioxidant that plays a role in collagen synthesis. To achieve a synergistic effect of collagen and ascorbic acid on all skin types, we prepared a product named "TEENIALL." In addition, we used a container to separate ascorbic acid and collagen to prevent the oxidation of ascorbic acid. To confirm the effects of TEENIALL, we first confirmed its penetrability in fibroblasts, keratinocytes, melanocyte, and human skin tissues. Thereafter, we confirmed the collagen synthesis ability in normal human fibroblasts. Based on the results of in vitro tests, we conducted a clinical trial (KCT0006916) on female volunteers, aged 40 to 59 years, with skin wrinkles and hyperpigmentation, to evaluate the effects of the product in improving skin wrinkles, skin lifting, and pigmentation areas before using the product, and after 2 and 4 weeks of using the product. The values of nine wrinkle parameters that were evaluated decreased and those for skin sagging, pigmentation, dermal density, and mechanical imprint (pressure) relief were improved. Skin wrinkle and pigmentation were evaluated to ensure that the improvement effect was maintained even after 1 week of discontinuing the product use. The evaluation confirmed that the effects were sustained compared to those after 4 weeks of using the product. Additionally, skin wrinkles, skin lifting, radiance, and moisture content in the skin improved immediately after using the product once. Based on the results of in vitro and ex vivo experiments and the clinical trial, we show that the product containing ascorbic acid and collagen was effective in alleviating skin aging.

A dose-dependent protective effect of n-3 PUFAs in photoaging by promoting collagen production through MAPK pathway in SKH-1 mouse model

BACKGROUND

Dietary supplementation of n-3 polyunsaturated fatty acids (n-3 PUFAs) can inhibit inflammation and oxidation of photoaging, but the effect and mechanism on regulation of dermis collagen remains poorly elucidated. The destruction of dermal collagen plays a crucial role in the process of long-term ultraviolet radiation (UVR) induced-photoaging, especially leading to deterioration of skin appearance and function.

METHODS

In this study, we explored the protective effect of n-3 PUFAs on the regulation of collagen through the MAPK pathway using the SKH-1 photoaging mouse model.

RESULTS

The results showed that n-3 PUFAs promoted collagen synthesis and reduced collagen degradation in a dose-dependent manner, which was mediated by the down-regulation of the MAPK pathway. In addition, n-3 PUFAs supplementation inhibited the production of MMP-1 and the UV-induced abnormal proliferation of keratinocytes. All these effects resulted in the remodeling of extracellular matrix (ECM) and finally made a significant improvement in the appearance of skin.

CONCLUSION

Overall, the present study suggested that dietary supplementation of n-3 PUFAs has the potential clinical prospect to prevent UV-induced skin damage and photoaging.

The Role of Bystander Effect in Ultraviolet A Induced Photoaging

Exposure to sunlight, mainly UVA, leads to typical changes in the features of the skin known as photoaging. UVA irradiation induces the expression of proteases that are responsible for the degradation of the extracellular matrix proteins to results in photoaging; it also downregulates the expression of proteins that are needed for the skin structure. Since, it is known that cells in the neighborhood of irradiated cells, but not directly exposed to it, often manifest responses like their irradiated counterparts, it is important to evaluate if these bystander cells too, can contribute to photoaging. UVA induced cell cycle arrest has been associated with photoaging, from flow cytometry analysis we found that there was an induction of cell cycle arrest at the G₁/S phase in the UVA-bystander cells. The expression of some key photoaging marker genes likes, matrix metalloproteinases (MMP-1, MMP-3, MMP-9), cyclooxygenase-2 (COX-2), collagen1 and elastin were assessed from qRT-PCR. Up-regulation of MMP-1 and COX-2, downregulation of collagen1 and elastin, along with suppression below normal expression for MMP-3 and MMP-9 was observed in the UVA-bystander A375 cells. Our findings suggest that UVA-bystander cells may contribute to the process of photoaging.

"Therapeutic uses of natural astaxanthin: An evidence-based review focused on human clinical trials"

Astaxanthin is a natural C40 carotenoid with numerous reported biological functions, most of them associated with its antioxidant and anti-inflammatory activity, standing out from other antioxidants as it has shown the highest oxygen radical absorbance capacity (ORAC), 100-500 times higher than ⍺-tocopherol and a 10 times higher free radical inhibitory activity than related antioxidants (α-tocopherol, α-carotene, β -carotene, lutein and lycopene). In vitro and in vivo studies have associated astaxanthin's unique molecular features with several health benefits, including neuroprotective, cardioprotective and antitumoral properties, suggesting its therapeutic potential for the prevention or co-treatment of dementia, Alzheimer, Parkinson, cardiovascular diseases and cancer. Benefits on skin and eye health promotion have also been reported, highlighting its potential for the prevention of skin photo-aging and the treatment of eye diseases like glaucoma, cataracts and uveitis. In this review, we summarize and discuss the currently available evidence on astaxanthin benefits, with a particular focus on human clinical trials, including a brief description of the potential mechanisms of action responsible for its biological activities.

