Induction of 15-lipoxygenase mRNA and protein in early atherosclerotic lesions

Enzymatically oxidized phospholipids assume center stage as essential regulators of innate immunity and cell death

Enzymatically oxidized phospholipids (eoxPLs) are formed through regulated processes by which eicosanoids or prostaglandins are attached to phospholipids (PLs) in immune cells. These eoxPLs comprise structurally diverse families of biomolecules with potent bioactivities, and they have important immunoregulatory roles in both health and disease. The formation of oxPLs through enzymatic pathways and their signaling capabilities are emerging concepts. This paradigm is changing our understanding of eicosanoid, prostaglandin, and PL biology in health and disease. eoxPLs have roles in cellular events such as ferroptosis, apoptosis, and blood clotting and diseases such as arthritis, diabetes, and cardiovascular disease. They are increasingly recognized as endogenous bioactive mediators and potential targets for drug development. This review will describe recent evidence that places eoxPLs and their biosynthetic pathways center stage in immunoregulation.

Emerging cellular functions of the lipid metabolizing enzyme 15-Lipoxygenase-1

The oxygenation of polyunsaturated fatty acids such as arachidonic and linoleic acid through lipoxygenases (LOXs) and cyclooxygenases (COXs) leads to the production of bioactive lipids that are important both in the induction of acute inflammation and its resolution. Amongst the several isoforms of LOX that are expressed in mammals, 15-LOX-1 was shown to be important both in the context of inflammation, being expressed in cells of the immune system, and in epithelial cells where the enzyme has been shown to crosstalk with a number of important signalling pathways. This review looks into the latest developments in understanding the role of 15-LOX-1 in different disease states with emphasis on the emerging role of the enzyme in the tumour microenvironment as well as a newly re-discovered form of cell death called ferroptosis. We also discuss future perspectives on the feasibility of use of this protein as a target for therapeutic interventions.

15-oxoeicosatetraenoic acid mediates monocyte adhesion to endothelial cell

Background

A great number of studies reported that 12/15-lipoxygenase (12/15-LO) played an important role in atherosclerosis. And its arachidonic acid(AA) metabolite, 15(S)-hydroperoxy-5,8,11,13-(Z,Z,Z,E)-eicosatetraenoic acid (15(S)-HETE), is demonstrated to mediate endothelial dysfunction. 15-oxo-5,8,11,13-(Z,Z,Z,E)-eicosatetraenoic acid (15-oxo-ETE) was formed from 15-hydroxyprostaglandin dehydrogenase (PGDH)-mediated oxidation of 15(S)-HETE. However, relatively little is known about the biological effects of 15-oxo-ETE in cardiovascular disease. Here, we explore the likely role of 15-lipoxygenase (LO)-1-mediated AA metabolism,15-oxo-ETE, in the early pathogenesis of atherosclerosis.

Methods

The 15-oxo-ETE level in serum was detected by means of liquid chromatography and online tandem mass spectrometry (LC-MS/MS). And the underlying mechanisms were illuminated by molecular techniques, including immunoblotting, MTT assay, immunocytochemistry and Immunohistochemistry.

Results

Increased 15-oxo-ETE level is found in in patients with acute myocardial infarction (AMI). After 15-oxo-ETE treatment, Human umbilical vein endothelial cells (HUVECs) showed more attractive to monocytes, whereas monocyte adhesion is suppressed when treated with PKC inhibitor. In ex vivo study, exposure of arteries from C57 mice and ApoE−/−mice to 15-oxo-ETE led to significantly increased E-selectin expression and monocyte adhesion.

Conclusions

This is the first report that 15-oxo-ETE promotes early pathological process of atherosclerosis by accelerating E-selectin expression and monocyte adhesion. 15-oxo-ETE -induced monocyte adhesion is partly attributable to activation of PKC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0518-2) contains supplementary material, which is available to authorized users.

Reactive Oxygen Species (ROS) Mediate p300-dependent STAT1 Protein Interaction with Peroxisome Proliferator-activated Receptor (PPAR)-γ in CD36 Protein Expression and Foam Cell Formation

Previously, we have demonstrated that 15(S)-hydroxyeicosatetranoic acid (15(S)-HETE) induces CD36 expression involving STAT1. Many studies have shown that peroxisome proliferator-activated receptor (PPAR)-γ mediates CD36 expression. Therefore, we asked the question whether these transcriptional factors interact with each other in the regulation of CD36 expression by 15(S)-HETE. Here, we show that STAT1 interacts with PPARγ in the induction of CD36 expression and foam cell formation by 15(S)-HETE. In addition, using molecular biological approaches such as EMSA, supershift EMSA, ChIP, re-ChIP, and promoter-reporter gene assays, we demonstrate that the STAT1 and PPARγ complex binds to the STAT-binding site at -107 nucleotides in the CD36 promoter and enhances its activity. Furthermore, the interaction of STAT1 with PPARγ depends on STAT1 acetylation, which is mediated by p300. In addition, our findings show that reactive oxygen species-dependent Syk and Pyk2 stimulation is required for p300 tyrosine phosphorylation and activation. Together, these results demonstrate that an interaction between STAT1, p300, and peroxisome proliferator-activated receptor-γ is required for 15(S)-HETE-induced CD36 expression, oxidized low density lipoprotein uptake, and foam cell formation, critical events underlying the pathogenesis of atherosclerosis.

Resveratrol ameliorates cisplatin-induced oxidative injury in New Zealand rabbits

This study investigated the preventive role of resveratrol in cisplatin-induced nephrotoxicity. The study used groups of New Zealand rabbits that were treated as follows: group C (cisplatin treated), group R (resveratrol treated), group R+C (resveratrol + cisplatin treatment), and group E (control group). Kidney levels of glutathione were significantly lower in group C than in groups E and R, whereas glutathione levels in group R+C were found to be similar to the control values. Malondialdehyde levels in group C were significantly higher than in groups E and R. However, malondialdehyde levels in group R+C were similar to group E. Kidney levels of nitric oxide were significantly higher in the cisplatin group than in the control, whereas nitric oxide levels were at basal values in group R+C. Cisplatin treatment significantly reduced kidney levels of glutathione peroxidase, superoxide dismutase, and catalase activity compared with those of group E, whereas resveratrol treatment significantly increased levels of glutathione peroxidase, superoxide dismutase, and catalase activity in group R+C. However, cisplatin injection did not affect mRNA levels of glutathione peroxidase, superoxide dismutase, or catalase enzymes. Histopathological and immunohistochemical analyses indicated that cisplatin caused kidney damage, which was mostly prevented by resveratrol treatment. In conclusion, resveratrol ameliorates cisplatin-induced oxidative injury in the kidney of rabbit.

ROS-dependent Syk and Pyk2-mediated STAT1 activation is required for 15(S)-hydroxyeicosatetraenoic acid-induced CD36 expression and foam cell formation

15(S)-Hydroxyeicosatetraenoic acid (15(S)-HETE), the major 15-lipoxygenase 1/2 (15-LO1/2) metabolite of arachidonic acid (AA), induces CD36 expression through xanthine oxidase and NADPH oxidase-dependent ROS production and Syk and Pyk2-dependent STAT1 activation. In line with these observations, 15(S)-HETE also induced foam cell formation involving ROS, Syk, Pyk2, and STAT1-mediated CD36 expression. In addition, peritoneal macrophages from Western diet-fed ApoE(-/-) mice exhibited elevated levels of xanthine oxidase and NADPH oxidase activities, ROS production, Syk, Pyk2, and STAT1 phosphorylation, and CD36 expression compared to those from ApoE(-/-):12/15-LO(-/-) mice and these events correlated with increased lipid deposits, macrophage content, and lesion progression in the aortic roots. Human atherosclerotic arteries also showed increased 15-LO1 expression, STAT1 phosphorylation, and CD36 levels as compared to normal arteries. Together, these findings suggest that 12/15-LO metabolites of AA, particularly 12/15(S)-HETE, might play a crucial role in atherogenesis by enhancing foam cell formation.

