Mechanism Of Phagocytosis Research Articles

Rab5 regulates the antimicrobial phagocytosis of hemocytes through class B scavenger receptor in Procambarus clarkii

The crucial involvement of Rab5 in regulating phagocytosis through mediating receptors, such as the Class B scavenger receptor (SRB), has been documented in higher animal species. However, little is known about the molecular mechanisms of Rab5-mediated phagocytosis in invertebrates. The present study aims to investigate whether the phagocytic function of hemocytes in Procambarus clarkii can be regulated by Rab5 through SRB. We first cloned the open reading frame of SRB from P. clarkii (defined as PcSRB), encoding a putative protein containing a typical CD36 domain. PcSRB was widely expressed in all tested tissues of P. clarkii and induced by viral and bacterial stimulation. The extracellular segment of PcSRB (PcSRB-EX) can agglutinate as well as bind with both Gram-positive (G+) and Gram-negative (G−) bacteria. Knockdown of PcSRB resulted in down-regulation of the phagocytic capacity and bactericidal activity against Aeromonas hydrophila, along with impaired expression of several phagocytosis-related genes and antimicrobial peptide (AMP) genes. PcSRB interference also affected the mRNA expression level of Tolls, indicating that PcSRB might function as a recognition receptor or co-receptor in the Toll signaling pathway. Furthermore, Rab5 interference significantly impaired the expression of PcSRB at both gene and protein levels, which confirmed its significant regulatory effect on PcSRB. Subsequently, we observed a significant decrease in the phagocytic activity and bacteria clearance of hemocytes when Rab5 and PcSRB were simultaneously knocked down. Additionally, there was a notable down-regulation in the expression levels of genes related to phagocytosis and AMPs. Overall, these findings provide preliminary evidence that Rab5 mediates PcSRB to influence the phagocytosis of P. clarkii hemocytes against A. hydrophila.

Lipid mediators in neutrophil biology: inflammation, resolution and beyond.

Acute inflammation is the body's first defense in response to pathogens or injury. Failure to efficiently resolve the inflammatory insult can severely affect tissue homeostasis, leading to chronic inflammation. Neutrophils play a pivotal role in eradicating infectious pathogens, orchestrating the initiation and resolution of acute inflammation, and maintaining physiological functions. The resolution of inflammation is a highly orchestrated biochemical process, partially modulated by a novel class of endogenous lipid mediators known as specialized pro-resolving mediators (SPMs). SPMs mediate their potent bioactions via activating specific cell-surface G protein-coupled receptors (GPCR). This review focuses on recent advances in understanding the multifaceted functions of SPMs, detailing their roles in expediting neutrophil apoptosis, promoting clearance by macrophages, regulating their excessive infiltration at inflammation sites, orchestrating bone marrow deployment, also enhances neutrophil phagocytosis and tissue repair mechanisms under both physiological and pathological conditions. We also focus on the novel role of SPMs in regulating bone marrow neutrophil functions, differentiation, and highlight open questions about SPMs' functions in neutrophil heterogeneity. SPMs play a pivotal role in mitigating excessive neutrophil infiltration and hyperactivity within pathological milieus, notably in conditions such as sepsis, cardiovascular disease, ischemic events, and cancer. This significant function highlights SPMs as promising therapeutic agents in the management of both acute and chronic inflammatory disorders.

Inhibition of ADORA3 promotes microglial phagocytosis and alleviates chronic ischemic white matter injury.

