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.

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 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.

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.

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.

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.

Endogenous interleukin 6 production in multiple myeloma patients treated with chimeric monoclonal anti-IL6 antibodies indicates the existence of a positive feed-back loop.

In vitro as well as in vivo observations have shown that IL6 plays a key role in the pathogenesis of multiple myeloma. Therefore we started a phase I/II dose escalating study with chimeric monoclonal anti-IL6 antibodies (cMab) in multiple myeloma (MM) patients resistant to second-line chemotherapy. Here we describe the pharmacological data as well as a new method for calculating the endogenous IL6 production. The cMab (CLB IL6/8; Kd: 6.25 x 10(-12) M) was given in two cycles of 14 daily infusions, starting on day 1 and day 28. Daily dose: 5 mg in patients 1-3, 10 mg in patients 4-6, and 20 mg in patients 7-9 (total dose 140, 280, and 560 mg of anti-IL6, respectively). Using the pharmacokinetic data of free IL6 and the binding characteristics of the cMab, the endogenous IL6 production could be calculated from day to day using a one-compartment open model. The median half-life time of this antibody was 17.6 d. No human antichimeric antibodies were induced. Pre-treatment median endogenous IL6 production in the MM patients was 60 micrograms/d (range 13.8-230; normal controls < 7 micrograms/d). During treatment with anti-IL6 cMabs, the endogenous IL6 production immediately decreased in all patients to below 3 micrograms/d and never reached the pre-treatment value during the treatment period, except in two patients who developed an active infection, resulting in an IL6 production of 128 and 1,208 micrograms/d, respectively. We concluded that in MM patients endogenous IL6 production is 2-30 times higher than in healthy individuals. The anti-IL6 cMab strongly suppress this endogenous IL6 production, probably by blocking a positive feed-back loop, but this cMab does not prevent infection-induced IL6 production. The chimeric anti-IL6 Mabs have a long half-life time, a low immunogenicity, and are able to block IL6-dependent processes in vivo.

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.

Phase I trial of subcutaneous interleukin-6 in patients with advanced malignancies.

PURPOSE: Based on preclinical evidence in murine models that interleukin-6 (IL-6) mediates regression of metastatic tumors, we performed a phase I study of recombinant human IL-6 in patients with refractory advanced malignancies to determine its pharmacokinetics, toxicities, and possible immunologic and antitumor effects. PATIENTS AND METHODS: Recombinant IL-6 was administered as a single subcutaneous dose daily for 7 days, with 7 days off therapy followed by another 7 days of IL-6. Doses were escalated in cohorts of three patients starting at 3 micrograms/kg/d, provided that toxicity at the preceding dose level was not dose-limiting. Dose-limiting toxicity was defined as grade III or IV major organ toxicity that did not resolve to grade II or less in 24 hours after stopping IL-6, using the National Cancer Institute Common Toxicity Criteria. Patients were treated with 3, 10, and 30 micrograms/kg/d IL-6 subcutaneously. RESULTS: Three patients each were treated at the 3- and 10-micrograms dose levels. Two of five patients treated with 30 micrograms/kg/d IL-6 subcutaneously had grade III major organ toxicity that required IL-6 therapy to be discontinued. All patients experienced fever, chills, and minor fatigue. Significant increases in C-reactive protein (CRP), fibrinogen, platelet counts, and lymphocyte IL-2 receptor levels were seen in patients at the 10- and 30-micrograms/kg dose levels. Decreases in albumin and hemoglobin were observed, particularly at the 30-micrograms/kg dose level. The half-life (T1/2 beta) was 4.2 hours, with a peak IL-6 level at 5 hours. No antitumor responses were seen. CONCLUSION: A safely tolerated dose of daily subcutaneous IL-6 is 10 micrograms/kg, with hepatotoxicity and cardiac arrhythmia being the dose-limiting toxicities at 30 micrograms/kg. Phase II trials of IL-6 administered subcutaneously daily for at least 7 days for two cycles with an intervening week of rest are recommended for phase II trials. However, patients with extensive replacement of liver by tumor and abnormal liver functions should receive IL-6 therapy with caution.

A phase I study of recombinant human leukemia inhibitory factor in patients with advanced cancer.

