Statins and ischemic stroke

Simvastatin improves clinical scores in a rabbit multiple infarct ischemic stroke model: synergism with a ROCK inhibitor but not the thrombolytic tissue plasminogen activator

Statins have pleiotropic neuroprotective effects in the central nervous system. In this study, we assessed the pharmacological effects of simvastatin on measures of behavior in New Zealand white rabbits embolized using a suspension of small-sized blood clots. For these studies, simvastatin was administered up to 3 hours following embolization, and behavior was measured 48 hours following embolization to calculate the dose of emboli (P(50) in mg) that produces neurological deficits in 50% of the rabbits. A treatment is considered neuroprotective if it significantly increases the P(50) compared to control. Simvastatin treatment (20mg/kg, bolus subcutaneous injection) significantly improved clinical function and increased the P(50) by 143% when administered 1 hour following embolization but was ineffective at 3 hours. In combination studies with the thrombolytic, tissue plasminogen activator (tPA) using a standard intravenous dose of 3.3mg/kg (20% bolus, 80% infused), we found that simvastatin could be safely administered with tPA to improve clinical scores; however, the maximum behavioral improvement with the combination treatment was similar to either monotherapy alone, both of which significantly improved behavior (p<0.05). It has been proposed that Simvastatin neuroprotection may be related to a variety of signaling pathways including Rho-kinase (ROCK). To determine if a ROCK mechanism is involved in simvastatin-induced neuroprotection following embolic strokes, we used pharmacological intervention with the ROCK inhibitor, fasudil. When fasudil was administered 30 minutes before simvastatin (given at 1 hour), there was an additional significant (p=0.0217) synergistic increase in behavioral function. However, fasudil as a monotherapy did not affect behavioral function in embolized rabbits. The study suggests that there may be an interaction between simvastatin treatment and the ROCK signaling pathway that should be further explored. Our results suggest that simvastatin treatment may have clinical benefit when used alone or in the presence of tPA, but the therapeutic window using a single-dose regimen is narrow.

Statins improve visual field alterations related to hypercholesterolemia

OBJECTIVE

To determine whether lipid-lowering treatment with diet or statins would provide beneficial effects on visual field alterations associated with hypercholesterolemia.

METHODS

180 subjects with hypercholesterolemia were randomly assigned to a low fat diet (diet group) or to a low fat diet plus 40 mg/day of pravastatin (pravastatin group). At the beginning of the study and 6 months after the assigned treatment, all subjects underwent a computerized perimetry test and a determination of plasma concentration of glucose, total cholesterol, LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C) and triglycerides.

RESULTS

At 6 months, both groups showed a significant decrease in total cholesterol, LDL-C and triglycerides compared to basal values, and a significant increase in the HDL-C. The pravastatin group had a significantly greater reduction in total cholesterol (-85+/-21 mg/dl) and LDL-C (-86+/-23 mg/dl) than the diet group (-28+/-9 and -28+/-10mg/dl, respectively). All perimetry parameters improved in both groups after the intervention period, although the improvement was greater in the pravastatin group. Using a general linear model, a significant effect of treatment with pravastatin compared to diet was observed in the improvement of all the perimetry parameters, whereas the change in LDL-C concentrations only had a significant effect on the improvement of one of them.

CONCLUSION

In subjects with hypercholesterolemia, the decrease of blood lipids improves visual field parameters. The major beneficial effect noted with pravastatin, compared to diet, suggests that this effect could be due to the lipid-lowering and pleiotropic actions.

