Biocompatibility of Polysulfone Hemodialysis Membranes and Its Mechanisms: Involvement of Fibrinogen and Its Integrin Receptors in Activation of Platelets and Neutrophils.

Activation of blood cells during hemodialysis is considered to be a significant determinant of biocompatibility of the hemodialysis membrane because it may affect patient health adversely through microvascular inflammation and oxidative stress. This study found very different cell activation among various polysulfone (PSf) hemodialysis membranes. For example, CX-U, a conventional PSf membrane, induced marked adhesion of platelets to its surface and increased surface expression of activated CD11b and production of reactive oxygen species (ROS) by neutrophils; while NV-U, a hydrophilic polymer-immobilized PSf membrane, caused little platelet adhesion and slight CD11b expression and ROS production by neutrophils. Analysis of the molecular mechanisms of the above phenomena on CX-U and NV-U indicated that anti-integrin GPIIb/IIIa antibody blocked platelet adhesion, and that the combination of anti-CD11b (integrin α subunit of Mac-1) and anti-integrin αvß3 antibodies blocked ROS production by neutrophils. Plasma-derived fibrinogen, a major ligand of GPIIb/IIIa, Mac-1, and αvß3 on membranes, was thus analyzed and found to be more adsorbed to CX-U than to NV-U. Moreover, comparison between five PSf membranes showed that the number of adherent platelets and neutrophil ROS production increased with increasing fibrinogen adsorption. These results suggested that fibrinogen, adsorbed on membranes, induced GPIIb/IIIa-mediated platelet activation and Mac-1/αvß3-mediated neutrophil activation, depending on the amount of adsorption. In conclusion, the use of biocompatible membranes like NV-U, which show lower adsorption of fibrinogen, is expected to reduce hemodialysis-induced inflammation and oxidative stress by minimizing cell activation.

Design and synthesis of novel p38α MAP kinase inhibitors: discovery of pyrazole-benzyl ureas bearing 2-molpholinopyrimidine moiety.

The discovery that pyrazole-benzyl urea derivatives bearing a 2-molpholinopyrimidine moiety are novel p38α inhibitors is described. A comparative view of the binding modes of SB-203580 and BIRB-796 by structural alignment of two X-ray co-crystal structures was utilized to identify this novel series. Modification of the benzyl group led to compound 2b, a highly potent p38α inhibitor. In in vivo studies, 2b inhibited the production of tumor necrosis factor-alpha in lipopolysaccharide-treated mouse in a dose-dependent manner. Furthermore, the results of a 5-day repeated oral dose toxicity study suggest that 2b has low hepatotoxicity.

A new hydrophilic polysulfone hemodialysis membrane can prevent platelet-neutrophil interactions and successive neutrophil activation.

PURPOSE:: Microaggregates have often been observed during hemodialysis and are clearly associated with complications of hemodialysis therapy. In this study, we aimed to clarify the effects of two polysulfone membranes, with different abilities to activate blood cells, on the formation of these microaggregates; we also investigated their molecular mechanisms. METHODS:: Human whole blood was circulated through a mini-module dialyzer using the membranes in vitro; platelet-neutrophil complexes in blood were determined by flow cytometry. Isolated human neutrophils were incubated with the membranes in plasma, in the presence or absence of platelets, followed by flow cytometric analysis of intracellular reactive oxygen species and cell-surface activated CD11b on neutrophils. RESULTS:: CX-U, a conventional polysulfone membrane with remarkable cell activation, induced the formation of platelet-neutrophil complexes; however, NV-U, a new hydrophilic polysulfone membrane with slight or no cell activation, did not cause complex formation. Moreover, CX-U-induced reactive oxygen species production and the increase in activated CD11b expression on neutrophils were enhanced by platelets. On the other hand, NV-U hardly affected neutrophil activation, regardless of whether platelets were present or not. The enhancement of CX-U-induced neutrophil activations by platelets was greatly inhibited by anti-CD62P antibody. CONCLUSION:: The ability of polysulfone membranes to activate blood cells is closely related to platelet-neutrophil interaction. Therefore, a biocompatible membrane, like NV-U, can be expected to prevent microaggregate formation during hemodialysis and avoid subsequent cell activation.

Novel SIL1 mutations and exclusion of functional candidate genes in Marinesco-Sjögren syndrome.

Marinesco-Sjögren syndrome (MSS) is a rare autosomal recessively inherited neurodegenerative disorder characterized by cerebellar ataxia, cataracts, mental retardation, and progressive myopathy. Recently, mutations in the SIL1 gene, which encodes an endoplasmic reticulum (ER) resident cochaperone, were identified as a major cause of MSS. We here report four novel mutations in SIL1, including the first missense substitution p.Leu457Pro described in MSS. In addition, we excluded three functional candidate genes, HSPA5, HYOU1, and AARS, as causative genes in SIL1 mutation-negative patients. To understand the mechanisms of disturbed SIL1 function, we studied the subcellular localization of the missense mutant Leu457Pro protein in COS-1 cells. Moreover, we studied a mutant protein lacking the putative C-terminal ER retrieval signal. In contrast to the wild-type protein's localization to ER and Golgi apparatus, both mutant proteins formed aggregates within the ER depending on the expression level. These data imply that aggregation of mutant proteins may contribute to MSS pathogenesis. The genetic background of a subgroup of patients with MSS remains uncovered.