Ischemic postconditioning mediates cardioprotection via PI3K/GSK-3β/β-catenin signaling pathway in ischemic rat myocardium

Previous studies have shown that PI3K/GSK-3β/β-catenin signaling pathway plays a vital role in ischemic preconditioning. The present study attempts to evaluate whether PI3K/GSK-3β/β-catenin signaling pathway might be responsible for the cardioprotection in ischemic postconditioning. Male Sprague-Dawley rats underwent 30 min of left anterior descending coronary artery occlusion and 2 h of reperfusion. One hundred twenty rats were randomized into six groups: sham, ischemia/reperfusion (I/R), ischemic postconditioning (Post), 15 μg · kg wortmannin (PI3K inhibitor) plus ischemic postconditioning (Wort + Post), wortmannin plus I/R (Wort + I/R), and 0.6 mg · kg SB216763 (GSK-3β inhibitor) plus I/R (SB + I/R). Wortmannin and SB216763 were administered, respectively, 10 and 5 min before reperfusion. Myocardial infarct size; number of apoptotic cardiomyocytes; total Akt, GSK-3β; phosphorylated Akt, GSK-3β; β-catenin in cytosol and nucleus; and Bcl-2 protein were assessed. It was found that Post and SB + I/R reduced infarct size (32.3% [SD, 2.8%], 32.7% [SD, 2.1%], vs. 53.4% [SD, 3.2%], respectively, P < 0.05) and apoptotic index of cardiomyocytes (23.2% [SD, 1.8%], 23.8% [SD, 1.8%], vs. 47.3% [SD, 5.8%], respectively, P < 0.05); compared with I/R, wortmannin abolished the cardioprotection of ischemic postconditioning. Post and SB + I/R increased phosphorylated Akt, phosphorylated GSK3β, β-catenin in cytosol and nucleus, and Bcl-2 expression versus I/R. These results indicate that ischemic postconditioning could induce myocardial protection via PI3K/GSK-3β/β-catenin signaling pathway, activation of which results in accumulation of β-catenin and upregulation of its target genes Bcl-2.     

Astragaloside IV stimulates angiogenesis and increases hypoxia-inducible factor-1α accumulation via phosphatidylinositol 3-kinase/Akt pathway

Astragaloside IV is the major active constituent of Astragalus membranaceus, which has been widely used for the treatment of cardiovascular diseases in China. The aim of this study was to determine the angiogenic effect of astragaloside IV and its underlying mechanism. We used the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay, Western blotting, real-time polymerase chain reaction, and immunofluorescence to detect the effect of astragaloside IV on proliferation of human umbilical vein endothelial cells (HUVECs), the phospho-Akt protein level, hypoxia-inducible factor-1α (HIF-1α) accumulation, vascular endothelial growth factor mRNA expression, and applied cell migration, tube formation, and chick chorioallantoic membrane assays to study the angiogenic effect of astragaloside IV. Results indicate that astragaloside IV promoted cell proliferation and stimulated HIF-1α accumulation during hypoxia. Mechanism studies revealed that astragaloside IV did not affect the degradation of HIF-1α protein or the level of HIF-1α mRNA. In contrast, astragaloside IV apparently activated the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, which regulates HIF-1α protein synthesis. Moreover, astragaloside IV also stimulated cell migration, increased tube formation, and promoted angiogenesis in the chick chorioallantoic membrane assay. All angiogenic effects of astragaloside IV were reversed by the PI3K inhibitor. Taken together, our data collectively reveal that astragaloside IV is a novel regulator of HIF-1α and angiogenesis through the PI3K/Akt pathway in HUVECs that are exposed to hypoxia.     

