Publications
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Dahl, Tuva Børresdatter; Jimenez, Ana Maria Teresa Quiles; Broch, Kaspar; Anstensrud, Anne Kristine; Gullestad, Lars & Andersen, Geir Øystein
[Show all 16 contributors for this article]
(2025).
The N-6 methyladenosine dynamics in STEMI and the effect of IL-6 inhibition - a hypothesis generating sub-study of the ASSAIL-MI trial.
Frontiers in Immunology.
16.
doi:
10.3389/fimmu.2025.1532325.
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Background: Epitranscriptomics, with m6A as the most prevalent in mammals, is a novel treatment target for inflammatory diseases, including cardiovascular diseases. However, little is known about m6A RNA-regulation during myocardial infarction (MI).
Methods: In this explorative sub-study of the ASSAIL-MI trial, we used whole blood samples from patients with acute ST-elevation MI (STEMI) (n=6) at admission and after 3–7 days, and from healthy control subjects (n=3). RNA was isolated, and m6A sites were analyzed using human m6A single nucleotide resolution microarray analysis. mRNA levels were analyzed using RNA sequencing analysis.
Results: Compared with controls, patients with STEMI had a strikingly different pattern of m6A deposition. In total, 845 m6A methylation sites in whole blood RNA were hypomethylated and 36 were hypermethylated compared with controls. Of the hypomethylated transcripts, 194 transcripts were lower expressed, while 197 transcripts were higher expressed. The m6A pattern changed from an overall hypomethylation at admission to an overall hypermethylation 3–7 day after admission. Anti-inflammatory treatment with tocilizumab further altered the m6A deposition.
Conclusions: In this hypothesis generating study, m6A deposition differs STEMI patients and healthy controls. The m6A pattern changes over the course of 3–7 days. This response is, at least to some degree, is modulated by blocking the IL-6 receptor. Our data may suggest that this post-transcriptional regulation of RNA is involved in the immune response during STEMI, highlighting its potential as a target for therapy in MI.
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Kindberg, Kristine Lovise Mørk; Broch, Kaspar; Andersen, Geir Øystein; Anstensrud, Anne Kristine; Åkra, Sissel & Woxholt, Sindre
[Show all 23 contributors for this article]
(2024).
Neutrophil Extracellular Traps in ST-Segment Elevation Myocardial Infarction: Reduced by Tocilizumab and Associated With Infarct Size.
JACC: Advances.
3(9).
doi:
10.1016/j.jacadv.2024.101193.
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Background - Interleukin-6-receptor inhibition with tocilizumab improves myocardial salvage in patients with ST-segment elevation myocardial infarction (STEMI). Reduced levels of neutrophil extracellular traps (NETs), which consist of nuclear material studded with proteins released upon neutrophil activation, might contribute to this effect.<p> <p>Objectives - The purpose of this study was to evaluate the effect of tocilizumab on NETs and investigate the association between NETs and myocardial injury in patients with STEMI.<p> <p>Methods - In the ASSAIL-MI study, 199 patients with STEMI were randomized to tocilizumab or placebo during percutaneous coronary intervention. In this substudy, we analyzed blood levels of the NET markers double-stranded deoxyribonucleic acid (dsDNA), myeloperoxidase-DNA, and citrullinated histone 3 (H3Cit) at admission and after 24 hours and 3 to 7 days. In a subgroup of patients, we assessed regulation of transcripts related to the formation of NETs. We also investigated associations between NET markers and the myocardial salvage index (MSI).<p> <p>Results - All NET markers were lower in the tocilizumab group than in the placebo group at 3 to 7 days (all P < 0.04). Several NET-related pathways were downregulated in the tocilizumab group. The beneficial effect of tocilizumab on the MSI seemed to be partly dependent on reduction of NETs (structural equation modeling: 0.05, P = 0.001 [dsDNA] and 0.02, P = 0.055 [H3Cit]). Patients with NETs in the 3 lowest quartiles had higher MSI than patients in quartile 4 (β = 10.9 [95% CI: 4.0-15.0] [dsDNA] and β = 8.9 [95% CI: 2.0-15.9] [H3Cit], both P = 0.01).<p> <p>Conclusions - NETs were reduced by tocilizumab and associated with myocardial injury. The effect of tocilizumab on MSI might be mediated through reduced NETs. (ASSessing the Effect of Anti-IL-6 Treatment in Myocardial Infarction: The ASSAIL-MI Trial [ASSAIL-MI]
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Holme, Fredric André; Huse, Camilla; Kong, Xiang Yi; Broch, Kaspar; Gullestad, Lars & Anstensrud, Anne Kristine
[Show all 15 contributors for this article]
(2024).
