ERK1-2 and p38 MAPK regulate MMP/TIMP balance and function in response to thrombospondin-1 fragments in the microvascular endothelium

Afatinib plus PEM and CBDCA overcome osimertinib resistance in EGFR-mutated NSCLC with high thrombospondin-1 expression

Osimertinib induces a marked response in non-small-cell lung cancer (NSCLC) patients harboring epidermal growth factor receptor (EGFR) gene mutations. However, acquired resistance to osimertinib remains an inevitable problem. In this study, we aimed to investigate osimertinib-resistant mechanisms and evaluate the combination therapy of afatinib and chemotherapy. We established osimertinib-resistant cell lines (PC-9-OR and H1975-OR) from EGFR-mutant lung adenocarcinoma cell lines PC-9 and H1975 by high exposure and stepwise method. Combination therapy of afatinib plus carboplatin (CBDCA) and pemetrexed (PEM) was effective in both parental and osimertinib-resistant cells. We found that expression of thrombospondin-1 (TSP-1) was upregulated in resistant cells using cDNA microarray analysis. We demonstrated that TSP-1 increases the expression of matrix metalloproteinases through integrin signaling and promotes tumor invasion in both PC-9-OR and H1975-OR, and that epithelial-to-mesenchymal transition (EMT) was involved in H1975-OR. Afatinib plus CBDCA and PEM reversed TSP-1-induced invasion ability and EMT changes in resistant cells. In PC-9-OR xenograft mouse models (five female Balb/c-Nude mice in each group), combination therapy strongly inhibited tumor growth compared with afatinib monotherapy (5 mg/kg, orally, five times per week) or CBDCA (75 mg/kg, intraperitoneally, one time per week) + PEM (100 mg/kg, intraperitoneally, one time per week) over a 28-day period. These results suggest that the combination of afatinib plus CBDCA and PEM, which effectively suppresses TSP-1 expression, may be a promising option in EGFR-mutated NSCLC patients after the acquisition of osimertinib resistance.

The molecular mechanism of thrombospondin family members in cardiovascular diseases

Cardiovascular diseases have been identified as vital factors in global morbidity and mortality in recent years. The available evidence suggests that various cytokines and pathological proteins participate in these complicated and changeable diseases. The thrombospondin (TSP) family is a series of conserved, multidomain calcium-binding glycoproteins that cause cell-matrix and cell-cell effects via interactions with other extracellular matrix components and cell surface receptors. The TSP family has five members that can be divided into two groups (Group A and Group B) based on their different structures. TSP-1, TSP-2, and TSP-4 are the most studied proteins. Among recent studies and findings, we investigated the functions of several family members, especially TSP-5. We review the basic concepts of TSPs and summarize the relevant molecular mechanisms and cell interactions in the cardiovascular system. Targeting TSPs in CVD and other diseases has a remarkable therapeutic benefit.

Scoping Review on Platelets and Tumor Angiogenesis: Do We Need More Evidence or Better Analysis?

Platelets are an active component of the tumor microenvironment (TME), involved in the regulation of multiple tumor processes, including angiogenesis. They are generated rich in angiogenic factors in their granules to actively participate in the hemostatic process by megakaryocytes and further enriched in angiogenic factors by all components of the tumor microenvironment to control the angiogenic process because of their preferential relationship with the endothelial component of vessels. In recent decades, the literature has reported a great deal of evidence on the role of platelets in tumor angiogenesis; however, it is unclear whether the number or mean volume of platelets and/or their content and localization in TME may have clinical relevance in the choice and management of therapy for the cancer patient. In this scoping review, we collected and critically reviewed the scientific evidence supporting a close relationship between platelets, cancer, and angiogenesis. The aim of this work was to define the landscape of platelet-activated angiogenesis in cancer progression and analyze what and how much evidence is present in the last 20 years in the literature at both the preclinical and clinical levels, to answer whether platelets could be a useful determinant for analyzing tumor angiogenesis. In conclusion, this scoping review indicates that there is much evidence, both preclinical and clinical, but in the preclinical context, studies demonstrate the direct involvement of platelets in tumor angiogenesis; in the clinical context the evidence is indirect, though strong, and the indication of how and to what extent platelet content contributes to tumor angiogenesis is lacking. So, do we need more evidence or better analysis? More molecular and quali-quantitative data is needed to translate the results obtained in preclinical studies into the clinical setting. This information about platelets, if correlated with tumor type and its biology, including tumor vasculature, type of angiogenesis, and patient characteristics (age, sex, comorbidities, drug treatments for chronic diseases) could be an important pa- rameter for correlating platelet biology to angiogenesis, for personalizing cancer therapy, and for clinical prognosis.

Lipopolysaccharide acting via toll-like receptor 4 transactivates the TGF-β receptor in vascular smooth muscle cells

Toll-like receptors (TLRs) recognise pathogen‑associated molecular patterns, which allow the detection of microbial infection by host cells. Bacterial-derived toxin lipopolysaccharide activates TLR4 and leads to the activation of the Smad2 transcription factor. The phosphorylation of the Smad2 transcription factor is the result of the activation of the transforming growth factor-β receptor 1 (TGFBR1). Therefore, we sought to investigate LPS via TLR4-mediated Smad2 carboxy terminal phosphorylation dependent on the transactivation of the TGFBR1. The in vitro model used human aortic vascular smooth muscle cells to assess the implications of TLR4 transactivation of the TGFBR1 in vascular pathophysiology. We show that LPS-mediated Smad2 carboxy terminal phosphorylation is inhibited in the presence of TGFBR1 inhibitor, SB431542. Treatment with MyD88 and TRIF pathway antagonists does not affect LPS-mediated phosphorylation of Smad2 carboxy terminal; however, LPS-mediated Smad2 phosphorylation was inhibited in the presence of MMP inhibitor, GM6001, and unaffected in the presence of ROCK inhibitor Y27632 or ROS/NOX inhibitor DPI. LPS via transactivation of the TGFBR1 stimulates PAI-1 mRNA expression. TLRs are first in line to respond to exogenous invading substances and endogenous molecules; our findings characterise a novel signalling pathway in the context of cell biology. Identifying TLR transactivation of the TGFBR1 may provide future insight into the detrimental implications of pathogens in pathophysiology.

Prognostic significance of LRIG2 and LRIG3 proteins in urothelial bladder carcinoma

Bladder carcinoma is the second most frequent cancer in Egyptian males. Leucine-rich and immunoglobulin-like domains (LRIGs) are usually dysregulated in various human tumors. The aim of this study is to explore the immunohistochemical expression of LRIG2 and LRIG3 in urothelial bladder carcinoma (UBC) and their relationship to patients clinicopathological data including survival. The study cohort included 79 UBC cases (14 non muscle invasive (NMI) and 65 muscle invasive (MI)). We assessed the associations of LRIG2 and LRIG3 expression with clinicopathological data, as well as progression-free and overall survival. Most of studied cases (>50%) express LRIG2 and LRIG3. Statistically significant association was observed between positivity for LRIG3 and muscle invasion (P = 0.001), high grade (P = 0.03), and female gender (P = 0.02). Moreover, positive LRIG2 staining was associated with early stage (T2) (P = 0.03), lymphovascular invasion (P = 0.004), and tendency to non-muscle invasive stage (P = 0.07). Grouping of cases according to positivity/negativity of both markers showed that cases with dual positivity for both proteins are associated with muscle invasion (P = 0.001) and paradoxically with prolonged overall survival (P = 0.037). We conclude that although the association of LRIG3 with MI and high-grade tumors, its expression is related to better survival. LRIG3 has the dominant role even if it coexists with LRIG2. The role of LRIG2 remains to be further investigated.

