The Impact of Integrin β2 on Granulocyte/Macrophage Progenitor Proliferation

Monocytes and macrophages: Origin, homing, differentiation, and functionality during inflammation

Monocytes and macrophages are essential components of innate immune system and have versatile roles in homeostasis and immunity. These phenotypically distinguishable mononuclear phagocytes play distinct roles in different stages, contributing to the pathophysiology in various forms making them a potentially attractive therapeutic target in inflammatory conditions. Several pieces of evidence have supported the role of different cell surface receptors expressed on these cells and their downstream signaling molecules in initiating and perpetuating the inflammatory response. In this review, we discuss the current understanding of the monocyte and macrophage biology in inflammation, highlighting the role of chemoattractants, inflammasomes, and integrins in the function of monocytes and macrophages during events of inflammation. This review also covers the recent therapeutic interventions targeting these mononuclear phagocytes at the cellular and molecular levels.

Revealing common differential mRNAs, signaling pathways, and immune cells in blood, glomeruli, and tubulointerstitium of lupus nephritis patients based on transcriptomic data

Lupus nephritis (LN) is a potentially fatal autoimmune disease. The purpose of this study was to find potential key molecular markers of LN to aid in the early diagnosis and management of the disease. Datasets GSE99967_blood, GSE32591_glomeruli, and GSE32591_tubulointerstitium were included in this study. Differentially expressed mRNAs (DEmRNAs) were identified between the normal control and LN groups using the limma package in R. Common DEmRNAs in the three datasets were taken. Subsequently, functional enrichment analysis, immune correlation analysis, receiver operating characteristic (ROC) curve analysis and real-time polymerase chain reaction (RT-PCR) verification were performed. In this study, 11 common DEmRNAs were obtained and all of them were up-regulated. In protein-protein interaction (PPI) networks, we found that MX dynamin like GTPase 1 (MX1) and radical S-adenosyl methionine domain containing 2 (RSAD2) had the highest interaction score (0.997). Functional enrichment analysis revealed that MX1 and RSAD2 were enriched in influenza A and hepatitis C signaling pathways. The area under the curve (AUC) values of interferon-induced protein 44 (IFI44) and MX1 in GSE32591_glomeruli and GSE32591_tubulointerstitium datasets are 1, which is worthy of further study on their diagnostic value and molecular mechanism. The xCell analysis showed abnormal distribution of granulocyte-macrophage progenitor (GMP) cells in blood, glomeruli, and tubulointerstitium. Pearson's correlation analysis found that GMP cells were significantly correlated with lactotransferrin (LTF) and cell cycle. Identification of common DEmRNAs and key pathways in the blood, glomeruli, and tubulointerstitium of patients with LN provides potential research directions for exploring the molecular mechanisms of the disease.

Exendin-4 attenuates atherosclerosis progression via controlling hematopoietic stem/progenitor cell proliferation

Beyond glycemic control, applications of glucagon-like peptide-1 receptor (GLP-1r) agonists (GLP-1 RAs) inhibit inflammation and plaque development in murine atherosclerotic models. However, whether they modulate hematopoietic stem/progenitor cells (HSPCs) to prohibit skewed myelopoiesis in hypercholesteremia remains unknown. In this study, GLP-1r expression in fluorescence-activated cell sorting (FACS)-sorted wild-type HSPCs was determined by capillary western blotting. Bone marrow cells (BMCs) of wild-type or GLP-1r-/- mice were transplanted into lethally irradiated low-density lipoprotein receptor deficient (LDLr-/-) recipients followed by high-fat diet (HFD) for chimerism analysis by FACS. In parallel, LDLr-/- mice were placed on HFD for 6 weeks and then treated with saline or Exendin-4 (Ex-4) for another 6 weeks. HSPC frequency and cell cycle were analyzed by FACS, and intracellular metabolite levels were assessed by targeted metabolomics. The results demonstrated that HSPCs expressed GLP-1r and transplantation of GLP-1r-/- BMCs resulted in skewed myelopoiesis in hypercholesterolemic LDLr-/- recipients. In vitro, Ex-4 treatment of FACS-purified HSPCs suppressed cell expansion and granulocyte production induced by LDL. In vivo, Ex-4 treatment inhibited plaque progression, suppressed HSPC proliferation, and modified glycolytic and lipid metabolism in HSPCs of hypercholesteremic LDLr-/- mice. In conclusion, Ex-4 could directly inhibit HSPC proliferation induced by hypercholesteremia.

