Effects of exogenous fatty acids and cholesterol on aminopeptidase activities in rat astroglia

Abstract

Several studies have addressed the interaction between fatty acids and lipids with central nervous system peptides. Because aminopeptidases (AP) are involved in the regulation of neuropeptides, this work studies several AP expressed in cultured astroglia, after exogenous addition of oleic and linoleic fatty acids and cholesterol to the culture medium. Alanyl-AP, arginyl-AP, cystyl-AP, leucyl-AP, tyrosyl-AP and pyroglutamyl-AP activities were analysed in whole cells using the corresponding aminoacyl-beta-naphthylamides as substrates. Oleic acid inhibits alanyl-AP, cystyl-AP and leucyl-AP activities, whereas linoleic acid inhibits alanyl-AP, arginyl-AP and tyrosyl-AP activities. Neither oleic acid nor linoleic acid modifies pyroglutamyl-AP activity. In contrast, cholesterol increases arginyl-AP, cystyl-AP, leucyl-AP, tyrosyl-AP and pyroglutamyl-AP activities, although it does not modify alanyl-AP activity. The changes reported here suggest that oleic and linoleic fatty acids and cholesterol can modulate peptide activities via their degradation route involving aminopeptidases; each of them being differentially regulated.

Oleic acid is a potent inhibitor of fatty acid and cholesterol synthesis in C6 glioma cells

“…These biochemical changes can be accompanied by alterations in the physical state of the membrane, for example in membrane fluidity (39). Moreover, the addition of C18:1 cis and C18:2 to cultured astrocytes decreases several aminopeptidase activities (17). Furthermore, it has been shown that C18:1 cis addition determines a dosedependent inhibition of GAP junction permeability in cultured rat astrocytes.…”

“…It has been shown that exogenous fatty acids may influence the fatty acid composition of neuronal and glial membranes (10)(11)(12)(13)(14), and these changes in turn can affect cellular metabolism and regulatory (15) and inflammatory processes (16). Furthermore, in primary cultures of rat astroglia, it has been shown that the addition of oleic and linoleic acids to the medium reduces several aminopeptidase activities (17).…”

“…Cultures were maintained at 37jC in a humidified atmosphere of 5% CO 2 . C6 cells were seeded at a density of 5 3 10 5 cells per 35 mm diameter Petri dishes; 24 h after plating, the medium was changed and, after another 24 h, sodium salts of different fatty acids at 99% of purity (C18:0, stearic acid; C18:1 cis, oleic acid, cis-D 9 -octadecaenoic acid; C18:1 trans, elaidic acid, trans-D 9 -octadecaenoic acid; C18:2, linoleic acid, all-cis-D 9,12 -octadecadienoic acid; C20:4, arachidonic acid, all-cis-D 5,8,11,14 -eicosatetraenoic acid; C20:5, all-cis-D 5,8,11,14,17 -eicosapentaenoic acid; C22:6, allcis-D 4,7,10,13,16,19 -docosahexaenoic acid) were added to the serumrich (10% FBS) medium, obtaining 100 mM final concentration, as reported by Salvati et al (24). Unless specified otherwise, cells were in contact with the exogenous fatty acid for a total period of 4 h. In each experiment and for each determination, control dishes without any fatty acid addition were used.…”

Angiotensinase Activity and Olive Oil Supplementation

“…In this way, Murphy (1995) has demonstrated that cultured astrocytes take up exogenous linoleic acid and incorporate its metabolites into phospholipids, and that the resulting changes in membrane fatty acid composition modify certain specific cell function properties. These chemical changes can be accompanied by changes in the physical state of the membrane, and could be responsible for the effects of fatty acids on RAS-regulating activities reported (Ramirez-Exposito et al, 2002). Moreover, it is well known that changes in the relative amounts of free fatty acids in the cellular membrane may be major factors in the physiological role of the membrane by changing membrane fluidity.…”

“…In fact, these fatty acids have been shown to lower arterial pressure in various models of experimental hypertension (Hui et al, 1991). Using primary cultured astroglia, we have described (Ramirez-Exposito et al, 2002) that the addition of oleic and linoleic fatty acids to the culture medium decreases, to different degrees, several RAS-regulating angiotensinases, whereas the presence of exogenous cholesterol in the medium increases them. Thus, our results showed a significant decrease of GluAP activity after incubation with oleic and linoleic fatty acids, which may indicate the existence of high levels of Ang II.…”