Concurrent beneficial (vitamin D production) and hazardous (cutaneous DNA damage) impact of repeated low-level summer sunlight exposures.

BACKGROUND: The concurrent impact of repeated low-level summer sunlight exposures on vitamin D production and cutaneous DNA damage, potentially leading to mutagenesis and skin cancer, is unknown. OBJECTIVES: This is an experimental study (i) to determine the dual impact of repeated low-level sunlight exposures on vitamin D status and DNA damage/repair (via both skin and urinary biomarkers) in light-skinned adults; and (ii) to compare outcomes following the same exposures in brown-skinned adults. METHODS: Ten white (phototype II) and six South Asian volunteers (phototype V), aged 23-59 years, received 6 weeks' simulated summer sunlight exposures (95% ultraviolet A/5% ultraviolet B, 1·3 standard erythemal doses three times weekly) wearing summer clothing exposing ~35% body surface area. Assessments made were circulating 25-hydroxyvitamin D [25(OH)D], immunohistochemistry for cyclobutane pyrimidine dimer (CPD)-positive nuclei and urinary biomarkers of direct and oxidative (8-oxo-deoxyguanosine) DNA damage. RESULTS: Serum 25(OH)D rose from mean 36·5 ± 13·0 to 54·3 ± 10·5 nmol L-1 (14·6 ± 5·2 to 21·7 ± 4·2 ng mL-1 ) in phototype II vs. 17·2 ± 6·3 to 25·5 ± 9·5 nmol L-1 (6·9 ± 2·5 to 10·2 ± 3·8 ng mL-1 ) in phototype V (P < 0·05). Phototype II skin showed CPD-positive nuclei immediately postcourse, mean 44% (range 27-84) cleared after 24 h, contrasting with minimal DNA damage and full clearance in phototype V (P < 0·001). The findings did not differ from those following single ultraviolet radiation (UVR) exposure. Urinary CPDs remained below the detection threshold in both groups; 8-oxo-deoxyguanosine was higher in phototype II than V (P = 0·002), but was unaffected by UVR. CONCLUSIONS: Low-dose summer sunlight exposures confer vitamin D sufficiency in light-skinned people concurrently with low-level, nonaccumulating DNA damage. The same exposures produce minimal DNA damage but less vitamin D in brown-skinned people. This informs tailoring of sun-exposure policies.

The endocannabinoid 2-arachidonoylglycerol (2-AG) and metabolizing enzymes during rat fetoplacental development: a role in uterine remodelling.

The main endocannabinoids (EC) identified in mammalian tissues are N-arachidonoylethanolamide (AEA, anandamide), and 2-arachidonoylglycerol (2-AG). AEA levels are critical in pregnancy, especially during implantation, decidualization, and placental development. As 2-AG functions in pregnancy are still largely undefined, we hypothesized that it may also have a role during fetoplacental development. We showed that 2-AG is not only present in the rat mesometrial decidua and plasma during fetoplacental development, but that both 2-AG synthesizing (diacylglycerol lipase) and degradation (monoacylglycerol lipase) enzymes are expressed by decidual cells. While lower concentrations of 2-AG induced apoptosis of rat primary decidual cells, via the CB1 receptor, higher concentrations induced a dramatic effect on cell morphology, cell viability and lactate dehydrogenase release, triggered through a mechanism independent of CB1. This study provides evidences that 2-AG fluctuation in maternal tissues throughout normal pregnancy is primarily regulated by its metabolizing enzymes. Together, these data supports the hypothesis that a deregulation of the endocannabinoid system through aberrant cannabinoid signalling may impact normal uterine remodelling process and consequently normal pregnancy.

N-acylethanolamine levels and expression of their metabolizing enzymes during pregnancy.

Decidualization is essential for a successful pregnancy and is a tightly regulated process influenced by the local microenvironment. Lipid-based mediators, such as the endocannabinoid anandamide, and other compounds that have cannabimimetic actions may act on the decidua during early pregnancy. In this study, the levels of N-arachidonoylethanolamine (anandamide) and two other N-acylethanolamines, N-oleoylethanolamine and N-palmitoylethanolamine, were measured in rat plasma and maternal tissues between d 8 and 19 of pregnancy by ultraperformance liquid chromatography tandem mass spectrometry. The spatiotemporal expression of N-acylethanolamine metabolizing enzymes in implantation units were also determined by quantitative PCR, Western blot, and immunohistochemistry and shown to vary with gestation being mainly localized in decidual cells. The data also indicated that plasma and tissues levels of all three N-acylethanolamines fluctuate throughout pregnancy. Tissue levels of endocannabinoids did not correlate with plasma, suggesting that during pregnancy, maternal tissue levels of endocannabinoids are primarily regulated by in situ production and degradation to create endocannabinoid gradients conducive to successful pregnancy.

