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PubMed1980

Treatment of malignant melanoma with dacarbazin (DTIC-DOME) with special reference to urinary excretion of 5-S-cysteinyldopa.

Seventeen patients were given DTIC, 200 mg/m2/day in five-day courses every four to six weeks. In four patients (stage II) treated on an adjuvant basis, tumor recurrence has been verified in three. Four of the palliatively treated patients were also given DTIC by regional intra-arterial infusion with minimal positive tumor effect and minimal toxicity. 5-S-cysteinyldopa excretion in urine was checked continuously in all patients. Tumor recurrence was revealed in two patients given DTIC on an adjuvant basis three and four months before clinical signs of tumor. In the palliatively treated patients, 5-S-cysteinyldopa excretion increased in 5/6 patients judged to have stable disease, before tumor progression was clinically detectable. The use of 5-S-cysteinyldopa examination is a valuable adjunct to the follow-up of the effect of DTIC therapy in melanoma patients.

Adult↗
PubMed1977

A facile one-step synthesis of cysteinyldopas using mushroom tyrosinase.

A convenient one-step procedure, based upon the tyrosinase co-oxidation of dopa and cysteine, is reported for the synthesis of 5-S-cysteinyldopa (I) in 74% yield. Secondary products of the reaction turned out to be 2-S-cysteinyldopa (II, 14%), 2,5-S, S-dicysteinyldopa (iv, 5%), and the hitherto unknown 6-S-cysteinyldopa (III, approximately 1%).

Cysteinyldopa↗
PubMed1983

The mechanism of toxicity of 5-S-cysteinyldopa to tumour cells. Hydrogen peroxide as a mediator of cytotoxicity.

5-S-Cysteinyldopa, a melanin precursor, has been shown to possess selective toxicity to tumour cells in vitro and in vivo. The mechanism of cytotoxicity of the catechol was studied in comparison with L-dopa and 5-S-cysteaminyldopamine. Growth inhibition of human neuroblastoma cell line of YT-nu by 5-S-cysteinyldopa was completely depressed by addition of catalase. Superoxide dismutase and five drugs thought to scavenge hydroxyl radicals or quench singlet oxygen had little effect on the cytotoxicity. Hydrogen peroxide itself was also cytotoxic at low concns. These results indicated that hydrogen peroxide was a mediator of the cytotoxicity of 5-S-cysteinyldopa. It is suggested that reaction of the catechol with cellular superoxide radicals contributes to the production of hydrogen peroxide in addition to autoxidation. Catalase reduced the cytotoxicity of L-dopa by half, while it had no inhibitory effect on the strong cytotoxicity of 5-S-cysteaminyldopamine.

Animals↗
PubMed1985

A pulse radiolysis investigation of the oxidation of the melanin precursors 3,4-dihydroxyphenylalanine (dopa) and the cysteinyldopas.

The unstable quinones of 3,4-dihydroxyphenylalanine (dopa) and the most abundant cysteinyldopa isomers (2S-, 5S- and 2,5S,S'-) have been generated rapidly via disproportionation of their respective semiquinones prepared pulse radiolytically by one-electron oxidation of the corresponding dopas with azide radicals. Dopaquinone decays via a base-catalysed unimolecular cyclisation yielding leucodopachrome which, under the present conditions, is immediately oxidised by remaining dopaquinone to form dopachrome and dopa back again. Addition of cysteine increased the rate of dopaquinone decay and precluded dopachrome formation. By contrast, the cysteinyldopa quinones decayed via an acid-catalysed unimolecular cyclisation involving the cysteine side chain to form a cyclic quinone-imine observed directly for the first time. These quinone-imine intermediates subsequently rearranged to more stable phenolic benzothiazine isomers. The addition of cysteine had little effect on cysteinyldopa quinone decay and did not prevent quinone-imine formation. The absorption spectra, extinction coefficients and rate constants for formation and decay of these various transient species involved in melanisation are reported.

Cyclization↗
PubMed1983

Non-enzymic oxidation of cysteinyldopa catalyzed by metallic ions.

1. Evidence is presented that under physiological conditions cysteinyldopa behaves similarly to catecholamines, e.g. adrenaline, in forming reversible complexes with various metallic cations. 2. As a rule, these complexes are stable under anaerobic conditions, but readily autoxidize in the presence of O2 to give the 1,4-benzothiazine acid (II) corresponding to one of the postulated intermediates in the biosynthesis of phaeomelanic pigments. 3. Copper catalyzed oxidation of cysteinyldopa proceeds differently to give the red-purple trichochrome F presumably via decarboxylation and oxidative coupling of the same benzothiazine intermediate. 4. The relevance of these in vitro experiments to the metabolism of cysteinyldopa is briefly discussed.

Catecholamines↗
PubMed2005

The pheomelanin precursor 5-S-cysteinyldopa protects melanocytes from membrane damage induced by ultraviolet A radiation.