Advances in hemorrhagic stroke therapy: conventional and novel approaches

Treatments for spontaneous intracerebral, thrombolytic-induced and intraventricular hemorrhages (IVH) are still at the preclinical or early clinical investigational stages. There has been some renewed interest in the use of surgical evacuation surgery or thrombolytics to remove hematomas, but these techniques can be used only for specific types of brain bleeding. The STICH (Surgical Trial in Intracerebral Haemorrhage) clinical trials should provide some insight into the potential for such techniques to counteract hematoma-induced damage and subsequently, morbidity and mortality. More recently, clinical trials (ATACH [Antihypertensive Treatment in Acute Cerebral Hemorrhage] and INTERACT [Intensive Blood Pressure Reduction in Acute Cerebral Hemorrhage Trial]) have begun testing whether or not regulating blood pressure affects the well-being of hemorrhage patients, but the findings thus far have not conclusively demonstrated a positive result. More promising trials, such as the early stage CHANT (Cerebral Hemorrhagic And NXY-059 Treatment) and the late stage FAST (Factor VIIa for Acute Hemorrhagic Stroke Treatment), have addressed whether or not manipulating oxidative stress and components of the blood coagulation cascade can achieve an improved prognosis following spontaneous hemorrhages. However, CHANT was halted prematurely because although it showed that the spin trap agent NXY-059 was safe, it also demonstrated that the drug was ineffective in treating acute ischemic stroke. In addition, the recombinant activated factor VII FAST trial recently concluded with only modestly positive results. Despite a beneficial effect on the primary end point of reducing hemorrhage volume, controlling the coagulation cascade with recombinant factor VIIa did not decrease the mortality rate. Consequently, Novo Nordisk has abandoned further development of the drug for the treatment of intracerebral hemorrhaging. Even though progress in hemorrhage therapy that successfully reduces the escalating morbidity and mortality rate associated with brain bleeding is slow, perseverance and applied translational drug development will eventually be productive. The urgent need for such therapy becomes more evident in light of concerns related to uncontrolled high blood pressure in the general population, increased use of blood thinners by the elderly (e.g., warfarin) and thrombolytics by acute ischemic stroke patients, respectively. The future of drug development for hemorrhage may require a multifaceted approach, such as combining drugs with diverse mechanisms of action. Because of the substantial benefit of factor VIIa in reducing hemorrhage volume, it should be considered as a prime drug candidate included in combination therapy as an off-label use if the FAST trial proves that the risk of thromboembolic events is not increased with drug administration. Other promising drugs that may be considered in combination include uncompetitive NMDA receptor antagonists (such as memantine), antioxidants, metalloprotease inhibitors, statins and erythropoietin analogs, all of which have been shown to reduce hemorrhage and behavioral deficits in one or more animal models.

Cholesterol, C-reactive protein, and cerebrovascular events following intensive and moderate statin therapy

BACKGROUND

While statins have been shown to reduce cerebrovascular events (CVE), the relationship between cholesterol, C-reactive protein (CRP), and CVE in patients treated with different statin strategies is still being explored.

METHODS

PROVE IT-TIMI 22 was a randomized trial of intensive (atorvastatin 80 mg/day) and moderate (pravastatin 40 mg/day) statin therapy in 4,162 patients with acute coronary syndromes followed for an average of 24 months; serial biomarkers allowed for an assessment of the lipid and non-lipid effects of statins as they relate to CVE.

RESULTS

In this study, 45 patients on intensive statin therapy and 40 patients on moderate statin therapy had a CVE during the study period (2.1% v. 1.9%, P = 0.62). While the lipid profiles of patients with and without CVE were similar, those with CVE had higher CRP levels at 30 days and 4 months (2.7 v. 1.9, 2.4 v. 1.7 mg/L; P = 0.012, P = 0.005). Day 30 CRP remained an independent predictor of CVE after adjusting for age, development of atrial fibrillation, diabetes, and prior CVE. Patients with low density lipoprotein (LDL) levels < 70 mg/dL and > or = 70 mg/dL had similar rates of CVE, while patients with CRP < 2 mg/L tended to have lower event rates when compared to those with higher levels. The lowest rates of CVE were seen in patients who had LDL < 70 mg/dL and CRP < 2 mg/L.

