Hematopoietic PGD Synthase Research Articles

Discovering potential asthma therapeutics targeting hematopoietic prostaglandin D2 synthase: An integrated computational approach

Allergic asthma, a chronic inflammatory illness that affects millions worldwide, has serious economic and health consequences. Despite advances in therapy, contemporary treatments have poor efficacy and negative effects. This study investigates hematopoietic prostaglandin D2 synthase (HPGDS) as a potential target for novel asthma therapies. Targeting HPGDS may provide innovative treatment methods. A library of phytochemicals was used to find putative HPGDS inhibitors by structure-based and ligand-based virtual screening. Among the 2295 compounds screened, four compounds (ZINC208828240, ZINC95627530, ZINC14727536, and ZINC14711790) demonstrated strong binding affinities of −10.4, −10.3, −9.2, −9.1 kcal/mol respectively with key residues, suggesting their potential as a highly effective HPGDS inhibitor. Molecular dynamics (MD) simulations and Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) computations were further performed to evaluate the stability and binding affinity of the complexes. MD simulations and MMPBSA confirmed that compound ZINC14711790 showed high stability and binding affinity (binding energy −31.52 kcal/mol) than other compounds, including HQL-79, suggesting that this compound might be used as promising inhibitors to treat asthma. RMSD and RMSF analysis also revealed that ZINC14711790 exhibited strong dynamic stability. The findings of this study show the efficacy of ZINC14711790 as HPGDS inhibitors with high binding affinity, dynamic stability, and appropriate ADMET profile.

Prediction of Future Parkinson Disease Using Plasma Proteins Combined With Clinical-Demographic Measures.

Identification of individuals at high risk of developing Parkinson disease (PD) several years before diagnosis is crucial for developing treatments to prevent or delay neurodegeneration. This study aimed to develop predictive models for PD risk that combine plasma proteins and easily accessible clinical-demographic variables. Using data from the UK Biobank (UKB), which recruited participants across the United Kingdom, we conducted a longitudinal study to identify predictors for incident PD. Participants with baseline plasma proteins and no PD were included. Through machine learning, we narrowed down predictors from a pool of 1,463 plasma proteins and 93 clinical-demographic. These predictors were then externally validated using the Parkinson's Progression Marker Initiative (PPMI) cohort. To further investigate the temporal trends of predictors, a nested case-control study was conducted within the UKB. A total of 52,503 participants without PD (median age 58, 54% female) were included. Over a median follow-up duration of 14.0 years, 751 individuals were diagnosed with PD (median age 65, 37% female). Using a forward selection approach, we selected a panel of 22 plasma proteins for optimal prediction. Using an ensemble tree-based Light Gradient Boosting Machine (LightGBM) algorithm, the model achieved an area under the receiver operating characteristic curve (AUC) of 0.800 (95% CI 0.785-0.815). The LightGBM prediction model integrating both plasma proteins and clinical-demographic variables demonstrated enhanced predictive accuracy, with an AUC of 0.832 (95% CI 0.815-0.849). Key predictors identified included age, years of education, history of traumatic brain injury, and serum creatinine. The incorporation of 11 plasma proteins (neurofilament light, integrin subunit alpha V, hematopoietic PGD synthase, histamine N-methyltransferase, tubulin polymerization promoting protein family member 3, ectodysplasin A2 receptor, Latexin, interleukin-13 receptor subunit alpha-1, BAG family molecular chaperone regulator 3, tryptophanyl-TRNA synthetase, and secretogranin-2) augmented the model's predictive accuracy. External validation in the PPMI cohort confirmed the model's reliability, producing an AUC of 0.810 (95% CI 0.740-0.873). Notably, alterations in these predictors were detectable several years before the diagnosis of PD. Our findings support the potential utility of a machine learning-based model integrating clinical-demographic variables with plasma proteins to identify individuals at high risk for PD within the general population. Although these predictors have been validated by PPMI, additional validation in a more diverse population reflective of the general community is essential.

Characterization and validation of fatty acid metabolism-related genes predicting prognosis, immune infiltration, and drug sensitivity in endometrial cancer.