PURPOSE: Leukemia inhibitory factor (LIF) is a pleiotropic molecule of the interleukin 6 family of cytokines. We aimed to examine the safety, pharmacokinetics, and biological effects of recombinant human LIF (rhLIF, emfilermin) in patients with advanced cancer. EXPERIMENTAL DESIGN: In stage 1 of the study, 34 patients received rhLIF or placebo (3:1 ratio) at doses of 0.25-16.0 micro g/kg/day or 4.0 micro g/kg three times daily for 7 days. In stage 2, 40 patients received rhLIF or placebo, either once daily for 14 days commencing the day after chemotherapy (0.25-8.0 micro g/kg/day) or for 7 days commencing the day before chemotherapy (4.0 micro g/kg three times daily). The chemotherapy was cisplatin 75 mg/m(2) and paclitaxel 135 mg/m(2). RESULTS: In stage 1, platelet counts increased in most patients, including those who received placebo. Blood progenitor cells increased in response to rhLIF. In stage 2, platelet recovery to baseline levels was earlier for patients receiving higher doses of rhLIF (>/=4.0 micro g/kg/day; P = 0.02). The neutrophil nadir after chemotherapy was less severe in patients receiving >/=4.0 micro g/kg/day of rhLIF. In stages 1 and 2, increases in C reactive protein were seen at higher doses. Several patients developed evidence of autonomic dysfunction, in particular impotence and episodic hypotension. The dose-limiting toxicities were hypotension and rigors. Pharmacokinetic studies demonstrated a short half-life (1-5 h) independent of dose. CONCLUSIONS: We demonstrated a biological effect of rhLIF on blood progenitor cells, C reactive protein levels, and hemopoietic recovery after chemotherapy.

The influence of modulating substances on tumor necrosis factor and interleukin-6 levels after injection of murine tumor necrosis factor or lipopolysaccharide in mice.

In this study, we investigated the influence of D-galactosamine (GalN), indomethacin, and dexamethasone on the pharmacokinetics of injected or induced tumor necrosis factor (TNF) and interleukin-6 (IL-6) after a bolus injection of murine TNF (mTNF) or lipopolysaccharide (LPS). It is well known that GalN treatment renders mice much more vulnerable to TNF or LPS lethality. Nevertheless, GalN had no influence on TNF clearance or IL-6 induction after mTNF injection; however, the induced TNF and IL-6 levels were considerably augmented by the GalN cotreatment when a high dose of LPS was injected (GalN was given as a single injection together with TNF or LPS). Indomethacin and dexamethasone, either of which shows a clear protection against TNF/LPS lethality in normal mice, did not change the clearance of injected mTNF, but both reduced the TNF-induced IL-6 levels. Indomethacin did not affect the level and clearance of LPS-induced TNF, whereas the induced IL-6 levels were significantly lower than in the control mice. The circulating TNF and IL-6 concentrations after LPS injection in mice pretreated with dexamethasone were very considerably reduced. Furthermore, neither agent had an influence on the number of TNF binding sites on hepatocytes. We conclude that the strongly enhanced sensitivity of GalN-treated mice towards mTNF-induced or LPS-induced lethality was not reflected in circulating TNF or IL-6 levels, and that dexamethasone and indomethacin both reduce circulating IL-6 concentrations in mice treated with TNF and LPS.

Increased interleukin 6 production by T cells derived from patients with atopic dermatitis.

Many immunologic aspects of atopic dermatitis have been studied, but basic pathobiologic mechanisms of this disease remain unknown. In this study, we measured the production of interleukin-6 (IL-6) by peripheral blood T cells and monocytes from patients with atopic dermatitis in comparison to normal control subjects and patients with chronic psoriasis. We found that peripheral blood T cells isolated from patients with atopic dermatitis produced significantly higher levels of IL-6 (36.1 +/- 5.1 units/ml, n = 22) than T cells derived from either normal subjects (12.6 +/- 1.9 units/ml, n = 22) or patients with chronic psoriasis (26.7 +/- 4.1 units/ml, n = 7). T-cell activation was also measured in the patients with atopic dermatitis by soluble serum IL-2 receptor levels and were found to be significantly higher (623.7 +/- 8.1 units/ml, n = 8) than normal subjects (357.2 +/- 26.0 units/ml, n = 8). In contrast to the increased production of IL-6 by T cells in atopic dermatitis, there was no significant difference in the IL-6 production by peripheral blood monocytes derived from patients with atopic dermatitis compared to normal subjects. Thus, peripheral blood T cells derived from patients with AD spontaneously produce increased amounts of IL-6 compared to T cells from normal subjects, which may reflect the increased activation state of T cells in atopic dermatitis. These data support the concept that activated T cells or subsets of T cells may be important effector cells in mediating inflammatory activity in atopic disease.

