Heparin and low molecular weight heparins may reduce brain damage evoked by ischaemia/reperfusion (I/R) injury, although their use is hampered by the risk of haemorrhage. Chemical and enzymatic modifications of K5 polysaccharide have shown the possibility to produce heparin-like compounds with low anticoagulant activity and strong anti-inflammatory effects. Using a rat model of transient cerebral I/R, we investigated the effects of an epimerised N-,O-sulfated K5 polysaccharide derivative, K5-N,OSepi, on the infarct size, motor activity and injury caused by ischaemia (30 min) and reperfusion. Reperfusion was allowed for 60 min or 1-5 days. Rats reperfused for 5 days showed an infarct volume of 30.7 +/- 3.1% and K5-N,OSepi (0.1-1 mg/kg) caused dose-dependent reduction in infarct size (maximum at 1 mg/kg: 13.1 +/- 2.1% infarct volume). This effect was associated with a significant improvement in motor performance. In the rat hippocampus, one of the brain areas most sensitive to I/R injury, I/R induced a robust increase in myeloperoxidase (MPO) activity, a marker of neutrophil infiltration, that was halved by K5-N,OSepi administration (66.38 +/- 7.75 microU MPO/tissue g, 30.78 +/- 5.67 microU MPO/tissue g, respectively). K5-N,OSepi drastically reduced the expression of cyclooxygenase-2, inducible-nitric-oxide-synthase and intercellular-adhesion-molecule-1. I/R-induced activation of nuclear factor-kB was attenuated by drug treatment. Furthermore, K5-N,OSepi administration was associated with a significant modulation of apoptosis markers, such as Bid and Bcl-2. In conclusion, the results demonstrated that the sulfated semi-synthetic K5 derivative K5-N,OSepi protects the brain against I/R injury by disrupting multiple levels of the apoptotic and inflammatory cascade, including inhibition of NF-kappaB activation.