IgE secretion is attenuated by an inhibitor of proteolytic processing of CD23 (FcεRII)

CD23, the low-affinity IgE receptor, is up-regulated on interleukin (IL)-4-stimulated B cells and monocytes, with a concomitant increase in the release of soluble fragments of CD23 (sCD23) into the medium by proteolytic processing of the surface-bound intact CD23. The effect of inhibition of the processing of CD23 on IgE production in human and mouse cells and in a mouse model in vivo was evaluated. CD23 processing to sCD23 from RPMI 8866 (a human Epstein-Barr virus-transformed B cell line) cell membranes was inhibited by a broad-spectrum matrix-metalloprotease inhibitor, batimastat, with an IC₅₀ of 0.15 μM. Batimastat also inhibited CD23 processing in whole RPMI 8866 cells as well as in IL-4-stimulated purified human monocytes with similar IC₅₀. Batimastat inhibited IgE production from IL-4/anti-CD40-stimulated human tonsil B cells as well as mouse splenic B cells in a manner consistent with inhibition of CD23 processing. Release of soluble fragments of CD23 in the cell supernatants of tonsil B cells was inhibited over the concentration range of 1–10 μM batimastat and intact cell surface CD23 was increased on mouse splenic B cells in the presence of these concentrations of batimastat. IgE production of IL-4-stimulated human peripheral blood mononuclear cells was also blocked by 1–10 μM batimastat, again with comparable inhibition of sCD23 release over the same concentration range. Finally, in a mouse model of IgE production, batimastat inhibited IgE production in response to ovalbumin challenge as determined by serum IgE levels. Taken together, the data support a role of CD23 in IgE production and point to CD23 processing to sCD23 as a therapeutically relevant control point in the regulation of IgE synthesis.     

Microbial and histopathological study of the vibriosis caused by Vibrio vulnificus serovar E in eels: the metalloprotease Vvp is not an essential lesional factor

Vibrio vulnificus biotype 2 serovar E (Bt2-serE) is a zoonotic pathogen that causes a haemorrhagic septicaemia in eels, called warm water vibriosis. The main objective of the present work was to study the onset of the eel vibriosis from the microbiological and histopathological viewpoint, as well as to ascertain the role of the protease Vvp as a lesional factor by comparing the histopathological lesions caused by the wild strain and its vvp deficient derivative. The wild-type strain was observed to attach to the gills, where it multiplied following saturation dynamics, subsequently invading the blood stream and reaching the internal organs. Here it reached population sizes that are notably lower than those associated with other fish septicaemia. Parallel to bacterial growth, there was a notable decrease in haematocrit values and haemoglobin concentration in blood as well as extensive haemorrhages in all the analysed organs. The main histopathological lesions were detected in the head kidney in the form of extensive necrosis affecting the haematopoietic tissue. Very few bacteria were visualized in the different organs, most of which were close to blood cells and capillary vessels, which is compatible with the results obtained in the microbiological study. The same lesions were produced when extracellular products (ECPs) were injected instead of bacteria or when the vvp-defective mutant or its ECPs were injected. The overall results suggest that the pathology caused by V. vulnificus in the eel is not caused by massive bacterial growth in the blood and internal organs but, rather, by the effect of potent toxic factors other than the metalloprotease, which have yet to be determined.     

Recombinant fragilysin isoforms cause E-cadherin cleavage of intact cells and do not cleave isolated E-cadherin

The fragilysin (BFT) is a protein secreted by enterotoxigenic Bacteroides fragilis strains. BFT contains zinc-binding motif which was found in the metzincins family of metalloproteinases. In this study, we generated three known recombinant isoforms of BFT using Escherichia coli, tested their activity and examined whether E-cadherin is a substrate for BFTs. BFT treatment of HT-29 cells induced endogenous E-cadherin cleavage, and this BFT activity requires the native structure of zinc-binding motif. At the same time recombinant BFTs did not cleave recombinant E-cadherin or E-cadherin in isolated cell fractions. It indicates that E-cadherin may be not direct substrate for BFT. We also detected and identified proteins released into the cultural medium after HT-29 cells treatment with BFT. The role of these proteins in pathogenesis and cell response to BFT remains to be determined.     

Ⅰ型血小板结合蛋白基序的解聚蛋白样金属蛋白酶的研究进展

Ⅰ型血小板结合蛋白基序的解聚蛋白样金属蛋白酶(ADAMTS)是一种新型Zn2+依赖的分泌型金属蛋白酶。近来,ADAMTS的结构分析显示,凝血敏感蛋白的超甲基化使得癌基因、抑癌基因和mRNA的稳定性发生了改变,并在关节炎发生中与软骨聚集蛋白聚糖水解有关。补体-纤维-骨变形蛋白结构域CUB参与vWF剪切,与血小板减少性紫癜发生有关。这些进展都为今后的疾病诊断和治疗提供新的思考方向。