Cell membrane disruption stimulates cAMP and Ca2+ signaling to potentiate cell membrane resealing in neighboring cells

Repair of traumatic lesions to the plasmalemma of neurons and other cells: Commonalities, conflicts, and controversies

Neuroscientists and Cell Biologists have known for many decades that eukaryotic cells, including neurons, are surrounded by a plasmalemma/axolemma consisting of a phospholipid bilayer that regulates trans-membrane diffusion of ions (including calcium) and other substances. Cells often incur plasmalemmal damage via traumatic injury and various diseases. If the damaged plasmalemma is not rapidly repaired within minutes, activation of apoptotic pathways by calcium influx often results in cell death. We review publications reporting what is less-well known (and not yet covered in neuroscience or cell biology textbooks): that calcium influx at the lesion sites ranging from small nm-sized holes to complete axonal transection activates parallel biochemical pathways that induce vesicles/membrane-bound structures to migrate and interact to restore original barrier properties and eventual reestablishment of the plasmalemma. We assess the reliability of, and problems with, various measures (e.g., membrane voltage, input resistance, current flow, tracer dyes, confocal microscopy, transmission and scanning electron microscopy) used individually and in combination to assess plasmalemmal sealing in various cell types (e.g., invertebrate giant axons, oocytes, hippocampal and other mammalian neurons). We identify controversies such as plug versus patch hypotheses that attempt to account for currently available data on the subcellular mechanisms of plasmalemmal repair/sealing. We describe current research gaps and potential future developments, such as much more extensive correlations of biochemical/biophysical measures with sub-cellular micromorphology. We compare and contrast naturally occurring sealing with recently-discovered artificially-induced plasmalemmal sealing by polyethylene glycol (PEG) that bypasses all natural pathways for membrane repair. We assess other recent developments such as adaptive membrane responses in neighboring cells following injury to an adjacent cell. Finally, we speculate how a better understanding of the mechanisms involved in natural and artificial plasmalemmal sealing is needed to develop better clinical treatments for muscular dystrophies, stroke and other ischemic conditions, and various cancers.

The cellular response to plasma membrane disruption for nanomaterial delivery

Delivery of nanomaterials into cells is of interest for fundamental cell biological research as well as for therapeutic and diagnostic purposes. One way of doing so is by physically disrupting the plasma membrane (PM). Several methods that exploit electrical, mechanical or optical cues have been conceived to temporarily disrupt the PM for intracellular delivery, with variable effects on cell viability. However, apart from acute cytotoxicity, subtler effects on cell physiology may occur as well. Their nature and timing vary with the severity of the insult and the efficiency of repair, but some may provoke permanent phenotypic alterations. With the growing palette of nanoscale delivery methods and applications, comes a need for an in-depth understanding of this cellular response. In this review, we summarize current knowledge about the chronology of cellular events that take place upon PM injury inflicted by different delivery methods. We also elaborate on their significance for cell homeostasis and cell fate. Based on the crucial nodes that govern cell fitness and functionality, we give directions for fine-tuning nano-delivery conditions.

Cellular Signalling and Photobiomodulation in Chronic Wound Repair

Photobiomodulation (PBM) imparts therapeutically significant benefits in the healing of chronic wounds. Chronic wounds develop when the stages of wound healing fail to progress in a timely and orderly frame, and without an established functional and structural outcome. Therapeutic benefits associated with PBM include augmenting tissue regeneration and repair, mitigating inflammation, relieving pain, and reducing oxidative stress. PBM stimulates the mitochondria, resulting in an increase in adenosine triphosphate (ATP) production and the downstream release of growth factors. The binding of growth factors to cell surface receptors induces signalling pathways that transmit signals to the nucleus for the transcription of genes for increased cellular proliferation, viability, and migration in numerous cell types, including stem cells and fibroblasts. Over the past few years, significant advances have been made in understanding how PBM regulates numerous signalling pathways implicated in chronic wound repair. This review highlights the significant role of PBM in the activation of several cell signalling pathways involved in wound healing.

