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The purpose of this study was to investigate the effects that photobiomodulation therapy might produce in cells, in particular, related to their structure. Thus, this paper presents the results of morphological changes in fibroblasts following low-intensity light illumination. Mouse fibroblasts were grown on glass coverslips on either 4 kPa or 16 kPa gels, to mimic normal tissue conditions. Cells were photo-irradiated with laser light at either 625 nm or 808 nm (total energies ranging from 34 to 47 J). Cells were fixed at 5 min, 1 h, or 24 h after photo-irradiation, stained for both actin filaments and the cell nucleus, and imaged by confocal microscopy. A non-light exposed group was also imaged. A detailed analysis of the images demonstrated that the total polymerized actin and number of actin filaments decrease, while the nucleus area increases in treated cells shortly after photo-irradiation, regardless of substrate and wavelength. This experiment indicated that photobiomodulation therapy could change the morphological properties of cells and affect their cytoskeleton. Further investigations are required to determine the specific mechanisms involved and how this phenomenon is related to the photobiomodulation therapy mechanisms of action.

An optogenetic strategy allowing light-mediated recruitment of distinct cytoskeletal motor proteins to specific organelles is established; this technique enabled rapid and reversible activation or inhibition of the transport of organelles such as peroxisomes, recycling endosomes and mitochondria with high spatiotemporal accuracy, and the approach was also applied to primary neurons to demonstrate optical control of axonal growth by recycling endosome repositioning. Light-touch manipulation of cellular organelles How does the position of organelles within a cell influence cellular functions? In the absence of strategies to control intracellular organelle positioning with spatiotemporal precision, it has been difficult to answer this question. Lukas Kapitein and colleagues have developed an optogenetic strategy, based on light-mediated recruitment of distinct cytoskeletal motor proteins to their specific cargo organelles that allows such cellular manipulations. Using the new technique it is possible to rapidly and reversibly activate or inhibit the transport of specific organelles and demonstrate local modulation of organelle distributions — including peroxisomes, recycling endosomes and mitochondria — with high spatiotemporal accuracy. The authors demonstrate local modulation of organelle distributions for peroxisomes, recycling endosomes and mitochondria. They also applied this approach in primary neurons to establish optical control of axon outgrowth. Proper positioning of organelles by cytoskeleton-based motor proteins underlies cellular events such as signalling, polarization and growth 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . For many organelles, however, the precise connection between position and function has remained unclear, because strategies to control intracellular organelle positioning with spatiotemporal precision are lacking. Here we establish optical control of intracellular transport by using light-sensitive heterodimerization to recruit specific cytoskeletal motor proteins (kinesin, dynein or myosin) to selected cargoes. We demonstrate that the motility of peroxisomes, recycling endosomes and mitochondria can be locally and repeatedly induced or stopped, allowing rapid organelle repositioning. We applied this approach in primary rat hippocampal neurons to test how local positioning of recycling endosomes contributes to axon outgrowth and found that dynein-driven removal of endosomes from axonal growth cones reversibly suppressed axon growth, whereas kinesin-driven endosome enrichment enhanced growth. Our strategy for optogenetic control of organelle positioning will be widely applicable to explore site-specific organelle functions in different model systems.

Photothermal cancer therapy has attracted considerable interest for cancer treatment in recent years, but the effective photothermal agents remain to be explored before this strategy can be applied clinically. In this study, we therefore develop flower-like molybdenum disulfide (MoS 2 ) nanoflakes and investigate their potential for photothermal ablation of cancer cells. MoS 2 nanoflakes are synthesized via a facile hydrothermal method and then modified with lipoic acid-terminated polyethylene glycol (LA-PEG), endowing the obtained nanoflakes with high colloidal stability and very low cytotoxicity. Upon irradiation with near infrared (NIR) laser at 808 nm, the nanoflakes showed powerful ability of inducing higher temperature, good photothermal stability and high photothermal conversion efficiency. The in vitro photothermal effects of MoS 2 -PEG nanoflakes with different concentrations were also evaluated under various power densities of NIR 808-nm laser irradiation and the results indicated that an effective photothermal killing of cancer cells could be achieved by a low concentration of nanoflakes under a low power NIR 808-nm laser irradiation. Furthermore, cancer cell in vivo could be efficiently destroyed via the photothermal effect of MoS 2 -PEG nanoflakes under the irradiation. These results thus suggest that the MoS 2 -PEG nanoflakes would be as promising photothermal agents for future photothermal cancer therapy.

