EPR characteristics of free radicals in DOPA–melanin–moxifloxacin complexes at ambient level of UVA radiation

Changes in Electron Paramagnetic Resonance Parameters Caused by Addition of Amphotericin B to Cladosporium cladosporioides Melanin and DOPA-Melanin-Free Radical Studies

Cladosporium cladosporioides are the pigmented soil fungi containing melanin. The aim of this work was to determine the influence of amphotericin B on free radicals in the natural melanin isolated from pigmented fungi Cladosporium cladosporioides and to compare it with the effect in synthetic DOPA-melanin. Electron paramagnetic resonance (EPR) spectra were measured at X-band (9.3 GHz) with microwave power in the range of 2.2-70 mW. Amplitudes, integral intensities, linewidths of the EPR spectra, and g factors, were analyzed. The concentrations of free radicals in the tested melanin samples were determined. Microwave saturation of EPR lines indicates the presence of pheomelanin in addition to eumelanin in Cladosporium cladosporioides. o-Semiquinone free radicals in concentrations ~1020 [spin/g] exist in the tested melanin samples and in their complexes with amphotericin B. Changes in concentrations of free radicals in the examined synthetic and natural melanin point out their participation in the formation of amphotericin B binding to melanin. A different influence of amphotericin B on free radical concentration in Cladosporium cladosporioides melanin and in DOPA-melanin may be caused by the occurrence of pheomelanin in addition to eumelanin in Cladosporium cladosporioides. The advanced spectral analysis in the wide range of microwave powers made it possible to compare changes in the free radical systems of different melanin polymers. This study is important for knowledge about the role of free radicals in the interactions of melanin with drugs.

Antioxidant Properties of Platycladus orientalis Flavonoids for Treating UV-Induced Damage in Androgenetic Alopecia Hair

BACKGROUND

Androgenetic alopecia (AGA) causes thinning hair, but poor hair quality in balding areas and damage from UV radiation have been overlooked. Plant extracts like Platycladus orientalis flavonoids (POFs) may improve hair quality in AGA. This study examines POFs' effectiveness in treating AGA-affected hair and repairing UV-induced damage.

METHODS

Hair samples were analyzed using scanning electron microscopy (SEM) to examine surface characteristics, electron paramagnetic resonance (EPR) spectroscopy to measure free radicals in the hair, and spectrophotometry to assess changes in hair properties.

RESULTS

POFs effectively removed hydroxyl radicals from keratinocytes and had antioxidant properties. They also reduced UV-induced damage to AGA hair by mitigating the production of melanin free radicals. Following POF treatment, the reduction in peroxidized lipid loss in AGA hair was notable at 59.72%, thereby effectively delaying the progression of hair color change. Moreover, protein loss decreased by 191.1 μ/g and tryptophan loss by 15.03%, ultimately enhancing hair's tensile strength.

CONCLUSION

compared to healthy hair, hair damaged by AGA shows more pronounced signs of damage when exposed to UV radiation. POFs help protect balding hair by reducing oxidative damage and slowing down melanin degradation.

Streptomycin generates oxidative stress in melanin-producing cells: In vitro study with EPR spectroscopy evidence

Streptomycin (STR) is an aminoglycoside antibiotic with a broad-spectrum of activity and ototoxic potential. The mechanism of STR-induced inner ear damage has not been fully elucidated. It was previously found that STR binds to melanin, which may result in the accumulation of the drug in melanin-containing tissues. Melanin pigment is present in various parts of the inner ear, including the cochlea and vestibular organ. The present study aimed to assess if streptomycin generates oxidative stress and affects melanogenesis in normal human melanocytes. Moreover the variation of free radical concentration in STR-treated melanocytes was examined by electron paramagnetic resonance spectroscopy (EPR). We found that STR decreases cell metabolic activity and reduces melanin content. The observed changes in the activity of antioxidant enzymes activity in HEMn-DPs treated with streptomycin may suggest that the drug affects redox homeostasis in melanocytes. In this work EPR study expanded knowledge about free radicals in interactions of STR and melanin in melanocytes. The results may help elucidate the mechanisms of STR toxicity on pigment cells, including melanin-producing cells in the inner ear. This is important because understanding the mechanism of STR-induced ototoxicity would be helpful in developing new therapeutic strategies to protect patients' hearing.

