Apoptosis: the germs of death

From the initial recognition that programmed cell suicide existed, to the elucidation of the underlying death and survival pathways at the molecular level, the story of apoptosis has unfolded rapidly. But much still remains to be discovered.

Reliability of McConnell's classification of patellar orientation in symptomatic and asymptomatic subjects

STUDY DESIGN

Test-retest reliability study with blinded testers.

OBJECTIVES

To determine the intratester reliability of the McConnell classification system and to determine whether the intertester reliability of this system would be improved by one-on-one training of the testers, increasing the variability and numbers of subjects, blinding the testers to the absence or presence of patellofemoral pain syndrome, and adhering to the McConnell classification system as it is taught in the "McConnell Patellofemoral Treatment Plan" continuing education course.

BACKGROUND

The McConnell classification system is currently used by physical therapy clinicians to quantify static patellar orientation. The measurements generated from this system purportedly guide the therapist in the application of patellofemoral tape and in assessment of the efficacy of treatment interventions on changing patellar orientation.

METHODS AND MEASURES

Fifty-six subjects (age range, 21-65 years) provided a total of 101 knees for assessment. Seventy-six knees did not produce symptoms. A researcher who did not participate in the measuring process determined that 17 subjects had patellofemoral pain syndrome in 25 knees. Two testers concurrently measured static patellar orientation (anterior/posterior and medial/lateral tilt, medial/lateral glide, and patellar rotation) on subjects, using the McConnell classification system. Repeat measures were performed 3-7 days later. A kappa (kappa) statistic was used to assess the degree of agreement within each tester and between testers.

RESULTS

The kappa coefficients for intratester reliability varied from -0.06 to 0.35. Intertester reliability ranged from -0.03 to 0.19.

CONCLUSION

The McConnell classification system, in its current form, does not appear to be very reliable. Intratester reliability ranged from poor to fair, and intertester reliability was poor to slight. This system should not be used as a measurement tool or as a basis for treatment decisions.

Peripheral blood mononuclear cells from patients with rheumatoid arthritis spontaneously secrete vascular endothelial growth factor (VEGF): specific up-regulation by tumour necrosis factor-alpha (TNF-alpha) in synovial fluid

This study was designed to investigate VEGF production from peripheral blood mononuclear cells (PBMC) from patients with rheumatoid arthritis (RA) compared with healthy controls and to identify the predominant cellular source in PBMC isolated from RA patients. The regulation of PBMC VEGF production by cytokines and synovial fluid (SF) was studied. PBMC were isolated from RA patients and healthy controls and stimulated with lipopolysaccharide (LPS), IL-1beta, IL-4, IL-6, IL-8, IL-10, TNF-alpha and transforming growth factor-beta (TGF-beta) isoforms for varying time points up to 72 h at 37 degrees C/5% CO2. The effect of SF on VEGF secretion by PBMC was also studied. Supernatant VEGF levels were measured using a flt-1 receptor capture ELISA. RA patients had significantly higher spontaneous production of VEGF compared with controls, and monocytes were identified as the predominant cellular source. RA PBMC VEGF production was up-regulated by TGF-beta isoforms and TNF-alpha and down-regulated by IL-4 and IL-10, with no effect observed with IL-1beta, IL-6 and IL-8. Antibody blocking experiments confirmed that TNF-alpha and not TGF-beta isoforms in SF increased VEGF secretion by RA PBMC. These results emphasize the importance of monocytes as a source of VEGF in the pathophysiology of RA. Several cytokines known to be present in SF can modulate the level of VEGF secretion, but the predominant effect of SF in VEGF up-regulation is shown to be dependent on TNF-alpha.

