Red Blood Cells Homeostatically Bind Mitochondrial DNA through TLR9 to Maintain Quiescence and to Prevent Lung Injury

Detection of Human Papillomavirus DNA on Red Blood Cells in Patients With Cervical Cancer

Red blood cells (RBCs) have the potential to bind and harbor viral DNA, providing a novel approach to detecting human papillomavirus (HPV). Red blood cells incubated with fluorescently labeled HPV CpG acquired HPV DNA in a concentration-dependent manner. Red blood cells incubated with HPV-positive cervical cancer cells (CaSki cell line) acquired HPV 16 DNA detected by quantitative polymerase chain reaction (PCR). Consistent with these results, HPV 16 DNA was detected by quantitative PCR on RBCs from five patients with cervical cancer or dysplasia but not on healthy control RBCs. Detection of HPV 16 DNA on RBCs from patients with cervical cancer underscores the potential of RBC-bound DNA as a substrate for future blood-based HPV screening.

The involvement of mitochondria in erythrocyte pathology and diseases: from mechanisms to therapeutic strategies

Erythrocytes, as the predominant cellular components within the bloodstream, are crucial for the maintenance of physiological health. Mitochondria, known as cellular powerhouses and metabolic regulators, play a critical role in the maturation of the erythroid lineage. The absence of mitochondria in red blood cells upon completing their maturation process is a defining characteristic of their development. Dysregulation of mitochondrial metabolism has been associated with the onset and progression of various diseases. Mitochondrial metabolic disorders, along with the involvement of mitochondria in the induction of oxidative stress and the activation of immune responses, significantly contribute to the pathogenesis of diverse hematologic disorders, particularly in sickle cell disease. This review offers a comprehensive overview of the role of mitochondria in disorders related to abnormal erythropoiesis, immune responses, and hemolysis, as well as evaluating potential therapeutic strategies that target mitochondria. Ultimately, we emphasize the necessity for future research to elucidate the involvement of mitochondria in red blood cell disorders, which may inform the development of novel diagnostic and therapeutic approaches.

Efficient Sleep, Enhanced Attention: Exploring the Interplay With RBC-Inflammation Mechanisms in Hypoxic High-Altitude Areas

Purpose

The complex interplay between sleep and attention, especially in the suppression of environmental information, is not well understood. This study investigates the bidirectional influence between sleep quality and executive control-an essential aspect of attention-and seeks to uncover the biological pathways involved in this relationship in hypoxic high-altitude areas.

Patients and Methods

We recruited 140 han Chinese juniors from Tibet University, all originally from lowland areas. Participants underwent an attention network test with concurrent electroencephalography to assess attentional function. Sleep quality was evaluated using the Pittsburgh Sleep Quality Index, while the Symptom Check-List-90 and a standard physical examination measured overall health status. A breaking continuous flash suppression task gauged conscious perception breakthrough capacity.

Results

Our findings reveal a bidirectional link between sleep quality and executive control function, which appears to be related to an inflammatory response associated with erythrocyte attributes. Specifically, the P1 and N1 orienting amplitudes mediated the effects of sleep on executive control. This relationship suggests that executive control may, in turn, regulate sleep patterns, with implications for mental health. We also found that enhanced sleep efficiency was correlated with a balance between alerting functions and executive control.

Conclusion

The study establishes that sleep quality and executive control are interlinked via an inflammatory response related to red blood cell characteristics, impacting mental health. Better sleep correlates with improved cognitive performance, suggesting that sleep is crucial for optimal attention resource management and overall cognitive well-being. This enhances our knowledge of the biological foundations of the sleep-attention interaction.

Mitochondrial DNA signals driving immune responses: Why, How, Where?

There has been a recent expansion in our understanding of DNA-sensing mechanisms. Mitochondrial dysfunction, oxidative and proteostatic stresses, instability and impaired disposal of nucleoids cause the release of mitochondrial DNA (mtDNA) from the mitochondria in several human diseases, as well as in cell culture and animal models. Mitochondrial DNA mislocalized to the cytosol and/or the extracellular compartments can trigger innate immune and inflammation responses by binding DNA-sensing receptors (DSRs). Here, we define the features that make mtDNA highly immunogenic and the mechanisms of its release from the mitochondria into the cytosol and the extracellular compartments. We describe the major DSRs that bind mtDNA such as cyclic guanosine-monophosphate-adenosine-monophosphate synthase (cGAS), Z-DNA-binding protein 1 (ZBP1), NOD-, LRR-, and PYD- domain-containing protein 3 receptor (NLRP3), absent in melanoma 2 (AIM2) and toll-like receptor 9 (TLR9), and their downstream signaling cascades. We summarize the key findings, novelties, and gaps of mislocalized mtDNA as a driving signal of immune responses in vascular, metabolic, kidney, lung, and neurodegenerative diseases, as well as viral and bacterial infections. Finally, we define common strategies to induce or inhibit mtDNA release and propose challenges to advance the field.

Archaea-inspired deoxyribonuclease I liposomes prevent multiple organ dysfunction in sepsis

Neutrophil extracellular traps (NETs) and circulating cell-free DNA (cfDNA) are pivotal in driving excessive inflammation and organ damage during sepsis, with their levels correlating positively with sepsis severity in both patients and murine models. Despite the ability of deoxyribonuclease I (DNase I) to degrade NETs and cfDNA, its short half-life and rapid degradation limit its therapeutic effectiveness. To address this challenge, we developed a methyl-branched liposome fused with a red blood cell membrane for the systemic delivery of DNase I (DNase I/Rm-Lipo). The efficacy of DNase I/Rm-Lipo was evaluated in the stimulated immune cells and septic model. The data confirmed that DNase I/Rm-Lipo efficiently removed excess NETs and cfDNA in activated neutrophils. Following injection, DNase I/Rm-Lipo exhibited an extended circulation time, effectively suppressing neutrophil activation and regulating macrophage polarization to mitigate inflammation and prevent organ dysfunction in septic mice. These findings highlight the therapeutic potential of DNase I/Rm-Lipo as a promising candidate for sepsis management by targeting the degradation of NETs and cfDNA.

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.

The protective effect of Chlorella vulgaris against diclofenac toxicity in Clarias gariepinus: haemato-immunological parameters and spleen histological features as outcome markers

Introduction

Diclofenac (DCF) is a commonly utilized medication in the non-steroidal anti-inflammatory drug category that is released into aquatic systems in significant amounts. Chlorella vulgaris (C. vulgaris) is rich in active phytochemicals known for their haemato-immunological boosting properties.

Methods

Our objective was to investigate the haemato-immunological protective properties of Chlorella in mitigating the toxic effects of DCF. Five groups of Clarias gariepinus, each comprising 36 fish, were assigned over a two-week period. The groups were assigned as follows: control group, which received a basal diet only; DCF1 group, which received a basal diet and was exposed to 20 μg/L of DCF; DCF2 group, which received a basal diet and was exposed to 10 mg/L of DCF; and Chlorella +DCF1 and Chlorella+DCF2 groups, which were exposed to the same DCF doses as Groups 2 and 3, respectively, while also being fed a diet containing 25% Chlorella.

