Jitka Čejková

Effect of UVA and UVB Irradiation on the Metabolic Profile of Rabbit Cornea and Lens Analysed by HR-MAS 1H NMR Spectroscopy

Purpose:The aim of the study was to investigate the metabolic profiles of intact rabbit corneas and lenses exposed to UVA and UVB radiation by using high-resolution (HR) magic angle spinning (MAS) 1H nuclear magnetic resonance (NMR) spectroscopy and pattern recognition methods. Methods:Adult albino rabbits were exposed to UVA (366 nm, 0.589 J/cm2) or UVB (312 nm, 1.667 J/cm2) radiation for 8 min, once a day for 5 days. Three days after the last irradiation day, samples of corneas and lenses were dissected. HR-MAS 1H NMR spectroscopy combined with pattern recognition methods (principal component analysis and soft independent modelling of class analogy) and one-way ANOVA were applied to obtain metabolic information from intact corneal and lens tissue. Results: UVB irradiation caused statistically significant metabolic changes in the rabbit corneas. A decrease in metabolites as ascorbate (84%), myo-inositol (59%), hypotaurine (91%) and choline (76%) was observed. Exposure to UVA radiation caused no significant metabolic alteration in this tissue. The metabolic profile of the rabbit lenses showed no detectable changes after UVA or UVB exposure. Conclusions:The combination of HR-MAS 1H NMR spectroscopy and multivariate methods proved effective to analyse intact corneal and lens tissue after exposure to UV radiation of different wavelengths. By avoiding extraction methods and obtaining complete metabolic profiles from one sample, HR-MAS 1H NMR spectroscopy provided important information about metabolic alteration occurring in rabbit corneal and lens tissue after UV exposure.

Oxidative Stress to the Cornea, Changes in Corneal Optical Properties, and Advances in Treatment of Corneal Oxidative Injuries

Oxidative stress is involved in many ocular diseases and injuries. The imbalance between oxidants and antioxidants in favour of oxidants (oxidative stress) leads to the damage and may be highly involved in ocular aging processes. The anterior eye segment and mainly the cornea are directly exposed to noxae of external environment, such as air pollution, radiation, cigarette smoke, vapors or gases from household cleaning products, chemical burns from splashes of industrial chemicals, and danger from potential oxidative damage evoked by them. Oxidative stress may initiate or develop ocular injury resulting in decreased visual acuity or even vision loss. The role of oxidative stress in the pathogenesis of ocular diseases with particular attention to oxidative stress in the cornea and changes in corneal optical properties are discussed. Advances in the treatment of corneal oxidative injuries or diseases are shown.

Histochemical Study of Leukocyte Elastase Activity in Alkali-Burned Rabbit Cornea

In order to contribute to a better understanding of the role of leukocyte elastase in corneal melting after a severe alkali burn, the in situ appearance and activity of this enzyme in the rabbit cornea was examined. For this reason, a histochemical approach using cryostat sections on membranes and a gel incubation medium with the very sensitive substrate Mu-Ala-Ala-Pro-Val-7-amino-4-trifluoromethylcoumarin (Enzyme Systems Products, Livermore, Calif., USA) was employed. In contrast to the normal rabbit cornea where leukocyte elastase activity was absent, in alkali-burned cornea a high enzyme activity in inflammatory cells (particularly polymorphonuclear leukocytes) was present. The extracellular release of leukocyte elastase into the substantia propria of the corneal stroma was associated with disintegration of the corneal stroma and the appearance of corneal ulcers. These results show that leukocyte elastase is associated with corneal destruction after a severe alkali burn.