Adenosine A3 receptor (ADORA3) belongs to the adenosine receptor families and the role of ADORA3 in vascular dementia (VaD) is largely unexplored. The present study sought to determine the therapeutic role of ADORA3 antagonist in a mouse model of VaD. The GSE122063 dataset was selected to screen the differential expression genes and pathways between VaD patients and controls. A mouse model of bilateral carotid artery stenosis (BCAS) was established. The cognitive functions were examined by the novel object recognition test, Y maze test, and fear of conditioning test. The white matter injury (WMI) was examined by 9.4 T MRI, western blot, and immunofluorescence staining. The mechanisms of ADORA3-regulated phagocytosis by microglia were examined using qPCR, western blot, dual immunofluorescence staining, and flow cytometry. The expression of ADORA3 was elevated in brain tissues of VaD patients and ADORA3 was indicated as a key gene for VaD in the GSE122063. In BCAS mice, the expression of ADORA3 was predominantly elevated in microglia in the corpus callosum. ADORA3 antagonist promotes microglial phagocytosis to myelin debris by facilitating cAMP/PKA/p-CREB pathway and thereby ameliorates WMI and cognitive impairment in BCAS mice. The therapeutic effect of ADORA3 antagonist was partially reversed by the inhibition of the cAMP/PKA pathway. ADORA3 antagonist alleviates chronic ischemic WMI by modulating myelin clearance of microglia, which may be a potential therapeutic target for the treatment of VaD.

Abstract 3612: Preclinical & clinical activity of autologous mRNA engineered chimeric antigen receptor monocytes for targeted cancer immunotherapy

Abstract Introduction: The tumor microenvironment (TME) is a dynamic and multifaceted system that comprises largely myeloid lineage immune cells including neutrophils, macrophages, dendritic cells and monocytes. When activated, these cells are can effectively infiltrate TME and orchestrate anti-tumor immune response. Reprogramming myeloid cells by arming them with a tumor specific chimeric antigen receptor (CAR) presents an attractive strategy to overcome current limitations in solid tumor treatment. In this study, we present the isolation and mRNA-based engineering of monocytes with chimeric antigen receptors (CARs), followed by their in vivo application for cancer treatment in rodent models and in human T cell lymphoma patients. Results: Engineered monocytes demonstrated the abilities to infiltrate the TME, undergo activation, and differentiate into macrophages and dendritic cells. Upon CAR activation, these reprogrammed myeloid cells utilized both direct and indirect mechanisms to eliminate tumor cells. This included direct tumor cell killing through phagocytosis and TNF-associated mechanisms. Furthermore, engineered monocytes exhibited the capacity to recruit natural killer (NK) cells and T cells to the TME. In the case of T cells, these engineered myeloid cells facilitated the presentation of neoantigens to T cells and stimulate an adaptive immune response. In patients with T cell lymphoma, treatment with engineered monocytes expressing a CAR targeting CD5 exhibited a favorable safety profile and was associated with TME remodeling, expansion of novel T cell clones, and promising survival outcomes. Conclusions: These findings underscore the potential of reprogrammed myeloid cells as a novel avenue for cancer immunotherapy, offering hope for improved treatments and outcomes in the fight against cancer. Citation Format: Yuxiao Wang, Michele Gerber, Michael Gorgievski, Josephine D'Alessandro, Neha Diwanji, Ronald Vale, Siddhartha Mukherjee, Daniel Getts. Preclinical & clinical activity of autologous mRNA engineered chimeric antigen receptor monocytes for targeted cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3612.

Shape-dependent cellular uptake of iron oxide nanorods: mechanisms of endocytosis and implications on cell labeling and cellular delivery.

The effects of nanoparticle morphology, especially size and shape, on their interactions with cells are of great interest in understanding the fate of nanoparticles in biological systems and designing them for biomedical applications. While size and shape-dependent cell behavior, endocytosis mechanism, and subcellular distribution of nanoparticles have been investigated extensively with gold and other nanoparticles, studies on iron oxide nanoparticles (IONP), one of the most promising and well-thought-of nanomaterials in biomedical applications, were limited. In this study, we synthesized oligosaccharide-coated water-soluble iron oxide nanorods (IONR) with different core sizes (nm) and different aspect ratios (i.e., length/width), such as IONR(L) at 140/6 nm and IONR(S) at 50/7 nm as well as spherical IONP (20 nm). We investigated how their sizes and shapes affect uptake mechanisms, localization, and cell viability in different cell lines. The results of transmission electron microscopy (TEM) and confocal fluorescence microscopic imaging confirmed the internalization of these nanoparticles in different types of cells and subsequent accumulation in the subcellular compartments, such as the endosomes, and into the cytosol. Specifically, IONR(L) exhibited the highest cellular uptake compared to IONR(S) and spherical IONP, 1.36-fold and 1.17-fold higher than that of spherical IONP in macrophages and pediatric brain tumor medulloblastoma cells, respectively. To examine the cellular uptake mechanisms preferred by the different IONR and IONP, we used different endocytosis inhibitors to block specific cellular internalization pathways when cells were treated with different nanoparticles. The results from these blocking experiments showed that IONR(L) enter macrophages and normal kidney cells through clathrin-mediated, dynamin-dependent, and macropinocytosis/phagocytosis pathways, while they are internalized in cancer cells primarily via clathrin/caveolae-mediated and phagocytosis mechanisms. Overall, our findings provide new insights into further development of magnetic IONR-based imaging probes and drug delivery systems for biomedical applications.

