Akt1 signaling regulates integrin activation, matrix recognition, and fibronectin assembly

Triciribine attenuates pathological neovascularization and vascular permeability in a mouse model of proliferative retinopathy

Proliferative retinopathies are the leading cause of irreversible blindness in all ages, and there is a critical need to identify novel therapies. We investigated the impact of triciribine (TCBN), a tricyclic nucleoside analog and a weak Akt inhibitor, on retinal neurovascular injury, vascular permeability, and inflammation in oxygen-induced retinopathy (OIR). Post-natal day 7 (P7) mouse pups were subjected to OIR, and treated (i.p.) with TCBN or vehicle from P14-P16 and compared with age-matched, normoxic, vehicle or TCBN-treated controls. P17 retinas were processed for flat mounts, immunostaining, Western blotting, and qRT-PCR studies. Fluorescein angiography, electroretinography, and spectral domain optical coherence tomography were performed on days P21, P26, and P30, respectively. TCBN treatment significantly reduced pathological neovascularization, vaso-obliteration, and inflammation marked by reduced TNFα, IL6, MCP-1, Iba1, and F4/80 (macrophage/microglia markers) expression compared to the vehicle-treated OIR mouse retinas. Pathological expression of VEGF (vascular endothelial growth factor), and claudin-5 compromised the blood-retinal barrier integrity in the OIR retinas correlating with increased vascular permeability and neovascular tuft formation, which were blunted by TCBN treatment. Of note, there were no changes in the retinal architecture or retinal cell function in response to TCBN in the normoxia or OIR mice. We conclude that TCBN protects against pathological neovascularization, restores blood-retinal barrier homeostasis, and reduces retinal inflammation without adversely affecting the retinal structure and neuronal function in a mouse model of OIR. Our data suggest that TCBN may provide a novel therapeutic option for proliferative retinopathy.

The human ion channel TRPM2 modulates migration and invasion in neuroblastoma through regulation of integrin expression

Transient receptor potential channel TRPM2 is highly expressed in many cancers and involved in regulation of key physiological processes including mitochondrial function, bioenergetics, and oxidative stress. In Stage 4 non-MYCN amplified neuroblastoma patients, high TRPM2 expression is associated with worse outcome. Here, neuroblastoma cells with high TRPM2 expression demonstrated increased migration and invasion capability. RNA sequencing, RT-qPCR, and Western blotting demonstrated that the mechanism involved significantly greater expression of integrins α1, αv, β1, and β5 in cells with high TRPM2 expression. Transcription factors HIF-1α, E2F1, and FOXM1, which bind promoter/enhancer regions of these integrins, were increased in cells with high TRPM2 expression. Subcellular fractionation confirmed high levels of α1, αv, and β1 membrane localization and co-immunoprecipitation confirmed the presence of α1β1, αvβ1, and αvβ5 complexes. Inhibitors of α1β1, αvβ1, and αvβ5 complexes significantly reduced migration and invasion in cells highly expressing TRPM2, confirming their functional role. Increased pAkt^Ser473 and pERK^{Thr202/Tyr204}, which promote migration through mechanisms including integrin activation, were found in cells highly expressing TRPM2. TRPM2 promotes migration and invasion in neuroblastoma cells with high TRPM2 expression through modulation of integrins together with enhancing cell survival, negatively affecting patient outcome and providing rationale for TRPM2 inhibition in anti-neoplastic therapy.

Palmitic acid inhibits prostate cancer cell proliferation and metastasis by suppressing the PI3K/Akt pathway

AIMS

Prostate cancer is one of the most frequent causes of cancer death in men worldwide, and novel drugs for prostate cancer therapies are still being developed. Palmitic acid is a common saturated long-chain fatty acid that is known to exhibit anti-inflammatory and metabolic regulatory effects and antitumor activities in several types of tumors. The present study aims to explore the antiproliferative and antimetastatic activities of palmitic acid on human prostate cancer cells and the underlying mechanism.

MAIN METHODS

MTT and colony formation assays were utilized to determine the antiproliferative effect of palmitic acid. Cell metastasis was evaluated by wound healing, Transwell migration and invasion assay. The in vivo anticancer effect was assessed by a nude mouse xenograft model of prostate cancer. The involved molecular mechanisms were investigated by flow cytometry and Western blot analysis.

KEY FINDINGS

Palmitic acid significantly suppressed prostate cancer cell growth in vitro and in vivo. Treatment with palmitic acid induced G1 phase arrest, which was associated with downregulation of cyclin D1 and p-Rb and upregulation of p27. In addition, palmitic acid could inhibit prostate cancer cell metastasis, in which suppression of PKCζ and p-Integrinβ1 and an increase in E-cadherin expression might be involved. Furthermore, a mechanistic study indicated that palmitic acid inhibited the key molecules of the PI3K/Akt pathway to block prostate cancer proliferation and metastasis.

SIGNIFICANCE

Our findings suggested the antitumor potential of palmitic acid for prostate cancer by targeting the PI3K/Akt pathway.

Akt-independent effects of triciribine on ACE2 expression in human lung epithelial cells: Potential benefits in restricting SARS-CoV2 infection

The severe acute respiratory syndrome coronavirus 2 that causes coronavirus disease 2019 (COVID-19) binds to the angiotensin-converting enzyme 2 (ACE2) to gain cellular entry. Akt inhibitor triciribine (TCBN) has demonstrated promising results in promoting recovery from advanced-stage acute lung injury in preclinical studies. In the current study, we tested the direct effect of TCBN on ACE2 expression in human bronchial (H441) and lung alveolar (A549) epithelial cells. Treatment with TCBN resulted in the downregulation of both messenger RNA and protein levels of ACE2 in A549 cells. Since HMGB1 plays a vital role in the inflammatory response in COVID-19, and because hyperglycemia has been linked to increased COVID-19 infections, we determined if HMGB1 and hyperglycemia have any effect on ACE2 expression in lung epithelial cells and whether TCBN has any effect on reversing HMGB1- and hyperglycemia-induced ACE2 expression. We observed increased ACE2 expression with both HMGB1 and hyperglycemia treatment in A549 as well as H441 cells, which were blunted by TCBN treatment. Our findings from this study, combined with our previous reports on the potential benefits of TCBN in the treatment of acute lung injury, generate reasonable optimism on the potential utility of TCBN in the therapeutic management of patients with COVID-19.

Ubiquitous expression of Akt1 p.(E17K) results in vascular defects and embryonic lethality in mice

Proteus syndrome is a progressive overgrowth disorder with vascular malformations caused by mosaic expression of the AKT1 c.49G > A, p.(E17K) activating variant which was predicted to cause lethality if expressed ubiquitously. To test that hypothesis, we used the ACTB-Cre gene to activate a conditional Akt1 p.(E17K) allele in the mouse. No offspring that was heterozygous for both Cre and the conditional allele (βA-Akt1WT/flx) was viable. Fewer than expected numbers of βA-Akt1WT/flx embryos were seen beginning at E11.5, but a few survived until E17.5. The phenotype ranged from mild to severe, but generally βA-Akt1WT/flx embryos had fewer visible blood vessels and more hemorrhages than their wild-type littermates, which was suggestive of a vascular abnormality. Examination of E13.5 limb skin showed a primitive capillary network with increased branching complexity and abnormal patterning compared with wild-type skin. By E15.5, wild-type skin had undergone angiogenesis and formed a hierarchical network of remodeled vessels, whereas in βA-Akt1WT/flx embryos, the capillary network failed to remodel. Mural cell coverage of the blood vessels was also reduced in βA-Akt1WT/flx skin compared with that of wild type. Restricting expression of Akt1E17K to endothelial, cardiac or smooth muscle cells resulted in viable offspring and remodeled vasculature and did not recapitulate the βA-Akt1WT/flx phenotype. We conclude that ubiquitous expression of Akt1E17K suppresses remodeling and inhibits the formation of a normal skin vasculature. We postulate that this failure prevents proper circulation necessary to support the growing embryo and that it is the result of interactions of multiple cell types with increased AKT signaling.

Netrin-4 expression by human endothelial cells inhibits endothelial inflammation and senescence

Netrin-4, recognized in neural and vascular development, is highly expressed by mature endothelial cells. The function of this netrin-4 in vascular biology after development has remained unclear. We found that the expression of netrin-4 is highly regulated in endothelial cells and is important for quiescent healthy endothelium. Netrin-4 expression is upregulated in endothelial cells cultured under laminar flow conditions, while endothelial cells stimulated with tumor necrosis factor alpha resulted in decreased netrin-4 expression. Targeted reduction of netrin-4 in endothelial cells resulted in increased expression of vascular cell adhesion molecule 1 and intercellular adhesion molecule 1. Besides, these endothelial cells were more prone to monocyte adhesion and showed impaired barrier function, measured with electric cell-substrate impedance sensing, as well as in an 'organ-on-a-chip' microfluidic system. Importantly, endothelial cells with reduced levels of netrin-4 showed increased expression of the senescence-associated markers cyclin-dependent kinase inhibitor-1 and -2A, an increased cell size and decreased ability to proliferate. Consistent with the gene expression profile, netrin-4 reduction was accompanied with more senescent associated β-galactosidase activity, which could be rescued by adding netrin-4 protein. Finally, using human decellularized kidney extracellular matrix scaffolds, we found that pre-treatment of the scaffolds with netrin-4 increased numbers of endothelial cells adhering to the matrix, showing a pro-survival effect of netrin-4. Taken together, netrin-4 acts as an anti-senescence and anti-inflammation factor in endothelial cell function and our results provide insights as to maintain endothelial homeostasis and supporting vascular health.

