Premature senescence in human melanocytes after exposure to solar UVR: An exosome and UV-miRNA connection

The Pigmentation of Blue Light Is Mediated by Both Melanogenesis Activation and Autophagy Inhibition through OPN3-TRPV1

Blue light, a high-energy radiation in the visible light spectrum, was recently reported to induce skin pigmentation. In this study, we investigated the involvement of TRPV1-mediated signaling along with OPN3 in blue light-induced melanogenesis as well as its signaling pathway. Operating downstream target of OPN3 in blue light-induced melanogenesis, blue light activated TRPV1 and upregulated its expression, resulting in calcium influx. Calcium ion induced the activation of calcium/calmodulin-dependent protein kinase II and MAPK. It also downregulated clusterin expression, leading to the nuclear translocation of PAX3, ultimately affecting melanin synthesis. In addition, blue light interfered with autophagy-mediated regulation of melanosomes by decreasing not only the interaction between clusterin and LC3B but the expression of activating transcription factor family. These findings demonstrate that the pigmenting effects of blue light are mediated by calcium/calmodulin-dependent protein kinase II- and MAPK-mediated signaling as well as clusterin-dependent inhibition of autophagy through OPN3-TRPV1-calcium influx, suggesting, to our knowledge, a previously unreported signaling pathway through which blue light regulates melanocyte biology. Furthermore, these results suggest that TRPV1 and clusterin could be potential therapeutic targets for blue light-induced pigmentation due to prolonged exposure to blue light.

Role of non‑coding RNAs in UV‑induced radiation effects (Review)

Ultraviolet (UV) is divided into UVA (long-wave, 320-400 nm), UVB (middle-wave, 280-320 nm) and UVC (short-wave, 100-280 nm) based on wavelength. UV radiation (UVR) from sunlight (UVA + UVB) is a major cause of skin photodamage including skin inflammation, aging and pigmentation. Accidental exposure to UVC burns the skin and induces skin cancer. In addition to the skin, UV radiation can also impair visual function. Non-coding RNAs (ncRNAs) are a class of functional RNAs that do not have coding activity but can control cellular processes at the post-transcriptional level, including microRNA (miRNA), long non-coding RNA (lncRNA) and circulatory RNA (circRNA). Through a review of the literature, it was determined that UVR can affect the expression of various ncRNAs, and that this regulation may be wavelength specific. Functionally, ncRNAs participate in the regulation of photodamage through various pathways and play pathogenic or protective regulatory roles. In addition, ncRNAs that are upregulated or downregulated by UVR can serve as biomarkers for UV-induced diseases, aiding in diagnosis and prognosis assessment. Therapeutic strategies targeting ncRNAs, including the use of natural drugs and their extracts, have shown protective effects against UV-induced photodamage. In the present review, an extensive summarization of previous studies was performed and the role and mechanism of ncRNAs in UV-induced radiation effects was reviewed to aid in the diagnosis and treatment of UV-related diseases.

The acid sphingomyelinase inhibitor imipramine enhances the release of UV photoproduct-containing DNA in small extracellular vesicles in UVB-irradiated human skin

Nucleic acids, lipids, and other cell components can be found within different types of extracellular vesicles (EVs), which include apoptotic bodies (ABs), large extracellular vesicles (LEVs), and small extracellular vesicles (SEVs). Release of LEVs from cells can be reduced by genetic or pharmacological inhibition of the enzyme acid sphinogomyelinase (aSMase), and indeed several studies have demonstrated a role for the clinically approved aSMase inhibitor imipramine in blocking LEV release, including in response to UVB exposure. Given that exposure of keratinocytes to UVB radiation results in the generation of UVR photoproducts in DNA that can subsequently be found in association with ABs and SEVs, we examined how imipramine impacts the release of extracellular DNA containing UVR photoproducts at an early time point after UVR exposure. Using several different model systems, including cultured keratinocytes in vitro, discarded human surgical skin ex vivo, and skin biopsies obtained from treated human subjects, these pilot studies suggest that imipramine treatment stimulates the release of CPD-containing, SEV-associated DNA. These surprising findings indicate that LEV and SEV generation pathways could be linked in UVB-irradiated cells and that imipramine may exacerbate the systemic effects of extracellular UVR-damaged DNA throughout the body.

