Development of Selective Inhibitors and Substrate of Matrix Metalloproteinase-12

Matrix metalloproteinase-12 gene regulation by a PPAR alpha agonist in human monocyte-derived macrophages

MMP-12, a macrophage-specific matrix metalloproteinase with large substrate specificity, has been reported to be highly expressed in mice, rabbits and human atherosclerotic lesions. Increased MMP-12 from inflammatory macrophages is associated with several degenerative diseases such as atherosclerosis. In this manuscript, we show that IL-1beta, a proinflammatory cytokine found in atherosclerotic plaques, increases both mRNA and protein levels of MMP-12 in human monocyte-derived macrophages (HMDM). Since peroxisome proliferator-activated receptors (PPARs), such as PPARalpha and PPARgamma, are expressed in macrophages and because PPAR activation exerts an anti-inflammatory effect on vascular cells, we have investigated the effect of PPARalpha and gamma isoforms on MMP-12 regulation in HMDM. Our results show that MMP-12 expression (mRNA and protein) is down regulated in IL-1beta-treated macrophages only in the presence of a specific PPARalpha agonist, GW647, in a dose-dependent manner. In contrast, this inhibitory effect was abolished in IL-1beta-stimulated peritoneal macrophages isolated from PPARalpha(-/-) mice and treated with the PPARalpha agonist, GW647. Moreover, reporter gene transfection experiments using different MMP-12 promoter constructs showed a reduction of the promoter activities by approximately 50% in IL-1beta-stimulated PPARalpha-pre-treated cells. However, MMP-12 promoter analysis did not reveal the presence of a PPRE response element. The IL-1beta effect is known to be mediated through the AP-1 binding site. Mutation of the AP-1 site, located at -81 in the MMP-12 promoter region relative to the transcription start site, followed by transfection analysis, gel shift and ChIP experiments revealed that the inhibitory effect was the consequence of the protein-protein interaction between GW 647-activated PPARalpha and c-Fos or c-Jun transcription factors, leading to inhibition of their binding to the AP-1 motif. These studies suggest that PPARalpha agonists may be used therapeutically, not only for lipid disorders, but also to prevent inflammation and atheromatous plaque rupture, where their ability to inhibit MMP-12 expression in HMDM may be beneficial.

Molecular determinants of matrix metalloproteinase-12 covalent modification by a photoaffinity probe: insights into activity-based probe development and conformational variability of matrix metalloproteinases

Mass spectroscopy, microsequencing, and site-directed mutagenesis studies have been performed to identify in human matrix metalloelastase (hMMP-12) residues covalently modified by a photoaffinity probe, previously shown to be able to covalently label specifically the active site of matrix metalloproteinases (MMPs). Results obtained led us to conclude that photoactivation of this probe in complex with hMMP-12 affects a single residue in human MMP-12, Lys(241), through covalent modification of its side chain epsilon NH(2) group. Because x-ray and NMR studies of hMMP-12 indicate that Lys(241) side chain is highly flexible, our data reveal the existence of particular Lys(241) side-chain conformation in which the epsilon NH(2) group points toward the photolabile group of the probe, an event explaining the high levels of cross-linking yield between hMMP-12 and the probe. Lys(241) is not conserved in MMPs, thus differences in cross-linking yields observed with this probe between MMP members may be linked to the residue variability observed at position 241 in this family.

Upregulation of elastase proteins results in aortic dilatation in mucopolysaccharidosis I mice

Mucopolysaccharidosis I (MPS I), known as Hurler syndrome in the severe form, is a lysosomal storage disease due to alpha-L-iduronidase (IDUA) deficiency. It results in fragmentation of elastin fibers in the aorta and heart valves via mechanisms that are unclear, but may result from the accumulation of the glycosaminoglycans heparan and dermatan sulfate. Elastin fragmentation causes aortic dilatation and valvular insufficiency, which can result in cardiovascular disease. The pathophysiology of aortic disease was evaluated in MPS I mice. MPS I mice have normal elastic fiber structure and aortic compliance at early ages, which suggests that elastin assembly is normal. Elastin fragmentation and aortic dilatation are severe at 6 months, which is temporally associated with marked increases in mRNA and enzyme activity for two elastin-degrading proteins, matrix metalloproteinase-12 (MMP-12) and cathepsin S. Upregulation of these genes likely involves activation of STAT proteins, which may be induced by structural stress to smooth muscle cells from accumulation of glycosaminoglycans in lysosomes. Neonatal intravenous injection of a retroviral vector normalized MMP-12 and cathepsin S mRNA levels and prevented aortic disease. We conclude that aortic dilatation in MPS I mice is likely due to degradation of elastin by MMP-12 and/or cathepsin S. This aspect of disease might be ameliorated by inhibition of the signal transduction pathways that upregulate expression of elastase proteins, or by inhibition of elastase activity. This could result in a treatment for patients with MPS I, and might reduce aortic aneurism formation in other disorders.