The Role of Cell Proliferation and Extracellular Matrix Accumulation Induced by Food Additive Butylated Hydroxytoluene in Uterine Leiomyoma

Leiomyoma is the most common benign uterine tumor in reproductive-age women. Increasing numbers of studies are focusing on the effects of environmental exposure on the incidence and progression of tumors. One major step taken in the food industry is the addition of food preservatives to maintain freshness. Butylated hydroxytoluene (BHT) is a synthetic phenolic antioxidant, which is widely used as an additive to develop fat-soluble characteristics, as well as in cosmetics and rubber. Previous studies also highlighted that BHT may be related to increased fibrosis capacity and carcinogenic effects. In this study, we explored the effects of the commonly used food additive BHT on leiomyoma progression, and the related mechanism. The exposure of the ELT-3 leiomyoma cell line to BHT for 48 h increased the proliferative effect. Since leiomyoma progression is related to increases in extracellular matrix (ECM) accumulation and matrix metalloproteinase (MMP), BHT could effectively increase ECM-related protein expression, as well as MMP-2 and MMP-9 protein expression. This increase in ECM, in response to BHT, may be linked to the activation of the phosphoinositide 3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK) signaling pathway. Through PI3K inhibition, BHT’s effect on leiomyoma progression could be partially modulated. These results suggest the harmful effect of BHT exposure on leiomyoma progression may relate to PI3K modulation. However, an in vivo study is necessary to confirm these findings.

Regenerative cross talk between cardiac cells and macrophages

Aside from the first week postnatal, murine heart regeneration is restricted and responses to damage follow classic fibrotic remodeling. Recent transcriptomic analyses have suggested that significant cross talk with the sterile immune response could maintain a more embryonic-like signaling network that promotes acute, transient responses. However, with age, this response-likely mediated by neonatal yolk sac macrophages-then transitions to classical macrophage-mediated, cardiac fibroblast (CF)-based remodeling of the extracellular matrix (ECM) after myocardial infarction (MI). The molecular mechanisms that govern the change with age and drive fibrosis via inflammation are poorly understood. Using multiple ribonucleic acid sequencing (RNA-Seq) datasets, we attempt to resolve the relative contributions of CFs and macrophages in the bulk-healing response of regenerative (postnatal day 1) and nonregenerative hearts (postnatal day 8+). We performed an analysis of bulk RNA-Seq datasets from myocardium and cardiac fibroblasts as well as a single-cell RNA-Seq dataset from cardiac macrophages. MI-specific pathway differences revealed that nonregenerative hearts generated more ECM and had larger matricellular responses correlating with inflammation, produced greater chemotactic gradients to recruit macrophages, and expressed receptors for danger-associated molecular patterns at higher levels than neonates. These changes could result in elevated stress-response pathways compared with neonates, converging at NF-κB and activator protein-1 (AP-1) signaling. Profibrotic gene programs, which greatly diverge on day 3 post MI, lay the foundation for chronic fibrosis, and thus postnatal hearts older than 7 days typically exhibit significantly less regeneration. Our analyses suggest that the macrophage ontogenetic shift in the heart postnatally could result in detrimental stress signaling that suppresses regeneration.NEW & NOTEWORTHY Immediately postnatal mammalian hearts are able to regenerate after infarction, but the cells, pathways, and molecules that regulate this behavior are unclear. By comparing RNA-Seq datasets from regenerative mouse hearts and older, nonregenerative hearts, we are able to identify biological processes that are hallmarks of regeneration. We find that sterile inflammatory processes are upregulated in nonregenerative hearts, initiating profibrotic gene programs 3 days after myocardial infarction that can cause myocardial disease.

High Fat Diet Dysbiotic Mechanism of Decreased Gingival Blood Flow

The gut microbiome has a very important role in human health and its influence on the development of numerous diseases is well known. In this study, we investigated the effect of high fat diet (HFD) on the onset of dysbiosis, gingival blood flow decreases, and the periodontal matrix remodeling. We established a dysbiosis model (HFD group) and probiotic model by Lactobacillus rhamnosus GG (LGG) treatment for 12weeks. Fecal samples were collected 24h before mice sacrificing, while short chain fatty acids (SCFA) analysis, DNA extraction, and sequencing for metagenomic analysis were performed afterwards. After sacrificing the animals, we collected periodontal tissues and conducted comprehensive morphological and genetic analyses. While HFD reduced Bacteroidetes, SCFA, and gingival blood flow, this type of diet increased Firmicutes, lipopolysaccharide (LPS) binding protein, TLR4, pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), matrix metalloproteinases (MMP-2 and MMP-9) expression, and also altered markers of bone resorption (OPG and RANKL). However, LGG treatment mitigated these effects. Thus, it was observed that HFD increased molecular remodeling via inflammation, matrix degradation, and functional remodeling and consequently cause reduced gingival blood flow. All of these changes may lead to the alveolar bone loss and the development of periodontal disease.

THBS1 regulates trophoblast fusion through a CD36-dependent inhibition of cAMP, and its upregulation participates in preeclampsia

Preeclampsia is a pregnancy complication which threatens the survival of mothers and fetuses. It originates from abnormal placentation, especially insufficient fusion of the cytotrophoblast cells to form the syncytiotrophoblast. In this study, we found that THBS1, a matricellular protein that mediates cell-to-cell and cell-to-matrix interactions, is downregulated during the fusion of primary cytotrophoblast and BeWo cells, but upregulated in the placenta of pregnancies complicated by preeclampsia. Also, THBS1 was observed to interact with CD36, a membrane signal receptor and activator of the cAMP signaling pathway, to regulate the fusion of cytotrophoblast cells. Overexpression of THBS1 inhibited the cAMP signaling pathway and reduced the BeWo cells fusion ratio, while the effects of THBS1 were abolished by a CD36-blocking antibody. Our results suggest that THBS1 signals through a CD36-mediated cAMP pathway to regulate syncytialization of the cytotrophoblast cells, and that its upregulation impairs placental formation to cause preeclampsia. Thus, THBS1 can serve as a therapeutic target regarding the mitigation of abnormal syncytialization and preeclampsia.