Endometrial cancer is considered to be the second most common tumor of the female reproductive system, and patients diagnosed with advanced endometrial cancer have a poor prognosis. The influence of fatty acid metabolism in the prognosis of patients with endometrial cancer remains unclear. We constructed a prognostic risk model using transcriptome sequencing data of endometrial cancer and clinical information of patients from The Cancer Genome Atlas (TCGA) database via least absolute shrinkage and selection operator regression analysis. The tumor immune microenvironment was analyzed using the CIBERSORT algorithm, followed by functional analysis and immunotherapy efficacy prediction by gene set variation analysis. The role of model genes in regulating endometrial cancer in vitro was verified by CCK-8, colony formation, wound healing, and transabdominal invasion assays, and verified in vivo by subcutaneous tumor transplantation in nude mice. A prognostic model containing 14 genes was constructed and validated in 3 cohorts and clinical samples. The results showed differences in the infiltration of immune cells between the high-risk and low-risk groups, and that the high-risk group may respond better to immunotherapy. Experiments in vitro confirmed that knockdown of epoxide hydrolase 2 (EPHX2) and acyl-CoA oxidase like (ACOXL) had an inhibitory effect on EC cells, as did overexpression of hematopoietic prostaglandin D synthase (HPGDS). The same results were obtained in experiments in vivo. Prognostic models related to fatty acid metabolism can be used for the risk assessment of endometrial cancer patients. Experiments in vitro and in vivo confirmed that the key genes HPGDS, EPHX2, and ACOXL in the prognostic model may affect the development of endometrial cancer.

Hematopoietic Prostaglandin D Synthase Is Increased in Mast Cells and Pericytes in Autopsy Myocardial Specimens from Patients with Duchenne Muscular Dystrophy.

The leading cause of death for patients with Duchenne muscular dystrophy (DMD), a progressive muscle disease, is heart failure. Prostaglandin (PG) D2, a physiologically active fatty acid, is synthesized from the precursor PGH2 by hematopoietic prostaglandin D synthase (HPGDS). Using a DMD animal model (mdx mice), we previously found that HPGDS expression is increased not only in injured muscle but also in the heart. Moreover, HPGDS inhibitors can slow the progression of muscle injury and cardiomyopathy. However, the location of HPGDS in the heart is still unknown. Thus, this study investigated HPGDS expression in autopsy myocardial samples from DMD patients. We confirmed the presence of fibrosis, a characteristic phenotype of DMD, in the autopsy myocardial sections. Additionally, HPGDS was expressed in mast cells, pericytes, and myeloid cells of the myocardial specimens but not in the myocardium. Compared with the non-DMD group, the DMD group showed increased HPGDS expression in mast cells and pericytes. Our findings confirm the possibility of using HPGDS inhibitor therapy to suppress PGD2 production to treat skeletal muscle disorders and cardiomyopathy. It thus provides significant insights for developing therapeutic drugs for DMD.

In Silico Design, Synthesis, and Evaluation of PROTAC Against Hematopoietic Prostaglandin D Synthase.

Chemical protein knockdown technology using proteolysis-targeting chimeras (PROTACs) to hijack the endogenous ubiquitin-proteasome system is a powerful strategy to degrade disease-related proteins. This chapter describes in silico design of a hematopoietic prostaglandin D synthase (H-PGDS) degrader, PROTAC(H-PGDS), using a docking simulation of the ternary complex of H-PGDS/PROTAC/E3 ligase as well as the synthesis of the designed PROTAC(H-PGDS)s and evaluation of their H-PGDS degradation activity.

Roles of lipocalin-type and hematopoietic prostaglandin D synthases in mouse retinal angiogenesis

Normal angiogenesis is essential for retinal development and maintenance of visual function in the eye, and its abnormality can cause retinopathy and other eye diseases. Prostaglandin D2 is an anti-angiogenic lipid mediator produced by lipocalin-type PGD synthase (L-PGDS) or hematopoietic PGD synthase (H-PGDS). However, the exact role of these PGD synthases remains unclear. Therefore, we compared the roles of these synthases in murine retinal angiogenesis under physiological and pathological conditions. On postnatal day (P) 8, the WT murine retina was covered with an elongated vessel. L-PGDS deficiency, but not H-PGDS, reduced the physiological vessel elongation with sprouts increase. L-PGDS expression was observed in endothelial cells and neural cells. In vitro, L-PGDS inhibition increased the hypoxia-induced vascular endothelial growth factor expression in isolated endothelial cells, inhibited by a prostaglandin D2 metabolite, 15-deoxy-Δ12,14 -PGJ2 (15d-PGJ2) treatment. Pericyte depletion, using antiplatelet-derived growth factor receptor-β antibody, caused retinal hemorrhage with vessel elongation impairment and macrophage infiltration in the WT P8 retina. H-PGDS deficiency promoted hemorrhage but inhibited the impairment of vessel elongation, while L-PGDS did not. In the pericyte-depleted WT retina, H-PGDS was expressed in the infiltrated macrophages. Deficiency of the D prostanoid receptor also inhibited the vessel elongation impairment. These results suggest the endogenous role of L-PGDS signaling in physiological angiogenesis and that of H-PGDS/D prostanoid 1 signaling in pathological angiogenesis.

