Mitochondrial dysfunction as a trigger of innate immune responses and inflammation

Effect of fungal indoor air pollutant 1-octen-3-ol on levels of reactive oxygen species and nitric oxide as well as dehydrogenases activities in drosophila melanogaster males

Fungal pollution of indoor environments contributes to several allergic symptoms and represents a public health problem. It is well-established that 1-octen-3-ol, also known as mushroom alcohol, is a fungal volatile organic compound (VOC) commonly found in damp indoor spaces and responsible for the typical musty odor. Previously it was reported that exposure to 1-octen-3-ol induced inflammations and disrupted mitochondrial morphology and bioenergetic rate in Drosophila melanogaster. The aim of this study was to examine the influence of 1-octen-3-ol on dehydrogenase activity, apoptotic biomarkers, levels of nitric oxide (NO) and reactive oxygen species (ROS), as well as antioxidant enzymes activities. D. melanogaster flies were exposed to an atmosphere containing 1-octen-3-ol (2.5 or ∞l/L) for 24 hr. Data demonstrated that 1-octen-3-ol decreased dehydrogenases activity and NO levels but increased ROS levels accompanied by stimulation of glutathione-S-transferase (GST) and superoxide dismutase (SOD) activities without altering caspase 3/7 activation. These findings indicate that adverse mitochondrial activity effects following exposure of D. melanogaster to 1-octen-3-ol, a fungal VOC, may be attributed to oxidant stress. The underlying mechanisms involved in adverse consequences of indoor fungal exposure appear to be related to necrotic but not apoptotic mechanisms. The adverse consequences were sex-dependent with males displaying higher sensitivity to 1-octen-3-ol. Based upon on the fact that the fly genome shares nearly 75% of disease-related genes to human exposure to this fungus may explain the adverse human responses to mold especially for males.

Alterations of Mitochondrial Network by Cigarette Smoking and E-Cigarette Vaping

Toxins present in cigarette and e-cigarette smoke constitute a significant cause of illnesses and are known to have fatal health impacts. Specific mechanisms by which toxins present in smoke impair cell repair are still being researched and are of prime interest for developing more effective treatments. Current literature suggests toxins present in cigarette smoke and aerosolized e-vapor trigger abnormal intercellular responses, damage mitochondrial function, and consequently disrupt the homeostasis of the organelle's biochemical processes by increasing reactive oxidative species. Increased oxidative stress sets off a cascade of molecular events, disrupting optimal mitochondrial morphology and homeostasis. Furthermore, smoking-induced oxidative stress may also amalgamate with other health factors to contribute to various pathophysiological processes. An increasing number of studies show that toxins may affect mitochondria even through exposure to secondhand or thirdhand smoke. This review assesses the impact of toxins present in tobacco smoke and e-vapor on mitochondrial health, networking, and critical structural processes, including mitochondria fission, fusion, hyper-fusion, fragmentation, and mitophagy. The efforts are focused on discussing current evidence linking toxins present in first, second, and thirdhand smoke to mitochondrial dysfunction.

5-Aminolevulinic acid has the potential to prevent bladder dysfunction in cyclophosphamide-induced hemorrhagic cystitis

OBJECTIVES

To investigate the effects of pretreatment with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate on bladder dysfunction in cyclophosphamide-induced hemorrhagic cystitis in rats.

METHODS

Male Wistar rats (340-460 g) were pretreated with vehicle or with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate (100/157 or 300/471 mg/kg/day, po) once daily for 7 days before cystometry. Saline or cyclophosphamide (150 mg/kg, ip) was administered 2 days before cystometry. Cystometry was performed under urethane anesthesia (0.8 g/kg, ip) via a catheter inserted into the bladder. After cystometry, bladder tissues were collected to perform hematoxylin and eosin staining for pathological evaluation (neutrophil infiltration, edema, and bleeding scores), and for enzyme-linked immunosorbent assay and real-time polymerase chain reaction for investigating tissue levels of myeloperoxidase, and mRNA levels of haem oxygenase-1 as a cytoprotective molecule.

RESULTS

Compared to controls, cyclophosphamide induced a shorter intercontraction interval, lower bladder compliance, increased number of non-voiding contractions, and increased pathological scores and myeloperoxidase expression in the bladder. Pretreatment with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate (300/471 mg/kg/day) significantly improved cyclophosphamide-induced intercontraction interval shortening and increases in number of non-voiding contractions and neutrophil infiltration/bleeding scores and enhanced haem oxygenase-1 expression in the bladder. In addition, cyclophosphamide-induced decreases in bladder compliance and increases in myeloperoxidase were not detected with 5-aminolevulinic acid hydrochloride combined with sodium ferrous citrate pretreatment.

CONCLUSIONS

Pretreatment with 5-aminolevulinic acid expects protective effects on bladder dysfunction in cyclophosphamide-induced hemorrhagic cystitis by improving inflammatory changes in bladder tissues perhaps via up-regulation of haem oxygenase-1.

Mice lacking the mitochondrial exonuclease MGME1 develop inflammatory kidney disease with glomerular dysfunction

Mitochondrial DNA (mtDNA) maintenance disorders are caused by mutations in ubiquitously expressed nuclear genes and lead to syndromes with variable disease severity and tissue-specific phenotypes. Loss of function mutations in the gene encoding the mitochondrial genome and maintenance exonuclease 1 (MGME1) result in deletions and depletion of mtDNA leading to adult-onset multisystem mitochondrial disease in humans. To better understand the in vivo function of MGME1 and the associated disease pathophysiology, we characterized a Mgme1 mouse knockout model by extensive phenotyping of ageing knockout animals. We show that loss of MGME1 leads to de novo formation of linear deleted mtDNA fragments that are constantly made and degraded. These findings contradict previous proposal that MGME1 is essential for degradation of linear mtDNA fragments and instead support a model where MGME1 has a critical role in completion of mtDNA replication. We report that Mgme1 knockout mice develop a dramatic phenotype as they age and display progressive weight loss, cataract and retinopathy. Surprisingly, aged animals also develop kidney inflammation, glomerular changes and severe chronic progressive nephropathy, consistent with nephrotic syndrome. These findings link the faulty mtDNA synthesis to severe inflammatory disease and thus show that defective mtDNA replication can trigger an immune response that causes age-associated progressive pathology in the kidney.

We have addressed the controversy of the role of the mitochondrial genome and maintenance exonuclease 1 (MGME1) in mtDNA metabolism by characterization of knockout mice. Our findings show that loss of MGME1 leads to increased de novo formation of linear deleted mtDNA, thus contradicting previous report that MGME1 degrades long linear mtDNA molecules. In addition, we report that loss of MGME1 leads to age-associated pathology manifested as progressive weight loss, cataract and retinopathy. Aged knockout mice also develop kidney inflammation leading to glomerular changes, fibrosis and nephrotic syndrome. Defective mtDNA replication causing the formation of linear deleted mtDNA can thus trigger an immune response that leads to the development of progressive kidney disease in ageing animals.

DNA damage contributes to neurotoxic inflammation in Aicardi-Goutières syndrome astrocytes

Aberrant induction of type I IFN is a hallmark of the inherited encephalopathy Aicardi-Goutières syndrome (AGS), but the mechanisms triggering disease in the human central nervous system (CNS) remain elusive. Here, we generated human models of AGS using genetically modified and patient-derived pluripotent stem cells harboring TREX1 or RNASEH2B loss-of-function alleles. Genome-wide transcriptomic analysis reveals that spontaneous proinflammatory activation in AGS astrocytes initiates signaling cascades impacting multiple CNS cell subsets analyzed at the single-cell level. We identify accumulating DNA damage, with elevated R-loop and micronuclei formation, as a driver of STING- and NLRP3-related inflammatory responses leading to the secretion of neurotoxic mediators. Importantly, pharmacological inhibition of proapoptotic or inflammatory cascades in AGS astrocytes prevents neurotoxicity without apparent impact on their increased type I IFN responses. Together, our work identifies DNA damage as a major driver of neurotoxic inflammation in AGS astrocytes, suggests a role for AGS gene products in R-loop homeostasis, and identifies common denominators of disease that can be targeted to prevent astrocyte-mediated neurotoxicity in AGS.

Targeting the multifaceted roles of mitochondria in intracerebral hemorrhage and therapeutic prospects

Intracerebral hemorrhage (ICH) is a severe, life-threatening subtype of stoke that constitutes a crucial health and socioeconomic problem worldwide. However, the current clinical treatment can only reduce the mortality of patients to a certain extent, but cannot ameliorate neurological dysfunction and has a high recurrence rate. Increasing evidence has demonstrated that mitochondrial dysfunction occurs in the early stages of brain injury and participates in all stages of secondary brain injury (SBI) after ICH. As the energy source of cells, various pathobiological processes that lead to SBI closely interact with the mitochondria, such as oxidative stress, calcium overload, and neuronal injury. In this review, we discussed the structure and function of mitochondria and the abnormal morphological changes after ICH. In addition, we discussed recent research on the involvement of mitochondrial dynamics in the pathological process of SBI after ICH and introduced the pathological variations and related molecular mechanisms of mitochondrial dysfunction in the occurrence of brain injury. Finally, we summarized the latest progress in mitochondrion-targeted agents for ICH, which provides a direction for the development of emerging therapeutic strategies targeting the mitochondria after ICH.

