Role of the renin-angiotensin system in the pathogenesis of intimal hyperplasia: therapeutic potential for prevention of vein graft failure?

Urotensin II receptor deficiency ameliorates ligation-induced carotid intimal hyperplasia partially through the RhoA-YAP1 pathway

Intimal hyperplasia (IH) is a common pathological feature of vascular proliferative diseases, such as atherosclerosis and restenosis after angioplasty. Urotensin II (UII) and its receptor (UTR) are widely expressed in cardiovascular tissues. However, it remains unclear whether the UII/UTR system is involved in IH. Right unilateral common carotid artery ligation was performed and maintained for 21 days to induce IH in UTR knockout (UTR-/-) and wild-type (WT) mice. Histological analysis revealed that compared with WT mice, UTR-deficient mice exhibited a decreased neointimal area, angiostenosis and intima-media ratio. Immunostaining revealed fewer smooth muscle cells (SMCs), endothelial cells and macrophages in the lesions of UTR-/- mice than in those of WT mice. Protein interaction analysis suggested that the UTR may affect cell proliferation by regulating YAP and its downstream target genes. In vitro experiments revealed that UII can promote the proliferation and migration of SMCs, and western blotting also revealed that UII increased the protein expression of RhoA, CTGF, Cyclin D1 and PCNA and downregulated p-YAP protein expression, while these effects could be partly reversed by urantide. To evaluate the translational value of UTRs in IH management, WT mice were also treated with two doses of urantide, a UTR antagonist, to confirm the benefit of UTR blockade in IH progression. A high dose of urantide (600 μg/kg/day), rather than a low dose (60 μg/kg/day), successfully improved ligation-induced IH compared with that in mice receiving vehicle. The results of the present study suggested that the UII/UTR system may regulate IH partly through the RhoA-YAP signaling pathway.

Hydrogen Sulphide Release via the Angiotensin Converting Enzyme Inhibitor Zofenopril Prevents Intimal Hyperplasia in Human Vein Segments and in a Mouse Model of Carotid Artery Stenosis

OBJECTIVE

Hypertension is a major risk factor for intimal hyperplasia (IH) and re-stenosis following vascular and endovascular interventions. Preclinical studies suggest that hydrogen sulphide (H₂S), an endogenous gasotransmitter, limits re-stenosis. While there is no clinically available pure H₂S releasing compound, the sulfhydryl containing angiotensin converting enzyme inhibitor zofenopril is a source of H₂S. Here, it was hypothesised that zofenopril, due to H₂S release, would be superior to other non-sulfhydryl containing angiotensin converting enzyme inhibitors (ACEi) in reducing intimal hyperplasia.

METHODS

Spontaneously hypertensive male Cx40 deleted mice (Cx40^-/-) or wild type (WT) littermates were randomly treated with enalapril 20 mg or zofenopril 30 mg. Discarded human vein segments and primary human smooth muscle cells (SMCs) were treated with the active compound enalaprilat or zofenoprilat. IH was evaluated in mice 28 days after focal carotid artery stenosis surgery and in human vein segments cultured for seven days ex vivo. Human primary smooth muscle cell (SMC) proliferation and migration were studied in vitro.

RESULTS

Compared with control animals (intima/media thickness 2.3 ± 0.33 μm), enalapril reduced IH in Cx40^-/- hypertensive mice by 30% (1.7 ± 0.35 μm; p = .037), while zofenopril abrogated IH (0.4 ± 0.16 μm; p < .002 vs. control and p > .99 vs. sham operated Cx40^-/- mice). In WT normotensive mice, enalapril had no effect (0.9665 ± 0.2 μm in control vs. 1.140 ± 0.27 μm; p > .99), while zofenopril also abrogated IH (0.1623 ± 0.07 μm; p < .008 vs. control and p > .99 vs. sham operated WT mice). Zofenoprilat, but not enalaprilat, also prevented IH in human vein segments ex vivo. The effect of zofenopril on carotid and SMCs correlated with reduced SMC proliferation and migration. Zofenoprilat inhibited the mitogen activated protein kinase and mammalian target of rapamycin pathways in SMCs and human vein segments.

CONCLUSION

Zofenopril provides extra beneficial effects compared with non-sulfhydryl ACEi in reducing SMC proliferation and re-stenosis, even in normotensive animals. These findings may hold broad clinical implications for patients suffering from vascular occlusive diseases and hypertension.