The plasma levels of the endocannabinoid, anandamide, increase with the induction of labour.

OBJECTIVE: Plasma anandamide (AEA) levels have previously been shown to be elevated in labour and defective cannabinoid receptor type 1 signalling in mice has been shown to be associated with elevation of corticotrophin-releasing hormone and spontaneous onset of preterm labour. We measured plasma AEA levels in women undergoing induction of labour to define the changes during the transition from the nonlabouring to labouring state. DESIGN: A longitudinal observational study. SETTING: A large UK teaching hospital. POPULATION: Term pregnant women undergoing induction of labour. METHODS: Blood was collected from women before induction of labour and again when they were in active labour. Plasma AEA was extracted and measured using ultraperformance liquid chromatography-tandem mass spectrometry. MAIN OUTCOME MEASURES: The primary outcome variable was change in plasma AEA levels from the nonlabouring to the labouring state. The secondary outcome was induction-to-delivery interval. RESULTS: There was a 1.5-fold increase in mean plasma AEA levels from 1.20 +/- 0.57 nm in the nonlabouring state to 1.82 +/- 0.87 nm in the labouring state (P < 0.0001). Induction-to-delivery interval was predicted by both Bishop's score (P < 0.0001) and percentage change in plasma AEA levels (P < 0.0001). There was a negative correlation between the percentage change in plasma AEA level and the induction-to-delivery interval (r = - 0.28; P = 0.0481). This means that the greater the rise in the plasma AEA levels the shorter the duration of labour. CONCLUSIONS: Plasma AEA levels increase with active labour and the negative correlations between percentage change in plasma AEA levels and induction-to-delivery interval suggest that AEA is likely to be involved in the physiological mechanisms of labour. Whether this increase is essential for myometrial contraction is unclear and needs further investigation.

Characterization and comparison of recombinant human and rat TRPV1 receptors: effects of exo- and endocannabinoids.

BACKGROUND: TRPV1 is a ligand-gated ion channel whose activation by capsaicin increases intracellular Ca(2+) ([Ca(2+)](i)). TRPV1 and cannabinoid CB(1) receptor activation are capable of eliciting analgesia. In this study, using recombinant human (h) and rat (r) TRPV1 receptors expressed in HEK293 cells, we have performed a comparison of both TRPV1 species at 22 and 37 degrees C and compared endo- and exocannabinoid activity at both receptors. METHODS: [Ca(2+)](i) was measured in Fura-2-loaded HEK293(hTRPV1) and HEK293(rTRPV1) cells. To assess native CB(1) receptor activity, [(35)S]GTPgammaS binding to membranes prepared from rat cerebellum was measured. RESULTS: Both capsaicin (pEC(50) rat approximately 6.9 and pEC(50) human approximately 6.8 at 37 degrees C) and anandamide (pEC(50) rat approximately 5.3 and pEC(50) human approximately 5.8 at 37 degrees C) produced a concentration-dependent increase in [Ca(2+)](i) in rat and human systems and at 22 and 37 degrees C. In HEK293(rTRPV1) cells, anandamide appeared to be a partial agonist. Capsazepine demonstrated competitive antagonism at both human and rat TRPV1 receptors and at both temperatures studied. Capsazepine effects were not temperature dependent: pK(B) at rTRPV1 was 5.98 at 22 degrees C and 6.02 at 37 degrees C, and pK(B) at hTRPV1 was 6.76 at 22 degrees C and 6.75 at 37 degrees C. However, there was a consistent 6-fold increase in capsazepine potency for hTRPV1 relative to rTRPV1. The exocannabinoid Delta(9)-tetrahydrocannabinol failed to increase [Ca(2+)](i), although its solvent ethanol was an effective TRPV1 activator. In the [(35)S]GTPgammaS binding assay using rat cerebellar membranes, anandamide (pEC(50) approximately 5.8) and Delta(9)-tetrahydrocannabinol (pEC(50) approximately 7.1), but not capsaicin, stimulated binding. Delta(9)-tetrahydrocannabinol was a partial agonist. pEC(50) values for anandamide at rTRPV1 and rCB(1) were similar. CONCLUSIONS: There were small differences in the pharmacology of rat and human TRPV1 receptors. Whilst capsaicin activated TRPV1 and Delta(9)-tetrahydrocannabinol activated CB(1), anandamide is an endogenous agonist for both receptor systems.