AI molecular property prediction for Parkinson's Disease reveals potential repurposing drug candidates based on the increase of the expression of PINK1.

BACKGROUND AND OBJECTIVE: Parkinson's Disease (PD), a common neurodegenerative disorder and one of the major current challenges in neuroscience and pharmacology, may potentially be tackled by the modern AI techniques employed in drug discovery based on molecular property prediction. The aim of our study was to explore the application of a machine learning setup for the identification of the best potential drug candidates among FDA approved drugs, based on their predicted PINK1 expression-enhancing activity. METHODS: Our study relies on supervised machine learning paradigm exploiting in vitro data and utilizing the scaffold splits methodology in order to assess model's capability to extract molecular patterns and generalize from them to new, unseen molecular representations. Models' predictions are combined in a meta-ensemble setup for finding new pharmacotherapies based on the predicted expression of PINK1. RESULTS: The proposed machine learning setup can be used for discovering new drugs for PD based on the predicted increase of expression of PINK1. Our study identified nitazoxanide as well as representatives of imidazolidines, trifluoromethylbenzenes, anilides, nitriles, stilbenes and steroid esters as the best potential drug candidates for PD with PINK1 expression-enhancing activity on or inside the cell's mitochondria. CONCLUSIONS: The applied methodology allows to reveal new potential drug candidates against PD. Next to novel indications, it allows also to confirm the utility of already known antiparkinson drugs, in the new context of PINK1 expression, and indicates the potential for simultaneous utilization of different mechanisms of action.

Radical Scavenging Is Not Involved in Thymoquinone-Induced Cell Protection in Neural Oxidative Stress Models.

Thymoquinone (TQ), an active compound from Nigella sativa seeds, is often described as a pharmacologically relevant compound with antioxidative properties, while the synthesis of TQ in the plant via oxidations makes it inapplicable for scavenging radicals. Therefore, the present study was designed to reassess the radical scavenging properties of TQ and explore a potential mode of action. The effects of TQ were studied in models with mitochondrial impairment and oxidative stress induced by rotenone in N18TG2 neuroblastoma cells and rotenone/MPP+ in primary mesencephalic cells. Tyrosine hydroxylase staining revealed that TQ significantly protected dopaminergic neurons and preserved their morphology under oxidative stress conditions. Quantification of the formation of superoxide radicals via electron paramagnetic resonance showed an initial increase in the level of superoxide radicals in the cell by TQ. Measurements in both cell culture systems revealed that the mitochondrial membrane potential was tendentially lowered, while ATP production was mostly unaffected. Additionally, the total ROS levels were unaltered. In mesencephalic cell culture under oxidative stress conditions, caspase-3 activity was decreased when TQ was administered. On the contrary, TQ itself tremendously increased the caspase-3 activity in the neuroblastoma cell line. Evaluation of the glutathione level revealed an increased level of total glutathione in both cell culture systems. Therefore, the enhanced resistance against oxidative stress in primary cell culture might be a consequence of a lowered caspase-3 activity combined with an increased pool of reduced glutathione. The described anti-cancer ability of TQ might be a result of the pro-apoptotic condition in neuroblastoma cells. Our study provides evidence that TQ has no direct scavenging effect on superoxide radicals.

The Link between Iron Turnover and Pharmacotherapy in Transplant Patients.

Iron is a transition metal that plays a crucial role in several physiological processes. It can also exhibit toxic effects on cells, due to its role in the formation of free radicals. Iron deficiency and anemia, as well as iron overload, are the result of impaired iron metabolism, in which a number of proteins, such as hepcidin, hemojuvelin and transferrin, take part. Iron deficiency is common in individuals with renal and cardiac transplants, while iron overload is more common in patients with hepatic transplantation. The current knowledge about iron metabolism in lung graft recipients and donors is limited. The problem is even more complex when we consider the fact that iron metabolism may be also driven by certain drugs used by graft recipients and donors. In this work, we overview the available literature reports on iron turnover in the human body, with particular emphasis on transplant patients, and we also attempt to assess the drugs' impact on iron metabolism, which may be useful in perioperative treatment in transplantology.