The purine metabolite inosine monophosphate accelerates myelopoiesis and acute pancreatitis progression

Hyperglycemia-induced myelopoiesis and atherosclerotic progression occur in mice with type I diabetes. However, less is known about the effects of metabolites on myelopoesis in type 2 diabetes. Here, we use fluorescence-activated cell sorting to analyze the proliferation of granulocyte/monocyte progenitors (GMP) in db/db mice. Using targeted metabolomics, we identify an increase in inosine monophosphate (IMP) in GMP cells of 24-week-old mice. We show that IMP treatment stimulates cKit expression, ribosomal S6 activation, GMP proliferation, and Gr-1⁺ granulocyte production in vitro. IMP activates pAkt in non-GMP cells. In vivo, using an established murine acute pancreatitis (AP) model, administration of IMP-treated bone marrow cells enhances the severity of AP. This effect is abolished in the presence of a pAkt inhibitor. Targeted metabolomics show that plasma levels of guanosine monophosphate are significantly higher in diabetic patients with AP. These findings provid a potential therapeutic target for the control of vascular complications in diabetes.

Metabolomics analysis reveals that inosine monophosphate, a purine metabolite, promotes myelopoiesis and contributes to severe acute pancreatitis in db/db mice.

CD18 controls the development and activation of monocyte-to-macrophage axis during chronic schistosomiasis

Schistosomiasis is a neglected tropical disease caused by worms of the genus Schistosoma spp. The progression of disease results in intense tissue fibrosis and high mortality rate. After egg deposition by adult worms, the inflammatory response is characterized by the robust activation of type 2 immunity. Monocytes and macrophages play critical roles during schistosomiasis. Inflammatory Ly6C^high monocytes are recruited from the blood to the inflammatory foci and differentiate into alternatively activated macrophages (AAMs), which promote tissue repair. The common chain of β₂-integrins (CD18) regulates monocytopoiesis and mediates resistance to experimental schistosomiasis. There is still limited knowledge about mechanisms controlled by CD18 that impact monocyte development and effector cells such as macrophages during schistosomiasis. Here, we show that CD18^low mice chronically infected with S. mansoni display monocyte progenitors with reduced proliferative capacity, resulting in the accumulation of the progenitor cell denominated proliferating-monocyte (pMo). Consequently, inflammatory Ly6C^high and patrolling Ly6C^low monocytes are reduced in the bone marrow and blood. Mechanistically, low CD18 expression decreases Irf8 gene expression in pMo progenitor cells, whose encoded transcription factor regulates CSFR1 (CD115) expression on the cell surface. Furthermore, low CD18 expression affects the accumulation of inflammatory Ly6C^high CD11b⁺ monocytes in the liver while the adoptive transference of these cells to infected-CD18^low mice reduced the inflammatory infiltrate and fibrosis in the liver. Importantly, expression of Il4, Chil3l3 and Arg1 was downregulated, CD206⁺PD-L2⁺ AAMs were reduced and there were lower levels of IL-10 in the liver of CD18^low mice chronically infected with S. mansoni. Overall, these findings suggest that CD18 controls the IRF8-CD115 axis on pMo progenitor cells, affecting their proliferation and maturation of monocytes. At the same time, CD18 is crucial for the appropriate polarization and function of AAMs and tissue repair during chronic schistosomiasis.

M2 Macrophages Enhance the Cementoblastic Differentiation of Periodontal Ligament Stem Cells via the Akt and JNK Pathways

Although macrophage (Mφ) polarization has been demonstrated to play crucial roles in cellular osteogenesis across the cascade of events in periodontal regeneration, how polarized Mφ phenotypes influence the cementoblastic differentiation of periodontal ligament stem cells (PDLSCs) remains unknown. In the present study, human monocyte leukemic cells (THP-1) were induced into M0, M1, and M2 subsets, and the influences of these polarized Mφs on the cementoblastic differentiation of PDLSCs were assessed in both conditioned medium-based and Transwell-based coculture systems. Furthermore, the potential pathways and cyto-/chemokines involved in Mφ-mediated cementoblastic differentiation were screened and identified. In both systems, M2 subsets increased cementoblastic differentiation-related gene/protein expression levels in cocultured PDLSCs, induced more PDLSCs to differentiate into polygonal and square cells, and enhanced alkaline phosphatase activity in PDLSCs. Furthermore, Akt and c-Jun N-terminal Kinase (JNK) signaling was identified as a potential pathway involved in M2 Mφ-enhanced PDLSC cementoblastic differentiation, and cyto-/chemokines (interleukin (IL)-10 and vascular endothelial growth factor [VEGF]) secreted by M2 Mφs were found to be key players that promoted cell cementoblastic differentiation by activating Akt signaling. Our data indicate for the first time that Mφs are key modulators during PDLSC cementoblastic differentiation and are hence very important for the regeneration of multiple periodontal tissues, including the cementum. Although the Akt and JNK pathways are involved in M2 Mφ-enhanced cementoblastic differentiation, only the Akt pathway can be activated via a cyto-/chemokine-associated mechanism, suggesting that players other than cyto-/chemokines also participate in the M2-mediated cementoblastic differentiation of PDLSCs. Stem Cells 2019;37:1567-1580.