RESUMEN

Defense against intracellular acidification of breast cancer tissue depends on net acid extrusion via Na+,HCO3--cotransporter NBCn1/Slc4a7 and Na+/H+-exchanger NHE1/Slc9a1. NBCn1 is increasingly recognized as breast cancer susceptibility protein and promising therapeutic target, whereas evidence for targeting NHE1 is discordant. Currently, selective small molecule inhibitors exist against NHE1 but not NBCn1. Cellular assays-with some discrepancies-link NHE1 activity to proliferation, migration, and invasion; and disrupted NHE1 expression can reduce triple-negative breast cancer growth. Studies on human breast cancer tissue associate high NHE1 expression with reduced metastasis and-in some molecular subtypes-improved patient survival. Here, we evaluate Na+/H+-exchange and therapeutic potential of the NHE1 inhibitor cariporide/HOE-642 in murine ErbB2-driven breast cancer. Ex vivo, cariporide inhibits net acid extrusion in breast cancer tissue (IC50 = 0.18 µM) and causes small decreases in steady-state intracellular pH (pHi). In vivo, we deliver cariporide orally, by osmotic minipumps, and by intra- and peritumoral injections to address the low oral bioavailability and fast metabolism. Prolonged cariporide administration in vivo upregulates NBCn1 expression, shifts pHi regulation towards CO2/HCO3--dependent mechanisms, and shows no net effect on the growth rate of ErbB2-driven primary breast carcinomas. Cariporide also does not influence proliferation markers in breast cancer tissue. Oral, but not parenteral, cariporide elevates serum glucose by ∼1.5 mM. In conclusion, acute administration of cariporide ex vivo powerfully inhibits net acid extrusion from breast cancer tissue but lowers steady-state pHi minimally. Prolonged cariporide administration in vivo is compensated via NBCn1 and we observe no discernible effect on growth of ErbB2-driven breast carcinomas.

Asunto(s)

Neoplasias de la Mama , Proliferación Celular , Guanidinas , Receptor ErbB-2 , Intercambiador 1 de Sodio-Hidrógeno , Sulfonas , Guanidinas/farmacología , Femenino , Animales , Receptor ErbB-2/metabolismo , Receptor ErbB-2/genética , Receptor ErbB-2/antagonistas & inhibidores , Intercambiador 1 de Sodio-Hidrógeno/metabolismo , Intercambiador 1 de Sodio-Hidrógeno/antagonistas & inhibidores , Intercambiador 1 de Sodio-Hidrógeno/genética , Ratones , Humanos , Sulfonas/farmacología , Proliferación Celular/efectos de los fármacos , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/patología , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/genética , Simportadores de Sodio-Bicarbonato/metabolismo , Simportadores de Sodio-Bicarbonato/genética , Simportadores de Sodio-Bicarbonato/antagonistas & inhibidores , Línea Celular Tumoral , Concentración de Iones de Hidrógeno

RESUMEN

Prediabetes is a risk state that defines a high chance of developing diabetes and cardiovascular disease. Oxidative stress mediated by hyperglycemia-induced production of reactive species could play a crucial role in this context. In the present study, we investigated whether the anion exchange capability mediated by AE1 (SLC4A1), which is sensitive to oxidative stress, was altered in human red blood cells (RBCs) obtained from prediabetic volunteers. In addition, we assessed the precise composition of bioactive compounds and the potential benefits of finger lime juice extract (Citrus australasica, Faustrime cultivar) in counteracting oxidative stress-related functional alterations. Human RBCs from normal and prediabetic volunteers were incubated with 50 µg/mL juice extract for 2 h at 25°C. Juice extract restored alterations of the anion exchange capability mediated by AE1 and prevented the structural rearrangements of AE1 and α/ß-spectrin in prediabetic RBCs. AE1 functional and structural alterations were not associated with an increase in lipid peroxidation or protein oxidation at the level of the plasma membrane. An increased production of intracellular ROS, which provoked the oxidation of hemoglobin to methemoglobin, both reverted by juice extract, was instead observed. Importantly, juice extract also induced a reduction in glycated hemoglobin levels in prediabetic RBCs. Finally, juice extract blunted the overactivation of the endogenous antioxidant enzymes catalase and superoxide dismutase and prevented glutathione depletion in prediabetic RBCs. These findings contribute to clarifying cellular and molecular mechanisms related to oxidative stress and glycation events that may influence RBC and systemic homeostasis in prediabetes, identify AE1 as a sensitive biomarker of RBC structural and function alterations in prediabetes and propose finger lime juice extract as a natural antioxidant for the treatment and/or prevention of the complications associated with the prediabetic condition.