Results

Exposure to both doses of DCF significantly decreased erythrocyte count, hemoglobin content, white blood cell count, phagocytic index, and lysozyme activity, while increased eosinophil and neutrophil % in an equipotent manner. The low dose caused a more pronounced reduction in packed cell volume (PCV)% and large lymphocyte% compared to the high dose. A significant decline in platelet count was observed only with the low DCF dose, while the high dose led to a decrease in monocyte%. DCF intoxication led to a dose-related decrease in small lymphocyte% and an increase in erythrocyte morphological alterations and interleukin (IL)-6 levels. The DCF2 group exhibited a higher increase in apoptotic RBCs than the DCF1 group. Intervention with Chlorella alongside the two DCF doses significantly normalized RBC count and eosinophil %, increased PCV% and small lymphocyte%, and decreased erythrocyte abnormalities to an equal extent. Large lymphocyte% in the Chlorella+DCF1 group was successfully restored to normal levels. Phagocytic index and lysozyme activity in the supplemented groups were lower, while IL-6 levels were higher than in the DCF groups. The percentage of apoptotic cells decreased with Chlorella administration, with the Chlorella+DCF1 group showing fewer apoptotic cells than the Chlorella+DCF2 group. Histopathological deterioration and excessive collagen deposition were observed in the spleen of DCF groups, while notable improvements were seen following C. vulgaris supplementation.

Conclusion

These findings suggest that dietary inclusion of C. vulgaris may antagonize the haemato-cytological abnormalities induced by DCF intoxication.

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.

Red blood cells capture and deliver bacterial DNA to drive host responses during polymicrobial sepsis

Red blood cells (RBCs), traditionally recognized for their role in transporting oxygen, play a pivotal role in the body's immune response by expressing TLR9 and scavenging excess host cell-free DNA. DNA capture by RBCs leads to accelerated RBC clearance and triggers inflammation. Whether RBCs can also acquire microbial DNA during infections is unknown. Murine RBCs acquire microbial DNA in vitro, and bacterial DNA-induced (bDNA-induced) macrophage activation was augmented by WT, but not Tlr9-deleted, RBCs. In a mouse model of polymicrobial sepsis, RBC-bound bDNA was elevated in WT mice but not in erythroid Tlr9-deleted mice. Plasma cytokine analysis in these mice revealed distinct sepsis clusters characterized by persistent hypothermia and hyperinflammation in the most severely affected mice. RBC Tlr9 deletion attenuated plasma and tissue IL-6 production in the most severely affected group. Parallel findings in humans confirmed that RBCs from patients with sepsis harbored more bDNA than did RBCs from healthy individuals. Further analysis through 16S sequencing of RBC-bound DNA illustrated distinct microbial communities, with RBC-bound DNA composition correlating with plasma IL-6 in patients with sepsis. Collectively, these findings unveil RBCs as overlooked reservoirs and couriers of microbial DNA, capable of influencing host inflammatory responses in sepsis.

Red Blood Cell-Related Parameters in Rheumatoid Arthritis: Clinical Value and Immunological Significance

Rheumatoid arthritis (RA) is characterized by chronic inflammation and autoimmunity. Moreover, the disease activity, co-morbidities, and prognosis of RA are closely associated with changes in red blood cell (RBC)-related parameters. The role of these parameters in RA has therefore been extensively studied. Accordingly, this article summarizes and analyzes the close relationship of RBC-related parameters such as RBC count, hemoglobin, and RBC distribution width with disease activity, co-morbidities, and prognosis in RA by reviewing the available literature. In addition, given the immunomodulatory functions of RBCs, their surface proteins, contents, and microparticles are involved in the immunomodulatory process during RA. Overall, this review aims to assess the important clinical value and immunological significance of RBCs and their related parameters in the monitoring and management of RA, thus providing a reference for the clinical diagnosis and treatment of RA and the direction for the research on RBC-related immunity.

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.

The emerging role of mtDNA release in sepsis: Current evidence and potential therapeutic targets

Sepsis is a systemic inflammatory reaction caused by infection, and severe sepsis can develop into septic shock, eventually leading to multiorgan dysfunction and even death. In recent years, studies have shown that mitochondrial damage is closely related to the occurrence and development of sepsis. Recent years have seen a surge in concern over mitochondrial DNA (mtDNA), as anomalies in this material can lead to cellular dysfunction, disruption of aerobic respiration, and even death of the cell. In this review, we discuss the latest findings on the mechanisms of mitochondrial damage and the molecular mechanisms controlling mitochondrial mtDNA release. We also explored the connection between mtDNA misplacement and inflammatory activation. Additionally, we propose potential therapeutic targets of mtDNA for sepsis treatment.

Elevated mtDNA content in RBCs promotes oxidative stress may be responsible for faster senescence in men

BACKGROUND

Both we and others have found that RBC counts are significantly lower in older compared to younger. However, when gender is factored in, a significant age-related decrease of RBC counts is observed only in men but not in women.

METHODS

qPCR and confocal microscopy were used to detect the presence of mtDNA in RBCs. Flow cytometry and specific inhibitors were used to determine how RBCs uptake cf-mtDNA. The peripheral blood was collected from 202 young adults and 207 older adults and RBC and plasma were isolated. The levels of TLR9+RBCs and apoptotic RBCs after uptake of cf-mtDNA by RBCs were measured by flow cytometry. The kit detects changes in SOD and MDA levels after cf-mtDNA uptake by RBCs. Young RBCs (YR) and old RBCs (OR) from single individuals were separated by Percoll centrifugation.

RESULTS

We found a significant decrease in RBC counts and a significant increase in the RDW with aging only in men. We also found that significantly elevated mtDNA content in RBCs was observed only in men during aging and was not found in women. Further studies demonstrated that RBCs could take up cf-mtDNA via TLR9, and the uptake of mtDNA might lead to a decrease in the RBC number and an increase in RDW due to an increase of oxidative stress.

CONCLUSIONS

The RBC mtDNA content might be a potential marker of RBC aging and the elevated RBC mtDNA content might be the cause of faster senescence in males than females.

Unveiling the role of mtDNA in Liver-Kidney Crosstalk: Insights from trichloroethylene hypersensitivity syndrome

In specific pathological conditions, addressing liver injury may yield favorable effects on renal function through the phenomenon of liver-kidney crosstalk. Mitochondrial DNA (mtDNA) possesses the capability to trigger downstream pathways of inflammatory cytokines, ultimately leading to immune-mediated organ damage. Consequently, understanding the intricate molecular mechanisms governing mtDNA involvement in diseases characterized by liver-kidney crosstalk is of paramount significance. This study seeks to elucidate the role of mtDNA in conditions marked by liver-kidney crosstalk. In previous clinical cases, it has been observed that patients with Trichloroethylene Hypersensitivity Syndrome (TCE-HS) who experience severe liver injury often also exhibit renal injury. In this study, patients diagnosed with trichloroethylene hypersensitivity syndrome were recruited from Shenzhen Occupational Disease Control Center. And Balb/c mice were treated with trichloroethylene. The correlation between liver and kidney injuries in patients with TCE-HS was assessed using Enzyme-Linked Immunosorbent Assay (ELISA). Alterations in mtDNA levels were examined in mouse hepatocytes, red blood cells (RBCs), and renal tubular epithelial cells utilizing immunofluorescence and PCR techniques. TCE-sensitized mice exhibited a significant increase in reactive oxygen species (ROS) and the opening of the mitochondrial permeability transition pore in hepatocytes, resulting in the release of mtDNA. Furthermore, heightened levels of mtDNA and Toll-like Receptor 9 (TLR9) expression were observed in RBCs. Additional experiments demonstrated elevated expression of TLR9 and its downstream mediator MyD88 in renal tubule epithelial cells of TCE-sensitized mice. In vitro investigations confirmed that mtDNA activates the TLR9 pathway in TCMK-1 cells. Collectively, these results suggest that mtDNA released from mitochondrial damage in hepatocytes is carried by RBCs to renal tubular epithelial cells and mediates inflammatory injury in renal tubular epithelial cells through activation of the TLR9 receptor.

