Visible light. Part I: Properties and cutaneous effects of visible light

Impact of blue light on skin pigmentation in patients with melasma

BACKGROUND

The difference in skin pigmentation induced by blue light between melasma patients and healthy people has not been reported. This study aimed to explore the impact of different doses of blue light irradiation on the pigmentation of the skin of non-exposed areas in female melasma patients with III-IV-type skin and healthy women.

MATERIALS AND METHODS

This observational study enrolled patients with melasma and healthy people at the First Affiliated Hospital of Kunming Medical University between January and April 2021. The outcomes were the degree of pigmentation, ΔL*, and ΔITA* values.

RESULTS

Forty-two (21/group) participants were enrolled. After irradiation with different doses of blue light, different degrees of pigmentation could be observed in the irradiated area of the skin of female melasma patients and healthy women. The △L* and △ITA* values in the irradiated area of the skin of healthy women were higher than in female melasma patients after blue light irradiation at 20 J/cm2 (p < 0.05). There were no significant differences in the pigmentation scores, △L* values, and △ITA* values in the irradiated areas of skin at different time points after irradiation with the other doses of blue light (p > 0.05).

CONCLUSION

Blue light at 20 J/cm2 induced a smaller change in pigmentation in melasma patients than in healthy women, but the effect of blue light at 40-80 J/cm2 was similar.

The Beneficial Role of Photobiomodulation in Neurodegenerative Diseases

Photobiomodulation (PBM), also known as Low-level Laser Therapy (LLLT), involves the use of light from a laser or light-emitting diode (LED) in the treatment of various disorders and it has recently gained increasing interest. Progressive neuronal loss with attendant consequences such as cognitive and/or motor decline characterize neurodegenerative diseases. The available therapeutic drugs have only been able to provide symptomatic relief and may also present with some side effects, thus precluding their use in treatment. Recently, there has been an exponential increase in interest and attention in the use of PBM as a therapy in various neurodegenerative diseases in animal studies. Because of the financial and social burden of neurodegenerative diseases on the sufferers and the need for the discovery of potential therapeutic inventions in their management, it is pertinent to examine the beneficial effects of PBM and the various cellular mechanisms by which it modulates neural activity. Here, we highlight the various ways by which PBM may possess beneficial effects on neural activity and has been reported in various neurodegenerative conditions (Alzheimer's disease, Parkinson's disease, epilepsy, TBI, stroke) with the hope that it may serve as an alternative therapy in the management of neurodegenerative diseases because of the biological side effects associated with drugs currently used in the treatment of neurodegenerative diseases.

Effects of multiwavelength photobiomodulation for the treatment of traumatic soft tissue injuries associated with bone fractures: A double-blind, randomized controlled clinical trial

This study evaluated the efficacy and safety of multiwavelength photobiomodulation (MPBM) in healing soft tissue injuries associated with tibial and/or ankle fractures. Participants were randomized into the MPBM or control group. Primary outcome was wound healing, measured by the Bates-Jensen scale. Assessments were performed daily. Twenty-seven hospitalized adults were included. MPBM showed an improvement in the daily mean Bates-Jensen scale (MPBM 32.1 vs. control 34.2; p = 0.029), daily mean pain score change (MPBM 0.5 vs. control 0.2; p = 0.04) and occurrence of infection at the site of the external fixator pins (MPBM 15.3% vs. control 57.1%; p = 0.02). MPBM group also showed faster-wound resolution (MPBM 13.1 vs. control 23.1 days). Subgroup analysis showed improvement in the MPBM group among less severe patients on the Bates-Jensen scale (MPBM 27.4 vs. control 34.7; p = 0.0081) and mean time for wound resolution (MPBM 7.0 vs. control 14.6 days; p = 0.03). MPBM appears safe and effective in reducing wound resolution time, infection in the surgical pin sites, reported pain and time before definitive surgery.

Sun exposure, a relevant exposome factor in acne patients and how photoprotection can improve outcomes

BACKGROUND

Acne pathophysiology includes a complex interaction among inflammatory mediators, hyperseborrhea, alteration of keratinization and follicular colonization by Propionibacterium acnes.

AIMS

To describe the impact of the exposome on acne and how photoprotection can improve outcomes.

