Does Ultraviolet Irradiation Reduce Platelet Reactivity and Improve Coronary Microvascular Function in Man?

Hypertension Clinical Trial

Official title:

Does Ultraviolet Irradiation Reduce Platelet Reactivity and Improve Coronary Microvascular Function in Man?

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT01785511
• Other study ID #: UVA Study
• Status: Completed
• Phase: N/A
• First received: June 20, 2012
• Last updated: February 19, 2013
• Start date: March 2012
• Est. completion date: August 2012

Study information

• Verified date: February 2013
• Source: University of Edinburgh
• Contact: n/a
• Is FDA regulated: No
• Health authority: United Kingdom: National Research Ethics Committee
• Study type: Interventional

Clinical Trial Summary

Endothelium derived nitric oxide (NO) regulates vascular tone and blood pressure in man. NO also inhibits platelet aggregation and mediates a variety of beneficial anti-inflammatory and repair mechanisms. NO may also be a mediator in the release of the endogenous fibrinolytic factor, tissue-plasminogen activating factor (t-PA) from the endothelium.1 Via these actions it plays a very important role in protection of the vasculature from atherothrombosis and clinical sequelae such as myocardial infarction and stroke.

Visible and ultraviolet (UV) light relax vascular smooth muscles by producing NO in a phenomenon known as photorelaxation.2 The investigators have demonstrated significant stores of pre-formed, bound NO and other nitrosospecies in human skin, which are rapidly released upon exposure to UVA.3 The investigators have demonstrated recently that serum nitrite and nitroso-species are increased after standing in a UVA phototherapy cabinet and that local UVA exposure is associated with increased forearm arterial blood flow that is independent of skin temperature. The investigators have also demonstrated a fall in mean arterial blood pressure in subjects exposed UVA.

Cardiovascular morbidity and the prevalence of hypertension vary with latitude. The investigators hypothesise that some of this geographical variation may be explained by a diminished sunlight/UVA exposure with attendant negative effects upon NO bio-availability.4 To further examine the potential beneficial effects of UVA exposure we will examine the effects of whole-body UVA upon platelet activation and upon myocardial/coronary arterial flow reserve. The investigators will correlate these measures with systemic nitrate, nitrite and nitroso-species content in healthy volunteers.

HYPOTHESES

1. UVA irradiation enhances coronary flow reserve in healthy volunteers.

2. UVA irradiation suppresses platelet activation in healthy volunteers.

3. UVA irradiation enhances the release of endogenous fibrinolytic factors in healthy volunteers.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 12
• Est. completion date: August 2012
• Est. primary completion date: August 2012
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Male
• Age group: 18 Years to 45 Years

Eligibility

Inclusion Criteria:

• Healthy male volunteers aged between 18-45 years (inclusive).

Exclusion Criteria:

• Inability to provide informed consent

• Co-existent systemic disease (including any history of asthma, reactive airways disease or hypertension)

• Contraindication to UVA treatment

• Any history of cardiac conduction abnormality (including bundle branch block or atrial fibrillation)

• Smoker

• Current intake of aspirin, other non-steroid anti-inflammatory medications or any regular medication.

• Recent infective/inflammatory condition

• Echocardiographic evidence of left ventricular hypertrophy (left ventricular septal diameter >1.2 cm in diastole), systolic dysfunction or significant valvular stenosis or regurgitation.

Study Design

Allocation: Randomized, Intervention Model: Crossover Assignment, Masking: Open Label, Primary Purpose: Basic Science

Related Conditions & MeSH terms

• Hypertension

Intervention

Radiation:
• UVA Radiation
UVA radiation exposure for 20 minutes

Locations

Country	Name	City	State
United Kingdom	University of Edinburgh	Edinburgh	Lothian

Sponsors (1)

Lead Sponsor	Collaborator
University of Edinburgh

Country where clinical trial is conducted

United Kingdom, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Coronary Flow Reserve	Change in coronary flow assessed pre and post UVA radiation versus control	0, 20, 40 and 60 mins	No
Secondary	Platelet Activation	Platelet activation assessed using platelet monocyte activity	0, 20, 40 and 60 mins	No
Secondary	Endogenous Fibrinolysis	Assessed using flow cytometry	0, 20, 40 and 60 minutes	No