CYP11A1-derived vitamin D3 products protect against UVB-induced inflammation and promote keratinocytes differentiation

UVB radiation mediates inflammatory responses causing skin damage and defects in epidermal differentiation. 1α,25-Dihydroxyvitamin D3 (1,25(OH)2D3) interacts with the vitamin D3 receptor (VDR) to regulate inflammatory responses. Additionally, 1,25(OH)2D3/VDR signaling represents a potential therapeutic target in the treatment of skin disorders associated with inflammation and poor differentiation of keratinocytes. Since the protective effect of 1,25(OH)2D3 against UVB-induced skin damage and inflammation is recognized, CYP11A1-derived vitamin D3-hydroxyderivatives including 20(OH)D3, 1,20(OH)2D3, 20,23(OH)2D3 and 1,20,23(OH)3D3 were tested for their anti-inflammatory and skin protection properties in UVB-irradiated human epidermal keratinocytes (HEKn). HEKn were treated with secosteroids for 24 h pre- and post-UVB (50 mJ/cm2) irradiation. Secosteroids modulated the expression of the inflammatory response genes (IL-17, NF-κB p65, and IκB-α), reducing nuclear-NF-κB-p65 activity and increasing cytosolic-IκB-α expression as well as that of pro-inflammatory mediators, IL-17, TNF-α, and IFN-γ. They stimulated the expression of involucrin (IVL) and cytokeratin 10 (CK10), the major markers of epidermal differentiation, in UVB-irradiated cells. We conclude that CYP11A1-derived hydroxyderivatives inhibit UVB-induced epidermal inflammatory responses through activation of IκB-α expression and suppression of NF-kB-p65 activity and its downstream signaling cytokines, TNF-α, and IFN-γ, as well as by inhibiting IL-17 production and activating epidermal differentiation.

UV-B responses in the spotlight: Dynamic photoreceptor interplay and cell-type specificity

Plants are constantly exposed to a multitude of external signals, including light. The information contained within the full spectrum of light is perceived by a battery of photoreceptors, each with specific and shared signalling outputs. Recently, it has become clear that UV-B radiation is a vital component of the electromagnetic spectrum, guiding growth and being crucial for plant fitness. However, given the large overlap between UV-B specific signalling pathways and other photoreceptors, understanding how plants can distinguish UV-B specific signals from other light components deserves more scrutiny. With recent evidence, we propose that UV-B signalling and other light signalling pathways occur within distinct tissues and cell-types and that the contribution of each pathway depends on the type of response and the developmental stage of the plant. Elucidating the precise site(s) of action of each molecular player within these signalling pathways is key to fully understand how plants are able to orchestrate coordinated responses to light within the whole plant body. Focusing our efforts on the molecular study of light signal interactions to understand plant growth in natural environments in a cell-type specific manner will be a next step in the field of photobiology.

The Conversion and Degradation of Sulphaguanidine under UV and Electron Beam Irradiation Using Fluorescence

The work presents a spectral-luminescent study of the sulfaguanidine transformation in water under a pulsed e-beam and UV irradiation of an UVb-04 bactericidal mercury lamp (from 180 to 275 nm), KrCl (222 nm), XeBr (282 nm) and XeCl (308 nm) excilamps. Fluorescent decay curves have been used in our analysis of the sulfaguanidine decomposition. The conversion of antibiotic under e-beam irradiation for up to 1 min was more than 80%, compared with UV radiation: UVb-04-26%, XeBr - 20%. KrCl and XeCl - about 10%. At the end of 64 min of irradiation with UVb-04 and XeBr lamps, the conversion was 99%. During irradiation with these lamps, sulfaguanidine almost completely decomposed and passed into the final fluorescent photoproducts. After e-beam irradiated at the end of 13 min the decrease in sulfaguanidine was 93%. At the same time, the formation of sulfaguanidine transformation products was minimal compared to UV irradiation. The effect of UV irradiation and a powerful e-beam on the decomposition mechanisms of sulfaguanidine are significantly different, which is manifested in various changes in the absorption and fluorescence spectra.

Ionocyte Immunolocalization and the Effects of Ultraviolet Radiation on Their Abundance and Distribution in the Alenins of Caspian Sea Salmon, Salmo trutta caspius

OBJECTIVE

On a global scale, stratospheric ozone depletion has caused an increase in UV-B radiation reaching the earth's surface. Ultraviolet radiation has long been suspected to be harmful to aquatic organisms.

MATERIALS AND METHODS

In order to study ionocyte localization (by Na(+)/K(+)-ATPase immunolocalization) and the effects of UV radiation on the ionocytes of skin and gills, the alevins of Salmo trutta caspius were exposed to different doses of UV radiation [unit low doses (ULD) of: 60 µw/cm(2) UVC; 100 µw/cm(2) UVB and 40 µw/cm(2) UVA and unit high doses (UHD) of: 90 µw/cm(2) UVC; 130 µw/cm(2) UVB and 50 µw/cm(2) UVA] using two adjustable F8T5 UV-B, 302 nm lamps (Japan) for 15 minutes once a day in laboratory conditions. Alevins not subjected to UV exposure served as a control group.

RESULTS

In both UV exposure groups, all the alevins died on the ninth day. No mortality was observed in the control group. The Na(+)/K(+)-ATPase immunolocalization study indicated that ionocytes were located, in lessening order, on the yolk sac, trunk, gills, opercula and rarely on the head skin. Immunohistochemical results showed significant reduction in the number of ionocytes on the yolk sac, with lesser reduction on the trunk in both UV exposure groups. In contrast, the number of immunofluorescence cells on the gill was significantly elevated. Our results also showed that the size of ionocytes was reduced on the trunk and yolk sac in the UV exposure groups, but not significantly. Deformation and destruction of ionocytes on the yolk sac and trunk were observed with scanning electron microscope (SEM) in the UV exposure groups.

CONCLUSION

Our results showed that ionocytes were located mainly on the yolk sac, in lesser amounts on the trunk, gills and opercula, and rarely also on the head skin of alevins. UV radiation caused deformation and reduction in the number and size of ionocytes on the trunk and yolk sac. As the skin cells of trout alevins possess essential functions for respiration, osmoregulation, excretion and defense during this stage of life, the observed damage may have contributed to their suddenly mortality in the UV exposure condition.