Regulation of the Complement System by Pentraxins

The role of gamma globulin, complement component 1q, factor B, properdin, body temperature, C-reactive protein and serum amyloid alpha to the activity and the function of the human complement system and its pathways

The complement system plays a crucial role in orchestrating the activation and regulation of inflammation within the human immune system. Three distinct activation pathways-classical, lectin, and alternative-converge to form the common lytic pathway, culminating in the formation of the membrane-attacking complex that disrupts the structure of pathogens. Dysregulated complement system activity can lead to tissue damage, autoimmune diseases, or immune deficiencies. In this study, the antimicrobial activity of human serum was investigated by using a bioluminescent microbe probe, Escherichia coli (pEGFPluxABCDEamp). This probe has previously been used to determine the antimicrobial activity of complement system and the polymorphonuclear neutrophils. In this study, blocking antibodies against key serum activators and components, including IgG, complement component 1q, factor B, and properdin, were utilized. The influence of body temperature and acute phase proteins, such as C reactive protein (CRP) and serum amyloid alpha (SAA), on the complement system was also examined. The study reveals the critical factors influencing complement system activity and pathway function. Alongside crucial factors like C1q and IgG, alternative pathway components factor B and properdin played pivotal roles. Results indicated that the alternative pathway accounted for approximately one third of the overall serum antimicrobial activity, and blocking this pathway disrupted the entire complement system. Contrary to expectations, elevated body temperature during inflammation did not enhance the antimicrobial activity of human serum. CRP demonstrated complement activation properties, but at higher physiological concentrations, it exhibited antagonistic tendencies, dampening the response. On the other hand, SAA enhanced the serum's activity. Overall, this study sheds a light on the critical factors affecting both complement system activity and pathway functionality, emphasizing the importance of a balanced immune response.

sMR and PTX3 levels associate with COVID-19 outcome and survival but not with Long COVID

Biomarkers for monitoring COVID-19 disease course are lacking. Study aim was to identify biomarkers associated with disease severity, survival, long-term outcome, and Long COVID. As excessive macrophages activation is a hallmark of COVID-19 and complement activation is key in this, we selected the following proteins involved in these processes: PTX3, C1q, C1-INH, C1s/C1-INH, and sMR. EDTA-plasma concentrations were measured in 215 patients and 47 controls using ELISA. PTX3, sMR, C1-INH, and C1s/C1-INH levels were associated with disease severity. PTX3 and sMR were also associated with survival and long-term immune recovery. Lastly, sMR levels associate with ICU admittance. sMR (AUC 0.85) and PTX3 (AUC 0.78) are good markers for disease severity, especially when used in combination (AUC 0.88). No association between biomarker levels and Long COVID was observed. sMR has not previously been associated with COVID-19 disease severity, ICU admittance or survival and may serve as marker for disease course.

Post-COVID Trajectory of Pentraxin 3 Plasma Levels Over 6 Months and Their Association with the Risk of Developing Post-Acute Depression and Anxiety

BACKGROUND AND OBJECTIVES

Clinical manifestations of coronavirus disease 2019 (COVID-19) often persist after acute disease resolution. Underlying molecular mechanisms are unclear. The objective of this original article was to longitudinally measure plasma levels of markers of the innate immune response to investigate whether they associate with and predict post-COVID symptomatology.

METHODS

Adult patients with previous severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection during the first pandemic wave who underwent the 6-month multidisciplinary follow-up were included. Plasma levels of pentraxin 3 (PTX3), the complement components C3a and C5a, and chitinase-3 like-protein-1 (CHI3L1) were measured at hospital admission during acute disease (baseline) and at 1 and 6 months after hospital discharge. Associations with post-COVID-19 sequelae at 6 months were investigated using descriptive statistic and multiple regression models.

RESULTS

Ninety-four COVID-19 patients were included. Baseline PTX3, C5a, C3a, and CHI3L1 did not predict post-COVID-19 sequelae. The extent of the reduction of PTX3 over time (delta PTX3) was associated with lower depressive and anxiety symptoms at 6 months (both p < 0.05). When entering sex, age, need for intensive care unit or non-invasive ventilation during hospital stay, psychiatric history, and baseline PTX3 as nuisance covariates into a generalized linear model (GLM), the difference between baseline and 6-month PTX3 levels (delta PTX3) significantly predicted depression (χ2 = 4.66, p = 0.031) and anxiety (χ2 = 4.68, p = 0.031) at 6 months. No differences in PTX3 levels or PTX3 delta were found in patients with or without persistent or new-onset other COVID-19 symptoms or signs at 6 months. Plasma levels of C3a, C5a, and CHI3L1 did not correlate with PTX3 levels at either time point and failed to associate with residual or de novo respiratory or systemic clinical manifestations of the disease at 6 months.

CONCLUSIONS

A lower reduction of plasma PTX3 after acute COVID-19 associates with the presence of depression and anxiety, suggesting an involvement of inflammation in post-COVID-19 psychopathology and a potential role of PTX3 as a biomarker.

SAP deletion promotes malignant insulinoma progression by inducing CXCL12 secretion from CAFs via the CXCR4/p38/ERK signalling pathway

Malignant insulinoma is an extremely rare type of functioning pancreatic neuroendocrine tumour with a high degree of malignancy and a high incidence of metastasis. However, it is still unclear how malignant insulinomas develop and metastasize. Serum amyloid P component (SAP), a member of the pentraxin protein family, is an acute-phase protein secreted by liver cells. The role of SAP in insulinoma and the related mechanism are still unknown. To determine the effect of SAP on insulinoma, we crossed Rip1-Tag2 mice, which spontaneously develop insulinoma, and SAP knockout (KO) mice to generate Rip1-Tag2;SAP-/- mice. We found that SAP deletion significantly promoted the growth, invasion and metastasis of malignant insulinoma through C-X-C motif chemokine ligand 12 (CXCL12) secreted by cancer-associated fibroblasts (CAFs). Further study showed that SAP deletion promoted CXCL12 secretion by CAFs through the CXCR4/p38/ERK signalling pathway. These findings reveal a novel role and mechanism of SAP in malignant insulinoma and provide direct evidence that SAP may be a therapeutic agent for this disease.

Re-visiting humoral constitutive antibacterial heterogeneity in bloodstream infections

Although cellular immunity has garnered much attention in the era of single-cell technologies, humoral innate immunity has receded in priority due to its presumed limited roles. Hence, despite the long-recognised bactericidal activity of serum-a functional characteristic of constitutive humoral immunity-much remains unclear regarding mechanisms underlying its inter-individual heterogeneity and clinical implications in bloodstream infections. Recent work suggests that the immediate antimicrobial effect of humoral innate immunity contributes to suppression of the excessive inflammatory responses to infection by reducing the amount of pathogen-associated molecular patterns. In this Personal View, we propose the need to re-explore factors underlying the inter-individual heterogeneity in serum antibacterial competence as a new approach to better understand humoral innate immunity and revisit the clinical use of measuring serum antibacterial activity in the management of bacterial bloodstream infections. Given the current emphasis on subtyping sepsis, a serum bactericidal assay might prove useful in defining a distinct sepsis endotype, to enable more personalised management.

Different inflammatory signatures based on CSF biomarkers relate to preserved or diminished brain structure and cognition

Neuroinflammation is a hallmark of Alzheimer's disease (AD) and both positive and negative associations of individual inflammation-related markers with brain structure and cognitive function have been described. We aimed to identify inflammatory signatures of CSF immune-related markers that relate to changes of brain structure and cognition across the clinical spectrum ranging from normal aging to AD. A panel of 16 inflammatory markers, Aβ42/40 and p-tau181 were measured in CSF at baseline in the DZNE DELCODE cohort (n = 295); a longitudinal observational study focusing on at-risk stages of AD. Volumetric maps of gray and white matter (GM/WM; n = 261) and white matter hyperintensities (WMHs, n = 249) were derived from baseline MRIs. Cognitive decline (n = 204) and the rate of change in GM volume was measured in subjects with at least 3 visits (n = 175). A principal component analysis on the CSF markers revealed four inflammatory components (PCs). Of these, the first component PC1 (highly loading on sTyro3, sAXL, sTREM2, YKL-40, and C1q) was associated with older age and higher p-tau levels, but with less pathological Aβ when controlling for p-tau. PC2 (highly loading on CRP, IL-18, complement factor F/H and C4) was related to male gender, higher body mass index and greater vascular risk. PC1 levels, adjusted for AD markers, were related to higher GM and WM volumes, less WMHs, better baseline memory, and to slower atrophy rates in AD-related areas and less cognitive decline. In contrast, PC2 related to less GM and WM volumes and worse memory at baseline. Similar inflammatory signatures and associations were identified in the independent F.ACE cohort. Our data suggest that there are beneficial and detrimental signatures of inflammatory CSF biomarkers. While higher levels of TAM receptors (sTyro/sAXL) or sTREM2 might reflect a protective glia response to degeneration related to phagocytic clearance, other markers might rather reflect proinflammatory states that have detrimental impact on brain integrity.

