Ceramide Imbalance and Impaired TLR4-Mediated Autophagy in BMDM of an ORMDL3-Overexpressing Mouse Model

The inhibition of ORMDL3 prevents Alzheimer's disease through ferroptosis by PERK/ATF4/HSPA5 pathway

Alzheimer's disease (AD) is a neurodegenerative disease with high incidence and widespread attention. There is currently no clear clarification of the pathogenesis. However, ORMDL3 causes ferroptosis in AD, and the potential mechanisms remain unclear. So, this study explore the function of ORMDL3 on ferroptosis in AD and its potential regulatory mechanisms. APPswe/PS1dE9 mice and C57BL/6 mice were induced into the mice model. The murine microglial BV-2 cells also were induced into the vitro model. In serum samples of AD patients, ORMDL3 mRNA expression levels were upregulated. The serum ORMDL3 levels expression was positively related to the ADL score or MoCA score in AD patients. The serum ORMDL3 expression level was positively related to MMSE score or Hcy levels in AD patients. The mRNA expression of ORMDL3 in the hippocampal tissue of the mice model of AD was upregulated at one, four and eight months. The protein expression of ORMDL3 was upregulated in the mice model of AD. ORMDL3 promoted Alzheimer's disease, and increased oxidative response and ferroptosis in a model of AD. PERK/ATF4/HSPA5 pathway is one important signal pathway for the effects of ORMDL3 in a model of AD. Collectively, these data suggested that ORMDL3 promoted oxidative response and ferroptosis in a model of AD by the PERK/ATF4/HSPA5 pathway, which might be a novel target spot mechanism of ferroptosis in AD and may serve as a regulator of AD-induced ferroptosis.

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.

Selenium Deficiency Induces Autophagy in Chicken Bursa of Fabricius Through ChTLR4/MyD88/NF-κB Pathway

To explore the role of ChTLR4/MyD88/NF-κB signaling pathway on autophagy induced by selenium (Se) deficiency in the chicken bursa of Fabricius, autophagosome formation in the bursa of Fabricius was observed by transmission electron microscopy. Quantitative real-time PCR (qRT-PCR) and Western blot were used to detect the expression of ChTLR4 and its signaling pathway molecules (MyD88, TRIF, and NF-κB), inflammatory factors (IL-1β, IL-8, and TNF-α), and autophagy-related factors (ATG5, Beclin1, and LC3-II) in the Se-deficient chicken bursa of Fabricius at different ages. The results showed that ChTLR4/MyD88/NF-κB signaling pathway was activated in the chicken bursa of Fabricius and autophagy was induced at the same time by Se deficiency. In order to verify the relationship between the autophagy and ChTLR4/MyD88/NF-κB signaling pathway, HD11 cells were used to establish the normal C group, low Se group, and low Se + TLR4 inhibitor (TAK242) group. The results demonstrated that autophagy could be hindered when the TLR4 signaling pathway was inhibited under Se deficiency. Furthermore, autophagy double-labeled adenovirus was utilized to verify the integrity of autophagy flow induced by Se deficiency in HD11 cells. The results showed that it appeared to form a complete autophagy flow under the condition of Se deficiency and could be blocked by TAK242. In summary, we found that Se deficiency was involved in the chicken bursa of Fabricius autophagy occurring by activating the ChTLR4/MyD88/NF-κB pathway.

Crosstalk between ORMDL3, serine palmitoyltransferase, and 5-lipoxygenase in the sphingolipid and eicosanoid metabolic pathways

