Induction of matrix metalloproteinase gene transcription by nitric oxide and mechanisms of MMP-1 gene induction in human melanoma cell lines

Enhancement of Nitric Oxide Bioavailability by Modulation of Cutaneous Nitric Oxide Stores

The generation of nitric oxide (NO) in the skin plays a critical role in wound healing and the response to several stimuli, such as UV exposure, heat, infection, and inflammation. Furthermore, in the human body, NO is involved in vascular homeostasis and the regulation of blood pressure. Physiologically, a family of enzymes termed nitric oxide synthases (NOS) generates NO. In addition, there are many methods of non-enzymatic/NOS-independent NO generation, e.g., the reduction of NO derivates (NODs) such as nitrite, nitrate, and nitrosylated proteins under certain conditions. The skin is the largest and heaviest human organ and contains a comparatively high concentration of these NODs; therefore, it represents a promising target for many therapeutic strategies for NO-dependent pathological conditions. In this review, we give an overview of how the cutaneous NOD stores can be targeted and modulated, leading to a further accumulation of NO-related compounds and/or the local and systemic release of bioactive NO, and eventually, NO-related physiological effects with a potential therapeutical use for diseases such as hypertension, disturbed microcirculation, impaired wound healing, and skin infections.

The role of extracellular matrix in tumour angiogenesis: the throne has NOx servants

The extracellular matrix (ECM) dynamics in tumour tissue are deregulated compared to the ECM in healthy tissue along with disorganized architecture and irregular behaviour of the residing cells. Nitric oxide (NO) as a pleiotropic molecule exerts different effects on the components of the ECM driving or inhibiting augmented angiogenesis and tumour progression and tumour cell proliferation and metastasis. These effects rely on the concentration of NO within the tumour tissue, the nature of the surrounding microenvironment and the sensitivity of resident cells to NO. In this review article, we summarize the recent findings on the correlation between the levels of NO and the ECM components towards the modulation of tumour angiogenesis in different types of cancers. These are discussed principally in the context of how NO modulates the expression of ECM proteins resulting in either the promotion or inhibition of tumour growth via tumour angiogenesis. Furthermore, the regulatory effects of individual ECM components on the expression of the NO synthase enzymes and NO production were reviewed. These findings support the current efforts for developing effective therapeutics for cancers.

Association of Key Genes and Pathways with Atopic Dermatitis by Bioinformatics Analysis

Background

Atopic dermatitis is a chronic inflammatory disease of the skin. It has a high prevalence worldwide and affected persons are prone to recurrent attacks, seriously affecting the physical and mental of patients. The exact etiology of the disease is still unclear.

Material/Methods

There are 7 datasets on atopic dermatitis in the Gene Expression Omnibus database, including 142 lesional and 134 non-lesional skin biopsy samples. Differential analysis was performed after datasets were integrated by robust multi-array average method. Functional modules of GSE99802 were explored by weighted gene co-expression network analysis. The 4 most important modules were enriched into the pathways by Metascape.

Results

Significantly differentially expressed genes included 41 upregulated and 10 downregulated genes. The following 5 of the most important upregulated genes had the strongest association with atopic dermatitis. SERPINB3&4 promote inflammation and impaired skin barrier function in the early stage of atopic dermatitis. S100A9 aggravates the inflammatory response by inducing the activation of toll-like receptor 4, neutrophil chemotaxis, neutrophilic inflammation, and the amplification of interleukin-8. MMP1 is the key protease of skin collagen degradation, keeping the extracellular matrix in dynamic balance. MMP12 induces the aggregation of various inflammatory cells into inflammatory tissue. The enriched pathways of each module mainly include Cellular responses to external stimuli, Metabolism of RNA and Translation, and Infectious disease.

Conclusions

The associated pathways and genes not only help us understand the molecular mechanism of the disease, but also provide research directions or targets for accurate diagnosis and treatment.

The role of nitric oxide in melanoma

Nitric oxide (NO) is a small gaseous signaling molecule that mediates its effects in melanoma through free radical formation and enzymatic processes. Investigations have demonstrated multiple roles for NO in melanoma pathology via immune surveillance, apoptosis, angiogenesis, melanogenesis, and on the melanoma cell itself. In general, elevated levels of NO prognosticate a poor outcome for melanoma patients. However, there are processes where the relative concentration of NO in different environments may also serve to limit melanoma proliferation. This review serves to outline the roles of NO in melanoma development and proliferation. As demonstrated by multiple in vivo murine models and observations from human tissue, NO may promote melanoma formation and proliferation through its interaction via inhibitory immune cells, inhibition of apoptosis, stimulation of pro-tumorigenic cytokines, activation of tumor associated macrophages, alteration of angiogenic processes, and stimulation of melanoma formation itself.

Collateral Growth in the Peripheral Circulation: A Review

Arterial occlusive diseases are a major cause of morbidity and death in the United States. The enlargement of pre-existing vessels, which bypass the site of arterial occlusion, provide a natural way for the body to compensate for such obstructions. Individuals differ in their capacity to develop collateral vessels. In recent years much attention has been focused upon therapy to promote collateral development, primarily using individual growth factors. Such studies have had mixed results. Persistent controversies exist regarding the initiating stimuli, the processes involved in enlargement, the specific vessels that should be targeted, and the most appropriate terminology. Consequently, it is now recognized that more research is needed to extend our knowledge of the complex process of collateral growth. This basic science review addresses five questions essential in understanding current problems in collateral growth research and the development of therapeutic interventions.

Oleic acid activates MMPs up-regulation through SIRT1/PPAR-γ inhibition: a probable linkage between obesity and coronary arterial disease

Obesity is positively related to the growing prevalence of coronary arterial disease (CAD). It is well established in terms of the plasma concentrations of free fatty acid (FFA) that are up-regulated in cases associating with obesity. Oleic acid (OA) is known as the most abundant monounsaturated fatty acid in the human circulatory system. Several pro-atherosclerotic responses of OA have been established. Sirtuin 1 (SIRT1) acts as a key role in regulating the normal physical function in smooth muscle cells (SMCs). SIRT1 activation is developed as a novel approach to delay the progression of atherosclerotic injuries. However, the mechanism is still unclear as to whether OA affects SIRT1 expression and its activity in SMCs. We confirmed that OA treatment represses SIRT1 and peroxisome proliferator-activated receptors-γ levels in SMCs. Moreover, OA enhances by transforming the growth factor-β1 (TGF-β1) release via activation of NF-κB. OA causes NO production by inducing the inducible nitric oxide synthase overexpression, thereby promoting the secretions of matrix metalloproteinases-1 (MMP-1) and MMP-3. Overall, we suggested that OA enhances MMPs activation through SIRT1 down-regulation. Therefore, our findings might provide a novel route for developing new therapeutic treatments for FFAs-related CADs.

