Inhibition of matrix metalloproteinase-9 secretion by dimethyl sulfoxide and cyclic adenosine monophosphate in human monocytes

Figure 7 Amyloid-β peptide-induced matrix-metalloproteinase-9 secretion occurs much later than tumor necrosis factor α secretion. THP-1 monocytes were treated with amyloid-β peptide (17 μmol/L) for 6, 24 and 48 h. Cells were collected, centrifuged at 500 g for 10 min and supernatant assessed for matrix-metalloproteinase-9 (MMP-9) and tumor necrosis factor α (TNFα). A: SDS-PAGE/WB of cell supernatants. Lane 1 is an MMP-9 standard; and B: Densitometry of Panel A (left plot). Each data bar is the average ± standard error for three independent densitometry measurements. Enzyme-linked immuno sorbent assay determination of TNFα levels in cell supernatants (right plot). Each data bar is the average ± standard error for three independent measurements. Statistical differences (^aP < 0.05 or ^bP < 0.01) between MMP-9 or TNFα secretion at different amyloid-β peptide treatment times are shown with an asterisk. Aβ42: Amyloid-β peptide; MMP-9: Matrix-metalloproteinase-9; TNFα: Tumor necrosis factor α.