Plasma mtDNA as a possible contributor to and biomarker of inflammation in rheumatoid arthritis

OBJECTIVES

Neutrophil extracellular trap formation and cell-free DNA (cfDNA) contribute to the inflammation in rheumatoid arthritis (RA), but it is unknown if mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) is more abundant in the circulation. It is unclear if DNA concentration measurements may assist in clinical decision-making.

METHODS

This single-center prospective observational study collected plasma from consecutive RA patients and healthy blood donors. Platelets were removed, and mtDNA and nDNA copy numbers were quantified by polymerase chain reaction (PCR).

RESULTS

One hundred six RA patients and 85 healthy controls (HC) were recruited. Circulating median mtDNA copy numbers were increased 19.4-fold in the plasma of patients with RA (median 1.1 x108 copies/mL) compared to HC (median 5.4 x106 copies/mL, p<0.0001). Receiver operating characteristics (ROC) curve analysis of mtDNA copy numbers identified RA patients with high sensitivity (92.5%) and specificity (89.4%) with an area under the curve (AUC) of 0.97, p <0.0001 and a positive likelihood ratio of 8.7. Demographic, serological (rheumatoid factor (RF) positivity, anti-citrullinated protein antibodies (ACPA) positivity) and treatment factors were not associated with DNA concentrations. mtDNA plasma concentrations, however, correlated significantly with disease activity score-28- erythrocyte sedimentation rate (DAS28-ESR) and increased numerically with increasing DAS28-ESR and clinical disease activity index (CDAI) activity. MtDNA copy numbers also discriminated RA in remission (DAS28 <2.6) from HC (p<0.0001). Also, a correlation was observed between mtDNA and the ESR (p = 0.006, R= 0.29). Similar analyses showed no significance for nDNA.

CONCLUSION

In contrast to nDNA, mtDNA is significantly elevated in the plasma of RA patients compared with HC. Regardless of RA activity, the abundance of circulating mtDNA is a sensitive discriminator between RA patients and HC. Further validation of the diagnostic value of mtDNA testing is required.

Role of mitochondrial DNA level in epidural-related maternal fever: a single-centre, observational, pilot study

INTRODUCTION

Epidural analgesia has been associated with intrapartum maternal fever development. Epidural-related maternal fever (ERMF) is believed to be based on a non-infectious inflammatory reaction. Circulating cell-free mitochondrial deoxyribonucleic acid (mtDNA) is one of the possible triggers of sterile inflammatory processes; however, a connection has not been investigated so far. Therefore, this study aimed to investigate cell-free mtDNA alterations in women in labour with ERMF in comparison with non-febrile women.

MATERIAL AND METHODS

A total of 60 women in labour were assessed for maternal temperature every 4 h and blood samples were obtained at the beginning and after delivery. Depending on the analgesia and the development of fever (axillary temperature ≥ 37.5 °C), the women were allocated either to the group of no epidural analgesia (n = 17), to epidural analgesia no fever (n = 34) or to ERMF (n = 9). Circulating cell-free mtDNA was analysed in the maternal plasma for the primary outcome whereas secondary outcomes include the evaluation of inflammatory cytokine release, as well as placental inflammatory signs.

RESULTS

Of the women with epidural analgesia, 20% (n = 9) developed ERMF and demonstrated a decrease of circulating mtDNA levels during labour (p = 0.04), but a trend towards higher free nuclear DNA. Furthermore, women with maternal pyrexia showed a 1.5 fold increased level of Interleukin-6 during labour. A correlation was found between premature rupture of membranes and ERMF.

CONCLUSIONS

The pilot trial revealed an evident obstetric anaesthesia phenomenon of maternal fever due to epidural analgesia in 20% of women in labour, demonstrating counterregulated free mtDNA and nDNA. Further work is urgently required to understand the connections between the ERMF occurrence and circulating cell-free mtDNA as a potential source of sterile inflammation.

TRIAL REGISTRATION

NCT0405223 on clinicaltrials.gov (registered on 25/07/2019).

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.

Inverse associations of cord blood mitochondrial DNA copy number with childhood adiposity

OBJECTIVE

The objective of this study was to examine associations between umbilical cord mitochondrial DNA copy number (mtDNAcn) and adiposity across childhood.

METHODS

In a prospective birth cohort of Dominican and African American children from New York City, New York (1998-2006), mtDNAcn was measured in cord blood. Children (N = 336) were evaluated for their height, weight, and bioimpedance at age 5, 7, 9, and 11 years. We used linear mixed-effects models to assess associations of mtDNAcn tertiles in cord blood with child BMI, BMI z scores, fat mass index, and body fat percentage. Latent class growth models and interactions between mtDNAcn and child age or child age2 were used to assess associations between age and adiposity trajectories.

RESULTS

BMI was, on average, 1.5 kg/m2 higher (95% CI: 0.58, 2.5) in individuals with mtDNAcn in the low- compared with the middle-mtDNAcn tertile. Results were similar for BMI z score, fat mass index, and body fat percentage. Moreover, children in the low-mtDNAcn group had increased odds of being in an "increasing" or "high-stable" adiposity class.

CONCLUSIONS

Lower mtDNAcn at birth may predict greater childhood adiposity, highlighting the potential key role of perinatal mitochondrial function in adiposity during development.

A tight interplay between platelet activation and mitochondrial DNA release promotes platelet storage lesion in platelet concentrates

BACKGROUND AND OBJECTIVES

Platelet storage lesion (PSL) adversely affects the quality of platelet concentrates (PCs). Platelets are prone to activation during storage. Moreover, elevated free mitochondrial DNA (mtDNA) levels in PCs are associated with a higher risk of adverse transfusion reactions. Therefore, we aimed to evaluate the correlation between platelet activation markers and mtDNA release during PC storage.

MATERIALS AND METHODS

Six PCs prepared by the platelet-rich plasma method were assessed for free mtDNA copy number using quantitative real-time PCR and CD62P (P-selectin) expression by flow cytometry on days 0 (PC collection day), 3, 5 and 7 of storage. Lactate dehydrogenase (LDH) activity, pH, platelet count, mean platelet volume (MPV) and platelet distribution width (PDW) were measured as well. The correlation between free mtDNA and other PSL parameters, and the correlation between all parameters, was determined.

RESULTS

Significant increases in free mtDNA, MPV and PDW, and a significant decrease in platelet count and pH were observed. CD62P expression and LDH activity elevated significantly, particularly on storage days 5-7 and 0-3, respectively. Moreover, a moderate positive correlation (r = 0.61) was observed between free mtDNA and CD62P expression. The r values between free mtDNA and LDH, pH, platelet count, MPV and PDW were 0.81, -0.72, -0.49, 0.81 and 0.77, respectively.

CONCLUSION

The interplay between platelet activation and mtDNA release in promoting PSL in PCs may serve as a promising target for future research on applying additive solutions and evaluating the quality of PCs to improve transfusion and clinical outcomes.

Circulating Mitochondrial DNA Is Associated With High Levels of Fatigue in Two Independent Sarcoidosis Cohorts

BACKGROUND

Patients with sarcoidosis who develop severe clinical phenotypes of pulmonary fibrosis or multiorgan disease experience debilitating symptoms, with fatigue being a common chief complaint. Studies that have investigated this patient-related outcome measure (PROM) have used the Fatigue Assessment Scale (FAS), a self-reported questionnaire that reflects mental and physical domains. Despite extensive work, its cause is unknown and treatment options remain limited. Previously, we showed that the plasma of patients with sarcoidosis with extrapulmonary disease endorsing fatigue was enriched for mitochondrial DNA (mtDNA), a ligand for the innate immune receptor toll-like receptor 9 (TLR9). Through our cross-disciplinary platform, we investigated a relationship between sarcoidosis-induced fatigue and circulating mtDNA.

RESEARCH QUESTION

Is there a psychobiologic mechanism that connects sarcoidosis-induced fatigue and mtDNA-mediated TLR9 activation?

STUDY DESIGN AND METHODS

Using a local cohort of patients at Yale (discovery cohort) and the National Institutes of Health-sponsored Genomic Research in Alpha-1 Antitrypsin Deficiency and Sarcoidosis study (validation cohort), we scored the FAS and quantified in the plasma, mtDNA concentrations, TLR9 activation, and cytokine levels.

RESULTS

Although FAS scores were independent of corticosteroid use and Scadding stage, we observed a robust association between FAS scores, which included mental and physical domains, and multiorgan sarcoidosis. Subsequently, we identified a significant correlation between plasma mtDNA concentrations and all domains of fatigue. Additionally, we found that TLR9 activation is associated with all aspects of the FAS and partially mediates this PROM through mtDNA. Last, we found that TLR9-associated soluble mediators in the plasma are independent of all facets of fatigue.

INTERPRETATION

Through our cross-disciplinary translational platform, we identified a previously unrecognized psychobiologic connection between sarcoidosis-induced fatigue and circulating mtDNA concentrations. Mechanistic work that investigates the contribution of mtDNA-mediated innate immune activation in this PROM and clinical studies with prospective cohorts has the potential to catalyze novel therapeutic strategies for this patient population and those with similar conditions.