Insights into the diverse effects of nitric oxide on tumor biology

Among its many roles in cellular biology, nitric oxide (·NO) has long been associated with cancers both as a protumorigenic and as an antitumorigenic agent. The dual nature of this signaling molecule in varied settings is attributable to its temporal and concentration-dependent effects that produce different phenotypes. The steady-state ·NO concentration within the cell is a balance between its rate of enzymatic synthesis from the three nitric oxide synthase (NOS) isoforms and consumption via numerous metabolic pathways and demonstrates strong dependence on the tissue oxygen concentration. NOS expression and ·NO production are often deregulated and associated with numerous types of cancers with dissimilar prognostic outcomes. ·NO influences several facets of tumor initiation and progression including DNA damage, chronic inflammation, angiogenesis, epithelial-mesenchymal transition, and metastasis, to name a few. The role of ·NO as an epigenetic modulator has also recently emerged and has potentially important mechanistic implications in regulating transcription of oncogenes and tumor-suppressor genes. ·NO-derived cellular adducts such as dinitrosyliron complexes and the formation of higher nitrogen oxides further alter its cellular behavior. Among anticancer strategies, the use of NOS as a prognostic biomarker and modulation of ·NO production for therapeutic benefit have gained importance over the past decade. Numerous ·NO-releasing drugs and NOS inhibitors have been evaluated in preclinical and clinical settings to arrest tumor growth. Taken together, ·NO affects various arms of cancer signaling networks. An overview of this complex interplay is provided in this chapter.

Nitric oxide in cancer metastasis

Cancer metastasis is the spread and growth of tumor cells from the original neoplasm to further organs. This review analyzes the role of nitric oxide (NO), a signaling molecule, in the regulation of cancer formation, progression, and metastasis. The action of NO on cancer relies on multiple factors including cell type, metastasis stage, and organs involved. Various chemotherapy drugs cause cells to release NO, which in turn induces cytotoxic death of breast, liver, and skin tumors. However, NO has also been clinically connected to a poor cancer prognosis because of its role in angiogenesis and intravasation. This supports the claim that NO can be characterized as both pro-metastatic and anti-metastatic, depending on specific factors. The inhibition of cell proliferation and anti-apoptosis pathways by NO donors has been proposed as a novel therapy to various cancers. Studies suggest that NO-releasing non-steroidal anti-inflammatory drugs act on cancer cells in several ways that may make them ideal for cancer therapy. This review summarizes the biological significance of NO in each step of cancer metastasis, its controversial effects for cancer progression, and its therapeutic potential.

Effect of small interfering RNAs on matrix metalloproteinase 1 expression

Three small double strand siRNAs (506-MMP1, 859-MMP1 and 891-MMP1), each contains 25-26 nucleotides, with high specific to human MMP1 were designed according to mRNA sequence of human MMP1 (NCBI, NM_002421). To monitor the MMP1 gene expression, the total RNAs of human skin fibroblast (Detroit 551, BCRC 60118) were extracted. One human matrix metalloproteinase 1 (MMP1) partial sequence cDNA, included all the three siRNA target sequences, amplified specifically via RT-PCR and PCR reactions, and three synthesized siRNA target DNAs were cloned individually into pAcGFP1-N3 with green fluorescent protein (GFP). These reporter plasmids were then transfected individually into malignant melanoma (MeWo, BCRC 60540) and the GFP was detected after 48 h. Fluorescence results indicated that the 859 siRNA revealed highest inhibitory ability (almost 90%), and was, accordingly, transfected into MeWo cells. According to the real-time quantitative PCR and western blot, the exhibition ability to silence MMP1 gene expression was 85-89%.

β3-adrenergic receptor activity modulates melanoma cell proliferation and survival through nitric oxide signaling

We have recently shown in B16F10 melanoma cells that blockade of β3-adrenergic receptors (β3-ARs) reduces cell proliferation and induces apoptosis, likely through the involvement of nitric oxide (NO) signaling. Here, we tested the hypothesis that the effects of β3-AR blockade on melanoma cells are mainly mediated by a decrease in the activity of the NO pathway, possibly due to reduced expression of inducible NO synthase (iNOS). B16F10 cells were used. Nitrite production, iNOS expression, cell proliferation, and apoptosis were evaluated. β3-AR blockade with L-748,337 reduced basal nitrite production, while β3-AR stimulation with BRL37344 increased it. The effects of β3-AR blockade were prevented by NOS activation, while the effects of β3-AR activation were prevented by NOS inhibition. Treatments increasing nitrite production also increased iNOS expression, while treatments decreasing nitrite production reduced iNOS expression. Among the different NOS isoforms, experiments using L-748,337 or BRL37344 with activators or inhibitors targeting specific NOS isoforms demonstrated a prominent role of iNOS in nitrite production. β3-AR blockade decreased cell proliferation and induced apoptosis, while β3-AR activation had the opposite effects. The effects of β3-AR blockade/activation were prevented by iNOS activation/inhibition, respectively. Taken together, these results demonstrate that iNOS-produced NO is a downstream effector of β3-ARs and that the beneficial effects of β3-AR blockade on melanoma B16F10 cell proliferation and apoptosis are functionally linked to reduced iNOS expression and NO production. Although it is difficult to extrapolate these data to the clinical setting, the targeted inhibition of the β3-AR-NO axis may offer a new therapeutic perspective to treat melanomas.

In vivo modulation of iNOS pathway in hepatocellular carcinoma by Nigella sativa

OBJECTIVE

Nitric oxide (NO) and inducible nitric oxide synthase enzyme (iNOS) have been implicated in various tumors. Hepatocellular carcinoma is a highly aggressive form of solid tumor. The lack of effective therapy necessitates the introduction of novel therapeutic strategies to counter this disease. Nigella sativa (NS) has been shown to have specific health benefits. The aim of this study was to investigate the in vivo modulation of the iNOS pathway by NS ethanolic extract (NSEE) and the implications of this effect as an antitumor therapeutic approach against diethylnitrosamine (DENA)-induced hepatocarcinogenesis.

METHODS

Rats were divided into four groups, normal control, NSEE control, cancer control, and NSEE-DENA groups. The diagnosis of cancer was based on alpha-fetoprotein (AFP) levels and histological variations. Serum NO, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels and serum iNOS activity were measured. Liver iNOS expression was investigated by reverse transcriptase (RT)-PCR and western blot assays.

RESULTS

Serum AFP, NO, TNF-α, and IL-6 levels and iNOS enzyme activity were significantly increased in rats treated with DENA. Significant up-regulation of liver iNOS mRNA and protein expression was also observed. Subsequent treatment with NSEE significantly reversed these effects and improved the histopathological changes in malignant liver tissue which appeared after treatment with DENA, without any toxic effect when given alone.

CONCLUSION

These results provide evidence that attenuation of the iNOS pathway and suppression of the inflammatory response mediated by TNF-α, and IL-6 could be implicated in the antitumor effect of NSEE. As such, our findings hold great promise for the utilization of NS as an effective natural therapeutic agent in the treatment of hepatocarcinogenesis.

