Wild-Type KRAS Allele Effects on Druggable Targets in KRAS Mutant Lung Adenocarcinomas

KRAS mutations are one of the most common oncogenic drivers in non-small cell lung cancer (NSCLC) and in lung adenocarcinomas in particular. Development of therapeutics targeting KRAS has been incredibly challenging, prompting indirect inhibition of downstream targets such as MEK and ERK. Such inhibitors, unfortunately, come with limited clinical efficacy, and therefore the demand for developing novel therapeutic strategies remains an urgent need for these patients. Exploring the influence of wild-type (WT) KRAS on druggable targets can uncover new vulnerabilities for the treatment of KRAS mutant lung adenocarcinomas. Using commercially available KRAS mutant lung adenocarcinoma cell lines, we explored the influence of WT KRAS on signaling networks and druggable targets. Expression and/or activation of 183 signaling proteins, most of which are targets of FDA-approved drugs, were captured by reverse-phase protein microarray (RPPA). Selected findings were validated on a cohort of 23 surgical biospecimens using the RPPA. Kinase-driven signatures associated with the presence of the KRAS WT allele were detected along the MAPK and AKT/mTOR signaling pathway and alterations of cell cycle regulators. FoxM1 emerged as a potential vulnerability of tumors retaining the KRAS WT allele both in cell lines and in the clinical samples. Our findings suggest that loss of WT KRAS impacts on signaling events and druggable targets in KRAS mutant lung adenocarcinomas.

Integrative analysis of epigenomics, transcriptomics, and proteomics to identify key targets and pathways of Weining granule for gastric cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Weining granule (WNG) is a "Qi-Enriching and Kidney-Tonifying, Spleen-Reinforcing and Stasis-Removing" formula for gastric cancer (GC). Past research we noted WNG inhibited cell growth and raised apoptosis in GC. However, the underlying mechanism of WNG for GC have yet to be systematically clarified.

AIM OF THE STUDY

We sought to characterize the molecular landscape of GC cells in vitro after WNG treated, to identify the molecular targets and pathways that were associated with WNG for inducing the apoptosis of GC cells, and further to clarify underlying molecular mechanism of WNG for GC.

MATERIALS AND METHODS

We performed the techniques of RNA sequencing, tandem mass tags (TMT) based quantitative proteomics, and reduced representation bisulfite sequencing (RRBS) in WNG-treated/or untreated SGC-7901 GC cells to gain a comprehensive molecular portrait of WNG treatment. Then we integrated methylomics, transcriptomics, and proteomics data to carry out the bioinformatics analysis, and constructed the protein-protein interaction (PPI) network to identify molecular targets, and to discover the underlying signaling pathways associated with WNG for GC by network analysis. Besides, we verified the candidate target genes by Kaplan-Meier plotter database.

RESULTS

We identified 1249 significant differentially expressed genes (DEGs) from RNA expression datasets, 191 significant differentially abunabundant proteins (DAPs) from proteomics datasets, and 8293 significant differentially methylated regions (DMRs) from DNA methylation datasets. GO and KEGG analysis showed DEGs, DAPs, and DMRs enriched in the cancer-related biological processes of calcium signaling pathway, pathways in cancer, metabolic pathways, MAPK signaling pathway, PI3K-Akt signaling pathway, and transcriptional misregulation in cancer. We integrated three profile datasets and performed network analysis to distinguish the hub genes, and finally the genes of SOD2, HMOX1, MMP1, SRXN1, NOTCH1, MAPK14, TXNIP, VEGFA, POLR2F, and HSPA9 were identified. The Kaplan-Meier plotter confirmed that SOD2, MMP1, SRXN1, NOTCH1, MAPK14, TXNIP, VEGFA, and HSPA9 were significantly correlated with OS in GC patients (P < 0.01), while HMOX1 and POLR2F expression were not significantly relevant to survival of GC patients (P > 0.01).

CONCLUSIONS

SOD2, MMP1, SRXN1, NOTCH1, MAPK14, TXNIP, VEGFA, and HSPA9 were the predictive pharmaceutical targets of WNG for GC. The anticancer function of WNG was significantly associated with the pathways of focal adhesion pathway, PI3K-Akt signaling pathway, MAPK signaling pathway, and Wnt signaling pathway.

l-Theanine Prevents Long-Term Affective and Cognitive Side Effects of Adolescent Δ-9-Tetrahydrocannabinol Exposure and Blocks Associated Molecular and Neuronal Abnormalities in the Mesocorticolimbic Circuitry

Chronic adolescent exposure to Δ-9-tetrahydrocannabinol (THC) is linked to elevated neuropsychiatric risk and induces neuronal, molecular and behavioral abnormalities resembling neuropsychiatric endophenotypes. Previous evidence has revealed that the mesocorticolimbic circuitry, including the prefrontal cortex (PFC) and mesolimbic dopamine (DA) pathway are particularly susceptible to THC-induced pathologic alterations, including dysregulation of DAergic activity states, loss of PFC GABAergic inhibitory control and affective and cognitive abnormalities. There are currently limited pharmacological intervention strategies capable of preventing THC-induced neuropathological adaptations. l-Theanine is an amino acid analog of l-glutamate and l-glutamine derived from various plant sources, including green tea leaves. l-Theanine has previously been shown to modulate levels of GABA, DA, and glutamate in various neural regions and to possess neuroprotective properties. Using a preclinical model of adolescent THC exposure in male rats, we report that l-theanine pretreatment before adolescent THC exposure is capable of preventing long-term, THC-induced dysregulation of both PFC and VTA DAergic activity states, a neuroprotective effect that persists into adulthood. In addition, pretreatment with l-theanine blocked THC-induced downregulation of local GSK-3 (glycogen synthase kinase 3) and Akt signaling pathways directly in the PFC, two biomarkers previously associated with cannabis-related psychiatric risk and subcortical DAergic dysregulation. Finally, l-theanine powerfully blocked the development of both affective and cognitive abnormalities commonly associated with adolescent THC exposure, further demonstrating functional and long-term neuroprotective effects of l-theanine in the mesocorticolimbic system.SIGNIFICANCE STATEMENT With the increasing trend of cannabis legalization and consumption during adolescence, it is essential to expand knowledge on the potential effects of adolescent cannabis exposure on brain development and identify potential pharmacological strategies to minimize Δ-9-tetrahydrocannabinol (THC)-induced neuropathology. Previous evidence demonstrates that adolescent THC exposure induces long-lasting affective and cognitive abnormalities, mesocorticolimbic dysregulation, and schizophrenia-like molecular biomarkers that persist into adulthood. We demonstrate for the first time that l-theanine, an amino acid analog of l-glutamate and l-glutamine, is capable of preventing long-term THC side effects. l-Theanine prevented the development of THC-induced behavioral aberrations, blocked cortical downregulation of local GSK-3 (glycogen synthase kinase 3) and Akt signaling pathways, and normalized dysregulation of both PFC and VTA DAergic activity, demonstrating powerful and functional neuroprotective effects against THC-induced developmental neuropathology.

Pinellia ternata attenuates carotid artery intimal hyperplasia and increases endothelial progenitor cell activity via the PI3K/Akt signalling pathway in wire-injured rats

CONTEXT

Clinically, Pinellia ternata (Thunb.) Breit. (Araceae) (PT) has been widely used in the treatment of atherosclerosis and hyperlipidaemia, but the underlying mechanisms are still not clearly understood.

OBJECTIVE

This research was conducted to confirm the mechanism by which PT affects carotid artery intimal hyperplasia.

MATERIALS AND METHODS

An intestinal hyperplasia Sprague-Dawley rat model was established by carotid artery injury. The rats were randomly divided into five groups (n = 8): sham, model, PT (with daily intragastric administration of 10 g/mL/kg PT tubers water extract), PT+LY294002 (with intraperitoneal injection of 50 mg/kg LY294002 + 10 g/mL/kg PT) and endothelial progenitor cells (EPCs) (with injection of 5 × 10⁵/cells), and treated for 4 or 8 weeks.

RESULTS

HE staining showed that PT attenuated intimal hyperplasia. RT-PCR, Western blotting and immunohistochemistry showed that PT increased the expression of vascular endothelial growth factor (VEGF) and eNOS in the atherosclerotic carotid artery. PT increased the Dil-acLDL⁺/FITC-UEA-1⁺ population (from 0.41 ± 0.085% to 0.60 ± 0.092%) in the blood, decreased TCHO, TG, LDL-C, IL-6 and TNF-α levels, and increased HDL-C and IL-10 levels in the blood. However, these changes were reversed by the PI3K/Akt pathway inhibitor LY294002.

DISCUSSION AND CONCLUSIONS

PT can be developed as an atherosclerosis and carotid intimal hyperplasia treatment drug. Therefore, further study will focus on the effects of PT on intimal hyperplasia in wire-injured atherosclerosis patients and explore in depth some other relevant molecular mechanisms.

Piperlonguminine and Piperine Analogues as TrxR Inhibitors that Promote ROS and Autophagy and Regulate p38 and Akt/mTOR Signaling

The natural products piperlongumine and piperine have been shown to inhibit cancer cell proliferation through elevation of reactive oxidative species (ROS) and eventually cell death, but only have modest cytotoxic potencies. A series of 14 novel phenylallylidenecyclohexenone analogues based on piperlongumine and piperine therefore were designed and synthesized, and their pharmacological properties were evaluated. Most of the compounds produced antiproliferative activities against five human cancer cells with IC50 values lower than those of piperlongumine and piperine. Among these, compound 9m exerted the most potent antiproliferative activity against drug-resistant Bel-7402/5-FU human liver cancer 5-FU resistant cells (IC50 = 0.8 μM), which was approximately 10-fold lower than piperlongumine (IC50 = 8.4 μM). Further, 9m showed considerably lower cytotoxicity against LO2 human normal liver epithelial cells compared to Bel-7402/5-FU. Mechanistically, compound 9m inhibited thioredoxin reductase (TrxR) activity, increased ROS levels, reduced mitochondrial transmembrane potential (MTP), and induced autophagy in Bel-7402/5-FU cells via regulation of autophagy-related proteins LC3, p62, and beclin-1. Finally, 9m activated significantly the p38 signaling pathways and suppressed the Akt/mTOR signaling pathways. In conclusion, 9m could be a promising candidate for the treatment of drug-resistant cancer cells and, as such, warrants further investigation.

