Effect of specialized pro-resolving lipid mediators in the regulation of vascular tone and inflammation in human saphenous vein.

Specialized pro-resolving lipid mediators (SPMs), derived from polyunsaturated fatty acids are important mediators in the resolution of inflammation. Recent studies have focused on the effects of SPMs in cardiovascular health and diseases. However, little is known about the effect SPMs on human vascular tone. Therefore, in this study it is aimed to investigate the effect of various SPMs including resolvin D- and E-series, maresin-1 (MaR1) and lipoxin-A4 (LxA4) on the vascular tone of human isolated saphenous vein (SV) preparations under inflammatory conditions. In addition, we aimed to evaluate the effects of SPMs on the release of pro-inflammatory mediators, monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF- α) from human SV. Pretreatment of isolated of human SV with resolvin E1 (RvE1), resolvin D1 (RvD1) and MaR1 (100 nM, 18 h) significantly reduced the contractile responses to thromboxane A2 mimetic, U46619 whereas pretreatment with LxA4 and RvD2 (100 nM, 18 h) had no significant effect on the vascular tone of SV. Moreover, RvE1, RvD1 and MaR1 but not LxA4 and RvD2 (100 nM, 18 h) pretreatment diminished the release of MCP-1 and TNF-α from SV. In conclusion, our findings suggest that pre-treatment with RvE1, RvD1, and MaR1 could have potential benefits in decreasing graft vasospasm and vascular inflammation in SV.

Comparative study of coronary artery bypass graft materials: reduced contraction and ADMA levels in internal mammary artery versus saphenous vein.

BACKGROUND: Vasospasm and atherosclerosis due to low endothelial capacity are the most important causes of coronary artery bypass graft failure observed in internal mammary artery (IMA) and saphenous vein (SV). Vasospasm can be mimicked in in-vitro studies by inducing vasoconstriction of graft materials. In the present study, we aimed to compare the vascular contraction induced by several spasmogens including prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2α), phenylephrine (PE), leukotriene C4 (LTC4), LTD4, potassium chloride (KCl), and arachidonic acid between IMA and SV preparations. Furthermore, endothelial capacity, nitrite and asymmetric dimethylarginine (ADMA) levels were compared between two grafts. METHODS: By using organ bath, contractile responses induced by different spasmogens were compared between IMA and SV preparations derived from patients underwent coronary artery bypass surgery (N.=35). The endothelial capacity was determined by acetylcholine-induced (ACh) relaxation in PE-precontracted vessels. Nitrite and ADMA levels were measured in organ culture supernatant of IMA and SV preparations. RESULTS: Contractile responses induced by PGE2, PGF2α, PE, LTC4, LTD4, KCl and arachidonic acid were significantly lower in IMA preparations versus SV preparations. ACh-induced relaxation was significantly more prominent in IMA than SV preparations. Nitrite levels were greater and ADMA levels were lower in IMA versus SV preparations. CONCLUSIONS: IMA has reduced capacity to constrict to several vasoconstrictor agents. Furthermore, IMA has greater endothelial capacity associated with higher nitrite levels and lower ADMA levels. Our results support the greater patency rate observed in IMA versus SV preparations.

In search of pulmonary hypertension treatments: Effect of 17ß-estradiol on PGI2 pathway in human pulmonary artery.

INTRODUCTION: Prostacyclin (PGI2) is synthetized by PGI2 synthase (PGIS) and induces vasorelaxation via activation of cyclic AMP (cAMP) generating IP-receptor. Several components of the PGI2 signaling pathway are reduced in patients with pulmonary hypertension (PH). AIM: To study the effect of 17ß-estradiol (E2) on the PGI2 signaling pathway in human pulmonary arteries (HPA) and in their smooth muscle cells (hPASMC) derived from Group-3 PH and non-PH patients. METHODS: Following E2-treatments of isolated HPA and cultured hPASMC, we measured: 6-keto-Prostaglandin F1α (PGI2 stable metabolite) by ELISA, PGIS and IP protein levels by Western blot and HPA vasorelaxations with an organ bath system. RESULTS: Incubation with E2 (24/48 h, doses ≥ 10 nM) significantly increased the expression of PGIS in hPASMC derived from both PH (65-98%) and non-PH (21-33%) patients, whereas incubation with E2 (2 h, 0.1 and 1 µM) increased 6-keto-PGF1α production in HPA from Group-3 PH patients only, and did not affect 6-keto-PGF1α production in hPASMC from either non-PH or Group-3 PH patients. Increases in IP receptor expression were observed following 10 mM E2-treatment of hPASMC from non-PH (33% after 48 h) and Group-3 PH (23% after 24 h) patient lungs. Finally, preincubation with 100 nM E2 significantly increased arachidonic acid-induced vasorelaxation of HPA from non-PH patient lungs but not of HPA from Group-3 PH patient lungs. CONCLUSION: E2-treatment may help to restore the PGI2-pathway in Group-3 PH.

