ER Stress is Involved in Mast Cells Degranulation via IRE1α/miR-125/Lyn Pathway in an Experimental Intracerebral Hemorrhage Mouse Model

Edaravone attenuates cerebral inflammation by inhibiting mast cells degranulation via ROS/STIM1 signaling pathway in HIE model

Mast cells (MCs) degranulation is responsible for the occurrence and development of neuroinflammation after hypoxic-ischemic encephalopathy (HIE). Stromal interaction molecule 1 (STIM1) serves as a Ca2+ sensor on the endoplasmic reticulum. It has been demonstrated that the supression of STIM1 impedes degranulation of MCs in numerous prior investigations. This study aimed to explore the impact of edaravone, an oxygen radical scavenger, on MCs degranulation in HIE rat model, and to explore the contribution of reactive oxygen species (ROS)/STIM1 pathway in mediating MCs degranulation. Nine-day old undetermined gender rat pups were experienced hypoxic-ischemic (HI) injury and edaravone was administered intraperitoneally at 10 min after HI insults. CM4620, an inhibitor of STIM1, was administered intraperitoneally at 10 min after HI insults to elucidate the possible mechanisms. TTC staining, Western blot analysis, immunofluorescence staining, brain water content, cerebral blood flow, toluidine blue staining, Nissl staining, and neurobehavioral test were conducted. The results demonstrated that tryptase, STIM1, tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) were increased after HI, and edaravone significantly improved neurobehavioral outcomes, reduced brain water content, decreased infarct area, reduced the accumulation of ROS, decreased the degranulation of MCs, and downregulated the protein expression of tryptase, STIM1, IL-6 and TNF-α. CM4620 inhibited MCs degranulation and downregulated the expression of STIM1, tryptase, IL-6, TNF-α. In conclusion, the current investigation revealed that edaravone attenuates MCs degranulation and neuroinflammation, at least partially, via ROS/STIM1 pathway after HI injury.

A Systematic Review of MicroRNAs in Hemorrhagic Neurovascular Disease: Cerebral Cavernous Malformations as a Paradigm

Hemorrhagic neurovascular diseases, with high mortality and poor outcomes, urge novel biomarker discovery and therapeutic targets. Micro-ribonucleic acids (miRNAs) are potent post-transcriptional regulators of gene expression. They have been studied in association with disease states and implicated in mechanistic gene interactions in various pathologies. Their presence and stability in circulating fluids also suggest a role as biomarkers. This review summarizes the current state of knowledge about miRNAs in the context of cerebral cavernous malformations (CCMs), a disease involving cerebrovascular dysmorphism and hemorrhage, with known genetic underpinnings. We also review common and distinct miRNAs of CCM compared to other diseases with brain vascular dysmorphism and hemorrhage. A systematic search, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline, queried all peer-reviewed articles published in English as of January 2025 and reported miRNAs associated with four hemorrhagic neurovascular diseases: CCM, arteriovenous malformations, moyamoya disease, and intracerebral hemorrhage. The PubMed systematic search retrieved 154 articles that met the inclusion criteria, reporting a total of 267 unique miRNAs identified in the literature on these four hemorrhagic neurovascular diseases. Of these 267 miRNAs, 164 were identified in preclinical studies, while 159 were identified in human subjects. Seventeen miRNAs were common to CCM and other hemorrhagic diseases. Common and unique disease-associated miRNAs in this systematic review motivate novel mechanistic hypotheses and have potential applications in diagnostic, predictive, prognostic, and therapeutic contexts of use. Much of current research can be considered hypothesis-generating, reflecting association rather than causation. Future areas of mechanistic investigation are proposed alongside approaches to analytic and clinical validations of contexts of use for biomarkers.