Innate immune sensing of cell death in disease and therapeutics

Innate immunity, cell death and inflammation underpin many aspects of health and disease. Upon sensing pathogens, pathogen-associated molecular patterns or damage-associated molecular patterns, the innate immune system activates lytic, inflammatory cell death, such as pyroptosis and PANoptosis. These genetically defined, regulated cell death pathways not only contribute to the host defence against infectious disease, but also promote pathological manifestations leading to cancer and inflammatory diseases. Our understanding of the underlying mechanisms has grown rapidly in recent years. However, how dying cells, cell corpses and their liberated cytokines, chemokines and inflammatory signalling molecules are further sensed by innate immune cells, and their contribution to further amplify inflammation, trigger antigen presentation and activate adaptive immunity, is less clear. Here, we discuss how pattern-recognition and PANoptosome sensors in innate immune cells recognize and respond to cell-death signatures. We also highlight molecular targets of the innate immune response for potential therapeutic development.

A Prospective Study of the Association of IL6 with the Critical Unit and Their Effect on in-Hospital Mortality in Critically Ill Patients

Purpose

We previously proposed a new concept, the "critical unit", which covers the structural integrity and function of mitochondria and endothelium. Injury of the critical unit plays a key role in the development of critical illnesses. High levels of inflammation may lead to abnormalities of the critical unit, which is an important mechanism for critical illnesses, and both inflammation and critical unit dysfunction may affect patient prognosis. Here we evaluated the correlation between interleukin-6 (IL6) and the critical unit biomarkers in critically ill patients and the impact of both on prognosis.

Patients and Methods

This study included adult patients admitted to the intensive care unit for various reasons from January 1st to May 31st, 2023. Baseline characteristics, intensive care unit parameters, and laboratory test and outcome data were obtained from the electronic medical records system. Critical unit parameters were measured using polymerase chain reaction and enzyme-linked immunosorbent assay methods. Correlations were examined between IL6, critical unit parameters, and various outcomes.

Results

In critically ill patients, IL6 was closely associated with all the critical unit biomarkers (activated partial thromboplastin time, sphingosine 1-phosphate, mitochondrial DNA, mitochondrial fission 1, and Parkin) and the prognoses of patients. A nomogram was constructed using the critical unit biomarkers to predict the in-hospital mortality of critically ill patients. The area under the curve for the mortality prediction model was 0.708. In sensitivity analyses, the predictive effect was better in the non-surgery and tumor groups compared with the surgery and non-tumor groups, with area under the curve values of 0.885 and 0.891, respectively.

Conclusion

Our study innovatively integrated mitochondrial and endothelial markers in the critical unit to comprehensively evaluate patient prognosis, which may be a trend in the future assessment of critically ill patients. There are few such studies, and ours may promote the progress of related research.

Human red blood cells express the RNA sensor TLR7

Red blood cells (RBCs) express the nucleic acid-binding toll-like receptor 9 (TLR9) and bind CpG-containing DNA. However, whether human RBCs express other nucleic acid-binding TLRs is unknown. Here we show that human RBCs express the RNA sensor TLR7. TLR7 is present on the red cell membrane and is associated with the RBC membrane protein Band 3. In patients with SARS-CoV2-associated sepsis, TLR7-Band 3 interactions in the RBC membrane are increased when compared with healthy controls. In vitro, RBCs bind synthetic ssRNA and RNA from ssRNA viruses. Thus, RBCs may serve as a previously unrecognized sink for exogenous RNA, expanding the repertoire of non-gas exchanging functions performed by RBCs.

The potential therapeutic effects of exosomes derived from bone marrow mesenchymal stem cells on ileum injury of a rat sepsis model (histological and immunohistochemical study)

Sepsis denotes a serious high mortality concern. The study was designed to evaluate the effect of mesenchymal stem cell exosomes (MSC-exosomes) on the evolution of the animal model of sepsis. In this study, 36 rats were distributed into three groups, (I) controls, (II) LPS-treated, and (III) LPS+MSC-EVs. Sepsis was simulated by administering E. coli-LPS to the laboratory animals. Group III was given MSC-exosomes four hours after the LPS injection. Forty-eight hours later rats were sacrificed. Ileum samples were excised, and processed for the histological assessment, immunohistochemical identification of CD44, and inducible nitric oxide synthase (iNOS). Ileum homogenate was used to estimate tumor necrosis factor α (TNF α) besides Cyclooxygenase-2 (COX 2). PCR was used for the detection of interleukin 1α (IL‑1α), and interleukin 17 (IL‑17). Statistical and morphometrical analysis was done. The LPS-treated group showed increased TNF-α, IL‑1α, IL‑17, and decreased COX 2. LPS administration led to cytoplasmic vacuolization of enterocytes, an increase in the vasculature, and cellular infiltrations invaded the lamina propria. There was a significant rise in goblet cells and the proportion of collagen fibers. Ultrastructurally, the enterocytes displayed nuclear irregularity, rough endoplasmic reticulum (rER) dilatation, and increased mitochondria number. Sepsis induces a significant increase in iNOS and a decrease in CD44 immune expressions. LPS+MSC-EVs group restored normal ileum structure and revealed a significant elevation in CD44 and a reduction in iNOS immunoreactions. LPS-sepsis induced an obvious ileum inflammatory deterioration ameliorated by MSC-exosomes, mostly through their antioxidant, anti-inflammatory, and anti-apoptotic properties.

Erythrocytes of the common carp are immune sentinels that sense pathogen molecular patterns, engulf particles and secrete pro-inflammatory cytokines against bacterial infection

Introduction

Red blood cells (RBCs), also known as erythrocytes, are underestimated in their role in the immune system. In mammals, erythrocytes undergo maturation that involves the loss of nuclei, resulting in limited transcription and protein synthesis capabilities. However, the nucleated nature of non-mammalian RBCs is challenging this conventional understanding of RBCs. Notably, in bony fishes, research indicates that RBCs are not only susceptible to pathogen attacks but express immune receptors and effector molecules. However, given the abundance of RBCs and their interaction with every physiological system, we postulate that they act in surveillance as sentinels, rapid responders, and messengers.

Methods

We performed a series of in vitro experiments with Cyprinus carpio RBCs exposed to Aeromonas hydrophila, as well as in vivo laboratory infections using different concentrations of bacteria.

Results

qPCR revealed that RBCs express genes of several inflammatory cytokines. Using cyprinid-specific antibodies, we confirmed that RBCs secreted tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ). In contrast to these indirect immune mechanisms, we observed that RBCs produce reactive oxygen species and, through transmission electron and confocal microscopy, that RBCs can engulf particles. Finally, RBCs expressed and upregulated several putative toll-like receptors, including tlr4 and tlr9, in response to A. hydrophila infection in vivo.

