Effect of antioxidant enzymes on experimental uveitis in rats

Superoxide Dismutase 1 Nanoparticles (Nano-SOD1) as a Potential Drug for the Treatment of Inflammatory Eye Diseases

Inflammatory eye diseases remain the most common clinical problem in ophthalmology. The secondary processes associated with inflammation, such as overproduction of reactive oxygen species (ROS) and exhaustion of the endogenous antioxidant system, frequently lead to tissue degeneration, vision blurring, and even blindness. Antioxidant enzymes, such as copper-zinc superoxide dismutase (SOD1), could serve as potent scavengers of ROS. However, their delivery into the eye compartments represents a major challenge due to the limited ocular penetration. This work presents a new therapeutic modality specifically formulated for the eye on the basis of multilayer polyion complex nanoparticles of SOD1 (Nano-SOD1), which is characterized by appropriate storage stability and pronounced therapeutic effect without side reactions such as eye irritation; acute, chronic, and reproductive toxicity; allergenicity; immunogenicity; mutagenicity even at high doses. The ability of Nano-SOD1 to reduce inflammatory processes in the eye was examined in vivo in rabbits with a model immunogenic uveitis-the inflammation of the inner vascular tract of the eye. It was shown during preclinical studies that topical instillations of Nano-SOD1 were much more effective compared to the free enzyme in decreasing uveitis manifestations. In particular, we noted statistically significant differences in such inflammatory signs in the eye as corneal and conjunctival edema, iris hyperemia, and fibrin clots. Moreover, Nano-SOD1 penetrates into interior eye structures more effectively than SOD itself and retains enzyme activity in the eye for a much longer period of time, decreasing inflammation and restoring antioxidant activity in the eye. Thus, the presented Nano-SOD1 can be considered as a potentially useful therapeutic agent for the treatment of ocular inflammatory disorders.

Superoxide Dismutase 1 Nanozyme for Treatment of Eye Inflammation

Use of antioxidants to mitigate oxidative stress during ocular inflammatory diseases has shown therapeutic potential. This work examines a nanoscale therapeutic modality for the eye on the base of antioxidant enzyme, superoxide dismutase 1 (SOD1), termed "nanozyme." The nanozyme is produced by electrostatic coupling of the SOD1 with a cationic block copolymer, poly(L-lysine)-poly(ethyleneglycol), followed by covalent cross-linking of the complexes with 3,3'-dithiobis(sulfosuccinimidylpropionate) sodium salt. The ability of SOD1 nanozyme as well as the native SOD1 to reduce inflammatory processes in the eye was examined in vivo in rabbits with immunogenic uveitis. Results suggested that topical instillations of both enzyme forms demonstrated anti-inflammatory activity; however, the nanozyme was much more effective compared to the free enzyme in decreasing uveitis manifestations. In particular, we noted statistically significant differences in such inflammatory signs in the eye as the intensities of corneal and iris edema, hyperemia of conjunctiva, lens opacity, fibrin clots, and the protein content in aqueous humor. Clinical findings were confirmed by histological data. Thus, SOD1-containing nanozyme is potentially useful therapeutic agent for the treatment of ocular inflammatory disorders.

[Effects of dexamethasone and superoxide dismutase instillations on clinical course of uveitis and local biochemical processes (experimental study)]

AIM

to evaluate and compare the effect of topical superoxide dismutase (SOD), which is an antioxidant enzyme, dexamethasone, and a combination of these on the course of experimental uveitis in rabbits as well as biochemical parameters of aqueous and vitreous humor.

MATERIAL AND METHODS

Acute uveitis was induced in 16 rabbits by a double injection (subcutaneous and intravitreal) of normal horse serum. Of them 12 animals, divided into 3 groups of 4 each, received topical SOD, dexamethasone, or both daily for 7 days. The remaining 4 rabbits (8 eyes) were treated with placebo and, thus, constituted the control group. On day 8 the following parameters were measured in aqueous humor: protein concentration, antioxidant activity, SOD activity, α2-macroglobulin level, and leukocyte number. Total protein and albumin levels in vitreous humor were also determined.

RESULTS

The effects of SOD and dexamethasone instillations were considered similar in many parameters. However, SOD was associated with a greater increase in antioxidant activity and a greater decrease in aqueous humor leukocytes, while dexamethasone was more effective in decreasing aqueous humor α2-macroglobulin and vitreous humor protein and albumin. The substances had a synergistic effect on iridal edema as well as aqueous humor leukocyte number and α2-macroglobulin level. CONCLUSION. Adding SOD to the complex therapy of uveitis results in lower inflammation intensity and enhanced dexamethasone effect.

