Plasma YKL-40 and CHI3L1 in systemic inflammation and sepsis-experience from two prospective cohorts

Identifying the genetic association between rheumatoid arthritis and the risk of infectious diseases

BACKGROUND

Previous evidence suggests an association between rheumatoid arthritis (RA) and infectious diseases, but the causal relationship remains unclear. This study sought to explore causal associations between RA and five common infections: pneumonia, sepsis, urinary tract infections (UTI), skin and subcutaneous tissue infections (SSTI), and bacterial intestinal infections (BII).

METHODS

To identify the causal links, we adopted a Mendelian randomization (MR) design utilizing the inverse variance weighted (IVW), weighted median (WM), and MR-Egger approaches. Univariable MR (UVMR) and multivariable MR (MVMR) analyses were performed using pooled genome-wide association studies (GWAS) data. Additionally, various sensitivity analyses were conducted to ensure the reliability of the results.

RESULTS

In the UVMR analysis, RA was potentially associated with elevated risks of pneumonia (OR = 1.034, 95% CI: 1.016-1.052, P < 0.001) and sepsis (OR = 1.079, 95% CI: 1.048-1.110, P = 3.507E-07). This association remained significant after adjusting for smoking, alcohol consumption, or type 2 diabetes mellitus (T2DM) in the MVMR analysis. However, no causal links were found between RA and UTI, SSTI, and BII. Sensitivity analyses showed no detectable heterogeneity or pleiotropy, strengthening the causal inference of results.

CONCLUSION

Our study provides strong evidence of the association between RA and increased risks of pneumonia and sepsis. Further research is required to validate these findings and elucidate the underlying mechanisms. Key Points • It remains unclear whether the increased susceptibility to infections in RA stems from a genetic predisposition or results from immunosuppressive treatments. • The MR method is employed to assess the relationship between RA and common infectious diseases. • Our MR study supports a potential causal relationship between RA and elevated risks of pneumonia and sepsis.

YKL-40 levels in cerebrospinal fluid serve as a diagnostic biomarker for post-neurosurgical bacterial meningitis in patients with stroke

INTRODUCTION

Previous studies have reported that YKL-40 can serve as a biomarker of infectious diseases and different stroke types. However, evidence supporting its role in diagnosing post-neurosurgical bacterial meningitis (PNBM) remains lacking.

METHODS

A total of 110 patients with stroke who underwent neurosurgical treatment were recruited. Among these, 36 were diagnosed with PNBM based on the results of bacterial culture/Gram staining or cerebrospinal fluid (CSF) characteristics. CSF levels of YKL-40 and other biomarkers with potential diagnostic utility for PNBM were statistically analysed using univariate and logistic regression models. Receiver operating characteristic (ROC) analysis was performed to investigate diagnostic efficiency.

RESULTS

According to univariate analysis, CSF levels of glucose, total protein, white blood cells, polymorphocytes, and YKL-40, as well as the CSF-to-blood glucose ratio, were significantly different between the PNBM and non-PNBM groups. Logistic regression analysis revealed that glucose (p = 0.026), total protein (p = 0.028), and YKL-40 (p = 0.006) levels in the CSF may have independent diagnostic utility for PNBM. Among the three biomarkers, CSF-to-blood glucose (area under the receiver operating characteristic curve [AUC] 0.9208) and YKL-40 (AUC 0.9587) demonstrated strong diagnostic utility.

CONCLUSION

CSF levels of YKL-40, glucose, and total protein played independent roles in the diagnosis of PNBM in patients with stroke.

Evaluation of the relationship between YKL-40 level and clinical severity in patients with Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is a widespread tick-borne viral disease. YKL-40 (also known as chitinase-3-like-1 protein) is an acute phase protein released by various immune cells. The purpose of this study was to investigate the relationship between YKL-40 level and the clinical course and prognosis of CCHF. The study included 78 patients who were admitted to our hospital between April 15 and 30 August 2022 and had a positive polymerase chain reaction test result for CCHF. The patients were divided into two groups, severe and non-severe. In addition, a control group consisting of 22 healthy people was established. Mean serum YKL-40 levels were significantly higher in patients than controls (106.8 ng/mL ± 91.2 and 47.1 ng/mL ± 35.3, respectively; p < 0.001). However, mean YKL-40 levels were also significantly higher in patients with severe CCHF compared to non-severe cases (173.3 ± 112.3 and 67.5 ± 41.7, respectively; p < 0.001). A comparison of the 10 exitus patients and the 68 survivors revealed significantly higher YKL-40 levels in the exitus group (mean: 214.0 ± 139.0 and 92.8 ± 73.6, respectively; p = 0.001). A receiver operating characteristic analysis for YKL-40 levels to distinguish between severe and non-severe patients found an area under the curve of 0.925. YKL-40 levels were measured with a sensitivity of 97% and a specificity of 84% with a cutoff value of 90.7 ng/mL. YKL-40 levels measured at the time of hospital presentation in patients with CCHF can be used as a biomarker for clinical course and prognosis.

Targeting STAT6 to mitigate sepsis-induced muscle atrophy and weakness: Modulation of mitochondrial dysfunction, ferroptosis, and CHI3L1-Mediated satellite cell loss

Sepsis-induced muscle weakness is a debilitating consequence of prolonged critical illness, often associated with a poor prognosis. While recent research has shown that STAT6 functions as an inhibitor of myogenesis, its role in sepsis-induced muscle weakness remains unclear. In this study, we hypothesized that inhibiting STAT6 could attenuate sepsis-induced muscle atrophy and weakness, and we explored the underlying mechanisms. Leveraging a microarray dataset from sepsis patients, we identified significant enrichment of genes related to muscle function, ferroptosis, and the p53 signalling pathway in muscle tissue from sepsis patients. Using a murine sepsis model induced by cecum ligation and puncture (CLP), we explore the multifaceted role of STAT6 inhibition. Our findings demonstrate that STAT6 inhibition effectively attenuates muscle atrophy, enhances grip strength, preserves mitochondrial integrity, and modulates ferroptosis in septic mice. Additionally, we identify elevated levels of CHI3L1 in septic muscle tissue, which are significantly reduced by STAT6 inhibition. In-depth analysis of primary muscle satellite cells reveals that CHI3L1 overexpression is associated with increased expression of key regulators of satellite cell myogenicity, while negatively impacting cell viability. Silencing CHI3L1 expression mitigates satellite cell injury and loss, highlighting its pivotal role in sepsis-induced muscle damage. In summary, this study unveils the potential of STAT6 as a therapeutic target for mitigating sepsis-induced muscle atrophy and weakness. Our findings underscore the regulation of mitochondrial dysfunction, ferroptosis, and CHI3L1-mediated satellite cell damage by STAT6, offering promising avenues for therapeutic intervention in the management of sepsis-induced muscle weakness.

