Abnormal regulation of soluble and anchored IL-6 receptor in monocytes from patients with essential thrombocythemia.
OBJECTIVE
In a previous study, we found increased plasma soluble receptor for interleukin-6 (sIL-6R) levels in patients with essential thrombocythemia (ET) that could promote megakaryopoiesis through IL-6 binding and further interaction with the signal transducer gp130. Here we have searched for the cell source of sIL-6R within mononuclear cells in these patients and the underlying abnormalities involved in its overproduction.


METHODS
Thirty patients with the diagnosis of ET were studied. sIL-6R levels were measured by enzyme-linked immunosorbent assay technique in the supernatants of peripheral monocyte and lymphocyte cultures. Expression of membrane-anchored IL-6R was determined by flow cytometry. In order to study the mechanism of sIL-6R production, tumor necrosis factor-α protease inhibitor was added to specifically block IL-6R shedding. Gene expression of sIL-6R levels were evaluated by reverse transcription polymerase chain reaction.


RESULTS
Monocytes were the main source of sIL-6R. Besides, in ET patients, monocyte sIL-6R release was higher than that of controls (p = 0.0014). Lymphocytes enhanced monocyte sIL-6R production by cell-mediated contact in normal controls, but this cooperation could not be seen in patients. Membrane expression of IL-6R was increased after monocyte adhesion in ET. sIL-6R synthesis was upregulated in most patients, while messenger RNA was normal.


CONCLUSIONS
Our results indicate that ET monocytes are responsible for sIL-6R overproduction within mononuclear cells through synthesis upregulation. In addition, the lack of cooperation of lymphocytes in monocyte sIL-6R production in ET could be due to a monocyte abnormality. The agonistic effect of sIL-6R on IL-6 action could contribute to the exacerbated megakaryocytic growth in ET.
Goette
Nora P
NP
Sección Hematología Investigación, UE IDIM-CONICET, Instituto Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina. npgoette@gmail.com
Lev
Paola R
PR
Heller
Paula G
PG
Glembotsky
Ana C
AC
Chazarreta
Carlos D
CD
Salim
Juan P
JP
Molinas
Felisa C
FC
Marta
Rosana F
RF
D000293:Adolescent; D000328:Adult; D000368:Aged; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D053614:Janus Kinase 2 / Q000235:genetics; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000378:metabolism*; D009154:Mutation; D019947:Receptors, Interleukin-6 / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012995:Solubility; D013920:Thrombocythemia, Essential / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
C508603:IL6R protein, human; D019947:Receptors, Interleukin-6; C507924:JAK2 protein, human; D053614:Janus Kinase 2