Metalloproteinases and vulnerable atherosclerotic plaques

Plaque rupture is the main cause of myocardial infarctions and strokes. Ruptured plaques have thin, highly inflamed, and collagen-poor fibrous caps that contain elevated levels of proteases, including metalloproteinases (MMPs), which might weaken plaque caps and promote rupture. On the other hand, MMPs facilitate migration and proliferation vascular smooth muscle cells, which should promote fibrous cap stability. Given the dual effects of MMPs, therapies should selectively target harmful MMPs or the processes that cause MMP activity to rise to destructive levels.

Design, synthesis, and metal binding of novelPseudo- oligopeptides containing two phosphinic acid groups

Phosphinic compounds have potential as amide-bond mimetics in the development of novel peptidomimetics, enzyme inhibitors, and metal-binding ligands. Novel pseudo-oligopeptides with two phosphinic acid groups embedded in the peptide backbone serving as amide-bond surrogates, Psi[P(O,OH)--CH(2)], were targeted. A series of linear and cyclic pseudo-oligopeptides with two phosphinic acid groups arrayed at different positions in the peptide sequence were designed, including Ac--Phe--{(R,S)--AlaPsi[P(O,OH)--CH(2)]Gly}(2)--NH(2) (P2), Ac--NH--(R,S)--AlaPsi[P(O,OH)--CH(2)]Gly--Phe--(R,S)--AlaPsi[P(O,OH)--CH(2)]Gly--NH(2) (P3), Ac--NH--(R,S)--AlaPsi[P(O,OH)--CH(2)]Gly--Phe--Phe--(R,S) --AlaPsi[P(O,OH)--CH(2)]Gly--NH(2) (P4), cyclo{NH--(R,S)--AlaPsi[P(O,OH)--CH(2)]Gly--Phe}(2) (P5), and cyclo[NH--(R,S)--AlaPsi[P(O,OH)--CH(2)]Gly--Phe--Phe](2) (P6). They were synthesized via conventional Fmoc chemistry on solid support utilizing Fmoc-protected phosphinic acid-containing pseudo-dipeptide fragment, i.e. Fmoc--(R,S)--AlaPsi[P(O,OCH(3))--CH(2)]Gly--OH. The pseudo-peptides containing two phosphinic acid groups exhibited the highest binding affinity and selectivity for Fe(III) among the 10-metal ions screened by ESI-MS analysis--Cu(II), Zn(II), Co(II), Ni(II), Mn(II), Fe(II), Fe(III), Al(III), Ga(III), and Gd(III). P4 and P6 with 11-atom linkages between the two phosphinic acids preferred intramolecular metal binding to form 1:1 ligand/metal complexes. As revealed by competition experiments, P4 showed the highest relative binding affinity among the six compounds tested. Noteworthy, P4 also showed higher relative binding affinity than similar dihydroxamate-containing pseudo-peptides reported previously. The novel structural prototype and facile synthesis along with selective and potent Fe(III) binding strongly suggest that pseudo-peptides containing the two or more phosphinic groups as amide-bond surrogates deserve further exploration in medicinal chemistry.

