A distinct class of hematopoietic stem cells develop from the human yellow bone marrow.

Aging and metabolic diseases are accompanied by systemic inflammation, but the mechanisms that induce this state are not known. We developed a human bone-marrow organoid system to explore mechanisms underlying metabolic-disease associated systemic inflammation. We find that a distinct type of hematopoietic stem cell (HSC) develops in the adipose-rich, yellow bone marrow, which is known to gradually replace the hematopoietic red marrow as we age and during metabolic disease. Unlike HSCs derived from the red bone marrow, HSCs derived from the yellow bone marrow have higher proliferation rates, increase myeloid differentiation, skew towards pro-inflammatory M1 macrophage differentiation, and express a distinct transcriptomic profile associated with responsiveness to wounding. Yellow marrow-derived HSCs express higher levels of the leptin receptor, which we find to be further increased in patients with type 2 diabetes. Our work demonstrates that the human long bone yellow marrow is a niche for a distinct class of HSCs which could underlie hematopoietic dysfunction during aging and metabolic disease processes suggesting a shared inflammaging mechanism.

New scaffolds for type II JAK2 inhibitors overcome the acquired G993A resistance mutation.

Recurrent JAK2 alterations are observed in myeloproliferative neoplasms, B-cell acute lymphoblastic leukemia, and other hematologic malignancies. Currently available type I JAK2 inhibitors have limited activity in these diseases. Preclinical data support the improved efficacy of type II JAK2 inhibitors, which lock the kinase in the inactive conformation. By screening small molecule libraries, we identified a lead compound with JAK2 selectivity. We highlight analogs with on-target biochemical and cellular activity and demonstrate in vivo activity using a mouse model of polycythemia vera. We present a co-crystal structure that confirms the type II binding mode of our compounds with the "DFG-out" conformation of the JAK2 activation loop. Finally, we identify a JAK2 G993A mutation that confers resistance to the type II JAK2 inhibitor CHZ868 but not to our analogs. These data provide a template for identifying novel type II kinase inhibitors and inform further development of agents targeting JAK2 that overcome resistance.

Lipase regulation of cellular fatty acid homeostasis as a Parkinson's disease therapeutic strategy.

Synucleinopathy (Parkinson's disease (PD); Lewy body dementia) disease-modifying treatments represent a huge unmet medical need. Although the PD-causing protein α-synuclein (αS) interacts with lipids and fatty acids (FA) physiologically and pathologically, targeting FA homeostasis for therapeutics is in its infancy. We identified the PD-relevant target stearoyl-coA desaturase: inhibiting monounsaturated FA synthesis reversed PD phenotypes. However, lipid degradation also generates FA pools. Here, we identify the rate-limiting lipase enzyme, LIPE, as a candidate target. Decreasing LIPE in human neural cells reduced αS inclusions. Patient αS triplication vs. corrected neurons had increased pSer129 and insoluble αS and decreased αS tetramer:monomer ratios. LIPE inhibition rescued all these and the abnormal unfolded protein response. LIPE inhibitors decreased pSer129 and restored tetramer:monomer equilibrium in αS E46K-expressing human neurons. LIPE reduction in vivo alleviated αS-induced dopaminergic neurodegeneration in Caenorhabditis elegans. Co-regulating FA synthesis and degradation proved additive in rescuing PD phenotypes, signifying co-targeting as a therapeutic strategy.

Geometrical variations of two manganese(II) complexes with closely related quinoline-based tripodal ligands.

