Platelet-activating factor receptor-deficient mice are protected from experimental sleep apnea-induced learning deficits

Intermittent hypoxia (IH) during sleep, a hallmark of sleep apnea, is associated with neurobehavioral impairments, regional neurodegeneration and increased oxidative stress and inflammation in rodents. Platelet-activating factor (PAF) is an important mediator of both normal neural plasticity and brain injury. We report that mice deficient in the cell surface receptor for PAF (PAFR-/-), a bioactive mediator of oxidative stress and inflammation, are protected from the spatial reference learning deficits associated with IH. Furthermore, PAFR-/- exhibit attenuated elevations in inflammatory signaling (cyclo-oxygenase-2 and inducible nitric oxide synthase activities), degradation of the ubiquitin-proteasome pathway and apoptosis observed in wild-type littermates (PAFR+/+) exposed to IH. Collectively, these findings indicate that inflammatory signaling and neurobehavioral impairments induced by IH are mediated through PAF receptors.     

Downregulation of p300/CBP-associated factor inhibits cardiomyocyte apoptosis via suppression of NF-κB pathway in ischaemia/reperfusion injury rats

Cardiomyocyte apoptosis is the main reason of cardiac injury after myocardial ischaemia-reperfusion (I/R) injury (MIRI), but the role of p300/CBP-associated factor (PCAF) on myocardial apoptosis in MIRI is unknown. The aim of this study was to investigate the main mechanism of PCAF modulating cardiomyocyte apoptosis in MIRI. The MIRI model was constructed by ligation of the rat left anterior descending coronary vessel for 30 min and reperfusion for 24 h in vivo. H9c2 cells were harvested after induced by hypoxia for 6 h and then reoxygenation for 24 h (H/R) in vitro. The RNA interference PCAF expression adenovirus was transfected into rat myocardium and H9c2 cells. The area of myocardial infarction, cardiac function, myocardial injury marker levels, apoptosis, inflammation and oxidative stress were detected respectively. Both I/R and H/R remarkably upregulated the expression of PCAF, and downregulation of PCAF significantly attenuated myocardial apoptosis, inflammation and oxidative stress caused by I/R and H/R. In addition, downregulation of PCAF inhibited the activation of NF-κB signalling pathway in cardiomyocytes undergoing H/R. Pretreatment of lipopolysaccharide, a NF-κB pathway activator, could blunt these protective effects of PCAF downregulation on myocardial apoptosis in MIRI. These results highlight that downregulation of PCAF could reduce cardiomyocyte apoptosis by inhibiting the NF-κB pathway, thereby providing protection for MIRI. Therefore, PCAF might be a promising target for protecting against cardiac dysfunction induced by MIRI.     

Downregulation of p300/CBP‐associated factor inhibits cardiomyocyte apoptosis via suppression of NF‐κB pathway in ischaemia/reperfusion injury rats

Cardiomyocyte apoptosis is the main reason of cardiac injury after myocardial ischaemia‐reperfusion (I/R) injury (MIRI), but the role of p300/CBP‐associated factor (PCAF) on myocardial apoptosis in MIRI is unknown. The aim of this study was to investigate the main mechanism of PCAF modulating cardiomyocyte apoptosis in MIRI. The MIRI model was constructed by ligation of the rat left anterior descending coronary vessel for 30 min and reperfusion for 24 h in vivo. H9c2 cells were harvested after induced by hypoxia for 6 h and then reoxygenation for 24 h (H/R) in vitro. The RNA interference PCAF expression adenovirus was transfected into rat myocardium and H9c2 cells. The area of myocardial infarction, cardiac function, myocardial injury marker levels, apoptosis, inflammation and oxidative stress were detected respectively. Both I/R and H/R remarkably upregulated the expression of PCAF, and downregulation of PCAF significantly attenuated myocardial apoptosis, inflammation and oxidative stress caused by I/R and H/R. In addition, downregulation of PCAF inhibited the activation of NF‐κB signalling pathway in cardiomyocytes undergoing H/R. Pretreatment of lipopolysaccharide, a NF‐κB pathway activator, could blunt these protective effects of PCAF downregulation on myocardial apoptosis in MIRI. These results highlight that downregulation of PCAF could reduce cardiomyocyte apoptosis by inhibiting the NF‐κB pathway, thereby providing protection for MIRI. Therefore, PCAF might be a promising target for protecting against cardiac dysfunction induced by MIRI.     