Effect of UVA radiation on the Nrf2 signalling pathway in human skin cells

The harmful effects of low energy UVA photons (315-400 nm) are associated with the massive production of reactive oxygen species resulting in oxidative stress. In response to oxidative damage, NF-E2-related factor 2 (Nrf2) is translocated to the nucleus and drives the expression of detoxication and antioxidant enzymes. UVA's effect on Nrf2 has been quite well characterised in dermal fibroblasts. However, there is a dearth of such information for keratinocytes. This study aimed to evaluate and compare the effect of UVA radiation on the Nrf2 pathway and oxidative stress related proteins in primary human dermal fibroblasts (NHDF), epidermal keratinocytes (NHEK) and human keratinocyte cell line HaCaT. NHDF were exposed to doses of 2.5-7.5 J/cm², NHEK and HaCaT to 10-20 J/cm² using a solar simulator. Effects on Nrf2 translocation were evaluated after 1, 3 and 6 h and Nrf2-controlled proteins (heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1), glutathione reductase (GSR), glutathione-S-transferase (GST), interleukine-6 (IL-6), and matrix metalloproteinases (MMP-1, MMP-2)) after 3, 6 and 24 h. The results showed the fastest Nrf2 translocation was in UVA-irradiated HaCaT (1 h), persisting until the subsequent time interval (3 h), while in primary keratinocytes the effect of radiation was minimal. In NHDF, UVA-stimulated Nrf2 translocation was conspicuous 3 h after UVA treatment. In NHDF, most of the studied proteins (NQO1, HO-1, GSR, GSTM1 and MMP-1) showed the highest level 24 h after UVA exposure, except for MMP-2 and IL-6 which had their highest level at a shorter time incubation interval (3 h). In NHEK, NQO1, HO-1 and GST were increased 6 h after UVA exposure, GSR and MMP-2 level was slightly below or above the control level, and MMP-1 and IL-6 increased at shorter time intervals. When comparing NHEK and HaCaT, these cells displayed contrary responses in most of the Nrf2-controlled proteins. Thus, primary keratinocytes cannot be replaced with HaCaT when studying cell signalling such as the Nrf2 driven pathway and Nrf2-controlled proteins.

N-Terminal Acetylation and C-Terminal Amidation of Spirulina platensis-Derived Hexapeptide: Anti-Photoaging Activity and Proteomic Analysis

Ultraviolet (UV) irradiation is a potent inducer for skin photoaging. This paper investigated the anti-photoaging effects of the acetylated and amidated hexapeptide (AAH), originally identified from Spirulina platensis, in (Ultraviolet B) UVB-irradiated Human immortalized keratinocytes (Hacats) and mice. The results demonstrated that AAH had much lower toxicity on Hacats than the positive matrixyl (81.52% vs. 5.32%). Moreover, AAH reduced MDA content by 49%; increased SOD, CAT, and GSH-Px activities by 103%, 49%, and 116%, respectively; decreased MMP-1 and MMP-3 expressions by 27% and 29%, respectively, compared to UVB-irradiated mice. Employing isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics, 60 differential proteins were identified, and major metabolic pathways were determined. Network analysis indicated that these differential proteins were mapped into an interaction network composed of two core sub-networks. Collectively, AAH is protective against UVB-induced skin photoaging and has potential application in skin care cosmetics.

Glycolic acid attenuates UVB-induced aquaporin-3, matrix metalloproteinase-9 expression, and collagen degradation in keratinocytes and mouse skin

Ultraviolet-B exposure causes an inflammatory response, photoaged skin, and degradation of extracellular matrix proteins including collagen and elastin. The regulation of these genes was suggested as an important mechanism to attenuate skin aging. Glycolic acid (GA) is commonly present in fruits and recently used to treat dermatological diseases. We reported that GA slows down cell inflammation and aging caused by UVB. Little is known about GA retarding the skin premature senescence or how to impede these events. To investigate the potential of GA to regulate the expression of MMPs and collagen, GA was topically applied onto human keratinocytes and the C57BL/6J mice dorsal skin. In the present study, we demonstrated that GA reduced UVB-induced type-I procollagen expression and secretory collagen levels. GA reverted and dose-dependently increased the level of aquaporin-3 (AQP3), the expression of which was down-regulated by UVB. The UV-induced MMP-9 level and activity were reduced by GA pre-treatment. Concomitantly, GA reverted mitogen-activated protein kinase (MMP-9) activation and inhibited the extracellular signal-regulated kinase activation (p38, pERK) triggered by UVB. The animal model also presented that GA attenuated the wrinkles caused by UVB on the mouse dorsal skin. Finally, GA triggers the transient receptor potential vanilloid-1 (TRPV-1) channel to initiate the anti-photoaging mechanism in keratinocytes. These findings clearly indicated that the mechanisms of GA promote skin protection against UVB-induced photoaging and wrinkle formation. GA might be an important reagent and more widely used to prevent UVB-induced skin aging.

PER, a Circadian Clock Component, Mediates the Suppression of MMP-1 Expression in HaCaT Keratinocytes by cAMP

Skin circadian clock system responds to daily changes, thereby regulating skin functions. Exposure of the skin to UV irradiation induces the expression of matrix metalloproteinase-1 (MMP-1) and causes DNA damage. It has been reported both DNA repair and DNA replication are regulated by the circadian clock in mouse skin. However, the molecular link between circadian clock and MMP-1 has little been investigated. We found PERIOD protein, a morning clock component, represses the expression of MMP-1 in human keratinocytes by using a PER-knockdown strategy. Treatment with siPer3 alleviated the suppression of MMP-1 expression induced by forskolin. Results revealed PER3 suppresses the expression of MMP-1 via cAMP signaling pathway. Additionally, we screened for an activator of PER that could repress the expression of MMP-1 using HaCaT cell line containing PER promoter-luciferase reporter gene. Results showed Lespedeza capitate extract (LCE) increased PER promoter activity. LCE inhibited the expression of MMP-1 and its effect of LCE was abolished in knockdown of PER2 or PER3, demonstrating LCE can repress the expression of MMP-1 through PER. Since circadian clock component PER can regulate MMP-1 expression, it might be a new molecular mechanism to develop therapeutics to alleviate skin aging and skin cancer.