Matrix metalloproteinase inhibition protects rat livers from prolonged cold ischemia-warm reperfusion injury

Matrix metalloproteinases (MMPs) have been implicated in the hepatic injury induced after cold ischemia-warm reperfusion (CI-WR), by altering the extracellular matrix (ECM), but their precise role remains unknown. The hepatic MMP expression was evaluated after 2 conditions of CI (4 degrees C for 24 and 42 hours: viable and nonviable livers) followed by different periods of WR, using isolated perfused rat livers. CI-WR induced moderate changes in hepatic MMP transcript levels not influenced by CI duration, whereas gelatinase activities accumulated in liver effluents. Therefore, the protective effect of a new phosphinic MMP inhibitor, RXP409, was tested after prolonged CI. RXP409 (10 microM) was added to the University of Wisconsin solution, and livers were preserved for 42 hours (4 degrees C), then reperfused for 1 hour in Krebs solution (37 degrees C), containing 20% erythrocytes. Liver viability parameters were recorded, and the extent of cell necrosis was evaluated on liver biopsies, using trypan blue nuclear uptake. Treatment with RXP409 significantly improved liver function (transaminase release and bile secretion) and liver injury. In particular, the MMP inhibitor significantly modified the extent of cell death from large clusters of necrotic hepatocytes as found in control livers (2%-60% of liver biopsies; mean, 26% +/- 9%) to isolated necrotic hepatocytes as found in treated livers (0.2%-12%; mean, 3% +/- 2%) (P < 0.05).

CONCLUSION

These data demonstrate that MMPs, by altering the ECM, play a major role in liver CI-WR injury leading to extensive hepatocyte necrosis and that their inhibition might prove to be a new strategy in improving preservation solutions.

Solution structure of inhibitor-free human metalloelastase (MMP-12) indicates an internal conformational adjustment

Macrophage metalloelastase or matrix metalloproteinase-12 (MMP-12) appears to exacerbate atherosclerosis, emphysema, aortic aneurysm, rheumatoid arthritis, and inflammatory bowel disease. An inactivating E219A mutation, validated by crystallography and NMR spectra, prevents autolysis of MMP-12 and allows us to determine its NMR structure without an inhibitor. The structural ensemble of the catalytic domain without an inhibitor is based on 2813 nuclear Overhauser effects (NOEs) and has an average RMSD to the mean structure of 0.25 A for the backbone and 0.61 A for all heavy atoms for residues Trp109-Gly263. Compared to crystal structures of MMP-12, helix B (hB) at the active site is unexpectedly more deeply recessed under the beta-sheet. This opens a pocket between hB and beta-strand IV in the active-site cleft. Both hB and an internal cavity are shifted toward beta-strand I, beta-strand III, and helix A on the back side of the protease. About 25 internal NOE contacts distinguish the inhibitor-free solution structure and indicate hB's greater depth and proximity to the sheet and helix A. Line broadening and multiplicity of amide proton NMR peaks from hB are consistent with hB undergoing a slow conformational exchange among subtly different environments. Inhibitor-binding-induced perturbations of the NMR spectra of MMP-1 and MMP-3 map to similar locations across MMP-12 and encompass the internal conformational adjustments. Evolutionary trace analysis suggests a functionally important network of residues that encompasses most of the locations adjusting in conformation, including 18 residues with NOE contacts unique to inhibitor-free MMP-12. The conformational change, sequence analysis, and inhibitor perturbations of NMR spectra agree on the network they identify between structural scaffold and the active site of MMPs.

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

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

Matrix metalloproteinase 11 (MMP-11; stromelysin-3) and synthetic inhibitors

Matrix metalloproteinase (MMP)-11, or Stromelysin 3, is a particular member of MMP family, a group of zinc-dependent endopeptidases involved in matrix degradation and tissue remodeling. Despite intense efforts since its first characterization 15 years ago, its role and target substrates in different diseases remain largely unknown. While mice with MMP-11 deficiency display no particular phenotype, analysis of different tumorigenesis models with these mice lead to the conclusion that MMP-11 promotes tumor development. In contrast with other MMPs, MMP-11 is unable to degrade any major extracellular matrix component and unlike most of other MMPs that are secreted as inactive proenzymes and activated extracellularly, MMP-11 is secreted under active form. MMP-11 may thus play a unique role in tissue remodeling processes, including those associated with tumor progression. Although MMP-11 and other MMPs have been considered as promising targets to combat cancer, a first series of clinical trials using broad-spectrum MMP inhibitors have not led to significant therapeutic benefits. These disappointing results highlight the need for better understanding of the exact role played by each MMP during the different stages of tumor progression. Among the different strategies to fill this gap, highly specific MMP inhibitors would be of great value. This review provides an update on the selectivity profile of phosphinic MMP-11 synthetic inhibitors developed and discusses the opportunities and limitations to identify inhibitors able to fully discriminate MMP-11 from the other MMPs.

