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Simple Summary: Our recent findings unveil a potential game-changer in cancer therapy. We have discovered that synthetic CB1 cannabinoids, specifically AM-404, arvanil, and olvanil, can surreptitiously orchestrate tunneling nanotubes, enhance cell viability, and promote scratch wound migration and epithelial–mesenchymal transition (EMT) in pancreatic PANC-1 and colorectal SW-620 cancer cells. Metastasizing cancer cells surreptitiously can adapt to metabolic activity during their invasion. By initiating their communications for invasion, cancer cells can reprogram their cellular activities to initiate their proliferation and migration and uniquely counteract metabolic stress during their progression. During this reprogramming process, cancer cells' metabolism and other cellular activities are integrated and mutually regulated by tunneling nanotube communications to alter their specific metabolic functional drivers of tumor growth and progression. Here, we investigated the in vitro effects of the synthetic CB1 cannabinoids AM-404, arvanil, and olvanil on human pancreatic PANC-1 and colorectal SW-620 cancer cell lines to understand further cellular behaviors and the potential risks of their use in cancer therapy. For the first time, the synthetic CB1 cannabinoids AM-404, arvanil, and olvanil significantly altered cancer cells in forming missile-like shapes to induce tunneling nanotube (TNT) communications in PANC-1 cells. Oseltamivir phosphate (OP) significantly prevented TNT formation. To assess the key survival pathways critical for pancreatic cancer progression, we used the AlamarBlue assay to determine synthetic CB1 cannabinoids to induce the cell's metabolic viability drivers to stage migratory intercellular communication. The synthetic CB1 cannabinoids significantly increased cell viability compared to the untreated control for PANC-1 and SW-620 cells, and this response was significantly reduced with the NMBR inhibitor BIM-23127, neuraminidase-1 inhibitor OP, and MMP-9 inhibitor (MMP-9i). CB1 cannabinoids also significantly increased N-cadherin and decreased E-cadherin EMT markers compared to the untreated controls, inducing the process of metastatic phenotype for invasion. BIM-23127, MMP9i, and OP significantly inhibited CB1 agonist-induced NFκB-dependent secretory alkaline phosphatase (SEAP) activity. To confirm this concept, we investigated the migratory invasiveness of PANC-1 and SW-620 cancer cells treated with the synthetic CB1 cannabinoids AM-404, arvanil, and olvanil in a scratch wound assay. CB1 cannabinoids significantly induced the rate of migration and invasiveness of PANC-1 cancer cells, whereas they had minimal effect on the rate of migration of already metastatic SW-620 cancer cells. Interestingly, olvanil-treated SW-620 cells significantly enhanced the migration rate and invasiveness of these cells. The data support the cellular and molecular mechanisms of the synthetic CB1 cannabinoids, orchestrating intercellular conduits to enhance metabolic drivers to stage migratory intercellular communication in pancreatic cancer cells. [ABSTRACT FROM AUTHOR]

An emerging theme in Parkinsons disease (PD) is the propagation of α-synuclein pathology as the disease progresses. Research involving the injection of preformed α-synuclein fibrils (PFFs) in animal models has recapitulated the pathological spread observed in PD patients. At the cellular and molecular levels, this intercellular spread requires the translocation of α-synuclein across various membrane barriers. Recent studies have identified subcellular organelles and protein machineries that facilitate these processes. In this review, we discuss the proposed pathways for α-synuclein intercellular transmission, including unconventional secretion, receptor-mediated uptake, endosome escape and nanotube-mediated transfer. In addition, we advocate for a rigorous examination of the evidence for the localization of α-synuclein in extracellular vesicles.

An emerging theme in Parkinson's disease (PD) is the propagation of α-synuclein pathology as the disease progresses. Research involving the injection of preformed α-synuclein fibrils (PFFs) in animal models has recapitulated the pathological spread observed in PD patients. At the cellular and molecular levels, this intercellular spread requires the translocation of α-synuclein across various membrane barriers. Recent studies have identified subcellular organelles and protein machineries that facilitate these processes. In this review, we discuss the proposed pathways for α-synuclein intercellular transmission, including unconventional secretion, receptor-mediated uptake, endosome escape and nanotube-mediated transfer. In addition, we advocate for a rigorous examination of the evidence for the localization of α-synuclein in extracellular vesicles. [ABSTRACT FROM AUTHOR]

