Biology subjects

Fujikawa, Y.

Publications and source records attributed to Fujikawa, Y..

4 recordsLinked to original sources

bioRxiv2025

Impact of Low-Dose Narrowband UV Radiation on Skin Tissue and Mast Cells in a Canine Model

Narrowband ultraviolet radiation (NB-UVR) therapy is widely utilized in dermatology worldwide. While the immunosuppressive effects of ultraviolet radiation are well-documented, its non-inflammatory effects remain poorly understood. This study evaluated the effects of sub-minimal erythema dose (MED) narrowband ultraviolet radiation using a canine model. The effects of narrowband-ultraviolet B (310 nm) and A2 wavelengths (320 and 330 nm) were compared. Initially, we demonstrated the therapeutic potential of NB-UVR in dogs with spontaneous atopic dermatitis (n = 6, p < 0.05). Following 300 mJ/cm{superscript 2} sub-MED ultraviolet radiation exposure, intradermal skin testing, skin mast cell counts, and RNA sequencing analysis were conducted. Additionally, cell viability (WST assay) and apoptosis (DAPI staining) were assessed in vitro using a canine mast cell line. Ultraviolet radiation exposure significantly reduced intradermal skin test scores across all wavelengths and decreased skin mast cell counts at 310 nm (n = 3, p < 0.05). In vitro, cell viability was significantly reduced at 310 and 320 nm (p < 0.05), and 310 nm irradiation specifically increased apoptotic cell numbers (p < 0.05). RNA sequencing identified 71 differentially expressed genes at 320 nm, with enrichment analysis highlighting muscle cell components and functions, potentially associated with arrector pili muscle activity. These findings suggest that 310 nm irradiation induces apoptosis, while 320 nm elicits non-inflammatory modulatory effects, highlighting distinct wavelength-specific therapeutic mechanisms of narrowband ultraviolet radiation.

immunology↗

bioRxiv2024

Systematic mutagenesis assay promotes comprehension of the strand-bias laws for mutations induced by oxidative DNA damage

We have recently developed an efficient and sensitive method for analyzing mutations caused by various environmental and endogenous factors which utilizes nucleotide-barcoded supF shuttle vector libraries with a multiplexed NGS assay, referred to hereafter as supF NGS assay. Ionizing-radiation-induced cancer is known to be difficult to distinguish from spontaneous cancer, especially in the case of low-dose and low-dose-rate exposure, and discerning the underlying mechanisms of ionizing-radiation-induced cancer, especially the relationship between mutagenesis and carcinogenesis, is likely to be an arduous task. In the present study, we have attempted to address the mutations characteristic for exposure to low levels of ionizing radiation by using the supF NGS assay. As a result, a significant increase in mutations was detected at cytosines and guanines within 5-TC-3:5-GA-3 sites following chronic gamma-irradiation at a dose-rate of 1 Gy per day for the duration of 2 days. Since the number of detected mutations exceeded the expectations based on the quantity of DNA-damage induced by irradiation, we proceeded to explore the possibilities that a single DNA-lesion induced by irradiation may cause amplification of mutations. For this purpose, we utilized shuttle vector libraries with a single 8-oxo-7,8-dihydroguanine (8-oxo-G)-damaged residue introduced at different sites via an in vitro enzymatic method. Through a set of experiments, we revealed that a single 8-oxo-G-damaged residue can become a trigger for peripheral mutagenesis; intense generation of strand-biased mutations occured at 5-TC-3:5-GA-3 sites with specific localization in the secondary structures of single-stranded DNA, more frequently than not at sites different from the 8-oxo-G-damaged sites. Thus, this study provides a novel prospect for the role of DNA-lesions induced by environmentally or endogenously generated ROS in additional mutations. The high-performance mutagenesis assay presented in this study will advance research aimed at uncovering the mechanisms of mutagenesis and the intricacies relevant to carcinogenesis.

cell biology↗

bioRxiv2021

Transcriptome and metabolome analyses revealed that narrowband 280 and 310 nm UV-B induce distinctive responses in Arabidopsis

