How and when to measure mitochondrial inner membrane potentials

Improvement on mitochondrial energy metabolism of Codonopsis pilosula (Franch.) Nannf. polysaccharide

Ethnopharmacological relevance

Codonopsis pilosula (Franch.) Nannf. (CP) is one of the most popular Qi-invigorating herbal medicines and has been extensively used to promote health and vitality in China for a long time. Codonopsis pilosula (Franch.) Nannf. polysaccharide (CPP) is the principal active components of CP, which is considered as the reason for CP widespread application. However, it has not been revealed that CPP exert a Qi-invigoration effect by protecting mitochondria and/or improving mitochondrial function in the existing traditional Chinese medicine theories.

Aim of the study

We extracted CPP from C. pilosula and investigated the effects of CPP on energy metabolism and mitochondrial protection.

Methods

Based on the mice chronic hypoxia model for imitating the energy deficiency state of the human body, which was administered with CPP by oral gavage daily for 10 days, mitochondrial permeability transition (MPT), lipid peroxidation product malondialdehyde (MDA) in brain, mitochondrial respiratory function, the levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in liver cells were assayed. Adenylate energy charge (AEC), total adenylate pool (TAP), ATP/ADP, and ATP/AMP ratios were calculated.

Results

CPP can inhibit the formation of MDA in mice brains, decrease oxygen consuming rate and respiratory control ratio (RCR) of liver mitochondria, increase levels of ATP, TAP and AEC in liver cells under chronic hypoxia condition.

Conclusion

CPP can possess and improve mitochondrial energy metabolism and bioenergetic levels.

KLRG1 identifies regulatory T cells with mitochondrial alterations that accumulate with aging

Recent studies using single-cell RNA sequencing technology have uncovered several subpopulations of CD4+ T cells that accumulate with aging. These age-associated T cells are emerging as relevant players in the onset of inflammaging and tissue senescence. Here, based on information provided by single-cell RNA sequencing data, we present a flow cytometry panel that allows the identification of age-associated T cell subsets in systematic larger analysis in mice. We use this panel to evaluate at the single-cell level mitochondrial and senescence marks in the different age-associated CD4+ T cell subpopulations. Our analysis identifies a subpopulation of regulatory T (Treg) cells that is characterized by the extracellular expression of the co-inhibitory molecule killer cell lectin-like receptor subfamily G member 1 (KLRG1) and accumulates with aging in humans and mice. KLRG1-expressing Treg cells display senescence features such as mitochondrial alterations, increased expression of cell-cycle regulators and genomic DNA damage. Functionally, KLRG1+ Treg cells show a reduced suppressive activity in vivo accompanied by a pro-inflammatory phenotype.

Exploring the cytotoxic effects of bioactive compounds from Alcea rosea against stem cell driven colon carcinogenesis

Seven compounds were isolated from ethyl acetate extract of Alcea rosea and were examined for their cytotoxicity against HCT116, HT29 and SW480 colon cancer cells. It was found that two compounds (C4 and C5) exhibited strong anti-colon cancer activities. These two compounds were used to study their properties that include MTT activity (with IC50 of C4 as 74.71, 129.0 and 131.4 µg/ml in HCT116, HT29 and SW480 respectively, whereas IC50 of C5 as 128.1, 168.4 and 225.8 µg/ml in HCT116, HT29 and SW480 cells respectively), colony formation activity, wound healing activity, spheroid formation activity, DAPI-PI staining, acridine-orange and ethidium bromide staining, ROS measurement, and rhodamine-123 staining in both HCT116 and HT29 colon cancer cells. Both the compounds showed significant increase in apoptosis as visualized by 4',6-diamidino-2-phenylindol/propidium iodide (DAPI-PI) and acridine orange/ethidium bromide (AO/EtBr) staining. The induction of apoptosis was further confirmed by the expressions of cleaved PARP and caspase 3. ROS generation and its effect on MMP were measured by staining cells with Dichloro-dihydro-fluorescein diacetate (DCFH-DA) and Rhodamine. Expression levels of EMT associated markers like Cyclin D1, Slug, Vimentin, and E-Cadherin were also studied. Both the compounds down regulate protein levels of Slug, Cyclin D1, and Vimentin in a concentration-dependent manner. Eeffect of C4 and C5 compounds on key signaling protein like Wnt3a, Notch1, and Shh were evaluated. Additionally, mRNA levels of these genes were also analyzed. C4 exhibited the best binding affinity when docked with Shh and Wnt3a and Notch1. Similarly, C5 exhibited - 8.8, -8.2 and - 7.6 kcal⋅mol- 1 with Shh, Wnt3a and Notch1. The present findings provide insight and immense scientific support and integrity to a piece of indigenous knowledge. However, validation in living organisms is necessary before progressing to clinical trials and advancing it into a marketable pharmaceutical product.