Structural analyses of the compounds di-µ-acetato-κ4 O:O'-bis-{[2-meth-oxy-N,N-bis-(quinolin-2-ylmeth-yl)ethanamine-κ4 N,N',N'',O]manganese(II)} bis-(tetra-phen-yl-borate) di-chloro-methane 1.45-solvate, [Mn2(C23O2)2(C23H23N3O)2](C24H20B)·1.45CH2Cl2 or [Mn(DQMEA)(µ-OAc)2Mn(DQMEA)](BPh4)2·1.45CH2Cl2 or [1](BPh4)2·1.45CH2Cl2, and (acetato-κO)[2-hy-droxy-N,N-bis(quinolin-2-ylmeth-yl)ethanamine-κ4 N,N',N'',O](methanol-κO)manganese(II) tetra-phenyl-borate methanol monosolvate, [Mn(CH3COO)(C22H21N3O)(CH3OH)](C24H20B)·CH3OH or [Mn(DQEA)(OAc)(CH3OH)]BPh4·CH3OH or [2]BPh4·CH3OH, by single-crystal X-ray diffraction reveal distinct differences in the geometry of coordination of the tripodal DQEA and DQMEA ligands to MnII ions. In the asymmetric unit, compound [1](BPh4)2·(CH2Cl2)1.45 crystallizes as a dimer in which each manganese(II) center is coordinated by the central amine nitro-gen, the nitro-gen atom of each quinoline group, and the meth-oxy-oxygen of the tetra-dentate DQMEA ligand, and two bridging-acetate oxygen atoms. The symmetric MnII centers have a distorted, octa-hedral geometry in which the quinoline nitro-gen atoms are trans to each other resulting in co-planarity of the quinoline rings. For each MnII center, a coordinated acetate oxygen participates in C-H⋯O hydrogen-bonding inter-actions with the two quinolyl moieties, further stabilizing the trans structure. Within the crystal, weak π-π stacking inter-actions and inter-molecular cation-anion inter-actions stabilize the crystal packing. In the asymmetric unit, compound [2]BPh4·CH3OH crystallizes as a monomer in which the manganese(II) ion is coordinated to the central nitro-gen, the nitro-gen atom of each quinoline group, and the alcohol oxygen of the tetra-dentate DQEA ligand, an oxygen atom of OAc, and the oxygen atom of a methanol ligand. The geometry of the MnII center in [2]BPh4·CH3OH is also a distorted octa-hedron, but the quinoline nitro-gen atoms are cis to each other in this structure. Hydrogen bonding between the acetate oxygen atoms and hydroxyl (O-H⋯O) and quinolyl (C-H⋯O and N-H⋯O) moieties of the DQEA ligand stabilize the complex in this cis configuration. Within the crystal, dimerization of complexes occurs by the formation of a pair of inter-molecular O3-H3⋯O2 hydrogen bonds between the coordinated hydroxyl oxygen of the DQEA ligand of one complex and an acetate oxygen of another. Additional hydrogen-bonding and inter-molecular cation-anion inter-actions contribute to the crystal packing.

A Stearoyl-Coenzyme A Desaturase Inhibitor Prevents Multiple Parkinson Disease Phenotypes in α-Synuclein Mice.

OBJECTIVE: Parkinson disease (PD) has useful symptomatic treatments that do not slow the neurodegenerative process, and no significant disease-modifying treatments are approved. A key therapeutic target in PD is α-synuclein (αS), which is both genetically implicated and accumulates in Lewy bodies rich in vesicles and other lipid membranes. Reestablishing αS homeostasis is a central goal in PD. Based on previous lipidomic analyses, we conducted a mouse trial of a stearoyl-coenzyme A desaturase (SCD) inhibitor ("5b") that prevented αS-positive vesicular inclusions and cytotoxicity in cultured human neurons. METHODS: Oral dosing and brain activity of 5b were established in nontransgenic mice. 5b in drinking water was given to mice expressing wild-type human αS (WT) or an amplified familial PD αS mutation (E35K + E46K + E61K ["3K"]) beginning near the onset of nigral and cortical neurodegeneration and the robust PD-like motor syndrome in 3K. Motor phenotypes, brain cytopathology, and SCD-related lipid changes were quantified in 5b- versus placebo-treated mice. Outcomes were compared to effects of crossing 3K to SCD1-/- mice. RESULTS: 5b treatment reduced αS hyperphosphorylation in E46K-expressing human neurons, in 3K neural cultures, and in both WT and 3K αS mice. 5b prevented subtle gait deficits in WT αS mice and the PD-like resting tremor and progressive motor decline of 3K αS mice. 5b also increased αS tetramers and reduced proteinase K-resistant lipid-rich aggregates. Similar benefits accrued from genetically deleting 1 SCD allele, providing target validation. INTERPRETATION: Prolonged reduction of brain SCD activity prevented PD-like neuropathology in multiple PD models. Thus, an orally available SCD inhibitor potently ameliorates PD phenotypes, positioning this approach to treat human α-synucleinopathies. ANN NEUROL 2021;89:74-90.

P2Y6 signaling in alveolar macrophages prevents leukotriene-dependent type 2 allergic lung inflammation.