NF-kappaB and apoptosis in mammary epithelial cells

A number of transcription factors have been identified as regulators of mammary development, including Stat5 and C/EBPbeta (1-3). In this review we summarize evidence which suggests that the NF-kappaB family of transcription factors also has a role in mammary gland development. NF-kappaB was originally described as a mediator of inflammatory reactions and cellular responses to viral pathogens. More recently it has been shown to possess an anti-apoptotic effect in a variety of cell types by regulating apoptosis-related genes. In the light of this function in other tissues, and the observation that aberrant activation of NF-kappaB can be associated with mammary tumors, we discuss the potential role of this transcription factor in modulating mammary epithelial apoptosis and involution of the mammary gland.

A collaborative effort to establish a long-term care benchmark process

Several long-term care facilities in the Rochester, NY, area developed a benchmark process that was customer driven, analytical in its approach to problem-solving, measurable, and flexible enough to be applicable to any area of care within the facilities. The facilities benefited by gaining a process that improves their operations and has a positive impact on residents' quality of life.

Circulating vascular endothelial growth factor is not increased during relapses of steroid-sensitive nephrotic syndrome

BACKGROUND

An uncharacterized circulating factor that increases vascular permeability has previously been described in childhood steroid-sensitive nephrotic syndrome (SSNS). The aim of this study was to determine whether this factor is vascular endothelial growth factor (VEGF), the recently described endothelial cell mitogen and enhancer of vascular permeability.

METHODS

Plasma and urine VEGF levels were measured in children with SSNS in both relapse and remission and in normal age- and sex-matched controls. Semiquantitative reverse transcriptase-polymerase chain reaction studies investigating VEGF mRNA expression were performed on peripheral blood mononuclear cells isolated from children with SSNS in relapse and controls. In two experimental models (one-hour and three-day follow-up postinfusion), Sprague-Dawley rats were intravenously administered 50 microg rVEGF to determine whether this induced either proteinuria or glomerular histologic change.

RESULTS

Plasma VEGF levels and urine VEGF/creatinine ratios were not elevated in SSNS relapse compared with remission and control samples. Peripheral blood mononuclear cell VEGF mRNA expression was no different in SSNS patients compared with controls. The administration of VEGF to rats induced an acute reversible fall in systemic blood pressure but did not result in the development of either proteinuria or glomerular histologic change.

CONCLUSION

Increased circulating VEGF levels are not responsible for the proteinuria observed during relapses of SSNS. Further studies are warranted to investigate intrarenal VEGF expression.

Sirolimus: a potent new immunosuppressant for liver transplantation

BACKGROUND

Sirolimus (rapamycin) is a new immunosuppressant that appears to be synergistic with cyclosporine in kidney transplantation, but with a different side-effect profile. This pilot study evaluated sirolimus in liver transplantation.

METHODS

Patients undergoing orthotopic liver transplantation for primary tumors (8), and later for nonmalignant disease (7), received one of three sirolimus-based immunosuppressive regimens. Protocol A comprised sirolimus, microemulsion cyclosporine (target whole blood concentration: 100 ng/ml), and prednisolone; protocol B omitted prednisolone; and protocol C was sirolimus alone. By 3 months after transplantation, all patients were receiving sirolimus as monotherapy.

RESULTS

Fifteen patients were treated with a follow-up of 117-806 days. Rejection was more common on monotherapy than double therapy, and absent on triple therapy. The drug was generally well tolerated, with only three patients discontinuing sirolimus: one for hyperlipidemia, one for pneumocystis pneumonia, and one for inability to tolerate the taste of the drug. Two patients discontinued cyclosporine early, both as a result of neurological complications; they continued on sirolimus monotherapy. Five patients died; one suffered a cardiac arrest, and four died from sepsis in association with graft-versus-host disease, recurrent tumor, a paralyzed right hemidiaphragm, and primary nonfunction.

CONCLUSIONS

Sirolimus combined with cyclosporine provided potent immunosuppression of liver allografts, and sirolimus monotherapy was adequate and well tolerated as maintenance therapy. Side effects of sirolimus over the short period of follow-up were uncommon and reversible with dose reduction or cessation of therapy.