The effect of terahertz (THz) radiation on deep tissues of human body has been considered negligible due to strong absorption by water molecules. However, we observed that the energy of THz pulses transmits a millimeter thick in the aqueous solution, possibly as a shockwave, and demolishes actin filaments. Collapse of actin filament induced by THz irradiation was also observed in the living cells under an aqueous medium. We also confirmed that the viability of the cell was not affected under the exposure of THz pulses. The potential of THz waves as an invasive method to alter protein structure in the living cells is demonstrated.

Cell biology's leading lights Green fluorescent protein and other genetically encodable optical reporters have revolutionized the study of cell function. Now Levskaya et al . describe a technology that adds a new dimension to cell biology by incorporating light-activated proteins from plants into mammalian cell signalling systems, leading to cells whose morphology and behaviour can be controlled by light. The system uses a reversible protein–protein interaction module from the Arabidopsis phytochrome-signalling network to reversibly translocate activators of the Rho-family GTPases to the plasma membrane. In principle, this advance makes it possible to design a variety of light-programmable reagents for a new generation of perturbative cell biology experiments. The use of light to precisely control cellular behaviour is a challenge that has only recently begun to be addressed. Here, a genetically encoded light-control system is demonstrated in mammalian cells. Based on a reversible protein–protein interaction from the phytochrome signalling network of Arabidopsis thaliana , the system is used to reversibly translocate activators of the Rho-family GTPases to the plasma membrane with high temporal and spatial resolution. Genetically encodable optical reporters, such as green fluorescent protein, have revolutionized the observation and measurement of cellular states. However, the inverse challenge of using light to control precisely cellular behaviour has only recently begun to be addressed; semi-synthetic chromophore-tethered receptors 1 and naturally occurring channel rhodopsins have been used to perturb directly neuronal networks 2 , 3 . The difficulty of engineering light-sensitive proteins remains a significant impediment to the optical control of most cell-biological processes. Here we demonstrate the use of a new genetically encoded light-control system based on an optimized, reversible protein–protein interaction from the phytochrome signalling network of Arabidopsis thaliana . Because protein–protein interactions are one of the most general currencies of cellular information, this system can, in principle, be generically used to control diverse functions. Here we show that this system can be used to translocate target proteins precisely and reversibly to the membrane with micrometre spatial resolution and at the second timescale. We show that light-gated translocation of the upstream activators of Rho-family GTPases, which control the actin cytoskeleton, can be used to precisely reshape and direct the cell morphology of mammalian cells. The light-gated protein–protein interaction that has been optimized here should be useful for the design of diverse light-programmable reagents, potentially enabling a new generation of perturbative, quantitative experiments in cell biology.

The biological effects of circularly polarized light on living cells are considered to be negligibly weak. Here, we show that the differentiation of neural stem cells into neurons can be accelerated by circularly polarized photons when DNA-bridged chiral assemblies of gold nanoparticles are entangled with the cells’ cytoskeletal fibres. By using cell-culture experiments and plasmonic-force calculations, we demonstrate that the nanoparticle assemblies exert a circularly-polarized-light-dependent force on the cytoskeleton, and that the light-induced periodic mechanical deformation of actin nanofibres with a frequency of 50 Hz stimulates the differentiation of neural stem cells into the neuronal phenotype. When implanted in the hippocampus of a mouse model of Alzheimer’s disease, neural stem cells illuminated following a polarity-optimized protocol reduced the formation of amyloid plaques by more than 70%. Our findings suggest that circularly polarized light can guide cellular development for biomedical use. Chiral photons can accelerate the differentiation of neural stem cells into neurons in vitro and in vivo when DNA-bridged chiral assemblies of gold nanoparticles are tightly entangled with the cells’ cytoskeletal fibres.

Low-intensity pulsed ultrasound (LIPUS) is a widely used non-invasive approach with therapeutic purposes since it provides physical stimulation with minimal thermal effects. The skin epithelium is the first barrier of the human body that interfaces with LIPUS and is subjected to the highest intensity. Little is known about the impact of LIPUS on the skin surface. This work investigates the biological effects of one-hour exposure to 1 MHz LIPUS on human keratinocytes HaCaT and tumoral SK-MEL-28 skin cells. Specifically, we evaluated the cellular state immediately after LIPUS treatment by analyzing cytogenetic endpoints and the response of cytoskeleton and cell junction proteins. Herein we demonstrate that LIPUS induces genomic damage as shown by an increase of chromosome malsegregation and a consequent decrease of cellular proliferation. The mechanical stimulus produced by LIPUS is also transmitted to the cytoskeletal compartment, inducing the expression and re-organization of junction proteins (i.e., E-cadherin and Desmosomes) and intermediate filaments (i.e., F-actin and Cytokeratins) with impact on cell morphology and cell adhesion. These in vitro results highlight the different outcomes following the cytogenetic damage and the resilience response exerted by the cytoskeleton upon mechanical stress, laying the foundation for future in vivo investigations.

