Kininostatin associates with membrane rafts and inhibits alpha(v)beta3 integrin activation in human umbilical vein endothelial cells

Small-Molecule Modulation of Lipid-Dependent Cellular Processes against Cancer: Fats on the Gunpoint

Lipid cell membrane composed of various distinct lipids and proteins act as a platform to assemble various signaling complexes regulating innumerous cellular processes which are strongly downregulated or altered in cancer cells emphasizing the still-underestimated critical function of lipid biomolecules in cancer initiation and progression. In this review, we outline the current understanding of how membrane lipids act as signaling hot spots by generating distinct membrane microdomains called rafts to initiate various cellular processes and their modulation in cancer phenotypes. We elucidate tangible drug targets and pathways all amenable to small-molecule perturbation. Ranging from targeting membrane rafts organization/reorganization to rewiring lipid metabolism and lipid sorting in cancer, the work summarized here represents critical intervention points being attempted for lipid-based anticancer therapy and future directions.

Contact pathway of coagulation and inflammation

The contact system, also named as plasma kallikrein-kinin system, consists of three serine proteinases: coagulation factors XII (FXII) and XI (FXI), and plasma prekallikrein (PK), and the nonenzymatic cofactor high molecular weight kininogen (HK). This system has been investigated actively for more than 50 years. The components of this system and their interactions have been elucidated from in vitro experiments, which indicates that this system is prothrombotic by activating intrinsic pathway, and proinflammatory by producing bioactive peptide bradykinin. Although the activation of the contact system have been implicated in various types of human disease, in only a few instances is its role clearly defined. In the last 10 years, our understanding of the contact system, particularly its biology and (patho)physiology has greatly increased through investigations using gene-modified animal models. In this review we will describe a revitalized view of the contact system as a critical (patho)physiologic mediator of coagulation and inflammation.

Nicotinamide phosphoribosyltransferase can affect metastatic activity and cell adhesive functions by regulating integrins in breast cancer

NAD(+) metabolism is an essential regulator of cellular redox reactions, energy pathways, and a substrate provider for NAD(+) consuming enzymes. We recently demonstrated that enhancement of NAD(+)/NADH levels in breast cancer cells with impaired mitochondrial NADH dehydrogenase activity, through augmentation of complex I or by supplementing tumor cell nutrients with NAD(+) precursors, inhibits tumorigenicity and metastasis. To more fully understand how aberrantly low NAD(+) levels promote tumor cell dissemination, we here asked whether inhibition of NAD(+) salvage pathway activity by reduction in nicotinamide phosphoribosyltransferase (NAMPT) expression can impact metastasis and tumor cell adhesive functions. We show that knockdown of NAMPT, the enzyme catalyzing the rate-limiting step of the NAD(+) salvage pathway, enhances metastatic aggressiveness in human breast cancer cells and involves modulation of integrin expression and function. Reduction in NAMPT expression is associated with upregulation of select adhesion receptors, particularly αvβ3 and β1 integrins, and results in increased breast cancer cell attachment to extracellular matrix proteins, a key function in tumor cell dissemination. Interestingly, NAMPT downregulation prompts expression of integrin αvβ3 in a high affinity conformation, known to promote tumor cell adhesive interactions during hematogenous metastasis. NAMPT has been selected as a therapeutic target for cancer therapy based on the essential functions of this enzyme in NAD(+) metabolism, cellular redox, DNA repair and energy pathways. Notably, our results indicate that incomplete inhibition of NAMPT, which impedes NAD(+) metabolism but does not kill a tumor cell can alter its phenotype to be more aggressive and metastatic. This phenomenon could promote cancer recurrence, even if NAMPT inhibition initially reduces tumor growth.

Cleaved high molecular weight kininogen stimulates JNK/FOXO4/MnSOD pathway for induction of endothelial progenitor cell senescence

OBJECTIVE

Recently we have reported that cleaved high molecular weight kininogen (HKa) accelerates the onset of endothelial progenitor cells (EPCs) senescence by induction of reactive oxygen species (ROS). However, the mechanisms by which HKa induces production of ROS remain unknown. In this study, we have shown that HKa induces EPC senescence via stimulation of c-Jun N-terminal kinases (JNK)-related pathway.

