Phagocytosis and the actin cytoskeleton

Comparative Analysis of HMC3 and C20 Microglial Cell Lines Reveals Differential Myeloid Characteristics and Responses to Immune Stimuli

Microglia are the primary resident immune cells of the central nervous system (CNS) that respond to injury and infections. Being critical to CNS homeostasis, microglia also have been shown to contribute to neurodegenerative diseases and brain cancer. Hence, microglia are regarded as a potential therapeutic target in CNS diseases, resulting in an increased demand for reliable in vitro models. Two human microglia cell lines (HMC3 and C20) are being used in multiple in vitro studies, however, the knowledge of their biological and immunological characteristics remains limited. Our aim was to identify and compare the biological changes in these immortalised immune cells under normal physiological and immunologically challenged conditions. Using high-resolution quantitative mass spectrometry, we have examined in-depth proteomic profiles of non-stimulated and LPS or IFN-γ challenged HMC3 and C20 cells. Our findings reveal that HMC3 cells responded to both treatments through upregulation of immune, metabolic, and antiviral pathways, while C20 cells showed a response associated with mitochondrial and immune activities. Additionally, the secretome analysis demonstrated that both cell lines release IL-6 in response to LPS, while IFN-γ treatment resulted in altered kynurenine pathway activity, highlighting distinct immune and metabolic adaptations.

Bergamot (Citrus bergamia) as a potential anti-stress agent: Counteracting cellular and physiological changes by sodium lauryl sulphate in Mytilus galloprovincialis

The present study was prompted by an interest in understanding the potentially beneficial effects of bergamot peel extract on the cellular and physiological performance of appropriate aquatic model organisms subjected to daily environmental challenges, namely pollution. In this regard, specimens of Mytilus galloprovincialis were exposed to Sodium Lauryl Sulphate (0.01 mg/L), an extract of bergamot peels (5 mg/L), and a solution of the two (SLS + BRG), for fourteen days. The immune response was evaluated by assessing the ability of haemocyte cells to engulf foreign elements in conjunction with the gene expression of γ-actin, which plays a key role in cytoskeletal rearrangement. The physiological response was analysed through the analysis of cell volume regulation (RVD assay) in digestive gland cells and cytotoxicity assays (Neutral red and Trypan blue) on both cell populations, which exhibited notable alterations. In addition, the gene expression of genes involved in antioxidant activity, including Cu/ZnSOD, MnSOD, Hsp70, and CYP4Y1, was evaluated. Significant differences were observed between the control (CTR) and treated groups, with a consistent trend evident in the CTR and BRG groups, which exhibited a similar pattern to the SLS-treated groups. In contrast, the groups treated with the combination of the two compounds (SLS + BRG) demonstrated a recovery.

Porphyromonas gingivalis Impairs Microglial Aβ Clearance in a Mouse Model

Porphyromonas gingivalis (Pg), a keystone pathogen in chronic periodontitis, has been identified as an emerging risk factor for Alzheimer's disease (AD). Pg can promote the accumulation of amyloid β protein (Aβ), a characteristic feature of AD pathology. However, the underlying mechanism, particularly in Aβ clearance, remains poorly understood. Here, by using 3 different strains of Pg, ATCC33277, W50, and W83, we discovered that APP/PS1 mice infected with all 3 Pg strains showed decreased microglial Aβ internalization, increased Aβ deposition in the brain, and impaired cognitive function. Using in vitro experiments, we further demonstrated that all 3 Pg strains inhibited microglial Aβ clearance, where gingipains, a group of toxic proteases derived from Pg, were involved. Gingipains were shown to hydrolyze CD14, subsequently impeding the CD14-mediated Vav-Rac/Cdc42 signaling cascade, which ultimately suppressed phagocytosis. Gingipain inhibitor could effectively restore microglial Aβ clearance and diminish Aβ deposition, leading to improved cognitive function in Pg-infected APP/PS1 mice. These findings may provide new insights into the mechanism through which Pg impairs microglial Aβ clearance to aggravate AD phenotypes, suggesting that gingipain inhibitors could be potential therapeutics for treating Pg-associated AD.

Differential infection dynamics in mononuclear and polymorphonuclear cells during Salmonella Typhimurium infection and in vitro exposure to diazoxon

S. Typhimurium bacteria cause one of the most recurrent gastrointestinal diseases worldwide. This bacterium can settle in the gastrointestinal tract and internalize into different cellular strains, causing the formation of cellular reservoirs that subsequently lead to systemic dissemination. Exogenous factors such as pesticide exposure can also cause immunological alterations, increasing susceptibility to bacterial infection. The present work evaluated the infection capacity of Salmonella Typhimurium, during a short period (1 h) on mononuclear and polymorphonuclear cells previously exposed to diazoxon (1 h, during 4 h). Mononuclear cells were infected more frequently and in greater magnitude than polymorphonuclear cells. However, when actin polymerization and the release of reactive oxygen species (ROS) were analyzed, polymorphonuclear cells showed increased activity. These processes were evidenced by conformational changes during infection. This suggests differential dynamics of S. Typhimurium infection in mononuclear and polymorphonuclear cells previously exposed to diazoxon.

Mastitis-related Staphylococcus aureus-derived extracellular vesicles induce a pro-inflammatory response in bovine monocyte-derived macrophages

Staphylococcus aureus (S. aureus) is one of the most common causative agents of mammary gland infection and mastitis, but the specific role of S. aureus-derived extracellular vesicles (SaEVs) in mastitis has been poorly studied to date. Here, we aimed to investigate the response of bovine monocyte-derived macrophages (boMdM) to SaEVs of the genotype B (GTB) mastitis-related strain M5512B. Specifically, we evaluated the effects on the actin cytoskeleton, gene expression, and the SaEV proteomic cargo. Furthermore, we assessed to what extent the cellular and molecular response of boMdM to SaEVs differed from peripheral mononuclear blood cells (PBMCs) used for in vitro derivation of the former. We observed that SaEVs induced morphological changes in boMdM, leading to a pro-inflammatory and pyroptosis-related increased gene expression. Additionally, our study revealed that boMdM and PBMCs exhibited stimulus-specific differing responses. The proteomic analysis of SaEVs identified clusters of proteins related to virulence and antibiotic resistance, supporting the theory that S. aureus might use EVs to evade host defences and colonize the mammary gland. Our results bring new insights into how SaEVs might impact the host during an S. aureus infection, which can be useful for future S. aureus vaccine development.

