Transient mitochondrial permeability transition pore opening mediates preconditioning-induced protection

Background - Transient (low-conductance) opening of the mitochondrial permeability transition pore (mPTP) may limit mitochondrial calcium load and mediate mitochondrial reactive oxygen species (ROS) signaling. We hypothesize that transient mPTP opening and ROS mediate the protection associated with myocardial preconditioning and mitochondrial uncoupling.Methods and Results - Isolated perfused rat hearts were subjected to 35 minutes of ischemia/ 120 minutes of reperfusion, and the infarct-risk-volume ratio was determined by tetrazolium staining. Inhibiting mPTP opening during the preconditioning phase with cyclosporine-A (CsA, 0.2 mumol/L) or sanglifehrin-A (SfA, 1.0 mumol/L) abolished the protection associated with ischemic preconditioning (IPC) ( 20.2 +/- 3.6% versus 45.9 +/- 2.5% with CsA, 49.0 +/- 7.1% with SfA; P < 0.001); and pharmacological preconditioning with diazoxide (Dzx, 30 mu mol/L) (22.1 +/- 2.7% versus 46.3 +/- 3.0% with CsA, 48.4 +/- 5.5% with SfA; P < 0.001), CCPA ( the adenosine A1-receptor agonist, 200 nmol/L) (24.9 +/- 4.5% versus 54.4 +/- 6.6% with CsA, 42.6 +/- 9.0% with SfA; P < 0.001), or 2,4-dinitrophenol (DNP, the mitochondrial uncoupler, 50 mu mol/L) (15.7 +/- 2.7% versus 40.8 +/- 5.5% with CsA, 34.3 +/- 3.1% with SfA; P < 0.001), suggesting that mPTP opening during the preconditioning phase is required to mediate protection in these settings. Inhibiting ROS during the preconditioning protocols with N-mercaptopropionylglycine (MPG, 1 mmol/L) also abolished the protection associated with IPC (20.2 +/- 3.6% versus 47.1 +/- 3.8% with MPG; P < 0.001), diazoxide (22.1 +/- 2.7% versus 56.3 +/- 3.8% with MPG; P < 0.001), and DNP (15.7 +/- 2.7% versus 50.7 +/- 6.6% with MPG; P < 0.001) but not CCPA (24.9 +/- 4.5% versus 26.5 +/- 8.4% with MPG; P = NS). Further experiments in adult rat myocytes demonstrated that diazoxide induced CsA-sensitive, low-conductance transient mPTP opening (represented by a 28 +/- 3% reduction in mitochondrial calcein fluorescence compared with control; P < 0.01).Conclusions - We report that the protection associated with IPC, diazoxide, and mitochondrial uncoupling requires transient mPTP opening and ROS

Ischaemic injuries

Professor Derek Yellon and Dr Sean Davidson discuss their research on preventing injury to the heart from ischaemia-reperfusion and the potentially protective role of exosome

Cardio-oncology Issues in Lymphoma Patients

Advances in Lymphoma management have resulted in significant improvements in patient outcomes over the last 50 years. Despite these developments, cardiotoxicity from lymphoma treatments remains an important cause of mortality and morbidity in this cohort of patients. We outlined the most common cardiotoxicities associated with lymphoma treatments and their respective investigation and management strategies, including the role of cardiac pre-assessment and late effects monitoring

Comparison of small extracellular vesicles isolated from plasma by ultracentrifugation or size-exclusion chromatography: yield, purity and functional potential

Interest in small extracellular vesicles (sEVs) as functional carriers of proteins and nucleic acids is growing continuously. There are large numbers of sEVs in the blood, but lack of standardised methods for sEV isolation greatly limits our ability to study them. In this report, we use rat plasma to systematically compare two commonly used techniques for isolation of sEVs: ultracentrifugation (UC-sEVs) and size-exclusion chromatography (SEC-sEVs). SEC-sEVs had higher particle number, protein content, particle/protein ratios and sEV marker signal than UC-sEVs. However, SEC-sEVs also contained greater amounts of APOB+ lipoproteins and large quantities of non-sEV protein. sEV marker signal correlated very well with both particle number and protein content in UC-sEVs but not in all of the SEC-sEV fractions. Functionally, both UC-sEVs and SEC-sEVs isolates contained a variety of proangiogenic factors (with endothelin-1 being the most abundant) and stimulated migration of endothelial cells. However, there was no evident correlation between the promigratory potential and the quantity of sEVs added, indicating that non-vesicular co-isolates may contribute to the promigratory effects. Overall, our findings suggest that UC provides plasma sEVs of lower yields, but markedly higher purity compared to SEC. Furthermore, we show that the functional activity of sEVs can depend on the isolation method used and does not solely reflect the sEV quantity. These findings are of importance when working with sEVs isolated from plasma- or serum-containing conditioned medium

