Tyrosinase Expression Research Articles

Inhibitory potential of 7-hydroxycoumarin-3-carboxylic acid against tyrosinase and its effect on the preservation of fresh-sliced apples

Excessive tyrosinase expression leads to pigmented diseases in humans and browning in plants, necessitating effective tyrosinase inhibitors. This study investigated the inhibitory effect and mechanism of 7-hydroxycoumarin-3-carboxylic acid (7-HC-3-CA) on tyrosinase. Using UV–visible absorption spectroscopy, we found that 7-HC-3-CA effectively inhibited tyrosinase activity, with an IC50 value of 364 ± 1.3 μM. Enzyme kinetics, fluorescence methods and molecular simulation techniques revealed that 7-HC-3-CA acted as a reversible and competitive inhibitor, forming a stable complex with tyrosinase through hydrophobic interactions and hydrogen bonding. This altered the microenvironment of Tyr and Trp residues, causing the structural stretching and conformational changes that diminish catalytic activity.Preservation experiments demonstrated that 0.5 mM 7-HC-3-CA significantly reduced mass loss and decreased browning of fresh-sliced apples. It also lowered polyphenol oxidase activity from 0.22 to 0.18 and delayed phenolic oxidation, enhancing total phenolic content from 0.34 to 0.54, thereby controlling browning and extending storage life. Cell assays indicated that 0.5 mM 7-HC-3-CA had no significant impact on cell proliferation, with viability over 80 %. Acute toxicity tests proved that 0.5 mM of 7-HC-3-CA is completely non-lethal to KM mice. In conclusion, this study confirmed 7-HC-3-CA was a viable and safe antibrowning agent and revealed its potential application in the field of food preservation.

Modelling human neuronal catecholaminergic pigmentation in rodents recapitulates age-related neurodegenerative deficits

One key limitation in developing effective treatments for neurodegenerative diseases is the lack of models accurately mimicking the complex physiopathology of the human disease. Humans accumulate with age the pigment neuromelanin inside neurons that synthesize catecholamines. Neurons reaching the highest neuromelanin levels preferentially degenerate in Parkinson’s, Alzheimer’s and apparently healthy aging individuals. However, this brain pigment is not taken into consideration in current animal models because common laboratory species, such as rodents, do not produce neuromelanin. Here we generate a tissue-specific transgenic mouse, termed tgNM, that mimics the human age-dependent brain-wide distribution of neuromelanin within catecholaminergic regions, based on the constitutive catecholamine-specific expression of human melanin-producing enzyme tyrosinase. We show that, in parallel to progressive human-like neuromelanin pigmentation, these animals display age-related neuronal dysfunction and degeneration affecting numerous brain circuits and body tissues, linked to motor and non-motor deficits, reminiscent of early neurodegenerative stages. This model could help explore new research avenues in brain aging and neurodegeneration.

Spitz melanoma with MAP3K8::ABLIM1 rearrangement: a case report with review of the literature

BackgroundSpitz tumors are relatively uncommon melanocytic lesions, typically affecting a relatively younger population but can be encountered at any age. They are characterized by a proliferation of melanocytes with epithelioid and/or spindled cytomorphology features, and interpretation is often challenging. The majority of these tumors are driven by kinase fusions or HRAS mutations. MAP3K8 fusions, although rare, are characteristic genomic events in Spitz tumors, especially in more atypical or malignant lesions.Case presentationHere, we present the case of a 43-year-old woman with a clinically cystic mass in her right groin, histologically characterized as a spindle and epithelioid cell malignant tumor. Immunohistochemistry revealed diffuse expression of S100 protein, tyrosinase and SOX10, patchy weak PRAME, HMB45 and Melan-A reactivity, and negative staining for BRAF V600E. Next-generation sequencing analysis revealed the presence of a MAP3K8::ABLIM1 fusion gene, as well as GRIN2A and TERT promoter mutations. The morphology, immunohistochemistry and molecular analysis confirmed Spitz melanoma with molecular features suggesting a worse prognosis.ConclusionThis case introduces a novel fusion partner of MAP3K8 in the context of Spitz melanoma and expands the morphologic and molecular spectrum of Spitz melanoma.

Anti-Melanogenic Effects of a Polysaccharide Isolated from Undaria pinnatifida Sporophyll Extracts.

