PPARG and rheumatoid arthritis: Activation of PPARγ by troglitazone has been shown to inhibit expression of 5-lipoxygenase in rheumatoid arthritis synovial fibroblasts [57], lipoxygenase inhibitors can activate PPARγ in breast cancer cells [58] and COX-2 expression in macrophages has been postulated to be regulated by negative feedback mediated by PPARγ [59].