p38 MAPK in regulating cellular responses to ultraviolet radiation

Specific Knockdown of the NDUFS4 Gene Reveals Important Roles of Ferroptosis in UVB-induced Photoaging

Ultraviolet (UV) irradiation significantly contributes to photoaging. Ferroptosis, an iron-dependent cell death mode recently identified, plays a key role in UVB-induced skin photoaging. This study examines the functions and regulatory mechanisms of ferroptosis in this regard. Characterized by increased intracellular iron and reactive oxygen species (ROS), ferroptosis is associated with mitochondrial function and structure. Through RNA sequencing, we identified NADH: ubiquinone oxidoreductase subunit S4 (NDUFS4), a gene implicated in UVB-mediated photoaging, and explored its role in ferroptosis by NDUFS4 knockdown. In vitro, inhibiting NDUFS4 reduced ferroptosis, decreased ROS and matrix metallopeptidase 1 levels, and increased collagen type I alpha 1 chain, glutathione peroxidase 4 (GPX4), ferritin heavy chain 1, and solute carrier family 7 member 11 levels, suggesting a reinforced ferroptosis protective mechanism. Additionally, NDUFS4 regulates ferroptosis via the mitogen-activated protein kinase (MAPK) pathway, with its knockdown reducing p38 and ERK phosphorylation and elevating GPX4 levels, enhancing ferroptosis resistance. Animal experiments supported these findings, demonstrating that Ferrostatin-1, a ferroptosis inhibitor, significantly mitigated UVB-induced skin photoaging and related protein expression. This study uncovers NDUFS4's novel role in regulating ferroptosis and provides new insights into ferroptosis-mediated UVB-induced skin photoaging.

Mechanistic studies on protective effects of total flavonoids from Ilex latifolia Thunb. on UVB-radiated human keratinocyte cell line (HaCaT cells) based on network pharmacology and molecular docking technique

The aim of the present research is to investigate anti-UVB radiation activity of total flavonoids from Ilex latifolia Thunb. (namely large-leaved Kuding tea) on human keratinocyte cell line (HaCaT cells) based on network pharmacology and molecular docking technique. Network pharmacology was used to screen target genes of active ingredients from Ilex latifolia Thunb. associated with UVB irradiation. The possible signaling pathways were analyzed by KEGG enrichment and verified by cellular experiments. Molecular docking was used to assess the affinity between the active ingredients and the core targets. The prediction of network pharmacology and molecular docking was identified by series experiment in UVB-irradiated HaCaT cells. Network pharmacology results showed that the active ingredients of Ilex latifolia Thunb. for anti-UVB irradiation were mainly flavonoids, and the possible signaling pathways were involved in PI3K-AKT, apoptosis, MAPKs, NF-κB, and JAK-STAT3. Molecular docking indicated key binding activity between AKT1-Glycitein, STAT3-Formononetin, CASP3-Formononetin, TNF-Kaempferol, CASP3-Luteolin, and AKT1-Quercetin. The total flavonoid pretreatment (0.25-1.0 mg/mL) down-regulated the expression of IL-6, IL-1β, and TNF-α in the cells determined by ELISA. The expression of phosphor PI3K, phosphor AKT, phosphor JAK, phosphor STAT3, phosphor JNK, and phosphor p38 MAPKs and COX-2 proteins in cytosolic and NF-κB p65 protein in nucleus were down-regulated and determined by western blot. It also protected UVB-irradiated cells from apoptosis by reducing apoptosis rate and down-regulating active-caspase 3. In a word, the total flavonoid treatment protected HaCaT cells from UVB injuries effectively, and the potential mechanism involves PI3K-AKT, JAK-STAT3, MAPK, and NF-κB pathway by anti-inflammatory and apoptosis action in cells. The mechanism in vivo experiment needs to be further confirmed in future.

Exploring the anti-skin inflammation substances and mechanism of Paeonia lactiflora Pall. Flower via network pharmacology-HPLC integration

BACKGROUND

Paeonia lactiflora Pall. (PL) is widely used in China as a homologous plant of medicine and food. PL flower is rich in bioactive substances with anti-inflammatory effects, while the pathogenesis of skin inflammation is complex and the specific mechanism is not clear, the current treatment of skin inflammation is mainly hormonal drugs, and hormonal drugs have obvious toxic side effects. The research on the treatment of skin inflammation by PL flowers is relatively small, so this study provides a basis for the development and utilisation of PL resources.

OBJECTIVE

Our study was to investigate the interventional effects of PL flower extracts on skin inflammation and thus to understand its functional role in the treatment of skin inflammation and its molecular mechanisms.

METHODS

The major active substances in PL flower extracts were investigated by the HPLC-DAD method, and the potential targets of action were predicted by network pharmacology, which was combined with in vitro experimental validation to explore the mechanism of PL flower extracts on the regulation of skin inflammation. The HPLC-DAD analysis identified seven major active components in PL flower extracts, and in response to the results, combined with the potential mechanism of network pharmacological prediction with skin inflammation, the PL flower extract is closely related to MAPK and NF-κB signaling pathways. In addition, we also investigated the interventional effects of PL flower extract on skin inflammation by western blot detection of MAPK signaling pathway and NF-κB signaling pathway proteins in cells.

RESULT

Seven active components were identified and quantified from the extract of PL flowers, including Gallic acid, 1,2,3,4,6-O-Pentagalloylglucose, Oxypaeoniflorin, Paeoniflorin, Albiflorin, Benzoyloxypeoniflorin, and Rutin. It was predicted targets for the treatment of skin inflammation, with PPI showing associations with targets such as TNF, MAPK1, and IL-2. KEGG enrichment analysis revealed that the main signaling pathways involved included MAPK and T cell receptor signaling pathways. Cell experiments showed that the peony flower extract could inhibit the release of NO and inflammatory factors, as well as reduce ROS levels and inhibit cell apoptosis. Furthermore, the extract was found to inhibit the activation of the MAPK and NF-κB signaling pathways in cells.

CONCLUSIONS

In this study, we found that PL flower extract can inhibit the production of cell inflammatory substances, suppress the release of inflammatory factors, and deactivate inflammatory signaling pathways, further inhibiting the production of cell inflammation. This indicates that PL flower extract has a therapeutic effect on skin inflammation.

Elaeagnus umbellata Fruit Extract Protects Skin from Ultraviolet-Mediated Photoaging in Hairless Mice

Photoaging refers to the accumulation of skin damage which includes wrinkle formation, loss of elasticity, and epidermal thickening due to repeated ultraviolet (UV) irradiation. The present study investigated the protective effects of Elaeagnus umbellata fruit extract (Elaea) on UV-mediated photoaged skin of SKH1 hairless mice and compared the effects of Elaea with ascorbic acid. Although there was no difference in body weight between groups during experimental period, oral administration of 50-200 mg/kg Elaea once daily for 15 weeks significantly prevented an increase in skin weight, epithelial thickening of epidermis, and apoptosis caused by UV irradiation. Skin replica and histopathological analyses revealed that Elaea dose-dependently decreased wrinkle and microfold formation. In addition, Elaea administration restored UV-mediated reduction in type I collagen and hyaluronan through the inhibition of matrix metalloproteinases and p38 mitogen-activated protein kinase expression. Moreover, Elaea suppressed UV-dependent increases in superoxide anion production, fatty acid oxidation, and protein nitration by up-regulating antioxidant system. Furthermore, Elaea alleviated infiltration of inflammatory cells in UV-irradiated skin. The preventive effects of 100 mg/kg Elaea administration against UV-induced photoaging were similar to those by 100 mg/kg ascorbic acid. Collectively, the present study suggests that the E. umbellata fruit is a promising edible candidate to prevent skin photoaging.

Role of reactive oxygen species in ultraviolet-induced photodamage of the skin

Reactive oxygen species (ROS), such as superoxides (O2 •-) and hydroxyl groups (OH·), are short-lived molecules containing unpaired electrons. Intracellular ROS are believed to be mainly produced by the mitochondria and NADPH oxidase (NOX) and can be associated with various physiological processes, such as proliferation, cell signaling, and oxygen homeostasis. In recent years, many studies have indicated that ROS play crucial roles in regulating ultraviolet (UV)-induced photodamage of the skin, including exogenous aging, which accounts for 80% of aging. However, to the best of our knowledge, the detailed signaling pathways, especially those related to the mechanisms underlying apoptosis in which ROS are involved have not been reviewed previously. In this review, we elaborate on the biological characteristics of ROS and its role in regulating UV-induced photodamage of the skin.

Sesamin attenuates UVA-induced keratinocyte injury via inhibiting ASK-1-JNK/p38 MAPK pathways

BACKGROUND

Ultraviolet (UV) exposure-stimulated reactive oxygen species (ROS) formation in keratinocytes is a crucial factor in skin aging. Phytochemicals have become widely popular for protecting the skin from UV-induced cell injury. Sesamin (SSM) has been shown to play a role in extensive pharmacological activity and exhibit photoprotective effects.

