Amyloid-β oligomers stimulate microglia through a tyrosine kinase dependent mechanism

Dhawan, Gunjan; Floden, Angela M.; Combs, Colin K.

doi:10.1016/j.neurobiolaging.2011.10.027

Cited by 97 publications

(81 citation statements)

References 58 publications

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“…No Aβ plaque-like structures were detectable using antibodies against monomeric or oligomeric Aβ. Staining with anti-CD68 antibody to detect macrophages did not reveal any differences in islet macrophage infiltration suggesting local overexpression of APP within islets did not result in local Aβ-mediated immune activation as is known to occur in the central nervous system (Dhawan, et al 2012; Jimenez, et al 2008). As expected, mouse glucagon was localized primarily at the islet periphery.…”

Section: Resultsmentioning

confidence: 88%

Amyloid precursor protein in pancreatic islets

Kulas

Puig

Combs

2017

Journal of Endocrinology

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The amyloid precursor protein (APP) has been extensively investigated for its role in the production of amyloid beta (Aβ), a plaque forming peptide in Alzheimer’s disease (AD). Epidemiological evidence suggests type 2 diabetes is a risk factor for AD. The pancreas is an essential regulator of blood glucose levels through the secretion of the hormones insulin and glucagon. Pancreatic dysfunction is a well characterized consequence of type 1 and type 2 diabetes. In this study we have examined the expression and processing of pancreatic APP to test the hypothesis that APP may play a role in pancreatic function and the pathophysiology of diabetes. Our data demonstrates the presence of APP within the pancreas, including pancreatic islets in both mouse and human samples. Additionally, we report that the APP/PS1 mouse model of AD overexpresses APP within pancreatic islets, although this did not result in detectable levels of Aβ. We compared whole pancreas and islet culture lysates by western blot from C57BL/6 (WT), APP−/−, and APP/PS1 mice and observed APP-dependent differences in the total protein levels of GLUT4, IDE and BACE2. Immunohistochemistry for BACE2 detected high levels in pancreatic α cells. Additionally, both mouse and human islets processed APP to release sAPP into cell culture media. Moreover, sAPP stimulated insulin but not glucagon secretion from islet cultures. We conclude that APP and its metabolites are capable of influencing the basic physiology of the pancreas, possibly through the release of sAPP acting in an autocrine or paracrine manner.

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Section: Resultsmentioning

confidence: 88%

Amyloid precursor protein in pancreatic islets

Kulas

Puig

Combs

2017

Journal of Endocrinology

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“…TNFα is one of the major cytokines secreted from microglia upon activation, and LPS and Aβ are well-characterized stimulators of TNFα production and release (Dhawan et al, 2012; Lee et al, 1993; Nagai et al, 2001). Thus, we tested whether SIM-A9 cells responded to these stimulatory agents by increasing TNFα secretion.…”

Section: Resultsmentioning

confidence: 99%

“…This in vitro model system provides a versatile tool, allowing direct application of exogenous stimulating or inhibiting agents to microglia, collection of secreted factors, and observation of microglial activities such as migration, proliferation and phagocytosis. In our laboratory, primary microglial cultures are routinely isolated from mixed cultures of neonatal mouse cerebral cortices and utilized to investigate responses to inflammatory stimuli as well as efficacy of anti-inflammatory agents (Dhawan et al, 2012; Floden et al, 2005; Nagamoto-Combs and Combs, 2010; Rojanathammanee et al, 2013; Sondag et al, 2009; Woster and Combs, 2007). However, isolation of primary microglia cultures requires a cumbersome procedure involving dissociation of brain tissue and 14 days of pre-culturing as a mixed cell population (Floden et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

