Temporal relationship between MMP production and angiogenic process in HUVECs

Resistance to tyrosine kinase inhibitors promotes renal cancer progression through MCPIP1 tumor-suppressor downregulation and c-Met activation

Tyrosine kinase inhibitors (TKIs) are the most commonly used targeted therapeutics in clear-cell renal cell carcinoma (ccRCC); however, drug resistance limits their utility and can lead to tumor "flare-up" and progression. In this study, we show that RCC resistance to sunitinib and sorafenib involves different mechanisms and leads to increased malignancy. Sunitinib decreased tumor growth and cell motility along with increased E-cadherin expression and secretion of the proangiogenic cytokines IL6 and IL8, which activated senescence in ccRCC cells and led to VE-cadherin phosphorylation, enhancing tumor angiogenesis. Sorafenib resistance increased the levels of mesenchymal markers and the secretion of MMP9, which cleaved VE-cadherin and disrupted endothelial cell integrity. Both sunitinib resistance and sorafenib resistance led to activation of the c-Met receptor IRAK1 and downregulation of the tumor suppressor MCPIP1, resulting in an increase in the metastasis of resistant cells, possibly due in part to enhanced vascularization of ccRCC. MCPIP1 overexpression partially overcame resistance to these drugs by decreasing micrometastasis and decreasing the expression of factors involved in tumorigenesis. In tumor samples from ccRCC patients, we observed a significant increase in the level of the c-Met receptor, IRAK1 and a decrease in MCPIP1 with respect to normal kidney tissue. Our results indicate separate novel mechanisms for sunitinib and sorafenib resistance, which both lead to MCPIP1 inhibition and ccRCC progression. The presented study suggests caution in the treatment of RCC with TKIs, which may lead to the unintended outcome of tumor progression.

Multiple Targets Directed Multiple Ligands: An In Silico and In Vitro Approach to Evaluating the Effect of Triphala on Angiogenesis

Angiogenesis is critical in both physiological and pathological conditions and targeting angiogenesis is a promising strategy for the development of therapies against cancer; however, cells develop resistance to anti-angiogenic therapy, necessitating a more effective strategy. Natural medicines have been used in anti-cancer therapy for many years, but the mechanisms behind these have not generally been explored. Triphala churna (THL), an Indian ayurvedic herbal formulation made from the dried fruits of three medicinal plants, is used as a herbal drug for the treatment of various diseases, including cancer. THL contains over fifteen phytochemicals with different pharmacological effects, especially inhibition of tumor progression. In this study, we examined the effect of these compounds against different targets using docking and in vitro studies. Results showed that THL has a prediction efficacy of (−)436.7, and it inhibited angiogenesis by blocking multiple components of the VEGF/VEGFR2 signaling pathway. The anti-angiogenic effect was mediated by the combined effect of the two top ranked phytochemicals, punicalagin (−424.8) and chebulagic acid (−414.8). The new approach developed in this study to determine the potential efficacy of herbal formulation could be a useful strategy to assess the efficacy of different herbal formulations.

A cell surface display fluorescent biosensor for measuring MMP14 activity in real-time

Despite numerous recent advances in imaging technologies, one continuing challenge for cell biologists and microscopists is the visualization and measurement of endogenous proteins as they function within living cells. Achieving this goal will provide a tool that investigators can use to associate cellular outcomes with the behavior and activity of many well-studied target proteins. Here, we describe the development of a plasmid-based fluorescent biosensor engineered to measure the location and activity of matrix metalloprotease-14 (MMP14). The biosensor design uses fluorogen-activating protein technology coupled with a MMP14-selective protease sequence to generate a binary, “switch-on” fluorescence reporter capable of measuring MMP14 location, activity, and temporal dynamics. The MMP14-fluorogen activating protein biosensor approach is applicable to both short and long-term imaging modalities and contains an adaptable module that can be used to study many membrane-bound proteases. This MMP14 biosensor promises to serve as a tool for the advancement of a broad range of investigations targeting MMP14 activity during cell migration in health and disease.

