Participation of bradykinin, cannabinoid, and vanilloid receptors in the infarct-limiting effect of adaptation to normobaric hypoxia

Известно, что при хронической умеренной гипоксии формируется неспецифическая резистентность миокарда к повреждению при ишемии и следующей за ней реперфузии. Однако рецепторные механизмы формирования подобной устойчивости исследованы недостаточно. Цель исследования - изучение участия брадикининовых, каннабиноидных и ванилоидных рецепторов (TRPV1-каналов) в реализации инфаркт-лимитирующего эффекта хронической нормобарической гипоксии. Методика. Исследование выполнено на самцах крыс Вистар адаптированных к гипоксии, для чего животных подвергали непрерывной нормобарической гипоксии (ННГ) в течение 21 сут при 12% pO2, 0,3% pCO2. У крыс воспроизводили коронароокклюзию наложением лигатуры на левую нисходящую коронарную артерию в ее верхней трети на 45 мин. Реперфузию осуществляли путем освобождения лигатуры с визуальным контролем возобновления коронарного кровообращения по гиперемии ишемизированной области. Продолжительность реперфузии 2 ч. Для выявления зоны риска лигатуру вновь затягивали и в аорту вводили 5%-й раствор перманганата калия. Участок миокарда, не подвергшийся ишемии, окрашивался, неокрашенный участок являлся зоной риска. Срезы левого желудочка толщиной 2 мм окрашивали 1% раствором 2,3,5-трифенилтетразолия (37 °С, 30 мин). Размер зоны некроза и зоны риска определяли планиметрически с помощью программы Ellipse 2.02 (ViDiTo, Чешская республика). Для ингибирования каннабиноидных СВ1-рецепторов и СВ2-рецепторов использовали соответственно их селективные антагонисты римонабант (1 мг/кг) и AM630 (2,5 мг/кг); селективный антагонист HOE140 (50 мкг/кг) применяли для инактивации брадикининовых B2-рецепторов, капсазепин (3 мг/кг) - ванилоидных рецепторов (TRPV1-каналов). Все антагонисты вводили за 15 мин до коронароокклюзии. Результаты. Показано, что размер некротического повреждения миокарда у крыс адаптированных к гипоксии составляет 33% процента от размера зоны риска (53% у неадаптированных), что свидетельствует о выраженном инфаркт-лимитирующем эффекте. Этот эффект не проявлялся при ингибировании B2-брадикинировых рецепторов. Блокада каннабиноидных или ванилоидных рецепторов не влияла на инфаркт-лимитирующее действие ННГ. Следовательно, инфаркт-лимитирующий эффект ННГ зависит от активации брадикининовых B2-рецепторов, адаптационное повышение толерантности сердца к ишемии/реперфузии не зависит от каннабиноидных или ванилоидных рецепторов. Заключение. Брадикининовые рецепторы можно рассматривать в качестве одного из ключевых механизмов формирования инфаркт-лимитирующего действия ННГ. Учитывая данные о важной роли опиоидных рецепторов в кардиопротекции при ННГ, можно говорить о реализации инфаркт-лимитирующего эффекта хронической гипоксии через Gi/o-протеин-сопряженные опиоидные и брадикининовые рецепторы. Каннабиноидные рецепторы и TRPV1-каналы не участвуют в инфаркт-лимитирующем действии адаптации к нормобарической гипоксии. Aim. Chronic moderate hypoxia is known to induce nonspecific myocardial resistance to ischemia-reperfusion injury. However, receptor-mediated mechanisms of this resistance are understudied. The aim of this study was to investigate the involvement of bradykinin, cannabinoid, and vanilloid (TRPV1 channel) receptors in development of the infarction-limiting effect of chronic normobaric hypoxia (CNH). Methods. The study was performed on male Wistar rats exposed to CNH at 12% pO2 and 0.3% pCO2 for 21 days. Coronary occlusion was induced by ligation of the left descending coronary artery at the upper third of the artery for 45 min, which was followed by 2-h reperfusion produced by releasing the ligature under visual control of the recovery of coronary blood flow by hyperemia of the ischemic area. For detection of the area at risk, the ligature was tightened again, and 5% potassium permanganate solution was infused into the aorta to stain the nonischemic myocardial area. 2-mm sections of the left ventricle were stained with 1% solution of 2,3,4-triphenyl tetrazolium (37 oC, 30 min). Necrotic area and area at risk were measured planimetrically with the tEllipse 2.02 (ViDiTo, Czech Republic) software. Cannabinoid CB1 and CB2 receptors were inhibited with their respective antagonists, rimonabant (1 mg/kg) and AM630 (2.5 mg/kg); bradykinin B2 receptors were inactivated with the selective antagonist HOE140 (50 μg/kg); and vanilloid receptors (TRPV1 channels) were inhibited with capsazepine (3 mg/kg). All antagonists were administered 15 minutes prior to coronary occlusion. Results. The size of necrotic area was 33% of the area at risk in rats adapted to hypoxia vs. 53% in non-adapted rats. This infarct-limiting effect of adaptation to hypoxia was abolished by inhibition of B2-bradykinin receptors. Blockade of cannabinoid or vanilloid receptors did not change the infarct-limiting effect of CNH. Therefore, the infarction-limiting effect of CNH depends on activation of bradykinin B2 receptors but not of cannabinoid or vanilloid receptors. Conclusion. Activation of bradykinin receptors can be considered a key mechanism of the infarct-limiting effect of CNH. Since opioid receptors are known to play an important role in CNH cardioprotection, the infarct-limiting effect of CNH may be mediated by Gi/o-coupled opioid and bradykinin receptors. Cannabinoid receptors and TRV1-channels do not contribute to the infarct-limiting effect of adaptation to normobaric hypoxia.

