Elevated levels of plasma mitochondrial DNA DAMPs are linked to clinical outcome in severely injured human subjects

Major Traumatic Injury and Exposure to Mitochondrial-Derived Damage-Associated Molecular Patterns Promotes Neutrophil Survival Accompanied by Stabilisation of the Anti-Apoptotic Protein Mcl-1

Traumatic injury leads to an extension of the half-life of circulating neutrophils. However, how quickly neutrophil apoptosis is delayed post-injury is currently unknown, as are the underlying mechanisms and factors that promote this extension of lifespan. During the ultra-early (≤1 h) and acute (4-12 and 48-72 h) post-injury phases, we collected blood samples from 73 adult trauma patients. Following ex vivo culture, neutrophil apoptosis was measured, alongside caspase-3 activation and expression of the anti-apoptotic protein Mcl-1. To identify factors that may promote neutrophil survival post-trauma, neutrophils from healthy controls (HCs) were cultured with mitochondrial-derived damage-associated molecular patterns (mtDAMPs) or mitochondrial DNA (mtDNA). Accompanied by reduced mitochondrial membrane depolarisation, delayed Mcl-1 turnover, and reduced caspase-3 activation, the ex vivo lifespan of neutrophils from trauma patients was significantly enhanced in a protein synthesis-independent manner within minutes to hours after injury. Neutrophils from HCs exhibited delayed apoptosis when cultured in media supplemented with trauma patient serum, which occurred alongside stabilisation of Mcl-1. Culturing HCs neutrophils with mtDAMPs or mtDNA significantly delayed apoptosis rates, promoted stabilisation of Mcl-1, and reduced caspase-3 activation. The release of mtDAMPs from damaged tissue may drive post-trauma immune dysregulation by promoting the survival of dysfunctional neutrophils.

Oxidative damage to lung mitochondrial DNA is a key contributor to the development of chemical lung injury

Humans exposed to chlorine (Cl2) due to industrial accidents or acts of terrorism may develop lung injury culminating to Acute Respiratory Distress syndrome and death from respiratory failure. Early molecular targets of inhaled oxidant gases suitable for pharmacologic modulation have not been established. Because the mitochondrial genome is highly sensitive to oxidant stress, we tested the hypothesis that mice exposure to Cl2 gas causes oxidative damage to the mitochondrial DNA (mtDNA) that triggers the development of acute and chronic lung injury. Cl2 gas-exposed C57BL/6 mice and returned to room air, developed progressive loss of lung DNA glycosylase OGG1, followed by oxidative mtDNA damage. This resulted in activation of inflammatory pathways by circulating DNA, progressive increased airway resistance, alveolar injury and acute pulmonary edema due to loss of epithelial amiloride-sensitive sodium channels. Mice not succumbing acutely displayed a delayed syndrome of progressive increase in airway resistance and emphysematous-like changes in lung morphology. Global proteomics of lungs harvested 24 h post Cl2 exposure revealed alterations in over 1500 lung proteins, including 14 key mitochondrial proteins. Intranasal instillation of a recombinant protein targeting OGG1 to mitochondria (mitoOGG1) at 1 h post exposure decreased oxidized lung mtDNA, alterations to the lung and mitochondrial proteomes, severity of the acute and delayed lung injury and increased survival. These data show that injury to the mt-genome is a key contributor to the development of acute and chronic lung injury after Cl2 gas exposure and point to mtDNA oxidation as a target for pharmacologic intervention.

Investigating the impact of mitochondrial DNA: Insights into blood transfusion reactions and mitigation strategies

BACKGROUND AND OBJECTIVES

Although transfusion reactions occur in less than 2% of recipients, they are currently one of the most serious concerns in blood transfusion. Damage-associated molecular patterns (DAMPs) are released from injured, stressed or dead cells, leading to inflammation and immune system activation. One of the recognized DAMPs is mitochondrial DNA (mtDNA). It is found in various blood products, including fresh frozen plasma (FFP), red blood cell units (RBCUs) and platelet concentrates (PCs), and can induce adverse reactions in recipients by stimulating the innate immune system and inflammatory cellular pathways. The aim of this study was to investigate the factors influencing the release of mtDNA in various blood products and its subsequent impact on transfusion reactions.

MATERIALS AND METHODS

In this study, mtDNA, mitochondrial DNA, mtDNA DAMPs, extracellular mtDNA, blood products, blood components and transfusion reactions between 2009 and 2023 were searched in Google Scholar, PubMed and Scopus databases.

RESULTS

This study has demonstrated the presence of mtDNA in the extracellular milieu of various blood products, including PCs, FFP and RBCUs. Understanding the determinants of mtDNA release and its implications for transfusion safety is critical. Strategies aimed at reducing mtDNA release, such as optimizing preparation techniques and donor selection criteria, hold promise for reducing transfusion-related complications.

CONCLUSION

By addressing these factors, healthcare providers can enhance the safety and efficacy of blood transfusion practices, ultimately improving patient outcomes.

Emerging concepts in the molecular cell biology and functions of mammalian erythrocytes

Erythrocytes, or red blood cells, are essential components of vertebrate blood, comprising approximately 45% of human blood volume. Their distinctive features, including small size, biconcave shape, extended lifespan (∼115 days), and lack of a nucleus or other membrane-bound organelles, make them unique among mammalian cell types. Traditionally regarded as passive carriers of oxygen and carbon dioxide, erythrocytes were long thought to function merely as hemoglobin-filled sacs, incapable of gene expression or roles beyond gas transport. However, advancements in molecular biology have revealed a more complex picture. Recent studies have identified various RNA types within erythrocytes, demonstrated globin mRNA translation, and uncovered miRNA-mediated defenses against Plasmodium infection. Beyond gas exchange, erythrocytes play critical roles in regulating regional blood flow via nitric oxide, contribute to innate immunity through toll-like receptors, transport amino acids between tissues, and maintain water homeostasis. Furthermore, emerging technologies have repurposed erythrocytes as drug-delivery vehicles, opening new avenues for therapeutic applications. This review highlights these recent discoveries and explores the expanding functional landscape of erythrocytes, shedding light on their multifaceted roles in physiology and medicine.

Hemorrhagic Shock and Mitochondria: Pathophysiology and Therapeutic Approaches

Severe injuries and some pathologies associated with massive bleeding, such as maternal hemorrhage, gastrointestinal and perioperative bleeding, and rupture of an aneurysm, often lead to major blood loss and the development of hemorrhagic shock. A sharp decrease in circulating blood volume triggers a vicious cycle of vasoconstriction and coagulopathy leading to ischemia of all internal organs and, in severe decompensated states, ischemia of the brain and heart. The basis of tissue damage and dysfunction in hemorrhagic shock is an interruption in the supply of oxygen and substrates for energy production to the cells, making the mitochondria a source and target of oxidative stress and proapoptotic signaling. Based on these mechanisms, different strategies are proposed to treat the multiple organ failure that occurs in shock. The main direction of such treatment is to provide the cells with a sufficient amount of substrates that utilize oxidative phosphorylation at different stages and increase the efficiency of energy production by the mitochondria. These strategies include restoring the efficiency of mitochondrial complexes, for example, by restoring the nicotinamide adenine dinucleotide (NAD) pool. Another direction is approaches to minimize oxidative stress as well as apoptosis, which are primarily dependent on the mitochondria. There are also a number of other methods to reduce mitochondrial dysfunction and improve the quality of the mitochondrial population. In this review, we consider such strategies for the treatment of hemorrhagic shock and show the promise of therapeutic approaches aimed at restoring the bioenergetic functions of the cell and protecting mitochondria.

Loss-of-function mitochondrial DNA polymerase gamma variants cause vascular smooth muscle cells to secrete a diffusible mitogenic factor

Introduction

Mitochondrial dysfunction promotes vascular aging and disease through diverse mechanisms beyond metabolic supply, including calcium and radical signaling and inflammation. Mitochondrial DNA (mtDNA) replication by the POLG-encoded mitochondrial DNA polymerase (POLG) is critical for mitochondrial health. Loss-of-function POLG variants are associated with a predisposition to hypertension. We hypothesized that impaired POLG, through reduced mtDNA copy number or other mechanisms, would promote smooth muscle hypertrophy or hyperplasia that drives vascular remodeling associated with hypertension.

Methods

We characterized the effect of over-expressing POLG variants that were previously observed in a cohort of hypertensive patients (p.Tyr955Cys, p.Arg964Cys, p.Asn1098Ile, and p.Arg1138Cys) in A7r5 cells.