The role of the complement system in disc degeneration and Modic changes

Disc degeneration and vertebral endplate bone marrow lesions called Modic changes are prevalent spinal pathologies found in chronic low back pain patients. Their pathomechanisms are complex and not fully understood. Recent studies have revealed that complement system proteins and interactors are dysregulated in disc degeneration and Modic changes. The complement system is part of the innate immune system and plays a critical role in tissue homeostasis. However, its dysregulation has also been associated with various pathological conditions such as rheumatoid arthritis and osteoarthritis. Here, we review the evidence for the involvement of the complement system in intervertebral disc degeneration and Modic changes. We found that only a handful of studies reported on complement factors in Modic changes and disc degeneration. Therefore, the level of evidence for the involvement of the complement system is currently low. Nevertheless, the complement system is tightly intertwined with processes known to occur during disc degeneration and Modic changes, such as increased cell death, autoantibody production, bacterial defense processes, neutrophil activation, and osteoclast formation, indicating a contribution of the complement system to these spinal pathologies. Based on these mechanisms, we propose a model how the complement system could contribute to the vicious cycle of tissue damage and chronic inflammation in disc degeneration and Modic changes. With this review, we aim to highlight a currently understudied but potentially important inflammatory pathomechanism of disc degeneration and Modic changes that may be a novel therapeutic target.

Identification of systemic biomarkers and potential drug targets for age-related macular degeneration

Purpose

Since age-related macular degeneration (AMD) is tightly associated with aging and cellular senescence, objective of this study was to investigate the association between plasma levels of senescence-related proteins (SRPs) and risk of AMD.

Design

The whole study was based on two-sample Mendelian randomization (MR) analysis.

Methods

For MR analysis, the primary approach for MR analysis was the inverse-variance weighted (IVW) method and the heterogeneity and pleiotropy of results were tested. The instrumental single-nucleotide polymorphisms (SNPs) associated with 110 SRPs were filtered and selected from a large genome-wide association study (GWAS) for plasma proteome involving 35,559 participants. The GWAS data of AMD was obtained from FinnGen consortium (6,157 AMD cases and 288,237 controls) and further validated by using data from UK Biobank consortium (3,553 AMD cases and 147,089 controls).

Results

The MR results at both discovery and validation stages supported the causality (IVW-P < 0.00045) between plasma levels of 4 SRPs (C3b, CTNNB1, CCL1, and CCL3L1) and the risk of AMD and supported potential causality (IVW-P < 0.05) between other 10 SRPs and risk of AMD. No heterogeneity or pleiotropy in these results was detected.

Conclusion

Our findings supported that high plasma levels of C3b, CTNNB1, CCL1, and CCL3L1 were associated with increased risk of AMD, thereby highlighting the role of systemic inflammation in AMD pathogenesis and providing the rationale for developing new preventative and therapeutic strategies.

Indoor microbial exposure increases complement component C3a and C-reactive protein concentrations in serum

Indoor exposure to microbial growth, caused by moisture damage, has been an established health risk for several decades. It is likely that a damp indoor environment contains biological pollutants that trigger both the innate and adaptive branches of the immune system. In this study, we investigated the association between moisture damage related microbial exposure and serum C3a, C5a and CRP concentrations in Finnish adults. Serum C3a and CRP concentrations were elevated in individuals exposed to moisture damage and microbial growth in an indoor air environment. The elevated concentrations may be due to environmental factors present in moisture-damaged buildings. Complement activation and the resulting proinflammatory cleavage products may be a driving factor in inflammatory responses following exposure to indoor moisture damage and related microbial growth.

Pentraxin 3: A promising therapeutic target for cardiovascular diseases

Cardiovascular disease (CVD) is the primary global cause of death, and inflammation is a crucial factor in the development of CVDs. The acute phase inflammatory protein pentraxin 3 (PTX3) is a biomarker reflecting the immune response. Recent research indicates that PTX3 plays a vital role in CVDs and has been investigated as a possible biomarker for CVD in clinical trials. PTX3 is implicated in the progression of CVDs through mechanisms such as exacerbating vascular endothelial dysfunction, affecting angiogenesis, and regulating inflammation and oxidative stress. This review summarized the structure and function of PTX3, focusing on its multifaceted effects on CVDs, such as atherosclerosis, myocardial infarction, and hypertension. This may help in explaining the varying PTX3 functions and usage, as well as in utilizing target organs to manage diseases. Moreover, elucidating the opposite role of PTX3 in the cardiovascular system will demonstrate the therapeutic and predictive potential in human diseases.

Transcriptional Host Responses to Infection with Streptococcus suis in a Porcine Precision-Cut Lung Slice Model: Between-Strain Differences Suggest Association with Virulence Potential

Streptococcus suis is a porcine and zoonotic pathogen in the upper respiratory tract, expressing different capsular serotypes and virulence-associated factors. Given its genomic and phenotypic diversity, the virulence potential of S. suis cannot be attributed to a single factor. Since strong inflammatory response is a hallmark of S. suis infection, the objective of this study was to investigate the differences in transcriptional host responses to two serotype 2 and one serotype 9 strains. Both serotypes are frequently found in clinical isolates. We infected porcine precision-cut lung slices (PCLSs) with two serotype 2 strains of high (strain S10) and low (strain T15) virulence, and a serotype 9 strain 8067 of moderate virulence. We observed higher expression of inflammation-related genes during early infection with strains T15 and 8067, in contrast to infection with strain 10, whose expression peaked late. In addition, bacterial gene expression from infected PCLSs revealed differences, mainly of metabolism-related and certain virulence-associated bacterial genes amongst these strains. We conclude that the strain- and time-dependent induction of genes involved in innate immune response might reflect clinical outcomes of infection in vivo, implying rapid control of infection with less virulent strains compared to the highly virulent strain S10.

Plasma pentraxin 3 in idiopathic inflammatory myopathies: a possible new biomarker of disease activity

Pentraxin-3 (PTX3) is a component of humoral innate immunity with essential functions both in promotion and resolution of inflammation. We aimed to study the PTX3 in the plasma and in the muscle of patients with idiopathic inflammatory myopathies (IIM) and whether PTX3 may correlate with disease activity. Plasma PTX3 levels were assessed in 20 patients with IIMs, 10 dermatomyositis (DM), and 10 polymyositis (PM), compared to 10 patients with rheumatoid arthritis (RA) and 10 healthy donors (HDs) aged, sex, and body mass index matched. Disease activity in IIMs was assessed by Myositis Disease Activity Assessment Visual Analog Scale (MYOACT), while disease activity score on 28 joints (DAS28) was used for RA patients. Muscle histopathology and immunohistochemical (IHC) analyses were also performed. Mean plasma PTX3 levels were significantly higher in IIM patients than HDs (518 ± 260 pg/ml vs. 275 ± 114 pg/ml, P = 0.009). Linear regression analysis adjusted for age, sex, and disease duration showed a direct correlation between PTX3 and CPK levels (β: 0.590), MYOACT (β: 0.759), and physician global assessment of disease activity (β: 0.832) in IIMs. No association between PTX3 levels and DAS28 was found in RA. Global PTX3 pixel fraction was higher in IIM than HDs muscle, but a lower PTX3 expression was found in perifascicular areas of DM and in myofibers with sarcolemmal staining for membrane attack complement. PTX3 plasma levels were increased in IIMs and correlated with disease activity suggesting a possible role as biomarker of disease activity. PTX3 showed a different distribution in DM or PM muscle.

Pentraxin-3 and neonatal sepsis: a systematic review and meta-analysis

Aim: The potential bond between pentraxin-3 levels and neonatal sepsis has been the center of research in many primary studies. The aim of the current meta-analysis is to examine whether there are differences among pentraxin-3 levels in septic and in healthy neonates.Materials and Methods: Our search strategy included the systematic search of the following databases: MEDLINE, Clinicaltrials.gov, Cochrane Central Register of Controlled Trials (CENTRAL), Google Scholar, using a structured algorithm. Statistical analysis of the overall outcome was done using Revman 5.4 software while leave-one-out and meta-regression analysis were done using the R software. Quality assessment of the included studies was done using the Newcastle-Ottawa scale.Results: Pentraxin-3 levels were found to be higher in newborns affected by sepsis than in healthy neonates with an MD = 7.66 [95% CI 0.89, 14.42 (p = .03, I² = 99%)]. Subgroup analysis, based on the country of origin of the included study, led to I² = 0 with an MD = 1.25 with 95% CI [0.82, 1.69], p < 10^-5. Publication bias was assessed using the trim and fill method together with visual inspection of the funnel plots, showcasing no missing studies.Conclusion: The results of our study show that pentraxin-3 is elevated in neonates with sepsis making it a potential biomarker that needs to be assessed for its diagnostic accuracy in future cohort studies.

Pentraxins in invertebrates and vertebrates: From structure, function and evolution to clinical applications

The immune system is divided into two broad categories, consisting of innate and adaptive immunity. As recognition and effector factors of innate immunity and regulators of adaptive immune responses, lectins are considered to be important defense chemicals against microbial pathogens, cell trafficking, immune regulation, and prevention of autoimmunity. Pentraxins, important members of animal lectins, play a significant role in protecting the body from pathogen infection and regulating inflammatory reactions. They can recognize and bind to a variety of ligands, including carbohydrates, lipids, proteins, nucleic acids and their complexes, and protect the host from pathogen invasion by activating the complement cascade and Fcγ receptor pathways. Based on the primary structure of the subunit, pentraxins are divided into short and long pentraxins. The short pentraxins are comprised of C-reactive protein (CRP) and serum amyloid P (SAP), and the most important member of the long pentraxins is pentraxin 3 (PTX3). The CRP and SAP exist in both vertebrates and invertebrates, while the PTX3 may be present only in vertebrates. The major ligands and functions of CRP, SAP and PTX3 and three activation pathways involved in the complement system are summarized in this review. Their different characteristics in various animals including humans, and their evolutionary trees are analyzed. The clinical applications of CRP, SAP and PTX3 in human are reviewed. Some questions that remain to be understood are also highlighted.