The transmembrane protein LRIG2 increases tumor progression in skin carcinogenesis

Over the last few decades, the number of cases of non‐melanoma skin cancer (NMSC) has risen to over 3 million cases every year worldwide. Members of the ERBB receptor family are important regulators of skin development and homeostasis and, when dysregulated, contribute to skin pathogenesis. In this study, we investigated leucine‐rich repeats and immunoglobulin‐like domains 2 (LRIG2), a transmembrane protein involved in feedback loop regulation of the ERBB receptor family during NMSC. LRIG2 was identified to be up‐regulated in various types of squamous cell carcinoma (SCC), but little is known about LRIG2 in cutaneous SCC (cSCC). To investigate the function of LRIG2 in cSCC in vivo, we generated a skin‐specific LRIG2 overexpressing transgenic mouse line (LRIG2‐TG) using the Tet‐Off system. We employed the 7,12‐dimethylbenz(a)anthracene/12‐O‐tetra‐decanoylphorbol‐13‐acetate (DMBA/TPA) two‐stage chemical carcinogenesis model and analyzed the skin during homeostasis and tumorigenesis. LRIG2‐TG mice did not exhibit alterations in skin development or homeostasis but showed an interaction between LRIG2 and thrombospondin‐1, which is often involved in angiogenesis and tumorigenesis. However, during carcinogenesis, transgenic animals showed significantly increased tumor progression and a more rapid development of cSCC. This was accompanied by changes in the ERBB system. After a single TPA application, inflammation of the epidermis was enhanced during LRIG2 overexpression. In human skin samples, LRIG2 expression was identified in the basal layer of the epidermis and in hair follicles of normal skin, but also in cSCC samples. In conclusion, epidermal LRIG2 excess is associated with activated EGFR/ERBB4‐MAPK signaling and accelerated tumor progression in experimentally induced NMSC, suggesting LRIG2 as a potential oncoprotein in skin.

Shear Stress Modulates the Expression of Thrombospondin-1 and CD36 in Endothelial Cells in vitro and during Shear Stress-Induced Angiogenesis in vivo

Binding of thrombospondin-1 (TSP-1) to the CD36 receptor inhibits angiogenesis and induces apoptosis in endothelial cells (EC). Conversely, matrix-bound TSP-1 supports vessel formation. In this study we analyzed the shear stress-dependent expression of TSP-1 and CD36 in endothelial cells in vitro and in vivo to reveal its putative role in the blood flow-induced remodelling of vascular networks. Shear stress was applied to EC using a cone-and-plate apparatus and gene expression was analyzed by RT-PCR, Northern and Western blot. Angiogenesis in skeletal muscles of prazosin-fed (50 mg/1 drinking water; 4 d) mice was assessed by measuring capillary-to-fiber (C/F) ratios. Protein expression in whole muscle homogenates (WMH) or BS-1 lectin-enriched EC fractions (ECF) was analyzed by Western blot. Shear stress down-regulated TSP-1 and CD36 expression in vitro in a force- and time-dependent manner sustained for at least 72 h and reversible by restoration of no-flow conditions. In vivo, shear stress-driven increase of C/F in prazosin-fed mice was associated with reduced expression of TSP-1 and CD36 in ECF, while TSP-1 expression in WMH was increased. Down-regulation of endothelial TSP-1/CD36 by shear stress suggests a mechanism for inhibition of apoptosis in perfused vessels and pruning in the absence of flow. The increase of extra-endothelial (e.g. matrix-bound) TSP-1 could support a splitting type of vessel growth.

Aortic dysfunction in metabolic syndrome mediated by perivascular adipose tissue TNFα- and NOX2-dependent pathway

NEW FINDINGS

What is the central question of this study? Tumour necrosis factor-α (TNFα) has been shown to impair vascular function, but the impact of thoracic aorta perivascular adipose tissue (tPVAT)-derived TNFα on tPVAT and aortic function in metabolic syndrome is unknown. What is the main finding and its importance? Release of TNFα by tPVAT causes production of reactive oxygen species in tPVAT through activation of an NADPH-oxidase 2 (NOX2)-dependent pathway, activates production of aortic reactive oxygen species and mediates aortic stiffness, potentially through matrix metalloproteinase 9 activity. Neutralization of TNFα and/or inhibition of NOX2 blocks the tPVAT-induced impairment of aortic function. These data partly implicate tPVAT NOX2 and TNFα in mediating the vascular pathology of metabolic syndrome.

ABSTRACT

Perivascular adipose tissue (PVAT) is recognized for its vasoactive effects, but it is unclear how metabolic syndrome impacts thoracic aorta (t)PVAT and the subsequent effect on functional and structural aortic stiffness. Thoracic aorta and tPVAT were removed from 16- to 17-week-old lean (LZR, n = 16) and obese Zucker rats (OZR, n = 16). The OZR presented with aortic endothelial dysfunction, assessed by wire myography, and increased aortic stiffness, assessed by elastic modulus. The OZR tPVAT exudate further exacerbated the endothelial dysfunction, reducing nitric oxide and endothelium-dependent relaxation (P < 0.05). Additionally, OZR tPVAT exudate had increased MMP9 activity (P < 0.05) and further increased the elastic modulus of the aorta after 72 h of co-culture (P < 0.05). We found that the observed aortic dysfunction caused by OZR tPVAT was mediated through increased production and release of tumour necrosis factor-α (TNFα; P < 0.01), which was dependent on tPVAT NADPH-oxidase 2 (NOX2) activity. The OZR tPVAT release of reactive oxygen species and subsequent aortic dysfunction were inhibited by TNFα neutralization and/or inhibition of NOX2. Additionally, we found that OZR tPVAT had reduced activity of the active sites of the 20S proteasome (P < 0.05) and reduced superoxide dismutase activity (P < 0.01). In conclusion, metabolic syndrome causes tPVAT dysfunction through an interplay between TNFα and NOX2 that leads to tPVAT-mediated aortic stiffness by activation of aortic reactive oxygen species and increased MMP9 activity.

Multi-Carotenoids at Physiological Levels Inhibit VEGF-Induced Tube Formation of Endothelial Cells and the Possible Mechanisms of Action Both In Vitro and Ex Vivo

Carotenoids have been shown to exhibit antiangiogenic activities. Several studies have indicated that carotenoids used in combination were more effective on antioxidation and anticancer actions than carotenoids used singly. However, it is unclear whether multi-carotenoids have antiangiogenic effects. We investigated the effects of multi-carotenoids at physiological plasma levels of Taiwanese (abbreviated as MCT, with a total of 1.4 μM) and Americans (abbreviated as MCA, with a total of 1.8 μM), and of post-supplemental plasma levels (abbreviated as HMC with a total of 3.55 μM) on vascular endothelial growth factor (VEGF)-induced tube formation in human umbilical vein endothelial cells (HUVECs) and rat aortic rings. MCT, MCA, and HMC inhibited VEGF-induced migration, invasion, and tube formation of HUVECs as well as new vessels formation in rat aortic rings. MCT, MCA, and HMC inhibited activities o\f matrix metalloproteinase (MMP)-2, urokinase plasminogen activator, and phosphorylation of VEGF receptor 2 induced by VEGF. Moreover, MCT, MCA, and HMC significantly upregulated protein expression of tissue inhibitors of MMP-2 and plasminogen activator inhibitor-1. These results demonstrate the antiangiogenic effect of multi-carotenoids both in vitro and ex vivo with possible mechanistic actions involving attenuation of VEGF receptor 2 phosphorylation and extracellular matrix degradation.

