Severe septic patients with mitochondrial DNA haplogroup JT show higher survival rates: a prospective, multicenter, observational study

TREM2 protects against inflammation by regulating the release of mito-DAMPs from hepatocytes during liver fibrosis

BACKGROUND

Liver fibrosis typically develops as a result of chronic liver injury, which involves inflammatory and regenerative processes. The triggering receptor expressed on myeloid cells 2 (TREM2), predominantly expressing in hepatic non-parenchymal cells, plays a crucial role in regulating the function of macrophages. However, its mechanism in liver fibrosis remains poorly defined.

METHODS

Experimental liver fibrosis models in wild type and TREM2-/- mice, and in vitro studies with AML-12 cells and Raw264.7 cells were conducted. The expression of TREM2 and related molecular mechanism were evaluated by using samples from patients with liver fibrosis.

RESULTS

We demonstrated that TREM2 was upregulated in murine model with liver fibrosis. Mice lacking TREM2 exhibited reduced phagocytosis activity in macrophages following carbon tetrachloride (CCl4) intoxication. As a result, there was an increased accumulation of necrotic apoptotic hepatocytes. Additionally, TREM2 knockout aggravated the release of mitochondrial damage-associated molecular patterns (mito-DAMPs) from dead hepatocytes during CCl4 exposure, and further promoted the occurrence of macrophage-mediated M1 polarization. Then, TREM2-/- mice showed more serious fibrosis pathological changes. In vitro, the necrotic apoptosis inhibitor GSK872 effectively alleviated the release of mito-DAMPs in AML-12 cells after CCl4 intoxication, which confirmed that mito-DAMPs originated from dead liver cells. Moreover, direct stimulation of Raw264.7 cells by mito-DAMPs from liver tissue can induce intracellular inflammatory response. More importantly, TREM2 was elevated and inflammatory factors were markedly accumulated surrounding dead cells in the livers of human patients with liver fibrosis.

CONCLUSION

Our study highlights that TREM2 serves as a negative regulator of liver fibrosis, suggesting its potential as a novel therapeutic target.

Mitochondrial DNA Haplogroups and Delirium During Sepsis

OBJECTIVES

Studies suggest that mitochondrial dysfunction underlies some forms of sepsis-induced organ failure. We sought to test the hypothesis that variations in mitochondrial DNA haplogroup affect susceptibility to sepsis-associated delirium, a common manifestation of acute brain dysfunction during sepsis.

DESIGN

Retrospective cohort study.

SETTING

Medical and surgical ICUs at a large tertiary care center.

PATIENTS

Caucasian and African American adults with sepsis.

MEASUREMENTS AND MAIN RESULTS

We determined each patient's mitochondrial DNA haplogroup using single-nucleotide polymorphisms genotyping data in a DNA databank and extracted outcomes from linked electronic medical records. We then used zero-inflated negative binomial regression to analyze age-adjusted associations between mitochondrial DNA haplogroups and duration of delirium, identified using the Confusion Assessment Method for the ICU. Eight-hundred ten patients accounted for 958 sepsis admissions, with 802 (84%) by Caucasians and 156 (16%) by African Americans. In total, 795 patient admissions (83%) involved one or more days of delirium. The 7% of Caucasians belonging to mitochondrial DNA haplogroup clade IWX experienced more delirium than the 49% in haplogroup H, the most common Caucasian haplogroup (age-adjusted rate ratio for delirium 1.36; 95% CI, 1.13-1.64; p = 0.001). Alternatively, among African Americans the 24% in haplogroup L2 experienced less delirium than those in haplogroup L3, the most common African haplogroup (adjusted rate ratio for delirium 0.60; 95% CI, 0.38-0.94; p = 0.03).

CONCLUSIONS

Variations in mitochondrial DNA are associated with development of and protection from delirium in Caucasians and African Americans during sepsis. Future studies are now required to determine whether mitochondrial DNA and mitochondrial dysfunction contribute to the pathogenesis of delirium during sepsis so that targeted treatments can be developed.

