Regulation of endothelial matrix metalloproteinase-2 by hypoxia/reoxygenation

Paeoniflorin protects human EA.hy926 endothelial cells against gamma-radiation induced oxidative injury by activating the NF-E2-related factor 2/heme oxygenase-1 pathway

Pulmonary endothelial cells have been demonstrated to have a critical role in the pathogenesis of radiation-induced lung injury. Our preliminary experiments indicated that paeoniflorin protected human EA.hy926 endothelial cells from radiation-induced oxidative injury. This study was designed to confirm the protective effect of paeoniflorin against radiation-induced endothelial cellular damage and to elucidate the underlying mechanisms. Preincubation of EA.hy926 cells with paeoniflorin before γ-radiation resulted in significant inhibition of apoptosis, a decrease in mitochondrial membrane potential and enhanced cell viability. In particular, we showed that paeoniflorin significantly reduced the formation of intracellular reactive oxygen species (ROS), the level of malondialdehyde (MDA) and lactate dehydrogenase (LDH) leakage, and enhanced production of the endogenous antioxidants, glutathione (GSH) and superoxide dismutase (SOD) in EA.hy926 cells. Treatment of these cells with paeoniflorin significantly induced HO-1 expression. Moreover, paeoniflorin promoted the nuclear translocation of nuclear factor erythroid 2 related factor-2 (Nrf-2). The paeoniflorin-induced HO-1 expression was abrogated by Nrf2 siRNA. Furthermore, inhibition of HO-1 with zinc protoporphyrin IX (ZNPP) significantly reversed the protective effect of paeoniflorin against radiation-induced damage in EA.hy926 cells. Our findings confirmed that paeoniflorin protected EA.hy926 cells against radiation-induced injury through the Nrf2/HO-1 pathway.

Angiostatin inhibits endothelial MMP-2 and MMP-14 expression: a hypoxia specific mechanism of action

Angiostatin is an angiogenesis inhibitor in part generated by and released from platelets. Since platelets upon thrombus formation can give rise to areas of hypoxia, we investigated the effects of angiostatin on endothelial cell migration and apoptosis during hypoxia. Human microvascular endothelial cells (HMVEC-L) were exposed to angiostatin under normoxic or hypoxic conditions. Apoptosis was measured by flow-cytometry. HMVEC-L migration was studied using a modified Boyden Chamber assay, in which migration is MMP-dependent. MMP-2, MMP-14, and VEGF levels were measured using immunoblot, Q-PCR and ELISA. During hypoxia HMVEC-L were protected from angiostatin-induced apoptosis due to increased hypoxia-induced VEGF expression. However, MMP-dependent migration of HMVEC-L was inhibited by angiostatin under hypoxic but not normoxic conditions. Angiostatin decreased MMP-2 at the gene and protein levels only in HMVEC-L exposed to hypoxia. A similar result was obtained for MMP-14. Higher angiostatin concentrations, as would be seen during thrombosis, induced HMVEC-L apoptosis, which was not rescued by VEGF. Under hypoxic conditions angiostatin's primary anti-angiogenic mechanism is likely inhibition of endothelial cell MMP-dependent endothelial cell migration. Only at higher concentrations does angiostatin induce endothelial cell death. This study identifies a novel angiostatin anti-angiogenesis mechanism that is only triggered under pathological-like conditions.

Pulsed high oxygen induces a hypoxic-like response in human umbilical endothelial cells and in humans

It has been proposed that relative changes of oxygen availability, rather than steady-state hypoxic or hyperoxic conditions, play an important role in hypoxia-inducible factor (HIF) transcriptional effects. According to this hypothesis describing the "normobaric oxygen paradox", normoxia following a hyperoxic event is sensed by tissues as an oxygen shortage, upregulating HIF-1 activity. With the aim of confirming, at cellular and at functional level, that normoxia following a hyperoxic event is "interpreted" as a hypoxic event, we report a combination of experiments addressing the effects of an intermittent increase of oxygen concentration on HIF-1 levels and the activity level of specific oxygen-modulated proteins in cultured human umbilical vein endothelial cells and the effects of hemoglobin levels after intermittent breathing of normobaric high (100%) and low (15%) oxygen in vivo in humans. Our experiments confirm that, during recovery after hyperoxia, an increase of HIF expression occurs in human umbilical vein endothelial cells, associated with an increase of matrix metalloproteinases activity. These data suggest that endothelial cells "interpret" the return to normoxia after hyperoxia as a hypoxic stimulus. At functional level, our data show that breathing both 15 and 100% oxygen 30 min every other day for a period of 10 days induces an increase of hemoglobin levels in humans. This effect was enhanced after the cessation of the oxygen breathing. These results indicate that a sudden decrease in tissue oxygen tension after hyperoxia may act as a trigger for erythropoietin synthesis, thus corroborating the hypothesis that "relative" hypoxia is a potent stimulator of HIF-mediated gene expressions.

Expression of MMP-2, TIMP-2, TGF-β1, and decorin in Dupuytren's contracture

To investigate the mechanisms underlying matrix deposition in Dupuytren's disease, the expression of gelatinase A (MMP-2), the tissue inhibitor of metalloproteinase-2 (TIMP-2), transforming growth factor beta 1 (TGF-β1), decorin (DCN), and periostin was studied. The level of relative MMP-2 activation was investigated using zymography. The mRNA expression of MMP-2, TIMP-2, TGF-β1, and DCN was detected using reverse transcription polymerase chain reaction (RT-PCR), while the presence of protein was detected using immunohistochemical (IHC) and Western blot techniques. The level of MMP-2 activation was significantly elevated in tissues with Dupuytren's contracture. RT-PCR demonstrated significantly higher expression of MMP-2, TIMP-2, TGF-β1, and DCN mRNA in the pathological tissues; and the IHC and immunoblotting studies revealed elevated expression of TGF-β1, DCN, and periostin. The balance between MMP-2 and TIMP-2 was disrupted in patients with Dupuytren's disease. TGF-β1, DCN, and periostin are involved in extracellular matrix (ECM) homeostasis in Dupuytren's contracture.

Matrix metalloproteinases

Remodeling of extracellular matrix is crucial for many physiological (cell migration, proliferation, growth, and development) and pathological (remodeling of heart, carcinogenesis, metastasis, etc.) events. Thus, the interaction between cells and extracellular matrix plays a key role in normal development and differentiation of organism and many pathological states as well. Changes in extracellular matrix are regulated by a system of proteolytic enzymes that are responsible for proteolysis of huge quantity of extracellular matrix components. Matrix metalloproteinases (MMPs) represent the main group of regulating proteases in ECM. Ability of matrix metalloproteinases to modify the structural integrity of tissues is essential for certain aspects of normal physiology and pathology. The ability to process molecules such as growth factors, receptors, adhesion molecules, other proteinases, and proteinase inhibitors makes MMPs potent controllers of physiological and pathological events in the cell microenvironment. Overactivation of MMPs has been implicated in numerous disease states.

Benzyl isothiocyanate suppresses pancreatic tumor angiogenesis and invasion by inhibiting HIF-α/VEGF/Rho-GTPases: pivotal role of STAT-3

Our previous studies have shown that benzyl isothiocyanate (BITC) suppresses pancreatic tumor growth by inhibiting STAT-3; however, the exact mechanism of tumor growth suppression was not clear. Here we evaluated the effects and mechanism of BITC on pancreatic tumor angiogenesis. Our results reveal that BITC significantly inhibits neovasularization on rat aorta and Chicken-Chorioallantoic membrane. Furthermore, BITC blocks the migration and invasion of BxPC-3 and PanC-1 pancreatic cancer cells in a dose dependant manner. Moreover, secretion of VEGF and MMP-2 in normoxic and hypoxic BxPC-3 and PanC-1 cells was significantly suppressed by BITC. Both VEGF and MMP-2 play a critical role in angiogenesis and metastasis. Our results reveal that BITC significantly suppresses the phosphorylation of VEGFR-2 (Tyr-1175), and expression of HIF-α. Rho-GTPases, which are regulated by VEGF play a crucial role in pancreatic cancer progression. BITC treatment reduced the expression of RhoC whereas up-regulated the expression of tumor suppressor RhoB. STAT-3 over-expression or IL-6 treatment significantly induced HIF-1α and VEGF expression; however, BITC substantially suppressed STAT-3 as well as STAT-3-induced HIF-1α and VEGF expression. Finally, in vivo tumor growth and matrigel-plug assay show reduced tumor growth and substantial reduction of hemoglobin content in the matrigel plugs and tumors of mice treated orally with 12 µmol BITC, indicating reduced tumor angiogenesis. Immunoblotting of BITC treated tumors show reduced expression of STAT-3 phosphorylation (Tyr-705), HIF-α, VEGFR-2, VEGF, MMP-2, CD31 and RhoC. Taken together, our results suggest that BITC suppresses pancreatic tumor growth by inhibiting tumor angiogenesis through STAT-3-dependant pathway.

