Effects of sex and pro-inflammatory cytokines on context discrimination memory

The Impact of Biological Sex And High-Fat High-Fructose Diet on Brain Dysfunction in an Animal Model of Sepsis

The aim of this study was to evaluate long-term inflammatory, biochemical and behavioral parameters in adult male and female Wistar rats submitted to a model of high-fat and high fructose diet and sepsis. In the study we used 8-month-old male and female rats. High-fat and high fructose diet was provided for 4 months, and sepsis was induced shortly afterwards. Behavioral tests were performed at 10, 30 and 60 days after sepsis induction, at 30- and 60-days metabolic parameters, leptin and cytokines (prefrontal cortex and hippocampus) were determined. High-fat and high-fructose diet was able to induce glucose intolerance. Sepsis favored anxious behavior at 10 days after sepsis, remaining at 30 days and with apparent improvement at 60 days in females and maintenance of behavior in males. Cognitive damage was observed both at 30 and 60 days in animals from both groups. Plasma metabolic parameters were elevated only males exposed to a high-fat high-fructose diet and submitted to CLP only at 30 days. Long-term brain inflammation was not consistently affected both by sex and high-fat and high fructose diet.The relationship between high-fat and high fructose diet, gender and sepsis is still contradictory, as are the mechanisms involved in this paradox. Models and analyses need to be standardized in order to better understand how this event occurs.

Middle-aged females are resistant to LPS-induced learning deficits: Sex comparison

Preclinical data have repeatedly shown learning and memory disruption following administration of the bacterial endotoxin lipopolysaccharide (LPS). Normal aging is reported to enhance vulnerability to LPS-induced cognitive impairments. However, a limitation is the primary use of male subjects. Recent evidence indicates sex-related differences in vulnerability to LPS-induced cognitive deficits [1,2], with young females showing resilience. Whether middle-aged females are susceptible to LPS-induced cognitive impairment is unknown. The current experiment compared associative learning in young and middle-aged male and female C57BL/6J mice following a systemic LPS challenge. While LPS impaired acquisition of the two-way active avoidance conditioning task in adult and middle-aged males, females' learning was unaffected. The sex difference in LPS-induced cognitive impairments appears unrelated to responsivity to LPS, as males and females mount a comparable sickness-like response. Additionally, relative to males, females produce higher brain levels of interleukin-6 (IL-6) and comparable splenic IL-6 levels following LPS. These data demonstrate that female resilience to LPS-induced learning deficits persists into middle age, whereas males are vulnerable as both young and middle-aged adults. Our findings confirm the importance of considering sex as a biological variable and extend the existing literature by evaluating sex-related responsivity to LPS in middle-aged males and females.

N-acetyltransferase 10 mediates cognitive dysfunction through the acetylation of GABABR1 mRNA in sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a critical neurological complication of sepsis and represents a crucial factor contributing to high mortality and adverse prognosis in septic patients. This study explored the contribution of NAT10-mediated messenger RNA (mRNA) acetylation in cognitive dysfunction associated with SAE, utilizing a cecal ligation and puncture (CLP)-induced SAE mouse model. Our findings demonstrate that CLP significantly upregulates NAT10 expression and mRNA acetylation in the excitatory neurons of the hippocampal dentate gyrus (DG). Notably, neuronal-specific Nat10 knockdown improved cognitive function in septic mice, highlighting its critical role in SAE. Proteomic analysis, RNA immunoprecipitation, and real-time qPCR identified GABABR1 as a key downstream target of NAT10. Nat10 deletion reduced GABABR1 expression, and subsequently weakened inhibitory postsynaptic currents in hippocampal DG neurons. Further analysis revealed that microglia activation and the release of inflammatory mediators lead to the increased NAT10 expression in neurons. Microglia depletion with PLX3397 effectively reduced NAT10 and GABABR1 expression in neurons, and ameliorated cognitive dysfunction induced by SAE. In summary, our findings revealed that after CLP, NAT10 in hippocampal DG neurons promotes GABABR1 expression through mRNA acetylation, leading to cognitive dysfunction.

Minding the Gap: Exploring Neuroinflammatory and Microglial Sex Differences in Alzheimer's Disease

Research into Alzheimer's Disease (AD) describes a link between AD and the resident immune cells of the brain, the microglia. Further, this suspected link is thought to have underlying sex effects, although the mechanisms of these effects are only just beginning to be understood. Many of these insights are the result of policies put in place by funding agencies such as the National Institutes of Health (NIH) to consider sex as a biological variable (SABV) and the move towards precision medicine due to continued lackluster therapeutic options. The purpose of this review is to provide an updated assessment of the current research that summarizes sex differences and the research pertaining to microglia and their varied responses in AD.

Sex-dependent deficits in associative learning across multiple LPS doses

Activation of the immune system by administration of the bacterial endotoxin lipopolysaccharide (LPS) impairs cognitive and neural plasticity processes. For instance, acute LPS exposure has been reported to impair memory consolidation, spatial learning and memory, and associative learning. However, the inclusion of both males and females in basic research is limited. Whether LPS-induced cognitive deficits are comparable in males and females is currently unclear. Therefore, the present study evaluated sex differences in associative learning following administration of LPS at a dose (i.e., 0.25 mg/kg) that impairs learning in males and higher LPS doses (i.e., 0.325 - 1 mg/kg) across multiple experiments. Adult male and female C57BL/6J mice were trained in a two-way active avoidance conditioning task following their respective treatments. Results showed that LPS had sex-dependent effects on associative learning. The 0.25 mg/kg LPS dose impaired learning in males, consistent with prior work. However, LPS, at any of the doses employed across three experiments, did not disrupt associative learning in females. Female mice were resistant to learning deficits despite showing heightened levels of select proinflammatory cytokines in response to LPS. Collectively, these findings demonstrate that the learning impairments resulting from acute LPS exposure are sex-dependent.

Sex, sepsis and the brain: defining the role of sexual dimorphism on neurocognitive outcomes after infection

Sexual dimorphisms exist in multiple domains, from learning and memory to neurocognitive disease, and even in the immune system. Male sex has been associated with increased susceptibility to infection, as well as increased risk of adverse outcomes. Sepsis remains a major source of morbidity and mortality globally, and over half of septic patients admitted to intensive care are believed to suffer some degree of sepsis-associated encephalopathy (SAE). In the short term, SAE is associated with an increased risk of in-hospital mortality, and in the long term, has the potential for significant impairment of cognition, memory, and acceleration of neurocognitive disease. Despite increasing information regarding sexual dimorphism in neurologic and immunologic systems, research into these dimorphisms in sepsis-associated encephalopathy remains critically understudied. In this narrative review, we discuss how sex has been associated with brain morphology, chemistry, and disease, sexual dimorphism in immunity, and existing research into the effects of sex on SAE.