Paraoxonase-1 activity determination via paraoxon substrate yields no significant difference in mild hyperhomocysteinemia.

Elevated plasma homocystein (Hcy) level has been recognized as an important risk factor for a number of cardiovascular diseases, peripheral arterial occlusive disease and venous thrombosis. A part of Hcy in the organism is turned to homocysteine thiolactone (HcyT) via a ring closure reaction, which gains rate in hyperhomocysteinemia, and in turn undergoes a hydrolytic reaction back to Hcy by paraoxonase enzyme (PON). Since this is a protective reflex action enzyme against hyperhomocysteinemia, we investigated how a mild hyperhomocysteinemic nutritional habit affected serum PON activity in a population-based study. The difference detected via enzymatic activity using the paraoxon substrate was statistically non-significant (p=0.19), suggesting a defective performance to reflect the expected significance. Determination of serum PON activity via substrate paraoxon yielded no significant difference in an acute mild hyperhomocysteinemic diet model in humans.

Epigenetic perturbations in the pathogenesis of mustard toxicity; hypothesis and preliminary results.

Among the most readily available chemical warfare agents, sulfur mustard (SM), also known as mustard gas, has been the most widely used chemical weapon. SM causes debilitating effects that can leave an exposed individual incapacitated for days to months; therefore delayed SM toxicity is of much greater importance than its ability to cause lethality. Although not fully understood, acute toxicity of SM is related to reactive oxygen and nitrogen species, oxidative stress, DNA damage, poly(ADP-ribose) polymerase (PARP) activation and energy depletion within the affected cell. Therefore several antioxidants and PARP inhibitors show beneficial effects against acute SM toxicity. The delayed toxicity of SM however, currently has no clear mechanistic explanation. One third of the 100,000 Iranian casualties are still suffering from the detrimental effects of SM in spite of the extensive treatment. We, therefore, made an attempt whether epigenetic aberrations may contribute to pathogenesis of mustard poisoning. Preliminary evidence reveals that mechlorethamine (a nitrogen mustard derivative) exposure may not only cause oxidative stress, DNA damage, but epigenetic perturbations as well. Epigenetic refers to the study of changes that influence the phenotype without causing alteration of the genotype. It involves changes in the properties of a cell that are inherited but do not involve a change in DNA sequence. It is now known that in addition to mutations, epimutations contribute to a variety of human diseases. Under light of preliminary results, the current hypothesis will focus on epigenetic regulations to clarify mustard toxicity and the use of drugs to correct possible epigenetic defects.