AIM

To assess the protective effect of SSM on UVA-irradiated keratinocytes and determine its potential antiphotoaging effect.

METHODS

HaCaT keratinocytes pretreated with SSM were exposed to UVA radiation at 8 J/cm2 for 10 min. Cell viability and oxidative stress indicators were evaluated using a cell counting kit-8 and lactate dehydrogenase (LDH), malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) assay kits. Apoptosis and intracellular ROS levels were analyzed using annexin V-fluorescein isothiocyanate/propyridine iodide and dichlorodihydrofluorescein diacetate staining, respectively. Protein levels of matrix metalloprotein-1 (MMP-1), MMP-9, Bax/Bcl-2, and mitogen-activated protein kinase (MAPK) pathway proteins, phospho-apoptosis signal-regulating kinase-1 (p-ASK-1)/ASK-1, phospho-c-Jun N-terminal protein kinase (p-JNK)/JNK, and p-p38/p38 were determined using western blotting.

RESULTS

Sesamin showed no cytotoxicity until 160 μmol/L on human keratinocytes. Sesamin pretreatment (20 and 40 μM) reversed the suppressed cell viability, increased LDH release and MDA content, decreased cellular antioxidants GSH and SOD, and elevated intracellular ROS levels, which were induced by UVA irradiation. Additionally, SSM inhibited the expression of Bax, MMP-1, and MMP-9 and stimulated Bcl-2 expression. In terms of the regulatory mechanisms, we demonstrated that SSM inhibits the phosphorylation of ASK-1, JNK, and p38.

CONCLUSION

The results suggest that SSM attenuates UVA-induced keratinocyte injury by inhibiting the ASK-1-JNK/p38 MAPK pathways.

Protective effect of Salvia plebeia R. Br ethanol extract on UVB-induced skin photoaging in vitro and in vivo

BACKGROUND

UV exposure is one of the primary factors responsible for photoaging, causing the increase in matrix metalloproteinases (MMPs) and the reduction in collagen. Salvia plebeia R. Br (SP), as an herbaceous plant, contains abundant flavonoids and possesses excellent anti-inflammatory and antioxidant activities. This study aimed to investigate the photoprotective effects of SP on UVB-induced photodamage in immortalized human keratinocytes (HaCaTs) and Kunming mice, as well as its main active components such as homoplantaginin (HP).

METHODS

CCK-8 was applied to detect the cell viability in UVB-irradiated or non-irradiated HaCaTs. Commercial kits were used to evaluate the levels of ROS, MDA, SA-β-Gal, MMP-1, and IL-6. The expression of MAPK and TGF-β/Smad pathways was detected by western blot. HE and Masson's trichrome staining were performed to examine the epidermis thickness and collagen degradation of Kunming mice.

RESULTS

Our results found that SP and HP notably decreased UVB-induced ROS, MDA, and SA-β-Gal production, and inhibited MMP-1 and IL-6 secretion by inhibiting the MAPK signaling pathway. In addition, SP and HP significantly promoted type I procollagen synthesis by activation of TGF-β/Smad pathway. Consistently, the in vivo experiments also indicated that SP and HP had a photoprotective effect, which significantly reversed UVB-induced epidermis thickness and collagen degradation.

CONCLUSION

This study demonstrated that SP effectively could protect skin from UVB-induced photoaging, while HP acted as the active substance in SP. All these findings provided a new strategy for skin photoaging treatment.

Involvement of the p38 MAPK-NLRC4-Caspase-1 Pathway in Ionizing Radiation-Enhanced Macrophage IL-1β Production

Macrophages are abundant immune cells in the tumor microenvironment and are crucial in regulating tumor malignancy. We previously reported that ionizing radiation (IR) increases the production of interleukin (IL)-1β in lipopolysaccharide (LPS)-treated macrophages, contributing to the malignancy of colorectal cancer cells; however, the mechanism remained unclear. Here, we show that IR increases the activity of cysteine-aspartate-specific protease 1 (caspase-1), which is regulated by the inflammasome, and cleaves premature IL-1β to mature IL-1β in RAW264.7 macrophages. Irradiated RAW264.7 cells showed increased expression of NLRC4 inflammasome, which controls the activity of caspase-1 and IL-1β production. Silencing of NLRC4 using RNA interference inhibited the IR-induced increase in IL-1β production. Activation of the inflammasome can be regulated by mitogen-activated protein kinase (MAPK)s in macrophages. In RAW264.7 cells, IR increased the phosphorylation of p38 MAPK but not extracellular signal-regulated kinase and c-Jun N-terminal kinase. Moreover, a selective inhibitor of p38 MAPK inhibited LPS-induced IL-1β production and NLRC4 inflammasome expression in irradiated RAW264.7 macrophages. Our results indicate that IR-induced activation of the p38 MAPK-NLRC4-caspase-1 activation pathway in macrophages increases IL-1β production in response to LPS.

Isolation, characterization and anti-UVB irradiation activity of an extracellular polysaccharide produced by Lacticaseibacillus rhamnosus VHPriobi O17

The purpose of this study was to isolate exopolysaccharides (EPS) from lactic acid bacteria (LAB) and evaluate EPS anti-UVB viability. Lacticaseibacillus rhamnosus VHPriobi O17 with high EPS production was screened from 34 strains of LAB. The EPS (OP-2) produced by L. rhamnosus VHPriobi O17 was purified by alcohol precipitation and DEAE-μSphere anion exchange chromatography. By ion chromatography, FT-IR spectrum and gel column chromatography, EPS (OP-2) was a novel Man-like polysaccharide with the weight-averaged molecular of 84.2 kDa. The EPS (OP-2) can effectively alleviate HaCaT cells apoptosis and overproduction of reactive oxygen species (ROS) induced by UVB. The results also showed that it inhibited the release of pro-inflammatory cytokines (IL-1α, IL-6 and IL-8); and suppressed the phosphorylation cascade of JNK and p38 MAPK to reduce the expression level of active-caspase3, ultimately prevented cell apoptosis. Thus, the EPS produced by L. rhamnosus VHPriobi O17 have the potential to be used for human anti-UVB irradiation.

Sebocytes contribute to melasma onset

Melasma is a hyperpigmentary disorder with photoaging features, whose manifestations appear on specific face areas, rich in sebaceous glands (SGs). To explore the SGs possible contribution to the onset, the expression of pro-melanogenic and inflammatory factors from the SZ95 SG cell line exposed to single or repetitive ultraviolet (UVA) radiation was evaluated. UVA up-modulated the long-lasting production of α-MSH, EDN1, b-FGF, SCF, inflammatory cytokines and mediators. Irradiated SZ95 sebocyte conditioned media increased pigmentation in melanocytes and the expression of senescence markers, pro-inflammatory cytokines, and growth factors regulating melanogenesis in fibroblasts cultures. Cocultures experiments with skin explants confirmed the role of sebocytes on melanogenesis promotion. The analysis on sebum collected from melasma patients demonstrated that in vivo sebocytes from lesional areas express the UVA-activated pathways markers observed in vitro. Our results indicate sebocytes as one of the actors in melasma pathogenesis, inducing prolonged skin cell stimulation, contributing to localized dermal aging and hyperpigmentation.

Discovery of novel paeonol-based derivatives against skin inflammation in vitro and in vivo

T-LAK-cell-originated protein kinase (TOPK), a novel member of the mitogen-activated protein kinase family, is considered an effective therapeutic target for skin inflammation. In this study, a series (A − D) of paeonol derivatives was designed and synthesised using a fragment growing approach, and their anti-inflammatory activities against lipopolysaccharide (LPS)-induced nitric oxide production in RAW264.7 cells were tested. Among them, compound B12 yielded the best results (IC₅₀ = 2.14 μM) with low toxicity (IC₅₀ > 50 µM). Preliminary mechanistic studies indicated that this compound could inhibit the TOPK-p38/JNK signalling pathway and phosphorylate downstream related proteins. A murine psoriasis-like skin inflammation model was used to determine its therapeutic effect.

Concentrated growth factor inhibits UVA-induced photoaging in human dermal fibroblasts via the MAPK/AP-1 pathway

Ultraviolet (UV) radiation-induced photoaging is one of the contributors to skin aging. UV light triggers oxidative stress, producing a large number of matrix metalloproteinases (MMPs) and degrading the extracellular matrix in skin cells, thereby causing a series of photoaging symptoms. Concentrated growth factor (CGF) is a leukocyte- and platelet-rich fibrin biomaterial that plays a protective role in the occurrence and development of skin photoaging. In the present study, we investigated the underlying mechanism of CGF in the UVA-induced photoaging of human dermal fibroblasts (HDFs). A primary culture of HDFs was isolated from normal human facial skin. The cells were treated with CGF following UVA radiation. Proliferation of cells was detected using MTT assay, followed by measurement of reactive oxygen species (ROS) using immunofluorescence assay and flow cytometry. The mRNA and protein expression levels of P38, c-Jun, and MMP-1 were detected using real-time polymerase chain reaction and Western blot, respectively. CGF was found to improve cell viability by inhibiting the production of ROS and reducing oxidative damage. In addition, there was lower expression of p38 and c-Jun at the mRNA and protein levels following CGF treatment, thus resulting in the inhibition of MMP-1 expression. Our results suggest that CGF could protect HDFs against UVA-induced photoaging by blocking the P38 mitogen-activated protein kinase/activated protein-1 (P38MAPK/AP-1) signaling pathway. These findings provide a new clinical strategy for the prevention of skin photoaging.

