Structural Insight into the Stereoselective Inhibition of MMP-8 by Enantiomeric Sulfonamide Phosphonates

Influence of N-arylsulfonamido d-valine N-substituents on the selectivity and potency of matrix metalloproteinase inhibitors

To develop matrix metalloproteinase inhibitors (MMPIs) for both therapy and medicinal imaging by fluorescence-based techniques or positron-emission tomography (PET), a small library of eighteen N-substituted N-arylsulfonamido d-valines were synthesized and their potency to inhibit two gelatinases (MMP-2, and MMP-9), two collagenases (MMP-8, and MMP-13) and macrophage elastase (MMP-12) was determined in a Structure-Activity-Relation study with ({4-[3-(5-methylthiophen-2-yl)-1,2,4-oxadiazol-5-yl]phenyl}sulfonyl)-d-valine (1) as a lead. All compounds were shown to be more potent MMP-2/-9 inhibitors (nanomolar range) compared to other tested MMPs. This is a remarkable result considering that a carboxylic acid group is the zinc binding moiety. The compound with a terminal fluoropropyltriazole group at the furan ring (P1' substituent) was only four times less potent in inhibiting MMP-2 activity than the lead compound 1, making this compound a promising probe for PET application (after using a prosthetic group approach to introduce fluorine-18). Compounds with a TEG spacer and a terminal azide or even a fluorescein moiety at the sulfonylamide N atom (P2' substituent) were almost as active as the lead structure 1, making the latter derivative a suitable fluorescence imaging tool.

Structural and functional role of invariant water molecules in matrix metalloproteinases: a data-mining approach

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases known to degrade extracellular matrix (ECM). Being involved in many biological and physiological processes of tissue remodeling, MMPs play a crucial role in many pathological conditions such as arthritis, cancer, cardiovascular diseases, etc. Typically, MMPs possess a propeptide, a zinc-containing catalytic domain, a hinge region and a hemopexin domain. Based on their structural domain organization and substrates, MMPs are classified into six different classes, viz. collagenases, stromelysins, gelatinases, matrilysins, membrane-type and other MMPs. As per previous studies, a set of invariant water (IW) molecules of MMP-1 (a collagenase) play a significant role in stabilizing their catalytic domain. However, a functional role of IW molecule in other classes of MMPs has not been reported yet. Thus, in this study, IW molecules of MMPs from different classes were located and their plausible role(s) have been assigned. The results suggest that IW molecules anchor the structurally and functionally essential metal ions present in the vicinity of the active site of MMPs. Further, they (in)directly interlink different structural features and bridge the active site metal ions of MMPs. This study provides the key IW molecules that are structurally and functionally relevant to MMPs and hence, in turn, might facilitate the development of potent generalized inhibitor(s) against different classes of MMPs. Communicated by Ramaswamy H. Sarma.

A robust classification-dependent multi-molecular modelling study on some biphenyl sulphonamide based MMP-8 inhibitors

Matrix metalloproteinases (MMPs) are a group of zinc and calcium-dependent endopeptidases, which contribute to different physiological and biological activities via extracellular matrix (ECM) degradation. Matrix metalloproteinase-8 (MMP-8) belongs to type-II collagenases of the MMP family that has contribution in several physiological disorders such as cardiovascular diseases, joint, renal, digestive and respiratory disorders as well as in cancer. In clinical study, MMP-8 is found to be associated with periodontal disease condition. Therefore, MMP-8 specific inhibitors should be developed to target these disorders. The biphenyl sulphonamide (BPS) moiety is one of the crucial structural characteristics found in several MMP-8 inhibitors. Here, different classification-based molecular modelling methods were used to explore the structural features that lead to the activity variation of a series of MMP-8 inhibitors possessing a BPS moiety. Our current classification-based structural analysis of these BPS-derived MMP-8 inhibitors was able to identify the importance of several structural features such as the tetrahydroisoquinoline and N-Boc pyridyl groups, which have positive influences on MMP-8 inhibition. This study was also reflected the importance of the zinc-binding groups (ZBGs) like the hydroxamate and phosphonate for potent and sub-nanomolar range MMP-8 inhibition, which may benefit the development of highly potent MMP-8 inhibitors.

Cell-based assays and molecular simulation reveal that the anti-cancer harmine is a specific matrix metalloproteinase-3 (MMP-3) inhibitor

The biological activities of harmine have been a much clearer picture in recent years, which include anti-tumor, anti-inflammation and cytotoxic properties. Numerous in vitro and in vivo animal models have confirmed its activities, but its mode of action remains a relative unsolved issue. We therefore investigated harmine for its effects on MMP-3 and the molecular interaction was also simulated. The human glioma cancer cell line, U-87 MG cells, was subjected to different concentrations (1-10 μM) of harmine for 24 h. Methylthiazol tetrazolium (MTT) test, half maximal inhibitory concentration (IC50), western blot analysis, enzyme-linked immunosorbent assay and molecular docking through BIOVIA DiscoveryStudio™ were performed. These results showed that although harmine stimulation in vitro has very little or no effects on MMP-3 expression by U-87 MG cells, the treatment of harmine decreases MMP-3 activity in a dose dependent manner. It was further calculated that 7.9 μM is the IC50 towards MMP-3. Using a molecular dynamic simulation approach, we identified the N2, methyl of C1 and benzene ring of harmine interact with Zn²⁺ (2.4 Å), His205 (2.4 Å) and His211 (2.4 Å) as well as Val163 (2.7 Å) at the active site of MMP-3, respectively, and thus conferred a striking specific binding advantage. Taken altogether, the present study evidences that harmine acts as an MMP-3 inhibitor specially targeting the enzymatic active site and possibly efficiently ameliorates MMP-3-driven malignant and inflammatory diseases.

