Elsevier

Resuscitation

Volume 76, Issue 1, January 2008, Pages 89-94
Resuscitation

Experimental paper
Soluble epoxide hydrolase gene deletion reduces survival after cardiac arrest and cardiopulmonary resuscitation

https://doi.org/10.1016/j.resuscitation.2007.06.031Get rights and content

Summary

The P450 eicosanoids epoxyeicosatrienoic acids (EETs) are produced by cytochrome P450 arachidonic acid epoxygenases and metabolized through multiple pathways, including soluble epoxide hydrolase (sEH). Pharmacological inhibition and gene deletion of sEH protect against ischemia/reperfusion injury in brain and heart, and against hypertension-related end-organ damage in kidney. We tested the hypothesis that sEH gene deletion improves survival, recovery of renal function and pathologic ischemic renal damage following transient whole-body ischemia induced by cardiac arrest (CA) and resuscitation. Mice with targeted deletion of sEH (sEH knockout, sEHKO) and C57Bl/6 wild-type control mice were subjected to 10-min CA, followed by cardiopulmonary resuscitation (CPR). Survival in wild-type mice was 93% and 80% at 10 min and 24 h after CA/CPR (n = 15). Unexpectedly, survival in sEHKO mice was significantly lower than WT. Only 56% of sEHKO mice survived for 10 min (n = 15, p = 0.014 compared to WT) and no mice survived for 24 h after CA/CPR (p < 0.0001 versus WT). We conclude that sEH plays an important role in cardiovascular regulation, and that reduced sEH levels or function reduces survival from cardiac arrest.

Introduction

The P450 epoxygenase pathway metabolizes arachidonic acid (AA) into biologically active eicosanoids referred to as epoxyeicosatrienoic acids (EETs).1 In the systemic circulation, EETs are primarily produced by vascular endothelium, where they serve as an endothelium-derived hyperpolarizing factor (EDHF).2 As such, EETs play an important role in regulating tissue perfusion in several organs, including heart, brain and kidney. However, EETs are short-lived, mainly due to metabolic conversion by soluble epoxide hydrolase (sEH) into dihydroxyeicosatrienoic acids (DHETs).3 Recent reports suggest that sEH inhibition is protective against cardiovascular disease, including hypertension-related end-organ damage.4, 5 In agreement with these reports, we have also shown that sEH inhibition is protective against stroke-related ischemic brain damage.6 Furthermore, sEH gene deletion in sEH knockout (sEHKO) mice renders these mice resistant to angiotensin II-induced hypertension.7 More recently, using an isolated perfused heart, Seubert et al. demonstrated that sEHKO mice exhibit improved ventricular function after myocardial ischemia.8 However, the impact of sEH gene deletion on survival and end-organ tissue damage in an in vivo model of whole-body ischemia remains unknown. Furthermore, vasodilation, while beneficial in focal ischemia, could be detrimental during cardiac resuscitation as it would lower the coronary perfusion pressure and critically compromise myocardial blood flow. Therefore, in the current study, we used an in vivo mouse model of cardiac arrest (CA) followed by cardiopulmonary resuscitation (CPR) to test the hypothesis that sEHKO mice demonstrate improved survival, renal functional recovery and attenuated pathologic ischemic renal damage. We here report the very significant, yet surprising, finding that sEH gene deletion, which protects against ischemic damage in an isolated heart preparation, impedes CPR and worsens survival after CA in vivo. This is a novel finding, with important clinical implications related to understanding mechanisms and developing new therapeutic agents for the prevention of and the facilitation of recovery from cardiac arrest.

Section snippets

Materials and methods

The study was conducted in accordance with the National Institute of Health guidelines for the care and use of animals in research and protocols were approved by the institutional animal care and use committee. The sEHKO strain was obtained from Dr. Frank Gonzalez at the National Institutes of Health, where it was originated. Gene disruption strategy and phenotype are described elsewhere.7 The strain has been backcrossed to C57Bl/6 for at least six generations; and therefore, homozygous sEHKO

Results

There were no significant differences between WT and sEHKO mice with regard to pre-arrest body weight, baseline or mean intra-arrest rectal temperature (Table 1, n = 15 per group). Both strains of mice were subjected to identical protocol of 10-min normothermic cardiac arrest, followed by cardiopulmonary resuscitation (CPR) under isoflurane anesthesia. In WT mice, restoration of spontaneous circulation (ROSC) was observed in all mice (15/15, 100%), which required 12.0 ± 0.5 mcg of epinephrine and

Discussion

The main finding of our study is that sEH gene deletion renders mice refractory to cardiopulmonary resuscitation (CPR) after cardiac arrest (CA). The sEHKO mice required significantly higher doses of epinephrine and longer CPR time, demonstrated delayed blood pressure recovery after CPR and suffered significantly higher mortality compared to wild-type control mice. Our findings suggest that sEH plays an important role in recovery from cardiac arrest, likely due to its EETs-metabolizing function.

Conflict of interest statement

None.

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    A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2007.06.031.

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