Assessing mitochondrial dysfunction in cells

Determinants of increased muscle insulin sensitivity of exercise-trained versus sedentary normal weight and overweight individuals

The athlete's paradox states that intramyocellular triglyceride accumulation associates with insulin resistance in sedentary but not in endurance-trained humans. Underlying mechanisms and the role of muscle lipid distribution and composition on glucose metabolism remain unclear. We compared highly trained athletes (ATHL) with sedentary normal weight (LEAN) and overweight-to-obese (OVWE) male and female individuals. This observational study found that ATHL show higher insulin sensitivity, muscle mitochondrial content, and capacity, but lower activation of novel protein kinase C (nPKC) isoforms, despite higher diacylglycerol concentrations. Notably, sedentary but insulin sensitive OVWE feature lower plasma membrane-to-mitochondria sn-1,2-diacylglycerol ratios. In ATHL, calpain-2, which cleaves nPKC, negatively associates with PKCε activation and positively with insulin sensitivity along with higher GLUT4 and hexokinase II content. These findings contribute to explaining the athletes' paradox by demonstrating lower nPKC activation, increased calpain, and mitochondrial partitioning of bioactive diacylglycerols, the latter further identifying an obesity subtype with increased insulin sensitivity (NCT03314714).

Altered mitochondria-associated ER membrane (MAM) function shifts mitochondrial metabolism in amyotrophic lateral sclerosis (ALS)

Mitochondrial function is modulated by its interaction with the endoplasmic reticulum (ER). Recent research indicates that these contacts are disrupted in familial models of amyotrophic lateral sclerosis (ALS). We report here that this impairment in the crosstalk between mitochondria and the ER impedes the use of glucose-derived pyruvate as mitochondrial fuel, causing a shift to fatty acids to sustain energy production. Over time, this deficiency alters mitochondrial electron flow and the active/dormant status of complex I in spinal cord tissues, but not in the brain. These findings suggest mitochondria-associated ER membranes (MAM domains) play a crucial role in regulating cellular glucose metabolism and that MAM dysfunction may underlie the bioenergetic deficits observed in ALS.

New molecular mechanisms to explain the neuroprotective effects of insulin-like growth factor II in a cellular model of Parkinson's disease

INTRODUCTION

One of the hallmarks of Parkinsońs Disease (PD) is oxidative distress, leading to mitochondrial dysfunction and neurodegeneration. Insulin-like growth factor II (IGF-II) has been proven to have antioxidant and neuroprotective effects in some neurodegenerative diseases, including PD. Consequently, there isgrowing interest in understanding the different mechanisms involved in the neuroprotective effect of this hormone.

OBJECTIVES

To clarify the mechanism of action of IGF-II involved in the protective effect of this hormone.

METHODS

The present study was carried out on a cellular model PD based on the incubation of dopaminergic cells (SN4741) in a culture with the toxic 1-methyl-4-phenylpyridinium (MPP+), in the presence of IGF-II. This model undertakes proteomic analyses in order to understand which molecular cell pathways might be involved in the neuroprotective effect of IGF-II. The most important proteins found in the proteomic study were tested by Western blot, colorimetric enzymatic activity assay and immunocytochemistry. Along with the proteomic study, mitochondrial morphology and function were also studied by transmission electron microscopy and oxygen consumption rate. The cell cycle was also analysed using 7AAd/BrdU staining, and flow cytometry.

RESULTS

The results obtained indicate that MPP+, MPP++IGF-II treatment and IGF-II, when compared to control, modified the expression of 197, 246 proteins and 207 respectively. Some of these proteins were found to be involved in mitochondrial structure and function, and cell cycle regulation. Including IGF-II in the incubation medium prevents the cell damage induced by MPP+, recovering mitochondrial function and cell cycle dysregulation, and thereby decreasing apoptosis.

CONCLUSION

IGF-II improves mitochondrial dynamics by promoting the association of Mitofilin with mitochondria, regaining function and redox homeostasis. It also rebalances the cell cycle, reducing the amount of apoptosis and cell death by the regulation of transcription factors, such as Checkpoint kinase 1.

High-Resolution Respirometry Methodology for Bioenergetic and Metabolic Studies in Intact Brain Slices

The brain is critically dependent on energetic substrates as it consumes circa 20% of glucose and oxygen under normal physiological conditions. Although different cell types and at different locations might experience particular specificities in the utilization of these substrates, overall, mitochondrial oxidative phosphorylation supports the most efficient energy transduction process, enabling the complete oxidation of glucose to CO2 coupled to ATP synthesis in the presence of O2. Impairment of mitochondrial bioenergetics has been identified as an early event in many brain diseases and aging. Thus, novel methodologies to readily assess mitochondrial respiration in brain tissue, while preserving cellular and mitochondrial architecture and overcoming the serious drawbacks of studies using isolated mitochondrial preparations, are needed. Here we describe a methodology for studying functional parameters defining tissue metabolic respiration in brain hippocampal slices. The methodology can be used for physiological, pharmacological, and toxicological studies.

Mitochondria at the crossroad of dysregulated inflammatory and metabolic processes in bipolar disorders

In last few decades, considerable evidence has emphasized the significant involvement of mitochondria, often referred to as the "powerhouse of the cell," in the pathophysiology of bipolar disorder (BD). Given crucial mitochondrial functions in cellular metabolism and inflammation, both of which are compromised in BD, this perspective review examines the central role of mitochondria in inflammation and metabolism within the context of this disorder. We first describe the significance of mitochondria in metabolism before presenting the dysregulated inflammatory and metabolic processes. Then, we present a synthetic and hypothetical model of the importance of mitochondria in those dysfunctional pathways. The article also reviews different techniques for assessing mitochondrial function and discuss diagnostic and therapeutic implications. This review aims to improve the understanding of the inflammatory and metabolic comorbidities associated with bipolar disorders along with mitochondrial alterations within this context.

From Ca2+ dysregulation to heart failure: β-adrenoceptor activation by RKIP postpones molecular damages and subsequent cardiac dysfunction in mice carrying mutant PLNR9C by correction of aberrant Ca2+-handling

Impaired cardiomyocyte Ca2+ handling is a central hallmark of heart failure (HF), which causes contractile dysfunction and arrhythmias. However, the underlying molecular mechanisms and the precise contribution of defects in Ca2+-cycling regulation in the development of HF are still not completely resolved. Here, we used transgenic mice that express a human mutation in the cardiomyocyte Ca2+-regulator phospholamban (PLNR9C-tg) causing severe HF due to a reduction in Ca2+ reuptake into the sarco(endo)plasmic reticulum (SR). PLNR9C-induced HF is a rapidly progressing condition characterized by prominent Ca2+ cycling and relaxation defects and premature death of mutation carriers. We found that endoplasmic reticulum (ER) and mitochondrial function are affected even before transition to overt HF. Early correction of aberrant Ca2+ cycling by cardiac expression of the Raf kinase inhibitor protein (RKIP), an endogenous activator of β-adrenoceptors (βAR), delayed the cellular alterations, functional failure and prolonged lifespan. Our study highlights the importance of early and persistent correction of Ca2+ dynamics, not only for excitation/contraction coupling, but also for the prevention of rather irreparable events on cardiac energetics and ER stress adaptations. The latter may even impede with later onset of Ca2+-related therapeutic interventions and should gain more focus for HF treatment.

The role of mitochondrial DNA variants and dysfunction in the pathogenesis and progression of multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system (CNS). The etiology of MS remains elusive, with a complex interplay of genetic and environmental factors contributing to its pathogenesis. Recent studies showed mitochondrial DNA (mtDNA) as a potential player in the development and progression of MS. These studies encompassed mtDNA variants, copy number variations, and haplogroups. This narrative review aims to synthesize the current understanding of the role of mtDNA's in MS. The findings of this review suggest that mtDNA may indeed play a role in the development and progression of MS. Several studies have reported an association between mtDNA variants and increased susceptibility to MS, while others have found a link between mtDNA copy number variations and disease severity. Furthermore, specific mtDNA haplogroups have been demonstrated to confer protection against MS. MtDNA alterations may make neurons and oligodendrocytes more susceptible to inflammatory and oxidative stress, causing demyelination and axonal degeneration in MS patients. In conclusion, this review underscores the potential significance of mtDNA in the pathogenesis of MS and highlights the need for further research to fully elucidate its role. A deeper understanding of mtDNA's involvement in MS may pave the way for the development of novel therapeutic strategies to combat this debilitating disease.