Identification of Broad-Spectrum MMP Inhibitors by Virtual Screening

Matrix metalloproteinases (MMPs) are the family of proteases that are mainly responsible for degrading extracellular matrix (ECM) components. In the skin, the overexpression of MMPs as a result of ultraviolet radiation triggers an imbalance in the ECM turnover in a process called photoaging, which ultimately results in skin wrinkling and premature skin ageing. Therefore, the inhibition of different enzymes of the MMP family at a topical level could have positive implications for photoaging. Considering that the MMP catalytic region is mostly conserved across different enzymes of the MMP family, in this study we aimed to design a virtual screening (VS) workflow to identify broad-spectrum MMP inhibitors that can be used to delay the development of photoaging. Our in silico approach was validated in vitro with 20 VS hits from the Specs library that were not only structurally different from one another but also from known MMP inhibitors. In this bioactivity assay, 18 of the 20 compounds inhibit at least one of the assayed MMPs at 100 μM (with 5 of them showing around 50% inhibition in all the tested MMPs at this concentration). Finally, this VS was used to identify natural products that have the potential to act as broad-spectrum MMP inhibitors and be used as a treatment for photoaging.

Inhibitors of gelatinases (MMP-2 and MMP-9) for the management of hematological malignancies

Matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) are collectively known as gelatinases whereas MMP-2 is gelatinase-A and MMP-9 is termed as gelatinase-B. Gelatinases and other matrix metalloproteinases (MMPs) have long been associated with solid tumor invasion, metastasis and angiogenesis. However, there is paucity of data available regarding the role of gelatinases in hematological malignancies. Recent studies have shown that gelatinases activities or functions are correlated with hematological malignancies. Strategies for designing more specific gelatinase inhibitors like catalytic (CAT) domain inhibitors and hemopexin (PEX) domain inhibitors as well as signaling pathway based or gelatinase expression inhibitors had been reported against hematologic malignant cells. Several substrate based non-selective to non-substrate based relatively selective synthetic matrix metalloproteinase inhibitors (MMPIs) had been developed. Few MMPIs had reached in clinical trials during the period of 1990s-2000s. Unfortunately the anti-tumor and anti-metastatic efficacies of these MMPIs were not justified with patients having several advanced stage solid tumor cancers in any substantial number of clinical trials. Till date not a single MMPI passed phase III clinical trials designed for advanced metastatic cancers due to adverse events as well as lack of ability to show uniformity in disease prolongation. With the best of our knowledge no clinical trial study has been reported with small molecule synthetic inhibitors against hematological malignancies. This review looks at the outcome of clinical trials of MMPIs for advanced stage solid tumors. This can therefore, act as a learning experience for future development of successful gelatinase inhibitors for the management of hematological malignancies.

Mechanisms of Lower Extremity Vein Dysfunction in Chronic Venous Disease and Implications in Management of Varicose Veins

Chronic venous disease (CVD) is a common venous disorder of the lower extremities. CVD can be manifested as varicose veins (VVs), with dilated and tortuous veins, dysfunctional valves and venous reflux. If not adequately treated, VVs could progress to chronic venous insufficiency (CVI) and lead to venous leg ulcer (VLU). Predisposing familial and genetic factors have been implicated in CVD. Additional environmental, behavioral and dietary factors including sedentary lifestyle and obesity may also contribute to CVD. Alterations in the mRNA expression, protein levels and proteolytic activity of matrix metalloproteinases (MMPs) have been detected in VVs and VLU. MMP expression/activity can be modulated by venous hydrostatic pressure, hypoxia, tissue metabolites, and inflammation. MMPs in turn increase proteolysis of different protein substrates in the extracellular matrix particularly collagen and elastin, leading to weakening of the vein wall. MMPs could also promote venous dilation by increasing the release of endothelium-derived vasodilators and activating potassium channels, leading to smooth muscle hyperpolarization and relaxation. Depending on VVs severity, management usually includes compression stockings, sclerotherapy and surgical removal. Venotonics have also been promoted to decrease the progression of VVs. Sulodexide has also shown benefits in VLU and CVI, and recent data suggest that it could improve venous smooth muscle contraction. Other lines of treatment including induction of endogenous tissue inhibitors of metalloproteinases (TIMPs) and administration of exogenous synthetic inhibitors of MMPs are being explored, and could provide alternative strategies in the treatment of CVD.

Challenges with matrix metalloproteinase inhibition and future drug discovery avenues

INTRODUCTION

Matrix metalloproteinases have been in the scope of pharmaceutical drug discovery for decades as promising targets for drug development. Until present, no modulator of the enzyme class survived clinical trials, all failing for various reasons. Nevertheless, the target family did not lose its attractiveness and there is ever more evidence that MMP modulators are likely to overcome the hurdles and result in successful clinical therapies.

AREAS COVERED

This review provides an overview of past efforts that were taken in the development of MMP inhibitors and insight into promising strategies that might enable drug discovery in the field in the future. Small molecule inhibitors as well as biomolecules are reviewed.