Leukotrienes (LTs) and sphingolipids are critical lipid mediators participating in numerous cellular signal transduction events and developing various disorders, such as bronchial hyperactivity leading to asthma. Enzymatic reactions initiating production of these lipid mediators involve 5-lipoxygenase (5-LO)-mediated conversion of arachidonic acid to LTs and serine palmitoyltransferase (SPT)-mediated de novo synthesis of sphingolipids. Previous studies have shown that endoplasmic reticulum membrane protein ORM1-like protein 3 (ORMDL3) inhibits the activity of SPT and subsequent sphingolipid synthesis. However, the role of ORMDL3 in the synthesis of LTs is not known. In this study, we used peritoneal-derived mast cells isolated from ORMDL3 KO or control mice and examined their calcium mobilization, degranulation, NF-κB inhibitor-α phosphorylation, and TNF-α production. We found that peritoneal-derived mast cells with ORMDL3 KO exhibited increased responsiveness to antigen. Detailed lipid analysis showed that compared with WT cells, ORMDL3-deficient cells exhibited not only enhanced production of sphingolipids but also of LT signaling mediators LTB₄, 6t-LTB₄, LTC₄, LTB₅, and 6t-LTB₅. The crosstalk between ORMDL3 and 5-LO metabolic pathways was supported by the finding that endogenous ORMDL3 and 5-LO are localized in similar endoplasmic reticulum domains in human mast cells and that ORMDL3 physically interacts with 5-LO. Further experiments showed that 5-LO also interacts with the long-chain 1 and long-chain 2 subunits of SPT. In agreement with these findings, 5-LO knockdown increased ceramide levels, and silencing of SPTLC1 decreased arachidonic acid metabolism to LTs to levels observed upon 5-LO knockdown. These results demonstrate functional crosstalk between the LT and sphingolipid metabolic pathways, leading to the production of lipid signaling mediators.

Orosomucoid-like protein 3, rhinovirus and asthma

The genetic variants of orosomucoid-like protein 3 (ORMDL3) gene are associated with highly significant increases in the number of human rhinovirus (HRV)-induced wheezing episodes in children. Recent investigations have been focused on the mechanisms of ORMDL3 in rhinovirus infection for asthma and asthma exacerbations. ORMDL3 not only regulates major human rhinovirus receptor intercellular adhesion molecule 1 expression, but also plays pivotal roles in viral infection through metabolisms of ceramide and sphingosine-1-phosphate, endoplasmic reticulum (ER) stress, ER-Golgi interface and glycolysis. Research on the roles of ORMDL3 in HRV infection will lead us to identify new biomarkers and novel therapeutic targets in childhood asthma and viral induced asthma exacerbations.

ORMDL3 Functions as a Negative Regulator of Antigen-Mediated Mast Cell Activation via an ATF6-UPR-Autophagy-Dependent Pathway

Antigen (Ag)-mediated mast cell activation plays a critical role in the immunopathology of IgE-dependent allergic diseases. Restraining the signaling cascade that regulates the release of mast cell-derived inflammatory mediators is an attractive therapeutic strategy to treat allergic diseases. Orosomucoid-like-3 (ORMDL3) regulates the endoplasmic reticulum stress (ERS)-induced unfolded protein response (UPR) and autophagy. Although ERS/UPR/autophagy pathway is crucial in Ag-induced mast cell activation, it is unknown whether ORMDL3 regulates the ERS/UPR/autophagy pathway during mast cell activation. In this study, we found that ORMDL3 expression was downregulated in Ag-activated MC/9 cells. Overexpression of ORMDL3 significantly inhibited degranulation, and cytokine/chemokine production, while the opposite effect was observed with ORMDL3 knockdown in MC/9 cells. Importantly, ORMDL3 overexpression upregulated mediators of ERS-UPR (SERCA2b, ATF6) and autophagy (Beclin 1 and LC3BII). Knockdown of ATF6 and/or inhibition of autophagy reversed the decreased degranulation and cytokine/chemokine expression caused by ORMDL3 overexpression. Moreover, in vivo knockdown of ORMDL3 and/or ATF6 enhanced passive cutaneous anaphylaxis (PCA) reactions in mouse ears. These data indicate that ORMDL3 suppresses Ag-mediated mast cell activation via an ATF6 UPR-autophagy dependent pathway and thus, attenuates anaphylactic reaction. This highlights a potential mechanism to intervene in mast cell mediated diseases.

Mechanisms Targeting the Unfolded Protein Response in Asthma

Lung cells are constantly exposed to various internal and external stressors that disrupt protein homeostasis. To cope with these stimuli, cells evoke a highly conserved adaptive mechanism called the unfolded protein response (UPR). UPR stressors can impose greater protein secretory demands on the endoplasmic reticulum (ER), resulting in the development, differentiation, and survival of these cell types to meet these increasing functional needs. Dysregulation of the UPR leads to the development of the disease. The UPR and ER stress are involved in several human conditions, such as chronic inflammation, neurodegeneration, metabolic syndrome, and cancer. Furthermore, potent and specific compounds that target the UPR pathway are under development as future therapies. The focus of this review is to thoroughly describe the effects of both internal and external stressors on the ER in asthma. Furthermore, we discuss how the UPR signaling pathway is activated in the lungs to overcome cellular damage. We also present an overview of the pathogenic mechanisms, with a brief focus on potential strategies for pharmacological interventions.

