Pharmacokinetics of [125I]-recombinant human interleukin-11: 1. Absorption, distribution and excretion after subcutaneous administration to male rats

Absorption, distribution, metabolism and excretion of [125I]-rhIL-11 (recombinant human interleukin-11) after subcutaneous administration in rats were investigated. After a single administration, the concentration of radioactivity in the tissues was 2-6-fold higher in the liver and kidneys, and slightly higher in the gastrointestinal tract as compared to the plasma concentration. However, since the concentration in the other tissues was lower than the plasma concentration, the transport of rhIL-11 into tissues appeared to be low. Tissue radioactivity rapidly diminished, thus accumulation of rhIL-11 in tissues was thought to be low. Excretion of radioactivity into urine and feces was almost complete 72 h after administration, with 88.5% of the dosed radioactivity being found in urine and 7.9% in feces. When [125I]-rhIL-11 was administered to bile-duct cannulated rats, 44.4% of the dosed radioactivity was excreted into bile up to 48 h after administration. Most radioactivity in bile and urine was found in the TCA supernatant and low molecular weight fraction by HPLC analysis, indicating that rhIL-11 was eliminated from the body by metabolism.

Blood thrombopoietin, IL-6 and IL-11 levels in patients with agnogenic myeloid metaplasia

Agnogenic myeloid metaplasia (AMM) is a disease characterized by bone marrow megakaryocyte hyperplasia and clusters of megakaryocytes, in which many of the megakaryocytes are atypical. In order to elucidate the mechanisms of megakaryocytosis, ELISA assays of blood levels of thrombopoietin (TPO), interleukin-6 (IL-6) and interleukin-11 (IL-11) were done in 45 patients with AMM and compared with normal volunteer controls. Higher blood TPO levels were found in AMM than in controls (P < 0.0001), and blood TPO levels were correlated with the degree of marrow fibrosis (P = 0.0078). Blood levels of IL-6 were also significantly higher in AMM, when compared with controls (P < 0.0001). However, no correlation was found between blood IL-6 levels and degree of marrow fibrosis. No correlation was found between either TPO or IL-6 and the number of blood platelet counts, the number of marrow megakaryocytes, WBC counts, or the degree of splenomegaly. Blood IL-11 levels were undetectable in most patients and no significant difference was found in AMM as compared to controls. The present study demonstrated that, while in idiopathic thrombocytopenic purpura (ITP) or aplastic anemia, blood TPO levels are relatively correlated with the numbers of platelet and/or megakaryocyte mass, blood TPO levels do not correlate with blood platelet counts, or marrow megakaryocyte mass in AMM. Therefore, in AMM, other mechanisms such as the number of TPO receptors on platelets or megakaryocytes, c-MPL receptor abnormalities, abnormal production of TPO mRNA and so on, will have to be studied. Furthermore, TPO may play a significant role in the pathogenesis of marrow fibrosis; IL-6 may be a factor in the development of marrow megakaryocytosis but its elevated blood levels may represent a secondary immune phenomenon; and IL-11 probably does not play a significant role in causing marrow megakaryocytosis in this disease.

Thrombopoietin in patients with congenital thrombocytopenia and absent radii: elevated serum levels, normal receptor expression, but defective reactivity to thrombopoietin

The pathophysiology of thrombocytopenia in the syndrome of thrombocytopenia with absent radii (TAR) is not yet understood. We examined thrombopoietin (TPO) serum levels and the in vitro reactivity of platelets to TPO in five patients affected with TAR syndrome. We found elevated TPO serum levels in all patients tested, excluding a TPO production defect as cause for thrombocytopenia in TAR syndrome. In addition, we found similar expression of the TPO receptor c-Mpl on the surface of platelets from TAR patients (5 of 5) and a similar molecular weight of the receptor as compared with healthy controls (4 of 4). Platelet response to adenosine diphosphate or thrombin receptor agonist peptide SFLLRN (TRAP) was normal in TAR patients. However, in contrast to results with healthy controls we could show absence of in vitro reactivity of platelets from TAR patients to recombinant TPO as measured by testing TPO synergism to adenine diphosphate and TRAP in platelet activation. TPO induced tyrosine phosphorylation of platelet proteins was completely absent (3 of 4) or markedly decreased (1 of 4). Our results indicate that defective megakaryocytopoiesis/thrombocytopoiesis in TAR syndrome is not caused by a defect in TPO production but a lack of response to TPO in the signal transduction pathway of c-Mpl.

