Cytotoxic versus anti-inflammatory effects in HeLa, Jurkat T and human peripheral blood cells caused by guaianolide-type sesquiterpene lactones

Four guaianolide type sesquiterpene lactones (SL), namely the new 1,2-dihydro-3-oxo-costic acid guaianyl ester 3β-O-(1,2-didehydro-3-oxo-costoyloxy)-4β,10β-dihydroxy- guaia-1(2)-en-6β,12-olide (1) and 3β-O-(1,2-didehydro-3-oxo-costoyloxy)-4β,10β-dihydroxy- guaia-1(2)-en-6α,12-olide (2), as well as the known moroccolide A [5αH-2β,4-epoxy-3β-hydroxy-guaia-1(10),11(13)-dien- 6β,12-olide, 3] and 3β-O-(2-methylbutyryl)-moroccolide A [5αH-2β,4-epoxy-3β-(2-methylbutyryloxy)-guaia-1(10),11(13)- dien-6β,12-olide, 4] were examined for their cytotoxic and anti-inflammatory effects in HeLa, Jurkat T and human peripheral blood mononuclear cells. Compounds 1, 2 and 4 were found to exert a strong cytotoxicity similar in potency in all investigated cell types, whereas 3 was significantly less active. Along with the cytotoxic effect compounds 1 and 4 showed a potent and comparable down-regulation of the mRNAs of the house-keeping genes β-actin and GAP-DH in PBMCs after 20 h. In contrast, the down-regulation of the PMA-induced mRNA levels of the NF-κB-driven pro-inflammatory genes IL-2, IL-6, GM-CSF, TNF-α, and IL-1β in PBMCs is significantly stronger with compound 4. Compound 3 did not significantly modulate cytokine mRNAs levels at biochemically relevant concentrations. The electromobility shift assay (EMSA), revealed a stronger inhibition of NF-κB for 1 (IC₅₀ 2.5 μM) than for 4 (IC₅₀ 5 μM). Both compounds were also subjected to an IL-6 luciferase reporter gene assay and showed IC₅₀ values of 1.0 (1) and 1.2 μM (4). Thus, the NF-κB inhibition measured by EMSA, as well as the IL-6 luciferase assay did not reflect the differential modulation of pro-inflammatory genes measured with RT-rt-PCR.