This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dibbs, Z. Articles by Mann, D. L. Search for Related Content PubMed PubMed Citation Articles by Dibbs, Z. Articles by Mann, D. L.

CLINICAL STUDIES

Natural variability of circulating levels of cytokines and cytokine receptors in patients with heart failure: implications for clinical trials

Ziad Dibbs, MD^* , John Thornby, PhD^* , B. G. White, PhD and Douglas L. Mann, MD, FACC^*

^* Winters Center for Heart Failure Research, Cardiology Section, Department of Medicine, Veterans Administration Medical Center, USA
Baylor College of Medicine, Houston, Texas, USA
Clinical Cardiovascular Research, LLC, Gaithersburg, Maryland, USA

Manuscript received October 5, 1998; revised manuscript received January 25, 1999, accepted February 24, 1999.

Reprint requests and correspondence: Dr. Douglas L. Mann, Cardiology Research (151C), VA Medical Center, 2002 Holcombe Blvd, Houston, Texas 77030
dmann{at}bcm.tmc.edu

	Abstract

Top Abstract Methods Results Discussion References

 
OBJECTIVES

The purpose of this study was to examine the variability in cytokines and cytokine receptors in patients with heart failure in comparison with a group of healthy control subjects who were free of cardiovascular disease.

BACKGROUND

Despite increasing interest in cytokines as mediators of disease progression in heart failure and the recent interest in suppressing cytokines in clinical studies, the extent of variability in cytokines and cytokine receptors is largely unknown. This information is important for interpreting the results of studies in which changes in cytokine levels are measured in response to a specific form of therapy.

METHODS

Circulating levels of tumor necrosis factor-alpha (TNF-), and soluble TNF receptors (types 1 and 2), as well as interleukin (IL)-6 and IL-6 receptor were measured on a daily, weekly and monthly basis in heart failure patients (New York Heart Association class IIIa and IIIb; n = 10) and healthy volunteer subjects (n = 10). Measurements of cytokines and cytokine receptors were performed on plasma samples by enzyme-linked immunoassay. The daily, weekly and monthly degree of variability in cytokine and cytokine receptor levels was assessed by determining the coefficient of variation each point in time.

RESULTS

The coefficient of variation for TNF- and IL-6 levels increased over time in patients with heart failure; moreover, the coefficient of variation in heart failure subjects was significantly greater for IL-6 than for TNF-. The coefficient of variation in cytokine receptor levels was minimal, and did not differ significantly between heart failure and control subjects.

CONCLUSIONS

In patients with heart failure the degree of natural variability in circulating cytokine levels increases with time, and is greater for IL-6 than for TNF-. Accordingly, the results of the present study suggest that the sample size needed to show a statistically significant change in the circulating level of a given cytokine will vary depending on the specific cytokine that is being measured, as well as the time period over which that cytokine is being assayed.

Abbreviations and Acronyms   ANOVA = analysis of variance   IL-6 = interleukin-6   NYHA = New York Heart Association   sIL-6R = soluble interleukin-6 receptor   sTNFR1 = soluble type 1 TNF receptor   sTNFR2 = soluble type 1 TNF receptor   TNF- = tumor necrosis factor-alpha

To assess the influence of a given therapeutic intervention from either a clinical or biologic point of view, it is essential to understand the natural degree of variability in the end points that are being targeted for therapeutic intervention. Thus far, however, the extant information with respect to the natural variability in cytokines and cytokine receptors in patients with heart failure has been extremely limited (12,13). Moreover, there is no information with regard to whether or not the degree of cytokine variability in subjects with heart failure is more or less than the degree of variability that is observed in healthy subjects. Therefore, the purpose of this study was to prospectively assess the degree of daily, weekly and monthly variability in cytokines and cytokine receptors in patients with moderate to advanced heart failure in comparison with a group of healthy volunteers who were studied over a similar time period.

	Methods

Top Abstract Methods Results Discussion References

 
Subject demographics.   To examine the natural variability of cytokines and cytokine receptors in patients with heart failure, we selected 10 consecutive volunteers from the heart failure clinic at the Houston Veterans Affairs Medical Center. All of the patients had New York Heart Association (NYHA) classification class III heart failure, and were on stable medical therapy for at least one month before enrollment in the study. The patients had to give informed consent and be available for the daily, weekly and monthly follow-up visits during the four-month duration of the study. The cohort of control subjects for this study comprised healthy volunteers selected randomly from the Houston Veterans Affairs Medical Center population. All of these subjects were screened for the absence of organic heart disease by history, physical examination, 12-lead electrocardiography and two-dimensional echocardiography. Heart failure and normal volunteers were excluded from the study if they had a viral or bacterial infection within a two-week period of the study. The research protocol was approved by the Institutional Board for Human Subject Research for Baylor College of Medicine.

After the initial baseline visit (day 1), each of the control and heart failure subjects had a total of seven follow-up visits, including visits on days 2, 3, 8 (week 2), 15 (week 3), 22 (week 4), 50 (week 8) and 78 (week 12). This permitted the assessment of variability in cytokine and cytokine receptor levels on a daily (days 1 to 3), weekly (weeks 1 to 4) and monthly (months 1 to 4) basis.

