Cannabidiol and Cannabigerol Modify the Composition and Physicochemical Properties of Keratinocyte Membranes Exposed to UVA.

The action of UVA radiation (both that derived from solar radiation and that used in the treatment of skin diseases) modifies the function and composition of keratinocyte membranes. Therefore, this study aimed to assess the effects of phytocannabinoids (CBD and CBG), used singly and in combination, on the contents of phospholipids, ceramides, lipid rafts and sialic acid in keratinocyte membranes exposed to UVA radiation, together with their structure and functionality. The phytocannabinoids, especially in combination (CBD+CBG), partially prevented increased levels of phosphatidylinositols and sialic acid from occurring and sphingomyelinase activity after the UVA exposure of keratinocytes. This was accompanied by a reduction in the formation of lipid rafts and malondialdehyde, which correlated with the parameters responsible for the integrity and functionality of the keratinocyte membrane (membrane fluidity and permeability and the activity of transmembrane transporters), compared to UVA-irradiated cells. This suggests that the simultaneous use of two phytocannabinoids may have a protective effect on healthy cells, without significantly reducing the therapeutic effect of UV radiation used to treat skin diseases such as psoriasis.

In Silico Analysis Reveals the Modulation of Ion Transmembrane Transporters in the Cerebellum of Alzheimer's Disease Patients.

Alzheimer's disease (AD) is the most common neurodegenerative disorder. AD hallmarks are extracellular amyloid ß (Aß) plaques and intracellular neurofibrillary tangles in the brain. It is interesting to notice that Aß plaques appear in the cerebellum only in late stages of the disease, and then it was hypothesized that it can be resistant to specific neurodegenerative mechanisms. However, the role of cerebellum in AD pathogenesis is not clear yet. In this study, we performed an in silico analysis to evaluate the transcriptional profile of cerebellum in AD patients and non-AD subjects in order to deepen the knowledge on its role in AD. The analysis evidenced that only the molecular function (MF) "active ion transmembrane transporter activity" was overrepresented. Regarding the 21 differentially expressed genes included in this MF, some of them may be involved in the ion dyshomeostasis reported in AD, while others assumed, in the cerebellum, an opposite regulation compared to those reported in other brain regions in AD patients. They might be associated to a protective phenotype, that may explain the initial resistance of cerebellum to neurodegeneration in AD. Of note, this MF was not overrepresented in prefrontal cortex and visual cortex indicating that it is a peculiarity of the cerebellum.

The affinity of transthyretin for T3 or T4 does not determine which form of the hormone accumulates in the choroid plexus.

Normal development of the brain is dependent on the required amounts of thyroid hormones (THs) reaching specific regions of the brain during each stage of ontogeny. Many proteins are involved with regulation of TH bioavailability in the brain: the TH distributor protein transthyretin (TTR), TH transmembrane transporters (e.g. MCT8, MCT10, LAT1, OATP1C1) and deiodinases (D1, D2 and D3) which either activate or inactivate THs. Previous studies revealed that in mammals, T4, but not T3, accumulated in the choroid plexus and then entered the cerebrospinal fluid. In all mammalian species studied so far, TTR binds T4 with higher affinity than T3, whereas TTR in non-mammalian vertebrates binds T3 with higher affinity than T4. We investigated if the form of TH preferentially bound by TTR influenced the form of the TH that accumulated in the choroid plexus and consequently other areas of the brain. We measured the mRNA levels corresponding to TTR, MCT8, MCT10, LAT1, OATP1C1, D1, D2 and D3 in the brains of chickens at 11days post-hatching. TTR, D3 and OATP1C1 expression were found to be highly concentrated in the choroid plexus. D1, MCT8 and MCT10 mRNA levels were slightly greater in the choroid plexus than in other areas of the brain while D2 mRNA levels were lower. LAT1 mRNA was evenly expressed throughout the brain. Therefore, the choroid plexus appears to be a structure which exhibits sophisticated control of TH levels within the brain. We also measured the uptake of intravenously injected 125I-T3 and 125I-T4 into brains of chickens of the same age. 125I-T4 but not 125I-T3 accumulated in the choroid plexus and optic lobes. Therefore, the form of TH preferentially bound by TTR does not determine the form of TH that accumulates in the choroid plexus and other areas of the brain. As for mammals, T3 present in the avian brain therefore seems mainly produced locally by conversion of T4 into T3 by D2.

Molecular parameters and transmembrane transport mechanism of imidazolium-functionalized binols.

We describe the molecular parameters governing the transmembrane activity of imidazolium-functionalized anion transporters and present a detailed mechanistic study. These ionophores adopt a mobile-carrier mechanism for short methyl and butyl chains, a combined mobile-carrier/transmembrane-pore mechanism for octyl and dodecyl chains, and form transmembrane aggregates for hexadecyl chains.

Protein Binder Toolbox for Studies of Solute Carrier Transporters.