METHODS AND RESULTS

Treatment of human EPCs with HKa for 72h stimulated JNK phosphorylation at Thr183/Tyr185, and FOXO4 phosphorylation at Thr451, Concomitantly, upregulated the expression of MnSOD at protein and mRNA levels in a concentration-dependent manner. HKa increased intracellular level of H2O2, without affecting the expression of catalase. To narrow down the functional domain of HKa, recombinant proteins of human HK heavy chain (HC, 19-380aa) and light chain (LC, 390-644aa) were generated. HC, but not LC, increased senescence of EPCs and intracellular ROS levels, to a similar extent with HKa. Moreover, HC at 50 nM increased FOXO4 phosphorylation at Thr451 and the protein level of MnSOD in EPCs.

CONCLUSION

These results demonstrate that HKa accelerates the onset of EPC senescence by stimulating JNK/FOXO4/MnSOD pathway, its effect is mediated by the HC.

High molecular weight kininogen binds phosphatidylserine and opsonizes urokinase plasminogen activator receptor-mediated efferocytosis

Phagocytosis of apoptotic cells (efferocytosis) is essential for regulation of immune responses and tissue homeostasis and is mediated by phagocytic receptors. In this study, we found that urokinase plasminogen activator receptor (uPAR) plays an important role in internalization of apoptotic cells and also characterized the underlying mechanisms. In a flow cytometry-based phagocytic assay, uPAR-deficient macrophages displayed significant defect in internalization but not tethering of apoptotic cells. When uPAR-deficient mice were challenged with apoptotic cells, they exhibited pronounced splenomegaly resulting from accumulation of abundant apoptotic cells in spleen. Overexpression of uPAR in HEK-293 cells enhanced efferocytosis, which was inhibited by Annexin V and phosphatidylserine (PS) liposome, suggesting that uPAR-mediated efferocytosis is dependent on PS. In serum lacking high m.w. kininogen (HK), a uPAR ligand, uPAR-mediated efferocytosis was significantly attenuated, which was rescued by replenishment of HK. As detected by flow cytometry, HK selectively bound to apoptotic cells, but not viable cells. In purified systems, HK was specifically associated with PS liposome. HK binding to apoptotic cells induced its rapid cleavage to the two-chain form of HK (HKa) and bradykinin. Both the H chain and L chain of HKa were associated with PS liposome and apoptotic cells. HKa has higher binding affinity than HK to uPAR. Overexpression of Rac1/N17 cDNA inhibited uPAR-mediated efferocytosis. HK plus PS liposome stimulated a complex formation of CrkII with p130Cas and Dock-180 and Rac1 activation in uPAR-293 cells, but not in control HEK-293 cells. Thus, uPAR mediates efferocytosis through HK interaction with PS on apoptotic cells and activation of the Rac1 pathway.

Cleaved high-molecular-weight kininogen accelerates the onset of endothelial progenitor cell senescence by induction of reactive oxygen species

OBJECTIVE

Cleaved high-molecular-weight kininogen (HKa), an activation product of the plasma kallikrein-kinin system, inhibits endothelial cell functions. We questioned whether HKa affects the function of endothelial progenitor cells (EPCs) and accelerates their senescence.

METHODS AND RESULTS

Treatment with HKa for 2 weeks markedly inhibited the formation of large colonies and proliferation of EPCs on collagen surfaces, whereas HKa did not affect collagen-mediated EPC adhesion and survival. Concomitantly, treated EPCs displayed flattened and giant cell morphological changes and formation of intracellular vacuoles. As determined by acidic β-galactosidase staining, HKa increased senescent EPCs by 2- and >3-fold after culture for 1 and 2 weeks, respectively. In addition, HKa suppressed the telomerase activity of EPCs. HKa concentration-dependently increased the generation of intracellular reactive oxygen species (ROS) and markedly upregulated p38 kinase phosphorylation and prosenescence molecule p16(INK4a) expression. SB203580, a p38 inhibitor, attenuated the level of HKa-enhanced p16(INK4a) expression. Either quenching of ROS or inhibition of p38 kinase prevented HKa-induced EPC senescence.

CONCLUSIONS

HKa accelerates the onset of EPC senescence by activating the ROS-p38 kinase-p16(INK4a) signaling cascade. This novel activity of HKa points out the likelihood of HKa serving as an endogenous inducer of EPC senescence.

