Neuroprotection by hypoxic preconditioning involves oxidative stress-mediated expression of hypoxia-inducible factor and erythropoietin.

Abstract

BACKGROUND AND PURPOSE:

Hypoxic preconditioning is an endogenous protection against subsequent lethal hypoxia, but the mechanism involved is not understood. Hypoxia is followed by reactive oxygen species (ROS) production and induces hypoxia-inducible factor (HIF) and its downstream factor erythropoietin (Epo), which is associated with neuroprotection. We hypothesized that these endogenous processes may contribute to hypoxic preconditioning.

METHODS:

We used a mouse neuronal culture model, with 2 hours of hypoxia as preconditioning followed by 15 hours of hypoxic insult, and examined the expression of HIF-1alpha, Epo, and their downstream proteins by Western blotting. Copper/zinc-superoxide dismutase (SOD1) transgenic (Tg) mice were used to detect the effect of ROS. Cell survival and apoptosis were detected by mitogen-activated protein 2 quantification, apoptotic-related DNA fragmentation, and caspase-3 fragmentation. Antisense Epo was used to block endogenously produced Epo.

RESULTS:

Hypoxic preconditioning was protective in wild-type (Wt) neurons but not in neurons obtained from SOD1 Tg mice. In Wt neurons, HIF-1alpha and Epo expression showed a greater increase after hypoxia compared with Tg neurons and reached a higher level with preconditioned hypoxia, followed by pJak2, pStat5, and nuclear factor kappaB (NF-kappaB) expression. Antisense Epo decreased these downstream proteins and the neuroprotection of hypoxic preconditioning.

CONCLUSIONS:

Hypoxic preconditioning induces ROS, which may downregulate the threshold for production of HIF-1alpha and Epo expression during subsequent lethal hypoxia, thus exerting neuroprotection through the Jak2-Stat5 and NF-kappaB pathways.

• Authors: Jing Liu, Purnima Narasimhan, Fengshan Yu, Pak H Chan
• Journal: Stroke (Stroke) Vol. 36 Issue 6 Pg. 1264-9 (Jun 2005) ISSN: 1524-4628 [Electronic] United States
• PMID: 15890996 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Hypoxia-Inducible Factor 1
• NF-kappa B
• Neuroprotective Agents
• Oligonucleotides, Antisense
• Proto-Oncogene Proteins
• Reactive Oxygen Species
• Recombinant Proteins
• STAT5 Transcription Factor
• Erythropoietin
• Superoxide Dismutase
• Protein-Tyrosine Kinases
• Jak2 protein, mouse
• Janus Kinase 2
• Mitogen-Activated Protein Kinase 1
• Casp3 protein, mouse
• Caspase 3
• Caspases

Topics

• Animals
• Apoptosis
• Blotting, Western
• Caspase 3
• Caspases (metabolism)
• Cell Survival
• Cells, Cultured
• DNA Fragmentation
• Erythropoietin (pharmacology)
• Heterozygote
• Hypoxia (metabolism)
• Hypoxia-Inducible Factor 1 (metabolism)
• Ischemic Preconditioning
• Janus Kinase 2
• Mice
• Mice, Transgenic
• Mitogen-Activated Protein Kinase 1 (metabolism)
• NF-kappa B (metabolism)
• Neurons (metabolism)
• Neuroprotective Agents (pharmacology)
• Oligonucleotides, Antisense (pharmacology)
• Oxidative Stress
• Protein-Tyrosine Kinases (metabolism)
• Proto-Oncogene Proteins (metabolism)
• Reactive Oxygen Species
• Recombinant Proteins
• Reverse Transcriptase Polymerase Chain Reaction
• STAT5 Transcription Factor (metabolism)
• Superoxide Dismutase (genetics, metabolism, physiology)