A novel MT-ATP6 variant associated with complicated ataxia in two unrelated Italian patients: case report and functional studies.

BACKGROUND: MT-ATP6 is a mitochondrial gene which encodes for the intramembrane subunit 6 (or A) of the mitochondrial ATP synthase, also known asl complex V, which is involved in the last step of oxidative phosphorylation to produce cellular ATP through aerobic metabolism. Although classically associated with the NARP syndrome, recent evidence highlights an important role of MT-ATP6 pathogenic variants in complicated adult-onset ataxias. METHODS: We describe two unrelated patients with adult-onset cerebellar ataxia associated with severe optic atrophy and mild cognitive impairment. Whole mitochondrial DNA sequencing was performed in both patients. We employed patients' primary fibroblasts and cytoplasmic hybrids (cybrids), generated from patients-derived cells, to assess the activity of respiratory chain complexes, oxygen consumption rate (OCR), ATP production and mitochondrial membrane potential. RESULTS: In both patients, we identified the same novel m.8777 T > C variant in MT-ATP6 with variable heteroplasmy level in different tissues. We identifed an additional heteroplasmic novel variant in MT-ATP6, m.8879G > T, in the patients with the most severe phenotype. A significant reduction in complex V activity, OCR and ATP production was observed in cybrid clones homoplasmic for the m.8777 T > C variant, while no functional defect was detected in m.8879G > T homoplasmic clones. In addition, fibroblasts with high heteroplasmic levelsof m.8777 T > C variant showed hyperpolarization of mitochondrial membranes. CONCLUSIONS: We describe a novel pathogenic mtDNA variant in MT-ATP6 associated with adult-onset ataxia, reinforcing the value of mtDNA screening within the diagnostic workflow of selected patients with late onset ataxias.

Genetic variability of Aedes aegypti (Diptera: Culicidae) in El Salvador and Honduras: presence of a widespread haplotype and implications for mosquito control.

BACKGROUND: This study examined population genetics of Aedes aegypti in El Salvador and Honduras, two adjacent countries in Central America. Aedes aegypti is associated with yellow fever, dengue, chikungunya, and Zika. Each year, thousands of cases of dengue are typically reported in El Salvador and Honduras. METHODS: In El Salvador, collections were obtained from five Departments. In Honduras, samples were obtained from six municipalities in four Departments. Mitochondrial DNA cytochrome oxidase I (COI) was sequenced, and consensus sequences were combined with available sequences from El Salvador to determine haplotype number, haplotype diversity, nucleotide diversity, and Tajima's D. A haplotype network was produced to examine the relationship between genotypes. RESULTS: In El Salvador, there were 17 haplotypes, while in Honduras there were 4 haplotypes. In both El Salvador and Honduras, Haplotype 1 is most abundant and widespread. In El Salvador, haplotype H2 was also widespread in 10 of 11 sampled municipalities, but it was not present in Honduras. The capital of El Salvador (San Salvador) and the eastern region of ES had the highest haplotype diversity of regions sampled. CONCLUSIONS: Haplotype 1 and H2 each belong to different phylogenetic lineages of Ae. aegypti. The most geographically widespread haplotype (H1) may have been present the longest and could be a remnant from previous eradication programs. These data may contribute to future control programs for Ae. aegypti in the two countries.

Genetic diversity, phylogeography, and maternal origin of yak (Bos grunniens).

