Paraoxonase 1 in endothelial cells impairs vasodilation induced by arachidonic acid lactone metabolite.

INTRODUCTION: Paraoxonase 1 (PON1) is a high density lipoprotein (HDL)-associated lactonase, which is known for its antiatherogenic properties. Previous studies in PON1 knockout (PON1KO) mice revealed that PON1KO mice have low blood pressure, which is inversely correlated with the renal levels of the cytochrome P450 -derived arachidonic acid metabolite 5,6-epoxyeicosatrienoic acid (5,6-EET). Our previous studies revealed that 5,6-EET is unstable, transforming to the δ-lactone isomer 5,6-δ-DHTL, an endothelium-derived hyperpolarizing factor (EDHF) that mediates vasodilation, and it is a potential substrate for PON1. AIM: To elucidate the role of PON1 in the modulation of vascular resistance via the regulation of the lactone-containing metabolite 5,6-δ-DHTL. RESULTS: In mouse resistance arteries, PON1 was found to be present and active in the endothelial layer. Vascular reactivity experiments revealed that 5,6-δ-DHTL dose-dependently dilates PON1KO mouse mesenteric arteries significantly more than wild type (w.t.) resistance arteries. Pre-incubation with HDL or rePON1 reduced 5,6-δ-DHTL-dependent vasodilation. FACS analyses and confocal microscopy experiments revealed that fluorescence-tagged rePON1 penetrates into human endothelial cells' (ECs') in both dose- and time- dependent manner, accumulate in the perinuclear compartment, and retains its lactonase activity in the cells. The presence of rePON1, but not the presence of PON1 loss-of-lactonase-activity mutant, reduced the Ca2+ influx in the ECs mediated by 5,6-δ-DHTL. CONCLUSION: PON1 lactonase activity in the endothelium affects vascular dilation by regulating Ca2+ influx mediated by the lactone-containing EDHF 5,6-δ-DHTL.

5,6-δ-DHTL, a stable metabolite of arachidonic acid, is a potential EDHF that mediates microvascular dilation.

OBJECTIVE: Prominent among the endothelium-derived hyperpolarizing factors (EDHFs) are the Cytochrome P450 (CYP) epoxygenase-derived arachidonic acid metabolites-the epoxyeicosatrienoic acids (EETs), that are known as vasodilators in the microcirculation. Among the EET isomers, 5,6-EET undergoes rapid lactonization in aqueous solution to the more stable 5,6-δ DHTL (5,6-dihydroxytrienoic lactone) isomer. It is unclear whether this metabolic transformation maintains its vasodilator potential and what is the mechanism of action. Thus, the aim of this study was to investigate the capacity of the lactone isomer, 5,6- δ DHTL, to induce dilation of arterioles and explore the endothelial Ca2+ response mechanism. APPROACH AND RESULTS: In isolated human microvessels 5,6- δ DHTL induced a dose dependent vasodilation, that was inhibited by mechanical denudation of the endothelial layer. This 5,6- δ DHTL -dependent dilation was partially reduced in the presence of L-NAME (NOS inhibitor) or the NO-scavenger, cPTIO (by 19.7%, which was not statistically significantly). In human endothelial cells, 5,6- δ DHTL induced an increase in intracellular Ca2+([Ca2+]i) in a dose dependent manner. This increase in [Ca2+]i was similar to that induced by the 5,6-EET isomer, and significantly higher than observed by administering the hydrolytic dihydroxy isomer, 5,6-DHET. Further experiments aimed to investigate the mechanism of action revealed, that the 5,6-δ DHTL-mediated ([Ca2+]i elevation was reduced by IP3 and ryanodine antagonists, but not by antagonists to the TRPV4 membrane channel. Similar to their effect on the dilation response in the arteries, NO inhibitors reduced the 5,6-δ DHTL-mediated ([Ca2+]i elevation by 20%. Subsequent 5,6-δ DHTL -dependent K+ ion efflux from endothelial cells, was abolished by the inhibition of small and intermediate conductance KCa. CONCLUSIONS: The present study shows that 5,6-δ DHTL is a potential EDHF, that dilates microvessels through a mechanism that involves endothelial dependent Ca2+ entry, requiring endothelial hyperpolarization. These results suggest the existence of additional lactone-containing metabolites that can be derived from the PUFA metabolism and which may function as novel EDHFs.