METHODS

A narrative review of the literature was carried out; searches with Google Scholar and Pubmed from January 1992 to November 2022 were performed. The keywords used were "acne," "sunscreens," "photoprotection," "cosmetics," "cosmeceuticals," "pathogenesis," "etiology," "exposome," "sunlight," "stress," "lack of sleep," "diet," "postinflammatory hyperpigmentation," "pollution," "exposome," "ultraviolet radiation," and "visible light."

RESULTS

Environmental factors such as solar radiation, air pollution, tobacco consumption, psychological stress, diverse microorganisms, nutrition, among others, can trigger or worsen acne. Solar radiation can temporarily improve lesions. However, it can induce proinflammatory and profibrotic responses, and produce post-inflammatory hyperpigmentation and/or post-inflammatory erythema. While photoprotection is widely recommended to acne patients, only four relevant studies were found. Sunscreens can significantly improve symptomatology or enhance treatment and can prevent post-inflammatory hyperpigmentation. Furthermore, they can provide camouflage and improve quality of life. Based on acne pathogenesis, optimal sunscreens should have emollient, antioxidant and sebum controlling properties.

CONCLUSIONS

The exposome and solar radiation can trigger or worsen acne. UV light can induce post-inflammatory hyperpigmentation/erythema, and can initiate flares. The use of specifically formulated sunscreens could enhance adherence to topical or systemic therapy, camouflage lesions (tinted sunscreens), decrease inflammation, and reduce the incidence of post-inflammatory hyperpigmentation/erythema.

Opsin 3 mediates UVA-induced keratinocyte supranuclear melanin cap formation

Solar ultraviolet (UV) radiation-induced DNA damage is a major risk factor for skin cancer development. UV-induced redistribution of melanin near keratinocyte nuclei leads to the formation of a supranuclear cap, which acts as a natural sunscreen and protects DNA by absorbing and scattering UV radiation. However, the mechanism underlying the intracellular movement of melanin in nuclear capping is poorly understood. In this study, we found that OPN3 is an important photoreceptor in human epidermal keratinocytes and is critical for UVA-mediated supranuclear cap formation. OPN3 mediates supranuclear cap formation via the calcium-dependent G protein-coupled receptor signaling pathway and ultimately upregulates Dync1i1 and DCTN1 expression in human epidermal keratinocytes via activating calcium/CaMKII, CREB, and Akt signal transduction. Together, these results clarify the role of OPN3 in regulating melanin cap formation in human epidermal keratinocytes, greatly expanding our understanding of the phototransduction mechanisms involved in physiological function in skin keratinocytes.

A Review of Applications and Intracellular Mechanisms of Intense Pulsed Light in Eyelid Inflammatory Diseases

Objective: To evaluate relevant clinical outcomes and conclude possible mechanisms of intense pulsed light (IPL) in eyelid inflammation. Background: IPL devices were primarily applied in cutaneous vascular malformations and have been used in ocular diseases for about 20 years, mostly including meibomian gland dysfunction (MGD), blepharitis, and ocular rosacea. Recent findings: Seventy-two original clinical researches were included, 57 for MGD, 4 for blepharitis or blepharitis-related keratoconjunctivitis, and 11 for rosacea. Dry eye symptoms, (tear) break-up time (BUT), and meibomian structure and/or functions were improved in most patients, but production of reactive oxygen species is an important link in the photobiomodulation mediated by IPL, which can influence numerous signal pathways to achieve anti-inflammatory, anti-infective, and prodifferentiation effects. Conclusions: The evidence suggests that IPL is an effective therapeutic tool for most patients with MGD, but more clinical evidence is needed for other indications.

Effects and Mechanism of the Leontopodium alpinum Callus Culture Extract on Blue Light Damage in Human Foreskin Fibroblasts

Leontopodium alpinum is an important source of raw material for food, medicine, and modern cosmetics. The purpose of this study was to develop a new application for protection against blue light damage. To investigate the effects and mechanism of action of Leontopodium alpinum callus culture extract (LACCE) on blue light damage, a blue-light-induced human foreskin fibroblast damage model was established. The contents of collagen (COL-I), matrix metalloproteinase 1 (MMP-1), and opsin 3 (OPN3) were detected using enzyme-linked immunosorbent assays and Western blotting. The calcium influx and reactive oxygen species (ROS) levels were measured via flow cytometry and the results showed that the LACCE (10-15 mg/mL) promoted the production of COL-I, inhibited the secretion of MMP-1, OPN3, ROS and calcium influx, and may play a role in inhibiting the activation of blue light on the OPN3-calcium pathway. Thereafter, high-performance liquid chromatography and ultra-performance liquid chromatography-tandem mass spectrometry were used to quantitatively analyze the contents of nine active ingredients in the LACCE. The results indicated that LACCE has an anti-blue-light-damage effect and provides theoretical support for the development of new raw materials in the natural food, medicine, and skin care industries.

