Photoreceptor outer segment and retinal pigment epithelium in vitamin E deficient rats. An electron microscopic and electron histochemical study

Arterial Hypertension and the Hidden Disease of the Eye: Diagnostic Tools and Therapeutic Strategies

Hypertension is a major cardiovascular risk factor that is responsible for a heavy burden of morbidity and mortality worldwide. A critical aspect of cardiovascular risk estimation in hypertensive patients depends on the assessment of hypertension-mediated organ damage (HMOD), namely the generalized structural and functional changes in major organs induced by persistently elevated blood pressure values. The vasculature of the eye shares several common structural, functional, and embryological features with that of the heart, brain, and kidney. Since retinal microcirculation offers the unique advantage of being directly accessible to non-invasive and relatively simple investigation tools, there has been considerable interest in the development and modernization of techniques that allow the assessment of the retinal vessels’ structural and functional features in health and disease. With the advent of artificial intelligence and the application of sophisticated physics technologies to human sciences, consistent steps forward have been made in the study of the ocular fundus as a privileged site for diagnostic and prognostic assessment of diverse disease conditions. In this narrative review, we will recapitulate the main ocular imaging techniques that are currently relevant from a clinical and/or research standpoint, with reference to their pathophysiological basis and their possible diagnostic and prognostic relevance. A possible non pharmacological approach to prevent the onset and progression of retinopathy in the presence of hypertension and related cardiovascular risk factors and diseases will also be discussed.

Molecular Mechanisms Underlying the Therapeutic Role of Vitamin E in Age-Related Macular Degeneration

The eye is particularly susceptible to oxidative stress and disruption of the delicate balance between oxygen-derived free radicals and antioxidants leading to many degenerative diseases. Attention has been called to all isoforms of vitamin E, with α-tocopherol being the most common form. Though similar in structure, each is diverse in antioxidant activity. Preclinical reports highlight vitamin E’s influence on cell physiology and survival through several signaling pathways by activating kinases and transcription factors relevant for uptake, transport, metabolism, and cellular action to promote neuroprotective effects. In the clinical setting, population-based studies on vitamin E supplementation have been inconsistent at times and follow-up studies are needed. Nonetheless, vitamin E’s health benefits outweigh the controversies. The goal of this review is to recognize the importance of vitamin E’s role in guarding against gradual central vision loss observed in age-related macular degeneration (AMD). The therapeutic role and molecular mechanisms of vitamin E’s function in the retina, clinical implications, and possible toxicity are collectively described in the present review.

Evidence for the photoprotective effects of vitamin E

The antioxidant vitamin E (alpha-tocopherol) may protect both animal and plant cell membranes from light-induced damage. The various biochemical and biophysical modes of protection are considered. An examination is made of the evidence that vitamin E plays an important prophylactic role against a number of serious light-induced diseases and conditions of the eye (cataractogenesis and retinal photodeterioration) and skin (erythrocyte photohemolysis, photoerythema, photoaging and photocarcinogenesis) that are mediated by photooxidative damage to cell membranes.

Gas chromatography-mass spectrometry method for determination of phospholipid peroxides; I. Transesterification to form methyl esters

The purpose of this study is to develop methods for determining the chemical species of lipid peroxides that occur in various types of tissue pathology. Experiments are aimed at determining the phospholipid peroxides associated with retinal degeneration as the initial test case. Phospholipid hydroperoxides are synthesized by photosensitized oxidation, chemically characterized and used to develop an effective and simplified method to identify and measure phospholipid hydroperoxides by gas chromatography-mass spectrometry (GC-MS). A sensitive reverse phase high performance liquid chromatography (HPLC) method is also presented to separate peroxidized phospholipids from phospholipids. For GC-MS, phospholipid peroxides are reduced with sodium borohydride and transesterified to form fatty acid methyl esters using a mild quaternary ammonium hydroxide catalyst. The hydroxyl groups produced by reducing the hydroperoxides are formed into trimethylsilyl ethers and GC-MS is employed (with electron ionization and negative ion chemical ionization) to identify oxidized fatty acids at the 10 ng level. Photooxidation of (palmitoyl)(linoleoyl) phosphatidylcholine yielded equal amounts of the conjugated (9 and 13 isomers) and the nonconjugated (10 and 12 isomers) linoleoyl hydroperoxides. Photooxidation of rat retina total lipids yielded oxidation products of oleolyl (18:1) esters as well as the conjugated and nonconjugated oxidation products of arachidonoyl (20:4) and docosahexaenoyl (22:6) esters virtually all of which arise from phospholipids. The nonconjugated products are of interest as indicators of photosensitized light damage in retina and other tissues. It is notable that all the possible singly oxidized products are found with the exception of the 4, 5 and 7 hydroperoxides of 22:6 and the 5 hydroperoxide of 20:4. It appears that the approach of singlet oxygen is strongly inhibited in the sterically hindered region near the phospholipid head groups.