Neuregulin-1 attenuates hemolysis- and ischemia induced-cerebrovascular inflammation associated with sickle cell disease

Objectives: Individuals with sickle cell disease (SCD) are at severely heightened risk for cerebrovascular injury and acute cerebrovascular events, including ischemic and hemorrhagic stroke, potentially leading to impaired development and life-long physical and cognitive disabilities. Cerebrovascular injury specific to SCD includes inflammation caused by underlying conditions of chronic hemolysis and reduced cerebrovascular perfusion. The objectives of this study were to investigate whether expression of neuregulin-1β (NRG-1), an endogenous neuroprotective polypeptide, is increased in SCD or experimental conditions mimicking the hemolysis and ischemic conditions of SCD, and to determine if treatment with exogenous NRG-1 reduces markers of cerebrovascular inflammation.

Materials and methods: Plasma and brain-specific NRG-1 levels were measured in transgenic SCD mice. Endogenous NRG-1 levels and response to experimental conditions of excess heme and ischemia were measured in cultured human brain microvascular cells and astrocytes. Pre-treatment with NRG-1 was used to determine NRG-1's ability to ameliorate resultant cerebrovascular inflammation.

Results: Plasma and brain-specific NRG-1 were elevated in transgenic SCD mice compared to healthy controls. Neuregulin-1 expression was significantly increased in cultured human microvascular cells and astrocytes exposed to excess heme and ischemia. Pre-treatment with NRG-1 reduced inflammatory chemokine (CXCL-1 and CXCL-10) and adhesion molecule (ICAM-1 and VCAM-1) expression and increased pro-angiogenic factors (VEGF-A) in microvascular cells and astrocytes exposed to excess heme and ischemia.

Conclusions: Elevated NRG-1 in SCD is likely a protective endogenous response to ongoing cerebrovascular insults caused by chronic hemolysis and reduced cerebrovascular perfusion. Administration of NRG-1 to reduce cerebrovascular inflammation may be therapeutically beneficial in SCD and warrants continued investigation.