Eupatilin with PPARα agonistic effects inhibits TNFα-induced MMP signaling in HaCaT cells

Eupatilin (5,7-dihydroxy-3,4,6-trimethoxyflavone) is a flavonoid compound exhibiting several beneficial biological activities, including neuroprotection, anti-cancer, antinociception, chondroprotection, anti-oxidation, and anti-inflammation. Our previous study demonstrated that eupatilin specifically activates peroxisome proliferator-activated receptor alpha (PPARα) through direct binding. The PPAR subfamily includes ligand-dependent transcription factors that consist of three isotypes: PPARα, PPARβ/δ, and PPARγ. All isotypes are involved in inflammation, epidermal proliferation/differentiation and skin barrier function. Among them, PPARα regulates lipid and glucose metabolism and skin homeostasis. In this study, we confirm that the ability of eupatilin as a PPARα activator significantly inhibited tumor necrosis factor-alpha (TNFα)-induced matrix metalloproteinase (MMP)-2/-9 expression and proteolytic activity in HaCaT human epidermal keratinocytes. Furthermore, we found that eupatilin subsequently suppressed IκBα phosphorylation, blocked NF-κB p65 nuclear translocation and down-regulated MAPK/AP-1 signaling via PPARα activation. Taken together, our data suggest that eupatilin inhibits TNFα-induced MMP-2/-9 expression by suppressing NF-κB and MAPK⁄AP-1 pathways via PPARα. Our findings suggest the usefulness of eupatilin for preventing skin aging.

Skin delivery of epigallocatechin-3-gallate (EGCG) and hyaluronic acid loaded nano-transfersomes for antioxidant and anti-aging effects in UV radiation induced skin damage

The present work attempts to develop and statistically optimize transfersomes containing EGCG and hyaluronic acid to synergize the UV radiation-protective ability of both compounds, along with imparting antioxidant and anti-aging effects. Transfersomes were prepared by thin film hydration technique, using soy phosphatidylcholine and sodium cholate, combined with high-pressure homogenization. They were characterized with respect to size, polydispersity index, zeta potential, morphology, entrapment efficiency, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), in vitro antioxidant activity and ex vivo skin permeation studies. Cell viability, lipid peroxidation, intracellular ROS levels and expression of MMPs (2 and 9) were determined in human keratinocyte cell lines (HaCaT). The composition of the transfersomes was statistically optimized by Design of Experiments using Box–Behnken design with four factors at three levels. The optimized transfersome formulation showed vesicle size, polydispersity index and zeta potential of 101.2 ± 6.0 nm, 0.245 ± 0.069 and −44.8 ± 5.24 mV, respectively. FTIR and DSC showed no interaction between EGCG and the selected excipients. XRD results revealed no form conversion of EGCG in its transfersomal form. The optimized transfersomes were found to increase the cell viability and reduce the lipid peroxidation, intracellular ROS and expression of MMPs in HaCaT cells. The optimized transfersomal formulation of EGCG and HA exhibited considerably higher skin permeation and deposition of EGCG than that observed with plain EGCG. The results underline the potential application of the developed transfersomes in sunscreen cream/lotions for improvement of UV radiation-protection along with deriving antioxidant and anti-aging effects.

Role of Matrix Metalloproteinases in Photoaging and Photocarcinogenesis

Matrix metalloproteinases (MMPs) are zinc-containing endopeptidases with an extensive range of substrate specificities. Collectively, these enzymes are able to degrade various components of extracellular matrix (ECM) proteins. Based on their structure and substrate specificity, they can be categorized into five main subgroups, namely (1) collagenases (MMP-1, MMP-8 and MMP-13); (2) gelatinases (MMP-2 and MMP-9); (3) stromelysins (MMP-3, MMP-10 and MMP-11); (4) matrilysins (MMP-7 and MMP-26); and (5) membrane-type (MT) MMPs (MMP-14, MMP-15, and MMP-16). The alterations made to the ECM by MMPs might contribute in skin wrinkling, a characteristic of premature skin aging. In photocarcinogenesis, degradation of ECM is the initial step towards tumor cell invasion, to invade both the basement membrane and the surrounding stroma that mainly comprises fibrillar collagens. Additionally, MMPs are involved in angiogenesis, which promotes cancer cell growth and migration. In this review, we focus on the present knowledge about premature skin aging and skin cancers such as basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma, with our main focus on members of the MMP family and their functions.

Youngiasides A and C Isolated from Youngia denticulatum Inhibit UVB-Induced MMP Expression and Promote Type I Procollagen Production via Repression of MAPK/AP-1/NF-κB and Activation of AMPK/Nrf2 in HaCaT Cells and Human Dermal Fibroblasts

This study investigated the effects of youngiaside A (YA), youngiaside C (YC), and Youngia denticulatum extract (YDE) on extrinsic aging and assessed its molecular mechanisms in UVB-irradiated HaCaT keratinocytes and human dermal fibroblasts (HDFs). The results showed that YA, YC, and YDE decreased matrix metalloproteinase (MMP) expression and production in HaCaT cell and HDFs and increased collagen expression and production in HDFs. In addition, YA, YC, and YDE significantly increased antioxidant enzyme expression, thereby down-regulating UVB-induced reactive oxygen species (ROS) production and ROS-induced mitogen-activated protein kinase (MAPK) and activator protein-1 (AP-1) signaling in HaCaT cells. Furthermore, YA, YC, and YDE reduced phosphorylation of IκBα and IKKα/β, blocked nuclear factor-κB (NF-κB) p65 nuclear translocation, and strongly suppressed pro-inflammatory mediators. Finally, YA, YC, and YDE augmented UVB-induced adenosine monophosphate activated protein kinase (AMPK) phosphorylation and YA and YC did not inhibit MMP-1 production in AMPK inhibitor or nuclear factor-erythroid 2-related factor-2 (Nrf2) siRNA-treated HaCaT cells. The results suggest that these compounds could be potential therapeutic agents for prevention and treatment of skin photoaging.