DNA chip technology

A mini-revolution is sweeping the world of science and medicine. DNA chip or microarray technology will have a more profound impact than other recent major advances, including DNA sequencing and the polymerase chain reaction (PCR). This mini-review explains the technology, its scope, and impact on science and medicine, as well as its cost and possible limitations.

A survey of U.K. centres on implant failures

This study investigated the experience of endossoseus implants in the U.K. - how success rates compare with other countries; the common causes of failure; early detection, definition and treatment of the failing implant. Information was gathered by means of a questionnaire sent to 120 centres in the U.K. Thirty-nine centres responded to the survey, reporting on a total of 5328 implants which had been placed over an average time period of 6.5 years. A mean failure rate of 4.3% was reported in the mandible with 16% in the maxilla. The survey showed that 11 different implant systems were in use and that implants were used to support an overdenture in 56% of cases, and bridgework in 26%. The definition of the failing implant and the causes of failure were unclear, with a wide range of opinions given. A combination of methods were used to treat the failing implant including surgical techniques and chemotherapeutic agents, but the long-term success of these treatments was uncertain. Failure rates especially in the maxilla at some of the centres appear higher than have been previously suggested in the U.K. or abroad. Universal agreement on the criteria for 'success' and 'failure' of fixtures is needed along with agreed treatment protocols for the failing implant.

Estimates of distance by claudicants and vascular surgeons are inherently unreliable

Claudication distance and maximum walking distance are both measures of disability. Estimates of the distances which a patient with intermittent claudication can walk are commonly used by vascular surgeons as surrogate measures of handicap. We studied how accurately distance was estimated by 70 patients with intermittent claudication, and by 100 British vascular surgeons. Patients and vascular surgeons estimated actual distances of 30 m and 34 m, respectively. Estimates were 46 m median (range 2.7-402 m) for claudicants, and 46 m median (range 15.2-186 m) for vascular surgeons, median over estimates of 52% and 34% respectively. Claudicants' errors can easily be eliminated by accurate and appropriate measurement of claudication and maximum walking distances but interpretation of the data by surgeons is dependent on their own ability to estimate distance. Flawed perceptions by patients and their surgeons of the disability of reduced walking distance illustrates the need for reliable measures of handicap on which to base therapeutic decisions in patients with intermittent claudication.

A 3- to 6-year study of overdentures supported by hydroxyapatite-coated endosseous dental implants

PURPOSE

The purpose of this study was to evaluate the clinical effectiveness of hydroxyapatite-coated cylindrical implants to support overdentures. These implants were placed between 1990 and 1994 and have been followed up over a period of 3 to 6 years.

MATERIALS AND METHODS

One hundred thirty-nine Calcitek dental implants were placed in 43 patients to support 14 maxillary and 30 mandibular overdentures. Standardized clinical review procedures were used.

RESULTS

At exposure all the implants were found to be osseointegrated. To date only 7 implants (5%) have completely failed and two associated overdentures (5%) have been lost. The cumulative survival rate of all implants over 6 years was 92%. However, if failure is defined by the loss of more than 4 mm of cervical bone, 33 implants could be classified as being in the process of failing. Using these figures, interval success rates as low as 82% were found by year 6, and the cumulative success rate would fall to 39%. Maxillary survival and success rates were significantly lower than mandibular rates, at 38% and 10%, respectively, by year 5.

CONCLUSION

Failure rates were higher in the maxillary arch, in poor quality bone, in smokers, and where implants were opposed by a natural dentition or an implant-supported prosthesis. The results suggest that the cervical bone level adjacent to the Calcitek cylindrical hydroxyapatite-coated implant failed to establish a steady state, particularly in the maxillary arch. Doubts remain regarding the long-term prognosis of these cylindrical implants.

