Elastic stockings, hydroxyethylrutosides or both for the treatment of post-thrombotic syndrome

1. Glowacki R, Jakubowski H Cross-talk between CYS-34 and lysine residues in human serum albumin revealed by N-homocysteinylation. J Biol Chem 2004; 279: 10864–71. 2. Jakubowski H, Ambrosius WT, Pratt JH. Genetic determinants of homocysteine thiolactonase activity in humans: implications for atherosclerosis. FEBS Lett 2001; 491: 35–9. 3. Voetsch B, Loscalzo. Genetic determinants of the arterial thrombosis. Arterioscler Thromb Vasc Biol 2004; 24: 216–29. pitalisation. Phenylacetate hydrolase activity was assayed on these blood samples using serum vacutainer tubes to avoid calcium chelation. The colorimetric assay was run as described (5) using phenylacetate as substrate. Phenylacetate degrading activity of PON1 is independent of the coding region polymorphisms (position 55 and 192) of this gene and thus is more reflective of the concentration of PON1 protein present (7). It is unclear whether this activity reflects the actual activity of the PON1 towards endogenous substrates such as HTL. Neither HTL degrading activity, nor HTL concentrations have been assayed in this study. The precise HTL level in human plasma has been reported for six persons (8). An inverse correlation was found between Hcy concentration and phenylacetate hydrolase activity (r = 0.36, y = –0.34x + 22,01, ddl = 110, t = 4,09, p <0.001 – Fig. 1). Thus, the level of Hcy appears to be one of the determinants of phenyl-acetate hydrolase activity in serum. While several mechanisms could account for such an effect, the observations made in hyperhomocysteinemic mice suggest that Hcy could negatively regulate PON1 gene expression in the liver which would result in decreased serum PON1 activity. It is unknown whether this Hcy effect is direct or not, however, the fact that Hcy is itself a product of PON1 activity suggests an autoregulatory mechanism whereby increased Hcy concentrations lead to the retroinhibition of the enzyme gene expression. The observations shown here could have implications for the delineation of the mechanism of Hcy action. Indeed, it is known that altered PON1 activity as observed in individuals carrying the polymorphisms at position 55 and 192 constitutes a susceptibility marker for cardiovascular disease.This is likely due to the lipoproteins-protective anti oxidant effect of PON1 and possibly to its ability to degrade HTL. The repression of serum PON1 activity could be one of the steps leading to Hcy toxicity. Alternatively, our data also suggest that PON1 level could be an additional determinant of the Hcy plasma concentration.