Melatonin as a possible antidote to UV radiation induced cutaneous damages and immune-suppression: An overview

Melatonin hyalurosomes as a powerful antioxidant for combating skin damage induced by UV radiation

Extrinsic skin aging is caused by chronic skin photodamage. The present study aims to inspect the role of nanoencapsulation of melatonin (MEL) in hyalurosomes in combating UVB-induced skin damage to take advantage of the hydrating penetration enhancing and antiaging effects of hyaluronic acid along with the powerful antioxidant effects of MEL. Measurement of particle size, zeta potential, encapsulation efficiency and in vitro MEL release were carried out. The in vivo photoprotective effects of MEL were tested in rats. A histopathological examination was conducted, and antioxidant and anti-inflammatory markers were measured along with estimating the expression of P38 MAPK, P-ERK and P-JNK. Particle size and zeta potential of MEL hyalurosomes were 285.9 nm and -26.3 mV with 95% entrapment efficiency and provided a sustained release profile for 48h. In vivo, results revealed the superior effect of MEL hyalurosomes in protecting skin against UVB-induced damage and reducing the levels of inflammatory mediators like TNF-α and IL6 compared with MEL suspension. However, they had a prominent role in increasing the levels of antioxidants. These findings may be accredited to the effect of nanoencapsulation in enhancing skin penetration and deposition of MEL besides the effect of hyaluronic acid as a powerful antiaging tool.

The influence of phototherapy on circadian melatonin and sleep regulation and potential benefits of these pathways in the management of vitiligo: a narrative review : Vitiligo, phototherapy, sleep and melatonin

Ultraviolet B narrow band (UVB-NB) phototherapy is the gold standard treatment for vitiligo, primarily due to its immunomodulatory effects. Additionally, it may influence circadian melatonin balance, that may indirectly induce sleep regulation, which in turn could potentially contribute to vitiligo improvement. The association between melatonin, vitiligo and phototherapy has been little investigated. The aim of this study was to evaluate the current evidence regarding the effects of circadian melatonin regulation and sleep, particularly during vitiligo treatment with phototherapy. We undertook a narrative review to synthetize the evidence on this association through the MEDLINE/PubMed database, using combined search terms: melatonin, vitiligo, phototherapy, and circadian rhythm (sleep). A total of 56 articles were included. There are few studies on this relationship, and conflicting findings. Some studies have suggested that UV exposure and phototherapy might benefit vitiligo by stimulating melanocytes, which have melatonin receptors, and this could potentially synchronize the circadian regulation of melatonin. This improved melatonin balance could result in better sleep quality further enhancing the antiinflammatory properties of melatonin and contributing to vitiligo improvement. Less is known about the possible effects of the use of topical melatonin, with or without phototherapy, to treat vitiligo lesions. In conclusion, there is some evidence that circadian melatonin regulation plays an important role in the course of vitiligo, both through sleep regulation and its anti-inflammatory properties. The evidence suggests that the systemic and physiological properties of melatonin, especially its circadian behavior regulated by phototherapy, may be more effective in respect of vitiligo improvement than the use of topical melatonin. However, the effects of the oral intake of melatonin are less clear. Phototherapy, as a potential modulator of circadian melatonin rhythm, that influences sleep and clinical improvement of vitiligo, needs further examination, as does the use of melatonin as an adjuvant treatment to UVB phototherapy in vitiligo.

