Anita Gianella

Statins: Multiple Mechanisms of Action in the Ischemic Brain

Although substantial epidemiological studies have failed to find a correlation between cholesterol levels and stroke, clinical trials have shown that HMG-CoA reductase inhibitors (or statins, the most potent hypocholesterolemic drugs available) greatly reduce the incidence of stroke. These clinical observations have opened the way to a number of studies of the non—cholesterol-dependent (or pleiotropic) effects in animal models of stroke, indicating that the neuroprotection is attributable to multiple activities. One of the main protective mechanisms elicited by statin administration is the increase in nitric oxide bioavailability that regulates cerebral perfusion and improves endothelial function, but others include antioxidant properties, the inhibition of inflammatory responses, immunomodulatory actions, the regulation of progenitor cells, and the stabilization of atherosclerotic plaques. Many of these effects are due to the inhibited synthesis of isoprenoid intermediates, which serve as lipid attachments for a variety of intracellular signaling molecules. This article describes the mechanisms involved in the neuroprotective effects of statins. NEUROSCIENTIST 13(3):208—213, 2007.

Rosuvastatin, but not Simvastatin, Provides End-Organ Protection in Stroke-Prone Rats by Antiinflammatory Effects

Objective—Brain abnormalities, preceded by a systemic inflammation, develop in spontaneously hypertensive stroke-prone rats (SHRSP). In this model, we investigated whether the hydrophilic statin, rosuvastatin, influences the development of inflammation associated with brain abnormalities. Because differences in hydrophilicity/hydrophobicity contribute to the differences in statin pharmacology, we also evaluated the effects of simvastatin, a lipophilic molecule Methods and Results—SHRSP, fed a high-salt diet, were treated long-term with vehicle or rosuvastatin (1 and 10 mg/kg per day). Brain abnormalities developed after 40±5 days and after 60±5 days of salt loading, in vehicle-treated and in rosuvastatin-treated (1 mg/kg per day) SHRSP, respectively. After 100 days of treatment, no damage was detectable in 30% of the rats treated with the highest dose of the drug. In comparison with vehicle-treated SHRSP, rosuvastatin treatment attenuated the transcription of monocyte chemoattractant protein-1, transforming growth factor-&bgr;1, IL-1&bgr;, and tumor necrosis factor-&agr; in the kidney, and of P-selectin in brain vessels and increased the transcription of endothelial nitric oxide synthase mRNA in the aorta. Urinary excretion of acute-phase proteins increased with time in vehicle-treated animals but remained negligible in drug-treated animals. These effects are independent of changes in physiological parameters. Treatment of SHRSP with simvastatin (2 to 20 mg/kg per day) did not exert any protective effect. Conclusions—Rosuvastatin attenuates inflammatory processes associated with cerebrovascular disease.

Activation of NF-kB and ERK1/2 after permanent focal ischemia is abolished by simvastatin treatment

We investigated the effects of simvastatin treatment on the expression of IL-1beta and MCP-1, the activity of NF-kB, and the signaling pathways related to NF-kB activation in a rat model of permanent middle cerebral artery occlusion (pMCAO). IL-1beta and MCP-1 expression, determined using RT-PCR, was enhanced by pMCAO; this effect was inhibited by the administration of simvastatin before ischemia. Pre-treatment with simvastatin abolished the ischemia-induced activation of NF-kB observed in vehicle-treated animals. The evaluation of signal transduction pathways, including extracellular signal-regulated kinase (ERK1/2), SAPK/JNK 46/54 and p38, indicated that only ERK1/2 phosphorylation was enhanced by ischemia, and this activation was prevented by simvastatin. ERK1/2-inhibitor, U0126, reduced brain ischemia but not cytokine induction. These results provide evidence that the HMG-CoA reductase inhibitor induces its effect in the protection of ischemic brain damage with a more complex mechanism which also involve anti-inflammatory properties rather than simple inhibition of ERK1/2 signaling pathway.

