Remote Ischemic Conditioning is neuroprotective in experimental necrotizing enterocolitis
Background/Purpose: Necrotizing enterocolitis (NEC) remains one of the most severe gastrointestinal emergencies affecting premature babies, and around 50% of NEC survivors suffer from neurodevelopmental delay. Remote ischemic conditioning (RIC) has emerged as a promising tool in protecting distant organs against inflammatory damage. We have shown that experimental NEC induces neuroinflammation and that RIC can reduce not only the intestinal damage related to NEC but also the associated neuroinflammation. We aimed to investigate the mechanism of neuroprotection by RIC in NEC-induced cerebral injury.
Methods: NEC was induced in postnatal day 5 (p5) mice (wild type and eNOS knockout) using hypoxia, formula gavage feeding, and oral lipopolysaccharide (4mg/kg). On p6 and p8, RIC was given using a tourniquet in the right limb (5 minutes ischemia followed by 5 minutes reperfusion; repeated for 4 times). Breastfed pups served as control. Brains were harvested on p9. Zonula occludens-1 (tight junction), metallopeptidase-9 (MMP9), an endopeptidase which digests the extracellular matrix of endothelial cells, protein expression (Western) was assessed.
Results: Compared to control, NEC pups had decreased protein expression of ZO-1, while RIC rescued the expression. Compared to control, MMP9 expression increased in NEC, and decreased to control levels in RIC pups (Fig. A). We confirmed that eNOS expression decreased in NEC. This protective effect of RIC did not occur in eNOS-/-mice (Fig. B).
Conclusion: Remote ischemic conditioning can reduce the brain injury associated with NEC by rescuing the brain-blood barrier function and decreasing MMP9 activity through the eNOS pathway. Remote ischemic conditioning is a simple maneuver with great translational potential to prevent cerebral injury secondary to necrotizing enterocolitis.