Erythropoietin attenuates loss of potassium chloride co-transporters following prenatal brain injury

Abstract

Therapeutic agents that restore the inhibitory actions of γ-amino butyric acid (GABA) by modulating intracellular chloride concentrations will provide novel avenues to treat stroke, chronic pain, epilepsy, autism, neurodegenerative and cognitive disorders. During development upregulation of the potassium-chloride co-transporter KCC2, and the resultant switch from excitatory to inhibitory responses to GABA guides the formation of essential inhibitory circuits. Importantly, maturation of inhibitory mechanisms is also central to the development of excitatory circuits and proper balance between excitatory and inhibitory networks in the developing brain. Loss of KCC2 expression occurs in postmortem samples from human preterm infant brains with white matter lesions. Here we show late gestation brain injury in a rat model of extreme prematurity impairs the developmental upregulation of potassium chloride co-transporters during a critical postnatal period of circuit maturation in CA3 hippocampus by inducing a sustained loss of oligomeric KCC2 via a calpain-dependent mechanism. Further, administration of erythropoietin (EPO) in a clinically relevant postnatal dosing regimen following the prenatal injury protects the developing brain by reducing calpain activity, restoring oligomeric KCC2 expression and attenuating KCC2 fragmentation, thus providing the first report of a safe therapy to address deficits in KCC2 expression. Together, these data indicate it is possible to reverse abnormalities in KCC2 expression during the postnatal period, and potentially reverse deficits in inhibitory circuit formation central to cognitive impairment and epileptogenesis.

Preclinical Models of Encephalopathy of Prematurity

“…In this model following injury, O4-immunoreactive immature oligodendrocytes are most affected and their loss correlates with decreased survival and maturation[69], with the most notable reductions in O4+ and O1+ stages of the lineage[35], consistent with previous reports by other investigators[70]. This model also demonstrates premature loss of the subplate, reduced KCC2 expression, and a lower seizure threshold and impaired gait[25,26,55]. Detailed analyses of other components of EoP including loss of thalamic and GABAergic neurons, and the contribution of placental pathology is underway.…”

Preschool Assessment of Preterm Infants Treated With Darbepoetin and Erythropoietin

“…Doses in the DANCE (Darbepoetin Administration in Neonates undergoing Cooling for Encephalopathy) study were similar to the darbepoetin doses administered in our original randomized controlled trial, 8 although term infants only received 2 doses 1 week apart in the DANCE study, compared with up to 10 weekly doses in our study. Longterm developmental assessments of infants enrolled in these term neuroprotection studies are ongoing.…”

“…The neuroprotective mechanisms of ESAs include decreased neuronal apoptosis, decreased inflammation, promotion of oligodendrocyte differentiation and maturation, and improved white matter survival. [1][2][3][4][5][6][7][8][9] These biological mechanisms of neuroprotection may be revealed through MRI. 26 All children enrolled in the BRITE study underwent MRI, and analyses of total and regional brain volume, cortical thickness, surface area, spectroscopy, total and regional cerebral blood flow, and diffusion tensor imaging are nearing completion.…”

“…Recent studies in animals and humans evaluating the nonhematopoietic effects of erythropoiesis-stimulating agents (ESAs) suggest a neuroprotective potential via such mechanisms as increased oligodendrogenesis, decreased inflammation, decreased oxidative injury, and decreased apoptosis. [1][2][3][4][5][6][7][8][9] We previously reported 18-to 22-month outcomes on our prospective, randomized, masked study in preterm infants randomly assigned to receive ESAs or placebo 10 and hypothesized that ESA recipients would have higher composite cognitive scores measured by using the Bayley Scales of Infant Development III (BSID-III). 11 Indeed, those very low birth weight infants receiving erythropoietin or darbepoetin alfa (hereafter "darbepoetin") had significantly higher composite cognitive scores, including higher scores on a scale of executive function.…”

Cation-chloride cotransporters in neuronal development, plasticity and disease

“…The downregulation of KCC2 is part of a spectrum of changes associated with cellular de-differentiation following neuronal trauma 15,176 . In parallel with, or as a result of, changes in its serine 940 phosphorylation status 32,141 , KCC2 is cleaved at its C-terminal domain by the Ca 2+ - and brain-derived neurotrophic factor (BDNF)-activated protease calpain, leading to a loss of a ~20–40 kDa fragment 23,150,151,286 (FIG. 1d) and reduction of both total and surface-expressed KCC2 protein.…”