Zhong-yuan Xia

Synergy of isoflurane preconditioning and propofol postconditioning reduces myocardial reperfusion injury in patients

Either isoflurane preconditioning or high-dose propofol treatment has been shown to attenuate myocardial IRI (ischaemia/reperfusion injury) in patients undergoing CABG (coronary artery bypass graft) surgery. It is unknown whether isoflurane and propofol may synergistically attenuate myocardial injury in patients. The present study investigated the efficacy of IsoPC (isoflurane preconditioning), propofol treatment (postconditioning) and their synergy in attenuating postischaemic myocardial injury in patients undergoing CABG surgery using CPB (cardiopulmonary bypass). Patients (n = 120) selected for CABG surgery were randomly assigned to one of four groups (n = 30 each). After induction, anaesthesia was maintained either with fentanyl and midazolam (control; group C); with propofol at 100 μg x kg(-1) of body weight x min(-1) before and during CPB followed by propofol at 60 μg x kg(-1) of body weight x min(-1) for 15 min after aortic declamping (group P); with isoflurane 1-1.5% end tidal throughout the surgery (group I) or with isoflurane 1-1.5% end tidal before CPB and switching to propofol at 100 μg x kg(-1) of body weight x min(-1) during CPB followed by propofol at 60 μg x kg(-1) of body weight x min(-1) for 15 min after aortic declamping (group IP, i.e. IsoPC plus propofol postconditioning). A joint isoflurane and propofol anaesthesia regimen synergistically reduced plasma levels of cTnI (cardiac troponin I) and CK-MB (creatine kinase MB) and f-FABP (heart-type fatty acid-binding protein) (all P < 0.05 compared with control, group P or group I) and facilitated postoperative myocardial functional recovery. During reperfusion, myocardial tissue eNOS (endothelial NO synthase) protein expression in group IP was significantly higher, whereas nitrotyrosine protein expression was lower than those in the control group. In conclusion, a joint isoflurane preconditioning and propofol anaesthesia regimen synergistically attenuated myocardial reperfusion injury in patients.

Ginsenoside Rb1 preconditioning enhances eNOS expression and attenuates myocardial ischemia/reperfusion injury in diabetic rats.

Diabetes mellitus is associated with decreased NO bioavailability in the myocardium. Ginsenoside Rb1 has been shown to confer cardioprotection against ischemia reperfusion injury. The aim of this study was to investigate whether Ginsenoside Rb1 exerts cardioprotective effects during myocardial ischemia-reperfusion in diabetic rats and whether this effect is related to increase the production of NO via enhancing eNOS expression in the myocardium. The myocardial I/R injury were induced by occluding the left anterior descending artery for 30 min followed by 120 min reperfusion. An eNOS inhibitor L-NAME or Rb1 were respectively administered 25 min or 10 min before inducing ischemia. Ginsenoside Rb1 preconditioning reduced myocardial infarct size when compared with I/R group. Ginsenoside Rb1 induced myocardial protection was accompanied with increased eNOS expression and NO concentration and reduced plasma CK and LDH (P < 0.05). Moreover, the myocardial oxidative stress and tissue histological damage was attenuated by Ginsenoside Rb1 (P < 0.05). L-NAME abolished the protective effects of Ginsenoside Rb1. It is concluded that Ginsenoside Rb1 protects against myocardium ischemia/reperfusion injury in diabetic rat by enhancing the expression of eNOS and increasing the content of NO as well as inhibiting oxidative stress.

L-arginine enhances nitrative stress and exacerbates tumor necrosis factor-α toxicity to human endothelial cells in culture: Prevention by propofol

Supplementation of L-arginine, a nitric oxide precursor, during the late phase of myocardial ischemia/reperfusion increases myocyte apoptosis and exacerbates myocardial injury, but the underlying mechanism is unclear. During myocardial ischemia/reperfusion, apoptosis of endothelial cells precedes that of cardiomyocyte. Tumor necrosis factor-α (TNF) production is increased during myocardial ischemia/reperfusion, which may exacerbate myocardial injury by inducing endothelial cell apoptosis. We postulated that L-arginine may exacerbate TNF-induced endothelial cell apoptosis by enhancing peroxynitrite-mediated nitrative stress. Cultured human umbilical vein endothelial cells were either not treated (control) or treated with TNF alone or with TNF in the presence of L-arginine, the nonselective nitric oxide synthase inhibitor N (omega)-nitro-L-arginine (L-NNA), propofol (an anesthetic that scavenges peroxynitrite), or L-arginine plus propofol, respectively, for 24 hours. TNF increased intracellular superoxide and hydrogen peroxide production accompanied by increases of inducible nitric oxide synthase (iNOS) protein expression and nitric oxide production. This was accompanied by increased protein expression of nitrotyrosine, a fingerprint of peroxynitrite and an index of nitrative stress, and increased endothelial cell apoptosis. L-arginine did not enhance TNF-induced increases of superoxide and peroxynitrite production but further increased TNF-induced increase of nitrotyrosine production and exacerbated TNF-mediated cell apoptosis. L-NNA and propofol, respectively, reduced TNF-induced nitrative stress and attenuated TNF cellular toxicity. The L-arginine-mediated enhancement of nitrative stress and TNF toxicity was attenuated by propofol. Thus, under pathological conditions associated with increased TNF production, L-arginine supplementation may further exacerbate TNF cellular toxicity by enhancing nitrative stress.