Tunneling nanotubes (TNTs) are fine, nanometer-sized membrane connections between distant cells that provide an efficient communication tool for cellular organization. TNTs are thought to play a critical role in cellular behavior, particularly in cancer cells. The treatment of aggressive cancers such as glioblastoma remains challenging due to their high potential for developing therapy resistance, high infiltration rates, uncontrolled cell growth, and other aggressive features. A better understanding of the cellular organization via cellular communication through TNTs could help to find new therapeutic approaches. In this study, we investigate the properties of TNTs in two glioblastoma cell lines, U87 MG and LN229, including measurements of their diameter by high-resolution live-cell stimulated emission depletion (STED) microscopy and an analysis of their length, morphology, lifetime, and formation by live-cell confocal microscopy. In addition, we discuss how these fine compounds can ideally be studied microscopically. In particular, we show which membrane-labeling method is suitable for studying TNTs in glioblastoma cells and demonstrate that live-cell studies should be preferred to explore the role of TNTs in cellular behavior. Our observations on TNT formation in glioblastoma cells suggest that TNTs could be involved in cell migration and serve as guidance. [ABSTRACT FROM AUTHOR]

BACKGROUND: Mitochondrial dysfunction leads to cellular senescence and apoptosis, exacerbating tissue damage. Intercellular mitochondrial transfer in injured cells restores mitochondrial function, offering potential therapeutic strategies for mitochondria-related diseases.OBJECTIVE: To review the effects and regulatory mechanisms of intercellular mitochondrial transfer.METHODS: A comprehensive literature search was conducted on mitochondrial transfer between cells in the CNKI and PubMed databases from 2014 to 2024.The Chinese and English search terms used were “mitochondrial transfer, tunneling nanotubes, gap junctions, microvesicles, cell fusion.” Eventually, a total of 74 articles were analyzed.RESULTS AND CONCLUSION: (1) The present review provides a comprehensive overview of the four principal mechanisms underlying mitochondrial transfer between cells, encompassing tunneling nanotubes, gap junctions, cell fusion, and microvesicles. (2) This article provides a comprehensive analysis of the pivotal roles played by intercellular mitochondrial transfer, encompassing material exchange, transmission of information, enhancement of host cell mitochondrial function, attenuation of oxidative stress, augmentation of cellular proliferation activity, anti-inflammatory effects, and anti-aging properties. (3) The article provides a comprehensive overview of the main regulatory mechanisms involved in cell mitochondria transfer. These include the promotion of tunneling nanotube formation and mitochondrial transfer by Miro 1, dependence of tunneling nanotubes-mediated mitochondrial transfer on host cell cyclic ADP ribose hydrolase expression, induction of tunneling nanotube formation in an oxidative stress environment, Ca2+-dependent gap junctions, influence of Cx43 on gap junction formation, contribution of Ras1 and actin activation to cell fusion, and involvement of actin and Rab6 in the regulation of mitochondrial exocytosis,activation of actin and NAD+-CD38-cADPR-Ca2+ signaling pathways for promoting mitochondrial entry. (4) The transfer of mitochondria occurs via tunneling nanotubes, gap junctions, microvesicles, and cell fusion under the influence of cell signaling proteins, proteins associated with cellular dynamics, and oxidative stress. (5) Mitochondrial transfer plays a pivotal role in facilitating both material and information exchange between cells, thereby intimately linking to the onset and progression of diseases, which can provide new ideas for the treatment of mitochondria-related diseases. However, further investigations are warranted to unravel the effects and regulatory mechanisms of intercellular mitochondrial transfer. [ABSTRACT FROM AUTHOR]

Cancer-associated fibroblasts (CAFs) have distinct roles within the tumor microenvironment, which can impact the mode and efficacy of tumor cell migration. CAFs are known to increase invasion of less-aggressive breast cancer cells through matrix remodeling and leader-follower dynamics. Here, we demonstrate that CAFs communicate with breast cancer cells through the formation of contact-dependent tunneling nanotubes (TNTs), which allow for the exchange of cargo between cell types. CAF mitochondria are an integral cargo component and are sufficient to increase the 3D migration of cancer cells. This cargo transfer results in an increase inmitochondrial ATP production in cancer cells, whereas it has a negligible impact on glycolytic ATP production. Manually increasing mitochondrial oxidative phosphorylation (OXPHOS) by providing extra substrates for OXPHOS fails to enhance cancer cell migration unless glycolysis is maintained at a constant level. Together, these data indicate that tumor-stromal cell crosstalk via TNTs and the associated metabolic symbiosis is a finely controlled mechanism by which tumor cells co-opt their microenvironment to promote cancer progression and may become a potential therapeutic target. [ABSTRACT FROM AUTHOR]

The prognosis of patients with multiple myeloma (MM) has improved dramatically with the introduction of new therapeutic drugs, but the disease eventually becomes drug-resistant, following an intractable and incurable course. A myeloma niche (MM niche) develops in the bone marrow microenvironment and plays an important role in the drug resistance mechanism of MM. In particular, adhesion between MM cells and bone marrow stromal cells mediated by adhesion molecules induces cell adhesion-mediated drug resistance (CAM-DR). Analyses of the role of mitochondria in cancer cells, including MM cells, has revealed that the mechanism leading to drug resistance involves exchange of mitochondria between cells (mitochondrial transfer) via tunneling nanotubes (TNTs) within the MM niche. Here, we describe the discovery of these drug resistance mechanisms and the identification of promising therapeutic agents primarily targeting CAM-DR, mitochondrial transfer, and TNTs.