Prostaglandin D2 regulates Escherichia coli-induced inflammatory responses through TLR2, TLR4, and NLRP3 in macrophages

Prostaglandin D2 (PGD2) synthesis is closely associated with the innate immune response mediated by pattern recognition receptors (PPRs). We determined PGD2 synthesis whether mediated by Toll-like receptor 2 (TLR2), TLR4 and Nod-like receptor pyrin domain-containing protein 3 (NLRP3) in Escherichia coli (E. coli)-, lipopolysaccharide (LPS)- and Braun lipoprotein (BLP)-stimulated macrophages. Our data demonstrate that TLR2, TLR4, and NLRP3 could regulate the synthesis of PGD2 through cyclo-oxygenase-2 (COX-2) and hematopoietic PGD synthase (H-PGDS) in E. coli-, LPS- or BLP-stimulated macrophages, suggesting that TLR2, TLR4, and NLRP3 are critical in regulating PGD2 secretion by controlling PGD2 synthetase expression in E. coli-, LPS- or BLP-stimulated macrophages. The H-PGDS (a PGD2 specific synthase) inhibitor pre-treatment could down-regulate the secretion of TNF-α, RANTES and IL-10 in LPS- and E. coli-stimulated macrophage. Meanwhile, H-PGDS inhibitor could down-regulate the secretion of TNF-α, while up-regulated RANTES and IL-10 secretion in BLP-stimulated macrophages, suggesting that PGD2 could regulate the secretion of cytokines and chemokines in E. coli-, LPS- or BLP-stimulated macrophages. Furthermore, exogenous PGD2 regulates the secretion of cytokines and chemokines through activation of MAPK and NF-κB signaling pathways after E. coli-, LPS- or BLP stimulation in macrophages. Taken together, PGD2 is found able to regulate E. coli-induced inflammatory responses through TLR2, TLR4, and NLRP3 in macrophages.

Computer-Aided Designing Peptide Inhibitors of Human Hematopoietic Prostaglandin D2 Synthase Combined Molecular Docking and Molecular Dynamics Simulation.

Human hematopoietic prostaglandin D2 synthase (HPGDS) is involved in the production of prostaglandin D2, which participates in various physiological processes, including inflammation, allergic reactions, and sleep regulation. Inhibitors of HPGDS have been investigated as potential anti-inflammatory agents. For the investigation of potent HPGDS inhibitors, we carried out a computational modeling study combining molecular docking and molecular dynamics simulation for selecting and virtual confirming the designed binders. We selected the structure of HPGDS (PDB ID: 2CVD) carrying its native inhibitor compound HQL as our research target. The random 5-mer peptide library was created by building the 3-D structure of random peptides using Rosetta Buildpeptide and performing conformational optimization. Molecular docking was carried out by accommodating the peptides into the location of their native binder and then conducting docking using FlexPepDock. The two peptides RMYYY and VMYMI, which display the lowest binding energy against HPGDS, were selected to perform a comparative study. The interaction of RMYYY and VMYMI against HPGDS was further confirmed using molecular dynamics simulation and aligned with its native binder, HQL. We show the selected binders to have stronger binding energy and more frequent interactions against HPGDS than HQL. In addition, we analyzed the solubility, hydrophobicity, charge, and bioactivity of the generated peptides, and we show that the selected strong binder may be further used as therapeutic drugs.

