Modulation of Phospholipase A2 Membrane Activity by Anti-inflammatory Drugs.

The phospholipase A2 (PLA2) superfamily consists of lipolytic enzymes that hydrolyze specific cell membrane phospholipids and have long been considered a central hub of biosynthetic pathways, where their lipid metabolites exert a variety of physiological roles. A misregulated PLA2 activity is associated with mainly inflammatory-derived pathologies and thus has shown relevant therapeutic potential. Many natural and synthetic anti-inflammatory drugs (AIDs) have been proposed as direct modulators of PLA2 activity. However, despite the specific chemical properties that these drugs share in common, little is known about the indirect modulation able to finely tune membrane structural changes at the precise lipid-binding site. Here, we use a novel experimental strategy based on differential scanning calorimetry to systematically study the structural properties of lipid membrane systems during PLA2 cleavage and under the influence of several AIDs. For a better understanding of the AIDs-membrane interaction, we present a comprehensive and comparative set of molecular dynamics (MD) simulations. Our thermodynamic results clearly demonstrate that PLA2 cleavage is hindered by those AIDs that significantly reduce the lipid membrane cooperativity, while the rest of the AIDs oppositely tend to catalyze PLA2 activity to different extents. On the other hand, our MD simulations support experimental results by providing atomistic details on the binding, insertion, and dynamics of each AID on a pure lipid system; the drug efficacy to impact membrane cooperativity is related to the lipid order perturbation. This work suggests a membrane-based mechanism of action for diverse AIDs against PLA2 activity and provides relevant clues that must be considered in its modulation.

Cryo-EM structure of the cytoplasmic domain of murine transient receptor potential cation channel subfamily C member 6 (TRPC6).

The kidney maintains the internal milieu by regulating the retention and excretion of proteins, ions, and small molecules. The glomerular podocyte forms the slit diaphragm of the ultrafiltration filter, whose damage leads to progressive kidney failure and focal segmental glomerulosclerosis (FSGS). The canonical transient receptor potential 6 (TRPC6) ion channel is expressed in the podocyte, and mutations in its cytoplasmic domain cause FSGS in humans. In vitro evaluation of disease-causing mutations in TRPC6 has revealed that these genetic alterations result in abnormal ion channel gating. However, the mechanism whereby the cytoplasmic domain modulates TRPC6 function is largely unknown. Here, we report a cryo-EM structure of the cytoplasmic domain of murine TRPC6 at 3.8 Å resolution. The cytoplasmic fold of TRPC6 is characterized by an inverted dome-like chamber pierced by four radial horizontal helices that converge into a vertical coiled-coil at the central axis. Unlike other TRP channels, TRPC6 displays a unique domain swap that occurs at the junction of the horizontal helices and coiled-coil. Multiple FSGS mutations converge at the buried interface between the vertical coiled-coil and the ankyrin repeats, which form the dome, suggesting these regions are critical for allosteric gating modulation. This functionally critical interface is a potential target for drug design. Importantly, dysfunction in other family members leads to learning deficits (TRPC1/4/5) and ataxia (TRPC3). Our data provide a structural framework for the mechanistic investigation of the TRPC family.

Structure-function analyses of the ion channel TRPC3 reveal that its cytoplasmic domain allosterically modulates channel gating.

The transient receptor potential ion channels support Ca2+ permeation in many organs, including the heart, brain, and kidney. Genetic mutations in transient receptor potential cation channel subfamily C member 3 (TRPC3) are associated with neurodegenerative diseases, memory loss, and hypertension. To better understand the conformational changes that regulate TRPC3 function, we solved the cryo-EM structures for the full-length human TRPC3 and its cytoplasmic domain (CPD) in the apo state at 5.8- and 4.0-Å resolution, respectively. These structures revealed that the TRPC3 transmembrane domain resembles those of other TRP channels and that the CPD is a stable module involved in channel assembly and gating. We observed the presence of a C-terminal domain swap at the center of the CPD where horizontal helices (HHs) transition into a coiled-coil bundle. Comparison of TRPC3 structures revealed that the HHs can reside in two distinct positions. Electrophysiological analyses disclosed that shortening the length of the C-terminal loop connecting the HH with the TRP helices increases TRPC3 activity and that elongating the length of the loop has the opposite effect. Our findings indicate that the C-terminal loop affects channel gating by altering the allosteric coupling between the cytoplasmic and transmembrane domains. We propose that molecules that target the HH may represent a promising strategy for controlling TRPC3-associated neurological disorders and hypertension.