Higher peripheral blood mitochondrial DNA copy number and relative telomere length in under 48 years Indonesian breast cancer patients

OBJECTIVE

Breast cancer is the leading cause of cancer incidence and mortality among Indonesian women. A comprehensive investigation is required to enhance the early detection of this disease. Mitochondrial DNA copy number (mtDNA-CN) and relative telomere length (RTL) have been proposed as potential biomarkers for several cancer risks, as they are linked through oxidative stress mechanisms. We conducted a case-control study to examine peripheral blood mtDNA-CN and RTL patterns in Indonesian breast cancer patients (n = 175) and healthy individuals (n = 181). The relative ratios of mtDNA-CN and RTL were determined using quantitative real-time PCR (qPCR).

RESULTS

Median values of mtDNA-CN and RTL were 1.62 and 0.70 in healthy subjects and 1.79 and 0.73 in breast cancer patients, respectively. We found a positive association between peripheral blood mtDNA-CN and RTL (p < 0.001). In under 48 years old breast cancer patients, higher peripheral blood mtDNA-CN (mtDNA-CN ≥ 1.73 (median), p = 0.009) and RTL (continuous variable, p = 0.010) were observed, compared to the corresponding healthy subjects. We also found a significantly higher 'High-High' pattern of mtDNA-CN and RTL in breast cancer patients under 48 years old (p = 0.011). Our findings suggest that peripheral blood mtDNA-CN and RTL could serve as additional minimally invasive biomarkers for breast cancer risk evaluation.

Mitochondrial Fraction of Circulating Cell-Free DNA as an Indicator of Human Pathology

Circulating cell-free DNA (ccfDNA) of mitochondrial origin (ccf-mtDNA) consists of a minor fraction of total ccfDNA in blood or in other biological fluids. Aberrant levels of ccf-mtDNA have been observed in many pathologies. Here, we introduce a simple and effective standardized Taqman probe-based dual-qPCR assay for the simultaneous detection and relative quantification of nuclear and mitochondrial fragments of ccfDNA. Three pathologies of major burden, one malignancy (Breast Cancer, BrCa), one inflammatory (Osteoarthritis, OA) and one metabolic (Type 2 Diabetes, T2D), were studied. Higher levels of ccf-mtDNA were detected both in BrCa and T2D in relation to health, but not in OA. In BrCa, hormonal receptor status was associated with ccf-mtDNA levels. Machine learning analysis of ccf-mtDNA datasets was used to build biosignatures of clinical relevance. (A) a three-feature biosignature discriminating between health and BrCa (AUC: 0.887) and a five-feature biosignature for predicting the overall survival of BrCa patients (Concordance Index: 0.756). (B) a five-feature biosignature stratifying among T2D, prediabetes and health (AUC: 0.772); a five-feature biosignature discriminating between T2D and health (AUC: 0.797); and a four-feature biosignature identifying prediabetes from health (AUC: 0.795). (C) a biosignature including total plasma ccfDNA with very high performance in discriminating OA from health (AUC: 0.934). Aberrant ccf-mtDNA levels could have diagnostic/prognostic potential in BrCa and Diabetes, while the developed multiparameter biosignatures can add value to their clinical management.

Circulating cell-free mitochondrial DNA as a diagnostic and prognostic biomarker in chronic and late acute graft-versus-host disease in children

In an earlier study, we found that mitochondrial DNA (mtDNA) concentration is elevated in adults with chronic graft-versus-host disease (cGvHD), acting as an endogenous source of TLR9 agonists to augment B-cell responses. To validate this in children, we evaluated mtDNA plasma expression in a large pediatric cohort (ABLE/PBMTC 1202 study). Plasma cell-free mtDNA (cf-mtDNA) copy numbers were measured in 202 pediatric patients using quantitative Droplet Digital polymerase chain reaction (ddPCR). Two evaluations were performed: 1) before the onset of cGvHD or late acute graft-versus-host disease (aGvHD) at day 100 ± 14 days and 2) at the time of cGvHD onset compared with time-matched non-cGvHD controls. We found that cf-mtDNA copy numbers were not affected by immune reconstitution post-hematopoietic stem cell transplantation but were higher on day 100 before the onset of late aGvHD and at the onset of cGvHD. We found that cf-mtDNA was not impacted by previous aGvHD, but correlated with the early onset, NIH moderate/severe cGvHD, and did not correlate with other immune cell populations, cytokines, or chemokines but did with the metabolites spermine and taurine. Similar to adults, children have elevated plasma cf-mtDNA concentrations at the early onset of cGvHD, especially in NIH moderate/severe cGvHD, elevation with late aGvHD, and associated with metabolites involved in mitochondrial function.

Plasma Cell-Free Mitochondrial DNA as a Marker of Geriatric Syndromes in Older Adults With HIV

BACKGROUND

Older people with HIV experience more comorbidities and geriatric syndromes than their HIV-negative peers, perhaps due to residual inflammation despite suppressive antiretroviral therapy. Cell-free mitochondrial DNA (cfmtDNA) released during necrosis-mediated cell death potentially acts as both mediator and marker of inflammatory dysregulation. Thus, we evaluated plasma cfmtDNA as a potential biomarker of geriatric syndromes.

METHODS

Participants underwent the Montreal Cognitive Assessment (MoCA), frailty testing, and measurement of plasma cfmtDNA by qPCR and inflammatory markers including C-reactive protein, interleukin-6 (IL-6), interferon gamma, and tumor necrosis factor alpha in this cross-sectional study.

RESULTS

Across 155 participants, the median age was 60 years (Q1, Q3: 56, 64), one-third were female, and 92% had HIV-1 viral load <200 copies/mL. The median MoCA score was 24 (21, 27). The plasma cfmtDNA level was higher in those with cognitive impairment (MoCA <23) ( P = 0.02 by the t test) and remained significantly associated with cognitive impairment in a multivariable logistic regression model controlling for age, sex, race, CD4 T-cell nadir, HIV-1 viremia, and depression. Two-thirds of participants met the criteria for a prefrail or frail state; higher plasma cfmtDNA was associated with slow walk and exhaustion but not overall frailty state. Cognitive dysfunction was not associated with C-reactive protein, IL-6, interferon gamma, or tumor necrosis factor alpha, and frailty state was only associated with IL-6.

CONCLUSIONS

Plasma cfmtDNA may have a role as a novel biomarker of cognitive dysfunction and key components of frailty. Longitudinal investigation of cfmtDNA is warranted to assess its utility as a biomarker of geriatric syndromes in older people with HIV.

Dietary supplementation of gingerols- and shogaols-enriched ginger root extract attenuate pain-associated behaviors while modulating gut microbiota and metabolites in rats with spinal nerve ligation

Neuroinflammation is a central factor in neuropathic pain (NP). Ginger is a promising bioactive compound in NP management due to its anti-inflammatory property. Emerging evidence suggests that gut microbiome and gut-derived metabolites play a key role in NP. We evaluated the effects of two ginger root extracts rich in gingerols (GEG) and shogaols (SEG) on pain sensitivity, anxiety-like behaviors, circulating cell-free mitochondrial DNA (ccf-mtDNA), gut microbiome composition, and fecal metabolites in rats with NP. Sixteen male rats were divided into four groups: sham, spinal nerve ligation (SNL), SNL+0.75%GEG in diet, and SNL+0.75%SEG in diet groups for 30 days. Compared to SNL group, both SNL+GEG and SNL+SEG groups showed a significant reduction in pain- and anxiety-like behaviors, and ccf-mtDNA level. Relative to the SNL group, both SNL+GEG and SNL+SEG groups increased the relative abundance of Lactococcus, Sellimonas, Blautia, Erysipelatoclostridiaceae, and Anaerovoracaceae, but decreased that of Prevotellaceae UCG-001, Rikenellaceae RC9 gut group, Mucispirillum and Desulfovibrio, Desulfovibrio, Anaerofilum, Eubacterium siraeum group, RF39, UCG-005, Lachnospiraceae NK4A136 group, Acetatifactor, Eubacterium ruminantium group, Clostridia UCG-014, and an uncultured Anaerovoracaceae. GEG and SEG had differential effects on gut-derived metabolites. Compared to SNL group, SNL+GEG group had higher level of 1'-acetoxychavicol acetate, (4E)-1,7-Bis(4-hydroxyphenyl)-4-hepten-3-one, NP-000629, 7,8-Dimethoxy-3-(2-methyl-3-buten-2-yl)-2H-chromen-2-one, 3-{[4-(2-Pyrimidinyl)piperazino]carbonyl}-2-pyrazinecarboxylic acid, 920863, and (1R,3R,7R,13S)-13-Methyl-6-methylene-4,14,16-trioxatetracyclo[11.2.1.0∼1,10∼.0∼3,7∼]hexadec-9-en-5-one, while SNL+SEG group had higher level for (±)-5-[(tert-Butylamino)-2'-hydroxypropoxy]-1_2_3_4-tetrahydro-1-naphthol and dehydroepiandrosteronesulfate. In conclusion, ginger is a promising functional food in the management of NP, and further investigations are necessary to assess the role of ginger on gut-brain axis in pain management.

