Al(3+)-mediated changes on membrane fluidity affects the activity of PI-PLC but not of PLC

Novel 3D printed bioactive SiC orthopedic screw promotes bone growth associated activities by macrophages, neurons, and osteoblasts

Ceramic additive manufacturing currently relies on binders or high-energy lasers, each with limitations affecting final product quality and suitability for medical applications. To address these challenges, our laboratory has devised a surface activation technique for ceramic particles that eliminates the necessity for polymer binders or high-energy lasers in ceramic additive manufacturing. We utilized this method to 3D print bioactive SiC orthopedic screws and evaluated their properties. The study's findings reveal that chemical oxidation of SiC activated its surface, enabling 3D printing of orthopedic screws in a binder jet printer. Post-processing impregnation with NaOH and/or NH4OH strengthened the scaffold by promoting silica crystallization or partial conversion of silicon oxide into silicon nitride. The silica surface of the SiC 3D printed orthopedic screws facilitated osteoblast and neuron adhesion and extensive axon synthesis. The silicate ions released from the 3D printed SiC screws favorably modulated macrophage immune responses toward an M1 phenotype as indicated by the inhibition of TNFα secretions and of reactive oxygen species (ROS) expression along with the promotion of IL6R shedding. In contrast, under the same experimental conditions, Ti ions released from Ti6Al4V discs promoted macrophage TNFα secretion and ROS expression. In vivo tests demonstrated direct bone deposition on the SiC scaffold and a strong interfacial bond between the implanted SiC and bone. Immunostaining showed innervation, mineralization, and vascularization of the newly formed bone at the interface with SiC. Taken altogether, the 3D printed SiC orthopedic screws foster a favorable environment for wound healing and bone regeneration. The novel 3D printing method, based on ceramic surface activation represents a significant advancement in ceramic additive manufacturing and is applicable to a wide variety of materials.

Bioglass could increase cell membrane fluidity with ion products to develop its bioactivity

OBJECTIVES

Silicate bioactive glass (BG) has been widely demonstrated to stimulate both of the hard and soft tissue regeneration, in which ion products released from BG play important roles. However, the mechanism by which ion products act on cells on cells is unclear.

MATERIALS AND METHODS

Human umbilical vein endothelial cells and human bone marrow stromal cells were used in this study. Fluorescence recovery after photobleaching and generalized polarization was used to characterize changes in cell membrane fluidity. Migration, differentiation and apoptosis experiments were carried out. RNA and protein chip were detected. The signal cascade is simulated to evaluate the effect of increased cell membrane fluidity on signal transduction.

RESULTS

We have demonstrated that ion products released from BG could effectively enhance cell membrane fluidity in a direct and physical way, and Si ions may play a major role. Bioactivities of BG ion products on cells, such as migration and differentiation, were regulated by membrane fluidity. Furthermore, we have proved that BG ion products could promote apoptosis of injured cells based on our conclusion that BG ion products increased membrane fluidity.

CONCLUSIONS

This study proved that BG ion products could develop its bioactivity on cells by directly enhancing cell membrane fluidity and subsequently affected cell behaviours, which may provide an explanation for the general bioactivities of silicate material.

Serum metallome in pregnant women and the relationship with congenital malformations of the central nervous system: a case-control study

BACKGROUND

Congenital malformations of the central nervous system (CNS) consist of a wide range of birth defects of multifactorial origin.

METHODS

Concentrations of 44 metals were determined by Inductively Coupled Plasma Mass Spectrometry in serum of 111 mothers in the second trimester of pregnancy who carried a malformed fetus and compared them with serum concentrations of the same metals in 90 mothers with a normally developed fetus at the same week of pregnancy. Data are reported as means ± standard deviations.

RESULTS

We found a direct relationship between congenital defects of the CNS and maternal serum concentration of aluminum: it was statistically higher in women carrying a fetus with this class of malformation, compared both to mothers carrying a fetus with another class of malformation (6.45 ± 15.15 μg/L Vs 1.44 ± 4.21 μg/L, p < 0.0006) and to Controls (i.e. mothers carrying a normally-developed fetus) (6.45 ± 15.15 μg/L Vs 0.11 ± 0.51 μg/L, p < 0.0006). Moreover, Aluminum abundances were below the limit of detection in the majority of control samples.

CONCLUSION

CAluminum may play a role in the onset of central nervous system malformations, although the exact Aluminum species and related specific type of malformation needs further elucidation.

Aluminum ions alter the function of non-specific phospholipase C through the changes in plasma membrane physical properties

The first indication of the aluminum (Al) toxicity in plants growing in acidic soils is the cessation of root growth, but the detailed mechanism of Al effect is unknown. Here we examined the impact of Al stress on the activity of non-specific phospholipase C (NPC) in the connection with the processes related to the plasma membrane using fluorescently labeled phosphatidylcholine. We observed a rapid and significant decrease of labeled diacylglycerol (DAG), product of NPC activity, in Arabidopsis seedlings treated with AlCl₃. Interestingly, an application of the membrane fluidizer, benzyl alcohol, restored the level of DAG during Al treatment. Our observations suggest that the activity of NPC is affected by Al-induced changes in plasma membrane physical properties.