Discussion

Overall, the RBC repertoire of pattern recognition receptors, their secretion of effector molecules, and their swift response make them immune sentinels capable of rapidly detecting and signaling the presence of foreign pathogens. By studying the interaction between a bacterium and erythrocytes, we provide novel insights into how the latter may contribute to overall innate and adaptive immune responses of teleost fishes.

Higher Molecular Injury at Diagnosis of Acute Cellular Rejection Increases the Risk of Lung Allograft Failure: A Clinical Trial

Rationale: The association of acute cellular rejection (ACR) with chronic lung allograft dysfunction (CLAD) in lung transplant recipients has primarily been described before consensus recommendations incorporating restrictive phenotypes. Furthermore, the association of the degree of molecular allograft injury during ACR with CLAD or death remains undefined. Objectives: To investigate the association of ACR with the risk of CLAD or death and to further investigate if this risk depends on the degree of molecular allograft injury. Methods: This multicenter, prospective cohort study included 188 lung transplant recipients. Subjects underwent serial plasma collections for donor-derived cell-free DNA (dd-cfDNA) at prespecified time points and bronchoscopy. Multivariable Cox proportional-hazards analysis was conducted to analyze the association of ACR with subsequent CLAD or death as well as the association of dd-cfDNA during ACR with risk of CLAD or death. Additional outcomes analyses were performed with episodes of ACR categorized as "high risk" (dd-cfDNA ⩾ 1%) and "low risk" (dd-cfDNA < 1%). Measurements and Main Results: In multivariable analysis, ACR was associated with the composite outcome of CLAD or death (hazard ratio [HR], 2.07 [95% confidence interval (CI), 1.05-4.10]; P = 0.036). Elevated dd-cfDNA ⩾ 1% at ACR diagnosis was independently associated with increased risk of CLAD or death (HR, 3.32; 95% CI, 1.31-8.40; P = 0.012). Patients with high-risk ACR were at increased risk of CLAD or death (HR, 3.13; 95% CI, 1.41-6.93; P = 0.005), whereas patients with low-risk status ACR were not. Conclusions: Patients with ACR are at higher risk of CLAD or death, but this may depend on the degree of underlying allograft injury at the molecular level. Clinical trial registered with www.clinicaltrials.gov (NCT02423070).

Red blood cells function as reservoirs of tumor DNA

Novel screening techniques for early detection of lung cancer are urgently needed. Profiling circulating tumor cell-free DNA (ctDNA) has emerged as a promising tool for biopsy-free tumor genotyping. However, both the scarcity and short half-life of ctDNA substantially limit the sensitivity and clinical utility of ctDNA detection methodologies. Our discovery that red blood cells (RBCs) sequester mitochondrial DNA opens a new avenue for detecting circulating nucleic acids, as RBCs represent an unrecognized reservoir of circulating nucleic acid. Here, we show that RBCs acquire tumor DNA following coculture with lung cancer cell lines harboring Kirsten rat sarcoma viral oncogene homolog (KRAS) and epidermal growth factor receptor (EGFR) mutations. RBC-bound tumor DNA is detectable in patients with early-stage non-small cell lung cancer (NSCLC) but not in healthy controls by qPCR. Our results collectively uncover a previously unrecognized yet easily accessible reservoir of tumor DNA, offering a promising foundation for future RBC-based tumor diagnostics.NEW & NOTEWORTHY We present a novel method for lung cancer detection by revealing RBCs as a reservoir for tumor DNA, overcoming the limitations of current circulating tumor ctDNA methodologies. By demonstrating that RBCs can capture tumor DNA, including critical mutations found in lung cancer, we provide a promising, biopsy-free avenue for early cancer diagnostics. This discovery opens up exciting possibilities for developing RBC-based diagnostic tools, significantly enhancing the sensitivity and clinical utility of noninvasive cancer detection.

Nomogram for Predicting Central Nervous System Infection Following Traumatic Brain Injury in the Elderly

OBJECTIVE

This study aims to identify risk factors for central nervous system (CNS) infection in elderly patients hospitalized with traumatic brain injury (TBI) and to develop a reliable predictive tool for assessing the likelihood of CNS infection in this population.

METHOD

We conducted a retrospective study on 742 elderly TBI patients treated at Tangdu Hospital, China. Clinical data was randomly split into training and validation sets (7:3 ratio). By conducting univariate and multivariate logistic regression analysis in the training set, we identified a list of variables to develop a nomogram for predicting the risk of CNS infection. We evaluated the performance of the predictive model in both cohorts respectively, using receiver operating characteristics curves, calibration curves, and decision curve analysis.

RESULTS

Results of the logistic analysis in the training set indicated that surgical intervention (P = 0.007), red blood cell count (P = 0.019), C-reactive protein concentration (P < 0.001), and cerebrospinal fluid leakage (P < 0.001) significantly predicted the occurrence of CNS infection in elderly TBI patients. The model constructed based on these variables had high predictive capability (area under the curve-training = 0.832; area under the curve-validation = 0.824) as well as clinical utility.

CONCLUSIONS

A nomogram constructed based on several key predictors reasonably predicts the risk of CNS infection in elderly TBI patients upon hospital admission. The model of the nanogram may contribute to timely interventions and improve health outcomes among affected individuals.

Factors Influencing Venous Remodeling in the Development of Varicose Veins of the Lower Limbs

One of the early symptoms of chronic venous disease (CVD) is varicose veins (VV) of the lower limbs. There are many etiological environmental factors influencing the development of chronic venous insufficiency (CVI), although genetic factors and family history of the disease play a key role. All these factors induce changes in the hemodynamic in the venous system of the lower limbs leading to blood stasis, hypoxia, inflammation, oxidative stress, proteolytic activity of matrix metalloproteinases (MMPs), changes in microcirculation and, consequently, the remodeling of the venous wall. The aim of this review is to present current knowledge on CVD, including the pathophysiology and mechanisms related to vein wall remodeling. Particular emphasis has been placed on describing the role of inflammation and oxidative stress and the involvement of extracellular hemoglobin as pathogenetic factors of VV. Additionally, active substances used in the treatment of VV were discussed.

Intravenous Senescent Erythrocyte Vaccination Modulates Adaptive Immunity and Splenic Complement Production

Targeted delivery of vaccines to the spleen remains a challenge. Inspired by the erythrophagocytotic process in the spleen, we herein report that intravenous administration of senescent erythrocyte-based vaccines profoundly alters their tropism toward splenic antigen-presenting cells (APCs) for imprinting adaptive immune responses. Compared with subcutaneous inoculation, intravenous vaccination significantly upregulated splenic complement expression in vivo and demonstrated synergistic antibody killing in vitro. Consequently, intravenous senescent erythrocyte vaccination produces potent SARS-CoV-2 antibody-neutralizing effects, with potential protective immune responses. Moreover, the proposed senescent erythrocyte can deliver antigens from resected tumors and adjuvants to splenic APCs, thereby inducing a personalized immune reaction against tumor recurrence after surgery. Hence, our findings suggest that senescent erythrocyte-based vaccines can specifically target splenic APCs and evoke adaptive immunity and complement production, broadening the tools for modulating immunity, helping to understand adaptive response mechanisms to senescent erythrocytes better, and developing improved vaccines against cancer and infectious diseases.