Use of Simvastatin, Fibrin Clots, and Their Combination to Improve Human Ovarian Tissue Grafting for Fertility Restoration After Anti-Cancer Therapy

Anticancer treatments, particularly chemotherapy, induce ovarian damage and loss of ovarian follicles. There are limited options for fertility restoration, one of which is pre-chemotherapy cryopreservation of ovarian tissue. Transplantation of frozen-thawed human ovarian tissue from cancer survivors has resulted in live-births. There is extensive follicular loss immediately after grafting, probably due to too slow graft revascularization. To avoid this problem, it is important to develop methods to improve ovarian tissue neovascularization. The study's purpose was to investigate if treatment of murine hosts with simvastatin or/and embedding human ovarian tissue within fibrin clots can improve human ovarian tissue grafting (simvastatin and fibrin clots promote vascularization). There was a significantly higher number of follicles in group A (ungrafted control) than in group B (untreated tissue). Group C (simvastatin-treated hosts) had the highest levels of follicle atresia. Group C had significantly more proliferating follicles (Ki67-stained) than groups B and E (simvastatin-treated hosts and tissue embedded within fibrin clots), group D (tissue embedded within fibrin clots) had significantly more proliferating follicles (Ki67-stained) than group B. On immunofluorescence study, only groups D and E showed vascular structures that expressed both human and murine markers (mouse-specific platelet endothelial cell adhesion molecule, PECAM, and human-specific von Willebrand factor, vWF). Peripheral human vWF expression was significantly higher in group E than group B. Diffuse human vWF expression was significantly higher in groups A and E than groups B and C. When grafts were not embedded in fibrin, there was a significant loss of human vWF expression compared to groups A and E. This protocol may be tested to improve ovarian implantation in cancer survivors.

Distinct P2Y Receptors Mediate Extension and Retraction of Microglial Processes in Epileptic and Peritumoral Human Tissue

Microglia exhibit multiple, phenotype-dependent motility patterns often triggered by purinergic stimuli. However, little data exist on motility of human microglia in pathological situations. Here we examine motility of microglia stained with a fluorescent lectin in tissue slices from female and male epileptic patients diagnosed with mesial temporal lobe epilepsy or cortical glioma (peritumoral cortex). Microglial shape varied from ramified to amoeboid cells predominantly in regions of high neuronal loss or closer to a tumor. Live imaging revealed unstimulated or purine-induced microglial motilities, including surveillance movements, membrane ruffling, and process extension or retraction. At different concentrations, ADP triggered opposing motilities. Low doses triggered process extension. It was suppressed by P2Y12 receptor antagonists, which also reduced process length and surveillance movements. Higher purine doses caused process retraction and membrane ruffling, which were blocked by joint application of P2Y1 and P2Y13 receptor antagonists. Purinergic effects on motility were similar for all microglia tested. Both amoeboid and ramified cells from mesial temporal lobe epilepsy or peritumoral cortex tissue expressed P2Y12 receptors. A minority of microglia expressed the adenosine A2A receptor, which has been linked with process withdrawal of rodent cells. Laser-mediated tissue damage let us test the functional significance of these effects. Moderate damage induced microglial process extension, which was blocked by P2Y12 receptor antagonists. Overall, the purine-induced motility of human microglia in epileptic tissue is similar to that of rodent microglia in that the P2Y12 receptor initiates process extension. It differs in that retraction is triggered by joint activation of P2Y1/P2Y13 receptors.SIGNIFICANCE STATEMENT Microglial cells are brain-resident immune cells with multiple functions in healthy or diseased brains. These diverse functions are associated with distinct phenotypes, including different microglial shapes. In the rodent, purinergic signaling is associated with changes in cell shape, such as process extension toward tissue damage. However, there are little data on living human microglia, especially in diseased states. We developed a reliable technique to stain microglia from epileptic and glioma patients to examine responses to purines. Low-intensity purinergic stimuli induced process extension, as in rodents. In contrast, high-intensity stimuli triggered a process withdrawal mediated by both P2Y1 and P2Y13 receptors. P2Y1/P2Y13 receptor activation has not previously been linked to microglial morphological changes.

Hyaluronic Acid Binding to TLR4 Promotes Proliferation and Blocks Apoptosis in Colon Cancer

Hyaluronic acid (HA), a constituent of the extracellular matrix, promotes colorectal cancer growth. CD44 is a relevant HA receptor in this context. However, HA is also a ligand for TLR4, a receptor of significance in colorectal cancer. In this study, we examine the relative contribution of HA interactions with CD44 and TLR4 in colon tumorigenesis. Colorectal cancer models included Apc^Min/+ mice, azoxymethane/dextran sodium sulfate (AOM-DSS), and CT26 tumor isografts. We used knockout mice and CT26 colorectal cancer cells with CRISPR knockdown of CD44 and TLR4. HA activity was modulated by PEP1 (a 12-mer peptide that blocks HA from binding its receptors), hyaluronidase (which promotes HA degradation), or 4-MU (HA synthesis inhibitor). Blockade of HA binding via PEP1 decreased growth in all colorectal cancer models and in cell culture. The effects were significant in WT and with CD44 deletion, but not with TLR4 deletion. In the AOM-DSS model, mice deficient in CD44 or TLR4 had fewer tumors. CD44- and TLR4-deficient CT26 isografts grew more slowly, exhibiting decreased tumor cell proliferation and increased apoptosis. In vitro, endogenous HA blocked LPS binding to TLR4 suggesting that HA is a relevant TLR4 ligand in colon cancer. Finally, PEP1 enhanced tumor radiation sensitivity in the isograft model. Together, these results indicate that HA binding to TLR4, as well as CD44, plays a key role in colon tumorigenesis. These findings also raise the possibility that an agent that blocks HA binding, such as PEP1, may be useful as an adjuvant therapy in colon cancer.

Knockdown of STAT3 targets a subpopulation of invasive melanoma stem-like cells

Transcription factor signal transducer and activator of transcription 3 (STAT3) is constitutively activated in many cancers, including melanomas. Active, phosphorylated STAT3 contributes to tumor growth and formation of the immunosuppressive tumor microenvironment. Recent evidence suggests an important role of STAT3 in self-renewal of cancer stem-like cells (CSCs). In the present study, we aimed to determine the expression and role of active STAT3 in melanoma CSCs. We found the increased levels of phosphorylated (Y705) STAT3 in CSC sphere cultures derived from three human and murine melanoma cells. Knockdown of STAT3 did not affect basal proliferation, but reduced sphere forming capacity of two human melanoma cell lines. Moreover, the level of active STAT3 was elevated in rhodamine 123 negative subpopulations of CSCs sorted from three melanoma cell lines. We found that focal adhesion kinase (FAK) and AKT signaling pathways, implicated in the regulation of cell migration and invasion, were up-regulated in melanoma CSCs. Moreover, expression of SERPINA3, which regulates melanoma invasion, was increased in melanoma CSCs sphere cultures, which correlated with augmented cell invasion in Matrigel. Our findings show that STAT3 is activated and supports maintenance of melanoma CSCs. It suggests that STAT3 could serve as a potential target to impair tumor progression or recurrence.

Genome atlas analysis based profiling of Akt pathway genes in the early and advanced human prostate cancer

Recent studies conducted in the mouse and cellular models suggest a stage-specific, differential effect of Akt activity modulation on tumor growth and metastasis in various cancers. In prostate cancer (PCa), although the deletion of Akt1 gene in a neuroendocrine model of TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) blunted oncogenic transformation and tumor growth, Akt1 suppression in the advanced PCa resulted in the activation of transforming growth factor-β pathway and enhanced metastasis to the lungs. Such a dual role for the Akt isoforms and its signaling partners has not been investigated in human PCa. In the current study, we performed genomic database analysis of Akt isoforms and associated pathway molecules in human prostate adenocarcinoma, castration-resistant PCa, neuroendocrine PCa and metastatic PCa for mutations, genetic alterations, mRNA and protein expressions and activating phosphorylations from cBioportal. Results from the protein data analysis from the cBioportal were compared to the results of our data on human PCa tissue analysis and the cellular effects of Akt1 suppression using MK-2206 on PCa cell aggressiveness. Our study indicates the existence of a dual role for Akt1 in PCa and warrants a large-scale analysis of the early and advanced stage PCa clinical samples for further clarity.

