Complement and contact system activation in acute congestive heart failure patients

Pitfalls in complement analysis: A systematic literature review of assessing complement activation

Background

The complement system is an essential component of our innate defense and plays a vital role in the pathogenesis of many diseases. Assessment of complement activation is critical in monitoring both disease progression and response to therapy. Complement analysis requires accurate and standardized sampling and assay procedures, which has proven to be challenging.

Objective

We performed a systematic analysis of the current methods used to assess complement components and reviewed whether the identified studies performed their complement measurements according to the recommended practice regarding pre-analytical sample handling and assay technique. Results are supplemented with own data regarding the assessment of key complement biomarkers to illustrate the importance of accurate sampling and measuring of complement components.

Methods

A literature search using the Pubmed/MEDLINE database was performed focusing on studies measuring the key complement components C3, C5 and/or their split products and/or the soluble variant of the terminal C5b-9 complement complex (sTCC) in human blood samples that were published between February 2017 and February 2022. The identified studies were reviewed whether they had used the correct sample type and techniques for their analyses.

Results

A total of 92 out of 376 studies were selected for full-text analysis. Forty-five studies (49%) were identified as using the correct sample type and techniques for their complement analyses, while 25 studies (27%) did not use the correct sample type or technique. For 22 studies (24%), it was not specified which sample type was used.

Conclusion

A substantial part of the reviewed studies did not use the appropriate sample type for assessing complement activation or did not mention which sample type was used. This deviation from the standardized procedure can lead to misinterpretation of complement biomarker levels and hampers proper comparison of complement measurements between studies. Therefore, this study underlines the necessity of general guidelines for accurate and standardized complement analysis

Serum Proteomic Changes in Dogs with Different Stages of Chronic Heart Failure

Simple Summary

Canine MMVD is a progressive chronic disease with variable clinical signs, with some patients remaining completely asymptomatic while others develop CHF. Here, the aims of the pilot study were to evaluate serum proteins by proteomic analysis in dogs at different stages of chronic heart failure (CHF) due to degenerative mitral valve disease (MMVD), and how these proteins can change after a conventional treatment. Study revealed 157 different proteins; 11 were up- and 21 down-regulated at a statistically significant level in dogs with CHF compared to controls. Based on the bioinformatic analysis, protein–protein interactions between complement proteins, fibrinogen subtypes and others (albumin precursor, serpins, inter-alpha-trypsin inhibitor heavy chain, fetuin, clusterin, apolipoproteins, and alpha-glycoproteins) showed that pathophysiology of CHF seems to be more sophisticated than we had thought. These proteins are associated with several cellular, biologic, and metabolic processes such as immune-inflammatory responses, hemostasis, oxidative stress, and energy metabolism, which might be detrimental in the progression of canine CHF. Their molecular and biological functions as well as roles in the signaling pathways, such as inflammation, cadherin signaling, nicotinic acetylcholine receptor signaling and Wnt signaling make them possible biomarkers and therapeutic targets for the diagnosis and treatments in dogs with different stages of CHF.

Abstract

MMVD, the most common cause of CHF in dogs, is a chronic disease with variable clinical signs, with some patients remaining asymptomatic while others develop CHF. Here, we aimed to evaluate serum proteins by proteomic analysis in dogs at different stages of CHF due to MMVD, and proteome behaviors after conventional treatment. A total of 32 dogs were divided equally into four groups—stage A (healthy/controls), stage B2 (asymptomatic), stage C and stage D (symptomatic)—according to the ACVIM consensus. Serum proteomes were evaluated using LC/MS-based label-free differential proteome analysis. The study revealed 157 different proteins; 11 were up- and 21 down-regulated in dogs with CHF compared to controls. In stage B2 dogs, angiotensinogen (AGT) was up-regulated, but immunoglobulin iota chain-like, lipopolysaccharide-binding protein, and carboxypeptidase (CPN) were down-regulated. In stage C dogs, complement C3 (C3) and inter-alpha-trypsin inhibitor heavy chain were up-regulated, but hemopexin, and actin-cytoplasmic-1 (ACT-1) were down-regulated. In stage D dogs, AGT was up-regulated, whereas tetranectin, paraoxonase-1, adiponectin and ACT-1 were down-regulated. A decrease in CPN, C3 and AGT and an increase in ACT-1 were observed after treatment of dogs in stage C. This pilot study identified that dogs at different stages of CHF show different serum protein composition which has potential to be biomarker for diagnose and treatment monitorization.

