Acetylcholine for Blood Vessel Function

(CAP NOVA Trial)

Overseen By Anna Stanhewicz, PhD

Age: 18 - 65

Sex: Any

Trial Phase: Phase < 1

Sponsor: University of Iowa

Must not be taking: Stimulants, Antihypertensives, Statins

Disqualifiers: Cardiovascular, Metabolic, Renal, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Approved in 2 Jurisdictions This treatment is already approved in other countries

Compensation: Varies

Number of Visits: 1

56 Participants Needed

Trial Summary

Will I have to stop taking my current medications?

The trial requires that you do not use medications that could affect blood vessel function, like stimulants or blood pressure medications, within 8 weeks before joining. If you're on such medications, you may need to stop them to participate.

What evidence supports the effectiveness of the drug Acetylcholine for improving blood vessel function?

Research shows that Acetylcholine can lower blood pressure by causing blood vessels to widen through a process involving nitric oxide, a natural substance that helps relax blood vessels. This effect has been observed in studies with mice and human cells, suggesting that Acetylcholine may help improve blood vessel function. ^{1 2 3 4 5}

Is acetylcholine generally safe for use in humans?

Acetylcholine has been studied in humans and animals for its effects on blood vessels, showing it can cause blood vessels to widen (vasodilation) without significant safety concerns reported in these studies. ^{4 6 7 8 9}

How does the drug acetylcholine differ from other treatments for blood vessel function?

Acetylcholine is unique because it works by stimulating the release of nitric oxide from the lining of blood vessels, which helps them relax and improve blood flow. This mechanism is different from many other treatments that may not directly target the endothelial cells (cells lining the blood vessels) to produce this effect. ^{1 10 11 12 13}

What is the purpose of this trial?

The increase in skin blood flow in response to rapid local heating of the skin (i.e., cutaneous vasodilation) is commonly used to assess nitric oxide (NO)-dependent dilation and overall microvascular function. Historically, rapid local heating to 42°C was considered the standard approach for these assessments. More recently, many investigators have adopted rapid local to 39°C instead, based on its larger dependency on NO and therefore improved ability to quantify NO-dependent dilation without the use of pharmacological techniques. However, to date, only one direct methodological comparison between these protocols has been performed. In this study, the investigators use the blood vessels in the skin as a representative vascular bed for examining mechanisms of microvascular dysfunction in humans. Using a minimally invasive technique (intradermal microdialysis for the local delivery of pharmaceutical agents) they examine the blood vessels in a nickel-sized area of the skin in young adults ages 18 - 30 years old. Local heating of the skin at the microdialysis sites is used to explore differences in mechanisms governing microvascular control. As a compliment to these measurements, the investigators also have participants fill out a variety of surveys to assess things such as sleep quality, physical activity, daily stressors, etc.

Eligibility Criteria

This trial is for young adults aged 18-30 who are interested in participating in a study examining blood vessel function in the skin. The study involves local heating of the skin and filling out surveys related to lifestyle factors like sleep, physical activity, and stress.

Inclusion Criteria

I am either a man or a woman.

Exclusion Criteria

Pregnancy (including a positive urine pregnancy test) or breast-feeding

I have taken medication that could affect blood vessel function in the last 8 weeks.

Non-English-speaking. Participants need to understand English to follow instructions and comply with procedures conducted during the screening and experimental visits.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Baseline Assessment

Participants undergo baseline assessments including microvascular blood flow response to acetylcholine and local heat at 42°C and 39°C using laser-Doppler flowmetry and intradermal microdialysis.

1 day

1 visit (in-person, average of 4 hours)

Follow-up

Participants are monitored for any adverse effects and overall health status after the baseline assessment.

4 weeks

Treatment Details

Interventions

• Acetylcholine

Trial Overview The trial is testing how well blood vessels in the skin respond to heat as a way to assess nitric oxide-dependent dilation. It compares two different temperatures (39°C and 42°C) using intradermal microdialysis—a technique that delivers drugs directly into the skin.

Participant Groups

Group I: assessment of microvascular endothelial function Experimental Treatment 1 Intervention

The investigators use intradermal microdialysis to deliver acetylcholine, L-NAME, and acetylcholine + L-NAME to the cutaneous microvasculature.

Acetylcholine is already approved in United States, European Union for the following indications:

Approved in United States as Miochol-E System Pak for:

• Anterior segment surgery where rapid miosis may be required

Approved in European Union as Acetylcholine for:

• Anterior segment surgery where rapid miosis may be required

Who Is Running the Clinical Trial?