Anti-angiogenic effect of chebulagic acid involves inhibition of the VEGFR2- and GSK-3β-dependent signaling pathways

Inhibition of angiogenesis is a useful strategy to prevent cancer growth by targeting new vessels that grow to nourish actively proliferating tumor cells. Endothelial cells can use a number of different pathways to cause angiogenesis, and each step in these pathways can be targeted. The use of multi-targeted drugs is gaining much importance in this scenario. Our previous results have shown that chebulagic acid (a benzopyran tannin present in the fruits of Terminalia chebula) has anti-angiogenic properties. Thus, this study was designed to examine the molecular mechanism for the anti-angiogenic effects of chebulagic acid. Results from our investigations using molecular docking studies and human umbilical vein endothelial cells in culture suggested that chebulagic acid inhibits both GSK-3β-dependent β-catenin phosphorylation (an important mediator of VE-cadherin–β-catenin signaling) and VEGFR2 phosphorylation, which is an important step in VEGF signaling. Chebulagic acid inhibits angiogenesis by blocking both the VEGF–VEGFR2 complex and cell–cell contact dependent downstream signaling pathways.

Matrix Metalloproteinases in Myocardial Infarction and Heart Failure

Cardiovascular disease is the leading cause of death, accounting for 600,000 deaths each year in the United States. In addition, heart failure accounts for 37% of health care spending. Matrix metalloproteinases (MMPs) increase after myocardial infarction (MI) and correlate with left ventricular dysfunction in heart failure patients. MMPs regulate the remodeling process by facilitating extracellular matrix turnover and inflammatory signaling. Due to the critical role MMPs play during cardiac remodeling, there is a need to better understand the pathophysiological mechanism of MMPs, including the biological function of the downstream products of MMP proteolysis. Future studies developing new therapeutic targets that inhibit specific MMP actions to limit the development of heart failure post-MI are warranted. This chapter focuses on the role of MMPs post-MI, the efficiency of MMPs as biomarkers for MI or heart failure, and the future of MMPs and their cleavage products as targets for prevention of post-MI heart failure.

Morus alba Leaf Lectin (MLL) Sensitizes MCF-7 Cells to Anoikis by Inhibiting Fibronectin Mediated Integrin-FAK Signaling through Ras and Activation of P38 MAPK

Lectins are a unique class of carbohydrate binding proteins/glycoproteins, and many of them possess anticancer properties. They can induce cell cycle arrest and apoptosis, inhibit protein synthesis, telomerase activity and angiogenesis in cancer cells. In the present study, we have demonstrated the effect of Morus alba leaf lectin (MLL) on anoikis induction in MCF-7 cells. Anoikis induction in cancer cells has a significant role in preventing early stage metastasis. MLL treatment in monolayers of MCF-7 cells caused significant detachment of cells in a time and concentration dependent manner. The detached cells failed to re-adhere and grew even to culture plates coated with different matrix proteins. DNA fragmentation, membrane integrity studies, annexin V staining, caspase 9 activation and upregulation of Bax/Bad confirmed that the detached cells underwent apoptosis. Upregulation of matrix metalloproteinase 9 (MMP-9) caused a decrease in fibronectin (FN) production which facilitated the cells to detach by blocking the FN mediated downstream signaling. On treatment with MLL, we have observed downregulation of integrin expression, decreased phosphorylation of focal adhesion kinase (FAK), loss in FAK-integrin interaction and active Ras. MLL treatment downregulated the levels of phosphorylated Akt and PI3K. Also, we have studied the effect of MLL on two stress activated protein kinases p38 MAPK and JNK. p38 MAPK activation was found to be elevated, but there was no change in the level of JNK. Thus our study substantiated the possible antimetastatic effect of MLL by inducing anoikis in MCF-7 cells by activation of caspase 9 and proapoptotic Bax/Bad by blockage of FN mediated integrin/FAK signaling and partly by activation of p38 MAPK.

