Stimulation of cultured melanocytes in medium containing a serum substitute: Ultroser-G

Distinct Anti-Fibrotic Effects of Exosomes Derived from Endothelial Colony-Forming Cells Cultured Under Normoxia and Hypoxia

Background

The therapeutic potential of endothelial colony-forming cells (ECFCs) may be impaired in an ischemic environment. Direct injection of ECFCs is not an effective method of rescuing the ischemic heart, but exosomes derived from these cells may be a promising therapeutic tool. However, exosomes produced under normoxia and hypoxia may not be identical. Therefore, the purpose of this study was to investigate alterations in the anti-fibrotic effects of hypoxia-treated ECFC-derived exosomes and the underlying mechanism involved.

Material/Methods

ECFCs were isolated from peripheral blood and exosomes were collected from ECFCs treated with normoxia (nor-exo) or hypoxia (hyp-exo). Effects of exosomes on cardiac fibroblast activation were evaluated in vitro. MicroRNAs (miRNAs) inside the exosomes were extracted and compared using next-generation RNA sequencing. Predicted target mRNAs of miR-10b-5p were validated using a dual-luciferase reporter gene assay method.

Results

Nor-exo significantly ameliorated cardiac fibroblast activation in vitro. These effects were attenuated in the hyp-exo-treated group. miR-10b-5p was enriched in nor-exo but not in hyp-exo. Dual-luciferase reporter gene assay found that both SMAD-specific E3 ubiquitin protein ligase 1 (Smurf1) and histone deacetylase 4 (HDAC4) mRNAs were inhibited by miR-10b-5p. The expression of neutral sphingomyelinase 2 (N-SMase2) was decreased in hypoxia ECFCs, and this result was consistent with the changes in miR-10b-5p in hyp-exo.

Conclusions

Due to a reduction of miR-10b-5p, which targets the fibrotic genes Smurf1 and HDAC4, the anti-fibrotic effects of hyp-exo were abolished.

Calcineurin activity and inhibition in skin and (epi)dermal cell cultures

Calcineurin (Cn) is the target of the immunosuppressive drugs cyclosporine A (CsA), tacrolimus (Trl), and pimecrolimus (Prl). Trl and Prl are often used topically for treatment of various skin diseases. The Cn inhibitors CsA and Trl are mostly used for maintenance therapy of transplant patients. Their long-term use, however, causes a dramatic increase in skin cancer risk. By using a newly developed assay for Cn measurement in blood, we were able to demonstrate Cn activity in total skin homogenates. A significantly higher activity was found in epidermis compared to dermis. In skin cell cultures, fibroblasts showed the highest activity as compared to keratinocytes and melanocytes. Of the Cn inhibitors, Trl showed stronger inhibition than CsA and Prl (57 and 55% in fibroblast and keratinocyte cultures, respectively). Also, the lowest IC(50) (the half maximal inhibitory concentration) values were found for Trl (0.5 and 1.3 nM in two different fibroblast cultures). Cn activity and its inhibition can thus be studied in dermatological samples. The effects of Cn inhibition in fibroblasts and keratinocytes may be of influence on the overall functioning of the skin immune system.

New high-performance liquid chromatographic method for sensitive determination of pheomelanin in biological materials by precolumn fluorescence derivatization with naphthalene-2,3-dicarboxaldehyde

