Possible treatment for UVB-induced skin injury: Anti-inflammatory and cytoprotective role of metformin in UVB-irradiated keratinocytes

ATG5-mediated keratinocyte ferroptosis promotes M1 polarization of macrophages to aggravate UVB-induced skin inflammation

Autophagy participates in the regulation of ferroptosis. Among numerous autophagy-related genes (ATGs), ATG5 plays a pivotal role in ferroptosis. However, how ATG5-mediated ferroptosis functions in UVB-induced skin inflammation is still unclear. In this study, we unveil that the core ferroptosis inhibitor GPX4 is significantly decreased in human skin tissue exposed to sunlight. We report that ATG5 deletion in mouse keratinocytes strongly protects against UVB-induced keratinocyte ferroptosis and skin inflammation. Mechanistically, ATG5 promotes the autophagy-dependent degradation of GPX4 in UVB-exposed keratinocytes, which leads to UVB-induced keratinocyte ferroptosis. Furthermore, we find that IFN-γ secreted by ferroptotic keratinocytes facilitates the M1 polarization of macrophages, which results in the exacerbation of UVB-induced skin inflammation. Together, our data indicate that ATG5 exacerbates UVB-induced keratinocyte ferroptosis in the epidermis, which subsequently gives rise to the secretion of IFN-γ and M1 polarization. Our study provides novel evidence that targeting ATG5 may serve as a potential therapeutic strategy for the amelioration of UVB-caused skin damage.

Azulene and Its Derivatives as Potential Compounds in the Therapy of Dermatological and Anticancer Diseases: New Perspectives against the Backdrop of Current Research

The scientific article focuses on the role of azulene and its derivatives in the therapy of dermatological diseases, presenting the latest laboratory and clinical research as well as prospects for further studies. In a synthetic literature review, various databases such as PubMed, Scopus, Web of Science, and the Database of Polish Scientific Journals were queried to select relevant articles concerning azulene. The conclusions drawn from the thematic analysis of the studies emphasize the multifaceted pharmacological actions of azulene and its derivatives including their anti-inflammatory properties, potential anticancer effects, photoprotective abilities, alleviation of itching, management of atopic dermatitis, and treatment of erectile dysfunction. However, there are certain limitations associated with the application of unmodified azulene on the skin, particularly related to photodecomposition and the generation of reactive oxygen species under UV radiation. These effects, in turn, necessitate further research on the safety of azulene and azulene-derived substances, especially regarding their long-term use and potential application in phototherapy. The authors of this work emphasize the necessity of conducting further preclinical and clinical studies to fully understand the mechanisms of action. Incorporating azulene and its derivatives into the therapy of dermatological disorders may represent an innovative approach, thereby opening new treatment avenues for patients.

Extracellular vesicles derived from mesenchymal stem cells: the wine in Hebe's hands to treat skin aging

Owing to its constant exposure to the external environment and various stimuli, skin ranks among the organs most vulnerable to manifestations of aging. Preventing and delaying skin aging has become one of the prominent research subjects in recent years. Mesenchymal stem cells (MSCs) are multipotent stem cells derived from mesoderm with high self-renewal ability and multilineage differentiation potential. MSC-derived extracellular vesicles (MSC-EVs) are nanoscale biological vesicles that facilitate intercellular communication and regulate biological behavior. Recent studies have shown that MSC-EVs have potential applications in anti-aging therapy due to their anti-inflammatory, anti-oxidative stress, and wound healing promoting abilities. This review presents the latest progress of MSC-EVs in delaying skin aging. It mainly includes the MSC-EVs promoting the proliferation and migration of keratinocytes and fibroblasts, reducing the expression of matrix metalloproteinases, resisting oxidative stress, and regulating inflammation. We then briefly discuss the recently discovered treatment methods of MSC-EVs in the field of skin anti-aging. Moreover, the advantages and limitations of EV-based treatments are also presented.

