Effect of rosiglitazone on cardiac electrophysiology, infarct size and mitochondrial function in ischaemia and reperfusion of swine and rat heart

Rosiglitazone, a peroxisome proliferator-activated receptor γ agonist, has been used to treat type 2 diabetes. Despite debates regarding its cardioprotection, the effects of rosiglitazone on cardiac electrophysiology are still unclear. This study determined the effect of rosiglitazone on ventricular fibrillation (VF) incidence, VF threshold (VFT), defibrillation threshold (DFT) and mitochondrial function during ischaemia and reperfusion. Twenty-six pigs were used. In each pig, either rosiglitazone (1 mg kg(-1)) or normal saline solution was administered intravenously for 60 min. Then, the left anterior descending coronary artery was ligated for 60 min and released to promote reperfusion for 120 min. The cardiac electrophysiological parameters were determined at the beginning of the study and during the ischaemia and reperfusion periods. The heart was removed, and the area at risk and infarct size in each heart were determined. Cardiac mitochondria were isolated for determination of mitochondrial function. Rosiglitazone did not improve the DFT and VFT during the ischaemia-reperfusion period. In the rosiglitazone group, the VF incidence was increased (58 versus 10%) and the time to the first occurrence of VF was decreased (3 ± 2 versus 19 ± 1 min) in comparison to the vehicle group (P < 0.05). However, the infarct size related to the area at risk in the rosiglitazone group was significantly decreased (P < 0.05). In the cardiac mitochondria, rosiglitazone did not alter the level of production of reactive oxygen species and could not prevent mitochondrial membrane potential changes. Rosiglitazone increased the propensity for VF, and could neither increase defibrillation efficacy nor improve cardiac mitochondrial function.     

Interleukin‐37 ameliorates myocardial ischaemia/reperfusion injury in mice

Innate immune and inflammatory responses are involved in myocardial ischaemia/reperfusion (I/R) injury. Interleukin (IL)‐37 is a newly identified member of the IL‐1 family, and functions as a fundamental inhibitor of innate immunity and inflammation. However, its role in myocardial I/R injury remains unknown. I/R or sham operations were performed on male C57BL/6J mice. I/R mice received an injection of recombinant human IL‐37 or vehicle, immediately before reperfusion. Compared with vehicle treatment, mice treated with IL‐37 showed an obvious amelioration of the I/R injury, as demonstrated by reduced infarct size, decreased cardiac troponin T level and improved cardiac function. This protective effect was associated with the ability of IL‐37 to suppress production of proinflammatory cytokines, chemokines and neutrophil infiltration, which together contributed to a decrease in cardiomyocyte apoptosis and reactive oxygen species (ROS) generation. In addition, we found that IL‐37 inhibited the up‐regulation of Toll‐like receptor (TLR)‐4 expression and nuclear factor kappa B (NF‐kB) activation after I/R, while increasing the anti‐inflammatory IL‐10 level. Moreover, the administration of anti‐IL‐10R antibody abolished the protective effects of IL‐37 in I/R injury. In‐vitro experiments further demonstrated that IL‐37 protected cardiomyocytes from apoptosis under I/R condition, and suppressed the migration ability of neutrophils towards the chemokine LIX. In conclusion, IL‐37 plays a protective role against mouse myocardial I/R injury, offering a promising therapeutic medium for myocardial I/R injury.     