Neoplastic transformation is accompanied by critical changes in cell mechanical properties, including reduced cell elasticity. By leveraging such mechanical flaw, exposure to low intensity therapeutic ultrasounds (LITUS) has been proposed as a tool for selective killing of cancer cells. Here, we have developed dynamic models to address the morpho-mechanical differences between prostate cancer and non-tumoral counterparts and studied the effects of LITUS on cell viability. We show that LITUS exposure (1 MHz) leads to cancer-selective cytoskeletal disruption associated to loss of nuclear envelope integrity, DNA damage marked by γH2AX and 53BP1 foci, and release of DNA into the cytosol with activation of the cGAS–STING signaling cascade. Mechanistically, the LINC complex, which connects the cytoskeleton to nucleoskeleton and chromosomes, is critical to mediate nuclear rupture triggered by LITUS. Accordingly, genetic ablation of the LINC component SUN2 tuned down DNA damage and cGAS–STING signaling while the inactivation of the endosomal sorting complex (ESCRT), required for the transport machinery that preserves the nuclear envelope integrity, enhanced cell killing by LITUS. In conclusion, LITUS induce cancer cell DNA damage and an innate immune response, this suggesting LITUS treatment as a mechanobiology-driven anti-neoplastic strategy.

Although cancer immunotherapy is effective against hematological malignancies, it is less effective against solid tumors due in part to significant metabolic challenges present in the tumor microenvironment (TME), where infiltrated CD8 + T cells face fierce competition with cancer cells for limited nutrients. Strong metabolic suppression in the TME is often associated with impaired T cell recruitment to the tumor site and hyporesponsive effector function via T cell exhaustion. Increasing evidence suggests that mitochondria play a key role in CD8 + T cell activation, effector function, and persistence in tumors. In this study, we showed that there was an increase in overall mitochondrial function, including mitochondrial mass and membrane potential, during both mouse and human CD8 + T cell activation. CD8 + T cell mitochondrial membrane potential was closely correlated with granzyme B and IFN-γ production, demonstrating the significance of mitochondria in effector T cell function. Additionally, activated CD8 + T cells that migrate on ICAM-1 and CXCL12 consumed significantly more oxygen than stationary CD8 + T cells. Inhibition of mitochondrial respiration decreased the velocity of CD8 + T cell migration, indicating the importance of mitochondrial metabolism in CD8 + T cell migration. Remote optical stimulation of CD8 + T cells that express our newly developed “OptoMito-On” successfully enhanced mitochondrial ATP production and improved overall CD8 + T cell migration and effector function. Our study provides new insight into the effect of the mitochondrial membrane potential on CD8 + T cell effector function and demonstrates the development of a novel optogenetic technique to remotely control T cell metabolism and effector function at the target tumor site with outstanding specificity and temporospatial resolution.

Epidemiological studies on workers employed at the Mayak plutonium enrichment plant have demonstrated an association between external gamma ray exposure and an elevated risk of ischemic heart disease (IHD). In a previous study using fresh-frozen post mortem samples of the cardiac left ventricle of Mayak workers and non-irradiated controls, we observed radiation-induced alterations in the heart proteome, mainly downregulation of mitochondrial and structural proteins. As the control group available at that time was younger than the irradiated group, we could not exclude age as a confounding factor. To address this issue, we have now expanded our study to investigate additional samples using archival formalin-fixed paraffin-embedded (FFPE) tissue. Importantly, the control group studied here is older than the occupationally exposed (>500 mGy) group. Label-free quantitative proteomics analysis showed that proteins involved in the lipid metabolism, sirtuin signaling, mitochondrial function, cytoskeletal organization, and antioxidant defense were the most affected. A histopathological analysis elucidated large foci of fibrotic tissue, myocardial lipomatosis and lymphocytic infiltrations in the irradiated samples. These data highlight the suitability of FFPE material for proteomics analysis. The study confirms the previous results emphasizing the role of adverse metabolic changes in the radiation-associated IHD. Most importantly, it excludes age at the time of death as a confounding factor.