Ultraviolet radiation regulates cortisol activity in a waveband-dependent manner in human skin ex vivo.

BACKGROUND: 11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1), 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2), and glucocorticoids (GC) and their receptor (GR) play a key role in tissue-specific regulation of GC action. OBJECTIVES: To determine the expression of genes encoding 11ß-HSD1 (HSD11B1), 11ß-HSD2 (HSD11B2) and GR (GRα; also known as NC3R1) and their protein products, and levels of cortisol in human skin explants and/or cocultured keratinocytes/melanocytes after treatment with ultraviolet (UV) A, B or C wavebands. METHODS: Skin from foreskins and/or cocultured human keratinocytes/melanocytes were irradiated with UVA, UVB or UVC (skin) and incubated for 12 and 24 h. Methods of reverse transcription-polymerase chain reaction, Western blotting, enzyme-linked immunosorbent assay and immunohistochemistry (IHC) were used to determine expression and localization of corresponding genes or antigens. RESULTS: UVB enhanced the HSD11B1 gene and protein expression in a dose-dependent manner, while UVA had no effect. Similarly, UVC increased 11ß-HSD1 protein product as measured by IHC. UVB and UVC enhanced cortisol production and decreased epidermal GR expression, while UVA had no detectable effects. Although both UVA and UVB stimulated HSD11B2 gene expression, only UVA increased 11ß-HSD2 protein product levels with UVB and UVC having no effect. CONCLUSIONS: We suggest that these differential, waveband-dependent effects of UV radiation on the expression of cutaneous HSD11B1, HSD11B2 and GRα genes and their corresponding protein products, and cortisol production are to protect and/or restore the epidermal barrier homeostasis against disruption caused by the elevated cortisol level induced by UVB and UVC.

Reintroduction of a classic vitamin D ultraviolet source.

As early as 1930 sunlamps claiming to provide ultraviolet (UV) exposure to make vitamin D were sold to the public in the US and Canada for home use. Today even with dietary supplementation of vitamin D many people do not get enough solar UV exposure to maintain sufficient vitamin D levels. There is growing interest in the availability of sunlamps for this purpose. The original Sperti Sunlamp, with label claiming vitamin D benefit was approved by the American Medical Association in 1940 as a sunlamp. This intermediate pressure mercury lamps ultraviolet B emission lines, at 297, 302, and 313 nm are able to convert 7-dehydrocholesterol in the skin to vitamin pre-D3 initiating the natural process of vitamin D formation. Today's KBD Vitamin D lamp, an updated model of the earlier type source. In order to comply with modern safety guidance, the source is filtered to remove unnecessary UVC radiation and is equipped with a timer to control the dose administered. The 5 min timer provides an exposure, at 20 in. from the user's skin, of one standard erythemal dose (SED). The SED represents a suberythemal dose for even the most sensitive skin type I individual.

Popcorn worker's lung: in vitro exposure to diacetyl, an ingredient in microwave popcorn butter flavoring, increases reactivity to methacholine.

Workers who inhale microwave popcorn butter flavorings experience decrements in lung function and can develop clinical bronchiolitis obliterans, i.e., "popcorn worker's lung" (Kreiss, K., Gomaa, A., Kullman, G., Fedan, K., Simoes, E.J., Enright, P.L., 2002. Clinical bronchiolitis obliterans in workers at a microwave-popcorn plant. N. Engl. J. Med. 347, 330-338.). In a rat inhalation model, vapors of an artificial butter flavoring damaged the epithelium of the upper and lower airways (Hubbs, A.F., Battelli, L.A., Goldsmith, W.T., Porter, D.W., Frazer, D., Friend, S., Schwegler-Berry, D., Mercer, R.R., Reynolds, J.S., Grote, A., Castranova, V., Kullman, G., Fedan, J.S., Dowdy, J., Jones, W.G., 2002. Necrosis of nasal and airway epithelium in rats inhaling vapors of artificial butter flavoring. Toxicol. Appl. Pharmacol. 185, 128-135.). Diacetyl, a butter flavoring component, is a major volatile ketone in the popcorn-processing workplace. We investigated the effects of diacetyl on epithelium of guinea pig isolated airway preparations and the effects of diacetyl in vitro on reactivity to bronchoactive agents. In the isolated, perfused trachea preparation, diacetyl added to the intraluminal (mucosal) bath elicited responses that began with contraction (threshold ca. 3 mM) and ended with relaxation. After a 4-h incubation with intraluminal diacetyl (3 mM), contractions to extraluminal (serosal) methacholine (MCh) were slightly increased; however, sensitivity to intraluminally (mucosally) applied MCh was increased by 10-fold. Relaxation responses of MCh (3 x 10(-7) M)-contracted tracheas to extraluminally applied terbutaline and intraluminally applied 120 mM KCl, to evoke epithelium-derived relaxing factor release, were unaffected by diacetyl. Exposure of the tracheal epithelium in Ussing chambers to diacetyl decreased transepithelial potential difference and resistance. These findings suggest that diacetyl exposure compromised epithelial barrier function, leading to hyperreactivity to mucosally applied MCh. The respiratory epithelium appears to serve as an initial target for the toxic effects of diacetyl in the airways.

