Usefulness of cytokines interleukin-6 and interleukin-2R concentrations in diagnosing active infective endocarditis involving native valves

Biomarkers for prediction of mortality in left-sided infective endocarditis

BACKGROUND

Evidence regarding biomarkers for risk prediction in patients with infective endocarditis (IE) is limited. We aimed to investigate the value of a panel of biomarkers for the prediction of in-hospital mortality in patients with IE.

METHODS

Between 2016 and 2018, consecutive IE patients admitted to the emergency department were prospectively included. Blood concentrations of nine biomarkers were measured at admission (D0) and on the seventh day (D7) of antibiotic therapy: C-reactive protein (CRP), sensitive troponin I (s-cTnI), procalcitonin, B-type natriuretic peptide (BNP), neutrophil gelatinase-associated lipocalin (NGAL), interleukin 6 (IL6), tumor necrosis factor α (TNF-α), proadrenomedullin, alpha-1-acid glycoprotein, and galectin 3. The primary endpoint was in-hospital mortality.

RESULTS

Among 97 patients, 56% underwent cardiac surgery, and in-hospital mortality was 27%. At admission, six biomarkers were independent predictors of in-hospital mortality: s-cTnI (OR 3.4; 95%CI 1.8-6.4; P<0.001), BNP (OR 2.7; 95%CI 1.4-5.1; P=0.002), IL-6 (OR 2.06; 95%CI 1.3-3.7; P=0.019), procalcitonin (OR 1.9; 95%CI 1.1-3.2; P=0.018), TNF-α (OR 1.8; 95%CI 1.1-2.9; P=0.019), and CRP (OR 1.8; 95%CI 1.0-3.3; P=0.037). At admission, S-cTnI provided the highest accuracy for predicting mortality (area under the ROC curve: s-cTnI 0.812, BNP 0.727, IL-6 0.734, procalcitonin 0.684, TNF-α 0.675, CRP 0.670). After 7 days of antibiotic therapy, BNP and inflammatory biomarkers improved their performance (s-cTnI 0.814, BNP 0.823, IL-6 0.695, procalcitonin 0.802, TNF-α 0.554, CRP 0.759).

CONCLUSION

S-cTnI concentration measured at admission had the highest accuracy for mortality prediction in patients with IE.

Inflammatory Response in Infective Endocarditis

Endocarditis remains a devastating disease with a high mortality despite timely diagnosis and treatment. The mainstays of treatment include appropriate antibiotics and when indicated, removal of the septic focus. This sounds extremely simple and belies the necessity for a sophisticated multidisciplinary approach to its treatment, the success of which depends not just on the right antibiotic at the right dosage via the right portal, but also on a profound understanding of the inflammatory and infective pathophysiology at work. This review aims at assisting both the clinician and the lab-based physician in the task.

Cytokine Signature in Infective Endocarditis

Infective endocarditis (IE) is a severe disease with high mortality rate. Cytokines participate in its pathogenesis and may contribute to early diagnosis improving the outcome. This study aimed to evaluate the cytokine profile in IE. Serum concentrations of interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12 and tumor necrosis factor (TNF)-α were measured by cytometric bead array (CBA) at diagnosis in 81 IE patients, and compared with 34 healthy subjects and 30 patients with non-IE infections, matched to the IE patients by age and gender. Mean age of the IE patients was 47±17 years (range, 15–80 years), and 40 (50%) were male. The IE patients had significantly higher serum concentrations of IL-1β, IL-6, IL-8, IL-10 and TNF-α as compared to the healthy individuals. The median levels of IL-1β, TNF-α and IL-12 were higher in the IE than in the non-IE infections group. TNF-α and IL-12 levels were higher in staphylococcal IE than in the non-staphylococcal IE subgroup. There was a higher proportion of both low IL-10 producers and high producers of IL-1β, TNF-α and IL-12 in the staphylococcal IE than in the non-staphylococcal IE subgroup. This study reinforces a relationship between the expression of proinflammatory cytokines, especially IL-1β, IL-12 and TNF-α, and the pathogenesis of IE. A lower production of IL-10 and impairment in cytokine network may reflect the severity of IE and may be useful for risk stratification.