Abstract 3162: Genome-scale metabolic modeling suggests novel molecular targets in ER-positive breast cancer

Abstract High expression of the epithelial splicing regulatory protein 1 (ESRP1) is correlated with poor prognosis in estrogen receptor positive (ER+) breast cancer and acquired resistance to tamoxifen/endocrine therapies. Our previous study revealed a novel functionality of ESRP1 in metabolic dysregulation by affecting lipid metabolism and oxidoreductase processes. To further understand how metabolic programming is affected by ESRP1 expression and identify novel therapeutic targets, we developed systems biology models to explore ER+ breast cancer metabolism. Flux balance analysis (FBA) is a computational approach to predict steady-state fluxes through metabolic reactions by posing cellular “objectives” such as maximization of biomass, ATP, or minimization of reactive oxygen species that reflect selective pressures posed by the tumor microenvironment or therapeutic insults. Our custom FBA pipeline leverages transcriptomic data, mutation information, and thermodynamic constraints to generate personalized genome-scale metabolic models. In this study, 100 ESRP1-high and 100 ESRP1-low tumors from the TCGA Breast Cancer Invasive Carcinoma dataset were simulated and compared; in a secondary analysis, we simulated metabolic rerouting of tamoxifen-resistant LCC2 cells and fulvestrant-resistant LCC9 cells upon ESRP1 knockdown. The intersection of statistically significant (p < 0.05) reactions that were altered in both the TCGA and cell line contexts suggested that changes in eicosanoid metabolism and androgen and estrogen synthesis pathways are highly involved in ESRP1's role in breast cancer prognosis and resistance to endocrine therapies. Eicosanoid-utilizing enzymes are consistently altered between the ESRP1-low and high conditions; Hematopoietic prostaglandin D synthase (HPGDS), prostaglandin I2 synthase (PTDIS), and thromboxane A synthase 1 (TBXAS1) are druggable. Furthermore, reactions associated with cytosolic and lysosomal 4-hydroxy-17beta-estradiol production, catalyzed by the enzymes myeloperoxidase, lactoperoxidase, and peroxiredoxin 6, also emerged as consistently altered across the groups. The findings from this methodology have suggested novel metabolic targets to overcome tamoxifen/endocrine therapy resistance in ER+ breast cancer. Experimental validation of these targets is currently underway. Citation Format: Zachary B. Mudge, Kristof Kovacs, Melissa L. Kemp, Sunil S. Badve, Yesim Gokmen-Polar. Genome-scale metabolic modeling suggests novel molecular targets in ER-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3162.

CRBN ligand expansion for hematopoietic prostaglandin D2 synthase (H-PGDS) targeting PROTAC design and their in vitro ADME profiles

An increasing number of research reports are describing modifications of the E3 ligand, in particular, cereblon (CRBN) ligands, to improve the chemical and metabolic stabilities as well as the physical properties of PROTACs. In this study, phenyl-glutarimide (PG) and 6-fluoropomalidomide (6-F-POM), recently used as CRBN ligands for PROTAC design, were applied to hematopoietic prostaglandin D2 synthase (H-PGDS)-targeted PROTACs. Both PROTAC-5 containing PG and PROTAC-6 containing 6-F-POM were found to have potent activities to induce H-PGDS degradation. Furthermore, we obtained in vitro ADME data on the newly designed PROTACS as well as our previously reported PROTACs(H-PGDS) series. Although all PROTACs(H-PGDS) are relatively stable toward metabolism, they had poor PAMPA values. Nevertheless, PROTAC-5 showed Papp values similar to TAS-205, which is in Phase 3 clinical trials, and is expected to be the key to improving the pharmacokinetics of PROTACs.

HPGDS is a novel prognostic marker associated with lipid metabolism and aggressiveness in lung adenocarcinoma.