Labeling and isolating cell specific neuronal mitochondria and their functional analysis in mice post stroke

Dendritic and axonal plasticity, which mediates neurobiological recovery after a stroke, critically depends on the mitochondrial function of neurons. To investigate, in vivo, neuronal mitochondrial function at the stroke recovery stage, we employed Mito-tag mice combined with cerebral cortical infection of AAV9 produced from plasmids carrying Cre-recombinase controlled by two neuronal promoters, synapsin-I (SYN1) and calmodulin-kinase IIa to induce expression of a hemagglutinin (HA)-tagged enhanced green fluorescence protein (EGFP) that localizes to mitochondrial outer membranes of SYN1 positive (SYN+) and CaMKIIa positive (CaMKIIa+) neurons. These mice were then subjected to permanent middle cerebral artery occlusion (MCAO) and sacrificed 14 days post stroke. Neuronal mitochondria were then selectively isolated from the fresh brain tissues excised from the ischemic core (IC), ischemic boundary zone (IBZ), as well as from the homologous contralateral hemisphere (CON) by anti-HA magnetic beads for functional analyses. We found that the bead pulled neuronal specific mitochondria were co-precipitated with GFP and enriched with mitochondrial markers, e.g. voltage-dependent anion channel, cytochrome C, and COX IV, but lacked the Golgi protein RCAS1 as well as endoplasmic reticulum markers: Heme‑oxygenase 1 and Calnexin, indicating that specific neuronal mitochondria have been selectively isolated. Western-blot data showed that oxidative phosphorylation (OXPHOS) components in SYN+ and CAMKII+ neuronal mitochondria were significantly decreased in the IBZ and further decreased in the IC compared to the contralateral tissue, which was associated with the significant reductions of mitochondrial function indicated by oxygen consumption rate (OCR) (p < 0.05, respectively, for both neuron types). These data suggest dysfunction of neuronal mitochondria post stroke is present during the stroke recovery stage. Collectively, for the first time, we demonstrated that using a Mito-tag mouse line combined with AAV9 carrying Cre recombinase approach, neuronal specific mitochondria can be efficiently isolated from the mouse brain to investigate their functional changes post stroke.

Dysregulation of mitochondria, apoptosis and mitophagy in Leber's hereditary optic neuropathy with MT-ND1 3635G>A mutation

Leber's hereditary optic neuropathy (LHON) is a maternal inherited disorder, primarily due to mitochondrial DNA (mtDNA) mutations. This investigation aimed to assess the pathogenicity of m.3635G>A alteration known to confer susceptibility to LHON. The disruption of electrostatic interactions among S110 of the MT-ND1 and the side chain of E4, along with the carbonyl backbone of M1 in the NDUFA1, was observed in complex I of cybrids with m.3635G>A. This disturbance affected the complex I assembly activity by changing the mitochondrial respiratory chain composition and function. In addition, the affected cybrids exhibited notable deficiencies in complex I activities, including impaired mitochondrial respiration and depolarization of its membrane potential. Apoptosis was also stimulated in the mutant group, as witnessed by the secretion of cytochrome c and activation of PARP, caspase 3, 7, and 9 compared to the control. Furthermore, the mutant group exhibited decreased levels of autophagy protein light chain 3, accumulation of autophagic substrate P62, and impaired PINK1/Parkin-dependent mitophagy. Overall, the current study has confirmed the crucial involvement of the alteration of the m.3635G>A gene in the development of LHON. These findings contribute to a deeper comprehension of the pathophysiological mechanisms underlying LHON, providing a fundamental basis for further research.

A Comparison of the Mitochondrial Performance between Migratory and Sedentary Mimid Thrushes

Birds exhibit a variety of migration strategies. Because sustained flapping flight requires the production of elevated levels of energy compared to typical daily activities, migratory birds are well-documented to have several physiological adaptations to support the energy demands of migration. However, even though mitochondria are the source of ATP that powers flight, the respiratory performance of the mitochondria is almost unstudied in the context of migration. We hypothesized that migratory species would have higher mitochondrial respiratory performance during migration compared to species that do not migrate. To test this hypothesis, we compared variables related to mitochondrial respiratory function between two confamilial bird species-the migratory Gray Catbird (Dumetella carolinensis) and the non-migratory Northern Mockingbird (Mimus polyglottos). Birds were captured at the same location along the Alabama Gulf Coast, where we assumed that Gray Catbirds were migrants and where resident Northern Mockingbirds live year-round. We found a trend in citrate synthase activity, which suggests that Gray Catbirds have a greater mitochondrial volume in their pectoralis muscle, but we observed no other differences in mitochondrial respiration or complex enzymatic activities between individuals from the migrant vs. the non-migrant species. However, when we assessed the catbirds included in our study using well-established indicators of migratory physiology, birds fell into two groups: a group with physiological parameters indicating a physiology of birds engaged in migration and a group with the physiology of birds not migrating. Thus, our comparison included catbirds that appeared to be outside of migratory condition. When we compared the mitochondrial performance of these three groups, we found that the mitochondrial respiratory capacity of migrating catbirds was very similar to that of Northern Mockingbirds, while the catbirds judged to be not migrating were lowest. One explanation for these observations is these species display very different daily flight behaviors. While the mockingbirds we sampled were not breeding nor migrating, they are highly active birds, living in the open and engaging in flapping flights throughout each day. In contrast, Gray Catbirds live in shrubs and fly infrequently when not migrating. Such differences in baseline energy needs likely confounded our attempt to study adaptations to migration.

Mechanisms that Alter Capacity for Adenosine Triphosphate Production and Oxidative Phosphorylation: Insights from Avian Migration

Avian migration is among the most energetically demanding feats observed in animals. Studies evaluating the physiological underpinnings of migration have repeatedly shown that migratory birds display numerous adaptations that ultimately supply the flight muscle mitochondria with abundant fuel and oxygen during long-distance flights. To make use of this high input, the organs and mitochondria of migrants are predicted to display several traits that maximize their capacity to produce adenosine triphosphate (ATP). This review aims to introduce readers to several mechanisms by which organs and mitochondria can alter their capacity for oxidative phosphorylation and ATP production. The role of organ size, mitochondrial volume, substrate, and oxygen delivery to the electron transport system are discussed. A central theme of this review is the role of changes in electron chain complex activity, mitochondrial morphology and dynamics, and supercomplexes in allowing avian migrants and other taxa to alter the performance of the electron transport system with predictable shifts in demand. It is my hope that this review will serve as a springboard for future studies exploring the mechanisms that alter bioenergetic capacity across animal species.

Chronic undernutrition impairs renal mitochondrial respiration accompanied by intense ultrastructural damage in juvenile rats

This study investigated whether chronic undernutrition alters the mitochondrial structure and function in renal proximal tubule cells, thus impairing fluid transport and homeostasis. We previously showed that chronic undernutrition downregulates the renal proximal tubules (Na++K+)ATPase, the main molecular machine responsible for fluid transport and ATP consumption. Male rats received a multifactorial deficient diet, the so-called Regional Basic Diet (RBD), mimicking those used in impoverished regions worldwide, from weaning to a juvenile age (3 months). The diet has a low content (8 %) of poor-quality proteins, low lipids, and no vitamins compared to control (CTR). We investigated citrate synthase activity, mitochondrial respiration (oxygraphy) in phosphorylating and non-phosphorylating conditions with different substrates/inhibitors, potential across the internal membrane (Δψ), and anion superoxide/H2O2 formation. The data were correlated with ultrastructural alterations evaluated using transmission electron microscopy (TEM) and focused ion beam scanning electron microscopy (FIB-SEM). Citrate synthase activity decreased (∼50 %) in RBD rats, accompanied by a similar reduction in respiration in non-phosphorylating conditions, maximum respiratory capacity, and ATP synthesis. The Δψ generation and its dissipation after carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone remained unmodified in the survival mitochondria. H2O2 production increased (∼100 %) after Complex II energization. TEM demonstrated intense matrix vacuolization and disruption of cristae junctions in a subpopulation of RBD mitochondria, which was also demonstrated in the 3D analysis of FIB-SEM tomography. In conclusion, chronic undernutrition impairs mitochondrial functions in renal proximal tubules, with profound alterations in the matrix and internal membrane ultrastructure that culminate with the compromise of ATP supply for transport processes.

A Mitochondrial Perspective on the Demands of Reproduction

The cost of supporting traits that increase mating opportunities and maximize the production of quality offspring is paid in energy. This currency of reproduction is enabled by bioenergetic adaptations that underlie the flexible changes in energy utilization that occur with reproduction. This review considers the traits that contribute to variation in the capacity of an organ to produce ATP. Further, it synthesizes findings from studies that have evaluated bioenergetic adaptations to the production of sexually selected traits and performance during reproduction and the role of change in mitochondrial respiratory performance in the tradeoff between reproduction and longevity. Cumulatively, these works provide evidence that in selecting for redder males, female finches will likely mate with a male with high mitochondrial respiratory performance and, potentially, a higher probability of mitonuclear compatibility. Females from diverse taxa allocate more to reproduction when the respiratory performance of mitochondria or density of the inner mitochondrial membrane in the liver or skeletal muscle is higher. Finally, reproduction does not appear to have persistent negative effects on mitochondrial respiratory performance, countering a role for mitochondria in the trade-off between reproduction and longevity. I close by noting that adaptations that improve mitochondrial respiratory performance appear vital for optimizing reproductive fitness.

How and when to measure mitochondrial inner membrane potentials

The scientific literature on mitochondria has increased significantly over the years due to findings that these organelles have widespread roles in the onset and progression of pathological conditions such as metabolic disorders, neurodegenerative and cardiovascular diseases, inflammation, and cancer. Researchers have extensively explored how mitochondrial properties and functions are modified in different models, often using fluorescent inner mitochondrial membrane potential (ΔΨm) probes to assess functional mitochondrial aspects such as protonmotive force and oxidative phosphorylation. This review provides an overview of existing techniques to measure ΔpH and ΔΨm, highlighting their advantages, limitations, and applications. It discusses drawbacks of ΔΨm probes, especially when used without calibration, and conditions where alternative methods should replace ΔΨm measurements for the benefit of the specific scientific objectives entailed. Studies investigating mitochondria and their vast biological roles would be significantly advanced by the understanding of the correct applications as well as limitations of protonmotive force measurements and use of fluorescent ΔΨm probes, adopting more precise, artifact-free, sensitive, and quantitative measurements of mitochondrial functionality.

