Derivatives of 2,5-Diaryl-1,3-Oxazole and 2,5-Diaryl-1,3,4-Oxadiazole as Environment-Sensitive Fluorescent Probes for Studies of Biological Membranes

Marine Polysaccharides Carrageenans Enhance Eryptosis and Alter Lipid Order of Cell Membranes in Erythrocytes

Aim In the current study, hemocompatibility of three major commercially available types of carrageenans (ι, κ and λ) was investigated focusing on eryptosis.

MATERIALS AND METHODS

Carrageenans of ι-, κ- and λ-types were incubated with washed erythrocytes (hematocrit 0.4%) at 0-1-5-10 g/L for either 24 h or 48 h. Incubation was followed by flow cytometry-based quantitative analysis of eryptosis parameters, including cell volume, cell membrane scrambling and reactive oxygen species (ROS) production, lipid peroxidation markers and confocal microscopy-based evaluation of intracellular Ca2+ levels, assessment of lipid order in cell membranes and the glutathione antioxidant system. Confocal microscopy was used to assess carrageenan cellular internalization using rhodamine B isothiocyanate-conjugated carrageenans.

RESULTS

All three types of carrageenans were found to trigger eryptosis. Pro-eryptotic properties were type-dependent and λ-carrageenan had the strongest impact inducing phosphatidylserine membrane asymmetry, changes in cell volume, Ca2+ signaling and oxidative stress characterized by ROS overproduction, activation of lipid peroxidation and severe glutathione system depletion. Eryptosis induction by carrageenans does not require their uptake by erythrocytes. Changes in physicochemical properties of cell membrane were also type-dependent. No carrageenan-induced generation of superoxide and hydroxyl radicals was observed in cell-free milieu.

CONCLUSIONS

Our findings suggest that ι-, κ- and λ-types trigger eryptosis in a type-dependent manner and indicate that carrageenans can be further investigated as potential eryptosis-regulating therapeutic agents.

Orally administered gadolinium orthovanadate GdVO4:Eu3+ nanoparticles do not affect the hydrophobic region of cell membranes of leukocytes

AIM

To assess the phospholipid bilayer of white blood cells (WBCs) and the ability of leukocytes to generate reactive oxygen species (ROS) in rats orally exposed to GdVO₄:Eu³⁺ nanoparticle (VNP) solution for 2 weeks by fluorescent probes-ortho-hydroxy derivatives of 2,5-diaryl‑1,3‑oxazole.

METHODS

Steady-state fluorescence spectroscopy, i.e., a study by the environment-sensitive fluorescent probes 2‑(2'-OH-phenyl)-5-(4'-phenyl-phenyl)-1,3-oxazole (probe O6O) and 2‑(2'-OH-phenyl)-phenanthro[9,10]-1,3-oxazole (probe PH7), and flow cytometry, i.e., analysis of 2',7'-dichlorofluorescein (DCF), a product of a dye 2',7'-dichlorodihydrofluorescein diacetate (H₂DCFDA), fluorescence in CD45⁺/7-aminoactinomycin D (7-AAD)^- cells, were used to evaluate the state of cell membranes and reactive oxygen species (ROS) generation in leukocytes of rats orally exposed to gadolinium orthovanadate nanoparticles(VNPs).

RESULTS

No significant changes were detected in the spectra of the fluorescent probes bound to the WBCs from the rats orally exposed to nanoparticles in comparison with the corresponding spectra of the probes bound to the cells from the control group of animals. This indicates that in the case of the rats orally exposed to nanoparticles, no noticeable changes in physicochemical properties (i.e., in the polarity and the proton-donor ability) are observed in the lipid membranes of WBCs in the region where the probes locate. There was no statistically significant difference in the amount of ROS^high viable leukocytes in rats treated with VNPs and control samples.

CONCLUSION

Neither changes in the physical and chemical properties of the leukocyte membranes nor in ROS generation by WBCs are detected in the rats orally exposed to VNP solution for 2 weeks.