Rotenone Modulates Caenorhabditis elegans Immunometabolism and Pathogen Susceptibility

Mitochondria are central players in host immunometabolism as they function not only as metabolic hubs but also as signaling platforms regulating innate immunity. Environmental exposures to mitochondrial toxicants occur widely and are increasingly frequent. Exposures to these mitotoxicants may pose a serious threat to organismal health and the onset of diseases by disrupting immunometabolic pathways. In this study, we investigated whether the Complex I inhibitor rotenone could alter C. elegans immunometabolism and disease susceptibility. C. elegans embryos were exposed to rotenone (0.5 µM) or DMSO (0.125%) until they reached the L4 larval stage. Inhibition of mitochondrial respiration by rotenone and disruption of mitochondrial metabolism were evidenced by rotenone-induced detrimental effects on mitochondrial efficiency and nematode growth and development. Next, through transcriptomic analysis, we investigated if this specific but mild mitochondrial stress that we detected would lead to the modulation of immunometabolic pathways. We found 179 differentially expressed genes (DEG), which were mostly involved in detoxification, energy metabolism, and pathogen defense. Interestingly, among the down-regulated DEG, most of the known genes were involved in immune defense, and most of these were identified as commonly upregulated during P. aeruginosa infection. Furthermore, rotenone increased susceptibility to the pathogen Pseudomonas aeruginosa (PA14). However, it increased resistance to Salmonella enterica (SL1344). To shed light on potential mechanisms related to these divergent effects on pathogen resistance, we assessed the activation of the mitochondrial unfolded protein response (UPRmt), a well-known immunometabolic pathway in C. elegans which links mitochondria and immunity and provides resistance to pathogen infection. The UPRmt pathway was activated in rotenone-treated nematodes further exposed for 24 h to the pathogenic bacteria P. aeruginosa and S. enterica or the common bacterial food source Escherichia coli (OP50). However, P. aeruginosa alone suppressed UPRmt activation and rotenone treatment rescued its activation only to the level of DMSO-exposed nematodes fed with E. coli. Module-weighted annotation bioinformatics analysis was also consistent with UPRmt activation in rotenone-exposed nematodes consistent with the UPR being involved in the increased resistance to S. enterica. Together, our results demonstrate that the mitotoxicant rotenone can disrupt C. elegans immunometabolism in ways likely protective against some pathogen species but sensitizing against others.

Assessing Mitochondrial DNA Release into the Cytosol and Subsequent Activation of Innate Immune-related Pathways in Mammalian Cells

Mitochondria have emerged as key drivers of mammalian innate immune responses, functioning as signaling hubs to trigger inflammation and orchestrating metabolic switches required for phagocyte activation. Mitochondria also contain damage-associated molecular patterns (DAMPs), molecules that share similarity with pathogen-associated molecular patterns (PAMPs) and can engage innate immune sensors to drive inflammation. The aberrant release of mitochondrial DAMPs during cellular stress and injury is an increasingly recognized trigger of inflammatory responses in human diseases. Mitochondrial DNA (mtDNA) is a particularly potent DAMP that engages multiple innate immune sensors, although mounting evidence suggests that cytosolic mtDNA is primarily detected via the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway. cGAS and STING are widely expressed in mammalian cells and serve as key regulators of type I interferon and cytokine expression in both infectious and inflammatory diseases. Despite growing roles for the mtDNA-cGAS-STING axis in human disease, assays to quantify mtDNA release into the cytosol and approaches to link mtDNA to cGAS-STING signaling are not standardized, which increases the possibility for experimental artifacts and misinterpretation of data. Here, we present a series of protocols for assaying the release of mtDNA into the cytosol and subsequent activation of innate immune signaling in mammalian cells. We highlight genetic and pharmacological approaches to induce and inhibit mtDNA release from mitochondria. We also describe immunofluorescence microscopy and cellular fractionation assays to visualize morphological changes in mtDNA and quantify mtDNA accumulation in the cytosol. Finally, we include protocols to examine mtDNA-dependent cGAS-STING activation by RT-qPCR and western blotting. These methods can be performed with standard laboratory equipment and are highly adaptable to a wide range of mammalian cell types. They will permit researchers working across the spectrum of biological and biomedical sciences to accurately and reproducibly measure cytosolic mtDNA release and resulting innate immune responses. © 2022 Wiley Periodicals LLC. Basic Protocol 1: siRNA-mediated knockdown of TFAM to induce mtDNA instability, cytosolic release, and activation of the cGAS-STING pathway Alternate Protocol: Pharmacological induction of mtDNA release and cGAS-STING activation using ABT-737 and Q-VD-OPH Basic Protocol 2: Isolation and quantitation of DNA from cytosolic, mitochondrial, and nuclear fractions Basic Protocol 3: Pharmacological inhibition of mtDNA replication and release.

Pathophysiology of Heart Failure: A Role for Peripheral Blood Mononuclear Cells Mitochondrial Dysfunction?

Heart failure (HF) is a leading cause of hospitalization in patients aged more than 65 years and is associated with high mortality rates. A better comprehension of its physiopathology is still needed, and, in addition to neurohormonal systems and sodium glucose co-transporter 2 modulations, recent studies focus on the mitochondrial respiration of peripheral blood circulating cells (PBMCs). Thus, cardiovascular metabolic risk factors and cellular switch with an increased neutrophil/lymphocytes ratio might favor the decreased PBMC mitochondrial respiration observed in relation with HF severity. PBMCs are implicated in the immune system function and mitochondrial dysfunction of PBMC, potentially induced by their passage through a damaged heart and by circulating mitoDAMPs, which can lead to a vicious circle, thus sustaining negative cardiac remodeling during HF. This new approach of HF complex pathophysiology appears to be a promising field of research, and further studies on acute and chronic HF with reduced or preserved LVEF are warranted to better understand whether circulating PBMC mitochondrial function and mitoDAMPs follow-ups in HF patients might show diagnosis, prognosis or therapeutic usefulness.

Age-related Activation of Cyclic GMP-AMP synthase-Stimulator of Interferon Genes Signaling in the Auditory System is Associated with Presbycusis in C57BL/6J Male Mice

Presbycusis, or age-related hearing loss (ARHL), is primarily associated with sensory or transduction nerve cell degeneration in the peripheral and/or central auditory systems. During aging, the auditory system shows mitochondrial dysfunction and increased inflammatory responses. Mitochondrial dysfunction promotes leakage of mitochondrial DNA (mtDNA) into the cytosol, which activates the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway to induce type I interferon and inflammatory responses. However, whether this pathway is involved in the occurrence and development of ARHL is unknown. This study aimed to determine whether there are age-related changes in the levels of cytosolic mtDNA and cGAS-STING pathway activation in the auditory pathway and to explore their relationship with ARHL. The results showed that cGAS-positive immunoreactive cells were observed in the cochlea, inferior colliculus, and auditory cortex. Levels of cytosolic mtDNA, cGAS, STING, phosphorylated interferon regulatory factor 3, and cytokines were significantly increased in the cochlea, inferior colliculus, and auditory cortex of 6-, 9-, and 12-month-old mice compared with 3-month-old mice. These findings suggested that cytosolic mtDNA may play an important role in the pathogenesis of ARHL by activating cGAS-STING-mediated type I interferon and inflammatory responses.

Neuroinflammation and Mitochondrial Dysfunction Link Social Stress to Depression

Major depressive disorder is a debilitating mental illness and a leading cause of global disease burden. While many etiological factors have been identified, social stress is a highly prevalent causative factor for the onset of depression. Unfortunately, rates of depression continue to increase around the world, and the recent COVID-19 pandemic has further exacerbated this mental health crisis. Though several therapeutic strategies are available, nearly 50% of patients who receive treatment never reach remission. The exact mechanisms by which social stress exposure promotes the development of depression are unclear, making it challenging to develop novel and more effective therapeutics. However, accumulating evidence points to a role for stress-induced neuroinflammation, particularly in treatment-resistant patients. Moreover, recent evidence has expanded the concept of the pathogenesis of depression to mitochondrial dysfunction, suggesting that the combined effects of social stress on mitochondria and inflammation may synergize to facilitate stress-related depression. In this chapter, we review evidence for neuroinflammation and mitochondrial dysfunction in the pathogenesis of social stress-induced depression and discuss these in the context of novel therapeutic targets for the treatment of depression.