BACKGROUND: There is no consensus as to the origin of the domestic yak (Bos grunniens). Previous studies on yak mitochondria mainly focused on mitochondrial displacement loop (D-loop), a region with low phylogenetic resolution. Here, we analyzed the entire mitochondrial genomes of 509 yaks to obtain greater phylogenetic resolution and a comprehensive picture of geographical diversity. RESULTS: A total of 278 haplotypes were defined in 509 yaks from 21 yak breeds. Among them, 28 haplotypes were shared by different varieties, and 250 haplotypes were unique to specific varieties. The overall haplotype diversity and nucleotide diversity of yak were 0.979 ± 0.0039 and 0.00237 ± 0.00076, respectively. Phylogenetic tree and network analysis showed that yak had three highly differentiated genetic branches with high support rate. The differentiation time of clades I and II were about 0.4328 Ma, and the differentiation time of clades (I and II) and III were 0.5654 Ma. Yushu yak is shared by all haplogroups. Most (94.70%) of the genetic variation occurred within populations, and only 5.30% of the genetic variation occurred between populations. The classification showed that yaks and wild yaks were first clustered together, and yaks were clustered with American bison as a whole. Altitude had the highest impact on the distribution of yaks. CONCLUSIONS: Yaks have high genetic diversity and yak populations have experienced population expansion and lack obvious phylogeographic structure. During the glacial period, yaks had at least three or more glacial refugia.

Speciation patterns of Aedes mosquitoes in the Scutellaris Group: a mitochondrial perspective.

The Scutellaris Group of Aedes comprises 47 mosquito species, including Aedes albopictus. While Ae. albopictus is widely distributed, the other species are mostly found in the Asia-Pacific region. Evolutionary history researches of Aedes species within the Scutellaris Group have mainly focused on Ae. albopictus, a species that raises significant public health concerns, neglecting the other species. In this study, we aimed to assess genetic diversity and estimate speciation times of several species within the Scutellaris Group. Mosquitoes were therefore collected from various Asia-Pacific countries. Their mitochondrial cytochrome c oxidase subunit 1 (cox1) and subunit 3 (cox3) sequences were analyzed alongside those of other Scutellaris Group species available in the GenBank database. To estimate the divergence time, we analyzed 1849 cox1 gene sequences from 21 species, using three species (Aedes aegypti, Aedes notoscriptus and Aedes vigilax) as outgroups. We found that most of the speciation dates occurred during the Paleogene and the Neogene periods. A separation between the Scutellaris Subgroup and the Albopictus Subgroup occurred approximately 64-61 million years ago (MYA). We also identified a split between species found in Asia/Micronesia and those collected in Melanesia/Polynesia approximately 36-35 MYA. Our findings suggest that the speciation of Aedes species within the Scutellaris Group may be driven by diversity in mammalian hosts, climate and environmental changes, and geological dynamics rather than human migration.

Mechanisms and pathologies of human mitochondrial DNA replication and deletion formation.

Human mitochondria possess a multi-copy circular genome, mitochondrial DNA (mtDNA), that is essential for cellular energy metabolism. The number of copies of mtDNA per cell, and their integrity, are maintained by nuclear-encoded mtDNA replication and repair machineries. Aberrant mtDNA replication and mtDNA breakage are believed to cause deletions within mtDNA. The genomic location and breakpoint sequences of these deletions show similar patterns across various inherited and acquired diseases, and are also observed during normal ageing, suggesting a common mechanism of deletion formation. However, an ongoing debate over the mechanism by which mtDNA replicates has made it difficult to develop clear and testable models for how mtDNA rearrangements arise and propagate at a molecular and cellular level. These deletions may impair energy metabolism if present in a high proportion of the mtDNA copies within the cell, and can be seen in primary mitochondrial diseases, either in sporadic cases or caused by autosomal variants in nuclear-encoded mtDNA maintenance genes. These mitochondrial diseases have diverse genetic causes and multiple modes of inheritance, and show notoriously broad clinical heterogeneity with complex tissue specificities, which further makes establishing genotype-phenotype relationships challenging. In this review, we aim to cover our current understanding of how the human mitochondrial genome is replicated, the mechanisms by which mtDNA replication and repair can lead to mtDNA instability in the form of large-scale rearrangements, how rearranged mtDNAs subsequently accumulate within cells, and the pathological consequences when this occurs.

The Impact of Mitochondria in Ovarian Cancer Cell Metabolism, Proliferation, and Metastasis.