Transcriptome-wide RNA sequencing analysis of rat skeletal muscle feed arteries. II. Impact of exercise training in obesity

We employed next-generation RNA sequencing (RNA-Seq) technology to determine the extent to which exercise training alters global gene expression in skeletal muscle feed arteries and aortic endothelial cells of obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Transcriptional profiles of the soleus and gastrocnemius muscle feed arteries (SFA and GFA, respectively) and aortic endothelial cell-enriched samples from rats that underwent an endurance exercise training program (EndEx; n = 12) or a interval sprint training program (IST; n = 12) or remained sedentary (Sed; n = 12) were examined. In response to EndEx, there were 39 upregulated (e.g., MANF) and 20 downregulated (e.g., ALOX15) genes in SFA and 1 upregulated (i.e., Wisp2) and 1 downregulated (i.e., Crem) gene in GFA [false discovery rate (FDR) < 10%]. In response to IST, there were 305 upregulated (e.g., MANF, HSPA12B) and 324 downregulated genes in SFA and 101 upregulated and 66 downregulated genes in GFA, with an overlap of 32 genes between arteries. Furthermore, in aortic endothelial cells, there were 183 upregulated (e.g., eNOS, SOD-3) and 141 downregulated (e.g., ATF3, Clec1b, npy, leptin) genes with EndEx and 71 upregulated and 69 downregulated genes with IST, with an overlap of 35 between exercise programs. Expression of only two genes (Tubb2b and Slc9a3r2) was altered (i.e., increased) by exercise in all three arteries. The finding that both EndEx and IST produced greater transcriptional changes in the SFA compared with the GFA is intriguing when considering the fact that treadmill bouts of exercise are associated with greater relative increases in blood flow to the gastrocnemius muscle compared with the soleus muscle.

The transcription factor CREB enhances interleukin-17A production and inflammation in a mouse model of atherosclerosis

The enzyme 15-lipoxygenase (15-LO) plays a role in atherogenesis (also known as atherosclerosis), but the underlying mechanisms are unclear. We found that 15(S)-hydroxyeicosatetraenoic acid [15(S)-HETE], the major 15-LO-dependent metabolite of arachidonic acid, stimulated the production of reactive oxygen species (ROS) by monocytes through the xanthine oxidase-mediated activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. ROS production led to the Syk-, Pyk2-, and mitogen-activated protein kinase (MAPK)-dependent production of the proinflammatory cytokine interleukin-17A (IL-17A) in a manner that required the transcription factor CREB (cyclic adenosine monophosphate response element-binding protein). In addition, this pathway was required for the 15(S)-HETE-dependent migration and adhesion of monocytes to endothelial cells. Consistent with these observations, we found that peritoneal macrophages from apolipoprotein E-deficient (ApoE-/-) mice fed a high-fat diet (a mouse model of atherosclerosis) exhibited increased xanthine oxidase and NADPH oxidase activities; ROS production; phosphorylation of Syk, Pyk2, MAPK, and CREB; and IL-17A production compared to those from similarly fed ApoE-/-:12/15-LO-/- mice. These events correlated with increased lipid deposits and numbers of monocytes and macrophages in the aortic arches of ApoE-/- mice, which resulted in atherosclerotic plaque formation. Together, these observations suggest that 15(S)-HETE exacerbates atherogenesis by enhancing CREB-dependent IL-17A production and inflammation.

Inducible endothelium-derived hyperpolarizing factor: role of the 15-lipoxygenase-EDHF pathway

Endothelium-derived hyperpolarizing factors (EDHFs) regulate vascular tone by contributing to the vasorelaxations to shear stress and endothelial agonists such as bradykinin and acetylcholine. 15(S)-Hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA) and 11(R),12(S),15(S)-trihydroxyeicosatrienoic acid (11,12,15-THETA) are endothelial metabolites of the 15-lipoxygenase (15-LO) pathway of arachidonic acid metabolism and are EDHFs. 11,12,15-THETA activates small conductance, calcium-activated potassium channels on smooth muscle cells causing membrane hyperpolarization, and relaxation. Expression levels of 15-LO in the endothelium regulate the activity of the 15-LO/15-H-11,12-EETA/11,12,15-THETA pathway and its contribution to vascular tone. Regulation of its expression is by transcriptional, translational, and epigenetic mechanisms. Hypoxia, hypercholesterolemia, atherosclerosis, anemia, estrogen, interleukins, and possibly other hormones increase 15-LO expression. An increase in 15-LO results in increased synthesis of 15-H-11,12-EETA and 11,12,15-THETA, increased membrane hyperpolarization, and enhanced contribution to relaxation by endothelial agonists. Thus, the 15-LO pathway represents the first example of an inducible EDHF. In addition to 15-LO metabolites, a number of chemicals have been identified as EDHFs and their contributions to vascular tone vary with species and vascular bed. The reason for multiple EDHFs has evaded explanation. However, EDHF functioning as constitutive EDHFs or inducible EDHFs may explain the need for chemically and biochemically distinct pathways for EDHF activity and the variation in EDHFs between species and vascular beds. This new EDHF classification provides a framework for understanding EDHF activity in physiological and pathological conditions.

12/15-Lipoxygenase mediates high-fat diet-induced endothelial tight junction disruption and monocyte transmigration: a new role for 15(S)-hydroxyeicosatetraenoic acid in endothelial cell dysfunction

A convincing body of evidence suggests that 12/15-lipoxygenase (12/15-LO) plays a role in atherosclerosis. However, the mechanisms of its involvement in the pathogenesis of this disease are not clear. Therefore, the purpose of this study is to understand the mechanisms by which 12/15-LO mediates endothelial dysfunction. 15(S)-Hydroxyeicosatetraenoic acid (15(S)-HETE), the major 12/15-LO metabolite of arachidonic acid (AA), induced endothelial barrier permeability via Src and Pyk2-dependent zonula occluden (ZO)-2 tyrosine phosphorylation and its dissociation from the tight junction complexes. 15(S)-HETE also stimulated macrophage adhesion to the endothelial monolayer in Src and Pyk2-dependent manner. Ex vivo studies revealed that exposure of arteries from WT mice to AA or 15(S)-HETE led to Src-Pyk2-dependent ZO-2 tyrosine phosphorylation, tight junction disruption, and macrophage adhesion, whereas the arteries from 12/15-LO knock-out mice are protected from these effects of AA. Feeding WT mice with a high-fat diet induced the expression of 12/15-LO in the arteries leading to tight junction disruption and macrophage adhesion and deletion of the 12/15-LO gene disallowed these effects. Thus, the findings of this study provide the first evidence of the role of 12/15-LO and its AA metabolite, 15(S)-HETE, in high-fat diet-induced endothelial tight junction disruption and macrophage adhesion, the crucial events underlying the pathogenesis of atherosclerosis.

Fluoride in low concentration modifies expression and activity of 15 lipoxygenase in human PBMC differentiated monocyte/macrophage

Epidemiological and experimental evidences demonstrate positive correlation between environmental and occupational fluoride exposure and risk to various cardio-respiratory disorders. That fore we decided to examine the effect of fluorides on activity and expression of 15LOX enzyme which is implicated in biosynthesis of inflammatory mediators. Expression of 15LOX-1 and -2 enzymes mRNA and protein was analyzed using RT PCT and immunoblotting methods respectively whereas HPLC method was used to measure the levels of 15 lipoxygenases end products. Additionally AA and LA concentration in cells was measured using GC method. We observed that fluoride in small concentration may significantly decrease activity of 15LOX-1 and -2 in human PBMC macrophages and then concentration of its end products: 15-HETE, 12-HETE and 9+13-HODE, what may cause development of inflammation through the cholesterol arrest into the macrophages and its differentiation to foam cell. Noted by our team overexpression of the 15LOX-1 enzyme in macrophages after addition of lowest fluoride concentrations (1 and 3 μM) may be aimed at fighting inflammation development and excessive intracellular lipid accumulation. But highest fluoride concentrations (6 and 10 μM) added to cell culture slowly declined expression of this enzyme probably because of developing inflammation. Additional 15LOX-2 expression in macrophages after fluoride addition was low in 1 and 3 μM concentrations, but increased significantly after 10 μM fluoride addition what may suggest developing acute inflammation, because 15LOX-2 is associated to increased local hypoxia. This study indicated that even in small concentrations fluorides changes the amounts and activity of 15 LOX-1 and -2 enzymes taking part in the development of inflammatory process.