ADAR1 p110 Enhances Adhesion of Tumor Cells to Extracellular Matrix in Hepatocellular Carcinoma via Up-Regulating ITGA2 Expression

BACKGROUND Intrahepatic and distant metastases could be the major cause of treatment failure in hepatocellular carcinoma (HCC). The deep mechanism of HCC metastasis is closely related to the interaction between integrins and extracellular matrix (ECM) in tumor microenvironment. MATERIAL AND METHODS In vitro cell adhesion assay was performed to determine the capability of adhering to ECM elements of HCC cells. To modulate the expression status of ADAR1 p110 in tumor cells, lentivirus system was applied. Meanwhile, patients' HCC samples and orthotopic xenograft mouse model were used for verifying our in vitro data. RESULTS ADAR1 p110 could strongly enhance the adhesion of HCC tumor cells to ECM, which was usually regarded as the initiation of tumor invasion. Such phenotype was caused due to up-regulation of ITGA2 both in mRNA and protein level. Moreover, specimen collected from HCC patients revealed a positive correlation between ADAR1 and ITGA2. Finally, ADAR1 p110 promoted HCC metastasis was verified when we applied orthotopic xenograft mouse model. CONCLUSIONS ADAR1 could enhance HCC metastasis by promoting tumor cells adhering to ECM via increasing ITGA2 expression. This phenomenon could provide novel information to better understanding the mechanism of HCC metastasis procedure.

Thymosin β4 for the treatment of acute stroke: neurorestorative or neuroprotective?

INTRODUCTION

Thymosin β4 (Tβ4) is a 5K peptide which influences cellular migration by inhibiting organization of the actin-cytoskeleton. Treatment of acute stroke presently involves use of rt-PA and/or endovascular treatment with thrombectomy, both of which have time limitations. Therefore, development of a treatment beyond these times is necessary as most stroke patients present beyond these time limits. A drug which could be administered within 24 h from symptom onset would provide substantial benefit.

AREAS COVERED

This review summarizes the data and results of two in-vivo studies testing Tβ4 in an embolic stroke model of young and aged rats. In addition, we describe in-vitro investigations of the neurorestorative and neuroprotective properties of Tβ4 in a variety of neuroprogenitor and oligoprogenitor cell models.

EXPERT OPINION

Tβ4 acts as a neurorestorative agent when employed in a young male rat model of embolic stroke while in an aged model it acts a neuroprotectant. However evaluation of Tβ4 as a treatment of stroke requires further preclinical evaluation in females and in males and females with comorbidities such as, hypertension and diabetes in models of embolic stroke to further define the mechanism of action and potential as a treatment of stroke in humans.

DT-13 Inhibits Proliferation and Metastasis of Human Prostate Cancer Cells Through Blocking PI3K/Akt Pathway

DT-13, a saponin monomer 13 from the dwarf lilyturf tuber, was reported to exhibit anti-inflammatory, hepatoprotective, cardioprotective as well as antitumor activities in a number of tumor cells. Prostate cancer is the second leading cause of cancer death in males, discovery of novel antitumor drug for therapy of prostate cancer is expected. Aiming to evaluate whether DT-13 could become a candidate to treat prostate cancer, we recently investigated the antitumor effect of DT-13 on human prostate cancer cells and the underlying mechanism. DT-13 was found to effectively inhibit proliferation and metastasis of prostate cancer PC3 and DU145 cell lines in a dose-dependent manner. Treatment by DT-13 resulted in a mitochondria-mediated apoptosis, which was accompanied by the chromatin condensation and nuclear shrinkage in the prostate cancer cells. Moreover, DT-13 caused remarkable upregulation of Bax, Bad, Cytochrome C, cleaved -caspase 3, -caspase 9 and -PARP, in contrast to the downregulation of Bcl-2. Nevertheless, no obvious change in intracellular ROS level was observed after DT-13 treatment. We further demonstrated that DT-13 could inhibit PC3 cell metastasis in which suppression of Integrinβ1 and MMP2/9 might be involved. Western blot analysis indicated DT-13 significantly decreased the phosphorylation of PDK1, Akt, mTOR as well as p70S6K, suggesting the pro-apoptotic and anti-metastatic effects of DT-13 on prostate cancer cells might be attributed to the blockade of PI3K/Akt pathway. Collectively, our findings suggest DT-13 is worthy of further investigation as a drug candidate for the treatment of prostate cancer.

Modulation in the microRNA repertoire is responsible for the stage-specific effects of Akt suppression on murine neuroendocrine prostate cancer

Recent studies indicate a stage-specific, differential role for the oncogene Akt on various cancers. In prostate cancer (PCa), suppression of Akt activity in the advanced stages promoted transforming growth factor-β (TGFβ) pathway-mediated epithelial-to-mesenchymal transition (EMT) and metastasis to the lungs. In the current study, we performed Affymetrix analysis to compare the expression profile of microRNAs in the mouse prostate tissues collected at the prostatic inter-epithelial neoplasia (PIN) stage from Transgenic adenocarcinoma of the mouse (TRAMP)/Akt1^+/+ versus TRAMP/Akt1^–/– mice, and at the advanced stage from TRAMP/Akt1^+/+ mice treated with triciribine (Akt inhibitor) versus DMSO-treated control. Our analysis demonstrates that in the early stage, Akt1 in the TRAMP prostate tumors express a set of miRNAs responsible for regulating cancer cell survival, proliferation, and tumor growth, whereas, in the advanced stages, a different set of miRNAs that promote EMT and cancer metastasis is expressed. Our study has identified novel Akt-regulated signature microRNAs in the early and advanced PCa and demonstrates their differential effects on PCa growth and metastasis.

LRP1 is required for novobiocin-mediated fibronectin turnover

Fibronectin (FN) plays a major role in the stability and organization of the extracellular matrix (ECM). We have previously demonstrated that FN interacts directly with Hsp90, as well as showing that the Hsp90 inhibitor novobiocin results in FN turnover via a receptor mediated process. However, the receptor involved has not been previously identified. LRP1 is a ubiquitous receptor responsible for the internalisation of numerous ligands that binds both Hsp90 and FN, and therefore we investigated whether LRP1 was involved in novobiocin-mediated FN turnover. FN, LRP1 and Hsp90 could be isolated in a common complex, and inhibition of Hsp90 by novobiocin increased the colocalisation of FN and LRP1. Novobiocin induced an increase (at low concentrations) followed by a loss of FN that was primarily derived from extracellular matrix-associated FN and led to a concomitant increase in intracellular FN. The effect of novobiocin was specific to LRP1-expressing cells and could be recapitulated by an LRP1 blocking antibody and the allosteric C-terminal Hsp90 inhibitor SM253, but not the N-terminal inhibitor geldanamycin. Together these data suggest that LRP1 is required for FN turnover in response to Hsp90 inhibition by novobiocin, which may have unintended physiological consequences in contexts where C-terminal Hsp90 inhibition is to be used therapeutically.

Isoform-specific effects of transforming growth factor β on endothelial-to-mesenchymal transition

Endothelial-to-mesenchymal transition (EndMT) was first reported in the embryogenesis. Recent studies show that EndMT also occurs in the disease progression of atherosclerosis, cardiac and pulmonary fibrosis, pulmonary hypertension, diabetic nephropathy, and cancer. Although transforming growth factor β (TGFβ) is crucial for EndMT, it is not clear which isoform elicits a predominant effect. The current study aims to directly compare the dose-dependent effects of TGFβ1, TGFβ2, and TGFβ3 on EndMT and characterize the underlying mechanisms. In our results, all three TGFβ isoforms induced EndMT in human microvascular endothelial cells after 72 hr, as evidenced by the increased expression of mesenchymal markers N-cadherin and α-smooth muscle actin as well as the decreased expression of endothelial nitric oxide synthase. Interestingly, the effect of TGFβ2 was the most pronounced. At 1 ng/ml, only TGFβ2 treatment resulted in significantly increased phosphorylation (activation) of Smad2/3 and p38-MAPK and increased expression of mesenchymal transcription factors Snail and FoxC2. Intriguingly, we observed that treatment with 1 ng/ml TGFβ1 and TGFβ3, but not TGFβ2, resulted in an increased expression of TGFβ2, thus indicating that EndMT with TGFβ1 and TGFβ3 treatments was due to the secondary effects through TGFβ2 secretion. Furthermore, silencing TGFβ2 using small interfering RNA blunted the expression of EndMT markers in TGFβ1- and TGFβ3-treated cells. Together, our results indicate that TGFβ2 is the most potent inducer of EndMT and that TGFβ1- and TGFβ3-induced EndMT necessitates a paracrine loop involving TGFβ2.

