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Chemopreventive Agents
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
Ergothioneine (Figure 12.35) is an unusual naturally occurring amino acid with significant antioxidant activity. Structurally, it is identical to the amino acid histidine (in the betaine or zwitterion form) except for the addition of a thiol group at the C2-position of the 5-membered imidazole ring. It was discovered in 1909 in the sclerotia of Claviceps purpurea (the ergot fungus) which gave rise to its name, and was subsequently found in semen, blood, and various mammalian tissues such as the kidneys and liver. Its structure was determined much later in 1911, and it was not synthesized until 1951. It is claimed to be an “antioxidant vitamin” with cancer chemopreventive and cardiovascular properties, and is available worldwide as a dietary supplement. Structures of the two canonical forms of ergothioneine, the thione and thiol species. The thione form is the most stable species in solution, which means that the C2-sulfur atom of ergothioneine is less nucleophilic compared to other cellular thiols such as glutathione.
Inhalation Toxicity of Metal Particles and Vapors
Published in Jacob Loke, Pathophysiology and Treatment of Inhalation Injuries, 2020
Zinc, cadmium, and mercury form strong covalent bonds resulting in stable chelates. This particularly affects thiol groups, which are frequently an active component of the structure of enzymes and so act as a major focus for the toxic action of these metals. The relative affinity for thiol groups is Hg > Cd > Zn. Zn is least toxic, being an essential trace element for which the body has homeostatic control. There is no homeostatic control for either Hg or Cd. Mercury toxicity is higher than that of cadmium because of its greater electropositivity, solubility, absorbability, and tissue penetration. Both have a cumulative effect which is eventually toxic.
Radiation Syndromes and Their Modifications
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
The thiols include cysteine, 2-mercaptoethylamine (cysteamine), cystamine, aminoethylisothiourea dihydrobromide (AET), and 2-mercaptoethylguanidine (MEG). Sulfhydryl (SH) amines are strong reducing agents at physiological temperature and pH. The DRF values for various compounds varies from 1.4 to 2.0. Other features of these compounds are described below.
Evaluation of the role of thiol / disulfide homeostasis in the etiology of idiopathic male infertility with a novel and automated assay
Published in Systems Biology in Reproductive Medicine, 2022
Uygar Micoogullari, Mehmet Caglar Cakici, Furkan Umut Kilic, Erdem Kisa, Burak Ozcift, Alper Caglayan, Salim Neselioglu, Omer Faruk Karatas, Ozcan Erel
Thiol-disulfide homeostasis is vital because it is involved in numerous functions such as detoxification, apoptosis, antioxidant protection, signal transduction, as well as regulation of transcription factors, enzymatic activity, and signaling mechanisms (Circu and Aw 2010; Erel and Neselioglu 2014; Cabrillana et al. 2016; Alsalman et al. 2018). Thiols have strong antioxidant capacities in their sulfhydryl groups, containing sulfur and hydrogen atoms covalently bonded to a carbon atom. This disulfide bond is also called a disulfide bridge or SS-bond. Total thiol represents the total number of reducible/oxidizable sulfur atoms in serum. It denotes both the two sulfides in each disulfide and the sum of one sulfur atom in each native thiol. Thiols play a crucial role in protecting cells from the harmful effects of ROS (Erel and Neselioglu 2014; Eren et al. 2015). The majority of the plasma thiol pool consists primarily of albumin and other proteins. A small portion consists of low molecular weight thiols such as glutathione, cysteine, cysteinyl glycine, γ-glutamylcysteine, and homocysteine (Erel and Neselioglu 2014). ROS oxidize thiol groups of proteins, cysteine residues, and low molecular weight compounds to form reversible disulfide bond structures. The thiol-disulfide balance can be reached by reducing those disulfide bonds to thiols again. Thiols in the blood are oxidized first in response to an increase in ROS (Erel and Neselioglu 2014).
Copper and levonorgestrel containing intrauterine devices: comparison of their effect on oxidative stress markers
Published in Gynecological Endocrinology, 2021
Gul Nihal Buyuk, Z. Asli Oskovi-Kaplan, Hatice Kansu-Celik, Salim Neselioglu, Ozcan Erel, Yaprak Engin-Ustun
Reactive oxygen radical species are produced during the aerobic metabolic pathways and these species play a role in signal transduction, enzyme activation, immune functions, gene expression, apoptosis and production in disulfide bonds in newly synthesized proteins [7]. When the balance of the reactive oxygen species and the antioxidants are impaired, oxidative stress is mentioned. There are several markers of the increased oxidative stress. Thiols are organic molecules which contain sulfhydryl group as an antioxidant and they eliminate the reactive oxygen radicals by using non-enzymatic pathways and play an important role in detoxification [8]. Thiol/disulfide homeostasis plays an important role in antioxidant protection, detoxification, signal transduction, apoptosis, regulation of enzymatic activity and transcription factors, and cellular signaling mechanisms. The parameters of the thiol-disulfide homeostasis are native thiol, total thiol and disulfide ratios and they are proposed as a novel marker for oxidative stress [8]. Abnormal thiol/disulfide homeostasis state is involved in the pathogenesis of various acute and chronic diseases [9–11].
Does plasma thiol and disulphide be a new marker for prostate cancer in prostate-specific antigen level between 10 and 20 ng/ml?
Published in The Aging Male, 2020
Ramazan Topaktaş, Ahmet Ürkmez, Musab Ali Kutluhan, Selahattin Çalışkan, Özcan Erel
Oxidative stress due to excessive production of reactive oxygen species causes damages to DNA, protein, and lipids. Oxidative protein damage causes irreversible modifications in serum and tissue proteins. Thiols are essential and potent anti-oxidant molecules containing a functional sulfhydryl group protecting organism against the harmful effects of oxidative stress damage. In 2014, Erel et al. defined thiol/disulphide homeostasis for the first time and demonstrated its measurability in serum [7]. These disulphide bonds can be reduced back to the thiols, resulting in the formation of a dynamic thiol/disulphide homeostasis, which plays a crucial role in antioxidation, and, therefore, it is believed that to play a role in the pathogenesis of numerous diseases such as diabetes, coronary artery disease, and cancer [8–10]. We also investigated the clinical importance of thiol and disulphide in patients with 2.5 and 20 ng/mL PSA levels. According to the results of our literature search, this is the first known study on the comparison of thiol, disulphide and PSA in the diagnosis of PCa thus our study provides original data on this important issue. The present study, plasma native thiol, total thiol, and disulphide levels were investigated as an alternative marker to PSA in the diagnosis of PCa in our tertiary referral center.