Nanomaterials in Medicine: Understanding Cellular Uptake, Localization, and Retention for Enhanced Disease Diagnosis and Therapy.

Nanomaterials (NMs) have emerged as promising tools for disease diagnosis and therapy due to their unique physicochemical properties. To maximize the effectiveness and design of NMs-based medical applications, it is essential to comprehend the complex mechanisms of cellular uptake, subcellular localization, and cellular retention. This review illuminates the various pathways that NMs take to get from the extracellular environment to certain intracellular compartments by investigating the various mechanisms that underlie their interaction with cells. The cellular uptake of NMs involves complex interactions with cell membranes, encompassing endocytosis, phagocytosis, and other active transport mechanisms. Unique uptake patterns across cell types highlight the necessity for customized NMs designs. After internalization, NMs move through a variety of intracellular routes that affect where they are located subcellularly. Understanding these pathways is pivotal for enhancing the targeted delivery of therapeutic agents and imaging probes. Furthermore, the cellular retention of NMs plays a critical role in sustained therapeutic efficacy and long-term imaging capabilities. Factors influencing cellular retention include nanoparticle size, surface chemistry, and the cellular microenvironment. Strategies for prolonging cellular retention are discussed, including surface modifications and encapsulation techniques. In conclusion, a comprehensive understanding of the mechanisms governing cellular uptake, subcellular localization, and cellular retention of NMs is essential for advancing their application in disease diagnosis and therapy. This review provides insights into the intricate interplay between NMs and biological systems, offering a foundation for the rational design of next-generation nanomedicines.

An effective and robust genetic algorithm with hybrid multi-strategy and mechanism for airport gate allocation

Gate allocation is a combinatorial scheduling problem with multi-constraint and multi-objective. It is challenging to solve this problem when the size of flights increases continuously. As an adaptive technology with a random search ability, the genetic algorithm (GA) has been widely used for resource scheduling and combinatorial optimization. However, it is prone to slow convergence and falling into local optimal solutions. Therefore, an effective and robust GA based on hybrid multi-strategy of reverse learning, interval probability mutation, and phagocytosis mechanism, called RPIP-GA, is proposed to implement a new airport gate-allocation method. In the RPIP-GA, the population is divided into several subpopulations based on the fitness values of all individuals to prevent population degradation and improve population quality. The reverse learning strategy with elite retention is designed to initialize the population, expand the global search space, improve the quality of the original solution, and increase the population diversity. The phagocytosis mechanism is employed to implement a crossover operation to enhance the convergence rate and local search ability. An interval probability mutation technique is designed to improve the local search ability in the early stage and prevent falling into the local optimum in the later stage. The effectiveness of the RPIP-GA is validated using 45 complex functions selected from the benchmark functions and CEC 2017, 22 real-world engineering problems selected from CEC 2011, and an actual gate allocation problem via comparisons with the GA, PSO, GSA, DNLGSA, WMSDE, PADE, HIRCGA, and other algorithms. The experimental results show that the RPIP-GA can obtain optimal results with improved stability in most cases. The maximum allocation rate of actual airport gates reaches 98%, and the average convergence accuracy increases by 19% compared with that of the GA. The data used in the study is publicly available from the GitHub repository (https://github.com/xiaocangjiu).

Osteoimmune Properties of Mesoporous Bioactive Nanospheres: A Study on T Helper Lymphocytes.