Results

AlphaFold modeling of the POLG holoenzyme complexed with DNA predicted changes in the catalytic site in the p.Tyr955Cys and p.Asn1098Ile variants, while p.Arg964Cys and p.Arg1138Cys showed minimal effects. The POLG variants reduced mtDNA copy number, assessed by immunofluorescence and droplet digital PCR, by up to 27% in the order p.Tyr955Cys > p.Arg964Cys > p.Asn1098Ile > p.Arg1138Cys relative to wild-type-transfected cultures. Loss of mtDNA was reduced in cultures grown in low serum and glucose media, but the cell density was increased in the same rank order in both 10% serum and 1% serum. POLG constructs contained a Myc epitope, the counterstaining for which showed that the mtDNA copy number was reduced in both transfected cells and untransfected neighbors. Live-cell imaging of mitochondrial membrane potential with TMRM and radical oxygen species production with MitoSOX showed little effect of the POLG variants. POLG variants had little effect on oxygen consumption, assessed by Seahorse assay. Live-cell imaging growth analyses again showed increased growth in A7r5 cells transfected with p.Tyr955Cys but a decreased growth with p.Arg1138Cys, while p.Tyr955Cys increased growth of HeLa cells. Conditioned media from HeLa cells transfected with POLG variants reduced doubling times in naïve cultures. Pharmacologically, wedelolactone and MitoTEMPOL, but not indomethacin or PD98059, suppressed the mitogenic effects of p.Tyr955Cys and p.Arg964Cys in A7r5 cells.

Discussion

We conclude that POLG dysfunction induces secretion of a mitogenic signal from A7r5 and HeLa cells even when changes in mtDNA copy number are below the limit of detection. Such mitogenic stimulation could stimulate hypertrophic remodeling that could contribute to drug-resistant hypertension in patient populations with loss-of-function POLG variants.

Targeting Inflammation After Hemorrhagic Shock as a Molecular and Experimental Journey to Improve Outcomes: A Review

Hemorrhagic shock continues to be a major contributor to trauma-related fatalities globally, posing a significant and intricate pathophysiological challenge. The condition is marked by injury and blood loss, which activate molecular cascades that can quickly become harmful. The inflammatory response exhibits a biphasic pattern, beginning with a hyper-inflammatory phase that transitions into immunosuppression, posing significant obstacles to effective therapeutic interventions. This review article explores the intricate molecular mechanisms driving inflammation in hemorrhagic shock, emphasizing cellular signaling pathways, endothelial dysfunction, and immune activation. We discuss the role of molecular biomarkers in tracking disease progression and stratifying risk, with a focus on markers of endothelial dysfunction and inflammatory mediators as potential prognostic tools. Additionally, we assess therapeutic strategies, spanning traditional approaches like hemostatic resuscitation to advanced immunomodulatory treatments. Despite promising advancements in molecular monitoring and targeted therapies, challenges persist in bridging experimental findings with clinical applications. Future efforts must prioritize understanding the dynamic progression of inflammatory pathways and refining the timing of interventions to improve outcomes in hemorrhagic shock management.

Mitochondria break free: Mitochondria-derived vesicles in aging and associated conditions

Mitophagy is the intracellular recycling system that disposes damaged/inefficient mitochondria and allows biogenesis of new organelles to ensure mitochondrial quality is optimized. Dysfunctional mitophagy has been implicated in human aging and diseases. Multiple evolutionarily selected, redundant mechanisms of mitophagy have been identified, but their specific roles in human health and their potential exploitation as therapeutic targets are unclear. Recently, the characterization of the endosomal-lysosomal system has revealed additional mechanisms of mitophagy and mitochondrial quality control that operate via the production of mitochondria-derived vesicles (MDVs). Circulating MDVs can be isolated and characterized to provide an unprecedented opportunity to study this type of mitochondrial recycling in vivo and to relate it to human physiology and pathology. Defining the role of MDVs in human physiology, pathology, and aging is hampered by the lack of standardized methods to isolate, validate, and characterize these vesicles. Hence, some basic questions about MDVs remain unanswered. While MDVs are generated directly through the extrusion of mitochondrial membranes within the cell, a set of circulating extracellular vesicles leaking from the endosomal-lysosomal system and containing mitochondrial portions have also been identified and warrant investigation. Preliminary research indicates that MDV generation serves multiple biological roles and contributes to restoring cell homeostasis. However, studies have shown that MDVs may also be involved in pathological conditions. Therefore, further research is warranted to establish when/whether MDVs are supporting disease progression and/or are extracting damaged mitochondrial components to alleviate cellular oxidative burden and restore redox homeoastasis. This information will be relevant for exploiting these vesicles for therapeutic purpose. Herein, we provide an overview of preclinical and clinical studies on MDVs in aging and associated conditions and discuss the interplay between MDVs and some of the hallmarks of aging (mitophagy, inflammation, and proteostasis). We also outline open questions on MDV research that should be prioritized by future investigations.

Oxidative Injury to Lung Mitochondrial DNA is a Key Contributor for the Development of Chemical Lung Injury

The mechanisms and extent to which inhalation of oxidant gases damage the mitochondrial genome contributing to the development of acute and chronic lung injury have not been investigated. C57BL/6 mice exposed to chlorine (Cl 2 ) gas and returned to room air, developed progressive loss of lung DNA glycosylase OGG1, significant oxidative injury to mtDNA, decreased intact lung mitochondrial (mt) DNA, generation of inflammatory pathway by DAMPs causing airway and alveolar injury with significant mortality. Global proteomics identified over 1400 lung proteins with alteration of key mitochondrial proteins at 24 h post Cl 2 exposure. Intranasal instillation of a recombinant protein containing mitochondrial targeted OGG1 (mitoOGG1) post exposure, decreased oxidative injury to mtDNA, lung mitochondrial proteome, severity of the acute and chronic lung injury and increased survival. These data show that injury to the mt-genome is a key contributor to the development of acute and chronic lung injury.

Correlation between circulating cell-free mitochondrial DNA content and severity of knee degeneration in patients with knee osteoarthritis: a cross-sectional study

BACKGROUND

Knee osteoarthritis (KOA) is characterized by mitochondrial damage and increased inflammation. Circulating cell-free mitochondrial DNA (ccf-mtDNA), which originates from damaged mitochondria, is an endogenous damage-associated molecular pattern (DAMPs) molecule that may trigger inflammation and is recognized as a potential biomarker for various diseases. In this study, we investigated the potential association between plasma ccf-mtDNA content and its use as a diagnostic biomarker in patients with KOA.

METHODS

We collected plasma samples from patients with KOA and healthy controls (HC). Subsequently, quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect ccf-mtDNA content in the plasma samples. We used the Kellgren-Lawrence (K-L) classification criteria to classify patients with KOA into four grades: I-IV. Disease severity in patients with KOA was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Next, Spearman analysis was performed to observe the correlation between ccf-mtDNA content and the K-L classification and WOMAC score. Logistic regression analysis was used to evaluate the relationship between ccf-mtDNA and KOA risk.

RESULTS

In total, we enrolled 60 patients with KOA and HC who were matched for age, sex, and body mass index (BMI). We found that plasma ccf-mtDNA contents were significantly higher in patients with KOA (median, 2.44; quartile range, 1.10-3.79) than in HC (median, 1.08; quartile range, 0.52-2.12) (P < 0.0001). Plasma ccf-mtDNA content sequentially increased following the KOA class I-IV group (P = 0.040) and positively correlated with the K-L classification (r = 0.369, P = 0.004) and WOMAC scores (r = 0.343, P = 0.007). The ccf-mtDNA content did not significantly differ between patients with bilateral and those with single KOA (P = 0.083). Patients with high levels of ccf-mtDNA had a significantly increased risk of KOA compared with those with low levels of ccf-mtDNA (odds ratio [OR], 4.15, 95% confidence interval [CI], 1.71-10.07; P = 0.002). Quartile analysis revealed a significant dose-dependent association (P trend < 0.001).

CONCLUSION

Our study's findings showed that plasma ccf-mtDNA was highly expressed in patients with KOA compared with HC. Furthermore, ccf-mtDNA content is significantly associated with the severity and risk of KOA. Therefore, its detection may provide insight into the prevention and treatment of KOA.

Serum mitochondrial-encoded NADH dehydrogenase 6 and Annexin A1 as novel biomarkers for mortality prediction in critically ill patients with sepsis

Objectives

Formyl peptide receptor 1 (FPR1) is a member of G protein-coupled receptor (GPCR) family that detects potentially danger signals characterized by the appearance of N-formylated peptides which originate from either bacteria or host mitochondria during organ injury, including sepsis. Mitochondrial-encoded NADH dehydrogenase 6 (MT-ND6) and Annexin A1 (ANXA1), as mitochondrial damage-associated molecular patterns (mtDAMPs) agonist and endogenous agonist of FPR1 respectively, interact with FPR1 regulating polymorphonuclear leukocytes (PMNs) function and inflammatory response during sepsis. However, there is no direct evidence of MT-ND6 or ANXA1 in the circulation of patients with sepsis and their potential role in clinical significance, including diagnosis and mortality prediction during sepsis.