Mechanism of thromboxane receptor-induced vasoconstriction in human saphenous vein.

Saphenous vein (SV) is one of the most widely used graft material in patients undergoing coronary artery bypass graft surgery (CABG). Thromboxane A2 (TXA2) is implicated in graft failure by inducing vasoconstriction and platelet aggregation. The aim of this study is to investigate the mechanism involved in TXA2-induced vasoconstriction in human SV. The role of different inhibitors and blockers on U46619 (TXA2-mimetic)-induced vasoconstriction is investigated by using an isolated organ bath system. Relaxation responses to several mediators are evaluated in SV pre-contracted with U46619 and compared with those pre-contracted with phenylephrine. Our results demonstrate that U46619-induced contraction is completely blocked by myosin light chain kinase inhibitor ML-9 or TP receptor antagonist BAY u3405. Furthermore, U46619-induced contraction is partially inhibited by phospholipase C inhibitor U73122, protein kinase C inhibitor calphostin C, Rho-kinase inhibitor Y-27632, L-type calcium channel blocker nifedipine, store-operated channel inhibitor SKF96365 or removal of extracellular calcium. Relaxation responses to NO donor (sodium nitroprusside), guanylate cyclase (GC) stimulator (riociguat), phosphodiesterase (PDE) inhibitors (sildenafil, IBMX), adenylate cyclase (AC) activator (forskolin) and acetylcholine (ACh) are markedly reduced when U46619 is used as a pre-contraction agent. Our results demonstrate that influx of extracellular Ca2+ (through L-type calcium channels and store-operated calcium channels) and intracellular Ca2+ release together with Ca2+ sensitization (through Rho-kinase activation) are necessary components for TXA2-induced vasoconstriction in SV. Moreover, more pronounced decrease in vasorelaxation induced by several mediators (SNP, riociguat, sildenafil, IBMX, forskolin, and ACh) in the presence of U46619 when compared with phenylephrine suggests that there is a crosstalk between the TP receptor signaling pathway and PDE, AC, GC enzymes. We believe that the investigation of mechanism of the TXA2-induced vasoconstriction in SV will provide additional information for the prevention of SV graft failure.

In Vitro Effects of Eicosapentaenoic and Docosahexaenoic Acid on the Vascular Tone of a Human Saphenous Vein: Influence of Precontractile Agents.

BACKGROUND: Cardiovascular effects of omega-3 polyunsaturated fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been widely reported. However, there are limited studies concerning their effects on human blood vessels. Therefore, the aim of this study was to investigate the direct vascular effects of EPA and DHA on the human saphenous vein (SV) precontracted with either prostaglandin F2α (PGF2α), or thromboxane A2 analogue (U46619), or norepinephrine (NE). Moreover, we aimed to investigate the protein expression of free fatty acid receptor 4 (FFAR4) in human SV. METHODS: Pretreatment of human SV rings with EPA and DHA (100 µM, 30 min) was tested on vascular reactivity induced by PGF2α (10 nM to 5 µM), NE (10 nM to 100 µM), and U46619 (1 nM to 100 nM). In addition, direct relaxant effects of EPA/DHA (1-100 µM) were tested in human SV rings precontracted by PGF2α, NE, and U46619. Furthermore, the involvement of potassium channels on their vascular effects was investigated in the presence of the nonselective K+ channel inhibitor tetraethylammonium chloride. RESULTS: Pretreatment with EPA and DHA resulted in a significant decrease in vascular reactivity induced by U46619 and PGF2α compared to NE. In the presence of TEA, the relaxant effects of EPA and DHA were significantly decreased in SV preparations precontracted by U46619 and PGF2α for DHA. Furthermore, FFAR-4 protein was expressed in tissue extracts of human SV. CONCLUSIONS: Our study demonstrates that both EPA and DHA reduce the increased vascular tone elicited by contractile agents on the human SV and that the direct vasorelaxant effect is likely to involve potassium channels.