Circulating levels of cytokines and cytokine receptors.   The methods for measuring cytokines and cytokine receptors have been reported previously in detail, and were adhered to throughout this protocol (14,15). All cytokine and cytokine receptor assays were performed using commercially available enzyme-linked immunosorbent assay kits (Quantikine HS, R & D Systems, Minneapolis, Minnesota) as described previously (14,15). All assays for cytokines and cytokine soluble receptors were measured in duplicate. In addition, we performed serial dilutions to be certain that the level of cytokine immunoreactivity declined in a manner parallel to the standard curve (16). All samples for a given patient were analyzed on the same enzyme-linked immunosorbent assay plate to minimize intraassay variability. The intraassay coefficients of variation for tumor necrosis factor-alpha (TNF-), interleukin-6 (IL-6), soluble type 1 TNF receptor (sTNFR1), soluble type 2 TNF receptor (sTNFR2) and soluble IL-6 receptor (sIL-6R) are 6.1%, 3.7%, 5.0%, 2.8% and 4.5%, respectively. The respective interassay coefficients of variation for TNF-, IL-6, sTNFR1, sTNFR2 and sIL-6R are 7.8%, 3.6%, 5.2%, 3.6% and 5.1%. The lower limit of sensitivity of these kits for detecting cytokines and cytokine receptors is (pg/ml): TNF- (0.18), IL-6 (0.09), sTNFR1 (3.5), sTNFR2 (1.0) and sIL-6R (0.5) (14).

For these studies we assessed the variability in circulating levels of TNF- and IL-6, based on the repeated observation that these cytokines are consistently elevated in heart failure (2,17). We elected not to measure circulating levels of IL-1-beta, based on the observation from this laboratory (unpublished observation) and other laboratories (18–20) that circulating levels of IL-1-beta are not elevated in patients with heart failure. In addition to measuring cytokines, we also elected to measure circulating levels of the soluble cytokine receptors, because these receptors have been shown to regulate the bioactivity of TNF- and IL-6. For example, sTNFR1 and sTNFR2 have been shown to neutralize the effects of TNF- (21), whereas sIL-6R has been shown to increase the bioactivity of circulating IL-6 (22).

Variability in circulating levels of cytokines and cytokine receptors.   To assess the variability of cytokines, we determined the coefficient of variation for the levels of cytokines and cytokine receptors for heart failure and control subjects (23). The coefficient of variation was defined as the standard deviation of the cytokine or cytokine receptor levels divided by the mean level of the respective cytokine or cytokine receptor level (24). Accordingly, the daily coefficient of variation for individual patients was obtained by determining the mean and standard deviation for the cytokine or cytokine receptor levels on days 1, 2 and 3 of the study. Similarly, the weekly and monthly coefficient of variation for individual patients was obtained, respectively, by determining the mean and standard deviation for the cytokine or cytokine receptor levels on week 1 (day 1), 2, 3, 4 (weekly variability) and on week 1 (day 1), week 4, week 8 and week 12 (monthly variability) of the study. The average daily, weekly and monthly coefficient of variation for all patients was determined from the mean of the daily, weekly and monthly coefficients of variation for individual patients.

Statistical analysis.   Neither the cytokine nor the cytokine receptor data were normally distributed; therefore, these data were subjected to logarithmic transformation (14,25). However, to permit comparison with results from other studies, both the cytokine and cytokine receptor data are presented as mean ± SEM. A nonpaired t test was used to compare all continuous variables (age, heart rate, blood pressure and ejection fraction) in the heart failure and control subjects, whereas a Fisher exact test or chi-square test was used for the nominal variables (gender, race). The log-normalized coefficient of variation for the daily, weekly and monthly variability in cytokine and cytokine receptor levels between control and heart failure subjects was compared using a nonpaired t test. To confirm that this analysis was robust, we repeated the analysis using the Wilcoxon rank-sum test on non–log-transformed data. Two-way repeated measures analysis of variance (ANOVA) was used to test for mean differences between and within heart failure and control subjects in circulating cytokines and cytokine receptors as a function of time. The Pearson product–moment correlation analysis of the log-normalized data was used to test for significant relationships between cytokines and individual patient age. To confirm that this parametric analysis was robust, we repeated the above analysis using the Spearman rank-order test on non–log-transformed data. Data (Cary, North Carolina) were analyzed using Sigma Stat (Chicago, Illinois), Primer (McGraw Hill, New York, New York) and SAS statistical packages. A significant difference was said to exist at p < 0.05.