Serum thrombopoietin and interleukin 6 concentrations in tumour patients and response to chemotherapy-induced thrombocytopenia

The relation between the number of platelets in blood and the concentrations of immunoreactive thrombopoietin (TPO), interleukin 6 and interleukin 11 (IL-6, IL-11) was studied in the sera of 32 normal subjects, of 29 untreated tumour patients and of 6 tumour patients following chemotherapy with ifosfamide, carboplatin and etoposide (ICE). Platelet counts, TPO and IL-6 concentrations were higher than normal in blood of tumour patients before chemotherapy. However, no statistical relation existed between these variables. Following chemotherapy, the number of circulating platelets decreased reaching a nadir at d 10-13, while the serum concentration of TPO increased concomitantly. Circulating IL-6 did not increase during chemotherapy-induced thrombocytopenia. IL-11 was not detectable in any serum. Thus, the reactive thrombocytosis in tumour patients could be related to elevated TPO and IL-6 levels. In contrast to circulating TPO, however, neither serum IL-6 nor IL-11 levels increase significantly in thrombocytopenia following myelosuppressive. chemotherapy.

The synovial expression and serum levels of interleukin-6, interleukin-11, leukemia inhibitory factor, and oncostatin M in rheumatoid arthritis

OBJECTIVE

To determine the expression of interleukin-6 (IL-6), IL-11, leukemia inhibitory factor (LIF), and oncostatin M (OSM) and their major cellular sources in the joints of rheumatoid arthritis (RA) patients, as well as the correlation of circulating levels of these IL-6-type cytokines and C-reactive protein (CRP).

METHODS

Messenger RNA (mRNA) and protein levels for IL-6, IL-11, LIF, and OSM were determined by using reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

RESULTS

Cells isolated from the synovium of RA patients expressed mRNA for IL-6, IL-11, LIF, and OSM at higher levels than did synovial cells from osteoarthritis (OA) patients, and spontaneously released greater quantities of these proteins in culture. Fibroblast cell lines derived from RA synovium were able to produce IL-6, IL-11, and LIF, but not OSM, when stimulated with IL-1 and tumor necrosis factor alpha. OSM was found to be produced spontaneously by synovial tissue macrophages. IL-6, IL-11, LIF, and OSM were present in synovial fluid from the RA patients; levels of IL-6, LIF, and OSM were present in significantly greater quantities in RA patients than in OA patients. However, only IL-6 was significantly elevated in the serum of RA patients and correlated with the serum CRP level, while other IL-6-type cytokines were not detected.

CONCLUSION

IL-6, IL-11, LIF, and OSM are all produced in large amounts at the site of disease activity, but IL-6 derived from synovial fibroblasts may be the major hormone-like mediator that induces the hepatic synthesis of acute-phase proteins in RA.

Pharmacokinetics of recombinant human interleukin-11 (rhIL-11) in healthy male subjects

AIMS

To study the pharmacokinetics of recombinant human interleukin-11 (rhIL-11) in healthy male volunteers following subcutaneous (s.c.) and intravenous (i.v.) administration.