Hypoxia increases membranal and secreted HLA-DR in endothelial cells, rendering them T-cell activators

Transplantation involves preoperative ischemic periods that contribute to endothelial cell (EC) dysfunction and T-cell activation, leading to graft rejection. As hypoxia is a major constituent of ischemia, we evaluated its effect on the ability of ECs to express HLA-DR, which is required for presentation of antigens to T cells, and by itself serves as an important target for allogeneic T cells. Primary human umbilical vein ECs (HUVEC) and the human endothelial cell line EaHy926 were incubated in normoxia or hypoxia (PO(2) < 0.3%). Hypoxia increased the membranal expression (by 4-6 fold, P < 0.01) and secretion (by sixfold, P < 0.05) of HLA-DR protein, without influencing the accumulation of its mRNA. Alternative splicing, attenuated trafficking, or shedding from the plasma membrane were not observed, but the lysosomal inhibitor bafilomycin A1 reduced HLA-DR secretion. Hypoxia-induced endothelial HLA-DR elevated and diminished the secretion of IL-2 and IL-10, respectively, from co-cultured allogeneic CD4(+) T cells in a HLA-DR-dependent manner, as demonstrated by the use of monoclonal anti-HLA-DR. Our results indicate a yet not fully understood post-translational mechanism(s), which elevate both membranal and soluble HLA-DR expression. This elevation is involved in allogeneic T-cell activation, highlighting the pivotal role of ECs in ischemia/hypoxia-associated injury and graft rejection.

Matrix metalloproteinase inhibitor properties of tetracyclines: therapeutic potential in cardiovascular diseases

Matrix metalloproteinases (MMPs) are a family of proteases best known for their capacity to proteolyse several proteins of the extracellular matrix. Their increased activity contributes to the pathogenesis of several cardiovascular diseases. MMP-2 in particular is now considered to be also an important intracellular protease which has the ability to proteolyse specific intracellular proteins in cardiac muscle cells and thus reduce contractile function. Accordingly, inhibition of MMPs is a growing therapeutic aim in the treatment or prevention of various cardiovascular diseases. Tetracyclines, especially doxycycline, have been frequently used as important MMP inhibitors since they inhibit MMP activity independently of their antimicrobial properties. In this review we will focus on the intracellular actions of MMPs in some cardiovascular diseases including ischemia and reperfusion (I/R) injury, inflammatory heart diseases and septic shock; and explain how tetracyclines, as MMP inhibitors, have therapeutic actions to treat such diseases. We will also briefly discuss how MMPs can be intracellularly regulated and activated by oxidative stress, thus cleaving several important proteins inside cells. In addition to their potential therapeutic effects, MMP inhibitors may also be useful tools to understand the biological consequences of MMP activity and its respective extra- and intracellular effects.

Cellular apoptosis susceptibility (CSE1L/CAS) protein in cancer metastasis and chemotherapeutic drug-induced apoptosis

The cellular apoptosis susceptibility (CSE1L/CAS) protein is highly expressed in cancer, and its expression is positively correlated with high cancer stage, high cancer grade, and worse outcomes of patients. CSE1L (or CAS) regulates chemotherapeutic drug-induced cancer cell apoptosis and may play important roles in mediating the cytotoxicities of chemotherapeutic drugs against cancer cells in cancer chemotherapy. CSE1L was originally regarded as a proliferation-associated protein and was thought to regulate the proliferation of cancer cells in cancer progression. However, the results of experimental studies showed that enhanced CSE1L expression is unable to increase proliferation of cancer cells and CSE1L regulates invasion and metastasis but not proliferation of cancer cells. Recent studies revealed that CSE1L is a secretory protein, and there is a higher prevalence of secretory CSE1L in the sera of patients with metastatic cancer. Therefore, CSE1L may be a useful serological marker for screening, diagnosis and prognosis, assessment of therapeutic responses, and monitoring for recurrence of cancer. In this paper, we review the expression of CSE1L in cancer and discuss why CSE1L regulates the invasion and metastasis rather than the proliferation of cancer.

The role of hypoxia in bone marrow-derived mesenchymal stem cells: considerations for regenerative medicine approaches

Bone marrow-derived mesenchymal stem cells (MSCs) have demonstrated potential for regenerative medicine strategies. Knowledge of the way these cells respond to their environment in in vitro culture and after implantation in vivo is crucial for successful therapy. Oxygen tension plays a pivotal role in both situations. In vivo, a hypoxic environment can lead to apoptosis, but hypoxic preconditioning of MSCs and overexpression of prosurvival genes like Akt can reduce hypoxia-induced cell death. In cell culture, hypoxia can increase proliferation rates and enhance differentiation along the different mesenchymal lineages. Hypoxia also modulates the paracrine activity of MSCs, causing upregulation of various secretable factors, among which are important angiogenic factors such as vascular endothelial growth factor and interleukin-6 (IL6). Finally, hypoxia plays an important role in mobilization and homing of MSCs, primarily by its ability to induce stromal cell-derived factor-1 expression along with its receptor CXCR4. This article reviews the current literature on the effects of hypoxia on MSCs and aims to elucidate its potential role in regenerative medicine strategies.

Maternal hypoxia increases the activity of MMPs and decreases the expression of TIMPs in the brain of neonatal rats

A recent study has shown that increased activity of matrix metalloproteinases-2 and metalloproteinases-9 (MMP-2 and MMP-9) has detrimental effect on the brain after neonatal hypoxia. The present study determined the effect of maternal hypoxia on neuronal survivability and the activity of MMP-2 and MMP-9, as well as the expression of tissue inhibitors of metalloproteinase 1 and 2 (TIMP-1 and TIMP-2) in the brain of neonatal rats. Pregnant rats were exposed to 10.5% oxygen for 6 days from the gestation day 15 to day 21. Pups were sacrificed at day 0, 4, 7, 14, and 21 after birth. Body weight and brain weight of the pups were measured at each time point. The activity of MMP-2 and MMP-9 and the protein abundance of TIMP-1 and TIMP-2 were determined by zymography and Western blotting, respectively. The tissue distribution of MMPs was examined by immunofluorescence staining. The neuronal death was detected by Nissl staining. Maternal hypoxia caused significant decreases in body and brain size, increased activity of MMP-2 at day 0, and increased MMP-9 at day 0 and 4. The increased activity of the MMPs was accompanied by an overall tendency towards a reduced expression of TIMPs at all ages with the significance observed for TIMPs at day 0, 4, and 7. Immunofluorescence analysis showed an increased expression of MMP-2, MMP-9 in the hippocampus at day 0 and 4. Nissl staining revealed significant cell death in the hippocampus at day 0, 4, and 7. Functional tests showed worse neurobehavioral outcomes in the hypoxic animals.

Resuscitation of hypoxic newborn piglets with supplementary oxygen induces dose-dependent increase in matrix metalloproteinase-activity and down-regulates vital genes

The optimal oxygen concentration for newborn resuscitation is still discussed. Oxygen administration during reoxygenation may induce short- and long-term pathologic changes via oxidative stress and has been associated to later childhood cancer. The aim was to study changes in oxidative stress-associated markers in liver and lung tissue of newborn pigs after acute hypoxia followed by reoxygenation for 30 min with 21, 40, or 100% oxygen compared with room air or to ventilation with 100% oxygen without preceding hypoxia. Nine hours after resuscitation, we found a dose-dependent increase in the matrix metalloproteinase gelatinase activity in liver tissue related to percentage oxygen supply by resuscitation (100% versus 21%; p = 0.002) pointing at more extensive tissue damage. Receiving 100% oxygen for 30 min without preceding hypoxia decreased the expression of VEGFR2 and TGFBR3 mRNA in liver tissue, but not in lung tissue. MMP-, VEGF-, and TGFbeta-superfamily are vital for the development, growth, and functional integrity of most tissues and our data rise concern about both short- and long-term consequences of even a brief hyperoxic exposure.

Hypoxia-reoxygenation increase invasiveness of PANC-1 cells through Rac1/MMP-2

Pancreatic cancer is an aggressive malignancy with proclivity to early metastasis. High expression and activation of the collagenase matrix metalloproteinase-2 (MMP-2) have been found in human pancreatic cancer tissues, being these increased levels of active MMP-2 correlated to tumor invasion and metastasis. Hypoxia and reoxygenation (H-R) are critical pathophysiological conditions during ischemia-reperfusion injury, which has been shown to enhance both invasion and metastasis. In the present study, we investigated the effects of H-R on MMP-2 levels and the invasiveness properties of human pancreatic cancer cells PANC-1. Using specific inhibitors, we found that H-R treatment of these tumor cells induced secretion and activation of MMP-2, which was required for H-R-stimulated basement membrane degradation and cell invasion. Our results also indicate that signaling events involved in H-R-enhanced PANC-1 invasiveness comprehend PI3K-dependent activation of Rac1, which mediated the formation of NADPH-generated reactive oxygen species responsible for MMP-2 secretion and activation.

