Menstrual- and gender-dependent variations in circulating IL-1 agonists, antagonists, and binding proteins.

This study tested the hypotheses that sex-related differences in circulating binding proteins for interleukin- 1beta (IL- 1beta ) exist and that these binding proteins affect immunoassays for IL-1beta and IL-1Ra. 125I-labeled IL-1beta was added to human plasma samples, then chromatographed. The percentages of total radioactivity eluting in a high-molecular-weight peak were 21.0 + 0.8 for men (n = 6), 19.1+/-0.9 for follicular phase women (n = 6), and 18.0+/-0.8 in luteal phase women (n = 6; men vs. women, P = 0.032; follicular vs. luteal, P = 0.035), and correlated with plasma sIL-1RII concentrations (r = 0.647, P = 0.007). Plasma IL-1beta immunoreactivity did not correspond to concurrent cellular secretion rates due, in part, to interference in the IL-1beta assay by sIL-1RII. Correspondence between plasma IL-1Ra levels and cellular secretion rates was observed only after serial dilutions of the samples. These results indicate that plasma IL-1beta binding capacity differs between men and women and that sIL-1RII is a major contributing factor. Furthermore, relating plasma IL-1 isoform immunoreactivity to functional measures (tracer binding) or concurrent release by isolated cells can lead to insights about assay interferences that may exist in plasma.

Monocyte cytokine production in an elderly population: effect of age and inflammation.

OBJECTIVE: To determine the association among aging, inflammation, and cytokine production by peripheral blood mononuclear cells. POPULATION AND METHODS: We examined production of interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), IL-1 receptor antagonist (IL-1Ra), and IL-6 in 711 elderly participants in the Framingham Heart Study (mean age, 79 y) and 21 young healthy volunteers (mean age, 39 y). The elderly subjects were categorized by serum C-reactive protein (CRP) concentration, a marker of systemic inflammation. RESULTS: Production of IL-6 (p < .00001) and IL-1Ra (p < .00001) was higher in the elderly subjects than in the control group. IL-6 production increased with increasing CRP, whereas IL-1RA was uniformly elevated in elderly subjects regardless of CRP. However, we found no difference in the production of IL-1 beta or TNF-alpha between the young and elderly groups, regardless of CRP status. IL-6 population correlated with IL-1 beta (r = .36, p < .0001) and TNF-alpha production (r = .25, p < .0001), but IL-1Ra production did not. CONCLUSION: Production of IL-6 and IL-1Ra--but not IL-1 beta or TNF-alpha--was increased in the elderly compared to healthy, young subjects. The increase in IL-6 also correlated with increased production of CRP, a marker of inflammation. However, IL-1Ra was increased in the elderly independently of CRP production. Although limited by the small control group, these data suggest that dysregulation of some inflammatory cytokines occurs with age, but the role of inflammation in aging remains unclear.

Effect of acquired immune deficiency syndrome wasting on the protein metabolic response to acute exercise.

Wasting is a major complication of human immunodeficiency virus (HIV) infection, which remains prevalent even in the era of highly-active antiretroviral therapy. We have previously shown that progressive resistance exercise can increase lean body mass (LBM) significantly in patients with wasting, and that exercise does not increase circulating HIV RNA concentrations. We examined the effect of 1 bout of moderately difficult exercise on whole body protein kinetics in 10 patients with HIV wasting and 12 patients with HIV infection without wasting. At baseline, there were no differences between the groups in whole body leucine flux, oxidation, or nonoxidative leucine disposal (NOLD, a measure of whole body protein synthesis). Six days after exercise, NOLD was significantly higher in the wasted patients compared with the nonwasted ones (82.2 +/- 16.7 v 66.5 +/- 15.2 micromol/kg LBM/h, P <.03). The change in NOLD between baseline and day 6 was significantly different between the 2 groups (+9.0 +/- 9.2 v -3.3 +/- 5.7 micromol/kg LBM/h, P <.02). These data indicate that the ability to respond to exercise with protein synthesis is maintained in HIV wasting.

Eccentric exercise markedly increases c-Jun NH(2)-terminal kinase activity in human skeletal muscle.

