Lactadherin and procoagulant activities of red blood cells in cyclosporine induced thrombosis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The side effects of cyclosporine therapy include thromboembolic complications. However, the mechanisms underlying the hypercoagulable state induced by cyclosporine are not fully understood. Cyclosporine binds to red blood cells (RBCs) with a high affinity in circulation and alters the membranes of RBCs. Therefore, we propose that such alterations in RBCs membranes play a role in cyclosporine-induced coagulopathy and this disorder may be rectified by lactadherin, a phosphatidylserine binding protein.</p><p><b>METHODS</b>RBCs from healthy adults were treated with various concentrations of cyclosporine. Procoagulant activity of the RBC membrane was measured by the single stage recalcification time and confirmed by detection of tenase and thrombin assembly through enzymatic assays. Inhibition assays of coagulation were carried out in the presence of lactadherin, annexin V or antitissue factor. Phosphatidylserine exposure was detected by flow cytometry and confocal microscopy through binding with fluorescein isothiocyanate (FITC)-labeled lactadherin as well as FITC annexin V.</p><p><b>RESULTS</b>RBCs treated with cyclosporine demonstrated increased procoagulant activity. Cyclosporine treatment markedly shortened the clotting time of RBCs ((305 +/- 10) seconds vs (366 +/- 15) seconds) and increased the generation of intrinsic factor Xase ((7.68 +/- 0.99) nmol/L vs (2.86 +/- 0.11) nmol/L) and thrombin ((15.83 +/- 1.37) nmol/L vs (4.88 +/- 0.13) nmol/L). Flow cytometry and confocal microscopy indicated that cyclosporine treatment induced an increased expression of phosphatidylserine on the RBC membrane. Lactadherin was more sensitive in detecting phosphatidylserine exposure of the RBC membrane than annexin V. The modulating effect of procoagulant activity was concomitant with and dependent on phosphatidylserine exposure. Blocking of phosphatidylserine with lactadherin effectively inhibited over 90% of FXa generation and prothrombinase activity and prolonged coagulation time.</p><p><b>CONCLUSIONS</b>Procoagulant properties of RBCs membranes resulting from phosphatidylserine exposure may play an important role in cyclosporine-induced thrombosis. Lactadherin can be used as a sensitive probe for phosphatidylserine detection. Its high affinity for phosphatidylserine may provide a new approach for the treatment of cyclosporine induced thrombogenic properties.</p>

The mechanism of arsenic trioxide on apoptosis of human flbroblast-like synoviocytes of rheumatoid arthritis / 中华风湿病学杂志

Objective To observe the effects of arsenic trioxide (ATO) on apoptosis of human fibrob- last-like synoviocytes of rheumatoid arthritis (HFLS-RA) and to study the mechanism.Methods HFLS-RA were cultured with standard medium as control group or with mediums supplemented with 0.5,2,8?mol/L ATO respectively.The apoptosis of HFLS-RA cultured for 72 h with different concentrations of ATO were in- vestigated under electron microscope.Apoptosis exponent was measured by terminal deoxynucleotidyl transf erase-mediated dUTP nick-end labeling (TUNEL).To detect the proliferation of HFLS-RA euhured with ATO,MTr assay were carded out in 5 consecutive days.Moreover,the NF-kB mRNA level of HFLS-RA was measured by RT-PCR after treated with ATO for 24 h.Results ATO induced the apoptosis of HFLS-RA. Apoptosis exponent was increased in a dose dependent manner in TUNEL experiment,especially in the cells treated with 2 and 8?mol/L ATO (P＜0.05).HFLS-RA proliferation was inhibited in both dose and time de- pendent manner when cultured with ATO.Meanwhile,the NF-kB mRNA level was decreased in ATO treated groups,which was especially significant in mediums cultured in higher than 2?mol/L ATO (P＜0.05).Con- clusion ATO depresses the proliferation of HFLS-RA and may increase the apoptosis by decreasing the ex- pression of NF-kB mRNA.These findings suggest that ATO have the potential to be a novel therapeutic agents for rheumatoid arthritis.