YKL-40 as a biomarker in various inflammatory diseases: A review

YKL-40 or Chitinase-3-Like Protein 1 (CHI3L1) is a highly conserved glycoprotein that binds heparin and chitin in a non-enzymatic manner. It is a member of the chitinase protein family 18, subfamily A, and unlike true chitinases, YKL-40 is a chitinase-like protein without enzymatic activity for chitin. Although its accurate function is yet unknown, the pattern of its expression in the normal and disease states suggests its possible engagement in apoptosis, inflammation and remodeling or degradation of the extracellular matrix. During an inflammatory response, YKL-40 is involved in a complicated interaction between host and bacteria, both promoting and attenuating immune response and potentially being served as an autoantigen in a vicious circle of autoimmunity. Based on its pathophysiology and mechanism of action, the aim of this review was to summarize research on the growing role of YKL-40 as a persuasive biomarker for inflammatory diseases' early diagnosis, prediction and follow-up (e.g., cardiovascular, gastrointestinal, endocrinological, immunological, musculoskeletal, neurological, respiratory, urinary, infectious) with detailed structural and functional background of YKL-40.

Association of autoimmune diseases with the occurrence and 28-day mortality of sepsis: an observational and Mendelian randomization study

BACKGROUND

Observational studies have indicated a potential association between autoimmune diseases and the occurrence of sepsis, with an increased risk of mortality among affected patients. However, whether a causal relationship exists between the two remains unknown.

METHODS

In the Mendelian randomization (MR) study, we accessed exposure Genome-wide association study (GWAS) data from both the MRC Integrative Epidemiology Unit (MRC-IEU) and the FinnGen consortium. GWAS data for sepsis and its 28-day mortality were obtained from MRC-IEU. We employed univariable, multivariable, and reverse MR analyses to explore potential associations between autoimmune disorders and sepsis and its 28-day mortality. Additionally, a two-step mediation MR analysis was performed to investigate indirect factors possibly influencing the relationship between autoimmune disorders and sepsis. Afterward, we conducted an observational analysis to further explore the relationship between autoimmune disease and occurrence as well as 28-day mortality of sepsis using a real-world database (the MIMIC-IV database). A cohort of 2537 patients diagnosed with autoimmune disease were extracted from the database for analysis. Multivariable logistic regression models were used to confirm the association between autoimmune diseases and the occurrence of sepsis, as well as the 28-day mortality associated with sepsis.

RESULTS

In univariable MR analysis, there appeared to be causal relationships between genetically predicted type 1 diabetes (OR = 1.036, 95% CI = 1.023-1.048, p = 9.130E-09), rheumatoid arthritis (OR = 1.077, 95% CI = 1.058-1.097, p = 1.00E-15) and sepsis, while a potential causal link was observed between celiac disease and sepsis (OR = 1.013, 95% CI = 1.002-1.024, p = 0.026). In a subsequent multivariable MR analysis, only rheumatoid arthritis was found to be independently associated with the risk of sepsis (OR = 1.138, 95% CI = 1.044-1.240, p = 3.36E-03). Furthermore, there was no causal link between autoimmune disorders and 28-day mortality from sepsis. In reverse MR analysis, sepsis was suggested to potentially trigger the onset of psoriasis (OR = 1.084, 95% CI = 1.040-1.131, p = 1.488E-04). In the real-world observational study, adjusting for multiple confounders, rheumatoid arthritis (OR = 1.34, 95% CI = 1.11-1.64, p = 0.003) and multiple sclerosis (OR = 1.31, 95% CI = 1.03-1.68, p = 0.02) were associated with a higher risk of sepsis. In addition, we did not find that autoimmune diseases were associated with 28-day mortality from sepsis.

CONCLUSION

Both in observational and MR analysis, only rheumatoid arthritis is highly correlated with occurrence of sepsis. However, autoimmune disease was not associated with an increased 28-day mortality in patient with sepsis. Sepsis may increase the risk of developing psoriasis.

Location-based prediction model for Crohn's disease regarding a novel serological marker, anti-chitinase 3-like 1 autoantibodies

BACKGROUND

Defective neutrophil regulation in inflammatory bowel disease (IBD) is thought to play an important role in the onset or manifestation of IBD, as it could lead to damage of the intestinal mucosal barrier by the infiltration of neutrophils in the inflamed mucosa and the accumulation of pathogens. Like neutrophils in the context of innate immune responses, immunoglobulin A (IgA) as an acquired immune response partakes in the defense of the intestinal epithelium. Under normal conditions, IgA contributes to the elimination of microbes, but in connection with the loss of tolerance to chitinase 3-like 1 (CHI3L1) in IBD, IgA could participate in CHI3L1-mediated improved adhesion and invasion of potentially pathogenic microorganisms. The tolerance brake to CHI3L1 and the occurrence of IgA autoantibodies to this particular target, the exact role and underlying mechanisms of CHI3L1 in the pathogenesis of IBD are still unclear.

AIM

To determine the predictive potential of Ig subtypes of a novel serological marker, anti-CHI3L1 autoantibodies (aCHI3L1) in determining the disease phenotype, therapeutic strategy and long-term disease course in a prospective referral cohort of adult IBD patients.

METHODS

Sera of 257 Crohn's disease (CD) and 180 ulcerative colitis (UC) patients from a tertiary IBD referral center of Hungary (Division of Gastroenterology, Department of Internal Medicine, Faculty of Medicine, University of Debrecen) were assayed for IgG, IgA, and secretory IgA (sIgA) type aCHI3L1 by enzyme-linked immunosorbent assay using recombinant CHI3L1, along with 86 healthy controls (HCONT).

RESULTS

The IgA type was more prevalent in CD than in UC (29.2% vs 11.1%) or HCONT (2.83%; P < 0.0001 for both). However, sIgA subtype aCHI3L1 positivity was higher in both CD and UC patients than in HCONT (39.3% and 32.8% vs 4.65%, respectively; P < 0.0001). The presence of both IgA and sIgA aCHI3L1 antibodies was associated with colonic involvement (P < 0.0001 and P = 0.038, respectively) in patients with CD. Complicated disease behavior at sample procurement was associated with aCHI3L1 sIgA positivity (57.1% vs 36.0%, P = 0.009). IgA type aCH3L1 was more prevalent in patients with frequent relapse during the disease course in the CD group (46.9% vs 25.7%, P = 0.005). In a group of patients with concomitant presence of pure inflammatory luminal disease and colon involvement at the time of diagnosis, positivity for IgA or sIgA type aCH3L1 predicted faster progression towards a complicated disease course in time-dependent models. This association disappeared after merging subgroups of different disease locations.

CONCLUSION

CHI3L1 is a novel neutrophil autoantigenic target in IBD. The consideration of antibody classes along with location-based prediction may transform the future of serology in IBD.