Structural insights into the biological functions of the long pentraxin PTX3

Soluble pattern recognition molecules (PRMs) are a heterogenous group of proteins that recognize pathogen- and danger-associated molecular patterns (PAMPs and DAMPs, respectively), and cooperate with cell-borne receptors in the orchestration of innate and adaptive immune responses to pathogenic insults and tissue damage. Amongst soluble PRMs, pentraxins are a family of highly conserved proteins with distinctive structural features. Originally identified in the early 1990s as an early inflammatory gene, PTX3 is the prototype of long pentraxins. Unlike the short pentraxin C reactive protein (CRP), whose expression is mostly confined to the liver, PTX3 is made by several immune and non-immune cells at sites of infection and inflammation, where it intercepts fundamental aspects of infection immunity, inflammation, and tissue remodeling. Of note, PTX3 cross talks to components of the complement system to control cancer-related inflammation and disposal of pathogens. Also, it is an essential component of inflammatory extracellular matrices (ECMs) through crosslinking of hyaluronic acid and turn-over of provisional fibrin networks that assemble at sites of tissue injury. This functional diversity is mediated by unique structural characteristics whose fine details have been unveiled only recently. Here, we revisit the structure/function relationships of this long pentraxin in light of the most recent advances in its structural biology, with a focus on the interplay with complement and the emerging roles as a component of the ECM. Differences to and similarities with the short pentraxins are highlighted and discussed.

Healthy lifestyle linked to innate immunity and lipoprotein metabolism: a cross-sectional comparison using untargeted proteomics

This study used untargeted proteomics to compare blood proteomic profiles in two groups of adults that differed widely in lifestyle habits. A total of 52 subjects in the lifestyle group (LIFE) (28 males, 24 females) and 52 in the control group (CON) (27 males, 25 females) participated in this cross-sectional study. Age, education level, marital status, and height did not differ significantly between LIFE and CON groups. The LIFE and CON groups differed markedly in body composition, physical activity patterns, dietary intake patterns, disease risk factor prevalence, blood measures of inflammation, triglycerides, HDL-cholesterol, glucose, and insulin, weight-adjusted leg/back and handgrip strength, and mood states. The proteomics analysis showed strong group differences for 39 of 725 proteins identified in dried blood spot samples. Of these, 18 were downregulated in the LIFE group and collectively indicated a lower innate immune activation signature. A total of 21 proteins were upregulated in the LIFE group and supported greater lipoprotein metabolism and HDL remodeling. Lifestyle-related habits and biomarkers were probed and the variance (> 50%) in proteomic profiles was best explained by group contrasts in indicators of adiposity. This cross-sectional study established that a relatively small number of proteins are associated with good lifestyle habits.

Molecular characterization of complement regulatory factor CD46 in Trachinotus ovatus and its role in the antimicrobial immune responses and complement regulation

CD46, as a cofactor of complement I factor, not only regulates the complement system but also functions as a pathogen receptor and is involved in controlling early pathogen infection through autophagy. In this study, a new CD46 gene (ToCD46) was identified from golden pompano (Trachinotus ovatus), which showed higher sequence homology with other teleosts CD46. Homology comparison showed that ToCD46 had higher sequence homology (46.95-52.85%) with other teleosts CD46 and lower homology with mammal. Tissue expression profile analysis showed that ToCD46 was generally expressed in all tissues with the highest expression level in liver, followed by head kidney, and showed different patterns of up-regulation in immune-related tissues after stimulation by Streptococcus agalactiae and Vibrio alginolyticus. The hemolytic activity analysis and apoptosis assay showed that rToCD46 decreased the hemolytic activity of serum of golden pompano and effectively inhibited the damage of A549 cells, suggesting that ToCD46 might be involved in the regulation of complement activation of golden pompano. In vitro antibacterial experiments showed that rToCD46 had antibacterial activity against gram negative bacteria V. alginolyticus but no effect on positive bacteria S. agalactiae. These results suggest that ToCD46 may be involved in the immune response of golden pompano to pathogens, which will provide important basic information for elucidating the evolutionary history of the complement system of golden pompano.

Differential expression of genes involved in the chronic response to intracortical microelectrodes

Brain-Machine Interface systems (BMIs) are clinically valuable devices that can provide functional restoration for patients with spinal cord injury or improved integration for patients requiring prostheses. Intracortical microelectrodes can record neuronal action potentials at a resolution necessary for precisely controlling BMIs. However, intracortical microelectrodes have a demonstrated history of progressive decline in the recording performance with time, inhibiting their usefulness. One major contributor to decreased performance is the neuroinflammatory response to the implanted microelectrodes. The neuroinflammatory response can lead to neurodegeneration and the formation of a glial scar at the implant site. Historically, histological imaging of relatively few known cellular and protein markers has characterized the neuroinflammatory response to implanted microelectrode arrays. However, neuroinflammation requires many molecular players to coordinate the response - meaning traditional methods could result in an incomplete understanding. Taking advantage of recent advancements in tools to characterize the relative or absolute DNA/RNA expression levels, a few groups have begun to explore gene expression at the microelectrode-tissue interface. We have utilized a custom panel of ∼813 neuroinflammatory-specific genes developed with NanoString for bulk tissue analysis at the microelectrode-tissue interface. Our previous studies characterized the acute innate immune response to intracortical microelectrodes. Here we investigated the gene expression at the microelectrode-tissue interface in wild-type (WT) mice chronically implanted with nonfunctioning probes. We found 28 differentially expressed genes at chronic time points (4WK, 8WK, and 16WK), many in the complement and extracellular matrix system. Further, the expression levels were relatively stable over time. Genes identified here represent chronic molecular players at the microelectrode implant sites and potential therapeutic targets for the long-term integration of microelectrodes. STATEMENT OF SIGNIFICANCE: Intracortical microelectrodes can record neuronal action potentials at a resolution necessary for the precise control of Brain-Machine Interface systems (BMIs). However, intracortical microelectrodes have a demonstrated history of progressive declines in the recording performance with time, inhibiting their usefulness. One major contributor to the decline in these devices is the neuroinflammatory response against the implanted microelectrodes. Historically, neuroinflammation to implanted microelectrode arrays has been characterized by histological imaging of relatively few known cellular and protein markers. Few studies have begun to develop a more in-depth understanding of the molecular pathways facilitating device-mediated neuroinflammation. Here, we are among the first to identify genetic pathways that could represent targets to improve the host response to intracortical microelectrodes, and ultimately device performance.

A biofunctional review of C-reactive protein (CRP) as a mediator of inflammatory and immune responses: differentiating pentameric and modified CRP isoform effects

C-reactive protein (CRP) is an acute phase, predominantly hepatically synthesized protein, secreted in response to cytokine signaling at sites of tissue injury or infection with the physiological function of acute pro-inflammatory response. Historically, CRP has been classified as a mediator of the innate immune system, acting as a pattern recognition receptor for phosphocholine-containing ligands. For decades, CRP was envisioned as a single, non-glycosylated, multi-subunit protein arranged non-covalently in cyclic symmetry around a central void. Over the past few years, however, CRP has been shown to exist in at least three distinct isoforms: 1.) a pentamer of five identical globular subunits (pCRP), 2.) a modified monomer (mCRP) resulting from a conformational change when subunits are dissociated from the pentamer, and 3.) a transitional isoform where the pentamer remains intact but is partially changed to express mCRP structural characteristics (referred to as pCRP* or mCRPm). The conversion of pCRP into mCRP can occur spontaneously and is observed under commonly used experimental conditions. In careful consideration of experimental design used in published reports of in vitro pro- and anti-inflammatory CRP bioactivities, we herein provide an interpretation of how distinctive CRP isoforms may have affected reported results. We argue that pro-inflammatory amplification mechanisms are consistent with the biofunction of mCRP, while weak anti-inflammatory mechanisms are consistent with pCRP. The interplay of each CRP isoform with specific immune cells (platelets, neutrophils, monocytes, endothelial cells, natural killer cells) and mechanisms of the innate immune system (complement), as well as differences in mCRP and pCRP ligand recognition and effector functions are discussed. This review will serve as a revised understanding of the structure-function relationship between CRP isoforms as related to inflammation and innate immunity mechanisms.

High Levels of C-Reactive Protein with Low Levels of Pentraxin 3 as Biomarkers for Central Serous Chorioretinopathy

Purpose

To investigate the association between the 2 acute phase proteins, C-reactive protein (CRP) and pentraxin 3 (PTX3) with central serous chorioretinopathy (CSCR), as PTX3 is a glucocorticoid-induced protein.

Design

Cross-sectional multicenter study.

Participants

Patients with CSCR compared with age- and sex-matched healthy participants.

Methods

Patients with CSCR from 3 centers in Europe were included in the study. The clinical form of CSCR was recorded. Blood samples from patients with CSCR and healthy participants were sampled, and high-sensitivity CRP and PTX3 levels were measured in the serum.

Main Outcome Measures

C-reactive protein and PTX3 serum level comparison between patients with CSCR with age- and sex-matched healthy participants.

Results

Although CRP levels were higher in patients with CSCR (n = 216) than in age- and sex-matched controls (n = 130) (2.2 ± 3.2 mg/l vs. 1.5 mg/l ± 1.4, respectively, P = 0.037), PTX3 levels were lower in patients with CSCR (10.5 ± 19.9 pg/ml vs. 87.4 ± 73.2 pg/ml, respectively, P < 0.001). There was no significant difference in CRP or PTX3 levels between patients with acute/recurrent and chronic CSCR.