Naringin acts as a TRPV1 antagonist to attenuate UVB-induced senescence and damage in HaCaT cells

This study aimed to explore the mechanism of naringin (Nar) in alleviating ultraviolet B (UVB)-induced HaCaT cell senescence and damage. Human keratinocytes (HaCaT cells) were divided into control, UVB, UVB + Nar, UVB + Cap, and UVB + Nar + Cap groups. Analysis was performed using the MTT assay to assess cell viability, flow cytometry to measure the apoptosis level, SA-β-Gal staining to observe cellular senescence, and Western blot to assess protein levels of TRPV1, p16, p53, p21, matrix metalloproteinase (MMP)-1, and MMP-9. Both UVB irradiation and capsaicin (Cap) treatment upregulated the expression of TRPV1 in HaCaT cells, inhibited cell proliferation, promoted apoptosis, and increased the expression of p16, p53, p21, MMP-1, and MMP-9. Nar treatment reversed the above effects via inhibition of TRPV1 expression, thereby relieving senescence and cell damage induced by UVB irradiation. Taken together, these findings suggest that Nar can reduce UVB-induced senescence and damage in HaCaT cells by acting as an antagonist of TRPV1.

Inhibition of cutaneous heat-sensitive Ca2+ -permeable transient receptor potential vanilloid 3 channels alleviates UVB-induced skin lesions in mice

Ultraviolet B (UVB) radiation causes skin injury by trigging excessive calcium influx and signaling cascades in the skin keratinocytes. The heat-sensitive Ca2+ -permeable transient receptor potential vanilloid 3 (TRPV3) channels robustly expressed in the keratinocytes play an important role in skin barrier formation and wound healing. Here, we report that inhibition of cutaneous TRPV3 alleviates UVB radiation-induced skin lesions. In mouse models of ear swelling and dorsal skin injury induced by a single exposure of weak UVB radiation, TRPV3 genes and proteins were upregulated in quantitative real-time PCR and Western blot assays. In accompany with TRPV3 upregulations, the expressions of proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were also increased. Knockout of the TRPV3 gene alleviates UVB-induced ear swelling and dorsal skin inflammation. Furthermore, topical applications of two selective TRPV3 inhibitors, osthole and verbascoside, resulted in a dose-dependent attenuation of skin inflammation and lesions. Taken together, our findings demonstrate the causative role of overactive TRPV3 channel function in the development of UVB-induced skin injury. Therefore, topical inhibition of TRPV3 may hold potential therapy or prevention of UVB radiation-induced skin injury.

In Vitro and In Vivo Evaluation of Metformin Hydrochloride Hydrogels Developed with Experimental Design in the Treatment of Burns

Burns alter the normal skin barrier and affect various host defense processes that help prevent infections. An ineffective repair process can lead to serious damage, such as the onset of an infection or skin loss, which can then harm the surrounding tissues and ultimately the entire organism. This study aims to prepare in situ gels containing metformin hydrochloride, a compound known for its wound healing properties. To achieve this, in situ gels were prepared using three different gelling agents (Poloxamer 407®, Carbopol 934®, and sodium carboxymethyl cellulose (Na-CMC)) and three different concentrations of metformin hydrochloride (4 mg/g, 6 mg/g, and 8 mg/g), which were optimized through experimental design. Metformin concentration and gelling agent type were independent variables, and the loaded amount and the percentage of metformin released after 150 min were chosen as dependent variables in the optimization process. After determining the optimum values of the dependent variables according to the ANOVA analysis results, in vivo studies were conducted with optimized hydrogel formulations. Two groups, each consisting of seven Wistar rats with a burn model, were treated with metformin-poloxamer 407® gels at doses of 4 mg/g and 8 mg/g for 29 days. The results were then compared to untreated and placebo gel groups. Rats treated with in situ Poloxamer 407® hydrogels containing metformin hydrochloride showed a significant reduction in the size of the burned area after 29 days of treatment. However, for a comprehensive understanding of the wound healing mechanism, further studies such as immuno-histochemical and cell culture studies are needed.