Preclinical evidence for mitochondrial DNA as a potential blood biomarker for chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious dose-limiting side effect of several first-line chemotherapeutic agents including paclitaxel, oxaliplatin and bortezomib, for which no predictive marker is currently available. We have previously shown that mitochondrial dysfunction is associated with the development and maintenance of CIPN. The aim of this study was to evaluate the potential use of mitochondrial DNA (mtDNA) levels and complex I enzyme activity as blood biomarkers for CIPN. Real-time qPCR was used to measure mtDNA levels in whole blood collected from chemotherapy- and vehicle-treated rats at three key time-points of pain-like behaviour: prior to pain development, at the peak of mechanical hypersensitivity and at resolution of pain-like behaviour. Systemic oxaliplatin significantly increased mtDNA levels in whole blood prior to pain development. Furthermore, paclitaxel- and bortezomib-treated animals displayed significantly higher levels of mtDNA at the peak of mechanical hypersensitivity. Mitochondrial complex I activity in whole blood was assessed with an ELISA-based Complex I Enzyme Activity Dipstick Assay. Complex I activity was not altered by any of the three chemotherapeutic agents, either prior to or during pain-like behaviour. These data demonstrate that blood levels of mtDNA are altered after systemic administration of chemotherapy. Oxaliplatin, in particular, is associated with higher mtDNA levels before animals show any pain-like behaviour, thus suggesting a potential role for circulating mtDNA levels as non-invasive predictive biomarker for CIPN.

Aldosterone suppresses cardiac mitochondria

Elevated serum aldosterone promotes arterial hypertension, cardiac hypertrophy, and diastolic dysfunction. However, the effect of elevated aldosterone levels on cardiac mitochondria remains unclear. We used primary cultures of mouse cardiomyocytes to determine whether aldosterone has direct effects on cardiomyocyte mitochondria, and aldosterone-infused mice as a preclinical model to evaluate the impact of aldosterone in vivo. We show that aldosterone suppressed mtDNA copy number and SOD2 expression via the mineralocorticoid receptor (MR)-dependent regulation of NADPH oxidase 2 (NOX2) and generation of reactive oxygen species (ROS) in primary mouse cardiomyocytes. Aldosterone suppressed cardiac mitochondria adenosine triphosphate production, which was rescued by N-acetylcysteine. Aldosterone infusion for 4 weeks in mice suppressed the number of cardiac mitochondria, mtDNA copy number, and SOD2 protein expression. MR blockade by eplerenone or the administration of N-acetylcysteine prevented aldosterone-induced cardiac mitochondrial damage in vivo. Similarly, patients with primary aldosteronism had a lower plasma leukocyte mtDNA copy number. Plasma leukocyte mtDNA copy number was positively correlated with 24-hour urinary aldosterone level and left ventricular mass index. In conclusion, aldosterone suppresses cardiac mitochondria in vivo and directly via MR activation of ROS pathways.

Plasma circulating cell-free mitochondrial DNA in depressive disorders

Background

Plasma circulating cell-free mitochondrial DNA (ccf-mtDNA) is an immunogenic molecule and a novel biomarker of psychiatric disorders. Some previous studies reported increased levels of ccf-mtDNA in unmedicated depression and recent suicide attempters, while other studies found unchanged or decreased ccf-mtDNA levels in depression. Inconsistent findings across studies may be explained by small sample sizes and between-study variations in somatic and psychiatric co-morbidity or medication status.

Methods

We measured plasma ccf-mtDNA in a cohort of 281 patients with depressive disorders and 49 healthy controls. Ninety-three percent of all patients were treated with one or several psychotropic medications. Thirty-six percent had a personality disorder, 13% bipolar disorder. All analyses involving ccf-mtDNA were a priori adjusted for age and sex.

Results

Mean levels in ccf-mtDNA were significantly different between patients with a current depressive episode (n = 236), remitted depressive episode (n = 45) and healthy controls (n = 49) (f = 8.3, p<0.001). Post-hoc tests revealed that both patients with current (p<0.001) and remitted (p = 0.002) depression had lower ccf-mtDNA compared to controls. Within the depressed group there was a positive correlation between ccf-mtDNA and “inflammatory depression symptoms” (r = 0.15, p = 0.02). We also found that treatment with mood stabilizers lamotrigine, valproic acid or lithium was associated with lower ccf-mtDNA (f = 8.1, p = 0.005).

Discussion

Decreased plasma ccf-mtDNA in difficult-to-treat depression may be partly explained by concurrent psychotropic medications and co-morbidity. Our findings suggest that ccf-mtDNA may be differentially regulated in different subtypes of depression, and this hypothesis should be pursued in future studies.

The Effects of Korean Red Ginseng on Biological Aging and Antioxidant Capacity in Postmenopausal Women: A Double-Blind Randomized Controlled Study

Postmenopausal women are vulnerable to aging and oxidative stress due to reduced estrogen. Previous studies have shown that Korean red ginseng (KRG) has beneficial effects on aging and antioxidant capacity. Therefore, we evaluated the effects of KRG on biological aging and antioxidant capacity in postmenopausal women. This study conducted a double-blinded, placebo-controlled clinical trial. The participants were randomly administered KRG or a placebo, and the following metrics were measured: mitochondria DNA (mtDNA) copy number as an indicator of biological aging and, total antioxidant status (TAS) as a marker of antioxidant capacity. Clinical symptoms of fatigue, as measured by the fatigue severity scale, were assessed before and after KRG administration. There were 63 participants, of whom 33 received KRG and 30 received a placebo. The mtDNA copy number (KRG group: 1.58 ± 2.05, placebo group: 0.28 ± 2.36, p = 0.023) and TAS (KRG group: 0.11 ± 0.25 mmol/L, placebo group: −0.04 ± 0.16 mmol/L, p = 0.011) increased and the fatigue severity scale (KRG group: −7 ± 12, placebo group: −1 ± 11, p = 0.033) decreased significantly more in the KRG group than the placebo group. KRG significantly increased the mtDNA copy number, total antioxidant status, and improved symptoms of fatigue in postmenopausal women.

Blood mitochondrial DNA copy number: What are we counting?

There is growing scientific interest to develop scalable biological measures that capture mitochondrial (dys)function. Mitochondria have their own genome, the mitochondrial DNA (mtDNA). It has been proposed that the number of mtDNA copies per cell (mtDNA copy number; mtDNAcn) reflects mitochondrial health. The common availability of stored DNA material or existing DNA sequencing data, especially from blood and other easy-to-collect samples, has made its quantification a popular approach in clinical and epidemiological studies. However, the interpretation of mtDNAcn is not univocal, and either a reduction or elevation in mtDNAcn can indicate dysfunction. The major determinants of blood-derived mtDNAcn are the heterogeneous cell type composition of leukocytes and platelet abundance, which can change with time of day, aging, and with disease. Hematopoiesis is a likely driver of blood mtDNAcn. Here we discuss the rationale and available methods to quantify mtDNAcn, the influence of blood cell type variations, and consider important gaps in knowledge that need to be resolved to maximize the scientific value around the investigation of blood mtDNAcn.

Mitochondrial genome copy number measured by DNA sequencing in human blood is strongly associated with metabolic traits via cell-type composition differences

BACKGROUND

Mitochondrial genome copy number (MT-CN) varies among humans and across tissues and is highly heritable, but its causes and consequences are not well understood. When measured by bulk DNA sequencing in blood, MT-CN may reflect a combination of the number of mitochondria per cell and cell-type composition. Here, we studied MT-CN variation in blood-derived DNA from 19184 Finnish individuals using a combination of genome (N = 4163) and exome sequencing (N = 19034) data as well as imputed genotypes (N = 17718).

RESULTS

We identified two loci significantly associated with MT-CN variation: a common variant at the MYB-HBS1L locus (P = 1.6 × 10-8), which has previously been associated with numerous hematological parameters; and a burden of rare variants in the TMBIM1 gene (P = 3.0 × 10-8), which has been reported to protect against non-alcoholic fatty liver disease. We also found that MT-CN is strongly associated with insulin levels (P = 2.0 × 10-21) and other metabolic syndrome (metS)-related traits. Using a Mendelian randomization framework, we show evidence that MT-CN measured in blood is causally related to insulin levels. We then applied an MT-CN polygenic risk score (PRS) derived from Finnish data to the UK Biobank, where the association between the PRS and metS traits was replicated. Adjusting for cell counts largely eliminated these signals, suggesting that MT-CN affects metS via cell-type composition.

CONCLUSION

These results suggest that measurements of MT-CN in blood-derived DNA partially reflect differences in cell-type composition and that these differences are causally linked to insulin and related traits.

Association of plasma mitochondrial DNA with COPD severity and progression in the SPIROMICS cohort

BACKGROUND

There is a lack of mechanism-driven, clinically relevant biomarkers in chronic obstructive pulmonary disease (COPD). Mitochondrial dysfunction, a proposed disease mechanism in COPD, is associated with the release of mitochondrial DNA (mtDNA), but plasma cell-free mtDNA has not been previously examined prospectively for associations with clinical COPD measures.

METHODS

P-mtDNA, defined as copy number of mitochondrially-encoded NADH dehydrogenase-1 (MT-ND1) gene, was measured by real-time quantitative PCR in 700 plasma samples from participants enrolled in the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) cohort. Associations between p-mtDNA and clinical disease parameters were examined, adjusting for age, sex, smoking status, and for informative loss to follow-up.

RESULTS

P-mtDNA levels were higher in participants with mild or moderate COPD, compared to smokers without airflow obstruction, and to participants with severe COPD. Baseline increased p-mtDNA levels were associated with better CAT scores in female smokers without airflow obstruction and female participants with mild or moderate COPD on 1-year follow-up, but worse 6MWD in females with severe COPD. Higher p-mtDNA levels were associated with better 6MWD in male participants with severe COPD. These associations were no longer significant after adjusting for informative loss to follow-up.

CONCLUSION

In this study, p-mtDNA levels associated with baseline COPD status but not future changes in clinical COPD measures after accounting for informative loss to follow-up. To better characterize mitochondrial dysfunction as a potential COPD endotype, these results should be confirmed and validated in future studies.

