Lipofuscin accumulation in extraocular muscle of rats deficient in vitamins E and A

The effects of ageing and a vitamin E-deficient diet on the lipopigment content of rat hippocampal and Purkinje neurones

This study examined associations between a vitamin E-deficient diet, ageing and aspects of the morphology of neuronal lipopigment in rat hippocampal and Purkinje neurones. Groups of rats given a standard diet were killed at 6, 12, 18 and 25 months of age, while a group which had received a vitamin E-deficient diet from 1-18 months were killed at 18 months of age. Lipopigment within a neuronal cell body consists of a number of discrete regions of varying size. These were identified by fluorescence microscopy and a photograph for each individual neurone was projected onto paper, so that the outlines of the discrete regions of lipopigment could be drawn and subjected to morphometric measurements. Both ageing and vitamin E deficiency in relation to hippocampal neurones and vitamin E deficiency in relation to Purkinje neurones (in which ageing effects were not examined), were associated with a significant (< 0.05) increase in the mean total area (per rat) enclosed by the lipopigment outlines. For both vitamin E deficiency and ageing this increase was associated with both an increase in the number of relatively large discrete lipopigment regions and a decrease in the number of relatively small discrete lipopigment regions. The findings in relation to vitamin E deficiency could be explained by an increased rate of lipopigment formation, involving processes which also occur in ageing.

Age pigments in different populations of peripheral neurons in vivo and in vitro

The distribution and ultrastructure of lipopigments in the rat sympathetic, vagus and spinal ganglion neurons were studied in vivo and in vitro using fluorescence and electron microscopy. Newborn, 3-6 mo and 24-30 mo-old male Wistar rats were used. In vivo, the age pigments in the sympathetic neurons showed a tendency to form unipolar or bipolar caps, whereas in the vagus and spinal ganglion neurons pigment granules were packed in the peripheral area of the perikarya during aging. Ultrastructurally, lipid-like vacuoles and a rather homogeneous matrix were the components shared by pigment bodies of all types of peripheral neurons. However, pigment granules in sympathetic neurons frequently had a third, osmiophilic component, which likely represents neuromelanin. In vitro, the cytoplasmic area occupied by autofluorescent pigments was increased in most of the neurons. Some neurons, however, showed the same amount of lipopigments as in vivo. In electron microscopy, age pigment granules typical of each type of neuron were found, and their number and intracellular distribution seemed to be comparable with those in vivo. In most of the neurons cultured from all ages and of all types of ganglion, there appeared to be accumulations of another, very homogeneous and large type of pigment body. In some cases, they were structurally connected with classical pigment bodies or they had a finger print-like substructure. Large homogeneous pigment bodies were also seen in surrounding satellite cells. All these changes were most frequently seen in cultures of spinal ganglia from old animals. It is concluded that although classical age pigments maintain their characteristics in cultured peripheral neurons, there is, in addition, a rapid accumulation of ceroid-like pigments, which may be caused by the inability of the cultured neurons to cope with increased peroxidative damage.

Effect of vitamin E and selenium supplement on the aging peripheral neurons of the male Sprague-Dawley rat

The effect of life-long diets containing different concentrations of selenium and vitamin E on the age pigment accumulation in the rat superior cervical ganglion, vagal ganglion and dorsal root ganglion, was studied using microspectrofluorometry. All types of ganglia showed unchanged amounts of age pigments at low or high concentrations of selenium, whereas dietary concentration of vitamin E regulated age pigment content in the dorsal root ganglion, but not in the superior cervical and vagal ganglion. Vitamin E deficiency induced a three-fold increase in age pigment content in dorsal root ganglion at 8 months of age, whereas high vitamin E concentration was associated with a lesser amount of pigments at 18 months of age. Emission spectra of age pigment recorded from the dorsal root ganglion and vagal ganglion were different from that from the superior cervical ganglion, but were independent of dietary concentrations of selenium or vitamin E. The results suggest that exogenous antioxidants may play a more crucial role in lipid peroxidation and accumulation of age pigment in dorsal root ganglion than in autonomic ganglia.

Relationship between dietary retinol and lipofuscin in the retinal pigment epithelium

A variety of evidence suggests that autoxidation of cellular components probably plays a significant role in the age-related accumulation of lipofuscin, or age-pigment, in the mammalian retinal pigment epithelium (RPE). Among the likely candidates for conversion into RPE lipofuscin fluorophores via autoxidative mechanisms are vitamin A compounds, which are present in the retina and RPE in high concentrations. Vitamin E, an important lipid antioxidant, is likely to inhibit vitamin A autoxidation. Experiments were conducted to evaluate the significance of vitamin A autoxidation in the deposition of lipofuscin in the RPE. Albino rats were fed diets either supplemented with or lacking vitamin E. Each of these two groups of animals was further subdivided into three groups which were fed different levels of vitamin A palmitate: none, 14.0 mumol/kg diet, and 80.5 mumol/kg diet. After 26 weeks, the animals were killed and the RPE lipofuscin contents were determined by both fluorescence measurements and quantitative ultrastructural morphometry. Vitamin A palmitate deficiency led to significant reductions in RPE lipofuscin deposition, relative to the amounts of this pigment present in the groups receiving vitamin A palmitate in their diets. The relative magnitude of the vitamin A effect was greater in the vitamin E-supplemented groups than in the groups fed the diets deficient in vitamin E. This finding suggests that vitamin E interacts with vitamin A ester metabolites in vivo in a more complex manner than simply acting as an antioxidant protectant. Rats fed the diets containing the higher level of vitamin A palmitate failed to display elevated RPE lipofuscin contents relative to those in the rats fed 14.0 mumol of vitamin A palmitate/kg diet. Failure of high vitamin A intake to enhance RPE lipofuscin deposition may have been due to the fact that intake of vitamin A above normal levels did not lead to an elevation in vitamin A content of the retinal tissue. Establishing an effect of vitamin A deficiency on RPE lipofuscin deposition and characterization of the interactions between vitamins E and A are important steps toward defining precisely the molecular and cellular mechanisms underlying age-pigment accumulation in the RPE.