דו״ח מאומת

Premature graying of hair (PGH) being a very common entity for which pharmacotherapy and reversibility are not properly addressed. Therefore, this systematic review was conducted to address these issues. For this relevant study were selected from various databases including PubMed, EMBASE, OVID, Web of science, Scopus, and Google Scholar till January 20, 2019. Studies which reported risk factors, co-morbid conditions associated with PGH, its pharmacotherapy and reversal were included in the study. Although many risk factors are reported in literature, smoking, vitamin deficiency (B12, folic acid, and B7), mineral deficiency (low serum calcium and serum ferritin) are found to be associated with PGH. Other important risk factors are family history of PGH, obesity, high B.P, lack of exercise, drugs, genetic syndromes, dyslipidemia, thyroid disorders, hyperuricemia, and alteration in liver function. PGH is found to be an important marker of CAD, more so in case of smoker. Among different pharmacotherapeutic management options, low grade recommendation (2A) is given to calcium pantothenate, PABA, calcium pantothenate + PABA combination. Anu-tailam is the only herbal agent evaluated in clinical research settings. Finally, treating the accompanying pathologies led to the reversal of the disease in many cases.…

PMID: 32654282

Premature hair graying (PHG) is the early loss of natural hair color, influenced by genetic, biological, and environmental factors. This review discusses the significant psychological impacts of PHG and explores its underlying mechanisms, related health conditions, and available treatments. The review examines the roles of genetics, oxidative stress, and lifestyle factors such as smoking and diet in premature graying. It also considers associated medical conditions and current and emerging treatment options. This overview aims to improve understanding of PHG and its broader implications.…

PMID: 39697103

Melanins are natural pigments of skin, hair and eyes and can be classified into two main types: brown to black eumelanin and yellow to reddish-brown pheomelanin. Biosynthesis of melanins takes place in melanosomes, which are specialized cytoplasmic organelles of melanocytes - dendritic cells located in the basal layer of the epidermis, uveal tract of the eye, hair follicles, as well as in the inner ear, central nervous system and heart. Melanogenesis is a multistep process and begins with the conversion of amino acid L-tyrosine to DOPAquinone. The addition of cysteine or glutathione to DOPAquinone leads to the intermediates formation, followed by subsequent transformations and polymerization to the final product, pheomelanin. In the absence of thiol compounds DOPAquinone undergoes an intramolecular cyclization and oxidation to form DOPAchrome, which is then converted to 5,6-dihydroksyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Eumelanin is formed by polymerization of DHI and DHICA and their quinones. Regulation of melanogenesis is achieved by physical and biochemical factors. The article presents the intracellular signaling pathways: cAMP/PKA/CREB/MITF cascade, MAP kinases cascade, PLC/DAG/PKCβ cascade and NO/cGMP/PKG cascade, which are involved in the regulation of expression and activity of the melanogenesis-related proteins by ultraviolet radiation and endogenous agents (cytokines, hormones). Activity of the key melanogenic enzyme, tyrosinase, is also affected by pH and temperature. Many pharmacologically active substances are able to inhibit or stimulate melanin biosynthesis, as evidenced by in vitro studies on cultured pigment cells.…

PMID: 27356601

Tyrosinases are nearly ubiquitously distributed in all domains of life. They are essential for pigmentation and are important factors in wound healing and primary immune response. Their active site is characterized by a pair of antiferromagnetically coupled copper ions, CuA and CuB, which are coordinated by six histidine residues. Such a "type 3 copper centre" is the common feature of tyrosinases, catecholoxidases and haemocycanins. It is also one of several other copper types found in the multi-copper oxidases (ascorbate oxidase, laccase). The copper pair of tyrosinases binds one molecule of atmospheric oxygen to catalyse two different kinds of enzymatic reactions: (1) the ortho-hydroxylation of monophenols (cresolase activity) and (2) the oxidation of o-diphenols to o-diquinones (catecholase activity). The best-known function is the formation of melanins from L-tyrosine via L-dihydroxyphenylalanine (L-dopa). The complicated hydroxylation mechanism at the active centre is still not completely understood, because nothing is known about their tertiary structure. One main reason for this deficit is that hitherto tyrosinases from eukaryotic sources could not be isolated in sufficient quantities and purities for detailed structural studies. This is not the case for prokaryotic tyrosinases from different Streptomyces species, having been intensively characterized genetically and spectroscopically for decades. The Streptomyces tyrosinases are non-modified monomeric proteins with a low molecular mass of ca. 30kDa. They are secreted to the surrounding medium, where they are involved in extracellular melanin production. In the species Streptomyces, the tyrosinase gene is part of the melC operon. Next to the tyrosinase gene (melC2), this operon contains an additional ORF called melC1, which is essential for the correct expression of the enzyme. This review summarizes the present knowledge of bacterial tyrosinases, which are promising models in order to get more insights in structure, enzymatic reactions and functions of "type 3 copper" proteins in general.…