Mast cell-mediated microRNA functioning in immune regulation and disease pathophysiology

Upon stimulation and activation, mast cells (MCs) release soluble mediators, including histamine, proteases, and cytokines. These mediators are often stored within cytoplasmic granules in MCs and may be released in a granulated form. The secretion of cytokines and chemokines occurs within hours following activation, with the potential to result in chronic inflammation. In addition to their role in allergic inflammation, MCs are components of the tumor microenvironment (TME). MicroRNAs (miRNAs) are small RNA molecules that do not encode proteins, but regulate post-transcriptional gene expression by binding to the 3' non-coding regions of mRNAs. This plays a crucial role in the function of MC, including the key processes of MC proliferation, maturation, apoptosis, and activation. It has been demonstrated that miRNAs are also present in extracellular vesicles (EVs) secreted by MCs. EVs derived from MCs mediate intercellular communication by carrying miRNAs, affecting various diseases including allergic diseases, intestinal disorders, neuroinflammation, and tumors. These findings provide important insights into the therapeutic mechanisms and targets of miRNAs in MCs that affect diseases. This review discusses the relevance of miRNA production by MCs in regulating their own activity and the effect of miRNAs putatively produced by other cells in the control of MC activity and their participation in selected pathologies.

Single-cell multiomics reveals simvastatin inhibits pan-cancer epithelial-mesenchymal transition via the MEK/ERK pathway in XBP1+ mast cells

Distant metastasis is the leading cause of cancer-related mortality, and achieving survival benefits through advancements in systemic therapy remains challenging. Mast cells play a dual role in shaping the tumor microenvironment (TME) and influencing distant metastasis, underscoring the significant research value of targeting mast cells for systemic therapy in advanced cancer. We investigated variations in mast cell infiltration levels in primary and metastatic malignancies using immunocyte infiltration analysis. Mast cell subsets were identified from pan-cancer distant metastasis single-cell sequencing data through dimensionality reduction clustering and cell type annotation, combined with cell trajectory and communication network analyses. A prognostic model was established using WGCNA and 12 machine learning algorithms to identify potential mast cell targets. Drug sensitivity and Mendelian randomization analyses were conducted to select potential drugs targeting mast cells, and their effects on epithelial-mesenchymal transition (EMT) were validated through in vitro experiments, including wound healing, transwell, and western blot assays. Results revealed that activated mast cells show increased infiltration in metastatic tumors, correlating with poor survival duration. XBP1+ mast cells were identified as key components of the inhibitory TME, potentially involved in EMT activation. Simvastatin was identified as a potential drug, reversing EMT induced by XBP1+ mast cells in pan-cancer. Aberrant activation of MEK/ERK signaling in XBP1+ mast cells can stimulate cancer cell EMT by modulating degranulation, while Simvastatin can inhibit EMT by suppressing degranulation.

Naringin Alleviates Intestinal Fibrosis by Inhibiting ER Stress-Induced PAR2 Activation

Fibrosis characterized by intestinal strictures is a common complication of Crohn's disease (CD), without specific antifibrotic drugs, which usually relies on surgical intervention. The transcription factor XBP1, a key component of endoplasmic reticulum (ER) stress, is required for degranulation of mast cells and linked to PAR2 activation and fibrosis. Many studies have confirmed that naringin (NAR) can inhibit ER stress and reduce organ fibrosis. We hypothesized that ER stress activated the PAR2-induced epithelial-mesenchymal transition process by stimulating mast cell degranulation to release tryptase and led to intestinal fibrosis in CD patients; NAR might play an antifibrotic role by inhibiting ER stress-induced PAR2 activation. We report that the expression levels of XBP1, mast cell tryptase, and PAR2 are upregulated in fibrotic strictures of CD patients. Molecular docking simulates the interaction of NAR and spliced XBP1. ER stress stimulates degranulation of mast cells to secrete tryptase, activates PAR2-induced epithelial-mesenchymal transition process, and promotes intestinal fibrosis in vitro and vivo experiments, which is inhibited by NAR. Moreover, F2rl1 (the coding gene of PAR2) deletion in intestinal epithelial cells decreases the antifibrotic effect of NAR. Hence, the ER stress-mast cell tryptase-PAR2 axis can promote intestinal fibrosis, and NAR administration can alleviate intestinal fibrosis by inhibiting ER stress-induced PAR2 activation.