Abstract Background Micro RNA of Marsupenaeus japonicas has been known to promote apoptosis of tumor cells. However, the detailed mechanisms are not well understood. Results Using tomographic microscope, which can detect the internal structure of cells, we observed breast tumor cells following treatment of the miRNA. Intriguingly, we found that mitochondria migrate to an adjacent tumor cells through a tunneling nanotube. To recapitulate this process, we engineered a microfluidic device through which mitochondria were transferred. We show that this mitochondrial transfer process released endonuclease G (Endo G) into tumor cells, which we referred to herein as unsealed mitochondria. Importantly, Endo G depleted mitochondria alone did not have tumoricidal effects. Moreover, unsealed mitochondria had synergistic apoptotic effects with subtoxic dose of doxorubicin thereby mitigating cardiotoxicity. Conclusions Together, we show that the mitochondrial transfer through microfluidics can provide potential novel strategies towards tumor cell death.

Tumor cells can respond to therapeutic agents by morphologic alternations including formation of tunneling nanotubes. Using tomographic microscope, which can detect the internal structure of cells, we found that mitochondria within breast tumor cells migrate to an adjacent tumor cell through a tunneling nanotube. To investigate the relationship between mitochondria and tunneling nanotubes, mitochondria were passed through a microfluidic device that mimick tunneling nanotubes. Mitochondria, through the microfluidic device, released endonuclease G (Endo G) into adjacent tumor cells, which we referred to herein as unsealed mitochondria. Although unsealed mitochondria did not induce cell death by themselves, they induced apoptosis of tumor cells in response to caspase‐3. Importantly, Endo G‐depleted mitochondria were ineffective as lethal agents. Moreover, unsealed mitochondria had synergistic apoptotic effects with doxorubicin in further increasing tumor cell death. Thus, we show that the mitochondria of microfluidics can provide novel strategies toward tumor cell death. [ABSTRACT FROM AUTHOR]

The prognosis of patients with multiple myeloma (MM) has improved dramatically with the introduction of new therapeutic drugs, but the disease eventually becomes drug-resistant, following an intractable and incurable course. A myeloma niche (MM niche) develops in the bone marrow microenvironment and plays an important role in the drug resistance mechanism of MM. In particular, adhesion between MM cells and bone marrow stromal cells mediated by adhesion molecules induces cell adhesion-mediated drug resistance (CAM-DR). Analyses of the role of mitochondria in cancer cells, including MM cells, has revealed that the mechanism leading to drug resistance involves exchange of mitochondria between cells (mitochondrial transfer) via tunneling nanotubes (TNTs) within the MM niche. Here, we describe the discovery of these drug resistance mechanisms and the identification of promising therapeutic agents primarily targeting CAM-DR, mitochondrial transfer, and TNTs. [ABSTRACT FROM AUTHOR]

Background: Micro RNA of Marsupenaeus japonicas has been known to promote apoptosis of tumor cells. However, the detailed mechanisms are not well understood. Results: Using tomographic microscope, which can detect the internal structure of cells, we observed breast tumor cells following treatment of the miRNA. Intriguingly, we found that mitochondria migrate to an adjacent tumor cells through a tunneling nanotube. To recapitulate this process, we engineered a microfluidic device through which mitochondria were transferred. We show that this mitochondrial transfer process released endonuclease G (Endo G) into tumor cells, which we referred to herein as unsealed mitochondria. Importantly, Endo G depleted mitochondria alone did not have tumoricidal effects. Moreover, unsealed mitochondria had synergistic apoptotic effects with subtoxic dose of doxorubicin thereby mitigating cardiotoxicity. Conclusions: Together, we show that the mitochondrial transfer through microfluidics can provide potential novel strategies towards tumor cell death. [ABSTRACT FROM AUTHOR]

Tunneling nanotubes (TNTs) are thin membrane tubular structures that interconnect physically separated cells. Growing evidence indicates that TNTs play unique roles in various diseases by facilitating intercellular transfer of signaling and organelles, suggesting TNTs as a potential target for disease treatment. The efficiency of TNT-dependent communication is largely determined by the number of TNTs between cells. Though TNTs are physically fragile structures, the mechanical properties of TNTs and the determinants of their mechanical stability are still unclear. Here, using atomic force microscope (AFM) and microfluidic techniques, we investigated the mechanical behavior and abundance of TNTs in human embryonic kidney (HEK293) cells upon the application of forces. AFM measurements demonstrate that TNTs are elastic structures with an apparent spring constant of 79.1 ± 16.2 pN/μm. The stiffness and membrane tension of TNTs increase by length. TNTs that elongate slower than 0.5 μm/min display higher mechanical stability, due to the growth rate of F-actin inside TNTs being limited at 0.26 μm/min. Importantly, by disturbing the cytoskeleton, membrane, or adhesion proteins of TNTs, we found that F-actin and cadherin connection dominantly determines the tensile strength and flexural strength of TNTs respectively. It may provide new clues for screening TNT-interfering drugs that alter the stability of TNTs.

