C-reactive protein enhances activation of coagulation system and inflammatory response through dissociating into monomeric form in antineutrophil cytoplasmic antibody-associated vasculitis

Low platelet count at diagnosis of anti-neutrophil cytoplasmic antibody-associated vasculitis is correlated with the severity of disease and renal prognosis

Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is an autoimmune disease that involves inflammation of blood vessels. There is increasing evidence that platelets play a crucial role not only in hemostasis but also in inflammation and innate immunity. In this study, we explored the relationship between platelet count, clinical characteristics, and the prognosis of patients with AAV. We divided 187 patients into two groups based on their platelet count. Clinicopathological data and prognostic information were retrospectively gathered from medical records. Univariate and multivariate regression analyses were used to identify risk factors for prognosis, including end-stage renal disease (ESRD) and mortality. The cutoff point for platelet count was set at 264.5 × 109/L, as determined by the receiver operating characteristic (ROC) curve for predicting progression to ESRD in patients with AAV. We observed patients with low platelet count (platelets < 264.5 × 109/L) had lower leukocytes, hemoglobin, complement, acute reactants, and worse renal function (P for eGFR < 0.001). They were also more likely to progress to ESRD or death compared to the high platelet count group (platelets > 264.5 × 109/L) (P < 0.0001, P = 0.0338, respectively). Low platelet count was potentially an independent predictor of poor renal prognosis in the multivariate regression analysis [HR 1.670 (95% CI 1.019-2.515), P = 0.014]. Lower platelet count at diagnosis is associated with more severe clinical characteristics and impaired renal function. Therefore, platelet count may be an accessible prognostic indicator for renal outcomes in patients with AAV.

The Role of Anti-mCRP Autoantibodies in Lupus Nephritis

Background

Lupus nephritis is characterized by multiple autoantibodies production. However, there are few autoantibodies associated with disease activity and prognosis. CRP exists in at least two conformationally distinct forms: native pentameric C-reactive protein (pCRP) and modified/monomeric CRP (mCRP). Autoantibodies against mCRP are prevalent in sera of patients with lupus nephritis and are reported to be pathogenic.

Summary

The levels of serum anti-mCRP autoantibodies are associated with clinical disease activity, tubulointerstitial lesions, treatment response, and prognosis in patients with lupus nephritis. The key epitope of mCRP was amino acid 35-47. Furthermore, emerging evidence indicated that anti-mCRP autoantibodies could participate in the pathogenesis of lupus nephritis by forming in situ immune complexes or interfering with the biological functions of mCRP, such as binding to complement C1q and factor H.

Key Messages

Here, we review the recent advances in the prevalence, clinical-pathological associations, and potential pathogenesis of anti-mCRP autoantibodies in lupus nephritis, which may provide a promising novel therapeutic strategy for lupus nephritis.

Urinary Modified C-Reactive Protein is Closely Associated with Tubulointerstitial Lesions in Lupus Nephritis

Objective

Modified C-reactive protein (mCRP) is known to be involved in the upregulation and amplification of the local inflammatory response. This study investigated the circulating and local levels of mCRP and their relevance to clinicopathological features in patients with lupus nephritis.

Methods

Ninety-five patients with renal biopsy-proven lupus nephritis and 30 normal controls were enrolled in this study. Plasma and urinary mCRP were screened by enzyme-linked immunosorbent assay (ELISA). The renal deposition of mCRP was detected by immunohistochemistry and immunofluorescence staining. A human proximal tubular epithelial cell line (HK2 cells) was incubated with purified IgG from lupus nephritis, and the production of CRP by HK2 cells was further evaluated.

Results

Plasma and urinary levels of mCRP increased significantly in patients with lupus nephritis compared with normal controls (P = 0.013, P < 0.001, respectively). The urinary mCRP levels were associated with interstitial inflammatory cell infiltration (r = 0.514, P < 0.001) and interstitial fibrosis (r = 0.270, P = 0.008). The ROC-AUC of the urinary mCRP levels for diagnosing tubulointerstitial lesions was 0.766. The urinary mCRP levels were closely associated with poor outcomes (HR: 1.204, 95% CI: 1.029-1.409, P = 0.020). However, no correlations were found of the plasma mCRP levels with clinicopathological data or the prognosis of lupus nephritis. CRP was mostly deposited in the renal tubules in patients with lupus nephritis, and the expression of CRP was significantly correlated with tubulointerstitial lesion indices. Immunofluorescence staining showed that mCRP could colocalize with IgG in tubules. Lupus nephritis-derived IgG could induce CRP production by HK2 cells.