Endothelial nitric oxide and 15-lipoxygenase-1 metabolites independently mediate relaxation of the rabbit aorta

Endothelial 15-lipoxygenase-1 (15-LO-1) metabolites of arachidonic acid (AA), 11,12,15-trihydroxyeicosatrienoic acid (THETA) and 15-hydroxy-11,12-epoxyeicosatrienoic acid (HEETA) and nitric oxide (NO) mediate relaxations to acetylcholine (ACH). However, interactions between NO and the 15-LO-1 pathway have not been explored. Therefore, the effect of physiological and pharmacological concentrations of NO on 15-LO activity and relaxation was studied in rabbit aorta. In indomethacin-treated aortic rings, maximal ACH relaxations of 91.3±4.0%, decreased to 54.5±3.0% by the NO synthase inhibitor, nitro-l-arginine (LNA), to 49.8±3% by the guanylate cyclase (GC) inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, to 63.7±4.9% by the lipoxygenase (LO) inhibitor, nordihydroguaiaretic acid (NDGA) and were completely inhibited by the combination of LNA and NDGA. AA relaxations were not affected by GC inhibition but were reduced by LO inhibition. The NO donor, dipropylenetriamine-NONOate (DPTA) caused concentration-related relaxations (EC(50)=4.7×10(-6)M). Aortic metabolism of (14)C-AA to THETA and HEETA was not altered by EC(50) concentrations of DPTA but were reduced 10-fold by 10(-3)M DPTA. In LNA-treated aorta, DPTA (3×10(-6)M) caused relaxations of 38.2.5±4%. Maximum relaxations to ACH did not differ in the presence and absence 3×10(-6)M DPTA (49.5±5% and 44.2±4%, respectively). These results indicate that NO and 15-LO-1 act in parallel to mediate ACH relaxations and NO does not alter 15-LO-1 activity.

Two single nucleotide polymorphisms in ALOX15 are associated with risk of coronary artery disease in a Chinese Han population

Arachidonate 12/15-lipoxygenase (12/15-LOX) has been implicated in the pathogenesis of atherosclerosis, but with contradicting results. The aim of this study was to investigate the association of two polymorphisms in ALOX15 and the risk of coronary artery disease (CAD) in a Chinese Han population. A total of 519 unrelated CAD patients and 608 unrelated control subjects of the Chinese Han population were recruited in the case-control study. Two tagSNPs, rs7217186:T>C and rs2619112:G>A, were selected and genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The carriers of the C allele (the CC homozygote and the CT heterozygote) of rs7217186:T>C and the carriers of the A allele (the AA homozygote and the GA heterozygote) of rs2619112:G>A displayed elevated odds ratios (ORs) for CAD compared with the TT homozygotes and GG homozygotes, respectively, after adjusting for other potential confounders including age, sex, body mass index, systolic blood pressure, diastolic blood pressure, glucose, triglyceride, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and smoking status (adjusted odds ratio [OR] = 3.2, 95% confidence interval [CI]: 1.335-7.665, P = 0.009 and adjusted OR = 3.5, 95% CI: 1.343-9.330, P = 0.011). In stratified analyses, after adjusting those aforementioned confounders, the CC and CT genotypes of rs7217186:T>C were associated with a greater risk of CAD in subjects <60 years (adjusted OR = 5.7, 95% CI: 1.557-21.097, P = 0.009) and in females (adjusted OR = 9.3, 95% CI: 1.048-82.213, P = 0.045). For rs2619112:G>A, subjects (<60 years) carrying the A allele had a greater risk of CAD than the GG homozygotes (adjusted OR = 4.9, 95% CI: 1.215-19.547, P = 0.025); the male carriers of A allele also had a greater risk (adjusted OR = 3.5, 95% CI: 1.136-11.006, P = 0.029). In summary, the present study shows that after adjustment for other confounding CAD factors, rs7217186:T>C and rs2619112:G>A of ALOX15 are associated with increased risk of CAD in this Chinese Han population.

Chronic hypoxia enhances 15-lipoxygenase-mediated vasorelaxation in rabbit arteries

15-Lipoxygenase (15-LO-1) metabolizes arachidonic acid (AA) to 11,12,15-trihydroxyeicosatrienoic acids (THETAs) and 15-hydroxy-11,12-epoxyeicosatrienoic acids (HEETA) that dilate rabbit arteries. Increased endothelial 15-LO-1 expression enhances arterial relaxations to agonists. We tested the effect of hypoxia on 15-LO-1 expression, THETA and HEETA synthesis, and relaxations in rabbit arteries. The incubation of rabbit aortic endothelial cells and isolated aortas in 0.7% O(2) increased 15-LO-1 expression. Rabbits were housed in a hypoxic atmosphere of 12% O(2) for 5 days. 15-LO-1 expression increased in the endothelium of the arteries of rabbits in 12% O(2) compared with room air. THETA and HEETA synthesis was also enhanced in aortas and mesenteric arteries. AA hyperpolarized the smooth muscle cells in indomethacin- and phenylephrine-treated mesenteric arteries of hypoxic rabbits from -29.4 +/- 1 to -50.1 +/- 3 mV. The hyperpolarization to AA was less in arteries of normoxic rabbits (from -26.0 +/- 2 to -37 +/- 2 mV). This AA-induced hyperpolarization was inhibited by the 15-LO inhibitor BW-755C. Nitric oxide and prostaglandin-independent maximum relaxations to acetylcholine (79.7 +/- 2%) and AA (38.3 +/- 4%) were enhanced in mesenteric arteries from hypoxic rabbits compared with the normoxic rabbits (49.7 +/- 6% and 19.9 +/- 2%, respectively). These relaxations were inhibited by BW-755C and nordihydroguaiaretic acid. Therefore, hypoxia increased the relaxations to agonists in the rabbit mesenteric arteries by enhancing endothelial 15-LO-1 expression and synthesis of the hyperpolarizing factors THETA and HEETA.

No association of two functional polymorphisms in human ALOX15 with myocardial infarction

The 12/15-lipoxygenase plays a janus-role in inflammation with pro-inflammatory and anti-inflammatory effects in cell systems and even opposite effects on atherosclerosis in two different animal species. Screening of the human 15-lipoxygenase (ALOX15) gene detected a polymorphic C to T substitution at position c.-292, which led to three times higher ALOX15 activity in macrophages and showed a trend to be atheroprotective in a small case-control study for coronary artery disease (CAD). A second polymorphism at position c.1693C>T leading to an T560M exchange and an inactive enzyme was recently associated with increased CAD. We now investigated whether these polymorphisms or a certain haplotype of ALOX15 are associated with myocardial infarction (MI) in a case-control subset from the population-based MONIKA/KORA cohort S3. Six polymorphisms in ALOX15 were analyzed in 2629 participants to cover all major haplotypes with a frequency higher than 1% in the Caucasian population. None of the polymorphism was associated with MI but a rare ALOX15 haplotype showed a significant protective effect on the risk for MI (p=0.03). However, none of the polymorphisms or haplotypes was associated with CRP levels. These data suggest that ALOX15 may play a less prominent role during later stages of atherosclerosis involving atherothrombotic mechanisms than eventually during early plaque development.

