Amyloid precursor protein (APP) is a member of the APP family of proteins, and different enzymatic processing leads to the production of several derivatives that are shown to have distinct biological ...functions. APP is involved in the pathology of Alzheimer’s disease (AD), the most common neurodegenerative disorder causing dementia. Furthermore, it is believed that individuals with Down syndrome (DS) have increased APP expression, due to an extra copy of chromosome 21 (Hsa21), that contains the gene for APP. Nevertheless, the physiological function of APP remains unclear. It is known that APP plays an important role in neural growth and maturation during brain development, possibly by influencing proliferation, cell fate specification and neurogenesis of neural stem cells (NSCs). Proteolytic cleavage of APP occurs mainly via two mutually exclusive pathways, the non-amyloidogenic pathway or the amyloidogenic pathway. Other alternative pathways (η-secretase, δ-secretase and meprin pathways) have also been described for the physiological processing of APP. The different metabolites generated from these pathways, including soluble APPα (sAPPα), soluble APPβ (sAPPβ), β-amyloid (Aβ) peptides and the APP intracellular domain (AICD), have different functions determined by their structural differences, equilibrium and concentration with respect to other fragments derived from APP. This review discusses recent observations regarding possible functions of APP and its proteolytic derivatives in the biology and phenotypic specification of NSCs. This can be important for a better understanding of the pathogenesis and the development of future therapeutic applications for AD and/or DS, diseases in which alterations in neurogenesis have been described.
Recent studies have demonstrated in vivo synergistic immunosuppressive and anti‐inflammatory capacity of dexamethasone (Dx) and naproxen (NAP) in collagen‐induced arthritis (CIA) rats. However, the ...molecular basis of this synergistic effect is barely understood. The low solubility of these drugs and their adverse effects hamper their efficacy on the treatment of inflammatory processes making nanoparticulated systems promising candidates to overcome these drawbacks. The aim of this work is the preparation of polymeric nanoparticles (NPs) that combine NAP and Dx in different concentrations, and the evaluation of the expression of key genes related to autoimmune diseases like CIA. To do so, self‐assembled polymeric NPs that incorporate covalently‐linked NAP and physically entrapped Dx are designed to have hydrodynamic properties that, according to bibliography, may improve retention and colocalization of both drugs at inflammation sites. The rapid uptake of NPs by macrophages is demonstrated using coumarine‐6‐loaded NPs. Dx is efficiently encapsulated and in vitro biological studies demonstrate that the Dx‐loaded NAP‐bearing NPs are noncytotoxic and reduce lipopolysaccharide‐induced NO released levels at any of the tested concentrations. Moreover, at the molecular level, a significant synergistic reduction of Il12b transcript gene expression when combining Dx and NAP is demonstrated.
This paper describes the preparation of new self‐assembled bioactive naproxen (NAP)‐containing polymeric NPs loaded with dexamethasone (Dx). Their potential to achieve spatiotemporal colocalization of Dx/NAP combination at inflamed areas through fast uptake by macrophages is demonstrated as well as, the synergistic reduction of Il12b transcript levels and, hence, the reduction of IL12 and IL23 levels, key players in autoimmune diseases.
Brain CD11c+ cells share features with microglia and dendritic cells (DCs). Sterile inflammation increases brain CD11c+ cells, but their phenotype, origin, and functions remain largely unknown. We ...report that, after cerebral ischemia, microglia attract DCs to the inflamed brain, and astroglia produce Flt3 ligand, supporting development and expansion of CD11c+ cells. CD11c+ cells in the inflamed brain are a complex population derived from proliferating microglia and infiltrating DCs, including a major subset of OX40L+ conventional cDC2, and also cDC1, plasmacytoid, and monocyte-derived DCs. Despite sharing certain morphological features and markers, CD11c+ microglia and DCs display differential expression of pattern recognition receptors and chemokine receptors. DCs excel CD11c− and CD11c+ microglia in the capacity to present antigen through MHCI and MHCII. Of note, cDC1s protect from brain injury after ischemia. We thus reveal aspects of the dynamics and functions of brain DCs in the regulation of inflammation and immunity.
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•Microglia and DCs have distinct transcriptional profiles and functions in ischemia•DCs excel over microglia in antigen presentation upon brain ischemia•Ischemic microglia release chemokines attracting DCs, in particular cDC1 through CCR1•cDC1 exert beneficial effects in brain ischemia
CD11c+ dendritic cells infiltrate the brain after ischemic injury and share some features with microglia. Gallizioli et al. show that dendritic cells exhibit a transcriptional profile different from microglia and excel in antigen presentation. Microglia attract different DC subsets via chemokines, especially cDC1 that exert beneficial functions in cerebral ischemia.
