An improved method for isolation of mitochondria from cell lines that enables reconstitution of calcium-dependent processes

Development of a cell-penetrating peptide-based nanocomplex for long-term delivery of intact mitochondrial DNA into epithelial cells

Gene therapy approaches for mitochondrial DNA (mtDNA)-associated damage/diseases have thus far been limited, and despite advancements in single gene therapy for mtDNA mutations and progress in mitochondrial transplantation, no method exists for restoring the entire mtDNA molecule in a clinically translatable manner. Here, we present for the first time a strategy to deliver an exogenous, fully intact, and healthy mtDNA template into cells to correct endogenous mtDNA mutations and deletions, with the potential to be developed into an efficient pan-therapy for inherited and/or acquired mtDNA disorders. More specifically, the novel therapeutic nanoparticle complex used in our study was generated by combining a cell-penetrating peptide (CPP) with purified mtDNA, in conjunction with a mitochondrial targeting reagent. The generated nanoparticle complexes were found to be taken up by cells and localized to mitochondria, with exogenous mtDNA retention/maintenance, along with mitochondrial RNA and protein production, observed in mitochondria-depleted ARPE-19 cells at least 4 weeks following a single treatment. These data demonstrate the feasibility of restoring mtDNA in cells via a CPP carrier, with the therapeutic potential to correct mtDNA damage independent of the number of gene mutations found within the mtDNA.

Hypotonic Swelling Method for the Isolation of Pure Mitochondria From Primary Human Skeletal Myoblasts for Proteomic Studies

Mitochondria play a fundamental role in energy metabolism, particularly in high-energy-demand tissues such as skeletal muscle. Understanding the proteomic composition of mitochondria in these cells is crucial for elucidating the mechanisms underlying muscle physiology and pathology. However, effective isolation of mitochondria from primary human skeletal muscle cells has been challenging due to the complex cellular architecture and the propensity for contamination with other organelles. Here, we compared four different methods to isolate mitochondria from primary human skeletal myoblasts regarding total protein yield, mitochondrial enrichment capacity and purity of the isolated fraction. We presented a modified method that combines differential centrifugation with a hypotonic swelling step and a subsequent purification process to minimise cellular contamination. We validated our method by demonstrating its ability to obtain highly pure mitochondrial fractions, as confirmed by Western Blot with mitochondrial, cytosolic and nuclear markers. We demonstrated that proteomic analysis can be performed with isolated mitochondria. Our approach provides a valuable tool for investigating mitochondrial dynamics, biogenesis and function in the context of skeletal muscle biology in health and disease. This methodological advancement opens new avenues for mitochondrial research and its implications in myopathies, sarcopenia, cachexia and metabolic disorders.

In silico directed evolution of Anabas testudineus AtMP1 antimicrobial peptide to improve in vitro anticancer activity

Various studies have demonstrated that directed evolution is a powerful tool in enhancing protein properties. In this study, directed evolution was used to enhance the efficacy of synthesised Anabas testudineus AtMP1 antimicrobial peptides (AMPs) in inhibiting the proliferation of cancer cells. The modification of antimicrobial peptides (AMPs) and prediction of peptide properties using bioinformatic tools were carried out using four databases, including ADP3, CAMP-R3, AMPfun, and ANTICP. One modified antimicrobial peptide (AMP), ATMP6 (THPPTTTTTTTTTTTTTAAPARTT), was chosen based on its projected potent anticancer effect, taking into account factors such as amino acid length, net charge, anticancer activity score, and hydrophobicity. The selected AMPs were subjected to study in deep-learning databases, namely ToxIBTL and ToxinPred2, to predict their toxicity. Furthermore, the allergic properties of these antimicrobial peptides (AMPs) were verified by utilising AllerTOP and AllergenFP. Based on the results obtained from the database study, it was projected that antimicrobial peptides (AMPs) demonstrate a lack of toxicity towards human cells that is indicative of the broader population. After 48 hours of incubation, the IC50 values of ATMP6 against the HS27 and MDA-MB-231 cell lines were found to be 48.03 ± 0.013 µg/ml and 7.52 ± 0.027 µg/ml, respectively. The IC50 values of the original peptide ATMP1 against the MDA-MB-231 and HS27 cell lines were determined to be 59.6 ± 0.14 µg/ml and 8.25 ± 0.14 µg/ml, respectively, when compared. Furthermore, the results indicated that the injection of ATMP6 induced apoptosis in the MDA-MB-231 cell lines. The present investigation has revealed new opportunities for advancing novel targeted peptide therapeutics to tackle cancer.

