1α,25 dihydroxyvitamin D3 enhances cellular defences against UV-induced oxidative and other forms of DNA damage in skin

The photo-protective role of vitamin D in the microalga Emiliania huxleyi

An essential interaction between sunlight and eukaryotes involves vitamin D production through exposure to ultraviolet (UV) radiation. While extensively studied in vertebrates, the role of vitamin D in non-animal eukaryotes like microalgae remains unclear. Here, we investigate the potential involvement of vitamin D in the UV-triggered response of Emiliania huxleyi, a microalga inhabiting shallow ocean depths that are exposed to UV. Our results show that E. huxleyi produces vitamin D2 and D3 in response to UV. We further demonstrate that E. huxleyi responds to external administration of vitamin D at the transcriptional level, regulating protective mechanisms that are also responsive to UV. Our data reveal that vitamin D addition enhances algal photosynthetic performance while reducing harmful reactive oxygen species buildup. This study contributes to understanding the function of vitamin D in E. huxleyi and its role in non-animal eukaryotes, as well as its potential importance in marine ecosystems.

1,25-Dihydroxyvitamin D3 Suppresses UV-Induced Poly(ADP-Ribose) Levels in Primary Human Keratinocytes, as Detected by a Novel Whole-Cell ELISA

Photoprotective properties of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) to reduce UV-induced DNA damage have been established in several studies. UV-induced DNA damage in skin such as single or double strand breaks is known to initiate several cellular mechanisms including activation of poly(ADP-ribose) (pADPr) polymerase-1 (PARP-1). DNA damage from UV also increases extracellular signal-related kinase (ERK) phosphorylation, which further increases PARP activity. PARP-1 functions by using cellular nicotinamide adenine dinucleotide (NAD+) to synthesise pADPr moieties and attach these to target proteins involved in DNA repair. Excessive PARP-1 activation following cellular stress such as UV irradiation may result in excessive levels of cellular pADPr. This can also have deleterious effects on cellular energy levels due to depletion of NAD+ to suboptimal levels. Since our previous work indicated that 1,25(OH)2D3 reduced UV-induced DNA damage in part through increased repair via increased energy availability, the current study investigated the effect of 1,25(OH)2D3 on UV-induced PARP-1 activity using a novel whole-cell enzyme- linked immunosorbent assay (ELISA) which quantified levels of the enzymatic product of PARP-1, pADPr. This whole cell assay used around 5000 cells per replicate measurement, which represents a 200-400-fold decrease in cell requirement compared to current commercial assays that measure in vitro pADPr levels. Using our assay, we observed that UV exposure significantly increased pADPr levels in human keratinocytes, while 1,25(OH)2D3 significantly reduced levels of UV-induced pADPr in primary human keratinocytes to a similar extent as a known PARP-1 inhibitor, 3-aminobenzamide (3AB). Further, both 1,25(OH)2D3 and 3AB as well as a peptide inhibitor of ERK-phosphorylation significantly reduced DNA damage in UV-exposed keratinocytes. The current findings support the proposal that reduction in pADPr levels may be critical for the function of 1,25(OH)2D3 in skin to reduce UV-induced DNA damage.

In vitro photoprotective potential of aryl-sandwiched (thio)semicarbazones against UVA mediated cellular and DNA damage

The most prevalent solar ultraviolet radiation is ultraviolet-A (UVA) radiation. It is the inducer of reactive oxygen species (ROS), a potent mediator of inflammation and photocarcinogenesis. Regular application of sunscreens containing UVA filters is an effective preventive measure in mitigating the risk associated with the formation of dermal carcinoma. Therefore, the development of new photoprotective agents is of great need. The current work examined the in vitro photoprotection of the aryl-linked (thio)semicarbazone derivatives against UVA-mediated DNA damage, inflammation, reactive nitrogen species (RNS), and ROS. Except for the inflammatory cytokine assay, which was carried out on the human monocytic leukemia (THP-1) cell line, all tests were conducted on the human dermal fibroblast (BJ) cell line. In comparison to benzophenone (reference compound), the compound (2Z, 2'Z)-2,2'-(1,3-Phenylenebis (methanylylidene)) bis (hydrazine-1-carbothioamide) (DD-21) demonstrated considerable protection against UVA-induced damage. Compared to the UVA-irradiated control, DD-21 significantly decreased the levels of nitric oxide (NO) and ROS (p < 0.001). In the presence of DD-21, the release of UVA-induced pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), was also significantly reduced (p < 0.05). Moreover, it was observed that DD-21 protected the cells from UVA-mediated DNA strand breaks and also inhibited the formation of cyclobutane pyrimidine dimers (CPDs) upon comparison to the UVA-exposed control cells (p < 0.001). In conclusion, the findings of this study revealed that DD-21 exhibits remarkable photoprotective properties, thus demonstrating its potential as a candidate UVA filter.

The Over-Irradiation Metabolite Derivative, 24-Hydroxylumister-ol3, Reduces UV-Induced Damage in Skin

The hormonal form of vitamin D₃, 1,25(OH)₂D₃, reduces UV-induced DNA damage. UV exposure initiates pre-vitamin D₃ production in the skin, and continued UV exposure photoisomerizes pre-vitamin D₃ to produce "over-irradiation products" such as lumisterol₃ (L₃). Cytochrome P450 side-chain cleavage enzyme (CYP11A1) in skin catalyzes the conversion of L₃ to produce three main derivatives: 24-hydroxy-L₃ [24(OH)L₃], 22-hydroxy-L₃ [22(OH)L₃], and 20,22-dihydroxy-L₃ [20,22(OH)L₃]. The current study investigated the photoprotective properties of the major over-irradiation metabolite, 24(OH)L₃, in human primary keratinocytes and human skin explants. The results indicated that treatment immediately after UV with either 24(OH)L₃ or 1,25(OH)₂D₃ reduced UV-induced cyclobutane pyrimidine dimers and oxidative DNA damage, with similar concentration response curves in keratinocytes, although in skin explants, 1,25(OH)₂D₃ was more potent. The reductions in DNA damage by both compounds were, at least in part, the result of increased DNA repair through increased energy availability via increased glycolysis, as well as increased DNA damage recognition proteins in the nucleotide excision repair pathway. Reductions in UV-induced DNA photolesions by either compound occurred in the presence of lower reactive oxygen species. The results indicated that under in vitro and ex vivo conditions, 24(OH)L₃ provided photoprotection against UV damage similar to that of 1,25(OH)₂D₃.

Probing photoprotection properties of lipophilic chain conjugated thiourea-aryl group molecules to attenuate ultraviolet-A induced cellular and DNA damages

Ultraviolet-A (UVA) radiation is a major contributor to reactive oxygen species (ROS), reactive nitrite species (RNS), inflammation, and DNA damage, which causes photoaging and photocarcinogenesis. This study aimed to evaluate the UVA protective potential of lipophilic chain conjugated thiourea-substituted aryl group molecules against UVA-induced cellular damages in human dermal fibroblasts (BJ cell line). We tested a series of nineteen (19) molecules for UVA photoprotection, from which 2',5'-dichlorophenyl-substituted molecule DD-04 showed remarkable UVA protection properties compared to the reference (benzophenone). The results indicate that DD-04 significantly reduced intracellular ROS and nitric oxide (NO) as compared to the UVA-irradiated control (p < 0.001). Moreover, the compound DD-04 showed anti-inflammatory activity as it significantly reduced the levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) pro-inflammatory cytokines produced by THP-1 (human monocytic) cells (p < 0.05). DNA damage was also prevented by DD-04 treatment in the presence of UVA. It was observed that DD-04 significantly reduced the number of cyclobutane pyrimidine dimers (CPDs) when compared to the UVA-irradiated control (p < 0.001). Finally, the DNA strand breaks were checked and a single intact DNA band was seen upon treatment with DD-04 in the presence of UVA. In conclusion, DD-04 can be considered a potential candidate UVA filter due to its photoprotective potential.