Suppression of Akt1-β-catenin pathway in advanced prostate cancer promotes TGFβ1-mediated epithelial to mesenchymal transition and metastasis

Akt1 is essential for the oncogenic transformation and tumor growth in various cancers. However, the precise role of Akt1 in advanced cancers is conflicting. Using a neuroendocrine TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model, we first show that the genetic ablation or pharmacological inhibition of Akt1 in mice blunts oncogenic transformation and prostate cancer (PCa) growth. Intriguingly, triciribine (TCBN)-mediated Akt inhibition in 25-week old, tumor-bearing TRAMP mice and Akt1 gene silencing in aggressive PCa cells enhanced epithelial to mesenchymal transition (EMT) and promoted metastasis to the lungs. Mechanistically, Akt1 suppression leads to increased expression of EMT markers such as Snail1 and N-cadherin and decreased expression of epithelial marker E-cadherin in TRAMP prostate, and in PC3 and DU145 cells. Next, we identified that Akt1 knockdown in PCa cells results in increased production of TGFβ1 and its receptor TGFβ RII, associated with a decreased expression of β-catenin. Furthermore, treatment of PCa cells with ICG001 that blocks nuclear translocation of β-catenin promoted EMT and N-cadherin expression. Together, our study demonstrates a novel role of the Akt1-β-catenin-TGFβ1 pathway in advanced PCa.

KCa1.1 channels regulate β1-integrin function and cell adhesion in rheumatoid arthritis fibroblast-like synoviocytes

Large-conductance calcium-activated potassium channel (KCa1.1; BK, Slo1, MaxiK, KCNMA1) is the predominant potassium channel expressed at the plasma membrane of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) isolated from the synovium of patients with RA. It is a critical regulator of RA-FLS migration and invasion and therefore represents an attractive target for the therapy of RA. However, the molecular mechanisms by which KCa1.1 regulates RA-FLS invasiveness have remained largely unknown. Here, we demonstrate that KCa1.1 regulates RA-FLS adhesion through controlling the plasma membrane expression and activation of β₁ integrins, but not α₄, α₅, or α₆ integrins. Blocking KCa1.1 disturbs calcium homeostasis, leading to the sustained phosphorylation of Akt and the recruitment of talin to β₁ integrins. Interestingly, the pore-forming α subunit of KCa1.1 coimmunoprecipitates with β₁ integrins, suggesting that this physical association underlies the functional interaction between these molecules. Together, these data outline a new signaling mechanism by which KCa1.1 regulates β₁-integrin function and therefore invasiveness of RA-FLSs.-Tanner, M. R., Pennington, M. W., Laragione, T., Gulko, P. S., Beeton, C. KCa1.1 channels regulate β₁-integrin function and cell adhesion in rheumatoid arthritis fibroblast-like synoviocytes.

Modulation of long-term endothelial-barrier integrity is conditional to the cross-talk between Akt and Src signaling

Although numerous studies have implicated Akt and Src kinases in vascular endothelial growth factor (VEGF) and Angiopoietin-1 (Ang-1)-induced endothelial-barrier regulation, a link between these two pathways has never been demonstrated. We determined the long-term effects of Akt inhibition on Src activity and vice versa, and in turn, on the human microvascular endothelial cell (HMEC) barrier integrity at the basal level, and in response to growth factors. Our data showed that Akt1 gene knockdown increases gap formation in HMEC monolayer at the basal level. Pharmacological inhibition of Akt, but not Src resulted in exacerbated VEGF-induced vascular leakage and impaired Ang-1-induced HMEC-barrier protection in vitro at 24 hr. Whereas inhibition of Akt had no effect on VEGF-induced HMEC gap formation in the short term, inhibition of Src blunted this process. In contrast, inhibition of Akt disrupted the VEGF and Ang-1 stabilized barrier integrity in the long-term while inhibition of Src did not. Interestingly, both long-term Akt inhibition and Akt1 gene knockdown in HMECs resulted in increased Tyr416 phosphorylation of Src. Treatment of HMECs with transforming growth factor-β1 (TGFβ1) that inhibited Akt Ser473 phosphorylation in the long-term, activated Src through increased Tyr416 phosphorylation and decreased HMEC-barrier resistance. The effect of TGFβ1 on endothelial-barrier breakdown was blunted in Akt1 deficient HMEC monolayers, where endothelial-barrier resistance was already impaired compared to the control. To our knowledge, this is the first report demonstrating a direct cross-talk between Akt and Src in endothelial-barrier regulation.

Akt1 promotes stimuli-induced endothelial-barrier protection through FoxO-mediated tight-junction protein turnover

Vascular permeability regulated by the vascular endothelial growth factor (VEGF) through endothelial-barrier junctions is essential for inflammation. Mechanisms regulating vascular permeability remain elusive. Although 'Akt' and 'Src' have been implicated in the endothelial-barrier regulation, it is puzzling how both agents that protect and disrupt the endothelial-barrier activate these kinases to reciprocally regulate vascular permeability. To delineate the role of Akt1 in endothelial-barrier regulation, we created endothelial-specific, tamoxifen-inducible Akt1 knockout mice and stable ShRNA-mediated Akt1 knockdown in human microvascular endothelial cells. Akt1 loss leads to decreased basal and angiopoietin1-induced endothelial-barrier resistance, and enhanced VEGF-induced endothelial-barrier breakdown. Endothelial Akt1 deficiency resulted in enhanced VEGF-induced vascular leakage in mice ears, which was rescued upon re-expression with Adeno-myrAkt1. Furthermore, co-treatment with angiopoietin1 reversed VEGF-induced vascular leakage in an Akt1-dependent manner. Mechanistically, our study revealed that while VEGF-induced short-term vascular permeability is independent of Akt1, its recovery is reliant on Akt1 and FoxO-mediated claudin expression. Pharmacological inhibition of FoxO transcription factors rescued the defective endothelial barrier due to Akt1 deficiency. Here we provide novel insights on the endothelial-barrier protective role of VEGF in the long term and the importance of Akt1-FoxO signaling on tight-junction stabilization and prevention of vascular leakage through claudin expression.

Overexpressing IRS1 in Endothelial Cells Enhances Angioblast Differentiation and Wound Healing in Diabetes and Insulin Resistance

The effect of enhancing insulin's actions in endothelial cells (ECs) to improve angiogenesis and wound healing was studied in obesity and diabetes. Insulin receptor substrate 1 (IRS1) was overexpressed in ECs using the VE-cadherin promoter to create ECIRS1 TG mice, which elevated pAkt activation and expressions of vascular endothelial growth factor (VEGF), Flk1, and VE-cadherin in ECs and granulation tissues (GTs) of full-thickness wounds. Open wound and epithelialization rates and angiogenesis significantly improved in normal mice and high fat (HF) diet-induced diabetic mice with hyperinsulinemia in ECIRS1 TG versus wild type (WT), but not in insulin-deficient diabetic mice. Increased angioblasts and EC numbers in GT of ECIRS1 mice were due to proliferation in situ rather than uptake. GT in HF-fed diabetic mice exhibited parallel decreases in insulin and VEGF-induced pAkt and EC numbers by >50% without changes in angioblasts versus WT mice, which were improved in ECIRS1 TG mice on normal chow or HF diet. Thus, HF-induced diabetes impaired angiogenesis by inhibiting insulin signaling in GT to decrease the differentiation of angioblasts to EC, which was normalized by enhancing insulin's action targeted to EC, a potential target to improve wound healing in diabetes and obesity.

Enhancing the Three-Dimensional Structure of Adherent Gingival Fibroblasts and Spheroids via a Fibrous Protein-Based Hydrogel Cover

Tissue engineering-based therapies rely on the delivery of monolayered fibroblasts on two-dimensional polystyrene-coated and extracellular matrix (ECM) surfaces to regenerate connective tissues. However, this approach may fail to mimic their three-dimensional (3D) native architecture and function. We hypothesize that ECM fibrous proteins, which direct the migration of cells in vivo, may attach and guide polystyrene- and Matrigel™-ECM (M-ECM)-adherent fibroblasts to rearrangement into large multicellular macrostructures with the ability to proliferate. Gingival monolayered fibroblasts and their derived spheroids were added and adhered to tissue culture polystyrene and M-ECM surfaces. The cells were covered with a layer of collagen1 hydrogel combined with vitronectin, fibronectin or fibrin, or 10% M-ECM. The development of 3D cell constructs was characterized by epifluorescence and confocal scanning microscope image analysis. The ECM turnover and the proliferative capabilities of the fibroblasts were determined via gene expression profiling of collagen1, fibronectin, matrix metalloproteinase/metallopeptidase 2, Nanog, and SRY (sex-determining region Y)-box2 (Sox2). Expression of the Sox2 protein was followed by immunostaining. The collagen1 protein had the strongest effect on monolayered and spheroid cell rearrangements, forming large spherical shapes and fused 3D macroconstructs. The addition of fibrin protein was typically required to achieve a similar effect on M-ECM-adherent monolayered fibroblasts. The spheroid fusion process was followed by an increase in cell density and the formation of tight clusters. The fused spheroids continued to maintain their intracellular ECM turnover and proliferation capacities. Collagen1 is a valuable component in the rearrangement of adherent fibroblast monolayers and spheroids. Fibroblast spheroids should preferably be used as basic building blocks to assemble multicellular connective tissue-like macrostructures.