Cedrol, a Sesquiterpene Alcohol, Enhances the Anticancer Efficacy of Temozolomide in Attenuating Drug Resistance via Regulation of the DNA Damage Response and MGMT Expression

Glioblastoma (GBM) is a common and aggressive brain tumor with a median survival of 12-15 months. Temozolomide (TMZ) is a first-line chemotherapeutic agent used in GBM therapy, but the occurrence of drug resistance limits its antitumor activity. The natural compound cedrol has remarkable antitumor activity and is derived from Cedrus atlantica. In this study, we investigated the combined effect of TMZ and cedrol in GBM cells in vitro and in vivo. The TMZ and cedrol combination treatment resulted in consistently higher suppression of cell proliferation via regulation of the AKT and MAPK signaling pathways in GBM cells. The combination treatment induced cell cycle arrest, cell apoptosis, and DNA damage better than either drug alone. Furthermore, cedrol reduced the expression of proteins associated with drug resistance, including O⁶-methlyguanine-DNA-methyltransferase (MGMT), multidrug resistance protein 1 (MDR1), and CD133 in TMZ-treated GBM cells. In the animal study, the combination treatment significantly suppressed tumor growth through the induction of cell apoptosis and decreased TMZ drug resistance. Moreover, cedrol-treated mice exhibited no significant differences in body weight and improved TMZ-induced liver damage. These results imply that cedrol may be a potential novel agent for combination treatment with TMZ for GBM therapy that deserves further investigation.

Triclosan induces PC12 cells injury is accompanied by inhibition of AKT/mTOR and activation of p38 pathway

Triclosan (TCS) has been widely used as a disinfectant and antiseptic in multiple consumer and healthcare products due to its clinical effectiveness against various bacteria, fungi and protozoa. Recently, several studies have reported the adverse effects of TCS on various nerve cells, arousing concerns about its potential neurotoxicity. The present study aimed to investigate the neurotoxicity of TCS in rat pheochromocytoma PC12 cells. After differentiation, the stabilized PC12 cells were treated with 1, 10, 50 μM TCS for 12 h. At the end of the treatment, the generation of reactive oxygen species (ROS), protein expression of apoptotic-related genes, AMPK-AKT/mTOR, as well as p38 in PC12 cells were determined. The concentrations were chosen based on the results of cell viability and lactic dehydrogenase (LDH) assays in response to TCS treatment (ranging from 0.001 to 100 μM) for varied time periods. The results showed that TCS is cytotoxic to PC12 cells, causing decreased cell viability accompanied by increased LDH release. TCS treatment at 10 and 50 μM for 12 h increased the mRNA and protein expression of the pro-apoptotic gene Bax, while Bcl-2 levels remained unchanged. Moreover, an increase in the generation of reactive oxygen species (ROS) was found in TCS-treated PC12 cells at the concentrations of 1 and 10 μM. Pretreatment with 100 μM N-acetyl cysteine (NAC- ROS scavenger) for 1 h normalized the ROS generations in TCS-treated PC12 cells. Additionally, the suppression of the phosphorylation of Akt and mTOR was observed in TCS-treated PC12 cells at 10 and 50 μM for 12 h, concomitant with the activation of p38 MAPK pathway at 50 μM TCS. However, there were no effects of TCS on the phosphorylation of AMPK in these cells. Taken together, these results suggest that TCS may cause adverse effects and oxidative stress in PC12 cells accompanied by inhibition of Akt/mTOR and activation of p38.

Ancistrolikokine E3, a 5,8'-Coupled Naphthylisoquinoline Alkaloid, Eliminates the Tolerance of Cancer Cells to Nutrition Starvation by Inhibition of the Akt/mTOR/Autophagy Signaling Pathway

PANC-1 human pancreatic cancer cells are characterized by their ability to proliferate aggressively under hypovascular and hypoxic conditions in the tumor microenvironment, displaying a remarkable tolerance to nutrition starvation. The antiausterity strategy is a new approach in anticancer drug discovery aiming at the identification of potent agents that inhibit preferentially the survival of tumor cells during a limited supply of nutrients and oxygen. The new 5,8'-coupled naphthyldihydroisoquinoline alkaloid ancistrolikokine E₃ (4), isolated from the Congolese liana Ancistrocladus likoko, showed potent preferential cytotoxicity against PANC-1 cells under nutrient-deprived conditions, with a PC₅₀ value of 2.5 μM, without exhibiting toxicity in normal, nutrient-rich medium. The compound was found to induce dramatic alterations in cell morphology, leading to cell death. Moreover, it inhibited significantly PANC-1 cell migration and colony formation in a concentration-dependent manner. This study on 4 provides the first live evidence of the effect of a naphthyldihydroisoquinoline alkaloid against PANC-1 cells in nutrient-deprived medium. Mechanistic investigations conducted suggest that compound 4 is a potent inhibitor of the activation of the Akt/mTOR pathway. Furthermore, it inhibited the expression levels of the key autophagy regulators Atg5, Atg12, Beclin-1, LC3-I, and LC3-II. The results demonstrated that ancistrolikokine E₃ (4) is a potent early-stage inhibitor of the autophagy pathway in PANC-1 human pancreatic cancer cells. Ancistrolikokine E₃ (4) and related naphthylisoquinoline alkaloids are promising potential lead compounds for anticancer drug development based on the antiausterity strategy.

HDL-apoA-I induces the expression of angiopoietin like 4 (ANGPTL4) in endothelial cells via a PI3K/AKT/FOXO1 signaling pathway

BACKGROUND

High Density Lipoprotein (HDL) and its main protein component, apolipoprotein A-I (apoA-I), have numerous atheroprotective functions on various tissues including the endothelium. Therapies based on reconstituted HDL containing apoA-I (rHDL-apoA-I) have been used successfully in patients with acute coronary syndrome, peripheral vascular disease or diabetes but very little is known about the genomic effects of rHDL-apoA-I and how they could contribute to atheroprotection.

OBJECTIVE

The present study aimed to understand the endothelial signaling pathways and the genes that may contribute to rHDL-apoA-I-mediated atheroprotection.

METHODS

Human aortic endothelial cells (HAECs) were treated with rHDL-apoA-I and their total RNA was analyzed with whole genome microarrays. Validation of microarray data was performed using multiplex RT-qPCR. The expression of ANGPTL4 in EA.hy926 endothelial cells was determined by RT-qPCR and Western blotting. The contribution of signaling kinases and transcription factors in ANGPTL4 gene regulation by HDL-apoA-I was assessed by RT-qPCR, Western blotting and immunofluorescence using chemical inhibitors or siRNA-mediated gene silencing.

RESULTS

It was found that 410 transcripts were significantly changed in the presence of rHDL-apoA-I and that angiopoietin like 4 (ANGPTL4) was one of the most upregulated and biologically relevant molecules. In validation experiments rHDL-apoA-I, as well as natural HDL from human healthy donors or from transgenic mice overexpressing human apoA-I (TgHDL-apoA-I), increased ANGPTL4 mRNA and protein levels. ANGPTL4 gene induction by HDL was direct and was blocked in the presence of inhibitors for the AKT or the p38 MAP kinases. TgHDL-apoA-I caused phosphorylation of the transcription factor forkhead box O1 (FOXO1) and its translocation from the nucleus to the cytoplasm. Importantly, a FOXO1 inhibitor or a FOXO1-specific siRNA enhanced ANGPTL4 expression, whereas administration of TgHDL-apoA-I in the presence of the FOXO1 inhibitor or the FOXO1-specific siRNA did not induce further ANGPTL4 expression. These data suggest that FOXO1 functions as an inhibitor of ANGPTL4, while HDL-apoA-I blocks FOXO1 activity and induces ANGPTL4 through the activation of AKT.

CONCLUSION

Our data provide novel insights into the global molecular effects of HDL-apoA-I on endothelial cells and identify ANGPTL4 as a putative mediator of the atheroprotective functions of HDL-apoA-I on the artery wall, with notable therapeutic potential.

Chronic cannabis promotes pro-hallucinogenic signaling of 5-HT2A receptors through Akt/mTOR pathway

Long-term use of potent cannabis during adolescence increases the risk of developing schizophrenia later in life, but to date, the mechanisms involved remain unknown. Several findings suggest that the functional selectivity of serotonin 2A receptor (5-HT2AR) through inhibitory G-proteins is involved in the molecular mechanisms responsible for psychotic symptoms. Moreover, this receptor is dysregulated in the frontal cortex of schizophrenia patients. In this context, studies involving cannabis exposure and 5-HT2AR are scarce. Here, we tested in mice the effect of an early chronic Δ9-tetrahydrocannabinol (THC) exposure on cortical 5-HT2AR expression, as well as on its in vivo and in vitro functionality. Long-term exposure to THC induced a pro-hallucinogenic molecular conformation of the 5-HT2AR and exacerbated schizophrenia-like responses, such as prepulse inhibition disruption. Supersensitive coupling of 5-HT2AR toward inhibitory Gαi1-, Gαi3-, Gαo-, and Gαz-proteins after chronic THC exposure was observed, without changes in the canonical Gαq/11-protein pathway. In addition, we found that inhibition of Akt/mTOR pathway by rapamycin blocks the changes in 5-HT2AR signaling pattern and the supersensitivity to schizophrenia-like effects induced by chronic THC. The present study provides the first evidence of a mechanistic explanation for the relationship between chronic cannabis exposure in early life and increased risk of developing psychosis-like behaviors in adulthood.

Pogostone induces autophagy and apoptosis involving PI3K/Akt/mTOR axis in human colorectal carcinoma HCT116 cells

ETHNOPHAMACOLOGICAL RELEVANCE

Pogostemon cablin is a medicinal herb widely used to treat gastrointestinal diseases in many Asian countries. Pogostone is an important constituent of Pogostemon cablin, and possesses various bioactivitys. In this study, we performed to investigate the anti-colorectal tumor property of Pogostone by inducing aurophagy and apoptosis in human colorectal cancer cells, and to define the potential molecular mechanisms.

