Alter Infarct Size Research Articles

Growth/differentiation factor 15 (GDF15) expression in the heart after myocardial infarction and cardioprotective effect of pre-ischemic rGDF15 administration

Growth/differentiation factor-15 (GDF15) is considered an unfavourable prognostic biomarker for cardiovascular disease in clinical data, while experimental studies suggest it has cardioprotective potential. This study focuses on the direct cardiac effects of GDF15 during ischemia–reperfusion injury in Wistar male rats, employing concentrations relevant to patients at high cardiovascular risk. Initially, we examined circulating levels and heart tissue expression of GDF15 in rats subjected to ischemia–reperfusion and sham operations in vivo. We then evaluated the cardiac effects of GDF15 both in vivo and ex vivo, administering recombinant GDF15 either before 30 min of ischemia (preconditioning) or at the onset of reperfusion (postconditioning). We compared infarct size and cardiac contractile recovery between control and rGDF15-treated rats. Contrary to our expectations, ischemia–reperfusion did not increase GDF15 plasma levels compared to sham-operated rats. However, cardiac protein and mRNA expression increased in the infarcted zone of the ischemic heart after 24 h of reperfusion. Notably, preconditioning with rGDF15 had a cardioprotective effect, reducing infarct size both in vivo (65 ± 5% in control vs. 42 ± 6% in rGDF15 groups) and ex vivo (60 ± 4% in control vs. 45 ± 4% in rGDF15 groups), while enhancing cardiac contractile recovery ex vivo. However, postconditioning with rGDF15 did not alter infarct size or the recovery of contractile parameters in vivo or ex vivo. These novel findings reveal that the short-term exogenous administration of rGDF15 before ischemia, at physiologically relevant levels, protects the heart against ischemia–reperfusion injury in both in vivo and ex vivo settings. The ex vivo results indicate that rGDF15 operates independently of the inflammatory, endocrine and nervous systems, suggesting direct and potent cardioprotective properties against ischemia–reperfusion injury.

Alpha 7 Nicotinic Acetylcholine Receptor Agonist PHA 568487 Reduces Acute Inflammation but Does Not Affect Cardiac Function or Myocardial Infarct Size in the Permanent Occlusion Model.

Stimulation of the alpha 7 nicotinic acetylcholine receptor (α7nAChR) has shown beneficial effects in several acute inflammatory disease models. This study aims to examine whether treatment with the selective α7nAChR agonist PHA 568487 can dampen inflammation and thereby improve cardiac function after myocardial infarction in mice. The possible anti-inflammatory properties of α7nAChR agonist PHA 568487 were tested in vivo using the air pouch model and in a permanent occlusion model of acute myocardial infarction in mice. Hematologic parameters and cytokine levels were determined. Infarct size and cardiac function were assessed via echocardiography 24 h and one week after the infarction. Treatment with α7nAChR agonist PHA 568487 decreased 12 (CCL27, CXCL5, IL6, CXCL10, CXCL11, CXCL1, CCL2, MIP1a, MIP2, CXCL16, CXCL12 and CCL25) out of 33 cytokines in the air pouch model of acute inflammation. However, α7nAChR agonist PHA 568487 did not alter infarct size, ejection fraction, cardiac output or stroke volume at 24 h or at 7 days after the myocardial infarction compared with control mice. In conclusion, despite promising immunomodulatory effects in the acute inflammatory air pouch model, α7nAChR agonist PHA 568487 did not affect infarct size or cardiac function after a permanent occlusion model of acute myocardial infarction in mice. Consequently, this study does not strengthen the hypothesis that stimulation of the α7nAChR is a future treatment strategy for acute myocardial infarction when reperfusion is lacking. However, whether other agonists of the α7nAChR can have different effects remains to be investigated.

Cardiac Myocyte-Specific Overexpression of FASTKD1 Prevents Ventricular Rupture After Myocardial Infarction.

Background The mitochondrial mRNA-binding protein FASTKD1 (Fas-activatedserine/threonine[FAST] kinase domain-containing protein 1) protects myocytes from oxidative stress in vitro. However, the role of FASTKD1 in the myocardium in vivo is unknown. Therefore, we developed cardiac-specific FASTKD1 transgenic mice to test the effects of this protein on experimental myocardial infarction (MI). Methods and Results Transgenic mouse lines with cardiac myocyte-specific overexpression of FASTKD1 to varying degrees were generated. These mice displayed normal cardiac morphological features and function at the gross and microscopic levels. Isolated cardiac mitochondria from all transgenic mouse lines showed normal mitochondrial function, ATP levels, and permeability transition pore activity. Male nontransgenic and transgenic mice from the highest-expressing line were subjected to 8 weeks of permanent coronary ligation. Of nontransgenic mice, 40% underwent left ventricular free wall rupture within 7 days of MI compared with 0% of FASTKD1-overexpressing mice. At 3 days after MI, FASTKD1 overexpression did not alter infarct size. However, increased FASTKD1 resulted in decreased neutrophil and increased macrophage infiltration, elevated levels of the extracellular matrix component periostin, and enhanced antioxidant capacity compared with control mice. In contrast, markers of mitochondrial fusion/fission and apoptosis remained unaltered. Instead, transcriptomic analyses indicated activation of the integrated stress response in the FASTKD1 transgenic hearts. Conclusions Cardiac-specific overexpression of FASTKD1 results in viable mice displaying normal cardiac morphological features and function. However, these mice are resistant to MI-induced cardiac rupture and display altered inflammatory, extracellular matrix, and antioxidant responses following MI. Moreover, these protective effects were associated with enhanced activation of the integrated stress response.