Efficient BLG-Cre mediated gene deletion in the mammary gland

Using the phage P1-derived Cre/loxP recombination system, we have developed a strategy for efficient mammary tissue specific inactivation of floxed genes. Transgenic mice were generated which express Cre DNA-recombinase under the control of the mammary gland specific promoter of the ovine beta-lactoglobulin (BLG) gene. To test the specificity of Cre mediated recombination, we crossed these mice to animals harbouring a floxed DNA ligase I allele. We show that the BLG-Cre construct specifies mammary specific gene deletion, and furthermore that it is temporally regulated, predominantly occurring during lactation. We fully characterised the extent of gene deletion in one line (line 74). In this strain the virgin gland is characterised by low levels (7%) of Cre mediated deletion, whereas 70-80% of cells within the lactating mammary gland have undergone recombination. Immunohistochemistry and indirect in situ PCR were used respectively to demonstrate that both Cre protein and Cre activity were evenly distributed throughout the population of secretory epithelial cells. The level of background recombination in non-mammary tissues was found to be < or = 1.1%, irrespective of mammary gland developmental status. Crossing the transgenic BLG-Cre strain described here to mice harbouring other floxed alleles will facilitate the functional analysis of those genes during differentiation and development of the mammary gland.

How well are complete dentures copied?

OBJECTIVE

To assess how accurately the same set of complete dentures could be copied by 12 different laboratories.

DESIGN

A prospective study.

SETTINGS

Completed by commercial laboratories used by GDPs in England (1996). Results were analysed and controlled by a university department.

SUBJECTS (MATERIALS) AND METHODS

The master set was constructed to include a midline diastema and a bilateral posterior crossbite. Twelve sets of silicone moulds of the master denture were prepared. GDPs selected commercial laboratories of their choice to receive the work.

MAIN OUTCOME MEASURES

All stages of the work were compared with the master dentures by returning them to a specially adapted articulator. Analysis was completed using preset criteria.

RESULTS

Only five of the returned copies were considered to have both good quality acrylic resin work and clear details of the teeth in wax. Only four cases reproduced the diastema. After processing, the occlusal vertical dimension had been increased in eight of the cases and the bilateral crossbite had been eliminated in all cases.

CONCLUSIONS

None of the final copy dentures were considered an accurate copy of the master dentures. There is considerable scope for further training of dental technicians in this important technique.

Updated measurements from CREAM & CREDO & implications for environment & shielding models

Flight data obtained between 1995 and 1997 from the Cosmic Radiation Environment Monitors CREAM & CREDO carried on UoSat-3, Space Shuttle, STRV-1a (Space Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electronics Experiment Spacecraft) have been added to the dataset affording coverage since 1990. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are observed, the former comprising a factor three increase at high latitudes and the latter a general increase accompanied by a westward drift. Comparison of particle fluxes and linear energy transfer spectra is made with improved environment & radiation transport calculations which account for shield distributions and secondary particles. While there is an encouraging convergence between predictions and observations, significant improvements are still required, particularly in the treatrnent of locally produced secondary particles.

Characterization of a nucleoside/proton symporter in procyclic Trypanosoma brucei brucei

Adenosine transport at 22 degrees C in procyclic forms of Trypanosoma brucei brucei was investigated using an oil-inhibitor stop procedure for determining initial rates of adenosine uptake in suspended cells. Adenosine influx was mediated by a single high affinity transporter (Km 0.26 +/- 0.02 microM, Vmax 0.63 +/- 0.18 pmol/10(7) cells s-1). Purine nucleosides, with the exception of tubercidin (7-deazaadenosine), and dipyridamole inhibited adenosine influx (Ki 0.18-5.2 microM). Purine nucleobases and pyrimidine nucleosides and nucleobases had no effect on adenosine transport. This specificity of the transporter appears to be similar to the previously described P1 adenosine transporter in bloodstream forms of trypanosomes. Uptake of adenosine was Na+-independent, but ionophores reducing the membrane potential and/or the transmembrane proton gradient (monitored with the fluorescent probes bis-(1,3-diethylthiobarbituric acid)-trimethine oxonol and 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein acetoxymethyl ester, respectively) inhibited adenosine transport. Similarly, an increase in extracellular pH from 7.3 to 8.0 reduced adenosine influx by 30%. A linear correlation was demonstrated between the rate of adenosine transport and the protonmotive force. Adenosine uptake was accompanied by a proton influx in base-loaded cells and was also shown to be electrogenic. These combined results indicate that transport of adenosine in T. brucei brucei procyclics is protonmotive force-driven and strongly suggest that the adenosine transporter functions as an H+ symporter.