Effects of the nitric oxide donor JS-K on the blood-tumor barrier and on orthotopic U87 rat gliomas assessed by MRI

Nitric oxide (NO) released from NO donors can be cytotoxic in tumor cells and can enhance the transport of drugs into brain tumors by altering blood-tumor barrier permeability. The NO donor JS-K [O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate] releases NO upon enzymatic activation selectively in cells overexpressing glutathione-S-transferases (GSTs) such as gliomas. Thus, JS-K-dependent NO effects - especially on cell viability and vascular permeability - were investigated in U87 glioma cells in vitro and in an orthotopic U87 xenograft model in vivo by magnetic resonance imaging (MRI). In vitro experiments showed dose-dependent antiproliferative and cytotoxic effects in U87 cells. In addition, treatment of U87 cells with JS-K resulted in a dose-dependent activation of soluble guanylate cyclase and intracellular accumulation of cyclic guanosine monophosphate (cGMP) which was irreversibly inhibited by the selective inhibitor of soluble guanylate cyclase ODQ (1H-[1,2,4]oxadiazolo(4,3a)quinoxaline-1-one). Using dynamic contrast enhanced MRI (DCE-MRI) as a minimally invasive technique, we demonstrated for the first time a significant increase in the DCE-MRI read-out initial area under the concentration curve (iAUC60) indicating an acute increase in blood-tumor barrier permeability after i.v. treatment with JS-K. Repeated MR imaging of animals with intracranial U87 gliomas under treatment with JS-K (3.5 μmol/kg JS-K 3×/week) and of untreated controls on day 12 and 19 after tumor inoculation revealed no significant changes in tumor growth, edema formation or tumor perfusion. Immunohistochemical workup of the brains showed a significant antiproliferative effect of JS-K in the gliomas. Taken together, in vitro and in vivo data suggest that JS-K has antiproliferative effects in U87 gliomas and opens the blood-tumor barrier by activation of the NO/cGMP signaling pathway. This might be a novel approach to facilitate entry of therapeutic drugs into brain tumors. DCE-MRI is a non-invasive, repeatable imaging modality to monitor biological effects of NO donors and other experimental therapeutics in intracranial tumor models.

The yin and yang of nitric oxide in cancer progression

Nitric oxide (NO) is a short-lived, pleiotropic molecule that affects numerous critical functions in the body. Presently, there are markedly conflicting findings in the literature regarding NO and its role in carcinogenesis and tumor progression. NO has been shown to have dichotomous effects on cellular proliferation, apoptosis, migration, invasion, angiogenesis and many other important processes in cancer biology. It has been shown to be both pro- and antitumorigenic, depending on the concentration and the tumor microenvironment in question. NO is generated by three isoforms of NO synthase (NOS) that are widely expressed and sometimes upregulated in human tumors. Due to its vast array of physiological functions, it presents a huge challenge to researchers to discover its true potential in cancer biology and consequently, its use in anticancer therapies. In this study, we review the current knowledge in this area, with an emphasis placed on NO modulation as an anticancer therapy, focusing on NO-donating drugs and NOS inhibitors.

Emerging avenues linking inflammation and cancer

The role of inflammation in carcinogenesis has been extensively investigated and well documented. Many biochemical processes that are altered during chronic inflammation have been implicated in tumorigenesis. These include shifting cellular redox balance toward oxidative stress; induction of genomic instability; increased DNA damage; stimulation of cell proliferation, metastasis, and angiogenesis; deregulation of cellular epigenetic control of gene expression; and inappropriate epithelial-to-mesenchymal transition. A wide array of proinflammatory cytokines, prostaglandins, nitric oxide, and matricellular proteins are closely involved in premalignant and malignant conversion of cells in a background of chronic inflammation. Inappropriate transcription of genes encoding inflammatory mediators, survival factors, and angiogenic and metastatic proteins is the key molecular event in linking inflammation and cancer. Aberrant cell signaling pathways comprising various kinases and their downstream transcription factors have been identified as the major contributors in abnormal gene expression associated with inflammation-driven carcinogenesis. The posttranscriptional regulation of gene expression by microRNAs also provides the molecular basis for linking inflammation to cancer. This review highlights the multifaceted role of inflammation in carcinogenesis in the context of altered cellular redox signaling.

Insidious role of nitric oxide in migration/invasion of colon cancer cells by upregulating MMP-2/9 via activation of cGMP-PKG-ERK signaling pathways

Nitric oxide (NO), an uncharged free radical is implicated in various physiological and pathological processes. The present study is an investigation on the effect of NO on proliferation, apoptosis and migration of colon cancer cells. Colon adenocarcinoma cells, WiDr, were used for the in vitro experiments. Tissues from colon adenocarcinoma, adjacent normal and inflammatory tissue and lymph node with metastasis were evaluated for iNOS, MMP-2/9 and Fra-1/Fra-2. NO increases the proliferation of cancer cells and simultaneously prevents apoptosis. Expression of MMP-2/9, RhoB and Rac-1 was enhanced by NO in a time dependent manner. Further, NO increased phosphorylation of ERK1/2 and induced nuclear translocation of Fra-1 and Fra-2. Electrophoretic mobility shift analysis and use of deletion mutant promoter constructs identified role of AP-1 in NO-mediated regulation of MMP-2/9. iNOS, MMP-2/9, Fra-1 and Fra-2 in normal and colon adenocarcinoma tissues were analyzed and it was found that increased expression of these proteins in cancer when compared to normal provides support to our in vitro findings. The study showed that the NO-cGMP-PKG promotes MMP-2/9 expression by activating ERK-1/2 and AP-1. This study reveals the insidious role of NO in imparting tumor aggressiveness.

Matrix metalloproteinase-1 expression enhances tumorigenicity as well as tumor-related angiogenesis and is inversely associated with TIMP-4 expression in a model of glioblastoma

Herein we continue the study of matrix metalloproteinase-1 (MMP-1) with respect to glioblastoma multiforme (GBM) cell tumorigenicity and angiogenesis. A model of tumorigenicity with cells stably altered to over-express or knock-down MMP-1 revealed that it significantly increases tumor incidence and size. Organized endothelial growth in human umbilical vein endothelial cell (HUVEC)-GBM co-cultures was significantly increased in the presence of MMP-1. CD31 analysis of model tumors elucidated a substantial recruitment of endothelium in MMP-1 enhanced samples. Antibody arrays indicated an inverse expression of certain anti-angiogenic factors with respect to MMP-1, the most notable of which was a significant increase in tissue inhibitor of metalloproteinases-4 (TIMP-4) in the absence of MMP-1, as validated by immunoblot.

