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1.
PLoS Comput Biol ; 18(7): e1009994, 2022 07.
Article in English | MEDLINE | ID: covidwho-1993429

ABSTRACT

Host response to infection involves the activation of the complement system leading to the production of anaphylatoxins C3a and C5a. Complement factor C5a exerts its effect through the activation of C5aR1, chemotactic receptor 1, and triggers the G protein-coupled signaling cascade. Orthosteric and allosteric antagonists of C5aR1 are a novel strategy for anti-inflammatory therapies. Here, we discuss recent crystal structures of inactive C5aR1 in terms of an inverted orientation of helix H8, unobserved in other GPCR structures. An analysis of mutual interactions of subunits in the C5aR1-G protein complex has provided new insights into the activation mechanism of this distinct receptor. By comparing two C5aR receptors C5aR1 and C5aR2 we explained differences between their signaling pathways on the molecular level. By means of molecular dynamics we explained why C5aR2 cannot transduce signal through the G protein pathway but instead recruits beta-arrestin. A comparison of microsecond MD trajectories started from active and inactive C5aR1 receptor conformations has provided insights into details of local and global changes in the transmembrane domain induced by interactions with the Gα subunit and explained the impact of inverted H8 on the C5aR1 activation.


Subject(s)
Complement C5a , Signal Transduction , Complement C5a/metabolism , beta-Arrestins/metabolism
2.
Front Immunol ; 13: 834988, 2022.
Article in English | MEDLINE | ID: covidwho-1817941

ABSTRACT

Patients with COVID-19 present with a wide variety of clinical manifestations. Thromboembolic events constitute a significant cause of morbidity and mortality in patients infected with SARS-CoV-2. Severe COVID-19 has been associated with hyperinflammation and pre-existing cardiovascular disease. Platelets are important mediators and sensors of inflammation and are directly affected by cardiovascular stressors. In this report, we found that platelets from severely ill, hospitalized COVID-19 patients exhibited higher basal levels of activation measured by P-selectin surface expression and had poor functional reserve upon in vitro stimulation. To investigate this question in more detail, we developed an assay to assess the capacity of plasma from COVID-19 patients to activate platelets from healthy donors. Platelet activation was a common feature of plasma from COVID-19 patients and correlated with key measures of clinical outcome including kidney and liver injury, and APACHEIII scores. Further, we identified ferritin as a pivotal clinical marker associated with platelet hyperactivation. The COVID-19 plasma-mediated effect on control platelets was highest for patients that subsequently developed inpatient thrombotic events. Proteomic analysis of plasma from COVID-19 patients identified key mediators of inflammation and cardiovascular disease that positively correlated with in vitro platelet activation. Mechanistically, blocking the signaling of the FcγRIIa-Syk and C5a-C5aR pathways on platelets, using antibody-mediated neutralization, IgG depletion or the Syk inhibitor fostamatinib, reversed this hyperactivity driven by COVID-19 plasma and prevented platelet aggregation in endothelial microfluidic chamber conditions. These data identified these potentially actionable pathways as central for platelet activation and/or vascular complications and clinical outcomes in COVID-19 patients. In conclusion, we reveal a key role of platelet-mediated immunothrombosis in COVID-19 and identify distinct, clinically relevant, targetable signaling pathways that mediate this effect.


Subject(s)
Blood Platelets/immunology , COVID-19/immunology , Complement C5a/metabolism , Receptor, Anaphylatoxin C5a/metabolism , Receptors, IgG/metabolism , SARS-CoV-2/physiology , Thromboembolism/immunology , Adult , Aminopyridines/pharmacology , Cells, Cultured , Female , Hospitalization , Humans , Male , Morpholines/pharmacology , Platelet Activation , Pyrimidines/pharmacology , Severity of Illness Index , Signal Transduction , Syk Kinase/antagonists & inhibitors
3.
Front Immunol ; 12: 767376, 2021.
Article in English | MEDLINE | ID: covidwho-1556073

