c-jun amino-terminal kinase and mitogen activated protein kinase 1/2 mediate hepatocyte growth factor-induced migration of brain endothelial cells

PGE2 -induced migration of human brain endothelial cell is mediated though protein kinase A in cooperation of EP receptors

PGE₂ plays a critical role in angiogenesis, ischemic, and neuro-inflammatory disorders of the brain, which breakdown the blood-brain barrier (BBB). However, the effects of PGE₂ on human brain endothelial cell (HBECs) migration, a key process in the angiogenic response and BBB stability, are not well defined. In this study, we investigated the mechanism of PGE₂ in HBECs migration in vitro. Here we showed that PGE₂ stimulated migration of HBECs in a dose-time and matrix-dependent manner, evaluated by the Boyden chamber assay, but other prostanoids failed to do so. PGE₂ receptor (EP2; butaprost), EP3 (sulprostone), and EP4 (PGE₁ -OH) receptor agonists stimulated HBECs migration, but the silencing of EP significantly attenuated this effect. EP1 agonist (11-trinor PGE₁ ) had no effect on HBECs migration on silencing of the EP1 receptor. We further showed that PGE₂ stimulated cAMP production and activated protein kinase A (PKA), whereas pretreatment with the adenyl cyclase inhibitor (dideoxyadenosine; 1 μM) or PKA inhibitors, H89 (0.5 μM)/PKAI (1 μM), completely abrogated PGE₂ -induced migration. Furthermore, silencing of the EP2/EP4 receptors significantly inhibited PGE₂ -induced cAMP and PKA activation, whereas EP3 receptor silencing failed to do so. These results suggest that PGE₂ regulates HBEC migration via cooperation of EP2, EP3, and EP4 receptors. Coupling of PGE₂ to these receptors resulted in increased production of cAMP, which regulates HBEC migration via PKA pathway. The elucidation of molecular events involved is critical for the development of targeted strategies to treat cerebrovascular diseases associated with dysregulated angiogenesis.

A BMP7 Variant Inhibits Tumor Angiogenesis In Vitro and In Vivo through Direct Modulation of Endothelial Cell Biology

Bone morphogenetic proteins (BMPs), members of the TGF-β superfamily, have numerous biological activities including control of growth, differentiation, and vascular development. Using an in vitro co-culture endothelial cord formation assay, we investigated the role of a BMP7 variant (BMP7v) in VEGF, bFGF, and tumor-driven angiogenesis. BMP7v treatment led to disruption of neo-endothelial cord formation and regression of existing VEGF and bFGF cords in vitro. Using a series of tumor cell models capable of driving angiogenesis in vitro, BMP7v treatment completely blocked cord formation. Pre-treatment of endothelial cells with BMP7v significantly reduced their cord forming ability, indicating a direct effect on endothelial cell function. BMP7v activated the canonical SMAD signaling pathway in endothelial cells but targeted gene knockdown using shRNA directed against SMAD4 suggests this pathway is not required to mediate the anti-angiogenic effect. In contrast to SMAD activation, BMP7v selectively decreased ERK and AKT activation, significantly decreased endothelial cell migration and down-regulated expression of critical RTKs involved in VEGF and FGF angiogenic signaling, VEGFR2 and FGFR1 respectively. Importantly, in an in vivo angiogenic plug assay that serves as a measurement of angiogenesis, BMP7v significantly decreased hemoglobin content indicating inhibition of neoangiogenesis. In addition, BMP7v significantly decreased angiogenesis in glioblastoma stem-like cell (GSLC) Matrigel plugs and significantly impaired in vivo growth of a GSLC xenograft with a concomitant reduction in microvessel density. These data support BMP7v as a potent anti-angiogenic molecule that is effective in the context of tumor angiogenesis.

PKCε-mediated c-Met endosomal processing directs fluctuant c-Met-JNK-paxillin signaling for tumor progression of HepG2

