Naegleria fowleriLysate Induces Strong Cytopathic Effects and Pro-inflammatory Cytokine Release in Rat Microglial Cells

Abstract

Naegleria fowleri, a ubiquitous free-living ameba, causes fatal primary amebic meningoencephalitis in humans. N. fowleri trophozoites are known to induce cytopathic changes upon contact with microglial cells, including necrotic and apoptotic cell death and pro-inflammatory cytokine release. In this study, we treated rat microglial cells with amebic lysate to probe contact-independent mechanisms for cytotoxicity, determining through a combination of light microscopy and scanning and transmission electron microscopy whether N. fowleri lysate could effect on both necrosis and apoptosis on microglia in a time- as well as dose-dependent fashion. A 51Cr release assay demonstrated pronounced lysate induction of cytotoxicity (71.5%) toward microglial cells by 24 hr after its addition to cultures. In an assay of pro-inflammatory cytokine release, microglial cells treated with N. fowleri lysate produced TNF-α, IL-6, and IL-1β, though generation of the former 2 cytokines was reduced with time, and that of the last increased throughout the experimental period. In summary, N. fowleri lysate exerted strong cytopathic effects on microglial cells, and elicited pro-inflammatory cytokine release as a primary immune response.

Fowlerstefin, a cysteine protease inhibitor of Naegleria fowleri, induces inflammatory responses in BV-2 microglial cells in vitro

“…Until now, the functional relevance of microglial cells with N. fowleri infection has been investigated. Trophozoites of N. fowleri induce the production of several pro-inflammatory cytokines such as IL-1α, IL-1β, IL-6 and TNF in microglial cells [14,36]. N. fowleri lysates induce IL-1β and IL-6 production in astrocytes or rat microglial cells [18,36].…”

“…Trophozoites of N. fowleri induce the production of several pro-inflammatory cytokines such as IL-1α, IL-1β, IL-6 and TNF in microglial cells [14,36]. N. fowleri lysates induce IL-1β and IL-6 production in astrocytes or rat microglial cells [18,36]. The ESP of N. fowleri stimulates BV-2 microglial cells to produce IL-1α and TNF via NF-κB-and AP-1-dependent MAPK signaling pathways [17].…”

“…Molecules secreted by N. fowleri may also hasten neuronal cell death or damage via indirect cytolytic activity. The secreted cytotoxic molecules, in concert with cellular debris originated from the lysed brain cells, may also attract microglial cells to the focal sites of N. fowleri infection [17,36]. Fowlerstefin stimulates BV-2 microglial cells to produce pro-inflammatory cytokines including IL-6 and TNF.…”

Morphological and functional changes of microglia cultured under different oxygen concentrations and the analysis of related mechanisms

“…When pathological changes such as stroke, trauma, infection, tumor and central nervous system degenerative diseases appear in the central nervous system, the microglia are activated and a large number of neurotoxic factors such as IL-1β and TNF-α are released, which triggers a series of inflammatory reactions and leads to the activation and migration of microglia around the area of the lesion ( 10 – 13 ). A serious immune response to the body occurs when the microglia activation process is out of control, which aggravates central nervous system injury ( 14 , 15 ). At present, there are relatively few studies regarding the microglia.…”

NLRP3 Inflammasome Activation in THP-1 Target Cells Triggered by Pathogenic Naegleria fowleri

“…In addition, N. fowleri induces host innate defense mechanisms, such as mucin secretion (MUC5AC) and local inflammation (IL-8 and IL-1␤), in respiratory epithelial cells via reactive oxygen species (ROS) production (12). As a contact-independent mechanism, target microglial cells treated with N. fowleri lysate showed a primary immune response via strong cytopathic changes and proinflammatory cytokine release (13). In addition, IL-1␤ and IL-6 activated the inflammatory responses of astrocytes against the N. fowleri infection via the modulation of mitogen-activated protein (MAP) kinases and AP-1 (14).…”