TRIAL REGISTRATION

 ClinicalTrials.gov NCT01969344 (SPIROMICS).

NETosis as a Pathogenic Factor for Heart Failure

Heart failure threatens the lives of patients and reduces their quality of life. Heart failure, especially heart failure with preserved ejection fraction, is closely related to systemic and local cardiac persistent chronic low-grade aseptic inflammation, microvascular damage characterized by endothelial dysfunction, oxidative stress, myocardial remodeling, and fibrosis. However, the initiation and development of persistent chronic low-grade aseptic inflammation is unexplored. Oxidative stress-mediated neutrophil extracellular traps (NETs) are the main immune defense mechanism against external bacterial infections. Furthermore, NETs play important roles in noninfectious diseases. After the onset of myocardial infarction, atrial fibrillation, or myocarditis, neutrophils infiltrate the damaged tissue and aggravate inflammation. In tissue injury, damage-related molecular patterns (DAMPs) may induce pattern recognition receptors (PRRs) to cause NETs, but whether NETs are directly involved in the pathogenesis and development of heart failure and the mechanism is still unclear. In this review, we analyzed the markers of heart failure and heart failure-related diseases and comorbidities, such as mitochondrial DNA, high mobility box group box 1, fibronectin extra domain A, and galectin-3, to explore their role in inducing NETs and to investigate the mechanism of PRRs, such as Toll-like receptors, receptor for advanced glycation end products, cGAS-STING, and C-X-C motif chemokine receptor 2, in activating NETosis. Furthermore, we discussed oxidative stress, especially the possibility that imbalance of thiol redox and MPO-derived HOCl promotes the production of 2-chlorofatty acid and induces NETosis, and analyzed the possibility of NETs triggering coronary microvascular thrombosis. In some heart diseases, the deletion or blocking of neutrophil-specific myeloperoxidase and peptidylarginine deiminase 4 has shown effectiveness. According to the results of current pharmacological studies, MPO and PAD4 inhibitors are effective at least for myocardial infarction, atherosclerosis, and certain autoimmune diseases, whose deterioration can lead to heart failure. This is essential for understanding NETosis as a therapeutic factor of heart failure and the related new pathophysiology and therapeutics of heart failure.

Low frequency mitochondrial DNA heteroplasmy SNPs in blood, retina, and [RPE+choroid] of age-related macular degeneration subjects

Purpose

Mitochondrial (mt) DNA damage is associated with age-related macular degeneration (AMD) and other human aging diseases. This study was designed to quantify and characterize mtDNA low-frequency heteroplasmy single nucleotide polymorphisms (SNPs) of three different tissues isolated from AMD subjects using Next Generation Sequencing (NGS) technology.

Methods

DNA was extracted from neural retina, [RPE+choroid] and blood from three deceased age-related macular degeneration (AMD) subjects. Entire mitochondrial genomes were analyzed for low-frequency heteroplasmy SNPs using NGS technology that independently sequenced both mtDNA strands. This deep sequencing method (average sequencing depth of 30,000; range 1,000–100,000) can accurately differentiate low-frequency heteroplasmy SNPs from DNA modification artifacts. Twenty-three ‘hot-spot’ heteroplasmy mtDNA SNPs were analyzed in 222 additional blood samples.

Results

Germline homoplasmy SNPs that defined mtDNA haplogroups were consistent in the three tissues of each subject. Analyses of SNPs with <40% heteroplasmy revealed the blood had significantly greater numbers of heteroplasmy SNPs than retina alone (p≤0.05) or retina+choroid combined (p = 0.008). Twenty-three ‘hot-spot’ mtDNA heteroplasmy SNPs were present, with three being non-synonymous (amino acid change). Four ‘hot-spot’ heteroplasmy SNPs (m.1120C>T, m.1284T>C, m.1556C>T, m.7256C>T) were found in additional samples (n = 222). Five heteroplasmy SNPs (m.4104A>G, m.5320C>T, m.5471G>A, m.5474A>G, m.5498A>G) declined with age. Two heteroplasmy SNPs (m.13095T>C, m.13105A>G) increased in AMD compared to Normal samples. In the heteroplasmy SNPs, very few transversion mutations (purine to pyrimidine or vice versa, associated with oxidative damage) were found and the majority were transition changes (purine to purine or pyrimidine to pyrimidine, associated with replication errors).

Conclusion

Within an individual, the blood, retina and [RPE+choroid] contained identical homoplasmy SNPs representing inherited germline mtDNA haplogroup. NGS methodology showed significantly more mtDNA heteroplasmy SNPs in blood compared to retina and [RPE+choroid], suggesting the latter tissues have substantial protection. Significantly higher heteroplasmy levels of m.13095T>C and m.13105A>G may represent potential AMD biomarkers. Finally, high levels of transition mutations suggest that accumulation of heteroplasmic SNPs may occur through replication errors rather than oxidative damage.

Extracellular DNA Correlates with Intestinal Inflammation in Chemically Induced Colitis in Mice

Circulating extracellular DNA (ecDNA) is known to worsen the outcome of many diseases. ecDNA released from neutrophils during infection or inflammation is present in the form of neutrophil extracellular traps (NETs). It has been shown that higher ecDNA concentration occurs in a number of inflammatory diseases including inflammatory bowel disease (IBD). Enzymes such as peptidyl arginine deiminases (PADs) are crucial for NET formation. We sought to describe the dynamics of ecDNA concentrations and fragmentation, along with NETosis during a mouse model of chemically induced colitis. Plasma ecDNA concentration was highest on day seven of dextran sulfate sodium (DSS) intake and the increase was time-dependent. This increase correlated with the percentage of cells undergoing NETosis and other markers of disease activity. Relative proportion of nuclear ecDNA increased towards more severe colitis; however, absolute amount decreased. In colon explant medium, the highest concentration of ecDNA was on day three of DSS consumption. Early administration of PAD4 inhibitors did not alleviate disease activity, but lowered the ecDNA concentration. These results uncover the biological characteristics of ecDNA in IBD and support the role of ecDNA in intestinal inflammation. The therapeutic intervention aimed at NETs and/or nuclear ecDNA has yet to be fully investigated.

Asthma and its relationship to mitochondrial copy number: Results from the Asthma Translational Genomics Collaborative (ATGC) of the Trans-Omics for Precision Medicine (TOPMed) program

Background

Mitochondria support critical cellular functions, such as energy production through oxidative phosphorylation, regulation of reactive oxygen species, apoptosis, and calcium homeostasis.

Objective

Given the heightened level of cellular activity in patients with asthma, we sought to determine whether mitochondrial DNA (mtDNA) copy number measured in peripheral blood differed between individuals with and without asthma.

Methods

Whole genome sequence data was generated as part of the Trans-Omics for Precision Medicine (TOPMed) Program on participants from the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-ethnicity (SAPPHIRE) and the Study of African Americans, Asthma, Genes, & Environment II (SAGE II). We restricted our analysis to individuals who self-identified as African American (3,651 asthma cases and 1,344 controls). Mitochondrial copy number was estimated using the sequencing read depth ratio for the mitochondrial and nuclear genomes. Respiratory complex expression was assessed using RNA-sequencing.

Results

Average mitochondrial copy number was significantly higher among individuals with asthma when compared with controls (SAPPHIRE: 218.60 vs. 200.47, P<0.001; SAGE II: 235.99 vs. 223.07, P<0.001). Asthma status was significantly associated with mitochondrial copy number after accounting for potential explanatory variables, such as participant age, sex, leukocyte counts, and mitochondrial haplogroup. Despite the consistent relationship between asthma status and mitochondrial copy number, the latter was not associated with time-to-exacerbation or patient-reported asthma control. Mitochondrial respiratory complex gene expression was disproportionately lower in individuals with asthma when compared with individuals without asthma and other protein-encoding genes.

Conclusions

We observed a robust association between asthma and higher mitochondrial copy number. Asthma having an effect on mitochondria function was also supported by lower respiratory complex gene expression in this group.

Bioactive Plasma Mitochondrial DNA Is Associated With Disease Progression in Scleroderma-Associated Interstitial Lung Disease

OBJECTIVE

Systemic sclerosis-associated interstitial lung disease (SSc-ILD) is characterized by variable clinical outcomes, activation of innate immune pattern-recognition receptors (PRRs), and accumulation of α-smooth muscle actin (α-SMA)-expressing myofibroblasts. The aim of this study was to identify an association between these entities and mitochondrial DNA (mtDNA), an endogenous ligand for the intracellular DNA-sensing PRRs Toll-like receptor 9 (TLR-9) and cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS/STING), which has yet to be determined.

METHODS

Human lung fibroblasts (HLFs) from normal donors and SSc-ILD explants were treated with synthetic CpG DNA and assayed for α-SMA expression and extracellular mtDNA using quantitative polymerase chain reaction for the human MT-ATP6 gene. Plasma MT-ATP6 concentrations were evaluated in 2 independent SSc-ILD cohorts and demographically matched controls. The ability of SSc-ILD and control plasma to induce TLR-9 and cGAS/STING activation was evaluated with commercially available HEK 293 reporter cells. Plasma concentrations of type I interferons (IFNs), interleukin-6 (IL-6), and oxidized DNA were measured using electrochemiluminescence and enzyme-linked immunosorbent assay-based methods. Extracellular vesicles (EVs) precipitated from plasma were evaluated for MT-ATP6 concentrations and proteomics via liquid chromatography mass spectrometry.