IcyHot analgesic topical cream limits cardiac injury in rodents

Little is known whether topical analgesic creams, whose natural products enter the blood stream after application, affect myocardial infarct size. Here we tested whether topical analgesic creams can trigger remote cardioprotection and the mechanism involved. Male Sprague Dawley rats were used for an in vivo rodent model consisting of 30 minutes left anterior descending coronary artery ischemia and 2 hours of reperfusion followed by infarct size assessment. The topical analgesic IcyHot, applied to the abdomen prior to ischemia, reduced myocardial infarct size versus control (41 ± 3* vs 62 ± 1, n= 6/group, *P < 0.001). In contrast, the topical analgesic creams Preparation H, Aspercreme Heat, or Tiger Balm did not alter infarct size. IcyHot, unlike Preparation H, increased circulating methyl salicylate levels during reperfusion (3.0 ± 0.6 vs 0.4 ± 0.2 mg/dL, n = 6, *P < 0.001, measured at the internal jugular vein). Methyl salicylate (10 μM) applied to isolated adult cardiac myocytes during reoxygenation reduced cell death when compared to vehicle (21% ± 2%* vs 30% ± 2% of trypan blue positive cells, n = 9/group, *P < 0.01). Further, treatment with the TRP ankyrin 1 (TRPA1) inhibitors TCS-5861528 (1 μM) or AP-18 (1 μM) blocked the methyl salicylate-induced protective effect in isolated adult cardiomyocytes. In intact rodents, either of the TRPA1 inhibitors (1 mg/kg, intravenous) given prior to IcyHot topical application blocked IcyHot-induced infarct size reduction. IcyHot also reduced infarct size when applied 24 hours prior to myocardial ischemia or during myocardial ischemia versus control. Together, these findings support IcyHot analgesic cream can trigger remote cardioprotection through releasing methyl salicylate into the bloodstream with cardioprotection occurring by a TRPA1-dependent mechanism.

Abstract WMP80: Inflammation in Aging Increases Ischemic Stroke Burden

Rationale: Acute increases the risk for stroke and adverse outcomes following stroke, such as disability and death. Aging is characterized by increased circulating inflammatory agonists, including interferons (IFNs), and hyperactive platelets. However, whether IFNs generated during aging enhance platelet activation to promote ischemic stroke remains uncertain. Objective: We determined whether IFNs regulate platelet activation and ischemic stroke during human and murine aging. Methods: Younger (8-12 weeks) or aged (&gt;18 months) male mice were stimulated in vivo with IFNα or vehicle control (t=4 days). Mice were then subject to the transient middle cerebral artery occlusion stroke model (t=1 hour followed by reperfusion for 24 hours). Mortality and stroke infarct size were determined. In parallel, we assessed the expression of interferon-sensitive genes (ISGs) and platelet activation from IFN or control treated mice. We also examined platelet activation and ISGs in platelets from younger (age&lt;45) and older (age&gt;65) adults. Results: In aged mice, IFNα significantly increased infarct size (56.2±5.5mm 3 vs 27.3 ±3.0 mm 3 , p&lt;0.0001) and mortality (55% vs. 10%, p&lt;0.05) compared to control mice. Consistent with a greater stroke burden, IFNα significantly worsened neurological outcomes. Ex vivo, IFNα significantly increased fibrinogen uptake and platelet aggregation. In comparison, IFNα did not alter infarct size or mortality in younger mice. We next dissected the mechanism controlling IFNα-induced platelet aggregation and stroke. We identified that interferon-induced transmembrane proteins (IFITMs, a type of ISGs) were upregulated in platelets from aged mice and older humans (settings where IFNs and platelet activation are increased). IFITMs also increased significantly in platelets following IFNα simulation in vivo . Deletion of IFITMs was sufficient to rescue IFNα-induced platelet aggregation and thrombosis-related mortality. Conclusion: In aging, IFNα increases platelet aggregation, stroke burden, stroke-related mortality, and neurological deficits. This pathway critically involves platelet IFITMs, which are upregulated in aging and functionally control fibrinogen uptake, platelet aggregation, and thrombosis.

