Dietary Cinnamaldehyde Activation of TRPA1 Antagonizes High-Salt-Induced Hypertension Through Restoring Renal Tubular Mitochondrial Dysfunction.

Background: The renal proximal tubule (RPT) plays a pivotal role in regulating sodium reabsorption and thus blood pressure (BP). Transient receptor potential ankyrin 1 (TRPA1) has been reported to protect against renal injury by modulating mitochondrial function. We hypothesize that the activation of TRPA1 by its agonist cinnamaldehyde may mitigate high-salt intake-induced hypertension by inhibiting urinary sodium reabsorption through restoration of renal tubular epithelial mitochondrial function.

Methods: Trpa1-deficient (Trpa1-/-) mice and wild-type (WT) mice were fed standard laboratory chow [normal diet (ND) group, 0.4% salt], standard laboratory chow with 8% salt [high-salt diet (HS) group], or standard laboratory chow with 8% salt plus 0.015% cinnamaldehyde [high-salt plus cinnamaldehyde diet (HSC) group] for 6 months. Urinary sodium excretion, reactive oxygen species (ROS) production, mitochondrial function, and the expression of sodium hydrogen exchanger isoform 3 (NHE3) and Na+/K+-ATPase of RPTs were determined.

Results: Chronic dietary cinnamaldehyde supplementation reduced tail systolic BP and 24-hour ambulatory arterial pressure in HS-fed WT mice. Compared with the mice fed HS, cinnamaldehyde supplementation significantly increased urinary sodium excretion, inhibited excess ROS production, and alleviated mitochondrial dysfunction of RPTs in WT mice. However, these effects of cinnamaldehyde were absent in Trpa1-/- mice. Furthermore, chronic dietary cinnamaldehyde supplementation blunted HS-induced upregulation of NHE3 and Na+/K+-ATPase in WT mice but not Trpa1-/- mice.

Conclusions: The present study demonstrated that chronic activation of Trpa1 attenuates HS-induced hypertension by inhibiting urinary sodium reabsorption through restoring renal tubular epithelial mitochondrial function. Renal TRPA1 may be a potential target for the management of excessive dietary salt intake-associated hypertension.