Actin-based protrusions called cytonemes are reported to function in cell communication by supporting events such as morphogen gradient establishment and pattern formation. Despite the crucial roles of cytonemes in cell signaling, the molecular mechanism for cytoneme establishment remains elusive. In this study, we showed that the leukocyte common antigen-related (LAR) receptor protein tyrosine phosphatase plays an important role in cytoneme-like protrusion formation. Overexpression of LAR in HEK293T cells induced the formation of actin-based protrusions, some of which exceeded 200 µm in length and displayed a complex morphology with branches. Upon focusing on the regulation of LAR dimerization or clustering and the resulting regulatory effects on LAR phosphatase activity, we found that longer and more branched protrusions were formed when LAR dimerization was artificially induced and when heparan sulfate was applied. Interestingly, although the truncated form of LAR lacking phosphatase-related domains promoted protrusion formation, the phosphatase-inactive forms did not show clear changes, suggesting that LAR dimerization triggers the formation of cytoneme-like protrusions in a phosphatase-independent manner. Our results thus emphasize the importance of LAR and its dimerization in cell signaling. This article has an associated First Person interview with the first author of the paper.

Mitochondrial encephalomyopathies are disorders caused by mitochondrial and nuclear DNA mutations which affect the nervous and muscular systems. Current therapies for mitochondrial encephalomyopathies are inadequate and mostly palliative. However, stem cell‐derived mitochondria transplantation has been demonstrated to play an key part in metabolic rescue, which offers great promise for mitochondrial encephalomyopathies. Here, we summarize the present status of stem cell therapy for mitochondrial encephalomyopathy and discuss mitochondrial transfer routes and the protection mechanisms of stem cells. We also identify and summarize future perspectives and challenges for the treatment of these intractable disorders based on the concept of mitochondrial transfer from stem cells. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) and Parkinson's disease (PD) are characterized by brain accumulation of aggregated amyloid-beta (Aβ) and alpha-synuclein (αSYN), respectively. In order to develop effective therapies, it is crucial to understand how the Aβ/αSYN aggregates can be cleared. Compelling data indicate that neuroinflammatory cells, including astrocytes and microglia, play a central role in the pathogenesis of AD and PD. However, how the interplay between the two cell types affects their clearing capacity and consequently the disease progression remains unclear.Methods: The aim of the present study was to investigate in which way glial crosstalk influences αSYN and Aβ pathology, focusing on accumulation and degradation. For this purpose, human-induced pluripotent cell (hiPSC)-derived astrocytes and microglia were exposed to sonicated fibrils of αSYN or Aβ and analyzed over time. The capacity of the two cell types to clear extracellular and intracellular protein aggregates when either cultured separately or in co-culture was studied using immunocytochemistry and ELISA. Moreover, the capacity of cells to interact with and process protein aggregates was tracked using time-lapse microscopy and a customized "close-culture" chamber, in which the apical surfaces of astrocyte and microglia monocultures were separated by a <1 mm space.Results: Our data show that intracellular deposits of αSYN and Aβ are significantly reduced in co-cultures of astrocytes and microglia, compared to monocultures of either cell type. Analysis of conditioned medium and imaging data from the "close-culture" chamber experiments indicate that astrocytes secrete a high proportion of their internalized protein aggregates, while microglia do not. Moreover, co-cultured astrocytes and microglia are in constant contact with each other via tunneling nanotubes and other membrane structures. Notably, our live cell imaging data demonstrate that microglia, when attached to the cell membrane of an astrocyte, can attract and clear intracellular protein deposits from the astrocyte.Conclusions: Taken together, our data demonstrate the importance of astrocyte and microglia interactions in Aβ/αSYN clearance, highlighting the relevance of glial cellular crosstalk in the progression of AD- and PD-related brain pathology. [ABSTRACT FROM AUTHOR]

An emerging theme in Parkinson's disease (PD) is the propagation of α-synuclein pathology as the disease progresses. Research involving the injection of preformed α-synuclein fibrils (PFFs) in animal models has recapitulated the pathological spread observed in PD patients. At the cellular and molecular levels, this intercellular spread requires the translocation of α-synuclein across various membrane barriers. Recent studies have identified subcellular organelles and protein machineries that facilitate these processes. In this review, we discuss the proposed pathways for α-synuclein intercellular transmission, including unconventional secretion, receptor-mediated uptake, endosome escape and nanotube-mediated transfer. In addition, we advocate for a rigorous examination of the evidence for the localization of α-synuclein in extracellular vesicles., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wu and Schekman.)