Germacrane sesquiterpenes isolated from the rhizome of Curcuma xanthorrhiza Roxb. inhibit UVB-induced upregulation of MMP-1, -2, and -3 expression in human keratinocytes

Four sesquiterpenes were isolated from the rhizome of Curcuma xanthorrhiza Roxb.: furanodiene (1), germacrone (2), furanodienone (3), and 13-hydroxygermacrone (4). Importantly, this was the first time compounds 1 and 4 were isolated from this plant. The chemical structures of these compounds were determined using 1D- and 2D-nuclear magnetic resonance, infrared spectroscopy, and electron ionization mass spectrometry analyses. Among the isolated compounds, compounds 2 and 4 inhibited UVB-induced upregulation of the mRNA and protein expression levels of MMP-1, MMP-2, and MMP-3 in human keratinocytes (HaCaT). Moreover, this upregulation occurred in a dose-dependent manner over the range of 1-10 μM for each compound.

Anti-photoaging effect of aaptamine in UVB-irradiated human dermal fibroblasts and epidermal keratinocytes

Chronic exposure to ultraviolet (UV) irradiation causes sunburn, inflammatory responses, skin cancer, and photoaging. Photoaging, in particular, generates reactive oxygen species (ROS) that stimulate mitogen-activated protein kinase (MAPK) signaling and transcription factors. UV irradiation also activates matrix metalloproteinases (MMPs) expression and inactivates collagen synthesis. Aaptamine, a marine alkaloid isolated from the marine sponge, has been reported to have antitumor, antimicrobial, antiviral, and antioxidant activities. However, the photo-protective effects of aaptamine have not been elucidated. In this study, our data demonstrated that aaptamine deactivated UVB-induced MAPK and activator protein-1 signaling by suppressing ROS, resulting in attenuating the expression of MMPs in UVB-irradiated human dermal fibroblasts. Aaptamine also decreased proinflammatory cytokines such as cyclooxygenase-2, tumor necrosis factor-α, interleukin-1β, and nuclear factor-kappa B subunits in UVB-irradiated human keratinocytes. In conclusion, we suggest that aaptamine represents a novel and effective strategy for treatment and prevention of photoaging.

UVA irradiation induced heme oxygenase-1: a novel phototherapy for morphea

Long wave UVA radiation (340-400 nm) causes detrimental as well as beneficial effects on human skin. Studies of human skin fibroblasts irradiated with UVA demonstrate increased expression of both antifibrotic heme oxygenase-1 (HO-1) and matrix metalloproteinase 1 (MMP-1). The use of UVA-induced MMP-1 is well-studied in treating skin fibrotic conditions such as localized scleroderma, now called morphea. However, the role that UVA-induced HO-1 plays in phototherapy of morphea has not been characterized. In the present manuscript, we have illustrated and reviewed the biological function of HO-1 and the use of UVA1 wavebands (340-400 nm) for phototherapy; the potential use of HO-1 induction in UVA therapy of morphea is also discussed.

Pinus densiflora extract protects human skin fibroblasts against UVB-induced photoaging by inhibiting the expression of MMPs and increasing type I procollagen expression

Exposure to ultraviolet (UV) light can cause skin photoaging, which is associated with upregulation of matrix metalloproteinases (MMPs) and downregulation of collagen synthesis. It has been reported that MMPs, especially MMP-1, MMP-3 and MMP-9, decrease the elasticity of the dermis by degrading collagen. In this study, we assessed the effects of Pinus densiflora extract (PDE) on photoaging and investigated its mechanism of action in human skin fibroblast (Hs68) cells after UVB exposure using real-time polymerase chain reaction, Western blot analysis, and enzymatic activity assays. PDE exhibited an antioxidant activity and inhibited elastase activities in vitro. We also found that PDE inhibited UVB-induced cytotoxicity, MMP-1 production and expression of MMP-1, -3 and -9 mRNA in Hs68 cells. In addition, PDE decreased UVB-induced MMP-2 activity and MMP-2 mRNA expression. Moreover, PDE prevented the decrease of type I procollagen mediated by exposure to UVB irradiation, an effect that is linked to the upregulation and downregulation of Smad3 and Smad7, respectively. Another effect of UV irradiation is to stimulate activator protein 1 (AP-1) activity via overexpression of c-Jun/c-Fos, which, in turn, upregulates MMP-1, -3, and -9. In this study, we found that PDE suppressed UV-induced c-Jun and c-Fos mRNA expression. Taken together, these results demonstrate that PDE regulates UVB-induced expression of MMPs and type I procollagen synthesis by inhibiting AP-1 activity and restoring impaired Smad signaling, suggesting that PDE may be useful as an effective anti-photoaging agent.

Biological and metabolic response in STS-135 space-flown mouse skin

There is evidence that space flight condition-induced biological damage is associated with increased oxidative stress and extracellular matrix (ECM) remodeling. To explore possible mechanisms, changes in gene expression profiles implicated in oxidative stress and in ECM remodeling in mouse skin were examined after space flight. The metabolic effects of space flight in skin tissues were also characterized. Space Shuttle Atlantis (STS-135) was launched at the Kennedy Space Center on a 13-day mission. Female C57BL/6 mice were flown in the STS-135 using animal enclosure modules (AEMs). Within 3-5 h after landing, the mice were euthanized and skin samples were harvested for gene array analysis and metabolic biochemical assays. Many genes responsible for regulating production and metabolism of reactive oxygen species (ROS) were significantly (p < 0.05) altered in the flight group, with fold changes >1.5 compared to AEM control. For ECM profile, several genes encoding matrix and metalloproteinases involved in ECM remodeling were significantly up-/down-regulated following space flight. To characterize the metabolic effects of space flight, global biochemical profiles were evaluated. Of 332 named biochemicals, 19 differed significantly (p < 0.05) between space flight skin samples and AEM ground controls, with 12 up-regulated and 7 down-regulated including altered amino acid, carbohydrate metabolism, cell signaling, and transmethylation pathways. Collectively, the data demonstrated that space flight condition leads to a shift in biological and metabolic homeostasis as the consequence of increased regulation in cellular antioxidants, ROS production, and tissue remodeling. This indicates that astronauts may be at increased risk for pathophysiologic damage or carcinogenesis in cutaneous tissue.

