Human mast cell line-1 (HMC-1) cells exhibit a membrane capacitance increase when dialysed with high free-Ca(2+) and GTPγS containing intracellular solution

Annexin A1 Mimetic Peptide Ac2-26 Modulates the Function of Murine Colonic and Human Mast Cells

Mast cells (MCs) are main effector cells in allergic inflammation and after activation, they release stored (histamine, heparin, proteases) and newly synthesized (lipid mediators and cytokines) substances. In the gastrointestinal tract the largest MC population is located in the lamina propria and submucosa whereas several signals such as the cytokine IL-4, seem to increase the granule content and to stimulate a remarkable expansion of intestinal MCs. The broad range of MC-derived bioactive molecules may explain their involvement in many different allergic disorders of the gastrointestinal tract. Annexin A1 (AnxA1) is a 37 KDa glucocorticoid induced monomeric protein selectively distributed in certain tissues. Its activity can be reproduced by mimetic peptides of the N-terminal portion, such as Ac2-26, that share the same receptor FPR-L1. Although previous reports demonstrated that AnxA1 inhibits MC degranulation in murine models, the effects of exogenous peptide Ac2-26 on intestinal MCs or the biological functions of the Ac2-26/FPR2 system in human MCs have been poorly studied. To determine the effects of Ac2-26 on the function of MCs toward the possibility of AnxA1-based therapeutics, we treated WT and IL-4 knockout mice with peptide Ac2-26, and we examined the spontaneous and compound 48/80 stimulated colonic MC degranulation and cytokine production. Moreover, in vitro, using human mast cell line HMC-1 we demonstrated that exogenous AnxA1 peptide is capable of interfering with the HMC-1 degranulation in a direct pathway through formyl peptide receptors (FPRs). We envisage that our results can provide therapeutic strategies to reduce the release of MC mediators in inflammatory allergic processes.

Dictamnine is an effective anti-anaphylactoid compound acting via the MrgX2 receptor located on mast cells

Anaphylactoid reactions are potentially fatal allergic diseases caused by mast cells (MCs), which release histamine and lipid mediators under certain stimuli. Therefore, there is an urgent need to develop new drug candidates to treat anaphylactoid reactions. The MrgX2 receptor mediates anaphylactoid reactions that cause inflammatory diseases. Cortex dictamni is a Chinese herb used for treating allergy-related diseases; however, its active compound is still unknown and its mechanism of action has not yet been reported. The aim of this study was to screen the anti-anaphylactoid compound from C. dictamni extracts. An MrgX2/CMC-HPLC method was established for screening MrgX2-specific compounds retained from the alcohol extract of C. dictamni. A mouse model of hindpaw extravasation was used to evaluate the anti-anaphylactoid effect of this ingredient. Intracellular Ca²⁺ mobilization was assessed using a calcium imaging assay. Enzyme immunoassays were performed to measure cytokine and chemokine release levels. The molecular signaling pathways were explored by western blotting. As a result, dictamnine was identified as an effective compound using the MrgX2/CMC method, which remarkably suppressed MC intracellular Ca²⁺ mobilization and the release of de novo degranulated substances, and inhibited PKC-PLCγ-IP3R-associated protein signaling molecules. Hence, dictamnine is a novel therapeutic candidate for anaphylactoid reactions via MrgX2.

Determination of Dielectric Properties of Cells using AC Electrokinetic-based Microfluidic Platform: A Review of Recent Advances

Cell dielectric properties, a type of intrinsic property of cells, can be used as electrophysiological biomarkers that offer a label-free way to characterize cell phenotypes and states, purify clinical samples, and identify target cancer cells. Here, we present a review of the determination of cell dielectric properties using alternating current (AC) electrokinetic-based microfluidic mechanisms, including electro-rotation (ROT) and dielectrophoresis (DEP). The review covers theoretically how ROT and DEP work to extract cell dielectric properties. We also dive into the details of differently structured ROT chips, followed by a discussion on the determination of cell dielectric properties and the use of these properties in bio-related applications. Additionally, the review offers a look at the future challenges facing the AC electrokinetic-based microfluidic platform in terms of acquiring cell dielectric parameters. Our conclusion is that this platform will bring biomedical and bioengineering sciences to the next level and ultimately achieve the shift from lab-oriented research to real-world applications.