This study examines intra- and intercellular trafficking of mesoporous silica nanoparticles along microtubular highways, with an emphasis on intercellular bridges connecting interphase and telophase cells. The study of nanoparticle trafficking within and between cells during all phases of the cell cycle is relevant to payload destination and dilution, and impacts delivery of therapeutic or diagnostic agents. Super-resolution stochastic optical reconstruction and sub-airy unit image acquisition, the latter combined with Huygens deconvolution microscopy, enable single nanoparticle and microtubule resolution. Combined structural and functional data provide enhanced details on biological processes, with an example of mitotic inheritance during cancer cell trivision.

The appearance of alpha-synuclein-positive inclusion bodies (Lewy bodies) and the loss of catecholaminergic neurons are the primary pathological hallmarks of Parkinson’s disease (PD). However, the dysfunction of mitochondria has long been recognized as a key component in the progression of the disease. Dysfunctional mitochondria can in turn lead to dysregulation of calcium homeostasis and, especially in dopaminergic neurons, raised mean intracellular calcium concentration. As calcium binding to alpha-synuclein is one of the important triggers of alpha-synuclein aggregation, mitochondrial dysfunction will promote inclusion body formation and disease progression. Increased reactive oxygen species (ROS) resulting from inefficiencies in the electron transport chain also contribute to the formation of alpha-synuclein aggregates and neuronal loss. Recent studies have also highlighted defects in mitochondrial clearance that lead to the accumulation of depolarized mitochondria. Transaxonal and intracytoplasmic translocation of mitochondria along the microtubule cytoskeleton may also be affected in diseased neurons. Furthermore, nanotube-mediated intercellular transfer of mitochondria has recently been reported between different cell types and may have relevance to the spread of PD pathology between adjacent brain regions. In the current review, the contributions of both intracellular and intercellular mitochondrial dynamics to the etiology of PD will be discussed.

Background: B-cell lymphoma 2 (Bcl-2), a protein involved in apoptosis, has been proven to have carcinogenic potential and is well documented. With the recent advancement in optical technology, it has become possible to observe subcellular organelles such as mitochondria in real-time without the need for staining. Consequently, we have examined the movement of mitochondria in cancer cells, correlating it with the regulation of Bcl-2., Methods: Using a tomographic microscope, which can detect the internal structure of cells, we observed lung tumor cells. Cells were exposed to a laser beam (λ = 520 nm) inclined at 45°, and holographic images were recorded up to a depth of 30 µm of reconstruction., Results: Intriguingly, lung tumor cells rapidly expelled mitochondria upon the attachment of Bcl-2 or B-cell lymphoma extra-large (Bcl-xL) inhibitors. On the other hand, we observed that tumor cells hijack mitochondria from T cells. The hijacked mitochondria were not immediately linked to tumor cell death, but they played a role in assisting granzyme B-induced tumor cell death. Due to lower levels of Bcl-2 and Bcl-xL on the mitochondria of T cells compared to lung tumor cells, immune cells depleted of Bcl-2 and Bcl-xL were co-cultured with the tumor cells., Conclusions: As a result, a more effective tumor cell death induced by granzyme B was observed. Additionally, further enhanced anticancer immune response was observed in vivo . Together, we show that modified mitochondria of T cells can provide potential novel strategies towards tumor cell death., Competing Interests: The authors declare that they have no conflict of interest., (Copyright 2024, Kim.)

The appearance of alpha-synuclein-positive inclusion bodies (Lewy bodies) and the loss of catecholaminergic neurons are the primary pathological hallmarks of Parkinson's disease (PD). However, the dysfunction of mitochondria has long been recognized as a key component in the progression of the disease. Dysfunctional mitochondria can in turn lead to dysregulation of calcium homeostasis and, especially in dopaminergic neurons, raised mean intracellular calcium concentration. As calcium binding to alpha-synuclein is one of the important triggers of alpha-synuclein aggregation, mitochondrial dysfunction will promote inclusion body formation and disease progression. Increased reactive oxygen species (ROS) resulting from inefficiencies in the electron transport chain also contribute to the formation of alpha-synuclein aggregates and neuronal loss. Recent studies have also highlighted defects in mitochondrial clearance that lead to the accumulation of depolarized mitochondria. Transaxonal and intracytoplasmic translocation of mitochondria along the microtubule cytoskeleton may also be affected in diseased neurons. Furthermore, nanotube-mediated intercellular transfer of mitochondria has recently been reported between different cell types and may have relevance to the spread of PD pathology between adjacent brain regions. In the current review, the contributions of both intracellular and intercellular mitochondrial dynamics to the etiology of PD will be discussed. [ABSTRACT FROM AUTHOR]