The Reassessed Potential of SARS-CoV-2 Attenuation for COVID-19 Vaccine Development-A Systematic Review.

Live-attenuated SARS-CoV-2 vaccines received relatively little attention during the COVID-19 pandemic. Despite this, several methods of obtaining attenuated coronaviruses are known. In this systematic review, the strategies of coronavirus attenuation, which may potentially be applied to SARS-CoV-2, were identified. PubMed, Scopus, Web of Science and Embase databases were searched to identify relevant articles describing attenuating mutations tested in vivo. In case of coronaviruses other than SARS-CoV-2, sequence alignment was used to exclude attenuating mutations that cannot be applied to SARS-CoV-2. Potential immunogenicity, safety and efficacy of the attenuated SARS-CoV-2 vaccine were discussed based on animal studies data. A total of 27 attenuation strategies, used to create 101 different coronaviruses, have been described in 56 eligible articles. The disruption of the furin cleavage site in the SARS-CoV-2 spike protein was identified as the most promising strategy. The replacement of core sequences of transcriptional regulatory signals, which prevents recombination with wild-type viruses, also appears particularly advantageous. Other important attenuating mutations encompassed mostly the prevention of evasion of innate immunity. Sufficiently attenuated coronaviruses typically caused no meaningful disease in susceptible animals and protected them from challenges with virulent virus. This indicates that attenuated COVID-19 vaccines may be considered as a potential strategy to fight the threat posed by SARS-CoV-2.

The Reassessed Impact of Nicotine against Neurotoxicity in Mesencephalic Dopaminergic Cell Cultures and Neuroblastoma N18TG2 Cells.

Neuroprotective effects of nicotine are still under debate, so further studies on its effectiveness against Parkinson's disease are required. In our present study, we used primary dopaminergic cell cultures and N18TG2 neuroblastoma cells to investigate the effect of nicotine and its neuroprotective potential against rotenone toxicity. Nicotine protected dopaminergic (tyrosine hydroxylase immunoreactive) neurons against rotenone. This effect was not nAChR receptor-dependent. Moreover, the alkaloid at a concentration of 5 µM caused an increase in neurite length, and at a concentration of 500 µM, it caused an increase in neurite count in dopaminergic cells exposed to rotenone. Nicotine alone was not toxic in either cell culture model, while the highest tested concentration of nicotine (500 µM) caused growth inhibition of N18TG2 neuroblastoma cells. Nicotine alone increased the level of glutathione in both cell cultures and also in rotenone-treated neuroblastoma cells. The obtained results may be helpful to explain the potential neuroprotective action of nicotine on neural cell cultures.

Machine learning enabled identification of potential SARS-CoV-2 3CLpro inhibitors based on fixed molecular fingerprints and Graph-CNN neural representations.

AIM: Rapidly developing AI and machine learning (ML) technologies can expedite therapeutic development and in the time of current pandemic their merits are particularly in focus. The purpose of this study was to explore various ML approaches for molecular property prediction and illustrate their utility for identifying potential SARS-CoV-2 3CLpro inhibitors. MATERIALS AND METHODS: We perform a series of drug discovery screenings based on supervised ML models operating in different ways on molecular representations, encompassing shallow learning methods based on fixed molecular fingerprints, Graph Convolutional Neural Network (Graph-CNN) with its self-learned molecular representations, as well as ML methods based on combining fixed and Graph-CNN learned representations. RESULTS: Results of our ML models are compared both with respect to the aggregated predictive performance in terms of ROC-AUC based on the scaffold splits, as well as on the granular level of individual predictions, corresponding to the top ranked repurposing candidates. This comparison reveals both certain characteristic homogeneity regarding chemical and pharmacological classification, with a prevalence of sulfonamides and anticancer drugs, as well as identifies novel groups of potential drug candidates against COVID-19. CONCLUSIONS: A series of ML approaches for molecular property prediction enables drug discovery screenings, illustrating the utility for COVID-19. We show that the obtained results correspond well with the already published research on COVID-19 treatment, as well as provide novel insights on potential antiviral characteristics inferred from in vitro data.