Time course of intermittent hypoxia-induced impairments in resistance artery structure and function

We previously demonstrated that chronic exposure to intermittent hypoxia (CIH) impairs endothelium-dependent vasodilation in rats. To determine the time course of this response, rats were exposed to CIH for 3, 14, 28, or 56 days. Then, we measured acetylcholine- and nitroprusside-induced vasodilation in isolated gracilis arteries. Also, we measured endothelial and inducible nitric oxide synthase, nitrotyrosine, and collagen in the arterial wall and urinary isoprostanes. Endothelium-dependent vasodilation was impaired after 2 weeks of CIH. Three days of CIH was not sufficient to produce this impairment and longer exposures (i.e. 4 and 8 weeks) did not exacerbate it. Impaired vasodilation was accompanied by increased collagen deposition. CIH elevated urinary isoprostane excretion, whereas there was no consistent effect on either isoform of nitric oxide synthase or nitrotyrosine. Exposure to CIH produces functional and structural deficits in skeletal muscle resistance arteries. These impairments develop within 2 weeks after initiation of exposure and they are accompanied by systemic evidence of oxidant stress.

Desferroxamine infusion increases cerebral blood flow: a potential association with hypoxia-inducible factor-1

Finding an effective means to improve cerebral perfusion during hypoxic/ischaemic stress is essential for neuroprotection. Studies in animal models of stroke have shown that desferroxamine activates HIF-1 (hypoxia-inducible factor-1), reduces brain damage and promotes functional recovery. The present study was designed to investigate the effects of desferroxamine infusion on the cerebral circulation in humans. Fifteen volunteers were enrolled in a randomized double-blind placebo-controlled crossover study. We measured cerebral blood flow velocity by transcranial Doppler ultrasonography in the middle cerebral artery, arterial blood pressure, end-tidal CO(2), as well as HIF-1 protein and serum lactate dehydrogenase concentrations in response to 8 h of desferroxamine compared with placebo infusion. Cerebrovascular resistance was calculated from the ratio of steady-state beat-to-beat values for blood pressure to blood flow velocity. We found that desferroxamine infusion was associated with a significant cerebral vasodilation. Moreover, decreased cerebrovascular resistance was temporally correlated with an increased HIF-1 protein concentration as well as HIF-1 transcriptional activation, as measured by serum lactate dehydrogenase concentration. The findings of the present study provide preliminary data suggesting that activators of HIF-1, such as desferroxamine, may protect neurons against ischaemic injury by dilating cerebral vessels and enhancing cerebral perfusion.

Effect of Furosemide Infusion on Renal Hemodynamics and Angiogenesis Gene Expression in Acute Renal Ischemia/Reperfusion

Loop diuretics are known to affect renal hemodynamics and possibly gene transcription, but the specific effect of furosemide on renal angiogenesis gene expression after acute ischemia is not known. We utilized an acute renal failure model in rats to test the hypothesis that furosemide improves renal hemodynamics and alters the transcriptional signature of acute ischemic nephropathy. Twenty-four male Sprague-Dawley rats were anesthetized by the intraperitoneal administration of 50 mg/kg urethane. Animals were divided into four groups (n = 6 each): (1) sham-operated group infused with saline; (2) sham-operated group infused with 30 microg/kg/hr furosemide (equivalent to a human dosage of 2 mg/hr); (3) unilateral renal ischemia (1 hr, left renal artery cross-clamping) followed by 6 hr of reperfusion; and (4) renal ischemia/ reperfusion (I/R) with furosemide. Renal artery blood flow (RBF), renal cortical perfusion (RCP), and renal corticomedullary tissue oxygen tension (PO2) were recorded throughout. Following 6 hr of reperfusion, left kidney RNA was used to probe microarrays. Gene expression was measured as percent positive control and confirmed using reverse transcriptase polymerase chain reaction. Physiologic data were analyzed by calculating area under the curve, and gene expression data were compared by using multiple analysis of variance with Tukey's post-hoc tests. Furosemide significantly increased RBF (P < 0.05) and PO2 (P < 0.05) in postischemic kidneys. Furosemide attenuated nine of the 13 ischemia-induced and 41 of 78 ischemia-suppressed angiogenesis-related genes. This attenuation was statistically significant (P < 0.05) for 17 I/R injury-suppressed genes. Data from this rat model of ischemic nephropathy suggest that furosemide improves renal hemodynamics and attenuates ischemia-related changes in gene expression.

Chronic hypoxia inhibits MMP-2 activation and cellular invasion in human cardiac myofibroblasts

Cardiac myofibroblasts are pivotal to adaptive remodelling after myocardial infarction (MI). These normally quiescent cells invade and proliferate as a wound healing response, facilitated by activation of matrix metalloproteinases, particularly MMP-2. Following MI these reparative events occur under chronically hypoxic conditions yet the mechanisms by which hypoxia might modulate MMP-2 activation and cardiac myofibroblast invasion have not been investigated. Human cardiac myofibroblasts cultured in collagen-supplemented medium were exposed to normoxia (20% O₂) or hypoxia (1% O₂) for up to 48 h. Secreted levels of total and active MMP-2 were quantified using gelatin zymography, TIMP-2 and membrane-associated MT1-MMP were quantified with ELISA, whole cell MT1-MMP by immunoblotting and immunocytochemistry and MT1-MMP mRNA with real-time RT-PCR. Cellular invasion was assessed in modified Boyden chambers and migration by scratch wound assay.

In the human cardiac myofibroblast, MT1-MMP was central to MMP-2 activation and activated MMP-2 necessary for invasion, confirmed by gene silencing. MMP-2 activation was substantially attenuated by hypoxia (P < 0.001), paralleled by inhibition of myofibroblast invasion (P < 0.05). In contrast, migration was independent of either MT1-MMP or MMP-2. Reduced membrane expression of MT1-MMP (P < 0.05) was responsible for the hypoxic reduction of MMP-2 activation, with no change in either total MMP-2 or TIMP-2. In conclusion, hypoxia reduces MMP-2 activation and subsequent invasion of human cardiac myofibroblasts by reducing membrane expression of MT1-MMP and may delay healing after MI. Regulation of these MMPs remains an attractive target for therapeutic intervention.

Hypoxia upregulates angiogenesis and synovial cell migration in rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is characterised by invasion of cartilage, bone and tendon by inflamed synovium. Previous studies in our laboratory have shown that hypoxia is a feature of RA synovitis. In the present study, we investigated the consequences of hypoxia on angiogenesis and synovial fibroblast migration in RA.

METHODS

Synovial tissue was harvested from RA patients, and synovial membrane cells were cultured under conditions either of hypoxia (1% oxygen) or normoxia (21% oxygen). Protein levels of matrix metalloproteinases (MMPs) and angiogenic factors were measured, while RNA was extracted for PCR quantification of MMPs/tissue inhibitors of MMP (TIMPs) and angiogenic factors. Migration of RA synovial fibroblasts through collagen, and the effect of RA synovial cell supernatants in an in vitro angiogenesis assay, were utilised to determine the functional relevance of changes in mRNA/protein.

RESULTS

We observed upregulation under hypoxic conditions of MMPs responsible for collagen breakdown, specifically collagenase MMP-8, and the gelatinases MMP-2 and MMP-9, at both mRNA and protein levels. Increased MT1-MMP mRNA was also observed, but no effect on TIMP-1 or TIMP-2 was detected. RA fibroblast migration across collagen was significantly increased under hypoxic conditions, and was dependent on MMP activity. Furthermore, expression of angiogenic stimuli, such as vascular endothelial growth factor (VEGF), and VEGF/placental growth factor heterodimer, was also increased. Crucially, we show for the first time that hypoxia increased the angiogenic drive of RA cells, as demonstrated by enhanced blood vessel formation in an in vitro angiogenesis assay.

CONCLUSIONS

Hypoxia may be responsible for rendering RA synovial lining proangiogenic and proinvasive, thus leading to the debilitating features characteristic of RA.

