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

This study has been completed.
Sponsor:
Information provided by (Responsible Party):
University of Edinburgh
ClinicalTrials.gov Identifier:
NCT01785511
First received: June 20, 2012
Last updated: February 19, 2013
Last verified: February 2013
  Purpose

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.

Condition Intervention
Hypertension
Radiation: UVA Radiation

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Open Label
Primary Purpose: Basic Science
Official Title: Does Ultraviolet Irradiation Reduce Platelet Reactivity and Improve Coronary Microvascular Function in Man?

Resource links provided by NLM:


Further study details as provided by University of Edinburgh:

Primary Outcome Measures:
  • Coronary Flow Reserve [ Time Frame: 0, 20, 40 and 60 mins ] [ Designated as safety issue: No ]
    Change in coronary flow assessed pre and post UVA radiation versus control


Secondary Outcome Measures:
  • Platelet Activation [ Time Frame: 0, 20, 40 and 60 mins ] [ Designated as safety issue: No ]
    Platelet activation assessed using platelet monocyte activity

  • Endogenous Fibrinolysis [ Time Frame: 0, 20, 40 and 60 minutes ] [ Designated as safety issue: No ]
    Assessed using flow cytometry


Enrollment: 12
Study Start Date: March 2012
Study Completion Date: August 2012
Primary Completion Date: August 2012 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Sham Comparator: Sham UVA
sham exposure will be provided by covering the UVA lamps with space blanket.
Radiation: UVA Radiation
UVA radiation exposure for 20 minutes
Experimental: UVA Radiation
Patients will be exposed to UVA radiation for 20 minutes
Radiation: UVA Radiation
UVA radiation exposure for 20 minutes

  Eligibility

Ages Eligible for Study:   18 Years to 45 Years
Genders Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes
Criteria

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.
  Contacts and Locations
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Please refer to this study by its ClinicalTrials.gov identifier: NCT01785511

Locations
United Kingdom
University of Edinburgh
Edinburgh, Lothian, United Kingdom, Eh16 4SA
Sponsors and Collaborators
University of Edinburgh
Investigators
Principal Investigator: Ninian Lang, MbChB University of Edinburgh
  More Information

No publications provided

Responsible Party: University of Edinburgh
ClinicalTrials.gov Identifier: NCT01785511     History of Changes
Other Study ID Numbers: UVA Study
Study First Received: June 20, 2012
Last Updated: February 19, 2013
Health Authority: United Kingdom: National Research Ethics Committee

Keywords provided by University of Edinburgh:
hypertension
UV radiation
coronary flow reserve
nitric oxide

Additional relevant MeSH terms:
Hypertension
Vascular Diseases
Cardiovascular Diseases

ClinicalTrials.gov processed this record on July 23, 2014