Nitric oxide-mediated invasion in Barrett's high-grade dysplasia and adenocarcinoma

Nitric oxide (NO) has been shown to induce double strand DNA breaks in Barrett's oesophagus (BO) and in other cancers has a role in invasion. The specific aims of this study were to investigate whether NO can induce invasion in cells representative of different stages of Barrett's progression and to determine possible underlying mechanisms. Physiological concentrations of NO that mimic luminal production of NO from dietary sources enhanced invasion in cell lines from high-grade dysplasia (GihTERT) and oesophageal adenocarcinoma (FLO) but not a non-dysplastic Barrett's cell line (QhTERT). Real-time reverse transcription-polymerase chain reaction revealed that NO induced expression of matrix metalloproteinase (MMP)-1, -3, -7, -9 and -10 and tissue inhibitor of metalloproteinase (TIMP)-1, -2 and -3 in these cell lines. Furthermore, ex vivo treatment of Barrett's biopsy samples with NO induced increases in MMP-1 and TIMP-1 expression, suggesting that NO enhances invasion through deregulating MMP and TIMP expression in epithelial cells. In keeping with these findings, microarray analysis and immunohistochemistry performed on biopsy samples showed enhanced expression of MMP-1, -3, -7 and -10 and TIMP-1 in the progression from non-dysplastic BO to adenocarcinoma, although this could not be directly attributed to the effect of NO. Thus, NO may play a role in Barrett's carcinogenesis through deregulating MMP and TIMP expression to enhance invasive potential.

Targeting nitric oxide for cancer therapy

A blueprint for the ideal anticancer molecule would include most of the properties of nitric oxide (NO•), but the ability to exploit these characteristics in a therapeutic setting requires a detailed understanding of the biology and biochemistry of the molecule. These properties include the ability of NO• to affect tumour angiogenesis, metastasis, blood flow and immuno surveillance. Furthermore NO• also has the potential to enhance both radio- and chemotherapy. However, all of these strategies are dependent on achieving appropriate levels of NO•, since endogenous levels of NO• appear to have a clear role in tumour progression. This review aims to summarize the role of NO• in cancer with particular emphasis on how the properties of NO• can be exploited for therapy.

Salivary antioxidants and metalloproteinases in juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common autoimmune inflammatory disease in children; joint inflammation is the hallmark of the disease. Thirty-five children with JIA were studied, of whom 26 had active disease and 14 were receiving anti-TNF therapy (5 with Infliximab, 9 with Etanercept). Sixteen healthy controls also were studied. Saliva samples were obtained for analysis of anti-oxidant status, metalloproteinases (MMPs) and sialochemistry. The total antioxidant status was significantly higher in the saliva of all JIA patients, whether treated (P = 0.014) or not treated (P = 0.038) with anti-TNF agents. The increase in antioxidant status (TAS) in the saliva of the active patients was nearly two times higher than that of non-active patients (P = 0.01). MMP levels were significantly lower in JIA patients than in controls. MMP-9, MMP-3 and MMP-2 were lower in JIA patients without anti-TNF treatment by 36.7% (P = 0.01), 30.0% (P = 0.0001) and 10.7% (P = 0.0001), respectively. A greater reduction in MMP levels was observed in the group of patients treated with anti-TNF drugs: MMP-9, MMP-3 and MMP-2 were lower than in controls by 51.1% (P = 0.0001), 61.5% (P = 0.0001) and 55.4% (P = 0.0001), respectively. Children with JIA exhibited a significantly higher salivary antioxidant activity and significantly lower MMP levels. Anti-TNF treatment was associated with a further decrease in MMP levels in the saliva of JIA patients while an active state of JIA was associated with a further increase in the salivary antioxidant activity. Anti-TNF treatment may modulate the degradation process during the course of arthritis by inhibition of the activity of MMP.

A matrix metalloproteinase-1/protease activated receptor-1 signaling axis promotes melanoma invasion and metastasis

Hallmarks of malignant melanoma are its propensity to metastasize and its resistance to treatment, giving patients with advanced disease a poor prognosis. The transition of melanoma from non-invasive radial growth phase (RGP) to invasive and metastatically competent vertical growth phase (VGP) is a major step in tumor progression, yet the mechanisms governing this transformation are unknown. Matrix Metalloproteinase-1 (MMP-1) is highly expressed by VGP melanomas, and is thought to contribute to melanoma progression by degrading type I collagen within the skin to facilitate melanoma invasion. Protease activated receptor-1 (PAR-1) is activated by MMP-1, and is also expressed by VGP melanomas. However, the effects MMP-1 signaling through PAR-1 have not been examined in melanoma. Here, we demonstrate that an MMP-1/PAR-1 signaling axis exists in VGP melanoma, and is necessary for melanoma invasion. Introduction of MMP-1 into RGP melanoma cells induced gene expression associated with tumor progression and promoted invasion in vitro, and enhanced tumor growth and conferred metastatic capability in vivo. This study demonstrates that both the type I collagenase and PAR-1 activating functions of MMP-1 are required for melanoma progression, and suggests that MMP-1 may be a major contributor to the transformation of melanoma from non-invasive to malignant disease.

Induction of matrix metalloproteinase-1 and glioma cell motility by nitric oxide

High grade gliomas invariably recur due in a large part to tumor cells permeating normal brain in an inaccessible, diffuse manner. Previous work demonstrates that the expression of matrix metalloproteinases (MMP) contributes to this characteristic. Not only can MMPs assist a cell in traversing its environment by clearing extracellular matrix molecules, but they can also impact non-traditional downstream signals that affect a cell's ability to interact and respond to its surroundings. Contributions to the induction of MMP expression and functional significance in glioma are still under investigation. Evidence in other cancer settings indicates that nitric oxide (NO) may play a role in tumor/cell progression that can influence MMP production. Matrix metalloproteinase-1 (MMP-1), also known as interstitial collagenase, and the constitutive nitric oxide synthases (NOS) have been shown to be over-expressed in high grade gliomas. In the current study we investigated the potential involvements of NO with regard to MMP-1 and functional glioma cell movement. With the treatment of the NO donor sodium nitroprusside (SNP), there was significant induction of MMP-1 mRNA, secreted MMP-1 protein and motility of glioma cell lines within 48 h. RNA inhibition of MMP-1 through transient transfection of three MMP-1 specific siRNAs revealed a marked abrogation of the NO-mediated induction of motility. In addition, application of the NOS inhibitor N(omega)-Nitro-L-arginine methyl ester (L-NAME) impaired movement of glioma cells. These data provide evidence for a regulatory axis of high grade glioma cell movement from NO through MMP-1, with NOS inhibitor results showing promise for future pharmacologic investigation.

Diesel exhaust particles activate the matrix-metalloproteinase-1 gene in human bronchial epithelia in a beta-arrestin-dependent manner via activation of RAS

BACKGROUND

Diesel exhaust particles (DEPs) are globally relevant air pollutants that exert a detrimental human health impact. However, mechanisms of damage by DEP exposure to human respiratory health and human susceptibility factors are only partially known. Matrix metalloproteinase-1 (MMP-1) has been implied as an (etio)pathogenic factor in human lung and airway diseases such as emphysema, chronic obstructive pulmonary disease, chronic asthma, tuberculosis, and bronchial carcinoma and has been reported to be regulated by DEPs.

OBJECTIVE

We elucidated the molecular mechanisms of DEPs' up-regulation of MMP-1.

