Severe inflammation in new-borns induces long-term cognitive impairment by activation of IL-1β/KCC2 signaling during early development
Donghang Zhang, Yujiao Yang, Yaoxin Yang, Jin Liu, Tao Zhu, Han Huang, Cheng Zhou
Abstract
Abstract Background Neonatal sepsis can induce long-term cognitive impairment in adolescence or adulthood, but the underlying molecular mechanism is not fully understood. The expression of K + -Cl – co-transporter 2 (KCC2) plays a pivotal role in the GABAergic shift from depolarizing to hyperpolarizing during early postnatal development. In this study, we aimed to determine whether neonatal severe inflammation-induced cognitive impairment was associated with the expression of KCC2 during early development. Methods Neonatal severe inflammation was established by intraperitoneal injection of high dose lipopolysaccharide (LPS, 1 mg kg –1 ) in postnatal day 3 (P3) rats. The Morris water maze task and fear conditioning test were used to investigate long-term cognitive functions. ELISA, RT-PCR and Western blotting were used to examine the expression levels of proinflammatory cytokines and KCC2. Perforated patch-clamping recordings were used to determine the GABAergic shift. Results Neonatal severe inflammation led to long-term cognitive impairment in rats. Meanwhile, sustained elevation of interleukin-1 beta (IL-1β) levels was found in the hippocampus until P30 after LPS injection. Elevated expression of KCC2 and hyperpolarized GABA reversal potential (E GABA ) were observed in CA1 hippocampal pyramidal neurons from the P7-P10 and P14-P16 rats after LPS injection. Specific knockdown of IL-1β mRNA expression rescued the elevated expression of KCC2 and the hyperpolarized E GABA at P7-P10 and P14-P16. Accordingly, specific knockdown of IL-1β or KCC2 expression improved the cognitive impairment induced by neonatal severe inflammation. Conclusions Sustained elevation of IL-1β in the hippocampus may induce cognitive impairment by upregulation of KCC2 during early development.