α7 Nicotinic Acetylcholine Receptor Regulates the Function and Viability of L Cells

Enteroendocrine L cells secrete the incretin hormone glucagon-like peptide-1 (GLP-1), and they also express the α7 nicotinic acetylcholine receptor (α7nAChR), which may regulate GLP-1 secretion. Here, GTS-21, a selective α7nAChR agonist, was used to examine the effect of α7nAChR activation in L-cell lines, mouse intestinal primary cell cultures, and C57BL/6 mice. GTS-21 stimulated GLP-1 secretion in vitro, and this effect was attenuated by an α7nAChR antagonist or by α7nAChR-specific small interfering RNA. Under in vitro cell culture conditions of glucotoxicity, GTS-21 restored GLP-1 secretion and improved L-cell viability while also acting in vivo to raise levels of circulating GLP-1 in mice. To assess potential signaling mechanisms underlying these actions of GTS-21, we first monitored Ca2+, cAMP, and phosphatidylinositol 3-kinase (PI3K) activity. As expected for a GLP-1 secretagogue promoting Ca2+ influx through α7nAChR cation channels, [Ca2+]i increased in response to GTS-21, but [cAMP]i was unchanged. Surprisingly, pharmacological inhibition of growth factor signaling pathways revealed that GTS-21 also acts on the PI3K-protein kinase B-mammalian target of rapamycin pathway to promote L-cell viability. Moreover, the Ca2+ chelator BAPTA-AM counteracted GTS-21‒stimulated PI3K activity, thereby indicating unexpected crosstalk of L-cell Ca2+ and growth factor signaling pathways. Collectively, these data demonstrate that α7nAChR activation enhances GLP-1 secretion by increasing levels of cytosolic Ca2+ while also revealing Ca2+- and PI3K-dependent processes of α7nAChR activation that promote L-cell survival.

[Triptolide induces oxidative stress and apoptosis and activates PIK3/Akt signaling pathway in TM4 sertoli cells]

OBJECTIVE

To investigate the effect of triptolide (TP) on oxidative stress and apoptosis in TM4 sertoli cells and related molecular mechanism.

METHODS

TM4 cells were incubated with different concentrations of triptolide for 24 h, then collected for further experiments. Cell proliferation analysis was used to measure the inhibitive effect of triptolide on proliferation of TM4 cells; DCFH-DA (6-carboxy-2',7'-dichlorofluorescein diacetate) probe was used to stain the TM4 cells, the level change of intracellular ROS was discovered through flow cytometry; the TM4 cells were stained by Annexin V-FITC/PI to detect whether triptolide induced apoptosis in the TM4 cells; Protein was extracted from the TM4 cells in control and triptolide group. Western blot was performed to determine the expression of apoptosis marker protein cleaved-PARP and PI3K/Akt signaling pathway-related proteins [p-Akt (Ser473), Akt, p-mTOR (Ser2448), mTOR, p-p70S6K (Thr389), p70S6K].

RESULTS

Cell proliferation analysis revealed that triptolide reduced the TM4 cells viability significantly compared with control group in a dosage-dependent manner [10 nmol/L: (73.77±20.95)%, 100 nmol/L: (51.60±10.43)%, 500 nmol/L: (44.34±5.78)%]; The level of intracellular ROS in the TM4 cells was significantly induced in a dosage-dependent manner (P<0.01); triptolide remarkably induced early-stage and late-stage apoptosis in the TM4 cells [control: (3.84±1.50)%, 100 nmol/L: (13.04±2.03)%, 200 nmol/L: (16.24±1.34)%, 400 nmol/L: (18.76±3.45)%]; The expression of cleaved-PARP was significantly upregulated in the TM4 cells after incubation with triptolide (P<0.01); The expression levels of p-Akt/Akt and p-p70S6K/p70s6k were significantly increased compared with control group (P<0.01). No significant change was observed among the expression levels of p-mTOR/mTOR (P>0.05).

CONCLUSION

In vitro studies showed that triptolide could effectively suppress the proliferation and induce apoptosis of TM4 sertoli cells. The oxidative stress was upregulated after incubation with triptolide, which may be one of the mechanisms of cytotoxicity in TM4 cells. Treatment of triptolide led to activation of Akt and p70S6K, indicating that the PI3K/Akt signaling pathway may be involved in response to oxidative stress in TM4 cells. The activation of PI3K/Akt signaling pathway was one of the molecular mechanisms involved in triptolide-mediated oxidative stress in TM4 cells. Our study provides insight into alleviating reproductive toxicity of triptolide in clinical and developing male contraceptive.

Synergistic Anti-Cancer Effects of AKT and SRC Inhibition in Human Pancreatic Cancer Cells

PURPOSE

To investigate the effect of combined inhibition of protein kinase B (AKT) and SRC on the growth and metastatic potential of human pancreatic cancer cells.

MATERIALS AND METHODS

AKT and SRC were inhibited using 10-DEBC and PP2, respectively. The expression of their messenger RNAs were down-regulated by specific small interfering RNA (siRNA). Changes in pancreatic cancer cell growth and metastatic potential were determined using a cell viability assay and a xenotransplant model of pancreatic cancer, as well as cell migration and invasion assays. Signal proteins were analyzed by Western blot.

RESULTS

The inhibitors 10-DEBC and PP2 suppressed cell proliferation in a dose-dependent fashion in pancreatic cancer cell lines MIA PaCa-2 and PANC-1. The simultaneous inhibition of AKT and SRC at low concentrations resulted in a significant suppression of cell proliferation. Knockdown of AKT2 and SRC using siRNAs also significantly decreased cell proliferation. In a pancreatic cancer model, combined treatment with 10-DEBC and PP2 also significantly suppressed the growth of pancreatic cancer. Application of 10-DEBC with PP2 significantly reduced the metastatic potential of pancreatic cancer cells by inhibiting migration and invasion. The combined inhibition suppressed the phosphorylation of mTOR and ERK in pancreatic cancer cells.

CONCLUSION

Combined targeting of AKT and SRC resulted in a synergistic efficacy against human pancreatic cancer growth and metastasis.

Gastrin Protects Against Myocardial Ischemia/Reperfusion Injury via Activation of RISK (Reperfusion Injury Salvage Kinase) and SAFE (Survivor Activating Factor Enhancement) Pathways

BACKGROUND

Ischemia/reperfusion injury (IRI) is one of the most predominant complications of ischemic heart disease. Gastrin has emerged as a regulator of cardiovascular function, playing a key protective role in hypoxia. Serum gastrin levels are increased in patients with myocardial infarction, but the pathophysiogical significance of this finding is unknown. The purpose of this study was to determine whether and how gastrin protects cardiac myocytes from IRI.

METHODS AND RESULTS

Adult male Sprague-Dawley rats were used in the experiments. The hearts in living rats or isolated Langendorff-perfused rat hearts were subjected to ischemia followed by reperfusion to induce myocardial IRI. Gastrin, alone or with an antagonist, was administered before the induction of myocardial IRI. We found that gastrin improved myocardial function and reduced the expression of myocardial injury markers, infarct size, and cardiomyocyte apoptosis induced by IRI. Gastrin increased the phosphorylation levels of ERK1/2 (extracellular signal-regulated kinase 1/2), AKT (protein kinase B), and STAT3 (signal transducer and activator of transcription 3), indicating its ability to activate the RISK (reperfusion injury salvage kinase) and SAFE (survivor activating factor enhancement) pathways. The presence of inhibitors of ERK1/2, AKT, or STAT3 abrogated the gastrin-mediated protection. The protective effect of gastrin was via CCK2R (cholecystokinin 2 receptor) because the CCK2R blocker CI988 prevented the gastrin-mediated protection of the heart with IRI. Moreover, we found a negative correlation between serum levels of cardiac troponin I and gastrin in patients with unstable angina pectoris undergoing percutaneous coronary intervention, suggesting a protective effect of gastrin in human cardiomyocytes.

CONCLUSIONS

These results indicate that gastrin can reduce myocardial IRI by activation of the RISK and SAFE pathways.

Silibinin from Silybum marianum Stimulates Embryonic Stem Cell Vascular Differentiation via the STAT3/PI3-K/AKT Axis and Nitric Oxide

Silibinin, the bioactive compound of milk thistle (Silybum marianum), exerts tissue protective and regenerative effects that may include stem cell differentiation toward vascular cells. The purpose of the present study was to investigate whether silibinin stimulates blood vessel formation from mouse embryonic stem (ES) cells and to unravel the underlying signaling cascade. Vascular branching points were assessed by confocal laser scanning microscopy and computer-assisted image analysis of CD31-positive cell structures. Protein expression of vascular markers and activation of protein kinases were determined by western blot. Nitric oxide (NO) generation was investigated by use of the fluorescent dye 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate. Silibinin dose-dependently increased CD31-positive vascular branching points in embryoid bodies cultivated from ES cells. This was paralleled by increase of protein expression levels for the endothelial-specific markers vascular endothelial cadherin (VE-cadherin), vascular endothelial growth factor receptor 2, and hypoxia-inducible factor-1α. Moreover, silibinin increased activation of endothelial nitric oxide synthase (eNOS), which boosted generation of NO in embryoid bodies and enhanced phosphorylation of signal transducer and activator of transcription 3 (STAT3) as well as phosphoinositide 3-kinase (PI3-K) and AKT. Vasculogenesis, VE-cadherin expression, STAT3 and AKT phosphorylation, NO generation, and eNOS phosphorylation were inhibited by the small molecule STAT3 inhibitor Stattic, AKT inhibitor VIII, the PI3-K inhibitor LY294002, or the NOS inhibitor Nω-Nitro-L-arginine methyl ester hydrochloride. In conclusion, our findings indicate that silibinin induces vasculogenesis of ES cells via activation of STAT3, PI3-K, and AKT, which regulate NO generation by eNOS.

Inhibition of migration and invasion by berberine via inactivation of PI3K/Akt and p38 in human retinoblastoma cell line

BACKGROUND

As a clinically important natural isoquinoline alkaloid, berberine has been reported to possess various pharmacological effects.

OBJECTIVES

This study was aimed to investigate the effect of berberine on cell migration and invasion in human retinoblastoma (Rb) cells.

MATERIAL AND METHODS

The cytotoxicity of berberine was estimated by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay. After being stimulated with berberine under various concentrations, the cell migration and invasion were evaluated by transwell assay. Then, the expression levels of epithelial-mesenchymal transition (EMT) markers were determined by quantitative reverse transcription PCR (qRT-PCR) and western blot analysis. Furthermore, the phosphorylation levels of protein kinase B (Akt) and p38 were detected by western blot analysis. Finally, the effect of phosphatidylinositol-3-kinase (PI3K) and p38 inhibitors on cell migration and invasion was estimated by transwell assay. Untreated cells acted as control for all the experiments.