Review of Laser Treatments for Post-Inflammatory Hyperpigmentation in Skin of Color

Post-inflammatory hyperpigmentation is an extremely common disorder of pigmentation in skin of color. It most frequently and severely affects phototypes that are rich in melanin and often has a chronic and unpredictable course. It presents significant treatment challenges and often requires a multi-factorial approach. We review the literature available for the optimal use of laser-based devices in the treatment of post-inflammatory hyperpigmentation, particularly for Fitzpatrick skin phototypes III-VI. For the treatment of post-inflammatory hyperpigmentation in skin of color, lasers remain second line to topical agents based on the variable response, cost, and risk of complications with laser use. For post-inflammatory hyperpigmentation resistant to topicals, laser devices, particularly neodymium:yttrium-aluminum-garnet and fractional photothermolysis systems, can provide adjunctive treatment in skin of color patients when appropriate parameters are used. Future studies would benefit from an objective and consistent assessment to assist with a systematic analysis.

Photoprotection in skin of color

As populations in many parts of the world are projected to become more racially diverse over the coming decades, we must better understand the unique characteristics of the skin of populations with skin of color (SOC). This review aims to highlight important physiologic and clinical considerations of photoprotection in SOC. Ultraviolet radiation and visible light affect dark and light skin differently. SOC populations have historically not been informed on photoprotection to the same degree as their light skinned counterparts. This has exacerbated dermatologic conditions in which SOC populations are disproportionately affected, such as hyperpigmentary disorders. Patients should be encouraged to utilize multiple methods of photoprotection, ranging from avoidance of sunlight during peak intensity hours, seeking shade, wearing sun-protective clothing and wide-brimmed hat, and applying sunscreen. Ideal sunscreens for SOC populations include those with UVA-PF/SPF ratios ≥ 2/3 and tinted sunscreens to protect against VL. Although there have been increased efforts recently, more research into photoprotection for SOC and targeted public education are required to disseminate photoprotection resources that are patient-centered and evidence-based.

The cutaneous effects of blue light from electronic devices: a systematic review with health hazard identification

The biologic effects of visible light, particularly blue light, on the skin at doses and irradiances representative of sunlight have been established. Recent research studies investigated the effects of blue light (BL) from electronic screen devices; however, it is unclear if the evidence can be generalized to real life. The aim of this systematic review was to evaluate available evidence regarding clinical effects of BL emitted from electronic devices on human skin using the framework established by the Office of Health Assessment and Translation (OHAT). A systematic literature search was conducted by two librarians in Ovid MEDLINE, Embase.com, and Web of Science for relevant articles published from 1946 to March 2022. In vitro and in vivo studies that investigated the effects of BL from electronic devices on skin were included. From the 87 articles gathered from database searches and 1 article identified from citation search, only 9 met the inclusion criteria (6 in vitro and 3 in vivo studies). Human and animal literature with the highest level of evidence ratings were considered with mechanistic data to form one of five human hazard identifications for each outcome category using the OHAT protocol: (1) known, (2) presumed, (3) suspected, (4) not classifiable, or (5) not identified to be a hazard to humans. Literature-based evidence integration did not identify exposure to BL from electronic devices as a hazard to skin pigmentation, redness, yellowness, or melasma exacerbation. Exposure to BL from electronic devices was not classified as a skin photoaging hazard. Low confidence in representative exposure characterization drove high OHAT risk-of-bias ratings for the majority of included studies. While these conclusions hold true for the limited existing data, a larger number of future studies with high-confidence evidence are needed to verify and strengthen hazard identification conclusions.