CHI3L1 promotes myocardial fibrosis via regulating lncRNA TUG1/miR-495-3p/ETS1 axis

Abnormal levels of CHI3L1 and lnc TUG1 are often associated with myocardial fibrosis, and their specific expressions may be closely related to the process of myocardial fibrosis. In addition, CHI3L1 was found to significantly up-regulate the expression of lncTUG1. Therefore, this study further explored the major role of CHI3L1 in regulating the progression of myocardial fibrosis. Myocardial fibrosis in mice was established using an angiotensin (Ang II) model, and the degree of myocardial fibrosis was assessed by qPCR, western blot and pathological techniques. HL-1 cells with overexpression and silencing of CHI3L1 were constructed, and the cell migration ability was detected using the Transwell method. Biological information was used to predict the potential target miRNA of lnc TUG1, and the interaction between them was verified by dual luciferase reporter assay. Using functional rescue assay and the rAAV9 technique, CHI3L1 was verified to affect the fibrotic process of myocardial cells by regulating the lnc TUG1/miR-495-3p/ETS1 axis in vitro and in vivo. The myocardial fibrosis index in the model group was significantly upregulated, and expression of both CHI3L1 and lnc TUG1 was upregulated. Pathological results revealed fibrosis and collagen deposition in the myocardium. Overexpression of lnc TUG1 reversed the inhibitory effect of CHI3L1 silencing on myocardial fibrosis. Mechanistically, CH3L1 upregulates the expression of lnc TUG1, and lnc TUG1 weakens the inhibition of ETS1 through sponge absorption of miR-495-3p, promoting the process of myocardial fibrosis.

Serum YKL-40 as a Potential Biomarker for Sepsis in Term Neonates-A Pilot Study

Although YKL-40 is a promising diagnostic biomarker of sepsis in adults, its value in neonatal sepsis is not known. The study objectives included assessing the levels and diagnostic value of serum YKL-40 in term neonates with sepsis and comparing YKL-40 with other commonly used inflammatory biomarkers. In this pilot case-control study, 45 term neonates (30 septic and 15 non-septic, as controls), 4 to 28 days old, were prospectively studied. The International Pediatric Sepsis Consensus Conference criteria were applied to diagnose sepsis. During the acute phase (admission) and remission of sepsis, blood samples were collected from cases (while from controls they were only collected once) for routine laboratory tests, cultures, and the measurement of serum YKL-40 levels via Elisa. In the acute phase of sepsis, YKL-40 levels were significantly elevated in comparison with remission (p = 0.004) and controls (p = 0.003). YKL-40 levels did not differ significantly between patients in remission and controls (p = 0.431). Upon admission, YKL-40 levels correlated positively with white blood count, absolute neutrophil count, and CRP levels. Via ROC analysis, it was shown that YKL-40 levels upon admission were a significant indicator of sepsis (AUC = 0.771; 95% CI 0.632-0.911; p = 0.003). Serum YKL-40 might be considered as an adjuvant biomarker of sepsis in term neonates.

Novel plasma protein biomarkers from critically ill sepsis patients

BACKGROUND

Despite the high morbidity and mortality associated with sepsis, the relationship between the plasma proteome and clinical outcome is poorly understood. In this study, we used targeted plasma proteomics to identify novel biomarkers of sepsis in critically ill patients.

METHODS

Blood was obtained from 15 critically ill patients with suspected/confirmed sepsis (Sepsis-3.0 criteria) on intensive care unit (ICU) Day-1 and Day-3, as well as age- and sex-matched 15 healthy control subjects. A total of 1161 plasma proteins were measured with proximal extension assays. Promising sepsis biomarkers were narrowed with machine learning and then correlated with relevant clinical and laboratory variables.

RESULTS

The median age for critically ill sepsis patients was 56 (IQR 51-61) years. The median MODS and SOFA values were 7 (IQR 5.0-8.0) and 7 (IQR 5.0-9.0) on ICU Day-1, and 4 (IQR 3.5-7.0) and 6 (IQR 3.5-7.0) on ICU Day-3, respectively. Targeted proteomics, together with feature selection, identified the leading proteins that distinguished sepsis patients from healthy control subjects with ≥ 90% classification accuracy; 25 proteins on ICU Day-1 and 26 proteins on ICU Day-3 (6 proteins overlapped both ICU days; PRTN3, UPAR, GDF8, NTRK3, WFDC2 and CXCL13). Only 7 of the leading proteins changed significantly between ICU Day-1 and Day-3 (IL10, CCL23, TGFα1, ST2, VSIG4, CNTN5, and ITGAV; P < 0.01). Significant correlations were observed between a variety of patient clinical/laboratory variables and the expression of 15 proteins on ICU Day-1 and 14 proteins on ICU Day-3 (P < 0.05).

CONCLUSIONS

Targeted proteomics with feature selection identified proteins altered in critically ill sepsis patients relative to healthy control subjects. Correlations between protein expression and clinical/laboratory variables were identified, each providing pathophysiological insight. Our exploratory data provide a rationale for further hypothesis-driven sepsis research.

Conserved YKL-40 changes in mice and humans after postoperative delirium

Delirium is a common postoperative neurologic complication among older adults. Despite its prevalence (14%-50%) and likely association with inflammation, the exact mechanisms that underpin postoperative delirium are unclear. This project aimed to characterize systemic and central nervous system (CNS) inflammatory changes following surgery in mice and humans. Matched plasma and cerebrospinal fluid (CSF) samples from the "Investigating Neuroinflammation Underlying Postoperative Brain Connectivity Changes, Postoperative Cognitive Dysfunction, Delirium in Older Adults" (INTUIT; NCT03273335) study were compared to murine endpoints. Delirium-like behavior was evaluated in aged mice using the 5-Choice Serial Reaction Time Test (5-CSRTT). Using a well established orthopedic surgical model in the FosTRAP reporter mouse we detected neuronal changes in the prefrontal cortex, an area implicated in attention, but notably not in the hippocampus. In aged mice, plasma interleukin-6 (IL-6), chitinase-3-like protein 1 (YKL-40), and neurofilament light chain (NfL) levels increased after orthopedic surgery, but hippocampal YKL-40 expression was decreased. Given the growing evidence for a YKL-40 role in delirium and other neurodegenerative conditions, we assayed human plasma and CSF samples. Plasma YKL-40 levels were similarly increased after surgery, with a trend toward a greater postoperative plasma YKL-40 increase in patients with delirium. However, YKL-40 levels in CSF decreased following surgery, which paralleled the findings in the mouse brain. Finally, we confirmed changes in the blood-brain barrier (BBB) as early as 9 h after surgery in mice, which warrants more detailed and acute evaluations of BBB integrity following surgery in humans. Together, these results provide a nuanced understanding of neuroimmune interactions underlying postoperative delirium in mice and humans, and highlight translational biomarkers to test potential cellular targets and mechanisms.

A novel biomarker in acute cholecystitis: YKL-40

BACKGROUND

The lack of a specific biomarker that can be used in the diagnosis of acute cholecystitis, a common cause of admission to the emergency department, delays physician efforts to diagnose and treat these patients. Therefore, the aim of this study was to measure plasma YKL-40 levels and investigate their diagnostic value in patients with acute cholecystitis (AC).