MATERIALS AND METHODS

In vitro, The anti-tumor activity of pogostone was assessed using MTT assay. Autophagy was monitored by transmission electron microscopy observation and mRFP-GFP-LC3 fluorescence analysis in colorectal tumor cell line. Apoptosis was measured by flow cytometry and annexinV-FITC/PI staining. The protein expressions or activition of LC3-Ⅱ, AKT, mTOR, caspase-3 and caspase-7 were detected through western blotting. In vivo, the anti-tumor effect of pogostone was tested with HCT116 colorectal tumor cells transplantation tumor model. The expression of Ki-67 was determined by Immunohistochemistry staining and the apoptosis was evaluated using TUNEL assay.

RESULTS

In vitro, pogostone exhibits significant anti-tumor activity against human cancer cell lines, especially for HCT116 (18.7±1.93μg/ml). Transmission electron microscopy observation, mRFP-GFP-LC3 fluorescence analysis, flow cytometry and assay and western blotting detection revealed that the anti-colorectal tumor activity of pogostone was dependent on inducing autophagy and apoptosis through up-regulating the expression of LC3-Ⅱ, cleaved caspase-7 and caspase-3, and decreasing the phosphorylation of AKT/mTOR. In vivo, 150mg/kg pogostone inhibited the HCT116 tumor growth in immunodeficient mice with an inhibitory rate of 43.3%, decreased the expression of Ki67, and induced apoptosis in three days.

CONCLUSION

Pogostone showed anti-colorectal tumor effects by inducing autophagy and apoptosis involving PI3K/Akt/mTOR axis. Thus, pogostone may be a promising lead compound to be further developed for cancer therapy.

Palmitic acid triggers cell apoptosis in RGC-5 retinal ganglion cells through the Akt/FoxO1 signaling pathway

Hallmarks of the pathophysiology of glaucoma are oxidative stress and apoptotic death of retinal ganglion cells (RGCs). Lipotoxicity, involving a series of pathological cellular responses after exposure to elevated levels of fatty acids, leads to oxidative stress and cell death in various cell types. The phosphatidylinositol-3-kinase/protein kinase B/Forkhead box O1 (PI3K/Akt/FoxO1) pathway is crucial for cell survival and apoptosis. More importantly, FoxO1 gene has been reported to confer relatively higher risks for eye diseases including glaucoma. However, little information is available regarding the interaction between FoxO1 and RGC apoptosis, much less a precise mechanism. In the present study, immortalized rat retinal ganglion cell line 5 (RGC-5) was used as a model to study the toxicity of palmitic acid (PA), as well as underlying mechanisms. We found that PA exposure significantly decreased cell viability by enhancing apoptosis in RGC-5 cells, as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. PA also induced a remarkable increase in reactive oxygen species and malondialdehyde. Moreover, PA significantly decreased the level of phospho-Akt and phospho-FoxO1 in cells. Finally, shRNA knockdown and plasmid overexpression studies displayed that downregulation of Akt protein or upregulation of FoxO1 protein augmented cell death, while knockdown of FoxO1 or overexpression of Akt1 abolished PA-induced cell death. Collectively, our results indicated that PA-induced cell death is mediated through modulation of Akt/FoxO1 pathway activity.

The Osmopressor-Induced Angiopoietin-1 Secretion in Plasma and Subsequent Activation of the Tie-2/Akt/eNOS Signaling Pathway in Red Blood Cell

BACKGROUND

Water ingestion induces the osmopressor response, which typically presents as increased total peripheral vascular resistance in young healthy subjects. A previous study has suggested that the RBC membrane receptor is involved in osmopressor stress. Recent studies have indicated nitric oxide synthase phosphorylation in RBCs. However, the main process in signaling pathway activation to elicit such a response is unknown. Herein, we hypothesized that hypo-osmotic stress following water ingestion modulates the eNOS/NO pathway, thereby alternating vascular resistance.

METHODS

We included 24 young, healthy subjects. Physiological parameters and blood samples were collected at 5 minutes before and 25 and 50 minutes after 50 ml water, 500 ml water, or 500 ml normal saline ingestion. A human receptor tyrosine kinase (RTK) phosphorylation antibody array was used to simultaneously detect and monitor the biological activation pathways in RBCs.

RESULTS

Of the 71 RTKs assayed during the osmopressor response, several RTKs were significantly upregulated, including Tie-2 and Tie-1. Plasma angiopoietin-1 levels significantly increased at 25 minutes after 500 ml water ingestion compared to those at baseline. Simultaneous phosphorylation of Tie-2, Akt, and eNOS in RBCs occurred. RBCs in vitro were stimulated with angiopoietin-1, Tie-2, or 0.8% saline and showed significant increase in Tie-2, Akt, and eNOS phosphorylation upon angiopoietin-1 treatment and enhanced activation upon cotreatment of angiopoietin-1 and 0.8% saline.

CONCLUSIONS

The hypo-osmotic stimulus of water ingestion increases angiopoietin-1 secretion and subsequently activates the Tie-2/Akt/eNOS signaling pathway in RBCs, thereby revealing a novel biological mechanism simultaneously occurring with the osmopressor response.

The novel exercise-induced hormone irisin protects against neuronal injury via activation of the Akt and ERK1/2 signaling pathways and contributes to the neuroprotection of physical exercise in cerebral ischemia

BACKGROUND

Irisin is a novel exercise-induced myokine involved in the regulation of adipose browning and thermogenesis. In this study, we investigated the potential role of irisin in cerebral ischemia and determined whether irisin is involved in the neuroprotective effect of physical exercise in mice.

MATERIALS AND METHODS

The middle cerebral artery occlusion (MCAO) model was used to produce cerebral ischemia in mice. First, the plasma irisin levels and changes in expression of the irisin precursor protein FNDC5 in skeletal muscle were determined post ischemic stroke. Second, the association between plasma irisin levels and the neurological deficit score, brain infarct volume, or plasma concentrations of tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β in mice with MCAO were evaluated. Third, the therapeutic effect of irisin on ischemic brain injury was evaluated in vivo and in vitro. Recombinant irisin was injected directly into the tail vein 30min after the MCAO operation, and then the effects of irisin treatment on brain infarct volume, neurological deficit, neuroinflammation, microglia activation, monocyte infiltration, oxidative stress and intracellular signaling pathway activation (Akt and ERK1/2) were measured. Irisin was also administered in cultured PC12 neuronal cells with oxygen and glucose deprivation (OGD). Finally, to assess the potential involvement of irisin in the neuroprotection of physical exercise, mice were exercised for 2weeks and an irisin neutralizing antibody was injected into these mice to block irisin 1h before the MCAO operation.

RESULTS

The plasma irisin concentration and intramuscular FNDC5 protein expression decreased after ischemic stroke. Plasma irisin levels were negatively associated with brain infarct volume, the neurological deficit score, plasma TNF-α and plasma IL-6 concentrations. In OGD neuronal cells, irisin protected against cell injury. In mice with MCAO, irisin treatment reduced the brain infarct volume, neurological deficits, brain edema and the decline in body weight. Irisin treatment inhibited activation of Iba-1⁺ microglia, infiltration of MPO-1⁺ monocytes and expression of both TNF-α and IL-6 mRNA. Irisin significantly suppressed the levels of nitrotyrosine, superoxide anion and 4-hydroxynonenal (4-HNE) in peri-infarct brain tissues. Irisin treatment increased Akt and ERK1/2 phosphorylation, while blockade of Akt and ERK1/2 by specific inhibitors reduced the neuroprotective effects of irisin. Finally, the exercised mice injected with irisin neutralizing antibody displayed more severe neuronal injury than the exercised mice injected with control IgG.

CONCLUSION

Irisin reduces ischemia-induced neuronal injury via activation of the Akt and ERK1/2 signaling pathways and contributes to the neuroprotective effect of physical exercise against cerebral ischemia, suggesting that irisin may be a factor linking metabolism and cardio-cerebrovascular diseases.

Clivorine, an otonecine pyrrolizidine alkaloid from Ligularia species, impairs neuronal differentiation via NGF-induced signaling pathway in cultured PC12 cells

BACKGROUND

Pyrrolizidine alkaloids (PAs) are commonly found in many plants including those used in medical therapeutics. The hepatotoxicities of PAs have been demonstrated both in vivo and in vitro; however, the neurotoxicities of PAs are rarely mentioned.

PURPOSE

In this study, we aimed to investigate in vitro neurotoxicities of clivorine, one of the PAs found in various Ligularia species, in cultured PC12 cells.

STUDY DESIGN

PC12 cell line was employed to first elucidate the neurotoxicity and the underlying mechanism of clivorine, including cell viability and morphology change, neuronal differentiation marker and signaling pathway.

METHODS

PC12 cells were challenged with series concentrations of clivorine and/or nerve growth factor (NGF). The cell lysates were collected for MTT assay, trypan blue staining, immunocytofluorescent staining, qRT-PCR and western blotting.

RESULTS

Clivorine inhibited cell proliferation and neuronal differentiation evidenced by MTT assay and dose-dependently reducing neurite outgrowth, respectively. In addition, clivorine decreased the level of mRNAs encoding for neuronal differentiation markers, e.g. neurofilaments and TrkA (NGF receptor). Furthermore, clivorine reduced the NGF-induced the phosphorylations of TrkA, protein kinase B and cAMP response element-binding protein in cultured PC12 cells.

CONCLUSION

Taken together, our results suggest that clivorine might possess neurotoxicities in PC12 cells via down-regulating the NGF/TrkA/Akt signaling pathway. PAs not only damage the liver, but also possess neurotoxicities, which could possibly result in brain disorders, such as depression.

The natural secolignan peperomin E induces apoptosis of human gastric carcinoma cells via the mitochondrial and PI3K/Akt signaling pathways in vitro and in vivo

BACKGROUND

Peperomin E (PepE) is a type of secolignan that is a major component of the plant Peperomia dindygulensis. It has been shown to exert anticancer effects in various cancer cell lines; however, the effects of PepE on human gastric cancer remain unexplored.

