Hypoxic-ischemic brain injury stimulates inflammatory response and enzymatic activities in the hippocampus of neonatal rats.

Brain damage from neonatal hypoxia-ischemia (HI) plays a major role in neonatal mortality and morbidity. Using the Rice-Vannucci model of HI in rats, we verified that 8 days after HI injury, adenosine deaminase (ADA), N-acetyl-glucosaminidase (NAG) and myeloperoxidase (MPO) activities increased in the left hemisphere hippocampus (HI group); however, the activity of 5'-nucleotidase (5'NT) remained unchanged. In the hematoxylin-eosin analysis (HE), we detected selective and delayed degeneration of hippocampal pyramidal neurons and astroglial reaction accompanied by glial fibrillary acidic protein (GFAP)-positive and vimentin-positive in the immunohistochemistry analysis in the HI group compared with the control group. We observed the selective necrosis of neurons, vascular endothelial proliferation and inflammatory response accompanied by the increase of the key enzyme of adenosine metabolism in the HI group. The increase of ADA activity, despite the 5'NT activity was not altered, indicates the predominance of ADA activity in the postischemic homeostasis of extra cellular adenosine. The presence of leukocytes into the ischemic areas displays the possible importance of the neutrophil-macrophages associated with the increase of MPO and NAG activities 8 days after HI. These findings may contribute to the evaluation of some consequences of the damage caused by neonatal HI.