Shen-Fu Injection Preconditioning Inhibits Myocardial Ischemia-Reperfusion Injury in Diabetic Rats: Activation of eNOS via the PI3K/Akt Pathway

The aim of this paper is to investigate whether Shen-fu injection (SFI), a traditional Chinese medicine, could attenuate myocardial ischemia-reperfusion (MI/R) injury in diabetes. Streptozotocin-induced diabetic rats were randomly assigned to the Sham, I/R, SFI preconditioning, and SFI plus wortmannin (a phosphatidylinositol 3-kinase inhibitor) groups. After the treatment, hearts were subjected to 30 min of coronary artery occlusion and 2 h reperfusion except the Sham group. Myocardial infarct size and cardiomyocytes apoptosis were increased significantly in MI/R group as compared with the Sham group. SFI preconditioning significantly decreased infarct size, apoptosis, caspase-3 protein expression, MDA level in myocardial tissues, and plasma level of CK and LDH but increased p-Akt, p-eNOS, bcl-2 protein expression, and SOD activity compared to I/R group. Moreover, SFI-induced cardioprotection was abolished by wortmannin. We conclude that SFI preconditioning protects diabetic hearts from I/R injury via PI3K/Akt-dependent pathway.

Propofol Ameliorates Hyperglycemia-Induced Cardiac Hypertrophy and Dysfunction via Heme Oxygenase-1/Signal Transducer and Activator of Transcription 3 Signaling Pathway in Rats

Objectives:Heme oxygenase-1 is inducible in cardiomyocytes in response to stimuli such as oxidative stress and plays critical roles in combating cardiac hypertrophy and injury. Signal transducer and activator of transcription 3 plays a pivotal role in heme oxygenase-1-mediated protection against liver and lung injuries under oxidative stress. We hypothesized that propofol, an anesthetic with antioxidant capacity, may attenuate hyperglycemia-induced oxidative stress in cardiomyocytes via enhancing heme oxygenase-1 activation and ameliorate hyperglycemia-induced cardiac hypertrophy and apoptosis via heme oxygenase-1/signal transducer and activator of transcription 3 signaling and improve cardiac function in diabetes. Design:Treatment study. Setting:Research laboratory.Subjects: Sprague-Dawley rats. Interventions:In vivo and in vitro treatments. Measurements and Main Results:At 8 weeks of streptozotocin-induced type 1 diabetes in rats, myocardial 15-F2t-isoprostane was significantly increased, accompanied by cardiomyocyte hypertrophy and apoptosis and impaired left ventricular function that was coincident with reduced heme oxygenase-1 activity and signal transducer and activator of transcription 3 activation despite an increase in heme oxygenase-1 protein expression as compared to control. Propofol infusion (900 &mgr;g/kg/min) for 45 minutes significantly improved cardiac function with concomitantly enhanced heme oxygenase-1 activity and signal transducer and activator of transcription activation. Similar to the changes seen in diabetic rat hearts, high glucose (25 mmol/L) exposure for 48 hours led to cardiomyocyte hypertrophy and apoptosis, both in primary cultured neonatal rat cardiomyocytes and in H9c2 cells compared to normal glucose (5.5 mmol/L). Hypertrophy was accompanied by increased reactive oxygen species and malondialdehyde production and caspase-3 activity. Propofol, similar to the heme oxygenase-1 inducer cobalt protoporphyrin, significantly increased cardiomyocyte heme oxygenase-1 and p-signal transducer and activator of transcription protein expression and heme oxygenase-1 activity and attenuated high-glucose-mediated cardiomyocyte hypertrophy and apoptosis and reduced reactive oxygen species and malondialdehyde production (p < 0.05). These protective effects of propofol were abolished by heme oxygenase-1 inhibition with zinc protoporphyrin and by heme oxygenase-1 or signal transducer and activator of transcription 3 gene knockdown. Conclusions:Heme oxygenase-1/signal transducer and activator of transcription 3 signaling plays a critical role in propofol-mediated amelioration of hyperglycemia-induced cardiomyocyte hypertrophy and apoptosis, whereby propofol improves cardiac function in diabetic rats.

