Protecting human skin from sun exposure is a complex issue that involves unclear aspects of the interaction between light and tissue. A persistent misconception is that visible light is safe for the ...skin, although several lines of evidence suggest otherwise. Here, we show that visible light can damage melanocytes through melanin photosensitization and singlet oxygen (1O2) generation, thus decreasing cell viability, increasing membrane permeability, and causing both DNA photo-oxidation and necro-apoptotic cell death. UVA (355 nm) and visible (532 nm) light photosensitize 1O2 with similar yields, and pheomelanin is more efficient than eumelanin at generating 1O2 and resisting photobleaching. Although melanin can protect against the cellular damage induced by UVB, exposure to visible light leads to pre-mutagenic DNA lesions (i.e., Fpg- and Endo III-sensitive modifications); these DNA lesions may be mutagenic and may cause photoaging, as well as other health problems, such as skin cancer.
Skin cells present many endogenous photosensitizers (ePS) that interact with light, generating oxidizing species, causing molecular damage in proteins, lipids, and nucleic acids, and consequently ...triggering cellular and organelle malfunction. Several cell lines with terminal differentiation are susceptible to accumulating non-digestible pigments, such as lipofuscin or melanin-lipofuscin. Besides being hallmarks of aging, both pigments can work as photosensitizers, increasing and expanding the toxicity of sunlight to the range of visible light (VL, 400–700 nm). In here we review the literature to describe the mechanisms by which the photosensitized oxidation reactions induced by VL cause DNA damage. We aim to provide the mechanistic background needed to improve the current strategies of photoprotection.
Alzheimer's disease (AD) is the most common type of dementia in the elderly. Several hypotheses emerged from AD pathophysiological mechanisms. However, no neuronal protective or regenerative drug is ...available nowadays. Researchers still work in drug development and are finding new molecular targets to treat AD. Therefore, this study aimed to summarize main advances in AD pharmacological therapy. Clinical trials registered in the National Library of Medicine database were selected and analyzed accordingly to molecular targets, therapeutic effects, and safety profile. The most common outcome was the lack of efficacy. Only seven trials concluded that tested drugs were safe and induced any kind of therapeutic improvement. Three works showed therapeutic effects followed by toxicity. In addition to aducanumab recent FDA approval, antibodies against amyloid-β (Aβ) showed no noteworthy results. 5-HT6 antagonists, tau inhibitors and nicotinic agonists' data were discouraging. However, anti-Aβ vaccine, BACE inhibitor and anti-neuroinflammation drugs showed promising results.
This study aimed to evaluate red and amber light-emitting diode protocols for facial rejuvenation at the same light dose.
The demand for minimally invasive cosmetic procedures to address skin aging ...has grown throughout the world.
red and amber photobiomodulation (PBM) has been shown to improve collagen synthesis. Meanwhile, red PBM has already been studied in clinical trials; however, a comparison of the use of different wavelengths at the same light dose to reduce periocular wrinkles has not yet been performed.
This split-face, randomized clinical trial recruited 137 women (40-65 years old) presenting with skin phototypes II-IV and Glogau photoaging scale types II-IV. The individuals received 10 sessions for 4 weeks of red (660 nm) and amber (590 nm) PBM (3.8 J/cm
), one at each side of the face. The outcomes, measured before and after the treatments, were the periocular wrinkle volume measured by VisioFace
RD equipment; hydration measured by the Corneometer CM 825; skin elasticity measured by the Cutometer Dual MPA 580; and quality of life determined by adapted versions of validated questionnaires Melasma Quality of Life Scale-Brazilian Portuguese (MelasQoL-BP) and Skindex-29.
There was a significant reduction in wrinkle volume after red (31.6%) and amber (29.9%) PBM. None of the treatments improved skin hydration and viscoelasticity. Both questionnaires showed improvements in participants' quality of life.
PBM, both at red and amber wavelengths, is an effective tool for rejuvenation, producing a 30% wrinkle volume reduction. The technique has strong potential in patients with diabetes or those presenting with keloids, conditions for which highly inflammatory rejuvenating procedures are not indicated. Clinical trial registration number: REBEC-6YFCBM.
