To investigate the ability of a commercial extract from the medicinal plant Artemisia annua to modulate production of the cytokine, tumor necrosis factor-alpha (TNF-α), and the cyclooxygenase (COX) inflammatory marker, prostaglandin E2 (PGE2) in activated neutrophils.
Neutrophils were harvested from rat whole blood and cultured in the presence of plant extract or control samples. Neutrophils, except unactivated control cells, were activated with 10 μg/mL lipopolysaccharide (LPS). The cells were cultured with a range of different concentrations of the A. annua extracts (400–1 μg/mL) and artemisinin (200 and 100 μg/mL) and the supernatants were then tested by enzyme-linked immunosorbent assay (ELISA) for the concentrations of TNF-α and PGE2. Each sample was assayed in triplicate. Positive controls with an inhibitor were assayed in triplicate: chloroquine 2.58 and 5.16 μg/mL for TNF-α, and ibuprofen 400 μg/mL for PGE2. An unsupplemented group was also assessed in triplicate as a baseline control.
Neutrophils were stimulated to an inflammatory state by the addition of LPS. A. annua extract significantly inhibited TNF-α production by activated neutrophils in a dose-dependent manner. There was complete inhibition by the A. annua extract at 200, 100, and 50 μg/mL (all P≤0.0003). At A. annua extract concentrations of 25, 10, and 5 μg/mL, TNF-α production was inhibited by 89% (P<0.0001), 54% (P=0.0002), and 38% (P=0.0014), respectively. A. annua 1 μg/mL did not significantly inhibit TNF-α production (8.8%; P>0.05). Concentrations of 400, 200, and 100 μg/mL A. annua extract significantly inhibited PGE2 production by 87% (P=0.0128), 91% (P=0.0017), and 93% (P=0.0114), respectively.
An extract of A. annua was shown to be a potent inhibitor of TNF-α and a strong inhibitor of PGE2 production in activated neutrophils at the concentrations tested. Further studies are warranted with this promising plant extract.