Role of transforming growth factor ?1 in microvascular endothelial cell apoptosis associated with thrombotic thrombocytopenic purpura and hemolytic-uremic syndrome

Abstract

Primary human microvascular endothelial cells (MVEC) of restricted lineage undergo apoptosis when exposed to plasma from patients with thrombotic thrombocytopenic purpura (TTP) and sporadic hemolytic-uremic syndrome (HUS). This reflects the pathology and tissue distribution of lesions in vivo. As extracellular matrix (ECM) is critical to MVEC survival, and cytokines which regulate ECM, such as transforming growth factor (TGF)-beta1, have been reported anecdotally to be altered in TTP/HUS, we examined the role of TGF-beta1 and two ECM proteins, fibronectin and thrombospondin (TSP), in these disorders. Levels of active TGF-beta1 were elevated in acute but not convalescent phases of TTP/sporadic HUS, as well as TTP associated with human immunodeficiency virus infection and use of the anti-platelet drug ticlopidine. MVEC from tissues susceptible to TTP-mediated apoptosis showed little active TGF-beta1 production when exposed to TTP plasmas. In contrast, pulmonary MVEC and large-vessel EC, which are resistant to TTP-linked pathology, showed marked induction of TGF-beta1 following TTP plasma exposure. Exogenous TGF-beta1 suppressed TTP plasma-mediated apoptosis in susceptible MVEC in association with blockade of cell entry into S phase. Soluble TSP, devoid of detectable bound TGF-beta1, had a similar effect, which paralleled its ability to induce TGF-beta1 production in MVEC. In vivo, TSP deposition was diminished markedly in involved tissues of TTP patients. These data highlight the role of TGF-beta1 and ECM in TTP and suggest that differential production of TGF-beta1 by MVEC may play a role in their sensitivity or resistance to TTP/sporadic HUS-mediated apoptosis in vitro and in vivo.

Synergistic interactions between interferon-γ and TRAIL modulate c-FLIP in endothelial cells, mediating their lineage-specific sensitivity to thrombotic thrombocytopenic purpura plasma–associated apoptosis

“…We found no difference in circulating TNF-␣ levels between patients with TTP (1.32 Ϯ 0.29 pg/mL) and controls (1.19 Ϯ 0.35 pg/mL; P ϭ .14), nor was there a difference in IFN-␥ plasma levels (mean, 1.08 Ϯ 0.18 pg/mL for patients vs 1.09 Ϯ 0.11 pg/mL for controls; P ϭ .87). The levels of IFN-␥ and TNF-␣ for our patients are somewhat lower than those seen in other TTP cohorts (mean circulating IFN-␥, 6.5 pg/mL 8 and 14 pg/mL [range, 0-28 pg/mL]) 6 ; mean TNF-␣ of 11.4 pg/mL 8 and 5.2 pg/mL (range, 0-36.8 pg/mL) 25 ). TRAIL has not previously been investigated in TTP.…”

Transforming growth factor-β1 protects against pulmonary artery endothelial cell apoptosis via ALK5

“…Several studies suggest that TGF-␤1 causes endothelial cell apoptosis (29,42,46). Others demonstrate that TGF-␤1 promotes endothelial cell survival (27,35,43) and protects against hypoxia-induced endothelial cell apoptosis (19). The seemingly controversial findings suggest that the role of TGF-␤1 in endothelial cell apoptosis may be cell type specific.…”

Thienopyridine‐linked thrombotic microangiopathy: association with endothelial cell apoptosis and activation of MAP kinase signalling cascades

“…Endothelial cells (3 × 10 6 /condition) were pelleted, resuspended in cold PBS containing 2 mmol/l EDTA, 2 mmol/l EGTA and 0·2 mmol/l phenylmethylsulphonyl fluride (PMSF), microcentrifuged, and cell pellets resuspended in 0·1 ml extraction buffer (1% NP‐40, 150 mmol/l NaCl, 10 mmol/l Tris–HCl, pH 7·5, 2 mmol/l EDTA, 2 mmol/l EGTA, and the protease inhibitors leupeptin, aprotinin, pepstatin and PMSF). After incubation for 30 min on ice, extracts were centrifuged at 13 000 g for 15 min, subjected to 7·5% sodium dodecyl sulphate‐polyacrylamide gel electrophoresis, and immunoblotting performed, as described (Mauro et al , 2001). Rabbit anti‐44/42 ERK‐1/2 antibody and murine monoclonal anti‐phospho‐p44/42 ERK‐1/2 antibody were used at 1:1000 and 1:2000 dilutions respectively.…”

“…Thirdly, it has been postulated that VWF multimer size may be under the control not only of ADAMTS13, but also of TSP‐1, which could act as a disulphide bond reductase through its properdin type 1 domains (Xie et al , 2001). In TTP/sporadic HUS, plasma and tissue levels of TSP‐1 are markedly suppressed (Mauro et al , 2001; Xie et al , 2001), and antibodies against the TSP‐1 receptor CD36 have been seen in TTP (Schultz et al , 1998). Alterations in TSP‐1 may also modify the clinical phenotype of TTP (Pimanda et al , 2003).…”