Melatonin hyalurosomes in collagen thermosensitive gel as a potential repurposing approach for rheumatoid arthritis management via the intra-articular route

Despite the fact that several rheumatoid arthritis treatments have been utilized, none of them achieved complete joint healing and has been accompanied by several side effects that compromise patient compliance. This study aims to provide an effective safe RA treatment with minimum side effects through the encapsulation of melatonin (MEL) in hyalurosomes and loading these hyalurosomes in collagen thermos-sensitive poloxamer 407 (PCO) hydrogels, followed by their intra-articular administration in AIA model rats. In vitro characterization of MEL-hyalurosomes and PCO hydrogel along with in vivo evaluation of the selected formulation were conducted. Particle size, PDI and EE % of the selected formulation were 71.5 nm, 0.09 and 90 %. TEM micrographs demonstrated that the particles had spherical shape with no aggregation signs. Loading PCO hydrogels with MEL-hyalurosomes did not cause significant changes in pH although it increased its viscosity and injection time. FTIR analysis showed that no interactions were noted among the delivery system components. In vivo results revealed the superior effect of MEL-hyalurosomes PCO hydrogel over MEL-PCO hydrogel and blank PCO hydrogels in improving joint healing, cartilage repair, pannus formation and cell infiltrations. Also, MEL-hyalurosomes PCO hydrogel group showed comparable levels of TNF-α, IL1, MDA, NRF2 and HO-1 with the negative control group. These findings highlight the MEL encapsulation role in augmenting its pharmacological effects along with the synergistic effect of hyaluronic acid in hyalurosomes and collagen in PCO hydrogel in promoting joint healing.

Melatonin as a Repurposed Drug for Melanoma Treatment

Melanoma is the most aggressive type of skin cancer, with a greater risk of metastasis and a higher prevalence and mortality rate. This cancer type has been demonstrated to develop resistance to the known treatment options such as conventional therapeutic agents and targeted therapy that are currently being used as the standard of care. Drug repurposing has been explored as a potential alternative treatment strategy against disease pathophysiologies, including melanoma. To that end, multiple studies have suggested that melatonin produced by the pineal gland possesses anti-proliferative and oncostatic effects in experimental melanoma models. The anticarcinogenic activity of melatonin is attributed to its ability to target a variety of oncogenic signaling pathways, including the MAPK pathways which are involved in regulating the behavior of cancer cells, including cell survival and proliferation. Additionally, preclinical studies have demonstrated that melatonin in combination with chemotherapeutic agents exerts synergistic effects against melanoma. The goal of this review is to highlight the mechanistic insights of melatonin as a monotherapy or combinational therapy for melanoma treatment.

Hunting down NLRP3 inflammasome: An executioner of radiation-induced injury

Radiotherapy is one of the mainstream treatment modalities for several malignancies. However, radiation-induced injury to surrounding normal tissues limits its efficacy. The NLRP3 inflammasome is an essential mechanism of innate immunity that reacts to challenges from endogenous danger signals and pathological microbes. A growing body of evidence has demonstrated a key role of NLRP3 inflammasome in the pathogenesis of radiation-induced tissue injury. Despite accumulating evidence, the potential value of the NLRP3 inflammasome in the management of radiation-induced tissue injury is not adequately recognized. We conducted a literature review to characterize the relationship between NLRP3 inflammasome and radiation injury. By analyzing recent evidence, we identify NLRP3 inflammasome as one of the executioners of radiation-induced injury, since it responds to the challenges of radiation, induces cell pyroptosis and tissue dysfunction, and initiates non-resolving inflammation and fibrosis. Based on these concepts, we propose early intervention/prevention strategies targeting NLRP3 inflammasome in a radiation context, which may help resolve imperative clinical problems.

Solar and geomagnetic activity reduces pulmonary function and enhances particulate pollution effects

BACKGROUND

Increased solar and geomagnetic activity (SGA) may alter sympathetic nervous system activity, reduce antioxidant activity, and modulate physiochemical processes that contribute to atmospheric aerosols, all which may reduce pulmonary function.

OBJECTIVES

Investigate associations between forced expiratory volume at 1 s (FEV1) and forced vital capacity (FVC) with SGA, and assess whether SGA enhances adverse effects of particulate pollution, black carbon (BC) and particulate matter ≤2.5 μm in diameter (PM2.5).

METHODS

We conducted a repeated measures analysis in 726 Normative Aging Study participants (Boston, Massachusetts, USA) between 2000 and 2017, using interplanetary magnetic field (IMF), planetary K index (Kp), and sunspot number (SSN) as SGA measures. Linear mixed effects models were used to assess exposure moving averages up to 28 days for both SGA and pollution.