Remote ischemic preconditioning (RIPC) protects against endothelial dysfunction in a human model of systemic inflammation: a randomized clinical trial

Objective: Inflammation, oxidative stress, and endothelial dysfunction are known to contribute to ischemia-reperfusion injury. Remote ischemic preconditioning (RIPC) protects from endothelial dysfunction and the damage induced by ischemia-reperfusion. Using intensive periodontal treatment (IPT), an established human model of acute systemic inflammation, we investigated whether RIPC prevents endothelial dysfunction and modulates systemic levels of inflammation and oxidative stress. Approach and Results: Forty-nine participants with periodontitis were randomly allocated to receive either 3 cycles of ischemia-reperfusion on the upper limb (N=24, RIPC) or a sham procedure (N=25, control) before IPT. Endothelial function assessed by flow-mediated dilatation of the brachial artery, inflammatory cytokines, markers of vascular injury, and oxidative stress were evaluated at baseline, day 1, and day 7 after IPT. Twenty-four hours post-IPT, the RIPC group had lower levels of IL-10 (interleukin-10) and IL-12 (interleukin-12) compared with the control group (P<0.05). RIPC attenuated the IPT-induced increase in IL-1β (interleukin-1β), E-selectin, sICAM-3 (soluble intercellular adhesion molecule 3), and sTM (soluble thrombomodulin) levels between the baseline and day 1 (P for interaction <0.1). Conversely, oxidative stress was differentially increased at day1 in the RIPC group compared with the control group (P for interaction <0.1). This was accompanied by a better flow-mediated dilatation (mean difference 1.75% [95% CI, 0.428–3.07], P=0.011). After 7 days from IPT, most of the inflammatory markers, endothelial-dependent and -independent vasodilation, were similar between groups. Conclusions: RIPC prevented acute endothelial dysfunction by modulation of inflammation and oxidation processes in patients with periodontitis following exposure to an acute inflammatory stimulus

Wake Up and Smell the Coffee: Yet Another No Go for Cardiac Patients?: Editorial to “Caffeinated Coffee Blunts the Myocardial Protective Effects of Statins Against Ischemia–reperfusion Injury in the Rat” by Ye et al.

Contains fulltext : 69414.pdf (publisher's version ) (Closed access

Cardioprotection mediated by exosomes is impaired in the setting of type II diabetes but can be rescued by the use of non-diabetic exosomes in vitro

Many patients with ischaemic heart disease also have diabetes. As myocardial infarction is a major cause of mortality and morbidity in these patients, treatments that increase cell survival in response to ischaemia and reperfusion are needed. Exosomes-nano-sized, lipid vesicles released from cells-can protect the hearts of non-diabetic rats. We previously showed that exosomal HSP70 activates a cardioprotective signalling pathway in cardiomyocytes culminating in ERK1/2 and HSP27 phosphorylation. Here, we investigated whether the exosomal cardioprotective pathway remains intact in the setting of type II diabetes. Exosomes were isolated by differential centrifugation from non-diabetic and type II diabetic patients, from non-diabetic and Goto Kakizaki type II diabetic rats, and from normoglycaemic and hyperglycaemic endothelial cells. Exosome size and number were not significantly altered by diabetes. CD81 and HSP70 exosome markers were increased in diabetic rat exosomes. However, exosomes from diabetic rats no longer activated the ERK1/2 and HSP27 cardioprotective pathway and were no longer protective in a primary rat cardiomyocytes model of hypoxia and reoxygenation injury. Hyperglycaemic culture conditions were sufficient to impair protection by endothelial exosomes. Importantly, however, exosomes from non-diabetic rats retained the ability to protect cardiomyocytes from diabetic rats. Exosomes from diabetic plasma have lost the ability to protect cardiomyocytes, but protection can be restored with exosomes from non-diabetic plasma. These results support the concept that exosomes may be used to protect cardiomyocytes against ischaemia and reperfusion injury, even in the setting of type II diabetes