EXPERT OPINION

Despite the lack of successful clinical trials in the past, there is ongoing research in the field of MMP modulation, proving the target class has not lost its appeal to pharmaceutical research. With ever-growing insights from different scientific fields that shed light on previously unknown correlations, it is now time to use synergies deriving from biological knowledge, chemical structure generation, and clinical application to reach the ultimate goal of bringing MMP derived drugs on a broad front for the benefit of patients into therapeutic use.

Synthesis, antiinflammatory activity, and molecular docking studies of bisphosphonic esters as potential MMP-8 and MMP-9 inhibitors

Bisphosphonic acids (or bisphosphonates) have been successfully used in the clinic treatment of bone diseases for over decades. Additionally, the antiinflammatory activity of these compounds has been gaining attention. In our previous work, we synthesized and in vivo evaluated the bisphosphonic esters 1 and 2, finding a moderate edema inhibition upon oral and topical administration on BALB/c mice. Thus, in this work, the bioisosteric replacement of an amide functional group for an ester afforded the new bisphosphonates 3-6, which had a moderate oral edema inhibition (25 mg/kg dose) and a significant topical antiinflammatory activity (2 mg/ear) on BALB/c mice, with 6 being the most active hit (55.9% edema inhibition), comparable to the positive control (55.5% edema inhibition) on a TPA topical model. Next, to assess the acute toxicity of the synthesized derivatives, test animals were administered with 50-100 mg/kg of 3-6, respectively, by an oral route, and after 14 days, neither lethality nor a significative weight loss were observed. Finally, a structure-activity relationship (SAR) and a molecular docking analysis of 3-6 helped us to explain the trend observed in biological tests. Considering all these aspects, we propose the inhibition of MMP-8 and MMP-9 as a possible action mechanism of the synthesized derivatives.

Bone-Seeking Matrix Metalloproteinase Inhibitors for the Treatment of Skeletal Malignancy

Matrix metalloproteinases (MMPs) are a family of enzymes involved at different stages of cancer progression and metastasis. We previously identified a novel class of bisphosphonic inhibitors, selective for MMPs crucial for bone remodeling, such as MMP-2. Due to the increasing relevance of specific MMPs at various stages of tumor malignancy, we focused on improving potency towards certain isoforms. Here, we tackled MMP-9 because of its confirmed role in tumor invasion, metastasis, angiogenesis, and immuno-response, making it an ideal target for cancer therapy. Using a computational analysis, we designed and characterized potent MMP-2/MMP-9 inhibitors. This is a promising approach to develop and clinically translate inhibitors that could be used in combination with standard care therapy for the treatment of skeletal malignancies.

Functional Roles of Matrix Metalloproteinases and Their Inhibitors in Melanoma

The extracellular matrix (ECM) plays an important role in the regulation of the tissue microenvironment and in the maintenance of cellular homeostasis. Several proteins with a proteolytic activity toward several ECM components are involved in the regulation and remodeling of the ECM. Among these, Matrix Metalloproteinases (MMPs) are a class of peptidase able to remodel the ECM by favoring the tumor invasive processes. Of these peptidases, MMP-9 is the most involved in the development of cancer, including that of melanoma. Dysregulations of the MAPKs and PI3K/Akt signaling pathways can lead to an aberrant overexpression of MMP-9. Even ncRNAs are implicated in the aberrant production of MMP-9 protein, as well as other proteins responsible for the activation or inhibition of MMP-9, such as Osteopontin and Tissue Inhibitors of Metalloproteinases. Currently, there are different therapeutic approaches for melanoma, including targeted therapies and immunotherapies. However, no biomarkers are available for the prediction of the therapeutic response. In this context, several studies have tried to understand the diagnostic, prognostic and therapeutic potential of MMP-9 in melanoma patients by performing clinical trials with synthetic MMPs inhibitors. Therefore, MMP-9 may be considered a promising molecule for the management of melanoma patients due to its role as a biomarker and therapeutic target.

Challenges in Matrix Metalloproteinases Inhibition

Matrix metalloproteinases are enzymes that degrade the extracellular matrix. They have different substrates but similar structural organization. Matrix metalloproteinases are involved in many physiological and pathological processes and there is a need to develop inhibitors for these enzymes in order to modulate the degradation of the extracellular matrix (ECM). There exist two classes of inhibitors: endogenous and synthetics. The development of synthetic inhibitors remains a great challenge due to the low selectivity and specificity, side effects in clinical trials, and instability. An extensive review of currently reported synthetic inhibitors and description of their properties is presented.

The Rebirth of Matrix Metalloproteinase Inhibitors: Moving Beyond the Dogma

The pursuit of matrix metalloproteinase (MMP) inhibitors began in earnest over three decades ago. Initial clinical trials were disappointing, resulting in a negative view of MMPs as therapeutic targets. As a better understanding of MMP biology and inhibitor pharmacokinetic properties emerged, it became clear that initial MMP inhibitor clinical trials were held prematurely. Further complicating matters were problematic conclusions drawn from animal model studies. The most recent generation of MMP inhibitors have desirable selectivities and improved pharmacokinetics, resulting in improved toxicity profiles. Application of selective MMP inhibitors led to the conclusion that MMP-2, MMP-9, MMP-13, and MT1-MMP are not involved in musculoskeletal syndrome, a common side effect observed with broad spectrum MMP inhibitors. Specific activities within a single MMP can now be inhibited. Better definition of the roles of MMPs in immunological responses and inflammation will help inform clinic trials, and multiple studies indicate that modulating MMP activity can improve immunotherapy. There is a U.S. Food and Drug Administration (FDA)-approved MMP inhibitor for periodontal disease, and several MMP inhibitors are in clinic trials, targeting a variety of maladies including gastric cancer, diabetic foot ulcers, and multiple sclerosis. It is clearly time to move on from the dogma of viewing MMP inhibition as intractable.