Conclusion

Urinary mCRP levels were significantly increased, and urinary mCRP might be a biomarker for tubulointerstitial lesions in patients with lupus nephritis. Renal CRP could be produced by tubular epithelial cells after stimulation by lupus nephritis-derived IgG, and the local presence of mCRP might play a critical role in the development of tubulointerstitial lesions.

NETs-Induced Thrombosis Impacts on Cardiovascular and Chronic Kidney Disease

Arterial and venous thrombosis constitute a major source of morbidity and mortality worldwide. Association between thrombotic complications and cardiovascular and other chronic inflammatory diseases are well described. Inflammation and subsequent initiation of thrombotic events, termed immunothrombosis, also receive growing attention but are still incompletely understood. Nevertheless, the clinical relevance of aberrant immunothrombosis, referred to as thromboinflammation, is evident by an increased risk of thrombosis and cardiovascular events in patients with inflammatory or infectious diseases. Proinflammatory mediators released from platelets, complement activation, and the formation of NETs (neutrophil extracellular traps) initiate and foster immunothrombosis. In this review, we highlight and discuss prominent and emerging interrelationships and functions between NETs and other mediators in immunothrombosis in cardiovascular disease. Also, with patients with chronic kidney disease suffering from increased cardiovascular and thrombotic risk, we summarize current knowledge on neutrophil phenotype, function, and NET formation in chronic kidney disease. In addition, we elaborate on therapeutic targeting of NETs-induced immunothrombosis. A better understanding of the functional relevance of antithrombotic mediators which do not increase bleeding risk may provide opportunities for successful therapeutic interventions to reduce thrombotic risk beyond current treatment options.

Association of ATG7 gene polymorphisms with microscopic polyangiitis in Chinese individuals

Microscopic polyangiitis (MPA) is a type of antineutrophil cytoplasmic antibody (ANCA)-related vasculitis. Autophagy-related gene 7 (ATG7) protects against complicated disorder states in model organisms, but the way ATG7 dysfunction contributes to MPA remains elusive. This investigation assessed the impacts of ATG7 single-nucleotide polymorphisms (SNPs) on microscopic polyangiitis (MPA) in China. A total of 211 controls and 214 MPA patients were recruited and analyzed. Polymerase chain reaction (PCR) and high-throughput sequencing were adopted to detect the ATG7 SNPs (rs75492008, rs2594966, rs6442260 and rs8154), and stratification analysis, different genetic models and differences in allele and genotype frequencies were evaluated. Haplotype evaluation was performed after linkage disequilibrium (LD) analyses, and interactions between alleles were assessed. Generalized multifactor dimensionality reduction (GMDR) was adopted to analyze SNP-SNP interactions among the four ATG7 SNPs and phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and unc-nc-like autophagy activating kinase 1 (ULK1) SNPs previously studied by our team. Relationships between ATG7 polymorphisms, disease activity biomarkers and therapeutic effects in MPA were analyzed. Sex stratification analysis of the rs2594966 GG genotype with codominant and recessive models showed OR=3.42, 95% CI [1.19-9.80], P=0.041 and OR=3.31, 95% CI [1.23-8.90], P=0.012, respectively. Haplotype G-G-C-T was related to an increased MPA risk (OR=1.5, 95% CI [0.999-2.266], P=0.029). Permutation testing of GMDR suggested that ATG7 rs6442260 and rs8154, PIK3CA rs1607237, and ULK1 rs4964879 might interact with each other in MPA development (P<0.05). Among 214 MPA patients, 79 available complete follow-up clinical datasets were gathered from September 2009 to October 2020, showing that rs75492008 and rs4964879 affect the correlation between C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) in MPA activity. Patients with rs8154 TT and rs1607237 CC genotypes had better clinical treatment effects (P<0.05). Gene polymorphisms may be related to MPA in China, exhibiting correlation with MPA activity indicators, treatment and prognosis.

