Simvastatin-Ezetimibe enhances growth factor expression and attenuates neuron loss in the hippocampus in a model of intracerebral hemorrhage

Abstract

Intracerebral hemorrhage (ICH) is a common and severe neurological disorder associated with high morbidity and mortality rates. Despite extensive research into its pathology, there are no clinically approved neuroprotective treatments for ICH. Increasing evidence has revealed that inflammatory responses mediate the pathophysiological processes of brain injury following ICH. Experimental ICH was induced by direct infusion of 100 μL fresh (non-heparinized) autologous whole blood into the right basal ganglia of Sprague-Dawley rats at a constant rate (10 μL/min). The simvastatin group was administered simvastatin (15 mg/kg) and the combination therapy group was administered simvastatin (10 mg/kg) and ezetimibe (10 mg/kg). Magnetic resonance imaging (MRI), the forelimb use asymmetry test, the Morris water maze test, and two biomarkers were used to evaluate the effect of simvastatin and combination therapy. MRI imaging revealed that combination therapy resulted in significantly reduced perihematomal edema. Biomarker analyses revealed that both treatments led to significantly reduced endothelial inflammatory responses. The forelimb use asymmetry test revealed that both treatment groups had significantly improved neurological outcomes. The Morris water maze test revealed improved neurological function after combined therapy, which also led to less neuronal loss in the hippocampal CA1 region. In conclusion, simvastatin-ezetimibe combination therapy can improve neurological function, attenuate the endothelial inflammatory response and lead to less neuronal loss in the hippocampal CA1 region in a rat model of ICH.

Keywords: hippocampus; intracerebral hemorrhage; neurological outcome; perihematomal edema; simvastatin; simvastatin-ezetimibe.

Figure 1

Photomicrographs showing immunohistochemical staining (NeuN) of the rat hippocampal CA1 region at different magnification. The survival neurons with different intensity of NeuN staining in the hippocampal CA1.

Figure 2

Analyses of ICAM‐1 revealing no significant differences among the control, simvastatin, and combination therapy groups (a). The simvastatin group exhibited significantly elevated BDNF levels at all time points, while the combination therapy group exhibited significantly elevated BDNF levels at the 24‐h and 72‐h time points (b). *P < 0.05 for Bonferroni post hoc comparison vs. the simvastatin group; P < 0.05 for Bonferroni post hoc comparison vs. the combination group. Data are presented as means ± standard errors. ICAM‐1, intercellular adhesion molecule‐1; BDNF, brain‐derived neurotrophic factor.

Figure 3

The two therapy groups exhibited significant improvements in neurological function (a). *P < 0.05 for Bonferroni post hoc comparison vs. the control group. The Morris water maze test demonstrated better neurological functioning in the combination therapy group than in the control group (b). *P < 0.05 for the Bonferroni post hoc comparison vs. the combination therapy group.

Figure 4

There were no significant reductions in hematoma size in the control, simvastatin, or combination therapy groups (a). An analysis of perihematomal edema revealed that only the combination therapy group had significant reductions in perihematomal edema on day 7 after injury (b). T2 map image, black arrow indicating hematoma and red arrow indicating perihematomal edema (c). *P < 0.05.

Figure 5

Increased intracellular adhesion molecule‐1 expression was noted in the control group (no treatment), and greater brain‐derived neurotrophic factor (BDNF) expression was noted in the therapy groups relative to the control group.

Figure 6

Photomicrographs of immunohistochemical staining of rat hippocampal CA1 in the (a) combination therapy, (b) simvastatin, (c) control, and (d) sham groups using antibodies specific for NeuN. (e) Cell number mean ± SEM (via Aperio software analysis) indicating different staining intensities across groups. The survival neurons with different intensity of NeuN staining were demonstrated in Figure  1. *P < 0.05, **P < 0.01, ***P < 0.005 (Student’s t‐test).