Differential detection of immune cell activation by label-free radiation pressure force

Label-free radiation pressure force analysis using a microfluidic platform is applied to the differential detection of innate immune cell activation. Murine-derived peritoneal macrophages (IC-21) are used as a model system and the activation of IC-21 cells by lipopolysaccharide (LPS) and interferon gamma (IFN-γ) to M1 pro-inflammatory phenotype is confirmed by RNA gene sequencing and nitric oxide production. The mean cell size determined by radiation pressure force analysis increases slightly after the activation (4 to 6%) and the calculated percentage of population overlaps between the control and the activated group after 14 and 24 h stimulations are at 79% and 77%. Meanwhile the mean cell velocity decreases more significantly after the activation (14% to 15%) and the calculated percentage of population overlaps between the control and the activated group after 14 and 24 h stimulations are only at 14% and 13%. The results demonstrate that the majority of the activated cells acquire a lower velocity than the cells from the control group without changes in cell size. For comparison label-free flow cytometry analysis of living IC-21 cells under the same stimulation conditions are performed and the results show population shifts towards larger values in both forward scatter and side scatter, but the calculated percentage of population overlaps in all case are significant (70% to 83%). Cell images obtained during radiation pressure force analysis by a CCD camera, and by optical microscopy and atomic force microscopy (AFM) reveal correlations between the cell activation by LPS/IFN-γ, the increase in cell complexity and surface roughness, and enhanced back scattered light by the activated cells. The unique relationship predicted by Mie's theory between the radiation pressure force exerted on the cell and the angular distribution of the scattered light by the cell which is influenced by its size, complexity, and surface conditions, endows the cell velocity based measurement by radiation pressure force analysis with high sensitivity in differentiating immune cell activation.

Monocytes Expose Factor XIII-A and Stabilize Thrombi against Fibrinolytic Degradation

Factor XIII (FXIII) is a transglutaminase that promotes thrombus stability by cross-linking fibrin. The cellular form, a homodimer of the A subunits, denoted FXIII-A, lacks a classical signal peptide for its release; however, we have shown that it is exposed on activated platelets. Here we addressed whether monocytes expose intracellular FXIII-A in response to stimuli. Using flow cytometry, we demonstrate that FXIII-A antigen and activity are up-regulated on human monocytes in response to stimulation by IL-4 and IL-10. Higher basal levels of the FXIII-A antigen were noted on the membrane of the monocytic cell line THP-1, but activity was significantly enhanced following stimulation with IL-4 and IL-10. In contrast, treatment with lipopolysaccharide did not upregulate exposure of FXIII-A in THP-1 cells. Quantification of the FXIII-A activity revealed a significant increase in THP-1 cells in total cell lysates following stimulation with IL-4 and IL-10. Following fractionation, the largest pool of FXIII-A was membrane associated. Monocytes were actively incorporated into the fibrin mesh of model thrombi. We found that stimulation of monocytes and THP-1 cells with IL-4 and IL-10 stabilized FXIII-depleted thrombi against fibrinolytic degradation, via a transglutaminase-dependent mechanism. Our data suggest that monocyte-derived FXIII-A externalized in response to stimuli participates in thrombus stabilization.

A size dependent evaluation of the cytotoxicity and uptake of nanographene oxide

Different sizes of nanographene oxide flakes trigger different cytotoxicity response. Formation of big cellular vacuoles and cells increase size.

Role of p38 Mitogen-Activated Protein Kinase (MAPK) for Vacuole Formation in Lipopolysaccharide (LPS)-Stimulated Macrophages

The role of p38 mitogen-activated protein kinase (MAPK) on vacuole formation in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells was examined. LPS definitely induced the formation of vacuoles in RAW 264.7 cells and SB202190 as a p38 specific inhibitor also induced slight vacuole formation. The simultaneous treatment with LPS and SB202190 induced many more vacuoles in RAW 264.7 cells than the treatment with LPS or SB202190 alone, and the vacuoles were extraordinarily large in size. On the other hand, an inactive inhibitor of p38 MAPK did not augment LPS-induced vacuole formation. Further, the inhibitors of other MAPKs and nuclear factor (NF)-kappaB pathways did not affect it. The extraordinarily large vacuoles in RAW 264.7 cells treated with LPS and SB202190 were possibly formed via fusion of small vacuoles. However, SB202190 did not augment vacuole formation in CpG DNA or interferon (IFN)-gamma-stimulated RAW 264.7 cells. The role of p38 MAPK in the vacuole formation in LPS-stimulated macrophages is discussed.

Lipid A structures containing novel lipid moieties: synthesis and adjuvant properties

Structurally well-defined immune stimulatory molecules are important components of new generation molecular vaccines. In this paper, the design and synthesis of two lipid A analogues containing an unnatural tri-lipid acyl group are described. In a totally synthetic liposomal vaccine system, these re-designed lipid A analogues demonstrate potent immune stimulatory properties including antigen specific T-cell activation.

Diphosphoryl lipid A from Rhodobacter sphaeroides blocks the binding and internalization of lipopolysaccharide in RAW 264.7 cells

Diphosphoryl lipid A derived from the nontoxic LPS of Rhodobacter sphaeroides (RsDPLA) has been shown to be a powerful LPS antagonist in both human and murine cell lines. In addition, RsDPLA also can protect mice against the lethal effects of toxic LPS. In this study, we complexed both the deep rough LPS from Escherichia coli D31 m4 (ReLPS) and RsDPLA with 5- and 30-nm colloidal gold and compared their binding to the RAW 264.7 cell line by electron microscopy. Both ReLPS and RsDPLA bound to the cells with the following observations. First, binding studies revealed that pretreatment with RsDPLA completely blocked the binding and thus internalization of ReLPS-gold conjugates to these cells at both 37 degrees C and 4 degrees C. Second, ReLPS was internalized via micropinocytosis (noncoated plasma membrane invaginations) involving formation of caveolae-like structures and leading to the formation of micropinocytotic vesicles, macropinocytosis (or phagocytosis), formation of clathrin-coated pits (receptor mediated), and penetration through plasma membrane into cytoplasm. Third, in contrast, RsDPLA was internalized predominantly via macropinocytosis. These studies show for the first time that RsDPLA blocks the binding and thus internalization of LPS as observed by scanning and transmission electron microscopy.