Glutathione deficiency intensifies ischaemia‐reperfusion induced cardiac dysfunction and oxidative stress

The efficacy of glutathione (GSH) in protecting ischaemia‐reperfusion (I‐R) induced cardiac dysfunction and myocardial oxidative stress was studied in open‐chest, stunned rat heart model. Female Sprague–Dawley rats were randomly divided into three experimental groups: (1) GSH‐depletion, by injection of buthionine sulphoxamine (BSO, 4 mmol kg^–1, i.p.) 24 h prior to I‐R, (2) BSO injection (4 mmol kg^–1, i.p.) in conjunction with acivicin (AT125, 0.05 mmol kg^–1, i.v.) infusion 1 h prior to I‐R, and (3) control (C), receiving saline treatment. Each group was further divided into I‐R, with surgical occlusion of the main left coronary artery (LCA) for 30 min followed by 20 min reperfusion, and sham. Myocardial GSH content and GSH : glutathione disulphide (GSSG) ratio were decreased by ?50% (P < 0.01) in both BSO and BSO + AT125 vs. C. Ischaemia‐reperfusion suppressed GSH in both left and right ventricles of C (P < 0.01) and left ventricles of BSO and BSO + AT125 (P < 0.05). Contractility (+dP/dt and –dP/dt) in C heart decreased 55% (P < 0.01) after I and recovered 90% after I‐R, whereas ±dP/dt in BSO decreased 57% (P < 0.01) with ischaemia and recovered 76 and 84% (P < 0.05), respectively, after I‐R. For BSO + AT125, ±dP/dt were 64 and 76% (P < 0.01) lower after ischaemia, and recovered only 67 and 61% (P < 0.01) after I‐R. Left ventricular systolic pressure in C, BSO and BSO + AT125 reached 95 (P > 0.05) 87 and 82% (P < 0.05) of their respective sham values after I‐R. Rate‐pressure double product was 11% (P > 0.05) and 25% (P < 0.05) lower in BSO and BSO + AT125, compared with Saline, respectively. BSO and BSO + AT125 rats demonstrated significantly lower liver GSH and heart Mn superoxide dismutase activity than C rats after I‐R. These data indicate that GSH depletion by inhibition of its synthesis and transport can exacerbate cardiac dysfunction inflicted by in vivo I‐R. Part of the aetiology may involve impaired myocardial antioxidant defenses and whole‐body GSH homeostasis.     

Sca‐1+ cardiac fibroblasts promote development of heart failure

The causative effect of GM‐CSF produced by cardiac fibroblasts to development of heart failure has not been shown. We identified the pathological GM‐CSF‐producing cardiac fibroblast subset and the specific deletion of IL‐17A signaling to these cells attenuated cardiac inflammation and heart failure. We describe here the CD45^?CD31^?CD29⁺mEF‐SK4⁺PDGFRα⁺Sca‐1⁺periostin⁺ (Sca‐1⁺) cardiac fibroblast subset as the main GM‐CSF producer in both experimental autoimmune myocarditis and myocardial infarction mouse models. Specific ablation of IL‐17A signaling to Sca‐1⁺periostin⁺ cardiac fibroblasts (Postn^CreIl17ra^fl/fl) protected mice from post‐infarct heart failure and death. Moreover, Postn^CreIl17ra^fl/fl mice had significantly fewer GM‐CSF‐producing Sca‐1⁺ cardiac fibroblasts and inflammatory Ly6C^hi monocytes in the heart. Sca‐1⁺ cardiac fibroblasts were not only potent GM‐CSF producers, but also exhibited plasticity and switched their cytokine production profiles depending on local microenvironments. Moreover, we also found GM‐CSF‐positive cardiac fibroblasts in cardiac biopsy samples from heart failure patients of myocarditis or ischemic origin. Thus, this is the first identification of a pathological GM‐CSF‐producing cardiac fibroblast subset in human and mice hearts with myocarditis and ischemic cardiomyopathy. Sca‐1⁺ cardiac fibroblasts direct the type of immune cells infiltrating the heart during cardiac inflammation and drive the development of heart failure.     