Pentobarbital modifies the lipid raft-protein interaction: A first clue about the anesthesia mechanism on NMDA and GABAA receptors.

Recent studies have shown that anesthetic agents alter the physical properties of lipid rafts on model membranes. However, if this destabilization occurs in brain membranes, altering the lipid raft-protein interaction, remains unknown. We analyzed the effects produced by pentobarbital (PB) on brain plasma membranes and lipid rafts in vivo. We characterized for the first time the thermotropic behavior of plasma membranes, synaptosomes, and lipid rafts from rat brain. We found that the transition temperature from the ordered gel to disordered liquid phase of lipids is close to physiological temperature. We then studied the effect of PB on protein composition of lipid rafts. Our results show a reduction of the total protein associated to rafts, with a higher reduction of the NMDAR compared to the GABAA receptor. Both receptors are considered the main targets of PB. In general, our results suggest that lipid rafts could be plausible mediators in anesthetic action.

Insights into the mechanism of crotamine and potential targets involved in obesity-related metabolic pathways.

Crotamine (Ctm) is a peptide isolated from Crotalus durissus terrificus venom. This molecule has been demonstrated to diminish body weight gain and enhance browning in adipose tissue, glucose tolerance, and insulin sensitivity; hence, it has been postulated as an anti-obesogenic peptide. However, the mechanism to elicit the anti-obesogenic effects has yet to be elucidated. Thus, we investigated the possible interaction of Ctm with receptors involved in obesity-related metabolic pathways through protein-protein docking and molecular dynamics refinement. To test the anti-obesogenic mechanism of Ctm, we selected and retrieved 18 targets involved in obesity-related drug discovery from Protein Data Bank. Then, we performed protein-protein dockings. The best three Ctm-target models were selected and refined by molecular dynamics simulations. Molecular docking demonstrated that Ctm was able to interact with 13 of the 18 targets tested. Having a better docking score with glucagon-like peptide-1 receptor (GLP-1R) (-1430.2 kcal/mol), DPP-IV (dipeptidyl peptidase-IV) (-1781.7 kcal/mol) and α-glucosidase (-1232.3 kcal/mol). These three models were refined by molecular dynamics. Ctm demonstrated a higher affinity for GLP-1R (ΔG: -41.886 ± 2.289 kcal/mol). However, Ctm interaction was more stable with DPP-IV (RMSD: 0.360 ± 0.015 nm, Radius of gyration: 2.781 ± 0.009 nm). Moreover, the number of interactions and the molecular mechanics energies of Ctm residues suggest that the interaction of Ctm with these receptors is mainly mediated by basic-hydrophobic dyads Y1-K2, W31-R32, and W33-R34. Together, all these results allow elucidating a possible molecular mechanism behind the previously described anti-obesogenic effects.

A revisited history of cacao domestication in pre-Columbian times revealed by archaeogenomic approaches.

Humans have a long history of transporting and trading plants, contributing to the evolution of domesticated plants. Theobroma cacao originated in the Neotropics from South America. However, little is known about its domestication and use in these regions. In this study, ceramic residues from a large sample of pre-Columbian cultures from South and Central America were analyzed using archaeogenomic and biochemical approaches. Here we show, for the first time, the widespread use of cacao in South America out of its native Amazonian area of origin, extending back 5000 years, likely supported by cultural interactions between the Amazon and the Pacific coast. We observed that strong genetic mixing between geographically distant cacao populations occurred as early as the middle Holocene, in South America, driven by humans, favoring the adaptation of T. cacao to new environments. This complex history of cacao domestication is the basis of today's cacao tree populations and its knowledge can help us better manage their genetic resources.

Linoleic acid improves PIEZO2 dysfunction in a mouse model of Angelman Syndrome.