Pheomelanin and pheomelanin precursors have been implicated as risk factors for induction of melanoma by ultraviolet radiation. The pheomelanin precursor, 5-S-cysteinyldopa, has been shown to sensitise DNA to oxidative damage by ultraviolet radiation. We here show that 5-S-cysteinyldopa significantly protects melanocytes from membrane damage (permeability) induced by ultraviolet A radiation. Thus, 5-S-cysteinyldopa, may at the same time sensitise DNA and protect membranes from damage induced by ultraviolet radiation.

Animals↗
PubMed1983

Determination of urinary 5-S-cysteinyldopa by high-performance liquid chromatography.

A high-performance ion-pair liquid chromatographic method with electrochemical detection is described, which is suitable for routine determination of urinary 5-S-cysteinyldopa. The clean-up procedure includes a first purification step on the cation exchanger AG 50 W (H +). After desorption from the resin at moderately raised pH the catecholic amino acid is adsorbed on alumina at pH 8.6, washed and finally desorbed by elution with perchloric acid. By the combined clean-up procedures, easily oxidized compounds are eliminated, which otherwise cause a number of interfering peaks in the chromatography. The synthesis of 5-S-cysteinyl-L-3,4-dihydroxyphenyl [2,3-3H]alanine is described, and this tritium-labelled 5-S-cysteinyldopa is used to determine the recovery in the sample. The precision (C.V. = 5.7% at low and C.V. = 4.9% at high 5-S-cysteinyldopa concentration) and recovery (105.0 +/- 8.6%) were satisfactory. The mean urinary excretion was 0.34 +/- 0.13 (S.D.) mumol per 24 h (range 0.02-0.58 mumol per 24 h) in healthy subjects (n = 24) and in patients with melanoma metastates (n = 13) the excretion ranged from 0.9 to 4.8 mumol per 24 h.

Chromatography, High Pressure Liquid↗
PubMed1982

Novel free radicals in synthetic and natural pheomelanins: distinction between dopa melanins and cysteinyldopa melanins by ESR spectroscopy.

Synthetic pheomelanins from enzymic oxidation of the 3,4-dihydroxyphenylalanine (dopa) derivative 5-S-cysteinyldopa have been examined by ESR spectroscopy. These alkalisoluble polymers contain a novel kind of free radical that is spectroscopically distinct from that found in eumelanins. Delocalization of the unpaired electron onto a nitrogen atom and the ability of the radical to chelate complexing metal ions strongly suggest an o-semiquinonimine structure. The synthetic pheomelanin was compared with natural red pigments extracted from human red hair and from red chicken feathers. Spectroscopically, the chicken feather pheomelanin is almost identical to synthetic cysteinyldopa pheomelanin. In contrast, the pigment from red hair has a major spectral component very similar to that found in dopa melanin, with a smaller component corresponding to that found in cysteinyldopa melanin.

Cysteinyldopa↗
PubMed1978

5-S-cysteinyldopa excretion after treatment with 8-methoxypsoralen and UVA light.

The excretion of the specific melanocytic metabolite 5-S-cysteinyldopa was studied in patients with psoriasis treated by 8-methoxypsoralen and UVA light. A pronounced increase was found after only 2 days treatment, although no increase in pigmentation could yet be observed. Peak values for urinary 5-S-cysteinyldopa were noted after 1 or 2 weeks treatment. Increase in pigmentation persisted after the excretion maxima for 5-S-cysteinyldopa.

Adult↗
PubMed1985

Plasma 5-S-cysteinyldopa concentrations in oculocutaneous albinism.

5-S-cysteinyldopa concentrations were determined by high-pressure liquid chromatography and electrochemical detection in plasma from normally pigmented patients and patients with oculocutaneous albinism, both tyrosinase-positive and tyrosinase-negative. The plasma 5-S-cysteinyldopa concentrations were similar in all three groups, suggesting that 5-S-cysteinyldopa can be produced by mechanisms which do not involve tyrosinase.

Albinism↗
PubMed1981

Urinary excretion of 5-S-cysteinyldopa in healthy Japanese.

Urinary excretion of 5-S-cysteinyldopa was investigated in 20 healthy Japanese (10 men and 10 women). The values of excretion varied between 46 and 193 microgram/24 h. The mean (+/- S.D.) was 96 1 +/- 9.8 microgram/24 h. It was higher in the men than in the women, being 13 +/- 15 vis-a-vis 80.8 +/- 11.4 microgram/24 h. This finding indicates that 5-S-cysteinyldopa is formed and excreted by active melanocytes even in Mongoloids. The excretion of dopa and dopamine was found not correlative with the excretion of 5-S-cysteinyldopa.

Adolescent↗
PubMed1983

Diastereomers of 5-S-cysteinyldopa.

Diastereomers of 5-S-cysteinyldopa formed from D-dopa and L-cysteine or from L-dopa and D-cysteine can be separated from 5-S-cysteinyldopa formed from L-dopa and L-cysteine by liquid chromatography. The diastereomers have a great potential as internal standards in the analysis of 5-S-cysteinyldopa. They can be used as reference substances in the differentiation of stereospecific enzymatic oxidation of dopa from non-specific oxidation.

