Relationship between cardiovascular diseases and circulating cell-free nucleic acids in human plasma

Cardiovascular disease treatment using traditional Chinese medicine：Mitochondria as the Achilles' heel

Cardiovascular disease (CVD), involving the pathological alteration of the heart or blood vessels, is one of the main causes of disability and death worldwide, with an estimated 18.6 million deaths per year. CVDs are caused by a variety of risk factors, including inflammation, hyperglycemia, hyperlipidemia, and increased oxidative stress. Mitochondria, the hub of ATP production and the main generator of reactive oxygen species (ROS), are linked to multiple cellular signaling pathways that regulate the progression of CVD and therefore are recognized as an essential target for CVD management. Initial treatment of CVD generally focuses on diet and lifestyle interventions; proper drugs or surgery can prolong or save the patient's life. Traditional Chinese medicine (TCM), a holistic medical care system with an over 2500-year history, has been proven to be efficient in curing CVD and other illnesses, with a strengthening effect on the body. However, the mechanisms underlying TCM alleviation of CVD remain elusive. Recent studies have recognized that TCM can alleviate cardiovascular disease by manipulating the quality and function of mitochondria. This review systematically summarizes the association of mitochondria with cardiovascular risk factors, and the relationships between mitochondrial dysfunction and CVD progression. We will investigate the research progress of managing cardiovascular disease by TCM and cover widely used TCMs that target mitochondria for the treatment of cardiovascular disease.

Cell-Free Mitochondrial DNA as a Potential Biomarker for Astronauts' Health

Background

Space travel–associated stressors such as microgravity or radiation exposure have been reported in astronauts after short‐ and long‐duration missions aboard the International Space Station. Despite risk mitigation strategies, adverse health effects remain a concern. Thus, there is a need to develop new diagnostic tools to facilitate early detection of physiological stress.

Methods and Results

We measured the levels of circulating cell‐free mitochondrial DNA in blood plasma of 14 astronauts 10 days before launch, the day of landing, and 3 days after return. Our results revealed a significant increase of cell‐free mitochondrial DNA in the plasma on the day of landing and 3 days after return with vast ~2 to 355‐fold interastronaut variability. In addition, gene expression analysis of peripheral blood mononuclear cells revealed a significant increase in markers of inflammation, oxidative stress, and DNA damage.

Conclusions

Our study suggests that cell‐free mitochondrial DNA abundance might be a biomarker of stress or immune response related to microgravity, radiation, and other environmental factors during space flight.

Accurate Measurement of Cellular and Cell-Free Circulating Mitochondrial DNA Content from Human Blood Samples Using Real-Time Quantitative PCR

Changes in circulating mitochondrial DNA (mtDNA) are widely used to indicate mitochondrial dysfunction in common non-genetic diseases where mitochondrial dysfunction may play a role. However, the methodology being used is not always specific and reproducible, and most studies use whole blood rather than evaluating cellular and cell-free mtDNA separately. Cellular mtDNA is contained within the mitochondrion and encodes vital subunits of the OXPHOS machinery. Conversely, cell-free mtDNA can have harmful effects, triggering inflammatory responses and potentially contributing to pathogenic processes. In this chapter, we describe a protocol to accurately measure the amount of cellular and cell-free human mtDNA in peripheral blood. Absolute quantification is carried out using real-time quantitative PCR (qPCR) to quantify cellular mtDNA, measured as the mitochondrial genome to nuclear genome ratio (designated the Mt/N ratio) in whole blood and peripheral blood mononuclear cells (PBMCs) and the number of mtDNA copies per μL in plasma and serum. We describe how to (1) separate whole blood into PBMCs, plasma, and serum fractions, (2) prepare DNA from each of these fractions, (3) prepare dilution standards for absolute quantification, (4) carry out qPCR for either relative or absolute quantification from test samples, (5) analyze qPCR data, and (6) calculate the sample size to adequately power studies. The protocol presented here is suitable for high-throughput use and can be modified to quantify mtDNA from other body fluids, human cells, and tissues.