Methods

A prospective cohort study was conducted in ICU within a large academic hospital. We measured serum MT-ND6 or ANXA1 in a cohort of patients with sepsis in ICU (n=180) and patients with non-sepsis in ICU (n=60) by Enzyme-linked immunosorbent assays (ELISA). The ROC curve and Kaplan Meier analysis was used to evaluate the diagnostic and prognostic ability of two biomarkers for patients with sepsis.

Results

The concentration of MT-ND6 and ANXA1 were significantly elevated in the patients with sepsis, and the diagnostic values of MT-ND6 (0.789) for sepsis patients was second only to SOFA scores (AUC = 0.870). Higher serum concentrations of MT-ND6 (>1.41 ng/ml) and lower concentrations of ANXA1 (< 8.09 ng/mL) were closely related to the higher mortality in patients with sepsis, with the predictive values were 0.705 and 0.694, respectively. When patients with sepsis classified based on four pro-inflammation and two anti-inflammation cytokines, it was shown that combination of MT-ND6 and ANXA1 obviously improved the predictive values in the septic patients with mixed hyperinflammation or immunosuppression phenotypes.

Conclusion

Our findings provide valuable models testing patient risk prediction and strengthen the evidence for agonists of FPR1, MT-ND6 and ANXA1, as novel biomarker for patient selection for novel therapeutic agents to target mtDAMPs and regulator of GPCRs in sepsis.

Molecular basis of sepsis: A New insight into the role of mitochondrial DNA as a damage-associated molecular pattern

Sepsis remains a critical challenge in the field of medicine, claiming countless lives each year. Despite significant advances in medical science, the molecular mechanisms underlying sepsis pathogenesis remain elusive. Understanding molecular sequelae is gaining deeper insights into the roles played by various damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) in disease pathogenesis. Among the known DAMPs, circulating cell-free mitochondrial DNA (mtDNA) garners increasing attention as a key player in the immune response during sepsis and other diseases. Mounting evidence highlights numerous connections between circulating cell-free mtDNA and inflammation, a pivotal state of sepsis, characterized by heightened inflammatory activity. In this review, we aim to provide an overview of the molecular basis of sepsis, particularly emphasizing the role of circulating cell-free mtDNA as a DAMP. We discuss the mechanisms of mtDNA release, its interaction with pattern recognition receptors (PRRs), and the subsequent immunological responses that contribute to sepsis progression. Furthermore, we discuss the forms of cell-free mtDNA; detection techniques of circulating cell-free mtDNA in various biological fluids; and the diagnostic, prognostic, and therapeutic implications offering insights into the potential for innovative interventions in sepsis management.

Monocytes perturbation implicated in the association of stress hyperglycemia with postoperative poor prognosis in non-diabetic patients with Stanford type-A acute aortic dissection

OBJECTIVES

The study aimed to investigate the interaction of intraoperative stress hyperglycemia with monocyte functions and their impact on major adverse events (MAEs) in acute aortic dissection (AAD) patients who underwent open repair surgery.

METHODS

A total of 321 adults who underwent open surgery for AAD at two tertiary medical centers in China were enrolled in the study. The primary endpoint was defined as the incidence and characteristics of perioperative stress hyperglycemia. The secondary endpoints included the incidence of postoperative MAEs, postoperative monocyte counts and inflammatory cytokine expression. Multi-logistic, linear regression and receiver operating characteristic (ROC) curve analyses were used to establish relationships between intraoperative time-weighted average glucose (TWAG), day-one postoperative monocyte counts, serum inflammatory cytokines and postoperative outcomes. In addition, in vitro experiments were conducted to evaluate changes in the inflammatory features of monocytes under high glucose conditions.

RESULTS

Intraoperative hyperglycemia, as indicated by a TWAG level over 142 mg/dL, was associated with elevated postoperative monocyte counts and inflammatory cytokines, which correlated with extended intensive care unit (ICU) stays and worsened outcomes. In vitro, high glucose treatment induced mitochondrial impairment in monocytes, increased the release of inflammatory cytokines and the proportion of classical monocytes from AAD patients.

CONCLUSIONS

Intraoperative stress hyperglycemia, in combination with day-one postoperative monocyte counts, were clinically significant for predicting adverse outcomes in AAD patients undergoing open repair surgery. Elevated glucose concentrations shaped the inflammatory features of monocytes in AAD by impairing mitochondrial functions.

Deleterious effects of plasma-derived cellular debris in a porcine model of hemorrhagic shock

BACKGROUND

Recent studies identify large quantities of inflammatory cellular debris within Fresh Frozen Plasma (FFP). As FFP is a mainstay of hemorrhagic shock resuscitation, we used a porcine model of hemorrhagic shock and ischemia/reperfusion to investigate the inflammatory potential of plasma-derived cellular debris administered during resuscitation.

METHODS

The porcine model of hemorrhagic shock included laparotomy with 35 % hemorrhage (Hem), 45 min of ischemia from supraceliac aortic occlusion with subsequent clamp release (IR), followed by protocolized resuscitation for 6 h. Cellular debris (Debris) was added to the resuscitation phase in three groups. The four groups consisted of Hem + IR (n = 4), Hem + IR + Debris (n = 3), Hem + Debris (n = 3), and IR + Debris (n = 3). A battery of laboratory, physiologic, cytokine, and outcome data were compared between groups.

RESULTS

As expected, the Hem + IR group showed severe time dependent decrements in organ function and physiologic parameters. All animals that included both IR and Debris (Hem + IR + Debris or IR + Debris) died prior to the six-hour end point, while all animals in the Hem + IR and Hem + Debris survived. Cytokines measured at 30-60 min after initiation of resuscitation revealed significant differences in IL-18 and IL-1β between all groups.

CONCLUSIONS

Ischemia and reperfusion appear to prime the immune system to the deleterious effects of plasma-derived cellular debris. In the presence of ischemia and reperfusion, this model showed the equivalency of 100 % lethality when resuscitation included quantities of cellular debris at levels routinely administered to trauma patients during transfusion of FFP. A deeper understanding of the immunobiology of FFP-derived cellular debris is critical to optimize resuscitation for hemorrhagic shock.

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.

Mitochondrial DNA levels in perfusate and bile during ex vivo normothermic machine correspond with donor liver quality

Ex vivo normothermic machine perfusion (NMP) preserves donor organs and permits real-time assessment of allograft health, but the most effective indicators of graft viability are uncertain. Mitochondrial DNA (mtDNA), released consequent to traumatic cell injury and death, including the ischemia-reperfusion injury inherent in transplantation, may meet the need for a biomarker in this context. We describe a real time PCR-based approach to assess cell-free mtDNA during NMP as a universal biomarker of allograft quality. Measured in the perfusate fluid of 29 livers, the quantity of mtDNA correlated with metrics of donor liver health including International Normalized Ratio (INR), lactate, and warm ischemia time, and inversely correlated with inferior vena cava (IVC) flow during perfusion. Our findings endorse mtDNA as a simple and rapidly measured feature that can inform donor liver health, opening the possibility to better assess livers acquired from extended criteria donors to improve organ supply.

Apoptosis dysfunction: unravelling the interplay between ZBP1 activation and viral invasion in innate immune responses

Apoptosis plays a pivotal role in pathogen elimination and maintaining homeostasis. However, viruses have evolved strategies to evade apoptosis, enabling their persistence within the host. Z-DNA binding protein 1 (ZBP1) is a potent innate immune sensor that detects cytoplasmic nucleic acids and activates the innate immune response to clear pathogens. When apoptosis is inhibited by viral invasion, ZBP1 can be activated to compensate for the effect of apoptosis by triggering an innate immune response. This review examined the mechanisms of apoptosis inhibition and ZBP1 activation during viral invasion. The authors outlined the mechanisms of ZBP1-induced type I interferon, pyroptosis and necroptosis, as well as the crosstalk between ZBP1 and the cGAS-STING signalling pathway. Furthermore, ZBP1 can reverse the suppression of apoptotic signals induced by viruses. Intriguingly, a positive feedback loop exists in the ZBP1 signalling pathway, which intensifies the innate immune response while triggering a cytokine storm, leading to tissue and organ damage. The prudent use of ZBP1, which is a double-edged sword, has significant clinical implications for treating infections and inflammation.