	Results

Top Abstract Methods Results Discussion References

 
Subject demographics.   Table 1 summarizes the demographics for the subjects with heart failure (n = 10) and the normal volunteers (n = 10). As shown, the mean age for the heart failure group was significantly higher than that for the control group (p < 0.001). The subjects in the heart failure and control groups were primarily male, reflecting the demographics of the Houston Veterans Administration Hospital; there was, however, no significant difference in the frequency of male and female subjects between the two groups. The racial composition of the two groups was not significantly different (p = 0.48), and consisted of eight white subjects and two African-American subjects in the heart failure cohort, and six white subjects, three African American subjects and one Asian-American subject in the control group. All the heart failure patients had stable NYHA class IIIa or IIIb heart failure and were not edematous at the time they were enrolled in the study. The patients’ functional class remained stable throughout the study. The etiology of heart failure was ischemic in origin in 60% of the patients; the remaining 40% of the patients were considered to have idiopathic dilated cardiomyopathy. The heart failure patients were on standard triple therapy for heart failure, including angiotensin-converting enzyme inhibitors (100%), digoxin (80%) and diuretics (90%). There were no changes in the dosages of these drugs during the three-month period of observation. At the time that these studies were conducted, the use of beta-adrenergic blocking agents for heart failure was not routinely recommended; therefore, only one of the heart failure patients was using a beta-blocker. None of the heart failure patients nor the control subjects was taking medications that were known to alter TNF- or IL-6 levels. As shown in Table 1, there was no significant difference in the baseline heart rate, systolic blood pressure and diastolic blood pressure between the heart failure and control subjects. However, the mean ejection fraction was significantly lower in the heart failure patients when compared with control subjects (p < 0.001).

View larger version (16K): [in this window] [in a new window]   Figure 1 Circulating levels of tumor necrosis factor-alpha (TNF-) (A) and soluble TNF receptor type 1 (sTNFR1) (B) and type 2 (sTNFR2) (C) in heart failure (HF) and control subjects. To determine whether circulating levels of cytokine and cytokine receptors increased over time, the mean levels of TNF-, sTNFR1 and sTNFR2 were determined on a monthly basis for a period of 4 months (see Methods for details). Heart failure patients are depicted by solid squares, and healthy control subjects are depicted by open squares.

View larger version (18K): [in this window] [in a new window]   Figure 2 Circulating levels of interleukin-6 (IL-6) (A) and soluble IL-6 receptor (sIL-6R) (B) in heart failure (HF) and control subjects. To determine whether circulating levels of cytokine and cytokine receptors increased over time, the mean levels of IL-6 and sIL-6R were determined on a monthly basis for a period of 4 months (see Methods for details). Heart failure patients are depicted by solid squares, and healthy control subjects are depicted by open squares.

View larger version (19K): [in this window] [in a new window]   Figure 3 Variability in circulating tumor necrosis factor-alpha (TNF-) levels in heart failure and control subjects. The degree of TNF- variability was assessed by determining the coefficient of variation (CV) (see Methods) for daily, weekly and monthly TNF- levels. Each data point shown reflects the CV for a given subject. Heart failure patients are depicted by closed diamonds, and healthy control subjects are depicted by open squares. The mean ± SEM of the CVs in each group are shown to the right of each scatter plot. * = p < 0.05 compared with control subjects.

View larger version (16K): [in this window] [in a new window]   Figure 4 Variability in circulating interleukin-6 (IL-6) levels in heart failure and control subjects. The degree of IL-6 variability was assessed by determining the coefficient of variation (CV) (see Methods) for daily, weekly and monthly IL-6 levels. Each data point shown reflects the CV for a given subject. Heart failure patients are depicted by closed diamonds, and healthy control subjects are depicted by open squares. The mean ± SEM of the CVs in each group are shown to the right of each scatter plot. * = p < 0.05 compared with control subjects.

	Discussion

Top Abstract Methods Results Discussion References

 
Despite the increasing interest in the role that cytokines play as potential mediators of disease progression in heart failure, and the increasing interest in modulating cytokine levels in clinical heart failure studies (6–11,26), virtually nothing is known with respect to the natural variability in circulating levels of cytokines and cytokine receptors in patients with heart failure. To address this deficiency we prospectively examined the variability in circulating levels of cytokine and cytokine receptors in subjects with moderate to advanced heart failure (NYHA class IIIa and IIIb). Analysis of the aggregate data permits at least two important conclusions to be drawn. First, the degree of cytokine variability appears to depend not only on the cytokine that is being measured, but also on the time course over which that cytokine is being assessed. For example, we observed that the daily and weekly variability in circulating TNF- levels was significantly lower in heart failure patients than in healthy subjects (Fig. 3). However, TNF- variability increased approximately twofold with time in the heart failure subjects, with the result that the monthly variability in TNF- levels was not significantly different between heart failure and control subjects (Fig. 3). In contrast to the findings with TNF-, there was a great deal of variability in IL-6 levels in both heart failure and normal subjects (Fig. 4), regardless of whether the variability was assessed on a daily, weekly or monthly basis. Although there was no difference in the daily and weekly variability in IL-6 levels between subjects with heart failure and normal volunteers, we observed that there was a small but statistically significant increase in monthly variability in IL-6 levels in patients with heart failure when compared with normal volunteers (Fig. 4). Moreover, there was an approximately fourfold increase in IL-6 variability in the heart failure patients with time. Finally, when we compared the average coefficient of variation for cytokine levels in heart failure patients, we observed that the extent of weekly and monthly variability was significantly greater for IL-6 when compared with TNF-. The observed differences in variability in circulating cytokine levels in the heart failure and control subjects did not appear to be related to increasing cytokine levels over the three-month period of the study (Fig. 1 and 2), nor to age-related differences between the heart failure and control subjects, insofar as we did not observe a significant relationship between age and cytokine variability for either group of subjects, consistent with previous studies in healthy subjects that have not observed a correlation between age and TNF- and IL-6 variability (27,28). Furthermore, the natural variability in cytokine levels in the present study was unlikely to be due to intra- or interassay variability alone, since the observed variability in cytokines was well in excess of the analytical variability of the assay methodology used in the present study (14). The second conclusion to be drawn from these studies is that the natural variability in circulating levels of cytokine receptors in heart failure and normal subjects is less than that observed for the respective cognate cytokines (Table 2). Moreover, the variability in cytokine receptors was not significantly different in heart failure patients compared with the normal subjects (Table 2).