Electron Microscopy-Based Comparison and Investigation of the Morphology of Exosomes Derived from Hepatocellular Carcinoma Cells Isolated at Different Centrifugal Speeds

Exosomes derived from hepatocellular carcinoma (HCC) cells are nanovesicles and are involved in the occurrence and development of HCC, they also serve as important carriers and drug targets of nanodrug delivery systems. The external shape and internal structure of exosomes are important indexes of identification, and isolated intact morphology is crucial to biological function integrity. However, given their susceptibility to various influencing factors, the external shape and internal structure of exosomes derived from HCC cells remain incompletely studied. In this study, exosomes purified from HCC cells were isolated at different centrifugation speeds and examined via multiple electron microscopy (EM) techniques. The results demonstrate that exosomes possess a nearly spherical shape and bilipid membranous vesicle with a concave cavity structure containing electron-dense and coated vesicles, suggesting the possible existence of subpopulations of exosomes with specific functions. The exosomes isolated at ultracentrifugation (UC) speed (≥110,000×g) presented irregular and diverse external morphologies, indicating the effect on the integrity of the exosomes. Transforming growth factor signaling bioactive substances (TGF-β1, S100A8, and S100A9) can be found in exosomes by performing Western blotting, showing that the internal content is associated with metastasis of HCC. These findings show that EMelectron microscopy and UC speed can affect exosome characteristics, including external shape, internal structure, and content of bioactive substances. The electron-dense and coated vesicles that had been discovered in exosomes might become new additional morphological features, which could help to improve the interpretation of experimental results and widen our understanding of exosome morphology.

Effects of Boswellia Serrata Roxb. and Curcuma longa L. in an In Vitro Intestinal Inflammation Model Using Immune Cells and Caco-2

Inflammatory bowel diseases, which consist of chronic inflammatory conditions of the colon and the small intestine, are considered a global disease of our modern society. Recently, the interest toward the use of herbal therapies for the management of inflammatory bowel diseases has increased because of their effectiveness and favourable safety profile, compared to conventional drugs. Boswellia serrata Roxb. and Curcuma longa L. are amongst the most promising herbal drugs, however, their clinical use in inflammatory bowel diseases is limited and little is known on their mechanism of action. The aim of this work was to investigate the effects of two phytochemically characterized extracts of B. serrata and C. longa in an in vitro model of intestinal inflammation. Their impact on cytokine release and reactive oxygen species production, as well as the maintenance of the intestinal barrier function and on intestinal mucosa immune cells infiltration, has been evaluated. The extracts showed a good protective effect on the intestinal epithelium at 1 µg/mL, with TEER values increasing by approximately 1.5 fold, compared to LPS-stimulated cells. C. longa showed an anti-inflammatory mechanism of action, reducing IL-8, TNF-α and IL-6 production by approximately 30%, 25% and 40%, respectively, compared to the inflammatory stimuli. B. serrata action was linked to its antioxidant effect, with ROS production being reduced by 25%, compared to H₂O₂-stimulated Caco-2 cells. C. longa and B. serrata resulted to be promising agents for the management of inflammatory bowel diseases by modulating in vitro parameters which have been identified in the clinical conditions.

Assessment of Serum sTREM-1 as a Marker of Subclinical Inflammation in Diarrhea-Predominant Patients with Irritable Bowel Syndrome

BACKGROUND

Irritable bowel disease (IBS) is viewed upon as a functional disorder of subclinical inflammatory changes in recent years, and there is no reliable biomarker. Triggering receptor expressed on myeloid cells 1 (TREM-1), also produced in a soluble form (sTREM-1), is involved in the activation of inflammatory cascades of intracellular events and may play a role in pathogenesis of IBS.

AIM

To investigate whether serum sTREM-1 level can be used as a marker of subclinical inflammation in D-IBS.

METHODS

Abdominal pain was quantified by a validated questionnaire. Expression level of TREM-1 in colonic mucosa as well as sTREM-1 level in serum was also detected. Furthermore, we investigated the involvement of TREM-1-associated macrophage activation in IBS-like visceral hypersensitivity.

RESULTS

No evidence for obvious inflammation was found in D-IBS patients. Serum sTREM-1 level in D-IBS patients was significantly higher than that in HCs, which was also significantly correlated with abdominal pain scores. We showed a marked increase in the proportion of TREM-1-expressing macrophages in D-IBS, which was significantly correlated with abdominal pain scores. Functionally, gadolinium chloride (GdCl₃), a macrophage selective inhibitor, or LP17, the TREM-1-specific peptide, significantly suppressed the visceral hypersensitivity in trinitrobenzene sulfonic acid (TNBS)-treated mice with IBS-like visceral hypersensitivity.

CONCLUSIONS

Serum sTREM-1 level is significantly higher in D-IBS patients and positively correlates with abdominal pain, which may be initiated by TREM-1-associated macrophage activation, indicating the existence of subclinical inflammation in D-IBS. Therefore, serum sTREM-1 is a potential marker of subclinical inflammation in D-IBS.

