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PN2 164/1.10.2007 Conf. Dr. Alexandru Babes
Published abstracts:

MCS-Ab-162, a natural compound extracted from Helleborus purpurascens, is an antagonist of the polymodal receptor TRPV1

Cristian Neacsu1, Cristian Ciobanu1, Oana Toader1, Geza Szegli2, Franz Kerek3 and Alexandru Babes1

 

1 Department of Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania
2 Cantacuzino Institute for Microbiology and Immunology, Bucharest, Romania
3 Donatur GmbH, Martinsried, Germany

Natural compounds are known to have a variety of anti-inflammatory and analgesic effects. We report that MCS-Ab-162, extracted from the roots of Helleborus purpurascens, inhibits the capsaicin- and acid-induced increases in intracellular calcium concentration ([Ca2+]i) mediated by TRPV1 in cultured dorsal root ganglion (DRG) neurons. DRG neurons were held in primary culture for 24 hours. Changes in [Ca2+]i were measured with microfluorimetry, using the calcium indicator Calcium Green-1 AM. The control experiment consisted in 5 consecutive applications of the specific TRPV1 agonist capsaicin (300 nM for 15s, at 4 min interval) or of an acidic extracellular solution (pH 5.5 for 15 s, at 4 min interval). In another set of experiments, the neurons were pre-treated with MCS-Ab-162 (1 µg/ml) for 2 min before and during the 3rd application of capsaicin (or pH 5.5). In the experiments carried out with acidic solutions, a saturating concentration of capsaicin (2 µM) was applied at the end of the experiment, in order to distinguish capsaicin-sensitive from capsaicin-insensitive neurons. MCS-Ab-162 induced a profound (~80%) inhibition of the response to capsaicin, and a smaller (~50%) inhibition of the response to pH 5.5 in capsaicin-sensitive DRG neurons. In both cases the effect was reversible within 4 min of washing out. In contrast, MCS-Ab-162 had no effect on the increases in [Ca2+]i induced by pH 5.5 in capsaicin-insensitive DRG neurons, most likely mediated by acid-sensing ion channels (ASICs). The increases in [Ca2+]i induced by the specific TRPA1 agonist cinnamaldehyde were also not reduced in the presence of MCS-Ab-162. In patch-clamp experiments, MCS-Ab-162 (1 µg/ml) was able to block almost fully the capsaicin-induced inward currents in DRG neurons held at -60 mV, in both the whole-cell mode and in excised outside-out patches. Taken together, our results indicate that MCS-Ab-162 is a specific antagonist of the polymodal receptor TRPV1, inhibiting its activation by both capsaicin and acidic solutions. As TRPV1 is known to play an essential role in inflammatory heat hyperalgesia, we believe that MCS-Ab-162 is a promising candidate for treating inflammatory pain states such as arthritis.

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