Tape stripping the stratum corneum for biomarkers of ultraviolet radiation exposure at sub-erythemal dosages: a study in human volunteers.

PURPOSE: Prevalence of skin cancer is rapidly increasing. There is a need for non-invasive biomarkers to assess efficacy of prevention strategies aiming at reduction of exposure to ultraviolet radiation (UVR). Recently, stratum corneum (SC) biomarkers were applied in various inflammatory skin diseases. Here, we explore their suitability as candidate biomarkers for UVR. MATERIAL AND METHODS: Twelve volunteers were exposed to a UVB-dose of 0.72 SED, three times a week, during three weeks. As candidate biomarkers, cis-isomers of urocanic acid (cUCA) and 25 immunological mediators were measured in the SC. RESULTS: Eight immunological markers significantly changed from baseline. Of them, IL-1RA/IL-1α and a placental growth factor (PIGF) showed gradual changes during UVR-exposure (p < 0.01 for linear trend). cUCA increased sharply already after the first exposure, however, reached a plateau in the second week. CONCLUSIONS: SC represents a promising, non-invasive alternative to skin biopsy in detecting UVR-induced changes. cUCA is the marker of choice for assessment of single UVR-exposure; however, it is less suitable for cumulative UVR-dose. Immunological markers including IL-1RA/IL-1α and PIGF showed gradual changes, and therefore are convenient for monitoring chronic UVR-exposure. These candidate biomarkers might facilitate assessment of the efficacy of preventive measures in the workplace and general population.

Moderate UV Exposure Enhances Learning and Memory by Promoting a Novel Glutamate Biosynthetic Pathway in the Brain.

Sunlight exposure is known to affect mood, learning, and cognition. However, the molecular and cellular mechanisms remain elusive. Here, we show that moderate UV exposure elevated blood urocanic acid (UCA), which then crossed the blood-brain barrier. Single-cell mass spectrometry and isotopic labeling revealed a novel intra-neuronal metabolic pathway converting UCA to glutamate (GLU) after UV exposure. This UV-triggered GLU synthesis promoted its packaging into synaptic vesicles and its release at glutamatergic terminals in the motor cortex and hippocampus. Related behaviors, like rotarod learning and object recognition memory, were enhanced after UV exposure. All UV-induced metabolic, electrophysiological, and behavioral effects could be reproduced by the intravenous injection of UCA and diminished by the application of inhibitor or short hairpin RNA (shRNA) against urocanase, an enzyme critical for the conversion of UCA to GLU. These findings reveal a new GLU biosynthetic pathway, which could contribute to some of the sunlight-induced neurobehavioral changes.

Modulation of multiple sclerosis by sunlight exposure: role of cis-urocanic acid.

The role of cis-urocanic acid (UCA) as a UV-mediated immunomodulator in MS patients was investigated. Plasma levels of cis-UCA were significantly lower in MS patients compared to controls. Stimulation of MBP- and MOG-specific T cells in the presence of cis-UCA, significantly increased IL-10, and inhibited IFN-γ production. PBMCs cultured in the presence of cis-UCA increased CD4(+)CD25(+)FoxP3(+) regulatory T cell percentages. Dendritic cells cultured in the presence of cis-UCA significantly reduced Ag presentation capacity. Finally, cis-UCA activated the 5-HT2A receptor, inducing the increase in phosphorylated forms of ERK 1/2 and JNK2. Thus, in addition to vitamin D, cis-UCA also appears to be an additional UV-mediated immunomodulator.

Prolonged increase of cis-urocanic acid levels in human skin and urine after single total-body ultraviolet exposures.

Cis-urocanic acid (cis-UCA), a mediator of immunosuppression, is formed from trans-UCA upon UV-exposure of the skin. This study describes a liquid chromatographic method for the simultaneous quantification of cis- and trans-UCA in skin, urine and plasma of nonirradiated volunteers. It also describes cis- and trans-UCA kinetics in UV-irradiated volunteers. New procedures to remove interfering substances from urine and plasma are reported. Normal levels of cis-UCA in skin, urine and plasma of nonirradiated volunteers were 0.5 nmol/cm2, 0.03 mumol/mmol creatinine (median 0.00) and undetectable and those of trans-UCA were 17.1 nmol/cm2, 1.36 mumol/ mmol creatinine and 0.5 microM, respectively. Upon single total body UVB (290-320 nm) exposures of 250 J/m2, epidermal cis-UCA levels immediately reached a maximum and returned to basic levels 3 weeks later. The cis-UCA levels in urine reached a maximum in 5-12 h postirradiation and reached baseline values in 8-12 days. Additionally, a single total body UVA (320-400 nm) irradiation of 200 kJ/m2 yielded a similar pattern. The kinetics of cis-UCA in plasma could not be followed due to low concentrations; however, that of skin and urine was informative in relation to solar exposures and phototherapy.