Effect of environmental exposures on cancer risk: Emerging role of non-coding RNA shuttled by extracellular vesicles

Environmental and lifestyle exposures have a huge impact on cancer risk; nevertheless, the biological mechanisms underlying this association remain poorly understood. Extracellular vesicles (EVs) are membrane-enclosed particles actively released by all living cells, which play a key role in intercellular communication. EVs transport a variegate cargo of biomolecules, including non-coding RNA (ncRNA), which are well-known regulators of gene expression. Once delivered to recipient cells, EV-borne ncRNAs modulate a plethora of cancer-related biological processes, including cell proliferation, differentiation, and motility. In addition, the ncRNA content of EVs can be altered in response to outer stimuli. Such changes can occur either as an active attempt to adapt to the changing environment or as an uncontrolled consequence of cell homeostasis loss. In either case, such environmentally-driven alterations in EV ncRNA might affect the complex crosstalk between malignant cells and the tumor microenvironment, thus modulating the risk of cancer initiation and progression. In this review, we summarize the current knowledge about EV ncRNAs at the interface between environmental and lifestyle determinants and cancer. In particular, we focus on the effect of smoking, air and water pollution, diet, exercise, and electromagnetic radiation. In addition, we have conducted a bioinformatic analysis to investigate the biological functions of the genes targeted by environmentally-regulated EV microRNAs. Overall, we draw a comprehensive picture of the role of EV ncRNA at the interface between external factors and cancer, which could be of great interest to the development of novel strategies for cancer prevention, diagnosis, and therapy.

DNA Containing Cyclobutane Pyrimidine Dimers Is Released from UVB-Irradiated Keratinocytes in a Caspase-Dependent Manner

Solar radiation induces the formation of cyclobutane pyrimidine dimers (CPDs) and other UV photoproducts in the genomic DNA of epidermal keratinocytes. Although CPDs have been detected in urine from UV- and sun-exposed individuals, the pathway by which they arrive there and the mechanisms by which UV-induced DNA damage in the skin has systemic effects throughout the body are not clear. Consistent with previous reports that DNA associates with small extracellular vesicles that are released from a variety of cell types, we observed that a small fraction of CPDs formed in genomic DNA after UVB exposure can later be detected in the culture medium. These extracellular CPDs are found within large fragments of histone-associated DNA and are released in a time- and UVB dose‒dependent manner. Moreover, studies with both cultured cells and human skin explants revealed that CPD release into the extracellular environment is blocked by caspase inhibition, which indicates a role for apoptotic signaling in CPD release from UVB-irradiated keratinocytes. Finally, we show that this released CPD-containing DNA can be taken up by other keratinocytes. These results therefore provide possible mechanisms for the export of damaged DNA from UVB-irradiated cells and for systemic effects of UVB exposure throughout the body.

SCA® Slows the Decline of Functional Parameters Associated with Senescence in Skin Cells

The identification of compounds and natural ingredients that can counteract tissue stress and dysfunction induced by aging in skin cells is warranted. Here, we investigated the activity of the secretion from the snail Cryptomphalus aspersa (SCA^®), an active compound with well-established beneficial effects on skin integrity and aging. To determinate its senescence-regulation mechanisms, we used a model where damage was induced by hydrogen peroxide (H₂O₂). The results showed that SCA^® positively modulated factors involved in cell senescence such as β-galactosidase and cell morphology, secretory efficiency markers (SIRT1/6 and carboxymethyl-lysine), and metabolic and redox homeostasis (mTOR and ROS). This study demonstrated a novel compound that is activity-modulating, reduces cell senescence, and increases longevity to maintain skin homeostasis and functionality.

Genome-Wide RNA Sequencing Analysis in Human Dermal Fibroblasts Exposed to Low-Dose Ultraviolet A Radiation

Ultraviolet A (UVA) radiation can pass through the epidermis and reach the dermal skin layer, contributing to photoaging, DNA damage, and photocarcinogenesis in dermal fibroblasts. High-dose UVA exposure induces erythema, whereas low-dose, long-term UVA exposure causes skin damage and cell senescence. Biomarkers for evaluating damage caused by low-dose UVA in fibroblasts are lacking, making it difficult to develop therapeutic agents for skin aging and aging-associated diseases. We performed RNA-sequencing to investigate gene and pathway alterations in low-dose UVA-irradiated human skin-derived NB1RGB primary fibroblasts. Differentially expressed genes were identified and subjected to Gene Ontology and reactome pathway analysis, which revealed enrichment in genes in the senescence-associated secretory phenotype, apoptosis, respiratory electron transport, and transcriptional regulation by tumor suppressor p53 pathways. Insulin-like growth factor binding protein 7 (IGFBP7) showed the lowest p-value in RNA-sequencing analysis and was associated with the senescence-associated secretory phenotype. Protein–protein interaction analysis revealed that Fos proto-oncogene had a high-confidence network with IGFBP7 as transcription factor of the IGFBP7 gene among SASP hit genes, which were validated using RT-qPCR. Because of their high sensitivity to low-dose UVA radiation, Fos and IGFBP7 show potential as biomarkers for evaluating the effect of low-dose UVA radiation on dermal fibroblasts.