Anticancer activity of synthetic bis(indolyl)methane-ortho-biaryls against human cervical cancer (HeLa) cells

Bis(indolyl)methane appended biaryls were designed, synthesized and evaluated in human cervical cancer cell lines (HeLa) for their anticancer activities and compared against normal rat cardiac myoblasts (H9C2) cells. Compounds 1-12 were synthesized, with variations in one of the phenyl unit, in a single step by condensation of biaryl-2-carbaldehydes with indole in the presence of para-toluenesulfonic acid. Compound 1 exhibited a GI50 value of 11.00 ± 0.707 μM and the derivatives, compounds 4 and 11 showed a GI50 value of 8.33 ± 0.416 μM and 9.13 ± 0.177 μM respectively in HeLa cells and was found to be non-toxic to H9C2 cells up to 20 μM. Furthermore, compounds 1, 4 and 11 induced caspase dependent cellular apoptosis in a concentration-dependent manner, reduced mitochondrial membrane potential, inhibited the cell migration and downregulated the production of MMP-2 and MMP-9 in HeLa cells.

Tricin, flavonoid from Njavara reduces inflammatory responses in hPBMCs by modulating the p38MAPK and PI3K/Akt pathways and prevents inflammation associated endothelial dysfunction in HUVECs

Previous studies revealed the potent anti-inflammatory activity of tricin, the active component of Njavara rice bran. Here, we report the involvement of specific signaling pathways in the protective effect of tricin against LPS induced inflammation in hPBMCs and the role of tricin in modulating endothelial dysfunction in LPS induced HUVECs. Pretreatment with tricin (15μM) significantly inhibited the release of TNF-α and was comparable to the specific pathway blockers like ERK inhibitor (PD98059), JNK inhibitor (SP600125) and p38 inhibitor (SB203580), whereas an increased release of TNF-α was observed in PI3K/Akt inhibitor (LY294002) treated cells. Tricin alone and combination treatment of tricin and SB203580 showed more significant inhibition of activation of COX-2 and TNF-α than that of SB203580 alone treated group. Combination treatment of tricin and LY294002 showed increased activation of COX-2 and TNF-α, proved that PI3K activation is essential for the anti-inflammatory effect of tricin. Studies conducted on HUVECs revealed the protective effect of tricin against endothelial dysfunction associated with LPS induced inflammation by inhibiting the activation of proinflammatory mediators like TNF-α, IFN-γ, MCP 1 by modulating NF-κB and MAPK signaling pathways. ELISA and flow cytometric analysis again confirmed the protection of tricin against endothelial damage, especially from the decreased activation of cell adhesion molecules like ICAM-1, VCAM-1 and E-Selectin upon tricin treatment. This work establishes the mechanism behind the potent anti-inflammatory activity of the flavonoid tricin.

NO-dependent proliferation and migration induced by Vitamin D in HUVEC

Recently, Vitamin D (Vit. D) has gained importance in cellular functions of a wide range of extraskeletal organs and target tissues, other than bone. In particular, Vit. D has displayed important beneficial effects in the cardiovascular system. Although little is known about the mechanism by which this response is exerted, a Vit. D-induced eNOS-dependent nitric oxide (NO) production in endothelial cells (EC) has been reported. The aim of this study was to evaluate whether Vit. D administration could affect human EC proliferation and/or migration through NO production. For this purpose, HUVEC (human umbilical vein endothelial cells) were used to evaluate Vit. D effects on cell proliferation and migration in a 3D matrix. Experiments were also performed in the presence of the specific VDR ligand ZK159222 and eNOS inhibitor L-NAME. This study demonstrated that Vit. D can promote both HUVEC proliferation and migration in a 3D matrix. These effects were NO dependent, since HUVEC proliferation and migration were abrogated along with Vit. D induced MMP-2 expression by inhibiting eNOS activity by L-NAME. These findings support the role of Vit. D in the angiogenic process, suggesting new applications for Vit. D in tissue repair and wound healing.

Dynamic interplay between breast cancer cells and normal endothelium mediates the expression of matrix macromolecules, proteasome activity and functional properties of endothelial cells

BACKGROUND

Breast cancer-endothelium interactions provide regulatory signals facilitating tumor progression. The endothelial cells have so far been mainly viewed in the context of tumor perfusion and relatively little is known regarding the effects of such paracrine interactions on the expression of extracellular matrix (ECM), proteasome activity and properties of endothelial cells.