AI drug discovery screening for COVID-19 reveals zafirlukast as a repurposing candidate.

AIMS: Over the past few years, AI has been considered as potential important area for improving drug development and in the current urgent need to fight the global COVID-19 pandemic new technologies are even more in focus with the hope to speed up this process. The purpose of our study was to identify the best repurposing candidates among FDA-approved drugs, based on their predicted antiviral activity against SARS-CoV-2. MATERIALS AND METHODS: This article describes a drug discovery screening based on a supervised machine learning model, trained on in vitro data encoded in chemical fingerprints, representing particular molecular substructures. Predictive performance of our model has been evaluated using so-called scaffold splits offering a state-of-the-art setup for assessing model's ability to generalize to new chemical spaces, critical for drug repurposing applications. KEY FINDINGS: Our study identified zafirlukast as the best repurposing candidate for COVID-19. SIGNIFICANCE: Zafirlukast could be potent against COVID-19 both due to its predicted antiviral properties and its ability to attenuate the so called cytokine storm. Thus, these two critical mechanisms of action may be combined in one drug as a novel and promising pharmacotherapy in the current pandemic.

Calcium and Phosphate Levels are Among Other Factors Associated with Metabolic Syndrome in Patients with Normal Weight.

BACKGROUND AND PURPOSE: We aimed to assess the association between calcium and phosphorous and metabolic syndrome (MetS) in normal-weight individuals. PATIENTS AND METHODS: The study sample comprised 460 normal-weight (body mass index <25kg/m2) adults aged 18-35 years. The diagnosis of MetS was based on the presence of at least two of the following: 1) systolic blood pressure (SBP) ≥130 mmHg or diastolic blood pressure (DBP) ≥85 mmHg, 2) triglycerides (TG) >150 mg/dl, 3) high-density lipoprotein cholesterol (HDL-C) <1 mmol/in men and <1.2 mmol/l in women, 4) total cholesterol (TC) >5.2 mmol/l, and 5) fasting glucose (FBG) >5.55 mmol/l. RESULTS: Patients with MetS were more often male and slightly older and they had a higher body mass index (BMI) and waist circumference. By definition, patients with MetS had higher levels of BP, GLC, glycated hemoglobin A1c, TC, low-density lipoprotein cholesterol (LDL-C), TG, and apolipoprotein B but significantly lower concentrations of HDL-C and apolipoprotein A. Moreover, subjects with MetS had higher activity of the liver enzymes alanine aminotransferase, alkaline phosphatase and gamma-glutamyl transpeptidase (GGTP). Higher concentrations of uric acid, creatinine and albumin (ALB) were also observed in subjects with MetS. The factors associated with MetS in the multivariate analysis were higher GGTP activity (OR per 5 unit increase - 1.23 (1.11-1.37); p<0.0001), a higher BMI (OR - 1.28 (1.1-1.52); p=0.003), a higher concentration of calcium (OR per 0.1 mmol/l increase - 1.79 (1.21-2.7); p=0.004), higher ALB levels (OR per 5 g/l increase - 1.76 (1.11-2.95), p=0.02); higher phosphorous levels (OR per 0.1 mmol/l increase - 0.82 (0.67-0.99); p=0.04), and a good household situation (odds ratio (OR) - 0.58 95% confidence interval (CI) (0.31-1.07); p=0.08). CONCLUSION: Calcium and phosphorus levels are significantly associated with MetS in normal-weight individuals.

Genetically determined metabolism of nicotine and its clinical significance.