Hepatocyte growth factor (HGF) induced c-Met signaling play critical roles in the progression of hepatocellular carcinoma (HCC). However, c-Met targeting approaches suffered resistance and side effect, thus identification of more suitable downstream targets is needed. Recently, we demonstrated HGF-induced fluctuant ERK/paxillin signaling within 24h. We further examined the underlying mechanisms for fluctuant c-Met/JNK/paxillin signal cascade within 12h. HGF-induced phosphorylation of c-Met, JNK, and paxillin (Ser178) shared a common fluctuation pattern characterized by an initial peak at 0.5h, a middle drop at 4h, and a later peak at 10h. Dynasore, the inhibitor of dynamin, suppressed HGF-induced c-Met internalization and phosphorylation of JNK and paxillin (Ser178) at 0.5h, indicating that endosome formation is required for initial signal enhancement. Further, depletion of PKCε not only enhanced HGF-induced phosphorylation of JNK and paxillin (Ser178) but also prevented c-Met degradation at 0.5h, suggesting that PKCε mediated c-Met degradation for signal declination. On the other hand, HGF induced colocalizations of both phosphorylated JNK and paxillin with the endosomal recycling protein GGA3 at 10h and depletion of GGA3 abolished membrane recycling of c-Met and phosphorylation of JNK/paxillin at the same time point. Interestingly, HGF induced GGA3 phosphorylation in a PKCε-dependent manner during 0.5-4h, which is associated with c-Met degradation in the same period. Finally, HGF-induced cell migration, invasion and intrahepatic metastasis of HepG2 were prevented by the inhibitors of endocytosis. Our results suggest that critical endosomal components are promising therapeutic targets for preventing HGF-induced progression of HCC.

Arachidonic acid induces brain endothelial cell apoptosis via p38-MAPK and intracellular calcium signaling

Arachidonic acid (AA), a bioactive fatty acid whose levels increase during neuroinflammation, contributes to cerebral vascular damage and dysfunction. However, the mode of injury and underlying signaling mechanisms remain unknown. Challenge of primary human brain endothelial cells (HBECs) with AA activated a stress response resulting in caspase-3 activation, poly(ADP-ribose) polymerase cleavage, and disruption of monolayer integrity. AA also induced loss of mitochondrial membrane potential and cytochrome c release consistent with activation of intrinsic apoptosis. HBEC stimulation with AA resulted in sustained p38-MAPK activation and subsequent phosphorylation of mitogen-activated protein kinase activated protein-2 (MAPKAP-2) kinase and heat shock protein-27 (Hsp27). Conversely, other unsaturated and saturated fatty acids had no effect. Pharmacological and RNA interference-mediated p38α or p38β suppression abrogated AA signaling to caspase-3 and Hsp27, suggesting involvement of both p38 isoforms in AA-induced HBEC apoptosis. Hsp27 silencing also blocked caspase-3 activation. AA stimulated intracellular calcium release, which was attenuated by inositol 1,4,5-trisphosphate (IP3) receptor antagonists. Blockade of intracellular calcium release decreased caspase-3 activation, but had no effect on AA-induced p38-MAPK activation. However, inhibition of p38-MAPK or blockade of intracellular calcium mobilization abrogated AA-induced cytochrome c release. AA-induced caspase-3 activation was abrogated by pharmacological inhibition of lipooxygenases. These findings support a previously unrecognized signaling cooperation between p38-MAPK/MAPKAP-2/Hsp27 and intracellular calcium release in AA-induced HBEC apoptosis and suggest its relevance to neurological disorders associated with vascular inflammation.

Profiling the dynamics of a human phosphorylome reveals new components in HGF/c-Met signaling

Protein phosphorylation is a dynamic and reversible event that greatly influences cellular function. Identifying the key regulatory elements that determine cellular phenotypes during development and oncogenesis requires the ability to dynamically monitor proteome-wide events. Here, we report the development of a new strategy to monitor dynamic changes of protein phosphorylation in cells and tissues using functional protein microarrays as the readout. To demonstrate this technology's ability to identify condition-dependent phosphorylation events, human protein microarrays were incubated with lysates from cells or tissues under activation or inhibition of c-Met, a receptor tyrosine kinase involved in tissue morphogenesis and malignancy. By comparing the differences between the protein phosphorylation profiles obtained using the protein microarrays, we were able to recover many of the proteins that are known to be specifically activated (i.e., phosphorylated) upon c-Met activation by the hepatocyte growth factor (HGF). Most importantly, we discovered many proteins that were differentially phosphorylated by lysates from cells or tissues when the c-Met pathway was active. Using phosphorylation-specific antibodies, we were able to validate several candidate proteins as new downstream components of the c-Met signaling pathway in cells. We envision that this new approach, like its DNA microarray counterpart, can be further extended toward profiling dynamics of global protein phosphorylation under many different physiological conditions both in cellulo and in vivo in a high-throughput and cost-effective fashion.