Cytokine variability in heart failure.   Although the precise reason(s) for the differences in the variability in circulating TNF- and IL-6 levels in heart failure subjects is not known, there are several potential explanations that warrant discussion. One possible explanation for the differing degrees of variability between these two cytokines may relate to the differing degree of stabilization of these proteins in the peripheral circulation. That is, although TNF- and IL-6 are known to bind to, and to be stabilized by their circulating cognate receptors (29–31), the degree of stabilization may be quantitatively different for each cytokine. For example, we observed that the ratio ([mol/liter]/[mol/liter]) of (sTNFR1 + sTNFR2)/TNF- ranged 2,100 to 2,700 for the healthy volunteers and heart failure subjects in this study, whereas the ratio of sIL-6R/IL-6 ([mol/liter]/[mol/liter]) ranged 3 to 6. Thus, the increased variability that we and others have observed for IL-6 may relate, at least in part, to the possibility that IL-6 is degraded more rapidly in the periphery than TNF- is. Further support for the point of view that increased stability may account for the differing degrees of variability in TNF- and IL-6 levels is suggested by the observation that the absolute levels of circulating TNF receptors increase in direct response to increased TNF- levels ("receptor shedding") (32), whereas the response of IL-6 receptors to increasing levels of IL-6 is quite variable, and may increase, decrease or remain the same (33–35). Indeed, in the present study we noted that there was an approximately twofold increase in sTNFR1 and sTNFR2 in heart failure patients, where the levels of sIL-6R were not significantly different in the healthy subjects and the patients with heart failure (Fig. 2) (36,37). The previous statements notwithstanding, it should be recognized that a number of proteins other than sIL-6R may serve as chaperones for IL-6, and that the transport and stabilization of this molecule is likely to be very complex (31). A second, intriguing explanation for the decreased variability in TNF- levels in the heart failure subjects may relate to the general loss of biologic variability that has been observed repeatedly in heart failure patients. That is, previous studies have reported a loss in heart rate variability (38), and loss in neurohormonal variability in patients with heart failure (39,40). Indeed, it has been suggested that loss of "variability reserve" (41) is a sign of a biologic system that is persistently activated, and may therefore respond less well to superimposed physiologic/pathologic stimuli (42). However, although this concept may explain the loss of variability in TNF-, it does not explain the higher degree of variability in IL-6 levels that we observed in the heart failure patients. A third explanation for the difference in variability between TNF- and IL-6 in our study might simply relate to the inherent differences in their circadian or seasonal variation in IL-6 levels.

Although a full discussion of the natural variability in cytokines and cytokine receptors in health and disease is beyond the intended scope of this discussion, it bears emphasis that the results of the present study are qualitatively similar to those reported by Masson et al. (13), who studied the natural variability in IL-6 and sTNFR1 levels in 18 heart failure subjects (NYHA class II/III) over a three-week period. The calculated coefficient of variation for IL-6 and sTNFR1 in their study was 195% and 7%, respectively, which was somewhat higher than we observed in the present study. Although the reasons for the greater degree of variability in IL-6 levels in the study by Masson et al. (13) are not known, they may relate to the fact that these investigators determined cytokine variability based on two measurements three weeks apart, whereas we assessed IL-6 variability based on cytokine determinations at four separate time points, each one week apart. The results of the present study differ somewhat from those reported by Dutka et al. (12), who measured TNF- levels serially every three months for one year in patients with NYHA class IV heart failure. These investigators did not directly determine a coefficient of variation for TNF- levels in their study, but did report that TNF- levels were below the limit of detection of their assay on at least one occasion in all 16 of their patients, thus leading them to conclude that there was "considerable between and within patient variation" in TNF- levels in their study. The most likely explanation for the difference between their report and the present study is that the TNF- assay they used was 150-fold less sensitive than the one used in the present study. Thus, it is possible that the inability to detect a circulating TNF- level in their study was the result of the assay that was employed, as opposed to a high degree of variability in TNF- levels in their patients with heart failure. However, we cannot exclude the possibility that the NYHA class IV patients in their study may have had a greater degree of variability in TNF- levels than the NYHA class III patients we examined in the present study.

