MCC950 improves lipopolysaccharide­induced systemic inflammation in mice by relieving pyroptosis in blood neutrophils.

Sepsis is an infection-induced systemic inflammatory response syndrome accompanied by multiple organ injury and failure. MCC950, an inhibitor of NLR family pyrin domain containing 3 (NLRP3), can alleviate the inflammatory response and relieve inflammation-induced injury. The aim of the present study was to explore the efficacy of MCC950 in lipopolysaccharide (LPS)-induced inflammation and elucidate the underlying mechanisms. Based on a prior study, C57BL/6 mice were divided into three groups: Control, LPS, and LPS + MCC950. The mice were administered 10 mg/kg LPS to induce sepsis and 10 mg/kg MCC950 to treat sepsis 6 h before and after LPS injection. Histopathological imaging revealed organ morphology and damage during inflammation, and MCC950 alleviated organ damage and dysfunction. MCC950 prevented LPS-induced inflammatory responses by reducing inflammatory cytokine levels in the blood. To explore the mechanism by which MCC950 functions, blood neutrophils were isolated and a series of tests were performed. As revealed by measuring reactive oxygen species levels and Annexin V/PI staining of neutrophils, MCC950 reduced oxidative stress and programmed death induced by LPS. Western blotting was used to assess the protein levels of pyroptosis-related markers, including GSDMD, NLRP3, and caspase-1, in neutrophils to further explore the form of death. MCC950 reduced LPS-induced pyroptosis in neutrophils. The results of the survival analysis revealed that MCC950 increased the survival rates of mice within 72 h of LPS injection. MCC950 may be an effective treatment for sepsis that targets neutrophil pyroptosis.

LncRNA CDKN2B-AS1 interacts with LIN28B to exacerbate sepsis-induced acute lung injury by inducing HIF-1α/NLRP3-mediated pyroptosis.

Sepsis-associated acute lung injury (ALI) is a life-threatening condition in intensive care units with high mortality. LncRNAs have been confirmed to participate in the underlying pathogenesis of septic ALI. This study investigated the biological functions of lncRNA CDKN2B-AS1 in septic ALI and its potential mechanism.BEAS-2B cells were challenged with lipopolysaccharide (LPS) and mice were subjected to caecal ligation and puncture (CLP) to induce septic ALI in vitro and in vivo. The expression levels of CDKN2B-AS1, LIN28B, HIF-1α, and pyroptosis-related molecules were assessed by qRT-PCR or Western blotting. The production of IL-1ß and IL-18 was detected by ELISA. BEAS-2B cell pyroptosis was examined by flow cytometry. The interaction between LIN28B and CDKN2B-AS1/HIF-1α was validated by RIP and RNA pull-down assays. Colocalization of CDKN2B-AS1 and LIN28B was observed by FISH. ALI was determined by HE staining, the lung wet-to-dry (W/D) weight ratio, inflammatory cell numbers, and total protein concentration in bronchoalveolar lavage fluid (BALF). Caspase-1 expression in the lung tissues was examined by immunohistochemical staining.CDKN2B-AS1 was upregulated in BEAS-2B cells after LPS stimulation. CDKN2B-AS1 knockdown inhibited pyroptosis in LPS-exposed BEAS-2B cells in vitro and the lung tissues of septic mice in vivo. Mechanistically, CDKN2B-AS1 interacted with LIN28B to enhance HIF-1α stability. Rescue experiments showed that HIF-1α overexpression counteracted the inhibitory effect of sh-CDKN2B-AS1 on LPS-induced pyroptosis. CDKN2B-AS1 bound to LIN28B to trigger NLRP3-mediated pyroptosis by stabilizing HIF-1α, which promoted sepsis-induced ALI. CDKN2B-AS1 might be a novel therapeutic target for this disease.

An analytical method for the determination of glyphosate and aminomethylphosphoric acid using an anionic polar pesticide column and the application in urine and serum from glyphosate poisoning patients.

An analytical method for the determination of glyphosate (GLY) and aminomethylphosphoric acid (AMPA) in biological fluid samples (serum and urine) from poisoning patients using liquid chromatography-tandem mass spectrometry (LC-MS/MS) is established. After the sample pretreatment, including protein precipitation and a modified liquid-liquid extraction method, the chromatographic separation was conducted on a trifunctional modified hydrophilic column. The mobile phases in the gradient program were 2.5% formic acid aqueous solution and acetonitrile. The multiple reaction monitoring (MRM) models and the isotope-labeled internal standards were used in the acquisition process. Good linearities and satisfying recovery rates were obtained in two sample matrices with good RSDs. The detection limits of GLY and AMPA were <2 µg L-1, which were close to those obtained in our previous research. The established method was applied to biological samples from five patients with glyphosate intoxication. The analysis of the trend for the concentration of GLY and AMPA in two biological samples was investigated, and the difference in the downward trend of AMPA in urine was found in patients with a relatively higher concentration of GLY in serum.

Mature B cells and mesenchymal stem cells control emergency myelopoiesis.

