Therapeutic Advances in Cardiovascular Disease

Introduction: p27^Kip1 is a cyclin kinase inhibitor that induces cell cycle arrest. In this study, the efficacy of fusion protein TAT- p27^Kip1 to inhibit cell proliferation in rat perivascular injured carotid arteries was tested.

Methods: The cDNA of p27^Kip1 and GFP (green fluorescein protein) fused to the TAT epitope, which allows cell penetration, yielded TAT-p27 ^Kip1 and TAT-GFP fusion proteins. In vitro biological activity on cell proliferation was evaluated by [³H] thymidine DNA incorporation in rabbit aortic endothelial cells (REC). An in vivo model used a silicone collar filled with saline positioned around the carotid vessel for 14 days to produce an increased adventitia cross-sectional area.

Results: TAT-p27^Kip1 inhibited REC proliferation in vitro using either 100, 200, and 500 nM compared to control (88.2 ± 4.4, 81.3 ± 7, 71.9 ± 4.2 vs. 100 ± 6.7%, N = 3, respectively, p < 0.05). This response was stable for purified proteins stored at -20•C for at least 23 days. In vivo , TAT-p27^Kip1 solution reduced adventitia cross-sectional area in a dose-dependent manner compared to TAT-GFP (area in mm² — TAT-p27^Kip1: 200 nM, 0.160 ± 0.018; 500 nM, 0.050 ± 0.005 vs. TAT-GFP: 500 nM, 0.595 ± 0.066 vs. the contralateral: 0.047 ± 0.005, N = 7, p < 0.01).

Conclusion: Taken together, these results provide evidence that TAT-p27^Kip1 can inhibit vascular cells proliferation. It is the first successful demonstration that the cell permeable TAT-p27^Kip1 has potential as a vascular anti-proliferative agent.

Restenosis is an important limitation of percutaneous coronary interventions (PCI). In-stent restenosis is mainly due to neointimal hyperplasia, a proliferative process modulated by inflammatory mechanisms. Numerous technical and pharmacological means have been tested to reduce restenosis rates, with frequently disappointing clinical results. Drug-eluting stents (DES) have demonstrated a high efficacy in reducing restenosis, but there are some associated problems that limit its generalized utilization. Glucocorticoids (GC), as potent anti-inflammatory agents, may exert beneficial effects on neointimal proliferation. Clinical studies with oral and intracoronary GC therapy have demonstrated reduction in restenosis rates in selected patients. Although further investigations are warranted, GC might have a potential role for restenosis prevention in selected cases.

The economic aspects of hypertension are critical to modern medicine. The medical, economic, and human costs of untreated and inadequately controlled hypertension are enormous. Hypertension is distributed unequally and with iniquity in different countries and regions of the world. Treatment of hypertension requires an investment over many years to prolong disease-free quality years of life. The high prevalence and high cost of the disease impacts on the microeconomics and macroeconomics of countries and regions. The criteria used for inclusion in clinical guidelines for hypertension impact on the cost and cost/utility of diagnosis or treatment.

Statins play an important role in brain ischemia. These drugs reduce cholesterol levels, which have been related to a reduction in vascular event risk, but they also have other functions besides cholesterol metabolism, called pleiotropic effects. Statins play an important role during the acute phase of ischemia, and might have neuroprotective effects, as they act in several mechanisms during the acute phase of stroke, such as in nitric oxide (NO) and glutamate metabolism, inflammation, platelet aggregation, immune responses and apoptosis. They also have other functions that can be related, with better long-term outcome, to neurorepair mechanisms. Statins promote angiogenesis, endogenous cell proliferation, neurogenesis and new synapse formation.