Angelman syndrome (AS) is a neurogenetic disorder characterized by intellectual disability and atypical behaviors. AS results from loss of expression of the E3 ubiquitin-protein ligase UBE3A from the maternal allele in neurons. Individuals with AS display impaired coordination, poor balance, and gait ataxia. PIEZO2 is a mechanosensitive ion channel essential for coordination and balance. Here, we report that PIEZO2 activity is reduced in Ube3a deficient male and female mouse sensory neurons, a human Merkel cell carcinoma cell line and female human iPSC-derived sensory neurons with UBE3A knock-down, and de-identified stem cell-derived neurons from individuals with AS. We find that loss of UBE3A decreases actin filaments and reduces PIEZO2 expression and function. A linoleic acid (LA)-enriched diet increases PIEZO2 activity, mechano-excitability, and improves gait in male AS mice. Finally, LA supplementation increases PIEZO2 function in stem cell-derived neurons from individuals with AS. We propose a mechanism whereby loss of UBE3A expression reduces PIEZO2 function and identified a fatty acid that enhances channel activity and ameliorates AS-associated mechano-sensory deficits.

Ciliated Peritrichous Protozoa in a Tezontle-Packed Sequencing Batch Reactor as Potential Indicators of Water Quality.

The presence of colonial and solitary ciliated peritrichous protozoa was determined in a Sequencing Batch Reactor system filled with tezontle, a volcanic rock, economic, and abundant material that can be found in some parts of the world, like Mexico. The presence of these protozoa was related to the removal efficiencies of organic matter. Also, two novel staining techniques are proposed for staining both colonial and solitary peritrichous protozoa. The results show that tezontle promotes the growth of solitary and colonial ciliated peritrichous protozoa, which, once identified, could be used as indicators of the efficiency of the wastewater treatment process. Additionally, the staining techniques established in the current study allowed the precise observation of protozoan nuclei. They can represent a useful complementary methodology for identifying protozoan species present in water treatment processes, along with the already existing identification techniques. The number and variety of protozoa found in the system may be considered potential bioindicators of water quality during biological treatments.

Ca2+-mediated enhancement of anesthetic diffusion across phospholipid multilamellar systems.

Although sharing common properties with other divalent cations, calcium ions induce fine-tuned electrostatic effects essential in many biological processes. Not only related with protein structure or ion channels, calcium is also determinant for other biomolecules such as lipids or even drugs. Cellular membranes are the first interaction barriers for drugs. Depending on their hydrophilic, hydrophobic or amphipathic properties, they have to overcome such barriers to permeate and diffuse through inner lipid bilayers, cells or even tissues. In this context, the role of calcium in the permeation of cationic amphiphilic drugs (CADs) through lipid membranes is not well understood. We combine differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) to investigate the effect of Ca2+ on the interlamellar diffusion kinetics of the local anesthetic tetracaine (TTC) in multilamellar artificial membrane systems. Our DSC results show the interesting phenomenon that TTC diffusion can be modified in two different ways in the presence of Ca2+. Furthermore, TTC diffusion exhibits a thermal-dependent membrane interaction in the presence of Ca2+. The FTIR results suggest the presence of ion-dipole interactions between Ca2+ and the carbonyl group of TTC, leading us to hypothesize that Ca2+ destabilizes the hydration shell of TTC, which in turn diffuses deeper into the multilamellar lipid structures. Our results demonstrate the relevance of the Ca2+ ion in the drug permeation and diffusion through lipid bilayers.

Cardio-respiratory responses of the 6-minute walk test in patients with refractory heart failure during the preoperative period for heart transplant surgery.

BACKGROUND: The six-minute walk test (6MWT) has been used to assess functional capacity, clinical status and prognosis. There are a very few descriptions in the literature on the safety and metabolic impact of the test, especially in patients with severe heart failure, awaiting cardiac transplantation. OBJECTIVE: The aim of the present study was to assess the cardiovascular responses and correlate the performance on the 6MWT with clinical status. METHOD: From 15 initial candidates, twelve patients (10 males) aged 52 +/- 8 years were submitted to a comprehensive clinical evaluation. The patients performed the 6MWT with electrocardiographic and perceived exertion monitoring in addition to determination of blood lactate concentration. Patients were followed up for 12 months. RESULTS: The patients walked 399.4 +/- 122.5 meters, reaching a perceived exertion (PE) of 14.3 +/- 1.5 and an increase of 34% in resting heart rate. Two patients exhibited a greater severity of arrhythmia prior to the 6MWT, which did not increase during exertion. Four patients exhibited a significant increase in blood lactate levels (>5 mmol/dL) and three interrupted the test prematurely. The distance walked (D) revealed a correlation with the ejection fraction (%) and functional classification (NYHA). After 12 months of follow up, three patients died and seven were re-hospitalized due to heart failure decompensation. CONCLUSION: Clinical and electrocardiographic behavior suggests that the 6MWT is safe, but may be considered of high intensity for some patients with severe heart failure. Variables related to the performance on the 6MWT may be associated to worsening clinical status in this population.