Selenium inhibits 15-hydroperoxyoctadecadienoic acid-induced intracellular adhesion molecule expression in aortic endothelial cells

Increased intracellular adhesion molecule 1 (ICAM-1) expression and enhanced monocyte recruitment to the endothelium are critical steps in the early development of atherosclerosis. The 15-lipoxygenase 1 (15-LOX1) pathway can generate several proinflammatory eicosanoids that are known to enhance ICAM-1 expression within the vascular endothelium. Oxidative stress can exacerbate endothelial cell inflammatory responses by modifying arachidonic acid metabolism through the 15-LOX1 pathway. Because selenium (Se) influences the oxidant status of cells and can modify the expression of eicosanoids, we investigated the role of this micronutrient in modifying ICAM-1 expression as a consequence of enhanced 15-LOX1 activity. Se supplementation reduced ICAM-1 expression in bovine aortic endothelial cells, an effect that was reversed with 15-LOX1 overexpression or treatment with exogenous 15-hydroperoxyoctadecadienoic acid (15-HPETE). ICAM-1 expression increased proportionately when intracellular15-HPETE levels were allowed to accumulate. However, changes in intracellular 15-HETE levels did not seem to affect ICAM-1 expression regardless of Se status. Our results indicate that Se supplementation can reduce 15-HPETE-induced expression of ICAM-1 by controlling the intracellular accumulation of this fatty acid hydroperoxide in endothelial cells.

Class A scavenger receptor-mediated macrophage adhesion requires coupling of calcium-independent phospholipase A(2) and 12/15-lipoxygenase to Rac and Cdc42 activation

Class A scavenger receptors (SR-A) participate in multiple macrophage functions including adhesion to modified extracellular matrix proteins present in various inflammatory disorders such as atherosclerosis and diabetes. By mediating macrophage adhesion to modified proteins and increasing macrophage retention, SR-A may contribute to the inflammatory process. Eicosanoids produced after phospholipase A(2) (PLA(2))-catalyzed release of arachidonic acid (AA) are important regulators of macrophage function and inflammatory responses. The potential roles of AA release and metabolism in SR-A-mediated macrophage adhesion were determined using macrophages adherent to modified protein. SR-A-dependent macrophage adhesion was abolished by selectively inhibiting calcium-independent PLA(2) (iPLA(2)) activity and absent in macrophages isolated from iPLA(2) beta(-/-) mice. Our results further demonstrate that 12/15-lipoxygenase (12/15-LOX)-derived, but not cyclooxygenase- or cytochrome P450-dependent epoxygenase-derived AA metabolites, are specifically required for SR-A-dependent adhesion. Because of their role in regulating actin polymerization and cell adhesion, Rac and Cdc42 activation were also examined and shown to be increased via an iPLA(2)- and LOX-dependent pathway. Together, our results identify a novel role for iPLA(2)-catalyzed AA release and its metabolism by 12/15-LOX in coupling SR-A-mediated macrophage adhesion to Rac and Cdc42 activation.

Umbilical cord blood-derived progenitor cells enhance muscle regeneration in mouse hindlimb ischemia model

Progenitor cell therapy is a potential new treatment option for ischemic conditions in the myocardium and skeletal muscles. However, it remains unclear whether umbilical cord blood (UCB)-derived progenitor cells can provide therapeutic effects in ischemic muscles and whether ex vivo gene transfer can be used for improving the effect. In this study, the use of a lentiviral vector led to efficient transduction of both UCB-derived hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Our method resulted in a long-term transgene expression and did not alter the differentiation potential of either HSCs or MSCs. In addition, we studied the therapeutic potential of CD133(+) and MSC progenitor cells transduced ex vivo with lentiviruses encoding the mature form of vascular endothelial growth factor D (VEGF-D(DeltaNDeltaC)) or the enhanced green fluorescent protein (eGFP) marker gene in a nude mouse model of skeletal muscle ischemia. Progenitor cells enhanced the regeneration of ischemic muscles without a detectable long-term engraftment of either CD133(+) or MSC progenitor cells. Our results show that, rather than directly participating in angiogenesis or skeletal myogenesis, UCB-derived progenitor cells indirectly enhance the regenerative capacity of skeletal muscle after acute ischemic injury. However, VEGF-D gene transfer of progenitor cells did not improve the therapeutic effect in ischemic muscles.

The two faces of the 15-lipoxygenase in atherosclerosis

Chronic inflammation plays a major role in atherogenesis and understanding the role of inflammation and its resolution will offer novel approaches to interfere with atherogenesis. The 15(S)-lipoxygenase (15-LOX) plays a janus-role in inflammation with pro-inflammatory and anti-inflammatory effects in cell cultures and primary cells and even opposite effects on atherosclerosis in two different animal species. There is evidence for a pro-atherosclerotic effect of 15-LOX including the direct contribution to LDL oxidation and to the recruitment of monocytes to the vessel wall, its role in angiotensin II mediated mechanisms and in vascular smooth muscle cell proliferation. In contrast to the pro-atherosclerotic effects of 15-LOX, there is also a broad line of evidence that 15-LOX metabolites of arachidonic and linoleic acid have anti-inflammatory effects. The 15-LOX arachidonic acid metabolite 15-HETE inhibits superoxide production and polymorphonuclear neutrophil (PMN) migration across cytokine-activated endothelium and can be further metabolized to the anti-inflammatory lipoxins. These promote vasorelaxation in the aorta and counteract the action of most other pro-inflammatory factors like leukotrienes and prostanoids. Anti-atherogenic properties are also reported for the linoleic acid oxidation product 13-HODE through inhibition of adhesion of several blood cells to the endothelium. Furthermore, there is evidence that 15-LOX is involved in the metabolism of the long-chain omega-3 fatty acid docosahexaenoic acid (DHA) leading to a family of anti-inflammatory resolvins and protectins. From these cell culture and animal studies the role of the 15-LOX in human atherosclerosis cannot be predicted. However, recent genetic studies characterized the 15-LOX haplotypes in Caucasians and discovered a functional polymorphism in the human 15-LOX promoter. This will now allow large studies to investigate an association of 15-LOX with coronary artery disease and to answer the question whether 15-LOX is pro- or anti-atherogenic in humans.

Adenoviral expression of 15-lipoxygenase-1 in rabbit aortic endothelium: role in arachidonic acid-induced relaxation

Endothelium-dependent vasorelaxation of the rabbit aorta is mediated by either nitric oxide (NO) or arachidonic acid (AA) metabolites from cyclooxygenase (COX) and 15-lipoxygenase (15-LO) pathways. 15-LO-1 metabolites of AA, 11,12,15-trihydroxyeicosatrienoic acid (THETA), and 15-hydroxy-11,12-epoxyeicosatrienoic acid (HEETA) cause concentration-dependent relaxation. We tested the hypothesis that in the 15-LO pathway of AA metabolism, 15-LO-1 is sufficient and is the rate-limiting step in inducing relaxations in rabbit aorta. Aorta and rabbit aortic endothelial cells were treated with adenoviruses containing human 15-LO-1 cDNA (Ad-15-LO-1) or beta-galactosidase (Ad-beta-Gal). Ad-15-LO-1-transduction increased the expression of a 75-kDa protein corresponding to 15-LO-1, detected by immunoblotting with an anti-human15-LO-1 antibody, and increased the production of HEETA and THETA from [(14)C]AA. Immunohistochemical studies on Ad-15-LO-1-transduced rabbit aorta showed the presence of 15-LO-1 in endothelial cells. Ad-15-LO-1-treated aortic rings showed enhanced relaxation to AA (max 31.7 +/- 3.2%) compared with Ad-beta-Gal-treated (max 12.7 +/- 3.2%) or control nontreated rings (max 13.1 +/- 1.6%) (P < 0.01). The relaxations in Ad-15-LO-1-treated aorta were blocked by the 15-LO inhibitor cinnamyl-3,4-dihydroxy-a-cyanocinnamate. Overexpression of 15-LO-1 in the rabbit aortic endothelium is sufficient to increase the production of the vasodilatory HEETA and THETA and enhance the relaxations to AA. This confirms the role of HEETA and THETA as endothelium-derived relaxing factors.