ER stress promotes mitochondrial DNA mediated type-1 interferon response in beta-cells and interleukin-8 driven neutrophil chemotaxis

Beta-cell destruction in type 1 diabetes (T1D) results from the combined effect of inflammation and recurrent autoimmunity. Accumulating evidence suggests the engagement of cellular stress during the initial stage of the disease, preceding destruction and triggering immune cell infiltration. While the role of the endoplasmic reticulum (ER) in this process has been largely described, the participation of the other cellular organelles, particularly the mitochondria which are central mediator for beta-cell survival and function, remains poorly investigated. Here, we have explored the contribution of ER stress, in activating type-I interferon signaling and innate immune cell recruitment. Using human beta-cell line EndoC-βH1 exposed to thapsigargin, we demonstrate that induction of cellular stress correlates with mitochondria dysfunction and a significant accumulation of cytosolic mitochondrial DNA (mtDNA) that triggers neutrophils migration by an IL8-dependent mechanism. These results provide a novel mechanistic insight on how ER stress can cause insulitis and may ultimately facilitate the identification of potential targets to protect beta-cells against immune infiltration.

Mitochondria-targeted nanoparticles in treatment of neurodegenerative diseases

Neurodegenerative diseases (NDs) are a class of heterogeneous diseases that includes Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Mitochondria play an important role in oxidative balance and metabolic activity of neurons; therefore, mitochondrial dysfunction is associated with NDs and mitochondria are considered a potential treatment target for NDs. Several obstacles, including the blood-brain barrier (BBB) and cell/mitochondrial membranes, reduce the efficiency of drug entry into the target lesions. Therefore, a variety of neuron mitochondrial targeting strategies has been developed. Among them, nanotechnology-based treatments show especially promising results. Owing to their adjustable size, appropriate charge, and lipophilic surface, nanoparticles (NPs) are the ideal theranostic system for crossing the BBB and targeting the neuronal mitochondria. In this review, we discussed the role of dysfunctional mitochondria in ND pathogenesis as well as the physiological barriers to various treatment strategies. We also reviewed the use and advantages of various NPs (including organic, inorganic, and biological membrane-coated NPs) for the treatment and diagnosis of NDs. Finally, we summarized the evidence and possible use for the promising role of NP-based theranostic systems in the treatment of mitochondrial dysfunction-related NDs.

TIGAR plays neuroprotective roles in KA-induced excitotoxicity through reducing neuroinflammation and improving mitochondrial function

Excitotoxicity refers to the ability of excessive extracellular excitatory amino acids to damage neurons via receptor activation. It is a crucial pathogenetic process in neurodegenerative diseases. TP53 is confirmed to be involved in excitotoxicity. It is demonstrated that TP53 induced glycolysis and apoptotic regulator (TIGAR)-regulated metabolic pathway can protect against neuronal injury. However, the role of TIGAR in excitotoxicity and specific mechanisms is still unknown. In this study, an in vivo excitotoxicity model was constructed via stereotypical kainic acid (KA) injection into the striatum of mice. KA reduced TIGAR expression levels, neuroinflammatory responses and mitochondrial dysfunction. TIGAR overexpression could reverse KA-induced neuronal injury by reducing neuroinflammation and improving mitochondrial function, thereby exerting neuroprotective effects. Therefore, this study could provide a potential therapeutic target for neurodegenerative diseases.

TNF leads to mtDNA release and cGAS/STING-dependent interferon responses that support inflammatory arthritis

Tumor necrosis factor (TNF) is a key driver of several inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, and psoriasis, in which affected tissues show an interferon-stimulated gene signature. Here, we demonstrate that TNF triggers a type-I interferon response that is dependent on the cyclic guanosine monophosphate-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. We show that TNF inhibits PINK1-mediated mitophagy and leads to altered mitochondrial function and to an increase in cytosolic mtDNA levels. Using cGAS-chromatin immunoprecipitation (ChIP), we demonstrate that cytosolic mtDNA binds to cGAS after TNF treatment. Furthermore, TNF induces a cGAS-STING-dependent transcriptional response that mimics that of macrophages from rheumatoid arthritis patients. Finally, in an inflammatory arthritis mouse model, cGAS deficiency blocked interferon responses and reduced inflammatory cell infiltration and joint swelling. These findings elucidate a molecular mechanism linking TNF to type-I interferon signaling and suggest a potential benefit for therapeutic targeting of cGAS/STING in TNF-driven diseases.

Overexpression of SIRT3 Suppresses Oxidative Stress-induced Neurotoxicity and Mitochondrial Dysfunction in Dopaminergic Neuronal Cells

Sirtuin 3 (SIRT3), a well-known mitochondrial deacetylase, is involved in mitochondrial function and metabolism under various stress conditions. In this study, we found that the expression of SIRT3 was markedly increased by oxidative stress in dopaminergic neuronal cells. In addition, SIRT3 overexpression enhanced mitochondrial activity in differentiated SH-SY5Y cells. We also showed that SIRT3 overexpression attenuated rotenone- or H₂O₂-induced toxicity in differentiated SH-SY5Y cells (human dopaminergic cell line). We further found that knockdown of SIRT3 enhanced rotenone- or H₂O₂-induced toxicity in differentiated SH-SY5Y cells. Moreover, overexpression of SIRT3 mitigated cell death caused by LPS/IFN-γ stimulation in astrocytes. We also found that the rotenone treatment increases the level of SIRT3 in Drosophila brain. We observed that downregulation of sirt2 (Drosophila homologue of SIRT3) significantly accelerated the rotenone-induced toxicity in flies. Taken together, these findings suggest that the overexpression of SIRT3 mitigates oxidative stress-induced cell death and mitochondrial dysfunction in dopaminergic neurons and astrocytes.

Treadmill running prevents atrophy differently in fast- versus slow-twitch muscles in a rat model of rheumatoid arthritis

To investigate the effects of treadmill running on two different types of skeletal muscle, we established a rat model of collagen-induced arthritis (CIA). The skeletal muscles studied were the extensor digitorum longus (EDL), which is rich in fast-twitch muscle fibers, and the soleus, which is rich in slow-twitch muscle fibers. The histological and transcriptional changes in these muscles at 14 and 44 days after immunosensitization were compared between rats that were forced to exercise (CIA ex group) and free-reared CIA rats (CIA no group). Change in protein expression was examined on day 14 after a single bout of treadmill running. Treadmill running had different effects on the relative muscle weight and total and fiber cross-sectional areas in each muscle type. In the soleus, it prevented muscle atrophy. Transcriptional analysis revealed increased eukaryotic translation initiation factor 4E (Eif4e) expression on day 14 and increased Atrogin-1 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression on day 44 in the soleus in the CIA ex group, suggesting an interaction between muscle type and exercise. A single bout of treadmill running increased the level of Eif4e and p70S6K and decreased that of Atrogin-1 in the soleus on day 14. Treadmill running prevented muscle atrophy in the soleus in a rat model of rheumatoid arthritis via activation of mitochondrial function, as evidenced by increased PGC-1α expression.

The Toxicity of Wiped Dust and Airborne Microbes in Individual Classrooms Increase the Risk of Teachers' Work-Related Symptoms: A Cross-Sectional Study

Background: The causes and pathophysiological mechanisms of building-related symptoms (BRS) remain open. Objective: We aimed to investigate the association between teachers’ individual work-related symptoms and intrinsic in vitro toxicity in classrooms. This is a further analysis of a previously published dataset. Methods: Teachers from 15 Finnish schools in Helsinki responded to the symptom survey. The boar sperm motility inhibition assay, a sensitive indicator of mitochondrial dysfunction, was used to measure the toxicity of wiped dust and cultured microbial fallout samples collected from the teachers’ classrooms. Results: 231 teachers whose classroom toxicity data had been collected responded to the questionnaire. Logistic regression analysis adjusted for age, gender, smoking, and atopy showed that classroom dust intrinsic toxicity was statistically significantly associated with the following 12 symptoms reported by teachers (adjusted ORs in parentheses): nose stuffiness (4.1), runny nose (6.9), hoarseness (6.4), globus sensation (9.0), throat mucus (7.6), throat itching (4.4), shortness of breath (12.2), dry cough (4.7), wet eyes (12.7), hypersensitivity to sound (7.9), difficulty falling asleep (7.6), and increased need for sleep (7.7). Toxicity of cultured microbes was found to be associated with nine symptoms (adjusted ORs in parentheses): headache (2.3), nose stuffiness (2.2), nose dryness (2.2), mouth dryness (2.8), hoarseness (2.2), sore throat (2.8), throat mucus (2.3), eye discharge (10.2), and increased need for sleep (3.5). Conclusions: The toxicity of classroom dust and airborne microbes in boar sperm motility inhibition assay significantly increased teachers’ risk of work-related respiratory and ocular symptoms. Potential pathophysiological mechanisms of BRS are discussed.