Effect of combined supplementation with vitamin E and alpha‐lipoic acid on myocardial performance during in vivo ischaemia‐reperfusion

Reactive oxygen species (ROS) contribute significantly to myocardial ischaemia‐reperfusion (I‐R) injury. Recently the combination of the antioxidants vitamin E (VE) and alpha‐lipoic acid (α‐LA) has been reported to improve cardiac performance and reduce myocardial lipid peroxidation during in vitro I‐R. The purpose of these experiments was to investigate the effects of VE and α‐LA supplementation on cardiac performance, incidence of dysrhythmias and biochemical alterations during an in vivo myocardial I‐R insult. Female Sprague–Dawley rats (4‐months old) were assigned to one of the two dietary treatments: (1) control diet (CON) or (2) VE and α‐LA supplementation (ANTIOXID). The CON diet was prepared to meet AIN‐93M standards, which contains 75 IU VE kg^–1 diet. The ANTIOXID diet contained 10 000 IU VE kg^–1 diet and 1.65 g α‐LA kg^–1 diet. After the 14‐week feeding period, significant differences (P < 0.05) existed in mean myocardial VE levels between dietary groups. Animals in each experimental group were subjected to an in vivo I‐R protocol which included 25 min of left anterior coronary artery occlusion followed by 10 min of reperfusion. No group differences (P > 0.05) existed in cardiac performance (e.g. peak arterial pressure or ventricular work) or the incidence of ventricular dysrhythmias during the I‐R protocol. Following I‐R, two markers of lipid peroxidation were lower (P < 0.05) in the ANTIOXID animals compared with CON. These data indicate that dietary supplementation of the antioxidants, VE and α‐LA do not influence cardiac performance or the incidence of dysrhythmias but do decrease lipid peroxidation during in vivo I‐R in young adult rats.     

二氮嗪后处理对离体大鼠心功能及线粒体心磷脂的影响

目的:建立离体大鼠心肌缺血/再灌注损伤模型,观察二氮嗪(diazoxide,D)后处理对缺血/再灌注损伤离体大鼠心功能及线粒体心磷脂的影响,并探讨ATP敏感性钾通道在二氮嗪后处理心肌保护中的作用。方法:采用Langendorff装置建立离体大鼠心肌缺血/再灌注损伤模型,将SD大鼠随机分为对照组(control)、缺血再灌注模型组(I/R)、二氮嗪后处理组(I/R+D)、5-羟葵酸拮抗二氮嗪后处理组(I/R+5-HD+D),每组8只,均先灌注平衡20 min。Control组:灌注平衡后续灌70 min;I/R组:缺血前灌注4℃ST.Thomas停跳液,全心缺血40 min,再灌30 min;I/R+D组:全心缺血40 min,缺血后给予含二氮嗪(50μmol/L)的K-H液灌注5 min后,再灌25 min;I/R+5-HD+D组:二氮嗪后处理前给予含5-羟葵酸(100μmol/L)的K-H液灌注5 min,再灌20 min。观察各组续(再)灌注末心率、冠脉流出液量、心功能、心肌酶学及心肌线粒体心磷脂的变化。结果:各组续(再)灌注末比较,I/R组较control组及I/R+D组心率减慢、冠脉流出液量降低,心功能明显受损,心肌酶增加,心磷酯含量减少,但与I/R+5-HD+D无明显差异。结论:二氮嗪后处理通过增加线粒体心磷脂含量,减少心肌酶的释放,改善心脏功能,减轻心肌的再灌注损伤,产生心肌保护作用。5-羟葵酸能够完全阻断二氮嗪的心肌保护作用。     

iRhom2 regulates CSF1R cell surface expression and non‐steady state myelopoiesis in mice