METHODS

This study was carried out between February 2020 and September 2020 in the adult emergency department of a tertiary university hospital. Permission was obtained from the Ethics Committee of Scientific Research on 03/02/2020 with Decision No. 03/16. The study included 80 patients who were diagnosed with acute cholecystitis and 80 healthy volunteers without known chronic diseases.

RESULTS

The median YKL-40 protein level was 798.66 pq/mL in the patient group and 392.45 pq/mL in the control group. A statistically significant difference in YKL-40 protein levels was found between the two groups. YKL-40 protein levels were significantly higher in patients diagnosed with acute cholecystitis than in healthy individuals (p < 0.001). A positive correlation was found between YKL-40 protein levels and ALT, AST, LDH, and GGT levels (r = 0.272, p = 0.015; r = 0.397, p < 0.001; r = 0.386, p < 0.001; and r = 0.264, p = 0.018; respectively).

CONCLUSION

When evaluated together with physical examination, radiological imaging and other laboratory parameters, we think that plasma YKL-40 levels can be used effectively in the diagnosis of acute cholecystitis.

Severity Biomarkers in Puumala Hantavirus Infection

Annually, over 10,000 cases of hemorrhagic fever with renal syndrome (HFRS) are diagnosed in Europe. Puumala hantavirus (PUUV) causes most of the European HFRS cases. PUUV causes usually a relatively mild disease, which is rarely fatal. However, the severity of the infection varies greatly, and factors affecting the severity are mostly unrevealed. Host genes are known to have an effect. The typical clinical features in PUUV infection include acute kidney injury, thrombocytopenia, and increased vascular permeability. The primary target of hantavirus is the endothelium of the vessels of different organs. Although PUUV does not cause direct cytopathology of the endothelial cells, remarkable changes in both the barrier function of the endothelium and the function of the infected endothelial cells occur. Host immune or inflammatory mechanisms are probably important in the development of the capillary leakage. Several immunoinflammatory biomarkers have been studied in the context of assessing the severity of HFRS caused by PUUV. Most of them are not used in clinical practice, but the increasing knowledge about the biomarkers has elucidated the pathogenesis of PUUV infection.

[Value of serum YKL-40 in the diagnosis of anti-MDA5-positive patients with dermatomyositis complicated with severe pulmonary injury]

OBJECTIVE

To investigate the value of serum and bronchoalveolar lavage fluid (BALF) chitinase-3-like-1 protein (YKL-40) in the diagnosis of anti-melanoma differentiation-associated gene 5 (MDA5)-positive dermatomyositis (DM) patients complicated with serious pulmonary injury, including rapidly progressive interstitial lung disease (RP-ILD) and pulmonary infection.

METHODS

Anti-MDA5 antibodies positive patients with DM who were hospitalized in the Department of Rheumatology of China-Japan Friendship Hospital from 2013 to 2018 were involved in this study. Demographic information, clinical, laboratory and imaging data were retrospectively collected. ELISA was used to detect the serum and BALF levels of YKL-40. The receiver operating characteristic (ROC) curve was drawn, and the area under ROC curve (AUC) was used to evaluate the diagnostic value of serum YKL-40 for pulmonary injury.Interstitial lung disease (ILD) was confirmed by chest high-resolution CT (HRCT). RP-ILD was defined as progressive respiratory symptoms such as dyspnea and hypoxemia within 3 months, and/or deterioration of interstitial changes or appearace of new pulmonary interstitial lesions on chest HRCT. Pulmonary infection was considered as positive pathogens detected in qualified sputum, blood, bronchoalveolar lavage fluid or lung biopsy specimens.

RESULTS

A total of 168 anti-MDA5-positive DM patients including 108 females and 60 males were enrolled in the study. Of these patients, 154 had ILD, and 66(39.3%) of them presented RP-ILD. Seventy patients with pulmonary infection were confirmed by etiology. In the patients with RP-ILD, 39 (59.1%) of them were complicated with pulmonary infection. While only 31 cases(30.4%) had pulmonary infection in the non-RP-ILD patients. The incidence of pulmonary infection in the patients with RP-ILD was significantly higher than that of those with non-RP-ILD (P < 0.001). The serum YKL-40 levels in the RP-ILD patients with pulmonary infection were the highest compared with RP-ILD without pulmonary infection, non-RP-ILD with pulmonary infection and non-RP-ILD without pulmonary infection groups among all the patients [83 (42-142) vs. 42 (21-91) vs. 43 (24-79) vs. 38 (22-69), P < 0.01].The sensitivity, specificity and AUC of serum YKL-40 in the diagnosis of RP-ILD complicated with pulmonary infection were 75%, 67%, and 0.72, respectively. The AUC of diagnosed of anti-MDA5 positive DM patients complicated with RP-ILD and pulmonary infection was higher than that of patients complicated with only RP-ILD and only pulmonary infection (0.72 vs. 0.54 and 0.55, Z=2.10 and 2.11, P < 0.05).

CONCLUSION

The prognosis of anti-MDA5-positive DM patients with RP-ILD and pulmonary infection were poor. Serum YKL-40 level can be used as a helpful tool for the diagnosis of coexistence of these conditions in the patients.

Chitinase 3 like 1 is a regulator of smooth muscle cell physiology and atherosclerotic lesion stability

AIMS

Atherosclerotic cerebrovascular disease underlies the majority of ischaemic strokes and is a major cause of death and disability. While plaque burden is a predictor of adverse outcomes, plaque vulnerability is increasingly recognized as a driver of lesion rupture and risk for clinical events. Defining the molecular regulators of carotid instability could inform the development of new biomarkers and/or translational targets for at-risk individuals.

METHODS AND RESULTS

Using two independent human endarterectomy biobanks, we found that the understudied glycoprotein, chitinase 3 like 1 (CHI3L1), is up-regulated in patients with carotid disease compared to healthy controls. Further, CHI3L1 levels were found to stratify individuals based on symptomatology and histopathological evidence of an unstable fibrous cap. Gain- and loss-of-function studies in cultured human carotid artery smooth muscle cells (SMCs) showed that CHI3L1 prevents a number of maladaptive changes in that cell type, including phenotype switching towards a synthetic and hyperproliferative state. Using two murine models of carotid remodelling and lesion vulnerability, we found that knockdown of Chil1 resulted in larger neointimal lesions comprised by de-differentiated SMCs that failed to invest within and stabilize the fibrous cap. Exploratory mechanistic studies identified alterations in potential downstream regulatory genes, including large tumour suppressor kinase 2 (LATS2), which mediates macrophage marker and inflammatory cytokine expression on SMCs, and may explain how CHI3L1 modulates cellular plasticity.

CONCLUSION

CHI3L1 is up-regulated in humans with carotid artery disease and appears to be a strong mediator of plaque vulnerability. Mechanistic studies suggest this change may be a context-dependent adaptive response meant to maintain vascular SMCs in a differentiated state and to prevent rupture of the fibrous cap. Part of this effect may be mediated through downstream suppression of LATS2. Future studies should determine how these changes occur at the molecular level, and whether this gene can be targeted as a novel translational therapy for subjects at risk of stroke.