Asunto(s)

Proteína 1 de Intercambio de Anión de Eritrocito , Citrus , Eritrocitos , Estrés Oxidativo , Extractos Vegetales , Estado Prediabético , Humanos , Citrus/química , Eritrocitos/metabolismo , Eritrocitos/efectos de los fármacos , Estado Prediabético/metabolismo , Estado Prediabético/tratamiento farmacológico , Extractos Vegetales/farmacología , Extractos Vegetales/química , Proteína 1 de Intercambio de Anión de Eritrocito/metabolismo , Estrés Oxidativo/efectos de los fármacos , Jugos de Frutas y Vegetales/análisis , Masculino , Femenino , Persona de Mediana Edad , Adulto , Antioxidantes/farmacología , Antioxidantes/metabolismo , Antioxidantes/química

RESUMEN

CONTEXT: Hereditary distal renal tubular acidosis caused by SLC4A1 gene mutation (SLC4A1-dRTA) is a rare hereditary form of renal tubular acidosis. Rickets or osteomalacia is a common complication of SLC4A1-dRTA, and seriously affects patients' daily life. However, studies on the bone microstructure in SLC4A1-dRTA are limited. OBJECTIVE: This work aimed to evaluate the bone microstructure of SLC4A1-dRTA patients, compared to age- and sex-matched healthy controls and X-linked hypophosphatemic rickets (XLH) patients. METHODS: This was a retrospective study on eleven SLC4A1-dRTA patients. Clinical manifestations, biochemical and radiographical examinations were characterized. Bone microstructure was examined in seven SLC4A1-dRTA patients, seven healthy controls and twenty-one XLH patients using high-resolution peripheral quantitative computed tomography (HR-pQCT). RESULTS: Skeletal symptoms, including fracture, bone pain, and lower limb deformity, were presented in 72.7% of SLC4A1-dRTA patients. Short stature was presented in 63.6% of the patients. SLC4A1-dRTA patients had significantly lower volumetric BMD in the distal tibia, and more severe deteriorated trabecular bone in the distal radius and tibia than healthy controls. SLC4A1-dRTA patients had significantly more severe deteriorated trabecular bone in the distal radius and distal tibia compared to XLH patients. With long-term alkaline therapy, SLC4A1-dRTA patients had alleviation in bone pain, increase in height. CONCLUSIONS: Skeletal lesions were common clinical manifestations in SLC4A1-dRTA patients. Compared with XLH, another common type of rickets, SLC4A1-dRTA patients had more severe trabecular bone microstructure damage, further supporting the necessity of early diagnosis and timely treatment of the disease.

