Superoxide Dismutase and Catalase Activities in the Retina during Experimental Diabetes and Electric Stimulation of the Paleocerebellar Cortex

Fatty acid oxidation and photoreceptor metabolic needs

Photoreceptors have high energy demands and a high density of mitochondria that produce ATP through oxidative phosphorylation (OXPHOS) of fuel substrates. Although glucose is the major fuel for CNS brain neurons, in photoreceptors (also CNS), most glucose is not metabolized through OXPHOS but is instead metabolized into lactate by aerobic glycolysis. The major fuel sources for photoreceptor mitochondria remained unclear for almost six decades. Similar to other tissues (like heart and skeletal muscle) with high metabolic rates, photoreceptors were recently found to metabolize fatty acids (palmitate) through OXPHOS. Disruption of lipid entry into photoreceptors leads to extracellular lipid accumulation, suppressed glucose transporter expression, and a duel lipid/glucose fuel shortage. Modulation of lipid metabolism helps restore photoreceptor function. However, further elucidation of the types of lipids used as retinal energy sources, the metabolic interaction with other fuel pathways, as well as the cross-talk among retinal cells to provide energy to photoreceptors is not fully understood. In this review, we will focus on the current understanding of photoreceptor energy demand and sources, and potential future investigations of photoreceptor metabolism.

Morphologic and biochemical changes in the retina and sclera induced by form deprivation high myopia in guinea pigs

BACKGROUND

To study the morphologic and biochemical changes in the retina and sclera induced by form deprivation high myopia (FDHM) in guinea pigs and explore the possible mechanisms of FDHM formation.

METHODS

Forty 3-week-old guinea pigs were randomized into the blank control (Group I, 20 cases) and model groups (20 cases). In the model group, the right eyes of the guinea pigs were sutured for 8 weeks to induce FDHM (Group II) and the left eyes were considered a self-control group (Group III). The refractive errors were measured with retinoscopy. The anterior chamber depth (AC), lens thickness (L), vitreous chamber depth (V) and axial length (AL) were measured using ultrasonometry A. Retinal and scleral morphology and ultrastructural features were observed with light and electron microscopy. The malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in the retina and sclera were detected with a chemical colorimetric assay.

RESULTS

After 8 weeks of stitching, the refractive errors of Group II changed from (+ 3.59 ± 0.33) D to (- 7.96 ± 0.55) D, and these values were significantly higher than those of Group I (+ 0.89 ± 0.32) D and Group III (- 0.55 ± 0.49) D (P < 0.05). The vitreous chamber depth (4.12 ± 0.13) mm and axial length (8.93 ± 0.22) mm of Group II were significantly longer than those of Group I [(3.71 ± 0.23) mm and (7.95 ± 0.37) mm, respectively] and Group III [(3.93 ± 0.04) mm and (8.01 ± 0.15) mm, respectively] (P < 0.05). With the prolongation of form deprivation (FD), the retina and scleral tissues showed thinning, the ganglion cell and inner and outer nuclear layers of the retina became decreased, and the arrangement was disordered. In Group II, the SOD activity was significantly lower than that in Group I and Group III; the MDA content was significantly higher than that in Group I and Group III. The differences were statistically significant (P < 0.05).

CONCLUSIONS

These findings suggested that in the FDHM guinea pigs model, the refractive errors, the vitreous chamber depth, and axial length increased significantly with prolongation of monocular FD time, and morphological structural changes in the retina and sclera were observed. Oxygen free radicals might participate in the formation of FDHM.

Subcutaneous delivery of tauroursodeoxycholic acid rescues the cone photoreceptors in degenerative retina: A promising therapeutic molecule for retinopathy

Inherited retinal degeneration (RD) comprises a heterogeneous group of retinopathies that rank among the main causes of blindness. Tauroursodeoxycholic acid (TUDCA) is taurine conjugate hydrophilic bile acid that demonstrates profound protective effects against a series of neurodegenerative diseases related to oxidative stress. This study sought to evaluate the TUDCA induced effects of on a pharmacologically induced RD animal model by electroretinogram (ERG) examination, behavior tests, morphological analysis and immunochemistry assay. Massive photoreceptor degeneration in mice retina was induced by an intraperitoneal administration of N-methyl-N-nitrosourea(MNU). Subcutaneous delivery of TUDCA inhibits effectively the photoreceptor loss and visual impairments in the MNU administered mice. In the retinal flat-mounts of TUDCA treated mice, the cone photoreceptors were efficiently preserved. Furthermore, the multi-electrodes array (MEA) was used to detect the firing activities of retinal ganglion cells within the inner retinal circuits. TUDCA therapy could restrain the spontaneous firing response, enhance the light induced firing response, and preserve the basic configurations of ON-OFF signal pathway in degenerative retinas. Our MEA assay provided an example to evaluate the potency of pharmacological compounds on retinal plasticity. TUDCA affords these protective effects by modulating apoptosis and alleviating oxidative stress in the degenerative retina. In conclusion, TUDCA therapy can ameliorate the photoreceptor degeneration and rectify the abnormities in visual signal transmission. These findings suggest that TUDCA might act as a potential medication for these retinopathies with progressive photoreceptor degeneration.

Link between cardiac function and the antioxidative defense mechanism in aged rats

Aging presents profound structural and physiological changes in the cardiovascular system. Oxidative stress, a major contributing factor during the aging process, has been involved in various age-related cardiovascular pathologies. Nevertheless, the underlying mechanism of oxidative stress in the aging heart is still unclear. This study was designed to determine whether changes in cardiac structure and function in aged rats were associated with decreases in the antioxidative defense mechanism. Young (3-month-old) and aged (24-month-old) rats were used in this study, and the differences in function, structure, antioxidative capacity and the expression of antioxidative-related proteins between the two groups were compared. By using echocardiography, we observed that compared to young rats, the left ventricular internal end-diastolic diameter (LVID; d) and left ventricular volume at diastole (LV Vol; d) were significantly increased in aged rats, while the MV E/A (E wave and A wave ratio, the ratio of peak velocity of early to late filling of mitral inflow), which represents heart diastolic function, was significantly decreased in aged rats. In addition, we observed degenerative histological modifications and an increased number of apoptotic cells in aged rats. We further detected the protein expression of catalase (CAT), glutathione synthetase (GSS), superoxide dismutase-1 (SOD-1), heme oxygenase-1 (HO-1) and NADPH: quinone oxidoreductase 1 (NQO1) in cardiac tissue. Western blot results showed that the expression of GSS was significantly decreased and that the expressions of CAT, SOD-1, and HO-1 were slightly decreased in aged rats. Immunohistochemistry results further confirmed the decreased expression of GSS, SOD-1 and NQO1 in cardiomyocytes in aged rats. Taken together, our data suggest that aging may affect the morphology and function of the heart by oxidative stress and the antioxidative defense mechanism.