The potential pathogenic roles of S100A8/A9 and S100A12 in patients with MPO-ANCA-positive vasculitis

Background

The significance of S100A8/A9 and S100A12 in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) has not been clarified. This study was dedicated to exploring the potential pathogenic roles of S100A8/A9 and S100A12 in patients with myeloperoxidase (MPO)-ANCA-positive vasculitis.

Methods

Serum and urine concentrations of S100A8/A9 and S100A12 of forty-two AAV patients were evaluated. The influence of S100A8/A9 and S100A12 on the chemotaxis, the apoptosis, the release of IL-1β, the complement activation, the respiratory burst, as well as the neutrophil extracellular traps (NETs) formation of MPO-ANCA-activated neutrophils was investigated.

Results

The serum and urine S100A8/A9 and S100A12 of active MPO-AAV significantly increased (compared with inactive AAV and healthy controls, p < 0.001) and were correlated with the severity of the disease. In vitro study showed that S100A8/A9 and S100A12 activated the p38 MAPK/NF-κB p65 pathway, increased the chemotaxis index (CI) and the release of IL-1β, extended the life span, and enhanced the complement activation ability of MPO-ANCA-activated neutrophils. The Blockade of TLR4 and RAGE inhibited the effects of S100A8/A9 and S100A12. All above-mentioned effects of S100A8/A9 and S100A12 were ROS-independent because neither S100A8/A9 nor S100A12 enhanced the ROS formation and NETs formation of MPO-ANCA-activated neutrophils.

Conclusion

S100A8/A9 and S100A12 serve as markers for assessing the disease severity, and they may also play a role in MPO-AAV pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00513-4.

CRP immunodeposition and proteomic analysis in abdominal aortic aneurysm

OBJECTIVE

The molecular mechanisms of the degeneration of the aortic wall in abdominal aortic aneurysm (AAA) are poorly understood. The monomeric form of C-reactive protein (mCRP) is deposited in damaged cardiovascular organs and aggravates the prognosis; however, it is unknown whether mCRP is deposited in the degenerated aorta of abdominal aortic aneurysm (AAA). We investigated whether mCRP is deposited in AAA and examined the associated pathogenic signaling pathways.

METHODS

Twenty-four cases of AAA were analyzed and their histological features were compared according to the level of serum CRP and the degree of mCRP deposition. Proteomic analysis was performed in AAA cases with strong and diffuse CRP immunopositivity (n = 7) and those with weak, focal, and junctional CRP immunopositivity (n = 3).

RESULTS

mCRP was deposited in the aortic specimens of AAA in a characteristic pattern that coincided with the lesion of the diminished elastic layer of the aortic wall. High serum CRP level was associated with stronger mCRP immunopositivity and a larger maximal diameter of aortic aneurysm. Proteomic analysis in AAA showed that multiple proteins were differentially expressed according to mCRP immunopositivity. Also, ingenuity pathway analysis showed that pathways associated with atherosclerosis, acute phase response, complement system, immune system, and coagulation were enriched in AAA cases with high mCRP immunopositivity.

CONCLUSIONS

AAA showed a characteristic deposition of mCRP, and multiple potentially pathologic signaling pathways were upregulated in AAA cases with strong CRP immunopositivity. mCRP and the aforementioned pathological pathways may serve as targets for managing the progression of AAA.

Monomeric C-reactive protein promotes platelets to release mitochondrial DNA in anti-neutrophil cytoplasmic antibody-associated vasculitis

Although high level of circulating C-reactive protein (pCRP) is considered as a biomarker for disease activity, the significance of CRP in the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) has not been clarified. We once reported in AAV, pentameric CRP (pCRP) could dissociate into monomeric CRP (mCRP) and activate platelets. Recent studies have demonstrated that the activated platelets can release mitochondrial DNA (mtDNA). The purpose of this study was to further study the relationship between mCRP and platelets in AAV. We found the plasma level of mCRP in AAV patients was significantly higher than that of normal control and positively correlated with the proportion of mCRP-positive platelets. Platelets isolated from one normal donor could be activated by plasma from 5 AAV patients and this effect could be attenuated when mCRP had been removed. Only 0.1 μg/mL of recombinant mCRP was needed for inducing platelets to release mtDNA via interaction with lipid raft and through p38 MAPK/NF-κB pathway. The mCRP binding on platelets depended on the C-terminal octapeptide (aa 199-206). The released mtDNA did not induce respiratory burst alone, but enhanced the ANCA-induced neutrophils respiratory burst after binding Toll-like receptor 9 (TLR9). The mtDNA released by mCRP-activated platelets also enhanced thrombin generation of plasma. In conclusion, our data demonstrate that mCRP can bind platelets via interaction with lipid raft and induce the release of mtDNA. The released mtDNA can enhance the pathogenicity of ANCA and promote activation of coagulation system in AAV.