PURPOSE

The aim of this study was to investigate the effectiveness of PepE as a treatment of gastric cancer and to identify the underlying mechanisms of its anticancer activity.

STUDY DESIGN

The efficacy of PepE was examined using human gastric carcinoma SGC-7901, BGC-823, MKN-45 cell lines and normal gastric epithelial GES-1 cell line as an in vitro model and SGC-7901 xenograft mice as an in vivo model.

METHODS

Cell viability assays were used to examine the anticancer effect of 0-204.8µM concentrations of PepE in vitro. Additionally, flow cytometry and western blotting were used to elucidate the mechanism with a particular focus on apoptosis. SGC-7901 cells were injected into BALB/c mice, which were then treated with 5 or 15mg/kg/day dose of PepE. The in vivo activity of PepE was investigated by measuring tumors and conducting immunohistochemistry experiments. The safety of PepE was investigated by measuring blood biochemical parameters and conducting histopathological analysis. Taxol was used throughout as a positive control.

RESULTS

The results showed that PepE exhibited antiproliferative effects against gastric cancer cells and induced their apoptosis in a dose dependent manner with lower toxicity against normal gastric epithelial cells. Mechanistic evaluations indicated that PepE induced apoptosis by reducing the mitochondrial membrane potential (MTP), inducing cytochrome C release from mitochondria, reducing the ratio of Bcl-2/Bax and Bcl-xl/Bad, increasing activation of caspase-3, and decreasing the levels of PI3K and pAkt. The apoptotic effect of PepE on SGC-7901 cells was partially blocked by an Akt activator SC79. PepE potently inhibited in vivo tumor growth with no obvious toxicity following subcutaneous inoculation of SGC-7901 cells in nude mice.

CONCLUSIONS

These findings indicate that PepE can inhibit cell proliferation and induce apoptosis of gastric cancer cells through mitochondrial and PI3K/Akt signaling pathways with relative safety and may be a novel effective chemotherapeutic agent against gastric cancer.

Lithium ions attenuate serum-deprivation-induced apoptosis in PC12 cells through regulation of the Akt/FoxO1 signaling pathways

RATIONALE

Lithium is currently used in the treatment of mental illness. We have previously reported that lithium stimulated the protein kinase B/Forkhead box O1 (Akt/FoxO1) pathway in rats. However, little information is available regarding its neuroprotective role of this pathway and underlying mechanisms.

OBJECTIVES

PC12 cells treated with serum deprivation were used as a toxicity model to study the protective effect of lithium and its underlying mechanisms.

METHODS

Cell viability was determined by methyl thiazolyl tetrazolium assay and Hoechst staining. FoxO1 subcellular location and its overexpression were used to study the underlying mechanisms. Various pathway inhibitors were used to investigate the possible pathways, while the phosphorylation of Akt and FoxO1 was analyzed by Western blot.

RESULTS

Lithium pretreatment dose-dependently reduced PC12 cell apoptosis induced by serum starvation. The protective effect of lithium was abolished by LY294002, a PI3K-specific inhibitor, and Akt inhibitor Akt inhibitor VIII, whereas mitogen-activated protein kinase kinase (MEK kinase) inhibitor U0126 had no effect. Lithium induced the phosphorylation of Akt and FoxO1 in a time- and concentration-dependent manner. Lithium-induced phosphorylation of Akt and FoxO1 is mediated by the PI3K/Akt pathway. Serum deprivation caused nuclear translocation of FoxO1 while application of lithium reversed the effect of serum deprivation. Moreover, overexpression of FoxO1 enhanced cell apoptosis induced by serum withdrawal. Finally, lithium was found to reduce the exogenous and endogenous FoxO1 protein levels in PC12 cells in a concentration-dependent fashion.

CONCLUSIONS

The protective effect of lithium against serum starvation cell death is mediated by the PI3K/Akt/FoxO1 pathway.

Cigarette smoke exposure triggers the autophagic cascade via activation of the AMPK pathway in mice

We previously demonstrated that cigarette smoke (CS) exposure decreases primordial follicle counts and induces autophagy in ovarian granulosa cells in preference to apoptosis. Therefore, the objective of this study was to investigate molecular targets underlying smoke-induced activation of the reparative autophagy pathway in the ovary. Briefly, ovarian homogenates were prepared from adult female mice exposed to mainstream CS twice daily for 8 wk, using a whole-body exposure system. A gene array revealed that CS exposure induced a greater than 2-fold significant increase in the expression of proautophagic genes Cdkn1b, Map1lc3a, Bad, and Sqstm1/p62. A significant increase in Prkaa2, Pik3c3, and Maplc31b expression, as well as a significant decrease in Akt1 and Mtor expression, was detected by quantitative PCR. The 5'-AMP-activated protein kinase catalytic subunit (AMPK) alpha1 + alpha2 and ATG7 protein expression was significantly increased, whereas AKT1, mTOR, CDKN1B/p27, and CXCR4 proteins were significantly decreased in CS exposed versus control ovaries. Up-regulation of AMPK alpha1 + alpha2, a known initiator of autophagic signaling, and ATG7 further suggests activation of the autophagy cascade. Two prosurvival factors, AKT and mTOR, were decreased in expression, an outcome that favors induction of the autophagy pathway, whereas decreased levels of CDKN1B is suggestive of cell cycle dysregulation. In summary, our data suggest that CS exposure induces ovarian follicle loss through induction of the autophagic cascade via the AMPK pathway together with inhibition of antiautophagic markers AKT and mTOR. We further postulate that toxicant-induced dysregulation of reparative autophagy is a novel pathway central to impaired follicle development and subfertility.

Update on Head and Neck Cancer: Current Knowledge on Epidemiology, Risk Factors, Molecular Features and Novel Therapies

Tobacco use and alcohol consumption are the main risk factors associated with head and neck squamous cell carcinoma (SCC) development due to their cytotoxic and mutagenic effects on the exposed epithelia of the upper aerodigestive tract. Epstein-Barr virus (EBV) and high-risk human papillomaviruses (HPVs), both encoding viral oncoproteins able to interfere with cell cycle control, have been recognized as the etiological agents of nasopharynx carcinoma and a fraction of oropharyngeal carcinoma, respectively. Head and neck SCC is a deadly disease and despite innovative treatments represents a major challenge for patients. Recently, a number of genomic studies have highlighted the molecular heterogeneity of head and neck SCC based on methylation profiles, microRNA expression, mutated genes and new druggable pathways which may represent new targets for cancer-tailored therapies. To date, cetuximab is the only FDA-approved anti-epidermal growth factor receptor therapy for the treatment of head and neck SCC. In addition, a number of monoclonal antibodies targeting AKT, mTOR and PI3K pathways are under evaluation. Several therapeutic vaccines against HPV16 and EBV proteins are also under study. The purpose of this article is to review the epidemiology, pathogenesis and molecular features of head and neck SCC, with an emphasis on new therapies.

The synergistic killing of AML cells co-cultured with HS-5 bone marrow stromal cells by As2O3 and the PI3K/Akt signaling pathway inhibitor LY294002

We aimed to investigate whether a combination of resistance to arsenic trioxide (As2O3) and the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway inhibitor LY294002 can inhibit the proliferation of AML cells in the bone marrow microenvironment. Three AML cell lines were grown with HS-5 human bone marrow stromal cells in adherent co-cultures. The inhibitory effects of As2O3 alone or in combination with LY294002 on the proliferation of these co-cultured AML cells were observed. The PI3K/Akt signaling pathway was detected by Western Blot in co-cultured AML cells cultured alone or treated with As2O3 alone or in combination with LY294002. Our results demonstrate that AML cells adhered to stroma exhibited significantly reduced sensitivity to As2O3. The resistance can be partially abolished by inhibiting the PI3K/Akt pathway. The administration of As2O3 in combination with a PI3K/Akt signaling pathway inhibitor may be expected to become a new approach to the treatment of AML.

Ophiobolin O isolated from Aspergillus ustus induces G1 arrest of MCF-7 cells through interaction with AKT/GSK3β/cyclin D1 signaling

Ophiobolin O is a member of ophiobolin family, which has been proved to be a potent anti-tumor drug candidate for human breast cancer. However, the anti-tumor effect and the mechanism of ophiobolin O remain unclear. In this study, we further verified ophiobolin O-induced G1 phase arrest in human breast cancer MCF-7 cells, and found that ophiobolin O reduced the phosphorylation level of AKT and GSK3β, and induced down-regulation of cyclin D1. The inverse docking (INVDOCK) analysis indicated that ophiobolin O could bind to GSK3β, and GSK3β knockdown abolished cyclin D1 degradation and G1 phase arrest. Pre-treatment with phosphatase inhibitor sodium or thovanadate halted dephosphorylation of AKT and GSK3β, and blocked ophiobolin O-induced G1 phase arrest. These data suggest that ophiobolin O may induce G1 arrest in MCF-7 cells through interaction with AKT/GSK3β/cyclin D1 signaling. In vivo, ophiobolin O suppressed tumor growth and showed little toxicity in mouse xenograft models. Overall, these findings provide theoretical basis for the therapeutic use of ophiobolin O.

The effect to IL-3Ralpha, downstream PI3k/Akt signaling of all-trans retinoic acid and arsenic trioxide in NB4 cells

All-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) are the classic drugs used for induction therapy of acute promyelocytic leukemia (APL). IL-3Ralpha (CD123) is a specific marker of acute myeloid leukemia stem cells (AML-LSCs). The over-expression of IL-3Ralpha in patients with AML is related to high white blood cells counts, high percentages of blast cells, and poor prognosis. Moreover, in some studies, IL-3Ralpha has been considered a new detection marker of minimal residual disease in the bone marrow from patients with APL. In contrast to ATRA, As2O3 reduces both mRNA and protein expression of IL-3Ralpha and inhibits the activity of PI3K/Akt after 24 h, 48 h, and 72 h of exposure. Furthermore, NB4 cells adhered to the human stroma cell line HS-5 cells were used as an in vitro model of APL cells in the bone marrow microenvironment. Our results demonstrate that adhesion to HS-5 cells up-regulated IL-3Ralpha protein expression and activated the downstream PI3K/Akt signaling pathway in NB4 cells. Compared with ATRA, As2O3 more potently inhibits proliferation of NB4 cells adhered to stroma cells.

