The impact of early life stress and immune challenge on behavior and glia cells alteration in late adolescent rats

Early Life Stress Negatively Impacts Spatial Learning Acquisition and Increases Hippocampal CA1 Microglial Activation After a Mild Traumatic Brain Injury in Adult Male Rats

Early life stress (ELS) affects neurogenesis and spatial learning, and increases neuroinflammation after a pediatric mild traumatic brain injury (mTBI). Previous studies have shown that ELS has minimal effects in juveniles but shows age-dependent effects in adults. Hence, we aimed to evaluate the effects of ELS in adult male rats after an mTBI. Maternal separation for 180 min per day (MS180) during the first 21 post-natal (P) days was used as the ELS model. At P110, the rats were subjected to a mild controlled cortical impact injury (2.6 mm) or sham surgery. Spatial learning was evaluated in the Morris water maze (MWM) 14 days after surgery and both microglial activation and neurogenesis were quantified. The results indicate that MS180 + mTBI, but not control (CONT) + mTBI, rats show deficiencies in the acquisition of spatial learning. mTBI led to comparable increases in microglial activation in both the hilus and cortical regions for both groups. However, MS180 + mTBI rats exhibited a greater increase in microglial activation in the ipsilateral CA1 hippocampus subfield compared with CONT + mTBI. Interestingly, for the contralateral CA1 region, this effect was observed exclusively in MS180 + mTBI. ELS and mTBI independently caused a decrease in hippocampal neurogenesis and this effect was not increased further in MS180 + mTBI rats. The findings demonstrate that ELS and mTBI synergistically affect cognitive performance and neuroinflammation, thus supporting the hypothesis that increased inflammation resulting from the combination of ELS and mTBI could underlie the observed effects on learning.

Developmental and adult stress: effects of steroids and neurosteroids

In humans, exposure to early life adversity has profound implications for susceptibility to developing neuropsychiatric disorders later in life. Studies in rodents have shown that stress experienced during early postnatal life can have lasting effects on brain development. Glucocorticoids and sex steroids are produced in endocrine glands and the brain from cholesterol; these molecules bind to nuclear and membrane-associated steroid receptors. Unlike other steroids that can also be made in the brain, neurosteroids bind specifically to neurotransmitter receptors, not steroid receptors. The relationships among steroids, neurosteroids, and stress are multifaceted and not yet fully understood. However, studies demonstrating altered levels of progestogens, androgens, estrogens, glucocorticoids, and their neuroactive metabolites in both developmental and adult stress paradigms strongly suggest that these molecules may be important players in stress effects on brain circuits and behavior. In this review, we discuss the influence of developmental and adult stress on various components of the brain, including neurons, glia, and perineuronal nets, with a focus on sex steroids and neurosteroids. Gaining an enhanced understanding of how early adversity impacts the intricate systems of brain steroid and neurosteroid regulation could prove instrumental in identifying novel therapeutic targets for stress-related conditions.

The role of the stress system in recovery after traumatic brain injury: A tribute to Bruce S. McEwen

Traumatic brain injury (TBI) represents a major public health concern. Although the majority of individuals that suffer mild-moderate TBI recover relatively quickly, a substantial subset of individuals experiences prolonged and debilitating symptoms. An exacerbated response to physiological and psychological stressors after TBI may mediate poor functional recovery. Individuals with TBI can suffer from poor stress tolerance, impairments in the ability to evaluate stressors, and poor initiation (and cessation) of neuroendocrine stress responses, all of which can exacerbate TBI-mediated dysfunction. Here, we pay tribute to the pioneering neuroendocrinologist Dr. Bruce McEwen by discussing the ways in which his work on stress physiology and allostatic loading impacts the TBI patient population both before and after their injuries. Specifically, we will discuss the modulatory role of hypothalamic-pituitary-adrenal axis responses immediately after TBI and later in recovery. We will also consider the impact of stressors and stress responses in promoting post-concussive syndrome and post-traumatic stress disorders, two common sequelae of TBI. Finally, we will explore the role of early life stressors, prior to brain injuries, as modulators of injury outcomes.

6-Shogaol improves behavior and memory in Wistar rats prenatally exposed to lipopolysaccharide

OBJECTIVE

6-Shogaol, bioactive compound of Zingiber officinale Roscoe, has anti-inflammatory, antioxidant, and neuroprotective properties. The objective of the present study was to verify the effect of 6-shogaol on behavioral parameters in a preclinical model based on a maternal immune activation (MIA) by lipopolysaccharide (LPS).

METHODOLOGY

Twelve pregnant Wistar rats received 100-μg/kg LPS or saline solution on gestational day (GD) 9.5. Male offspring participated in the study and in the postnatal day (PND) 30 and 55 were supplemented with 6-shogaol or saline solution, by gavage at a dose of 10 mg/kg/day, orally for 5 days. In the PND 35 and 60 was performed the behavioral tests: grooming, crossing, and rearing that evaluated repetitive movements, anxiety, and interest in the new, respectively, and the inhibitory avoidance test that evaluated short-term (STM) and long-term memory (LTM).

RESULT

Prenatal exposure to LPS increased the grooming and crossing episodes at different ages and reduced rearing episodes in PND 37. Treatment with 6-shogaol reversed these parameters. In the inhibitory avoidance test, an improvement of memory was identified with 6-shogaol in the STM and LTM at both ages comparing training and test session of treated groups and between groups.

CONCLUSION

Administration of 6-shogaol reverses the stereotypy, exploratory behavior, and memory impairment in prenatal LPS-exposed offspring, acting as a promising therapeutic component against brain disorders associated with the process of MIA.