Long-chain fatty acids and ethanol affect the properties of membranes in Drosophila melanogaster larvae

The predominance of polyunsaturated fatty acids in the butterfly Morpho peleides before and after metamorphosis

We hypothesized that the polyunsaturated fatty acids of the butterfly were probably derived from the diet and that there might be a great loss of body fat during metamorphosis. To substantiate these hypotheses, we analyzed the fatty acid composition and content of the diet, the larva, and the butterfly Morpho peleides. Both the diet and the tissues of the larva and butterfly had a high concentration of polyunsaturated fatty acids. In the diet, linolenic acid accounted for 19% and linoleic acid for 8% of total fatty acids. In the larva, almost 60% of the total fatty acids were polyunsaturated: linolenic acid predominated at 42% of total fatty acids, and linoleic acid was at 17%. In the butterfly, linolenic acid represented 36% and linoleic acid represented 11% of total fatty acids. The larva had a much higher total fatty acid content than the butterfly (20.2 vs. 6.9 mg). Our data indicate that the transformation from larva to butterfly during metamorphosis drastically decreased the total fatty acid content. There was bioenhancement of polyunsaturated fatty acids from the diet to the larva and butterfly. This polyunsaturation of membranes may have functional importance in providing membrane fluidity useful in flight.

Comparative aspects of sperm membrane fatty acid composition in silver (Vulpes vulpes) and blue (Alopex lagopus) foxes, and their relationship to cell cryopreservation

Cryogenic protocols have been developed for the storage of farmed silver fox (Vulpes vulpes) spermatozoa. However, these same protocols and modifications of these protocols have failed to satisfactorily preserve spermatozoa collected from farmed blue foxes (Alopex lagopus). Because cryogenic success has been linked to membrane composition, the plasma membrane lipid composition of farmed blue fox and silver fox spermatozoa was studied. Silver fox spermatozoal membranes have significantly higher levels of docosapentaenoic acid (DPA; 22:5, n-6) compared to blue fox spermatozoa, and blue fox spermatozoal membranes have significantly higher levels of stearic acid (18:0). Silver fox spermatozoal membranes not only have a higher ratio of unsaturated/saturated membrane fatty acids, but also higher levels of membrane desmosterol and cholesterol.

Sperm membrane fatty acid composition in the Eastern grey kangaroo (Macropus giganteus), koala (Phascolarctos cinereus), and common wombat (Vombatus ursinus) and its relationship to cold shock injury and cryopreservation success

Marsupial spermatozoa tolerate cold shock well, but differ in cryopreservation tolerance. In an attempt to explain these phenomena, the fatty acid composition of the sperm membrane from caput and cauda epididymides of the Eastern grey kangaroo, koala, and common wombat was measured and membrane sterol levels were measured in cauda epididymidal spermatozoa. While species-related differences in the levels of linolenic acid (18:3, n-6) and arachidonic acid (20:4, n-6) were observed in caput epididymal spermatozoa, these differences failed to significantly alter the ratio of unsaturated/saturated membrane fatty acids. However in cauda epididymidal spermatozoa, the ratio of unsaturated/saturated membrane fatty acids in koala and kangaroo spermatozoa was approximately 7.6 and 5.2, respectively; substantially higher than any other mammalian species so far described. Koala spermatozoal membranes had a higher ratio of unsaturated/saturated membrane fatty acids than that of wombat spermatozoa (t = 3.81; df = 4; p < or = 0.02); however, there was no significant difference between wombat and kangaroo spermatozoa. The highest proportions of DHA (22:6, n-3), the predominant membrane fatty acid in cauda epididymidal spermatozoa, were found in wombat and koala spermatozoa. While species-related differences in membrane sterol levels (cholesterol and desmosterol) were observed in cauda epididymidal spermatozoa, marsupial membrane sterol levels are very low. Marsupial spermatozoal membrane analyses do not support the hypothesis that a high ratio of saturated/unsaturated membrane fatty acids and low membrane sterol levels predisposes spermatozoa to cold shock damage. Instead, cryogenic tolerance appears related to DHA levels.

Drosophila melanogaster, a genetic model system for alcohol research

In its natural environment, which consists of fermenting plant materials, the fruit fly Drosophila melanogaster encounters high levels of ethanol. Flies are well equipped to deal with the toxic effects of ethanol; they use it as an energy source and for lipid biosynthesis. The primary ethanol-metabolizing pathway in flies involves the enzymes alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH); their role in adaptation to ethanol-rich environments has been studied extensively. The similarity between Drosophila and mammals is not restricted to the manner in which they metabolize ethanol; behaviors elicited by ethanol exposure are also remarkably similar in these organisms. Flies show signs of acute intoxication, which range from locomotor stimulation at low doses to complete sedation at higher doses, they develop tolerance upon intermittent ethanol exposure, and they appear to like ethanol, showing preference for ethanol-containing media. Molecular genetic analysis of ethanol-induced behaviors in Drosophila, while still in its early stages, has already revealed some surprising parallels with mammals. The availability of powerful tools for genetic manipulation in Drosophila, together with the high degree of conservation at the genomic level, make Drosophila a promising model organism to study the mechanism by which ethanol regulates behavior and the mechanisms underlying the organism's adaptation to long-term ethanol exposure.