Mitochondrial dysfunctions are significantly implicated in cancer initiation, progression, and metastasis, which have been shown for several cancers including ovarian cancer.An increase in mitochondrial dysfunction is also associated with drug resistance along with cancer progression, which in part is related to its specific microenvironment that is characterized by ascites, low glucose levels, and hypoxia that causes ovarian cancer cells to switch to mitochondrial respiration to enable their survival. Peritoneal ascitic fluid accumulation is a specific feature of ovarian cancer, and it is a major cause of its metastatic spread that also presents challenges for effective treatment. Among the treatment difficulties for ovarian cancer is the mutation rate and frequency of mtDNA in ovarian cancer tissue that can affect the efficiency of chemotherapeutic drugs. The varied and multiple mutations of different types enable metabolic reprogramming, cancer cell proliferation, and drug resistance.New specific information on mechanisms underlying several of the mitochondrial dysfunctions has led to proposing various mitochondrial determinants as targets for ovarian cancer therapy, which include targeting specific mitochondrial proteins and phosphoproteins as well as reactive oxygen species (ROS) that accumulate abnormally in cancer cells. Because of the genetically and histologically heterogeneous nature of the disease, combination therapy approaches will be necessary to combat the disease and achieve progress in effective treatment of ovarian cancer. This chapter will address (1) mitochondrial vulnerabilities underlying dysfunction and disease; (2) mitochondrial dysfunction in ovarian cancer; (3) present treatment difficulties for ovarian cancer and new potential treatment strategies to target ovarian cancer mitochondrial metabolism; and (4) biobehavioral factors influencing ovarian cancer development.

Transport activity regulates mitochondrial bioenergetics and biogenesis in renal tubules.

Renal tubules are featured with copious mitochondria and robust transport activity. Mutations in mitochondrial genes cause congenital renal tubulopathies, and changes in transport activity affect mitochondrial morphology, suggesting mitochondrial function and transport activity are tightly coupled. Current methods of using bulk kidney tissues or cultured cells to study mitochondrial bioenergetics are limited. Here, we optimized an extracellular flux analysis (EFA) to study mitochondrial respiration and energy metabolism using microdissected mouse renal tubule segments. EFA detects mitochondrial respiration and glycolysis by measuring oxygen consumption and extracellular acidification rates, respectively. We show that both measurements positively correlate with sample sizes of a few centimeter-length renal tubules. The thick ascending limbs (TALs) and distal convoluted tubules (DCTs) critically utilize glucose/pyruvate as energy substrates, whereas proximal tubules (PTs) are significantly much less so. Acute inhibition of TALs' transport activity by ouabain treatment reduces basal and ATP-linked mitochondrial respiration. Chronic inhibition of transport activity by 2-week furosemide treatment or deletion of with-no-lysine kinase 4 (Wnk4) decreases maximal mitochondrial capacity. In addition, chronic inhibition downregulates mitochondrial DNA mass and mitochondrial length/density in TALs and DCTs. Conversely, gain-of-function Wnk4 mutation increases maximal mitochondrial capacity and mitochondrial length/density without increasing mitochondrial DNA mass. In conclusion, EFA is a sensitive and reliable method to investigate mitochondrial functions in isolated renal tubules. Transport activity tightly regulates mitochondrial bioenergetics and biogenesis to meet the energy demand in renal tubules. The system allows future investigation into whether and how mitochondria contribute to tubular remodeling adapted to changes in transport activity.

Biochemical and molecular evaluation of oxidative stress and mitochondrial damage in fruit fly exposed to carmoisine.

BACKGROUND: In today's world, appearance is an important factor in almost all areas of our lives. Therefore, it has become common to use dyes to color foods to make them look appetizing and visually appealing. However, food additives have negative effects on biochemical processes in cells at both high and low doses. METHODS AND RESULTS: This study investigated the effect of carmoisine, a commonly used food coloring, on oxidative stress and damage parameters in Drosophila melanogaster in terms of both enzymatic and gene expression. The change in mitochondrial DNA copy number (mtDNA-CN), a marker of oxidative stress, was also examined. When the data obtained were analyzed, it was observed that carmoisine caused a significant decrease in GSH levels depending on the increase in dose. SOD, CAT, GPx, and AChE enzyme activities and gene expression levels were also found to be significantly decreased. All groups also showed a significant decrease in mtDNA-CN. The effect of carmoisine on Drosophila melanogaster morphology was also investigated in our study. However, no significant change was observed in terms of morphological development in any group. CONCLUSIONS: When all the findings were evaluated together, it was observed that carmoisin triggered oxidative stress and these effects became more risky at high doses. Therefore, we believe that the consumer should be made more aware of the side effects of azo dyes in food and that the type and concentration of each substance added to food should be specified.

