The potential role of stress and sex steroids in heritable effects of sevoflurane

Neurobehavioral Abnormalities in Offspring of Young Adult Male Rats With a History of Traumatic Brain Injury

Children of parents with traumatic brain injury (TBI) are more likely to develop psychiatric disorders. This association is usually attributed to TBI-induced changes in parents' personality and families' social environment. We tested the hypothesis that offspring of young adult male rats with TBI develop neurodevelopmental abnormalities in the absence of direct social contact with sires. Male Sprague-Dawley rats (F0 generation) in the TBI group underwent moderate TBI via a midline fluid percussion injury that involved craniectomy under sevoflurane (SEVO) anesthesia for 40 min on post-natal Day 60 (P60), while F0 rats in the control group were placed in a new cage, one per cage, for the equivalent time duration. A subset of F0 rats was sacrificed on P66 to assess acute changes in hypothalamic-pituitary-adrenal (HPA) axis and inflammation markers. The remaining F0 males were mated with naive females on P90 to generate offspring (F1 generation). The F0 males and F1 males and females were sequentially evaluated in the elevated plus maze, for pre-pulse inhibition of acoustic startle, in the Morris water maze, and for resting and stress levels of serum corticosterone starting on ∼P105 (F0) and ∼P60 (F1), followed by tissue collection for further analyses. Acutely, the F0 TBI males had messenger RNA (mRNA) transcripts altered to support an increased hypothalamic and hippocampal Na+-K+-Cl- (Slc12a2) Cl- importer / K+-2Cl- (Slc12a5) Cl- exporter ratio and decreased hippocampal glucocorticoid receptors (Nr3c1), as well as increased serum levels of corticosterone, interleukin-1β (IL-1β), and biomarkers of activated hippocampal microglia and astrocytes. Long-term, F0 TBI rats exhibited increased corticosterone concentrations at rest and under stress, anxiety-like behavior, impaired sensory-motor gating, and impaired spatial memory. These abnormalities were underpinned by reduced mRNA levels of hypothalamic and hippocampal mineralocorticoid receptors (Nr3c2), hippocampal Nr3c1, and hypothalamic brain-derived neurotrophic factor (Bdnf), as well as elevated serum levels of IL-1β, and biomarkers of activated hippocampal microglia and astrocytes. F1 male offspring of TBI sires exhibited abnormalities in all behavioral tests, while their F1 female counterparts had abnormal pre-pulse inhibition responses only. F1 male offspring of TBI sires also had reduced mRNA levels of hippocampal Nr3c1 and Nr3c2, as well as hypothalamic and hippocampal Bdnf, whereas increases in inflammatory markers were more profound in F1 females. These findings suggest that offspring of sires with a history of a moderate TBI that involved craniectomy under SEVO anesthesia for 40 min, develop sex-dependent neurobehavioral abnormalities in the absence of direct social interaction between the sire and the offspring.

Epigenetic Mechanisms of Postoperative Cognitive Impairment Induced by Anesthesia and Neuroinflammation

Cognitive impairment after surgery is a common problem, affects mainly the elderly, and can be divided into postoperative delirium and postoperative cognitive dysfunction. Both phenomena are accompanied by neuroinflammation; however, the precise molecular mechanisms underlying cognitive impairment after anesthesia are not yet fully understood. Anesthesiological drugs can have a longer-term influence on protein transcription, thus, epigenetics is a possible mechanism that impacts on cognitive function. Epigenetic mechanisms may be responsible for long-lasting effects and may implicate novel therapeutic approaches. Hence, we here summarize the existing literature connecting postoperative cognitive impairment to anesthesia. It becomes clear that anesthetics alter the expression of DNA and histone modifying enzymes, which, in turn, affect epigenetic markers, such as methylation, histone acetylation and histone methylation on inflammatory genes (e.g., TNF-alpha, IL-6 or IL1 beta) and genes which are responsible for neuronal development (such as brain-derived neurotrophic factor). Neuroinflammation is generally increased after anesthesia and neuronal growth decreased. All these changes can induce cognitive impairment. The inhibition of histone deacetylase especially alleviates cognitive impairment after surgery and might be a novel therapeutic option for treatment. However, further research with human subjects is necessary because most findings are from animal models.