METHODS/RESULTS

Using permanent and primary human bronchial epithelial (HBE) cells at air-liquid interface, we show that DEPs activate the human MMP-1 gene via RAS and subsequent activation of RAF-MEK-ERK1/2 mitogen-activated protein kinase signaling, which can be scaffolded by beta-arrestins. Short interfering RNA mediated beta-arrestin1/2 knockout eliminated formation, subsequent nuclear trafficking of phosphorylated ERK1/2, and resulting MMP-1 transcriptional activation. Transcriptional regulation of the human MMP-1 promoter was strongly influenced by the presence of the -1607GG polymorphism, present in 60-80% of humans, which led to striking up-regulation of MMP-1 transcriptional activation.

CONCLUSION

Our results confirm up-regulation of MMP-1 in response to DEPs in HBE and provide new mechanistic insight into how these epithelia, the first line of protection against environmental insults, up-regulate MMP-1 in response to DEP inhalation. These mechanisms include a role for the human -1607GG polymorphism as a susceptibility factor for an accentuated response, which critically depends on the ability of beta-arrestin1/2 to generate scaffolding and nuclear trafficking of phosphorylated ERK1/2.

Nitric oxide initiates progression of human melanoma via a feedback loop mediated by apurinic/apyrimidinic endonuclease-1/redox factor-1, which is inhibited by resveratrol

It is well recognized that nitric oxide (NO) is involved in tumor progression, including melanoma. Measurement of proliferative and metastatic capacity by MTS and Matrigel invasion assays, respectively, was done and showed that NO-treated melanoma cells exhibited a higher capacity compared with control, especially metastatic Lu1205 cells. Apurinic/apyrimidinic endonuclease-1/redox factor-1 (APE/Ref-1) is a multifunctional protein and its role in tumor biology has attracted considerable attention. To determine whether APE/Ref-1 plays a role in mediating NO stimulation of melanoma progression, we investigated the effect of DETA/NO on levels of APE/Ref-1 and related downstream targets [activator protein-1 (AP-1)/JunD, matrix metalloproteinase-1 (MMP-1), Bcl-2, and inducible nitric oxide synthase (iNOS)] by Western blot and reverse transcription-PCR analysis. Following DETA/NO treatment, APE/Ref-1 and other downstream molecules were induced. Knockdown of APE/Ref-1 or AP-1/JunD by specific small interfering RNA markedly reversed the induction by NO stress of target proteins. These results present evidence for the existence of a functional feedback loop contributing to progression and metastasis of melanoma cells. Resveratrol has been shown to be an APE/Ref-1 inhibitor and significant decreases in AP-1/JunD, MMP-1, Bcl-2, and iNOS protein levels occurred after exposure to resveratrol. This phenolic antioxidant may be an appropriate choice for combining with other compounds that develop resistance by up-regulation of these molecules.

Understanding signaling cascades in melanoma

Understanding regulatory pathways involved in melanoma development and progression has advanced significantly in recent years. It is now appreciated that melanoma is the result of complex changes in multiple signaling pathways that affect growth control, metabolism, motility and the ability to escape cell death programs. Here we review the major signaling pathways currently known to be deregulated in melanoma with an implication to its development and progression. Among these pathways are Ras, B-Raf, MEK, PTEN, phosphatidylinositol-3 kinase (PI3Ks) and Akt which are constitutively activated in a significant number of melanoma tumors, in most cases due to genomic change. Other pathways discussed in this review include the [Janus kinase/signal transducer and activator of transcription (JAK/STAT), transforming growth factor-beta pathways which are also activated in melanoma, although the underlying mechanism is not yet clear. As a paradigm for remodeled signaling pathways, melanoma also offers a unique opportunity for targeted drug development.

Targeting NOX, INOS and COX-2 in inflammatory cells: chemoprevention using food phytochemicals

Biological, biochemical and physical stimuli activate inflammatory leukocytes, such as macrophages, resulting in induction and synthesis of proinflammatory proteins and enzymes, together with free radicals, as innate immune responses. On the other hand, chronic and dysregulated activation of some inducible enzymes, including NADPH oxidase (NOX), inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, have been shown to play pivotal roles in the development of certain inflammatory diseases such as oncogenesis. While the use of synthetic agents, especially those targeting molecules, is an attractive and reasonable approach to prevent carcinogenesis, it should be noted that traditional herbs and spices also exist along with their active constituents, which have been demonstrated to disrupt inflammatory signal transduction pathways. In this mini-review, the molecular mechanisms of activation or induction of NOX, iNOS and COX-2, as well as some food phytochemicals with marked potential to regulate those key inflammatory molecules, are highlighted. For example, 1'-acetoxychavicol acetate, which occurs in the rhizomes of the subtropical Zingiberaceae plant, has been shown to attenuate NOX-derived superoxide generation in macrophages, as well as lipopolysaccharide-induced nitric oxide and prostaglandin E(2) production through the suppression of iNOS and COX-2 synthesis, respectively. Notably, this phytochemical has exhibited a wide range of cancer prevention activities in several rodent models of inflammation-associated carcinogenesis. Herein, the cancer preventive potentials of several food phytochemicals targeting the induction of NOX, iNOS and COX-2 are described.

Anti-inflammatory effects of Lactobacillus brevis (CD2) on periodontal disease

OBJECTIVES

To analyze the anti-inflammatory effects of Lactobacillus brevis extracts on periodontitis patients and to investigate the involved mechanisms in vitro on activated macrophages.

METHODS

Eight healthy subjects and 21 patients with chronic periodontitis were enrolled to analyze the effect of L. brevis-containing lozenges on periodontitis-associated symptoms and signs. Before and after the treatment, the patients received a complete periodontal examination. Saliva samples, collected before and after treatment, were analyzed for metalloproteinase and nitric oxide synthase (NOS) activity, immunoglobulin-A (IgA), prostaglandin E(2) (PGE(2)) and gamma-interferon (IFN-gamma) levels. Arginine deiminase (AD) and NOS activities were determined through a radiometric assay. Metalloproteinases were assayed by zymogram and Western blotting, whereas IgA, PGE(2) and IFN-gamma were assayed by enzyme-linked imunosorbent assay tests.

RESULTS

The treatment led to the total disappearance or amelioration of all analyzed clinical parameters in all patients. This was paralleled to a significant decrease of nitrite/nitrate, PGE(2), matrix metalloproteinase, and IFN-gamma levels in saliva samples.

CONCLUSION

Our results suggest that the anti-inflammatory effects of L. brevis could be attributed to the presence of AD which prevented nitric oxide generation. Our findings give further insights into the knowledge of the molecular basis of periodontitis and have a potential clinical significance, giving the experimental ground for a new innovative, simple and efficacious therapeutical approach of periodontal disease.

