Modulation of the expression and activity of cathepsin S in reconstructed human skin by neohesperidin dihydrochalcone.

Dysregulation of cathepsin S (Cat S), a cysteine protease involved in extracellular-matrix and basement membrane (BM) degradation, is a concomitant feature of several inflammatory skin diseases. Therefore, Cat S has been suggested as a potential therapeutic target. Flavonoids, which were identified as regulatory molecules of various proteolytic enzymes, exert beneficial effects on skin epidermis. Herein, thirteen flavonoid compounds were screened in vitro and in silico and neohesperidin dihydrochalcone (NHDC) was identified as a potent, competitive, and selective inhibitor (Ki=8±1 µM) of Cat S. Furthermore, Cat S-dependent hydrolysis of nidogen-1, a keystone protein of BM architecture, as well elastin, collagens I and IV was impaired by NHDC, while both expression and activity of Cat S were significantly reduced in NHDC-treated human keratinocytes. Moreover, a reconstructed human skin model showed a significant decrease of both mRNA and protein levels of Cat S after NHDC treatment. Conversely, the expression of nidogen-1 was significantly increased. NHDC raised IL-10 expression, an anti-inflammatory cytokine, and mediated STAT3 signaling pathway, which in turn dampened Cat S expression. Our findings support that NHDC may represent a valuable scaffold for structural improvement and development of Cat S inhibitors to preserve the matrix integrity and favor skin homeostasis during inflammatory events.

In silico and in vitro mapping of specificity patterns of glycosaminoglycans towards cysteine cathepsins B, L, K, S and V.

Human cysteine cathepsins are lysosomal proteases, which are involved in different biological processes. Their enzymatic activity can be regulated by glycosaminoglycans (GAGs): long linear periodic negatively charged polysaccharides, which dimeric building blocks consist of uronic acid and hexosamine monosaccharide units. In this study, molecular docking simulations of chondroitin 4-sulfate, chondroitin 6-sulfate, heparin, heparan sulfate, dermatan sulfate and hyaluronic acid of various chain lengths were performed with cathepsins B, L, K, S and V and followed by molecular dynamics-based refinement and binding free energy analysis. We concluded that electrostatics might be a driving force for cathepsin-GAG interactions; indeed as in most of characterised systems, the increase of GAG chain length consequently leads to a more pronounced effect on the strength of cathepsin-GAG interactions. Results also suggest that binding of GAGs at different regions on cathepsins surface affect differently their enzymatic activity and could is dependent on cathepsin and GAG type. Present data contribute to systematic description of cathepsin-GAG interactions, which is helpful in understanding the subtle molecular mechanisms of protease regulation behind their biological functions.

[Mitochondrial ceruloplasmin of mammals].

Using immunoblotting method it was found out that ceruloplasmin (Cp) polypeptides are revealed in mitochondria of rats, isolated from brain, liver, testicles and mammary gland. Cp is localized in matrix and inner membranes of mitochondria. Its molecular weight corresponds to the non-glycosilated form of the protein. Computer analysis did not reveal any sequences homologous to the signal peptide for mitochondria protein import (SPMPI) in the rat chromosomal Cp gene. However the analysis of homologous to Cp sequences, presented in databases, detected SPMPI in the human processed Cp pseudogene. Cp pseudogene region of 984 nucleotides long is translated in the only reading frame to the polypeptide of 328 a.a. long including 66 a.a of SPMPI at N-terminus. The predicted protein with the exception of SPMPI is identical to the corresponding Cp fragment at 92%, it has 20 amino acid substitutions, 8 of which are significant. His-X-His motif, typical for copper containing ferroxidases, is located in the centre of a molecule. Potential copper-binding site appears as a result of proline to histidine substitution at 923 position along Cp sequence. The product of Cp pseudogene transcription was detected in the human cultured cells of HepG2 and HuTu 80 cell lines using RT-PCR strategy. 30 kDa polypeptide that interacts with human Cp antibodies was found in mitochondria of HuTu 80 cells. The possible biological role of mitochondrial Cp is under discussion.