Exploring mitochondrial DNA copy number in circulating cell-free DNA and extracellular vesicles across cardiovascular health status: A prospective case-control pilot study.

Cardiovascular disease (CVD) is a leading global cause of mortality, difficult to predict in advance. Evidence indicates that the copy number of mitochondrial DNA (mtDNAcn) in blood is altered in individuals with CVD. MtDNA released into circulation may act as a mediator of inflammation, a recognized factor in the development of CVD, in the long distance. This pilot study aims to test if levels of mtDNAcn in buffy coat DNA (BC-mtDNA), in circulating cellfree DNA (cf-mtDNA), or in DNA extracted from plasma extracellular vesicles (EV-mtDNA) are altered in CVD patients and if they can predict heart attack in advance. A group of 144 people with different CVD statuses (50 that had CVD, 94 healthy) was selected from the LifeLines Biobank according to the incidence of new cardiovascular event monitored in 6 years (50 among controls had heart attack after the basal assessment). MtDNAcn was quantified in total cf-DNA and EV-DNA from plasma as well as in buffy coat. EVs have been characterized by their size, polydispersity index, count rate, and zeta potential, by Dynamic Light Scattering. BC-mtDNAcn and cf-mtDNAcn were not different between CVD patients and healthy subjects. EVs carried higher mtDNAcn in subject with a previous history of CVD than controls, also adjusting the analysis for the EVs derived count rate. Despite mtDNAcn was not able to predict CVD in advance, the detection of increased EV-mtDNAcn in CVD patients in this pilot study suggests the need for further investigations to determine its pathophysiological role in inflammation.

A circular network of adenosine-mediated mitochondrial dysfunction as coregulators of acute myocardial infarction.

This study aims to explore the molecular mechanisms and associated pathways of myocardial infarction (MI). We employed a variety of analytical methods, including Mendelian Randomization (MR) analysis, transcriptome microarray data analysis, gene function and pathway enrichment analysis, untargeted metabolomic mass spectrometry analysis, and gene-metabolite interaction network analysis. The MR analysis results revealed a significant impact of mitochondrial DNA copy number on MI and coronary artery bypass grafting. Transcriptome analysis unveiled numerous differentially expressed genes associated with myocardial ischemia, with enrichment observed in cardiac function and energy metabolism pathways. Metabolomic analysis indicated a significant downregulation of mitochondrial regulation pathways in ischemic myocardium. T500 metabolite quantification analysis identified 90 differential metabolites between MI and Sham groups, emphasizing changes in metabolites associated with energy metabolism. Gene-metabolite interaction network analysis revealed the significant roles of key regulatory molecules such as HIF1A, adenosine, TBK1, ATP, NRAS, and EIF2AK3, in the pathogenesis of myocardial ischemia. In summary, this study provides important insights into the molecular mechanisms of MI and highlights interactions at multiple molecular levels, contributing to the establishment of new theoretical foundations for the diagnosis and treatment of MI.

A forensic genetic investigation reveals a captive origin for a wild alien population of raccoons in Italy.

Invasive alien species have extensively impacted the ecosystems, where they may affect the native biodiversity. The North American raccoon Procyon lotor is one of the most successful invaders in Europe since its introduction in the early twentieth century. In Italy, a wild population was first established in the North at the beginning of the 2000s following a local introduction event. A further self-sustaining population was reported ten years later in Central Italy. To support an official investigation by the authorities, who suspected a captive origin of the free-ranging raccoons in Central Italy, we used nuclear and mitochondrial DNA markers, combined with different statistical approaches, to characterise their gene pool and trace the source of the founders. Results revealed that founders came from a private zoo-park from which they had inadvertently escaped, soon establishing a reproductive population in the wild. Additionally, our mitochondrial DNA data were used to supplement the haplotype variability known to date in captive and wild raccoons from Europe, Asia and their native range. The comparisons allowed us to update previous networks based on the control region with a new mitochondrial lineage, which had not been detected so far.