Clearance of 125I-labeled interleukin-6 from brain into blood following intracerebroventricular injection in rats.

To test the hypothesis that interleukin-6 (IL-6) induced within the brain can be released into peripheral blood, 125I-labeled IL-6 was injected into the lateral cerebral ventricle of rats, and its concentration in peripheral blood followed serially. Acid-precipitable tracer appeared within 5 min of injection and entered the blood following first-order kinetics (fractional rate, 0.0116 +/- 0.0022/min). Comparison of areas under the curve of intracerebroventricular (icv) vs. iv injection showed that 37.1-46.5% of tracer injected into the lateral cerebral ventricle appeared in the blood over a 4-h period. icv IL-6 exits at least in part via venous drainage (superior sagittal sinus/aortic concentration gradient was 1.47 +/- 0.23 and 3.05 +/- 0.87 in two separate groups). Prior icv injection of human IL-1beta (100 ng) did not alter rate of degradation or of exit ofradioiodine-labeled IL-6 from the brain. These studies indicate that a relatively high proportion of IL-6 that arises in the brain enters the peripheral circulation. Direct secretion of IL-6 from brain to blood may be a mechanism by which the brain modifies peripheral metabolic, endocrine, and immune activity.

PEGylation of interleukin-6 effectively increases its thrombopoietic potency.

The in vivo thrombopoietic activity of polyethylene glycol-modified interleukin-6 (MPEG-IL-6), in which 54% of the 14 lysine amino groups of IL-6 were coupled with PEG, was compared to that of native IL-6. Native IL-6 and MPEG-IL-6, which showed about 51% of the specific bioactivity of native IL-6, were administered subcutaneously to mice every 2 days for 7 days. Native IL-6 increased not only the peripheral platelet count, but also the plasma-IgG1 level in a dose-dependent manner. MPEG-IL-6 showed about 500 times higher thrombopoietic potency than native IL-6. Further, in comparison to native IL-6, MPEG-IL-6 did not enhance IgG1 production as much as it enhanced platelet production. MPEG-IL-6 significantly stimulated platelet recovery in mice treated with 5-fluorouracil, whereas the administration of native IL-6 had a negligible effect. The plasma half-life of MPEG-IL-6 was about 100-fold longer than that of native IL-6. The decrease in the plasma clearance of MPEG-IL-6 was thought to be due, in part, to the shielding of the proteolytic sites in the IL-6 molecule by the PEG chain. The uptake of IL-6 by the reticuloendothelial system, such as the liver and spleen, was markedly limited by PEGylation. The PEGylation of IL-6 markedly enhanced the blood-residency of IL-6, resulting in effective augmentation of its thrombopoietic activity and a marked decrease in its side-effects. These findings suggest that MPEG-IL-6 may be a potential candidate for thrombopoietic agent.

Pentoxifylline improves survival and reduces tumor necrosis factor, interleukin-6, and endothelin-1 in fulminant intra-abdominal sepsis in rats.