Synergistic cytotoxicity of BIIB021 with triptolide through suppression of PI3K/Akt/mTOR and NF-κB signal pathways in thyroid carcinoma cells

The effec.t of BIIB021, a novel heat shock protein 90 (hsp90) inhibitor, on survival of thyroid carcinoma cells has not been evaluated. In this study, the impact of BIIB021 alone or in combination with the histone acetyltransferase inhibitor triptolide on survival of thyroid carcinoma cells was identified. In 8505C and TPC-1 thyroid carcinoma cells, BIIB021 caused cell death in conjunction with alterations in expression of hsp90 client proteins. Cotreatment of both BIIB021 and triptolide, compared with treatment of BIIB021 alone, decreased cell viability, and increased the percentage of dead cells and cytotoxic activity. All of the combination index values were lower than 1.0, suggesting synergistic activity of BIIB021 with triptolide in induction of cytotoxicity. In treatment of both BIIB021 and triptolide, compared with treatment of BIIB021 alone, the protein levels of total and phospho-p53, and cleaved caspase-3 were elevated, while those of total Akt, phospho-mTOR, phospho-4EBP1, phospho-S6K, phospho-NF-κB, survivin, X-linked inhibitor of apoptosis protein (xIAP), cellular inhibitor of apoptosis protein (cIAP) and acetyl. histone H4 were reduced. These results suggest that BIIB021 has a cytotoxic activity accompanied by regulation of hsp90 client proteins in thyroid carcinoma cells. Moreover, the synergism between BIIB021 and triptolide in induction of cytotoxicity is associated with the inhibition of PI3K/Akt/mTOR and NF-κB signal pathways, the underexpression of survivin and the activation of DNA damage response in thyroid carcinoma cells.     

Down-regulated PLAC8 promotes hepatocellular carcinoma cell proliferation by enhancing PI3K/Akt/GSK3β/Wnt/β-catenin signaling

Hepatocellular carcinoma (HCC) is a common, prevalent malignancy. Its poor prognosis is mainly related to high rate of diagnosis in non-curable stages, in which patients are suitable for palliative treatment. Placenta-specific 8 (PLAC8), also known as Onzin, is a small, highly conserved, cysteine-rich protein. In current study, we found that PLAC8 is prominently decreased in HCC tissues compared with adjacent tissues and patients with low level of PLAC8 suffered a poor prognosis. In addition, cellular function assays demonstrate that down-regulated PLAC8 promotes cell viability, proliferation and tumor formation both in vitro and in vivo. Furthermore, we validate that down-regulated PLAC8 enhances the activity of PI3K/Akt/GSK3β and Wnt/β-catenin signaling to promote cell proliferation. Moreover, we proved that highly expressed miR-185-5p targets PLAC8 in HCC tissues. In conclusion, our findings enlarged our knowledge about the roles of PLAC8 in HCC progression and miR-185-5p/PLAC8/β-catenin axis might be a novel pathway for HCC treatment.     

Bisoprolol,a β1 antagonist,protects myocardial cells from ischemia–reperfusion injury via PI3K/AKT/GSK3β pathway

The aim of this work was to explore whether bisoprolol plays a protective role in cardiomyocytes against ischemia–reperfusion injury via PI3K/AKT/ GSK3β pathway. We pretreated male Sprague Dawley (SD) rats with bisoprolol by oral administration prior to 0.5 h ischemia/4 h reperfusion. Myocardial infarct size and serum levels of cTnI and CK-MB were measured. In vitro, H9c2 cells were treated with hypoxia and reoxygenation, followed by measurement of cell viability, apoptosis, ROS production, cytometry, activities of AKT, GSK3β, and p-38 in the presence and absence of GSK3β siRNA. We found that bisoprolol reduced infarct size from 44% in I/R group to 31% in treated group (P < 0.05). The levels of cTnI and CK-MB were decreased from 286 ± 7 pg/mL and 32.2 ± 2 ng/mL in I/R group to 196 ± 2 pg/mL and 19.6 ± 0.9 ng/mL in the treated group, respectively (P < 0.05). Bisoprolol also increased cell viability while decreased apoptosis and ROS production in the treatment of hypoxia/ reoxygenation. Furthermore, bisoprolol increased AKT and GSK3β phosphorylation, an effect that was immediately eliminated by LY294002. GSK3β-specific siRNA experiment further confirmed that bisoprolol protected the myocardium against hypoxia/reoxygenation-induced injury via suppressing GSK3β activity. In conclusion, bisoprolol protected myocardium against ischemia–reperfusion injury via the PI3K/AKT/ GSK3β pathway.     