Effect of UV on the susceptibility of acid-soluble Skh-1 hairless mouse collagen to collagenase.

BACKGROUND/PURPOSE: Photoaging of the skin is a result of chronic exposure to environmental ultraviolet radiation (UV). The milieu provided by the extracellular matrix, which significantly influences the behaviour of resident fibroblasts, depends critically on the supermolecular collagen structure. We ask whether direct photochemical treatment of type I collagen with solar wavelengths capable of reaching the dermis can modify the substrate's susceptibility to collagenase in a model in vitro system. METHODS: Acid- extracted Skh-1 hairless mouse collagen samples were irradiated with 0-140 J/cm2 of radiation from bank of filtered FS lamp (UVB/UVA = 0.33, fluence rate = 0.81 mW/cm2). Subsequent to UV irradiation, collagen samples were coupled with fluorescein isothiocyanate (FITC) and assayed for susceptibility to bacterial collagenase by monitoring the appearance of supernatant FITC fluorescence (a measure of lysed collagen) over time of incubation. As a 'reference', unirradiated commercial FITC-labelled citrate-soluble collagen (Elastin Products, Owensville, MO 65066, USA) was similarly analysed. RESULTS: Unirradiated mouse collagen had a lower rate of cleavage than did the calfskin sample. Irradiation of unlabelled mouse collagen for 0-48 h (0-140 J/cm2 total UV) rendered the sample more soluble, with concomitant chain degradation, cross-linking and loss of intrinsic collagen fluorescence. At irradiation time's >/= 4 h (>/=11.7 J/cm2), the irradiated collagen was significantly more susceptible to bacterial collagenase digestion. DISCUSSION: It appears that the rate of cleavage depends on the superstructure of the collagen, since the kinetics of collagen cleavage differ for two collagen samples having essentially the same primary structure. Cleavage kinetics may depend on the 'maturity' (solubility) of the collagen. The observation that UV-damaged mouse collagen is a better substrate for collagenase than the intact sample may be illustrative of a mechanism whereby damaged collagen targets itself for selective attack by collagenase.

Necrosis of nasal and airway epithelium in rats inhaling vapors of artificial butter flavoring.

As the result of a high prevalence of fixed airways obstruction in workers at a microwave popcorn manufacturing plant, we examined the hypothesis that vapors of butter flavoring used in the manufacture of microwave popcorn and other foods can produce airway injury in rats. Rats were exposed to vapors liberated from heated butter flavoring. Rats were exposed for 6 h by inhalation and were necropsied 1 day after exposure. The exposure was found by GC-MS analysis to be a complex mixture of various organic gases with the major peaks consisting of diacetyl (2,3-butanedione), acetic acid, acetoin (3-hydroxy-2-butanone), butyric acid, acetoin dimers, 2-nonanone, and delta-alkyl lactones. Diacetyl was used as a marker of exposure concentration. In the lung, butter flavoring vapors containing 285-371 ppm diacetyl caused multifocal, necrotizing bronchitis, which was most consistently present in the mainstem bronchus. Alveoli were unaffected. Butter flavoring vapors containing 203-371 ppm diacetyl caused necrosuppurative rhinitis, which affected all four levels of the nose. Within the posterior two nasal levels (T3 and T4), necrosis and inflammation was principally localized to the nasopharyngeal duct. Control rats were unaffected. Therefore, concentrations of butter flavoring vapors that can occur during the manufacture of foods are associated with epithelial injury in the nasal passages and pulmonary airways of rats.