Use of plasma mitochondrial DNA levels for determining disease severity and prognosis in pediatric sepsis: a case control study

BACKGROUND

The mortality rate due to severe sepsis is approximately 30-60%. Sepsis readily progresses to septic shock and multiple organ dysfunction, representing a significant problem in the pediatric intensive care unit (PICU). The aim of this study was to explore the value of plasma mitochondrial DNA (mtDNA) for early diagnosis and prognosis in children with sepsis.

METHODS

A total of 123 children with sepsis who were hospitalized in the Hunan Children's Hospital PICU from July 2013 to December 2014 were divided into the general sepsis group (n = 70) and severe sepsis group (n = 53) based on diagnostic standards. An additional 30 children with non-sepsis infection and 30 healthy children were randomly selected as a control group. Patients' plasma was collected during admission to the PICU. A pediatric critical illness score (PCIS) was also calculated. The plasma mtDNA level was examined using real-time polymerase chain reaction technology, and other parameters including routine laboratory values; blood lactate, procalcitonin (PCT), and C-reactive protein (CRP) levels; and data on survival were collected and compared among the groups.

RESULTS

The plasma mtDNA level in the sepsis group than that in the non-sepsis infection and healthy groups. The plasma mtDNA level was significantly higher in the severe sepsis than in the general sepsis group (p < 0.001). A lower PCIS was associated with a higher plasma mtDNA level (p < 0.001). A higher number of organs with dysfunction was associated with higher plasma mtDNA levels (p < 0.001). Plasma mtDNA levels were higher among patients with elevated alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, creatinine, lactate dehydrogenase, creatine kinase, myoglobin, creatine kinase MB, and troponin than in those with values within the normal range. The mtDNA level was higher among non-survivors than among survivors, and this difference was significant. mtDNA showed a prognostic prediction value similar to that of lactate, PCT, and CRP.

CONCLUSIONS

Plasma mtDNA levels may be a suitable biomarker for diagnosis and prognosis in children with sepsis.

Involvement of Mitochondrial Disorders in Septic Cardiomyopathy

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. It remains a leading cause of death worldwide, despite the development of various therapeutic strategies. Cardiac dysfunction, also referred to as septic cardiomyopathy, is a frequent and well-described complication of sepsis and associated with worse clinical outcomes. Recent research has increased our understanding of the role of mitochondrial dysfunction in the pathophysiology of septic cardiomyopathy. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Lower mitochondrial dysfunction in survivor septic patients with mitochondrial DNA haplogroup JT

OBJECTIVE

The comparison on mitochondrial function between severe septic patients and healthy control subjects according to mitochondrial deoxyribonucleic acid (mtDNA) haplogroup has not been previously reported; and this was the objective of the current study.

METHODS

Prospective, multicenter, observational study. We obtained blood samples from 198 severe septic patients at days 1, 4 and 8 of severe sepsis diagnosis and from 96 sex- and age-matched healthy controls to determine mtDNA haplogroup and platelet respiratory complex IV (CIV) specific activity. The endpoint of the study was 30-day mortality.

RESULTS

We included 198 severe septic patients (38 with mtDNA haplogroup JT and 160 with mtDNA haplogroup non-JT) and 96 healthy control subjects (16 with mtDNA haplogroup JT and 80 with mtDNA haplogroup non-JT). We have no found statistically significant differences in platelet CIV specific activity between healthy controls and survivor severe septic patients with mtDNA haplogroup JT at days 1, 4 and 8 of severe sepsis diagnosis; and the remaining severe septic patients showed lower platelet CIV specific activity than healthy controls with the same mtDNA haplogroup.

CONCLUSIONS

The new finding of our study was that survivor severe septic patients and healthy controls with mtDNA haplogroup JT showed no different platelet Civ specific activity.

Mitochondrial DNA in innate immune responses and inflammatory pathology

Mitochondrial DNA (mtDNA) - which is well known for its role in oxidative phosphorylation and maternally inherited mitochondrial diseases - is increasingly recognized as an agonist of the innate immune system that influences antimicrobial responses and inflammatory pathology. On entering the cytoplasm, extracellular space or circulation, mtDNA can engage multiple pattern-recognition receptors in cell-type- and context-dependent manners to trigger pro-inflammatory and type I interferon responses. Here, we review the expanding research field of mtDNA in innate immune responses to highlight new mechanistic insights and discuss the physiological and pathological relevance of this exciting area of mitochondrial biology.

