Effects of the marine toxin palytoxin on human skin keratinocytes: role of ionic imbalance.

Palytoxin (PLTX), a marine toxin identified in Palythoa zoanthid corals and Ostreopsis dinoflagellates, represents an increasing hazard for human health. Recently, dermatological problems have been associated to cutaneous exposure to PLTX during Ostreopsis blooms arising the need for experimental data characterizing PLTX effects on the skin. This study highlights in vitro the cytotoxic effects of PLTX on human keratinocytes (HaCaT cell line). A short time exposure (4h) to PLTX reduced mitochondrial activity (MTT assay), cell mass (SRB assay) and plasma membrane integrity (LDH leakage) with different potencies: EC50 values of 6.1 ± 1.3×10⁻¹¹, 4.7 ± 0.9 × 10⁻¹° M and 1.8 ± 0.1 × 10⁻8 M, respectively. PLTX effect on mitochondrial activity was ouabain- and Na+-sensitive, but only partially sensitive to removal of Ca²+ ions. One hour exposure to the toxin also induced a Na+-dependent and Ca²+-independent superoxide anion production. These results indicate that among the chain of intracellular events following the interaction of PLTX with the Na+/K+-ATPase the first and crucial step is the increased intracellular Na+ concentration that triggers a sequence of cell dysfunction involving mitochondrial affection and oxidative stress, leading to an irreversible cell death. The PLTX concentrations inducing cytotoxicty seem to be lower than those of potential cutaneous human exposure during Ostreopsis ovata blooms, indicating the harmful potential of the toxin.

New polyhydroxylated triterpenes and anti-inflammatory activity of Salvia hierosolymitana.

Salvia hierosolymitana (Lamiaceae) leaves were investigated for their topical anti-inflammatory properties following a bioassay-guided fractionation. The chloroform extract showed a strong inhibition of the Croton oil-induced ear oedema in mice, comparable to that of indomethacin. Phytochemical and pharmacological investigations of this extract led to the isolation of eight anti-inflammatory polyhydroxylated triterpenes of the ursane and oleanane series. Four of them are new compounds, whose structures were elucidated by NMR and mass spectroscopy as 3beta, 6alpha,23-trihydroxyurs-12,19(29)-dien-28-oic acid, 23-( TRANS-P-coumaroyloxy)-3beta, 6alpha,30-trihydroxyurs-12-en-28-oic acid, 2alpha,3beta-dihydroxyolean-28-oic acid and 24-nor-2alpha,3beta-dihydroxyolean-4(23),12-ene.