Protection against in vivo focal myocardial ischemia/reperfusion injury-induced arrhythmias and apoptosis by Hesperidin

Among the heart diseases, ischemia and reperfusion (I/R) induced arrhythmias contribute to episodes of sudden death. Cardiac arrhythmias during ischemia reperfusion are believed to be related to oxidative stress. Therefore, the aim of this study was to examine whether treatment with Hesperidin alleviates arrhythmias and infarct size in experimentally-induced myocardial I/R injury using an in vivo rat model. In this study haemodynamics parameters, markers of inflammation, biomarkers of oxidative stress and tissue nitrite level and infarct size of the heart were estimated in various groups. I/R showed a significant decrease in tissue nitrite and antioxidant level and significant increase in arrhythmias, inflammation and myocardial cell apoptosis. Treatment with Hesperidin showed a significant increase in tissue nitrite, antioxidant level and reduction in inflammation, arrhythmias and apoptosis. In conclusion, the protecting effect of Hesperidin in I/R induced arrhythmias is due to reduction in inflammation and oxidative stress.     

Cannabidiol protects against hepatic ischemia/reperfusion injury by attenuating inflammatory signaling and response, oxidative/nitrative stress, and cell death

Ischemia/reperfusion (I/R) is a pivotal mechanism of liver damage after liver transplantation or hepatic surgery. We have investigated the effects of cannabidiol (CBD), the nonpsychotropic constituent of marijuana, in a mouse model of hepatic I/R injury. I/R triggered time-dependent increases/changes in markers of liver injury (serum transaminases), hepatic oxidative/nitrative stress (4-hydroxy-2-nonenal, nitrotyrosine content/staining, and gp91phox and inducible nitric oxide synthase mRNA), mitochondrial dysfunction (decreased complex I activity), inflammation (tumor necrosis factor α (TNF-α), cyclooxygenase 2, macrophage inflammatory protein-1α/2, intercellular adhesion molecule 1 mRNA levels; tissue neutrophil infiltration; nuclear factor κB (NF-κB) activation), stress signaling (p38MAPK and JNK), and cell death (DNA fragmentation, PARP activity, and TUNEL). CBD significantly reduced the extent of liver inflammation, oxidative/nitrative stress, and cell death and also attenuated the bacterial endotoxin-triggered NF-κB activation and TNF-α production in isolated Kupffer cells, likewise the adhesion molecule expression in primary human liver sinusoidal endothelial cells stimulated with TNF-α and attachment of human neutrophils to the activated endothelium. These protective effects were preserved in CB2 knockout mice and were not prevented by CB1/2 antagonists in vitro. Thus, CBD may represent a novel, protective strategy against I/R injury by attenuating key inflammatory pathways and oxidative/nitrative tissue injury, independent of classical CB1/2 receptors.     

MicroRNA-21 mediates the protective role of emulsified isoflurane against myocardial ischemia/reperfusion injury in mice by targeting SPP1

Isoflurane has demonstrated to exert protective impacts against ischemia/reperfusion (I/R) injury in some organs. This research explored the role of emulsified isoflurane (EI) in myocardial I/R injury through the interaction with microRNA-21 (miR-21). The myocardial I/R injury mouse models established by coronary artery ligation were respectively treated with EI, miR-21 mimic/inhibitor or silenced secreted phosphoprotein 1 (SPP1) plasmids. Then, the pathology, fibrosis and cardiomyocyte apoptosis in mouse myocardial tissues were observed. Furthermore, the expression levels of miR-21, SPP1, oxidative stress indices, inflammatory factors and apoptotic proteins in mouse myocardial tissues were determined. The targeting relation between miR-21 and SPP1 was confirmed. MiR-21 was poorly expressed and SPP1 was highly expressed in myocardial I/R injury mice. EI treatment, elevated miR-21, or silenced SPP1 improved cardiac function and suppressed the oxidative stress, myocardial fibrosis, inflammatory reaction and cardiomyocyte apoptosis in myocardial I/R injury mice, thereby reliving the myocardial I/R injury. These therapeutic effects of EI were repressed by miR-21 inhibition. Additionally, SPP1 was targeted by miR-21. Results in our research indicated that miR-21 mediated the therapeutic effect of EI on myocardial I/R injury in mice by targeting SPP1. This study may provide a novel treatment strategy for myocardial I/R injury.     