Topical metformin 30% gel in the treatment of acne vulgaris in women, a split face, placebo-controlled study

Acne vulgaris (AV), a widely common disorder, that negatively affects the quality of life. Metformin is a relatively safe, cheap and well tolerated drug that is widely used in the treatment of Diabetes. Systemic metformin has demonstrated promising results in treating acne, while topically it was studied for melasma and recalcitrant central centrifugal cicatricial alopecia. To study the safety and efficacy of topical metformin 30% in the treatment of AV. Twenty-seven female AV patients were asked to blindly apply metformin and placebo gels to either side of the face for 12 weeks. AV lesion count was performed at baseline, at each visit and 4 weeks after end of treatment. At the end of the treatment period, the treated side showed significant improvement of comedones, papules and nodules but not pustules. Although, lesions count increased 1 month after stopping treatment, comedones and papules numbers were still significantly less on the metformin side compared to placebo. No side effects were reported. The limited number of patients studied and the limited follow-up period. The metformin effect was not studied on cellular and molecular levels. Topical metformin nanoemulsion gel can be a promising safe and effective treatment of AV.

Metformin derivatives - Researchers' friends or foes?

Metformin has been used for ages to treat diabetes mellitus due to its safety profile and low cost. However, metformin has variable pharmacokinetics in patients, and due to its poor oral absorption, the therapeutic doses are relatively high, causing unpleasant gastrointestinal adverse effects. Therefore, novel derivatives of metformin have been synthesized during the past decades. Particularly, after the mid-2000 s, when organic cation transporters were identified as the main metformin carriers, metformin derivatives have been under intensive investigation. Nevertheless, due to the biguanide structure, derivatives of metformin have been challenging to synthesize. Moreover, the mechanisms of metformin's action are not fully understood to date, and since it has multifunctional properties, the interests have switched to re-purposing for other diseases. Indeed, metformin derivatives have been demonstrated in many cases to be more effective than metformin itself and have the potential to be used in different diseases, including several types of cancers and neurodegenerative diseases. On the other hand, the pleiotropic nature of metformin and its derivatives can also create challenges. Not all properties are fit for all diseases. In this review, the history of the development of metformin-like compounds is summarized, and insights into their potential for future drug discovery are discussed.

Enhanced In Vitro Anti-Photoaging Effect of Degraded Seaweed Polysaccharides by UV/H2O2 Treatment

The high molecular weight and poor solubility of seaweed polysaccharides have limited their function and application. In this study, ultraviolet/hydrogen peroxide (UV/H2O2) treatment was used to prepare low-molecular-weight seaweed polysaccharides from Sargassum fusiforme. The effects of UV/H2O2 treatment on the physicochemical properties and anti-photoaging activity of S. fusiforme polysaccharides were studied. UV/H2O2 treatment effectively degraded polysaccharides from S. fusiforme (DSFPs), reducing their molecular weight from 271 kDa to 26 kDa after 2 h treatment. The treatment did not affect the functional groups in DSFPs but changed their molar percentage of monosaccharide composition and morphology. The effects of the treatment on the anti-photoaging function of S. fusiforme polysaccharides were investigated using human epidermal HaCaT cells in vitro. DFSPs significantly improved the cell viability and hydroxyproline secretion of UVB-irradiated HaCaT cells. In particular, DSFP-45 obtained from UV/H2O2 treatment for 45 min showed the best anti-photoaging effect. Moreover, DSFP-45 significantly increased the content and expression of collagen I and decreased those of pro-inflammatory cytokines, including interleukin-1β, interleukin-6, and tumor necrosis factor-α. Thus, UV/H2O2 treatment could effectively improve the anti-photoaging activity of S. fusiforme polysaccharides. These results provide some insights for developing novel and efficient anti-photoaging drugs or functional foods from seaweed polysaccharides.

