Signaling via the prostaglandin E2 receptor EP4 exerts neuronal and vascular protection in a mouse model of cerebral ischemia
Xibin Liang, … , Milton Merchant, Katrin Andreasson
Xibin Liang, … , Milton Merchant, Katrin Andreasson
Published October 3, 2011
Citation Information: J Clin Invest. 2011;121(11):4362-4371. https://doi.org/10.1172/JCI46279.
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Research Article Neuroscience

Signaling via the prostaglandin E2 receptor EP4 exerts neuronal and vascular protection in a mouse model of cerebral ischemia

Abstract

Stroke is the third leading cause of death in the United States. Fewer than 5% of patients benefit from the only intervention approved to treat stroke. Thus, there is an enormous need to identify new therapeutic targets. The role of inducible cyclooxygenase (COX-2) activity in stroke and other neurologic diseases is complex, as both activation and sustained inhibition can engender cerebral injury. Whether COX-2 induces cerebroprotective or injurious effects is probably dependent on which downstream prostaglandin receptors are activated. Here, we investigated the function of the PGE2 receptor EP4 in a mouse model of cerebral ischemia. Systemic administration of a selective EP4 agonist after ischemia reduced infarct volume and ameliorated long-term behavioral deficits. Expression of EP4 was robust in neurons and markedly induced in endothelial cells after ischemia-reperfusion, suggesting that neuronal and/or endothelial EP4 signaling imparts cerebroprotection. Conditional genetic inactivation of neuronal EP4 worsened stroke outcome, consistent with an endogenous protective role of neuronal EP4 signaling in vivo. However, endothelial deletion of EP4 also worsened stroke injury and decreased cerebral reperfusion. Systemic administration of an EP4 agonist increased levels of activated eNOS in cerebral microvessels, an effect that was abolished with conditional deletion of endothelial EP4. Thus, our data support the concept of targeting protective prostaglandin receptors therapeutically after stroke.

Authors

Xibin Liang, Lu Lin, Nathaniel S. Woodling, Qian Wang, Christoph Anacker, Tingting Pan, Milton Merchant, Katrin Andreasson

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Figure 6

Endothelial EP4 regulates eNOS activation in cerebral microvasculature in vivo.

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Endothelial EP4 regulates eNOS activation in cerebral microvasculature i...
(A) AE1-329 or vehicle was administered to 3-month-old male C57B6 mice (0.3 mg/kg s.c.), and levels of total Akt, phospho-Akt, total eNOS, and Ser1177 phospho-eNOS were measured in acutely isolated cerebral microvessels at 1 and 5 hours by quantitative Western analysis. Total Akt, phospho-Akt, total eNOS, and phospho-eNOS were increased 5 hours after AE1-329 administration. A representative Western blot is shown; lanes were run on the same gel but were noncontiguous (white lines). (B) Quantification of densitometric values normalized to actin demonstrated significant increases in total and phospho-Akt and in total and phospho-eNOS 5 hours after AE1-329 administration. n = 6–9 per condition. *P < 0.05; **P < 0.01; ***P < 0.001. (C) AE1-329 or vehicle was administered to 3-month-old male VECad-Cre-ERT2;EP4+/+ and VECad-Cre-ERT2;EP4lox/lox mice (0.3 mg/kg s.c.), and microvessels were isolated 5 hours after agonist administration. Western analysis demonstrated induction of phospho-Akt and phospho-eNOS in VECad-Cre-ERT2;EP4+/+ mice that was absent in VECad-Cre-ERT2;EP4lox/lox mice. All samples were on the same blot. (D) Quantification of densitometric values normalized to actin demonstrated significant increases in microvessel total Akt, phospho-Akt, total eNOS, and phospho-eNOS levels 5 hours after AE1-329 administration in VECad-Cre-ERT2;EP4+/+ mice; such increases were not seen in VECad-Cre-ERT2;EP4lox/lox mice. n = 3 per group. *P < 0.05; **P < 0.01.