Involvement of the δ-opioid receptor in exercise-induced cardioprotection.

NEW FINDINGS: What is the central question of this study? Does the δ-opioid receptor trigger exercise-induced cardioprotection against ischaemia-reperfusion injury? What is the main finding and its importance? In exercised hearts, the δ-opioid receptor appears to trigger cardioprotection against ischaemia-reperfusion-induced tissue necrosis but not apoptosis. ABSTRACT: Endogenous opioids mediate exercise-induced cardioprotection against ischaemia-reperfusion (IR) injury, although the opioid receptor subtype mediating this effect is unknown. We investigated whether the δ-opioid receptor mediates exercise-induced cardioprotection against IR injury. Endogenous opioids are produced in various tissues, including the heart and skeletal muscle; therefore, we also sought to identify the effect of exercise on circulating endogenous opioid as well as transcript, protein and receptor expression in heart and skeletal muscle. Male Sprague-Dawley rats (n = 73) were assigned randomly to treadmill exercise or sedentary treatments. Cardiac tissue and serum were harvested 0, 20 and 120 min following exercise and from sedentary animals (n = 32) to quantify effects on proenkephalin and δ-opioid receptor mRNA and protein levels, as well as serum enkephalin. Skeletal muscle (soleus) was harvested at identical time points for determination of proenkephalin protein and mRNA. A separate group of rats (n = 41) were randomly assigned to sham operation (Sham; surgical control), sedentary (Sed), exercise (Ex) or exercise + Î´-opioid receptor antagonist (ExD; naltrindole, 5 mg kg(-1) i.p.) and received IR by left anterior descending coronary artery ligation in vivo. After IR, tissues were harvested to quantify treatment effects on necrosis and apoptosis. Cardiac proenkephalin mRNA expression increased following exercise (0 min, P = 0.03; 120 min, P = 0.021), while soleus expression was unaffected. Exercise-induced changes in serum enkephalin were undetectable. After IR, tissue necrosis was elevated in Sed and ExD hearts (P < 0.001 and P = 0.003, respectively) compared with the Sham group, while the Ex group was partly protected. After IR, apoptosis was evident in Sed hearts (P = 0.016), while Ex and ExD hearts were protected. Data suggest that cardioprotective opioids are produced by the heart, but not by the soleus. After IR, the δ-opioid receptor may mediate, in part, cardioprotection against necrosis but not apoptosis.

The relationship of pressure ulcers, race, and socioeconomic conditions after spinal cord injury.

OBJECTIVE: To identify risks factors associated with pressure ulcers (PrU) after spinal cord injury (SCI) by examining race and indicators of socioeconomic status (measured by income and education). We hypothesize African Americans will have a greater risk for PrUs than whites, but this relationship will be mediated by the 2 socioeconomic status indicators. DESIGN: Cohort study. SETTING: A large rehabilitation hospital in the southeastern US. PARTICIPANTS: 1466 white and African American adults at least 1-year post-traumatic SCI. OUTCOME MEASURES: (a) PrUs in the past year, (b) current PrU, (c) surgery to repair a PrU since injury. RESULTS: In preliminary analyses, race was significantly associated with having a current PrU and with having surgery to repair a PrU since injury. In multivariable analyses, the relationships of PrU with having a current PrU and with having surgery to repair a PrU were both mediated by income and education such that the relationships were no longer significant. Lower income was associated with increased odds of each PrU outcome. After controlling for other variables in the model, education was associated with increased odds of having a current PrU. CONCLUSION: These findings help clarify the relationships between race and socioeconomic status with PrUs after SCI. Specifically, a lack of resources, both financial and educational, is associated with worse PrU outcomes. These results can be used by both providers and policy makers when considering prevention and intervention strategies for PrUs among people with SCI.