Neuroprotective effects of 1‐O‐hexyl‐2,3,5‐trimethylhydroquinone on ischaemia/reperfusion‐induced neuronal injury by activating the Nrf2/HO‐1 pathway

1‐O‐Hexyl‐2,3,5‐trimethylhydroquinone (HTHQ), a lipophilic phenolic agent, has an antioxidant activity and reactive oxygen species (ROS) scavenging property. However, the role of HTHQ on cerebral ischaemic/reperfusion (I/R) injury and the underlying mechanisms remain poorly understood. In the present study, we demonstrated that HTHQ treatment ameliorated cerebral I/R injury in vivo, as demonstrated by the decreased infarct volume ration, neurological deficits, oxidative stress and neuronal apoptosis. HTHQ treatment increased the levels of nuclear factor erythroid 2–related factor 2 (Nrf2) and its downstream antioxidant protein, haeme oxygenase‐1 (HO‐1). In addition, HTHQ treatment decreases oxidative stress and neuronal apoptosis of PC12 cells following hypoxia and reperfusion (H/R) in vitro. Moreover, we provided evidence that PC12 cells were more vulnerable to H/R‐induced oxidative stress after si‐Nrf2 transfection, and the HTHQ‐mediated protection was lost in PC12 cells transfected with siNrf2. In conclusion, these results suggested that HTHQ possesses neuroprotective effects against oxidative stress and apoptosis after cerebral I/R injury via activation of the Nrf2/HO‐1 pathway.     

microRNA-340-5p inhibits hypoxia/reoxygenation-induced apoptosis and oxidative stress in cardiomyocytes by regulating the Act1/NF-κB pathway

MicroRNAs (miRNAs) have been reported to play critical roles in the occurrence, progression, and treatment of many cardiovascular diseases. However, the molecular mechanism by which miRNA regulates target gene expression in ischemia-reperfusion (I/R) injury in acute myocardial infarction (AMI) is not entirely clear. MiR-340-5p was reported to be downregulated in acute ischemic stroke. However, it still remains unknown whether miR-340-5p is mediated in the pathogenesis process of I/R injury after AMI. In the present study, male C57BL/6 J mice and H9C2 cardiomyocytes were used as experimental models. Real-time polymerase chain reaction analysis, Western blot analysis, and the terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling immunofluorescence staining assay were conducted to examine related indicators in the study. We confirmed that the expression of miR-340-5p is downregulated after I/R in AMI mice and hypoxia/reperfusion (H/R)-induced cardiomyocytes. miR-340-5p could inhibit apoptosis and oxidative stress in H/R-induced H9C2 cells via downregulating activator 1 (Act1). The inhibiting action of miR-340-5p on H/R-induced apoptosis and oxidative stress in cardiomyocytes was partially reversed after Act1 overexpression. Moreover, the results showed that the NF-κB pathway may be mediated in the role of miR-340-5p on H/R-induced cardiomyocyte apoptosis and oxidative stress. We demonstrated that upregulation of miR-340-5p suppresses apoptosis and oxidative stress induced by H/R in H9C2 cells by inhibiting Act1. Therapeutic strategies that target miR-340-5p, Act1, and the NF-κB pathway could be beneficial for the treatment of I/R injury after AMI.     