Antagonists of the type 1 cysteinyl leukotriene receptor (CysLT1R) are widely used to treat asthma and allergic rhinitis, with variable response rates. Alveolar macrophages express UDP-specific P2Y6 receptors that can be blocked by off-target effects of CysLT1R antagonists. Sensitizing intranasal doses of an extract from the house dust mite Dermatophagoides farinae (Df) sharply increased the levels of UDP detected in bronchoalveolar lavage fluid of mice. Conditional deletion of P2Y6 receptors before sensitization exacerbated eosinophilic lung inflammation and type 2 cytokine production in response to subsequent Df challenge. P2Y6 receptor signaling was necessary for dectin-2-dependent production of protective IL-12p40 and Th1 chemokines by alveolar macrophages, leading to activation of NK cells to generate IFN-γ. Administration of CysLT1R antagonists during sensitization blocked UDP-elicited potentiation of IL-12p40 production by macrophages in vitro, suppressed the Df-induced production of IL-12p40 and IFN-γ in vivo, and suppressed type 2 inflammation only in P2Y6-deficient mice. Thus, P2Y6 receptor signaling drives an innate macrophage/IL-12/NK cell/IFN-γ axis that prevents inappropriate allergic type 2 immune responses on respiratory allergen exposure and counteracts the Th2 priming effect of CysLT1R signaling at sensitization. Targeting P2Y6 signaling might prove to be a potential additional treatment strategy for allergy.

COX-1 mediates IL-33-induced extracellular signal-regulated kinase activation in mast cells: Implications for aspirin sensitivity.

BACKGROUND: Classical FcεRI-induced mast cell (MC) activation causes synthesis of arachidonic acid (AA)-derived eicosanoids (leukotriene [LT] C4, prostaglandin [PG] D2, and thromboxane A2), which mediate vascular leak, bronchoconstriction, and effector cell chemotaxis. Little is known about the significance and regulation of eicosanoid generation in response to nonclassical MC activation mechanisms. OBJECTIVES: We sought to determine the regulation and significance of MC-derived eicosanoids synthesized in response to IL-33, a cytokine critical to innate type 2 immunity. METHODS: We used an ex vivo model of mouse bone marrow-derived mast cells and an IL-33-dependent in vivo model of aspirin-exacerbated respiratory disease (AERD). RESULTS: IL-33 potently liberates AA and elicits LTC4, PGD2, and thromboxane A2 production by bone marrow-derived mast cells. Unexpectedly, the constitutive function of COX-1 is required for IL-33 to activate group IVa cytosolic phospholipase A2 with consequent AA release for synthesis of all eicosanoids, including CysLTs. In contrast, COX-1 was dispensable for FcεRI-driven CysLT production. Inhibition of COX-1 prevented IL-33-induced phosphorylation of extracellular signal-related kinase, an upstream effector of cytosolic phospholipase A2, which was restored by exogenous PGH2, implying that the effects of COX-1 required its catalytic function. Administration of a COX-1-selective antagonist to mice completely prevented the generation of both PGD2 and LTC4 in a model of AERD in which MC activation is IL-33 driven. CONCLUSIONS: MC-intrinsic COX-1 amplifies IL-33-induced activation in the setting of innate type 2 immunity and might help explain the phenomenon of therapeutic desensitization to aspirin by nonselective COX inhibitors in patients with AERD.

Type 2 Cysteinyl Leukotriene Receptors Drive IL-33-Dependent Type 2 Immunopathology and Aspirin Sensitivity.

Cysteinyl leukotrienes (cysLTs) facilitate mucosal type 2 immunopathology by incompletely understood mechanisms. Aspirin-exacerbated respiratory disease, a severe asthma subtype, is characterized by exaggerated eosinophilic respiratory inflammation and reactions to aspirin, each involving the marked overproduction of cysLTs. Here we demonstrate that the type 2 cysLT receptor (CysLT2R), which is not targeted by available drugs, is required in two different models to amplify eosinophilic airway inflammation via induced expression of IL-33 by lung epithelial cells. Endogenously generated cysLTs induced eosinophilia and expanded group 2 innate lymphoid cells (ILC2s) in aspirin-exacerbated respiratory disease-like Ptges-/- mice. These responses were mitigated by deletions of either Cysltr2 or leukotriene C4 synthase (Ltc4s). Administrations of either LTC4 (the parent cysLT) or the selective CysLT2R agonist N-methyl LTC4 to allergen sensitized wild-type mice markedly boosted ILC2 expansion and IL-5/IL-13 generation in a CysLT2R-dependent manner. Expansion of ILC2s and IL-5/IL-13 generation reflected CysLT2R-dependent production of IL-33 by alveolar type 2 cells, which engaged in a bilateral feed-forward loop with ILC2s. Deletion of Cysltr1 blunted LTC4-induced ILC2 expansion and eosinophilia but did not alter IL-33 induction. Pharmacological blockade of CysLT2R prior to inhalation challenge of Ptges-/- mice with aspirin blocked IL-33-dependent mast cell activation, mediator release, and changes in lung function. Thus, CysLT2R signaling, IL-33-dependent ILC2 expansion, and IL-33-driven mast cell activation are necessary for induction of type 2 immunopathology and aspirin sensitivity. CysLT2R-targeted drugs may interrupt these processes.