Dehydration stress alters the mitogen-activated-protein kinase signaling and chaperone stress response in Xenopus laevis

In arid conditions, the African Clawed frog Xenopus laevis enters a state of estivation dormancy as an adaptive survival strategy. Under estivation, X. laevis experience severe dehydration stress as 25-35% of total body water is lost. Dehydration in X. laevis can lead to periods of hypoxia due to elevated blood viscosity that impedes tissue perfusion. To understand how X. laevis survives under such stress, we studied the regulation pattern of key mitogen-activated protein kinases (MAPK) and their downstream transcription factors, along with several heat shock proteins in the oxygen sensitive brain and heart tissue of X. laevis under dehydration stress. Our study revealed that the activation phosphorylation residues of MAPK including JNK and MSK and their downstream transcription factors c-Jun and ATF2 are significantly decreased in the heart under dehydration. Given that JNK, c-Jun, and ATF2 are known positive regulators of apoptosis, this regulatory pattern suggest that a state of pro-survival signals may be established in the dehydrated heart. In support of this, protein levels of HSP60, a pro-apoptotic mitochondrial chaperone, was also downregulated in the heart in response to dehydration stress. In the brain tissue, most proteins remain unchanged with the exception of the apoptosis regulating p53 transcription factor, which showed a significant decrease in its activating phosphorylation residue under dehydration. Overall, our study revealed that in the Xenopus brain and heart, a specific suppression pattern of MAPK, transcription factors, and HSP takes place to potentially establish a state of pro-survival under dehydration stress.

Understanding the role of p38 and JNK mediated MAPK pathway in response to UV-A induced photoaging in Caenorhabditis elegans

Premature aging of the skin, principally induced by the UV radiations is called as photoaging, characterized by an increase in the level of ROS and the damage of the collagen layer leading to the damage of the cells. Mitogen activated Protein kinase (MAPK) pathway is known to mediate photoaging by controlling the level of ROS and initiating detoxification. Caenorhabditis elegans, a known model to analyze photoaging was used to understand the role of MAPK pathway (p38 and JNK) during UV-A mediated photoaging. Gene specific mutants of p38 MAPK pathway showed reduced survival when exposed to UV-A suggesting that UV-A mediated photoaging was dependent on this pathway. Also, the role of SKN-1 in eliciting response against UV-A was analyzed with the help of GFP tagged strains and qPCR analysis. Further, UV-A did not have any impact on the lifespan of JNK pathway mutants suggesting the importance of the pathway in eliciting a response against UV-A exposure, which was further validated by Western blot analysis. Overall, this study suggests that MAPK pathway could play an important part in initiating and eliciting a response by the host against UV-A exposure, by which it could be used as a marker to analyze the effects of photoaging.

Melatonin attenuates the detrimental effects of UVA irradiation in human dermal fibroblasts by suppressing oxidative damage and MAPK/AP-1 signal pathway in vitro

BACKGROUND

People living in Mediterranean countries are mostly exposed to solar ultraviolet (UV) radiation that damages skin and results in photoaging which involves activation of epidermal growth factor receptor (EGFR) and downstream signal transduction through mitogen-activated protein kinases (MAPKs) in fibroblasts. Generation of reactive oxygen/nitrogen species by UV radiation is also critical for EGFR and MAPKs activation. MAPKs are responsible for activation of AP-1 subunits in the nucleus which induce matrix metalloproteinases. Melatonin, along with its metabolites, are known to be the most effective free radical scavenger and protective agent due to its ability to react with various radicals, lipophilic/hydrophilic structures.

OBJECTIVES

In this study, we investigated the effects of melatonin on UVA-irradiated primary human dermal fibroblasts (HDFs) by following the alteration of molecules from cell membrane to the nucleus and oxidative/nitrosative damage status of the cells in a time-dependent manner which have not been clearly elucidated yet.

METHODS

To mimic UVA dosage in Mediterranean countries, HDFs were exposed to UVA with sub-cytotoxic dosage (20 J/cm² ) after pretreatment with melatonin (1 μmol/L) for 1 hour. Changes in the activation of the molecules and oxidative/nitrosative stress damage were analyzed at different time points.

RESULTS

Our results clearly show that melatonin decreases UVA-induced oxidative/nitrosative stress damage in HDFs. It also suppresses phosphorylation of EGFR, activation of MAPK/AP-1 signal transduction pathway and production of matrix metalloproteinases in a time-dependent manner.

CONCLUSION

Melatonin can be used as a protective agent for skin damage against intracellular detrimental effects of relatively high dosage of UVA irradiation.

Focal brain lesions induced with ultraviolet irradiation

Lesion and inactivation methods have played important roles in neuroscience studies. However, traditional techniques for creating a brain lesion are highly invasive, and control of lesion size and shape using these techniques is not easy. Here, we developed a novel method for creating a lesion on the cortical surface via 365 nm ultraviolet (UV) irradiation without breaking the dura mater. We demonstrated that 2.0 mWh UV irradiation, but not the same amount of non-UV light irradiation, induced an inverted bell-shaped lesion with neuronal loss and accumulation of glial cells. Moreover, the volume of the UV irradiation-induced lesion depended on the UV light exposure amount. We further succeeded in visualizing the lesioned site in a living animal using magnetic resonance imaging (MRI). Importantly, we also observed using an optical imaging technique that the spread of neural activation evoked by adjacent cortical stimulation disappeared only at the UV-irradiated site. In summary, UV irradiation can induce a focal brain lesion with a stable shape and size in a less invasive manner than traditional lesioning methods. This method is applicable to not only neuroscientific lesion experiments but also studies of the focal brain injury recovery process.

Fish Scale Collagen Peptides Protect against CoCl2/TNF-α-Induced Cytotoxicity and Inflammation via Inhibition of ROS, MAPK, and NF-κB Pathways in HaCaT Cells

Skin diseases associated with inflammation or oxidative stress represent the most common problem in dermatology. The present study demonstrates that fish scale collagen peptides (FSCP) protect against CoCl₂-induced cytotoxicity and TNF-α-induced inflammatory responses in human HaCaT keratinocyte cells. Our study is the first to report that FSCP increase cell viability and ameliorate oxidative injury in HaCaT cells through mechanisms mediated by the downregulation of key proinflammatory cytokines, namely, TNF-α, IL-1β, IL-8, and iNOS. FSCP also prevent cell apoptosis by repressing Bax expression, caspase-3 activity, and cytochrome c release and by upregulating Bcl-2 protein levels in CoCl₂- or TNF-α-stimulated HaCaT cells. In addition, the inhibitory effects of FSCP on cytotoxicity and the induction of proinflammatory cytokine expression were found to be associated with suppression of the ROS, MAPK (p38/MAPK, ERK, and JNK), and NF-κB signaling pathways. Taken together, our data suggest that FSCP are useful as immunomodulatory agents in inflammatory or immune-mediated skin diseases. Furthermore, our results provide new insights into the potential therapeutic use of FSCP in the prevention and treatment of various oxidative- or inflammatory stress-related inflammation and injuries.

MCPIP1 contributes to the inflammatory response of UVB-treated keratinocytes

BACKGROUND

Monocyte chemoattractant protein-1-induced protein-1 (MCPIP1), also known as regnase-1, negatively regulates many cellular processes including the cellular response to inflammatory agents, differentiation, viability, and proliferation. It possesses a PilT N-terminus (PIN) domain that is directly involved in regulating the stability of transcripts and miRNAs by recognizing stem loop structures and degrading them by endonucleolytic cleavage.

OBJECTIVE

We investigated the role of MCPIP1 in the response of human primary keratinocytes to UVB stress.

METHODS

Keratinocytes were treated with UVB, siRNA against MCPIP1, pharmacological inhibitors of signaling pathways, or subjected to control treatments. The mRNA and protein levels of MCPIP1 and MCPIP1-dependent changes gene expression were analyzed by quantitative (Q)-RT-PCRs and Western blots. Secretion of TNFα and IL-8 was determined by ELISA.