RESULTS

Normal HLFs and SSc-ILD fibroblasts developed increased α-SMA expression and MT-ATP6 release following CpG stimulation. Plasma mtDNA concentrations were increased in the 2 SSc-ILD cohorts, reflective of ventilatory decline, and were positively associated with both TLR-9 and cGAS/STING activation as well as type I IFN and IL-6 expression. Plasma mtDNA was not oxidized and was conveyed by EVs displaying a proteomics profile consistent with a multicellular origin.

CONCLUSION

These findings demonstrate a previously unrecognized connection between EV-encapsulated mtDNA, clinical outcomes, and intracellular DNA-sensing PRR activation in SSc-ILD. Further study of these interactions could catalyze novel mechanistic and therapeutic insights into SSc-ILD and related disorders.

Plasma mtDNA copy numbers are associated with GSTK1 expression and inflammation in type 2 diabetes

AIMS

Mitochondrial dysfunction is involved in the pathogenesis of type 2 diabetes. Glutathione S-transferase kappa 1 (GSTK1) is critical to maintain mitochondrial function and homeostasis. We aimed to investigate whether a potential link exists between mitochondrial DNA (mtDNA) copy numbers and inflammation, non-esterified fatty acids (NEFA) and GSTK1 expression in type 2 diabetes.

METHODS

We assessed mtDNA copy numbers in plasma and GSTK1 expression in white blood cells in 123 people with type 2 diabetes and in 121 healthy controls using a quantitative polymerase chain reaction (qPCR). An automatic chemistry or immunoassay analyser was used to determine serum glucose, lipids and inflammatory markers. Multiple linear regression and multivariable logistic regression models were used to evaluate associations and risks.

RESULTS

Compared with healthy controls, individuals with diabetes showed higher mtDNA copy numbers (t = -3.938, P < 0.001) and lower GSTK1 expression (Z = -2.985, P = 0.002). mtDNA copy number was associated with type 2 diabetes risk [odds ratio (OR) = 1.80, 95% confidence intervals (CI) 1.25-2.58, P = 0.001] after controlling for confounding factors. In individuals with diabetes, mtDNA copy number was negatively associated with GSTK1 expression (β = -0.235, P = 0.036) and positively associated with serum high-sensitive C-reactive protein (hsCRP) (β = 0.839, P < 0.001), tumour necrosis factor alpha (TNF-α) (β = 0.549, P < 0.001), interleukin-6 (IL-6) (β = 0.589, P = 0.006) and NEFA (β = 0.001, P = 0.020). In the diabetic group, individuals with an abnormal increase in NEFA, hsCRP, TNF-α and IL-6 showed significantly elevated mtDNA copy numbers (all P < 0.05).

CONCLUSIONS

mtDNA copy numbers in plasma might have an important role in the progression of diabetic chronic inflammation via inhibition of GSTK1 and could be a potential biomarker for type 2 diabetes.

Mitochondrial damage-associated inflammation highlights biomarkers in PRKN/PINK1 parkinsonism

There is increasing evidence for a role of inflammation in Parkinson's disease. Recent research in murine models suggests that parkin and PINK1 deficiency leads to impaired mitophagy, which causes the release of mitochondrial DNA (mtDNA), thereby triggering inflammation. Specifically, the CGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) pathway mitigates activation of the innate immune system, quantifiable as increased interleukin-6 (IL6) levels. However, the role of IL6 and circulating cell-free mtDNA in unaffected and affected individuals harbouring mutations in PRKN/PINK1 and idiopathic Parkinson's disease patients remain elusive. We investigated IL6, C-reactive protein, and circulating cell-free mtDNA in serum of 245 participants in two cohorts from tertiary movement disorder centres. We performed a hypothesis-driven rank-based statistical approach adjusting for multiple testing. We detected (i) elevated IL6 levels in patients with biallelic PRKN/PINK1 mutations compared to healthy control subjects in a German cohort, supporting the concept of a role for inflammation in PRKN/PINK1-linked Parkinson's disease. In addition, the comparison of patients with biallelic and heterozygous mutations in PRKN/PINK1 suggests a gene dosage effect. The differences in IL6 levels were validated in a second independent Italian cohort; (ii) a correlation between IL6 levels and disease duration in carriers of PRKN/PINK1 mutations, while no such association was observed for idiopathic Parkinson's disease patients. These results highlight the potential of IL6 as progression marker in Parkinson's disease due to PRKN/PINK1 mutations; (iii) increased circulating cell-free mtDNA serum levels in both patients with biallelic or with heterozygous PRKN/PINK1 mutations compared to idiopathic Parkinson's disease, which is in line with previous findings in murine models. By contrast, circulating cell-free mtDNA concentrations in unaffected heterozygous carriers of PRKN/PINK1 mutations were comparable to control levels; and (iv) that circulating cell-free mtDNA levels have good predictive potential to discriminate between idiopathic Parkinson's disease and Parkinson's disease linked to heterozygous PRKN/PINK1 mutations, providing functional evidence for a role of heterozygous mutations in PRKN or PINK1 as Parkinson's disease risk factor. Taken together, our study further implicates inflammation due to impaired mitophagy and subsequent mtDNA release in the pathogenesis of PRKN/PINK1-linked Parkinson's disease. In individuals carrying mutations in PRKN/PINK1, IL6 and circulating cell-free mtDNA levels may serve as markers of Parkinson's disease state and progression, respectively. Finally, our study suggests that targeting the immune system with anti-inflammatory medication holds the potential to influence the disease course of Parkinson's disease, at least in this subset of patients.

Associations between Cell-Free Mitochondrial DNA and Inflammation, and Their Clinical Implications for Patients on Hemodialysis: A Prospective Multicenter Cohort Study

BACKGROUND

Cell-free mitochondrial DNA (cf-mtDNA) has recently been in the spotlight as an endogenously produced danger molecule that can potentially elicit inflammation. However, its clinical and prognostic implications are uncertain in patients undergoing hemodialysis.

METHODS

We examined the association of baseline cf-mtDNA categorized as tertiles with health-related quality of life (HRQOL), inflammatory cytokines, and mortality in a multicenter prospective cohort of 334 patients on hemodialysis. To better understand cf-mtDNA-mediated inflammation, we measured cytokine production after in vitro stimulation of bone marrow-derived macrophages (BMDMs) with mtDNA.

RESULTS

The higher cf-mtDNA tertile had a longer dialysis vintage, a greater comorbidity burden, and increased levels of inflammatory markers, including high-sensitivity-C-reactive protein, tumor necrosis factor-alpha, CXCL16, and osteoprotegerin. In particular, mtDNA augmented inflammatory cytokine release from BMDMs by lipopolysaccharide, the levels of which are reported to be increased in hemodialysis patients. Although the patients with higher levels of cf-mtDNA generally had lower (poorer) scores for HRQOL, cf-mtDNA was not associated with all-cause mortality in hemodialysis patients.

CONCLUSION

cf-mtDNA was correlated with poor clinical status and modestly associated with impaired quality of life in patients on hemodialysis. In proinflammatory milieu in end-stage renal disease, these associations may be attributed to the boosting effects of cf-mtDNA on inflammation.

Inverse relationship between leukocyte telomere length attrition and blood mitochondrial DNA content loss over time

Leukocyte telomere length (LTL) and whole blood mitochondrial DNA (WB mtDNA) content are aging markers impacted by chronic diseases such as human immunodeficiency virus (HIV) infection. We characterized the relationship between these two markers in 312 women ≥12 years of age living with HIV and 300 HIV-negative controls. We found no relationship between the two markers cross-sectionally. In multivariable models, age, ethnicity, HIV, and tobacco smoking were independently associated with shorter LTL, and the former three with lower WB mtDNA. Longitudinally, among a subgroup of 228 HIV participants and 68 HIV-negative controls with ≥2 biospecimens ≥1 year apart, an inverted pattern was observed between the rates of change in LTL and WB mtDNA content per year, whereby faster decline of one was associated with the preservation of the other. Furthermore, if HIV viral control was not maintained between visits, increased rates of both LTL attrition and WB mtDNA loss were observed. We describe a novel relationship between two established aging markers, whereby rates of change in LTL and WB mtDNA are inversely related. Our findings highlight the importance of maintaining HIV viral control, the complementary longitudinal relationship between the two markers, and the need to consider both in aging studies.

Diverse roles of mtDNA in schizophrenia: Implications in its pathophysiology and as biomarker for cognitive impairment

Schizophrenia (SZ) is a mental disorder characterized by neurocognitive dysfunctions and a reduction in occupational and social functioning. Several studies have provided evidence for mitochondrial dysfunction in the pathophysiology of SZ. In this sense, it is known that the addition of genetic variations in mitochondrial DNA (mtDNA) impairs oxidative phosphorylation of enzymatic complexes in mitochondria, resulting in ATP depletion and subsequent enhancement of reactive oxygen species; this is associated with cellular degeneration and apoptosis observed in some neuropsychiatric disorders. As a consequence of mitochondrial dysfunction, an increase in circulating cell-free mtDNA fragments can occur, which has been observed in individuals with SZ. Moreover, due to the bacterial origin of mitochondria, these cell-free mtDNA fragments in blood plasma may induce inflammatory and immunogenic responses, especially when their release is enhanced in specific disease conditions. However, the exact mechanism by which mtDNA could be released into blood plasma is not yet clear. Therefore, the aims of this review article were to discuss the participation of mtDNA genetic variations in physiopathologic mechanisms of SZ, and to determine the status of the disease and the possible ensuing changes over time by using circulating cell-free mtDNA fragments as a biomarker.