Transporters of the solute carrier superfamily (SLCs) are responsible for the transmembrane traffic of the majority of chemical substances in cells and tissues and are therefore of fundamental biological importance. As is often the case with membrane proteins that can be heavily glycosylated, a lack of reliable high-affinity binders hinders their functional analysis. Purifying and reconstituting transmembrane proteins in their lipidic environments remains challenging and standard approaches to generate binders for multi-transmembrane proteins, such as SLCs, channels or G protein-coupled receptors (GPCRs) are lacking. While generating protein binders to 27 SLCs, we produced full length protein or cell lines as input material for binder generation by selected binder generation platforms. As a result, we obtained 525 binders for 22 SLCs. We validated the binders with a cell-based validation workflow using immunofluorescent and immunoprecipitation methods to process all obtained binders. Finally, we demonstrated the potential applications of the binders that passed our validation pipeline in structural, biochemical, and biological applications using the exemplary protein SLC12A6, an ion transporter relevant in human disease. With this work, we were able to generate easily renewable and highly specific binders against SLCs, which will greatly facilitate the study of this neglected protein family. We hope that the process will serve as blueprint for the generation of binders against the entire superfamily of SLC transporters.

Transmembrane Transporter Constructed from PlatinumMetal-organic Cage.

A perylene diimide-based metal-organic cage (MOC4c) was found to be an efficient transmembrane transporter for ions and small molecules through the internal cavity of the cage. MOC4c could selectively transport different anions, as evidenced by vesicle-based fluorescenceassays and planar lipid bilayer-based current recordings.Furthermore, MOC4c appears tofacilitate calcein transport across the lipid bilayer membrane of a livingcell, suggesting that MOC4c could be used as a biologicaltool for small molecule drugstransmembrane transportation.

Acidosis tubular renal en niños: conceptos actuales de diagnóstico y tratamiento / Renal tubular acidosis in children: state of the art, diagnosis and treatment

Recientemente se ha detectado un sobre-diagnóstico de acidosis tubular renal (ATR) en niños mexicanos, posiblemente por errores de diagnóstico y desconocimiento de la fisiopatología y bioquímica molecular del padecimiento. El objetivo de la presente publicación es facilitar el conocimiento y la realización del diagnóstico acertado de la ATR, que es una condición clínica poco frecuente a escala mundial. La ATR es la alteración del metabolismo ácido-base producida por el defecto de reabsorción del bicarbonato en los túbulos renales proximales (ATRp o proximal tipo 2) o de la excreción de hidrogeniones en la nefrona distal (ATRd o distal tipo 1). La ATR tipo 4 (hipercaliémica) obedece a alteraciones del metabolismo de la aldosterona. La ATR puede ser primaria, secundaria, adquirida o hereditaria. Las principales alteraciones ocurren en proteínas como la anhidrasa carbónica (AC II y IV), la H+ATPasa, el intercambiador HCO3-/Cl- (AE1) y el cotransportador Na+/HCO3- (NBCe1). El diagnóstico debe incluir la demostración de acidosis metabólica hiperclorémica con hiato aniónico sanguíneo normal (en sangre arterial o arterializada), pH sanguíneo menor a 7.35 en pacientes con acidosis metabólica descompensada (aunque puede encontrarse normal en los casos con compensación completa), alteración del hiato aniónico urinario y del gradiente urinario/sanguíneo de la pCO2. En el caso de la ATR secundaria, es importante determinar el diagnóstico de la enfermedad sistémica que la origina. Con frecuencia, los criterios diagnósticos se acompañan de diversos síntomas como anorexia, poliuria, polidipsia, detención del crecimiento, raquitismo, nefrocalcinosis, litiasis renal y sordera temprana o tardía (en la ATRd). El tratamiento alcalino depende del tipo de la ATR: bicarbonato de sodio para la ATRp o bicarbonato o citrato de potasio para la ATRd. La administración de calcio y vitamina D depende del grado de la alteración ósea.

Overdiagnosis of renal tubular acidosis (RTA) has been recently detected in Mexican children, perhaps due to diagnostic errors as well as in a lack of knowledge regarding the pathophysiology and molecular biochemistry involved in this illness. The objective of the present study is to facilitate the knowledge and diagnosis of RTA, a clinical condition infrequently seen worldwide. RTA is an alteration of the acid-base equilibrium due to a bicarbonate wasting in the proximal renal tubules (proximal RTA, pRTA or type 2 RTA) or due to a distal nephron hydrogen ion excretion defect (distal RTA, dRTA or type 1 RTA). Hyperkalemic, or type 4 RTA, is due to alterations in aldosterone metabolism. RTA may be primary, secondary, acquired or hereditary and frequently presents secondary to an array of systemic diseases, usually accompanied by multiple renal tubular defects. The main defect occurs in the transmembrane transporters such as carbonic anhydrase (CA I and II), H+-ATPase, HCO3-/Cl- (AE1) exchanger and Na+/HCO3- (NBCe1) cotransporter. Diagnosis should include the presence of hyperchloremic metabolic acidosis with normal serum anion gap (done in an arterial or arterialized blood sample), lack of appetite, polyuria, thirst, growth failure, and rickets; nephrocalcinosis and renal stones (in dRTA); abnormal urine anion gap and abnormal urine/serum pCO2 gradient. Diagnosis of a primary systemic disease must be made in cases of secondary RTA. Bicarbonate or potassium citrate therapy, as well as potassium, calcium and vitamin D administration depends on the type and severity of the RTA.