Curcumin alleviates lipopolysaccharide induced sepsis and liver failure by suppression of oxidative stress-related inflammation via PI3K/AKT and NF-κB related signaling

In many liver disorders, oxidative stress-related inflammation and apoptosis are important pathogenic components, finally resulting in acute liver failure. Erythropoietin and its analogues are well known to influence the interaction between apoptosis and inflammation in brain and kidney. The study is to clarify the effect of curcumin, a natural plant phenolic food additive, on lipopolysaccharides (LPS)-induced acute liver injury of mice with endotoxemia and associated molecular mechanism from inflammation, apoptosis and oxidative stress levels. And curcumin, lowered serum cytokines, including Interleukin 1beta (IL-1β), Interleukin 6 (IL-6) and tumor necrosis factor (TNF-α), and improved liver apoptosis through suppressing phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway and inhibiting Cyclic AMP-responsive element-binding protein (CREB)/Caspase expression, and decreased oxidative stress-associated protein expression, mainly involving 2E1 isoform of cytochrome P450/nuclear factor E2-related factor 2/reactive oxygen species (CYP2E/Nrf2/ROS) signaling pathway, as well as liver nitric oxide (NO) production in LPS-induced mice. Moreover, curcumin regulated serum alanine transaminase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP), accelerated liver antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione peroxidase (GSH-px) levels, and inhibited activation of the mitogen-activated protein kinases/c-Jun NH2-terminal kinase (P38/JNK) cascade in the livers of LPS-induced rats. Thus, curcumin treatment attenuates LPS-induced PI3K/AKT and CYP2E/Nrf2/ROS signaling and liver injury. Strategies to inhibit inflammation and apoptosis signaling may provide alternatives to the current clinical approaches to improve oxidative responses of endotoxemia.     

Pleural injury and pleurisy‐induced progelatinase B/proMMP‐9 is associated with markers of neutrophil degranulation

Objective. Progelatinase B/proMMP‐9 has recently been identified as an indicator of pleural inflammation, presumably originating from granulocytes. The aim of this study was to verify the origin of progelatinase B by simultaneous estimation of specific markers of neutrophil recruitment and activation in pleural effusions following induced pleurisy and pleural injury. Material and methods. Sixty‐three samples of pleural fluid from patients undergoing therapeutic talc pleurodesis (n = 8) and explorative thoracoscopy (n = 3) collected before and at different time intervals after the intervention were analyzed for progelatinase B and neutrophil gelatinase‐associated lipocalin (NGAL)‐gelatinase complex by substrate electrophoresis, for myeloperoxidase (MPO) and interleukin‐8 (IL‐8) by immunoadsorbent sandwich assay, as well as for leukocyte count, C‐reactive protein (CRP) and total protein (TP). Results. A significant increase in free and NGAL‐complexed progelatinase B, MPO and IL‐8 was recorded within 48?h following treatment in all subjects. Progelatinase B was strongly correlated with NGAL‐gelatinase complex (r = 0.88, p = 0.001), MPO (r = 0.81, p = 0.001), neutrophil count (r = 0.75, p = 0.01) and IL‐8 (r = 0.71, p = 0.001), but not with CRP and TP. Conclusions. The results support the neutrophil origin of the proenzyme, which confirms progelatinase B as an indicator of a local inflammatory reaction. Quantifying the inflammatory reaction may be helpful in the evaluation of both the technical variants of therapeutic pleurodesis and finer discrimination of paraneoplastic effusions.     

