The critical role of mast cell-derived hypoxia-inducible factor-1α in regulating mast cell function

Hot under the clot: venous thrombogenesis is an inflammatory process

ABSTRACT

Venous thrombosis (VT) is a serious medical condition in which a blood clot forms in deep veins, often causing limb swelling and pain. Current antithrombotic therapies carry significant bleeding risks resulting from targeting essential coagulation factors. Recent advances in this field have revealed that the cross talk between the innate immune system and coagulation cascade is a key driver of VT pathogenesis, offering new opportunities for potential therapeutic interventions without inducing bleeding complications. This review summarizes and discusses recent evidence from preclinical models on the role of inflammation in VT development. We highlight the major mechanisms by which endothelial cell activation, Weibel-Palade body release, hypoxia, reactive oxygen species, inflammasome, neutrophil extracellular traps, and other immune factors cooperate to initiate and propagate VT. We also review emerging clinical data describing anti-inflammatory approaches as adjuncts to anticoagulation in VT treatment. Finally, we identify key knowledge gaps and future directions that could maximize the benefit of anti-inflammatory therapies in VT. Identifying and targeting the inflammatory factors driving VT, either at the endothelial cell level or within the clot, may pave the way for new therapeutic possibilities for improving VT treatment and reducing thromboembolic complications without increasing bleeding risk.

Mast cells in colorectal cancer tumour progression, angiogenesis, and lymphangiogenesis

The characteristics of the tumour cells, as well as how tumour cells interact with their surroundings, affect the prognosis of cancer patients. The resident cells in the tumour microenvironment are mast cells (MCs), which are known for their functions in allergic responses, but their functions in the cancer milieu have been hotly contested. Several studies have revealed a link between MCs and the development of tumours. Mast cell proliferation in colorectal cancer (CRC) is correlated with angiogenesis, the number of lymph nodes to which the malignancy has spread, and patient prognosis. By releasing angiogenic factors (VEGF-A, CXCL 8, MMP-9, etc.) and lymphangiogenic factors (VEGF-C, VEGF-D, etc.) stored in granules, mast cells play a significant role in the development of CRC. On the other hand, MCs can actively encourage tumour development via pathways including the c-kit/SCF-dependent signaling cascade and histamine production. The impact of MC-derived mediators on tumour growth, the prognostic importance of MCs in patients with various stages of colorectal cancer, and crosstalk between MCs and CRC cells in the tumour microenvironment are discussed in this article. We acknowledge the need for a deeper comprehension of the function of MCs in CRC and the possibility that targeting MCs might be a useful therapeutic approach in the future.

Focus on mast cells in the tumor microenvironment: Current knowledge and future directions

Mast cells (MCs) are crucial cells participating in both innate and adaptive immune processes that play important roles in protecting human health and in the pathophysiology of various diseases, such as allergies, cardiovascular diseases, and autoimmune diseases. In the context of tumors, MCs are a non-negligible population of immune cells in the tumor microenvironment (TME). In most tumor types, MCs accumulate in both the tumor tissue and the surrounding tissue. MCs interact with multiple components of the TME, affecting TME remodeling and the tumor cell fate. However, controversy persists regarding whether MCs contribute to tumor progression or trigger an anti-tumor immune response. This review focuses on the context of the TME to explore the specific properties and functions of MCs and discusses the crosstalk that occurs between MCs and other components of the TME, which affect tumor angiogenesis and lymphangiogenesis, invasion and metastasis, and tumor immunity through different mechanisms. We also anticipate the potential role of MCs in cancer immunotherapy, which might expand upon the success achieved with existing cancer therapies.

Small extracellular vesicles from iPSC-derived mesenchymal stem cells ameliorate tendinopathy pain by inhibiting mast cell activation

Aim: This study aimed to explore the effect of small extracellular vesicles from induced pluripotent stem cell-derived mesenchymal stem cells (iMSC-sEVs) on acute pain and investigate the underlying mechanisms. Materials & methods: The pathology of tendons was accessed by hematoxylin and eosin staining, immunohistochemical and immunofluorescent staining. The pain degree was measured by pain-related behaviors. In vitro, we performed β-hexosaminidase release assay, RT-qPCR, toluidine blue staining, ELISA and RNA sequencing. Results: iMSC-sEVs effectively alleviated acute pain in tendinopathy as well as inhibiting activated mast cell infiltration and interactions with nerve fibers in vivo. In vitro, iMSC-sEVs reduced the degranulation of mast cells and the expression of proinflammatory cytokines and genes involved in the HIF-1 signaling pathway. Conclusion: This study demonstrated that iMSC-sEVs relieved tendinopathy-related pain through inhibiting mast cell activation via the HIF-1 signaling pathway.