Comparative effects of biodynes, tocotrienol-rich fraction, and tocopherol in enhancing collagen synthesis and inhibiting collagen degradation in stress-induced premature senescence model of human diploid fibroblasts

Biodynes, tocotrienol-rich fraction (TRF), and tocopherol have shown antiaging properties. However, the combined effects of these compounds on skin aging are yet to be investigated. This study aimed to elucidate the skin aging effects of biodynes, TRF, and tocopherol on stress-induced premature senescence (SIPS) model of human diploid fibroblasts (HDFs) by determining the expression of collagen and MMPs at gene and protein levels. Primary HDFs were treated with biodynes, TRF, and tocopherol prior to hydrogen peroxide (H₂O₂) exposure. The expression of COL1A1, COL3A1, MMP1, MMP2, MMP3, and MMP9 genes was determined by qRT-PCR. Type I and type III procollagen proteins were measured by Western blotting while the activities of MMPs were quantified by fluorometric Sensolyte MMP Kit. Our results showed that biodynes, TRF, and tocopherol upregulated collagen genes and downregulated MMP genes (P < 0.05). Type I procollagen and type III procollagen protein levels were significantly increased in response to biodynes, TRF, and tocopherol treatment (P < 0.05) with reduction in MMP-1, MMP-2, MMP-3, and MMP-9 activities (P < 0.05). These findings indicated that biodynes, TRF, and tocopherol effectively enhanced collagen synthesis and inhibited collagen degradation and therefore may protect the skin from aging.

Fucosterol inhibits matrix metalloproteinase expression and promotes type-1 procollagen production in UVB-induced HaCaT cells

Ultraviolet (UV) radiation damages human skin and causes skin diseases such as epidermal hyperplasia, sunburn, inflammatory responses and photoaging. Photoaging is associated with upregulated matrix metalloproteinase (MMP) expression and downregulated collagen synthesis. Fucosterol, which is isolated from marine brown algae, has been reported to possess antioxidant and anticancer activities; however, its effects on photoaging are unknown. This study assessed the effects of fucosterol on photoaging and investigated its mechanisms of action in UV-irradiated immortalized human keratinocytes (HaCaT) by enzyme-linked immunosorbent assay, semi-quantitative reverse transcription-polymerase chain reaction, Western blot analysis and 2',7'-dichlorofluorescein diacetate assay. Our results showed that fucosterol attenuated UV-induced MMP and inflammatory cytokine expression by deactivating mitogen-activated protein kinases (MAPKs) induced by reactive oxygen species. Fucosterol also increased type-I procollagen and antioxidant enzyme expression. Taken together, fucosterol regulates the expression of MMPs and type-I procollagen in UV-irradiated HaCaT by modulating MAPK, suggesting it as a potential candidate for prevention and treatment of skin aging.

TIMP-2 fusion protein with human serum albumin potentiates anti-angiogenesis-mediated inhibition of tumor growth by suppressing MMP-2 expression

TIMP-2 protein has been intensively studied as a promising anticancer candidate agent, but the in vivo mechanism underlying its anticancer effect has not been clearly elucidated by previous works. In this study, we investigated the mechanism underlying the anti-tumor effects of a TIMP-2 fusion protein conjugated with human serum albumin (HSA/TIMP-2). Systemic administration of HSA/TIMP-2 effectively inhibited tumor growth at a minimum effective dose of 60 mg/kg. The suppressive effect of HSA/TIMP-2 was accompanied by a marked reduction of in vivo vascularization. The anti-angiogenic activity of HSA/TIMP-2 was directly confirmed by CAM assays. In HSA/TIMP-2-treated tumor tissues, MMP-2 expression was profoundly decreased without a change in MT1-MMP expression of PECAM-1-positive cells. MMP-2 mRNA was also decreased by HSA/TIMP-2 treatment of human umbilical vein endothelial cells. Zymographic analysis showed that HSA/TIMP-2 substantially decreased extracellular pro-MMP-2 activity (94–99% reduction) and moderately decreased active MMP-2 activity (10–24% reduction), suggesting MT1-MMP-independent MMP-2 modulation. Furthermore, HSA/TIMP-2 had no effect on in vitro active MMP-2 activity and in vivo MMP-2 activity. These studies show that HSA/TIMP-2 potentiates anti-angiogenic activity by modulating MMP-2 expression, but not MMP-2 activity, to subsequently suppress tumor growth, suggesting an important role for MMP-2 expression rather than MMP-2 activity in anti-angiogenesis.

In vitro and in vivo skin anti-aging evaluation of gel containing niosomes loaded with a semi-purified fraction containing gallic acid from Terminalia chebula galls

CONTEXT

The galls of Terminalia chebula Retz. (Combretaceae) frequently appear in many Thai Lanna medicinal plant recipes for promotion of longevity.

OBJECTIVE

The objective of this study was to evaluate the skin anti-aging of gel containing niosomes loaded with a semi-purified fraction containing gallic acid from T. chebula galls.

METHOD

The semi-purified fraction containing phenolic compounds including gallic acid isolated from T. chebula galls loaded in non-elastic or elastic niosomes, and its developed gel, were evaluated for rabbit skin irritation by the closed patch test and skin anti-aging in human volunteers by measuring skin elasticity and roughness.

RESULTS

Gel containing the fraction unloaded (SS) or loaded in non-elastic (SN) or elastic (SE) niosomes and gallic acid loaded in non-elastic (GN) or elastic (GE) niosomes showed no skin irritation, whereas the unloaded gallic acid (GS) gave the irritation in rabbit's skin by the closed patch test. The % parameter changes of skin elastic recovery and skin elastic extension when applied with SN and SE gels were +28.73 and +32.57; -21.25 and -22.63%, respectively. SN and SE gel also showed a significant decrease of the maximum and average roughness values with the parameter changes of -29.43 and -32.38; -39.47 and -35.28%, respectively.