Nitric oxide and vascular remodeling: Spotlight on the kidney

Extracellular matrix (ECM) remodeling with successive tissue fibrosis is a key feature of chronic cardiovascular diseases, including atherosclerosis and restenosis. The atherogenic changes underlying these pathologies result from chronification of an acute repair response towards injurious and inflammatory stimuli. Thereby functional tissue is replaced by excessive ECM deposition. In the kidney, impaired remodeling is a major cause of perivascular, interstitial, and glomerular fibrosis but also a common complication of chronic hypertension. Experimental evidence points to the matrix metalloproteases (MMPs) and their intrinsic inhibitors, the tissue inhibitors of MMPs as key mediators of atherogenic and fibrotic pathologies. Mechanistically, a deregulation in ECM turnover tightly correlates with an increased production and release of proinflammatory and profibrotic factors including interleukin-1beta, transforming growth factor beta, angiotensin II, and reactive oxygen species. Unlike these factors the pleiotropic messenger molecule nitric oxide (NO) by acting as the major physiological vasodilator has emerged as one of the most atheroprotective factors. However, under inflammatory conditions NO does acquire proatherogenic and profibrotic properties thereby exacerbating tissue fibrosis. In this review, the mechanisms underlying both opposing properties of NO on perivascular ECM remodeling will exemplarily be discussed for renal fibrosis with a particular focus on the MMPs and intrinsic protease inhibitors.

The chemoinvasion assay: a method to assess tumor and endothelial cell invasion and its modulation

Invasive and metastatic cells, as well as endothelial cells, must cross basement membranes (BMs) in order to disseminate or to form new blood vessels. The chemoinvasion assay using the reconstituted BM Matrigel in Boyden blind-well chambers is a very rapid, easy, inexpensive and flexible test that can be used to quantify the invasive potential of most cell types; it can be applied to detect the migratory activity associated with matrix degradation and can also be adapted to study the selective degrading activity on different matrix substrates. Transwell inserts can also be used. Once the optimal experimental conditions are empirically determined for specific cellular models, the chemoinvasion assay can be used for the screening of inhibitors of invasiveness and angiogenesis, or to select for invasive cellular populations. This protocol can be completed in 9 h.

Kaposi's sarcoma-associated herpesvirus infection promotes invasion of primary human umbilical vein endothelial cells by inducing matrix metalloproteinases

Matrix metalloproteinases (MMPs) play important roles in cancer invasion, angiogenesis, and inflammatory infiltration. Kaposi's sarcoma is a highly disseminated angiogenic tumor of proliferative endothelial cells linked to infection by Kaposi's sarcoma-associated herpesvirus (KSHV). In this study, we showed that KSHV infection increased the invasiveness of primary human umbilical vein endothelial cells (HUVEC) in a Matrigel-based cell invasion assay. KSHV-induced cell invasion was abolished by an inhibitor of MMPs, BB-94, and occurred in both autocrine- and paracrine-dependent fashions. Analysis by zymography and Western blotting showed that KSHV-infected HUVEC cultures had increased secretion of MMP-1, -2, and -9. KSHV increased the secretion of MMP-2 within 1 h following infection without upregulating its mRNA expression level. In contrast, the secretion of MMP-1 and -9 was not increased until 6 h after KSHV infection and was correlated with the upregulation of their mRNA expression levels. Promoter analysis by reporter assays and electrophoretic mobility shift assays identified an AP-1 cis-element as the dominant KSHV-responsive site in the MMP-1 promoter. Together, these results suggest that KSHV infection modulates the production of multiple MMPs to increase cell invasiveness and thus contributes to the pathogenesis of KSHV-induced malignancies.

Matrix metalloproteinases in lung: multiple, multifarious, and multifaceted

The matrix metalloproteinases (MMPs), a family of 25 secreted and cell surface-bound neutral proteinases, process a large array of extracellular and cell surface proteins under normal and pathological conditions. MMPs play critical roles in lung organogenesis, but their expression, for the most part, is downregulated after generation of the alveoli. Our knowledge about the resurgence of the MMPs that occurs in most inflammatory diseases of the lung is rapidly expanding. Although not all members of the MMP family are found within the lung tissue, many are upregulated during the acute and chronic phases of these diseases. Furthermore, potential MMP targets in the lung include all structural proteins in the extracellular matrix (ECM), cell adhesion molecules, growth factors, cytokines, and chemokines. However, what is less known is the role of MMP proteolysis in modulating the function of these substrates in vivo. Because of their multiplicity and substantial substrate overlap, MMPs are thought to have redundant functions. However, as we explore in this review, such redundancy most likely evolved as a necessary compensatory mechanism given the critical regulatory importance of MMPs. While inhibition of MMPs has been proposed as a therapeutic option in a variety of inflammatory lung conditions, a complete understanding of the biology of these complex enzymes is needed before we can reasonably consider them as therapeutic targets.

Elastin-elastases and inflamm-aging

Degradation of elastin, the main amorphous component of elastic fibers, by elastases belonging to the serine, metallo, or cysteine families leads to the generation of elastin fragments, designated as elastokines in keeping with their cytokine-like properties. Generation of elastokines from one of the longest lived protein in human might represent a strong tissue repair signal. Indeed, they (1) exhibit potent chemotactic activity for leukocytes, (2) stimulate fibroblast and smooth muscle cell proliferation, and (3) display proangiogenic activity as potent as VEGF. However, continuous exposure of cells to these matrikines, through increased elastase(s) expression with age, can contribute to the formation of a chronic inflammatory state, that is, inflamm-aging. Importantly, binding of elastokines to S-Gal, their cognate receptor, proved to stimulate matrix metalloproteinase expression in normal and cancer cells. Besides, these elastin fragments can polarize lymphocytes toward a Th-1 response or induce an osteogenic response in smooth muscle cells, and arterial wall calcification. In this chapter, emphasis will be made on the contribution of elastokines on the genesis of age-related arterial wall diseases, particularly abdominal aortic aneurysms (AAAs). An elastokine theory of AAAs progression will be proposed. Age is one main risk factor of cancer incidence and development. The myriad of biological effects exerted by elastokines on stromal and inflammatory cells led us to hypothesize that they might be main actors in elaborating a favorable cancerization field in melanoma; for instance these peptides could catalyze the vertical growth phase transition in melanoma through increased expression of gelatinase A and membrane-type 1 matrix metalloproteinase.

Nitric oxide, a double edged sword in cancer biology: Searching for therapeutic opportunities

Nitric oxide (NO) is a pleiotropic molecule critical to a number of physiological and pathological processes. The last decade has witnessed major advances in dissecting NO biology and its role in cancer pathogenesis. However, the complexity of the interactions between different levels of NO and several aspects of tumor development/progression has led to apparently conflicting findings. Furthermore, both anti-NO and NO-based anticancer strategies appear effective in several preclinical models. This paradoxical dichotomy is leaving investigators with a double challenge: to determine the net impact of NO on cancer behavior and to define the therapeutic role of NO-centered anticancer strategies. Only a comprehensive and dynamic view of the cascade of molecular and cellular events underlying tumor biology and affected by NO will allow investigators to exploit the potential antitumor properties of drugs interfering with NO metabolism. Available data suggest that NO should be considered neither a universal target nor a magic bullet, but rather a signal transducer to be modulated according to the molecular makeup of each individual cancer and the interplay with conventional antineoplastic agents.