RESULTS

The concentrations of berberine for further studies were controlled in a range of 0 to 100 μM. The cell migration and invasion were both suppressed by berberine in a dose-dependent manner compared to the control (p < 0.05 or p < 0.001). Berberine remarkably down-regulated expression of E-cadherin and up-regulated expression of vimentin and α-SMA compared to the control (p < 0.01 or p < 0.001). Furthermore, the phosphorylation levels of Akt and p38 were both down-regulated by berberine in comparison to the control. Furthermore, the addition of berberine accompanied by LY294002 or SB203580 significantly suppressed cell migration and invasion compared to the addition of berberine alone (p < 0.05).

CONCLUSIONS

Berberine suppressed cell migration and invasion via inactivation of PI3K/Akt and p38.

A Novel Strategy to Prevent Advanced Atherosclerosis and Lower Blood Glucose in a Mouse Model of Metabolic Syndrome

Cardiovascular disease caused by atherosclerosis is the leading cause of mortality associated with type 2 diabetes and metabolic syndrome. Insulin therapy is often needed to improve glycemic control, but it does not clearly prevent atherosclerosis. Upon binding to the insulin receptor (IR), insulin activates distinct arms of downstream signaling. The IR-Akt arm is associated with blood glucose lowering and beneficial effects, whereas the IR-Erk arm might exert less desirable effects. We investigated whether selective activation of the IR-Akt arm, leaving the IR-Erk arm largely inactive, would result in protection from atherosclerosis in a mouse model of metabolic syndrome. The insulin mimetic peptide S597 lowered blood glucose and activated Akt in insulin target tissues, mimicking insulin's effects, but only weakly activated Erk and even prevented insulin-induced Erk activation. Strikingly, S597 retarded atherosclerotic lesion progression through a process associated with protection from leukocytosis, thereby reducing lesional accumulation of inflammatory Ly6C^hi monocytes. S597-mediated protection from leukocytosis was accompanied by reduced numbers of the earliest bone marrow hematopoietic stem cells and reduced IR-Erk activity in hematopoietic stem cells. This study provides a conceptually novel treatment strategy for advanced atherosclerosis associated with metabolic syndrome and type 2 diabetes.

Fibroblast Growth Factor 21 Protects Photoreceptor Function in Type 1 Diabetic Mice

Retinal neuronal abnormalities occur before vascular changes in diabetic retinopathy. Accumulating experimental evidence suggests that neurons control vascular pathology in diabetic and other neovascular retinal diseases. Therefore, normalizing neuronal activity in diabetes may prevent vascular pathology. We investigated whether fibroblast growth factor 21 (FGF21) prevented retinal neuronal dysfunction in insulin-deficient diabetic mice. We found that in diabetic neural retina, photoreceptor rather than inner retinal function was most affected and administration of the long-acting FGF21 analog PF-05231023 restored the retinal neuronal functional deficits detected by electroretinography. PF-05231023 administration protected against diabetes-induced disorganization of photoreceptor segments seen in retinal cross section with immunohistochemistry and attenuated the reduction in the thickness of photoreceptor segments measured by optical coherence tomography. PF-05231023, independent of its downstream metabolic modulator adiponectin, reduced inflammatory marker interleukin-1β (IL-1β) mRNA levels. PF-05231023 activated the AKT-nuclear factor erythroid 2-related factor 2 pathway and reduced IL-1β expression in stressed photoreceptors. PF-05231023 administration did not change retinal expression of vascular endothelial growth factor A, suggesting a novel therapeutic approach for the prevention of early diabetic retinopathy by protecting photoreceptor function in diabetes.

Combination of melatonin and rapamycin for head and neck cancer therapy: Suppression of AKT/mTOR pathway activation, and activation of mitophagy and apoptosis via mitochondrial function regulation

Head and neck squamous cell carcinoma (HNSCC) clearly involves activation of the Akt mammalian target of rapamycin (mTOR) signalling pathway. However, the effectiveness of treatment with the mTOR inhibitor rapamycin is often limited by chemoresistance. Melatonin suppresses neoplastic growth via different mechanisms in a variety of tumours. In this study, we aimed to elucidate the effects of melatonin on rapamycin-induced HNSCC cell death and to identify potential cross-talk pathways. We analysed the dose-dependent effects of melatonin in rapamycin-treated HNSCC cell lines (Cal-27 and SCC-9). These cells were treated with 0.1, 0.5 or 1 mmol/L melatonin combined with 20 nM rapamycin. We further examined the potential synergistic effects of melatonin with rapamycin in Cal-27 xenograft mice. Relationships between inhibition of the mTOR pathway, reactive oxygen species (ROS), and apoptosis and mitophagy reportedly increased the cytotoxic effects of rapamycin in HNSCC. Our results demonstrated that combined treatment with rapamycin and melatonin blocked the negative feedback loop from the specific downstream effector of mTOR activation S6K1 to Akt signalling, which decreased cell viability, proliferation and clonogenic capacity. Interestingly, combined treatment with rapamycin and melatonin-induced changes in mitochondrial function, which were associated with increased ROS production, increasing apoptosis and mitophagy. This led to increase cell death and cellular differentiation. Our data further indicated that melatonin administration reduced rapamycin-associated toxicity to healthy cells. Overall, our findings suggested that melatonin could be used as an adjuvant agent with rapamycin, improving effectiveness while minimizing its side effects.

Manganese-12 acetate suppresses the migration, invasion, and epithelial-mesenchymal transition by inhibiting Wnt/β-catenin and PI3K/AKT signaling pathways in breast cancer cells

BACKGROUND

Breast cancer is the leading cause of cancer-related death in the world, and it is of great value to reveal the molecular mechanisms of breast cancer progression and develop new therapeutic targets.

METHODS

Transwell assay is used to analyze the migration and invasion of breast cancer cells. Real-time PCR and western blotting assay are applied to detect the expression levels of epithelial-mesenchymal transition markers and the key members of Wnt/β-catenin and PI3K/AKT signaling pathways.

RESULTS

Manganese-12 acetate (Mn12Ac) significantly inhibited the migration and invasion of MCF7 and MDA-MB-231 breast cancer cells. Western blotting assay further showed that Mn12Ac significantly upregulated E-cadherin, and downregulated N-cadherin and vimentin. We further found that Mn12Ac reduced the mRNA expressions of epithelial-mesenchymal transition-associated transcription factors snail, slug, twist1, and ZEB1 using real-time PCR assay. Importantly, we further found that Mn12Ac significantly reduced the Wnt1 and β-catenin protein expressions, and suppressed the phosphorylation of PI3K and AKT in MCF7 and MDA-MB-231 breast cancer cells. Very interestingly, we also showed that Mn12Ac decreased the mRNA and protein expressions of programmed cell death ligand 1.

CONCLUSION

Taken together, our results suggested that Mn12Ac inhibited the migration, invasion, and epithelial-mesenchymal transition by regulating Wnt/β-catenin and PI3K/AKT signaling pathways in breast cancer.

The importance of negative determinants as modulators of CK2 targeting. The lesson of Akt2 S131

CK2 is a pleiotropic S/T protein kinase (formerly known as casein kinase 2) which is attracting increasing interest as therapeutic target, and the identification of its substrates is a crucial step in determining its involvement in different pathological conditions. We recently found that S131 of Akt2 (homologous to the well established CK2 target S129 of Akt1) is not phosphorylated by CK2 either in vitro or in vivo, although the consensus sequence recognized by CK2 (S/T-x-x-E/D/pS/pT) is conserved in it. Here, by exploiting synthetic peptides, in cell transfection experiments, and computational analysis, we show that a single sequence element, a T at position n+1, hampers phosphorylation, causing an α-helix structure organization which prevents the recognition of its own consensus by CK2. Our results highlight the role of negative determinants as crucial modulators of CK2 targeting and corroborate the concept that Akt1 and Akt2 display isoform specific features. Experiments with synthetic peptides suggest that Akt2 S131 could be phosphorylated by kinases of the Plk (Polo-like kinase) family, which are insensitive to the presence of the n+1 T. The low phylogenetic conservation of the Akt2 sequence around S131, as opposed to the extremely well-conserved Akt1 homologous sequence, would indicate a dominant positive role in the selective pressure only for the Akt1 phosphoacceptor site committed to undergo phosphorylation by CK2. By contrast, Akt2 S131 may mediate the response to specific physio/pathological conditions, being consequently shielded against basal CK2 targeting.

Inhibition of COX-2 and 5-LOX regulates the progression of colorectal cancer by promoting PTEN and suppressing PI3K/AKT pathway

For colorectal cancer (CRC) patients, local and systemic inflammatory responses have been extensively reported to closely associate with patient survival. However, the specific signaling pathways responsible for carcinogenic responses are unclear. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a negative regulator of PI3K/AKT pathway that is gradually inactivated in cancers through mutation, loss of heterozygosity and others epigenetic mechanisms. In addition, COX and LOX metabolic pathways of arachidonic acid (AA) play a crucial role in promoting adenoma development. The aim of this study is to clarify the relationship of COX, LOX and PTEN/PI3K/AKT pathway. Results showed that the over-expressed COX and LOX in cancer cells can be targeted to decrease the expression of PTEN. After using corresponding inhibitors, this condition was significantly improved and promoted apoptosis, inhibited invasion, proliferation and the production of reactive oxygen species. And for COX-2-/- or 5-LOX-/- Apc^Min/+ mice, the PI3K/AKT pathway was further inhibited via promoting PTEN. Furthermore, weakened oxidative stress, inhibited adenoma growth, and improved survival rate. All findings indicated that PTEN was indirectly targeted by these enzyme inhibitors and acted as the potential therapeutic target for colorectal cancer therapy. In short, COX-2 or 5-LOX deletion and its inhibitors enhanced activity of PTEN and suppressed cell and adenoma progression through PI3K/AKT pathway in colorectal cancer.

Gonadotropin-Dependent Neuregulin-1 Signaling Regulates Female Rat Ovarian Granulosa Cell Survival

Mammalian ovarian follicular development and maturation of an oocyte competent to be fertilized and develop into an embryo depends on tightly regulated, spatiotemporally orchestrated crosstalk among cell death, survival, and differentiation signals through extra- and intraovarian signals, as well as on a permissive ovarian follicular microenvironment. Neuregulin-1 (NRG1) is a member of the epidermal growth factor-like factor family that mediates its effects by binding to a member of the erythroblastoma (ErbB) family. Our experimental results suggest gonadotropins promote differential expression of NRG1 and erbB receptors in granulosa cells (GCs), and NRG1 in theca cells during follicular development, and promote NRG1 secretions in the follicular fluid (FF) of rat ovaries. During the estrous cycle of rat, NRG1 and erbB receptors are differentially expressed in GCs and correlate positively with serum gonadotropins and steroid hormones. Moreover, in vitro experimental studies suggest that the protein kinase C inhibitor staurosporine (STS) causes the physical destruction of GCs by the activation of caspase-3. Exogenous NRG1 treatment of GCs delayed onset of STS-induced apoptosis and inhibited cleaved caspase-3 expressions. Moreover, exogenous NRG1 treatment of GCs alters STS-induced death by maintaining the expression of ErbB2, ErbB3, pAkt, Bcl2, and BclxL proteins. Taken together, these studies demonstrate that NRG1 is gonadotropin dependent, differentially regulated in GCs and theca cells, and secreted in ovarian FF as an intracellular survival factor that may govern follicular maturation.