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Effects of Endotoxin on Neutrophil-Mediated Ischemia/Reperfusion Injury in the Rat Heart In Vivo

Experimental Biology and Medicine ◽

10.1177/153537020122600409 ◽

2001 ◽

Vol 226 (4) ◽

pp. 320-327 ◽

Cited By ~ 8

Author(s):

Brian P. Lipton ◽

Joseph B. Delcarpio ◽

Kathleen H. McDonough

Keyword(s):

At Risk ◽

Reperfusion Injury ◽

Ischemia Reperfusion Injury ◽

Isolated Heart ◽

Ischemia Reperfusion ◽

Left Ventricular ◽

Necrotic Area ◽

Area At Risk

We have previously shown that a nonlethal dose of lipopolysaccharide (LPS) decreases L-selectin expression of neutrophils (PMNs), thereby preventing PMN-mediated reperfusion injury in the isolated heart. In the present study we determined whether or not that dose of LPS would protect hearts during in vivo ischemia and reperfusion by preventing PMN-induced reperfusion injury. Rats receiving saline vehicle showed marked myocardial injury (necrotic area/area at risk = 82% ± 2%) and significant depression in left ventricular function as assessed in the isolated isovolumic heart preparation at constant flow rates of 5, 10, 15, and 20 ml/min. The administration of LPS (100 μg/kg body wt) 7 hr prior to ischemia resulted in a reduction in myocardial damage (necrotic area/area at risk = 42% ± 3%) and preservation of function. Myocardial function was similar to that of sham ischemic saline- and LPS-treated rats. Moreover, PMN infiltration as determined by histology was quantitatively more severe in hearts of saline-treated rats than in hearts of LPS-treated rats. Isolated hearts from vehicle- and LPS-treated animals undergoing sham ischemia in vivo recovered to the same extent after in vitro ischemia/reperfusion, suggesting that LPS did not induce protection by altering intrinsic properties of the heart. Our results indicate that LPS-induced protection of the heart from in vivo PMN-mediated ischemia/reperfusion injury may be due to decreased L-selectin expression of PMNs in LPS-treated animals.

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Abstract 212: Cd4+ T-cell Activation By T-cell Receptor Engagement Contributes To Myocardial Ischemia-reperfusion Injury

Circulation Research ◽

10.1161/res.113.suppl_1.a212 ◽

2013 ◽

Vol 113 (suppl_1) ◽

Author(s):

Ulrich Hofmann ◽

Denise Mathes ◽

Johannes Weirather ◽

Niklas Beyersdorf ◽

Thomas Kerkau ◽

...

