Haptoglobin Attenuates Cerebrospinal Fluid Hemoglobin-Induced Neurological Deterioration in Sheep

Bart R Thomson; Nina Schwendinger; Katrin Beckmann; Thomas Gentinetta; Daniel Couto; Sandra Wymann; Valérie Verdon; Raphael M Buzzi; Kevin Akeret; Peter W Kronen; Eva M Weinberger; Ulrike Held; Frauke Seehusen; Henning Richter; Dominik J Schaer; Michael Hugelshofer

doi:10.1007/s12975-024-01254-9

Haptoglobin Attenuates Cerebrospinal Fluid Hemoglobin-Induced Neurological Deterioration in Sheep

Transl Stroke Res. 2024 Apr 23. doi: 10.1007/s12975-024-01254-9. Online ahead of print.

Authors

Bart R Thomson^{1

2}, Nina Schwendinger¹, Katrin Beckmann³, Thomas Gentinetta⁴, Daniel Couto⁴, Sandra Wymann⁴, Valérie Verdon⁴, Raphael M Buzzi², Kevin Akeret¹, Peter W Kronen^{5

6}, Eva M Weinberger¹, Ulrike Held⁷, Frauke Seehusen⁸, Henning Richter^{6

9}, Dominik J Schaer^#², Michael Hugelshofer^#^{10

11}

Affiliations

¹ Department of Neurosurgery, Clinical Neuroscience Center, Universitätsspital and University of Zurich, Zurich, Switzerland.
² Division of Internal Medicine, Universitätsspital and University of Zurich, Zurich, Switzerland.
³ Neurology Service, Department of Small Animals, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
⁴ CSL Biologics Research Centre, Swiss Institute for Translational and Entrepreneurial Medicine, CSL, sitem-insel, Bern, Switzerland.
⁵ Veterinary Anaesthesia Services - International, Winterthur, Switzerland.
⁶ Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, Zurich, Switzerland.
⁷ Department of Biostatistics and Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
⁸ Laboratory of Animal Model Pathology, Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
⁹ Diagnostic Imaging Research Unit (DIRU), Clinic for Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
¹⁰ Department of Neurosurgery, Clinical Neuroscience Center, Universitätsspital and University of Zurich, Zurich, Switzerland. Michael.Hugelshofer@usz.ch.
¹¹ Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, Zurich, Switzerland. Michael.Hugelshofer@usz.ch.

^# Contributed equally.

PMID: 38652234
DOI: 10.1007/s12975-024-01254-9

Abstract

Secondary brain injury (SBI) occurs with a lag of several days post-bleeding in patients with aneurysmal subarachnoid hemorrhage (aSAH) and is a strong contributor to mortality and long-term morbidity. aSAH-SBI coincides with cell-free hemoglobin (Hb) release into the cerebrospinal fluid. This temporal association and convincing pathophysiological concepts suggest that CSF-Hb could be a targetable trigger of SBI. However, sparse experimental evidence for Hb's neurotoxicity in vivo defines a significant research gap for clinical translation. We modeled the CSF-Hb exposure observed in aSAH patients in conscious sheep, which allowed us to assess neurological functions in a gyrencephalic species. Twelve animals were randomly assigned for 3-day bi-daily intracerebroventricular (ICV) injections of either Hb or Hb combined with the high-affinity Hb scavenger protein haptoglobin (Hb-Hp, CSL888). Repeated CSF sampling confirmed clinically relevant CSF-Hb concentrations. This prolonged CSF-Hb exposure over 3 days resulted in disturbed movement activity, reduced food intake, and impaired observational neuroscores. The Hb-induced neurotoxic effects were significantly attenuated when Hb was administered with equimolar haptoglobin. Preterminal magnetic resonance imaging (MRI) showed no CSF-Hb-specific structural brain alterations. In both groups, histology demonstrated an inflammatory response and revealed enhanced perivascular histiocytic infiltrates in the Hb-Hp group, indicative of adaptive mechanisms. Heme exposure in CSF and iron deposition in the brain were comparable, suggesting comparable clearance efficiency of Hb and Hb-haptoglobin complexes from the intracranial compartment. We identified a neurological phenotype of CSF-Hb toxicity in conscious sheep, which is rather due to neurovascular dysfunction than structural brain injury. Haptoglobin was effective at attenuating CSF-Hb-induced neurological deterioration, supporting its therapeutic potential.

Keywords: CSF-Hb; Haptoglobin; Repeated exposure; Therapeutic benefit.

Abstract

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