Lung adenocarcinoma (LUAD) is the most common respiratory globallywith a poor prognosis. Lipid metabolism is extremely important for the occurrence and development of cancer. However, the role of genes involved in lipid metabolism in LUAD development is unclear. We aimed to identify the abnormal lipid metabolism pathway of LUAD, construct a novel prognostic model of LUAD, and discover novel biomarkers involved in lipid metabolism inLUAD. Based on differentially expressed genes involved in lipid metabolism in LUAD samples from The Cancer Genome Atlas (TCGA), abnormal lipid metabolism pathways in LUAD were analyzed. The lasso penalized regression analysis was performed on the TCGA cohort (training set) to construct a risk score formula. The predictive ability of the risk score was validated in the Gene Expression Omnibus (GEO) dataset (validation set) using Kaplan-Meier analysis and ROC curves. Finally, based on CRISPR gene editing technology, hematopoietic prostaglandin D synthase (HPGDS) was knocked out in A549 cell lines, the changes in lipid metabolism-related markers were detected by western blotting, and the changes in cell migration were detected by transwellassay. Based on the differential genes between lung cancer tissue and normal tissue, we found that the arachidonic acid metabolism pathway is an abnormal lipid metabolism pathway in both lung adenocarcinoma and lung squamous cell carcinoma. Based on the sample information of TCGA and abnormally expressed lipid metabolism-related genes, a 9-gene prognostic risk score was successfully constructed and validated in the GEO dataset. Finally, we found that knockdown of HPGDS in A549 cell lines promoted lipid synthesis and is more invasive than in control cells. Rescue assays showed that ACSL1 knockdown reversed the pro-migration effects of HPGDS knockdown. The knockdown of HPGDS promoted migration response by upregulating the expression of the lipid metabolism key enzymes ACSL1 and ACC. The genes involved in lipid metabolism are associated with the occurrence and development of LUAD. HPGDS can be a therapeutic target of a potential lipid metabolism pathway in LUAD, and the therapeutic target of lipid metabolism genes in LUAD should be studied further.

Overexpressing HPGDS in adipose-derived mesenchymal stem cells reduces inflammatory state and improves wound healing in type 2 diabetic mice

BackgroundIn diabetes, delayed wound healing was considered as the result of excessive recruitment and retention of pro-inflammatory cells and factors. Hematopoietic prostaglandin D synthase (HPGDS) was identified from differently expressed genes of diabetic human foot skin. HPGDS is responsible for the production of prostaglandin D2 (PGD2), an inflammatory mediator. Therefore, we aim to explore whether HPGDS could be a therapeutic target in the diabetic wound (DW).MethodIn this study, we compared gene expression profilings of diabetic human foot skin and non-diabetic human foot skin from the Gene Expression Omnibus database. We detected the characteristics of immune components in diabetic mice wound and investigated the role and underlying mechanism of the differently expressed Hpgds for the diabetic wound healing. For in vivo studies, we engineered ADSC to overexpress Hpgds (ADSCHpgds) and evaluated its effects on diabetic wound healing using a full-thickness skin wound model. For in vitro studies, we evaluated the role of ADSCHpgds conditioned medium and PGD2 on Lipopolysaccharide (LPS) induced macrophage.ResultsHpgds was significantly down-regulated in type 2 diabetic mice wound and its deficiency delayed normal wound healing. ADSCHpgds accelerated DW healing by reducing neutrophil and CD8T cell recruitment, promoting M2 macrophage polarization and increasing the production of growth factors. ADSCHpgds conditioned medium showed superior capability in promoting M2 macrophage transition than conditioned medium derived from ADSC alone.ConclusionOur results demonstrated that Hpgds is required for wound healing, and ADSCHpgds could accelerate DW healing by improving anti-inflammatory state and normalizing the proliferation phase of wound healing in mice. These findings provide a new insight in the therapeutic strategy of diabetic wound.

Hematopoietic Prostaglandin D2 Synthase Controls Tfh/Th2 Communication and Limits Tfh Antitumor Effects

T follicular helper (Tfh) cells are a subset of CD4+ T cells essential in immunity and have a role in helping B cells produce antibodies against pathogens. However, their role during cancer progression remains unknown. The mechanism of action of Tfh cells remains elusive because contradictory data have been reported on their protumor or antitumor responses in human and murine tumors. Like Tfh cells, Th2 cells are also involved in humoral immunity and are regularly associated with tumor progression and poor prognosis, mainly through their secretion of IL4. Here, we showed that Tfh cells expressed hematopoietic prostaglandin D2 (PGD2) synthase in a pSTAT1/pSTAT3-dependent manner. Tfh cells produced PGD2, which led to recruitment of Th2 cells via the PGD2 receptor chemoattractant receptor homologous molecule expressed on Th type 2 cells (CRTH2) and increased their effector functions. This cross-talk between Tfh and Th2 cells promoted IL4-dependent tumor growth. Correlation between Th2 cells, Tfh cells, and hematopoietic PGD2 synthase was observed in different human cancers and associated with outcome. This study provides evidence that Tfh/Th2 cross-talk through PGD2 limits the antitumor effects of Tfh cells and, therefore, could serve as a therapeutic target.