The Diversity of Liquid Biopsies and Their Potential in Breast Cancer Management

Analyzing blood as a so-called liquid biopsy in breast cancer (BC) patients has the potential to adapt therapy management. Circulating tumor cells (CTCs), extracellular vesicles (EVs), cell-free DNA (cfDNA) and other blood components mirror the tumoral heterogeneity and could support a range of clinical decisions. Multi-cancer early detection tests utilizing blood are advancing but are not part of any clinical routine yet. Liquid biopsy analysis in the course of neoadjuvant therapy has potential for therapy (de)escalation.Minimal residual disease detection via serial cfDNA analysis is currently on its way. The prognostic value of blood analytes in early and metastatic BC is undisputable, but the value of these prognostic biomarkers for clinical management is controversial. An interventional trial confirmed a significant outcome benefit when therapy was changed in case of newly emerging cfDNA mutations under treatment and thus showed the clinical utility of cfDNA analysis for therapy monitoring. The analysis of PIK3CA or ESR1 variants in plasma of metastatic BC patients to prescribe targeted therapy with alpesilib or elacestrant has already arrived in clinical practice with FDA-approved tests available and is recommended by ASCO. The translation of more liquid biopsy applications into clinical practice is still pending due to a lack of knowledge of the analytes' biology, lack of standards and difficulties in proving clinical utility.

MicroRNA Profiling of Red Blood Cells for Lung Cancer Diagnosis

BACKGROUND

Despite extensive endeavors to establish cell-free circulating biomarkers for lung cancer diagnosis, clinical adoption remains elusive. Noteworthy, emergent evidence suggests the pivotal roles of red blood cells (RBCs) and their derivatives in tumorigenesis, illuminating potential avenues for diagnostic advancements using blood cell-derived microRNAs (miRNAs).

METHODS

We executed microarray analyses on three principal blood cell types-RBCs, peripheral blood mononuclear cells (PBMCs), and neutrophils-encompassing 26 lung cancer patients and 26 healthy controls. Validation was performed using droplet digital PCR within an additional cohort comprising 42 lung cancer and 39 control cases.

RESULTS

Our investigation unearthed distinct miRNA profiles associated with lung cancer across all examined blood cell types. Intriguingly, RBC-miRNAs emerged as potential novel biomarkers for lung cancer, an observation yet to be documented. Importantly, integrating miRNAs from disparate blood cell types yielded a superior diagnostic accuracy for lung cancer over individual cell-type miRNAs. Subsequently, we formulated three diagnostic panels, adeptly discerning non-small cell lung cancer, adenocarcinoma, and squamous cell carcinoma, maintaining consistency across various disease stages.

CONCLUSION

RBC-derived molecules introduce novel cancer biomarkers, and exploiting miRNA profiles across varied blood cell types unveils a promising frontier for lung cancer's early detection and histological classification.

Immunomodulatory role of mitochondrial DAMPs: a missing link in pathology?

In accordance with the endosymbiotic theory, mitochondrial components bear characteristic prokaryotic signatures, which act as immunomodulatory molecules when released into the extramitochondrial compartment. These endogenous immune triggers, called mitochondrial damage-associated molecular patterns (mtDAMPs), have been implicated in the pathogenesis of various diseases, yet their role remains largely unexplored. In this review, we summarise the available literature on mtDAMPs in diseases, with a special focus on respiratory diseases. We highlight the need to bolster mtDAMP research using a multipronged approach, to study their effect on specific cell types, receptors and machinery in pathologies. We emphasise the lacunae in the current understanding of mtDAMPs, particularly in their cellular release and the chemical modifications they undergo. Finally, we conclude by proposing additional effects of mtDAMPs in diseases, specifically their role in modulating the immune system.

Surface toll-like receptor 9 on immune cells and its immunomodulatory effect

Toll like receptor 9 (TLR9) has been considered as a crucial intracellular pattern recognition receptor in the immune system, which can directly or indirectly mediate innate and adaptive immune responses by recognizing CpG DNA in endosomes to initiate its downstream signaling. However, TLR9 can also be expressed on the membrane surface of some immune and non-immune cells, called surface TLR9 (sTLR9), which covers the TLR9 and its immunomodulatory role with a mysterious veil. In this review, we mainly focus on the sTLR9 expressed on neutrophils, B cells and erythrocytes, and its immunomodulatory roles displayed alone or in coordination with endosomal TLR9 (eTLR9), providing a theoretical reference for the application of its modulators.

Plasmodium falciparum infection reshapes the human microRNA profiles of red blood cells and their extracellular vesicles

Plasmodium falciparum, a human malaria parasite, develops in red blood cells (RBCs), which represent approximately 70% of all human blood cells. Additionally, RBC-derived extracellular vesicles (RBC-EVs) represent 7.3% of the total EV population. The roles of microRNAs (miRNAs) in the consequences of P. falciparum infection are unclear. Here, we analyzed the miRNA profiles of non-infected human RBCs (niRBCs), ring-infected RBCs (riRBCs), and trophozoite-infected RBCs (trRBCs), as well as those of EVs secreted from these cells. Hsa-miR-451a was the most abundant miRNA in all RBC and RBC-EV populations, but its expression level was not affected by P. falciparum infection. Overall, the miRNA profiles of RBCs and their EVs were altered significantly after infection. Most of the differentially expressed miRNAs were shared between RBCs and their EVs. A target prediction analysis of the miRNAs revealed the possible identity of the genes targeted by these miRNAs (CXCL10, OAS1, IL7, and CCL5) involved in immunomodulation.

Increased red blood cell deformation in children and adolescents after SARS-CoV-2 infection

Severe coronavirus disease 2019 (COVID-19) is associated with hyperinflammation, hypercoagulability and hypoxia. Red blood cells (RBCs) play a key role in microcirculation and hypoxemia and are therefore of special interest in COVID-19 pathophysiology. While this novel disease has claimed the lives of many older patients, it often goes unnoticed or with mild symptoms in children. This study aimed to investigate morphological and mechanical characteristics of RBCs after SARS-CoV-2 infection in children and adolescents by real-time deformability-cytometry (RT-DC), to investigate the relationship between alterations of RBCs and clinical course of COVID-19. Full blood of 121 students from secondary schools in Saxony, Germany, was analyzed. SARS-CoV-2-serostatus was acquired at the same time. Median RBC deformation was significantly increased in SARS-CoV-2-seropositive compared to seronegative children and adolescents, but no difference could be detected when the infection dated back more than 6 months. Median RBC area was the same in seropositive and seronegative adolescents. Our findings of increased median RBC deformation in SARS-CoV-2 seropositive children and adolescents until 6 months post COVID-19 could potentially serve as a progression parameter in the clinical course of the disease with an increased RBC deformation pointing towards a mild course of COVID-19.