Thioredoxin reductase regulates the induction of haem oxygenase-1 expression in aortic endothelial cells

Certain selenoproteins such as GPX-1 (glutathione peroxidase-1) and TrxR1 (thioredoxin reductase-1) possess important antioxidant defence functions in vascular endothelial cells. Reduced selenoprotein activity during dietary selenium (Se) deficiency can result in a compensatory increase of other non-Se-dependent antioxidants, such as HO-1 (haem oxygenase-1) that may help to counteract the damaging effects of oxidant stress. However, the role of individual selenoproteins in regulating vascular-derived protective gene responses such as HO-1 is less understood. Using an oxidant stress model based on Se deficiency in BAECs (bovine aortic endothelial cells), we sought to determine whether TrxR1 activity may contribute to the differential regulation of HO-1 expression as a function of altered redox environment. Se-sufficient BAECs up-regulated HO-1 expression following stimulation with the pro-oxidant, 15-HPETE (15-hydroperoxyeicosatetraenoic acid), and levels of this antioxidant inversely correlated with EC apoptosis. While Se-deficient BAECs exhibited higher basal levels of HO-1, it was not up-regulated upon 15-HPETE treatment, which resulted in significantly higher levels of pro-apoptotic markers. Subsequent results showed that HO-1 induction depended on the activity of TrxR1, as proved with chemical inhibitor studies and direct inhibition with TrxR1 siRNA. Finally, restoring intracellular levels of the reduced substrate Trx (thioredoxin) in Sedeficient BAECs was sufficient to increase HO-1 activation following 15-HPETE stimulation. These data provide evidence for the involvement of the Trx/TrxR system, in the regulation of HO-1 expression in BAECs during pro-oxidant challenge.

Inhibition of carcinogenesis in transgenic mouse models over-expressing 15-lipoxygenase in the vascular wall under the control of murine preproendothelin-1 promoter

Oxygenases are a family of enzymes that dioxygenate unsaturated fatty acids, thus initiating membrane oxidation and signaling molecule synthesis. The lipoxygenases (LOs), a family of lipid-peroxidizing enzymes that induce structural and metabolic changes in the cell in a number of pathophysiological conditions, belong to the oxygenases family. This class of enzymes has several subgroups, named 5-, 8-, 12- and 15-LOs, and these LO-isoforms are capable of oxygenating arachidonic and linoleic acid. 15-LOs were reported to play an inhibitory role in tumor angiogenesis and, consequently, they slow down carcinogenesis. It has been suggested that its anti-carcinogenic effect is conferred by promoting cell differentiation and apoptosis. Using transgenic mice that over-express 15-LO-1 in endothelial cells under the regulation of the murine preproendothelin-1 promoter, we studied its effect on tumor and metastasis growth. We found that 15-LO-1 inhibited tumor and metastasis growth in the transgenic mice in two different models of cancer (mammary gland and Lewis lung carcinoma). This inhibition was concomitant with a higher number of apoptotic cells in the metastases of the transgenic mice and with a complicated network of multiple small blood vessels. This finding targets 15-LO as a new candidate in the treatment of carcinogenesis.

Modulating effects of cholesterol feeding and simvastatin treatment on platelet-activating factor acetylhydrolase activity and lysophosphatidylcholine concentration

BACKGROUND

Platelet-activating factor acetylhydrolyse (PAF-AH) is an enzyme that degrades PAF and bioactive oxidized lipids. However, it has been reported to be a risk factor for coronary heart disease. The present study examined the effects of cholesterol feeding and simvastatin treatment on plasma PAF-AH activity.

METHODS

Japanese White rabbits (n=22) were fed a diet containing 0.3% cholesterol and 3% corn oil for 1 month, and then divided into two groups that continued to receive this diet with (treated) or without (control) treatment with simvastatin (0.01%) for another 2 months.

RESULTS

Cholesterol feeding increased and simvastatin treatment decreased apolipoprotein (apo) B-containing lipoprotein subfractions as characterized by capillary isotachophoresis, serum levels of total cholesterol, phospholipids, LDL-C, apoE, plasma and LDL-associated PAF-AH (LDL-PAF-AH) activities, and plasma lyso-PC concentration. Cholesterol feeding also increased apoB levels but decreased the LDL-PAF-AH/LDL-C ratio and did not change the plasma PAF-AH/lyso-PC ratio. Simvastatin treatment did not affect apoB levels and only slightly increased the LDL-PAF-AH/LDL-C ratio. Secretion of PAF-AH activity from monocyte-derived macrophages was increased by cholesterol feeding but not affected by simvastatin treatment. These results indicate that PAF-AH activity is increased by cholesterol feeding due to increased secretion of PAF-AH activity from macrophages and that PAF-AH activity is decreased by simvastatin due to increased removal of lipid and enzyme contents of LDL particles.

CONCLUSION

Cholesterol elevation by cholesterol feeding and cholesterol-lowering by simvastatin modulate plasma PAF-AH activity by different mechanisms.

Antioxidant properties of two novel 2-biphenylmorpholine compounds (EP2306 and EP2302) in vitro and in vivo

The oxidation of low-density lipoprotein (LDL) is an important event in the development of atherosclerosis. In the present study, the antioxidant properties of two novel 2-biphenylmorpholine compounds (EP2306 and EP2302) were studied. Both compounds inhibited dose-dependently the in vitro oxidation of LDL induced by copper ions. EP2306 and EP2302 increased significantly the lag phase of the oxidation reaction at 0.1 and 10 microM, respectively, whereas they reduced the rate of the reaction at 1 and 10 microM, respectively. This inhibitory effect was not due to a free radical scavenging or copper-chelating activity of EP2300 compounds. Moreover, EP2306 and EP2302 inhibited 12-lipoxygenase activity dose-dependently with IC50 values of 454 and 318 microM, respectively, but had no effect on 15-lipoxygenase activity. In hyperlipidaemic rabbits treated with EP2306 for 4 weeks, there was a decrease in thiobarbituric acid-reactive substance (TBARS) levels and a significant increase in total peroxyl radical-trapping potential (TRAP) levels as compared to control animals. The present data suggest that EP2300 compounds are effective inhibitors of copper-mediated LDL oxidation in vitro. Moreover, EP2306 acts as an antioxidant in hyperlipidaemic rabbits, a property which could be beneficial in reducing atherosclerosis.

Role of monocytes in atherogenesis

This review focuses on the role of monocytes in the early phase of atherogenesis, before foam cell formation. An emerging consensus underscores the importance of the cellular inflammatory system in atherogenesis. Initiation of the process apparently hinges on accumulating low-density lipoproteins (LDL) undergoing oxidation and glycation, providing stimuli for the release of monocyte attracting chemokines and for the upregulation of endothelial adhesive molecules. These conditions favor monocyte transmigration to the intima, where chemically modified, aggregated, or proteoglycan- or antibody-complexed LDL may be endocytotically internalized via scavenger receptors present on the emergent macrophage surface. The differentiating monocytes in concert with T lymphocytes exert a modulating effect on lipoproteins. These events propagate a series of reactions entailing generation of lipid peroxides and expression of chemokines, adhesion molecules, cytokines, and growth factors, thereby sustaining an ongoing inflammatory process leading ultimately to lesion formation. New data emerging from studies using transgenic animals, notably mice, have provided novel insights into many of the cellular interactions and signaling mechanisms involving monocytes/macrophages in the atherogenic processes. A number of these studies, focusing on mechanisms for monocyte activation and the roles of adhesive molecules, chemokines, cytokines and growth factors, are addressed in this review.