Textbook oxidative phosphorylation needs to be rewritten

Oxidative phosphorylation (OxPhos) is the energy-transfer process that generates most of our ATP, fueled by proton and electrical gradients across the inner mitochondrial membrane. A new surprising finding by Hernansanz-Agustín et al. demonstrates that between one-third and half of this gradient is attributable to Na+, transported in exchange for protons within complex I.

The Effects of Circadian Rhythm on Lead-Induced Toxicity in the DBC1.2 Olfactory Dark Basal Cell Line

BACKGROUND/OBJECTIVES

This study evaluated changes in circadian clock genes and mitochondrial function in a lead (Pb)-induced toxicity model of an olfactory epithelial cell line.

METHODS

The DBC1.2 olfactory dark basal cell line was used. Dexamethasone shock was used to reset the circadian clock 24 h (Group 1) and 36 h (Group 2) after seeding. Then, 60 h after seeding, the cells were treated with or without Pb (II) nitrate in HEPES buffer for 1 h. Mitochondrial function and cell viability were evaluated 84 h after seeding.

RESULTS

Mitochondrial function under Pb exposure was significantly impaired in Group 1 compared with Group 2. Cell numbers and viability did not significantly differ between groups. The mitochondrial membrane potential was significantly higher in Group 1 than Group 2, both without and with Pb exposure.

CONCLUSIONS

The circadian rhythm can alter the sensitivity to Pb-induced toxicity and mitochondrial damage in olfactory cells.

Approaches to investigate tissue-resident innate lymphocytes metabolism at the single-cell level

Tissue-resident innate immune cells have important functions in both homeostasis and pathological states. Despite advances in the field, analyzing the metabolism of tissue-resident innate lymphocytes is still challenging. The small number of tissue-resident innate lymphocytes such as ILC, NK, iNKT and γδ T cells poses additional obstacles in their metabolic studies. In this review, we summarize the current understanding of innate lymphocyte metabolism and discuss potential pitfalls associated with the current methodology relying predominantly on in vitro cultured cells or bulk-level comparison. Meanwhile, we also summarize and advocate for the development and adoption of single-cell metabolic assays to accurately profile the metabolism of tissue-resident immune cells directly ex vivo.

Monitoring retro-translocation of proteins from the mitochondrial intermembrane space

Mitochondria play multiple essential roles in eukaryotic cells. To perform their functions, mitochondria require an adequate supply of externally produced proteins and an intact two-membrane structure. The structure of mitochondrial membranes separates these organelles from their cytosolic environment, with proteins that make up the mitochondrial proteome either being embedded into or enveloped by these membranes. From the experimental point of view, the structural properties of mitochondria contribute to the relative ease of isolating these organelles from other cellular components. The ability to isolate intact mitochondria and analyze them in a well-controlled environment opens up the possibility of tracking any proteins that enter or escape the membrane-formed enclosure. This chapter discusses assays that monitor the movement of proteins out of mitochondria through intact membranes. These protocols provide insight into the mechanisms behind mitochondrial protein quality control. It was discovered that the retro-translocation of IMS proteins regulates the protein content of this specific sub-compartment of the organelle. Additionally, proteins can move out of the mitochondria to resolve failed import events. Assays based on isolated mitochondria precisely tackle such intricate 'dance' of proteins crossing mitochondrial membranes during import and export, maintaining the dynamics of the organellar proteome.

Mitochondrial redox state, bioenergetics, and calcium transport in caloric restriction: A metabolic nexus

Mitochondria congregate central reactions in energy metabolism, many of which involve electron transfer. As such, they are expected to both respond to changes in nutrient supply and demand and also provide signals that integrate energy metabolism intracellularly. In this review, we discuss how mitochondrial bioenergetics and reactive oxygen species production is impacted by dietary interventions that change nutrient availability and impact on aging, such as calorie restriction. We also discuss how dietary interventions alter mitochondrial Ca2+ transport, regulating both mitochondrial and cytosolic processes modulated by this ion. Overall, a plethora of literature data support the idea that mitochondrial oxidants and calcium transport act as integrating signals coordinating the response to changes in nutritional supply and demand in cells, tissues, and animals.

Understanding mitochondrial potassium channels: 33 years after discovery

Mitochondrial investigations have extended beyond their traditional functions, covering areas such as ATP synthesis and metabolism. Mitochondria are now implicated in new functional areas such as cytoprotection, cellular senescence, tumor function and inflammation. The basis of these new areas still relies on fundamental biochemical/biophysical mitochondrial functions such as synthesis of reactive oxygen species, mitochondrial membrane potential, and the integrity of the inner mitochondrial membrane i.e., the passage of various molecules through the mitochondrial membranes. In this view transport of potassium cations, known as the potassium cycle, plays an important role. It is believed that K+ influx is mediated by various potassium channels present in the inner mitochondrial membrane. In this article, we present an overview of the key findings and characteristics of mitochondrial potassium channels derived from research of many groups conducted over the past 33 years. We propose a list of six fundamental observations and most important ideas dealing with mitochondrial potassium channels. We also discuss the contemporary challenges and future prospects associated with research on mitochondrial potassium channels.