Tumor-Associated Macrophages Nano-Reprogrammers Induce "Gear Effect" to Empower Glioblastoma Immunotherapy

Glioblastoma (GBM), the most malignant brain tumor with high prevalence, remains highly resistant to the existing immunotherapies due to the significant immunosuppression within tumor microenvironment (TME), predominantly manipulated by M2-phenotypic tumor-associated macrophages (M2-TAMs). Here in this work, an M2-TAMs targeted nano-reprogrammers, MG5-S-IMDQ, is established by decorating the mannose molecule as the targeting moiety as well as the toll-like receptor (TLR) 7/8 agonist, imidazoquinoline (IMDQ) on the dendrimeric nanoscaffold. MG5-S-IMDQ demonstrated an excellent capacity of penetrating the blood-brain barrier (BBB) as well as selectively targeting M2-TAMs in the GBM microenvironment, leading to a phenotype transformation and function restoration of TAMs shown as heightened phagocytic activity toward tumor cells, enhanced cytotoxic effects, and improved tumor antigen cross-presentation capability. In the meantime, by induction of a function-oriented "gear effect", MG5-S-IMDQ treatment extended its impact systemically by enhancing the infiltration of type I conventional dendritic cells (cDC1s) into the tumor sites and bolstering adaptive immune responses. In sum, by precisely working on M2-TAMs as a unique target in tumor situ, the nano-reprogrammers successfully established a robust immune network that worked synergistically to combat tumors. This facile nanoplatform-based immunomodulatory strategy, serving as a powerful and convenient immune monotherapy or as a complementary treatment alongside other therapies like surgery, provided deep insights for advancing translational study in GBM.

Dysregulation of septin cytoskeletal organization in the trabecular meshwork contributes to ocular hypertension

Ocular hypertension, believed to result partly from increased contractile activity, cell adhesive interactions, and stiffness within the trabecular meshwork (TM), is a major risk factor for glaucoma, a leading cause of blindness. However, the identity of molecular mechanisms governing organization of actomyosin and cell adhesive interactions in the TM remains limited. Based on our previous findings, in which proteomics analyses revealed elevated levels of septins, including septin-9 in human TM cells treated with the ocular hypertensive agent dexamethasone, here, we evaluated the effects of septin-9 overexpression, deficiency, and pharmacological targeting in TM cells. These studies demonstrated a profound impact on actomyosin organization, cell adhesion, contraction, and phagocytosis. Overexpression raised intraocular pressure (IOP) in mice, while inhibition increased cell permeability. In addition, we replicated a significant association between a common variant (rs9038) in SEPT9 with IOP in the Genetic Epidemiology Research on Adult Healthy and Aging (GERA) cohort. Collectively, these data reveal a link between dysregulated septin cytoskeletal organization in the TM and increased IOP, likely due to enhanced cell contraction, adhesive interactions, and fibrotic activity. This suggests that targeting the septin cytoskeleton could offer a novel approach for lowering IOP in patients with glaucoma.

Citrus pectin modulates chicken peripheral blood mononuclear cell proteome in vitro

Citrus pectin (CP) is a dietary fiber used in animal nutrition with anti-inflammatory properties. CP downregulates chicken immunoregulatory monocytes' functions, like chemotaxis and phagocytosis, in vitro. The molecular underlying background is still unknown. This study investigated the activity of CP on chicken peripheral blood mononuclear cells (PBMC) proteome. An overall number of 1503 proteins were identified and quantified. The supervised sparse variant partial least squares-discriminant analysis (sPLS-DA) for paired data highlighted 373 discriminant proteins between CP-treated and the control group, of which 50 proteins with the highest abundance in CP and 137 in the control group were selected for Gene Ontology (GO) analyses using ProteINSIDE. Discriminant Protein highly abundant in CP-treated cells were involved in actin cytoskeleton organization and negative regulation of cell migration. Interestingly, MARCKSL1, a chemotaxis inhibitor, was upregulated in CP-treated cells. On the contrary, CP incubation downregulated MARCKS, LGALS3, and LGALS8, which are involved in cytoskeleton rearrangements, cell migration, and phagocytosis. In conclusion, these results provide a proteomics background to the anti-inflammatory activity of CP, demonstrating that the in vitro downregulation of phagocytosis and chemotaxis is related to changes in proteins related to the cytoskeleton.

Flagellate bacteria-mediated tumour antigen delivery: A novel approach to enhance dendritic cell activation for in situ cancer vaccination

In situ vaccination is a therapeutic approach aimed at exploiting tumour antigens available at a tumour site to induce tumour-specific adaptive immune responses. Antigens released from dying tumour cells are assumed to be taken up by activated dendritic cells and presented to T cells that seek out and destroy tumour cells. This process is significantly impeded in the immunosuppressive microenvironment of tumours. There is a growing trend in in situ vaccine strategies that utilize bacteria as natural adjuvants or as factories for cytokines, aiming to enhance the presentation of in situ antigens by antigen-presenting cells. Recently, a novel approach using flagellate bacteria-mediated antigen delivery to activate dendritic cells has been proposed. This method actively facilitates the delivery of intratumoral antigens, improving their presentation for in situ cancer vaccination. Here, we highlight how flagellate bacteria-mediated antigen delivery enhances the immune activation capabilities of in situ vaccines. Meanwhile, we provide perspectives and outlooks on these promising antigen delivery technologies.

Nanoparticle Targeting Strategies for Lipid and Polymer-Based Gene Delivery to Immune Cells In Vivo

Lipid nanoparticles and polymeric nanoparticles are promising biomaterial platforms for robust intracellular DNA and mRNA delivery, highlighted by the widespread use of nanoparticle- (NP) based mRNA vaccines to help end the COVID-19 pandemic. Recent research has sought to adapt this nanotechnology to transfect and engineer immune cells in vivo. The immune system is an especially appealing target due to its involvement in many different diseases, and ex vivo-engineered immune cell therapies like chimeric antigen receptor (CAR) T therapy have already demonstrated remarkable clinical success in certain blood cancers. Although gene delivery can potentially address some of the cost and manufacturing concerns associated with current autologous immune cell therapies, transfecting immune cells in vivo is challenging. Not only is extrahepatic NP delivery to lymphoid organs difficult, but immune cells like T cells have demonstrated particular resistance to transfection. Despite these challenges, the modular nature of NPs allows researchers to examine critical structure-function relationships between a particle's properties and its ability to specifically engineer immune cells in vivo. Herein, several nanomaterial components are outlined, including targeting ligands, nucleic acid cargo, chemical properties, physical properties, and the route of administration to specifically target NPs to immune cells for optimal in vivo transfection.

In vitro impact of Bisphenol A on the immune functions of primary cultured hemocytes of Pacific abalone (Haliotis discus hannai)

This study investigated the toxic effects of Bisphenol A (BPA) on the Pacific abalone (Haliotis discus hannai) using in vitro assays with primary cultured hemocytes. The abalone hemocytes were exposed to BPA concentrations up to 100 μM to assess cytotoxicity. Subsequently, hemocytes were exposed to sublethal BPA concentrations (LC20 = 2.3 μM and LC50 = 5.8 μM) for 48 h, and we evaluated the cellular immune responses of hemocytes via flow cytometry. Results showed no significant differences between LC20 and control groups, but LC50 exposure significantly reduced phagocytosis and oxidative capacities while increasing nitric oxide production. These findings suggest that BPA exposure negatively affects the immune system of the Pacific abalone, which makes them more susceptible to infections and other stressors in their natural environment. The study also implies that in vitro assays utilizing primary cultured abalone hemocytes may serve as effective proxies for quantifying the cytotoxic effects of chemical pollutants.

