The transcription factors that regulate differentiation into the monocyte subset in bone marrow have not yet been identified. Here we found that the orphan nuclear receptor NR4A1 controlled the ...differentiation of Ly6C- monocytes. Ly6C- monocytes, which function in a surveillance role in circulation, were absent from Nr4a1-/- mice. Normal numbers of myeloid progenitor cells were present in Nr4a1-/- mice, which indicated that the defect occurred during later stages of monocyte development. The defect was cell intrinsic, as wild-type mice that received bone marrow from Nr4a1-/- mice developed fewer patrolling monocytes than did recipients of wild-type bone marrow. The Ly6C- monocytes remaining in the bone marrow of Nr4a1-/- mice were arrested in S phase of the cell cycle and underwent apoptosis. Thus, NR4A1 functions as a master regulator of the differentiation and survival of 'patrolling' Ly6C- monocytes.
NR4A1 (Nur77) is a nuclear receptor that is expressed in macrophages and within atherosclerotic lesions, yet its function in atherosclerosis is unknown.
Nur77 regulates the development of monocytes, ...particularly patrolling Ly6C(-) monocytes that may be involved in resolution of inflammation. We sought to determine how absence of nuclear receptor subfamily 4, group A, member 1 (NR4A1) in hematopoietic cells affected atherosclerosis development.
Nur77(-/-) chimeric mice on a Ldlr(-/-) background showed a 3-fold increase in atherosclerosis development when fed a Western diet for 20 weeks, despite having a drastic reduction in Ly6C(-) patrolling monocytes. In a second model, mice deficient in both Nur77 and ApoE (ApoE(-/-)Nur77(-/-)) also showed increased atherosclerosis after 11 weeks of Western diet. Atherosclerosis was associated with a significant change in macrophage polarization toward a proinflammatory phenotype, with high expression of tumor necrosis factor-α and nitric oxide and low expression of Arginase-I. Moreover, we found increased expression of toll-like receptor 4 mRNA and protein in Nur77(-/-) macrophages as well as increased phosphorylation of the p65 subunit of NFκB. Inhibition of NFκB activity blocked excess activation of Nur77(-/-) macrophages.
We conclude that the absence of Nur77 in monocytes and macrophages results in enhanced toll-like receptor signaling and polarization of macrophages toward a proinflammatory M1 phenotype. Despite having fewer monocytes, Nur77(-/-) mice developed significant atherosclerosis when fed a Western diet. These studies indicate that Nur77 is a novel target for modulating the inflammatory phenotype of monocytes and macrophages and may be important for regulation of atherogenesis.
The recovery of whale populations from centuries of exploitation will have important management and ecological implications due to greater exposure to anthropogenic activities and increasing prey ...consumption. Here, a Bayesian population model integrates catch data, estimates of abundance, and information on genetics and biology to assess the recovery of western South Atlantic (WSA) humpback whales (
). Modelling scenarios evaluated the sensitivity of model outputs resulting from the use of different data, different model assumptions and uncertainty in catch allocation and in accounting for whales killed but not landed. A long period of exploitation drove WSA humpback whales to the brink of extinction. They declined from nearly 27 000 (95% PI = 22 800-33 000) individuals in 1830 to only 450 (95% PI = 200-1400) whales in the mid-1950s. Protection led to a strong recovery and the current population is estimated to be at 93% (95% PI = 73-100%) of its pre-exploitation size. The recovery of WSA humpback whales may result in large removals of their primary prey, the Antarctic krill (
), and has the potential to modify the community structure in their feeding grounds. Continued monitoring is needed to understand how these whales will respond to modern threats and to climate-driven changes to their habitats.
Myth
Corticosteroid injection for the treatment of pain is known to decrease the efficacy of the adenovirus vector-based vaccines for COVID-19.
Fact
There is currently no direct evidence to suggest ...that a corticosteroid injection before or after the administration of an adenovirus vector-based COVID-19 vaccine decreases the efficacy of the vaccine. However, based on the known timeline of hypothalamic-pituitary-adrenal axis suppression following epidural and intraarticular corticosteroid injections, and the timeline of the reported peak efficacy of the Janssen and AstraZeneca vaccines, physicians should consider timing an elective corticosteroid injection such that it is administered no less than 2 weeks prior to and no less than 2 weeks following a COVID-19 adenovirus vector-based vaccine dose, whenever possible. We emphasize the importance of risk/benefit analysis and shared decision making in determining the timing of corticosteroid injections for pain indications in relation to receipt of a COVID-19 vaccine given that patient-specific factors will vary.