Focus on the Contribution of Oxidative Stress in Skin Aging

Skin aging is one of the most evident signs of human aging. Modification of the skin during the life span is characterized by fine lines and wrinkling, loss of elasticity and volume, laxity, rough-textured appearance, and pallor. In contrast, photoaged skin is associated with uneven pigmentation (age spot) and is markedly wrinkled. At the cellular and molecular level, it consists of multiple interconnected processes based on biochemical reactions, genetic programs, and occurrence of external stimulation. The principal cellular perturbation in the skin driving senescence is the alteration of oxidative balance. In chronological aging, reactive oxygen species (ROS) are produced mainly through cellular oxidative metabolism during adenosine triphosphate (ATP) generation from glucose and mitochondrial dysfunction, whereas in extrinsic aging, loss of redox equilibrium is caused by environmental factors, such as ultraviolet radiation, pollution, cigarette smoking, and inadequate nutrition. During the aging process, oxidative stress is attributed to both augmented ROS production and reduced levels of enzymatic and non-enzymatic protectors. Apart from the evident appearance of structural change, throughout aging, the skin gradually loses its natural functional characteristics and regenerative potential. With aging, the skin immune system also undergoes functional senescence manifested as a reduced ability to counteract infections and augmented frequency of autoimmune and neoplastic diseases. This review proposes an update on the role of oxidative stress in the appearance of the clinical manifestation of skin aging, as well as of the molecular mechanisms that underline this natural phenomenon sometimes accelerated by external factors.

UV-induced DNA Damage in Skin is Reduced by CaSR Inhibition

The epidermis maintains a cellular calcium gradient that supports keratinocyte differentiation from its basal layers (low) to outer layers (high) leading to the development of the stratum corneum, which resists penetration of UV radiation. The calcium‐sensing receptor (CaSR) expressed in keratinocytes responds to the calcium gradient with signals that promote differentiation. In this study, we investigated whether the CaSR is involved more directly in protection from UV damage in studies of human keratinocytes in primary culture and in mouse skin studied in vivo. siRNA‐directed reductions in CaSR protein levels in human keratinocytes significantly reduced UV‐induced direct cyclobutane pyrimidine dimers (CPD) by ~80% and oxidative DNA damage (8‐OHdG) by ~65% compared with control transfected cells. Similarly, in untransfected cells, the CaSR negative modulator, NPS‐2143 (500 nm), reduced UV‐induced CPD and 8‐OHdG by ~70%. NPS‐2143 also enhanced DNA repair and reduced reactive oxygen species (ROS) by ~35% in UV‐exposed keratinocytes, consistent with reduced DNA damage after UV exposure. Topical application of NPS‐2143 also protected hairless Skh:hr1 mice from UV‐induced CPD, oxidative DNA damage and inflammation, similar to the reductions observed in response to the well‐known photoprotection agent 1,25(OH)₂D₃ (calcitriol). Thus, negative modulators of the CaSR offer a new approach to reducing UV‐induced skin damage.

Vitamin D Enhances Anticancer Properties of Cediranib, a VEGFR Inhibitor, by Modulation of VEGFR2 Expression in Melanoma Cells

Regardless of the recent groundbreaking introduction of personalized therapy, melanoma continues to be one of the most lethal skin malignancies. Still, a substantial proportion of patients either fail to respond to the therapy or will relapse over time, representing a challenging clinical problem. Recently, we have shown that vitamin D enhances the effectiveness of classical chemotherapeutics in the human malignant melanoma A375 cell line. In search for new combination strategies and adjuvant settings to improve melanoma patient outcomes in the current study, the effects of cediranib (AZD2171), an oral tyrosine kinase inhibitor of VEGFR1-3, PDGFR, and c-KIT, used in combination either with 1,25(OH)₂D₃ or with low-calcemic analog calcipotriol were tested on four human malignant melanoma cell lines (A375, MNT-1, RPMI-7951, and SK-MEL-28). Melanoma cells were pretreated with vitamin D and subsequently exposed to cediranib. We observed a marked decrease in melanoma cell proliferation (A375 and SK-MEL-28), G2/M cell cycle arrest, and a significant decrease in melanoma cell mobility in experimental conditions used (A375). Surprisingly, concurrently with a very desirable decrease in melanoma cell proliferation and mobility, we noticed the upregulation of VEGFR2 at both protein and mRNA levels. No effect of vitamin D was observed in MNT-1 and RPMI-7951 melanoma cells. It seems that vitamin D derivatives enhance cediranib efficacy by modulation of VEGFR2 expression in melanoma cells expressing VEGFR2. In conclusion, our experiments demonstrated that vitamin D derivatives hold promise as novel adjuvant candidates to conquer melanoma, especially in patients suffering from vitamin D deficiency. However, further extensive research is indispensable to reliably assess their potential benefits for melanoma patients.

Evidence for Involvement of Nonclassical Pathways in the Protection From UV-Induced DNA Damage by Vitamin D-Related Compounds

The vitamin D hormone, 1,25dihydroxyvitamin D₃ (1,25(OH)₂D₃), and related compounds derived from vitamin D₃ or lumisterol as a result of metabolism via the enzyme CYP11A1, have been shown, when applied 24 hours before or immediately after UV irradiation, to protect human skin cells and skin from DNA damage due to UV exposure, by reducing both cyclobutane pyrimidine dimers (CPD) and oxidative damage in the form of 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐OHdG). We now report that knockdown of either the vitamin D receptor or the endoplasmic reticulum protein ERp57 by small, interfering RNA (siRNA) abolished the reductions in UV‐induced DNA damage with 20‐hydroxyvitamin D₃ or 24‐hydroxylumisterol_3, as previously shown for 1,25(OH)₂D₃. Treatment with 1,25(OH)₂D₃ reduced oxygen consumption rates in UV‐exposed and sham‐exposed human keratinocytes and reduced phosphorylation of cyclic AMP response binding element protein (CREB). Both these actions have been shown to inhibit skin carcinogenesis after chronic UV exposure, consistent with the anticarcinogenic activity of 1,25(OH)₂D₃. The requirement for a vitamin D receptor for the photoprotective actions of 1,25(OH)₂D₃ and of naturally occurring CYP11A1‐derived vitamin D–related compounds may explain why mice lacking the vitamin D receptor in skin are more susceptible to UV‐induced skin cancers, whereas mice lacking the 1α‐hydroxylase and thus unable to make 1,25(OH)₂D₃ are not more susceptible. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Protective effects of 1,25 dihydroxyvitamin D3 and its analogs on ultraviolet radiation-induced oxidative stress: a review

The active vitamin D compound, 1,25-dihydroxyvitamin D3 (1,25D) is produced in skin cells following exposure to ultraviolet radiation (UV) from the sun. However, there are many harmful effects of UV which include DNA damage caused by direct absorption of UV, as well as that caused indirectly via UV-induced reactive oxygen species (ROS). Interestingly, 1,25D and analogs have been shown to reduce both direct and indirect UV-induced DNA damage in skin cells. This was accompanied by reductions in ROS and in nitric oxide products with 1,25D following UV. Moreover, following acute UV exposure, 1,25D has been demonstrated to increase p53 levels in skin, which would presumably allow for repair of cells with damaged DNA, or apoptosis of cells with irreparably damaged DNA. Previous studies have also shown that p53 reduces intracellular ROS. Furthermore, 1,25D has been shown to induce metallothioneins, which are potent free radical scavengers. In addition to these protective effects, 1,25D has been demonstrated to inhibit stress-activated c-Jun N-terminal kinases following UV exposure, and to increase levels of the stress-induced protein heme oxygenase-1 in a model of oxidative stress. Herein, we discuss the protective effects of 1,25D and analogs in the context of UV, oxidative stress and skin cancer.