Sulfatase-mediated manipulation of the astrocyte-Schwann cell interface

Schwann cell (SC) transplantation following spinal cord injury (SCI) may have therapeutic potential. Functional recovery is limited however, due to poor SC interactions with host astrocytes and the induction of astrogliosis. Olfactory ensheathing cells (OECs) are closely related to SCs, but intermix more readily with astrocytes in culture and induce less astrogliosis. We previously demonstrated that OECs express higher levels of sulfatases, enzymes that remove 6-O-sulfate groups from heparan sulphate proteoglycans, than SCs and that RNAi knockdown of sulfatase prevented OEC-astrocyte mixing in vitro. As human OECs are difficult to culture in large numbers we have genetically engineered SCs using lentiviral vectors to express sulfatase 1 and 2 (SC-S1S2) and assessed their ability to interact with astrocytes. We demonstrate that SC-S1S2s have increased integrin-dependent motility in the presence of astrocytes via modulation of NRG and FGF receptor-linked PI3K/AKT intracellular signaling and do not form boundaries with astrocytes in culture. SC-astrocyte mixing is dependent on local NRG concentration and we propose that sulfatase enzymes influence the bioavailability of NRG ligand and thus influence SC behavior. We further demonstrate that injection of sulfatase expressing SCs into spinal cord white matter results in less glial reactivity than control SC injections comparable to that of OEC injections. Our data indicate that sulfatase-mediated modification of the extracellular matrix can influence glial interactions with astrocytes, and that SCs engineered to express sulfatase may be more OEC-like in character. This approach may be beneficial for cell transplant-mediated spinal cord repair. GLIA 2016 GLIA 2017;65:19-33.

The fibronectin III-1 domain activates a PI3-Kinase/Akt signaling pathway leading to αvβ5 integrin activation and TRAIL resistance in human lung cancer cells

Background

Fibronectin is a mechanically sensitive protein which is organized in the extracellular matrix as a network of interacting fibrils. The lung tumor stroma is enriched for fibronectin which is thought to contribute to metastasis and drug resistance. Fibronectin is an elastic, multi-modular protein made up of individually folded domains, some of which can stretch in response to increased mechanical tension. Very little is known about the relationship of fibronectin’s unfolded domains to lung cancer resistance to chemotherapy. In the present study, we evaluated the impact of unfolding the first Type III domain of fibronectin (FnIII-1c) on TNF-related apoptosis inducing ligand (TRAIL) resistance.

Methods

NCI-H460 non-small cell lung cancer cells were treated with FnIII-1c then assessed for TRAIL-induced apoptosis. Subsequent analysis of FnIII-1c-mediated signaling pathways was also completed. Human non-small cell lung cancer tissue sections were assessed for the expression of vitronectin by immunohistochemistry.

Results

FnIII-1c inhibited TRAIL-induced activation of caspase 8 and subsequent apoptosis in NCI-H460 lung cancer cells. FnIII-1c treatment was associated with the activation of the phosphatidylinositol-3-kinase/alpha serine/threonine kinase (PI3K/Akt) pathway and the αvβ5 integrin receptor for vitronectin, both of which were required for TRAIL resistance. Immunohistochemical staining of sections from non-small cell lung cancers showed that vitronectin was localized around blood vessels and in the tumor-stroma interface.

Conclusions

Unfolding of Type III domains within the fibronectin matrix may promote TRAIL resistance through the activation of a PI3K/Akt/αvβ5 signaling axis and point to a novel mechanism by which changes in secondary structure of fibronectin contribute to cancer cell resistance to apoptosis.

Chelerythrine chloride induces apoptosis in renal cancer HEK-293 and SW-839 cell lines

Previous studies have demonstrated that the benzo[c]phenanthridine alkaloid chelerythrine chloride (CC) has inhibitory effects on various tumors. However, the anticancer activity of CC and its underlying mechanisms have not been elucidated in renal cancer cells. The present study examined the effects of CC on growth inhibition and apoptosis of renal cancer cells in vitro and in vivo. Flow cytometry and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays revealed that CC markedly suppressed the growth of HEK-293 and human renal cancer SW-839 cells in a time- and dose-dependent manner. The xenograft mouse model, which was performed in nude mice, exhibited a reduced tumor growth following CC treatment. In addition, the present study revealed that CC significantly decreased the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt, which was accompanied by upregulation of p53, B-cell lymphoma 2 (Bcl-2)-associated X protein, cleaved caspase-3 and cleaved poly (adenosine diphosphate-ribose) polymerase (PARP), and downregulation of Bcl-2, caspase-3 and PARP. Furthermore, the use of PD98059, a specific mitogen-activated protein kinase kinase inhibitor, potentiated the proapoptotic effects of CC, which indicated that CC may induce apoptosis in renal cancer cells partly via inhibition of ERK activity. Overall, the results of the present study demonstrated that CC may be developed as a potential anticancer treatment for patients with renal cancer.

Stability and function of adult vasculature is sustained by Akt/Jagged1 signalling axis in endothelium

The signalling pathways operational in quiescent, post-development vasculature remain enigmatic. Here we show that unlike neovascularization, endothelial Akt signalling in established vasculature is crucial not for endothelial cell (EC) survival, but for sustained interactions with pericytes and vascular smooth muscle cells (VSMCs) regulating vascular stability and function. Inducible endothelial-specific Akt1 deletion in adult global Akt2KO mice triggers progressive VSMC apoptosis. In hearts, this causes a loss of arteries and arterioles and, despite a high capillary density, diminished vascular patency and severe cardiac dysfunction. Similarly, endothelial Akt deletion induces retinal VSMC loss and basement membrane deterioration resulting in vascular regression and retinal atrophy. Mechanistically, the Akt/mTOR axis controls endothelial Jagged1 expression and, thereby, Notch signalling regulating VSMC maintenance. Jagged1 peptide treatment of Akt1ΔEC;Akt2KO mice and Jagged1 re-expression in Akt-deficient endothelium restores VSMC coverage. Thus, sustained endothelial Akt1/2 signalling is critical in maintaining vascular stability and homeostasis, thereby preserving tissue and organ function.

The Akt pathway integrates multiple signals, but whether it affects vasculature function is debatable. Here the authors show that Akt pathway shutdown in adult mouse endothelium causes destabilization of vasculature leading to cardiac and retinal dysfunction, due to decreased levels of Jagged1 and impaired Notch signaling.

miR-17-92 plays an oncogenic role and conveys chemo-resistance to cisplatin in human prostate cancer cells

The mir-17-92 cluster consists of six mature miRNAs and is implicated in diverse human cancers by targeting mRNAs involved in distinct pathways that either promote or inhibit carcinogenesis. However, the molecular mechanism underlying the mir-17-92 cluster-mediated pro-tumorigenic or anti-tumorigenic effects has not been clearly elucidated in prostate cancer. In the present study, the role of the mir-17-92 cluster in diverse aspects of prostate cancer cells has been thoroughly investigated. Forced introduction of the mir-17-92 cluster into the androgen-independent DU145 prostate cancer cells evidently promoted cell growth due to disruption of the balance between cellular proliferation and apoptosis. Overexpression of the mir-17-92 cluster significantly improved the migration and invasion of the DU145 cells, attributed to the induction of integrin β-1. Notably, the mir-17-92 cluster conveyed chemo-resistance to cisplatin. We demonstrated that the mir-17-92 cluster suppressed the expression of inhibitor of the AKT signaling pathway and activated the AKT pathway subsequently, which played a central role in regulating cellular proliferation, apoptosis and chemo-resistance. Continuously activated ERK1/2 signaling also contributed importantly to these processes. The present study provides key evidence for crucial oncogenic role of the miR-17-92 cluster in prostate cancer cells. Further investigations are warranted to determine whether miR-17-92 cluster can be targeted for future treatment of human prostate cancer.

The Roles of PI3K/AKT/mTOR and MAPK/ERK Signaling Pathways in Human Pheochromocytomas

Objectives. The roles of PI3K/AKT/mTOR and MAPK/ERK pathways involved in the pathogenesis of pheochromocytoma and paraganglioma (PPGL) were demonstrated mostly by in vitro studies with rat or mouse cells and were mainly studied at transcriptional level. This study aimed to investigate the effect of these pathways on the proliferation of human PPGL cells and the activation of these pathways in PPGLs. Methods. Human PPGL cells were treated with sunitinib and inhibitors of PI3K (LY294002), MEK1/2 (U0126), and mTORC1/2 (AZD8055). Cell proliferation was detected by MTT assay. Protein phosphorylation was detected by Western blotting. Results. In most PPGLs, AKT, ERK1/2, and mTOR were activated. LY294002 (10 μM), U0126 (10 μM), AZD8055 (1 μM), and sunitinib (1 μM) inhibited PPGL cell proliferation in ten primary cultures of tissues, including four from patients with gene mutations. MEK1/2 inhibitor decreased mTOR phosphorylation. Inhibition of mTOR reduced phosphorylation of AKT and ERK1/2. Sunitinib inhibited phospho-ERK1/2 and phospho-mTOR. Conclusion. Our study suggested that PI3K/AKT/mTOR and MAPK/ERK signaling pathways play vital roles in human PPGL and are activated in most PPGLs. Inhibiting multiple pathways might be a novel therapeutic approach for PPGLs.