Donepezil provides neuroprotective effects against brain injury and Alzheimer's pathology under conditions of cardiac ischemia/reperfusion injury

Cardiac ischemia/reperfusion (I/R) injury induces brain pathology. Donepezil, a well-known acetylcholine esterase (AChE) inhibitor, has been proven to exert neuroprotective effects against several neurodegenerative diseases. However, the comprehensive mechanism regarding the therapeutic potential of donepezil on the brain under cardiac I/R injury remains obscure. Here, we hypothesized that treatment with donepezil ameliorates brain pathology following cardiac I/R injury by decreasing blood brain barrier (BBB) breakdown, oxidative stress, neuroinflammation, mitochondrial dysfunction, mitochondrial dynamics imbalance, microglial activation, amyloid-beta (Aβ) accumulation, neuronal apoptosis, and dendritic spine loss. Forty-eight adult male Wistar rats were subjected to surgery for cardiac I/R injury. Then, rats were randomly divided into four groups to receive either (1) saline (vehicle group), donepezil 3 mg/kg via intravenously administered (2) before ischemia (pretreatment group), (3) during ischemia (ischemia group), or (4) at the onset of reperfusion (reperfusion group). At the end of cardiac I/R paradigm, the brains were evaluated for BBB breakdown, brain inflammation, oxidative stress, mitochondrial function, mitochondrial dynamics, microglial morphology, Aβ production, neuronal apoptosis, and dendritic spine density. Administration of donepezil at all time points equally showed an attenuation of brain damage in response to cardiac I/R injury, as indicated by increased expression of BBB junction protein, reduced brain inflammation and oxidative stress, improved mitochondrial function and mitochondrial dynamics, and alleviated Aβ accumulation and microglial activation, resulting in protection of neuronal apoptosis and preservation of dendritic spine number. These findings suggest that donepezil potentially protects brain pathology caused by cardiac I/R injury regardless the timing of treatment.     

Daphnetin protects hippocampal neurons from oxygen-glucose deprivation–induced injury

Daphnetin, a coumarin derivative extracted from Daphne odora var., was reported to possess a neuroprotective effect. Recently, it has been demonstrated that daphnetin attenuates ischemia/reperfusion (I/R) injury. However, the role of daphnetin in cerebral I/R injury and the potential mechanism have not been fully understood. The present study aimed to explore the regulatory roles of daphnetin on oxygen-glucose deprivation/reoxygenation (OGD/R)–induced cell injury in a model of hippocampal neurons. Our results demonstrated that daphnetin improved cell viability and reduced the lactate dehydrogenase leakage in OGD/R–stimulated hippocampal neurons. In addition, daphnetin inhibited oxidative stress and cell apoptosis in hippocampal neurons after OGD/R stimulation. Furthermore, daphnetin significantly enhanced the nuclear translocation of the nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression in hippocampal neurons exposed to OGD/R. Knockdown of Nrf2 blocked the protective effect of daphnetin on OGD/R–induced hippocampal neurons. In conclusion, these findings demonstrated that daphnetin attenuated oxidative stress and neuronal apoptosis after OGD/R injury through the activation of the Nrf2/HO-1 signaling pathway in hippocampal neurons. Thus, daphnetin may be a novel therapeutic agent for cerebral I/R injury.     

Protective effects of chlorogenic acid against ischemia/reperfusion injury in rat liver: molecular evidence of its antioxidant and anti-inflammatory properties

Hepatic ischemia and reperfusion injury (I/R) is accompanied by excessive reactive oxygen species and resultant sterile inflammation. Chlorogenic acid (CGA), one of the most abundant polyphenols in the human diet, has been shown to exert potent anti-inflammatory, antibacterial and antioxidant activities. Thus, the purpose of the present study was to investigate protective effects of CGA and its molecular mechanisms against hepatic I/R injury. Rats were subjected to 60 min of partial hepatic ischemia followed by 5 h of reperfusion. CGA (2.5, 5 and 10 mg/kg, ip) was administered twice: 10 min prior to ischemia and 10 min before reperfusion. CGA treatment resulted in marked improvement of hepatic function and histology, and suppressed oxidative stress, as indicated by hepatic lipid peroxidation and glutathione level. Levels of serum tumor necrosis factor-α, inducible nitric oxide synthase and cyclooxygenase-2 protein and mRNA expressions were up-regulated after I/R; these effects were attenuated by CGA. Immunoblot results showed that CGA reduced I/R-induced toll-like receptor 4 overexpression, nuclear translocation of nuclear factor kappa B and interferon regulatory factor-1, high-mobility group box-1 release into extracellular milieu, and enhanced heme oxygenase-1 expression and nuclear translocation of nuclear factor erythroid 2-related factor 2. Our results suggest that CGA alleviates I/R-induced liver injury and that this protection is likely due to inhibition of inflammatory response and enhancement of antioxidant defense systems. Therefore, CGA might have potential as an agent for use in clinical treatment of hepatic I/R injury.     