Plasma membrane disruption (PMD) formation and repair in mechanosensitive tissues

Mammalian cells employ an array of biological mechanisms to detect and respond to mechanical loading in their environment. One such mechanism is the formation of plasma membrane disruptions (PMD), which foster a molecular flux across cell membranes that promotes tissue adaptation. Repair of PMD through an orchestrated activity of molecular machinery is critical for cell survival, and the rate of PMD repair can affect downstream cellular signaling. PMD have been observed to influence the mechanical behavior of skin, alveolar, and gut epithelial cells, aortic endothelial cells, corneal keratocytes and epithelial cells, cardiac and skeletal muscle myocytes, neurons, and most recently, bone cells including osteoblasts, periodontal ligament cells, and osteocytes. PMD are therefore positioned to affect the physiological behavior of a wide range of vertebrate organ systems including skeletal and cardiac muscle, skin, eyes, the gastrointestinal tract, the vasculature, the respiratory system, and the skeleton. The purpose of this review is to describe the processes of PMD formation and repair across these mechanosensitive tissues, with a particular emphasis on comparing and contrasting repair mechanisms and downstream signaling to better understand the role of PMD in skeletal mechanobiology. The implications of PMD-related mechanisms for disease and potential therapeutic applications are also explored.

Plasma membrane repair involvement in parasitic and other pathogen infections

Intracellular pathogens depend on specific mechanisms to be able to gain entry and survive into their host cells. For this, they subvert pathways involved in physiological cellular processes. Here we are going to focus on how two protozoan parasites, Trypanosoma cruzi and Leishmania sp, which may cause severe diseases in humans, use plasma membrane repair (PMR) mechanisms to gain entry in host intracellular environment. T. cruzi is the causative agent of Chagas disease, a disease originally endemic of central and South America, but that has become widespread around the globe. T. cruzi is able to invade any nucleated cell, but muscle cells are usually the main targets during chronic disease. During host cell contact, the parasite interacts with proteins at the host cell surface and may cause damage to their membrane, which has been shown to be responsible for inducing intracellular calcium increase and PMR-related events that culminate with parasite internalization. The same was recently observed for Leishmania sp, when infecting nonprofessional phagocytic cells, such as fibroblasts. Other pathogens, such as viruses or bacteria may also use PMR-related events for invasion and vacuole escape/maturation. In some cases, PMR may also be responsible to modulate pathogen intracellular development. These other PMR roles in pathogen infections will also be briefly discussed.

In silico studies reveal RSc1154 and RhlE as temperature-related pathogenic proteins of Ralstonia solanacearum

This study aimed to explore the temperature-related pathogenic mechanism of Ralstonia solanacearum infection in tomato (Lycopersicon esculentum Mill.). Based on bioinformatics analysis of microarray dataset (GSE33657), the co-differentially expressed genes (co-DEGs) ribonucleic acids were identified in R. solanacearum GMI1000-infected L. esculentum Mill., which was cultured at 20°C and 28°C, in rich medium containing casamino acids, peptone, and glucose (CPG) and planta. In total, 63 upregulated co-DEGs and 57 downregulated co-DEGs were identified between 20°C and 28°C in the CPG and planta groups. Protein-protein interaction network revealed 70 protein interaction pairs and 59 nodes. Notably, iolG, iolE, ioll and RSc1248 played critical roles in the network. The subcellular localization and functional annotation showed that the increased expressed proteins were mainly localized in the inner cell membrane, while those with decreased expression were localized in the cytoplasm. Furthermore, these proteins were mainly enriched in regulation of DNA-templated transcription. RSc1154 and RhlE were predicted to be temperature-related pathogenic genes for R. solanacearum in tomato. Furthermore, phosphorelay signal transduction system function might play an important role in R. solanacearum infection. The candidate genes were verified by quantitative real-time PCR, and the results were consistent with gene expression profile.

