Harmine is an inflammatory inhibitor through the suppression of NF-κB signaling

Harmine is a major constituent in a hallucinogenic botanical mixture ayahuasca and medical plant Peganum harmala L. The plant is used for various illnesses and exhibits anti-inflammatory activity. However, the active constituents remain unclear. Here, we screened the seven alkaloids in P. harmala for their anti-inflammatory activity using an nuclear factor-κB (NF-κB) reporter assay. We found that harmine and harmol could inhibit NF-κB transactivity. As the most abundant compound, harmine inhibited tumor necrosis factor-α (TNF-α)- and lipopolysaccharides (LPS)-induced NF-κB transactivity and nuclear translocation in mouse macrophage RAW 264.7 cells. The mRNA and protein levels of NF-κB downstream inflammatory cytokines also reduced. In an LPS-challenged mouse model, harmine markedly averted inflammatory damage of the lung, and decreased serum TNF-α, interleukin-1β (IL-1β) and IL-6 levels. Our data indicate that harmine may exert the anti-inflammatory effect by inhibition of the NF-κB signaling pathway and harmine is probably responsible for the anti-inflammatory effects of P. harmala.