Alpha-tocopherol protects against oxidative damage to lipids of the rod outer segments of the equine retina

Oxidative stress is a possible risk factor for eye diseases. Lipid peroxidation is one of the major events induced by oxidative stress and is particularly active in polyunsaturated fatty acid (PUFA)-rich biomembranes. This work evaluated endogenous lipid antioxidants, in vitro non-enzymatic lipid peroxidation of rod outer segment membranes (ROS), the fatty acid composition during oxidative damage of total lipids from equine retina and ROS, and the protective action of alpha-tocopherol (alpha-Toc). The major lipid soluble antioxidant was alpha-Toc followed by retinoids and carotenoids. The retina contained a high percentage of PUFAs, mainly docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6). Lipid peroxidation of the equine ROS, induced by Fe(2+)-ascorbate, was monitored using chemiluminescence (CL) with or without pre-treatment with alpha-Toc. With alpha-Toc pre-treatment, CL values were significantly decreased. The most abundant fatty acid was 22:6n-3. After 3h incubation, 95% of total PUFAs were destroyed by peroxidation, whereas in alpha-Toc pre-treated ROS the percentage was significantly decreased. The results show that the retina has an endogenous lipid soluble antioxidant system. ROS were highly sensitive to oxidative damage, since their fatty acid composition was markedly modified during the lipid peroxidation process. The protective role of alpha-Toc as an antioxidant was evident and it could be used in the treatment of equine ocular diseases in which free radicals are involved.

Free radical mediated photoreceptor damage in uveitis

Uveitis is a major cause of blindness, with the visual loss that occurs being due primarily to retinal tissue damage. The tissue damage is mediated mainly by phagocytic inflammatory cells, such as macrophages, by the release of various proteolytic enzymes, arachidonic acid metabolites, cytokines and free radicals. The latter are found to be potent cytotoxic agents that readily cause tissue damage by peroxidation of lipid cell membranes. Recent studies of experimental uveitis indicate that other potent oxidants are generated in uveitis by macrophages. One of these is ONOO-, which is formed from *NO and O(-)2. The macrophages generate *NO preferentially in the outer retina following iNOS expression. In these phagocytes, outer retinal proteins, especially arrestin, are found to be potent iNOS inducers. Current studies of RPE show that these cells protect the retina from ONOO- mediated damage in uveitis by releasing a novel protein called retinal pigment epithelial protective protein. This protein is found to suppress O(-)2 and *NO generation by the phagocytes, in both in vitro and in vivo uveitis models. The protective protein expression is restricted to RPE, its suppressive effect is a result of the inhibition of the phosphorylation of cytosolic proteins, p47-phox, required for the assembly of NADPH and activation of NFkappaB, which are required for generation of 0(-)2 and expression of iNOS respectively. Either pharmacologically or chemically, up-regulation of RPP generation could help in preventing retinal degeneration in uveitis or other degenerative dis

Oral vitamins C and E as additional treatment in patients with acute anterior uveitis: a randomised double masked study in 145 patients

AIM

To investigate the effect of additional oral vitamins C and E on acute anterior uveitis.

METHODS

A placebo controlled double masked study on the effect of vitamin C 500 mg in combination with vitamin E 100 mg twice daily in 145 patients with acute anterior uveitis. As a primary end point variable, laser cell/flare measurements were performed. Best corrected and stenopeic visual acuity (VA) testing and clinical variable scores were measured.

RESULTS

Laser flare measurements (ph/s) before treatment were 207.1 (SD 258) in the vitamin group and 143.6 (156) in the placebo group. After 3 days corresponding values were 80.2 (129) and 54.7 (82), after 7 days 89.2 (187) (12.5) and 85.8 (208), after 14 days 47.1 (109.5) and 40.5 (116) after 28 days 23.1 (53.6) and 23.1 (48), and after 56 days 15.6 (26) and 15.3 (17). There was no significant difference in time trend between the two treatment groups (RMANOVA; p = 0.53). Baseline VA (logMAR) was 0.106 (0.241) in the vitamin group and 0.128 (0.456) in the placebo group. VA after 3 days was 0. 236 (0.293) and 0.344 ( 0.489), after 7 days 0.204 (0.292) and 0.292 (0.479), after 14 days 0.162 (0.274) and 0.193 (0.454), after 28 days 0.096 (0.232) and 0.158 (0.436), and 0.026 (0.213) and 0.106 (0. 437) after 56 days. Although no significant difference in time trend was detected, evaluation of the VA data of the last time point (56 days) by means of the Mann-Whitney test showed a significantly better VA in the vitamin group (p = 0.01).

CONCLUSIONS

There was no significant effect of vitamins C and E on laser flare measurements. The significant effect of the oral vitamins on visual acuity at 8 weeks after start of the oral vitamins C and E may indicate a protective effect in patients with acute anterior uveitis.