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Lipocortin 1 (LC1) has been shown to increase in neuronal damage and act as a neuroprotectant and a neurotrophic factor. IL-1beta acts as a mediator of inflammation and has been reported as a potent inducer of various neurotrophic factors including nerve growth factor and fibroblast growth factor. In this study, we investigated the relationship between LC1 and IL-1beta in cultured rat astrocytes. Time-and dose-dependent experiments of IL-1beta on rat cortical astrocytes in culture revealed that the expression of LC1 mRNA was significantly augmented by IL-1beta at 8 h, 10 ng/ml. In addition, IL-1beta evoked an extracellular secretion of LC1 without its cytotoxic effects. The effect of IL-1beta was completely abolished when we treated cells with inhibitor of mitogen-activated protein kinases (MAPKs) (PD98059) (25 microM), phospholipase A(2) inhibitor mepacrine (30 microM) and protein synthesis inhibitor cycloheximide (CHX) (10 microg/ml). This suggests that induction of LC1 by IL-1beta is through a MAPKs and phospholipaseA(2) pathway and requires protein synthesis. These results indicate that IL-1beta released in the central nervous system (CNS) injury can stimulate the transcription of the LC1 gene. Subsequent synthesis and release of LC1 may provide trophic support to neurons and modulate the action of IL-1beta in brain damage.

In brain slices from young (postnatal day (P) 10–15) rat somatosensory cortex, real-time neuronal intracellular Cl − concentration ([Cl − ] i ) recordings were made by an optical technique measuring 6-methoxy- N -ethlquinolinium iodide (MEQ) fluorescence. Oxygen–glucose deprivation (in vitro model of ischemia) induced a long-lasting [Cl − ] i increase preceded by a rapid, transient [Cl − ] i decrease that could not be inhibited by blockers of Cl − pumps, Cl − channels, or Cl − antiporters, but was sensitive to cation–Cl − cotransporter inhibitors (bumetanide and furosemide). Use of low external Na + or high external K + revealed that the Na + ,K + –2Cl − cotransporter was inhibited by bumetanide and furosemide, whereas the K + –Cl − cotransporter was preferentially inhibited by furosemide under our experimental conditions. With a reduced inward driving force for Na + (reducing Na + ,K + –2Cl − cotransport), the transient [Cl − ] i decrease was only rarely induced by oxygen–glucose deprivation. In contrast, with a reduced outward driving force for K + (reducing K + –Cl − cotransport), the transient [Cl − ] i decrease still occurred. These results suggest that the transient [Cl − ] i decrease was primarily mediated by a rapid inhibition of the inwardly directed Na + ,K + –2Cl − cotransporter. Reverse transcriptase-polymerase chain reaction (RT-PCR) experiments suggested that the isoform involved is NKCC1. We hypothesize that the initial rapid Cl − efflux might effectively delay the irreversible Cl − influx that mediates neuronal injury.