Simvastatin preserves myocardial perfusion and coronary microvascular permeability in experimental hypercholesterolemia independent of lipid lowering

Purinergic Regulation of Endothelial Barrier Function

Increased vascular permeability is a hallmark of several cardiovascular anomalies, including ischaemia/reperfusion injury and inflammation. During both ischaemia/reperfusion and inflammation, massive amounts of various nucleotides, particularly adenosine 5'-triphosphate (ATP) and adenosine, are released that can induce a plethora of signalling pathways via activation of several purinergic receptors and may affect endothelial barrier properties. The nature of the effects on endothelial barrier function may depend on the prevalence and type of purinergic receptors activated in a particular tissue. In this review, we discuss the influence of the activation of various purinergic receptors and downstream signalling pathways on vascular permeability during pathological conditions.

Pathophysiological coronary and microcirculatory flow alterations in aortic stenosis

Regulation of coronary blood flow is maintained through a delicate balance of ventriculoarterial and neurohumoral mechanisms. The aortic valve is integral to the functions of these systems, and disease states that compromise aortic valve integrity have the potential to seriously disrupt coronary blood flow. Aortic stenosis (AS) is the most common cause of valvular heart disease requiring medical intervention, and the prevalence and associated socio-economic burden of AS are set to increase with population ageing. Valvular stenosis precipitates a cascade of structural, microcirculatory, and neurohumoral changes, which all lead to impairment of coronary flow reserve and myocardial ischaemia even in the absence of notable coronary stenosis. Coronary physiology can potentially be normalized through interventions that relieve severe AS, but normality is often not immediately achievable and probably requires continued adaptation. Finally, the physiological assessment of coronary artery disease in patients with AS represents an ongoing challenge, as the invasive physiological measures used in current cardiology practice are yet to be validated in this population. This Review discusses the key concepts of coronary pathophysiology in patients with AS through presentation of contemporary basic science and data from animal and human studies.

Study of Endothelio- and Osteoprotective Effects of Combination of Rosuvastatin with L-Norvaline in Experiment

The experiment was carried out on 120 female white Wistar rats, to study the endothelio- and osteoprotective action of the combination of rosuvastatin with L-norvaline in the model of experimental osteoporosis. It was found that, after ovariectomy in rats, endothelial dysfunction of the vessels of the microcirculatory bed of bone tissue develops, leading to the appearance of osteoporosis, but the combination of the studied drugs prevents the decrease in the level of microcirculation in the bone tissue, thereby preventing the thinning of bone trabeculae and preventing the occurrence of microfractures in them.

Importance of the lipid-related pathways in the association between statins, mortality, and cardiovascular disease risk: The Multi-Ethnic Study of Atherosclerosis

PURPOSE

Estimating how much of the impact of statins on coronary heart diseases (CHD), cardiovascular disease (CVD), and mortality risk is attributable to their effect on low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and triglycerides.

METHODS

A semi-parametric g-formula estimator together with data from the Multi-Ethnic Study of Atherosclerosis (a prospective multi-center cohort study) was utilized to perform a mediation analysis. A total of 5280 participants, men and women of various race/ethnicities from multiple sites across the United States, were considered in the current study.

RESULTS

The adherence adjusted total relative risk reduction (RRR) estimate (95% confidence interval) of statins on CHD was 14% (-16%, 37%), and the indirect component through LDL was 23% (-4%, 58%). For CVD, the total RRR was 23% (2%, 40%), and the indirect component through LDL was 5% (-13%, 25%). The total RRR of mortality was 18% (-1%, 35%), and the indirect component through LDL was -4% (-17%, 12%). The estimated indirect components through HDL and triglycerides were close to zero with narrow confidence intervals for all 3 outcomes.

CONCLUSIONS

The estimated effect of statins on mortality, CVD, and CHD appeared to be independent of their estimated effect on HDL and triglycerides. Our study provides evidence that the preventive effect of statins on CHD could be attributed in large part to their effect on LDL. Our g-formula estimator is a promising approach to elucidate pathways, even if it is hard to make firm conclusions for the LDL pathway on mortality and CVD.

Long-term statin use before primary percutaneous coronary intervention improves treatment outcomes of acute myocardial infarction

Numerous studies have reported that high-dose statin loading therapy prior to primary percutaneous coronary intervention (PPCI) improves the clinical outcomes of patients following acute myocardial infarction (AMI). However, little is known about the effects of long-term statin use prior to PPCI on such outcomes. Therefore, the aim of the present analysis was to clarify the effects of long-term statin use before PPCI on the treatment outcomes of patients following AMI. The records of 213 patients who had AMI and met the inclusion criteria were retrospectively reviewed. Patients were divided into two groups: A control group (n=178) who had received no statin pretreatment before AMI onset, and a statin group (n=35) who had received statin treatment for ≥1 month before AMI onset. All patients received a standard treatment regimen for the secondary prevention of coronary artery disease after PPCI. Baseline clinical variables, details of the PPCI procedure and clinical outcomes within 3 months after treatment were reviewed. Patients in the statin group were significantly older than those in the control group (P=0.003). Compared with the control group, there was a greater proportion of patients with hyperlipidemia and previous angina pectoris in the statin group. There were no differences in the use of other drugs (aspirin, β-blockers and angiotensin-converting enzyme inhibitors) prior to PPCI between the two groups. The corrected TIMI frame count (cTFC) was significantly lower in the statin group than in the control group (24.1±12.8 vs. 29.4±14.3, respectively; P=0.043). Multivariable linear regression analysis showed that long-term statin use before AMI was a significant predictor of cTFC after PPCI (P=0.012). Furthermore, the incidence of major adverse cardiac events within 3 months after PPCI was higher in the control group than in the statin group (16.8 vs. 2.9%, respectively; P=0.032). Logistic regression analysis showed that previous statin use was associated with the incidence of major adverse cardiac events within 3 months after treatment (P=0.012). The results of the present study demonstrate that long-term statin use prior to PPCI improved treatment outcomes after AMI in actual clinical practice.

Improved outcome after primary vitrectomy in diabetic patients treated with statins

PURPOSE

To evaluate the effect of preoperative statin treatment on the outcome of primary vitrectomy in type 1 and 2 diabetic patients.

METHODS

In this open, observational institutional study, a total of 192 eyes of 171 type 1 and 2 adult diabetic patients admitted for primary vitrectomy for management of sight-threatening forms of diabetic retinopathy were divided according to the use of lipid-lowering therapy: those with statin treatment (79 eyes of 73 patients) and those taking no statin medication (113 eyes of 98 patients). One-month best-corrected visual acuity (BCVA) gain and cumulative 12-month revitrectomy frequency were analyzed.