Circular RNA Profile in Atherosclerotic Disease: Regulation during ST-Elevated Myocardial Infarction.
International Journal of Molecular Sciences.
ISSN 1661-6596.
25(16),
p. 1–15.
doi:
10.3390/ijms25169014.
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Circular (circ) RNAs are non-coding RNAs with important functions in the nervous system, cardiovascular system, and cancer. Their role in atherosclerosis and myocardial infarction (MI) remains poorly described. We aim to investigate the potential circRNAs in immune cells during atherogenesis and examine the most regulated during MI and the modulation by interleukin (IL)-6 receptor inhibition by tocilizumab. Wild-type (WT) and ApoE−/− mice were fed an atherogenic diet for 10 weeks, and the circRNA profile was analyzed by circRNA microarray. Whole blood from patients with ST-elevated MI (STEMI) and randomized to tocilizumab (n = 21) or placebo (n = 19) was collected at admission, 3–7 days, and at 6 months, in addition to samples from healthy controls (n = 13). Primers for human circRNA were designed, and circRNA levels were measured using RT-qPCR. mRNA regulation of predicted circRNA targets was investigated by RNA sequencing. The expression of 867 circRNAs differed between atherogenic and WT mice. In STEMI patients, circUBAC2 was significantly lower than in healthy controls. CircANKRD42 and circUBAC2 levels were inversely correlated with troponin T, and for circUBAC2, an inverse correlation was also seen with final infarct size at 6 months. The predicted mRNA targets for circUBAC2 and circANKRD42 were investigated and altered levels of transcripts involved in the regulation of inflammatory/immune cells, apoptosis, and mitochondrial function were found. Finally, tocilizumab induced an up-regulation of circANKRD42 and circUBAC2 3–7 days after percutaneous coronary intervention. CircRNA levels were dysregulated in STEMI, potentially influencing the immune system, apoptosis, and mitochondrial function.
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Murphy, Sarah Louise Mikalsen; Balzer, Nora Reka; Ranheim, Trine; Sagen, Ellen Lund; Huse, Camilla & Bjerkeli, Vigdis
[Show all 19 contributors for this article]
(2024).
Extracellular matrix remodelling pathway in peripheral blood mononuclear cells from severe COVID-19 patients: an explorative study.
Frontiers in Immunology.
15.
doi:
10.3389/fimmu.2024.1379570.
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There is a reciprocal relationship between extracellular matrix (ECM) remodelling and inflammation that could be operating in the progression of severe COVID-19. To explore the immune-driven ECM remodelling in COVID-19, we in this explorative study analysed these interactions in hospitalised COVID-19 patients. RNA sequencing and flow analysis were performed on peripheral blood mononuclear cells. Inflammatory mediators in plasma were measured by ELISA and MSD, and clinical information from hospitalised COVID-19 patients (N=15) at admission was included in the analysis. Further, we reanalysed two publicly available datasets: (1) lung tissue RNA-sequencing dataset (N=5) and (2) proteomics dataset from PBCM. ECM remodelling pathways were enriched in PBMC from COVID-19 patients compared to healthy controls. Patients treated at the intensive care unit (ICU) expressed distinct ECM remodelling gene profiles compared to patients in the hospital ward. Several markers were strongly correlated to immune cell subsets, and the dysregulation in the ICU patients was positively associated with plasma levels of inflammatory cytokines and negatively associated with B-cell activating factors. Finally, our analysis of publicly accessible datasets revealed (i) an augmented ECM remodelling signature in inflamed lung tissue compared to non-inflamed tissue and (ii) proteomics analysis of PBMC from severe COVID-19 patients demonstrated an up-regulation in an ECM remodelling pathway. Our results may suggest the presence of an interaction between ECM remodelling, inflammation, and immune cells, potentially initiating or perpetuating pulmonary pathology in severe COVID-19.