The influence of pentoxifylline (PTX) on mortality and some important mediators was studied in a model of cecal perforation with fulminant intra-abdominal sepsis in rats. Cumulative mortality was registered in three groups of animals: untreated sepsis (n = 36), sepsis + PTX 20 mg/kg/24 h (n = 24), and sepsis + PTX 80 mg/kg/24 h (n = 24). PTX therapy was started at sepsis induction or after 4 h, and mortality was reduced from 89% in untreated sepsis to 60-66% in the PTX groups. Levels of sepsis mediators were studied in two groups: untreated sepsis and sepsis + PTX 40 mg/kg started 1 h after sepsis induction. In both groups 6-10 animals were sacrificed at 4 and 8 h to measure blood levels of bacteria, endotoxin, tumor necrosis factor (TNF), interleukin-6 (IL-6), endothelin-1, lactate, neutrophils, and packed cell volume. Cecal perforation gave high levels of bacteria, endotoxin, TNF, IL-6, and endothelin-1, leading to dehydration, lactacidosis, neutropenia, and death. Treatment with PTX did not modify dehydration, neutropenia, or concentrations of bacteria and endotoxin. Release of endothelin-1 was delayed, TNF burst was nearly abolished, and levels of IL-6 and lactate were substantially suppressed. In summary, PTX improves survival and reduces blood concentrations of TNF, IL-6, lactate, and endothelin-1 in fulminant intra-abdominal sepsis in rats. The primary effect of PTX in this sequence is probably reduction of TNF.

Glutamine dipeptides-supplemented parenteral nutrition reverses gut mucosal structure and interleukin-6 release of rat intestinal mononuclear cells after hemorrhagic shock.

Glutamine is an essential substrate for gut mucosal structure, but the role for gut immune function is not fully known. To determine the effect on gut cytokine release in relation to bacterial translocation and gut morphology, a nonlethal hemorrhagic shock (30 min, 30 mmHg) was performed in male Wistar rats followed by 4 days of different way of feeding. A conventional total parenteral nutrition (TPN) solution was compared with an isocaloric and isonitrogenous TPN solution supplemented with alanin-L-glutamine and glycyl-L-glutamine. An enteral chow-fed control group was included. Gut mononuclear cells and splenic macrophages were obtained and endotoxin-induced supernatant tumor necrosis factor-alpha (TNF) and interleukin-6 (IL-6) bioactivity was measured. Histological specimen of the small bowel were taken and mesenteric lymph nodes (MLN) were separated. Enteral feeding following hemorrhagic shock was accompanied by a normal mucosal structure and no bacterial translocation could be detected. TPN was characterized by suppression of cytokine release in gut mononuclear cells and splenic macrophages compared with the enteral-fed control (p < .05). Decreased TNF and IL-6 release was associated with a significantly increased mucosal injury score (p < .05) and a high incidence of bacterial translocation to MLN (66%, p < .05 vs. control). Supplementation of glutamine-dipeptides did not prevent TPN-induced bacterial translocation to MLN (p < .05 vs. control) but significantly improved mucosal injury (p < .05 vs. TPN). Down-regulation of TNF release in TPN-fed rats could not be reversed by glutamine dipeptides while IL-6 release was significantly increased compared with TPN-fed animals (p < .05), and no difference to enteral-fed controls could be found. Enteral nutrition following hemorrhagic shock is superior to parenteral nutrition with regard to mucosal structure, cytokine release, and bacterial translocation. Supplementation of TPN with glutamine dipeptides could reverse TPN-induced suppression of IL-6 release and improved mucosal structure, which may be beneficial in various disease conditions in which TPN is an integrated part of patients management.

Possible role of cytokines in cellular proliferation of the skin transplanted onto nude mice.

BACKGROUND AND DESIGN: In recent studies on the behavior of aged skin transplanted onto nude mice, the epidermis of aged and young skin showed an increase in proliferation and thickness following engraftment, and became almost identical. The aim of this study was to ascertain a possible role for the release of local cytokines in this phenomenon. Grafted human skin was injected intradermally with anti-interleukin-6 (IL) and anti-IL-1 alpha, and comparisons of epidermal thymidine incorporation and thickness were made. Grafts injected with irrelevant antibodies served as control. RESULTS: Interleukin-6 and IL-1 alpha expression were studied in grafts by immunoperoxidase staining. Only IL-6 expression was found in the 1-month grafts. Intradermal injections of anti-IL-1 alpha and anti-IL-6 showed an inhibitory effect on cellular proliferation in the epidermis. A significant difference in the response of epidermal proliferation and, consequently, in thickness was found in samples injected with anti-IL-1 alpha and anti-IL-6 compared with those injected with irrelevant antibodies. CONCLUSIONS: These data may indicate that local cytokines released by the keratinocytes are involved in the cellular proliferative activity in skin engrafted onto the mice.