Investigations on the antiinflammatory way of action of a Harpagophytum extract using microarray technology

Preparations from the tubers Harpagophytum procumbens are monographed and used in the treatment of degenerative rheumatic diseases, but a clear antiinflammatory mode of action is still lacking. Several in vitro investigations revealed inhibitory effects on COX-2, iNOS, NF-kB, MMP-9 and MMP-2 and, in very high concentrations, on TNF-alpha.

We tried a new approach to gather new information on the antiinflammatory way of action of Harpagophytum by using the microarray ('gene chip') technology.

THP-1 cells were incubated with 50µg/ml Harpagophytum procumbens dry extract (DER 1.5–3: 1; 60% ethanol; A. Vogel Bioforce AG) for 1 hour, afterwards stimulated with 0.1µg LPS/ml and then incubated for 18 hours. The isolated mRNA was transcribed to cDNA and labelled and then transferred on a Whole Human Genome Chip (Agilent Technologies).

The Harpagophytum extract inhibited only few genes statistically significant. From these genes, we investigated with rt-PCR those further which are involved in inflammatory and/or rheumatic diseases and in particular some genes which are regulated by the TLR-4 pathway.

The Harpagophytum extract showed after an incubation time of 3 hours an antiinflammatory effect by inhibiting the transcription of NF-kB, TNF-α, CCl₂ and MMP9.

These experiments confirm there is no distinct antiinflammatory way of action but rather a moderate inhibition of several inflammatory targets.