Quantification of Circulating Cell Free Mitochondrial DNA in Extracellular Vesicles with PicoGreen™ in Liquid Biopsies: Fast Assessment of Disease/Trauma Severity

The analysis of circulating cell free DNA (ccf-DNA) is an emerging diagnostic tool for the detection and monitoring of tissue injury, disease progression, and potential treatment effects. Currently, most of ccf-DNA in tissue and liquid biopsies is analysed with real-time quantitative PCR (qPCR) that is primer- and template-specific, labour intensive and cost-inefficient. In this report we directly compare the amounts of ccf-DNA in serum of healthy volunteers, and subjects presenting with various stages of lung adenocarcinoma, and survivors of traumatic brain injury using qPCR and quantitative PicoGreen™ fluorescence assay. A significant increase of ccf-DNA in lung adenocarcinoma and traumatic brain injury patients, in comparison to the group of healthy human subjects, was found using both analytical methods. However, the direct correlation between PicoGreen™ fluorescence and qPCR was found only when mitochondrial DNA (mtDNA)-specific primers were used. Further analysis of the location of ccf-DNA indicated that the majority of DNA is located within lumen of extracellular vesicles (EVs) and is easily detected with mtDNA-specific primers. We have concluded that due to the presence of active DNases in the blood, the analysis of DNA within EVs has the potential of providing rapid diagnostic outcomes. Moreover, we speculate that accurate and rapid quantification of ccf-DNA with PicoGreen™ fluorescent probe used as a point of care approach could facilitate immediate assessment and treatment of critically ill patients.

The Impact of Circulating Tumor Cells on Venous Thromboembolism and Cardiovascular Events in Bladder Cancer Patients Treated with Radical Cystectomy

BACKGROUND

Cancer is a relevant risk factor for venous thromboembolism (VTE). Circulating tumor cells (CTC) are associated with an increased risk of VTE in breast cancer. In addition, circulating cell-free nucleic acids have been associated with cardiovascular events (CVE).

OBJECTIVE

To investigate the association of CTC status and the risk of VTE as well as CVE in urothelial carcinoma of the bladder (UCB) patients treated with radical cystectomy (RC).

METHODS

We collected data of 189 UCB patients treated with RC at our institution. Blood samples were acquired preoperatively and analyzed for CTC using the CellSearch^® system. Thirty-day postoperative complications were extracted from digital charts and graded according to the Clavien-Dindo classification (CDC). Moreover, each patient's individual Comprehensive Complication Index^® (CCI^®) was calculated.

RESULTS

CTC were present in 43 patients (22.8%). Overall, six patients experienced VTE (3.2%) and eight patients (4.2%) experienced CVE. There was no association of VTE or CVE according to CTC status. In total, 168 patients (89%) experienced a total of 801 complications, of which the majority was classified as "minor" (CDC grade ≤ IIIa; 79%). There was no association between CTC status and any grade of a complication or CCI^®. Presence of CTC was associated with more aggressive clinicopathological UCB features.

CONCLUSIONS

The overall rate of VTE and CVE was low in our study. Presence of CTC was neither associated with an increased risk of VTE nor CVE in UCB patients treated with RC. According to this study, CTC are not a qualified biomarker for individualized thromboprophylaxis management in these patients.

Impacts of elevated pCO2 on Mediterranean mussel (Mytilus galloprovincialis): Metal bioaccumulation, physiological and cellular parameters

Ocean acidification alters physiology, acid-base balance and metabolic activity in marine animals. Near future elevated pCO₂ conditions could be expected to influence the bioaccumulation of metals, feeding rate and immune parameters in marine mussels. To better understand such impairments, a series of laboratory-controlled experiment was conducted by using a model marine mussel, Mytilus galloprovincialis. The mussels were exposed to three pH conditions according to the projected CO₂ emissions in the near future (one ambient: 8.10 and two reduced: 7.80 and 7.50). At first, the bioconcentration of Ag and Cd was studied in both juvenile (2.5 cm) and adult (5.1 cm) mussels by using a highly sensitive radiotracer method (^110mAg and ¹⁰⁹Cd). The uptake and depuration kinetics were followed 21 and 30 days, respectively. The biokinetic experiments demonstrated that the effect of ocean acidification on bioconcentration was metal-specific and size-specific. The uptake, depuration and tissue distribution of ^110mAg were not affected by elevated pCO₂ in both juvenile and adult mussels, whereas ¹⁰⁹Cd uptake significantly increased with decreasing pH in juveniles but not in adults. Regardless of pH, ^110mAg accumulated more efficiently in juvenile mussels than adult mussels. After executing the biokinetic experiment, the perturbation was sustained by using the same mussels and the same experimental set-up, which enabled us to determine filtration rate, haemocyte viability, lysosomal membrane stability, circulating cell-free nucleic acids (ccf-NAs) and protein (ccf-protein) levels. The filtration rate and haemocyte viability gradually decreased by increasing pCO₂ level, whereas the lysosomal membrane stability, ccf-NAs, and ccf-protein levels remained unchanged in the mussels exposed to elevated pCO₂ for eighty-two days. This study suggests that acidified seawater partially shift metal bioaccumulation, physiological and cellular parameters in the mussel Mytilus galloprovincialis.