Sex Differences in Photoprotective Responses to 1,25-Dihydroxyvitamin D3 in Mice Are Modulated by the Estrogen Receptor-β

Susceptibility to photoimmune suppression and photocarcinogenesis is greater in male than in female humans and mice and is exacerbated in female estrogen receptor-beta knockout (ER-β-/-) mice. We previously reported that the active vitamin D hormone, 1,25-dihydroxyvitamin D3 (1,25(OH)2D), applied topically protects against the ultraviolet radiation (UV) induction of cutaneous cyclobutane pyrimidine dimers (CPDs) and the suppression of contact hypersensitivity (CHS) in female mice. Here, we compare these responses in female versus male Skh:hr1 mice, in ER-β-/-/-- versus wild-type C57BL/6 mice, and in female ER-blockaded Skh:hr1 mice. The induction of CPDs was significantly greater in male than female Skh:hr1 mice and was more effectively reduced by 1,25(OH)2D in female Skh:hr1 and C57BL/6 mice than in male Skh:hr1 or ER-β-/- mice, respectively. This correlated with the reduced sunburn inflammation due to 1,25(OH)2D in female but not male Skh:hr1 mice. Furthermore, although 1,25(OH)2D alone dose-dependently suppressed basal CHS responses in male Skh:hr1 and ER-β-/- mice, UV-induced immunosuppression was universally observed. In female Skh:hr1 and C57BL/6 mice, the immunosuppression was decreased by 1,25(OH)2D dose-dependently, but not in male Skh:hr1, ER-β-/-, or ER-blockaded mice. These results reveal a sex bias in genetic, inflammatory, and immune photoprotection by 1,25(OH)2D favoring female mice that is dependent on the presence of ER-β.

The enzyme-modified comet assay: Past, present and future

The enzyme-modified comet assay was developed in order to detect DNA lesions other than those detected by the standard version (single and double strand breaks and alkali-labile sites). Various lesion-specific enzymes, from the DNA repair machinery of bacteria and humans, have been combined with the comet assay, allowing detection of different oxidized and alkylated bases as well as cyclobutane pyrimidine dimers, mis-incorporated uracil and apurinic/apyrimidinic sites. The enzyme-modified comet assay has been applied in different fields - human biomonitoring, environmental toxicology, and genotoxicity testing (both in vitro and in vivo) - as well as in basic research. Up to now, twelve enzymes have been employed; here we describe the enzymes and give examples of studies in which they have been applied. The bacterial formamidopyrimidine DNA glycosylase (Fpg) and endonuclease III (EndoIII) have been extensively used while others have been used only rarely. Adding further enzymes to the comet assay toolbox could potentially increase the variety of DNA lesions that can be detected. The enzyme-modified comet assay can play a crucial role in the elucidation of the mechanism of action of both direct and indirect genotoxins, thus increasing the value of the assay in the regulatory context.

Latest Evidence Regarding the Effects of Photosensitive Drugs on the Skin: Pathogenetic Mechanisms and Clinical Manifestations

Photosensitivity induced by drugs is a widely experienced problem, concerning both molecule design and clinical practice. Indeed, photo-induced cutaneous eruptions represent one of the most common drug adverse events and are frequently an important issue to consider in the therapeutic management of patients. Phototoxicity and photoallergy are the two different pathogenic mechanisms involved in photosensitization. Related cutaneous manifestations are heterogeneous, depending on the culprit drug and subject susceptibility. Here we report an updated review of the literature with respect to pathogenic mechanisms of photosensitivity, clinical manifestations, patient management, and prediction and evaluation of drug-induced photosensitivity. We present and discuss principal groups of photosensitizing drugs (antimicrobials, nonsteroidal anti-inflammatory drugs, anti-hypertensives, anti-arrhythmics, cholesterol, and glycemia-lowering agents, psychotropic drugs, chemotherapeutics, etc.) and their main damage mechanisms according to recent evidence. The link between the drug and the cutaneous manifestation is not always clear; more investigations would be helpful to better predict drug photosensitizing potential, prevent and manage cutaneous adverse events and find the most appropriate alternative therapeutic strategy.

Protection from Ultraviolet Damage and Photocarcinogenesis by Vitamin D Compounds

Exposure of skin cells to UV radiation results in DNA damage, which if inadequately repaired, may cause mutations. UV-induced DNA damage and reactive oxygen and nitrogen species also cause local and systemic suppression of the adaptive immune system. Together, these changes underpin the development of skin tumours. The hormone derived from vitamin D, calcitriol (1,25-dihydroxyvitamin D₃) and other related compounds, working via the vitamin D receptor and at least in part through endoplasmic reticulum protein 57 (ERp57), reduce cyclobutane pyrimidine dimers and oxidative DNA damage in keratinocytes and other skin cell types after UV. Calcitriol and related compounds enhance DNA repair in keratinocytes, in part through decreased reactive oxygen species, increased p53 expression and/or activation, increased repair proteins and increased energy availability in the cell when calcitriol is present after UV exposure. There is mitochondrial damage in keratinocytes after UV. In the presence of calcitriol, but not vehicle, glycolysis is increased after UV, along with increased energy-conserving autophagy and changes consistent with enhanced mitophagy. Reduced DNA damage and reduced ROS/RNS should help reduce UV-induced immune suppression. Reduced UV immune suppression is observed after topical treatment with calcitriol and related compounds in hairless mice. These protective effects of calcitriol and related compounds presumably contribute to the observed reduction in skin tumour formation in mice after chronic exposure to UV followed by topical post-irradiation treatment with calcitriol and some, though not all, related compounds.

Antiproliferative activity of side-chain truncated vitamin D analogs (PRI-1203 and PRI-1204) against human malignant melanoma cell lines

Vitamin D compounds are versatile molecules widely considered as promising agents in cancer prevention and treatment, including melanoma. Previously we investigated series of double point modified vitamin D₂ analogs as well as non-calcemic 20S-hydroxyvitamin D₃ and 21-hydroxypregnacalciferol as to their anti-melanoma activity. Surprisingly, short side-chain vitamin D analogs were found to be biologically active compounds. Thus, here we tested novel derivatives of pregnacalciferol with an additional hydroxyl at the end of the truncated side chain, PRI-1203 and PRI-1204, as to their potency against human melanoma A375 and RPMI7951 cell lines. Tested compounds are geometric isomers, with 19-methylene positioned in PRI-1203 like in a calcitriol molecule, but reversed in the PRI-1204 analog to the (5E,7E) geometry (5,6-trans). We noticed a decrease in cells viability exerted by PRI-1203. The antiproliferative effect of PRI-1204 was very low, emphasizing the importance of the natural 19-methylene geometry in the PRI-1203. PRI-1203 was also effective in inhibition of A375 melanoma cells migration. PRI-1203, but not PRI-1204, increased the percentage of A375 and RPMI7951 melanoma cells in the G0/G1 phase of cell cycle, possibly in a p21 and p27 independent manner. Both, analogs have very low effect on the level of CYP24A1 mRNA, in comparison to active form of vitamin D - 1.25(OH)2D3. In addition, both tested compounds failed to elicit VDR translocation to the nucleus. Thus, it could be postulated that side chain shortening strongly affects binding of analogs to VDR and activation of genomic responses, however do not impair their antiproliferative activities.