Chromatography, Liquid↗
PubMed1983

Urine excretion of 5-S-cysteinyldopa and serum sialic acid as tumor markers in human melanomas.

This study examines 5-S-cysteinyldopa, which is a melanoma-associated marker, and sialic acid whose increase appears to be a common feature of numerous cancers. In spite of some interferences due to sun exposure, 5-S-cysteinyldopa seems a significant indicator of metastases; the difference between 46 metastasis-negative and 34 metastasis-positive melanomas is significant at P less than 0.001. Cerebral metastases give little or no increase. In contrast with the 75% of patients who keep normal 5-S-cysteinyldopa excretion, all melanoma patients have elevated sialic acid. No difference occurs between glycoprotein carbohydrates of controls and patients after pronase digestion and con A chromatography. The use of those two parameters in association is proposed to have a proper index of tumor burden or success of therapy.

Adult↗
PubMed1977

5-S-cysteinyldopa in the urine of melanoma patients.

A newly discovered amino acid, 5-S-cysteinyldopa, present in the urine of healthy subjects is excreted in pathological amounts in many patients suffering from melanoma metastases. Increased excretion of 5-S-cysteinyldopa may be observed before metastases become clinically evident. Determination of 5-S-cysteinyldopa is superior to determination of dopa+dopamine in the diagnosis of melanoma metastases.

Adult↗
PubMed1978

Free and bound 5-S-cysteinyldopa and dopa in human malignant melanomas.

Free dopa and 5-S-cysteinyldopa were extracted from two human melanomas. Subsequent hydrolysis of carefully washed melanoma tissue released dopa and 5-S-cysteinyldopa, indication the presence of these catechol amino acids in proteins. Cysteinyldopa-containing proteins may represent the antigens previously demonstrated in human melanomas.

Cysteinyldopa↗
PubMed1979

Intracellular distribution of dopa and 5-S-cysteinyldopa in pigment cells with minimal pigment formation.

The hypothesis that only melanosomal catecholic amino acids contribute to melanin formation was tested by studying adult bovine eyes in which pigment synthesis is considered to be low or absent. Dopa and 5-S-cysteinyldopa were investigated in different cell fractions of the choroid and retinal pigment epithelium of cattle. Most of the dopa and 5-S-cysteinyldopa was found in the cytoplasm and very little in the large granule fraction. The presence of cysteinyldopa in the adult eye is evidence of tyrosinase activity, but the catechol amino acids in the cytoplasm probably do not give rise to melanin formation. It is assumed that they instead are excreted from the cells.

Animals↗
PubMed2003

Comparison of prognostic significance of serum 5-S-Cysteinyldopa, LDH and S-100B protein in Stage III-IV malignant melanoma.

5-S-cysteinyldopa is a precursor of pheomelanin. S-100B protein is a low molecular weight, acidic, calcium binding, cytoplasmatic protein. LDH was defined as the most important serum parameter in disseminated melanoma. The aim of the present study was to compare the prognostic values of serum 5-S-Cysteinyldopa, S-100B and LDH concentrations in Stage III-IV melanoma patients. Serum samples were taken from 179 Stage III-IV melanoma patients at diagnosis. Serum 5-S-CD concentrations were determined by HPLC, S-100B protein by immunoluminometric assay while LDH by UV kinetic method. The mean/median concentrations of LDH, S-100B protein and 5-S-CD in Stage III patients ranged around the normal level. In Stage IV, the markers ranked as S100B = 5-S-CD > LDH for sensitivity, S-100B > LDH > 5-S-CD for specificity and LDH = S100B = 5-S-CD for positive predictive value, respectively. Furthermore, mean marker concentrations of patients with progressive disease differed significantly from nonprogresssive cases (when staging categories have been disregarded). Survival analysis indicated, that the initially elevated LDH and S-100B level in Stage IV disease predicts comparably short survival. Results of our study suggest that these serum marker values correlate well with Stages and disease progression. In Stage IV melanoma, the markers had appropriate sensitivity, high specificity as well as important positive predictive value. Among the studied serum markers S-100B protein and LDH proved to be similarly reliable in respect to the clinical outcome.

Adult↗
PubMed1982

Conjugation of dopa and 5-S-cysteinyldopa with cysteine mediated by superoxide radical.

cytotoxicity of catechols has been ascribed to their binding with proteins through sulfhydryl groups. Superoxide radical (O2-) generated in hypoxanthine-xanthine oxidase system at pH 7.4 mediated conjugation of dopa with cysteine to form cysteinyldopas. Similarly, 5-S-cysteinyldopa gave 2,5-S,S-dicysteinyldopa. The rates of oxidation of the catechols by O2- appear to be comparable to that of reduction of nitro-blue tetrazolium by O2-. These results suggest that catechols may exert cytotoxicity in cells where biochemical defence against O2- or the quinone oxidation products is not sufficient.

Catalase↗