Treatment Effect of Phototherapy with Low-Level Energy in Patients with Allergic Rhinitis: A Single-Arm Observational Study

Allergic rhinitis is one of the most common health challenges and has a chronic and repetitive course that requires symptomatic treatment. We aimed to investigate the effect of phototherapy on allergic rhinitis and how long it takes to demonstrate treatment effect. Twenty-one patients who were diagnosed with allergic rhinitis using the skin prick test were enrolled. Red light (660 nm) and infrared light (940 nm) with a low power energy of 5 mW were used three times a day at intervals of at least 5 h. The Rhinoconjuntivitis Quality of Life Questionnaire (RQLQ) and a visual analog scale (VAS) were used to measure the changes in symptoms. The median RQLQ and VAS scores before treatment were 62 (49-81.5) and 3 (2-5) points, respectively. The RQLQ score improved significantly at two and four weeks after treatment (52 [39-62.5]) and 46.0 [30.5-57.0], respectively). The VAS scores also improved significantly at two and four weeks after treatment. Nasal obstruction and rhinorrhea improved significantly at one week after the procedure. Low-power (5 mW) light irradiation (660 nm red light and 940 nm infrared) was effective in improving the symptoms of allergic rhinitis. In addition, symptom improvement became clear approximately a week after use. Further studies are required to reach a definitive conclusion.

Review on photoprotection: a clinician’s guide to the ingredients, characteristics, adverse effects, and disease-specific benefits of chemical and physical sunscreen compounds

Photoprotection is a critical health prevention strategy to reduce the deleterious effects of ultraviolet radiation (UVR) and visible light (VL). Methods of photoprotection are reviewed in this paper, with an emphasis on sunscreen. The most appropriate sunscreen formulation for personal use depends on several factors. Active sunscreen ingredients vary in their protective effect over the UVR and VL spectrum. There are dermatologic diseases that cause photosensitivity or that are aggravated by a particular action spectrum. In these situations, sunscreen suggestions can address the specific concern. Sunscreen does not represent a single entity. Appropriate personalized sunscreen selection is critical to improve compliance and clinical outcomes. Health care providers can facilitate informed product selection with awareness of evolving sunscreen formulations and counseling patients on appropriate use. This review aims to summarize different forms of photoprotection, discuss absorption of sunscreen ingredients, possible adverse effects, and disease-specific preferences for chemical, physical or oral agents that may decrease UVR and VL harmful effects.

Visible red light does not induce DNA damage in human dermal fibroblasts

Visible red light (RL) therapy is a rapidly expanding treatment option for dermatological conditions, including acne, psoriasis and chronic wounds. It is currently unknown if high fluences of RL induce DNA damage via reactive oxygen species (ROS) stress or other pathways. Our lab previously demonstrated that RL generates ROS in human dermal fibroblasts (HDFs). Other studies show that UV and blue light generate ROS and DNA damage in fibroblasts. This study aims to determine if RL induces DNA damage in HDFs. We found that 320 J/cm² , 640 J/cm² and 1280 J/cm² RL (633 ± 6 nm) did not measurably increase DNA damage in the form of cyclobutane pyrimidine dimers (CPD) or 6-4 photoproducts (6-4PP) immediately, 3 hours and 24 hours following irradiation. Our study further supports that RL therapy is safe in human skin fibroblasts.

The Effects of Blue Light on Human Fibroblasts and Diabetic Wound Healing

Diabetes is a serious threat to global health and is among the top 10 causes of death. The Diabetic foot ulcer (DFU) is among the most common and severe complications of the disease. Bacterial infections are common; therefore, timely aggressive management, using multidisciplinary management approaches is needed to prevent complications, morbidity, and mortality, particularly in view of the growing cases of antibiotic-resistant bacteria. Photobiomodulation (PBM) involves the application of low-level light at specific wavelengths to induce cellular photochemical and photophysical responses. Red and near-infrared (NIR) wavelengths have been shown to be beneficial, and recent studies indicate that other wavelengths within the visible spectrum could be helpful as well, including blue light (400–500 nm). Reports of the antimicrobial activity and susceptibility of blue light on several strains of the same bacterium show that many bacteria are less likely to develop resistance to blue light treatment, meaning it is a viable alternative to antibiotic therapy. However, not all studies have shown positive results for wound healing and fibroblast proliferation. This paper presents a critical review of the literature concerning the use of PBM, with a focus on blue light, for tissue healing and diabetic ulcer care, identifies the pros and cons of PBM intervention, and recommends the potential role of PBM for diabetic ulcer care.