RESULTS

Increases in IMF, Kp Index and SSN from the day of the pulmonary function test averaged through day 28 of were associated with a significant decrement in FEV1 and FVC, after adjusting for potential confounders. There were greater effects for longer moving averages and enhanced effects of PM2.5 and BC on FEV1 and FVC with increased SGA. For example, for each inter-quartile increase (4.55 μg/m3) in average PM2.5 28 days before testing, low IMF (10th percentile: 3.2 nT) was associated with a -21.4 ml (95 % CI: -60.8, 18.1) and -7.1 ml (95 % CI: -37.7, 23·4) decrease in FVC and FEV1, respectively; high IMF (90th percentile: 9.0 nT) was associated with a -120.7 ml (95 % CI:-166.5, -74.9) and -78.6 ml (95 % CI: -114.3, -42·8) decrease in FVC and FEV1, respectively.

DISCUSSION

Increased periods of solar and geomagnetic activity may directly contribute to impaired pulmonary function and also enhance effects of PM2.5 and BC. Since exposure to solar activity is ubiquitous, stricter measures in reducing air pollution exposures are warranted, particularly in elderly populations.

Melatonin photoreactivity: phosphorescence formation and quenching processes

Studies of melatonin photoreactivity in water solutions: An effect of an external heavy atom I− on UV/Vis absorption, fluorescence and phosphorescence spectra is explored. The data allowed determination of relevant energetics for the system.The heavy atom effect (HAE) of I− on melatonin is clearly found to induce an intersystem crossing from the lowest energy singlet state to the lowest energy triplet state (T1) by a state mixing. Lifetime for the first excited triplet states of melatonin in association with I− and quenching rates for halomethanes (CH2X2, CHX3, CY4, X = Cl, Br, Y = Cl) are determined from Time-Correlated Single-Photon Counting decay curves for the phosphorescence. Dramatic alterations in quenching rate constants with quenchers as CH2X2 < CHX3 < CX4 and Cl < Br are attributed to energy transfer from an I−…Me*(T1) complex to low-lying electronic states of the halomethanes followed by dissociation to form R and X fragments. Relevance of the melatonin photoreactivity to photosensitizer properties in organic media is discussed.

Graphical abstract

Melatonin as an antioxidant agent in disease prevention: A biochemical focus

Abstract:

In the recent years, free radicals and oxidative stress have been found to be associated with aging, cancer, atherosclerosis, neurodegenerative disorders, diabetes, and inflammatory diseases. Confirming the role of oxidants in numerous pathological situations including cancer, developing antioxidants as therapeutic platforms is needed. It has been well established that melatonin and its derived metabolites function as endogenous free-radical scavengers and broad spectrum antioxidants. To achieve this function, melatonin can directly detoxify reactive oxygen and reactive nitrogen species and indirectly overexpress antioxidant enzymes while suppressing the activity of pro-oxidant enzymes. Many investigations have also confirmed the role of melatonin and its derivatives in different physiological processes and therapeutic functions such as controlling the circadian rhythm and immune functions. This review aimed to focus on melatonin as a beneficial agent for the stimulation of antioxidant enzymes and inhibition of lipid peroxidation and to evaluate its contribution to protection against oxidative damages. In addition, the clinical application of melatonin in several diseases is discussed. Finally, the safety and efficacy of melatonin in clinical backgrounds is also reviewed.

