Semisynthetic supra plasma expanders: a new class of therapeutics to improve microcircualtion in sickle cell anaemia.

Compromised microcirculation and endothelial dysfunction are hallmarks of sickle cell disease (SCD). EAF PEG Haemoglobin (Hb) and EAF PEG Albumin (Alb) represent a novel class of semisynthetic colloidal supra plasma expanders that improve microcirculation. The therapeutic activity of supra plasma expanders to attenuate vaso-occlusion and restore the haemodynamic functions in patients with SCD has been investigated using NY1DD, a transgenic mouse model of mild SCD without anaemia. Vaso-occlusion and perturbation of haemodynamics are amplified in NY1DD by hypoxia-reoxygenation protocol. EAF P5K6 Alb and Alb T12 (Alb conjugated with 12 copies of antioxidant tempo) attenuate vaso-occlusion when infused at the start of reoxygenation. However, only EAF PEG Alb restores haemodynamics close to levels in control C57BL. EAF P5K6 Alb-T12, active plasma expander conjugated with antioxidant, completely clears vaso-occlusion and restores normal haemodynamics. EAF PEG Hb also completely clears vaso-occlusion and restores normal haemodynamics. Pretreating NY1DD with EAF PEG Hb protects it from hypoxia reoxygenation-induced damages. EAF P5K6 Alb T12 attenuates the endothelial dysfunction in S + S Antilles mice as reflected by the vasodilatory response of its arteries and arterioles to vaso-dilators. Active plasma expanders are novel therapeutics to restore normal haemodynamics in SCD patients to improve tissue oxygenation during episodes of painful vaso-occlusive crisis. Abbreviations: 2-IT: 2-immothiolane; Mal-T: 4-Maleimido tempo; Alb: human serum albumin (HSA); Alb-T12: human albumin conjugated with 12 copies of tempo; EAF: extension arm facilitated; EAF PEG Hb: extension arm facilitated PEGylated haemoglobin; EAF PEG Alb: extension arm facilitated PEGylated albumin; EAF P3K6 Hb: extension arm facilitated PEGylated haemoglobin conjugated with 6 copies of PEG3K; EAF P5K6 Alb T12: extension arm facilitated PEGylated albumin conjugated with 6 copies of PEG5K and 12 copies of tempo; Hb: haemoglobin; HAS: human serum albumin (Alb); PEG: polyethylene glycol; MP4: MalPEG Hb, is formulated at 4.2 g/dL in lactated Ringer's solution, a product of Sangart; SCD: sickle cell disease; NO: nitric oxide; SEC: size exclusive chromatography; Vrbc: red cell velocity; Q: volumetric flow rates, Q; SNP: sodium nitroprusside.

Inhibition of tumor necrosis factor alpha-mediated NFkappaB activation and leukocyte adhesion, with enhanced endothelial apoptosis, by G protein-linked receptor (TP) ligands.

Tumor necrosis factor (TNF) alpha is a critical mediator of inflammation; however, TNFalpha is rarely released alone and the "cross-talk" between different classes of inflammatory mediators is largely unexplored. Thromboxane A(2) (TXA(2)) is released during I/R injury and exerts its effects via a G protein-linked receptor (TP). In this study, we found that TXA(2) mimetics stimulate leukocyte adhesion molecule (LAM) expression on endothelium via TPbeta. The potential interaction between TXA(2) and TNFalpha in altering endothelial survival and LAM expression was examined. IBOP, a TXA(2) mimetic, attenuated TNFalpha-induced LAM expression in vitro, in a concentration-dependent manner, by preventing TNFalpha-enhanced gene expression, and also reduced TNFalpha-induced leukocyte adhesion to endothelium both in vitro and in vivo. IBOP abrogated TNFalpha-induced NFkappaB activation in endothelial cells, as determined by reduced IkappaB phosphorylation and NFkappaB nuclear translocation, by inhibiting the assembly of signaling intermediates with the intracellular domain of TNF receptors 1 and 2 in response to TNFalpha. This inhibition resulted from the Galpha(q)-mediated enhancement of STAT1 activation and was reversed by anti-STAT1 antisense oligonucleotides. TNFalpha-mediated TNFR1-FADD association and caspase 8 activation were not inhibited by IBOP co-stimulation, however, resulting in a 2.6-fold increase in endothelial cell apoptosis. By stimulating the vessel wall and inducing endothelial cell apoptosis, TXA(2), in combination with TNFalpha, may hamper the angiogenic response during inflammation or ischemia, thus reducing revascularization and tissue viability.