Eccentric contractions require the lengthening of skeletal muscle during force production and result in acute and prolonged muscle injury. Because a variety of stressors, including physical exercise and injury, can result in the activation of the c-Jun NH(2)-terminal kinase (JNK) intracellular signaling cascade in skeletal muscle, we investigated the effects of eccentric exercise on the activation of this stress-activated protein kinase in human skeletal muscle. Twelve healthy subjects (7 men, 5 women) completed maximal concentric or eccentric knee extensions on a KinCom isokinetic dynamometer (10 sets, 10 repetitions). Percutaneous needle biopsies were obtained from the vastus lateralis muscle 24 h before exercise (basal), immediately postexercise, and 6 h postexercise. Whereas both forms of exercise increased JNK activity immediately postexercise, eccentric contractions resulted in a much higher activation (15.4 +/- 4.5 vs. 3.5 +/- 1.4-fold increase above basal, eccentric vs. concentric). By 6 h after exercise, JNK activity decreased back to baseline values. In contrast to the greater activation of JNK with eccentric exercise, the mitogen-activated protein kinase kinase 4, the immediate upstream regulator of JNK, was similarly activated by concentric and eccentric exercise. Because the activation of JNK promotes the phosphorylation of a variety of transcription factors, including c-Jun, the results from this study suggest that JNK may be involved in the molecular and cellular adaptations that occur in response to injury-producing exercise in human skeletal muscle.

Effects of progressive resistance training on immune response in aging and chronic inflammation.

The effects of 12 wk of progressive resistance strength training on in vivo and in vitro immune parameters were evaluated in a controlled study of eight subjects with rheumatoid arthritis (RA), eight healthy young (22-30 yr), and eight healthy elderly (65-80 yr) individuals. Six healthy elderly (65-80 yr) nontraining control subjects were also evaluated to account for seasonal and psychosocial effects. Training subjects exercised at 80% of their one-repetition maximum and performed eight repetitions per set, three sets per session on a twice weekly basis. Peripheral blood mononuclear cell (PBMC) subpopulations, cytokine and prostaglandin (PG) E2 production, proliferative response, and delayed type hypersensitivity (DTH) skin response were measured before and after 12 wk of training. Training did not induce changes in PBMC subsets, interleukin (IL)-1 beta, tumor necrosis factor-alpha (TNF), IL-6, IL-2, or PGE2 production, lymphocyte proliferation, or DTH response in any of the training groups, compared with control subjects. These data suggest that 12 wk of high-intensity progressive resistance strength training does not affect immune function in young or elderly healthy individuals or subjects with RA.

Effects of prior exercise on eccentric exercise-induced neutrophilia and enzyme release.

PURPOSE: The purpose of this study was to determine the effects of prior exercise on changes in circulating neutrophils, neutrophil activation, and myocellular enzymes following a standardized bout of eccentric exercise. METHODS: Twenty-four male volunteers were randomized into three groups (N = 8). Group C performed 10 sets of 10 eccentric contractions of the quadriceps muscles with both legs (100% of the concentric IRM). Group D and Group F exercised for 2 h at 56%VO2max on a cycle ergometer followed by a similar bout of eccentric contractions. Group F also received 7.5 mL x kg(-1) of a carbohydrate-electrolyte beverage every 30 min during the submaximal exercise, whereas group D received no fluid. RESULTS: Body weight remained unchanged in groups C and F and decreased in group D by 1.56 +/- 0.34 kg. Ultrastructural Z-Band damage increased three-fold following exercise and remained elevated 3 d after exercise but was not different among groups. Circulating neutrophils were elevated more in group D compared with those in group C immediately after the exercise or rest period, and this difference persisted 3 h after the eccentric exercise. Serum lactoferrin concentrations increased 3.3-fold after exercise in all groups (P < 0.01). Creatine kinase levels (CK) rose in all subjects, with subjects in Group F and D having a significantly greater rise in CK after exercise compared with those in group C. CONCLUSIONS: These data indicate that submaximal exercise followed by a bout of eccentric exercise results in similar amounts of myofibrillar injury with a larger neutrophil response and CK release.

Acute phase responses and cytokine secretion in chronic fatigue syndrome.

