Abstract Exogenously provided NGF enhances cognitive performance in impaired rodents and humans and is currently a promising compound for the treatment of dementia. To investigate whether ...NGF-dependent cognitive improvement may be due in part to increased hippocampal neurogenesis, adult and aged male rats were treated with NGF or vehicle intracerebroventricularly for 6 or 20 days followed by evaluation of cholinergic parameters and hippocampal neurogenesis. We show that NGF increases hippocampal cholinergic activity as rapidly as 3 days after initiation of treatment. NGF treatment for 6 days did not affect proliferation of progenitor cells in the dentate gyrus granule cell layer (GCL). However, continuous NGF infusion enhanced survival of new neurons in the GCL of young adult, but not aged rats. Taken together, these findings suggest that NGF, likely mediated through increased cholinergic tone, promotes neurogenesis in the adult hippocampus, which may relate to the nootropic action of NGF.
PLAUR encodes the urokinase receptor (uPAR), which promotes cell survival, migration, and resistance to targeted cancer therapeutics in glioblastoma cells in culture and in mouse model systems. ...Herein, we show that patient survival correlates inversely with PLAUR mRNA expression in gliomas of all grades, in glioblastomas, and in the subset of glioblastomas that demonstrate the mesenchymal gene expression signature. PLAUR clusters with genes that define the more aggressive mesenchymal subtype in transcriptome profiles of glioblastoma tissue and glioblastoma cells in neurospheres, which are enriched for multipotent cells with stem cell-like qualities. When PLAUR was over-expressed or silenced in glioblastoma cells, neurosphere growth and expression of mesenchymal subtype biomarkers correlated with uPAR abundance. uPAR also promoted glioblastoma cell survival in neurospheres. Constitutively-active EGF Receptor (EGFRvIII) promoted neurosphere growth; however, unlike uPAR, EGFRvIII did not induce the mesenchymal gene expression signature. Immunohistochemical analysis of human glioblastomas showed that uPAR is typically expressed by a small sub-population of the cancer cells; it is thus reasonable to conclude that this subpopulation of cells is responsible for the effects of PLAUR on patient survival. We propose that uPAR-expressing glioblastoma cells demonstrate a mesenchymal gene signature, an increased capacity for cell survival, and stem cell-like properties.
In the peripheral nervous system, Schwann cells (SCs) demonstrate surveillance activity, detecting injury and undergoing trans‐differentiation to support repair. SC receptors that detect peripheral ...nervous system injury remain incompletely understood. We used RT‐PCR to profile ionotropic glutamate receptor expression in cultured SCs. We identified subunits required for assembly of N‐methyl‐D‐aspartic acid (NMDA) receptors (NMDA‐Rs), α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptors, and kainate receptors. Treatment of SCs with 40–100 μM glutamate or with 0.5–1.0 μM NMDA robustly activated Akt and ERK1/2. The response was transient and bimodal; glutamate concentrations that exceeded 250 μM failed to activate cell signaling. Phosphoprotein profiling identified diverse phosphorylated proteins in glutamate‐treated SCs in addition to ERK1/2 and Akt, including p70 S6‐kinase, glycogen synthase kinase‐3, ribosomal S6 kinase, c‐Jun, and cAMP response element binding protein. Activation of SC signaling by glutamate was blocked by EGTA and dizocilpine and by silencing expression of the NMDA‐R NR1 subunit. Phosphoinositide 3‐kinase/PI3K functioned as an essential upstream activator of Akt and ERK1/2 in glutamate‐treated SCs. When glutamate or NMDA was injected directly into crush‐injured rat sciatic nerves, ERK1/2 phosphorylation was observed in myelinated and nonmyelinating SCs. Glutamate promoted SC migration by a pathway that required PI3K and ERK1/2. These results identified ionotropic glutamate receptors and NMDA‐Rs, specifically, as potentially important cell signaling receptors in SCs. —Campana, W. M., Mantuano, E., Azmoon, P., Henry, K., Banki, M. A., Kim, J. H., Pizzo, D. P., Gonias, S. L. Ionotropic glutamate receptors activate cell signaling in response to glutamate in Schwann cells. FASEB J. 31, 1744–1755 (2017) www.fasebj.org
The prevalence of diabetic nephropathy continues to rise, highlighting the importance of investigating and discovering novel treatment strategies. TRB3 is a kinase-like molecule that modifies ...cellular survival and metabolism and interferes with signal transduction pathways. Herein, we report that TRB3 expression is increased in the kidneys of type 1 and type 2 diabetic mice. TRB3 is expressed in conditionally immortalized podocytes; however, it is not stimulated by elevated glucose. The diabetic milieu is associated with increased oxidative stress and circulating free fatty acids (FFA). We show that reactive oxygen species (ROS) such as H(2)O(2) and superoxide anion (via the xanthine/xanthine oxidase reaction) as well as the FFA palmitate augment TRB3 expression in podocytes. C/EBP homologous protein (CHOP) is a transcription factor that is associated with the endoplasmic reticulum stress response. CHOP expression increases in diabetic mouse kidneys and in podocytes treated with ROS and FFA. In podocytes, transfection of CHOP increases TRB3 expression, and ROS augment recruitment of CHOP to the proximal TRB3 promoter. MCP-1/CCL2 is a chemokine that contributes to the inflammatory injury associated with diabetic nephropathy. In these studies, we demonstrate that TRB3 can inhibit basal and stimulated podocyte production of MCP-1. In summary, enhanced ROS and/or FFA associated with the diabetic milieu induce podocyte CHOP and TRB3 expression. Because TRB3 inhibits MCP-1, manipulation of TRB3 expression could provide a novel therapeutic approach in diabetic kidney disease.