University of Iowa

Lead Sponsor

Trials

486

Recruited

934,000+

Findings from Research

Administration of recombinant choline acetyltransferase (ChAT) in mice with angiotensin II-induced hypertension significantly reduced blood pressure through nitric oxide-dependent vasodilation, demonstrating its potential as a therapeutic intervention.

A modified version of ChAT, PEG-ChAT, showed a longer-lasting effect on lowering blood pressure compared to regular ChAT, suggesting that enhancing the stability of ChAT could improve its efficacy in treating hypertension.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Systemic administration of choline acetyltransferase decreases blood pressure in murine hypertension. Stiegler, A., Li, JH., Shah, V., et al.[2023]

The M3 muscarinic acetylcholine receptor is crucial for mediating both vasodilation in intact ophthalmic arteries and vasoconstriction in arteries without endothelium, as shown in studies using M3 receptor-deficient mice and wild-type controls.

In endothelium-removed arteries, acetylcholine-induced vasoconstriction was significantly reduced in M3R(-/-) mice, highlighting the M3 receptor's role in cholinergic responses, while responses to other agents like nitric oxide remained unaffected, indicating a specific mechanism of action for the M3 receptor.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Role of the M3 muscarinic acetylcholine receptor subtype in murine ophthalmic arteries after endothelial removal. Gericke, A., Steege, A., Manicam, C., et al.[2021]

Acetylcholine causes a rapid dilation of cerebral blood vessels in guinea pigs, which is mediated by nitric oxide release and can be blocked by atropine, indicating its role in regulating blood flow.

In conditions where nitric oxide production is inhibited, acetylcholine can lead to a slow vasoconstriction, suggesting that under certain circumstances, it may worsen blood flow during brain ischemia due to endothelial damage.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Nitric oxide synthase inhibitors unmask acetylcholine-mediated constriction of cerebral vessels in the in vitro isolated guinea-pig brain. Librizzi, L., Folco, G., de Curtis, M.[2019]

Acetylcholine (Ach) stimulates nitric oxide (NO) production in human brain microvascular endothelial cells through a calcium-dependent mechanism, specifically via M5 muscarinic receptors, which are crucial for this process.

The study reveals that the increase in intracellular calcium concentration induced by Ach is essential for NO release, highlighting the role of M5-mAchRs and calcium signaling in regulating cerebral blood flow.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Muscarinic M5 receptors trigger acetylcholine-induced Ca2+ signals and nitric oxide release in human brain microvascular endothelial cells. Zuccolo, E., Laforenza, U., Negri, S., et al.[2020]

Alzheimer's disease (AD) patients showed impaired blood flow regulation in the brain, indicated by increased damping in flow responses and lower resting flow velocities compared to healthy controls.

Treatment with acetylcholinesterase inhibitors (AChEI) like donepezil improved these blood flow responses in a dose-dependent manner, suggesting that enhancing cholinergic function may help restore blood supply to active neurons in AD.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Acetylcholine esterase inhibitor donepezil improves dynamic cerebrovascular regulation in Alzheimer patients. Rosengarten, B., Paulsen, S., Molnar, S., et al.[2022]

All five muscarinic receptor subtypes were found in murine ophthalmic arteries, with M(3) and M(5) receptors showing higher expression levels, indicating their potential importance in vascular function.

The study revealed that M(3) receptors play a crucial role in regulating the dilation of ophthalmic arteries in response to acetylcholine, as their absence significantly impaired this response, while M(5) receptors did not affect this mechanism.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cholinergic responses of ophthalmic arteries in M3 and M5 muscarinic acetylcholine receptor knockout mice. Gericke, A., Mayer, VG., Steege, A., et al.[2021]

Acetylcholine (ACh) induces hyperpolarization and relaxation of the guinea pig coronary artery, but this effect is dependent on the presence of the endothelium, as removing it abolishes these responses.

The study suggests that ACh's ability to relax blood vessels involves both endothelial-derived factors stimulating guanylate cyclase and hyperpolarization of smooth muscle, highlighting the importance of endothelial function in vascular responses.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of ACh on electrical and mechanical activity in guinea pig coronary arteries. Keef, KD., Bowen, SM.[2017]

In a study involving 20 normotensive volunteers, both acetylcholine (ACh) and methacholine (MCh) caused dose-dependent vasodilation, with MCh being significantly more potent, likely due to the rapid degradation of ACh in plasma.

The findings suggest that the M3 muscarinic receptor subtype primarily mediates cholinergic vasodilation in the forearm resistance vasculature, as indicated by the rank order of potency of receptor antagonists used in the study.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

In vivo characterization of vasodilating muscarinic-receptor subtypes in humans. Bruning, TA., Hendriks, MG., Chang, PC., et al.[2019]

Acetylcholine (ACh) can trigger calcium (Ca2+) influx in rabbit aortic endothelial cells without needing to deplete intracellular calcium stores, indicating a novel mechanism of action for ACh in these cells.