Pheomelanin is an important type of melanin distributed in the skin, eye and hair in the mammal, which is of great social, clinical and cosmetic significance. In this study, a new HPLC method with fluorescence detection is described originally for the sensitive determination of pheomelanin in biological materials. The pheomelanin polymer is decomposed into two specific degradation products, 3-amino-4-hydroxyphenylalanine (3-AHP) and 4-amino-3- hydroxyphenylalanine (4-AHP) with hydriodic acid. Then the two AHP isomers are derivatized using a fluorescent probe naphthalene-2,3-dicarboxaldehyde in the presence of cyanide. The resulting highly stable 2-substituted 1-cyanobenz[f] isoindole derivatives were separated on a 5NH(2)-MS aminopropyl packed HPLC column with binary isocratic elution profile and detected fluorimetrically. The assay shows high sensitivity of 0.11nM (2.2fmol per injection, the lowest reported) at signal-to-noise ratio of 3 for each AHPs, good accuracy and precision (RSDs<3.1%), and linearity (range of 0.02-10microM, r>0.995). The results obtained by using fluorescence detection have been compared with other detection systems (electrochemical and UV). The sensitivity can increase from 100 to respect electrochemical detection and 30000 times respect UV detection. The method has been used for the quantitative determination of pheomelanin in various biological samples, including cell cultures from five types of melanoma cell lines of human and rat origin, hair samples of various colors, melanoma tissue and the urines from human melanoma patients and healthy subjects. This original application of HPLC-fluorescence detection represents a powerful tool for investigating pheomelanin synthesis in vitro and in vivo under physiological and pathophysiological conditions.

The Combined Effects of Extracts Containing Carotenoids and Vitamins E and C on Growth and Pigmentation of Cultured Human Melanocytes

In the present study, we investigated the effects of tomato extract (TE) containing lycopene and palm fruit extract (PE) rich in carotenoids on the growth and pigmentation of melanocyte cultures of Caucasian origin. The extracts were tested at different concentrations and in combination with vitamins E and C. Melanocytes with basic and increased (tyrosine-induced) pigmentation were treated in short-term and long-term experiments. Prevention of UVA-induced DNA damage was studied by using the comet assay. Melanocytes with stimulated melanin production showed reduced growth. Incubation of the cells with TE/PE (20/4 microg/ml) in combination with 35 microM vitamin E and 100 microM vitamin C (COMB 20/4) reduced this growth inhibition, especially in the long-term cultures. Increased production of melanin pigment was obtained when the cells were treated with 2.5 x and 10 x higher concentrations of the TE/PE and the same concentration of vitamins E and C (COMB 50/10 and 200/40). Reduced DNA damage was found after UVA irradiation in cells preincubated with COMB 50/10. The results indicate that the presence of carotenoids from TE and PE in combination with vitamins E and C may influence growth and pigmentation in melanocyte monocultures. Depending on the concentration of the carotenoid mixtures, their presence may provide some protection against the melanogenic intermediates and/or exogenous DNA damage.

Melanin protects melanocytes and keratinocytes against H2O2-induced DNA strand breaks through its ability to bind Ca2+

Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) are produced in the skin under the influence of UV radiation. These compounds are highly reactive and can induce DNA lesions in epidermal cells. Melanin is considered to protect human skin against DNA damage by absorbing UV radiation. We have investigated whether melanin can, in addition, offer protection against the effects of H(2)O(2) in human melanocytes and HaCaT keratinocytes. In the present study, it was shown that 40 and 100 microM H(2)O(2) increased the number of DNA strand breaks as measured using the comet assay, in melanocytes of Caucasian origin. In melanocytes of the same origin in which melanin levels were increased by culturing in presence of 10 mM NH(4)Cl and elevated l-tyrosine, H(2)O(2)-induced DNA damage was reduced compared to that in control melanocytes. Similarly, HaCaT cells that were loaded with melanin were better protected against H(2)O(2)-induced DNA strand breaks than control HaCaT cells. These protective effects of melanin were mimicked by the intracellular Ca(2+)-chelator BAPTA. Thus, BAPTA reduced the level of H(2)O(2)-induced DNA strand breaks in melanocytes. Like BAPTA, melanin is known to be a potent chelator of Ca(2+) and this was confirmed in the present study. It was shown that melanin levels in melanocytic cells correlated directly with intracellular Ca(2+) binding capacity and, in addition, correlated inversely with H(2)O(2)-induced increases in intracellular Ca(2+). Our results show that melanin may have an important role in regulating intracellular Ca(2+) homeostasis and it is suggested that melanin protects against H(2)O(2)-induced DNA strand breaks in both melanocytes and keratinocytes and through its ability to bind Ca(2+).