Quantification of mitochondrial DNA damage and copy number in circulating blood of patients with systemic sclerosis by a qPCR-based assay

Background

Although not fully understood, oxidative stress has been implicated in the pathogenesis of different autoimmune diseases such as systemic sclerosis. Accumulating evidence indicates that oxidative stress can induce mitochondrial DNA (mtDNA) damage and variations in mtDNA copy number (mtDNAcn).

Objective

The aim of this study was to explore mtDNAcn and oxidative DNA damage byproducts in peripheral blood of patients with systemic sclerosis and healthy controls.

Methods

Forty six patients with systemic sclerosis and forty nine healthy subjects were studied. Quantitative real-time PCR used to measure the relative mtDNAcn and the oxidative damage (oxidized purines) of each sample.

Results

The mean mtDNAcn was lower in patients with systemic sclerosis than in healthy controls whereas the degree of mtDNA damage was significantly higher in cases as compared to controls. Moreover, there was a negative correlation between mtDNAcn and oxidative DNA damage.

Study limitations

The lack of simultaneous analysis and quantification of DNA oxidative damage markers in serum or urine of patients with systemic sclerosis and healthy controls.

Conclusion

These data suggest that alteration in mtDNAcn and increased oxidative DNA damage may be involved in the pathogenesis of systemic sclerosis.

Mitochondrial DNA Copy-Number Variation and Pancreatic Cancer Risk in the Prospective EPIC Cohort

BACKGROUND

Mitochondrial DNA (mtDNA) copy number in peripheral blood has been found to be associated with risk of developing several cancers. However, data on pancreatic ductal adenocarcinoma (PDAC) are very limited.

METHODS

To further our knowledge on this topic, we measured relative mtDNA copy number by a quantitative real-time PCR assay in peripheral leukocyte samples of 476 PDAC cases and 357 controls nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.

RESULTS

We observed lower mtDNA copy number with advancing age (P = 6.54 × 10-5) and with a high body mass index (BMI) level (P = 0.004) and no association with sex, smoking behavior, and alcohol consumption. We found an association between increased mtDNA copy number and decreased risk of developing PDAC with an odds ratios (OR) of 0.35 [95% confidence interval (CI), 0.16-0.79; P = 0.01] when comparing the fifth quintile with the first using an unconditional logistic regression and an OR of 0.19 (95% CI, 0.07-0.52; P = 0.001) with a conditional analysis. Analyses stratified by BMI showed an association between high mtDNA copy number and decreased risk in the stratum of normal weight, consistent with the main analyses.

CONCLUSIONS

Our results suggest a protective effect of a higher number of mitochondria, measured in peripheral blood leukocytes, on PDAC risk.

IMPACT

Our findings highlight the importance of understanding the mitochondrial biology in pancreatic cancer.

Cell-free mitochondrial DNA increases in maternal circulation during healthy pregnancy: a prospective, longitudinal study

Mitochondrial DNA (mtDNA) exposed to the extracellular space due to cell death has immunostimulatory properties. Case-control studies reported a positive association between odds of developing preeclampsia and circulating mtDNA. These findings are based on relative quantification protocols that do not allow determination of absolute concentrations of mtDNA and are highly sensitive to nuclear DNA contamination. Furthermore, circulating mtDNA concentrations in response to normal pregnancy, which is an inflammatory state characterized by continuous placental cell apoptosis, have not been established. The main objective of this study was to determine longitudinal changes in circulating mtDNA from preconception to first trimester, third trimester, and postpartum in healthy pregnant women. Absolute real-time PCR quantification of mtDNA and nuclear DNA (nDNA) was performed on whole genomic extracts from serum using TaqMan probes and chemistry. Serum cell-free mtDNA and nDNA concentrations were greater in late pregnancy as compared with early pregnancy and postpartum. Pregnant women carrying neonates at the upper quartile of birth length distribution had higher concentrations of mtDNA in late pregnancy compared with pregnancies carrying neonates at the lower quartile. The correlation between circulating mtDNA and nDNA concentrations varied by sex (i.e., pregnancies carrying female vs. male fetuses). This study is the first to establish temporal patterns of circulating cell-free mtDNA concentrations in normal human pregnancy using absolute DNA quantification techniques. Concentrations of circulating mtDNA in normal pregnancy may be used as reference values for the development of clinical prognostic or diagnostic tests in pregnant women with, or at risk of developing, gestational complications.

Plasma Mitochondrial DNA Levels Are Associated With ARDS in Trauma and Sepsis Patients

BACKGROUND

Critically ill patients who develop ARDS have substantial associated morbidity and mortality. Circulating mitochondrial DNA (mtDNA) released during critical illness causes endothelial dysfunction and lung injury in experimental models. This study hypothesized that elevated plasma mtDNA is associated with ARDS in critically ill patients with trauma and sepsis.

METHODS

Plasma mtDNA concentrations were measured at ED presentation and approximately 48 h later in separate prospective cohorts of critically ill patients with trauma and sepsis. ARDS was classified according to the Berlin definition. The association of mtDNA with ARDS was tested by using multivariable logistic regression, adjusted for covariates previously shown to contribute to ARDS risk in each population.

RESULTS

ARDS developed in 41 of 224 (18%) trauma patients and in 45 of 120 (38%) patients with sepsis. Forty-eight-hour mtDNA levels were significantly associated with ARDS (trauma: OR, 1.58/log copies/μL; 95% CI, 1.14-2.19 [P = .006]; sepsis: OR, 1.52/log copies/μL; 95% CI, 1.12-2.06 [P = .007]). Plasma mtDNA on presentation was not significantly associated with ARDS in either cohort. In patients with sepsis, 48-h mtDNA was more strongly associated with ARDS among those with a nonpulmonary infectious source (OR, 2.20/log copies/μL; 95% CI, 1.36-3.55 [P = .001], n = 69) than those with a pulmonary source (OR, 1.04/log copies/μL; 95% CI, 0.68-1.59 [P = .84], n = 51; P = .014 for interaction).

CONCLUSIONS

Plasma mtDNA levels were associated with incident ARDS in two critical illness populations. Given supportive preclinical data, our findings suggest a potential link between circulating mtDNA and lung injury and merit further investigation as a potentially targetable mediator of ARDS.

Mitogenomic diversity in Sacred Ibis Mummies sheds light on early Egyptian practices

The ancient catacombs of Egypt harbor millions of well-preserved mummified Sacred Ibis (Threskiornis aethiopicus) dating from ~600BC. Although it is known that a very large number of these ‘votive’ mummies were sacrificed to the Egyptian God Thoth, how the ancient Egyptians obtained millions of these birds for mummification remains unresolved. Ancient Egyptian textual evidences suggest they may have been raised in dedicated large-scale farms. To investigate the most likely method used by the priests to secure birds for mummification, we report the first study of complete mitochondrial genomes of 14 Sacred Ibis mummies interred ~2500 years ago. We analysed and compared the mitogenomic diversity among Sacred Ibis mummies to that found in modern Sacred Ibis populations from throughout Africa. The ancient birds show a high level of genetic variation comparable to that identified in modern African populations, contrary to the suggestion in ancient hieroglyphics (or ancient writings) of centralized industrial scale farming of sacrificial birds. This suggests a sustained short-term taming of the wild migratory Sacred Ibis for the ritual yearly demand.

Seasonal modification of the associations of exposure to polycyclic aromatic hydrocarbons or phthalates of cellular aging

Exposure to polycyclic aromatic hydrocarbons (PAHs) and phthalates link to oxidative stress and inflammatory response, which exert cellular aging. However, modification effect of seasonal factor on the association of PAHs or phthalates exposure with relative telomere length (RTL) or mitochondrial DNA copy number (mtDNA-CN) has remained unclear. In this pilot study, 106 subjects were from an urban population (n = 1240) who lived in the two districts in Wuhan city, China. Participants completed physical examinations and provided 191 blood samples for RTL and mtDNA-CN analysis and 627 urine samples for monohydroxylated-PAHs (OH-PAHs) and phthalate metabolites measurements in the winter and summer seasons. We assessed the associations of urinary OH-PAHs or phthalates metabolites with RTL or mtDNA-CN by linear regression analysis and linear mixed-effect models. We found that urinary OH-PAHs were positively associated with mtDNA-CN at lag 2 day and 3-day moving average, but negatively related to RTL at lag 0, lag 1 and lag 2 day and 3-day moving average (p < 0.05). Urinary phthalate metabolites were negatively associated with mtDNA lag 0, lag 1 and lag 2 day and 3-day moving average, but positively related to RTL at lag 0 day (p < 0.05). Seasonal factor modified the association of urinary OH-PAHs with mtDNA-CN as well as urinary phthalate metabolites with RTL. In vitro experiment showed that under certain conditions, benzo[a]pyrene increased mtDNA-CN at 48 h and di (2-ethylhexyl) phthalate did RTL at 24 h in HepG2 cells. Seasonal variations in the metabolisms of PAHs or phthalates in human body may affect the relation of PAHs or phthalates exposure with cellular aging.