RESUMEN

BACKGROUND: Altered expression and activity of solute carrier family 4 member 4 (SLC4A4) could affect the growth, survival and metastasis of tumor cells. Currently, the role of SLC4A4 in lung adenocarcinoma (LUAD) immunotherapy and prognosis was not entirely clear. METHODS: We analyzed SLC4A4 expression in LUAD tissues and cell lines using quantitative reverse transcription-polymerase chain reaction, Western blotting, and immunohistochemistry. The effects of SLC4A4 overexpression on angiogenesis, cell migration, invasion, and epithelial-mesenchymal transition were examined. Public databases helped construct a risk model evaluating SLC4A4's expression on LUAD prognosis and immunotherapy response. Additionally, a xenograft model, flow cytometry, and enzyme-linked immunosorbent assay further explored SLC4A4's role in tumor immune microenvironment infiltration. RESULTS: Upregulation of SLC4A4 promoted apoptosis in the LUAD cell line and significantly inhibited the migration and invasive ability of cancer cells (P<0.01). A total of 10 key genes (including SIGLEC6, RHOV, PIR, MOB3B, MIR3135B, LPAR6, KRT8, ITGA2, CPS1, and C6) were screened according to SLC4A4 expression, immune score and stromal score, and a prognostic model with good outcome was constructed (AUC values of which in the training cohort at 1,3, and 5 years reached 0.73, 0.73, and 0.72, respectively). Importantly, we demonstrated that high expression of SLC4A4 was able to increase the proliferation level and cytokine secretion of CD8+ T cells for the purpose of promoting the immune system response to LUAD. CONCLUSION: Our study revealed that SLC4A4 can serve as a prognostic indicator for LUAD, providing new insights into the treatment and diagnosis of LUAD.

Asunto(s)

Adenocarcinoma del Pulmón , Biomarcadores de Tumor , Movimiento Celular , Neoplasias Pulmonares , Microambiente Tumoral , Humanos , Animales , Neoplasias Pulmonares/inmunología , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Neoplasias Pulmonares/mortalidad , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Adenocarcinoma del Pulmón/inmunología , Adenocarcinoma del Pulmón/genética , Adenocarcinoma del Pulmón/patología , Adenocarcinoma del Pulmón/mortalidad , Línea Celular Tumoral , Ratones , Microambiente Tumoral/inmunología , Pronóstico , Regulación Neoplásica de la Expresión Génica , Transición Epitelial-Mesenquimal , Femenino , Ratones Desnudos , Masculino , Progresión de la Enfermedad , Apoptosis , Ensayos Antitumor por Modelo de Xenoinjerto

RESUMEN

Plastic material versatility has resulted in a substantial increase in its use in several sectors of our everyday lives. Consequently, concern regarding human exposure to nano-plastics (NPs) and micro-plastics (MPs) has recently increased. It has been shown that plastic particles entering the bloodstream may adhere to the erythrocyte surface and exert adverse effects following erythrocyte aggregation and adhesion to blood vessels. Here, we explored the effects of polystyrene nano-plastics (PS-NPs) and micro-plastics (PS-MPs) on human erythrocytes. Cellular morphology, binding/internalization of PS-NPs and PS-MPs, oxidative stress parameters, as well as the distribution and anion exchange capability of band 3 (anion exchanger 1; SLC4A1) have been analyzed in human erythrocytes exposed to 1 µg/mL PS-NPs or PS-MPs for 3 and 24 h, respectively. The data obtained showed significant modifications of the cellular shape after exposure to PS-NPs or PS-MPs. In particular, a significantly increased number of acanthocytes, echinocytes and leptocytes were detected. However, the percentage of eryptotic cells (<1 %) was comparable to physiological conditions. Analytical cytology and confocal microscopy showed that PS-NPs and PS-MPs bound to the erythrocyte plasma membrane, co-localized with estrogen receptors (Erα/ERß), and were internalized. An increased trafficking from the cytosol to the erythrocyte plasma membrane and abnormal distribution of ERs were also observed, consistent with ERα-mediated binding and internalization of PS-NPs. An increased phosphorylation of ERK1/2 and AKT kinases indicated that an activation of the ER-modulated non-genomic pathway occurred following exposure to PS-NPs and PS-MPs. Interestingly, PS-NPs or PS-MPs caused a significant production of reactive oxygen species, resulting in an increased lipid peroxidation and protein sulfhydryl group oxidation. Oxidative stress was also associated with an altered band 3 ion transport activity and increased oxidized haemoglobin, which led to abnormal clustering of band 3 on the plasma membrane. Taken together, these findings identify cellular events following the internalization of PS-NPs or PS-MPs in human erythrocytes and contribute to elucidating potential oxidative stress-related harmful effects, which may affect erythrocyte and systemic homeostasis.