Dose-Dependent Response to the Environmental Pollutant Dichlorodipheniletylhene (DDE) in HepG2 Cells: Focus on Cell Viability and Mitochondrial Fusion/Fission Proteins

Dichlorodiphenyldichloroethylene (DDE), the primary persistent metabolite of dichlorodiphenyltrichloroethane (DDT), has toxic effects on cells, but its dose-dependent impact on mitochondrial proteins involved in mitochondrial fusion and fission processes associated with cell viability impairment has not yet been analysed. Mitochondrial fusion and fission processes are critical to maintaining the mitochondrial network and allowing the cell to respond to external stressors such as environmental pollutants. Fusion processes are associated with optimizing mitochondrial function, whereas fission processes are associated with removing damaged mitochondria. We assessed the effects of different DDE doses, ranging between 0.5 and 100 µM, on cell viability and mitochondrial fusion/fission proteins in an in vitro hepatic cell model (human hepatocarcinomatous cells, HepG2); the DDE induced a decrease in cell viability in a dose-dependent manner, and its effect was enhanced in conditions of coincubation with dietary fatty acids. Fusion protein markers exhibited an inverted U-shape dose-response curve, showing the highest content in the 2.5–25 μM DDE dose range. The fission protein marker was found to increase significantly, leading to an increased fission/fusion ratio with high DDE doses. The low DDE doses elicited cell adaption by stimulating mitochondrial dynamics machinery, whereas high DDE doses induced cell viability loss associated with mitochondrial dynamics to shift toward fission. Present results are helpful to clarify the mechanisms underlying the cell fate towards survival or death in response to increasing doses of environmental pollutants.

Insights into Cadmium-Induced Carcinogenesis through an In Vitro Study Using C3H10T1/2Cl8 Cells: The Multifaceted Role of Mitochondria

In this paper, we report the metabolic characterization of two foci, F1 and F3, obtained at the end of Cell Transformation Assay (CTA), performed by treating C3H10T1/2Cl8 mouse embryo fibroblasts with 1 μM CdCl₂ for 24 h. The elucidation of the cadmium action mechanism can be useful both to improve the in vitro CTA and to yield insights into carcinogenesis. The metabolism of the two foci was investigated through Seahorse and enzyme activity assays; mitochondria were studied in confocal microscopy and reactive oxygen species were detected by flow cytometry. The results showed that F1 focus has higher glycolytic and TCA fluxes compared to F3 focus, and a more negative mitochondrial membrane potential, so that most ATP synthesis is performed through oxidative phosphorylation. Confocal microscopy showed mitochondria crowded in the perinuclear region. On the other hand, F3 focus showed lower metabolic rates, with ATP mainly produced by glycolysis and damaged mitochondria. Overall, our results showed that cadmium treatment induced lasting metabolic alterations in both foci. Triggered by the loss of the Pasteur effect in F1 focus and by mitochondrial impairment in F3 focus, these alterations lead to a loss of coordination among glycolysis, TCA and oxidative phosphorylation, which leads to malignant transformation.

Neuroimmune mechanisms of cognitive impairment in a mouse model of Gulf War illness

Gulf War Illness (GWI) is a chronic, multi-symptom disorder affecting approximately 30 percent of the nearly 700,000 Veterans of the 1991 Persian Gulf War. GWI-related chemical (GWIC) exposure promotes immune activation that correlates with cognitive impairment and other symptoms of GWI. However, the molecular mechanisms and signaling pathways linking GWIC to inflammation and neurological symptoms remain unclear. Here we show that acute exposure of murine macrophages to GWIC potentiates innate immune signaling and inflammatory cytokine production. Using an established mouse model of GWI, we report that neurobehavioral changes and neuroinflammation are attenuated in mice lacking the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) and NOD-, LRR- or pyrin domain-containing protein 3 (NLRP3) innate immune pathways. In addition, we report sex differences in response to GWIC, with female mice showing more pronounced cognitive impairment and hippocampal astrocyte hypertrophy. In contrast, male mice display a GWIC-dependent upregulation of proinflammatory cytokines in the plasma that is not present in female mice. Our results indicate that STING and NLRP3 are key mediators of the cognitive impairment and inflammation observed in GWI and provide important new information on sex differences in this model.

Emerging methods for and novel insights gained by absolute quantification of mitochondrial DNA copy number and its clinical applications

The past thirty years have seen a surge in interest in pathophysiological roles of mitochondria, and the accurate quantification of mitochondrial DNA copy number (mCN) in cells and tissue samples is a fundamental aspect of assessing changes in mitochondrial health and biogenesis. Quantification of mCN between studies is surprisingly variable due to a combination of physiological variability and diverse protocols being used to measure this endpoint. The advent of novel methods to quantify nucleic acids like digital polymerase chain reaction (dPCR) and high throughput sequencing offer the ability to measure absolute values of mCN. We conducted an in-depth survey of articles published between 1969 -- 2020 to create an overview of mCN values, to assess consensus values of tissue-specific mCN, and to evaluate consistency between methods of assessing mCN. We identify best practices for methods used to assess mCN, and we address the impact of using specific loci on the mitochondrial genome to determine mCN. Current data suggest that clinical measurement of mCN can provide diagnostic and prognostic value in a range of diseases and health conditions, with emphasis on cancer and cardiovascular disease, and the advent of means to measure absolute mCN should improve future clinical applications of mCN measurements.

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) activates Aryl hydrocarbon receptor (AhR) mediated ROS and NLRP3 inflammasome/p38 MAPK pathway inducing necrosis in cochlear hair cells

Tetrabromodiphenyl ether (BDE-47) is widely used as commercial flame retardants that can be released into the environment and finally enter human body through the food chain. It has been identified to generate neurotoxicity, but little is known about auditory damage and the underlying mechanism following BDE-47 exposure. This study aimed to assess the cell viability with BDE-47 concentration ranging from 0 to 150 μM in mouse organ of Corti-derived cell lines (HEI-OC1). Aryl hydrocarbon receptor (AhR) as an environmental sensor, reactive oxygen species (ROS), NLRP3 inflammasome and p38 MAPK pathways were detected. Results: (1) BDE-47 inhibited the viability in a time- and dose-dependent way in HEI-OC1 cells. Cell cycle was arrested in G1 phase by BDE-47; (2) Elevated intracellular ROS, LDH levels and necrosis were found, which was alleviated by pretreatment with ROS scavenger N-acetylcysteine (NAC); (3) AhR plays an essential role in ligand-regulated transcription factor activation by exogenous environmental compounds. We found increased expression of AhR and decreased downstream targets of CYP 1A1 and CYP 1B1 in BDE-47-treated HEI-OC1 cells, which was reversed by the AhR antagonist CH-223191 for 2 h before BDE-47 exposure. No significant change was detected in CYP 2B; (4) Enhanced expressions of NLRP3 and caspase-1 were induced by BDE-47, with up-regulations of both pro-inflammatory factors for IL-1β, IL-6 and TNF-α, and anti-inflammatory factors for IL-4, IL-10 and IL-13, but down-regulation for IL-1α; (5) Additionally, the p38 MAPK signaling pathway was activated with increased phosphorylation levels of MKK/3/6, p38 MAPK and NF-kB. Overall, our findings illustrate a role of AhR in ROS-induced necrosis of cochlear hair cells by BDE-47 exposure, in which NLRP3 inflammasome and p38 MAPK signaling pathways are activated. The current study first elucidates the sense of hearing damage induced by BDE-47, and cell-specific or mixture exposures in vivo or human studies are needed to confirm this association.

Mitochondrial Nucleic Acid as a Driver of Pathogenic Type I Interferon Induction in Mendelian Disease

The immune response to viral infection involves the recognition of pathogen-derived nucleic acids by intracellular sensors, leading to type I interferon (IFN), and downstream IFN-stimulated gene, induction. Ineffective discrimination of self from non-self nucleic acid can lead to autoinflammation, a phenomenon implicated in an increasing number of disease states, and well highlighted by the group of rare genetic disorders referred to as the type I interferonopathies. To understand the pathogenesis of these monogenic disorders, and polyfactorial diseases associated with pathogenic IFN upregulation, such as systemic lupus erythematosus and dermatomyositis, it is important to define the self-derived nucleic acid species responsible for such abnormal IFN induction. Recently, attention has focused on mitochondria as a novel source of immunogenic self nucleic acid. Best appreciated for their function in oxidative phosphorylation, metabolism and apoptosis, mitochondria are double membrane-bound organelles that represent vestigial bacteria in the cytosol of eukaryotic cells, containing their own DNA and RNA enclosed within the inner mitochondrial membrane. There is increasing recognition that a loss of mitochondrial integrity and compartmentalization can allow the release of mitochondrial nucleic acid into the cytosol, leading to IFN induction. Here, we provide recent insights into the potential of mitochondrial-derived DNA and RNA to drive IFN production in Mendelian disease. Specifically, we summarize current understanding of how nucleic acids are detected as foreign when released into the cytosol, and then consider the findings implicating mitochondrial nucleic acid in type I interferonopathy disease states. Finally, we discuss the potential for IFN-driven pathology in primary mitochondrial disorders.