Bioactive mesoporous glass nanospheres (nanoMBGs) charged with antiosteoporotic drugs have great potential for the treatment of osteoporosis and fracture prevention. In this scenario, cells of the immune system are essential both in the development of disease and in their potential to stimulate therapeutic effects. In the present work, we hypothesize that nanoMBGs loaded with ipriflavone can exert a positive osteoimmune effect. With this objective, we assessed the effects of non-loaded and ipriflavone-loaded nanoparticles (nanoMBGs and nanoMBG-IPs, respectively) on CD4+ Th2 lymphocytes because this kind of cell is implicated in the inhibition of osseous loss by reducing the RANKL/OPG relationship through the secretion of cytokines. The results indicate that nanoMBGs enter efficiently in CD4+ Th2 lymphocytes, mainly through phagocytosis and clathrin-dependent mechanisms, without affecting the function of these T cells or inducing inflammatory mediators or oxidative stress, thus maintaining the reparative Th2 phenotype. Furthermore, the incorporation of the anti-osteoporotic drug ipriflavone reduces the potential unwanted inflammatory response by decreasing the presence of ROS and stimulating intracellular anti-inflammatory cytokine release like IL-4. These results evidenced that nanoMBG loaded with ipriflavone exerts a positive osteoimmune effect.

Untangling the Role of TREM2 in Conjugation with Microglia in Neuronal Dysfunction: A Hypothesis on a Novel Pathway in the Pathophysiology of Alzheimer's Disease.

Alzheimer's disease (AD) is a complex neurodegenerative disorder involving heterogenous pathophysiological characteristics, which has become a challenge to therapeutics. The major pathophysiology of AD comprises amyloid-β (Aβ), tau, oxidative stress, and apoptosis. Recent studies indicate the significance of Triggering receptor expressed on myeloid cells 2 (TREM2) and its mutant variants in AD. TREM2 are the transmembrane receptors of microglial cells that performs a broad range of physiological cell processes. Phagocytosis of Aβ is one of the physiological roles of TREM2, which plays a pivotal role in AD progression. R47H, a mutant variant of TREM2, increases the risk of AD by impairing TREM2-Aβ binding. Inconclusive evidence regarding the TREM2 signaling cascade mechanism of Aβ phagocytosis motivates the current review to propose a new hypothesis. The review systematically assesses the cross talk between TREM2 and other AD pathological domains and the influence of TREM2 on amyloid and tau seeding. Disease associated microglia (DAM), a novel state of microglia with unique transcriptional and functional signatures reported in neurodegenerative conditions, also depend on the TREM2 pathway for its differentiation. DAM is suggested to have a neuroprotective role. We hypothesize that TREM2, along with its signaling adaptors and endogenous proteins, play a key role in ameliorating Aβ clearance. We indicate that TREM2 has the potential to ameliorate the Aβ burden, though with differential clearance ability and may act as a potential therapeutic target.

Apolipoprotein E Polymorphism Impacts White Matter Injury Through Microglial Phagocytosis After Experimental Subarachnoid Hemorrhage

Apolipoprotein E (apoE, protein; APOE, gene), divided into three alleles of E2, E3 and E4 in humans, is associated with the progression of white matter lesion load. However, mechanism evidence has not been reported regarding the APOE genotype in early white matter injury (WMI) under subarachnoid hemorrhage (SAH) conditions. In the present study, we investigated the effects of APOE gene polymorphisms, by constructing microglial APOE3 and APOE4-specific overexpression, on WMI and underlying mechanisms of microglia phagocytosis in a mice model of SAH. A total of 167 male C57BL/6J mice (weight 22–26 g) were used. SAH and bleeding environment were induced by endovascular perforation in vivo and oxyHb in vitro, respectively. Multi-technology approaches, including immunohistochemistry, high throughput sequencing, gene editing for adeno-associated viruses, and several molecular biotechnologies were used to validate the effects of APOE polymorphisms on microglial phagocytosis and WMI after SAH. Our results revealed that APOE4 significantly aggravated the WMI and decreased neurobehavioral function by impairing microglial phagocytosis after SAH. Indicators negatively associated with microglial phagocytosis increased like CD16, CD86 and the ratio of CD16/CD206, while the indicators positively associated with microglial phagocytosis decreased like Arg-1 and CD206. The increased ROS and aggravating mitochondrial damage demonstrated that the damaging effects of APOE4 in SAH may be associated with microglial oxidative stress-dependent mitochondrial damage. Inhibiting mitochondrial oxidative stress by Mitoquinone (mitoQ) can enhance the phagocytic function of microglia. In conclusion, anti-oxidative stress and phagocytosis protection may serve as promising treatments in the management of SAH.