Therapeutic implications of disorders of cell death signalling: membranes, micro-environment, and eicosanoid and docosanoid metabolism

Disruptions of cell death signalling occur in pathological processes, such as cancer and degenerative disease. Increased knowledge of cell death signalling has opened new areas of therapeutic research, and identifying key mediators of cell death has become increasingly important. Early triggering events in cell death may provide potential therapeutic targets, whereas agents affecting later signals may be more palliative in nature. A group of primary mediators are derivatives of the highly unsaturated fatty acids (HUFAs), particularly oxygenated metabolites such as prostaglandins. HUFAs, esterified in cell membranes, act as critical signalling molecules in many pathological processes. Currently, agents affecting HUFA metabolism are widely prescribed in diseases involving disordered cell death signalling. However, partly due to rapid metabolism, their role in cell death signalling pathways is poorly characterized. Recently, HUFA-derived mediators, the resolvins/protectins and endocannabinoids, have added opportunities to target selective signals and pathways. This review will focus on the control of cell death by HUFA, eicosanoid (C20 fatty acid metabolites) and docosanoid (C22 metabolites), HUFA-derived lipid mediators, signalling elements in the micro-environment and their potential therapeutic applications. Further therapeutic approaches will involve cell and molecular biology, the multiple hit theory of disease progression and analysis of system plasticity. Advances in the cell biology of eicosanoid and docosanoid metabolism, together with structure/function analysis of HUFA-derived mediators, will be useful in developing therapeutic agents in pathologies characterized by alterations in cell death signalling.

c-Jun N-terminal kinase phosphorylation of MARCKSL1 determines actin stability and migration in neurons and in cancer cells

Cell migration is a fundamental biological function, critical during development and regeneration, whereas deregulated migration underlies neurological birth defects and cancer metastasis. MARCKS-like protein 1 (MARCKSL1) is widely expressed in nervous tissue, where, like Jun N-terminal protein kinase (JNK), it is required for neural tube formation, though the mechanism is unknown. Here we show that MARCKSL1 is directly phosphorylated by JNK on C-terminal residues (S120, T148, and T183). This phosphorylation enables MARCKSL1 to bundle and stabilize F-actin, increase filopodium numbers and dynamics, and retard migration in neurons. Conversely, when MARCKSL1 phosphorylation is inhibited, actin mobility increases and filopodium formation is compromised whereas lamellipodium formation is enhanced, as is cell migration. We find that MARCKSL1 mRNA is upregulated in a broad range of cancer types and that MARCKSL1 protein is strongly induced in primary prostate carcinomas. Gene knockdown in prostate cancer cells or in neurons reveals a critical role for MARCKSL1 in migration that is dependent on the phosphorylation state; phosphomimetic MARCKSL1 (MARCKSL1(S120D,T148D,T183D)) inhibits whereas dephospho-MARCKSL1(S120A,T148A,T183A) induces migration. In summary, these data show that JNK phosphorylation of MARCKSL1 regulates actin homeostasis, filopodium and lamellipodium formation, and neuronal migration under physiological conditions and that, when ectopically expressed in prostate cancer cells, MARCKSL1 again determines cell movement.

Matrix-Bound VEGF Mimetic Peptides: Design and Endothelial Cell Activation in Collagen Scaffolds

Long term survival and success of artificial tissue constructs depend greatly on vascularization. Endothelial cell (EC) differentiation and vasculature formation are dependent on spatio-temporal cues in the extracellular matrix that dynamically interact with cells, a process difficult to reproduce in artificial systems. Here we present a novel bifunctional peptide that mimics matrix-bound vascular endothelial growth factor (VEGF) and can be used to encode spatially controlled angiogenic signals in collagen scaffolds. The peptide is comprised of a collagen mimetic domain that was previously reported to bind to type I collagen by a unique hybridization mechanism, and a VEGF mimetic domain with pro-angiogenic activity. Circular dichroism and collagen binding studies confirm the triple helical structure and the collagen binding affinity of the collagen mimetic domain, and EC culture studies demonstrate the peptide's ability to induce endothelial cell morphogenesis and network formation as a matrix-bound factor in 2D and 3D collagen scaffolds. We also show spatial modification of collagen substrates with this peptide that allows localized EC activation and network formation. These results demonstrate that the peptide can be used to present spatially directed angiogenic cues in collagen scaffolds, which may be useful for engineering organized microvasculature.