Associations between YKL-40 and markers of disease severity and death in patients with necrotizing soft-tissue infection

Background

Necrotizing soft-tissue infection (NSTI) is a severe and fast-progressing bacterial infection. Prognostic biomarkers may provide valuable information in treatment guidance and decision-making, but none have provided sufficient robustness to have a clinical impact. YKL-40 may reflect the ongoing pathological inflammatory processes more accurately than traditional biomarkers as it is secreted by the activated immune cells, but its prognostic yields in NSTI remains unknown. For this purpose, we investigated the association between plasma YKL-40 and 30-day mortality in patients with NSTI, and assessed its value as a marker of disease severity.

Methods

We determined plasma YKL-40 levels in patients with NSTI (n = 161) and age-sex matched controls (n = 65) upon admission and at day 1, 2 and 3.

Results

Baseline plasma YKL-40 was 1191 ng/mL in patients with NSTI compared with 40 ng/mL in controls (p < 0.001). YKL-40 was found to be significantly higher in patients with septic shock (1942 vs. 720 ng/mL, p < 0.001), and in patients receiving renal-replacement therapy (2382 vs. 1041 ng/mL, p < 0.001). YKL-40 correlated with Simplified Acute Physiology Score II (Rho 0.33, p < 0.001). Baseline YKL-40 above 1840 ng/mL was associated with increased risk of 30-day mortality in age-sex-comorbidity adjusted analysis (OR 3.77, 95% CI; 1.59–9.24, p = 0.003), but after further adjustment for Simplified Acute Physiology Score II no association was found between YKL-40 and early mortality.

Conclusion

High plasma YKL-40 to be associated with disease severity, renal-replacement therapy and risk of death in patients with NSTI. However, YKL-40 is not an independent predictor of 30-day mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06760-x.

CHI3L1 in the pathophysiology and diagnosis of liver diseases

Chitinase 3-like protein 1(CHI3L1) participates in physiological and pathophysiological process, such as cell survival, cell proliferation, tissue remodeling, angiogenesis, etc. Some studies demonstrated that CHI3L1 is liver-enriched and has better application value in staging liver fibrosis than platelet ratio index(APRI) and fibrosis-4 index(FIB-4) and that CHI3L1 can be used in monitoring the prognosis of hepatocellular carcinoma (HCC). In this review, we summarized the pathophysiological role and the diagnostic value of CHI3L1 in liver fibrosis in different background and HCC.

Biomarkers of sepsis: time for a reappraisal

INTRODUCTION

Sepsis biomarkers can have important diagnostic, therapeutic, and prognostic functions. In a previous review, we identified 3370 references reporting on 178 different biomarkers related to sepsis. In the present review, we evaluate the progress in the research of sepsis biomarkers.

METHODS

Using the same methodology as in our previous review, we searched the PubMed database from 2009 until September 2019 using the terms "Biomarker" AND "Sepsis." There were no restrictions by age or language, and all studies, clinical and experimental, were included.

RESULTS

We retrieved a total of 5367 new references since our previous review. We identified 258 biomarkers, 80 of which were new compared to our previous list. The majority of biomarkers have been evaluated in fewer than 5 studies, with 81 (31%) being assessed in just a single study. Apart from studies of C-reactive protein (CRP) or procalcitonin (PCT), only 26 biomarkers have been assessed in clinical studies with more than 300 participants. Forty biomarkers have been compared to PCT and/or CRP for their diagnostic value; 9 were shown to have a better diagnostic value for sepsis than either or both of these biomarkers. Forty-four biomarkers have been evaluated for a role in answering a specific clinical question rather than for their general diagnostic or prognostic properties in sepsis.

CONCLUSIONS

The number of biomarkers being identified is still increasing although at a slower rate than in the past. Most of the biomarkers have not been well-studied; in particular, the clinical role of these biomarkers needs to be better evaluated.

Complement related pattern recognition molecules as markers of short-term mortality in intensive care patients

OBJECTIVES

To evaluate the complement related pattern recognition molecules (PRMs) PTX3, MBL, CL-11, ficolin-2 and -3, along with the established marker CRP, to predict 28-day mortality and disease severity of sepsis in patients admitted to the intensive care unit (ICU).

METHODS

In a single-center, prospective, observational study 547 patients were included over a period of 18 months. Blood samples were obtained at admission to the ICU and the following 4 days.

RESULTS

PTX3 baseline levels were significantly higher in non-survivors compared to survivors, whereas MBL and ficolin-2 levels were significantly lower in non-survivors compared to survivors. A PTX3 level above the median was independently associated with 28-day mortality in the adjusted analysis including age, sex, chronic disease and immunosuppression (HR 1.87, 95% CI [1.41-2.48], p < 0.0001), while a MBL level above the median was associated with increased chance of survival (HR 0.75, 95% CI [0.57-0.98], p = 0.034). Ficolin-2 was only borderline significant (HR 0.79, 95% CI [0.60-1.03], p = 0.084). In a ROC analysis PTX3 was superior to CRP in predicting septic shock.

CONCLUSIONS

PTX3, MBL and CRP levels were independently associated with 28-day mortality in ICU patients. PTX3 was a better marker of septic shock compared to CRP.

Elevated plasma YKL-40 and risk of infectious disease: a prospective study of 94665 individuals from the general population

OBJECTIVES

YKL-40 is an acute phase protein elevated in patients with infectious and inflammatory diseases. We tested the hypothesis that baseline elevated YKL-40 is associated with increased risk of future infectious disease in healthy individuals in the general population.

METHODS

We prospectively followed 94 665 individuals from the Danish general population for up to 23 years and analysed for plasma YKL-40 levels (n = 21 584) and CHI3L1 rs4950928 genotype (n = 94 184). Endpoints were any infection, bacterial pneumonia, urinary tract infection, skin infection, sepsis, diarrhoeal disease, and other infections.

RESULTS

For YKL-40 percentile category 91-100% versus 0-33%, the multifactorially and C-reactive protein (CRP) adjusted hazard ratios were 1.71 (95% confidence interval 1.50-1.96; p 4 × 10^-14) for any infection, 1.97 (1.64-2.37; p 4 × 10^-13) for bacterial pneumonia, 1.62 (1.24-2.11; p 0.002) for urinary tract infection, 1.74 (1.31-2.32; p 2 × 10^-4) for skin infection, 1.76 (1.25-2.46; p 0.004) for sepsis, 1.90 (1.29-2.78; p 0.002) for diarrhoeal disease and 2.71 (1.38-5.35; p 0.01) for other infections. In multifactorially and CRP-adjusted models, a twofold increase in YKL-40 was associated with increased risk of all infectious disease endpoints. Mendelian randomization did not support causality, as CHI3L1 rs4950928 was associated with 94% and 190% higher YKL-40 levels (for CG and CC versus GG genotype), but not with increased risk of any infectious disease endpoint.

DISCUSSION

Baseline elevated plasma YKL-40 was not a cause but a strong marker of increased risk of future infectious diseases in individuals in the general population.

