Efficacy and safety of sirukumab in Japanese patients with active rheumatoid arthritis who were refractory or intolerant to anti-tumor necrosis factor therapy: Subgroup analysis of a randomized, double-blind, multicenter, phase 3 study (SIRROUND-T).

OBJECTIVE: To evaluate the efficacy and safety of sirukumab, a human anti-interleukin six monoclonal antibody, in Japanese patients with rheumatoid arthritis who were refractory to anti-tumor necrosis factor therapy. METHODS: This subgroup analysis, based on a double-blind, placebo-controlled, 52-week phase 3, global study (SIRROUND-T) assessed the American College of Rheumatology (ACR) 20 response at week 16 (primary endpoint). Secondary endpoints: ACR 50, Disease Activity Score in 28 joints-C reactive protein, Health Assessment Questionnaire-Disability Index and safety were assessed. Results 116/878 patients received sirukumab 50 mg/4 weeks (q4w, n = 35), 100 mg/2 weeks (q2w, n = 44) or placebo (n = 37) subcutaneously. Significantly more patients achieved ACR 20 response at week 16 with sirukumab (50 mg q4w:20 [57.1%]; p < .001, 100 mg q2w:24 [54.5%]; p = .001) versus placebo (7 [18.9%]); consistent significant improvement in secondary endpoints at week 24 and 52 was observed. At week 24, incidence of treatment-emergent adverse events (TEAEs) was numerically higher with sirukumab groups (50 mg q4w:29 [82.9%]; 100 mg q2w:38 [86.4%] versus placebo (28 [75.7%]); however, at week 52, sirukumab combined groups had comparable incidence of TEAEs. CONCLUSION: Efficacy findings through 52 weeks were comparable between sirukumab doses in Japanese patients and consistent with primary SIRROUND-T study results. No new safety signals were observed.

Acute administration of IL-6 improves indices of hepatic glucose and insulin homeostasis in lean and obese mice.

Obesity can lead to impairments in hepatic glucose and insulin homeostasis, and although exercise is an effective treatment, the molecular targets remain incompletely understood. As IL-6 is an exercise-inducible cytokine, we aimed to identify whether IL-6 itself influences hepatic glucose and insulin homeostasis and whether this response differs during obesity. In vivo, male mice were fed a low-fat diet (LFD; 10% kcal) or a high-fat diet (HFD; 60% kcal) for 7 wk, which induced obesity and hepatic lipid accumulation. LFD- and HFD-fed mice were injected with IL-6 (400 ng, 75 min) or PBS and then with insulin (1 U/kg; ~15 min) or saline, at which point livers were collected. In both LFD- and HFD-fed mice, IL-6 decreased blood glucose and mRNA expression of gluconeogenic genes alongside increased phosphorylation of AKT in comparison to PBS controls, and this occurred without changes in circulating insulin. To determine whether this effect of IL-6 was directly on the liver, we completed in vitro isolated primary hepatocyte experiments from chow-fed mice and cultured with or without exposure to free fatty acid (250 µm palmitate and 250 µm oleate, 24 h) to induce lipid accumulation. In both control and free fatty acid-treated hepatocytes, IL-6 (20 ng/ml, 75 min) slightly attenuated insulin-stimulated (10 nM; ~15 min) AKT phosphorylation. Together, these data suggest that IL-6 may lead to improvements in indices of hepatic glucose and insulin homeostasis in vivo; however, this is likely due to an indirect effect on the hepatocyte. NEW & NOTEWORTHY In this study, we used lean and obese mice and found that a single injection of IL-6 improved glucose tolerance, decreased hepatic gluconeogenic gene expression, and increased hepatic phosphorylation of AKT. In primary hepatocytes cultured under control and lipid-laden conditions, IL-6 had a mild, but deleterious, effect on phosphorylation of AKT. Our results show that the beneficial effects of IL-6 on glucose and insulin homeostasis, in vivo, are maintained in obesity.

Tumor-targeting properties of novel immunocytokines based on murine IL1ß and IL6.

