DITERPENOIDS FROM GERMANDER, AN HERBAL MEDICINE, INDUCE APOPTOSIS IN ISOLATED RAT HEPATOCYTES

Background & Aims: Germander was withdrawn from the market after ifs u se for weight control caused an epidemic of hepatitis, Its toxicity wa s shown to be caused by diterpenoids and their cytochrome P4503A-media ted metabolic activation into electrophilic metabolites that deplete c ellular thiols, The aim of the present study was to determine the mech anisms of cell death, Me?hods: isolated rat hepatocytes were incubated for 2 hours with germander diterpenoids (100 mu g/mL). Results: Diter penoids decreased cell glutathione, increased cytosolic [Ca2+], activa ted Ca2+-dependent tissue transglutaminase forming a cross-linked prot ein scaffold, and caused internucleosomal DNA fragmentation and the ul trastructural features of apoptosis. Cell death was prevented by decre asing metabolic activation (with troleandomycin), preventing depletion of glutathione (with cystine), blocking activation of Ca2+-modulated enzymes (With calmidazolium), or inhibiting internucleosomal DNA fragm entation (with aurintricarboxylic acid), Apoptosis was increased acid diterpenoids caused overexpression of p53 and interleukin 1 beta-conve rting enzyme in rats treated with dexamethasone (cytochrome P4503A ind ucer), Apoptosis was also increased by a diet deficient in sulfur amin o, acids, Conclusions: The germander furano diterpenoids cause apoptos is within 2 hours in isolated rat hepatocytes. Electrophilic metabolit es may stimulate apoptosis by decreasing thiols, increasing [Ca2+], an d activating Ca2+-dependent transglutaminase and endonucleases.