New Pathways for the Skin's Stress Response: The Cholinergic Neuropeptide SLURP-1 Can Activate Mast Cells and Alter Cytokine Production in Mice

Background: The alpha7 nicotinic acetylcholine receptor (Chrna7) plays an essential anti-inflammatory role in immune homeostasis and was recently found on mast cells (MC). Psychosocial stress can trigger MC hyperactivation and increases pro-inflammatory cytokines in target tissues such as the skin. If the cholinergic system (CS) and Chrna7 ligands play a role in these cascades is largely unknown.

Objective: To elucidate the role of the CS in the response to psychosocial stress using a mouse-model for stress-triggered cutaneous inflammatory circuits.

Methods: Key CS markers (ACh, Ch, SLURP-1, SLURP-2, Lynx1, Chrm3, Chrna7, Chrna9, ChAT, VAChT, Oct3, AChE, and BChE) in skin and its MC (sMC), MC activation, immune parameters (TNFα, IL1β, IL10, TGFβ, HIF1α, and STAT3) and oxidative stress were analyzed in skin from 24 h noise-stressed mice and in cultured MC (cMC) from C57BL/6 or Chrna7-Knockout mice.

Results: First, Chrna7 and SLURP-1 mRNA were exclusively upregulated in stressed skin. Second, histomorphometry located Chrna7 and SLURP-1 in nerves and sMC and demonstrated upregulated contacts and increased Chrna7+ sMC in stressed skin, while 5 ng/mL SLURP-1 degranulated cMC. Third, IL1β+ sMC were high in stressed skin, and while SLURP-1 alone had no significant effect on cMC cytokines, it upregulated IL1β in cMC from Chrna7-KO and in IL1β-treated wildtype cMC. In addition, HIF1α+ sMC were high in stressed skin and Chrna7-agonist AR-R 17779 induced ROS in cMC while SLURP-1 upregulated TNFα and IL1β in cMC when HIF1α was blocked.

Conclusions: These data infer that the CS plays a role in the regulation of stress-sensitive inflammatory responses but may have a surprising pro-inflammatory effect in healthy skin, driving IL1β expression if SLURP-1 is involved.

The Regulation of Intestinal Inflammation and Cancer Development by Type 2 Immune Responses

The gut is among the most complex organs of the human body. It has to exert several functions including food and water absorption while setting up an efficient barrier to the outside world. Dysfunction of the gut can be life-threatening. Diseases of the gastrointestinal tract such as inflammatory bowel disease, infections, or colorectal cancer, therefore, pose substantial challenges to clinical care. The intestinal epithelium plays an important role in intestinal disease development. It not only establishes an important barrier against the gut lumen but also constantly signals information about the gut lumen and its composition to immune cells in the bowel wall. Such signaling across the epithelial barrier also occurs in the other direction. Intestinal epithelial cells respond to cytokines and other mediators of immune cells in the lamina propria and shape the microbial community within the gut by producing various antimicrobial peptides. Thus, the epithelium can be considered as an interpreter between the microbiota and the mucosal immune system, safeguarding and moderating communication to the benefit of the host. Type 2 immune responses play important roles in immune-epithelial communication. They contribute to gut tissue homeostasis and protect the host against infections with helminths. However, they are also involved in pathogenic pathways in inflammatory bowel disease and colorectal cancer. The current review provides an overview of current concepts regarding type 2 immune responses in intestinal physiology and pathophysiology.

Oxygen Sensing and Viral Replication: Implications for Tropism and Pathogenesis

The ability to detect and respond to varying oxygen tension is an essential prerequisite to life. Several mechanisms regulate the cellular response to oxygen including the prolyl hydroxylase domain (PHD)/factor inhibiting HIF (FIH)-hypoxia inducible factor (HIF) pathway, cysteamine (2-aminoethanethiol) dioxygenase (ADO) system, and the lysine-specific demethylases (KDM) 5A and KDM6A. Using a systems-based approach we discuss the literature on oxygen sensing pathways in the context of virus replication in different tissues that experience variable oxygen tension. Current information supports a model where the PHD-HIF pathway enhances the replication of viruses infecting tissues under low oxygen, however, the reverse is true for viruses with a selective tropism for higher oxygen environments. Differences in oxygen tension and associated HIF signaling may play an important role in viral tropism and pathogenesis. Thus, pharmaceutical agents that modulate HIF activity could provide novel treatment options for viral infections and associated pathological conditions.

