Curcumin pyrazole blocks lipopolysaccharide-induced inflammation via suppression of JNK activation in RAW 264.7 macrophages.

BACKGROUND

Targeting inflammatory macrophages and their products is an effective method for controlling inflammation. The pyrazole analog of curcumin (curcumin pyrazole, PYR) has been reported to possess superior anti-inflammatory activity to curcumin (CUR). However, the role of PYR anti-inflammatory activity in macrophages has not yet been elucidated.

OBJECTIVE

To examine the anti-inflammatory effects of PYR and CUR in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages and determine the role of mitogen-activated protein kinases (MAPK) in their activity.

METHODS

Nitrite level was investigated by the Griess assay. The expression of inducible nitric oxide (NO) synthase, cyclooxygenase-2 (COX-2), and MAPK proteins were analyzed by western blot analysis. The pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and interleukin-6 (IL-6) were measured by enzyme-linked immunosorbent assay.

RESULTS

LPS-induced NO secretion in RAW 264.7 macrophages was potently inhibited by PYR (IC50 = 3.7 ± 0.16 μM), at a higher efficacy than CUR (IC50 = 11.0 ± 0.59 μM). Treatment with identical concentrations of PYR and CUR demonstrated that PYR drastically inhibited iNOS and COX-2 expression, whereas CUR only blocked COX-2. PYR reduced the LPS-induced secretion of TNF-α to a greater extent than CUR and both similarly reduced IL-1β and IL-6 levels. Activation of c-Jun N-terminal kinase (JNK) MAPK was significantly decreased in LPS-activated RAW 264.7 macrophages upon PYR but not CUR treatment.

CONCLUSIONS

PYR exhibited a more potent anti-inflammatory activity than CUR. This activity is partly mediated by PYR-depended inhibition of the JNK signaling pathway and underscores the utility of PYR as an anti-inflammatory agent in macrophages.