A case for measuring both cellular and cell-free mitochondrial DNA as a disease biomarker in human blood

Circulating mitochondrial DNA (mtDNA), widely studied as a disease biomarker, comprises of mtDNA located within mitochondria, indicative of mitochondrial function, and cell-free (cf) mtDNA linked to inflammation. The purpose of this study was to determine the ranges of, and relationship between, cellular and cf mtDNA in human blood. Whole blood from 23 controls (HC) and 20 patients with diabetes was separated into peripheral blood mononuclear cells (PBMCs), plasma, and serum. Total DNA was isolated and mtDNA copy numbers were determined using absolute quantification. Cellular mtDNA content in PBMCs was higher than in peripheral blood and a surprisingly high level of cf mtDNA was present in serum and plasma of HC, with no direct relationship between cellular and cf mtDNA content within individuals. Diabetes patients had similar levels of cellular mtDNA compared to healthy participants but a significantly higher cf mtDNA content. Furthermore, only in patients with diabetes, we observed a correlation between whole blood and plasma mtDNA levels, indicating that the relationship between cellular and cf mtDNA content is affected by disease status. In conclusion, when evaluating mtDNA in human blood as a biomarker of mitochondrial dysfunction, it is important to measure both cellular and cf mtDNA.

Guidelines for the Preanalytical Conditions for Analyzing Circulating Cell-Free DNA

Circulating cell-free DNA (cfDNA) isolated from blood has been identified as a potential biomarker in numerous fields, and has been the object of intensive research over the past decade, although its original discovery dates back 60 years. While it is already used routinely in commercial and clinical practice in oncology and prenatal testing, other potential applications have emerged, including for diabetes, cardiovascular diseases, organ transplantation, autoimmune diseases, sepsis, trauma, and sport management. As with the discovery and development of any biomarker, preanalytical requirements and documentation are as important as analytical requirements. Except for the case of noninvasive prenatal testing and prenatal diagnosis, the implementation of cfDNA in a clinical setting remains limited because of the lack of standardization of cfDNA analysis. In particular, only a few attempts have been made to collect and pool scientific data on the relevant preanalytical factors, and no standard operating procedure has yet been set. For this report, we have performed a thorough and systematic search via MEDLINE® for relevant preanalytical variables and patient factors. These form the basis of the guidelines we propose for analyzing nuclear cfDNA.

Quantitative analysis of individual cell-free DNA concentration before and after penetrating trauma

INTRODUCTION

Cell-free DNA (cfDNA) elevations were remarked in the blood of trauma patients. Published increases refer to comparative values of a healthy control group, ignoring thereby inter- and intra-individual differences under normal conditions. The aim of this study was to quantify cfDNA in patients in the time course of a planned orthopedic surgery, which constitutes the advantage of obtaining individual pre- and post-trauma values for each patient. By this approach, a basis should be established for the potential future application of cfDNA as biomarker for the detection of mild injuries related to volunteer experiments in forensic biomechanics.

METHODS

Plasma samples of ten patients obtaining knee or hip arthroplasty were analyzed quantitatively for cfDNA by real-time qPCR the day prior operation (Prior), immediately afterwards (Day0), and the day after the surgery (Day1).

RESULTS

Prior values exhibited a broad range, indicating pronounced inter-individual differences in the basic level of cfDNA. After surgery, levels were significantly elevated on both days (Wilcoxon test p = 0.002). In nine patients, highest values were measured on Day0, whereby a fold change of 19 was remarked once. After Day0, values decreased, though they did not reach Prior values until Day1 in nine patients.

CONCLUSION

Endoprosthesis surgery represents a well-defined trauma scenario for the measurement of individual cfDNA elevations. The analysis of pre- to post-trauma alterations lay the groundwork for the application of cfDNA as biomarker for the detection of minor injuries in the field of forensic biomechanics.