Pharmacokinetics of stable isotopically labeled L-histidine in humans and the assessment of in vivo histidine ammonia lyase activities.

The pharmacokinetics of L-histidine in humans has been investigated to evaluate the in vivo histidine ammonia lyase system for the conversion of L-histidine to urocanic acid. Two healthy volunteers (subjects A and B) received a single 100-mg oral dose of L-[3,3-2H2,1',3'-15N2]histidine. Blood and urine samples were obtained over 24 hr after the administration and analyzed by stable isotope dilution ms. Labeled L-histidine was rapidly absorbed, and a maximum plasma concentration of L-histidine was observed at 30 min (1057.6 ng/ml) in subject A and at 60 min (1635.6 ng/ml) in subject B after oral administration. Pharmacokinetic parameters were calculated based on a two-compartment model. Labeled L-histidine in subject A (t1/2 = 1.0 hr) was eliminated approximately twice faster than that in subject B (t1/2 = 1.9 hr). Total body clearances were 70.0 liters/hr in subject A and 30.0 liters/hr in subject B. The low ratios of the renal clearance to the total body clearance (1.04% for subject A and 0.43% for subject B) indicated that most of L-histidine was eliminated via the nonrenal processes. L-Histidine was rapidly metabolized to urocanic acid. Maximum plasma concentrations of urocanic acid were 59.61 ng/ml at 30 min for subject A and 46.10 ng/ml at 60 min for subject B. The slope of the plot of urinary excretion rate of urocanic acid vs. the plasma concentration of unchanged L-histidine was demonstrated to reflect the metabolic clearance of L-histidine to urocanic acid. The method of evaluating the in vivo human histidine ammonia lyase activities discussed in this study offers a significant value with regard to the biochemical and clinical elucidations of the heterogeneity of histidinemia.

Characterization of a monoclonal antibody to cis-urocanic acid: detection of cis-urocanic acid in the serum of irradiated mice by immunoassay.

Cis-urocanic acid (cis-UCA), which is formed from the naturally occurring trans-isomer on ultraviolet (UV) irradiation, has been suggested as a photoreceptor for and mediator of the suppressive effects of UV irradiation on systemic immune responses. Trans-UCA is located predominantly in the stratum corneum, and the extent of isomerization to cis-UCA may be analysed by high-performance liquid chromatography (HPLC) of skin extracts. Such an analysis is not suitable for other tissues. In this study a murine monoclonal antibody to cis-UCA was prepared and tested by ELISA using UCA isomers conjugated to protein as antigens. The interaction of the antibody with structural analogues of UCA was assessed by competitive inhibition ELISA which indicated that the antibody had a high specificity for cis-UCA. Screening of sera at various times after UVB irradiation of mice by competitive inhibition ELISA using the monoclonal antibody showed that cis-UCA was present, probably in an unbound form, for at least 2 days after the exposure. Thus, cis-UCA produced in the epidermis following UVB irradiation reaches the serum a few hours later. The implications of this finding for the generation of suppressed immune responses are discussed.

Simultaneous determination of stable isotopically labelled L-histidine and urocanic acid in human plasma by stable isotope dilution mass spectrometry.

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of stable isotopically labelled L-histidine (L-[3,3-2H2,1',3'-15N2]histidine, L-His-[M + 4]) and urocanic acid ([3-2H,1',3'-15N2]urocanic acid, UA-[M + 3]) in human plasma was developed using DL-[2,3,3,5'-2H4,2'-13C,1',3'-15N2]histidine (DL-His-[M + 7]) and [2,3,5'-2H3,2'-13C,1',3'-15N2]urocanic acid (UA-[M + 6]) as internal standards. L-Histidine and urocanic acid were derivatized to alpha N-(trifluoroacetyl)-imN-(ethoxycarbonyl)-L-histidine n-butyl ester and imN-(ethoxycarbonyl)urocanic acid n-butyl ester. Quantification was carried out by selected ion monitoring of the molecular ions of the respective derivatives of L-His-[M + 4], DL-His-[M + 7], UA-[M + 3] and UA-[M + 6]. The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for measuring plasma concentrations of L-His-[M + 4] and UA-[M + 3] following administration of trace amounts of L-His-[M + 4] to humans.