Teachers' work-related non-literature-known building-related symptoms are also connected to indoor toxicity: A cross-sectional study

A previous study showed that classical building-related symptoms (BRS) were related to indoor dust and microbial toxicity via boar sperm motility assay, a sensitive method for measuring mitochondrial toxicity. In this cross-sectional study, we analyzed whether teachers' most common work-related non-literature-known BRS (nBRS) were also associated with dust or microbial toxicity. Teachers from 15 schools in Finland completed a questionnaire evaluating 20 nBRS including general, eye, respiratory, hearing, sleep, and mental symptoms. Boar sperm motility assay was used to measure the toxicity of extracts from wiped dust and microbial fallout samples collected from teachers' classrooms. 231 teachers answered a questionnaire and their classroom toxicity data were recorded. A negative binomial mixed model showed that teachers' work-related nBRS were 2.9-fold (95% CI: 1.2-7.3) higher in classrooms with highly toxic dust samples compared to classrooms with non-toxic dust samples (p = 0.024). The RR of work-related nBRS was 1.8 (95% CI: 1.1-2.9) for toxic microbial samples (p = 0.022). Teachers' BRS appeared to be broader than reported in the literature, and the work-related nBRS were associated with toxic dusts and microbes in classrooms.

Interleukin-6 as potential mediator of long-term neuropsychiatric symptoms of COVID-19

The majority of COVID-19 survivors experience long-term neuropsychiatric symptoms such as fatigue, sleeping difficulties, depression and anxiety. We propose that neuroimmune cross-talk via inflammatory cytokines such as interleukin-6 (IL-6) could underpin these long-term COVID-19 symptoms. This hypothesis is supported by several lines of research, including population-based cohort and genetic Mendelian Randomisation studies suggesting that inflammation is associated with fatigue and sleeping difficulties, and that IL-6 could represent a possible causal driver for these symptoms. Immune activation following COVID-19 can disrupt T helper 17 (TH17) and regulatory T (Treg) cell responses, affect central learning and emotional processes, and lead to a vicious cycle of inflammation and mitochondrial dysfunction that amplifies the inflammatory process and results in immuno-metabolic constraints on neuronal energy metabolism, with fatigue being the ultimate result. Increased cytokine activity drives this process and could be targeted to interrupt it. Therefore, whether persistent IL-6 dysregulation contributes to COVID-19-related long-term fatigue, sleeping difficulties, depression, and anxiety, and whether targeting IL-6 pathways could be helpful for treatment and prevention of long COVID are important questions that require investigation. This line of research could inform new approaches for treatment and prevention of long-term neuropsychiatric symptoms of COVID-19. Effective treatment and prevention of this condition could also help to stem the anticipated rise in depression and other mental illnesses ensuing this pandemic.

Mitochondrial fission, integrity and completion of mitophagy require separable functions of Vps13D in Drosophila neurons

A healthy population of mitochondria, maintained by proper fission, fusion, and degradation, is critical for the long-term survival and function of neurons. Here, our discovery of mitophagy intermediates in fission-impaired Drosophila neurons brings new perspective into the relationship between mitochondrial fission and mitophagy. Neurons lacking either the ataxia disease gene Vps13D or the dynamin related protein Drp1 contain enlarged mitochondria that are engaged with autophagy machinery and also lack matrix components. Reporter assays combined with genetic studies imply that mitophagy both initiates and is completed in Drp1 impaired neurons, but fails to complete in Vps13D impaired neurons, which accumulate compromised mitochondria within stalled mito-phagophores. Our findings imply that in fission-defective neurons, mitophagy becomes induced, and that the lipid channel containing protein Vps13D has separable functions in mitochondrial fission and phagophore elongation.

Effects of Selenium on MAC-T Cells in Bovine Mastitis: Transcriptome Analysis of Exosomal mRNA Interactions

Selenium, a micronutrient, is indispensable for maintaining normal metabolic functions in animals and plants. Selenium has shown promise in terms of its effect on the immune function, ability to control inflammation, and ability to improve bovine mammary gland health. Bovine mastitis remains a major threat to dairy herds globally and has economically significant impacts. The exosomes are a new mode of intercellular communication. Exosomal transfer of mRNAs, microRNAs, and proteins between cells affects the protein production of recipient cells. The development of novel high-throughput omics approaches and bioinformatics tools will help us understand the effects of selenium on immunobiology. However, the differential expression of mRNAs in bovine mammary epithelial cell-derived exosomes has rarely been studied. In the present study, differences in the exosomal transcriptome between control and selenium-treated MAC-T cells were identified by RNA sequencing and transcriptome analysis. The results of mRNA profiling revealed 1978 genes in exosomes that were differentially expressed between the selenium-treated and control cells. We selected and analyzed 91 genes that are involved in inflammation, redox reactions, and immune cell function related to mastitis. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed enrichment pathways involved in selenoproteins and the Ras/PI3K/AKT, MAPK, and FOXO signaling pathways. Our results revealed that selenium may play a crucial role in immune and inflammatory regulation by influencing the differential expression of exosomal mRNAs of key genes in bovine mastitis.

Chronic chlorpyrifos exposure induces oxidative stress, apoptosis and immune dysfunction in largemouth bass (Micropterus salmoides)

This study was undertaken to (a) evaluate the destructive effects of chronic exposure to low-dose of chlorpyrifos (CPF) on antioxidant system and immune function in largemouth bass (Micropterus salmoides), and (b) to examine whether dietary supplementation of curcumin can mitigate the adverse effects induced by CPF contamination. The experiment consisted of three groups (with three replicates, 30 fish per replicate) which lasted for 60 days: A control group (without CPF exposure or CU application), CP group (exposed to 0.004 mg/L of CPF), and CU group (exposed to 0.004 mg/L of CPF and fed a diet containing 100 mg curcumin per kg feed). The results showed that CPF contamination leads to reduced weight gain, severe histopathological lesions, decreased activity of antioxidant enzymes and down-regulated expression of antioxidant-related genes. Moreover, CPF upregulated the expression of pro-inflammatory genes such as TNF-α, IL-8, IL-15, downregulated anti-inflammatory genes TGF-β1, IL-10, and promoted apoptosis through overexpression of Caspase-3, Caspase-8, caspase-9 and Bax. In addition, curcumin supplementation showed significant improvement in oxidative stress, apoptosis and immune dysfunction, but the improved effect gradually weakened during the exposure last. Gas chromatography-mass spectrometry (GC-MS) analysis for accumulation of CPF in muscle supported the changes of general physiological structure, excessive apoptotic responses, abnormal antioxidant and immune system functions and posed potential human health risks to children based on target hazard quotient. These results suggested that chronic exposure to CPF can cause oxidative stress, apoptosis and immune dysfunction, and that curcumin have the potential to reduce pesticides residues in fish. This also highlights the importance of monitoring pesticides residues in aquatic products and aquaculture aquatic environments.

Distinct Mitochondrial Pathologies Caused by Mutations of the Proximal Tubular Enzymes EHHADH and GATM

The mitochondria of the proximal tubule are essential for providing energy in this nephron segment, whose ATP generation is almost exclusively oxygen dependent. In addition, mitochondria are involved in a variety of metabolic processes and complex signaling networks. Proximal tubular mitochondrial dysfunction can therefore affect renal function in very different ways. Two autosomal dominantly inherited forms of renal Fanconi syndrome illustrate how multifaceted mitochondrial pathology can be: Mutation of EHHADH, an enzyme in fatty acid metabolism, results in decreased ATP synthesis and a consecutive transport defect. In contrast, mutations of GATM, an enzyme in the creatine biosynthetic pathway, leave ATP synthesis unaffected but do lead to mitochondrial protein aggregates, inflammasome activation, and renal fibrosis with progressive renal failure. In this review article, the distinct pathophysiological mechanisms of these two diseases are presented, which are examples of the spectrum of proximal tubular mitochondrial diseases.

Melinacidin-Producing Acrostalagmus luteoalbus, a Major Constituent of Mixed Mycobiota Contaminating Insulation Material in an Outdoor Wall

Occupants may complain about indoor air quality in closed spaces where the officially approved standard methods for indoor air quality risk assessment fail to reveal the cause of the problem. This study describes a rare genus not previously detected in Finnish buildings, Acrostalagmus, and its species A. luteoalbus as the major constituents of the mixed microbiota in the wet cork liner from an outdoor wall. Representatives of the genus were also present in the settled dust in offices where occupants suffered from symptoms related to the indoor air. One strain, POB8, was identified as A. luteoalbus by ITS sequencing. The strain produced the immunosuppressive and cytotoxic melinacidins II, III, and IV, as evidenced by mass spectrometry analysis. In addition, the classical toxigenic species indicating water damage, mycoparasitic Trichoderma, Aspergillus section Versicolores, Aspergillus section Circumdati, Aspergillus section Nigri, and Chaetomium spp., were detected in the wet outdoor wall and settled dust from the problematic rooms. The offices exhibited no visible signs of microbial growth, and the airborne load of microbial conidia was too low to explain the reported symptoms. In conclusion, we suggest the possible migration of microbial bioactive metabolites from the wet outdoor wall into indoor spaces as a plausible explanation for the reported complaints.

