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Diseases of the Nervous System
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
Neurological impairments in this condition include speech defects, convulsions, and ataxia. There are, however, normal individuals who do not exhibit severe abnormality of mental function. This inborn error is related to an anomaly in histidine metabolism.54 Normally, the most important pathways in the conversion of this amino acid are the formation of formiminoglutamic acid and glutamic acid via urocanic acid (Figure 24). In patients with histidinemia, the transformation of histidine to urocanic acid is interrupted. In consequence, histidine accumulates in blood and cerebrospinal fluid. The urinary excretion of histidine and its metabolites is elevated, and as expected from the location of the enzyme, urocanic acid is absent from the perspiration of the affected subjects.
Photoimmunology: Effects of Ultraviolet B Radiation on Cutaneous Photocarcinogenesis and Allergic Contact Sensitivity
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
Ponciano D. Cruz, Paul R. Bergstresser
Urocanic acid is synthesized normally in skin in the trans-isomerized form via deamination of the amino acid histidine within keratinocytes. Following absorption of UVB radiation, trans-urocanic acid is converted to the cis-isomer. In vivo studies in mice and in vitro systems have indicated that cis-urocanic acid can induce suppression of T-cell-mediated responses directed at contact sensitizers and viral antigens (37–39). In a report in hairless mice, it was also suggested that ds-urocanic acid can act as a promoter for UVB-induced squamous cell cancer (40).
Effects of solar radiation, air pollution, and artificial blue light on the skin
Published in Roger L. McMullen, Antioxidants and the Skin, 2018
As a major chromophore component of the stratum corneum, trans-urocanic acid has received considerable attention in the literature. It is derived from the metabolism of histidine during the decomposition of filaggrin during epidermal differentiation. The absorption spectrum and chemical structure of trans-urocanic acid is provided in Figure 4.7.14 The large absorption peak in the UVB region of the spectrum is thought to offer a great deal of protection for cellular amino acids and nucleic acid bases. On the other hand, trans-urocanic acid undergoes photoisomerization to cis-urocanic acid when exposed to UV irradiation, optimally at 300–310 nm. This transformation results in photosensitization and plays a major role in photoimmunosuppression.
The study of metabolism and metabolomics in a mouse model of silica pulmonary fibrosis based on UHPLC-QE-MS
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2022
Min Qiu, Ling Qin, Yonghe Dong, Junbing Ma, Zheng Yang, Zhixiang Gao
The control vs. 2 mg silica group showed dysregulated histidine metabolism, and the levels of l-histidine and urocanic acid involved in this pathway increased significantly. l-Histidine plays an important role in many biological processes such as proton buffering, scavenging of reactive oxygen species and erythropoiesis [19]. The increase in l-histidine levels may indicate that the physiological defence processes such as proton buffering and scavenging of reactive oxygen species cannot be executed normally. During histidine metabolism, histidine is enzymatically transformed into urocanic acid, which is eventually converted into glutamate, which in turn can be converted into the antioxidant glutathione in the body. The increased levels of l-histidine and urocanic acid may indicate the imbalance in histidine metabolism and the disruption of normal body function under the influence of silica [20].
Anti-inflammatory effect of Arnica montana in a UVB radiation-induced skin-burn model in mice
Published in Cutaneous and Ocular Toxicology, 2020
Josiéle da Silva Prade, Eveline Costeira Bálsamo, Franciele Romero Machado, Márcia Rósula Poetini, Vandreza Cardoso Bortolotto, Stífani Machado Araújo, Larissa Londero, Silvana Peterini Boeira, Carla Pohl Sehn, Marcelo Gomes de Gomes, Marina Prigol, Leandro Cattelan Souza
UVB-induced skin damage is generally associated with overproduction of ROS and depletion of antioxidant defence mechanisms25. UV radiation is absorbed by various chromophores in the skin, such as melanin, DNA, RNA, proteins, aromatic amino acids, such as tyrosine and tryptophan, urocanic acid, among others25,26. This absorption of UV radiation generates different photochemical reactions and secondary interactions, which ultimately produce ROS and result in a harmful effect when exposure occurs in excess25,26. It has been shown that chronic exposure to UVB can lead to skin carcinogenesis and early skin aging27. Moreover, UVB radiation has extensive biological effects on the skin, leading to a variety of adverse skin reactions including erythema, edema, burns, hyperplasia, inflammation and immunosuppression28,29.
Insights into future therapeutics for atopic dermatitis
Published in Expert Opinion on Pharmacotherapy, 2018
Taylor Edwards, Nupur U. Patel, Amy Blake, Samantha Prabakaran, Danielle Reimer, Steven R. Feldman, Lindsay C. Strowd
Urocanic acid (UCA) produces natural moisturizing factor, a component that has been studied in the pathogenesis of AD for many years [19]. When epidermal levels of UCA are decreased, the pH of the skin is not as well regulated and AD is more severe. Cis-UCA is a topical cream thought to improve barrier function of the skin by suppressing inflammation and restoring the pH [19]. In a study of patients with AD, 5% cis-UCA emulsion cream decreased transepidermal water loss and erythema more than vehicle in patients with mild-to-moderate AD within 10 days of use. Improved physician global assessment (PGA) and EASI were also seen to a greater degree in the 5% cis-UCA arm but results were not statistically significant [19]. One phase 2 trial comparing 2.5% and 5% cis-UCA emulsion cream to placebo and 0.1% protopic ointment in adult patients with moderate or severe chronic AD has been completed but results are not yet published (NCT01320579).