Self-DNA driven inflammation in COVID-19 and after mRNA-based vaccination: lessons for non-COVID-19 pathologies

The coronavirus disease 2019 (COVID-19) pandemic triggered an unprecedented concentration of economic and research efforts to generate knowledge at unequalled speed on deregulated interferon type I signalling and nuclear factor kappa light chain enhancer in B-cells (NF-κB)-driven interleukin (IL)-1β, IL-6, IL-18 secretion causing cytokine storms. The translation of the knowledge on how the resulting systemic inflammation can lead to life-threatening complications into novel treatments and vaccine technologies is underway. Nevertheless, previously existing knowledge on the role of cytoplasmatic or circulating self-DNA as a pro-inflammatory damage-associated molecular pattern (DAMP) was largely ignored. Pathologies reported 'de novo' for patients infected with Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)-2 to be outcomes of self-DNA-driven inflammation in fact had been linked earlier to self-DNA in different contexts, e.g., the infection with Human Immunodeficiency Virus (HIV)-1, sterile inflammation, and autoimmune diseases. I highlight particularly how synergies with other DAMPs can render immunogenic properties to normally non-immunogenic extracellular self-DNA, and I discuss the shared features of the gp41 unit of the HIV-1 envelope protein and the SARS-CoV 2 Spike protein that enable HIV-1 and SARS-CoV-2 to interact with cell or nuclear membranes, trigger syncytia formation, inflict damage to their host's DNA, and trigger inflammation - likely for their own benefit. These similarities motivate speculations that similar mechanisms to those driven by gp41 can explain how inflammatory self-DNA contributes to some of most frequent adverse events after vaccination with the BNT162b2 mRNA (Pfizer/BioNTech) or the mRNA-1273 (Moderna) vaccine, i.e., myocarditis, herpes zoster, rheumatoid arthritis, autoimmune nephritis or hepatitis, new-onset systemic lupus erythematosus, and flare-ups of psoriasis or lupus. The hope is to motivate a wider application of the lessons learned from the experiences with COVID-19 and the new mRNA vaccines to combat future non-COVID-19 diseases.

Trauma-induced innate immune activation and disseminated intravascular coagulation

Dysregulated innate immunity participates in the pathomechanisms of disseminated intravascular coagulation (DIC) in trauma-induced coagulopathy. Accidental and regulated cell deaths and neutrophil extracellular traps release damage-associated molecular patterns (DAMPs), such as histones, nuclear and mitochondrial DNA, and high-mobility group box 1, into circulation immediately after trauma. DAMP-induced inflammation activation releases tissue factor-bearing procoagulant extracellular vesicles through gasdermin D-mediated pore formation and plasma membrane rupture by regulated cell death. DAMPs also evoke systemic inflammation, platelet, coagulation activation, and impaired fibrinolysis associated with endothelial injury, leading to the dysfunction of anticoagulation systems, which are the main pathophysiological mechanisms of DIC. All these processes induce systemic thrombin generation in vivo, not restricted to the injury sites immediately after trauma. Thrombin generation at the site of injury stops bleeding and maintains homeostasis. However, DIC associated with endothelial injury generates massive thrombin, enhancing protease-activated, receptor-mediated bidirectional interplays between inflammation and coagulation, aggravating the diverse actions of thrombin and disturbing homeostasis. Insufficiently regulated thrombin causes disseminated microvascular thrombosis, resulting in tissue hypoxia due to reduced oxygen delivery, and mitochondrial dysfunction due to DAMPs causes tissue dysoxia. In addition, DAMP-induced calcium influx and overload, as well as neutrophil activation, play a role in endothelial cell injury. Tissue hypoxia and cytotoxicity result in multiple organ dysfunction in DIC after trauma. Controls against dysregulated innate immunity evoking systemic inflammation, thrombin generation, and cytotoxicity are key issues in improving the prognosis of DIC in trauma-induced coagulopathy.

Restoring the infected powerhouse: Mitochondrial quality control in sepsis

Sepsis is a dysregulated host response to an infection, characterized by organ failure. The pathophysiology is complex and incompletely understood, but mitochondria appear to play a key role in the cascade of events that culminate in multiple organ failure and potentially death. In shaping immune responses, mitochondria fulfil dual roles: they not only supply energy and metabolic intermediates crucial for immune cell activation and function but also influence inflammatory and cell death pathways. Importantly, mitochondrial dysfunction has a dual impact, compromising both immune system efficiency and the metabolic stability of end organs. Dysfunctional mitochondria contribute to the development of a hyperinflammatory state and loss of cellular homeostasis, resulting in poor clinical outcomes. Already in early sepsis, signs of mitochondrial dysfunction are apparent and consequently, strategies to optimize mitochondrial function in sepsis should not only prevent the occurrence of mitochondrial dysfunction, but also cover the repair of the sustained mitochondrial damage. Here, we discuss mitochondrial quality control (mtQC) in the pathogenesis of sepsis and exemplify how mtQC could serve as therapeutic target to overcome mitochondrial dysfunction. Hence, replacing or repairing dysfunctional mitochondria may contribute to the recovery of organ function in sepsis. Mitochondrial biogenesis is a process that results in the formation of new mitochondria and is critical for maintaining a pool of healthy mitochondria. However, exacerbated biogenesis during early sepsis can result in accumulation of structurally aberrant mitochondria that fail to restore bioenergetics, produce excess reactive oxygen species (ROS) and exacerbate the disease course. Conversely, enhancing mitophagy can protect against organ damage by limiting the release of mitochondrial-derived damage-associated molecules (DAMPs). Furthermore, promoting mitophagy may facilitate the growth of healthy mitochondria by blocking the replication of damaged mitochondria and allow for post sepsis organ recovery through enabling mitophagy-coupled biogenesis. The remaining healthy mitochondria may provide an undamaged scaffold to reproduce functional mitochondria. However, the kinetics of mtQC in sepsis, specifically mitophagy, and the optimal timing for intervention remain poorly understood. This review emphasizes the importance of integrating mitophagy induction with mtQC mechanisms to prevent undesired effects associated with solely the induction of mitochondrial biogenesis.

DANGER Signals Activate G -Protein Receptor Kinases Suppressing Neutrophil Function and Predisposing to Infection After Tissue Trauma

OBJECTIVE

Injured tissue predisposes the subject to local and systemic infection. We studied injury-induced immune dysfunction seeking novel means to reverse such predisposition.

BACKGROUND

Injury mobilizes primitive "DANGER signals" [danger-associated molecular patterns (DAMPs)] activating innate immunocyte (neutrophils, PMN) signaling and function. Mitochondrial formyl peptides activate G -protein coupled receptors (GPCR) like formyl peptide receptor-1. Mitochondrial DNA and heme activate toll-like receptors (TLR9 and TLR2/4). GPCR kinases (GRKs) can regulate GPCR activation.

METHODS

We studied human and mouse PMN signaling elicited by mitochondrial DAMPs (GPCR surface expression; protein phosphorylation, or acetylation; Ca 2+ flux) and antimicrobial functions [cytoskeletal reorganization, chemotaxis (CTX), phagocytosis, bacterial killing] in cellular systems and clinical injury samples. Predicted rescue therapies were assessed in cell systems and mouse injury-dependent pneumonia models.

RESULTS

Mitochondrial formyl peptides activate GRK2, internalizing GPCRs and suppressing CTX. Mitochondrial DNA suppresses CTX, phagocytosis, and killing through TLR9 through a novel noncanonical mechanism that lacks GPCR endocytosis. Heme also activates GRK2. GRK2 inhibitors like paroxetine restore functions. GRK2 activation through TLR9 prevented actin reorganization, implicating histone deacetylases (HDACs). Actin polymerization, CTX, bacterial phagocytosis, and killing were also rescued, therefore, by the HDAC inhibitor valproate. Trauma repository PMN showed GRK2 activation and cortactin deacetylation, which varied with severity and was most marked in patients developing infections. Either GRK2 or HDAC inhibition prevented loss of mouse lung bacterial clearance, but only the combination rescued clearance when given postinjury.

CONCLUSIONS

Tissue injury-derived DAMPs suppress antimicrobial immunity through canonical GRK2 activation and a novel TLR-activated GRK2-pathway impairing cytoskeletal organization. Simultaneous GRK2/HDAC inhibition rescues susceptibility to infection after tissue injury.

Surviving Sepsis After Burn Campaign

INTRODUCTION

The Surviving Sepsis Campaign was developed to improve outcomes for all patients with sepsis. Despite sepsis being the primary cause of death after thermal injury, burns have always been excluded from the Surviving Sepsis efforts. To improve sepsis outcomes in burn patients, an international group of burn experts developed the Surviving Sepsis After Burn Campaign (SSABC) as a testable guideline to improve burn sepsis outcomes.

METHODS

The International Society for Burn Injuries (ISBI) reached out to regional or national burn organizations to recommend members to participate in the program. Two members of the ISBI developed specific "patient/population, intervention, comparison and outcome" (PICO) questions that paralleled the 2021 Surviving Sepsis Campaign [1]. SSABC participants were asked to search the current literature and rate its quality for each topic. At the Congress of the ISBI, in Guadalajara, Mexico, August 28, 2022, a majority of the participants met to create "statements" based on the literature. The "summary statements" were then sent to all members for comment with the hope of developing an 80% consensus. After four reviews, a consensus statement for each topic was created or "no consensus" was reported.

RESULTS

The committee developed sixty statements within fourteen topics that provide guidance for the early treatment of sepsis in burn patients. These statements should be used to improve the care of sepsis in burn patients. The statements should not be considered as "static" comments but should rather be used as guidelines for future testing of the best treatments for sepsis in burn patients. They should be updated on a regular basis.

