[Show abstract][Hide abstract] ABSTRACT: To circumvent the early lethality of manganese superoxide dismutase (SOD2)-deficient mice, we have used a skin-specific strategy with introduction of loxP sites flanking exon 3 of the SOD2 gene. To our surprise, when breeding a female keratin 14 Cre transgenic mouse to a SOD2 "floxed" male mouse, due to keratin 14 promoter-driven Cre expression in the oocytes, all offspring were heterozygous for SOD2. In sharp contrast to initial publications on SOD2(+/-) mice, the herein reported mice on a mixed genetic background (C57BL/6 x 129/Ola) in their heterozygous state (SOD(+/-)) revealed distinct ultrastructural damage of the myocard, with swelling and disruption of mitochondria and accumulation of lipid droplets, increased nitrotyrosine formation, and lipid peroxidation as well as activation of apoptosis signaling pathways in the heart in vivo. Strikingly, and so far unreported, we found a substantial decrease in the activity of the cytosolic copper, zinc superoxide dismutase (SOD1) in the heart tissue of SOD2(+/-) mice, suggesting that the breakdown of mitochondrial membranes in the heart of SOD2(+/-) mice results in the enhanced release of superoxide anion radicals or derivatives thereof with subsequent inactivation of cytosolic SOD1. This model may be particularly suited to long-term studies on age-related heart failure as well as other age-related diseases and the polygenic base of tissue-specific responses to oxidative injury.
Free Radical Biology and Medicine 07/2005; 38(11):1458-70. DOI:10.1016/j.freeradbiomed.2005.02.009 · 5.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Phospholipid-hydroperoxide glutathione peroxidase (PHGPx) exhibits high specific activity in reducing phosphatidylcholine hydroperoxides (PCOOHs) and thus may play a central role in protecting the skin against UV irradiation-triggered detrimental long term effects like cancer formation and premature skin aging. Here we addressed the role of PHGPx in the protection against UV irradiation-induced expression of matrix metalloproteinase-1 (MMP-1). For this purpose, we created human dermal fibroblast cell lines overexpressing human PHGPx. Overexpression led to a significant increase in PHGPx activity. In contrast to a maximal 4.5-fold induction of specific MMP-1 mRNA levels in vector-transfected cells at 24 h after UVA irradiation, no MMP-1 induction occurred at any studied time point after UVA treatment of PHGPx-overexpressing fibroblasts. As interleukin-6 (IL-6) was earlier shown to mediate the UVA induction of MMP-1, we studied whether PHGPx overexpression might interfere with the NFkappaB-mediated IL-6 induction and downstream signaling. Using transient transfections of IL-6 promoter constructs containing NFkappaB binding sites, we observed a high induction of the reporter gene luciferase in vector-transfected control cells and a significantly lower induction in PHGPx-overexpressing fibroblasts following UVA irradiation. Consistently both UVA irradiation and treatment of fibroblasts with PCOOHs led to phosphorylation and nuclear translocation of the p65 subunit, whereas cells overexpressing PHGPx exhibited impaired NFkappaB activation, p65 phosphorylation, and nuclear translocation. In line with this, the PHGPx-overexpressing fibroblasts showed a reduced constitutive and UVA irradiation-induced IL-6 release. After incubating PHGPx-overexpressing cells with PCOOHs a reduced induction of IL-6 was observed. This together with the suppression of UVA irradiation-induced IL-6 release in the presence of Trolox, a chain breaker of PCOOH-initiated lipid peroxidation, indicates that UVA irradiation-induced PCOOHs and subsequent lipid peroxides initiate the NFkappaB-mediated induction of IL-6, which mediates the induction of MMP-1. Our finding is particularly relevant in light of the already available small molecule mimetics of PHGPx.