Signaling pathways involved in adaptive responses to cell membrane disruption

Plasma membrane disruption occurs frequently in many animal tissues. Cell membrane disruption induces not only a rapid and massive influx of Ca²⁺ into the cytosol but also an efflux or release of various signaling molecules, such as ATP, from the cytosol; in turn, these signaling molecules stimulate a variety of pathways in both wounded and non-wounded neighboring cells. These signals first trigger cell membrane repair responses in the wounded cell but then induce an adaptive response, which results in faster membrane repair in the event of future wounds in both wounded and non-wounded neighboring cells. In addition, signaling pathways stimulated by membrane disruption induce other adaptive responses, including cell survival, regeneration, migration, and proliferation. This chapter summarizes the role of intra- and intercellular signaling pathways in adaptive responses triggered by cell membrane disruption.

Transmission of Mechanical Information by Purinergic Signaling

The skeleton constantly interacts and adapts to the physical world. We have previously reported that physiologically relevant mechanical forces lead to small repairable membrane injuries in bone-forming osteoblasts, resulting in release of ATP and stimulation of purinergic (P2) calcium responses in neighboring cells. The goal of this study was to develop a theoretical model describing injury-related ATP and ADP release, their extracellular diffusion and degradation, and purinergic responses in neighboring cells. After validation using experimental data for intracellular free calcium elevations, ATP, and vesicular release after mechanical stimulation of a single osteoblast, the model was scaled to a tissue-level injury to investigate how purinergic signaling communicates information about injuries with varying geometries. We found that total ATP released, peak extracellular ATP concentration, and the ADP-mediated signaling component contributed complementary information regarding the mechanical stimulation event. The total amount of ATP released governed spatial factors, such as the maximal distance from the injury at which purinergic responses were stimulated. The peak ATP concentration reflected the severity of an individual cell injury, allowing to discriminate between minor and severe injuries that released similar amounts of ATP because of differences in injury repair, and determined temporal aspects of the response, such as signal propagation velocity. ADP-mediated signaling became relevant only in larger tissue-level injuries, conveying information about the distance to the injury site and its geometry. Thus, we identified specific features of extracellular ATP and ADP spatiotemporal signals that depend on tissue mechanoresilience and encode the severity, scope, and proximity of the mechanical stimulus.

Autocrine purinergic signaling stimulated by cell membrane disruption is involved in both cell membrane repair and adaptive response in MDCK cells

Disruption and repair of plasma membranes is normally observed in many animal tissues. Recent studies demonstrated that wounding of Madin-Darby canine kidney cells potentiates membrane repair in cells adjacent to wounded cells via paracrine purinergic signaling. The present study demonstrated that cyclic adenosine monophosphate signaling in a wounded cell was induced by autocrine purinergic signaling, and protein kinase A potentiates membrane resealing for repeated wounds in those cells. Furthermore, the present study revealed that an increase in the intracellular free Ca²⁺ concentration upon cell membrane disruption was not only due to Ca²⁺ influx through the wound site, but also because of autocrine purinergic signaling. Although the influx of extracellular Ca²⁺ is essential for membrane resealing, the present study suggested that an increase in the intracellular free Ca²⁺ concentration induced by autocrine signaling accelerates membrane resealing of the initial cell membrane disruption.

Cellular mechanisms and signals that coordinate plasma membrane repair

Plasma membrane forms the barrier between the cytoplasm and the environment. Cells constantly and selectively transport molecules across their plasma membrane without disrupting it. Any disruption in the plasma membrane compromises its selective permeability and is lethal, if not rapidly repaired. There is a growing understanding of the organelles, proteins, lipids, and small molecules that help cells signal and efficiently coordinate plasma membrane repair. This review aims to summarize how these subcellular responses are coordinated and how cellular signals generated due to plasma membrane injury interact with each other to spatially and temporally coordinate repair. With the involvement of calcium and redox signaling in single cell and tissue repair, we will discuss how these and other related signals extend from single cell repair to tissue level repair. These signals link repair processes that are activated immediately after plasma membrane injury with longer term processes regulating repair and regeneration of the damaged tissue. We propose that investigating cell and tissue repair as part of a continuum of wound repair mechanisms would be of value in treating degenerative diseases.