Is the Technology Era Aging You? A Review of the Physiologic and Psychologic Toll of Technology Use

BACKGROUND

Technology use is at an all-time high and its potential impact on psychological and physiologic health should be explored.

OBJECTIVE

The objective of this narrative review was to identify the role of technology use on health and well-being.

MATERIALS AND METHODS

Authors performed a review of PubMed and publications of the World Health Organization, Department of Defense, and Centers for Disease Control and Prevention to determine the impact of technology regarding electromagnetic radiation (EM), posture and mobility, sleep disturbance, and psychological stress and well-being.

RESULTS

Studies on the impact of EM were conflicting, with about 45% reporting negative consequences and 55% reporting no effect. Radiofrequency EM (RF-EM) may more significantly affect fibroblasts and immature cells. Device use was implicated in worsening cognitive focus, imbalance, and sleep. Social media use affects self-esteem and mental health and is associated with up to 33% presence of addiction. Effects seem to be dose related and more pronounced in younger ages.

CONCLUSION

Technology use significantly affects sleep, mental health, and cognitive function. Seeking psychological help, limiting social media use, and reducing use before sleep may partially mitigate these effects. The impact of EM is undetermined, but the WHO lists RF-EM as a potential carcinogen.

Optical Behavior of Human Skin Substitutes: Absorbance in the 200-400 nm UV Range

The most recent generation of bioengineered human skin allows for the efficient treatment of patients with severe skin defects. Despite UV sunlight can seriously affect human skin, the optical behavior in the UV range of skin models is still unexplored. In the present study, absorbance and transmittance of the UGRSKIN bioartificial skin substitute generated with human skin cells combined with fibrin-agarose biomaterials were evaluated for: UV-C (200−280 nm), -B (280−315 nm), and -A (315−400 nm) spectral range after 7, 14, 21 and 28 days of ex vivo development. The epidermis of the bioartificial skin substitute was able to mature and differentiate in a time-dependent manner, expressing relevant molecules able to absorb most of the incoming UV radiation. Absorbance spectral behavior of the skin substitutes showed similar patterns to control native skin (VAF > 99.4%), with values 0.85−0.90 times lower than control values at 7 and 14- days and 1.05−1.10 times the control values at 21- and 28-days. UV absorbance increased, and UV transmission decreased with culture time, and comparable results to the control were found at 21 and 28 days. These findings support the use of samples corresponding to 21 or 28 days of development for clinical purposes due to their higher histological similarities with native skin, but also because of their absorbance of UV radiation.

Immunomodulatory Properties of Immune Checkpoint Inhibitors-More than Boosting T-Cell Responses?

The approval of immune checkpoint inhibitors (ICI) that serve to enhance effector T-cell anti-tumor responses has strongly improved success rates in the treatment of metastatic melanoma and other tumor types. The currently approved ICI constitute monoclonal antibodies blocking cytotoxic T-lymphocyte-associated protein (CTLA)-4 and anti-programmed cell death (PD)-1. By this, the T-cell-inhibitory CTLA-4/CD80/86 and PD-1/PD-1L/2L signaling axes are inhibited. This leads to sustained effector T-cell activity and circumvents the immune evasion of tumor cells, which frequently upregulate PD-L1 expression and modulate immune checkpoint molecule expression on leukocytes. As a result, profound clinical responses are observed in 40-60% of metastatic melanoma patients. Despite the pivotal role of T effector cells for triggering anti-tumor immunity, mounting evidence indicates that ICI efficacy may also be attributable to other cell types than T effector cells. In particular, emerging research has shown that ICI also impacts innate immune cells, such as myeloid cells, natural killer cells and innate lymphoid cells, which may amplify tumoricidal functions beyond triggering T effector cells, and thus improves clinical efficacy. Effects of ICI on non-T cells may additionally explain, in part, the character and extent of adverse effects associated with treatment. Deeper knowledge of these effects is required to further develop ICI treatment in terms of responsiveness of patients to treatment, to overcome resistance to ICI and to alleviate adverse effects. In this review we give an overview into the currently known immunomodulatory effects of ICI treatment in immune cell types other than the T cell compartment.