Undaria pinnatifida is a temperate brown alga known to exert free radical-scavenging and anti-inflammatory effects. In this study, we investigated the skin-whitening effects of U. pinnatifida sporophyll extracts (UPEs) in α-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 melanoma cells. The crude polysaccharide fraction (UPF) was obtained via ethanol precipitation. Four polysaccharide fractions (UPF1-4) were isolated and purified using ion-exchange column chromatography, and their anti-melanogenic activity was evaluated. UPF3 exhibited the highest anti-melanogenic activity, showing the highest sulfate (39.79%), fucose (143 μg/mg), and galactose (208 μg/mg) contents. UPF3 significantly inhibited intracellular tyrosinase activity in B16F10 cells. We also evaluated the melanogenic signaling pathway to determine the mechanism of action of UPF3 in melanongenesis. UPF3 reduced the expression of tyrosinase-related protein-1 (TRP-1), tyrosinase-related protein-2 (TRP-2), and tyrosinase, which play important roles in melanin production. Therefore, UPF3 has high potential for use in skin-whitening functional pharmaceuticals and cosmetics.

Heterologous expression of bacterial tyrosinase and its applications in biological hair dyeing and DOPA modification of hydrolyzed silk fibroin

Tyrosinase is a copper-containing polyphenol oxidase widely applied in the food, cosmetics, pharmaceutical, and other industries. Currently, the production of commercial tyrosinase primarily relies on extraction from fungi, which has high costs, low purity, low specific activity, and poor stability. The objective of this study is to obtain highly expressed bacterial tyrosinase with potential for industrial applications. The bacterial tyrosinases from five different sources were heterologously expressed in Escherichia coli BL21(DE3), and the tyrosinases TyrBm and TyrVs derived from Bacillus megaterium and Verrucomicrobium spinosum were obtained with the enzyme activities of (16.1±0.2) U/mL and (48.6±0.9) U/mL, respectively. After protein purification, we compared the enzymatic properties of TyrBm and TyrVs, which revealed that TyrVs exhibited better thermal stability and higher substrate specificity than TyrBm. On the basis of characterizing TyrVs with high catalytic performance, we established a biological hair dyeing system based on TyrVs catalysis to achieve in-situ catalytic hair dyeing. The color washing fastness test measured the ∆E value less than 7.38±0.64 after simulated 14-day cleaning. To facilitate the rapid separation of catalytic products and enzymes, we successfully constructed an immobilized enzyme TyrVs-CipA dependent on self-assembly label CipA and applied this enzyme in the DOPA modification of hydrolyzed silk fibroin (HSF). The immobilized enzyme continuously catalyzed HSF for more than seven cycles, resulting in a single DOPA modification degree exceeding 70.00%. Further investigations demonstrated that DOPA modification enhances the scavenging activity of HSF towards DPPH and O2- radicals by 507.80% and 78.23%, respectively. This study provides a technical foundation for the development of environmentally friendly biological hair dye based on tyrosinase and biomaterials for tissue engineering.

Enhancing Anti-Hyperpigmentation Efficacy: A Review on Herbal Nanodelivery System

Hyperpigmentation refers to a condition characterized by excessive skin pigmentation, leading to darkened areas on the skin. This condition can significantly affect physical appearance and have adverse effects on emotional and psychological well-being. The use of commercial skinlightening products for hyperpigmentation therapy often entails significant side effects, prompting the exploration and development of herbal products as alternative anti-hyperpigmentation agents. Herbs act as anti-hyperpigmentation agents through various mechanisms, including inhibiting the expression and activity of tyrosinase, as well as reducing the uptake and distribution of melanosomes. The advancement of nanoparticle delivery systems represents a significant stride in enhancing the efficacy of herbal compounds, overcoming the limitations associated with conventional phytochemical formulations. Herbal plants incorporated into nanoparticle delivery systems demonstrate superior activity as anti-hyperpigmentation agents compared to their conventional extract counterparts. Various nanoparticle formulations employed include zinc oxide and gold nanoparticles, nanovesicles, nanosponges, nanoliposomes, Nanostructured Lipid Carriers (NLC), and Solid Lipid Nanoparticles (SLN). This narrative review aims to explore natural ingredients, diverse nanoparticle formulations, and the impacts of nanoparticle delivery of herbs as anti-hyperpigmentation agents, drawing insights from both preclinical and clinical studies. This review is intended to provide a foundation for the future development of herbal nanoparticle delivery systems.

