Sphingosine 1-phosphate attenuates peroxide-induced apoptosis in HaCaT cells cultured in vitro.

BACKGROUND: Sphingosine 1-phosphate (S1P) is a sphingolipid mediator that elicits a wide array of physiological responses in various types of mammalian cells. Among the numerous biological activities elicited by S1P is protection from apoptotic cell death, which seems to take place through the cell-surface S1P receptor and the downstream phosphoinositide 3'-OH kinase (PI3-K)/Akt pathway. It is unclear whether and how S1P protects human keratinocytes from hydrogen peroxide (H2 O2 )-induced apoptosis. AIM: We investigated the effects of S1P on apoptotic cell death in HaCaT cells, spontaneously immortalized human keratinocytes. METHODS: HaCaT cells were treated with hydrogen peroxide (H2 O2 ) 1-2 mmol/L as an inducer of apoptosis. Cellular apoptosis was assessed with terminal dUTP nick-end labelling (TUNEL), WST-8 and immunoblot assays. RESULTS: In WST-8 and TUNEL assays, S1P pretreatment (1 µmol/L for 30 min) attenuated H2 O2 -induced cell death. Promotion of the cleavage of caspase-3 by H2 O2 was markedly attenuated when cells had been preincubated with S1P. S1P markedly potentiated phosphorylation (activation) of Akt in the presence of H2 O2 . Wortmannin, a selective inhibitor of the PI3-K/Akt pathway, significantly suppressed S1P-induced attenuation of caspase-3 cleavage promoted by H2 O2 . CONCLUSIONS: S1P, a sphingolipid mediator, attenuates H2 O2 -induced apoptosis of HaCaT cells, by promoting phosphorylation of the Akt pathway.

Urinary biomarker of oxidative stress in patients with psoriasis vulgaris and atopic dermatitis.

BACKGROUND: The involvement of oxidative stress in the pathogenesis of various skin disorders has been suggested for decades. However, few clinical studies have assessed oxidative stress in skin diseases. The easiest and least invasive method to assess oxidative stress in patients may be the measurement of oxidation products in urine. OBJECTIVE: This study aims to assess oxidative stress in psoriasis and atopic dermatitis patients. METHODS: Urine samples were collected from 29 psoriasis patients (25 males and 4 females), 21 atopic dermatitis patients (14 males and 7 females) and 20 healthy controls (16 males and 4 females). The severity and extent of psoriasis and atopic dermatitis was assessed by their area and severity index. We measured nitrate as a metabolite of nitric oxide, malondialdehyde as a major lipid oxidation product, and 8-hydroxydeoxyguanosine (8-OHdG) as a DNA oxidation marker. RESULTS: Urinary nitrate and 8-OHdG levels, but not malondialdehyde, were significantly higher in psoriasis patients than those in healthy controls. On the contrary, only urinary nitrate level was significantly higher in atopic dermatitis patients than those in healthy controls. The severity and extent of both psoriasis and atopic dermatitis significantly correlated with urinary nitrate level and malondialdehyde level, but it did not correlate with urinary 8-OHdG level. CONCLUSIONS: Measurement of these three urinary oxidative products is non-invasive. Above all, measurement of urinary nitrate may be most useful in the clinical assessment of oxidative stress in both psoriasis and atopic dermatitis patients. There is a possibility that urinary 8-OHdG level may indicate the different pathogenesis between psoriasis and atopic dermatitis.