The Drosophila chemokine–like Orion bridges phosphatidylserine and Draper in phagocytosis of neurons

Phagocytic clearance of degenerating neurons is triggered by "eat-me" signals exposed on the neuronal surface. The conserved neuronal eat-me signal phosphatidylserine (PS) and the engulfment receptor Draper (Drpr) mediate phagocytosis of degenerating neurons in Drosophila. However, how PS is recognized by Drpr-expressing phagocytes invivo remains poorly understood. Using multiple models of dendrite degeneration, we show that the Drosophila chemokine-like protein Orion can bind to PS and is responsible for detecting PS exposure on neurons; it is supplied cell-non-autonomously to coat PS-exposing dendrites and to mediate interactions between PS and Drpr, thus enabling phagocytosis. As a result, the accumulation of Orion on neurons and on phagocytes produces opposite outcomes by potentiating and suppressing phagocytosis, respectively. Moreover, the Orion dosage is a key determinant of the sensitivity of phagocytes to PS exposed on neurons. Lastly, mutagenesis analyses show that the sequence motifs shared between Orion and human immunomodulatory proteins are important for Orion function. Thus, our results uncover a missing link in PS-mediated phagocytosis in Drosophila and imply conserved mechanisms of phagocytosis of neurons.

Rab26 promotes macrophage phagocytosis through regulation of MFN2 trafficking to mitochondria.

Acute respiratory distress syndrome (ARDS) is an inflammatory disorder of the lungs caused by bacterial or viral infection. Timely phagocytosis and clearance of pathogens by macrophages are important in controlling inflammation and alleviating ARDS. However, the precise mechanism of macrophage phagocytosis remains to be explored. Here, we show that theexpression of Rab26 is increased in Escherichia coli- or Pseudomonas aeruginosa-stimulated bone marrow-derived macrophages. Knocking out Rab26 reduced phagocytosis and bacterial clearance by macrophages. Rab26 interacts with mitochondrial fusion protein mitofusin-2 (MFN2) and affects mitochondrial reactive oxygen species generation by regulating MFN2 transport. The levels of MFN2 in mitochondria were reduced in Rab26-deficient bone marrow-derived macrophages, and the levels of mitochondrial reactive oxygen species and ATP were significantly decreased. Knocking down MFN2 using small interfering RNA resulted in decreased phagocytosis and killing ability of macrophages. Rab26 knockout reduced phagocytosis and bacterial clearance by macrophages in vivo, significantly increased inflammatory factors, aggravated lung tissue damage, and increased mortality in mice. Our results demonstrate that Rab26 regulates phagocytosis and clearance of bacteria by mediating the transport of MFN2 to mitochondria in macrophages, thus alleviating ARDS in mice and potentially in humans.

Anti-Tumor Strategies by Harnessing the Phagocytosis of Macrophages.

Macrophages are essential for the human body in both physiological and pathological conditions, engulfing undesirable substances and participating in several processes, such as organism growth, immune regulation, and maintenance of homeostasis. Macrophages play an important role in anti-bacterial and anti-tumoral responses. Aberrance in the phagocytosis of macrophages may lead to the development of several diseases, including tumors. Tumor cells can evade the phagocytosis of macrophages, and "educate" macrophages to become pro-tumoral, resulting in the reduced phagocytosis of macrophages. Hence, harnessing the phagocytosis of macrophages is an important approach to bolster the efficacy of anti-tumor treatment. In this review, we elucidated the underlying phagocytosis mechanisms, such as the equilibrium among phagocytic signals, receptors and their respective signaling pathways, macrophage activation, as well as mitochondrial fission. We also reviewed the recent progress in the area of application strategies on the basis of the phagocytosis mechanism, including strategies targeting the phagocytic signals, antibody-dependent cellular phagocytosis (ADCP), and macrophage activators. We also covered recent studies of Chimeric Antigen Receptor Macrophage (CAR-M)-based anti-tumor therapy. Furthermore, we summarized the shortcomings and future applications of each strategy and look into their prospects with the hope of providing future research directions for developing the application of macrophage phagocytosis-promoting therapy.

