Impact of the neutrophil response to granulocyte colony-stimulating factor on the risk of hemorrhage when used in combination with tissue plasminogen activator during the acute phase of experimental stroke

Background: granulocyte colony-stimulating factor (g-csf) is a pharmacologic agent inducing neutrophil mobilization and a new candidate for neuroprotection and neuroregeneration in stroke. its effects when used in combination with tissue plasminogen activator (tpa) were explored during the acute phase of ischemic stroke. methods: we used a middle cerebral artery occlusion (mcao) model of cerebral ischemia,associated with treatment with tpa,in male spontaneously hypertensive rats (shr). granulocyte colony-stimulating factor (g-csf; 60 μg/kg) was injected just before tpa. neutrophil response in peripheral blood and in the infarct area was quantified in parallel to the infarct volume. protease matrix metallopeptidase 9 (mmp-9) release from circulating neutrophils was analyzed by immunochemistry and zymography. vascular reactivity and hemorrhagic volume in the infarct area was also assessed. results: twenty four hours after ischemia and tpa,g-csf administration induced a significant increase of neutrophils in peripheral blood (p < 0.05). at 72 hours post-ischemia,g-csf was significantly associated with an increased risk of hemorrhage in the infarct area (2.5 times more likely; p < 0.05) and significant cerebral endothelium-dependent dysfunction. ex vivo,an increased mmp-9 release from neutrophils after tpa administration correlated to the increased hemorrhagic risk (p < 0.05). in parallel,g-csf administration was associated with a decreased neutrophil infiltration in the infarct area (-50%; p < 0.05),with a concomitant significant neuroprotective effect (infarct volume: -40%; p < 0.05). conclusions: we demonstrate that g-csf potentiates the risk of hemorrhage in experimental stroke when used in combination with tpa by inducing neutrophilia. this effect is concomitant to an increased mmp-9 release from peripheral neutrophils induced by the tpa treatment. these results highlight the potential hemorrhagic risk of associating g-csf to thrombolysis during the acute phase of stroke. © 2014 gautier et al.