Curcumin induces apoptosis via simultaneously targeting AKT/mTOR and RAF/MEK/ERK survival signaling pathways in human leukemia THP-1 cells

BACKGROUND

Curcumin is a multi-targeted anti-cancer agent. However, there are few studies on its anti-leukemia activity in human acute monocytic leukemia. Here, we study the effect and mechanisms of curcumin on acute monocytic leukemia.

METHODS

The acute monocytic leukemia cell line THP-1 was used as in vitro cell model to explore the anti-leukemia effects and mechanisms of curcumin. Cell proliferation was measured by MTT assay, cell apoptosis bodies were observed using a light microscope, cell apoptosis rate was evaluated by flow cytometry, and the expression alterations of growth-sinaling proteins were detected by Western blotting.

RESULTS

Curcumin inhibited cell proliferation and induced cell apoptosis in time- and dose- dependent manner in THP-1 cells. Curcumin significantly inhibited the activations of AKT/mTOR and RAF/MEK/ERK signaling pathways simultaneously.

CONCLUSION

This study demonstrates that curcumin inhibits proliferation and induces apoptosis in THP-1 cells via inhibiting the activations of AKT/mTOR and RAF/MEK/ERK signaling pathways simultaneously. Our data suggest that curcumin is a promising anti-tumor agent in acute monocytic leukemia.

Insulin-mediated oxidative stress and DNA damage in LLC-PK1 pig kidney cell line, female rat primary kidney cells, and male ZDF rat kidneys in vivo

Hyperinsulinemia, a condition with excessively high insulin blood levels, is related to an increased cancer incidence. Diabetes mellitus is the most common of several diseases accompanied by hyperinsulinemia. Because an elevated kidney cancer risk was reported for diabetic patients, we investigated the induction of genomic damage by insulin in LLC-PK1 pig kidney cells, rat primary kidney cells, and ZDF rat kidneys. Insulin at a concentration of 5nM caused a significant increase in DNA damage in vitro. This was associated with the formation of reactive oxygen species (ROS). In the presence of antioxidants, blockers of the insulin, and IGF-I receptors, and a phosphatidylinositol 3-kinase inhibitor, the insulin-mediated DNA damage was reduced. Phosphorylation of protein kinase B (PKB or AKT) was increased and p53 accumulated. Inhibition of the mitochondrial and nicotinamide adenine dinucleotide phosphatase oxidase-related ROS production reduced the insulin-mediated damage. In primary rat cells, insulin also induced genomic damage. In kidneys from healthy, lean ZDF rats, which were infused with insulin to yield normal or high blood insulin levels, while keeping blood glucose levels constant, the amounts of ROS and the tumor protein (p53) were elevated in the high-insulin group compared with the control level group. ROS and p53 were also elevated in diabetic obese ZDF rats. Overall, insulin-induced oxidative stress resulted in genomic damage. If the same mechanisms are active in patients, hyperinsulinemia might cause genomic damage through the induction of ROS contributing to the increased cancer risk, against which the use of antioxidants and/or ROS production inhibitors might exert protective effects.

Plasma rich in quercetin metabolites induces G2/M arrest by upregulating PPAR-γ expression in human A549 lung cancer cells

In this study, we incubated human A549 lung cancer cells with quercetin-metabolite-enriched plasma (QMP) obtained from Mongolian gerbils 2 h after quercetin feeding (100 mg/kg body wt/week). We investigated the effects of QMP on the growth of A549 cells and the possible mechanisms for these effects. We found that QMP but not control plasma (CP) reduced the cell growth in A549 cells. QMP led to cell cycle arrest at the G (2)/M phase by downregulating the expression of cdk1 and cyclin B. QMP but not CP or quercetin itself significantly increased PPAR- γ expression (p < 0.05), which was accompanied by an increase of phosphatase and tensin homologue deleted on the chromosome ten level and a decrease of phosphorylation of Akt. Furthermore, quercetin-3-glucuronide and quercetin-3'-sulfate also significantly increased PPAR- γ expression in A549 cells. GW9662, a PPAR- γ antagonist, significantly suppressed the effects of 10 % QMP on cell proliferation and on the expression of cyclin B and cdk1. Taken together, these data suggest that the activation of PPAR- γ plays an important role, at least in part, in the antiproliferative effects of quercetin metabolites.

Sorafenib downregulates ERK/Akt and STAT3 survival pathways and induces apoptosis in a human neuroblastoma cell line

Neuroblastoma is a common solid tumor in children and its tumorigenicity is enhanced by the expression of survival pathways such as Akt and signal transducer and activator of transcription 3 (STAT3). Sorafenib is a multikinase inhibitor that also inhibits STAT3 signaling and induces apoptosis. In this study, we will examine the efficacy of sorafenib on a human neuroblastoma cell line (SK-N-AS) and also investigate its possible mechanisms. After cells reached 50-60% confluence, they were treated with various concentrations of sorafenib (0, 0.1, 1, 5, 10 and 20 microM) for different periods of time. The cell viability and apoptosis were determined by MTS colorimetric assay and TUNEL, respectively. Phosphorylation of Akt1/2/3 (p-Akt1/2/3), extracellular signal-regulated kinase 1/2 (p-ERK1/2), STAT3 (p-STAT3), and AMP-activated protein kinase alpha subunit (p-AMPKalpha) were determined with Western blot. The results indicate that as early as 2 hours post-treatment, cell viability was significantly decreased at 10 microM concentration. In 24 hours or longer treatment groups, sorafenib at 5 microM and above significantly decreased cell viability. TUNEL assay showed a significant increased of apoptosis in 5 and 20 microM treatment groups 24 hours after treatment. Western blots showed a decrease of p-ERK1/2, p-Akt1/2/3, p-STAT3, and p-AMPKalpha expression levels in various sorafenib treatment groups. Our results indicate that sorafenib significantly decreased cell viability and increased apoptosis in human neuroblastoma cell line in association with down-regulation of p-ERK1/2, p-Akt, p-STAT3 survival pathways. These data suggested potential clinical application of sorafenib in the treatment of neuroblastoma.

4-Hydroxynonenal enhances MMP-2 production in vascular smooth muscle cells via mitochondrial ROS-mediated activation of the Akt/NF-kappaB signaling pathways

4-Hydroxynonenal (HNE) accumulates at atherosclerotic lesions, but its role in the progression of atherosclerosis is not clear. Considering the role of matrix metalloproteinases (MMP) in plaque destabilization, we investigated the mechanism by which HNE induces MMP production in vascular smooth muscle cells (VSMC). VSMC stimulated by HNE (1.0 microM) produced enzymatically active MMP-2 with an increased promoter activity, which was abolished by mutation of the NF-kappaB binding site in the promoter region. The increased NF-kappaB activity with subsequent MMP-2 production by HNE was significantly attenuated by transfection with Akt siRNA as well as by pretreatment with the PI3K/Akt inhibitors LY294002 (10 microM) and SH-5 (1.0 microM). The phosphorylation of Akt occurred as early as 5 min in VSMC exposed to HNE and was markedly attenuated by inhibition of mitochondrial reactive oxygen species (ROS). Furthermore, the impact of mitochondrial ROS on HNE-induced Akt phosphorylation with subsequent MMP-2 production was also demonstrated in mitochondrial function-deficient VSMC, as well as in cells transfected with manganese superoxide dismutase. Taken together, these results suggest that HNE enhances MMP-2 production in VSMC via mitochondrial ROS-mediated activation of the Akt/NF-kappaB signaling pathways.

PDK-1/AKT pathway as a novel therapeutic target in rhabdomyosarcoma cells using OSU-03012 compound

Rhabdomyosarcoma (RMS) is the most common paediatric soft-tissue sarcoma including two major subtypes, alveolar rhabdomyosarcoma (ARMS) and embryonal rhabdomyosarcoma (ERMS). Increasing evidence suggests that oncogenesis of RMS involves multistages of signalling protein dysregulation which may include prolonged activation of serine/threonine kinases such as phosphoinositide-dependant kinase-1 (PDK-1) and AKT. To date, whether PDK-1/AKT pathway is activated in RMS is unknown. This study was to examine phosphorylation status of AKT and to evaluate a novel small molecular inhibitor, OSU-03012 targeting PDK-1 in RMS. We examined phosphorylation levels of AKT using ARMS and ERMS tissue microarray and immunohistochemistry staining. Our results showed phospho-AKT^Thr308 level is elevated 42 and 35% in ARMS and ERMS, respectively. Phospho-AKT^Ser473 level is also increased 43% in ARMS and 55% in ERMS. Furthermore, we showed that OSU-03012 inhibits cell viability and induces apoptosis in ARMS and ERMS cell lines (RH30, SMS-CTR), which express elevated phospho-AKT levels. Normal cells are much less sensitive to OSU-03012 and in which no detectable apoptosis was observed. This study showed, for the first time, that PDK-1/AKT pathway is activated in RMS and may play an important role in survival of RMS. PDK-1/AKT pathway may be an attractive therapeutic target for cancer intervention in RMS using OSU-03012.