CONCLUSION

In PROVE IT--TIMI 22, achieved LDL levels did not appear to independently impact the rate of CVE. In contrast, patients with elevated CRP levels were at higher risk of stroke or transient ischemic attack, reinforcing the link between inflammation and CVE. The goal of this PROVE IT-TIMI 22 sub-study was to examine the relationship between cholesterol, CRP, and CVE in patients on intensive and moderate statin therapy. The achieved lipid levels were similar in patients with and without a CVE; however, the achieved levels of CRP were higher in patients who subsequently developed a stroke or TIA. These findings further support the relationship between inflammation and CVE.

Direct inhibition by a statin of TNFalpha-induced leukocyte recruitment in rat pial venules - in vivo confocal microscopic study

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have been shown to block leukocyte-endothelial interaction independently of their cholesterol-lowering properties. The effects of statins are generally attributed to a decrease in mevalonate caused by inhibition of HMG-CoA reductase, which results in an increase of nitric oxide (NO). However, a recent in vitro study demonstrated a novel effect which depended on the lipophilicity of statin and appeared to be unrelated to HMG-CoA reductase inhibition. The purpose of this study is to investigate whether the proposed mechanism actually operates in vivo. We examined the effects of simvastatin (lipophilic) and pravastatin (hydrophilic) on leukocyte behavior in a tumor necrosis factor alpha (TNFalpha)-induced leukocyte recruitment model. Leukocyte adhesion and rolling were examined in pial venules of rat brain by using confocal laser scanning microscopy after labeling leukocytes with rhodamine 6G. Experiments were conducted 4h after TNFalpha injection (0.5microg) in six groups: control, TNFalpha alone, TNFalpha + vehicle of simvastatin, TNFalpha + simvastatin (20mg/kg, 2ml/kg), TNFalpha + vehicle of pravastatin, and TNFalpha + pravastatin (40mg/kg, 2ml/kg). Statins and vehicles were injected subcutaneously for 3 days. TNFalpha caused a marked increase in rolling and adhered leukocytes. The number of adhered leukocytes in the simvastatin group was significantly less than in the vehicle group (276 +/- 38 cells/mm(2) versus 1155 +/- 89 cells/mm(2), P < 0.01), whereas pravastatin had little effect. Both simvastatin and pravastatin showed a tendency to decrease the number of rolling leukocytes, but there were no significant differences among TNFalpha-treated groups. Up-regulation of endothelial nitric oxide synthase (eNOS) mRNA or increased expression of P-selectin or intercellular adhesion molecule-1 (ICAM-1) was not observed, and therefore cannot account for the simvastatin-induced reduction of adhered leukocytes. Markedly different effect on leukocyte adhesion between simvastatin and pravastatin under comparable level of HMG-CoA reductase inhibitor was demonstrated in in vivo as was shown in in vitro study.

Cerebral microvascular responses to hypercholesterolemia: roles of NADPH oxidase and P-selectin

Although hypercholesterolemia is widely accepted as a major risk factor for coronary artery and peripheral vascular diseases, its role in the pathogenesis of stroke is controversial. The objectives of this study were to determine how hypercholesterolemia affects the cerebral microcirculation under resting conditions and after ischemia-reperfusion (I/R). Platelet- and leukocyte-endothelial cell interactions and oxidant production (using the oxidant-sensitive fluorochrome dihydrorhodamine-123) were monitored by intravital videomicroscopy in the cerebral microvasculature of mice placed on either a normal (ND) or cholesterol-enriched diet (HCD). Platelets labeled with carboxyfluorescein diacetate succinimidyl ester (CFDASE) and leukocytes labeled with rhodamine 6G were seen to roll and firmly adhere, with a corresponding increase in oxidant production, in venules of mice on HCD, but not ND. Immunoneutralization of P-selectin attenuated the platelet- and leukocyte-endothelial cell interactions and the enhanced oxidant production associated with HCD. A GPIIb/IIIa blocking antibody did not alter the blood cell-vessel wall interactions to HCD. Mice deficient in the NADPH oxidase subunit gp91(phox) exhibited significantly blunted platelet and leukocyte recruitment responses to HCD. Focal I/R also elicited inflammatory and prothrombogenic responses in cerebral venules and these were exaggerated in mice on HCD. These results implicate an oxidant-dependent, P-selectin-mediated mechanism in the blood cell-vessel wall interactions induced by hypercholesterolemia in the brain and demonstrate that the deleterious effects of I/R on the brain are exacerbated by this cardiovascular risk factor.