Metabolism and Functions of Amino Acids in the Skin

Amino acids are the building blocks of all proteins, including the most abundant fibrous proteins in the skin, as keratins, collagen and elastin. Sagging and wrinkled skin are features of chronic sun-damaged and aged uncared skin, and they are mainly associated with the deterioration of collagen and elastic fibers. The maintenance of skin structures by self-repair processes is essential to skin health. Thus, amino acids significantly impact the appearance of the skin. Amino acids are important nutrients required for (a) wound healing promotion and repair of the damaged skin; (b) acid-base balance and water retention in cellular layers, such as stratum corneum; (c) protection against sunlight damage; (d) maintenance of an appropriate skin microbiome. This review highlights the contribution of all proteinogenic amino acids and some related metabolites to the skin structures as constituents of the main cutaneous proteins or as signaling molecules for the regulation and determination of skin physiology.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Protective effect of a topical sunscreen formulation fortified with melatonin against UV-induced photodermatitis: an immunomodulatory effect via NF-κB suppression

Objective: Melatonin and pumpkin seed oil, along with US FDA approved UV filters were incorporated into a formulation for enhancement of UV protection by exerting an antioxidant effect. The objective of this study was to assess the protective effect of this formulation against ultraviolet (UV) radiation-induced photo dermatitis in rats, which is an established model to study the aetiopathogenic mechanisms in psoriasis vulgaris, as the former exhibits the same features to those of clinical psoriasis vulgaris in humans. Materials and methods: The animals were segregated into five groups (6/group) and all received their respective formulations dermally prior to chronic UV irradiation for 28 days. The test, placebo, and standard groups; received the test, placebo, and standard formulations respectively; whereas the positive control group received only UV radiation. A normal control group was also maintained. Disease and treatment status were analyzed using various techniques by euthanizing the rats after 28 days. Results: The test formulation was able to ameliorate the UV-induced increase in skin fold, epidermal thickness, and skin edema; inhibit the reduction of hydroxyproline content and incidence of LPO within the skin tissues of exposed animals. The formulation was also able to inhibit the release of proinflammatory cytokines; IFN-γ, IL-1β, IL-6, and TNF-α; and upregulation of NF-κB and COX-2 genes caused by chronic UV exposure. Conclusion: It can be stated that melatonin included in the newly formulated sunscreen was able to inhibit the induction of photodermatitis via immunoregulation of inflammatory cytokines along with NF-κB and COX-2 genes.

Potential use of melatonin in skin cancer treatment: A review of current biological evidence

Skin cancer, particularly melanoma, is a leading cause of death worldwide. The therapeutic methods for this malignancy are not effective, and due to the side effects of these treatments, applying an appropriate alternative or complementary treatment is important. According to available data, melatonin as the main product of the pineal gland has oncostatic and antitumoral properties. Also, melatonin acts as an anti-inflammatory and reactive oxygen species inducer agent which suppresses the growth of tumors. It also has apoptosis induction characteristics through regulating signaling pathways, including heat shock protein 70, nuclear factor-erythroid 2 p45-related factor 2 and others. Thus, adding melatonin to chemo- and radiotherapy may have synergistic therapeutic effects and increase the survival time in patients with skin cancer. Few clinical studies have evaluated the efficacy of melatonin in skin cancer. Based on the related mechanisms, this review discusses about how melatonin may improve outcomes in skin cancer patients.

Amelioration of UV radiation-induced photoaging by a combinational sunscreen formulation via aversion of oxidative collagen degradation and promotion of TGF-β-Smad-mediated collagen production

The presence of 40-50% more UV radiation in high altitude areas renders the plethora of sunscreen products available in the market virtually ineffective. In this light of event, four US FDA approved UV filters were combined with melatonin and pumpkin seed oil to produce a broad spectrum sunscreen cream, which is envisaged to provide optimum sunprotection along with enhanced antioxidant activity. The objective of this study is to evaluate the protective effect of the sunscreen cream against UV radiation-induced skin photoaging in adult Wistar albino rats and identify its possible underlying mechanism. Wistar rats were exposed to broad spectrum UV radiation for 28 days. The test group received the sunscreen formulation dermally every day prior to UV radiation. The effects of the formulation against UV induced symptoms; viz. skin thickness and edema, in vivo antioxidant activities, inflammatory cytokines, collagen content, histopathological examination and expression of specific genes established the protective activity of the formulation. The test formulation was able to mitigate the harmful effects of UV radiation by increasing in vivo SOD, GSH-Px, CAT and collagen levels; decreasing skin edema, skin thickness and cytokines like IL-6, IL-1β, TNF-α and TGF-β1. UV radiation induced changes in histological architecture and arrangement of collagen and elastin fibers were also prevented by the test formulation. Finally, the formulation was able to regulate the expression of COL3A1, COX-2, bFGF, VEGF-C, Smad2, Smad4, Smad7 genes which induced significant photoprotective activity. The sunscreen formulation ameliorated UV induced photoaging by preventing oxidative collagen degradation and augmentation of TGF-β-Smad-mediated collagen production.