SGC–cGMP–PKG pathway stimulation protects the healthy but not the failing right ventricle of rats against ischemia and reperfusion injury

BackgroundTo investigate whether modulation of the sGC–cGMP–PKG pathway protects against ischemia and reperfusion injury in the healthy and the failing right ventricle (RV). MethodsHearts from male Wistar rats with a healthy RV (n=39) or a hypertrophic and failing RV induced by pulmonary trunk banding (n=57) were isolated and perfused in a pressure-controlled modified Langendorff setup. The isolated hearts were randomized to control, ischemic preconditioning (IPC, 2×5min of global ischemia), a phosphodiesterase-5 (PDE5) inhibitor vardenafil (66nM) alone and in combination with a cGMP-dependent protein kinase (PKG) blocker KT 5823 (1μM). Failing hearts were exposed to the same protocols and to soluble guanylate cyclase stimulation/activation, and phosphodiesterase 9 inhibition. All interventions were followed by 40min of global ischemia and 120min of reperfusion. The effects on the RV were evaluated by measurement of the infarct size/area-at-risk ratio (IS/AAR). ResultsIn healthy hearts, IPC and pharmacological preconditioning with vardenafil reduced RV infarct size. PKG blockade by KT-5823 did not alter infarct size per se but abolished the cardioprotective effect of vardenafil. In the hypertrophic and failing hearts, none of the conditioning strategies altered RV infarct size. ConclusionPDE-5 inhibition by vardenafil protects the healthy right ventricle against ischemia and reperfusion injury by a PKG dependent mechanism. Neither ischemic preconditioning nor pharmacologic stimulation of the sGC–cGMP–PKG pathway induces cardioprotection in the hypertrophic and failing RV.

Neuronal HIF-1α and HIF-2α deficiency improves neuronal survival and sensorimotor function in the early acute phase after ischemic stroke

Hypoxia-inducible factors mediate adaptive responses to ischemia, among others, by induction of anti- and pro-survival genes. Thus, the impact of HIF on neuronal survival upon stroke is controversial. Therefore, neuron-specific knockout mice deficient for Hif1a and Hif2a were exposed to inspiratory hypoxia or ischemia–reperfusion injury. Both Hif1a- and Hif2a-deficient mice showed no altered infarct and edema size, suggesting that both HIF-α subunits might compensate for each other. Accordingly, hypoxic HIF-target gene regulation was marginally affected with exception of anti-survival Bnip3 and pro-survival erythropoietin. In the early acute stage upon stroke, Hif1a/Hif2a double knockout mice exhibited significantly reduced expression of the anti-survival Bnip3, Bnip3L, and Pmaip1. Accordingly, global cell death and edema were significantly reduced upon 24 h but not 72 h reperfusion. Behavioral assessment indicated that Hif1a/Hif2a-deficient mice initially performed better, but became significantly more impaired after 72 h accompanied by increased apoptosis and reduced angiogenesis. Our findings suggest that in neurons HIF-1 and HIF-2 have redundant functions for cellular survival under ischemic conditions. By contrast, lack of anti-survival factors in Hif1a/Hif2a-deficient mice might protect from early acute neuronal cell death and neurological impairment, indicating a benefit of HIF-pathway inhibition in neurons in the very acute phase after ischemic stroke.

Apolipoprotein A1 Regulates Coenzyme Q10 Absorption, Mitochondrial Function, and Infarct Size in a Mouse Model of Myocardial Infarction

HDL and apolipoprotein A1 (apoA1) concentrations inversely correlate with risk of death from ischemic heart disease; however, the role of apoA1 in the myocardial response to ischemia has not been well defined. To test whether apoA1, the primary HDL apolipoprotein, has an acute anti-inflammatory role in ischemic heart disease, we induced myocardial infarction via direct left anterior descending coronary artery ligation in apoA1null (apoA1−/−) and apoA1heterozygous (apoA1+/−) mice. We observed that apoA1+/− and apoA1−/− mice had a 52% and 125% increase in infarct size as a percentage of area at risk, respectively, compared with wild-type (WT) C57BL/6 mice. Mitochondrial oxidation contributes to tissue damage in ischemia–reperfusion injury. A substantial defect was present at baseline in the electron transport chain of cardiac myocytes from apoA1−/− mice localized to the coenzyme Q (CoQ) pool with impaired electron transfer (67% decrease) from complex II to complex III. Administration of coenzyme Q10 (CoQ10) to apoA1null mice normalized the cardiac mitochondrial CoQ pool and reduced infarct size to that observed in WT mice. CoQ10 administration did not significantly alter infarct size in WT mice. These data identify CoQ pool content leading to impaired mitochondrial function as major contributors to infarct size in the setting of low HDL/apoA1. These data suggest a previously unappreciated mechanism for myocardial stunning, cardiac dysfunction, and muscle pain associated with low HDL and low apoA1 concentrations that can be corrected by CoQ10 supplementation and suggest populations of patients that may benefit particularly from CoQ10 supplementation.