Therapeutic implications of exosomes in the treatment of radiation injury

Radiotherapy is one of the main cancer treatments, but it may damage normal tissue and cause various side effects. At present, radioprotective agents used in clinics have side effects such as nausea, vomiting, diarrhea and hypotension, which limit their clinical application. It has been found that exosomes play an indispensable role in radiation injury. Exosomes are lipid bilayer vesicles that carry various bioactive substances, such as proteins, lipids and microRNA (miRNA), that play a key role in cell-to-cell communication and affect tissue injury and repair. In addition, studies have shown that radiation can increase the uptake of exosomes in cells and affect the composition and secretion of exosomes. Here, we review the existing studies and discuss the effects of radiation on exosomes and the role of exosomes in radiation injury, aiming to provide new insights for the treatment of radiation injury.

Secretory Autophagy Forges a Therapy Resistant Microenvironment in Melanoma

Melanoma is the most aggressive skin cancer characterized by high mutational burden and large heterogeneity. Cancer cells are surrounded by a complex environment, critical to tumor establishment and progression. Thus, tumor-associated stromal components can sustain tumor demands or impair cancer cell progression. One way to manage such processes is through the regulation of autophagy, both in stromal and tumor cells. Autophagy is a catabolic mechanism that provides nutrients and energy, and it eliminates damaged organelles by degradation and recycling of cellular elements. Besides this primary function, autophagy plays multiple roles in the tumor microenvironment capable of affecting cell fate. Evidence demonstrates the existence of novel branches in the autophagy system related to cytoplasmic constituent's secretion. Hence, autophagy-dependent secretion assembles a tangled network of signaling that potentially contributes to metabolism reprogramming, immune regulation, and tumor progression. Here, we summarize the current awareness regarding secretory autophagy and the intersection with exosome biogenesis and release in melanoma and their role in tumor resistance. In addition, we present and discuss data from public databases concerning autophagy and exosome-related genes as important mediators of melanoma behavior. Finally, we will present the main challenges in the field and strategies to translate most of the pre-clinical findings to clinical practice.

Skin Aging, Cellular Senescence and Natural Polyphenols

The skin, being the barrier organ of the body, is constitutively exposed to various stimuli impacting its morphology and function. Senescent cells have been found to accumulate with age and may contribute to age-related skin changes and pathologies. Natural polyphenols exert many health benefits, including ameliorative effects on skin aging. By affecting molecular pathways of senescence, polyphenols are able to prevent or delay the senescence formation and, consequently, avoid or ameliorate aging and age-associated pathologies of the skin. This review aims to provide an overview of the current state of knowledge in skin aging and cellular senescence, and to summarize the recent in vitro studies related to the anti-senescent mechanisms of natural polyphenols carried out on keratinocytes, melanocytes and fibroblasts. Aged skin in the context of the COVID-19 pandemic will be also discussed.

Extracellular Vesicles: Footprints of environmental exposures in the aging process?

PURPOSE OF THE REVIEW

Extracellular vesicles (EVs) are nano-sized lipid particles that participate in intercellular signaling through the trafficking of bioactive molecules from parental cells to recipient ones. This well-orchestrated communication system is crucial for the organism to respond to external cues in a coordinated manner; indeed, environmental and lifestyle exposures can modify both EV number and content, with consequences on cellular metabolism and homeostasis. In particular, a growing body of evidence suggests that exposome-induced changes in EV profile could regulate the aging process, both at the cellular and organismal levels. Here, we provide an overview of the role played by ambient-induced EVs on aging and age-related diseases. Among the several environmental factors that can affect the communication network operated by EVs, we focused on air pollution, ultraviolet light, diet, and physical exercise. Moreover, we performed a miRNA target analysis, to support the role of EV-miRNA emerging from the literature in the context of aging.