Cytokine profiles linked to fatal outcome in infective prosthetic valve endocarditis

Infective endocarditis is a disease normally of bacterial cause which affects the endocardic tissue, specifically the valves (native or prosthetic). It is a serious illness and mortality rates remain high, ranging between 20% and 40%. Previous reports have evidenced the potential role of cytokines in the diagnosis of this disease, but no information is available on their relationship with outcome. We recruited 26 consecutive patients with late prosthetic valve endocarditis requiring surgical treatment according to Duke criteria. Eight cytokines were measured in plasma in the first 24 h following diagnosis by using a Bio-Rad multiplex assay. Levels of IL-6, IL-8 and interferon gamma (IFN-γ) were higher in non survivors. Receiver operating characteristic curve analysis evidenced that IL-6, IL-8 and IFN-γ behaved as good diagnostic tests for identifying those patients with fatal outcome (area under the curve, CI 95%, p): IL-6: [0.81 (0.61-1.00) 0.012]; IL-8 [0.76 (0.56-0.96) 0.035]; IFN-γ [0.79 (0.59-0.99) 0.021]. Levels of IL-6, IL-8 and IFN-γ correlated positively between them, indicating that they are produced as consequence of a simultaneous response to the infection. Our findings support the participation of IL-6, IL-8 and IFN-γ in the events linked to fatal outcome in infective prosthetic valve endocarditis.

Use of a human-like low-grade bacteremia model of experimental endocarditis to study the role of Staphylococcus aureus adhesins and platelet aggregation in early endocarditis

Animal models of infective endocarditis (IE) induced by high-grade bacteremia revealed the pathogenic roles of Staphylococcus aureus surface adhesins and platelet aggregation in the infection process. In humans, however, S. aureus IE possibly occurs through repeated bouts of low-grade bacteremia from a colonized site or intravenous device. Here we used a rat model of IE induced by continuous low-grade bacteremia to explore further the contributions of S. aureus virulence factors to the initiation of IE. Rats with aortic vegetations were inoculated by continuous intravenous infusion (0.0017 ml/min over 10 h) with 10(6) CFU of Lactococcus lactis pIL253 or a recombinant L. lactis strain expressing an individual S. aureus surface protein (ClfA, FnbpA, BCD, or SdrE) conferring a particular adhesive or platelet aggregation property. Vegetation infection was assessed 24 h later. Plasma was collected at 0, 2, and 6 h postinoculation to quantify the expression of tumor necrosis factor (TNF), interleukin 1α (IL-1α), IL-1β, IL-6, and IL-10. The percentage of vegetation infection relative to that with strain pIL253 (11%) increased when binding to fibrinogen was conferred on L. lactis (ClfA strain) (52%; P = 0.007) and increased further with adhesion to fibronectin (FnbpA strain) (75%; P < 0.001). Expression of fibronectin binding alone was not sufficient to induce IE (BCD strain) (10% of infection). Platelet aggregation increased the risk of vegetation infection (SdrE strain) (30%). Conferring adhesion to fibrinogen and fibronectin favored IL-1β and IL-6 production. Our results, with a model of IE induced by low-grade bacteremia, resembling human disease, extend the essential role of fibrinogen binding in the initiation of S. aureus IE. Triggering of platelet aggregation or an inflammatory response may contribute to or promote the development of IE.

Lipopolysaccharide-binding protein: a new biomarker for infectious endocarditis?

BACKGROUND

Infectious endocarditis (IE) is a bacterial infection of the endocardium. Diagnosis is based on results obtained from echocardiography, blood cultures, and molecular genetic screening for bacteria and on data for inflammatory markers such as the leukocyte (WBC) count and the C-reactive protein (CRP) concentration. The aim of the present study was to evaluate lipopolysaccharide-binding protein (LBP) as a supportive biomarker for the diagnosis and therapeutic monitoring of IE.

METHODS

We measured LBP and CRP concentrations and WBC counts in 57 IE patients at hospital admission, 40 patients with noninfectious heart valve diseases (HVDs), and 55 healthy blood donors. The progression of these 3 markers and the influence of cardiac surgery on them were evaluated in 29 IE patients and 21 control patients.

