Neurotrophin-3, but not nerve growth factor, promotes survival of human intestinal mast cells

Evaluating the effects of circulating inflammatory proteins as drivers and therapeutic targets for severe COVID-19

Objective

The relationships between circulating inflammatory proteins and COVID-19 have been observed in previous cohorts. However, it is not unclear which circulating inflammatory proteins may boost the risk of or protect against COVID-19.

Methods

We performed Mendelian randomization (MR) analysis using GWAS summary result of 91 circulating inflammation-related proteins (N = 14,824) to assess their causal impact on severe COVID-19. The COVID-19 phenotypes encompassed both hospitalized (N = 2,095,324) and critical COVID-19 (N = 1,086,211). Moreover, sensitivity analyses were conducted to evaluate the robustness and reliability.

Results

We found that seven circulating inflammatory proteins confer positive causal effects on severe COVID-19. Among them, serum levels of IL-10RB, FGF-19, and CCL-2 positively contributed to both hospitalized and critical COVID-19 conditions (OR: 1.10~1.16), while the other 4 proteins conferred risk on critical COVID-19 only (OR: 1.07~1.16), including EIF4EBP1, IL-7, NTF3, and LIF. Meanwhile, five proteins exert protective effects against hospitalization and progression to critical COVID-19 (OR: 0.85~0.95), including CXCL11, CDCP1, CCL4/MIP, IFNG, and LIFR. Sensitivity analyses did not support the presence of heterogeneity in the majority of MR analyses.

Conclusions

Our study revealed risk and protective inflammatory proteins for severe COVID-19, which may have vital implications for the treatment of the disease.

MEFV and NLRP3 Inflammasome Expression Is Attributed to Immature Macrophages and Correlates with Serum Inflammatory Proteins in Crohn´s Disease Patients

Inflammasomes are intracellular protein complexes whose activation results in proinflammatory cytokines. Inflammasomes are implicated in Crohn´s disease (CD) pathogenesis, yet the contribution of inflammasomes in intestinal epithelial cells (IECs) versus lamina propria (LP) macrophages is poorly understood. Whether inflammasome expression in intestinal tissue reflects the serum inflammatory protein profile of patients is also not known. We aimed to determine the intestinal cell types where inflammasome expression is increased in CD and if they correlate with the serum protein profile. RT-PCR and NanoString nCounter technology were used to characterize inflammasome gene expression in CD patients and controls. The mucosa, LP and IEC cell fractions and FACS-sorted cells were analyzed. Proximity extension assay with a 92-protein panel was used to determine the serum inflammatory protein profile. Compositional analysis was used to correlate ileum inflammasome gene expression with intestinal mononuclear phagocyte populations. We show that NLRP3 and MEFV inflammasome sensors and downstream effector expression including IL-1β are increased in inflamed mucosa of IBD patients and correlate with disease activity. Inflammasome gene expression increased with the abundance of immature intestinal macrophages, and increased IL-1β released by CD LP cells correlated with immature macrophage frequency. Inflammasome gene expression was also increased in circulating monocytes, the precursors of immature intestinal macrophages. Finally, the serum inflammatory profile of CD patients correlates with ileal expression of genes related to NLRP3 and MEFV inflammasomes. Overall, we show that MEFV and NLRP3 inflammasome expression in CD intestine is attributed to the accumulation of immature macrophages and correlates with serum inflammatory proteins.

New Insights into the Pathogenesis of Systemic Mastocytosis

Mastocytosis is a type of myeloid neoplasm characterized by the clonal, neoplastic proliferation of morphologically and immunophenotypically abnormal mast cells that infiltrate one or more organ systems. Systemic mastocytosis (SM) is a more aggressive variant of mastocytosis with extracutaneous involvement, which might be associated with multi-organ dysfunction or failure and shortened survival. Over 80% of patients with SM carry the KIT D816V mutation. However, the KIT D816V mutation serves as a weak oncogene and appears to be a late event in the pathogenesis of mastocytosis. The management of SM is highly individualized and was largely palliative for patients without a targeted form of therapy in past decades. Targeted therapy with midostaurin, a multiple kinase inhibitor that inhibits KIT, has demonstrated efficacy in patients with advanced SM. This led to the recent approval of midostaurin by the United States Food and Drug Administration and European Medicines Agency. However, the overall survival of patients treated with midostaurin remains unsatisfactory. The identification of genetic and epigenetic alterations and understanding their interactions and the molecular mechanisms involved in mastocytosis is necessary to develop rationally targeted therapeutic strategies. This review briefly summarizes recent developments in the understanding of SM pathogenesis and potential treatment strategies for patients with SM.