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Woxholt, Sindre; Ueland, Thor; Aukrust, Pål; Anstensrud, Anne Kristine; Broch, Kaspar & Tøllefsen, Ingvild Maria
[Show all 15 contributors for this article]
(2024).
Effect of tocilizumab on endothelial and platelet-derived CXC-chemokines and their association with inflammation and myocardial injury in STEMI patients undergoing primary PCI.
International Journal of Cardiology.
ISSN 0167-5273.
418.
doi:
10.1016/j.ijcard.2024.132613.
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Background: Tocilizumab improves myocardial salvage in ST-elevation myocardial infarction (STEMI) patients when administered before percutaneous coronary intervention (PCI). The mechanisms underlying ischemia-reperfusion injury remain unclear. In this sub-study, we investigated whether endothelial and platelet-derived CXC chemokines are involved, as they represent inflammatory mediators from two cell types relevant to myocardial infarction. Associations between these chemokines and neutrophils, C-reactive protein (CRP), troponin T (TnT), myocardial salvage index (MSI), microvascular obstruction (MVO), and infarct size. Methods: This is a sub-study of the ASSAIL-MI trial, a double-blind clinical trial that randomized 199 STEMI patients to receive either 280 mg tocilizumab (n = 101) or placebo (n = 98) intravenously before PCI. Blood samples were collected prior to infusion, at day 1–2, 3–7, and at 3 and 6 months. Heparin was administered before baseline in 150 patients, while 49 received it after. We measured CXC-chemokines CXCL4, CXCL5, CXCL6, CXCL7, and CXCL12 using immunoassays. Cardiac MRI was performed in the first week and at 6 months. Results: Tocilizumab did not significantly affect CXC-chemokines levels. Although some correlations were observed between chemokine levels and neutrophil counts and CRP, none of the CXC chemokines were associated with infarct size, MSI, MVO, or TnT levels. Notably, CXCL 12 levels increased in patients who received heparin before baseline, while other CXC-chemokines decreased significantly. Conclusion: This study suggests that the beneficial effects of tocilizumab in STEMI patients are not due to changes in circulating endothelial or platelet-derived CXC-chemokines, compared to placebo. However, heparin significantly influences the levels of these chemokines.
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Woxholt, Sindre; Ueland, Thor; Aukrust, Pål; Anstensrud, Anne Kristine; Broch, Kaspar & Tøllefsen, Ingvild Maria
[Show all 20 contributors for this article]
(2023).
Cytokine pattern in patients with ST-elevation myocardial infarction treated with the interleukin-6 receptor antagonist tocilizumab.
Open heart.
10(2),
p. 1–8.
doi:
10.1136/openhrt-2023-002301.
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Background Tocilizumab improves myocardial salvage index (MSI) in patients with ST-elevation myocardial infarction (STEMI), but its mechanisms of action are unclear. Here, we explored how cytokines were affected by tocilizumab and their correlations with neutrophils, C-reactive protein (CRP), troponin T, MSI and infarct size. Methods STEMI patients were randomised to receive a single dose of 280 mg tocilizumab (n=101) or placebo (n=98) before percutaneous coronary intervention. Blood samples were collected before infusion of tocilizumab or placebo at baseline, during follow-up at 24–36, 72–168 hours, 3 and 6 months. 27 cytokines were analysed using a multiplex cytokine assay. Cardiac MRI was performed during hospitalisation and 6 months. Results Repeated measures analysis of variance showed significant (p<0.001) between-group difference in changes for IL-6, IL-8 and IL-1ra due to an increase in the tocilizumab group during hospitalisation. IL-6 and IL-8 correlated to neutrophils in the placebo group (r=0.73, 0.68, respectively), which was attenuated in the tocilizumab group (r=0.28, 0.27, respectively). A similar pattern was seen for MSI and IL-6 and IL-8 in the placebo group (r=−0.29, –0.25, respectively) in patients presenting ≤3 hours from symptom onset, which was attenuated in the tocilizumab group (r=−0.09,–0.14, respectively). Conclusions Tocilizumab increases IL-6, IL-8 and IL-1ra in STEMI. IL-6 and IL-8 show correlations to neutrophils/CRP and markers of cardiac injury in the placebo group that was attenuated in the tocilizumab group. This may suggest a beneficial effect of tocilizumab on the ischaemia-reperfusion injury in STEMI patients.
