Hypoxia/ischemia modulates G protein-coupled receptor kinase 2 and beta-arrestin-1 levels in the neonatal rat brain.
OBJECTIVE
Neurotransmitters, neuropeptides, chemokines, and many other molecules signal through G protein-coupled receptors (GPCRs). GPCR kinases (GRKs) and beta-arrestins play a crucial role in regulating the responsiveness of multiple GPCRs. Reduced expression of GRK and beta-arrestins leads to supersensitization of GPCRs and will thereby increase the response to neuropeptides and neurotransmitters. We analyzed GRK and beta-arrestin expression after cerebral hypoxia/ischemia (HI).


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 beta-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 beta-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.
Lombardi
Maria Stella
MS
Laboratory for Psychoneuroimmunology, University Medical Center Utrecht, Netherlands.
van den Tweel
Evelyn
E
Kavelaars
Annemieke
A
Groenendaal
Floris
F
van Bel
Frank
F
Heijnen
Cobi J
CJ
D000818:Animals; D000831:Animals, Newborn; D019390:Arrestins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D001921:Brain / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D001923:Brain Chemistry; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D005260:Female; D054769:G-Protein-Coupled Receptor Kinase 2; D005786:Gene Expression Regulation; D000860:Hypoxia; D020925:Hypoxia-Ischemia, Brain / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D051552:beta-Adrenergic Receptor Kinases; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins
C000605256:Arrb1 protein, rat; D019390:Arrestins; D012333:RNA, Messenger; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D017868:Cyclic AMP-Dependent Protein Kinases; C496569:Grk2 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2