Continuous Heliox Breathing and the Extent of Anatomic Zone of Noreflow and Necrosis Following Ischemia/Reperfusion in the Rabbit Heart

Background:Nitrogen may contribute to reperfusion injury. Some studies have shown that helium as a replacement for nitrogen in breathing gas (heliox) reduces cell necrosis after ischemia/reperfusion when used in a preconditioning fashion (intermittent heliox exposure). Our aim was to test whether heliox, breathed continuously throughout the ischemic and reperfusion periods, reduced necrosis and a marker of reperfusion injury, the no-reflow phenomenon.Methods and Results:Anesthetized, open-chest rabbits received 30 min coronary artery occlusion/3 hrs reperfusion. Before CAO rabbits were randomized to heliox (30% oxygen + 70% helium, n=8) or air supplemented with oxygen to achieve blood gas values within physiologic range (n = 8). Rabbits received the appropriate mix during ischemic and reperfusion periods. Infarct size (% risk zone) and no-reflow defect were measured at the end of the reperfusion period. The ischemic risk zone was similar in both groups (28% of left ventricle in heliox and 29% in control). Heliox breathing did not reduce necrosis; infarct size, expressed as a percentage of the risk region was 44±4% in the heliox group and 49±5% in controls, p = 0.68. The extent of the no-reflow defect was not altered by heliox, either expressed as a percent of the risk region (29±4% in heliox and 28±3% in control) or as a percent of the necrotic zone (65±5% in heliox and 59±8% in control).Heliox treatment had no effect on hemodynamic parameters or arterial blood gas values.Conclusion:Continuous heliox breathing does not appear to be cardioprotective in the setting of acute myocardial infarction in the rabbit model. Heliox respiration administered during 30 minutes of ischemia and 180 minutes of reperfusion did not alter infarct size or the extent of no-reflow.

Influence of exercise training on ischemic brain injury in type 1 diabetic rats

While exercise training (ExT) appears to influence cerebrovascular function during type 1 diabetes (T1D), it is not clear whether this beneficial effect extends to protecting the brain from ischemia-induced brain injury. Thus our goal was to examine whether modest ExT could influence transient focal ischemia-induced brain injury along with nitric oxide synthase (NOS)-dependent dilation of cerebral (pial) arterioles during T1D. Sprague-Dawley rats were divided into four groups: nondiabetic sedentary, nondiabetic ExT, diabetic (streptozotocin; 50 mg/kg ip) sedentary, and diabetic ExT. In the first series of studies, we measured infarct volume in all groups of rats following right MCA occlusion for 2 h, followed by 24 h of reperfusion. In a second series of studies, a craniotomy was performed over the parietal cortex, and we measured responses of pial arterioles to an endothelial NOS (eNOS)-dependent, a neuronal NOS (nNOS)-dependent, and a NOS-independent agonist in all groups of rats. We found that sedentary diabetic rats had significantly larger total, cortical, and subcortical infarct volumes following ischemia-reperfusion than sedentary nondiabetic, nondiabetic ExT, and diabetic ExT rats. Infarct volumes were similar in sedentary nondiabetic, ExT nondiabetic, and ExT diabetic rats. In contrast, ExT did not alter infarct size in nondiabetic compared with sedentary nondiabetic rats. In addition, ExT diabetic rats had impaired eNOS- and nNOS-dependent, but not NOS-independent, vasodilation that was restored by ExT. Thus ExT of T1D rats lessened ischemic brain injury following middle cerebral artery occlusion and restored impaired eNOS- and nNOS-dependent vascular function. Since the incidence of ischemic stroke is increased during T1D, we suggest that our finding are significant in that modest ExT may be a viable preventative therapeutic approach to lessen ischemia-induced brain injury that may occur in T1D subjects.

Abstract 407: Role of Apoa1 in Regulating Mitochondrial Function in Acute Myocardial Infarction

Background: High density lipoprotein (HDL) and apoA-I levels inversely correlate with risk of death from ischemic heart disease; however, the role of apoA-I in myocardial response to ischemia has not been well defined. Methods and results: To test whether apoA-I, the primary HDL apolipoprotein, has an acute anti-inflammatory role in ischemic heart disease, we induced myocardial infarctions in apoA-I -/- and apoA-1 heterozygotic animals. We observed a 52% increase in infarct size as a percent of area at risk in heterozygotic and a 125% increase in apoA-I null animals compared to wild-type mice. Mitochondrial oxidation contributes to tissue damage in ischemic reperfusion injury, and we found a significant defect in the electron transport chain of cardiac myocytes from apoA-I -/- mice. This was localized to the coenzyme Q pool that impaired electron transfer from complex II to complex III. Administration of CoQ10 to apoA-I null animals normalized the cardiac mitochondrial CoQ pool, and it reduced infarct size to that observed of wild type animals. CoQ10 administration did not significantly alter infarct size in wild-type mice. Conclusions: These data identify CoQ pool size and impaired mitochondrial function as major contributors to infarct size in the setting of low HDL/apoA-I. These data suggest a previously unappreciated mechanism for myocardial stunning, cardiac dysfunction, and muscle pain associated with low HDL/apoA-I levels that can be corrected by CoQ10 supplementation and suggest populations of patients that may particularly benefit from CoQ10 supplementation.