CONCLUSION

The semi-purified fraction loaded in niosomes indicated not only higher chemical stability of gallic acid containing in the fraction, but also more in vivo anti-aging activities than the unloaded fraction when incorporated in gel.

Iron sensitizes keratinocytes and fibroblasts to UVA-mediated matrix metalloproteinase-1 through TNF-α and ERK activation

Oestrogen deficiency is regarded as the main causative factor in postmenopausal skin ageing and photoageing. While women after menopause experience low levels of oestrogen because of cease of ovarian function, they are also exposed to high levels of iron as a result of cessation of menstruation. In this study, we investigated whether this increase in iron presents a risk to the postmenopausal skin. Because of the lack of appropriate animal models to closely mimic the low oestrogen and high iron conditions, we tested the hypothesis in a high iron and low oestrogen culture model. Here, we showed that primary human dermal fibroblasts exposed to iron did not affect the baseline levels of matrix metalloproteinase-1 (MMP-1) activity. However, the iron-exposed fibroblasts were sensitized to UVA exposure, which resulted in a synergistic increase in MMP-1. UVA activated the three members of MAPK family: ERKs, p38, and JNKs. Additional activation of ERKs by iron contributed to the synergistic increases. Primary normal human epidermal keratinocytes (NHEK) did not respond to iron or UVA exposure as measured by MMP-1, but produced tumor necrosis factor-alpha (TNF-α) in the media, which then stimulated MMP-1 in fibroblasts. Our results indicate that iron and UVA increase MMP-1 activity in dermal fibroblasts not only directly through ERK activation but also by an indirect paracrine loop through TNF-α released by NHEK. We conclude that in addition to oestrogen deficiency, increased iron as a result of menopause could be a novel risk factor by sensitizing postmenopausal skin to solar irradiation.

Differential expression of oxidative stress and extracellular matrix remodeling genes in low- or high-dose-rate photon-irradiated skin

Changes in the expression of genes implicated in oxidative stress and in extracellular matrix (ECM) remodeling and selected protein expression profiles in mouse skin were examined after exposure to low-dose-rate or high-dose-rate photon irradiation. ICR mice received whole-body γ rays to total doses of 0, 0.25, 0.5 and 1 Gy at dose rates of 50 cGy/h or 50 cGy/min. Skin tissues were harvested for characterization at 4 h after irradiation. For oxidative stress after low-dose-rate exposure, 0.25, 0.5 and 1 Gy significantly altered 27, 23 and 25 genes, respectively, among 84 genes assessed (P < 0.05). At doses as low as 0.25 Gy, many genes responsible for regulating the production of reactive oxygen species (ROS) were significantly altered, with changes >2-fold compared to 0 Gy. For an ECM profile, 18-20 out of 84 genes were significantly up- or downregulated after low-dose-rate exposure. After high-dose-rate irradiation, of 84 genes associated with oxidative stress, 16, 22 and 22 genes were significantly affected after 0.25, 0.5 and 1 Gy, respectively. Compared to low-dose-rate radiation, high-dose-rate exposure resulted in different ECM gene expression profiles. The most striking changes after low-dose-rate or high-dose-rate exposure on ECM profiles were on genes encoding matrix metalloproteinases (MMPs), e.g., Mmp2 and Mmp15 for low dose rate and Mmp9 and Mmp11 for high dose rate. Immunostaining for MMP-2 and MMP-9 proteins showed radiation dose rate-dependent differences. These data revealed that exposure to low total doses with low-dose-rate or high-dose-rate photon radiation induced oxidative stress and ECM-associated alterations in gene expression profiles. The expression of many genes was differentially regulated by different total dose and/or dose-rate regimens.

In vivo identification of solar radiation-responsive gene network: role of the p38 stress-dependent kinase

Solar radiation is one of the most common threats to the skin, with exposure eliciting a specific protective cellular response. To decrypt the underlying mechanism, we used whole genome microarrays (Agilent 44K) to study epidermis gene expression in vivo in skin exposed to simulated solar radiation (SSR). We procured epidermis samples from healthy Caucasian patients, with phototypes II or III, and used two different SSR doses (2 and 4 J/cm(2)), the lower of which corresponded to the minimal erythemal dose. Analyses were carried out five hours after irradiation to identify early gene expression events in the photoprotective response. About 1.5% of genes from the human genome showed significant changes in gene expression. The annotations of these affected genes were assessed. They indicated a strengthening of the inflammation process and up-regulation of the JAK-STAT pathway and other pathways. Parallel to the p53 pathway, the p38 stress-responsive pathway was affected, supporting and mediating p53 function. We used an ex vivo assay with a specific inhibitor of p38 (SB203580) to investigate genes the expression of which was associated with active p38 kinase. We identified new direct p38 target genes and further characterized the role of p38. Our findings provide further insight into the physiological response to UV, including cell-cell interactions and cross-talk effects.

In vitro anti-aging activities of Terminalia chebula gall extract

CONTEXT

The Thai Lanna region has its own folklores and wisdoms in various fields such as traditional medicines. The galls of Terminalia chebula Retz. (Combretaceae) frequently appear in many Thai Lanna medicinal plant recipes for promoting longevity.

OBJECTIVES

To investigate the in vitro anti-aging activities of the extracts from 15 plants including T. chebula gall selected from the Thai medicinal plant recipes that have been traditionally used for longevity.

MATERIALS AND METHODS

The plant extracts were prepared by four extraction methods including hot (HW) and cold (CW) aqueous processes and hot (HM) and cold (CM) methanol processes. These extracts were tested for antioxidative and tyrosinase inhibition activity as well as the proliferative and MMP-2 inhibition activity on early aging human skin fibroblasts in order to evaluate their in vitro anti-aging activity.