RESULTS

In multivariate linear regression, diabetic patients with statin treatment had a better 1-month BCVA improvement than did those without statin treatment (absolute difference 0.26, 95% confidence interval [CI] 0.02-0.50, p = 0.028). Subgroup analysis revealed that diabetic patients on statin had better postoperative BCVA improvement when preoperative status included partial or panretinal laser photocoagulation (p = 0.042 and p = 0.049) and anti-vascular endothelial growth factor therapy (p = 0.011). Moreover, diabetic patients with preoperative macular edema (p = 0.009), vitreous hemorrhage (p<0.001), proliferative retinopathy (p<0.001), or tractional retinal detachment (p = 0.010) had better BCVA recovery if receiving statin. In Cox proportional hazards regression model, revitrectomies in our 12-month follow-up were less frequent in diabetic patients on statin treatment (hazard ratio 0.28, 95% CI 0.08-0.93, p = 0.037).

CONCLUSIONS

These data provide novel insight into the potential clinical benefit for patients with sight-threatening diabetic retinopathy undergoing vitrectomy treated with statin.

Endothelial protective genes induced by statin are mimicked by ERK5 activation as triggered by a drug combination of FTI-277 and GGTI-298

BACKGROUND

Statins are potent inhibitors of cholesterol biosynthesis and are clinically beneficial in preventing cardiovascular diseases, however, the therapeutic utility of these drugs is limited by myotoxicity. Here, we explored the mechanism of statin-mediated activation of ERK5 in the human endothelium with the goal of identifying compounds that confer endothelial protection but are nontoxic to muscle.

METHODS

An ERK5-one hybrid luciferase reporter transfected into COS-7 cells with pharmacological and molecular manipulations dissected the signaling pathway leading to statin activation of ERK5. qRT-PCR of HUVEC cells documented the transcriptional activation of endothelial-protective genes. Lastly, morphological and cellular ATP analysis, and induction of atrogin-1 in C2C12 myotubes were used to assess statin-induced myopathy.

RESULTS

Statin activation of ERK5 is dependent on the cellular reduction of GGPPs. Furthermore, we found that the combination of FTI-277 (inhibitor of farnesyl transferase) and GGTI-298 (inhibitor of geranylgeranyl transferase I) mimicked the statin-mediated activation of ERK5. FTI-277 and GGTI-298 together recapitulated the beneficial effects of statins by transcriptionally upregulating anti-inflammatory mediators such as eNOS, THBD, and KLF2. Finally, C2C12 skeletal myotubes treated with both FTI-277 and GGTI-298 evoked less morphological and cellular changes recognized as biomarkers of statin-associated myopathy.

CONCLUSIONS

Statin-induced endothelial protection and myopathy are mediated by distinct metabolic intermediates and co-inhibition of farnesyl transferase and geranylgeranyl transferase I confer endothelial protection without myopathy.

GENERAL SIGNIFICANCE

The combinatorial FTI-277 and GGTI-298 drug regimen provides a promising alternative avenue for endothelial protection without myopathy.

Perlecan deficiency causes endothelial dysfunction by reducing the expression of endothelial nitric oxide synthase

Perlecan is a major heparan sulfate proteoglycan found in the subendothelial extracellular matrix of the vascular wall. The aim of this study was to investigate the role of perlecan in the regulation of vascular tone. A previously developed conditional perlecan‐deficient mouse model was used to measure changes in the isometric force of isolated aortic rings. The vessels were first precontracted with phenylephrine, and then treated with increasing concentrations of vasorelaxants. Endothelium‐dependent relaxation, elicited by acetylcholine, was significantly reduced in the perlecan‐deficient aortas, whereas endothelium‐independent relaxation caused by the exogenous nitric oxide donor sodium nitroprusside remained well preserved. The expression of the endothelial nitric oxide synthase (eNOS) gene, detected by real‐time polymerase chain reaction, was significantly decreased in the perlecan‐deficient aortas. The expression of eNOS protein detected using Western blotting was also significantly decreased in the perlecan‐deficient aortas. We examined the role of perlecan in eNOS gene expression by creating perlecan knockdown human aortic endothelial cells using small interfering RNA (siRNA) for perlecan. Perlecan gene expression was significantly reduced in the perlecan siRNA‐treated cells, resulting in a significant decrease in eNOS gene expression. Perlecan deficiency induced endothelial dysfunction, as indicated by a reduction in endothelium‐dependent relaxation due, at least partly, to a reduction in eNOS expression. These findings suggest that perlecan plays a role in the activation of eNOS gene expression during normal growth processes.

Perlecan deficiency induced endothelial dysfunction at least partly, to a reduction in eNOS expression. These findings suggest that perlecan plays a role in the activation of the eNOS expression during normal growth processes.

Atorvastatin worsens left ventricular diastolic dysfunction and endothelial dysfunction of epicardial coronary arteries in normocholesterolemic porcine with left ventricular hypertrophy

Statins have pleiotropic effects that can reverse endothelial dysfunction and prevent the development of left ventricular hypertrophy (LVH). The goal of this study was to assess the effect of treatment with atorvastatin on the endothelial dysfunction of epicardial coronary arteries and the development of LVH in a porcine model. LVH was induced through 2 months of aortic banding (AB) of the ascending aorta. Experimental groups were (1) sham untreated: without AB, (2) LVH untreated: with AB, and (3,4) LVH treated: with AB treated with 40 and 80 mg of atorvastatin, respectively, for 60 days, and (5) sham treated: without AB treated with 80 mg of atorvastatin for 60 days. Vascular reactivity studies were performed in organ chambers experiments. NO bioavailability was assessed using cyclic guanosine monophosphate quantification. Oxidative stress levels were measured by quantifying angiotensin II) and nitrite/nitrate levels. LVH and LV diastolic function were evaluated using echocardiography. Atorvastatin decreased endothelium-dependent relaxations and cyclic guanosine monophosphate levels in all treated animals. Angiotensin II levels were increased, whereas nitrite levels were similar among groups (P > 0.05). LV diastolic dysfunction and LVH were significantly greater in all treated animals (P < 0.01). High-density lipoprotein levels and low-density lipoprotein levels were significantly decreased in animals receiving atorvastatin (P < 0.05). In this swine model of LVH, atorvastatin did not prevent LVH development or coronary endothelial dysfunction and resulted in worsening of the LV diastolic dysfunction.

