Differential production of interleukin-6 and tumor necrosis factor-α in primary rat astrocyte cultures using two distinct methods of microglia elimination

Abstract

Hepatic encephalopathy (HE) is a neurocognitive disorder due to acute or chronic liver failure as well as portosystemic bypass. Both neuroinflammation and oxidative stress have been strongly implicated in the pathogenesis of HE. An increasing body of evidence suggests that in the development of these mechanisms astrocytes may be involved. With regard of HE, this aspect of astrocytes is, however, neglected. While several studies focus on astrocytes related to the above-mentioned pathological processes, the applied in vitro models are generated by diverse methods, which make the results difficult to compare with each other. In addition, these astrocyte cultures frequently contain microglia as well, complicating the interpretation of results. Therefore, we applied enriched primary rat astrocyte cultures generated by microglia elimination via shaking or the combination of cytosine β-d-arabinofuranoside hydrochloride (AraC) and l-leucine methyl ester (LME). We examine whether some HE-relevant pathological factors, such as ammonia, manganese (Mn), lipopolysaccharide (LPS), and H2O2 could elicit oxidative stress and cytokine production in astrocytes. Mn exposure increased the oxidative stress in astrocytes in a time-dependent manner; furthermore, we could detect tumor necrosis factor (TNF)-α production in both cultures at resting state. In addition, it was around 10-fold higher in the cultures after shaking. LPS increased TNF-α secretion in cultures after shaking, but not in cultures after AraC + LME treatment. In contrast, interleukin (IL)-6 was detectable only in the AraC + LME-treated cultures. In conclusion, we have demonstrated that HE-relevant factors evoke oxidative stress and cytokine production, albeit depending on the elimination method used.