The bradykinin-cGMP-PKG pathway augments insulin sensitivity via upregulation of MAPK phosphatase-5 and inhibition of JNK

Bradykinin (BK) promotes insulin sensitivity and glucose uptake in adipocytes and other cell types. We demonstrated that in rat adipocytes BK enhances insulin-stimulated glucose transport via endothelial nitric oxide synthase, nitric oxide (NO) generation, and decreased activity of the mitogen-activated protein kinase (MAPK) JNK (c-Jun NH₂-terminal kinase). In endothelial cells, NO increases soluble guanylate cyclase (sGC) activity, which, in turn, activates protein kinase G (PKG) by increasing cGMP levels. In this study, we investigated whether BK acts via the sGC-cGMP-PKG pathway to inhibit the negative effects of JNK on insulin signaling and glucose uptake in rat adipocytes. BK augmented cGMP concentrations. The BK-induced enhancement of insulin-stimulated glucose uptake was mimicked by the sGC activator YC-1 and a cell-permeable cGMP analog, CPT-cGMP, and inhibited by the sGC inhibitor ODQ and the PKG inhibitor KT 5823. Transfection of dominant-negative PKG reduced the BK augmentation of insulin-induced Akt phosphorylation. The activation of JNK and ERK1/2 by insulin was attenuated by BK, which was mediated by the sGC-cGMP-PKG pathway. Whereas insulin-stimulated phosphorylation of upstream activators of JNK and ERK, i.e., MKK4 and MEK1/2, was unaffected, BK augmented insulin-mediated induction of MKP-5 mRNA and protein levels. Furthermore, zaprinast, a phosphodiesterase inhibitor, enhanced cGMP and MKP-5 and prolonged the action of BK. These data indicate that BK enhances insulin action by inhibition of negative feedback by JNK and ERK via upregulation of MKP-5, mediated by the sGC-cGMP-PKG signaling pathway.

Dihydrocapsaicin (DHC) enhances the hypothermia-induced neuroprotection following ischemic stroke via PI3K/Akt regulation in rat

OBJECTIVE

Hypothermia has demonstrated neuroprotection following ischemia in preclinical studies while its clinical application is still very limited. The aim of this study was to explore whether combining local hypothermia in ischemic territory achieved by intra-arterial cold infusions (IACIs) with pharmacologically induced hypothermia enhances therapeutic outcomes, as well as the underlying mechanism.

METHODS

Sprague-Dawley rats were subjected to right middle cerebral artery occlusion (MCAO) for 2h using intraluminal hollow filament. The ischemic rats were randomized to receive: 1) pharmacological hypothermia by intraperitoneal (i.p.) injection of dihydrocapsaicin (DHC); 2) physical hypothermia by IACIs for 10min; or 3) the combined treatments. Extent of brain injury was determined by neurological deficit, infarct volume, and apoptotic cell death at 24h and/or 7d following reperfusion. ATP and ROS levels were measured. Expression of p-Akt, cleaved Caspase-3, pro-apoptotic (AIF, Bax) and anti-apoptotic proteins (Bcl-2, Bcl-xL) was evaluated at 24h. Finally, PI3K inhibitor was used to determine the effect of p-Akt.

RESULTS

DHC or IACIs each exhibited hypothermic effect and neuroprotection in rat MCAO models. The combination of pharmacological and physical approaches led to a faster and sustained reduction in brain temperatures and improved ischemia-induced injury than either alone (P<0.01). Furthermore, the combination treatment favorably increased the expression of anti-apoptotic proteins and decreased pro-apoptotic protein levels (P<0.01 or 0.05). This neuroprotective effect was largely blocked by p-Akt inhibition, indicating a potential role of Akt pathway in this mechanism (P<0.01 or 0.05).

CONCLUSIONS

The combination approach is able to enhance the efficiency of hypothermia and efficacy of hypothermia-induced neuroprotection following ischemic stroke. The findings here move us a step closer towards translating this long recognized TH from bench to bedside.

Proliferative, anti-apoptotic and immune-enhancing effects of L-arginine in culture of skin fibroblasts

Semi-essential amino acid L-arginine may be of fundamental importance in various intracellular and intercellular pathways related to skin repair and wound healing. Our current study was aimed to explore the effect of L-arginine on skin fibroblast (L929) signaling pathways involved in cell proliferation (Akt-pAkt kinase, Erk/pErk1/2 kinase, JNK/pJNK kinase and pStat-1), apoptosis (Bcl2 and Bax) and immune defense (NF-κB and CD26). Significant upregulation of Erk (p<0.011), pErk (p<0.017) and JNK (p<0.002) was documented, while the rise was not significant for pJNK kinase. The Akt/pAkt signaling pathway did not change significantly for the above-mentioned time and dose, while pStat-1 was significantly down regulated (p<0.011). The exposure of skin fibroblasts to L-arginine increased anti-apoptotic Bcl2/Bax stoichiometry ratio (p<0.05), obtained by calculation of their individual quantities. L-arginine was able to elicit NF-κB signaling through the increase of p65 active subunit level (p<0.004), while CD26 surface antigen level was not significantly changed. In conclusion, the exposure of skin fibroblasts to L-arginine may help in maintaining and stimulating skin fibroblast proliferative, anti-apoptotic and immune defense function. Therefore, the proposed L-arginine dose may be used for tissue regeneration application, which would be of importance in regenerative medicine, skin rejuvenation approaches and wound healing.

GDF11 Attenuates Development of Type 2 Diabetes via Improvement of Islet β-Cell Function and Survival

Growth differentiation factor 11 (GDF11) has been implicated in the regulation of islet development and a variety of aging conditions, but little is known about the physiological functions of GDF11 in adult pancreatic islets. Here, we showed that systematic replenishment of GDF11 not only preserved insulin secretion but also improved the survival and morphology of β-cells and improved glucose metabolism in both nongenetic and genetic mouse models of type 2 diabetes (T2D). Conversely, anti-GDF11 monoclonal antibody treatment caused β-cell failure and lethal T2D. In vitro treatment of isolated murine islets and MIN6 cells with recombinant GDF11 attenuated glucotoxicity-induced β-cell dysfunction and apoptosis. Mechanistically, the GDF11-mediated protective effects could be attributed to the activation of transforming growth factor-β/Smad2 and phosphatidylinositol-4,5-bisphosphate 3-kinase-AKT-FoxO1 signaling. These findings suggest that GDF11 repletion may improve β-cell function and mass and thus may lead to a new therapeutic approach for T2D.

[Effects of β-asarone on Epithelial-Mesenchymal Transition of Gastric Cancer in Nude Mice]

Objective To observe the effects of β-asarone on epithelial-mesenchymal transition (EMT) of human gastric cancer MGC-803 cells in BALB/c nude mice,and to study its possible molecular mechanism. Methods Gastric cancer MGC-803 cells were subcutaneously inoculated to nude mice for preparing transplanted tumor model. Totally 24 nude mice were then divided into the negative control group (model) , the positive control group (5-FU,25 mg/kg) , the high dose β-asarone group (100 mg/ kg) , the low dose β-asarone group (50 mg/kg) , 8 in each group. Corresponding medicines were adminis- tered to rats in respective group by gastrogavage, once per day for 10 successive days. The mice were sacrificed at the end of the intervention, and the tumor inhibition rate was calculated. The expressions of E-cadherin, N-cadherin, Snail, phosphatidylinositol 3-kinase (PI3K), phosphorylation of phosphatidylinositol 3-kinase ( p-PI3K ) , serine/threonine kinase ( AKT) , phosphorylation of serine/threonine kinase (p-AKT) were detected by Real-time PCR and Western Blot. Results Compared with the model group, the volume of transplanted tumor was obviously reduced in 5-FU group and β-asarone groups from day7 to day 11 (P <0.05). Protein and mRNA expressions of N-cadherin, Snail, p-PI3K, p-AKT decreased, and protein and mRNA expressions of E-cadherin increased in 5-FU group and β-asarone groups (P < 0. 05). Conclusions β-asarone could inhibit proliferation ability of gastric cancer cells, and its mecha- nism might be associated with down-regulating P13K/AKT signal pathway of gastric cancer cells and re- straining EMT of gastric cancer cells.

Amphetamines promote mitochondrial dysfunction and DNA damage in pulmonary hypertension

Amphetamine (AMPH) or methamphetamine (METH) abuse can cause oxidative damage and is a risk factor for diseases including pulmonary arterial hypertension (PAH). Pulmonary artery endothelial cells (PAECs) from AMPH-associated-PAH patients show DNA damage as judged by γH2AX foci and DNA comet tails. We therefore hypothesized that AMPH induces DNA damage and vascular pathology by interfering with normal adaptation to an environmental perturbation causing oxidative stress. Consistent with this, we found that AMPH alone does not cause DNA damage in normoxic PAECs, but greatly amplifies DNA damage in hypoxic PAECs. The mechanism involves AMPH activation of protein phosphatase 2A, which potentiates inhibition of Akt. This increases sirtuin 1, causing deacetylation and degradation of HIF1α, thereby impairing its transcriptional activity, resulting in a reduction in pyruvate dehydrogenase kinase 1 and impaired cytochrome c oxidase 4 isoform switch. Mitochondrial oxidative phosphorylation is inappropriately enhanced and, as a result of impaired electron transport and mitochondrial ROS increase, caspase-3 is activated and DNA damage is induced. In mice given binge doses of METH followed by hypoxia, HIF1α is suppressed and pulmonary artery DNA damage foci are associated with worse pulmonary vascular remodeling. Thus, chronic AMPH/METH can induce DNA damage associated with vascular disease by subverting the adaptive responses to oxidative stress.