Reduced nonprotein thiols inhibit activation and function of MMP-9: implications for chemoprevention

Clinical studies demonstrate a positive correlation between the extent of matrix metalloproteinase (MMP) activation and malignant progression of precancerous lesions. Therefore, identification of effective, well-tolerated MMP inhibitors represents a rational chemopreventive strategy. A variety of agents, including proteinases and thiol-oxidizing compounds, activate MMPs by initiating release of the propeptide's cysteine sulfur "blockage" of the MMP active site. Despite the importance of the propeptide's cysteine thiol in preserving MMP latency, limited studies have evaluated the effects of reduced thiols on MMP function. This study investigated the effects of two naturally occurring nonprotein thiols, i.e., glutathione (GSH) and N-acetylcysteine (NAC), on activation, function, and cellular-extracellular matrix interactions of the basement-membrane-degrading gelatinase, MMP-9. Our results reveal that NAC and GSH employ protein S-thiolation to inhibit organomercurial activation of pro-MMP-9. Gelatinase activity assays showed that GSH and NAC significantly inhibited MMP-9 but not MMP-2 function, implying isoform structural specificity. Immunoblot analyses, which suggested GSH interacts with MMP-9's active-site Zn, were corroborated by computational molecular modeling. Cell invasion assays revealed that NAC enhanced endostatin's ability to inhibit human cancer cell invasion. Collectively, these data demonstrate that nonprotein thiols suppress MMP-9 activation and function and introduce the prospect for their use in chemopreventive applications.

Antitumor activity of JS-K [O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate] and related O2-aryl diazeniumdiolates in vitro and in vivo

The literature provides evidence that metabolic nitric oxide (NO) release mediates the cytotoxic activities (against human leukemia and prostate cancer xenografts in mice) of JS-K, a compound of structure R(2)N-N(O)=NO-Ar for which R(2)N is 4-(ethoxycarbonyl)piperazin-1-yl and Ar is 2,4-dinitrophenyl. Here we present comparative data on the potencies of JS-K and 41 other O(2)-arylated diazeniumdiolates as inhibitors of HL-60 human leukemia cell proliferation, as well as in the NCI 51-cell-line screen for six of them. The data show JS-K to be the most potent of the 42 in both screens and suggest that other features of its structure and metabolism besides NO release may contribute importantly to its activity. Results with control compounds implicate JS-K's arylating ability, and the surprisingly low IC(50) value of the N-(ethoxycarbonyl)piperazine byproduct of NO release suggests a role for the R(2)N moiety. In addition to the above-mentioned in vivo activities, JS-K is shown here to be carcinostatic in a rat liver cancer model.

Ets-1 expression promotes epithelial cell transformation by inducing migration, invasion and anchorage-independent growth

Ets-1 is the prototype of the family of ETS transcription factors. In human tumors, Ets-1 is expressed in endothelial cells and fibroblasts of the tumor stroma and is proposed to play a role in tumor vascularization and invasion by upregulating expression of matrix-degrading proteases. In human carcinomas, Ets-1 is also expressed by neoplastic cells, but little is known about the functional implications of this observation. We have addressed the role of Ets-1 in epithelial HeLa tumor cells by selecting stably Ets-1 over and underexpressing HeLa cells. Ets-1 expression increases the transformed phenotype of HeLa cells, by promoting cell migration, invasion and anchorage-independent growth, while Ets-1 downregulation reduces cell attachment. In correlation with these results, Ets-1 upregulation increases integrinbeta2 expression but not that of other integrins. These results suggest that, in addition to its role in the tumor stroma, Ets-1 may also promote tumor development and progression by increasing neoplastic transformation.

Transcriptional signatures of environmentally relevant exposures in normal human mammary epithelial cells: benzo[a]pyrene

Changes in gene expression in a panel of primary normal human mammary epithelial cell strains, developed from healthy breast tissue obtained at reduction mammoplasty from different donors, in response to benzo[a]pyrene exposure have been investigated. It was expected that both gene expression changes common to cell strains derived from different donors as well as inter-individual variation would be observed. Therefore, the strategy that has been adopted is to identify potentially important changes, or useful changes from a biomonitoring perspective, using gene-array technology and a small number of donors; then investigate selected transcription responses using a large number of tissue donors and a cheaper method of transcript detection (real-time polymerase chain reaction). Here we report results from four primary normal human mammary epithelial cell strains that were treated with benzo[a]pyrene in vitro for either 6 or 24 h. Transcription was monitored using high-density oligonucleotide arrays (Affymetrix HuGeneFL). Total RNA was used for the preparation of labeled targets that were hybridized to microarrays containing probes representing more than 6800 human genes and expressed sequence tags. Gene expression data were analyzed using the GeneChip software (MAS 5.0). Altered gene expression patterns were observed in response to benzo[a]pyrene in human mammary epithelial cell strains from different donors. Specifically, the dioxin inducible cytochrome P450 CYP1B1 was consistently induced in response to 6 and 24 h exposure to benzo[a]pyrene in cell strains from all four donors. Two other genes that were relatively consistently induced were IL1beta and MMP1. Less consistent changes in other metabolism genes (CYP1A1, CYP11B2, and NQO1) and certain cell cycle control genes GOS2 and AF1Q were also induced, while EGR1 was suppressed. Although no change in p53 transcription was observed, an accumulation of p53 protein was detected using antibodies. A similar accumulation of Waf1 (p21) was also observed using immunohistochemistry, this was expected since p53 is p21's transcription factor. Significant inter-individual variations in both the levels and patterns of gene expression were observed, in response to benzo[a]pyrene exposure. These studies provide a complementary approach to molecular epidemiology for the investigation of differential susceptibility to chemical carcinogens, and specifically polycyclic aromatic hydrocarbons.

Molecular mechanism for activation and regulation of matrix metalloproteinases during bacterial infections and respiratory inflammation

Matrix metalloproteinases (MMPs) are critical mediators of tissue remodeling. Inappropriate regulation of MMPs causes many pathological events, including microbial invasion and inflammatory tissue damage. Some of the bacterial exoproteinases can effectively activate pro-MMPs (inactive zymogens) via limited proteolysis around their autoinhibitory domains. In addition, overproduction of nitric oxide (NO) may contribute to respiratory inflammation via the formation of reactive nitrogen species (RNS). Several studies have identified regulatory properties of NO/RNS on biomolecules due to functional modification of their cysteine residues. In fact, NO/RNS can mediate activation and expression of MMPs, because RNS can interact with a cysteine switch in the autoinhibitory domain, thus converting proMMPs into their active forms without proteolysis. Many studies have indicated that NO/RNS can participate in expression of various genes that affect immune-inflammatory responses, including MMPs. Although NO in some cases upregulates MMPs, S -nitrosothiols downregulate MMP-9 expression by suppressing the NF-kappaB pathway. While microbial proteinases cause excessive activation of MMPs and contribute to microbial pathogenesis, NO/RNS may modulate expression and activation of MMPs as well as various inflammatory mediators, depending on the redox status at sites of inflammation. Therefore, appropriate regulation of MMPs may be of potential therapeutic value for various infections and inflammatory lung diseases.