Release of damaged mitochondrial DNA: A novel factor in stimulating inflammatory response.

Mitochondrial DNA (mtDNA) is a circular double-stranded genome that exists independently of the nucleus. In recent years, research on mtDNA has significantly increased, leading to a gradual increase in understanding of its physiological and pathological characteristics. Reactive oxygen species (ROS) and other factors can damage mtDNA. This damaged mtDNA can escape from the mitochondria to the cytoplasm or extracellular space, subsequently activating immune signaling pathways, such as NLR family pyrin domain protein 3 (NLRP3), and triggering inflammatory responses. Numerous studies have demonstrated the involvement of mtDNA damage and leakage in the pathological mechanisms underlying various diseases including infectious diseases, metabolic inflammation, and immune disorders. Consequently, comprehensive investigation of mtDNA can elucidate the pathological mechanisms underlying numerous diseases. The prevention of mtDNA damage and leakage has emerged as a novel approach to disease treatment, and mtDNA has emerged as a promising target for drug development. This article provides a comprehensive review of the mechanisms underlying mtDNA-induced inflammation, its association with various diseases, and the methods used for its detection.

Questioning inbreeding: Could outbreeding affect productivity in the North African catfish in Thailand?

The North African catfish (Clarias gariepinus) is a significant species in aquaculture, which is crucial for ensuring food and nutrition security. Their high adaptability to diverse environments has led to an increase in the number of farms that are available for their production. However, long-term closed breeding adversely affects their reproductive performance, leading to a decrease in production efficiency. This is possibly caused by inbreeding depression. To investigate the root cause of this issue, the genetic diversity of captive North African catfish populations was assessed in this study. Microsatellite genotyping and mitochondrial DNA D-loop sequencing were applied to 136 catfish specimens, collected from three populations captured for breeding in Thailand. Interestingly, extremely low inbreeding coefficients were obtained within each population, and distinct genetic diversity was observed among the three populations, indicating that their genetic origins are markedly different. This suggests that outbreeding depression by genetic admixture among currently captured populations of different origins may account for the low productivity of the North African catfish in Thailand. Genetic improvement of the North African catfish populations is required by introducing new populations whose origins are clearly known. This strategy should be systematically integrated into breeding programs to establish an ideal founder stock for selective breeding.

High intragenomic, intergenomic, and phenotypic diversity in pulcherrimin-producing Metschnikowia yeasts indicates a special mode of genome evolution.

In molecular systematics, the delimitation of yeast species is based on the notion that the barcode differences are smaller within species than between them. The most widely used barcodes are segments of the chromosomal repeats coding for ribosomal RNAs that are homogenised in yeasts. The analysis of these segments of the type strains of ten species recently merged in Metschnikowia pulcherrima and 37 new isolates demonstrated that this is not the case in this species. The intragenomic diversity significantly exceeded the threshold gaps used to differentiate related yeast species. Large segments of the D1/D2 domains were not diverse within the genomes and could therefore be used to determine the taxonomic affiliation of the isolates. The genome structures of the isolates were compared by RAPD and the RFLP of the mitochondrial DNA. Both patterns were highly heterogeneous. The sequence analysis of the PUL4 gene (a member of the PUL gene cluster involved in pulcherrimin production) revealed very high intragenomic differences, suggesting that the genomes may be chimerised. Three phenotypic traits related to the antimicrobial antagonism characteristic of the species were also highly diverse and prone to reversible segregation resembling epigenetic processes (silencing and reactivation of regulators) rather than mutations and back-mutations. These features make M. pulcherrima unique among yeasts and indicate that it evolves in a non-standard way.

Nuclear sequences of mitochondrial origin in domestic yak.