Deoxyarbutin targets mitochondria to trigger p53-dependent senescence of glioblastoma cells

Cellular senescence is a natural barrier of the transition from premalignant cells to invasive cancer. Pharmacological induction of senescence has been proposed as a possible anticancer strategy. In this study, we found that deoxyarbutin inhibited the growth of glioblastoma (GBM) cells by inducing cellular senescence, independent of tyrosinase expression. Instead, deoxyarbutin induced mitochondrial oxidative stress and damage. These aberrant mitochondria were key to the p53-dependent senescence of GBM cells. Facilitating autophagy or mitigating mitochondrial oxidative stress both suppressed p53 expression and alleviated cellular senescence induced by deoxyarbutin. Thus, our study reveals that deoxyarbutin induces mitochondrial oxidative stress to trigger the p53-dependent senescence of GBM cells. Importantly, deoxyarbutin treatment resulted in accumulation of p53, induction of cellular senescence, and inhibition of tumor growth in a subcutaneous tumor model of mouse. In conclusion, our study reveals that deoxyarbutin has therapeutic potential for GBM by inducing mitochondrial oxidative stress for p53-dependent senescence of GBM cells.

Antioxidant and Skin-Whitening Efficacy of a Novel Decapeptide (DP, KGYSSYICDK) Derived from Fish By-Products.

The skin is vulnerable to damage from ultraviolet rays and oxidative stress, which can lead to aging and pigmentation issues. This study investigates the antioxidant and whitening efficacy of a decapeptide (DP, KGYSSYICDK) derived from marine fish by-products and evaluates its potential as a new skin-whitening agent. DP demonstrated high antioxidant activity, showing comparable or superior performance to Vitamin C (Vit. C) in ferric reducing antioxidant power (FRAP) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. In hydrogen peroxide (H2O2)-treated HaCaT cells, DP increased cell viability and reduced reactive oxygen species (ROS) generation. Furthermore, DP inhibited tyrosinase activity and decreased melanin production in α-melanocyte stimulating hormone (α-MSH)-induced B16F10 melanoma cells in a dose-dependent manner. Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that DP reduces the mRNA expression of MITF, tyrosinase, and MC1R, thus suppressing melanin production. DP exhibits strong binding interactions with multiple amino acid residues of tyrosinase, indicating potent inhibitory effects on the enzyme. These results suggest that DP possesses significant antioxidant and whitening properties, highlighting its potential as a skin-whitening agent. Future research should focus on optimizing DP's structure and exploring structure-activity relationships.

Melanin Synthesis Gene Inhibition Effect through Inhibition of Tyrosinase and TRPs Expression of Coriandrum sativum-derived Exosome

Purpose: This study investigated the skin-whitening effects achieved through suppressing melanin synthesis using exosomes derived from Coriandrum sativum (C. sativum). Methods: We examined the characteristics of C. sativum exosomes (CSEs) using nanoparticle tracking analysis, which revealed an average size of 152.3 nm and a concentration of 3.0×1010 particles/mL. A cytotoxicity evaluation was conducted on B16F0 cells to assess cellular safety of CSEs. We investigated the skin-whitening effects of CSEs by quantifying melanin synthesis gene expression using RT-PCR. Results: CSE concentrations less than 1.5 × 108 particles/mL did not negatively affect cellular activity. Furthermore, CSE treatment significantly decreased the expression of key genes involved in melanin synthesis such as tyrosinase, TRP-1, and TRP-2 by 75.6%, 89.1%, and 88.7%, respectively. Conclusion: CSEs hold promise as functional cosmetic ingredients that promote skin whitening by inhibiting key genes involved in melanin production.

Tyrosinase-induced neuromelanin accumulation triggers rapid dysregulation and degeneration of the mouse locus coeruleus.