Opposing effects of ATP and adenosine on barrier function of rat coronary microvasculature

ATP can differentially affect the micro- and macrovascular endothelial barrier. It has been shown that it can both increase and/or decrease macromolecule permeability of microvascular endothelial cells and microvessels, in vivo. We hypothesised that the barrier stabilising effect is mediated by ATP itself via P2 receptors, while barrier-disrupting effect is mediated by its metabolite adenosine via adenosine receptors. The effects of ATP, ADP, AMP and adenosine on barrier function were studied in cultured rat coronary microvascular endothelial monolayers (RCEC) in vitro, as well as in rat mesentery vessels, and in rat hearts in vivo. ATP and ADP showed a biphasic effect on permeability of RCEC monolayers with a reduction followed by a later increase in albumin permeability. The permeability decreasing effect of ATP was enhanced by ecto-nucleotidase inhibitor ARL67156 while permeability increasing effect was enhanced by apyrase, an extracellular ecto-nucleotidase. Moreover, the permeability increasing effect was abrogated by adenosine receptor antagonists, 8-phenyltheophylline (8-PT) and DMPX. Adenosine and adenosine receptor agonists 5'-(N-ethylcarboxamido)-adenosine (NECA), CGS21680, and R-PIA enhanced albumin permeability which was antagonised by 8-PT, A(1), and A(2) but not by A(3) receptor antagonists. Likewise, immunofluorescence microscopy of VE-cadherin and actin showed that NECA induces a disturbance of intercellular junctions. Pre-incubation of ATP antagonised the effects of NECA on permeability, actin cytoskeleton and intercellular junctions. Similar effects of the applied substances were observed in rat mesentery artery by determining the vascular leakage using intravital microscopy as well as in rat hearts by assessing myocardial water contents in vivo. In conclusion, the study demonstrates that in RCEC, ATP, ADP, and its metabolite adenosine play opposing roles on endothelial barrier function.

Relationship between surface area of nonperfused myocardium and extravascular extraction of contrast agent following coronary microembolization

Myocardial microvascular permeability and coronary sinus concentration of muscle metabolites have been shown to increase after myocardial ischemia due to epicardial coronary artery occlusion and reperfusion. However, their association with coronary microembolization is not well defined. This study tested the hypothesis that acute coronary microembolization increases microvascular permeability in the porcine heart. The left anterior descending perfusion territories of 34 anesthetized pigs (32 ± 3 kg) were embolized with equal volumes of microspheres of one of three diameters (10, 30, or 100 μm) and at three different doses for each size. Electron beam computed tomography (EBCT) was used to assess in vivo, microvascular extraction of a nonionic contrast agent (an index of microvascular permeability) before and after microembolization with microspheres at baseline and during adenosine infusion. A high-resolution three-dimensional microcomputed tomography (micro-CT) scanner was subsequently used to obtain ex vivo, the volume and corresponding surface area of the embolized myocardial islands within the perfusion territories of the microembolized coronary artery. EBCT-derived microvascular extraction of contrast agent increased within minutes after coronary microembolization (P < 0.001 vs. baseline and vs. control values). The increase in coronary microvascular permeability was highly correlated to the micro-CT-derived total surface area of the nonperfused myocardium (r = 0.83, P < 0.001). In conclusion, myocardial extravascular accumulation of contrast agent is markedly increased after coronary microembolization and its magnitude is in proportion to the surface area of the interface between the nonperfused and perfused territories.

The anti-ischemic and anti-anginal properties of statins

Angina pectoris resulting from myocardial ischemia afflicts half of all patients with coronary heart disease (CHD). Chronic angina remains a major public health burden despite state-of-the-art therapies, and improvement in survival from myocardial infarction and CHD has only increased its prevalence. There is growing experimental and clinical evidence pointing to the anti-ischemic and anti-anginal properties of statins. Some data suggest that the degree of anti-ischemic efficacy of statins may be comparable to the current standard pharmacologic and mechanical strategies. The pleiotropic effects of statins are postulated to be primarily responsible for their anti-ischemic and anti-anginal properties. These include improvement of endothelial function, enhancement of the ischemic vasodilatory response, modulation of inflammation, and protection from ischemia-reperfusion injury. The anti-ischemic effects of statins further strengthen their role as a crucial component of the optimal medical therapy for CHD.

Simvastatin preserves diastolic function in experimental hypercholesterolemia independently of its lipid lowering effect

OBJECTIVE

Isolated diastolic dysfunction is present in 40% of heart failure patients. It has been attributed to myocardial fibrosis and related to cardiovascular risk factor exposure. We hypothesized that simvastatin will improve these dynamics in experimental hypercholesterolemia (HC).

METHODS

Three groups of pigs were studied after 12 weeks of normal (N) diet, HC diet, or HC diet with simvastatin (80 mg/day) treatment. Cardiac function was assessed by electron beam computed tomography (EBCT) and percentage of myocardium occupied by microvessels (myocardial vascular fraction) was calculated by micro-CT. Collagen content was determined by Sirius red staining and confirmed by a quantitative, hydroxyoproline-based assay.

RESULTS

Compared with N, LDL serum concentration was higher in HC and HC+simvastatin (1.0±0.1 vs. 7.9±1.7 and 9.6±1.2 mmol/L, p<0.05 for both). Cardiac early diastolic filling was reduced in HC compared with N (102.4±11.3 vs. 151.1±12.1 mL/s; p<0.05) but restored in HC+simvastatin (176.8±21.3 mL/s, p<0.05 vs. HC). Compared with N, myocardial vascular fraction was higher in HC but not in HC+simvastatin (1.98±0.84 vs. 4.48±0.31 and 2.95±0.95%; p<0.05 for HC vs. N). Myocardial collagen content was higher in HC than in HC+simvastatin and N (4.72±1.03 vs. 1.62±0.12 and 1.21±0.24% area staining; p<0.05 for HC vs. N), which was attributable mainly to an increase in collagen III (2.90±0.48 vs. 1.62±0.12 and 1.21±0.24% area staining; p<0.05 for HC vs. N).

CONCLUSIONS

Simvastatin is able to prevent diastolic dysfunction in experimental HC independent of its lipid lowering effect. This beneficial effect is, at least partially, due to a decrease in myocardial fibrosis and angiogenesis.