Impact of angiotensin receptor blockers on mortality after hospitalization for symptomatic lower extremity artery disease

AIMS

The objective was to assess the association between angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB) prescription at discharge in patients hospitalized for symptomatic lower extremity artery disease (LEAD) and 1-year mortality.

METHODS AND RESULTS

The COPART registry is a multicentre, prospective, observational, cohort study which includes consecutive patients hospitalized for symptomatic LEAD in four French academic centres. All-cause mortality during a 1-year follow-up after hospital discharge was compared between patients with ARB, patients with ACEI and patients without ARB or ACEI. Analyses were performed using Cox models. As a sensitivity analysis, a propensity score (PS)-matching analysis was carried out. Among 1981 patients, 421 had ARB (21.3%), 766 ACEI (38.7%), and 794 no ACEI/ARB (40.1%) at discharge. During the 1-year follow-up, incidence rates for mortality were 12.6/100 person-years [95% confidence interval (CI) 9.7-16.1] for patients with ARB, 15.8/100 person-years (95% CI 13.4-18.6) for patients with ACEI and 19.8/100 person-years for patients without ACEI/ARB (95% CI 17.2-22.8). In a multivariate Cox model, ARB at discharge was associated with decreased mortality compared with no ACEI/ARB, hazard ratio (HR) 0.68 (95% CI 0.49-0.95), and with ACEI, HR 0.69 (95% CI 0.49-0.97). These results are consistent with those obtained by the Cox analyses in the PS-matched sample: HR 0.68 (95% CI 0.47-0.98) for patients with ARB compared with no ARB.

CONCLUSION

Angiotensin receptor blockers at discharge after hospitalization for symptomatic LEAD is associated with a better survival compared with ACEI or no ACEI/ARB.

Preventing treatment failures in coronary artery disease: what can we learn from the biology of in-stent restenosis, vein graft failure, and internal thoracic arteries?

Coronary artery disease (CAD) remains one of the most important causes of morbidity and mortality worldwide, and the availability of percutaneous or surgical revascularization procedures significantly improves survival. However, both strategies are daunted by complications which limit long-term effectiveness. In-stent restenosis (ISR) is a major drawback for intracoronary stenting, while graft failure is the limiting factor for coronary artery bypass graft surgery (CABG), especially using veins. Conversely, internal thoracic artery (ITA) is known to maintain long-term patency in CABG. Understanding the biology and pathophysiology of ISR and vein graft failure (VGF) and mechanisms behind ITA resistance to failure is crucial to combat these complications in CAD treatment. This review intends to provide an overview of the biological mechanisms underlying stent and VGF and of the potential therapeutic strategy to prevent these complications. Interestingly, despite being different modalities of revascularization, mechanisms of failure of stent and saphenous vein grafts are very similar from the biological standpoint.

Upper Extremity Pulse Pressure Predicts Amputation-Free Survival after Lower Extremity Bypass

Increased pulse pressure reflects pathologic arterial stiffening and predicts cardiovascular events and mortality. The effect of pulse pressure on outcomes in lower extremity bypass patients remains unknown. We thus investigated whether preoperative pulse pressure could predict amputation-free survival in patients undergoing lower extremity bypass for atherosclerotic occlusive disease. An institutional database identified 240 included patients undergoing lower extremity bypass from 2005 to 2014. Preoperative demographics, cardiovascular risk factors, operative factors, and systolic and diastolic blood pressures were recorded, and compared between patients with pulse pressures above and below 80 mm Hg. Factors were analyzed in bi- and multivariable models to assess independent predictors of amputation-free survival. Kaplan-Meier analysis was performed to evaluate the temporal effect of pulse pressure ≥80 mm Hg on amputation-free survival. Patients with a pulse pressure ≥80 mm Hg were older, male, and had higher systolic and lower diastolic pressures. Patients with pulse pressure <80 mm Hg demonstrated a survival advantage on Kaplan-Meier analysis at six months (log-rank P = 0.003) and one year (P = 0.005) postoperatively. In multivariable analysis, independent risk factors for decreased amputation-free survival at six months included nonwhite race, tissue loss, infrapopliteal target, and preoperative pulse pressure ≥80 mm Hg (hazard ratio 2.60; P = 0.02), while only tissue loss and pulse pressure ≥80 mm Hg (hazard ratio 2.30, P = 0.02) remained predictive at one year. Increased pulse pressure is independently associated with decreased amputation-free survival in patients undergoing lower extremity bypass. Further efforts to understand the relationship between increased arterial stiffness and poor outcomes in these patients are needed.