ABSTRACT

Evidence supports a role of complement anaphylatoxin C5a in the pathophysiology of COVID-19. However, information about the evolution and impact of C5a levels after hospital discharge is lacking. We analyzed the association between circulating C5a levels and the clinical evolution of hospitalized patients infected with SARS-CoV-2. Serum C5a levels were determined in 32 hospitalized and 17 non-hospitalized patients from Clinica Universidad de Navarra. One hundred and eighty eight serial samples were collected during the hospitalization stay and up to three months during the follow-up. Median C5a levels were 27.71 ng/ml (25th to 75th percentile: 19.35-34.96) for samples collected during hospitalization, versus 16.76 ng/ml (12.90-25.08) for samples collected during the follow-up (p<0.001). There was a negative correlation between serum C5a levels and the number of days from symptom onset (p<0.001). C5a levels also correlated with a previously validated clinical risk score (p<0.001), and was associated with the severity of the disease (p<0.001). An overall reduction of C5a levels was observed after hospital discharge. However, elevated C5a levels persisted in those patients with high COVID-19 severity (i.e. those with a longest stay in the hospital), even after months from hospital discharge (p=0.020). Moreover, high C5a levels appeared to be associated with the presence of long-term respiratory symptoms (p=0.004). In conclusion, serum C5a levels remain high in severe cases of COVID-19, and are associated with the presence of respiratory symptoms after hospital discharge. These results may suggest a role for C5a in the long-term effects of COVID-19 infection.


Subject(s)
COVID-19/blood , Complement C5a/metabolism , Patient Discharge/statistics & numerical data , Aged , COVID-19/complications , COVID-19/immunology , Female , Follow-Up Studies , Hospitalization , Humans , Immunity, Innate , Male , Middle Aged , Respiration Disorders/blood , Respiration Disorders/etiology , Respiration Disorders/immunology , Risk Factors , SARS-CoV-2 , Severity of Illness Index
4.
J Clin Immunol ; 41(7): 1607-1620, 2021 10.
Article in English | MEDLINE | ID: covidwho-1298388

ABSTRACT

The complement system, a network of highly-regulated proteins, represents a vital part of the innate immune response. Over-activation of the complement system plays an important role in inflammation, tissue damage, and infectious disease severity. The prevalence of MERS-CoV in Saudi Arabia remains significant and cases are still being reported. The role of complement in Middle East Respiratory Syndrome coronavirus (MERS-CoV) pathogenesis and complement-modulating treatment strategies has received limited attention, and studies involving MERS-CoV-infected patients have not been reported. This study offers the first insight into the pulmonary expression profile including seven complement proteins, complement regulatory factors, IL-8, and RANTES in MERS-CoV infected patients without underlying chronic medical conditions. Our results significantly indicate high expression levels of complement anaphylatoxins (C3a and C5a), IL-8, and RANTES in the lungs of MERS-CoV-infected patients. The upregulation of lung complement anaphylatoxins, C5a, and C3a was positively correlated with IL-8, RANTES, and the fatality rate. Our results also showed upregulation of the positive regulatory complement factor P, suggesting positive regulation of the complement during MERS-CoV infection. High levels of lung C5a, C3a, factor P, IL-8, and RANTES may contribute to the immunopathology, disease severity, ARDS development, and a higher fatality rate in MERS-CoV-infected patients. These findings highlight the potential prognostic utility of C5a, C3a, IL-8, and RANTES as biomarkers for MERS-CoV disease severity and mortality. To further explore the prediction of functional partners (proteins) of highly expressed proteins (C5a, C3a, factor P, IL-8, and RANTES), the computational protein-protein interaction (PPI) network was constructed, and six proteins (hub nodes) were identified.


