Table_1_Unique pathways downstream of TLR-4 and TLR-7 activation: sex-dependent behavioural, cytokine, and metabolic consequences.DOCX

IntroductionPost-infection syndromes are characterised by fatigue, muscle pain, anhedonia, and cognitive impairment; mechanistic studies exploring these syndromes have focussed on pathways downstream of Toll-like receptor (TLR) 4 activation. Here, we investigated the mechanistic interplay between behaviour, metabolism, and inflammation downstream of TLR-7 activation compared to TLR-4 activation in male and female CD1 mice.MethodsAnimals received either a TLR-4 (LPS; 0.83 mg/kg) or TLR-7 (R848, 5 mg/kg) agonist, or saline, and behaviour was analysed in an Open Field (OF) at 24 h (n = 20/group). Plasma, liver, and prefrontal cortex (PFC) were collected for gene expression analysis at 24 h and 1H-NMR metabolomics.ResultsTLR-4 and TLR-7 activation decreased distance travelled and rearing in the OF, but activation of each receptor induced distinct cytokine responses and metabolome profiles. LPS increased IL-1β expression and CXCL1 in the PFC, but TLR7 activation did not and strongly induced PFC CXCL10 expression. Thus, TLR7 induced sickness behaviour is independent of IL-1β expression. In both cases, the behavioural response to TLR activation was sexually dimorphic: females were more resilient. However, dissociation was observed between the resilient female mice behaviour and the levels of gene cytokine expression, which was, in general, higher in the female mice. However, the metabolic shifts induced by immune activation were better correlated with the sex-dependent behavioural dimorphisms; increased levels of antioxidant potential in the female brain are intrinsic male/female metabolome differences. A common feature of both TLR4 and TLR7 activation was an increase in N-acetyl aspartate (NAA) in the PFC, which is likely be an allostatic response to the challenges as sickness behaviour is inversely correlated with NAA levels.DiscussionThe results highlight how the cytokine profile induced by one PAMP cannot be extrapolated to another, but they do reveal how the manipulation of the conserved metabolome response might afford a more generic approach to the treatment of post-infection syndromes.

感染后综合征以疲劳、肌肉疼痛、快感缺乏和认知障碍为特征；探究这些综合征的机制研究主要聚焦于Toll样受体4（TLR4）激活下游的途径。本研究旨在探讨TLR-7激活与TLR-4激活在雄性和雌性CD1小鼠中行为、代谢和炎症下游的机制相互作用。方法：动物接受TLR-4（LPS；0.83 mg/kg）或TLR-7（R848，5 mg/kg）激动剂，或生理盐水处理，并在24小时后（每组n = 20）在开放场（OF）中分析行为。在24小时和1H-NMR代谢组学分析中收集血浆、肝脏和前额叶皮层（PFC）用于基因表达分析。结果：TLR-4和TLR-7激活降低了OF中的行进距离和站立时间，但每个受体的激活都诱导了不同的细胞因子反应和代谢组学特征。LPS增加了PFC中的IL-1β表达和CXCL1，而TLR7激活则没有，且强烈诱导了PFC中的CXCL10表达。因此，TLR7诱导的疾病行为与IL-1β表达无关。在两种情况下，对TLR激活的行为反应均表现出性别二态性：雌性更具抵抗力。然而，在雌性小鼠的抵抗力行为与基因细胞因子表达水平之间观察到分离，通常在雌性小鼠中表达更高。然而，由免疫激活引起的代谢转变与性别依赖的行为二态性有更好的相关性；雌性大脑中抗氧化潜力水平的增加是雌雄代谢组内在差异。TLR4和TLR7激活的共同特征是PFC中N-乙酰天冬氨酸（NAA）水平的增加，这可能是对挑战的代偿性反应，因为疾病行为与NAA水平呈负相关。讨论：结果表明，一种病原相关分子模式（PAMP）诱导的细胞因子特征不能外推到另一种，但它们揭示了通过操纵保守的代谢组学反应可能为治疗感染后综合征提供更通用的方法。