Peter G. Mitchell

Matrix metalloproteinases are involved in C-terminal and interglobular domain processing of cartilage aggrecan in late stage cartilage degradation.

Monoclonal antibody (MAb) technology was used to examine aggrecan metabolites and the role of aggrecanases and matrix metalloproteinases (MMPs) in proteolysis of the interglobular domain (IGD) and C-terminus of aggrecan. An in vitro model of progressive cartilage degradation characterized by early proteoglycan loss and late stage collagen catabolism was evaluated in conjunction with a broad-spectrum inhibitor of MMPs. We have for the first time demonstrated that IGD cleavage by MMPs occurs during this late stage cartilage degeneration, both as a primary event in association with glycosaminoglycan (GAG) release from the tissue and secondarily in trimming of aggrecanase-generated G1 metabolites. Additionally, we have shown that MMPs were responsible for C-terminal catabolism of aggrecan and generation of chondroitin sulfate (CS) deficient aggrecan monomers and that this aggrecan truncation occurred prior to detectable IGD cleavage by MMPs. The onset of this later stage MMP activity was also evident by the generation of MMP-specific link protein catabolites in this model culture system. Recombinant MMP-1, -3 and -13 were all capable of C-terminally truncating aggrecan with at least two cleavage sites N-terminal to the CS attachment domains of aggrecan. Through analysis of aggrecan metabolites in pathological synovial fluids from human, canine and equine sources, we have demonstrated the presence of aggrecan catabolites that appear to have resulted from similar C-terminal processing of aggrecan as that induced in our in vitro culture systems. Finally, by developing a new MAb recognizing a linear epitope in the IGD of aggrecan, we have identified two novel aggrecan metabolites generated by an as yet unidentified proteolytic event. Collectively, these results suggest that C-terminal processing of aggrecan by MMPs may contribute to the depletion of cartilage GAG that leads to loss of tissue function in aging and disease. Furthermore, analysis of aggrecan metabolites resulting from both C-terminal and IGD cleavage by MMPs may prove useful in monitoring different stages in the progression of cartilage degeneration.

PROTONMOTIVE CYTOCHROME SYSTEM OF MITOCHONDRIA

My main aim in this paper is to consider four simple questions about the mitochondrial cytochrome system, originally named and broadly defined by David Keilin: 1. What is it? 2. Where is it? 3. What does it do? 4. How does it do it? The attempted answers mostly depend on a review of published experimental knowledge and theory, but I also make use of the results of a few previously unpublished experiments that have recently been done by Jennifer Moyle in my laboratory. This paper does not follow a historical narrative. Therefore, I would like to remark at the outset that the painstaking work of a multitude of biochemists has contributed to the synthesis attempted here. Many of the threads have been ably drawn together in reviews by Tsoo

Synthesis and biological activity of piperazine-Based dual MMP-13 and TNF-α converting enzyme inhibitors

Abstract A series of novel MMP-13 and TNF-α converting enzyme inhibitors based on piperazine 2-hydroxamic acid scaffolds are described. The TACE, MMP-1 and MMP-13 activity of these inhibitors as well as the effect of substitution of the piperazine nitrogen and the P-1′ benzyloxy tailpiece is discussed. Moderate in vivo activity is observed with several members of this group.

Difluoroketones as inhibitors of matrix metalloprotease-13

Substrate-like difluoroketones have been prepared as potential inhibitors of MMP-13. Weak inhibition was seen with the key target 2. This and the more potent activity of intermediate 7b illustrates that hydrated ketones can be used to inhibit MMP-13 and perhaps other members of this class of enzymes.

Inhibitors of MMP-1: an examination of P1′ Cα gem-disubstitution in the succinamide hydroxamate series

Abstract The effect of P 1 ′ C α gem-disubstitution in a series of succinamide hydroxamate inhibitors of MMP-1 has been investigated. While in all cases P 1 ′ gem-disubstitution led to loss of potency relative to the corresponding P 1 ′ isobutyl and phenyl compounds 1 and 3 , respectively, the loss of activity was less pronounced in certain instances, e.g., the P 1 ′ gem-cyclohexyl analogue 12 IC 50 = 0.15 μM).

Inhibitors of MMP-1: an examination of P1′ Cα gem-disubstitution in the N-carboxyalkylamine and glutaramide carboxylate series

Abstract Modification of the N-carboxyalkylamine 3 by independent replacement of the P1′ NH group for CH2 and introduction of P1′ gem-cyclohexyl substitution affords compounds 5 and 6a which retain appreciable activity against MMP-1 (IC50s = 0.023 μM and 0.09 μM, respectively). The glutaramide 7a which incorporates both these structural changes also retains potent activity (IC50 = 0.038 μM).