Ovarian ageing: the role of mitochondria in oocytes and follicles

BACKGROUND

There is a great inter-individual variability of ovarian ageing, and almost 20% of patients consulting for infertility show signs of premature ovarian ageing. This feature, taken together with delayed childbearing in modern society, leads to the emergence of age-related ovarian dysfunction concomitantly with the desire for pregnancy. Assisted reproductive technology is frequently inefficacious in cases of ovarian ageing, thus raising the economic, medical and societal costs of the procedures.

OBJECTIVE AND RATIONAL

Ovarian ageing is characterized by quantitative and qualitative alteration of the ovarian oocyte reserve. Mitochondria play a central role in follicular atresia and could be the main target of the ooplasmic factors determining oocyte quality adversely affected by ageing. Indeed, the oocyte is the richest cell of the body in mitochondria and depends largely on these organelles to acquire competence for fertilization and early embryonic development. Moreover, the oocyte ensures the uniparental transmission and stability of the mitochondrial genome across the generations. This review focuses on the role played by mitochondria in ovarian ageing and on the possible consequences over the generations.

SEARCH METHODS

PubMed was used to search the MEDLINE database for peer-reviewed original articles and reviews concerning mitochondria and ovarian ageing, in animal and human species. Searches were performed using keywords belonging to three groups: 'mitochondria' or 'mitochondrial DNA'; 'ovarian reserve', 'oocyte', 'ovary' or 'cumulus cells'; and 'ageing' or 'ovarian ageing'. These keywords were combined with other search phrases relevant to the topic. References from these articles were used to obtain additional articles.

OUTCOMES

There is a close relationship, in mammalian models and humans, between mitochondria and the decline of oocyte quality with ageing. Qualitatively, ageing-related mitochondrial (mt) DNA instability, which leads to the accumulation of mtDNA mutations in the oocyte, plays a key role in the deterioration of oocyte quality in terms of competence and of the risk of transmitting mitochondrial abnormalities to the offspring. In contrast, some mtDNA haplogroups are protective against the decline of ovarian reserve. Quantitatively, mitochondrial biogenesis is crucial during oogenesis for constituting a mitochondrial pool sufficiently large to allow normal early embryonic development and to avoid the untimely activation of mitochondrial biogenesis. Ovarian ageing also seriously affects the dynamic nature of mitochondrial biogenesis in the surrounding granulosa cells that may provide interesting alternative biomarkers of oocyte quality.

WIDER IMPLICATIONS

A fuller understanding of the involvement of mitochondria in cases of infertility linked to ovarian ageing would contribute to a better management of the disorder in the future.

Association between mitochondrial DNA haplogroup and myelodysplastic syndromes

Polymorphisms in mitochondrial DNA (mtDNA) are used to group individuals into haplogroups reflecting human global migration and are associated with multiple diseases, including cancer. Here, we evaluate the association between mtDNA haplogroup and risk of myelodysplastic syndromes (MDS). Cases were identified by the Minnesota Cancer Surveillance System. Controls were identified through the Minnesota State driver's license/identification card list. Because haplogroup frequencies vary by race and ethnicity, we restricted analyses to non-Hispanic whites. We genotyped 15 mtSNPs that capture common European mitochondrial haplogroup variation. We used SAS v.9.3 (SAS Institute, Cary, NC) to calculate odds ratios (OR) and 95% confidence intervals (CI) overall and stratified by MDS subtype and IPSS-R risk category. We were able to classify 215 cases with confirmed MDS and 522 controls into one of the 11 common European haplogroups. Due to small sample sizes in some subgroups, we combined mt haplogroups into larger bins based on the haplogroup evolutionary tree, including HV (H + V), JT (J + T), IWX (I + W + X), UK (U + K), and Z for comparisons of cases and controls. Using haplogroup HV as the reference group, we found a statistically significant association between haplogroup JT and MDS (OR = 0.58, 95% CI 0.36, 0.92, P = 0.02). No statistically significant heterogeneity was observed in subgroup analyses. In this population-based study of MDS, we observed an association between mtDNA haplogroup JT and risk of MDS. While previously published studies provide biological plausibility for the observed association, further studies of the relationship between mtDNA variation and MDS are warranted in larger sample sizes. © 2016 Wiley Periodicals, Inc.