AGGF1 protects from myocardial ischemia/reperfusion injury by regulating myocardial apoptosis and angiogenesis

Angiogenic factor with G patch and FHA domains 1 (AGGF1) is a newly identified proangiogenic protein, which plays an important role in vascular disease and angiogenesis. However, its role in myocardial ischemia/reperfusion (I/R) injury remains unknown. This study investigated whether AGGF1 is involved in the pathogenesis of mouse myocardial I/R injury and the underlying mechanisms. Wild-type (WT) C57BL/6 J mice were treated at 30 min prior to I/R injury with anti-AGGF1 neutralizing antibody (3 mg/kg) or recombinant human AGGF1 (rhAGGF1, 0.25 mg/kg). After I/R injury, the infarct size, the number of TUNEL-positive cardiomyocytes, Bax/Bcl2 ratio, inflammatory cytokine expression and angiogenesis were markedly increased as compared with sham control. Treatment of WT mice with anti-AGGF1 neutralizing antibody resulted in exaggeration of myocardial I/R injury but reducing angiogenesis. In contrast, administration of rhAGGF1 markedly reversed these effects. Furthermore, anti-AGGF1- or rhAGGF1-mediated effects on I/R-induced cardiac apoptosis, inflammation and angiogenesis were dose dependent. In addition, the protective effects of AGGF1 on cardiomyocyte apoptosis and inflammation were confirmed in cultured cardiomyocytes after I/R. Finally, these effects were associated with activation of ERK1/2, Stat3 and HIF-1α/VEGF pathways and inhibition of activation of NF-κB, p53 and JNK1/2 pathways. In conclusion, we report the first in vivo and in vitro evidence that AGGF1 reduces myocardial apoptosis and inflammation and enhances angiogenesis, leading to decreased infarct size after I/R injury. These results may provide a novel therapeutic approach for ischemic heart diseases.     

Endogenous HMGB1 contributes to ischemia-reperfusion-induced myocardial apoptosis by potentiating the effect of TNF-α/JNK

High-mobility group box 1 (HMGB1) is a nuclear protein that has been implicated in the myocardial inflammation and injury induced by ischemia-reperfusion (I/R). The purpose of the present study was to assess the role of HMGB1 in myocardial apoptosis induced by I/R. In vivo, myocardial I/R induced an increase in myocardial HMGB1 expression and apoptosis. Inhibition of HMGB1 (A-box) ameliorated the I/R-induced myocardial apoptosis. In vitro, isolated cardiac myocytes were challenged with anoxia-reoxygenation (A/R; in vitro correlate to I/R). A/R-challenged myocytes also generated HMGB1 and underwent apoptosis. Inhibition of HMGB1 attenuated the A/R-induced myocyte apoptosis. Exogenous HMGB1 had no effect on myocyte apoptosis. However, inhibition of HMGB1 attenuated myocyte TNF-α production after the A/R was challenged; surprisingly, HMGB1 itself did not induce myocyte TNF-α production. Exogenous TNF-α induced a moderate proapoptotic effect on the myocytes, an effect substantially potentiated by coadministration of HMGB1. It is generally accepted that apoptosis induced by TNF-α is regulated by the balance of activation of c-Jun NH(2)-terminal kinase (JNK) and NF-κB. Indeed, in the present study, TNF-α increased the phosphorylation status of JNK and p65, a subunit of NF-κB; HMGB1 greatly potentiated TNF-α-induced JNK phosphorylation. Furthermore, inhibition of JNK (SP-600125) prevented the myocyte apoptosis induced by a TNF-α/HMGB1 cocktail. Finally, A/R increased HMGB1 production in both wild-type and toll-like receptor 4-deficient myocytes; however, deficiency in toll-like receptor 4 diminished A/R-induced myocyte apoptosis, TNF-α, and JNK activation. Our results indicate that myocyte-derived HMGB1 and TNF-α work in concert to promote I/R-induced myocardial apoptosis through JNK activation.     