RESULTS

UVB treatment of keratinocytes induced upregulation of MCPIP1 at the mRNA level after 4-8h and at the protein level after 8-16h. MCPIP1 abundance depended on NF-κB activity. Using an siRNA strategy, we found that diminished MCPIP1 resulted in an up-regulation of transcripts coding for IL-8, TNFα, COX-2, and BCL-2, as well as an enhanced release of IL-8. Moreover, decreased phosphorylation of NF-κB and p38 signaling pathways were observed in addition to a slight up-regulation of ERK1/2 directly after UVB treatment. Twenty-four hours later, decreased phosphorylation was observed only for NF-κB and p38. Furthermore, in MCPIP1-suppressed cells, the levels of pro-apoptotic Puma, the phosphorylated form of p53 and the abundance of its target p21 as well as the activity of caspase 3 decreased, while the level of cyclin D1 increased.

CONCLUSION

MCPIP1 contributes to the UVB response of keratinocytes by altering metabolic and apoptotic processes and the release of inflammatory mediators.

Feedback inhibition of CREB signaling by p38 MAPK contributes to the negative regulation of steroidogenesis

BACKGROUND

Steroidogenesis is a complex, multi-steps biological process in which, cholesterol precursor is converted to steroids in a tissue specific and tropic hormone dependent manner. Given that steroidogenesis is achieved by coordinated functioning of multiple tissue specific enzymes, many steroids intermediates/metabolites are generated during this process. Both the steroid products as well as major lipoprotein cholesterol donor, high-density lipoprotein 3 (hHDL₃) have the potential to negatively regulate steroidogenesis via increased oxidative stress/reactive oxygen species (ROS) generation.

METHODS

In the current study, we examined the effects of treatment of a mouse model of steroidogenesis, Y1-BS1 adrenocortical tumor cells with pregnenolone, 22(R)-Hydroxycholesterol [22(R)-diol] or hHDL₃ on ROS production, phosphorylation status of p38 MAPK and cAMP response element-binding protein (CREB), CREB transcriptional activity and mRNA expression of StAR, CPY11A1/P450scc and antioxidant enzymes, superoxide dismutases [Cu,ZnSOD (SOD1), MnSOD (SOD2)], catalase (CAT) and glutathione peroxidase 1 (GPX1). We also detected the steroid product in p38 MAPK inhibitor treated Y1 cells by HPLC-MS / MS.

RESULTS

Treatment of Y1 cells with H₂O₂ greatly enhanced the phosphorylation of both p38 MAPK and CREB protein. Likewise, treatment of cells with pregnenolone, 22(R) diol or hHDL₃ increased ROS production measured with the oxidation-sensitive fluorescent probe 2',7'-Dichlorofluorescin diacetate (DCFH-DA). Under identical experimental conditions, treatment of cells with these agents also increased the phosphorylation of p38 MAPK and CREB. This increased CREB phosphorylation however, was associated with its decreased transcriptional activity. The stimulatory effects of pregnenolone, 22(R)-diol and hHDL₃ on CREB phosphorylation was abolished by a specific p38 MAPK inhibitor, SB203580. Pregnenolone, and 22(R) diol but not hHDL₃ upregulated the mRNA expression of SOD1, SOD2 and GPX1, while down-regulated the mRNA levels of StAR and CYP11A1. The p38 inhibitor SB203580 could increase the steroid production in HDL3, 22(R)-diol or pregnenolone treated cells.

CONCLUSION

Our data demonstrate induction of a ROS/p38 MAPK -mediated feedback inhibitory pathway by oxy-cholesterol and steroid intermediates and products attenuates steroidogenesis via inhibition of CREB transcriptional activity.

CD1a+ and CD83+ Langerhans cells are reduced in lower lip squamous cell carcinoma

BACKGROUND

Actinic cheilitis (AC) is a potentially malignant lesion diagnosed in the lip of patients chronically exposed to the sun that may give rise to a fully invasive lower lip squamous cell carcinoma (LLSCC). It is known that ultraviolet radiation causes dendritic cells (DCs) depletion in the epidermis, but the role of this cellular population in lip cancer progression remains uncertain. Therefore, this study investigated the distribution of DCs in normal, dysplastic and neoplastic tissues of the lower lip.

METHODS

Thirteen cases of lower lip mucocele, 42 of ACs and 21 of LLSCC were retrieved and original diagnoses confirmed by two oral pathologists, who further classified ACs as low- and high-risk lesions. Immunoreactions against CD1a and CD83 identified immature and mature DCs, respectively.

RESULTS

Immature CD1a+ Langerhans cells (LCs) were significantly decreased in LLSCC when compared to morphologically normal (P < 0.009) and dysplastic epitheliums (P < 0.003), whereas mature CD83+ LCs were significantly decreased in LLSCC when compared to normal epithelium (P = 0.038). There was no significant difference between low- and high-risk ACs regarding CD1a+ and CD83+ LCs (P > 0.05), but ACs demonstrated a lower concentration of CD1a+ LCs than normal epithelium (P < 0.009). There was no significant difference in the distribution of CD1a+ and CD83+ interstitial dendritic cells (IDCs) in the connective tissue among the studied groups (P > 0.05).

CONCLUSION

These results suggest that depletion of epithelial LCs, but not IDCs in the connective tissue, would represent an important step for lip cancer development.

Licochalcone A, a polyphenol present in licorice, suppresses UV-induced COX-2 expression by targeting PI3K, MEK1, and B-Raf

Licorice is a traditional botanical medicine, and has historically been commonly prescribed in Asia to treat various diseases. Glycyrrhizin (Gc), a triterpene compound, is the most abundant phytochemical constituent of licorice. However, high intake or long-term consumption of Gc has been associated with a number of side effects, including hypertension. However, the presence of alternative bioactive compounds in licorice with anti-carcinogenic effects has long been suspected. Licochalcone A (LicoA) is a prominent member of the chalcone family and can be isolated from licorice root. To date, there have been no reported studies on the suppressive effect of LicoA against solar ultraviolet (sUV)-induced cyclooxygenase (COX)-2 expression and the potential molecular mechanisms involved. Here, we show that LicoA, a major chalcone compound of licorice, effectively inhibits sUV-induced COX-2 expression and prostaglandin E2 PGE₂ generation through the inhibition of activator protein 1 AP-1 transcriptional activity, with an effect that is notably more potent than Gc. Western blotting analysis shows that LicoA suppresses sUV-induced phosphorylation of Akt/ mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinases (ERK)1/2/p90 ribosomal protein S6 kinase (RSK) in HaCaT cells. Moreover, LicoA directly suppresses the activity of phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase kinase (MEK)1, and B-Raf, but not Raf-1 in cell-free assays, indicating that PI3K, MEK1, and B-Raf are direct molecular targets of LicoA. We also found that LicoA binds to PI3K and B-Raf in an ATP-competitive manner, although LicoA does not appear to compete with ATP for binding with MEK1. Collectively, these results provide insight into the biological action of LicoA, which may have potential for development as a skin cancer chemopreventive agent.

UV-B radiation-induced oxidative stress and p38 signaling pathway involvement in the benthic copepod Tigriopus japonicus

Ultraviolet B (UV-B) radiation presents an environmental hazard to aquatic organisms. To understand the molecular responses of the intertidal copepod Tigriopus japonicus to UV-B radiation, we measured the acute toxicity response to 96 h of UV-B radiation, and we also assessed the intracellular reactive oxygen species (ROS) levels, glutathione (GSH) content, and antioxidant enzyme (GST, GR, GPx, and SOD) activities after 24 h of exposure to UV-B with LD50 and half LD50 values. Also, expression patterns of p53 and hsp gene families with phosphorylation of p38 MAPK were investigated in UV-B-exposed copepods. We found that the ROS level, GSH content, and antioxidant enzyme activity levels were increased with the transcriptional upregulation of antioxidant-related genes, indicating that UV-B induces oxidative stress by generating ROS and stimulating antioxidant enzymatic activity as a defense mechanism. Additionally, we found that p53 expression was significantly increased after UV-B irradiation due to increases in the phosphorylation of the stress-responsive p38 MAPK, indicating that UV-B may be responsible for inducing DNA damage in T. japonicus. Of the hsp family genes, transcriptional levels of hsp20, hsp20.7, hsp70, and hsp90 were elevated in response to a low dose of UV-B radiation (9 kJ m(-2)), suggesting that these hsp genes may be involved in cellular protection against UV-B radiation. In this paper, we performed a pathway-oriented mechanistic analysis in response to UV-B radiation, and this analysis provides a better understanding of the effects of UV-B in the intertidal benthic copepod T. japonicus.

The ethyl acetate fraction of Sargassum muticum attenuates ultraviolet B radiation-induced apoptotic cell death via regulation of MAPK- and caspase-dependent signaling pathways in human HaCaT keratinocytes

CONTEXT

Our previous work demonstrated that an ethyl acetate extract derived from Sargassum muticum (Yendo) Fenshol (SME) protected human HaCaT keratinocytes against ultraviolet B (UVB)-induced oxidative stress by increasing antioxidant activity in the cells, thereby inhibiting apoptosis.