Beneficial Regulation of Cellular Oxidative Stress Effects, and Expression of Inflammatory, Angiogenic, and the Extracellular Matrix Remodeling Proteins by 1α,25-Dihydroxyvitamin D3 in a Melanoma Cell Line

The causes of cancer include the cellular accumulation reactive oxygen species (ROS), which overrides the cellular antioxidants such as superoxide dismutase, from intrinsic aging, genetics, and exposure to environmental pollutants and ultraviolet (UV) radiation. The ROS damage biomolecules such as DNA (including p53 gene), RNA, and lipids, and activate inflammatory, angiogenic, and extracellular matrix (ECM) remodeling proteins; which collectively facilitate carcinogenesis. The 1α,25-dihydroxyvitamin D3 (Vitamin D) has anti-carcinogenic potential from its antioxidant, anti-inflammatory, and endocrine properties. We examined the anti-carcinogenic mechanism of vitamin D through the beneficial regulation of oxidative stress effects (oxidative DNA/RNA damage, superoxide dismutase expression, membrane damage, and p53 promoter activity), and expression (at the protein, mRNA and/or promoter levels) of inflammatory mediators (interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α)), angiogenic mediators (transforming growth factor-β (TGF-β), and vascular endothelial growth factor (VEGF)), and the ECM remodeling proteins (matrix metalloproteinases (MMP)-1 and MMP-2) by vitamin D in melanoma cells. Vitamin D inhibited oxidative DNA/RNA damage and membrane damage; and stimulated superoxide dismutase expression and p53 promoter activity in melanoma cells. It inhibited the expression of IL-1, TNF-α, TGF-β, VEGF, MMP-1 and MMP-2 by transcriptional or post-transcriptional mechanisms. We conclude that vitamin D is beneficial to melanoma cells through the inhibition of oxidative DNA/RNA damage, membrane damage, and the expression of inflammatory, angiogenic and ECM remodeling proteins; and the stimulation of superoxide dismutase expression and p53 promoter activity.

UV increases skin-derived 1α,25-dihydroxyvitamin D3 production, leading to MMP-1 expression by altering the balance of vitamin D and cholesterol synthesis from 7-dehydrocholesterol

The skin is a unique site in the human body that has the capacity to synthesize the active form of vitamin D, 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃), from 7-dehydrocholesterol (7DHC) upon UV irradiation. Keratinocytes express both 25-hydroxylase (CYP27A1 and CYP2R1) and 1α-hydroxylase (CYP27B1), critical enzymes involved in active vitamin D synthesis. Here, we investigated the effect of skin-derived 1α,25(OH)₂D₃, synthesized purely within the keratinocytes, on MMP-1 expression. Treatment of human epidermal keratinocytes with 1α,25(OH)₂D_3, but not 7DHC or 25OHD₃, significantly increased MMP-1 expression. UV irradiation increases 1α,25(OH)₂D₃ levels, and ketoconazole inhibits UV-induced production of 1α,25(OH)₂D₃. Upregulation of MMP-1 by UV was reversed by inhibition of 1α,25(OH)₂D₃ synthesis using ketoconazole or CYP27B1 siRNA. In keratinocytes, 7DHC is a substrate for both cholesterol and 1α,25(OH)₂D₃ synthesis. We demonstrated that UV irradiation leads to decreased expression of DHCR7 (7-dehydrocholesterol reductase), the enzyme that converts 7DHC to cholesterol. Inhibition of DHCR7 with its inhibitor BM15766 decreased cholesterol synthesis and increased UV-induced MMP-1 expression, which was attenuated by ketoconazole. These findings suggest that UV-induced reduction of DHCR7 leads to a decrease in cholesterol synthesis, thereby increasing 7DHC availability for 1α,25(OH)₂D₃ production, which enhances MMP-1 expression. Finally, UV irradiation in human skin in vivo significantly increased CYP27B1 mRNA and decreased DHCR7 mRNA expression. Taken together, we demonstrate here that skin-derived 1α,25(OH)₂D₃ significantly increases MMP-1 expression in human keratinocytes, a previously unappreciated function of 1α,25(OH)₂D_3. Moreover, UV irradiation upregulates the enzyme CYP27B1, which leads to 1α,25(OH)₂D₃ synthesis, but downregulates the cholesterol-producing enzyme DHCR7, both of which collectively lead to increased MMP-1 expression in human keratinocytes. This pathway may be exploited to develop a novel cutaneous anti-aging agent that blocks local cutaneous 1α,25(OH)₂D₃ synthesis.

The Beneficial Regulation of Extracellular Matrix and Heat Shock Proteins, and the Inhibition of Cellular Oxidative Stress Effects and Inflammatory Cytokines by 1α, 25 dihydroxyvitaminD3 in Non-Irradiated and Ultraviolet Radiated Dermal Fibroblasts

Intrinsic skin aging and photoaging, from exposure to ultraviolet (UV) radiation, are associated with altered regulation of genes associated with the extracellular matrix (ECM) and inflammation, as well as cellular damage from oxidative stress. The regulatory properties of 1α, 25dihydroxyvitamin D3 (vitamin D) include endocrine, ECM regulation, cell differentiation, photoprotection, and anti-inflammation. The goal of this research was to identify the beneficial effects of vitamin D in preventing intrinsic skin aging and photoaging, through its direct effects as well as its effects on the ECM, associated heat shock proteins (HSP-47, and -70), cellular oxidative stress effects, and inflammatory cytokines [interleukin (IL)-1 and IL-8] in non-irradiated, UVA-radiated, UVB-radiated dermal fibroblasts. With regard to the ECM, vitamin D stimulated type I collagen and inhibited cellular elastase activity in non-irradiated fibroblasts; and stimulated type I collagen and HSP-47, and inhibited elastin expression and elastase activity in UVA-radiated dermal fibroblasts. With regard to cellular protection, vitamin D inhibited oxidative damage to DNA, RNA, and lipids in non-irradiated, UVA-radiated and UVB-radiated fibroblasts, and, in addition, increased cell viability of UVB-radiated cells. With regard to anti-inflammation, vitamin D inhibited expression of Il-1 and IL-8 in UVA-radiated fibroblasts, and stimulated HSP-70 in UVA-radiated and UVB-radiated fibroblasts. Overall, vitamin D is predominantly beneficial in preventing UVA-radiation induced photoaging through the differential regulation of the ECM, HSPs, and inflammatory cytokines, and protective effects on the cellular biomolecules. It is also beneficial in preventing UVB-radiation associated photoaging through the stimulation of cell viability and HSP-70, and the inhibition of cellular oxidative damage, and in preventing intrinsic aging through the stimulation of type I collagen and inhibition of cellular oxidative damage.

Neuroendocrine Aspects of Skin Aging

Skin aging is accompanied by a gradual loss of function, physiological integrity and the ability to cope with internal and external stressors. This is secondary to a combination of complex biological processes influenced by constitutive and environmental factors or by local and systemic pathologies. Skin aging and its phenotypic presentation are dependent on constitutive (genetic) and systemic factors. It can be accelerated by environmental stressors, such as ultraviolet radiation, pollutants and microbial insults. The skin’s functions and its abilities to cope with external stressors are regulated by the cutaneous neuroendocrine systems encompassing the regulated and coordinated production of neuropeptides, neurohormones, neurotransmitters and hormones, including steroids and secosteroids. These will induce/stimulate downstream signaling through activation of corresponding receptors. These pathways and corresponding coordinated responses to the stressors decay with age or undergo pathological malfunctions. This affects the overall skin phenotype and epidermal, dermal, hypodermal and adnexal functions. We propose that skin aging can be attenuated or its phenotypic presentation reversed by the topical use of selected factors with local neurohormonal activities targeting specific receptors or enzymes. Some of our favorite factors include melatonin and its metabolites, noncalcemic secosteroids and lumisterol derivatives, because of their low toxicity and their desirable local phenotypic effects.