Enzymes of the cytochrome P-450 (CYP 450) which belong to the family of oxidase enzymes, are present in cells of all organisms and play a major role in the first phase of xenobiotic metabolism. There are several isoenzymes of CYP 450 that show differences in the speed of metabolism: poor-, extensive- and ultra-rapid. Nicotine undergoes biotransformation in the liver mainly by the CYP2A6 isoform of CYP 450. There are many polymorphic isoforms of CYP2A6 affecting the metabolism of nicotine. There are also several CYP2A6 activity inhibitors and inducers among commonly used drugs. The ability of CYP2A6 isozymes to activate certain procancerogenic substances present in cigarette smoke makes their polymorphism more significant. Moreover, some isoforms may have also influence on the risk of lung cancer development by affecting the enzymatic activation of tobacco-specific nitrosamines. Metabolism of nicotine, mainly through CYP2A6, has also many clinical implications, such as efficacy and safety of the nicotine replacement therapy (NRT) or occurrence of several diseases. In summary, type of the nicotine metabolism may be a potential predictor of the clinical outcomes in patients with cardiovascular disease, addicted to nicotine and in those using NRT. The purpose of this work is to summarize current knowledge on variation in genetically determined metabolism of nicotine and its clinical significance.

Kanamycin induces free radicals formation in melanocytes: An important factor for aminoglycosides ototoxicity.

Ototoxicity is well-documented but not fully understood undesirable side effect of aminoglycoside antibiotic, kanamycin. Kanamycin is capable of binding to melanin biopolymers-natural pigments of the skin, hair, and eyes. Melanin-producing cells, melanocytes, are also present in the inner ear and are known to be necessary for normal hearing. It was considered that melanin content in the inner ear may influence aminoglycoside-induced ototoxic effect. The impact of kanamycin on melanocytes homeostasis may thus play role in the antibiotic-induced ototoxic effect. Previously, we demonstrated that kanamycin disturbs homeostasis in light-pigmented melanocytes. To investigate if/how melanization contributes to this phenomenon, the study using in vitro model of dark-pigmented melanocytes is required. Spectrophotometric measurements and electron paramagnetic resonance (EPR) spectroscopy analysis were performed. Kanamycin induced a concentration-dependent loss in HEMn-DP melanocytes viability. The value of IC 50 was estimated to be 5.0 mM. Modulation of the activity of analyzed antioxidant enzymes and increased production of free radicals as well as the decrease of the melanin content were observed. Our results confirmed that kanamycin generates oxidative stress in melanocytes. The increased level of free radicals caused by kanamycin may be responsible for the imbalance of antioxidant defense and the reduction of melanin content in melanocytes. The role of melanin in the mechanism of kanamycin-induced hearing impairment was discussed and the obtained results were compared with the previously demonstrated data concerning light-pigmented melanocytes.

Slower nicotine metabolism among postmenopausal Polish smokers.

BACKGROUND: A non-invasive phenotypic indicator of the rate of nicotine metabolism is nicotine metabolite ratio (NMR) defined as a ratio of two major metabolites of nicotine - trans-3'-hydroxycotinine/cotinine. The rate of nicotine metabolism has important clinical implications for the likelihood of successful quitting with nicotine replacement therapy (NRT). We conducted a study to measure NMR among Polish smokers. METHODS: In a cross-sectional study of 180 daily cigarette smokers (42% men; average age 34.6±13.0), we collected spot urine samples and measured trans-3'-hydroxycotinine (3-HC) and cotinine levels with LC-MS/MS method. We calculated NMR (molar ratio) and analyzed variations in NMR among groups of smokers. RESULTS: In the whole study group, an average NMR was 4.8 (IQR 3.4-7.3). The group of women below 51 years had significantly greater NMR compared to the rest of the population (6.4; IQR 4.1-8.8 vs. 4.3; IQR 2.8-6.4). No differences were found among group ages of male smokers. CONCLUSIONS: This is a first study to describe variations in nicotine metabolism among Polish smokers. Our findings indicate that young women metabolize nicotine faster than the rest of population. This finding is consistent with the known effects of estrogen to induce CYP2A6 activity. Young women may require higher doses of NRT or non-nicotine medications for most effective smoking cessation treatment.