Effect of UV irradiation on type I collagen fibril formation in neutral collagen solutions.

BACKGROUND: Collagens have the well-known ability to spontaneously self-associate to form fibrils at physiological temperature and neutral pH in vitro and in vivo. Because solar UV may photochemically alter collagen, the kinetics of fibril formation may be modified. Thus, we have begun a systematic study of the effect of various UV wavebands on fibril formation. METHODS: Citrate-soluble calf skin collagen (Elastin Products) was dissolved at 0.05% in 0.5 M HOAc, dialyzed over 2 days into two changes of 0.0327 M phosphate buffer, pH 7.0 at 4 degrees C, and centrifuged at 48,000 x g. Photolysis was carried out at 4 degrees C with either (a) UVC (UVG-11 lamp), (b) filtered solar-simulating radiation (SSR) or UVA (SSR or UVL-21 lamp filtered with a 2.0 mm Schott WG 345 filter). Gelation was commenced by rapidly raising the temperature from 8 degrees C to 33 degrees C. Nucleation and growth were followed by turbidimetric measurements at 400 nm. RESULTS: UVC radiation (0-17.3 J/cm2) resulted in a dose-dependent decrease in the rate of fibril growth. Under these conditions, concomitant collagen crosslinking and degradation occurred. Fibril nucleation, a prerequisite for growth, was rapid (threshold approximately 2 min) and was not affected by UVC, UVA or SSR. SSR (0-1,320 J/cm2) caused a small decrease in growth rate and in the degree of fibril formation. UVA radiation (0-1,080 J/cm2) had a similar effect. "Direct" photochemical damage thus paralleled absorption via various collagen chromophores, with UVC>SSR approximately UVA. The presence of riboflavin (RF) resulted in groundstate interactions that markedly altered both nucleation and growth kinetics. Irradiation with 29.6 J/ cm2 UVA in the presence of RF photosensitizer caused relatively minor additional changes in fibrillation kinetics. CONCLUSIONS: These results collectively indicate that fibril formation is markedly dependent on specific ground state interactions and relatively insensitive to nonspecific UV damage. On the other hand, fibrils thus formed from photochemically altered collagen may have altered structural properties that could have subtle but unfavorable effects on the local dermal milieu in vivo. Notwithstanding, the relative insensitivity of fibrillogenesis to non-specific photochemical damage probably represents a favorable adaptation, overall, which tends to conserve the mechanical integrity of the skin.

Topical W-7 inhibits ultraviolet radiation-induced melanogenesis in Skh:HR2 pigmented hairless mice.

We studied the effect of N-(6-aminohexyl)-5-chloro-1-napthalenesulfonamide (W-7) on ultraviolet radiation (UVR)-induced melanogenesis (tanning) in Skh:HR2 pigmented hairless mice. Topically pretreated mice were exposed to subminimal edematogenic as well as edematogenic UVR doses to establish whether W-7-UVR-induced edema prophylaxis allows increased melanogenesis while preventing edema. Ultraviolet light-irradiated vehicle control animals developed visible tans; however, both W-7-treated groups failed to tan. Topical W-7 before UVR exposure inhibited UVR induction of dopa oxidase activity in melanocytes by 49% (P = 0.029) and inhibited UVR-induced deposition of melanin in the epidermis by 88% (P = 0.006). Topical W-7 blocked 23% of the UVR but this blockage could not account for the inhibition of dopa oxidase and melanization. We conclude that, in addition to preventing edema, W-7 inhibits UVR-induced melanogenesis, possibly by affecting Ca(2+)-calmodulin and/or protein kinase C-dependent processes.

Attenuation of ultraviolet radiation-induced edema and erythema with topical calmodulin and protein kinase C inhibitors.