Vascular endothelial growth factor (VEGF) is released from platelets during blood clotting: implications for measurement of circulating VEGF levels in clinical disease

1. Dysregulated vascular endothelial growth factor (VEGF) expression has been reported in several pathological states based upon evidence of elevated serum VEGF levels. Using two immunoassays for VEGF, this study determines normal plasma and serum VEGF ranges, determines which are more likely to reflect circulating VEGF levels and investigates a potential contribution of VEGF from platelets to VEGF levels detected in serum. 2. The presence of soluble VEGF receptor, sflt-1, at a molar excess of 7:1 significantly reduced measured VEGF levels in both assays. Serum VEGF levels were higher than plasma levels in children [(mean +/- S.E.M.) 306.1 +/- 39.4 versus 107.4 +/- 24.9 pg/ml, P < 0.0001] and adults (249.4 +/- 46.4 versus 76.1 +/- 10.7 pg/ml, P < 0.0001). Serum VEGF increased with clotting time (P = 0.0005 t0 compared with 2 h samples); plasma VEGF levels were not affected by time between sampling and centrifugation. 3. Calcium-induced clotting of platelet-rich but not platelet-poor plasma induced VEGF release with a proportional response between platelet count and VEGF level and isolated platelets released significant quantities of VEGF upon incubation with thrombin. Reverse transcriptase-PCR studies confirmed that platelets express VEGF121 and VEGF165 mRNA. 4. These data suggest that plasma is the preferred medium to measure VEGF levels; a significant and highly variable platelet-mediated secretion of VEGF during the clotting process invalidates the use of serum as an indicator of circulating VEGF levels in disease states.

Activated human neutrophils express vascular endothelial growth factor (VEGF)

The neutrophil (PMN) influx in the acute inflammatory response is associated with a local increase in vascular permeability and oedema. Vascular endothelial growth factor (VEGF), a growth factor known to have potent vascular permeability-enhancing properties in addition to being an endothelial cell mitogen and a chemo-attractant for mononuclear cells, has previously been shown to be expressed by mononuclear cells and platelets, though PMN VEGF expression has not been reported. PMNs isolated from healthy adult volunteers (n = 16) were incubated for 4 h at 37 degrees C in the presence of tumour necrosis factor alpha (TNF-alpha) (5 ng/ml) and serum opsonized zymozan (SOZ) (500 micrograms/ml). Supernatant VEGF levels were measured using a sandwich antibody capture immuno-assay. Median (interquartile range) VEGF levels were significantly increased in PMN supernatants following stimulation with both TNF-alpha [347 pg/ml (264-385 pg/ml)] and SOZ [506 pg/ml (407-593 pg/ml)] compared with control values [78 pg/ml (78-87 pg/ml)]. Time course experiments with SOZ stimulated PMNs showed that the majority of VEGF production occurred within the first hour (1 h mean VEGF level 318 pg/ml, 4 h mean VEGF level 451 pg/ml). RT-PCR studies showed that PMNs express mRNA for the two common VEGF splice variants, VEGF121 and VEGF165. PMN VEGF production may be central to the classic acute phase response to injury and the chemo-attraction of other leukocytes to the source of injury.

