Predisposition to cortical neurodegenerative changes in brains of hypertension prone rats.

BACKGROUND: Substantial evidence suggests that hypertension is a significant risk factor for cognitive decline. However, it is unclear whether the genetic predisposition to hypertension is also associated with cellular dysfunction that promotes neurodegeneration. METHODS: Changes in blood pressure were evaluated following dietary salt-loading or administration of a regular diet in Sabra Normotensive (SBN/y) and Sabra Hypertension-prone rats (SBH/y). We performed quantitative RT-PCR and immunofluorescence staining in brain cortical tissues before salt loading and 6 and 9 months after salt loading. To examine the expression of brain cortical proteins involved in the gene regulation (Histone Deacetylase-HDAC2; Histone Acetyltransferase 1-HAT1), stress response (Activating Transcription Factor 4-ATF4; Eukaryotic Initiation Factor 2- eIF2α), autophagy (Autophagy related 4A cysteine peptidase- Atg4a; light-chain 3-LC3A/B; mammalian target of rapamycin complex 1- mTORC1) and apoptosis (caspase-3). RESULTS: Prior to salt loading, SBH/y compared to SBN/y expressed a significantly higher level of cortical HAT1 (protein), Caspase-3 (mRNA/protein), LC3A, and ATF4 (mRNA), lower levels of ATG4A (mRNA/protein), LC3A/B, HDAC2 (protein), as well as a lower density of cortical neurons. Following dietary salt loading, SBH/y but not SBN/y developed high blood pressure. In hypertensive SBH/y, there was significant upregulation of cortical HAT1 (protein), Caspase-3 (protein), and eIF2α ~ P (protein) and downregulation of HDAC2 (protein) and mTORC1 (mRNA), and cortical neuronal loss. CONCLUSIONS: The present findings suggest that genetic predisposition to hypertension is associated in the brain cortex with disruption in autophagy, gene regulation, an abnormal response to cellular stress, and a high level of cortical apoptosis, and could therefore exacerbate cellular dysfunction and thereby promote neurodegeneration.

[INVOLVEMENT OF EPIGENETIC REGULATION IN CEREBRAL CELL DEATH FOLLOWING TRAUMATIC BRAIN INJURY IN A RAT MODEL].

INTRODUCTION: Traumatic brain injuries (TBI) are a major cause of mortality and disability among young adults. TBI are characterized by primary injury, the result of a mechanical impact to the cranium and a secondary injury, a series of molecular mechanism processes developing thereafter. Cerebral cells modify their gene and protein expression as a result of the injury. Epigenetic modifications have a key role as regulators of gene transcription and may simultaneously be involved in the regulation of the molecular pathways following TBI. However, the mechanisms are unknown. OBJECTIVES: To clarify whether modification in the expression of Histone Acetyl Transferase1 (HAT1) and Histone deacetylase2 (HDAC 2) occurs during secondary brain damage. METHODS: Rat diffused head injury model was used; 72 hours post injury animals were sacrificed and the brains were removed for immunohistochemistry staining with Caspase 3, HAT1 and HDAC2 antibodies. We compared these stains in the perilesional versus the contralateral cortex. RESULTS: An increase of Caspase 3 stained cells were observed in the perilesional cortex. HAT1 expression was elevated and HDAC2 expression reduced in the injured cortex. CONCLUSIONS: TBI induced modifications in the expression of epigenetic factors were concomitant with increases in apoptotic cell death. The mitochondria involved in the apoptotic processes is a target for epigenetic regulation and also influences it at the same time. DISCUSSION: This study contributes to the understanding of epigenetic modification following TBI. Further study on the relationship between mitochondrial activity and epigenetic regulation has to be performed in order to develop novel drugs and therapies for TBI.