In vitro effects of undifferentiated callus extracts from Plantago major L, Rhodiola rosea L and Silybum marianum L in normal and malignant human skin cells

Background and objectives

The occurrence of non-melanoma and melanoma skin cancers is currently increasing rapidly with one in every three cancers diagnosed as a skin cancer. A useful strategy to control the progression of skin cancer could be the use of plant flavonoids that suppress pro-inflammatory cytokines involved in tumor initiation and progression. In this study, the anti-inflammatory and antioxidant activity of undifferentiated callus extracts from Plantago major L, Silybum marianum L and Rhodiola rosea L was investigated both in normal and malignant skin cells.

Methods

Antioxidant activity of the extracts was analyzed by using the Trolox Equivalent Antioxidant Capacity (TEAC) assay. High-Performance Thin-Layer Chromatography (HPTLC) was performed to demonstrate the phytochemical profile, and the total flavonoid content was analyzed with an aluminum chloride colorimetric method. The anti-inflammatory effect was investigated by cell treatments using the plant extracts. Thereafter, the possible suppression of induced IL-6 response was measured from the cultured skin cancer cell lines A2058 and A431, and normal primary keratinocytes with Enzyme-Linked Immunosorbent Assay (ELISA).

Results

The HPTLC analysis assessed that the extracts contained a complex phytochemical profile that was rich in phenolic and flavonoid compounds. Dose response assays showed that concentrations between 15 and 125 μg/mL of all three plant extracts could be used to investigate an effect on the IL-6 production. The S. marianum extract had the most pronounced anti-inflammatory effect, which significantly inhibited induced IL-6 production in both normal keratinocytes and skin cells derived from epidermal carcinoma. The extract from S. marianum also had the highest flavonoid content and showed the highest antioxidant activity of the three extracts tested.

Conclusion

All in all, we have confirmed that undifferentiated callus extracts of S. marianum possess properties such as antioxidant and anti-inflammatory activities in both normal and malignant keratinocytes, and thus could be a promising agent controlling the pro-inflammatory IL-6 production.

Handelin protects human skin keratinocytes against ultraviolet B-induced photodamage via autophagy activation by regulating the AMPK-mTOR signaling pathway

Handelin is a natural ingredient extracted from Chrysanthemum boreale flowers that has been shown to decrease stress-related cell death, prolong lifespan, and promote anti-photoaging. However, whether handelin inhibits ultraviolet (UV) B stress-induced photodamage remains unclear. In the present study, we investigate whether handelin has protective properties on skin keratinocytes under UVB irradiation. Human immortalized keratinocytes (HaCaT keratinocytes) were pretreated with handelin for 12 h before UVB irradiation. The results indicated that handelin protects keratinocytes against UVB-induced photodamage by activating autophagy. However, the photoprotective effect of handelin was suppressed by an autophagic inhibitor (wortmannin) or the transfection of keratinocytes with a small interfering RNA targeting ATG5. Notably, handelin reduced mammalian target of rapamycin (mTOR) activity in UVB-irradiated cells in a manner similar to that shown by the mTOR inhibitor rapamycin. Adenosine monophosphate-activated protein kinase (AMPK) activity was also induced by handelin in UVB-damaged keratinocytes. Finally, certain effects of handelin, including autophagy induction, mTOR activity inhibition, AMPK activation, and reduction of cytotoxicity, were suppressed by an AMPK inhibitor (compound C). Our data suggest that handelin effectively prevents photodamage by protecting skin keratinocytes against UVB-induced cytotoxicity via the regulation of AMPK/mTOR-mediated autophagy. These findings provide novel insights that can aid the development of therapeutic agents against UVB-induced keratinocyte photodamage.

Τhe Endless Beauty of Metformin: Does It Also Protect from Skin Aging? A Narrative Review

Metformin has shown multiple effects beyond its widely known antidiabetic effect. Impressively, it has already been proposed as an anti-aging factor. However, the potentially protective role of metformin in skin aging, the most common manifestation of aging, is not well examined. Existing evidence based on experimental studies suggests a potential anti-aging effect on skin. Proposed molecular skin anti-aging mechanisms of metformin include mainly reduction of nuclear factor kappa B (NF-κB) (p65) activity. Moreover, metformin appears to inhibit ultraviolet B (UVB)-induced secretion of pro-inflammatory cytokines. Nonetheless, data is still limited, and so more studies are needed. Importantly, we need more studies conducted in humans to further examine this interesting potential. Until then, whether oral administration of metformin or local use of the agent could be used to delay skin aging remains to be answered.