Higher prevalence of secretory CSE1L/CAS in sera of patients with metastatic cancer

Metastatic markers are highly useful diagnostic and prognostic indicators of cancer metastasis. Herein, we report that secretory CSE1L/CAS, a cellular apoptosis susceptibility protein, is a new marker for metastatic cancer. CAS was colocalized with matrix metalloproteinase-2 in vesicles surrounding the outside of MCF-7 cell membranes, and the COOH-terminal domain of CAS was associated with matrix metalloproteinase-2-containing vesicles. Immunohistochemical staining for CAS was positive in the stroma and gland lumens of human metastatic cancer tissues. CAS was also detected in conditioned medium from B16-F10 melanoma cells and more frequently in the sera of patients with metastatic cancer than in sera from patients with primary cancer. Specifically, the prevalence of serum CAS in serum samples from 146 patients was 58.2% (32 of 55), 32.0% (8 of 25), and 12.1% (8 of 66) for patients with metastatic, invasive, and primary cancers, respectively. Our results suggest that CAS is a secretory protein associated with cancer metastasis, which may have clinical utility in metastatic cancer screening and diagnosis.

Immunomodulation by chronobiologically-based glucocorticoids treatment for multiple sclerosis relapses

This study compares the effects of daytime versus nighttime intravenous glucocorticoid treatment of multiple sclerosis (MS) relapses for several immune indicators. The levels of serum CRP, TNFalpha, ESR, MMP-2, MMP-9, TIMP-1, and TIMP-2 were determined at trial entry and at day 7 post therapy initiation in 35 MS patients. Serum MMP-9 protein levels were differentially affected by treatment regimen, and were significantly lower after nighttime treatment. Both treatment protocols led to a similar reduction of ESR, CRP and TNFalpha. These findings provide preliminary characterization of biomarkers in the application of chronobiology-based glucocorticoid therapeutics in MS and other immune disorders.

TNF alpha-mediated disruption of spermatogenesis in response to Sertoli cell injury in rodents is partially regulated by MMP2

Mono-(2-ethylhexyl) phthalate (MEHP)-induced Sertoli cell injury in peripubertal rodents results in the stimulation of germ cell apoptosis through an interaction of FAS/FASL between these two cell types. During this peripubertal period, an early spike in the incidence of germ cell apoptosis occurs during the first wave of spermatogenesis and is essential for the development of functional spermatogenesis in adults. Our previous observations revealed that soluble tumor necrosis factor alpha (sTNFA) released by germ cells after MEHP exposure consequently resulted in a robust induction of FASL by Sertoli cells. Metalloproteinases (MPs) are essential for processing the TNFA precursor to its soluble form and its ability to bind to TNFRSF1A. The activity of MPs is regulated by the tissue inhibitors of MPs (TIMPs) family. Herein we report that TIMP2 is predominately expressed in Sertoli cells and that protein levels decrease in a time-dependent manner after MEHP exposure. The secretion of matrix MP 2 (MMP2) in primary rat Sertoli cell-germ cell cocultures is induced after MEHP exposure, and its activity increases in a time-dependent manner. The addition of SB-3CT, a specific gelatinase inhibitor, decreases the activity of MMP2 and significantly reduces MEHP-enhanced sTNFA production in primary cocultures. In vivo challenges with SB-3CT decrease sTNFA and reduce MEHP-induced testicular germ cell apoptosis. In primary cocultures, MEHP exposure causes a 9.46-fold increase in sTNFA, while the addition of recombinant MMP2 protein results in a 5.4-fold increase in sTNFA, suggesting that MEHP-induced MMP2 is in part responsible for the activation of TNFA in the testis. Taken together, these observations indicate the distinct role of specific MPs in response to toxicant-induced Sertoli cell injury, providing further insights into the mechanism by which Sertoli cells control the sensitivity of germ cells to undergo apoptosis.

In vitro and in vivo wound healing-promoting activities of β-lapachone

Impaired wound healing is a serious problem for diabetic patients. Wound healing is a complex process that requires the cooperation of many cell types, including keratinocytes, fibroblasts, endothelial cells, and macrophages. β-Lapachone, a natural compound extracted from the bark of the lapacho tree ( Tabebuia avellanedae), is well known for its antitumor, antiinflammatory, and antineoplastic effects at different concentrations and conditions, but its effects on wound healing have not been studied. The purpose of the present study was to investigate the effects of β-lapachone on wound healing and its underlying mechanism. In the present study, we demonstrated that a low dose of β-lapachone enhanced the proliferation in several cells, facilitated the migration of mouse 3T3 fibroblasts and human endothelial EAhy926 cells through different MAPK signaling pathways, and accelerated scrape-wound healing in vitro. Application of ointment with or without β-lapachone to a punched wound in normal and diabetic ( db/ db) mice showed that the healing process was faster in β-lapachone-treated animals than in those treated with vehicle only. In addition, β-lapachone induced macrophages to release VEGF and EGF, which are beneficial for growth of many cells. Our results showed that β-lapachone can increase cell proliferation, including keratinocytes, fibroblasts, and endothelial cells, and migration of fibroblasts and endothelial cells and thus accelerate wound healing. Therefore, we suggest that β-lapachone may have potential for therapeutic use for wound healing.

Effect of mini-tyrosyl-tRNA synthetase on ischemic angiogenesis, leukocyte recruitment, and vascular permeability

Mini-tyrosyl-tRNA synthetase (mini-TyrRS), the N-terminal domain of tyrosyl-tRNA synthetase, is a recently identified protein released by endothelial cells that exhibits angiogenic and leukocyte chemoattractant, ELR-motif (Glu-Leu-Arg)-dependent activities in vitro. We sought to determine whether exogenous mini-TyrRS exerts these and other cytokine-like actions in physiological and pathological settings in vivo. High-dose mini-TyrRS (600 microg.kg(-1).day(-1)) augmented while low-dose mini-TyrRS (3 microg.kg(-1).day(-1)), unexpectedly, inhibited angiogenesis in the ischemic mouse ear. Enhanced angiogenesis was associated with increased CD45- and CD4-positive leukocyte accumulation. Mini-TyrRS also had biphasic actions on both basal and mustard oil-evoked and VEGF-evoked leakage of Evan's blue dye-albumin in nonischemic ear and in endothelial cell monolayers, that is, low-dose inhibited and high-dose augmented leakage. Mutation of the ELR motif of mini-TyrRS abolished the above activities. Mini-TyrRS was reduced (immunoblot) in extracts of ischemic calf muscle and in thoracic aorta explants exposed to hypoxia or VEGF. Inhibition of VEGF with a soluble Flt1 "trap" protein abolished this hypoxic-induced reduction in mini-TyrRS in aorta explants. These data show that mini-TyrRS has dose-dependent biphasic effects on ischemic angiogenesis and vascular permeability in vivo, that is, antiangiogenic and antipermeability activities at low concentration and proangiogenic, propermeability activities at high concentrations.

Increased inorganic phosphate induces human endothelial cell apoptosis in vitro

Chronic kidney disease with hyperphosphatemia is associated with accelerated atherosclerosis and endothelial dysfunction. However, the contribution of high serum phosphate levels to endothelial injury is incompletely understood. The aim of this work was to evaluate the responses of endothelial cells to elevated levels of extracellular phosphate in vitro. High phosphate in concentrations similar to those observed in uremia-associated hyperphosphatemia (>2.5 mM) induced apoptosis in two endothelial cell lines (EAhy926 cells and GM-7373 cells). This effect was enhanced when cells were incubated for 24 h in the presence of 2.8 mM calcium instead of 1.8 mM. By treating cells with 0.5 or 1.0 mM phosphonoformic acid, an inhibitor of the phosphate transporter, death was completely prevented. The process of phosphate-induced apoptosis was further characterized by increased oxidative stress, as detected by increased ROS generation and disruption of the mitochondrial membrane potential at approximately 2 h after treatment, followed by caspase activation. These findings show that hyperphosphatemia causes endothelial cell apoptosis, a process that impairs endothelial integrity. Endothelial cell injury induced by high phosphate concentrations may be an initial event leading to vascular complications in patients with chronic kidney disease.

Graded hypoxia modulates the invasive potential of HT1080 fibrosarcoma and MDA MB231 carcinoma cells

Spatial and temporal oxygen heterogeneity exists in most solid tumour microenvironments due to an inadequate vascular network supplying a dense population of tumour cells. An imbalance between oxygen supply and demand leads to hypoxia within a significant proportion of a tumour, which has been correlated to the likelihood of metastatic dissemination in both rodent tumour models and human patients. Experimentally, it has been demonstrated that near-anoxic in vitro exposure results in transiently increased metastatic potential in some tumour cell lines. The purpose of this study was to examine the effect of graded low oxygen conditions on the invasive phenotype of human tumour cells using an in vitro model of basement membrane invasion, in which we measured oxygen availability directly at the invasion surface of the transwell chamber. Our results show a relationship between culture vessel geometry and time to achieve hypoxia which may affect the interpretation of low oxygen experiments. We exposed the human tumour cell lines, HT1080 and MDA MB231, to graded normobaric oxygen (5% O(2)-0.2% O(2)) either during or prior to in vitro basement membrane invasion to simulate conditions of intravasation and extravasation. A secondary aim was to investigate the potential regulation of matrix metalloproteinase activity by oxygen availability. We identified significant reductions in invasive ability under low oxygen conditions for the HT1080 cell line and an increase in invasion at intermediate oxygen conditions for the MDA MB231 cell line. There were differences in the absolute activity of the individual matrix metalloproteinases, MMP-2, -9, -14, between the two cell lines, however there were no significant changes following exposure to hypoxic conditions. This study demonstrates cell line specific effects of graded oxygen levels on invasive potential and suggests that intermediate levels of low oxygen may increase metastatic dissemination.

