Effects Of Gestational Inflammation On Age-related Cognitive Decline And Hippocampal Gdnf-GFRα1 Levels In F1 And F2 Generations Of CD-1 Mice

BackgroundIt has been reported that age-associated cognitive decline(AACD)accelerated by maternal lipopolysaccharide(LPS)insult during late pregnancy can be transmitted to the second generation in a sex-specificity manner.In turn,recent studies indicated that glial cell line‐derived neurotrophic factor(GDNF)and its cognate receptor(GFRα1)are critical for normal cognitive function.Decreased GDNF-GFRα1 expression could result in declined cognitive function in mice.Thus,we wondered whether the accelerated age-associated cognitive decline induced by maternal LPS injection during late pregnancy was related to GDNF-GFRα1 expression? Whether this cognitive impairment could be transmitted to the next generation in a sex-specific manner?ObjectiveBased on this evidence,we aimed to explore whether Gdnf-GFRα1 expression contributes to cognitive decline in the F1 and F2 generations of mouse dams exposed to lipopolysaccharide(LPS)during late gestation,and to evaluate also the potential interference effect of pro-inflammatory cytokines.MethodsDuring gestational days 15-17,pregnant CD-1 mice(8-10 weeks old)received a daily intraperitoneal injection of LPS(50 μg/kg)or saline(control).In utero LPS-exposed F1 generation mice were selectively mated to produce F2 generation mice.To test for effects of lineage on a second generation,the F2 generation was divided into the following four groups(n=10 mice/group): 1)Mother-LPS(maternal lineage of LPS;LPS females mating with wild-type males);2)Father-LPS(paternal lineage of LPS;LPS males mating with wild-type females);3)Parents-LPS(parental lineage of LPS;LPS females mating with non-littermate LPS males);4)Control(CON;control females mating with control males).In F1 and F2 mice aged 3 and 15 months,performance on the Morris water maze(MWM)was evaluated as a measure of learning and memory functions,western blotting and RT-PCR were used for analyses of hippocampal Gdnf-GFRα1 expression,and ELISA was used to analyse IL-1β,IL-6 and TNF-αlevels in serum.Results1)MWM performance: In the F1 generation,compared with the 3-month-old CON group,the 15-month-old CON group showed worse learning and memory performance.Secondly,LPS mice had longer swimming latency and swimming distance,and lower percentage of swimming time and swimming distance than age-matched CON mice at age of 15 months.In the F2 generation,compared to the F2-CON group,Parent-LPS group had longer swimming latency,and the Father-LPS group had longer swimming distance at 15 months.In addition,the 15-months-old Parents-LPS and Father-LPS groups had lower percentage of swimming time and swimming distance than F2-CON group.2)GDNF and GFRα1 protein and mRNA levels: In the F1 generation,the 15-month-old CON group showed lower levels of GDNF and GFRα1expression than the 3-month-old CON group.Moreover,LPS mice showed lower hippocampal GDNF and GFRα1 expression levels compared with the CON group at the age of 15 months.In the F2 generation,the 15-month-old Father-and Parent-LPS groups had worse learning and memory performance than the F2-CON group.3)serum IL-1β,IL-6 and TNF-α levels: In F1 generation,the levels of serum IL-1β,IL-6 and TNF-α were higher in the 15-month-old CON group than in the 3-month-old CON group.At age of 3 and 15 months,LPS groups had higher levels of IL-1β,IL-6,and TNF-α than CON groups.In the F2 generation,the3-month-old Father-LPS group had higher levels of IL-1β,IL-6 and TNF-α than the F2-CON group and the Parents-LPS group(Ps < 0.05).4)Correlation between performance in MWM and Gdnf-GFRα1 expression levels:In F1 generation,the expression levels of Gdnf-GFRα1 in 15-month-old LPS group was positively correlated with swimming distance and negatively correlated with swimming distance percentage.In F2 generation,the levels of Gdnf-GFRα1 expression in the 15-month-old Parents-and Father-LPS groups were positively correlated with swimming distance and negatively correlated with the percentage of swimming distance.However,after controlling for serum IL-1β,IL-6,and TNF-α levels,the correlations between Gdnf-GFRα1 expression levels and MWM were significantly reduced.SummaryOur findings indicate that accelerated AACD by maternal LPS exposure could be transmitted across at least two generations through declined Gdnf and GFRα1 expression,mainly via paternal linage.