OBJECTIVE

The aim of the current study was to further elucidate the anti-apoptotic mechanism of SME against UVB-induced cell damage.

MATERIALS AND METHODS

The expression levels of several apoptotic-associated and mitogen-activated kinase (MAPK) signaling proteins were determined by western blot analysis of UVB-irradiated HaCaT cells with or without prior SME treatment. In addition, the loss of mitochondrial membrane potential (Δψm) was detected using flow cytometry or confocal microscopy and the mitochondria membrane-permeate dye, JC-1. Apoptosis was assessed by quantifying DNA fragmentation and apoptotic body formation. Furthermore, cell viability was evaluated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.

RESULTS

SME absorbed electromagnetic radiation in the UVB range (280-320 nm) of the UV/visible light spectrum. SME also increased Bcl-2 and Mcl-1 expression in UVB-irradiated cells and decreased the Bax expression. Moreover, SME inhibited the UVB-induced disruption of mitochondrial membrane potential and prevented UVB-mediated increases in activated caspase-9 and caspase-3 (an apoptotic initiator and executor, respectively) levels. Notably, treatment with a pan-caspase inhibitor enhanced the anti-apoptotic effects of SME in UVB-irradiated cells. Finally, SME reduced the UVB-mediated phosphorylation of p38 MAPK and JNK, and prevented the UVB-mediated dephosphorylation of Erk1/2 and Akt.

DISCUSSION AND CONCLUSION

The present results indicate that SME safeguards HaCaT keratinocytes from UVB-mediated apoptosis by inhibiting a caspase-dependent signaling pathway.

Wild chrysanthemum extract prevents UVB radiation-induced acute cell death and photoaging

Wild chrysanthemum (Chrysanthemum indicum L.) is traditionally used in folk medicine as an anti-inflammatory agent. It is also used in the southwest plateau region of China to prevent ultraviolet-induced skin damage. However, the role and mechanism by which wild chrysanthemum prevents UV-induced skin damage and photoaging have never been investigated in vitro. In the present study, we found that aqueous extracts from wild chrysanthemum strongly reduced high-dose UVB-induced acute cell death of human immortalized keratinocytic HaCat cells. Wild chrysanthemum extract was also demonstrated to reduce low-dose UVB-induced expression of the photoaging-related matrix metalloproteinases MMP-2 and MMP-9. The ROS level elevated by UVB irradiation was strongly attenuated by wild chrysanthemum extract. Further study revealed that wild chrysanthemum extract reduced UVB-triggered ERK1/2 and p38 MAPK phosphorylation and their protective role, which is partially dependent on inhibiting p38 activation. These results suggest that wild chrysanthemum extract can protect the skin from UVB-induced acute skin damage and photoaging by reducing the intracellular reactive oxygen species (ROS) level and inhibiting p38 MAPK phosphorylation. The present study confirmed the protective role of wild chrysanthemum against UV-induced skin disorders in vitro and indicated the possible mechanism. Further study to identify the active components in wild chrysanthemum extract would be useful for developing new drugs for preventing and treating skin diseases, including skin cancer and photoaging, induced by UV irradiation.

Neuroprotection elicited by P2Y13 receptors against genotoxic stress by inducing DUSP2 expression and MAPK signaling recovery

Nucleotides activating P2Y13 receptors display neuroprotective actions against different apoptotic stimuli in cerebellar granule neurons. In the present study, P2Y13 neuroprotection was analyzed in conditions of genotoxic stress. Exposure to cisplatin and UV radiation induced caspase-3-dependent apoptotic cell death, and p38 MAPK signaling de-regulation. Pre-treatment with P2Y13 nucleotide agonist, 2methyl-thio-ADP (2MeSADP), restored granule neuron survival and prevented p38 long-lasting activation induced by cytotoxic treatments. Microarray gene expression analysis in 2MeSADP-stimulated cells revealed over-representation of genes related to protein phosphatase activity. Among them, dual-specificity phosphatase-2, DUSP2, was validated as a transcriptional target for P2Y13 receptors by QPCR. This effect could explain 2MeSADP ability to dephosphorylate a DUSP2 substrate, p38, reestablishing the inactive form. In addition, cisplatin-induced p38 sustained activation correlated perfectly with progressive reduction in DUSP2 expression. In conclusion, P2Y13 receptors regulate DUSP2 expression and contribute to p38 signaling homeostasis and survival in granule neurons.

Protective effect of indole-3-pyruvate against ultraviolet b-induced damage to cultured HaCaT keratinocytes and the skin of hairless mice

Previous investigations demonstrated that pyruvate protects human keratinocytes against cell damage stemming from exposure to ultraviolet B (UVB) radiation. This study endeavoured to elucidate the protective capacity of aromatic pyruvates (e.g., phenylpyruvate (PPyr), 4-hydroxyphenylpyruvate (HPPyr), and indole-3-pyruvate (IPyr)) against UVB-induced injury to skin cells, both in vitro and in vivo. Cultured human HaCaT keratinocytes were irradiated with UVB light (60 mJ/cm²) and maintained with or without test compounds (1–25 mM). In addition, the dorsal skin of hairless mice (HR-1) was treated with test compounds (100 µmol) and exposed to UVB light (1 J/cm²) for two times. The ability of the test compounds to ameliorate UVB-induced cytotoxicity and inflammation was then assessed. Aromatic pyruvates reduced cytotoxicity in UVB-irradiated HaCaT keratinocytes, and also diminished the expression of interleukin 1β (IL-1β) and interleukin 6 (IL-6). IPyr was more efficacious than either PPyr or HPPyr. Furthermore, only IPyr inhibited cyclooxygenase-2 (Cox-2) expression at both the mRNA and the protein level in UVB-treated keratinocytes. Topical application of IPyr to the dorsal skin of hairless mice reduced the severity of UVB-induced skin lesions, the augmentation of dermal thickness, and transepithelial water loss. Overproduction of IL-1β and IL-6 in response to UVB radiation was also suppressed in vivo by the topical administration of IPyr. These data strongly suggest that IPyr might find utility as a UVB-blocking reagent in therapeutic strategies to lessen UVB-induced inflammatory skin damage.

Regulation of MSK1-Mediated NF-κB Activation Upon UVB Irradiation

Nuclear Factor Kappa-B (NF-κB) is a transcription factor that controls expression of genes involved in the immune and inflammatory responses as well as being a key component in the onset of cancers. In this study, we provided evidence that mitogen- and stress-activated protein kinase (MSK1) is responsible for a noncanonical late-phase activation of NF-κB upon UVB irradiation. Our data demonstrated that following UVB irradiation, MSK1 is activated via phosphorylation at the 24 h time point coinciding with translocation of NF-κB into the nucleus. Investigations into the signaling pathways upstream of MSK1 through the use of specific inhibitors for mitogen-activated protein kinase and p38 revealed that both kinases are required for full phosphorylation during the late phase (24 h), while p38 is paramount for phosphorylation during the early phase (6 h). Electromobility shift assays (EMSA) showed that inhibition of MSK1 resulted in a marked reduction in NF-κB binding affinity without altering the nuclear translocation of NF-κB. Supershift EMSA implicate that the p65, but not p50, isoform of NF-κB is involved in late-phase activation in response to UVB irradiation. Together, the results of these studies shed light onto a novel pathway of MSK1-mediated late-phase activation of NF-κB in response to UVB irradiation.

UVB-stimulated TNFα release from human melanocyte and melanoma cells is mediated by p38 MAPK

Ultraviolet (UV) radiation activates cell signaling pathways in melanocytes. As a result of altered signaling pathways and UV-induced cellular damage, melanocytes can undergo oncogenesis and develop into melanomas. In this study, we investigated the effect of UV-radiation on p38 MAPK (mitogen-activated protein kinase), JNK and NFκB pathways to determine which plays a major role in stimulating TNFα secretion in human HEM (melanocytes) and MM96L (melanoma) cells. MM96L cells exhibited 3.5-fold higher p38 activity than HEM cells at 5 min following UVA + B radiation and 1.6-fold higher JNK activity at 15–30 min following UVB+A radiation, while NFκB was minimally activated in both cells. Irradiated HEM cells had the greatest fold of TNFα secretion (UVB: 109-fold, UVA + B: 103-fold & UVB+A: 130-fold) when co-exposed to IL1α. The p38 inhibitor, SB202190, inhibited TNFα release by 93% from UVB-irradiated HEM cells. In the UVB-irradiated MM96L cells, both SB202190 and sulfasalazine (NFκB inhibitor) inhibited TNFα release by 52%. Although, anisomycin was a p38 MAPK activator, it inhibited TNFα release in UV-irradiated cells. This suggests that UV-mediated TNFα release may occur via different p38 pathway intermediates compared to those stimulated by anisomycin. As such, further studies into the functional role p38 MAPK plays in regulating TNFα release in UV-irradiated melanocyte-derived cells are warranted.

