LAUSR

Abstract We recently reported that cerebral sodium‐glucose transporter type 1 (SGLT‐1) plays a role in exacerbation of cerebral ischemia. However, the mechanism by which cerebral SGLT‐1 acts remains unclear. Here we demonstrated that sodium influx through cerebral SGLT‐1 exacerbates cerebral ischemic neuronal damage. SGLT‐specific sodium ion influx was induced using &agr;‐methyl‐D‐glucopyranoside (&agr;‐MG). Intracellular sodium concentrations in primary cortical neurons were estimated using sodium‐binding benzofuran isophthalate fluorescence. SGLT‐1 knockdown in primary cortical neurons and mice was achieved using SGLT‐1 siRNA. The survival rates of primary cultured cortical neurons were assessed using biochemical assays 1 day after treatment. Middle cerebral artery occlusion (MCAO) was used to generate a focal cerebral ischemic model in SGLT‐1 knockdown mice. The change in fasting blood glucose levels, infarction development, and behavioral abnormalities were assessed 1 day after MCAO. Treatment with 200 mM &agr;‐MG induced a continuous increase in the intracellular sodium concentration, and this increase was normalized after &agr;‐MG removal. Neuronal SGLT‐1 knockdown had no effect on 100 &mgr;M H2O2‐induced neuronal cell death; however, the knockdown prevented the neuronal cell death induced by 17.5 mM glucose and the co‐treatment of 100 &mgr;M H2O2/8.75 mM glucose. Neuronal SGLT‐1 knockdown also suppressed the cell death induced by &agr;‐MG alone and the co‐treatment of 100 &mgr;M H2O2/0.01 mM &agr;‐MG. Our in vivo results showed that the exacerbation of cerebral ischemic neuronal damage induced by the intracerebroventricular administration of 5.0 &mgr;g &agr;‐MG/mouse was ameliorated in cerebral SGLT‐1 knockdown mice. Thus, sodium influx through cerebral SGLT‐1 may exacerbate cerebral ischemia‐induced neuronal damage. Abbreviations: SGLT: sodium‐glucose transporter; DIV: Day in vitro; SBFI: sodium‐binding benzofuran isophthalate; STD: standard; PBS: phosphate‐buffered saline; BSA: bovine serum albumin; MAP2: microtubule‐associated protein 2; DAPI: 4′,6‐diamidino‐2‐phenylindole; siRNA: small interfering RNA; SDS: sodium dodecyl sulfate; TBS: tris buffered saline; TBS‐T: TBS containing 0.1% Tween 20; GAPDH: glyceraldehyde‐3‐phosphate dehydrogenase; HRP: horseradish peroxidase; H2O2: hydrogen peroxide; WST‐8: 2‐(2‐methoxy‐4‐nitrophenyl)‐3‐(4‐nitrophenyl)‐5‐(2,4‐disulfophenyl)‐2H‐tetrazolium; i.c.v.: intracerebroventricular; MCAO: middle cerebral artery occlusion; FBG: Fasting blood glucose; TTC: 2,3,5‐triphenyltetrazolium chloride; NDS: neurological deficit score; SEM: standard errors of the mean.