Suppression of NF-κB Reduces Myocardial No-Reflow

No-reflow phenomenon is a risk factor which severely compromises the benefits of coronary revascularization in patients with acute myocardial infarction. Inflammatory response, as an essential component of cardiac ischemia/reperfusion (I/R) injury, has been suggested to contribute to the myocardial no-reflow. Since nuclear factor kappa B (NF-κB) is a key mediator of inflammation, we reasoned that inhibition of NF-κB might reduce the extent of no-reflow. To test this hypothesis, the left circumflex coronary arteries of New Zealand white male rabbits were ligated for 1.5 h, followed by reperfusion for 1 h to induce I/R injury. Pretreatment of the rabbits with a specific NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), significantly attenuated neutrophil infiltration in the no-reflow area as well as the expansion of no-reflow. These beneficial effects were associated with a marked reduction in the serum levels of myocardial induced I/R tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and CXCL16. Consistently, simulative I/R culture of human umbilical vein endothelial cells (HUVECs) resulted in an increase of TNF-α, ICAM-1 and CXCL16, and all of these changes were significantly suppressed by pretreatment of the cells with PDTC or with siRNA-mediated p65 knockdown. Our data thus suggest that inhibition of NF-κB may reduce I/R-associated myocardial no-reflow through reduction of myocardial inflammation.     

Inhibition of cathepsin S attenuates myocardial ischemia/reperfusion injury by suppressing inflammation and apoptosis

Myocardial ischemia/reperfusion (I/R) injury leads to high mortality and morbidity due to the incomplete understanding of the underlying mechanism and the consequent lack of effective therapy. The present study revealed and validated key candidate genes in relation to inflammation and apoptosis pathways underlying myocardial I/R injury. Cathepsin S was identified as the top hub protein based on the protein–protein interaction analysis, and, thus, its role during myocardial I/R injury was further investigated. Myocardial I/R in mice resulted in significantly increased levels of myocardial injury biomarkers (cardiac troponin I, lactic dehydrogenase, and creatinine kinase‐MB) and inflammatory cytokines (interleukin‐1β [IL‐1β], IL‐6, and tumor necrosis factor‐α), elevated apoptosis rate, and upregulated protein expression of cleaved caspase‐8, cleaved caspase‐3, and cleaved poly ADP‐ribose polymerase. These abovementioned changes were blocked by two different selective cathepsin S inhibitors, LY3000328 or MIV‐247. Moreover, Kaplan–Meier survival plot showed that cathepsin S inhibition improved 21‐day survival rate following myocardial I/R injury. This study demonstrated that the inhibition of cathepsin S alleviated myocardial I/R‐induced injury by suppressing inflammation and apoptosis, which may be used in clinical applications of cardioprotection.     

Vitamin D ameliorates hepatic ischemic/reperfusion injury in rats

Vitamin D, most commonly associated with the growth and remodeling of bone, has been shown to ameliorate ischemia/reperfusion injury (IRI) in some tissues, yet its underlying mechanism remains elusive. This study was designed to examine the protective effect of vitamin D, if any, against hepatic IRI in rats and the underlying mechanism involved. Adult female Wistar rats were randomly divided into control, sham-operated (sham), ischemia/reperfusion (I/R), and ischemic-reperfused vitamin D-treated (vit D) groups. Rats in the I/R and vit D groups were subjected to partial (70 %) hepatic ischemia for 45 min, followed by 1 h of reperfusion. Vitamin D was given to rats orally in a dose of 500 IU/kg daily for 2 weeks before being subjected to I/R. Markers of liver damage, oxidative stress, inflammation and apoptosis were evaluated. Hepatic morphology was also examined. Vit D-treated rats had significantly lower serum levels of alanine aminotransferase, aspartate aminotransferase, and γ glutamyl transferase compared to rats in the I/R group. Also, vit D-treated rats showed a significant decrease in malondialdehyde, interleukin-1 beta, interleukin-6, tumor necrosis factor-α, nuclear factor κB, B cell leukemia/lymphoma 2-associated X protein, cytochrome c, and caspase-3 levels, with higher levels of glutathione peroxidase and B cell lymphoma 2 protein levels in liver tissues compared to I/R rats. Histological examination showed less damaged liver tissues with amelioration of apoptotic signs in the vit D group compared to the I/R group. In conclusion, vitamin D supplementation ameliorates hepatic IRI mostly by alleviating the inflammatory-apoptotic response mediated by the oxidative reperfusion injury insult.     

