The human gene (PTGS2) encoding an inducible isozyme of prostaglandin-endoperoxide synthase (prostaglandin-endoperoxide synthase 2) that is distinct from the well-characterized and constitutive isozyme (prostaglandin-endoperoxide synthase l), was isolated using a polymerase-chain reaction-generated cDNA fragment probe for human prostaglandin-endoperoxide synthase 2. Nucleotide sequence analysis of the entire human prostaglandin-endoperoxide-synthase-2 gene demonstrated that it is more than 8.3 kb in size and consists of ten exons; this gene is very similar to the murine and chicken prostaglandin-endoperoxide-synthase-2 genes. The structures of exons in the human prostaglandin-endoperoxide-synthase-2 gene were also similar 'to those of the human prostaglandin-endoperoxide-synthase-1 gene (PTGS1). However, the sizes of introns in the human prostaglandin-endoperoxide-synthase-2 gene were generally smaller than those of the human prostaglandin-endoperoxide-synthase-1 gene. Primer-extension analysis indicated that the transcriptional-start site is 134 bases upstream of the translational-initiation site. The sequence of the 1.69-kb region of nucleotides preceding the transcriptional-start site and the first 0.8-kb intron contained a canonical TATA box and various transcriptional-regulatory elements (CArG box, NF-IL6, PEA-1, myb, GATA-1, xenobiotic-response element, CAMP-response element, NF-KB, PEA-3, Sp-1 and 12-0-tetradecanoyl-phorbol-13-acetate-response element). The nucleotide sequence of the 5'-flanking region (275 bp) of the human prostaglandin-endoperoxide-synthase-2 gene showed 63 % similarity to the sequence of murine prostaglandin-endoperoxide-synthase-2/TISIO gene, but essentially no homology to the chicken prostaglandin-endoperoxide-synthase-2 gene, and human and murine prostaglandin-endoperoxide-synthase-1 genes. A fluorescence in situ hybridization study showed that the human genes coding for prostaglandin-endoperoxide synthase 1 (PTGSI) and prostaglandinendoperoxidase synthase 2 (PTGS2) were mapped to distinct chromosomes 9q32-q33.3 and 1q25.2-q25.3, respectively, indicating that these genes are not genetically linked.Prostaglandin-endoperoxide synthase catalyzes the first committed step of the biosynthesis of prostaglandins, thromboxanes and prostacyclin [ 1, 21. Recent studies indicated that at least two distinct isozymes exist for prostaglandin-endoperoxide synthase (prostaglandin-endoperoxide synthase 1 and prostaglandin-endoperoxide synthase 2) [3 -61. The constitutive isozyme prostaglandin-endoperoxide synthase 1 was
Objective-Plasma platelet-activating factor (PAF) acetylhydrolase (AH) is an enzyme bound with lipoproteins that degrades not only PAF but also PAF-like oxidized phospholipids that are proposed to promote atherosclerosis. In this study, we investigated the distribution of PAF-AH protein among lipoprotein classes by using adenovirus-mediated gene transfer in mice, and we examined its effects on lipoprotein oxidation and foam cell formation of macrophages. Methods and Results-Adenovirus-mediated overexpression of PAF-AH in mice resulted in a 76-to 140-fold increase in plasma PAF-AH activity. Contrary to the previous report, overexpressed human PAF-AH protein was bound to very low density lipoprotein, intermediate density lipoprotein, low density lipoprotein, and high density lipoprotein (HDL). All the lipoproteins with overexpressed human PAF-AH revealed more resistance against oxidative stress, which was associated with lower levels in autoantibody against oxidized low density lipoprotein in the plasma. In addition, HDL with human PAF-AH inhibited foam cell formation and facilitated cholesterol efflux in macrophages. Key Words: platelet-activating factor acetylhydrolase Ⅲ oxidative stress Ⅲ adenovirus Ⅲ foam cell formation Ⅲ cholesterol efflux P latelet-activating factor (PAF) acetylhydrolase (AH) is a calcium-independent enzyme that degrades PAF, a bioactive phospholipid mediator for allergic and inflammatory processes, to a biologically inactive lyso-PAF. Plasma PAF-AH, 1 of the 3 PAF-AH isoforms identified so far, is produced from macrophages and exists in the plasma in the form bound with lipoproteins; the other 2 isoforms are found only in tissues. Seventy percent to 83% of the plasma PAF-AH protein exists on LDL, and 11% to 30% exists on HDL in human plasma. 1,2 An interchange between the 2 lipoproteins has been reported in plasma PAF-AH. 1 In mice, it has been recognized that PAF-AH is associated primarily with HDL and minimally with VLDL 3,4 and that neither murine PAF-AH nor human PAF-AH has been proposed to bind to murine LDL. 5 An observational study has shown that plasma PAF-AH activity is altered in atherosclerotic diseases. 6 Oxidation of LDL, in which PAF-like oxidized phospholipids are produced on the LDL surface, is one of the key factors in the early stages of atherosclerosis. 7 Besides catalyzing PAF, plasma PAF-AH protein hydrolyzes PAF-like oxidized phospholipids, thereby most likely inactivating the biologically active mediator. However, the products of this reaction include oxidized fatty acids and lysophosphatidylcholine, 8 which are potentially inflammatory mediators that could amplify atherogenesis. Therefore, it is not fully clear whether PAF-AH is antiatherogenic or proatherogenic in humans. There was one report documenting that high PAF-AH activity is associated with an increased risk of coronary artery disease in humans. 6 However, it is not conclusive whether PAF-AH is a causative agent of coronary artery disease or just a marker. A recent animal study demonstrated that overexpressi...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.