Qing Wang1 2, Xiannan Tang1, Raymond A. Swanson1, Midori A. Yenari1
1Department of Neurology, University of California, San Francisco & the San Francisco Veterans Affairs Medical Center, California  94121, USA
2 Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University,
Tianhe Road 600, Guangzhou, Guangdong 510630, P.R. China

Pyruvate is a key intermediate in glucose metabolism, but is also a free radical scavenger. The purpose of this study is to assess the neuroprotective and anti-inflammatory effects of pyruvate following transient MCAO in rats. SD rats (n=8/group) were subjected to 2 hours of MCAO, and pyruvate (500mg/kg, IP) was administered 10 minutes before reperfusion. 24 hours later, infarct size, neurological deficits, physiological parameters, NF-kB translocation, microglial activation and neutrophil infiltration were evaluated. Pyruvate did not affect physiological parameters but significantly reduced infarct volume by 71.25 % (46.20 ± 10.1 mm2 vs 160.49 ± 21.6 mm2 P<0.01). This was accompanied by improvement in behavioral tests, including forelimb-placement, elevated body swing test, cylinder test, and Bederson score (P<0.05). Pyruvate treatment reduced the number of neutrophils stained by MPO by 45% (46±2.68/HPF vs 25± 1.69/ HPF, P<0.001 n=7/group) compared with the vehicle-treated group. Microglial activation measured by ED1 staining was reduced by 40% (30± 2.5/HPF vs 18±1.2/HPF, P<0.001). Isolectin B4 positive cells were also reduced by 52% (52±2.57/HPF vs 25±1.7/HPF, P<0.001). Immunohistochemistry showed that pyruvate reduced numbers of nuclear NF-kB staining from 31% (MCAO) to 7% (MCAO+pyruvate) (P<0.001). As a positive control, a set of rats (n=3/group) was given LPS (5mg/kg, IP) to cause brain inflammation without cell death. LPS increased nuclear staining of NF-kB and this was almost completely abolished by pyruvate (19% for LPS vs 0.5% for LPS+pyruvate, P<0.001). NF-kB’s DNA binding capacity increased by 4.57 and 4.80 folds for LPS and MCAO treatment respectively compared with control (7.68% for control vs 39.13% and 44.56% for LPS and MCAO, respectively, P<0.001). Pyruvate reduced NF-kB activation in LPS and MCAO groups (18.7 ± 1.5% for MCAO + pyruvate and 17.53 ± 1.4% for LPS+ pyruvate vs 44.56 ± 3.9% for MCAO and 39.13 ± 2.4% for LPS, P<0.001, n=7/group). Western blot of MMP9, a NFkB regulated gene, showed increased MMP9 protein by 4 and 3.70 folds for LPS and MCAO treatment, respectively compared with shams (9.36±0.73 % for shams vs.37.39±11.97% and 34.86±8.21% for LPS (P<0.01) and MCAO (P=0.01), respectively, n=3/grp). Pyruvate treatment profoundly reduced MMP9 increases due to LPS administration and MCAO (11.54 ± 1.27% for MCAO + pyruvate and 10.78 ± 1.32% for LPS+ pyruvate, P<0.01 vs. no treatment). Taken together, these results strongly suggest that neuroprotective effects of pyruvate on MCAO may be closely correlated to its anti-inflammatory effect, possibly at the transcriptional level.  
【Key Words】: middle cerebral artery occlusion, pyruvate, cerebral ischemia, stroke, inflammation, neuroprotection.