Subject(s)
Chemokine CCL5/genetics , Chemokine CCL5/metabolism , Complement C3a/metabolism , Complement C5a/metabolism , Coronavirus Infections/diagnosis , Interleukin-8/metabolism , Lung/metabolism , Middle East Respiratory Syndrome Coronavirus/physiology , Aged , Biomarkers/metabolism , Complement C3a/genetics , Complement C5a/genetics , Coronavirus Infections/metabolism , Coronavirus Infections/mortality , Female , Humans , Interleukin-8/genetics , Male , Middle Aged , Prognosis , Severity of Illness Index , Survival Analysis , Up-Regulation
5.
Med Sci (Paris) ; 37(4): 333-341, 2021 Apr.
Article in French | MEDLINE | ID: covidwho-1174712

ABSTRACT

The complement system is an essential component of the innate immune system. Its excessive activation during COVID-19 contributes to cytokine storm, disease-specific endothelial inflammation (endotheliitis) and thrombosis that comes with the disease. Targeted therapies of complement inhibition in COVID-19, in particular blocking the C5a-C5aR1 axis have to be taken into account in the establishment of potential biomarkers and development of therapeutic strategies in the most severe forms of the disease.


TITLE: Implication de la cascade du complément dans les formes sévères de COVID-19. ABSTRACT: Le système du complément est un composant essentiel du système immunitaire inné. Son activation excessive au cours de la COVID-19 participe à l'orage cytokinique, à l'inflammation endothéliale (endothélite) et aux thromboses qui accompagnent la maladie. Bloquer le complément, notamment l'axe C5a-C5aR1, par des thérapies spécifiques représente un espoir thérapeutique dans les formes les plus sévères de la maladie.


Subject(s)
COVID-19/immunology , COVID-19/pathology , Complement Activation/physiology , Complement System Proteins/physiology , Animals , COVID-19/metabolism , Complement C5a/immunology , Complement C5a/metabolism , Cytokine Release Syndrome/etiology , Cytokine Release Syndrome/immunology , Cytokine Release Syndrome/pathology , Humans , Inflammation/complications , Inflammation/immunology , Inflammation/pathology , SARS-CoV-2/immunology , Severity of Illness Index , Signal Transduction/immunology
6.
Trends Immunol ; 41(11): 965-967, 2020 11.
Article in English | MEDLINE | ID: covidwho-834446

ABSTRACT

The current pandemic of coronavirus disease (COVID-19) caused by SARS-CoV-2 is a significant global health challenge. A recent study by Carvelli and colleagues now demonstrates the involvement of complement C5a and its receptor C5aR1 in disease progression and suggests that blockade of the C5a-C5aR1 axis may represent a potential therapeutic strategy against COVID-19.


Subject(s)
Betacoronavirus/immunology , Complement C5a/immunology , Coronavirus Infections/immunology , Pneumonia, Viral/immunology , Receptor, Anaphylatoxin C5a/immunology , Animals , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal/pharmacology , Betacoronavirus/drug effects , Betacoronavirus/physiology , COVID-19 , Complement C5a/metabolism , Coronavirus Infections/therapy , Coronavirus Infections/virology , Disease Models, Animal , Humans , Pandemics , Pneumonia, Viral/therapy , Pneumonia, Viral/virology , Receptor, Anaphylatoxin C5a/metabolism , Receptors, G-Protein-Coupled/immunology , Receptors, G-Protein-Coupled/metabolism , SARS-CoV-2 , Signal Transduction/drug effects , Signal Transduction/immunology
7.
J Thromb Haemost ; 18(9): 2110-2117, 2020 09.
Article in English | MEDLINE | ID: covidwho-623519

