Comparison of plasma mitochondrial DNA copy number in asymptomatic and symptomatic COVID-19 patients

The protein interaction of mitochondrial transcription factors A and B2 is associated with 30-day survival in critical COVID-19

Introduction

Repair of mitochondrial damage seems pivotal for clinical recovery and determining outcome in patients with critical COVID-19. However, reliable biomarkers for non-invasively assessing mitochondrial repair in peripheral blood of critically ill COVID-19 patients are currently lacking. Accordingly, we sought to assess different surrogates of mitochondrial repair in peripheral blood and correlate these measurements with clinical outcome in patients with critical COVID-19.

Methods

In this prospective multicentric cohort study, 88 critically ill COVID-19 patients were enrolled across three German intensive care units. Gene products of mitochondrial quality control (MFN2, PINK, TFAM, TFB2M) and the mtDNA copy number were measured in peripheral blood mononuclear cells. Furthermore, the protein interactions between TFAM and TFB2M were quantified. Patients were stratified regarding 30-day mortality.

Results

Transcript levels of the assessed mRNA markers of mitochondrial quality control were not associated with clinical outcome. In contrast, more than 10.7 protein interactions per cell were associated with a 74% 30-day survival (37 out of 50), while 10.7 or fewer protein interactions per cell were associated with a 32% 30-day survival (12 out of 38; p < 0.001). Furthermore, multivariable Cox regression analysis revealed TFAM-TFB2M protein interaction as an independent predictor for 30-day survival (HR: 3.2; 95% CI: 1.6 to 6.5; p < 0.001).

Discussion

Our findings indicate that TFAM-TFB2M protein interactions, identified as a novel biomarker, are strongly and independently associated with 30-day survival in critical COVID-19. Therefore, our data suggest a significant impact of mitochondrial repair and quality control on clinical outcome in critical COVID-19.

Extracellular Vesicles Alter Trophoblast Function in Pregnancies Complicated by COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and resulting coronavirus disease (COVID-19) cause placental dysfunction, which increases the risk of adverse pregnancy outcomes. While abnormal placental pathology resulting from COVID-19 is common, direct infection of the placenta is rare. This suggests that pathophysiology associated with maternal COVID-19, rather than direct placental infection, is responsible for placental dysfunction. We hypothesized that maternal circulating extracellular vesicles (EVs), altered by COVID-19 during pregnancy, contribute to placental dysfunction. To examine this hypothesis, we characterized circulating EVs from pregnancies complicated by COVID-19 and tested their effects on trophoblast cell physiology in vitro. Trophoblast exposure to EVs isolated from patients with an active infection (AI), but not controls, altered key trophoblast functions including hormone production and invasion. Thus, circulating EVs from participants with an AI, both symptomatic and asymptomatic cases, can disrupt vital trophoblast functions. EV cargo differed between participants with COVID-19, depending on the gestational timing of infection, and Controls, which may contribute to the disruption of the placental transcriptome and morphology. Our findings show that COVID-19 can have effects throughout pregnancy on circulating EVs, and circulating EVs are likely to participate in placental dysfunction induced by COVID-19.

Cytosolic nucleic acid sensing as driver of critical illness: mechanisms and advances in therapy

Nucleic acids from both self- and non-self-sources act as vital danger signals that trigger immune responses. Critical illnesses such as acute respiratory distress syndrome, sepsis, trauma and ischemia lead to the aberrant cytosolic accumulation and massive release of nucleic acids that are detected by antiviral innate immune receptors in the endosome or cytosol. Activation of receptors for deoxyribonucleic acids and ribonucleic acids triggers inflammation, a major contributor to morbidity and mortality in critically ill patients. In the past decade, there has been growing recognition of the therapeutic potential of targeting nucleic acid sensing in critical care. This review summarizes current knowledge of nucleic acid sensing in acute respiratory distress syndrome, sepsis, trauma and ischemia. Given the extensive research on nucleic acid sensing in common pathological conditions like cancer, autoimmune disorders, metabolic disorders and aging, we provide a comprehensive summary of nucleic acid sensing beyond critical illness to offer insights that may inform its role in critical conditions. Additionally, we discuss potential therapeutic strategies that specifically target nucleic acid sensing. By examining nucleic acid sources, sensor activation and function, as well as the impact of regulating these pathways across various acute diseases, we highlight the driving role of nucleic acid sensing in critical illness.