Killing of Kras-Mutant Colon Cancer Cells via Rac-Independent Actin Remodeling by the βGBP Cytokine, a Physiological PI3K Inhibitor Therapeutically Effective In Vivo

Activating mutations in Kras are the most frequent mutations in human cancer. They define a subset of patients who do not respond to current therapies and for whom prognosis is poor. Oncogenic Kras has been shown to deregulate numerous signaling pathways of which the most intensively studied are the Ras/extracellular signal-regulated kinase cascade and the phosphoinositide 3-kinase (PI3K)/Akt cascade. However, to date, there are no effective targeted therapies in the clinic against Kras-mutant cancers. Here, we report that the β-galactoside-binding protein (βGBP) cytokine, a physiologic inhibitor of class I PI3Ks, is a potent activator of apoptosis in Kras-mutant colorectal cancer cells, even when coharboring mutant-activated PIK3CA. Our study unveils an elective route to intrinsic and extrinsic apoptosis, which involves the cytoskeleton. Early events are inhibition of PI3K activity and Rac-independent actin rearrangement assignable to phosphoinositide changes at the plasma membrane. Cyclin E deregulation, arrest of DNA synthesis, and checkpoint kinase 2 activation underscore events critical to the activation of an intrinsic apoptotic program. Clustering of CD95/Fas death receptors underscore events critical to the activation of extrinsic apoptosis. In nude mice, we present the first evidence that xenograft tumor development is strongly inhibited by Hu-r-βGBP. Taken together, our results open a new therapeutic opportunity to a subset of patients refractive to current treatments. This first demonstration of therapeutic efficacy against Kras-mutant colon cancer suggests that Hu-r-βGBP may also be therapeutically effective against other cancers harboring activating Ras mutations as well as PIK3CA mutations. Mol Cancer Ther; 11(9); 1884-93. ?2012 AACR.     

Upregulation of Tim-3 and PD-1 expression is associated with tumor antigen–specific CD8+ T cell dysfunction in melanoma patients