Dasatinib inhibits TGFβ-induced myofibroblast differentiation through Src-SRF Pathway

Persistent myofibroblast differentiation is a hallmark of fibrotic diseases. Myofibroblasts are characterized by de novo expression of alpha smooth muscle actin (αSMA) and excess fibronectin assembly. Recent studies provide conflicting reports on the effects of tyrosine kinase inhibitor dasatinib on myofibroblast differentiation and fibrosis. Also, it is not fully understood whether dasatinib modulates myofibroblast differentiation by targeting Src kinase. Herein, we investigated the effect of dasatinib on cSrc and transforming growth factor-β (TGFβ)-induced myofibroblast differentiation in vitro. Our results indicated that selective Src kinase inhibition using PP2 mimicked the effect of dasatinib in attenuating myofibroblast differentiation as evident by blunted αSMA expression and modest, but significant inhibition of fibronectin assembly in both NIH 3T3 and fibrotic human lung fibroblasts. Mechanistically, our data showed that dasatinib modulates αSMA synthesis through Src kinase-mediated modulation of serum response factor expression. Collectively, our results demonstrate that dasatinib modulates myofibroblast differentiation through Src-SRF pathway. Thus, dasatinib could potentially be a therapeutic option in fibrotic diseases.

The Akt inhibitor, triciribine, ameliorates chronic hypoxia-induced vascular pruning and TGFβ-induced pulmonary fibrosis

BACKGROUND AND PURPOSE

Interstitial lung disease accounts for a group of chronic and progressive disorders associated with severe pulmonary vascular remodelling, peripheral vascular rarefaction and fibrosis, thus limiting lung function. We have previously shown that Akt is necessary for myofibroblast differentiation, a critical event in organ fibrosis. However, the contributory role of the Akt-mTOR pathway in interstitial lung disease and the therapeutic benefits of targeting Akt and mTOR remain unclear.

EXPERIMENTAL APPROACH

We investigated the role of the Akt-mTOR pathway and its downstream molecular mechanisms in chronic hypoxia- and TGFβ-induced pulmonary vascular pruning and fibrosis in mice. We also determined the therapeutic benefits of the Akt inhibitor triciribine and the mTOR inhibitor rapamycin for the treatment of pulmonary fibrosis in mice.

KEY RESULTS

Akt1(-) (/) (-) mice were protected from chronic hypoxia-induced peripheral vascular pruning. In contrast, hyperactivation of Akt1 induced focal fibrosis similar to TGFβ-induced fibrosis. Pharmacological inhibition of Akt, but not the Akt substrate mTOR, inhibited hypoxia- and TGFβ-induced pulmonary vascular rarefaction and fibrosis. Mechanistically, we found that Akt1 modulates pulmonary remodelling via regulation of thrombospondin1 (TSP1) expression. Hypoxic Akt1(-) (/) (-) mice lungs expressed less TSP1. Moreover, TSP1(-) (/) (-) mice were resistant to adMyrAkt1-induced pulmonary fibrosis.

CONCLUSIONS AND IMPLICATIONS

Our study identified Akt1 as a novel target for the treatment of interstitial lung disease and provides preclinical data on the potential benefits of the Akt inhibitor triciribine for the treatment of interstitial lung disease.

CD99 inhibits CD98-mediated β1 integrin signaling through SHP2-mediated FAK dephosphorylation

The human CD99 protein is a 32-kDa type I transmembrane glycoprotein, while CD98 is a disulfide-linked 125-kDa heterodimeric type II transmembrane glycoprotein. It has been previously shown that CD99 and CD98 oppositely regulate β1 integrin signaling, though the mechanisms by which this regulation occurs are not known. Our results revealed that antibody-mediated crosslinking of CD98 induced FAK phosphorylation at Y397 and facilitated the formation of the protein kinase Cα (PKCα)-syntenin-focal adhesion kinase (FAK), focal adhesions (FAs), and IPP-Akt1-syntenin complex, which mediates β1 integrin signaling. In contrast, crosslinking of CD99 disrupted the formation of the PKCα-syntenin-FAK complex as well as FA via FAK dephosphorylation. The CD99-induced dephosphorylation of FAK was apparently mediated by the recruitment of Src homology region 2 domain-containing phosphatase-2 (SHP2) to the plasma membrane and subsequent activation of its phosphatase activity. Further consequences of the activation of SHP2 included the disruption of FAK-talin and talin-β1 integrin interactions and attenuation in the formation of the IPP-Akt1-syntenin complex at the plasma membrane, which resulted in reduced cell-ECM adhesion. This report uncovers the molecular mechanisms underlying the inverse regulation of β1 integrin signaling by CD99 and CD98 and may provide a novel therapeutic approach to treat inflammation and cancer.

p70 S6-kinase mediates the cooperation between Akt1 and Mek1 pathways in fibroblast-mediated extracellular matrix remodeling

Previous studies have demonstrated both synergistic and opposing effects of Akt and Mek1/2 in various cell functions and disease states. Furthermore, Akt has been reported to inhibit and activate cRaf/Mek pathway, suggesting that their mutual interaction and cooperation may be cell type, stimuli and/or context specific. While PI3-kinase/Akt and cRaf/Mek pathways have been implicated in the regulation of extracellular matrix (ECM) remodeling, mutual interactions between these two pathways and their specific contributions to the events leading to ECM synthesis and assembly is not clear. We investigated the specific role of Akt1 and Mek1 in ECM synthesis and assembly by NIH 3T3 fibroblasts and how these effects were reconciled to mediate overall ECM remodeling. Our study identified that cooperation between Akt1 and Mek1 is necessary to mediate ECM synthesis. Whereas Akt1 activation resulted in Mek1 activation as evidenced by increased ERK1/2 phosphorylation, Mek1 inhibition using U0126 or DN-Mek1 resulted in enhanced Akt1 phosphorylation. Interestingly, both Akt1 and Mek1 activities were needed for the synthesis and assembly of ECM. The effect of Akt1 and Mek1 on ECM synthesis was reconciled through the activation of p70 S6-kinase via phosphorylation at T421/S424 and S411, respectively. Furthermore, Akt1 and Mek1 cooperated in mediating ECM assembly via activation of integrin β1. Together, we show for the first time that Akt1 and Mek1 pathways cooperate in the regulation of ECM remodeling by the fibroblasts.

pGlcNAc Nanofiber Treatment of Cutaneous Wounds Stimulate Increased Tensile Strength and Reduced Scarring via Activation of Akt1

Treatment of cutaneous wounds with poly-N-acetyl-glucosamine containing nanofibers (pGlcNAc), a novel polysaccharide material derived from a marine diatom, results in increased wound closure, antibacterial activities and innate immune responses. We have shown that Akt1 plays a central role in the regulation of these activities. Here, we show that pGlcNAc treatment of cutaneous wounds results in a smaller scar that has increased tensile strength and elasticity. pGlcNAc treated wounds exhibit decreased collagen content, increased collagen organization and decreased myofibroblast content. A fibrin gel assay was used to assess the regulation of fibroblast alignment in vitro. In this assay, fibrin lattice is formed with two pins that provide focal points upon which the gel can exert force as the cells align from pole to pole. pGlcNAc stimulation of embedded fibroblasts results in cellular alignment as compared to untreated controls, by a process that is Akt1 dependent. We show that Akt1 is required in vivo for the pGlcNAc-induced increased tensile strength and elasticity. Taken together, our findings suggest that pGlcNAc nanofibers stimulate an Akt1 dependent pathway that results in the proper alignment of fibroblasts, decreased scarring, and increased tensile strength during cutaneous wound healing.

Insulin-like growth factor 1 increases apical fibronectin in blastocysts to increase blastocyst attachment to endometrial epithelial cells in vitro

STUDY QUESTION

Does insulin-like growth factor 1 (IGF1) increase adhesion competency of blastocysts to increase attachment to uterine epithelial cells in vitro?

SUMMARY ANSWER

IGF1 increases apical fibronectin on blastocysts to increase attachment and invasion in an in vitro model of implantation.

WHAT IS KNOWN ALREADY

Fibronectin integrin interactions are important in attachment of blastocysts to uterine epithelial cells at implantation.