Edaravone Maintains AQP4 Polarity Via OS/MMP9/β-DG Pathway in an Experimental Intracerebral Hemorrhage Mouse Model

Oxidative stress (OS) is the main cause of secondary damage following intracerebral hemorrhage (ICH). The polarity expression of aquaporin-4 (AQP4) has been shown to be important in maintaining the homeostasis of water transport and preventing post-injury brain edema in various neurological disorders. This study primarily aimed to investigate the effect of the oxygen free radical scavenger, edaravone, on AQP4 polarity expression in an ICH mouse model and determine whether it involves in AQP4 polarity expression via the OS/MMP9/β-dystroglycan (β-DG) pathway. The ICH mouse model was established by autologous blood injection into the basal nucleus. Edaravone or the specific inhibitor of matrix metalloproteinase 9 (MMP9), MMP9-IN-1, called MMP9-inh was administered 10 min after ICH via intraperitoneal injection. ELISA detection, neurobehavioral tests, dihydroethidium staining (DHE staining), intracisternal tracer infusion, hematoxylin and eosin (HE) staining, immunofluorescence staining, western blotting, Evans blue (EB) permeability assay, and brain water content test were performed. The results showed that OS was exacerbated, AQP4 polarity was lost, drainage function of brain fluids was damaged, brain injury was aggravated, expression of AQP4, MMP9, and GFAP increased, while the expression of β-DG decreased after ICH. Edaravone reduced OS, restored brain drainage function, reduced brain injury, and downregulated the expression of AQP4, MMP9. Both edaravone and MMP9-inh alleviated brain edema, maintained blood-brain barrier (BBB) integrity, mitigated the loss of AQP4 polarity, downregulated GFAP expression, and upregulated β-DG expression. The current study suggests that edaravone can maintain AQP4 polarity expression by inhibiting the OS /MMP9/β-DG pathway after ICH.

Role and mechanisms of mast cells in brain disorders

Mast cells serve as crucial effector cells within the innate immune system and are predominantly localized in the skin, airways, gastrointestinal tract, urinary and reproductive tracts, as well as in the brain. Under physiological conditions, brain-resident mast cells secrete a diverse array of neuro-regulatory mediators to actively participate in neuroprotection. Meanwhile, as the primary source of molecules causing brain inflammation, mast cells also function as the "first responders" in brain injury. They interact with neuroglial cells and neurons to facilitate the release of numerous inflammatory mediators, proteases, and reactive oxygen species. This process initiates and amplifies immune-inflammatory responses in the brain, thereby contributing to the regulation of neuroinflammation and blood-brain barrier permeability. This article provides a comprehensive overview of the potential mechanisms through which mast cells in the brain may modulate neuroprotection and their pathological implications in various neurological disorders. It is our contention that the inhibition of mast cell activation in brain disorders could represent a novel avenue for therapeutic breakthroughs.

The phosphokinase activity of IRE1ɑ prevents the oxidative stress injury through miR-25/Nox4 pathway after ICH

BACKGROUND

Endoplasmic reticulum (ER) stress and oxidative stress are the major pathologies encountered after intracerebral hemorrhage (ICH). Inositol-requiring enzyme-1 alpha (IRE1α) is the most evolutionarily conserved ER stress sensor, which plays a role in monitoring and responding to the accumulation of unfolded/misfolded proteins in the ER lumen. Recent studies have shown that ER stress is profoundly related to oxidative stress in physiological or pathological conditions. The purpose of this study was to investigate the role of IRE1α in oxidative stress and the potential mechanism.

METHODS

A mouse model of ICH was established by autologous blood injection. The IRE1α phosphokinase inhibitor KIRA6 was administrated intranasally at 1 h after ICH, antagomiR-25 and agomiR-25 were injected intraventricularly at 24 h before ICH. Western blot analysis, RT-qPCR, immunofluorescence staining, hematoma volume, neurobehavioral tests, dihydroethidium (DHE) staining, H2O2 content, brain water content, body weight, Hematoxylin and Eosin (HE) staining, Nissl staining, Morris Water Maze (MWM) and Elevated Plus Maze (EPM) were performed.

RESULTS

Endogenous phosphorylated IRE1α (p-IRE1α), miR-25-3p, and Nox4 were increased in the ICH model. Administration of KIRA6 downregulated miR-25-3p expression, upregulated Nox4 expression, promoted the level of oxidative stress, increased hematoma volume, exacerbated brain edema and neurological deficits, reduced body weight, aggravated spatial learning and memory deficits, and increased anxiety levels. Then antagomiR-25 further upregulated the expression of Nox4, promoted the level of oxidative stress, increased hematoma volume, exacerbated brain edema and neurological deficits, whereas agomiR-25 reversed the effects promoted by KIRA6.

CONCLUSION

The IRE1α phosphokinase activity is involved in the oxidative stress response through miR-25/Nox4 pathway in the mouse ICH brain.