Cudraflavone C Induces Tumor-Specific Apoptosis in Colorectal Cancer Cells through Inhibition of the Phosphoinositide 3-Kinase (PI3K)-AKT Pathway

Cudraflavone C (Cud C) is a naturally-occurring flavonol with reported anti-proliferative activities. However, the mechanisms by which Cud C induced cytotoxicity have yet to be fully elucidated. Here, we investigated the effects of Cud C on cell proliferation, caspase activation andapoptosis induction in colorectal cancer cells (CRC). We show that Cud C inhibits cell proliferation in KM12, Caco-2, HT29, HCC2998, HCT116 and SW48 CRC but not in the non-transformed colorectal epithelial cells, CCD CoN 841. Cud C induces tumor-selective apoptosis via mitochondrial depolarization and activation of the intrinsic caspase pathway. Gene expression profiling by microarray analyses revealed that tumor suppressor genes EGR1, HUWE1 and SMG1 were significantly up-regulated while oncogenes such as MYB1, CCNB1 and GPX2 were down-regulated following treatment with Cud C. Further analyses using Connectivity Map revealed that Cud C induced a gene signature highly similar to that of protein synthesis inhibitors and phosphoinositide 3-kinase (PI3K)-AKT inhibitors, suggesting that Cud C might inhibit PI3K-AKT signaling. A luminescent cell free PI3K lipid kinase assay revealed that Cud C significantly inhibited p110β/p85α PI3K activity, followed by p120γ, p110δ/p85α, and p110α/p85α PI3K activities. The inhibition by Cud C on p110β/p85α PI3K activity was comparable to LY-294002, a known PI3K inhibitor. Cud C also inhibited phosphorylation of AKT independent of NFκB activity in CRC cells, while ectopic expression of myristoylated AKT completely abrogated the anti-proliferative effects, and apoptosis induced by Cud C in CRC. These findings demonstrate that Cud C induces tumor-selective cytotoxicity by targeting the PI3K-AKT pathway. These findings provide novel insights into the mechanism of action of Cud C, and indicate that Cud C further development of Cud C derivatives as potential therapeutic agents is warranted.

Citrulline directly modulates muscle protein synthesis via the PI3K/MAPK/4E-BP1 pathway in a malnourished state: evidence from in vivo, ex vivo, and in vitro studies

Citrulline (CIT) is an endogenous amino acid produced by the intestine. Recent literature has consistently shown CIT to be an activator of muscle protein synthesis (MPS). However, the underlying mechanism is still unknown. Our working hypothesis was that CIT might regulate muscle homeostasis directly through the mTORC1/PI3K/MAPK pathways. Because CIT undergoes both interorgan and intraorgan trafficking and metabolism, we combined three approaches: in vivo, ex vivo, and in vitro. Using a model of malnourished aged rats, CIT supplementation activated the phosphorylation of S6K1 and 4E-BP1 in muscle. Interestingly, the increase in S6K1 phosphorylation was positively correlated (P < 0.05) with plasma CIT concentration. In a model of isolated incubated skeletal muscle from malnourished rats, CIT enhanced MPS (from 30 to 80% CIT vs. Ctrl, P < 0.05), and the CIT effect was abolished in the presence of wortmannin, rapamycin, and PD-98059. In vitro, on myotubes in culture, CIT led to a 2.5-fold increase in S6K1 phosphorylation and a 1.5-fold increase in 4E-BP1 phosphorylation. Both rapamycin and PD-98059 inhibited the CIT effect on S6K1, whereas only LY-294002 inhibited the CIT effect on both S6K1 and 4E-BP1. These findings show that CIT is a signaling agent for muscle homeostasis, suggesting a new role of the intestine in muscle mass control.

6-C-(E-phenylethenyl)naringenin induces cell growth inhibition and cytoprotective autophagy in colon cancer cells

6-C-(E-phenylethenyl)naringenin (6-CEPN) is a small molecule found in naringenin fortified fried beef. It has been shown to suppress colon cancer cell proliferation, but the underlying mechanisms are not fully understood. Here we demonstrate that 6-CEPN suppresses tumour cell proliferation through cell cycle arrest in G1 phase, induces necrotic cell death and autophagy in colon cancer cells. Blockade of autophagy by knockdown of the essential autophagy proteins, Atg7 or beclin-1, resulted in aggravated cell death in response to 6-CEPN treatment. In addition, genome-wide transcriptome expression profiling by RNA-sequencing revealed that 6-CEPN-mediated gene expression pattern was extremely similar to the transcriptome response induced by a RAS inhibitor salirasib (farnesylthiosalicylic acid [FTS; salirasib]). Subsequent molecular biological and biochemical experiments demonstrated that 6-CEPN indeed strongly inhibited RAS activation, leading to the inhibition of the downstream effector pathways c-Raf/mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase kinase and phosphoinositide 3-kinase/AKT/mammalian target of rapamycin. More importantly, our computational molecular docking data showed that 6-CEPN could bind to the active site of isoprenylcysteine carboxyl methyltransferase (Icmt), a critical enzyme for the activation of RAS. Icmt activity assay showed that 6-CEPN inhibited its activity significantly. Knockdown of Icmt by siRNA attenuated 6-CEPN-mediated autophagy and cell death. The present study demonstrates that 6-CEPN induces cell growth inhibition and cytoprotective autophagy in colon cancer cells, at least in part, though inhibition of the Icmt/RAS signalling pathways.

A phase I pharmacokinetic and pharmacodynamic study of the oral mitogen-activated protein kinase kinase (MEK) inhibitor, WX-554, in patients with advanced solid tumours

PURPOSE

We performed a multi-centre phase I study to assess the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of the orally available small molecule mitogen-activated protein kinase kinase (MEK) 1/2 inhibitor, WX-554, and to determine the optimal biological dose for subsequent trials.

EXPERIMENTAL DESIGN

Patients with treatment-refractory, advanced solid tumours, with adequate performance status and organ function were recruited to a dose-escalation study in a standard 3 + 3 design. The starting dose was 25 mg orally once weekly with toxicity, PK and PD guided dose-escalation with potential to explore alternative schedules.

RESULTS

Forty-one patients with advanced solid tumours refractory to standard therapies and with adequate organ function were recruited in eight cohorts up to doses of 150 mg once weekly and 75 mg twice weekly. No dose-limiting toxicities were observed during the study, and a maximum tolerated dose (MTD) was not established. The highest dose cohorts demonstrated sustained inhibition of extracellular signal-regulated kinase (ERK) phosphorylation in peripheral blood mononuclear cells following ex-vivo phorbol 12-myristate 13-acetate stimulation. There was a decrease of 70 ± 26% in mean phosphorylated (p)ERK in C1 day 8 tumour biopsies when compared with pre-treatment tumour levels in the 75 mg twice a week cohort. Prolonged stable disease (>6 months) was seen in two patients, one with cervical cancer and one with ampullary carcinoma.

CONCLUSIONS

WX-554 was well tolerated, and an optimal biological dose was established for further investigation in either a once or twice weekly regimens. The recommended phase 2 dose is 75 mg twice weekly.

Different dietary energy intake affects skeletal muscle development through an Akt-dependent pathway in Dorper × Small Thin-Tailed crossbred ewe lambs

The objective of this experiment was to investigate the mechanisms through which different levels of dietary energy affect postnatal skeletal muscle development in ewe lambs. Twelve Dorper × Small Thin-Tailed crossbred ewe lambs (100 d of age; 20 ± 0.5 kg BW) were selected randomly and divided into 2 groups in a completely randomized design. Animals were offered identical diets at 100% or 65% of ad libitum intake. Lambs were euthanized when BW in the ad libitum group reached 35 kg and the semitendinosus muscle was sampled. Final BW and skeletal muscle weight were decreased (P < 0.01) by feed restriction. Both muscle fiber size distribution and myofibril cross-sectional area were altered by feed restriction. Insulin-like growth factor 1 (IGF-1) messenger RNA (mRNA) content was decreased (P < 0.05) when lambs were underfed, whereas no difference for IGF-2 mRNA expression was observed (P > 0.05). Feed restriction altered phosphor-Akt protein abundance (P < 0.01). Moreover, the mammalian target of rapamycin (mTOR) pathway was inhibited by feed restriction, which was associated with decreased phosphor-mTOR, phosphorylated eukaryotic initiation factor 4E binding protein 1 (phosphor-4EBP1), and phosphorylated ribosomal protein S6 kinase (phosphor-S6K). Both mRNA expression of myostatin and its protein content were elevated in feed-restricted ewe lambs (P < 0.05). In addition, mRNA expression of both muscle RING finger 1 and muscle atrophy F-box was increased when ewe lambs were underfed. In summary, feed restriction in young growing ewe lambs attenuates skeletal muscle hypertrophy by inhibiting protein synthesis and increasing protein degradation, which may act through the Akt-dependent pathway.

[Sunitinib induces autophagy via suppressing Akt/mTOR pathway in renal cell carcinoma]

OBJECTIVE

To determine the mechanism of sunitinib-induced autophagy in renal cell carcinoma cells.

METHODS

MTS assay was applied to detect the cell viability alteration under the treatment of sunitinib (2, 8 μmol/L). The sunitinib-induced autophagy as well as cell apoptosis was measured and compared after knocking down autophagy-related protein Beclin1 and microtubule associated protein 1 light chain 3 fusion protein (LC3) by RNA interference. The transmission electron microscope was used to observe the formation of autophagosomes in ACHN cells. The fluorescence microscope was used to monitor distribution and aggregation of endogenous LC3-II. The expressions of protein such as LC3-II, the autophagic regulation molecules protein kinase B/ mammalian target of rapamycin (Akt/mTOR) and the symbol of apoptosis poly ADP-ribose polymerase (PARP) were capable to be detected by immunoblotting assay.

RESULTS

Sunitinib was able to significantly trigger cell viability loss in the renal carcinoma cell ACHN, which was both in a concentration-dependent and time-dependent manner (P<0.05). After reducing the autophagy by knocking down Beclin1 and LC3, the number of cleavage of PARP was increased remarkably, whereas there was nearly not any cleavage in the mock group. By the transmission electron microscope, there were more autophagic vacuoles in ACHN cells after being administrated with sunitininb compared with the control. And the nuclear-to-cytosol translocation as well as aggregation of LC3-II was presented after sunitinib treatment by the fluorescence microscope, which was the proof of the enhanced autophagy. According to the immunoblotting, sunitinib was able to increase the accumulation of LC3-II . At the same time, the result of sunitinib combined with chloroquine, a drug which blocked the fusion of autophagosomes and lysosomes, demonstrated that the increasing amount of LC3-II was due to the enhanced autophagy flux by sunitinib treatment in ACHN cells. However, phosphorylation of Akt as well as mTOR was decreased at the same time. The rapamycin (mTOR inhibitor) or knocking down Akt subunits could change the sunitinib-induced LC3 -II accumulation, whereas overexpression of Akt subunits decreased the autophagic flux, indicating that Akt/mTOR was the target of sunitinib in autophagy.

CONCLUSION

Sunitinib induced autophagy via suppressing Akt/mTOR pathway, and the autophagy was involved in apopotosis.

