EAAC1 gene deletion reduces adult hippocampal neurogenesis after transient cerebral ischemia

Abstract

Several studies have demonstrated that excitatory amino acid carrier-1 (EAAC1) gene deletion exacerbates hippocampal and cortical neuronal death after ischemia. However, presently there are no studies investigating the role of EAAC1 in hippocampal neurogenesis. In this study, we tested the hypothesis that reduced cysteine transport into neurons by EAAC1 knockout negatively affects adult hippocampal neurogenesis under physiological or pathological states. This study used young mice (aged 3–5 months) and aged mice (aged 11–15 months) of either the wild-type (WT) or EAAC1−/− genotype. Ischemia was induced through the occlusion of bilateral common carotid arteries for 30 minutes. Histological analysis was performed at 7 or 30 days after ischemia. We found that both young and aged mice with loss of the EAAC1 displayed unaltered cell proliferation and neuronal differentiation, as compared to age-matched WT mice under ischemia-free conditions. However, neurons generated from EAAC1−/− mice showed poor survival outcomes in both young and aged mice. In addition, deletion of EAAC1 reduced the overall level of neurogenesis, including cell proliferation, differentiation, and survival after ischemia. The present study demonstrates that EAAC1 is important for the survival of newly generated neurons in the adult brain under physiological and pathological conditions. Therefore, this study suggests that EAAC1 plays an essential role in modulating hippocampal neurogenesis.

Role of Excitatory Amino Acid Carrier 1 (EAAC1) in Neuronal Death and Neurogenesis After Ischemic Stroke

“…Nevertheless, a study showed that cystine transport by cystine/glutamate antiporter (xCT) is not essential for novel proliferation in the DG, which illuminates the importance of EAAC1 as the main cysteine importer of cysteine in hippocampal regional mitosis. Our previous study showed that EAAC1 is important for the survival of newborn neurons in the adult hippocampus under physiological and ischemic conditions [46]. We found that there are no differences in cell proliferation and neuronal differentiation in both young and aged EAAC1 −/− mice under ischemia-free conditions compared to the age-matched WT mice.…”

“…Neurons that are differentiating can be detected by doublecortin (DCX), proopiomelanocortin (POMC), or neuronal nuclei (NeuN) antibodies. It has been reported that newly generated neurons in the dentate gyrus and striatum are GABAergic interneurons, with the former requiring two maturation steps and the latter needing only one [36,43,45,46]. The markers used to track down cellular mitosis in the rodent DG are as follows: Type I cells are marked by GFAP+Hes5+ or Nestin+Sox1+Sox2+BLBP (brain lipid-binding protein)+; Type II cells are marked by Nestine+Sox1+Sox2+BLBP+ or Mash1+ or Prox1+NeuroD+; type III cells are marked by NeuroD1+DCX+; and mature neurons are marked by NeuN+ [44].…”

“…However, to genuinely represent neurogenesis, those NSCs should develop into normal functioning neurons. Thus, behavior tests or molecular markers must be followed up after certain periods of time, usually 3-4 weeks [43,46,51].…”

“…Such an example is NAC. The effectiveness of NAC has been shown in many studies on the ischemia-reperfusion state to prove that defects of EAAC1 are related to neural damage and neural production at the same time because NAC provides cellular cysteine [34,46]. The main impairment of oxidative stress in neurogenesis comes from depleting the cellular energy supply, and NAC can also intervene and elevate the proliferation rate.…”

Zinc transporter 3 modulates cell proliferation and neuronal differentiation in the adult hippocampus

“…41 Additionally, concentrations of hydrogen peroxide and superoxide play a role in the choice to either enter or exit the cell cycle. 42 In support of these observations, we previously demonstrated that newly generated neurons are exposed to oxidative stress at specific developmental timepoints, potentially explaining effects on hippocampal neurogenesis 43 observed in these animals. To test this, we used ZN which is zinc chloride mixed with NAC in 1:2 M ratio to increase brain zinc and cysteine levels.…”