Herbal Compounds and Toxins Modulating TRP Channels

Abstract

Although the benefits are sometimes obvious, traditional or herbal medicine is regarded with skepticism, because the mechanism through which plant compounds exert their powers are largely elusive. Recent studies have shown however that many of these plant compounds interact with specific ion channels and thereby modulate the sensing mechanism of the human body. Especially members of the Transient Receptor Potential (TRP) channels have drawn large attention lately as the receptors for plant-derived compounds such as capsaicin and menthol. TRP channels constitute a large and diverse family of channel proteins that can serve as versatile sensors that allow individual cells and entire organisms to detect changes in their environment. For this family, a striking number of empirical views have turned into mechanismbased actions of natural compounds. In this review we will give an overview of herbal compounds and toxins, which modulate TRP channels.

Evidence for the functional involvement of members of the TRP channel family in the uptake of Na+ and NH4 + by the ruminal epithelium

“…Capsaicin is known as a specific TRPV1 agonist [13,60]. Application of 100 μmol·l −1 to the mucosal standard NH 4 + buffer solution resulted in a significant decrease in current (ΔI scPeak = −3.25 ± 1.16 μA·cm −2 ; N/n = 4/6; p < 0.05) with subsequent washout (N/n = 4/6, Fig.…”

“…For further characterization, fragrant monoterpenoids that are known to interact with TRP channels of olfactory epithelia were added to the mucosal side of the tissue [60]. The serosal side of the epithelium was superfused with the standard NaCl buffer (pH 7.4) during all experiments.…”

“…In particular, we tested the response of the native epithelium to a number of monoterpenoids. These compounds are known for their highly specific interaction with channels of the transient receptor potential (TRP) channel family [14,40], famously allowing mammals to distinguish between the fragrance of a multitude of herbal compounds in a highly selective manner [42,60].…”

“…These genes encode for integral membrane proteins consisting of six transmembrane spanning segments, the assembly of which as homotetramers or heterotetramers results in the formation of cation-selective channels [39,43]. Channels of this family were initially identified in sensory organs [36], where various stimuli including light, heat, cold, or odorants lead to an opening of the channels with influx of Ca 2+ and Na + [42,60]. However, it is increasingly emerging that TRP channels also play important functional roles in many nonsensory tissues [39].…”

Targeting TRP channels for chronic cough: from bench to bedside

“…TRP channels are known as cellular sensors (Clapham 2003), as they respond to changes including temperature, stretch, chemicals, oxidation, osmolarity and pH (Picazo-Juárez et al 2011;Moran et al 2011) in the cellular environment. They are also sensors for certain herbs, spices, venoms and toxins (Vriens et al 2008). This family of ion channels has 28 members in six subfamilies (TRPC, TRPV, TRPM, TRPA, TRPP, TRPML) based on sequence homology and amino acid sequence (Clapham 2003), and all have six transmembrane domains with the pore situated between domains 5 and 6, variable degrees of ankyrin repeats and an intracellular N and C terminus (Caterina et al 1997;Ramsey et al 2006).…”