Knock-down of glutaminase 2 expression decreases glutathione, NADH, and sensitizes cervical cancer to ionizing radiation

Phosphate-activated mitochondrial glutaminase (GLS2) is suggested to be linked with elevated glutamine metabolism. It plays an important role in catalyzing the hydrolysis of glutamine to glutamate. The present study was to investigate the potent effect of GLS2 on radioresistance of cervical carcinoma. GLS2 was examined in 144 cases of human cervical cancer specimens (58 radioresistant specimens, 86 radiosensitive specimens) and 15 adjacent normal cervical specimens with immunohistochemistry. HeLa cells were treated with a cumulative dose of 50Gy X-rays, over 6months, yielding the resistant sub-line HeLaR. The expressions of GLS2 were measured by Western blot. Radioresistance was tested by colony survival assay. Apoptosis was determined by flow cytometry. The levels of glutathione (GSH), reactive oxygen species (ROS), NAD(+)/NADH ratio and NADP(+)/NADPH ratio were detected by quantization assay kit. Xenografts were used to confirm the effect of GLS2 on radioresistance in vivo. The expressions of GLS2 were significantly enhanced in tumor tissues of radioresistant patients compared with that in radiosensitive patients. In vitro, the radioresistant cell line HeLaR exhibited significantly increased GLS2 levels than its parental cell line HeLa. GLS2 silenced radioresistant cell HeLaR shows substantially enhanced radiosensitivity with lower colony survival and higher apoptosis in response to radiation. In vivo, xenografts with GLS2 silenced HeLaR were more sensitive to radiation. At the molecular level, knock-down of GLS2 increased the intracellular ROS levels of HeLaR exposed to irradiation by decreasing the productions of antioxidant GSH, NADH and NADPH. GLS2 may have an important role in radioresistance in cervical cancer patients.

p38 MAPK Signaling in Pemphigus: Implications for Skin Autoimmunity

p38 mitogen activated protein kinase (p38 MAPK) signaling plays a major role in the modulation of immune-mediated inflammatory responses and therefore has been linked with several autoimmune diseases. The extent of the involvement of p38 MAPK in the pathogenesis of autoimmune blistering diseases has started to emerge, but whether it pays a critical role is a matter of debate. The activity of p38 MAPK has been studied in great detail during the loss of keratinocyte cell-cell adhesions and the development of pemphigus vulgaris (PV) and pemphigus foliaceus (PF). These diseases are characterised by autoantibodies targeting desmogleins (Dsg). Whether autoantibody-antigen interactions can trigger signaling pathways (such as p38 MAPK) that are tightly linked to the secretion of inflammatory mediators which may perpetuate inflammation and tissue damage in pemphigus remains unclear. Yet, the ability of p38 MAPK inhibitors to block activation of the proapoptotic proteinase caspase-3 suggests that the induction of apoptosis may be a consequence of p38 MAPK activation during acantholysis in PV. This review discusses the current evidence for the role of p38 MAPK in the pathogenesis of pemphigus. We will also present data relating to the targeting of these cascades as a means of therapeutic intervention.

Isoflavonoid-Rich Flemingia macrophylla Extract Attenuates UVB-Induced Skin Damage by Scavenging Reactive Oxygen Species and Inhibiting MAP Kinase and MMP Expression

In this study, we investigated the antioxidant activity and anti-photoaging properties of an extract of Flemingia macrophylla, a plant rich in isoflavonoid content. Pretreatment of fibroblasts with Flemingia macrophylla extract (FME) inhibited elastase activity, promoted the protein expression of type I procollagen, and attenuated the phosphorylation of mitogen-activated protein (MAP) kinase and the protein expression of matrix-metalloproteinase- (MMP-) 1, 3, and 9. The IC₅₀ values were 2.1 μg/mL for DPPH radical scavenging ability, 366.8 μg/mL for superoxide anion scavenging ability, 178.9 μg/mL for hydrogen peroxide scavenging ability, and 230.9 μg/mL for hydroxyl radical scavenging ability. Also, exposure of erythrocytes to various concentrations of FME (50–500 μg/mL) resulted in a dose- and time-dependent inhibition of AAPH-induced hemolysis. In human fibroblasts, FME at 10 μg/mL was shown to be a potent scavenger of UV-induced reactive oxygen species (ROS). The antioxidant and anti-photoaging properties of FME make it an ideal anti-intrinsic aging and anti-photoaging agent.

Inhibition of p53-dependent, but not p53-independent, cell death by U19 protein from human herpesvirus 6B

Infection with human herpesvirus (HHV)-6B alters cell cycle progression and stabilizes tumor suppressor protein p53. In this study, we have analyzed the activity of p53 after stimulation with p53-dependent and -independent DNA damaging agents during HHV-6B infection. Microarray analysis, Western blotting and confocal microscopy demonstrated that HHV-6B-infected cells were resistant to p53-dependent arrest and cell death after γ irradiation in both permissive and non-permissive cell lines. In contrast, HHV-6B-infected cells died normally through p53-independet DNA damage induced by UV radiation. Moreover, we identified a viral protein involved in inhibition of p53 during HHV-6B-infection. The protein product from the U19 ORF was able to inhibit p53-dependent signaling following γ irradiation in a manner similar to that observed during infection. Similar to HHV-6B infection, overexpression of U19 failed to rescue the cells from p53-independent death induced by UV radiation. Hence, infection with HHV-6B specifically blocks DNA damage-induced cell death associated with p53 without inhibiting the p53-independent cell death response. This block in p53 function can in part be ascribed to the activities of the viral U19 protein.

ATR and MKP1 play distinct roles in response to UV-B stress in Arabidopsis

Ultraviolet-B (UV-B) stress activates MAP kinases (MAPKs) MPK3 and MPK6 in Arabidopsis. MAPK activity must be tightly controlled in order to ensure an appropriate cellular outcome. MAPK phosphatases (MKPs) effectively control MAPKs by dephosphorylation of phosphothreonine and phosphotyrosine in their activation loops. Arabidopsis MKP1 is an important regulator of MPK3 and MPK6, and mkp1 knockout mutants are hypersensitive to UV-B stress, which is associated with reduced inactivation of MPK3 and MPK6. Here, we demonstrate that MPK3 and MPK6 are hyperactivated in response to UV-B in plants that are deficient in photorepair, suggesting that UV-damaged DNA is a trigger of MAPK signaling. This is not due to a block in replication, as, in contrast to atr, the mkp1 mutant is not hypersensitive to the replication-inhibiting drug hydroxyurea, hydroxyurea does not activate MPK3 and MPK6, and atr is not impaired in MPK3 and MPK6 activation in response to UV-B. We further show that mkp1 leaves and roots are UV-B hypersensitive, whereas atr is mainly affected at the root level. Tolerance to UV-B stress has been previously associated with stem cell removal and CYCB1;1 accumulation. Although UV-B-induced stem cell death and CYCB1;1 expression are not altered in mkp1 roots, CYCB1;1 expression is reduced in mkp1 leaves. We conclude that the MKP1 and ATR pathways operate in parallel, with primary roles for ATR in roots and MKP1 in leaves.

Sunlight UV-induced skin cancer relies upon activation of the p38α signaling pathway

The activation of cellular signal transduction pathways by solar ultraviolet (SUV) irradiation plays a vital role in skin tumorigenesis. Although many pathways have been studied using pure ultraviolet A (UVA) or ultraviolet B (UVB) irradiation, the signaling pathways induced by SUV (i.e., sunlight) are not understood well enough to permit improvements for prevention, prognosis, and treatment. Here, we report parallel protein kinase array studies aimed at determining the dominant signaling pathway involved in SUV irradiation. Our results indicated that the p38-related signal transduction pathway was dramatically affected by SUV irradiation. SUV (60 kJ UVA/m(2)/3.6 kJ UVB/m(2)) irradiation stimulates phosphorylation of p38α (MAPK14) by 5.78-fold, MSK2 (RPS6KA4) by 6.38-fold, and HSP27 (HSPB1) by 34.56-fold compared with untreated controls. By investigating the tumorigenic role of SUV-induced signal transduction in wild-type and p38 dominant-negative (p38 DN) mice, we found that p38 blockade yielded fewer and smaller tumors. These results establish that p38 signaling is critical for SUV-induced skin carcinogenesis.

Ultraviolet radiation effects on the proteome of skin cells

Proteomic studies to date have had limited use as an investigative tool in the skin's response to UV radiation. These studies used cell lines and reconstructed skin and have shown evidence of cell injury with oxidative damage and stress induced heat shock proteins. Others changes included altered cytokeratin and cytoskeletal proteins with enhanced expression of TRIM29 as the keratinocytes regenerate. The associated DNA repair requires polη, Rad18/Rad16 and Rev1. In the whole animal these events would be associated with inflammation, remodelling of the epidermis and modulation of the immune response. Longer term changes include ageing and skin cancers such as melanoma, squamous cell carcinoma and basal cell carcinoma. In the future proteomics will be used to explore these important aspects of photobiology. Better characterisation of the proteins involved should lead to a greater understanding of the skin's response to UV radiation.