Flavonoids and cellular stress: a complex interplay affecting human health

Flavonoid consumption has beneficial effects on human health, however, clinical evidence remains often inconclusive due to high interindividual variability. Although this high interindividual variability has been consistently observed in flavonoid research, the potential underlying reasons are still poorly studied. Especially the knowledge on the impact of health status on flavonoid responsiveness is limited and merits more investigation. Here, we aim to highlight the bidirectional interplay between flavonoids and cellular stress. First, the state-of-the-art concerning inflammatory stress and mitochondrial dysfunction is reviewed and a comprehensive overview of recent in vitro studies investigating the impact of flavonoids on cellular stress, induced by tumor necrosis factor α, lipopolysaccharide and mitochondrial stressors, is given. Second, we critically discuss the influence of cellular stress on flavonoid uptake, accumulation, metabolism and cell responses, which has, to our knowledge, never been extensively reviewed before. Next, we advocate the innovative insight that stratification of the general population based on health status can reveal subpopulations that benefit more from flavonoid consumption. Finally, suggestions are given for the development of future cell models that simulate the physiological micro-environment, including interindividual variability, since more mechanistic research is needed to establish scientific-based personalized food recommendations for specific subpopulations.

Focus on the Complex Interconnection between Cancer, Narcolepsy and Other Neurodegenerative Diseases: A Possible Case of Orexin-Dependent Inverse Comorbidity

Simple Summary

This narrative review first describes from several points of view the complex interrelationship between cancer and neurodegeneration, with special attention to the mechanisms that might underlie an inverse relationship between them. In particular, the mechanisms that might induce an imbalance between cell apoptotic and proliferative stimuli are discussed. Second, the review summarizes findings on orexins and their involvement in narcolepsy, neurodegenerative diseases, and cancer, starting from epidemiological data then addressing laboratory findings, animal models, and human clinical observational and interventional investigations. Important research efforts are warranted on these topics, as they might lead to novel therapeutic approaches to both neurodegenerative diseases and cancer.

Abstract

Conditions such as Alzheimer’s (AD) and Parkinson’s diseases (PD) are less prevalent in cancer survivors and, overall, cancer is less prevalent in subjects with these neurodegenerative disorders. This seems to suggest that a propensity towards one type of disease may decrease the risk of the other. In addition to epidemiologic data, there is also evidence of a complex biological interconnection, with genes, proteins, and pathways often showing opposite dysregulation in cancer and neurodegenerative diseases. In this narrative review, we focus on the possible role played by orexin signaling, which is altered in patients with narcolepsy type 1 and in those with AD and PD, and which has been linked to β-amyloid brain levels and inflammation in mouse models and to cancer in cell lines. Taken together, these lines of evidence depict a possible case of inverse comorbidity between cancer and neurodegenerative disorders, with a role played by orexins. These considerations suggest a therapeutic potential of orexin modulation in diverse pathologies such as narcolepsy, neurodegenerative disorders, and cancer.

Mitochondrial DNA leakage induces odontoblast inflammation via the cGAS-STING pathway

Background

Mitochondrial DNA (mtDNA) is a vital driver of inflammation when it leaks from damaged mitochondria into the cytosol. mtDNA stress may contribute to cyclic GMP-AMP synthase (cGAS) stimulator of interferon genes (STING) pathway activation in infectious diseases. Odontoblasts are the first cells challenged by cariogenic bacteria and involved in maintenance of the pulp immune and inflammatory responses to dentine-invading pathogens. In this study, we investigated that mtDNA as an important inflammatory driver participated in defending against bacterial invasion via cGAS-STING pathway in odontoblasts.

Methods

The normal tissues, caries tissues and pulpitis tissues were measured by western blotting and immunohistochemical staining. Pulpitis model was built in vitro to evaluated the effect of the cGAS-STING pathway in odontoblast-like cell line (mDPC6T) under inflammation. Western blot and real-time PCR were performed to detect the expression of cGAS-STING pathway and pro-inflammatory cytokines. The mitochondrial function was evaluated reactive oxygen species (ROS) generated by mitochondria using MitoSOX Red dye staining. Cytosolic DNA was assessed by immunofluorescent staining and real-time PCR in mDPC6T cells after LPS stimulation. Furthermore, mDPC6T cells were treated with ethidium bromide (EtBr) to deplete mtDNA or transfected with isolated mtDNA. The expression of cGAS-STING pathway and pro-inflammatory cytokines were measured.

Results

The high expression of cGAS and STING in caries and pulpitis tissues in patients, which was associated with inflammatory progression. The cGAS-STING pathway was activated in inflamed mDPC6T. STING knockdown inhibited the nuclear import of p65 and IRF3 and restricted the secretion of the inflammatory cytokines CXCL10 and IL-6 induced by LPS. LPS caused mitochondrial damage in mDPC6T, which promoted mtDNA leakage into the cytosol. Depletion of mtDNA inhibited the cGAS-STING pathway and nuclear translocation of p65 and IRF3. Moreover, repletion of mtDNA rescued the inflammatory response, which was inhibited by STING knockdown.

Conclusion

Our study systematically identified a novel mechanism of LPS-induced odontoblast inflammation, which involved mtDNA leakage from damaged mitochondria into the cytosol stimulating the cGAS-STING pathway and the inflammatory cytokines IL-6 and CXCL10 secretion. The mtDNA-cGAS-STING axis could be a potent therapeutic target to prevent severe bacterial inflammation in pulpitis.

The Roles of Dietary, Nutritional and Lifestyle Interventions in Adipose Tissue Adaptation and Obesity

The obesity and the associated non-communicable diseases (NCDs) are globally increasing in their prevalence. While the modern-day lifestyle required less ventilation of metabolic energy through muscular activities, this lifestyle transition also provided the unlimited accession to foods around the clock, which prolong the daily eating period of foods that contained high calorie and high glycemic load. These situations promote the high continuous flux of carbon substrate availability in mitochondria and induce the indecisive bioenergetic switches. The disrupted bioenergetic milieu increases the uncoupling respiration due to the excess flow of the substrate-derived reducing equivalents and reduces ubiquinones into the respiratory chain. The diversion of the uncoupling proton gradient through adipocyte thermogenesis will then alleviate the damaging effects of free radicals to mitochondria and other organelles. The adaptive induction of white adipose tissues (WAT) to beige adipose tissues (beAT) has shown beneficial effects on glucose oxidation, ROS protection and mitochondrial function preservation through the uncoupling protein 1 (UCP1)-independent thermogenesis of beAT. However, the maladaptive stage can eventually initiate with the persistent unhealthy lifestyles. Under this metabolic gridlock, the low oxygen and pro-inflammatory environments promote the adipose breakdown with sequential metabolic dysregulation, including insulin resistance, systemic inflammation and clinical NCDs progression. It is unlikely that a single intervention can reverse all these complex interactions. A comprehensive protocol that includes dietary, nutritional and all modifiable lifestyle interventions, can be the preferable choice to decelerate, stop, or reverse the NCDs pathophysiologic processes.

Microvesicles released from pneumolysin-stimulated lung epithelial cells carry mitochondrial cargo and suppress neutrophil oxidative burst

Microvesicles (MVs) are cell-derived extracellular vesicles that have emerged as markers and mediators of acute lung injury (ALI). One of the most common pathogens in pneumonia-induced ALI is Streptococcus pneumoniae (Spn), but the role of MVs during Spn lung infection is largely unknown. In the first line of defense against Spn and its major virulence factor, pneumolysin (PLY), are the alveolar epithelial cells (AEC). In this study, we aim to characterize MVs shed from PLY-stimulated AEC and explore their contribution in mediating crosstalk with neutrophils. Using in vitro cell and ex vivo (human lung tissue) models, we demonstrated that Spn in a PLY-dependent manner stimulates AEC to release increased numbers of MVs. Spn infected mice also had higher levels of epithelial-derived MVs in their alveolar compartment compared to control. Furthermore, MVs released from PLY-stimulated AEC contain mitochondrial content and can be taken up by neutrophils. These MVs then suppress the ability of neutrophils to produce reactive oxygen species, a critical host-defense mechanism. Taken together, our results demonstrate that AEC in response to pneumococcal PLY release MVs that carry mitochondrial cargo and suggest that these MVs regulate innate immune responses during lung injury.

Elevated type I interferon responses potentiate metabolic dysfunction, inflammation, and accelerated aging in mtDNA mutator mice

Mitochondrial dysfunction is a key driver of inflammatory responses in human disease. However, it remains unclear whether alterations in mitochondria-innate immune cross-talk contribute to the pathobiology of mitochondrial disorders and aging. Using the polymerase gamma (POLG) mutator model of mitochondrial DNA instability, we report that aberrant activation of the type I interferon (IFN-I) innate immune axis potentiates immunometabolic dysfunction, reduces health span, and accelerates aging in mutator mice. Mechanistically, elevated IFN-I signaling suppresses activation of nuclear factor erythroid 2-related factor 2 (NRF2), which increases oxidative stress, enhances proinflammatory cytokine responses, and accelerates metabolic dysfunction. Ablation of IFN-I signaling attenuates hyperinflammatory phenotypes by restoring NRF2 activity and reducing aerobic glycolysis, which combine to lessen cardiovascular and myeloid dysfunction in aged mutator mice. These findings further advance our knowledge of how mitochondrial dysfunction shapes innate immune responses and provide a framework for understanding mitochondria-driven immunopathology in POLG-related disorders and aging.