STUDY DESIGN, SIZE, DURATION

Mouse blastocysts (hatched or near completion of hatching) were cultured in serum starved (SS) medium with varying treatments for 24, 48 or 72 h. Treatments included 10 ng/ml IGF1 in the presence or absence of the PI3 kinase inhibitor LY294002, an IGF1 receptor (IGF1R) neutralizing antibody or fibronectin. Effects of treatments on blastocysts were measured by attachment of blastocysts to Ishikawa cells, blastocyst outgrowth and fibronectin and focal adhesion kinase (FAK) localization and expression. Blastocysts were randomly allocated into control and treatment groups and experiments were repeated a minimum of three times with varying numbers of blastocysts used in each experiment. FAK and integrin protein expression on Ishikawa cells was quantified in the presence or absence of IGF1.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Fibronectin expression and localization in blastocysts was studied using immunofluorescence and confocal microscopy. Global surface expression of integrin αvβ3, β3 and β1 was measured in Ishikawa cells using flow cytometry. Expression levels of phosphorylated FAK and total FAK were measured in Ishikawa cells and blastocysts by western blot and image J analysis. Blastocyst outgrowth was quantified using image J analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

The presence of IGF1 significantly increased mouse blastocyst attachment to Ishikawa cells compared with SS conditions (P < 0.01). IGF1 treatment resulted in distinct apical fibronectin staining on blastocysts, which was reduced by the PI3 kinase inhibitor LY294002. This coincided with a significant increase in blastocyst outgrowth in the presence of IGF1 (P < 0.01) or fibronectin (P < 0.001), which was abolished by LY294002 (P < 0.001). Apical expression of integrin αvβ3, β3 and β1 in Ishikawa cells was unaltered by IGF1. However, IGF1 increased phosphorylated FAK (P < 0.05) and total FAK expression in Ishikawa cells. FAK signalling is linked to integrin activation and can affect the integrins' ability to bind and recognize extracellular matrix proteins such as fibronectin. Treatment of blastocysts with IGF1 before co-culture with Ishikawa cells increased their attachment (P < 0.05). This effect was abolished in the presence of LY294002 (P < 0.001) or an IGF1R neutralizing antibody (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study uses an in vitro model of attachment that uses mouse blastocysts and human endometrial cells. This involves a species crossover and although this use has been well documented as a model for attachment (as human embryo numbers are limited) the results should be interpreted carefully.

WIDER IMPLICATIONS OF THE FINDINGS

This study presents mechanisms by which IGF1 improves attachment of blastocysts to Ishikawa cells and documents for the first time how IGF1 can increase adhesion competency in blastocysts. Failure of the blastocyst to implant is the major cause of human assisted reproductive technology (ART) failure. As growth factors are absent during embryo culture, their addition to embryo culture medium is a potential avenue to improve IVF success. In particular, IGF1 could prove to be a potential treatment for blastocysts before transfer to the uterus in an ART setting.

Up-regulation of thrombospondin-2 in Akt1-null mice contributes to compromised tissue repair due to abnormalities in fibroblast function

Vascular remodeling is essential for tissue repair and is regulated by multiple factors, including thrombospondin-2 (TSP2) and hypoxia/VEGF-induced activation of Akt. In contrast to TSP2 knock-out (KO) mice, Akt1 KO mice have elevated TSP2 expression and delayed tissue repair. To investigate the contribution of increased TSP2 to Akt1 KO mice phenotypes, we generated Akt1/TSP2 double KO (DKO) mice. Full-thickness excisional wounds in DKO mice healed at an accelerated rate when compared with Akt1 KO mice. Isolated dermal Akt1 KO fibroblasts expressed increased TSP2 and displayed altered morphology and defects in migration and adhesion. These defects were rescued in DKO fibroblasts or after TSP2 knockdown. Conversely, the addition of exogenous TSP2 to WT cells induced cell morphology and migration rates that were similar to those of Akt1 KO cells. Akt1 KO fibroblasts displayed reduced adhesion to fibronectin with manganese stimulation when compared with WT and DKO cells, revealing an Akt1-dependent role for TSP2 in regulating integrin-mediated adhesions; however, this effect was not due to changes in β1 integrin surface expression or activation. Consistent with these results, Akt1 KO fibroblasts displayed reduced Rac1 activation that was dependent upon expression of TSP2 and could be rescued by a constitutively active Rac mutant. Our observations show that repression of TSP2 expression is a critical aspect of Akt1 function in tissue repair.

Differential effects of Akt1 signaling on short- versus long-term consequences of myocardial infarction and reperfusion injury

A specific role for Akt1 in events following myocardial infarction (MI) and ischemia/reperfusion (I/R) injury is not known. We aimed to determine whether Akt1 deletion in in vivo mouse models of MI and after ischemia I/R injury would alter myocyte survival, cardiac function, and fibrosis. Akt1(+/+) and Akt1(-/-) mice were subjected to MI and I/R, followed by assessment of downstream signaling events and functional consequences. Although no difference in infarct size following short-term MI was observed between Akt1(+/+) and Akt1(-/-) mice, I/R caused substantially more cardiomyocyte apoptosis and tissue damage in Akt1(-/-) mice compared with Akt1(+/+). Importantly, these effects were reversed upon pretreatment with GSK-3 inhibitor SB415286. Counterintuitively, Akt1(-/-) hearts exhibited improved cardiac function following long-term MI compared with Akt1(+/+) and were associated with reduced fibrosis in the left ventricle (LV). Our results demonstrate that Akt1-mediated inhibition of GSK-3 activity is critical for cardioprotection following I/R. However, in the long term, Akt1 contributes to fibrosis in post-MI hearts and might exacerbate cardiac dysfunction showing dichotomous role for Akt1 in cardiac remodeling after MI. Our data suggest that better understanding of the Akt1/GSK-3 pathway may provide insights for better therapeutic strategies in post-MI tissues.

Multiple roles of toll-like receptor 4 in colorectal cancer

Toll-like receptor (TLR) signaling has been implicated in the inflammatory responses in intestinal epithelial cells (IECs). Such inflammatory signals mediate complex interactions between commensal bacteria and TLRs and are required for IEC proliferation, immune response, repair, and homeostasis. The upregulation of certain TLRs in colorectal cancer (CRC) tissues suggests that TLRs may play an essential role in the prognosis of chronic and inflammatory diseases that ultimately culminate in CRC. Here, we provide a comprehensive review of the literature on the involvement of the TLR pathway in the initiation, progression, and metastasis of CRC, as well as inherited genetic variation and epigenetic regulation. The differential expression of TLRs in epithelial cells has also been discussed. In particular, we emphasize the physiological role of TLR4 in CRC development and pathogenesis, and propose novel and promising approaches for CRC therapeutics with the aid of TLR ligands.

Androgen receptor enhances cell adhesion and decreases cell migration via modulating β1-integrin-AKT signaling in hepatocellular carcinoma cells

The androgen receptor (AR) has been shown to promote the initiation and development of hepatocellular carcinoma (HCC) during the early stage of the disease process and to suppress HCC cell invasion during the later stages of the disease. The mechanisms governing these dual yet opposite roles have yet to be elucidated. Using carcinogen-induced HCC in vivo mouse models and the in vitro human HCC cell line SKhep1, we found that knockout of AR in primary HCC cells led to a decrease in HCC cell focal adhesion capacity compared to cells from wildtype mice. Similar results were obtained after adding functional AR into human HCC SKhep1 cells. Further analysis revealed that the role AR plays in adhesion of HCC cells is governed, at least in part, by its ability to up-regulate β1-integrin and activate the PI3K/AKT pathway. We also found that AR-β1-integrin-mediated cell adhesion suppresses cell migration. Those findings indicate that the AR-β1-integrin-PI3K/AKT signaling pathway might play a role in the bimodal function of AR on cell adhesion and migration at the cellular level.

Multimodal imaging reveals a role for Akt1 in fetal cardiac development

Even though congenital heart disease is the most prevalent malformation, little is known about how mutations affect cardiovascular function during development. Akt1 is a crucial intracellular signaling molecule, affecting cell survival, proliferation, and metabolism. The aim of this study was to determine the role of Akt1 on prenatal cardiac development. In utero echocardiography was performed in fetal wild-type, heterozygous, and Akt1-deficient mice. The same fetal hearts were imaged using ex vivo micro-computed tomography (μCT) and histology. Neonatal hearts were imaged by in vivo magnetic resonance imaging. Additional ex vivo neonatal hearts were analyzed using histology and real-time PCR of all three groups. In utero echocardiography revealed abnormal blood flow patterns at the mitral valve and reduced contractile function of Akt1 null fetuses, while ex vivo μCT and histology unraveled structural alterations such as dilated cardiomyopathy and ventricular septum defects in these fetuses. Further histological analysis showed reduced myocardial capillaries and coronary vessels in Akt1 null fetuses. At neonatal age, Akt1-deficient mice exhibited reduced survival with reduced endothelial cell density in the myocardium and attenuated cardiac expression of vascular endothelial growth factor A and collagen Iα1. To conclude, this study revealed a central role of Akt1 in fetal cardiac function and myocardial angiogenesis inducing fetal cardiomyopathy and reduced neonatal survival. This study links a specific physiological phenotype with a defined genotype, namely Akt1 deficiency, in an attempt to pinpoint intrinsic causes of fetal cardiomyopathies.