A systematic review of the uses of metformin in dermatology

Metformin is an established staple drug in the management of Type 2 diabetes mellitus. In this systematic review, we sought to establish the clinical utility of metformin in a range of dermatological conditions. The pathophysiology of acne vulgaris and polycystic ovarian syndrome (PCOS) is well suited to the pharmacological profile of metformin, and we found evidence for its efficacy in managing these conditions. We found some evidence for the use of metformin particularly in acne and PCOS; however, the evidence base is of mixed quality. There is scope for clinicians to consider metformin as an adjunct therapy in acne and PCOS. There is generally insufficient evidence to recommend metformin in other dermatological conditions.

Hemin protects UVB-induced skin damage through inhibiting keratinocytes apoptosis and reducing neutrophil infiltration

Ultraviolet-B (UVB) exposure on the skin triggers apoptosis, oxidative stress and acute inflammatory responses, which eventually increases the risk of various skin disorders. Hemin, an iron-binding porphyrin, has been clinically used for porphyria treatment. However, whether hemin contributes to the skin protection against UVB injury remains to be elucidated. Here, we found that hemin treatment (10 and 20 mg/kg) by intraperitoneal administration could dramatically relieve UVB irradiation-induced skin damage featured by erythema, edema, epidermal hyperplasia and collagen loss in C57BL/6 J mice. Importantly, hemin treatment attenuated UVB irradiation-triggered cell apoptosis in skin epidermis. Consistently, hemin (10, 20 μM) treatment decreased Caspase-3 activation and protected against UVB-induced apoptosis in HaCaT cells. Besides, hemin treatment reduced the infiltration of neutrophils in skin under UVB irradiation, thus restrained neutrophil extracellular traps (NET) formation and myeloperoxidase (MPO) release. We further revealed that hemin inhibited the expression of inflammation associated cytokines and chemokines in UVB-induced HaCaT cells and blocked the chemotaxis of dHL-60 cells to preconditioned media from HaCaT culture upon UVB irradiation. Furthermore, hemin inhibited the excessive maturation and mobilization of bone marrow neutrophils and rectified the proportion of abnormally elevated neutrophils in the blood under UVB irradiation. In conclusion, our study showed that hemin treatment protects against UVB-induced skin damage through inhibiting keratinocytes apoptosis, and suppressing neutrophils infiltration in the skin via externally restraining the keratinocyte attraction and internally regulating bone marrow neutrophil maturation and mobilization, suggesting that hemin is an effective drug candidate for the therapy of UVB damage.

Reduction of miR-133a-3p contributes to apoptosis and gasdermin E-mediated pyroptosis of keratinocytes in skin exposed to ultraviolet B radiation

Engagement of regulated cell death in keratinocytes plays a crucial role in the pathogenesis and development of skin disorders associated with UV radiation. However, it remains unclear how microRNAs (miRNAs) participate in the regulation of UV-caused keratinocyte death. In this study, we found that miR-133a-3p was decreased in the epidermis of UVB-challenged mice and UVB-irradiated keratinocyte cell line HaCaT cells. The intradermal injection of agomir miR-133a-3p ameliorated skin damage of UVB-challenged mice, especially epidermal necrosis. Meanwhile, the injection inhibited apoptosis indicator PARP cleavage and pyroptosis indicator GSDME cleavage in the epidermis. In UVB-challenged HaCaT cells, transfection of miR-133a-3p mimic or inhibitor alleviated or aggravated UVB-induced apoptosis and GSDME-mediated pyroptosis respectively. miR-133a-3p was also involved in the effects of metformin treatment on alleviating skin damage in UVB-challenged mice and on inhibiting apoptosis and GSDME-mediated pyroptosis in UVB-irradiated HaCaT cells. We confirmed that CYLD is a target gene of miR-133a-3p and participates in the protective effects of miR-133a-3p on inhibiting UVB-caused apoptosis and GSDME-mediated pyroptosis in keratinocytes. This study indicates a pivotal role for miR-133a-3p of keratinocytes in UVB-caused skin damage. Alleviating skin photodamage by restoring the decrease of miR-133a-3p can be considered a potential therapeutic approach.

