ADAMTS13 reduces VWF-mediated acute inflammation following focal cerebral ischemia in mice

BACKGROUND

ADAMTS13 cleaves hyperactive ultra-large von Willebrand factor (ULVWF) multimers into smaller and less active forms. It remains unknown whether VWF-mediated inflammatory processes play a role in the enhanced brain injury due to ADAMTS13 deficiency.

OBJECTIVE

We tested the hypothesis that the deleterious effect of ADAMTS13 deficiency on ischemic brain injury is mediated through VWF-dependent enhanced vascular inflammation.

METHODS

Transient focal cerebral ischemia was induced by 60 min of occlusion of the right middle cerebral artery. Myeloperoxidase (MPO) activity and inflammatory cytokines in the infarcted region were evaluated 23 h after reperfusion injury. Neutrophil infiltration within the infarct and surrounding areas was quantitated by immunohistochemistry.

RESULTS

We report that ADAMTS13-deficient mice exhibited significantly enlarged infarct size, concordant with increased myeloperoxidase (MPO) activity, neutrophil infiltration and expression of the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). In contrast, VWF-deficient mice exhibited significantly reduced MPO activity, neutrophil infiltration and inflammatory cytokine induction, demonstrating a role of VWF in these inflammatory processes. Mice deficient for both ADAMTS13 and VWF exhibited an identical reduction of the same inflammatory parameters, demonstrating that the increased inflammation observed in ADAMTS13-deficient mice is VWF dependent. Finally, the increased infarct size observed in ADAMTS13-deficient mice was completely abrogated by prior immunodepletion of neutrophils, demonstrating a causal role for acute inflammation in the enhanced brain injury that occurs in the setting of ADAMTS13 deficiency.

CONCLUSION

These findings provide new evidence for ADAMTS13 in reducing VWF-mediated acute cerebral inflammation following ischemic stroke.

Persisting Vasculitis After Pneumococcal Meningitis

INTRODUCTION

Bacterial meningitis is associated with a high mortality and a high incidence of neurological sequelae. Parainfectious vasculitis leading to ischemic brain damage is a known complication of bacterial meningitis but its treatment is uncertain.

METHODS AND RESULTS

We report the case of a 53-year-old man with pneumococcal meningitis who developed numerous ischemic lesions in the brainstem and basal ganglia caused by parainfectious vasculitis. Clinical and radiological improvement was observed after delayed corticosteroid initiation. Symptomatic vasculitis relapsed after steroid withdrawal and stabilized after reintroduction of the immunosuppressive therapy. Although the cerebrospinal fluid (CSF) contained high levels of MMP-9 at the time of symptomatic vasculitis, a significant decrease of the enzyme accompanied the introduction of corticotherapy and the regression of vasculitic symptoms. No relation between the level of MMP-9 and the white blood cell count in CSF could be found.

CONCLUSION

Parainfectious vasculitis may respond to late corticosteroid treatment. MMP-9 level in CSF may be a marker of vasculitic complication in bacterial meningitis.