RESULTS

Serum LBP concentrations were significantly higher in IE patients [mean (SD), 33.41 (32.10) mg/L] compared with HVD patients [6.67 (1.82) mg/L, P < 0.0001] and healthy control individuals [5.61 (1.20) mg/L]. The progression in the LBP concentration during therapy of IE patients correlated with the changes in the CRP concentration. The 2 markers were equally influenced by antibiotic treatment and surgical intervention.

CONCLUSIONS

Serial LBP measurement may provide an effective and useful tool for evaluating the response to therapy in IE patients. We found a strong correlation between LBP and CRP concentrations; LBP has a tendency to increase earlier in cases of reinfection.

Getting to the heart of the problem: serological and molecular techniques in the diagnosis of infective endocarditis

Infective endocarditis is diagnosed using the Duke criteria, which rely predominantly on cardiac imaging and recovery of a causative organism from the bloodstream. These criteria can be inconclusive, particularly when blood cultures remain sterile either due to the fastidious nature of the infecting organism or prior antibiotic therapy. Serology and, more recently, molecular techniques have been investigated as a solution to the problematic negative blood culture. The detection of elevated antibody levels has proved particularly useful in the diagnosis of those patients infected with organisms that cannot be cultured using standard laboratory methods, whilst molecular methods have been successfully used in the detection of both fastidious pathogens and those inhibited by prior antibiotic therapy. In view of recent and ongoing developments in the field of molecular diagnostics, these techniques will become increasingly important not only in the routine investigation of infectious disease, but specifically the diagnosis of endocarditis.

[The heart in cases of viral, bacterial and parasitic infections]

The heart can be the primary target for a viral, bacterial or parasitic infection (primary myocarditis/inflammatory cardiomyopathy). It can also participate in the "collateral damage" due to toxins, chemo- and cytokines, autoreactive antibodies or the native and acquired immune response through T- and B-cells, monocytes and macrophages (secondary myocarditis/inflammatory cardiomyopathy), when it is not the dominant organ of the disease. Infective agents show remarkable organ specificity: viral infections, toxic and autoreactive processes affect primarily the myocardium and the pericardium, whereas bacterial infections prefer endothelial surfaces and cause endocarditis and, less frequently, pericarditis. They are even discussed as part of the inflammatory process involved in coronary artery disease. Infective agents and their adequate diagnosis and treatment are discussed for these clinical entities according to current guidelines and clinical pathways.

Extension of antimicrobial treatment in patients with left-sided native valve endocarditis based on elevated C-reactive protein values

The aim of this non-randomized study was to investigate whether there is any benefit in the extension of antimicrobial treatment in patients with left-sided native valve endocarditis in whom C-reactive protein levels are still elevated after a standard course of therapy. There was no statistically significant difference in outcome between the group of patients in which treatment was extended in comparison to the group in which treatment was ended at the recommended time. It is unlikely that there is much to gain from extending treatment based on elevated C-reactive protein levels alone.

Glucosyltransferases of viridans group streptococci modulate interleukin-6 and adhesion molecule expression in endothelial cells and augment monocytic cell adherence

Recruitment of monocytes plays important roles during vegetation formation and endocardial inflammation in the pathogenesis of infective endocarditis (IE). Bacterial antigens or modulins can activate endothelial cells through the expression of cytokines or adhesion molecules and modulate the recruitment of leukocytes. We hypothesized that glucosyltransferases (GTFs), modulins of viridans group streptococci, may act directly to up-regulate the expression of adhesion molecules and also interleukin-6 (IL-6) to augment monocyte attachment to endothelial cells. Using primary cultured human umbilical vein endothelial cells (HUVECs) as an in vitro model, we demonstrated that GTFs (in the cell-bound or free form) could specifically modulate the expression of IL-6, and also adhesion molecules, in a dose- and time-dependent manner. Results of inhibition assays suggested that enhanced expression of adhesion molecules was dependent on the activation of nuclear factor kappaB (NF-kappaB) and extracellular signal-regulated kinase and that p38 mitogen-activated protein kinase pathways also contributed to the release of IL-6. Streptococcus-infected HUVECs or treatment with purified IL-6 plus soluble IL-6 receptor alpha enhanced the expression of ICAM-1 and the adherence of the monocytic cell line U937. These results suggest that streptococcal GTFs might play an important role in recruiting monocytic cells during inflammation in IE through induction of adhesion molecules and IL-6, a cytokine involved in transition from neutrophil to monocyte recruitment.

