Aims: Propofol, clinically named as Diprivan is an intravenous anesthetic known to cause hypotension in patients presenting for surgery. We have investigated the vasodilatory signaling cascade by which propofol causes hypotension using both in vivo and in vitro experimental approaches.
Methods and Results: Using high-fidelity microtip transducer catheter, mean arterial blood pressure (MAP) was measured in control, transient receptor potential ankyrin subtype 1 knock-out (TRPA1-/-), transient receptor potential vanilloid 1 knock-out (TRPV1-/-) and TRPA1-TRPV1 double-knockout mice (TRPAV-/-) in the presence and absence of L-NAME (an endothelial nitric oxide synthase inhibitor) and penitrem A [a big-conductance calcium gated (BKCa) channel inhibitor]. To further support our in-vivo data, murine coronary microvessels were isolated and cannulated for vasoreactivity studies. Furthermore, NO production from endothelial cells isolated from mouse aorta was also measured and immunocytochemical (ICC) studies were performed to show the intracellular localization of TRPA1 and TRPV1. Our in-vivo data shows that the characteristic propofol-induced depressor response is dependent on TRPA1-NO-BKCa pathway. Interestingly, vasoreactivity studies in isolated murine left anterior ascending (LAD) arteries demonstrate that TRPA1 and TRPV1 communicate with each other and propofol-induced vasodilation is dependent on both TRPA1 and TRPV1. Moreover our data also suggest that NO production and BK channel activation are the downstream mediators in this pathway. Finally, we demonstrate that NO production is attenuated in primary endothelial cells isolated from TRPAV-/- mice. ICC data also shows the co-localization of these channels in mouse aortic endothelial cells.
Conclusions:This is the first study which has shown that propofol-induced vasodilation involves TRPA1 in-vivo and also there is an implication of cross-talk between TRPA1 and TRPV1 in the coronary bed. Furthermore by understanding the mechanisms by which this anesthetic causes hypotension and coronary dilation will help to mitigate the potential harmful side-effects of anesthesia in patients with little cardiovascular reserve. This will in turn ensure a better and faster post-operative recovery in patients, especially benefiting those suffering from diabetes and other cardiovascular disorders.