Chemical composition and phagocyte immunomodulatory activity of Ferula iliensis essential oils

Abstract

Essential oil extracts from Ferula iliensis have been used traditionally in Kazakhstan for treatment of inflammation and other illnesses. Because little is known about the biologic activity of these essential oils that contributes to their therapeutic properties, we analyzed their chemical composition and evaluated their phagocyte immunomodulatory activity. The main components of the extracted essential oils were (E)-propenyl sec-butyl disulfide (15.7-39.4%) and (Z)-propenyl sec-butyl disulfide (23.4-45.0%). Ferula essential oils stimulated [Ca²⁺]_i mobilization in human neutrophils and activated ROS production in human neutrophils and murine bone marrow phagocytes. Activation of human neutrophil [Ca²⁺]_i flux by Ferula essential oils was dose-dependently inhibited by capsazepine, a TRPV1 channel antagonist, indicating that TRPV1 channels mediate this response. Furthermore, Ferula essential oils stimulated Ca²⁺ influx in TRPV1 channel-transfected HEK293 cells and desensitized the capsaicin-induced response in these cells. Additional molecular modeling with known TRPV1 channel agonists suggested that the active component is likely to be (Z)-propenyl sec-butyl disulfide. Our results provide a cellular and molecular basis to explain at least part of the beneficial therapeutic properties of FEOs.

Keywords: calcium flux; molecular modeling; neutrophil; reactive oxygen species; transient receptor potential vanilloid 1 channel.

Figure 1.. Chemical structures of (E/Z)-propenyl sec-butyl disulfides found in FEOs.

*Location of the chiral center for (R/S) enantiomers.

Figure 2.. FEOs activate neutrophil Ca²⁺ mobilization.

(A) Human neutrophils were treated with 50 µg/ml FEO_Rfl, 50 µg/ml FEO_Fr, 5 nM fMLF (positive control), or 1% DMSO (negative control), and [Ca²⁺]_i flux was monitored for the indicated times (arrow indicates when treatment was added). Data are from 1 experiment, representative of 3 independent experiments. (B) Human neutrophils were treated with the indicated concentrations of FEO_Rfl, FEO_Fr, or 1% DMSO (negative control), and [Ca²⁺]_i flux was monitored. The data are presented as the maximum change in [Ca²⁺]_i (max–min) induced by the indicated essential oil concentrations. For both panels the data are from 1 experiment, representative of 3 independent experiments.

Figure 3.. FEOs activate ROS production by phagocytic leukocytes.

(A) Kinetics of bone marrow leukocyte ROS production activated by FEO_Fr and FEO_Rfr. Bone marrow leukocytes were treated with 1% DMSO (negative control), FEO_Fr (12.5 µg/ml), or FEO_Rfr (12.5 µg/ml), and the kinetics of ROS production was monitored with an L-012-amplified assay system. Additional specificity controls include samples containing 100 U SOD and 0.1% Triton X100, as indicated. Data from 1 experiment of 3 independent experiments is shown. (B and C) Mouse bone marrow phagocytes (B) and human neutrophils (C) were treated with the indicated concentrations of FEO_Fl, FEO_Fr, or 1% DMSO (negative control), and ROS production was monitored. Data are the mean ± sd of triplicate samples from 1 experiment, representative of 3 independent experiments.

Figure 4.. Capsazepine inhibits neutrophil Ca²⁺ mobilization induced by FEO_Fr and capsaicin.

(A) Human neutrophils were pretreated with 50 µM of capsazepine for 15 min, followed by treatment with 50 µg/ml FEO_Fr. (B) Human neutrophils were pretreated with 50 µM of capsazepine for 15 min, followed by treatment with 50 µM capsaicin. For both experiments, [Ca²⁺]_i flux was monitored for the indicated times (arrow indicates when treatment was added). A vehicle control (1% DMSO) was included in all experiments. The data are from 1 experiment, representative of 2 independent experiments.

Figure 5.. TRPV1 channel-dependent stimulation of Ca²⁺ influx by FEO_Fr.

HEK293 cells transfected with TRPV1 channels (V1-HEK293) (A) and nontransfected cells (B) were exposed to the indicated concentrations of FEO_Fr, and real-time Ca²⁺ recordings were collected. ATP (10 µM) was used as a positive control in nontransfected cells, to demonstrate receptor viability. (C) V1-HEK293 cells were subjected to repetitive treatments of FEO_Fr (10 µg/ml) to demonstrate desensitization of the TRPV1 channel, followed by a single application of capsaicin (100 nM) to assess postdesensitization responses. Representative traces from 5 experiments are shown.