Downregulated CHI3L1 alleviates skeletal muscle stem cell injury in a mouse model of sepsis

Sepsis is an acute systemic inflammatory response of the body to microbial infection and a life-threatening condition associated with multiple organ failure. Recent data suggest that sepsis survivors present with long-term myopathy due to the dysfunction of skeletal muscle stem cells and satellite cells. Accumulating studies have implicated chitinase-3-like-1 protein (CHI3L1) in a variety of infectious diseases, specifically sepsis. Therefore, the aim of the present study is to elucidate the potential mechanism by which CHI3L1 is involved in the injury of skeletal muscle stem cells in mouse models of sepsis. An in vitro cell model was developed by lipopolysaccharide (LPS) and in vivo mouse model of sepsis was induced by CRP-like protein (CLP). To elucidate the biological significance behind the silencing of CHI3L1, modeled skeletal muscle stem cells and mice were treated with siRNA against CHI3L1 or overexpressed CHI3L1. Highly expressed CHI3L1 was found in skeletal muscle tissues of mice with sepsis. Besides, siRNA-mediated silencing of CHI3L1 was revealed to increase Bcl-2 expression along with cell proliferation, while diminishing Bax expression, cell apopstosis as well as serum levels of TNF-α, IL-1β, INF-γ, IL-10, and IL-6. Taken conjointly, this present study provided evidence suggesting that downregulation of CHI3L1 has the potential to prevent the injury of skeletal muscle stem cells in mice with sepsis. Collectively, CHI3L1 may serve as a valuable therapeutic strategy in alleviating sepsis.

Glycoprotein YKL-40 Is Elevated and Predicts Disease Severity in Puumala Hantavirus Infection

Most cases of hemorrhagic fever with renal syndrome (HFRS) in Europe are caused by the Puumala hantavirus (PUUV). Typical features of the disease are increased vascular permeability, acute kidney injury (AKI), and thrombocytopenia. YKL-40 is an inflammatory glycoprotein involved in various forms of acute and chronic inflammation. In the present study, we examined plasma YKL-40 levels and the associations of YKL-40 with disease severity in acute PUUV infection. A total of 79 patients treated in Tampere University Hospital during 2005–2014 were studied. Plasma YKL-40 was measured in the acute phase, the recovery phase, and one year after hospitalization. Plasma YKL-40 levels were higher during the acute phase compared to the recovery phase and one year after hospitalization (median YKL-40 142 ng/mL, range 11–3320, vs. 45 ng/mL, range 15–529, vs. 32 ng/mL, range 3–213, p < 0.001). YKL-40 level was correlated with the length of hospital stay (r = 0.229, p = 0.042), the levels of inflammatory markers—that is, blood leukocytes (r = 0.234, p = 0.040), plasma C-reactive protein (r = 0.332, p = 0.003), and interleukin-6 (r = 0.544, p < 0.001), and maximum plasma creatinine level (r = 0.370, p = 0.001). In conclusion, plasma YKL-40 levels were found to be elevated during acute PUUV infection and correlated with the overall severity of the disease, as well as with the degree of inflammation and the severity of AKI.

Chitinase-3-like 1 is a biomarker of acute kidney injury and mortality in paediatric severe malaria

Background

Chitinase-3-like 1 (CHI3L1) is a glycoprotein elevated in paediatric severe malaria, and an emerging urinary biomarker of acute kidney injury (AKI). Based on the hypothesis that elevated CHI3L1 levels in malaria are associated with disease severity, the relationship between plasma CHI3L1 levels, AKI and mortality was investigated in Ugandan children enrolled in a clinical trial evaluating inhaled nitric oxide (iNO) as an adjunctive therapy for severe malaria.

Methods

Plasma CHI3L1 levels were measured daily for 4 days in children admitted to hospital with severe malaria and at day 14 follow up. AKI was defined using the Kidney Disease: Improving Global Outcomes consensus criteria. This is a secondary analysis of a randomized double-blind placebo-controlled trial of iNO versus placebo as an adjunctive therapy for severe malaria. Inclusion criteria were: age 1–10 years, and selected criteria for severe malaria. Exclusion criteria included suspected bacterial meningitis, known chronic illness including renal disease, haemoglobinopathy, or severe malnutrition. iNO was administered by non-rebreather mask for up to 72 h at 80 ppm.

Results

CHI3L1 was elevated in patients with AKI and remained higher over hospitalization (p < 0.0001). Admission CHI3L1 levels were elevated in children who died. By multivariable analysis logCHI3L1 levels were associated with increased risk of in-hospital death (relative risk, 95% CI 4.10, 1.32–12.75, p = 0.015) and all-cause 6 month mortality (3.21, 1.47–6.98, p = 0.003) following correction for iNO and AKI. Treatment with iNO was associated with delayed CHI3L1 recovery with a daily decline of 34% in the placebo group versus 29% in the iNO group (p = 0.012). CHI3L1 levels correlated with markers of inflammation (CRP, sTREM-1, CXCL10), endothelial activation (Ang-2, sICAM-1) and intravascular haemolysis (LDH, haem, haemopexin).

Conclusions

CHI3L1 is a novel biomarker of malaria-associated AKI and an independent risk factor for mortality that is associated with well-established pathways of severe malaria pathogenesis including inflammation, endothelial activation, and haemolysis.

Trial registration Clinicaltrials.gov, NCT01255215. Registered December 7th 2010

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2225-5) contains supplementary material, which is available to authorized users.

Validation of two multiplex platforms to quantify circulating markers of inflammation and endothelial injury in severe infection

Biomarkers can prognosticate outcome and enable risk-stratification. In severe infection, focusing on multiple markers reflecting pathophysiological mechanisms of organ injury could enhance management and pathway-directed therapeutics. Limited data exist on the performance of multiplex biomarker platforms. Our goal was to compare endothelial and immune activation biomarkers in severe pediatric infections using two multiplex platforms. Frozen plasma from 410 children presenting to the Jinja Regional Hospital in Uganda with suspected infection was used to measure biomarkers of endothelial (Angiopoietin-2, sFlt-1, sVCAM-1, sICAM-1) and immune (IL-6, IP-10, sTNFR-1, CHI3L1) activation. Two multiplex platforms (Luminex®, Ella^TM) based on monoclonal antibody sandwich immunoassays using biotin-streptavidin conjugate chemistry were selected with reagents from R&D Systems. The two platforms differed in ease and time of completion, number of samples per assay, and dynamic concentration range. Intra-assay variability assessed using a coefficient of variation (CV%) was 2.2–3.4 for Luminex® and 1.2–2.9 for Ella^TM. Correlations for biomarker concentrations within dynamic range of both platforms were best for IL-6 (ρ = 0.96, p<0.0001), IP-10 (ρ = 0.94, p<0.0001) and sFlt-1 (ρ = 0.94, p<0.0001). Agreement between concentrations obtained by both methods assessed by the Bland-Altman test varied, with best agreement for CHI3L1. Our data suggest that biomarkers of endothelial and immune activation can be readily measured with multiplex platforms. Luminex® and Ella^TM produced reliable results with excellent CV% values. The Ella^TM platform was more automated and completed in 75 minutes, potentially compatible with near-patient use. Trends in concentrations obtained by these methods were highly correlated, although absolute values varied, suggesting caution is required when comparing data from different multiplex platforms.