Extracellular vesicles (EVs)' journey in recipient cells: from recognition to cargo release

Extracellular vesicles (EVs) are nano-sized bilayer vesicles that are shed or secreted by virtually every cell type. A variety of biomolecules, including proteins, lipids, coding and non-coding RNAs, and mitochondrial DNA, can be selectively encapsulated into EVs and delivered to nearby and distant recipient cells, leading to alterations in the recipient cells, suggesting that EVs play an important role in intercellular communication. EVs play effective roles in physiology and pathology and could be used as diagnostic and therapeutic tools. At present, although the mechanisms of exosome biogenesis and secretion in donor cells are well understood, the molecular mechanism of EV recognition and uptake by recipient cells is still unclear. This review summarizes the current understanding of the molecular mechanisms of EVs' biological journey in recipient cells, from recognition to uptake and cargo release. Furthermore, we highlight how EVs escape endolysosomal degradation after uptake and thus release cargo, which is crucial for studies applying EVs as drug-targeted delivery vehicles. Knowledge of the cellular processes that govern EV uptake is important to shed light on the functions of EVs as well as on related clinical applications.

PIEZO1 targeting in macrophages boosts phagocytic activity and foam cell apoptosis in atherosclerosis

The rising incidences of atherosclerosis have necessitated efforts to identify novel targets for therapeutic interventions. In the present study, we observed increased expression of the mechanosensitive calcium channel Piezo1 transcript in mouse and human atherosclerotic plaques, correlating with infiltration of PIEZO1-expressing macrophages. In vitro administration of Yoda1, a specific agonist for PIEZO1, led to increased foam cell apoptosis and enhanced phagocytosis by macrophages. Mechanistically, PIEZO1 activation resulted in intracellular F-actin rearrangement, elevated mitochondrial ROS levels and induction of mitochondrial fragmentation upon PIEZO1 activation, as well as increased expression of anti-inflammatory genes. In vivo, ApoE-/- mice treated with Yoda1 exhibited regression of atherosclerosis, enhanced stability of advanced lesions, reduced plaque size and necrotic core, increased collagen content, and reduced expression levels of inflammatory markers. Our findings propose PIEZO1 as a novel and potential therapeutic target in atherosclerosis.

Oxidized LDL regulates efferocytosis through the CD36-PKM2-mtROS pathway

Macrophage efferocytosis, the process by which phagocytes engulf and remove apoptotic cells (ACs), plays a critical role in maintaining tissue homeostasis. Efficient efferocytosis prevents secondary necrosis, mitigates chronic inflammation, and impedes atherosclerosis progression. However, the regulatory mechanisms of efferocytosis under atherogenic conditions remain poorly understood. We previously demonstrated that oxidized LDL (oxLDL), an atherogenic lipoprotein, induces mitochondrial reactive oxygen species (mtROS) in macrophages via CD36. In this study, we demonstrate that macrophage mtROS facilitate continual efferocytosis through a positive feedback mechanism. However, oxLDL disrupts continual efferocytosis by dysregulating the internalization of ACs. This disruption is mediated by an overproduction of mtROS. Mechanistically, oxLDL/CD36 signaling promotes the translocation of cytosolic PKM2 to mitochondria, facilitated by the chaperone GRP75. Mitochondrial PKM2 then binds to Complex III of the electron transport chain, inducing mtROS production. This study elucidates a novel regulatory mechanism of efferocytosis in atherosclerosis, providing potential therapeutic targets for intervention.

SUMMARY

Macrophages clear apoptotic cells through a process called efferocytosis, which involves mitochondrial ROS. However, the atherogenic oxidized LDL overstimulates mitochondrial ROS via the CD36-PKM2 pathway, disrupting continual efferocytosis. This finding elucidates a novel molecular mechanism that explains defects in efferocytosis, driving atherosclerosis progression.

PTP1B phosphatase dampens iPSC-derived neutrophil motility and antimicrobial function

Neutrophils are rapidly recruited to sites of infection and are critical for pathogen clearance. Therapeutic use of primary neutrophils has been limited, as they have a short lifespan and are not amenable to genetic manipulation. Human induced pluripotent stem cells (iPSCs) can provide a robust source of neutrophils for infusion and are genetically tractable. However, current work has indicated that dampened intracellular signaling limits iPSC-derived neutrophil (iNeutrophil) cellular activation and antimicrobial response. Here, we show that protein tyrosine phosphatase 1B (PTP1B) inhibits intracellular signaling and dampens iNeutrophil effector function. Deletion of the PTP1B phosphatase increased PI3K and ERK signaling and was associated with increased F-actin polymerization, cell migration, and phagocytosis. In contrast, other effector functions like NETosis and reactive oxygen species production were reduced. PTP1B-deficient neutrophils were more responsive to Aspergillus fumigatus and displayed rapid recruitment and control of hyphal growth. Accordingly, depletion of PTP1B increased production of inflammatory factors including the neutrophil chemokine interleukin-8. Taken together, these findings suggest that PTP1B limits iNeutrophil motility and antimicrobial function.

Magnetic Particle Imaging Reveals that Iron-Labeled Extracellular Vesicles Accumulate in Brains of Mice with Metastases

The incidence of breast cancer remains high worldwide and is associated with a significant risk of metastasis to the brain that can be fatal; this is due, in part, to the inability of therapeutics to cross the blood-brain barrier (BBB). Extracellular vesicles (EVs) have been found to cross the BBB and further have been used to deliver drugs to tumors. EVs from different cell types appear to have different patterns of accumulation and retention as well as the efficiency of bioactive cargo delivery to recipient cells in the body. Engineering EVs as delivery tools to treat brain metastases, therefore, will require an understanding of the timing of EV accumulation and their localization relative to metastatic sites. Magnetic particle imaging (MPI) is a sensitive and quantitative imaging method that directly detects superparamagnetic iron. Here, we demonstrate MPI as a novel tool to characterize EV biodistribution in metastatic disease after labeling EVs with superparamagnetic iron oxide (SPIO) nanoparticles. Iron-labeled EVs (FeEVs) were collected from iron-labeled parental primary 4T1 tumor cells and brain-seeking 4T1BR5 cells, followed by injection into the mice with orthotopic tumors or brain metastases. MPI quantification revealed that FeEVs were retained for longer in orthotopic mammary carcinomas compared to SPIOs. MPI signal due to iron could only be detected in brains of mice bearing brain metastases after injection of FeEVs, but not SPIOs, or FeEVs when mice did not have brain metastases. These findings indicate the potential use of EVs as a therapeutic delivery tool in primary and metastatic tumors.

The crosstalk between extracellular matrix proteins and Tau

Alzheimer's disease is progressive neurodegenerative disease characterize by the presence of extracellular accumulation of amyloid-β plaques and intracellular deposits of neurofibrillary tangles of Tau. Apart from axonal depositions pathological aggregated Tau protein is known to secrete into extracellular spaces and propagate through seeding mechanism. Microglia, the immune cells of the brain display modest ability to internalize the extracellular Tau and degrade it through endolysosomal pathway. However, the excessive burden of pathoproteins weakens the phagocytic ability of microglia. Extracellular supplementation of omega-3 fatty acids (n-3) may regulate the phagocytosis of microglia as they mediate the anti-inflammatory polarization of microglia through membrane lipid compositions changes. The internalization of extracellular Tau in the microglia is regulated by cortical membrane-associated actin remodeling driven by interplay of actin-binding proteins. On the other hand, Tau display capability bind and interact with various actin-binding protein owing to the presence of proline-rich domain in the structure and regulate their activation. In this study, we hypothesize that internalization of Tau in the presence of omega-3 fatty acids would propagate the Tau-mediated activation of actin-binding proteins as well as extracellular matrix and in turn modulate cortical actin remodeling for phagocytosis.

