Positive controls - anti-inflam assay with macrophages (Mar/08/2010 )

I have completed experiments showing the anti-inflammatory effect of 3 polyphenols on THP1 macrophages. There was a good reduction of IL-1B, IL-6 and TNF-alpha. However, I've just been told that I am missing a positive control.
Can anyone tell me if there is a compound that inhibits these cytokines in macrophages and would it be suitable as a control?
(I used PMA to differentiate monocytes to macrophages, then LPS to stimulate after incubation with polyphenols)

Any help/ advice would be most appreciated!

I use dexamethasone and aspirin as general anti-inflammatory positive controls. You probably don’t need aspirin with those cytokines (I typically look for PGs as well) but it can be interesting to see what effect it has.