The novel coronavirus SARS-CoV-2 causes COVID-19, a highly pathogenic viral infection threatening millions. The majority of the individuals infected are asymptomatic or mildly symptomatic showing typical clinical signs of common cold. However, approximately 20% of the patients can progress to acute respiratory distress syndrome (ARDS), evolving to death in about 5% of cases. Recently, angiotensin-converting enzyme 2 (ACE2) has been shown to be a functional receptor for virus entry into host target cells. The upregulation of ACE2 in patients with comorbidities may represent a propensity for increased viral load and spreading of infection to extrapulmonary tissues. This systemic infection is associated with higher neutrophil to lymphocyte ratio in infected tissues and high levels of pro-inflammatory cytokines leading to an extensive microthrombus formation with multiorgan failure. Herein we investigated whether SARS-CoV-2 can stimulate extracellular neutrophils traps (NETs) in a process called NETosis. We demonstrated for the first time that SARS-CoV-2 in fact is able to activate NETosis in human neutrophils. Our findings indicated that this process is associated with increased levels of intracellular Reactive Oxygen Species (ROS) in neutrophils. The ROS-NET pathway plays a role in thrombosis formation and our study suggest the importance of this target for therapy approaches against disease.
Clearance of apoptotic exudate neutrophils (efferocytosis) induces either pro- or anti-inflammatory responses in mouse macrophages depending on host genetic background. In this study, we investigated whether neutrophil efferocytosis induces a stable macrophage phenotype that could be recalled by late restimulation with LPS. Bone marrow-derived macrophages previously stimulated by pro- but not anti-inflammatory neutrophil efferocytosis expressed a regulatory/M2b phenotype characterized by low IL-12 and high IL-10 production following restimulation, increased expression of LIGHT/TNF superfamily 14, Th2-biased T cell responses, and permissive replication of Leishmania major. Induction of regulatory/M2b macrophages required neutrophil elastase activity and was partially dependent on TLR4 signaling. These results suggested that macrophage differentiation to a regulatory phenotype plays a role in resolution of inflammation but could contribute to increased humoral Ab responses and parasite persistence in the infected host.
The objective of our study was to evaluate the therapeutic potential of bone marrow mesenchymal stromal cells (MSC) in a rat model of severe chronic liver injury. Fourteen female Wistar rats were fed exclusively an alcoholic liquid diet and received intraperitoneal injections of carbon tetrachloride every other day during 15 weeks. After this period, eight animals (MSC group) had 1 ؋ 10 7 cells injected into the portal vein while six animals (placebo group) received vehicle. Blood analysis was performed to evaluate alanine aminotransferase (ALT), aspartate aminotransferase (AST), and albumin before cell therapy and 1 and 2 months after cell or placebo infusion. Fibrosis was evaluated before and 1 month after cell or placebo injection by liver biopsies. Two months after cell delivery, animals were sacrificed and histological analysis of the livers was performed. Fibrosis was quantified by histomorphometry. Biopsies obtained before cell infusion showed intense collagen deposition and septa interconnecting regenerative nodules. One month after cell injection, this result was unaltered and differences in fibrosis quantification were not found between MSC and placebo groups. ALT and AST returned to normal values 2 weeks after cell or placebo infusion, without significant differences between experimental groups. Two months after cell or placebo injection, albumin had also returned to normal values and histological results were maintained, again without differences between MSC and placebo groups. Therefore, under our experimental conditions, MSC were unable to reduce fibrosis or improve liver function in a rat model of severe chronic liver injury.
SummaryThe effects of capsular polysaccharides, galactoxylomannan (GalXM) and glucuronoxylomannan (GXM), from acapsular (GXM negative) and encapsulate strains of Cryptococcus neoformans were investigated in RAW 264.7 and peritoneal macrophages. Here, we demonstrate that GalXM and GXM induced different cytokines profiles in RAW 264.7 macrophages. GalXM induced production of TNF-a, NO and iNOS expression, while GXM predominantly induced TGF-b secretion. Both GalXM and GXM induced early morphological changes identified as autophagy and late macrophages apoptosis mediated by Fas/FasL interaction, a previously unidentified mechanism of virulence. GalXM was more potent than GXM at induction of Fas/FasL expression and apoptosis on macrophages in vitro and in vivo. These findings uncover a mechanism by which capsular polysaccharides from C. neoformans might compromise host immune responses.
Receptors of the P2X7 type have been demonstrated in granulocytes, monocytes/macrophages, B and T lymphocytes, and have been involved in several cellular mechanisms including those related to inflammation and immunological response. This study attempted to investigate the role of these receptors on the inflammatory and fibrogenic response in the kidneys of unilateral ureteral obstruction (UUO), by using P2X7 knockout mice (-/-). C57Bl6 mice were submitted to left UUO and killed after 7 and 14 days. Histopathology using hematoxylin-eosin, periodic-acid Schiff and Sirius-red staining, immunohistochemistry for macrophages, myofibroblasts, transforming growth factor-beta (TGF-beta)1 and P2X7, and immunofluorescence for apoptotic cells (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick-end labeling) were performed. Protocols were as follows: (1) control; (2) sham; (3) control P2X7 (-/-); (4) sham P2X7 (-/-); (5) UUO wild type (WT); (6) UUO P2X7 (-/-). Myofibroblasts and Sirius-red staining were significantly lower in UUO P2X7 (-/-) mice at days 7 and 14, compared to UUO WT. Kidneys from UUO P2X7 (-/-) mice showed reduced number of inflammatory cells at day 14 but not at day 7, compared to UUO WT. TGF-beta1 was less in UUO P2X7 (-/-) mice at days 7 and 14 when compared to UUO WT. Macrophage infiltration and tubular apoptosis were lower in UUO P2X7 (-/-) at day 14 but not at day 7, compared to UUO WT. P2X7 was expressed only in tubular epithelial cells at day 7 of UUO WT mice. These findings constitute the first evidence that P2X7 receptors are implicated in macrophage infiltration, collagen deposition and apoptosis in response to ureteral obstruction in mice.
In adult animals, bone marrow is the major site of blood cell production, which is controlled by interactions between the local stroma and blood cell progenitors. The endosteal/subendosteal environment comprises bone-lining and adjacent reticular cells and sustains haemopoietic stem cell (HSC) self-renewal, proliferation and differentiation. We have questioned the specific role of each of these stroma cells in controlling HSC fate. We have isolated two distinct stroma-cell populations containing subendosteal reticulocytes (F-RET) and osteoblasts (F-OST) from periosteum-free fragments of murine femurs by a two-step collagenase-digestion procedure. Both populations produce similar extracellular matrix (collagen I, laminin, fibronectin, decorin), except for collagen IV, which is low in F-OST. They also express osteogenic markers: osteopontin, osteonectin, bone sialoprotein and alkaline phosphatase (ALP). The quantity and activity of ALP are however higher in F-OST. When co-cultured with bone marrow mononuclear cells or lineage-negative haemopoietic progenitors, F-OST stroma induces low proliferation and high maintenance of early haemopoietic progenitors, whereas F-RET stroma induces high short-term proliferation and differentiation. Analysis by reverse transcription/polymerase chain reaction has revealed higher levels of Jagged-1 expression by F-OST cells than by the F-RET population. Thus, two adjacent stroma cells (subendosteal and endosteal) play distinct roles in controlling the stem-cell capacity and fate of HSC and probably contribute distinctly to HSC niche formation.
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