Protective effect of pyruvate against UVB-induced damage in HaCaT human keratinocytes

The protective effect of pyruvate against ultraviolet B (UVB)-induced damage was investigated in human immortalized keratinocytes (HaCaT cells). Although pyruvate did not inhibit UVB-induced stimulation of intracellular reactive oxygen species (ROS) levels, it did improve the survival rate of UVB-irradiated HaCaT cells. Furthermore, pyruvate suppressed the UVB-induced mRNA expression of inflammatory mediators such as interleukin (IL)-1α, IL-1β, IL-6 and cyclooxygenase-2 (Cox-2). This decrease was associated with the reduced secretion of IL-1α, IL-1β, IL-6 and prostaglandin E2 (PGE2) into culture media. In addition, pyruvate reversed the phosphorylation of p38 mitogen-activated protein kinase (MAPK), induced by UVB-irradiation, in HaCaT cells but increased p38 MAPK phosphorylation in sham-irradiated cells. UVB-induced production of IL-6 was inhibited by SB203580, a p38 MAPK inhibitor. These results suggested that pyruvate inhibits UVB-mediated inflammatory response by inhibiting the p38 MAPK activation.

Control of late apoptotic events by the p38 stress kinase in L-glutamine-deprived mouse hybridoma cells

L-Glutamine (Gln) starvation rapidly triggers apoptosis in Sp2/0-Ag14 (Sp2/0) murine hybridoma cells. Here, we report on the role played by the stress-activated kinase p38 mitogen-activated protein kinase (MAPK) in this process. p38 activation was detected 2 h after Gln withdrawal and, although treatment with the p38 inhibitor SB203580 did not prevent caspase activation in Gln-starved cells, it reduced the occurrence of both nuclear condensation/fragmentation and apoptotic body formation. Similarly, transfection of Sp2/0 cells with a dominant negative p38 MAPK reduced the incidence of nuclear pyknosis and apoptotic body formation following 2 h of Gln starvation. Gln withdrawal-induced apoptosis was blocked by the overexpression of the anti-apoptotic protein Bcl-xL or by the caspase inhibitor Z-VAD-fmk. Interestingly, Bcl-xL expression inhibited p38 activation, but Z-VAD-fmk treatment did not, indicating that activation of this MAPK occurs downstream of mitochondrial dysfunction and is independent of caspases. Moreover, the anti-oxidant N-acetyl-l-cysteine prevented p38 phosphorylation, showing that p38 activation is triggered by an oxidative stress. Altogether, our findings indicate that p38 MAPK does not contribute to the induction of apoptosis in Gln-starved Sp2/0 cells. Rather, Gln withdrawal leads to mitochondrial dysfunction, causing an oxidative stress and p38 activation, the latter contributing to the formation of late morphological features of apoptotic Sp2/0 cells.

10-Hydroxy-2-decenoic acid prevents ultraviolet A-induced damage and matrix metalloproteinases expression in human dermal fibroblasts

BACKGROUND

10-Hydroxy-2-decenoic acid (10-HDA) is a major fatty acid component of royal jelly, which has been reported to have a variety of beneficial pharmacological characteristics. However, the effects of 10-HDA on skin photoageing and its potential mechanism of action are unclear.

OBJECTIVE

We investigated the protective effects of 10-HDA on ultraviolet (UV) A-induced damage in human dermal fibroblasts (HDFs). We then explored the inhibitory effects of 10-HDA on UVA-induced matrix metalloproteinases (MMPs) expression and elucidated the signalling pathways controlling MMPs inhibition.

METHODS

Primary human dermal fibroblasts were exposed to UVA. Cell proliferation, cellular senescent state and collagen content were analysed using CCK-8, senescence-associated β-galactosidase staining and Sircol collagen assay, respectively. Fluorometric assays were performed to detect the formation of reactive oxygen species (ROS) in the cells. The mRNA levels of MMP-1, MMP-3 and type I (α1) collagen were determined by quantitative real-time PCR. Western blot was applied to detect the expression of MMP-1, MMP-3, JNK and p38 MAPK.

RESULTS

HDFs treated with 10-HDA were significantly protected from UVA-induced cytotoxicity, ROS, cellular senescence and stimulated collagen production. Moreover, 10-HDA suppressed the UVA-induced expression of MMP-1 and MMP-3 at both the transcriptional and protein levels. Treatment with 10-HDA also reduced the UVA-induced activation of the JNK and p38 MAPK pathways.

CONCLUSION

The data obtained in this study provide evidence that 10-HDA could prevent UVA-induced damage and inhibit MMP-1 and MMP-3 expressions. Therefore, 10-HDA may be a potential agent for the prevention and treatment of skin photoageing.

Radiation induces osteogenesis in human aortic valve interstitial cells

OBJECTIVE

Irradiation of the chest or chest wall has been shown to cause calcific aortic stenosis. However, the mechanisms are unknown. Aortic valve interstitial cells have been implicated in the pathogenesis of aortic stenosis; they have been shown to change from the phenotype of a myofibroblast to an osteoblastlike cell. We therefore hypothesized that irradiation of human aortic valve interstitial cells induces an osteogenic phenotype. In isolated human aortic valve interstitial cells, our purpose was to determine the effect of irradiation on the production of osteogenic factors: (1) bone morphogenetic protein 2, (2) osteopontin, (3) alkaline phosphatase, and (4) the transcription factor Runx2.

METHODS

Human aortic valve interstitial cells were isolated from normal aortic valves obtained from explanted hearts of patients undergoing cardiac transplantation (n = 4) and were grown in culture. The cells were grown to confluence, irradiated with 10 Gy using a cesium-137 irradiator, and then lysed 24 hours after irradiation. Cell lysates were analyzed via immunoblot and densitometry for bone morphogenetic protein 2, osteopontin, alkaline phosphatase, and Runx2. Statistical analysis was performed using analysis of variance, with P < .05 indicating significance.

RESULTS

Irradiation induced an osteogenic phenotype in human aortic valve interstitial cells. Irradiation induced a 2-fold increase in bone morphogenetic protein 2, a 7-fold increase in osteopontin, a 3-fold increase in alkaline phosphatase, and a 2-fold increase in Runx2.

CONCLUSIONS

Radiation induces an osteogenic phenotype in human aortic valve interstitial cells. The irradiated cells had a significantly increased expression of the osteogenic factors bone morphogenetic protein 2, osteopontin, alkaline phosphatase, and Runx2. These data offer mechanistic insight into the pathogenesis of radiation-induced valvular heart disease.

NF-κB-dependent microRNA-125b up-regulation promotes cell survival by targeting p38α upon ultraviolet radiation

UV-induced stress response involves expression change of a myriad of genes, which play critical roles in modulating cell cycle arrest, DNA repair, and cell survival. Alteration of microRNAs has been found in cells exposed to UV, yet their function in UV stress response remains elusive. Here, we show that UV radiation induces up-regulation of miR-125b, which negatively regulates p38α expression through targeting its 3'-UTR. Increase of miR-125b depends on UV-induced NF-κB activation, which enhances miR-125b gene transcription upon UV radiation. The DNA damage-responsive kinase ATM (ataxia telangiectasia mutated) is indispensable for UV-induced NF-κB activation, which may regulate p38α activation and IKKβ-dependent IκBα degradation in response to UV. Consequently, repression of p38α by miR-125b prohibits prolonged hyperactivation of p38α by UV radiation, which is required for protecting cells from UV-induced apoptosis. Altogether, our data support a critical role of NF-κB-dependent up-regulation of miR-125b, which forms a negative feedback loop to repress p38α activation and promote cell survival upon UV radiation.

Mitogen-activated protein kinases in mammalian oxidative stress responses

All aerobic organisms are exposed to oxidative stress during their lifetime and are required to respond appropriately for maintenance of their survival and homeostasis. Sustained exposure to oxidative stress has devastating effects in organisms, and, not surprisingly, oxidative stress has been implicated in numerous human diseases. Therefore, an understanding of how mammals respond to oxidative stress is crucial both biologically and clinically. Intracellular signaling pathways, which are activated in response to excessive oxygen radicals, play essential roles in overcoming oxidative stress. The mitogen-activated protein kinase (MAPK) signaling pathways are involved in diverse physiological processes, and are critical for induction of oxidative stress responses. In this review, we will discuss the physiological roles of MAPKs in oxidative stress, the upstream signaling pathways leading to MAPK activation, their regulation, and the MAPK downstream substrates, with a focus on mammalian systems.