Recruitment of monocytes into sites of inflammation is essential in the immune response. In cancer, recruited monocytes promote invasion, metastasis, and possibly angiogenesis. LDL receptor-related ...protein (LRP1) is an endocytic and cell-signaling receptor that regulates cell migration. In this study, we isografted PanO2 pancreatic carcinoma cells into mice in which LRP1 was deleted in myeloid lineage cells. Recruitment of monocytes into orthotopic and subcutaneous tumors was significantly increased in these mice, compared with control mice. LRP1-deficient bone marrow-derived macrophages (BMDM) expressed higher levels of multiple chemokines, including, most prominently, macrophage inflammatory protein-1α/CCL3, which is known to amplify inflammation. Increased levels of CCL3 were detected in LRP1-deficient tumor-associated macrophages (TAM), isolated from PanO2 tumors, and in RAW 264.7 macrophage-like cells in which LRP1 was silenced. LRP1-deficient BMDMs migrated more rapidly than LRP1-expressing cells in vitro. The difference in migration was reversed by CCL3-neutralizing antibody, by CCR5-neutralizing antibody, and by inhibiting NF-κB with JSH-23. Inhibiting NF-κB reversed the increase in CCL3 expression associated with LRP1 gene silencing in RAW 264.7 cells. Tumors formed in mice with LRP1-deficient myeloid cells showed increased angiogenesis. Although VEGF mRNA expression was not increased in LRP1-deficient TAMs, at the single-cell level, the increase in TAM density in tumors with LRP1-deficient myeloid cells may have allowed these TAMs to contribute an increased amount of VEGF to the tumor microenvironment. Our results show that macrophage density in tumors is correlated with cancer angiogenesis in a novel model system. Myeloid cell LRP1 may be an important regulator of cancer progression.
Patients with earlier age at onset of sporadic Alzheimer disease (AD) are more likely than those with later onset to present with atypical clinical and cognitive features. We sought to determine ...whether this age-related clinical and cognitive heterogeneity is mediated by different topographic distributions of tau-aggregate neurofibrillary tangles (NFTs) or by variable amounts of concomitant non-AD neuropathology.
The relative distribution of NFT density in hippocampus and midfrontal neocortex was calculated, and α-synuclein, TAR DNA binding protein 43 (TDP-43), and microvascular copathologies were staged, in patients with severe AD and age at onset of 51-60 (n = 40), 61-70 (n = 41), and >70 (n = 40) years. Regression, mediation, and mixed effects models examined relationships of pathologic findings with clinical features and longitudinal cognitive decline.