Keyword(s):

At Risk ◽

T Cells ◽

T Cell ◽

Infarct Size ◽

T Cell Receptor ◽

Ischemia Reperfusion Injury ◽

Ischemia Reperfusion ◽

Cell Receptor ◽

Area At Risk ◽

Infarct Area

Background: We have recently shown that CD4 + but not CD8 + T-cells contribute to ischemia-reperfusion injury of the myocardium. We therefore hypothesized that CD4 + T-cells become activated by autoantigen recognition via their T-cell receptor during reperfusion. Methods and Results: Infarct size as percent of the area-at-risk was determined by combined Evans` blue and triphenyltetrazolium (TTC) staining after 30 minutes of in vivo ischemia followed by 24 hours reperfusion in mice. After 24 hours of reperfusion there was a significantly increased population of CD4 + T-cells which expressed the surface protein CD40L in comparison to sham operated mice [n≥7; p<0.05; WT 10.8 ± 0.2% vs. sham 6.4 ± 0.5%]. CD40L is typically expressed in T-cells activated by T-cell receptor engagement. OT-II mice carry a transgenic T-cell receptor with specificity for an ovalbumin-derived peptide. These mice have a limited T-cell receptor repertoire, dominated by specificity for the irrelevant antigen ovalbumin. After 30 minutes of ischemia and 24 hours of reperfusion OT-II mice showed significantly reduction in infarct size [n≥4; p= 0.02; infarct/area at risk: OTII mice 38.9 ± 2.4% vs. WT mice 63.7 ± 6.6 % ]. Administration of a CD40L blocking antibody to wildtype mice also reduced infarct size when compared to administration of isotype-matched antibodies [n≥6; p = 0.03; infarct/ area at risk: anti-CD154 treatment 60.4 ± 3.4% vs. control 75.3 ± 4.1%]. CD4 + CD25 + Foxp3 + T-cells (natural T-regulatory cells) have a low activation threshold and constitute a T-cell subset with reactivity against autoantigens. Depletion of these cells by diphtheria-toxin application in a mouse model expressing the diphtheria-toxin receptor under the Foxp3 promotor also resulted in a significant reduction of infarct size when compared to diphtheria-toxin treated wildtype mice [n≥4; p=0.03; infarct/ area at risk: T reg -depleted DEREG mice 51.9± 3% vs. WT littermates 72.3± 2%]. Conclusion: Our results indicate that CD4 + T-cells that have been activated by an MHC class II/ T-cell receptor dependent mechanism, presumably by autoantigen recognition, contribute to myocardial ischemia-reperfusion injury.

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Beneficial effects of SPM-5185, a cysteine-containing NO donor in myocardial ischemia-reperfusion

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1992.263.3.h771 ◽

1992 ◽

Vol 263 (3) ◽

pp. H771-H777 ◽

Cited By ~ 4

Author(s):

M. R. Siegfried ◽

C. Carey ◽

X. L. Ma ◽

A. M. Lefer

Keyword(s):

At Risk ◽

Endothelial Dysfunction ◽

Myocardial Ischemia ◽

Ethyl Ester ◽

Ischemia Reperfusion ◽

Myocardial Oxygen Demand ◽

Area At Risk ◽

No Donor ◽

Beneficial Effects ◽

Myocardial Ischemia Reperfusion

Intravenous administration of SPM-5185 [N-nitratopivaloyl-S-(N–-acetylalanyl)-cysteine ethyl ester], a cysteine-containing nitric oxide (NO) donor, or SPM-5267 [pivaloyl-S-(N–-acetylalanyl)-cysteine ethyl ester], an analogue of SPM-5185 that lacks the NO moiety, was studied in a feline myocardial ischemia-reperfusion model. Administration of SPM-5185 (1 mg/kg), followed by a 2-mg.kg-1.h-1 infusion starting 10 min before reperfusion, resulted in significant protection 4.5 h postreperfusion. In the myocardial ischemia (MI)+SPM-5267 group, 38 +/- 4% of the area at risk was necrotic, whereas the necrotic area/area at risk was only 7 +/- 2% in the MI+SPM-5185 group (P less than 0.01). Moreover, SPM-5185 treatment markedly attenuated the endothelial dysfunction observed in the left anterior descending coronary artery after reperfusion by 50%. These beneficial effects occurred despite the absence of a significant change in myocardial oxygen demand, as measured by the pressure-rate index. In vitro experiments demonstrated that SMP-5185, but not SPM-5267, decreased adherence of neutrophils to the coronary vascular endothelium and decreased production of superoxide radicals. Therefore, a likely mechanism of the observed cardioprotection by SPM-5185 involves attenuation of polymorphonuclear leukocyte-induced endothelial dysfunction.

