ABSTRACT
Transgenic tomato plants were constructed with an empty vector (EV) or a vector expressing an apoA-I mimetic peptide, 6F. EV or 6F tomatoes were harvested, lyophilized, ground into powder, added to Western diet (WD) at 2.2% by weight, and fed to LDL receptor-null (LDLR(-/-)) mice at 45 mg/kg/day 6F. After 13 weeks, the percent of the aorta with lesions was 4.1 ± 4%, 3.3 ± 2.4%, and 1.9 ± 1.4% for WD, WD + EV, and WD + 6F, respectively (WD + 6F vs. WD, P = 0.0134; WD + 6F vs. WD + EV, P = 0.0386; WD + EV vs. WD, not significant). While body weight did not differ, plasma serum amyloid A (SAA), total cholesterol, triglycerides, and lysophosphatidic acid (LPA) levels were less in WD + 6F mice; P < 0.0295. HDL cholesterol and paroxonase-1 activity (PON) were higher in WD + 6F mice (P = 0.0055 and P = 0.0254, respectively), but not in WD + EV mice. Plasma SAA, total cholesterol, triglycerides, LPA, and 15-hydroxyeicosatetraenoic acid (HETE) levels positively correlated with lesions (P < 0.0001); HDL cholesterol and PON were inversely correlated (P < 0.0001). After feeding WD + 6F: i) intact 6F was detected in small intestine (but not in plasma); ii) small intestine LPA was decreased compared with WD + EV (P < 0.0469); and iii) small intestine LPA 18:2 positively correlated with the percent of the aorta with lesions (P < 0.0179). These data suggest that 6F acts in the small intestine and provides a novel approach to oral apoA-I mimetic therapy.
Subject(s)
Apolipoprotein A-I/chemistry , Peptides/chemistry , Peptides/therapeutic use , Animals , Apolipoproteins E/deficiency , Apolipoproteins E/genetics , Atherosclerosis/drug therapy , Cholesterol/blood , Female , Hydroxyeicosatetraenoic Acids/blood , Intestine, Small/metabolism , Solanum lycopersicum/genetics , Solanum lycopersicum/metabolism , Lysophospholipids/blood , Mice , Mice, Inbred C57BL , Mice, Knockout , Peptides/genetics , Peptides/metabolism , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , Receptors, LDL/deficiency , Receptors, LDL/genetics , Triglycerides/bloodABSTRACT
We examined whether reduced levels of Apolipoprotein A-I (apoA-I) in ovarian cancer patients are causal in ovarian cancer in a mouse model. Mice expressing a human apoA-I transgene had (i) increased survival (P < 0.0001) and (ii) decreased tumor development (P < 0.01), when compared with littermates, following injection of mouse ovarian epithelial papillary serous adenocarcinoma cells (ID-8 cells). ApoA-I mimetic peptides reduced viability and proliferation of ID8 cells and cis-platinum-resistant human ovarian cancer cells, and decreased ID-8 cell-mediated tumor burden in C57BL/6J mice when administered subcutaneously or orally. Serum levels of lysophosphatidic acid, a well-characterized modulator of tumor cell proliferation, were significantly reduced (>50% compared with control mice, P < 0.05) in mice that received apoA-I mimetic peptides (administered either subcutaneously or orally), suggesting that binding and removal of lysophosphatidic acid is a potential mechanism for the inhibition of tumor development by apoA-I mimetic peptides, which may serve as a previously unexplored class of anticancer agents.
Subject(s)
Apolipoprotein A-I/therapeutic use , Ovarian Neoplasms/drug therapy , Peptides/therapeutic use , Precancerous Conditions/drug therapy , Animals , Apolipoprotein A-I/pharmacology , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Disease Models, Animal , Drinking Behavior/drug effects , Female , Humans , Injections , Lysophospholipids/blood , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neoplasm Transplantation/pathology , Ovarian Neoplasms/blood , Ovarian Neoplasms/pathology , Peptides/pharmacology , Precancerous Conditions/pathology , Survival Analysis , Tumor Burden , WaterABSTRACT
Omega-6 (omega-6) polyunsaturated fatty acids (PUFA), abundant in the Western diet, are precursors for a number of key mediators of inflammation including the 2-series of prostaglandins (PG). PGE(2), a cyclooxygenase (COX) metabolite of arachidonic acid, a omega-6 PUFA, is a potent mediator of inflammation and cell proliferation. Dietary supplements rich in omega-3 PUFA reduce the concentrations of 2-series PG and increase the synthesis of 3-series PG (e.g., PGE(3)), which are believed to be less inflammatory. However, studies on cellular consequences of increases in 3-series PG in comparison to 2-series PG have not been reported. In this study, we compared the effects of PGE(2) and PGE(3) on (i) cell proliferation in NIH 3T3 fibroblasts, (ii) expression and transcriptional regulation of the COX-2 gene in NIH 3T3 fibroblasts, and (iii) the production of an inflammatory cytokine, IL-6, in RAW 264.7 macrophages. PGE(3), unlike PGE(2), is not mitogenic to NIH 3T3 fibroblasts. PGE(2) and PGE(3) both induce COX-2 mRNA via similar signaling mechanisms; however, compared with PGE(2), PGE(3) is significantly less efficient in inducing COX-2 gene expression. Furthermore, although both PGE(2) and PGE(3) induce IL-6 synthesis in RAW 264.7 macrophages, PGE(3) is substantially less efficient compared with PGE(2). We further show that increasing the omega-3 content of membrane phospholipid results in a decrease in mitogen-induced PGE(2) synthesis. Taken together, our data suggest that successful replacement of omega-6 PUFA with omega-3 PUFA in cell membranes can result in a decreased cellular response to mitogenic and inflammatory stimuli.