O-GlcNAcylation of RIPK1 rescues red blood cells from necroptosis

Necroptosis is a type of cell death with excessive inflammation and organ damage in various human diseases. Although abnormal necroptosis is common in patients with neurodegenerative, cardiovascular, and infectious diseases, the mechanisms by which O-GlcNAcylation contributes to the regulation of necroptotic cell death are poorly understood. In this study, we reveal that O-GlcNAcylation of RIPK1 (receptor-interacting protein kinase1) was decreased in erythrocytes of the mouse injected with lipopolysaccharide, resulting in the acceleration of erythrocyte necroptosis through increased formation of RIPK1-RIPK3 complex. Mechanistically, we discovered that O-GlcNAcylation of RIPK1 at serine 331 in human (corresponding to serine 332 in mouse) inhibits phosphorylation of RIPK1 at serine 166, which is necessary for the necroptotic activity of RIPK1 and suppresses the formation of the RIPK1-RIPK3 complex in Ripk1 ^-/- MEFs. Thus, our study demonstrates that RIPK1 O-GlcNAcylation serves as a checkpoint to suppress necroptotic signaling in erythrocytes.

Erythrocytes: Member of the Immune System that Should Not Be Ignored

Erythrocytes are the most abundant type of cells in the blood and have a relatively simple structure when mature; they have a long life-span in the circulatory system. The primary function of erythrocytes is as oxygen carriers; however, they also play an important role in the immune system. Erythrocytes recognize and adhere to antigens and promote phagocytosis. The abnormal morphology and function of erythrocytes are also involved in the pathological processes of some diseases. Owing to the large number and immune properties of erythrocytes, their immune functions should not be ignored. Currently, research on immunity is focused on immune cells other than erythrocytes. However, research on the immune function of erythrocytes and the development of erythrocyte-mediated applications is of great significance. Therefore, we aimed to review the relevant literature and summarize the immune functions of erythrocytes.

α1 Adrenoreceptor antagonism mitigates extracellular mitochondrial DNA accumulation in lung fibrosis models and in patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is increasingly associated with nerve-driven processes and endogenous innate immune ligands such as mitochondrial DNA (mtDNA). Interestingly, a connection between these entities has not been explored. Here, we report that noradrenaline (NA) derived from the lung's adrenergic nerve supply drives α-smooth muscle actin (αSMA)-expressing fibroblast accumulation via mechanisms involving α1 adrenoreceptors and mtDNA. Using the bleomycin model, we compared ablation of the lung's adrenergic nerve supply with surgical adrenal resection and found that NA derived from local but not adrenal sources contributes to experimentally induced lung fibrosis and the emergence of an αSMA+ve fibroblast population expressing adrenoreceptor α-1D (ADRA1D). Therapeutic delivery of the α1 adrenoreceptor antagonist terazosin reversed these changes and suppressed extracellular mtDNA accumulation. Cultured normal human lung fibroblasts displayed α1 adrenoreceptors and in response to costimulation with TGFβ1 and NA adopted ACTA2 expression and extracellular mtDNA release. These findings were opposed by terazosin. Evaluation of a previously studied IPF cohort revealed that patients prescribed α1 adrenoreceptor antagonists for nonpulmonary indications demonstrated improved survival and reduced concentrations of plasma mtDNA. Our observations link nerve-derived NA, α1 adrenoreceptors, extracellular mtDNA, and lung fibrogenesis in mouse models, cultured cells, and humans with IPF. Further study of this neuroinnate connection may yield new avenues for investigation in the clinical and basic science realms.

Melatonin ameliorates acute lung injury caused by paraquat poisoning by promoting PINK1 and BNIP3 expression

Paraquat (PQ) poisoning can result in multiple organ dysfunction syndrome, mainly manifesting as acute lung injury and acute respiratory distress syndrome. No specific cure exists for PQ poisoning. However, by scavenging mitochondrial DNA (mtDNA), the damage-associated molecular pattern during PQ poisoning, mitophagy can ameliorate the downstream inflammatory pathways activated by mtDNA. Melatonin (MEL), however, can promote the expression of PINK1 and BNIP3, which are key proteins involved in mitophagy. In this study, we first explored whether MT could reduce PQ-induced acute lung injury by affecting mitophagy in animal models, and then, we studied the specific mechanism associated with this process through in vitro experiments. We also evaluated MEL intervention in the PQ group, while inhibiting the expression of PINK1 and BNIP3, to further determine whether the protective effects of MEL are associated with its effect on mitophagy. We found that when the expression of PINK1 and BNIP3 was inhibited, MEL intervention could not reduce mtDNA leakage and the release of inflammatory factors caused by PQ exposure, suggesting that the protective effect of MEL was blocked. These results suggest that by promoting the expression of PINK1 and BNIP3 and activating mitophagy, MEL can reduce mtDNA/TLR9-mediated acute lung injury during PQ poisoning. The results of this study could provide guidance for the clinical treatment of PQ poisoning to reduce associated mortality.

Immune Mechanisms in Inflammatory Anemia

Maintaining the correct number of healthy red blood cells (RBCs) is critical for proper oxygenation of tissues throughout the body. Therefore, RBC homeostasis is a tightly controlled balance between RBC production and RBC clearance, through the processes of erythropoiesis and macrophage hemophagocytosis, respectively. However, during the inflammation associated with infectious, autoimmune, or inflammatory diseases this homeostatic process is often dysregulated, leading to acute or chronic anemia. In each disease setting, multiple mechanisms typically contribute to the development of inflammatory anemia, impinging on both sides of the RBC production and RBC clearance equation. These mechanisms include both direct and indirect effects of inflammatory cytokines and innate sensing. Here, we focus on common innate and adaptive immune mechanisms that contribute to inflammatory anemias using examples from several diseases, including hemophagocytic lymphohistiocytosis/macrophage activation syndrome, severe malarial anemia during Plasmodium infection, and systemic lupus erythematosus, among others.

Correlation between sphingomyelin and the membrane stability of mammalian erythrocytes

Lipid compositions of mammalian erythrocyte membranes are different among species. Therefore, the information on hemolysis from mammalian erythrocytes is useful to understand membrane properties of human erythrocytes. In this work, pressure-induced hemolysis and hypotonic one were examined using erythrocytes of human, sheep, cow, cat, dog, pig, horse, rat, and mouse. Pressure-induced hemolysis was suppressed by membrane sphingomyelin, whereas hypotonic hemolysis decreased upon increment of cell diameter. Mass spectra of erythrocyte membrane lipids demonstrated that sphingomyelin with an acyl chain 24:1 was associated with the suppression of pressure-induced hemolysis. In cow erythrocytes, pressure-induced hemolysis was greatly suppressed and the detachment of cytoskeletal proteins from the membrane under hypotonic conditions was also inhibited. Taken together, these results suggest that sphingomyelin with 24:1 fatty acid plays an important role in the stability of the erythrocyte membrane, perhaps via cholesterol.

Association of telomere length and mitochondrial DNA copy number, two biomarkers of biological aging, with the risk of venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE) is the third most common cardiovascular disease and occurs in all age groups, albeit the risk increases considerably with age. Previous research indicates mitochondrial dysfunction and telomere shortening in cardiovascular aging. However, in the context of VTE this has not been investigated in detail.

AIM

We aimed to explore biomarkers reflecting biological aging (i.e. human mitochondrial DNA copy number (mtDNA) and telomere length) and their association with VTE.

METHODS

mtDNA and telomere length were measured in a case-control study of 116 patients with a history of VTE and 128 age- and sex-matched healthy individuals from isolated blood using a qPCR-based assay kit. Cases had at least one unprovoked VTE event and were enrolled no earlier than 3 months after the last VTE event.