Prophylactic but not delayed administration of simvastatin protects against long-lasting cognitive and morphological consequences of neonatal hypoxic-ischemic brain injury, reduces interleukin-1beta and tumor necrosis factor-alpha mRNA induction, and does not affect endothelial nitric oxide synthase expression

BACKGROUND AND PURPOSE

Prophylactic administration of simvastatin has been shown to protect against brain damage and its long-lasting behavioral consequences in neonatal rats. To establish the drug treatment window, we evaluated the effectiveness of simvastatin administered at different intervals before and after stroke. Furthermore, we determined whether simvastatin affected endothelial nitric oxide synthase (eNOS) or inflammatory cytokines in brain tissue or cholesterol levels in serum.

METHODS

On postnatal day 7, male rats were subjected to hypoxia-ischemia (HI). The experiment included sham-operated controls and HI animals receiving daily saline or activated simvastatin (20 mg/kg) injections from postnatal day 1 to day 7 (HI-simvastatin 1-7 group), from postnatal day 4 to day 11 (HI-simvastatin 4-11 group), or from postnatal day 7 to day 14 (HI-simvastatin 7-14 group). The neuroprotective effect of simvastatin was evaluated at adulthood by means of behavioral and histological analyses. Cytokines and eNOS expression were assessed by reverse transcriptase-polymerase chain reaction and Western blotting.

RESULTS

Animals in both the HI-simvastatin 1-7 and HI-simvastatin 4-11 groups performed better than HI rats in either the T-maze or the circular water maze and showed significantly attenuated brain damage. Expression of interleukin-1beta and tumor necrosis factor-alpha mRNA in cortex was significantly increased in HI but not in HI-simvastatin 1-7 animals. In the same brain area, simvastatin treatment did not affect the increase of eNOS expression observed after HI.

CONCLUSIONS

These findings indicate that prophylactic but not delayed administration of simvastatin improves functional outcome in neonatal rat stroke. The reduced induction of cytokines suggests that the neuroprotective effect of simvastatin may be related to a dampening of the inflammatory response.

Beyond lipid-lowering: effects of statins on endothelial nitric oxide

Endothelial dysfunction is now recognised as an important process in the pathogenesis of atherosclerosis. Nitric oxide (NO) release by the endothelium regulates blood flow, inflammation and platelet aggregation, and consequently its disruption during endothelial dysfunction can decrease plaque stability and encourage the formation of atherosclerotic lesions and thrombi. Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) are often utilised in the prevention of coronary heart disease due to their efficacy at lowering lipid levels. However, statins may also prevent atherosclerotic disease by non-lipid or pleiotropic effects, for example, improving endothelial function by promoting the production of NO. There are various mechanisms whereby statins may alter NO release, such as inhibiting the production of mevalonate and important isoprenoid intermediates, thereby preventing the isoprenylation of the small GTPase Rho, which negatively regulates the expression of endothelial nitric oxide synthase (eNOS). Furthermore, statins may also increase eNOS activity via post-translational activation of the phosphatidylinositol 3-kinase/protein kinase Akt (PI3 K/Akt) pathway and/or through an interaction with the molecular chaperone heat-shock protein 90 (HSP90). Data suggest that statins may vary in their efficacy for enhancing the release of NO, and the mechanisms dictating these differences are not yet clear. By increasing NO production, statins may interfere with atherosclerotic lesion development, stabilise plaque, inhibit platelet aggregation, improve blood flow and protect against ischaemia. Therefore, the ability of statins to improve endothelial function through the release of NO may partially account for their beneficial effects at reducing the incidence of cardiovascular events.