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Murphy, Sarah Louise Mikalsen; Halvorsen, Bente; Holter, Jan Cato; Huse, Camilla; Tveita, Anders & Trøseid, Marius
[Show all 24 contributors for this article]
(2023).
Circulating markers of extracellular matrix remodelling in severe COVID-19 patients.
Journal of Internal Medicine.
ISSN 0954-6820.
294(6),
p. 784–797.
doi:
10.1111/joim.13725.
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Background Abnormal remodelling of the extracellular matrix (ECM) has generally been linked to pulmonary inflammation and fibrosis and may also play a role in the pathogenesis of severe COVID-19. To further elucidate the role of ECM remodelling and excessive fibrogenesis in severe COVID-19, we examined circulating levels of mediators involved in various aspects of these processes in COVID-19 patients.<p> <p>Methods Serial blood samples were obtained from two cohorts of hospitalised COVID-19 patients (n = 414). Circulating levels of ECM remodelling mediators were quantified by enzyme immunoassays in samples collected during hospitalisation and at 3-month follow-up. Samples were related to disease severity (respiratory failure and/or treatment at the intensive care unit), 60-day total mortality and pulmonary pathology after 3-months. We also evaluated the direct effect of inactivated SARS-CoV-2 on the release of the different ECM mediators in relevant cell lines. <p>Results Several of the measured markers were associated with adverse outcomes, notably osteopontin (OPN), S100 calcium-binding protein A12 and YKL-40 were associated with disease severity and mortality. High levels of ECM mediators during hospitalisation were associated with computed tomography thorax pathology after 3-months. Some markers (i.e. growth differential factor 15, galectin 3 and matrix metalloproteinase 9) were released from various relevant cell lines (i.e. macrophages and lung cell lines) in vitro after exposure to inactivated SARS-CoV-2 suggesting a direct link between these mediators and the causal agent of COVID-19. <p>Conclusion Our findings highlight changes to ECM remodelling and particularly a possible role of OPN, S100A12 and YKL-40 in the pathogenesis of severe COVID-19.
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Søraas, Arne Vasli; Grødeland, Gunnveig; Granerud, Beathe Kiland; Ueland, Thor; Lind, Andreas & Fevang, Børre
[Show all 32 contributors for this article]
(2022).
Breakthrough infections with the omicron and delta variants of SARS-CoV-2 result in similar re-activation of vaccine-induced immunity.
Frontiers in Immunology.
13:964525,
p. 1–12.
doi:
10.3389/fimmu.2022.964525.
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Background: Results showing that sera from double vaccinated individuals have minimal neutralizing activity against Omicron have been interpreted as indicating the need for a third vaccine dose for protection. However, there is little information about early immune responses to Omicron infection in double vaccinated individuals.
Methods: We measured inflammatory mediators, antibodies to the SARS-CoV-2 spike and nucleocapsid proteins, and spike peptide-induced release of interferon gamma in whole blood in 51 double-vaccinated individuals infected with Omicron, in 14 infected with Delta, and in 18 healthy controls. The median time points for the first and second samples were 7 and 14 days after symptom onset, respectively.
Findings: Infection with Omicron or Delta led to a rapid and similar increase in antibodies to the receptor-binding domain (RBD) of Omicron protein and spike peptide-induced interferon gamma in whole blood. Both the Omicron- and the Delta-infected patients had a mild and transient increase in inflammatory parameters.
