Cathepsin inhibition

Primate neurons show different vulnerability to transient ischemia and response to cathepsin inhibition. Acta Neuropathol (Berl) 104 267-272... 

More recently, miraziridine A (113) was isolated from a marine sponge related to Theonella mirabilis and shown to inhibit the cysteine protease cathepsin B. It has been shown that the aziridine ring plays a key role in this biological activity and gives rise to irreversible inhibition of cathepsins B and L, presumably through... 

The protective antiprotease -antitrypsin (AAT) inhibits several protease enzymes, including neutrophil elastase. In the presence of unopposed AAT activity, elastase attacks elastin, which is a major component of alveolar walls. A hereditary deficiency of AAT results in an increased risk for premature development of emphysema. In the inherited disease, there is an absolute deficiency of AAT. In emphysema resulting from cigarettesmoking, the imbalance is associated with increased protease activity or reduced activity of antiproteases. Activated inflammatory cells release several other proteases, including cathepsins and metalloproteinases. In addition, oxidative stress reduces antiprotease (or protective) activity. 

NO is recognized as a mediator of bone cell metabolism, where it regulates osteoblast and osteoclast activity [141-143]. Osteoporosis, which frequently occurs in postmenopausal women, is a systemic skeletal disease associated with abnormal bone resorption. Addition of NO or NO donors to osteoclasts in vitro results in a reduction in bone resorption, whereas NO synthase inhibitors increase bone resorption, both in vitro and in vivo. Further research has shown that NO reduces bone resorption, via inhibition of the cysteine protease cathepsin K, which is believed to be a key protease in bone resorption. Most of the NO donors, i.e., nitroglycerin, 3-... 

Libraries of hundreds to thousands of spatially separate inhibitors have been prepared and screened to identify small molecule inhibitors of the human protease cathepsin D and the essential malarial proteases, plasmepsins I and II. The best inhibitors do not incorporate any amino adds and possess high affinity (Kj<5 nM).1241 Furthermore, these lead compounds were optimized by combinatorial methods for good physicochemical properties and minimal binding to human serum albumin. The optimized inhibitors effectively block cathepsin D-mediated proteolysis in human hippocampyl slices and are currently being used to evaluate the therapeutic potential of cathepsin D inhibition in the treatment of Alzheimer s disease. Additionally, the plasmepsin inhibitors serve as promising leads for the treatment of malaria. 

C5a is inactivated by the myeloperoxidase-H202 system, which oxidises a methionine residue (Met 70) on the molecule group A streptococcal endo-proteinases also abolish chemotactic activity of C5a and related compounds. Neutrophil lysosomal enzymes (e.g. elastase and cathepsin G) also destroy C5a chemotactic activity, but as these proteases are inhibited by the serum antiproteinases, a -antiproteinase and a2-macroglobulin, the physiological role of neutrophilic proteases in the inactivation of C5a is questionable. Two chemotactic factor inactivators have been found in human serum an a-globulin that specifically and irreversibly inactivates C5-derived chemotactic factors, and a / -globulin that inactivates bacterial chemotactic factors. These activities are heat labile (destroyed by treatment at 56 °C for 30 min) and are distinct from those attributable to anaphylatoxin inactivator. An apparently specific inhibitor of C5-derived chemotactic activity has also been described in human synovial fluid and peritoneal fluid. This factor (molecular mass of 40 kDa) is heat stable and acts directly on C5a. 

The cytosolic targets of cathepsin D have not been ascertained. However, since we found that inhibition of cathepsin D prevented both release of cytochrome c and activation of caspase-3-like caspases, we suggest that cathepsin D exerts its effect upstream of both the release of cytochrome c from mitochondria and the onset of the caspase cascade. Cathepsin B seems to be of minor importance in this system, because we observed that the activity of cathepsin B decreased and the cathepsin B inhibitor CA074-Me had no influence on the rate of apoptosis (Kagedal et al 2001). 

The weak base chloroquine (30-300 pM, 30 minutes, either in the presence or absence of serum) increases the endosomal pH (83) within a few minutes (45), leading to pH values close to 6.3 in both endosomes and lysosomes and therefore preventing lysosomal degradation. As a mechanism of action, a direct inhibition of lysosomal hydrolases (cathepsin B1 and some phospholipases and lysophospholipases) is reported (82). In Kupffer cells, effects are tolerated at concentrations of 40 pM or less for up to four hours and are irreversible within two hours after medium replacement (82). 

Fig. 5.4 Monitoring of the enzymatic reaction and cathepsin B inhibition by ESI-MS. MS instrument Shimadzu LCMS-2010 single-stage quadrupole mass spectrometer, (a) The ESI-MS spectrum obtained after analysis of the enzyme reaction, containing the cleavage products AMC (m/z 175.9) and Z-FR (m/z 456.1) m/z 244.9 and m/z 329.9 belong to...

The sensitivity of the microfluidic system was determined by measuring calibration curves of four cathepsin B inhibitors. The inhibitors caused negative peaks in the product mass chromatograms by inhibiting cathepsin B and thus the substrate turnover. The measured order of afEnities of the four inhibitors is in agreement with the affinities determined in microtiter plate assays and the macro-scale system. 

In aminoglycoside-treated animals, the cells can be led to canonical apop-totic death through activation of caspases. Caspase-9 forms an apoptosome complex with cytochrome c and APAF-1 and leads to apoptosis through activation of caspase-3. Aminoglycosides activate caspases in auditory structures conversely, inhibition of caspase activity successfully blocks neomycin-induced vestibulotoxicity. In contrast, apoptotic markers were essentially absent in a mouse model of chronic kanamycin ototoxicity where death of auditory sensory cells ensued via cathepsins. The activation of cathepsin D was accompanied by the nuclear translocation of endonuclease G, necrotic cleavage of PARP, and activation of p,-calpain, all facets of necrotic cell death. 

This enzyme [EC 3.4.16.5] (also known as serine-type carboxypeptidase I, cathepsin A, carboxypeptidase Y, and lysosomal protective protein) is a member of the peptidase family SIO and catalyzes the hydrolysis of the peptide bond, with broad specificity, located at the C-terminus of a polypeptide. The pH optimum ranges from 4.5 to 6.0. The enzyme is irreversibly inhibited by diisopropyl fluorophosphate and is sensitive to thiolblocking reagents. 

Figure 6. An example of inter-family target hopping between human and viral aspartyl proteases. The aspartyl protease active site is located at a homodimer interface in HIV and within a single domain in Cathepsin D, so sequence and structure alignments between these proteins cannot be constructed. By using an approach independent of sequence or structure homology to directly align the sites, SiteSorter finds that the HIV protease and Cathepsin D substrate sites are highly similar (identical chemical groups within 1 A are colored dark blue). It has been verified experimentally that Cathepsin D is susceptible to inhibition by HIV-protease inhibitors. ...

The protease [APP secretase) responsible for the normal cleavage of APP through the PA4 segment is unknown, but a number of proteases, including calpain [D. H. Small et al. 1992), a serine protease, and cathepsin B [Cataldo et al. 1991), have been proposed. It remains to be determined whether therapy should be directed at enhancing the function of the secretase to accelerate the breakdown of the PA4 segment or at inhibiting the enzyme to reduce APP turnover. 

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