METHODS

RhIL-11 was infused intravenously at 10-50 micrograms kg-1 for 1 or 3 h, or administered subcutaneously at 3-50 micrograms kg-1 to volunteers. RhIL-11 was also administered at 3 micrograms kg-1 s.c. once daily for 7 days. Plasma and urinary concentrations were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

RhIL-11 showed linear pharmacokinetics after both intravenous infusion and s.c. administration. Comparison of t1/2 and MRT values after i.v. administration with those after s.c. administration indicated that rhIL-11 pharmacokinetics after s.c. administration were absorption rate-limited. Bioavailability after s.c. administration was about 65%. Since RhIL-11 was not detected in urine after a single 50 micrograms kg-1 s.c. dose, rhIL-11 was considered to be eliminated by metabolism. There was no significant change in the pharmacokinetic profile of rhIL-11 following repeated s.c. administration.

CONCLUSIONS

RhIL-11 demonstrated linear pharmacokinetics at these dose ranges after single and repeated s.c. administration or constant-rate i.v. infusion in healthy volunteers.

Circulating endogenous thrombopoietin, interleukin-3, interleukin-6 and interleukin-11 levels in patients undergoing allogeneic bone marrow transplantation

To elucidate the physiologic role of thrombopoietin (TPO) for hematologic reconstitution following allogeneic bone marrow transplantation (BMT), serum TPO levels as well as interleukin-3 (IL-3), IL-6 and IL-11 were serially measured in 55 samples from 3 patients who underwent allogeneic BMT using an enzyme-linked immunosorbent assay (ELISA). The TPO level was higher in the serum taken during marrow aplasia than in the pretransplant serum. The serum TPO levels and platelet counts showed a strong inverse relationship in all patients examined. We also sequentially measured endogenous serum TPO levels before and within 36 h after platelet transfusions. Endogenous serum TPO levels were inversely correlated with platelet mass following platelet transfusions. Serum levels of IL-3 had no apparent correlation with platelet counts and serum levels of IL-11 remained below the detection levels (31.3 pg/ml) in all samples. Serum levels of IL-6 were high during myeloaplasia and more upregulated in the febrile period. These findings support the view that TPO is the central regulator for megakaryopoiesis in vivo and the rationale for its clinical use after allogeneic BMT.

Differential mechanisms in the regulation of endogenous levels of thrombopoietin and interleukin-11 during thrombocytopenia: insight into the regulation of platelet production

The regulation of megakaryocytopoiesis and thrombopoiesis appears to be under the control of an array of hematopoietic growth factors. To determine the relationship of endogenous thrombopoietic cytokine levels and circulating platelet (PLT) counts, we measured the levels of thrombo-poietin (TPO), interleukin-11 (IL-11), and interleukin-6 (IL-6) in patients with significant thrombocytopenia secondary to both marrow hypoplasia and increased PLT destruction. Increased endogenous levels of TPO and IL-11, but not IL-6, were detected in bone marrow transplant patients with thrombocytopenia following myeloablative therapy (BMT/MAT) (TPO: 1,455.5 +/- 87.3 pg/mL, [PLT 39,600 +/- 7,800/microL], P < .001, n = 12; IL-11: 227.9 +/- 35 pg/mL, [PLT 32,900 +/- 57,000/microL], P < .05, n = 19; IL-6: 25.8 +/- 8.4 pg/mL, [PLT 32,800 +/- 5,057/microL], P > .05, n = 4] v normal donors [TPO < 150 pg/mL, n = 8; IL-11 < 50 pg/mL, n = 9; IL-6 < 10 pg/mL, n = 5 [PLT 203,000 +/- 7,500/microL]. There was a significant inverse correlation between endogenous levels of TPO and IL-11, but not IL-6, and PLT counts in the MAT/BMT patients (TPO: r = -0.57, P < .0001, n = 188; IL-11: r = -0.329, P < .0001, n = 249; IL-6: r = -0.1147, P > .05, n = 62). In patients with immune thrombocytopenia purpura (ITP), with decreased PLT survival, but intact bone marrow megakaryocytopoiesis, endogenous IL-11 levels were significantly increased (328.0 +/- 92.6 pg/mL, [PLT: 20,900 +/- 3,000/microL], P < .05, n = 25). However, endogenous TPO levels remained undetectable (< 150 pg/mL, [PLT 30,500 +/- 5,500/microL], n = 15). These results suggest that there may be differential mechanisms regulating endogenous TPO, IL-11, and IL-6 levels during acute thrombocytopenia and suggest that the absolute number of circulating PLTs may not always be the sole regulator of endogenous TPO levels. Other mpl-expressing cells of the megakaryocyte lineage may contribute to the regulation of circulating TPO levels as well. Our results also suggest IL-11 levels may in part, be regulated by a negative feedback loop based on circulating PLT counts, but also may, in part, be regulated by a variety of inflammatory agonists. Both TPO and IL-11, therefore, appear to be active thrombopoietic cytokines regulating, in part, megakaryocytopoiesis during states of acute thrombocytopenia.