Interpretation: The results suggest that two vaccine doses are sufficient to mount a rapid and potent immune response upon infection in healthy individuals of with the Omicron variant.
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Olsen, Maria Belland; Huse, Camilla; Sousa, Mirta; Murphy, Sarah Louise Mikalsen; Sarno, Antonio & Obermann, Tobias Sebastian
[Show all 20 contributors for this article]
(2022).
DNA Repair Mechanisms are Activated in Circulating Lymphocytes of Hospitalized Covid-19 Patients.
Journal of Inflammation Research.
15,
p. 6629–6644.
doi:
10.2147/JIR.S379331.
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Purpose: Reactive oxygen species (ROS) are an important part of the inflammatory response during infection but can also promote DNA damage. Due to the sustained inflammation in severe Covid-19, we hypothesized that hospitalized Covid-19 patients would be characterized by increased levels of oxidative DNA damage and dysregulation of the DNA repair machinery. Patients and Methods: Levels of the oxidative DNA lesion 8-oxoG and levels of base excision repair (BER) proteins were measured in peripheral blood mononuclear cells (PBMC) from patients (8-oxoG, n = 22; BER, n = 17) and healthy controls (n = 10) (Cohort 1). Gene expression related to DNA repair was investigated in two independent cohorts of hospitalized Covid-19 patients (Cohort 1; 15 patents and 5 controls, Cohort 2; 15 patients and 6 controls), and by publicly available datasets. Results: Patients and healthy controls showed comparable amounts of oxidative DNA damage as assessed by 8-oxoG while levels of several BER proteins were increased in Covid-19 patients, indicating enhanced DNA repair in acute Covid-19 disease. Furthermore, gene expression analysis demonstrated regulation of genes involved in BER and double strand break repair (DSBR) in PBMC of Covid-19 patients and expression level of several DSBR genes correlated with the degree of respiratory failure. Finally, by re-analyzing publicly available data, we found that the pathway Hallmark DNA repair was significantly more regulated in circulating immune cells during Covid-19 compared to influenza virus infection, bacterial pneumonia or acute respiratory infection due to seasonal coronavirus. Conclusion: Although beneficial by protecting against DNA damage, long-term activation of the DNA repair machinery could also contribute to persistent inflammation, potentially through mechanisms such as the induction of cellular senescence. However, further studies that also include measurements of additional markers of DNA damage are required to determine the role and precise molecular mechanisms for DNA repair in SARS-CoV-2 infection.
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Huse, Camilla; Anstensrud, Anne Kristine; Michelsen, Annika Elisabet; Ueland, Thor; Broch, Kaspar & Woxholt, Sindre
[Show all 29 contributors for this article]
(2022).
Interleukin-6 inhibition in ST-elevation myocardial infarction: Immune cell profile in the randomised ASSAIL-MI trial.
EBioMedicine.
80(104013).
doi:
10.1016/j.ebiom.2022.104013.
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We recently showed that interleukin (IL)-6 inhibition by tocilizumab improves myocardial salvage in ST-elevation myocardial infarction (STEMI). However, the mechanisms for this effect are not clear. Methods In this exploratory sub-study of the ASSAIL-MI trial, we examined leukocyte differential counts and their relation to myocardial salvage and peak troponin T (TnT) in STEMI patients randomised to tocilizumab (n = 101) or placebo (n = 98). We performed RNA-sequencing on whole blood (n = 40) and T cells (n = 20). B and T cell subpopulations were examined by flow cytometry (n = 69). Findings (i) STEMI patients had higher neutrophil counts at hospitalisation compared with stable angina patients. (ii) After percutaneous coronary intervention there was a gradual decline in neutrophils, which was significantly more pronounced in the tocilizumab group. (iii) The decrease in neutrophils in the tocilizumab group was associated with improved myocardial salvage and lower peak TnT. (iv) RNA-sequencing suggested that neutrophil function was also attenuated by tocilizumab. (v) B and T cell sub-populations changed only minimally after STEMI with minor effects of tocilizumab, supported as well by RNA-sequencing analyses of T cells. (vi) However, a low CD8+ count was associated with improved myocardial salvage in patients admitted to the hospital > 3 h after symptom onset. Interpretation Tocilizumab induced a rapid reduction in neutrophils and seemed to attenuate neutrophil function in STEMI patients potentially related to the beneficial effects of tocilizumab on myocardial salvage.