The low earth orbit environment observed using CREAM and CREDO

The Cosmic Radiation Environment and Dosimetry experiment (CREDO) has been operational on board the Advanced Photovoltaics & Electronics Experiment Spacecraft since August 1994. Extensive measurements of cosmic ray linear energy transfer spectra (using data to January 1996) and total dose (using data to November 1994) have been made, and compared with predictions of standard models. Detailed consideration of spacecraft shielding effects have been made. Predictions are shown to overestimate the measured linear energy transfer spectra. The CREAM experiment was flown on STS-63 in the SpaceHab module. Results show penetration of high energy electrons into the SpaceHab module.

What is the long-term outcome for patients with very small abdominal aortic aneurysms?

OBJECTIVE

To determine the long-term outcome for patients with abdominal aortic aneurysms (AAA) less than 4 cm in AP diameter (very small AAA).

DESIGN

Population-based screening study.

MATERIALS AND METHODS

One hundred and forty-two patients who had AAA less than 4 cm at presentation were assessed by ultrasound at intervals of 6-12 months. The records of these patients were reviewed.

RESULTS

During the period of follow-up the median annual growth rate for aneurysms while under 3.0 cm was 1 mm, rising to 2 mm when between 3.0 and 3.9 cm, and 3 mm when between 4.0 and 4.9 cm in diameter. Elective aneurysm repair was undertaken when aneurysms exceeded the threshold value, which itself increased from 4 cm to 5.5 cm in the 9 years of follow-up. More patients died with their aneurysm (n = 35) then underwent surgery (n = 23). There was one perioperative death, and three unrelated late deaths after resection. One aneurysm ruptured in a patient who had refused follow-up 5 years previously.

CONCLUSIONS

This study suggests that aneurysms less than 4.0 cm diameter are relatively benign, and questions the appropriateness of early intervention.

Claudication distance is poorly estimated and inappropriately measured

BACKGROUND

Claudication distance is the commonest measure of the disability caused by lower-limb occlusive arterial disease. The accuracy of claudication distance as a surrogate for handicap has been assessed.

METHODS

Seventy patients who attended a specialist vascular clinic with intermittent claudication were studied prospectively. Patients were asked to estimate their claudication distance and maximum walking distance before undergoing both a patient-controlled corridor walk and a fixed-speed treadmill walk.

RESULTS

The claudication distance reported by patients bore little relation to the distance recorded in the medical correspondence. There was no correlation between the estimated distance and the actual distance walked on either a patient-controlled corridor walk or a fixed-speed treadmill walk. Most patients were able to walk substantially further at their own speed on the corridor than on the treadmill at a slower speed.

CONCLUSION

Claudication distance is spuriously estimated, inaccurately reported, falsely recorded, inappropriately measured and usually misinterpreted. It is of little value in judging the need for treatment. Objective measures of the handicap caused by the disability of reduced walking distance are required if rational management decisions are to be made.

Successful use of size-mismatched liver allografts in children by delayed primary closure of the abdominal wall

Children who are too ill to await a liver graft of suitable size may be transplanted with a relatively oversized graft by leaving the abdominal wound partially open, the defect reduced being bridged with polypropylene mesh and the mesh reduced in stages until it can be removed and the wound directly closed. This technique has been used in seven children who received nine grafts (five reduced and four full size). Their mean age was 7.3 (range 0.5-11) months and mean weight 5.8 (range 2.3-7.2) kg. Progressive reduction in the size of the transplanted liver made primary closure possible in survivors in up to four stages. Over a follow-up period of 3 to 58 months, five of the nine grafts and five of the seven patients survived. No significant complications attributable to the technique were encountered. The technique of delayed primary abdominal wall closure may be of benefit in children at risk of graft failure because of a size-mismatched graft.

Differential activation of STATs 3 and 5 during mammary gland development

We have investigated the activity of STAT family members throughout a mammary developmental cycle. Transcripts for Stat 5 were upregulated during pregnancy whilst STAT1 and STAT3 mRNAs were expressed at constant levels. DNA binding complexes containing both STAT5a and 5b showed differing affinities for two naturally occurring STAT5 binding sites. In the involuting mammary gland STAT5 activity decreased whereas STAT3 was specifically activated. These observations reveal a complex pattern of activation of STAT factors during mammary growth, differentiation and remodelling and provide the first evidence for the involvement of STAT3 in development of the mammary gland.