CSF1R (colony stimulating factor 1 receptor) is the main receptor for CSF1 and has crucial roles in regulating myelopoeisis. CSF1R can be proteolytically released from the cell surface by ADAM17 (A disintegrin and metalloprotease 17). Here, we identified CSF1R as a major substrate of ADAM17 in an unbiased degradomics screen. We explored the impact of CSF1R shedding by ADAM17 and its upstream regulator, inactive rhomboid protein 2 (iRhom2, gene name Rhbdf2), on homeostatic development of mouse myeloid cells. In iRhom2‐/‐ mice, we found constitutive accumulation of membrane‐bound CSF1R on myeloid cells at steady state, although cell numbers of these populations were not altered. However, in the context of mixed bone marrow (BM) chimera, under competitive pressure, iRhom2‐/‐ BM progenitor‐derived monocytes, tissue macrophages and lung DCs showed a repopulation advantage over those derived from wild‐type (WT) BM progenitors, suggesting enhanced CSF1R signaling in the absence of iRhom2. In vitro experiments indicate that iRhom2‐/‐ Lin^?SCA‐1⁺c‐Kit⁺ (LSKs) cells, but not granulocyte‐macrophage progenitors (GMPs), had faster growth rates than WT cells in response to CSF1. Our results shed light on an important role of iRhom2/ADAM17 pathway in regulation of CSF1R shedding and repopulation of monocytes, macrophages and DCs.     

The influence of retrograde reperfusion on the ischaemia‐/ reperfusion injury after liver transplantation in the rat

Dysfunction of the graft after liver transplantation caused by ischaemia‐/reperfusion (I/R) injury is a serious clinical problem. The aim of this study was to evaluate the influence of different kinds of reperfusion on I/R injury in a rat model. Arterialized orthoptic rat liver treatment was performed on male LEWIS‐(RT¹)‐rats. Three groups (n = 7) were formed. Group I: antegrade reperfusion with a 6‐min delayed reperfusion via the hepatic artery. Group II: Antegrade reperfusion, simultaneously, via the portal vein and the hepatic artery. Group III: Retrograde reperfusion via the vena cava. Serum parameters were determined one, 24 and 48 h after operation. Furthermore, after 48 h, the liver was taken for histological assessment. After 48 h, rats of group III showed significantly lower aspartate amino transferase and alanine amino transferase serum levels compared with group I and group II rats. Forty‐eight hours after transplantation, glutamate dehydrogenase serum level was significantly lower in group III than in group II. In histology, group III livers showed significantly less necrotic spots than group I and group II livers. Maximum size of the necrotic spots was significantly lower in group III than in group I. Also, significantly more necrotic spots were seen in the ‘Rappaport′s zone’ 1 and 2 of group I than in group III. Our data suggested that the expression of I/R‐injury correlates with the type of reperfusion. Furthermore, under standard conditions, this study was able to demonstrate that in a rat model, the retrograde reperfusion leads to a lower expression of I/R‐injury than the antegrade reperfusion.     

Overlapping syndrome with familial partial lipodystrophy,Dunnigan variety and cardiomyopathy due to amino‐terminal heterozygous missense lamin A/C mutations

Subramanyam L, Simha V, Garg A. Overlapping syndrome with familial partial lipodystrophy, Dunnigan variety and cardiomyopathy due to amino‐terminal heterozygous missense lamin A/C mutations. Familial partial lipodystrophy, Dunnigan variety (FPLD) is a well‐recognized autosomal dominant disorder due to heterozygous missense mutations in lamin A/C (LMNA) gene. Most of the FPLD patients harbor mutations in the C‐terminal of the lamin A/C and do not develop cardiomyopathy. On the other hand, affected subjects from three FPLD pedigrees with heterozygous R28W, R60G and R62G LMNA mutations in the amino‐terminal had associated cardiomyopathy presenting as premature onset of congestive heart failure, dilated cardiomyopathy and conduction system disturbances. We report three new FPLD pedigrees presenting with cardiomyopathy associated with heterozygous LMNA mutations in the amino‐terminal region. Two of them had previously reported R60G and R62G mutations and one has a novel D192V mutation. Affected subjects belonging to the pedigree with heterozygous R62G mutation had atrial fibrillation and required pacemaker implantation. The affected subjects from the other pedigrees with R60G and D192V mutations developed severe cardiomyopathy requiring defibrillator implantation and cardiac transplantation before 30 years of age in some and premature death in the fourth decade in others. Thus, our report provides further evidence of association of a multisystem dystrophy syndrome in FPLD patients harboring amino‐terminal mutations in LMNA. Increased understanding of the genotype–phenotype association might help devise clinical strategies aimed at preventing devastating manifestations of cardiomyopathy including heart failure, arrhythmias and sudden death. Furthermore, the underlying molecular mechanisms by which these amino‐terminal mutations cause lipodystrophy as well as cardiomyopathy remain to be understood.     