Virus-like particle endocytosis pathways and presentation of captured antigens

The proteins of many viruses can be assembled into strictly organized structures virus-like particles bearing antigens of the original viruses and may also be artificially decorated with antigens of other pathogens. These particles contain no viral genome and lack infectivity but can be highly immunogenic and therefore being actively used for vaccine development. Undoubtedly, while designing vaccines, it is necessary to take into account information about the interaction of vaccine components with immune system particularly antigen-presenting cells. This is especially important for virus-like particles because, like other nanometer-sized particles, they can enter antigen-presenting cells using various endocytosis pathways. The latter exploit multiple receptors, generate endocytic vesicles of different sizes, and, most importantly, are associated with varying fates of captured material. Here we review the mechanisms of phagocytosis, macropinocytosis, clathrin-mediated endocytosis, rapid endophilin-mediated endocytosis, and several endocytic pathways associated with lipid rafts. The data are presented on the relationship between various endocytic pathways and sorting of absorbed cargo in early endosomes as well as enzymatic degradation of the late endosomes contents. We also describe the mechanisms of distribution of absorbed antigens within antigen-presenting cells to be loaded onto the class I and II major histocompatibility complex molecules. The data are presented on the endocytosis of various viruses during cell infection, as well as a comparative analysis of the endocytosis pathways for virus-like particles and related viruses. It has been noted that virus-like particles, along with the absorption pathway specific for parent virus, can rely on additional endocytic pathways to be also artificially targeted at the selected endocytic receptor and relevant absorption pathway. It allows to select or design particles with optimal endocytosis and antigen presentation to induce a protective immune response upon vaccination. It should be assumed that most prophylactic vaccines require particles that are well engulfed by antigen presenting cells and direct material to endolysosomal degradation, or particles whose uptake directs material to both late and static early endosomes, making antigens available for direct and cross presentations. Finally, we discuss virus-like particles for the delivery of drugs or genetically engineered constructs, as well as optimal endocytic pathways that should protect the payload of these particles from endolysosomal degradation.

Autophagy and LC3-associated phagocytosis: similarities and differences

Previously, autophagy was termed as a mechanism used by the cells with a lack of essential nutrients supporting homeostasis. Over the decade of studies, autophagy proved to be a more complex, ambiguous mechanism. Its activation depends on the nature of stimulus, type of immune cells and the final result. Both canonical and non-canonical autophagy, being similar in molecular events, but showing their own distinctive features, are key processes in protecting the body from penetration of intracellular pathogens, maintaining the required level of nutrients in the cell, and removing damaged organelles and cells. Canonical autophagy probably evolved as a homeostatic response to cellular stress and nutritional deficiencies, whereas non-canonical autophagy emerged as a response to suppression of inflammation. Non-canonical autophagy, hereinafter referred to as LC3-associated phagocytosis (LAP), combines the molecular mechanism of phagocytosis with an autophagy mechanism characterized by ingestion of exogenous pathogens, formation of phagosomes (laposomes) and enhanced fusion with lysosomes, followed by degradation of their contents.Significant differences were found between the processes of LAP- and canonical autophagy, which are similar in its mechanism of action. The presence of PI3K complexes in both processes, utilization and intracellular degradation of the “cargo” which is not required for the cells and organism proceeding in the lysosomes, and involvement of almost the same proteins provide similarity of their mechanisms. However, there are differences in the initiation of the processes, e.g., different types of PI3K complexes (in autophagy, PI3K III class 1 and 2 types; in LAP PI3K III, class 3 type), usage of reactive oxygen species in LAP, different types of regulatory proteins involved (ULK1, FIP200, ATG13 , Ambra1, WIPI2, ATG14 in autophagy; and Rubicon and NOX2 in LC3-associated phagocytosis), different number of layers in the membrane structure in which lysis occurs (double-membrane autophagolysosome and single-layer membrane in laposomes) clearly depict the variety of canonical and non-canonical autophagy. The two pathways are directed for different types of biological objects, i.e., intracellular pathogens, dysfunctional proteins and organelles in autophagy, and extracellular pathogens, apoptotic bodies, bacteria, utilized in LAP, thus making these mechanisms completely different in their significance.Collectively, the new data indicate that autophagy performed via both canonical and non-canonical pathways, has evolved into a host defense mechanism capable of resisting immunological and pathogenic stress and mediating immunological tolerance to both intra- and extracellular threats. The present review discusses fundamental molecular differences between these mechanisms, as well as their role in immunity, based on the latest literature data.