There is an increasing biotechnological interest in 'arming' therapeutic antibodies with bioactive payloads. Many antibody-cytokine fusion proteins (immunocytokines) have been described and some of these biopharmaceuticals have progressed to clinical studies. Here, we describe for the first time the expression and in vivo characterization of immunocytokines based on murine IL1ß and IL6. These potent pro-inflammatory cytokines were fused at the N-terminus or at the C-terminus of the monoclonal antibodies F8 (specific to the alternatively-spliced extra-domain A domain of fibronectin, a marker of tumor angiogenesis). All immunocytokines retained the binding properties of the parental antibody and were homogenous, when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size-exclusion chromatography, except for the N-terminal fusion of IL1ß which revealed the presence of glycosylated species. When analyzed by quantitative biodistribution analysis using radioiodinated protein preparations, F8 fusions with IL6 revealed a preferential accumulation at the tumor site for both cytokine orientations, whereas IL1ß fusions exhibited lower tumor to organ ratios and a slower blood clearance profile. The fusion proteins with the cytokine payload at the C-terminus were studied in therapy experiments in immunocompetent mice bearing F9 tumors. Immunocytokines based on IL1ß resulted in 10% body weight loss at a 5-µg dose, whereas IL6-based products caused a 5% body weight loss at a 225-µg dose. Both F8-IL1ß and F8-IL6 exhibited a <50% inhibition of tumor growth rate, which was substantially lower than the one previously reported for F8-TNF, a closely related pro-inflammatory immunocytokine. This study indicates that IL6 can be efficiently delivered to the tumor neo-vasculature by fusion with the F8 antibody. While F8-IL6 was not as potent as other F8-based immunocytokines that exhibit similar biodistribution profiles, the fusion protein sheds light on the different roles of pro-inflammatory cytokines in boosting immunity against the tumor.

Pharmacokinetics of natural and engineered secreted factors delivered by mesenchymal stromal cells.

Transient cell therapy is an emerging drug class that requires new approaches for pharmacological monitoring during use. Human mesenchymal stem cells (MSCs) are a clinically-tested transient cell therapeutic that naturally secrete anti-inflammatory factors to attenuate immune-mediated diseases. MSCs were used as a proof-of-concept with the hypothesis that measuring the release of secreted factors after cell transplantation, rather than the biodistribution of the cells alone, would be an alternative monitoring tool to understand the exposure of a subject to MSCs. By comparing cellular engraftment and the associated serum concentration of secreted factors released from the graft, we observed clear differences between the pharmacokinetics of MSCs and their secreted factors. Exploration of the effects of natural or engineered secreted proteins, active cellular secretion pathways, and clearance mechanisms revealed novel aspects that affect the systemic exposure of the host to secreted factors from a cellular therapeutic. We assert that a combined consideration of cell delivery strategies and molecular pharmacokinetics can provide a more predictive model for outcomes of MSC transplantation and potentially other transient cell therapeutics.

Platelet activation and platelet-leukocyte aggregation elicited in experimental colitis are mediated by interleukin-6.

There is growing evidence for an interdependence of inflammation, coagulation, and thrombosis in acute and chronic inflammatory diseases. Inflammatory bowel diseases (IBD) are associated with a hypercoagulable state and an increased risk of thromboembolism. Although the IBD-associated prothrombogenic state has been linked to the inflammatory response, the mediators that link these 2 conditions remain unclear. Recent evidence suggests that interleukin-6 (IL-6) may be important in this regard. The objective of this study was to more fully define the contribution of IL-6 to the altered platelet function that occurs during experimental colitis. The number of immature and mature platelets, activated platelets, and platelet-leukocyte aggregates were measured in wild-type and IL-6 mice with dextran sodium sulfate (DSS)-induced colonic inflammation. DSS treatment of WT mice was associated with significant increases in the number of both immature and mature platelets, activated platelets, and platelet-leukocyte aggregates. These platelet responses to DSS were not observed in IL-6 mice. Chronic IL-6 infusion (through an Alzet pump) in WT mice reproduced all of the platelet abnormalities observed in DSS-colitic mice. IL-6-infused mice also exhibited an acceleration of thrombus formation in arterioles, similar to DSS. These findings implicate IL-6 in the platelet activation and enhanced platelet-leukocyte aggregate formation associated with experimental colitis, and support a role for this cytokine as a mediator of the enhanced thrombogenesis in IBD.