is the main cause of bacterial pneumonia, a condition that currently produces significant global morbidity and mortality. The initial immune response to this bacterium occurs when the innate system ...recognizes common motifs expressed by many pathogens, events driven by pattern recognition receptors like the Toll-like family receptors (TLRs). In this study, lung myeloid-cell populations responsible for the innate immune response (IIR) against
, and their dependence on the TLR4-signaling axis, were analyzed in TLR4
and Myeloid-Differentiation factor-88 deficient (MyD88
) mice. Neutrophils and monocyte-derived cells were recruited in infected mice 3-days post-infection. Compared to wild-type mice, there was an increased bacterial load in both these deficient mouse strains and an altered IIR, although TLR4
mice were more susceptible to bacterial infection. These mice also developed fewer alveolar macrophages, weaker neutrophil infiltration, less Ly6C
monocyte differentiation and a disrupted classical and non-classical monocyte profile. The pro-inflammatory cytokine profile (CXCL1, TNF-α, IL-6, and IL-1β) was also severely affected by the lack of TLR4 and no induction of Th1 was observed in these mice. The respiratory burst (ROS production) after infection was profoundly dampened in TLR4
and MyD88
mice. These data demonstrate the complex dynamics of myeloid populations and a key role of the TLR4-signaling axis in the IIR to
, which involves both the MyD88 and TRIF (Toll/IL-1R domain-containing adaptor-inducing IFN-β) dependent pathways.
Aging and age-related diseases are strong risk factors for the development of neurodegenerative diseases. Neuroinflammation (NIF), as the brain's immune response, plays an important role in aged ...associated degeneration of central nervous system (CNS). There is a need for well characterized animal models that will allow the scientific community to understand and modulate this process.
We have analyzed aging-phenotypical and inflammatory changes of brain myeloid cells (bMyC) in a senescent accelerated prone aged (SAMP8) mouse model, and compared with their senescence resistant control mice (SAMR1). We have performed morphometric methods to evaluate the architecture of cellular prolongations and determined the appearance of Iba1
clustered cells with aging. To analyze specific constant brain areas, we have performed stereology measurements of Iba1
cells in the hippocampal formation. We have isolated bMyC from brain parenchyma (BP) and choroid plexus plus meningeal membranes (m/Ch), and analyzed their response to systemic lipopolysaccharide (LPS)-driven inflammation.
Aged 10 months old SAMP8 mice present many of the hallmarks of aging-dependent neuroinflammation when compared with their SAMR1 control, i.e., increase of protein aggregates, presence of Iba1
clusters, but not an increase in the number of Iba1
cells. We have further observed an increase of main inflammatory mediator IL-1β, and an augment of border MHCII
Iba1
cells. Isolated CD45
bMyC from brain parenchyma (BP) and choroid plexus plus meningeal membranes (m/Ch) have been analyzed, showing that there is not a significant increase of CD45
cells from the periphery. Our data support that aged-driven pro-inflammatory cytokine interleukin 1 beta (IL-1β) transcription is enhanced in CD45
BP cells. Furthermore, LPS-driven systemic inflammation produces inflammatory cytokines mainly in border bMyC, sensed to a lesser extent by the BP bMyC, showing that IL-1β expression is further augmented in aged SAMP8 compared to control SAMR1.
Our data validate the SAMP8 model to study age-associated neuroinflammatory events, but careful controls for age and strain are required. These animals show morphological changes in their bMyC cell repertoires associated to age, corresponding to an increase in the production of pro-inflammatory cytokines such as IL-1β, which predispose the brain to an enhanced inflammatory response after LPS-systemic challenge.
Embryonic megakaryopoiesis starts in the yolk sac on gestational day 7.5 as part of the primitive wave of hematopoiesis, and it continues in the fetal liver when this organ is colonized by ...hematopoietic progenitors between day 9.5 and 10.5, as the definitive hematopoiesis wave. We characterized the precise phenotype of embryo megakaryocytes in the liver at gestational day 11.5, identifying them as CD41
CD45-CD9
CD61
MPL
CD42c
tetraploid cells that express megakaryocyte-specific transcripts and display differential traits when compared to those present in the yolk sac at the same age. In contrast to megakaryocytes from adult bone marrow, embryo megakaryocytes are CD45
until day 13.5 of gestation, as are both the megakaryocyte progenitors and megakaryocyte/erythroid-committed progenitors. At gestational day 11.5, liver and yolk sac also contain CD41
CD45
and CD41
CD45
cells. These populations, and that of CD41
CD45
CD42c
cells, isolated from liver, differentiate in culture into CD41
CD45
CD42c
proplatelet-bearing megakaryocytes. Also present at this time are CD41
CD45
CD11b
cells, which produce low numbers of CD41
CD45
CD42c
megakaryocytes
, as do fetal liver cells expressing the macrophage-specific Csf receptor-1 (Csf1r/CD115) from MaFIA transgenic mice, which give rise poorly to CD41
CD45
CD42c
embryo megakaryocytes both
and
In contrast, around 30% of adult megakaryocytes (CD41
CD45
CD9
CD42c
) from C57BL/6 and MaFIA mice express CD115. We propose that differential pathways operating in the mouse embryo liver at gestational day 11.5 beget CD41
CD45
CD42c
embryo megakaryocytes that can be produced from CD41
CD45
or from CD41
CD45
cells, at difference from those from bone marrow.