Colorectal cancer-derived extracellular vesicles containing HSP70 enhance macrophage phagocytosis by up-regulating MARCO expression

In recent years, we have realized that extracellular vesicles (EVs) play a critical role in regulating the intercellular communication between tumor and immune cells in the tumor microenvironment (TME). Tumor-derived extracellular vesicles (TDEVs) profoundly affect the functional changes of tumor-associated macrophages (TAMs) and promote their M2 polarization. Meanwhile, macrophages have a strong phagocytic ability in phagocytosing apoptotic cells. Especially in the course of chemotherapy or radiotherapy, TAMs can phagocytose and remove apoptotic tumor cells, showing anti-inflammatory and pro-tumor effects. However, the underlying mechanisms by which TDEVs regulate macrophage phagocytosis of apoptotic tumor cells have not been fully elucidated. In this study, we focused on the effect of colorectal cancer-derived extracellular vesicles (CRC-EVs) on macrophages. We demonstrated that CRC-EVs enhanced macrophage phagocytosis of apoptotic CRC cells. We then determined that heat shock protein 70 (HSP70) carried in CRC-EVs was responsible for this effect by using mass spectrometry-based proteomic analysis and the CRISPR-Cas9 system. Through transcriptome sequencing of macrophages, we found that the enhanced phagocytosis of macrophages was mainly due to the up-regulation of the macrophage receptor with collagenous structure (MARCO). In addition, we confirmed that the up-regulation of MARCO was mediated by the AKT-STAT3 signaling pathway. Taken together, this study revealed a novel EVs-mediated macrophage phagocytosis mechanism involved in the clearance of apoptotic tumor cells in the TME. Targeting TDEVs may have potential therapeutic applications in tumor treatment.

The Implications of Microglial Regulation in Neuroplasticity-Dependent Stroke Recovery.

Stroke causes varying degrees of neurological deficits, leading to corresponding dysfunctions. There are different therapeutic principles for each stage of pathological development. Neuroprotection is the main treatment in the acute phase, and functional recovery becomes primary in the subacute and chronic phases. Neuroplasticity is considered the basis of functional restoration and neurological rehabilitation after stroke, including the remodeling of dendrites and dendritic spines, axonal sprouting, myelin regeneration, synapse shaping, and neurogenesis. Spatiotemporal development affects the spontaneous rewiring of neural circuits and brain networks. Microglia are resident immune cells in the brain that contribute to homeostasis under physiological conditions. Microglia are activated immediately after stroke, and phenotypic polarization changes and phagocytic function are crucial for regulating focal and global brain inflammation and neurological recovery. We have previously shown that the development of neuroplasticity is spatiotemporally consistent with microglial activation, suggesting that microglia may have a profound impact on neuroplasticity after stroke and may be a key therapeutic target for post-stroke rehabilitation. In this review, we explore the impact of neuroplasticity on post-stroke restoration as well as the functions and mechanisms of microglial activation, polarization, and phagocytosis. This is followed by a summary of microglia-targeted rehabilitative interventions that influence neuroplasticity and promote stroke recovery.