Interleukin-4 treatment reduces leukemia burden in acute myeloid leukemia.

Interleukin-4 (IL-4) is a signature cytokine pivotal in Type 2helper T cell (Th2) immune response, particularly in allergy and hypersensitivity. Interestingly, IL-4 increases endogenous levels of prostaglandin D2 (PGD2 ) and its metabolites, Δ12 -prostaglandin J2 (Δ12 -PGJ2 ) and 15-deoxy-Δ12,14 -prostaglandin J2 (15d-PGJ2 ), collectively called cyclopentenone PGs (CyPGs). However, the therapeutic role of IL-4 in hematologic malignancies remains unclear. Here, we employed a murine model of acute myeloid leukemia (AML), where human MLL-AF9 fusion oncoprotein was expressed in hematopoietic progenitor cells, to test the effect of IL-4 treatment in vivo. Daily intraperitoneal treatment with IL-4 at 60µg/kg/d significantly alleviated the severity of AML, as seen by decreased leukemia-initiating cells (LICs). The effect of IL-4 was mediated, in part, by the enhanced expression of hematopoietic- PGD2 synthase (H-PGDS) to effect endogenous production of CyPGs, through autocrine and paracrine signaling mechanisms. Similar results were seen with patient-derived AML cells cultured ex vivo with IL-4. Use of GW9662, a peroxisome proliferator-activated receptor gamma (PPARγ) antagonist, suggested endogenous CyPGs-PPARγ axis mediated p53-dependent apoptosis of LICs by IL-4. Taken together, our results reveal a beneficial role of IL-4 treatment in AML suggesting a potential therapeutic regimen worthy of clinical trials in patients with AML.

Identification of potential inhibitors for Hematopoietic Prostaglandin D2 synthase: Computational modeling and molecular dynamics simulations

To design a new therapeutic agent for Hematopoietic Prostaglandin D2 synthase (hPGDS), a set of 60 molecules with different molecular scaffolds were (range of pIC50 values are from 8.301 to 3.932) considered to create a pharmacophore model. Further, identification of potential hPGDS inhibitors were carried out by using virtual screening with different databases (from 15,74,182 molecules). The molecular screening was performed by using different sequential methods right from Pharmacophore based virtual screening, molecular docking, MM-GBSA studies and ADME property analysis. Based on the molecular screening and visual data analysis, 4 molecules were further subjected to molecular dynamics (MD) simulation study. Outcomes of the present study conclude with a new proposed molecule. Molecule SP1 show a good range of interaction with human hPGDS enzyme in comparison to the marketed compounds i.e., HQL-79, TFC-007, HPGDS inhibitor I and TAS-204.

Monocytes and Macrophages Serve as Potent Prostaglandin D2 Sources during Acute, Non-Allergic Pulmonary Inflammation.

Acute respiratory inflammation, most commonly resulting from bacterial or viral infection, is one of the leading causes of death and disability worldwide. The inflammatory lipid mediator prostaglandin D2 (PGD2) and its rate-limiting enzyme, hematopoietic PGD synthase (hPGDS), are well-known drivers of allergic pulmonary inflammation. Here, we sought to investigate the source and role of hPGDS-derived PGD2 in acute pulmonary inflammation. Murine bronchoalveolar monocytes/macrophages from LPS- but not OVA-induced lung inflammation released significant amounts of PGD2. Accordingly, human monocyte-derived macrophages expressed high basal levels of hPGDS and released significant levels of PGD2 after LPS/IFN-γ, but not IL-4 stimulation. Human peripheral blood monocytes secreted significantly more PGD2 than monocyte-derived macrophages. Using human precision-cut lung slices (PCLS), we observed that LPS/IFN-γ but not IL-4/IL-13 drive PGD2 production in the lung. HPGDS inhibition prevented LPS-induced PGD2 release by human monocyte-derived macrophages and PCLS. As a result of hPGDS inhibition, less TNF-α, IL-6 and IL-10 could be determined in PCLS-conditioned medium. Collectively, this dataset reflects the time-dependent release of PGD2 by human phagocytes, highlights the importance of monocytes and macrophages as PGD2 sources and suggests that hPGDS inhibition might be a potential therapeutic option for acute, non-allergic lung inflammation.