The Biochemical and Molecular Analysis of Changes in Melanogenesis Induced by UVA-Activated Fluoroquinolones-In Vitro Study on Human Normal Melanocytes

Fluoroquinolones cause phototoxic reactions, manifested as different types of skin lesions, including hyperpigmentation. The disturbances of melanogenesis indicate that fluoroquinolones may affect cellular processes in melanocytes. It has been reported that these antibiotics may bind with melanin and accumulate in pigmented cells. The study aimed to examine the changes in melanogenesis in human normal melanocytes exposed to UVA radiation and treated with lomefloxacin and moxifloxacin, the most and the least fluoroquinolone, respectively. The obtained results demonstrated that both tested fluoroquinolones inhibited melanogenesis through a decrease in tyrosinase activity and down-regulation of tyrosinase and microphthalmia-associated transcription factor production. Only lomefloxacin potentiated UVA-induced melanogenesis. Under UVA irradiation lomefloxacin significantly enhanced melanin content and tyrosinase activity in melanocytes, although the drug did not cause an increased expression of tyrosinase or microphthalmia-associated transcription factor. The current studies revealed that phototoxic activity of fluoroquinolones is associated with alterations in the melanogenesis process. The difference in phototoxic potential of fluoroquinolones derivatives may be connected with various effects on UVA-induced events at a cellular level.

Molecular and Biochemical Basis of Fluoroquinolones-Induced Phototoxicity-The Study of Antioxidant System in Human Melanocytes Exposed to UV-A Radiation

Phototoxicity of fluoroquinolones is connected with oxidative stress induction. Lomefloxacin (8-halogenated derivative) is considered the most phototoxic fluoroquinolone and moxifloxacin (8-methoxy derivative) the least. Melanin pigment may protect cells from oxidative damage. On the other hand, fluoroquinolone–melanin binding may lead to accumulation of drugs and increase their toxicity to skin. The study aimed to examine the antioxidant defense system status in normal melanocytes treated with lomefloxacin and moxifloxacin and exposed to UV-A radiation. The obtained results demonstrated that UV-A radiation enhanced only the lomefloxacin-induced cytotoxic effect in tested cells. It was found that fluoroquinolones alone and with UV-A radiation decreased superoxide dismutase (SOD) activity and SOD1 expression. UV-A radiation enhanced the impact of moxifloxacin on hydrogen peroxide-scavenging enzymes. In turn, lomefloxacin alone increased the activity and the expression of catalase (CAT) and glutathione peroxidase (GPx), whereas UV-A radiation significantly modified the effects of drugs on these enzymes. Taken together, both analyzed fluoroquinolones induced oxidative stress in melanocytes, however, the molecular and biochemical studies indicated the miscellaneous mechanisms for the tested drugs. The variability in phototoxic potential between lomefloxacin and moxifloxacin may result from different effects on the antioxidant enzymes.

Application of EPR spectroscopy to determine the influence of simvastatin concentration on free radicals in A-375 human melanoma malignum cells

Malignant melanoma is the most aggressive and lethal form of skin cancer. Therefore the search for new methods of the treatment for melanoma is needed. In this work simvastatin was tested as the substance of potential anticancer activity. The aim of this study was to determine the effect of simvastatin in different concentration on free radicals in A-375 human melanoma malignum cells. Free radicals and growth of A-375 melanoma cells cultured without and with simvastatin were examined. Free radicals were tested by the use of electron paramagnetic resonance (EPR) spectroscopy. o-Semiquinone free radicals existed in A-375 cells. Free radicals of the control A-375 cells and the cells cultured with simvastatin were homogeneously broadened. The growth of A-375 cells did not change for concentrations of simvastatin 0.1 μM and 0.3 μM, and it slightly decreased for concentration of this substance equal 1 μM, so these concentrations of simvastatin were not preferred for therapy. For the concentrations of simvastatin higher than 1 μM the growth of A-375 cells was considerably weakened. Simvastatin in the concentrations of 0.1 μM and 1 μM decreased free radical concentrations in A-375 cells. The concentrations of simvastatin of 3 μM and 5 μM accompanied by the strong cell damage and strong formation of free radicals in them were recommended for anticancer therapy of A-375 melanoma cells.

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.

Effect of simvastatin in different concentrations on free radicals in A-2058 human melanoma malignum cells-EPR studies

The influence of concentration of simvastatin (SIM) on free radicals in A-2058 human melanoma malignum cells was studied. The proliferation assay for melanoma A-2058 cells with SIM in concentration range from 0.1 to 20 µM was performed. SIM in the concentrations of 0.1, 0.3, and 1 μM only slightly changed the growth of A-2058 cells, but the growth of the cells considerably decreased for higher concentrations of SIM. Free radicals in the cells were examined by an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. o-Semiquinone free radicals with g-factors in the range of 2.0060 to 2.0065 were found in A-2058 cells. The asymmetric broad EPR spectra with linewidths (ΔB_pp ) from 0.87 to 1.25 mT were measured. The fast spin-lattice relaxation processes characterized all the tested cells. The free radical concentrations in the all A-2058 cells cultured with SIM were lower than in the control cells. The quenching of free radicals in A-2058 cells depended on concentration of SIM. This effect was the weakest for concentration of SIM of 3 μM. The strongest decrease of free radical concentration caused SIM in concentration of 1 μM.

