[Effects of catgut embedding and PGLA embedding at "Zusanli" (ST 36) on skin mast cells, substance P and histamine in healthy rats]

OBJECTIVE

To observe the effects of catgut embedding and polyglycolic acid/poly-lactic acid (PGLA) embedding at "Zusanli" (ST 36) on the activation of local skin mast cells (MC), and expression of substance P (SP) and histamine (HA), and to explore the mechanism of the temporal stimulation effect of acupoint catgut embedding and provide a foundation for further research on the initiation mechanism of acupoint catgut embedding.

METHODS

One hundred and sixty male SPF-grade SD rats were randomly divided into a blank group (10 rats), a sham-embedding group (50 rats), a catgut group (50 rats), and a PGLA group (50 rats). Each intervention group was further randomly divided into five subgroups according to the time points after intervention: 8 hours, 3 days, 7 days, 14 days, and 21 days, with 10 rats in each subgroup. One-time sham-embedding, catgut embedding and PGLA embedding was given at left "Zusanli" (ST 36) in each intervention group, respectively. The skin and subcutaneous connective tissue of the left "Zusanli" (ST 36) were collected at the corresponding time points after intervention, except for the blank group (only one day before intervention). Toluidine blue staining was used to detect MC count and degranulation, and immunohistochemical staining was used to detect the expression of SP and HA positive cells.

RESULTS

There was no significant difference in MC count between the subgroups of each intervention group and the blank group (P>0.05). There was no significant difference in MC count between the subgroups of the catgut group and the PGLA group (P>0.05). The MC count in the 8-hour subgroup of PGLA group was higher than that in the 8-hour subgroup of catgut group (P<0.05), while the MC count in the 21-day subgroup of PGLA group was lower than that in the 21-day subgroup of catgut group (P<0.05). Compared with the blank group, the degranulation rates of MC were increased in the 8-hour and 3-day subgroups of sham-embedding group, 8-hour, 3-day, and 7-day subgroups of catgut group, and 8-hour, 3-day, 7-day, and 14-day subgroups of PGLA group (P<0.01, P<0.05, P<0.001). There was no significant difference in the degranulation rate of MC between the subgroups of the catgut group and the PGLA group (P>0.05), and no significant difference in the degranulation rate of MC between the two embedding groups at the same time point (P>0.05). Compared with the blank group, the expression of SP positive cells was increased in the 8-hour subgroup of sham-embedding group, 8-hour, 3-day, 7-day, and 14-day subgroups of catgut group, and 3-day, 7-day, and 14-day subgroups of PGLA group (P<0.001, P<0.05). The expression of SP positive cells in the 7-day subgroup of catgut group was higher than that in the 8-hour subgroup of catgut group (P<0.05), while the expression of SP positive cells in the 14-day subgroup of catgut group was lower than that in the 7-day subgroup of catgut group (P<0.001). The expression of SP positive cells in the 7-day subgroup of PGLA group was higher than that in the 3-day subgroup of PGLA group (P<0.05), while the expression of SP positive cells in the 14-day subgroup of PGLA group was lower than that in the 7-day subgroup of PGLA group (P<0.01). There was no significant difference in the expression of SP positive cells between the subgroups of the two embedding groups at the same time point (P>0.05). Compared with the blank group, the expression of HA positive cells was increased in the 8-hour, 3-day subgroups of sham-embedding group, 8-hour, 3-day, 7-day, and 14-day subgroups of catgut group, and 8-hour, 3-day, 7-day, 14-day, and 21-day subgroups of PGLA group (P<0.001, P<0.01, P<0.05). The expression of HA positive cells in the 14-day subgroup of catgut group was lower than that in the 7-day subgroup of catgut group (P<0.05), while the expression of HA positive cells in the 3-day subgroup of PGLA group was higher than that in the 8-hour subgroup of PGLA group (P<0.05), and the expression of HA positive cells in the 14-day subgroup of PGLA group was lower than that in the 7-day subgroup of PGLA group (P<0.05). The expression of HA positive cells in the 3-day subgroup of PGLA group was higher than that in the 3-day subgroup of catgut group (P<0.05).

CONCLUSION

Catgut and PGLA embedding at "Zusanli" (ST 36) in healthy rats could induce changes in local skin MC, SP, and HA, which may be one of the mechanisms of the temporal stimulation effect after acupoint embedding. There are certain differences between different suture materials. A moderate inflammatory response in the acupoint area, mediated by MC and involving SP and HA, may be one of the initiating factors for the effect of acupoint catgut embedding.

