The Drosophila NPY-like system protects against chronic stress-induced learning deficit by preventing the disruption of autophagic flux.

Chronic stress may induce learning and memory deficits that are associated with a depression-like state in Drosophila melanogaster. The molecular and neural mechanisms underlying the etiology of chronic stress-induced learning deficit (CSLD) remain elusive. Here, we show that the autophagy-lysosomal pathway, a conserved cellular signaling mechanism, is associated with chronic stress in Drosophila, as indicated by time-series transcriptome profiling. Our findings demonstrate that chronic stress induces the disruption of autophagic flux, and chronic disruption of autophagic flux could lead to a learning deficit. Remarkably, preventing the disruption of autophagic flux by up-regulating the basal autophagy level is sufficient to protect against CSLD. Consistent with the essential role of the dopaminergic system in modulating susceptibility to CSLD, dopamine neuronal activity is also indispensable for chronic stress to induce the disruption of autophagic flux. By screening knockout mutants, we found that neuropeptide F, the Drosophila homolog of neuropeptide Y, is necessary for normal autophagic flux and promotes resilience to CSLD. Moreover, neuropeptide F signaling during chronic stress treatment promotes resilience to CSLD by preventing the disruption of autophagic flux. Importantly, neuropeptide F receptor activity in dopamine neurons also promotes resilience to CSLD. Together, our data elucidate a mechanism by which stress-induced excessive dopaminergic activity precipitates the disruption of autophagic flux, and chronic disruption of autophagic flux leads to CSLD, while inhibitory neuropeptide F signaling to dopamine neurons promotes resilience to CSLD by preventing the disruption of autophagic flux.

A pair of dopamine neurons mediate chronic stress signals to induce learning deficit in Drosophila melanogaster.

Chronic stress could induce severe cognitive impairments. Despite extensive investigations in mammalian models, the underlying mechanisms remain obscure. Here, we show that chronic stress could induce dramatic learning and memory deficits in Drosophila melanogaster The chronic stress-induced learning deficit (CSLD) is long lasting and associated with other depression-like behaviors. We demonstrated that excessive dopaminergic activity provokes susceptibility to CSLD. Remarkably, a pair of PPL1-γ1pedc dopaminergic neurons that project to the mushroom body (MB) γ1pedc compartment play a key role in regulating susceptibility to CSLD so that stress-induced PPL1-γ1pedc hyperactivity facilitates the development of CSLD. Consistently, the mushroom body output neurons (MBON) of the γ1pedc compartment, MBON-γ1pedc>α/ß neurons, are important for modulating susceptibility to CSLD. Imaging studies showed that dopaminergic activity is necessary to provoke the development of chronic stress-induced maladaptations in the MB network. Together, our data support that PPL1-γ1pedc mediates chronic stress signals to drive allostatic maladaptations in the MB network that lead to CSLD.

Intranasal mask for protecting the respiratory tract against viral aerosols.

The spread of many infectious diseases relies on aerosol transmission to the respiratory tract. Here we design an intranasal mask comprising a positively-charged thermosensitive hydrogel and cell-derived micro-sized vesicles with a specific viral receptor. We show that the positively charged hydrogel intercepts negatively charged viral aerosols, while the viral receptor on vesicles mediates the entrapment of viruses for inactivation. We demonstrate that when displaying matched viral receptors, the intranasal masks protect the nasal cavity and lung of mice from either severe acute respiratory syndrome coronavirus 2 or influenza A virus. With computerized tomography images of human nasal cavity, we further conduct computational fluid dynamics simulation and three-dimensional printing of an anatomically accurate human nasal cavity, which is connected to human lung organoids to generate a human respiratory tract model. Both simulative and experimental results support the suitability of intranasal masks in humans, as the likelihood of viral respiratory infections induced by different variant strains is dramatically reduced.

A High-Resolution Ternary Model Demonstrates How PEGylated 2D Nanomaterial Stimulates Integrin αv ß8 on Cell Membrane.

Bio-nano interfaces are integral to all applications of nanomaterials in biomedicine. In addition to peptide-ligand-functionalized nanomaterials, passivation on 2D nanomaterials has emerged as a new regulatory factor for integrin activation. However, the mechanisms underlying such ligand-independent processes are poorly understood. Here, using graphene oxide passivated with polyethylene glycol (GO-PEG) as a test bed, a ternary simulation model is constructed that also includes a membrane and both subunits of integrin αv ß8 to characterize GO-PEG-mediated integrin activation on the cell membrane in a ligand-independent manner. Combined with the experimental findings, production simulations of the ternary model show a three-phase mechanotransduction process in the vertical interaction mode. Specifically, GO-PEG first induces lipid aggregation-mediated integrin proximity, followed by transmembrane domain rotation and separation, leading to the extension and activation of extracellular domains. Thus, this study presents a complete picture of the interaction between passivated 2D nanomaterials and cell membranes to mediate integrin activation, and provides insights into the potential de novo design and rational use of novel desirable nanomaterials at diverse bio-nano interfaces.