Impact of chronic pre-treatment of statins on the level of systemic inflammation and myocardial perfusion in patients undergoing primary angioplasty

Statins have many favorable pleiotropic effects beyond their lipid-lowering properties. The aim of this study was to evaluate the impact of long-term statin pretreatment on the level of systemic inflammation and myocardial perfusion in patients with acute myocardial infarctions. This was a retrospective study of 1,617 patients with acute ST-segment elevation myocardial infarctions who underwent primary percutaneous coronary intervention <12 hours after the onset of symptoms. Angiographic no-reflow was defined as postprocedural Thrombolysis In Myocardial Infarction (TIMI) flow grade ≤2. Long-term statin pretreatment was significantly less common in the no-reflow group (6.2% vs 21%, p <0.001). The serum lipid profiles of the groups were similar (p >0.05 for all parameters). Baseline C-reactive protein levels (10 ± 8.2 vs 15 ± 14 mg/L, p <0.001) and the frequency of angiographic no-reflow (3.9% vs 14%, p <0.001) were significantly lower, and myocardial blush grade 3 was more common (50% vs 40%, p = 0.006) in the statin pretreatment group (n = 306). Moreover, the frequency of complete ST-segment resolution (>70%) (70% vs 59%, p <0.001) and the left ventricular ejection fraction were higher (49 ± 7.5% vs 46 ± 8.3%, p <0.001) and peak creatine kinase-MB was lower (186 ± 134 vs 241 ± 187 IU/L, p <0.001) in the statin-treated group. In conclusion, long-term statin pretreatment is associated with lower C-reactive protein levels on admission and better myocardial perfusion after primary percutaneous coronary intervention, leading to lower enzymatic infarct area and a more preserved left ventricular ejection fraction. This is a group effect independent of lipid-lowering properties.

Atherosclerosis induced by chronic inhibition of the synthesis of nitric oxide in moderately hypercholesterolaemic rabbits is suppressed by pitavastatin

BACKGROUND AND PURPOSE

It is not clear if the new 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor pitavastatin prevents atherogenesis by a direct effect. Statins have a cholesterol-lowering effect, so an accessible animal model of atherosclerosis showing only moderate hypercholesterolaemia as in humans, is needed. The effects of pitavastatin were evaluated on atherosclerotic lesions accumulating foam cells derived from macrophages, produced in rabbits with moderate hypercholesterolaemia by chronic inhibition of nitric oxide synthase (NOS).

EXPERIMENTAL APPROACH

White New Zealand rabbits were fed a 0.2% cholesterol diet with the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) in the same diet. Pitavastatin (0.1 and 0.3 mg x kg(-1)) was given orally once a day for 8 weeks. The aortic arch and thoracic aorta were analysed by histochemistry and atherosclerotic lesions were quantified. The effect of pitavastatin on adhesion of THP-1 cells to endothelial cells, and cholesterol content in RAW264.7 cells incubated with oxidized or acetylated LDL were also investigated.

KEY RESULTS

Atherosclerotic lesions containing foam cells were induced in a model of atherosclerosis in rabbits with moderate hypercholesterolaemia by chronic inhibition of NOS. The area of atherosclerotic lesions was diminished by pitavastatin administration. The adhesion of THP-1 cells and cholesteryl ester content in RAW macrophages were decreased by pitavastatin treatment.

CONCLUSION

Atherosclerosis induced by chronic inhibition of NOS in moderately hypercholesterolaemic rabbits was suppressed by pitavastatin via inhibition of macrophage accumulation and macrophage foam cell formation.

Residual microvascular risk in diabetes: unmet needs and future directions

The burden of microvascular disease in patients with type 2 diabetes mellitus continues to escalate worldwide. Current standards of care reduce but do not eliminate the risk of diabetic retinopathy, nephropathy or neuropathy in these patients. Correction of atherogenic dyslipidemia, which is characterized by elevated triglyceride levels and low levels of HDL cholesterol, might provide additional benefit. Whereas promising data have been published with respect to fibrate therapy for maculopathy, fenofibrate for diabetic retinopathy, and statin or fibrate therapy for diabetic nephropathy, further studies are warranted to define optimal management strategies for reducing the residual microvascular risk. Such strategies are especially relevant in cases of diabetic peripheral neuropathy, where even optimal care fails to affect disease progression. Identification of those factors that are most relevant to residual diabetes-related microvascular risk is a priority of an ongoing multinational epidemiological study. In this Review, we highlight an urgent need to address the issue of microvascular residual risk in patients with or at risk of type 2 diabetes mellitus.

The effect of beta-blockers on the diagnostic accuracy of vasodilator pharmacologic SPECT myocardial perfusion imaging

BACKGROUND

The effect of beta (beta) blockers on the accuracy, particularly the sensitivity, of vasodilator radionuclide myocardial perfusion imaging (MPI) is not entirely clear. This study aimed to further assess the effect of beta-blockers on the ability of MPI to identify significant and high-risk coronary artery disease (CAD).

METHODS AND RESULTS

For 555 patients who underwent vasodilator MPI and had coronary angiography within 90 days, global and per-vessel sensitivities and specificities were calculated, and were found to be similar between patients taking beta-blockers and those who were not. beta-blockers did not decrease the ability to detect patients with multivessel disease. Summed stress scores and summed rest scores were likewise similar in both groups. To account in part for catheterization referral bias and the potential of false-negative MPI studies in patients receiving beta-blockers, survival analysis was performed on 2646 patients with normal MPI studies who did not undergo cardiac catheterization and failed to demonstrate significant mortality difference related to the taking of beta-blockers.

CONCLUSIONS

beta-blocker therapy does not diminish the ability of vasodilator stress MPI to detect clinically significant CAD, nor hide the mortality risk of patients with normal studies not referred for catheterization.

Non-invasive Monitoring of Angiogenesis in Cardiology

Angiogenesis plays an important role in the pathophysiology of atherosclerosis and after myocardial infarction. Furthermore, angiogenesis has been the focus of many therapeutic strategies. In view of that, a direct and clear understanding of the role of these pathways in the living subject is needed. Molecular Imaging has emerged as a powerful tool to study biological processes non-invasively. In this review, evidence will be presented and discussed on the feasibility of different molecular imaging strategies to study the involvement of angiogenic pathways in the assessment of the atherosclerotic disease and as a tool to assess angiogenic therapy. Focus will be placed on those imaging modalities with the potential to be translated to clinical use.

Statin Therapy for Vascular Failure

There is increasing evidence that statins reduce cardiovascular events such as coronary artery disease or stroke in hypercholesterolemic patients in both primary and secondary prevention. The striking benefit achieved with statin treatments in patients with a wide range of cholesterol levels cannot be attributed to their cholesterol lowering effect alone. Substantial data has recently accumulated showing that statins exert various effects on multiple targets, namely pleiotropic effects, especially targeting the concept of 'vascular failure', including the improvement of vascular endothelial function, inhibition of vascular smooth muscle cell proliferation and migration, anti-inflammatory actions, anti-oxidative effects or stabilization of vulnerable plaques. These effects have potential in the treatments of coronary artery disease in various settings, such as prevention of its onset as well as its progression, or plaque rupture. Statin therapy should be more extensively applied even in normolipidemic patients if there are additional risk factors such as hypertension, diabetes mellitus, or others. Furthermore, statins may be used to intervene in earlier stage risk conditions such as postprandial hyperlipidemia or hyperglycemia, insulin resistant state, masked hypertension, or metabolic syndrome to further reduce mortality or morbidity of coronary artery disease and heart failure.