Heatstroke-induced acute kidney injury and the innate immune system

Heatstroke can cause multiple organ failure and systemic inflammatory response syndrome as the body temperature rises beyond the body's ability to regulate temperature in a hot environment. Previous studies have indicated that heatstroke-induced acute kidney injury (AKI) can lead to chronic kidney disease. Therefore, there is an urgent need to elucidate the mechanism of heatstroke-induced AKI and to establish methods for its prevention and treatment. Recent reports have revealed that innate immunity, including neutrophils, macrophages, lymphocytes, and mast cells, is deeply involved in heat-induced AKI. In this review, we will discuss the roles of each immune cell in heat-induced renal injury and their potential therapeutic use.

The exon-skipping oligonucleotide, KitStop, depletes tissue-resident mast cells in vivo to ameliorate anaphylaxis

Introduction

Anaphylaxis represents the most extreme and life-threatening form of allergic disease and is considered a medical emergency requiring immediate intervention. Additionally, some people with mastocytosis experience recurrent episodes of anaphylaxis during normal daily activities without exposure to known triggers. While acute therapy consists primarily of epinephrine and supportive care, chronic therapy relies mostly on desensitization and immunotherapy against the offending allergen, which is a time-consuming and sometimes unsuccessful process. These treatments also necessitate identification of the triggering allergen which is not always possible, and thus highlighting a need for alternative treatments for mast cell-mediated diseases.

Methods

The exon-skipping oligonucleotide KitStop was administered to mice intradermally, intraperitoneally, or systemically at a dose of 12.5 mg/kg. Local mast cell numbers were enumerated via peritoneal lavage or skin histology, and passive systemic anaphylaxis was induced to evaluate KitStop's global systemic effect. A complete blood count and biochemistry panel were performed to assess the risk of acute toxicity following KitStop administration.

Results

Here, we report the use of an exon-skipping oligonucleotide, which we have previously termed KitStop, to safely reduce the severity and duration of the anaphylactic response via mast cell depopulation in tissues. KitStop administration results in the integration of a premature stop codon within the mRNA transcript of the KIT receptor-a receptor tyrosine kinase found primarily on mast cells and whose gain-of-function mutation can lead to systemic mastocytosis. Following either local or systemic KitStop treatment, mice had significantly reduced mast cell numbers in the skin and peritoneum. In addition, KitStop-treated mice experienced a significantly diminished anaphylactic response using a model of passive systemic anaphylaxis when compared with control mice.

Discussion

KitStop treatment results in a significant reduction in systemic mast cell responses, thus offering the potential to serve as a powerful additional treatment modality for patients that suffer from anaphylaxis.

The mast cell: A Janus in kidney transplants

Mast cells (MCs) are innate immune cells with a versatile set of functionalities, enabling them to orchestrate immune responses in various ways. Aside from their known role in allergy, they also partake in both allograft tolerance and rejection through interaction with regulatory T cells, effector T cells, B cells and degranulation of cytokines and other mediators. MC mediators have both pro- and anti-inflammatory actions, but overall lean towards pro-fibrotic pathways. Paradoxically, they are also seen as having potential protective effects in tissue remodeling post-injury. This manuscript elaborates on current knowledge of the functional diversity of mast cells in kidney transplants, combining theory and practice into a MC model stipulating both protective and harmful capabilities in the kidney transplant setting.

Corrigendum: The mast cell: A Janus in kidney transplants

[This corrects the article DOI: 10.3389/fimmu.2023.1122409.].

Inhibition of MRGPRX2 but not FcεRI or MrgprB2-mediated mast cell degranulation by a small molecule inverse receptor agonist

Mas-related G protein-coupled receptor-X2 (MRGPRX2) expressed on mast cells (MCs) contributes to hypersensitivity reactions to cationic US-Food and Drug Administration (FDA) approved drugs such as the neuromuscular blocking agent, rocuronium. In addition, activation of MRGPRX2 by the neuropeptide substance P (SP) and the pro-adrenomedullin peptide (PAMP-12) is associated with a variety of cutaneous conditions such as neurogenic inflammation, pain, atopic dermatitis, urticaria, and itch. Thus, small molecules aimed at blocking MRGPRX2 constitute potential options for modulating IgE-independent MC-mediated disorders. Two inverse MRGPRX2 agonists, named C9 and C9-6, have recently been identified, which inhibit basal G protein activation and agonist-induced calcium mobilization in transfected HEK293 cells. Substance P serves as a balanced agonist for MRGPRX2 whereby it activates both G protein-mediated degranulation and β-arrestin-mediated receptor internalization. The purpose of this study was to determine if C9 blocks MRGPRX2's G protein and β-arrestin-mediated signaling and to determine its specificity. We found that C9, but not its inactive analog C7, inhibited degranulation in RBL-2H3 cells stably expressing MRGPRX2 in response to SP, PAMP-12 and rocuronium with an IC50 value of ~300 nM. C9 also inhibited degranulation as measured by cell surface expression of CD63, CD107a and β-hexosaminidase release in LAD2 cells and human skin-derived MCs in response to SP but not the anaphylatoxin, C3a or FcϵRI-aggregation. Furthermore, C9 inhibited β-arrestin recruitment and MRGPRX2 internalization in response to SP and PAMP-12. We found that a G protein-coupling defective missense MRGPRX2 variant (V282M) displays constitutive activity for β-arrestin recruitment, and that this response was significantly inhibited by C9. Rocuronium, SP and PAMP-12 caused degranulation in mouse peritoneal MCs and these responses were abolished in the absence of MrgprB2 or cells treated with pertussis toxin but C9 had no effect. These findings suggest that C9 could provide an important framework for developing novel therapeutic approaches for the treatment of IgE-independent MC-mediated drug hypersensitivity and cutaneous disorders.