This study addresses the hypothesis that clinical manifestations of chronic fatigue syndrome (CFS) are due in part to abnormal production of or sensitivity to cytokines such as interleukin-1beta (IL-1beta) and IL-6 under basal conditions or in response to a particular physical stress: 15 min of exercise consisting of stepping up and down on a platform adjusted to the height of the patella. The study involved 10 CFS patients and 11 age-, sex-, and activity-matched controls: of these, 6 patients and 4 controls were tested in both the follicular and the luteal phases of the menstrual cycle, and the remainder were tested in only one phase, for a total of 31 experimental sessions. Prior to exercise, plasma concentrations of the acute phase reactant alpha2-macroglobulin were 29% higher in CFS patients (P < 0.008) compared to controls. Secretion of IL-6 was generally higher for CFS patients (approximately 38%), however, this difference was statistically significant only if all values over a 3-day period were analyzed by repeated-measures ANOVA (P = 0.035). IL-6 secretion correlated with plasma alpha2-macroglobulin in control subjects at rest (R = 0.767, P = 0.001). Immediately after exercise, the CFS patients reported greater ratings of perceived exertion (P=0.027) compared to the healthy control subjects. Ratings of perceived exertion correlated with IL-1beta secretion by cells from healthy control subjects (R = 0.603, P = 0.022), but not from CFS patients, and IL-1beta secretion was not different between groups. Exercise induced a slight (< 12%) but significant (P = 0.006) increase in IL-6 secretion, but the responses of the CFS patients were not different than controls. Furthermore, no significant exercise-induced changes in body temperature or plasma alpha2-macroglobulin were observed. These data indicate that under basal conditions, CFS is associated with increased IL-6 secretion which is manifested by chronically elevated plasma alpha2-macroglobulin concentrations. These modest differences suggest that cytokine dysregulation is not a singular or dominant factor in the pathogenesis of CFS.

Abnormal homocysteine metabolism in rheumatoid arthritis.

OBJECTIVE: To assess total homocysteine (tHcy) metabolism in patients with rheumatoid arthritis (RA). METHODS: Assessments were performed to determine the fasting levels of tHcy and the increase in tHcy in response to methionine (Met) challenge in blood samples from 28 patients with RA and 20 healthy age-matched control subjects. RESULTS: Fasting levels of tHcy were 33% higher in the RA patients than in the control subjects (mean +/- SD 11.7 +/- 1.5 nmoles/ml versus 8.8 +/- 1.1 nmoles/ml; P < 0.01). Four hours after Met challenge, the increase in plasma tHcy levels (delta tHcy) was higher in the RA patients (20.9 +/- 10.4 nmoles/ml) than in the control subjects (15.5 +/- 1.6 nmoles/ml) (P < 0.02). In a subgroup analysis, the delta tHcy in patients taking methotrexate (12.9 +/- 2.2 nmoles/ml) did not differ from that in the control group, while the delta tHcy in patients not taking methotrexate (25.3 +/- 1.7 nmoles/ml) was significantly higher (P < 0.0001). CONCLUSION: Elevated tHcy levels occur commonly in patients with RA, and may explain some of the increased cardiovascular mortality seen in such patients. Studies of the prevalence and mechanism of hyperhomocysteinemia in RA are warranted.

Adjuvant arthritis as a model of inflammatory cachexia.

OBJECTIVE: To determine whether adjuvant arthritis (AA) leads to changes in body composition and cytokine production similar to those seen in patients with rheumatoid arthritis. METHODS: AA was induced in Lewis rats using Freund's complete adjuvant. Body cell mass was measured by determining the concentration of total exchangeable potassium using 42K gavage. Splenocyte production of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) was measured by bioassay. Weight and food intake were also measured. RESULTS: Animals that developed AA lost 6% of their body weight by the onset of clinically evident arthritis (day 14; P < 0.01) and lost 20% by the end of the inflammatory phase of AA (day 28; P < 0.0001). Body cell mass fell 24.7 +/- 8.6% (mean +/- SEM) in animals with AA, but did not change significantly in controls (increase of 6.3 +/- 7.9%) (P < 0.03). Pair-fed animals lost one-fourth of the weight lost by the animals with AA (P < 0.01), indicating that anorexia alone does not explain inflammatory cachexia. Weight loss was correlated with TNF alpha production by spleen mononuclear cells (r = 0.68, P < 0.007), and a weaker correlation was seen with IL-1 production (r = 0.45, P < 0.04). CONCLUSION: AA in rats is a useful model of inflammatory cachexia that mimics the human pathophysiology in important ways, and is consistent with cytokine-driven cachexia in chronic inflammatory arthritis.

Interleukin-1 beta, interleukin-1 receptor antagonist, and soluble interleukin-1 receptor type II secretion in chronic fatigue syndrome.