Conclusions

In patients with CSCR, high CRP and low PTX3 levels suggest a form of low-grade systemic inflammation together with a lack of glucocorticoid pathway activation, raising new hypotheses on the pathophysiology of CSCR.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

C-reactive protein binds to short phosphoglycan repeats of Leishmania secreted proteophosphoglycans and activates complement

Human C-reactive protein (CRP) binds to lipophosphoglycan (LPG), a virulence factor of Leishmania spp., through the repeating phosphodisaccharide region. We report here that both major components of promastigote secretory gel (PSG), the filamentous proteophosphoglycan (fPPG) and the secreted acid phosphatase (ScAP), are also ligands. CRP binding was mainly associated with the flagellar pocket when LPG deficient Leishmania mexicana parasites were examined by fluorescent microscopy, consistent with binding to secreted material. ScAP is a major ligand in purified fPPG from parasite culture as demonstrated by much reduced binding to a ScAP deficient mutant fPPG in plate binding assays and ligand blotting. Nevertheless, in sandfly derived PSG fPPG is a major component and the major CRP binding component. Previously we showed high avidity of CRP for LPG ligand required multiple disaccharide repeats. ScAP and fPPG only have short repeats but they retain high avidity for CRP revealed by surface plasmon resonance because they are found in multiple copies on the phosphoglycan. The fPPG from many species such as L. donovani and L. mexicana bound CRP strongly but L. tropica and L. amazonensis had low amounts of binding. The extent of side chain substitution of [-PO4-6Galβ1-4Manα1-] disaccharides correlates inversely with binding of CRP. The ligand for the CRP on different species all had similar binding avidity as the half maximal binding concentration was similar. Since the PSG is injected with the parasites into host blood pools and phosphoglycans (PG) are known to deplete complement, we showed that CRP makes a significant contribution to the activation of complement by PSG using serum from naive donors.

Divergent host innate immune response to the smooth-to-rough M. abscessus adaptation to chronic infection

Mycobacterium abscessus is a nontuberculous mycobacterium emerging as a significant pathogen for individuals with chronic lung disease, including cystic fibrosis and chronic obstructive pulmonary disease. Current therapeutics have poor efficacy. New strategies of bacterial control based on host defenses are appealing, but anti-mycobacterial immune mechanisms are poorly understood and are complicated by the appearance of smooth and rough morphotypes with distinct host responses. We explored the role of the complement system in the clearance of M. abscessus morphotypes by neutrophils, an abundant cell in these infections. M. abscessus opsonized with plasma from healthy individuals promoted greater killing by neutrophils compared to opsonization in heat-inactivated plasma. Rough clinical isolates were more resistant to complement but were still efficiently killed. Complement C3 associated strongly with the smooth morphotype while mannose-binding lectin 2 was associated with the rough morphotype. M. abscessus killing was dependent on C3, but not on C1q or Factor B; furthermore, competition of mannose-binding lectin 2 binding with mannan or N-acetyl-glucosamine during opsonization did not inhibit killing. These data suggest that M. abscessus does not canonically activate complement through the classical, alternative, or lectin pathways. Complement-mediated killing was dependent on IgG and IgM for smooth and on IgG for rough M. abscessus. Both morphotypes were recognized by Complement Receptor 3 (CD11b), but not CR1 (CD35), and in a carbohydrate- and calcium-dependent manner. These data suggest the smooth-to-rough adaptation changes complement recognition of M. abscessus and that complement is an important factor for M. abscessus infection.

Overview on the Link Between the Complement System and Auto-Immune Articular and Pulmonary Disease

Complement system (CS) dysregulation is a key factor in the pathogenesis of different autoimmune diseases playing a central role in many immune innate and adaptive processes. Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by ta breach of self-tolerance leading to a synovitis and extra-articular manifestations. The CS is activated in RA and seems not only to mediate direct tissue damage but also play a role in the initiation of RA pathogenetic mechanisms through interactions with citrullinated proteins. Interstitial lung disease (ILD) represents the most common extra-articular manifestation that can lead to progressive fibrosis. In this review, we focused on the evidence of CS dysregulation in RA and in ILD, and highlighted the role of the CS in both the innate and adaptive immune responses in the development of diseases, by using idiopathic pulmonary fibrosis as a model of lung disease. As a proof of concept, we dissected the evidence that several treatments used to treat RA and ILD such as glucocorticoids, pirfenidone, disease modifying antirheumatic drugs, targeted biologics such as tumor necrosis factor (TNF)-inhibitors, rituximab, tocilizumab, and nintedanib may act indirectly on the CS, suggesting that the CS might represent a potential therapeutic target in these complex diseases.

Reduced binding of apoE4 to complement factor H promotes amyloid-β oligomerization and neuroinflammation

The APOE4 variant of apolipoprotein E (apoE) is the most prevalent genetic risk allele associated with late-onset Alzheimer's disease (AD). ApoE interacts with complement regulator factor H (FH), but the role of this interaction in AD pathogenesis is unknown. Here we elucidate the mechanism by which isoform-specific binding of apoE to FH alters Aβ1-42-mediated neurotoxicity and clearance. Flow cytometry and transcriptomic analysis reveal that apoE and FH reduce binding of Aβ1-42 to complement receptor 3 (CR3) and subsequent phagocytosis by microglia which alters expression of genes involved in AD. Moreover, FH forms complement-resistant oligomers with apoE/Aβ1-42 complexes and the formation of these complexes is isoform specific with apoE2 and apoE3 showing higher affinity to FH than apoE4. These FH/apoE complexes reduce Aβ1-42 oligomerization and toxicity, and colocalize with complement activator C1q deposited on Aβ plaques in the brain. These findings provide an important mechanistic insight into AD pathogenesis and explain how the strongest genetic risk factor for AD predisposes for neuroinflammation in the early stages of the disease pathology.

C-Reactive Protein Levels Are Associated with Complement C4 Deposits and Interstitial Arteritis in ANCA-Associated Renal Vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a potentially life-threatening systemic small-vessel vasculitis that is characterized by pauci-immune glomerulonephritis in case of kidney involvement, representing a major denominator of AAV mortality. Innate immunity with complement system activation is increasingly recognized in the pathogenesis of AAV and as an attractive therapeutic target. Although C-reactive protein (CRP) was thought to be a passive, nonspecific marker of inflammation, recent studies indicate that CRP plays a key role in the innate immune system by recognizing pathogens and altered self-determinants. Elevated baseline CRP at disease onset of AAV has already been described as a determinant of poor long-term outcomes. However, its clinical implications at disease onset of AAV, with respect to vasculitis manifestations and complement system activation that might also affect long-term outcomes, remain elusive. CRP levels were retrospectively analyzed in 53 kidney-biopsy-confirmed cases of ANCA-associated renal vasculitis; a total of 138 disease controls were also evaluated. Univariate and multivariate regression analysis was performed on clinicopathological parameters associated with CRP levels in ANCA-associated renal vasculitis. Results: Compared to disease controls, CRP elevation was common in ANCA-associated renal vasculitis and associated with de novo disease (p = 0.0169), critical illness (p = 0.0346), and severe deterioration of kidney function (p = 0.0167), independent of extrarenal disease manifestations. As confirmed by multiple regression analysis, CRP levels were correlated with active lesions predominated by interstitial arteritis in renal vasculitis, specifically with MPO-ANCA seropositivity (p = 0.0017). Based on analysis of systemic complement system activation and intrarenal complement deposits, CRP elevation was correlated specifically with complement C4 deposits in interstitial arteries in the subgroup with myeloperoxidase (MPO)-ANCA seropositivity (p = 0.039). Finally, this association was independent of systemic complement system activation, as reflected by the consumption of respective complement components. Here, we expand our current understanding of CRP in ANCA-associated renal vasculitis not only as an inflammatory marker, but potentially also as being involved in the pathogenesis of kidney injury by interaction with the complement system.

Conformational state of C-reactive protein is critical for reducing immune complex-triggered type I interferon response: Implications for pathogenic mechanisms in autoimmune diseases imprinted by type I interferon gene dysregulation

Presence of autoantibodies targeting nuclear constituents, i.e., double-stranded DNA and small nuclear ribonucleoproteins (snRNPs), remain a cornerstone in systemic lupus erythematosus (SLE). Fcγ receptor IIa (FcγRIIa) dependent uptake of nucleic acid containing immune complexes (ICs) by plasmacytoid dendritic cells (PDCs) can activate toll-like receptors (TLRs) such as TLR7 and TLR9 resulting in type I interferon (IFN) production. Previously, the classical liver-derived acute-phase reactant C-reactive protein (CRP) has been suggested to reduce IC-induced type I IFN production, whereas monomeric (mCRP) vs. pentameric (pCRP) mediated effects have not yet been unraveled. Herein, peripheral blood mononuclear cells (PBMCs) or enriched blood DCs from healthy volunteers were stimulated with SLE sera, snRNP-IgG (ICs), or TLR ligands with or without pCRP, mCRP, or anti-FcγRIIa antibody. Type I IFNs and cytokine responses were investigated using quantitative PCR, ELISA, and flow cytometry. pCRP inhibited IFN gene expression in PBMCs and enriched DCs after incubation with ICs, compared to ICs alone, whereas mCRP had significantly less inhibitory effect. The effect was independent on the order in which IC or CRP was added to the cells. In addition, pCRP inhibited IFN induced by other TLR stimulators, implicating broader inhibitory effects induced by pCRP. We demonstrate pronounced immunoregulatory functions of CRP whereas the inhibitory properties were evidently dependent on CRP's intact conformational state. The inhibition of type I IFNs was not due to competition of FcγRs, or binding of CRP to the ICs. Our findings have implications for autoimmune IC-mediated conditions imprinted by type I IFN gene dysregulation.

