Abstract-Environmental cold is a nonmodifiable hypertension risk factor. Transient receptor potential melastatin subtype 8 (TRPM8) is a cold-sensing cation channel that can be activated by menthol, a compound with a naturally cold sensation in mint. Little is known about the effect of TRPM8 activation on vascular function and blood pressure. Here, we report that TRPM8 is abundantly expressed in the vasculature. TRPM8 activation by menthol attenuated vasoconstriction via RhoA/Rho kinase pathway inhibition in wild-type mice, but the effect was absent in TRPM8 −/− mice. Chronic dietary menthol blunted mesenteric arterial constriction and lowered blood pressure in genetic hypertensive rats via inhibition of RhoA/Rho kinase expression and activity in the vivo study. TRPM8 effect was associated with inhibition of intracellular calcium release from the sarcoplasmic reticulum, RhoA/Rho kinase activity, and sustained arterial contraction in the vitro study. Importantly, 8-week chronic menthol capsule treatment moderately lowered systolic blood pressure and diastolic blood pressure in prehypertensive individuals compared with the placebo group. Furthermore, chronic menthol capsule administration also improved flowmediated dilatation in prehypertensive individuals, but not in the placebo group. In conclusion, our study demonstrates that TRPM8 activation by menthol benefits vascular function and blood pressure by inhibiting calcium signaling-mediated RhoA/ Rho kinase activation in the vasculature. These findings add to the evidence that long-term dietary menthol treatment had
Materials and Methods
Animal TreatmentWe obtained male spontaneously hypertensive rats (SHR) and WistarKyoto rats (WKY) from Charles Rivers Laboratories (Malvern, PA) and obtained TRPM8 −/− mice from the laboratory of Dr Patapoutian.
6To maintain an isogenic strain, heterozygous knockout mice and their wild type (WT) littermates were maintained and used for experiments, as previously described 7 (online-only Data Supplement).
Cell CultureVascular smooth muscle cells (VSMCs) were obtained from the thoracic aortas of mice and cultured by the tissue explant method, as previously described 14 (online-only Data Supplement).
Intracellular Calcium MeasurementsFluorescence measurements were performed at 510 nm emission, with excitation wavelengths of 340 and 380 nm (Fluoroskan Ascent Fluorometer; Thermo Helsinki, Finland; online-only Data Supplement).
Blood Pressure MeasurementAnimals were implanted surgically with telemetric transmitters (Data Sciences International, MN), and 24-hour ambulatory systolic and diastolic pressures were measured by telemetry in conscious unrestrained animals 16 (online-only Data Supplement).
Prehypertensive Participant CharacteristicsPrehypertensive participants aged between 45 to 65 years were included in this study. The prehypertension diagnosis was based on systolic blood pressure (SBP) of 120 to 139 mm Hg or diastolic blood pressure of 80 to 89 mm Hg (online-only Data Supplement).
Flow-Mediated VasodilationFlow-mediated vasod...