Control of stress-induced apoptosis by freezing tolerance-associated wheat proteins during cryopreservation of rat hepatocytes

Mild heat shock at 40 °C increases levels of autophagy: Role of Nrf2

The exposure to low doses of stress induces an adaptive survival response that involves the upregulation of cellular defense systems such as heat shock proteins (Hsps), anti-apoptosis proteins, and antioxidants. Exposure of cells to elevated, non-lethal temperatures (39-41 °C) is an adaptive survival response known as thermotolerance, which protects cells against subsequent lethal stress such as heat shock (>41.5 °C). However, the initiating factors in this adaptive survival response are not understood. This study aims to determine whether autophagy can be activated by heat shock at 40 °C and if this response is mediated by the transcription factor Nrf2. Thermotolerant cells, which were developed during 3 h at 40 °C, were resistant to caspase activation at 42 °C. Autophagy was activated when cells were heated from 5 to 60 min at 40 °C. Levels of acidic vesicular organelles (AVOs) and autophagy proteins Beclin-1, LC3-II/LC3-I, Atg7, Atg5, Atg12-Atg5, and p62 were increased. When Nrf2 was overexpressed or depleted in cells, levels of AVOs and autophagy proteins were higher in unstressed cells, compared to the wild type. Stress induced by mild heat shock at 40 °C further increased levels of most autophagy proteins in cells with overexpression or depletion of Nrf2. Colocalization of p62 and Keap1 occurred. When Nrf2 levels are low, activation of autophagy would likely compensate as a defense mechanism to protect cells against stress. An improved understanding of autophagy in the context of cellular responses to physiological heat shock could be useful for cancer treatment by hyperthermia and the protective role of adaptive responses against environmental stresses.

Post-thaw application of ROCK-inhibitors increases cryopreserved T-cell yield

Emerging cell-based therapies such as CAR-T (Chimeric Antigen Receptor T) cells require cryopreservation to store and deliver intact and viable cells. Conventional cryopreservation formulations use DMSO to mitigate cold-induced damage, but do not address all the biochemical damage mechanisms induced by cold stress, such as programmed cell death (apoptosis). Rho-associated protein kinases (ROCK) are a key component of apoptosis, and their activation contributes to apoptotic blebbing. Here we demonstrate that the ROCK inhibitor fasudil hydrochloride, when supplemented into the thawing medium of T-cells increases the overall yield of healthy cells. Cell yield was highest using 5 or 10% DMSO cryopreservation solutions, with lower DMSO concentrations (2.5%) leading to significant physical damage to the cells. After optimisation, the post-thaw yield of T-cells increased by approximately 20% using this inhibitor, a significant increase in the context of a therapy. Flow cytometry analysis did not show a significant reduction in the relative percentage of cell populations undergoing apoptosis, but there was a small reduction in the 8 hours following thawing. Fasudil also led to a reduction in reactive oxygen species. Addition of fasudil into the cryopreservation solution, followed by dilution (rather than washing) upon thaw also gave a 20% increase in cell yield, demonstrating how this could be deployed in a cell-therapy context, without needing to change clinical thawing routines. Overall, this shows that modulation of post-thaw biochemical pathways which lead to apoptosis (or other degradative pathways) can be effectively targeted as a strategy to increase T-cell yield and function post-thaw.

Bridging polymer chemistry and cryobiology

Polymers, especially charged polymers, are the key to a sustainable future, as they have the capability to act as alternatives to plastics, reduce the impact of global warming, and offer solutions to global environmental pollution problems. Biomaterial polymers have proven to be incredibly effective in a multitude of applications, including clinical applications. In the fields of cryobiology and cryopreservation, polymers have emerged as credible alternatives to small molecules and other compounds, yielding excellent results. This review outlines the results of research in the areas of polymer chemistry and cryobiology, which have not been discussed together previously. Herein, we explain how recent polymer research has enabled the development of polymeric cryoprotectants with novel mechanisms and the development of novel methods for the intracellular delivery of substances, such as drugs, using a cryobiological technique called the freeze-concentration effect. Our findings indicate that interdisciplinary collaboration between cryobiologists and polymer chemists has led to exciting developments that will further cell biology and medical research.

