Blood micromolar concentrations of kaempferol afford protection against ischemia/reperfusion-induced damage in rat brain.

The slow time course of neurodegeneration after brain ischemia/reperfusion opened a realistic time window for the application of protective therapies to prevent spreading of brain damage. In this work, we studied the ability of micromolar concentrations of this flavonoid in the blood to protect against brain damage induced by transient focal cerebral ischemia in rats. Transient focal cerebral ischemia was induced by middle cerebral artery occlusion in adult rats and brain damage has been monitored by 2,3,5-triphenyltetrazolium chloride (TTC) staining, hematoxylin-eosin (H-E) staining, 'in situ' terminal deoxyribonucleotidyl transferase-mediated dUTP-fluorescein nick end labeling (TUNEL), 'in situ' metalloproteinase activity using DQ-gelatin and loss of anti-laminin staining. Intravenous injections of kaempferol, at a dose of 10-15 mumol/L of blood 30 min before the induction of a 60 min ischemia-episode and just after reperfusion, led to >90% and 70-80% (TTC, H-E, TUNEL) decrease of brain damage in the temporal-frontal areas of neocortex and striatum, respectively, but only 40-50% decrease of brain damage was observed in the hippocampus and vicinal caudal areas of the striatum. This treatment with kaempferol also produced a similar reduction of metalloproteinase activation and loss of anti-laminin staining in cortical and striatum infarct areas. Kaempferol treatment efficiently protected against nitrosative-oxidative stress after ischemia/reperfusion, as shown by nearly complete protection against the increase of protein nitrotyrosines, and also afforded strong protection against the increase of apoptotic cell death (TUNEL) and biochemical markers of apoptosis, such as caspase-9 activity and poly-(ADP-ribose) polymerase degradation. On these grounds, a potential new therapeutic role of kaempferol to acute treatment of ischemic stroke is suggested.