Loss of membrane fluidity and endocytosis inhibition are involved in rapid aluminum-induced root growth cessation in Arabidopsis thaliana

Aluminum (Al) toxicity is the main limiting factor in crop production on acid soils. The main symptom of Al toxicity is a rapid inhibition of root growth, but the mechanism of root growth cessation remains unclear. Here we examined the earliest changes in the plasma membrane and processes related to the membrane in the Arabidopsis thaliana root tip cells of roots grown in a hydropony. Al suppressed root growth within 2 min, inhibited endocytosis within 10 min of exposure and stabilized cortical microtubules within the first 30 min. Spectrofluorometric measurements of the plasma membrane isolated from Arabidopsis plants and labeled with the fluorescent probe laurdan showed that Al induced a reduction in membrane fluidity. Application of the membrane fluidizer, benzyl alcohol, restored partially membrane fluidity and also partially restored root growth during first 30 min of Al treatment. We concluded that Al-induced loss of membrane fluidity and endocytosis inhibition occurred very early during Al toxicity in plant roots and could be the earliest targets of Al treatment.

Impact of aluminum on the oxidation of lipids and enzymatic lipolysis in monomolecular films at the air/water interface

There is evidence that serious pathologies are associated with aluminum (Al). In the present work, the influence of Al on enzymatic lipolysis was studied with the aim to get more insight into the possible link between the Al-induced membrane modification and the cytotoxicity of the trivalent cation (AlIII). Lipid monolayers were used as model membranes. The monomolecular film technique allowed monitoring the Al-dependent modifications of the lipid monolayer properties and enzyme kinetics. Two enzymes, namely, Candida rugosa lipase and a calcium (CaII)-dependent phospholipase A2 from porcine pancreas, were used to catalyze the lipolysis of triglyceride and phosphoglyceride monolayers, respectively. The results obtained show that Al modifies both the monolayer structure and enzymatic reaction rates. While the enzymes used in this study can be considered as probes detecting lipid membrane properties, it cannot be excluded that in physiological conditions modulation of the enzyme action by the Al-bound membranes is among the reasons for Al toxicity.

Aluminum inhibits phosphatidic acid formation by blocking the phospholipase C pathway

Aluminum (Al(3+)) has been recognized as a main toxic factor in crop production in acid lands. Phosphatidic acid (PA) is emerging as an important lipid signaling molecule and has been implicated in various stress-signaling pathways in plants. In this paper, we focus on how PA generation is affected by Al(3+) using Coffea arabica suspension cells. We pre-labeled cells with [(32)P]orthophosphate ((32)Pi) and assayed for (32)P-PA formation in response to Al(3+). Treating cells for 15 min with either AlCl(3) or Al(NO(3))(3) inhibited the formation of PA. In order to test how Al(3+) affected PA signaling, we used the peptide mastoparan-7 (mas-7), which is known as a very potent stimulator of PA formation. The Al(3+) inhibited mas-7 induction of PA response, both before and after Al(3+) incubation. The PA involved in signaling is generated by two distinct phospholipid signaling pathways, via phospholipase D (PLD; EC: 3.1.4.4) or via Phospholipase C (PLC; EC: 3.1.4.3), and diacylglycerol kinase (DGK; EC 2.7.1.107). By labeling with (32)Pi for short periods of time, we found that PA formation was inhibited almost 30% when the cells were incubated with AlCl(3) suggesting the involvement of the PLC/DGK pathway. Incubation of cells with PLC inhibitor, U73122, affected PA formation, like AlCl(3) did. PLD in vivo activation by mas-7 was reduced by Al(3+). These results suggest that PA formation was prevented through the inhibition of the PLC activity, and it provides the first evidence for the role of Al toxicity on PA production.

Relevance of lipid polar headgroups on boron-mediated changes in membrane physical properties

Using liposomes composed of either brain phosphatidylcholine (PC), or binary mixtures of PC and phosphatidylserine (PS), galactolipids (GL), phosphatidylinositol (PI), cardiolipin (CL), phosphatidic acid (PA), or phosphatidylethanolamine (PE), we investigated the effects of graded amounts of boric acid (B, 0.5-1000 microM) on the following membrane physical properties: (a) surface potential, (b) lipid rearrangement through lateral phase separation, (c) fluidity, and (d) hydration. Incubation of the different populations of vesicles with B was associated with a small, but statistically significant, increase in membrane surface potential in PC, PC:PS, PC:GL, PC:PI, PC:PA, and PC:PE liposomes. B-induced lipid lateral rearrangement through lateral phase separation in PC, PC:PA, and PC:PE liposomes; but had no effects on PC:PS, PC:GL, and PC:PI liposomes. In PC liposomes B affected membrane fluidity at the water-lipid interface without affecting the hydrophobic core of the bilayer. In all the other binary liposomes studied, B increased membrane fluidity in both, the hydrophobic portion of the membrane and in the anionic domains. The above was associated with a decrease in the fluidity of the cationic domains. B (10-1000 microM) decreased membrane hydration regardless the composition of the liposomes. The obtained results demonstrate the ability of B to interact with membranes, and induce changes in membrane physical properties. Importantly, the extent of B-membrane interactions and the consequent effects were dependent on the nature of the lipid molecule; as such, B had greater affinity with lipids containing polyhydroxylated moieties such as GL and PI. These differential interactions may result in different B-induced modulations of membrane-associated processes in cells.