Muscarinic acetylcholine type 1 receptor antagonism activates TRPM3 to augment mitochondrial function and drive axonal repair in adult sensory neurons

OBJECTIVE

Antagonism of the muscarinic acetylcholine type 1 receptor (M1R) promotes sensory axon repair and is protective in peripheral neuropathy, however, the mechanism remains elusive. We investigated the role of the heat-sensing transient receptor potential melastatin-3 (TRPM3) cation channel in M1R antagonism-mediated nerve regeneration and explored the potential of TRPM3 activation to facilitate axonal plasticity.

METHODS

Dorsal root ganglion (DRG) neurons from adult control or diabetic rats were cultured and treated with TRPM3 agonists (CIM0216, pregnenolone sulfate) and M1R antagonists pirenzepine (PZ) or muscarinic toxin 7 (MT7). Ca2+ transients, mitochondrial respiration, AMP-activated protein kinase (AMPK) expression, and mitochondrial inner membrane potential were analyzed. The effect of M1R activation or blockade on TRPM3 activity mediated by phosphatidylinositol 4,5-bisphosphate (PIP2) was studied. Metabolic profiling of DRG neurons and human neuroblastoma SH-SY5Y cells was conducted.

RESULTS

M1R antagonism induced by PZ or MT7 increased Ca2+ influx in DRG neurons and was inhibited by TRPM3 antagonists or in the absence of extracellular Ca2+. TRPM3 agonists elevated Ca2+ levels, augmented mitochondrial respiration, AMPK activation and neurite outgrowth. M1R antagonism stimulated TRPM3 channel activity through inhibition of PIP2 hydrolysis to activate Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ)/AMPK, leading to augmented mitochondrial function and neuronal metabolism. DRG neurons with AAV-mediated shRNA knockdown of TRPM3 exhibited suppressed antimuscarinic drug-induced neurite outgrowth. TRPM3 agonists increased glycolysis and TCA cycle metabolites, indicating enhanced metabolism in DRG neurons and SH-SY5Y cells.

CONCLUSIONS

Activation of the TRPM3/CaMKKβ/AMPK pathway promoted collateral sprouting of sensory axons, positioning TRPM3 as a promising therapeutic target for peripheral neuropathy.

From eggs to adulthood: sustained effects of early developmental temperature and corticosterone exposure on physiology and body size in an Australian lizard

Developing animals are increasingly exposed to elevated temperatures as global temperatures rise as a result of climate change. Vertebrates can be affected by elevated temperatures during development directly, and indirectly through maternal effects (e.g. exposure to prenatal glucocorticoid hormones). Past studies have examined how elevated temperatures and glucocorticoid exposure during development independently affect vertebrates. However, exposure to elevated temperatures and prenatal corticosterone could have interactive effects on developing animals that affect physiology and life-history traits across life. We tested interactions between incubation temperature and prenatal corticosterone exposure in the delicate skink (Lampropholis delicata). We treated eggs with high or low doses of corticosterone and incubated eggs at 23°C (cool) or 28°C (warm). We measured the effects of these treatments on development time, body size and survival from hatching to adulthood and on adult hormone levels and mitochondrial respiration. We found no evidence for interactive effects of incubation temperature and prenatal corticosterone exposure on phenotype. However, incubation temperature and corticosterone treatment each independently decreased body size at hatching and these effects were sustained into the juvenile period and adulthood. Lizards exposed to low doses of corticosterone during development had elevated levels of baseline corticosterone as adults. Additionally, lizards incubated at cool temperatures had higher levels of baseline corticosterone and more efficient mitochondria as adults compared with lizards incubated at warm temperatures. Our results show that developmental conditions can have sustained effects on morphological and physiological traits in oviparous lizards but suggest that incubation temperature and prenatal corticosterone do not have interactive effects.

In Vitro and In Silico Evaluation of Syzygium aromaticum Essential Oil: Effects on Mitochondrial Function and Cytotoxic Potential Against Cancer Cells

The current study proposes the in vitro and in silico anticancer evaluation of clove (Syzygium aromaticum L.) essential oil (CEO). The steam hydrodistillation method used yielded 10.7% (wt) CEO. GC-MS analysis revealed that the obtained oil is rich in eugenol (75%), β-caryophyllene (20%), and α- caryophyllene (2.8%) and also contains several other minor components accounting for approximately 1.5%. The DPPH-based scavenging antioxidant activity was assessed for the obtained CEO, exhibiting an IC50 value of 158 μg/mL. The cytotoxic effects of CEO, its major component eugenol, and CEO solubilized with Tween-20 and PEG-400 were tested against both noncancerous HaCaT cells and HT-29 human colorectal adenocarcinoma, RPMI-7951 melanoma, A431 skin carcinoma, and NCI-H460 non-small lung cancer cells, using the Alamar Blue and LDH assay after 48 h treatment. The Tween-20 and PEG-400 CEO formulations, at 200 μg/mL, recorded the highest cytotoxic and selective effects against RPMI-7951 (72.75% and 71.56%), HT-29 (71.51% and 45.43%), and A431 cells (61.62% and 59.65%). Furthermore, CEO disrupted mitochondrial function and uncoupled oxidative phosphorylation. This effect was more potent for the CEO against the RPMI-7951 and HT-29 cells, whereas for the other two tested cell lines, a more potent inhibition of mitochondrial function was attributed to eugenol. The present study is the first to specifically investigate the effects of CEO and Tween-20 and PEG-400 CEO formulations on the mitochondrial function of RPMI-7951, HT-29, A431, and NCI-H460 cancer cell lines using high-resolution respirometry, providing novel insights into their impact on mitochondrial respiration and bioenergetics in cancer cells. The results obtained may explain the increased ROS production observed in cancer cell lines treated with eugenol and CEO. Molecular docking identified potential protein targets, related to the CEO anticancer activity, in the form of PI3Kα, where the highest active theoretical inhibitor was calamenene (-7.5 kcal/mol). Docking results also showed that calamenene was the overall most active theoretical inhibitor for all docked proteins and indicated a potential presence of synergistic effects among all CEO constituents.

Melatonin induces fiber switching by improvement of mitochondrial oxidative capacity and function via NRF2/RCAN/MEF2 in the vastus lateralis muscle from both sex Zücker diabetic fatty rats

The positive role of melatonin in obesity control and skeletal muscle (SKM) preservation is well known. We recently showed that melatonin improves vastus lateralis muscle (VL) fiber oxidative phenotype. However, fiber type characterization, mitochondrial function, and molecular mechanisms that underlie VL fiber switching by melatonin are still undefined. Our study aims to investigate whether melatonin induces fiber switching by NRF2/RCAN/MEF2 pathway activation and mitochondrial oxidative metabolism modulation in the VL of both sex Zücker diabetic fatty (ZDF) rats. 5-Weeks-old male and female ZDF rats (N = 16) and their age-matched lean littermates (ZL) were subdivided into two subgroups: control (C) and orally treated with melatonin (M) (10 mg/kg/day) for 12 weeks. Interestingly, melatonin increased oxidative fibers amounts (Types I and IIa) counteracting the decreased levels found in the VL of obese-diabetic rats, and upregulated NRF2, calcineurin and MEF2 expression. Melatonin also restored the mitochondrial oxidative capacity increasing the respiratory control ratio (RCR) in both sex and phenotype rats through the reduction of the proton leak component of respiration (state 4). Melatonin also improved the VL mitochondrial phosphorylation coefficient and modulated the total oxygen consumption by enhancing complex I, III and IV activity, and fatty acid oxidation (FAO) in both sex obese-diabetic rats, decreasing in male and increasing in female the complex II oxygen consumption. These findings suggest that melatonin treatment induces fiber switching in SKM improving mitochondrial functionality by NRF2/RCAN/MEF2 pathway activation.

CTRP6-mediated cardiac protection in heart failure via the AMPK/SIRT1/PGC-1α signalling pathway

Heart failure (HF) remains a significant global health concern with limited effective treatments available. C1q/TNF-related protein 6 (CTRP6) is a member of the CTRP family analogous to adiponectin and its role in HF pathogenesis remains unclear. Here, we investigated the impact of CTRP6 on HF progression. To mimic heart failure with reduced ejection fraction (HFrEF), we used isoproterenol injection in mice and administered adenovirus vectors expressing CTRP6 (Ad-CTRP6) via tail vein injection. We assessed cardiac function through echocardiography and histology. CTRP6's effects on hypertrophy, fibrosis, apoptosis, oxidative stress and mitochondrial function were analysed. Downstream pathways (phosphorylated AMP-activated protein kinase (p-AMPK), sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) were studied in heart tissues. In vitro, isoproterenol-stimulated H9c2 cardiomyocytes were treated with CTRP6 to examine viability, apoptosis, F-actin and signalling proteins. Compound C was used to assess AMPK involvement. CTRP6 expression was lower in the plasma of HF patients. In an isoproterenol-induced HFrEF mouse model, adenovirus-mediated overexpression of CTRP6 ameliorated cardiac dysfunction and reduced cardiomyocyte apoptosis, oxidative stress, inflammation and myocardial injury markers. Mechanistically, CTRP6 activation of the AMPK/SIRT1/PGC-1α signalling pathway restored mitochondrial homeostasis, evidenced by reduced mitochondrial reactive oxygen species levels, increased ATP content, and enhanced mitochondrial complex I/III activities in cardiac tissues. In vitro studies using isoproterenol-stimulated H9c2 cardiomyocytes corroborated these findings, demonstrating that CTRP6 upregulation attenuated hypertrophy, apoptosis, oxidative stress and mitochondrial dysfunction. Furthermore, these effects were partially reversed by the AMPK inhibitor Compound C, implicating the involvement of the AMPK pathway in CTRP6-mediated cardioprotection. CTRP6 alleviates HF progression through the AMPK/SIRT1/PGC-1α signalling pathway.