Expanding expression of the 5-lipoxygenase pathway within the arterial wall during human atherogenesis

Oxidation products of low-density lipoproteins have been suggested to promote inflammation during atherogenesis, and reticulocyte-type 15-lipoxygenase has been implicated to mediate this oxidation. In addition, the 5-lipoxygenase cascade leads to formation of leukotrienes, which exhibit strong proinflammatory activities in cardiovascular tissues. Here, we studied both lipoxygenase pathways in human atherosclerosis. The 5-lipoxygenase pathway was abundantly expressed in arterial walls of patients afflicted with various lesion stages of atherosclerosis of the aorta and of coronary and carotid arteries. 5-lipoxygenase localized to macrophages, dendritic cells, foam cells, mast cells, and neutrophilic granulocytes, and the number of 5-lipoxygenase expressing cells markedly increased in advanced lesions. By contrast, reticulocyte-type 15-lipoxygenase was expressed at levels that were several orders of magnitude lower than 5-lipoxygenase in both normal and diseased arteries, and its expression could not be related to lesion pathology. Our data support a model of atherogenesis in which 5-lipoxygenase cascade-dependent inflammatory circuits consisting of several leukocyte lineages and arterial wall cells evolve within the blood vessel wall during critical stages of lesion development. They raise the possibility that antileukotriene drugs may be an effective treatment regimen in late-stage disease.

Transient experimental anemia in cholesterol-fed rabbits induces systemic overexpression of the reticulocyte-type 15-lipoxygenase and protects from aortic lipid deposition

Oxidative modification of low-density lipoprotein has been implicated in atherogenesis and the lipid peroxidizing enzyme 12/15-lipoxygenase (12/15-LOX) was suggested to be involved. For this study, we induced a strong and long-lasting systemic overexpression of the 15-LOX, in female New Zealand White rabbits by transient experimental anemia. After the hematopoietic parameters had returned to normal, these animals and age-matched controls were fed a lipid-rich Western-type diet for 10 weeks. Analyzing the lipid deposition in the aortic wall, we found that the 15-LOX overexpressing rabbits deposited significantly (P<0.01) less cholesteryl linoleate in the thoracic aorta than the corresponding controls. Similar results were obtained when free cholesterol and cholesteryl oleate were quantified. However, in the aortic arch where lipid deposition was much more severe a similar trend was observed, but the effects were not significant any more. Comparative determination (lipoxygenase overexpressing vs. control animals) of various plasma parameters as well as histological inspections of major organs did not reveal any indications for major organ malfunction. These data suggest that transient experimental anemia, which is accompanied by a long-lasting overexpression of the reticulocyte-type 15-LOX protects cholesterol-fed rabbits from lipid deposition in the aortic wall.

Zinc and copper status in children with high family risk of premature cardiovascular disease

BACKGROUND

Zinc and copper are beneficial to health, growth and development, and also for the prevention of cardiovascular disease (CVD) with regards to improved dietary habits as a preliminary step in CVD prevention. This study was conducted among 2-18-year-old children with high family risk of premature CVD in comparison to controls.

SUBJECTS AND METHODS

One hundred randomly selected children whose parents had premature myocardial infarction were included in the study. The controls were 100 individuals randomly selected from the case group's neighbors and matched for age, sex, and socioeconomic status. A four-day food record questionnaire was used to assess zinc and copper intakes, and their serum levels were determined using Flame-Atomic Absorption Spectrophotometry. The data were analyzed by SPSS/Windows V6 software, using the Student's t and Mantel-Hanzel tests. Significance of differences was considered at P<0.05.

RESULTS

The daily zinc intake was significantly lower in the case than control group (6.89+/-2.97 vs. 8.30+/-2.45 mg, P=0.047). The mean serum zinc level was not significantly different between both groups (82.12+/-14.1 vs. 92.26+/-23.7 microg/dL, P>0.05). Zinc deficiency was more prevalent among the case in boys than their controls (58% vs. 18%, P=0.04). This difference was not significantly in girls (44% vs. 40%). The daily intake and serum level of copper were not significantly different between the case and control groups. No case of copper deficiency was found. The mean systolic blood pressure was not significantly different between the zinc-deficient and zinc-sufficient subjects. Although the mean diastolic blood pressure of the former was higher than the latter, there was no statistically significant difference. About 23.7% of all studied sample had mild-to-moderate degrees of failure to thrive, with significantly lower daily intake and serum zinc level than other subjects (5.14+/-1.06 mg, 82.09+/-12.74 microg/dL vs. 6.89+/-2.14 mg, 99.25+/-27.15 microg/dL, respectively, P<0.05).

CONCLUSION

It is recommended that emphasis be placed on the consumption of food rich in zinc by children, especially those with high family risk of premature CVD.

Mammalian arachidonate 15-lipoxygenases structure, function, and biological implications

Lipoxygenases (LOXs) constitute a heterogeneous family of lipid peroxidizing enzymes capable of oxygenating polyunsaturated fatty acids to their corresponding hydroperoxy derivatives. In mammals, LOXs are classified with respect to their positional specificity of arachidonic acid oxygenation into 5-, 8-, 12-, and 15-LOXs. Arachidonate 15-LOXs may be sub-classified into a reticulocyte-type (type-1) and an epidermis-type (type-2) enzyme. Since the leukocyte-type 12-LOXs are very similar to the reticulocyte-type 15-LOXs, these enzymes are designated 12/15-LOXs. Several LOX isoforms, in particular the reticulocyte-type 15-LOX and the human 5-LOX, are well characterized with respect to their structural and functional properties On the other hand, the biological role of most LOX-isozymes including the reticulocyte-type 15-LOC is far from clear. This review is intended to summarize the recent developments in 15-LOX research with particular emphasis to molecular enzymology and regulation of gene expression. In addition, the major hypotheses on the physiological and patho-physiological roles of 15-LOXs will be discussed briefly.

Effects of COX-2 inhibitors on aortic prostacyclin production in cholesterol-fed rabbits

Prostacyclin (PGI(2)) is a potent vasodilator and inhibitor of platelet aggregation that is produced by prostacyclin synthase via the cyclooxygenase (COX) pathway of arachidonic acid metabolism. We investigated the potential role of COX-2 in the production of vasoactive prostanoids by aortic tissue in a rabbit model of dietary cholesterol-induced atherosclerosis. COX-1 was detected as the major isoform by immunoblot analysis in extracts from aortas of normal and 8 week cholesterol-fed animals with COX-2 being induced in atherosclerotic plaques from cholesterol-fed animals. Aortic tissue from cholesterol-fed animals showed decreased levels of basal 6-keto-PGF(1 alpha) and PGE(2) production as compared to the normal controls but showed no difference with respect to their ability to synthesize these prostanoids in response to exogenous arachidonic acid. The highly selective COX-2 inhibitors rofecoxib and the furanone DFP at concentrations of up to 10 micromol/l had no effect on the arachidonic acid-dependent production of 6-keto-PGF(1 alpha), in contrast to indomethacin, which caused a complete inhibition at 0.5 micromol/l. Celecoxib caused a significant inhibition of 6-keto-PGF(1 alpha) at 10 micromol/l but had little effect when the dose was lowered to 1 micromol/l. Similar effects of these inhibitors were observed with respect to the production of PGE(2) and no major difference was observed between aortic tissues from normal and cholesterol-fed animals with regard to inhibitor sensitivity. These results indicate that in a rabbit model of early stage cardiovascular disease, the basal production of 6-keto-PGF(1 alpha) and PGE(2) by aortic tissue is decreased. Furthermore, COX-2 expression is induced in atherosclerotic plaques and may play a role in altering localized synthesis of prostanoids in these lesions but does not appear to significantly impact the arachidonic acid-dependent prostacylin production of aortic tissues, which is largely mediated by COX-1.