Dietary fatty acids fine-tune Piezo1 mechanical response.

Mechanosensitive ion channels rely on membrane composition to transduce physical stimuli into electrical signals. The Piezo1 channel mediates mechanoelectrical transduction and regulates crucial physiological processes, including vascular architecture and remodeling, cell migration, and erythrocyte volume. The identity of the membrane components that modulate Piezo1 function remain largely unknown. Using lipid profiling analyses, we here identify dietary fatty acids that tune Piezo1 mechanical response. We find that margaric acid, a saturated fatty acid present in dairy products and fish, inhibits Piezo1 activation and polyunsaturated fatty acids (PUFAs), present in fish oils, modulate channel inactivation. Force measurements reveal that margaric acid increases membrane bending stiffness, whereas PUFAs decrease it. We use fatty acid supplementation to abrogate the phenotype of gain-of-function Piezo1 mutations causing human dehydrated hereditary stomatocytosis. Beyond Piezo1, our findings demonstrate that cell-intrinsic lipid profile and changes in the fatty acid metabolism can dictate the cell's response to mechanical cues.

Purification and Reconstitution of TRPV1 for Spectroscopic Analysis.

Polymodal ion channels transduce multiple stimuli of different natures into allosteric changes; these dynamic conformations are challenging to determine and remain largely unknown. With recent advances in single-particle cryo-electron microscopy (cryo-EM) shedding light on the structural features of agonist binding sites and the activation mechanism of several ion channels, the stage is set for an in-depth dynamic analysis of their gating mechanisms using spectroscopic approaches. Spectroscopic techniques such as electron paramagnetic resonance (EPR) and double electron-electron resonance (DEER) have been mainly restricted to the study of prokaryotic ion channels that can be purified in large quantities. The requirement for large amounts of functional and stable membrane proteins has hampered the study of mammalian ion channels using these approaches. EPR and DEER offer many advantages, including determination of the structure and dynamic changes of mobile protein regions, albeit at low resolution, that might be difficult to obtain by X-ray crystallography or cryo-EM, and monitoring reversible gating transition (i.e., closed, open, sensitized, and desensitized). Here, we provide protocols for obtaining milligrams of functional detergent-solubilized transient receptor potential cation channel subfamily V member 1 (TRPV1) that can be labeled for EPR and DEER spectroscopy.

The use and domestication of Theobroma cacao during the mid-Holocene in the upper Amazon.

Cacao (Theobroma cacao L.) is an important economic crop, yet studies of its domestication history and early uses are limited. Traditionally, cacao is thought to have been first domesticated in Mesoamerica. However, genomic research shows that T. cacao's greatest diversity is in the upper Amazon region of northwest South America, pointing to this region as its centre of origin. Here, we report cacao use identified by three independent lines of archaeological evidence-cacao starch grains, absorbed theobromine residues and ancient DNA-dating from approximately 5,300 years ago recovered from the Santa Ana-La Florida (SALF) site in southeast Ecuador. To our knowledge, these findings constitute the earliest evidence of T. cacao use in the Americas and the first unequivocal archaeological example of its pre-Columbian use in South America. They also reveal the upper Amazon region as the oldest centre of cacao domestication yet identified.

Expression and Purification of the Pain Receptor TRPV1 for Spectroscopic Analysis.