FOXO1 regulates expression of a microRNA cluster on X chromosome

Phosphoinositol-3-kinase (PI3K) pathway is a crucial modulator of many physiological and pathophysiological phenomena, including aging, diabetes and cancer. Protein kinase Akt, a downstream effector of PI3K, controls a plethora of cellular functions, including gene transcription. A key mechanism connecting Akt activity to changes in gene expression is inhibitory phosphorylation of FOXO family of transcription factors. Accordingly, altered expression of FOXO targets may account for many biological consequences of PI3K/Akt signaling. While the previous efforts focused on FOXO-dependent regulation of protein-coding genes, non-coding RNA genes have emerged as equally important targets of many transcription factors. Therefore, we utilized a regulated form of FOXO1 to profile FOXO1-dependent changes in miRNA expression in human cells. Both microarray hybridization and next-generation sequencing revealed changes in the products of a miRNA cluster on X chromosome. Rapid induction of these miRNAs occurred independently of de novo protein synthesis. Furthermore, inhibition of PI3K in cancer cell lines caused derepression of these miRNAs, as would be expected for FOXO-regulated genes. Members of the major oncogenic cascades are significantly overrepresented among the predicted targets of the miRNAs, consistent with tumor-suppressive role of FOXO1. The discovered miRNAs represent new candidate mediators of FOXO1 functions and possible biomarkers of its activity.

Akt1 mediates α-smooth muscle actin expression and myofibroblast differentiation via myocardin and serum response factor

Myofibroblast (MF) differentiation, marked by the de novo expression of smooth muscle α-actin (αSMA) stress fibers, plays a central role in wound healing and its persistence is a hallmark of fibrotic diseases. We have previously shown that Akt1 is necessary for wound healing through matrix regulation. However, the role of Akt1 in regulating MF differentiation with implications in fibrosis remains poorly defined. Here, we show that sustained activation of Akt1 was associated with a 6-fold increase in αSMA expression and assembly; an effect that is blunted in cells expressing inactive Akt1 despite TGFβ stimulation. Mechanistically, Akt1 mediated TGFβ-induced αSMA synthesis through the contractile gene transcription factors myocardin and serum response factor (SRF), independent of mammalian target of rapamycin in mouse embryonic fibroblasts and fibroblasts overexpressing active Akt1. Akt1 deficiency was associated with decreased myocardin, SRF, and αSMA expressions in vivo. Furthermore, sustained Akt1-induced αSMA synthesis markedly decreased upon RNA silencing of SRF and myocardin. In addition to its integral role in αSMA synthesis, we also show that Akt1 mediates fibronectin splice variant expression, which is required for MF differentiation, as well as total fibronectin, which generates the contractile force that promotes MF differentiation. In summary, our results constitute evidence that sustained Akt1 activation is crucial for TGFβ-induced MF formation and persistent differentiation. These findings highlight Akt1 as a novel potential therapeutic target for fibrotic diseases.

Interference with akt signaling protects against myocardial infarction and death by limiting the consequences of oxidative stress

The intricacy of multiple feedback loops in the pathways downstream of Akt allows this kinase to control multiple cellular processes in the cardiovascular system and precludes inferring consequences of its activation in specific pathological conditions. Akt1, the major Akt isoform in the heart and vasculature, has a protective role in the endothelium during atherosclerosis. However, Akt1 activation may also have detrimental consequences in the cardiovascular system. Mice lacking both the high-density lipoprotein receptor SR-BI (scavenger receptor class B type I) and ApoE (apolipoprotein E), which promotes clearance of remnant lipoproteins, are a model of severe dyslipidemia and spontaneous myocardial infarction. We found that Akt1 was activated in these mice, and this activation correlated with cardiac dysfunction, hypertrophy, and fibrosis; increased infarct area; cholesterol accumulation in macrophages and atherosclerosis; and reduced life span. Akt1 activation was associated with inflammation, oxidative stress, accumulation of oxidized lipids, and increased abundance of CD36, a major sensor of oxidative stress, and these events created a positive feedback loop that exacerbated the consequences of oxidative stress. Genetic deletion of Akt1 in this mouse model resulted in decreased mortality, alleviation of multiple complications of heart disease, and reduced occurrence of spontaneous myocardial infarction. Thus, interference with Akt1 signaling in vivo could be protective and improve survival under dyslipidemic conditions by reducing oxidative stress and responses to oxidized lipids.

P38MAP kinase, but not phosphoinositol-3 kinase, signal downstream of glutamine-mediated fibronectin-integrin signaling after intestinal injury

Background

Glutamine appears to mediate protection against gut injury via multiple pathways. These include fibronectin-integrin, PI3-K/MAPK pathways, and activation of heat shock protein (HSP) response. We hypothesize there may be a relationship between these pathways mediating glutamine’s protection in intestinal epithelial-6 cells after heat stress. We assessed whether p38MAPK and PI3-K/Akt signaling are involved in glutamine’s cytoprotective mechanism and the role they play in glutamine-mediated protection in conjunction with fibronectin-integrin osmosignaling after hyperthermia.

Methods

Intestinal epithelial cells were treated for 15 min with glutamine, with/without the fibronectin-integrin interaction inhibitor GRGDSP, inactive control peptide GRGESP, p38MAPK inhibitor SB203580, or PI3-K/Akt inhibitor LY294002 under basal (37°C) and stressed (43°C or 44°C) conditions. Cell survival was measured via MTS assay 24 h post-heat stress (44°C × 50 min). Total p38MAPK, [T(P)¹⁸⁰/Y(P)¹⁸²]p38MAPK, total Akt, [S(P)⁴⁷³]Akt, HSP70, FN, and caspase-3 levels were determined via Western blot after non-lethal HS (43°C × 50 min). Additionally, HSP70 levels were assessed via Western blot and ELISA.

Results

We were able to show that GRGDSP and LY294002 attenuated glutamine’s protective effect. However, SB203580 increased cell survival after heat stress. LY294002 attenuated glutamine-mediated increases in fibronectin and in HSP70 expression after hyperthermia. GRGDSP increased glutamine-mediated attenuations in p38MAPK phosphorylation, but had no effect on glutamine-mediated augmentations in Akt phosphorylation.

Conclusions

These data suggest that glutamine is protective after heat stress by activating PI3-K/Akt signaling preventing fibronectin-integrin expression and increasing HSP70 expression. Furthermore, dephosphorylation of p38MAPK after heat stress plays an important role in glutamine-mediated cellular protection. However, p38MAPK, but not PI3-K/Akt, signals downstream of glutamine-mediated fibronectin-integrin signaling after hyperthermia.

P21 activated kinase-1 (Pak1) promotes prostate tumor growth and microinvasion via inhibition of transforming growth factor β expression and enhanced matrix metalloproteinase 9 secretion

P21-activated kinases (Paks) are major effectors downstream of the small Rho family of GTPases. Among the six isoforms, Pak1 is the most ubiquitous and the best characterized member. Previous studies have shown that inhibition of Pak6, which is predominantly present in the prostate compared with other tissues, inhibits prostate tumor growth in vivo. Even though Pak1 has been identified in normal prostatic epithelial cells and cancer cells, its specific role in the development of prostate cancer remains unclear. We report here that highly invasive prostate cancer cells express significantly higher levels of Pak1 protein compared with non-invasive prostate cancer cells. Furthermore, prostate tumor tissues and prostate cancer metastasized to lungs showed a higher expression of Pak1 compared with normal tissues. Interestingly, Pak6 protein expression levels did not change with the invasive/metastatic potential of the cancer cells or tumors. Although inhibition of Pak1, and not Pak6, resulted in impaired PC3 cell migration, the effects of Pak1 knockdown on transendothelial migration (microinvasion), tumor growth, and tumor angiogenesis was higher compared with Pak6 knockdown. Finally, gene array data revealed reduced expression of matrix metalloproteinase 9 with the ablation of either Pak1 or Pak6 gene expression in PC3 cells, whereas protein levels of TGFβ was elevated significantly with specific modulation of Pak1 activity or ablation of the Pak1 gene. Our observations suggest that although some level of functional redundancy exists between Pak1 and Pak6 in prostate cancer cells, targeting Pak1 is a potential option for the management of prostate tumor growth, microinvasion, and metastasis.

Defining Akt actions in muscle differentiation

Muscle development in childhood and muscle regeneration in adults are highly regulated processes that are necessary for reaching and maintaining optimal muscle mass and strength throughout life. Muscle repair after injury relies on stem cells, termed satellite cells, whose activity is controlled by complex signals mediated by cell-cell contact, by growth factors, and by hormones, which interact with genetic programs controlled by myogenic transcription factors. Insulin-like growth factors (IGFs) play key roles in muscle development and help coordinate muscle repair after injury, primarily by stimulating the phosphatidylinositol 3-kinase-Akt signaling pathway, and both in vitro and in vivo studies have shown that Akt kinase activity is critical for optimal muscle growth and regeneration. Here we find that of the two Akts expressed in muscle, Akt1 is essential for initiation of differentiation in culture and is required for normal myoblast motility, while Akt2 is dispensable. Although Akt2 deficiency did lead to diminished myotube maturation, as assessed by a decline in myofiber area and in fusion index, either Akt1 or Akt2 could restore these processes toward normal. Thus levels of Akt expression rather than distinct actions of individual Akt species are critical for normal myofiber development during the later stages of muscle differentiation.