Discovery of a Highly Potent and Selective Degrader Targeting Hematopoietic Prostaglandin D Synthase via In Silico Design.

Targeted protein degradation by proteolysis-targeting chimera (PROTAC) is one of the exciting modalities for drug discovery and biological discovery. It is important to select an appropriate linker, an E3 ligase ligand, and a target protein ligand in the development; however, it is necessary to synthesize a large number of PROTACs through trial and error. Herein, using a docking simulation of the ternary complex of a hematopoietic prostaglandin D synthase (H-PGDS) degrader, H-PGDS, and cereblon, we have succeeded in developing PROTAC(H-PGDS)-7 (6), which showed potent and selective degradation activity (DC50 = 17.3 pM) and potent suppression of prostaglandin D2 production in KU812 cells. Additionally, in a Duchenne muscular dystrophy model using mdx mice with cardiac hypertrophy, compound 6 showed better inhibition of inflammatory cytokines than a potent H-PGDS inhibitor TFC-007. Thus, our results demonstrated that in silico simulation would be useful for the rational development of PROTACs.

Hematopoietic Prostaglandin D Synthase Inhibitor PK007 Decreases Muscle Necrosis in DMD mdx Model Mice.

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness and wasting due to the lack of dystrophin protein. The acute phase of DMD is characterized by muscle necrosis and increased levels of the pro-inflammatory mediator, prostaglandin D2 (PGD2). Inhibiting the production of PGD2 by inhibiting hematopoietic prostaglandin D synthase (HPGDS) may alleviate inflammation and decrease muscle necrosis. We tested our novel HPGDS inhibitor, PK007, in the mdx mouse model of DMD. Our results show that hindlimb grip strength was two-fold greater in the PK007-treated mdx group, compared to untreated mdx mice, and displayed similar muscle strength to strain control mice (C57BL/10ScSn). Histological analyses showed a decreased percentage of regenerating muscle fibers (~20% less) in tibialis anterior (TA) and gastrocnemius muscles and reduced fibrosis in the TA muscle in PK007-treated mice. Lastly, we confirmed that the DMD blood biomarker, muscle creatine kinase activity, was also reduced by ~50% in PK007-treated mdx mice. We conclude that our HPGDS inhibitor, PK007, has effectively reduced muscle inflammation and fibrosis in a DMD mdx mouse model.

Mast Cell-Specific Deletion of Group III Secreted Phospholipase A2 Impairs Mast Cell Maturation and Functions.

Tissue-resident mast cells (MCs) have important roles in IgE-associated and -independent allergic reactions. Although microenvironmental alterations in MC phenotypes affect the susceptibility to allergy, understanding of the regulation of MC maturation is still incomplete. We previously reported that group III secreted phospholipase A2 (sPLA2-III) released from immature MCs is functionally coupled with lipocalin-type prostaglandin D2 (PGD2) synthase in neighboring fibroblasts to supply a microenvironmental pool of PGD2, which in turn acts on the PGD2 receptor DP1 on MCs to promote their proper maturation. In the present study, we reevaluated the role of sPLA2-III in MCs using a newly generated MC-specific Pla2g3-deficient mouse strain. Mice lacking sPLA2-III specifically in MCs, like those lacking the enzyme in all tissues, had immature MCs and displayed reduced local and systemic anaphylactic responses. Furthermore, MC-specific Pla2g3-deficient mice, as well as MC-deficient KitW-sh mice reconstituted with MCs prepared from global Pla2g3-null mice, displayed a significant reduction in irritant contact dermatitis (ICD) and an aggravation of contact hypersensitivity (CHS). The increased CHS response by Pla2g3 deficiency depended at least partly on the reduced expression of hematopoietic PGD2 synthase and thereby reduced production of PGD2 due to immaturity of MCs. Overall, our present study has confirmed that MC-secreted sPLA2-III promotes MC maturation, thereby facilitating acute anaphylactic and ICD reactions and limiting delayed CHS response.