Matrix metalloproteinase-9: Many shades of function in cardiovascular disease

Matrix metalloproteinase (MMP)-9, one of the most widely investigated MMPs, regulates pathological remodeling processes that involve inflammation and fibrosis in cardiovascular disease. MMP-9 directly degrades extracellular matrix (ECM) proteins and activates cytokines and chemokines to regulate tissue remodeling. MMP-9 deletion or inhibition has proven overall beneficial in multiple animal models of cardiovascular disease. As such, MMP-9 expression and activity is a common end point measured. MMP-9 cell-specific overexpression, however, has also proven beneficial and highlights the fact that little information is available on the underlying mechanisms of MMP-9 function. In this review, we summarize our current understanding of MMP-9 physiology, including structure, regulation, activation, and downstream effects of increased MMP-9. We discuss MMP-9 roles during inflammation and fibrosis in cardiovascular disease. By concentrating on the substrates of MMP-9 and their roles in cardiovascular disease, we explore the overall function and discuss future directions on the translational potential of MMP-9 based therapies.

Microarray analysis of Dupuytren's disease cells: the profibrogenic role of the TGF-β inducible p38 MAPK pathway

BACKGROUND

Dupuytren's disease (DD) is a nodular palmar fibromatosis that causes irreversible permanent contracture of fingers and results in the loss of hand function. Surgery still remains the only available solution for DD patients but cannot permanently cure the disease nor reduce high recurrence rates. With this rationale, we designed a study aimed at an improved understanding of the molecular mechanisms underlying DD. Our major focus was an analysis of the global gene expression profile and signalling pathways in DD cells with the aim of identifying novel biomarkers and/or therapeutic targets.

METHODS

Primary cells were cultured from surgically removed diseased and healthy tissue. Microarray expression analysis (HG-U133A array, Affymetrix) and qPCR was performed with total RNA isolated from primary DD cells. Mechanistic studies involving inhibition of p38 phosphorylation were performed on normal human fibroblasts' and primary DD cells' in vitro models. Expression of stem cell markers in primary fibroblasts/myofibroblasts was assessed as well.

RESULTS

We identified 3 p38MAPK signalling pathway regulatory genes, THBS1, GADD45α and NUAK1, all involved in cellular proliferation and production of the extracellular matrix proteins. Inhibition of the p38MAPK signalling pathway induced down-regulation of myofibroblast markers, α-smooth muscle actin and palladin. A stem-cell like subpopulation positive for CD90 marker was identified among primary DD cells.

CONCLUSION

The study reveals involvement of the p38 MAPK pathway as a possible signalling cascade in the pathogenesis of Dupuytren's disease. Moreover, a particular stem cell-like CD90(+) subpopulation was identified that might contribute to DD development.

The role of extracellular signal-related kinase during abdominal aortic aneurysm formation

BACKGROUND

It is hypothesized that activation of extracellular signal-related kinase (ERK) is critical in activating matrix metalloproteinases (MMPs) during abdominal aortic aneurysm (AAA) formation.

STUDY DESIGN

C57BL/6 male mice underwent either elastase or heat-inactivated elastase aortic perfusion (n = 9 per group). Mouse aortic smooth muscle cells were transfected with ERK-1 and 2 siRNA along with or without elastase treatment. Mouse and human aortic tissue were analyzed by Western blots, zymograms, and immunohistochemistry, and statistical analysis was done using Graphpad and Image J softwares.

RESULTS

Western blot and immunohistochemistry documented increased phospho-mitogen-activated protein kinase kinase-1/2 (pMEK-1/2; 153%, p = 0.270 by Western) and pERK (171%, p = 0.004 by Western blot) in the elastase perfused aortas. Male ERK-1(-/-) mice underwent elastase perfusion, and aortic diameter was determined at day 14. ERK-1(-/-) mice failed to develop AAA, and histologic analysis depicted intact collagen and elastin fibers in the aortas. Zymography of aortas of elastase-treated ERK-1(-/-) mice showed lower levels of proMMP2 (p < 0.005) and active MMP2 (p < 0.0001), as well as proMMP9 (p = 0.037) compared with C57BL/6 mice. siRNA transfection of ERK-1 and -2 significantly reduced formation of pro- and active MMP2 (p < 0.01 for both isoforms) in aortic smooth muscle cells treated with elastase in vitro. Human AAA tissue had significantly elevated levels of pMEK-1/2 (150%, p = 0.014) and pERK (159%, p = 0.013) compared with control tissues.

CONCLUSIONS

The MAPK (mitogen-activated protein kinase)/ERK pathway is an important modulator of MMPs during AAA formation. Targeting the ERK pathway by reagents that inhibit either the expression or phosphorylation of ERK isoforms could be a potential therapy to prevent AAA formation.

Nuclear localization of matrix metalloproteinases

Matrix metalloproteinases (MMPs) were originally identified as matrixin proteases that act in the extracellular matrix. Recent works have uncovered nontraditional roles for MMPs in the extracellular space as well as in the cytosol and nucleus. There is strong evidence that subspecialized and compartmentalized matrixins participate in many physiological and pathological cellular processes, in which they can act as both degradative and regulatory proteases. In this review, we discuss the transcriptional and translational control of matrixin expression, their regulation of intracellular sorting, and the structural basis of activation and inhibition. In particular, we highlight the emerging roles of various matrixin forms in diseases. The activity of matrix metalloproteinases is regulated at several levels, including enzyme activation, inhibition, complex formation and compartmentalization. Most MMPs are secreted and have their function in the extracellular environment. MMPs are also found inside cells, both in the nucleus, cytosol and organelles. The role of intracellular located MMPs is still poorly understood, although recent studies have unraveled some of their functions. The localization, activation and activity of MMPs are regulated by their interactions with other proteins, proteoglycan core proteins and / or their glycosaminoglycan chains, as well as other molecules. Complexes formed between MMPs and various molecules may also include interactions with noncatalytic sites. Such exosites are regions involved in substrate processing, localized outside the active site, and are potential binding sites of specific MMP inhibitors. Knowledge about regulation of MMP activity is essential for understanding various physiological processes and pathogenesis of diseases, as well as for the development of new MMP targeting drugs.

Toll-like receptor 2 induced angiogenesis and invasion is mediated through the Tie2 signalling pathway in rheumatoid arthritis

Background

Angiogenesis is a critical early event in inflammatory arthritis, facilitating leukocyte migration into the synovium resulting in invasion and destruction of articular cartilage and bone. This study investigates the effect of TLR2 on angiogenesis, EC adhesion and invasion using microvascular endothelial cells and RA whole tissue synovial explants ex-vivo.

Methods

Microvascular endothelial cells (HMVEC) and RA synovial explants ex vivo were cultured with the TLR2 ligand, Pam3CSK4 (1 µg/ml). Angiopoietin 2 (Ang2), Tie2 and TLR2 expression in RA synovial tissue was assessed by immunohistology. HMVEC tube formation was assessed using Matrigel matrix assays. Ang2 was measured by ELISA. ICAM-1 cell surface expression was assessed by flow cytometry. Cell migration was assessed by wound repair scratch assays. ECM invasion, MMP-2 and -9 expression were assessed using transwell invasion chambers and zymography. To examine if the angiopoietin/Tie2 signalling pathway mediates TLR2 induced EC tube formation, invasion and migration assays were performed in the presence of a specific neutralising anti-Tie2mAb (10 ug/ml) and matched IgG isotype control Ab (10 ug/ml).