STAT3 is a positive regulator of endothelial function in the brain

Signal Transducer and Activator of Transcription 3 (STAT3) is protective to the brain following ischemic injury. The function of STAT3 in cerebral endothelial cells (ECs) in response to ischemic injury has not been investigated. Since ablation of STAT3 specifically in neurons does not alter infarct size, endothelial STAT3 may be responsible for the STAT3‐mediated protection observed in the brain. We therefore hypothesized that STAT3 protects ECs from ischemic injury. We used primary mouse cerebrovascular ECs and subjected them to oxygen and glucose deprivation (OGD), an in vitro model of ischemia. Using Western blot analysis, we found that STAT3 protein levels and phosphorylation are regulated by OGD; they are decreased immediately following OGD, increasing by 24 hours of reoxygenation to exceed pre‐OGD levels. We show that attenuation of STAT3 signaling, by pharmacological inhibition, induces EC death and reduces both nitric oxide release and trans‐endothelial electrical resistance (TEER). STAT3 is therefore a positive regulator of correct endothelial function in the brain, playing an important role in determining susceptibility to ischemic damage. Since endothelial dysfunction is a contributing factor, as well as an outcome of pathological states, regulation of endothelial STAT3 may have important consequences in cerebrovascular disease. Supported by the American Heart Association.

Abstract P289: Cardiomyocyte-Specific, but Not Systemic, Rassf1A Deletion Is Protective Against Ischemia-Reperfusion Injury in the Heart

Our previous work demonstrated Rassf1A to be a critical mediator of Mst1 activation, the chief component of the mammalian Hippo pathway, in heart failure. In the setting of ischemia/reperfusion (I/R) injury, Mst1 is robustly activated in the heart; however, its regulation remains unclear. Further, the role of Rassf1A in I/R injury has not been investigated. Using genetically modified mice in which expression of Rassf1A is altered in a cell type-specific manner, we demonstrate that systemic deletion of rassf1a (KO) does not alter infarct size (36±4% vs 33±3%) or cardiac myocyte apoptosis (1.7±0.2% vs 2.1±0.4%) following I/R versus WT. Conversely, mice harboring deletion of rassf1a in cardiac myocytes (CKO) have smaller infarcts (38±3% vs 23±2%, p&lt;0.05) and less apoptosis (2.0±0.2% vs 0.9±0.2%) after I/R. Importantly, attenuation of Mst1 activation in ventricular homogenates was observed in both deletion models, implicating Rassf1A as a positive regulator of Mst1 during I/R. Langendorff global I/R injury yielded similar results - no protection in KO, yet significant protection in CKO hearts versus control mice, suggesting that native cardiac cells are sufficient to mediate this response. A candidate molecule screen found exaggerated TNF-α expression in KO hearts compared to WT (4.8±0.7% vs 1.0±0.3%), whereas TNF-α expression was attenuated in CKO hearts (0.9±0.2% vs 0.3±0.1%). Finally, WT and KO mice were administered TNF-α neutralizing or control IgG and subjected to I/R. KO hearts treated with TNF-α Ab, but not IgG, had reduced infarcts (19±4% vs 34±5%), but no significant reduction in infarct size was observed in WT mice given TNF-α Ab. Taken together these data suggest that TNF-α blockade prevents the deleterious consequences of Rassf1A deletion in non-myocytes while unmasking the protective effect of Rassf1A deletion in cardiac myocytes following I/R. Further, these results demonstrate the importance of non-myocytes in modulating cardiac myocyte survival and I/R injury.

Abstract 17228: Rassf1A Inhibits Akt Activation in Cardiac Fibroblasts and Protects Against Ischemia Reperfusion Injury in the Heart

Our previous work demonstrated Rassf1A to be a critical mediator of Mst1 activation, the chief component of the mammalian Hippo pathway, in heart failure. In the setting of ischemia/reperfusion (I/R) injury, Mst1 is robustly activated and promotes injury in the heart; however, its regulation remains unclear. Using genetically modified mice in which expression of Rassf1A is altered in a cell type-specific manner, we demonstrate that systemic deletion of rassf1a -/- (KO) does not alter infarct size (36±4% vs 33±3%) or cardiac myocyte apoptosis (1.7±0.2% vs 2.1±0.4%) following I/R versus WT. Conversely, mice harboring deletion of rassf1a in cardiac myocytes ( rassf1a flox/flox αMHC-Cre, CKO) have smaller infarcts (23±2 vs 38±3%, p&lt;0.05) and less apoptosis (0.9±0.2 vs 2.0±0.2%, p&lt;0.05) after I/R. Importantly, attenuation of Mst1 activation in ventricular homogenates was observed in both deletion models, implicating Rassf1A as a positive regulator of Mst1 during I/R. Langendorff global I/R injury yielded similar results - no protection in KO, yet significant protection in CKO hearts versus control mice, suggesting that native cardiac cells are sufficient to mediate this response. Using isolated cardiac fibroblast cultures we determined that Rassf1A negatively regulates activation of Akt in response to oxidative stress. Further, knockdown of endogenous Rassf1A causes increased NF-κB activity, a response mediated by Akt. A candidate molecule screen found exaggerated TNF-α expression in non-myocytes of KO hearts compared to WT (4.8±0.7fold, p&lt;0.05), whereas TNF-α expression was attenuated in CKO hearts (reduced 65±8% vs control, p&lt;0.05). Finally, WT and KO mice were administered TNF-α neutralizing antibody or control IgG and subjected to I/R. KO hearts treated with TNF-α Ab, but not IgG, had reduced infarcts (19±4% vs 34±5%, p&lt;0.05), but no significant reduction in infarct size was observed in WT mice given TNF-α Ab. Taken together these data suggest that TNF-α blockade prevents the deleterious consequences of Rassf1A deletion in non-myocytes while unmasking the protective effect of Rassf1A deletion in cardiac myocytes following I/R. Further, these results demonstrate the importance of non-myocytes in modulating cardiac myocyte survival and I/R injury

