Curcumin, the active constituent of turmeric, inhibits amyloid peptide-induced cytochemokine gene expression and CCR5-mediated chemotaxis of THP-1 monocytes by modulating early growth response-1 transcription factor

Epidemiological studies show reduced risk of Alzheimer's disease (AD) among patients using non-steroidal inflammatory drugs (NSAID) indicating the role of inflammation in AD. Studies have shown a chronic CNS inflammatory response associated with increased accumulation of amyloid peptide and activated microglia in AD. Our previous studies showed that interaction of Abeta(1-40) or fibrilar Abeta(1-42) caused activation of nuclear transcription factor, early growth response-1 (Egr-1), which resulted in increased expression of cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1beta, MCP-1 and IL-8) in monocytes. We determined whether curcumin, a natural product known to have anti-inflammatory properties, suppressed Egr-1 activation and concomitant expression of cytochemokines. We show that curcumin (12.5-25 muM) suppresses the activation of Egr-1 DNA-binding activity in THP-1 monocytic cells. Curcumin abrogated Abeta(1-40)-induced expression of cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1beta, MCP-1 and IL-8) in both peripheral blood monocytes and THP-1 cells. We found that curcumin inhibited Abeta(1-40)-induced MAP kinase activation and the phosphorylation of ERK-1/2 and its downstream target Elk-1. We observed that curcumin inhibited Abeta(1-40)-induced expression of CCR5 but not of CCR2b in THP-1 cells. This involved abrogation of Egr-1 DNA binding in the promoter of CCR5 by curcumin as determined by: (i) electrophoretic mobility shift assay, (ii) transfection studies with truncated CCR5 gene promoter constructs, and (iii) chromatin immunoprecipitation analysis. Finally, curcumin inhibited chemotaxis of THP-1 monocytes in response to chemoattractant. The inhibition of Egr-1 by curcumin may represent a potential therapeutic approach to ameliorate the inflammation and progression of AD.