Functional proteomics identify mannitol metabolism in serum resistance and therapeutic implications in Vibrio alginolyticus

Serum resistance is recognized as one of the most important pathogenic traits of bacterial pathogens, and no control measure is available. Based on our previous discovery that pathogenic Escherichia coli represses glycine, serine, and threonine metabolism to confer serum resistance and that the reactivation of this pathway by exogenous glycine could restore serum sensitivity, we further investigate the mechanism underlying the action of glycine in Vibrio alginolyticus. Thus, V. alginolyticus is treated with glycine, and the proteomic change is profiled with tandem mass tag-based quantitative proteomics. Compared to the control group, glycine treatment influences the expression of a total of 291 proteins. Among them, a trap-type mannitol/chloroaromatic compound transport system with periplasmic component, encoded by N646_0992, is the most significantly increased protein. In combination with the pathway enrichment analysis showing the altered fructose and mannitol metabolism, mannitol has emerged as a possible metabolite in enhancing the serum killing activity. To demonstrate this, exogenous mannitol reduces bacterial viability. This synergistic effect is further confirmed in a V. alginolyticus-Danio rerio infection model. Furthermore, the mechanism underlying mannitol-enabled serum killing is dependent on glycolysis and the pyruvate cycle that increases the deposition of complement components C3b and C5b-9 on the bacterial surface, whereas inhibiting glycolysis or the pyruvate cycle significantly weakened the synergistic effects and complement deposition. These data together suggest that mannitol is a potent metabolite in reversing the serum resistance of V. alginolyticus and has promising use in aquaculture.

MASP1 Gene Polymorphism and MASP-3 Serum Levels in Patients with Chronic Chagas Disease

INTRODUCTION

Chagas disease (CD), caused by Trypanosoma cruzi, is a major public health issue worldwide affecting 6-7 million people, mainly in Latin America. The complement system plays a crucial role in host immune defense against T. cruzi infection and during the chronic phase of CD; however, the role of the MBL-associated serine protease 1 (MASP1) gene encoding MASP-1, MASP-3, and MAp44 complement proteins has not yet been reported in CD. This study investigated the possible association between MASP1 gene polymorphisms and MASP-3 protein serum levels in chronic CD and its clinical forms.

METHODS

Five polymorphisms of MASP1 gene regulatory regions were genotyped in 214 patients with CD and 197 healthy controls (rs7609662 G>A, rs13064994 C>T, rs72549262 C>G, rs1109452 C>T and rs850314 G>A). MASP-3 serum levels were assessed in 70 patients and 66 healthy controls. Clinical data, serum levels of complement proteins (ficolin-2, ficolin-3 and MBL) and inflammatory markers (pentraxin-3 and hsCRP) were also included in the analyses.

RESULTS

A significant association of the MASP1 GC_CCA haplotype with CD (p_adj= 0.002; OR 3.17 [1.19-8.39]) and chronic chagasic cardiomyopathy (CCC) (p_adj= 0.013; OR 4.57 [1.37-15.16] was observed. MASP-3 and pentraxin-3 levels were positively correlated in the patients (rho = 0.62; p = 0.0001). MASP-3 levels were not associated with MASP1 polymorphisms or CD and its clinical forms. Furthermore, no correlation was observed between MASP-3 levels and that of ficolin-2, ficolin-3, MBL and hsCRP.

CONCLUSION

Our findings suggest a possible role for the MASP1 GC_CCA haplotype in susceptibility to chronic CD and CCC clinical forms.

The OSE complotype and its clinical potential

Cellular death, aging, and tissue damage trigger inflammation that leads to enzymatic and non-enzymatic lipid peroxidation of polyunsaturated fatty acids present on cellular membranes and lipoproteins. This results in the generation of highly reactive degradation products, such as malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), that covalently modify free amino groups of proteins and lipids in their vicinity. These newly generated neoepitopes represent a unique set of damage-associated molecular patterns (DAMPs) associated with oxidative stress termed oxidation-specific epitopes (OSEs). OSEs are enriched on oxidized lipoproteins, microvesicles, and dying cells, and can trigger sterile inflammation. Therefore, prompt recognition and removal of OSEs is required to maintain the homeostatic balance. This is partially achieved by various humoral components of the innate immune system, such as natural IgM antibodies, pentraxins and complement components that not only bind OSEs but in some cases modulate their pro-inflammatory potential. Natural IgM antibodies are potent complement activators, and 30% of them recognize OSEs such as oxidized phosphocholine (OxPC-), 4-HNE-, and MDA-epitopes. Furthermore, OxPC-epitopes can bind the complement-activating pentraxin C-reactive protein, while MDA-epitopes are bound by C1q, C3a, complement factor H (CFH), and complement factor H-related proteins 1, 3, 5 (FHR-1, FHR-3, FHR-5). In addition, CFH and FHR-3 are recruited to 2-(ω-carboxyethyl)pyrrole (CEP), and full-length CFH also possesses the ability to attenuate 4-HNE-induced oxidative stress. Consequently, alterations in the innate humoral defense against OSEs predispose to the development of diseases associated with oxidative stress, as shown for the prototypical OSE, MDA-epitopes. In this mini-review, we focus on the mechanisms of the accumulation of OSEs, the pathophysiological consequences, and the interactions between different OSEs and complement components. Additionally, we will discuss the clinical potential of genetic variants in OSE-recognizing complement proteins – the OSE complotype - in the risk estimation of diseases associated with oxidative stress.

Higher plasma IL-6 and PTX3 are associated with worse survival in left heart failure with pulmonary hypertension

Introduction

Left heart failure (LHF) is commonly complicated by pulmonary hypertension (PH), increasing morbidity and mortality. The present study aimed to evaluate the prognostic value of inflammatory proteins in LHF with PH (LHF-PH).

Materials and methods

The levels of 65 plasma proteins, analysed with proximity extension assay, were compared between healthy controls (n = 20), patients with LHF-PH (n = 67) comprising both HFpEF-PH (n = 31) and HFrEF-PH (n = 36), and in a LHF subpopulation before and after heart transplantation (HT, n = 19). Haemodynamic parameters were measured using right heart catheterization.

Results

Plasma levels of Interleukin 6 (IL-6) and Pentraxin related protein PTX3 (PTX3) were elevated in LHF-PH vs. controls (p < 0.001), and these decreased after HT compared to before HT (p < 0.001). Plasma IL-6 and PTX3 correlated to elevated NT-proBNP (r = 0.44, p = 0.0002 and r = 0.4, p = 0.0009, respectively). Additionally, IL-6 correlated with mean pulmonary arterial pressure (r = 0.4, p = 0.0009) and mean right atrial pressure (r = 0.51, p < 0.0001). Higher levels of IL-6 and PTX3 were associated with worse survival rates in patients with LHF-PH (Log rank p < 0.01).

Discussion

In patients with LHF-PH, higher plasma levels of IL-6 and PTX3 were associated with worse survival rates. Future larger studies to validate and investigate the direct clinical applicability of IL-6 and PTX3 as potential prognostic biomarkers are encouraged.

Mass spectrometry-based proteomics identify novel serum osteoarthritis biomarkers

Background

Osteoarthritis (OA) is a slowly developing and debilitating disease, and there are no validated specific biomarkers for its early detection. To improve therapeutic approaches, identification of specific molecules/biomarkers enabling early determination of this disease is needed. This study aimed at identifying, with the use of proteomics/mass spectrometry, novel OA-specific serum biomarkers. As obesity is a major risk factor for OA, we discriminated obesity-regulated proteins to target only OA-specific proteins as biomarkers.

Methods

Serum from the Osteoarthritis Initiative cohort was used and divided into 3 groups: controls (n=8), OA-obese (n=10) and OA-non-obese (n=10). Proteins were identified and quantified from the liquid chromatography–tandem mass spectrometry analyses using MaxQuant software. Statistical analysis used the Limma test followed by the Benjamini-Hochberg method. To compare the proteomic profiles, the multivariate unsupervised principal component analysis (PCA) followed by the pairwise comparison was used. To select the most predictive/discriminative features, the supervised linear classification model sparse partial least squares regression discriminant analysis (sPLS-DA) was employed. Validation of three differential proteins was performed with protein-specific assays using plasma from a cohort derived from the Newfoundland Osteoarthritis.

Results

In total, 509 proteins were identified, and 279 proteins were quantified. PCA-pairwise differential comparisons between the 3 groups revealed that 8 proteins were differentially regulated between the OA-obese and/or OA-non-obese with controls. Further experiments using the sPLS-DA revealed two components discriminating OA from controls (component 1, 9 proteins), and OA-obese from OA-non-obese (component 2, 23 proteins). Proteins from component 2 were considered related to obesity. In component 1, compared to controls, 7 proteins were significantly upregulated by both OA groups and 2 by the OA-obese. Among upregulated proteins from both OA groups, some of them alone would not be a suitable choice as specific OA biomarkers due to their rather non-specific role or their strong link to other pathological conditions. Altogether, data revealed that the protein CRTAC1 appears to be a strong OA biomarker candidate. Other potential new biomarker candidates are the proteins FBN1, VDBP, and possibly SERPINF1. Validation experiments revealed statistical differences between controls and OA for FBN1 (p=0.044) and VDPB (p=0.022), and a trend for SERPINF1 (p=0.064).

Conclusion

Our study suggests that 4 proteins, CRTAC1, FBN1, VDBP, and possibly SERPINF1, warrant further investigation as potential new biomarker candidates for the whole OA population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02801-1.