Inflammation in Metabolic and Cardiovascular Disorders-Role of Oxidative Stress

Cardiovascular diseases (CVD) constitute the main cause of death worldwide. Both inflammation and oxidative stress have been reported to be involved in the progress of CVD. It is well known that generation of oxidative stress during the course of CVD is involved in tissue damage and inflammation, causing deleterious effects such as hypertension, dysfunctional metabolism, endothelial dysfunction, stroke, and myocardial infarction. Remarkably, natural antioxidant strategies have been increasingly discovered and are subject to current scientific investigations. Here, we addressed the activation of immune cells in the context of ROS production, as well as how their interaction with other cellular players and further (immune) mediators contribute to metabolic and cardiovascular disorders. We also highlight how a dysregulated complement system contributes to immune imbalance and tissue damage in the context of increases oxidative stress. Additionally, modulation of hypothalamic oxidative stress is discussed, which may offer novel treatment strategies for type-2 diabetes and obesity. Together, we provide new perspectives on therapy strategies for CVD caused by oxidative stress, with a focus on oxidative stress.

iTRAQ-based proteomics reveals serum protein changes in hypertensive rats induced by a high-salt diet

High-salt diets may increase both hypertension and risk of cardiovascular diseases. Although high-salt diets can result in hypertension and impaired vascular function, the molecular mechanisms underlying these dysfunctions are not fully known. Thus, the aims of the present study were to identify key proteins and their signaling pathways and associated molecular mechanisms that may contribute to, as well as be potential biomarkers of, the pathogenesis of hypertension-related cardiovascular diseases. To that end, the present study identified and quantitated serum proteins that were differentially expressed in male rats fed regular chow (n = 4) and those fed a high-salt diet (n = 4) to induce hypertension. The serum was collected from both groups, and the proteins differentially expressed in the serum were identified and quantitated using isobaric tags for relative and absolute quantitation combined with liquid chromatography-tandem mass spectrometry. Of 396 identified proteins, 24 were differentially expressed between the groups: 19 proteins were significantly (P < 0.05) upregulated (> 1.2 fold change), and 5 were significantly downregulated (< 0.8 fold change). Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses indicated that these differentially expressed proteins may contribute to cardiovascular diseases via the roles they play in endothelial function, vascular remodeling, the coagulation cascade, and the complement system. In addition, phagosome processes and the integrin-associated focal adhesion signaling pathway were determined to be potential underlying molecular mechanisms. The key proteins identified in this study warrant further development as new therapeutic targets or biomarkers of cardiovascular diseases associated with high-salt diet-induced hypertension.

Complement Components sC5b-9 and CH50 Predict Prognosis in Heart Failure Patients Combined With Hypertension

BACKGROUND

Heart failure (HF), resulting from inflammation and vessel injury, is one of the leading causes of poor quality of life and premature death. The complement system plays a leading role in vessel integrity and inflammation response. However, the association between serum complement level and the prognosis of HF remains unclear.

METHODS

In our study, a total of 263 newly diagnosed hypertension patients with HF were included. Eight classical cardiovascular risk factors were collected, and plasma C3a, C3b, C5a, sC5b-9, and CH50 levels were detected.

RESULTS

Compared with the control group, plasma C5a (P<0.001), sC5b-9 (P<0.001), and CH50 (P = 0.004) levels of hypertension patients with HF were significantly increased. On the basis of univariate analysis, an older age, higher frequency of alcohol consumption, high level of body mass index, medium or high risk of hypertension, hyperlipidemia, and diabetes were poor prognostic factors whereas low levels of C5a, sC5b-9, and CH50 were associated with favorable overall survival (OS). When these factors fit into a multivariate regression model, patients with hyperlipidemia (P = 0.002, hazard ratio [HR] = 3.09), N-terminal pro-Brain Natriuretic Peptide (NT-pro-BNP) ≥ 14.8 (P < 0.001, HR = 11.14), sC5b-9 level ≥ 1,406.2 µg/ml (P = 0.180, HR = 5.51) or CH50 level ≥ 294.6 µg/ml (P < 0.001, HR = 4.57) remained statistically factors for worsened OS and regarded as independent risk factors. These independently associated risk factors were used to form an OS estimation nomogram. Nomogram demonstrated good accuracy in estimating the risk, with a bootstrap-corrected C index of 0.789.

CONCLUSIONS

sC5b-9 and CH50 levels are increased in hypertension patients with HF. Nomogram based on multivariate analysis has good accuracy in estimating the risk of OS.

The role of the complement factor B-arginase-polyamine molecular axis in uremia-induced cardiac remodeling in mice

The role of complement system in heart diseases is controversial. Besides, the mechanisms by which complement components participate in cardiac remodeling (CR) and heart failure during uremia are unclear. In this study, 5/6 nephrectomy was performed to adult mice to establish the uremic model and CR deteriorated over the course of uremia. Although complement pathways were not further activated over the course of the disease, soluble complement factor B (CFB) was upregulated at post-nephrectomy day 90 (PNx90) compared with PNx30. Further, CFB notably deteriorated CR in uremic mice but this effect was reversed by depletion of macrophages with liposomal clodronate. In vivo and in vitro CFB upregulated arginase 1 (ARG1) expression, increased ARG1 enzymatic activity, and stimulated the syntheses of ornithine, leading to polyamine overproduction in macrophages. Putrescine, an important polyamine, promoted cardiac fibroblast proliferation and collagen production, resulting in progressive CR. In vivo the inhibition of ARG1 activity with N^ω -hydroxyl-l-arginine remarkably improved the general survival rates, inhibited the infiltration of cardiac fibroblasts, and alleviated progression of CR in uremic mice. Taken together, the CFB-ARG1-putrescine axis is related to progression of CR and ARG1 hyperactivity in macrophages may provide a novel therapeutic target against the heart injury in uremia.