Molecular Imaging Probes Based on Matrix Metalloproteinase Inhibitors (MMPIs)

Matrix metalloproteinases (MMPs) are a family of zinc- and calcium-dependent endopeptidases which are secreted or anchored in the cell membrane and are capable of degrading the multiple components of the extracellular matrix (ECM). MMPs are frequently overexpressed or highly activated in numerous human diseases. Owing to the important role of MMPs in human diseases, many MMP inhibitors (MMPIs) have been developed as novel therapeutics, and some of them have entered clinical trials. However, so far, only one MMPI (doxycycline) has been approved by the FDA. Therefore, the evaluation of the activity of a specific subset of MMPs in human diseases using clinically relevant imaging techniques would be a powerful tool for the early diagnosis and assessment of the efficacy of therapy. In recent years, numerous MMPIs labeled imaging agents have emerged. This article begins by providing an overview of the MMP subfamily and its structure and function. The latest advances in the design of subtype selective MMPIs and their biological evaluation are then summarized. Subsequently, the potential use of MMPI-labeled diagnostic agents in clinical imaging techniques are discussed, including positron emission tomography (PET), single-photon emission computed tomography (SPECT) and optical imaging (OI). Finally, this article concludes with future perspectives and clinical utility.

Functionalization of α-hydroxyphosphonates as a convenient route to N-tosyl-α-aminophosphonates

Direct conversion of the α-hydroxyl group by para-toluenesulfonamide to yield α-(N-tosyl)aminophosphonates is reported. α-Aminophosphonates 23a,b-37a,b were obtained from the corresponding α-hydroxyphosphonates 6a,b-21a,b in the presence of K₂CO₃, via the retro-Abramov reaction of the appropriate aldehydes, 1-5. The subsequent formation of imines with simultaneous addition of diethyl phosphite provided access to the α-sulfonamide phosphonates 23a,b-37a,b with better diastereoselectivity than in the case of the Pudovik reaction. The mechanism for this transformation is proposed herein. When Cbz N-protected aziridine 9a,b and phenylalanine analogue 12a,b were exploited, intramolecular substitution was observed, leading to the corresponding epoxide 38 as the sole product, or oxazolidin-2-one 39 as a minor product. Analogous substitution was not observed in the case of proline 18a,b and serine 21a,b derivatives.

Stereochemical considerations in pharmacokinetic processes of representative antineoplastic agents

The vast majority of chemical drugs or drug candidates contain stereocenter(s) in their molecular structures. In these molecules, stereochemical properties are vital properties that influence or even determine their drug actions. Therefore, studying the stereochemical issues of drugs (or drug candidates) is necessary for rational drug use. These stereochemical issues are usually involved with the stereoselectivity in pharmacokinetic processes, especially in the metabolism process. Thus, the investigation of the stereochemical issues in drug metabolism process deserves great attention, especially in those chiral/prochiral antineoplastic agents exhibiting pharmacodynamics and toxicologic differences between stereoisomers. Published reviews concerning this certain issue are inspiring, however they were covering all drug types and only limited antineoplastic drugs were discussed. Here in this review, the research on stereochemical issues in pharmacokinetic processes of some representative antineoplastic agents were described, especially focusing on some newly developed compounds. We highlight the chemical transformations in pharmacokinetic processes of these chiral/prochiral compounds and discuss their different behaviors with metabolic enzymes or transporter proteins, to explicate the observed stereoselectivity intrinsically.

Dual targeting of cancer-related human matrix metalloproteinases and carbonic anhydrases by chiral N-(biarylsulfonyl)-phosphonic acids

A series of nanomolar phosphonate matrix metalloproteinase (MPP) inhibitors was tested for inhibitory activity against a panel of selected human carbonic anhydrase (CA, EC 4.2.1.1) isozymes, covering the cancer-associated CA IX and XII. None of the reported sulfonyl and sulfonylamino-derivatives sensitively affected the catalytic activity of the cytosolic isoforms CA I and II, which are considered off-target isoforms in view of their physiological role. The most active inhibitors were in the series of chiral N-(sulfonyl)phosphovaline derivatives, which showed good to excellent inhibitory activity over target CAs, with compound 15 presenting the best isoform-selectivity toward CA IX. We suggest here that the phosphonates have the potential as dual inhibitors of MMPs and CAs, both involved in tumor formation, invasion and metastasis.