Results

Ang2 and Tie2 were localised to RA synovial blood vessels, and TLR2 was localised to RA synovial blood vessels, sub-lining infiltrates and the lining layer. Pam3CSK4 significantly increased angiogenenic tube formation (p<0.05), and upregulated Ang2 production in HMVEC (p<0.05) and RA synovial explants (p<0.05). Pam3CSK4 induced cell surface expression of ICAM-1, from basal level of 149±54 (MFI) to 617±103 (p<0.01). TLR-2 activation induced an 8.8±2.8 fold increase in cell invasion compared to control (p<0.05). Pam3CSK4 also induced HMVEC cell migration and induced MMP-2 and -9 from RA synovial explants. Neutralisation of the Ang2 receptor, Tie2 significantly inhibited Pam3CSK4-induced EC tube formation and invasion (p<0.05).

Conclusion

TLR2 activation promotes angiogenesis, cell adhesion and invasion, effects that are in part mediated through the Tie2 signalling pathway, key mechanisms involved in the pathogenesis of RA.

Thrombospondin-1 as a Paradigm for the Development of Antiangiogenic Agents Endowed with Multiple Mechanisms of Action

Uncontrolled neovascularization occurs in several angiogenesis-dependent diseases, including cancer. Neovascularization is tightly controlled by the balance between angiogenic growth factors and antiangiogenic agents. The various natural angiogenesis inhibitors identified so far affect neovascularization by different mechanisms of action. Thrombospondin-1 (TSP-1) is a matricellular modular glycoprotein that acts as a powerful endogenous inhibitor of angiogenesis. It acts both indirectly, by sequestering angiogenic growth factors and effectors in the extracellular environment, and directly, by inducing an antiangiogenic program in endothelial cells following engagement of specific receptors including CD36, CD47, integrins and proteoglycans (all involved in angiogenesis ). In view of its central, multifaceted role in angiogenesis, TSP-1 has served as a source of antiangiogenic tools, including TSP-1 fragments, synthetic peptides and peptidomimetics, gene therapy strategies, and agents that up-regulate TSP-1 expression. This review discusses TSP-1-based inhibitors of angiogenesis, their mechanisms of action and therapeutic potential, drawing our experience with angiogenic growth factor-interacting TSP-1 peptides, and the possibility of exploiting them to design novel antiangiogenic agents.

Biological activities and molecular interactions of the C-terminal residue of thrombospondin-4, an epitome of acidic amphipathic peptides

C21, the C-terminal residue of thrombospondin-4 (TSP-4), was identified as a peptide growth factor during an investigation concerning erythropoietin-dependent, erythroid stimulating factors of endothelial origin. It is active in cultures of several human hematopoietic stem cells, skin fibroblasts and kidney epithelial cells and stimulates red cell formation in anemic mice. A method of affinity chromatography in the presence of high concentrations of Triton X-100, previously developed for identifying proteins associated with the TSP-1 receptor CD47, was utilized for the detection of C21 binding molecules and their detergent-resistant, associated partners. These experiments helped to delineate two different mechanisms of C21 action, which are compatible with its cell proliferating activity. As a cell matrix peptide, C21 binds to the osteopontin receptor CD44 and could act as an osteopontin antagonist, preventing the inhibition of primitive hematopoietic stem cell proliferation. TSP-1, another matrix protein, binds to C21 and could indirectly act as an antagonist, by shunting C21-CD44 interactions. The second mechanism is a direct effect of C21 on cell proliferation. The extremely rapid internalization and nuclear localization of the peptide could be explained by CD44-mediated internalization, followed by a microtubule-mediated transport towards the nucleus, or, eventually, direct membrane insertion. These alternative hypotheses are supported by previously observed membrane insertion of similar synthetic and viral acidic amphipathic peptides, the presence of microtubule-associated protein 1B (MAP1B) and dynactin in the triton-soluble complexes associated with C21 and the presence in such complexes of dual compartment proteins for nuclei and plasma membranes, such as MAP1B, AHNAK and CD44.

A new procedure for determining the genetic basis of a physiological process in a non-model species, illustrated by cold induced angiogenesis in the carp

BACKGROUND

Physiological processes occur in many species for which there is yet no sequenced genome and for which we would like to identify the genetic basis. For example, some species increase their vascular network to minimise the effects of reduced oxygen diffusion and increased blood viscosity associated with low temperatures. Since many angiogenic and endothelial genes have been discovered in man, functional homolog relationships between carp, zebrafish and human were used to predict the genetic basis of cold-induced angiogenesis in Cyprinus Carpio (carp). In this work, carp sequences were collected and built into contigs. Human-carp functional homolog relationships were derived via zebrafish using a new Conditional Stepped Reciprocal Best Hit (CSRBH) protocol. Data sources including publications, Gene Ontology and cDNA libraries were then used to predict the identity of known or potential angiogenic genes. Finally, re-analyses of cold carp microarray data identified carp genes up-regulated in response to low temperatures in heart and muscle.

RESULTS

The CSRBH approach outperformed all other methods and attained 8,726 carp to human functional homolog relationships for 16,650 contiguous sequences. This represented 3,762 non-redundant genes and 908 of them were predicted to have a role in angiogenesis. The total number of up-regulated differentially expressed genes was 698 and 171 of them were putatively angiogenic. Of these, 5 genes representing the functional homologs NCL, RHOA, MMP9, GRN and MAPK1 are angiogenesis-related genes expressed in response to low temperature.

CONCLUSION

We show that CSRBH functional homologs relationships and re-analyses of gene expression data can be combined in a non-model species to predict genes of biological interest before a genome sequence is fully available. Programs to run these analyses locally are available from http://www.cbrg.ox.ac.uk/~jherbert/.

Absence of thrombospondin-2 causes age-related dilated cardiomyopathy

BACKGROUND

The progressive shift from a young to an aged heart is characterized by alterations in the cardiac matrix. The present study investigated whether the matricellular protein thrombospondin-2 (TSP-2) may affect cardiac dimensions and function with physiological aging of the heart.

METHODS AND RESULTS

TSP-2 knockout (KO) and wild-type mice were followed up to an age of 60 weeks. Survival rate, cardiac function, and morphology did not differ at a young age in TSP-2 KO compared with wild-type mice. However, >55% of the TSP-2 KO mice died between 24 and 60 weeks of age, whereas <10% of the wild-type mice died. In the absence of TSP-2, older mice displayed a severe dilated cardiomyopathy with impaired systolic function, increased cardiac dilatation, and fibrosis. Ultrastructural analysis revealed progressive myocyte stress and death, accompanied by an inflammatory response and replacement fibrosis, in aging TSP-2 KO animals, whereas capillary or coronary morphology or density was not affected. Importantly, adeno-associated virus-9 gene-mediated transfer of TSP-2 in 7-week-old TSP-2 KO mice normalized their survival and prevented dilated cardiomyopathy. In TSP-2 KO animals, age-related cardiomyopathy was accompanied by increased matrix metalloproteinase-2 and decreased tissue transglutaminase-2 activity, together with impaired collagen cross-linking. At the cardiomyocyte level, TSP-2 deficiency in vivo and its knockdown in vitro decreased the activation of the Akt survival pathway in cardiomyocytes.