Thrombopoietic potential and serial repopulating ability of murine hematopoietic stem cells constitutively expressing interleukin 11

Based on transplantation studies with bone marrow cultured under various conditions, a role of interleukin 11 (IL-11) in the self-renewal and/or the differentiation commitment of hematopoietic stem cells has been indicated. To better evaluate the in vivo effects of IL-11 on stem/progenitor cell biology, lethally irradiated mice were serially transplanted with bone marrow cells transduced with a defective retrovirus, termed MSCV-mIL-11, carrying the murine IL-11 (mIL-11) cDNA and the bacterial neomycin phosphotransferase (neo) gene. High serum levels (i.e., > 1 ng/ml) of mIL-11 in all (20/20) primary and 86% (12/14) of secondary long-term reconstituted mice, as well as 86% (12/14) of tertiary recipients examined at 6 weeks posttransplant, demonstrated persistence of vector expression subsequent to transduction of bone marrow precursors functionally definable as totipotent hematopoietic stem cells. In agreement with results obtained with human IL-11 in other myeloablation models, ectopic mIL-11 expression accelerated recovery of platelets, neutrophils, and, to some extent, total leukocytes while preferentially increasing peripheral platelet counts in fully reconstituted mice. When analyzed 5 months posttransplant, tertiary MSCV-mIL-11 recipients had a significantly greater percentage of G418-resistant colony-forming cells in their bone marrow compared with control MSCV animals. Collectively, these data show that persistent stimulation of platelet production by IL-11 is not detrimental to stem cell repopulating ability; rather, they suggest that IL-11 expression in vivo may have resulted in enhanced maintenance of the most primitive hematopoietic stem cell compartment. The prolonged expression achieved by the MSCV retroviral vector, despite the presence of a selectable marker, contrasts with the frequent transcriptional extinction observed with other retroviral vectors carrying two genes. These findings have potentially important implications for clinical bone marrow transplantation and gene therapy of the hematopoietic system.

Circulating levels of IL-11 and leukaemia inhibitory factor (LIF) do not significantly participate in the production of acute-phase proteins by the liver

To investigate the contribution of IL-11 and LIF to acute-phase protein (APP) production, we first analysed the effects of IL-11 and LIF on production of C-reactive protein (CRP), fibrinogen, and haptoglobin by human primary hepatocytes. We also measured the serum levels of IL-11, LIF, and CRP in serum from patients with inflammatory rheumatic diseases to assess the role of these cytokines in the APP response in vivo. We included patients with conditions associated with a high APP response such as rheumatoid arthritis (RA) or spondylarthropathy (SpA), and others usually associated with a weak APP response such as systemic lupus erythematosus (SLE), in order to investigate whether these cytokines could account for the differences in APP responses. Our results showed that IL-11 and LIF induced only minimal stimulation on production of APP by human primary hepatocytes compared with IL-6, known as the major inducer. Serum levels of CRP were elevated in RA and SpA, and significantly higher than in SLE patients. Despite the presence of a high APP response in some of our patients and despite the fact that we used sensitive assays to measure IL-11 and LIF, serum levels of both cytokines were not detected in any of the tested sera. In conclusion, our results show that circulating levels of IL-11 or LIF do not contribute significantly to the production of APP in vivo, and that they do not account for the difference in APP response between SLE and other inflammatory rheumatic diseases.