Vitamin D and its low calcemic analogs modulate the anticancer properties of cisplatin and dacarbazine in the human melanoma A375 cell line

Melanoma represents a significant challenge in cancer treatment due to the high drug resistance of melanomas and the patient mortality rate. This study presents data indicating that nanomolar concentrations of the hormonally active form of vitamin D, 1α,25-dihydroxyvitamin D3 [1α,25(OH)₂D3], its non-calcemic analogues 20S-hydroxyvitamin D3 and 21-hydroxypregnacalciferol, as well as the low-calcemic synthetic analog calcipotriol, modulate the efficacy of the anticancer drugs cisplatin and dacarbazine. It was observed that vitamin D analogs sensitized melanoma A375 cells to hydrogen peroxide used as an inducer of oxidative stress. On the other hand, only 1α,25(OH)₂D3 resulted in a minor, but significant effect on the proliferation of melanoma cells treated simultaneously with dacarbazine, but not cisplatin. Notably, cisplatin (300 µM) exhibited a higher overall antiproliferative activity than dacarbazine. Cisplatin treatment of melanoma cells resulted in an induction of apoptosis as demonstrated by flow cytometry (accumulation of cells at the subG₁ phase of the cell cycle), whereas dacarbazine caused G₁/G₀ cell cycle arrest, with the effects being improved by pre-treatment with vitamin D analogs. Treatment with cisplatin resulted in an initial increase in the level of reactive oxygen species (ROS). Dacarbazine caused transient stimulation of ROS levels and the mitochondrial membrane potential (Δψ_m) (after 1 or 3 h of treatment, respectively), but the effect was not detectable following prolonged (24 h) incubation with the drug. Vitamin D exhibited modulatory effects on the cells treated with dacarbazine, decreasing the half maximal inhibitory concentration (IC₅₀) for the drug, stimulating G₁/G₀ arrest and causing a marked decrease in Δψ_m. Finally, cisplatin, dacarbazine and 1α,25(OH)₂D3 displayed modulatory effects on the expression of ROS and vitamin D-associated genes in the melanoma A375 cells. In conclusion, nanomolar concentrations of 1,25(OH)₂D₃ only had minor effects on the proliferation of melanoma cells treated with dacarbazine, decreasing the relative IC₅₀ value. However, co-treatment with vitamin D analogs resulted in the modulation of cell cycle and ROS responses, and affected gene expression, suggesting possible crosstalk between the signaling pathways of vitamin D and the anticancer drugs used in this study.

Mechanisms of and variables affecting UVR photoadaptation in human skin

Humans have been exposed to solar UV radiation since their appearance on Earth and evolution has enabled most individuals to adapt to this exposure, to some degree. UV radiation produces several deleterious effects in human skin and light-skinned individuals are at greatest risk for both acute and long-term negative effects such as DNA damage, sunburn, immune suppression and skin cancer. The benefits of photoadaptation, which leads to a decreased response after acclimatization, are that humans who have skin that is capable of photoadaptation can work and play in the sun with reduced fear of painful sunburn. However, the effects of photoadaptation on DNA damage and development of skin cancer are quite complex and less well-understood. In this article, we have reviewed the current state of knowledge of UVR photoadaptation in human skin. However, more studies are needed to explore the use of UVR photoadaptation to protect against critical endpoints, such as skin cancer.

Targeting Mitochondrial Oxidative Stress to Mitigate UV-Induced Skin Damage

Unmitigated UV radiation (UVR) induces skin photoaging and multiple forms of cutaneous carcinoma by complex pathways that include those mediated by UV-induced reactive oxygen species (ROS). Upon UVR exposure, a cascade of events is induced that overwhelms the skin’s natural antioxidant defenses and results in DNA damage, intracellular lipid and protein peroxidation, and the dysregulation of pathways that modulate inflammatory and apoptotic responses. To this end, natural products with potent antioxidant properties have been developed to prevent, mitigate, or reverse this damage with varying degrees of success. Mitochondria are particularly susceptible to ROS and subsequent DNA damage as they are a major intracellular source of oxidants. Therefore, the development of mitochondrially targeted agents to mitigate mitochondrial oxidative stress and resulting DNA damage is a logical approach to prevent and treat UV-induced skin damage. We summarize evidence that some existing natural products may reduce mitochondrial oxidative stress and support for synthetically generated mitochondrial targeted cyclic nitroxides as potential alternatives for the prevention and mitigation of UVR-induced skin damage.

In the search for reliable biomarkers for the early diagnosis of autism spectrum disorder: the role of vitamin D

Autism spectrum disorder (ASD) affects about 1% of the world's population. Vitamin D is thought to be essential for normal brain development and modulation of the immune system. Worldwide about 1 billion people are affected by vitamin D deficiency. High-sensitivity C-reactive protein (hs-CRP), cytochrome P450 2E1 (CYP2E1) and 8-hydroxy-2'-deoxyguanosine (8-OH-dG) are biomarkers related to inflammation and oxidative stress. In the present study, these biomarkers were together with serum 25-hydroxyvitamin D (25(OH)D₃) analyzed in 28 (mean age seven years) Saudi male patients with ASD. The study was conducted to determine if there is any relationship between vitamin D levels, the tested biomarkers and the presence and severity of ASD. The hope was to identify if these biomarkers may be useful for early ASD diagnosis. The Childhood Autism Rating Scale (CARS) and the Social Responsiveness Scale (SRS) were used to measure autism severity. The results of the ASD children were compared with 27 age and gender-matched neurotypical controls. The data indicated that Saudi patients with ASD have significantly lower plasma levels of 25(OH)D₃ than neurotypical controls (38 ng/ml compared to 56 ng/ml, respectively; [P = 0.001]). Surprisingly, the levels of CYP2E1 were lower in the children with ASD than the neurotypical controls (0.48 ± 0.08 vs. 69 ± 0.07 ng/ml, respectively; P = 0.001). The ASD children also had significantly higher levels of hs-CRP (0.79 ± 0.09 vs. 0.59 ± 0.09 ng/ml, respectively; P = 0.001) and 8-OH-dG (8.17 ± 1.04 vs. 4.13 ± 1.01 ng/ml, respectively; P = 0.001, compared to neurotypical age and gender-matched controls. The values for hs-CRP and 8-OH-dG did not correlate [P < 0.001] with autism severity. There was found a relationship between autism severity on the CARS scale and the levels of 25(OH)D₃ and CYP1B1. But this was not found for SRS. All four biomarkers seemed to have good sensitivity and specificity, but the sample size of the present study was too small to determine clinical usefulness. The findings also indicate that inadequate levels of vitamin D play a role in the etiology and severity of autism. Furthermore, the results of the present study suggest the possibility of using 25(OH)D₃, CYP1B1, hs-CRP and 8-OH-dG, preferably in combination, as biomarkers for the early diagnosis of ASD. However, further research is needed to evaluate this hypothesis.

Natural Antioxidants: Multiple Mechanisms to Protect Skin From Solar Radiation

Human skin exposed to solar ultraviolet radiation (UVR) results in a dramatic increase in the production of reactive oxygen species (ROS). The sudden increase in ROS shifts the natural balance toward a pro-oxidative state, resulting in oxidative stress. The detrimental effects of oxidative stress occur through multiple mechanisms that involve alterations to proteins and lipids, induction of inflammation, immunosuppression, DNA damage, and activation of signaling pathways that affect gene transcription, cell cycle, proliferation, and apoptosis. All of these alterations promote carcinogenesis and therefore, regulation of ROS levels is critical to the maintenance of normal skin homeostasis. Several botanical products have been found to exhibit potent antioxidant capacity and the ability to counteract UV-induced insults to the skin. These natural products exert their beneficial effects through multiple pathways, including some known to be negatively affected by solar UVR. Aging of the skin is also accelerated by UVR exposure, in particular UVA rays that penetrate deep into the epidermis and the dermis where it causes the degradation of collagen and elastin fibers via oxidative stress and activation of matrix metalloproteinases (MMPs). Because natural compounds are capable of attenuating some of the UV-induced aging effects in the skin, increased attention has been generated in the area of cosmetic sciences. The focus of this review is to cover the most prominent phytoproducts with potential to mitigate the deleterious effects of solar UVR and suitability for use in topical application.