Necroptosis-mediated HMGB1 secretion of keratinocytes as a key step for inflammation development in contact hypersensitivity

Keratinocyte necroptosis (with proinflammatory characteristic) is required for epidermal damage in contact hypersensitivity (CHS). In DNCB-induced CHS mice model, we observed the aggravated keratinocyte death and increased phosphorylation level of MLKL, RIPK3 and RIPK1. However, CHS skin lesion did not present in keratinocyte-specific Mlkl knockout mice. We validated that MLKL-mediated keratinocyte necroptosis is required for epidermal damage in response to immune microenvironment in CHS. Moreover, MLKL-mediated necroptosis deficiency or inhibition resulted in blocking recruitment and activation of inflammatory cells in CHS via reducing HMGB1 release in keratinocytes. This study suggests that MLKL-mediated keratinocyte necroptosis functions as a self-amplified actor in inflammatory responses and could be considered as an effective therapeutic target. It proposes an innovative prospective that inhibiting keratinocyte necroptosis can prevent the development of epidermal damage in CHS.

GSDME deficiency leads to the aggravation of UVB-induced skin inflammation through enhancing recruitment and activation of neutrophils

Gasdermin E (GSDME)-mediated pyroptosis is induced in keratinocytes of UVB-challenged skin. The role of GSDME in UVB-caused skin damage remains unknown. To explore the role of GSDME in UVB-induced skin inflammation. We compared differences in skin appearance, histological features, keratinocyte death modalities, infiltration of immune cells, and levels of some inflammatory cytokines between Gsdme^-/- mice and wild type (WT) mice after UVB exposure. We explored whether keratinocytes contribute to GSDME deficiency-caused aggravation of UVB-induced skin inflammation in GSDME knockdown keratinocyte cultured in vitro and keratinocyte-specific Gsdme conditional knockout mice. We used anti-Ly6G antibody to deplete neutrophils and explore their role in UVB-caused skin damage. Skin damage and neutrophils infiltration were aggravated in UVB-challenged Gsdme^-/- mice, compared with UVB-challenged WT mice. Apoptosis and necroptosis, which were initiated together with GSDME-mediated pyroptosis in UVB-challenged WT mice, were not enhanced in UVB-challenged Gsdme^-/- mice. Neutrophils activation indicators and its recruiting cytokines were increased in skin tissue of UVB-challenged Gsdme^-/- mice. However, GSDME knockdown did not lead to the further increase of mRNA and secretion of TNF-α and IL-6 in UVB-challenged keratinocytes. Skin damage was not aggravated in UVB-challenged Gsdme cKO mice. Neutrophils depletion alleviated UVB-caused skin damage in WT mice and Gsdme^-/- mice, and eliminated its aggravation in Gsdme^-/- mice. This study demonstrates that GSDME plays a restrictive role in UVB-induced skin damage through inhibiting excessive recruitment and activation of neutrophils in the immune microenvironment in UVB-caused skin inflammation. However, keratinocytes might not contribute to this restrictive function.

Photoaging: UV radiation-induced inflammation and immunosuppression accelerate the aging process in the skin

Background

Excessive exposure of the skin to UV radiation (UVR) triggers a remodeling of the immune system and leads to the photoaging state which is reminiscent of chronological aging. Over 30 years ago, it was observed that UVR induced an immunosuppressive state which inhibited skin contact hypersensitivity.