A novel cell line from spontaneously immortalized murine microglia

Nagamoto-Combs

Kulas

Combs

2014

Journal of Neuroscience Methods

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Background Purified microglia cultures are useful tools to study microglial behavior in vitro. Microglial cell lines serve as an attractive alternative to primary microglia culture, circumventing the costly and lengthy preparation of the latter. However, immortalization by genetic or pharmacologic manipulations may show altered physiology from primary microglia. New Method A novel microglial cell line was isolated from a primary glial culture of postnatal murine cerebral cortices. The culture contained a population of spontaneously transformed microglia that continued to divide without genetic or pharmacological manipulations. After several clones were isolated, one particular clone, SIM-A9, was analyzed for its microglial characteristics. Results SIM-A9 cells expressed macrophage/microglia-specific proteins, CD68 and Iba1. SIM-A9 cells were responsive to exogenous inflammatory stimulation with lipopolysaccharide and β-amyloid, triggering tyrosine kinase-based and NFκB signaling cascades as well as TNFα secretion. SIM-A9 cells also exhibited phagocytic uptake of fluorescent labeled β-amyloid and bacterial bioparticles. Furthermore, lipopolysaccharide increased the levels of inducible nitric oxide synthase and cyclooxygenase-2, whereas IL-4 stimulation increased arginase-1 levels demonstrating that SIM-A9 cells are capable of switching their profiles to pro- or anti-inflammatory phenotypes, respectively. Comparison with Existing Methods The use of SIM-A9 cells avoids expensive and lengthy procedures required for the preparation of primary microglia. Spontaneously immortalized SIM-A9 cells are expected to behave more comparably to primary microglia than virally transformed or pharmacologically induced microglial cell lines. Conclusions SIM-A9 cells exhibit key characteristics of cultured primary microglia and may serve as a valuable model system for the investigation of microglial behavior in vitro.

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“…Moreover, other studies have focused on understanding the role of c-Abl in dopaminergic neuronal cell death. Despite this, only scant evidence is available regarding the regulatory effects of c-Abl in microglial activation response (Dhawan et al, 2012). Consistent with the pro-inflammatory effect of c-Abl in an experimental model of AD (Schlatterer et al, 2011b), herein we show that an exaggerated c-Abl activation positively correlated with an accentuated NLRP3 inflammasome activation in microglial cells that were sequentially stimulated with LPS and ROT.…”

Section: Discussionmentioning

confidence: 99%

Involvement of c-Abl Kinase in Microglial Activation of NLRP3 Inflammasome and Impairment in Autolysosomal System

Lawana

Singh

Sarkar

et al. 2017

J Neuroimmune Pharmacol

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A growing body of evidence suggests that excessive microglial activation and pesticide exposure may be linked to the etiology of PD; however, the mechanisms involved remain elusive. Emerging evidence indicates that intracellular inflammasome complex namely NLRP3 complex is involved in the recognition and execution of host inflammatory response. Thus, in the present study, we investigated the hypothesis that NLRP3 inflammasome activation is linked to rotenone (ROT)-induced microglial activation which is dependent upon a priming stimulus by a pathogen-associated molecular pattern (PAMP) or damage associated molecular pattern (DAMP), respectively. Herein using both BV2 cells and primary microglial cells, we show that LPS priming and subsequent ROT stimulation enhanced NLRP3 inflammasome activation, c-Abl and PKCδ activation, mitochondrial dysfunction, NF-κB activation, and autophagic markers, while TFEB levels were decreased dramatically. Mechanistic studies revealed c-Abl acts as a proximal signal that exacerbated the activation of the afore mentioned markers. Intriguingly, siRNA-mediated depletion or pharmacological inhibition of c-Abl via dasatinib abrogated LPS and ROT-induced microglial activation response via attenuation of NLRP3 inflammasome activation, mitochondrial oxidative stress, and ALS dysfunction. Moreover, mitoTEMPO, a mitochondrial antioxidant, attenuated NLRP3 inflammasome activation effects via blockade of c-Abl and PKCδ activation. In LPS treated mice, dasatinib attenuated NLRP3 inflammasome activation, c-Abl and PKCδ activation; and sickness behavior. Together our findings identify an exaggerated ROS/c-Abl/NLRP3 signaling axis in the heightened microglial activation response evidenced in LPS-primed ROT-stimulated microglial cells and suggest that targeting c-Abl-regulated NLRP3 inflammasome signaling offers a novel therapeutic strategy for PD treatment.

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Amyloid-β oligomers stimulate microglia through a tyrosine kinase dependent mechanism

Cited by 97 publications

References 58 publications

Amyloid precursor protein in pancreatic islets

Amyloid precursor protein in pancreatic islets

A novel cell line from spontaneously immortalized murine microglia

Involvement of c-Abl Kinase in Microglial Activation of NLRP3 Inflammasome and Impairment in Autolysosomal System

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