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Mechanisms of Isoflurane-induced Myocardial Preconditioning in Rabbits

Anesthesiology ◽

10.1097/00000542-199903000-00024 ◽

1999 ◽

Vol 90 (3) ◽

pp. 812-821 ◽

Cited By ~ 50

Author(s):

Mohamed S. Ismaeil ◽

Igor Tkachenko ◽

Kurt A. Gamperl ◽

Robert F. Hickey ◽

Brian A. Cason

Keyword(s):

At Risk ◽

Potassium Channels ◽

Infarct Size ◽

Adenosine Triphosphate ◽

Ischemic Preconditioning ◽

Adenosine Receptors ◽

Coronary Occlusion ◽

Myocardial Infarct ◽

Myocardial Infarct Size ◽

Area At Risk

Background Isoflurane has cardioprotective effects that mimic the ischemic preconditioning phenomenon. Because adenosine triphosphate-sensitive potassium channels and adenosine receptors are implicated in ischemic preconditioning, the authors wanted to determine whether the preconditioning effect of isoflurane is mediated through these pathways. Methods Myocardial infarct size was measured in seven groups of propofol-anesthetized rabbits, each subjected to 30 min of anterolateral coronary occlusion followed by 3 h of reperfusion. Groups differed only in the pretreatments given, and controls received no pretreatment. An ischemia-preconditioned group was pretreated with 5 min of coronary occlusion and 15 min of reperfusion. An isoflurane-preconditioned group was pretreated with 15 min end-tidal isoflurane, 1.1%, and then 15 min of washout. An isoflurane-plus-glyburide group was administered 0.33 mg/kg glyburide intravenously before isoflurane pretreatment. An isoflurane plus 8-(p-sulfophenyl)-theophylline (SPT) group received 7.5 mg/kg SPT intravenously before isoflurane. Additional groups were administered identical doses of glyburide or SPT, but they were not pretreated with isoflurane. Infarct size and area at risk were defined by staining. Data were analyzed by analysis of variance or covariance. Results Infarct size, expressed as a percentage of the area at risk (IS:AR) was 30.2+/-11% (SD) in controls. Ischemic preconditioning and isoflurane preexposure reduced myocardial infarct size significantly, to 8.3+/-5% and 13.4+/-8.2% (P<0.05), respectively. Both glyburide and SPT pretreatment eliminated the preconditioning-like effect of isoflurane (IS:AR = 30.0+/-9.1% and 29.2+/-12.6%, respectively; P = not significant). Neither glyburide nor SPF alone increased infarct size (IS:AR = 33.9+/-7.6% and 31.8+/-12.7%, respectively; P = not significant). Conclusions Glyburide and SPT abolished the preconditioning-like effects of isoflurane but did not increase infarct size when administered in the absence of isoflurane. Isoflurane-induced preconditioning and ischemia-induced preconditioning share similar mechanisms, which include activation of adenosine triphosphate-sensitive potassium channels and adenosine receptors.

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Contrast echocardiography in acute myocardial ischemia. II. The effect of site of injection of contrast agent on the estimation of area at risk for necrosis after coronary occlusion

Journal of the American College of Cardiology ◽

10.1016/s0735-1097(85)80490-3 ◽

1985 ◽

Vol 6 (4) ◽

pp. 825-830 ◽

Cited By ~ 59

Author(s):

Sanjiv Kaul ◽

Linda D. Gillam ◽

Arthur E. Weyman

Keyword(s):

At Risk ◽

Myocardial Ischemia ◽

Contrast Agent ◽

Coronary Occlusion ◽

Contrast Echocardiography ◽

Acute Myocardial Ischemia ◽

Area At Risk

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Anesthetic-induced Preconditioning