PMID: 16423650

Tyrosinase (EC 1.14.18.1) is a binuclear copper enzyme responsible for the rate-limiting steps of melanogenesis, catalyzing the hydroxylation of L-tyrosine and oxidation of L-DOPA into o-quinones that polymerize melanin. Beyond its physiological role in pigmentation, tyrosinase is also implicated in food browning and oxidative stress-related disorders, making it a key target in cosmetic, food, and biomedical industries. This systematic review, conducted following PRISMA guidelines, aimed to identify and analyze microbial metabolites with tyrosinase inhibitory potential as sustainable alternatives to conventional inhibitors such as hydroquinone and kojic acid. Literature searches in Scopus and Web of Science (March 2025) yielded 156 records; after screening and applying inclusion criteria, 11 studies were retained for analysis. The inhibitors identified include indole derivatives, phenolic acids, peptides, and triterpenoids, mainly produced by fungi (e.g., <i>Ganoderma lucidum</i>, <i>Trichoderma</i> sp.), actinobacteria (<i>Streptomyces</i>, <i>Massilia</i>), and microalgae (<i>Spirulina</i>, <i>Synechococcus</i>). Reported IC₅₀ values ranged from micromolar to milli-molar levels, with methyl lucidenate F (32.23 µM) and <i>p</i>-coumaric acid (52.71 mM). Mechanisms involved competitive and non-competitive inhibition, as well as gene-level regulation. However, methodological heterogeneity, the predominance of mushroom tyrosinase assays, and limited human enzyme validation constrain translational relevance. Computational modeling, site-directed mutagenesis, and molecular dynamics are proposed to overcome these limitations. Overall, microbial metabolites exhibit promising efficacy, stability, and biocompatibility, positioning them as emerging preclinical candidates for the development of safer and more sustainable tyrosinase inhibitors.…

PMID: 41596661

The production of pigment in mammalian melanocytes requires the contribution of at least three melanogenic enzymes, tyrosinase and two other accessory enzymes called the tyrosinase-related proteins (Trp1 and Trp2), which regulate the type and amount of melanin. The last two proteins are paralogues to tyrosinase, and they appeared late in evolution by triplication of the tyrosinase gene. Tyrosinase is a copper-enzyme, and Trp2 is a zinc-enzyme. Trp1 has been more elusive, and the direct identification of its metal cofactor has never been achieved. However, due to its enzymatic activity and similarities with tyrosinase, it has been assumed as a copper-enzyme. Recently, recombinant human tyrosinase and Trp1 have been expressed in enough amounts to achieve for the first time their crystallization. Unexpectedly, it has been found that Trp1 contains a couple of Zn(II) at the active site. This review discusses data about the metal cofactor of tyrosinase and Trps. It points out differences in the studied models, and it proposes some possible points accounting for the apparent discrepancies currently appearing. Moreover, some proposals about the possible flexibility of the tyrosinase family to uptake copper or zinc are discussed.…