Histidinaemia in Sweden. Report on a neonatal screening programme.

Histidinaemia screening was included in the epidemiological survey of the Swedish neonatal screening programme, 1971-72. Dried blood samples on filter paper collected neonatally from 171,000 infants were analysed the Guthrie method. A blood histidine level above 0.96 mmol/1 (15 mg per 100 ml) was regarded as a positive test and was found in 639 infants - i.e., 1/270. No further diagnostic measures were taken until 1977 when stored dried blood samples from 273 infants with a positive screening test were analysed for urocanic acid. Four children had undetectable blood urocanic acid. They were studied and histidinaemia was confirmed in two children, and excluded in two. Both histidinaemia children had normal psychomotor development at 7 years of age, in spite of the fact that no dietary treatment was given. The incidence of histidinaemia in Sweden was estimated as 1/37,00, on the basis of neonatal screening. In addition, histidinaemia was diagnosed in four individuals who were not detected in the neonatal screening programme; of these, only one had an IQ less than 85. At present, general neonatal screening histidinaemia in Sweden does not seem justified.

[Newborn mass-screening programme for histidinaemia: increased efficiency through selective thin-layer chromatography (author's transl)]. / Neugeborenen-Massenscreening auf Histidinämie: Erhöhte Effizienz durch selektive Dünnschichtchromatographie

Histidinaemia, detected on urinary screening in cases which had not been discovered by neonatal blood screening induced us to lower the control limit for histidine from 6 to 4 mg/dl. This was possible by the development of a thin-layer chromatographic control method for the Guthrie test. The combination of thin-layer chromatography (TLC) and the Guthrie test (GT) proved to be considerably more efficient than the Guthrie test alone: among 44,510 newborn infants tested in the first six months of 1975 twice as many cases of histidinaemia were found (TLC + GT 6, GT 3) in spite of a gready lowered control rate (TLC + GT 0.4%, GT 2.4%). Of 87,729 newborn infants tested in 1975, 9 cases of histidinaemia were detected (incidence: 1 in 9,748). Only 4 of these infants showed initial blood levels of larger than or equal to 6 mg/dl. 5 children with histidinaemia, 3 with an initial level of 4 mg/dl and one each with 5 and 8 mg/dl, respectively, had to be put on a histidine-restricted diet becuase the blood histidine level was constantly elevated above 8 mg/dl. The further course of histidinaemia does not appear to correlated with the height of the initial blood histidine level.

[A routine method for thin layer chromatographic determination of urocanic acid in blood samples impregnated on filter paper cards (author's transl)]. / Routinemässige dünnschichtchromatographische Bestimmung von Urocannisäure aus blutgetränkten Filterpapierkarten

A method is described for mass screening at birth for histidinaemia. Blood samples are collected on filter paper cards, as used in the Guthrie test. These samples are transferred, together with standards of histidine and urocanic acid, to thin layer chromatography plates by a type of sandwich technique. The plates can be evaluated semiquantitatively, after development and detection with Pauly's reagent. The detection limit for both substances is less than 10 mg/1 (60 mumol/1). Greater sensitivity and absence of interference, greatly reduce the proportion of equivocal results compared with the Guthrie test.

[Mass screening for histidinaemia:rationalization by selective thin layer chromatography. First results]. / Rationalisierung des Histidinämie-Massenscreenings durch selektive Dünnschichtchromatographie

Since 1974 histidine and urocanic acid was estimated by thin layer chromatography (TLC) in all newborn infants in whom histidine blood levels had to be controlled because of an abnormal Guthrie-test. This entailed using dried blood spotted on filter paper to rationalize newborn screening for histidinaemia thus reducing the work involved. Three cases of histidinaemia were found amongst 66.064 newborn infants. In order to find these, 830 initialy suspicious Guthrie tests had to be checked. This is a control frequency of 1:80. 384 controls were necessitated by inhibition-zones, 482 by initialy elevated blood levels. Histidine and urocanic acid concentrations generally correlated well in the TLC; only 9 newborn infants showed results suggesting histidinaemia (elevated histidine and absent urocanic acid). All three histidinaemias discovered by Guthrie-test aswell were among them, so that in the end, with only 9 controls combining Guthrie-test and TLC, the same effectiveness could have been reached, as compared to 830, when using the Guthrie-test alone.