Biomolecular Pathways of Cryoinjuries in Low-Temperature Storage for Mammalian Specimens

Low-temperature preservation could effectively extend in vitro storage of biological materials due to delayed or suspended cellular metabolism and decaying as illustrated by the Arrhenius model. It is widely used as an enabling technology for a variety of biomedical applications such as cell therapeutics, assisted reproductive technologies, organ transplantation, and mRNA medicine. Although the technology to minimize cryoinjuries of mammalian specimens during preservation has been advanced substantially over past decades, mammalian specimens still suffer cryoinjuries under low-temperature conditions. Particularly, the molecular mechanisms underlying cryoinjuries are still evasive, hindering further improvement and development of preservation technologies. In this paper, we systematically recapitulate the molecular cascades of cellular injuries induced by cryopreservation, including apoptosis, necroptosis, ischemia-reperfusion injury (IRI). Therefore, this study not only summarizes the impact of low-temperature preservations on preserved cells and organs on the molecular level, but also provides a molecular basis to reduce cryoinjuries for future exploration of biopreservation methods, materials, and devices.

Regulation of endoplasmic reticulum stress by hesperetin: Focus on antitumor and cytoprotective effects

BACKGROUND

Cancer is still an all-times issue due to a large and even increasing number of deaths. Impaired genes regulating cell proliferation and apoptosis are targets for the development of novel cancer treatments.

HYPOTHESIS

Increased transcription of NADPH oxidase activator (NOXA), Bcl2-like11 (BIM), BH3-only proteins and p53 unregulated apoptosis modulator (PUMA) is caused by the imbalance between pro- and anti-apoptotic Bcl-2 proteins due to endoplasmic reticulum (ER) stress. The membranous network of ER is present in all eukaryotic cells. ER stress facilitates the interaction between Bax and PUMA, triggering the release of cytochrome C. As a main intracellular organelle, ER is responsible for translocation as well as post-translation modification and protein folding.

RESULTS

Hesperetin is a cytoprotective flavonone, which acts against ER stress and protects from cell damage induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Hesperetin inhibits lipid peroxidation induced by Fe²⁺ and l-ascorbic acid in rat brain homogenates.

CONCLUSION

This review deals with the anticancer effects of hesperetin regarding the regulation of ER stress as a principal mechanism in the pathogenesis of tumors.

Heat shock increases levels of reactive oxygen species, autophagy and apoptosis

Hyperthermia is a promising anticancer treatment used in combination with radiotherapy and chemotherapy. Temperatures above 41.5 °C are cytotoxic and hyperthermia treatments can target a localized area of the body that has been invaded by a tumor. However, non-lethal temperatures (39-41 °C) can increase cellular defenses, such as heat shock proteins. This adaptive survival response, thermotolerance, can protect cells against subsequent cytotoxic stress such as anticancer treatments and heat shock (>41.5 °C). Autophagy is another survival process that is activated by stress. This study aims to determine whether autophagy can be activated by heat shock at 42 °C, and if this response is mediated by reactive oxygen species (ROS). Autophagy was increased during shorter heating times (<60 min) at 42 °C in cells. Levels of acidic vesicular organelles (AVO) and autophagy proteins Beclin-1, LC3-II/LC-3I, Atg7 and Atg12-Atg5 were increased. Heat shock at 42 °C increased levels of ROS. Increased levels of LC3 and AVOs at 42 °C were inhibited by antioxidants. Therefore, increased autophagy during heat shock at 42 °C (<60 min) was mediated by ROS. Conversely, heat shock at 42 °C for longer times (1-3 h) caused apoptosis and activation of caspases in the mitochondrial, death receptor and endoplasmic reticulum (ER) pathways. Thermotolerant cells, which were developed at 40 °C, were resistant to activation of apoptosis at 42 °C. Autophagy inhibitors 3-methyladenine and bafilomycin sensitized cells to activation of apoptosis by heat shock (42 °C). Improved understanding of autophagy in cellular responses to heat shock could be useful for optimizing the efficacy of hyperthermia in the clinic.