Fluctuations in circulating cell-free mitochondrial and nuclear DNA copy numbers in blood plasma after anti-tuberculosis drug intake in patients with drug-susceptible tuberculosis

Biomarker research characterising the effect of anti-tuberculosis (TB) chemotherapy on systemic body response is still limited. In this study, we aimed to investigate fluctuations in circulating cell-free mitochondrial DNA (ccf-mtDNA) and circulating cell-free nuclear DNA (ccf-nDNA) copy number (CN) in blood plasma of patients with drug-susceptible TB (DS-TB) and to decipher factors related to these fluctuations. The results showed considerable changes in ccf-mtDNA CN in plasma samples before drug intake and 2 and 6 h afterwards, with high inter patient variability at each time point. Multivariate linear regression revealed that the dynamics of ccf-mtDNA CN was influenced by patients' age, ethambutol pharmacokinetics, and body-mass index (BMI); ethambutol exposure emerged as the most significant factor. Very low ccf-nDNA CN in all three time points with little variation was observed; none factors were strongly associated with ccf-nDNA. In conclusion, our study revealed the effect of anti-TB chemotherapy, age and BMI on acute changes in circulating ccf-mtDNA CN in blood plasma and highlighted the systemic, mitochondria-related effects of ethambutol in patients with TB. Further studies with larger cohorts are needed to understand the biological relevance of ccf-DNA in patients with TB and to validate its application in TB treatment monitoring.

HbA1c and leukocyte mtDNA levels as major factors associated with post-COVID-19 syndrome in type 2 diabetes patients

Post-COVID-19 syndrome (PCS) is an emerging health problem in people recovering from COVID-19 infection within the past 3-6 months. The current study aimed to define the predictive factors of PCS development by assessing the mitochondrial DNA (mtDNA) levels in blood leukocytes, inflammatory markers and HbA1c in type 2 diabetes patients (T2D) with regard to clinical phenotype, gender, and biological age. In this case-control study, 65 T2D patients were selected. Patients were divided into 2 groups depending on PCS presence: the PCS group (n = 44) and patients who did not develop PCS (n = 21) for up to 6 months after COVID-19 infection. HbA1c and mtDNA levels were the primary factors linked to PCS in different models. We observed significantly lower mtDNA content in T2D patients with PCS compared to those without PCS (1.26 ± 0.25 vs. 1.44 ± 0.24; p = 0.011). In gender-specific and age-related analyses, the mt-DNA amount did not differ significantly between the subgroups. According to the stepwise multivariate logistic regression analysis, low mtDNA content and HbA1c were independent variables associated with PCS development, regardless of oxygen, glucocorticoid therapy and COVID-19 severity. The top-performing model for PCS prediction was the gradient boosting machine (GBM). HbA1c and mtDNA had a notably greater influence than the other variables, indicating their potential as prognostic biomarkers.

Aging mitochondria in the context of SARS-CoV-2: exploring interactions and implications

The coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has presented global challenges with a diverse clinical spectrum, including severe respiratory complications and systemic effects. This review explores the intricate relationship between mitochondrial dysfunction, aging, and obesity in COVID-19. Mitochondria are vital for cellular energy provision and resilience against age-related macromolecule damage accumulation. They manage energy allocation in cells, activating adaptive responses and stress signals such as redox imbalance and innate immunity activation. As organisms age, mitochondrial function diminishes. Aging and obesity, linked to mitochondrial dysfunction, compromise the antiviral response, affecting the release of interferons, and worsening COVID-19 severity. Furthermore, the development of post-acute sequelae of SARS-CoV-2 infection (PASC), also known as long COVID has been associated with altered energy metabolism, and chronic immune dysregulation derived from mitochondrial dysfunction. Understanding the interplay between mitochondria, aging, obesity, and viral infections provides insights into COVID-19 pathogenesis. Targeting mitochondrial health may offer potential therapeutic strategies to mitigate severe outcomes and address long-term consequences in infected individuals.

