Soluble urokinase plasminogen activator receptor, the candidate prophetic biomarker in severe inflammatory response syndrome

Urokinase-type plasminogen activator receptor is required for impairing toll-like receptor 7 signaling on macrophage efferocytosis in lupus

The accumulation of apoptotic cells is one of the pathological characteristics of systemic lupus erythematosus (SLE). The expression of urokinase-type plasminogen activator receptor (uPAR) has been reported to be increased in SLE patients and to be involved in macrophage efferocytosis. Although the toll-like receptor 7 (TLR7) is also over-expressed in lupus, its relationship to uPAR and its role in macrophage efferocytosis in lupus is still unclear. In the present study, we revealed that apoptotic cells accumulate in the spleen, macrophage efferocytosis is impaired, and uPAR is increased in the spleen and peritoneal macrophages of the TLR7 agonist imiquimod (IMQ)-induced SLE mouse model. Moreover, TLR7 upregulated uPAR expression in the mouse macrophage RAW 264.7 cells in vitro. The same results were also obtained using peritoneal macrophages of female Balb/c mice. When uPAR levels in peritoneal macrophages were knocked down by siRNA or inhibited by the peptide inhibitor UPARANT, and cells further treated with the TLR7 agonist R848, efferocytosis of peritoneal macrophages on apoptotic cells was restored. These results indicated that TLR7 activation impaired efferocytosis via uPAR in mouse peritoneal macrophages. Furthermore, TLR7 regulated uPAR expression via ERK/JNK signaling in macrophages. These results suggest that uPAR may be an important factor related to the accumulation of apoptotic cells in SLE.

Preclinical evaluation of the urokinase receptor-derived peptide UPARANT as an anti-inflammatory drug

BACKGROUND

Inflammation plays a key role in the pathogenesis of several chronic diseases. The urokinase plasminogen activator receptor (uPAR) exerts a plethora of functions in both physiological and pathological processes, including inflammation.

OBJECTIVE AND DESIGN

In this study, we evaluated the anti-inflammatory effect of a novel peptide ligand of uPAR, UPARANT, in different animal models of inflammation.

SUBJECTS AND TREATMENT

Rats and mice were divided in different groups (n = 5) for single or repeated administration of vehicle (9% DMSO in 0.9% NaCl), UPARANT (6, 12 and 24 mg/kg) or dexamethasone (2 mg/kg). Animals were subjected to carrageenan-induced paw oedema or zymosan-induced peritonitis.

METHODS

UPARANT effects were tested on: (1) the carrageenan-induced paw oedema volume, (2) the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and the nitrite/nitrate (NOx) levels in the paw exudates, (3) cells recruitment into the peritoneal cavity after zymosan injection and (4) NOx levels in the peritoneal lavage.

RESULTS

UPARANT (12 and 24 mg/kg) reduced inflammation in both experimental paradigms. Analysis of pro-inflammatory enzymes revealed that administration of UPARANT reduced iNOS, COX2 and NO over-production.

CONCLUSIONS

Our study provides a solid evidence that UPARANT reduces the severity of inflammation in diverse animal models, thus representing a novel anti-inflammatory drug with potential advantages with respect to the typical steroidal agents.

Prognostic potential of 1,3-beta-d-glucan levels in bronchoalveolar lavage fluid samples

OBJECTIVES

The objective of this study was to investigate the prognostic potential of 1,3-beta-d-glucan (BDG) testing in bronchoalveolar lavage fluid (BALF) samples.

METHODS

A total of 300 BALF samples from 252 patients were investigated for BDG (Fungitell(®) assay). Prognostic potential of BALF BDG was evaluated by using: i.) Kaplan-Meier analysis, and ii.) multivariable Cox hazard regression analyses.

RESULTS

BALF BDG levels were found to be significantly higher in samples with Candida spp. colonization (p < 0.001). A total of 61/252 patients (24.2%) died within 90-days of BALF sampling (18.1% of patients with BALF BDG <200 pg/mL, 32.4% with BALF BDG ≥200 pg/mL). Kaplan-Meier analysis revealed that overall cumulative 90-day mortality was significantly higher in those with BALF BDG levels ≥200 pg/mL when compared to those with levels <200 pg/mL (log-rank p = 0.006, Breslow p = 0.005 and Tarone-Ware p = 0.005). The multivariable Cox regression analysis showed that BALF BDG levels were a strong predictor of 90-day overall mortality, with a hazard ratio of 1.048 (per 100 pg/mL increase of BALF BDG).

CONCLUSION

False positive BALF BDG results in the presence of Candida spp. colonization of the lower respiratory tract may explain the limited diagnostic potential of BALF BDG testing. In contrast, prognostic potential of BALF BDG may be promising.

Soluble urokinase plasminogen activator receptor levels are associated with severity of fibrosis in nonalcoholic fatty liver disease

The identification of individuals with severe liver fibrosis among patients with chronic liver disease is of major importance when evaluating prognosis, potential risk for complications, and when deciding treatment strategies. Although percutaneous liver biopsy is still considered a "gold standard" for staging of liver fibrosis, attempts to find reliable noninvasive markers of liver fibrosis are frequent. Inflammation is essential for the progression of fibrosis. The urokinase plasminogen activator and its receptor have been associated with hepatic inflammation and fibrosis in mice. High serum concentrations of soluble urokinase plasminogen activator receptor (suPAR) are suggested to be involved in inflammation, tissue remodeling, and cancer metastasis. Here, we evaluated serum suPAR as a noninvasive test to detect liver fibrosis in 82 well-characterized patients with nonalcoholic fatty liver disease (NAFLD), and in 38 untreated patients with chronic hepatitis C virus (HCV) infection at the time of their first liver biopsy. suPAR levels were increased in chronic liver disease compared with blood donors (P < 0.001). Patients with HCV had higher suPAR concentrations than patients with NAFLD (P < 0.002). suPAR levels were associated with the severity of fibrosis, particularly in NAFLD, but did not correlate with inflammation. Regarding the performance in predicting severity of fibrosis, suPAR was essentially as good as other commonly used noninvasive fibrosis scoring systems. The results in HCV confirm previous observations. However, this is the first study to investigate suPAR as a biomarker in NAFLD, and the results indicate that suPAR may constitute a severity marker related to fibrosis and prognosis rather than reflecting inflammation.

Soluble urokinase plasminogen activator receptor--a valuable biomarker in systemic lupus erythematosus?

Systemic lupus erythematosus (SLE) is a potentially severe autoimmune condition with an unpredictable disease course, often with fluctuations in disease activity over time. Long term inflammation and drug-related side-effects may subsequently lead to permanent organ damage, a consequence which is intimately connected to decreased quality of life and mortality. New lupus biomarkers that convey information regarding inflammation and/or organ damage are thus warranted. Today, there is no clinical biomarker that indicates the risk of damage accrual. Herein we highlight the urokinase plasminogen activator receptor (uPAR) and especially its soluble form (suPAR) that besides having biological functions in e.g. proteolysis, cell migration and tissue homeostasis, recently has emerged as a promising biomarker of inflammation and prognosis of several disorders. A strong association between suPAR and organ damage in SLE was recently demonstrated, and preliminary data (presented in this review) suggests the possibility of a predictive value of suPAR blood levels. The involvement of suPAR in the pathogenesis of SLE remains obscure, but its effects in leukocyte recruitment, phagocytic uptake of dying cells (efferocytosis) and complement regulation suggests that the central parts of the SLE pathogenesis could be regulated by suPAR, and vice versa.