Self-applied topical interventions for melasma: a systematic review and meta-analysis of data from randomized, investigator-blinded clinical trials

BACKGROUND

Melasma is a frequent dermatological condition. Although its relevance as a skin condition is primarily of cosmetic nature, it may affect the patients' well-being and quality of life. A broad range of treatment options is available, which makes it difficult to choose the most appropriate treatment.

OBJECTIVES

To summarise and critically appraise evidence from investigator-blinded RCTs on the efficacy and safety of self-applied topical interventions for melasma.

METHODS

We systematically searched MEDLINE and Cochrane CENTRAL for RCTs on topical, self-administered interventions for patients diagnosed with melasma. Eligibility was limited to RCTs that explicitly stated in their methods section (1) how they generated the random allocation sequence, and (2) that the study outcome assessor was blinded towards the participants' group allocation. Outcomes of interest included evaluator-assessed clinical scores (e.g., melasma area and severity index, MASI), quality of life, and patient-reported outcomes as well as safety outcomes. The study findings were meta-analysed, pooling data from studies on the same comparisons, if this was possible. We assessed confidence in the effect estimates using the GRADE approach.

RESULTS

Our searches yielded 1,078 hits. We included 36 studies reporting on 47 different comparisons of interventions. These included medical treatments such as 'triple combination cream' (TCC), over-the-counter cosmetic and herbal products, as well as sun creams covering different light spectra. Pooling data was possible for only two comparisons (topical tranexamic acid (TXA) vs. hydroquinone (HQ) and cysteamine vs. placebo). Direct comparisons were available for a variety of interventions; however, the reported outcomes varied largely. Overall, our confidence in the effect estimates ranged from very low to high.

CONCLUSION

Our findings indicate that TCC and its individual components HQ and tretinoin are effective in lightening melasma. Besides these established self-applied treatment options, we identified further medical as well as promising cosmetic and herbal product treatment approaches. Furthermore, evidence suggests that using broad-spectrum sunscreen covering both the visible and UV-light spectrum enhances the treatment efficacy of HQ. However, with mostly small RCTs comparing treatments directly, using a broad range of outcomes, further research is needed to draw conclusions about which treatment is most effective.

Photoprotection for Skin of Color

Photoprotection behaviors can mitigate skin damage caused by ultraviolet radiation, and common methods include seeking shade, avoiding sun exposure during peak daylight hours, wearing sun-protective clothing, applying sunscreen, and using sunglasses. While the role of sun protection in preventing sunburns, photoaging, and skin cancer is well established in fair-skinned populations, individuals with skin of color (SOC) are presumed to suffer fewer negative effects from solar radiation. Thus, the importance of photoprotection in this population is understudied and may be underestimated. In SOC populations, sun exposure is known to cause pigmentary disorders, photoaging, and basal cell carcinoma (BCC), highlighting the potential benefits of photoprotection. Although SOC populations tend to practice photoprotection by seeking shade and wearing sun-protective clothing, survey and interview-based studies have consistently found relatively low use of sunscreen among these populations. Common motivators for photoprotection in individuals with SOC include preventing sunburn and pigmentation, with the prevention of skin cancer being a less important reason. As a skin cancer risk behavior, indoor tanning is relatively rare in SOC populations, but its use may increase with acculturation to US norms. While more studies are necessary to clarify whether photoprotection behaviors may decrease skin cancer-related mortality in SOC populations, regular dermatologic care and counseling on photoprotection remain essential in patients with SOC for overall skin health.

Photoprotection by clothing: A review

Clothing is recognized by leading health agencies as a primary method to protect against the harmful effects of photodamage caused by ultraviolet (UV) radiation and visible light. The photoprotective capacity of clothing is commonly measured as the ultraviolet protective factor (UPF). While the technology driving photoprotective clothing has been well-established, there continues to be efforts to discover new materials to improve the UPF of clothing. Here, we show increased Google searches for photoprotective clothing over the last decade, suggesting a high level of public interest in photoprotective clothing. In addition, we investigate the frequency of UPF-graded photoprotective clothing sold by large retail stores featured in Fortune 1000. We review factors that alter the UPF of clothing and describe emerging textile technologies used to increase clothing's photoprotective capacity. Finally, we compare how photoprotective clothing is regulated among different countries, the importance of photoprotective clothing in occupational health, and research in visible light and clothing photoprotection.

