Discovering TRP Channels
(The following is an excerpt from my paper, "Solving the Riddle of Multiple Chemical Sensitivity: The Importance of TRP Channels," which can be downloaded from the home page of this site.)
Four months after the onset of my MCS, I stuck an air purifier in my car and drove up to Zion National Park to celebrate my 50th birthday in the most “safe” place I could imagine. However, an hour into a hike to the bottom of a gorgeous canyon in a remote area of the park, I had one of the worst MCS reactions I’d ever had – a complete headache-exploding, head-swimming, heart-slamming, throat-swelling, mouth-tingling reaction that sent me stumbling, panicked, back the way I came. Once I got away from the canyon bottom, I felt fine again. But it made zero sense to me to have a reaction there, I was far away from any other human beings and their scents and chemicals, I had eaten nothing but bland salicylate-free food that day. I was surrounded by nothing but pristine protected nature, and hiking at home in the Arizona desert always took away my reactions, not caused them. I had been feeling happy and easygoing in the preceding hour, so I simply couldn’t bend my mind to believe it was a stressed, hyperalert amygadala that had triggered the reaction. So what on earth had happened?
Later I would go online and google “flora and fauna of Zion canyon” and read that trees of the Salicilae famiy (willow trees) thronged the park’s canyon bottoms. There it was: salicylate, my nemesis. It never would have occurred to me that a tree could outgas a chemical that would set off an MCS reaction. I was horrified by this (I might never be able leave Arizona again!), but also fascinated by this. Exactly how had my body sensed that chemical was in the air?
I finally began asking myself questions I probably should have been asking months earlier. How does the human body ‘sense’ chemical irritants? Why and how might that sensing become dysfunctional? And, how was it possible that eating certain foods could evoke the exact same reactions as inhaling unrelated chemicals?
My questioning led me to revisit a post I had earlier seen on the Salicylate Sensitivity forum, but hadn’t really paid attention to at the time. Dated January 2011, the message posted by someone identified by “marieling,” said: “Basically people with food intolerance and quite a few other diseases have an over-expression of Transient Receptor Potential Cation Channels (TRP’s) - particularly TRPV1 and TRPA1.” Another poster identified as “black wizards” agreed and followed up with numerous links to studies on TRP channels – a group of ion channels in the surface membrane of sensory neurons. One of those links was to a 2004 paper by Martin Pall which asserted that the TRPV1 channel is the “target” of chemical irritants in MCS.
According to the paper, the TRPV1 receptor/channel is “a critical component in the ‘common chemical sense,’ located in the small C-fibers of the trigeminal nerve, which innervates a large part of the face, eyes, and upper airways, and provides an early warning for sensory irritation, telling the organism it has entered a zone of irritant chemicals.” As I read those words, I felt that jolt of excitement one feels when one discovers the key that will crack a long mysterious code.
Those posts and that paper launched me into months of research through the most recent studies on TRP channels. Though nearly all of the hundreds of TRP channel studies published over the past decade have looked at the channels in the broad context of chronic pain rather than the narrow context of MCS, chemical sensitivity is nothing if not a chronic pain condition. And as the pain is triggered by exposure to compounds which expressly activate TRP channels, I believe these “pain” studies also shed remarkable light on the most likely physiological mechanism underlying the development of many cases of MCS and salicylate sensitivity.
Next: The Stages of MCS