The role of vitamin E in atherogenesis: linking the chemical, biological and clinical aspects of the disease

Atherosclerosis is a disease involving both oxidative modifications and disbalance of the immune system. Vitamin E, an endogenous redox-active component of circulating lipoproteins and (sub)cellular membranes whose levels can be manipulated by supplementation, has been shown to play a role in the initiation and progression of the disease. Recent data reveal that the activities of vitamin E go beyond its redox function. Moreover, it has been shown that vitamin E can exacerbate certain processes associated with atherogenesis. In this essay we review the role of biology of atherosclerosis, and suggest that these two facets decide the clinical manifestation and outcome of the disease.

Rabbit atherosclerotic lesions express scavenger receptor AIII mRNA, a naturally occurring splice variant that encodes a non-functional, dominant negative form of the macrophage scavenger receptor

Macrophage class A scavenger receptor types I and II (SR-AI and II) mediate the uptake of oxidized LDL in atherosclerotic lesions. The recently described type III receptor (SR-AIII), which lacks amino acids encoded by exon 10 of the SR-A gene, is unable to mediate the uptake of ligands and acts as a dominant negative regulator in the trimeric SR-A molecule. To find out whether SR-AIII might play a role in the regulation of SR-A activity in the arterial wall, we studied its expression in normal and atherosclerotic aortic intima-medias of Watanabe heritable hyperlipidemic (WHHL) and cholesterol-fed New Zealand white (NZW) rabbits. SR-A mRNA was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with a SR-AIII-specific primer pair and with a primer pair suitable for both SR-AI and III. Very low SR-AI expression and no SR-AIII expression was found in the lesion-free aortic intima-medias of WHHL rabbits and control NZW rabbits. WHHL rabbit fatty streaks contained abundant SR-AI expression and low-level SR-AIII expression. In contrast, the numerous fatty streaks and fatty plaques appearing in the aortas of cholesterol-fed (14 weeks) NZW rabbits, and the fatty plaques of WHHL rabbits contained clearly detectable SR-AIII expression in addition to the abundant SR-AI expression. In addition, SR-AIII mRNA was detected in NZW and WHHL rabbit livers. The results suggest that in advanced atherosclerotic lesions, cells may protect themselves from the excessive uptake of oxidized lipoproteins by generating SR-A molecules which cannot bind modified LDL.

Interleukin (IL)-4 deficiency does not influence fatty streak formation in C57BL/6 mice

Abundant data is present to implicate oxidatively modified low-density lipoprotein (oxLDL) in enhanced atherogenesis. Among the factors involved in LDL oxidation, an important role has been attributed to human 15-lipoxygenase (LO) and its murine analog 12-LO. The expression of these peroxidizing enzymes is under the control of cytokines, the principal of which is IL-4. In the present study we tested the hypothesis that knocking out the IL-4 gene from C57BL/6 mice would result in suppression of fatty streaks. For this purpose, we have fed 45 female IL-4 transgenic knockout (IL-4T KO) and 45 wild-type (WT) mice an atherogenic diet for 15 weeks. Consecutive determinations of the lipid profile from both study groups were performed at monthly intervals, and fatty streak formation was assessed at the aortic sinus level, upon sacrifice. The two study groups did not differ significantly with respect to the lipid profile or the uptake and degradation of iodinated oxLDL by their peritoneal macrophages. We found that the endogenous deficiency of IL-4 did not confer protection from early atherosclerosis in the IL-4T KO as compared to their WT littermates (determined at the aortic sinus). Immunohistochemical studies, Western blots and 12/15-LO activity assays revealed the presence and activity of 12/15-LO in macrophages of WT mice as well as in IL-4T KO mice. Both did not differ significantly between the study groups. The data from this study imply that deficiency in IL-4 does not affect early atherosclerosis in C57BL/6 mice fed a high-cholesterol diet.

Rabbit extracellular superoxide dismutase: expression and effect on LDL oxidation

Extracellular superoxide dismutase (EC-SOD) is a secreted antioxidative enzyme with an abundant mRNA expression in kidney and arterial wall. In order to study expression and antioxidative function of EC-SOD, we cloned the rabbit ec-sod cDNA and produced the recombinant protein in cell culture. In vitro studies did not show a direct relationship between the amounts of synthesized mRNA and secreted protein activity, suggesting post-transcriptional regulation. The antiatherogenic role of EC-SOD was studied by determining the effect of EC-SOD on the oxidation (ox) of low density lipoprotein (LDL), and subsequent degradation of oxLDL in RAW 264 macrophages in vitro. It was found that recombinant EC-SOD reduced both the degradation of LDL in RAW 264 macrophages by 28-36% and its electrophoretic mobility caused by endothelial cell-mediated oxidation. It is therefore suggested that EC-SOD can act as a protective enzyme against the development of atherosclerosis.

Altered eicosanoid biosynthesis in selenium-deficient endothelial cells

Selenium (Se) is an integral part of the Se-dependent glutathione peroxidase (Se-GSH-Px) catalytic domain. By modulating the cellular levels of fatty acid hydroperoxides, Se-GSH-Px can influence key enzymes of arachidonic acid cascade, in this case cyclooxygenase (COX) and lipoxygenase (LOX). To investigate this phenomenon, the effects of cellular Se status on the enzymatic oxidation of arachidonic acid were investigated in bovine mammary endothelial cells (BMEC), which were cultured in either Se-deficient (-Se) or Se-adequate (+Se) media. When stimulated with calcium ionophore A23187, BMEC produced eicosanoids of both COX and LOX pathways. Compared with the Se-adequate cells, the production of prostaglandin I(2) (PGI(2)), prostaglandin F(2) (PGF(2alpha)), and prostaglandin E(2) (PGE(2)) was significantly decreased in Se-deficient cells, whereas the production of thromboxane A(2) (TXA(2)) was markedly increased in the -Se BMEC cultures. Although the enzymatic oxidation of arachidonic acid by the LOX pathway was found to be relatively less than by the COX pathway, the BMEC cultured in -Se media produced significantly more 15-hydroperoxyeicosatetraenoic acid (15-HPETE) than the +Se cells produced. Based on these results, we postulate that cellular Se status plays an important regulatory role in the enzymatic oxidation of arachidonic acid by the COX and LOX pathways. The altered eicosanoid biosynthesis, especially the overproduction of 15-HPETE, in -Se BMEC may be one of the underlying biochemical phenomena responsible for vascular dysfunction during Se deficiency.

Periadventitial lacZ gene transfer to pig carotid arteries using a biodegradable collagen collar or a wrap of collagen sheet with adenoviruses and plasmid-liposome complexes

BACKGROUND

Periadventitial gene therapy is a promising alternative for the treatment of stenosis, vessel wall thickening and other complications in vascular surgery.

METHODS

We compared lacZ gene transfer efficiency of DOTMA: DOPE (1:1 w/w) plasmid/liposome complexes and adenoviruses in pig carotid arteries using perivascular delivery with either a collagen collar or a wrap of collagen sheet. Safety of the gene transfer was studied by clinical chemistry, tissue pathology and PCR analysis of lung, liver, kidney, spleen, skeletal muscle and gonads.

RESULTS

Gene transfer efficiency using the periadventitial collar was fourfold higher than using the collagen wrap with adenovirus at 7 days (10.22 +/- 2.96 vs 2.78 +/- 1.28 positive cells/mm2; p = 0.18) and 4.3-fold at 14 days (13.46 +/- 3.49 vs 3.11 +/- 0.88 positive cells/mm2; p = 0.03). Gene transfer efficiency at 7 days with adenovirus was fivefold higher than with the plasmid/liposome complexes both using the collar (10.22 +/- 2.96 vs 2.07 +/- 0.95 positive cells/mm2; p = 0.01) and the collagen wrap (2.78 +/- 1.28 vs 0.45 +/- 0.35 positive cells/mm2; p = 0.03). No lacZ activity was detected in plasmid/liposome transfected arteries at 14 days. In spite of the local gene delivery methods a moderate systemic distribution of the transgene was detected in the major organs by PCR analysis.