An increase in intracellular calcium concentration Ca2+i is one of the first events to take place after brain ischemia. A key Ca2+i-regulated signaling molecule is the phosphatase calcineurin (CN), ...which plays important roles in the modulation of inflammatory cascades. Here, we have analyzed the role of endogenous regulator of CN 1 (Rcan1) in response to experimental ischemic stroke induced by middle cerebral artery occlusion.
Animals were subjected to focal cerebral ischemia with reperfusion. To assess the role of Rcan1 after stroke, we measured infarct volume after 48 h of reperfusion in Rcan1 knockout (KO) and wild-type (WT) mice. In vitro studies were performed in astrocyte-enriched cortical primary cultures subjected to 3% oxygen (hypoxia) and glucose deprivation (HGD). Adenoviral vectors were used to analyze the effect of overexpression of Rcan1-4 protein. Protein expression was examined by immunohistochemistry and immunoblotting and expression of mRNA by quantitative real-time Reverse-Transcription Polymerase Chain Reaction (real time qRT-PCR).
Brain ischemia/reperfusion (I/R) injury in vivo increased mRNA and protein expression of the calcium-inducible Rcan1 isoform (Rcan1-4). I/R-inducible expression of Rcan1 protein occurred mainly in astroglial cells, and in an in vitro model of ischemia, HGD treatment of primary murine astrocyte cultures induced Rcan1-4 mRNA and protein expression. Exogenous Rcan1-4 overexpression inhibited production of the inflammatory marker cyclo-oxygenase 2. Mice lacking Rcan1 had higher expression of inflammation associated genes, resulting in larger infarct volumes.
Our results support a protective role for Rcan1 during the inflammatory response to stroke, and underline the importance of the glial compartment in the inflammatory reaction that takes place after ischemia. Improved understanding of non-neuronal mechanisms in ischemic injury promises novel approaches to the treatment of acute ischemic stroke.
Increase in intracellular calcium (Ca2+i) is a key mediator of astrocyte signaling, important for activation of the calcineurin (CN)/nuclear factor of activated T cells (NFAT) pathway, a central ...mediator of inflammatory events. We analyzed the expression of matrix metalloproteinase 3 (Mmp3) in response to increases in Ca2+i and the role of the CN/NFAT pathway in this regulation. Astrocyte Mmp3 expression was induced by overexpression of a constitutively active form of NFATc3, whereas other MMPs and tissue inhibitor of metalloproteinases (TIMP) were unaffected. Mmp3 mRNA and protein expression was also induced by calcium ionophore (Io) and 2′(3′)‐O‐(4‐benzoylbenzoyl) adenosine 5′‐triphosphate (Bz‐ATP) and Mmp3 upregulation was prevented by the CN inhibitor cyclosporin A (CsA). Ca2+‐dependent astrocyte Mmp3 expression was also inhibited by actinomycin D, and a Mmp3 promoter luciferase reporter was efficiently activated by increased Ca2+i, indicating regulation at the transcriptional level. Furthermore, Ca2+/CN/NFAT dependent Mmp3 expression was confirmed in pure astrocyte cultures derived from neural stem cells (Ast‐NSC), demonstrating that the induced Mmp3 expression occurs in astrocytes, and not microglial cells. In an in vivo stab‐wound model of brain injury, MMP3 expression was detected in NFATc3‐positive scar‐forming astrocytes. Because Ca2+i increase is an early event in most brain injuries, these data support an important role for Ca2+/CN/NFAT‐induced astrocyte MMP3 expression in the early neuroinflammatory response. Understanding the molecular pathways involved in this regulation could provide novel therapeutic targets and approaches to promoting recovery of the injured brain.
Polymeric nanoparticles that combine dexamethasone and naproxen reduce inflammation and synergistically inhibit Interleukin-12b (
) transcription in macrophages. This effect can be the result of a ...cyclooxygenase-dependent or a cyclooxygenase-independent mechanism. The aim of this work is to obtain potent anti-inflammatory polymeric nanoparticles by the combination of dexamethasone and ketoprofen, one of the most efficient cyclooxygenase-inhibitors among non-steroidal anti-inflammatory drugs, with appropriate hydrodynamic properties to facilitate accumulation and co-release of drugs in inflamed tissue. Nanoparticles are spherical with hydrodynamic diameter (117 ± 1 nm), polydispersity (0.139 ± 0.004), and surface charge (+30 ± 1 mV), which confer them with high stability and facilitate both macrophage uptake and internalization pathways to favor their retention at the inflamed areas and lysosomal degradation and drug release, respectively. In vitro biological studies concluded that the dexamethasone-loaded ketoprofen-bearing system is non-cytotoxic and efficiently reduces lipopolysaccharide-induced nitric oxide release. The RT-qPCR analysis shows that the ketoprofen nanoparticles were able to reduce to almost basal levels the expression of tested pro-inflammatory markers and increase the gene expression of anti-inflammatory cytokines under inflammatory conditions. However, the synergistic inhibition of
observed in nanoparticles that combine dexamethasone and naproxen was not observed in nanoparticles that combine dexamethasone and ketoprofen, suggesting that the synergistic trans-repression of
observed in the first case was not mediated by cyclooxygenase-dependent pathways.
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