Interaction between PGI2 and ET-1 pathways in vascular smooth muscle from Group-III pulmonary hypertension patients.

Pulmonary hypertension (PH) is characterized by an elevation of mean pulmonary artery pressure and it is classified into five groups. Among these groups, PH Group-III is defined as PH due to lung disease or hypoxia. Prostacyclin (PGI2) analogues (iloprost, treprostinil) and endothelin-1 (ET-1) receptor antagonists (ERA) (used alone or in combination) are therapies used for treating PH. The mechanisms underlying the positive/negative effects of combination treatment are not well documented, and in this study, we tested the hypothesis that the combination of a PGI2 analogue (iloprost, treprostinil) and an ERA may be more effective than either drug alone to treat vasculopathies observed in PH Group-III patients. Using Western blotting, ETA and ETB receptor expression were determined in human pulmonary artery (HPA) preparations derived from control and PH Group-III patients, and the physiologic impact of altered expression ratios was assessed by measuring ET-1 induced contraction of ex vivo HPA and human pulmonary veins (HPV) in an isolated organ bath system. In addition, the effects of single agent or combination treatments with a PGI2 analogue and an ERA on ET-1 release and HPA smooth muscle cells (hPASMCs) proliferation were determined by ELISA and MTT techniques, respectively. Our results indicate that the increased ETA/ETB receptor expression ratio in HPA derived from PH Group-III patients is primarily governed by a greatly depressed ETB receptor expression. However, contractions induced by ET-1 are not impacted in HPA and HPV derived from PH Group-III patients as compared to controls. Also, we found that the combination of an ETA receptor antagonist (BQ123) with iloprost provides greater inhibition of hPASMCs proliferation (-48±14% control; -32±06% PH) than either agent alone. Of note, while the ETB receptor antagonist (BQ788) increases ET-1 production from PH Group-III patients' preparations (HPA, parenchyma), even under these more proliferative conditions, iloprost and treprostinil are still effective to inhibit hPASMCs proliferation (-22/-24%). Our findings may provide new insights for the treatment of PH Group-III by combining a PGI2 analogue and a selective ETA receptor antagonist.

Omega-3 polyunsaturated fatty acids reduce vascular tone and inflammation in human saphenous vein.

Dietary intake of omega-3 polyunsaturated fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been reported to have beneficial cardiovascular effects. However, little is known about the effect of EPA and DHA on human vascular tone. Therefore, the aim of this study is to evaluate the effect of EPA and DHA on vascular tone of the human saphenous vein (SV) obtained from patients undergoing coronary bypass operation under normal and inflammatory conditions. Moreover, we aimed to investigate the effect of EPA and DHA on the release of inflammatory mediators from SV. Pretreatment of SV with EPA and DHA (100µM, 18h) decreased the contractile response of SV to norepinephrine (NE) under normal and inflammatory conditions. Moreover, EPA and DHA pretreatment diminished increased Monocyte Chemoattractant Protein-1 (MCP-1) and Tumor Necrosis Factor-alpha (TNF-α) release from SV under inflammatory conditions. In conclusion, our results suggest that EPA and DHA pretreatment may be beneficial to counteract graft vasospasm and vascular inflammation in SV which are important factors in graft failure development. Therefore, dietary intake of EPA and DHA may have potential clinical applications in improving coronary bypass graft patency.

Decreased vasorelaxation induced by iloprost during acute inflammation in human internal mammary artery.