Deficiency of inducible nitric oxide synthase exacerbates hepatic fibrosis in mice fed high-fat diet

The role of inducible nitric oxide synthase (iNOS) in the progression of fibrosis during nonalcoholic steatohepatitis remains to be elucidated. This study examined the role of iNOS in the progression of fibrosis during steatohepatitis by comparing iNOS knockout (iNOS(-/-)) and wild-type (iNOS(+/+)) mice that were fed a high-fat diet. Severe fatty metamorphosis developed in the liver of iNOS(+/+) and iNOS(-/-) mice. Fibrotic changes were marked in iNOS(-/-) mice. Gelatin zymography showed that pro MMP-2 and pro MMP-9 protein expressions were more highly induced in iNOS(+/+) mice than in iNOS(-/-) mice. Active forms of MMP-2 and MMP-9 were clearly present only in the liver tissue of iNOS(+/+) mice. In situ zymography showed strong gelatinolytic activities in the liver tissue of iNOS(+/+) mice, but only spotty activity in iNOS(-/-)mice. iNOS may attenuate the progression of liver fibrosis in steatohepatitis, in part by inducing MMP-2 and MMP-9 expression and augmenting their activity.

Mitochondrial redox control of matrix metalloproteinases

Reactive oxygen species (ROS) are constantly generated in aerobic organisms during normal metabolism and in response to both internal and external stimuli. Imbalances in the production and removal of ROS have been hypothesized to play a causative role in numerous disease pathologies such as cancer, ischemia/reperfusion injury, and degenerative diseases such as photoaging, atherosclerosis, arthritis, and neurodegeneration. A feature often associated with these diseases is a malfunctioning of the connective tissue remodeling process due to increased activity of extracellular matrix-degrading metalloproteinases (MMPs). This review summarizes the evidence that implicates ROS as key regulators of MMP production and the importance of these interactions in disease pathologies.

Overexpression of Collagenase 1 (MMP-1) Is Mediated by the ERK Pathway in Invasive Melanoma Cells

Melanoma progresses as a multistep process where the thickness of the lesion and depth of tumor invasion are the best prognostic indicators of clinical outcome. Degradation of the interstitial collagens in the extracellular matrix is an integral component of tumor invasion and metastasis, and much of this degradation is mediated by collagenase-1 (MMP-1), a member of the matrix metalloproteinase (MMP) family. MMP-1 levels increase during melanoma progression where they are associated with shorter disease-free survival. The Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) pathway is a major regulator of melanoma cell proliferation. Recently, BRAF has been identified as a common site of activating mutations, and, although many reports focus on its growth-promoting effects, this pathway has also been implicated in progression toward metastatic disease. In this study, we describe four melanoma cell lines that produce high levels of MMP-1 constitutively. In each cell line the Ras/Raf/MEK/ERK pathway is constitutively active and is the dominant pathway driving the production of MMP-1. Activation of this pathway arises due to either an activating mutation in BRAF (three cell lines) or autocrine fibroblast growth factor signaling (one cell line). Furthermore, blocking MEK/ERK activity inhibits melanoma cell proliferation and abrogates collagen degradation, thus decreasing their metastatic potential. Importantly, this inhibition of invasive behavior can occur in the absence of any detectable changes in cell proliferation and survival. Thus, constitutive activation of this MAPK pathway not only promotes the increased proliferation of melanoma cells but is also important for the acquisition of an invasive phenotype.

Superoxide dismutases in malignant cells and human tumors

Reactive oxygen metabolites have multifactorial effects on the regulation of cell growth and the capacity of malignant cells to invade. Overexpression of the superoxide dismutases (SODs) in vitro increases cell differentiation, decreases cell growth and proliferation, and can reverse a malignant phenotype to a nonmalignant one. The situation in vivo is more complex due to multiple interactions of tumor cells with their environment. Numerous in vivo studies show that the superoxide dismutases can be highly expressed in aggressive human solid tumors. Furthermore, high SOD has occasionally been associated with a poor prognosis and with resistance to cytotoxic drugs and radiation. Most of the apparent conflicts between the above in vitro and in vivo observations can be reconciled by considering the net redox status of tumor cells in different environments. Administering high concentrations of SOD to cells in vitro is usually associated with a non- or less malignant phenotype, whereas secondary induction of SOD in tumors in vivo can be associated with an aggressive malignant transformation probably due to the altered (oxidative) redox state in the malignant cells. This concept suggests that for many types of tumors antioxidants could be used to diminish the invasive capability of malignant cells.

JS-K, a novel non-ionic diazeniumdiolate derivative, inhibits Hep 3B hepatoma cell growth and induces c-Jun phosphorylation via multiple MAP kinase pathways

JS-K, a non-ionic diazeniumdiolate derivative, is capable of arylating nucleophiles and spontaneously generating nitric oxide (NO) at physiological pH. This recently synthesized low molecular weight compound is shown here to be an inhibitor of cell growth with concomitant activation of mitogen-activated protein kinase (MAPK) members ERK, JNK, and p38 and their downstream effectors c-Jun and AP-1. Inhibitors of these MAPK pathways abrogated the growth inhibitory actions of JS-K. In addition to the well-described actions of JNK as a kinase for c-Jun, we show that c-Jun is also an ERK target. Furthermore, JS-K generated NO in culture and NO inhibitors antagonized both MAPK induction and the growth inhibitory effects of JS-K. These results suggest two possible mechanisms for the mediation of JS-K growth inhibitory actions, namely NO-induction of MAPK pathway constituents as well as possible arylation reactions. The data support the idea that prolonged MAPK activation by JS-K action is important in mediating its growth-inhibitory actions. JS-K thus represents a promising platform for novel growth inhibitory analog synthesis.

Nitric Oxide Signalling with a Special Focus on Lipid-Derived Mediators

The ways in which cells communicate among each other concerns all aspects of biology, from developmental processes to diseases. Nitric oxide (NO) is one of the most remarkable and unusual regulatory molecules. It is a labile free radical gas that is not stored but generated on demand, and has been implicated in an extraordinarily diverse range of physiological and pathophysiological functions. The modulation of cell signalling by free radicals is an emerging area of research that provides insight into the orchestration of cell adaptation to a changing microenvironment. In a multicellular organism this serves to coordinate complex physiological responses, such as inflammation. Cell signalling is also accompanied by rapid remodelling of membrane lipids by activated lipases. The discovery that NO, which does not reversibly interact with membrane receptors like conventional hormones and growth factors, targets enzymes such as phospholipase A2, sphingomyelinases or ceramidases, has stimulated growing interest in the crosstalk between redox and lipid signalling.