title: Propargylglycine inhibits hypotaurine/taurine synthesis and elevates cystathionine and homocysteine concentrations in primary mouse hepatocytes.
abstract: Our investigation showed that hepatocytes isolated from cysteine dioxygenase knockout mice (Cdo1(-/-)) had lower levels of hypotaurine and taurine than Cdo1 (+/+) hepatocytes. Interestingly, hypotaurine accumulates in cultured wild-type hepatocytes. DL-propargylglycine (PPG, inhibitor of cystathionine γ-lyase and H2S production) dramatically decreased both taurine and hypotaurine levels in wild-type hepatocytes compared to untreated cells. Addition of 2 mM PPG resulted in the decrease of the intracellular taurine levels: from 10.25 ± 5.00 observed in control, to 2.53 ± 0.68 nmol/mg protein (24 h of culture) and from 17.06 ± 9.40 to 2.43 ± 0.26 nmol/mg protein (control vs. PPG; 48 h). Addition of PPG reduced also intracellular hypotaurine levels: from 7.46 ± 3.55 to 0.31 ± 0.12 nmol/mg protein (control vs. PPG; 24 h) and from 4.54 ± 3.20 to 0.42 ± 0.11 nmol/mg protein (control vs. PPG; 48 h). The similar effects of PPG on hypotaurine and taurine levels were observed in culture medium. PPG blocked hypotaurine/taurine synthesis in wild-type hepatocytes, suggesting that it strongly inhibits cysteinesulfinate decarboxylase (pyridoxal 5'-phosphate-dependent enzyme) as well as cystathionine γ-lyase. In the presence of PPG, intracellular and medium cystathionine levels for both wild-type and Cdo1 (-/-) cells were increased. Addition of homocysteine or methionine resulted in higher intracellular concentrations of homocysteine, which is a cosubstrate for cystathionine β-synthase (CBS). It seems that PPG increases CBS-mediated desulfhydration by enhancing homocysteine levels in hepatocytes. There were no overall effects of PPG or genotype on intracellular or medium glutathione levels.
authors.affiliation: Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA, halina.jurkowska@uj.edu.pl.
authors.forename: Halina
authors.initials: H
authors.lastname: Jurkowska
authors.forename: Martha H
authors.initials: MH
authors.lastname: Stipanuk
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Hirschberger
authors.forename: Heather B
authors.initials: HB
authors.lastname: Roman
mesh_terms: D000480:Alkynes / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D003540:Cystathionine / Q000235:genetics / Q000378:metabolism*; D050558:Cysteine Dioxygenase / Q000235:genetics / Q000378:metabolism; D005260:Female; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D006710:Homocysteine / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D061251:Primary Cell Culture; D013654:Taurine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics
chemical_list: D000480:Alkynes; D006710:Homocysteine; D013654:Taurine; D003540:Cystathionine; C003949:hypotaurine; C009055:propargylglycine; D050558:Cysteine Dioxygenase; D005998:Glycine