The role of intestinal mast cell infiltration in irritable bowel syndrome

As an essential part of the immune system, mast cells (MCs) play an important role in the pathogenesis of irritable bowel syndrome (IBS). Accumulating evidence has identified altered MC count and density in intestinal mucosa of patients with IBS; however, conflicting findings yield inconsistent conclusions. Currently, most studies have suggested intestinal MC infiltration in IBS patients. Considering the pivotal role of MCs in IBS, it is necessary to achieve a better understanding about the pathological changes in the intestine. The risk factors for IBS, including dietary habits, psychological factors, infection, and dysbiosis, are implicated to induce intestinal MC infiltration. Mechanistically, food may trigger immune-related allergic reactions and affect the intestinal microbiota activity. Some exogenous pathogens and altered profile of commensal bacteria promote intestinal MC recruitment through promoted release of chemokines from epithelial cells or direct activation of the immune system. In addition, psychological factors may affect the microenvironment where MCs live. MCs have been proven to interact with the enteric neurons and other immunocytes, evidenced by the close proximity of MCs to neurons and regional altered immune system components. A variety of mediators released by the enteric neurons, immunocytes, and MCs per se, such as neurotrophins, neuropeptides, cytokines, and chemokines, may have stimulant effects on MCs by modulating the survival, proliferation, and recruitment process of MCs in the intestine. In this review, the associations between IBS and intestinal MC density and the underlying mechanisms are discussed.

Regenerative medicine and drug delivery: Progress via electrospun biomaterials

Worldwide research on electrospinning enabled it as a versatile technique for producing nanofibers with specified physio-chemical characteristics suitable for diverse biomedical applications. In the case of tissue engineering and regenerative medicine, the nanofiber scaffolds' characteristics are custom designed based on the cells and tissues specific needs. This fabrication technique is also innovated for the production of nanofibers with special micro-structure and secondary structure characteristics such as porous fibers, hollow structure, and core- sheath structure. This review attempts to critically and succinctly capture the vast number of developments reported in the literature over the past two decades. We then discuss their applications as scaffolds for induction of cells growth and differentiation or as architecture for being used as graft for tissue engineering. The special nanofibers designed for improving regeneration of several tissues including heart, bone, central nerve system, spinal cord, skin and ocular tissue are introduced. We also discuss the potential of the electrospinning in drug delivery applications, which is a critical factor for cell culture, tissue formation and wound healing applications.

The development of human mast cells. An historical reappraisal

The understanding of mast cell (MC) differentiation is derived mainly from in vitro studies of different stages of stem and progenitor cells. The hematopoietic lineage development of human MCs is unique compared to other myeloid-derived cells. Human MCs originate from CD34(+)/CD117(+)/CD13(+)multipotent hematopoietic progenitors, which undergo transendothelial recruitment into peripheral tissues, where they complete differentiation. Stem cell factor (SCF) is a major chemotactic factor for MCs and their progenitors. SCF also elicits cell-cell and cell-substratum adhesion, facilitates the proliferation, and sustains the survival, differentiation, and maturation, of MCs. Because MC maturation is influenced by local microenvironmental factors, different MC phenotypes can develop in different tissues and organs.

