Dual-modal metabolic analysis reveals hypothermia-reversible uncoupling of oxidative phosphorylation in neonatal brain hypoxia-ischemia

• DOI: 10.7554/elife.100129.1
• Publication Date: 2024-09-25T21:05:59Z
• Authors: Naidi Sun; Yu-Yo Sun; Rui Cao; Hong-Ru Chen; Yiming Wang; Elizabeth Fugate; Marchelle R Smucker; Yi-Min Kuo; P Ellen Grant; Diana M Lindquist; Chia-Yi Kuan; Song Hu
• Keywords: 03 medical and health sciences; 0302 clinical medicine; 3. Good health

Hypoxia-ischemia (HI), which disrupts the oxygen supply-demand balance in the brain by impairing blood oxygen supply and the cerebral metabolic rate of oxygen (CMRO 2 ), is a leading cause of neonatal brain injury. However, it is unclear how post-HI hypothermia helps to restore the balance, as cooling reduces CMRO 2 . Also, how transient HI leads to secondary energy failure (SEF) in neonatal brains remains elusive. Using photoacoustic microscopy, we examined the effects of HI on CMRO 2 in awake 10-day-old mice, supplemented by bioenergetic analysis of purified cortical mitochondria. Our results show that while HI suppresses ipsilateral CMRO 2 , it sparks a prolonged CMRO 2 -surge post-HI, associated with increased mitochondrial oxygen consumption, superoxide emission, and reduced mitochondrial membrane potential necessary for ATP synthesis—indicating oxidative phosphorylation (OXPHOS) uncoupling. Post-HI hypothermia prevents the CMRO 2 -surge by constraining oxygen extraction fraction, reduces mitochondrial oxidative stress, and maintains ATP and N-acetylaspartate levels, resulting in attenuated infarction at 24 hours post-HI. Our findings suggest that OXPHOS-uncoupling induced by the post-HI CMRO 2 -surge underlies SEF and blocking the surge is a key mechanism of hypothermia protection. Also, our study highlights the potential of optical CMRO 2 -measurements for detecting neonatal HI brain injury and guiding the titration of therapeutic hypothermia at the bedside.