Article: St John's Wort can cause photo-oxidative damage the the lens

Discussion in 'Optometry Archives' started by Francine, Sep 7, 2003.

  1. Francine

    Francine Guest

    1: Photochem Photobiol. 2003 Jul;78(1):88-92. Related Articles,

    Focal length variability and protein leakage as tools for measuring
    photooxidative damage to the lens.

    Wahlman J, Hirst M, Roberts JE, Prickett CD, Trevithick JR.

    Department of Biochemistry, University of Western Ontario, London,
    Ontario, Canada.

    Hypericin is the ingredient used to standardize the popular over-the-
    counter antidepressant medication St. John's Wort. Because hypericin
    readily produces singlet oxygen and other excited state
    intermediates, it is a very efficient phototoxic agent in the eye
    that can potentially induce the development of the cataract
    photooxidative mechanism. Hypericin absorbs in the UV and visible
    ranges, binds to the lens crystallins (alpha, beta and gamma) and
    damages these proteins through a photooxidative mechanism. Effects
    were measured previously using fluorescence, UV and mass
    spectrometry. We report here two additional methods to monitor lens
    damage: (1) measuring focal length variability using a ScanTox
    instrument and (2) measuring protein leakage from the damaged lens.
    Because nonenzymic glycation results in free radical production, we
    chose to use elevated glucose concentrations as a convenient model
    for studying oxidative stress. To compare and contrast photooxidative
    damage against oxidative damage to the lens, we also measured the
    focal length variability and protein leakage induced by the presence
    of elevated glucose concentrations. We found that the total
    accumulated protein leakage was positively correlated (r = 0.9) with
    variability in focal length. Lenses treated with hypericin and
    irradiated with UVB had an increase in focal length variability as
    compared with the lenses that were only UVB-irradiated. Lenses
    without UVB irradiation had much lower focal length variability than
    irradiated lenses. For non-hypericin-treated lenses, UVB-irradiated
    lenses had a larger variability (4.58 mm) than the unirradiated
    lenses (1.78 mm). The lenses incubated in elevated glucose
    concentrations had a focal length variability (3.23 mm) equivalent to
    that of the unirradiated hypericin-treated lenses (3.54 mm). We
    conclude that photooxidative damage by hypericin results in changes
    in the optical properties of the lens, protein leakage and finally
    cataract formation. In contrast to this, high concentrations of
    glucose induced protein leakage but not changes in optical properties
    or the opacity associated with a cataract. This work provides further
    evidence that people should protect their eyes from intense sunlight
    when taking St. John's Wort.

    PMID: 12929754 [PubMed - in process]
    Francine, Sep 7, 2003
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  2. Francine

    sqrrlbird Guest

    The FDA has a Public Health Advisory out on St. John's Wort as well.
    It has some nasty drun interactions. Personally, I wouldn't get near
    the stuff.

    February 10, 2000


    FDA/Center for Drug Evaluation and Research


    "Based on this study and reports in the medical literature, St. John's
    wort appears to be an inducer of an important metabolic pathway,
    cytochrome P450. As many prescription drugs used to treat conditions
    such as heart disease, depression, seizures, certain cancers or to
    prevent conditions such as transplant rejection or pregnancy (oral
    contraceptives) are metabolized via this pathway, health care
    providers should alert patients about these potential drug
    interactions to prevent loss of therapeutic effect of any drug
    metabolized via the cytochrome P450 pathway."



    sqrrlbird, Sep 7, 2003
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