PMID: 29473882

Non-neuronal dopamine production has not been understood despite dopamine function in non-neuronal tissues. Tyrosinase is a non-neuronal enzyme which converts tyrosine to L-DOPA (l-3,4-dihydroxyphenylalanine) and L-DOPA to l-dopaquinone for further melanin production. Since L-DOPA is a dopamine precursor in neurons, we hypothesized that tyrosinase-derived L-DOPA could alternatively be converted to dopamine. Therefore, this study investigated whether copper supplementation enhanced pigmentation and induced dopamine production via tyrosinase activation in APRE19 cells. Copper is known as a tyrosinase cofactor. In two separate experiments, we cultured ARPE19 in 1% FBS/DMEM with/without 10 μM copper sulfate for approximately 100 days. After 40-50 days, slight pigmentation with copper treatment was confirmed in the cell pellets, while no pigmentation was observed in the non-copper control. After 90-100 days, the pigmentation in the copper treatment group was obvious, while minimal pigmentation was observed in the non-copper control. Dopamine was not detected at 40-50 days in either group, while it was detected after 90-100 days of culture only in the copper-treated group. Tyrosinase mRNA expression was confirmed in both groups at a similar level, while tyrosinase protein expression was significantly higher in the copper treatment group than in the non-copper control. Thus, we determined that copper supplementation efficiently enhances pigmentation and induces dopamine production in long-term culture ARPE19, likely due to increased tyrosinase protein expression and activity. This is the first report showing the significance of copper in non-neuronal dopamine production of RPE cells, which suggests that tyrosinase may be responsible for non-neuronal dopamine production.…

PMID: 40591716

Copper is a cofactor for many cellular enzymes and transporters. It can be loaded onto secreted and endomembrane cuproproteins by translocation from the cytosol into membrane-bound organelles by ATP7A or ATP7B transporters, the genes for which are mutated in the copper imbalance syndromes Menkes disease and Wilson disease, respectively. Endomembrane cuproproteins are thought to incorporate copper stably on transit through the trans-Golgi network, in which ATP7A accumulates by dynamic cycling through early endocytic compartments. Here we show that the pigment-cell-specific cuproenzyme tyrosinase acquires copper only transiently and inefficiently within the trans-Golgi network of mouse melanocytes. To catalyse melanin synthesis, tyrosinase is subsequently reloaded with copper within specialized organelles called melanosomes. Copper is supplied to melanosomes by ATP7A, a cohort of which localizes to melanosomes in a biogenesis of lysosome-related organelles complex-1 (BLOC-1)-dependent manner. These results indicate that cell-type-specific localization of a metal transporter is required to sustain metallation of an endomembrane cuproenzyme, providing a mechanism for exquisite spatial control of metalloenzyme activity. Moreover, because BLOC-1 subunits are mutated in subtypes of the genetic disease Hermansky-Pudlak syndrome, these results also show that defects in copper transporter localization contribute to hypopigmentation, and hence perhaps other systemic defects, in Hermansky-Pudlak syndrome.…

PMID: 18650808

Copper (Cu) is an essential trace element for many biological processes. Cu homeostasis is generally well maintained by inbuilt controls in intestinal absorption, biliary excretion and intrahepatic storage. Copper deficiency disorders are rare. Acute Cu toxicity occurs occasionally in accidental poisoning with Cu sulfate. Chronic Cu toxicity in the form of liver cirrhosis and damage to other organs is seen classically in Wilson's Disease (genetic abnormality of Cu metabolism) and in the presumed environmental disorder Indian Childhood Cirrhosis (ICC). The clinical, epidemiological and treatment aspects of ICC are described. The evidence linking ICC to environmental Cu is (i) greatly increased hepatic Cu; (ii) early introduction of Cu contaminated milk boiled or stored in brass vessels; (iii) dramatic decline in ICC throughout the country coincident with change in feeding vessels; and (iv) continued long-term remission in d-penicillamine-treated patients after withdrawal of the drug. The nature and role of a second factor in the causation of ICC remains unclear, although a genetic predisposition is strongly suspected. Scattered reports of an ICC-like illness from the West (Idiopathic Cu Toxicosis, Endemic Tyrolean Infantile Cirrhosis), suggest that different mechanisms (environmental, genetic or both) can lead to the same end stage liver disease-'ecogenetic' disorders.…

PMID: 12472971