ABSTRACT
BACKGROUND: Pathological features of Alzheimer's disease (AD) include aggregation of amyloid beta (Aß) and tau protein. Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, has been implicated in the toxicity of aggregated Aß. It remains unclear whether MIF affects hyperphosphorylation and aggregation of tau. METHODS: The effects of MIF deficiency in tau hyperphosphorylation were examined in Mif (-/-) mice receiving intracerebroventricular (ICV) injection of streptozotocin (STZ) and in APP/PS1 transgenic mice mated with Mif (-/-) mice. MIF expression and astrocyte activation were evaluated in ICV-STZ mice using immunofluorescence staining. Cultured primary astrocytes were treated with high glucose to mimic STZ function in vitro, and the condition medium (CM) was collected. The level of tau hyperphosphorylation in neurons treated with the astrocyte CM was determined using Western blotting. RESULTS: MIF deficiency attenuated tau hyperphosphorylation in mice. ICV injection of STZ increased astrocyte activation and MIF expression in the hippocampus. MIF deficiency attenuated astrocyte activation in ICV-STZ mice. CM from high glucose-treated WT astrocytes increased tau hyperphosphorylation in cultured primary neurons, an effect absent from Mif (-/-) astrocytes and WT astrocytes treated with the MIF inhibitor ISO-1. ISO-1 had no direct effect on tau phosphorylation in cultured primary neurons. CONCLUSIONS: These results suggest that MIF deficiency is associated with reduced astrocyte activation and tau hyperphosphorylation in the mouse AD models tested. Inhibition of MIF and MIF-induced astrocyte activation may be useful in AD prevention and therapy.
Subject(s)
Alzheimer Disease/genetics , Macrophage Migration-Inhibitory Factors/deficiency , tau Proteins/metabolism , Alzheimer Disease/metabolism , Amyloid beta-Peptides/genetics , Animals , Astrocytes/drug effects , Astrocytes/metabolism , Body Weight/drug effects , Diabetes Mellitus, Experimental/metabolism , Diabetes Mellitus, Experimental/pathology , Female , Glucose/pharmacology , Macrophage Migration-Inhibitory Factors/antagonists & inhibitors , Macrophage Migration-Inhibitory Factors/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Neurons/drug effects , Neurons/metabolism , Phosphorylation , Primary Cell CultureABSTRACT
Tetramethylpyrazine (TMP) is one of the most important active ingredients of a Chinese herb Ligusticum wallichii Franchat, which is widely used for the treatment of cardiovascular diseases. Several factors may affect TMP exposure after topical administration, resulting in large variability and demanding further elucidation of drug distribution. This paper describes a new efficient reliable LC-MS/MS assay for the determination of TMP in dermal microdialysate, where TMP was separated on an Agilent C(18) column (3.5 µm, 100 mm × 2.1 mm i.d.) using a mixture of methanol, water and acetic acid (50:50:0.6, v/v/v) at a flow-rate of 0.3 mL/min. The retention time was 1.89 min for TMP and 1.17 min for the internal standard (caffeine). Histological analysis confirmed an inflammatory response to the microdialysis probes and the presence of a collagen capsule. The membrane extraction efficiency (percentage delivered to the tissue space) for TMP was not altered through the implant lifetime. The validation and sample analysis results showed that the method is precise, accurate and well suited to support dermal microdialysis experiments.