Triple-helical transition state analogues: a new class of selective matrix metalloproteinase inhibitors

Alterations in activities of one family of proteases, the matrix metalloproteinases (MMPs), have been implicated in primary and metastatic tumor growth, angiogenesis, and pathological degradation of extracellular matrix (ECM) components, such as collagen and laminin. Since hydrolysis of the collagen triple-helix is one of the committed steps in ECM turnover, we envisioned modulation of collagenolytic activity as a strategy for creating selective MMP inhibitors. In the present study, a phosphinate transition state analogue has been incorporated within a triple-helical peptide template. The template sequence was based on the alpha1(V)436-450 collagen region, which is hydrolyzed at the Gly(439)-Val(440) bond selectively by MMP-2 and MMP-9. The phosphinate acts as a tetrahedral transition state analogue, which mimics the water-bound peptide bond of a protein substrate during hydrolysis. The phosphinate replaced the amide bond between Gly-Val in the P1-P1' subsites of the triple-helical peptide. Inhibition studies revealed Ki values in the low nanomolar range for MMP-2 and MMP-9 and low to middle micromolar range for MMP-8 and MMP-13. MMP-1, MMP-3, and MT1-MMP/MMP-14 were not inhibited effectively. Melting of the triple-helix resulted in a decrease in inhibitor affinity for MMP-2. The phosphinate triple-helical transition state analogue has high affinity and selectivity for the gelatinases (MMP-2 and MMP-9) and represents a new class of protease inhibitors that maximizes potential selectivity via interactions with both prime and nonprime active site subsites as well as with secondary binding sites (exosites).

A Versatile Annulation Protocol toward Novel Constrained Phosphinic Peptidomimetics

The development of a novel 3-center 2-component annulation reaction between alpha,omega-carbamoylaldehydes and suitably monoalkylated phosphinic acids is reported. Depending on the starting alpha,omega-carbamoylaldehyde, diverse phosphinic scaffolds varying in the size of their rigidity element, the nature and stereochemistry of substituents, and the participation of heteroatoms in the azacyclic ring system can be obtained in one synthetic step and in high yield. In addition, this methodology allows the synthesis of Fmoc-protected constrained aminophosphinic acids that can be easily converted to suitable pseudodipeptide building blocks compatible with the requirements of peptide synthesis on the solid phase. Finally, the careful choice of both substituents and protecting groups can provide functionally diverse, orthogonally protected constrained scaffolds for extended derivatization of the target phosphinic peptidomimetic structures.

Crystal Structures of MMP-9 Complexes with Five Inhibitors: Contribution of the Flexible Arg424 Side-chain to Selectivity

Human matrix metalloproteinase 9 (MMP-9), also called gelatinase B, is particularly involved in inflammatory processes, bone remodelling and wound healing, but is also implicated in pathological processes such as rheumatoid arthritis, atherosclerosis, tumour growth, and metastasis. We have prepared the inactive E402Q mutant of the truncated catalytic domain of human MMP-9 and co-crystallized it with active site-directed synthetic inhibitors of different binding types. Here, we present the X-ray structures of five MMP-9 complexes with gelatinase-specific, tight binding inhibitors: a phosphinic acid (AM-409), a pyrimidine-2,4,6-trione (RO-206-0222), two carboxylate (An-1 and MJ-24), and a trifluoromethyl hydroxamic acid inhibitor (MS-560). These compounds bind by making a compromise between optimal coordination of the catalytic zinc, favourable hydrogen bond formation in the active-site cleft, and accommodation of their large hydrophobic P1' groups in the slightly flexible S1' cavity, which exhibits distinct rotational conformations of the Pro421 carbonyl group in each complex. In all these structures, the side-chain of Arg424 located at the bottom of the S1' cavity is not defined in the electron density beyond C(gamma), indicating its mobility. However, we suggest that the mobile Arg424 side-chain partially blocks the S1' cavity, which might explain the weaker binding of most inhibitors with a long P1' side-chain for MMP-9 compared with the closely related MMP-2 (gelatinase A), which exhibits a short threonine side-chain at the equivalent position. These novel structural details should facilitate the design of more selective MMP-9 inhibitors.

