Neutrophils contribute to intracerebral haemorrhages after treatment with recombinant tissue plasminogen activator following cerebral ischaemia

Background and purpose:

Polymorphonuclear neutrophils (PMNs) contribute to the vascular damage caused by transient cerebral ischaemia. Here we have evaluated the role of PMNs in intracerebral haemorrhage (ICH) induced in a model of thrombolysis with recombinant tissue plasminogen activator (t-PA) during the acute phase of cerebral ischaemia.

Experimental approach:

The middle cerebral artery (MCA) of male spontaneously hypertensive rats was occluded for 1 h followed by reperfusion and, 5 h later, infusion of thrombolytic products (generated in vitro by t-PA on autologous clots). Effects of pretreatment (before the MCA occlusion) with vinblastine (4 days before; 0.5 mg·kg⁻¹), monoclonal anti-neutrophil antibody (mAbRP3; 12 h, 0.3 mg·kg⁻¹) or saline on ICH, neutrophil infiltration, MCA vascular reactivity and brain infarct volume were assessed, 24 h after the beginning of reperfusion.

Key results:

Depletion of circulating neutrophils significantly reduced t-PA-induced ICH (vinblastine, 4.6 ± 1.0; mAbRP3, 5.2 ± 1.0 vs. saline, 10.8 ± 2.7 haemorrhages; P < 0.05). This depletion was associated with a decrease in cerebral infiltration by neutrophils and a decrease of endothelium-dependent, vascular dysfunction in isolated MCA, induced by the ischaemia/reperfusion and t-PA treatment. Brain infarct volume was significantly decreased after vinblastine treatment (159 ± 13 mm³ vs. 243 ± 16 mm³ with saline; P < 0.01) but not after depletion with mAbRP3 (221 ± 22 mm³).

Conclusions and implications:

Our results showed that pharmacological depletion of PMNs prevented t-PA-induced ICH, in parallel with a decrease in cerebral infiltration by PMNs and a decreased endothelial dysfunction in cerebral blood vessels.