Ciprofloxacin-mediated induction of S-phase cell cycle arrest and apoptosis in COLO829 melanoma cells.

BACKGROUND: Low effectiveness of anti-melanoma therapies makes it necessary to search for new drugs that could improve or replace the standard chemotherapy. Fluoroquinolones are a group of synthetic antibiotics, used in the treatment of wide range of bacterial infections. Moreover, this class of antibiotics has shown promising anti-tumor activity in several cancer cell lines. The aim of this study was to examine the effect of ciprofloxacin on cell viability, apoptosis and cell cycle distribution in COLO829 melanoma cells. METHODS: Cell viability was evaluated by the WST-1 assay. Cell cycle distribution and apoptosis in cells exposed to ciprofloxacin was analyzed by the use of fluorescence image cytometer NucleoCounter NC-3000. RESULTS: Ciprofloxacin decreased the cell viability in a dose- and time-dependent manner. For COLO829 cells treated with ciprofloxacin for 24 h, 48 h and 72 h the values of IC50 were found to be 0.74 mM, 0.17 mM and 0.10 mM, respectively. The oligonucleosomal DNA fragmentation was observed when the cells were exposed to ciprofloxacin in concentration of 1.0 mM for 48 h and 72 h. At lower ciprofloxacin concentrations (0.01 mM and 0.1 mM) cells were arrested in S-phase suggesting a mechanism related to topoisomerase II inhibition. Moreover, it was demonstrated that ciprofloxacin induced apoptosis as a result of mitochondrial membrane breakdown. CONCLUSIONS: The obtained results for COLO829 melanoma cells were compared with data for normal dark pigmented melanocytes and the use of ciprofloxacin as a potential anticancer drug for the treatment of melanoma in vivo was considered.

Phototoxic effect of oxytetracycline on normal human melanocytes.

Oxytetracycline is a broad-spectrum antibiotic, used in dermatology and veterinary medicine. Like other tetracyclines, it may evoke skin phototoxic reactions related to generation of reactive oxygen species (ROS). Melanins are biopolymers synthesised in melanocytes - highly specialised cells, localised in the basal layer of epidermis. Production of melanin is a defence mechanism against harmful effects of UV radiation, ROS and many chemical substances, including drugs. In the present study the influence of oxytetracycline and UVA radiation on darkly pigmented melanocytes viability, the melanogenesis process and the activity of antioxidant enzymes were analysed. The obtained results show that oxytetracycline decreases cell viability in a dose-dependent manner. It has also been stated that UVA radiation as well as simultaneous exposure to oxytetracycline and UVA radiation reduce melanocytes viability. The tested drug alone exhibits little effect on antioxidant enzymes activity and has no influence on the synthesis of melanin. However, simultaneous exposure of the cells to oxytetracycline and UVA radiation causes an increase of SOD and GPx activity, a decrease of CAT activity as well as stimulates melanogenesis. The obtained results suggest that phototoxicity of oxytetracycline towards normal human melanocytes depends on both time of UVA exposure and the drug concentration.

UVA radiation augments cytotoxic activity of psoralens in melanoma cells.

PURPOSE: Melanoma is an aggressive form of skin cancer. The aim of the study was to evaluate the influence of UVA radiation and psoralens: 5-methoxypsoralen (5-MOP) or 8-methoxypsoralen (8-MOP) on melanoma cells viability. MATERIALS AND METHODS: The amelanotic C32 and melanotic COLO829 human melanoma cell lines were exposed to increasing concentrations of psoralens (0.1-100 µM) in the presence or absence of UVA radiation. Cell viability was evaluated by the WST-1 assay. RESULTS: We demonstrated that 8-MOP, in contrast to 5-MOP, has no cytotoxic effect on both melanoma cell lines. Simultaneous exposure of cells to 8-MOP and UVA radiation caused significant cytotoxic response in C32 cells where the EC50 value was estimated to be 131.0 µM (UVA dose: 1.3 J/cm2) and 105.3 µM (UVA dose: 2.6 J/cm2). The cytotoxicity of 5-MOP on both C32 and COLO829 cells was significantly augmented by UVA radiation - the EC50 was estimated to be 22.7 or 7.9 µM (UVA dose: 1.3 J/cm2) and 24.2 or 7.0 µM (UVA dose: 2.6 J/cm2), respectively. CONCLUSIONS: The demonstrated high cytotoxic response after simultaneous exposure of melanoma cells to psoralens and UVA radiation in vitro suggests the usefulness of PUVA therapy to treat melanoma in vivo.