The δ-opioid receptor agonist DADLE at reperfusion protects the heart through activation of pro-survival kinases via EGF receptor transactivation

The specific δ-opioid receptor agonist [d-Ala2-d-Leu5]enkephalin (DADLE) protects against infarction in the heart when given before ischemia. In rabbit, this protection leads to phosphorylation of the pro-survival kinases Akt and extracellular signal-regulated kinase (ERK) and is dependent on transactivation of the epidermal growth factor receptor (EGFR). DADLE reportedly protects rat hearts at reperfusion. We therefore tested whether DADLE at reperfusion could protect isolated rabbit hearts subjected to 30 min of regional ischemia and 120 min of reperfusion and whether this protection is dependent on Akt, ERK, and EGFR. DADLE (40 nM) was infused for 1 h starting 5 min before reperfusion and reduced infarct size from 31.0 ± 2.3% in the control group to 14.6 ± 1.6% ( P = 0.01). This protection was abolished by cotreatment of the metalloproteinase inhibitor (MPI) and the EGFR inhibitor AG1478. In contrast, 20 nM DADLE, although known to be protective before ischemia, failed to protect. Western blotting revealed that DADLE's protection was correlated to increase in phosphorylation of the kinases Akt and ERK1 and -2 in reperfused hearts (2.5 ± 0.5, 1.6 ± 0.2, and 2.3 ± 0.7-fold of baseline levels, P < 0.05 vs. control). The DADLE-dependent increases in Akt and ERK1/2 phosphorylation were abolished by either MPI or AG1478, confirming a signaling through the EGFR pathway. Additionally, DADLE treatment increased phosphorylation of EGFR (1.4 ± 0.2-fold, P = 0.03 vs. control). Thus the δ-opioid agonist DADLE protects rabbit hearts at reperfusion through activation of the pro-survival kinases Akt and ERK and is dependent on the transactivation of the EGFR.

Nicotine inhibits apoptosis induced by cisplatin in human oral cancer cells

Oral cancer demonstrates a strong epidemiological association with smoking, but little is known about the effect of nicotine on oral cancer cell apoptosis. Nicotine, a major component of cigarette smoke, can regulate cell proliferation and angiogenesis and suppress apoptosis induced by chemotherapeutic drugs. The main aim of this study was to investigate the effects of nicotine on apoptosis induced by cisplatin, which is commonly used to treat advanced oral cancers, in the human oral cancer cell line Tca8113. The cells were stimulated with nicotine in the presence or absence of cisplatin, and apoptosis was assayed. The results showed that nicotine inhibited apoptosis induced by cisplatin. It was also observed that survivin played a role in the inhibitory effect of nicotine on apoptosis. Depletion of survivin reduced the protective effect of nicotine against cisplatin-induced apoptosis. Akt, a physiological survivin kinase, is activated by nicotine. Treatment of Tca8113 cells with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 blocked nicotine-induced survivin expression and enhanced cell apoptosis. These studies suggest that exposure to nicotine might negatively impact on the apoptotic potential of chemotherapeutic drugs, and that survivin plays a key role in the anti-apoptotic effect of nicotine. The Akt pathway may be required for nicotine function.

von Willebrand factor type D domain mutant of SVS-1/SUSD2, vWDm, induces apoptosis in HeLa cells

SVS-1/SUSD2 is a novel gene, which inhibits growth and reverses tumorigenic phenotypes of cancer cells in vitro. Here we report identification of a mutant of SVS-1, designated SVS-1-vWD(m), in which conserved amino acids GLLG at positions 591-594 in von Willebrand factor type D (vWD) domain are replaced by AAAA. As observed by laser confocal microscope, intracellular localization of the mutant protein has changed such that both the N-terminus and the C-terminus of SVS-1-vWD(m) were localized in the inner surface of the plasma membrane, whereas the N-terminus of SVS-1 was localized in the outer surface of the plasma membrane. Additionally, SVS-1-vWD(m) was processed much less efficiently and in a slightly different manner. In in vitro studies, adenovirus-mediated transduction of the SVS-1-vWD(m)gene induced growth suppression of HeLa cells in a dose-dependent manner, as the wild-type gene and inhibition of anchorage-independent growth. Of great interest is the finding that the mutant protein, vWD(m), but not the wild-type one induced apoptosis, as observed by nuclear as well as DNA fragmentation. Activation of caspase-3 and -9, but not caspase-8 or -12, was also demonstrated in vWD(m)-expressing cells. An inhibition of Akt phosphorylation, a major survival signaling component, also occurred in vWD(m)-expressing HeLa cells. Together these data suggest that vWD(m) induces apoptosis by inactivation of survival signaling component Akt and activation of caspase cascade (mitochondrial pathway) in HeLa cells. We propose SVS-1-vWD(m)as an alternative gene for use in developing new therapeutic strategies for the treatment of cancer.

Inhibition of mitogen-activated protein kinase and stimulation of Akt kinase signaling pathways: Two approaches with therapeutic potential in the treatment of neurodegenerative disease

The neurodegenerative diseases of adulthood, including Alzheimer's disease (AD) and Parkinson's disease (PD), pose an enormous and growing public health burden. Although effective symptomatic treatments exist for PD, and, to a lesser extent, for AD, there is no therapy for these disorders which will forestall their progression. With the rise of the concept of programmed cell death (PCD) came the realization that even in the absence of complete knowledge of proximate causes neuroprotection may nevertheless be possible by targeting the pathways of PCD. One set of signaling pathways that have been implicated in cell death are the mitogen-activated protein kinase (MAPK) pathways. The possibility of blocking these pathways and thereby providing neuroprotection has recently been put to the test in a clinical trial of a mixed lineage kinase inhibitor in the treatment of PD. Unfortunately, this trial failed to demonstrate a protective effect. Based on considerations related to the implementation of the trial, it would be premature to conclude that inhibition of MAPK signaling is a failed strategy. In spite of these negative results, the MAPK and related kinase pathways retain their importance as potential targets in PD. In relation to pathogenesis, the discovery of mutations in the mixed lineage kinase (MLK)-like kinase leucine-rich repeat kinase 2 (LRRK2) suggests a role for these kinases in regulating the viability of dopamine neurons. In relation to treatment, the survival signaling kinase Akt has been demonstrated in vivo to mediate striking neurotrophic and antiapoptotic effects. Thus, it is likely that therapeutic targets related to these kinase signaling pathways will emerge.

Genetic deletion of Trb3, the mammalian Drosophila tribbles homolog, displays normal hepatic insulin signaling and glucose homeostasis

Trb3, a mammalian homolog of Drosophila tribbles, was proposed as a suppressor of Akt activity, predominantly in conditions of fasting and diabetes. Given these prior studies, we sought to determine whether Trb3 plays a major role in modulating hepatic insulin sensitivity. To answer this question, we produced mice in which a lacZ reporter was knocked into the locus containing the gene Trib3, resulting in a Trib3 null animal. Trib3 expression analyses demonstrated that the Trib3 is expressed in liver, adipose tissues, heart, kidney, lung, skin, small intestine, stomach, and denervated, but not normal, skeletal muscle. Trib3(-/-) mice are essentially identical to their wild-type littermates in overall appearance and body composition. Phenotypic analysis of Trib3(-/-) mice did not detect any alteration in serum glucose, insulin, or lipid levels; glucose or insulin tolerance; or energy metabolism. Studies in Trib3(-/-) hepatocytes revealed normal Akt and glycogen synthase kinase- 3beta phosphorylation patterns, glycogen levels, and expressions of key regulatory gluconeogenic and glycolytic genes. These data demonstrate that deletion of Trib3 has minimal effect on insulin-induced Akt activation in hepatic tissue, and, as such, they question any nonredundant role for Trb3 in the maintenance of glucose and energy homeostasis in mice.

Involvement of P2X4 and P2Y12 receptors in ATP-induced microglial chemotaxis

We previously reported that extracellular ATP induces membrane ruffling and chemotaxis of microglia and suggested that their induction is mediated by the Gi/o-protein coupled P2Y(12) receptor (P2Y(12)R). Here we report discovering that the P2X(4) receptor (P2X(4)R) is also involved in ATP-induced microglial chemotaxis. To understand the intracellular signaling pathway downstream of P2Y(12)R that underlies microglial chemotaxis, we examined the effect of two phosphatidylinositol 3'-kinase (PI3K) inhibitors, wortmannin, and LY294002, on chemotaxis in a Dunn chemotaxis chamber. The PI3K inhibitors significantly suppressed chemotaxis without affecting ATP-induced membrane ruffling. ATP stimulation increased Akt phosphorylation in the microglia, and the increase was reduced by the PI3K inhibitors and a P2Y(12)R antagonist. These results indicate that P2Y(12)R-mediated activation of the PI3K pathway is required for microglial chemotaxis in response to ATP. We also found that the Akt phosphorylation was reduced when extracellular calcium was chelated, suggesting that ionotropic P2X receptors are involved in microglial chemotaxis by affecting the PI3K pathway. We therefore tested the effect of various P2X(4)R antagonists on the chemotaxis, and the results showed that pharmacological blockade of P2X(4)R significantly inhibited it. Knockdown of the P2X(4) receptor in microglia by RNA interference through the lentivirus vector system also suppressed the microglial chemotaxis. These results indicate that P2X(4)R as well as P2Y(12)R is involved in ATP-induced microglial chemotaxis.

Neuroprotective effects of steroid analogues on P19-N neurons

Naturally occurring neurosteroids are potent allosteric modulators of gamma-aminobutyric acid(A) receptor and through augmentation of gamma-aminobutyric acid(A) receptor function, can protect neuronal cells against N-methyl-d-aspartate receptor over-activation, ischemia and traumatic brain injury. In this study, mouse P19 cells were induced to differentiate into post-mitotic neurons and were subjected to excitotoxicity in the presence of N-methyl-d-aspartate. Novel synthetic analogues of the endogenous neurosteroids allopregnanolone and dehydroepiandrostrone, inhibited excitotoxic cell death of P19-N neurons, by directly maintaining the activation of PKB/Akt kinase and interfering with the intrinsic mitochondrial apoptotic pathway, preserving cytochrome c in the mitochondria and Bax in the cytoplasm. The efficiency and the potency of these neurosteroids were similar to those of allopregnanolone and dehydroepiandrostrone. Their effects were gamma-aminobutyric acid(A) receptor mediated, since they were abolished in the presence of bicuculline, an antagonist of receptor's function. In addition, the synthetic compounds retained the ability to alter gamma-aminobutyric acid(A) receptor subunit gene expression, but their effects on transcriptional activity were less pronounced than those of allopregnanolone and dehydroepiandrostrone. These results suggest that synthetic neurosteroids may serve as potent, membrane acting, neuroprotectants against N-methyl-d-aspartate receptor neurotoxicity on neuronal cells.