Extracellular Vesicle- and Mitochondria-Based Targeting of Non-Small Cell Lung Cancer Response to Radiation: Challenges and Perspectives

During the cell life cycle, extracellular vesicles (EVs) transport different cargos, including organelles, proteins, RNAs, DNAs, metabolites, etc., that influence cell proliferation and apoptosis in recipient cells. EVs from metastatic cancer cells remodel the extracellular matrix and cells of the tumor microenvironment (TME), promoting tumor invasion and metastatic niche preparation. Although the process is not fully understood, evidence suggests that EVs facilitate genetic material transfer between cells. In the context of NSCLC, EVs can mediate intercellular mitochondrial (Mt) transfer, delivering mitochondria organelle (MtO), mitochondrial DNA (mtDNA), and/or mtRNA/proteinaceous cargo signatures (MtS) through different mechanisms. On the other hand, certain populations of cancer cells can hijack the MtO from TME cells mainly by using tunneling nanotubes (TNTs). This transfer aids in restoring mitochondrial function, benefiting benign cells with impaired metabolism and enabling restoration of their metabolic activity. However, the impact of transferring mitochondria versus transplanting intact mitochondrial organelles in cancer remains uncertain and the subject of debate. Some studies suggest that EV-mediated mitochondria delivery to cancer cells can impact how cancer responds to radiation. It might make the cancer more resistant or more sensitive to radiation. In our review, we aimed to point out the current controversy surrounding experimental data and to highlight new paradigm-shifting modalities in radiation therapy that could potentially overcome cancer resistance mechanisms in NSCLC.

Hippocampal mitochondrial Ca++ in experimentally induced Alzheimer's disease, link to calpains and impact of vitamin D3 supplementation

Vitamin D impact on hippocampal mitochondrial Ca++ and calpains was not previously investigated in Alzheimer's disease (AD). The current work aimed to assess the alteration in hippocampal mitochondrial Ca++, ATP & ADP and hippocampal calpains' level in (AlCl3)-induced AD model, and the effect of 2 regimens of vitamin D supplementation on these alterations.

METHODS

Forty male Wistar rats were randomized into 4 groups; control, AD (AlCl3100 mg/kg, p.o. daily for 42 days), AD and vitamin D co-treated group (AlCl3 as in AD group with vitamin D3 400 IU/kg/day, p.o. for 42 days) and AD, followed by vitamin D3 group (AlCl3 was given as in AD group for 42 days, then vitamin D3 for two weeks). AD was assessed by hippocampal levels of Aβ42, p-tau and spatial memory assessment in Morris water maze. Hippocampal mitochondrial Ca++, ATP and ADP levels besides to calpain-1 & 2 and cytochrome C were assessed in addition to CA1 histological examination.

RESULTS

AD animals showed impaired mitochondrial function as denoted by high Ca++ and decreased ATP and ADP and elevated calpain-1 & 2 and cytochrome C. Hippocampal CA1 region showed increased degenerated neurons and reduced thickness of its pyramidal layer. Vitamin D administration minimized the hippocampal mitochondrial impairement induced by AD and mitigated histological alterations even when supplemented post AD establishment.

CONCLUSION

Vitamin D administration to AD rats breaks the deleterious loop in the hippocampus that involves increased Ca++, calpain activation, mitochondrial failure, neuronal degeneration and AD disease progression.