Evaluation of porcine myocardial microvascular permeability and fractional vascular volume using 64-slice helical computed tomography (CT)

OBJECTIVES

Myocardial microvascular permeability-surface area product (MPSP) and fractional vascular volume (FVV), indices of endothelial function and microvascular perfusion, can be noninvasively evaluated by electron beam computed tomography (EBCT), but it remains unknown whether comparable assessments can be obtained with 64-slice multidetector CT (CT-64).

METHODS

We studied 12 pigs with both EBCT and CT-64 in randomized order 1 week apart, before and during IV adenosine infusion. Myocardial attenuation changes in the cardiac wall were assessed after a central-venous injection of iopamidol. Time-attenuation curves were analyzed using both indicator-dilution and Patlak models to calculate MPSP and FVV.

RESULTS

CT-64 and EBCT assessments of basal MPSP obtained by the Patlak method were similar (0.37 +/- 0.03 vs. 0.37 +/- 0.04 mL/min/g), as was its response to adenosine, and correlated significantly (r = 0.87). Patlak FVV was also similar between CT-64 and EBCT at baseline (0.08 +/- 0.02 vs. 0.07 +/- 0.02 mL blood/mL) and during adenosine, and correlated well (r = 0.93). MPSP and FVV estimated by the indicator-dilution method were not significantly correlated.

CONCLUSIONS

CT-64 assessments of myocardial MPSP and FVV may not be reliable when using indicator-dilution analysis, likely due to its sensitivity to scan duration. However, CT-64 assessments obtained using the Patlak model are feasible.

Coronary endothelial dysfunction and hyperlipidemia are independently associated with diastolic dysfunction in humans

BACKGROUND

Coronary endothelial dysfunction (CED) and DHF are both associated with myocardial ischemia and CAD risk factors. The objective of the this study was to determine if CED and CAD factors are associated with diastolic dysfunction before the development of occlusive CAD or clinical heart failure.

METHODS

Patients with normal ejection fraction and nonocclusive CAD who underwent coronary endothelial function studies were identified. Left ventricular relaxation was assessed by tissue Doppler assessment of early diastolic ascent of the septal mitral annulus (Ea). Multiple linear regression was used to investigate whether coronary risk factors influenced diastolic function after adjusting for the presence of CED.

RESULTS

A total of 160 patients had adequate assessment of diastolic relaxation. With multiple linear regression models, %deltaCBF (P = .018) was associated with a higher Ea; in contrast, older age (P < .001), female sex (P = .028), higher left ventricular mass index (P = .016), and higher nonhigh-density lipoprotein cholesterol (P = .022) were associated with a lower Ea.

CONCLUSION

Coronary endothelial dysfunction and hyperlipidemia are independently associated with impaired relaxation in patients with normal ejection fraction in the absence of occlusive CAD and heart failure. The current study suggests a new potential mechanism for the development of endothelial and diastolic dysfunction in humans.

Simvastatin prevents coronary microvascular remodeling in renovascular hypertensive pigs

Patients with hypertension and chronic kidney disease are at risk for cardiovascular diseases, possibly related to inflammation. Statins have beneficial anti-inflammatory effects on vascular structure regardless of cholesterol reduction. It was hypothesized that alterations in myocardial microvascular structure in swine renovascular hypertension (RVH) would be improved by simvastatin treatment. Three groups of pigs were studied after 12 wk: normal (n = 7), RVH (n = 7), or RVH+simvastatin (RVH+S; 80 mg/d; n = 6). Left ventricular muscle mass and myocardial perfusion were determined in vivo using electron beam computed tomography, and myocardial samples then were scanned ex vivo using micro-computed tomography for measurement of the spatial density of myocardial microvessels (80 to 500 microm) in situ. Capillary density and myocardial expression of inflammatory and growth factors were determined in myocardial tissue. The effects of simvastatin on inflammation-induced tube formation were evaluated in vitro in human umbilical vein endothelial cells that were exposed to TNF-alpha. RVH and RVH+S had similarly increased arterial pressure and serum creatinine. However, left ventricular hypertrophy was prevented by simvastatin, and myocardial perfusion was increased. Compared with normal, RVH showed increased spatial density of microvessels (169.6 +/- 21 versus 107.7 +/- 15.2 vessels/cm(2); P < 0.05), which was decreased in RVH+S (72.5 +/- 14.9 vessels/cm(2)), whereas capillary density remained similar to normal. RVH also increased myocardial expression of inflammatory and growth factors, which were reversed by simvastatin. Furthermore, simvastatin attenuated TNF-alpha-induced angiogenesis in vitro. Simvastatin prevents myocardial microvascular remodeling and hypertrophy in experimental RVH independent of lipid lowering. This protective effect is partly mediated by blunted expression as well as angiogenic activity of inflammatory cytokines.

Impaired myocardial perfusion reserve in experimental hypercholesterolemia is independent of myocardial neovascularization

Our objective was to investigate the functional role of hypercholesterolemia-associated myocardial neovascularization in early atherosclerosis using the antiangiogenic thalidomide. Experimental atherosclerosis is characterized by myocardial neovascularization, associated with a decrease in myocardial perfusion response to challenge, coronary endothelial dysfunction, and high oxidative stress. However, the functional significance of these neovessels is not known. Three groups of pigs (n = 6 each) were studied after 12 wk of normal or hypercholesterolemic diet without (HC) or with thalidomide (HC + Thal). Myocardial perfusion and permeability were assessed at baseline and in response to cardiac challenge, using electron beam computed tomography, and coronary endothelial function was assessed using organ chambers. Myocardial samples were scanned ex vivo with a three-dimensional microscopic computed tomography scanner, and the spatial density of the myocardial microvessels was quantified. Growth factors and oxidative stress were measured in the myocardial tissue. As a results of these procedures, myocardial perfusion response to adenosine and dobutamine was blunted in both HC and HC + Thal pigs compared with normal pigs (P < 0.05, HC and HC + Thal vs. normal) as was the coronary endothelial function. Myocardial permeability response to adenosine was increased in both HC and HC + Thal pigs compared with normal pigs (P < 0.05, HC and HC + Thal vs. normal, and HC + Thal vs. HC). The microvascular density was increased in HC pigs compared with normal pigs but normalized in HC + Thal pigs (P < 0.001 HC vs. normal and HC + Thal). HC + Thal pigs showed decreased expression of Flk-1 and basic FGF but increased expression of VEGF compared with normal and HC pigs. Oxidative stress was increased in both HC and HC + Thal pigs compared with normal pigs. In conclusion, chronic administration of thalidomide attenuates myocardial neovascularization in experimental HC pigs without affecting myocardial perfusion response to stimulation. This suggests that the myocardial neovascularization may not contribute to the attenuated myocardial perfusion response in hypercholesterolemia.