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.

Human Mast Cell Line HMC1 Expresses Functional Mas-Related G-Protein Coupled Receptor 2

The Mas-related G-protein-coupled receptor X2 (MRGPRX2) is prominently expressed by mast cells and induces degranulation upon binding by different ligands. Its activation has been linked to various mast cell-related diseases, such as chronic spontaneous urticaria, atopic dermatitis and asthma. Therefore, inhibition of MRGPRX2 activity represents a therapeutic target for these conditions. However, the exact pathophysiology of this receptor is still unknown. In vitro research with mast cells is often hampered by the technical limitations of available cell lines. The human mast cell types LAD2 and HuMC (human mast cells cultured from CD34+ progenitor cells) most closely resemble mature human mast cells, yet have a very slow growth rate. A fast proliferating alternative is the human mast cell line HMC1, but they are considered unsuitable for degranulation assays due to their immature phenotype. Moreover, the expression and functionality of MRGPRX2 on HMC1 is controversial. Here, we describe the MRGPRX2 expression and functionality in HMC1 cells, and compare these with LAD2 and HuMC. We also propose a model to render HMC1 suitable for degranulation assays by pre-incubating them with latrunculin-B (Lat-B). Expression of MRGPRX2 by HMC1 was proven by RQ-PCR and flowcytometry, although at lower levels compared with LAD2 and HuMC. Pre-incubation of HMC1 cells with Lat-B significantly increased the overall degranulation capacity, without significantly changing their MRGPRX2 expression, phenotype or morphology. The MRGPRX2 specific compound 48/80 (C48/80) effectively induced degranulation of HMC1 as measured by CD63 membrane expression and β-hexosaminidase release, albeit in lower levels than for LAD2 or HuMC. HMC1, LAD2 and HuMC each had different degranulation kinetics upon stimulation with C48/80. Incubation with the MRGPRX2 specific inhibitor QWF inhibited C48/80-induced degranulation, confirming the functionality of MRGPRX2 on HMC1. In conclusion, HMC1 cells have lower levels of MRGPRX2 expression than LAD2 or HuMC, but are attractive for in vitro research because of their high growth rate and stable phenotype. HMC1 can be used to study MRGPRX2-mediated degranulation after pre-incubation with Lat-B, which provides the opportunity to explore MPRGRX2 biology in mast cells in a feasible way.

IL33 and Mast Cells-The Key Regulators of Immune Responses in Gastrointestinal Cancers?

The Interleukin (IL-)1 family IL33 is best known for eliciting type 2 immune responses by stimulating mast cells (MCs), regulatory T-cells (Tregs), innate lymphoid cells (ILCs) and other immune cells. MCs and IL33 provide critical control of immunological and epithelial homeostasis in the gastrointestinal (GI) tract. Meanwhile, the role of MCs in solid malignancies appears tissue-specific with both pro and anti-tumorigenic activities. Likewise, IL33 signaling significantly shapes immune responses in the tumor microenvironment, but these effects remain often dichotomous when assessed in experimental models of cancer. Thus, the balance between tumor suppressing and tumor promoting activities of IL33 are highly context dependent, and most likely dictated by the mixture of cell types responding to IL33. Adding to this complexity is the promiscuous nature by which MCs respond to cytokines other than IL33 and release chemotactic factors that recruit immune cells into the tumor microenvironment. In this review, we integrate the outcomes of recent studies on the role of MCs and IL33 in cancer with our own observations in the GI tract. We propose a working model where the most abundant IL33 responsive immune cell type is likely to dictate an overall tumor-supporting or tumor suppressing outcome in vivo. We discuss how these opposing responses affect the therapeutic potential of targeting MC and IL33, and highlight the caveats and challenges facing our ability to effectively harness MCs and IL33 biology for anti-cancer immunotherapy.