There are several limitations of the present study that bear emphasis. First, the overall sample size of the present study was relatively small, which was due in large part to the difficulty in finding stable heart failure patients who were willing to return to the hospital for the frequent visits. Nonetheless, this relatively small sample size did not preclude obtaining statistically significant results with respect to the variability in TNF- and IL-6 levels. Second, all patients had moderate heart failure (NYHA class IIIa and IIIb); accordingly it is unclear if our results will be relevant for patients with milder or more advanced degrees of heart failure. Nonetheless, the levels of cytokines in our study overlap with those reported for patients with NYHA IV heart failure (15). Thus, it is possible that our findings may also apply to patients with more advanced heart failure.

Conclusions.   In assessing the impact of a given therapeutic intervention from either a biologic or a statistical point of view, it is necessary to first understand the natural degree of variability in the end points that one has chosen to target. Given the recent interest in cytokines as therapeutic targets in the setting of heart failure, the results of the present study would appear to be important for at least two reasons. First, the results of the present study suggest that the sample size needed to show a statistically significant change in the circulating level of a given cytokine after a therapeutic intervention will vary, depending on the specific cytokine that is being measured, as well as the time period over which that cytokine is being assayed (Fig. 3 and 4, Table 3). As one theoretical example, the data in the present study suggest that for a given therapeutic intervention to detect a 15% change in either circulating TNF- or IL-6 levels over a four-month period (alpha = 0.05; power = 0.80), it would require a sample size of 21 and 377 patients, respectively (Table 3) to show a statistically significant difference. Thus, the sample size needed to show a statistically significant difference may vary at least 18-fold, depending on the particular cytokine that one intends to target. A second important, and potentially disconcerting implication of this study is that it may not be possible to relate specific changes in circulating levels of certain cytokines with specific changes in outcome measures in individual heart failure patients with any degree of confidence, because of the tremendous amount of intrasubject variability in cytokine levels. The above statements are in no way intended to offer a disparaging or discouraging commentary on the importance of assessing changes in circulating cytokines in the setting of heart failure; however, they do suggest that studies that are designed to assess changes in circulating cytokine levels in patients with heart failure should not be undertaken casually, and that all such studies should be appropriately designed to avoid drawing conclusions that may lack biologic or clinical significance.

	Acknowledgments

 
The authors gratefully acknowledge the secretarial assistance of Jana Grana, as well as the spirited technical assistance of Donna Espada, Adrienne Chee, Wendy Skinner and Dorellyn Lee-Jackson. We also would like to thank Dr. Andrew Schafer for his past and present support and guidance.

	Footnotes

 
This research was supported by research funds from Otsuka America Incorporated Pharmaceuticals, the Department of Veterans Affairs and the N.I.H. (P50 HL-O6H and RO1 HL58081-01).

	References

Top Abstract Methods Results Discussion References

 
1. Packer M. The neurohormonal hypothesis: a theory to explain the mechanism of disease progression in heart failure. J Am Coll Cardiol. 1992;20:248–254[Abstract]

2. Seta Y, Shan K, Bozkurt B, et al. Basic mechanisms in heart failure: the cytokine hypothesis. J Card Failure. 1996;2:243–249[CrossRef][Medline]

3. Suffredini AF, Fromm RE, Parker MM, et al. The cardiovascular response of normal humans to the administration of endotoxin. N Engl J Med. 1989;321:280–287[Abstract]

4. Millar AB, Singer M, Meager A, et al. Tumor necrosis factor in bronchopulmonary secretions of patients with adult respiratory distress syndrome. Lancet. 1989;2:712–713[CrossRef][Medline]

5. Hegewisch S, Weh HJ, Hossfeld DK. TNF-induced cardiomyopathy. Lancet. 1990;2:294–295

6. Mohler ERI, Sorensen LC, Ghali JK, et al. Role of cytokines in the mechanism of action of amlodipine: the PRAISE heart failure trial. J Am Coll Cardiol. 1997;30:35–41[Abstract]

7. Goldstein DJ, Moazami N, Seldomridge JA, et al. Circulatory resuscitation with left ventricular assist device support reduces interleukins 6 and 8 levels. Ann Thorac Surg. 1997;63:971–974[Abstract/Free Full Text]

8. Milani RV, Mehra MR, Endres S, et al. The clinical relevance of circulating tumor necrosis factor- in acute decompensated chronic heart failure without cachexia. Chest. 1996;110:992–997[Abstract/Free Full Text]

9. Deng MC, Erren M, Lutgen A, et al. Interleukin-6 correlates with hemodynamic impairment during dobutamine administration in chronic heart failure. Int J Cardiol. 1996;57:129–134[CrossRef][Medline]

10. Sliwa K, Skudicky D, Candy G, et al. Randomized investigation of effects of pentoxifylline on left ventricular performance in idiopathic dilated cardiomyopathy. Lancet. 1998;351:1091–1093[CrossRef][Medline]