Matrix Metalloproteinases, Vascular Remodeling, and Vascular Disease

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that degrade various proteins in the extracellular matrix (ECM). Typically, MMPs have a propeptide sequence, a catalytic metalloproteinase domain with catalytic zinc, a hinge region or linker peptide, and a hemopexin domain. MMPs are commonly classified on the basis of their substrates and the organization of their structural domains into collagenases, gelatinases, stromelysins, matrilysins, membrane-type (MT)-MMPs, and other MMPs. MMPs are secreted by many cells including fibroblasts, vascular smooth muscle (VSM), and leukocytes. MMPs are regulated at the level of mRNA expression and by activation through removal of the propeptide domain from their latent zymogen form. MMPs are often secreted in an inactive proMMP form, which is cleaved to the active form by various proteinases including other MMPs. MMPs degrade various protein substrates in ECM including collagen and elastin. MMPs could also influence endothelial cell function as well as VSM cell migration, proliferation, Ca²⁺ signaling, and contraction. MMPs play a role in vascular tissue remodeling during various biological processes such as angiogenesis, embryogenesis, morphogenesis, and wound repair. Alterations in specific MMPs could influence arterial remodeling and lead to various pathological disorders such as hypertension, preeclampsia, atherosclerosis, aneurysm formation, as well as excessive venous dilation and lower extremity venous disease. MMPs are often regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP ratio often determines the extent of ECM protein degradation and tissue remodeling. MMPs may serve as biomarkers and potential therapeutic targets for certain vascular disorders.

Matrix Metalloproteinase Inhibitors as Investigational and Therapeutic Tools in Unrestrained Tissue Remodeling and Pathological Disorders

Matrix metalloproteinases (MMPs) are zinc-dependent proteolytic enzymes that degrade various proteins in the extracellular matrix (ECM). MMPs may also regulate the activity of membrane receptors and postreceptor signaling mechanisms and thereby affect cell function. The MMP family includes collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs, and other MMPs. Inactive proMMPs are cleaved by other MMPs or proteases into active MMPs, which interact with various protein substrates in ECM and cell surface. MMPs regulate important biological processes such as vascular remodeling and angiogenesis and may be involved in the pathogenesis of cardiovascular disorders such as hypertension, atherosclerosis, and aneurysm. The role of MMPs is often assessed by measuring their mRNA expression, protein levels, and proteolytic activity using gel zymography. MMP inhibitors are also used to assess the role of MMPs in different biological processes and pathological conditions. MMP activity is regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP balance could determine the net MMP activity, ECM turnover, and tissue remodeling. Also, several synthetic MMP inhibitors have been developed. Synthetic MMP inhibitors include a large number of zinc-binding globulins (ZBGs), in addition to non-ZBGs and mechanism-based inhibitors. MMP inhibitors have been proposed as potential tools in the management of osteoarthritis, cancer, and cardiovascular disorders. However, most MMP inhibitors have broad-spectrum actions on multiple MMPs and could cause undesirable musculoskeletal side effects. Currently, doxycycline is the only MMP inhibitor approved by the Food and Drug Administration. New generation biological and synthetic MMP inhibitors may show greater MMP specificity and fewer side effects and could be useful in targeting specific MMPs, reducing unrestrained tissue remodeling, and the management of MMP-related pathological disorders.

Matrix Metalloproteinases in Remodeling of Lower Extremity Veins and Chronic Venous Disease

The veins of the lower extremity are equipped with efficient wall, contractile vascular smooth muscle (VSM), and competent valves in order to withstand the high venous hydrostatic pressure in the lower limb and allow unidirectional movement of deoxygenated blood toward the heart. The vein wall structure and function are in part regulated by matrix metalloproteinases (MMPs). MMPs are zinc-dependent endopeptidases that are secreted as inactive pro-MMPs by different cells in the venous wall including fibroblasts, VSM, and leukocytes. Pro-MMPs are activated by other MMPs, proteinases, and other endogenous and exogenous activators. MMPs degrade various extracellular matrix (ECM) proteins including collagen and elastin, and could affect other cellular processes including endothelium-mediated dilation, VSM cell migration, and proliferation as well as modulation of Ca²⁺ signaling and contraction in VSM. It is thought that increased lower limb venous hydrostatic pressure increases hypoxia-inducible factors and other MMP inducers such as extracellular matrix metalloproteinase inducer, leading to increased MMP expression/activity, ECM protein degradation, vein wall relaxation, and venous dilation. Vein wall inflammation and leukocyte infiltration cause additional increases in MMPs, and further vein wall dilation and valve degradation, that could lead to chronic venous disease and varicose veins (VVs). VVs are often presented as vein wall dilation and tortuosity, incompetent venous valves, and venous reflux. Different regions of VVs show different MMP levels and ECM proteins with atrophic regions showing high MMP levels/activity and little ECM compared to hypertrophic regions with little or inactive MMPs and abundant ECM. Treatment of VVs includes compression stockings, venotonics, sclerotherapy, or surgical removal. However, these approaches do not treat the cause of VVs, and other lines of treatment may be needed. Modulation of endogenous tissue inhibitors of metalloproteinases (TIMPs), and exogenous synthetic MMP inhibitors may provide new approaches in the management of VVs.

Catechol-based matrix metalloproteinase inhibitors with additional antioxidative activity

New catechol-containing chemical entities have been investigated as matrix metalloproteinase inhibitors as well as antioxidant molecules. The combination of the two properties could represent a useful feature due to the potential application in all the pathological processes characterized by increased proteolytic activity and radical oxygen species (ROS) production, such as inflammation and photoaging. A series of catechol-based molecules were synthesized and tested for both proteolytic and oxidative inhibitory activity, and the detailed binding mode was assessed by crystal structure determination of the complex between a catechol derivative and the matrix metalloproteinase-8. Surprisingly, X-ray structure reveals that the catechol oxygens do not coordinates the zinc atom.