Peroxisome Proliferator-Activated Receptor α Agonism Prevents Renal Damage and the Oxidative Stress and Inflammatory Processes Affecting the Brains of Stroke-Prone Rats

A growing body of evidence suggests that chronic kidney disease is a significant risk for cardiovascular events and stroke regardless of traditional risk factors. The aim of this study was to examine the effects of peroxisome proliferator-activated receptor (PPAR) agonists on the tissue damage affecting salt-loaded spontaneously hypertensive stroke-prone rats ( SHRSPs), an animal model that develops a complex pathology characterized by systemic inflammation, hypertension, and proteinuria and leads to end-organ injury (initially renal and subsequently cerebral). Compared with the PPARγ agonist rosiglitazone, the PPARα ligands fenofibrate and clofibrate significantly increased survival (p < 0.001) by delaying the occurrence of brain lesions monitored by magnetic resonance imaging (p < 0.001) and delaying increased proteinuria (p < 0.001). Fenofibrate completely prevented the renal disorder characterized by severe vascular lesions, tubular damage, and glomerular sclerosis, reduced the number of ED-1-positive cells and collagen accumulation, and decreased the renal expression of interleukin-1β, transforming growth factor β, and monocyte chemoattractant protein 1. It also prevented the plasma and urine accumulation of acute-phase and oxidized proteins, suggesting that the protection induced by PPARα agonists was at least partially caused by their anti-inflammatory and antioxidative properties. The results of this study demonstrate that PPAR agonism has beneficial effects on spontaneous brain and renal damage in SHRSPs by inhibiting systemic inflammation and oxidative stress, and they support carrying out future studies aimed at evaluating the effect of PPARα agonists on proteinuria and clinical outcomes in hypertensive patients with renal disease at increased risk of stroke.

Terutroban, a Thromboxane/Prostaglandin Endoperoxide Receptor Antagonist, Increases Survival in Stroke-Prone Rats by Preventing Systemic Inflammation and Endothelial Dysfunction: Comparison with Aspirin and Rosuvastatin

This study investigated the efficacy of terutroban, a specific thromboxane/prostaglandin endoperoxide receptor antagonist, on stroke incidence in spontaneously hypertensive stroke-prone rats (SHRSP). The effects of terutroban were compared with those of aspirin, another antiplatelet agent, and rosuvastatin, known to exert end-organ protection in SHRSP. Salt-loaded male SHRSP were treated orally once a day with vehicle, terutroban (30 mg/kg/day), aspirin (60 mg/kg/day), or rosuvastatin (10 mg/kg/day). Compared with vehicle, and regardless of any effect on blood pressure or serum thromboxane B2 levels, terutroban significantly increased survival (p < 0.001) as a consequence of a delayed brain lesion occurrence monitored by magnetic resonance imaging (p < 0.001), and a delayed increase of proteinuria (p < 0.001). Terutroban decreased cerebral mRNA transcription of interleukin-1β, transforming growth factor-β, and monocyte chemoattractant protein-1 after 6 weeks of dietary treatment. Terutroban also prevented the accumulation of urinary acute-phase proteins at high molecular weight, identified as markers of systemic inflammation, and assessed longitudinally by one-dimensional electrophoresis. Terutroban also has protective effects on the vasculature as suggested by the preservation of endothelial function and endothelial nitric-oxide synthase expression in isolated carotid arteries. These effects are similar to those obtained with rosuvastatin, and superior to those of aspirin. Terutroban increases survival in SHRSP by reducing systemic inflammation as well as preserving endothelial function. These data support clinical development of terutroban in the prevention of cerebrovascular and cardiovascular complications of atherothrombosis.

S 35171 exerts protective effects in spontaneously hypertensive stroke-prone rats by preserving mitochondrial function

S 35171 is one of a family of compounds that have been designed to protect mitochondrial function. We tested the hypothesis that S 35171 exerts protective effects in spontaneously hypertensive stroke-prone rats (SHRSPs), an animal model developing spontaneous brain damage preceded by proteinuria and systemic inflammation revealed by the urinary accumulation of acute-phase proteins (APPs) originating in the liver. Male SHRSPs fed a permissive diet received vehicle or S 35171 (10 mg/kg/day) started simultaneously with a high-sodium diet (group A) or after the establishment of proteinuria (group B). The drug delayed urinary APPs accumulation and the appearance of magnetic resonance imaging (MRI)-monitored brain lesions (after 62+/-3 days in group A, and 51+/-2 days in controls, P<0.01). The delay was more pronounced in group B as 30% of the animals survived the entire 90-day experimental period without brain abnormality. Proteomic analysis showed no significant alteration in the expression pattern of brain mitochondrial proteins, but the liver mitochondrial levels of carbamoylphosphate synthase I (CPS-I), an enzyme involved in urea metabolism) and the antioxidant peroxiredoxin-3 spot were affected by hypertension and S 35171. Stress reduces CPS-I and induces the peroxiredoxin-3 spot, whereas S 35171 brought about normal CPS-I expression and a 12-fold higher level of the peroxiredoxin-3 spot. As both enzymes are involved in maintaining mitochondrial functions, their increased expression after S 35171 treatment may be responsible for delaying the pathological condition that leads to the development of brain damage in SHRSPs.