Circadian rhythm of intraocular pressure

Intraocular pressure (IOP) plays a crucial role in glaucoma development, involving the dynamics of aqueous humor (AH). AH flows in from the ciliary body and exits through the trabecular meshwork (TM). IOP follows a circadian rhythm synchronized with the suprachiasmatic nucleus (SCN), the circadian pacemaker. The SCN resets peripheral clocks through sympathetic nerves or adrenal glucocorticoids (GCs). IOP's circadian rhythm is governed by circadian time signals, sympathetic noradrenaline (NE), and GCs, rather than the local clock. The activity of Na+/K+-ATPase in non-pigmented epithelial cells in the ciliary body can influence the nocturnal increase in IOP by enhancing AH inflow. Conversely, NE, not GCs, can regulate the IOP rhythm by suppressing TM macrophage phagocytosis and AH outflow. The activation of the β1-adrenergic receptor (AR)-mediated EPAC-SHIP1 signal through the ablation of phosphatidylinositol triphosphate may govern phagocytic cup formation. These findings could offer insights for better glaucoma management, such as chronotherapy.

Controling the cytoskeleton during CEACAM3-mediated phagocytosis

Phagocytosis, an innate defense mechanism of multicellular animals, is initiated by specialized surface receptors. A phagocytic receptor expressed by human polymorphonuclear granulocytes, the major professional phagocytes in our body, is one of the fastest evolving human proteins implying a special role in human biology. This receptor, CEACAM3, is a member of the CarcinoEmbryonic Antigen-related Cell Adhesion Molecule (CEACAM) family and dedicated to the immediate recognition and rapid internalization of human-restricted pathogens. In this focused contribution, we will review the special adaptations of this protein, which co-evolves with different species of mucosa-colonizing bacteria. While the extracellular Immunoglobulin-variable (IgV)-like domain recognizes various bacterial adhesins, an Immunoreceptor Tyrosine-based Activation Motif (ITAM)-like sequence in the cytoplasmic tail of CEACAM3 constitutes the central signaling hub to trigger actin rearrangements needed for efficient phagocytosis. A major emphasis of this review will be placed on recent findings, which have revealed the multi-level control of this powerful phagocytic device. As tyrosine phosphorylation and small GTPase activity are central for CEACAM3-mediated phagocytosis, the counterregulation of CEACAM3 activity involves the receptor-type protein tyrosine phosphatase J (PTPRJ) as well as the Rac-GTP scavenging protein Cyri-B. Interference with such negative regulatory circuits has revealed that CEACAM3-mediated phagocytosis can be strongly enhanced. In principle, the knowledge gained by studying CEACAM3 can be applied to other phagocytic systems and opens the door to treatments, which boost the phagocytic capacity of professional phagocytes.

MARCKS Inhibition Alters Bovine Neutrophil Responses to Salmonella Typhimurium

Neutrophils are innate immune cells that respond quickly to sites of bacterial infection and play an essential role in host defense. Interestingly, some bacterial pathogens benefit from exuberant neutrophil inflammation. Salmonella is one such pathogen that can utilize the toxic mediators released by neutrophils to colonize the intestine and cause enterocolitis. Because neutrophils can aid gut colonization during Salmonella infection, neutrophils represent a potential host-directed therapeutic target. Myristoylated alanine-rich C-kinase substrate (MARCKS) is an actin-binding protein that plays an essential role in many neutrophil effector responses. We hypothesized that inhibition of MARCKS protein would alter bovine neutrophil responses to Salmonella Typhimurium (STm) ex vivo. We used a MARCKS inhibitor peptide to investigate the role of MARCKS in neutrophil responses to STm. This study demonstrates that MARCKS inhibition attenuated STm-induced neutrophil adhesion and chemotaxis. Interestingly, MARCKS inhibition also enhanced neutrophil phagocytosis and respiratory burst in response to STm. This is the first report describing the role of MARCKS protein in neutrophil antibacterial responses.

Macrophage-mediated trogocytosis contributes to destroying human schistosomes in a non-susceptible rodent host, Microtus fortis

Schistosoma parasites, causing schistosomiasis, exhibit typical host specificity in host preference. Many mammals, including humans, are susceptible to infection, while the widely distributed rodent, Microtus fortis, exhibits natural anti-schistosome characteristics. The mechanisms of host susceptibility remain poorly understood. Comparison of schistosome infection in M. fortis with the infection in laboratory mice (highly sensitive to infection) offers a good model system to investigate these mechanisms and to gain an insight into host specificity. In this study, we showed that large numbers of leukocytes attach to the surface of human schistosomes in M. fortis but not in mice. Single-cell RNA-sequencing analyses revealed that macrophages might be involved in the cell adhesion, and we further demonstrated that M. fortis macrophages could be mediated to attach and kill schistosomula with dependence on Complement component 3 (C3) and Complement receptor 3 (CR3). Importantly, we provided direct evidence that M. fortis macrophages could destroy schistosomula by trogocytosis, a previously undescribed mode for killing helminths. This process was regulated by Ca2+/NFAT signaling. These findings not only elucidate a novel anti-schistosome mechanism in M. fortis but also provide a better understanding of host parasite interactions, host specificity and the potential generation of novel strategies for schistosomiasis control.

Genome analysis of Parmales, the sister group of diatoms, reveals the evolutionary specialization of diatoms from phago-mixotrophs to photoautotrophs

The order Parmales (class Bolidophyceae) is a minor group of pico-sized eukaryotic marine phytoplankton that contains species with cells surrounded by silica plates. Previous studies revealed that Parmales is a member of ochrophytes and sister to diatoms (phylum Bacillariophyta), the most successful phytoplankton group in the modern ocean. Therefore, parmalean genomes can serve as a reference to elucidate both the evolutionary events that differentiated these two lineages and the genomic basis for the ecological success of diatoms vs. the more cryptic lifestyle of parmaleans. Here, we compare the genomes of eight parmaleans and five diatoms to explore their physiological and evolutionary differences. Parmaleans are predicted to be phago-mixotrophs. By contrast, diatoms have lost genes related to phagocytosis, indicating the ecological specialization from phago-mixotrophy to photoautotrophy in their early evolution. Furthermore, diatoms show significant enrichment in gene sets involved in nutrient uptake and metabolism, including iron and silica, in comparison with parmaleans. Overall, our results suggest a strong evolutionary link between the loss of phago-mixotrophy and specialization to a silicified photoautotrophic life stage early in diatom evolution after diverging from the Parmales lineage.