Regulation of surface and soluble TNF receptor expression on human monocytes and synovial fluid macrophages by IL-4 and IL-10

By regulating monocyte and macrophage production of IL-1, its receptor, and its receptor antagonist, IL-4 and IL-10 may exert significant anti-inflammatory activity. We determined whether a similar multicomponent process controlling TNF activity was regulated by IL-4 and IL-10 in nonadherent monocytes and synovial fluid macrophages. Previous studies differed in their conclusions. For both the p75 and p55 TNF receptors, mRNA levels, surface receptor expression, and soluble receptor levels were measured for blood monocytes incubated in vitro for 17, 40, or 64 h with IL-4 or IL-10. The predominant TNF receptor on monocytes, the p75 receptor, was down-regulated by IL-4 at the mRNA level. In turn, both surface and soluble receptor levels on LPS-stimulated cells were reduced and the inhibitory effects were maintained for at least 64 h. In contrast, IL-10 increased surface and soluble p75 TNF receptor levels on monocytes for approximately 40 h, which reflected an increase in receptor mRNA. These studies suggest that IL-4 and IL-10 do not directly regulate the cleavage of TNF receptors from monocytes and macrophages. Addition of an Ab to IL-10 suggested that the stimulatory effects of LPS on p75 TNF receptor expression were due, at least in part, to LPS stimulation of IL-10 production and that IL-4 acted, in part, by decreasing IL-10 production. IL-4 was down-regulatory and IL-10 stimulatory for TNF receptor expression by synovial fluid macrophages. By increasing surface receptor levels, IL-10 enhanced the activities of TNF on monocytes for IL-1beta production. By increasing soluble TNF receptor levels, IL-10 may limit only temporarily the activity of other TNF-responsive cells. This study questions the benefit of IL-10 to resolving TNF-associated inflammation.

Regulation of surface and soluble TNF receptor expression on human monocytes and synovial fluid macrophages by IL-4 and IL-10

By regulating monocyte and macrophage production of IL-1, its receptor, and its receptor antagonist, IL-4 and IL-10 may exert significant anti-inflammatory activity. We determined whether a similar multicomponent process controlling TNF activity was regulated by IL-4 and IL-10 in nonadherent monocytes and synovial fluid macrophages. Previous studies differed in their conclusions. For both the p75 and p55 TNF receptors, mRNA levels, surface receptor expression, and soluble receptor levels were measured for blood monocytes incubated in vitro for 17, 40, or 64 h with IL-4 or IL-10. The predominant TNF receptor on monocytes, the p75 receptor, was down-regulated by IL-4 at the mRNA level. In turn, both surface and soluble receptor levels on LPS-stimulated cells were reduced and the inhibitory effects were maintained for at least 64 h. In contrast, IL-10 increased surface and soluble p75 TNF receptor levels on monocytes for approximately 40 h, which reflected an increase in receptor mRNA. These studies suggest that IL-4 and IL-10 do not directly regulate the cleavage of TNF receptors from monocytes and macrophages. Addition of an Ab to IL-10 suggested that the stimulatory effects of LPS on p75 TNF receptor expression were due, at least in part, to LPS stimulation of IL-10 production and that IL-4 acted, in part, by decreasing IL-10 production. IL-4 was down-regulatory and IL-10 stimulatory for TNF receptor expression by synovial fluid macrophages. By increasing surface receptor levels, IL-10 enhanced the activities of TNF on monocytes for IL-1beta production. By increasing soluble TNF receptor levels, IL-10 may limit only temporarily the activity of other TNF-responsive cells. This study questions the benefit of IL-10 to resolving TNF-associated inflammation.