CONCLUSIONS

This study shows that: (i) adenovirus delivered with the periadventitial collar or the collagen wrap is well tolerated and may become an efficient new tool in vascular gene therapy, and (ii) gene transfer vector delivered in the periadventitial collar reaches the target tissue more efficiently than the vector in the collagen wrap.

Improved gene transfer efficiency in liver with vesicular stomatitis virus G-protein pseudotyped retrovirus after partial liver resection and thymidine kinase-ganciclovir pre-treatment

Liver-directed gene therapy is a promising alternative for the treatment of various liver diseases. Pseudotyped (VSV-G) retroviruses can be produced in high titres which is essential to overcome the problem of low gene transfer efficiency detected previously with first generation Moloney murine (MMLV) retroviruses and plasmid vectors. We compared the lacZ gene transfer efficiency of MMLV retroviruses and VSV-G retroviruses in Watanabe heritable hyperlipidaemic rabbit liver using an intraportal administration route. Hepatocyte proliferation was stimulated by a partial (10%) liver resection and a thymidine kinase-ganciclovir treatment. We also studied the safety of the gene transfer by clinical chemistry, tissue pathology and PCR analysis of lung, kidney, spleen and gonads. Gene transfer efficiency with the VSV-G retrovirus was significantly higher than with the traditional MMLV-based retrovirus (9.5+/-5.26 vs 0.21+/-0.10 positive hepatocytes mm(-2), P<0.05). After a 12-month follow-up period no lacZ expression was detected in liver samples. No transgene was detected in plasma or in lung, kidney, spleen and gonads by PCR analysis 7 days after gene transfer. Transient increases were found in plasma c-reactive protein, aspartyl aminotransferase and alanine aminotransferase levels shortly after the operation with both types of retroviruses. VSV-G retrovirus was well tolerated and may become an efficient new tool in liver gene therapy. The absence of transgene in systemic circulation or in extrahepatic tissues including gonads is an important safety feature required for in vivo gene therapy.

Gene therapy for angiogenesis, restenosis and related diseases

Gene therapy may be useful for the treatment of atherosclerosis and related diseases. Gene transfer to vascular system can be performed both via intravascular and extravascular routes. Gene transfer to other tissues, such as liver and muscle, can also be used. The first clinical trials for the induction of therapeutic angiogenesis with VEGF gene transfer are under way, and preliminary results are promising. In the prevention of restenosis genes inhibiting cellular proliferation and increasing NO production, such as NOS and VEGF, have been used. However, more basic research is needed to fully understand pathophysiological mechanisms involved in conditions related to atherosclerosis. Also, further developments in gene transfer vectors and gene delivery techniques are required for the improvement of the efficacy of gene therapy.

Disruption of the 12/15-lipoxygenase gene diminishes atherosclerosis in apo E-deficient mice

Atherosclerosis may be viewed as an inflammatory disease process that includes early oxidative modification of LDLs, leading to foam cell formation. This "oxidation hypothesis" has gained general acceptance in recent years, and evidence for the role of lipoxygenases in initiation of, or participation in, the oxidative process is accumulating. However, the relative contribution of macrophage-expressed lipoxygenases to atherogenesis in vivo remains unknown. Here, we provide in vivo evidence for the role of 12/15-lipoxygenase in atherogenesis and demonstrate diminished plasma IgG autoantibodies to oxidized LDL epitopes in 12/15-lipoxygenase knockout mice crossbred with atherosclerosis-prone apo E-deficient mice (apo E-/-/L-12LO-/-). In chow-fed 15-week-old apo E-/-/L-12LO-/- mice, the extent of lesions in whole-aorta en face preparations (198 +/- 60 microm2) was strongly reduced (P < 0.001, n = 12) when compared with 12/15-lipoxygenase-expressing controls (apo E-/-/L-12LO+/+), which showed areas of lipid deposition (15,700 +/- 2,688 microm2) in the lesser curvature of the aortic arch, branch points, and in the abdominal aorta. These results were observed despite cholesterol, triglyceride, and lipoprotein levels that were similar to those in apo E-deficient mice. Evidence for reduced lesion development was observed even at 1 year of age in apo E-/-/L-12LO-/- mice. The combined data indicate a role for 12/15-lipoxygenase in the pathogenesis of atherosclerosis and suggest that inhibition of this enzyme may decrease disease progression.

The diversity of the lipoxygenase family. Many sequence data but little information on biological significance

Lipoxygenases form a family of lipid peroxidising enzymes, which oxygenate free and esterified polyenoic fatty acids to the corresponding hydroperoxy derivatives. They are widely distributed in both the plant and animal kingdoms. During the last couple of years more and more lipoxygenase isoforms have been discovered but for most of them the biological significance remains unclear. This review attempts to classify the currently known mammalian lipoxygenase isoforms and critically reviews the concepts for their biological importance.

Enhanced plasma cholesterol lowering effect of retrovirus-mediated LDL receptor gene transfer to WHHL rabbit liver after improved surgical technique and stimulation of hepatocyte proliferation by combined partial liver resection and thymidine kinase--ganciclovir treatment

In this study we report an improved method for in vivo gene transfer to liver. Repeated injections of Moloney murine leukemia virus-derived retroviruses containing LDL receptor cDNA were given to the portal vein in combination with a 10% partial liver resection and stimulation of hepatocyte proliferation by plasmid/liposome-mediated thymidine kinase gene transfer and ganciclovir treatment. The method was used for the treatment of LDL receptor deficiency in Watanabe heritable hyperlipidemic rabbits. We demonstrate an increase in hepatocyte proliferation index by thymidine kinase and ganciclovir treatment from 0.9 to 1.35% and a maximum of 35% decrease in total plasma cholesterol level 2-3 months after the gene transfer. A 20% decline was still present after a 52-week follow-up period. A 50% decrease was also observed in plasma triglycerides. Liver function tests indicated a transient increase in plasma alkaline phosphatase level up to 12 weeks after the gene transfer. In situ PCR and RT-PCR analyses indicated that the transgene was present in periportal areas and was transcribed to mRNA 1 week after the gene transfer. Because of the relatively simple and controllable technique we suggest that repeated retrovirus injections via a portal vein catheter together with the limited partial liver resection and plasmid/liposome-mediated thymidine kinase gene transfer-ganciclovir treatment may be used to improve the results of retrovirus-mediated liver gene therapy.

High expression of human 15-lipoxygenase induces NF-kappaB-mediated expression of vascular cell adhesion molecule 1, intercellular adhesion molecule 1, and T-cell adhesion on human endothelial cells

Expression of 15-lipoxygenase (15-LO) is induced over 100-fold in early fatty streak lesions. 15-LO activity leads to the production of specific lipid hydroperoxides, which can have major effects on the expression of proinflammatory genes involved in atherogenesis. We have used retrovirus-mediated gene transfer to achieve stable high expression of 15-LO in human endothelial ECV304 cells. These cells were used to study the effects of 15-LO on the expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1), activation of nuclear factor kappa B (NF-kappaB), and T-cell adhesion on endothelial cells. NF-kappaB activation was greatly potentiated by increased 15-LO activity in the stably transduced cells, and both VCAM-1 and ICAM-1 were significantly induced in these cells in response to tumor necrosis factor-alpha (TNF-alpha) and phorbol 12-myristate 13-acetate (PMA) stimulation, as studied by flow cytometry. The induction of ICAM-1 was sensitive to antioxidants in a dose-dependent manner. The adherence of Jurkat T cells on the 15-LO-expressing endothelial cells was markedly induced after PMA stimulation. These results indicate that 15-LO activity may be involved in the early pathogenesis of atherosclerosis by inducing VCAM-1 and ICAM-1 expression and by increasing T-cell adhesion on the endothelium.