11. Deswal A, Seta Y, Blosch CM, Mann DL. A phase I trial of tumor necrosis factor receptor (p75) fusion protein (TNFR:Fc) in patients with advanced heart failure. (abstr)Circulation. 1997;96:I1802

12. Dutka DP, Elborn JS, Delamere F, et al. Tumour necrosis factor-alpha in severe congestive cardiac failure. Br Heart J. 1993;70:141–143[Abstract/Free Full Text]

13. Masson S, Latini R, Bevilacqua M, et al. Within-patient variability of hormone and cytokine concentrations in heart failure. Pharmacol Res. 1998;37:213–217[CrossRef][Medline]

14. Torre-Amione G, Kapadia S, Benedict CR, et al. Proinflammatory cytokine levels in patients with depressed left ventricular ejection fraction: a report from the studies of left ventricular dysfunction (SOLVD). J Am Coll Cardiol. 1996;27:1201–1206[Abstract]

15. Torre-Amione G, Kapadia S, Lee J, et al. Expression and functional significance of tumor necrosis factor receptors in human myocardium. Circulation. 1995;92:1487–1493[Abstract/Free Full Text]

16. Cannon JG, Nerad JL, Poutsiaka DD, Dinarello CA. Measuring circulating cytokines. J Appl Physiol. 1993;75:1897–1902[Abstract/Free Full Text]

17. Bozkurt B, Shan K, Seta Y, et al. Tumor necrosis factor- and tumor necrosis factor receptors in human heart failure. Heart Failure Rev. 1996;1:211–219

18. Wiedermann CJ, Beimpold H, Herold M, et al. Increased levels of serum neopterin and decreased production of neutrophil superoxide anions in chronic heart failure with elevated levels of tumor necrosis factor-alpha. J Am Coll Cardiol. 1993;22:1897–1901[Abstract]

19. Katz SD, Rao R, Berman JW, et al. Pathophysiological correlates of increased serum tumor necrosis factor in patients with congestive heart failure: relation to nitric oxide-dependent vasodilation in the forearm circulation. Circulation. 1994;90:12–16[Abstract/Free Full Text]

20. Munger MA, Johnson B, Amber IJ, et al. Circulating concentrations of proinflammatory cytokines in mild or moderate heart failure secondary to ischemic or idiopathic dilated cardiomyopathy. Am J Cardiol. 1996;77:723–727[CrossRef][Medline]

21. Mohler KM, Torrance DS, Smith CA, et al. Soluble tumor necrosis factor (TNF) receptors are effective therapeutic agents in lethal endotoxemia and function simultaneously as both TNF carriers and TNF antagonists. J Immunol. 1993;151:1548–1561[Abstract]

22. Novick D, Shulman LM, Chen L, Revel M. Enhancement of interleukin 6 cytostatic effect on human breast carcinoma cells by soluble IL-6 receptor from urine and reversion by monoclonal antibody. Cytokine. 1992;4:6–11[CrossRef][Medline]

23. Rosenson RS, Tangney CC, Hafner JM. Intraindividual variability of fibrinogen levels and cardiovascular risk profile. Arterioscler Thromb. 1994;14:1928–1932[Abstract/Free Full Text]

24. Woolson RF. Statistical Methods for the Analysis of Biomedical Data. New York: John Wiley; 1987. p. 23–24

25. Benedict CR, Johnstone DE, Weiner DH, et al. Relation of neurohormonal activation to clinical variables and degree of ventricular dysfunction: a report from the registry of studies of left ventricular dysfunction. J Am Coll Cardiol. 1994;23:1410–1420[Abstract]

26. Sindhwani R, Yuen J, Hirsch H, et al. Reversal of low flow state attenuates immune activation in severe decompensated congestive heart failure. (abstr)Circulation. 1993;88:I255

27. Sothern RB, Roitman-Johnson B, Kanabrocki EL, et al. Circadian characteristics of circulating interleukin-6 in men. J Allergy Clin Immunol. 1995;95:1029–1035[CrossRef][Medline]

28. Young MR, Matthews JP, Kanabrocki EL, et al. Circadian rhythmometry of serum interleukin-2, interleukin-10, tumor necrosis factor-alpha, and granulocyte-macrophage colony-stimulating factor in men. Chronobiol Int. 1995;12:19–27[Medline]

29. Aderka D, Engelmann H, Maor Y, et al. Stabilization of the bioactivity of tumor necrosis factor by its soluble receptors. J Exp Med. 1992;175:323–329[Abstract/Free Full Text]

30. Peters M, Jacobs S, Ehlers M, et al. The function of the soluble interleukin6 (IL-6) receptor in vivo: sensitization of human soluble IL-6 receptor transgenic mice towards IL-6 and prolongation of the plasma half-life of IL-6. J Exp Med. 1996;183:1399–1406[Abstract/Free Full Text]

31. Ndubuisi MI, Patel K, Rayanade RJ, et al. Distinct classes of chaperoned IL-6 in human blood: differential immunological and biological availability. J Immunol. 1998;160:494–501[Abstract/Free Full Text]