RECENT FINDINGS

The overall emerging picture strongly supports a key regulatory role for EVs at the interface between external stimuli and cellular/organismal aging, thus providing novel insights into the molecular mechanisms linking a "healthy exposome" to well-being in old age. In addition, this knowledge will pave the way for research aimed at developing innovative antiaging strategies based on EVs.

Hyaluronan: A key player or just a bystander in skin photoaging?

Photoaged skin exhibits signs of inflammation, DNA damage and changes in morphology that are visible at the macroscopic and microscopic levels. Photoaging also affects the extracellular matrix (ECM) including hyaluronan (HA), the main polysaccharide component thereof. HA is a structurally simple but biologically complex molecule that serves as a water-retaining component and provides both a scaffold for a number of the proteins of the ECM and the ligand for cellular receptors. The study provides an overview of the literature concerning the changes in HA amount, size and metabolism, and the potential role of HA in photoaging. We also suggest novel HA contributions to photoaging based on our knowledge of the role of HA in other pathological processes, including the senescence and inflammation-triggered ECM reorganization. Moreover, we discuss potential direct or indirect intervention to mitigate photoaging that targets the hyaluronan metabolism, as well as supplementation.

Cellular Senescence and the Senescence-Associated Secretory Phenotype as Drivers of Skin Photoaging

Chronic exposure to UVR is known to disrupt tissue homeostasis, accelerate the onset of age-related phenotypes, and increase the risk for skin cancer-a phenomenon defined as photoaging. In this paper, we review the current knowledge on how UV exposure causes cells to prematurely enter cellular senescence. We describe the mechanisms contributing to the accumulation of senescent cells in the skin and how the persistence of cellular senescence can promote impaired regenerative capacity, chronic inflammation, and tumorigenesis associated with photoaging. We conclude by highlighting the potential of senolytic drugs in delaying the onset and progression of age-associated phenotypes in the skin.

Inhibition of the P53/P21 Pathway Attenuates the Effects of Senescent Nucleus Pulposus Cell-Derived Exosomes on the Senescence of Nucleus Pulposus Cells

Objective

The purpose of this paper is to investigate the effects of senescent nucleus pulposus cell (NPC)‐derived exosomes (SNPC‐Exo) and the roles of the P53/P21 pathway on the senescence of NPC.

Methods

The senescent phenotypes of NPC were induced by interleukin‐1β treatment. SNPC‐Exo was extracted from the culture medium of senescent NPC and purified by differential centrifugation. The structure of SNPC‐Exo was identified by transmission electron microscopy and western blot analysis was used to determine the exosomal marker proteins CD63 and Tsg101. Western blot analysis was performed to determine the relative expression levels of P16, P21, and P53 in NPC. Senescence‐associated β‐galactosidase (SA‐β‐gal) staining was used to stain the senescent NPC and a phase contrast microscope was used to observe and count the SA‐β‐gal staining of NPC. The proliferation of SNPC‐Exo‐treated NPC was assessed using growth curve analysis and the colony formation assay. The cell cycle of SNPC‐Exo‐treated NPC was determined by flow cytometry. NPC were transfected with siRNA to knock down P53 and P21 expression.

Results

Interleukin‐1β‐treated NPC had a higher percentage of SA‐β‐gal positive cells (45%) than the control group (20%) and showed an increase in the relative expression of P16, P21, and P53 (P < 0.05). SNPC‐Exo were positive for exosomal marker protein CD63 and Tsg 101 and negative for calnexin, and successfully internalized as previously described. SNPC‐Exo‐treated NPC showed an increase in the relative expression of P21 and P53 (P < 0.05). Compared with the control group, the SNPC‐Exo‐treated NPC showed a lower growth rate (3 times lower on the 5th day and 2 times lower on the 7th day), fewer colony‐forming units (12.0%), and a higher percentage of SA‐β‐gal‐positive NPC (50.0%). The SNPC‐Exo‐treated NPC contained more G1 phase cells (68.0%) and fewer S phase (15.5%) cells than the control group (53.0% in G1 phase, 33.5% in S phase). The expression of P21 and P53 significantly decreased in SNPC‐exo‐treated NPC after siRNA transfection (P < 0.05), followed by a higher growth rate (2 times higher on the 5th day and 1.5 times higher on the 7th day) and lower percentage of SA‐β‐gal‐positive NPC (22.5%). Moreover, the inhibition of the P53/P21 pathway promoted the SNPC‐Exo‐treated NPC to enter the S phase (from 15.5% to 25.3%).

Conclusion

The inhibition of the P53/P21 pathway attenuated the senescence of NPC induced by SNPC‐Exo.