Summary The gut microbiota can be altered by dietary interventions to prevent and treat various diseases. However, the mechanisms by which food products modulate commensals remain largely unknown. We demonstrate that plant-derived exosomes-like nanoparticles (ELNs) are taken up by the gut microbiota and contain RNAs that alter microbiome composition and host physiology. Ginger ELNs (GELNs) are preferentially taken up by Lactobacillaceae in a GELN lipid-dependent manner and contain microRNAs that target various genes in Lactobacillus rhamnosus (LGG). Among these, GELN mdo-miR7267-3p-mediated targeting of the LGG monooxygenase ycnE yields increased indole-3-carboxaldehyde (I3A). GELN RNAs or I3A, a ligand for aryl hydrocarbon receptor (AHR), are sufficient to induce production of IL-22, which is linked to barrier function improvement. These functions of GELN RNAs can ameliorate mouse colitis via IL-22-dependent mechanisms. These findings reveal how plant products and their effects on the microbiome may be used to target specific host processes to alleviate disease.

We have investigated the cell surface recognition mechanisms used by human monocyte-derived macrophages (MO ) in phagocytosis of intact aging human neutrophils (PMNs) undergoing apoptosis. This study shows that the adhesive protein thrombospondin (TSP) was present in the interaction, both associated with the MO surface and in solution at a mean concentration of 0.59 ,g/ml. The interaction was inhibited by treatment of MO (but not aged PMN) with cycloheximide, but could be "rescued" by replenishment with exogenous TSP. Under control conditions, MO recognition of aged PMNs was specifically potentiated by purified platelet TSP at 5 ,g/ml, present either in the interaction or if preincubated with either cell type, suggesting that TSP might act as a "molecular bridge" between the two cell types. In support, both aged PMN and MO were found to adhere to TSP, and phagocytosis of aged PMN was specifically inhibited by (a) excess soluble TSP; (b) antibodies to TSP that also inhibit TSP-mediated adhesion to aged PMN; and (c) down-regulation of M4 receptors for TSP by plating MO on TSP-coated surfaces. Furthermore, inhibition with mAbs / Arg-Gly-Asp-Ser peptide of the candidate MO receptors for TSP, CD36, and a,83 exerted synergistic effects on both MO recognition of aged PMN and MO adhesion to TSP, indicating that "two point" adhesion of TSP to these MO structures is involved in phagocytosis of aged PMN. Our findings indicate newly defined roles for TSP and CD36 in phagocytic clearance of senescent neutrophils, which may limit inflammatory tissue injury and promote resolution. (J. Clin. Invest. 1992.90:1513-1522

Exosomes are emerging mediators of intercellular communication; whether the release of exosomes has an effect on the exosome donor cells in addition to the recipient cells has not been investigated to any extent. Here, we examine different exosomal miRNA expression profiles in primary mouse colon tumour, liver metastasis of colon cancer and naive colon tissues. In more advanced disease, higher levels of tumour suppressor miRNAs are encapsulated in the exosomes. miR-193a interacts with major vault protein (MVP). Knockout of MVP leads to miR-193a accumulation in the exosomal donor cells instead of exosomes, inhibiting tumour progression. Furthermore, miR-193a causes cell cycle G1 arrest and cell proliferation repression through targeting of Caprin1, which upregulates Ccnd2 and c-Myc. Human colon cancer patients with more advanced disease show higher levels of circulating exosomal miR-193a. In summary, our data demonstrate that MVP-mediated selective sorting of tumour suppressor miRNA into exosomes promotes tumour progression.

Objective. To evaluate whether patients with systemic lupus erythematosus (SLE) have a higher rate of apoptosis in and secondary necrosis of polymorphonuclear neutrophils (PMNs) and macrophages compared with controls; to compare the rate of macrophage phagocytic clearance of apoptotic PMNs in patients with SLE and healthy controls; to evaluate whether in vitro PMN and macrophage apoptosis and secondary necrosis, and the ability of macrophages to phagocytose apoptotic bodies, are correlated with lupus disease activity; and to determine whether macrophage clearance of apoptotic bodies in patients with SLE and normal controls is related to certain serum factors.Methods. Thirty-six patients with SLE and 18 healthy, nonsmoking volunteers were studied. PMNs and monocytes were isolated from fresh blood and cultured in the presence of different sources of serum. Apoptotic PMNs and macrophages were examined by annexin V binding and morphology on May-Giemsastained cytopreparations, at different time points. The presence of secondary necrotic PMNs and macrophages was verified by staining with trypan blue. Macrophage phagocytosis of apoptotic PMNs was measured using a coded, observer-blinded, microscopically quantified phagocytosis assay. Cells were cultured in the presence of serum obtained from healthy subjects or from patients with SLE.Results. At 5 and 24 hours, the percentage of apoptotic PMNs from patients with SLE was significantly higher than that of PMNs from healthy subjects. At 24 and 48 hours, the percentage of secondary necrotic PMNs from patients with SLE was also significantly higher than the percentage of necrotic PMNs from controls. Serum from patients with SLE accelerated the rate of apoptosis in and secondary necrosis of PMNs from healthy subjects. Macrophages from SLE patients were less capable of phagocytosing apoptotic PMNs compared with macrophages obtained from controls. Macrophages from patients with active SLE were less capable of phagocytosing apoptotic PMNs than were macrophages from patients with inactive SLE, but the difference was not statistically significant. The percentage of phagocytosis of apoptotic PMNs by macrophages from SLE patients correlated negatively with the SLE Disease Activity Index, serum levels of anti-doublestranded DNA, and the erythrocyte sedimentation rate, and correlated positively with serum levels of C3, C4, and albumin, the hemoglobin level, and the leukocyte count. Serum from SLE patients not only significantly increased macrophage apoptosis in cells from healthy subjects but also remarkably down-regulated the clearance of apoptotic PMNs by macrophages from healthy subjects. In contrast, serum from healthy subjects significantly increased phagocytosis of apoptotic PMNs by macrophages from SLE patients.Conclusion. The observed increase of apoptotic PMNs and macrophages and the poor ability of macrophages from patients with SLE to phagocytose apoptotic bodies may indicate an impaired clearance mechanism, which may be mediated by factors in a patient's serum.Systemic lu...