Mitochondrial Haplogroups and Risk of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a serious and often fatal disease. It is a panvasculopathy of the pulmonary microcirculation characterized by vasoconstriction and arterial obstruction due to vascular proliferation and remodeling and ultimately right ventricular failure. Mitochondrial dysfunction is a universal finding in pulmonary vascular cells of patients with PAH, and is mechanistically linked to disease origins in animal models of pulmonary hypertension. Mitochondria have their own circular DNA (mtDNA), which can be subgrouped into polymorphic haplogroup variants, some of which have been identified as at-risk or protective from cardiovascular and/or neurodegenerative diseases. Here, we hypothesized that mitochondrial haplogroups may be associated with PAH. To test this, mitochondrial haplogroups were determined in a cohort of PAH patients and controls [N = 204 Caucasians (125 PAH and 79 controls) and N = 46 African Americans (13 PAH and 33 controls)]. Haplogroup L was associated with a lower rate of PAH as compared to macrohaplogroups N and M. When haplogroups were nested based on ancestral inheritance and controlled for age, gender and race, haplogroups M and HV, JT and UK of the N macro-haplogroup had significantly higher rates of PAH compared to the ancestral L (L0/1/2 and L3) (all p ≤ 0.05). Overall, the findings suggest that mitochondrial haplogroups influence risk of PAH and that a vulnerability to PAH may have emerged under the selective enrichment of specific haplogroups that occurred with the migration of populations out of Africa.

Septic patients with mitochondrial DNA haplogroup JT have higher respiratory complex IV activity and survival rate

OBJECTIVE

The influence of mitochondrial deoxyribonucleic acid (mtDNA) haplogroup or oxidative phosphorylation system (OXPHOS) function on survival of septic patients has been scarcely studied. However, the association between mtDNA haplogroup, OXPHOS capacity at diagnosis of severe sepsis, and survival has been not previously reported, and that was the objective of the present study.

METHODS

This was a prospective, multicenter, observational study. Blood samples from 198 patients at diagnosis of severe sepsis were analyzed to determine mtDNA haplogroup and platelet respiratory complex IV (CIV) specific activity. The end point of the study was 30-day survival.

RESULTS

Septic patients with mtDNA haplogroup JT showed higher 30-day survival than those with mtDNA haplogroup non-JT (31/38 [81.6%] vs 99/160 [61.9%]; P= .02). Septic patients with mtDNA haplogroup JT showed higher platelet CIV specific activity than those with mtDNA haplogroup non-JT (P= .002).

CONCLUSIONS

The main novel finding of our study, including the largest series providing data on platelet CIV specific activity according to mtDNA haplogroup in severe septic patients, was that those with mtDNA haplogroup JT showed higher survival and higher platelet CIV specific activity at diagnosis of severe sepsis than patients with mtDNA haplogroup non-JT.

Mitochondrial DNA sequence variation in multiple sclerosis

OBJECTIVE

To assess the influence of common mitochondrial DNA (mtDNA) sequence variation on multiple sclerosis (MS) risk in cases and controls part of an international consortium.

METHODS

We analyzed 115 high-quality mtDNA variants and common haplogroups from a previously published genome-wide association study among 7,391 cases from the International Multiple Sclerosis Genetics Consortium and 14,568 controls from the Wellcome Trust Case Control Consortium 2 project from 7 countries. Significant single nucleotide polymorphism and haplogroup associations were replicated in 3,720 cases and 879 controls from the University of California, San Francisco.

RESULTS

An elevated risk of MS was detected among haplogroup JT carriers from 7 pooled clinic sites (odds ratio [OR] = 1.15, 95% confidence interval [CI] = 1.07-1.24, p = 0.0002) included in the discovery study. The increased risk of MS was observed for both haplogroup T (OR = 1.17, 95% CI = 1.06-1.29, p = 0.002) and haplogroup J carriers (OR = 1.11, 95% CI = 1.01-1.22, p = 0.03). These haplogroup associations with MS were not replicated in the independent sample set. An elevated risk of primary progressive (PP) MS was detected for haplogroup J participants from 3 European discovery populations (OR = 1.49, 95% CI = 1.10-2.01, p = 0.009). This elevated risk was borderline significant in the US replication population (OR = 1.43, 95% CI = 0.99-2.08, p = 0.058) and remained significant in pooled analysis of discovery and replication studies (OR = 1.43, 95% CI = 1.14-1.81, p = 0.002). No common individual mtDNA variants were associated with MS risk.

