Oxidative stress of human skin fibroblasts by treatment with ultraviolet A (UVA) radiation has been shown to lead to an increase in levels of the heme catabolizing enzyme heme oxygenase 1 [heme, hydrogen-donor:oxygen oxidoreductase (a-methene-oxidizing, hydroxylating), EC 1.14.99.3] and the iron storage protein ferritin. Here we show that human skin fibroblasts, preirradiated with UVA, sustain less membrane damage during a subsequent exposure to UVA radiation than cells that had not been preirradiated. Pretreating cells with heme oxygenase 1 antsense oligonucleotide inhibited the irradiationdependent induction of both the heme oxygenase 1 enzyme and feritin and abolished the protective effect of preirradiation. Inhibition of the UVA preirradiation-dependent increase in femtin, but not heme oxygenase, with desferrioxamine also abolished the protection. This identifies heme oxygenase 1 as a crucial enzymatic intermediate in an oxidant stress-inducible antioxidant defense mechanis, involving ferritin, in human skin fibroblasts.Expression of the heme oxygenase 1 gene is enhanced by oxidative stress (1-6) including UVA radiation (320-380 nm) (7-9), a major component of sunlight. We have recently demonstrated that induction of the heme oxygenase enzyme [heme, hydrogen-donor:oxygen oxidoreductase (a-metheneoxidizing, hydroxylating), EC 1.14.99.3] by UVA irradiation of cultured human skin fibroblasts leads to an increase in ferritin (10). Ferritin constitutes the major storage site for nonmetabolized intracellular iron and therefore plays a critical role in regulating the availability of iron to catalyze such harmful reactions as the peroxidation oflipids and the Fenton reaction producing hydroxyl radicals. Recent studies have implicated intracellular ferritin in the protection of rat kidney (11) and cultured aortic endothelial cells (12) from oxidantinduced damage. This study was undertaken to determine whether a heme oxygenase-dependent increase in ferritin levels leads to an adaptive response in human skin fibroblasts. MATERIALS AND METHODS 2607The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

No abstract

We have examined the role of the nucleus and the membrane in the activation of nuclear factor (NF)-kappa B by oxidant stress generated via the UVA (320-380 nm) component of solar radiation. Nuclear extracts from human skin fibroblasts that had been irradiated with UVA at doses that caused little DNA damage contained activated NF-kappa B that bound to its recognition sequence in DNA. The UVA radiation-dependent activation of NF-kappa B in enucleated cells confirmed that the nucleus was not involved. On the other hand, UVA radiation-dependent activation of NF-kappa B appeared to be correlated with membrane damage, and activation could be prevented by alpha-tocopherol and butylated hydroxytoluene, agents that inhibited UVA radiation-dependent peroxidation of cell membrane lipids. The activation of NF-kappa B by the DNA damaging agents UVC (200-290 nm) and UVB (290-320 nm) radiation also only occurred at doses where significant membrane damage was induced, and, overall, activation was not correlated with the relative levels of DNA damage induced by UVC/UVB and UVA radiations. We conclude that the oxidative modification of membrane components may be an important factor to consider in the UV radiation-dependent activation of NF-kappa B over all wavelength ranges examined.

Activation of expression of the heme oxygenase (HO) gene appears to be involved in a cellular defense system in mammalian cells. We now demonstrate that while HO-1 mRNA levels are strongly inducible in dermal fibroblasts they are barely inducible in human epidermal keratinocytes following oxidative stress (UVA radiation and hydrogen peroxide). Paralleling this result was the observation that HO-2 mRNA levels were low in dermal fibroblasts but were high in epidermal keratinocytes. In neither case was the HO-2 gene inducible. The expression of the two HO genes led to enzymatic activity in both types of skin cells with an approximately 2.5-fold higher level of enzymatic activity present in keratinocytes compared with fibroblasts derived from the same biopsy. In addition, ferritin levels, which have been found to be augmented via the HO-dependent release of iron from endogenous heme sources, were two- to three-fold higher in keratinocytes compared with matching fibroblasts. This higher ferritin pool would result in an enhancement of cellular iron sequestering capacity that may confer increased resistance to oxidative stress. Indeed, keratinocytes showed less UVA radiation-dependent cell membrane damage than fibroblasts. These results are consistent with the hypothesis that HO expression in human epidermis and dermis is related to cellular defense mechanisms that operate in human skin.

Iron-dependent peroxidation of rat liver microsomes, enhanced by adriamycin, was measured in the presence of increasing concentrations of a-tocopherol, b-carotene and retinol at low and high ~0,. B-Carotene and a-tocopherol inhibited lipid peroxidation by more than 60% when present at concentrations greater than 50 nmol/mg microsomal protein at both high and low p0,. Retinol inhibited peroxidation by 39% at concentrations greater than 100 nmol/mg microsomal protein. This maximal level of inhibition by retinol was unaltered by p0,. However, b-carotene was more effective than a-tocopherol or retinol at a p0, of 4 mmHg, whereas a-tocopherol was more effective under aerobic conditions. Since adriamycin-dependent lipid peroxidation is maximal at low pO,, &carotene may play a role in protecting against this process.