We treated Skh:HR1 hairless albino mice, NSA mice and hairless albino guinea pigs topically with N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W7) or trifluoperazine (TFP) before or after ultraviolet (UV) irradiation. When applied before irradiation, W7 and TFP prevented edema in Skh-1 mice and W7 prevented UV-induced edema in NSA mice in a dose-dependent manner. Preirradiation treatment with 2% W7 reduced erythema in guinea pigs by 50%. Epidermal histology of UVR-treated Skh-1 mice pretreated with W7 before UVR was similar to unirradiated mice. W7 did not reverse or prevent these UV-induced effects when applied after irradiation. Neither TFP nor W7 absorbed UV based on forward scattering absorbance spectra; we conclude that neither are physical or chemical sunscreens. These results suggest that calmodulin and/or protein kinase C-dependent events are involved in manifesting some of the effects of UV irradiation on skin.

Diacylglycerol-induced melanogenesis in Skh-2 pigmented hairless mice.

We investigated the effect of topically applied diacylglycerols (DG) on melanogenesis in Skh-2 pigmented hairless mouse skin. Groups of mice were treated according to 4 different regimens of either 1,2-dioctanoyl-sn-glycerol (DOG) or 1-oleyl-2-acetyl-sn-glycerol (OAG) with or without ultraviolet irradiation (UVR). After the treatment regimens were completed, separated epidermal tissue was stained with L-dopa and thin sections of whole skin were stained by the Warthin-Starry method to detect melanin deposition. Quantification of the stained areas by digital image analysis disclosed that DOG treatment without UVR increased the dopa-positive area in skin in a dose-dependent manner but had no effect on melanin deposition. DG treatment acted synergistically with UVR to enhance melanogenesis, with synergism being more pronounced for melanin deposition than for dopa staining. DOG treatment prior to UVR also resulted in an enhanced melanogenic response to UVR, suggesting that DG increases the sensitivity of melanocytes to subsequent UVR by inducing dopa oxidase activity. OAG also enhanced UVR-induced melanogenesis in a dose-dependent manner and was at least as potent an inducer as was DOG. Because DG is known to activate protein kinase C, our results suggest that a protein kinase C-dependent process is involved in melanogenesis.

Stereotyped responding on a two-choice guessing task by marmosets and humans treated with amphetamine.

The performance of normal human volunteers and marmosets on a 2-choice guessing task was assessed after saline (control) or amphetamine administration. In human subjects the drug increased the number of alternation responses, which can be interpreted as an increase in stereotyped switching and which is similar to the response pattern produced by some groups of psychotic patients on the same task (Frith and Done 1983; Lyon et al. 1986). Marmosets treated with amphetamine showed an increase in perseverative responding compatible with that seen on other types of task. Our conclusion is that dopaminergic systems are involved in behavioural choice mechanisms and that a dysfunction of these systems may contribute to the symptomatology of psychosis.

Selective impairment of paired associate learning after administration of a centrally-acting adrenergic agonist (clonidine).

Eight normal volunteers had IV infusions of 200 micrograms clonidine (a centrally-acting adrenergic agonist which reduces noradrenaline release), and saline in a "double-blind" cross-over design. Clonidine reduced subjective estimates of arousal but did not affect performance on the Digit Symbol Substitution Test. Clonidine impaired paired-associate learning, but it did not affect performance on a number of measures of short and long term memory. The findings suggest either 1) that there is a specific (adrenergic) mechanism involved in the acquisition of novel associations, but not in other types of learning, or 2) that paired associate learning is more vulnerable than other learning tasks to disruption of adrenergic transmission.

Transient fall and subsequent return of high aldosterone secretion by adrenal adenoma during continued dexamethasone administration.

Plasma aldosterone concentration was consistently decreased by 50% or more in 6 patients with aldosterone-producing adenoma on the first day of dexamethasone administration, only to rise subsequently with continued use of dexamethasone while plasma cortisol concentration remained suppressed. The secondary rise in plasma aldosterone was not related to measured changes in known stimuli of aldosterone secretion. It is probable that the observations result from intrinsic alteration of aldosterone synthesis in the adenoma during prolonged ACTH suppression.