Translation of experimental cardioprotective capability of P2Y(12) inhibitors into clinical outcome in patients with ST-elevation myocardial infarction

We studied the translational cardioprotective potential of P2Y12 inhibitors against acute myocardial ischemia/reperfusion injury (IRI) in an animal model of acute myocardial infarction and in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). P2Y12 inhibitors may have pleiotropic effects to induce cardioprotection against acute myocardial IRI beyond their inhibitory effects on platelet aggregation. We compared the cardioprotective effects of clopidogrel, prasugrel, and ticagrelor on infarct size in an in vivo rat model of acute myocardial IRI, and investigated the effects of the P2Y12 inhibitors on enzymatic infarct size (48-h area-under-the-curve (AUC) troponin T release) and clinical outcomes in a retrospective study of STEMI patients from the CONDI-2/ERIC-PPCI trial using propensity score analyses. Loading with ticagrelor in rats reduced infarct size after acute myocardial IRI compared to controls (37 ± 11% vs 52 ± 8%, p  0.99 and 49 ± 9%, p > 0.99, respectively). Correspondingly, troponin release was reduced in STEMI patients treated with ticagrelor compared to clopidogrel (adjusted 48-h AUC ratio: 0.67, 95% CI 0.47–0.94). Compared to clopidogrel, the composite endpoint of cardiac death or hospitalization for heart failure within 12 months was reduced in STEMI patients loaded with ticagrelor (HR 0.63; 95% CI 0.42–0.94) but not prasugrel (HR 0.84, 95% CI 0.43–1.63), prior to PPCI. Major adverse cardiovascular events did not differ between clopidogrel, ticagrelor, or prasugrel. The cardioprotective effects of ticagrelor in reducing infarct size may contribute to the clinical benefit observed in STEMI patients undergoing PPCI

Extracellular histones are a target in myocardial ischaemia reperfusion injury.

Acute myocardial infarction causes lethal cardiomyocyte injury during ischaemia and reperfusion (I/R). Histones have been described as important Danger Associated Molecular Proteins (DAMPs) in sepsis. Aims The objective of this study was to establish whether extracellular histone release contributes to myocardial infarction. Methods and results Isolated, perfused rat hearts were subject to I/R. Nucleosomes and histone H4 release was detected early during reperfusion. Sodium-β-O-Methyl cellobioside sulfate (mCBS), a newly developed histone-neutralising compound, significantly reduced infarct size whilst also reducing the detectable levels of histones. Histones were directly toxic to primary adult rat cardiomyocytes in vitro. This was prevented by mCBS, or HIPe, a recently described, histone-H4 neutralizing peptide, but not by an inhibitor of TLR4, a receptor previously reported to be involved in DAMP-mediated cytotoxicity. Furthermore, TLR4-reporter HEK293 cells revealed that cytotoxicity of histone H4 was independent of TLR4 and NF-κB. In an in vivo rat model of I/R, HIPe significantly reduced infarct size. Conclusion Histones released from the myocardium are cytotoxic to cardiomyocytes, via a TLR4-independent mechanism. The targeting of extracellular histones provides a novel opportunity to limit cardiomyocyte death during I/R injury of the myocardium. Translational perspective Acute myocardial infarction causes lethal cardiomyocyte injury during ischaemia and reperfusion (I/R). New approaches are needed to prevent cardiomyocyte injury and limit final infarct size. We show that histones released from damaged cells, and histone-H4 in particular, causes rapid cardiomyocyte death during I/R. mCBS, a compounds targeting histones non-specifically, was cardioprotective in ex vivo rat hearts, while HIPe, a targeting histone H4 specifically, was cardioprotective in an in vivo rat model. HIPe may have potential as a therapeutic agent in the setting of acute myocardial infarction

Ontogeny of the pineal melatonin rhythm and implications for reproductive development in domestic ruminants

This review focuses on the important contribution that domestic ruminants have made to understanding the role of environmental photoperiod in the process of reproductive maturation. Evidence in the sheep, goat and deer indicate that the influence of photoperiod on growth and the onset of puberty is mediated by the pineal gland and secretion of the hormone melatonin. The ontogeny of the circadian melatonin rhythm is discussed in relation to its role in the timing of puberty for these ruminant species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29742/1/0000079.pd