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OpenTrials
Completed

NCT Number: NCT01785511

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

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.

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Key information

Conditions

Hypertension Cardiovascular Diseases Vascular Diseases

Age range

18 year–45 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

University of Edinburgh

Edinburgh, Lothian, Eh16 4SA, United Kingdom

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

UVA Radiation

Radiation

UVA radiation exposure for 20 minutes

Primary outcomes

  1. Coronary Flow Reserve

    Time frame: 0, 20, 40 and 60 mins

    Change in coronary flow assessed pre and post UVA radiation versus control

Secondary outcomes

  1. Platelet Activation

    Time frame: 0, 20, 40 and 60 mins

    Platelet activation assessed using platelet monocyte activity

  2. Endogenous Fibrinolysis

    Time frame: 0, 20, 40 and 60 minutes

    Assessed using flow cytometry

Sponsors and collaborators

Lead sponsor

University of Edinburgh

Other

Registry information

Important dates

Study start
2012
Primary completion
2012
Study completion
2012
First posted
Feb 7, 2013
Registry last updated
Feb 20, 2013

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

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This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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