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Kong, Xiang Yi; Huse, Camilla; Yang, Kuan; Øgaard, Jonas; Jimenez, Natalia Berges & Vik, Erik Sebastian
[Show all 24 contributors for this article]
(2021).
Endonuclease v regulates atherosclerosis through c-c motif chemokine ligand 2-mediated monocyte infiltration.
Journal of the American Heart Association (JAHA).
10(14).
doi:
10.1161/JAHA.120.020656.
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Background:
In cardiovascular diseases, atherosclerotic disorder are the most frequent and important with respect to morbidity and mortality. Inflammation mediated by immune cells is central in all parts of the atherosclerotic progress, and further understanding of the underlying mechanisms is needed. Growing evidence suggests that deamination of adenosine‐to‐inosine in RNA is crucial for a correct immune response; nevertheless, the role of adenosine‐to‐inosine RNA editing in atherogenesis has barely been studied. Several proteins have affinity for inosines in RNA, one being ENDOV (endonuclease V), which binds and cleaves RNA at inosines. Data on ENDOV in atherosclerosis are lacking.
Methods and Results:
Quantitative polymerase chain reaction on ENDOV mRNA showed an increased level in human carotid atherosclerotic plaques compared with control veins. Inosine‐ribonuclease activity as measured by an enzyme activity assay is detected in immune cells relevant for the atherosclerotic process. Abolishing EndoV in atherogenic apolipoprotein E‐deficient (ApoE−/−) mice reduces the atherosclerotic plaque burden, both in size and lipid content. In addition, in a brain stroke model, mice without ENDOV suffer less damage than control mice. Finally, lack of EndoV reduces the recruitment of monocytes to atherosclerotic lesions in atherogenic ApoE−/− mice.
Conclusions:
ENDOV is upregulated in human atherosclerotic lesions, and data from mice suggest that ENDOV promotes atherogenesis by enhancing the monocyte recruitment into the atherosclerotic lesion, potentially by increasing the effect of CCL2 activation on these cells.
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Christensen, Erik; Jørgensen, Marthe Jøntvedt; Nore, Kristin Grotle; Dahl, Tuva Børresdatter; Yang, Kuan & Ranheim, Trine
[Show all 16 contributors for this article]
(2021).
Critical COVID-19 is associated with distinct leukocyte phenotypes and transcriptome patterns.
Journal of Internal Medicine.
ISSN 0954-6820.
p. 1–16.
doi:
10.1111/joim.13310.
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Background Prognostic markers for disease severity and identification of therapeutic targets in COVID-19 are urgently needed. We have studied innate and adaptive immunity on protein and transcriptomic level in COVID-19 patients with different disease severity at admission and longitudinally during hospitalization. Methods Peripheral blood mononuclear cells (PBMCs) were collected at three time points from 31 patients included in the Norwegian SARS-CoV-2 cohort study and analysed by flow cytometry and RNA sequencing. Patients were grouped as either mild/moderate (n = 14), severe (n = 11) or critical (n = 6) disease in accordance with WHO guidelines and compared with patients with SARS-CoV-2-negative bacterial sepsis (n = 5) and healthy controls (n = 10). Results COVID-19 severity was characterized by decreased interleukin 7 receptor alpha chain (CD127) expression in naïve CD4 and CD8 T cells. Activation (CD25 and HLA-DR) and exhaustion (PD-1) markers on T cells were increased compared with controls, but comparable between COVID-19 severity groups. Non-classical monocytes and monocytic HLA-DR expression decreased whereas monocytic PD-L1 and CD142 expression increased with COVID-19 severity. RNA sequencing exhibited increased plasma B-cell activity in critical COVID-19 and yet predominantly reduced transcripts related to immune response pathways compared with milder disease. Conclusion Critical COVID-19 seems to be characterized by an immune profile of activated and exhausted T cells and monocytes. This immune phenotype may influence the capacity to mount an efficient T-cell immune response. Plasma B-cell activity and calprotectin were higher in critical COVID-19 while most transcripts related to immune functions were reduced, in particular affecting B cells. The potential of these cells as therapeutic targets in COVID-19 should be further explored.