Mitochondrial DNA sequences are frequently transferred into the nuclear genome, generating nuclear mitochondrial DNA sequences (NUMTs). Here, we analysed, for the first time, NUMTs in the domestic yak genome. We obtained 499 alignment matches covering 340.2 kbp of the yak nuclear genome. After a merging step, we identified 167 NUMT regions with a total length of ~ 503 kbp, representing 0.02% of the nuclear genome. We discovered copies of all mitochondrial regions and found that most NUMT regions are intergenic or intronic and mostly untranscribed. 98 different NUMT regions from domestic yak showed high homology with cow and/or wild yak genomes, suggesting selection or hybridization between domestic/wild yak and cow. To rule out the possibility that the identified NUMTs could be artifacts of the domestic yak genome assembly, we validated experimentally five NUMT regions by PCR amplification. As NUMT regions show high similarity to the mitochondrial genome can potentially pose a risk to domestic yak DNA mitochondrial studies, special care is therefore needed to select primers for PCR amplification of mitochondrial DNA sequences.

The effect of somatic mutations in mitochondrial DNA on the survival of patients with primary brain tumors.

AIM: To assess the presence of mitochondrial (mt) DNA somatic mutations, determine the relationship between clinicopathological characteristics and mutations, and assess the survival outcomes in Malay patients with primary brain tumors. METHODS: The study enrolled 54 patients with primary brain tumors. DNA extracted from paired tissue and blood samples was subjected to Sanger sequencing to identify alterations in the entire mtDNA. The associations between clinicopathological characteristics and mutations were evaluated. Cox-regression multivariate analysis was conducted to identify factors significantly associated with survival, and Kaplan-Meier analysis was used to compare the survival of patients with and without mutations. RESULTS: Overall, 29.6% of the patients harbored 19 somatic mutations distributed across 15 loci within the mtDNA. Notably, 36.8% of these mutations were not previously documented in MITOMAP. One newly identified mutation caused a frameshift in the ATPase6 gene, resulting in a premature stop codon. Three mutations were classified as deleterious in the MitImpact2 database. Overall, 1097 mtDNA polymorphisms were identified across 331 different locations. Patients with mutations exhibited significantly shorter survival than patients without mutations. CONCLUSIONS: mtDNA mutations negatively affected the survival outcomes of Malaysian patients with primary brain tumors. However, studies with larger samples are needed to confirm the association between mutation burden and survival rates.

Complete mitochondrial genome of critically endangered catfish Hemibagrus punctatus (Jerdon, 1849) and comparative analysis for insights into the phylogeny of hemibagrids through mitogenomic approach.

BACKGROUND: Hemibagrus punctatus (Jerdon, 1849) is a critically endangered bagrid catfish endemic to the Western Ghats of India, whose population is declining due to anthropogenic activities. The current study aims to compare the mitogenome of H. punctatus with that of other Bagrid catfishes and provide insights into their evolutionary relationships. METHODS AND RESULTS: Samples were collected from Hemmige Karnataka, India. In the present study, the mitogenome of H. punctatus was successfully assembled, and its phylogenetic relationships with other Bagridae species were studied. The total genomic DNA of samples was extracted following the phenol-chloroform isoamyl alcohol method. Samples were sequenced, and the Illumina paired-end reads were assembled to a contig length of 16,517 bp. The mitochondrial genome was annotated using MitoFish and MitoAnnotator (Iwasaki et al., 2013). A robust phylogenetic analysis employing NJ (Maximum composite likelihood) and ASAP methods supports the classification of H. punctatus within the Bagridae family, which validates the taxonomic status of this species. In conclusion, this research enriches our understanding of H. punctatus mitogenome, shedding light on its evolutionary dynamics within the Bagridae family and contributing to the broader knowledge of mitochondrial genes in the context of evolutionary biology. CONCLUSIONS: The study's findings contribute to a better understanding of the mitogenome of H. punctatus and provide insights into the evolutionary relationships within other Hemibagrids.

FGF21 attenuates neuroinflammation following subarachnoid hemorrhage through promoting mitophagy and inhibiting the cGAS-STING pathway.