Short-term in vitro exposure of Pinctada imbricata's haemocytes to Quaternium-15: exploring physiological and cellular responses

Since the 2000s, the pearl oyster Pinctada imbricata (Röding, 1798) has become established along the transitional waterways of the "Capo Peloro Lagoon" natural reserve, where it is now abundant due to its adaptability to different hydrological, climatic, environmental, and pollution conditions. This study aims to evaluate haemocyte immune-mediated responses in vitro to quaternium-15, a common pollutant in aquatic ecosystems. Cell viability and phagocytosis activity decreased when exposed to 0.1 or 1mg/L of quaternium-15. Moreover, decreasing phagocytosis was confirmed by gene expression modulation of actin, involved in cytoskeleton rearrangement. Effects on oxidative stress-related genes were also assessed (Cat, MnSod, Zn/CuSod, GPx). The qPCR data revealed alterations in antioxidant responses through gene dose- and time-dependent modulation. This study presents insights into the physiological responses and cellular mechanisms of P. imbricata haemocytes to environmental stressors, indicating that this species is useful as a novel bioindicator for future toxicological studies.

Intelectin enhances the phagocytosis of macrophages via CDC42-WASF2-ARPC2 signaling axis in Megalobrama amblycephala

Intelectin has been identified in various vertebrates and plays an important role in the host immune system. In our previous studies, recombinant Megalobrama amblycephala intelectin (rMaINTL) protein with excellent bacterial binding and agglutination activities enhances the phagocytic and killing activities of macrophages in M. amblycephala; however, the underlying regulatory mechanisms remain unclear. The present study showed that treatment with Aeromonas hydrophila and LPS induced the expression of rMaINTL in macrophages, and its level and distribution in macrophages or kidney tissue markedly increased after incubation or injection with rMaINTL. The cellular structure of macrophages was significantly affected after incubation with rMaINTL, resulting in an increased surface area and pseudopodia extension, which might contribute to enhancing the phagocytic ability of macrophages. Then, digital gene expression profiling analysis of the kidneys from rMaINTL-treated juvenile M. amblycephala identified some phagocytosis-related signaling factors that were enriched in pathways involved in the regulation of the actin cytoskeleton. In addition, qRT-PCR and western blotting verified that rMaINTL upregulated the expression of CDC42, WASF2, and ARPC2 in vitro and in vivo; however, the expression of these proteins was inhibited by a CDC42 inhibitor in macrophages. Moreover, CDC42 mediated the promotion of rMaINTL on actin polymerization by increasing the F-actin/G-actin ratio, which led to the extension of pseudopodia and remodeling of the macrophage cytoskeleton. Furthermore, the enhancement of macrophage phagocytosis by rMaINTL was blocked by the CDC42 inhibitor. These results suggested that rMaINTL induced the expression of CDC42 as well as the downstream signaling molecules WASF2 and ARPC2, thereby facilitating actin polymerization to promote cytoskeletal remodeling and phagocytosis. Overall, MaINTL enhanced the phagocytosis activity of macrophages in M. amblycephala via activation of the CDC42-WASF2-ARPC2 signaling axis.

Increasing stiffness promotes pulmonary retention of ligand-directed dexamethasone-loaded nanoparticle for enhanced acute lung inflammation therapy

Inhaled nanoparticles (NPs) need to penetrate the bronchial mucosa to deliver drug payloads deeply in the lung for amplified local therapy. However, the bronchial mucociliary barrier eliminates NPs rapidly, which considerably limits their mucosal penetration. In this study, we find that surface ligand modification and stiffness adjustment of NPs contribute to the significantly enhanced bronchial mucosal absorption and pulmonary retention of inhaled drugs. We utilize neonatal Fc receptor ligand (FcBP) to modify the rationally designed low stiffness NPs (Soft-NP) and high stiffness NPs (Stiff-NP) to target bronchial mucosa. In an acute lung inflammation rat model, after intranasal administration with dexamethasone-loaded NPs, Stiff-NP endowed with FcBP displays superior therapeutic effects. The in vitro data demonstrate that the promotion effect of FcBP to bronchial mucosal absorption of Stiff-NP dominates over Soft-NP. This could be attributed to the higher affinity between ligand-receptor when incorporating FcBP on the Stiff-NP surface. Meanwhile, high stiffness modulates more actin filaments aggregation to mediate endocytosis, along with strengthened Ca2+ signal to enhance exocytosis. Conclusively, we highlight that FcBP-modified NPs with higher stiffness would be a potential pulmonary drug delivery system.

Coronavirus and the Cytoskeleton of Virus-Infected Cells

The cytoskeleton, which includes actin filaments, microtubules, and intermediate filaments, is one of the most important networks in the cell and undertakes many fundamental life activities. Among them, actin filaments are mainly responsible for maintaining cell shape and mediating cell movement, microtubules are in charge of coordinating all cargo transport within the cell, and intermediate filaments are mainly thought to guard against external mechanical pressure. In addition to this, cytoskeleton networks are also found to play an essential role in multiple viral infections. Due to the COVID-19 epidemic, including SARS-CoV-2, SARS-CoV and MERS-CoV, so many variants have caused wide public concern, that any virus infection can potentially bring great harm to human beings and society. Therefore, it is of great importance to study coronavirus infection and develop antiviral drugs and vaccines. In this chapter, we summarize in detail how the cytoskeleton responds and participates in coronavirus infection by analyzing the possibility of the cytoskeleton and its related proteins as antiviral targets, thereby providing ideas for finding more effective treatments.

Comparative functional analysis of macrophage phagocytosis in Dagu chickens and Wenchang chickens

Phagocytosis of macrophages constitutes a powerful barrier to innate immunity. Differences in the phagocytic function of macrophages among chicken breeds have rarely been reported, and the molecular mechanisms underlying phagocytosis remain poorly understood. This study compared functional difference of macrophages in Dagu chickens, originated in Zhuanghe, Liaoning Province, China, and Wenchang chickens, originated from Hainan Island in the South China Sea, and explored the potential molecular mechanisms by integrated analysis of mRNA expression profiles of macrophages and whole genome sequencing. Immunological parameters in peripheral blood indicated that Dagu chickens were more resistant to Salmonella challenge at 28 days old. Phagocytosis index and phagocytosis rate of macrophages displayed Dagu chickens performed a significantly higher phagocytic ability of macrophages at 14 and 28 days old. Furthermore, comparative analysis of mRNA expression profiles of macrophages of two breeds at 28 days old revealed that 1136 differentially expressed genes (DEGs), and 22 DEGs (e.g., H2AFZ, SNRPA1, CUEDC2, S100A12) were found to be hub genes regulating phagocytosis by participating in different immunological biological signaling pathways. In addition, many DEGs and hub genes were under strong differentiation in genome between two breeds, the H2AFZ gene was an intersection of DEGs and hub genes. These results provided a comprehensive functional comparison and transcriptomic profiles of macrophages in Chinese native chicken breeds, and deepened our understanding of the genetic mechanism of innate immunity.