Photoexcitation of endogenous photosensitizers (ePS) in the human skin by sunlight culminates with the formation of electronic excited states, such as triplet excited states, singlet oxygen, and a ...variety of reactive oxygen and nitrogen species, either free radicals or two-electron oxidants. Considering the endogenous skin photosensitizers, melanin is the most abundant and is involved in photoprotection mechanisms, while lipofuscin is an unintentionally pigment accumulated during cell aging or oxidative stress. Both pigments severely increase the phototoxicity of visible light (VL) to skin cells. In the presence of these pigments, VL induces significant oxidative damage in nucleic acids, lipids and proteins, triggering regulated and unregulated cell death mechanisms. Besides, there is accumulation of premutagenic DNA lesions, indicated by the formamidopyrimidine glycosylase (Fpg)- and endonuclease III (Endo III)-sensitive sites in the nuclear DNA. As consequence of the photoinduced oxidative damage, skin cells, under the stimulus of VL release pro-inflammatory cytokines and metalloproteinases, prompting further cell death and skin aging. In this review we describe the photochemical properties of both melanin and lipofuscin pigments and discuss the consequences of their accumulation in terms of the phototoxicity of VL to the human skin.
Stress is an important factor in the development of several human pathologies. The response of rodents and humans to stress depends on many factors; some people and rodents develop stress-related ...mood disorders, such as depression and anxiety in humans, depression-like and anxiety-like behavior in mice and rats, while others report no new psychological symptoms in response to chronic or acute stress, and are considered susceptible and resilient to stress, respectively. Resilience is defined as the ability to thrive in the face of adversity and is a learned process that can help protect against occupational stressors and mental illnesses. There is growing interest in the underlying mechanisms involved in resilience and vulnerability to depression caused by stress, and some studies have demonstrated that individual variability in the way animals and humans respond to stress depends on several mechanisms, such as oxidative stress, neuronal plasticity, immunology and genetic factors, among others not discussed in this review, this review provides a general overview about this mechanism.
Alzheimer's disease (AD) is the leading cause of dementia in older adults, having a significant global burden and increasing prevalence. Current treatments for AD only provide symptomatic relief and ...do not cure the disease. Physical activity has been extensively studied as a potential preventive measure against cognitive decline and AD. Recent research has identified a hormone called irisin, which is produced during exercise, that has shown promising effects on cognitive function. Irisin acts on the brain by promoting neuroprotection by enhancing the growth and survival of neurons. It also plays a role in metabolism, energy regulation, and glucose homeostasis. Furthermore, irisin has been found to modulate autophagy, which is a cellular process involved in the clearance of protein aggregates, which are a hallmark of AD. Additionally, irisin has been shown to protect against cell death, apoptosis, oxidative stress, and neuroinflammation, all of which are implicated in AD pathogenesis. However, further research is needed to fully understand the mechanisms and therapeutic potential of irisin in AD. Despite the current gaps in knowledge, irisin holds promise as a potential therapeutic target for slowing cognitive decline and improving quality of life in AD patients.
We have studied the spectroscopic properties of hair (white, blond, red, brown, and black) under illumination with visible light, giving special emphasis to the photoinduced generation of singlet ...oxygen (
1O
2). Irradiation of hair shafts (λ
ex
>
400
nm) changed their properties by degrading the melanin. Formation of C3 hydroperoxides in the melanin indol groups was proven by
1H NMR. After 532-nm excitation, all hair shafts presented the characteristic
1O
2 emission (λ
em
=
1270
nm), whose intensity varied inversely with the melanin content.
