Hydroxylated Fatty Acids: The Role of the Sphingomyelin Synthase and the Origin of Selectivity

Sphingolipids are a class of lipids acting as key modulators of many physiological and pathophysiological processes. Hydroxylation patterns have a major influence on the biophysical properties of sphingolipids. In this work, we have studied the mechanism of action of hydroxylated lipids in sphingomyelin synthase (SMS). The structures of the two human isoforms, SMS1 and SMS2, have been generated through neural network supported homology. Furthermore, we have elucidated the reaction mechanism that allows SMS to recover the choline head from a phosphocholine (PC) and transfer it to ceramide, and we have clarified the role of the hydroxyl group in the interaction with the enzyme. Finally, the effect of partial inhibition of SMS on the levels of PC and sphingomyelin was calculated for different rate constants solving ordinary differential equation systems.

A Flavone-Based Solvatochromic Probe with A Low Expected Perturbation Impact on the Membrane Physical State

The study of the cell membrane is an ambitious and arduous objective since its physical state is regulated by a series of processes that guarantee its regular functionality. Among the different methods of analysis, fluorescence spectroscopy is a technique of election, non-invasive, and easy to use. Besides, molecular dynamics analysis (MD) on model membranes provides useful information on the possibility of using a new probe, following its positioning in the membrane, and evaluating the possible perturbation of the double layer. In this work, we report the rational design and the synthesis of a new fluorescent solvatochromic probe and its characterization in model membranes. The probe consists of a fluorescent aromatic nucleus of a 3-hydroxyflavone moiety, provided with a saturated chain of 18 carbon atoms and a zwitterionic head so to facilitate the anchoring to the polar heads of the lipid bilayer and avoid the complete internalization. It was possible to study the behavior of the probe in GUV model membranes by MD analysis and fluorescence microscopy, demonstrating that the new probe can efficiently be incorporated in the lipid bilayer, and give a color response, thanks to is solvatochromic properties. Moreover, MD simulation of the probe in the membrane supports the hypothesis of a reduced perturbation of the membrane physical state.

Plausible Emergence of Autocatalytic Cycles under Prebiotic Conditions

The emergence of life in a prebiotic world is an enormous scientific question of paramount philosophical importance. Even when life (in any sense we can define it) can be observed and replicated in the laboratory, it is only an indication of one possible pathway for life emergence, and is by no means be a demonstration of how life really emerged. The best we can hope for is to indicate plausible chemical–physical conditions and mechanisms that might lead to self-organizing and autopoietic systems. Here we present a stochastic simulation, based on chemical reactions already observed in prebiotic environments, that might help in the design of new experiments. We will show how the definition of simple rules for the synthesis of random peptides may lead to the appearance of networks of autocatalytic cycles and the emergence of memory.

Multifaceted Analyses of Isolated Mitochondria Establish the Anticancer Drug 2-Hydroxyoleic Acid as an Inhibitor of Substrate Oxidation and an Activator of Complex IV-Dependent State 3 Respiration

The synthetic fatty acid 2-hydroxyoleic acid (2OHOA) has been extensively investigated as a cancer therapy mainly based on its regulation of membrane lipid composition and structure, activating various cell fate pathways. We discovered, additionally, that 2OHOA can uncouple oxidative phosphorylation, but this has never been demonstrated mechanistically. Here, we explored the effect of 2OHOA on mitochondria isolated by ultracentrifugation from U118MG glioblastoma cells. Mitochondria were analyzed by shotgun lipidomics, molecular dynamic simulations, spectrophotometric assays for determining respiratory complex activity, mass spectrometry for assessing beta oxidation and Seahorse technology for bioenergetic profiling. We showed that the main impact of 2OHOA on mitochondrial lipids is their hydroxylation, demonstrated by simulations to decrease co-enzyme Q diffusion in the liquid disordered membranes embedding respiratory complexes. This decreased co-enzyme Q diffusion can explain the inhibition of disjointly measured complexes I–III activity. However, it doesn’t explain how 2OHOA increases complex IV and state 3 respiration in intact mitochondria. This increased respiration probably allows mitochondrial oxidative phosphorylation to maintain ATP production against the 2OHOA-mediated inhibition of glycolytic ATP production. This work correlates 2OHOA function with its modulation of mitochondrial lipid composition, reflecting both 2OHOA anticancer activity and adaptation to it by enhancement of state 3 respiration.

[Chronological age for the spontaneous resolution of vesicoureteral reflux]

OBJECTIVES

Vesicoureteral reflux (VUR) may have medical management, which implies prophylactic antibiotic therapy, control with serial urine cultures and imaging tests, such as annual voiding cystourethrogram (VCUG) or direct isotopic cystogram (DIC); or it may be surgical, when medical treatment fails, due to recurrent UTI or renal damage. We analyze the chronological age of the patient at which VUR resolve spontaneously, so that we know when we should have a more precise control with VCUG, avoiding a traumatic test and irradiation, but also avoiding to give prophylactic antibiotic without real need. We aim to associate age of resolution with VUR grade and side, and patient's gender.

METHODS

Retrospective study of patients with VUR under control at the Hospital Clinico of the Catholic University of Chile between 1996 and 2004.

INCLUSION CRITERIA

patients with the diagnosis of VUR grades I, II, and III obtained by VCUG, and spontaneous resolution of VUR on control VCUG or DIC, with no urological surgery, without bladder dysfunction or other urinary tract disorders. 156 patients were included.

RESULTS

73.5% are females, with a mean age at the time of resolution of 52.7 +/- 36 months. 74.3% of the patients had unilateral VUR. There were not statistically significant differences in the age of resolution between unilateral or bilateral VUR, or between different grades. There is a statistically significant difference in the age of resolution comparing gender (p < 0.0001), resolving between 12 and 17 months before in males.

CONCLUSIONS

VUR improves earlier in males than females, without differences between unilateral-bilateral, or VUR grade I, II and III. The control VCUG or DIC should be indicated in relation to the most probable chronological age of resolution, generally around 4 years of age, and not once a year, so avoiding irradiation and trauma, with a special consideration to the child gender.