Tauroursodeoxycholic acid reduces bile acid-induced apoptosis by modulation of AP-1

Ursodeoxycholic acid (UDCA) is used in the therapy of cholestatic liver diseases. Apoptosis induced by toxic bile acids plays an important role in the pathogenesis of liver injury during cholestasis and appears to be mediated by the human transcription factor AP-1. We aimed to study if TUDCA can decrease taurolitholic acid (TLCA)-induced apoptosis by modulating AP-1. TLCA (20 microM) upregulated AP-1 proteins cFos (26-fold) and JunB (11-fold) as determined by quantitative real-time PCR in HepG2-Ntcp hepatoma cells. AP-1 transcriptional activity increased by 300% after exposure to TLCA. cFos and JunB expression as well as AP-1 transcriptional activity were unaffected by TUDCA (75 microM). However, TUDCA significantly decreased TLCA-induced upregulation of cFos and JunB. Furthermore, TUDCA inhibited TLCA-induced AP-1 transcriptional activity and reduced TLCA-induced apoptosis. These data suggest that reversal of bile acid-induced AP-1 activation may be relevant for the antiapoptotic effect of TUDCA in liver cell

Bile Acid-induced Apoptosis in Hepatocytes Is Caspase-6-dependent

Apoptosis induced by hydrophobic bile acids is thought to contribute to liver injury during cholestasis. Caspase-6 is an executioner caspase that also appears to have regulatory functions in hematopoetic cell lines. We aimed to elucidate the role of caspase-6 in bile acid-induced apoptosis. The major human hydrophobic bile acid, glycochenodeoxycholic acid (GCDCA, 75 mu mol/liter), rapidly induced caspase-6 cleavage in HepG2-Ntcp human hepatoma cells. GCDCA-induced, but not tumor necrosis factor alpha-or etoposide-induced activation of effector caspases-3 and -7 was significantly reduced by 50% in caspase-6-deficient HepG2-Ntcp cells as well as in primary rat hepatocytes pretreated with a caspase-6 inhibitor. Inhibition of caspase-9 reduced GCDCA-induced activation of caspase-6, whereas inhibition of caspase-6 reduced activation of caspase-8 placing caspase-6 between caspase-9 and caspase-8. GCDCA also induced apoptosis in Fas-deficient Hep3B-Ntcp and HuH7-Ntcp hepatoma cells. In addition, GCDCA-induced apoptosis was reduced by 50% in FADD-deficient HepG2-Ntcp cells, whereas apoptosis induced by tumor necrosis factor alpha was reduced by 90%. Collectively, these observations suggest that GCDCA can induce hepatocyte apoptosis in the absence of death receptor signaling, presumably by a compensatory mitochondrial pathway. In conclusion, caspase-6 appears to play an important regulatory role in the promotion of bile acid-induced apoptosis as part of a feedback loo

Glucosinolates in Sisymbrium officinale (L.) Scop.: Comparative Analysis in Cultivated and Wild Plants and in Vitro Assays with T2Rs Bitter Taste Receptors

Sisymbrium officinale (L.) Scop., commonly known as “hedge mustard” or “the singer’s plant” is a wild plant common in Eurasian regions. Its cultivation is mainly dedicated to herboristic applications and it has only recently been introduced into Italy. The active botanicals in S. officinale are glucosinolates, generally estimated by using UV or high-performance liquid chromatography (HPLC). Using both techniques, we measured the total glucosinolates from S. officinale in different parts of the plant as roots, leaves, seeds, and flowers. A comparison was made for cultivated and wild samples, and for samples obtained with different pre-treatment and fresh, frozen, and dried storage conditions. Cultivated and wild plants have a comparable amount of total glucosinolates, while drying procedures can reduce the final glucosinolates content. The content in glucoputranjivin, which is the chemical marker for glucosinolates in S. officinale, has been determined using HPLC and a pure reference standard. Glucoputranjivin and two isothiocyanates from S. officinale have been submitted to in vitro assays with the platform of bitter taste receptors of the T2Rs family. The results show that glucoputranjivin is a selective agonist of receptor T2R16