An ACE-dependent increase in the amounts of activated Erk1/Erk2 in atrial interstitial cells may contribute as a molecular mechanism for the development of atrial fibrosis in patients with AF. These findings may have important impact on the treatment of AF.

AF is associated with the down-regulation of atrial AT(1)-R and the up-regulation of AT(2)-R proteins. These findings may help define the pathophysiological role of the angiotensin system in the structural remodeling of the fibrillating atria.

1. Cathepsin L was purified from rat liver lysosomes by cell fractionation, osmotic disruption of the lysosomes in the lysosomal mitochondria1 pellet, gel filtration of the lysosomal extract and chromatography on CM-Sephadex.2. Cathepsin L is a thiol proteinase and exists in several multiple forms visible on the disc electropherogram. By polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate, its molecular weight was found to be 23000-24000. The isoelectric points of the multiple forms of cathepsin L extended from pH 5.8 -6.1 ascertained by analytical isoelectric focusing.3. Using various protein substrates, cathepsin L was found to be the most active endopeptidase from rat liver lysosomes acting at pH 6 -7. In contrast to cathepsin B1, its capability of hydrolyzing N-substituted derivatives of arginine is low and it does not split esters. 4. Greatest activity is obtained close to pH 5.0 with 70-90% of maximal activity at pH 4.0 and pH 6.0 and 30 -40 0 4 at pH 7.0.5. The enzyme is strongly inhibited by leupeptin and the chloromethyl ketone of tosyl-lysine. Leupeptin acts as a pseudo-irreversible inhibitor.6. The enzyme is stable for several months at slightly acid pH values in the presence of thiol compounds in a deep-frozen state.Knowledge of the proteolytic enzymes in the cell is one of the preconditions in studying the molecular mechanism of intracellular protein breakdown. All organelles contain proteolytic activity in various amounts [l]. The lysosomes, in particular, are rich in proteinases. A cell fraction enriched in lysosomes showed at pH 3-4 as well as at pH 6-7 the highest activity hydrolyzing cell-derived proteins in comparison to all other cell organelles [l -61. From this finding it was to be concluded, that the lysosomes certainly play an important role in the overall process of intracellular proteolysis also at physiological pH. A wide variety of lysosomal proteinases has been investigated : cathepsin A (lysosomal carboxypeptidase A) [7-131, cathepsin B1 [7,12-201, cathepsin B2 (lysosomal carboxypeptidase B) [7,12 -14,20-221, cathepsin C (dipeptidyl aminopeptidase I) [7,12,13, Dedicated to Professor Horst Hanson on the occasion of his 65th birthday.Ahbveviation. Leu-CH2C1, 1 -chloro-3-amino-5-methyl-~-hexan-2-one; Tos-Lys-CH2C1, 7-amino-l-chloro-3-tosylamido-~-heptan-2-one ; Tos-Phe-CHzC1, l-chlor0-4-phenyl-3-tosylamido-~-butan-2-one; Bz-L-Arg-NHZ, or-N-benzoyl-L-arginine amide.Enzymes. Cathepsin L (EC 3.4.22.-); cathepsin B1 and B2 (EC 3.4.22.1); cathepsinc (EC 3.4.14.1); cathespin D (EC 3.4.23.5). 18,23,24],cathepsin D [6,7,12,13,23,25-311, cathepsin E [7,13] In studies on the proteolytic activity in a lysosomal extract we succeeded in separating cathepsins BI, C and D by gel filtration on Sephadex G-75. With cytosol proteins as well as with azocasein as substrates at pH 6 and 7, the main part of proteolytic activity was shown to be present in the protein fraction with molecular weights between 20000 and 30000 [2,43]. We could show that in addition to cathepsin B1, the...

Propolis, the resinous product collected by honey bees from plants, is used as folk medicine since ancient time. Recently, immunoregulatory and anti-inflammatory properties of propolis have been published. The detailed mechanisms of actions of propolis and its components on immune cells, however, are still unknown. Therefore, we studied the effects of different propolis extracts, of the flavonoids hesperidin and quercetin as well as of caffeic acid phenethyl ester (CAPE) on basic human immune cell functions. In detail, we measured the effects on DNA synthesis and production of different types of cytokines, namely IL-1β, IL-12, IL-2, IL-4, IL-10 and TGF-β1, of mitogen-activated peripheral blood mononuclear cells (PBMC) as well as of purified T lymphocytes. Our data clearly show that propolis as well as its constituents studied are capable of dosedependently suppressing phythemagglutinin (PHA)-induced DNA synthesis of PBMC and T cells. Moreover, cytokines produced by monocytes/macrophages (IL-1β, IL-12), by Th1 type (IL-2) as well as Th2 type (IL-4) lymphocytes were found to be also suppressed, whereas the production of TGF-β1 by T regulatory cells was ascertained to be increased. These data convincingly demonstrate that propolis has a direct regulatory effect on basic functional properties of immune cells which may be mediated by the Erk2 MAP-kinase signal pathway. Thus, the bee product propolis can be considered as a powerful natural anti-inflammatory medicine influencing different types of immune-responses probably via immunoregulatory T cells.

CD26 or dipeptidyl peptidase IV (DP IV) is expressed on various cell types, including T cells. Although T cells can receive activating signals via CD26, the physiological role of CD26/DP IV is largely unknown. We used the reversible DP IV inhibitor Lys[Z(NO2)]-pyrrolidide (I40) to dissect the role of DP IV in experimental autoimmune encephalomyelitis (EAE) and to explore the therapeutic potential of DP IV inhibition for autoimmunity. I40 administration in vivo decreased and delayed clinical and neuropathological signs of adoptive transfer EAE. I40 blocked DP IV activity in vivo and increased the secretion of the immunosuppressive cytokine TGF-β1 in spinal cord tissue and plasma during acute EAE. In vitro, while suppressing autoreactive T cell proliferation and TNF-α production, I40 consistently up-regulated TGF-β1 secretion. A neutralizing anti-TGF-β1 Ab blocked the inhibitory effect of I40 on T cell proliferation to myelin Ag. DP IV inhibition in vivo was not generally immunosuppressive, neither eliminating encephalitogenic T cells nor inhibiting T cell priming. These data suggest that DP IV inhibition represents a novel and specific therapeutic approach protecting from autoimmune disease by a mechanism that includes an active TGF-β1-mediated antiinflammatory effect at the site of pathology.