Letter by Madias Regarding Article, “Peripheral Nociception Associated With Surgical Incision Elicits Remote Nonischemic Cardioprotection via Neurogenic Activation of Protein Kinase C Signaling”

HomeCirculationVol. 121, No. 16Letter by Madias Regarding Article, “Peripheral Nociception Associated With Surgical Incision Elicits Remote Nonischemic Cardioprotection via Neurogenic Activation of Protein Kinase C Signaling” Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBLetter by Madias Regarding Article, “Peripheral Nociception Associated With Surgical Incision Elicits Remote Nonischemic Cardioprotection via Neurogenic Activation of Protein Kinase C Signaling” John E. Madias, MD John E. MadiasJohn E. Madias Mount Sinai School of Medicine, New York University, New York, NY Search for more papers by this author Originally published27 Apr 2010https://doi.org/10.1161/CIR.0b013e3181ddf949Circulation. 2010;121:e388To the Editor:The elegant study of Jones et al1 on peripheral nociception-based remote nonischemic preconditioning, published in the September 15, 2009, issue of Circulation, constitutes an advancement in the field of noninvasive cardioprotection for ischemic/reperfusion injury. Not only were the authors able to establish that peripheral skin nociception, resulting from abdominal surgical incision in their murine model and via the axis of neurogenic signaling–bradykinin stimulation of bradykinin 2 receptors–KATP channels, leads to marked reduction in eventual infarct size, but by implementing topical capsaicin in parallel experiments, they also showed that its selective stimulation of skin C sensory fibers leads to equally marked cardioprotection, as could be ascertained from a comparison of Figures 2 and 7 in their article. The authors emphasize that this novel cardioprotective phenomenon is associated with an 80% decrease in infarct size, the largest such beneficial effect described in a murine model. They stress that capsaicin is already approved by the Food and Drug Administration, is used to treat pain, and is devoid of serious adverse effects. Thus, if shown to be effective in humans, this simple therapy has the potential to reduce myocardial injury in the setting of ischemia/reperfusion, thereby reducing the extent and consequences of acute myocardial infarction. However, in reviewing the parallel experiments that these authors have carried out, one cannot overlook that the intervention (either abdominal incision or topical capsaicin application) was implemented before the inception of the 45 minutes of myocardial ischemia and the subsequent reperfusion. Thus, this study design allows the “therapeutic” interventions to qualify as nociception-based remote nonischemic preconditioning, whereas the clinical reality permits only “ischemic and nonischemic postconditioning” implementation for patients who have experienced an acute myocardial infarction. Perhaps the authors could supplement their observations by performing a study in which topical application of capsaicin is implemented after the inception of the 45-minute period of ischemia and during reperfusion; such additional experiments will provide clinical insight into what effects “capsaicin nonischemic postconditioning” could be expected to have in patients with an acute myocardial infarction already in progress before and after reperfusion therapy, by either primary percutaneous coronary intervention or thrombolysis. Whether postconditioning is beneficial in the setting of acute myocardial infarction is still controversial on the basis of animal studies in which very brief periods of coronary ischemic postconditioning in the early phase of reperfusion did not alter the extent of acute myocardial infarction in the rabbit,2 whereas remote postconditioning did reduce the infarct size in the pig.3 The authors could help by contributing in this pivotal area.DisclosuresNone. References 1 Jones WK, Fan GC, Liao S, Zhang JM, Wang Y, Weintraub NL, Kranias EG, Schultz JE, Lorenz J, Ren X. Peripheral nociception associated with surgical incision elicits remote nonischemic cardioprotection via neurogenic activation of protein kinase C signaling. Circulation. 2009; 120 (suppl): S1–S9.LinkGoogle Scholar2 Hale SL, Mehra A, Leeka J, Kloner RA. Postconditioning fails to improve no reflow or alter infarct size in an open-chest rabbit model of myocardial ischemia-reperfusion. Am J Physiol Heart Circ Physiol. 2008; 294: H421–H425.CrossrefMedlineGoogle Scholar3 Andreka G, Vertesaljai M, Szantho G, Font G, Piroth Z, Fontos G, Juhasz ED, Szekely L, Szelid Z, Turner MS, Ashrafian H, Frenneaux MP, Andreka P. Remote ischaemic postconditioning protects the heart during acute myocardial infarction in pigs. Heart. 2007; 93: 749–752.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails April 27, 2010Vol 121, Issue 16 Advertisement Article InformationMetrics https://doi.org/10.1161/CIR.0b013e3181ddf949PMID: 20421525 Originally publishedApril 27, 2010 PDF download Advertisement SubjectsAcute Coronary SyndromesMyocardial Infarction