The effect of intermittent hypoxia and fecal microbiota of OSAS on genes associated with colorectal cancer

Purpose

Colorectal cancer (CRC) is one of the common causes of cancer death worldwide. Obstructive sleep apnea syndrome (OSAS), sharing many risk factors in common with CRC, is prevalent among CRC patients. OSAS may promote the CRC development independently but the mechanism is still unknown. Intermittent hypoxia (IH) is one of the characteristics of OSAS, and hypoxia may influence the genes associated with CRC. Intestinal microbiota plays important role in CRC carcinogenesis, and OSAS patients have been shown to have intestinal microbiota dysbiosis. We hypothesized that IH and intestinal microbiota dysbiosis may be involved for CRC in patients with OSAS.

Methods

We established precancerous cell models of CRC with Immorto-Min colonic epithelial (IMCE) cells. First, the cells were exposed to IH in a special chamber for 4 h, 8 h, and 12 h. Feces from 6 patients with OSAS and 6 healthy controls were collected and made into sterile fecal fluid for incubation with IMCE cells for 12 h. The cells were then exposed to IH for 4 h, 8 h, and 12 h. After IH exposure, the expressions of genes and inflammation cytokines associated with CRC, such as β-catenin, STAT3, HIF-1α, IL-6, TNF-α, c-myc, and cyclinD1, were tested.

Results

IH activated the expression of HIF-1α and STAT3 both in mRNA and protein level (HIF-1α: P = 0.015 for mRNA level, P = 0.027 for protein level; STAT3: P = 0.023 for mRNA level, P = 0.023 for protein level), and promoted p-STAT3 shifting to the nucleus (P = 0.023). The mRNA of β-catenin (P = 0.022) and cyclinD1 (P = 0.023) was elevated, but there was no change for the β-catenin protein in the nucleus. Gut microbiota of OSAS patients promoted the expression of STAT3 (protein level: 0 h: P = 0.037; 4 h: P = 0.046; 8 h: P = 0.049; 12 h: P = 0.037), promoted p-STAT3 (4 h: P = 0.049; 8 h: P = 0.046; 12 h: P = 0.046) shifting to the nucleus, and also elevated the expression of IL-6 and TNF-α in mRNA level at 4 h (IL-6: P = 0.037, TNF-α: P = 0.037) and 8 h (IL-6: P = 0.037, TNF-α: P = 0.037). The protein of β-catenin in the nucleus was not affected by IH and gut microbiota from OSAS.

Conclusions

Our study demonstrated that IH and gut microbiota of patients with OSAS activated HIF-1α expression and STAT3 pathway in IMCE cells, with no influence on β-catenin pathway, which suggested that IH, STAT3 pathway, chronic inflammation, and intestinal microbiota dysbiosis may be involved in CRC carcinogenesis correlated with OSAS These findings must be interpreted cautiously and further research is necessary to clarify the causative steps in CRC development.

Endogenous sulfur dioxide is a novel inhibitor of hypoxia-induced mast cell degranulation

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Endogenous SO₂/AAT pathway exists in mast cells (MCs).

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Endogenous SO₂ is a novel MC membrane stabilizer under hypoxic circumstance.

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MC-derived SO₂ upregulates cAMP level, thereby suppressing MC degranulation.

Introduction

Mast cell (MC) degranulation is an important step in the pathogenesis of inflammatory reactions and allergies; however, the mechanism of stabilizing MC membranes to reduce their degranulation is unclear.

Methods

SO₂ content in MC culture supernatant was measured by HPLC-FD. The protein and mRNA expressions of the key enzymes aspartate aminotransferase 1 (AAT1) and AAT2 and intracellular AAT activity were detected. The cAMP level in MCs was detected by immunofluorescence and ELISA. The release rate of MC degranulation marker β-hexosaminidase was measured. The expression of AAT1 and cAMP, the MC accumulation and degranulation in lung tissues were detected.

Objectives

To exam whether an endogenous sulfur dioxide (SO₂) pathway exists in MCs and if it serves as a novel endogenous MC stabilizer.

Results

We firstly show the existence of the endogenous SO₂/AAT pathway in MCs. Moreover, when AAT1 was knocked down in MCs, MC degranulation was significantly increased, and could be rescued by a SO₂ donor. Mechanistically, AAT1 knockdown decreased the cyclic adenosine monophosphate (cAMP) content in MCs, while SO₂ prevented this reduction in a dose-independent manner. Pretreatment with the cAMP-synthesizing agonist forskolin or the cAMP degradation inhibitor IBMX significantly blocked the increase in AAT1 knockdown-induced MC degranulation. Furthermore, in hypoxia-stimulated MCs, AAT1 protein expression and SO₂ production were markedly down regulated, and MC degranulation was activated, which were blunted by AAT1 overexpression. The cAMP synthesis inhibitor SQ22536 disrupted the suppressive effect of AAT1 overexpression on hypoxia-induced MC degranulation. In a hypoxic environment, mRNA and protein expression of AAT1 was significantly reduced in lung tissues of rats. Supplementation of SO₂ elevated the cAMP level and reduced perivascular MC accumulation and degranulation in lung tissues of rats exposed to a hypoxic environment in vivo.