La activación de receptor activado por proliferadores peroxisómicos Beta/ Delta mejora la resistencia a insulina inducida porIL-6 en células hepáticas / No disponible

Introducción: La resistencia a la insulina precede y predice la presencia de diabetes mellitustipo 2, condición que supone un notable incremento del riesgo cardiovascular. La interleucina-6es uno de los mediadores que relacionan la inflamación crónica observada en estados de obesidad con la resistencia a la insulina a través de la activación de STAT3 (signal transducer and activator of transcription 3), con el consiguiente aumento de SOCS3 (suppressor of cytokinesignaling 3) en el hígado. El objetivo de este estudio ha sido evaluar si un agonista del receptor activado por proliferadores peroxisómicos (PPAR) / , GW501516, es capaz de evitar la activación de la vía de senalización IL-6/STAT3/SOCS3 y la resistencia a la insulina en células hepáticas. Material y métodos: Células HepG2 humanas se estimularon con IL-6 (20 ng/ml) en presenciao en ausencia de GW501516 (10 M). También analizamos el hígado de ratones salvajes y con deficiencia PPAR / . Los niveles de ARNm y proteínas se analizaron mediante las técnicas deRT-PCR y Western-Blot, respectivamente. Resultados: GW501516 evitó la fosforilación en Tyr705 y en Ser727 de STAT3 y el aumento deSOCS3 inducidas por la IL-6. Asimismo, el tratamiento con este fármaco evitó la activación por la IL-6 de la ERK1/2, una serina-treonina cinasa implicada en la fosforilación de STAT3 enSer727. Cabe destacar que el hígado de ratones deficientes en PPAR / mostró un aumento (..) (AU)

Introduction: Insulin resistance precedes and predicts the development of type 2 diabetes mellitus, a disease which increases the risk of cardiovascular events. Interleukin (IL)-6 is one of the mediators linking obesity-derived chronic inflammation with insulin resistance through activation of STAT3, with subsequent up regulation of suppressor of cytokine signaling 3 (SOCS3)in liver. The aim of this study was to evaluate whether peroxisome proliferator-activated receptor (PPAR) / agonist GW501516 prevented activation of the IL-6/STAT3/SOCS3 pathway and insulin resistance in hepatic cells. Material and methods: Human HepG2 cells were stimulated for 10 min with IL-6 (20 ng/mL)in the presence or in the absence of 10 M GW501516, then mRNA and protein levels were analyzed by RT-PCR or Western-Blot, respectively. In addition, we also analyzed protein levels from PPAR / null mice and wild-type mice livers. Results: GW501516 prevented IL-6-induced STAT3 phosphorylation on Tyr705 and Ser727 and avoided the increase in SOCS3 caused by this cytokine. In addition, this drug also preventedIL-6-dependent ERK1/2 phosphorylation, a serine-threonine protein kinase involved in STAT3phosphorylation on Ser727. Interestingly, livers from PPAR / null mice showed increased phosphorylations on Tyr 705 and Ser727 of STAT3 as well as phosphorylated ERK1/2 levels. Finally, all (..) (AU)

Autocrine modulation of glucose transporter SGLT2 by IL-6 and TNF-alpha in LLC-PK1 cells

We determined in cultured kidney epithelial cells (LLC-PK1) the effects of high glucose, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) on mRNA and protein expression of the renal glucose transporters SGLT1 and SGLT2. Cultured monolayers were incubated with similar concentrations of IL-6 and (..) (AU)

Acute effects of interleukin-6 infusion on apo-B-containing lipoprotein subclasses in humans.

IL-6 is believed to mediate the elevation in plasma TG and VLDL lipids in patients with sepsis. Previous studies of lipoprotein density fractions do not reveal the extent to which cytokines change the immunochemically distinct TG-rich (LpB:C, LpB:C:E, LpAII:B:C:D:E) and cholesterol-rich (LpB, LpB:E) apoB-containing subclasses present in VLDL. Therefore, we have directly measured these subclasses following their isolation by sequential immunoprecipitation in seven healthy male subjects during a 3-h infusion with recombinant human (rh) IL-6. Though plasma TG and apoB-containing particle number were unchanged by IL-6, the distribution of TG-rich subclasses was significantly altered. Compared to baseline values, LpB:E + LpB:C:E increased significantly at 0.5 h (p < 0.02) and were higher than saline-infused controls at 0.5 and 1 h (p < 0.05). At 0.5 h LpAII:B:C:D:E reciprocally declined from baseline (p < 0.01). While the pattern of change for total apoB showed an overall decline (p < 0.05), these changes in LpB:E + LpB:C:E and LpAII:B:C:D:E in IL-6 subjects differed from controls (p < 0.05; p < 0.01, respectively). These findings indicate that physiologic concentrations of IL-6 rapidly and selectively regulate the transport of apoB particles that contain apoE. Since apoE has immunomodulatory and host defense functions, these changes may be a previously unrecognized early step in the innate immune response.