The study found that both ACh and sarcoplasmic-endoplasmic reticulum Ca2+ ATPase blockers activated Ca2+ influx through similar pathways, suggesting that receptor activation and intracellular calcium store depletion may engage the same Ca2+ entry mechanisms.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Multiple mechanisms of activating Ca2+ entry in freshly isolated rabbit aortic endothelial cells. Wang, X., van Breemen, C.[2019]

Acetylcholine is not only a key neurotransmitter in the nervous system but also plays significant roles in nonneuronal tissues, including red blood cells, where it regulates various physiological processes.

Recent research highlights the importance of acetylcholine in red blood cell functions such as rheology, ion concentration balance, nitric oxide metabolism, and protein phosphorylation, suggesting potential new therapeutic targets for vascular health.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Nonneuronal cholinergic system in human erythrocytes: biological role and clinical relevance. de Almeida, JP., Saldanha, C.[2021]

Acetylcholine (ACh) induces three distinct types of vasomotion in porcine ear veins, with relaxation occurring at concentrations above 10(-9) M, which can be inhibited by atropine, indicating the involvement of muscarinic receptors.

The study found that intraluminal application of ACh resulted in stronger dilation and subsequent contraction compared to extraluminal application, suggesting that the receptors responsible for these responses are primarily located on the inside of the vessel wall.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effects of acetylcholine on different muscarinic receptors in the perfused porcine ear vein. Schneider, E., Felix, W.[2019]

Acetylcholine plays a crucial role in regulating blood vessel tone, which affects blood flow and pressure.

Understanding how acetylcholine influences blood vessel function can help in developing treatments for cardiovascular diseases.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Endothelial biology in humans: from acetylcholine testing in coronary arteries to personalized management of coronary heart disease. Berry, D.[2015]

Acetylcholine, traditionally thought to primarily cause blood vessel dilation, actually has a more complex role, often leading to constriction in many species, including humans, particularly in the coronary circulation.

The presence of both endothelium-derived relaxing factor (EDRF) and cholinergic constrictor receptors complicates our understanding of vascular responses, suggesting that cholinergic constriction may contribute to conditions like coronary artery spasm and sudden death.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cholinergic constriction in the general circulation and its role in coronary artery spasm. Kalsner, S.[2019]

References

1. England pubmed.ncbi.nlm.nih.gov

Systemic administration of choline acetyltransferase decreases blood pressure in murine hypertension. [2023]

2. United States pubmed.ncbi.nlm.nih.gov

Role of the M3 muscarinic acetylcholine receptor subtype in murine ophthalmic arteries after endothelial removal. [2021]

3. United States pubmed.ncbi.nlm.nih.gov

Nitric oxide synthase inhibitors unmask acetylcholine-mediated constriction of cerebral vessels in the in vitro isolated guinea-pig brain. [2019]

4. United States pubmed.ncbi.nlm.nih.gov

Muscarinic M5 receptors trigger acetylcholine-induced Ca2+ signals and nitric oxide release in human brain microvascular endothelial cells. [2020]

5. Germany pubmed.ncbi.nlm.nih.gov

Acetylcholine esterase inhibitor donepezil improves dynamic cerebrovascular regulation in Alzheimer patients. [2022]

6. United States pubmed.ncbi.nlm.nih.gov

Cholinergic responses of ophthalmic arteries in M3 and M5 muscarinic acetylcholine receptor knockout mice. [2021]

7. United States pubmed.ncbi.nlm.nih.gov

Effect of ACh on electrical and mechanical activity in guinea pig coronary arteries. [2017]

8. United States pubmed.ncbi.nlm.nih.gov

In vivo characterization of vasodilating muscarinic-receptor subtypes in humans. [2019]

9. Switzerland pubmed.ncbi.nlm.nih.gov

Multiple mechanisms of activating Ca2+ entry in freshly isolated rabbit aortic endothelial cells. [2019]

10. United States pubmed.ncbi.nlm.nih.gov

Nonneuronal cholinergic system in human erythrocytes: biological role and clinical relevance. [2021]

11. England pubmed.ncbi.nlm.nih.gov

Effects of acetylcholine on different muscarinic receptors in the perfused porcine ear vein. [2019]

12. England pubmed.ncbi.nlm.nih.gov

Endothelial biology in humans: from acetylcholine testing in coronary arteries to personalized management of coronary heart disease. [2015]

13. United States pubmed.ncbi.nlm.nih.gov

Cholinergic constriction in the general circulation and its role in coronary artery spasm. [2019]