Novel action of lignans isolated from Hernandia nymphaeifolia on Ca²⁺ signaling in human neutrophils

The effects of five lignans (epi-aschantin, epi-magnolin, epi-yangambin, deoxypodophyllotoxin, yatein) isolated from Hernandia nymphaeifolia (Presl.) Kubitzki (Hernandiaceae) on intracellular Ca²⁺ levels ([Ca²⁺]_i) in human neutrophils were investigated by using fura-2 as a fluorescent probe. In both Ca²⁺-containing and Ca²⁺-free media, the lignans (50-100 μM) did not alter basal [Ca²⁺]_i but inhibited the [Ca²⁺]_i increase induced by platelet activating factor (PAF, 10 μM), leukotriene B₄ (LTB₄, 0.2 μM), and thapsigargin (1 μM) to different extents. In Ca²⁺-free medium, after depleting stores of Ca²⁺ with PAF, LTB4 or thapsigargin, addition of 3 mM Ca²⁺ induced Ca²⁺ influx. Each of the lignans (50-100 μM) caused 39-89% inhibition of PAF-induced Ca²⁺ influx; whereas only epi-aschantin was able to inhibit LTB₄- and thapsigargin-induced Ca²⁺ influx by 54-79%. Together, the results suggest that in human neutrophils, these lignans did not alter basal [Ca²⁺]_i but inhibited Ca²⁺ movement induced by Ca²⁺ mobilizing agents.