Interleukin-6 stimulates thrombopoiesis through thrombopoietin: role in inflammatory thrombocytosis by Arthur Kaser, Gerald Brandacher, Wolfgang Steurer, Susanne Kaser, Felix A. Offner, Heinz Zoller, Igor Theurl, Walter Widder, Clemens Molnar, Othmar Ludwiczek, Michael B. Atkins, James W. Mier, and Herbert Tilg Blood Volume 98(9):2720-2725 November 1, 2001 ©2001 by American Society of Hematology

Plasma TPO levels in IL-6–treated cancer patients. Plasma TPO levels in IL-6–treated cancer patients. Circulating TPO levels in patients during 5-day continuous IL-6 infusion. Patients received 30 mg/kg per day rhIL-6. Venous blood was drawn, and plasma was analyzed for huTPO synthesis by specific ELISA. Data are expressed as mean ± SEM for n = 6. *P < .05 compared to baseline levels. Arthur Kaser et al. Blood 2001;98:2720-2725 ©2001 by American Society of Hematology

TPO mRNA expression and TPO plasma levels in IL-6–treated mice. TPO mRNA expression and TPO plasma levels in IL-6–treated mice. (A) To evaluate the in vivo effect of IL-6 on TPO mRNA, mice were treated with 4 doses of 1 μg mIL-6 (IL-6) or PBS–0.5% BSA (Control) at 12-hour intervals. Twelve hours after the last dose, messenger RNA was prepared from the liver, gel-electrophoresed, blotted onto nylon membranes, and hybridized with radioactively labeled mTPO and β-actin cDNA. The figure is representative of 3 independent experiments. (B) Plasma TPO in IL-6–treated mice. Mice were treated with 1 μg mIL-6 (▴) or PBS–0.5% BSA (■) at 12-hour intervals for 6 consecutive days. Venous blood was drawn, and plasma was analyzed for mTPO synthesis by specific ELISA. Data are presented as percentage change compared to baseline (control group, 734 ± 90 pg/mL; IL-6 group, 571 ± 77 pg/mL) for n = 6 per group. *P < .05 compared to baseline. Arthur Kaser et al. Blood 2001;98:2720-2725 ©2001 by American Society of Hematology

TPO mRNA expression in IL-6–treated HepG2 cells. TPO mRNA expression in IL-6–treated HepG2 cells. (A) To determine the effect of IL-6 on TPO mRNA levels in vitro, HepG2 cells were cultured with increasing concentrations of huIL-6 for 12 hours, total RNA extracted, gel-electrophoresed, blotted onto nylon membranes, and hybridized with radioactively labeled huTPO and β-actin cDNA. The figure is representative of 3 independent experiments. (B) Nuclear run-off transcription in IL-6–treated HepG2 cells. Nuclei of HepG2 cells cultured with huIL-6 (1 ng/mL) or left untreated were prepared after 24 hours of stimulation. Purification of nuclei and in vitro transcription were performed as described in “Materials and methods.” The left panel shows a representative hybridization. Densitometric evaluation of the respective experiment is presented in the right panel in arbitrary units as counts × mm−2 [huTPO]/counts × mm−2[β-actin]. Arthur Kaser et al. Blood 2001;98:2720-2725 ©2001 by American Society of Hematology

Platelet counts in C57BL/10 mice. Platelet counts in C57BL/10 mice. Mice were treated with 1 μg mIL-6 (▴) or PBS–0.5% BSA (■) every 12 hours for 6 consecutive days. Additionally, mice were injected with 500 μg rabbit anti-TPO pAb (open symbols) or irrelevant control rabbit IgG (filled symbols, dashed line). Venous blood was drawn on day 1 (pretreatment) and every second day thereafter and was analyzed for platelet counts. Data are expressed as mean ± SEM for n = 3 per group. The increase in platelet counts in mIL-6–treated animals was significant (P < .05), as were the differences between mIL-6 and mIL-6 plus anti-TPO pAb-treated mice (P < .05). Arthur Kaser et al. Blood 2001;98:2720-2725 ©2001 by American Society of Hematology