CONCLUSIONS

TSP-2 expression in the heart protects against age-dependent dilated cardiomyopathy.

Thrombospondins in the heart: potential functions in cardiac remodeling

Cardiac remodeling after myocardial injury involves inflammation, angiogenesis, left ventricular hypertrophy and matrix remodeling. Thrombospondins (TSPs) belong to the group of matricellular proteins, which are non-structural extracellular matrix proteins that modulate cell-matrix interactions and cell function in injured tissues or tumors. They interact with different matrix and membrane-bound proteins due to their diverse functional domains. That the expression of TSPs strongly increases during cardiac stress or injury indicates an important role for them during cardiac remodeling. Recently, the protective properties of TSP expression against heart failure have been acknowledged. The current review will focus on the biological role of TSPs in the ischemic and hypertensive heart, and will describe the functional consequences of TSP polymorphisms in cardiac disease.

Epidermal growth factor-like repeats of thrombospondins activate phospholipase Cgamma and increase epithelial cell migration through indirect epidermal growth factor receptor activation

Thrombospondin (TSP) 1 is a trimeric multidomain protein that contains motifs that recognize distinct host cell receptors coupled to multiple signaling pathways. Selected TSP1-induced cellular responses are tyrosine kinase-dependent, and TSP1 contains epidermal growth factor (EGF)-like repeats. Specific receptor interactions or functions for the EGF-like repeats have not been identified. We asked whether one or more biological responses to TSP1 might be explained through EGF receptor (EGFR) activation. In A431 cells, TSP1 increased autophosphorylation of Tyr-1068 of EGFR in a dose- and time-dependent manner. The ability of TSP1 to activate EGFR was replicated by the tandem EGF-like repeats as a recombinant protein. The three EGF-like repeats alone produced a high level of Tyr-1068 phosphorylation. EGF-like repeats from TSP2 and TSP4 also activated EGFR. Tyr-1068 phosphorylation was less when individual EGF-like repeats were tested or flanking sequences were added to the three EGF-like repeats. TSP1 and its EGF-like repeats also increased phosphorylation of EGFR Tyr-845, Tyr-992, Tyr-1045, Tyr-1086, and Tyr-1173, activated phospholipase Cgamma, and increased cell migration. No evidence was found for binding of the EGF-like repeats to EGFR. Instead, EGFR activation in response to TSP1 or its EGF-like repeats required matrix metalloprotease activity, including activity of matrix metalloprotease 9. Access to the ligand-binding portion of the EGFR ectodomain was also required. These findings suggest release of an endogenous EGFR ligand in response to ligation of a second unknown receptor by the TSPs.

The counteradhesive proteins, thrombospondin 1 and SPARC/osteonectin, open the tyrosine phosphorylation-responsive paracellular pathway in pulmonary vascular endothelia

Counteradhesive proteins are a group of genetically and structurally distinct multidomain proteins that have been grouped together for their ability to inhibit cell-substrate interactions. Three counteradhesive proteins that influence endothelial cell behavior include thrombospondin (TSP)1, (SPARC) (Secreted Protein Acidic and Rich in Cysteine), also known as osteonectin, and tenascin. More recently, these proteins have been shown to regulate not only cell-matrix interactions but cell-cell interactions as well. TSP1 increases tyrosine phosphorylation of components of the cell-cell adherens junctions or zonula adherens (ZA) and opens the paracellular pathway in human lung microvascular endothelia. The epidermal growth factor (EGF)-repeats of TSP1 activate the (EGF) receptor (EGFR) and ErbB2, and these two receptor protein tyrosine kinases (PTK)s participate in ZA protein tyrosine phosphorylation and barrier disruption in response to the TSP1 stimulus. For the barrier response to TSP1, EGFR/ErbB2 activation is necessary but insufficient. Protein tyrosine phosphatase (PTP)mu counter-regulates phosphorylation of selected tyrosine residues within the cytoplasmic domain of EGFR. Although tenascin, like TSP1, also contains EGF-like repeats and is known to activate EGFR, whether it also opens the paracellular pathway is unknown. In addition to TSP1, tenascin, and the other TSP family members, there are numerous other proteins that also contain EGF-like repeats and participate in hemostasis, wound healing, and tissue remodeling. EGFR not only responds to direct binding of EGF motif-containing ligands but can also be transactivated by a wide range of diverse stimuli. In fact, several established mediators of increased vascular permeability and/or lung injury, including thrombin, tumor necrosis factor-alpha, platelet-activating factor, bradykinin, angiopoietin, and H(2)O(2), transactivate EGFR. It is conceivable that EGFR serves a pivotal signaling role in a final common pathway for the pulmonary response to selected injurious stimuli. SPARC/Osteonectin also increases tyrosine phosphorylation of ZA proteins and opens the endothelial paracellular pathway in a PTK-dependent manner. The expression of the counteradhesive proteins is increased in response to a wide range of injurious stimuli. It is likely that these same molecules participate in the host response to acute lung injury and are operative during the barrier response within the pulmonary microvasculature.

Peroxynitrite inactivates human-tissue inhibitor of metalloproteinase-4

Peroxynitrite, via post-translational modifications to target proteins, contributes to cardiovascular injury and cancer. Since tissue inhibitor of metalloproteinase-4 (TIMP-4), the activity of which is impaired in both pathological conditions, has several amino acid residues susceptible to peroxynitrite, we investigated its role as a potential target of peroxynitrite. Peroxynitrite-induced nitration and oligomerization of TIMP-4 attenuated its inhibitory activity against MMP-2 activity and endothelial or tumor cell invasiveness. Moreover, cell treatment with peroxynitrite promoted the nitration of endogenous TIMP-4. HPLC/ESI-MS/MS analysis of peroxynitrite-treated TIMP-4 showed modifications at Y114, Y195, Y188 and Y190. In conclusion, TIMP-4 nitration might be a potential mechanism contributing to cardiovascular disease and cancer.

Thrombospondins in cancer

The thrombospondins (TSPs) are a family of five proteins that are involved in the tissue remodeling that is associated with embryonic development, wound healing, synaptogenesis, and neoplasia. These proteins mediate the interaction of normal and neoplastic cells with the extracellular matrix and surrounding tissue. In the tumor microenvironment, TSP-1 has been shown to suppress tumor growth by inhibiting angiogenesis and by activating transforming growth factor beta. TSP-1 inhibits angiogenesis through direct effects on endothelial cell migration and survival, and through effects on vascular endothelial cell growth factor bioavailability. In addition, TSP-1 may affect tumor cell function through interaction with cell surface receptors and regulation of extracellular proteases. Whereas the role of TSP-1 in the tumor microenvironment is the best characterized, the other TSPs may have similar functions. (Part of a Multi-author Review).