Apoptotic caspases suppress Mycobacterium bovis-induced IFN-β production in murine macrophage

Caspases are classified as inflammatory or apoptotic category. Inflammatory caspases participate in inflammasome activation, while apoptotic caspases mediate apoptotic activation. Previous studies have shown that apoptotic caspases prevent the production of IFN-β during apoptosis or virus infection. However, the relationship between apoptotic caspases and IFN-β production during intracellular bacterial infection is still unclear. Here, we investigated the role of apoptotic caspases in IFN-β production induced by Mycobacterium bovis (M. bovis) infection. M. bovis is an intracellular bacterium and belongs to the Mycobacterium tuberculosis complex. M. bovis infection can cause tuberculosis in animals and human beings. In the current study, we found that M. bovis infection triggered mitochondrial stress, which caused the leakage of cytochrome c into the cytoplasm, and in turn, activated the downstream caspase-9 and-3. Furthermore, our results showed that activation of apoptotic caspases reduced IFN-β production during M. bovis infection and vice versa. Confocal microscopy analysis revealed that apoptotic caspases prevented IFN-β production by decreasing p-IRF3 nuclear translocation. Our findings demonstrate that apoptotic caspases negatively regulate the production of IFN-β induced by an intracellular bacterial infection.

Neuroinflammatory Mechanisms of Mitochondrial Dysfunction and Neurodegeneration in Glaucoma

The exact mechanism of retinal ganglion cell loss in the pathogenesis of glaucoma is yet to be understood. Mitochondrial damage-associated molecular patterns (DAMPs) resulting from mitochondrial dysfunction have been linked to Leber's hereditary optic neuropathy and autosomal dominant optic atrophy, as well as to brain neurodegenerative diseases. Recent evidence shows that, in conditions where mitochondria are damaged, a sustained inflammatory response and downstream pathological inflammation may ensue. Mitochondrial damage has been linked to the accumulation of age-related mitochondrial DNA mutations and mitochondrial dysfunction, possibly through aberrant reactive oxygen species production and defective mitophagy. The present review focuses on how mitochondrial dysfunction may overwhelm the ability of neurons and glial cells to adequately maintain homeostasis and how mitochondria-derived DAMPs trigger the immune system and induce neurodegeneration.

Assessing the Association of Mitochondrial Function and Inflammasome Activation in Murine Macrophages Exposed to Select Mitotoxic Tri-Organotin Compounds

BACKGROUND

Mitochondrial function is implicated as a target of environmental toxicants and found in disease or injury models, contributing to acute and chronic inflammation. One mechanism by which mitochondrial damage can propagate inflammation is via activation of the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family, pyrin domain-containing receptor (NLRP)3 inflammasome, a protein complex that processes mature interleukin (IL)-1β. IL-1β plays an important role in the innate immune response and dysregulation is associated with autoinflammatory disorders.

OBJECTIVE

The objective was to evaluate whether mitochondrial toxicants recruit inflammasome activation and IL-1β processing.

METHOD

Murine macrophages (RAW 264.7) exposed to tri-organotins (triethyltin bromide (TETBr), trimethyltin hydroxide (TMTOH), triphenyltin hydroxide (TPTOH), bis(tributyltin)oxide) [Bis(TBT)Ox] were examined for pro-inflammatory cytokine induction. TMTOH and TETBr were examined in RAW 264.7 and bone marrow-derived macrophages for mitochondrial bioenergetics, reactive oxygen species (ROS) production, and inflammasome activation via visualization of aggregate formation, caspase-1 flow cytometry, IL-1β enzyme-linked immunosorbent assay and Western blots, and microRNA (miRNA) and mRNA arrays.

RESULTS

TETBr and TMTOH induced inflammasome aggregate formation and IL-1β release in lipopolysaccharide (LPS)-primed macrophages. Mitochondrial bioenergetics and mitochondrial ROS were suppressed. Il1a and Il1b induction with LPS or LPS+ATP challenge was diminished. Differential miRNA and mRNA profiles were observed. Lower miR-151-3p targeted cyclic adenosine monophosphate (cAMP)-mediated and AMP-activated protein kinase signaling pathways; higher miR-6909-5p, miR-7044-5p, and miR-7686-5p targeted Wnt beta-catenin signaling, retinoic acid receptor activation, apoptosis, signal transducer and activator of transcription 3, IL-22, IL-12, and IL-10 signaling. Functional enrichment analysis identified apoptosis and cell survival canonical pathways.

CONCLUSION

Select mitotoxic tri-organotins disrupted murine macrophage transcriptional response to LPS, yet triggered inflammasome activation. The differential response pattern suggested unique functional changes in the inflammatory response that may translate to suppressed host defense or prolong inflammation. We posit a framework to examine immune cell effects of environmental mitotoxic compounds for adverse health outcomes. https://doi.org/10.1289/EHP8314.

Early oral protein-containing diets following elective lower gastrointestinal tract surgery in adults: a meta-analysis of randomized clinical trials

Background

Although current guidelines make consensus recommendations for the early resumption of oral intake after surgery, a recent comprehensive meta-analysis failed to identify any patient-centered benefits. We hypothesized this finding was attributable to pooling studies providing effective protein-containing diets with ineffective non-protein liquid diets. Therefore, the aim of this paper was to investigate the safety and efficacy of early oral protein-containing diets versus later (traditional) feeding after elective lower gastrointestinal tract surgery in adults.

Methods

PubMed, Embase, and the China National Knowledge Infrastructure databases were searched from inception until 1 August 2019. Reference lists of retrieved studies were hand searched to identify randomized clinical trials reporting mortality. No language restrictions were applied. Study selection, risk of bias appraisal and data abstraction were undertaken independently by two authors. Disagreements were settled by obtaining an opinion of a third author. Majority decisions prevailed. After assessment of underlying assumptions, a fixed-effects method was used for analysis. The primary outcome was mortality. Secondary outcomes included surgical site infections, postoperative nausea and vomiting, serious postoperative complications and other key measures of safety and efficacy.

Results

Eight randomized clinical trials recruiting 657 patients were included. Compared with later (traditional) feeding, commencing an early oral protein-containing diet resulted in a statistically significant reduction in mortality (odds ratio [OR] 0.31, P = 0.02, I² = 0%). An early oral protein-containing diet also significantly reduced surgical site infections (OR 0.39, P = 0.002, I² = 32%), postoperative nausea and vomiting (OR 0.62, P = 0.04, I² = 37%), serious postoperative complications (OR 0.60, P = 0.01, I² = 25%), and significantly improved other major outcomes. No harms attributable to an early oral protein-containing diet were identified.

Conclusions

The results of this systematic review can be used to upgrade current guideline statements to a grade A recommendation supporting an oral protein-containing diet commenced before the end of postoperative day 1 after elective lower gastrointestinal surgery in adults.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13741-021-00179-3.

Mitochondria: Powering the Innate Immune Response to Mycobacterium tuberculosis Infection

Within the last decade, we have learned that damaged mitochondria activate many of the same innate immune pathways that evolved to sense and respond to intracellular pathogens. These shared responses include cytosolic nucleic acid sensing and type I interferon (IFN) expression, inflammasome activation that leads to pyroptosis, and selective autophagy (called mitophagy when mitochondria are the cargo). Because mitochondria were once bacteria, parallels between how cells respond to mitochondrial and bacterial ligands are not altogether surprising. However, the potential for cross talk or synergy between bacterium- and mitochondrion-driven innate immune responses during infection remains poorly understood. This interplay is particularly striking, and intriguing, in the context of infection with the intracellular bacterial pathogen Mycobacterium tuberculosis (Mtb). Multiple studies point to a role for Mtb infection and/or specific Mtb virulence factors in disrupting the mitochondrial network in macrophages, leading to metabolic changes and triggering potent innate immune responses. Research from our laboratories and others argues that mutations in mitochondrial genes can exacerbate mycobacterial disease severity by hyperactivating innate responses or activating them at the wrong time. Indeed, growing evidence supports a model whereby different mitochondrial defects or mutations alter Mtb infection outcomes in distinct ways. By synthesizing the current literature in this minireview, we hope to gain insight into the molecular mechanisms driving, and consequences of, mitochondrion-dependent immune polarization so that we might better predict tuberculosis patient outcomes and develop host-directed therapeutics designed to correct these imbalances.