Determination of Cell Membrane Capacitance and Conductance via Optically Induced Electrokinetics

Cell membrane capacitance and conductance are key pieces of intrinsic information correlated with the cellular dielectric parameters and morphology of the plasma membrane; these parameters have been used as electrophysiological biomarkers to characterize cellular phenotype and state, and they have many associated clinical applications. Here, we present our work on the non-invasive determination of cell membrane capacitance and conductance by an optically activated microfluidics chip. The model for determining the cell membrane capacitance and conductance was established by a single layer of the shell-core polarization model. Three-dimensional finite-element analyses of the positive and negative optically induced dielectrophoresis forces generated by the projected light arrays of spots were performed, thus providing a theoretical validation of the feasibility of this approach. Then, the crossover frequency spectra for four typical types of cells (Raji cells, MCF-7 cells, HEK293 cells, and K562 cells) were experimentally investigated by using a micro-vision based motion-tracking technique. The different responses of these cells to the positive and negative ODEP forces were studied under four different liquid conductivities by automatic observation and tracking of the cellular trajectory and texture during the cells' translation. The cell membrane capacitance and conductance were determined from the curve-fitted spectra, which were 11.1 ± 0.9 mF/m² and 782 ± 32 S/m², respectively, for Raji cells, 11.5 ± 0.8 mF/m² and 114 ± 28 S/m² for MCF-7 cells, 9.0 ± 0.9 mF/m² and 187 ± 22 S/m² for HEK293 cells, and 10.2 ± 0.7 mF/m² and 879 ± 24 S/m² for K562 cells. Furthermore, as an application of this technique, the membrane capacitances of MCF-7 cells treated with four different concentrations of drugs were acquired. This technique introduces a determination of cell membrane capacitance and conductance that yields statistically significant data while allowing information from individual cells to be obtained in a non-invasive manner.

Exosomes purified from a single cell type have diverse morphology

Extracellular vesicles (EVs) are produced by all known organisms and are important for cell communication and physiology. Great morphological diversity has been described regarding EVs found in body fluids such as blood plasma, breast milk, and ejaculate. However, a detailed morphological analysis has never been performed on exosomes when purified from a single cell type. In this study we analysed and quantified, via multiple electron microscopy techniques, the morphology of exosomes purified from the human mast cell line HMC-1. The results revealed a wide diversity in exosome morphology, suggesting that subpopulations of exosomes with different and specific functions may exist. Our findings imply that a new, more efficient way of defining exosome subpopulations is necessary. A system was proposed where exosomes were classified into nine different categories according to their size and shape. Three additional morphological features were also found in exosomes regardless of their morphological classification. These findings show that exosomes purified from a single cell line are also morphologically diverse, similar to previous observations for EVs in body fluids. This knowledge can help to improve the interpretation of experimental results and widen our general understanding of the biological functions of exosomes.

Clostridium difficile toxin B inhibits the secretory response of human mast cell line-1 (HMC-1) cells stimulated with high free-Ca²⁺ and GTPγS

Clostridium difficile toxins A and B (TcdA and TcdB) belong to the class of large clostridial cytotoxins and inactivate by glucosylation some low molecular mass GTPases of the Rho-family (predominantly Rho, Rac and Cdc42), known as regulators of the actin cytoskeleton. TcdA and B also represent the main virulence factors of the anaerobic gram-positive bacterium that is the causal agent of pseudomembranous colitis. In our study, TcdB was chosen instead of TcdA for the well-known higher cytotoxic potency. Inactivation of Rho-family GTPases by this toxin in our experimental conditions induced morphological changes and reduction of electron-dense mast cell-specific granules in human mast cell line-1 (HMC-1) cells, but not cell death or permeabilisation of plasma-membranes. Previously reported patch-clamp dialysis experiments revealed that high intracellular free-Ca(2+) and GTPγS concentrations are capable of inducing exocytosis as indicated by significant membrane capacitance (Cm) increases in HMC-1 cells. In this study, we investigated the direct effects of TcdB upon HMC-1 cell "stimulated" Cm increase, as well as on "constitutive" secretion of hexosaminidase and interleukin-16 (IL-16). Compared to untreated control cells, HMC-1 cells incubated with TcdB for 3-24h exhibited a significant reduction of the mean absolute and relative Cm increase in response to free-Ca(2+) and GTPγS suggesting an inhibition of secretory processes by TcdB. In conclusion, the HMC-1 cell line represents a suitable model for the study of direct effects of C. difficile toxins on human mast cell secretory activity.

Mast cell mediators: their differential release and the secretory pathways involved

Mast cells (MC) are widely distributed throughout the body and are common at mucosal surfaces, a major host-environment interface. MC are functionally and phenotypically heterogeneous depending on the microenvironment in which they mature. Although MC have been classically viewed as effector cells of IgE-mediated allergic diseases, they are also recognized as important in host defense, innate and acquired immunity, homeostatic responses, and immunoregulation. MC activation can induce release of pre-formed mediators such as histamine from their granules, as well as release of de novo synthesized lipid mediators, cytokines, and chemokines that play diverse roles, not only in allergic reactions but also in numerous physiological and pathophysiological responses. Indeed, MC release their mediators in a discriminating and chronological manner, depending upon the stimuli involved and their signaling cascades (e.g., IgE-mediated or Toll-like receptor-mediated). However, the precise mechanisms underlying differential mediator release in response to these stimuli are poorly known. This review summarizes our knowledge of MC mediators and will focus on what is known about the discriminatory release of these mediators dependent upon diverse stimuli, MC phenotypes, and species of origin, as well as on the intracellular synthesis, storage, and secretory processes involved.