Assessment of Myocardial Microvascular Function: New Opportunities in Fast Computed Tomography

It has been increasingly recognized that the initial site of cardiac damage in several forms of cardiovascular disease resides in the microcirculation. Noninvasive or minimally invasive evaluation of myocardial microvascular functional attributes, such as myocardial perfusion or microvascular permeability, could be an invaluable tool in the clinical practice. Advances in the field of computed tomography over the past three decades culminated in the advent of fast scanners, which show promise to provide both fine cardiac anatomic detail and quantification of the function of the myocardial microcirculation. This review describes the approach and utility of measurements of myocardial microvascular function obtained with state-of-the-art cardiac computed tomography.

Lipid-lowering therapy with statins, a new approach to antiarrhythmic therapy

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (statins) are the most effective and best-tolerated drugs to treat elevated levels of low-density lipoprotein cholesterol (LDL-C). In addition, they exhibit other effects unrelated to their lipid lowering effects (pleiotropic actions). In recent years, experimental and clinical evidence demonstrates that statins exert antiarrhythmic properties, reducing the recurrences of supraventricular and life-threatening ventricular arrhythmias both in patients with and without coronary artery disease (CAD). Thus, statins may constitute a novel therapeutic approach to cardiac arrhythmias. This article reviews the antiarrhythmic properties of statins as well as the possible mechanisms involved, including the lowering of LDL-C levels, the improvement of endothelial dysfunction and autonomic function, the stabilization of the atherosclerotic plaques, the antioxidant, antiinflammatory, antithrombotic and cardioprotective properties and the modulation of transmembrane ion fluxes.

Simvastatin inhibits tissue factor and plasminogen activator inhibitor-1 expression of glomerular mesangial cells in hypercholesterolemic rabbits

Tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) activity and/or expression are upregulated in hypercholesterolemia. Despite extensive research on anti-thrombotic effect of statins, little is known about their effects on TF and PAI-1 expression in glomerular mesangial cells under hypercholesterolemic condition. Male rabbits were fed on either normal or high-cholesterol diet for 8 weeks. Then cholesterol-fed rabbits were randomly assigned to simvastatin or starch. At the end of 12 weeks, glomerular mesangial cells were collected. The concentrations of TF and PAI-1 mRNA were detected by RT-PCR. The plasma activities of TF and PAI-1 were determined with enzyme linked immunosorbent assay (ELISA) and chromogenic substrate method, respectively. The atherogenic diet caused a consistent increase in serum concentrations of total cholesterol (TC) and serum triglyceride (TG) (p < 0.05), increased TF and PAI-1 mRNA expression in glomerular mesangial cells and plasma activities as compared to the normal diet (p < 0.01). Four-week simvastatin treatment resulted in significant decrease of mesangial TF and PAI-1 mRNA (p < 0.01), and also of the plasma activities of TF (p < 0.05) and PAI-1 (p < 0.01). These results suggest that simvastatin might protect kidney from the formation of microthrombus under hypercholesterolemic condition and might be a possible pathogenesis of obesity-related glomerulopathy.

Chronic antioxidant supplementation impairs coronary endothelial function and myocardial perfusion in normal pigs

Experimental studies have shown the beneficial effects of antioxidant supplementation on endothelial function in the presence of increased endogenous oxidative stress, whereas limited data are available under normal conditions. The present study tested the hypothesis that in normal pigs long-term antioxidants would have deleterious effects on the cardiovascular system. Normal domestic pigs (V, n=6) were studied 12 weeks after dietary supplementation with vitamin E (100 IU/kg per day) and vitamin C (1 g/day) and compared with normal controls (C, n=7). Myocardial perfusion and permeability index were evaluated by electron beam computed tomography after intravenous adenosine and dobutamine. Coronary endothelial function was evaluated in vitro by organ chamber and coronary tissue studied by immunoblotting and staining. Myocardial perfusion response was lower in V than in C after adenosine (10.1+/-4.5 versus 53.4+/-5.2%; P<0.01) and dobutamine (V, 78.4+/-8.1; C, 193.0+/-39.0%; P<0.05). The permeability index increased in V after adenosine (48.8+/-5.1%) and dobutamine (59.9+/-13.6%) and did not change in C. Coronary vasodilation to bradykinin and substance P was lower in V than in C. Moreover, in V, coronary nitrotyrosine and superoxide content was significantly higher than in C. The groups had similar total monomer expression of endothelial nitric oxide synthase, whereas the dimerized form, reflecting coupled enzyme, was lower in V. These findings suggest that long-term experimental antioxidant vitamin supplementation in normal pigs impairs myocardial perfusion and coronary endothelial function via an increased level of oxidative stress in the arterial wall, which may be partly related to the uncoupling of endothelial nitric oxide synthase and/or the direct prooxidant effect of vitamin radicals.

Chronic pre-treatment of statins is associated with the reduction of the no-reflow phenomenon in the patients with reperfused acute myocardial infarction

AIMS

Early statin treatment has beneficial effects on prognosis after acute coronary syndrome. The no-reflow phenomenon determines the prognosis after acute myocardial infarction. We investigated the effects of statin treatment before admission on the development of the no-reflow after infarction.

METHODS AND RESULTS

We performed intracoronary myocardial contrast echocardiography in 293 consecutive patients with acute myocardial infarction undergoing successful primary percutaneous coronary intervention. There were no significant differences in the incidence of the no-reflow between the patients with and without hypercholesterolaemia. The 33 patients receiving chronic statin treatment before admission had lower incidence of the no-reflow than those without it (9.1 and 34.6%, P=0.003). They also showed better wall motion, smaller left ventricular dimensions, and better ejection fraction at 4.9+/-2.2 months later. Multivariable logistic regression analysis revealed that statin pre-treatment was a significant predictor of the no-reflow along with anterior wall infarction, ejection fraction on admission, and additional ST-elevation after reperfusion, whereas total cholesterol was not.

CONCLUSION

Chronic pre-treatment with statins could preserve the microvascular integrity after acute myocardial infarction independent of lipid lowering, leading to better functional recovery.