Gender effect on vascular inflammation following bariatric surgery.

Studies have shown that mortality was reduced by 31.6% in patients that underwent bariatric surgery compared with the non-operative control group. However, in most surgical series the majority of patients were women, and men had higher post-operative mortality rates and a higher postoperative morbidity, regardless of weight. Our primary end point was to study gender effects on vascular inflammation following bariatric surgery for weight loss. Methods. A prospective study evaluated vascular inflammation in obese patients before and three months after bariatric surgery. Markers of vascular inflammation were measured - before surgery and three months afterwards. Results. One hundred and two patients (73 women and 29 men, 40.5 ± 12.3 years old) underwent bariatric surgery. Correlation was found between BMI change and waist circumference change (r = 0.658, P<0.001). Three months post-surgery, BMI was significantly decreased (p<0.001) (a decrease of 8.82), waist circumference was reduced (p<0.001) (a decrease of 17.33 cm). ICAM-1 levels and hs-CRP levels were decreased (both P = 0.0001). Gender differences seem to be borderline significant with respect to the prevalence of type II diabetes mellitus (men > women; P = 0.05) and hypertension (men > women; P = 0.06). In women, following bariatric surgery, BMI was decreased (p<0.001) (a decrease of 9.25), waist circumference was reduced (p<0.001) (a decrease of 18.8cm). ICAM-1 levels were decreased (p = 0.002) and hs-CRP levels were also decreased (P = 0.0001). In men, following bariatric surgery, BMI was decreased (p = 0.001) (a decrease of 8.1), waist circumference was reduced (p<0.005) (a decrease of 14.6cm); however, although ICAM-1 levels and hs-CRP levels were decreased the decreases were non-significant (both P = 0.09). Discussion. Our study examined gender effects of bariatric surgery on vascular inflammation. Bariatric surgery had no significant effect on biochemical inflammatory markers in male patients, while females undergoing the same kind of bariatric surgery for weight loss showed a significant decrease in these markers of inflammation. These results may explain the epidemiological data that described higher morbidity and mortality among obese men undergoing bariatric operation for weight loss. This is the first study that has demonstrated a gender difference in the inflammatory responses that may affect clinical outcome, and cardiovascular morbidity and mortality.

A decrease in VEGF and inflammatory markers is associated with diabetic proliferative retinopathy.