Effect of fluoroquinolones on melanogenesis in normal human melanocytes HEMn-DP: a comparative in vitro study.

PURPOSE: Fluoroquinolones are one of the most commonly prescribed classes of antibiotics. However, their use is often connected with high risk of phototoxic reactions that lead to various skin or eye disorders. The aim of this study was to examine the effect of ciprofloxacin, lomefloxacin, moxifloxacin and fluoroquinolone derivatives with different phototoxic potential, on the viability and melanogenesis in melanocytes. MATERIALS AND METHODS: Normal human epidermal melanocytes, dark pigmented (HEMn-DP) were used as an in vitro model system. The effect of the tested antibiotics on cell viability and melanization in pigmented cells was investigated using a spectrophotometric method. The WST-1 assay was used to detect the cytotoxic effect of antibiotics. RESULTS: Ciprofloxacin, lomefloxacin and moxifloxacin induced the concentration-dependent loss in melanocytes viability. The values of EC50 for the tested fluoroquinolone derivatives were found to be 2.0 mM for ciprofloxacin, 0.51 mM for lomefloxacin and 0.27 mM for moxifloxacin. The exposure of cells to different concentrations of the analyzed drugs resulted in decrease in melanin content and tyrosinase activity. The highest decrease was observed for lomefloxacin which may explain its high phototoxic potential in vivo. The role of melanin in the mechanism of the toxicity of fluoroquinolones was discussed and the obtained results were compared with the previously obtained data concerning light-pigmented melanocytes (HEMa-LP). CONCLUSIONS: The results obtained in vitro suggest that the phototoxic potential of fluoroquinolones in vivo depends on specific drug-melanin interaction, the ability of drugs to affect melanogenesis as well as on the degree of melanocytes pigmentation.

The effect of simultaneous exposure of HEMn-DP and HEMn-LP melanocytes to nicotine and UV-radiation on the cell viability and melanogenesis.

Nicotine is a main compound of tobacco plants and may affect more than a billion people all over the world that are permanently exposed to nicotine from cigarettes, various forms of smoking cessation therapies, electronic cigarettes or second-hand smoke. It is known that nicotine forms complexes with melanin what may lead to accumulation of this alkaloid in tissues of living organisms containing the pigment. This may affect the viability of cells and process of melanin biosynthesis that takes place in melanocytes. Although UV radiation is known to be a particular inductor of melanin biosynthesis, its simultaneous effect with nicotine on this process as well as the viability of human cells containing melanin have not been assessed so far. The aim of this study was to examine the simultaneous impact of nicotine and UV radiation on viability and melanogenesis in cultured normal human melanocytes dark (HEMn-DP) and light (HEMn-LP) pigmented. Nicotine together with UV radiation induced concentration-dependent loss in melanocytes viability. The higher cell loss was observed in dark pigmented melanocytes in comparison to light pigmented cells. Simultaneous exposure of cells to nicotine and UV radiation also caused changes in melanization process in both tested cell lines. The data suggest that simultaneous exposure of melanocytes to nicotine and UV radiation up-regulates melanogenesis and affects cell viability. Observed processes are more pronounced in dark pigmented cells.

Modulation of Melanogenesis and Antioxidant Status of Melanocytes in Response to Phototoxic Action of Doxycycline.