Curcumin induces G2/M arrest and apoptosis in cisplatin-resistant human ovarian cancer cells by modulating Akt and p38 MAPK

Curcumin, a major active component of turmeric, is known to induce apoptosis in several types of cancer cells, but little is known about its activity in chemoresistant cells. Hence, the aim of the present study was to investigate the anticancer properties of curcumin in cisplatin-resistant human ovarian cancer cells in vitro. The results indicated that curcumin inhibited the proliferation of both cisplatin-resistant (CR) and sensitive (CS) human ovarian cancer cells almost equally. Enhanced superoxide generation was observed in both CR and CS cells treated with curcumin. Curcumin induced G(2)/M phase cell-cycle arrest in CR cells by enhancing the p53 phosphorylation and apoptosis through the activation of caspase-3 followed by PARP degradation. Curcumin also inhibited the phosphorylation of Akt while the phosphorylation of p38 MAPK was enhanced. In summary, our results showed that curcumin inhibits the proliferation of cisplatin-resistant ovarian cancer cells through the induction of superoxide generation, G(2)/M arrest, and apoptosis.

Kainic acid induces early and transient autophagic stress in mouse hippocampus

Kainic acid (KA) treatment is a well-established model of hippocampal neuron death mediated in large part by KA receptor-induced excitotoxicity. KA-induced, delayed neuron death has been shown previously to follow the induction of seizures and exhibit characteristics of both apoptosis and necrosis. Growing evidence supports a role of autophagic stress-induced death of neurons in several in vitro and in vivo models of neuron death and neurodegeneration. However, whether autophagic stress also plays a role in KA-induced excitotoxicity has not been previously investigated. To examine whether KA alters the levels of proteins associated with or known to regulate the formation of autophagic vacuoles, we isolated hippocampal extracts from control mice and in mice following 2-16 h KA injection. KA induced a significant increase in the amount of LC3-II, a specific marker of autophagic vacuoles, at 4-6h following KA, which indicates a transient induction of autophagic stress. Levels of autophagy-associated proteins including ATG5 (conjugated to ATG12), ATG6 and ATG7 did not change significantly after treatment with KA. However, ratios of phospho-mTOR/mTOR were elevated from 6 to 16 h, and ratios of phospho-Akt/Akt were elevated at 16 h following KA treatment, suggesting a potential negative feedback loop to inhibit further stimulation of autophagic stress. Together these data indicate the transient induction of autophagic stress by KA which may serve to regulate excitotoxic death in mouse hippocampus.

Semaxinib (SU5416) as a therapeutic agent targeting oncogenic Kit mutants resistant to imatinib mesylate

Activating mutations in the Kit receptor are frequently observed in various malignancies, pointing Kit as a molecule of interest for drug inhibition. When mutated on Asp 816 (corresponding to Asp 814 in the mouse), as preferentially found in human mastocytosis and acute myeloid leukemia, Kit became non-sensitive to imatinib mesylate (Gleevec). Erythroleukemic cells isolated from Spi-1/PU.1 transgenic mice express Kit mutated at codon 814 (Kit(D814Y) or Kit(D814V)) or codon 818 (Kit(D818Y)). Using these cells in vitro, we demonstrate that the tyrosine kinase inhibitor SU5416 (Semaxinib) induces growth arrest and apoptosis independent of the mutation type by inhibiting the functions of Kit, including Kit autophosphorylation and activation of Akt, Erk1/Erk2 and Stat3 downstream signaling pathways. These findings indicate that SU5416 may be a promising tool to kill cancer cells driven by Kit oncogenic mutations that are resistant to treatment with imatinib mesylate.

Blocking of Akt/NF-kappaB signaling by pentoxifylline inhibits platelet-derived growth factor-stimulated proliferation in Brown Norway rat airway smooth muscle cells

The proliferation of airway smooth muscle cells (ASMC) can cause airway hyperresponsiveness (AHR). It has been reported that platelet-derived growth factor (PDGF) can stimulate the proliferation of ASMC through phosphatidylinositol 3-kinase (PI3 K) signaling pathway, which can activate Akt protein. Activated-Akt can activate downstream signal protein [p70S6 K, nuclear factor (NF)-kappaB, and extracellular signal regulated kinase (ERK)], increasing the cyclin D1 level and suppressing the transcription of p27Kip1 to enable cell cycle entry. This investigation demonstrated that pentoxifylline (PTX) inhibited the PDGF-stimulated proliferation of ASMC by suppressing activation of the Akt/NF-kappaB pathway. ASMC were treated with PTX for 48 h, which attenuated the PDGF-stimulated proliferation of ASMC. PTX and wortmannin, a PI3 K inhibitor, not only inhibited the PDGF-activated phosphorylation of Akt but also suppressed p70S6 K expression and IkappaBalpha degradation, inhibiting nuclear translocation and the DNA binding activity of NF-kappaB. However, PTX did not influence the phosphorylation of ERK1/2. The suppression of p70S6 K by rapamycin did not influence cyclin D1 expression in PDGF-stimulated cells. These data reveal that the down-regulation of the Akt/NF-kappaB signaling pathway by PTX inhibited the proliferation of ASMC. PTX may provide information on the pathogenesis of asthma.

Estrogen receptor protein interaction with phosphatidylinositol 3-kinase leads to activation of phosphorylated Akt and extracellular signal-regulated kinase 1/2 in the same population of cortical neurons: a unified mechanism of estrogen action

17Beta-estradiol (E2)-induced neuroprotection is dependent on mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K) signaling cascades. We sought to determine whether E2 neuroprotective mechanisms are mediated by a unified signaling cascade activated by estrogen receptor (ER)-PI3K interaction within the same population of neurons or whether E2 activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt are independent signaling events in different neuronal populations. Immunoprecipitation of E2-treated cortical neurons was conducted to determine a protein-protein interaction between ER and the PI3K regulatory subunit p85. Subsequently, cortical neurons were treated with E2 alone or in presence of MAPK inhibitors or PI3K inhibitors. Results of these analyses indicated a protein-protein interaction between ER and p85 that was time-dependent and consistent with the temporal profile for generation of Akt (pAkt) and ERK1/2 phosphorylation (pERK1/2). E2-induced phosphorylation of Akt, was first apparent at 10 min and maximal at 30 min. Simultaneously, E2-induced pERK1/2 was first apparent at 5-10 min and maximal at 30 min. Inhibition of PI3K completely blocked E2 activation of pAkt at 10 and 30 min and blocked E2 activation of ERK1/2 at 10 min, which revealed a PI3K-independent activation of ERK at 30 min. Double immunocytochemical labeling for pERK1/2 and pAkt demonstrated that E2 induced both signaling pathways in the same neurons. These results indicate a unified signaling mechanism for rapid E2 action that leads to the coordinated activation of both pERK1/2 and pAkt in the same population of neurons. Implications of these results for understanding estrogen mechanism of action in neurons and therapeutic development are considered.

Differential response of Akt to cyclic AMP modulates drug sensitivity

Although Akt is known to be associated with drug resistance, its role in cyclic AMP (cAMP)-related inhibition of cell proliferation is not clear. Here, we report that Akt modulates the sensitivity of hepatocellular carcinoma cells to cAMP. Treatment of hepatocellular carcinoma cell lines (HepG(2) and Bel-7402) with cAMP inhibited proliferation, with HepG(2) cells showing lower sensitivity to cAMP. Biochemical studies showed that cAMP increased FBS-stimulated Akt phosphorylation in HepG(2) cells, but completely inhibited FBS-stimulated Akt phosphorylation in Bel-7402 cells, suggesting that the differential response of Akt to cAMP in these two cell lines might contribute to their differential sensitivity. LY294002, a phosphatidylinositol 3-kinase inhibitor that inhibits FBS-stimulated Akt phosphorylation, restored the sensitivity of HepG(2) cells to cAMP and API-2 (Akt/protein kinase B signaling inhibitor-2) also showed similar effect. These results collectively indicate that the response level of Akt to cAMP may play a critical role in determining drug sensitivity.

Cyclic AMP synergistically enhances neuregulin-dependent ERK and Akt activation and cell cycle progression in Schwann cells

The elevation of intracellular cAMP synergistically enhances the neuregulin-dependent proliferation of cultured Schwann cells (SCs); however, the mechanism by which this occurs has not been completely defined. To better understand this mechanism, we investigated the effect of cAMP on the activation of the extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3-K)-Akt (PKB) pathways by heregulin, a member of the neuregulin family. Using primary cultures of adult SCs, we demonstrated that the adenylyl cyclase activator, forskolin, enhanced heregulin-dependent SC proliferation by reducing the time required for S-phase entry. When cAMP levels were increased, using either forskolin or a cell permeable analogue of cAMP, the heregulin-induced phosphorylation of ERK was converted from transient to sustained and the heregulin-induced phosphorylation of Akt was synergistically increased. Consistent with these observations, studies in which inhibitors of MEK, the upstream stimulating ERK kinase, and PI3-K were administered at different times following the onset of stimulation indicated that sustained high levels of both MEK/ERK and PI3-K/Akt activity before S-phase initiation were essential for S-phase entry. Overall, these novel results indicate that in neuregulin-stimulated SCs the activation of cAMP-mediated pathways accelerates G1-S progression by prolonging ERK activation and concurrently enhancing Akt activation.

