Dataset Information

Role of microglial amylin receptors in mediating beta amyloid (A?)-induced inflammation.

ABSTRACT:

Background

Neuroinflammation in the brain consequent to activation of microglia is viewed as an important component of Alzheimer's disease (AD) pathology. Amyloid beta (A?) protein is known to activate microglia and unleash an inflammatory cascade that eventually results in neuronal dysfunction and death. In this study, we sought to identify the presence of amylin receptors on human fetal and murine microglia and determine whether A? activation of the inflammasome complex and subsequent release of cytokines is mediated through these receptors.

Methods

The presence of dimeric components of the amylin receptor (calcitonin receptor and receptor activity modifying protein 3) were first immunohistochemically identified on microglia. Purified human fetal microglial (HFM) cultures were incubated with an in vivo microglial marker, DyLight 594-conjugated tomato lectin, and loaded with the membrane-permeant green fluorescent dye, Fluo-8L-AM for measurements of intracellular calcium [Ca²⁺]i. HFM and BV-2 cells were primed with lipopolysaccharide and then exposed to either human amylin or soluble oligomeric A?_1-42 prior to treatment with and without the amylin receptor antagonist, AC253. Changes in the inflammasome complex, NLRP3 and caspase-1, were examined in treated cell cultures with Western blot and fluorometric assays. RT-PCR measurements were performed to assess cytokine release. Finally, in vivo studies were performed in transgenic mouse model of AD (5xFAD) to examine the effects of systemic administration of AC253 on markers of neuroinflammation in the brain.

Results

Acute applications of human amylin or A?_1-42 resulted in an increase in [Ca²⁺]i that could be blocked by the amylin receptor antagonist, AC253. Activation of the NLRP3 and caspase-1 and subsequent release of cytokines, TNF? and IL-1?, was diminished by AC253 pretreatment of HFMs and BV2 cells. In vivo, intraperitoneal administration of AC253 resulted in a reduction in microglial markers (Iba-1 and CD68), caspase-1, TNF?, and IL-1?. These reductions in inflammatory markers were accompanied by reduction in amyloid plaque and size in the brains of 5xFAD mice compared to controls.

Conclusion

Microglial amylin receptors mediate A?-evoked inflammation, and amylin receptor antagonists therefore offer an attractive therapeutic target for intervention in AD.

SUBMITTER: Fu W

PROVIDER: S-EPMC5639602 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Role of microglial amylin receptors in mediating beta amyloid (Aβ)-induced inflammation.

Fu Wen W Vukojevic Vlatka V Patel Aarti A Soudy Rania R MacTavish David D Westaway David D Kaur Kamaljit K Goncharuk Valeri V Jhamandas Jack J

Journal of neuroinflammation 20171006 1

<h4>Background</h4>Neuroinflammation in the brain consequent to activation of microglia is viewed as an important component of Alzheimer's disease (AD) pathology. Amyloid beta (Aβ) protein is known to activate microglia and unleash an inflammatory cascade that eventually results in neuronal dysfunction and death. In this study, we sought to identify the presence of amylin receptors on human fetal and murine microglia and determine whether Aβ activation of the inflammasome complex and subsequent ...[more]

PMID: 28985759

Similar Datasets

Project description:Background: Alzheimer's disease (AD) is characterized by amyloid beta (A?) accumulation in the brain, which triggers the activation of microglia; in turn, microglia release neuroinflammatory factors capable of damaging neurons. Thus, a therapeutic approach targeting this sustained microglia-induced inflammatory response deserves investigation. Here, we examined whether oxiracetam (ORC), a nootropic of the racetam family, can indirectly prevent A?-induced neurotoxicity by attenuating microglial activation. Methods: A?42 oligomers were used to stimulate BV2 microglial cells, and the morphological changes and phagocytic capacity of BV2 cells were evaluated using fluorescence microscopy. We used quantitative reverse transcription polymerase chain reaction to assess the inhibitory effects of ORC on A?-induced mRNA levels of interleukin-1? (IL-1?), IL-6, and tumor necrosis factor-? (TNF-?); enzyme-linked immunosorbent assay was used to examine the productions of these cytokines. We also assessed the mRNA level of inducible nitric oxide synthase and the production of nitric oxide (NO). The conditioned medium from BV2 cells was used to culture hippocampal HT22 cells to assess indirect toxicity using the MTT assay. Results: ORC prevented the A?-induced activation of BV2 cells, as reflected by reduced morphological changes and phagocytic ability. In addition, ORC downregulated the expression of A?-induced cytokines (IL-1?, IL-6, and TNF-?) and the production of NO in BV2 cells. Furthermore, ORC protected HT22 cells from indirect damage evoked by A?-treated BV2 cell-conditioned medium, but not from direct A?-induced toxicity. Conclusions: ORC suppressed the activation of BV2 cells, decreased the production of A?-induced inflammatory molecules and NO in BV2 cells, and protected HT22 cells against indirect toxicity mediated by A?-treated BV2 cell-conditioned medium. Thus, ORC may exert a protective role in AD through attenuating the damage caused by inflammation and oxidative stress.