Interactions Between Immunomodulatory Biomaterials and Immune Microenvironment: Cues for Immunomodulation Strategies in Tissue Repair

The foreign body response (FBR) caused by biomaterials can essentially be understood as the interaction between the immune microenvironment and biomaterials, which has severely impeded the application of biomaterials in tissue repair. This concrete interaction occurs via cells and bioactive substances, such as proteins and nucleic acids. These cellular and molecular interactions provide important cues for determining which element to incorporate into immunomodulatory biomaterials (IMBs), and IMBs can thus be endowed with the ability to modulate the FBR and repair damaged tissue. In terms of cellular, IMBs are modified to modulate functions of immune cells, such as macrophages and mast cells. In terms of bioactive substances, proteins and nucleic acids are delivered to influence the immune microenvironment. Meanwhile, IMBs are designed with high affinity for spatial targets and the ability to self-adapt over time, which allows for more efficient and intelligent tissue repair. Hence, IMB may achieve the perfect functional integration in the host, representing a breakthrough in tissue repair and regeneration medicine.

Utility of serum complement factors C3 and C4 as biomarkers during therapeutic management of giant cell arteritis

OBJECTIVE

There is a strong unmet need for biomarkers in giant cell arteritis (GCA), as C-reactive protein (CRP) may be unreliable in patients treated with Tocilizumab (TCZ). We aimed to assess whether C3 and C4 are useful biomarkers in GCA patients, particularly in those treated with TCZ.

METHOD

We retrospectively enrolled all patients who underwent C3 and C4 measurement at baseline. All patients were evaluated at 3, 6, 12, and 24 months after diagnosis, as part of routine follow-up. Two assessments after the end of the observational period, in case of further relapses, were also included.

RESULTS

At baseline, mean ± sd levels (mg/dL) of C3 (133 ± 28.99) and C4 (25.9 ± 9.04) were within normal ranges. During follow-up, C3 and C4 decreased in patients attaining remission (107.07 ± 19.86, p = 0.0006; 19.86 ± 10.27, p = 0.01, respectively) and sustained remission (95.85 ± 18.04, p = 0.001; 15.61 ± 9.75, p = 0.006). In TCZ-treated patients, even stronger decreases in C3 (83.11 ± 19.66, p = 0.001) and C4 (8.26 ± 3.83, p < 0.0001) were observed, and their values were not correlated with CRP or erythrocyte sedimentation rate.

CONCLUSION

C3 and C4 do not seem useful in the diagnosis of GCA, as normal values do not rule out active vasculitis. However, C3 and C4 correlate with disease activity. As the low C4 levels found in TCZ-treated patients are not correlated with CRP, C4 should be evaluated as a potential biomarker of disease activity and treatment response.

Dysregulated Immunity in Pulmonary Hypertension: From Companion to Composer

Pulmonary hypertension (PH) represents a grave condition associated with high morbidity and mortality, emphasizing a desperate need for innovative and targeted therapeutic strategies. Cumulative evidence suggests that inflammation and dysregulated immunity interdependently affect maladaptive organ perfusion and congestion as hemodynamic hallmarks of the pathophysiology of PH. The role of altered cellular and humoral immunity in PH gains increasing attention, especially in pulmonary arterial hypertension (PAH), revealing novel mechanistic insights into the underlying immunopathology. Whether these immunophysiological aspects display a universal character and also hold true for other types of PH (e.g., PH associated with left heart disease, PH-LHD), or whether there are unique immunological signatures depending on the underlying cause of disease are points of consideration and discussion. Inflammatory mediators and cellular immune circuits connect the local inflammatory landscape in the lung and heart through inter-organ communication, involving, e.g., the complement system, sphingosine-1-phosphate (S1P), cytokines and subsets of, e.g., monocytes, macrophages, natural killer (NK) cells, dendritic cells (DCs), and T- and B-lymphocytes with distinct and organ-specific pro- and anti-inflammatory functions in homeostasis and disease. Perivascular macrophage expansion and monocyte recruitment have been proposed as key pathogenic drivers of vascular remodeling, the principal pathological mechanism in PAH, pinpointing toward future directions of anti-inflammatory therapeutic strategies. Moreover, different B- and T-effector cells as well as DCs may play an important role in the pathophysiology of PH as an imbalance of T-helper-17-cells (T_H17) activated by monocyte-derived DCs, a potentially protective role of regulatory T-cells (T_reg) and autoantibody-producing plasma cells occur in diverse PH animal models and human PH. This article highlights novel aspects of the innate and adaptive immunity and their interaction as disease mediators of PH and its specific subtypes, noticeable inflammatory mediators and summarizes therapeutic targets and strategies arising thereby.

Hidden threat in familial Mediterranean fever: subclinical inflammation, oxidative stress and their relationship with vitamin D status

BACKGROUND

Vitamin D levels have been investigated in children with familial Mediterranean fever (FMF), but the relationship between vitamin D status and inflammation/oxidative stress indicators could not be clearly demonstrated. This study aimed to investigate the relationship between subclinical inflammation/oxidative stress and vitamin D status in children with FMF during an attack-free period.

METHODS

In the cross-sectional study, ninety children with FMF in the attack-free period and 30 healthy children were included. Patients were grouped according to their vitamin D status (< 20, 20-29, and 30-100 ng/mL). The groups were compared in terms of pentraxin 3 (PTX-3), total oxidant status (TOS), and total antioxidant status (TAS). Multivariable linear regression analysis was performed to identify factors associated with vitamin D status.

RESULTS

PTX-3 levels were significantly higher in patients with vitamin D insufficiency (20-29 ng/mL) than in the group with vitamin D sufficient (30-100 ng/mL). Patients with vitamin D deficiency (< 20 ng/mL) had higher TOS. A strong negative correlation was observed between vitamin D levels and TOS (p = 0.003). Subclinical inflammation (PTX-3 ≥ 0.640) and high TOS levels were negatively associated with vitamin D levels.

The Long Pentraxin PTX3 as a New Biomarker and Pharmacological Target in Age-Related Macular Degeneration and Diabetic Retinopathy

Age related macular degeneration (AMD) and diabetic retinopathy (DR) are multifactorial, neurodegenerative and inflammatory diseases of the eye primarily involving cellular and molecular components of the outer and inner blood-retina barriers (BRB), respectively. Largely contributed by genetic factors, particularly polymorphisms in complement genes, AMD is a paradigm of retinal immune dysregulation. DR, a major complication of diabetes mellitus, typically presents with increased vascular permeability and occlusion of the retinal vasculature that leads, in the proliferative form of the disease, to neovascularization, a pathogenic trait shared with advanced AMD. In spite of distinct etiology and clinical manifestations, both pathologies share common drivers, such as chronic inflammation, either of immune (in AMD) or metabolic (in DR) origin, which initiates and propagates degeneration of the neural retina, yet the underlying mechanisms are still unclear. As a soluble pattern recognition molecule with complement regulatory functions and a marker of vascular damage, long pentraxin 3 (PTX3) is emerging as a novel player in ocular homeostasis and a potential pharmacological target in neurodegenerative disorders of the retina. Physiologically present in the human eye and induced in inflammatory conditions, this protein is strategically positioned at the BRB interface, where it acts as a “molecular trap” for complement, and modulates inflammation both in homeostatic and pathological conditions. Here, we discuss current viewpoints on PTX3 and retinal diseases, with a focus on AMD and DR, the roles therein proposed for this pentraxin, and their implications for the development of new therapeutic strategies.

C4d as a Practical Marker for Cutaneous Amyloidosis

ABSTRACT

Cutaneous amyloidosis (CA) is defined by the accumulation of amyloid in the dermis; it might be primary or secondary. The diagnosis is based on histopathological findings with the demonstration of amyloid deposits, confirmed by Congo red stain under the polarized light. Studies on other diagnostic markers are ongoing in the literature. The aim of this study was to demonstrate the utility of C4d staining in the recognition of amyloid in CA and using it as an alternative or substitute marker for the diagnosis. In this retrospective study, 199 skin biopsies with a clinical provisional diagnosis of CA were analyzed, the Congo red stain was performed, and, in a subgroup (n = 97) with histopathological findings probably for CA, C4d immunohistochemistry was assessed. Forty-eight cases of CA were detected. Congo red birefringence was positive in all cases, whereas in 14 cases, it was faded. In these 14 cases, the diagnosis of CA was made by means of Congo red fluorescence and Thioflavin T because the histopathological findings were highly suggestive for CA. All CA cases were positive with C4d, and in 12 of the 49 inflammatory dermatoses, C4d was positive. The interpretation of C4d immunohistochemistry can be performed more easily and rapidly than Congo red evaluation. The sensitivity and specificity of C4d were 100% and 75.5%, respectively. In our experience, C4d staining was a useful method for detecting amyloid deposits in CA. Although Congo red staining is the gold standard for amyloid detection, we propose C4d immunohistochemistry as a routine screening method or hybrid transition while further investigations are completed.

Gain-of-Function Mutations R249C and S250C in Complement C2 Protein Increase C3 Deposition in the Presence of C-Reactive Protein

The impairment of the alternative complement pathway contributes to rare kidney diseases such as atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy (C3G). We recently described an aHUS patient carrying an exceptional gain-of-function (GoF) mutation (S250C) in the classical complement pathway component C2 leading to the formation of hyperactive classical convertases. We now report the identification of the same mutation and another C2 GoF mutation R249C in two other patients with a glomerulopathy of uncertain etiology. Both mutations stabilize the classical C3 convertases by a similar mechanism. The presence of R249C and S250C variants in serum increases complement-dependent cytotoxicity (CDC) in antibody-sensitized human cells and elevates deposition of C3 on ELISA plates coated with C-reactive protein (CRP), as well as on the surface of glomerular endothelial cells. Our data justify the inclusion of classical pathway genes in the genetic analysis of patients suspected of complement-driven renal disorders. Also, we point out CRP as a potential antibody-independent trigger capable of driving excessive complement activation in carriers of the GoF mutations in complement C2.