Contrasting species-specific stress response to environmental pH determines the fate of coccolithophores in future oceans

Molecular mechanisms driving species-specific environmental sensitivity in coccolithophores are unclear but crucial in understanding species selection and adaptation to environmental change. This study examined proteomic and physiological changes in three species under varying pH conditions. We showed that changing pH drives intracellular oxidative stress and changes membrane potential. Upregulation in antioxidant, DNA repair and cell cycle-related protein-groups indicated oxidative damage across high (pH 8.8) and low pH (pH 7.6) compared to control pH (pH 8.2), and correlated with reduced growth rates. Upregulation of mitochondrial proteins suggested higher metabolite demand for restoring cellular homeostasis under pH-induced stress. Photosynthetic rates generally correlated with CO2 availability, driving higher net carbon fixation rates at low pH. The intracellular pH-buffering capacity of the coastal Chrysotila carterae and high metabolic adaptability in the bloom-forming Gephyrocapsa huxleyi will likely facilitate their adaptation to ocean acidification or artificial ocean alkalinisation. However, the pH sensitivity of the ancient open-ocean Coccolithus braarudii will possibly result in reduced growth and shrinking of its ecological niche.

WTAP-mediated m6A modification of TRIM22 promotes diabetic nephropathy by inducing mitochondrial dysfunction via ubiquitination of OPA1

OBJECTIVES

Diabetic nephropathy (DN) is one of the most serious microvascular complications of diabetes and is the most common cause of end-stage renal disease. Tripartite motif-containing (TRIM) proteins are a large family of E3 ubiquitin ligases that contribute to protein quality control by regulating the ubiquitin - proteasome system. However, the detailed mechanisms through which various TRIM proteins regulate downstream events have not yet been fully elucidated. The current research aimed to determine the function and mechanism of TRIM22 in DN.

METHODS

DN models were established by inducing HK-2 cells using high glucose (HG) and diabetic mice (db/db mice). Cell viability, apoptosis, mitochondrial reactive oxygen species, and mitochondrial membrane potential were detected by Cell Counting Kit-8 and flow cytometry, respectively. Pathological changes were evaluated using hematoxylin and eosin, periodic acid schiff and Masson staining. The binding between TRIM22 and optic atrophy 1 (OPA1) was analyzed using co-immunoprecipitation. The m6A level of TRIM22 5'UTR was detected using RNA immunoprecipitation.

RESULTS

TRIM22 was highly expressed in patients with DN. TRIM22 silencing inhibited HG-induced apoptosis and mitochondrial dysfunction in HK-2 cells. Promoting mitochondrial fusion alleviated TRIM22 overexpression-induced cell apoptosis, mitochondrial dysfunction in HK-2 cells, and kidney damage in mice. Mechanistically, TRIM22 interacted with OPA1 and induced its ubiquitination. Wilms tumor 1-associating protein (WTAP) promoted m6A modification of TRIM22 through the m6A reader insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1).

DISCUSSION

TRIM22 silencing inhibited the progression of DN by interacting with OPA1 and inducing its ubiquitination. Furthermore, WTAP promoted m6A modification of TRIM22 via IGF2BP1.

Analysis of stallion spermatozoa metabolism using Agilent Seahorse XFp Technology

Sperm metabolism consists of a sophisticated network of biochemical reactions and varies between species, resulting in different metabolic strategies for ATP production to maintain sperm functionality. ATP can be produced through glycolysis or in the mitochondria by oxidative phosphorylation (OXPHOS). Since OXPHOS is the predominant metabolic pathway in horses spermatozoa, various assessments of mitochondrial activity are used to evaluate fertility, utilizing techniques such as fluorescent probes analysed via microscopy or flow cytometry, and polarographic electrode assays to measure current flow in response to an applied voltage. Though, these methods are limited by low throughput, as they assess mitochondrial activity at a single time point under a specific treatment condition. This study explores, for the first time, the application of the Agilent Seahorse XFp Technology to evaluate metabolism in stallion spermatozoa. This method enables real-time measurement of cellular metabolism across multiple samples or experimental conditions simultaneously. Ejaculates from eight different stallions were collected, and pools were prepared from three of them. Sperm viability and mitochondrial activity were evaluated by fluorescence microscopy, sperm motility by a computer-assisted sperm analysis system, and sperm metabolism was analysed via the Seahorse XFp analyser. Results confirmed a preference for OXPHOS over glycolysis in ATP production in stallion sperm, with mitochondria contributing significantly to total ATP generation. The Seahorse XFp Technology proved effective in evaluating equine sperm bioenergetics, offering insights into metabolic pathways critical for sperm function. In conclusion, this technology grants a new method for high-throughput analysis of sperm metabolism and quality, which could be applied to future reproductive studies in male equine fertility.

Stress-induced premature senescence in high five cell cultures: a principal factor in cell-density effects

The Baculovirus Expression Vector System (BEVS) is highly valued in vaccine development, protein engineering, and drug metabolism research due to its biosafety, operational convenience, rapid scalability, and capacity for self-assembling virus-like particles. However, increasing cell density at the time of inoculation severely compromises the production capacity of BEVS, resulting in the "cell density effect". This study aimed to explore the mechanisms of the cell density effect through time-series analysis of transcriptomes and proteomes, with the goal of overcoming or alleviating the decline in productivity caused by increased cell density. The dynamic analysis of the omics of High Five cells under different CCI (cell density at infection) conditions showed that the impact of the "cell density effect" increased over time, particularly affecting genetic information processing, error repair, protein expression regulation, and material energy metabolism. Omics analysis of the growth stage of High Five cells showed that after 36 h of culture (cell density of about 1 × 106 cells/mL), the expression of ribosome-related proteins decreased, resulting in a rapid decrease in protein synthesis capacity, which was a key indicator of cell aging. Senescence verification experiments showed that cells began to show obvious early aging characteristics after 36 h, resulting in a decrease in the host cell's ability to resist stress. Overexpression and siRNA inhibition studies showed that the ndufa12 gene was a potential regulatory target for restricting the "cell density effect". Our results suggested that stress-induced premature senescence in High Five cell cultures, resulting in reduced energy metabolism and protein synthesis capabilities, was a critical factor contributing to cell density effects, and ultimately affecting virus production. In conclusion, this study provided new insights into managing virus production limitations due to cell density effects and offered innovative strategies to mitigate the adverse effects of cellular aging in biomanufacturing technologies.

Assessment of mitochondrial function and its prognostic role in sepsis: a literature review

Sepsis is characterized by a dysregulated and excessive systemic inflammatory response to infection, associated with vascular and metabolic abnormalities that ultimately lead to organ dysfunction. In immune cells, both non-oxidative and oxidative metabolic rates are closely linked to inflammatory responses. Mitochondria play a central role in supporting these cellular processes by utilizing metabolic substrates and synthesizing ATP through oxygen consumption. To meet fluctuating cellular demands, mitochondria must exhibit adaptive plasticity underlying bioenergetic capacity, biogenesis, fusion, and fission. Given their role as a hub for various cellular functions, mitochondrial alterations induced by sepsis may hold significant pathophysiological implications and impact on clinical outcomes. In patients, mitochondrial DNA concentration, protein expression levels, and bioenergetic profiles can be accessed via tissue biopsies or isolated peripheral blood cells. Clinically, monocytes and lymphocytes serve as promising matrices for evaluating mitochondrial function. These mononuclear cells are highly oxidative, mitochondria-rich, routinely monitored in blood, easy to collect and process, and show a clinical association with immune status. Hence, mitochondrial assessments in immune cells could serve as biomarkers for clinical recovery, immunometabolic status, and responsiveness to oxygen and vasopressor therapies in sepsis. These characteristics underscore mitochondrial parameters in both tissues and immune cells as practical tools for exploring underlying mechanisms and monitoring septic patients in intensive care settings. In this article, we examine pathophysiological aspects, key methods for measuring mitochondrial function, and prominent studies in this field.

Analyses of mitochondrial metabolism in diseases: a review on 13C magnetic resonance tracers

Metabolic diseases such as obesity, type 2 diabetes, and cardiovascular diseases have become a global health concern due to their widespread prevalence and profound impact on life expectancy, healthcare expenditures, and the overall economy. Devising effective treatment strategies and management plans for these diseases requires an in-depth understanding of the pathophysiology of the metabolic abnormalities associated with each disease. Mitochondrial dysfunction is intricately linked to a wide range of metabolic abnormalities and is considered an important biomarker for diseases. However, assessing mitochondrial functions in viable tissues remains a challenging task, with measurements of oxygen consumption rate (OCR) and ATP production being the most widely accepted approaches for evaluating the health of mitochondria in tissues. Measurements of cellular metabolism using carbon-13 (or 13C) tracers have emerged as a viable method for characterizing mitochondrial metabolism in a variety of organelles ranging from cultured cells to humans. Information on metabolic activities and mitochondrial functions can be obtained from magnetic resonance (MR) analyses of 13C-labeled metabolites in tissues and organs of interest. Combining novel 13C tracer technologies with advanced analytical and imaging tools in nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) offers the potential to detect metabolic abnormalities associated with mitochondrial dysfunction. These capabilities would enable accurate diagnosis of various metabolic diseases and facilitate the assessment of responses to therapeutic interventions, hence improving patient health and optimizing clinical outcomes.