Patients with later age at onset of AD were less likely to present with nonmemory complaints (odds ratio OR 0.46 per decade, 95% confidence interval CI 0.22-0.88), psychiatric symptoms (β = -0.66, 95% CI -1.15 to -0.17), and functional impairment (β = -1.25, 95% CI -2.34 to -0.16). TDP-43 (OR 2.00, 95% CI 1.23-3.35) and microvascular copathology (OR 2.02, 95% CI 1.24-3.40) were more common in later onset AD, and α-synuclein copathology was not related to age at onset. NFT density in midfrontal cortex (β = -0.51, 95% CI -0.72 to -0.31) and midfrontal/hippocampal NFT ratio (β = -0.18, 95% CI -0.26 to -0.10) were lower in those with later age at onset. Executive function (β = 0.48, 95% CI 0.09-0.90) and visuospatial cognitive deficits (β = 0.97, 95% CI 0.46-1.46) were less impaired in patients with later age at onset. Mediation analyses showed that the effect of age at onset on severity of executive function deficits was mediated by midfrontal/hippocampal NFT ratio (β = 0.21, 95% CI 0.08-0.38) and not by concomitant non-AD pathologies. Midfrontal/hippocampal NFT ratio also mediated an association between earlier age at onset and faster decline on tests of global cognition, executive function, and visuospatial abilities.
Worse executive dysfunction and faster cognitive decline in people with sporadic AD with earlier rather than later age at onset is mediated by greater relative midfrontal neocortical to hippocampal NFT burden and not by concomitant non-AD neuropathology.
Chronic pancreatitis is an inflammatory disease that causes progressive destruction of pancreatic acinar cells and, ultimately, loss of pancreatic function. We investigated the role of IκB kinase α ...(IKKα) in pancreatic homeostasis. Pancreas-specific ablation of IKKα (Ikkα(Δpan)) caused spontaneous and progressive acinar cell vacuolization and death, interstitial fibrosis, inflammation, and circulatory release of pancreatic enzymes, clinical signs resembling those of human chronic pancreatitis. Loss of pancreatic IKKα causes defective autophagic protein degradation, leading to accumulation of p62-mediated protein aggregates and enhanced oxidative and ER stress in acinar cells, but none of these effects is related to NF-κB. Pancreas-specific p62 ablation prevented ER and oxidative stresses and attenuated pancreatitis in Ikkα(Δpan) mice, suggesting that cellular stress induced by p62 aggregates promotes development of pancreatitis. Importantly, downregulation of IKKα and accumulation of p62 aggregates were also observed in chronic human pancreatitis. Our studies demonstrate that IKKα, which may control autophagic protein degradation through its interaction with ATG16L2, plays a critical role in maintaining pancreatic acinar cell homeostasis, whose dysregulation promotes pancreatitis through p62 aggregate accumulation.
Endolysosomal defects in neurons are central to the pathogenesis of prion and other neurodegenerative disorders. In prion disease, prion oligomers traffic through the multivesicular body (MVB) and ...are routed for degradation in lysosomes or for release in exosomes, yet how prions impact proteostatic pathways is unclear. We found that prion-affected human and mouse brain showed a marked reduction in Hrs and STAM1 (ESCRT-0), which route ubiquitinated membrane proteins from early endosomes into MVBs. To determine how the reduction in ESCRT-0 impacts prion conversion and cellular toxicity
, we prion-challenged conditional knockout mice (male and female) having
deleted from neurons, astrocytes, or microglia. The neuronal, but not astrocytic or microglial, Hrs-depleted mice showed a shortened survival and an acceleration in synaptic derangements, including an accumulation of ubiquitinated proteins, deregulation of phosphorylated AMPA and metabotropic glutamate receptors, and profoundly altered synaptic structure, all of which occurred later in the prion-infected control mice. Finally, we found that neuronal Hrs (nHrs) depletion increased surface levels of the cellular prion protein, PrP
, which may contribute to the rapidly advancing disease through neurotoxic signaling. Taken together, the reduced Hrs in the prion-affected brain hampers ubiquitinated protein clearance at the synapse, exacerbates postsynaptic glutamate receptor deregulation, and accelerates neurodegeneration.
Prion diseases are rapidly progressive neurodegenerative disorders characterized by prion aggregate spread through the central nervous system. Early disease features include ubiquitinated protein accumulation and synapse loss. Here, we investigate how prion aggregates alter ubiquitinated protein clearance pathways (ESCRT) in mouse and human prion-infected brain, discovering a marked reduction in Hrs. Using a prion-infection mouse model with neuronal Hrs (nHrs) depleted, we show that low neuronal Hrs is detrimental and markedly shortens survival time while accelerating synaptic derangements, including ubiquitinated protein accumulation, indicating that Hrs loss exacerbates prion disease progression. Additionally, Hrs depletion increases the surface distribution of prion protein (PrP
), linked to aggregate-induced neurotoxic signaling, suggesting that Hrs loss in prion disease accelerates disease through enhancing PrP
-mediated neurotoxic signaling.
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