Peritoneal resorption capacity for lipopolysaccharide and interleukin-6 in acute zymosan-induced chemical peritonitis.

AIM: To evaluate peritoneal resorption capacity for lipopolysaccharide (LPS) and interleukin-6 (IL-6) in a model of chemical peritonitis. METHODS: Zymosan peritonitis was induced in anesthetized rats. LPS was injected intraperitoneally to different groups at 4 h (n = 10), 8 h (n = 9), 12 h (n = 9), and 24 h (n = 9) after peritonitis and to a control group (n = 8). Similarly, IL-6 was injected intraperitoneally to different groups at 4 h (n = 9), 8 h (n = 10), 12 h (n = 10), and 24 h (n = 10) after peritonitis, and to a control group (n = 10). Plasma levels of LPS or IL-6 were measured immediately after intraperitoneal injections of LPS or IL-6, respectively, and at 5, 15, 30, 45, and 60 min later. RESULTS: There was no change over time in plasma LPS levels in the groups receiving LPS intraperitoneally (p = 0.4). There was highly significant change over time in the IL-6 level in the studied time periods in the groups receiving IL-6 intraperitoneally (p < 0.0001). There was an increase in the plasma IL-6 level when sampled at 4 h after peritonitis. CONCLUSION: There was a reduction of resorption capacity of inflamed peritoneum for inflammatory mediators in acute chemical peritonitis.

A multiple-dose pharmacokinetics of polyethylene glycol recombinant human interleukin-6 (PEG-rhIL-6) in rats.

Radiation therapy has been widely applied in cancer treatment. However, it often causes thrombocytopenia (deficiency of white blood cells) as an adverse effect. Recombinant human interleukin-6 (rhIL-6) has been found to be a very effective way against this thrombocytopenia, but IL-6 has low stability in blood, which reduces its efficacy. To increases the stability and half-life of rhIL-6, it was modified by polyethylene glycol (PEG). The pharmacokinetics and the tissue distribution of PEG-rhIL-6 labeled with (125)I were examined after subcutaneous injection in rats. The pharmacokinetic pattern of PEG-rhIL-6 was defined with linear-kinetics, and we fitted a one-compartment model with half-lives of 10.44-11.37 h (absorption, t(1/2Ka)) and 19.77-21.53 h (elimination, t(1/2Ke)), and peak concentrations at 20.51-21.96 h (t(peak)) in rats. Half-lives and t(peak) of PEG-rhIL-6 were longer than those of rhIL-6 previously reported. In the present study, for deposition of PEG-rhIL-6 in rats, the tissue distribution examination showed that blood was the major organ involved, rather than liver. However, as to the elimination of PEG-rhIL-6, the major organ was the kidney. The excretion fraction of the injection dose recovered from urine was 23.32% at 192 h after subcutaneous administration. Less than 6% of PEG-rhIL-6 was eliminated via the feces at 192 h. These results indicate that PEG-rhIL-6 is a good candidate drug formulation for patients with cancer.

Administration of anti-interleukin-6 monoclonal antibody prolongs cardiac allograft survival.

To investigate the effects of anti-IL-6 monoclonal antibody (anti-IL-6 mAb) on acute allograft rejection and the potential mechanisms in a mouse heart transplantation model. Heterotopical heart graft model was performed. The anti-IL-6 mAb was administered to recipient mice after cardiac grafting. Results were compared with administration of anti-IL-17 mAb or anti-IL-6 mAb+anti-IL-17 mAb (the 'double' treatment). The cardiac allograft survival was monitored by daily palpation in combination with histological evaluation. Quantitative polymerase chain reaction assay, mixed lymphocyte reaction, and flow cytometric analysis were employed to determine the mRNA expression of pro-inflammatory cytokines, allogeneic T-cell proliferation, and the proportion of CD4(+) CD25(+) Foxp3(+) regulatory T cells in graft-infiltrating lymphocytes and splenocytes of recipients, respectively. The results showed that the cardiac allograft survival in anti-IL-6 mAb-treated mice was prolonged significantly when compared with that of the untreated or anti-IL-17 mAb-treated mice. Meanwhile, the 'double-treated' did not prolong graft survival significantly when compared with those treated with anti-IL-6 mAb. The increase of graft survival induced by anti-IL-6 mAb was associated with reduced transcript levels for IFN-γ and IL-17, accompanied by a dramatic reduction of T-cell proliferation capacity to alloantigen stimuli and a higher proportion of Treg cells. Thus, anti-IL-6 mAb may be protective against acute rejection after cardiac transplantation through suppressing the activation of effector T cells and promoting the induction of Treg cells.

