Mechanisms of Erythropoietin-induced Brain Protection in Neonatal Hypoxia-Ischemia Rat Model

Abstract

Summary: Erythropoietin, a hemotopoietic growth factor, has brain protective actions. This study investigated the mechanisms of Recombinant Human EPO (rhEPO)-induced brain protection in neonates. An established rat hypoxia-ischemia model was used by ligation of the right common carotid artery of 7-day-old pups, followed by 90 minute of hypoxia (8% 0 2 and 92% N 2 ) at 37°C. Animals were divided into three groups: control, hypoxia-ischemia, and hypoxia-ischemia plus rhEPO treatment. In rhEPO treated pups, 300 units rhEPO was administered intraperitoneally 24 hours before hypoxia. rhEPO treatment (300 units) was administered daily for an additional 2 days. ELISA and immunohistochemistry examined the expression of EPO and EPOR. Brain weight, morphology, TUNEL assay, and DNA laddering evaluated brain protection. rhEPO abolished mortality (from 19% to 0%) during hypoxia insult, increased brain weight from 52% to 88%, reduced DNA fragmentation, and decreased TUNEL-positive cells. Real-time RT-PCR, Western blot, and immunohistochemistry revealed an enhanced expression of heat shock protein 27 (HSP27) in ischemic brain hemisphere. Double labeling of TUNEL with HSP27 showed most HSP27 positive cells were negative to TUNEL staining. rhEPO reduces brain injury, especially apoptotic cell death after neonatal hypoxia-ischemia, partially mediated by the activation of HSP27. Key Words: apoptosisbrain injury-heat shock protein-RT-PCR.

Erythropoietin after Focal Cerebral Ischemia Activates the Janus Kinase–Signal Transducer and Activator of Transcription Signaling Pathway and Improves Brain Injury in Postnatal Day 7 Rats

“…We did not detect any significant alteration in EpoR expression in the ischemic cortex from 1 to 7 d after focal ischemic insult in the Epo-treated pups compared with vehicle-treated pups. This issue is consistent with the findings that Epo treatment does not alter EpoR mRNA levels in a neurotoxic model (12) and that Epo application for 3 d does not down-regulate EpoR in a neonatal hypoxic-ischemic model (28). Recent data have also shown that carbamylated Epo or certain Epo mutants do not bind to the classical EpoR, but these Epo mutants were neuroprotective in vitro and in vivo (42).…”

“…In neonatal animals, Epo has been shown to reduce neurotoxicity of N-methyl-Daspartate receptor antagonists (12) and prevent brain injury in a P7 hypoxic-ischemic rat model (13,14,28) when the first dose is given before producing the injury. There are two important differences between our current study and previous ones.…”

“…The sham-operated group received only vehicle injection as normal control. The Epo dose and the schedule of administration were chosen according to previous protocols that evaluated the drug in a hypoxic-ischemic model in P7 rat pups (13,14,28). The treatment groups were randomly assigned, and the investigators who evaluated outcomes were blinded to the treatment received.…”

Role of erythropoietin in the brain

“…However, in neonatal or adult rats after focal brain ischemia, brain trauma or experimental autoimmune encephalomyelitis systemic or intraperitoneal administration of exogenous EPO is neuroprotective [52,89,90]. Intravenously administered EPO also provides protection in animal models for spinal cord injury with improved functional neurological status [91,92].…”

Future Perspectives in the Treatment of Incurable Gastric Cancer

“…Erythropoietin treatment reduces apoptotic cell death (Sun et al, 2004) and brain edema (Brissaud et al, 2010) and has an anti-inflammatory effect in the HI brain (Juul et al, 2009). It affects regenerative processes, promoting an increase in functional revascularization, in NSPC proliferation in the SVZ and in the number of new neurons that migrate to the striatum and to the cerebral cortex (Iwai et al, 2007).…”