Changes in circulating cell-free nuclear DNA and mitochondrial DNA of patients with adolescent idiopathic scoliosis

BACKGROUND

Adolescent idiopathic scoliosis (AIS) which characterized by complex three-dimensional deformity of spine has been difficult to cure because of the unknown etiopathology and uncertainty of progression. Nowadays, circulating cell-free (ccf) DNA was found to be a potential biomarker for several benign and malignant diseases. However, whether ccf DNA can be a biomarker for AIS has not been reported yet. In this study, we investigate the circulating cell-free nuclear DNA (ccf n-DNA) and mitochondrial DNA (ccf mt-DNA) concentrations in the plasma of patients with AIS and controls (CT), and the changed plasma ccf n-DNA and ccf mt-DNA levels and their association with clinical parameters were assessed.

METHODS

The plasma of peripheral blood from 69 AIS patients and 21 age-matched CT was collected for ccf DNA analysis. Quantitative PCR was used to detect ccf n-DNA and ccf mt-DNA levels, and correlation analyses between the ccf n-DNA and ccf mt-DNA levels and clinical characteristics were conducted. Receiver operator curves (ROC) were used to analyze the sensitivity and specificity of ccf n-DNA and ccf mt-DNA levels to different characteristics.

RESULTS

The plasma ccf n-DNA levels of both GAPDH and ACTB were significantly decreased in AIS patients compared with those in controls, while the plasma ccf mt-DNA levels did not changed. According to sex-related analyses, the ccf n-DNA levels in male CT-M was higher than that in female CT and male AIS, but the ccf n-DNA levels in female AIS was not significantly changed when compared with male AIS or female CT. However, the concentration of ccf mt-DNA in female AIS increased significantly when compared with male AIS. Surprisingly, Lenke type-related analyses suggested that Lenke type 1 patients had lower ccf n-DNA levels, whereas Lenke type 5 patients had higher ccf mt-DNA levels compared with those of controls. However, a lower sensitivity and specificity of AIS predicted by ccf n-DNA or ccf mt-DNA levels was observed, whether in total, by sex, or by Lenke type.

CONCLUSION

Although with no/little predictive accuracy of AIS/progressed AIS by ccf DNA levels, significantly changed plasma ccf DNA levels were observed in AIS patients compared with those in controls.

Plasma mitochondrial DNA is elevated in obese type 2 diabetes mellitus patients and correlates positively with insulin resistance

Cells damaged by mechanical or infectious injury release proinflammatory mitochondrial DNA (mtDNA) fragments into the circulation. We evaluated the relation between plasma levels of mtDNA fragments in obese type 2 diabetes mellitus (T2DM) patients and measures of chronic inflammation and insulin resistance. In 10 obese T2DM patients and 12 healthy control (HC) subjects, we measured levels of plasma cell-free mtDNA with quantitative real-time polymerase chain reaction, and mtDNA damage in skeletal muscle with quantitative alkaline Southern blot. Also, markers of systemic inflammation and oxidative stress in skeletal muscle were measured. Plasma levels of mtDNA fragments, mtDNA damage in skeletal muscle and plasma tumor necrosis factor α levels were greater in obese T2DM patients than HC subjects. Also, the abundance of plasma mtDNA fragments in obese T2DM patients levels positively correlated with insulin resistance. To the best of our knowledge, this is the first published evidence that elevated level of plasma mtDNA fragments is associated with mtDNA damage and oxidative stress in skeletal muscle and correlates with insulin resistance in obese T2DM patients. Plasma mtDNA may be a useful biomarker for predicting and monitoring insulin resistance in obese patients.

Predictors of ccf-mtDNA reactivity to acute psychological stress identified using machine learning classifiers: A proof-of-concept

OBJECTIVE

We have previously found that acute psychological stress may affect mitochondria and trigger an increase in serum mitochondrial DNA, known as circulating cell-free mtDNA (ccf-mtDNA). Similar to other stress reactivity measures, there are substantial unexplained inter-individual differences in the magnitude of ccf-mtDNA reactivity, as well as within-person differences across different occasions of testing. Here, we sought to identify psychological and physiological predictors of ccf-mtDNA reactivity using machine learning-based multivariate classifiers.

METHOD

We used data from serum ccf-mtDNA concentration measured pre- and post-stress in 46 healthy midlife adults tested on two separate occasions. To identify variables predicting the magnitude of ccf-mtDNA reactivity, two multivariate classification models, partial least-squares discriminant analysis (PLS-DA) and random forest (RF), were trained to discriminate between high and low ccf-mtDNA responders. Potential predictors used in the models included state variables such as physiological measures and affective states, and trait variables such as sex and personality measures. Variables identified across both models were considered to be predictors of ccf-mtDNA reactivity and selected for downstream analyses.

RESULTS

Identified predictors were significantly enriched for state over trait measures (X2 = 7.03; p = 0.008) and for physiological over psychological measures (X2 = 4.36; p = 0.04). High responders were more likely to be male (X2 = 26.95; p < 0.001) and differed from low-responders on baseline cardiovascular and autonomic measures, and on stress-induced reduction in fatigue (Cohen's d = 0.38-0.73). These group-level findings also accurately accounted for within-person differences in 90% of cases.

CONCLUSION

These results suggest that acute cardiovascular and psychological indices, rather than stable individual traits, predict stress-induced ccf-mtDNA reactivity. This work provides a proof-of-concept that machine learning approaches can be used to explore determinants of inter-individual and within-person differences in stress psychophysiology.

Circulating Mitochondrial DNA as Predictor of Mortality in Critically Ill Patients: A Systematic Review of Clinical Studies

BACKGROUND

Despite numerous publications on mitochondrial DNA (mtDNA) in the last decade it remains to be seen whether mtDNA can be used clinically. We conducted a systematic review to assess circulating cell-free mtDNA as a biomarker of mortality in critically ill patients.

METHODS

This systematic review was registered with PROSPERO (CRD42016046670). PubMed, CINAHL, the Cochrane Library, Embase, Scopus, and Web of Science, and reference lists of retrieved articles were searched. Studies measuring circulating cell-free mtDNA and reporting on all-cause mortality in critically ill adult and pediatric patients were included. The primary and secondary outcomes were mortality and morbidity, respectively.

RESULTS

Of the 1,566 initially retrieved publications, 40 studies were included, accounting for 3,450 critically ill patients. Substantial differences between studies were noted in how mtDNA was isolated and measured. Sixteen of the 40 included studies (40%) explored the association between mtDNA levels and mortality; of those 16 studies, 11 (68.8%) reported a statistically significant association. The area under the receiver operating characteristic (AUROC) curve for mtDNA and mortality was calculated for 10 studies and ranged from 0.61 to 0.95.

CONCLUSIONS

There is growing interest in mtDNA as a predictor of mortality in critically ill patients. Most studies are small, lack validation cohorts, and utilize different protocols to measure mtDNA. When reported, AUROC analysis usually suggests a statistically significant association between mtDNA and mortality. Standardization of mtDNA protocols and the completion of a large, prospective, multicenter trial may be warranted to firmly establish the clinical usefulness of mtDNA.

Prenatal exposure to thallium is associated with decreased mitochondrial DNA copy number in newborns: Evidence from a birth cohort study

BACKGROUND

Prenatal exposure to thallium is related to adverse birth outcomes. However, little is known about the effects of prenatal exposure to thallium on the mitochondrial DNA copy number (mtDNAcn) in newborns; such knowledge might reveal a potential mechanism linking maternal thallium exposure and adverse birth outcomes.

OBJECTIVE

To investigate the trimester-specific associations of maternal thallium exposure with cord blood leukocyte mtDNAcn.

METHODS

A total of 746 pregnant women with trimester-specific urinary samples and cord blood samples were recruited from Wuhan Children Hospital between November 2013 and March 2015 in Wuhan City, China. The concentration of thallium in maternal urine was quantified using inductively coupled plasma mass spectrometry (ICP-MS). Cord blood leukocyte mtDNAcn was measured by real-time quantitative polymerase chain reaction (qPCR). Trimester-specific associations of specific gravity (SG)-adjusted urinary thallium concentrations with mtDNAcn were estimated using a multiple informant model.

RESULTS

The geometric mean value of maternal urinary thallium was 0.34 μg/L, 0.36 μg/L, and 0.34 μg/L for the first, second, and third trimesters, respectively. Prenatal exposure to thallium during the first trimester, rather than during the second or the third trimester, was identified as negatively related to mtDNAcn. The multiple informant model showed a 10.4% lower level of mtDNAcn with each doubling increase of thallium levels (95% CI, -16.4%, -3.9%; P = 0.002). The observed associations were stronger among female newborns and among newborns born to older mothers.

CONCLUSIONS

The present study revealed a significant negative association between maternal thallium exposure during early pregnancy and cord blood leukocyte mtDNAcn in Chinese newborns, pointing to the important role of mitochondria as a target of thallium toxicity in early pregnancy.

Acute psychological stress increases serum circulating cell-free mitochondrial DNA

Intrinsic biological mechanisms transduce psychological stress into physiological adaptation that requires energy, but the role of mitochondria and mitochondrial DNA (mtDNA) in this process has not been defined in humans. Here, we show that similar to physical injury, exposure to psychological stress increases serum circulating cell-free mtDNA (ccf-mtDNA) levels. Healthy midlife adults exposed on two separate occasions to a brief psychological challenge exhibited a 2-3-fold increase in ccf-mtDNA, with no change in ccf-nuclear DNA levels, establishing the magnitude and specificity for ccf-mtDNA reactivity. In cell-based studies, we show that glucocorticoid signaling - a consequence of psychological stress in humans - is sufficient to induce mtDNA extrusion in a time frame consistent with stress-induced ccf-mtDNA increase. Collectively, these findings provide evidence that acute psychological stress induces ccf-mtDNA and implicate neuroendocrine signaling as a potential trigger for ccf-mtDNA release. Further controlled work is needed to confirm that observed increases in ccf-mtDNA result from stress exposure and to determine the functional significance of this effect.