Role of combining anticoagulant and antiplatelet agents in COVID-19 treatment: a rapid review

Although primarily affecting the respiratory system, COVID-19 causes multiple organ damage. One of its grave consequences is a prothrombotic state that manifests as thrombotic, microthrombotic and thromboembolic events. Therefore, understanding the effect of antiplatelet and anticoagulation therapy in the context of COVID-19 treatment is important. The aim of this rapid review was to highlight the role of thrombosis in COVID-19 and to provide new insights on the use of antithrombotic therapy in its management. A rapid systematic review was performed using preferred reporting items for systematic reviews. Papers published in English on antithrombotic agent use and COVID-19 complications were eligible. Results showed that the use of anticoagulants increased survival and reduced thromboembolic events in patients. However, despite the use of anticoagulants, patients still suffered thrombotic events likely due to heparin resistance. Data on antiplatelet use in combination with anticoagulants in the setting of COVID-19 are quite scarce. Current side effects of anticoagulation therapy emphasise the need to update treatment guidelines. In this rapid review, we address a possible modulatory role of antiplatelet and anticoagulant combination against COVID-19 pathogenesis. This combination may be an effective form of adjuvant therapy against COVID-19 infection. However, further studies are needed to elucidate potential risks and benefits associated with this combination.

A proposed role of neutrophil extracellular traps and their interplay with fibroblasts in ANCA-associated vasculitis lung fibrosis

ANCA-associated vasculitides (AAV) comprise three diseases: granulomatosis with polyangiitis, microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis. They are characterised by small vessel inflammation and have a broad range of clinical manifestations and multiorgan involvement which endanger the patient's life. An increasingly recognised complication of AAV, especially in MPA is lung fibrosis, for which no clearcut therapy in this context is available. The release of neutrophil extracellular traps (NETs) in these diseases has been related to the development of fibrosis, but the precise mechanisms are not fully unravelled. This review provides an overview of some of the important proteins known to compose NETs, and proposes some mechanisms by which these remarkable components may exert an impact on the different fibroblastic phenotypes leading to lung fibrosis.

Comorbidities and health-related quality of life in Patients with Antineutrophil Cytoplasmic Antibody (ANCA) - associated vasculitis

BACKGROUND AND OBJECTIVES

The optimization of immunosuppressive therapies has led to a marked improvement in the survival of ANCA-associated vasculitides (AAV). The main issue now appears to be the management of comorbidities and the improvement of quality of life. The objective of this review was to investigate the incidence and the impact of AAV-associated comorbidities, as well as the determinants of health-related quality of life (HRQoL).

METHODS

We performed a systematic literature review of articles published in Medline from 2001 to 04/28/2020. We selected relevant articles about AAV-associated comorbidities as well as HRQoL and fatigue. For each selected article, data on the incidence of comorbidity were extracted, and factors associated with the Mental component score (MCS) and the Physical component score (PCS) were identified.

RESULTS

Among the 10,993 references identified, 103 were retained for the final analysis. A significant increase in cardiovascular risk was evidenced, particularly for coronary artery disease and thromboembolic events, especially during the active phase of the disease. AAV was also associated with bronchiectasis, thyroid diseases and osteoporosis. A marked decrease in HRQoL and an increase in fatigue and anxiety were reported. Decrease in PCS and MCS was associated with fatigue, mood disorders, sleep disturbance, and/or unemployment.

CONCLUSION

The excess mortality of AAV is still a concern, partly in connection with cardiovascular and thromboembolic comorbidities. AAV patients also experiment a reduction in their HRQoL that requires integrated management. Patients with AAV need comorbidity management strategies to improve their quality of life and outcomes.