Ovine proinflammatory cytokines cross the murine blood-brain barrier by a common saturable transport mechanism.

OBJECTIVES: The cytokines interleukin (IL)-1beta and IL-6 are modulators of the neuroimmune axis and have been implicated in neuronal cell death cascades after ischemia or infection. Previous work has shown that some cross-species conservation exists between human and rodent blood-brain barrier (BBB) transport systems. To further assess cross-species conservation of cytokine transport across the BBB, the current studies investigated permeability and inhibition of ovine IL-1beta and IL-6 in the mouse. METHODS: IL-1beta or IL-6 was radioactively labeled with (131)I and injected into the jugular vein at time zero. A subset of mice received 1 or 3 microg/mouse of an unlabeled ovine or murine cytokine (IL-1beta or IL-6) to assess self- and/or cross-inhibition of transport. Permeability was assessed using multiple-regression analysis. RESULTS: There was a significant linear relationship for both ovine (131)I-IL-1beta and (131)I-IL-6 between brain/serum ratios and exposure time, indicating BBB permeability. Inclusion of 3 microg/mouse unlabeled ovine IL-1beta or IL-6 significantly reduced the transport of ovine (131)I-IL-1beta or (131)I-IL-6, respectively, across the BBB. Transport of both ovine (131)I-IL-1beta and (131)I-IL-6 was significantly inhibited by 1 microg/mouse of murine IL-1beta or IL-6, respectively. In contrast, 1 microg/mouse of unlabeled ovine IL-1beta or IL-6 did not inhibit the transport of murine (131)I-IL-1beta or (131)I-IL-6. CONCLUSIONS: Ovine IL-1beta and IL-6 cross the mouse BBB by saturable transport. Inhibition of transport by murine homologs indicates that both species use the same transport mechanisms. Conversely, an inability of ovine cytokines to significantly inhibit the transport of murine cytokines indicates that mouse BBB has a lower affinity for ovine than murine cytokines. Knowledge of species-conserved BBB transport mechanisms may facilitate the development of novel animal models of central nervous system pathogenesis.

Peritoneal resorption capacity for the inflammatory mediators in acute experimental Staphylococcus aureus peritonitis.

BACKGROUND: Elevations in both endotoxin and interleukin-6 (IL-6) concentrations in peritoneal exudates are a thousand times higher than their respective concentrations in the peripheral blood in patients with gram-positive or gram-negative peritonitis. We aimed in this study to evaluate the resorption capacity of the peritoneum for endotoxin and IL-6 in a model of bacterial (gram-positive) peritonitis. METHODS: Intraperitoneal (i.p.) injection of mucin-pretreated staphylococci in phosphate buffered saline (PBS) or of PBS alone was performed in 93 male Wistar rats. Studies of resorption were undertaken at time points of 4 hours (h), 8h, 12h and 24h. Endotoxin was intraperitoneally injected in 44 rats and IL-6 in 49 rats. After 0, 5, 10, 15, 30 and 60 minutes (min), blood was sampled. Endotoxin and IL-6 were measured using the limulus-amoebocyte-lysate (LAL) test and ELISA technique, respectively. RESULTS: No endotoxin or IL-6 was measured in the blood of controls. Plasma endotoxin and IL-6 levels were significantly high in the peritonitis groups. There was no further increase in endotoxin plasma levels after i.p. injection of endotoxin. Following i.p. injection of IL-6, there was an increase in IL-6 level over the time of sampling in the peripheral blood at 4h of peritonitis. CONCLUSION: There was a clear reduction in peritoneal resorption of endotoxin and IL-6 in this acute model of gram-positive peritonitis.