CONCLUSION

Members of the burn community from the around the world have developed the Surviving Sepsis After Burn Campaign guidelines with the goal of improving the outcome of sepsis in burn patients.

Plasma Exosome Hemoglobin Released During Surgery Is Associated With Cardiac Injury in Animal Model

BACKGROUND

Patients with valvular heart disease require cardiopulmonary bypass and cardiac arrest. Here, we test the hypothesis that exosomal hemoglobin formed during cardiopulmonary bypass mediates acute cardiac injury in humans and in an animal model system.

METHODS

Plasma exosomes were collected from arterial blood at baseline and 30 minutes after aortic cross-clamp release in 20 patients with primary mitral regurgitation and 7 with aortic stenosis. These exosomes were injected into Sprague-Dawley rats and studied at multiple times up to 30 days. Tissue was examined by hematoxylin and eosin stain, immunohistochemistry, transmission electron microscopy, and brain natriuretic peptide.

RESULTS

Troponin I levels increased from 36 ± 88 ng/L to 3622 ± 3054 ng/L and correlated with exosome hemoglobin content (Spearman r = 0.7136, < .0001, n = 24). Injection of exosomes isolated 30 minutes after cross-clamp release into Sprague-Dawley rats resulted in cardiomyocyte myofibrillar loss at 3 days. Transmission electron microscopy demonstrated accumulation of electron dense particles of ferritin within cardiomyocytes, in the interstitial space, and within exosomes. At 21 days after injection, there was myofibrillar and myosin breakdown, interstitial fibrosis, elevated brain natriuretic peptide, and left ventricle diastolic dysfunction measured by echocardiography/Doppler. Pericardial fluid exosomal hemoglobin content is fourfold higher than simultaneous plasma exosome hemoglobin, suggesting a cardiac source of exosomal hemoglobin.

CONCLUSIONS

Red blood cell and cardiac-derived exosomal hemoglobin may be involved in myocardial injury during cardiopulmonary bypass in patients with valvular heart disease.

The Diagnostic, Prognostic, and Therapeutic Potential of Cell-Free DNA with a Special Focus on COVID-19 and Other Viral Infections

Cell-free DNA (cfDNA) in human blood serum, urine, and other body fluids recently became a commonly used diagnostic marker associated with various pathologies. This is because cfDNA enables a much higher sensitivity than standard biochemical parameters. The presence of and/or increased level of cfDNA has been reported for various diseases, including viral infections, including COVID-19. Here, we review cfDNA in general, how it has been identified, where it can derive from, its molecular features, and mechanisms of release and clearance. General suitability of cfDNA for diagnostic questions, possible shortcomings and future directions are discussed, with a special focus on coronavirus infection.

Effect of Bariatric Surgery on Plasma Cell-Free Mitochondrial DNA, Insulin Sensitivity and Metabolic Changes in Obese Patients

While improvement of mitochondrial function after bariatric surgery has been demonstrated, there is limited evidence about the effects of bariatric surgery on circulatory cell-free (cf) mitochondrial DNA (mtDNA) and intracellular mtDNA abundance. Plasma and peripheral blood mononuclear (PBM) cells were isolated from healthy controls (HC) and bariatric surgery patients before surgery and 2 weeks, 3 months, and 6 months after surgery. At baseline, the plasma level of short cf-mtDNA (ND6, ~100 bp) fragments was significantly higher in obese patients compared to HC. But there was no significant variation in mean ND6 values post-surgery. A significant positive correlation was observed between preop plasma ND6 levels and HgbA1c, ND6 and HOMA-IR 2 weeks post-surgery, and mtDNA content 6 months post-surgery. Interestingly, plasma from both HC and obese groups at all time points post-surgery contains long (~8 kb) cf-mtDNA fragments, suggesting the presence of near-intact and/or whole mitochondrial genomes. No significant variation was observed in mtDNA content post-surgery compared to baseline data in both PBM and skeletal muscle samples. Overall, bariatric surgery improved insulin sensitivity and other metabolic parameters without significant changes in plasma short cf-mtDNA levels or cellular mtDNA content. Our study provides novel insights about possible molecular mechanisms underlying the metabolic effects of bariatric surgery and suggests the development of new generalized approaches to characterize cf-mtDNA.

Mitochondrial-Derived Vesicles: The Good, the Bad, and the Ugly

Mitophagy is crucial for maintaining mitochondrial quality. However, its assessment in vivo is challenging. The endosomal-lysosomal system is a more accessible pathway through which subtypes of extracellular vesicles (EVs), which also contain mitochondrial constituents, are released for disposal. The inclusion of mitochondrial components into EVs occurs in the setting of mild mitochondrial damage and during impairment of lysosomal function. By releasing mitochondrial-derived vesicles (MDVs), cells limit the unload of mitochondrial damage-associated molecular patterns with proinflammatory activity. Both positive and negative effects of EVs on recipient cells have been described. Whether this is due to the production of EVs other than those containing mitochondria, such as MDVs, holding specific biological functions is currently unknown. Evidence on the existence of different MDV subtypes has been produced. However, their characterization is not always pursued, which would be relevant to exploring the dynamics of mitochondrial quality control in health and disease. Furthermore, MDV classification may be instrumental in understanding their biological roles and promoting their implementation as biomarkers in clinical studies.

The immune suppressive properties of damage associated molecular patterns in the setting of sterile traumatic injury

Associated with the development of hospital-acquired infections, major traumatic injury results in an immediate and persistent state of systemic immunosuppression, yet the underlying mechanisms are poorly understood. Detected in the circulation in the minutes, days and weeks following injury, damage associated molecular patterns (DAMPs) are a heterogeneous collection of proteins, lipids and DNA renowned for initiating the systemic inflammatory response syndrome. Suggesting additional immunomodulatory roles in the post-trauma immune response, data are emerging implicating DAMPs as potential mediators of post-trauma immune suppression. Discussing the results of in vitro, in vivo and ex vivo studies, the purpose of this review is to summarise the emerging immune tolerising properties of cytosolic, nuclear and mitochondrial-derived DAMPs. Direct inhibition of neutrophil antimicrobial activities, the induction of endotoxin tolerance in monocytes and macrophages, and the recruitment, activation and expansion of myeloid derived suppressor cells and regulatory T cells are examples of some of the immune suppressive properties assigned to DAMPs so far. Crucially, with studies identifying the molecular mechanisms by which DAMPs promote immune suppression, therapeutic strategies that prevent and/or reverse DAMP-induced immunosuppression have been proposed. Approaches currently under consideration include the use of synthetic polymers, or the delivery of plasma proteins, to scavenge circulating DAMPs, or to treat critically-injured patients with antagonists of DAMP receptors. However, as DAMPs share signalling pathways with pathogen associated molecular patterns, and pro-inflammatory responses are essential for tissue regeneration, these approaches need to be carefully considered in order to ensure that modulating DAMP levels and/or their interaction with immune cells does not negatively impact upon anti-microbial defence and the physiological responses of tissue repair and wound healing.

Advancements in understanding the role of microRnas in regulating macrophage polarization during acute lung injury

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a critical and life-threatening illness that causes severe dyspnea, and respiratory distress and is often caused by a variety of direct or indirect factors that damage the alveolar epithelium and capillary endothelial cells, leading to inflammation factors and macrophage infiltration. Macrophages play a crucial role in the progression of ALI/ARDS, exhibiting different polarized forms at different stages of the disease that control the disease outcome. MicroRNAs (miRNA) are conserved, endogenous, short non-coding RNAs composed of 18-25 nucleotides that serve as potential markers for many diseases and are involved in various biological processes, including cell proliferation, apoptosis, and differentiation. In this review, we provide a brief overview of miRNA expression in ALI/ARDS and summarize recent research on the mechanism and pathways by which miRNAs respond to macrophage polarization, inflammation, and apoptosis. The characteristics of each pathway are also summarized to provide a comprehensive understanding of the role of miRNAs in regulating macrophage polarization during ALI/ARDS.

Mitochondrial DNA Release in Innate Immune Signaling

According to the endosymbiotic theory, most of the DNA of the original bacterial endosymbiont has been lost or transferred to the nucleus, leaving a much smaller (∼16 kb in mammals), circular molecule that is the present-day mitochondrial DNA (mtDNA). The ability of mtDNA to escape mitochondria and integrate into the nuclear genome was discovered in budding yeast, along with genes that regulate this process. Mitochondria have emerged as key regulators of innate immunity, and it is now recognized that mtDNA released into the cytoplasm, outside of the cell, or into circulation activates multiple innate immune signaling pathways. Here, we first review the mechanisms through which mtDNA is released into the cytoplasm, including several inducible mitochondrial pores and defective mitophagy or autophagy. Next, we cover how the different forms of released mtDNA activate specific innate immune nucleic acid sensors and inflammasomes. Finally, we discuss how intracellular and extracellular mtDNA release, including circulating cell-free mtDNA that promotes systemic inflammation, are implicated in human diseases, bacterial and viral infections, senescence and aging.