Conclusion

SO₂ serves as an endogenous MC stabilizer via upregulating the cAMP pathway under hypoxic circumstance.

iTRAQ-based proteomic and bioinformatic characterization of human mast cells upon infection by the influenza A virus strains H1N1 and H5N1

Mast cells can support the replication of influenza A virus, although how this occurs is poorly understood. In the present study, using quantitative MS, we analyzed the proteome of human mast cells infected with different influenza A virus strains at 12 h post-infection. Forty-one differentially expressed proteins were identified in human mast cells upon infection by the virulent H5N1 (A/Chicken/Henan/1/04) virus compared to the seasonal H1N1 (A/WSN/33) virus. Bioinformatic analyses confirmed that H1N1 significantly regulates the RNA degradation pathway via up-regulation of CCR4-NOT transcription complex subunit 4, whereas apoptosis could be suppressed by H5N1 via down-regulation of the tumor protein p53 signaling pathway with P ≤ 0.05 at 12 h post-infection. The hypoxia-inducible factor-1 signaling pathway of human mast cells is more susceptible to infection by H5N1 than by H1N1 virus.

Genomic and Bioinformatic Characterization of Mouse Mast Cells (P815) Upon Different Influenza A Virus (H1N1, H5N1, and H7N2) Infections

Influenza A virus (IAV) is a segmented negative-stranded RNA virus that brings a potentially serious threat to public health and animal husbandry. Mast cells play an important role in both the inherent and adaptive immune response. Previous studies have indicated that mast cells support the productive replication of H1N1, H5N1, and H7N2. To date, the distinct molecular mechanism behind the pathogenesis in mast cells among the three different viruses has been poorly understood. In this study, we investigated the genomic profiles in detail and the dynamic change of genomes regulated by different subtypes of IAV in mouse mast cells using microassays. Compared with any two of the three IAV-infected groups, many more differentially expressed genes (DEGs), cellular functions, and signaling pathways were confirmed in H1N1 or H7N2 group, with the H7N2 group showing the highest levels. However, few DEGs were detected and various cellular functions and signaling pathways were dramatically suppressed in the H5N1 group. With an in-depth study on the H1N1 and H7N2 groups, we demonstrated the essential role of the 5-HT signaling pathway and the cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) signaling pathway, which were preferentially activated in P815 cells infected by H1N1, and the crucial role of the HIF-1 signaling pathway that was preferentially activated in P815 cells infected by the H7N2 virus. Furthermore, real-time quantitative polymerase chain reaction (RT-qPCR) results showed significantly increased mRNA levels of 5-HT and PKG in H1N1-infected P815 cells and increased HIF-1 in H7N2-infected P815 cells. In addition, exosomes were preferentially secreted from H1N1-infected or H7N2-infected P815 cells and are potentially pivotal in innate immunity to fight IAV infection. This study provides novel information and insight into the distinct molecular mechanism of H1N1, H5N1, and H7N2 viruses in mast cells from the perspective of genomic profiles.

Mast cells are essential intermediaries in regulating IL-33/ST2 signaling for an immune network favorable to mucosal healing in experimentally inflamed colons

Mast cells (MCs) are potent tissue-resident immune cells that are distributed in the intraepithelial space of the intestine and have been implicated in regulating immune homeostasis and coordinating epithelial responses in inflamed mucosa of inflammatory bowel disease (IBD). IL-33 functions as an endogenous danger signal or alarmin in inflamed intestine segments. MCs highly express the IL-33 receptor ST2. However, the mechanisms underlying the immune regulation of MC-dependent IL-33/ST2 signaling at the barrier surface of the intestine remain largely unknown. We confirmed that MCs are required for the effective resolution of tissue damage using an experimental colitis model that allows for conditional ablation of MCs. After elucidating the IL-33 signaling involved in MC activity in the context of intestinal inflammation, we found that the function of restricted IL-33/ST2 signaling by MCs was consistent with an MC deficiency in response to the breakdown of the epithelial barrier. We observed that a tissue environment with a spectrum of protective cytokines was orchestrated by MC-dependent IL-33/ST2 signaling. Given the significant downregulation of IL-22 and IL-13 due to the loss of MC-dependent IL-33/ST2 signaling and their protective functions in inflammation settings, induction of IL-22 and IL-13 may be responsible for an immune network favorable to mucosal repair. Collectively, our data showed an important feedback loop in which cytokine cues from damaged epithelia activate MCs to regulate tissue environments essential for MC-dependent restoration of epithelial barrier function and maintenance of tissue homeostasis.