T-LAK cell-originated protein kinase (TOPK) phosphorylation of MKP1 protein prevents solar ultraviolet light-induced inflammation through inhibition of the p38 protein signaling pathway

Solar UV radiation is a major environmental factor that causes DNA damage, inflammation, and even skin cancer. T-LAK cell-originated protein kinase (TOPK) is expressed widely in both normal and cancer cells and functions to inhibit apoptosis and promote carcinogenesis. However, its function in inflammation is not known. The p38 MAPK signaling pathway plays an important role in solar UV light-induced inflammation. In this study, we found that TOPK negatively regulated the activity of p38α by phosphorylating the p38α-specific phosphatase MKP1 and enhancing the stability of MKP1. Notably, the absence of TOPK in mice resulted in a striking increase in skin inflammation. Therefore, we conclude that TOPK has a protective function in solar UV light-induced inflammation.

Inflammatory signaling compromises cell responses to interferon alpha

Interferon alpha (IFNα) is widely used for treatment of melanoma and certain other malignancies. This cytokine as well as the related IFNβ exerts potent anti-tumorigenic effects; however, their efficacy in patients is often suboptimal. Here, we report that inflammatory signaling impedes the effects of IFNα/β. Melanoma cells can secrete pro-inflammatory cytokines that inhibit cellular responses to IFNα/β via activating the ligand-independent pathway for the phosphorylation and subsequent ubiquitination and accelerated degradation of the IFNAR1 chain of type I IFN receptor. Catalytic activity of the p38 protein kinase was required for IFNAR1 downregulation and inhibition of IFNα/β signaling induced by proinflammatory cytokines such as interleukin 1 (IL-1). Activation of p38 kinase inversely correlated with protein levels of IFNAR1 in clinical melanoma specimens. Inhibition of p38 kinase augmented the inhibitory effects of IFNα/β on cell viability and growth in vitro and in vivo. The roles of inflammation and p38 protein kinase in regulating cellular responses to IFNα/β in normal and tumor cells are discussed.

Inhibitory Effects of Terminalia catappa on UVB-Induced Photodamage in Fibroblast Cell Line

This study investigated whether Terminalia catappa L. hydrophilic extract (TCLW) prevents photoaging in human dermal fibroblasts after exposure to UVB radiation. TCLW exhibited DPPH free radical scavenging activity and protected erythrocytes against AAPH-induced hemolysis. In the gelatin digestion assay, the rates of collagenase inhibition by TCL methanol extract, TCLW, and its hydrolysates were greater than 100% at the concentration of 1 mg/mL. We found that serial dilutions of TCLW (10–500 μg/mL) inhibited collagenase activity in a dose-dependent manner (82.3% to 101.0%). However, TCLW did not significantly inhibit elastase activity. In addition, TCLW inhibited MMP-1 and MMP-9 protein expression at a concentration of 25 μg/mL and inhibited MMP-3 protein expression at a concentration of 50 μg/mL. TCLW also promoted the protein expression of type I procollagen. We also found that TCLW attenuated the expression of MMP-1, -3, and -9 by inhibiting the phosphorylation of ERK, JNK, and p38. These findings suggest that TCLW increases the production of type I procollagen by inhibiting the activity of MMP-1, -3 and -9, and, therefore, has potential use in anti-aging cosmetics.

Merkel cell polyomavirus small T antigen mRNA level is increased following in vivo UV-radiation

Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer involving Merkel cells. Recently, a new human polyomavirus was implicated in MCC, being present in 80% of the samples analyzed. In virus-positive MCC, the Merkel cell polyomavirus (MCPyV) is clonally integrated into the patients DNA, and carries mutations in its large T antigen, leading to a truncated protein. In non-symptomatic tissue MCPyV can reside at very low levels. MCC is also associated with older age, immunosuppression and sun exposure. However, the link with solar exposure remains unknown, as the precise mechanism and steps involved between time of infection by MCPyV and the development of MCC. We thus investigated the potential impact of solar simulated radiation (SSR) on MCPyV transcriptional activity. We screened skin samples of 20 healthy patients enrolled in a photodermatological protocol based on in vivo-administered 2 and 4 J/cm(2) SSR. Two patients were infected with two new variants of MCPyV, present in their episomal form and RT-QPCR analyses on SSR-irradiated skin samples showed a specific and unique dose-dependent increase of MCPyV small t antigen transcript. A luciferase based in vitro assay confirmed that small t promoter is indeed UV-inducible. These findings demonstrate that solar radiation has an impact on MCPyV mRNA levels that may explain the association between MCC and solar exposure.

Proteomic profiling of human keratinocytes undergoing UVB-induced alternative differentiation reveals TRIpartite Motif Protein 29 as a survival factor

Background

Repeated exposures to UVB of human keratinocytes lacking functional p16^INK-4a and able to differentiate induce an alternative state of differentiation rather than stress-induced premature senescence.

Methodology/Principal Findings

A 2D-DIGE proteomic profiling of this alternative state of differentiation was performed herein at various times after the exposures to UVB. Sixty-nine differentially abundant protein species were identified by mass spectrometry, many of which are involved in keratinocyte differentiation and survival. Among these protein species was TRIpartite Motif Protein 29 (TRIM29). Increased abundance of TRIM29 following UVB exposures was validated by Western blot using specific antibody and was also further analysed by immunochemistry and by RT-PCR. TRIM29 was found very abundant in keratinocytes and reconstructed epidermis. Knocking down the expression of TRIM29 by short-hairpin RNA interference decreased the viability of keratinocytes after UVB exposure. The abundance of involucrin mRNA, a marker of late differentiation, increased concomitantly. In TRIM29-knocked down reconstructed epidermis, the presence of picnotic cells revealed cell injury. Increased abundance of TRIM29 was also observed upon exposure to DNA damaging agents and PKC activation. The UVB-induced increase of TRIM29 abundance was dependent on a PKC signaling pathway, likely PKCδ.

Conclusions/Significance

These findings suggest that TRIM29 allows keratinocytes to enter a protective alternative differentiation process rather than die massively after stress.

Sustained expression of NADPH oxidase 4 by p38 MAPK-Akt signaling potentiates radiation-induced differentiation of lung fibroblasts

Radiation-induced fibrosis (RIF) is a long-term adverse effect of curative radiotherapy; however, the distinct molecular mechanisms of RIF in neighboring normal tissue are not fully understood. We investigated the mechanisms underlying radiation-induced fibroblast differentiation into myofibroblasts. Lung fibroblasts produced reactive oxygen species (ROS) immediately after irradiation, the level of which remained increased for 24 h. The NADPH oxidase inhibitor, diphenyleneiodonium (DPI), suppressed ROS production and significantly decreased the radiation-induced expression of alpha-smooth muscle actin (alpha-SMA) and fibronectin (FN). The mRNA and protein expression of Nox4 was increased by radiation, and siRNA knockdown of Nox4 reduced alpha-SMA and FN levels. Increased phosphorylation of p38MAPK, Erk, and PI3k/Akt was observed after irradiation. Inhibitors of p38 MAPK and Akt, but not of Erk, reduced radiation-induced fibroblast differentiation and Nox4 expression. Notably, DPI partially decreased phosphorylation of p38MAPK and Akt, suggesting that p38MAPK, Akt, and Nox4 may cooperate in a positive feedback loop. Nox4 expression was also increased during bleomycin-induced fibroblast differentiation, and downregulation of Nox4 reduced alpha-SMA levels and extracellular matrix (ECM) accumulation. These results demonstrate that interfering Nox4 activation can be a potential strategy to disrupt fibrotic process.

Irradiation with heavy-ion particles changes the cellular distribution of human histone acetyltransferase HAT1

Hat1 was the first histone acetyltransferase identified; however, its biological function is still unclear. In this report, it is shown for the first time that human Hat1 has two isoforms. Isoform a has 418 amino acids (aa) and is localized exclusively in the nuclear matrix of normal human keratinocytes (NHKs). Isoform b has 334 aa and is located in the cytoplasm, the nucleoplasm, attached to the chromatin and to the nuclear matrix. Immunohistochemical analyses revealed that the bulk of Hat1 is confined to the nucleus, with much lesser amounts in the cytoplasm. Cells undergoing mitotic division have an elevated amount of Hat1 compared to those that are non-mitotic. Senescent cells, however, exhibit a higher concentration of Hat1 in the cytoplasm compare to proliferating cells and the amount of Hat1 in the nucleus decreases with the progression of senescence. NHKs exposed to hydrogen peroxide (H(2)O(2)) or to a beam of high mass and energy ion particles displayed bright nuclear staining for Hat1, a phenotype that was not observed in NHKs exposed to gamma-rays. We established that the enhanced nuclear staining for Hat1 in response to these treatments is regulated by the PI3K and the mitogen-activated protein kinase signaling pathways. Our observations clearly implicate Hat1 in the cellular response assuring the survival of the treated cells.