[Pharmacokinetics of PEG recombinant human interleukin-6 in rats].

OBJECTIVE: To study the pharmacokinetics and tissue distribution of PEG-rhIL-6 in rats after a single dose administration. METHODS: Pharmacokinetics and distribution of PEG-rhIL-6 in rats were studied by 125I isotope tracing method. Pharmacokinetic analysis was performed using 3P97 computer software. RESULTS: PEG-rhIL-6 declined in one-compartment model with half-lives of 10.44-11.37 h for t1/2 Ka, 19.77-21.53 h for t1/2 Ke and 20.51-21.96 h for T(pcak), respectively. PEG-rhIL-6 was mainly distributed in blood and excreted via urine. CONCLUSION: The half-lives of PEG-rhIL-6 are prolonged after being modified by PEG.

Procalcitonin in acute myocardial infarction.

OBJECTIVE: Procalcitonin (PCT) is released in severe bacterial infections, sepsis and in infection independent cases such as major surgery, multiple trauma, cardiogenic shock, burns, resuscitation, and after cardiac surgery. The aim of this study was to determine the levels and the kinetics of PCT in AMI and to investigate their possible correlation with the release of IL-6 and CRP. DESIGN-PATIENTS: The study included 60 patients (47 men, 63.2+/-14.8 years) with the diagnosis of AMI at admission. In all patients, serum levels of PCT, IL-6, CK-MB, TnI and CRP were measured at admission, at 3, 6, 12, 24, 48 and 72 h and at the seventh day. RESULTS: PCT was elevated in all patients with AMI. It was initially detected in serum approximately 2-3 h after the onset of the symptoms. The median value at admission was 1.3 ng/ml (95% CI: 0.89 to 1.80). The value of PCT showed an increase and reached a plateau after 12-24 h. The median value at 24 h was 3.57 ng/ml (95% CI: 2.89 to 4.55). PCT values fell to baseline (<0.5 ng/ml) by the seventh day. PCT was detected in serum earlier than CK-MB or TnI in 56 of the 60 patients (93.3%). The kinetics of PCT was similar to those of CK-MB and TnI. The maximal values of PCT were positively correlated with the maximal values of IL-6 (r = 0.59, P = 0.00) and of CRP (r = 0.65, P = 0.001). The maximal values of IL-6 were positively correlated with max CRP (r = 0.35, P = 0.045). CONCLUSIONS: PCT could be considered as a novel sensitive myocardial index. Its release in AMI is probably due to the inflammatory process that occurs during AMI.

Interleukin-6 in the maternal circulation reaches the rat fetus in mid-gestation.

Maternal systemic infection during pregnancy may expose the fetus to infectious agents and high levels of mediators of the resulting inflammatory response, such as IL-6 (IL-6). Increased fetal and maternal levels of IL-6 have been associated with adverse neonatal outcome but might also stress the fetus and contribute to cardiovascular and neuroendocrine dysfunction in adulthood. It is unclear whether interleukins cross the placental barrier, although this matter has been little studied. The aim of this study was therefore to investigate if IL-6 administered to pregnant rats in vivo is transferred to the fetus. We injected 125I IL-6 i.v. to pregnant dams at gestation day 11-13 (mid-gestation) or 17-19 (late gestation). We found 125I-IL-6 in the exposed fetuses as well as in amniotic fluids. Fetal 125I-IL-6 levels were markedly higher in animals injected in mid-gestation compared with late pregnancy (p < 0.01). This difference was mirrored in a 15-fold higher unidirectional materno-fetal clearance for 125I-IL-6 in mid-gestation (p < 0.01). We conclude that the permeability of the rat placental barrier to IL-6 is much higher in mid-gestation than in late pregnancy. Maternally derived IL-6 may directly induce fetal injury but also stimulate the release of fetal stress hormones resulting in stimuli or insults in neuroendocrine structures and hormonal axes which might lead to disease at adult age.

Receptor-mediated transport of LIF across blood-spinal cord barrier is upregulated after spinal cord injury.