The transient receptor potential vanilloid 1 (TRPV1) channel is an essential component of the cellular mechanism through which noxious stimuli evoke pain. Functional and structural characterizations of TRPV1 shed light on vanilloid activation, yet the mechanisms for temperature and proton gating remain largely unknown. Spectroscopic approaches are needed to understand the mechanisms by which TRPV1 translates diverse stimuli into channel opening. Here, we have engineered a minimal cysteine-less rat TRPV1 construct (eTRPV1) that can be stably purified and reconstituted for spectroscopic studies. Biophysical analyses of TRPV1 constructs reveal that the S5-pore helix loop influences protein stability and vanilloid and proton responses, but not thermal sensitivity. Cysteine mutants retain function and stability for double electron-electron resonance (DEER) and electron paramagnetic resonance (EPR) spectroscopies. DEER measurements in the closed state demonstrate that eTRPV1 reports distances in the extracellular vestibule, equivalent to those observed in the apo TRPV1 structure. EPR measurements show a distinct pattern of mobilities and spectral features, in detergent and liposomes, for residues at the pore domain that agree with their location in the TRPV1 structure. Our results set the stage for a systematic characterization of TRPV1 using spectroscopic approaches to reveal conformational changes compatible with thermal- and ligand-dependent gating.

Omega-3 Fatty Acids Modulate TRPV4 Function through Plasma Membrane Remodeling.

Dietary consumption of ω-3 polyunsaturated fatty acids (PUFAs), present in fish oils, is known to improve the vascular response, but their molecular targets remain largely unknown. Activation of the TRPV4 channel has been implicated in endothelium-dependent vasorelaxation. Here, we studied the contribution of ω-3 PUFAs to TRPV4 function by precisely manipulating the fatty acid content in Caenorhabditis elegans. By genetically depriving the worms of PUFAs, we determined that the metabolism of ω-3 fatty acids is required for TRPV4 activity. Functional, lipid metabolome, and biophysical analyses demonstrated that ω-3 PUFAs enhance TRPV4 function in human endothelial cells and support the hypothesis that lipid metabolism and membrane remodeling regulate cell reactivity. We propose a model whereby the eicosanoid's epoxide group location increases membrane fluidity and influences the endothelial cell response by increasing TRPV4 channel activity. ω-3 PUFA-like molecules might be viable antihypertensive agents for targeting TRPV4 to reduce systemic blood pressure.

Sterilization by Cooling in Isochoric Conditions: The Case of Escherichia coli.

High hydrostatic pressure (HHP) affects the structure, metabolism and survival of micro-organisms including bacteria. For this reason HHP is a promising treatment in the food industry. The aim of this work is to evaluate the effect of high pressure, under isochoric cooling conditions, on Escherichia coli, where such high pressure develops due to the fact water cannot expand. We combine survival curves obtained by spectrophotometry and images of atomic force microscopy in this study. Our results show that cooling at -20 and -30°C leads to a partial destruction of a Escherichia coli population. However, cooling at -15°C causes a total extermination of bacteria. This intriguing result is explained by the phase diagram of water. In the first case, the simultaneous formation of ice III and ice Ih crystals provides a safe environment for bacteria. In the second case (-15°C) Escherichia coli remains in a metastable and amorphous free-of-crystals liquid subjected to high pressure. Our work is the first experimental study carried out to inactivate Escherichia coli under isochoric cooling conditions. Unlike HHP, which is based on the application of an external load to augment the pressure, this technique only requires cooling. The method could be used for annihilation of other Escherichia coli strains and perhaps other micro-organisms.

The influence of non polar and polar molecules in mouse motile cells membranes and pure lipid bilayers.

We report an experimental study of mouse sperm motility that shows chief aspects characteristic of neurons: the anesthetic (produced by tetracaine) and excitatory (produced by either caffeine or calcium) effects and their antagonic action. While tetracaine inhibits sperm motility and caffeine has an excitatory action, the combination of these two substances balance the effects, producing a motility quite similar to that of control cells. We also study the effects of these agents (anesthetic and excitatory) on the melting points of pure lipid liposomes constituted by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and dipalmitoyl phosphatidic acid (DPPA). Tetracaine induces a large fluidization of the membrane, shifting the liposomes melting transition temperature to much lower values. The effect of caffeine is null, but its addition to tetracaine-doped liposomes greatly screen the fluidization effect. A high calcium concentration stiffens pure lipid membranes and strongly reduces the effect of tetracaine. Molecular Dynamics Simulations are performed to further understand our experimental findings at the molecular level. We find a strong correlation between the effect of antagonic molecules that could explain how the mechanical properties suitable for normal cell functioning are affected and recovered.