Hepatocyte growth factor induces a proangiogenic phenotype and mobilizes endothelial progenitor cells by activating Nox2

Hepatocyte growth factor (HGF) by stimulating the receptor tyrosine kinase c-Met induces angiogenesis and tissue regeneration. HGF has been shown to antagonize the angiotensin II-induced senescence of endothelial progenitor cells (EPCs), which is mediated by NADPH oxidase-dependent reactive oxygen species (ROS) formation. As growth factors, however, usually require ROS for their signaling, we hypothesized that the proangiogenic effects of HGF require NADPH oxidases and focused on the homolog Nox2, which is most abundantly expressed in EPCs and endothelial cells. Indeed, HGF increased the H(2)O(2) formation in EPCs and human umbilical vein endothelial cells (HUVECs), and this effect was not observed in Nox2-deficient cells. HGF induced the mobilization of EPCs and vascular outgrowth from aortic explants in wild-type (WT) but not Nox2(y/-) mice. HGF also stimulated migration and tube formation in HUVECs, and antisense oligonucleotides against Nox2 prevented this effect. To identify the signal transduction underlying these effects, we focused on the kinases Jak2 and Jnk. In HUVECs, HGF increased the phosphorylation of these in a Nox2-dependent manner as demonstrated by antisense oligonucleotides. Also, the HGF-induced Jak2-dependent activation of a STAT3 reporter construct was attenuated after downregulation of Nox2. Accordingly, the HGF-stimulated tube formation of HUVEC was blocked by inhibitors of Jak2 and Jnk. In vivo treatment with the Jnk inhibitor SP600125 blocked the HGF-induced mobilization of EPCs. Ex vivo, SP600125 blocked HGF-induced migration and tube formation. We conclude that HGF-induced mobilization of EPCs and the proangiogenic effects of the growth factor require a Nox2-dependent ROS-mediated activation of Jak2 and Jnk.

Hepatocyte growth factor-induced c-Src-phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathway inhibits dendritic cell activation by blocking IκB kinase activity

Hepatocyte growth factor modulates activation and antigen-presenting cell function of dendritic cells. However, the molecular basis for immunoregulation of dendritic cells by hepatocyte growth factor is undefined. In the current study, we demonstrate that hepatocyte growth factor exhibits inhibitory effect on dendritic cell activation by blocking IκB kinase activity and subsequent nuclear factor-κB activation. Inhibition of IκB kinase is mediated by hepatocyte growth factor-induced activation of c-Src. Proximal signaling events induced in dendritic cells by hepatocyte growth factor include a physical association of c-Src with the hepatocyte growth factor receptor c-MET and concomitant activation of c-Src. Activation of c-Src in turn establishes a complex consisting of phosphatidylinositol 3-kinase and c-MET, and promotes downstream activation of the phosphatidylinositol 3-kinase/AKT pathway and mammalian target of rapamycin. Blocking activation of c-Src, phosphatidylinositol 3-kinase and mammalian target of rapamycin prevents hepatocyte growth factor-induced inhibition of IκB kinase, nuclear factor-κB and dendritic cell activation. Notably, hepatocyte growth factor-stimulated c-Src activation results in induction of phosphatidylinositol 3-kinase complexes p85α/p110α and p85α/p110δ, which is required for activation of mammalian target of rapamycin, and consequent inhibition of IκB kinase and nuclear factor-κB activation. Our findings, for the first time, have identified the c-Src-phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathway that plays a pivotal role in mediating the inhibitory effects of hepatocyte growth factor on dendritic cell activation by blocking nuclear factor-κB signaling.

Fluid shear stress-induced JNK activity leads to actin remodeling for cell alignment

Fluid shear stress (FSS) exerted on endothelial cell (EC) surfaces induces actin cytoskeleton remodeling through mechanotransduction. This study was designed to determine whether FSS activates Jun N-terminal kinase (JNK), to examine the spatial and temporal distribution of active JNK relative to the actin cytoskeleton in ECs exposed to different FSS conditions, and to evaluate the effects of active JNK on actin realignment. Exposure to 15 and 20 dyn/cm(2) FSS induced higher activity levels of JNK than the lower 2 and 4 dyn/cm(2) flow conditions. At the higher FSS treatments, JNK activity increased with increasing exposure time, peaking 30 min after flow onset with an eightfold activity increase compared to cells in static culture. FSS-induced phospho-JNK co-localized with actin filaments at cell peripheries, as well as with stress fibers. Pharmacologically blocking JNK activity altered FSS-induced actin structure and distribution as a response to FSS. Our results indicate that FSS-induced actin remodeling occurs in three phases, and that JNK plays a role in at least one, suggesting that this kinase activity is involved in mechanotransduction from the apical surface to the actin cytoskeleton in ECs.