Anesthesiology ◽

10.1097/00000542-199711000-00023 ◽

1997 ◽

Vol 87 (5) ◽

pp. 1182-1190 ◽

Cited By ~ 155

Author(s):

Brian A. Cason ◽

A. Kurt Gamperl ◽

Robert E. Slocum ◽

Robert F. Hickey

Keyword(s):

At Risk ◽

Myocardial Ischemia ◽

Infarct Size ◽

Ischemic Preconditioning ◽

Coronary Occlusion ◽

Myocardial Infarct ◽

Group Analysis ◽

Myocardial Infarct Size ◽

Area At Risk ◽

Myocardial Preconditioning

Background Experimental evidence suggests that ATP-sensitive potassium channels are involved in myocardial ischemic preconditioning. Because some pharmacologic effects of isoflurane are mediated by K(ATP) channels, the authors tested the hypothesis: Isoflurane administration, before myocardial ischemia, can induce or mimic myocardial preconditioning. Methods Myocardial infarct size was measured in three groups of propofol-anesthetized rabbits, each subjected to 30 min of anterolateral coronary occlusion followed by 3 h of reperfusion. Groups differed in their pretreatment: Group 1 (control, N = 13) no pretreatment, Group 2 (ischemic preconditioning, N = 8), 5 min of coronary occlusion and 15 min of reperfusion; Group 3 (isoflurane pretreatment; N = 15), 15 min of isoflurane (1.1% end-tidal) and 15 min of washout. Hemodynamics were monitored serially. Myocardial infarct size and the area at risk were defined using triphenyltetrazolium chloride staining and fluorescent microspheres, respectively, and both were measured using computerized planimetry. Results Infarct size expressed as a percentage of area at risk was 23.4 +/- 8.5% (mean +/- SD) in the isoflurane group compared with 33.1 +/- 13.3% in controls, and 8.7 +/- 6.2% in the ischemia-preconditioned group. Analysis for coincidental regressions, followed by tests for equality of slope and elevation, showed that the linear relationship between infarct size and area at risk was significantly (P < 0.05) different in all three groups because of differences in line elevation. Minor differences in hemodynamic variables were found between groups, which were unlikely to account for the significant differences in infarct size. Conclusion Preadministration of isoflurane, before myocardial ischemia, reduces myocardial infarct size, and mimics myocardial preconditioning.

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Prevention of Isoflurane-induced Preconditioning by 5-Hydroxydecanoate and Gadolinium

Anesthesiology ◽

10.1097/00000542-200009000-00025 ◽

2000 ◽

Vol 93 (3) ◽

pp. 756-764 ◽

Cited By ~ 55

Author(s):

Vincent Piriou ◽

Pascal Chiari ◽

Sandra Knezynski ◽

Olivier Bastien ◽

Joseph Loufoua ◽

...

Keyword(s):

