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(Stroke. 2004;35:981.)
© 2004 American Heart Association, Inc.

Original Contributions

Hypoxia/Ischemia Modulates G Protein–Coupled Receptor Kinase 2 and ß-Arrestin-1 Levels in the Neonatal Rat Brain

Maria Stella Lombardi, PhD; Evelyn van den Tweel, MSc; Annemieke Kavelaars, PhD; Floris Groenendaal, MD, PhD; Frank van Bel, MD, PhD Cobi J. Heijnen, PhD

From the Laboratory for Psychoneuroimmunology (M.S.L., E.v.d.T., A.K., C.J.H.) and the Department of Neonatology (E.v.d.T., F.G., F.v.B.), University Medical Center Utrecht, Utrecht, Netherlands.

Correspondence to Prof Dr Cobi J. Heijnen, UMC Utrecht, KC03.068.0, Lundlaan 6, 3584 EA Utrecht, Netherlands. E-mail c.heijnen{at}azu.nl

Background and Purpose— Neurotransmitters, neuropeptides, chemokines, and many other molecules signal through G protein–coupled receptors (GPCRs). GPCR kinases (GRKs) and ß-arrestins play a crucial role in regulating the responsiveness of multiple GPCRs. Reduced expression of GRK and ß-arrestins leads to supersensitization of GPCRs and will thereby increase the response to neuropeptides and neurotransmitters. We analyzed GRK and ß-arrestin expression after cerebral hypoxia/ischemia (HI).

Materials and Methods— Twelve-day-old rat pups were exposed to 90 minutes of hypoxia (fraction of inspired oxygen [FiO₂] 0.08) after ligation of the right carotid artery, a procedure that induces unilateral damage in the right hemisphere. At 6, 12, 24, and 48 hours after HI, the left (hypoxic) and right (hypoxic/ischemic) hemispheres were analyzed for GRK and ß-arrestin protein and mRNA expression by Western blotting and real-time polymerase chain reaction, respectively. In addition, we analyzed GRK2 expression in the hippocampus by immunohistochemistry.

Results— HI downregulated GRK2 protein expression in both hemispheres at 24 to 48 hours after HI, and the effect was more pronounced in the ipsilateral hemisphere. HI induced no global change in GRK6 protein expression. However, GRK2 was markedly decreased in the hippocampal region of the ipsilateral hemisphere that will be severely damaged after HI. No changes in global mRNA levels for GRK2 were detected. In contrast, HI increased ß-arrestin-1 protein expression as well as mRNA levels at 6 to 12 hours after HI.

Conclusions— Neonatal HI-induced brain damage is associated with specific changes in the GPCR desensitization machinery. We hypothesize that these changes result in supersensitization of multiple GPCRs and might therefore contribute to HI-induced brain damage.

Key Words: hypoxia • ischemia • newborn • receptors, G-protein coupled

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