Downregulation of interleukin-6 and C-reactive protein underlies a novel inhibitory role of microRNA-136-5p in acute lower extremity deep vein thrombosis

Deep vein thrombosis (DVT) comprises a critical and common health condition with high incidence, mortality, and long-term adverse sequelae. Several differentially expressed microRNAs (miRNAs) have emerged as promising prognostic markers in DVT. The present study intended to explore the functional relevance of miR-136-5p in acute lower extremity DVT (LEDVT). Rat models of acute LEDVT were established and miR-136-5p expression was altered by agomir or antagomir to assess its effects. In addition, in vitro gain- and loss-experiments, prior to exposure to CoCl₂, were performed to investigate effects of miR-136-5p on human umbilical vein endothelial cell (HUVEC) apoptosis and levels of interleukin-6 (IL-6) and C-reactive protein (CRP). miR-136-5p was downregulated, whereas IL-6 and CRP were elevated in acute LEDVT patients. Notably, miR-136-5p was confirmed to target both IL-6 and CRP. Overexpression of miR-136-5p led to reduced length, weight, and ratio of weight to length of the venous thrombus. Furthermore, overexpressed miR-136-5p downregulated the expression of IL-6 and CRP, consequently inhibiting HUVEC apoptosis. Conjointly, our data indicate that the overexpression of miR-136-5p has the potential to bind to the 3’-UTR in the mRNAs for IL-6 and CRP and mitigate acute LEDVT, which provides a basis for new therapeutic targets in acute LEDVT treatment.

The plasma level of mCRP is linked to cardiovascular disease in antineutrophil cytoplasmic antibody-associated vasculitis

BACKGROUND

C-reactive protein (CRP) has two natural isomers: C-reactive protein pentamer (pCRP) and C-reactive protein monomer (mCRP). The levels of CRP are significantly elevated in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). mCRP not only activates the endothelial cells, platelets, leukocytes, and complements, but also has a proinflammatory structural subtype that can localize and deposit in inflammatory tissues. Thus, it regulates a variety of clinical diseases, such as ischemia/reperfusion (I/R) injury, Alzheimer's disease, age-related macular degeneration, and cardiovascular disease. We hypothesized that plasma mCRP levels are related to cardiovascular disease in AAV.

METHODS

In this cross-sectional study, 37 patients with AAV were assessed. Brain natriuretic peptide (BNP) and mCRP in plasma were assessed by enzyme-linked immunosorbent assay (ELISA). The acute ST-segment elevation myocardial infarction (STEMI) was diagnosed by coronary angiography, and the Gensini score calculated. Echocardiography evaluated the ejection fraction (EF%), left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and left ventricular mass index (LVMI). Estimated glomerular filtration rate (eGFR) was calculated based on serum creatinine, age, and gender.

RESULTS

The plasma level of mCRP in AAV was significantly higher than that in healthy volunteers (P < 0.001). Then, mCRP and CRP levels were compared with and without STEMI complications in AAV. The plasma level of mCRP was higher, but that of CRP was lower in STEMI. The plasma level of mCRP was correlated with Birmingham vasculitis activity score (BVAS), eGFR, BNP, EF%, LVEDV, LVESV, LVMI, and STEMI complications' Gensini score in AAV; however, CRP did not correlate with BNP, EF%, LVEDV, LVESV, LVMI, and Gensini score.

CONCLUSIONS

The plasma level of mCRP was related to cardiovascular diseases in AAV patients.

The role of beta-2-glycoprotein I in health and disease associating structure with function: More than just APS

Beta-2-Glycoprotein I (β2GPI) plays a number of essential roles throughout the body. β2GPI, C-reactive protein and thrombomodulin are the only three proteins that possess the dual capability to up and down regulate the complement and coagulation systems depending upon external stimulus. Clinically, β2GPI is the primary antigen in the autoimmune condition antiphospholipid syndrome (APS), which is typically characterised by pregnancy morbidity and vascular thrombosis. This protein is also capable of adopting at least two distinct structural forms, but it has been argued that several other intermediate forms may exist. Thus, β2GPI is a unique protein with a key role in haemostasis, homeostasis and immunity. In this review, we examine the genetics, structure and function of β2GPI in the body and how these factors may influence its contribution to disease pathogenesis. We also consider the clinical implications of β2GPI in the diagnosis of APS and as a potentially novel therapeutic target.

