Temporal impact of sepsis on Alzheimer's disease pathology and neuroinflammation

Epidemiological evidence has revealed an associative link between sepsis survivorship and increased risk of dementia, particularly Alzheimer's disease (AD). Paradoxically, population studies show females are less susceptible to sepsis but more vulnerable to post-sepsis dementia. Here, we examined the temporal impacts of sepsis in the context of AD by using an AD-amyloidosis model (TgCRND8) and their wild-type littermates and assessing outcomes at 7 days and 3 months post-sepsis in male and female mice. Following 7-days recovery, the microglia and astrocytes in AD-model mice were largely refractile to the systemic immune stimuli. Notably, the female AD-model mice accumulated higher hippocampal amyloid-beta (Aβ) burden and upregulated AD-type transcriptomic signature at this time. On the other hand, male AD-model mice showed no Aβ changes. At this time, the wild-type post-septic males, but not females, displayed robust astrocytosis, with nominal microgliosis. By 3 months post-sepsis, microgliosis was specifically elevated in wild-type females, indicating a prolonged central immune response. At this time, both male and female AD-model mice showed exacerbated Aβ and anxiety indices. Gene network analysis revealed a stronger immune response in females, while the male response was linked to estrogen receptor (ESR) signaling, with ERα protein upregulated in the brains of post-septic AD-model males. Together, our data highlights a sex-dimorphic temporal response in post-sepsis neuroinflammation, with ESR signaling playing a key role in males, while Aβ burden is affected similarly in both males and females.