The paradoxical coexistence of spontaneous tumor antigen–specific immune responses with progressive disease in cancer patients furthers the need to dissect the molecular pathways involved in tumor-induced T cell dysfunction. In patients with advanced melanoma, we have previously shown that the cancer-germline antigen NY-ESO-1 stimulates spontaneous NY-ESO-1–specific CD8⁺ T cells that up-regulate PD-1 expression. We also observed that PD-1 regulates NY-ESO-1–specific CD8⁺ T cell expansion upon chronic antigen stimulation. In the present study, we show that a fraction of PD-1⁺ NY-ESO-1–specific CD8⁺ T cells in patients with advanced melanoma up-regulates Tim-3 expression and that Tim-3⁺PD-1⁺ NY-ESO-1–specific CD8⁺ T cells are more dysfunctional than Tim-3⁻PD-1⁺ and Tim-3⁻PD-1⁻ NY-ESO-1–specific CD8⁺ T cells, producing less IFN-γ, TNF, and IL-2. Tim-3–Tim-3L blockade enhanced cytokine production by NY-ESO-1–specific CD8⁺ T cells upon short ex vivo stimulation with cognate peptide, thus enhancing their functional capacity. In addition, Tim-3–Tim-3L blockade enhanced cytokine production and proliferation of NY-ESO-1–specific CD8⁺ T cells upon prolonged antigen stimulation and acted in synergy with PD-1–PD-L1 blockade. Collectively, our findings support the use of Tim-3–Tim-3L blockade together with PD-1–PD-L1 blockade to reverse tumor-induced T cell exhaustion/dysfunction in patients with advanced melanoma.There is ample evidence that patients with melanoma can develop immune responses directed against antigens expressed by their own tumor (Boon et al., 2006). Among these antigens, cancer-germline antigens (CGAs) are expressed by tumors of many different histological types, including melanoma, but not by normal tissues, except testis. Because germ cells in testis do not express HLA molecules on their surface (Haas et al., 1988), CGAs represent strictly tumor-specific T cell targets (Boon et al., 2006). Among CGAs, NY-ESO-1 has been shown to stimulate spontaneous cellular and humoral responses that are detectable only in patients with advanced NY-ESO-1–expressing cancer (Stockert et al., 1998; Jäger et al., 2000; Mandic et al., 2005; Fourcade et al., 2008). Understanding the failure of spontaneous NY-ESO-1–specific T cell responses to promote regression of NY-ESO-1⁺ tumors is therefore critical for the design of novel therapeutic interventions aimed at overcoming tumor-induced immune escape.We have previously shown that the large majority of spontaneous NY-ESO-1–specific CD8⁺ T cells up-regulates programmed death 1 (PD-1) expression (Fourcade et al., 2009), which appears to be associated with T cell exhaustion/dysfunction in chronic viral infections in animals and humans (Barber et al., 2006; Day et al., 2006; Petrovas et al., 2006; Trautmann et al., 2006). We observed that PD-1 up-regulation on spontaneous NY-ESO-1–specific CD8⁺ T cells occurs along with T cell activation and is not directly associated with an inability to produce cytokines ex vivo upon stimulation with cognate antigen. Blockade of the PD-1–programmed death ligand 1 (PD-L1) pathway in combination with prolonged antigen stimulation with PD-L1⁺ APCs or melanoma cells augmented the frequencies of cytokine-producing, proliferating, and total NY-ESO-1–specific CD8⁺ T cells. Our findings are in line with previous studies of PD-1 expression by HIV- and SIV-specific CD8⁺ T cells, demonstrating that PD-1 is a regulator of antigen-specific CD8⁺ T cell expansion in the context of chronic antigen exposure, although it does not exhibit a major impact upon their functionality on a cell-per-cell basis (Petrovas et al., 2006, 2007). To further determine whether other molecular pathways are involved in tumor antigen–specific T cell dysfunction, we studied T cell immunoglobulin and mucin-domain–containing molecule 3 (Tim-3) expression on spontaneous NY-ESO-1–specific CD8⁺ T cells from patients with advanced melanoma and investigated whether Tim-3 up-regulation defines a subgroup of dysfunctional tumor antigen–specific CD8⁺ T cells. Tim-3 is a transmembrane protein constitutively expressed on Th1/Tc1 cells in mice and humans (Monney et al., 2002). Several lines of evidence support the role of Tim-3 as an inhibitory molecule that down-regulates effector Th1/Tc1 cell responses. In mice, blocking the Tim-3–Tim-3L pathway resulted in hyperproliferation of Th1-type cells and abrogated the induction of peripheral and transplantation tolerance (Sabatos et al., 2003; Sánchez-Fueyo et al., 2003). Tim-3 interacts with its ligand galectin-9 to induce cell death in Th1 cells (Zhu et al., 2005). In humans, Tim-3 expression is defective in CD4⁺ T cells producing high levels of IFN-γ, as well as those isolated from cerebrospinal fluid of patients with multiple sclerosis (Koguchi et al., 2006). Recently, Tim-3 up-regulation has been reported in HIV-specific and HCV-specific CD8⁺ T cells in patients with progressive HIV infection and chronic hepatitis C, respectively (Jones et al., 2008; Golden-Mason et al., 2009). Tim-3⁺ HIV- and HCV-specific CD8⁺ T cells were distinct from the PD-1⁺ CD8⁺ T cells and exhibited T cell dysfunction. However, it is unknown whether tumor antigen–specific CD8⁺ T cells in patients with advanced cancers express Tim-3.In this study, we show that a fraction of PD-1⁺ NY-ESO-1–specific CD8⁺ T cells, which represents the large majority of circulating NY-ESO-1–specific CD8⁺ T cells in patients with advanced melanoma, up-regulates Tim-3 expression. Tim-3⁺PD-1⁺ NY-ESO-1–specific CD8⁺ T cells are highly dysfunctional compared with Tim-3⁻PD-1⁺ and Tim-3⁻PD-1⁻ NY-ESO-1–specific CD8⁺ T cells. Tim-3–Tim-3L pathway blockade alone or in combination with PD-1–PD-L1 pathway blockade enhanced NY-ESO-1–specific CD8⁺ T cell numbers and functions. Collectively, our findings support the use of Tim-3–Tim-3L blockade in association with PD-1–PD-L1 blockade to reverse tumor-induced T cell exhaustion/dysfunction in patients with advanced melanoma.     

