Injury markers in two models of cerebral ischemia

Abstract

Introduction: Spatio-temporal indicators of injury are essential for the study of neuropathological processes and for developing therapeutic approaches for stroke.

Objective: This study sought to optimize the techniques of two cerebral ischemia models (focaland global) and to comparatively evaluate the progression of brain damage by analyzing markers of neurodegeneration.

Materials and methods: Wistar rats were subjected to temporary occlusion of the middle cerebral artery(t-MCAO) or four-vessel occlusion (4-VO), and surgical time, survival rate and neurological recovery were comparatively evaluated. Triphenyl tetrazolium was used to determine the distribution of the infarction, and Fluoro-Jade B was used as a marker of neurodegeneration. Astroglial immunoreactivity was assessed with an anti-glial fibrillary acidic protein (GFAP) antibody, and an anti-AT-8 antibody was used to detect hyperphosphorylated tau protein at 24, 48 and 72 hours post-ischemia.

Results: The cerebral ischemia models employed (t-MCAO and 4-VO) required less surgical time and presented less of a death risk compared to those in previous studies. In the focal model, Fluoro-Jadepositivecells and reactive astrocytes were observed in the cerebral cortex and the hippocampus at 24 hours post-ischemia. In the global model, we observed Fluoro-Jade-positive cells at 24 hours, and asignificant increase in the reactivity of GFAP was observed at 72 hours in the cortex and at 48 hours in the hippocampus. The immunoreactivity of hyperphosphorylated tau protein increased progressively, reaching a maximum at 72 hours post-ischemia in both models.

Conclusions: These results suggest that in the t-MCAO and 4-VO ischemia models, the expressionof Fluoro-Jade and GFAP indicates early neurodegeneration at 24 hours post-insult. In contrast, the immunoreactivity of the hyperphosphorylated tau protein marker (AT-8) progressively increases until72 hours post-insult, which suggests that the progression of excitotoxicity and alteration of enzymes involves the phosphorylation of cytoskeletal proteins.

doi: http://dx.doi.org/10.7705/biomedica.v33i2.830