Asunto(s)

Proteína 1 de Intercambio de Anión de Eritrocito , Eritrocitos , Estrés Oxidativo , Poliestirenos , Humanos , Poliestirenos/metabolismo , Eritrocitos/metabolismo , Eritrocitos/efectos de los fármacos , Proteína 1 de Intercambio de Anión de Eritrocito/metabolismo , Nanopartículas , Receptor alfa de Estrógeno/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Eriptosis/efectos de los fármacos , Microplásticos/toxicidad , Fosforilación , Proteína Quinasa 1 Activada por Mitógenos/metabolismo

RESUMEN

AIM: To identify the physiological role of the acid-base sensing enzyme, soluble adenylyl cyclase (sAC), in red blood cells (RBC) of the model teleost fish, rainbow trout. METHODS: We used: (i) super-resolution microscopy to determine the subcellular location of sAC protein; (ii) live-cell imaging of RBC intracellular pH (pHi) with specific sAC inhibition (KH7 or LRE1) to determine its role in cellular acid-base regulation; (iii) spectrophotometric measurements of haemoglobin-oxygen (Hb-O2) binding in steady-state conditions; and (iv) during simulated arterial-venous transit, to determine the role of sAC in systemic O2 transport. RESULTS: Distinct pools of sAC protein were detected in the RBC cytoplasm, at the plasma membrane and within the nucleus. Inhibition of sAC decreased the setpoint for RBC pHi regulation by ~0.25 pH units compared to controls, and slowed the rates of RBC pHi recovery after an acid-base disturbance. RBC pHi recovery was entirely through the anion exchanger (AE) that was in part regulated by HCO3 --dependent sAC signaling. Inhibition of sAC decreased Hb-O2 affinity during a respiratory acidosis compared to controls and reduced the cooperativity of O2 binding. During in vitro simulations of arterial-venous transit, sAC inhibition decreased the amount of O2 that is unloaded by ~11%. CONCLUSION: sAC represents a novel acid-base sensor in the RBCs of rainbow trout, where it participates in the modulation of RBC pHi and blood O2 transport though the regulation of AE activity. If substantiated in other species, these findings may have broad implications for our understanding of cardiovascular physiology in vertebrates.

RESUMEN

Dysfunction in ion channels or processes involved in maintaining ionic homeostasis is thought to lower the threshold for cortical spreading depression (CSD), and plays a role in susceptibility to associated neurological disorders, including pathogenesis of a migraine. Rare pathogenic variants in specific ion channels have been implicated in monogenic migraine subtypes. In this study, we further examined the channelopathic nature of a migraine through the analysis of common genetic variants in three selected ion channel or transporter genes: SLC4A4, SLC1A3, and CHRNA4. Using the Agena MassARRAY platform, 28 single-nucleotide polymorphisms (SNPs) across the three candidate genes were genotyped in a case-control cohort comprised of 182 migraine cases and 179 matched controls. Initial results identified significant associations between migraine and rs3776578 (p = 0.04) and rs16903247 (p = 0.05) genotypes within the SLC1A3 gene, which encodes the EAAT1 glutamate transporter. These SNPs were subsequently genotyped in an independent cohort of 258 migraine cases and 290 controls using a high-resolution melt assay, and association testing supported the replication of initial findings-rs3776578 (p = 0.0041) and rs16903247 (p = 0.0127). The polymorphisms are in linkage disequilibrium and localise within a putative intronic enhancer region of SLC1A3. The minor alleles of both SNPs show a protective effect on migraine risk, which may be conferred via influencing the expression of SLC1A3.