The locus coeruleus (LC), the major source of norepinephrine (NE) in the brain, is an early site of pathology in both Alzheimer's disease (AD) and Parkinson's disease (PD), and it undergoes catastrophic degeneration later in both disorders. Dysregulation of the LC is thought to contribute to prodromal symptoms of AD and PD such as anxiety and sleep disturbances, while frank LC-NE loss promotes cognitive decline. However, the mechanisms responsible for its selective vulnerability are unknown. The LC is among the only structures in the brain that produces appreciable amounts of neuromelanin (NM), a dark cytoplasmic pigment. It has been proposed that NM initially plays a protective role by sequestering toxic catecholamine metabolites and heavy metals, but may become harmful during aging as it overwhelms cellular machinery and is released during neurodegeneration. Rodents do not naturally produce NM, limiting the study of causal relationships between NM and LC pathology. Adapting a viral-mediated approach for expression of human tyrosinase, the enzyme responsible for peripheral melanin production, we successfully promoted pigmentation in mouse LC neurons that recapitulates key ultrastructural features of endogenous NM found in primates. Pigment expression results in LC neuron hyperactivity, reduced tissue NE levels, transcriptional changes, and novelty-induced anxiety phenotypes as early as 1-week post-injection. By 6-10 weeks, NM accumulation is associated with severe LC neuron neurodegeneration and microglial engulfment of the pigment granules, while the anxiety-like behavior is abated. These phenotypes are reminiscent of LC dysfunction and cell death in AD and PD, validating this model for studying the consequences of pigment accumulation in the LC as it relates to neurodegenerative disease.

Potential Wound Healing and Anti-Melanogenic Activities in Skin Cells of Aralia elata (Miq.) Seem. Flower Essential Oil and Its Chemical Composition.

Aralia elata (Miq.) Seem. (AES; family Araliaceae) is a medicinal plant and has been reported to have various bioactivities, including anticancer and hepatotoxicity protective activities. However, no studies have investigated the biological activities of AES or its extracts on skin. To address this, we aimed to explore the effect of AES-flower-derived absolute-type essential oil (AESFEO) on skin-related biological activities, especially skin wound healing and whitening-related responses in skin cells (human-derived keratinocytes [HaCaT cells] and melanocytes [B16BL6 cells]) and to identify the components of AESFEO. Cell biological activities were analyzed using WST and BrdU incorporation assays, ELISA, or by immunoblotting. In HaCaT cells, AESFEO promoted proliferation, type IV collagen production, and enhanced the phosphorylations of Erk1/2, p38 MAPK, JNK, and Akt. In B16BL6 cells, AESFEO reduced serum-induced proliferation, α-MSH-stimulated increases in melanin synthesis and tyrosinase activity, and α-MSH-induced increases in MITF, tyrosinase, TRP-1, and TRP-2 expressions. In addition, AESFEO inhibited the phosphorylation of Erk1/2, p38 MAPK, and JNK in α-MSH-stimulated B16BL6 cells. Eighteen compounds were identified in AESFEO by GC/MS. These results suggest that AESFEO has beneficial effects on keratinocyte activities related to skin wound healing and melanocyte activities related to inhibition of skin pigmentation. AESFEO may serve as a useful natural substance for developing agents that facilitate skin wound healing and inhibit melanogenesis.

Inhibitive Mechanism of Loquat Flower Isolate on Tyrosinase Activity and Melanin Synthesis in Mouse Melanoma B16 Cells.

Melanin naturally exists in organisms and is synthetized by tyrosinase (TYR); however, its over-production may lead to aberrant pigmentation and skin conditions. Loquat (Eriobotrya japonica (Thunb.) Lindl.) flowers contain a variety of bioactive compounds, while studies on their suppressive capabilities against melanin synthesis are limited. Loquat flower isolate product (LFP) was obtained by ethanol extraction and resin purification, and its inhibitory efficiency against TYR activity was investigated by enzyme kinetics and multiple spectroscopy analyses. In addition, the impact of LFP on melanin synthesis-related proteins' expression in mouse melanoma B16 cells was analyzed using Western blotting. HPLC-MS/MS analysis indicated that LFP was composed of 137 compounds, of which 12 compounds, including flavonoids (quercetin, isorhamnoin, p-coumaric acid, etc.) and cinnamic acid and its derivatives, as well as benzene and its derivatives, might have TYR inhibitory activities. LFP inhibited TYR activity in a concentration-dependent manner with its IC50 value being 2.8 mg/mL. The inhibition was an anti-competitive one through altering the enzyme's conformation rather than chelating copper ions at the active center. LFP reduced the expression of TYR, tyrosinase-related protein (TRP) 1, and TRP2 in melanoma B16 cells, hence inhibiting the synthesis of melanin. The research suggested that LFP had the potential to reduce the risks of hyperpigmentation caused by tyrosinase and provided a foundation for the utilization of loquat flower as a natural resource in the development of beauty and aging-related functional products.