Interruption of endothelin signaling modifies membrane type 1 matrix metalloproteinase activity during ischemia and reperfusion

The matrix metalloproteinases (MMPs), in particular, membrane type 1 MMP (MT1-MMP), are increased in the context of myocardial ischemia and reperfusion (I/R) and likely contribute to myocardial dysfunction. One potential upstream induction mechanism for MT1-MMP is endothelin (ET) release and subsequent protein kinase C (PKC) activation. Modulation of ET and PKC signaling with respect to MT1-MMP activity with I/R has yet to be explored. Accordingly, this study examined in vivo MT1-MMP activation during I/R following modification of ET signaling and PKC activation. With the use of a novel fluorogenic microdialysis system, myocardial interstitial MT1-MMP activity was measured in pigs (30 kg; n = 9) during I/R (90 min I/120 min R). Local ET(A) receptor antagonism (BQ-123, 1 microM) and PKC inhibition (chelerythrine, 1 microM) were performed in parallel microdialysis probes. MT1-MMP activity was increased during I/R by 122 +/- 10% (P < 0.05) and was unchanged from baseline with ET antagonism and/or PKC inhibition. Selective PKC isoform induction occurred such that PKC-betaII increased by 198 +/- 31% (P < 0.05). MT1-MMP phosphothreonine, a putative PKC phosphorylation site, was increased by 121 +/- 8% (P < 0.05) in the I/R region. These studies demonstrate for the first time that increased interstitial MT1-MMP activity during I/R is a result of the ET/PKC pathway and may be due to enhanced phosphorylation of MT1-MMP. These findings identify multiple potential targets for modulating a local proteolytic pathway operative during I/R.

Hypoxia down-regulates secretion of MMP-2, MMP-9 in porcine pulmonary artery endothelial and smooth muscle cells and the role of HIF-1

Primary cell culture, techniques of gene transfection, gelatin zymography, and Western blot were used to investigate the effect of hypoxia on the secretion of MMP-2 and MMP-9 in pulmonary artery endothelial cells (PAEC) and smooth muscle cells (PASMC), and the role of HIF-1. Our results showed that (1) after exposure to hypoxia for 24 h, the protein content and activity of MMP-2 in the PAEC medium as well as these of MMP-2 and MMP-9 in PASMC medium (P < 0. 01) decreased significantly in contrast to those in normoxic group (P < 0.05); (2) after transfection of wild type EPO3'-enhancer, a HIF-1 decoy, the content and activity of MMP-2 and MMP-9 in hypoxic mediums became higher than those in normoxic group (P < 0.01), while transfection of mutant EPO3'-enhancer didn't affect the hypoxia-induced down-regulation. It is concluded that hypoxia could inhibit the secretion and activity of MMP-2 and MMP-9 in PAEC and PASMC, which could be mitigated by the transfection of EPO3'-enhancer and that HIF-1 pathway might contribute to hypoxia-induced down-regulation of MMP-2 and MMP-9.

Review: implications of in vitro research on the effect of radiotherapy and chemotherapy under hypoxic conditions

As it is now well established that human solid tumors frequently contain a substantial fraction of cells that are hypoxic, more and more in vitro research is focusing on the impact of hypoxia on the outcome of radiotherapy and chemotherapy. Indeed, the efficacy of irradiation and many cytotoxic drugs relies on an adequate oxygen supply. Consequently, hypoxic regions in solid tumors often contain viable cells that are intrinsically more resistant to treatment with radiotherapy or chemotherapy. Moreover, efforts have been made to exploit hypoxia as a potential difference between malignant and normal tissues.Nowadays, a body of evidence indicates that oxygen deficiency clearly influences some major intracellular pathways such as those involved in cell proliferation, cell cycle progression, apoptosis, cell adhesion, and others. Obviously, when investigating the effects of radiotherapy or chemotherapy or both combined under hypoxic conditions, it is essential to consider the influences of hypoxia itself on the cell. In this review, we first focus on the effects of hypoxia per se on some critical biological pathways. Next, we sketch an overview of preclinical and clinical research on radiotherapy, chemotherapy, and chemoradiation under hypoxic conditions.

Acute actions and novel targets of matrix metalloproteinases in the heart and vasculature

Matrix metalloproteinases (MMPs) have been shown to play significant roles in a number of physiological as well as pathological processes. Best known to proteolyse components of the extracellular matrix, MMPs have recently been discovered to also target a growing list of proteins apart from these, both inside and outside the cell. MMPs have also been traditionally thought of as enzymes involved in chronic processes such as angiogenesis, remodelling and atherosclerosis on a days-week time-scale. However they are now understood to also act acutely in response to oxidative stress on a minutes time-scale on non-extracellular matrix substrates. This review focuses on the acute actions and both extracellular and intracellular targets of two prominent MMP family members, MMP-2 and -9, in cardiovascular diseases including ischaemia/reperfusion injury, inflammatory heart disease, septic shock and pre-eclampsia. Also discussed are various ways of regulating MMP activity, including post-translational mechanisms, the endogenous tissue inhibitors of metalloproteinases and pharmacological inhibitors. A comprehensive understanding of MMP biology is necessary for the development of novel pharmacological therapies to combat the impact of cardiovascular disease.

Global gene expression profiling in human lung cells exposed to cobalt

BACKGROUND

It has been estimated that more than 1 million workers in the United States are exposed to cobalt. Occupational exposure to 59 Co occurs mainly via inhalation and leads to various lung diseases. Cobalt is classified by the IARC as a possible human carcinogen (group 2B). Although there is evidence for in vivo and in vitro toxicity, the mechanisms of cobalt-induced lung toxicity are not fully known. The purpose of this work was to identify potential signatures of acute cobalt exposure using a toxicogenomic approach. Data analysis focused on some cellular processes and protein targets that are thought to be relevant for carcinogenesis, transport and biomarker research.

RESULTS

A time course transcriptome analysis was performed on A549 human pulmonary cells, leading to the identification of 85 genes which are repressed or induced in response to soluble 59 Co. A group of 29 of these genes, representing the main biological functions, was assessed by quantitative RT-PCR. The expression profiles of six of them were then tested by quantitative RT-PCR in a time-dependent manner and three modulations were confirmed by Western blotting. The 85 modulated genes include potential cobalt carriers (FBXL2, ZNT1, SLC12A5), tumor suppressors or transcription factors (MAZ, DLG1, MYC, AXL) and genes linked to the stress response (UBC, HSPCB, BNIP3L). We also identified nine genes coding for secreted proteins as candidates for biomarker research. Of those, TIMP2 was found to be down-regulated and this modulation was confirmed, in a dose-dependent manner, at protein level in the supernatant of exposed cells.

CONCLUSION

Most of these genes have never been described as related to cobalt stress and provide original hypotheses for further study of the effects of this metal ion on human lung epithelial cells. A putative biomarker of cobalt toxicity was identified.

Regulation of angiogenesis by hypoxia and hypoxia-inducible factors

Maintenance of oxygen homeostasis is critical for the survival of multicellular organs. As a result, both invertebrates and vertebrates have developed highly specialized mechanisms to sense changes in oxygen levels and to mount adequate cellular and systemic responses to these changes. Hypoxia, or low oxygen tension, occurs in physiological situations such as during embryonic development, as well as in pathological conditions such as ischemia, wound healing, and cancer. A primary effector of the adaptive response to hypoxia in mammals is the hypoxia-inducible factor (HIF) family of transcription regulators. These proteins activate the expression of a broad range of genes that mediate many of the responses to decreased oxygen concentration, including enhanced glucose uptake, increased red blood cell production, and the formation of new blood vessels via angiogenesis. This latter process is dynamic and results in the establishment of a mature vascular system that is indispensable for proper delivery of oxygen and nutrients to all cells in both normal tissue and hypoxic regions. Angiogenesis is essential for normal development and neoplastic disease as tumors must develop mechanisms to stimulate vascularization to meet increasing metabolic demands. The link between hypoxia and the regulation of angiogenesis is an area of intense research and the molecular details of this connection are still being elaborated. This chapter will provide an overview of current knowledge and highlight new insights into the importance of HIF and hypoxia in angiogenesis in both physiological and pathophysiological conditions.