Deciphering mechanisms controlling placental artery endothelial cell migration stimulated by vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) stimulated fetoplacental artery endothelial (oFPAE) cell migration and activated multiple signaling pathways including ERK2/1, p38MAPK, Jun N-terminal kinase (JNK1/2), v-Akt murine thymoma viral oncogene homolog 1 (Akt1), and c-Src in oFPAE cells. VEGF-induced cell migration was blocked by specific kinase inhibitors of JNK1/2 (SP600125), c-Src (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d] pyrimidine), and phosphatidylinositol 3-kinase/Akt (wortmannin) but not ERK2/1 (U0126) and p38MAPK (SB203580). VEGF-induced cell migration was associated with dynamic actin reorganization and focal adhesion as evidenced by increased stress fiber formation and phosphorylation of cofilin-1 and focal adhesion kinase (FAK) and paxillin. Inhibition of JNK1/2, c-Src, and phosphatidylinositol 3-kinase/Akt suppressed VEGF-induced stress fiber formation and cofilin-1 phosphorylation. c-Src inhibition suppressed VEGF-induced phosphorylation of focal adhesion kinase, paxillin, and focal adhesion. VEGF-induced cell migration requires endogenous nitric oxide (NO) as: 1) VEGF-stimulated phosphorylation of endothelial NO synthase (eNOS) via activation of Akt, JNK1/2, and Src; 2) a NO donor diethylenetriamine-NO-stimulated cell migration; and 3) NO synthase inhibition blocked VEGF-induced cell migration. Targeted down-regulation and overexpression of caveolin-1 both inhibited VEGF-induced cell migration. Caveolin-1 down-regulation suppressed VEGF-stimulated phosphorylation of Akt, JNK, eNOS, c-Src, and FAK; however, basal activities of c-Src and FAK were elevated in parallel with increased stress fiber formation and focal adhesion. Caveolin-1 overexpression also inhibited VEGF-induced phosphorylation of Akt, JNK, c-Src, FAK, and eNOS. Thus, VEGF-induced placental endothelial cell migration requires activation of complex pathways that are paradoxically regulated by caveolin-1.

Glioma cell death: cell-cell interactions and signalling networks

The prognosis for patients with malignant gliomas is poor, but improvements may emerge from a better understanding of the pathophysiology of glioma signalling. Recent therapeutic developments have implicated lipid signalling in glioma cell death. Stress signalling in glioma cell death involves mitochondria and endoplasmic reticulum. Lipid mediators also signal via extrinsic pathways in glioma cell proliferation, migration and interaction with endothelial and microglial cells. Glioma cell death and tumour regression have been reported using polyunsaturated fatty acids in animal models, human ex vivo explants, glioma cell preparations and in clinical case reports involving intratumoral infusion. Cell death signalling was associated with generation of reactive oxygen intermediates and mitochondrial and other signalling pathways. In this review, evidence for mitochondrial responses to stress signals, including polyunsaturated fatty acids, peroxidizing agents and calcium is presented. Additionally, evidence for interaction of glioma cells with primary brain endothelial cells is described, modulating human glioma peroxidative signalling. Glioma responses to potential therapeutic agents should be analysed in systems reflecting tumour connectivity and CNS structural and functional integrity. Future insights may also be derived from studies of signalling in glioma-derived tumour stem cells.

Involvement of Src tyrosine kinase in Escherichia coli invasion of human brain microvascular endothelial cells

Invasion of brain microvascular endothelial cells is a prerequisite for successful crossing of the blood-brain barrier by Escherichia coli (E. coli), but the underlying mechanism remains unclear. Here we showed activation of Src tyrosine kinase in E. coli K1 invasion of human brain microvascular endothelial cells (HBMEC). E. coli invasion of HBMEC and the E. coli-induced rearrangement of actin filaments were blocked by Src inhibitors. Overexpression of dominant-negative Src in HBMEC significantly attenuated E. coli invasion and the concomitant actin filaments rearrangement. Furthermore, E. coli K1-triggered phosphatidylinositol 3-kinase (PI3K) activation in HBMEC was effectively blocked by Src inhibitors and dominant-negative Src. These results demonstrated the involvement of Src and its interaction with PI3K in E. coli K1 invasion of HBMEC.