32. Joyce DA, Steer JH. Tumor necrosis factor alpha and interleukin-1 alpha stimulate late shedding of p75 TNF receptors but not p55 TNF receptors from human monocytes. J Interferon Cytokine Res. 1995;15:947–954[Medline]

33. Frieling JT, Van Deuren M, Wijdenes J, et al. Circulating interleukin-6 receptor in patients with sepsis syndrome. J Infect Dis. 1995;171:469–472[Medline]

34. Hisano S, Sakamoto K, Ishiko T, et al. IL-6 and soluble IL-6 receptor levels change differently after surgery both in the blood and in the operative field. Cytokine. 1997;9:447–452[CrossRef][Medline]

35. Angelis P, Scharf S, Mander A, et al. Serum interleukin-6 and interleukin-6 soluble receptor in Alzheimer’s disease. Neurosci Lett. 1998;244:106–108[CrossRef][Medline]

36. Torre-Amione G, Kapadia S, Lee J, et al. Tumor necrosis factor- and tumor necrosis factor receptors in the failing human heart. Circulation. 1996;93:704–711[Abstract/Free Full Text]

37. Ferrari R, Bachetti T, Confortini R, et al. Tumor necrosis factor soluble receptors in patients with various degrees of congestive failure. Circulation. 1995;92:1479–1486[Abstract/Free Full Text]

38. Stefenelli T, Bergler-Klein J, Globits S, et al. Heart rate behavior at different stages of congestive heart failure. Eur Heart J. 1992;13:902–907[Abstract/Free Full Text]

39. Gibelin P, Robillon JF, Candito M, et al. Nocturnal-diurnal changes of norepinephrine blood levels in patients with chronic cardiac insufficiency. Ann Cardiol Angeiol (Paris). 1992;41:321–325

40. Yoshino F, Sakuma N, Date T, et al. Diurnal change of plasma atrial natriuretic peptide concentrations in patients with congestive heart failure. Am Heart J. 1989;117:1316–1319[CrossRef][Medline]

41. Casolo G, Balli E, Fazi A, et al. Twenty-four-hour spectral analysis of heart rate variability in congestive heart failure secondary to coronary artery disease. Am J Cardiol. 1991;67:1154–1158[CrossRef][Medline]

42. Francis GS, Goldsmith SR, Ziesche SM, Cohn JN. Response of plasma norepinephrine and epinephrine to dynamic exercise in patients with congestive heart failure. Am J Cardiol. 1982;49:1152[CrossRef][Medline]

This article has been cited by other articles:

				M. T. Haren, T. K. Malmstrom, D. K. Miller, P. Patrick, H. M. Perry III, M. M. Herning, W. A. Banks, and J. E. Morley Higher C-Reactive Protein and Soluble Tumor Necrosis Factor Receptor Levels Are Associated With Poor Physical Function and Disability: A Cross-Sectional Analysis of a Cohort of Late Middle-Aged African Americans J Gerontol A Biol Sci Med Sci, October 7, 2009; (2009) glp148v1. [Abstract] [Full Text] [PDF]

				I. Tracchi, G. Ghigliotti, M. Mura, S. Garibaldi, P. Spallarossa, C. Barisione, V. Boasi, M. Brunelli, L. Corsiglia, A. Barsotti, et al. Increased neutrophil lifespan in patients with congestive heart failure Eur J Heart Fail, April 1, 2009; 11(4): 378 - 385. [Abstract] [Full Text] [PDF]

				T. Ueland, J. Kjekshus, S. S. Froland, T. Omland, I. B. Squire, L. Gullestad, K. Dickstein, and P. Aukrust Plasma Levels of Soluble Tumor Necrosis Factor Receptor Type I During the Acute Phase Following Complicated Myocardial Infarction Predicts Survival in High-Risk Patients J. Am. Coll. Cardiol., December 6, 2005; 46(11): 2018 - 2021. [Abstract] [Full Text] [PDF]

				L. Guilherme, P. Cury, L. M.F. Demarchi, V. Coelho, L. Abel, A. P. Lopez, S. E. Oshiro, S. Aliotti, E. Cunha-Neto, P. M.A. Pomerantzeff, et al. Rheumatic Heart Disease: Proinflammatory Cytokines Play a Role in the Progression and Maintenance of Valvular Lesions Am. J. Pathol., November 1, 2004; 165(5): 1583 - 1591. [Abstract] [Full Text] [PDF]

				T. Bachetti, L. Comini, E. Pasini, and R. Ferrari Anti-cytokine therapy in chronic heart failure: new approaches and unmet promises Eur. Heart J. Suppl., November 1, 2004; 6(suppl_F): F16 - F21. [Abstract] [Full Text] [PDF]

				V. M. Conraads, P. G. Jorens, L. S. De Clerck, H. K. Van Saene, M. M. Ieven, J. M. Bosmans, A. Schuerwegh, C. H. Bridts, F. Wuyts, W. J. Stevens, et al. Selective intestinal decontamination in advanced chronic heart failure: a pilot trial Eur J Heart Fail, June 1, 2004; 6(4): 483 - 491. [Abstract] [Full Text] [PDF]