Mitochondria in COVID-19: from cellular and molecular perspective

The rapid development of the COVID-19 pandemic resulted in a closer analysis of cell functioning during β-coronavirus infection. This review will describe evidence for COVID-19 as a syndrome with a strong, albeit still underestimated, mitochondrial component. Due to the sensitivity of host mitochondria to coronavirus infection, SARS-CoV-2 affects mitochondrial signaling, modulates the immune response, modifies cellular energy metabolism, induces apoptosis and ageing, worsening COVID-19 symptoms which can sometimes be fatal. Various aberrations across human systems and tissues and their relationships with mitochondria were reported. In this review, particular attention is given to characterization of multiple alterations in gene expression pattern and mitochondrial metabolism in COVID-19; the complexity of interactions between SARS-CoV-2 and mitochondrial proteins is presented. The participation of mitogenome fragments in cell signaling and the occurrence of SARS-CoV-2 subgenomic RNA within membranous compartments, including mitochondria is widely discussed. As SARS-CoV-2 severely affects the quality system of mitochondria, the cellular background for aberrations in mitochondrial dynamics in COVID-19 is additionally characterized. Finally, perspectives on the mitigation of COVID-19 symptoms by affecting mitochondrial biogenesis by numerous compounds and therapeutic treatments are briefly outlined.

Extracellular vesicles alter trophoblast function in pregnancies complicated by COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and resulting coronavirus disease (COVID-19) causes placental dysfunction, which increases the risk of adverse pregnancy outcomes. While abnormal placental pathology resulting from COVID-19 is common, direct infection of the placenta is rare. This suggests that pathophysiology associated with maternal COVID-19, rather than direct placental infection, is responsible for placental dysfunction and alteration of the placental transcriptome. We hypothesized that maternal circulating extracellular vesicles (EVs), altered by COVID-19 during pregnancy, contribute to placental dysfunction. To examine this hypothesis, we characterized maternal circulating EVs from pregnancies complicated by COVID-19 and tested their effects on trophoblast cell physiology in vitro . We found that the gestational timing of COVID-19 is a major determinant of circulating EV function and cargo. In vitro trophoblast exposure to EVs isolated from patients with an active infection at the time of delivery, but not EVs isolated from Controls, altered key trophoblast functions including hormone production and invasion. Thus, circulating EVs from participants with an active infection, both symptomatic and asymptomatic cases, can disrupt vital trophoblast functions. EV cargo differed between participants with COVID-19 and Controls, which may contribute to the disruption of the placental transcriptome and morphology. Our findings show that COVID-19 can have effects throughout pregnancy on circulating EVs and circulating EVs are likely to participate in placental dysfunction induced by COVID-19.

When Our Best Friend Becomes Our Worst Enemy: The Mitochondrion in Trauma, Surgery, and Critical Illness

Common for major surgery, multitrauma, sepsis, and critical illness, is a whole-body inflammation. Tissue injury is able to trigger a generalized inflammatory reaction. Cell death causes release of endogenous structures termed damage associated molecular patterns (DAMPs) that initiate a sterile inflammation. Mitochondria are evolutionary endosymbionts originating from bacteria, containing molecular patterns similar to bacteria. These molecular patterns are termed mitochondrial DAMPs (mDAMPs). Mitochondrial debris released into the extracellular space or into the circulation is immunogenic and damaging secondary to activation of the innate immune system. In the circulation, released mDAMPS are either free or exist in extracellular vesicles, being able to act on every organ and cell in the body. However, the role of mDAMPs in trauma and critical care is not fully clarified. There is a complete lack of knowledge how they may be counteracted in patients. Among mDAMPs are mitochondrial DNA, cardiolipin, N-formyl peptides, cytochrome C, adenosine triphosphate, reactive oxygen species, succinate, and mitochondrial transcription factor A. In this overview, we present the different mDAMPs, their function, release, targets, and inflammatory potential. In light of present knowledge, the role of mDAMPs in the pathophysiology of major surgery and trauma as well as sepsis, and critical care is discussed.