Anti-inflammatory cytokine interleukin-19 inhibits smooth muscle cell migration and activation of cytoskeletal regulators of VSMC motility

Vascular smooth muscle cell (VSMC) migration is an important cellular event in multiple vascular diseases, including atherosclerosis, restenosis, and transplant vasculopathy. Little is known regarding the effects of anti-inflammatory interleukins on VSMC migration. This study tested the hypothesis that an anti-inflammatory Th2 interleukin, interleukin-19 (IL-19), could decrease VSMC motility. IL-19 significantly decreased platelet-derived growth factor (PDGF)-stimulated VSMC chemotaxis in Boyden chambers and migration in scratch wound assays. IL-19 significantly decreased VSMC spreading in response to PDGF. To determine the molecular mechanism(s) for these cellular effects, we examined the effect of IL-19 on activation of proteins that regulate VSMC cytoskeletal dynamics and locomotion. IL-19 decreased PDGF-driven activation of several cytoskeletal regulatory proteins that play an important role in smooth muscle cell motility, including heat shock protein-27 (HSP27), myosin light chain (MLC), and cofilin. IL-19 decreased PDGF activation of the Rac1 and RhoA GTPases, important integrators of migratory signals. IL-19 was unable to inhibit VSMC migration nor was able to inhibit activation of cytoskeletal regulatory proteins in VSMC transduced with a constitutively active Rac1 mutant (RacV14), suggesting that IL-19 inhibits events proximal to Rac1 activation. Together, these data are the first to indicate that IL-19 can have important inhibitory effects on VSMC motility and activation of cytoskeletal regulatory proteins. This has important implications for the use of anti-inflammatory cytokines in the treatment of vascular occlusive disease.

The anti-inflammatory cytokine interleukin 19 is expressed by and angiogenic for human endothelial cells

OBJECTIVE

To characterize the expression and function of interleukin (IL) 19, a recently described T-helper 2 anti-inflammatory IL, on endothelial cell (EC) pathophysiological features.

METHODS AND RESULTS

The expression and effects of anti-inflammatory ILs on EC activation and development of angiogenesis are uncharacterized. We demonstrate by immunohistochemistry and immunoblot that IL-19 is expressed in inflamed, but not normal, human coronary endothelium and can be induced in cultured human ECs by serum and basic fibroblast growth factor. IL-19 is mitogenic and chemotactic, and it promotes EC spreading. IL-19 activates the signaling proteins STAT3, p44/42, and Rac1. In functional ex vivo studies, IL-19 promotes cordlike structure formation of cultured ECs and enhances microvessel sprouting in the mouse aortic ring assay. IL-19 induces tube formation in gelatinous protein (Matrigel) plugs in vivo.

CONCLUSIONS

To our knowledge, these data are the first to report expression of the anti-inflammatory agent, IL-19, in ECs; and the first to indicate that IL-19 is mitogenic and chemotactic for ECs and can induce the angiogenic potential of ECs.

Kininogens: More than cysteine protease inhibitors and kinin precursors

Two kininogens are found in mammalian sera: HK (high molecular weight kininogen) and LK (low molecular weight kininogen) with the exception of the rat which encompasses a third kininogen, T-Kininogen (TK). Kininogens are multifunctional glycosylated molecules related to cystatins (clan IH, family I25). They harbor three cystatin domains but only two of them are tight-binding inhibitors of cysteine cathepsins. HK and LK, but not TK, are precursors of potent peptide hormones, the kinins, which are released proteolytically by tissue and plasma kallikreins. Besides these classical features novel functions of kininogens have been recently discovered; they are described in the second part of this review. HKa, which corresponds to the kinin-free two-chain HK and its isolated domain D5 (kininostatin), possesses angiostatic and pro-apoptotic properties, inhibits the proliferation of endothelial cells and participates in the regulation of angiogenesis. Moreover, some HK-derived peptides display potent and broad-spectrum microbicidal properties against both Gram-positive and Gram-negative bacteria, and thus may offer a promising alternative to conventional antibiotic therapy. Of seminal interest, a kininogen-derived peptide inhibits activation of the contact phase system of coagulation and protects mice with invasive Streptococcus pyogenes infection from pulmonary lesions. On the other hand, TK is a biomarker of aging at the end of lifespan of elderly rats. However, although TK has been initially identified as an acute phase reactant, and earlier known as alpha-l-acute phase globulin, the increase of TK in liver and plasma is not known to relate to any inflammatory event during the senescence process.