Doxycycline is a commonly used tetracycline antibiotic showing the broad spectrum of antibacterial action. However, the use of this antibiotic is often connected with the risk of phototoxic reactions that lead to various skin disorders. One of the factors influencing the photosensitivity reactions is the melanin content in melanocytes. In this study, the impact of doxycycline and UVA irradiation on cell viability, melanogenesis and antioxidant defense system in cultured normal human epidermal melanocytes (HEMn-DP) was examined. The exposure of cells to doxycycline and UVA radiation resulted in concentration-dependent loss in melanocytes viability and induced melanin biosynthesis. Significant changes were stated in cellular antioxidant enzymes activity: SOD, CAT and GPx, which indicates alterations of antioxidant defense system. The results obtained in vitro may explain the mechanisms of phototoxic reactions that occur in normal human epidermal melanocytes in vivo after exposure of skin to doxycycline and UVA radiation.

Effect of tetracycline and UV radiation on melanization and antioxidant status of melanocytes.

Tetracycline is a semisynthetic antibiotic and is used in several types of infections against both gram-positive and gram-negative bacteria. This therapy is often associated with phototoxic reactions that occur after exposure to UV radiation and lead to photo-onycholysis, pseudoporphyria, solar urticaria and the fixed drug eruption in the skin. The phototoxic reactions may be related to the melanin content which, on one side may bind drugs - leading to their accumulation, and on the other side, they have photoprotective and antioxidant properties. In this study the effect of tetracycline and UVA irradiation on cell viability, biosynthesis of melanin and antioxidant defense system in cultured normal human epidermal melanocytes (HEMn-DP) was analyzed. The viability of the cells treated with tetracycline and exposed to UVA radiation decreased in a drug concentration-dependent manner. At the same time, the induction of the melanization process was observed. The significant alterations in antioxidant defense system, on the basis of changes in SOD, CAT and GPx activities, were stated. The obtained results may give explanation for the phototoxic effects of tetracycline therapy observed in skin cells exposed to UVA radiation.

Effect of nicotine on melanogenesis and antioxidant status in HEMn-LP melanocytes.

Nicotine is a natural ingredient of tobacco plants and is responsible for the addictive properties of tobacco. Nowadays nicotine is also commonly used as a form of smoking cessation therapy. It is suggested that nicotine may be accumulated in human tissues containing melanin. This may in turn affect biochemical processes in human cells producing melanin. The aim of this study was to examine the effect of nicotine on melanogenesis and antioxidant status in cultured normal human melanocytes HEMn-LP. Nicotine induced concentration-dependent loss in melanocytes viability. The value of EC50 was determined to be 7.43 mM. Nicotine inhibited a melanization process in human light pigmented melanocytes and caused alterations of antioxidant defense system. Significant changes in cellular antioxidant enzymes: superoxide dismutase and catalase activities and in hydrogen peroxide content were stated. The obtained results may explain a potential influence of nicotine on biochemical processes in melanocytes in vivo during long term exposition to nicotine.

Nicotine impact on melanogenesis and antioxidant defense system in HEMn-DP melanocytes.

Nicotine is a compound of tobacco plants and is responsible for addictive properties of tobacco which is used by about one billion of smokers all over the world. Recently, nicotine has drawn even more attention due to its presumed neuroprotective and antioxidant features as far as common use in various forms of smoking cessation therapies. It is suggested that nicotine may be accumulated in human tissues containing melanin. This may in turn influence biochemical processes in human cells producing melanin. The aim of this study was to examine the impact of nicotine on melanogenesis and antioxidant defense system in cultured normal human melanocytes (HEMn-DP). Nicotine induced concentration-dependent loss in melanocytes viability. The value of EC50 was determined to be 2.52 mM. Nicotine modulated melanin biosynthesis in normal human melanocytes. Significant changes in hydrogen peroxide content and cellular antioxidant enzymes: SOD, CAT, and GPx activities were stated in melanocytes exposed to nicotine, which indicates alterations of antioxidant defense system. The results obtained in vitro may explain a potential influence of nicotine on biochemical processes in melanocytes in vivo during long-term exposition to nicotine.