α-Synuclein is a soluble protein that is present in abundance in the brain, though its normal function in the healthy brain is poorly defined. Intraneuronal inclusions of α-synuclein, commonly referred to as Lewy pathology, are pathological hallmarks of a spectrum of neurodegenerative disorders referred to as α-synucleinopathies. Though α-synuclein is expressed predominantly in neurons, α-synuclein aggregates in astrocytes are a common feature in these neurodegenerative diseases. How and why α-synuclein ends up in the astrocytes and the consequences of this dysfunctional proteostasis in immune cells is a major area of research that can have far-reaching implications for future immunobiotherapies in α-synucleinopathies. Accumulation of aggregated α-synuclein can disrupt astrocyte function in general and, more importantly, can contribute to neurodegeneration in α-synucleinopathies through various pathways. Here, we summarize our current knowledge on how astrocytic α-synucleinopathy affects CNS function in health and disease and propose a model of neuroglial connectome altered by α-synuclein proteostasis that might be amenable to immune-based therapies. [ABSTRACT FROM AUTHOR]

Tunneling nanotubes (TNTs) are elastic tubular structures that physically link cells, facilitating the intercellular transfer of organelles, chemical signals, and electrical signals. Despite TNTs serving as a multifunctional pathway for cell-cell communication, the transmission of mechanical signals through TNTs and the response of TNT-connected cells to these forces remain unexplored. In this study, external mechanical forces were applied to induce TNT bending between rat kidney (NRK) cells using micromanipulation. These forces, transmitted via TNTs, induced reduced curvature of the actin cortex and increased membrane tension at the TNT-connected sites. Additionally, TNT bending results in an elevation of intracellular calcium levels in TNT-connected cells, a response attenuated by gadolinium ions, a non-selective mechanosensitive calcium channel blocker. The degree of TNT deflection positively correlated with decreased actin cortex curvature and increased calcium levels. Furthermore, stretching TNT due to the separation of TNT-connected cells resulted in decreased actin cortex curvature and increased intracellular calcium in TNT-connected cells. The levels of these cellular responses depended on the length changes of TNTs. Moreover, TNT connections influence cell migration by regulating cell rotation, which involves the activation of mechanosensitive calcium channels. In conclusion, our study revealed the transmission of mechanical signals through TNTs and the subsequent responses of TNT-connected cells, highlighting a previously unrecognized communication function of TNTs. This research provides valuable insights into the role of TNTs in long-distance intercellular mechanical signaling. • Tunneling nanotube (TNT)-transmitted forces modulate the actin cortex and membrane tension at TNT-connected sites. • TNT-induced changes in actin cortex and membrane tension activate mechanosensitive calcium channels in connected cells. • TNT connections influence cell rotation during migration involving the activation of mechanosensitive calcium channels. [ABSTRACT FROM AUTHOR]

Intra-neuronal protein aggregates made of fibrillar alpha-synuclein (α-syn) are the hallmark of Parkinson's disease (PD). With time, these aggregates spread through the brain following axonal projections. Understanding the mechanism of this spread is central to the study of the progressive nature of PD. Here we review data relevant to the uptake, transport and release of α-syn fibrils. We summarize several cell surface receptors that regulate the uptake of α-syn fibrils by neurons. The aggregates are then transported along axons, both in the anterograde and retrograde direction. The kinetics of transport suggests that they are part of the slow component b of axonal transport. Recent findings indicate that aggregated α-syn is secreted by neurons by non-canonical pathways that may implicate various molecular chaperones including USP19 and the DnaJ/Hsc70 complex. Additionally, α-syn fibrils may also be released and transmitted from neuron-to-neuron via exosomes and tunneling nanotubes. Understanding these different mechanisms and molecular players underlying α-syn spread is crucial for the development of therapies that could halt the progression of α-syn-related degenerative diseases. [ABSTRACT FROM AUTHOR]