Thrombospondin-1 and thrombospondin-2 mRNA and TSP-1 and TSP-2 protein expression in uterine fibroids and correlation to the genes COL1A1 and COL3A1 and to the collagen cross-link hydroxyproline

Uterine fibroids are composed of altered collagen fibrils and represent an arrested response to injury-initiating fibrosis. In many tissues, TSP-1 is secreted by adult macrophages and monocytes upon wounding and is involved in the activation of transforming growth factor beta. In the absence of TSP-1, the orchestrated process of wound healing is impaired. The authors obtained tissue from the edge and center of fibroids at the time of hysterectomy and compared them with adjacent myometrium. The pattern of TSP-1 and TSP-2 expression was correlated to that of COL1A1 and COL3A1. Collagen and hydroxyproline were increased in fibroids. Thrombospondin-1 was consistently underexpressed in both the edge and center of the fibroids, while COL1A1 and COL3A1 were consistently overexpressed. However, TSP-2 was inconsistently expressed. These findings lead to the conclusion that the underexpression of TSP-1 may contribute to the overall development of uterine fibroids.

Prostaglandin E2 regulates angiogenesis via activation of fibroblast growth factor receptor-1

Prostaglandin E(2) (PGE(2)) behaves as a mitogen in epithelial tumor cells as well as in many other cell types. We investigated the actions of PGE(2) on microvascular endothelial cells (capillary venular endothelial cells) with the purpose of delineating the signaling pathway leading to the acquisition of the angiogenic phenotype and to new vessel formation. PGE(2) (100 nM) produced activation of the fibroblast growth factor receptor 1 (FGFR-1), as measured by its phosphorylation, but not of vascular endothelial growth factor receptor 2. PGE(2) stimulated the EP3 subtype receptor, as deduced by abrogation of EP3 Galpha(i) subunit activity through pertussis toxin. Consistent with this result, in human umbilical venular endothelial cells missing the EP3 receptor, PGE(2) did not phosphorylate FGFR-1. Upon binding to its receptor, PGE(2) initiated an autocrine/paracrine signaling cascade involving the intracellular activation of c-Src, activation of matrix metalloproteinase (predominantly MMP2), which in turn caused the mobilization of membrane-anchored fibroblast growth factor-2 (FGF-2). In fact, in cells unable to release FGF-2 the transfection with both FGFR-1 and EP3 did not result in FGFR-1 phosphorylation in response to PGE(2). Relevance for the FGF2-FGFR-1 system was highlighted by confocal analysis, showing receptor internalization after cell exposure to the prostanoid. ERK1/2 appeared to be the distal signal involved, its phosphorylation being sensitive to either cSrc inhibitor or FGFR-1 blocker. Finally, PGE(2) stimulated cell migration and capillary formation in aortic rings, which were severely reduced by inhibitors of signaling molecules or by receptor antagonist. In conclusion, this study provides evidence for the involvement of FGFR-1 through FGF2 in eliciting PGE(2) angiogenic responses. This signaling pattern is similar to the autocrine-paracrine mechanism which operates in endothelial cells to support neovascular growth.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

EP2 prostanoid receptor promotes squamous cell carcinoma growth through epidermal growth factor receptor transactivation and iNOS and ERK1/2 pathways

In squamous cell carcinoma, the levels of nitric oxide (NO) derived from inducible NO synthase (iNOS) and prostaglandin E2 (PGE2) derived from cyclooxygenase-2 (COX-2) originated from tumor cells or tumor-associated inflammatory cells have been reported to correlate with tumor growth, metastasis, and angiogenesis. The present study examined the role of the iNOS signaling pathway in PGE2-mediated tumor invasiveness and proliferation in squamous cell carcinoma, A431, and SCC-9 cells. Cell invasion and proliferation promoted by PGE2 were blocked by iNOS silencing RNA or iNOS/guanylate cyclase (GC) pharmacological inhibition. Consistently, iNOS-GC pathway inhibitors blocked mitogen-activated protein kinase-ERK1/2 phosphorylation, which was required to mediate PGE2 functions. In vivo, in A431 cells implanted in nude mice, GC inhibition also decreased the tumor proliferation index and ERK1/2 activation. PGE2 effects were confined to the selective stimulation of the EP2 receptor subtype, leading to epidermal growth factor receptor (EGFR) transactivation via protein kinase A (PKA) and c-Src activation. EP2-mediated ERK1/2 activation and cell functions were abolished by inhibitors of PKA, c-Src, and EGFR, as well as by inhibiting iNOS pathway. Silencing of iNOS also impaired EGFR-induced ERK1/2 phosphorylation. These results indicate that iNOS/GC signaling is a downstream player in the control of EP2/EGFR-mediated tumor cell proliferation and invasion.

Fibroblast Growth Factor-2 Mediates Angiotensin-Converting Enzyme Inhibitor-Induced Angiogenesis in Coronary Endothelium

The beneficial effect exerted by angiotensin-converting enzyme inhibitors (ACEI) on vascular endothelium has been attributed to restoration of endothelial cell survival properties and improvement of angiogenesis. Fibroblast growth factor (FGF)-2 is an angiogenic factor for the microvascular endothelium, which tonically promotes endothelial cell growth and survival through an autocrine/paracrine mechanism. Here, we formulate the hypothesis that FGF-2 might contribute to the prosurvival/proangiogenic effect of ACEI. We investigated zofenoprilat and, in selected experiments, lisinopril, as representatives of ACEI. These compounds induced formation of pseudocapillaries in vessel fragments isolated from porcine coronary and human umbilical arteries by increasing endothelial cell growth up to 5-fold. Angiogenesis was abolished by inhibitors of nitric-oxide synthase (NOS) pathway and by anti-FGF-2 antibodies. Consistently, in cultured coronary endothelial cells (CVECs), ACEI up-regulated endothelial NOS (eNOS) and FGF-2 and induced mitogen-activated protein kinase extracellular signal-regulated kinase 1/2 activation. The overexpression of eNOS/FGF-2 produced, at the functional level, enhanced cell proliferation and migration, the latter effect being dose-dependent and maximal at 0.1 microM zofenoprilat. The importance of FGF-2 for the acquisition of the angiogenic phenotype elicited by ACEI was clearly demonstrated by the impairment of endothelial functions following transfection of CVECs with small interference RNA for FGF-2. Moreover, FGF-2 silencing greatly affected the nuclear translocation of the FGF receptor (FGFR)-1, highlighting the autocrine mode of action of FGF-2. At the endothelial membrane level, zofenoprilat appeared to activate the bradykinin B1 receptor, a known stimulant of FGF-2 expression. In conclusion, we show that ACEI exert protective/proangiogenic effects in microvascular coronary endothelial cells by activating the endogenous FGF-2/FGFR-1 system.