[Molecular mechanism underlying the inhibitory effect of propofol on lipopolysaccharide-induced pyroptosis of mouse bone marrow-derived macrophages]

OBJECTIVE

To investigate the molecular mechanism underlying the inhibitory effect of propofol on pyroptosis of macrophages.

METHODS

Macrophages derived from bone marrow were extracted and divided into three groups: control group, LPS+ATP group and propofol+LPS+ATP group. The control group was not given any treatment; LPS+ATP group was given LPS 1 μg/mL stimulation for 4 h, then ATP 4 mM stimulation for 1 h; Propofol+LPS+ATP group was given propofol+LPS 1 μg/mL stimulation for 4 h, then ATP stimulation for 1 h. After treatment, the supernatant and cells of cell culture were collected. the cell activity was detected by CCK8 and flow cytometry. The inflammatory cytokines IL-1βand IL-18 were detected by Elisa. Western blot was used to detect the expression of caspase-1 protein and TLR4 on cell membran Immunohistochemical fluorescence was used to detect apoptosis of cells.

RESULTS

LPS+ATP significantly decreased the viability of the macrophages and increased the cellular production of IL-1β and IL-18, activation of caspase-1 protein and the expression of TLR-4 on the cell membrane (P < 0.05). Treatment with propofol obviously reversed the changes induced by LPS+ATP.

CONCLUSIONS

LPS+ATP can induce pyroptosis of mouse bone marrow-derived macrophages, and propofol effectively inhibits such cell death, suggesting that propofol anesthesia is beneficial during operation and helps to regulate the immune function of in patients with sepsis.

Treatment of Allergic Asthma with Fenretinide Formulation (LAU-7b) Downregulates ORMDL Sphingolipid Biosynthesis Regulator 3 (Ormdl3) Expression and Normalizes Ceramide Imbalance

Zona pellucida binding protein 2 (Zpbp2) and ORMDL sphingolipid biosynthesis regulator 3 (Ormdl3), mapped downstream of Zpbp2, were identified as two genes associated with airway hyper-responsiveness (AHR). Ormdl3 gene product has been shown to regulate the biosynthesis of ceramides. Allergic asthma was shown to be associated with an imbalance between very-long-chain ceramides (VLCCs) and long-chain ceramides (LCCs). We hypothesized that Fenretinide can prevent the allergic asthma-induced augmentation of Ormdl3 gene expression, normalize aberrant levels of VLCCs and LCCs, and treat allergic asthma symptoms. We induced allergic asthma by house dust mite (HDM) in A/J WT mice and Zpbp2 KO mice expressing lower levels of Ormdl3 mRNA than WT. We investigated the effect of a novel formulation of Fenretinide, LAU-7b, on the AHR, inflammatory cell infiltration, mucus production, IgE levels, and ceramide levels. Although lower Ormdl3 expression, which was observed in Zpbp2 KO mice, was associated with lower AHR, allergic Zpbp2 KO mice were not protected from inflammatory cell infiltration, mucus accumulation, or aberrant levels of VLCCs and LCCs induced by HDM. LAU-7b treatment protects both the Zpbp2 KO and WT mice. The treatment significantly lowers the gene expression of Ormdl3, normalizes the VLCCs and LCCs, and corrects all the other phenotypes associated with allergic asthma after HDM challenge, except the elevated levels of IgE. LAU-7b treatment prevents the augmentation of Ormdl3 expression and ceramide imbalance induced by HDM challenge and protects both WT and Zpbp2 KO mice against allergic asthma symptoms. SIGNIFICANCE STATEMENT: Compared with A/J WT mice, KO mice with Zpbp2 gene deletion have lower AHR and lower levels of Ormdl3 expression. The novel oral clinical formulation of Fenretinide (LAU-7b) effectively lowers the AHR and protects against inflammatory cell infiltration and mucus accumulation induced by house dust mite in both Zpbp2 KO and WT A/J mice. LAU-7b prevents Ormdl3 overexpression in WT allergic mice and corrects the aberrant levels of very-long-chain and long-chain ceramides in both WT and Zpbp2 KO allergic mice.

