Published online 1 October 2009
Haematologica, Vol 94, Issue 11, 1603-1607 doi:10.3324/haematol.2009.007708
Copyright © 2009 by Ferrata Storti Foundation
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Platelet Disorders

High-dose dexamethasone regulates interleukin-18 and interleukin-18 binding protein in idiopathic thrombocytopenic purpura

Ning-ning Shan1,2, Xiao-juan Zhu1, Qian Wang2, Chun-yan Wang1, Ping Qin1, Jun Peng1,3, Ming Hou1,3

1 Haematology Oncology Centre, Qilu Hospital, Shandong University, Jinan
2 Department of Clinical Laboratory, Qilu Hospital, Shandong University, Jinan
3 The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital, Shandong University, Jinan, China

Correspondence: Ming Hou, M.D., Ph.D. Haematology Oncology Centre, Qilu Hospital, Shandong University, 107 West Wenhuaxi Rd, Jinan, Shandong 250012. E-mail:houming{at}medmail.com.cn

To evaluate the effects of high-dose dexamethasone (HD-DXM) on the balance of interleukin-18 (IL-18) and its endogenous antagonist IL-18 binding protein (IL-18BP) in ITP patients, IL-18, IL-18BP as well as IFN-{gamma}, IL-4 plasma levels and platelet counts were determined in 17 ITP patients receiving DXM 40 mg/day for four consecutive days and in 24 healthy subjects. Using RT-PCR, the mRNA expression of IL-18, IL-18BP, IFN-{gamma}, IL-4, T-box (T-bet) and GATA-binding protein 3(GATA-3) were studied in all subjects. The in vitro effects of DXM on IL-18BP and IL-18 of peripheral blood mononuclear cells (PBMCs) were studied by ELISA. HD-DXM administration increased IL-18BP and reduced IL-18 expression significantly (p<0.05), which resulted in a downregulation of IL-18/IL-18BP ratio p<0.05). In vitro, DXM had a significant effect on secretion of IL-18BP while diminishing IL-18 release from cultures of PBMCs. These results suggest that downregulation of IL-18/IL-18BP might account for its clinical efficacy of HD-DXM in active ITP.

Key words: interleukin-18, interleukin-18 binding protein, high-dose dexamethasone, idiopathic thrombocytopenic purpura.