Photodynamic therapy reduces viability, enhances itraconazole activity, and impairs mitochondrial physiology of Sporothrix brasiliensis

Sporothrix brasiliensis is the main agent of sporotrichosis in Brazil, with few therapeutic options. This study aimed to investigate the in vitro efficacy of photodynamic therapy using a diode laser (InGaAIP) in combination with the photosensitizer methylene blue against S. brasiliensis yeasts. Additionally, we evaluated the underexplored mitochondrial activity of S. brasiliensis and the impact of laser treatment on the fungal mitochondrial aspects post-treatment. Three strains of S. brasiliensis were used, including a non-wild-type strain to itraconazole. Yeast viability was determined by counting colony-forming units. For a comprehensive analysis of irradiated versus non-irradiated cells, we assessed combined therapy with itraconazole, scanning electron microscopy of cells, and mitochondrial activity. The latter included high-resolution respirometry, membrane potential analysis, and reactive oxygen species production. Methylene blue combined with photodynamic therapy inhibited the growth of the isolates, including the non-wild-type strain to itraconazole. Photodynamic therapy induced the production of reactive oxygen species, which negatively affected mitochondrial function, resulting in decreased membrane potential and cell death. Photodynamic therapy altered the ultrastructure and mitochondrial physiology of S. brasiliensis, suggesting a new therapeutic approach for sporotrichosis caused by this species.

DMT1 knockout abolishes ferroptosis induced mitochondrial dysfunction in C. elegans amyloid β proteotoxicity

Iron is critical for neuronal activity and metabolism, and iron dysregulation alters these functions in age-related neurodegenerative disorders, such as Alzheimer's disease (AD). AD is a chronic neurodegenerative disease characterized by progressive neuronal dysfunction, memory loss and decreased cognitive function. AD patients exhibit elevated iron levels in the brain compared to age-matched non-AD individuals. However, the degree to which iron overload contributes to AD pathogenesis is unclear. Here, we evaluated the involvement of ferroptosis, an iron-dependent cell death process, in mediating AD-like pathologies in C. elegans. Results showed that iron accumulation occurred prior to the loss of neuronal function as worms age. In addition, energetic imbalance was an early event in iron-induced loss of neuronal function. Furthermore, the loss of neuronal function was, in part, due to increased mitochondrial reactive oxygen species mediated oxidative damage, ultimately resulting in ferroptotic cell death. The mitochondrial redox environment and ferroptosis were modulated by pharmacologic processes that exacerbate or abolish iron accumulation both in wild-type worms and worms with increased levels of neuronal amyloid beta (Aβ). However, neuronal Aβ worms were more sensitive to ferroptosis-mediated neuronal loss, and this increased toxicity was ameliorated by limiting the uptake of ferrous iron through knockout of divalent metal transporter 1 (DMT1). In addition, DMT1 knockout completely suppressed phenotypic measures of Aβ toxicity with age. Overall, our findings suggest that iron-induced ferroptosis alters the mitochondrial redox environment to drive oxidative damage when neuronal Aβ is overexpressed. DMT1 knockout abolishes neuronal Aβ-associated pathologies by reducing neuronal iron uptake.

Triphenyltin isoselenocyanate: a novel nuclear retinoid X receptor ligand with antiproliferative and cytotoxic properties in cell lines derived from human breast cancer

Several commercially available triorganotin compounds were previously found to function as agonist ligands for nuclear retinoid X receptor (RXR) molecules. Triphenyltin isoselenocyanate (TPT-NCSe), a novel selenium atom containing a derivative of triorganotin origin, was found to represent a new cognate bioactive ligand for RXRs. TPT-NCSe displayed a concentration- and time-dependent decrease in the cell viability in both human breast carcinoma MCF-7 (estrogen receptor positive) and MDA‑MB‑231 (triple negative) cell lines. Reactive oxygen species levels generated in response to TPT-NCSe were significantly higher in both carcinoma cell lines treated with TPT-NCSe when compared to mock-treated samples. Treatment with 500 nM TPT-NCSe caused a decrease in SOD1 and increased SOD2 mRNA in MCF-7 cells. The levels of SOD2 mRNA were more increased following the treatment with TPT-NCSe along with 1 μM all-trans retinoic acid (AtRA) in MCF-7 cells. An increased superoxide dismutase SOD1 and SOD2 mRNA levels were also detected in combination treatment of 500 nM TPT-NCSe and 1 μM AtRA in TPT-NCSe-treated MDA-MB-231 cells. The data have also shown that TPT-NCSe induces apoptosis via a caspase cascade triggered by the mitochondrial apoptotic pathway. TPT-NCSe modulates the expression levels of apoptosis‑related proteins, Annexin A5, Bcl‑2 and BAX family proteins, and finally, it enhances the expression levels of its cognate nuclear receptor subtypes RXRalpha and RXRbeta.

Heart failure related fatigue: An exploratory analysis of serum osmolality from the national health and nutrition examination survey

BACKGROUND

Fatigue is a prominent symptom of heart failure (HF). However, underlying mechanisms remain poorly understood. Fluid volume status has been suggested as a physiologic mechanism of HF-related fatigue. Serum osmolality may fluctuate with changes in volume status associated with neurohormonal dysregulation. The relationship of fatigue to serum osmolality has not been assessed in adults with HF.

OBJECTIVES

Describe the relationship between serum osmolality and fatigue in adults with HF.

METHODS

We analyzed two waves of cross-sectional data from the National Health and Nutrition Examination Survey (2015-2016 and 2017-2018). Adults who self-reported having HF without select co-morbid conditions known to contribute to fatigue were included. Data were weighted to provide US national estimates, and complex sample design used for analyses. Sequential logistic regression was used to isolate the effect of serum osmolality on the odds of having fatigue.

RESULTS

Data from the sample represented 1.4 million Americans with HF (58.5 % male; median age 68 years), of whom 1,001,589 (67.9 %) reported fatigue. Participants with fatigue had lower serum osmolality compared to those without fatigue (t = -3.04, p = .009). Higher serum osmolality was associated with 8.8 % lower odds of experiencing fatigue when controlling for sex and body mass index (OR = 0.912, p = .007, CI 0.857 - 0.972).

CONCLUSIONS

HF-related fatigue is associated with lower serum osmolality. Low serum osmolality may indicate excess volume and the presence of a heightened neurohormonal response, both of which may influence fatigue. Alternatively, serum osmolality may directly affect other physiologic changes that may contribute to fatigue.

Ablating the glutaredoxin-2 (Glrx2) gene protects male mice against non-alcoholic fatty liver disease (NAFLD) by limiting oxidative distress

In the present study, we investigated the consequences of deleting the glutaredoxin-2 gene (Glrx2-/-) on the development of non-alcoholic fatty liver disease (NAFLD) in male and female C57BL6N mice fed a control (CD) or high-fat diet (HFD). We report that the HFD induced a significant increase in body mass in the wild-type (Wt) and Glrx2-/- male, but not female, mice, which was associated with the hypertrophying of the abdominal fat. Interestingly, while the Wt male mice fed the HFD developed NAFLD, the deletion of the Glrx2 gene mitigated vesicle formation, intrahepatic lipid accumulation, and fibrosis in the males. The protective effect associated with ablating the Glrx2 gene in male mice was due to enhancement of mitochondrial redox buffering capacity. Specifically, liver mitochondria from male Glrx2-/- fed a CD or HFD produced significantly less hydrogen peroxide (mtH2O2), had lower malondialdehyde levels, greater activities for glutathione peroxidase and thioredoxin reductase, and less protein glutathione mixed disulfides (PSSG) when compared to the Wt male mice fed the HFD. These effects correlated with the S-glutathionylation of α-ketoglutarate dehydrogenase (KGDH), a potent mtH2O2 source and key redox sensor in hepatic mitochondria. In comparison to the male mice, both Wt and Glrx2-/- female mice displayed almost complete resistance to HFD-induced body mass increases and the development of NAFLD, which was attributed to the superior redox buffering capacity of the liver mitochondria. Together, our findings show that modulation of mitochondrial S-glutathionylation signaling through Glrx2 augments resistance of male mice towards the development of NAFLD through preservation of mitochondrial redox buffering capacity. Additionally, our findings demonstrate the sex dimorphisms associated with the manifestation of NAFLD is related to the superior redox buffering capacity and modulation of the S-glutathionylome in hepatic mitochondria from female mice.