BACKGROUND: Subarachnoid hemorrhage (SAH) represents a form of cerebrovascular event characterized by a notable mortality and morbidity rate. Fibroblast growth factor 21 (FGF21), a versatile hormone predominantly synthesized by the hepatic tissue, has emerged as a promising neuroprotective agent. Nevertheless, the precise impacts and underlying mechanisms of FGF21 in the context of SAH remain enigmatic. METHODS: To elucidate the role of FGF21 in inhibiting the microglial cGAS-STING pathway and providing protection against SAH-induced cerebral injury, a series of cellular and molecular techniques, including western blot analysis, real-time polymerase chain reaction, immunohistochemistry, RNA sequencing, and behavioral assays, were employed. RESULTS: Administration of recombinant fibroblast growth factor 21 (rFGF21) effectively mitigated neural apoptosis, improved cerebral edema, and attenuated neurological impairments post-SAH. Transcriptomic analysis revealed that SAH triggered the upregulation of numerous genes linked to innate immunity, particularly those involved in the type I interferon (IFN-I) pathway and microglial function, which were notably suppressed upon adjunctive rFGF21 treatment. Mechanistically, rFGF21 intervention facilitated mitophagy in an AMP-activated protein kinase (AMPK)-dependent manner, thereby preventing mitochondrial DNA (mtDNA) release into the cytoplasm and dampening the activation of the DNA-sensing cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway. Conditional knockout of STING in microglia markedly ameliorated the inflammatory response and mitigated secondary brain injuries post-SAH. CONCLUSION: Our results present the initial evidence that FGF21 confers a protective effect against neuroinflammation-associated brain damage subsequent to SAH. Mechanistically, we have elucidated a novel pathway by which FGF21 exerts this neuroprotection through inhibition of the cGAS-STING signaling cascade.

Mitochondrial DNA in bronchoalveolar lavage fluid is associated with the prognosis of idiopathic pulmonary fibrosis: a single cohort study.

BACKGROUND: Extracellular mitochondrial DNA (mtDNA) is released from damaged cells and increases in the serum and bronchoalveolar lavage fluid (BALF) of idiopathic pulmonary fibrosis (IPF) patients. While increased levels of serum mtDNA have been reported to be linked to disease progression and the future development of acute exacerbation (AE) of IPF (AE-IPF), the clinical significance of mtDNA in BALF (BALF-mtDNA) remains unclear. We investigated the relationships between BALF-mtDNA levels and other clinical variables and prognosis in IPF. METHODS: Extracellular mtDNA levels in BALF samples collected from IPF patients were determined using droplet-digital PCR. Levels of extracellular nucleolar DNA in BALF (BALF-nucDNA) were also determined as a marker for simple cell collapse. Patient characteristics and survival information were retrospectively reviewed. RESULTS: mtDNA levels in serum and BALF did not correlate with each other. In 27 patients with paired BALF samples obtained in a stable state and at the time of AE diagnosis, BALF-mtDNA levels were significantly increased at the time of AE. Elevated BALF-mtDNA levels were associated with inflammation or disordered pulmonary function in a stable state (n = 90), while being associated with age and BALF-neutrophils at the time of AE (n = 38). BALF-mtDNA ≥ 4234.3 copies/µL in a stable state (median survival time (MST): 42.4 vs. 79.6 months, p < 0.001) and ≥ 11,194.3 copies/µL at the time of AE (MST: 2.6 vs. 20.0 months, p = 0.03) were associated with shorter survival after BALF collection, even after adjusting for other known prognostic factors. On the other hand, BALF-nucDNA showed different trends in correlation with other clinical variables and did not show any significant association with survival time. CONCLUSIONS: Elevated BALF-mtDNA was associated with a poor prognosis in both IPF and AE-IPF. Of note, at the time of AE, it sharply distinguished survivors from non-survivors. Given the trends shown by analyses for BALF-nucDNA, the elevation of BALF-mtDNA might not simply reflect the impact of cell collapse. Further studies are required to explore the underlying mechanisms and clinical applications of BALF-mtDNA in IPF.