Kallikrein protects against ischemic stroke by inhibiting apoptosis and inflammation and promoting angiogenesis and neurogenesis

Stroke-induced neurological deficits and mortality are often associated with timing of treatment after the onset of stroke. We showed that local delivery of the human tissue kallikrein gene into rat brain immediately after middle cerebral artery occlusion (MCAO) exerts neuroprotection. In this study, we investigated the effect of systemic delivery of the kallikrein gene 8 hr after MCAO. Expression of recombinant human tissue kallikrein after gene transfer was identified in the ischemic brain region and blood vessels. Intravenous injection of adenovirus encoding the kallikrein gene significantly reduced neurological deficit scores 2 and 7 days after gene transfer. Kallikrein gene transfer also reduced ischemia-reperfusion (I/R)-induced cerebral infarction and promoted the survival and migration of glial cells from penumbra to the ischemic core from 3 to 14 days after gene delivery. Kallikrein reduced I/R-induced apoptosis of neuronal cells and inhibited inflammatory cell accumulation in the ischemic brain. These effects were blocked by the kinin B2 receptor antagonist icatibant. In addition, kallikrein enhanced angiogenesis and promoted neurogenesis after I/R and the stimulatory effect of kinin on neuronal cell proliferation was confirmed in primary cultured neuronal cells. The protective effects of kallikrein, through the kinin B2 receptor, were accompanied by increased cerebral nitric oxide and Bcl-2 levels, Akt phosphorylation, and reduced NAD(P)H oxidase activity, superoxide production, Bax levels, and caspase-3 activity. These results indicate that delayed systemic administration of the kallikrein gene after onset of stroke protects against ischemic brain injury by inhibiting apoptosis and inflammation and by promoting angiogenesis and neurogenesis.

Novel human monoclonal antibodies to insulin-like growth factor (IGF)-II that potently inhibit the IGF receptor type I signal transduction function

The insulin-like growth factor (IGF) system plays an important role in a variety of physiologic processes and in diseases such as cancer. Although the role of the IGF system in cancer has been recognized many years ago, components of the system have only recently been targeted and shown to affect cell transformation, proliferation, survival, motility, and migration in tissue cultures and in mouse models of cancer. We have been hypothesizing that targeting IGF-II in addition to blocking its interaction with the IGF receptor type I (IGF-IR) would also allow to block that portion of the signal transduction through the insulin receptor that is due to its interaction with IGF-II. Lowering its level may also not induce up-regulation of its production as for IGF-I. Finally, targeting a diffusable ligand as IGF-II may not require penetration of the antibody inside tumors but could shift the equilibrium to IGF-II complexed with antibody so the ligand concentration would decrease in the tumor environment without the need for the antibody to penetrate the tumor. Here, we describe the identification and characterization of three novel anti-IGF-II fully human monoclonal antibodies. They bound with high (subnanomolar) affinity to IGF-II, did not cross-react with IGF-I and insulin, and potently inhibited signal transduction mediated by the IGF-IR interaction with IGF-II. The most potent neutralizer, IgG1 m610, inhibited phosphorylation of the IGF-IR and the insulin receptor, as well as phosphorylation of the downstream kinases Akt and mitogen-activated protein kinase with an IC(50) of the order of 1 nmol/L at IGF-II concentration of 10 nmol/L. It also inhibited growth of the prostate cancer cell line DU145 and migration of the breast cancer line cells MCF-7. These results indicate an immunotherapeutic potential of IgG1 m610 likely in combination with other antibodies and anticancer drugs but only further experiments in mouse models of cancer and human clinical trials could evaluate this possibility.

Molecular targets of the chemopreventive agent 1,4-phenylenebis (methylene)-selenocyanate in human non-small cell lung cancer

Clinical chemoprevention trials of lung cancer have been somewhat disappointing and the development of highly effective chemopreventive agents is urgently needed. We previously showed that the organoselenium 1,4-phenylenebis(methylene)selenocyanate (p-XSC) is a potent chemopreventive agent in numerous preclinical animal models including a lung tumor model that employs carcinogens found in tobacco smoke. The goal of this study is to define molecular targets that will be highly promising in the design of future chemoprevention trials of non-small cell lung cancer (NSCLC), which is by far the most common type of lung cancer cases. In the present investigation, we showed that p-XSC at several doses (2.5, 5, 10 and 20 microM) including physiological levels (2.5-5.0 microM) of selenium is capable of inhibiting cell growth in a dose-dependent manner and inducing apoptosis in three NSCLC cells (NCI-H460, NCI-1299 and A549). To clarify the mechanism involved at the molecular level, we focused only on NCI-460 cells and examined the effects of p-XSC on markers that are known to be critical in the development of NSCLC. Using western blot analysis, we showed that p-XSC reduced the expression of cyclooxygenase-2 (COX-2) and phospholipase A2 (PLA2); although p-XSC inhibited both Akt and p-Akt but its effect was not significant. Using cDNA microarray approach (3800 genes per array) we found that p-XSC upregulates 22 genes by > or = 2-fold while downregulates 13 genes by < or = 0.5-fold; these altered genes include transcriptional factors, growth factors and those involved in xenobiotic metabolism as well as pro- and anti-apoptotic genes. Expression of selected genes was confirmed by RT-PCR; p-XSC reduced the levels of COX-2, PLA2, NF-kappaB and Cyclin D1 but enhanced the levels of glutathione peroxidase-5. Collectively, the results of this study showed that p-XSC alters several molecular markers in a manner that can account for its inhibitory effect of cell growth and induction of apoptosis; therefore, p-XSC may be considered a promising candidate for clinical chemoprevention of NSCLC.

Modulation of amino acid uptake by TGF-β in lung myofibroblasts

Hormones such as insulin, growth factors, and cell stress stimulate system A amino acid transporter. Transforming growth factor-beta (TGF-beta) stimulates amino acid uptake thereby inducing cell proliferation, cellular hypertrophy, and matrix synthesis. Insulin appears to activate amino acid in smooth muscle cells via a phosphatidylinositol 3-kinase (PI3-kinase)-dependent pathway. We examine the effect and interaction of TGF-beta, insulin, and PI3-kinase activity on amino acid uptake in human lung myofibroblasts. TGF-beta treatment induced large increases in system A activity and a small delayed increase in the phosphorylation of protein kinase B, also termed phospho-Akt. In contrast, insulin induced small increases in system A activity and large increases in phospho-Akt levels. LY294002, a PI3-kinase inhibitor, blocked the TGF-beta-induced amino acid uptake only partially, but completely blocked TGF-beta-induced Akt phosphorylation. Moreover, the level of phospho-Smad3 was found to be high even when LY294002 blocked TGF-beta-induced phospho-Akt levels. Inhibition of PI3-kinase activity resulted in increase in Km, consistent with a major change in transporter activity without change in transporter number. The PI3-kinase inhibitor also did not change the amino acid transporter 2 (ATA2) mRNA levels. Taken together, these results suggest that TGF-beta induced Smad-3 and amino acid uptake through a PI3-kinase independent pathway.

Serotonin-induced growth of pulmonary artery smooth muscle requires activation of phosphatidylinositol 3-kinase/serine-threonine protein kinase B/mammalian target of rapamycin/p70 ribosomal S6 kinase 1

We have previously found that both mitogen-activated protein kinase (MAPK)- and Rho kinase (ROCK)-related signaling pathways are necessary for the induction of pulmonary artery smooth muscle cell (SMC) proliferation by serotonin (5-hydroxytryptamine [5-HT]). In the present study, we investigated the possible additional participation of a phosphatidylinositol 3-kinase (PI3K)/serine-threonine protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (S6K1) pathway in this growth response. We found transient activation of Akt (Ser473) and more prolonged activation of S6K1 by 5-HT. Inhibition of PI3K with Wortmannin and LY294002 completely blocked these activations, but not that of MAPK or the ROCK substrate myosin phosphatase targeting subunit. Similarly, inhibition of MAPK and ROCK failed to block the Akt activation. Inhibition of Akt with NL-71-101 and downregulation of Akt expression with Akt small interfering RNA blocked 5-HT-induced S6K1 phosphorylation. Wortmannin, LY294002, and NL-71-101 dose-dependently inhibited 5-HT-induced SMC proliferation. 5-HT stimulated mTOR phosphorylation and the mTOR inhibitor, rapamycin, blocked activations of S6K1 and S6 ribosomal protein, and inhibited 5-HT-induced SMC proliferation. Akt phosphorylation and cell proliferation were also blocked by the antioxidants, N-acetyl-l-cysteine, Ginko biloba 501, and tiron, the reduced nicotinamide adenine dinucleotide phosphate oxidase inhibitor, diphenyleneiodonium, and the 5-HT2 receptor antagonists ketanserin and mianserin, but not by the 5-HT serotonin transporter or 5-HT 1B/1D receptor antagonists. We conclude from these studies that a parallel PI3K- and reactive oxygen species-dependent Akt/mTOR/S6K1 pathway participates independently from MAPK and Rho/ROCK in the mitogenic effect of 5-HT on pulmonary artery SMCs. From these and other studies, we postulate that independent signaling pathways leading to 5-HT-induced SMC proliferation are initiated through multiple 5-HT receptors and serotonin transporter at the cell surface.

Synergistic antileukemic interactions between 2-medroxyestradiol (2-ME) and histone deacetylase inhibitors involve Akt down-regulation and oxidative stress

Interactions between the endogenous estradiol metabolite 2-medroxyestradiol (2-ME) and histone deacetylase inhibitors (HDACIs) have been investigated in human leukemia cells. Coadministration of subtoxic or marginally toxic concentrations of 2-ME and SAHA or sodium butyrate in diverse human leukemia-cell types resulted in a marked increase in oxidative damage (eg, generation of reactive oxygen species [ROSs]), mitochondrial injury (eg, cytochrome c release and Bax translocation), caspase activation, and apoptosis. These interactions were also noted in primary human leukemia cells but not in normal bone marrow CD34+ cells. Synergistic interactions between these agents were associated with inactivation of Akt and activation of c-Jun N-terminal kinase (JNK). Essentially all of these events were reversed by free radical scavengers such as the manganese superoxide dismutase (MnSOD) mimetic TBAP and catalase. Notably, treatment with 2-ME/HDACIs resulted in down-regulation of thioredoxin, MnSOD, and glutathione peroxidase. Enforced activation of Akt blocked 2-ME/HDACI-mediated mitochondrial injury, caspase activation, and JNK up-regulation, but not generation of ROSs. Pharmacologic or genetic (siRNA) interruption of the JNK pathway also significantly attenuated the lethality of this regimen. Together, these findings support a model in which antileukemic synergism between 2-ME and HDACIs stems primarily from induction of oxidative damage, leading in turn to Akt inactivation and JNK activation, culminating in mitochondrial injury and apoptosis. They also raise the possibility that these events may preferentially occur in leukemic versus normal hematopoietic cells.