Neuroserpin as an adjuvant therapy for hypothermia on brain injury in neonatal hypoxic-ischemic rats.

Abstract

Objective We aimed to assess the effects of neuroserpin and its combination with hypothermia on hypoxic-ischemic (HI) brain injury in neonatal rats. Neuroserpin is an axon-secreted serine protease inhibitor and is important for brain development, neuronal survival, and synaptic plasticity. Study Design Male Wistar-Albino rats on postnatal day 7 (P7) were randomly divided into five groups; sham group (n=10), hypoxic-ischemic (HI) (n=10), hypotermia (HIH) (n=10), neuroserpin (HIN) (n=10), and neuroserpin-hypotermia (HINH) (n=10). The P7 rat brain's maturation is similar to a late preterm human brain at 34-36 weeks of gestation. HI was induced in rats on postnatal day 7 (P7) as previously described. A single dose of 0,2 µM neuroserpin (HINH and HIN) or an equivalent volume of phosphate buffered saline (sham, HIH, and HI) was administered intraventricularly by a Hamilton syringe immediately after hypoxia. In the follow-up, pups were subjected to systemic hypothermia or normothermia for 2 hours. Euthanasia was performed for histopathological evaluation on P10. Apoptosis was detected by caspase-3 activity and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining and was counted in the hippocampus. Results: In comparison to the HI group, the TUNEL-positive and caspase-3-positive neurons in the sham, HIN, HIH, and HINH groups were considerably lower (13.4±1.0 vs. 1.9±0.9, 6.0±0.9, 5.3±1.6, and 4.0±1.1) (p <0.001) and (13.5±1.7 vs. 9.1±2.7, 4.8±1.0, 3.9±1.6 and 1.2±0.7) (p <0.001). HIN, HIH, and HINH, compared to the sham group, showed more TUNEL-positive and caspase-3-positive neurons (6.0±0.9, 5.3±1.6, 4.0±1.1 vs. 1.9±0.9) and (9.1±2.7, 4.8±1.0, 3.9±1.6 vs. 1.2±0.7) (p <0.001). The HINH group (synergistic effect) had significantly fewer TUNEL-positive neurons and caspase-3-positive neurons than the HIN group (4.0±1.1vs. 6.0±0.9) and ( 3.9±1.6 vs. 9.1±2.7) (p <0.001). In conclusion, our study showed that both neuroserpin alone and as an adjuvant treatment for hypothermia may have a neuroprotective effect on brain injury.