Methods

Original and review articles encompassing inflammation and immunosuppression in the photoaging and chronological aging processes were examined from major databases including PubMed, Scopus, and Google Scholar.

Results

Currently it is known that UVR treatment can trigger a cellular senescence and inflammatory state in the skin. Chronic low-grade inflammation stimulates a counteracting immunosuppression involving an expansion of immunosuppressive cells, e.g., regulatory T cells (Treg), myeloid-derived suppressor cells (MDSC), and regulatory dendritic cells (DCreg). This increased immunosuppressive activity not only suppresses the function of effector immune cells, a state called immunosenescence, but it also induces bystander degeneration of neighboring cells. Interestingly, the chronological aging process also involves an accumulation of pro-inflammatory senescent cells and signs of chronic low-grade inflammation, called inflammaging. There is also clear evidence that inflammaging is associated with an increase in anti-inflammatory and immunosuppressive activities which promote immunosenescence.

Conclusion

It seems that photoaging and normal aging evoke similar processes driven by the remodeling of the immune system. However, it is likely that there are different molecular mechanisms inducing inflammation and immunosuppression in the accelerated photoaging and the chronological aging processes.

Metformina en el tratamiento de enfermedades dermatológicas: una revisión narrativa

Objetivo

Revisar y discutir la evidencia actual del uso de la metformina como herramienta terapéutica en enfermedades cutáneas.

Diseño

Artículo original. Investigación cualitativa. Revisión narrativa.

Emplazamiento

Aragón y Murcia, España.

Participantes

Médicos Internos Residentes de Dermatología Médico-Quirúrgica y Venereología y de Atención Primaria y Comunitaria.

Métodos

Se ha realizado una revisión narrativa utilizando la base de datos bibliográfica PubMed con fecha de búsqueda el 27 de enero de 2022.

Resultados

La metformina ha demostrado ser efectiva en el tratamiento de dermatosis inflamatorias tales como el acné, hidrosadenitis supurativa, psoriasis y dermatitis de contacto alérgica. También ha demostrado propiedades antitumorales frente al carcinoma basocelular, carcinoma espinocelular y melanoma. De forma adicional, se ha descrito efectos beneficiosos del tratamiento adyuvante con metformina en pacientes con carcinoma basocelular que reciben terapia fotodinámica. En pacientes con dermatosis relacionadas con endocrinopatías tales como el hirsutismo, la acantosis nigricans y los xantomas eruptivos, el tratamiento con metformina ha demostrado efectividad terapéutica. El tratamiento tópico con metformina ha demostrado ser eficaz en el tratamiento del melasma. Finalmente se ha propuesto como un fármaco con propiedades antienvejecimiento cutáneo y favorecedoras de la cicatrización. Para ninguna de las indicaciones previamente descritas se han objetivado efectos adversos graves.

Conclusiones

La metformina es un tratamiento efectivo y seguro en el esquema terapéutico de dermatosis inflamatorias, neoplasias cutáneas, dermatosis relacionadas con endocrinopatías, melasma, envejecimiento cutáneo y cicatrización.

How good is the evidence that cellular senescence causes skin ageing?

Skin is the largest organ of the body with important protective functions, which become compromised with time due to both intrinsic and extrinsic ageing processes. Cellular senescence is the primary ageing process at cell level, associated with loss of proliferative capacity, mitochondrial dysfunction and significantly altered patterns of expression and secretion of bioactive molecules. Intervention experiments have proven cell senescence as a relevant cause of ageing in many organs. In case of skin, accumulation of senescence in all major compartments with ageing is well documented and might be responsible for most, if not all, the molecular changes observed during ageing. Incorporation of senescent cells into in-vitro skin models (specifically 3D full thickness models) recapitulates changes typically associated with skin ageing. However, crucial evidence is still missing. A beneficial effect of senescent cell ablation on skin ageing has so far only been shown following rather unspecific interventions or in transgenic mouse models. We conclude that evidence for cellular senescence as a relevant cause of intrinsic skin ageing is highly suggestive but not yet completely conclusive.

