Interleukin-12 increases interleukin 8 production and release by human polymorphonuclear neutrophils

Interleukin (IL) 12 is a heterodimeric cytokine mainly produced by phagocytes-important target cells for IL-12 in particular with a chemotactic effect-and antigen-presenting cells in response to various microorganisms. Because IL-8 is a strong chemokine for polymorphonuclear neutrophils (PMNs), we investigated the effect of IL-12 on PMN IL-8 production. IL-12 alone had no significant effect, but with lipopolysaccharide (LPS) it was additive at both protein and mRNA levels. Actinomycin D at the beginning of culture inhibited IL-8 mRNA induction, whereas late addition affected IL-8 transcript stability, suggesting gene transcription involvement. Results with parthenolide and tyrphostin AG490 suggest that nuclear factor-kappaB and signal transducer and activator of transcription 4 play a role. The IL-12 additive effect was restricted to IL-8 release, with no action on cell-associated IL-8. IL-12 additive effects occurred after 18 h of culture, with no marked up-regulation of IL-12 receptor expression, and were blocked by actinomycin D added after 16 h of culture. Tumor necrosis factor (TNF) alpha and interferon (IFN) gamma had intermediate roles; their specific inhibition reduced IL-12's effect. IL-12's chemotactic mechanism seemed mediated by overproduction and release of IL-8 by human PMNs in the presence of LPS, an effect involving TNF-alpha and IFN-gamma secretion. These results point to a new role for IL-12 in inflammation, through an autocrine amplification loop.

Intracellular pool of IL-10 receptors in specific granules of human neutrophils: differential mobilization by proinflammatory mediators

IL-10 has a wide range of effects tending to control inflammatory responses. We used flow cytometry to study IL-10 binding at the polymorphonuclear neutrophil (PMN) surface and its modulation by various proinflammatory agents. Little IL-10 bound to the surface of resting PMN. However, binding was strongly increased after stimulation with LPS and proinflammatory cytokines such as TNF and GM-CSF. IL-1 and IL-8 did not significantly modify IL-10 binding. Cycloheximide had no effect on TNF-induced IL-10 binding, strongly suggesting the release of a pre-existing pool of IL-10R rather than de novo receptor synthesis by PMN. This was confirmed by the inhibitory effect of pentoxifylline, an inhibitor of degranulation. The existence of an intracellular pool of IL-10R was shown by flow cytometry, immunocytochemical staining, and Western blotting with several anti-human IL-10R Abs. In subcellular fractions of resting PMN, IL-10R was mainly located in the specific granule fraction, and was absent from azurophil granules and cytosol. We also tested the mobilization of specific granules by measuring the release of lactoferrin, their reference marker. The differential effects of the proinflammatory agents on IL-10 binding matched their effects on lactoferrin release and may therefore be related to differential mobilization of specific granules by these agents. Furthermore, the kinetics of TNF-induced up-regulation of IL-10 binding to PMN ran parallel to the kinetics of the inhibitory effect of IL-10 on the oxidative burst, suggesting a key role of IL-10R mobilization from specific granules to the membranes in optimal regulation of inflammatory responses.

Plasma cytokines: what we are measuring

Immunoassays, in particular enzyme-linked immunosorbent assays, have become increasingly important tools for the measurement of plasma cytokines. However, many technical factors contribute to the complexity of their quantitation. The study of plasma cytokine levels is also of limited value, and complementary methods are now available to investigate and understand more precisely the involvement of cytokines in pathological processes.

[Quality of psychomotor recovery after colonoscopy under general anesthesia using propofol. Value of tests of awakening]

Achieving colonoscopy under general anaesthesia entails the problem of ambulatory-care anaesthesia, in particular because perception of patient's recovery determines to some extent the length of monitoring following colonoscopy. The aims of the study was to assess the quality of patient's recovery after a colonoscopy under general anaesthesia while using propofol, by means of psychomotor-tests. METHODS--Colonoscopy was performed in 40 patients according to the following anaesthetic protocol: induction: propofol 2 mg/kg, continuous support: propofol 10 mg/kg/h i.v. with a 50 mg bolus in case of insufficient sedation; series of 3 psychomotor-tests were performed the day before and 1 hour, 3 hours and 6 hours after colonoscopy. The 3 psychomotor-tests studied: coordination (Newman test), time-space orientation and short-term memory. RESULTS--Forty patients, 25 females and 15 males, underwent colonoscopy with general anaesthesia for an average time-period of 22 +/- 11 min. The mean dose of propofol used was 286 +/- 102 mg. Awakening was complete in all patients, according to physical criteria such as consciousness and cardiovascular status, 20 min after receiving colonoscopy. The average psychomotor-tests results over time were (as percentages of original values) (*P < 10(-3); **P < 0.05): [table: see text] At 6 hours, 35 patients (87.5%) had recovered to their original performance and at 3 hours, 30 patients (75%) retained 90% their former state as measured with 3 psychomotor-tests. Neither by age or sex nor by propofol doses used or length or anaesthesia, the study population differed significantly. CONCLUSION--Three hours after colonoscopy under general anaesthesia using propofol, 30 patients (75%) had recovered at least 90% to their initial performances. Newman test was the most disturbed but there was no predictive factor for the quality of recovery. Psychomotor-tests may be useful before authorizing early discharge after colonoscopy under general anaesthesia but other recommendations about conditions of discharge after sedation must be also implemented.