The Multiple Faces of C-Reactive Protein-Physiological and Pathophysiological Implications in Cardiovascular Disease

C-reactive protein (CRP) is an intriguing protein which plays a variety of roles in either physiological or pathophysiological states. For years it has been regarded merely as a useful biomarker of infection, tissue injury and inflammation, and it was only in the early 80s that the modified isoforms (mCRP) of native CRP (nCRP) appeared. It soon became clear that the roles of native CRP should be clearly discriminated from those of the modified form and so the impacts of both isoforms were divided to a certain degree between physiological and pathophysiological states. For decades, CRP has been regarded only as a hallmark of inflammation; however, it has since been recognised as a significant predictor of future episodes of cardiovascular disease, independent of other risk factors. The existence of modified CRP isoforms and their possible relevance to various pathophysiological conditions, suggested over thirty years ago, has prompted the search for structural and functional dissimilarities between the pentameric nCRP and monomeric mCRP isoforms. New attempts to identify the possible relevance between the diversity of structures and their opposing functions have initiated a new era of research on C-reactive protein. This review discusses the biochemical aspects of CRP physiology, emphasizing the supposed relevance between the structural biology of CRP isoforms and their differentiated physiological and pathophysiological roles.

Rethinking IL-6 and CRP: Why they are more than inflammatory biomarkers, and why it matters

Behavioral researchers have increasingly become interested in the idea that chronic, low-grade inflammation is a pathway through which social and behavioral variables exert long-term effects on health. Much research in the area employs putative inflammatory biomarkers to infer an underlying state of inflammation. Interleukin 6 (IL-6) and C-reactive protein (CRP, whose production is stimulated by IL-6) are arguably the two most commonly assayed biomarkers. Yet, in contrast with near-universal assumptions in the field, discoveries in immunology over the past two decades show that neither IL-6 nor CRP are unambiguous inflammatory markers. IL-6 operates through two distinct signaling pathways, only one of which is specifically upregulated during inflammation; both pathways have a complex range of effects and influence multiple physiological processes even in absence of inflammation. Similarly, CRP has two isoforms, one of which is produced locally in inflamed or damaged tissues. The other isoform is routinely produced in absence of inflammation and may have net anti-inflammatory effects. We propose a functional framework to account for the multiple actions of IL-6 and CRP. Specifically, we argue that both molecules participate in somatic maintenance efforts; hence elevated levels indicate that an organism is investing in protection, preservation, and/or repair of somatic tissue. Depending on the state of the organism, maintenance may be channeled into resistance against pathogens (including inflammation), pathogen tolerance and harm reduction, or tissue repair. The findings and framework we present have a range of potential implications for the interpretation of empirical findings in this area-a point we illustrate with alternative interpretations of research on socioeconomic status, stress, and depression.

An ELISA Assay for Quantifying Monomeric C-Reactive Protein in Plasma

Native C-reactive protein (nCRP) is a non-specific marker of inflammation being claimed as a bystander in several chronic disorders. Accumulating evidence indicates that nCRP dissociates to and acts primarily as the monomeric conformation (mCRP) at inflammatory loci. This suggests that mCRP may be a superior disease marker with improved specificity and clear causality to the underlying pathogenesis. However, the lack of a feasible assay to quantify mCRP in clinical samples precludes the assessment of that suggestion. Here we report the development of a sandwich ELISA assay for quantification of plasma mCRP using commercially available reagents. Our assay is reproducible and highly conformation-specific showing a reliable detection limit of 1 ng/mL. We further show that mCRP appears to be a better marker than nCRP in several skin-related autoimmune disorders. This assay thus provides a useful tool to examine the clinical significance and utility of mCRP.

Monomeric C-Reactive Protein Binds and Neutralizes Receptor Activator of NF-κB Ligand-Induced Osteoclast Differentiation

C-reactive protein (CRP) is an established marker of rheumatoid arthritis (RA) but with ill-defined actions in the pathogenesis. Here, we show that CRP regulates the differentiation of osteoclasts, a central mediator of joint inflammation and bone erosion in RA, in a conformation- and receptor activator of NF-κB ligand (RANKL)-dependent manner. CRP in the native conformation is ineffective, whereas the monomeric conformation (mCRP) actively modulates osteoclast differentiation through NF-κB and phospholipase C signaling. Moreover, mCRP can bind RANKL, the major driver of osteoclast differentiation, and abrogate its activities. The binding and inhibition of RANKL are mediated by the cholesterol binding sequence (CBS) of mCRP. Corroborating the in vitro results, CRP knockout exacerbates LPS-induced bone resorption in mice. These results suggest that mCRP may be protective in joint inflammation by inhibiting pathological osteoclast differentiation and that the CBS peptide could be exploited as a potential RANKL inhibitor.