Systemic inflammation halts lymphopoiesis and prioritizes myeloid cell production. How blood cell production switches from homeostasis to emergency myelopoiesis is incompletely understood. Here, we show that lymphotoxin-ß receptor (LTßR) signaling in combination with TNF and IL-1 receptor signaling in bone marrow mesenchymal stem cells (MSCs) down-regulates Il7 expression to shut down lymphopoiesis during systemic inflammation. LTßR signaling in MSCs also promoted CCL2 production during systemic inflammation. Pharmacological or genetic blocking of LTßR signaling in MSCs partially enabled lymphopoiesis and reduced monocyte numbers in the spleen during systemic inflammation, which correlated with reduced survival during systemic bacterial and viral infections. Interestingly, lymphotoxin-α1ß2 delivered by B-lineage cells, and specifically by mature B cells, contributed to promote Il7 down-regulation and reduce MSC lymphopoietic activity. Our studies revealed an unexpected role of LTßR signaling in MSCs and identified recirculating mature B cells as an important regulator of emergency myelopoiesis.

Competition between hematopoietic stem and progenitor cells controls hematopoietic stem cell compartment size.

Cellular competition for limiting hematopoietic factors is a physiologically regulated but poorly understood process. Here, we studied this phenomenon by hampering hematopoietic progenitor access to Leptin receptor+ mesenchymal stem/progenitor cells (MSPCs) and endothelial cells (ECs). We show that HSC numbers increase by 2-fold when multipotent and lineage-restricted progenitors fail to respond to CXCL12 produced by MSPCs and ECs. HSCs are qualitatively normal, and HSC expansion only occurs when early hematopoietic progenitors but not differentiated hematopoietic cells lack CXCR4. Furthermore, the MSPC and EC transcriptomic heterogeneity is stable, suggesting that it is impervious to major changes in hematopoietic progenitor interactions. Instead, HSC expansion correlates with increased availability of membrane-bound stem cell factor (mSCF) on MSPCs and ECs presumably due to reduced consumption by cKit-expressing hematopoietic progenitors. These studies suggest that an intricate homeostatic balance between HSCs and proximal hematopoietic progenitors is regulated by cell competition for limited amounts of mSCF.

Hematopoietic Stem Cell Niches and Signals Controlling Immune Cell Development and Maintenance of Immunological Memory.

Studies over the last couple of decades have shown that hematopoietic stem cells (HSCs) are critically dependent on cytokines such as Stem Cell Factor and other signals provided by bone marrow niches comprising of mesenchymal stem and progenitor cells (MSPCs) and endothelial cells (ECs). Because of their critical roles in HSC maintenance the niches formed by MSPCs and ECs are commonly referred to as HSC niches. For the most part, the signals required for HSC maintenance act in a short-range manner, which imposes the necessity for directional and positional cues in order for HSCs to localize and be retained properly in stem cell niches. The chemokine CXCL12 and its Gαi protein coupled receptor CXCR4, besides promoting HSC quiescence directly, also play instrumental roles in enabling HSCs to access bone marrow stem cell niches. Recent studies have revealed, however, that HSC niches also provide a constellation of hematopoietic cytokines that are critical for the production of most, if not all, blood cell types. Some hematopoietic cytokines, namely IL-7 and IL-15 produced by HSC niches, are not only required for lymphopoiesis but are also essential for memory T cell maintenance. Consequently, hematopoietic progenitors and differentiated immune cells, such as memory T cell subsets, also depend on the CXCL12/CXCR4 axis for migration into bone marrow and interactions with MSPCs and ECs. Similarly, subsets of antibody-secreting plasma cells also reside in close association with CXCL12-producing MSPCs in the bone marrow and require the CXCR4/CXCL12 axis for survival and long-term maintenance. Collectively, these studies demonstrate a broad range of key physiological roles, spanning blood cell production and maintenance of immunological memory, that are orchestrated by stem cell niches through a common and simple mechanism: CXCL12/CXCR4-mediated cell recruitment followed by receipt of a maintenance and/or instructive signal. A fundamental flaw of this type of cellular organization is revealed by myeloid and lymphoid leukemias, which target stem cell niches and induce profound transcriptomic changes that result in reduced hematopoietic activity and altered mesenchymal cell differentiation.

Should I Stay or Should I Flow: HSCs Are on the Move!

Stem cell biologists have been yearning to visualize hematopoietic stem cells (HSCs) in live animals since Kiel et al. (2005) first visualized them in bone cavities. With two recent papers from Christodoulou et al. (2020) and Upadhaya et al. (2020), we can all now see how HSCs behave in their niches!

Cell circuits between B cell progenitors and IL-7+ mesenchymal progenitor cells control B cell development.

B cell progenitors require paracrine signals such as interleukin-7 (IL-7) provided by bone marrow stromal cells for proliferation and survival. Yet, how B cells regulate access to these signals in vivo remains unclear. Here we show that proB and IL-7+ cells form a cell circuit wired by IL-7R signaling, which controls CXCR4 and focal adhesion kinase (FAK) expression and restricts proB cell movement due to increased adhesion to IL-7+CXCL12Hi cells. PreBCR signaling breaks this circuit by switching the preB cell behavior into a fast-moving and lower-adhesion state via increased CXCR4 and reduced FAK/α4ß1 expression. This behavioral change reduces preB cell exposure to IL-7, thereby attenuating IL-7R signaling in vivo. Remarkably, IL-7 production is downregulated by signals provided by preB cells with unrepaired double-stranded DNA breaks and by preB acute lymphoblastic leukemic cells. Combined, these studies revealed that distinct cell circuits control the quality and homeostasis of B cell progenitors.