Asunto(s)

Transportador 1 de Aminoácidos Excitadores , Predisposición Genética a la Enfermedad , Trastornos Migrañosos , Polimorfismo de Nucleótido Simple , Humanos , Trastornos Migrañosos/genética , Femenino , Masculino , Transportador 1 de Aminoácidos Excitadores/genética , Adulto , Estudios de Casos y Controles , Persona de Mediana Edad , Estudios de Asociación Genética

RESUMEN

The androgen receptor signaling inhibitor (ARSI) enzalutamide (Enz) has shown critical efficacy in the treatment of advanced prostate cancer (PCa). However, the development of drug resistance is a significant factor contributing to mortality in PCa patients. We aimed to explore the key mechanisms of Enz-resistance. Through analysis of GEO databases, we identified SLC4A4 as a novel driver in Enz resistance. Long-term Enz treatment leads to the up-regulation of SLC4A4, which in turn mediates P53 lactylation via the NF-κB/STAT3/SLC4A4 axis, ultimately leading to the development of Enz resistance and progression of PCa. SLC4A4 knockdown overcomes Enz resistance both in vitro and in vivo. Hence, our results suggest that targeting SLC4A4 could be a promising therapeutic strategy for Enz resistance. STATEMENT OF SIGNIFICANCE: SLC4A4 is a novel driver of enzalutamide resistance.

Asunto(s)

Benzamidas , Resistencia a Antineoplásicos , Nitrilos , Feniltiohidantoína , Neoplasias de la Próstata , Simportadores de Sodio-Bicarbonato , Animales , Humanos , Masculino , Ratones , Línea Celular Tumoral , Resistencia a Antineoplásicos/genética , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , FN-kappa B/metabolismo , FN-kappa B/genética , Feniltiohidantoína/farmacología , Feniltiohidantoína/uso terapéutico , Feniltiohidantoína/análogos & derivados , Neoplasias de la Próstata/tratamiento farmacológico , Neoplasias de la Próstata/genética , Neoplasias de la Próstata/patología , Transducción de Señal/efectos de los fármacos , Factor de Transcripción STAT3/metabolismo , Factor de Transcripción STAT3/genética , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo , Regulación hacia Arriba , Ensayos Antitumor por Modelo de Xenoinjerto , Simportadores de Sodio-Bicarbonato/genética

RESUMEN

Astrocytes play vital roles in blood-brain barrier (BBB) maintenance, yet how they support BBB integrity under normal or pathological conditions remains poorly defined. Recent evidence suggests that ion homeostasis is a cellular mechanism important for BBB integrity. In the current study, we investigated the function of an astrocyte-specific pH regulator, Slc4a4, in BBB maintenance and repair. We show that astrocytic Slc4a4 is required for normal astrocyte morphological complexity and BBB function. Multi-omics analyses identified increased astrocytic secretion of CCL2 coupled with dysregulated arginine-NO metabolism after Slc4a4 deletion. Using a model of ischemic stroke, we found that loss of Slc4a4 exacerbates BBB disruption, which was rescued by pharmacological or genetic inhibition of the CCL2-CCR2 pathway in vivo. Together, our study identifies the astrocytic Slc4a4-CCL2 and endothelial CCR2 axis as a mechanism controlling BBB integrity and repair, while providing insights for a therapeutic approach against BBB-related CNS disorders.

Asunto(s)

Astrocitos , Barrera Hematoencefálica , Quimiocina CCL2 , Receptores CCR2 , Accidente Cerebrovascular , Barrera Hematoencefálica/metabolismo , Barrera Hematoencefálica/patología , Astrocitos/metabolismo , Astrocitos/patología , Receptores CCR2/metabolismo , Animales , Quimiocina CCL2/metabolismo , Accidente Cerebrovascular/metabolismo , Accidente Cerebrovascular/patología , Ratones , Transducción de Señal , Masculino , Humanos , Ratones Endogámicos C57BL , Encéfalo/metabolismo , Encéfalo/patología