[Show abstract][Hide abstract] ABSTRACT: Reactive oxygen species generated in the skin by UV irradiation promote photoaging and photocarcinogenesis. The manganese (Mn) superoxide dismutase (SOD) is a primary antioxidant enzyme that crucially contributes to the homeostasis of oxygen radicals within the mitochondria, and thus critically participates in the control of senescence and tumor generation.
To determine whether repetitive UV-B exposure, as practiced for light hardening during phototherapy for various photodermatoses, can enhance the adaptive antioxidant response by up-regulating MnSOD activity in either the epidermal or the dermal skin compartment.
In vitro experiments to determine MnSOD activity levels in cultured human dermal fibroblasts and epidermal cells (HaCaT cells and primary keratinocytes) at different times after direct UV-B exposure or after incubation of human dermal fibroblasts with supernatants from UV-B-irradiated epidermal cells.
Photobiological research laboratory in a university dermatology department.
Irradiation of cultured human dermal fibroblasts and epidermal cells with UV-B.
Manganese SOD messenger RNA and activity levels in cultured irradiated or mock-treated skin cells.
No increase in MnSOD activity could be detected in fibroblasts or epidermal cells until 24 hours after UV-B irradiation. However, fibroblasts incubated with supernatants from UV-B-irradiated epidermal cells showed a marked increase in specific MnSOD messenger RNA and activity. Removal of interleukin 1alpha, interleukin 1beta, and tumor necrosis factor alpha from the supernatants led to a significant reduction of MnSOD mRNA in fibroblasts.
Irradiation of the epidermal cells with UV-B induced a release of soluble factors that amplified MnSOD activity in fibroblasts via a paracrine mechanism.
Archives of Dermatology 12/2002; 138(11):1473-9. · 4.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The skin is increasingly exposed to ambient UV-irradiation thus increasing risks for photooxidative damage with long-term detrimental effects like photoaging, characterized by wrinkles, loss of skin tone and resilience. Photoaged skin displays alterations in the cellular component and extracellular matrix with accumulation of disorganized elastin and its microfibrillar component fibrillin in the deep dermis and a severe loss of interstitial collagens, the major structural proteins of the dermal connective tissue. The unifying pathogenic agents for these changes are UV-generated reactive oxygen species (ROS) which deplete and damage non-enzymatic and enzymatic antioxidant defense systems of the skin. As well as causing permanent genetic changes, ROS activate cytoplasmic signal transduction pathways in resident fibroblasts that are related to growth, differentiation, senescence and connective tissue degradation. This review focuses on the role of UV-induced ROS in the photodamage of the skin resulting in clinical and biochemical characteristics of photoaging. In addition, the relationship of photoaging to intrinsic aging of the skin will be briefly discussed. A decrease in the overall ROS load by efficient sunscreens or other protective agents may represent promising strategies to prevent or at least minimize ROS-induced photoaging.
Journal of Photochemistry and Photobiology B Biology 11/2001; 63(1-3):41-51. DOI:10.1016/S1011-1344(01)00201-9 · 2.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In recent years, the exposure of human skin to environmental and artificial UV irradiation has increased dramatically. This is due not only to increased solar UV irradiation as a consequence of stratospheric ozone depletion, but also to inappropriate social behaviour with the use of tanning salons still being very popular in the public view. Besides this, leisure activities and a lifestyle that often includes travel to equatorial regions add to the individual annual UV load. In addition to the common long-term detrimental effects such as immunosuppression and skin cancer, the photo-oxidative damage due to energy absorption of UV photons in an oxygenized environment leads to quantitative and qualitative alterations of cells and structural macromolecules of the dermal connective tissue responsible for tensile strength, resilience and stability of the skin. The clinical manifestations of UV/reactive oxygen species (ROS)-induced disturbances result in photoaged skin with wrinkle formation, laxity, leathery appearance as well as fragility, impaired wound healing capacities and higher vulnerability. Strategies to prevent or at least minimize ROS-induced photo-ageing and intrinsic ageing of the skin necessarily include protection against UV irradiation and antioxidant homeostasis.