The inhibition of PI3K and NFκB promoted curcumin-induced cell cycle arrest at G2/M via altering polyamine metabolism in Bcl-2 overexpressing MCF-7 breast cancer cells

Bcl-2 protein has been contributed with number of genes which are involved in oncogenesis. Among the many targets of Bcl-2, NFκB have potential role in induction of cell cycle arrest. Curcumin has potential therapeutic effects against breast cancer through multiple signaling pathways. In this study, we investigated the role of curcumin in induction of cell cycle arrest via regulating of NFκB and polyamine biosynthesis in wt and Bcl-2+ MCF-7 cells. To examine the effect of curcumin on cell cycle regulatory proteins, PI3K/Akt, NFκB pathways and polyamine catabolism, we performed immunoblotting assay. In addition, cell cycle analysis was performed by flow cytometry. The results indicated that curcumin induced cell cycle arrest at G2/M phase by downregulation of cyclin B1 and Cdc2 and inhibited colony formation in MCF-7 wt cells. However, Bcl-2 overexpression prevented the inhibition of cell cycle associated proteins after curcumin treatment. The combination of LY294002, PI3K inhibitor, and curcumin induced cell cycle arrest by decreasing CDK4, CDK2 and cyclin E2 in Bcl-2+ MCF-7 cells. Moreover, LY294002 further inhibited the phosphorylation of Akt in Bcl-2+ MCF-7 cells. Curcumin could suppress the nuclear transport of NFκB through decreasing the interaction of P-IκB-NFκB. The combination of wedelolactone, NFκB inhibitor, and curcumin acted different on SSAT expression in wt MCF-7 and Bcl-2+ MCF-7 cells. NFκB inhibition increased the SSAT after curcumin treatment in Bcl-2 overexpressed MCF-7 cells. Inhibition of NFκB activity as well as suppression of ROS generation with NAC resulted in the partial relief of cells from G2/M checkpoint after curcumin treatment in wt MCF-7 cells. In conclusion, the potential role of curcumin in induction of cell cycle arrest is related with NFκB-regulated polyamine biosynthesis.     

USA300 methicillin-resistant Staphylococcus aureus bacteremia and the risk of severe sepsis: is USA300 methicillin-resistant Staphylococcus aureus associated with more severe infections?

USA300 methicillin-resistant Staphylococcus aureus (MRSA) is increasing as a cause of severe community-associated bacteremic infections. We assessed severe sepsis in response to infection in patients with USA300 MRSA compared to non-USA300 MRSA bacteremia. A cohort study was conducted from 1997 to 2008 comparing sepsis in response to infection in 271 patients with MRSA bacteremia from 4 VA hospitals. Sixty-seven (25%) patients with MRSA bacteremia were USA300 MRSA; 204 (75%) were non-USA300 MRSA. The proportion of MRSA bacteremia caused by USA300 MRSA increased over time (χ2 P < 0.0001). Adjusting for age and nosocomial infection, patients with USA300 MRSA bacteremia were more likely to have severe sepsis or septic shock in response to infection than patients with non-USA300 MRSA bacteremia (adjusted relative risk = 1.82; 95% confidence interval, 1.16-2.87; P = 0.01). This suggests that patients with USA300 MRSA are more likely to develop severe sepsis in response to their infection, which could be due to host or bacterial differences.     