Low-to-moderate fluoride exposure, relative mitochondrial DNA levels, and dental fluorosis in Chinese children

BACKGROUND

The alteration of mitochondrial DNA (mtDNA) content contributes to many diseases, however, little is known about its effect on the prevalence of dental fluorosis (DF).

OBJECTIVES

We conducted a cross-sectional study to investigate the association of low-to-moderate fluoride exposure with relative mtDNA levels in relation to DF in children.

METHODS

We recruited 616 resident children, aged 7-13 years, randomly from low-to-moderate fluoride areas in Tianjin, China. We measured the fluoride concentrations in drinking water and urine using the national standardized ion selective electrode method, and determined the relative levels of mtDNA using a quantitative real-time polymerase chain reaction assay. The association among fluoride exposure, relative mtDNA levels, and the prevalence of DF were examined using multivariable linear and logistic regression models. We also performed stratified and mediation analyses.

RESULTS

The relative mtDNA levels of participants in the DF group were significantly lower than in the non-DF group (0.95 ± 0.44 vs. 1.12 ± 0.45, P < 0.001). In the adjusted models, we found that a 1 mg/L increment in water fluoride concentration was associated with a 0.10-unit decrease in circulating relative mtDNA levels (95% CI: -0.14, -0.06) and a 2.85-fold increase (95% CI: 2.01, 3.92) in moderate DF prevalence. A 1 mg/L increment in urinary fluoride level was associated with a 0.12-unit decrease in circulating relative mtDNA levels (95% CI: -0.14, -0.09) and a 1.85-fold increase (95% CI: 1.39, 2.39) in moderate DF prevalence. Stratified analysis indicated a weaker positive association of DF prevalence with fluoride exposure, while a stronger inverse relationship with relative mtDNA levels in boys than in girls. Assuming causality, we estimated that circulating mtDNA levels mediated 13.0% (95% CI: 5.2, 28.7%) and 9.6% (95% CI: 4.7, 18.5%) of the estimated effect of a 1 mg/L increment in water fluoride and urinary fluoride on prevalence of moderate DF, respectively.

CONCLUSIONS

Gender potentially modifies the associations of DF prevalence with relative mtDNA levels and low-to-moderate fluoride exposure. The reduced circulating mtDNA levels may partly mediate the elevated prevalence of moderate DF in children under such exposure.

Mitochondrial damage-associated molecular patterns released by lung transplants are associated with primary graft dysfunction

Primary graft dysfunction (PGD) is a major limitation in short- and long-term lung transplant survival. Recent work has shown that mitochondrial damage-associated molecular patterns (mtDAMPs) can promote solid organ injury, but whether they contribute to PGD severity remains unclear. We quantitated circulating plasma mitochondrial DNA (mtDNA) in 62 patients, before lung transplantation and shortly after arrival to the intensive care unit. Although all recipients released mtDNA, high levels were associated with severe PGD development. In a mouse orthotopic lung transplant model of PGD, we detected airway cell-free damaged mitochondria and mtDNA in the peripheral circulation. Pharmacologic inhibition or genetic deletion of formylated peptide receptor 1 (FPR1), a chemotaxis sensor for N-formylated peptides released by damaged mitochondria, inhibited graft injury. An analysis of intragraft neutrophil-trafficking patterns reveals that FPR1 enhances neutrophil transepithelial migration and retention within airways but does not control extravasation. Using donor lungs that express a mitochondria-targeted reporter protein, we also show that FPR1-mediated neutrophil trafficking is coupled with the engulfment of damaged mitochondria, which in turn triggers reactive oxygen species (ROS)-induced pulmonary edema. Therefore, our data demonstrate an association between mtDAMP release and PGD development and suggest that neutrophil trafficking and effector responses to damaged mitochondria are drivers of graft damage.

Circulating mitochondrial DNA: New indices of type 2 diabetes-related cognitive impairment in Mexican Americans

Mitochondrial function has been implicated and studied in numerous complex age-related diseases. Understanding the potential role of mitochondria in disease pathophysiology is of importance due to the rise in prevalence of complex age-related diseases, such as type 2 diabetes (T2D) and Alzheimer's disease (AD). These two diseases specifically share common pathophysiological characteristics which potentially point to a common root cause or factors for disease exacerbation. Studying the shared phenomena in Mexican Americans is of particular importance due to the disproportionate prevalence of both T2D and AD in this population. Here, we assessed the potential role of mitochondria in T2D and cognitive impairment (CI) in a Mexican American cohort by analyzing blood-based indices of mitochondrial DNA copy number (mtDNACN) and cell-free mitochondrial DNA (CFmtDNA). These mitochondrial metrics were also analyzed for correlation with relevant neuropsychological variables and physiological data collected as indicators of disease and/or disease progression. We found mtDNACN to be significantly decreased in individuals with CI, while CFmtDNA was significantly elevated in T2D; further, CFmtDNA elevation was significantly exacerbated in individuals with both diseases. MtDNACN was found to negatively correlate with age and fatty acid binding protein concentration, while positively correlating with CFmtDNA as well as CERAD total recall score. Candidate gene SNP-set analysis was performed on genes previously implicated in maintenance and control of mitochondrial dynamics to determine if nuclear variants may account for variability in mtDNACN. The results point to a single significant locus, in the LRRK2/MUC19 region, encoding leucine rich repeat kinase 2 and mucin 19. This locus has been previously implicated in Parkinson's disease, among others; rs7302859 was the driver SNP. These combined findings further indicate that mitochondrial dysfunction (as assessed by proxy via mtDNACN) is intimately linked to both T2D and CI phenotypes as well as aging.

Association between circulating mononuclear cell mitochondrial DNA copy number and in-hospital mortality in septic patients: A prospective observational study based on the Sepsis-3 definition

Purpose

To explore the association between circulating mononuclear cell mitochondrial DNA copy number and the prognosis of sepsis patients based on the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3 definition).

Methods

A total of 200 adult patients who had recently devoloped sepsis were prospectively recruited as the study cohort. Demographic and clinical data were recorded along with a 28-day outcome. Mononuclear cell mtDNA copy number was assessed by quantitative PCR.

Results

The 28-day outcome of sepsis patients was significantly associated with circulating mononuclear cell mtDNA copy number. The median mononuclear cell relative mtDNA copy number of survivors was significantly higher than that of nonsurvivors (406.68, range 196.65–625.35 vs. 320.57, range 175.98–437.33, p = 0.001). The Cox proportional hazard survival model analysis indicated that mononuclear cell relative mtDNA copy number was significantly negative associated with the 28-day outcome. For every additional unit of mononuclear cell mtDNA relative copy number, the risk of death falls by 0.1% (HR = 0.999, 95% CI = 0.998 to 1.000, p = 0.017).

Conclusions

Our data indicate first that circulating mononuclear cellular mtDNA copy number might be helpful for outcome predictions in sepsis patients, and second that lower mtDNA copy number implied poor prognosis.

Mitochondrial dysfunction in affected skin and increased mitochondrial DNA in serum from patients with psoriasis

Psoriasis is characterized by keratinocyte proliferation and chronic inflammation, but the pathogenesis is still unclear. Dysregulated mitochondria (mt) could lead to reduced apoptosis and extracellular secretion of mtDNA, acting as "innate pathogen" triggering inflammation. Serum was obtained from healthy volunteers and psoriatic patients. Mitochondrial DNA was extracted from the serum and amplified with quantitative PCR (qPCR). Punch biopsies were obtained from lesional and non-lesional psoriatic skin (10 cm apart) and from healthy volunteers, were placed in RNA later and were stored at -80°C until RNA was extracted and cDNA was synthesized; gene expression of uncoupling protein 2 (UCP2), Dynamin-related protein 1 (Drp1) and calcineurin, involved in the regulation of mitochondria function, was detected with qPCR. Mitochondrial DNA was significantly increased (7s, P = 0.0496 and Cytochrome B, CytB, P = 0.0403) in the serum of psoriatic patients (n = 63) as compared to controls (n = 27). Gene expression was significantly reduced for UCP2 (P = 0.0218), Drp1 (P = 0.0001) and calcineurin (P = 0.0001) in lesional psoriatic skin, as compared to non-lesional or control skin. Increased serum extracellular mtDNA in psoriatic patients and decreased expression of mitochondrial regulatory proteins in psoriatic skin suggest increased inflammation and reduced keratinocyte apoptosis, respectively. Inhibitors of mtDNA secretion and/or UCP2 stimulants may be potential treatment options.

Mitochondrial mechanisms and therapeutics in ischaemia reperfusion injury

Acute kidney injury (AKI) remains a major problem in critically unwell children and young adults. Ischaemia reperfusion (IR) injury is a major contributor to the development of AKI in a significant proportion of these cases and mitochondria are increasingly recognised as being central to this process through generation of a burst of reactive oxygen species early in reperfusion. Mitochondria have additionally been shown to have key roles in downstream processes including activation of the immune response, immunomodulation, and apoptosis and necrosis. The recognition of the central role of mitochondria in IR injury and an increased understanding of the pathophysiology that undermines these processes has resulted in identification of novel therapeutic targets and potential biomarkers. This review summarises a variety of therapeutic approaches that are currently under exploration and may have potential in ameliorating AKI in children in the future.