METHODS

To address the effects of breast cancer cell (BCC) lines MDA-MB-231 and MCF-7 on the endothelial cells, two cell culture models were utilized; one involves endothelial cell culture in the presence of BCCs-derived conditioned media (CM) and the other co-culture of both cell populations in a Transwell system. Real-time PCR was utilized to evaluate gene expression, an immunofluorescence assay for proteasome activity, and functional assays (migration, adhesion and invasion) and immunofluorescence microscopy for cell integrity and properties.

RESULTS

BCC-CM decreases the cell migration of HUVEC. Adhesion and invasion of BCCs are favored by HUVEC and HUVEC-CM. HA levels and the expression of CD44 and HA synthase-2 by HUVEC are substantially upregulated in both cell culture approaches. Adhesion molecules, ICAM-1 and VCAM-1, are also highly upregulated, whereas MT1-MMP and MMP-2 expressions are significantly downregulated in both culture systems. Notably, the expression and activity of the proteasome β5 subunit are increased, especially by the action of MDA-MB-231-CM on HUVEC.

CONCLUSIONS AND GENERAL SIGNIFICANCE

BCCs significantly alter the expression of matrix macromolecules, proteasome activity and functional properties of endothelial cells. Deep understanding of such paracrine interactions will help to design novel drugs targeting breast cancer at the ECM level. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Inhibition of Angiogenesis In Vitro by Chebulagic Acid: A COX-LOX Dual Inhibitor

Angiogenesis is a crucial step in the growth of cancer and its metastasis. It is regulated by several endogenous factors which may stimulate or inhibit the new blood vessel growth. Besides these endogenous factors, several exogenous factors including some natural compounds are known to modulate angiogenesis. Angiogenesis being a potential target for drugs against a number of pathological conditions, search for compounds from natural sources that can affect angiogenesis is of great interest. The objective of our present study was to understand the effect of chebulagic acid, a COX-LOX dual inhibitor isolated from the fruits of Terminalia chebula Retz., on angiogenesis. The model systems used were rat aortic rings and human umbilical vein endothelial cells. The results showed that chebulagic acid exerts an antiangiogenic effect. This was evidenced from decreased sprouting in rat aortic rings and decrease in biochemical markers in endothelial cells treated with chebulagic acid. It downregulated the production of CD31, E-selectin, and vascular endothelial growth factor in human umbilical vein endothelial cells in culture (HUVEC). Further studies to understand the molecular mechanism of action of chebulagic acid revealed that CA exerts its anti angiogenic effect by modulating VE cadherin-β catenin signalling in human umbilical vein endothelial cells.

Procyanidins inhibit tumor angiogenesis by crosslinking extracellular matrix

OBJECTIVE

Procyanidins (PC) are widely available natural polyphenols. The present study is designed to investigate if PC can inhibit angiogenesis in lung adenocarcinoma xenografts through crosslinking vascular extracellular matrix (ECM) and preventing proteolysis by matrix metalloproteinases (MMPs).

METHODS

Using the in vitro MMP-2 proteolysis and in vivo subcutaneous implantation models, we investigated if PC crosslinking inhibits MMP-mediated proteolysis. Using a cultured cell detachment assay, an in vitro angiogenesis assay, and a cell proliferation assay, we investigated if PC inhibits MMP-2-mediated endothelial cell detachment, angiogenesis, and cell proliferation, respectively. Using tumor xenografts, we evaluated if PC can inhibit growth of lung adenocarcinoma.

RESULTS

PC crosslink vascular ECM proteins, protecting them against proteolysis by MMPs in vitro and in vivo, protecting cultured human umbilical vein endothelial cells from detachment by MMP-2, and inhibiting in vitro angiogenesis. However, PC (0.75-100 µg/ml) did not inhibit vascular and tumor cells proliferation. PC injections (30 mg PC/kg bodyweight) in situ had anticancer effects on xenografts of lung adenocarcinoma, most likely by inhibiting angiogenesis during ECM proteolysis by MMPs.

CONCLUSION

The results suggest that PC may be important MMP inhibitors that can be used as therapeutic anticancer agents.