Fabrication of Nerve Growth Factor Encapsulated Aligned Poly(ε-Caprolactone) Nanofibers and Their Assessment as a Potential Neural Tissue Engineering Scaffold

Peripheral nerve injury is a serious clinical problem to be solved. There has been no breakthrough so far and neural tissue engineering offers a promising approach to promote the regeneration of peripheral neural injuries. In this study, emulsion electrospinning technique was introduced as a flexible and promising technique for the fabrication of random (R) and aligned (A) Poly(ε-caprolactone) (PCL)-Nerve Growth Factor (NGF)&Bovine Serum Albumin (BSA) nanofibrous scaffolds [(R/A)-PCL-NGF&BSA], where NGF and BSA were encapsulated in the core while PCL form the shell. Random and aligned pure PCL, PCL-BSA, and PCL-NGF nanofibers were also produced for comparison. The scaffolds were characterized by Field Emission Scanning Electron Microscopy (FESEM) and water contact angle test. Release study showed that, with the addition of stabilizer BSA, a sustained release of NGF from emulsion electrospun PCL nanofibers was observed over 28 days. [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt; MTS] assay revealed that (R/A)-PCL-NGF and (R/A)-PCL-NGF&BSA scaffolds favored cell growth and showed no cytotoxicity to PC12 cells. Laser scanning confocal microscope images exhibited that the A-PCL-NGF&BSA scaffold increased the length of neurites and directed neurites extension along the fiber axis, indicating that the A-PCL-NGF&BSA scaffold has a potential for guiding nerve tissue growth and promoting nerve regeneration.

Mast cell function: a new vision of an old cell

Since first described by Paul Ehrlich in 1878, mast cells have been mostly viewed as effectors of allergy. It has been only in the past two decades that mast cells have gained recognition for their involvement in other physiological and pathological processes. Mast cells have a widespread distribution and are found predominantly at the interface between the host and the external environment. Mast cell maturation, phenotype and function are a direct consequence of the local microenvironment and have a marked influence on their ability to specifically recognize and respond to various stimuli through the release of an array of biologically active mediators. These features enable mast cells to act as both first responders in harmful situations as well as to respond to changes in their environment by communicating with a variety of other cells implicated in physiological and immunological responses. Therefore, the critical role of mast cells in both innate and adaptive immunity, including immune tolerance, has gained increased prominence. Conversely, mast cell dysfunction has pointed to these cells as the main offenders in several chronic allergic/inflammatory disorders, cancer and autoimmune diseases. This review summarizes the current knowledge of mast cell function in both normal and pathological conditions with regards to their regulation, phenotype and role.

Increased circulating levels of neurotrophins and elevated expression of their high-affinity receptors on skin and gut mast cells in mastocytosis

Patients with mastocytosis feature increased NT serum levels and elevated expression of modified NT receptors on skin and gut MCs. NTs might contribute to mastocytosis via increased migration of MC progenitors, MC differentiation, proliferation, and/or survival.

Mast cells and inflammation

Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.

Effects of neurotrophin 3 on gastric and colonic motility in awake rats

Neurotrophin 3 (NT3) and its receptors are expressed throughout the gastrointestinal tract, especially in the enteric nervous system. However, little is known about the effects of NT3 on gastrointestinal motility. To investigate the effects of NT3 on gastric or colonic motility under baseline conditions, after subdiaphragmatic vagotomy and in a model of postoperative ileus. Sprague-Dawley rats were equipped with strain gauge transducers on the gastric or colonic wall. Motility was recorded for 30 min, followed by i.v. administration of NT3 and motility-recording for another 60 min. Experiments were performed on three consecutive days and separately in a postoperative ileus model. To evaluate a vagal pathway, experiments were also performed on vagotomized rats. NT3 inhibited gastric motility. This inhibitory effect was reduced by subdiaphragmatic vagotomy. Preoperative treatment with NT3 prolonged the postoperative gastric ileus compared to vehicle treatment. Colonic motility in the intact animal was unchanged by NT3, but was increased postoperatively. NT3 treatment inhibited gastric but not colonic motility. This inhibition of gastric motility seems to be partly mediated by the vagus nerve. NT3 aggravates gastric postoperative ileus but attenuates colonic postoperative ileus, which corresponds to the observed positive effects of NT3 on constipated patients.