Isoflurane Postconditioning Protects against Reperfusion Injury by Preventing Mitochondrial Permeability Transition by an Endothelial Nitric Oxide Synthase–dependent Mechanism

The role of endothelial nitric oxide synthase (eNOS) in isoflurane postconditioning (IsoPC)-elicited cardioprotection is poorly understood. The authors addressed this issue using eNOS mice. In vivo or Langendorff-perfused mouse hearts underwent 30 min of ischemia followed by 2 h of reperfusion in the presence and absence of postconditioning produced with isoflurane 5 min before and 3 min after reperfusion. Ca+-induced mitochondrial permeability transition (MPT) pore opening was assessed in isolated mitochondria. Echocardiography was used to evaluate ventricular function. Postconditioning with 0.5, 1.0, and 1.5 minimum alveolar concentrations of isoflurane decreased infarct size from 56 +/- 10% (n = 10) in control to 48 +/- 10%, 41 +/- 8% (n = 8, P < 0.05), and 38 +/- 10% (n = 8, P < 0.05), respectively, and improved cardiac function in wild-type mice. Improvement in cardiac function by IsoPC was blocked by N-nitro-L-arginine methyl ester (a nonselective nitric oxide synthase inhibitor) administered either before ischemia or at the onset of reperfusion. Mitochondria isolated from postconditioned hearts required significantly higher in vitro Ca+ loading than did controls (78 +/- 29 microm vs. 40 +/- 25 microm CaCl2 per milligram of protein, n = 10, P < 0.05) to open the MPT pore. Hearts from eNOS mice displayed no marked differences in infarct size, cardiac function, and sensitivity of MPT pore to Ca+, compared with wild-type hearts. However, IsoPC failed to alter infarct size, cardiac function, or the amount of Ca+ necessary to open the MPT pore in mitochondria isolated from the eNOS hearts compared with control hearts. IsoPC protects mouse hearts from reperfusion injury by preventing MPT pore opening in an eNOS-dependent manner. Nitric oxide functions as both a trigger and a mediator of cardioprotection produced by IsoPC.

Increased cerebral ischemic damage during chronic alcohol consumption: role of NAD(P)H oxidase

We hypothesized that NAD(P)H oxidase may contribute to increased cerebral ischemic damage during chronic alcohol consumption. Sprague‐Dawley rats were randomly divided into four groups: nonalcohol‐fed, alcohol‐fed, nonalcohol‐fed plus apocynin‐treated, and alcohol‐fed plus apocynin‐treated. Alcohol (8 g/kg/day) was mixed into a liquid diet and given to rats for 8 weeks. Apocynin (7.5 mg/kg/day) was orally administrated for 4 weeks prior to the experiment. Rats were subjected to 2 hours of right middle cerebral artery occlusion (MCAO). Infarct volume and neurological score were assessed 24 hours after reperfusion. Superoxide production from ischemic border area was measured by lucigenin‐enhanced chemiluminescence. In addition, expression of NAD(P)H oxidase membrane subunit gp91phox in ischemic border area was analyzed by Western blot. Compared with nonalcohol‐fed rats, alcohol‐fed rats had a larger infarct volume, worse neurological score and higher superoxide production. Apocynin did not alter infarct size, neurological deficit or superoxide production in nonalcohol‐fed rats, but significantly reduced infarct size, improved neurological outcome and attenuated superoxide production in alcohol‐fed rats. Chronic alcohol consumption significantly increased gp91 phox expression compared with nonalcohol‐fed rats, and cerebral ischemia also significantly enhanced gp91 phox expression compared with nonischemic side. Apocynin treatment did not alter gp91 phox expression in either nonalcohol‐fed rats or alcohol‐fed rats. Our findings suggest that NAD(P)H oxidase may play an important role in increased cerebral ischemic damage during chronic alcohol consumption.