Hyperglycemia-Induced Inhibition of DJ-1 Expression Compromised the Effectiveness of Ischemic Postconditioning Cardioprotection in Rats

Ischemia postconditioning (IpostC) is an effective way to alleviate ischemia and reperfusion injury; however, the protective effects seem to be impaired in candidates with diabetes mellitus. To gain deep insight into this phenomenon, we explored the role of DJ-1, a novel oncogene, that may exhibit powerful antioxidant capacity in postconditioning cardioprotection in a rat model of myocardial ischemia reperfusion injury. Compared with normal group, cardiac DJ-1 was downregulated in diabetes. Larger postischemic infarct size as well as exaggeration of oxidative stress was observed, while IpostC reversed the above changes in normal but not in diabetic rats. DJ-1 was increased after ischemia and postconditioning contributed to a further elevation; however, no alteration of DJ-1 was documented in all subgroups of diabetic rats. Alteration of the cardioprotective PI3K/Akt signaling proteins may be responsible for the ineffectiveness of postconditioning in diabetes. There is a positive correlation relationship between p-Akt and DJ-1 but a negative correlation between infarct size and DJ-1, which may partially explain the interaction of DJ-1 and IpostC cardioprotection. Our result indicates a beneficial role of DJ-1 in myocardial ischemia reperfusion. Downregulation of cardiac DJ-1 may be responsible for the compromised diabetic heart responsiveness to IpostC cardioprotection.

Long non-coding RNA MALAT1 functions as a mediator in cardioprotective effects of fentanyl in myocardial ischemia-reperfusion injury.

Long non‐coding (lncRNA) MALAT1 can be increased by hypoxia or ischemic limbs. Also, downregulation of MALAT1 contributes to reduction of cardiomyocyte apoptosis. However, the functional involvement of MALAT1 in myocardial ischemia‐reperfusion (I/R) injury has not been defined. This study investigated the functional involvement of lncRNA‐MALAT1 in cardioprotective effects of fentanyl. HL‐1, a cardiac muscle cell line from the AT‐1 mouse atrial cardiomyocyte tumor lineage was pre‐treated with fentanyl and generated cell model of hypoxia‐reoxygenation (H/R). Relative expression of MALAT1, miR‐145, and Bnip3 mRNA in cells was determined by quantitative real‐time PCR. Cardiomyocyte H/R injury was indicated by lactate dehydrogenase (LDH) release and cell apoptosis. The results showed that fentanyl abrogates expression of responsive gene for H/R and induces downregulation of MALAT1 and Bnip3 and upregulation of miR‐145. We found that miR‐145/Bnip3 pathway was negatively regulated by MALAT1 in H/R‐HL‐1 cell with or without fentanyl treatment. Moreover, both MALAT1 overexpression and miR‐145 knockdown reverse cardioprotective effects of fentanyl, as indicated by increase in LDH release and cell apoptosis. The reversal effect of MALAT1 for fentanyl is confirmed in cardiac ischemia/reperfusion (I/R) mice. In summary, lncRNA‐MALAT1 is sensitive to H/R injury and abrogates cardioprotective effects of Fentanyl by negatively regulating miR‐145/Bnip3 pathway.

Ginsenoside Rb1 Treatment Attenuates Pulmonary Inflammatory Cytokine Release and Tissue Injury following Intestinal Ischemia Reperfusion Injury in Mice

Objective. Intestinal ischemia reperfusion (II/R) injury plays a critical role in remote organ dysfunction, such as lung injury, which is associated with nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. In the present study, we tested whether ginsenoside Rb1 attenuated II/R induced lung injury by Nrf2/HO-1 pathway. Methods. II/R injury was induced in male C57BL/6J mice by 45 min of superior mesenteric artery (SMA) occlusion followed by 2 hours of reperfusion. Ginsenoside Rb1 was administrated prior to reperfusion with or without ATRA (all-transretinoic acid, the inhibitor of Nrf2/ARE signaling pathway) administration before II/R. Results. II/R induced lung histological injury, which is accompanied with increased levels of malondialdehyde (MDA), interleukin- (IL-) 6, and tumor necrosis factor- (TNF-) α but decreased levels of superoxide dismutase (SOD) and IL-10 in the lung tissues. Ginsenoside Rb1 reduced lung histological injury and the levels of TNF-α and MDA, as well as wet/dry weight ratio. Interestingly, the increased Nrf2 and HO-1 expression induced by II/R in the lung tissues was promoted by ginsenoside Rb1 treatment. All these changes could be inhibited or prevented by ATRA. Conclusion. Ginsenoside Rb1 is capable of ameliorating II/R induced lung injuries by activating Nrf2/HO-1 pathway.

