Protein disulfide isomerase-A1 regulates intraplatelet reactive oxygen species-thromboxane A2 -dependent pathway in human platelets

BACKGROUND

Platelet-derived protein disulfide isomerase 1 (PDIA1) regulates thrombus formation, but its role in the regulation of platelet function is not fully understood.

AIMS

The aim of this study was to characterize the role of PDIA1 in human platelets.

METHODS

Proteomic analysis of PDI isoforms in platelets was performed using liquid chromatography tandem mass spectometry, and the expression of PDIs on platelets in response to collagen, TRAP-14, or ADP was measured with flow cytometry. The effects of bepristat, a selective PDIA1 inhibitor, on platelet aggregation, expression of platelet surface activation markers, thromboxane A2 (TxA2 ), and reactive oxygen species (ROS) generation were evaluated by optical aggregometry, flow cytometry, ELISA, and dihydrodichlorofluorescein diacetate-based fluorescent assay, respectively.

RESULTS

PDIA1 was less abundant compared with PDIA3 in resting platelets and platelets stimulated with TRAP-14, collagen, or ADP. Collagen, but not ADP, induced a significant increase in PDIA1 expression. Bepristat potently inhibited the aggregation of washed platelets induced by collagen or convulxin, but only weakly inhibited platelet aggregation induced by TRAP-14 or thrombin, and had the negligible effect on platelet aggregation induced by arachidonic acid. Inhibition of PDIA1 by bepristat resulted in the reduction of TxA2 and ROS production in collagen- or thrombin-stimulated platelets. Furthermore, bepristat reduced the activation of αIIbβ3 integrin and expression of P-selectin.

CONCLUSIONS

PDIA1 acts as an intraplatelet regulator of the ROS-TxA2 pathway in collagen-GP VI receptor-mediated platelet activation that is a mechanistically distinct pathway from extracellular regulation of αIIbβ3 integrin by PDIA3.

The impact of multiple sclerosis relapse treatment on migration of effector T cells--Preliminary study

Migration of inflammatory cells from the blood to the central nervous system (CNS) is crucial for development of multiple sclerosis (MS). Inhibition of this process would allow to control disease activity. The first step confirming this approach would be the analysis of the impact of effective MS relapse therapy on migration of effector T cells. The aim of the study was to analyze the influence of methylprednisolone (MP) on the migratory activity of effector CD4+ T cells from MS patients. Moreover, to study the potential mechanism of this process we studied expression of chemokine receptors on migrating cells.

MATERIAL AND METHODS

Peripheral blood samples were obtained from relapsing-remitting MS (RR-MS) patients during relapse (n=23) and from control group (n=23). After isolation CD4+ T cells were incubated with various concentrations of MP. Then they were stimulated in chemotaxis assay with chemokines CCL3 or CXCL10 or were used to CCR1 and CXCR3 expression analysis.

RESULTS

CXCL10- and CCL3-stimulated migration of CD4+ T cells was significantly increased in MS. MP was able to reduce in vitro migration of effector T cells induced by CXCL10, but not by CCL3. Inhibition by MP was dose-dependent. Expression of analyzed chemokine receptors was unaltered after MP incubation.

CONCLUSIONS

MP reduced CD4+ T cells migration induced by CXCL10 without affecting CXCR3 expression. These observations demonstrate one of the potential mechanisms of MP action in MS, distinct from inducing cell apoptosis, and suggests the new targets for development of more effective MS treatments.