Dietary reversal of experimental hypercholesterolemia improves endothelial dysfunction of epicardial arteries but not of small coronary vessels in pigs

Endothelial dysfunction is characterized by impaired vasodilation, increase of oxidative stress and inflammation. The current study was designed to test the hypothesis that reversal of hypercholesterolemic diet alone does not normalize all the parameters of endothelial dysfunction. After 10 weeks on a high-cholesterol diet, female juvenile pigs were randomized to normal diet (n=5, "Reversals") or continued on the same diet (n=6, "HC") for another 6 weeks. A control group of 11 pigs received a normal diet ("C"). Coronary epicardial and arteriolar endothelial function was tested in vitro. NFkappaB and p47phox expression was analyzed in epicardial arteries and myocardium, respectively. P47phox localization in coronary arteries was demonstrated with immunohistochemistry. Lipid levels normalized in Reversal pigs. Epicardial arteries of Reversals showed a normalized relaxation and NFkappaB expression compared to HC (p<0.05). Small vessel relaxation remained attenuated, and expression of p47phox in myocardial tissue was elevated in Reversals compared to C (p<0.05). Dietary lowering of serum cholesterol and LDL improves vascular function of epicardial arteries but neither of small vessels nor vascular oxidative stress within this time frame. Hence, dietary normalization of serum lipid levels alone may not be synonymous to normalization of the components of endothelial dysfunction.

Anti-Inflammatory Effects of Statins: Clinical Evidence and Basic Mechanisms

Chronic inflammation is a key feature of vascular disease states such as atherosclerosis. Multiple clinical studies have shown that a class of medications termed statins lower cardiovascular morbidity and mortality. Originally developed to lower serum cholesterol, increasing evidence suggests that these medications have potent anti-inflammatory effects that contribute to their beneficial effects in patients. Here, we discuss the clinical and experimental evidence underlying the anti-inflammatory effects of these agents.

Protective effects of simvastatin on coronary artery function in swine with acute infection

BACKGROUND

The risk for coronary events may rise during acute infection. Perturbation in coronary endothelial function emerges as one important link. We investigated whether simvastatin could protect the coronary arterial function from the adverse effects of acute infection in swine.

METHODS

Coronary endothelium-dependent and -independent vasomotor responses were assessed by Doppler velocimetry in 12 Chlamydia pneumoniae-infected and 6 sham-infected swine 2 weeks after intratracheal inoculation. Half of animals from the infection group were pre-treated with simvastatin (80 mg daily), while the remaining animals received placebo. The treatment was started 2 weeks prior to inoculation and continued until the end of the study. ANOVA was used for statistical calculations. Data are mean+/-S.D.

RESULTS

All animals inoculated with C. pneumoniae developed IgM antibodies against this organism. As compared to noninfected animals, peak-to-baseline coronary flow velocity (CFV) ratio after bradykinin was significantly decreased in infected animals regardless of statin treatment (p=0.01). Intracoronary 10(-6) M acetylcholine caused slight dilatory responses in both noninfected and infected-treated animals (CFV ratio: 1.6+/-0.2 and 1.4+/-0.2, respectively; p>0.1), while a velocity drop (CFV ratio: 0.7+/-0.1; p<0.01 versus noninfected-infected and treated), indicating constriction, was observed in infected-nontreated animals; 10(-5) M acetylcholine caused vasoconstriction in all animals, with a significantly more prolonged response in the infected-nontreated group (p<0.01). Intracoronary adenosine and SNP induced similar dilatory responses in all groups (p>0.5). There were no differences in markers of systemic inflammation (fibrinogen, amyloid, and CRP) and lipid profile (HDL, LDL and total cholesterol) between the groups (p>0.2).

CONCLUSION

Acute infection is associated with impairment of the muscarinic and kinin-related reactivity of coronary circulation. These functional abnormalities are in part prevented by simvastatin through mechanisms unrelated to lipid lowering.

The effects of prior use of atorvastatin on coronary blood flow after primary percutaneous coronary intervention in patients presenting with acute myocardial infarction

BACKGROUND

Statins exert a variety of favourable effects on the vascular system not directly related to their lipid lowering function known as pleiotropic effects. There are not enough data regarding the effects of prior statin use on coronary blood flow after percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI). Accordingly, in the present study, we aimed to investigate the effects of prior statin use on coronary blood flow after primary PCI in patients with AMI using the Thrombolysis In Myocardial Infarction (TIMI) frame count method.

METHODS

The study population consisted of 200 patients (161 men; mean age=62+/-7 years) referred to cardiology clinics with AMI who subsequently underwent successful primary PCI. The study population was divided into two groups according to statin use before primary PCI. Group 1 consisted of 98 patients (75 men; mean age=63+/-7 years) not taking statin and group 2 consisted of 102 patients (86 men; mean age=61+/-7 years) taking daily dose of at least 40 mg atorvastatin for at least 6 months. Coronary blood flow was determined by TIMI frame count method using the angiographic images obtained just after PCI and stenting.

RESULTS

Only mean TIMI frame count was detected to be significantly lower in patients taking at least 40 mg atorvastatin for at least 6 months compared with that of the patients taking no statin (P<0.001). After confounding variables were controlled for, the mean TIMI frame count of patients in group 2 was significantly lower than that of the patients in group 1 (P=0.001). Pain to balloon time and vessel type were detected as important confounding variables of TIMI frame count after analysis of covariances.

CONCLUSIONS

Prior statin use may improve coronary blood flow after PCI in patients with AMI, possibly by its beneficial effects on microvascular function.

Statin Therapy in Rheumatoid Arthritis

Rheumatoid arthritis, a chronic inflammatory polyarthritis that destroys synovial joints, is associated with systemic as well as local inflammation and with an increased risk of cardiovascular disease and death not fully explained by traditional cardiac risk factors. Statins (HMG-coA reductase inhibitors), medications originally designed to lower cholesterol, have been shown to have powerful effects on decreasing cardiovascular mortality rates in the general and high-risk populations. Not all of this protective benefit appears to be mediated by lowered cholesterol levels. Statins also influence multiple steps in the inflammatory process, including leukocyte migration and adhesion, T-cell stimulation, nitric oxide bioavailability, generation of free radicals, and angiogenesis. Recent studies show that statins may provide mild anti-inflammatory benefit in rheumatoid arthritis, in addition to reducing cardiovascular risk.

