Fig. 6

Soluble factors in SAA-stimulated microglia culture medium are responsible for the reduced tau phosphorylation in neurons. a Absence of a direct effect of SAA in tau phosphorylation in neurons. Primary cultures of mouse neurons were stimulated with 0.5 μM of SAA for 3, 6, and 12 h. The cells were collected, and tau phosphorylation was determined with Western blotting using specific antibodies recognizing phosphorylated tau at T205 and S396. β-actin was a loading control. b Experimental scheme showing stimulation of primary astrocytes and microglia with SAA (0.5 μM) or PBS for 6 h, removal of medium, addition of fresh medium and culture for 12 h, and collection of conditioned medium (CM) for stimulation of primary cultures of neurons. c Western blots showing the level of tau phosphorylation at T205 and S396 after stimulation with 50 % of CM from cultured astrocytes, as in b. d Western blots showing the level of tau phosphorylation at T205 and S396 after stimulation with CM from cultured microglia. The levels of tau phosphorylation at T205 and S396, as in d and similar samples receiving CM from cultured microglia, were quantified using densitometry, normalized against β-actin, and shown in bar graphs in (e; mean ± SEM shown, *p < 0.05; n = 3 independent cultures)