Effects of tumor necrosis factor alpha on taurine uptake in cultured rat astrocytes

Abstract

Taurine is known to play a major role in volume regulation in astrocytic swelling associated with stroke and brain trauma. Apart from brain edema, the severity of brain injury is related to the levels of inflammatory cytokines such as tumor necrosis factor α (TNFα). TNFα had been shown to be closely associated with brain edema formation since the neutralization of TNFα reduced brain edema. Considering taurine has osmoregulatory functions in astrocytes, experiments were performed to study the effects of TNFα on taurine uptake in cultured astrocytes. Astrocytes exposed to 20 ng/ml of TNFα for 48 h showed a 91% increase in taurine uptake and significant increase was observed after 24 h exposure. This cytokine caused neither significant changes in cell volume nor taurine release. The increased in taurine uptake induced by TNFα was unlikely resulted from the modification of Na+ movement because TNFα decreased tyrosine uptake, Na+-dependent transport system. In contrast to TNFα, interferon-γ (IFNγ) did not significantly affect taurine uptake. Taken together, our results did not support a suggestion that TNFα affects cell volume regulation via modulating taurine uptake in astrocytes. Increasing lines of evidence have demonstrated that taurine has anti-inflammatory and anti-oxidative effects, these findings therefore suggested that the increase in taurine uptake might be an adaptive response or a tool for astrocytes against oxidative stress.