PHOTOPROTECTION FOR ALL: CURRENT GAPS AND OPPORTUNITIES

The effects of solar radiation on human skin differ based on skin phototype, the presence or absence of photodermatoses, biological capacity to repair DNA damage, wavelength, intensity of sun exposure, geographic latitude, and other factors, underscoring the need for a more tailored approach to photoprotection. To date, the focus of photoprotection guidelines has been to prevent sunburn and DNA damage induced by ultraviolet (UV) radiation, both UVB and UVA; however, several recent studies have shown that visible light (VL) also generates reactive oxygen and nitrogen species that can contribute to skin damage and pigmentation on the skin, particularly in people of color. Therefore, dark-skinned individuals, while naturally better protected against UVB radiation by virtue of high eumelanin content in melanocytes, may need additional protection from VL-induced skin damage. The current options for photoprotection products need to expand, and potential strategies against VL include the addition of iron oxide, titanium dioxide, and biologically relevant antioxidants to sunscreen formulations, as well as supplementation with orally active antioxidants.

Impact of visible light on skin health: The role of antioxidants and free radical quenchers in skin protection

Until recently, the primary focus of photobiology has centered on the impact of UV radiation on skin health, including DNA damage and oncogenesis; however, the significant effects of visible light (VL) on skin remain grossly underreported. VL has been reported to cause erythema in individuals with light skin (Fitzpatrick skin types [FSTs] I-III) and pigmentary changes in individuals with dark skin types (FSTs IV-VI). These effects have importance in dermatologic diseases and potentially play a role in conditions aggravated by sun exposure, including phototoxicity in patients with FSTs I to III and post-inflammatory hyperpigmentation and melasma in patients with FSTs IV to VI. The induction of free radicals, leading to the generation of reactive species, is one driving mechanism of VL-induced skin pathologies, leading to the induction of melanogenesis and hyperpigmentation. Initial clinical studies have demonstrated the effectiveness of topical sunscreen with antioxidant combinations in inhibiting VL + UV-A1-induced erythema in FSTs I to III and reducing pigmentation in FSTs IV to VI. Antioxidants may help prevent the worsening of pigmentary disorders and can be incorporated into photoprotective strategies. It is essential that dermatologists and the public are aware of the impact of VL on skin, especially in patients with skin of color, and understand the available options for VL protection.

Light-induced nitric oxide release in the skin beyond UVA and blue light: Red & near-infrared wavelengths

Nitric oxide (NO) is omnipresent in the body and synthesized by 3 isoenzymes (nNOS, eNOS and iNOS), all detected in human skin. NO can be stored in a pool of compounds readily converted to NO following skin irradiation by UVR and blue light. This non-enzymatic (without NOS involvement) photolytic reaction mobilizes cutaneous stores of NO derivatives to the bloodstream, lowering blood pressure. However, with the likelihood of skin deleterious effects caused by UVR/blue light, safer wavelengths in the red/near-infrared (NIR) spectrum are becoming potential contenders to release cutaneous NO, possibly via NOS temperature-dependent effects. The use of red/NIR light to mobilize NO stores from the body's largest organ (the skin) is auspicious. This review focuses on UVR, blue, red, and NIR spectra and their capacity to release NO in human skin. PubMed and Google Scholar were used as article databases to find relevant publications related to this particular field.

Cellular Signalling and Photobiomodulation in Chronic Wound Repair

Photobiomodulation (PBM) imparts therapeutically significant benefits in the healing of chronic wounds. Chronic wounds develop when the stages of wound healing fail to progress in a timely and orderly frame, and without an established functional and structural outcome. Therapeutic benefits associated with PBM include augmenting tissue regeneration and repair, mitigating inflammation, relieving pain, and reducing oxidative stress. PBM stimulates the mitochondria, resulting in an increase in adenosine triphosphate (ATP) production and the downstream release of growth factors. The binding of growth factors to cell surface receptors induces signalling pathways that transmit signals to the nucleus for the transcription of genes for increased cellular proliferation, viability, and migration in numerous cell types, including stem cells and fibroblasts. Over the past few years, significant advances have been made in understanding how PBM regulates numerous signalling pathways implicated in chronic wound repair. This review highlights the significant role of PBM in the activation of several cell signalling pathways involved in wound healing.