Kinetics of Melanin Polymerization during Enzymatic and Nonenzymatic Oxidation

Melanin is an abundant biopigment in the animal kingdom, but its structure remains poorly understood. This is a substantial impediment to understanding the mechanistic origin of its observed functions. Proposed models of melanin structure include aggregates of both linear and macrocyclic units and noncovalently held monomers. Both models are broadly in agreement with current experimental data. To constrain the structural and kinetic models of melanin, experimental data of high resolution with chemical specificity accompanied by atomistic modeling are required. We have addressed this by obtaining electronic absorption, infrared, and ultraviolet resonance Raman (RR) spectra of melanin at several wavelengths of excitation that are sensitive to small changes in structure. From these experiments, we observed kinetics of the formation of different species en route to melanin polymerization. Exclusive chemical signatures of monomer 3,4-dihydroxyphenylalanine (dopa), intermediate dopachrome (DC), and early-time polymer are established through their vibrational bands at 1292, 1670, and 1616 cm^-1 respectively. Direct evidence of reduced heterogeneity of melanin oligomers in tyrosinase-induced formation is provided from experimental measurements of vibrational bandwidths. Models made with density functional theory show that the linear homopolymeric structures of 5,6-dihydroxyindole can account for experimentally observed wavenumbers and broad bandwidth in Raman spectra of dopa-melanin. We capture resonance Raman (RR) signature of DC, the intermediate stabilized by the enzyme tyrosinase, for the first time in an enzyme-assisted melanization reaction using 488 nm excitation wavelength and propose that this wavelength can be used to probe reaction intermediates of melanin formation in solution.

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.

EPR spectroscopy of chlorpromazine-induced free radical formation in normal human melanocytes

The purpose of this study was to estimate the effect of chlorpromazine on free radical concentration in HEMn-DP melanocytes using electron paramagnetic resonance (EPR) spectroscopy. It was found that chlorpromazine at concentrations of 1 × 10(-7) and 1 × 10(-6) M contributed to the formation of free radicals (g values ~2) in a dose-dependent manner. The increase in free radical formation was accompanied by an increase in cytotoxicity, as shown by a tetrazolium assay. Homogeneous broadening of EPR lines, slow spin-lattice relaxation processes, and strong dipolar interactions characterized all the tested cellular samples. The performed examination of free radical formation in cells exposed to different chlorpromazine concentrations confirmed the usefulness of electron paramagnetic resonance spectroscopy to determine the effect of a drug on free radical production in a cellular model system in vitro.

Effect of norfloxacin and moxifloxacin on melanin synthesis and antioxidant enzymes activity in normal human melanocytes

Fluoroquinolone antibiotics provide broad-spectrum coverage for a number of infectious diseases, including respiratory as well as urinary tract infections. One of the important adverse effects of these drugs is phototoxicity which introduces a serious limitation to their use. To gain insight the molecular mechanisms underlying the fluoroquinolones-induced phototoxic side effects, the impact of two fluoroquinolone derivatives with different phototoxic potential, norfloxacin and moxifloxacin, on melanogenesis and antioxidant enzymes activity in normal human melanocytes HEMa-LP was determined. Both drugs induced concentration-dependent loss in melanocytes viability. The value of EC50 for these drugs was found to be 0.5 mM. Norfloxacin and moxifloxacin suppressed melanin biosynthesis; antibiotics were shown to inhibit cellular tyrosinase activity and to reduce melanin content in melanocytes. When comparing the both analyzed fluoroquinolones, it was observed that norfloxacin possesses greater inhibitory effect on tyrosinase activity in melanocytes than moxifloxacin. The extent of oxidative stress in cells was assessed by measuring the activity of antioxidant enzymes: SOD, CAT, and GPx. It was observed that norfloxacin caused higher depletion of antioxidant status in melanocytes when compared with moxifloxacin. The obtained results give a new insight into the mechanisms of fluoroquinolones toxicity directed to pigmented tissues. Moreover, the presented differences in modulation of biochemical processes in melanocytes may be an explanation for various phototoxic activities of the analyzed fluoroquinolone derivatives in vivo.