Cardiovascular disease represents a continuum that starts with risk factors such as hypertension and progresses to atherosclerosis, end-organ damage, and ultimately to chronic heart failure (CHF) and premature death. Renin-angiotensin system (RAS) blockade with angiotensin converting enzyme (ACE) inhibitors and/or angiotensin II type 1 receptor blockers (ARBs) has turned out to be beneficial at all stages of this continuum. Several mechanisms govern the progression of structural myocardial damage to end-stage CHF. Chronic neuroendocrine activation fosters left ventricular remodeling and dilatation and leads to clinical symptoms of CHF via forward/backward failure. RAS inhibition is a cornerstone of neuroendocrine blockade in CHF patients, and combined RAS blockade is especially effective in patients presenting with repetitive cardiac decompensations. This review focuses on the therapeutic role of inhibitors of different RAS components in chronic heart failure caused by systolic left ventricular dysfunction.

Stroke is a leading cause of death and long-term disability in industrialized countries. Despite advances in understanding its pathophysiology, little progress has been made in the treatment of stroke. The currently available therapies have proven to be highly unsatisfactory (except thrombolysis) and attempts are being made to identify and characterize signaling proteins which could be exploited to design novel therapeutic modalities. The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that control lipid and glucose metabolism. PPARs regulate gene expression by binding with the retinoid X receptor (RXR) as a heterodimeric partner to specific DNA sequences, termed PPAR response elements. In addition, PPARs may modulate gene transcription also by directly interfering with other transcription factor pathways in a DNA-binding independent manner. To date, three different PPAR isoforms, designated α, β/δ, and γ, have been identified. Recently, they have been found to play an important role for the pathogenesis of various disorders of the central nervous system and accumulating data suggest that PPARs may serve as potential targets for treating ischemic stroke. Activation of all PPAR isoforms, but especially of PPARγ, was shown to prevent post-ischemic inflammation and neuronal damage in several in vitro and in vivo models, negatively regulating the expression of genes induced by ischemia/ reperfusion (I/R). This paper reviews the evidence and recent developments relating to the potential therapeutic effects of PPAR-agonists in the treatment of cerebral I/R injury.

Assessment of the propensity for vascular events has been based on measurement of risk factors predisposing one to vascular injury. These assessments are based on the strong associations between risk factors such as hypertension, cholesterol levels, smoking, and diabetes which were first described almost a half century ago. The more recent discovery of the relationship between ongoing inflammation and clinical outcomes has led to a variety of blood-based assays which may impart additional knowledge about an individual's propensity for future cardiovascular events. Vascular health is now better represented as a balance between ongoing injury and resultant vascular repair, mediated at least in part by circulating endothelial progenitor cells. To date, one's risk for vascular events has focused exclusively on assessing propensity for vascular damage, either by assessing conventional risk factors which were initially identified over half a century ago, or more recently by assessing markers of inflammation and other circulating factors which area related to subsequent clinical events. Circulating endothelial progenitor cells play important roles in accelerating endothelialization at areas of vascular damage, and EPC enumeration is a viable strategy for assessing reparative capacity. To date, EPC numbers have been correlated with the numbers of cardiovascular risk factors, extent of coronary disease, and future cardiovascular events. Given that EPC enumeration and functional characterization represent the only assessment of the reparative side of the balance between damage and renovation, this technique may offer independent and different assessment of propensity to cardiovascular injury, greatly improving risk stratification of patients.

Atrial Fibrillation (AF) is one of the most frequent arrhythmias, especially in elderly patients. Cardiac overload increases the incidence of AF. Clinical presentation of atrial fibrillation can occur as nonsustained paroxysms, persistent episodes and in chronic-permanent form. The physio-pathological mechanisms are:

• Circuit of multiple and anarchic re-entries

• Atrial fibrillatory conduction

• Re-entry circuit with fibrillatory conduction.

Remodeling (electrical or structural) facilitates the appearance and persistence of AF: Neurovegetative changes and cytosolic Ca overload facilitate AF. Interstitial atrial fibrosis, in which Renin-Angiotensin System (RAS) hyperactivity is a main aspect of remodeling. There is clinical evidence that supports the antiatrial fibrillatory actions of RAS blockade. Potential mechanisms are: (a) direct modulation of ionic channels, (b) hemodynamic improvement, (c) reduction of atrial stretching, (d) antifibrotic effects. There is less clinical evidence with antialdosterone drugs, but theoretically these might also be useful.