Expansion and evaluation of data characterizing the structural behavior of the pediatric abdomen.

Despite the importance of abdominal injuries in children involved in motor vehicle collisions, only two papers have reported experimental data quantifying the pediatric abdominal response to belt loading. One developed and characterized a porcine model of the pediatric abdomen and the other presented a series of tests performed on a single pediatric (7-year-old female) post-mortem human subject (PMHS) and used the data to evaluate the efficacy of the porcine model. The current paper presents the results from an additional pediatric (6-year-old female) PMHS test series and an expanded evaluation of the porcine model using the combined PMHS data. The two PMHS exhibited remarkably similar abdominal stiffness, both by level (upper and lower) and by rate (quasi-static and ∼2 m/s dynamic). Both PMHS and swine exhibited the same stiffness trend by abdominal level (lower stiffer than upper: 3444 N reaction force at 30.5 mm of displacement compared to 1756 N in the 6-year-old dynamic tests). The magnitude of lower abdomen stiffness was slightly less in the swine than in the PMHS (the average dynamic PMHS response was 1086 N greater than the porcine envelopes at 30.5 mm displacement) while the upper abdomen PMHS responses fit within the porcine response envelope.

Neuropatía femoral y hematoma bilateral de músculos psoas-iliaco asociados a tratamiento con warfarina / Femoral neuropathy and bilateral hematoma: psoas-iliac muscles associated with a warfarin treatment

Se presentó un hombre de 70 años que sufrió un hematoma bilateral de los músculos psoas-iliacos como consecuencia del tratamiento con warfarina. Después de 6 d de tratamiento analgésico, valores de índice internacional normalizado inferiores a 1,5 y control del sangrado, se indicó la warfarina para continuar la profilaxis por la prótesis valvular mecánica. Fue egresado con secuelas motoras por la neuropatía femoral y se ha mantenido con tratamiento fisioterapéutico. Se diagnosticó neuropatía por compresión del nervio femoral, por hematoma de los músculos psoas-ilíacos. Los casos de hematomas retroperitoneales son escasos en la literatura médica, en Cuba no encontramos casos publicados...

This is the case of a man suffered of a bilateral hematoma of psoas-iliac muscles as a consequence of warfarin treatment. After 6 days od analgesic treatment, values of INR lower than 1,5 and bleeding control warfarin was prescribed to continue the prophylaxis by mechanical valvular prosthesis. He was discharged with motor sequelae due to femoral neuropathy maintained with a physiotherapy treatment. A neuropathy by compression of femoral nerve due to hematoma of psoas-iliac muscles was diagnosed. The cases of retroperitoneal hematomas are scarce in medical literature and in Cuba there were not published cases...

Neuropatía femoral y hematoma bilateral de músculos psoas-iliaco asociados a tratamiento con warfarina / Femoral neuropathy and bilateral hematoma: psoas-iliac muscles associated with a warfarin treatment

Se presentó un hombre de 70 años que sufrió un hematoma bilateral de los músculos psoas-iliacos como consecuencia del tratamiento con warfarina. Después de 6 d de tratamiento analgésico, valores de índice internacional normalizado inferiores a 1,5 y control del sangrado, se indicó la warfarina para continuar la profilaxis por la prótesis valvular mecánica. Fue egresado con secuelas motoras por la neuropatía femoral y se ha mantenido con tratamiento fisioterapéutico. Se diagnosticó neuropatía por compresión del nervio femoral, por hematoma de los músculos psoas-ilíacos. Los casos de hematomas retroperitoneales son escasos en la literatura médica, en Cuba no encontramos casos publicados(AU)

This is the case of a man suffered of a bilateral hematoma of psoas-iliac muscles as a consequence of warfarin treatment. After 6 days od analgesic treatment, values of INR lower than 1,5 and bleeding control warfarin was prescribed to continue the prophylaxis by mechanical valvular prosthesis. He was discharged with motor sequelae due to femoral neuropathy maintained with a physiotherapy treatment. A neuropathy by compression of femoral nerve due to hematoma of psoas-iliac muscles was diagnosed. The cases of retroperitoneal hematomas are scarce in medical literature and in Cuba there were not published cases(AU)