Cadmium-induced hypertension is associated with renal myosin light chain phosphatase inhibition via increased T697 phosphorylation and p44 mitogen-activated protein kinase levels.

Abstract

Dietary intake of the heavy metal cadmium (Cd2+) is implicated in hypertension, but potassium supplementation reportedly mitigates hypertension. This study aims to elucidate the hypertensive mechanism of Cd2+. Vascular reactivity and protein expression were assessed in Cd2+-exposed rats for 8 weeks to determine the calcium-handling effect of Cd2+ and the possible signaling pathways and mechanisms involved. Cd2+ induced hypertension in vivo by significantly (p < 0.001) elevating systolic blood pressure (160 ± 2 and 155 ± 1 vs 120 ± 1 mm Hg), diastolic blood pressure (119 ± 2 and 110 ± 1 vs 81 ± 1 mm Hg), and mean arterial pressure (133 ± 2 and 125 ± 1 vs 94 ± 1 mm Hg) (SBP, DBP, and MAP, respectively), while potassium supplementation protected against elevation of these parameters. The mechanism involved augmentation of the phosphorylation of renal myosin light chain phosphatase targeting subunit 1 (MYPT1) at threonine 697 (T697) (2.58 ± 0.36 vs 1 ± 0) and the expression of p44 mitogen-activated protein kinase (MAPK) (1.78 ± 0.20 vs 1 ± 0). While acetylcholine (ACh)-induced relaxation was unaffected, 5 mg/kg b.w. Cd2+ significantly (p < 0.001) attenuated phenylephrine (Phe)-induced contraction of the aorta, and 2.5 mg/kg b.w. Cd2+ significantly (p < 0.05) augmented sodium nitroprusside (SNP)-induced relaxation of the aorta. These results support the vital role of the kidney in regulating blood pressure changes after Cd2+ exposure, which may be a key drug target for hypertension management. Given the differential response to Cd2+, it is apparent that its hypertensive effects could be mediated by myosin light chain phosphatase (MLCP) inhibition via phosphorylation of renal MYPT1-T697 and p44 MAPK. Further investigation of small arteries and the Rho-kinase/MYPT1 interaction is recommended.