Macrophage-tumor chimeric exosomes accumulate in lymph node and tumor to activate the immune response and the tumor microenvironment.

Despite multiple immunotherapeutic technologies that achieve potent T cell activation, effector T cells still lack efficiency because of the highly immunosuppressive conditions in the tumor microenvironment. Inspired by recent advances in nano-sized secreted vesicles known as exosomes as therapeutic agents and research revealing that circulating cancer cells have a "homing" capacity to return to the main tumor sites, we generated macrophage-tumor hybrid cells. We introduced nuclei isolated from tumor cells into activated M1-like macrophages to produce chimeric exosomes (aMT-exos). The aMT-exos were able to accumulate in both lymph nodes and diverse tumors of xenograft mice. They entered lymph nodes and primed T cell activation in both the classical antigen-presenting cell­induced immunostimulatory manner and a unique "direct exosome interaction" manner. aMT-exos also had strong "homing behavior" to tumor sites, where they ameliorated immunosuppression. They were effective in inducing tumor regression and extending survival in primary mouse models of lymphoma and breast and melanoma cancers. In addition, when combined with anti­programmed death 1 (a-PD1) treatment, aMT-exos were able to extend survival of metastatic and postsurgical tumor recurrence mouse models. Such a coactivation of the immune response and the tumor microenvironment enabled aMT-exos to confer efficient inhibition of primary tumors, tumor metastases, and postoperative tumor recurrence for personalized immunotherapy, which warrants further exploration in the clinical setting.

In vivo immunological response of exposure to PEGylated graphene oxide via intraperitoneal injection.

Polyethylene glycol functionalization is believed to have the capacity of endowing nanomaterials with stealth characteristics, which can diminish the arrest by macrophages and adverse immunological response. However, our previous study provided evidences that polyethylene glycol-functionalized graphene oxide (GOP) stimulated a strong immunological response to macrophages despite non-internalization in vitro, raising safety concerns and potential immunostimulation use of GOP. In light of this finding, we herein systematically study the in vivo immunological response upon the exposure to GOP via intraperitoneal injection. Taking cytokines production, cell types in the peritoneal fluid, biochemical index, hematology and histopathology as in vivo indicators, we demonstrate that GOP still remains the stealth-but-activating capacity on macrophages in a time and dose-dependent manner. Specifically, the immune response can be significantly elevated after a single high-dose injection, indicating that GOP can be a new candidate adjuvant for immunotherapy. For multiple low dose injections, the immune response is gentle, temporary, and tolerable, which manifests the biocompatibility of GOP in general drug delivery. The above results can thus provide guidance for safe and rational use of GOP for various biomedical applications.

The molecular mechanism of robust macrophage immune responses induced by PEGylated molybdenum disulfide.

Molybdenum disulfide (MoS2), a representative hexagonal transition metal dichalcogenide (TMD), has been extensively exploited in biomedical applications due to its unique physicochemical properties and biocompatibility. However, the lack of adequate data regarding how MoS2 activates immunological responses of macrophages remains a key concern for its risk assessment. Here, we employ a combined theoretical and experimental approach to investigate the interactions of MoS2 and PEGylated MoS2 (MoS2-PEG) with macrophages. We first perform molecular dynamics simulations to examine the atomic-detailed interactions of MoS2 and MoS2-PEG nanoflakes with a realistic model of the macrophage membrane. We show that a small MoS2 nanoflake (edge length of 2.86 nm) is capable of penetrating the macrophage membrane independent of its concentration. We also demonstrate that when initiated with a corner point-on configuration, the surface-bound PEG chains of MoS2-PEG hinder its membrane insertion process, leading to a prolonged passage through the membrane. Moreover, when placed in a face-on arrangement initially, the MoS2-PEG exhibits a lower binding free energy than pristine MoS2 after its adsorption on the membrane surface. The PEG chains can even insert and get buried in the outer leaflet of the membrane, providing additional contact for membrane adsorption. Our flow cytometric experiments then show that the responses of macrophages to either MoS2-PEG or MoS2 are significantly higher than that of the control (no nanomaterial stimulus), with MoS2-PEG eliciting stronger cytokine secretion than the pristine MoS2. The characteristics of slower/prolonged membrane penetration and stronger membrane adsorption of MoS2-PEG compared to pristine MoS2 explain why it triggers more sustained stimulation and higher cytokine secretion in macrophages as observed in our experiments. Our findings reveal the underlying molecular mechanism of how MoS2-PEG influences the immune responses and suggest its potential applications in nanomedicine involving immune stimulation.