Hypoxic Preconditioning Maintains GLT-1 Against Transient Global Cerebral Ischemia Through Upregulating Cx43 and Inhibiting c-Src

Abstract

Transient global cerebral ischemia (tGCI) causes excessive release of glutamate from neurons. Astrocytic glutamate transporter-1 (GLT-1) and glutamine synthetase (GS) together play a predominant role in maintaining glutamate at normal extracellular concentrations. Though our previous studies reported the alleviation of tGCI-induced neuronal death by hypoxic preconditioning (HPC) in hippocampal Cornu Ammonis 1 (CA1) of adult rats, the underlying mechanism has not yet been fully elaborated. In this study, we aimed to investigate the roles of GLT-1 and GS in the neuroprotection mediated by HPC against tGCI and to ascertain whether these roles can be regulated by connexin 43 (Cx43) and cellular-Src (c-Src) activity. We found that HPC decreased the level of extracellular glutamate in CA1 after tGCI via maintenance of GLT-1 expression and GS activity. Inhibition of GLT-1 expression with dihydrokainate (DHK) or inhibition of GS activity with methionine sulfoximine (MSO) abolished the neuroprotection induced by HPC. Also, HPC markedly upregulated Cx43 and inhibited p-c-Src expression in CA1 after tGCI, whereas inhibition of Cx43 with Gap26 dramatically reversed this effect. Furthermore, inhibition of p-c-Src with 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo (3, 4-d) pyrimidine (PP2) decreased c-Src activity, increased protein levels of GLT-1 and Cx43, enhanced GS activity, and thus reduced extracellular glutamate level in CA1 after tGCI. Collectively, our data demonstrated that reduced extracellular glutamate induced by HPC against tGCI through preventing the reduction of GLT-1 expression and maintaining GS activity in hippocampal CA1, which was mediated by upregulating Cx43 expression and inhibiting c-Src activity.

miR-137 prevents inflammatory response, oxidative stress, neuronal injury and cognitive impairment via blockade of Src-mediated MAPK signaling pathway in ischemic stroke

“…Likewise, miR-137 has been reported to target Src gene and inhibit its expression in colon cancer cells, slowing cancer progression [11]. Inhibiting Src activity also slows the progression of transient global cerebral ischemia [30]. Consistent with our results, knockout of Src alleviated cerebral infarction and neuronal injury in MCAO mice.…”

Connexin30 and Connexin43 show a time-of-day dependent expression in the mouse suprachiasmatic nucleus and modulate rhythmic locomotor activity in the context of chronodisruption

“…SCN electrical activity [56] and glutamine synthase activity [54] are high during the day/subjective day, independent of light input. An association between expression of Cx43 and glutamine synthase activity has been described [57]. Thus, synthesis, transport and/or integration of Cx43 into the membrane could be coupled to SCN neuronal activity and/or glutamine synthase activity.…”

Peroxisome proliferator‐activated receptor gamma participates in the acquisition of brain ischemic tolerance induced by ischemic preconditioning via glial glutamate transporter 1 in vivo and in vitro

“…It is well known that the up‐regulation of GLT‐1 contributes to the acquisition of BIT induced by preconditioning, including IPC and hypoxic preconditioning (Bigdeli et al ; Zhang et al ; Li et al ). However, the mechanism of GLT‐1 up‐regulation in this process is not yet well understood, although it has been suggested that it is related to p38 MAPK, connexin 43, and cellular src (Zhang et al ; Li et al ). The present study showed an additional mechanism of GLT‐1 up‐regulation induced by IPC, which was mediated by PPARγ.…”