Choline Acetyltransferase Administration Decrease Blood Pressure in a Murine Model of Hypertension

Abstract

Despite significant advances in anti-hypertensive therapy, more than half of hypertensive patients fail to control their blood pressure. The estimated morbidity associated with hypertension is over 30% worldwide, and many hypertensive patients progressively develop cardiovascular disease and chronic kidney disease. Thus, the development of novel antihypertensive therapies is required. Acetylcholine, released by cholinergic neurons and lymphocytes, is a major mediator of endothelium-dependent, arterial smooth muscle relaxation that decreases blood pressure. Here, we assessed the effects of choline acetyltransferase (ChAT), a rate-limiting enzyme in acetylcholine biosynthesis, on decreasing arterial blood pressure in a preclinical model of hypertension. Hypertension was induced in mice using subcutaneous infusion of angiotensin II via osmotic mini-pumps. A single injection of ChAT beginning as late as two weeks after induction of hypertension decreases mean arterial blood pressure (MAP) (121 ± 4 mmHg vehicle vs 107 ± 8 mmHg ChAT, p = 0.06). Acetylcholine acts on muscarinic receptors on endothelial cells and produces arterial relaxation by activating endothelial nitric oxide (NO) synthase that produces NO from L-arginine. To investigate whether ChAT administration stimulates these mechanisms of NO production, we pretreated mice with NOS inhibitor Nω -nitro-L-arginine methyl ester (L-NAME), and measured blood pressure following administration of ChAT. Administration of L-NAME significantly attenuates ChAT-mediated decrease in blood pressure (4.3 ± 6.1 %MAP × h vs25.4 ± 4.9 %MAP × h, p = 0.02). To increase the stability and decrease the immunogenicity of the exogenous ChAT, the protein was PEGylated by covalently coupling polyethylene glycol with ChAT. Activity analysis revealed that PEGylated ChAT (PEG-ChAT) retains enzymatic activity. A single intraperitoneal administration of PEG-ChAT significantly reduces MAP as compared to vehicle injection (121 ± 4.5 mmHg vehicle vs 102 ± 4 mmHg PEG-ChAT 1 mg/kg, p = 0.01). Finally, administration of ChAT and PEG-ChAT during the sleep cycle produces a robust decrease in arterial blood pressure. These observations present administration of ChAT as a novel therapeutic strategy for preventing the progression of established hypertension.