Transient Metabolic Alkalosis During Early Reperfusion Abolishes Helium Preconditioning Against Myocardial Infarction: Restoration of Cardioprotection by Cyclosporin A in Rabbits

Intracellular acidosis during early reperfusion after coronary artery occlusion was recently linked to cardioprotection resulting from myocardial ischemic postconditioning. We tested the hypotheses that transient alkalosis during early reperfusion abolishes helium preconditioning and that the mitochondrial permeability transition pore inhibitor cyclosporin A (CsA) restores the cardioprotective effects of helium during alkalosis in vivo. Rabbits (n = 36) instrumented for hemodynamics measurement were subjected to a 30-min left anterior descending coronary artery occlusion and 3-h reperfusion. The rabbits received 0.9% saline (control) or three cycles of 70% helium-30% oxygen administered for 5 min interspersed with 5 min of an air-oxygen mixture before left anterior descending coronary artery occlusion in the absence or presence of transient alkalosis (pH = 7.5) produced by administration of IV sodium bicarbonate (10 mEq) 2 min before reperfusion. Other rabbits preconditioned with helium received CsA (5 mg/kg) in the presence of alkalosis or CsA alone. Helium reduced myocardial infarct size (25% +/- 4% of left ventricular area at risk; P < 0.05) compared with control (44% +/- 6%). Alkalosis during early reperfusion did not alter infarct size alone (46% +/- 2%), but this intervention abolished helium-induced cardioprotection (45% +/- 3%). CsA restored reductions in infarct size produced by helium preconditioning in the presence of alkalosis (28% +/- 6%; P < 0.05 versus control) but did not affect myocardial necrosis alone (43% +/- 6%). The results demonstrate that transient alkalosis during early reperfusion abolishes helium preconditioning in rabbits. CsA restored helium-induced cardioprotection during alkalosis, suggesting that helium preconditioning inhibits mitochondrial permeability transition pore formation by maintaining intracellular acidosis during early reperfusion.

Simvastatin Restores Ischemic Preconditioning in the Presence of Hyperglycemia through a Nitric Oxide–mediated Mechanism

A growing body of evidence indicates that statins decrease perioperative cardiovascular risk and that these drugs may be particularly efficacious in diabetes. Diabetes and hyperglycemia abolish the cardioprotective effects of ischemic preconditioning (IPC). The authors tested the hypothesis that simvastatin restores the beneficial effects of IPC during hyperglycemia through a nitric oxide-mediated mechanism. Myocardial infarct size was measured in dogs (n = 76) subjected to coronary artery occlusion and reperfusion in the presence or absence of hyperglycemia (300 mg/dl) with or without IPC in separate groups. Additional dogs received simvastatin (20 mg orally daily for 3 days) in the presence or absence of IPC and hyperglycemia. Other dogs were pretreated with N-nitro-l-arginine methyl ester (30 mg intracoronary) with or without IPC, hyperglycemia, and simvastatin. Ischemic preconditioning significantly (P < 0.05) reduced infarct size (n = 7, 7 +/- 2%) as compared with control (n = 7, 29 +/- 3%). Hyperglycemia (n = 7), simvastatin (n = 7), N-nitro-l-arginine methyl ester alone (n = 7), and simvastatin with hyperglycemia (n = 6) did not alter infarct size. Hyperglycemia (n = 7, 24 +/- 2%), but not N-nitro-l-arginine methyl ester (n = 5, 10 +/- 1%), blocked the protective effects of IPC. Simvastatin restored the protective effects of IPC in the presence of hyperglycemia (n = 7, 14 +/- 1%), and this beneficial action was blocked by N-nitro-l-arginine methyl ester (n = 7, 29 +/- 4%). The results indicate that simvastatin restored the cardioprotective effects of IPC during hyperglycemia by nitric oxide-mediated signaling. The results also suggest that enhanced cardioprotective signaling could be a mechanism for statin-induced decreases in perioperative cardiovascular risk.

Soluble Epoxide Hydrolase Gene Deletion Is Protective Against Experimental Cerebral Ischemia

Cytochrome P450 epoxygenase metabolizes arachidonic acid to epoxyeicosatrienoic acids (EETs). EETs are produced in the brain and perform important biological functions, including vasodilation and neuroprotection. However, EETs are rapidly metabolized via soluble epoxide hydrolase (sEH) to dihydroxyeicosatrienoic acids (DHETs). We tested the hypothesis that sEH gene deletion is protective against focal cerebral ischemia through enhanced collateral blood flow. sEH knockout (sEHKO) mice with and without EETs antagonist 14, 15 epoxyeicosa-5(Z)-enoic acid (EEZE) were subjected to 2-hour middle cerebral artery occlusion (MCAO), and infarct size was measured at 24 hours of reperfusion and compared to wild-type (WT) mice. Local CBF rates were measured at the end of MCAO using iodoantipyrine (IAP) autoradiography, sEH protein was analyzed by Western blot and immunohistochemistry, and hydrolase activity and levels of EETs/DHETs were measured in brain and plasma using LC-MS/MS and ELISA, respectively. sEH immunoreactivity was detected in WT, but not sEHKO mouse brain, and was localized to vascular and nonvascular cells. 14,15-DHET was abundantly present in WT, but virtually absent in sEHKO mouse plasma. However, hydrolase activity and free 14,15-EET in brain tissue were not different between WT and sEHKO mice. Infarct size was significantly smaller, whereas regional cerebral blood flow rates were significantly higher in sEHKO compared to WT mice. Infarct size reduction was recapitulated by 14,15-EET infusion. However, 14,15-EEZE did not alter infarct size in sEHKO mice. sEH gene deletion is protective against ischemic stroke by a vascular mechanism linked to reduced hydration of circulating EETs.