The transcriptomic response of Hyphantria cunea (Drury) to the infection of Serratia marcescens Bizio based on full-length SMRT transcriptome sequencing

Hyphantria cunea (Drury) is a globally important forest pest. We found that the Serratia marcescens Bizio strain SM1 had insecticidal activity against H. cunea, but the transcriptomic response of H. cunea to SM1 were not clear. Therefore, we performed full-length sequencing of the transcriptomes of H. cunea larvae infected with SM1 and the control group. A total of 1,183 differentially expressed genes (DEGs) were identified by comparing the group infected with SM1 and the control group, including 554 downregulated genes and 629 upregulated genes. We found many downregulated genes in metabolic pathways. Furthermore, some of these downregulated genes were involved in cellular immunity, melanization, and detoxification enzymes, which showed that SM1 weakened H. cunea immunity. In addition, genes in the juvenile hormone synthesis pathway were upregulated, which was detrimental to the survival of H. cunea. This research analyzed the transcriptomic response of H. cunea to SM1 by high-throughput full-length transcriptome sequencing. The results provide useful information to explore the relationship between S. marcescens and H. cunea, and theoretical support for the application of S. marcescens and the control of H. cunea in the future.

Functional Role of AGAP2/PIKE-A in Fcγ Receptor-Mediated Phagocytosis

In phagocytes, cytoskeletal and membrane remodeling is finely regulated at the phagocytic cup. Various smaFll G proteins, including those of the Arf family, control these dynamic processes. Human neutrophils express AGAP2, an Arf GTPase activating protein (ArfGAP) that regulates endosomal trafficking and focal adhesion remodeling. We first examined the impact of AGAP2 on phagocytosis in CHO cells stably expressing the FcγRIIA receptor (CHO-IIA). In unstimulated CHO-IIA cells, AGAP2 only partially co-localized with cytoskeletal elements and intracellular compartments. In CHO-IIA cells, AGAP2 transiently accumulated at actin-rich phagocytic cups and increased Fcγ receptor-mediated phagocytosis. Enhanced phagocytosis was not dependent on the N-terminal GTP-binding protein-like (GLD) domain of AGAP2. AGAP2 deleted of its GTPase-activating protein (GAP) domain was not recruited to phagocytic cups and did not enhance the engulfment of IgG-opsonized beads. However, the GAP-deficient [R618K]AGAP2 transiently localized at the phagocytic cups and enhanced phagocytosis. In PLB-985 cells differentiated towards a neutrophil-like phenotype, silencing of AGAP2 reduced phagocytosis of opsonized zymosan. In human neutrophils, opsonized zymosan or monosodium urate crystals induced AGAP2 phosphorylation. The data indicate that particulate agonists induce AGAP2 phosphorylation in neutrophils. This study highlights the role of AGAP2 and its GAP domain but not GAP activity in FcγR-dependent uptake of opsonized particles.

Crosslinking of membrane CD13 in human neutrophils mediates phagocytosis and production of reactive oxygen species, neutrophil extracellular traps and proinflammatory cytokines

Aminopeptidase N, or CD13, is a cell membrane ectopeptidase highly expressed in myeloid cells. Through its enzymatic activity, CD13 regulates the activity of several bioactive peptides, such as endorphins and enkephalins, chemotactic peptides like MCP-1 and IL-8, angiotensin III, bradikinin, etc. In recent years, it has been appreciated that independently of its peptidase activity, CD13 can activate signal transduction pathways and mediate effector functions such as phagocytosis and cytokine secretion in monocytes and macrophages. Although neutrophils are known to express CD13 on its membrane, it is currently unknown if CD13 can mediate effector functions in these cells. Here, we show that in human neutrophils CD13 can mediate phagocytosis, which is dependent on a signaling pathway that involves Syk, and PI3-K. Phagocytosis mediated by CD13 is associated with production of reactive oxygen species (ROS). The level of phagocytosis and ROS production mediated by CD13 are similar to those through FcγRIII (CD16b), a widely studied receptor of human neutrophils. Also, CD13 ligation induces the release of neutrophil extracellular traps (NETs) as well as cytokine secretion from neutrophils. These results support the hypothesis that CD13 is a membrane receptor able to activate effector functions in human neutrophils.

Role of particle local curvature in cellular wrapping

Cellular uptake through membranes plays an important role in adsorbing nutrients and fighting infection and can be used for nanomedicine developments. Endocytosis is one of the pathways of cellular uptake which associate with elastic deformation of the membrane wrapping around the foreign particle. The deformability of the membrane is strongly regulated by the presence of a cortical cytoskeleton placed underneath the membrane. It is shown that shape and orientation of the particles influence on their internalization. Here, we study the role of particle local curvature in cellular uptake by investigating the wrapping of an elastic membrane around a long cylindrical object with an elliptical cross-section. The membrane itself is adhered to a substrate mimicking the cytoskeleton. Membrane wrapping proceeds differently whether the initial contact occurs at the target's highly curved part (vertical) or along its long side (horizontal). We obtain a wrapping phase diagram as a function of the membrane-cytoskeleton and the membrane-target adhesion energy, which includes three distinct regimes (unwrapped, partially wrapped and fully wrapped), separated by two phase transitions. We also provide analytical expressions for the boundaries between the different regimes which confirm that the transitions strongly depend on the orientation and aspect ratio of the nanowire.

Trained Immunity Provides Long-Term Protection against Bacterial Infections in Channel Catfish

Beta glucan exposure induced trained immunity in channel catfish that conferred long-term protection against Edwardsiella ictaluri and Edwardsiella piscicida infections one month post exposure. Flow cytometric analyses demonstrated that isolated macrophages and neutrophils phagocytosed higher amounts of E. ictaluri and E. piscicida. Beta glucan induced changes in the distribution of histone modifications in the monomethylation and trimethylation of H3K4 and modifications in the acetylation and trimethylation of H3K27. KEGG pathway analyses revealed that these modifications affected expressions of genes controlling phagocytosis, phagosome functions and enhanced immune cell signaling. These analyses correlate the histone modifications with gene functions and to the observed enhanced phagocytosis and to the increased survival following bacterial challenge in channel catfish. These data suggest the chromatin reconfiguration that directs trained immunity as demonstrated in mammals also occurs in channel catfish. Understanding the mechanisms underlying trained immunity can help us design prophylactic and non-antibiotic based therapies and develop broad-based vaccines to limit bacterial disease outbreaks in catfish production.

Nanoparticle entry into cells; the cell biology weak link

Nanoparticles (NP) are attractive options for the therapeutic delivery of active pharmaceutical drugs, proteins and nucleic acids into cells, tissues and organs. Research into the development and application of NP most often starts with a diverse group of scientists, including chemists, bioengineers and material and pharmaceutical scientists, who design, fabricate and characterize NP in vitro (Stage 1). The next step (Stage 2) generally investigates cell toxicity as well as the processes by which NP bind, are internalized and deliver their cargo to appropriate model tissue culture cells. Subsequently, in Stage 3, selected NP are tested in animal systems, mostly mouse. Whereas the chemistry-based development and analysis in Stage 1 is increasingly sophisticated, the investigations in Stage 2 are not what could be regarded as 'state-of-the-art' for the cell biology field and the quality of research into NP interactions with cells is often sub-standard. In this review we describe our current understanding of the mechanisms by which particles gain entry into mammalian cells via endocytosis. We summarize the most important areas for concern, highlight some of the most common mis-conceptions, and identify areas where NP scientists could engage with trained cell biologists. Our survey of the different mechanisms of uptake into cells makes us suspect that claims for roles for caveolae, as well as macropinocytosis, in NP uptake into cells have been exaggerated, whereas phagocytosis has been under-appreciated.