In plants, the UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8) perceives UV-B and induces UV-B responses including synthesis of UV-B absorbing phenolic compounds such as anthocyanins. UVR8 absorbs a range of UV-B (260-335 nm). However, the responsiveness of plants to each UV-B wavelength has not been intensively studied so far. Here, we performed transcriptome and metabolome analyses of Arabidopsis using UV light emitting diodes (LEDs) with peak wavelengths of 280 and 310 nm to investigate the differences in the wavelength-specific UV-B responses. Irradiation with both UV-LEDs induced gene expression of the transcription factor ELONGATED HYPOCOTYL 5 (HY5), which has a central role in the UVR8 signaling pathway. However, the overall transcriptomic and metabolic responses to 280 and 310 nm UV-LED irradiation were different. Most of the known UV-B-responsive genes, such as salicylic acid, jasmonic acid, and defense-related genes, responded only to 280 nm UV-LED irradiation. Lipids, polyamines and organic acids were the metabolites most affected by 280 nm UV-LED irradiation, whereas the effect of 310 nm UV-LED irradiation on the metabolome was considerably less. Enzymatic genes involved in the phenylpropanoid pathway upstream in anthocyanin biosynthesis were up-regulated only by 280 nm UV-LED irradiation. On the other hand, no enzymatic genes downstream in anthocyanin biosynthesis were induced by the UV-LEDs, but rather, they were down-regulated by 310 nm UV-LED irradiation. These results revealed that the responsivenesses of Arabidopsis to 280 and 310 nm UV-B were significantly different, suggesting that UV-B signaling is mediated by more complex pathways than the current model.

plant biology↗

bioRxiv2019

An integrated approach unravels a crucial structural property for the function of the insect steroidogenic Halloween protein Noppera-bo

Ecdysteroids are the principal insect steroid hormones essential for insect development and physiology. In the last 18 years, several enzymes responsible for ecdysteroid biosynthesis, encoded by Halloween genes, have been identified and well characterized, both genetically and biochemically. However, none of these proteins have yet been characterized at the tertiary structure level. Here, we report an integrated in silico, in vitro, and in vivo analyses of the Halloween glutathione S-transferase (GST) protein, Noppera-bo (Nobo). We determine crystal structures of Drosophila melanogaster Nobo (DmNobo) complexed with glutathione and 17{beta}-estradiol, a DmNobo inhibitor. 17{beta}-estradiol almost fully occupied the putative ligand-binding pocket, and a prominent hydrogen bond formed between Asp113 of DmNobo and 17{beta}-estradiol. Asp113 is essential for inhibiting DmNobo enzymatic activity by 17{beta}-estradiol, as 17{beta}-estradiol does not inhibit and physically interacts less with the Asp113Ala DmNobo point mutant. Asp113 is highly conserved among Nobo proteins, but not among other GSTs, implying that Asp113 is important for endogenous Nobo function. Indeed, a homozygous nobo allele possessing the Asp113Ala point mutation exhibits embryonic lethality with undifferentiated cuticle structure, a phenocopy of complete loss-of-function nobo homozygotes. These results suggest that the nobo family of GST proteins has acquired a unique amino acid residue, which seems to be essential for binding an endogenous sterol substrate to regulate ecdysteroid biosynthesis. This is the first study to reveal the structural characteristics of insect steroidogenic Halloween proteins. This study also provides basic insight into applied entomology for developing a new type of insecticides that specifically inhibit ecdysteroid biosynthesis.\n\nSignificance StatementInsect molting and metamorphosis are drastic and dynamic biological processes and, therefore, have fascinated many scientists. Ecdysteroids represent one class of insect hormones that are indispensable for inducing molting and metamorphosis. It is well known that proteins responsible for catalyzing ecdysteroid biosynthesis reactions are encoded by \"Halloween\" genes, most of which have names of ghosts and phantoms. However, no studies have focused on the structural properties of these biosynthetic proteins. In this study, we addressed this unsolved issue and successfully unraveled a structural property that is crucial for the function of the fruit fly Halloween protein, Noppera-bo (a Japanese faceless ghost). This is the first study to reveal the structural characteristics of an insect steroidogenic Halloween protein.

biochemistry↗