IFATS collection: Fibroblast growth factor-2-induced hepatocyte growth factor secretion by adipose-derived stromal cells inhibits postinjury fibrogenesis through a c-Jun N-terminal kinase-dependent mechanism

Adipose-derived stem/stromal cells (ASCs) not only function as tissue-specific progenitor cells but also are multipotent and secrete angiogenic growth factors, such as hepatocyte growth factor (HGF), under certain circumstances. However, the biological role and regulatory mechanism of this secretion have not been well studied. We focused on the role of ASCs in the process of adipose tissue injury and repair and found that among injury-associated growth factors, fibroblast growth factor-2 (FGF-2) strongly promoted ASC proliferation and HGF secretion through a c-Jun N-terminal kinase (JNK) signaling pathway. In a mouse model of ischemia-reperfusion injury of adipose tissue, regenerative changes following necrotic and apoptotic changes were seen for 2 weeks. Acute release of FGF-2 by injured adipose tissue was followed by upregulation of HGF. During the adipose tissue remodeling process, adipose-derived 5-bromo-2-deoxyuridine-positive cells were shown to be ASCs (CD31-CD34+). Inhibition of JNK signaling inhibited the activation of ASCs and delayed the remodeling process. In addition, inhibition of FGF-2 or JNK signaling prevented postinjury upregulation of HGF and led to increased fibrogenesis in the injured adipose tissue. Increased fibrogenesis also followed the administration of a neutralizing antibody against HGF. FGF-2 released from injured tissue acts through a JNK signaling pathway to stimulate ASCs to proliferate and secrete HGF, contributing to the regeneration of adipose tissue and suppression of fibrogenesis after injury. This study revealed a functional role for ASCs in the response to injury and provides new insight into the therapeutic potential of ASCs.

Identification of pro-angiogenic markers in blood vessels from stroked-affected brain tissue using laser-capture microdissection

Background

Angiogenesis correlates with patient survival following acute ischaemic stroke, and survival of neurons is greatest in tissue undergoing angiogenesis. Angiogenesis is critical for the development of new microvessels and leads to re-formation of collateral circulation, reperfusion, enhanced neuronal survival and improved recovery.

Results

Here, we have isolated active (CD105/Flt-1 positive) and inactive (CD105/Flt-1 minus (n=5) micro-vessel rich-regions from stroke-affected and contralateral tissue of patients using laser-capture micro-dissection. Areas were compared for pro- and anti-angiogenic gene expression using targeted TaqMan microfluidity cards containing 46 genes and real-time PCR. Further analysis of key gene de-regulation was performed by immunohistochemistry to define localization and expression patterns of identified markers and de novo synthesis by human brain microvessel endothelial cells (HBMEC) was examined following oxygen-glucose deprivation (OGD). Our data revealed that seven pro-angiogenic genes were notably up-regulated in CD105 positive microvessel rich regions. These were, beta-catenin, neural cell adhesion molecule (NRCAM), matrix metalloproteinase-2 (MMP-2), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), hepatocyte growth factor-alpha (HGF-alpha), monocyte chemottractant protein-1 (MCP-1) and and Tie-2 as well as c-kit. Immunohistochemistry demonstrated strong staining of MMP-2, HGF-alpha, MCP-1 and Tie-2 in stroke-associated regions of active remodeling in association with CD105 positive staining. In vitro, OGD stimulated production of Tie-2, MCP-1 and MMP-2 in HBMEC, demonstrated a de novo response to hypoxia.

Conclusion

In this work we have identified concurrent activation of key angiogenic molecules associated with endothelial cell migration, differentiation and tube-formation, vessel stabilization and stem cell homing mechanisms in areas of revascularization. Therapeutic stimulation of these processes in all areas of damaged tissue might improve morbidity and mortality from stroke.