In vivo, cells undergoing apoptosis are usually recognised and swiftly ingested by macrophages or neighbouring cells acting as semi-professional phagocytes. This review debates evidence that the contents of apoptotic cells represent a danger to the organism, being capable of injuring tissue directly or triggering autoimmune responses, concluding that phagocytic clearance of intact apoptotic cells is a safe disposal route. Indeed, new data suggest that, in certain circumstances, phagocytes ingesting apoptotic cells may actively downregulate inflammatory and immune responses. Consequently, increasing evidence that there may be factors capable of perturbing safe clearance of apoptotic cells in vivo suggests that failure of this process may be a hitherto unrecognised pathogenetic factor in inflammatory and autoimmune diseases. New treatments designed to promote safe phagocytic clearance of dying cells can be anticipated, and it may even prove possible to eliminate unwanted cells by inducing appearance of cell surface`eat me' signals.

Macrophage activation and persistent inflammation contribute to the pathological process of spinal cord injury (SCI). It was reported that M2 macrophages were induced at 3–7 days after SCI but M2 markers were reduced or eliminated after 1 week. By contrast, M1 macrophage response is rapidly induced and then maintained at injured spinal cord. However, factors that modulate macrophage phenotype and function are poorly understood. We developed a model to distinguished bone marrow derived macrophages (BMDMs) from residential microglia and explored how BMDMs change their phenotype and functions in response to the lesion-related factors in injured spinal cord. Infiltrating BMDMs expressing higher Mac-2 and lower CX3CR1 migrate to the epicenter of injury, while microglia expressing lower Mac-2 but higher CX3CR1 distribute to the edges of lesion. Myelin debris at the lesion site switches BMDMs from M2 phenotype towards M1-like phenotype. Myelin debris activate ATP-binding cassette transporter A1 (ABCA1) for cholesterol efflux in response to myelin debris loading in vitro. However, this homeostatic mechanism in injured site is overwhelmed, leading to the development of foamy macrophages and lipid plaque in the lesion site. The persistence of these cells indicates a pro-inflammatory environment, associated with enhanced neurotoxicity and impaired wound healing. These foamy macrophages have poor capacity to phagocytose apoptotic neutrophils resulting in uningested neutrophils releasing their toxic contents and further tissue damage. In conclusion, these data demonstrate for the first time that myelin debris generated in injured spinal cord modulates macrophage activation. Lipid accumulation following macrophage phenotype switch contributes to SCI pathology.

Phagocyte recognition and ingestion of intact cells undergoing apoptosis are key events in this generally important program of cell death. Insufficient phagocyte capacity for apoptotic cells can result in failure to clear dying cells before membrane integrity is lost, resulting in leakage of noxious cell contents and severe tissue damage. However, no means has been available to increase phagocytic clearance of apoptotic cells. We now report that transfection of the macrophage adhesion molecule CD36 into human Bowes melanoma cells specifically conferred greatly increased capacity to ingest apoptotic neutrophils, lymphocytes, and fibroblasts, comparable to that exhibited by macrophages. Furthermore, when CD36 was transfected into another cell type with limited capacity to take up apoptotic bodies, the monkey COS-7 cell, similar effects were observed. Therefore, CD36 gene transfer can confer "professional" capacity to ingest apoptotic cells upon "amateur" phagocytes.

Inflammation is a hallmark of cancer. Activated immune cells are intrinsically capable of homing to inflammatory sites. Using three inflammatory driven disease mouse models, we show that grapefruit-derived nanovectors (GNVs) coated with inflammatory related receptor enriched membranes of activated leukocytes (IGNVs) are enhanced for homing to inflammatory tumor tissues. Blocking LFA-1 or CXCR1 and CXCR2 on the IGNVs significantly inhibits IGNV homing to the inflammatory tissue. The therapeutic potential of IGNVs was further demonstrated by enhancing the chemotherapeutic effect as shown by inhibition of tumor growth in two tumor models and inhibiting the inflammatory effects of DSS induced mouse colitis. The fact that IGNVs are capable of homing to inflammatory tissue and that there is an overexpression of chemokines in diseased human tissue provides the rationale for using IGNVs to more directed delivery of therapeutic agents to inflammatory tumor sites and the use of IGNVs as personalized medicine for treatment of certain cancers.