RESULTS

The mtDNA copy number was significantly lower in VTE cases compared to controls (median [IQR]: 663 per diploid cells [78.75-2204.5] vs. 2832 per diploid cells [724-4350]; p < 0.001). After adjustment for age, sex, BMI, and smoking, mtDNA copy number was independently associated with VTE risk (odds ratio per increase in 400 mtDNA per diploid cell: 0.889, 95%CI 0.834-0.947). mtDNA copy numbers were significantly different between women and men (2375 [455-3737] women vs. 893 [152-3154] men; p < 0.001). The analysis of telomere length showed no significant difference between patients and healthy controls.

CONCLUSION

Lower mtDNA levels were found in patients with VTE compared to controls, indicating an association of biological aging with risk of VTE.

Mature Red Blood Cells Contain Long DNA Fragments and Could Acquire DNA from Lung Cancer Tissue

Red blood cells (RBC) are commonly known as cells with no nucleus or mitochondria and are assumed to be a transportation vehicle. This study confirms that RBC contain long DNA fragments inside with stain by both microscope and flow cytometry, which covers most nuclear and mitochondrial genome regions by next-generation sequencing (NGS). Such characteristics demonstrate a significant difference compared with A549 cell line or paired peripheral blood mononuclear cell as nucleated cells. To further explore the characteristics of RNA DNA, DNA from 20 RBC samples is sequenced by NGS. Interestingly, several gaps and multiple regions with copy number variation are observed significantly different between different samples, which could be used to distinguish samples with different health status accurately. Using an in vitro co-culture system, it is shown that RBC could absorb DNA-bearing tumorigenic mutations from cancer cell lines but requires cell-to-cell contact. Finally, based on a small scale clinical trial, it is confirmed that common genetic mutations of cancer tissues could be detected in RBC from patients with early-stage non-small-cell lung cancer. This study highlights a new biological phenomenon involving RBC and its translational potential as a novel liquid biopsy technology platform for early cancer screening and diagnosis of malignancy.

Oxidized Mitochondrial DNA Engages TLR9 to Activate the NLRP3 Inflammasome in Myelodysplastic Syndromes

Myelodysplastic Syndromes (MDSs) are bone marrow (BM) failure malignancies characterized by constitutive innate immune activation, including NLRP3 inflammasome driven pyroptotic cell death. We recently reported that the danger-associated molecular pattern (DAMP) oxidized mitochondrial DNA (ox-mtDNA) is diagnostically increased in MDS plasma although the functional consequences remain poorly defined. We hypothesized that ox-mtDNA is released into the cytosol, upon NLRP3 inflammasome pyroptotic lysis, where it propagates and further enhances the inflammatory cell death feed-forward loop onto healthy tissues. This activation can be mediated via ox-mtDNA engagement of Toll-like receptor 9 (TLR9), an endosomal DNA sensing pattern recognition receptor known to prime and activate the inflammasome propagating the IFN-induced inflammatory response in neighboring healthy hematopoietic stem and progenitor cells (HSPCs), which presents a potentially targetable axis for the reduction in inflammasome activation in MDS. We found that extracellular ox-mtDNA activates the TLR9-MyD88-inflammasome pathway, demonstrated by increased lysosome formation, IRF7 translocation, and interferon-stimulated gene (ISG) production. Extracellular ox-mtDNA also induces TLR9 redistribution in MDS HSPCs to the cell surface. The effects on NLRP3 inflammasome activation were validated by blocking TLR9 activation via chemical inhibition and CRISPR knockout, demonstrating that TLR9 was necessary for ox-mtDNA-mediated inflammasome activation. Conversely, lentiviral overexpression of TLR9 sensitized cells to ox-mtDNA. Lastly, inhibiting TLR9 restored hematopoietic colony formation in MDS BM. We conclude that MDS HSPCs are primed for inflammasome activation via ox-mtDNA released by pyroptotic cells. Blocking the TLR9/ox-mtDNA axis may prove to be a novel therapeutic strategy for MDS.

The ultimate tradeoff: how red cell adaptations to malaria alter the host response during critical illness

The human immune system evolved in response to pathogens. Among these pathogens, malaria has proven to be one of the deadliest and has exerted the most potent selective pressures on its target cell, the red blood cell. Red blood cells have recently gained recognition for their immunomodulatory properties, yet how red cell adaptations contribute to the host response during critical illness remains understudied. This review will discuss how adaptations that may have been advantageous for host survival might influence immune responses in modern critical illness. We will highlight the current evidence for divergent host resilience arising from the adaptations to malaria and summarize how understanding evolutionary red cell adaptations to malaria may provide insight into the heterogeneity of the host response to critical illness, perhaps driving future precision medicine approaches to syndromes affecting the critically ill such as sepsis and acute respiratory distress syndrome (ARDS).

Unexplored Roles of Erythrocytes in Atherothrombotic Stroke

Stroke constitutes the second highest cause of morbidity and mortality worldwide while also impacting the world economy, triggering substantial financial burden in national health systems. High levels of blood glucose, homocysteine, and cholesterol are causative factors for atherothrombosis. These molecules induce erythrocyte dysfunction, which can culminate in atherosclerosis, thrombosis, thrombus stabilization, and post-stroke hypoxia. Glucose, toxic lipids, and homocysteine result in erythrocyte oxidative stress. This leads to phosphatidylserine exposure, promoting phagocytosis. Phagocytosis by endothelial cells, intraplaque macrophages, and vascular smooth muscle cells contribute to the expansion of the atherosclerotic plaque. In addition, oxidative stress-induced erythrocytes and endothelial cell arginase upregulation limit the pool for nitric oxide synthesis, leading to endothelial activation. Increased arginase activity may also lead to the formation of polyamines, which limit the deformability of red blood cells, hence facilitating erythrophagocytosis. Erythrocytes can also participate in the activation of platelets through the release of ADP and ATP and the activation of death receptors and pro-thrombin. Damaged erythrocytes can also associate with neutrophil extracellular traps and subsequently activate T lymphocytes. In addition, reduced levels of CD47 protein in the surface of red blood cells can also lead to erythrophagocytosis and a reduced association with fibrinogen. In the ischemic tissue, impaired erythrocyte 2,3 biphosphoglycerate, because of obesity or aging, can also favor hypoxic brain inflammation, while the release of damage molecules can lead to further erythrocyte dysfunction and death.

Mitochondria as novel mediators linking gut microbiota to atherosclerosis that is ameliorated by herbal medicine: A review

Atherosclerosis (AS) is the main cause of cardiovascular disease (CVD) and is characterized by endothelial damage, lipid deposition, and chronic inflammation. Gut microbiota plays an important role in the occurrence and development of AS by regulating host metabolism and immunity. As human mitochondria evolved from primordial bacteria have homologous characteristics, they are attacked by microbial pathogens as target organelles, thus contributing to energy metabolism disorders, oxidative stress, and apoptosis. Therefore, mitochondria may be a key mediator of intestinal microbiota disorders and AS aggravation. Microbial metabolites, such as short-chain fatty acids, trimethylamine, hydrogen sulfide, and bile acids, also affect mitochondrial function, including mtDNA mutation, oxidative stress, and mitophagy, promoting low-grade inflammation. This further damages cellular homeostasis and the balance of innate immunity, aggravating AS. Herbal medicines and their monomers can effectively ameliorate the intestinal flora and their metabolites, improve mitochondrial function, and inhibit atherosclerotic plaques. This review focuses on the interaction between gut microbiota and mitochondria in AS and explores a therapeutic strategy for restoring mitochondrial function and intestinal microbiota disorders using herbal medicines, aiming to provide new insights for the prevention and treatment of AS.