Ethanol- and Fe(+2)-induced membrane lipid oxidation is not additive in developing chick brains

In order to study the effects of exogenous EtOH and/or Fe(+2) on membrane lipid peroxidation, exogenous EtOH, FeCl(2), FeCl(2) & EtOH, NaCl and NaCl & EtOH were injected into fertile chicken eggs. Controls were either shams or injected with saline. These injections were made at 0 days or 0-2 days of development and tissue removed at stage 37 (11 days of development). Embryonic exposure to exogenous EtOH and/or Fe(+2) promoted decreased brain mass, decreased levels of brain membrane polyunsaturated fatty acids, elevated levels of brain lipid hydroperoxides, and elevated levels of Fe(+2) within embryonic brain and liver. These alterations were more severe in triple-injected embryos (E0-2/E11) as compared to single-injected embryos (E0/E11). While exogenous treatments of either EtOH and/or FeCl(2) promoted increased levels of endogenous brain Fe(+2), the effects were not additive. These observations are consistent with the hypothesis that embryonic exposure to exogenous EtOH and/or Fe(+2) promotes brain membrane lipid peroxidation.

Alpha-tocopherol and gamma-tocopherol attenuate ethanol-induced changes in membrane fatty acid composition in embryonic chick brains

BACKGROUND

This project investigated whether or not EtOH-induced reductions in the levels of long-chain polyunsaturated membrane fatty acids could be attenuated by exogenous exposure to either alpha-tocopherol, gamma-tocopherol, or diallyl sulfide (DAS).

METHODS

At 0 days of development, fertile chicken eggs were injected with a single dose of either saline supplemented with various concentrations of EtOH, alpha- or gamma-tocopherol and EtOH, or DAS and EtOH. At 18 days of development, brains were isolated and subjected to membrane analyses.

RESULTS

When exposed to EtOH, concentrations ranging from 0-60.50 microm/Kg egg, dose-dependent decreases in the levels of brain 18:0, 18:1 (n-9), 18:2 (n-6), 18:3 (n-3), and 20:4 (n-6) were observed. These ethanol-induced changes in membrane fatty acid composition correlated with ethanol-induced reductions in brain mass, brain protein levels, acetylcholine esterase (AChE) activities and correlated with increased lipid hydroperoxide levels. Exposure to either 2.5 microm alpha-tocopherol/Kg egg and 6.050 mm EtOH/Kg egg, or 2.5 microm alpha-tocopherol/ Kg egg and 6.050 mm EtOH/Kg egg attenuated EtOH-induced changes in membrane fatty acid composition, brain mass, brain protein levels, AChE activities, and lipid hydroperoxide levels. Embryonic exposure to the cytochrome p450-2E1 inhibitor, diallyl sulfide (DAS), also attenuated EtOH-induced decreases in long-chain, unsaturated membrane fatty acids. However, embryonic exposure to DAS promoted abnormally low brain mass.

CONCLUSION

EtOH-induced reductions in the levels of brain long-chain polyunsaturated fatty acid are caused by lipid peroxidation.

A developmental profile of the effects of ethanol on the levels of chick brain phospholipids

The effects of embryonic exposure to ethanol on brain phospholipid levels were studied by injecting various concentrations of ethanol, ranging from 0 to 149 microns kg-1 egg, into fertile chicken eggs at 0 days of incubation. At 7, 9, 11, 15 and 18 days of incubation, brains were collected and the levels of total phospholipids and various phospholipid classes were measured. Although embryonic exposure to ethanol failed to influence total phospholipid levels, ethanol-induced changes in the levels of individual phospholipid classes were observed. Ethanol-induced increases in the levels of phosphatidylethanolamine (PE) and phosphatidylserine (PS) and ethanol-induced decreases in the levels of phosphatidylcholine (PC) were observed at 9, 11, 15 and 18 days of incubation. Ethanol-induced decreases in brain sphingomyelin (SP) levels were observed at 7 and 18 days of development. These ethanol-induced changes in brain phospholipid levels preceded detectable alcohol dehydrogenase (ADH) activities in both brain and liver.

Ethanol alters brain phospholipid levels which correlate with altered brain morphology

The effects of embryonic exposure on brain phospholipid levels were studied by injecting various concentrations of ethanol into fertile chicken eggs at 0 days of development. At 18 days of development, the levels of total phospholipids and various phospholipid classes were assayed in brain tissue and correlated to neuron densities within the cerebral hemispheres and the optic lobes. Although ethanol concentrations ranging from 0 to 3700 microns/Kg egg wt. failed to influence either total brain weight or total brain phospholipid levels, ethanol-induced changes in the levels of individual phospholipid classes were observed. When injected with 7 microns of ethanol/Kg egg wt., a 2- to 3-fold increase in brain phosphatidylethanolamine (PE) levels were observed with reduced levels of brain phosphatidylcholine (PC) and brain sphingomyelin (SP). When injected with 74 microns of ethanol/Kg egg wt., ethanol-induced increases in brain phosphatidylserine (PS) and PE were observed with ethanol-induced decreases in brain PC and SP. Cell fractionation studies demonstrated ethanol-induced increases in brain PE and PS and ethanol-induced decreases in brain PC and SP in nuclear, mitochondrial, and microsomal membranes. These ethanol-induced alterations in brain phospholipid profiles correlated with ethanol-induced reductions in neuron densities within the cerebral hemispheres and optic lobes.