At Risk ◽

Infarct Size ◽

Ischemic Preconditioning ◽

Coronary Occlusion ◽

Protective Mechanism ◽

Area At Risk ◽

Tetrazolium Chloride ◽

Risk Zone ◽

Isoflurane Group ◽

Stretch Activated Channels

Background Both mitochondrial adenosine triphosphate-sensitive potassium (MKATP) channels (selectively blocked by 5-hydroxydecanoate) and stretch-activated channels (blocked by gadolinium) have been involved in the mechanism of ischemic preconditioning. Isoflurane can reproduce the protection afforded by ischemic preconditioning. We sought to determine whether isoflurane-induced preconditioning may involve MKATP and stretch-activated channels. Methods Anesthetized open-chest rabbits underwent 30 min of coronary occlusion followed by 3 h of reperfusion. Before this, rabbits were randomized into one of six groups and underwent a treatment period consisting of either no intervention for 40 min (control group; n = 9) or 15 min of isoflurane inhalation (1.1% end tidal) followed by a 15-min washout period (isoflurane group; n = 9). The two groups received an intravenous bolus dose of either 5-hydroxydecanoate (5 mg/kg) or gadolinium (40 micromol/kg) before coronary occlusion and reperfusion (5-hydroxydecanoate, n = 9; gadolinium, n = 7). Two additional groups received 5-hydroxydecanoate or gadolinium before isoflurane exposure (isoflurane-5-hydroxydecanoate, n = 10; isoflurane-gadolinium, n = 8). Area at risk and infarct size were assessed by blue dye injection and tetrazolium chloride staining. Results Area at risk was comparable among the six groups (29 +/- 7, 30 +/- 5, 27 +/- 6, 35 +/- 7, 31 +/- 7, and 27 +/- 4% of the left ventricle in the control, isoflurane, isoflurane-5-hydroxydecanoate, 5-hydroxydecanoate, isoflurane-gadolinium, and gadolinium groups, respectively). Infarct size averaged 60 +/- 20% (SD) in untreated controls versus 54 +/- 27 and 65 +/- 15% of the risk zone in 5-hydroxydecanoate- and gadolinium-treated controls (P = nonsignificant). In contrast, infarct size in the isoflurane group was significantly reduced to 26 +/- 11% of the risk zone (P < 0.05 vs.control). Both 5-hydroxydecanoate and gadolinium prevented this attenuation: infarct size averaged 68 +/- 23 and 56 +/- 21% of risk zone in the isoflurane-5-hydroxydecanoate and isoflurane-gadolinium groups, respectively (P = nonsignificant vs.control). Conclusion 5-Hydroxydecanoate and gadolinium inhibited pharmacologic preconditioning by isoflurane. This result suggests that MKATP channels and mechanogated channels are probably involved in this protective mechanism.

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Deletion of the Semaphorin, Sema4D, but Not Inhibition of Sema4D Shedding by ADAM17, Impairs Platelet Function and Reduces Infarct Size After Myocardial Ischemia.

Blood ◽

10.1182/blood.v114.22.771.771 ◽

2009 ◽

Vol 114 (22) ◽

pp. 771-771

Author(s):

Li Zhu ◽

Tao Wang ◽

Hong Jiang ◽

Timothy J. Stalker ◽

Karen P. Fong ◽

...

Keyword(s):

At Risk ◽

T Cells ◽

Endothelial Cells ◽

Reperfusion Injury ◽

Platelet Function ◽

Ischemia Reperfusion Injury ◽

Fetal Liver ◽

Ischemia Reperfusion ◽

Area At Risk ◽

Fetal Liver Cells

Abstract Abstract 771 Introduction. Platelets are activated early during the reperfusion of ischemic myocardium, potentially exacerbating the extent of ischemia/reperfusion (I/R) injury. We have recently shown (Zhu, et al., PNAS 2007) that platelets express the semaphorin family member, sema4D, as do T-cells. Sema4D is a cell surface protein whose receptors are expressed by B-cells, monocytes and endothelial cells as well as platelets. Loss of sema4D expression in mice causes a defect in signaling downstream of the platelet collagen receptor, glycoprotein (GP) VI, inhibiting platelet function in vitro and in vivo, and reducing the extent of platelet hyperresponsiveness and atherothrombosis in the setting of dyslipidemia (Zhu, et al. ATVB 2009). Because of the role played by platelets, leukocytes and endothelial cells in reperfusion injury, here we asked whether loss of sema4D expression can also protect the heart, reducing the extent of damage following temporary ischemia. Methods. The left anterior descending coronary artery of anaesthetized mice was ligated for 45 min. After reperfusion for 48 hours, the mice were re-anesthetized and perfused with 2,3,5-triphenyltetrazolium chloride to measure the area of infarction. Fluorescent microspheres were used to delineate the area at risk. Comparisons were made between sema4D(−/−) and wild type mice produced by breeding sema4D(+/−) heterozygotes. Results. Although there was no difference between the sema4D(−/−) and WT mice with respect to either heart size or area at risk, we observed a substantial (57%) decrease in infarct size in the sema4D(−/−) mice expressed as a fraction of the area at risk (N=7-9, p<0.005). Since sema4D is shed from the surface of activated platelets and T-cells by the metalloprotease, ADAM17, producing a large bioactive fragment, we next asked whether the protection against ischemia/reperfusion injury conferred by the sema4D knockout is due to the loss of cell-associated or soluble sema4D. Chimeric mice were produced in which hematopoiesis was reconstituted in irradiated sema4D(+/+) mice using fetal liver cells from mouse embryos that lack functional ADAM17. This produces mice in which sema4D is expressed as usual in the hematopoietic lineages, but unable to be shed. Chimerism, inhibition of sema4D shedding and recovery of normal cell counts were confirmed after transplantation. The ischemia/reperfusion studies were repeated comparing chimeras reconstituted with ADAM17-deficient and ADAM17-replete fetal liver cells. In contrast to the sema4D knockout, the extent of infarction was the same whether or not ADAM17 was functional and sema4D was shed. Conclusions. Although the role of sema4D and its receptors have been studied most extensively in the context of T-cell interactions with B-cells, our previous studies have made a case for the involvement of sema4D in platelet:platelet and platelet:endothelial cell interactions. We now show for the first time that 1) loss of sema4D expression in mice confers protection against ischemia/reperfusion injury in the myocardium, and 2) preventing the formation of soluble, bioactive sema4D is insufficient to recapitulate this effect. Since sema4D and its receptors are expressed on more than just platelets, it cannot be concluded that the observed protection in the knockout is solely due to the absence of platelet sema4D. However, experience with other knockouts that reduce platelet function suggests that the defects that we have observed in sema4D(−/−) platelet function are likely to contribute. Regardless of whether expression on platelets is entirely or only partly responsible for the observed phenotype, sema4D is an interesting target for therapeutic intervention. Disclosures: No relevant conflicts of interest to declare.