Pathogenic Mechanisms of Secondary Organic Aerosols

Air pollution represents a major health problem and an economic burden. In recent years, advances in air pollution research has allowed particle fractionation and identification of secondary organic aerosol (SOA). SOA is formed from either biogenic or anthropogenic emissions, through a mass transfer from the gaseous mass to the particulate phase in the atmosphere. They can have deleterious impact on health and the mortality of individuals with chronic inflammatory diseases. The pleiotropic effects of SOA could involve different and interconnected pathogenic mechanisms ranging from oxidative stress, inflammation, and immune system dysfunction. The purpose of this review is to present recent findings about SOA pathogenic roles and potential underlying mechanisms focusing on the lungs; the latter being the primary exposed organ to atmospheric pollutants.

PM2.5 Synergizes With Pseudomonas aeruginosa to Suppress Alveolar Macrophage Function in Mice Through the mTOR Pathway

High concentrations of PM2.5 in enclosed broiler houses cause respiratory disorders in humans and animals. Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen that can induce severe respiratory disease in animals under stress or with abnormal immune functions. Alveolar macrophages are lung-resident immune cells that play important roles in lung host defence and immune balance. In this study, the mechanism by which PM2.5 synergizes with P. aeruginosa to damage alveolar macrophage function and induce inflammation was investigated. The results will provide a theoretical basis for improving the poultry breeding environment and preventing the recurrence of infection with P. aeruginosa. Alveolar macrophages were stimulated by PM2.5 collected in an enclosed broiler house and P. aeruginosa. Phagocytosis was determined by the neutral red test. The apoptosis rate and cytoskeleton changes were observed by flow cytometry assays and laser scanning confocal microscopy. Protein levels related to autophagy and the mTOR pathway were detected by Western blotting. The results indicated that PM2.5 in combination with P. aeruginosa could decrease phagocytosis, inhibit autophagy, increase apoptosis, and destroy the cytoskeleton in alveolar macrophages. In addition, alveolar macrophages had significantly increased expression of mTOR pathway-related proteins in response to the synergistic stimulation of PM2.5 and P. aeruginosa. The above results confirmed that PM2.5 in poultry houses synergized with P. aeruginosa to impede alveolar macrophage function and caused more severe respiratory system injuries through a process closely related to the activation of the mTOR signalling pathway.

Current Development of Nano-Drug Delivery to Target Macrophages

Macrophages are the most important innate immune cells that participate in various inflammation-related diseases. Therefore, macrophage-related pathological processes are essential targets in the diagnosis and treatment of diseases. Since nanoparticles (NPs) can be preferentially taken up by macrophages, NPs have attracted most attention for specific macrophage-targeting. In this review, the interactions between NPs and the immune system are introduced to help understand the pharmacokinetics and biodistribution of NPs in immune cells. The current design and strategy of NPs modification for specific macrophage-targeting are investigated and summarized.

Suppression of trabecular meshwork phagocytosis by norepinephrine is associated with nocturnal increase in intraocular pressure in mice

Intraocular pressure (IOP) is an important factor in glaucoma development, which involves aqueous humor (AH) dynamics, with inflow from the ciliary body and outflow through the trabecular meshwork (TM). IOP has a circadian rhythm entrained by sympathetic noradrenaline (NE) or adrenal glucocorticoids (GCs). Herein, we investigated the involvement of GC/NE in AH outflow. Pharmacological prevention of inflow/outflow in mice indicated a diurnal outflow increase, which was related to TM phagocytosis. NE showed a non-self-sustained inhibition in phagocytosis of immortalized human TM cells, but not GC. The pharmacological and reverse genetic approaches identified β1-adrenergic receptor (AR)-mediated exchange proteins directly activated by cyclic adenosine monophosphate (EPAC)-SHIP1 signal activation by ablation of phosphatidylinositol triphosphate, regulating phagocytic cup formation. Furthermore, we revealed the phagocytosis involvement in the β1-AR-EPAC-SHIP1-mediated nocturnal IOP rise in mice. These suggest that TM phagocytosis suppression by NE can regulate IOP rhythm through AH outflow. This discovery may aid glaucoma management.

Double‐edged sword role of shrimp miRNA explains an evolutionary language between shrimp‐pathogen interactions that unties the knot of shrimp infection

Shrimp production, using a small‐scale enclosed pond system, is a rapidly growing aquaculture sector, which is valued around USD 18.30 billion in 2020. Intensified shrimp culture leads to the outbreak of transmissible diseases to eventually cause a huge loss in the production process and thus the economy. Studies on microRNA (miRNA) reveal that miRNA has an influential role in the host‐pathogen interaction during an infection. Recently, shrimp miRNA has been shown to help pathogen‐like viruses for their replication and infection. Several shrimp miRNAs were reported to be involved in enhancing host immunity against viral infection, especially white spot syndrome virus (WSSV) infection and Vibrio infection caused by bacterial species, whereas some shrimp miRNAs were reported to be hijacked by WSSV and to enhance the viral replication and establish the infection in shrimp. This gives an insight into the double‐edged sword role played by shrimp miRNA during host‐pathogen interaction. In future, this role could be employed against the virus to strengthen the shrimp culture. In this review, we discuss the role of shrimp miRNA and their mechanism(s) associated with the establishment of host‐pathogen interaction during infection, which will reveal the complexity associated with shrimp infection.

Mechanical phenotyping reveals unique biomechanical responses in retinoic acid-resistant acute promyelocytic leukemia

All-trans retinoic acid (ATRA) is an essential therapy in the treatment of acute promyelocytic leukemia (APL), but nearly 20% of patients with APL are resistant to ATRA. As there are no biomarkers for ATRA resistance that yet exist, we investigated whether cell mechanics could be associated with this pathological phenotype. Using mechano-node-pore sensing, a single-cell mechanical phenotyping platform, and patient-derived APL cell lines, we discovered that ATRA-resistant APL cells are less mechanically pliable. By investigating how different subcellular components of APL cells contribute to whole-cell mechanical phenotype, we determined that nuclear mechanics strongly influence an APL cell's mechanical response. Moreover, decondensing chromatin with trichostatin A is especially effective in softening ATRA-resistant APL cells. RNA-seq allowed us to compare the transcriptomic differences between ATRA-resistant and ATRA-responsive APL cells and highlighted gene expression changes that could be associated with mechanical changes. Overall, we have demonstrated the potential of "physical" biomarkers in identifying APL resistance.