Increased co-expression of macrophage migration inhibitory factor and matrix metalloproteinase 9 is associated with tumor recurrence of meningioma

BACKGROUND AND OBJECTIVE

We detected the expression of MIF and matrix metalloproteinase 9 (MMP9) in meningiomas to determine whether they are valuable recurrence predictor for meningioma.

METHODS

67 cases of meningiomas, including 57 benign tumors (WHO grade I) and 10 non-benign tumors (WHO grade II and III), were collected, and expression of MIF and MMP9 in tissue microarray was evaluated immunohistochemically. The correlations between immunostainings and clinicopathological parameters, as well as the follow-up data of patients, were analyzed statistically.

RESULTS

Increased expressions of both MIF (58.2%, 39/67) and MMP9 (55.2%, 37/67) were significantly associated with microvessel density (MVD) of tumor, but only dual high-expression of MIF and MMP9 was in relation to tumor invasion (P=0.016) and tumor recurrence (P=0.001). Based on univariate analysis, histological grade, tumor invasion and co-expression of MIF and MMP9 were significant predictors for recurrence. However, only histological grade and co-expression of MIF and MMP9 in tumor were independent recurrence factors with a hazard ratio of 49.033 (P=0.002) and 37.766 (P=0.002) in multivariate analysis.

CONCLUSIONS

Together with histological grade, increased co-expression of MIF and MMP9 in tumor might be a valuable predictor for recurrence, especially for benign meningiomas.

Investigating metalloproteinases MMP-2 and MMP-9 mechanosensitivity to feedback loops involved in the regulation of in vitro angiogenesis by endogenous mechanical stresses

Angiogenesis is a complex morphogenetic process regulated by growth factors, but also by the force balance between endothelial cells (EC) traction stresses and extracellular matrix (ECM) viscoelastic resistance. Studies conducted with in vitro angiogenesis assays demonstrated that decreasing ECM stiffness triggers an angiogenic switch that promotes organization of EC into tubular cords or pseudo-capillaries. Thus, mechano-sensitivity of EC with regard to proteases secretion, and notably matrix metalloproteinases (MMPs), should likely play a pivotal role in this switching mechanism. While most studies analysing strain regulation of MMPs used cell cultured on stretched membranes, this work focuses on MMP expression during self-assembly of EC into capillary-like structures within fibrin gels, i.e. on conditions that mimics more closely the in vivo cellular mechanical microenvironment. The activity of MMP-2 and MMP-9, two MMPs that have a pivotal role in capillaries formation, has been monitored in pace with the progressive elongation of EAhy926 cells that takes place during the emergence of cellular cords. We found an increase of the zymogen proMMP-2 that correlates with the initial stages of EC cords formation. However, MMP-2 was not detected. ProMMP-9 secretion decreased, with levels of MMP-9 kept at a rather low value. In order to analyse more precisely the observed differences of EAhy926 response on fibrin and plastic substrates, we proposed a theoretical model of the mechano-regulation of proMMP-2 activation in the presence of type 2 tissue inhibitor of MMPs (TIMP-2). Using association/dissociation rates experimentally reported for this enzymatic network, the model adequately describes the synergism of proMMP-2 and TIMP-2 strain activation during pseudo-capillary morphogenesis. All together, these results provide a first step toward a systems biology approach of angiogenesis mechano-regulation by cell-generated extracellular stresses and strains.

Changes in expression of VE-cadherin and MMPs in endothelial cells: Implications for angiogenesis

The mechanism of cell-cell contact dependent regulation of pericellular proteolysis in angiogenesis was examined by studying the expression of MMPs using isolated HUVECs in culture. Zymography, Immunoblot and RT-PCR analysis showed that the production and secretion of matrixmetalloproteinase-2 and matrixmetalloproteinase-9 by HUVECs in culture were high when they remain as individual cells and significantly decreased during later stages of culture when cells developed cell-cell contact and tubular network-like structure. As MMPs decreased there was significant upregulation of VE-cadherin in cells undergoing angiogenic transition. Investigations to understand the signaling pathways downstream of VE-cadherin showed a relatively high level of β-catenin in the nucleus of endothelial cells in culture during initial stages and decrease in its levels in the nucleus, associated with an increase in the cytosol during later stages of culture. The distribution of β-catenin was found to be regulated by Tyr/Ser phosphorylation status of this protein. Cell-cell contact dependent downregulation of MMPs during angiogenesis was also observed in experiments using proangiogenic substances which caused a rapid rate of downregulation of MMP-2 and MMP-9 and absence of downregulation of MMPs when treated with anti-angiogenic agents.