Cyclooxygenase-2 (COX-2) induction in human internal mammary arteries (IMA) under inflammatory conditions has been associated with attenuated norepinephrine (NE)-induced vasoconstriction. This effect was associated with increased prostaglandin (PG) E2 and prostacyclin (PGI2) releases. The present study was designed to assess the role of these PG and their receptors (EP and IP, respectively) on the vascular reactivity during acute inflammation. Isolated IMA were cultured in the absence (Control conditions) or presence (Inflammatory conditions) of both interleukin-1 beta (IL-1ß) and lipopolysaccharide (LPS). The vasorelaxation and the increased content of cyclic adenosine monophosphate (cAMP) induced by iloprost, a PGI2 analogue, were significantly reduced under inflammatory conditions and restored in preparations cultured with the IP antagonist (CAY10441). Decreased cAMP levels under inflammatory conditions are due to at least increased phosphodiesterase (PDE) 4B expression. On the other hand, PGE2, thromboxane analogues and EP agonists-induced vasoconstrictions were not affected under inflammatory conditions. No vasorelaxation was observed with PGD2, PGE2 or the EP2/4 agonists in pre-contracted IMA. Finally, using RT-qPCR and immunohistochemistry, the COX-2, IP receptor and PGI2 synthase (PGIS) were detected. A significant increase of COX-2 and moderate increase of IP mRNA expression was observed under inflammatory conditions, whereas PGIS mRNA level was not affected. This study demonstrates that PGI2/IP receptor signalling and PGI2-induced relaxation are impaired in human IMA during acute inflammation, whereas the responses induced by other prostanoids are not affected. These results could explain some of the mechanisms of vascular dysfunction reported in inflammatory conditions.

Reverse Regulatory Pathway (H2S / PGE2 / MMP) in Human Aortic Aneurysm and Saphenous Vein Varicosity.

Hydrogen sulfide (H2S) is a mediator with demonstrated protective effects for the cardiovascular system. On the other hand, prostaglandin (PG)E2 is involved in vascular wall remodeling by regulating matrix metalloproteinase (MMP) activities. We tested the hypothesis that endogenous H2S may modulate PGE2, MMP-1 activity and endogenous tissue inhibitors of MMPs (TIMP-1/-2). This regulatory pathway could be involved in thinning of abdominal aortic aneurysm (AAA) and thickening of saphenous vein (SV) varicosities. The expression of the enzyme responsible for H2S synthesis, cystathionine-γ-lyase (CSE) and its activity, were significantly higher in varicose vein as compared to SV. On the contrary, the endogenous H2S level and CSE expression were lower in AAA as compared to healthy aorta (HA). Endogenous H2S was responsible for inhibition of PGE2 synthesis mostly in varicose veins and HA. A similar effect was observed with exogenous H2S and consequently decreasing active MMP-1/TIMP ratios in SV and varicose veins. In contrast, in AAA, higher levels of PGE2 and active MMP-1/TIMP ratios were found versus HA. These findings suggest that differences in H2S content in AAA and varicose veins modulate endogenous PGE2 production and consequently the MMP/TIMP ratio. This mechanism may be crucial in vascular wall remodeling observed in different vascular pathologies (aneurysm, varicosities, atherosclerosis and pulmonary hypertension).

Human perivascular adipose tissue dysfunction as a cause of vascular disease: Focus on vascular tone and wall remodeling.

Obesity is one of the major risk factors for the development of cardiovascular diseases. It is characterized by excessive or abnormal accumulation of adipose tissue, including depots which surround the blood vessels named perivascular adipose tissue (PVAT). PVAT plays endocrine and paracrine roles by producing large numbers of metabolically vasoactive adipokines. The present review outlines our current understanding of the beneficial roles of PVAT in vascular tone and remodeling in healthy subjects supported by clinical studies, highlighting different factors or mechanisms that could mediate protective effects of PVAT on vascular function. Most studies in humans show that adiponectin is the best candidate for the advantageous effect of PVAT. However, in pathological conditions especially obesity-related cardiovascular diseases, the beneficial effects of PVAT on vascular functions are impaired and transform into detrimental roles. This change is defined as PVAT dysfunction. In the current review, the contribution of PVAT dysfunction to obesity-related cardiovascular diseases has been discussed with a focus on possible mechanisms including an imbalance between beneficial and detrimental adipokines (commonly described as decreased levels of adiponectin and increased levels of leptin or tumor necrosis factor-alpha (TNFα)), increased quantity of adipose tissue, inflammation, cell proliferation and endothelial dysfunction. Finally, novel pharmacotherapeutic targets for the treatment of cardiovascular and metabolic disorders are addressed.