YTHDF2 Regulates Advanced Glycation End Products-Induced Melanogenesis through Inhibiting A20 Expression in Human Dermal Fibroblasts.

Fibroblast A20 suppresses advanced glycation end products (AGEs)-induced melanogenesis by inhibiting NLRP3 inflammasome activation. AGEs repress A20 expression and significantly m6A-methylate A20 mRNA in fibroblasts. YTHDF2 is the most studied m6A reader protein and can accelerate degradation of m6A-modified mRNA. Whether YTHDF2 regulates AGEs-induced A20 expression and pigmentation is unknown. In this study, we confirmed that YTHDF2 inversely regulated AGEs-BSA-inhibited A20 expression but facilitated AGEs-BSA-activated NF-κB signaling and NLRP3 inflammasome in fibroblasts via YTHDF2 knockdown and overexpression experiments. Mechanistically, YTHDF2 bound to m6A-modified A20 mRNA induced by AGEs-BSA and increased its degradation. Moreover, fibroblast YTHDF2 robustly promoted AGEs-BSA-induced IL-18 level in coculture supernatants and melanin content, tyrosinase activity, and expression of microphthalmia-associated transcription factor and tyrosinase in melanocytes, which were significantly blocked by IL-18 binding protein. Further, fibroblast YTHDF2 markedly increased AGEs-BSA-induced epidermal melanin level in cocultured ex vivo skin and MAPKs activation in melanocytes. Importantly, upregulated dermal YTHDF2 expression was negatively correlated with dermal A20 level and positively associated with both epidermal melanin and dermal AGEs content in sun-exposed skin and lesions of melasma and solar lentigo. These findings suggest that fibroblast YTHDF2 positively regulates AGEs-induced melanogenesis mainly via A20/ NF-κB /NLRP3 inflammasome/ IL-18 /MAPKs axis in an m6A-dependent manner and functions in photoaging-induced hyperpigmentation skin disorders.

Anti-melanogenic effects of porcine placenta peptides through inhibition of tyrosinase expression and activity

Anti-melanogenic effects of porcine placenta peptides through inhibition of tyrosinase expression and activity

Impact of Combined Phototherapy and Melanocyte Transplantation on Indicators of Vitiligo Activity.

To investigate the effect of phototherapy combined with melanocyte transplantation on the activity index of vitiligo. One hundred twenty patients with stable vitiligo were selected and divided into 2 groups: phototherapy group (n = 60) and phototherapy combined with melanocyte therapy group (n = 60). Patients' vitiligo activity scores before and 6 months after treatment, patients' skin pigmentation responses 6 months after treatment, and patients' new Koebner cases 6 months after treatment were compared. The expression of tyrosinase and Melan-A in the skin samples was analyzed by immunohistochemistry. The effect of skin surface repigmentation in the observation group was better than that in the control group (p < .05). The expression of tyrosinase and Melan-A in the observation group was higher than that in the control group (p < .05), indicating that the combined treatment could enhance the function of melanocytes. After 6 months of treatment, the incidence of the Koebner phenomenon in the observation group was lower than that in the control group (p < .05). The combination of phototherapy and melanocyte transplantation can obviously improve the activity index of vitiligo, slow down the spread of white spots, reduce the formation of new white spots, and reduce the occurrence of the Koebner phenomenon.

Tyrosinase inhibition prevents non-coplanar polychlorinated biphenyls and polybrominated diphenyl ethers-induced hyperactivity in developing zebrafish: Interaction between pigmentation and neurobehavior

Non-coplanar polychlorinated biphenyl (PCB) mixture Aroclor 1254 and polybrominated diphenyl ether (PBDE) BDE-47 are known to impede neurogenesis and neuronal development. We previously reported that exposure to PCB and PBDE leads to increased embryonic movement in zebrafish by decreasing dopamine levels. In this study, we studied the connection between the melanin and dopamine synthesis pathways in this context. Both genetic and chemical inhibition of tyrosinase, the rate-limiting enzyme in melanin synthesis, not only led to reduced pigmentation but also inhibit PCB/PBDE-induced embryonic hyperactivity. Furthermore, PCB and PBDE rarely affected tyrosinase expression in the potential pigment cells, suggesting that these compounds reduce dopamine through enzymatic regulation, including a competitive interaction for the substrate tyrosine. Our results provide new insights into the interactions between melanogenesis and dopaminergic neuronal activity, which may contribute to understanding the mechanisms underlying PCB/PBDE toxicity in developing organisms.

