Flavocoxid,a dual inhibitor of cyclooxygenase and 5-lipoxygenase,blunts pro-inflammatory phenotype activation in endotoxin-stimulated macrophages

Background and purpose:

The flavonoids, baicalin and catechin, from Scutellaria baicalensis and Acacia catechu, respectively, have been used for various clinical applications. Flavocoxid is a mixed extract containing baicalin and catechin, and acts as a dual inhibitor of cyclooxygenase (COX) and 5-lipoxygenase (LOX) enzymes. The anti-inflammatory activity, measured by protein and gene expression of inflammatory markers, of flavocoxid in rat peritoneal macrophages stimulated with Salmonella enteritidis lipopolysaccharide (LPS) was investigated.

Experimental approach:

LPS-stimulated (1 µg·mL⁻¹) peritoneal rat macrophages were co-incubated with different concentrations of flavocoxid (32–128 µg·mL⁻¹) or RPMI medium for different incubation times. Inducible COX-2, 5-LOX, inducible nitric oxide synthase (iNOS) and inhibitory protein κB-α (IκB-α) levels were evaluated by Western blot analysis. Nuclear factor κB (NF-κB) binding activity was investigated by electrophoretic mobility shift assay. Tumour necrosis factor-α (TNF-α) gene and protein expression were measured by real-time polymerase chain reaction and enzyme-linked immunosorbent assay respectively. Finally, malondialdehyde (MDA) and nitrite levels in macrophage supernatants were evaluated.

Key results:

LPS stimulation induced a pro-inflammatory phenotype in rat peritoneal macrophages. Flavocoxid (128 µg·mL⁻¹) significantly inhibited COX-2 (LPS = 18 ± 2.1; flavocoxid = 3.8 ± 0.9 integrated intensity), 5-LOX (LPS = 20 ± 3.8; flavocoxid = 3.1 ± 0.8 integrated intensity) and iNOS expression (LPS = 15 ± 1.1; flavocoxid = 4.1 ± 0.4 integrated intensity), but did not modify COX-1 expression. PGE₂ and LTB₄ levels in culture supernatants were consequently decreased. Flavocoxid also prevented the loss of IκB-α protein (LPS = 1.9 ± 0.2; flavocoxid = 7.2 ± 1.6 integrated intensity), blunted increased NF-κB binding activity (LPS = 9.2 ± 2; flavocoxid = 2.4 ± 0.7 integrated intensity) and the enhanced TNF-α mRNA levels (LPS = 8 ± 0.9; flavocoxid = 1.9 ± 0.8 n-fold/β-actin) induced by LPS. Finally, flavocoxid decreased MDA, TNF and nitrite levels from LPS-stimulated macrophages.

Conclusion and implications:

Flavocoxid might be useful as a potential anti-inflammatory agent, acting at the level of gene and protein expression.