In Vitro Effects of Lipopolysaccharide and Active Fragment of Beta Amyloid on The Morphology and Ultrastructure of Microglia

Abstract

Microglia are implicated in the regulation of neuroinflammation. Activation of microglia is associated with a wide variety of inflammatory and neurodegenerative pathologies and is characterised by the phenotypic shift of resting microglia into cells with macrophage-like morphology and upregulation of activation molecules. Here, we show that activation of microglia by lipopolysaccharide (LPS) or the active fragment of beta amyloid (Aβ25-35) entails morphological alterations, including ultrastructural changes as evaluated by transmission electron microscopy (TEM). Microglia were cultured from Sprague-Dawley neonatal rats and treated with 1g/ml LPS or 50g/ml A for 6 h. Cell morphology was assessed with FITC-tagged lectin. Ultrastructure of microglia was scrutinised with transmission electron microscopy (TEM).When viewed with fluorescent microscopy, LPS- and Aβ-treated microglia assumed a deramified shape with a condensed cytoplasm, typical of activated microglia. TEM revealed an increased number of enlarged, elongated and swollen mitochondria compared to resting microglia. Resting microglia also displayed mainly smooth endoplasmic reticulum (SER) whereas LPS-treated cells displayed polyribosomes and rough endoplasmic reticulum (RER). Aβ-treated microglia also displayed RER, but to a lesser extent compared to LPS. Distinct ultrastructural indicative of increased energy consumption and protein synthesis were observed in LPS- and A-activated microglia.