The effect of iodide iontophoresis on the antioxidative capacity of the tear fluid.

BACKGROUND: Environmental oxidative stress changing the properties of the tear fluid can lead to keratoconjunctivitis sicca (dry eye syndrome). The aim of this study was to determine whether iodide iontophoresis influences the antioxidative capacity (ACW = water soluble antioxidative capacity) of the tear fluid, and to compare iodide iontophoresis with other balneotherapeutic measures. METHODS: This prospective study evaluated 92 patients in four groups. Twenty-four patients were treated with iodide iontophoresis, 24 with other balneotherapeutic methods. Twenty-five patients received iodide iontophoresis combined with other balneotherapeutic methods and 21 persons received no treatment (control). Unstimulated tear fluid, serum and urine were collected. ACW was determined photochemically in tear fluid and serum; iodine was measured in urine photometrically. RESULTS: Iodide iontophoresis increases the ACW of the tear fluid but not the ACW of the serum. Other iodine therapies increase the ACW in serum but not in tear fluid. Iodine excretion in urine was increased in all treated groups compared to the control. CONCLUSION: The increase of ACW in tear fluid after iodide iontophoresis can support the defense mechanism of the eye against oxidative influence effects, which may alleviate the symptoms of keratoconjunctivitis sicca.

Dual method for the determination of peroxidase activity and total peroxides-iodide leads to a significant increase of peroxidase activity in human sera.

Peroxidases are very important enzymes, e.g., as preventive antioxidants by removing noxious peroxides from the blood. For this reason we evaluated a colorimetric method which detects the activity of endogenous peroxidases by their reaction with hydrogen peroxide, using tetramethylbenzidine as the chromogenic substrate. This assay design can be easily reversed by change of the variable compound to measure also total peroxides in plasma or serum. An increased total antioxidant status was reported previously by the addition of iodide to human serum. In this study iodide activated the endogenous peroxidases significantly in comparison to control sera and isomolar NaCl as well as horseradish peroxidase. Corresponding to the increased peroxidase activity a concomitant decrease of total peroxides occurred in the same samples. This exchangeable assay design is a beneficial opportunity to screen total peroxide levels as well as peroxidase activity in human sera without time-consuming preparations. The method proved to be simple and is favorable due to its specificity, reproducibility, and low costs. Moreover, we were able to find an explanation for the increased total antioxidant status in the presence of iodide, which is presumably an indirect protective effect via an enhanced activity of enzymatic antioxidants, thereby reducing endogenous peroxides.

Protection by iodide of lens from selenite-induced cataract.

BACKGROUND: Iodide has been used empirically against different age-related eye diseases, including cataract. The purpose of the present study was to investigate the effect of iodide on selenite-induced cataract in rat lens. METHODS: Young white rats received subcutaneously sodium selenite (20 and 30 nmol/g b.w.) on day 13 post partum (p.p.). Cataract development was measured by expert estimation and image data analysis. Potassium iodide (1.5 nmol/g b.w.) was given (1-5 times) i.p. at different times with respect to the selenite administration. Lens opacification was analyzed in selenite, selenite-iodide, iodide and control groups on day 7 after selenite administration. RESULTS: Iodide showed a significant protective effect against selenite cataract when injected 2 days (2 times) before selenite injection, i.e., on days 11 and 12 p.p. No significant effects on lens opacity were found: (1) after only one iodide injection (on day 12 p.p.), (2) after an initial iodide administration 1 h before selenite and (3) after injections of iodide once a day for 5 consecutive days. The protective effect of iodide was the same (about 50%) for both selenite doses used. CONCLUSIONS: There is a time-dependent protective influence of iodide against selenite cataract development. It is supposed that the anticataract effect of iodide could be based on direct or indirect antioxidant mechanisms.

Iodide protection from UVB irradiation-induced degradation of hyaluronate and against UVB-damage of human conjunctival fibroblasts.

BACKGROUND: To determine whether iodide protects from UVB irradiation-induced destruction of hyaluronate and against UVB injury of cultured human conjunctival fibroblasts. METHODS: Hyaluronate and primary cultured human conjunctival fibroblasts were incubated with various concentrations of iodide and then exposed to UV light irradiation of 312 nm. Hyaluronate destruction was determined by viscosity measurements. Cell viability was assessed with MTT assay. RESULTS: Iodide protects hyaluronate from UVB light-induced degradation of this macromolecule in a concentration-dependent manner. Incubation of human conjunctival fibroblasts with iodide inhibited cells from damage by UVB light. CONCLUSION: Iodide protects hyaluronate, a component of tear fluid and tissues of the anterior part of the eye, against UVB light-induced degradation. Also, injury of human conjunctival cells can be prevented by incubation with iodide before UVB irradiation. The mechanism of protection is likely to include an antioxidative reaction. To support the natural defence mechanisms of the eyes, the administration of an antioxidant such as iodide to artificial tears, for example, may help to prevent the damage of the eye provoked by oxidative stress.