Leukemia inhibitory factor (LIF) crosses the normal blood-brain and blood-spinal cord barrier (BBB) by a saturable transport system [Pan, W., Kastin, A.J., Brennan, J.M., 2000. Saturable entry of leukemia inhibitory factor from blood to the central nervous system. J. Neuroimmunol. 106, 172-180]. Since LIF is a cytokine beneficial to spinal cord regeneration, understanding the regulation of its transport across the injured BBB may help in the design of strategies for the treatment of spinal cord injury (SCI). In this study, we initially showed that transport of LIF is mediated by its specific receptor LIFRalpha (gp190), using both adult mice and monolayers of mouse brain microvessel endothelial cells. Permeation of radioactively labeled LIF was inhibited not only by excess unlabeled LIF, but also by a blocking antibody to the extracellular domain of gp190 LIFRalpha receptor. This showed that the saturable transport of LIF across the BBB involves LIFRalpha. We then tested the hypothesis that this transport system can be upregulated after SCI. SCI was generated by an established compression method at the upper lumbar level. Transport was studied 1 week after SCI, a time of tissue repair following ischemia and inflammation. Spinal cord uptake of 99mTc-albumin 10 min after intravenous injection was used as an indicator of paracellular permeability of the BBB, its small but significant increase at the injury site indicating the level of persistent BBB disruption. The uptake of 125I-LIF by the injured lumbar spinal cord was significantly greater than that in the uninjured controls as well as that of 99mTc-albumin. Both excess unlabeled LIF and the blocking antibody against LIFRalpha significantly suppressed the increased entry of 125I-LIF without affecting that of 99mTc-albumin. Thus, the increased blood-to-spinal cord permeation of LIF was not solely explained by barrier disruption but involved LIFRalpha. This enhanced transport correlated with increased expression of LIFRalpha shown by immunofluorescent staining and Western blot. Therefore, LIFR at the BBB provides an important target for therapeutic intervention.

Interleukin-6 in acute exercise and training: what is the biological relevance?

It is now recognized that contracting skeletal muscle may synthesize and release interleukin-6 (IL-6) into the interstitium as well as into the systemic circulation in response to a bout of exercise. Although several sources of IL-6 have been demonstrated, contracting muscles contributes to most of the IL-6 present in the circulation in response to exercise. The magnitude of the exercise-induced IL-6 response is dependent on intensity and especially duration of the exercise, while the mode of exercise has little effect. Several mechanisms may link muscle contractions to IL-6 synthesis: Changes in calcium homeostasis, impaired glucose availability, and increased formation of reactive oxygen species (ROS) are all capable of activating transcription factors known to regulate IL-6 synthesis. Via its effects on liver, adipose tissue, hypothalamic-pituitary-adrenal (HPA) axis and leukocytes, IL-6 may modulate the immunological and metabolic response to exercise. However, prolonged exercise involving a significant muscle mass in the contractile activity is necessary in order to produce a marked systemic IL-6 response. Furthermore, exercise training may reduce basal IL-6 production as well as the magnitude of the acute exercise IL-6 response by counteracting several potential stimuli of IL-6. Accordingly, a decreased plasma IL-6 concentration at rest as well as in response to exercise appears to characterize normal training adaptation.

Quasi-equilibrium pharmacokinetic model for drugs exhibiting target-mediated drug disposition.

PURPOSE: The aim of this study is to derive and evaluate an equilibrium model of a previously developed general pharmacokinetic model for drugs exhibiting target-mediated drug disposition (TMDD). METHODS: A quasi-equilibrium solution to the system of ordinary differential equations that describe the kinetics of TMDD was obtained. Computer simulations of the equilibrium model were carried out to generate plasma concentration-time profiles resulting from a large range of intravenous bolus doses. Additionally, the final model was fitted to previously published pharmacokinetic profiles of leukemia inhibitory factor (LIF), a cytokine that seems to exhibit TMDD, following intravenous administration of 12.5, 25, 100, 250, 500, or 750 microg/kg in sheep. RESULTS: Simulations show that pharmacokinetic profiles display steeper distribution phases for lower doses and similar terminal disposition phases, but with slight underestimation at early time points as theoretically expected. The final model well-described LIF pharmacokinetics, and the final parameters, which were estimated with relatively good precision, were in good agreement with literature values. CONCLUSIONS: An equilibrium model of TMDD is developed that recapitulates the essential features of the full general model and eliminates the need for estimating drug-binding microconstants that are often difficult or impossible to identify from typical in vivo pharmacokinetic data.