High mitochondrial DNA levels accelerate lung adenocarcinoma progression

Lung adenocarcinoma is a common aggressive cancer and a leading cause of mortality worldwide. Here, we report an important in vivo role for mitochondrial DNA (mtDNA) copy number during lung adenocarcinoma progression in the mouse. We found that lung tumors induced by KRASG12D expression have increased mtDNA levels and enhanced mitochondrial respiration. To experimentally assess a possible causative role in tumor progression, we induced lung cancer in transgenic mice with a general increase in mtDNA copy number and found that they developed a larger tumor burden, whereas mtDNA depletion in tumor cells reduced tumor growth. Immune cell populations in the lung and cytokine levels in plasma were not affected by increased mtDNA levels. Analyses of large cancer databases indicate that mtDNA copy number is also important in human lung cancer. Our study thus reports experimental evidence for a tumor-intrinsic causative role for mtDNA in lung cancer progression, which could be exploited for development of future cancer therapies.

Atrial pacing improves mitochondrial function in peripheral blood mononuclear cells in patients with cardiac implantable electronic devices

Mitochondrial dysfunction contributes significantly to the development of atrial fibrillation (AF). Conflicting data regarding the atrial pacing and the risk of AF existed, and the impact of atrial pacing on mitochondrial function remains unknown. Therefore, we sought to examine the association between atrial pacing percentage and mitochondrial function in patients with cardiovascular implantable electronic devices (CIEDs) with atrial pacing capability. This is a cross-sectional study involving 183 patients with CIEDs with atrial pacing capability. The oxidative stress and mitochondrial function were determined in peripheral blood mononuclear cells (PBMCs). Among 183 patients, 55.7% had permanent pacemakers, 7.7% had defibrillators, and 36.6% had cardiac resynchronization therapy. Mean age was 67.5 ± 14.7 yr with 51% being male. Mean left ventricular ejection fraction (LVEF) was 53.9 ± 16.8%. We demonstrated that the presence of atrial pacing above 50% correlated with higher levels of mitochondrial spared respiratory capacity (P = 0.043) and coupling efficiency (P = 0.045). After adjusting with multiple linear regression for age, sex, LVEF, history of AF, sick sinus syndrome, comorbidities, estimated glomerular filtration rate (eGFR), cardiac resynchronization therapy (CRT), and percentage of ventricular pacing, our findings revealed a statistically significant association between a higher percentage of atrial pacing and increased spared respiratory capacity (β, 0.217, P = 0.046), lower nonmitochondrial respiration (β, -0.230; P = 0.023), and proton leak (β, -0.247; P = 0.022). We demonstrated that atrial pacing enhances mitochondrial performance in PBMCs and left ventricular contractile performance in patients with CIEDs. This observation may serve as an additional support for the preventive effect of atrial pacing in the prevention of atrial arrhythmia.NEW & NOTEWORTHY Atrial pacing enhances mitochondrial spare respiratory capacity and reduces proton leak. This finding may provide further evidence supporting the preventive role of atrial pacing in reducing the risk of atrial fibrillation in patients with cardiac implantable electronic devices.

Age-Dependent Pathogenesis of Influenza A Virus H7N9 Mediated Through PB1-F2-Induced Mitochondrial DNA Release and Activation of cGAS-STING-NF-κB Signaling

Exactly why human infection of avian influenza A virus H7N9 causes more severe disease in the elderly remains elusive. In this study, we found that H7N9 PB1-F2 is a pathogenic factor in 15-18-month-old BALB/C mice (aged mice) but not in 6-8-week-old young adult mice (young mice). Recombinant influenza A virus with H7N9 PB1-F2-knockout was less pathogenic in aged mice as indicated with delayed weight loss. In contrast, survival of young mice infected with this virus was diminished. Furthermore, tissue damage, inflammation, proinflammatory cytokine and 2'3'-cGAMP production in the lung were less pronounced in infected aged mice despite no change in viral titer. cGAS is known to produce 2'3'-cGAMP to boost proinflammatory cytokine expression through STING-NF-κB signaling. We found that H7N9 PB1-F2 promoted interferon β (IFNβ) and chemokine gene expression in cultured cells through the mitochondrial DNA-cGAS-STING-NF-κB pathway. H7N9 PB1-F2 formed protein aggregate and caused mitochondrial cristae collapse, complex V-dependent electron transport dysfunction, reverse electron transfer-dependent oxidized mitochondrial DNA release to the cytoplasm and activation of cGAS-STING-NF-κB signaling. PB1-F2 N57 truncation, which is frequently observed in human circulating strains, mitigated H7N9 PB1-F2-mediated mitochondrial dysfunction and cGAS activation. In addition, we found that PB1-F2 of pathogenic avian influenza viruses triggered more robust cGAS activation than their human-adapted descendants. Our findings provide one explanation to age-dependent pathogenesis of H7N9 infection.

Antiallodynic and antihyperalgesic effects of decursin associated with correcting mitochondrial dysfunction and oxidative stress in type 1 diabetic mice

A substantial proportion of diabetic patients suffer a debilitating and persistent pain state, known as peripheral painful neuropathy that necessitates improved therapy or antidote. Decursin, a major active ingredient from Angelica gigas Nakai, has been reported to possess antidepressant activity in preclinical studies. As antidepressants have been typically used as standard agents against persistent neuropathic pain, this study aimed to probe the effect of decursin on neuropathic pain associated with streptozotocin-induced type 1 diabetes in male C57BL6J mice. The Hargreaves test and the von Frey test were used to assess pain-like behaviors, shown as heat hyperalgesia and mechanical allodynia respectively. Chronic treatment of diabetic mice with decursin not only ameliorated the established symptoms of heat hyperalgesia and mechanical allodynia, but also arrested the development of these pain states given preemptively at low doses. Although decursin treatment hardly impacted on metabolic disturbance in diabetic mice, it ameliorated exacerbated oxidative stress in pain-associated tissues, improved mitochondrial bioenergetics in dorsal root ganglion neurons, and restored nerve conduction velocity and blood flow in sciatic nerves. Notably, the analgesic actions of decursin were modified by pharmacologically manipulating redox status and mitochondrial bioenergetics. These findings unveil the analgesic activity of decursin, an effect that is causally associated with its bioenergetics-enhancing and antioxidant effects, in mice with type 1 diabetes.

Activation of innate immunity selectively compromises mitochondrial complex I, proline oxidation, and flight activity in the major arbovirus vector Aedes aegypti

Aedes aegypti females are natural vectors of important arboviruses such as dengue, zika, and yellow fever. Mosquitoes activate innate immune response signaling pathways upon infection, as a resistance mechanism to fight pathogens and limit their propagation. Despite the beneficial effects of immune activation for insect vectors, phenotypic costs ultimately affect their fitness. However, the underlying mechanisms that mediate these fitness costs remain poorly understood. Given the high energy required to mount a proper immune response, we hypothesized that systemic activation of innate immunity would impair flight muscle mitochondrial function, compromising tissue energy demand and flight activity. Here, we investigated the dynamic effects of activation of innate immunity by intra-thoracic zymosan injection on A. aegypti flight muscle mitochondrial metabolism. Zymosan injection significantly increased defensin A expression in fat bodies in a time-dependent manner that compromised flight activity. Although oxidant levels in flight muscle were hardly altered, ATP-linked respiratory rates driven by mitochondrial pyruvate+proline oxidation were significantly reduced at 24 h upon zymosan injection. Oxidative phosphorylation coupling was preserved regardless of innate immune response activation along 24 h. Importantly, rotenone-sensitive respiration and complex I-III activity were specifically reduced 24 h upon zymosan injection. Also, loss of complex I activity compromised ATP-linked and maximal respiratory rates mediated by mitochondrial proline oxidation. Finally, the magnitude of innate immune response activation negatively correlated with respiratory rates, regardless of the metabolic states. Collectively, we demonstrate that activation of innate immunity is strongly associated with reduced flight muscle complex I activity with direct consequences to mitochondrial proline oxidation and flight activity. Remarkably, our results indicate a trade-off between dispersal and immunity exists in an insect vector, underscoring the potential consequences of disrupted flight muscle mitochondrial energy metabolism to arbovirus transmission.

Potential probiotic Lactiplantibacillus plantarum strains alleviate TNF-α by regulating ADAM17 protein and ameliorate gut integrity through tight junction protein expression in in vitro model

BACKGROUND

Lactiplantibacillus species are extensively studied for their ability to regulate host immune responses and functional therapeutic potentials. Nevertheless, there is a lack of understanding on the mechanisms of interactions with the hosts during immunoregulatory activities.

METHODS

Two Lactiplantibacillus plantarum strains MKMB01 and MKMB02 were tested for probiotic potential following Indian Council of Medical Research (ICMR) guidelines. Human colorectal adenocarcinoma cells such as HT-29, caco-2, and human monocytic cell THP-1 were also used to study the potential of MKMB01 and MKMB02 in regulating the host immune response when challenged with enteric pathogen Salmonella enterica typhimurium. Cells were pre-treated with MKMB01 and MKMB02 for 4 h and then stimulated with Salmonella. qRT-PCR and ELISA were used to analyze the genes and protein expression. Confocal microscopy and field emission scanning electron microscopy (FESEM) were used to visualize the effects. An Agilent Seahorse XF analyzer was used to determine real-time mitochondrial functioning.