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Beck, Carole; Zegarra, Sergio Miguel Castaneda; Huse, Camilla; Xing, Mengtan & Oksenych, Valentyn
(2020).
Mediator of DNA Damage Checkpoint Protein 1 Facilitates V(D)J Recombination in Cells Lacking DNA Repair Factor XLF.
Biomolecules.
10(60).
doi:
10.3390/biom10010060.
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DNA double-strand breaks (DSBs) trigger the Ataxia telangiectasia mutated (ATM)-dependent DNA damage response (DDR), which consists of histone H2AX, MDC1, RNF168, 53BP1, PTIP, RIF1, Rev7, and Shieldin. Early stages of B and T lymphocyte development are dependent on recombination activating gene (RAG)-induced DSBs that form the basis for further V(D)J recombination. Non-homologous end joining (NHEJ) pathway factors recognize, process, and ligate DSBs. Based on numerous loss-of-function studies, DDR factors were thought to be dispensable for the V(D)J recombination. In particular, mice lacking Mediator of DNA Damage Checkpoint Protein 1 (MDC1) possessed nearly wild-type levels of mature B and T lymphocytes in the spleen, thymus, and bone marrow. NHEJ factor XRCC4-like factor (XLF)/Cernunnos is functionally redundant with ATM, histone H2AX, and p53-binding protein 1 (53BP1) during the lymphocyte development in mice. Here, we genetically inactivated MDC1, XLF, or both MDC1 and XLF in murine vAbl pro-B cell lines and, using chromosomally integrated substrates, demonstrated that MDC1 stimulates the V(D)J recombination in cells lacking XLF. Moreover, combined inactivation of MDC1 and XLF in mice resulted in synthetic lethality. Together, these findings suggest that MDC1 and XLF are functionally redundant during the mouse development, in general, and the V(D)J recombination, in particular.
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Zegarra, Sergio Miguel Castaneda; Huse, Camilla; Røsand, Øystein; Sarno, Antonio; Xing, Mengtan & Gago-Fuentes, Raquel
[Show all 14 contributors for this article]
(2019).
Generation of a mouse model lacking the non-homologous end-joining factor Mri/Cyren.
Biomolecules.
9:798(12),
p. 1–13.
doi:
10.3390/biom9120798.
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Classical non-homologous end joining (NHEJ) is a molecular pathway that detects, processes, and ligates DNA double-strand breaks (DSBs) throughout the cell cycle. Mutations in several NHEJ genes result in neurological abnormalities and immunodeficiency both in humans and mice. The NHEJ pathway is required for V(D)J recombination in developing B and T lymphocytes, and for class switch recombination in mature B cells. The Ku heterodimer formed by Ku70 and Ku80 recognizes DSBs and facilitates the recruitment of accessory factors (e.g., DNA-PKcs, Artemis, Paxx and Mri/Cyren) and downstream core factor subunits X-ray repair cross-complementing group 4 (XRCC4), XRCC4-like factor (XLF), and DNA ligase 4 (Lig4). Accessory factors might be dispensable for the process, depending on the genetic background and DNA lesion type. To determine the physiological role of Mri in DNA repair and development, we introduced a frame-shift mutation in the Mri gene in mice. We then analyzed the development of Mri-deficient mice as well as wild type and immunodeficient controls. Mice lacking Mri possessed reduced levels of class switch recombination in B lymphocytes and slow proliferation of neuronal progenitors when compared to wild type littermates. Human cell lines lacking Mri were as sensitive to DSBs as the wild type controls. Overall, we concluded that Mri/Cyren is largely dispensable for DNA repair and mouse development.
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Published
Apr. 12, 2023 3:37 PM
- Last modified
Sep. 26, 2023 3:01 PM