Sensors and Biosensors for C-Reactive Protein, Temperature and pH, and Their Applications for Monitoring Wound Healing: A Review

Wound assessment is usually performed in hospitals or specialized labs. However, since patients spend most of their time at home, a remote real time wound monitoring would help providing a better care and improving the healing rate. This review describes the advances in sensors and biosensors for monitoring the concentration of C-reactive protein (CRP), temperature and pH in wounds. These three parameters can be used as qualitative biomarkers to assess the wound status and the effectiveness of therapy. CRP biosensors can be classified in: (a) field effect transistors, (b) optical immunosensors based on surface plasmon resonance, total internal reflection, fluorescence and chemiluminescence, (c) electrochemical sensors based on potentiometry, amperometry, and electrochemical impedance, and (d) piezoresistive sensors, such as quartz crystal microbalances and microcantilevers. The last section reports the most recent developments for wearable non-invasive temperature and pH sensors suitable for wound monitoring.

The therapeutic effects of Periploca forrestii Schltr. Stem extracts on collagen-induced arthritis by inhibiting the activation of Src/NF-κB signaling pathway in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Periploca forrestii Schltr. is a classical traditional Chinese medicine (TCM) called Heilonggu (HLG) in China. According to the theory of TCM, it possesses the efficacy of eliminating wind and removing dampness. In clinical practice, it is commonly used for the treatment of rheumatoid arthritis. The present work aimed to evaluate the anti-rheumatism activity of HLG ethanol extract and reveal the underlying molecular mechanism by employing an animal model of collagen-induced rheumatoid arthritis (CIA) in rats.

MATERIALS AND METHODS

The CIA was induced in male Sprague-Dawley rats by intradermal injection of bovine collagen-II in complete Freund's adjuvant (CFA) at the base of tail. The rats received oral administration of HLG (200 and 400mg/kg) from day 1, with the treatment lasting for 28 days. A variety of indicators were measured for evaluation of anti-rheumatism effect, including paw swelling, arthritis scores, and histopathological changes. Furthermore, the serum levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and prostaglandin E2 (PGE2), as well as cyclooxygenase-2 (COX-2), nuclear factor NF-κB p65 and Src kinase in joint synovial tissues were detected to explore the possible mechanisms.

RESULTS

The administration of HLG significantly restored type II collagen-induced arthritis in rats as evidenced by decrease in paw swelling and inflammatory factors in serum. Meanwhile, this treatment also notably reduced NF-κB p65 and COX-2 expression. Surprisingly, the activity of Src kinase was also inhibited demonstrated by downregulation of phosphorylated Src.

CONCLUSION

Our results revealed that HLG possessed observable therapeutic action on collagen-induced arthritis by inhibiting the activation of Src and nuclear translocation of NF-κB in rats. HLG may serve as a potential candidate for the management of patients with RA.

Therapeutic effects of Caragana pruinosa Kom. roots extract on type II collagen-induced arthritis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Caragana pruinosa Kom. is a deciduous shrub belonging to the genus of Caragana (Leguminosae), and Caragana plants exhibit a wide range of interesting pharmacological properties including anti-inflammatory, analgesic, and anti-arthritis activity, etc.

AIM OF THE STUDY

This study was aimed to investigate the anti-arthritic effect of 80% EtOH extract from the roots of C. pruinosa (ERCP) on arthritis and explore the potential pharmacological mechanism.

MATERIALS AND METHODS

After collagen induced arthritis (CIA) were established in rats, the animals were orally administered with ERCP (130, 260 and 520mg/kg) for 30 days. During the treatment, the rats' body weights, arthritis indices and paw volumes were measured every 5 days. Subsequently, rats' blood samples were collected to determine TNF-α, IL-1β, IL-6, IL-10, and C-reactive protein (CRP) contents in serum. Then, rats were sacrificed and the hind paws and knee joints were collected for histopathological examination.

RESULTS

Our results indicated that ERCP significantly suppressed the inflammatory reactions and destructions in joints and synovial tissues. ERCP inhibited the paw swelling and arthritis index in CIA rats. Additionally, it decreased the levels of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and CRP, whereas increased that of IL-10.