CircRNA432 enhances the coelomocyte phagocytosis via regulating the miR-2008-ELMO1 axis in Vibrio splendidus-challenged Apostichopus japonicus

Circular RNAs (circRNAs) are a kind of extensive and diverse covalently closed circular endogenous RNA, which exert crucial functions in immune regulation in mammals. However, the functions and mechanisms of circRNAs in invertebrates are largely unclarified. In our previous work, 261 differentially expressed circRNAs including circRNA432 (circ432) were identified from skin ulcer syndrome (SUS) diseased sea cucumber Apostichopus japonicus by RNA-seq. To better address the functional role of sea cucumber circRNAs, circ432 was first found to be significantly induced by Vibrio splendidus challenge and LPS exposure in this study. Knock-down circ432 could depress the V. splendidus-induced coelomocytes phagocytosis. Moreover, circ432 is validated to serve as the sponge of miR-2008, a differential expressed miRNA in SUS-diseased sea cucumbers, by Argonaute 2-RNA immunoprecipitation (AGO2-RIP) assay, luciferase reporter assay and RNA fluorescence in situ hybridization (FISH) in vitro. Engulfment and cell motility protein 1 (AjELMO1) is further demonstrated to be the target of miR-2008, and silencing AjELMO1 inhibits the V. splendidus-induced coelomocytes phagocytosis, and this phenomenon could be further suppressed by supplementing with miR-2008 mimics, suggesting that circ432 might regulate coelomocytes phagocytosis via miR-2008-AjELMO1 axis. We further confirm that the depressed coelomocytes’ phagocytosis by circ432 silencing is consistent with the decreased abundance of AjELMO1, and could be recovered by miR-2008 inhibitors transfection. All our results provide the evidence that circ432 is involved in regulating pathogen-induced coelomocyte phagocytosis via sponge miR-2008 and promotes the abundance of AjELMO1. These findings will enrich the regulatory mechanism of phagocytosis in echinoderm and provide theoretical data for SUS disease prevention and control in sea cucumbers.

Thermal Deformation Behavior and Microstructure Evolution of GH4151 Alloy

Herein, an as‐cast GH4151 alloy is subjected to thermal compression at different temperatures and strain rates by a thermal simulation testing machine. The constitutive equation, dynamic recrystallization (DRX) model, and hot processing map are obtained from the stress–strain curves. The results show that the optimal heat processing conditions are 1100–1120 °C, 0.001–0.01 s−1 and 1100–1135 °C, 0.001–0.1 s−1. Electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) show that the recrystallization mechanism of GH4151 alloy is mainly discontinuous DRX (DDRX) and is supplemented by continuous DRX (CDRX). Deformation dislocations are eliminated by the phagocytosis mechanism of dislocations during recrystallization, and the subgrains and low‐angle grain boundaries are transformed into high‐angle grain boundaries, which finally form equiaxed grains. In addition, due to the pinning effect of γ′ phase on grain boundaries, the redissolution of γ′ phase during DRX greatly affects grain growth.

Role of α-synuclein in microglia: autophagy and phagocytosis balance neuroinflammation in Parkinson's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disease, and is characterized by accumulation of α-synuclein (α-syn). Neuroinflammation driven by microglia is an important pathological manifestation of PD. α-Syn is a crucial marker of PD, and its accumulation leads to microglia M1-like phenotype polarization, activation of NLRP3 inflammasomes, and impaired autophagy and phagocytosis in microglia. Autophagy of microglia is related to degradation of α-syn and NLRP3 inflammasome blockage to relieve neuroinflammation. Microglial autophagy and phagocytosis of released α-syn or fragments from apoptotic neurons maintain homeostasis in the brain. A variety of PD-related genes such as LRRK2, GBA and DJ-1 also contribute to this stability process. Further studies are needed to determine how α-syn works in microglia. A keyword-based search was performed using the PubMed database for published articles. In this review, we discuss the interaction between microglia and α-syn in PD pathogenesis and the possible mechanism of microglial autophagy and phagocytosis in α-syn clearance and inhibition of neuroinflammation. This may provide a novel insight into treatment of PD.