Cleaved high molecular weight kininogen inhibits tube formation of endothelial progenitor cells via suppression of matrix metalloproteinase 2

BACKGROUND AND OBJECTIVE

Endothelial progenitor cells (EPCs) contribute to postnatal neovascularization, thus promoting wide interest in their therapeutic potential in vascular injury and prevention of their dysfunction in cardiovascular diseases. Cleaved high molecular weight kininogen (HKa), an activation product of the plasma kallikrein-kinin system (KKS), inhibits the functions of differentiated endothelial cells including in vitro and in vivo angiogenesis. In this study, our results provided the first evidence that HKa is able to target EPCs and inhibits their tube forming capacity.

METHODS AND RESULTS

We determined the effect of HKa on EPCs using a three-dimensional vasculogenesis assay. Upon stimulation with vascular endothelial growth factor (VEGF) alone, EPCs formed vacuoles and tubes, and differentiated into capillary-like networks. As detected by gelatinolytic activity assay, VEGF stimulated secretion and activation of matrix metallopeptidase 2 (MMP-2), but not MMP-9, in the conditioned medium of 3D culture of EPCs. Specific inhibition or gene ablation of MMP-2, but not MMP-9, blocked the vacuole and tube formation by EPCs. Thus, MMP-2 is selectively required for EPC vasculogenesis. In a concentration-dependent manner, HKa significantly inhibited tube formation by EPCs and the conversion of pro-MMP-2 to MMP-2. Moreover, HKa completely blocked the association between pro-MMP-2 and alphavbeta3 integrin, and its inhibition of MMP-2 activation was dependent on the presence of alphavbeta3 integrin. In a purified system, HKa did not directly inhibit MMP-2 activity.

CONCLUSIONS

HKa inhibits tube forming capacity of EPCs by suppression of MMP-2 activation, which may constitute a novel link between activation of the KKS and EPC dysfunction.

Cleaved high molecular weight kininogen inhibits tube formation of endothelial progenitor cells via suppression of matrix metalloproteinase 2

BACKGROUND AND OBJECTIVE

Endothelial progenitor cells (EPCs) contribute to postnatal neovascularization, thus promoting wide interest in their therapeutic potential in vascular injury and prevention of their dysfunction in cardiovascular diseases. Cleaved high molecular weight kininogen (HKa), an activation product of the plasma kallikrein-kinin system (KKS), inhibits the functions of differentiated endothelial cells including in vitro and in vivo angiogenesis. In this study, our results provided the first evidence that HKa is able to target EPCs and inhibits their tube forming capacity.

METHODS AND RESULTS

We determined the effect of HKa on EPCs using a three-dimensional vasculogenesis assay. Upon stimulation with vascular endothelial growth factor (VEGF) alone, EPCs formed vacuoles and tubes, and differentiated into capillary-like networks. As detected by gelatinolytic activity assay, VEGF stimulated secretion and activation of matrix metallopeptidase 2 (MMP-2), but not MMP-9, in the conditioned medium of 3D culture of EPCs. Specific inhibition or gene ablation of MMP-2, but not MMP-9, blocked the vacuole and tube formation by EPCs. Thus, MMP-2 is selectively required for EPC vasculogenesis. In a concentration-dependent manner, HKa significantly inhibited tube formation by EPCs and the conversion of pro-MMP-2 to MMP-2. Moreover, HKa completely blocked the association between pro-MMP-2 and alphavbeta3 integrin, and its inhibition of MMP-2 activation was dependent on the presence of alphavbeta3 integrin. In a purified system, HKa did not directly inhibit MMP-2 activity.

CONCLUSIONS

HKa inhibits tube forming capacity of EPCs by suppression of MMP-2 activation, which may constitute a novel link between activation of the KKS and EPC dysfunction.

Aberrant processing of plasma vitronectin and high-molecular-weight kininogen precedes the onset of preeclampsia

To date, there is no reliable test to identify women in early pregnancy at risk of developing preeclampsia. Difference gel electrophoresis (DIGE) identified the plasma proteins vitronectin (VN) and high-molecular-weight kininogen (HK) in association with preeclampsia. In a longitudinal proteomics study, the plasma of preeclamptic patients (n = 6) was compared to healthy control participants (n = 6) before the onset of preeclampsia (week 20) and at the time of presentation with clinical disease (weeks 33-36). The 75-kd single-chain VN molecule increased 1.6- to 1.9-fold in preeclampsia, whereas the 65-kd moiety of the 2-chain VN molecule decreased 1.5- to 1.7-fold compared to healthy controls (P < .05). Immunoblots revealed differences in proteolytic processing of VN and/or HK in women who develop preeclampsia or preeclampsia further complicated by small-for-gestational-age. Vitronectin and HK may prove to be useful as early markers of fibrinolytic activity and neutrophil activation, which are known to be associated with preeclampsia.