				M. Cesari, B. W. J. H. Penninx, M. Pahor, F. Lauretani, A. M. Corsi, G. R. Williams, J. M. Guralnik, and L. Ferrucci Inflammatory Markers and Physical Performance in Older Persons: The InCHIANTI Study J. Gerontol. A Biol. Sci. Med. Sci., March 1, 2004; 59(3): M242 - M248. [Abstract] [Full Text] [PDF]

				D. Pesenti-Rossi, F. Godart, A. Dubar, and C. Rey Transcatheter Closure of Traumatic Ventricular Septal Defect: An Alternative to Surgery Chest, June 1, 2003; 123(6): 2144 - 2145. [Abstract] [Full Text] [PDF]

				V.M. Conraads, P. Beckers, J. Bosmans, L.S. De Clerck, W.J. Stevens, C.J. Vrints, and D.L. Brutsaert Combined endurance/resistance training reduces plasma TNF-{alpha} receptor levels in patients with chronic heart failure and coronary artery disease Eur. Heart J., December 1, 2002; 23(23): 1854 - 1860. [Abstract] [Full Text] [PDF]

				P. J. Pugh, R. D. Jones, T.H. Jones, and K. S. Channer Heart failure as an inflammatory condition: potential role for androgens as immune modulators Eur J Heart Fail, December 1, 2002; 4(6): 673 - 680. [Abstract] [Full Text] [PDF]

				W. S. Bradham, B. Bozkurt, H. Gunasinghe, D. Mann, and F. G. Spinale Tumor necrosis factor-alpha and myocardial remodeling in progression of heart failure: a current perspective Cardiovasc Res, March 1, 2002; 53(4): 822 - 830. [Abstract] [Full Text] [PDF]

				R. Kell, A. Haunstetter, T.J. Dengler, C. Zugck, W. Kubler, and M. Haass Do cytokines enable risk stratification to be improved in NYHA functional class III patients?. Comparison with other potential predictors of prognosis Eur. Heart J., January 1, 2002; 23(1): 70 - 78. [Abstract] [Full Text] [PDF]

				C. W. Lee, J. H. Lee, T.-H. Lim, H. S. Yang, M.-K. Hong, J.-K. Song, S.-W. Park, S.-J. Park, and J.-J. Kim Prognostic Significance of Cerebral Metabolic Abnormalities in Patients With Congestive Heart Failure Circulation, June 12, 2001; 103(23): 2784 - 2787. [Abstract] [Full Text] [PDF]

				W. W. Parmley How Many Medicines Do Patients With Heart Failure Need? Circulation, March 27, 2001; 103(12): 1611 - 1612. [Full Text] [PDF]

				T. Ohtsuka, M. Hamada, G. Hiasa, O. Sasaki, M. Suzuki, Y. Hara, Y. Shigematsu, and K. Hiwada Effect of beta-blockers on circulating levels of inflammatory and anti-inflammatory cytokines in patients with dilated cardiomyopathy J. Am. Coll. Cardiol., February 1, 2001; 37(2): 412 - 417. [Abstract] [Full Text] [PDF]

				M. Rauchhaus, W. Doehner, D. P. Francis, C. Davos, M. Kemp, C. Liebenthal, J. Niebauer, J. Hooper, H.-D. Volk, A. J. S. Coats, et al. Plasma Cytokine Parameters and Mortality in Patients With Chronic Heart Failure Circulation, December 19, 2000; 102(25): 3060 - 3067. [Abstract] [Full Text] [PDF]

				A. Ergul, C. A. Walker, A. Goldberg, S. C. Baicu, J. W. Hendrick, M. K. King, and F. G. Spinale ET-1 in the myocardial interstitium: relation to myocyte ECE activity and expression Am J Physiol Heart Circ Physiol, June 1, 2000; 278(6): H2050 - H2056. [Abstract] [Full Text] [PDF]

				W. Doehner and S.D. Anker TNF-{alpha} system in CHF Eur. Heart J., May 1, 2000; 21(9): 782 - 782. [PDF]

				P.P. Davey and H. Ashrafian New therapies for heart failure: is thalidomide the answer? QJM, May 1, 2000; 93(5): 305 - 311. [Abstract] [Full Text] [PDF]

				M. R. Mehrabi, H. Sinzinger, C. Ekmekcioglu, F. Tamaddon, K. Plesch, H. D Glogar, G. Maurer, T. Stefenelli, and I. M. Lang Accumulation of oxidized LDL in human semilunar valves correlates with coronary atherosclerosis Cardiovasc Res, March 1, 2000; 45(4): 874 - 882. [Abstract] [Full Text] [PDF]

				J. B. Young Angiotensin-converting enzyme inhibitors and cytokines in heart failure: dose and effect? J. Am. Coll. Cardiol., December 1, 1999; 34(7): 2068 - 2071. [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dibbs, Z. Articles by Mann, D. L. Search for Related Content PubMed PubMed Citation Articles by Dibbs, Z. Articles by Mann, D. L.