Deuterated polyunsaturated fatty acids inhibit photoirradiation-induced lipid peroxidation in lipid bilayers.

Lipid peroxidation (LPO) plays a key role in many age-related neurodegenerative conditions and other disorders. Light irradiation can initiate LPO through various mechanisms and is of importance in retinal and dermatological pathologies. The introduction of deuterated polyunsaturated fatty acids (D-PUFA) into membrane lipids is a promising approach for protection against LPO. Here, we report the protective effects of D-PUFA against the photodynamically induced LPO, using illumination in the presence of the photosensitizer trisulfonated aluminum phthalocyanine (AlPcS3) in liposomes and giant unilamellar vesicles (GUV), as assessed in four experimental models: 1) sulforhodamine B leakage from liposomes, detected with fluorescence correlation spectroscopy (FCS); 2) formation of diene conjugates in liposomal membranes, measured by absorbance at 234 nm; 3) membrane leakage in GUV assessed by optical phase-contrast intensity observations; 4) UPLC-MS/MS method to detect oxidized linoleic acid (Lin)-derived metabolites. Specifically, in liposomes or GUV containing H-PUFA (dilinoleyl-sn-glycero-3-phosphatidylcholine), light irradiation led to an extensive oxidative damage to bilayers. By contrast, no damage was observed in lipid bilayers containing 20% or more D-PUFA (D2-Lin or D10-docosahexanenoic acid). Remarkably, addition of tocopherol increased the dye leakage from liposomes in H-PUFA bilayers compared to photoirradiation alone, signifying tocopherol's pro-oxidant properties. However, in the presence of D-PUFA the opposite effect was observed, whereby adding tocopherol increased the resistance to LPO. These findings suggest a method to augment the protective effects of D-PUFA, which are currently undergoing clinical trials in several neurological and retinal diseases that involve LPO.

Alpha-tocopheryl succinate improves encapsulation, pH-sensitivity, antitumor activity and reduces toxicity of doxorubicin-loaded liposomes.

Doxorubicin (DOX) plays an important role in cancer treatment; however, high cardiotoxicity and low penetration in solid tumors are the main limitations of its use. Liposomal formulations have been developed to attenuate the DOX toxicity, but the technological enhancement of the liposomal formulation as well as the addition of another agent with antitumor properties, like alpha-tocopheryl succinate (TS), a semi-synthetic analog of vitamin E, could certainly bring benefits. Thus, in this study, it was proposed the development of liposomes composed of DOX and TS (pHSL-TS-DOX). A new DOX encapsulation method, without using the classic ammonium sulfate gradient with high encapsulation percentage was developed. Analysis of Small Angle X-ray Scattering (SAXS) and release study proved the pH-sensitivity of the developed formulation. It was observed stabilization of tumor growth using pHSL-TS-DOX when compared to free DOX. The toxicity tests showed the safety of this formulation since it allowed body weight initial recovery after the treatment and harmless to heart and liver, main target organs of DOX toxicity. The developed formulation also avoided the occurrence of myelosuppression, a typical adverse effect of DOX. Therefore, pHSL-TS-DOX is a promising alternative for the treatment of breast cancer since it has adequate antitumor activity and a safe toxicity profile.

Common-garden experiments reveal geographical variation in the interaction among Crotalaria pallida (Leguminosae: Papilionideae), Utetheisa ornatrix L. (Lepidoptera: Arctiidae), and extrafloral nectary visiting ants.

The study of geographical variation is a key approach to understand evolution of ecological interactions. We investigated geographical variation in the interaction among Crotalaria pallida (Leguminosae: Papilionideae), its specialized herbivore, Utetheisa ornatrix L. (Lepidoptera: Arctiidae), and ants attracted to extrafloral nectaries (EFNs). First, we used common-garden experiments with plants collected in different sites at different geographical scales to test for differences among populations in C. pallida attractiveness to ants. When we compared three populations from Southeast Brazil (150 km apart), the number of visiting ants per plant, and the percent of termite baits attacked by ants, were significantly different among plant populations. In a comparison of populations from SE Brazil and Florida (USA), there was no significant difference between the populations in the number of ants per plant or the frequency of baits attacked. Second, we tested in a common garden if U. ornatrix larvae present any behavior to avoid ant predation, and if there were genetic differences among populations. We observed that most larvae moved away from the vicinity of the EFNs (flowers and fruits) to the plant leaves. Of the larvae that moved to leaves, only 10% were attacked by ants while 89% of larvae that stayed near the fruit/flower were attacked. There was a significant difference among populations in the frequency of larvae that moved to the leaves and the frequency of larvae attacked by ants. We discuss the possible causes of the geographical differences observed and propose future research directions in this system.

Increased cation permeability in mutant mouse red blood cells with defective membrane skeletons.

Cellular cation homeostasis in mouse erythrocytes with defective membrane skeletons was examined in three mouse mutants, hemolytic anemia (sphha/sphha), spherocytosis (sph/sph), and normoblastosis (nb/nb), and compared with reticulocytes produced by repetitive bleeding of congenic normal mice. To assess reticulocyte maturity, nucleic acid and transferrin receptor contents were measured by fluorescence flow cytometry; mutant cells were somewhat more mature than normal reticulocytes by these criteria. Red blood cell (RBC) sodium contents (Nac+) in homozygous sphha/sphha, sph/sph, and nb/nb animals were 30.1 +/- 0.9, 28.9 +/- 0.3, and 26.9 +/- 1.5 mmol/L cell, respectively, whereas cellular potassium (Kc+) was 102 +/- 2.6, 101 +/- 7.8, and 97.4 +/- 3.0. Nac+ and Kc+ in normal reticulocyte preparations were 11.3 +/- 0.7 and 123 +/- 10, respectively. Net Na+ and K+ fluxes in the presence of ouabain were markedly increased in mutant RBCs. Sodium uptake was 14.8 +/- 1.6, 15.4 +/- 3.3, and 14.7 +/- 3.1 mmol/L cell/h in sphha/sphha, sph/sph, and nb/nb mutants, respectively, whereas K+ loss was 17.0 +/- 4.0, 15.0 +/- 3.8, and 14.1 +/- 2.6. Normal mouse reticulocytes gained Na+ at a rate of 3.9 +/- 1.0 mmol/L cell/h and lost K+ at 6.0 +/- 2.1, rates indistinguishable from those in mature mouse RBCs. Potassium loss from sphha/sphha and nb/nb cells was not dependent on the presence of a Na+ gradient, and net cation movements were insensitive to bumetanide (sphha/sphha and nb/nb RBCs) and to chloride replacement with sulfamate (nb/nb cells). We conclude that mutant mouse RBCs with dysfunctional membrane skeletons have increased passive permeability to monovalent cations. These findings support a role of the membrane skeleton in the maintenance of the membrane permeability barrier and suggest that the abnormal permeability associated with human hereditary spherocytosis and elliptocytosis may be a consequence of the membrane skeleton defects reported in these disorders.