Thioredoxin fusion construct enables high-yield production of soluble, active matrix metalloproteinase-8 (MMP-8) in Escherichia coli

Matrix metalloproteinases (MMPs) are crucial proteases in maintaining the health and integrity of many tissues, however their dysregulation often facilitates disease progression. In disease states these remodeling and repair functions support, for example, metastasis of cancer by both loosening the matrix around tumors to enable cellular invasion and by affecting proliferation and apoptosis, and they promote degradation of biological restorations by weakening the substrate to which the restoration is attached. As such, MMPs are important therapeutic targets. MMP-8 participates in cancer, arthritis, asthma and failure of dental fillings. MMP-8 differs from other MMPs in that it has an insertion that enlarges its active site. To elucidate the unique features of MMP-8 and develop selective inhibitors to this therapeutic target, a stable and active form of the enzyme is needed. MMP-8 has been difficult to express at high yield in a soluble, active form. Typically recombinant MMPs accumulate in inclusion bodies and complex methods are applied to refold and purify protein in acceptable yield. Presented here is a streamlined approach to produce in Escherichia coli a soluble, active, stable MMP-8 fusion protein in high yield. This fusion shows much greater retention of activity when stored refrigerated without glycerol. A variant of this construct that contains the metal binding claMP Tag was also examined to demonstrate the ability to use this tag with a metalloprotein. SDS-PAGE, densitometry, mass spectrometry, circular dichroism spectroscopy and an activity assay were used to analyze the chemical integrity and function of the enzyme.

Fluorinated matrix metalloproteinases inhibitors--Phosphonate based potential probes for positron emission tomography

Fluorine-containing inhibitors of matrix metalloproteinases (MMPs) can serve as lead structures for the development of (18)F-labeled radioligands. These compounds might be useful as non-invasive imaging probes to characterize pathologies associated with increased MMP activity. Results with a series of fluorinated analogs of a known biphenyl sulfonamide inhibitor have shown that fluorine can be incorporated into two different positions of the molecular scaffold without significant loss of potency in the nanomolar range. Additionally, the potential of a hitherto unknown fluorinated tertiary sulfonamide as MMP inhibitor has been demonstrated.

Regulation and involvement of matrix metalloproteinases in vascular diseases

Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases whose main function is to degrade and deposit structural proteins within the extracellular matrix (ECM). A dysregulation of MMPs is linked to vascular diseases. MMPs are classified into collagenases, gelatinases, membrane-type, metalloelastase, stromelysins, matrilysins, enamelysins, and unclassified subgroups. The production of MMPs is stimulated by factors such as oxidative stress, growth factors and inflammation which lead to its up- or down-regulation with subsequent ECM remodeling. Normally, excess activation of MMPs is controlled by their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs). An imbalance of MMPs and TIMPs has been implicated in hypertension, atherosclerotic plaque formation and instability, aortic aneurysms and varicose vein wall remodeling. Also, recent evidence suggests epigenetic regulation of some MMPs in angiogenesis and atherosclerosis. Over the years, pharmacological inhibitors of MMPs have been used to modify or prevent the development of the disease with some success. In this review, we discuss recent advances in MMP biology, and their involvement in the manifestation of vascular disease.

Selected organophosphorus compounds with biological activity. Applications in medicine

The purpose of this article is to provide an overview of the latest applications of organophosphorus compounds (OPs) that exhibit biological activity.

Ligand-induced expansion of the S1' site in the anthrax toxin lethal factor

The Bacillus anthracis lethal factor (LF) is one component of a tripartite exotoxin partly responsible for persistent anthrax cytotoxicity after initial bacterial infection. Inhibitors of the zinc metalloproteinase have been investigated as potential therapeutic agents, but LF is a challenging target because inhibitors lack sufficient selectivity or possess poor pharmaceutical properties. These structural studies reveal an alternate conformation of the enzyme, induced upon binding of specific inhibitors, that opens a previously unobserved deep pocket termed S1'(∗) which might afford new opportunities to design selective inhibitors that target this subsite.

Matrix Metalloproteinases as Regulators of Vein Structure and Function: Implications in Chronic Venous Disease

Lower-extremity veins have efficient wall structure and function and competent valves that permit upward movement of deoxygenated blood toward the heart against hydrostatic venous pressure. Matrix metalloproteinases (MMPs) play an important role in maintaining vein wall structure and function. MMPs are zinc-binding endopeptidases secreted as inactive pro-MMPs by fibroblasts, vascular smooth muscle (VSM), and leukocytes. Pro-MMPs are activated by various activators including other MMPs and proteinases. MMPs cause degradation of extracellular matrix (ECM) proteins such as collagen and elastin, and could have additional effects on the endothelium, as well as VSM cell migration, proliferation, Ca(2+) signaling, and contraction. Increased lower-extremity hydrostatic venous pressure is thought to induce hypoxia-inducible factors and other MMP inducers/activators such as extracellular matrix metalloproteinase inducer, prostanoids, chymase, and hormones, leading to increased MMP expression/activity, ECM degradation, VSM relaxation, and venous dilation. Leukocyte infiltration and inflammation of the vein wall cause further increases in MMPs, vein wall dilation, valve degradation, and different clinical stages of chronic venous disease (CVD), including varicose veins (VVs). VVs are characterized by ECM imbalance, incompetent valves, venous reflux, wall dilation, and tortuosity. VVs often show increased MMP levels, but may show no change or decreased levels, depending on the VV region (atrophic regions with little ECM versus hypertrophic regions with abundant ECM) and MMP form (inactive pro-MMP versus active MMP). Management of VVs includes compression stockings, venotonics, and surgical obliteration or removal. Because these approaches do not treat the causes of VVs, alternative methods are being developed. In addition to endogenous tissue inhibitors of MMPs, synthetic MMP inhibitors have been developed, and their effects in the treatment of VVs need to be examined.

