Evaluation of Hemorrhage and Edema Expansion, Including Effect on Neutrophil-Mediated Neuroinflammation in Intracerebral Hemorrhage, Using Ir-CPI, a Thromboinflammation Inhibitor

Intracerebral hemorrhage (ICH) is a subtype of stroke with a high mortality and functional disability rate. The inflammation and coagulation responses after ICH would accelerate the formation of perihematomal edema (PHE), resulting in brain herniation-related death and neurological deficits. Patients with ICH also frequently present with thrombotic events, including secondary intracerebral ischemic lesions and in-hospital thromboembolic complications. However, medical treatments for inflammation and safe prevention of thrombosis are lacking during the hyperacute phase of ICH. Ixodes ricinus-Contact Phase Inhibitor (Ir-CPI) is an inhibitor of both coagulation factors (Factors XIIa and XIa) and neutrophils, with proven antithrombotic effect in various animal models.

We evaluated the effects of Ir-CPI on PHE and hemorrhage volumes, on neutrophil infiltration and neuronal degeneration in mice using an ICH model.

ICH was induced by injecting collagenase into the right striatum. Mice were allocated to either PBS, Ir-CPI (30.7 mg/kg + 8.3 mg/kg/h) or enoxaparin (20 mg/kg) (n = [6-8]). Treatments were administered intravenously immediately after stroke induction as a bolus followed by a 3-day infusion. Dose of Ir-CPI used was previously proven to be antithrombotic in mice. P-values were calculated using a Kruskal-Wallis test with Dunn's multiple comparison test.

Ir-CPI did not increase PHE and hemorrhage volumes measured by magnetic resonance imaging 1 and 3 days after ICH, as compared to PBS. Ir-CPI decreased neutrophil infiltration and significantly decreased the number of neutrophil-releasing NETs at collagenase injection site (p < 0.05). Ir-CPI also reduced the number of degenerating neurons in the hemorrhagic zone (p < 0.05 at the injection site). In contrast, enoxaparin increased PHE and hemorrhage volumes as compared to Ir-CPI (p < 0.05) and PBS and had no significant impact on neutrophil infiltration and degenerating neurons.

Ir-CPI administration after ICH induction is safe, reduces neutrophil infiltration including neutrophil-releasing NETs, and attenuates neuronal degeneration.