Activated nuclear transcription factor kappaB in patients with myocarditis and dilated cardiomyopathy--relation to inflammation and cardiac function

OBJECTIVES AND BACKGROUND

Myocarditis is caused by various agents and autoimmune processes. It is unknown whether viral genome persistence represents inactive remnants of previous infections or whether it is attributed to ongoing adverse processes. The latter also applies to the course of autoimmune myocarditis. One principal candidate for an adverse remodeling is nuclear factor-kappaB (NFkappaB).

METHODS

A total of 93 patients with suspected myocarditis/cardiomyopathy was examined. Hemodynamics were assessed by echocardiography as well as right and left heart catheterization. Endomyocardial biopsies were taken from the left ventricle. Biopsies were examined by immunohistochemistry and PCR for viral genomes. Selective immunostaining of activated NFkappaB was performed.

RESULTS

NFkappaB was increased in patients with myocarditis when compared with controls (11.1+/-7.1% vs. 5.0+/-5.3%, P<0.005) whereas dilated cardiomyopathy showed no significant increase. Patients with myocarditis and preserved left ventricular function exhibited increased activated NFkappaB when compared with reduced function (r2=0.72, P<0.001). In parallel, inverse correlation of NFkappaB and left ventricular enddiasstolic volume was found (r2=0.43, P<0.02). Increased activated NFkappaB was found in adenovirus persistence when compared with controls (P=0.001). Only a trend of increased NFkappaB activation was seen in cytomegalovirus persistence. Parvovirus B19 persistence did not affect NFkappaB activation.

CONCLUSIONS

Increased activation of NFkappaB is related to inflammatory processes in myocarditis. Since activated NFkappaB correlates with left ventricular function, it could be assumed that NFkappaB activation occurs at early stages of inflammation. Potentially, NFkappaB could inhibit loss of cardiomyocytes by apoptosis and protect from cardiac dilation. Since NFkappaB is a crucial key transcription factor of inflammation, its prognostic and future therapeutic relevance should be addressed.

Glucosyltransferases of viridans streptococci are modulins of interleukin-6 induction in infective endocarditis

The glucosyltransferases (GTFs) of viridans streptococci, common pathogens of infective endocarditis, are extracellular proteins that convert sucrose into exopolysaccharides and glucans. GTFs B, C, and D of Streptococcus mutans are modulins that induce, in vitro and in vivo, the production of cytokines, in particular interleukin-6 (IL-6), from monocytes. The roles of S. mutans GTFs in infectivity and inflammation in situ were tested in a rat experimental model of endocarditis. No significant differences in infectivity, in terms of 95% infective dose and densities of bacteria inside vegetations, were observed between laboratory strain GS-5 and two clinical isolates or isogenic mutant NHS1DD, defective in the expression of GTFs. In aortic valves and surrounding tissues, IL-6 was detected by Western blots and immunostaining 24 h after GS-5 infection, was maintained over 72 h, and was followed by production of tumor necrosis factor alpha but not IL-1beta. Animals infected with NHS1DD showed markedly lower levels of IL-6 (less than 5% of that of parental GS-5-infected rats), while tumor necrosis factor alpha was unaffected. In contrast, animals infected with NHR1DD, another isogenic mutant expressing only GtfB, showed a much smaller reduction (down to 56%). These results suggest that GTFs are specific modulins that act during acute inflammation, inducing IL-6 from endothelial cells surrounding the infected valves without affecting bacterial colonization in vegetations, and that IL-6 might persist in chronic inflammation in endocarditis.

