Epidermal vitamin A and sunburn in man

Role of Fat-Soluble Vitamins A and D in the Pathogenesis of Influenza: A New Perspective

Reduced exposure to solar radiation, leading to a deficiency of vitamin D and hence impaired innate immunity, has been suggested as a trigger for influenza viral replication and as an explanation of seasonal influenza. Although this hypothesis accounts for many unexplained facts about the epidemiology of influenza, gaps remain in understanding the pathogenesis and manifestations of the disease. Several observations suggest a role for vitamin A compounds (retinoids) in the disease. This paper presents a new model of the etiopathogenesis of influenza, suggesting that host resistance and susceptibility depend importantly on the ratio of vitamin D to vitamin A activity. Retinoid concentrations within normal physiological limits appear to inhibit influenza pathogenesis whereas higher background concentrations (i.e., very low vitamin D : A ratios) increase the risk of severe complications of the disease. There is also evidence that influenza-induced or preexisting liver disease, diabetes, and obesity worsen the severity of infection, possibly via liver dysfunction and alterations in retinoid metabolism. The model could be tested by determining the presence of retinoids in the secretions of patients with influenza and by studies of retinoid profiles in patients and controls. Potential strategies for prevention and treatment are discussed.

Speculations on the origin of the ill-effects associated with the use of visual display terminals

There are increasing reports of a wide variety of unexplained ill-effects associated with the occupational use of visual display terminals (VDTs); these include psychological complaints such as headache, irritability, and fatigue, musculoskeletal pains, dry or burning eyes, deteriorating eyesight, cataracts, facial dermatitis, and pregnancy abnormalities. Many VDTs emit near-ultraviolet (UV-A) radiation in amounts ranging from 200 to 1500 times less than the present U.S. safety standard of 1.0 X 10(-3) W/cm2. Although the possibility of a radiation hazard from VDTs is widely discounted, various points of circumstantial evidence are marshalled in this paper in support of the hypothesis that prolonged exposure to even these low amounts of UV-A radiation may result in progressive increases in sensitivity to UV-A and in cumulative biologic damage. It is further proposed that UV-A produces the ill-effects by catabolizing vitamin A in skin and plasma into highly active metabolites, the gradual accumulation of which results in an endogenous form of vitamin A intoxication. In addition to producing the skin and systemic effects of hypervitaminosis A, these metabolites presumably enter the fetal circulation, leading to pregnancy abnormalities similar to those associated with high doses of the vitamin for the treatment of skin disorders.

UV irradiation and cutaneous vitamin A: an experimental study in rabbit and human skin

The effect of UV irradiation on the concentration of cutaneous retinoids (retinol and 3-dehydroretinol) in rabbit skin in vivo and in human skin in vitro was investigated. Irradiation with 4 different narrow-wavelength bands produced dose-dependent reductions of retinol in epidermis and dermis. The maximal effect was obtained at 334 nm, a wavelength which coincides with the absorption maximum for retinol in organic solutions. 3-Dehydroretinol was not reduced to the same extent as was retinol. In human skin the photodecomposition of retinol was most extensive in epidermis and progressively less so in dermis, presumably reflecting the extent to which 334 nm radiation penetrates the tissue. The regeneration of cutaneous retinol took over a week in the rabbit. The nutritional and biologic implications of the UV-induced reduction of cutaneous retinol remain to be established.

UV treatment of uraemic pruritus reduces the vitamin A content of the skin

The effect of phototherapy on uraemic pruritus and vitamin A content in serum and epidermis was investigated in ten patients with chronic renal failure. The patients and five healthy controls were given repeated whole-body irradiation of UV-A + UV-B (total dose 7.9 + 1.3 J cm-2). Serum and skin samples were obtained before and after the treatment. Serum samples were analysed for retinol, retinol-binding protein and carotene and epidermis samples for retinol, 3-dehydroretinol and carotene. Before treatment, the retinol concentrations in serum and epidermis were higher in patients than in controls. The treatment, which relieved seven patients of pruritus, reduced the epidermal retinol from 11.6 +/- 4.5 to 7.0 +/- 3.8 nmol g-1 protein (P less than 0.02). A similar reduction occurred in the controls (4.5 +/- 1.0 v. 1.7 +/- 1.0, P less than 0.01). No changes of epidermal 3-dehydroretinol, carotene or the serum parameters occurred in either patients or controls. The putative relationship between uraemic pruritus and hypervitaminosis A and the response of this condition to UV therapy is discussed.

Vitamin A in human skin: I. detection and identification of retinoids in normal epidermis

In an attempt to identify vitamin A and derivatives (retinoids) specimens of breast skin epidermis (0.5 g) were homogenized, freeze-dried and extracted with chloroform/methanol. The evaporated extract was partitioned repeatedly between petroleum ether and a mixture of ethanol and pH-adjusted water. This yielded 3 fractions of partially purified retinoids. High-pressure liquid chromatography (HPLC) of these fractions revealed the presence of the following retinoids given in order to their abundance in the epidermis: retinyl acyl esters, retinol, 3-dehydroretinyl acyl esters and retinoic acid. Small amounts of other retinoids may also be present. In order to obtain quantitative data it was essential to add internal retinoid standards and to completely hydrolyze the skin in KOH-ethanol before extraction. The retinoids were deconjugated by this procedure but, with the exception of retinaldehyde, were otherwise unchanged. The recoveries of the endogenous retinoids at HPLC were identical to those of the internal standards. The technique was reproducible and could be applied to the analysis of nanograms of retinol and dehydroretinol in small (10-30 mg) skin specimens. The amounts of acidic retinoids were usually below the detection limit of the method (less than 10 ng/g) but the approach may be useful at the higher levels attained during retinoid therapy.

Vitamin A in human skin: II Concentrations of carotene, retinol and dehydroretinol in various components of normal skin

Pro-vitamin A(beta-carotene) and the predominant forms of vitamin A in human skin (retinol and dehydroretinol) were analyzed in hydrolyzed specimens from 4 cadavers and 22 healthy subjects. Beta-carotene was identified in extracts of epidermis by its specific absorption spectrum. Vitamin A was determined by high-pressure liquid chromatography. The concentrations were related to the wet weight or protein content of the sample. The analysis of different skin compartments showed that the concentrations of the 3 constituents were usually related as follows: carotene greater than retinol greater than dehydroretinol. The concentrations were always higher in the epidermis than in the upper dermis. Skin surface lipids contained carotene and retinol but not in amounts sufficient to contribute to the higher epidermal values. Analysis of epidermal autopsies from 5 different skin areas (back, breast, arm, leg and foot) and of epidermal biopsies from the back of the healthy subjects showed that the interindividual differences were larger for carotene and dehydroretinol than for retinol, whereas the intraindividual variations were larger for retinol. The mean (+/- SD) concentrations of carotene, retinol and dehydroretinol in back skin epidermis of healthy subjects were 13 +/- 5, 1.7 +/- 0.4 and 0.4 +/- 0.2 microgram/g protein, respectively. No significant variations with age and sex were found.

Systemic protection by antioxidants against UVL-induced erythema

An antioxidant supplemented diet provided marked systemic protection against ultraviolet light mediated erythema in hairless mice. Among the individual constituents of the diet, butylated hydroxytoluene was most effective whereas glutathione and vitamins C and E afforded negligible protection. The mixture of antioxidants, and butylated hydroxytoluene individually, demonstrated diminished, but significant, protection when applied topically. The safety of this systemic photoprotectant and its clinical relevance at present is unknown.