Toll-like receptor 3 plays a role in myocardial infarction and ischemia/reperfusion injury

Innate immune and inflammatory responses mediated by Toll like receptors (TLRs) have been implicated in myocardial ischemia/reperfusion (I/R) injury. This study examined the role of TLR3 in myocardial injury induced by two models, namely, myocardial infarction (MI) and I/R. First, we examined the role of TLR3 in MI. TLR3 deficient (TLR3^−/−) and wild type (WT) mice were subjected to MI induced by permanent ligation of the left anterior descending (LAD) coronary artery for 21 days. Cardiac function was measured by echocardiography. Next, we examined whether TLR3 contributes to myocardial I/R injury. TLR3^−/− and WT mice were subjected to myocardial ischemia (45 min) followed by reperfusion for up to 3 days. Cardiac function and myocardial infarct size were examined. We also examined the effect of TLR3 deficiency on I/R-induced myocardial apoptosis and inflammatory cytokine production. TLR3^−/− mice showed significant attenuation of cardiac dysfunction after MI or I/R. Myocardial infarct size and myocardial apoptosis induced by I/R injury were significantly attenuated in TLR3^−/− mice. TLR3 deficiency increases B-cell lymphoma 2 (BCL2) levels and attenuates I/R-increased Fas, Fas ligand or CD95L (FasL), Fas-Associated protein with Death Domain (FADD), Bax and Bak levels in the myocardium. TLR3 deficiency also attenuates I/R-induced myocardial nuclear factor KappaB (NF-κB) binding activity, Tumor necrosis factor alpha (TNF-α) and Interleukin-1 beta (IL-1β) production as well as I/R-induced infiltration of neutrophils and macrophages into the myocardium. TLR3 plays an important role in myocardial injury induced by MI or I/R. The mechanisms involve activation of apoptotic signaling and NF-κB binding activity. Modulation of TLR3 may be an effective approach for ameliorating heart injury in heart attack patients.     

Nitric oxide mediates cardiac protection of tissue kallikrein by reducing inflammation and ventricular remodeling after myocardial ischemia/reperfusion

We assessed the role of nitric oxide (NO) and the kinin B2 receptor in mediating tissue kallikrein's actions in intramyocardial inflammation and cardiac remodeling after ischemia/reperfusion (I/R) injury. Adenovirus carrying the human tissue kallikrein gene was delivered locally into rat hearts 4 days prior to 30-minute ischemia followed by 24-hour or 7-day reperfusion with or without administration of icatibant, a kinin B2 receptor antagonist, or N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor. Kallikrein gene delivery improved cardiac contractility and diastolic function, reduced infarct size at 1 day after I/R without affecting mean arterial pressure. Kallikrein treatment reduced macrophage/monocyte and neutrophil accumulation in the infarcted myocardium in association with reduced intercellular adhesion molecule-1 levels. Kallikrein increased cardiac endothelial nitric oxide synthase phosphorylation and NO levels and decreased superoxide formation, TGF-beta1 levels and Smad2 phosphorylation. Furthermore, kallikrein reduced I/R-induced JNK, p38MAPK, IkappaB-alpha phosphorylation and nuclear NF-kappaB activation. In addition, kallikrein improved cardiac performance, reduced infarct size and prevented ventricular wall thinning at 7 days after I/R. The effects of kallikrein on cardiac function, inflammation and signaling mediators were all blocked by icatibant and L-NAME. These results indicate that tissue kallikrein through kinin B2 receptor and NO formation improves cardiac function, prevents inflammation and limits left ventricular remodeling after myocardial I/R by suppression of oxidative stress, TGF-beta1/Smad2 and JNK/p38MAPK signaling pathways and NF-kappaB activation.