Angiogenic effect of laminin involves modulation of cyclooxygenase-2 and prostaglandin levels

The molecular mechanism of the angiogenic effect of laminin (Ln) was studied using human umbilical vein endothelial cells (HUVECs) maintained in culture on Ln-1 substratum. High-pressure liquid chromatography analysis showed that in cells maintained on Ln, the levels of proangiogenic prostaglandin E(2) (PGE(2)) increased and that of antiangiogenic PGD(2) decreased. The angiogenic effect of PGE(2) and PGD(2) was confirmed by assessing the expression of CD31 and E-selectin in HUVECs. Immunoblot analysis, reverse transcription-polymerase chain reaction and cyclooxygenase (COX) assay showed increase in the expression and activity of COX-2 in cells maintained on Ln. Use of pharmacological inhibitors suggested that the modulation in the expression of COX-2 and thereby the levels of PGE(2) and PGD(2) in endothelial cells by Ln is mediated through the α(6)β(4) integrin-p38MAPK (mitogen-activated protein kinase)-NF-κB signaling pathway.

A novel composite construct increases the vascularization potential of PEG hydrogels through the incorporation of large fibrin ribbons

Developing a mechanism to vascularize tissue-engineered constructs is imperative for transplant function and integration, particularly when delivering hypoxia-sensitive tissues, such as pancreatic islets. Previous efforts have focused on bulk modifications of scaffold materials rendering the entire construct permissive to vessel penetration or the formation of a porous structure where vessels can infiltrate the empty spaces. Here, we describe a novel construct composed of large fibrin ribbons encapsulated within a poly(ethylene glycol) (PEG) hydrogel. The PEG/fibrin ribbon composite scaffold facilitates coculture of adhesive and nonadhesive cell types, thus providing closely neighboring environments with distinct material properties specific to the needs of two clinically relevant cell populations. This advantage is demonstrated here by the successful coculture of pancreatic islets in the PEG component and vessel-forming endothelial cells in entrapped fibrin ribbons. Transplanted endothelial cells can form anastomosies with host vasculature, suggesting that our cocultures may lead to more rapid scaffold vascularization. Additionally, we show that surface-seeded endothelial cells form multicellular projections that migrate into nonadhesive PEG hydrogels along permissive fibrin ribbons, further demonstrating composite construct vascularization potential. Distribution of large fibrin ribbons throughout PEG hydrogels provide a potential mechanism for vascularization of a well-established biomaterial without inherently changing its desirable properties.

Integration of blood outgrowth endothelial cells in dermal fibroblast sheets promotes full thickness wound healing

Vascularization is the cornerstone of wound healing. We introduced human blood outgrowth endothelial cells (hBOEC) in a self-assembled human dermal fibroblast sheet (hDFS), intended as a tissue-engineered dermal substitute with inherent vascular potential. hBOEC were functionally and molecularly different from early endothelial progenitor cells and human umbilical vein endothelial cells (HUVEC). hBOEC alone, unlike HUVEC, efficiently revascularized and re-oxygenated the wound bed, both by active incorporation into new vessels and by trophic stimulation of host angiogenesis in a dose-dependent manner. Furthermore, hBOEC alone, but not HUVEC, accelerated epithelial coverage and matrix organization of the wound bed. In addition, integration of hBOEC in hDFS not only further improved vascularization, epithelial coverage and matrix organization but also prevented excessive wound contraction. In vitro analyses with hBOEC, fibroblasts and keratinocytes revealed that these effects were both due to growth factor crosstalk and to short cutting hypoxia. Among multiple growth factors secreted by hBOEC, placental growth factor mediated at least in part the beneficial effects on keratinocyte migration and proliferation. Overall, this combined tissue engineering approach paves the way for clinical development of a fully autologous vascularized dermal substitute for patients with large skin defects that do not heal properly.