Mitochondria are a major target in hypoxic/ischemic injury. Mitochondrial impairment increases with age leading to dysregulation of molecular pathways linked to mitochondria. The perturbation of mitochondrial homeostasis and cellular energetics worsens outcome following hypoxic-ischemic insults in elderly individuals. In response to acute injury conditions, cellular machinery relies on rapid adaptations by modulating posttranslational modifications. Therefore, post-translational regulation of molecular mediators such as hypoxia-inducible factor 1α (HIF-1α), peroxisome proliferator-activated receptor γ coactivator α (PGC-1α), c-MYC, SIRT1 and AMPK play a critical role in the control of the glycolytic-mitochondrial energy axis in response to hypoxic-ischemic conditions. The deficiency of oxygen and nutrients leads to decreased energetic reliance on mitochondria, promoting glycolysis. The combination of pseudohypoxia, declining autophagy, and dysregulation of stress responses with aging adds to impaired host response to hypoxic-ischemic injury. Furthermore, intermitochondrial signal propagation and tissue wide oscillations in mitochondrial metabolism in response to oxidative stress are emerging as vital to cellular energetics. Recently reported intercellular transport of mitochondria through tunneling nanotubes also play a role in the response to and treatments for ischemic injury. In this review we attempt to provide an overview of some of the molecular mechanisms and potential therapies involved in the alteration of cellular energetics with aging and injury with a neurobiological perspective. [ABSTRACT FROM AUTHOR]

Intracellular aggregates of the α-synuclein protein result in cell loss and dysfunction in Parkinson's disease and atypical Parkinsonism, such as multiple system atrophy and dementia with Lewy bodies. Each of these neurodegenerative conditions, known collectively as α-synucleinopathies, may be characterized by a different suite of molecular triggers that initiate pathogenesis. The mechanisms whereby α-synuclein aggregates mediate cytotoxicity also remain to be fully elucidated. However, recent studies have implicated the cell-to-cell spread of α-synuclein as the major mode of disease propagation between brain regions during disease progression. Here, we review the current evidence for different modes of α-synuclein cellular release, movement and uptake, including exocytosis, exosomes, tunneling nanotubes, glymphatic flow and endocytosis. A more detailed understanding of the major modes by which α-synuclein pathology spreads throughout the brain may provide new targets for therapies that halt the progression of disease. [ABSTRACT FROM AUTHOR]

The role of extracellular vesicles (EVs) in mediating the immunosuppressory properties of mesenchymal stem cells (MSCs) has recently attracted remarkable scientific interest. The aim of this work was to analyze the transport mechanisms of membrane and cytoplasmic components between T lymphocytes and adipose tissue-derived MSCs (AD-MSCs), by focusing on the role of distinct populations of EVs, direct cell-cell contacts, and the soluble mediators per se in modulating T lymphocyte function. We found that neither murine thymocytes and human primary T cells nor Jurkat lymphoblastoid cells incorporated appreciable amounts of MSC-derived microvesicles (MVs) or exosomes (EXOs). Moreover, these particles had no effect on the proliferation and IFN-γ production of in vitro -stimulated primary T cells. In contrast, AD-MSCs incorporated large amounts of membrane components from T cells as an intensive uptake of EXOs and MVs could be observed. Interestingly, we found a bidirectional exchange of cytoplasmic components between human AD-MSCs and primary T lymphocytes, mediated by tunneling nanotubes (TNTs) derived exclusively from the T cells. In contrast, TNTs couldn't be observed between AD-MSCs and the Jurkat cells. Our results reveal a novel and efficient way of intercellular communication between MSCs and T cells, and may help a better understanding of the immunomodulatory function of MSCs. [ABSTRACT FROM AUTHOR]

The past decade has seen an explosion of research directed toward better understanding of the mechanisms of mesenchymal stem/stromal cell (MSC) function during rescue and repair of injured organs and tissues. In addition to delineating cell-cell signaling and molecular controls for MSC differentiation, the field has made particular progress in defining several other mechanisms through which administered MSCs can promote tissue rescue/repair. These include: 1) paracrine activity that involves secretion of proteins/peptides and hormones; 2) transfer of mitochondria by way of tunneling nanotubes or microvesicles; and 3) transfer of exosomes or microvesicles containing RNA and other molecules. Improved understanding of MSC function holds great promise for the application of cell therapy and also for the development of powerful cell-derived therapeutics for regenerative medicine. Focusing on these three mechanisms, we discuss MSC-mediated effects on immune cell responses, cell survival, and fibrosis and review recent progress with MSC-based or MSC-derived therapeutics. [ABSTRACT FROM AUTHOR]

Cell-to-cell communication is a critical requirement to coordinate behaviors of the cells in a community and thereby achieve tissue homeostasis and conservation of the multicellular organisms. Tunneling nanotubes (TNTs), as a cell-to-cell communication over long distance, allow for bi- or uni-directional transfer of cellular components between cells. Identification of inducing agents and the cell and molecular mechanism underling the formation of TNTs and their structural and functional features may lead to finding new important roles for these intercellular bridges in vivo and in vitro. During the last decade, research has shown TNTs have different structural and functional properties, varying between and within cell systems. In this review, we will focus on TNTs and their cell and molecular mechanism of formation. Moreover, the latest findings into their functional roles in physiological and pathological processes, such as signal transduction, micro and nano-particles delivery, immune responses, embryogenesis, cellular reprogramming, apoptosis, cancer, and neurodegenerative diseases initiation and progression and pathogens transfer, will be discussed. [ABSTRACT FROM AUTHOR]

