An understanding of the structure and composition of the myelin sheath is essential to understand the pathogenesis of demyelinating diseases such as multiple sclerosis (MS). The presence of citrulline in myelin proteins in particular myelin basic protein (MBP) causes an important change in myelin structure, which destabilizes myelin. The peptidylarginine deiminases (PADs) are responsible for converting arginine in proteins to citrulline. Two of these, PAD2 and PAD4, were localized to the myelin sheath by immunogold electron microscopy. Deimination of MBP by the recombinant forms of these enzymes showed that it was extensive, that is, PAD2 deiminated 18 of 19 arginyl residues in MBP, whereas PAD4 deiminated 14 of 19 residues. In the absence of PAD2 (the PAD2-knockout mouse) PAD4 remained active with limited deimination of arginyl residues. In myelin isolated from patients with MS, the amounts of both PAD2 and PAD4 enzymes were increased compared with that in normals, and the citrullinated proteins were also increased. These data support the view that an increase in citrullinated proteins resulting from increased PAD2 and 4 is an important change in the pathogenesis of MS. Peptidylarginine deiminases (PADs) are enzymes which deiminate arginyl residues in proteins. Five isozymes, termed PADs 1-4 and PAD6, are known, which have some tissue specificity, although PAD2 is widely distributed. 1 It is the principal PAD enzyme in brain, where it has been shown to be responsible for the deimination of arginyl residues in myelin basic protein (MBP), a principal protein in myelin 2 and a possible autoantigen in multiple sclerosis (MS). 3,4 The presence of other PAD enzymes in myelin has not been reported. For all PADs, the deimination reaction involves the conversion of arginyl residues in proteins to citrulline and the formation of ammonia. 5 The conversion of arginine to citrulline involves the loss of one positive charge from the protein for each arginine deiminated.In earlier studies, we reported that MBP isolated from white matter from normal human brain could be fractionated into several components by column chromatography. One of these components, which accounted for 20% of all the MBP, contained six citrullinyl residues, the sites of which we determined by protein sequencing. 6 More recently, the deimination has been shown to be more extensive by mass spectrometry with partial deimination of many arginines. 7 The loss of six positive charges accounted for the chromatographic behavior on the cation-exchange column. This same fraction isolated from patients with MS accounted for 45% of the total MBP, and in a case of fulminating MS, it accounted for 80-90% of all the MBP. 8 Instead of six arginyl residues in normal MBP, 6 18 of 19 arginyl residues in the Marburg's MBP were deiminated. In a number of in vitro studies in protein-lipid interaction systems, we showed that this deiminated protein was unable to compact lipid bilayers, causing destabilization, which might be the mechanism of demyelination. 9 Our recent studie...

Objective. To determine the expression of suppressor of cytokine signaling 3 (SOCS-3) in human articular chondrocytes and its functional consequences.Methods. Chondrocytes were isolated from the cartilage of patients with osteoarthritis (OA), patients with rheumatoid arthritis (RA), and trauma patients and from the healthy cartilage of patients with a femoral neck fracture. The human chondrocyte cell line G6 and primary bovine chondrocytes were used in validation experiments. SOCS-3 messenger RNA (mRNA) expression was measured by quantitative polymerase chain reaction, and SOCS-3 protein levels were determined by Western blotting and immunohistochemical analysis. Conclusion. This study demonstrated that both SOCS-3 mRNA and SOCS-3 protein are expressed in human arthritic chondrocytes and affect cellular responses involved in cartilage pathology.

The synthesis of asymmetric spherical nanoparticles has attracted great interest because their anisotropic structure can be used as unique building blocks for constructing advanced materials. In this article, we report the formation of hemispherical or truncated polystyrene/nanosaponite composite particles via one‐pot miniemulsion polymerization. It was found that the morphology of final composite latex particles strongly depends on the size of the nanoclay and its surface properties. Hemisphere or truncated sphere is the dominant morphology if the size of the nanoclay is larger than 100 nm. With the increase of the nanoclay content (up to 30 wt %), the fraction of hemispherical or truncated polystyrene/nanosaponite composite latex particles increased accordingly. The formation of hemispherical particles is possibly attributed to either the asymmetric growth of polymer chains on one side of the hydrophobically modified clay or the mechanical peeling‐off of large spherical particles between polymer and saponite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Background The intracellular suppressor of cytokine signaling (SOCS)-proteins are inducible and negative regulators in receptor signaling pathways of several cytokines, toll-like receptor ligands and some growth factors. We previously have shown in mice that SOCS3 is expressed in chondrocytes during arthritis [1]. Furthermore, SOCS3 overexpression inhibits the insulin-like growth factor (IGF)-1 response, the main anabolic factor for chondrocytes. Objectives To determine the expression and functional consequnces of SOCS3 in human articular chondrocytes. Methods Chondrocytes were isolated from articular cartilage of patients undergoing surgical joint replacement. The human immortalized chondrocyte cell line G6, human mesenchymal stem cell (MSC)-differentiated chondrocytes, and primary bovine chondrocytes were used for comparison. SOCS3 mRNA and protein levels were measured by quantitative PCR, western blotting and immunohistochemistry, respectively. Regulation of SOCS3 expression was examined following incubation with different cytokines and Toll-like receptor (TLR) agonists. To determine the effect of SOCS3 on the chondrocyte response to various stimuli, SOCS3 was either reduced by an inhibitor of SP1 (Mithramycin) or with short interference RNA, and enhanced by adenoviral transduction. Results The expression of SOCS3 was significantly enhanced in chondrocytes obtained from cartilage of osteoarthritis (OA) (ΔCt 3.4±1.0, n=18 patients) and rheumatoid arthritis (RA) (ΔCt 3.4±1.4, n=6) as compared to and healthy cartilage from fractures of neck of femur (NOF) patients (ΔCt 5.3±1.2, n=8). The expression of SOCS3 correlated markedly with other genes known to be expressed in arthritic chondrocytes such as RUNX2 (r=0.341), MMP13 (r=0.511), ADAMTS4 (r=0.779), and ADAMTS5 (r=0.647). No correlation was found with aggrecan expression and an inverse relationship was found with the collagen-type II gene Col2A1 (r=0.577). Western blots and imunohistochemisty confirmed the enhanced expression of SOCS3 at the protein level in arthritic cartilage. The expression of SOCS1 in chondrocytes was low and similar between the different patient groups. The expression of SOCS3 in the immortalized human chondrocyte cell-line (G6) and MSC-derived chondrocytes could be enhanced by interleukin-1 and conditioned medium of OA synovium explants. This was dependent on the transcription factor SP1 as the specific inhibitor mithramycin prevented SOCS3 upregulation in these cells. Forced expression of SOCS3 in bovine chondrocytes impairs several aspects of chondrocyte function, including nitiric oxide production and proteoglycan synthesis. Interestingly, a similar impairment of function was found in OA chondrocytes and knockdown of SOCS3 in these chondrocytes partially restored human chondrocyte function. Conclusions This study demonstrates that SOCS3 is highly expressed in human articular chondrocytes and affects cellular responses, which may have important implications for cartilage pathology in humans. References Smeets RL, Veenbergen S, Arntz...