Proteasome Biology Is Compromised in White Matter After Asphyxic Cardiac Arrest in Neonatal Piglets

Abstract

Background Neurological deficits in hypoxic‐ischemic encephalopathy, even with therapeutic hypothermia, are partially attributed to white matter injury. We theorized that proteasome insufficiency contributes to white matter injury. Methods and Results Neonatal piglets received hypoxia‐ischemia ( HI ) or sham procedure with normothermia, hypothermia, or hypothermia+rewarming. Some received a proteasome activator drug (oleuropein) or white matter–targeted, virus‐mediated proteasome knockdown. We measured myelin oligodendrocyte glycoprotein, proteasome subunit 20S (P20S), proteasome activity, and carbonylated and ubiquitinated protein levels in white matter and cerebral cortex. HI reduced myelin oligodendrocyte glycoprotein levels regardless of temperature, and myelin oligodendrocyte glycoprotein loss was associated with increased ubiquitinated and carbonylated protein levels. Ubiquitinated and carbonyl‐damaged proteins increased in white matter 29 hours after HI during hypothermia to exceed levels at 6 to 20 hours. In cortex, ubiquitinated proteins decreased. Ubiquitinated and carbonylated protein accumulation coincided with lower P20S levels in white matter; P20S levels also decreased in cerebral cortex. However, proteasome activity in white matter lagged behind that in cortex 29 hours after HI during hypothermia. Systemic oleuropein enhanced white matter P20S and protected the myelin, whereas proteasome knockdown exacerbated myelin oligodendrocyte glycoprotein loss and ubiquitinated protein accumulation after HI . At the cellular level, temperature and HI interactively affected macroglial P20S enrichment in subcortical white matter. Rewarming alone increased macroglial P20S immunoreactivity, but this increase was blocked by HI . Conclusions Oxidized and ubiquitinated proteins accumulate with HI ‐induced white matter injury. Proteasome insufficiency may drive this injury. Hypothermia did not prevent myelin damage, protect the proteasome, or preserve oxidized and ubiquitinated protein clearance after HI .

How to Improve the Antioxidant Defense in Asphyxiated Newborns—Lessons from Animal Models

“…On the other hand, H/I followed by 29 h of hypothermia increased the level of carbonylated proteins as compared to normothermia in new-born piglets. Similar results were observed in the white matter of the brain in neonatal piglets exposed to asphyxic cardiac arrest followed by short-duration hypothermia (6 and 20 h) [113]. DNA repair gene expression (DNA glycosylases OGG1, NEIL1 and NEIL3) was reduced in hypothermic pigs compared to the control or resuscitated group [114].…”

Comparison of wavelet and correlation indices of cerebral autoregulation in a pediatric swine model of cardiac arrest

“…The piglets were resuscitated with chest compressions, 100% oxygen, and epinephrine (100 µg/kg, intravenous). This model produces robust cortical and white matter injury 19,26,29,30 . Sham piglets received the same surgery but without hypoxia-asphyxia.…”

Hypoxia-Ischemia and Hypothermia Independently and Interactively Affect Neuronal Pathology in Neonatal Piglets with Short-Term Recovery

“…All piglets received IV vecuronium (0.2 mg/kg/h) to prevent shivering during hypothermia and to provide a consistent anesthetic to all piglets. This anesthetic regimen does not affect white matter apoptosis [19], cortical apoptosis [15], the unfolded protein response [20], or brain proteasomes [21] in our model. Phenylephrine or dopamine was initiated when necessary to maintain the mean arterial blood pressure above 45 mm Hg, which is the lower limit of autoregulation in neonatal swine [22].…”