Selective inhibition of PTEN preserves ischaemic post-conditioning cardioprotection in STZ-induced Type 1 diabetic rats: role of the PI3K/Akt and JAK2/STAT3 pathways

Patients with diabetes are vulnerable to MI/R (myocardial ischaemia/reperfusion) injury, but are not responsive to IPostC (ischaemic post-conditioning) which activates PI3K (phosphoinositide 3-kinase)/Akt (also known as PKB or protein kinase B) and JAK2 (Janus kinase 2)/STAT3 (signal transducer and activator of transcription 3) pathways to confer cardioprotection. We hypothesized that increased cardiac PTEN (phosphatase and tensin homologue deleted on chromosome 10), a major negative regulator of PI3K/Akt, is responsible for the loss of diabetic heart sensitivity to IPostC cardioprotecton. In STZ (streptozotocin)-induced Type 1 diabetic rats subjected to MI/R (30 min coronary occlusion and 120 min reperfusion), the post-ischaemic myocardial infarct size, CK-MB (creatine kinase-MB) and 15-F2t-isoprostane release, as well as cardiac PTEN expression were significantly higher than those in non-diabetic controls, concomitant with more severe cardiac dysfunction and lower cardiac Akt, STAT3 and GSK-3β (glycogen synthase kinase 3β) phosphorylation. IPostC significantly attenuated post-ischaemic infarct size, decreased PTEN expression and further increased Akt, STAT3 and GSK-3β phosphorylation in non-diabetic, but not in diabetic rats. Application of the PTEN inhibitor BpV (bisperoxovanadium) (1.0 mg/kg) restored IPostC cardioprotection in diabetic rats. HPostC (hypoxic post-conditioning) in combination with PTEN gene knockdown, but not HPostC alone, significantly reduced H/R (hypoxia/reoxygenation) injury in cardiac H9c2 cells exposed to high glucose as was evident from reduced apoptotic cell death and JC-1 monomer in cells, accompanied by increased phosphorylation of Akt, STAT3 and GSK-3β. PTEN inhibition/gene knockdown mediated restoration of IPostC/HPostC cardioprotection was completely reversed by the PI3K inhibitor wortmannin, and partially reversed by the JAK2 inhibitor AG490. Increased cardiac PTEN, by impairing PI3K/Akt and JAK2/STAT3 pathways, is a major mechanism that rendered diabetic hearts not responsive to post-conditioning cardioprotection.

Antioxidant N-acetylcysteine attenuates the reduction of Brg1 protein expression in the myocardium of type 1 diabetic rats.

Brahma-related gene 1 (Brg1) is a key gene in inducing the expression of important endogenous antioxidant enzymes, including heme oxygenase-1 (HO-1) which is central to cardioprotection, while cardiac HO-1 expression is reduced in diabetes. It is unknown whether or not cardiac Brg1 expression is reduced in diabetes. We hypothesize that cardiac Brg1 expression is reduced in diabetes which can be restored by antioxidant treatment with N-acetylcysteine (NAC). Control (C) and streptozotocin-induced diabetic (D) rats were treated with NAC in drinking water or placebo for 4 weeks. Plasma and cardiac free15-F2t-isoprostane in diabetic rats were increased, accompanied with increased plasma levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin 6 (IL-6), while cardiac Brg1, p-STAT3 and HO-1 protein expression levels were significantly decreased. Left ventricle weight/body weight ratio was higher, while the peak velocities of early (E) and late (A) flow ratio was lower in diabetic than in C rats. NAC normalized tissue and plasma levels of 15-F2t-isoprostane, significantly increased cardiac Brg1, HO-1 and p-STAT3 protein expression levels and reduced TNF-alpha and IL-6, resulting in improved cardiac function. In conclusion, myocardial Brg1 is reduced in diabetes and enhancement of cardiac Brg1 expression may represent a novel mechanism whereby NAC confers cardioprotection.