Daucane esters from laserwort (Laserpitium latifolium L.) inhibit cytokine and chemokine production in human lung epithelial cells

Abstract

Background: Laserwort, Laserpitium latifolium L. (Apiaceae), is a European medicinal plant. Its roots and rhizomes were traditionally used as a general tonic and to treat inflammatory and infective diseases.

Purpose: The anti-inflammatory potential of daucane esters, isolated from underground parts extract of L. latifolium and specific structural features that contribute to their activity were investigated. In addition, we studied their interference with the transactivation capacity of the Glucocorticoid Receptor when added together with a classic glucocorticoid (GC), dexamethasone (DEX). This particular property may be relevant in combination strategies, attempting to circumvent diabetogenic side effects of glucocorticoids upon long-term anti-inflammatory treatments.

Materials and methods: Nine L. latifolium daucane esters were isolated and elucidated as derivatives of desoxodehydrolaserpitin, laserpitin and a novel 2β-esterified laserpitinol analogue. Of all compounds effects on NF-κB- and AP-1-driven pro-inflammatory pathways were assessed using TNF- or PMA-induced reporter gene analysis in A549 cells. Daucanes with a strong and concentration-dependent inhibition of both NF-κB and AP-1, were tested for a potential effect on DEX-stimulated GR-driven Glucocorticoid Response Element (GRE) reporter gene activity. In addition, GRE-driven anti-inflammatory mRNA expression was determined (GILZ and DUSP1). Also anti-inflammatory properties were validated by monitoring effects on CCL-2, IL-6, IL-1β mRNA expression levels (qPCR) and on CCL-2 chemokine production (ELISA).

Results: Daucanes featuring an ester moiety and/or a hydroxy group at positions 2β, 6α and 10α and especially the novel 2β-esterified laserpitinol derivative that, in comparison to other isolated compounds, features an additional 9α-hydroxy group, demonstrated suppression of both NF-κB- and AP-1-dependent pro-inflammatory pathways. Remarkably, those entities competitively and concentration-dependently repressed GR-driven GRE-dependent reporter gene activities. The most active compounds inhibited CCL-2 protein excretion and compound 4 downregulated genes coding for IL-1β and IL-6 induced upon TNF treatment in A549. In absence of TNF, compound 4 upregulated the GRE-mediated anti-inflammatory gene GILZ, but not DUSP1.

Conclusions: Daucane esters are novel anti-inflammatory agents that may, in combination with GCs, potentially improve therapeutic benefit. These results contribute to the ongoing search for novel anti-inflammatory agents as safer alternatives to, or with, GCs.

Keywords: AP-1; Anti-inflammatory activity; Chemokine production; Glucocorticoid receptor; Inducible gene expression; NF-κB.