Suppression of heat-shock protein synthesis by short-chain fatty acids and alcohols

We have shown that ethanol, propanol and butanol (at 0.5-2%) and salts of butyric and propionic acids (at 8-40 mM) all cause a major reduction in heat-shock protein (hsp) synthesis when present in the growth medium of Drosophila cultured cells (Kc and SL2) subjected to either increased temperature or chemical stressors. Inhibition of normal protein synthesis in unstressed cells was comparatively slight, and the usual suppression of synthesis of non-heat-shock proteins in stressed cells was unaffected. Maximum suppression of hsp synthesis occurred only if inhibitors were added before initiation of the stress response, an observation that eliminates the possibility that these findings are due to non-specific, toxic effects. Suppression was accompanied by severely reduced levels of both hsp70 mRNA and active heat-shock factor (HSF). We conclude that the inhibitors act by suppressing the initiation of transcription of heat-shock genes.

At high dietary levels ethanol alters the structure of mid- and hindgut epithelial cells of Drosophila melanogaster larvae

The midgut of Drosophila melanogaster is a site of alcohol dehydrogenase (ADH) activity, the enzyme that catalyzes the first step in the major pathway for ethanol degradation. The effects of different levels of dietary ethanol on the ultrastructures of the guts of larvae of the Canton-S wild-type strain and the ADH-deficient, Adhn2, strain were ascertained. In wild-type larvae fed an ethanol-free, defined medium, the foregut epithelium was characterized by few glycogen rosettes and sparse microvilli that protruded into the gut's thick lumen lining. The midgut epithelium was typical of cells involved in absorption and active transport with abundant microvilli on the apical surface and membrane infoldings on the basal surface. In place of microvilli, the apical surface of the hindgut had membrane infoldings. The apical surfaces of both the mid- and hindgut epithelium were covered by a thick, electron-dense peritrophic membrane consisting of chitin. In both strains the subcellular damage that was correlated with ethanol levels in the diet was confined to the midgut and hindgut regions. Damage to gut cells in the form of disrupted mitochondria, dilated rough endoplasmic reticulum, low densities of glycogen rosettes and protein granules, high numbers of autophagic vacuoles, and the presence of myelin whirls was extensive in Canton-S strain larvae fed a high ethanol diet. A low dietary concentration of ethanol induced changes in gut ultrastructure of Adhn2 larvae similar to the changes that were observed in wild-type larvae fed the higher ethanol concentrations, but the basal infoldings were more dilated in the Adhn2 larvae. At high dietary concentrations the disruption of mid- and hindgut cells by ethanol appeared great enough to interfere with the digestion and absorption of nutrients.

Dietary ethanol stimulates the activity of phosphatidylcholine-specific phospholipase D and the formation of phosphatidylethanol in Drosophila melanogaster larvae

When administered in the diet to third instar Drosophila melanogaster larvae, short chain primary alcohols reduce phosphatidylcholine (PC) levels. The ethanol-induced reductions in larval PC may be in part due to an increase in the activity of PC-specific phospholipase D (PC-specific PLD, EC 3.1.4.4). PC-specific PLD not only hydrolyzes PC, but it also apparently catalyzes the formation of phosphatidylethanol. PC-specific PLD activity was also stimulated by 200 mM ethanol, methanol, isopropanol, n-butanol, and n-propanol. In vitro studies indicated that Drosophila PC-specific PLD activities were enhanced by submicromolar concentrations of Ca2+ and by GTP-gamma S. In vivo studies utilizing [14C]lyso-palmitoyl phosphatidylcholine indicated that dietary ethanol promoted the flux of label into triacylglycerol, 1,2 diacylglycerol, and fatty acid ethyl esters, while the label in PC decreased.

Dietary ethanol reduces phosphatidylcholine levels and inhibits the uptake of dietary choline in Drosophila melanogaster larvae

1. Low to moderate concentrations of dietary ethanol (200 mM to 600 mM) significantly increased the level of phosphatidylethanolamine (PE), while phosphatidylcholine (PC) levels decreased in third instar larvae. This was seen in both ethanol tolerant and intolerant strains of Drosophila melanogaster, indicating that the reduction of PC is not associated with a high level of ethanol tolerance. 2. The phospholipid changes were not ethanol-specific. Larvae fed ethanol, n-butanol, isopropanol, methanol, and n-propanol exhibited similar changes. 3. At 200 mM concentrations, dietary ethanol acted as a competitive inhibitor for the larval uptake of dietary choline. At higher concentrations, dietary ethanol acted as a noncompetitive inhibitor. This ethanol-induced inhibition of dietary choline uptake can only partially explain the ethanol-induced reductions in larval PC.