Gelatinase A activity in Dupuytren's disease

PURPOSE

Dupuytren's contracture is a fibroproliferative disorder of the hand characterized by an abnormal myofibroblast and fibroblast proliferation and extracellular matrix deposition leading to retraction and deformation of the palm. Recent studies have shown that molecules of extracellular matrix may coordinate morphogenesis, cell differentiation, and most importantly, fibrogenesis in tissue. Gelatinase A (MMP-2) is a member of the matrix metalloproteinase family of proteolytic enzymes that contribute to remodeling the extracellular matrix by degrading its components. The aim of this study was to determine the level of MMP-2 activation in the palmar fascia of patients with Dupuytren's contracture with reference to the clinical stages of disease progression and recurrence of the contracture after surgery.

METHODS

The level of relative MMP-2 activation, expressed by the active to latent MMP-2 ratio, was investigated with use of zymography and computerized densitometry in 16 normal and 71 pathologic tissues characterizing different clinical stages of the disease progression.

RESULTS

We found that the level of MMP-2 activation was significantly elevated in the palmar fascias with Dupuytren's contracture compared with normal tissues. We did not find statistically significant differences between groups with different stages of the disease progression. We also did not find a relation between a high level of MMP-2 activation and the recurrence in the area of surgically treated Dupuytren's contracture.

CONCLUSIONS

The differences in MMP-2 activation between contractured and normal fascia suggest a participation of this enzyme in the promotion of Dupuytren's disease. We did not find a relationship, however, between the level of MMP-2 activation and the secondary contracture.

Induction of matrix metalloproteinase-2 enhances systemic arterial contraction after hypoxia

This study was carried out to determine the role of increased vascular matrix metalloproteinase-2 (MMP-2) expression in the changes in systemic arterial contraction after prolonged hypoxia. Rats and mice were exposed to hypoxia (10% and 8% O(2), respectively) or normoxia (21% O(2)) for 16 h, 48 h, or 7 days. Aortae and mesenteric arteries were either mounted in organ bath myographs or frozen in liquid nitrogen. MMP-2 inhibition with cyclic CTTHWGFTLC (CTT) reduced contraction to phenylephrine (PE) in aortae and mesenteric arteries from rats exposed to hypoxia for 7 days but not in vessels from normoxic rats. Similarly, CTT reduced contraction to Big endothelin-1 (Big ET-1) in aortae from rats exposed to hypoxia for 7 days. Responses to PE were reduced in hypoxic MMP-2(-/-) mice compared with MMP-2(+/+) mice. Increased contraction to Big ET-1 after hypoxia was observed in MMP-2(+/+) mice but not in MMP-2(-/-) mice. Rat aortic MMP-2 and membrane type 1 (MT1)-MMP protein levels and MMP activity were increased after 7 days of hypoxia. Rat aortic MMP-2 and MT1-MMP mRNA levels were increased in the deep medial vascular smooth muscle. We conclude that hypoxic induction of MMP-2 expression potentiates contraction in systemic conduit and resistance arteries. This may preserve the capacity to regulate the systemic circulation in the transition between the alterations in vascular tone and structural remodeling that occurs during prolonged hypoxic epochs.

Fenoldopam improves corticomedullary oxygen delivery and attenuates angiogenesis gene expression in acute ischemic renal injury

BACKGROUND/AIMS

Vasoactive compounds are known to affect intrarenal hemodynamics and gene transcription, but specific effects of fenoldopam in the setting of acute renal ischemia are not known. We utilized a rat model of acute ischemic nephropathy to test the hypothesis that fenoldopam improves corticomedullary tissue oxygen tension (PtO2) and attenuates angiogenesis gene expression in acute renal ischemia.

METHODS

Rats anesthetized with 50 mg/kg urethane were divided into 4 groups (n = 6 each): (1) sham with infusion of 0.9% saline; (2) sham with infusion of 0.1 microg x kg(-1) x min(-1) fenoldopam; (3) unilateral renal ischemia followed by 6 h of reperfusion with saline, and (4) ischemia/reperfusion with fenoldopam. Renal artery blood flow (RBF), renal cortical perfusion (RCP), and PtO2 were recorded throughout. Total RNA from left kidneys was used to probe microarrays. Gene expression was measured as percent positive control (GAPDH) and confirmed using RT-PCR.

RESULTS

Fenoldopam significantly increased RBF (p < 0.05), RCP (p < 0.01) and PtO2 (p <0.01) in both non-ischemic and post-ischemic kidneys. Fenoldopam attenuated 11 of the 13 ischemia-induced genes and 44 of 78 ischemia-suppressed genes. This attenuation was statistically significant (p < 0.05) for five genes.

CONCLUSION

Data from this rat model of ischemic nephropathy suggest that fenoldopam improves intrarenal hemodynamics and attenuates ischemia-related changes in angiogenesis gene expression.

Hypoxia-inducible factor-1 (HIF-1)

Adaptation to low oxygen tension (hypoxia) in cells and tissues leads to the transcriptional induction of a series of genes that participate in angiogenesis, iron metabolism, glucose metabolism, and cell proliferation/survival. The primary factor mediating this response is the hypoxia-inducible factor-1 (HIF-1), an oxygen-sensitive transcriptional activator. HIF-1 consists of a constitutively expressed subunit HIF-1beta and an oxygen-regulated subunit HIF-1alpha (or its paralogs HIF-2alpha and HIF-3alpha). The stability and activity of the alpha subunit of HIF are regulated by its post-translational modifications such as hydroxylation, ubiquitination, acetylation, and phosphorylation. In normoxia, hydroxylation of two proline residues and acetylation of a lysine residue at the oxygen-dependent degradation domain (ODDD) of HIF-1alpha trigger its association with pVHL E3 ligase complex, leading to HIF-1alpha degradation via ubiquitin-proteasome pathway. In hypoxia, the HIF-1alpha subunit becomes stable and interacts with coactivators such as cAMP response element-binding protein binding protein/p300 and regulates the expression of target genes. Overexpression of HIF-1 has been found in various cancers, and targeting HIF-1 could represent a novel approach to cancer therapy.

Modifying the soil to affect the seed: role of stromal-derived matrix metalloproteinases in cancer progression

In the 1980's, as the importance of matrix metalloproteinases (MMPs) in cancer progression was discovered, it was recognized that in most tumors these proteases were abundantly and sometimes exclusively expressed not by tumor cells, but by normal host-derived cells like fibroblasts, vascular endothelial cells, myofibroblasts, pericytes or inflammatory cells that contribute to the tumor microenvironment. Later experiments in mice deficient in specific MMPs revealed that host-derived MMPs play a critical role not only in tumor cell invasion, but also in carcinogenesis, angiogenesis, vasculogenesis and metastasis. Tumor cells secrete many factors, cytokines and chemokines that directly or indirectly increase the expression of these MMPs in the tumor microenvironment where they exert extracellular matrix (ECM) degrading and sheddase activities. The knowledge of the complex role that stromal-derived MMPs play in the interaction between tumor cells and stromal cells should allow us to consider specific windows in cancer treatment when MMP inhibition could have a valuable therapeutic effect.

Multipotential mesenchymal stem cells are mobilized into peripheral blood by hypoxia

MSCs constitute a population of multipotential cells giving rise to adipocytes, osteoblasts, chondrocytes, and vascular-smooth muscle-like hematopoietic supportive stromal cells. It remains unclear whether MSCs can be isolated from adult peripheral blood under stationary conditions and whether they can be mobilized in a way similar to hematopoietic stem cells. In this report, we show that MSCs are regularly observed in the circulating blood of rats and that the circulating MSC pool is consistently and dramatically increased (by almost 15-fold) when animals are exposed to chronic hypoxia. The immunophenotype and the adipocytic, osteoblastic, and chondrocytic differentiation potential of circulating MSCs were similar to those of bone marrow MSCs. Hypoxia-induced mobilization appears to be specific for MSCs since total circulating hematopoietic progenitor cells were not significantly increased. Our data provide an in vivo model amenable to analysis of MSC-mobilizing factors.