The impact of environmental enrichment on the murine inflammatory immune response

Living in a mentally and physically stimulating environment has been suggested to have a beneficial effect on the immune response. This study investigates these effects, utilizing a 2-week program of environmental enrichment (EE) and 2 models of acute inflammation: zymosan-induced peritonitis (ZIP) and the cecal ligation and puncture (CLP) model of sepsis. Our results revealed that following exposure to EE, mice possessed a significantly higher circulating neutrophil to lymphocyte ratio compared with control animals. When subject to ZIP, EE animals exhibit enhanced neutrophil and macrophage influx into their peritoneal cavity. Corresponding results were found in CLP, where we observed an improved capacity for enriched animals to clear systemic microbial infection. Ex vivo investigation of leukocyte activity also revealed that macrophages from EE mice presented an enhanced phagocytic capacity. Supporting these findings, microarray analysis of EE animals revealed the increased expression of immunomodulatory genes associated with a heightened and immunoprotective status. Taken together, these results provide potentially novel mechanisms by which EE influences the development and dynamics of the immune response.

A housing period as little as 2 weeks in an enriched environment with an increase in spatial and sensorial stimuli improved the ability of mice to clear infections.

Cathelicidin Insufficiency in Patients with Fatal Leptospirosis

Leptospirosis causes significant morbidity and mortality worldwide; however, the role of the host immune response in disease progression and high case fatality (>10-50%) is poorly understood. We conducted a multi-parameter investigation of patients with acute leptospirosis to identify mechanisms associated with case fatality. Whole blood transcriptional profiling of 16 hospitalized Brazilian patients with acute leptospirosis (13 survivors, 3 deceased) revealed fatal cases had lower expression of the antimicrobial peptide, cathelicidin, and chemokines, but more abundant pro-inflammatory cytokine receptors. In contrast, survivors generated strong adaptive immune signatures, including transcripts relevant to antigen presentation and immunoglobulin production. In an independent cohort (23 survivors, 22 deceased), fatal cases had higher bacterial loads (P = 0.0004) and lower anti-Leptospira antibody titers (P = 0.02) at the time of hospitalization, independent of the duration of illness. Low serum cathelicidin and RANTES levels during acute illness were independent risk factors for higher bacterial loads (P = 0.005) and death (P = 0.04), respectively. To investigate the mechanism of cathelicidin in patients surviving acute disease, we administered LL-37, the active peptide of cathelicidin, in a hamster model of lethal leptospirosis and found it significantly decreased bacterial loads and increased survival. Our findings indicate that the host immune response plays a central role in severe leptospirosis disease progression. While drawn from a limited study size, significant conclusions include that poor clinical outcomes are associated with high systemic bacterial loads, and a decreased antibody response. Furthermore, our data identified a key role for the antimicrobial peptide, cathelicidin, in mounting an effective bactericidal response against the pathogen, which represents a valuable new therapeutic approach for leptospirosis.

Lung Metabolic Activation as an Early Biomarker of Acute Respiratory Distress Syndrome and Local Gene Expression Heterogeneity

BACKGROUND

Acute respiratory distress syndrome (ARDS) is an inflammatory condition comprising diffuse lung edema and alveolar damage. ARDS frequently results from regional injury mechanisms. However, it is unknown whether detectable inflammation precedes lung edema and opacification and whether topographically differential gene expression consistent with heterogeneous injury occurs in early ARDS. The authors aimed to determine the temporal relationship between pulmonary metabolic activation and density in a large animal model of early ARDS and to assess gene expression in differentially activated regions.

METHODS

The authors produced ARDS in sheep with intravenous lipopolysaccharide (10 ng ⋅ kg ⋅ h) and mechanical ventilation for 20 h. Using positron emission tomography, the authors assessed regional cellular metabolic activation with 2-deoxy-2-[(18)F]fluoro-D-glucose, perfusion and ventilation with NN-saline, and aeration using transmission scans. Species-specific microarray technology was used to assess regional gene expression.

RESULTS

Metabolic activation preceded detectable increases in lung density (as required for clinical diagnosis) and correlated with subsequent histologic injury, suggesting its predictive value for severity of disease progression. Local time courses of metabolic activation varied, with highly perfused and less aerated dependent lung regions activated earlier than nondependent regions. These regions of distinct metabolic trajectories demonstrated differential gene expression for known and potential novel candidates for ARDS pathogenesis.

CONCLUSIONS

Heterogeneous lung metabolic activation precedes increases in lung density in the development of ARDS due to endotoxemia and mechanical ventilation. Local differential gene expression occurs in these early stages and reveals molecular pathways relevant to ARDS biology and of potential use as treatment targets.

YKL-40, CCL18 and SP-D predict mortality in patients hospitalized with community-acquired pneumonia

BACKGROUND AND OBJECTIVE

The aim of this study was to investigate the prognostic value of four biomarkers, YKL-40, chemokine (C-C motif) ligand 18 (CCL18), surfactant protein-D (SP-D) and CA 15-3, in patients admitted with community-acquired pneumonia (CAP). These markers have been studied extensively in chronic pulmonary disease, but in acute pulmonary disease their prognostic value is unknown.

METHODS

A total of 289 adult patients who were hospitalized with CAP and participated in a randomized controlled trial were enrolled. Biomarker levels were measured on the day of admission. Intensive care unit admission, 30-day, 1-year and long-term mortality (median follow-up of 5.4 years, interquartile range (IQR): 4.7-6.1) were recorded as outcomes.

RESULTS

Median YKL-40 and CCL18 levels were significantly higher and levels of SP-D were significantly lower in CAP patients compared to healthy controls. Significantly higher YKL-40, CCL18 and SP-D levels were found in patients classified in pneumonia severity index classes 4-5 and with a CURB-65 score ≥2 compared to patients with less severe pneumonia. Furthermore, these three markers were significant predictors for long-term mortality in multivariate analysis and compared with C-reactive protein and procalcitonin level on admission, area under the curves were higher for 30-day, 1-year and long-term mortality. CA 15-3 levels were less predictive.

CONCLUSION

YKL-40, CCL18 and SP-D levels were higher in patients with more severe pneumonia, possibly reflecting the extent of pulmonary inflammation. Of these, YKL-40 most significantly predicts mortality for CAP.