Acid sphingomyelinase regulates TH 2 cytokine release and bronchial asthma

BACKGROUND

Allergic diseases and especially allergic asthma are widespread diseases with high prevalence in childhood, but also in adults. Acid sphingomyelinase (ASM) is a key regulator of the sphingolipid pathway. Previous studies defined the association of ASM with the pathogenesis of T_H 1-directed lung diseases like cystic fibrosis and acute lung injury. Here, we define the role of ASM in T_H 2-regulated allergic bronchial asthma.

METHODS

To determine the role of Asm under baseline conditions, wild-type (WT) and Asm^-/- mice were ventilated with a flexiVent setup and bronchial hyperresponsiveness was determined using acetylcholine. Flow cytometry and cytokine measurements in bronchoalveolar lavage fluid and lung tissue were followed by in vitro T_H 2 differentiations with cells from WT and Asm^-/- mice and blockade of Asm with amitriptyline. As proof of principle, we conducted an ovalbumin-induced model of asthma in WT- and Asm^-/-  mice.

RESULTS

At baseline, Asm^-/- mice showed better lung mechanics, but unaltered bronchial hyperresponsiveness. Higher numbers of Asm^-/- T cells in bronchoalveolar lavage fluid released lower levels of IL-4 and IL-5, and these results were paralleled by decreased production of typical T_H 2 cytokines in Asm^-/- T lymphocytes in vitro. This phenotype could be imitated by incubation of T cells with amitriptyline. In the ovalbumin asthma model, Asm^-/- animals were protected from high disease activity and showed better lung functions and lower levels of eosinophils and T_H 2 cytokines.

CONCLUSION

Asm deficiency could induce higher numbers of T_H 2 cells in the lung, but those cells release decreased T_H 2 cytokine levels. Hereby, Asm^-/- animals are protected from bronchial asthma, which possibly offers novel therapeutic strategies, for example, with ASM blockade.

Efficacy of Optimized Treatment Protocol Using LAU-7b Formulation against Ovalbumin (OVA) and House Dust Mite (HDM) -Induced Allergic Asthma in Atopic Hyperresponsive A/J Mice

PURPOSE

To assess the efficacy of the novel clinical formulation of fenretinide (LAU-7b) for the treatment of allergic asthma. To study the association between LAU-7b treatment in allergic asthma and the modulation of very long chain ceramides (VLCC).

METHODS

We used two allergens (OVA and HDM) to induce asthma in mouse models and we established a treatment protocol with LAU-7b. The severity of allergic asthma reaction was quantified by measuring the airway resistance, quantifying lung inflammatory cell infiltration (Haematoxylin and eosin stain) and mucus production (Periodic acid Schiff satin). IgE levels were measured by ELISA. Immunophenotyping of T cells was done using Fluorescence-activated cell sorting (FACS) analysis. The analysis of the specific species of lipids and markers of oxidation was performed using mass spectrometry.

RESULTS

Our data demonstrate that 10 mg/kg of LAU-7b was able to protect OVA- and HDM-challenged mice against increase in airway hyperresponsiveness, influx of inflammatory cells into the airways, and mucus production without affecting IgE levels. Treatment with LAU-7b significantly increased percentage of regulatory T cells and CD4⁺ IL-10-producing T cells and significantly decreased percentage of CD4⁺ IL-4-producing T cells. Our data also demonstrate a strong association between the improvement in the lung physiology and histology parameters and the drug-induced normalization of the aberrant distribution of ceramides in allergic mice.

CONCLUSION

9 days of 10 mg/kg of LAU-7b daily treatment protects the mice against allergen-induced asthma and restores VLCC levels in the lungs and plasma.

Trafficking of Stretch-Regulated TRPV2 and TRPV4 Channels Inferred Through Interactomics

Transient receptor potential cation channels are emerging as important physiological and therapeutic targets. Within the vanilloid subfamily, transient receptor potential vanilloid 2 (TRPV2) and 4 (TRPV4) are osmo- and mechanosensors becoming critical determinants in cell structure and activity. However, knowledge is scarce regarding how TRPV2 and TRPV4 are trafficked to the plasma membrane or specific organelles to undergo quality controls through processes such as biosynthesis, anterograde/retrograde trafficking, and recycling. This review lists and reviews a subset of protein–protein interactions from the TRPV2 and TRPV4 interactomes, which is related to trafficking processes such as lipid metabolism, phosphoinositide signaling, vesicle-mediated transport, and synaptic-related exocytosis. Identifying the protein and lipid players involved in trafficking will improve the knowledge on how these stretch-related channels reach specific cellular compartments.