In silico identification and in vitro assessment of a potential anti-breast cancer activity of antimicrobial peptide retrieved from the ATMP1 Anabas testudineus fish peptide

A previous study has shown that synthetic antimicrobial peptides (AMPs) derived from Anabas testudineus (ATMP1) could in-vitro inhibit the progression of breast cancer cell lines. In this study, we are interested in studying altered versions of previous synthetic AMPs to gain some insight into the peptides functions. The AMPs were altered and subjected to bioinformatics prediction using four databases (ADP3, CAMP-R3, AMPfun, and ANTICP) to select the highest anticancer activity. The bioinformatics in silico analysis led to the selection of two AMPs, which are ATMP5 (THPPTTTTTTTTTTTYTAAPATTT) and ATMP6 (THPPTTTTTTTTTTTTTAAPARTT). The in silico analysis predicted that ATMP5 and ATMP6 have anticancer activity and lead to cell death. The ATMP5 and ATMP6 were submitted to deep learning databases (ToxIBTL and ToxinPred2) to predict the toxicity of the peptides and to (AllerTOP & AllergenFP) check the allergenicity. The results of databases indicated that AMPs are non-toxic to normal human cells and allergic to human immunoglobulin. The bioinformatics findings led to select the highest active peptide ATMP5, which was synthesised and applied for in-vitro experiments using cytotoxicity assay MTT Assay, apoptosis detection using the Annexin V FTIC-A assay, and gene expression using Apoptosis PCR Array to evaluate the AMP's anticancer activity. The antimicrobial activity is approved by the disc diffusion method. The in-vitro experiments analysis showed that ATMP5 had the activity to inhibit the growth of the breast cancer cell line (MDA-MB-231) after 48 h and managed to arrest the cell cycle of the MDA-MB-231, apoptosis induction, and overexpression of the p53 by interaction with the related apoptotic genes. This research opened up new opportunities for developing potential and selective anticancer agents relying on antimicrobial peptide properties.

Mechanical characterization of isolated mitochondria under conditions of oxidative stress

Mechanical properties have been proven to be a pivotal parameter to enhance our understanding of living systems. While research during the last decades focused on cells and tissues, little is known about the role of organelle mechanics in cell function. Here, mitochondria are of specific interest due to their involvement in numerous physiological and pathological processes, e.g., in the production and homeostasis of reactive oxygen species (ROS). Using real-time fluorescence and deformability cytometry, we present a microfluidic technology that is capable to determine the mechanical properties of individual mitochondria at a throughput exceeding 100 organelles per second. Our data on several thousands of viable mitochondria isolated from rat C6 glial cells yield a homogenous population with a median deformation that scales with the applied hydrodynamic stress. In two proof-of-principle studies, we investigated the impact of exogenously and endogenously produced ROS on mitochondria mechanics. Exposing C6 cells to hydrogen peroxide (H₂O₂) triggers superoxide production and leads to a reduction in mitochondria size while deformation is increased. In a second study, we focused on the knockout of tafazzin, which has been associated with impaired remodeling of the mitochondrial membrane and elevated levels of ROS. Interestingly, our results reveal the same mechanical alterations as observed after the exposure to H₂O₂, which points to a unified biophysical mechanism of how mitochondria respond to the presence of oxidative stress. In summary, we introduce high-throughput mechanical phenotyping into the field of organelle biology with potential applications for understanding sub-cellular dynamics that have not been accessible before.

Mitochondrial C3a Receptor Activation in Oxidatively Stressed Epithelial Cells Reduces Mitochondrial Respiration and Metabolism