Methylsulfonylmethane promotes melanogenesis via activation of JNK in Mel-Ab cells.

Methylsulfonylmethane (MSM), which contains organic sulphur, has been used for a long time as a medicinal ingredient because of its benefits to human health. MSM is reported to be protective against certain skin disorders, but it is unknown whether it affects melanin synthesis. Therefore, in our current research, we examined the possibility of MSM controlling the production of melanin in Mel-Ab melanocytes. In Mel-Ab cells, melanin contents and tyrosinase activities were assessed and quantified. The expression of microphthalmia-associated transcription factor (MITF) and tyrosinase was evaluated using western blot analysis, while MSM-induced signalling pathways were investigated. The MSM treatment significantly resulted in a dose-dependent increase in melanin production. Furthermore, MSM elevated melanin-related proteins, including MITF and tyrosinase. However, the rate-limiting enzyme of melanin production, tyrosinase, was not directly influenced by it. Therefore, we investigated potential melanogenesis-related signalling pathways that may have been triggered by MSM. Our findings showed that MSM did not influence the signalling pathways associated with glycogen synthase kinase 3β, cAMP response-element binding protein, extracellular signal-regulated kinase, or p38 mitogen-activated protein kinase. However, MSM phosphorylated c-Jun N-terminal kinases/stress-activated protein kinase (JNK/SAPK), which is known to induce melanogenesis. SP600125, a specific JNK inhibitor, inhibited MSM-induced melanogenesis. Taken together, our study indicates that MSM induces melanin synthesis and may serve as a therapeutic option for hypopigmentary skin disorders such as vitiligo.

NAcM-OPT protects keratinocytes from H2O2-induced cell damage by promoting autophagy.

This study aimed to investigate the protective effect of NAcM-OPT, a small molecule inhibitor of defective in cullin neddylation 1 (DCN1), on H2O2-induced oxidative damage in keratinocytes. Immortalized human keratinocytes (HaCaT cells) were treated with NAcM-OPT and exposed to oxidative stress. CCK-8 assays were used to measure cell viability. The mGFP-RFP-LC3 dual fluorescent autophagy indicator system was utilized to evaluate changes in autophagic flux. Western blotting was used to measure the expression of the autophagy-related proteins LC3 and Beclin 1. Keratinocytes were treated with the autophagy activator rapamycin, and HaCaT cell supernatant was added to PIG1 cells (immortalized human melanocytes), followed by evaluation of tyrosinase (TYR) expression via qRT-PCR. NAcM-OPT increased cell viability and cell proliferation. Furthermore, this molecule promoted autophagic flux through increased expression of autophagy-related proteins under H2O2-induced oxidative stress. Additionally, rapamycin increased the mRNA levels of TYR in PIG1 cells. Moreover, NAcM-OPT alleviated mitochondrial damage, restored mitochondrial function, and upregulated the expression of NFE2L2, HO1, NQO1, and GCLM. Importantly, NAcM-OPT also increased epidermal thickness, follicle length, and melanin synthesis under oxidative stress in vivo. These findings suggest that NAcM-OPT may be a promising small molecule antioxidant drug for the treatment of vitiligo.

Anti-Melanogenic and Anti-Inflammatory Effects of 2'-Hydroxy-4',6'-dimethoxychalcone in B16F10 and RAW264.7 Cells.