Chronic fatigue syndrome is a condition that affects women in disproportionate numbers, and that is often exacerbated in the premenstrual period and following physical exertion. The signs and symptoms, which include fatigue, myalgia, and low-grade fever, are similar to those experienced by patients infused with cytokines such as interleukin-1. The present study was carried out to test the hypotheses that (1) cellular secretion of interleukin-1 beta (IL-1 beta), interleukin-1 receptor antagonist (IL-1Ra), and soluble interleukin-1 receptor type II (IL-1sRII) is abnormal in female CFS patients compared to age- and activity-matched controls; (2) that these abnormalities may be evident only at certain times in the menstrual cycle; and (3) that physical exertion (stepping up and down on a platform for 15 min) may accentuate differences between these groups. Isolated peripheral blood mononuclear cells from healthy women, but not CFS patients, exhibited significant menstrual cycle-related differences in IL-1 beta secretion that were related to estradiol and progesterone levels (R2 = 0.65, P < 0.01). IL-1Ra secretion for CFS patients was twofold higher than controls during the follicular phase (P = 0.023), but luteal-phase levels were similar between groups. In both phases of the menstrual cycle, IL-1sRII release was significantly higher for CFS patients compared to controls (P = 0.002). The only changes that might be attributable to exertion occurred in the control subjects during the follicular phase, who exhibited an increase in IL-1 beta secretion 48 hr after the stress (P = 0.020). These results suggest that an abnormality exists in IL-1 beta secretion in CFS patients that may be related to altered sensitivity to estradiol and progesterone. Furthermore, the increased release of IL-1Ra and sIL-1RII by cells from CFS patients is consistent with the hypothesis that CFS is associated with chronic, low-level activation of the immune system.

Protein metabolism in rheumatoid arthritis and aging. Effects of muscle strength training and tumor necrosis factor alpha.

OBJECTIVE: To determine the effects of rheumatoid arthritis (RA) on whole-body protein metabolism. METHODS: We examined protein metabolism and its hormonal and cytokine mediators before and 12 weeks after progressive resistance muscle strength training in 8 healthy young (mean +/- SD age 25 +/- 2 years) and 8 healthy elderly (70 +/- 5 years) men and women, and in 8 adults with RA (42 +/- 13 years). An additional 6 healthy elderly subjects (69 +/- 3 years) served as a swimming-only control group. RESULTS: Subjects with RA had higher rates of protein breakdown than did young or elderly healthy subjects (79.9 +/- 17.2 versus 60.3 +/- 5.8 and 63.7 +/- 12.4 mumoles/gm total body potassium/hour, respectively, P < 0.05), while there was no effect of age per se. Patients treated with methotrexate had normal rates of protein breakdown (P < 0.01 versus RA without methotrexate; P not significant versus healthy young subjects). Increased protein catabolism in RA was no longer evident after strength training. In multiple regression analysis, levels of tumor necrosis factor alpha (TNF alpha) (r = 0.47, P = 0.01) and growth hormone (r = -0.51, P = 0.006) were associated with protein breakdown, and plasma glucagon levels were inversely correlated with protein synthesis (r = -0.45, P = 0.02). Growth hormone (r = -0.56, P = 0.002) and glucagon (r = 0.45, P = 0.04, levels were associated with protein oxidation. CONCLUSION: Adults with RA have increased whole-body protein breakdown, which correlates with growth hormone, glucagon, and TNF alpha production.

Hormonal influences on stress-induced neutrophil mobilization in health and chronic fatigue syndrome.

This investigation tested the hypotheses that women diagnosed with chronic fatigue syndrome (CFS) would exhibit significantly greater systemic indices of exercise-induced leukocyte mobilization and inflammation (neutrophilia, lactoferrin release, complement activation) than controls matched for age, weight, and habitual activity and that responses in the luteal phase of the menstrual cycle would be greater than in the follicular phase. Subjects stepped up and down on a platform adjusted to the height of the patella for 15 min, paced by metronome. Blood samples were collected under basal conditions (the day before exercise) and following exercise for determination of circulating neutrophils and plasma concentrations of lactoferrin, C3a des arg, and creatine kinase. Complete, 24-hr urine collections were made for determination of cortisol excretion. For all subjects, circulating neutrophil counts increased 33% (P < 0.0001) and lactoferrin increased 27% (P = 0.0006) after exercise, whereas plasma C3a des arg and creatine kinase did not increase. No indication of an exaggerated or excessive response was observed in the CFS patients compared to the controls. In healthy women, circulating neutrophil numbers exhibited previously described relationships with physiological variables: basal neutrophil counts correlated with plasma progesterone concentrations (R = 0.726, P = 0.003) and the exercise-induced neutrophilia correlated with both urinary cortisol (R = 0.660, P = 0.007) and plasma creatine kinase (R = 0.523, P = 0.038) concentrations. These relationships were not observed in the CFS patients (R = 0.240, P = 0.370; R = 0.042, P = 0.892; and R = 0.293, P = 0.270; respectively). These results suggest that normal endocrine influences on the circulating neutrophil pool may be disrupted in patients with CFS.