Cytokine response in lower extremity ischaemia/reperfusion

We studied the local and systemic concentrations of pro-inflammatory cytokines produced during acute lower extremity ischaemia and following reperfusion in 19 patients undergoing thromboembolectomy of the femoral artery. Blood samples were taken from the femoral vein (local response) and radial artery (systemic response) in the ischaemic (baseline) phase, and 2, 12 and 24 h post-reperfusion. Associated lung injury was measured by the alveolar-arterial (A-a) oxygen gradient and post-reperfusion femoral vein plasma concentrations of creatinine kinase and lactic dehydrogenase were also measured. Local and systemic concentrations of interleukin (IL)-2 receptor and IL-6 (but not IL-1 beta) increased significantly after reperfusion. IL-8 concentration increased significantly in the radial artery. The high and progressively increasing concentration of IL-6 in the femoral vein suggests local production. The parallel increase in creatinine kinase concentration and A-a oxygen gradient indicates that IL-6 plays an important role in acute arterial occlusion and reperfusion injury.

Increase in interleukin-6 in the first hour after coronary stenting: an early marker of the inflammatory response

BACKGROUND

Inflammation after coronary stenting presages adverse outcomes after percutaneous coronary intervention (PCI). While changes in inflammatory markers have been defined 24-72 hours after PCI, potential changes during the first few hours have not. This study was designed to determine if a systemic inflammatory response could be measured within the first hour after stenting.

METHODS

Patients (n = 25) undergoing coronary stenting, with predominantly (n = 23) acute coronary syndromes were enrolled prospectively in this registry. Blood samples were collected before PCI, and 10 minutes, 1 hour and 18-24 hours later. No patient received a glycoprotein IIb-IIIa inhibitor. Concentrations of C-reactive protein (CRP), interleukin-6 (IL-6), and interleukin-1 receptor antagonist (IL-1Ra) and soluble CD40 ligand (sCD40L) were measured using ELISA.

RESULTS

CRP and sCD40L did not change in the first hour after stenting. By contrast, IL-6 increased in the first hour (before = 7.6 +/- 7.7 pg/ml, 1 hour = 12 +/- 12 pg/ml; p < 0.001). The concentration of IL-1Ra tended to be greater after 1 hour (before = 426 +/- 261 pg/ml, 1 hour = 511 +/- 406 pg/ml; p = 0.11). Increase in IL-1Ra was apparent only in female subjects (p = 0.004 for the difference in trend between the two genders). A correlation was not observed between the increase in IL-6 at 1 hour and the increase in CRP at 24 hours (r = -0.21).

CONCLUSIONS

In patients undergoing coronary stenting, increase in IL-6 can be detected 1 hour after PCI, and thus IL-6 may be an early initiator of the systemic inflammatory response to stenting.

Interleukin-6 and Cardiovascular Diseases

Inflammatory cytokines are important for both cardiovascular scientists and practicing clinicians. Interleukin-6 (IL-6) has been emphasized by reports of elevated circulating as well as intracardiac IL-6 levels in patients with congestive heart failure (CHF). IL-6 may contribute to the progression of myocardial damage and dysfunction in chronic heart failure syndrome resulting from different causes. As the cause of CHF in cardiomyopathy, myocarditis, allograft rejection, and left ventricular assist device (LVADs) conditions, circulating IL-6 levels are associated with the severity of left ventricular dysfunction, and are also strong predictors of subsequent clinical outcomes. Continuous and excessive production of IL-6 promotes myocardial injury by breaking down both cytokine networks and viral clearance under viral myocarditis. Although IL-6 is likely important in the process of viral antigen presentation, early activation of immune responses and attenuation of viral replication also appear to be significant in an animal model of viral myocarditis. IL-6 can cause cardiac hypertrophy through the IL-6 signal transducing receptor component, glycoprotein 130. There are several interesting cases of cardiac myxoma complicated with mediastinal lymphadenopathy or left ventricular hypertrophy. Increased expression of IL-6 is observed in the myocardium of all donor hearts showing marked dysfunction. Myocardial IL-6 concentrations are also significantly higher in LVAD candidates compared with advanced heart failure patients. Although the IL-6 family plays a central role in the pathophysiology of cardiovascular diseases, it remains to be determined whether the IL-6 family is beneficial or detrimental. Future study will be needed to resolve this question.