Synthesis and antitumor activities of novel rhein α-aminophosphonates conjugates

Several rhein α-aminophosphonates conjugates (5a-5q) were synthesized and evaluated for in vitro cytotoxicity against HepG-2, CNE, Spca-2, Hela and Hct-116 cell lines. Some compounds showed relatively high cytotoxicity. Especially, compound 5i exhibited the strongest cytotoxicity against Hct-116 cells (IC50 was 5.32 μM). All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. The mechanism of compound 5i was preliminarily investigated by Hoechst 33258 staining, JC-1 mitochondrial membrane potential staining and flow cytometry, which indicated that the compound 5i induced apoptosis in Hct-116 cancer cells. Cell cycle analysis showed that these compound 5i mainly arrested Hct-116 cells in G1 stage. The effects of 5i on the activation of caspases expression indicated that 5i might induce apoptosis via the membrane death receptor pathways. In addition, the binding properties of a model analog 5i to DNA were investigated by methods (UV-vis, fluorescence, CD spectroscopy and FRET-melting) in compare with that of rhein. Results indicated that 5i showed moderate ability to interact ct-DNA.

Arylamino methylene bisphosphonate derivatives as bone seeking matrix metalloproteinase inhibitors

The complexity of matrix metalloproteinase inhibitors (MMPIs) design derives from the difficulty in carefully addressing their inhibitory activity towards the MMP isoforms involved in many pathological conditions. In particular, specific metalloproteinases, such as MMP-2 and MMP-9, are key regulators of the 'vicious cycle' occurring between tumor metastases growth and bone remodeling. In an attempt to devise new approaches to selective inhibitor derivatives, we describe novel bisphosphonate bone seeking MMP inhibitors (BP-MMPIs), capable to be selectively targeted and to overcome undesired side effects of broad spectrum MMPIs. In vitro activity (IC50 values) for each inhibitor was determined against MMP-2, -8, -9 and -14, because of their relevant role in skeletal development and renewal. The results show that BP-MMPIs reached IC50 values of enzymatic inhibition in the low micromolar range. Computational studies, used to rationalize some trends in the observed inhibitory profiles, suggest a possible differential binding mode in MMP-2 that explains the selective inhibition of this isoform. In addition, survival assay was conducted on J774 cell line, a well known model system used to evaluate the structure-activity relationship of BPs for inhibiting bone resorption. The resulting data, confirming the specific activity of BP-MMPIs, and their additional proved propensity to bind hydroxyapatite powder in vitro, suggest a potential use of BP-MMPIs in skeletal malignancies.

Synthesis, cytotoxicity, DNA binding and apoptosis of rhein-phosphonate derivatives as antitumor agents

Several rhein-phosphonate derivatives (5a-c) were synthesized and evaluated for in vitro cytotoxicity against HepG-2, CNE, Spca-2, Hela and Hct-116 cell lines. Some compounds showed relatively high cytotoxicity. Especially compounds 5b exhibited the strongest cytotoxicity against HepG-2 and Spca-2 cells (IC50 was 8.82 and 9.01 µM), respectively. All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. Further experiments proved that 5b could disturb the cell cycle in HepG-2 cells and induce apoptosis. In addition, the binding properties of a model conjugate 5b to DNA were investigated by methods (UV-Vis, fluorescence, CD spectroscopy). Results indicated that 5b showed moderate ability to interact ct-DNA.

Insight towards the conserved water mediated recognition of catalytic and structural Zn(+2) ions in human Matrix Metalloproteinase-8 enzyme: A study by MD-simulation methods

Human matrix metalloproteinase-8 (hMMP-8) plays a important role in the progression of colorectal cancer, metastasis, multiple sclerosis and rheumetoid arthritis. Extensive MD-simulation of the PDB and solvated structures of hMMP-8 has revealed the presence of few conserved water molecules around the catalytic and structural zinc (ZnC and ZnS) ions. The coordination of two conserved water molecules (W and WS) to ZnS and the H-bonding interaction of WS to S151 have indicated the plausible involvement of that metal ion in the catalytic process. Beside this the coupling of ZnC and ZnS metal ions (ZnC - W(H) (W(1))…..W(2) ….H(162) - ZnS) through two conserved hydrophilic centers (occupied by water molecules) may also provide some rational on the recognition of two zinc ions which were separated by ~13 Å in their X-ray structures. This unique recognition of both the Zn(+2) ions in the enzyme through conserved water molecules may be implemented/ exploited for the design of antiproteolytic agent using water mimic drug design protocol.

Advances in studies on collagenase inhibitors

Matrix metalloproteinases (MMPs) play an important role in many physiological and pathological processes. Development of MMP inhibitors, in particular collagenase inhibitors, for the treatment of arthritis has been more challenging, undoubtedly. Small-molecular-weight collagenase inhibitors may be classified into several different arbitrary structural classes, depending on the catalytic zinc-binding function as well as other structural elements of the inhibitors. This chapter tries to make an attempt in providing the reader with an overall flavor of the type of scaffolds reported in the past few years along with the molecular modeling studies.