Mechanisms and prevention of UV-induced melanoma

Melanoma is the deadliest form of skin cancer and its incidence is rising, creating a costly and significant clinical problem. Exposure to ultraviolet (UV) radiation, namely UVA (315-400 nm) and UVB (280-315 nm), is a major risk factor for melanoma development. Cumulative UV radiation exposure from sunlight or tanning beds contributes to UV-induced DNA damage, oxidative stress, and inflammation in the skin. A number of factors, including hair color, skin type, genetic background, location, and history of tanning, determine the skin's response to UV radiation. In melanocytes, dysregulation of this UV radiation response can lead to melanoma. Given the complex origins of melanoma, it is difficult to develop curative therapies and universally effective preventative strategies. Here, we describe and discuss the mechanisms of UV-induced skin damage responsible for inducing melanomagenesis, and explore options for therapeutic and preventative interventions.

Enhanced Repair of UV-Induced DNA Damage by 1,25-Dihydroxyvitamin D3 in Skin Is Linked to Pathways that Control Cellular Energy

Inadequately repaired post-UV DNA damage results in skin cancers. DNA repair requires energy but skin cells have limited capacity to produce energy after UV insult. We examined whether energy supply is important for DNA repair after UV exposure, in the presence of 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), which reduces UV-induced DNA damage and photocarcinogenesis in a variety of models. After UV exposure of primary human keratinocytes, the addition of 1,25(OH)₂D₃ increased unscheduled DNA synthesis, a measure of DNA repair. Oxidative phosphorylation was depleted in UV-irradiated keratinocytes to undetectable levels within an hour of UV irradiation. Treatment with 1,25(OH)₂D₃ but not vehicle increased glycolysis after UV. 2-Deoxyglucose-dependent inhibition of glycolysis abolished the reduction in cyclobutane pyrimidine dimers by 1,25(OH)₂D₃, whereas inhibition of oxidative phosphorylation had no effect. 1,25(OH)₂D₃ increased autophagy and modulated PINK1/Parkin consistent with enhanced mitophagy. These data confirm that energy availability is limited in keratinocytes after exposure to UV. In the presence of 1,25(OH)₂D₃, glycolysis is enhanced along with energy-conserving processes such as autophagy and mitophagy, resulting in increased repair of cyclobutane pyrimidine dimers and decreased oxidative DNA damage. Increased energy availability in the presence of 1,25(OH)₂D₃ is an important contributor to DNA repair in skin after UV exposure.

An open-label clinical trial assessing the efficacy and safety of Bend Skincare Anti-Aging Formula on minimal erythema dose in skin

BACKGROUND/PURPOSE

Sunburn and other health risks associated with excess sun exposure place huge economic burdens on societies, and create discomfort and disease within susceptible individuals. Oral supplements that reduce sunburn may be advantageous. This study evaluated the safety and efficacy of Bend Skincare Anti-Aging Formula to ameliorate sunburn induced with a solar simulator.

METHODS

Subjects (n = 28) with Fitzpatrick skin phototypes I, II, or III took 4 capsules daily of the supplement providing 1400 mg of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA), 120 mg of gamma-linolenic acid (GLA), 5 mg of lutein, 2.5 mg of zeaxanthin, and 1000 IU of vitamin D3 for 8 weeks. Skin on each subject's back was exposed to a progressive sequence of timed ultraviolet (UV) radiation exposure doses at baseline, and after 4- and 8-week treatment to determine their minimal erythema dose (MED). Results were compared before and after treatment using 3 paired t tests and subsequently 3 linear mixed models.

RESULTS

Treatment significantly improved tolerance to UV exposure as evidenced by increased MED at 4 and 8 weeks compared with baseline (P < .001). This protection increased with prolonged use of Bend Skincare Anti-Aging Formula as demonstrated by progressively increased MED between baseline and 4 weeks, and again between 4 and 8 weeks (P < .001). Nearly 86% of patients responded to treatment within 4 weeks and 100% of patients responded by the end of the study, resulting in a 39% mean increase in MED at 4 weeks, and an 84% mean increase in MED at 8 weeks compared with baseline. Treatment was well tolerated with no product associated adverse events (AE) and only a few mild and expected side effects.

CONCLUSION

Bend Skincare Anti-Aging Formula safely and effectively provides significant skin photoprotection that increases with continued use.

Bioactive forms of vitamin D selectively stimulate the skin analog of the hypothalamus-pituitary-adrenal axis in human epidermal keratinocytes

Ultraviolet radiation B stimulates both the production of vitamin D3 in the skin and the activation of the skin analog of the hypothalamic-pituitary-adrenal axis (HPA) as well as the central HPA. Since the role of vitamin D3 in the regulation of the HPA is largely unknown, we investigated the impact of 1,25(OH)2D3 and its noncalcemic analogs, 20(OH)D3 and 21(OH)pD, on the expression of the local HPA in human epidermal keratinocytes. The noncalcemic analogs showed similar efficacy to 1,25(OH)2D3 in stimulating the expression of neuropeptides, CRF, urocortins and POMC, and their receptors, CRFR1, CRFR2, MC1R, MC2R, MC3R and MC4R. Interestingly, unlike other secosteroids, the activity of 21(OH)pD did not correlate with induction of differentiation, suggesting a separate but overlapping mechanism of action. Thus, biologically active forms of vitamin D can regulate different elements of the local equivalent of the HPA with implications for the systemic HPA.

A Topical Mitochondria-Targeted Redox-Cycling Nitroxide Mitigates Oxidative Stress-Induced Skin Damage

Skin is the largest human organ, and it provides a first line of defense that includes physical, chemical, and immune mechanisms to combat environmental stress. Radiation is a prevalent environmental stressor. Radiation-induced skin damage ranges from photoaging and cutaneous carcinogenesis caused by UV exposure, to treatment-limiting radiation dermatitis associated with radiotherapy, to cutaneous radiation syndrome, a frequently fatal consequence of exposures from nuclear accidents. The major mechanism of skin injury common to these exposures is radiation-induced oxidative stress. Efforts to prevent or mitigate radiation damage have included development of antioxidants capable of reducing reactive oxygen species. Mitochondria are particularly susceptible to oxidative stress, and mitochondrial-dependent apoptosis plays a major role in radiation-induced tissue damage. We reasoned that targeting a redox cycling nitroxide to mitochondria could prevent reactive oxygen species accumulation, limiting downstream oxidative damage and preserving mitochondrial function. Here we show that in both mouse and human skin, topical application of a mitochondrially targeted antioxidant prevents and mitigates radiation-induced skin damage characterized by clinical dermatitis, loss of barrier function, inflammation, and fibrosis. Further, damage mitigation is associated with reduced apoptosis, preservation of the skin's antioxidant capacity, and reduction of irreversible DNA and protein oxidation associated with oxidative stress.

Disruption of Vitamin D and Calcium Signaling in Keratinocytes Predisposes to Skin Cancer

1,25 dihydroxyvitamin D (1,25(OH)₂D), the active metabolite of vitamin D, and calcium regulate epidermal differentiation. 1,25(OH)₂D exerts its effects through the vitamin D receptor (VDR), a transcription factor in the nuclear hormone receptor family, whereas calcium acts through the calcium sensing receptor (Casr), a membrane bound member of the G protein coupled receptor family. We have developed mouse models in which the Vdr and Casr have been deleted in the epidermis (^epidVdr^−∕− and ^epidCasr^−∕−). Both genotypes show abnormalities in calcium induced epidermal differentiation in vivo and in vitro, associated with altered hedgehog (HH) and β–catenin signaling that when abnormally expressed lead to basal cell carcinomas (BCC) and trichofolliculomas, respectively. The Vdr^−∕− mice are susceptible to tumor formation following UVB or chemical carcinogen exposure. More recently we found that the keratinocytes from these mice over express long non-coding RNA (lncRNA) oncogenes such as H19 and under express lncRNA tumor suppressors such as lincRNA-21. Spontaneous tumors have not been observed in either the ^epidVdr^−∕− or ^epidCasr^−∕−. But in mice with epidermal specific deletion of both Vdr and Casr (^epidVdr^−∕−/^epidCasr^−∕− [DKO]) tumor formation occurs spontaneously when the DKO mice are placed on a low calcium diet. These results demonstrate important interactions between vitamin D and calcium signaling through their respective receptors that lead to cancer when these signals are disrupted. The roles of the β–catenin, hedgehog, and lncRNA pathways in predisposing the epidermis to tumor formation when vitamin D and calcium signaling are disrupted will be discussed.

