Spent hops (Humulus Lupulus L.) extract as modulator of the inflammatory response in lipopolysaccharide stimulated RAW 264.7 macrophages.

Macrophages play important roles in acute and chronic inflammation. Upon their activation, they secrete a variety of mediators, including eicosanoids, nitric oxide and cytokines, which play different roles in the stimulation and resolution of inflammatory processes. There is a continuous search for selective modulators of these processes. Natural polyphenols and polyphenol-rich extracts have been found to possess preventive and therapeutic potential, including by their anti-inflammatory effects. In this study, the inhibition of the formation of inflammatory mediators by the spent hops extract (SHE), a polyphenol-rich extract from Humulus Lupulus L., was examined using lipopolysaccharide (LPS)- activated murine macrophages (RAW 264.7). The SHE suppressed inter alia the interleukin-6 (IL-6) mRNA expression to 32% in LPS-activated macrophages and to 61% at a protein level (at 25 μg/mL). SHE reduced both the cyclooxygenase-2 (COX-2) mRNA expression to 47% and their protein expression to 32%. Not only did SHE inhibit the IL-6 and COX-2 levels but also decreased both inducible nitric oxide synthase (iNOS) protein expression to 2% at 25 μg/mL and nitric oxide (NO) production for all tested concentrations. The inhibited expression of these inflammatory molecules was likely caused by the reduced activity of nuclear factor-κB (NF-κB). Both mRNA and protein expression of NF-κB was decreased to 38% and 42%, respectively. These results provide the first evidence that SHE decreases the expression of proinflammatory cytokines and inflammatory mediators, which merits further studies to investigate the potential of SHE as anti-inflammatory preparation.