Luteolin exerts pro-apoptotic effect and anti-migration effects on A549 lung adenocarcinoma cells through the activation of MEK/ERK signaling pathway

An increasing amount of evidence suggests that luteolin, a common dietary flavonoid that is widely distributed in plants and foods, has been shown to be protective against cancer. However, the precise underlying mechanisms of its action against lung cancer are still poorly understood. In the present study, we investigated whether luteolin exhibits the anti-cancer effect in lung cancer through the induction of cell apoptosis and inhibition of cell migration, and whether mitogen-activated protein kinases (MAPKs) and Akt signaling pathways are required. Results revealed that luteolin exerted an anti-proliferation effect in a dose- and time-dependent manner in A549 lung adenocarcinoma cells, and induced apoptosis with a concomitant increase in the activation of caspases-3 and -9, diminution of Bcl-2, elevation in Bax expression, and the phosphorylation of MEK and its down-stream kinase ERK, as well as the activation of Akt. Luteolin also dramatically inhibited cell motility and migration in A549 cells. The inhibitor of MEK-ERK pathway protected against luteolin-induced cell death and suppressed the apoptosis-inducing and anti-migratory effects of luteolin, suggesting MEK-ERK signaling pathway plays an important role in mediating the pro-apoptotic effect and anti-migration effects of luteolin. Taken together, this study provides a new insight into the mode of action of luteolin on lung cancer.

Ellagitannin-rich cloudberry inhibits hepatocyte growth factor induced cell migration and phosphatidylinositol 3-kinase/AKT activation in colon carcinoma cells and tumors in Min mice

Berries have been found to inhibit colon carcinogenesis in animal models, and thus represent a potential source of compounds for prevention and treatment of colorectal cancer. The mechanistic basis for their effects is not well understood. We used human colon carcinoma cells and Min mice to investigate the effects of ellagitannin-rich cloudberry (Rubus chamaemorus) extract on cancer cell migration and underlying cell signaling. Intrinsic and hepatocyte growth factor (HGF) -induced cell motility in human HT29 and HCA7 colon carcinoma cells was assessed carrying out cell scattering and scratch wound healing assays using time-lapse microscopy. Activation of Met, AKT, and ERK in cell lines and tumors of cloudberry-fed Min mice were determined using immunoprecipitation, Western blot and immunohistochemical analyses. Cloudberry extract significantly inhibited particularly HGF-induced cancer cell migration in both cell lines. Cloudberry extract inhibited the Met receptor tyrosine phosphorylation by HGF and strongly suppressed HGF-induced AKT and ERK activation in both HT29 and HCA7 cells. Consistently, cloudberry feeding (10% w/w freeze-dried berries in diet for 10 weeks) reduced the level of active AKT and prevented phosphoMet localization at the edges in tumors of Min mice. These results indicate that cloudberry reduces tumor growth and cancer cell motility by inhibiting Met signaling and consequent activation of phosphatidylinositol 3-kinase/AKT in vitro and in tumors in vivo. As the Met receptor is recognized to be a major target in cancer treatment, our results suggest that dietary phytochemicals may have therapeutic value in reducing cancer progression and metastasis.

Urotensin II-induced insulin resistance is mediated by NADPH oxidase-derived reactive oxygen species in HepG2 cells

AIM: To investigated the effects of urotensin II (UII) on hepatic insulin resistance in HepG2 cells and the potential mechanisms involved.

METHODS: Human hepatoma HepG2 cells were cultured with or without exogenous UII for 24 h, in the presence or absence of 100 nmol/L insulin for the last 30 min. Glucose levels were detected by the glucose-oxidase method and glycogen synthesis was analyzed by glycogen colorimetric/fluorometric assay. Reactive oxygen species (ROS) levels were detected with a multimode reader using a 2′,7′-dichlorofluorescein diacetate probe. The protein expression and phosphorylation levels of c-Jun N-terminal kinase (JNK), insulin signal essential molecules such as insulin receptor substrate -1 (IRS-1), protein kinase B (Akt), glycogen synthase kinase-3β (GSK-3β), and glucose transporter-2 (Glut 2), and NADPH oxidase subunits such as gp91^phox, p67^phox, p47^phox, p40^phox, and p22^phox were evaluated by Western blot.

RESULTS: Exposure to 100 nmol/L UII reduced the insulin-induced glucose consumption (P < 0.05) and glycogen content (P < 0.01) in HepG2 cells compared with cells without UII. UII also abolished insulin-stimulated protein expression (P < 0.01) and phosphorylation of IRS-1 (P < 0.05), associated with down-regulation of Akt (P < 0.05) and GSK-3β (P < 0.05) phosphorylation levels, and the expression of Glut 2 (P < 0.001), indicating an insulin-resistance state in HepG2 cells. Furthermore, UII enhanced the phosphorylation of JNK (P < 0.05), while the activity of JNK, insulin signaling, such as total protein of IRS-1 (P < 0.001), phosphorylation of IRS-1 (P < 0.001) and GSK-3β (P < 0.05), and glycogen synthesis (P < 0.001) could be reversed by pretreatment with the JNK inhibitor SP600125. Besides, UII markedly improved ROS generation (P < 0.05) and NADPH oxidase subunit expression (P < 0.05). However, the antioxidant/NADPH oxidase inhibitor apocynin could decrease UII-induced ROS production (P < 0.05), JNK phosphorylation (P < 0.05), and insulin resistance (P < 0.05) in HepG2 cells.

CONCLUSION: UII induces insulin resistance, and this can be reversed by JNK inhibitor SP600125 and antioxidant/NADPH oxidase inhibitor apocynin targeting the insulin signaling pathway in HepG2 cells.

[Effect of DJ-1 silencing by RNA interference on growth of xenografted human laryngeal squamous cell carcinoma Hep-2 cells in nude mice]

Objective: To investigate the effect of silencing DJ-1 on xenografted human laryngeal squamous cell carcinoma (LSCC) Hep-2 cells in nude mice. Methods: Xenograft model of human LSCC was established by subcutaneous transplantation of Hep-2 cells in 24 nude mice. The LSCC-bearing nude mice were randomly divided into 3 groups (n=8 in each):DJ-1 siRNA low dose group and DJ-1 siRNA high dose group were injected in tumors with 20 μg of DJ-1 siRNA or 40 μg of DJ-1 siRNA in 50 μL, respectively; control group was injected with 5% glucose solution in 50 μL, twice a week for 3 weeks. The weight and size of tumors were measured before injection. The animals were sacrificed 48 h after the final treatment, and the tumors were harvested and weighed. The apoptosis and proliferation of tumor cells were determined; the expressions of Caspase-3 and Ki-67 in tumor specimens were detected with immunohistochemistry. The expression of DJ-1, PTEN, survivin mRNA and protein in tumor tissues were detected by RT-PCR and Western blotting, respectively. Results: Tumor weight in low dose group[(0.66±0.15)g] and high dose group[(0.48±0.11)g] were significantly lower than that in control group[(0.83±0.16)g, all P<0.05]. The inhibition rates of low dose group and high dose group were (20.48±0.18)% and (42.16±0.13)%, respectively. Immunohistochemistry showed that the expression of Caspase-3 was increased and Ki-67 was reduced in tumor specimens, compared with the control group (all P<0.05). RT-PCR and Western blot results showed that in low dose group and high dose group the mRNA and protein expression of DJ-1 and survivin significantly decreased (all P<0.05), while PTEN mRNA and protein content increased (all P<0.05). Conclusion: High dose DJ-1 siRNA can inhibit the tumor growth in human LSCC xenograft nude mouse model, which indicates that down-regulating DJ-1 and survivin, and up-regulating PTEN expression may lead to blockage of PI3K-PKB/Akt signaling pathway and promoting tumor cell apoptosis.

Urocortin attenuates myocardial fibrosis in diabetic rats via the Akt/GSK-3β signaling pathway

OBJECTIVE

Urocortin, a novel identified corticotropin-releasing factor-related endocrinal peptide, has been shown to play an essential role in cardioprotection. Until recently, whether urocortin can protect the heart against diabetic cardiomyopathy (DCM) remained unclear. Herein, we evaluated the cardioprotective effect of urocortin on cardiac dysfunction, inflammation, and fibrosis and demonstrated the potential mechanism in a diabetic rat model.

METHODS

Diabetic rats were randomly divided into 4 groups: diabetic control group, urocortin, urocortin + astressin (a selective CRF receptor 2 antagonist) and urocortin + triciribine (an Akt pathway blocker). Cardiac catheterization was performed to evaluate cardiac function. The levels of creatine phosphokinase isoenzyme (CK-MB), plasma brain natriuretic peptide (BNP), myocardial collagen volume fraction (CVF) and left ventricular mass index (LVWI) were measured. Inflammatory factors (transforming growth factor beta 1, TGF-β1; connective tissue growth factor, CTGF) and activation of signaling proteins (Akt, GSK-3β) were also detected using western blot.

RESULTS

DCM was successfully induced by the injection of streptozotocin (STZ) as evidenced by abnormal heart mass and cardiac function as well as the imbalance of extracellular matrix homeostasis. Rats in the DCM group showed increased mRNA and protein levels of LVWI, BNP, CK-MB, CVF, TGF-β1 and CTGF compared to the control group, which were accompanied with diminished phosphorylation of Akt and GSK-3β. Interestingly, myocardial dysfunction, cardiac fibrosis, and inflammation were suppressed by urocortin in the heart of diabetic rats. Moreover, inhibition of phosphorylation of Akt and GSK-3β was also reversed by urocortin. These effects of urocortin were suppressed by astressin. In addition, triciribine partially reduced the effects of urocortin on myocardial dysfunction, inflammation, and cardiac fibrosis.

CONCLUSIONS

These results suggest that urocortin exhibits a therapeutic benefit in the treatment of DCM by attenuating fibrosis and inflammation. Furthermore, inhibition of the Akt/GSK-3β signaling pathway may be partially responsible for these effects.

Neuregulin-1β promotes glucose uptake via PI3K/Akt in neonatal rat cardiomyocytes

Nrg1β is critically involved in cardiac development and also maintains function of the adult heart. Studies conducted in animal models showed that it improves cardiac performance under a range of pathological conditions, which led to its introduction in clinical trials to treat heart failure. Recent work also implicated Nrg1β in the regenerative potential of neonatal and adult hearts. The molecular mechanisms whereby Nrg1β acts in cardiac cells are still poorly understood. In the present study, we analyzed the effects of Nrg1β on glucose uptake in neonatal rat ventricular myocytes and investigated to what extent mTOR/Akt signaling pathways are implicated. We show that Nrg1β enhances glucose uptake in cardiomyocytes as efficiently as IGF-I and insulin. Nrg1β causes phosphorylation of ErbB2 and ErbB4 and rapidly induces the phosphorylation of FAK (Tyr(861)), Akt (Thr(308) and Ser(473)), and its effector AS160 (Thr(642)). Knockdown of ErbB2 or ErbB4 reduces Akt phosphorylation and blocks the glucose uptake. The Akt inhibitor VIII and the PI3K inhibitors LY-294002 and Byl-719 abolish Nrg1β-induced phosphorylation and glucose uptake. Finally, specific mTORC2 inactivation after knockdown of rictor blocks the Nrg1β-induced increases in Akt-p-Ser(473) but does not modify AS160-p-Thr(642) or the glucose uptake responses to Nrg1β. In conclusion, our study demonstrates that Nrg1β enhances glucose uptake in cardiomyocytes via ErbB2/ErbB4 heterodimers, PI3Kα, and Akt. Furthermore, although Nrg1β activates mTORC2, the resulting Akt-Ser(473) phosphorylation is not essential for glucose uptake induction. These new insights into pathways whereby Nrg1β regulates glucose uptake in cardiomyocytes may contribute to the understanding of its regenerative capacity and protective function in heart failure.