The tunneling nanotube (TNT) is a newly discovered, long and thin tubular structure between cells. In this study, we established a co-culture system for rat primary astrocytes and C6 glioma cells and found that TNTs formed between them. Most of the TNTs initiated from astrocytes towards C6 glioma cells. The formation of TNTs depended on p53. In addition, hydrogen peroxide increased the number of TNTs in the co-culture system. Established TNTs reduced the proliferation of C6 glioma cells. Our data suggest that TNTs between astrocytes and glioma cells facilitate substance transfer and therefore alter the properties, including the proliferation potential, of glioma cells. [ABSTRACT FROM AUTHOR]

Abstract: Lipid nanotubes interconnecting mammalian cells, sometimes referred to as tunneling nanotubes, have recently received increased attention, as their importance in intercellular transport and communication has been recognized. We present a set of microfabrication procedures for the deliberate formation of intercellular nanotube links between single mammalian cells, employing microneedle manipulation protocols, developed earlier for nanotube-vesicle networks. Cell-to-cell connections were established, and their effectiveness for intercellular transport of molecular cargo was demonstrated. We initiate transport of ions and fluorescein diphosphate, a prefluorescent enzyme substrate, between cells, and demonstrate the validity and effectiveness of artificially created nanotube connections for cell-to-cell communication. We thus provide a new experimental model for probing cell-to-cell communication, which we deem the foundation for man-made network architectures involving biological cells. This model can greatly facilitate fundamental studies of cell-to-cell communication modes, the exchange of cell constituents and components, and the dynamics of biochemical reactions in native network environments. [Copyright &y& Elsevier]

Abstract: The development of multi-cellular organisms involves a comprehensive and tightly regulated cell-to-cell communication system to coordinate the activity and behavior of individual cells. Diverse signaling pathways ranging from receptor-mediated signal transduction to contact-dependent communication via gap junctions achieve these complex interactions. In this review, we will focus on a new type of intercellular connection, the tunneling nanotube (TNT), which has been observed in many cell types in vitro and recently also in developing embryos of different species in vivo. We will summarize the latest insights into their functional roles in cell-to-cell signaling with a particular focus on the TNT-dependent electrical coupling between developing embryonic cells. Finally, potential implications of these new findings in the light of developmental processes, particularly in cell migration, will be discussed. [Copyright &y& Elsevier]

Abstract: Tunneling nanotubes (TNTs) are nanoscaled, F-actin containing membrane tubes that connect cells over several cell diameters. They facilitate the intercellular exchange of diverse components ranging from small molecules to organelles and pathogens. In conjunction with recent findings that TNT-like structures exist in tissue, they are expected to have important implications in cell-to-cell communication. In this review we will focus on a new function of TNTs, namely the transfer of electrical signals between remote cells. This electrical coupling is not only determined by the biophysical properties of the TNT, but depends on the presence of connexons interposed at the membrane interface between TNT and the connected cell. Specific features of this coupling are compared to conventional gap junction communication. Finally, we will discuss possible down-stream signaling pathways of this electrical coupling in the recipient cells and their putative effects on different physiological activities. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics. [Copyright &y& Elsevier]

Precise coordination of various cell types and tissues represents a substantial prerequisite for the development and maintenance of multicellular organisms. Therefore, eukaryotic cells have developed a variety of complex structures, including synapses or gap junctions. Recently, thin membranous channels, termed “tunnelling nanotubes,” were discovered. Tunnelling nanotubes interconnect miscellaneous animal cells and are assumed to be involved in important physiological and pathological mechanisms, such as the intercellular spread of diverse pathogens. This phenomenon shows striking similarities to plant tissues, where cells are connected via membranous channels, called plasmodesmata. Emerging evidence suggests that the discovery of tunnelling nanotubes may enforce reconsideration of previous conceptions of intercellular communication, additionally providing novel perspectives concerning early evolution of multicellular life-forms. [ABSTRACT FROM AUTHOR]

Abstract: Organelle exchange between cells via tunneling nanotubes (TNTs) is a recently described form of intercellular communication. Here, we show that the selective elimination of filopodia from PC12 cells by 350nM cytochalasin B (CytoB) blocks TNT formation but has only a weak effect on the stability of existing TNTs. Under these conditions the intercellular organelle transfer was strongly reduced, whereas endocytosis and phagocytosis were not affected. Furthermore, the transfer of organelles significantly correlated with the presence of a TNT-bridge. Thus, our data support that in PC12 cells filopodia-like protrusions are the principal precursors of TNTs and CytoB provides a valuable tool to selectively interfere with TNT-mediated cell-to-cell communication. [Copyright &y& Elsevier]