Hypoxia stimulates breast carcinoma cell invasion through MT1-MMP and MMP-2 activation

The process of cancer cell invasion involves degradation of the extracellular matrix (ECM) by proteases, integrin adhesion and cell motility. The role of ECM degrading proteases on the hypoxia-induced invasion of breast carcinoma cells was investigated. Hypoxia markedly increased the invasion capacity of MDA-MB-231 and MDA-MB-435 breast carcinoma cell lines. Matrix metalloproteinase (MMP) inhibitors blocked the hypoxia-induced invasion, whereas other protease inhibitors had no effect. Antibodies or siRNAs blocking either membrane type-1 MMP (MT1-MMP) or MMP-2 were effective in reducing the hypoxia-induced invasion. Serum-free reconstitution experiments confirmed the involvement of the MT1-MMP/MMP-2/tissue inhibitor of metalloproteinase-2 complex in this hypoxia-induced response. Overexpression of MT1-MMP in a poorly invasive breast cancer cell line, T47-D, promoted hypoxia-induced invasion and MMP-2 activation. Cell surface accumulation and activation of MT1-MMP without apparent regulation at the mRNA or protein levels indicated a post-translational adaptive response to hypoxia. Inhibition of the small GTPase RhoA eliminated the hypoxia-induced invasion and blocked the localization of MT1-MMP to the plasma membrane. Zymographic and molecular analysis of human breast tumors showed a strong correlation between hypoxic microenvironments and MMP-2 activation without changes in MT1-MMP expression. Our studies suggest that hypoxic tumor microenvironments promote breast cancer invasion through an MT1-MMP-dependent mechanism.

Cytokine-mediated modulation of MMPs and TIMPs in multipotential neural precursor cells

Recent studies have implicated the inflammatory process during experimental allergic encephalomyelitis (EAE) in triggering migration and differentiation of transplanted neural precursors cells (NPCs) into the inflamed white matter. The pro-inflammatory cytokines tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma are key factors in the pathogenesis of brain inflammation in EAE and were shown to enhance NPCs migration in vitro. As cell migration is dependent on extracellular matrix remodeling, involving proteolytic enzyme members of the matrix metalloproteinase (MMPs) family, we characterized the profile of expression of MMPs and their endogenous inhibitors (TIMPs) in rat NPCs, and evaluated the effects of TNF-alpha, IFN-gamma and IFN-beta, a clinically proven modulator of brain inflammation, on the expression of these molecules. Newborn rat striatal NPCs were expanded in spheres as nestin+, PSA-NCAM+ and NG2(-) cells, which can differentiate into astrocytes, oligodendrocytes and neurons. NPCs' gelatinase activities of MMP-2 and MMP-9, as determined by zymography, were increased by TNF-alpha, and to a lesser extent by IFN-gamma. Semi-quantitative RT-PCR indicated that TNF-alpha also upregulated MMP-9 mRNA levels. IFN-beta suppressed the TNF-alpha-induced levels of secreted MMP-9 and MMP-2, while enhancing the expression of TIMP-1 and TIMP-2 mRNA. These results suggest that MMPs activity is induced in NPCs by pro-inflammatory cytokines to mobilize them for promoting reparative processes. IFN-beta, on the other hand, appears to have an anti-proteolytic influence that may attenuate such NPC-mediated repair processes.

Angiogenic transcriptome of human microvascular endothelial cells: Effect of hypoxia, modulation by atorvastatin

Hypoxia changes expression of angiogenic genes. Statins were also reported to affect blood vessel formation. However, data on the effects of statins on endothelial cells in hypoxia are limited. Here, effect of hypoxia and atorvastatin was assessed in human microvascular endothelial cells (HMEC-1). Hypoxia (1% O2) up-regulated vascular endothelial growth factor-A (VEGF-A) but, unexpectedly, it decreased interleukin-8 (IL-8) and placenta growth factor (PlGF) expression. Atorvastatin (0.1-1 microM) attenuated PlGF in HMEC-1 in normoxia while it decreased VEGF-A and IL-8 production both in normoxia and hypoxia. Notably, the expression of VEGF-D, macrophage scavenger receptor-1 (MSR1), transforming growth factor beta receptor III (TGFbetaR3) and inhibitor of DNA binding 3 (ID3) was augmented by atorvastatin in cells cultured in normoxia, while in hypoxia the statin attenuated their expression. These data showed that hypoxia influenced in the opposite way the expression of major endothelial genes, augmenting VEGF-A and decreasing IL-8 and PlGF. The influence of atorvastatin on angiogenic gene expression is complex, and final pro- or anti-angiogenic outcome of statin therapy remains to be established for numerous angiogenesis-related diseases.

Ischemia injury alters endothelial cell properties of kidney cortex: stimulation of MMP-9

Although ischemia is the leading cause of acute renal failure in human, there is little information on the remodeling the kidney endothelium matrix during ischemic injury. In this study, we investigated the activity and expression of MMP-2 and MMP-9, in an isolated endothelial fraction following an acute in vivo reversible ischemia induced in rats by vascular clamping. Ischemia increased serum creatinine levels 1.4-fold, hallmark of acute renal failure. Isolation of the endothelial cell fraction was performed by affinity chromatography using an anti-PECAM-1 antibody. The isolated fraction was assessed by Western blotting analysis of endothelial cell markers. The positively selected fractions were enriched in the endothelial markers eNOS and PECAM-1 by 128-fold and 44-fold, respectively. Gelatin zymography showed that ischemia strongly stimulated proteolytic activity of proMMP-2 (1.8-fold), proMMP-9 (3-fold) and MMP-9 (4-fold) in the endothelial fractions. Western blot analysis indicated that TIMP-2 protein level increased by 3.2-fold in the endothelial fractions during ischemia. Surprisingly, TIMP-1 was absent from the endothelial preparations but was easily detected in the non-endothelial cells. Levels of the endocytic receptor LRP were increased by 2-fold during ischemia in the endothelial fractions. Occludin, a known in vivo MMP-9 substrate, was partly degraded in the endothelial fractions during ischemia, suggesting that the MMP-9 which was upregulated during ischemia was functional. These data suggest that ischemia in kidney could lead to the degradation of the vascular basement membrane and to increased permeability. This suggests new therapeutic approaches for ischemic pathologies by targeting MMP-9 and its regulators.

Hypoxia of endothelial cells leads to MMP-2-dependent survival and death

Exposure of endothelial cells (ECs) to hypoxia has separately been shown to induce their angiogenesis or death. Matrix metalloproteinase (MMP)-2 is associated with EC angiogenesis, although recent studies also implicate this molecule in EC death. We studied the effect of hypoxia in the absence or presence of TNF-alpha (characteristic of the inflammatory microenvironment accompanying hypoxia) on MMP-2 expression and its role in angiogenesis (proliferation, migration, and tube formation) and in the death of primary human umbilical vein endothelial cells (HUVECs). Hypoxia alone (24-48 h in 0.3% O(2) in the hypoxic chamber) and furthermore, when combined with TNF-alpha, significantly enhanced MMP-2 expression and activity. Hypoxia also led to a reduction in membrane type 1 MMP (MT1-MMP) and tissue inhibitor of metalloproteinase-2 mRNA and protein while enhancing the expression of alpha(v)beta(3) integrin and the cytoskeletal protein phosphopaxillin. Moreover, hypoxia led to colocalization of alpha(v)beta(3) and MMP-2, but not MT1-MMP, with phosphopaxillin in ECs. These results suggest MT1-MMP-independent activation of MMP-2 during hypoxia and support interactions between the ECM, integrins, and the cytoskeleton in hypoxia-induced MMP-2-related functions. Hypoxia enhanced EC migration in an MMP-2-dependent manner while leading to a reduction of cell number via their apoptosis, which was also dependent on MMP-2. In addition, hypoxia caused an aberrant tubelike formation on Matrigel that appeared to be unaffected by MMP-2. The hypoxia-induced, MMP-2-dependent migration of ECs is in accordance with the proangiogenic role ascribed to MMP-2, while the involvement of this protease in the hypoxia-related death of ECs supports an additional apoptotic role for this protease. Hence, in the hypoxic microenvironment, MMP-2 appears to have a dual autocrine role in determining the fate of ECs.