1O
2 lifetime was also shown to vary with hair type, being five times shorter in black hair than in blond hair, indicating the role of melanin as a
1O
2 suppressor. Lifetime ranged from tenths of a nanosecond to a few microseconds, which is much shorter than the lifetime expected for
1O
2 in the solvents in which the hair shafts were suspended, indicating that
1O
2 is generated and suppressed inside the hair structure. Both eumelanin and pheomelanin were shown to produce and to suppress
1O
2, with similar efficiencies. The higher amount of
1O
2 generated in blond hair and its longer lifetime is compatible with the stronger damage that light exposure causes in blond hair. We propose a model to explain the formation and suppression of
1O
2 in hair by photosensitization of melanin with visible light and the deleterious effects that an excess of visible light may cause in hair and skin.
Mixed-Cell Type Choroidal Melanoma in a Middle-Aged Woman Frinhani, Mirelly Aparecida Nolasco; Pestana, Rebeca Alves; Dantas, Giuliane Stefane Braga ...
Revista Brasileira de Cancerologia,
05/2023, Volume:
69, Issue:
2
Journal Article
Peer reviewed
Open access
Introduction: Melanomas are malignant neoplasms that occur in various anatomical sites, including the eye. Ocular melanomas account for 5% of all melanomas and are mainly described in Caucasian and ...older individuals. This study describes the clinical and pathological characteristics of uveal (choroid) melanoma in a Caucasian patient. Case report: A 41-year-old Caucasian female patient, brown eyes, without history of ophthalmological diseases or family history of cancer experienced pain and loss of visual acuity in the left eye. On clinical examination, an increase of ocular pressure was detected. Ultrasound showed a mushroom-like neoformation. Moreover, magnetic resonance imaging showed a mass with spontaneous hypersignal on T1-weighted images, intense gadolinium enhancement, and marked hyposignal on T2-weighted images. The patient was referred to the Oncology Ophthalmology department for enucleation due to suspected uveal melanoma. Anatomopathological analysis revealed a blackened mass in the eyeball. Histologically, the mass comprised spindle cells (50%) and epithelioid cells (50%). A diagnosis of choroidal melanoma was established based on the identification of ophthalmoscopic, imaging, and histological characteristics of the tumor. Conclusion: Choroidal melanomas usually occur in males, clear-eyed, and older individuals. A wide variety of ocular lesions may mimic choroidal melanoma, which should be included in the differential diagnosis of choroidal nevus and peripheral hemorrhages.
Upon excitation by visible light (VL), melanin engages in photosensitization reactions, generating singlet oxygen (1O2) and causing oxidative damage to biomolecules via both type I and type II ...mechanisms. Therefore, VL irradiation may be used to perturb the survival and growth of pigmented melanoma lesions. However, this hypothesis has not been investigated previously, and there is no information regarding the effectiveness of this wavelength of light on melanomas. Therefore, this hypothesis needs to be tested in vivo, as VL has also been shown to stimulate tumor growth via photo biomodulation. This study aimed to determine the effect of melanin photosensitization following exposure to VL in cultured B16-F10 cells and melanoma lesions induced in mice. Cell viability was evaluated by the MTT assay after irradiation with blue, green, and red lights (466 nm, 532 nm, and 630 nm, respectively). Singlet oxygen (1O2) was investigated in melanin extracted from M+B16-F10 cells. Melanin-loaded M+B16-F10 cells showed a significant reduction in viability (∼30%) and 1O2 generation only after irradiation with 532 nm light. Mice were divided into groups with carcinogenesis induction (C+) or without induction (control, C-), irradiated (I+) with green light (GL 36 J.cm−2) at 7-day intervals or without irradiation (I-). The average tumor size (TAS) and pigmentation were quantified using a caliper and ImageJ software, respectively. After seven weeks, skin samples were collected from all groups for histopathological analysis. Statistical analysis was performed using Origin 2021 and GraphPad Prism 9®. The C-/I+ group showed initial pigmentation but no histological changes following irradiation. C+/I- showed tumor progression up to three times the initial volume, whereas the C+/I+ group presented a significant ∼20% decrease in TAS. These results suggest that photosensitization of melanin by GL (532 nm) reduces the viability of M+B16-F10 cells, decreases TAS, and prevents the growth of melanoma in C57BL6 mice.
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