Peritoneal fibrosis is a frequent complication of peritoneal dialysis following repeated low grade inflammatory and pro-fibrotic insults. This pathological process may lead to ultrafiltration failure and eventually to the discontinuing of the therapy. Fibrosis is linked to epithelial to mesenchymal transition (EMT) of the peritoneal mesothelial cells, which acquire invasive and fibrogenic abilities. Here, we analyzed the role of the transforming growth factor-activated kinase-1 (TAK1) in the EMT of primary mesothelial cells from human peritoneum. The inhibition of TAK1 in mesenchymal-like mesothelial cells from the effluents of patients undergoing peritoneal dialysis led to the reacquisition of the apical to basolateral polarity, to increased expression of epithelial and to down-regulation of mesenchymal markers. TAK1 inhibition also resulted in decreased migratory/invasive abilities of effluent-derived mesothelial cells. Simultaneous inhibition of ERK1/2 and TAK1 pathways did not lead to an additive effect in the reacquisition of the epithelial phenotype. Inhibition of TAK1 also blocked EMT in vitro and reduced the levels of PAI-1, which is involved in fibrosis and invasion. Analysis of signalling pathways downstream of TAK1 involved in EMT induction, showed that TAK1 inhibition reduced the transcriptional activity of NF-κB and Smad3, as well as the phosphorylation of c-jun, while enhancing Smad1–5–8 activity. These results demonstrate that TAK1 is a cross-point in a network including different pro-EMT transcription factors, such as NF-κB, Snail, AP-1 and Smads. The identification of TAK1 as a main biochemical mediator of EMT and fibrosis in mesothelial cells from human peritoneum and the study of signalling pathways induced by its activity may be relevant in the design of new therapies aimed to counteract peritoneal fibrosis.

Platelet membrane glycoprotein Ib (GPIb) is a major receptor for von Willebrand factor and thrombin, which plays a key role in the initial development of thrombi. Two polymorphisms (HPA-2 and VNTR) that affect phenotype have been described in GPIb. The relevance of these polymorphisms to thrombotic disease was investigated by genotypic identification in three case-control studies: 104 case patients with acute cerebrovascular disease (CVD), 101 case patients with acute coronary heart disease (CHD), 95 patients with deep venous thrombosis (DVT), and one control age-, sex-, and race-matched for each case patient. Results show that the C/B genotype of the VNTR and the HPA-2b polymorphisms of GPIb are strongly associated with increased risk of coronary heart disease and cerebral vascular disease but not with deep vein thrombosis. These two polymorphisms of GPIb may represent newly identified risk factors for arterial thrombotic disease, but not for venous thrombosis.© 1998 by The American Society of Hematology.

SummaryThe platelet membrane glycoprotein (GP) Ibα plays a key role in the initial formation of thrombi. Polymorphisms (VNTR and HPA-2) in this receptor are associated with increased risk of coronary heart disease (CHD) and cerebral vascular disease (CVD). We investigated whether a recently described polymorphism (S/R), due to a single base change (T → C) five nucleotides upstream the initiator codon of GPIbα, might influence the expression of the protein, and be implicated in the development of arterial thrombosis.One hundred and thirty nine healthy individuals provided blood samples for DNA analysis of platelet GPIbα polymorphisms, and for flow cytometric analysis of the surface expression of the receptor. A group of 20 S/R normal individuals and an identical number of S/S participants, age and sex matched, was investigated for the analysis of the density of various platelet receptors. The distribution of the S/R polymorphism was also analyzed in two case/control studies including 104 CVD patients, 101 CHD patients, and one control age, sex, and environmental risk factors matched for each case patient. Surface density of GPIbα showed no wide variations between individuals, was not influenced by the presence of S or R alleles, nor associated with the VNTR or HPA-2 polymorphisms. The prevalence of the S/R genotype among CVD and CHD patients was not distinct from that in the control groups. We conclude that the S/R polymorphism of GPIbα, flanking the initiator codon of the receptor, does not seem to be associated with surface levels of the protein, and is not an independent risk factor for arterial thrombosis.