Abstract
Perinatal hypoxia-ischemia is associated with disruption of cortical gamma-aminobutyric acid (GABA)ergic interneurons and their surrounding perineuronal nets, which may contribute to persisting neurological deficits. Blockade of connexin43 hemichannels using a mimetic peptide can alleviate seizures and injury after hypoxia-ischemia. In this study, we tested the hypothesis that connexin43 hemichannel blockade improves the integrity of cortical interneurons and perineuronal nets. Term-equivalent fetal sheep received 30 min of bilateral carotid artery occlusion, recovery for 90 min, followed by a 25-h intracerebroventricular infusion of vehicle or a mimetic peptide that blocks connexin hemichannels or by a sham ischemia + vehicle infusion. Brain tissues were stained for interneuronal markers or perineuronal nets. Cerebral ischemia was associated with loss of cortical interneurons and perineuronal nets. The mimetic peptide infusion reduced loss of glutamic acid decarboxylase-, calretinin-, and parvalbumin-expressing interneurons and perineuronal nets. The interneuron and perineuronal net densities were negatively correlated with total seizure burden after ischemia. These data suggest that the opening of connexin43 hemichannels after perinatal hypoxia-ischemia causes loss of cortical interneurons and perineuronal nets and that this exacerbates seizures. Connexin43 hemichannel blockade may be an effective strategy to attenuate seizures and may improve long-term neurological outcomes after perinatal hypoxia-ischemia.
Highlights
Perinatal hypoxic-ischemic encephalopathy remains a major cause of brain damage in term and near-term infants worldwide [1]
Note that ischemia + vehicle animals showed aggregates of dark parvalbumin and calretinin staining in the cytoplasm of some cortical neurons, which were not observed in sham control and ischemia + peptide animals
The present study demonstrates that blockade of connexin43 hemichannel opening with a mimetic peptide during early recovery from HI in term-equivalent fetal sheep improved survival of cortical GABAergic interneurons and prevented loss of cortical Perineuronal nets (PNNs) after 7 days of recovery
Summary
Perinatal hypoxic-ischemic encephalopathy remains a major cause of brain damage in term and near-term infants worldwide [1]. GABA and is expressed in all GABAergic interneurons, while parvalbumin+, calretinin+, and calbindin+ interneurons form the major GABAergic interneuron subtypes. Experimental and human studies show that cortical interneurons are critical for normal cognitive processes, including executive function, learning, memory, and intelligence [2,4,5,6]. Limited human studies have shown altered interneuron function after neonatal brain injury, including reduced cortical interneuron migration, loss of cortical GABAergic interneurons, and reduced GABAergic signaling [4,7]. Disruption of cortical inhibitory interneuron circuits may contribute to disability after moderate to severe hypoxic-ischemic encephalopathy in term infants
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