The combination of L-arginine and ischaemic post-conditioning at the onset of reperfusion limits myocardial injury in the pig

Aim: To investigate whether ischaemic post‐conditioning (IPoC) combined with i.v. infusion of the nitric oxide (NO) substrate l ‐arginine at the onset of reperfusion exerts cardioprotective effect that is superior to either treatment given separately. Methods: Twenty‐six anesthetized pigs were subjected to coronary artery (left anterior descending artery, LAD) ligation for 40 min followed by 4 h reperfusion. The pigs were randomized into five different groups receiving either i.v. vehicle, i.v. l ‐arginine, IPoC 4 × 60 s together with i.v. vehicle or IPoC together with i.v. l ‐arginine and a group with IPoC 8 × 30 s. All infusions were started 10 min before reperfusion. Results: The infarct size of the vehicle group was 82 ± 4% of the area at risk. l ‐Arginine alone (79 ± 8%), IPoC 4 × 60 s vehicle (86 ± 3%) or IPoC 8 × 30 s vehicle (94 ± 7%) did not affect infarct size. l ‐Arginine together with IPoC significantly reduced infarct size to 59 ± 4% (P < 0.01). Except for higher LAD flow during early reperfusion in the IPoC l ‐arginine group, haemodynamic parameters did not differ between the four main groups. Heart rate and rate pressure product were lower during ischaemia and reperfusion in the IPoC 8 × 30 s vehicle group. In comparison with the vehicle group, there were no changes in the expression of Akt, phosphorylated Akt Ser⁴⁷³, inducible NO synthase, endothelial NO synthase (eNOS) or phosphorylated eNOS Ser¹¹⁷⁷ in the ischaemic/reperfused myocardium. Conclusion: l ‐Arginine given systemically at the onset of reperfusion protects the pig heart against ischaemia and reperfusion injury only when combined with IPoC. These results indicate that the combination of the two treatment strategies exerts cardioprotection.     

Mobilization without immune depletion fails to restore immunological tolerance or preserve beta cell function in recent onset type 1 diabetes

Granulocyte colony‐stimulating factor (G‐CSF) has been used to restore immune competence following chemoablative cancer therapy and to promote immunological tolerance in certain settings of autoimmunity. Therefore, we tested the potential of G‐CSF to impact type 1 diabetes (T1D) progression in patients with recent‐onset disease [n = 14; n = 7 (placebo)] and assessed safety, efficacy and mechanistic effects on the immune system. We hypothesized that pegylated G‐CSF (6 mg administered subcutaneously every 2 weeks for 12 weeks) would promote regulatory T cell (T_reg) mobilization to a degree capable of restoring immunological tolerance, thus preventing further decline in C‐peptide production. Although treatment was well tolerated, G‐CSF monotherapy did not affect C‐peptide production, glycated haemoglobin (HbA1c) or insulin dose. Mechanistically, G‐CSF treatment increased circulating neutrophils during the 12‐week course of therapy (P < 0·01) but did not alter T_reg frequencies. No effects were observed for CD4⁺ : CD8⁺ T cell ratio or the ratio of naive : memory (CD45RA⁺/CD45RO⁺) CD4⁺ T cells. As expected, manageable bone pain was common in subjects receiving G‐CSF, but notably, no severe adverse events such as splenomegaly occurred. This study supports the continued exploration of G‐CSF and other mobilizing agents in subjects with T1D, but only when combined with immunodepleting agents where synergistic mechanisms of action have previously demonstrated efficacy towards the preservation of C‐peptide.     