Complementary Roles of Short and Long Pentraxins in the Complement-Mediated Immune Response to Aspergillus fumigatus Infections

The ubiquitous mold Aspergillus fumigatus is the major etiologic agent of invasive aspergillosis, a life-threatening infection amongst immune compromised individuals. An increasing body of evidence indicates that effective disposal of A. fumigatus requires the coordinate action of both cellular and humoral components of the innate immune system. Early recognition of the fungal pathogen, in particular, is mediated by a set of diverse soluble pattern recognition molecules (PRMs) that act as "ancestral antibodies" inasmuch as they are endowed with opsonic, pro-phagocytic and killing properties. Pivotal is, in this respect, the contribution of the complement system, which functionally cooperates with cell-borne pattern recognition receptors (PRRs) and other soluble PRMs, including pentraxins. Indeed, complement and pentraxins form an integrated system with crosstalk, synergism, and regulation, which stands as a paradigm of the interplay between PRMs in the mounting and orchestration of antifungal immunity. Following upon our past experience with the long pentraxin PTX3, a well-established immune effector in the host response to A. fumigatus, we recently reported that this fungal pathogen is targeted in vitro and in vivo by the short pentraxin Serum Amyloid P component (SAP) too. Similar to PTX3, SAP promotes phagocytosis and disposal of the fungal pathogen via complement-dependent pathways. However, the two proteins exploit different mechanisms of complement activation and receptor-mediated phagocytosis, which further extends complexity and integration of the complement-pentraxin crosstalk in the immune response to A. fumigatus. Here we revisit this crosstalk in light of the emerging roles of SAP as a novel PRM with antifungal activity.

Evaluation of the relationship between pentraxin 3 (PTX3) rs2305619 (281A/G) and rs1840680 (1449A/G) polymorphisms and the clinical course of COVID-19

Macrophage activation syndrome (MAS) is one of the main causes of morbidity and mortality in patients with coronavirus disease 2019 (COVID-19). This study aimed to investigate the relationship between the pentraxin 3 (PTX3) gene polymorphisms rs2305619 (281A/G) and rs1840680 (1449A/G) and the development of MAS in patients with COVID-19. The study included a total of 94 patients aged 18-45 who were diagnosed as having COVID-19 between June and December 2020. PTX3 281A/G and 1449A/G polymorphism frequencies were evaluated. PTX3 281A/G allele and genotype frequencies did not deviate from Hardy-Weinberg (HW) equilibrium in the MAS or non-MAS group (χ2 : 0.049, df: 2, p = 0.976, χ2 : 0.430, df: 2, p = 0.806). PTX3 1449A/G allele and genotype frequencies deviated significantly from HW equilibrium in the non-MAS group (χ2 : 6.794, df: 2, p = 0.033) but not in the MAS group (χ2 : 2.256, df: 2, p = 0.324). The AG genotype was significantly more frequent in the non-MAS group, while the AA genotype was significantly more frequent in the MAS group (χ2 : 11.099, df: 2, p= 0.004). Analysis of the PTX3 1449A/G polymorphism showed that individuals with the GG genotype had higher serum PTX3 levels than those with the AA and AG genotypes (p = 0.001 for both). Analysis of the PTX3 1449A/G polymorphism in patients with COVID-19 showed that those with the AG genotype were relatively more protected from MAS compared with individuals with the AA genotype. In addition, lower serum PTX3 levels are observed in patients carrying the A allele.

Adjuvant Lineage-Negative Cell Therapy as a Potential Silencer of the Complement-Mediated Immune System in ALS Patients

ALS remains a fatal, neurodegenerative motor neuron disease. Numerous studies seem to confirm that innate immune system is involved in the pathophysiology of ALS. Hence, the assessment of the complement system and attempts to modify its activity remain the target of medical intervention in ALS. In the present study, three intrathecal administrations of autologous bone marrow-derived lineage-negative (Lin^–) cells were performed every 6 weeks in 20 sporadic ALS patients. The concentrations of various complement components in the cerebrospinal fluid and plasma at different time points after cell injection were quantified using a Luminex multiplex. The results of the complement system were correlated with the level of leukocytes, neutrophils, lymphocytes, fibrinogen and CRP in the peripheral blood and the functional status of ALS patients using Norris and ALS-FRSr scales. The study showed a statistically significant decrease in plasma C3b concentration in all 7th days after cell application. In parallel, a peak decrease in neutrophil count and CRP level was observed on days 5–7, with a simultaneous maximum clinical improvement on days 7–28 of each Lin^– cell administration. Adjuvant Lin^– cell therapy appears to have the silencing potential on the complement-mediated immune system and thus suppress pro-inflammatory reactions responsible for neurodegeneration. However, further in-depth studies are necessary to address this issue.

Pattern Recognition Proteins: First Line of Defense Against Coronaviruses

The rapid outbreak of COVID-19 caused by the novel coronavirus SARS-CoV-2 in Wuhan, China, has become a worldwide pandemic affecting almost 204 million people and causing more than 4.3 million deaths as of August 11 2021. This pandemic has placed a substantial burden on the global healthcare system and the global economy. Availability of novel prophylactic and therapeutic approaches are crucially needed to prevent development of severe disease leading to major complications both acutely and chronically. The success in fighting this virus results from three main achievements: (a) Direct killing of the SARS-CoV-2 virus; (b) Development of a specific vaccine, and (c) Enhancement of the host's immune system. A fundamental necessity to win the battle against the virus involves a better understanding of the host's innate and adaptive immune response to the virus. Although the role of the adaptive immune response is directly involved in the generation of a vaccine, the role of innate immunity on RNA viruses in general, and coronaviruses in particular, is mostly unknown. In this review, we will consider the structure of RNA viruses, mainly coronaviruses, and their capacity to affect the lungs and the cardiovascular system. We will also consider the effects of the pattern recognition protein (PRP) trident composed by (a) Surfactant proteins A and D, mannose-binding lectin (MBL) and complement component 1q (C1q), (b) C-reactive protein, and (c) Innate and adaptive IgM antibodies, upon clearance of viral particles and apoptotic cells in lungs and atherosclerotic lesions. We emphasize on the role of pattern recognition protein immune therapies as a combination treatment to prevent development of severe respiratory syndrome and to reduce pulmonary and cardiovascular complications in patients with SARS-CoV-2 and summarize the need of a combined therapeutic approach that takes into account all aspects of immunity against SARS-CoV-2 virus and COVID-19 disease to allow mankind to beat this pandemic killer.

Evaluating pentraxin-3 and hypersensitivity CRP expression in obese pregnancies

OBJECTIVE

This study was designed to evaluate the correlation between serum pentraxin-3 (PTX3)/hypersensitivity CRP (hs-CRP) expression and obesity during pregnancy and their application as inflammatory biomarkers in obese pregnant women.

MATERIALS AND METHODS

Pregnant women scheduled to experience a single-birth at our hospital between 2016 and 2017 were selected for this nested case-control study. These patients were evaluated for age and gestational age in the first trimester (11-14 weeks), had their body mass index (BMI) calculated and were subjected to an OGTT between Week 24 and 28 of pregnancy. Obese patients with normal OGTT and a BMI of ≥30 kg/m² in the second trimester were selected as the obese group (OBE, n = 80), and non-obese pregnant women with normal OGTT with a BMI of <30 kg/m² were selected as the control group (CON, n = 80). ELISA was used to detect the expression of PTX3 and hs-CRP.

RESULTS

The expression of both PTX3 and hs-CRP increased in both groups, with increasing gestational age (P < 0.05). However, hs-CRP level in Group OBE was increased, compared to that in the healthy control (P < 0.01), during the second trimester. PTX3 expression was also significantly higher in OBE samples than in the control (P < 0.05), during the third trimester; correlation analysis demonstrated that PTX3 was positively correlated with hs-CRP, BMI, fasting plasma glucose and HOMA-IR.

CONCLUSIONS

The expression levels of both PTX3 and hs-CRP increased with increasing gestational age, and PTX3 expression was related to BMI, which serves to confirm the inflammatory response in these patients.

Increased Susceptibility and Intrinsic Apoptotic Signaling in Neurons by Induced HDAC3 Expression

Purpose

Inhibition or targeted deletion of histone deacetylase 3 (HDAC3) is neuroprotective in a variety neurodegenerative conditions, including retinal ganglion cells (RGCs) after acute optic nerve damage. Consistent with this, induced HDAC3 expression in cultured cells shows selective toxicity to neurons. Despite an established role for HDAC3 in neuronal pathology, little is known regarding the mechanism of this pathology.

Methods

Induced expression of an HDAC3-mCherry fusion protein in mouse RGCs was accomplished by transduction with AAV2/2-Pgk-HDAC3-mCherry. Increased susceptibility to optic nerve damage in HDAC3-mCherry expressing RGCs was evaluated in transduced mice that received acute optic nerve crush surgery. Expression of HDAC3-FLAG or HDAC3-mCherry was induced by nucleofection or transfection of plasmids into differentiated or undifferentiated 661W tissue culture cells. Immunostaining for cleaved caspase 3, localization of a GFP-BAX fusion protein, and quantitative RT-PCR was used to evaluate HDAC3-induced damage.