RESULTS

At 0.1 mg/mL, the CW extract of T. chebula gall exhibited the highest DPPH radical scavenging activity with scavenging of 84.64% +/- 2.22%, whereas ascorbic acid, alpha-tocopherol and butylated hydroxyl toluene gave 96.50% +/- 0.1%, 35.74% +/- 0.2% and 27.43% +/- 0.1%, respectively. The CW extract of T. chebula gall indicated the highest stimulation index (SI) on normal human fibroblast proliferation of 1.441 which was more active than ascorbic acid (SI 1.21). This extract has also demonstrated MMP-2 inhibition on fibroblasts determined by zymography 1.37 times more potent than ascorbic acid.

DISCUSSION AND CONCLUSION

This study has confirmed the traditional use of T. chebula gall in many Thai medicinal plant recipes for longevity which will be beneficial for further development of anti-aging products.

Silibinin prevents TPA-induced MMP-9 expression and VEGF secretion by inactivation of the Raf/MEK/ERK pathway in MCF-7 human breast cancer cells

Matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression are pivotal steps in cancer metastasis. Herein, we investigated the effect of silibinin, a major constituent (flavanolignan) of the fruits of Silybum marianum, on 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced MMP-9 and VEGF expression in MCF-7 human breast cancer cells. The expression of MMP-9 and VEGF in response to TPA was increased, whereas TPA-induced MMP-9 and VEGF expression was decreased by silibinin. To investigate the regulatory mechanism of silibinin on TPA-induced MMP-9 and VEGF expression, we pretreated cells with various inhibitors, such as UO126 (MEK1/2 inhibitor), SP600125 (JNK inhibitor), and SB203580 (p38 inhibitor). Interestingly, TPA-induced MMP-9 expression was significantly inhibited by UO126, but not by SP600125 and SB203580. In addition, we pretreated cells with 100 microM silibinin prior to TPA treatment. TPA-induced MEK and ERK phosphorylation was significantly decreased by silibinin in MCF7 cells. TPA-induced VEGF expression was also suppressed by UO126. On the other hand, we found that adenoviral constitutive active-MEK (Ad-CA-MEK) significantly increased MMP-9 and VEGF expression. Taken together, we suggest that the inhibition of TPA-induced MMP-9 and VEGF expression by silibinin is mediated by the suppression of the Raf/MEK/ERK pathway in MCF-7 breast cancer cells.

Berberine suppresses TNF-alpha-induced MMP-9 and cell invasion through inhibition of AP-1 activity in MDA-MB-231 human breast cancer cells

Invasion of cancer cell induced by matrix metalloproteinase-9 (MMP-9) is one of pivotal steps in cancer metastasis. Herein, we investigated how cell invasion was regulated by berberine (BBR), an isoquinoline derivative alkaloid compound, in MDA-MB-231 human breast cancer cells. The basal level of MMP-9 activity and expression was dose-dependently increased by TNF-α, while TNF-α-induced MMP-9 gelatinase activity and expression was decreased by BBR. To investigate regulatory mechanism of TNF-α-induced MMP-9 expression, we pretreated cells with UO126 (MEK inhibitor), SB203580 (p38 inhibitor) and SP600125 (JNK inhibitor), respectively. Interestingly, TNF-α-induced MMP-9 activity and expression was decreased by UO126 and SB203580, but not by SP600125. Therefore, we further examined the effects of BBR on TNF-α-induced AP-1 DNA binding activity which is a downstream target of ERK and p38. Our data showed that TNF-α-induced AP-1 DNA binding activity was inhibited by BBR. Finally, we investigated the effect of BBR on TNF-α-induced cell invasion. TNF-α-induced cell invasion was significantly decreased by BBR treatment. Taken together, we suggest that TNF-α-induced MMP-9 expression and cell invasion are decreased by BBR through the suppression of AP-1 DNA binding activity in MDA-MB-231 human breast cancer cells.

Berberine prevents UV-induced MMP-1 and reduction of type I procollagen expression in human dermal fibroblasts

Matrix metalloproteinases (MMPs) induction and type I procollagen reduction in photoaging of the skin due to exposure to ultraviolet (UV) irradiation. Therefore, regulation of these genes has been suggested to be a useful tool to abolish skin aging. In this study, antioxidative plant ingredients used in traditional Chinese medicine, berberine (BBR) was investigated for their capacity to regulate MMP-1 and type I procollagen expression in human dermal fibroblasts. Our results showed that both basal and UV-induced MMP-1 expression was decreased by BBR. On the other hand, type I procollagen expression was dose-dependently increased by it. In addition, UV-induced reduction of type I procollagen expression is recovered by it. Therefore, we suggest that BBR may be a possible candidate for anti-skin aging agent.

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.

Cholesterol inhibits MMP-9 expression in human epidermal keratinocytes and HaCaT cells

Cholesterol is a major component of skin lipids and acts as a regulator of vesicular trafficking and signal transduction. However, the function of cholesterol on matrix metalloproteinases (MMPs) expression of human skin is not fully understood. Here, we investigated the effects of cholesterol on MMP-9 expression in normal human keratinocytes (NHK) and HaCaT cells. Basal level of MMP-9 expression was decreased by cholesterol in NHK. On the other hand, MMP-9 expression was increased by the cholesterol depletion agent, methyl-beta-cyclodextrin (MbetaCD), while it was inhibited by cholesterol repletion in HaCaT cells. MbetaCD induced ERK and JNK phosphorylation were prevented by cholesterol repletion. The inhibition of ERK and JNK decreased MbetaCD-induced MMP-9 expression. Therefore, our results suggest that cholesterol regulates MMP-9 expression through ERK and JNK-dependent pathways.