Identification and experimental validation of mitochondria-related genes biomarkers associated with immune infiltration for sepsis

Background

Sepsis remains a complex condition with incomplete understanding of its pathogenesis. Further research is needed to identify prognostic factors, risk stratification tools, and effective diagnostic and therapeutic targets.

Methods

Three GEO datasets (GSE54514, GSE65682, and GSE95233) were used to explore the potential role of mitochondria-related genes (MiRGs) in sepsis. WGCNA and two machine learning algorithms (RF and LASSO) were used to identify the feature of MiRGs. Consensus clustering was subsequently carried out to determine the molecular subtypes for sepsis. CIBERSORT algorithm was conducted to assess the immune cell infiltration of samples. A nomogram was also established to evaluate the diagnostic ability of feature biomarkers via "rms" package.

Results

Three different expressed MiRGs (DE-MiRGs) were identified as sepsis biomarkers. A significant difference in the immune microenvironment landscape was observed between healthy controls and sepsis patients. Among the DE-MiRGs, NDUFB3 was selected to be a potential therapeutic target and its significant elevated expression level was confirmed in sepsis using in vitro experiments and confocal microscopy, indicating its significant contribution to the mitochondrial quality imbalance in the LPS-simulated sepsis model.

Conclusion

By digging the role of these pivotal genes in immune cell infiltration, we gained a better understanding of the molecular immune mechanism in sepsis and identified potential intervention and treatment strategies.

Mitochondria-derived vesicles and their potential roles in kidney stone disease

Recent evidence has shown significant roles of mitochondria-derived vesicles (MDVs) in mitochondrial quality control (MQC) system. Under mild stress condition, MDVs are formed to carry the malfunctioned mitochondrial components, such as mitochondrial DNA (mtDNA), peptides, proteins and lipids, to be eliminated to restore normal mitochondrial structure and functions. Under severe oxidative stress condition, mitochondrial dynamics (fission/fusion) and mitophagy are predominantly activated to rescue mitochondrial structure and functions. Additionally, MDVs generation can be also triggered as the major MQC machinery to cope with unhealthy mitochondria when mitophagy is unsuccessful for eliminating the damaged mitochondria or mitochondrial fission/fusion fail to recover the mitochondrial structure and functions. This review summarizes the current knowledge on MDVs and discuss their roles in physiologic and pathophysiologic conditions. In addition, the potential clinical relevance of MDVs in therapeutics and diagnostics of kidney stone disease (KSD) are emphasized.

ROLE OF PEPTIDYLARGININE DEIMINASE AND NEUTROPHIL EXTRACELLULAR TRAPS IN INJURIES: FUTURE NOVEL DIAGNOSTICS AND THERAPEUTIC TARGETS

ABSTRACT

Injuries lead to an early systemic inflammatory state with innate immune system activation. Neutrophil extracellular traps (NETs) are a complex of chromatin and proteins released from the activated neutrophils. Although initially described as a response to bacterial infections, NETs have also been identified in the sterile postinjury inflammatory state. Peptidylarginine deiminases (PADs) are a group of isoenzymes that catalyze the conversion of arginine to citrulline, termed citrullination or deimination. PAD2 and PAD4 have been demonstrated to play a role in NET formation through citrullinated histone 3. PAD2 and PAD4 have a variety of substrates with variable organ distribution. Preclinical and clinical studies have evaluated the role of PADs and NETs in major trauma, hemorrhage, burns, and traumatic brain injury. Neutrophil extracellular trap formation and PAD activation have been shown to contribute to the postinjury inflammatory state leading to a detrimental effect on organ systems. This review describes our current understanding of the role of PAD and NET formation following injury and burn. This is a new field of study, and the emerging data appear promising for the future development of targeted biomarkers and therapies in trauma.

Circulating mitochondrial DNA is associated with anemia in newly diagnosed hematologic malignancies

Recent reports discovered that red blood cells (RBCs) could scavenge cell-free mitochondrial DNA (mtDNA), which drives the accelerated erythrophagocytosis and innate immune activation characterized by anemia and inflammatory cytokine production. However, the clinical value of the circulating mtDNA copy number alterations in hematologic malignancies is poorly understood. Our data showed that in comparison to healthy group, the patients group had significantly higher mtDNA and histone H4 levels. Moreover, we observed that RBC-bound mtDNA and histone H4 were negatively correlated with hemoglobin in patients. In addition, cytokines and chemokines levels in patients differed significantly from normal controls (21 higher, 7 lower). Our study suggested that both circulating mtDNA and histone H4 were associated with anemia in hematologic malignancies, which helps to further understand the potential mechanism of anemia development in patients with hematologic malignancies. This information may play a vital role in the specific therapeutic interventions for leukemia in the future.

Mitochondrial reactivity following acute exposure to experimental pain testing in people with HIV and chronic pain

Background: Physical stressors can cause a physiological response that can contribute to an increase in mitochondrial dysfunction and Mitochondrial DNA damage (mtDNA damage). People living with HIV (PWH) are more likely to suffer from chronic pain and may be more susceptible to mitochondrial dysfunction following exposure to a stressor. We used Quantitative Sensory Testing (QST) as an acute painful stressor in order to investigate whether PWH with/without chronic pain show differential mitochondrial physiological responses. Methods: The current study included PWH with (n = 26), and without (n = 29), chronic pain. Participants completed a single session that lasted approximately 180 min, including QST. Blood was taken prior to and following the QST battery for assays measuring mtDNA damage, mtDNA copy number, and mtDNA damage-associated molecular pattern (DAMP) levels (i.e., ND1 and ND6). Results: We examined differences between those with and without pain on various indicators of mitochondrial reactivity following exposure to QST. However, only ND6 and mtDNA damage were shown to be statistically significant between pain groups. Conclusion: PWH with chronic pain showed greater mitochondrial reactivity to laboratory stressors. Consequently, PWH and chronic pain may be more susceptible to conditions in which mitochondrial damage/dysfunction play a central role, such as cognitive decline.

T-Cell Mediated Immunity in Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and frequently lethal skin cancer with neuroendocrine characteristics. MCC can originate from either the presence of MCC polyomavirus (MCPyV) DNA or chronic ultraviolet (UV) exposure that can cause DNA mutations. MCC is predominant in sun-exposed regions of the body and can metastasize to regional lymph nodes, liver, lungs, bone, and brain. Older, light-skinned individuals with a history of significant sun exposure are at the highest risk. Previous studies have shown that tumors containing a high number of tumor-infiltrating T-cells have favorable survival, even in the absence of MCPyV DNA, suggesting that MCPyV infection enhances T-cell infiltration. However, other factors may also play a role in the host antitumor response. Herein, we review the impact of tumor infiltrating lymphocytes (TILs), mainly the CD4⁺, CD8⁺, and regulatory T-cell (Tregs) responses on the course of MCC, including their role in initiating MCPyV-specific immune responses. Furthermore, potential research avenues related to T-cell biology in MCC, as well as relevant immunotherapies are discussed.

Mitochondrial DNA as a Candidate Marker of Multiple Organ Failure after Cardiac Surgery

Assess the level of mitochondrial DNA depending on the presence of multiple organ failure in patients after heart surgery. The study included 60 patients who underwent surgical treatment of valvular heart disease using cardiopulmonary bypass. Uncomplicated patients were included in the 1st group (n = 30), patients with complications and multiple organ failure (MOF) were included in the 2nd group (n = 30). Serum mtDNA levels were determined by quantitative real-time polymerase chain reaction with fluorescent dyes. Mitochondrial DNA gene expression did not differ between group before surgery. Immediately after the intervention, cytochrome B gene expression was higher in the group with MOF, and it remained high during entire follow-up period. A similar trend was observed in cytochrome oxidase gene expression. Increased NADH levels of gene expressions during the first postoperative day were noted in both groups, the expression showed tendency to increase on the third postoperative day. mtDNA gene expression in the "MOF present" group remained at a higher level compared with the group without complications. A positive correlation was reveled between the severity of MOF according to SOFA score and the level of mtDNA (r = 0.45; p = 0.028) for the end-point "First day". The ROC analysis showed that mtDNA circulating in plasma (AUC = 0.605) can be a predictor of MOF development. The level of mtDNA significantly increases in case of MOF, irrespective of its cause. (2) The expression of mtDNA genes correlates with the level of MOF severity on the SOFA score.

Circulating mitochondrial cell-free DNA dynamics in patients with mycobacterial pulmonary infections: Potential for a novel biomarker of disease

Objectives

Human mitochondrial cell-free DNA (Mt-cfDNA) may serve as a useful biomarker for infectious processes. We investigated Mt-cfDNA dynamics in patients with pulmonary mycobacterial infections to determine if this novel biomarker could be used to differentiate disease states and severity.