A shared mechanism of adhesion modulation for tenascin-C and fibulin-1

Adhesion modulatory proteins are important effectors of cell-matrix interactions during tissue remodeling and regeneration. They comprise a diverse group of matricellular proteins that confer antiadhesive properties to the extracellular matrix (ECM). We compared the inhibitory effects of two adhesion modulatory proteins, fibulin-1 and tenascin-C, both of which bind to the C-terminal heparin-binding (HepII) domain of fibronectin (FN) but are structurally distinct. Here, we report that, like tenascin-C, fibulin-1 inhibits fibroblast spreading and cell-mediated contraction of a fibrin-FN matrix. These proteins act by modulation of focal adhesion kinase and extracellular signal-regulated kinase signaling. The inhibitory effects were bypassed by lysophosphatidic acid, an activator of RhoA GTPase. Fibroblast response to fibulin-1, similar to tenascin-C, was dependent on expression of the heparan sulfate proteoglycan syndecan-4, which also binds to the HepII domain. Therefore, blockade of HepII-mediated signaling by competitive binding of fibulin-1 or tenascin-C represents a shared mechanism of adhesion modulation among disparate modulatory proteins.

Regulation of angiogenesis: apoptotic cues from the ECM

The extracellular matrix (ECM) acts both as a physical scaffold for cells and as a repository for growth factors. Moreover, ECM structure and physical-chemical properties convey precise information to cells that profoundly influences their biology by interactions with cell surface receptors termed integrins. During angiogenesis, the perivascular ECM plays a critical role in determining the proliferative, invasive and survival responses of the local vascular cells to the angiogenic growth factors. Dynamic changes in both the ECM and the local vascular cells act in concert to regulate new blood vessel growth. The digestion of ECM components by proteolysis is critical for the invasive capacity of endothelial cells, but also creates ECM fragments, which antagonize the mechanosensory function of integrins, and can be apoptogenic. Here, we discuss the roles of integrins in modulating cellular responses to a changing ECM, in particular the regulation of survival and invasion among invasive endothelial cells.

Signaling through urokinase and urokinase receptor in lung cancer cells requires interactions with beta1 integrins

The urokinase receptor (uPAR) is upregulated upon tumor cell invasion and correlates with poor lung cancer survival. Although a cis-interaction with integrins has been ascribed to uPAR, whether this interaction alone is critical to urokinase (uPA)- and uPAR-dependent signaling and tumor promotion is unclear. Here we report the functional consequences of point mutations of uPAR (H249A-D262A) that eliminate beta1 integrin interactions but maintain uPA binding, vitronectin attachment and association with alphaV integrins, caveolin and epidermal growth factor receptor. Disruption of uPAR interactions with beta1 integrins recapitulated previously reported findings with beta1-integrin-derived peptides that attenuated matrix-dependent ERK activation, MMP expression and in vitro migration by human lung adenocarcinoma cell lines. The uPAR mutant cells acquired enhanced capacity to adhere to vitronectin via uPAR-alphaVbeta5-integrin, rather than through the uPAR-alpha3beta1-integrin complex and they were unable to initiate uPA signaling to activate ERK, Akt or Stat1. In an orthotopic lung cancer model, uPAR mutant cells exhibited reduced tumor size compared with cells expressing wild-type uPAR. Taken together, the results indicate that uPAR-beta1-integrin interactions are essential to signals induced by integrin matrix ligands or uPA that support lung cancer cell invasion in vitro and progression in vivo.

Proteomic analysis of the hyaloid vascular system regression during ocular development

We describe a proteomic approach to investigate the differential protein expression patterns and identify the physiologically relevant angiogenic and antiangiogenic factors involved in the hyaloid vascular system regression. Differentially expressed proteins were identified using two-dimensional gel electrophoresis followed by nanoflow chromatography coupled with tandem mass spectrometry. These proteins are expected to provide insight as to their function in the early maintenance and eventual regression of the hyaloid vascular system.