ABSTRACT

COVID-19 is frequently accompanied by a hypercoagulable inflammatory state with microangiopathic pulmonary changes that can precede the diffuse alveolar damage characteristic of typical acute respiratory distress syndrome (ARDS) seen in other severe pathogenic infections. Parallels with systemic inflammatory disorders such as atypical hemolytic uremic syndrome (aHUS) have implicated the complement pathway in the pathogenesis of COVID-19, and particularly the anaphylatoxins C3a and C5a released from cleavage of C3 and C5, respectively. C5a is a potent cell signalling protein that activates a cytokine storm-a hyper-inflammatory phenomenon-within hours of infection and the innate immune response. However, excess C5a can result in a pro-inflammatory environment orchestrated through a plethora of mechanisms that propagate lung injury, lymphocyte exhaustion, and an immune paresis. Furthermore, disruption of the homeostatic interactions between complement and extrinsic and intrinsic coagulation pathways contributes to a net pro-coagulant state in the microvasculature of critical organs. Fatal COVID-19 has been associated with a systemic inflammatory response accompanied by a pro-coagulant state and organ damage, particularly microvascular thrombi in the lungs and kidneys. Pathologic studies report strong evidence of complement activation. C5 blockade reduces inflammatory cytokines and their manifestations in animal studies, and has shown benefits in patients with aHUS, prompting investigation of this approach in the treatment of COVID-19. This review describes the role of the complement pathway and particularly C5a and its aberrations in highly pathogenic virus infections, and therefore its potential as a therapeutic target in COVID-19.


Subject(s)
Blood Coagulation , COVID-19/immunology , Complement Activation , Complement C3a/metabolism , Complement C5a/metabolism , Inflammation/metabolism , Animals , Atypical Hemolytic Uremic Syndrome/complications , Atypical Hemolytic Uremic Syndrome/immunology , COVID-19/complications , COVID-19/pathology , Complement Inactivating Agents/pharmacology , Cytokines/metabolism , Hemoglobinuria, Paroxysmal/complications , Hemoglobinuria, Paroxysmal/immunology , Homeostasis , Humans , Immunity, Innate , Lung Diseases , Lung Injury , Signal Transduction
8.
Cytokine ; 133: 155151, 2020 09.
Article in English | MEDLINE | ID: covidwho-437203

ABSTRACT

Patients with COVID-19 who require ICU admission might have the cytokine storm. It is a state of out-of-control release of a variety of inflammatory cytokines. The molecular mechanism of the cytokine storm has not been explored extensively yet. The attachment of SARS-CoV-2 spike glycoprotein with angiotensin-converting enzyme 2 (ACE2), as its cellular receptor, triggers complex molecular events that leads to hyperinflammation. Four molecular axes that may be involved in SARS-CoV-2 driven inflammatory cytokine overproduction are addressed in this work. The virus-mediated down-regulation of ACE2 causes a burst of inflammatory cytokine release through dysregulation of the renin-angiotensin-aldosterone system (ACE/angiotensin II/AT1R axis), attenuation of Mas receptor (ACE2/MasR axis), increased activation of [des-Arg9]-bradykinin (ACE2/bradykinin B1R/DABK axis), and activation of the complement system including C5a and C5b-9 components. The molecular clarification of these axes will elucidate an array of therapeutic strategies to confront the cytokine storm in order to prevent and treat COVID-19 associated acute respiratory distress syndrome.


Subject(s)
Betacoronavirus/metabolism , Coronavirus Infections/immunology , Coronavirus Infections/metabolism , Cytokines/metabolism , Inflammation/metabolism , Peptidyl-Dipeptidase A/metabolism , Pneumonia, Viral/immunology , Pneumonia, Viral/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Angiotensin-Converting Enzyme 2 , Betacoronavirus/pathogenicity , Bradykinin/metabolism , COVID-19 , Complement C5a/immunology , Complement C5a/metabolism , Complement C5b/immunology , Complement C5b/metabolism , Coronavirus Infections/enzymology , Humans , Inflammation/enzymology , Inflammation/immunology , Models, Molecular , Pandemics , Pneumonia, Viral/enzymology , Proto-Oncogene Proteins/metabolism , Receptors, G-Protein-Coupled/metabolism , Renin-Angiotensin System/immunology , SARS-CoV-2
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