NRAS and EPHB6 mutation rates differ in metastatic melanomas of patients in the North Island versus South Island of New Zealand

Melanoma, the most aggressive skin cancer type, is responsible for 75% of skin cancer related deaths worldwide. Given that New Zealand (NZ) has the world's highest melanoma incidence, we sought to determine the frequency of mutations in NZ melanomas in recurrently mutated genes. NZ melanomas were from localities distributed between North (35°S-42°S) and South Islands (41°S-47°S). A total of 529 melanomas were analyzed for BRAF exon 15 mutations by Sanger sequencing, and also by Sequenom MelaCarta MassARRAY. While, a relatively low incidence of BRAFV600E mutations (23.4%) was observed overall in NZ melanomas, the incidence of NRAS mutations in South Island melanomas was high compared to North Island melanomas (38.3% vs. 21.9%, P=0.0005), and to The Cancer Genome Atlas database (TCGA) (38.3% vs. 22%, P=0.0004). In contrast, the incidence of EPHB6G404S mutations was 0% in South Island melanomas, and was 7.8% in North Island (P=0.0002). Overall, these data suggest that melanomas from geographically different regions in NZ have markedly different mutation frequencies, in particular in the NRAS and EPHB6 genes, when compared to TCGA or other populations. These data have implications for the causation and treatment of malignant melanoma in NZ.

New Pathogenic Concepts and Therapeutic Approaches to Oxidative Stress in Chronic Kidney Disease

In chronic kidney disease inflammatory processes and stimulation of immune cells result in overproduction of free radicals. In combination with a reduced antioxidant capacity this causes oxidative stress. This review focuses on current pathogenic concepts of oxidative stress for the decline of kidney function and development of cardiovascular complications. We discuss the impact of mitochondrial alterations and dysfunction, a pathogenic role for hyperuricemia, and disturbances of vitamin D metabolism and signal transduction. Recent antioxidant therapy options including the use of vitamin D and pharmacologic therapies for hyperuricemia are discussed. Finally, we review some new therapy options in diabetic nephropathy including antidiabetic agents (noninsulin dependent), plant antioxidants, and food components as alternative antioxidant therapies.

Vitamin D derivatives enhance cytotoxic effects of H2O2 or cisplatin on human keratinocytes

Although the skin production of vitamin D is initiated by ultraviolet radiation type B (UVB), the role vitamin D plays in antioxidative or pro-oxidative responses remains to be elucidated. We have used immortalized human HaCaT keratinocytes as a model of proliferating epidermal cells to test the influence of vitamin D on cellular response to H2O2 or the anti-cancer drug, cisplatin. Incubation of keratinocytes with 1,25(OH)2D3 or its low calcemic analogues, 20(OH)D3, 21(OH)pD or calcipotriol, sensitized cells to ROS resulting in more potent inhibition of keratinocyte proliferation by H2O2 in the presence of vitamin D compounds. These results were supported by cell cycle and apoptosis analyses, and measurement of the mitochondrial transmembrane potentials (MMP), however some unique properties of individual secosteroids were observed. Furthermore, in HaCaT keratinocytes treated with H2O2, 1,25(OH)2D3, 21(OH)pD and calcipotriol stimulated the expression of SOD1 and CAT genes, but not SOD2, indicating a possible role of mitochondria in ROS-modulated cell death. 1,25(OH)2D3 also showed a short-term, protective effect on HaCaT keratinocytes, as exemplified by the inhibition of apoptosis and the maintenance of MMP. However, with prolonged incubation with H2O2 or cisplatin, 1,25(OH)2D3 caused an acceleration in the death of the keratinocytes. Therefore, we propose that lead vitamin D derivatives can protect the epidermis against neoplastic transformation secondary to oxidative or UV-induced stress through activation of vitamin D-signaling. Furthermore, our data suggest that treatment with low calcemic vitamin D analogues or the maintenance of optimal level of vitamin D by proper supplementation, can enhance the anticancer efficacy of cisplatin.

Chemical excitation of electrons: A dark path to melanoma

Sunlight's ultraviolet wavelengths induce cyclobutane pyrimidine dimers (CPDs), which then cause mutations that lead to melanoma or to cancers of skin keratinocytes. In pigmented melanocytes, we found that CPDs arise both instantaneously and for hours after UV exposure ends. Remarkably, the CPDs arising in the dark originate by a novel pathway that resembles bioluminescence but does not end in light: First, UV activates the enzymes nitric oxide synthase (NOS) and NADPH oxidase (NOX), which generate the radicals nitric oxide (NO) and superoxide (O2(-)); these combine to form the powerful oxidant peroxynitrite (ONOO(-)). A fragment of the skin pigment melanin is then oxidized, exciting an electron to an energy level so high that it is rarely seen in biology. This process of chemically exciting electrons, termed "chemiexcitation", is used by fireflies to generate light but it had never been seen in mammalian cells. In melanocytes, the energy transfers radiationlessly to DNA, inducing CPDs. Chemiexcitation is a new source of genome instability, and it calls attention to endogenous mechanisms of genome maintenance that prevent electronic excitation or dissipate the energy of excited states. Chemiexcitation may also trigger pathogenesis in internal tissues because the same chemistry should arise wherever superoxide and nitric oxide arise near cells that contain melanin.

Nucleotide Excision Repair and Vitamin D--Relevance for Skin Cancer Therapy

Ultraviolet (UV) radiation is involved in almost all skin cancer cases, but on the other hand, it stimulates the production of pre-vitamin D3, whose active metabolite, 1,25-dihydroxyvitamin D3 (1,25VD3), plays important physiological functions on binding with its receptor (vitamin D receptor, VDR). UV-induced DNA damages in the form of cyclobutane pyrimidine dimers or (6-4)-pyrimidine-pyrimidone photoproducts are frequently found in skin cancer and its precursors. Therefore, removing these lesions is essential for the prevention of skin cancer. As UV-induced DNA damages are repaired by nucleotide excision repair (NER), the interaction of 1,25VD3 with NER components can be important for skin cancer transformation. Several studies show that 1,25VD3 protects DNA against damage induced by UV, but the exact mechanism of this protection is not completely clear. 1,25VD3 was also shown to affect cell cycle regulation and apoptosis in several signaling pathways, so it can be considered as a potential modulator of the cellular DNA damage response, which is crucial for mutagenesis and cancer transformation. 1,25VD3 was shown to affect DNA repair and potentially NER through decreasing nitrosylation of DNA repair enzymes by NO overproduction by UV, but other mechanisms of the interaction between 1,25VD3 and NER machinery also are suggested. Therefore, the array of NER gene functioning could be analyzed and an appropriate amount of 1.25VD3 could be recommended to decrease UV-induced DNA damage important for skin cancer transformation.

Vitamin D Supplementation Does Not Improve the Severity or the Resolution of Ultraviolet B-Induced Acute Erythema

BACKGROUND

Whether vitamin D supplementation alleviates the severity of ultraviolet B (UVB)-induced erythema and/or facilitates its resolution remains undetermined.

OBJECTIVE

To study the effect of oral vitamin D on UVB-induced erythema and its resolution in fair-skinned subjects.