Mechanisms of non-opioid analgesics beyond cyclooxygenase enzyme inhibition

Non-opioid analgesics including both selective and non-selective cyclooxygenase (COX) inhibitors and acetaminophen are the most widely used treatments for pain. Inhibition of COX is thought to be largely responsible for both the therapeutic and adverse effects of this class of drugs. Accumulating evidence over the past two decades has demonstrated effects of non-opioids beyond the inhibition of COX and prostaglandin synthesis that might also explain their therapeutic and adverse effects. These include their interaction with endocannabinoids, nitric oxide, monoaminergic, and cholinergic systems. Moreover, the recent development of microarray technology that allows the study of human gene expression suggests multiple pathways that may be related to the analgesic and anti-inflammatory effects of non-opioids. The present review will discuss the multiple actions of non-opioids and their interactions with these systems during inflammation and pain, suggesting that COX inhibition is an incomplete explanation for the actions of non-opioids and proposes the involvement of multiple selective targets for their analgesic, as well as, their adverse effects.

Modulation of cyclooxygenase in endothelial cells by fibronectin: relevance to angiogenesis

Cyclooxygenases (COX), which catalyze the formation of prostaglandins (PGs), have been implicated in angiogenesis. Adhesion of endothelial cells (ECs) to extracellular matrix (ECM) induces the expression of COX-2 and PG production. The present study was carried out to analyze the influence of the adhesive ECM protein, fibronectin (FN), in modulating COX expression and its implications to angiogenesis using in vitro cultures of human umbilical vein ECs. RT-PCR analysis showed that the level of COX-2 mRNA was significantly high while that of COX-1 decreased in ECs maintained on FN. On treatment with p38 MAPK inhibitor and anti-alpha(5)beta(1) integrin antibody, FN dependent effect on COX expression was not observed. Analysis by ELISA and immunoblotting confirmed FN-dependent upregulation of COX-2 protein. The ratio of PG E(2):PG D(2) was significantly high in cells maintained on FN and on treatment with p38 MAPK inhibitor, the relative level of PG D(2) increased and that of PG E(2) decreased. Concomitant with the modulation of COX-2 and changes in PGs, ECs maintained on FN showed angiogenic response in an alpha(5)beta(1) integrin/p38 MAPK dependent manner as evidenced by the expression of angiogenic markers, CD 31 and E-selectin. These results suggest a FN-alpha(5)beta(1)/FAK/p38 MAPK dependent upregulation of COX-2 causing a shift in the relative levels of PGs in HUVECs which contributes to the angiogenic effect of FN.

Modulation of angiogenic factors by ursolic acid

Investigations were carried out to understand the molecular basis of the effect of ursolic acid on angiogenesis by analysing its effects on the expression of modulators of angiogenesis by HUVECs in culture. Treatment with ursolic acid increased the expression of adhesion molecules such as E-selectin, CD-31 and I-CAM, upregulated angiogenic growth factors such as VEGF and FGF-2 and their receptors and caused increase in the ratio of PGE(2) to PGD(2). Reversal of the effect of ursolic acid by inhibition of PI3K-Akt pathway and increase in the level of phospho Akt suggest that the ursolic acid effect is mediated through PI3K-Akt pathway.

Expression of cell adhesion proteins and proteins related to angiogenesis and fatty acid metabolism in benign, atypical, and anaplastic meningiomas