CONCLUSIONS

Identification and validation of mitochondrial genetic variants associated with MS and PPMS may lead to new targets for treatment and diagnostic tests for identifying potential responders to interventions that target mitochondria.

Mitochondrial DNA Haplogroup A may confer a genetic susceptibility to AIDS group from Southwest China

The acquired immunodeficiency syndrome (AIDS) in humans was one of the chronic infections caused by human immunodeficiency virus (HIV), and the interactions between viral infection and mitochondrial energetic implicated that mitochondrial DNA (mtDNA) variation(s) may effect genetic susceptibility to AIDS. Thus, to illustrate the maternal genetic structure and further identify whether mtDNA variation(s) can effect HIV infection among southwest Chinese AIDS group, the whole mtDNA control region sequences of 70 AIDS patients and 480 health individuals from southwest China were analyzed here. Our results indicated the plausible recent genetic admixture results of AIDS group; comparison of matrilineal components between AIDS and matched Han groups showed that mtDNA haplogroup A (p = 0.048, OR = 3.006, 95% CI = 1.109-8.145) has a significant higher difference between the two groups; further comparison illustrated that mtDNA mutations 16,209 (p = 0.046, OR = 2.607, 95% CI = 0.988-6.876) and 16,319 (p = 0.009, OR = 2.965, 95% CI = 1.278-6.876) have significant differences between AIDS and matched control groups, and both of which were the defining variations of mtDNA haplogroup A, they further confirmed that mtDNA haplogroup A may confer genetic susceptibility to AIDS. Our results suggested that haplogroup A may confer a genetic susceptibility to AIDS group from Southwest China.

Higher platelet cytochrome oxidase specific activity in surviving than in non-surviving septic patients

Introduction

In a previous study with 96 septic patients, we found that circulating platelets in 6-months surviving septic patients showed higher activity and quantity of cytochrome c oxidase (COX) normalized by citrate synthase (CS) activity at moment of severe sepsis diagnosis than non-surviving septic patients. The objective of this study was to estimate whether COX specific activity during the first week predicts 1-month sepsis survival in a larger cohort of patients.

Methods

Using a prospective, multicenter, observational study carried out in six Spanish intensive care units with 198 severe septic patients, we determined COX activity per proteins (COXact/Prot) in circulating platelets at day 1, 4 and 8 of the severe sepsis diagnosis. Endpoints were 1-month and 6-months mortality.

Results

Survivor patients (n = 130) showed higher COXact/Prot (P < 0.001) than non-survivors (n = 68) at day 1, 4 and 8 of severe sepsis diagnosis. More than a half of the 6-months survivor patients showed an increase in their COXact/Prot from day 1 to 8. However, most of the 1-month non-survivors exhibited a decrease in their COXact/Prot from day 1 to 8. Multiple logistic regression analyses showed that of platelet COXact/Prot > 0.30 mOD/min/mg at day 1 (P = 0.002), 4 (P = 0.006) and 8 (P = 0.02) was associated independently with 1-month mortality. Area under the curve of COXact/Prot at day 1, 4 and 8 to predict 30-day survival were 0.70 (95% CI = 0.63-0.76; P < 0.001), 0.71 (95% CI = 0.64-0.77; P < 0.001) and 0.71 (95% CI = 0.64-0.78; P < 0.001), respectively.

Conclusions

The new findings of our study, to our knowledge the largest series reporting data about mitochondrial function during follow-up in septic patients, were that septic patients that survive 1-month have a higher platelet cytochrome oxidase activity at moment of sepsis diagnosis and during the first week than non-survivors, and that platelet cytochrome oxidase activity at moment of sepsis diagnosis and during the first week could be used as biomarker to predict the clinical outcome in septic patients.