UVA induces retinal photoreceptor cell death via receptor interacting protein 3 kinase mediated necroptosis

MLKL, a new actor of UVB-induced apoptosis in human diploid dermal fibroblasts

Ultraviolet radiation (UVR) is a major environmental mutagen. In skin, UVR can initiate cancer through the induction of mutagenic DNA damage and promote its progression. An important cancer prevention mechanism is the regulated cell death (RCD), which can safely dispose of damaged cells. Apoptosis, a well-known RCD, is known to be activated by UVR, but part of the mechanism and proteins involved in UVR-induced apoptosis are still to be discovered. Receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) are two proteins involved in necroptosis, a form of RCD. Here, we have evaluated the implication of RIPK3 and MLKL in UVB-induced cell death in human diploid dermal fibroblasts. Our results show that RIPK3 and MLKL play opposite roles in UVB-induced cell death, in a necroptosis independent pathway. We showed that RIPK3 protects cells from UVB cell death, while MLKL sensitizes cells to UVB-induced apoptosis. Taken together these results are the first to show the implication of RIPK3 and MLKL in survival and apoptosis, respectively, bringing two new actors in UVB-induced cell death pathway.

Protein expression of nucleolar protein 12 in the retina and its implication in protection of retina from UV irradiation damage

Nucleolar protein 12 (NOL12), one of the nucleolar proteins which are primarily expressed in the nucleolus and play key roles in RNA metabolism, cell proliferation, cell cycle, and cell survival, is widely expressed in various species and multiple organs. Although it has been reported that the mRNA of Drosophila NOL12 homolog viriato is expressed in the eyes of Drosophila, the protein expression of NOL12 in mammalian eyes remains to be elucidated. In this study, we showed through immunohistochemistry that NOL12 was present in the rat retina, with predominant distribution in the cytoplasm of the retinal neuronal cells. In the human retinoblastoma cell line WERI-Rb1, we found that altering NOL12 expression led to a change in WERI-Rb1 cell viability. Knocking down NOL12 expression decreased cell viability. In contrast, overexpressing NOL12 increased cell viability. Furthermore, increasing NOL12 expression inhibited ultraviolet (UV)-induced apoptosis. These findings demonstrated that NOL12 may play an important protective role in retinal cells. In the WERI-Rb1 cells exposed to UV irradiation, we detected that NOL12 was degraded, but this degradation could be attenuated by a pan-Caspase inhibitor. Notably, the inhibitory effect of NOL12 against UV-induced apoptosis could be restrained by increasing the expression of ATR serine/threonine kinase (ATR), a kinase that, when activated by severe DNA damage, can result in apoptosis. We also found that upregulating NOL12 inhibited the activation of ATR caused by UV irradiation. Additionally, inhibiting ATR activity reduced apoptosis resulting from both silencing NOL12 expression and UV exposure. Thus, NOL12 may protect against UV irradiation-induced retinal damage by inhibiting ATR activity.

Applications of Ultraviolet and Sub-ultraviolet Dermatoscopy in Neoplastic and Non-neoplastic Dermatoses: A Systematic Review

Dermatoscopy is a non-invasive and cost-efficient imaging technique augmenting clinical examination in neoplastic and non-neoplastic dermatoses. Recently, novel dermatoscopic techniques based on principles of reflectance/absorption and excited fluorescence have been developed. However, comprehensive data on their applications are sparse, and terminology is inconsistent. In this systematic review, we addressed the principles of ultraviolet (UV) imaging and proposed categorization based on spectral characteristics and signal acquisition, as well as discussed documented and potential clinical applications, safety measures during examination, and limitations associated with reflectance and fluorescence dermatoscopy. A literature search was conducted in the PubMed medical database until 2 December 2023 according to PRISMA guidelines, and 28 papers fit the scope of this review, whereas additional relevant articles were included to provide broader context regarding the chosen terminology, chromophores described, safety of sub-UV/UV, and regulations for light-emitting devices. UV and sub-UV dermatoscopy, categorized into different methods on the basis of the emitted wavelength and signal acquisition process (reflectance versus fluorescence), augment conventional dermatoscopy by optimizing safety margins in melanoma, facilitating early detection of tumor recurrence, and enhancing visualization in non-neoplastic conditions, including pigmentation disorders, intertrigo, papulo-desquamative dermatoses, and beyond. The review highlights the limitations of these techniques, including difficulty in differentiating melanin from hemoglobin, challenges in evaluating uneven surfaces, and artifacts. Although UV dermatoscopy complements conventional dermatoscopy, clinicians should be aware of their peculiarities, artifacts, limitations, and safety concerns to optimize their diagnostic accuracy and ensure patient's safety.