Eculizumab effect on the hemostatic state in patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by a hypercoagulable state associated with acute hemolysis. Eculizumab is used to reduce the intensity of intravascular hemolysis in PNH patients. The hemostatic status of three patients with PNH was assessed during eculizumab treatment by D-dimer assay and the global assays: thromboelastography (TEG), thrombin generation test (TGТ), and thrombodynamics (TD). In the state of hemolytic crisis before the therapy D-dimer concentration was increased in two patients accompanied by hypercoagulation changes in TEG parameter angle (α). TD parameter the clot growth velocity (V) revealed hypercoagulability while TGT parameter ETP was within the normal range in all patients. The lactate dehydrogenase (LDH) activity decreased during the 8months of eculizumab therapy. The physical health was improved, the frequency of hemolytic crisis decreased. Patients periodically exhibited hypercoagulable state: the mean values α=38±11° (with normal range 20-40°), ETP=1311±442nM·min (with normal range 800-1560nM·min), V=31±4µm/min (with normal range 20-29µm/min). During the eculizumab therapy two patients had the repeated clinical manifestation of acute hemolytic crisis, the parameters of the global tests were increased compared to the previous measurement. The global hemostasis tests TEG, TGT and TD revealed hypercoagulability in patients with PNH during eculizumab therapy.

[Study of NO action on calcium-activated potassium channel of the rat artery smooth muscle cells]. / Issledovanie deistviia NO na kal'tsii-aktiviruemyi kalievyi kanal gladkomyshechnykh kletok arterii krysy.

Nitric oxide (NO) released from the endothelium or from NO-donors is a powerful vasodilator. Its effect is mediated partly by vascular smooth muscle high conductance calcium-activated potassium (Kca) channels. Contradictory data exist as to whether NO activated the KCa channel directly or indirectly via protein kinase G (PKG). Thus the hypothesis that NO-donors can activate the KCa directly was investigated using the patch-clamp technique and freshly isolated smooth muscle cells from the rat tail artery. In inside-out experiments, the activity of KCa-channels was increased 1.61 +/- 0.20-fold (n = 10) by 10 microM SNP and 1.45 +/- 0.17-fold (n = 8) by 10 microM SNAP. However, the activity of KCa channels was also increased 1.46 +/- 0.20-fold (n = 8) by addition of the experimental bath solution. Thus these results suggest that NO released from NO-donors cannot activate KCa channel of the rat tail artery smooth muscle cells directly.

[Nitric oxide activates Ca2+ activated potassium current in rat tail artery smooth muscle cells via cGMP-dependent mechanism]. / NO aktiviruet vykhodiashchii Ca2+-aktiviruemyi K+-tok gladkomyshechnykh kletok khvostovoi arterii krysy cherez cGMP-zavisimyi mekhanizm.

Mechanisms of nitric oxide (NO) action on K(Ca) channels were investigated using patch-clamp technique and freshly isolated smooth muscle cells from rat tail artery. In whole-cell experiments, the outward current was increased 6,64-/+0,72-fold (n=10) by 100 microM sodium nitroprusside (SNP), which was significantly different compared with 1,07-/+0,03-fold (n=8) increase of the outward current by addition of experimental bath solution. In the presence of 300 nM iberiotoxin, the specific blocker of K(Ca) channels, the outward current was not altered by 100 microM SNP. In addition, in the presence of 1 microM Rp-8-Br-PET-CGWS, the specific protein kinase G-inhibitor, the outward current was not affected by 100 microM SNP. These results suggest that NO released from NO-donors stimulates K(Ca) current in rat tail artery smooth muscle cells by activating protein kinase G and not by direct effect on the channel 1.