Oat (Avena sativa) Extract against Oxidative Stress-Induced Apoptosis in Human Keratinocytes

Oat (Avena sativa) is well known for its various health benefits. The protective effect of oat extract against oxidative stress-induced apoptosis in human keratinocytes HaCaT was determined. First, extracts of two varieties of oat, Daeyang and Choyang, were analyzed for fat-soluble antioxidants such as α-tocotrienol, γ-oryzanols, lutein and zeaxanthin using an UPLC system and for antioxidant activity using a DPPH assay. Specifically, an 80% ethanol extract of Daeyang oat (Avena sativa cv. Daeyang), which had high amounts of antioxidants and potent radical scavenging activity, was further evaluated for protective effect against oxidative stress-induced cell death, intracellular reactive oxygen species levels, the phosphorylation of DNA damage mediating genes such as H2AX, checkpoint kinase 1 and 2, and p53 and the activation of apoptotic genes such as cleaved caspase-3 and 7 and poly (ADP-ribose) polymerase in HaCaT cells. The Daeyang and Choyang oat 80% ethanol extracts had 26.9 and 24.1 mg/100 g γ-oryzanols, 7.69 and 8.38 mg/100 g α-tocotrienol, 1.25 and 0.34 mg/100 g of lutein and 1.20 and 0.17 mg/100 g of zeaxanthin, respectively. The oat 80% ethanol extract treatment (Avena sativa cv. Daeyang) had a protective effect on oxidative stress-induced cell death in HaCaT cells. In addition, the oat 80% ethanol extracts led to a significant decrease in the intracellular ROS level at a concentration of 50-200 μg/mL, the attenuation of DNA damage mediating genes and the inhibition of apoptotic caspase activities in a dose dependent manner (50-200 μg/mL). Thus, the current study indicates that an oat (Avena sativa cv. Daeyang) extract rich in antioxidants, such as polyphenols, avenanthramides, γ-oryzanols, tocotrienols and carotenoids, has a protective role against oxidative stress-induced keratinocyte injuries and that oat may a useful source for oxidative stress-associated skin damage.

Metformin and Risk of Malignant Brain Tumors in Patients with Type 2 Diabetes Mellitus

The risk of malignant brain tumors associated with metformin use has rarely been investigated in humans. This retrospective cohort study investigated such an association. Patients with new-onset type 2 diabetes mellitus diagnosed from 1999 to 2005 in the nationwide database of Taiwan’s national health insurance were used to enroll study subjects. We first identified an unmatched cohort of 153,429 ever users and 16,222 never users of metformin. A cohort of 16,222 ever users and 16,222 never users matched on propensity score was then created from this unmatched cohort. All patients were followed up from 1 January 2006 until 31 December 2011. The incidence density was calculated and hazard ratios were derived from Cox regression incorporated with the inverse probability of treatment weighting using a propensity score. The results showed that 27 never users and 155 ever users developed malignant brain tumors in the unmatched cohort. The incidence rate was 37.11 per 100,000 person-years in never users and 21.39 per 100,000 person-years in ever users. The overall hazard ratio comparing ever users versus never users was 0.574 (95% confidence interval: 0.381–0.863). The respective hazard ratios comparing the first (<27.13 months), second (27.13–58.33 months), and third (>58.33 months) tertiles of cumulative duration of metformin therapy versus never users were 0.897 (0.567–1.421), 0.623 (0.395–0.984), and 0.316 (0.192–0.518). In the matched cohort, the overall hazard ratio was 0.317 (0.149–0.673) and the respective hazard ratios were 0.427 (0.129–1.412), 0.509 (0.196–1.322), and 0.087 (0.012–0.639) for the first, second, and third tertile of cumulative duration of metformin therapy. In conclusion, this study shows a risk reduction of malignant brain tumors associated with metformin use in a dose–response pattern. The risk reduction is more remarkable when metformin has been used for approximately 2–5 years.