Non-invasive study of gelatinases in sun-exposed and unexposed healthy human skin based on measurements in stratum corneum

Gelatinases, which belong to the family of matrix metalloproteinases, degrade various components of skin, and may be involved in photoaging, since they are upregulated by low-dose UV exposure to the skin. However, their behavior in healthy human skin is still unclear. In the present study, gelatinases was specifically detected in stratum corneum (SC) of skin from sun-exposed sites, including the face, in healthy humans, but not in SC of skin from unexposed sites. Following experimental UVB irradiation of the abdomen in volunteers, gelatinases were detected in tape-stripped SC from the site for several weeks, and subsequently disappeared. The appearance of gelatinase in SC after a lag time consistent with SC turnover is considered to reflect upregulation of gelatinase expression in keratinocytes in response to UVB-exposure of the skin. A survey of gelatinases in facial SC samples collected by tape-stripping from the cheeks of 100 healthy women revealed that the enzyme was present in 90% of subjects. These results, taken together, suggest that gelatinase is constantly upregulated by sunlight in the facial epidermis of most women during their daily lives, and may be an etiological factor in photoaging, e.g., by promoting wrinkle formation.

JUN siRNA regulates matrix metalloproteinase-2 expression, microvascular endothelial growth and retinal neovascularisation

Transcription factors link changes in the extracellular environment with alterations in gene expression. As such, these molecules serve as attractive targets for intervention in pathological settings. Since JUN has been linked with microvascular disease in humans, we hypothesised that small interfering RNA (siRNA) targeting this immediate-early gene may be useful agents that suppress endothelial growth and neovascularisation. Here we show that Jun siRNA inhibits Jun mRNA and protein expression in murine microvascular endothelial cells, blocks cell proliferation and suppresses migration in a scratch-wound assay. It also inhibits three-dimensional tubular formation on basement membrane extracts and reduces angiogenesis in mice bearing Matrigel plugs as subcutaneous implants. Single intravitreal administration of Jun siRNA reduces neovascularisation in a murine model of proliferative retinopathy, and suppresses endothelial JUN and matrix metalloproteinase-2 (MMP-2) immunoreactivity in retinal vessels, data supported by its repression of MMP-2 expression and gelatinolytic activity in vitro. Co-administration of TGFbeta with the siRNA reverses this neovascular inhibitory effect, which is in turn abrogated by cis-9-octadecenoyl-N-hydroxylamide, consistent with the involvement of a metalloproteinase such as MMP-2. Thus, JUN siRNA can serve as a specific inhibitor of aberrant endothelial and neovascular growth.

UVA-mediated down-regulation of MMP-2 and MT1-MMP coincides with impaired angiogenic phenotype of human dermal endothelial cells

UVA irradiation, dose-dependently (5-20 J/cm2), was shown to impair the morphogenic differentiation of human microvascular endothelial cells (HMECs) on Matrigel. Parallely, UVA down-regulated the expression of MMP-2 and MT1-MMP, both at the protein and the mRNA levels. On the contrary, the production of MMP-1 and TIMP-1 by HMECs increased following UVA treatment. The inhibitory effect of UVA on MMP expression and pseudotubes formation was mediated by UVA-generated singlet oxygen (1O2). The contribution of MT1-MMP, but not TIMP-1, to the regulation of HMECs' angiogenic phenotype following UVA irradiation was suggested using elastin-derived peptides and TIMP-1 blocking antibody, respectively.

Autogenous bone chips: influence of a new piezoelectric device (PiezosurgeryR) on chip morphology, cell viability and differentiation

AIM

The aim of the present study was to investigate the influence of a new piezoelectric device, designed for harvesting autogenous bone chips from intra-oral sites, on chip morphology, cell viability and differentiation.

METHODS

A total of 69 samples of cortical bone chips were randomly gained by either (1) a piezoelectric device (PS), or (2) conventional rotating drills (RD). Shape and size of the bone chips were compared by means of morphometrical analysis. Outgrowing osteoblasts were identified by means of alkaline phosphatase activity (AP), immunhistochemical staining for osteocalcin (OC) synthesis and reverse transcriptase-polymerase chain reaction phenotyping.

RESULTS

In 88.9% of the RD and 87.9% of the PS specimens, an outgrowth of adherent cells nearby the bone chips was observed after 6-19 days. Confluence of cells was reached after 4 weeks. Positive staining for AP and OC identified the cells as osteoblasts. The morphometrical analysis revealed a statistically significant more voluminous size of the particles collected with PS than RD.

CONCLUSION

Within the limits of the present study, it may be concluded that both the harvesting methods are not different from each other concerning their detrimental effect on viability and differentiation of cells growing out of autogenous bone chips derived from intra-oral cortical sites.

Thioredoxin secreted upon ultraviolet A irradiation modulates activities of matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 in human dermal fibroblasts

Regulation of the balance of matrix metalloproteinase-2 (MMP-2) and its tissue inhibitor (TIMP-2) by thioredoxin (Trx) was investigated in human dermal fibroblasts. Expression and secretion of Trx and Trx reductase 1 (TR1) was increased after ultraviolet (UV) A irradiation. A significant increase in proMMP-2 activity and a decrease of TIMP-2 activity in supernatants of UVA-irradiated fibroblasts were observed in gelatin and reverse zymography compared to non-irradiated fibroblasts. Removal of Trx or TR1 by immunoprecipitation diminished these changes in proMMP-2 activity. Incubation with 5, 5'-dithio-bis-2-nitrobenzoic acid (DTNB) also suppressed these changes. Incubation with recombinant Trx or TR decreased TIMP-2 activity and increased MMP-2 activity. UVA-irradiated fibroblasts, transiently transfected with a dominant-negative mutant or wild-type Trx, showed down- or upregulation of proMMP-2 activities, respectively, without significant change of protein amount. In conclusion, thioredoxin secreted by UVA irradiation is involved in the regulation of MMP-2 and TIMP-2 activities through its redox activity in human dermal fibroblasts.

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.