Neuregulin improves response to glucose tolerance test in control and diabetic rats

Neuregulin (NRG) is an EGF-related growth factor that binds to the tyrosine kinase receptors ErbB3 and ErbB4, thus inducing tissue development and muscle glucose utilization during contraction. Here, we analyzed whether NRG has systemic effects regulating glycemia in control and type 2 diabetic rats. To this end, recombinant NRG (rNRG) was injected into Zucker diabetic fatty (ZDF) rats and their respective lean littermates 15 min before a glucose tolerance test (GTT) was performed. rNRG enhanced glucose tolerance without promoting the activation of the insulin receptor (IR) or insulin receptor substrates (IRS) in muscle and liver. However, in control rats, rNRG induced the phosphorylation of protein kinase B (PKB) and glycogen synthase kinase-3 (GSK-3) in liver but not in muscle. In liver, rNRG increased ErbB3 tyrosine phosphorylation and its binding to phosphatidylinositol 3-kinase (PI3K), thus indicating that rNRG activates the ErbB3/PI3K/PKB signaling pathway. rNRG increased glycogen content in liver but not in muscle. rNRG also increased the content of fructose-2,6-bisphosphate (Fru-2,6-P2), an activator of hepatic glycolysis, and lactate in liver but not in muscle. Increases in lactate were abrogated by wortmannin, a PI3K inhibitor, in incubated hepatocytes. The liver of ZDF rats showed a reduced content of ErbB3 receptors, entailing a minor stimulation of the rNRG-induced PKB/GSK-3 cascade and resulting in unaltered hepatic glycogen content. Nonetheless, rNRG increased hepatic Fru-2,6-P2 and augmented lactate both in liver and in plasma of diabetic rats. As a whole, rNRG improved response to the GTT in both control and diabetic rats by enhancing hepatic glucose utilization.

IGF-1 protects dopamine neurons against oxidative stress: association with changes in phosphokinases

Insulin-like growth factor-1 (IGF-1) is an endogenous peptide transported across the blood brain barrier that is protective in several brain injury models, including an acute animal model of Parkinson's disease (PD). Motor deficits in PD are due largely to the progressive loss of nigrostriatal dopaminergic neurons. Thus, we examined the neuroprotective potential of IGF-1 in a progressive model of dopamine deficiency in which 6-hydroxydopamine (6-OHDA) is infused into the striatum. Rats received intrastriatal IGF-1 (5 or 50 µg) 6 h prior to infusion of 4 µg 6-OHDA into the same site and were euthanized 1 or 4 weeks later. Both concentrations of IGF-1 protected tyrosine hydroxylase (TH) immunoreactive terminals in striatum at 4 weeks but not at 1 week, indicating that IGF-induced restoration of the dopaminergic phenotype occurred over several weeks. TH-immunoreactive cell loss was only attenuated with 50 µg IGF-1. We then examined the effect of striatal IGF-1 on the Ras/ERK1/2 and PI3K/Akt pathways to ascertain whether their activation correlated with IGF-1-induced protection. Striatal and nigral levels of phospho-ERK1/2 were maximal 6 h after IGF-1 infusion and, with the exception of an increase in nigral pERK2 at 48 h, returned to basal levels by 7 days. Phospho-Akt (Ser473) was elevated 6-24 h post-IGF-1 infusion in both striatum and substantia nigra concomitant with inhibition of pro-death GSK-3β, a downstream target of Akt. These results suggest that IGF-1 can protect the nigrostriatal pathway in a progressive PD model and that this protection is preceded by activation of key pro-survival signaling cascades.

Neuroprotective effects of ginseng protein on PI3K/Akt signaling pathway in the hippocampus of D-galactose/AlCl3 inducing rats model of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer disease (AD) is a progressive neurodegenerative disease, with progressive memory loss, cognitive deterioration, and behavioral disorders. Ginseng (Panax ginseng C.A. Meyer) is widely used in China to treat various kinds of nervous system disorders. The study aimed to explore the therapeutic effect of ginseng protein (GP) on Alzheimer's disease and its correlation with the PI3K/Akt signaling pathway to understand the mechanism underlying the neuroprotective effect of ginseng.

MATERIAL AND METHODS

The AD rat model was established by intraperitoneally injecting D-galactose [60mg/(kgd)] followed by intragastrically administering AlCl3 [40mg/(kgd)] for 90 days. From day 60, the GP groups were intragastrically administered with GP 0.05 or 0.1g/kg twice daily for 30 days. The ethology of rats was tested by Morris water maze test. The content of Aβ1-42 and p-tau in the hippocampus of rats was detected by enzyme-linked immunosorbent assay. The expression of mRNAs and proteins of PI3K, Akt, phosphorylated Akt (p-Akt), Bcl-2, and Bax in the hippocampus was detected by real-time quantitative reverse transcription polymerase chain reaction and Western blot assay.

RESULTS

GP was found to significantly improve the memory ability of AD rats and prolong the times of crossing the platform and the percentage of residence time in the original platform quadrant of spatial probe test. GP also reduced the content of Aβ1-42 and p-tau and improved the mRNA and protein expression of PI3K, p-Akt/Akt, and Bcl-2/Bax in the hippocampus.

CONCLUSIONS

GP could improve the memory ability and reduce the content of Aβ1-42 and p-tau in AD rats. The anti-AD effects of GP were in part mediated by PI3K/Akt signaling pathway activation.

Diosmectite-zinc oxide composite improves intestinal barrier restoration and modulates TGF-β1, ERK1/2, and Akt in piglets after acetic acid challenge

The present study evaluated the beneficial effect of diosmectite-zinc oxide composite (DS-ZnO) on improving intestinal barrier restoration in piglets after acetic acid challenge and explored the underlying mechanisms. Twenty-four 35-d-old piglets (Duroc × Landrace × Yorkshire), with an average weight of 8.1 kg, were allocated to 4 treatment groups. On d 1 of the trial, colitis was induced via intrarectal injection of acetic acid (10 mL of 10% acetic acid [ACA] solution for ACA, DS-ZnO, and mixture of diosmectite [DS] and ZnO [DS+ZnO] groups) and the control group was infused with saline. Twenty-four hours after challenged, piglets were fed with the following diets: 1) control group (basal diet), 2) ACA group (basal diet), 3) DS-ZnO group (basal diet supplemented with DS-ZnO), and 4) DS+ZnO group (mixture of 1.5 g diosmectite [DS]/kg and 500 mg Zn/kg from ZnO [equal amount of DS and ZnO in the DS-ZnO treatment group]). On d 8 of the trial, piglets were sacrificed. The results showed that DS-ZnO supplementation improved (P < 0.05) ADG, ADFI, and transepithelial electrical resistance and decreased (P < 0.05) fecal scores, crypt depth, and fluorescein isothiocyanate-dextran 4 kDa (FD4) influx as compared with ACA group. Moreover, DS-ZnO increased (P < 0.05) occludin, claudin-1, and zonula occluden-1 expressions; reduced (P < 0.05) caspase-9 and caspase-3 activity and Bax expression; and improved (P < 0.05) Bcl2, XIAP, and PCNA expression. Diosmectite-zinc oxide composite supplementation also increased (P < 0.05) TGF-β1 expression and ERK1/2 and Akt activation. These results suggest that DS-ZnO attenuates the acetic acid-induced colitis by improving mucosa barrier restoration, inhibiting apoptosis, and improving intestinal epithelial cells proliferation and modulation of TGF-β1 and ERK1/2 and Akt signaling pathway.

Combined effects of mineral trioxide aggregate and human placental extract on rat pulp tissue and growth, differentiation and angiogenesis in human dental pulp cells

OBJECTIVE

The aim of this study was to evaluate the combined effects of mineral trioxide aggregate (MTA) and human placental extract (HPE) on cell growth, differentiation and in vitro angiogenesis of human dental pulp cells (HDPCs) and to identify underlying signal transduction mechanisms. In vivo dental pulp responses in rats for a pulp-capping agent were examined.

MATERIALS AND METHODS

MTS assay. ALP activity test, alizarin red S staining and RT-PCR for marker genes were carried out to evaluate cell growth and differentiation. HUVEC migration, mRNA expression and capillary tube formation were measured to evaluate angiogenesis. Signal transduction was analysed using Western blotting and confocal microscopy. The pulps of rat maxillary first molars were exposed and capped with either MTA or MTA plus HPE. Histologic observation and scoring were performed.

RESULTS

Compared to treatment of HDPCs with either HPE or MTA alone, the combination of HPE and MTA increased cell growth, ALP activity, mineralized nodules and expression of marker mRNAs. Combination HPE and MTA increased migration, capillary tube formation and angiogenic gene expression compared with MTA alone. Activation of Akt, mammalian target of rapamycin (mTOR), p38, JNK and ERK MAPK, Akt, and NF-κB were significantly increased by combining HPE and MTA compared with MTA alone. Pulp capping with MTA plus HPE in rats showed superior dentin bridge formation, odontoblastic layers and dentinal tubules and lower inflammatory cell response, compared to the MTA alone group.

CONCLUSIONS

This study demonstrates for the first time that the use of MTA with HPE promotes cell growth, differentiation and angiogenesis in HDPCs, which were associated with mTOR, MAPK and NF-κB pathways. Direct pulp capping with HPE plus MTA showed superior results when compared with MTA alone. Thus, the combination of MTA and HPE may be useful for regenerative endodontics.

Nanoparticle Delivered Human Biliverdin Reductase-Based Peptide Increases Glucose Uptake by Activating IRK/Akt/GSK3 Axis: The Peptide Is Effective in the Cell and Wild-Type and Diabetic Ob/Ob Mice

Insulin's stimulation of glucose uptake by binding to the IRK extracellular domain is compromised in diabetes. We have recently described an unprecedented approach to stimulating glucose uptake. KYCCSRK (P2) peptide, corresponding to the C-terminal segment of hBVR, was effective in binding to and inducing conformational change in the IRK intracellular kinase domain. Although myristoylated P2, made of L-amino acids, was effective in cell culture, its use for animal studies was unsuitable. We developed a peptidase-resistant formulation of the peptide that was efficient in both mice and cell culture systems. The peptide was constructed of D-amino acids, in reverse order, and blocked at both termini. Delivery of the encapsulated peptide to HepG2 and HSKM cells was confirmed by its prolonged effect on stimulation of glucose uptake (>6 h). The peptide improved glucose clearance in both wild-type and Ob/Ob mice; it lowered blood glucose levels and suppressed glucose-stimulated insulin secretion. IRK activity was stimulated in the liver of treated mice and in cultured cells. The peptide potentiated function of IRK's downstream effector, Akt-GSK3-(α, β) axis. Thus, P2-based approach can be used for improving glucose uptake by cells. Also, it allows for screening peptides in vitro and in animal models for treatment of diabetes.