Methods

Patients with pulmonary tuberculosis (PTB), latent tuberculosis infection (LTBI), and nontuberculous mycobacterial-lung disease (NTM-LD) were enrolled at a tertiary care hospital in Taiwan between June 2018 and August 2021. Human Mt-cfDNA and nuclear-cfDNA (Nu-cfDNA) copy numbers were estimated by quantitative polymerase chain reaction. Variables associated with PTB and 2-month sputum culture-positivity, indicating poor treatment response, were assessed using logistic regression.

Results

Among 97 patients with PTB, 64 with LTBI, and 51 with NTM-LD, Mt-cfDNA levels were higher in patients with PTB than in LTBI (p=0.001) or NTM-LD (p=0.006). In the Mycobacterium tuberculosis-infected population, Mt-cfDNA levels were highest in smear-positive PTB patients, followed by smear-negative PTB (p&lt;0.001), and were lowest in LTBI persons (p=0.009). A Mt-cfDNA, but not Nu-cfDNA, level higher than the median helped differentiate culture-positive PTB from culture-negative PTB and LTBI (adjusted OR 2.430 [95% CI 1.139–5.186], p=0.022) and differentiate PTB from NTM-LD (adjusted OR 4.007 [1.382–12.031], p=0.011). Mt-cfDNA levels decreased after 2 months of treatment in PTB patients (p=0.010). A cutoff Mt-cfDNA level greater than 62.62 x 106 copies/μL-plasma was associated with a 10-fold risk of 2-month culture-positivity (adjusted OR 9.691 [1.046–89.813], p=0.046).

Conclusion

Elevated Mt-cfDNA levels were associated with PTB disease and failed sputum conversion at 2 months in PTB patients, and decreased after treatment.

The role of mitochondria in rheumatic diseases

The mitochondrion is an intracellular organelle thought to originate from endosymbiosis between an ancestral eukaryotic cell and an α-proteobacterium. Mitochondria are the powerhouses of the cell, and can control several important processes within the cell, such as cell death. Conversely, dysregulation of mitochondria possibly contributes to the pathophysiology of several autoimmune diseases. Defects in mitochondria can be caused by mutations in the mitochondrial genome or by chronic exposure to pro-inflammatory cytokines, including type I interferons. Following the release of intact mitochondria or mitochondrial components into the cytosol or the extracellular space, the bacteria-like molecular motifs of mitochondria can elicit pro-inflammatory responses by the innate immune system. Moreover, antibodies can target mitochondria in autoimmune diseases, suggesting an interplay between the adaptive immune system and mitochondria. In this Review, we discuss the roles of mitochondria in rheumatic diseases such as systemic lupus erythematosus, antiphospholipid syndrome and rheumatoid arthritis. An understanding of the different contributions of mitochondria to distinct rheumatic diseases or manifestations could permit the development of novel therapeutic strategies and the use of mitochondria-derived biomarkers to inform pathogenesis.

Circulating mtDNA and Impaired Intestinal Barrier after Gastrointestinal Surgery Are Correlated with Postoperative SIRS

BACKGROUND

This prospective study aimed to explore the correlation between circulating mitochondrial DNA (mtDNA), intestinal barrier function impairment, and postoperative SIRS in patients undergoing gastrointestinal surgery.

METHODS

Patients were recruited into this study after signing an informed consent form. Circulating mitochondrial DNA and serum DAO concentrations were measured preoperatively and on day 1 and day 7 postoperatively. Postoperative vitals, routine tests, and biochemical indicators were recorded in detail.

RESULTS

Forty patients undergoing gastrointestinal surgery were recruited for and completed this study. Patients were divided into non-fever, fever, and SIRS groups according to their postoperative temperature and other corresponding indexes. The mtDNA was expressed as the number of PCR cycles using three specific sequences. Circulating mtDNA tended to increase in patients after gastrointestinal surgery, but the difference was not significant. Nevertheless, mtDNA in the SIRS group was significantly higher than in patients in the fever and non-fever groups (p < 0.05). Serum DAO showed a trend of increase on the first day after surgery compared with that before surgery, but the difference was not significant (p > 0.05). However, patients in the SIRS group showed a significant increase (p < 0.05) compared with the others. Both circulating mtDNA and DAO showed a downward trend on the seventh day after surgery.

CONCLUSIONS

Circulating mtDNA presented a trend of increase after gastrointestinal surgery, and the degree of the increased fold was related to the extent of the inflammation response. In general, the intestinal barrier damage indicator DAO was the same as mtDNA and tended to increase after gastrointestinal surgery and then gradually decrease, which may play a synergistic role in inducing postoperative fever and SIRS.

Antimicrobial Challenge in Acute Care Surgery

The burden of infections in acute care surgery (ACS) is huge. Surgical emergencies alone account for three million admissions per year in the United States (US) with estimated financial costs of USD 28 billion per year. Acute care facilities and ACS patients represent boost sanctuaries for the emergence, development and transmission of infections and multi-resistant organisms. According to the World Health Organization, healthcare-associated infections affected around 4 million cases in Europe and 1.7 million in the US alone in 2011 with 39,000 and 99,000 directly attributable deaths, respectively. In this scenario, antimicrobial resistance arose as a public-health emergency that worsens patients' morbidity and mortality and increases healthcare costs. The optimal patient care requires the application of comprehensive evidence-based policies and strategies aiming at minimizing the impact of healthcare associated infections and antimicrobial resistance, while optimizing the treatment of intra-abdominal infections. The present review provides a snapshot of two hot topics, such as antimicrobial resistance and systemic inflammatory response, and three milestones of infection management, such as source control, infection prevention, and control and antimicrobial stewardship.

Expanding role of deoxyribonucleic acid-sensing mechanism in the development of lifestyle-related diseases

In lifestyle-related diseases, such as cardiovascular, metabolic, respiratory, and kidney diseases, chronic inflammation plays a causal role in their pathogenesis; however, underlying mechanisms of sterile chronic inflammation are not well-understood. Previous studies have confirmed the damage of cells in these organs in the presence of various risk factors such as diabetes, dyslipidemia, and cigarette smoking, releasing various endogenous ligands for pattern recognition receptors. These studies suggested that nucleic acids released from damaged tissues accumulate in these tissues, acting as an endogenous ligand. Undamaged DNA is an integral factor for the sustenance of life, whereas, DNA fragments, especially those from pathogens, are potent activators of the inflammatory response. Recent studies have indicated that inflammatory responses such as the production of type I interferon (IFN) induced by DNA-sensing mechanisms which contributes to self-defense system in innate immunity participates in the progression of inflammatory diseases by the recognition of nucleic acids derived from the host, including mitochondrial DNA (mtDNA). The body possesses several types of DNA sensors. Toll-like receptor 9 (TLR9) recognizes DNA fragments in the endosomes. In addition, the binding of DNA fragments in the cytosol activates cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS), resulting in the synthesis of the second messenger cyclic GMP-AMP (cGAMP). The binding of cGAMP to stimulator of interferon genes (STING) activates NF-κB and TBK-1 signaling and consequently the production of many inflammatory cytokines including IFNs. Numerous previous studies have demonstrated the role of DNA sensors in self-defense through the recognition of DNA fragments derived from pathogens. Beyond the canonical role of TLR9 and cGAS-STING, this review describes the role of these DNA-sensing mechanism in the inflammatory responses caused by endogenous DNA fragments, and in the pathogenesis of lifestyle-related diseases.

NOT ALL CELL-FREE MITOCHONDRIAL DNA IS EQUAL IN TRAUMA PATIENTS

ABSTRACT

Mitochondrial DNA (mtDNA) acts as a proinflammatory damage-associated molecular pattern that stimulates innate immune activation via Toll-like receptor 9, similarly to bacterial DNA. A number of clinical studies have measured elevated cell-free mtDNA in the plasma of trauma patients, thought to originate from tissue injury and inflammatory processes; however, the magnitude of this increase, the absolute concentration, and the association with poor outcomes varies considerably across studies. Measurements of cell-free mtDNA in healthy individuals have shown that the majority of "cell-free" mtDNA (>95%) can be centrifuged/filtered from plasma in the size range of 0.45 to 5 μm, suggesting that there are larger forms of mtDNA-containing complexes in the plasma that could be considered cell-free. Whether this is true for trauma patients (and other relevant disease states) and the clinical relevance of the larger forms of mtDNA is unknown. These findings from healthy individuals also suggest that the centrifugation speeds used to generate cell-free plasma (which are rarely consistent among studies) could result in mixed populations of cell-free mtDNA that could confound associations with outcomes. We demonstrate in this study of 25 major trauma patients that the majority of the cell-free mtDNA in trauma patient plasma (>95%) is removed after centrifugation at 16,000g. Despite the larger forms of mtDNA being predominant, they do not correlate with outcomes or expected parameters such as injury/shock severity, multiple organ failure, and markers of inflammation, whereas low-molecular-weight cell-free mtDNA correlates strongly with these variables.