Inhibitor Fingerprinting of Matrix Metalloproteases Using a Combinatorial Peptide Hydroxamate Library

We report the inhibitor fingerprints of seven matrix metalloproteases, representing all five established families of this important class of enzymes, against a highly diversified small-molecule library. A total of 1400 peptide hydroxamates were individually prepared by systematically permuting both natural and unnatural amino acids across the P1', P2', and P3' positions, thereby generating an inhibitor library with three-pronged structural diversity. High-throughput screenings were efficiently conducted in microtiter plate format, providing a rapid and quantitative determination of inhibitor potency across the panel of enzymes. Despite similarities in substrate preferences and structural homologies within this class of enzymes, our findings revealed distinct patterns of inhibition for each MMP against varied chemical scaffolds. The resulting inhibitor fingerprints readily facilitated the identification of inhibitors with good potency as well as desirable selectivity, potentially minimizing adverse effects when developing such leads into candidate drugs. The strategy also offers a novel method for the functional classification of matrix metalloproteases, on the basis of the characteristic profiles obtained using the diverse set of inhibitors. This approach thus paves the way forward in lead identification by providing a rapid and quantitative method for selectivity screening at the outset of the drug discovery process.

Double dearomatization of bis(diphenylphosphinamides) through anionic cyclization. A facile route of accessing multifunctional systems with antitumor properties

The sequential one-pot double dearomatization of bis(N-benzyl-P,P-diphenylphosphinamides) via anionic cyclization is described for the first time. Protonation and alkylation of the dearomatized dianions provide bis(tetrahydro-2,1-benzazaphospholes) in good yield and with very high regio- and stereocontrol. Acid-catalyzed methanolysis of the bisheterocycles affords bis(methyl gamma-aminophosphinates) stereospecifically. The doubly phosphorylated systems proved to be active against a series of cancer cell lines.

Chemoselective Protection of Solid-Phase Compatible Fmoc-Phosphinic Building Blocks

An efficient four-step synthetic strategy able to fully discriminate hydroxyphosphinyl and carboxylic groups of Fmoc-phosphinic building blocks and related analogues has been developed. The proposed method applies selective acidic removal of the phenacyl (Pac) group from the hydroxyphosphinyl functionality and protection by the 1-adamantyl (Ad) group. Reductive removal of the Pac group from the carboxylic functionality leads to Fmoc-protected phosphinic pseudodipeptidic units suitable for phosphinic peptide and library development using solid-phase peptide synthesis (SPPS).

Do metalloproteinases destabilize vulnerable atherosclerotic plaques?

PURPOSE OF REVIEW

Atherosclerotic plaque rupture and thrombosis underlie most myocardial infarctions. Matrix metalloproteinases are a family of enzymes that remodel the extracellular matrix. Metalloproteinases could stabilize rupture-prone plaques by promoting smooth muscle cell migration and proliferation. Alternatively, metalloproteinases could destabilize vulnerable plaques by promoting matrix destruction, angiogenesis, leucocyte infiltration, and apoptosis. Evidence is reviewed from genetically modified mice and human biomarker and genetic studies that sheds light on this dual role of metalloproteinases.

RECENT FINDINGS

Inhibition of metalloproteinases in mice using tissue inhibitors of metalloproteinases increases plaque stability; however, double knockouts of apolipoprotein E with matrix metalloproteinase 2, 3, 7, 9, 12, and 13 have more or less stable plaques, consistent with harmful or protective effects of individual metalloproteinases. Overexpression studies in mice or rabbits show that high activities of matrix metalloproteinase 9 and 12 decrease stability. Biomarker and human genetic studies demonstrate that increased metalloproteinase activity is associated with vascular repair or myocardial infarction.

SUMMARY

Recent studies reinforce evidence for a dual role of matrix metalloproteinases in plaque stabilization and rupture, which probably depends on the stage, site, and severity of disease. Dysregulated metalloproteinase activity in end-stage coronary artery disease appears a valid target for therapy.