Interleukin-18 promoter −137 G/C polymorphism (rs187238) is associated with biochemical markers of renal function and cardiovascular disease in type 2 diabetes patients

BackgroundInterleukin-18 (IL-18), a proinflammatory and proatherogenic cytokine, has been associated with type 2 diabetes, metabolic syndrome, stroke and coronary artery disease. Some studies have indicated that the IL-18 promoter −137 G/C polymorphism seems to be associated with changes in the IL-18 expression and may contribute to the development of cardiovascular disease (CVD). The aim of this study was to evaluate the association between −137 G/C polymorphism and the levels of IL-18, biochemical markers for cardiovascular disorders, anthropometric profile and cardiovascular disease in Brazilian patients with type 2 diabetes (T2DM). Design & Methods. Study subjects comprised 125 T2DM patients undergoing follow-up at a reference endocrinology service in northeastern Brazil. The −137G/C polymorphism in the IL-18 gene and serum IL-18 levels were determined by using allele-specific polymerase chain reaction (PCR) and enzyme-linked immune assay (ELISA), respectively. The anthropometric parameters were assessed using a Body Composition Monitor with Scale, and the laboratory data were measured using an automatic analyzer as well as spectrophotometric analysis. Results. The genotype distribution of IL-18 –137 G/C genetic polymorphism was significantly different among T2DM patients with and without CVD. The results show an association between the CC genotype of −137G/C polymorphism and CVD in T2DM patients (p < 0.001). Serum levels of IL-18 were significantly higher in CC carriers (843.1 pg/mL) compared with GG or GC carriers (303.6 pg/mL and 292.0 pg/mL, respectively). In addition, the present study showed that carriers of the CC genotype also had significantly higher concentrations of creatinine and albuminuria than carriers of the GG or GC genotypes (p < 0.05 in both). Conclusion. These results suggest that Brazilian T2DM patients with the CC genotype seem to show a predisposition to CVD, as well as an elevation in markers of renal function.     

Cardioprotective effect of therapeutic hypothermia at 34°C against ischaemia/reperfusion injury mediated by PI3K and nitric oxide in a rat isolated heart model

Aim

Therapeutic hypothermia (TH) is widely used as a cardioprotective treatment for cardiac arrest. TH at 30-32 °C during ischaemia and reperfusion has a cardioprotective effect. The aims of the study were to examine whether TH at 34 °C with late induction (immediately after the start of reperfusion) has a cardioprotective effect and to determine if this effect is mediated by nitric oxide (NO) and phosphatidylinositol 3′-kinase (PI3K).

Methods

Langendorff perfusion of Sprague-Dawley rat hearts was initiated at 75 mmHg at 37 °C. Left ventricle infarct sizes were evaluated by triphenyltetrazolium chloride staining after Langendorff perfusion in 6 groups (each n = 7): control group; ischaemia group, with 34 °C TH during ischaemia for 30 min and reperfusion for 180 min; reperfusion group, with 34 °C TH induced solely during the reperfusion period; the l-NAME (NO synthase inhibitor), LY294002, and wortmannin (PI3K inhibitors) groups, which were treated similarly to the reperfusion group with the addition of each compound.

Results

TH reduced the left ventricle infarct size from 54.2 ± 14.8% of the control group to 11.9 ± 6.3% (ischaemia group, p < 0.001) and to 23.5 ± 10.5% (reperfusion group, p < 0.001). l-NAME, LY294002, and wortmannin reversed the cardioprotective effect of TH induced during reperfusion to 42.5 ± 10.6% (p = 0.009), 40.9 ± 4.1% (p = 0.021), and 51.9 ± 13.0% (p < 0.001), respectively. Circulatory temperatures reached 34 °C within 5 min in all groups subjected to TH.

Conclusions

TH of 34 °C showed a cardioprotective effect even with late initiation of cooling during reperfusion. The effect was mediated by NO and PI3K.