Neonatal Hypoxia/Ischemia Is Associated With Decreased Inflammatory Mediators After Erythropoietin Administration

Abstract

Background and Purpose— Erythropoietin (EPO), a hematopoietic growth factor, has been shown to be neuroprotective when administered as either a pretreatment or posttreatment. This study tested the hypothesis that one of the mechanisms of protection afforded by posttreatment with recombinant human EPO (rh-EPO) is an anti-inflammatory effect via inhibition of interleukin (IL)-1β. Methods— Seven-day-old rat pups were subjected to unilateral carotid artery ligation followed by 90 minutes of hypoxia (8% O 2 at 37°C). Pups were divided into the following groups: control, hypoxia/ischemia, and hypoxia/ischemia plus rh-EPO. In the rh-EPO–treated pups, rh-EPO (5 U/g body weight IP) was administered starting 24 hours after the insult and then for 2 additional days. Samples were collected at 3, 7, 14, and 21 days after the insult. IL-1β mRNA and protein levels were determined by quantitative real-time reverse transcription–polymerase chain reaction and ELISA. Tumor necrosis factor (TNF)-α mRNA levels were determined by colorimetric microplate assay. Results— rhEPO attenuated brain injury, as assessed by brain weight, and attenuated both the hypoxia/ischemia–induced increases in IL-1β mRNA and protein levels. TNF-α mRNA levels did not increase at 3 to 14 days after the hypoxic/ischemic insult. Conclusions— Administration of exogenous rh-EPO starting 24 hours after a hypoxic/ischemic insult is neuroprotective in the neonatal rat. This neuroprotective activity prevented the secondary, delayed rise in IL-1β and attenuated the infiltration of leukocytes into the ipsilateral hemisphere.