Tailoring the physicochemical properties of nanomaterials for immunomodulation

Immunomodulation is poised to revolutionize the treatment of cancer, autoimmune diseases, and many other inflammation-related disorders. The immune system in these conditions can be either activated or suppressed by nanocarriers loaded with bioactive molecules. Although immunomodulation via these therapeutics has long been recognized, and a broad range of nanocarriers have been designed to accommodate varied usages, less studies have focused on the effects of nanomaterial physicochemical properties on immune responses, especially the immunity altered by nanocarrier materials alone. Conclusions are sometimes seemly inconsistent due to the complexities of nanomaterials and the immune system. An in-depth understanding of the nanocarrier-induced immune responses is essential for clinical applications. In this review, we summarize recent studies of the immune responses influenced by nanomaterial physicochemical properties with an emphasis on the intrinsic features of nanomaterials that modulate the innate and adaptive immunities. We then provide our perspectives on the design of nanomaterials for immunomodulation.

Effect of micro- and nanoparticle shape on biological processes

In the drug delivery field, there is beyond doubt that the shape of micro- and nanoparticles (M&NPs) critically affects their biological fate. Herein, following an introduction describing recent technological advances for designing nonspherical M&NPs, we highlight the role of particle shape in cell capture, subcellular distribution, intracellular drug delivery, and cytotoxicity. Then, we discuss theoretical approaches for understanding the effect of particle shape on internalization by the cell membrane. Subsequently, recent advances on shape-dependent behaviors of M&NPs in the systemic circulation are detailed. In particular, the interaction of M&NPs with blood proteins, biodistribution, and circulation under flow conditions are analyzed. Finally, the hurdles and future directions for developing nonspherical M&NPs are underscored.

Phagocytic Uptake of Polymeric Particles by Immune Cells under Flow Conditions

Particles injected intravenously are thought to be cleared by macrophages residing in the liver and spleen, but they also encounter circulating immune cells. It remains to be established if the circulating cells can take up particles while flowing and if the uptake capacity is similar under static and flow conditions. Here, we use an in vitro peristaltic pump setup that mimics pulsatile blood flow to determine if immune cells take up particles under constant fluidic flow. We use polystyrene particles of varying sizes as the model of a polymeric particle for these studies. Our results show that the immune cells do phagocytose under flow conditions. We demonstrate that cell lines representing myeloid cells, primary human neutrophils, and monocytes take up submicrometer-sized particles at similar or better rates under flow compared to static conditions. Experiments with whole human blood show that, even under the crowding effects of red blood cells, neutrophils and monocytes take up particles while flowing. Together, these data suggest that circulating immune cells are likely to phagocytose intravenously injected particulates, which has implications for the design of particles to evade or target these cells.

Shotgun analysis to identify differences in protein expression between granulocytes and hyalinocytes of the European flat oyster Ostrea edulis

Recovery of wild populations of the European flat oyster Ostrea edulis is important for ecosystem health and conservation of this species, because native oyster populations have dramatically declined or disappeared in most European waters. Diseases have contributed to oyster decline and are important constrains for oyster recovery. Understanding oyster immune system should contribute to design effective strategies to fight oyster diseases. Haemocytes play a pivotal role in mollusc immune responses protecting from infection. Two main types of haemocytes, granulocytes and hyalinocytes, are distinguished in O. edulis. A study aiming to explore differential functions between both haemocyte types and, thus, to enrich the knowledge of Ostrea edulis immune system, was performed by comparing the proteome of the two haemolymph cell types, using a shotgun approach through liquid chromatography (LC) coupled to mass spectrometry (MS). Cells from oyster haemolymph were differentially separated by Percoll density gradient centrifugation. Shotgun LC-MS/MS performance allowed the identification of 145 proteins in hyalinocytes and 138 in the proteome of granulocytes. After a comparative analysis, 55 proteins with main roles in defence were identified, from which 28 were representative of granulocytes and 27 of hyalinocytes, plus 11 proteins shared by both cell types. Different proteins involved in signal transduction, apoptosis, oxidative response, processes related with the cytoskeleton and structure, recognition and wound healing were identified as representatives of each haemocyte type. Important signalling pathways in the immune response such as MAPK, Ras and NF-κβ seemed to be more relevant for granulocytes, while the Wnt signalling pathway, particularly relevant for wound healing, more relevant in hyalinocytes. The differences in proteins involved in recognition and in cytoskeleton and structure suggest differential specialisation in processes of phagocytosis and internalisation of pathogens between haemocyte types. Apoptosis seemed more active in granulocytes. The differences in proteins involved in oxidative response also suggest different redox processes in each cell type.

Cellular uptake of polylactide particles induces size dependent cytoskeletal remodeling in antigen presenting cells

Phagocytosis of particulate vaccine delivery systems is a critical immune mechanism involved in antigen capture and processing by macrophages and dendritic cells. The internalization and degradation of the particles involve a complex sequence of events. This process coordinates lipids, signaling proteins, and the cytoskeleton. Dynamic changes in the actin cytoskeleton are essential for phagocytosis and antigen presentation. Knowledge regarding the correlation of surface properties, attached ligand density and geometric size of particles with the efficiency of phagocytosis may facilitate their design and application. To investigate this, polylactide biodegradable particles with different diameters (2-4 μm and 200-300 nm) were exposed to murine macrophages and dendritic cells and the effect of size on a series of cellular responses was evaluated. Cellular uptake studies using microscopy and flow cytometry showed size dependent internalization of particles, with nanoparticles accumulating in cells at a faster rate. The particles induced homoaggregation of cells and also showed cytoskeletal remodeling that could be inhibited by cytochalasin-D. Scanning electron microscopy images showed the time dependent formation of phagocytic cups and invaginations that promote particle uptake. The particles were observed to co-localized with the endo-lysosomal compartments after phagocyotosis. In our experiments, particle mediated immunoactivation, antigen processing and cytokine secretion have shown a good correlation with the uptake process. These findings would allow a better understanding of the process of particle uptake and may be instrumental in the rational design of optimal vaccine delivery systems.

Polystyrene nanoplastics and microplastics can act as Trojan horse carriers of benzo(a)pyrene to mussel hemocytes in vitro

In this work we studied the ability of polystyrene (PS) nanoplastics (NPs) and microplastics (MPs) to transfer benzo(a)pyrene (BaP) to mussel hemocytes and to produce toxic effects in vitro. For this, intracellular fate and toxicity of PS NPs (0.05 μm) and MPs (0.5 and 4.5 μm) alone or with BaP and of BaP alone were assessed. Particles of 0.05 and 0.5 µm largely aggregated in the exposure medium whereas presence of BaP reduced particle aggregation. Cells internalized PS NPs and MPs alone or with BaP and these were found inside and outside lysosomes, depending on their size. PS particles alone or with BaP were cytotoxic to hemocytes only at the highest concentrations tested. The same was true for most sublethal endpoints except for increased phagocytic activity provoked by NPs and 0.5 μm MPs at lower concentrations. Plastic particles appeared to be the main drivers for reduced plasma membrane integrity and increased phagocytic and lysosomal activities whereas BaP appeared to contribute more to reduced cell viability and phagocytosis and increased ROS production and genotoxicity. Overall, PS NPs and MPs can act as carriers of BaP to mussel hemocytes, rising concerns about risks plastics associated to pollutants may pose to aquatic organisms.