Diabetic retinopathy is the most severe ocular complication of diabetes mellitus (DM), is associated with micro-vascular damage. The more advanced stage, proliferative diabetic retinopathy, has been linked to an increased risk of cardiovascular morbidity and mortality. Our hypothesis was that inflammatory and angiogenic markers will detect the different stages of type 2 diabetes, and may predict development of micro-vascular damage. Methods. Seventy three type II diabetic patients were randomly assigned to three groups (A - 25 patients {12 males], no diabetic retinopathy; B - 25 patients {19 males], non-proliferative retinopathy; and C - 23 patients {13 males], proliferative retinopathy),when they came for a routine follow-up visit in the ophthalmologic outpatient clinic. Twenty-three healthy subjects (14 males) served as controls. High-sensitivity C reactive protein (hs-CRP), soluble vascular cell adhesion molecule 1(sVCAM-1) and vascular endothelial growth factor (VEGF) were studied. Results. The duration of type II diabetes differed between group A (9 ± 6 years) and B (17 ± 9 years) patients (p = 0.001). No such difference was revealed between groups B and C (19 ± 6 years) (p = 0.30). A difference in hemoglobin A1C (HBgA1C) levels was detected between groups A (7.1 ± 2.7%) and B (8.5 ± 1.5%) (p = 0.02), but none was found between groups B and C (8.5 ± 1.6%) (p = 0.98). Only six patients (out of 23) used insulin treatment in group A, compared with 16 in group B (out of 25) and 17 in group C (out of 25) (p = 0.004). All three groups of diabetic patients were older (62.8 ± 10.8, 61.9 ± 9.4, 59.2 ± 10.3 years, respectively) than the controls(44.3 ± 11.6 years) (p≤0.001). Hs-CRP levels were higher in diabetic patients (4,391 ± 4,175, 4,109 ± 4,533, 3,005 ± 3,842 ng/mL, respectively) than in controls (1,659 ± 1,866 ng/mL); however, only the levels in patients of groups A (p = 0.01) and B (p = 0.03) were significantly different from those of the controls, in contrast to group C, which did not differ (p = 0.180). Similar findings were observed for sVCAM-1 (706 ± 347, 746 ± 328, 638 ± 208 ng/mL, respectively, vs. controls {552 ± 143 ng/mL]); sVCAM-1 levels of groups A and B, but not C, differed from the controls (p = 0.05, p = 0.01 and p = 0.125, respectively). With the exception of group B (p = 0.03), soluble VEGF DM type II levels (493 ± 353, 625 ± 342, 368 ± 223 pg/mL, respectively) did not vary from those of the controls (392 ± 355 pg/mL, p≥0.05). However, as the disease progressed, there was a significant decrease in VEGF levels, accompanied by a significant difference between groups B and C (p = 0.006). Conclusions. Patients with diabetes type 2with no-retinopathy and with non-proliferative retinopathy had high levels of inflammatory and angiogenic markers, which decreased in patients with diabetic proliferative retinopathy. Biomarkers of inflammation and angiogenesis may detect the progression of diabetic vascular disease and may lead towards earlier interventions that would prevent systemic complications.

Endothelial dysfunction is reversible in Helicobacter pylori-positive subjects.

BACKGROUND: Studies have shown an association between Helicobacter pylori (HP) infection and atherosclerosis. Although epidemiological studies have suggested an association between HP infection and atherosclerosis, the issue is still controversial. It is not clear whether HP eradication will reverse endothelial damage and prevent cardiovascular events. METHODS: Thirty-one dyspeptic subjects (16 men, 15 women; 50.8 ± 16.7 years) were diagnosed as HP positive using histopathological evaluation. Eleven dyspeptic subjects (5 men, 6 women; 55.4 ± 9.3 years) were negative to HP (controls). Interleukin-6 level and vascular measurements (ankle brachial index and flow-mediated diameter percent change) were done twice: on entry and 3 months afterwards. HP-positive subjects were treated with the triple therapy. RESULTS: Thirty-one HP-positive subjects (50.8 ± 16.7 years, 16 men, weight 79.6 ± 14.8 kg, height 1.70 ± 0.1 m, body mass index [BMI] 27.5 ± 4.4, waist circumference 97.6 ± 16.7 cm) were treated accordingly. There were 11 HP-negative subjects (controls) (55.4 ± 9.3 years, 5 men, weight 83.4 ± 16.8 kg, height 1.68 ± 0.1 m, BMI 29.6 ± 6.1, waist circumference 104.4 ± 13.7 cm). No difference in age (P=.27), weight (P=.51), height (P=.50), BMI (P=.30), or waist circumference (P=.20) was observed. HP-positive subjects had severe endothelial dysfunction (-1.26 ± 8.4%) that improved after treatment (8.4 ± 9.0%) (P=.001). HP-negative subjects had endothelial dysfunction (1.9 ± 9.7%) that was not improved (5.6 ± 8.3%) (P=.41). Interleukin-6 levels in serum were not elevated in HP-positive subjects before or after HP eradication (8.4 ± 17.5 vs 13.5 ± 30.7 pg/mL; P=.45). CONCLUSIONS: The novel finding of our study was that HP eradication can improve endothelial dysfunction.