Matrix metalloproteinase inhibitors as investigative tools in the pathogenesis and management of vascular disease

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade various components of the extracellular matrix (ECM). MMPs could also regulate the activity of several non-ECM bioactive substrates and consequently affect different cellular functions. Members of the MMPs family include collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs, and others. Pro-MMPs are cleaved into active MMPs, which in turn act on various substrates in the ECM and on the cell surface. MMPs play an important role in the regulation of numerous physiological processes including vascular remodeling and angiogenesis. MMPs may also be involved in vascular diseases such as hypertension, atherosclerosis, aortic aneurysm, and varicose veins. MMPs also play a role in the hemodynamic and vascular changes associated with pregnancy and preeclampsia. The role of MMPs is commonly assessed by measuring their gene expression, protein amount, and proteolytic activity using gel zymography. Because there are no specific activators of MMPs, MMP inhibitors are often used to investigate the role of MMPs in different physiologic processes and in the pathogenesis of specific diseases. MMP inhibitors include endogenous tissue inhibitors (TIMPs) and pharmacological inhibitors such as zinc chelators, doxycycline, and marimastat. MMP inhibitors have been evaluated as diagnostic and therapeutic tools in cancer, autoimmune disease, and cardiovascular disease. Although several MMP inhibitors have been synthesized and tested both experimentally and clinically, only one MMP inhibitor, i.e., doxycycline, is currently approved by the Food and Drug Administration. This is mainly due to the undesirable side effects of MMP inhibitors especially on the musculoskeletal system. While most experimental and clinical trials of MMP inhibitors have not demonstrated significant benefits, some trials still showed promising results. With the advent of new genetic and pharmacological tools, disease-specific MMP inhibitors with fewer undesirable effects are being developed and could be useful in the management of vascular disease.

Identification of novel matrix metalloproteinase inhibitors by screening of phenol fragments library

In the last 20 years, a great variety of synthetic, low molecular weight MMP inhibitors (MMPIs) have been synthesized and tested, although none has reached clinical utility. Exploration of novel ZBGs and development of non-hydroxamate MMPI has become a focus in current research. It's well-known that polyphenols can produce beneficial effects on human health by their antioxidant properties as well as they have the ability to block gelatinase activity. In this work we tested a series of selected phenols as MMP inhibitors. The most interesting hit (B6) shows sub-micromolar activity against MMP-2 (IC(50) 0.59  ±  0.05 µM, LE = 1.07) and a fairly good selectivity spectrum.

Biphenyl sulfonylamino methyl bisphosphonic acids as inhibitors of matrix metalloproteinases and bone resorption

A number of matrix metalloproteinases (MMPs), proteins important in the balance of bone remodeling, play a critical role both in cancer metastasis and in bone matrix turnover associated with the presence of cancer cells in bone. Here, we report the synthesis and biological evaluation of a new class of MMP inhibitors characterized by a bisphosphonate function as the zinc binding group. Since the bisphosphonate group is also implicated in osteoclast inhibition and provides a preferential affinity to biological apatite, the new molecules can be regarded as bone-seeking medicinal agents. Docking experiments were performed to clarify the mode of binding of bisphosphonate inhibitors in the active site of MMP-2. The most promising of the studied bisphosphonates showed nanomolar inhibition against MMP-2 and resulted in potent inhibition of osteoclastic bone resorption in vitro.

Matrix metalloproteinase inhibitors: a critical appraisal of design principles and proposed therapeutic utility

Matrix metalloproteinases (MMPs) play an important role in tissue remodelling associated with various physiological and pathological processes, such as morphogenesis, angiogenesis, tissue repair, arthritis, chronic heart failure, chronic obstructive pulmonary disease, chronic inflammation and cancer metastasis. As a result, MMPs are considered to be viable drug targets in the therapy of these diseases. Despite the high therapeutic potential of MMP inhibitors (MMPIs), all clinical trials have failed to date, except for doxycycline for periodontal disease. This can be attributed to (i) poor selectivity of the MMPIs, (ii) poor target validation for the targeted therapy and (iii) poorly defined predictive preclinical animal models for safety and efficacy. Lessons from previous failures, such as recent discoveries of oxidative/nitrosative activation and phosphorylation of MMPs, as well as novel non-matrix related intra- and extracellular targets of MMP, give new hope for MMPI development for both chronic and acute diseases. In this article we critically review the major structural determinants of the selectivity and the milestones of past design efforts of MMPIs where 2-/3-dimensional structure-based methods were intensively applied. We also analyse the in vitro screening and preclinical/clinical pharmacology approaches, with particular emphasis on drawing conclusions on how to overcome efficacy and safety problems through better target validation and design of preclinical studies.

To bind zinc or not to bind zinc: an examination of innovative approaches to improved metalloproteinase inhibition

This short review highlights some recent advances in matrix metalloproteinase inhibitor (MMPi) design and development. Three distinct approaches to improved MMP inhibition are discussed: (1) the identification and investigation of novel zinc-binding groups (ZBGs), (2) the study of non-zinc-binding MMPi, and (3) mechanism-based MMPi that form covalent adducts with the protein. Each of these strategies is discussed and their respective advantages and remaining challenges are highlighted. The studies discussed here bode well for the development of ever more selective, potent, and well-tolerated MMPi for treating several important disease pathologies.