RESULTS

Both probiotic strains could defend against Salmonella by maintaining gut integrity via expressing tight junction proteins (TJPs), MUC-2, and toll-like receptors (TLRs) negative regulators such as single Ig IL-1-related receptor (SIGIRR), toll-interacting protein (Tollip), interleukin-1 receptor-associated kinase (IRAK)-M, A20, and anti-inflammatory transforming growth factor-β and interleukin-10. Both strains also downregulated the expression of pro-inflammatory cytokines/chemokines interleukin-1β, monocyte chemoattractant protein (MCP)-1, tumor necrosis factor-alpha (TNF-α), interleukin 6, and nitric oxide (NO). Moreover, TNF-α sheddase protein, a disintegrin and metalloproteinase domain 17 (ADAM17), and its regulator iRhom2 were downregulated by both strains. Moreover, the bacteria also ameliorated Salmonella-induced mitochondrial dysfunction by restoring bioenergetic profiles, such as non-mitochondrial respiration, spare respiratory capacity (SRC), basal respiration, adenosine triphosphate (ATP) production, and maximal respiration.

CONCLUSIONS

MKMB01 and MKMB02 can reduce pathogen-induced gut-associated disorders and therefore should be further explored for their probiotic potential.

Polydatin Prevents Electron Transport Chain Dysfunction and ROS Overproduction Paralleled by an Improvement in Lipid Peroxidation and Cardiolipin Levels in Iron-Overloaded Rat Liver Mitochondria

Increased intramitochondrial free iron is a key feature of various liver diseases, leading to oxidative stress, mitochondrial dysfunction, and liver damage. Polydatin is a polyphenol with a hepatoprotective effect, which has been attributed to its ability to enhance mitochondrial oxidative metabolism and antioxidant defenses, thereby inhibiting reactive oxygen species (ROS) dependent cellular damage processes and liver diseases. However, it has not been explored whether polydatin is able to exert its effects by protecting the phospholipid cardiolipin against damage from excess iron. Cardiolipin maintains the integrity and function of electron transport chain (ETC) complexes and keeps cytochrome c bound to mitochondria, avoiding uncontrolled apoptosis. Therefore, the effect of polydatin on oxidative lipid damage, ETC activity, cytochrome levels, and ROS production was explored in iron-exposed rat liver mitochondria. Fe2+ increased lipid peroxidation, decreased cardiolipin and cytochromes c + c1 and aa3 levels, inhibited ETC complex activities, and dramatically increased ROS production. Preincubation with polydatin prevented all these effects to a variable degree. These results suggest that the hepatoprotective mechanism of polydatin involves the attenuation of free radical production by iron, which enhances cardiolipin levels by counteracting membrane lipid peroxidation. This prevents the loss of cytochromes, improves ETC function, and decreases mitochondrial ROS production.

Cannabidiol modulates hippocampal genes involved in mitochondrial function, ribosome biogenesis, synapse organization, and chromatin modifications

BACKGROUND

Cannabidiol (CBD) is one of the main cannabinoids present in Cannabis sativa female flowers. Previous investigation has already provided insights into the CBD molecular mechanism; however, there is no transcriptome data for CBD effects on hippocampal subfields. Here, we investigate transcriptomic changes in dorsal and ventral CA1 of adult mice hippocampus after 100 mg/kg of CBD administration (i.p.) for one or seven consecutive days.

METHODS

C57BL/6JUnib mice were treated with either vehicle or CBD for 1 or 7 days. The collected brains were sectioned, and the hippocampal sub-regions were laser microdissected for RNA-Seq analysis.

RESULTS

The transcriptome analysis following 7 days of CBD administration indicates the differential expression of 1559 genes in dCA1 and 2924 genes in vCA1. Furthermore, GO/KEGG analysis identified 88 significantly enriched biological process and 26 significantly enriched pathways for dCBD7, whereas vCBD7 revealed 128 enriched BPs and 24 pathways.

CONCLUSION

This dataset indicates a widespread decrease of electron transport chain and ribosome biogenesis transcripts in CA1, while chromatin modifications and synapse organization transcripts were increased following CBD administration for 7 days.

Prenylated xanthones from mangosteen (Garcinia mangostana) target oxidative mitochondrial respiration in cancer cells

Mangosteen (Garcinia mangostana) is well-known for its nutritional value and health benefits. Breast cancer is the most common cancer and the leading cause of cancer-related mortality among females worldwide. Here we show that the prenylated xanthones, α-mangostin, γ-mangostin, 9-hydroxycalabaxanthone (9-HCX), and garcinone E from the mangosteen pericarp exhibit cytotoxicity against a panel of human cancer cell lines including lung adenocarcinoma (A549), cervical carcinoma (HeLa), prostatic carcinoma (DU 145), pancreatic carcinoma (MIA PaCa-2), hepatocellular carcinoma (Hep G2), bladder urothelial cancer (5637), as well as the triple-negative breast cancer cells MDA-MB-231. In line with its higher predicted bioactivity score compared to other prenylated xanthones, 9-HCX induced the strongest antiproliferative and proapoptotic effects in MDA-MB-231 breast cancer xenografts in vivo. In different in vitro models, we demonstrate that prenylated xanthones from G. mangostana target mitochondria in cancer cells by inhibition of the mitochondrial respiratory chain complex II (α-mangostin, γ-mangostin, and garcinone E) and complex III (9-HCX) as shown in isolated mitochondria. Accordingly, oxidative mitochondrial respiration (OXPHOS) was inhibited, mitochondrial proton leak increased, and adenosine triphosphate (ATP) synthesis decreased as analyzed by Seahorse assay in MDA-MB-231 cells. Hence, the prenylated xanthones increased mitochondrial superoxide levels, induced mitochondrial membrane permeabilization, and initiated caspase 3/7-mediated apoptosis in MDA-MB-231 triple-negative breast cancer cells. Thus, prenylated xanthones from Garcinia mangostana exhibit anticancer activity based on interference with the mitochondrial respiration.

The Different Responsiveness of C3- and C5-deficient Murine BM Cells to Oxidative Stress Explains Why C3 Deficiency, in Contrast to C5 Deficiency, Correlates with Better Pharmacological Mobilization and Engraftment of Hematopoietic Cells

The liver-derived circulating in peripheral blood and intrinsic cell-expressed complement known as complosome orchestrate the trafficking of hematopoietic stem/progenitor cells (HSPCs) both during pharmacological mobilization and homing/engraftment after transplantation. Our previous research demonstrated that C3 deficient mice are easy mobilizers, and their HSPCs engraft properly in normal mice. In contrast, C5 deficiency correlates with poor mobilization and defects in HSPCs' homing and engraftment. The trafficking of HSPCs during mobilization and homing/engraftment follows the sterile inflammation cues in the BM microenvironment caused by stress induced by pro-mobilizing drugs or myeloablative conditioning for transplantation. Therefore, to explain deficiencies in HSPC trafficking between C3-KO and C5-KO mice, we evaluated the responsiveness of C3 and C5 deficient cells to low oxidative stress. As reported, oxidative stress in BM is mediated by the activation of purinergic signaling, which is triggered by the elevated level of extracellular adenosine triphosphate (eATP) and by the activation of the complement cascade (ComC). In the current work, we noticed that BM lineage negative cells (lin-) isolated from C3-KO mice display several mitochondrial defects reflected by an impaired ability to adapt to oxidative stress. In contrast, C5-KO-derived BM cells show a high level of adaptation to this challenge. To support this data, C3-KO BM lin- cells were highly responsive to eATP stimulation, which correlates with enhanced levels of reactive oxygen species (ROS) generation and more efficient activation of intracellular Nlrp3 inflammasome. We conclude that the enhanced sensitivity of C3-KO mice cells to oxidative stress and better activation of the Nox2-ROS-Nlrp3 inflammasome signaling axis explains the molecular level differences in trafficking between C3- and C5-deficient HSPCs.

Analysis of the Respiratory Activity in the Antarctic Yeast Rhodotorula mucilaginosa M94C9 Reveals the Presence of Respiratory Supercomplexes and Alternative Elements

The respiratory activities of mitochondrial complexes I, II, and IV were analyzed in permeabilized Rhodotorula mucilaginosa cells and isolated mitochondria, and the kinetic parameters K0.5 and Vmax were obtained. No difference in substrate affinities were found between mitochondria and permeabilized cells. The activities of the components of the mitochondrial respiratory chain of the Antarctic yeast R. mucilaginosa M94C9 were identified by in-gel activity and SDS-PAGE. The mitochondria exhibited activity for the classical components of the electron transport chain (Complexes I, II, III, and IV), and supercomplexes were formed by a combination of the respiratory complexes I, III, and IV. Unfortunately, the activities of the monomeric and dimeric forms of the F1F0-ATP synthase were not revealed by the in-gel assay, but the two forms of the ATP synthase were visualized in the SDS-PAGE. Furthermore, two alternative pathways for the oxidation of cytosolic NADH were identified: the alternative NADH dehydrogenase and the glycerol-3-phosphate dehydrogenase. In addition, an NADPH dehydrogenase and a lactate cytochrome b2 dehydrogenase were found. The residual respiratory activity following cyanide addition suggests the presence of an alternative oxidase in cells.