Potential signaling pathways of acute endurance exercise-induced cardiac autophagy and mitophagy and its possible role in cardioprotection

Cardiac myocytes are terminally differentiated cells and possess extremely limited regenerative capacity; therefore, preservation of mature cardiac myocytes throughout the individual’s entire life span contributes substantially to healthy living. Autophagy, a lysosome-dependent cellular catabolic process, is essential for normal cardiac function and mitochondria maintenance. Therefore, it may be reasonable to hypothesize that if endurance exercise promotes cardiac autophagy and mitochondrial autophagy or mitophagy, exercise-induced cardiac autophagy (EICA) or exercise-induced cardiac mitophagy (EICM) may confer propitious cellular environment and thus protect the heart against detrimental stresses, such as an ischemia–reperfusion (I/R) injury. However, although the body of evidence supporting EICA and EICM is growing, the molecular mechanisms of EICA and EICM and their possible roles in cardioprotection against an I/R injury are poorly understood. Here, we introduce the general mechanisms of autophagy in an attempt to integrate potential molecular pathways of EICA and EICM and also highlight a potential insight into EICA and EICM in cardioprotection against an I/R insult.     

Participation of Na/Ca‐exchanger and sarcoplasmic reticulum in the high [K]o‐protection against ischaemia‐reperfusion dysfunction in rat hearts

Aim: Na/Ca‐exchanger (NCX) and sarcoplasmic reticulum (SR) roles during the protection by a cardioplegic solution (25 mm K and 0.5 mm Ca, CPG) against ischaemia‐reperfusion was studied. Methods: Contractile performance (CP) and high energy phosphates contents (HEP) were evaluated in isolated ventricles from rats. They were pre‐treated with Krebs (C) or CPG and submitted to no‐flow ischaemia and reperfusion (I–R). KB‐R7943 5 μm (inhibitor of NCX in reverse mode), 8 mm caffeine and ionic changes were used pre‐ischaemically to evaluate each pathway role. Results: During R, CP recovered to 77 ± 8% of basal in CPG‐hearts vs. 55 ± 8% (P < 0.05) in C‐ones. CPG avoided the increases in end diastolic pressure (LVEDP) and in PCr/ATP ratio during I–R. Low [Na]_o (78 mm ) under both, CPG‐2 mm Ca and C, increased further the LVEDP during I–R. LVEDP was also transiently increased by caffeine‐CPG, but not modified by KB‐R7943. The recovery of CP during reperfusion of CPG‐hearts was decreased either, by caffeine (to ～75%), low [Na]_o‐2 mm Ca‐CPG (to ～40%) and KB‐R7943 (to ～16%). Conclusions: CPG protected hearts from ischaemic contracture by attenuating the fall in ATP and removing diastolic Ca by means of NCX in forward mode. Moreover, CPG induces higher CP recovery during reperfusion by participation of SR and NCX in reverse mode. This work remarks the use of CPG based on the functional role of these Ca handling‐mechanisms in a pathophysiological condition as ischaemia‐reperfusion.     

Correlation between liver cell necrosis and circulating alanine aminotransferase after ischaemia/reperfusion injuries in the rat liver

