Objective: To study the effects of cerebellar fastigial nucleus (FN) electrical stimulation on telomerase reverse transcriptase expression and mitochondrial apoptotic pathway in rats with focal cerebral ischemia and reperfusion.
Methods: A total of 100 adult male Wistar rats were randomly divided into 3 groups: sham operation group, modeling group (2-hour cerebral ischemia, followed by 24, 48 & 72-hour reperfusion) and FN-stimulating group (electrical stimulation of FN for 1-hour one day before 2-hour cerebral ischemia, followed by 24, 48 & 72-hour reperfusion). HE (hematoxylin and eosin) and TTC (triphenyl tetrazolium chloride) staining were used to observe the morphological changes in rat brain and measure the ischemic lesion volumes. The expressions of TERT (telomerase reverse transcriptase) and Bax were detected by immunohistochemical methods and apoptotic cells by TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling). The co-expression of TERT and Bax was detected by immunofluorescence double-labeling plus laser confocal microscopy.
Results: The morphological changes in rat brain were less greater in the FN-stimulating group than those in the modeling group. And the size of the cerebral infarct was significantly smaller in the FN-stimulating group (78.1 ± 2.9, 83.1 ± 4.5, 83.7 ± 4.8) than that in the modeling group (120.9 ± 8.2, 137.0 ± 4.2, 141.1 ± 3.3) (P < 0.05) at all reperfusion time points. As compared with the modeling group (16.1 ± 2.7, 16.9 ± 2.4, 11.6 ± 3.5), the FN-stimulating group (31.1 ± 3.5, 30.0 ± 3.4, 18.9 ± 3.3) had a significantly larger number of TERT-positive cells (P < 0.05) and a significantly reduced number of TUNEL-positive cells (49.6 ± 2.8, 67.0 ± 3.7, 46.8 ± 3.2 vs 40.2 ± 3.1, 54.8 ± 2.8, 37.3 ± 2.4) (P < 0.05). The number of Bax-positive cells at different reperfusion time points in the FN-stimulating group was not significantly different from those in the modeling group (P > 0.05). TERT partially co-localized with Bax in the cytoplasm. The number of double-labeled cells was significantly higher in the FN-stimulating group than that in the modeling group (14.1 ± 1.3, 12.9 ± 2.4, 9.0 ± 2.0 vs 8.2 ± 1.1, 6.3 ± 2.4, 6.0 ± 2.9) (P < 0.05).
Conclusion: The expression of TERT significantly increases after a stimulation of FN. TERT may bind to Bax and inhibit Bax-mediated apoptosis by suppressing the mitochondrial relocalization of Bax from cytosol.