Results

Induced expression of exogenous HDAC3 in RGCs by viral-mediated gene transfer resulted in modest levels of cell death but significantly increased the sensitivity of these neurons to axonal damage. Undifferentiated 661W retinal precursor cells were resilient to induced HDAC3 expression, but after differentiation, HDAC3 induced GFP-BAX recruitment to the mitochondria and BAX/BAK dependent activation of caspase 3. This was accompanied by an increase in accumulation of transcripts for the JNK2/3 kinases and the p53-regulated BH3-only gene Bbc3/Puma. Cell cycle arrest of undifferentiated 661W cells did not increase their sensitivity to HDAC3 expression.

Conclusions

Collectively, these results indicate that HDAC3-induced toxicity to neurons is mediated by the intrinsic apoptotic pathway.

Factors Affecting Photodynamic Therapy and Anti-Tumor Immune Response

Photodynamic Therapy (PDT) is a cancer therapy involving the systemic injection of a Photosensitizer (PS) that localizes to some extent in a tumor. After an appropriate time (ranging from minutes to days), the tumor is irradiated with red or near-infrared light either as a surface spot or by interstitial optical fibers. The PS is excited by the light to form a long-lived triplet state that can react with ambient oxygen to produce Reactive Oxygen Species (ROS) such as singlet oxygen and/or hydroxyl radicals, that kill tumor cells, destroy tumor blood vessels, and lead to tumor regression and necrosis. It has long been realized that in some cases, PDT can also stimulate the host immune system, leading to a systemic anti-tumor immune response that can also destroy distant metastases and guard against tumor recurrence. The present paper aims to cover some of the factors that can affect the likelihood and efficiency of this immune response. The structure of the PS, drug-light interval, rate of light delivery, mode of cancer cell death, expression of tumor-associated antigens, and combinations of PDT with various adjuvants all can play a role in stimulating the host immune system. Considering the recent revolution in tumor immunotherapy triggered by the success of checkpoint inhibitors, it appears that the time is ripe for PDT to be investigated in combination with other approaches in clinical scenarios.

Predictive value of pentraxin-3 on disease severity and mortality risk in patients with hemorrhagic fever with renal syndrome

BACKGROUND

Hemorrhagic fever with renal syndrome (HFRS) caused by Hantaan virus is characterized by systemic immunopathological injury. Pentraxin-3 is an acute-phase reactant involved in the processes of inflammation and infection. This study aimed to investigate the levels of plasma pentraxin-3 and evaluate its predictive value on disease severity and mortality risk in patients with HFRS.

METHODS

This was a prospective real-world observational study. The concentrations of plasma pentraxin-3 were measured by enzyme linked immunosorbent assay (ELISA) in 105 HFRS patients and 27 healthy controls. We analyzed the clinical relevance between pentraxin-3 and clinical subtyping, hospital stay and conventional laboratory parameters of HFRS patients. Considering the prognosis (death) as the primary endpoint, the levels of pentraxin-3 between survivors and non-survivors were compared, and its association with mortality was assessed by Kaplan-Meier survival analysis. The predictive potency of pentraxin-3 for mortality risk in HFRS patients was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

The levels of pentraxin-3 during the acute phase were increased with the aggravation of the disease, and showed the highest expression in critical-type patients (P < 0.05). Pentraxin-3 demonstrated significant correlations with conventional laboratory parameters (WBC, PLT, AST, ALB, APTT, Fib) and the length of hospital stay. Compared with the survivors, non-survivors showed higher levels of pentraxin-3 and worse expressions of conventional laboratory parameters during the acute phase. The Kaplan-Meier survival curves showed that high levels of pentraxin-3 during the acute phase were significantly associated with the death in HFRS patients. Pentraxin-3 demonstrated significant predictive value for the mortality risk of HFRS patients, with the area under ROC curve (AUC) of 0.753 (95%CI: 0.593 ~ 0.914, P = 0.003).

CONCLUSIONS

The detection of plasma pentraxin-3 might be beneficial to the evaluation of disease severity and to the prediction of mortality risk in HFRS patients.

Pentraxin-3-mediated complement activation in a swine model of renal ischemia/reperfusion injury

Pentraxins are a family of evolutionarily conserved pattern recognition molecules with pivotal roles in innate immunity and inflammation, such as opsonization of pathogens during bacterial and viral infections. In particular, the long Pentraxin 3 (PTX3) has been shown to regulate several aspects of vascular and tissue inflammation during solid organ transplantation.

Our study investigated the role of PTX3 as possible modulator of Complement activation in a swine model of renal ischemia/reperfusion (I/R) injury.

We demonstrated that I/R injury induced early PTX3 deposits at peritubular and glomerular capillary levels. Confocal laser scanning microscopy revealed PTX3 deposits co-localizing with CD31⁺ endothelial cells. In addition, PTX3 was associated with infiltrating macrophages (CD163), dendritic cells (SWC3a) and myofibroblasts (FSP1). In particular, we demonstrated a significant PTX3-mediated activation of classical (C1q-mediated) and lectin (MBL-mediated) pathways of Complement. Interestingly, PTX3 deposits co-localized with activation of the terminal Complement complex (C5b-9) on endothelial cells, indicating that PTX3-mediated Complement activation occurred mainly at the renal vascular level. In conclusion, these data indicate that PTX3 might be a potential therapeutic target to prevent Complement-induced I/R injury.

Pentraxin 3 is a diagnostic and prognostic marker for ovarian epithelial cancer patients based on comprehensive bioinformatics and experiments

BACKGROUND

Ovarian epithelial cancer is one of the leading malignant tumors in gynecology and lacks effective diagnostic and prognostic markers. Our study aims to screen and verify ovarian epithelial cancer biomarkers.

METHODS

GSE18520 and GSE26712 were downloaded from the GEO database. The "limma" and "WGCNA" packages were used to explore hub genes. The Kaplan-Meier Plotter database was used for survival analysis of the hub genes. Immunohistochemical analysis was used to identify the expression level of Pentraxin 3 in ovarian epithelial cancer samples.

RESULTS

In this study, we integrated and analyzed two datasets, GSE18520 and GSE26712, and a total of 238 differentially expressed genes (DEGs) were screened out. Enrichment analysis showed that these DEGs were related to collagen-containing extracellular matrix and other pathways. Further application of WGCNA (weighted gene coexpression network analysis) identified 15 gene modules, with the purple module showing the highest correlation with ovarian epithelial cancer. Twenty-five genes were shared between the purple module and DEGs, 13 genes were related to the prognosis of ovarian epithelial cancer patients, and the PTX3 gene had the highest hazardous risk (HR) value. We performed immunohistochemical analyses on the 255 Pentraxin-3 (PTX3)-based clinical samples. PTX3 was found to be overexpressed in ovarian epithelial cancer and related to the degree of differentiation. The Cox proportional hazard model indicates that high PTX3 expression is an independent risk factor for the prognosis of ovarian epithelial cancer patients.

CONCLUSIONS

In conclusion, through WGCNA and a series of comprehensive bioinformatics analyses, PTX3 was first identified as a novel diagnostic and prognostic biomarker for ovarian epithelial cancer.

Modulated Electro-Hyperthermia Induces a Prominent Local Stress Response and Growth Inhibition in Mouse Breast Cancer Isografts

Modulated electro-hyperthermia (mEHT) is a selective cancer treatment used in human oncology complementing other therapies. During mEHT, a focused electromagnetic field (EMF) is generated within the tumor inducing cell death by thermal and nonthermal effects. Here we investigated molecular changes elicited by mEHT using multiplex methods in an aggressive, therapy-resistant triple negative breast cancer (TNBC) model. 4T1/4T07 isografts inoculated orthotopically into female BALB/c mice were treated with mEHT three to five times. mEHT induced the upregulation of the stress-related Hsp70 and cleaved caspase-3 proteins, resulting in effective inhibition of tumor growth and proliferation. Several acute stress response proteins, including protease inhibitors, coagulation and heat shock factors, and complement family members, were among the most upregulated treatment-related genes/proteins as revealed by next-generation sequencing (NGS), Nanostring and mass spectrometry (MS). pathway analysis demonstrated that several of these proteins belong to the response to stimulus pathway. Cell culture treatments confirmed that the source of these proteins was the tumor cells. The heat-shock factor inhibitor KRIBB11 reduced mEHT-induced complement factor 4 (C4) mRNA increase. In conclusion, mEHT monotherapy induced tumor growth inhibition and a complex stress response. Inhibition of this stress response is likely to enhance the effectiveness of mEHT and other cancer treatments.

C-Reactive Protein Triggers Cell Death in Ischemic Cells

C-reactive protein (CRP) is the best-known acute phase protein. In humans, almost every type of inflammation is accompanied by an increase of CRP concentration. Until recently, the only known physiological function of CRP was the marking of cells to initiate their phagocytosis. This triggers the classical complement pathway up to C4, which helps to eliminate pathogens and dead cells. However, vital cells with reduced energy supply are also marked, which is useful in the case of a classical external wound because an important substrate for pathogens is disposed of, but is counterproductive at internal wounds (e.g., heart attack or stroke). This mechanism negatively affects clinical outcomes since it is established that CRP levels correlate with the prognosis of these indications. Here, we summarize what we can learn from a clinical study in which CRP was adsorbed from the bloodstream by CRP-apheresis. Recently, it was shown that CRP can have a direct effect on blood pressure in rabbits. This is interesting in regard to patients with high inflammation, as they often become tachycardic and need catecholamines. These two physiological effects of CRP apparently also occur in COVID-19. Parts of the lung become ischemic due to intra-alveolar edema and hemorrhage and in parallel CRP increases dramatically, hence it is assumed that CRP is also involved in this ischemic condition. It is meanwhile considered that most of the damage in COVID-19 is caused by the immune system. The high amounts of CRP could have an additional influence on blood pressure in severe COVID-19.