Circulating liver enzymes such as alanine transaminase are often used as markers of hepatocellular damage. Ischaemia/reperfusion (I/R) injury is an inevitable consequence of prolonged liver ischaemia. The aim of this study was to examine the correlation between liver enzymes and volume of liver cell necrosis after ischaemia/reperfusion injuries, using design‐unbiased stereological methods. Forty‐seven male Wistar rats were subjected to 1 h of partial liver ischaemia, followed by either 4 or 24 h of reperfusion. Within each group, one‐third of animals were subjected to ischaemic preconditioning and one‐third to ischaemic postconditioning. At the end of reperfusion, blood and liver samples were collected for analysis. The volume of necrotic liver tissue was subsequently correlated to circulating markers of I/R injury. Correlation between histological findings and circulating markers was performed using Pearson's correlation coefficient. Alanine transferase peaked after 4 h of reperfusion; however, at this time‐point, only mild necrosis was observed, with a Pearson's correlation coefficient of 0.663 (P = 0.001). After 24 h of reperfusion, alanine aminotransferase was found to be highly correlated to the degree of hepatocellular necrosis R = 0.836 (P = 0.000). Furthermore, alkaline phosphatase (R = 0.806) and α‐2‐macroglobulin (R = 0.655) levels were also correlated with the degree of necrosis. We show for the first time that there is a close correlation between the volume of hepatocellular necrosis and alanine aminotransferase levels in a model of I/R injury. This is especially apparent after 24 h of reperfusion. Similarly, increased levels of alkaline phosphatase and α‐2‐macroglobulin are correlated to the volume of liver necrosis.     

Tollip is a critical mediator of cerebral ischaemia–reperfusion injury

Toll‐like receptor (TLR) signalling plays an important role in regulating cerebral ischaemia–reperfusion (I/R) injury. Toll‐interacting protein (Tollip) is an endogenous negative modulator of TLR signalling that is involved in several inflammatory diseases. Our previous study showed that Tollip inhibits overload‐induced cardiac remodelling. However, the role of Tollip in neurological disease remains unknown. In the present study, we proposed that Tollip might contribute to the progression of stroke and confirmed this hypothesis. We found that Tollip expression was significantly increased in I/R‐challenged brain tissue of humans, mice and rats in vivo and in primary neurons subjected to oxygen and glucose deprivation in vitro, indicating the involvement of Tollip in I/R injury. Next, using genetic approaches, we revealed that Tollip deficiency protects mice against I/R injury by attenuating neuronal apoptosis and inflammation, as demonstrated by the decreased expression of pro‐apoptotic and pro‐inflammatory genes and the increased expression of anti‐apoptotic genes. By contrast, neuron‐specific Tollip over‐expression exerted the opposite effect. Mechanistically, the detrimental effects of Tollip on neuronal apoptosis and inflammation following I/R injury were largely mediated by the suppression of Akt signalling. Additionally, to further support our findings, a Tollip knockout rat strain was generated via CRISPR‐Cas9‐mediated gene inactivation. The Tollip‐deficient rats were also protected from I/R injury, based on dramatic decreases in neuronal apoptosis and ischaemic inflammation through Akt activation. Taken together, our findings demonstrate that Tollip acts as a novel modulator of I/R injury by promoting neuronal apoptosis and ischaemic inflammation, which are largely mediated by suppression of Akt signalling. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

S100A12 promotes inflammation and apoptosis in ischemia/reperfusion injury via ERK signaling in vitro study using PC12 cells

S100A12 is a member of S100 calcium‐binding proteins with effect to promote inflammation in brain damage and stroke. However, the role of S100A12 in ischemia/reperfusion (I/R) remains to be clarified. This study aimed to explore the effect of S100A12 on I/R and discover the possible mechanism. Oxygen‐glucose deprivation and reperfusion (OGD/R) was used to induce I/R injury model in vitro. Knockdown or overexpression of S100A12 was utilized to explore the role of S100A12 in I/R‐induced inflammation and apoptosis. Results indicated that S100A12 expression was dramatically upregulated after OGD/R. Knockdown of S100A12 inhibited, while overexpression of S100A12 enhanced, the activation of ERK1/2 protein. OGD/R also triggered the occurrence of inflammation and oxidative stress, while these effects were blunted by S100A12 silencing and aggravated by S100A12 overexpression, and the presence of MAP kinase signaling system (ERK) inhibitor MK‐8353 counteracted the effect of S100A12 overexpression. Besides, S100A12 silencing abolished, while its overexpression restored, the OGD/R‐induced increased apoptosis rate and pro‐apoptotic proteins expression. Similarly, ERK inhibitor MK‐8353 reversed the effects of S100A12 overexpression. In conclusion, S100A12 promoted OGD/R‐induced inflammation, oxidative stress and apoptosis via activation of ERK signaling in vitro.     