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CRYAB and HSPB2 deficiency alters cardiac metabolism and paradoxically confers protection against myocardial ischemia in aging mice

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01363.2006 ◽

2007 ◽

Vol 293 (5) ◽

pp. H3201-H3209 ◽

Cited By ~ 35

Author(s):

Ivor J. Benjamin ◽

Yiru Guo ◽

Sathyanarayanan Srinivasan ◽

Sihem Boudina ◽

Ryan P. Taylor ◽

...

Keyword(s):

At Risk ◽

Infarct Size ◽

Ischemic Preconditioning ◽

Coronary Occlusion ◽

Ex Vivo ◽

Double Knockout ◽

Area At Risk ◽

Small Molecular Weight ◽

Calcium Dependent

The abundantly expressed small molecular weight proteins, CRYAB and HSPB2, have been implicated in cardioprotection ex vivo. However, the biological roles of CRYAB/HSPB2 coexpression for either ischemic preconditioning and/or protection in situ remain poorly defined. Wild-type (WT) and age-matched (∼5–9 mo) CRYAB/HSPB2 double knockout (DKO) mice were subjected either to 30 min of coronary occlusion and 24 h of reperfusion in situ or preconditioned with a 4-min coronary occlusion/4-min reperfusion × 6, before similar ischemic challenge (ischemic preconditioning). Additionally, WT and DKO mice were subjected to 30 min of global ischemia in isolated hearts ex vivo. All experimental groups were assessed for area at risk and infarct size. Mitochondrial respiration was analyzed in isolated permeabilized cardiac skinned fibers. As a result, DKO mice modestly altered heat shock protein expression. Surprisingly, infarct size in situ was reduced by 35% in hearts of DKO compared with WT mice (38.8 ± 17.9 vs. 59.8 ± 10.6% area at risk, P < 0.05). In DKO mice, ischemic preconditioning was additive to its infarct-sparing phenotype. Similarly, infarct size after ischemia and reperfusion ex vivo was decreased and the production of superoxide and creatine kinase release was decreased in DKO compared with WT mice ( P < 0.05). In permeabilized fibers, ADP-stimulated respiration rates were modestly reduced and calcium-dependent ATP synthesis was abrogated in DKO compared with WT mice. In conclusion, contrary to expectation, our findings demonstrate that CRYAB and HSPB2 deficiency induces profound adaptations that are related to 1) a reduction in calcium-dependent metabolism/respiration, including ATP production, and 2) decreased superoxide production during reperfusion. We discuss the implications of these disparate results in the context of phenotypic responses reported for CRYAB/HSPB2-deficient mice to different ischemic challenges.

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