Melanin has a role in Ca2+ homeostasis in human melanocytes

We have examined whether melanin affects Ca2+ homeostasis in cultured normal human melanocytes. Intracellular Ca2+ concentrations ([Ca2+]i), were measured in four Caucasian and in three Negroid melanocyte cultures. Under resting conditions [Ca2+]i was around 100 nM in all cultures, but differences between cells within cultures were observed. All cultures responded to endothelin-1 (ET-1) with increases in [Ca2+]i and there were no differences between Caucasian and Negroid cultures. However, large differences in responses between cells within cultures were observed, indicating that melanocyte cultures are very heterogeneous. The addition of 2.5 mM CaCl2 to melanocytes kept in Ca2+-free medium resulted in rapid and transient increases in [Ca2+]i of up to 1500 nM. These increases were on average more than two times smaller in melanocyte cultures established from Negroid donors compared with Caucasian cultures. In addition, well melanized Caucasian melanocytes, cultured in the presence of 400 microM tyrosine and 10 mM NH4Cl, showed a reduced increase in cytoplasmic Ca2+ concentration upon the addition of extracellular Ca2+. The difference in maintaining Ca2+ homeostasis between poorly and well melanized melanocytes may be the result of the clearance of cytoplasmic Ca2+ into melanosomes and the greater capacity for this in the more pigmented melanocytes.

Melanin offers protection against induction of cyclobutane pyrimidine dimers and 6-4 photoproducts by UVB in cultured human melanocytes

The goal of this investigation was to correlate the melanin content in human pigmentary cells with the generation of UVB-induced photoproducts and to examine the relationship between the melanin content and the removal of the photoproducts. Cultured melanocytes from light-skinned individuals synthesized less melanin and produced more cyclobutane pyrimidine dimers and 6-4 photoproducts upon UVB exposure than did melanocytes from black skin. Tyrosine-stimulated melanogenesis provided protection against DNA damage in both cell types. In another set of pigmented cell lines a ratio between eumelanin and pheomelanin was determined. The assessment of association between DNA damage induction and the quantity and quality of melanin revealed that eumelanin concentration correlated better with DNA protection than pheomelanin. Skin type-I and skin type-VI melanocytes, congenital nevus (CN)-derived cells and skin type-II melanocytes from a multiple-melanoma patient were grown in media with low or high L-tyrosine concentration. The cells were irradiated with 200 J/m2 UVB, and the levels of the photoproducts were determined immediately and after 6 and 24 h. Once again the induction of the photoproducts was mitigated by increased melanogenesis, and it was inversely correlated with the skin type. No significant differences were found for the removal of photoproducts in the cultures of skin types I and VI and CN cells. No indications of a delay in the removal of photoproducts in the melanocytes from the multiple-melanoma patient were found either.

(Pheo)melanin photosensitizes UVA-induced DNA damage in cultured human melanocytes

The question of whether melanins are photoprotecting and/or photosensitizing in human skin cells continues to be debated. To evaluate the role of melanin upon UVA irradiation, DNA single-strand breaks (ssb) were measured in human melanocytes differing only in the amount of pigment produced by culturing at two different concentrations, basic (0.01 mM) or high (0.2 mM), of L-tyrosine, the main precursor of melanin. In parallel, pheo- and total melanin contents of the cells were determined. Identical experiments were performed with two melanocyte cultures derived from a skin type I and a skin type VI individual. For the first time the correlation between UVA-induced genotoxicity and pheo-/total melanin content has been investigated. We observed that cultured in basic medium, the skin type VI melanocytes contained 10 times more total melanin and about seven times more pheomelanin than the skin type I melanocytes. Elevation of tyrosine level in the culture medium resulted in an increase of both pheo- and total melanin levels in both melanocyte cultures; however, the melanin composition of skin type I melanocytes became more pheomelanogenic, whereas that of skin type VI melanocytes remained the same. The skin type VI melanocytes cultured in basic medium demonstrated a very high sensitivity (1.18 ssb per 10(10) Da per kJ per m2) toward UVA that is probably related to their high pheo- and total melanin content. Their UVA sensitivity, however, did not change after increasing their melanin content by culturing at high tyrosine concentration. In contrast, the skin type I melanocytes demonstrated a low sensitivity (0.04 ssb per 10(10) Da per kJ per m2) toward UVA when cultured in basic medium, but increasing their melanin content resulted in a 3-fold increase in their UVA sensitivity (0.13 ssb per 10(10) Da per kJ per m2). These results demonstrate that UVA-irradiated cultured human melanocytes are photosensitized by their own synthesized chromophores, most likely pheomelanin and/or melanin intermediates.