Cellular basis of sex disparities in human cardiac electrophysiology

Aim: Sex disparities in electrocardiogram variables and dysrhythmia susceptibility exist, notably in long QT syndrome (LQTS) and Brugada syndrome, but the underlying mechanisms in man are unknown. We studied the cellular basis of sex distinctions in human cardiac electrophysiology and dysrhythmia susceptibility using mathematical models of human ventricular myocytes. Methods: We implemented sex differences in the Priebe–Beuckelmann and ten Tusscher–Noble–Noble–Panfilov human ventricular cell models by modifying densities of the L‐type Ca²⁺ current (I_Ca,L), transient outward K⁺ current (I_to), and rapid delayed rectifier K⁺ current (I_Kr), according to experimental data from male and female hearts of various species. Sex disparities in transmural repolarization were studied in transmural strands of cells with ion current densities based on canine experimental data. Results: Female cells have longer action potential duration (APD), steeper APD‐heart rate relationship, larger transmural APD heterogeneity, and a greater susceptibility to pro‐dysrhythmogenic early afterdepolarizations (EADs) than male cells. Conversely, male cells have more prominent phase‐1 repolarization and are more susceptible to all‐or‐none repolarization. Conclusion: Sex differences in I_Ca,L, I_to and I_Kr densities may explain sex disparities in human cardiac electrophysiology. Female cells exhibit a limited ‘repolarization reserve’ as demonstrated by their larger susceptibility to EADs, which, combined with their larger transmural electrical heterogeneity, renders them more vulnerable to tachydysrhythmias in LQTS. Conversely, male cells have a limited ‘depolarization reserve’, as shown by their larger susceptibility to all‐or‐none repolarization, which facilitates tachydysrhythmias in Brugada syndrome. These general principles may also apply to dysrhythmia susceptibility in common disease.     

大鼠肝缺血再灌注损伤对心脏能量代谢和结构的影响及其机制

目的：探讨肝缺血再灌注损伤对心脏能量代谢和结构的影响及其可能的发生机制。方法：健康雄性Wistar大鼠48只，随机分为对照组、缺血30 min组（I组）及缺血30 min再灌注即刻组、2 h组、4 h组和6 h组（I/R组、I/R 2 h组、I/R 4 h组和I/R 6 h组），每组8只。用偶氮显色法测定血清中的内毒素，用放射免疫法测定心肌组织胰岛素和胰岛素抗体，取心肌制备组织匀浆测丙二醛（MDA）、髓过氧化物酶（MPO），乳酸含量。 结果：在肝缺血再灌注损伤过程中，内毒素在I组和I/R组达到高峰，随着再灌注时间的延长逐渐下降，但仍高于对照组（P<0.05）。I组及I/R各组MDA的含量明显高于对照组，在I/R 2 h组、I/R 4 h组、I/R 6 h组差别更为明显（P＜0.05）；再灌注各组MPO活性明显高于对照组、I组（P＜0.05）；随着再灌注时间的延长，心肌组织中乳酸含量明显增加（P＜0.05），但在I/R 6 h组呈下降趋势（P＜0.05）；胰岛素的含量在I/R 4 h组和I/R 6 h组明显下降（P＜0.05）；而胰岛素抗体在各组间无显著差异（P＞0.05）。结论：肝缺血再灌注损伤过程中，肠源性内毒素吸收入血及肝脏解毒功能的降低所致的内毒素血症可能是引起心脏能量代谢和结构改变的始动环节。