Role of inflammatory marker YKL-40 in the diagnosis, prognosis and cause of cardiovascular and liver diseases

This review summarizes present evidence for the role of YKL-40 in the diagnosis, prognosis and cause of cardiovascular and alcoholic liver disease. The question of whether YKL-40 is merely a marker or a causal factor in the development of cardiovascular and liver disease is addressed, with emphasis on the Mendelian randomization design. The Mendelian randomization approach uses genetic variants associated with lifelong high plasma YKL-40 levels that are largely unconfounded and not prone to reverse causation. Thus, the approach mimics a controlled double-blind randomized trial, but it uses genetic variants rather than a drug and placebo, and like a blinded trial, it allows inference about causality. Moreover, the review also covers background on the molecular biology and functions of YKL-40, YKL-40 levels in healthy individuals and reference range, and the role of YKL-40 as a biomarker of cardiovascular and alcoholic liver disease. YKL-40 is a plasma protein named after its three N-terminal amino acids, Y (tyrosine), K (lysine) and L (leucine), and its molecular weight of 40 kDa. It is produced by local inflammatory cells in inflamed tissues, such as lipid-laden macrophages inside the vessel wall and perhaps also hepatic stellate cells. Observational studies show that plasma YKL-40 levels are elevated in patients with cardiovascular and liver disease and are associated with disease severity and prognosis. Furthermore, elevated plasma YKL-40 levels in apparently healthy individuals are associated with a 2-fold increased risk of future ischemic stroke and venous thromboembolism, but not with myocardial infarction, suggesting that YKL-40 could play a role in the formation of embolisms rather than atherosclerosis per se. Further, elevated YKL-40 levels combined with excessive alcohol consumption are associated with 10-years risk of alcoholic liver cirrhosis of up to 7%, suggesting that YKL-40 can be used as a strong noninvasive marker of predicting alcoholic liver cirrhosis. Importantly, in Mendelian randomization studies, genetically elevated plasma YKL-40 levels were not associated with risk of cardiovascular and alcoholic liver disease, thus suggesting that plasma YKL-40 does not play a causal role in the development of these diseases. Despite this, plasma YKL-40 levels may play a role in disease progression after diagnosis, and inhibition of YKL-40 activity might be a novel therapy in some cardiovascular and liver diseases.

Biomarkers of Endothelial Activation Are Associated with Poor Outcome in Critical Illness

Background

Endothelial activation plays a role in organ dysfunction in the systemic inflammatory response syndrome (SIRS). Angiopoietin-1 (Ang-1) promotes vascular quiescence while angiopoietin-2 (Ang-2) mediates microvascular leak. Circulating levels of Ang-1 and Ang-2 in patients with SIRS could provide insight on risks for organ dysfunction and death distinct from inflammatory proteins. In this study, we determined if biomarkers of endothelial activation and inflammation exhibit independent associations with poor outcomes in SIRS.

Methods

We studied 943 critically ill patients with SIRS admitted to an Intensive Care Unit (ICU) of an academic medical center. We measured plasma levels of endothelial markers (Ang-1, Ang-2, soluble vascular cell adhesion molecule-1 (sVCAM-1)) and inflammatory markers (interleukin-6 (IL-6), interleukin-8 (IL-8), granulocyte-colony stimulating factor (G-CSF), soluble tumor necrosis factor receptor-1 (sTNFR-1)) within 24 hours of enrollment. We tested for associations between each marker and 28 day mortality, shock, and day 3 sequential organ failure assessment (SOFA) score. For 28 day mortality, we performed sensitivity analysis for those subjects with sepsis and those with sterile inflammation. We used multivariate models to adjust for clinical covariates and determine if associations identified with endothelial activation markers were independent of those observed with inflammatory markers.

Results

Higher levels of all biomarkers were associated with increased 28 day mortality except levels of Ang-1 which were associated with lower mortality. After adjustment for comorbidities and sTNFR-1 concentration, a doubling of Ang-1 concentration was associated with lower 28 day mortality (Odds ratio (OR) = 0.81; p<0.01), shock (OR = 0.82; p<0.001), and SOFA score (β = -0.50; p<0.001), while Ang-2 concentration was associated with increased mortality (OR = 1.55; p<0.001), shock (OR = 1.51; p<0.001), and SOFA score (β = +0.63; p<0.001). sVCAM-1 was not independently associated with SIRS outcomes.

Conclusions

In critically ill patients with SIRS, early measurements of Ang-1 and Ang-2 are associated with death and organ dysfunction independently of simultaneously-measured markers of inflammation.

Host response biomarkers in the diagnosis of sepsis: a general overview

Critically ill patients who display a systemic inflammatory response syndrome (SIRS) are prone to develop nosocomial infections. The challenge remains to distinguish as early as possible among SIRS patients those who are developing sepsis. Following a sterile insult, damage-associated molecular patterns (DAMPs) released by damaged tissues and necrotic cells initiate an inflammatory response close to that observed during sepsis. During sepsis, pathogen-associated molecular patterns (PAMPs) trigger the release of host mediators involved in innate immunity and inflammation through identical receptors as DAMPs. In both clinical settings, a compensatory anti-inflammatory response syndrome (CARS) is concomitantly initiated. The exacerbated production of pro- or anti-inflammatory mediators allows their detection in biological fluids and particularly within the bloodstream. Some of these mediators can be used as biomarkers to decipher among the patients those who developed sepsis, and eventually they can be used as prognosis markers. In addition to plasma biomarkers, the analysis of some surface markers on circulating leukocytes or the study of mRNA and miRNA can be helpful. While there is no magic marker, a combination of few biomarkers might offer a high accuracy for diagnosis.

Airway, but not serum or urinary, levels of YKL-40 reflect inflammation in early cystic fibrosis lung disease

BACKGROUND

Cystic fibrosis (CF) lung disease begins in early life and is progressive with the major risk factor being an exaggerated inflammatory response. Currently, assessment of neutrophilic inflammation in early cystic fibrosis (CF) lung disease relies on bronchoalveolar lavage (BAL). The chitinase-like protein YKL-40 is raised in sputum and serum of adults with CF. We investigated YKL-40 in BAL, serum and urine to determine whether this reflected inflammation and infection in young children with CF.

METHODS

YKL-40 was measured in matched samples of BAL, serum and urine obtained from 36 infants and young children with CF participating in an early surveillance program. Levels were compared to clinical data and markers of inflammation detected in the lung.

RESULTS

YKL-40 in BAL correlated with pulmonary infection [β=1.30 (SE 0.34), p < 0.001] and BAL markers of inflammation [macrophage number: r2 = 0.34, p < 0.001; neutrophil number: r2 = 0.74, p < 0.001; neutrophil elastase: r2 = 0.47, p < 0.001; CXCL8: r2 = 0.45, p < 0.001; IL-β: r2 = 0.62, p < 0.001]. YKL-40 was detectable in serum but levels did not correlate with BAL levels in the same individuals (r2 = 0.04, p = 0.14) or with inflammatory markers. YKL-40 was below the limit of detection in urine (30 pg/ml).

CONCLUSIONS

This study demonstrates that levels of the chitinase-like protein YKL-40 reflect airway inflammation and infection in early CF lung disease. The lack of increased YKL-40 in serum in the absence of systemic inflammation limits the benefit of this potential biomarker in early disease.