Biodistribution and brain permeability of the extracellular domain of neuregulin-1-β1

Neuregulin-1 (NRG1) belongs to a large family of growth and differentiation factors with a key role in the development and maintenance of the brain. Genetic association of NRG1 within brain disorders such as Alzheimer's disease, schizophrenia and neuroprotective properties of certain NRG1 isoforms have led to a variety of studies in corresponding disease models. In the present work, we investigated NRG1 with regard to its peripheral and central biodistribution after systemic application.We first-time radiolabeled the entire biologically active extracellular domain of NRG1 isotype-β1 (NRG1-β1 ECD; aa 2-246) with iodine-125 and administered it peripherally to healthy adult C57Bl6 mice. Blood kinetics and relative organ distribution of 125I-labeled NRG1-β1 ECD were determined. The blood level of NRG1-β1 ECD peaked within the first hour after intraperitoneal (i.p.) application. The brain-blood ratios of 125I-labeled NRG1-β1 ECD were time-dependently 150-370% higher compared to the brain impermeable control, 131I-labeled bovine serum albumin. Autoradiographs of brain slices demonstrated that 125I-labeled NRG1-β1 ECD accumulated in several regions of the brain e.g. frontal cortex, striatum and ventral midbrain containing the substantia nigra. In addition we found histochemical and biochemical evidence that phosphorylation of the NRG1 prototype receptor ErbB4 was increased in these regions after systemic application of NRG1-β1 ECD.Our data suggest that NRG1-β1 ECD passes the blood-brain barrier and activates cerebral ErbB4 receptors.

► The extracellular domain (ECD) of neuregulin (NRG)-1-β1 is a neurotrophic factor. ► NRG1-β1 ECD (26.9 kDa) was first-time radiolabeled with iodine-125. ► Peripherally administered 125I-labeled NRG1-β1 ECD penetrates the BBB. ► Peripherally administered NRG1-β1 ECD phosphorylates cerebral ErbB4 receptors. ► NRG1-β1 ECD appears to have therapeutic potential for neurodegenerative diseases.