Inflammation-Related Changes in Mood Disorders and the Immunomodulatory Role of Lithium

Mood disorders are chronic, recurrent diseases characterized by changes in mood and emotions. The most common are major depressive disorder (MDD) and bipolar disorder (BD). Molecular biology studies have indicated an involvement of the immune system in the pathogenesis of mood disorders, and showed their correlation with altered levels of inflammatory markers and energy metabolism. Previous reports, including meta-analyses, also suggested the role of microglia activation in the M1 polarized macrophages, reflecting the pro-inflammatory phenotype. Lithium is an effective mood stabilizer used to treat both manic and depressive episodes in bipolar disorder, and as an augmentation of the antidepressant treatment of depression with a multidimensional mode of action. This review aims to summarize the molecular studies regarding inflammation, microglia activation and energy metabolism changes in mood disorders. We also aimed to outline the impact of lithium on these changes and discuss its immunomodulatory effect in mood disorders.

Garciesculenxanthone B induces PINK1-Parkin-mediated mitophagy and prevents ischemia-reperfusion brain injury in mice

Mitophagy is a selective form of autophagy involving the removal of damaged mitochondria via the autophagy-lysosome pathway. PINK1-Parkin-mediated mitophagy is one of the most important mechanisms in cardiovascular disease, cerebral ischemia-reperfusion (I/R) injury, and neurodegenerative diseases. In this study we conducted an image-based screening in YFP-Parkin HeLa cells to discover new mitophagy regulators from natural xanthone compounds. We found that garciesculenxanthone B (GeB), a new xanthone compound from Garcinia esculenta, induced the formation of YFP-Parkin puncta, a well known mitophagy marker. Furthermore, treatment with GeB dose-dependently promoted the degradation of mitochondrial proteins Tom20, Tim23, and MFN1 in YFP-Parkin HeLa cells and SH-SY5Y cells. We revealed that GeB stabilized PINK1 and triggered Parkin translocation to the impaired mitochondria to induce mitophagy, and these effects were abolished by knockdown of PINK1. Finally, in vivo experiments demonstrated that GeB partially rescued ischemia-reperfusion-induced brain injury in mice. Taken together, our findings demonstrate that the natural compound GeB can promote the PINK1-Parkin-mediated mitophagy pathway, which may be implicated in protection against I/R brain injury.

Impaired Mitochondrial Mobility in Charcot-Marie-Tooth Disease

Charcot-Marie-Tooth (CMT) disease is a progressive, peripheral neuropathy and the most commonly inherited neurological disorder. Clinical manifestations of CMT mutations are typically limited to peripheral neurons, the longest cells in the body. Currently, mutations in at least 80 different genes are associated with CMT and new mutations are regularly being discovered. A large portion of the proteins mutated in axonal CMT have documented roles in mitochondrial mobility, suggesting that organelle trafficking defects may be a common underlying disease mechanism. This review will focus on the potential role of altered mitochondrial mobility in the pathogenesis of axonal CMT, highlighting the conceptional challenges and potential experimental and therapeutic opportunities presented by this "impaired mobility" model of the disease.

Novel Short-Chain Quinones to Treat Vision Loss in a Rat Model of Diabetic Retinopathy

Diabetic retinopathy (DR), one of the leading causes of blindness, is mainly diagnosed based on the vascular pathology of the disease. Current treatment options largely focus on this aspect with mostly insufficient therapeutic long-term efficacy. Mounting evidence implicates mitochondrial dysfunction and oxidative stress in the central etiology of DR. Consequently, drug candidates that aim at normalizing mitochondrial function could be an attractive therapeutic approach. This study compared the mitoprotective compounds, idebenone and elamipretide, side-by-side against two novel short-chain quinones (SCQs) in a rat model of DR. The model effectively mimicked type 2 diabetes over 21 weeks. During this period, visual acuity was monitored by measuring optokinetic response (OKR). Vision loss occurred 5–8 weeks after the onset of hyperglycemia. After 10 weeks of hyperglycemia, visual function was reduced by 65%. From this point, the right eyes of the animals were topically treated once daily with the test compounds. The left, untreated eye served as an internal control. Only three weeks of topical treatment significantly restored vision from 35% to 58–80%, while visual acuity of the non-treated eyes continued to deteriorate. Interestingly, the two novel SCQs restored visual acuity better than idebenone or elamipretide. This was also reflected by protection of retinal pathology against oxidative damage, retinal ganglion cell loss, reactive gliosis, vascular leakage, and retinal thinning. Overall, mitoprotective and, in particular, SCQ-based compounds have the potential to be developed into effective and fast-acting drug candidates against DR.

The mitochondrial protein ERAL1 suppresses RNA virus infection by facilitating RIG-I-like receptor signaling

Mitochondria not only serve as a platform for innate immune signaling transduction but also enhance immune responses by releasing mitochondrial DNA and RNA into the cytoplasm. However, whether mitochondrial matrix proteins could be liberated and involved in immune responses remains enigmatic. Here, we identify the mitochondrial protein ERA G-protein-like 1 (ERAL1) as a mitochondrial antiviral signaling protein (MAVS)-interacting protein by using proximity-based labeling technology. ERAL1 deficiency markedly reduces the downstream antiviral signaling triggered by RNA viruses. Moreover, ERAL1-deficient mice are more susceptible to lethality following RNA virus infection than wild-type mice. After virus infection, ERAL1 is released from mitochondria through the BAX/BAK pore. The cytosolic ERAL1 facilitates lysine 63 (K63)-linked ubiquitination of retinoicacid inducible gene-1 (RIG-I)/melanoma differentiation-associated gene 5 (MDA5) and promotes downstream MAVS polymerization, thus positively regulating antiviral responses.

Tricarboxylic Acid (TCA) Cycle Intermediates: Regulators of Immune Responses

The tricarboxylic acid cycle (TCA) is a series of chemical reactions used in aerobic organisms to generate energy via the oxidation of acetylcoenzyme A (CoA) derived from carbohydrates, fatty acids and proteins. In the eukaryotic system, the TCA cycle occurs completely in mitochondria, while the intermediates of the TCA cycle are retained inside mitochondria due to their polarity and hydrophilicity. Under cell stress conditions, mitochondria can become disrupted and release their contents, which act as danger signals in the cytosol. Of note, the TCA cycle intermediates may also leak from dysfunctioning mitochondria and regulate cellular processes. Increasing evidence shows that the metabolites of the TCA cycle are substantially involved in the regulation of immune responses. In this review, we aimed to provide a comprehensive systematic overview of the molecular mechanisms of each TCA cycle intermediate that may play key roles in regulating cellular immunity in cell stress and discuss its implication for immune activation and suppression.

Mitochondrion: a sensitive target for Pb exposure

Pb exposure is a worldwide environmental contamination issue which has been of concern to more and more people. Exposure to environmental Pb and its compounds through food and respiratory routes causes toxic damage to the digestive, respiratory, cardiovascular and nervous systems, etc. Children and pregnant women are particularly vulnerable to Pb. Pb exposure significantly destroys children's learning ability, intelligence and perception ability. Mitochondria are involved in various life processes of eukaryotes and are one of the most sensitive organelles to various injuries. There is no doubt that Pb-induced mitochondrial damage can widely affect various physiological processes and cause great harm. In this review, we summarized the toxic effects of Pb on mitochondria which led to various pathological processes. Pb induces mitochondrial dysfunction leading to the increased level of oxidative stress. In addition, Pb leads to cell apoptosis via mitochondrial permeability transition pore (MPTP) opening. Also, Pb can stimulate the development of mitochondria-mediated inflammatory responses. Furthermore, Pb triggers the germination of autophagy via the mitochondrial pathway and induces mitochondrial dysfunction, disturbing intracellular calcium homeostasis. In a word, we discussed the effects of Pb exposure on mitochondria, hoping to provide some references for further research and better therapeutic options for Pb exposure.

In vitro cytotoxicity study of superparamagnetic iron oxide and silica nanoparticles on pneumocyte organelles

Inhalation is the main route of nanoparticles (NP) exposure during manufacturing. Although many mechanisms of toxicity have been described, the interaction of NP with relevant pneumocytes organelles is not widely understood. Considering that the physicochemical properties of NP influence their toxicological responses, the objective of this study was to evaluate whether exposure to different NP, crystalline Fe₃O₄ NP and amorphous SiO₂ NP could alter pneumocytes organelles in alveolar epithelial cells. To achieve this goal, cell viability, ultrastructural changes, lysosomal damage, mitochondrial membrane potential (MMP), lipid droplets (LD) formation and cytokines production were evaluated by MTT, electron microscopy, lysotracker red staining, JC-1, Oil Red staining and Milliplex® assay respectively. Both NP were observed within lamellar bodies (LB), lysosomes, and cytoplasm causing morphological changes. Exposure to SiO₂ NP at 6 h induced lysosomal activation, but not Fe₃O₄ NP. MMP decreased and LD increased at the highest concentrations after both NP exposure. Pro-inflammatory cytokines were released only after SiO₂ NP exposure at 48 h. These results indicate that SiO₂ NP have a greater impact than Fe₃O₄ NP on organelles responsible for energy, secretion, degradation and metabolism in pneumocytes leading to the development of respiratory disorders or the exacerbation of preexisting conditions. Therefore, the established biocompatibility for amorphous NP has to be reconsidered.