Complement component 3 fragment C3a is an anaphylatoxin involved in promoting cellular responses important in immune response and host defense. Its receptor (C3a receptor, C3aR) is distributed on the plasma membrane; however, lysosomal localization in immune cells has been reported. Oxidative stress increases intracellular reactive oxygen species (ROS), and ROS activate complement signaling in immune cells and metabolic reprogramming. Here we tested oxidative stress and intracellular complement in mitochondrial dysfunction in RPE cells using high resolution live-cell imaging, and metabolism analysis in isolated mitochondria using Seahorse technology. While C3aR levels were unaffected by oxidative stress, its cell membrane levels decreased and mitochondrial (mt) localization increased. Trafficking was dependent on endocytosis, utilizing endosomal-to-mitochondrial cargo transfer. H₂O₂-treatment also increased C3a-mtC3aR co-localization dose-dependently. In isolated mitochondria from H₂O₂-treated cells C3a increased mitochondrial Ca²⁺ uptake, that could be inhibited by C3aR antagonism (SB290157), mitochondrial Ca²⁺ uniporter blocker (Ru360), and Gαi-protein inhibition (pertussis toxin, PTX); and inhibited mitochondrial repiration in an SB290157- and PTX-dependent manner. Specifically, mtC3aR activation inhibited state III ADP-driven respiration and maximal respiratory capacity. Mitochondria from control cells did not respond to C3a. Furthermore, transmitochondrial cybrid ARPE-19 cells harboring J haplogroup mitochondria that confer risk for age-related macular degeneration, showed high levels of mtC3aR and reduced ATP production upon C3a stimulation. Our findings suggest that oxidative stress increases mtC3aR, leading to altered mitochondrial calcium uptake and ATP production. These studies will have important implication in our understanding on the balance of extra- and intracellular complement signaling in controlling cellular health and dysfunction.

Isolation of Mitochondria from Retinal Pigment Epithelial Cell Cultures and an Application of High-Resolution Respirometric Assay (XFe96 Seahorse Assay)

Intracellular Ca²⁺ is strictly regulated to maintain optimal levels for function of cellular organelles as well as mitochondrial respiratory signaling at the tricarboxylic acid cycle and electron transport chain level. Optimal Ca²⁺ concentration for these processes vary between cell types. Furthermore, exposure of mitochondria to sustained, elevated levels of Ca²⁺ induces mitochondrial Ca²⁺ overload and damage to mitochondrial oxidative phosphorylation and ATP production. Isolated mitochondria are widely used to study mitochondrial physiology and drug effects on mitochondrial metabolism and respiratory function. However, isolated mitochondria are easily damaged during the mitochondrial isolation process. The present article describes a mitochondrial isolation method using Ca²⁺-chelation to minimize mitochondrial damage. We follow up the isolation process with an application that requires an optimized buffer Ca²⁺ concentration: the characterization of their respiratory function using a high-resolution respirometric assay.

p53-Dependent pathway and the opening of mPTP mediate the apoptosis of co-cultured Sertoli-germ cells induced by microcystin-LR

Microcystin-LR (MC-LR), a potent endotoxin, can induce reproductive toxicity. In order to investigate the role and mechanisms of apoptosis (p53-dependent and mitochondrial pathways) of germ cells induced by MC-LR, the co-cultured primary Sertoli-germ cells from Sprague-Dawley rats were used for the experiments. Expression levels of proteins, genes, and mitochondrial membrane potential (MMP) were obtained after exposing co-cultured Sertoli-germ cells to MC-LR with or without the addition of the p53 inhibitor, pifithrin-α (PFT-α), and MMP inhibitor, cyclosporin A (CsA). Results indicated that MC-LR could activate p53-dependent pathway-associated proteins in Sertoli-germ cells, leading to a decrease in MMP (indicating the opening of mitochondrial permeability transition pore [mPTP] and the release of Cytochrome-c [Cyt-c]) from the mitochondria into the cytoplasm and eventually the induction of apoptosis. PFT-α inhibited the expression ofp53, ameliorated the MMP of the co-cultured Sertoli-germ cells, and prevented the release of Cyt-c from the mitochondria into the cytoplasm, which reduces the occurrence of apoptosis. Similarly, the decreased release of Cyt-c from the mitochondria into the cytoplasm and the declined level of apoptosis in Sertoli-germ cells induced by MC-LR were observed after the addition of CsA. These results indicated that the apoptosis of the co-cultured Sertoli-germ cells induced by MC-LR was mediated by the p53-dependent pathway, with the involvement of the opening of mPTP.