Spastin regulates ER-mitochondrial contact sites and mitochondrial homeostasis

Mitochondria-endoplasmic reticulum (ER) contact sites (MERCs) emerged to play critical roles in numerous cellular processes, and their dysregulation has been associated to neurodegenerative disorders. Mutations in the SPG4 gene coding for spastin are among the main causes of hereditary spastic paraplegia (HSP). Spastin binds and severs microtubules, and the long isoform of this protein, namely M1, spans the outer leaflet of ER membrane where it interacts with other ER-HSP proteins. Here, we showed that overexpressed M1 spastin localizes in ER-mitochondria intersections and that endogenous spastin accumulates in MERCs. We demonstrated in different cellular models that downregulation of spastin enhances the number of MERCs, alters mitochondrial morphology, and impairs ER and mitochondrial calcium homeostasis. These effects are associated with reduced mitochondrial membrane potential, oxygen species levels, and oxidative metabolism. These findings extend our knowledge on the role of spastin in the ER and suggest MERCs deregulation as potential causes of SPG4-HSP disease.

Troxerutin Delays Skin Keratinocyte Senescence Induced by Ionizing Radiation Both In Vitro and In Vivo

BACKGROUNDS

With the increasing demand for beauty and a healthy lifespan, studies regarding anti-skin aging have drawn much more attention than ever before. Skin cellular senescence, the primary cause of skin aging, is characterized by a cell cycle arrest in proliferating cells along with a senescence-associated secretory phenotype (SASP), which can be triggered by various internal or external stimuli.

AIMS

Recent studies have made significant progress in the fields of anti-senescence and anti-aging. However, little is known about the roles and functions of natural compounds, particularly flavonoids, in skin cellular senescence studies.

METHODS

In this study, using strategies including ionizing radiation (IR), senescence-associated β galactosidase assay (SA-β-Gal), immunofluorescence (IF), flow cytometry, PCR array, as well as in vivo experiments, we investigated the effects and roles of troxerutin (Trx), a natural flavonoid, in skin keratinocyte senescence.

RESULTS

We found that Trx delays skin keratinocyte senescence induced by IR. Mechanistically, Trx protects the skin keratinocyte cells from senescence by alleviating reactive oxygen species (ROS) accumulation, mitochondrial dysfunction, and DNA damage caused by IR. In addition, Trx was also proved to relieve skin senescence and SASP secretion in vivo induced by IR stimulation.

CONCLUSIONS

Altogether, our findings pointed to a new function of Trx in delaying stress-induced skin keratinocyte senescence, and should thus provide theoretical foundations for exploring novel strategies against skin aging.

Senescence Rejuvenation through Reduction in Mitochondrial Reactive Oxygen Species Generation by Polygonum cuspidatum Extract: In Vitro Evidence

Oxidative stress caused by reactive oxygen species (ROS) is one of the major causes of senescence. Strategies to reduce ROS are known to be important factors in reversing senescence, but effective strategies have not been found. In this study, we screened substances commonly used as cosmetic additives to find substances with antioxidant effects. Polygonum cuspidatum (P. cuspidatum) extract significantly reduced ROS levels in senescent cells. A novel mechanism was discovered in which P. cuspidatum extract reduced ROS, a byproduct of inefficient oxidative phosphorylation (OXPHOS), by increasing OXPHOS efficiency. The reduction in ROS by P. cuspidatum extract restored senescence-associated phenotypes and enhanced skin protection. Then, we identified polydatin as the active ingredient of P. cuspidatum extract that exhibited antioxidant effects. Polydatin, which contains stilbenoid polyphenols that act as singlet oxygen scavengers through redox reactions, increased OXPHOS efficiency and subsequently restored senescence-associated phenotypes. In summary, our data confirmed the effects of P. cuspidatum extract on senescence rejuvenation and skin protection through ROS reduction. This novel finding may be used as a treatment in senescence rejuvenation in clinical and cosmetic fields.

An evolving roadmap: using mitochondrial physiology to help guide conservation efforts

The crucial role of aerobic energy production in sustaining eukaryotic life positions mitochondrial processes as key determinants of an animal's ability to withstand unpredictable environments. The advent of new techniques facilitating the measurement of mitochondrial function offers an increasingly promising tool for conservation approaches. Herein, we synthesize the current knowledge on the links between mitochondrial bioenergetics, ecophysiology and local adaptation, expanding them to the wider conservation physiology field. We discuss recent findings linking cellular bioenergetics to whole-animal fitness, in the current context of climate change. We summarize topics, questions, methods, pitfalls and caveats to help provide a comprehensive roadmap for studying mitochondria from a conservation perspective. Our overall aim is to help guide conservation in natural populations, outlining the methods and techniques that could be most useful to assess mitochondrial function in the field.

Purpurin ameliorated neuropathic allodynia and hyperalgesia by modulating neuronal mitochondrial bioenergetics and redox status in type 1 diabetic mice

A substantial proportion of diabetic patients suffer a debilitating and persistent pain state, known as peripheral painful neuropathy that necessitates improved therapy or antidote. Purpurin, a natural anthraquinone compound from Rubia tinctorum L., has been reported to possess antidepressant activity in preclinical studies. As antidepressants have been typically used as standard agents against persistent neuropathic pain, this study aimed to probe the effect of purpurin on neuropathic pain associated with streptozotocin-induced type 1 diabetes in male C57BL6J mice. The Hargreaves test and the von Frey test were used to assess the pain-like behaviors, shown as heat hyperalgesia and mechanical allodynia respectively. Chronic treatment of diabetic mice with purpurin not only ameliorated the established symptoms of heat hyperalgesia and mechanical allodynia, but also arrested the development of these pain states given preemptively at low doses. Although purpurin treatment hardly impacted on metabolic disturbance in diabetic mice, it ameliorated exacerbated oxidative stress in pain-associated tissues, improved mitochondrial bioenergetics in dorsal root ganglion neurons and restored nerve conduction velocity in sciatic nerves. Notably, the analgesic actions of purpurin were modified by pharmacologically manipulating redox status and mitochondrial bioenergetics. These findings unveil the analgesic activity of purpurin, an effect that is causally associated with its bioenergetics-enhancing and antioxidant effects, in mice with type 1 diabetes.

ER Stress and Mitochondrial Perturbations Regulate Cell Death in Retinal Detachment: Exploring the Role of HIF1α

Purpose

Retinal detachment (RD) leads to photoreceptor (PR) hypoxia due to separation from the retinal pigment epithelium (RPE). Hypoxia stabilizes retinal hypoxia-inducible factor 1-alpha (HIF1α), crucial for PR survival during RD. This study explores the regulatory role of HIF1α in PR cell survival pathways during RD.

Methods

Experimental RD was created in C57BL/6J and HIF1αΔrod mice by injecting 1% hyaluronic acid into the subretinal space. The 661W photoreceptor cells were exposed to hypoxic conditions. Markers of endoplasmic reticulum stress (ERS), mitophagy, and accumulation of polyubiquinated proteins were evaluated using RT-PCR and western blot analyses. Cell death of PR cells was quantified using trypan blue exclusion assay and TUNEL staining. Retinal cell death was assessed using a DNA fragmentation assay.

Results

In C57BL/6J mice and 661W cells, there were increases in HIF1α protein levels: 2.2-fold after RD (P = 0.04) and threefold after hypoxia (P = 0.057). Both the in vivo and in vitro RD models showed increased protein expression of ERS markers (including BIP, CHOP, and IRE1α), mitophagy markers (Parkin, PINK, and FUNDC1), and polyubiquitinated proteins. In 661W cells, hypoxia resulted in a loss of mitochondrial membrane potential, an increase in mitochondrial reactive oxygen species, and a decrease in intracellular adenosine triphosphate levels. Lack of HIF1α in rods blocked the upregulation of mitophagy markers after RD.

Conclusions

RD results in the activation of ERS, mitophagy, mitochondrial dysfunction, and accumulation of polyubiquitinated proteins. Results suggest a role for HIF1α in activation of the mitophagy pathway after RD, which may serve to protect the PR cells.

The mode of action of different organochlorine pesticides families in mammalians

Organochlorine pesticides (OCPs) show differences in their chemical structure, mechanism of toxicity, and target organisms. However, OCPs also have some common characteristics such as high persistence in the environment, bioaccumulation, and toxicity which lead to health issues. Nowadays, the toxicity of OCPs is well known, but we still do not know all the specific molecular mechanisms leading to their toxicity in mammalians. Therefore, this review aims to collect data about the mode of action of various classes of OCPs, highlighting their differences and common behavioural reactions in the human and animal body. To discuss the OCPs molecular pathways and fate in different systems of the body, three organochlorine insecticides were selected (Dichlorodiphenyltrichloroethane, Hexachlorocyclohexane and Chlordecone), regarding to their widespread use, with consequent effects on the ecosystem and human health. Their common biological responses at the molecular scale and their different interactions in human and animal bodies were highlighted and presented.

Targeting Mitochondrial Dysfunction for the Prevention and Treatment of Metabolic Disease by Bioactive Food Components

Dysfunctional mitochondria have been linked to the pathogenesis of obesity-associated metabolic diseases. Excessive energy intake impairs mitochondrial biogenesis and function, decreasing adenosine-5'-triphosphate production and negatively impacting metabolically active tissues such as adipose tissue, skeletal muscle, and the liver. Compromised mitochondrial function disturbs lipid metabolism and increases reactive oxygen species production in these tissues, contributing to the development of insulin resistance, type 2 diabetes, and non-alcoholic fatty liver disease. Recent studies have demonstrated the therapeutic potential of bioactive food components, such as resveratrol, quercetin, coenzyme Q10, curcumin, and astaxanthin, by enhancing mitochondrial function. This review provides an overview of the current understanding of how these bioactive compounds ameliorate mitochondrial dysfunction to mitigate obesity-associated metabolic diseases.