[Effect of glutaredoxin on oxidative stress of umbilical vein endothelial cell exposed to Porphyromonas gingivalis lipo- polysaccharide]

OBJECTIVE

This study measures the glutaredoxin (Grx) gene and protein expression in umbilical vein endothelial cells upon exposure to Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS). The involvement of the Akt-signaling pathway is also determined.

METHODS

EA-hy926 cells were pretreated with 1,000 ng · mL⁻¹ P. gingivalis LPS for 4, 12, 18, and 24 h, and then real-time reverse transcription polymerase chain reaction was employed to detect Grx1 expression. The effect of Grx on Akt activity was investigated using Western blot for the control, LPS (1,000 ng · mL⁻¹ LPS), and carmus- tine (BCNU) groups (1,000 ng · mL⁻¹ LPS, and the EA-hy926 cells were pretreated with 25 μmol · ml⁻¹ BCNU for 30 min).

RESULTS

Gene expression of Grx1 significantly increased in LPS group compared with that in the control group. The Grx1 expression reached the peak level in 12 h, and the variation between the expression in 4 and 12 h was significant (P < 0.05). After 12 h, the protein levels of Grx and phosphorylated-Akt (p-Akt) significantly increased in the LPS group (P < 0.05), whereas the BCNU group showed a considerable decrease in both Grx and p-Akt expression levels (P < 0.05). Moreover, a slight difference was observed in the total Akt protein levels in the three groups (P > 0.05).

CONCLUSION

Grx expression increased upon exposure of EA-hy926 cells to the LPS. Akt activity could be inhibited by BCNU (a Grx inhibitor), which indicated that Akt might act as a downstream regulator of Grx.

Irisin improves endothelial function in obese mice through the AMPK-eNOS pathway

Irisin is a novel hormone secreted by myocytes. Lower levels of irisin are independently associated with endothelial dysfunction in obese subjects. The objective of this study was to explore whether irisin exerts a direct vascular protective effect on endothelial function in high-fat-diet-induced obese mice. Male C57BL/6 mice were given chow or a high-fat diet with or without treatment with irisin. Aortic endothelial function was determined by measuring endothelium-dependent vasodilatation (EDV). Nitric oxide (NO) in the aorta was determined. The effect of irisin on the levels of AMP-activated protein kinase (AMPK), Akt, and endothelial NO synthase (eNOS) phosphorylation in endothelial cells was determined. Human umbilical vein endothelial cells were used to study the role of irisin in the AMPK-eNOS pathway. Acetylcholine-stimulated EDV was significantly lower in obese mice compared with control mice. Treatment of obese mice with irisin significantly enhanced EDV and improved endothelial function. This beneficial effect of irisin was partly attenuated in the presence of inhibitors of AMPK, Akt, and eNOS. Treatment of obese mice with irisin enhanced NO production and phosphorylation of AMPK, Akt, and eNOS in endothelial cells. These factors were also enhanced by irisin in human umbilical vein endothelial cells in vitro. Suppression of AMPK expression by small interfering RNA blocked irisin-induced eNOS and Akt phosphorylation and NO production. We have provided the first evidence that irisin improves endothelial function in aortas of high-fat-diet-induced obese mice. The mechanism for this protective effect is related to the activation of the AMPK-eNOS signaling pathway.

Role of IGF-I in follistatin-induced skeletal muscle hypertrophy

Follistatin, a physiological inhibitor of myostatin, induces a dramatic increase in skeletal muscle mass, requiring the type 1 IGF-I receptor/Akt/mTOR pathway. The aim of the present study was to investigate the role of IGF-I and insulin, two ligands of the IGF-I receptor, in the follistatin hypertrophic action on skeletal muscle. In a first step, we showed that follistatin increases muscle mass while being associated with a downregulation of muscle IGF-I expression. In addition, follistatin retained its full hypertrophic effect toward muscle in hypophysectomized animals despite very low concentrations of circulating and muscle IGF-I. Furthermore, follistatin did not increase muscle sensitivity to IGF-I in stimulating phosphorylation of Akt but, surprisingly, decreased it once hypertrophy was present. Taken together, these observations indicate that increased muscle IGF-I production or sensitivity does not contribute to the muscle hypertrophy caused by follistatin. Unlike low IGF-I, low insulin, as obtained by streptozotocin injection, attenuated the hypertrophic action of follistatin on skeletal muscle. Moreover, the full anabolic response to follistatin was restored in this condition by insulin but also by IGF-I infusion. Therefore, follistatin-induced muscle hypertrophy requires the activation of the insulin/IGF-I pathway by either insulin or IGF-I. When insulin or IGF-I alone is missing, follistatin retains its full anabolic effect, but when both are deficient, as in streptozotocin-treated animals, follistatin fails to stimulate muscle growth.

Chronic rapamycin treatment exacerbates metabolism and does not down-regulate mTORC2/Akt signaling in diabetic mice induced by high-fat diet and streptozotocin

Rapamycin, a classical inhibitor of the mammalian target of rapamycin (mTOR), has been intensively studied for its role in metabolism and verified to induce metabolic defects through mTORC2/Akt pathway. However, disparity of the results exists depending on the differences of the animal models or the detailed procedures. Moreover, data regarding the effect of rapamycin treatment in diabetic models are sparse. Therefore, we investigated its influence on glucose and lipid metabolism, and further analyzed its effect on the mTORC2/Akt pathway in a high-fat diet- and streptozotocin-induced diabetic mice model. Three-weeks old C57BL/6J mice were fed with a high fat diet (60 kcal% fat) and intraperitoneally injected with streptozotocin (100 mg/kg) at 6 weeks of age. Rapamycin (2 mg/kg) was orally given to the mice daily for consecutive 6 weeks. Body weight, blood lipid parameters and HbA(1c)% values were evaluated. Oral glucose test and insulin tolerance test were performed. Furthermore, western blot assay was applied to investigate the protein epression levels of Akt and PKCα, two key targets of the mTORC2/Akt pathway. Rapamycin-treated diabetic mice demonstrated less weight gain, more profound symptoms of polydipsia, polyphagia and polyuria, significant liver fat accumulation and exacerbated metabolic disorders including insulin resistance, hyperglycemia and dyslipidemia. Contrary to what have been expected, though significantly inhibiting mTORC1/S6K1 signaling, chronic rapamycin treatment failed to down-regulate mTORC2/Akt pathway. Our findings provide evidence that chronic rapamycin treatment may exacerbate metabolism in diabetic subjects and does not down-regulate mTORC2/Akt signialing in a high-fat diet- and streptozotocin-induced diabetic mice model.

Novel effects of simvastatin on uterine fibroid tumors: in vitro and patient-derived xenograft mouse model study

OBJECTIVE

Uterine leiomyomas represent a common gynecologic problem with no satisfactory long-term medical treatment. The purpose of this study is to examine the effects of simvastatin on uterine leiomyoma, both in vitro and in vivo.

STUDY DESIGN

This is a laboratory-based experimental study. For in vitro studies, we used human and rat leiomyoma cells. For in vivo studies, we used immunodeficient mice supplemented with estrogen/progesterone pellets xenografted with human leiomyoma tissue explant.

RESULTS

For in vitro studies, cells were treated with different concentrations of simvastatin for 48 hours. Simvastatin induced dose-dependent apoptosis in leiomyoma cells as measured by a fluorometric caspase-3 activity assay, and inhibited proliferation as demonstrated by an (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay (both were significant at 5 and 10 μM). In addition, simvastatin decreased Akt signaling pathway phosphorylation as examined using Western blot analysis. For in vivo studies, animals were treated for 28 days with simvastatin (20 μg/gm body weight/day) vs vehicle control. The treatment inhibited tumor growth as measured weekly using calipers and/ or ultrasound (P < .01). Finally, simvastatin decreased expression of the proliferation marker Ki67 in xenograft tumor tissue as examined by immunohistochemistry (P = .02).

CONCLUSION

Simvastatin can be a promising treatment for uterine leiomyoma. Further studies, including pharmacokinetic and drug delivery studies, are required.

Neuroprotection induced by sevoflurane-delayed post-conditioning is attributable to increased phosphorylation of mitochondrial GSK-3β through the PI3K/Akt survival pathway

BACKGROUND AND PURPOSE

Post-conditioning with volatile anesthetics can create ischemic tolerance against cerebral ischemia-reperfusion injury. The present study was designed to determine whether delayed exposure to sevoflurane could induce ischemic tolerance and if this effect was dependent on increasing phosphorylated Akt-Ser473 and GSK-3β-Ser9 expression in the mitochondria, via a mechanism involving the PI3K/Akt pathway.

METHODS

Adult male Sprague-Dawley rats were subjected to focal cerebral ischemia. Sevoflurane post-conditioning was achieved by administration of 2.5% sevoflurane for 60 min, 15 min after reperfusion. Phosphorylated Akt-Ser473 and GSK-3β-Ser9 in the cytosol and mitochondria of the ischemic penumbra were evaluated 4, 12, 24, and 72 h after reperfusion. Neurological deficit score and activity of caspase-3 and -9 were evaluated 24 and 72 h after reperfusion. Apoptosis, as measured by TUNEL staining and cerebral infarct size,was determined 24h after reperfusion.

RESULTS

Sevoflurane-delayed post-conditioning significantly increased levels of phosphorylated Akt-Ser473 and GSK-3β-Ser9 in the mitochondria and inhibited the activities of caspase-3 and -9, showing an improved neurological deficit score and a decreased infarct size. However, LY294002, a selective PI3K inhibitor, not only eliminated the neuroprotection of sevoflurane, as indicated by an increased infarct size and a larger number of TUNEL-positive cells, but also reversed the elevation of p-Akt and p-GSK-3β expression in the mitochondria induced by sevoflurane post-conditioning.

CONCLUSIONS

Our data suggested that delayed application of sevoflurane after reperfusion provides neuroprotection by activating phosphorylated Akt-Ser473 and GSK-3β-Ser9 in the mitochondria via the PI3K/Akt pathway.

