Modulatory effects of GLT-1 enhancer, MC-100093, on glutamate uptake and associated signaling pathways in female and male alcohol preferring rats exposed to ethanol.

BACKGROUND

Ethanol consumption disrupts glutamate homeostasis in several brain regions. The uptake of extracellular glutamate is regulated in the majority by the astrocytic glutamate transporter 1 (GLT-1), and cystine-glutamate exchanger (xCT) contributes to this regulatory effect. Chronic ethanol consumption is well known to downregulate GLT-1 expression in several reward brain regions, including the nucleus accumbens (NAc).

OBJECTIVES

Recently, we reported that a novel beta-lactam, MC-100093, attenuated ethanol consumption and normalized the expression of GLT-1 in the subregions of the NAc. Based on these findings, we aimed in this study to determine the dose-dependent effect of MC-100093 in attenuating ethanol consumption and whether this attenuating effect is associated with restoration of glutamate uptake. In addition, we focused on whether the effects of MC-100093 on GLT-1 are mediated through the mammalian target of rapamycin (mTOR), protein kinase B (Akt), and nuclear factor-kappa B (NF-κB) signaling pathways.

METHODS

Male and female alcohol-preferring (P) rats are grouped into 4 groups. Other than control groups all the 3 groups had free access to ethanol (15% and 30% v/v), and water for 5 weeks. On week 6, rats received intraperitoneal injection (i.p.) of MC-100093 at a dosage of 100 or 150 mg/kg, or saline, for 5 days. The Na+ dependent and Na+ independent glutamate uptake is measured by radioactive glutamate uptake assay. The expression of GLT-1, xCT, mTOR, phospho-Akt (p-Akt), kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IkBa), and NF-κB are determined by Western blot analysis.

RESULTS

MC-100093 treatment reduced ethanol drinking in male and female P rats. MC-100093 was associated with an increase in Na+-dependent and Na+-independent glutamate uptake. Furthermore, MC-100093 treatment attenuated ethanol-induced decrease in GLT-1, xCT, NF-κB, and p-Akt expression in the NAc.

CONCLUSIONS

These findings demonstrate that MC-100093 attenuated ethanol consumption and regulated glutamate uptake through normalizing GLT-1 expression.