Abstract
Myth
Corticosteroid injection for the treatment of pain and inflammation is known to decrease the efficacy of the messenger ribonucleic acid (mRNA) vaccines for coronavirus disease 2019 ...(COVID-19).
Fact
There is currently no direct evidence to suggest that a corticosteroid injection before or after the administration of an mRNA COVID-19 vaccine decreases the efficacy of the vaccine.
However, based on the known timeline of hypothalamic-pituitary-adrenal (HPA) axis suppression following epidural and intraarticular corticosteroid injections, and the timeline of the reported peak efficacy of the Pfizer-BioNTech and Moderna vaccines, physicians should consider timing an elective corticosteroid injection such that it is administered no less than 2 weeks prior to a COVID-19 mRNA vaccine dose and no less than 1 week following a COVID-19 mRNA vaccine dose, whenever possible.
Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are implicated in the progression and outcome of a variety of pathological states, from cancer to infection. Our previous work has ...identified three antimicrobial peptides differentially expressed by PMN-MDSCs compared to conventional neutrophils isolated from dogs, mice, and human patients with cancer. We therefore hypothesized that PMN-MDSCs in dogs with cancer possess antimicrobial activity. In the current work, we observed that exposure of PMN-MDSCs to Gram-negative bacteria (
) increased the expression of reactive oxygen species by the PMN-MDSCs, indicating that they are capable of initiating an anti-microbial response. Electron microscopy revealed that the PMN-MDSCs phagocytosed Gram-negative and Gram-positive (
) bacterial species. Lysis of bacteria within some of the PMN-MDSCs suggested bactericidal activity, which was confirmed by the recovery of significantly lower numbers of bacteria of both species following exposure to PMN-MDSCs isolated from tumor-bearing dogs. Our data therefore indicate that PMN-MDSCs isolated from dogs with cancer, in common with PMNs, have phagocytic and bactericidal activity. This nexus of immunosuppressive and antimicrobial activity reveals a hitherto unrecognized function of MDSCs.
Hematopoiesis is maintained throughout life by self-renewing hematopoietic stem cells (HSCs) that differentiate to produce both myeloid and lymphoid cells. The NR4A family of orphan nuclear ...receptors, which regulates cell fate in many tissues, appears to play a key role in HSC proliferation and differentiation. Using a NR4A1(GFP) BAC transgenic reporter mouse we have investigated NR4A1 expression and its regulation in early hematopoiesis. We show that NR4A1 is most highly expressed in a subset of Lin(-) Sca-1(+) c-Kit(+) CD48(-) CD150(+) long-term (LT) HSCs, and its expression is tightly associated with HSC quiescence. We also show that NR4A1 expression in HSCs is induced by PGE2, a known enhancer of stem cell engraftment potential. Finally, we find that both NR4A1(GFP+) and NR4A1(GFP-) HSCs successfully engraft primary and secondary irradiated hosts; however, NR4A1(GFP+) HSCs are distinctly myeloid-biased. These results show that NR4A1 expression identifies a highly quiescent and distinct population of myeloid-biased LT-HSCs.
•Suppressor cells were assessed for the first time in dogs with myasthenia gravis•Numerical alteration was not observed in myeloid-derived suppressor cells•Numerical alteration was not observed in ...regulatory T cells•No correlation was found between suppressor cell frequency and clinical course
Myasthenia gravis (MG) is a T cell-dependent, B cell-mediated autoimmune disease. Little is known about its cellular pathogenesis in dogs. This study provides the first preliminary assessment of the frequency of myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) in the peripheral blood of dogs with seropositive generalized MG. No alteration in frequency of either MDSCs or Tregs in dogs with MG was observed when compared to those in either seronegative dogs with diagnoses other than MG, or healthy dogs. A longitudinal study in three dogs with MG revealed no correlation between the relative numbers of either population and the clinical course of disease. Neither the frequency of MDSCs nor of Tregs showed a correlation with anti-AChR antibody titer in dogs with MG. These findings suggest that aberrations in the frequency of either immunosuppressive population do not occur in MG, but they need to be validated in large-scale prospective studies.
Cell fate decisions in metazoans are regulated by Notch signals. During lymphoid development, Notch influences a series of cell fate decisions involving multipotent progenitors. This review focuses ...on current views and lingering uncertainties about Notch function in lymphoid cells.
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