Squamosamide Derivative FLZ Protects Pancreatic β-Cells from Glucotoxicity by Stimulating Akt-FOXO1 Pathway

Chronic hyperglycemia increases apoptosis and reduces glucose-stimulated insulin secretion. Although protective agents have been searched extensively, none has been found so far. Here we tested FLZ, a synthetic derivative of squamosamide from a Chinese herb, as a potential candidate for antiglucotoxicity in INS-1E cells and mouse islets. Chronic culture of β-cells in 30 mM glucose caused progressive reduction of cell viability, accompanied with increased apoptosis and reduced insulin secretion. These effects on apoptosis and insulin were reversed by FLZ in a dose-dependent manner. FLZ treatment also increased forkhead box O1 protein phosphorylation and reduced its nuclear location. On the contrary, FLZ increased pancreatic and duodenal homeobox-1 expression and its nuclear localization, an effect mediated by increased p-Akt. Consistently, Akt selective inhibitor MK-2206 completely abolished antiglucotoxicity effect of FLZ. Furthermore, FLZ treatment increased cytosolic ATP/ADP ratio. Taken together, our results suggest that FLZ could be a potential therapeutic agent to treat the hyperglycemia-induced β-cell failure.

Hypoglycemic Activity through a Novel Combination of Fruiting Body and Mycelia of Cordyceps militaris in High-Fat Diet-Induced Type 2 Diabetes Mellitus Mice

Diabetes mellitus (DM) is currently ranked among leading causes of death worldwide in which type 2 DM is reaching an epidemic proportion. Hypoglycemic medications for type 2 DM have either proven inadequate or posed adverse effects; therefore, the Chinese herbal products are under investigation as an alternative treatment. In this study, a novel combination of fruiting body and mycelia powder of herbal Cordyceps militaris number 1 (CmNo1) was administered to evaluate their potential hypoglycemic effects in high-fat diet- (HFD-) induced type 2 DM in C57BL/6J mice. Body weight, fasting blood glucose (FBG), oral glucose tolerance test (OGTT), and blood biochemistry indexes were measured. Results indicated that CmNo1 lowered the blood glucose level by increasing insulin sensitivity, while no change in body weight was observed. Increased protein expression of IRS-1, pIRS-1, AKT, pAKT, and GLUT-4 in skeletal muscle and adipose tissue was found indicating restoration of insulin signaling. Additionally, PPAR-γ expression in adipose tissue restored the triglyceride and cholesterol levels. Finally, our results suggest that CmNo1 possesses strong hypoglycemic, anticholesterolemic, and antihypertriglyceridemic actions and is more economical alternate for DM treatment.

Substance P promotes diabetic corneal epithelial wound healing through molecular mechanisms mediated via the neurokinin-1 receptor

Substance P (SP) is a neuropeptide, predominantly released from sensory nerve fibers, with a potentially protective role in diabetic corneal epithelial wound healing. However, the molecular mechanism remains unclear. We investigated the protective mechanism of SP against hyperglycemia-induced corneal epithelial wound healing defects, using type 1 diabetic mice and high glucose-treated corneal epithelial cells. Hyperglycemia induced delayed corneal epithelial wound healing, accompanied by attenuated corneal sensation, mitochondrial dysfunction, and impairments of Akt, epidermal growth factor receptor (EGFR), and Sirt1 activation, as well as decreased reactive oxygen species (ROS) scavenging capacity. However, SP application promoted epithelial wound healing, recovery of corneal sensation, improvement of mitochondrial function, and reactivation of Akt, EGFR, and Sirt1, as well as increased ROS scavenging capacity, in both diabetic mouse corneal epithelium and high glucose-treated corneal epithelial cells. The promotion of SP on diabetic corneal epithelial healing was completely abolished by a neurokinin-1 (NK-1) receptor antagonist. Moreover, the subconjunctival injection of NK-1 receptor antagonist also caused diabetic corneal pathological changes in normal mice. In conclusion, the results suggest that SP-NK-1 receptor signaling plays a critical role in the maintenance of corneal epithelium homeostasis, and that SP signaling through the NK-1 receptor contributes to the promotion of diabetic corneal epithelial wound healing by rescued activation of Akt, EGFR, and Sirt1, improvement of mitochondrial function, and increased ROS scavenging capacity.

Combined cetuximab and celecoxib treatment exhibits a synergistic anticancer effect on human oral squamous cell carcinoma in vitro and in vivo

The aim of the present study was to evaluate the potency of epidermal growth factor receptor (EGFR) pathway inhibition achieved by combining cetuximab (CET), an anti-EGFR monoclonal antibody, and celecoxib (CXB), a cyclooxygenase-2 (COX-2) inhibitor, in oral squamous cell carcinoma (OSCC) in vitro and in vivo. The OSCC cell line, HSC3, was treated with CET (0-400 μg/ml), CXB (0-40 μM), or a combination of both at a range of concentrations. Cell proliferation, apoptosis, migration and invasion were determined to assess the anticancer effects in vitro. The in vivo effects of CET and CXB on tumor cell growth were examined using an OSCC xenograft nude mouse model. In addition, downstream protein expression levels of EGFR, p-EGFR, PI3K, p-PI3K, AKT and p-Akt were evaluated by western blot analysis. It was found that the combination of low concentrations of CET and CXB significantly suppressed the proliferation, migration and invasion of the HSC3 tumor cells and decreased PEG2 production and VEGF expression in vitro, and inhibited tumor growth in vivo compared to the action of either agent alone. The results also showed that this combination significantly induced apoptosis and increased caspase-3 and caspase-8 activity compared to the action of either agent alone (P<0.01). Furthermore, the combination treatment significantly reduced the expression of p-EGFR, p-PI3K and p-Akt in the HSC3 cell line, which may contribute to the inhibition of tumor growth. Taken together, our findings revealed that the additive combination of CET and CXB is a potential drug candidate for the treatment of OSCC.

Activation of glucagon-like peptide-1 receptor inhibits tumourigenicity and metastasis of human pancreatic cancer cells via PI3K/Akt pathway

AIMS

It has been reported that glucagon-like peptide-1 (GLP-1) agents are associated with an increased risk of pancreatic cancer in patients with type 2 diabetes. Reports have indicated that GLP-1 promotes pancreatic metaplasia and premalignant lesions. The aims of this study were to determine the effects of GLP-1-based therapy on pancreatic cancer cells.

METHODS

Immunohistochemistry was used to investigate GLP-1 receptor (GLP-1R) expression in 30 human pancreatic cancer tissues. We also analysed associated clinicopathological data and each patient's prognosis. Two human pancreatic cancer cell lines were used to evaluate the in vitro effects of the GLP-1R agonist liraglutide on cell growth, migration and invasion. Mouse xenograft models of human pancreatic cancer were established to evaluate the effects of liraglutide in vivo.

RESULTS

Human pancreatic cancer tissues showed lower levels or a lack of GLP-1R expression when compared with levels in the tumour-adjacent pancreatic tissues. Negative GLP-1R expression occurred more frequently in advanced tumours with larger diameters and lymphatic metastasis, and was associated with a poor prognosis. GLP-1R activation with liraglutide inhibited tumourigenicity and metastasis of human pancreatic cancer cells in vitro and in vivo. Akt activation was dose-dependently inhibited by liraglutide, and the PI3K inhibitors, LY294002 and wortmannin, displayed similar suppressive effects to liraglutide in human pancreatic cancer cells.

CONCLUSIONS

GLP-1R activation has an antitumour effect on human pancreatic cancers via inhibition of the PI3K/Akt pathway. This finding suggests that GLP-1-based therapies may be beneficial, rather than harmful, in treating type 2 diabetic patients with pancreatic cancer.

Puerarin protects against β-amyloid-induced microglia apoptosis via a PI3K-dependent signaling pathway

Puerarin extracted from Radix puerariae is well-known for its anti-oxidative and neuroprotective activities. In this study, we investigated the protective effect of puerarin on amyloid-β protein (Aβ)-induced cytotoxicity and its potential mechanisms in BV-2 and primary microglial cells. We found that pretreatment with puerarin afforded protection against Aβ-induced cytotoxicity through inhibiting apoptosis in BV-2 and primary microglial cells. This result was also confirmed by the activated caspase-3 assay. Phospho-Akt and Bcl-2 expression increased after pretreatment with puerarin in BV-2 and primary microglial cells exposed to Aβ, whereas Bax expression and cytochrome c release decreased. In addition, puerarin treatment prevented the loss of mitochondrial membrane potential and reactive oxygen species production. Interestingly, these effects of puerarin against Aβ insult were abolished by LY294002, an inhibitor of PI3K phosphorylation. Taken together, these findings suggest that puerarin prevents Aβ-induced microglial apoptosis via the activation of PI3K/Akt signaling pathway, and might be a potential preventive or therapeutic agent for Alzheimer's disease.

[Resveratrol attenuates hypoxia-reperfusion injury induced rat myocardium microvascular endothelial cell dysfunction through upregulating PI3K/Akt/SVV pathways]

OBJECTIVE

To detect the role of surviving (SVV) in the protective effect of resveratrol against hypoxia/reperfusion injury (H/RI) of cardiac microvascular endothelial cells (CMECs).

METHODS

CMECs isolated from the hearts of adult rats were exposed to hypoxia (94% N₂, 5% CO₂, 1% O₂) for 2 h followed by 4 h reoxygenation (95% O₂, 5% CO₂). The cell proliferation of CMECs was measured by MTT assay and Transwell method was used to detect migration ability of CMEC, PI-AnnexinV double staining and flow cytometry technique were employed to observe the apoptotic rate of CMECs. The SVV protein expression was detected with Western blot method.

RESULTS

Compared to control group, the proliferation (0.19 ± 0.03 vs. 0.42 ± 0.07, P < 0.01) and migration ((28 ± 2)/5HPF vs. (50 ± 3)/5 HPF, P < 0.01) abilities were impaired and the apoptosis index ((19.7 ± 0.8)% vs. (5.4 ± 0.3)%, (P < 0.05) of CMEC was increased after H/RI. The proliferation (0.36 ± 0.07 vs. 0.19 ± 0.03, P < 0.05) and migration ((55 ± 3)/5HPF vs. (28 ± 2)/5HPF, P < 0.05) abilities of CMEC were significantly improved while the apoptosis index ((9.6 ± 0.7)% vs. (19.7 ± 0.8)%, P < 0.05) was significantly decreased in H/RI+resveratrol group compared to H/RI group.SVV protein expression was also upregulated in H/RI+resveratrol group compared to H/RI group (P < 0.05). To further ascertain the role of SVV in the protective effects of resveratrol, PI3K specific inhibitor LY294002 was added to H/RI+resveratrol group, the proliferation (0.25 ± 0.05 vs. 0.36 ± 0.07, P < 0.05) and migration ((34 ± 3)/5HPF vs. (55 ± 3)/5HPF, P < 0.05) abilities were significantly decreased, the apoptosis index ((16.2 ± 0.6)% vs. (9.6 ± 0.7)%, P < 0.05) was increased and the protein expression of SVV was downregulated (P < 0.05) in LY294002+H/RI+resveratrol group compared to H/RI+resveratrol group.

CONCLUSION

Resveratrol could significantly reduce H/RI induced apoptosis and attenuate H/RI induced cardiac microvascular endothelial cells dysfunction through up-regulating PI3K/Akt/SVV pathways.