Most meningiomas are benign tumours of arachnoidal origin, although a small number have high proliferative rates and invasive properties which complicate complete surgical resection and are associated with increased recurrence rates. Few prognostic indicators exist for meningiomas and further research is necessary to identify factors that influence tumour invasion, oedema and recurrence. Paraffin sections from 25 intracranial meningiomas were analysed for expression of the proteins vascular endothelial growth factor (VEGF), VEGF receptors Flt1 and Flk1, E-cadherin, metalloproteinases 2 and 9 (MMP2, MMP9), CD44, receptor for hyaluronic acid-mediated motility (RHAMM), hyaluronic acid (HA), CD45, cyclooxygenase 2 (COX2), brain fatty acid binding protein (BFABP), Ki67, and proliferating cell nuclear antigen (PCNA). Correlations among protein expression were found for several markers of proliferation (Ki67, PCNA, MI) and microvessel density (MVD). COX2 expression increased with increasing with tumour grade and correlated with Ki67, PCNA, MI, MVD, and BFABP. BFABP expression also correlated with Ki67 and PCNA expression. Relationships were also identified among angiogenic factors (VEGF, Flt1, Flk1) and proliferation markers. Oedema was found to correlate with MMP9 expression and MMP9 also correlated with proliferation markers. No correlations were found for MMP2, E-cadherin, or CD44 in meningiomas. In conclusion Ki67, PCNA, MI, MVD, BFABP, and COX2 were significantly correlated with meningioma tumour grade and with each other. These findings, by correlating both intracellular fatty acid transport and eicosanoid metabolism with tumour proliferation, as determined by Ki67 labelling and mitotic index, suggest fatty acids are involved in the progression of meningiomas.

Opposing effects of curcuminoids on serum stimulated and unstimulated angiogenic response

Curcumin is known to be a potent wound healer. Despite this, studies on curcumin using certain model systems have shown it to be anti-angiogenic. Results of the present investigations suggest that curcumin causes opposing effects on angiogenesis in serum stimulated and unstimulated conditions. The evidence in support of this are: (a) in serum free conditions, curcumin promoted sprouting in rat aortic ring, increased vascular density in CAM and induced morphological changes indicative of angiogenic phenotype in HUVECs and rat aortic endothelial cells in culture, (b) increased the expression of biochemical markers of angiogenesis such as CD 31, E-selectin, VEGF and VEGFR-2 in HUVECs on treatment with curcumin, and (c) supplementation of curcumin along with serum caused decrease in CD 31 and E-selectin levels, downregulation of VEGF, angiopoietin-1 and VEGFR-2 and delayed formation of capillary network-like structure. Proangiogenic effect of the individual components of the natural curcumin differed and the presence of the three components in the natural mixture has a synergistic effect. Effect of curcuminoids in the absence of serum appears to depend on VEGF as (a) anti-VEGF antibody blocked the effect of curcuminoids (b) curcuminoids caused decrease in PAR modification of VEGF increasing its biological activity. Treatment with curcuminoids in serum-free conditions resulted in activation of PI3K-Akt pathway; but in serum-supplemented condition, curcuminoids caused inhibition of the MAPK pathways thereby inhibiting the expression of angiogenic phenotype. These results suggest that PI3K-Akt and MAPK pathways involved in the expression of angiogenic phenotype respond differently to the extracellular microenvironment.

Angiogenic response of endothelial cells to heparin-binding domain of fibronectin

Interaction of endothelial cells with cell-binding domain of fibronectin through integrin receptors is important in the process of angiogenesis. The present study was designed to examine the role of heparin-binding domain of fibronectin in angiogenesis using human umbilical vein endothelial cells. Attachment of endothelial cells in vitro to heparin-binding domain of fibronectin was inhibited by heparin. Chick chorioallantoic membrane assay revealed the proangiogenic nature of heparin-binding domain. Analysis by reverse transcription-polymerase chain reaction showed an increase in the expression of vascular endothelial growth factor and its receptor mRNA. Enzyme-linked immunosorbent assay showed a significant increase in the level of vascular endothelial growth factor secreted by cells maintained on heparin-binding domain. Treatment with calphostin C, an inhibitor of protein kinase C, decreased the expression of vascular endothelial growth factor receptor 2. Chick chorioallantoic membrane assay showed that the vascular endothelial growth factor secreted by cells maintained on heparin-binding domain was biologically more active, which appeared to be due to a decrease in its poly-adenosine diphosphate ribosylation. Binding assays showed that heparin-binding domain preferably binds unmodified vascular endothelial growth factor as compared to intact fibronectin. It is concluded that the heparin-binding domain of fibronectin by itself can promote angiogenesis in endothelial cells possibly by interaction with cell surface heparan sulphate proteoglycans involving protein kinase C dependent signaling and making available more active form of vascular endothelial growth factor to the cells.