BAALC Is a Key Mediator of Leukemia Development in Congenital Neutropenia

We recently reported high frequency of cooperating acquired CSF3R and RUNX1 mutations in severe congenital neutropenia (CN) patients that developed AML or MDS. CN is a pre-leukemic bone marrow failure syndrome (BMFS) and longitudinal retrospective analysis of CN bone marrow samples allows identification of the pathological intracellular events that lead to leukemogenic transformation.In the present study, we report the identification of a key mechanism of leukemogenesis in CN. We made use of the induced pluripotent stem cell (iPSC) model and embryoid body (EB)-based in vitro hematopoietic differentiation of iPSCs generated from a CN patient harboring ELANE mutation before (CN-iPSCs) and after (CN/AML-iPSCs) overt AML. CN/AML-iPSCs clones revealed CSF3R and RUNX1 mutations and trisomy 21. EB-based hematopoietic differentiation revealed that CN-iPSCs produced similar amounts of CD34+ cells, but approximately 2-fold reduction of mature granulocytes and CFU-G colonies in CFU-assay, as compared to healthy donor-derived iPSCs. CN/AML-iPSCs produced CD34+ cells but did not differentiate into mature granulocytes at all.Analysis of the gene expression profiles of five CN/AML patients including our index patient, revealed that genes upregulated in early hematopoietic stem/progenitor cells (HSPCs), such as Brain And Acute Leukemia, Cytoplasmic (BAALC), Hematopoietic Prostaglandin D Synthase (HPGDS), Natriuretic Peptide Receptor 3 (NPR3) and CD109 were markedly increased in CN/AML blasts harboring both RUNX1 and CSF3R mutations, as compared to hematopoietic cells prior to leukemia. This genetic signature suggests transformation of hematopoietic cells into more primitive hematopoietic progenitors after acquisition of CSF3R and RUNX1 mutations. We were able to confirm strong increase of BAALC, HPGDS, NPR3 and CD109 mRNA levels in CD34+ cells derived from CN/AML-iPSCs, as compared to CN-iPSCs, suggesting that our iPSC-model is reliable to study leukemogenesis.In order to evaluate which of these candidate genes (BAALC, HPGDS, NPR3 and CD109)is responsible for the leukemogenic transformation in CN, we generated CN/AML-iPSCs clones deficient for one selected genes. We established CRISPR-Cas9-mediated gene knockout using transfection of CN/AML-iPSCs with pSpCas9(BB)-2A-GFP vector expressing Cas9 and sgRNA, that were designed to specifically target first exon of each candidate gene. CN/AML-iPSCs transfected with specific sgRNAs were sorted and single cell clones were analyzed further.Knockout of the selected genes did not affect survival and pluripotency of CN/AML-iPSCs and we were able to study EB-based hematopoietic differentiation of gene-edited CN/AML-iPSCs clones. Interestingly, knockout of HPGDS, NPR3 or CD109 did not correct defective granulocytic differentiation of CN/AML-iPSCs, whereas knockout of BAALC in CN/AML-iPSCs resulted in the tremendous increase of the granulocytic differentiation, as assessed by FACS, CFU assay, morphological analysis of cytospin preparations and nitroblue tetrazolium (NBT) assay. Granulocytic differentiation of BAALC -deficient CN/AML-iPSCs was comparable to CN-iPSCs, but was still reduced in comparison to healthy donor-derived iPSCs.These data clearly showed that knockout of BAALC in CN/AML-iPSCs overcomes differentiation block at the early hematopoietic progenitor cell stage, demonstrating a fundamental role of BAALC in leukemia development in CN. BAALC, HPGDS and CD109 are known to be markedly up-regulated in RUNX1 -mutated de novo AML and qRT-PCR of CD34+ cells generated from BAALC -knockout CN/AML-iPSCs revealed a decrease of mRNA expression levels of BAALC, HPGDS and CD109 . At the same time, knockout of RUNX1 in CN/AML-iPSCs using CRISPR/Cas9-editing revealed even higher decrease of mRNA levels of BAALC, NPR3 and CD109 . These data suggest that HPGDS and CD109 up-regulation is downstream of RUNX1 -mediated BAALC induction in AML.Taken together, we established a reliable in vitro model to study leukemogenesis in the pre-leukemic BMFS, using CN as an example. With the help of this model, we identified BAALC up-regulation as a key “leukemogenic” factor downstream of RUNX1 and CSF3R mutations. Based on these observations, we conclude that inhibition of BAALC in hematopoietic cells of CN patients may prevent leukemogenic transformation of hematopoiesis or eliminate AML blasts in CN-AML. DisclosuresNo relevant conflicts of interest to declare.