METHODS

UVB-induced erythema was quantified using a Chroma Meter® in 50 volunteers 48 h before and 10 days after the random administration of 200,000 IU vitamin D (n = 40) or placebo (n = 10). Resolution of erythema in both groups was assessed by chromametry 24, 48, and 72 h after vitamin D administration.

RESULTS

No statistical difference between erythema values before and after administration in the vitamin D-supplemented group (p = 0.44) or the placebo group (p = 0.34) was noted. No statistical difference was evident between both groups with respect to resolution of erythema (p = 0.30).

CONCLUSION

Oral vitamin D supplementation neither improves protection against UVB-induced erythema nor facilitates its resolution.

Photochemistry. Chemiexcitation of melanin derivatives induces DNA photoproducts long after UV exposure

Mutations in sunlight-induced melanoma arise from cyclobutane pyrimidine dimers (CPDs), DNA photoproducts that are typically created picoseconds after an ultraviolet (UV) photon is absorbed at thymine or cytosine. We found that in melanocytes, CPDs are generated for >3 hours after exposure to UVA, a major component of the radiation in sunlight and in tanning beds. These "dark CPDs" constitute the majority of CPDs and include the cytosine-containing CPDs that initiate UV-signature C→T mutations. Dark CPDs arise when UV-induced reactive oxygen and nitrogen species combine to excite an electron in fragments of the pigment melanin. This creates a quantum triplet state that has the energy of a UV photon but induces CPDs by energy transfer to DNA in a radiation-independent manner. Melanin may thus be carcinogenic as well as protective against cancer. These findings also validate the long-standing suggestion that chemically generated excited electronic states are relevant to mammalian biology.

The consequences for human health of stratospheric ozone depletion in association with other environmental factors

Ozone depletion, climate and human health.

The diffuse component of erythemal ultraviolet radiation

The diffuse (Dif) component of ultraviolet radiation (UVR) plays an important role in the daily exposure of humans to solar radiation.

An unexpected role: UVA-induced release of nitric oxide from skin may have unexpected health benefits

UVR has deleterious and beneficial effects on human health. In this issue, Liu et al. (2014) show that UVA decreases blood pressure and increases blood flow and heart rate in humans, which is beneficial to the cardiovascular system. This is likely mediated by UVA causing release of nitric oxide (NO) from skin stores. This mediator may have additional effects on human health.

The impact of vitamin D in breast cancer: genomics, pathways, metabolism

Nuclear receptors exert profound effects on mammary gland physiology and have complex roles in the etiology of breast cancer. In addition to receptors for classic steroid hormones such as estrogen and progesterone, the nuclear vitamin D receptor (VDR) interacts with its ligand 1α,25(OH)₂D₃ to modulate the normal mammary epithelial cell genome and subsequent phenotype. Observational studies suggest that vitamin D deficiency is common in breast cancer patients and that low vitamin D status enhances the risk for disease development or progression. Genomic profiling has characterized many 1α,25(OH)₂D₃ responsive targets in normal mammary cells and in breast cancers, providing insight into the molecular actions of 1α,25(OH)₂D₃ and the VDR in regulation of cell cycle, apoptosis, and differentiation. New areas of emphasis include regulation of tumor metabolism and innate immune responses. However, the role of VDR in individual cell types (i.e., epithelial, adipose, fibroblast, endothelial, immune) of normal and tumor tissues remains to be clarified. Furthermore, the mechanisms by which VDR integrates signaling between diverse cell types and controls soluble signals and paracrine pathways in the tissue/tumor microenvironment remain to be defined. Model systems of carcinogenesis have provided evidence that both VDR expression and 1α,25(OH)₂D₃ actions change with transformation but clinical data regarding vitamin D responsiveness of established tumors is limited and inconclusive. Because breast cancer is heterogeneous, analysis of VDR actions in specific molecular subtypes of the disease may help to clarify the conflicting data. The expanded use of genomic, proteomic and metabolomic approaches on a diverse array of in vitro and in vivo model systems is clearly warranted to comprehensively understand the network of vitamin D regulated pathways in the context of breast cancer.

Role of Vitamin D Metabolism and Activity on Carcinogenesis

The vitamin D endocrine system regulates a broad variety of independent biological processes, and its deficiency is associated with rickets, bone diseases, diabetes, cardiovascular diseases, and tuberculosis. Cellular and molecular studies have also shown that it is implicated in the suppression of cancer cell invasion, angiogenesis, and metastasis. Sunlight exposure and consequent increased circulating levels of vitamin D are associated with reduced occurrence and a reduced mortality in different histological types of cancer, including those resident in the skin, prostate, breast, colon, ovary, kidney, and bladder. The vitamin D receptor (VDR) as a steroid hormone superfamily of nuclear receptors is highly expressed in epithelial cells at risk for carcinogenesis, providing a direct molecular link by which vitamin D status impacts on carcinogenesis. Because VDR expression is retained in many human tumors, vitamin D status may be an important modulator of cancer progression in persons living with cancer. The aim of this review is to highlight the relationship between vitamin D, VDR, and cancer, summarizing several mechanisms proposed to explain the potential protective effect of vitamin D against the development and progression of cancer.

Fisetin attenuates hydrogen peroxide-induced cell damage by scavenging reactive oxygen species and activating protective functions of cellular glutathione system

Hydrogen peroxide (H2O2) can induce cell damage by generating reactive oxygen species (ROS), resulting in DNA damage and cell death. The aim of this study is to elucidate the protective effects of fisetin (3,7,3',4',-tetrahydroxy flavone) against H2O2-induced cell damage. Fisetin reduced the level of superoxide anion, hydroxyl radical in cell free system, and intracellular ROS generated by H2O2. Moreover, fisetin protected against H2O2-induced membrane lipid peroxidation, cellular DNA damage, and protein carbonylation, which are the primary cellular outcomes of H2O2 treatment. Furthermore, fisetin increased the level of reduced glutathione (GSH) and expression of glutamate-cysteine ligase catalytic subunit, which is decreased by H2O2. Conversely, a GSH inhibitor abolished the cytoprotective effect of fisetin against H2O2-induced cells damage. Taken together, our results suggest that fisetin protects against H2O2-induced cell damage by inhibiting ROS generation, thereby maintaining the protective role of the cellular GSH system.

Vitamin D and death by sunshine

Exposure to sunlight is the major cause of skin cancer. Ultraviolet radiation (UV) from the sun causes damage to DNA by direct absorption and can cause skin cell death. UV also causes production of reactive oxygen species that may interact with DNA to indirectly cause oxidative DNA damage. UV increases accumulation of p53 in skin cells, which upregulates repair genes but promotes death of irreparably damaged cells. A benefit of sunlight is vitamin D, which is formed following exposure of 7-dehydrocholesterol in skin cells to UV. The relatively inert vitamin D is metabolized to various biologically active compounds, including 1,25-dihydroxyvitamin D3. Therapeutic use of vitamin D compounds has proven beneficial in several cancer types, but more recently these compounds have been shown to prevent UV-induced cell death and DNA damage in human skin cells. Here, we discuss the effects of vitamin D compounds in skin cells that have been exposed to UV. Specifically, we examine the various signaling pathways involved in the vitamin D-induced protection of skin cells from UV.

Novel vitamin D compounds and skin cancer prevention

As skin cancer is one of the most costly health issues in many countries, particularly in Australia, the possibility that vitamin D compounds might contribute to prevention of this disease is becoming increasingly more attractive to researchers and health communities. In this article, important epidemiologic, mechanistic and experimental data supporting the chemopreventive potential of several vitamin D-related compounds are explored. Evidence of photoprotection by the active hormone, 1α,25dihydroxyvitamin D3, as well as a derivative of an over-irradiation product, lumisterol, a fluorinated analog and bufalin, a potential vitamin D-like compound, are provided. The aim of this article is to understand how vitamin D compounds contribute to UV adaptation and potentially, skin cancer prevention.