CONCLUSION

Our results suggested ERCP has significant anti-arthritic effect on CIA rats, and the pharmacological mechanisms are related to the down-regulation of TNF-α, IL-1β, IL-6 and CRP and the up-regulation of IL-10.

An Intrinsically Disordered Motif Mediates Diverse Actions of Monomeric C-reactive Protein

Most proinflammatory actions of C-reactive protein (CRP) are only expressed following dissociation of its native pentameric assembly into monomeric form (mCRP). However, little is known about what underlies the greatly enhanced activities of mCRP. Here we show that a single sequence motif, i.e. cholesterol binding sequence (CBS; a.a. 35-47), is responsible for mediating the interactions of mCRP with diverse ligands. The binding of mCRP to lipoprotein component ApoB, to complement component C1q, to extracellular matrix components fibronectin and collagen, to blood coagulation component fibrinogen, and to membrane lipid component cholesterol, are all found to be markedly inhibited by the synthetic CBS peptide but not by other CRP sequences tested. Likewise, mutating CBS in mCRP also greatly impairs these interactions. Functional experiments further reveal that CBS peptide significantly reduces the effects of mCRP on activation of endothelial cells in vitro and on acute induction of IL-6 in mice. The potency and specificity of CBS are critically determined by the N-terminal residues Cys-36, Leu-37, and His-38; while the versatility of CBS appears to originate from its intrinsically disordered conformation polymorphism. Together, these data unexpectedly identify CBS as the major recognition site of mCRP and suggest that this motif may be exploited to tune the proinflammatory actions of mCRP.

Do neutrophil extracellular traps contribute to the heightened risk of thrombosis in inflammatory diseases?

Thrombotic events, both arterial and venous, are a major health concern worldwide. Further, autoimmune diseases, such as systemic lupus erythematosus, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, and antiphospholipid syndrome, predispose to thrombosis, and thereby push the risk for these morbid events even higher. In recent years, neutrophils have been identified as important players in both arterial and venous thrombosis. Specifically, chromatin-based structures called neutrophil extracellular traps (NETs) play a key role in activating the coagulation cascade, recruiting platelets, and serving as scaffolding upon which the thrombus can be assembled. At the same time, neutrophils and NETs are emerging as important mediators of pathogenic inflammation in the aforementioned autoimmune diseases. Here, we first review the general role of NETs in thrombosis. We then posit that exaggerated NET release contributes to the prothrombotic diatheses of systemic lupus erythematosus, ANCA-associated vasculitis, and antiphospholipid syndrome.

Elevated serum uric acid after injury correlates with the early acute kidney in severe burns

OBJECTIVE

Early acute kidney injury (AKI) is one of the most serious and common complications in the early stage of severe burns, but the pathological mechanisms still need to be elucidated. High uric acid (UA) has been found to be correlated with renal dysfunction in some experimental and clinical studies; however, the study of the dynamic correlation between AKI and UA in severe burns is still lacking.

METHODS

The diagnosis and classification of AKI were performed according to RIFLE criteria, UA, serum creatinine (Scr), estimated glomerular filtration rate (eGFR), C-reactive protein (CRP) and lactic acid (LA) were dynamically monitored within 2 days after injury in 59 severely burned patients.

RESULTS

Within 2 days after injury, AKI occurred in 23 of 59 patients (risk in 12 cases, injury in seven cases and failure in four cases), UA level in AKI patients was significantly higher than that in No-AKI patients, and referring to the cutoff level of UA (375.5 μmol/l) from ROC curve for predicting AKI, the abnormal increase of UA levels was earlier than acute deterioration of renal function in most of the AKI patients after injury. Among AKI patients, the Scr/eGFR levels were closely related to UA levels for 2 days after injury. Moreover, UA level in cases with severe grade of AKI was significantly higher than that in those with less severe grade of AKI. Furthermore, there was a positive correlation between UA and CRP for 2 days after injury in AKI patients, and a significant correlation between CRP and Scr/eGFR was found 1 day after injury. The positive correlation was also found between LA and UA after injury in AKI patients.

CONCLUSION

The results suggest that elevated serum UA after injury due to hypoxia is closely correlated with early AKI after severe burns, and UA-related aberrant inflammation also appears to be one of the pathogenic factors, providing the useful information for potential therapy.