Roles of MMP-2/-9 in cardiac dysfunction during early multiple organ failure in an ovine animal model

Biventricular dilation and severe cardiac dysfunction are observed during septic shock. However, when endotoxemia and vasoconstrictor-masked hypovolemia work in concert in the pathogenesis of shock, the clinical scenario is more adverse compared to one of the insults acting alone. Matrix metalloproteinases (MMPs) are involved in chronic and acute heart failure by degrading the mechanical scaffold of the heart and several intracellular proteins. Therefore, the roles of MMP-2, MMP-9, MT1-MMP, focal adhesion kinase (FAK), and Paxillin in hearts of early multiple organ failure induced by norfenefrine-masked hypovolemia and endotoxemia were investigated in an ovine model. Experimental groups included (1) norfenefrine-masked hypovolemia plus endotoxemia (NMH+ENDO) (n=6), (2) norfenefrine-masked hypovolemia without endotoxemia (NMH) (n=6), (3) recurrent endotoxemia during normovolemia (ENDO) (n=6), and (4) healthy untreated controls (CON) (n=3). Apoptosis was determined by TUNEL-staining. Gel zymography revealed significantly increased MMP-2 activity in NMH+ENDO compared to ENDO and controls. MMP-9 activity was significantly elevated in all experimental groups. MMP-2 was significantly increased at the protein level, while MMP-9 was unaltered. MT1-MMP was not significantly changed in any group. Increased MMP activities were associated with cardiac deterioration. MMP-2/-9 activity and phosphorylated Paxillin (p-Paxillin) expression correlated positively with cardiomyocyte apoptosis. This study underscores the pivotal roles of MMP in acute cardiac dysfunction during early multiple organ failure in combined vasoconstrictor-masked hypovolemic and endotoxemia shock.

Resuscitation of hypoxic piglets with 100% O2 increases pulmonary metalloproteinases and IL-8

We hypothesized that resuscitation with 100% O2 compared with 21% O2 is detrimental to pulmonary tissue. The pulmonary injury was assessed by matrix metalloproteinase (MMP) activity, oxidative stress, IL-8, and histology 2.5 h after resuscitation from a hypoxic state. In pulmonary tissue extracts, MMP activity was analyzed by broad matrix-degrading capacity (total MMP) and zymography. MMP-2 mRNA expression was evaluated by quantitative real-time PCR. Total endogenous antioxidant capacity was measured by the oxygen radical absorbance capacity (ORAC) assay, and IL-8 was analyzed by ELISA technique. In bronchoalveolar lavage (BAL) fluid, MMPs were analyzed by zymography. In pulmonary tissue, pro- and active MMP-2 levels were increased in piglets that were resuscitated with 100% O2 compared with 21% O2. Pro-MMP-9, total MMP activity, and MMP-2 mRNA levels were significantly increased in resuscitated piglets compared with baseline. Net gelatinolytic activity increased in submucosa and blood vessels after 100% O2 and only in the blood vessels after 21% O2. Compared with baseline, ORAC values were considerably lowered in the resuscitated piglets and significantly reduced in the 100% O2 versus 21% O2 group. In BAL fluid, both pro-MMP-9 and pro-MMP-2 increased 2-fold in the 100% O2 group compared with 21% O2. Moreover, IL-8 concentration increased significantly in piglets that were resuscitated with 100% O2 compared with 21% O2, suggesting a marked proinflammatory response in the pulmonary tissue. Altogether, these data strongly suggest that caution must be taken when applying pure O2 to the newborn infant.

Role of MMP-2 in inhibiting Na+ dependent Ca2+ uptake by H2O2 in microsomes isolated from pulmonary smooth muscle

Treatment of microsomes (preferentially enriched with endoplasmic reticulum) isolated from bovine pulmonary artery smooth muscle tissue with H2O2 (1 mM) markedly stimulated matrix metalloproteinase activity and also inhibited Na+ dependent Ca2+ uptake. Electron micrograph revealed that H2O2 (1 mM) does not cause any damage to the microsomes. MMP-2 and TIMP-2 were determined to be the ambient protease and corresponding antiprotease of the microsomes. Pretreatment with vitamin E (1 mM) and TIMP-2 (50 microg/ml) reversed the effect produced by H2O2 (1 mM) on Na+ dependent Ca2+ uptake in the microsomes. However, H2O2 (1 mM) caused changes in MMP-2 activity and Na+ dependent Ca2+ uptake were not reversed upon pretreatment of the microsomes with a low concentration of 5 microg/ml of TIMP-2 which otherwise reversed MMP-2 (1 microg/ml) mediated increase in 14C-gelatin degradation and inhibition of Na+ dependent Ca2+ uptake. Combined treatment of the microsomes with a low dose of MMP-2 (0.5 microg/ml) and H2O2 (0.5 mM) inhibited Na+ dependent Ca2+ uptake in the microsomes compared to the respective low dose of either of them. Direct treatment of TIMP-2 (5 microg/ml) with H2O2 (1 mM) abolished the inhibitory effect of the inhibitor on 14C-gelatinolytic activity elicited by 1 microg/ml of MMP-2. Thus, one of the mechanisms by which H2O2 activates MMP-2 could be due to inactivation of TIMP-2 by the oxidant. The resulting activation of MMP-2 subsequently inhibits Na+ dependent Ca2+ uptake in the microsomes.

Hypoxia inducible factor pathways as targets for functional foods

The etiology of most chronic angiogenic diseases such as rheumatoid arthritis, atherosclerosis, diabetes complications, and cancer includes the presence of pockets of hypoxic cells growing behind aerobic cells and away from blood vessels. Hypoxic cells are the result of uncontrolled growth and insufficient vascularization and have undergone a shift from aerobic to anaerobic metabolism. Cells respond to hypoxia by stimulating the expression of hypoxia inducible factor (HIF), which is critical for survival under hypoxic conditions and in embryogenesis. HIF is a heterodimer consisting of the O2-regulated subunit, HIF-1alpha, and the constitutively expressed aryl hydrocarbon receptor nuclear translocator, HIF-1beta. Under hypoxic conditions, HIF-1alpha is stable, accumulates, and migrates to the nucleus where it binds to HIF-1beta to form the complex (HIF-1alpha + HIF-1beta). Transcription is initiated by the binding of the complex (HIF-1alpha + HIF-1beta) to hypoxia responsive elements (HREs). The complex [(HIF-1alpha + HIF-1beta) + HREs] stimulates the expression of genes involved in angiogenesis, anaerobic metabolism, vascular permeability, and inflammation. Experimental and clinical evidence show that these hypoxic cells are the most aggressive and difficult angiogenic disease cells to treat and are a major reason for antiangiogenic and conventional treatment failure. Hypoxia occurs in early stages of disease development (before metastasis), activates angiogenesis, and stimulates vascular remodeling. HIF-1alpha has also been identified under aerobic conditions in certain types of cancer. This review summarizes the role of hypoxia in some chronic degenerative angiogenic diseases and discusses potential functional foods to target the HIF-1alpha pathways under hypoxic and normoxic conditions. It is reported that dietary quinones, semiquinones, phenolics, vitamins, amino acids, isoprenoids, and vasoactive compounds can down-regulate the HIF-1 pathways and therefore the expression of several proangiogenic factors. Considering the lack of efficiency or the side effects of synthetic antiangiogenic drugs at clinical trials, down-regulation of hypoxia-induced angiogenesis by use of naturally occurring functional foods may provide an effective means of prevention.

Biological inferences from a mathematical model of comedo ductal carcinoma in situ of the breast

The growth of a tumour in a duct is examined in order to model ductal carcinoma in situ (DCIS) of the breast, the earliest known stage of breast cancer. Interactions between the expansive forces created by tumour cell proliferation and the stresses that develop in the compliant basement membrane are studied using numerical and analytical techniques. Particular attention focuses on the impact that proteolytic enzymes have on the tumour's progression. As the tumour expands and the duct wall deforms, the tumour cells are subjected to mechanical and nutritional stresses caused by high pressures and oxygen deprivation. Such stresses may stimulate the cells to produce proteolytic enzymes that degrade the duct wall, making it more compliant and prone to penetration by the tumour cells. We use our model to compare these two hypotheses for enzyme production and find that mechanical stress is likely the dominant mechanism, with the wall deforming most at the centre of the duct. We then discuss the biological implications of our theoretical results and suggest possible directions for future work.

Hypoxia Is Important in the Biology and Aggression of Human Glial Brain Tumors

We investigated whether increasing levels of tissue hypoxia, measured by the binding of EF5 [2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide] or by Eppendorf needle electrodes, were associated with tumor aggressiveness in patients with previously untreated glial brain tumors. We hypothesized that more extensive and severe hypoxia would be present in tumor cells from patients bearing more clinically aggressive tumors. Hypoxia was measured with the 2-nitroimidazole imaging agent EF5 in 18 patients with supratentorial glial neoplasms. In 12 patients, needle electrode measurements were made intraoperatively. Time to recurrence was used as an indicator of tumor aggression and was analyzed as a function of EF5 binding, electrode values and recursive partitioning analysis (RPA) classification. On the basis of EF5 binding, WHO grade 2 tumors were characterized by modest cellular hypoxia (pO2s approximately 10%) and grade 3 tumors by modest-to-moderate hypoxia (pO2s approximately 10%- 2.5%). Severe hypoxia (approximately 0.1% oxygen) was present in 5 of 12 grade 4 tumors. A correlation between more rapid tumor recurrence and hypoxia was demonstrated with EF5 binding, but this relationship was not predicted by Eppendorf measurements.