Chalcone is a type of flavonoid compound that is widely biosynthesized in plants. Studies have shown that consuming flavonoids from fruits and vegetables or applying individual ingredients reduces the risk of skin disease. However, the effects of chalcone on melanogenesis and inflammation have not been fully investigated. The aim of this study was to evaluate the anti-melanogenic and anti-inflammatory effects of 2'-hydroxy-3,4'-dimethoxychalcone (3,4'-DMC), 2'-hydroxy-4,4'-dimethoxychalcone (4,4'-DMC), 2'-hydroxy-3',4'-dimethoxychalcone (3',4'-DMC), and 2'-hydroxy-4',6'-dimethoxychalcone (4',6'-DMC). Among the derivatives of 2'-hydroxy-4'-methoxychalcone, 4',6'-DMC demonstrated the most potent melanogenesis-inhibitory and anti-inflammatory effects. As evidenced by various biological assays, 4',6'-DMC showed no cytotoxicity and notably decreased the expression of tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2 enzymes. Furthermore, it reduced cellular melanin content and intracellular tyrosinase activity in B16F10 melanoma cells by downregulating microphthalmia-associated transcription factor (MITF), cAMP-dependent protein kinase (PKA), cAMP response element-binding protein (CREB), p38, c-Jun N-terminal kinase (JNK), β-catenin, glycogen synthase kinase-3β (GSK3β), and protein kinase B (AKT) proteins, while upregulating extracellular signal-regulated kinase (ERK) and p-β-catenin. Additionally, treatment with 4',6'-DMC significantly mitigated the lipopolysaccharide (LPS)-induced expression of NO, PGE2, inflammatory cytokines, COX-2, and iNOS proteins. Overall, 4',6'-DMC treatment notably alleviated LPS-induced damage by reducing nuclear factor kappa B (NF-κB), p38, JNK protein levels, and NF-kB/p65 nuclear translocation. Finally, the topical applicability of 4',6'-DMC was evaluated in a preliminary human skin irritation test and no adverse effects were found. These findings suggest that 4',6'-DMC may offer new possibilities for use as functional ingredients in cosmeceuticals and ointments.

Changes in the level of tyrosinase expression in the retinal pigment epithelium during the development of experimental optic nerve degeneration

BACKGROUND: With optic nerve degeneration of various origins, retinal neurons are the most vulnerable, and their state under these conditions has been studied in sufficient detail. At the same time, the retinal pigment epithelium plays a very important role, realizing the synthesis of melanin and performing antioxidant, phagocytic, transport, protective, and homeostatic functions. Tyrosinase serves as a key enzyme in melanogenesis by cells of this epithelium. The development of methods for early diagnosis of optic nerve atrophy is extremely important due to the fact that functional visual impairments appear later than structural ones, at more advanced stages of the disease. The retinal pigment epithelium cannot be insensitive to the processes that occur during optic nerve degeneration. That is why its study in experimental degeneration of the optic nerve is necessary for a more complete understanding of the processes occurring in the visual analyzer under these conditions. AIM: To study changes in the level of tyrosinase expression in the retinal pigment epithelium at different development stages of experimental optic nerve degeneration based on morphological data. MATERIAL AND METHODS: The subjects of the study were 40 rat eyes after creating a model of optic nerve atrophy using methanol. The animals were divided into five groups: the first group — control; the second to fifth groups included animals whose eyes were enucleated 1, 3, 6 and 9 weeks after the creation of the aminophylline-methanol model of optic nerve atrophy, respectively. The retinal pigment epithelium was studied using fluorescent antibodies to tyrosinase Tyrosinase Mouse Monoclonal. Immunofluorescence staining was performed on fixed transverse sections of the eyeball. Statistical analysis and visualization of the obtained data were carried out using the environment for statistical computing R 4.2.2. RESULTS: A comparative analysis of the results obtained revealed that the level of tyrosinase expression in the fifth group was on average 4.21 times [95% confidence interval (CI) 2.49–7.13, p=0.00076], 9.31 times (95% CI 5.47–15.85, p=0.00033), 2.63 times (95% CI 1.51–4.58, p=0.0009) and 3.44 times (95% CI 1.96–6.03, p=0.00055) higher compared to the first, second, third and fourth groups, respectively. The level of tyrosinase in experimental samples in the first, third and fourth groups was statistically higher compared to the level of tyrosinase in the second group by an average of 2.21 times (95% CI 1.33–3.66, p=0.0003), 3.53 times (95% CI 2.08–6.02, p=0.00069) and 2.71 times (95% CI 1.58–4.65, p=0.00022), respectively. CONCLUSION: As degenerative processes develop in the optic nerve fibers under these conditions, the integrity of the retinal pigment epithelium is disrupted, which is characterized by an increase in antibodies to tyrosinase in the retinal pigment epithelium of experimental animals.