Modulating endoplasmic reticulum stress attenuates mast cell degranulation

OBJECTIVES

Degranulation of mast cells leads to direct allergic symptoms. The underlying mechanism needs to be explored further. Endoplasmic reticulum (ER) stress is involved in the pathogenesis of allergic conditions. The objective of this study is to gain a better understanding of the mechanism of mast cell degranulation.

METHODS

Bone marrow derived mast cells and mast cells isolated from the airway tissues were prepared. The role of ER stress in mediating the release of mast cells was tested. RNA sequencing (RNAseq) was used to investigate the genetic activities of mast cells.

RESULTS

Our observation showed that sensitization increased ER stress in mast cells. X-box-1 binding protein (XBP1) activity was linked to mast cell degranulation. Modulation of ER stress or XBP1 expression regulates the release of the mast cell mediator. XBP1 promoted the mediator release of mast cells by activating spleen tyrosine kinase (Syk). Activation of eukaryotic initiation factor 2a (eIF2a) inhibited XBP1 in mast cells. Semaphorin 3A was effective in preventing experimental allergic rhinitis (AR) due to its ability to suppress the release of mast cell mediators.

CONCLUSIONS

ER stress is associated with the mast cell degranulation. By inhibiting XBP1, the crucial molecule of ER stress, mast cell degranulation can be suppressed and experimental AR can be mitigated.

MicroRNAs modulate neuroinflammation after intracerebral hemorrhage: Prospects for new therapy

Intracerebral hemorrhage (ICH) is the most common subtype of hemorrhagic stroke. After ICH, blood components extravasate from vessels into the brain, activating immune cells and causing them to release a series of inflammatory mediators. Immune cells, together with inflammatory mediators, lead to neuroinflammation in the perihematomal region and the whole brain, and neuroinflammation is closely related to secondary brain injury as well as functional recovery of the brain. Despite recent progress in understanding the pathophysiology of ICH, there is still no effective treatment for this disease. MicroRNAs (miRNAs) are non-coding RNAs 17-25 nucleotides in length that are generated naturally in the human body. They bind complementarily to messenger RNAs and suppress translation, thus regulating gene expression at the post-transcriptional level. They have been found to regulate the pathophysiological process of ICH, particularly the neuroinflammatory cascade. Multiple preclinical studies have shown that manipulating the expression and activity of miRNAs can modulate immune cell activities, influence neuroinflammatory responses, and ultimately affect neurological functions after ICH. This implicates the potentially crucial roles of miRNAs in post-ICH neuroinflammation and indicates the possibility of applying miRNA-based therapeutics for this disease. Thus, this review aims to address the pathophysiological roles and molecular underpinnings of miRNAs in the regulation of neuroinflammation after ICH. With a more sophisticated understanding of ICH and miRNAs, it is possible to translate these findings into new pharmacological therapies for ICH.

Endoplasmic Reticulum Homeostasis Regulates TLR4 Expression and Signaling in Mast Cells

The endoplasmic reticulum (ER) is a dynamic organelle that responds to demand in secretory proteins by undergoing expansion. The mechanisms that control the homeostasis of ER size and function involve the activation of the unfolded protein response (UPR). The UPR plays a role in various effector functions of immune cells. Mast cells (MCs) are highly granular tissue-resident cells and key drivers of allergic inflammation. Their diverse secretory functions in response to activation through the high-affinity receptor for IgE (FcεRI) suggest a role for the UPR in their function. Using human cord blood-derived MCs, we found that FcεRI triggering elevated the expression level and induced activation of the UPR transducers IRE1α and PERK, accompanied by expansion of the ER. In mouse bone marrow-derived MCs and peritoneal MCs, the ER underwent a more moderate expansion, and the UPR was not induced following MC activation. The deletion of IRE1α in mouse MCs did not affect proliferation, survival, degranulation, or cytokine stimulation following FcεRI triggering, but it did diminish the surface expression of TLR4 and the consequent response to LPS. A similar phenotype was observed in human MCs using an IRE1α inhibitor. Our data indicate that the ER of MCs, primarily of humans, undergoes a rapid remodeling in response to activation that promotes responses to TLR4. We suggest that IRE1α inhibition can be a strategy for inhibiting the hyperactivation of MCs by LPS over the course of allergic responses.