Expression of fibrinogen-like protein 2 (Fgl2) on Toll-like receptor 9 (TLR9) expression in autoimmune myelitis

Toll-like receptor 9 (TLR9) can participate in the signal transduction of activated immune cells and induce myelitis and other autoimmune diseases. The effector molecule fibrin-like protein 2 (Fgl2) plays a role in regulating the body's autoimmune signaling pathway. They both have the conditions for the treatment of this disease target. The objective of this work was to investigate the effect of Fgl2 on the expression of DNA receptor TLR9 in autoimmune myelitis. 140 rats were randomly divided into a normal control group, an autoimmune myelitis group, a low-dose Fgl2 group, a middle-dose Fgl2 group, a higher-dose Fgl2 group, a high-dose Fgl2 group, and a methylprednisolone group. Different injection methods were used in each group. The changes of rat behavior and disease were recorded, and brain and spinal cord tissue slices were made for observation. The results showed that in the high dose Fgl2 group, the incidence of disease was 15 %, the nerve injury score was 1.0 ± 0.15, the body weight change was -5.8 ± 1.24 g, the number of spinal cord tissue injury was 1.82 ± 0.44, the number of TLR9 positive cells in the brain tissue was 7.53 ± 1.84, and the number of TLR9 positive cells in spinal cord tissue was 5.02 ± 1.81. These indexes were lower than those in other Fgl2 groups and significantly lower than those in autoimmune myelitis group (P < 0.05). The average incubation period of the disease was 13.66 ± 0.41 days, which was significantly higher than that of the autoimmune myelitis group (P < 0.05). It can be observed that TLR9 signaling pathway played an important role in the occurrence and development of autoimmune myelitis. With the increase of Fgl2 dose, the number of TLR9 positive cells decreased gradually. Fgl2 treatment can reduce the expression of inflammatory factors and the severity of dysfunction in autoimmune myelitis, inhibit the expression of TLR9, and improve the condition of autoimmune myelitis.

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.

Recent applications of immunomodulatory biomaterials for disease immunotherapy

Immunotherapy is used to regulate systemic hyperactivation or hypoactivation to treat various diseases. Biomaterial-based immunotherapy systems can improve therapeutic effects through targeted drug delivery, immunoengineering, etc. However, the immunomodulatory effects of biomaterials themselves cannot be neglected. In this review, we outline biomaterials with immunomodulatory functions discovered in recent years and their applications in disease treatment. These biomaterials can treat inflammation, tumors, or autoimmune diseases by regulating immune cell function, exerting enzyme-like activity, neutralizing cytokines, etc. The prospects and challenges of biomaterial-based modulation of immunotherapy are also discussed.

Mitochondrial antioxidant SkQ1 decreases inflammation following hemorrhagic shock by protecting myocardial mitochondria

Background: Hemorrhagic shock (HS) is a type of hypovolemic shock characterized by hemodynamic instability, tissue hypoperfusion and cellular hypoxia. In pathophysiology, the gradual accumulation of reactive oxygen species (ROS) damages the mitochondria, leading to irreversible cell damage and the release of endogenous damage-associated molecular patterns (DAMPs) including mitochondrial DAMPs (MTDs), eventually triggering the inflammatory response. The novel mitochondria-targeted antioxidant SkQ1 (Visomitin) effectively eliminate excessive intracellular ROS and exhibits anti-inflammatory effects; however, the specific role of SkQ1 in HS has not yet been explicated. Methods and results: A 40% fixed-blood-loss HS rat model was established in this study. Transmission electron microscopy showed that after HS, the myocardial mitochondrial ultrastructure was damaged and the mtDNA release in circulation was increased and the differentially expressed genes were significantly enriched in mitochondrial and ROS-related pathways. Mitochondria-targeted antioxidant SkQ1 attenuated the increased ROS induced by HS in myocardial tissues and by oxygen-glucose deprivation (OGD) in cardiomyocytes. Ultrastructurally, SkQ1 protected the myocardial mitochondrial structure and reduced the release of the peripheral blood mtDNA after HS. RNA-seq transcriptome analysis showed that 56.5% of the inflammation-related genes, which altered after HS, could be significantly reversed after SkQ1 treatment. Moreover, ELISA indicated that SkQ1 significantly reversed the HS-induced increases in the TNF-α, IL-6, and MCP-1 protein levels in rat peripheral blood. Conclusion: HS causes damage to the rat myocardial mitochondrial structure, increases mtDNA release and ROS contents, activates the mitochondrial and ROS-related pathways, and induces systemic inflammatory response. The mitochondrial antioxidant SkQ1 can improve rat myocardial mitochondria ultrastructure, reduce mtDNA and ROS contents, and decrease inflammation by protecting myocardial mitochondria, thereby playing a novel protective role in HS.

Immunomodulatory roles of red blood cells

PURPOSE OF THE REVIEW

To discuss recent advances supporting the role of red blood cells (RBCs) in the host immune response.

RECENT FINDINGS

Over the last century, research has demonstrated that red blood cells exhibit functions beyond oxygen transport, including immune function. Recent work indicates that the nucleic acid sensing receptor, toll-like receptor 9 (TLR9), is expressed on the RBC surface and implicated in innate immune activation and red cell clearance during inflammatory states. In addition to this DNA-sensing role of RBCs, there is growing evidence that RBCs may influence immune function by inducing vascular dysfunction. RBC proteomics and metabolomics have provided additional insight into RBC immune function, with several studies indicating changes to RBC membrane structure and metabolism in response to severe acute respiratory syndrome coronavirus 2 infection. These structural RBC changes may even provide insight into the pathophysiology of the 'long-coronavirus disease 2019' phenomenon. Finally, evidence suggests that RBCs may influence host immune responses via complement regulation. Taken together, these recent findings indicate RBCs possess immune function. Further studies will be required to elucidate better how RBC immune function contributes to the heterogeneous host response during inflammatory states.

SUMMARY

The appreciation for nongas exchanging, red blood cell immune functions is rapidly growing. A better understanding of these RBC functions may provide insight into the heterogeneity observed in the host immune response to infection and inflammation.

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.

TLR9: A friend or a foe

The innate immune system is a primary protective line in our body. It confers its protection through different pattern recognition receptors (PRRs), especially toll like receptors (TLRs). Toll like receptor 9 (TLR9) is an intracellular TLR, expressed in different immunological and non-immunological cells. Release of cellular components, such as proteins, nucleotides, and DNA confers a beneficial inflammatory response and maintains homeostasis for removing cellular debris during normal physiological conditions. However, during pathological cellular damage and stress signals, engagement between mtDNA and TLR9 acts as an alarm for starting inflammatory and autoimmune disorders. The controversial role of TLR9 in different diseases baffled scientists if it has a protective or deleterious effect after activation during insults. Targeting the immune system, especially the TLR9 needs further investigation to provide a therapeutic strategy to control inflammation and autoimmune disorders.