Melatonin in Edible and Non-Edible Plants

The concept of melatonin has become more important recently both in plants and in human who utilize plants for nutritional and health purposes. Melatonin, synthesized from L-tryptophan by enzyms, protects plants against difficult conditions. People have consumed these plants for their antioxidant, immunomodulator, antiinflammatory and anticancer effects. In parts of edible and non-edible plants, levels of melatonin are determined by cyclodextrin-modified micellar electrokinetic chromatography, enzyme-linked immuno sorbent assay, radioimmunoassay, high-performance liquid chromatography, liquid chromatography with electrochemical detection, liquid chromatography with fluorimetric detection, liquid chromatography-mass spectrometry, and liquid chromatography-ultraviolet spectrophotometry. In this review, biosynthesis of melatonin in both animal and plants, function of melatonin in plant kingdom, especially in medicinal/edible and nonedible plants, and detection of phytomelatonin content in those plants are presented.

Air pollution, UV irradiation and skin carcinogenesis: what we know, where we stand and what is likely to happen in the future?

The link between air pollution, UV irradiation and skin carcinogenesis has been demonstrated within a large number of epidemiological studies. Many have shown the detrimental effect that UV irradiation can have on human health as well as the long-term damage which can result from air pollution, the European ESCAPE project being a notable example. In total, at present around 2800 different chemical substances are systematically released into the air. This paper looks at the hazardous impact of air pollution and UV and discusses: 1) what we know; 2) where we stand; and 3) what is likely to happen in the future. Thereafter, we will argue that there is still insufficient evidence of how great direct air pollution and UV irradiation are as factors in the development of skin carcinogenesis. However, future prospects of progress are bright due to a number of encouraging diagnostic and preventive projects in progress at the moment.

Prevention of ultraviolet radiation‑induced immunosuppression by sunscreen in Candida albicans‑induced delayed‑type hypersensitivity

Ultraviolet (UV) radiation-induced immunosuppression leading to skin cancer has received increased attention in previous years. The present study aimed to investigate the immunoprotection offered by Anthelios sunscreen in a mouse model of Candida albicans-induced delayed-type hypersensitivity. Anthelios sunscreen was applied to the skin on the dorsal skin of BALB/c mice treated with a sub-erythema dose of solar-simulated radiation. Delayed-type hypersensitivity was induced by immunization with Candida albicans. Changes in the skin thickness of the foot pads were measured, and immunosuppression rates were also evaluated. The expression levels of CD207, CD80 and CD86 in the Langerhans cells were semi-quantitatively detected using Western blotting and immunohistochemical assays. The delayed-type hypersensitivity mouse model was successfully established. The minimal erythema doses of UVA and UVB exposure to the mice were 2,000 and 145 mJ/cm², respectively. The immunosuppression rates in the sunscreen group and non-sunscreen group were 24.39 and 65.85%, respectively (P<0.01). The results of the Western blotting and immunohistochemistry showed that the expression levels of CD207 (P<0.01), CD80 (P<0.05) and CD86 (P<0.01) were higher in the sunscreen group, compared with those in the non-sunscreen group. UV exposure reduced Candida albicans antigen-induced delayed-type hypersensitivity. Anthelios sunscreen was found to protect the skin from immunosuppression through the activation of epidermal Langerhans cells.