Hepatocyte growth factor suppresses ischemic cerebral edema in rats with microsphere embolism

The present study was aimed at determining whether human recombinant hepatocyte growth factor (HGF) ameliorates cerebral edema induced by microsphere embolism (ME). Rats were injected with 700 microspheres (48 microm in diameter). Continuous administration of HGF at 13 microg/3 days/animal into the right ventricle was started from 10 min after embolism to the end of the experiment by using an osmotic pump. On day 3 after the ME, the rats were anesthetized, and their brains were perfused with an isotonic mannitol solution to eliminate constituents in the vascular and extracellular spaces. Thereafter, tissue water and cation contents were determined. A significant increase in tissue water content of the right hemisphere by ME was seen. This ME-induced increase in water content was associated with increases in tissue sodium and calcium ion contents and decreases in tissue potassium and magnesium ion contents of the right hemisphere. The treatment of the animal with HGF suppressed the increases in water and sodium and calcium ion contents, but not the decreases in potassium and magnesium ion contents. These results suggest that HGF suppresses the formation of ischemic cerebral edema provoked intracellularly in rats with ME.

AIF-1 expression regulates endothelial cell activation, signal transduction, and vasculogenesis

Endothelial cell (EC) activation plays a key role in vascular inflammation, thrombosis, and angiogenesis. Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic, calcium-binding, inflammation-responsive scaffold protein that has been implicated in the regulation of inflammation. The expression and function of AIF-1 in EC is uncharacterized, and the purpose of this study was to characterize AIF-1 expression and function in ECs. AIF-1 expression colocalized with CD31-positive ECs in neointima of inflamed human arteries but not normal arteries. AIF-1 is detected at low levels in unstimulated EC, but expression can be increased in response to serum and soluble factors. Stable transfection of AIF-1 small interfering RNA (siRNA) in ECs reduced AIF-1 protein expression by 73% and significantly reduced EC proliferation and migration (P < 0.05 and 0.001). Rescue of AIF-1 expression restored both proliferation and migration of siRNA-expressing ECs, and AIF-1 overexpression enhanced both of these activities, suggesting a strong association between AIF-1 expression and EC activation. Activation of mitogen-activated protein kinase p44/42 and PAK1 was significantly reduced in siRNA ECs challenged with inflammatory stimuli. Reduction of AIF-1 expression did not decrease EC tube-like structure or microvessel formation from aortic rings, but overexpression of AIF-1 did significantly increase the number and complexity of these structures. These data indicate that AIF-1 expression plays an important role in signal transduction and activation of ECs and may also participate in new vessel formation.

Expression of hepatocyte growth factor and c-Met after spinal cord injury in rats

Since hepatocyte growth factor (HGF) plays a pivotal role in the development of the central nervous system and pathological conditions, we examined the long-term changes in the mRNA and protein expression of HGF and its receptor c-Met after spinal cord injury (SCI) in rats. HGF mRNA was significantly increased from 7 days after SCI in the injured segment, and the peak was at 7 days after SCI as assessed by real-time RT-PCR. Importantly, c-met mRNA expression was up-regulated from 1 day after SCI, and reached a peak at 14 days after SCI. Although up-regulation of HGF and c-met mRNA expression in the injured segment gradually decreased, the increased expression level persisted until 56 days after SCI. Consistent with HGF mRNA expression, HGF protein level was significantly increased mainly in the injured region, which persisted until 56 days after SCI. Immunohistochemistry showed that most of GFAP-positive reactive astrocytes expressed HGF and c-Met both on 14 days and 56 days after SCI. Staining with the mitotic indicator, bromodeoxyuridine (BrdU), revealed that a small number of BrdU-incorporated cells were co-localized with HGF/GFAP-positive or c-Met/GFAP-positive cells both on 14 and 56 days. These data suggest that HGF and c-Met were up-regulated mainly in the reactive astrocytes around the injured region in the subacute to chronic stage of spinal cord injury. Since HGF plays a critical role in neurotrophic activity, activation of the HGF/c-Met signaling system might be involved in the process of post-traumatic regeneration.

Immunologic and Stress Responses Following Video-Assisted Thoracic Surgery and Open Pulmonary Lobectomy in Early Stage Lung Cancer

Conventional open major surgery evokes an injury response involving endocrine, neural, and immunologic mechanisms. The immunologic responses are characterized by release of cytokines, inflammatory mediators, and acute-phase proteins and by adverse disturbances in immune cell function. The use of a minimal access approach strategy is associated with a significant reduction in the cytokine response, as exemplified by reduced interleukin-6 levels and a corresponding reduction in acute-phase protein generation with reduced C-reactive protein levels. Circulating immune cell function and numbers also are better preserved. These changes have been demonstrated in comparing open with video-assisted thoracoscopic surgery (VATS) lobectomy and, together with further investigation into local immune function, may offer some insight into the excellent survival data reported for VATS resection of stage I non-small cell lung cancer.