Angiotensin II, as well as 5-hydroxytriptamine, is a potent vasospasm inducer of saphenous vein graft for coronary artery bypass grafting in patients with diabetes mellitus

Diabetes mellitus (DM) is an important risk factor for adverse outcomes of coronary artery bypass grafting. The bypass grafts harvested from patients with DM tend to go into spasm after their implantation into the coronary circulation. To clarify the contribution of 5-hydroxytriptamine (5-HT) and angiotensin II (AngII) in the bypass graft spasm, we examined the contractile reactivity to 5-HT or AngII of isolated human endothelium-denuded saphenous vein (SV) harvested from DM and non-DM patients. The 5-HT-induced constriction of the SV was significantly augmented in the DM group than in the non-DM group, which is similar to our previous report. AngII-induced constriction of the SV was also significantly augmented in the DM group than the non-DM group. Especially in the non-DM group, the AngII-induced maximal vasoconstriction was markedly lower than the 5-HT-induced one. Meanwhile, the increasing rates of AngII-induced vasoconstriction in the DM group to the non-DM group were significantly greater than those of 5-HT-induced vasoconstriction. These results indicate that 5-HT is a potent inducer of SV graft spasm in both DM and non-DM patients, while AngII is a potent inducer of SV graft spasm only in patients with DM. Furthermore, the protein level of AngII AT₁ receptor (AT₁R), but not the protein level of 5-HT_2A receptor, in the membrane fraction of the SV smooth muscle cells of DM patients was significantly increased as compared with that of the non-DM patients. These results suggest that the mechanism for hyperreactivity to AngII in the SV from DM patients is due to, at least in part, the increase in the amount of AT₁R on membrane of the SV smooth muscle cells.

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The vasoconstrictive reactivity to 5-HT was significantly enhanced in the DM.

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The vasoconstrictive reactivity to AngII was significantly enhanced in the DM.

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In DM patients, the hyperreactivity to AngII was significantly higher than that to 5-HT.

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The protein level AT₁ R in membrane fraction of saphenous vein smooth muscle was significantly increased in the DM.

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AngII could be a potent inducer of SV graft spasm only in DM patients.

Use of plasma renin activity to monitor mineralocorticoid treatment in dogs with primary hypoadrenocorticism: desoxycorticosterone versus fludrocortisone

Background

Measurement of plasma renin activity (PRA) is the gold standard for monitoring mineralocorticoid treatment in humans with primary hypoadrenocorticism (PH).

Objectives

To compare PRA in dogs with newly diagnosed PH, dogs with diseases mimicking PH, and healthy dogs, and evaluate measurement of PRA to monitor therapeutic effects in dogs with PH treated with different mineralocorticoids.

Animals

Eleven dogs with newly diagnosed PH (group 1), 10 dogs with diseases mimicking PH (group 2), 21 healthy dogs (group 3), 17 dogs with treated PH (group 4).

Methods

In group 1, PRA was measured before treatment and at different times after initiating treatment. In groups 2 and 3, PRA was measured at initial presentation only. In group 4, no baseline PRA was obtained but PRA was measured once or every 1–6 months during treatment. Mineralocorticoid treatment consisted of fludrocortisone acetate (FC) or desoxycorticosterone pivalate (DOCP).

Results

Plasma renin activity before treatment was increased in dogs with PH compared to normal dogs and dogs with diseases mimicking PH with median activity of 27, 0.8, and 1.0 ng/mL/h, respectively. In dogs with PH, PRA decreased and normalized with mineralocorticoid treatment using DOCP but not with FC. In dogs treated with DOCP, PRA was lower than in dogs treated with FC. Plasma sodium concentrations were higher and potassium concentrations were lower with DOCP treatment compared to FC treatment.

Conclusion and Clinical Importance

Plasma renin activity is a reliable tool for monitoring mineralocorticoid treatment. DOCP treatment more effectively suppresses PRA compared to FC in dogs with PH.

Mast cells and vascular diseases

Mast cells are increasingly being recognized as effector cells in many cardiovascular conditions. Many mast-cell-derived products such as tryptase and chymase can, through their enzymic action, have detrimental effects on blood vessel structure while mast cell-derived mediators such as cytokines and chemokines can perpetuate vascular inflammation. Mice lacking mast cells have been developed and these are providing an insight into how mast cells are involved in cardiovascular diseases and, as knowledge increase, mast cells may become a viable therapeutic target to slow progression of cardiovascular disease.