Innate immunity and immunotherapy for hemorrhagic shock

Hemorrhagic shock (HS) is a shock result of hypovolemic injury, in which the innate immune response plays a central role in the pathophysiology ofthe severe complications and organ injury in surviving patients. During the development of HS, innate immunity acts as the first line of defense, mediating a rapid response to pathogens or danger signals through pattern recognition receptors. The early and exaggerated activation of innate immunity, which is widespread in patients with HS, results in systemic inflammation, cytokine storm, and excessive activation of complement factors and innate immune cells, comprised of type II innate lymphoid cells, CD4⁺ T cells, natural killer cells, eosinophils, basophils, macrophages, neutrophils, and dendritic cells. Recently, compelling evidence focusing on the innate immune regulation in preclinical and clinical studies promises new treatment avenues to reverse or minimize HS-induced tissue injury, organ dysfunction, and ultimately mortality. In this review, we first discuss the innate immune response involved in HS injury, and then systematically detail the cutting-edge therapeutic strategies in the past decade regarding the innate immune regulation in this field; these strategies include the use of mesenchymal stem cells, exosomes, genetic approaches, antibody therapy, small molecule inhibitors, natural medicine, mesenteric lymph drainage, vagus nerve stimulation, hormones, glycoproteins, and others. We also reviewed the available clinical studies on immune regulation for treating HS and assessed the potential of immune regulation concerning a translation from basic research to clinical practice. Combining therapeutic strategies with an improved understanding of how the innate immune system responds to HS could help to identify and develop targeted therapeutic modalities that mitigate severe organ dysfunction, improve patient outcomes, and reduce mortality due to HS injury.

Role of released mitochondrial DNA in acute lung injury

Acute lung injury(ALI)/acute respiratory distress syndrome(ARDS) is a form of acute-onset hypoxemic respiratory failure characterised by an acute, diffuse, inflammatory lung injury, and increased alveolar-capillary permeability, which is caused by a variety of pulmonary or nonpulmonary insults. Recently, aberrant mitochondria and mitochondrial DNA(mtDNA) level are associated with the development of ALI/ARDS, and plasma mtDNA level shows the potential to be a promising biomarker for clinical diagnosis and evaluation of lung injury severity. In mechanism, the mtDNA and its oxidised form, which are released from impaired mitochondria, play a crucial role in the inflammatory response and histopathological changes in the lung. In this review, we discuss mitochondrial outer membrane permeabilisation (MOMP), mitochondrial permeability transition pore(mPTP), extracellular vesicles (EVs), extracellular traps (ETs), and passive release as the principal mechanisms for the release of mitochondrial DNA into the cytoplasm and extracellular compartments respectively. Further, we explain how the released mtDNA and its oxidised form can induce inflammatory cytokine production and aggravate lung injury through the Toll-like receptor 9(TLR9) signalling, cytosolic cGAS-stimulator of interferon genes (STING) signalling (cGAS-STING) pathway, and inflammasomes activation. Additionally, we propose targeting mtDNA-mediated inflammatory pathways as a novel therapeutic approach for treating ALI/ARDS.

The Good and the Bad: Monocytes' and Macrophages' Diverse Functions in Inflammation

Monocytes and macrophages are central players of the innate immune response and play a pivotal role in the regulation of inflammation. Thereby, they actively participate in all phases of the immune response, from initiating inflammation and triggering the adaptive immune response, through to the clearance of cell debris and resolution of inflammation. In this review, we described the mechanisms of monocyte and macrophage adaptation to rapidly changing microenvironmental conditions and discussed different forms of macrophage polarization depending on the environmental cues or pathophysiological condition. Therefore, special focus was placed on the tight regulation of the pro- and anti-inflammatory immune response, and the diverse functions of S100A8/S100A9 proteins and the scavenger receptor CD163 were highlighted, respectively. We paid special attention to the function of pro- and anti-inflammatory macrophages under pathological conditions.

T Cell Extracellular Traps: Tipping the Balance Between Skin Health and Disease

The role of extracellular traps (ETs) in the innate immune response against pathogens is well established. ETs were first identified in neutrophils and have since been identified in several other immune cells. Although the mechanistic details are not yet fully understood, recent reports have described antigen-specific T cells producing T cell extracellular traps (TETs). Depending on their location within the cutaneous environment, TETs may be beneficial to the host by their ability to limit the spread of pathogens and provide protection against damage to body tissues, and promote early wound healing and degradation of inflammatory mediators, leading to the resolution of inflammatory responses within the skin. However, ETs have also been associated with worse disease outcomes. Here, we consider host-microbe ET interactions by highlighting how cutaneous T cell-derived ETs aid in orchestrating host immune responses against Cutibacterium acnes (C. acnes), a commensal skin bacterium that contributes to skin health, but is also associated with acne vulgaris and surgical infections following joint-replacement procedures. Insights on the role of the skin microbes in regulating T cell ET formation have broad implications not only in novel probiotic design for acne treatment, but also in the treatment for other chronic inflammatory skin disorders and autoimmune diseases.

Increased level of free-circulating MtDNA in maintenance hemodialysis patients: Possible role in systemic inflammation

Background

Mitochondrial DNA (MtDNA) exposed to the extracellular space due to cell death and stress has immunostimulatory properties. However, the clinical significance of circulating MtDNA in maintenance hemodialysis (MHD) patients and the precise mechanism of its emergence have yet to be investigated.

Methods

This cross‐sectional study consisted of 52 MHD patients and 32 age‐ and sex‐matched healthy controls. MHD patients were further categorized into high and low circulating cell‐free MtDNA (ccf‐MtDNA) groups based on the median value. Copy number of MtDNA was quantified using TaqMan‐based qPCR. Plasma cytokines were measured using ELISA kits. Reactive oxygen species (ROS) and mitochondrial membrane potential (Δψm) in peripheral blood mononuclear cells (PBMCs) were detected using DCFH‐DA or JC‐1 staining.

Results

The copy numbers of ccf‐MtDNA in patients with MHD were higher than those in healthy controls, and these alterations were correlated with changes of cytokines TNF‐α and IL‐6. Adjusted model in multivariate analysis showed that the presence of anuria and longer dialysis vintage were independently associated with higher levels of ccf‐MtDNA. Meanwhile, although not statistically significant, an inverse correlative trend between urinary MtDNA and ccf‐MtDNA was observed in patients with residual urine. Afterward, using PBMCs as surrogates for mitochondria‐rich cells, we found that patients in the high ccf‐MtDNA group exhibited a significantly higher ROS production and lower Δψm in cells.

Conclusions

Our data suggested that changes in ccf‐MtDNA correlate with the degree of inflammatory status in MHD patients, and that the excessive MtDNA may be caused by mitochondrial dysfunction and reduced urinary MtDNA excretion.

IFI16-STING-NF-κB signaling controls exogenous mitochondrion-induced endothelial activation

Mitochondria released from injured cells activate endothelial cells (ECs), fostering inflammatory processes, including allograft rejection. The stimulator of interferon genes (STING) senses endogenous mitochondrial DNA, triggering innate immune activation via NF-κB signaling. Here, we show that exogenous mitochondria exposure induces EC STING-NF-κB activation, promoting EC/effector memory T cell adhesion, which is abrogated by NF-κB and STING inhibitors. STING activation in mitochondrion-activated ECs is independent of canonical cGMP-AMP synthetase sensing/signaling, but rather is mediated by interferon gamma-inducible factor 16 (IFI16) and can be inhibited by IFI16 inhibition. Internalized mitochondria undergo mitofusion and STING-dependent mitophagy, leading to selective sequestration of internalized mitochondria. The exposure of donor hearts to exogenous mitochondria activates murine heart ECs in vivo. Collectively, our results suggest that IFI16-STING-NF-κB signaling regulates exogenous mitochondrion-induced EC activation and mitophagy, and exogenous mitochondria foster T cell-mediated CoBRR. These data suggest a novel, donor-directed, therapeutic approach toward mitigating perioperative allograft immunogenicity.

Systemic inflammatory response syndrome is triggered by mitochondrial damage (Review)

Mitochondria are key organelles of cellular energy metabolism; both mitochondrial function and metabolism determine the physiological function of cells and serve an essential role in immune responses. Key damage‑associated molecular patterns (DAMPs), such as mitochondrial DNA and N‑formyl peptides, released following severe trauma‑induced mitochondrial damage may affect the respiratory chain, enhance oxidative stress and activate systemic inflammatory responses via a variety of inflammation‑associated signaling pathways. Severe trauma can lead to sepsis, multiple organ dysfunction syndrome and death. The present review aimed to summarize the pathophysiological mechanisms underlying the effects of human mitochondrial injury‑released DAMPs on triggering systemic inflammatory responses and to determine their potential future clinical applications in preventing and treating sepsis.