Melanogenesis in cultured melanocytes can be substantially influenced by L-tyrosine and L-cysteine

We investigated the effect of varying concentration of 1-tyrosine and 1-cysteine in culture medium on melanin production by human skin melanocytes (skin phototype II/III). In addition to the analyses of dopa oxidase activity and total melanin, pheomelanin production in the cells was assessed by high-performance liquid chromatography determinations of pheomelanin degradation products, 3-aminotyrosine and 4-amino-3-hydroxyphenylalanine. As another marker for pheomelanin, melanosomal sulfur was determined by the use of X-ray microanalysis. With varying concentration of both amino acids, profound changes in the pigmentation patterns of the melanocytes were observed. A high concentration of 1-tyrosine (0.2 mM) was always connected with increased pigmentation. In combination with a low 1-cysteine content we saw an increase in tyrosinase activity and the highest melanin content. At high concentrations of both 1-tyrosine and 1-cysteine, the melanocytes showed reduced tyrosinase activity and they produced notably more pheomelanin. In case of the pheomelanin measurements by high-performance liquid chromatography and the sulfur detection with X-ray microanalysis, strongly increased concentrations were found when cells were maintained in high 1-tyrosine medium as compared with those grown with low 1-tyrosine. This was especially true for the combination with low 1-cysteine showing that the 1-tyrosine content of the medium strongly influences not only the eumelanin but also the pheomelanin production in the cultured melanocyte. It can be concluded that variations in the concentrations of 1-tyrosine and 1-cysteine in culture medium can be used to regulate the melanogenetic phenotype under in vitro conditions.

Determination of pheomelanin by measurement of aminohydroxyphenylalanine isomers with high-performance liquid chromatography

We describe an improved method for the analysis of pheomelanin in biological samples. The method is based on a chemical degradation of the melanin polymer and HPLC analysis of specific degradation products. Hydriodic hydrolysis provides 4-amino-3-hydroxyphenylalanine (AHP) and 3-amino-l-tyrosine (AT) which are detected with an electrochemical detector. We have examined each step of the analysis and the results are presented in this paper. First the samples are hydrolyzed for 16 h. AT and AHP are then isolated from the hydrolysates by ion-exchange chromatography and then separated and quantitated by HPLC and electrochemical detection. The method shows good reproducibility with a total imprecision below 5.6%. The linearity of the method was shown from 0 to 490 ng AT and 0 to 850 ng AHP per sample, using a melanoma cell suspension (27 mg protein/ml) with up to 24-fold dilutions of the original sample. For cultured "normal" human melanocytes a minimal amount of 0.1 mg protein is sufficient for analysis of pheomelanin in the samples. This method provides the opportunity to study the composition of the formed melanin in cell lines, cultured in different growth media.

Effective elimination of fibroblasts in cultures of melanocytes by lowering calcium concentration in TPA depleted medium following geneticin treatment

Melanocytes grow well in culture media supplemented with phorbol ester. However, phorbol ester is metabolically stable and has prolonged effects on multiple cellular responses. Different groups have reported that they could cultivate melanocytes without phorbol ester. However, in medium without phorbol esters contaminating fibroblasts are often difficult to eliminate. We have developed an improved method of eliminating fibroblasts using geneticin in serum free medium with bFGF, endothelin-1 and no phorbol ester. Treatment with a low concentration of geneticin effectively eliminated contaminating fibroblasts and was not harmful to melanocytes if geneticin was added initially in a high calcium media (2 mM) followed by a change to a low (0.09 mM) calcium media immediately after removal of the geneticin. With this technique we could easily establish pure melanocyte culture. This culture method will provide a useful tool for studies on melanocyte cellular response without the influence of phorbol ester.