Progress in clinical neurosciences: The 'antiplatelet' agents and the role of the endothelium

Clinical and pathological improvement in stroke-prone spontaneous hypertensive rats related to the pleiotropic effect of cilostazol

BACKGROUND AND PURPOSE

Cerebral infarction is a major cause of death or decreasing activities of daily living. This study aimed to investigate the efficacy of commonly used antiplatelet drugs on stroke and motor and cognitive functions in relation to oxidative stress markers and insulin-like growth factor 1 receptor (IGF-1R).

METHODS

Stroke-prone spontaneously hypertensive rats were treated with vehicle, aspirin, clopidogrel, and cilostazol from 8 to 10 weeks of age. Physiological parameters, regional cerebral blood flow, and serum lipids were examined. Motor and cognitive functions were evaluated weekly by the Rotorod and water maze task. Spontaneous infarct volume, oxidative stress markers for lipid, protein, and DNA at the ischemic boundary zone of spontaneous infarction, and the IGF-1R-positive cell ratio in the hippocampus were immunohistochemically examined in brain sections. IGF-1Rβ expression in the hippocampus was assessed by Western blotting.

RESULTS

The antiplatelet drugs, cilostazol and clopidogrel, reduced the spontaneous infarct volume more than aspirin. Only cilostazol improved motor and cognitive functions with a significant increase (P<0.05) in the memory-related IGF-1R-positive ratio and IGF-1Rβ expression in the hippocampus. Cilostazol reduced the 4 oxidative stress markers in affected neurons in stroke-prone spontaneously hypertensive rats regardless of blood pressure, regional cerebral blood flow, or serum lipid levels.

CONCLUSIONS

The present results suggest that a possible pleiotropic effect of cilostazol resulted in the reduction of spontaneous infarct volume and preservation of motor and spatial cognitive functions. The increase of IGF-1R-positive cells in the hippocampal CA1 region could partly explain the preservation of spatial cognitive function in stroke-prone spontaneously hypertensive rats.

Platelet-leukocyte interactions link inflammatory and thromboembolic events in ischemic stroke

Stroke is a common and often fatal event, and, in survivors, it is accompanied by a high risk of recurrence. Ischemic stroke is associated with abnormal platelet activity and thrombus formation. In addition to their roles in the development of acute thrombi, platelets serve as a bridge for leukocytes within the vasculature. Myeloid leukocytes are critical mediators of atherosclerosis and atherothrombosis. Interactions between platelets and leukocytes foster an inflammatory and thrombotic milieu that influences lesion progression, facilitates plaque rupture, and triggers thrombus formation and embolization. Accordingly, antiplatelet agents, including aspirin, dipyridamole, and clopidogrel, are recommended therapies for most patients with a history of stroke. In addition to mitigating thrombosis, antiplatelet drugs have direct and indirect effects on inflammation, which may translate to enhanced clinical efficacy.

Imaging of structural changes in endothelial cells and thrombus formation at the site of FeCl(3)-induced injuries in mice cremasteric arteries

AIM

We investigated thrombus formation at the site of functional injury to endothelial cells by FeCl(3).

METHODS

After preparation of cremasteric arteries of mice, controlled endothelial injury was induced by application of FeCl(3). Endothelial cells were rendered fluorescent by addition of FITC (fluorescein isothiocyanate)-labeled isolectin B4. Circulating platelets and leukocytes were made fluorescent by rhodamine 6G. Three-dimensional (3D) growth of thrombi was visualized in real time. Effects of aspirin and clopidogrel pre-treatments on the growth of thrombi were investigated in vivo as well as in an ex vivo flow chamber system.

RESULTS

Endothelial cells were tightly bound to each other to protect local thrombus formation. Platelets started to adhere to endothelial cells when FeCl(3) was applied. Three-dimensional growth of thrombi, which takes 10.6+/-7.5 minutes for complete occlusion in control, can be visualized with our imaging system. Aspirin pre-treatment at the dose tested did not influence either endothelial injury or platelet thrombus growth, while clopidogrel pretreatment significantly inhibited 3D growth and prolonged occlusion time up to 64.6+/-25.3 minutes (100 mg/kg). A similar inhibiting effect of clopidogrel was reproduced in ex vivo flow chamber experiments.

CONCLUSIONS

We have developed an in vivo system to detect thrombus formation after functional damage to the endothelium.