ERK1/2 and p38 MAP kinase control MMP-2, MT1-MMP, and TIMP action and affect cell migration: a comparison between mesothelioma and mesothelial cells

Pleural malignant mesothelioma is a locally aggressive tumor of mesothelial cell origin. In other tumor types high expression of matrix metalloproteinase (MMP)-2, together with membrane-type1-MMP (MT1-MMP), and low levels of the tissue inhibitor of MMP (TIMP)-2 have been correlated with aggressive tumor progression and low survival rates. Therefore, we compared the expression and activation of these three factors and their regulation by two mesothelioma associated growth factors, platelet-derived growth factor (PDGF)-BB, and transforming growth factor (TGF)-beta1 in six human mesothelioma and one mesothelial cell line. Polymerase chain reaction (PCR), immunoblotting, zymography, and small inhibitory RNAs (siRNA) were used to study gene expression, protein activation, and signal transduction. To proof the relevance of our in vitro data immunohistochemistry was performed in tissue sections. PDGF-BB induced, while TGF-beta1 inhibited cell proliferation. PDGF-BB was a chemoattractant for mesothelial cells, and its effect was increased in the presence of TGF-beta1. TGF-beta1 stimulated the de novo synthesis of pro-MMP-2 in both cell types. Pro-MMP-2 synthesis involved p38 MAP kinase. In cell culture and tissue sections only mesothelial cells expressed MT1-MMP. Migration of mesothelioma cells was dependent on the presence of MT1-MMP. Migration, but not proliferation of mesothelioma cells was inhibited by oleoyl-N-hydroxylamide, TIMP-2, and siRNA for MT1-MMP. Our data suggest that in mesothelioma cells the phosphorylation of p38 MAP kinase is deregulated and is involved in pro-MMP-2 expression. Mesothelioma progression depends on an interaction with mesothelial cells that provide MT1-MMP necessary to activate pro-MMP-2 to facilitate migration through an extracellular matrix (ECM) layer.

Regulation of tumor angiogenesis by thrombospondin-1

Angiogenesis plays a critical role in the growth and metastasis of tumors. Thrombospondin-1 (TSP-1) is a potent angiogenesis inhibitor, and down-regulation of TSP-1 has been suggested to alter tumor growth by modulating angiogenesis in a variety of tumor types. Expression of TSP-1 is up-regulated by the tumor suppressor gene, p53, and down-regulated by oncogenes such as Myc and Ras. TSP-1 inhibits angiogenesis by inhibiting endothelial cell migration and proliferation and by inducing apoptosis. In addition, activation of transforming growth factor beta (TGF-beta) by TSP-1 plays a crucial role in the regulation of tumor progression. An understanding of the molecular basis of TSP-1-mediated inhibition of angiogenesis and tumor progression will aid in the development of novel therapeutics for the treatment of cancer.

Type I collagen is a molecular target for inhibition of angiogenesis by endogenous thrombospondin-1

Three-dimensional explant cultures of muscle tissue were used to characterize secreted proteins regulated by endogenous levels of the angiogenesis modulator thrombospondin (TSP)-1. Explants from TSP1 null mice exhibit enhanced neovascularization associated with increased endothelial outgrowth but decreased outgrowth of perivascular smooth muscle cells . The absence of endogenous TSP1 did not diminish activation of latent transforming growth factor-beta and moderately decreased matrix metalloproteinase levels. However, significant changes in other secreted proteins were observed. Endogenous TSP1 decreased mRNA levels for collagens Ialpha1, Ialpha2, and IIIalpha1 and laminin alpha4 and increased collagen IValpha1 mRNA expression. Endogenous TSP1 also decreased the level of type I collagen protein produced by the vascular outgrowths. Collagens Ialpha1, Ialpha2, and IIIalpha1 are known tumor endothelial markers, suggesting that TSP1 coordinately regulates a set of extracellular matrix genes that reverse the angiogenic switch. Suppression of collagen Ialpha1 or Ialpha2 mRNAs using antisense morpholinos inhibited outgrowth in TSP1 null explants and proliferation of TSP1 null endothelial cells, indicating that type I collagen synthesis is limiting for this neovascularization response.

Inhibition of endogenous nitric oxide in the heart enhances matrix metalloproteinase-2 release

Matrix metalloproteinase (MMP) activity is upregulated in pathologies such as atherosclerosis during which endogenous nitric oxide (NO) biosynthesis is reduced. Diminished levels of NO, an antioxidant species, may result in higher oxidative stress. Oxidants are capable of activating MMPs from their zymogen forms. We examined whether basal biosynthesis of NO in the coronary circulation regulates MMP-2 activity. In isolated rat hearts perfused with Krebs-Henseleit buffer at a constant flow of 10 ml min(-1), we measured the release of MMP-2 into the coronary effluent by gelatin zymography. The main gelatinolytic activity of 72-kDa corresponds to MMP-2. Infusion of the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) concentration dependently increased coronary perfusion pressure (CPP) (by 48+/-11 mmHg with 100 microM) and enhanced the release of the 72-kDa MMP-2 in the effluent. Coinfusion of the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 1 microM) with L-NAME abolished both the increase in CPP and the enhanced MMP-2 release. The thromboxane A2 mimetic U46619 increased CPP to the same extent as L-NAME without increasing 72-kDa activity in the effluent, suggesting that MMP-2 release is not caused simply by enhanced perfusion pressure. Infusion of either L-NAME or U46619 did not significantly enhance LDH release. L-NAME infusion concentration dependently increased the level of lipid hydroperoxides in homogenates prepared from the perfused hearts. Coinfusion of SNAP prevented this increase. These data reveal another cytoprotective mechanism of endogenous NO biosynthesis in the heart, the inhibition of MMP-2 release.

Cyclic strain-mediated regulation of vascular endothelial cell migration and tube formation

Hemodynamic forces exerted by blood flow (cyclic strain, shear stress) affect the initiation and progression of angiogenesis; however, the precise signaling mechanism(s) involved are unknown. In this study, we examine the role of cyclic strain in regulating bovine aortic endothelial cell (BAEC) migration and tube formation, indices of angiogenesis. Considering their well-documented mechanosensitivity, functional inter-dependence, and involvement in angiogenesis, we hypothesized roles for matrix metalloproteinases (MMP-2/9), RGD-dependent integrins, and urokinase plasminogen activator (uPA) in this process. BAECs were exposed to equibiaxial cyclic strain (5% strain, 1Hz for 24h) before their migration and tube formation was assessed by transwell migration and collagen gel tube formation assays, respectively. In response to strain, both migration and tube formation were increased by 1.83+/-0.1- and 1.84+/-0.1-fold, respectively. Pertussis toxin, a Gi-protein inhibitor, decreased strain-induced migration by 45.7+/-32% and tube formation by 69.8+/-13%, whilst protein tyrosine kinase (PTK) inhibition with genistein had no effect. siRNA-directed attenuation of endothelial MMP-9 (but not MMP-2) expression/activity decreased strain-induced migration and tube formation by 98.6+/-41% and 40.7+/-31%, respectively. Finally, integrin blockade with cRGD peptide and siRNA-directed attenuation of uPA expression reduced strain-induced tube formation by 85.7+/-15% and 84.7+/-31%, respectively, whilst having no effect on migration.

CONCLUSIONS

Cyclic strain promotes BAEC migration and tube formation in a Gi-protein-dependent PTK-independent manner. Moreover, we demonstrate for the first time a putative role for MMP-9 in both strain-induced events, whilst RGD-dependent integrins and uPA appear only to be involved in strain-induced tube formation.