First annual Mario S. Verani, MD, Memorial lecture: clinical value of myocardial perfusion imaging in coronary artery disease

I am honored to give this lecture in memory of Dr Mario S. Verani, a friend and a respected colleague in the field of nuclear cardiology. Dr Verani made many immense contributions to the field of nuclear cardiology during his lifetime. He was a pioneer in the field of pharmacologic stress imaging and played a leading role in validating the utility of intravenous adenosine infusion for stress imaging in detecting significant coronary stenoses and assessing prognosis. He and his colleagues at Baylor reported that pharmacologic stress imaging could separate high- and low-risk patient subsets after acute myocardial infarction, particularly among patients who underwent thrombolytic therapy. He informed us that certain drugs that patients took could influence perfusion defect severity. This work led to a clinical study showing that ischemic defect size could be substantially reduced with medical therapy in patients who had recently had an acute infarction. An outcome of this observation was the launching of the INSPIRE (adenosINe technetium-99m Sestamibi single-photon emission computed tomography Post-InfaRction Evaluation) trial in which postinfarction patients are randomized to medical therapy or revascularization. Dr Verani was an able debater when assigned the position for advocating for stress radionuclide perfusion imaging against stress echocardiography. He engaged in these debates with substantial knowledge but always with a touch of humor. Dr Verani's courage was an inspiration to all of us during his illness. His legacy as a pioneer will endure as the field of nuclear cardiology continues to mature and expand.

Long-term antioxidant intervention improves myocardial microvascular function in experimental hypertension

Hypertension increases oxidative stress, which can impair myocardial microvascular function and integrity. However, it is yet unclear whether long-term antioxidant intervention in early hypertension would preserve myocardial perfusion and vascular permeability responses to challenge. Pigs were studied after 12 weeks of renovascular hypertension without (n=8) or with daily supplementation of antioxidants (100 IU/kg vitamin E and 1 g vitamin C, n=6), and compared with normal controls (n=7). Myocardial perfusion and microvascular permeability were measured in vivo by electron beam computed tomography before and after 2 cardiac challenges (intravenous adenosine and dobutamine). Basal left ventricular muscle mass was also obtained. Mean arterial pressure was significantly increased in both groups of hypertensive animals (without and with antioxidants, 123+/-9 and 126+/-4 mm Hg, respectively, versus normal, 101+/-4 mm Hg; both P<0.05), but muscle mass was not different among the groups. The impaired myocardial perfusion response to adenosine observed in hypertensives (normal, +51+/-14%; P<0.05 versus baseline; hypertension, +14+/-15%; P=0.3 versus baseline) was preserved in hypertensive pigs that received antioxidants (+44+/-15%; P=0.01 compared with baseline). Long-term antioxidant intervention also preserved subendocardial microvascular permeability responses in hypertension. On the other hand, antioxidant intervention had little effect on the hypertension-induced myocardial vascular dysfunction observed in response to dobutamine. This study demonstrates that the impaired myocardial perfusion and permeability responses to increased cardiac demand in early hypertension are significantly improved by long-term antioxidant intervention. These results support the involvement of oxidative stress in myocardial vascular dysfunction in hypertension and suggest a role for antioxidant strategies to preserve the myocardial microvasculature.

Lipid-lowering-independent effects of simvastatin on the kidney in experimental hypercholesterolaemia

BACKGROUND

Hypercholesterolaemia (HC), an independent risk factor for renal injury, is associated with formation of oxidized low-density-lipoprotein (ox-LDL), increased oxidative-stress and renal inflammation. HMG-CoA-reductase inhibitors are commonly used in HC, but their effects on renal haemodynamics and function in HC are poorly understood.

METHODS

Pigs were studied after a 12-week normal diet, a 2% high-cholesterol diet (HC) or an HC diet supplemented with simvastatin (HC+simvastatin, 80 mg/day) (n=6-8 each group). Renal haemodynamics and function were quantified in vivo with electron-beam computed tomography (EBCT). Shock-frozen renal tissue was subsequently studied using immunohistochemistry.

RESULTS

LDL cholesterol was similarly increased in HC and HC+simvastatin. Simvastatin-treated animals showed increased expression of endothelial nitric-oxide-synthase (eNOS), and decreased expression of the ox-LDL receptor LOX-1 in renal endothelial cells. Simvastatin also decreased tubular immunoreactivity of inducible-NOS, nitrotyrosine, nuclear-factor-kappaB, and tubuloglomerular trichrome staining. These were associated with a significant increase in cortical (6.1+/-0.1 vs 5.0+/-0.3 and 5.0+/-0.1 ml/min/cc, respectively, P<0.001) and medullary perfusion in HC+simvastatin compared to normal and HC.

CONCLUSIONS

Simvastatin attenuated the inflammatory and pro-oxidative environment as well as fibrosis in kidneys in pigs with diet-induced HC, in association with enhanced renal perfusion. These cholesterol-lowering-independent changes imply novel renoprotective effects of statins in the setting of HC and atherosclerosis.

Targets for pharmacological intervention of endothelial hyperpermeability and barrier function

Many diseases share the common feature of vascular leakage, and endothelial barrier dysfunction is often the underlying cause. The subsequent stages of endothelial barrier dysfunction contribute to endothelial hyperpermeability. Vasoactive agents induce loss of junctional integrity, a process that involves actin-myosin interaction. Subsequently, the interaction of leukocytes amplifies leakage by the leukocyte-derived mediators. The processes mainly occur at the postcapillary venules. The whole microvascular bed, including the capillaries, becomes involved in vascular leakage by the induction of angiogenesis. Plasma leakage results from gaps between endothelial cells as well as by the induction of transcellular transport pathways. Several mechanisms can improve endothelial barrier function, depending on the tissue affected and the cause of hyperpermeability. They include blockade of specific receptors and elevation of cyclic AMP (cAMP) by agents such as beta(2)-adrenergic agents. However, current therapies based on these principles often fail. Recent research has identified several new promising targets for pharmacological therapy. Endogenous compounds were also found with barrier-improving characteristics. Important insights were obtained in the different pathways involved in barrier dysfunction. Such insights regard the regulation of endothelial contraction and endothelial junction integrity: inhibitors of RhoA activation and Rho kinase represent a potentially valuable group of agents with endothelial hyperpermeability reducing properties, and strategies to target vascular endothelial growth factor (VEGF)-mediated edema are under current investigation. In clinical practice, not only tools to improve an impaired endothelial barrier function are necessary. Sometimes, a controlled, temporal, and local increase in permeability can also be desired, for example, with the aim to enhance drug delivery. Therefore, vessel leakiness is also being exploited to enable tissue access of liposomes, viral vectors, and other therapeutic agents that do not readily cross healthy endothelium. This review discusses strategies for targeting signaling molecules in therapies for diseases involving altered endothelial permeability.