RESUMEN

Cellular and organism survival depends upon the regulation of pH, which is regulated by highly specialized cell membrane transporters, the solute carriers (SLC) (For a comprehensive list of the solute carrier family members, see: https://www.bioparadigms.org/slc/ ). The SLC4 family of bicarbonate (HCO3-) transporters consists of ten members, sorted by their coupling to either sodium (NBCe1, NBCe2, NBCn1, NBCn2, NDCBE), chloride (AE1, AE2, AE3), or borate (BTR1). The ionic coupling of SLC4A9 (AE4) remains controversial. These SLC4 bicarbonate transporters may be controlled by cellular ionic gradients, cellular membrane voltage, and signaling molecules to maintain critical cellular and systemic pH (acid-base) balance. There are profound consequences when blood pH deviates even a small amount outside the normal range (7.35-7.45). Chiefly, Na+-coupled bicarbonate transporters (NCBT) control intracellular pH in nearly every living cell, maintaining the biological pH required for life. Additionally, NCBTs have important roles to regulate cell volume and maintain salt balance as well as absorption and secretion of acid-base equivalents. Due to their varied tissue expression, NCBTs have roles in pathophysiology, which become apparent in physiologic responses when their expression is reduced or genetically deleted. Variations in physiological pH are seen in a wide variety of conditions, from canonically acid-base related conditions to pathologies not necessarily associated with acid-base dysfunction such as cancer, glaucoma, or various neurological diseases. The membranous location of the SLC4 transporters as well as recent advances in discovering their structural biology makes them accessible and attractive as a druggable target in a disease context. The role of sodium-coupled bicarbonate transporters in such a large array of conditions illustrates the potential of treating a wide range of disease states by modifying function of these transporters, whether that be through inhibition or enhancement.

Asunto(s)

Bicarbonatos , Simportadores de Sodio-Bicarbonato , Simportadores de Sodio-Bicarbonato/genética , Simportadores de Sodio-Bicarbonato/metabolismo , Bicarbonatos/metabolismo , Bicarbonato de Sodio , Sodio/metabolismo , Proteínas de Transporte de Membrana , Concentración de Iones de Hidrógeno

RESUMEN

AIM: In this report, we performed a comprehensive analysis of data in colorectal cancer (CRC), to elucidate the association among Solute Carrier Family 4 Member 4 (SLC4A4) and the abundance of immunological features and immune cell infiltration in CRC, and to explore the impact of SLC4A4 on the CRC tumor microenvironment. BACKGROUND: Colorectal cancer (CRC) cases with advanced or distal metastases experience a survival rate of less than 20%, with the lack of spectral therapeutic targets and prognostic markers posing a significant challenge for CRC treatment. SLC4A4 may be a CRC-targeted therapy for which there is currently inadequate evidence Objective: To deeply and systematically reveal the characteristics of the tumor microenvironment created by SLC4A4. METHODS: We downloaded RNA sequencing files (TCGA-COADREAD), clinical data for Colon Cancer (COAD) and Rectal Cancer (READ) from the Cancer Genome Atlas. We evaluated the spearman correlation of SLC4A4 with immune features, Tracking Tumor Immunophenotype (TIP) score, and immune checkpoint gene expression. SLC4A4/immunity-related differentially expressed genes (DEGs) were identified in SLC4A4 expression groups and immune groups, and an assessment system for predicting CRC prognosis was constructed based on univariate COX and multivariate COX analyses. Based on the prognostic factors in CRC, we also constructed a nomogram to assess the survival risk status of CRC. Besides, we evaluated the potential association of SLC4A4 to immunotherapy. RESULTS: We found that SLC4A4 expression trended positively with immune checkpoint expression (PD-L1, CTLA4) and promoted infiltration of 27 immune cells. SLC4A4 promoted the infiltration of CD8 T cells, Dendritic cells, Macrophage, NK cells, and Th1 cells in CRC, shaping the inflammatory tumor microenvironment. Up-regulation of SLC4A4 expression might promote drug response to Anti-FGFR3_therapy, Anti-PPARG_therapy, Nivolumab, Ipilimumab in CRC patients, and down-regulation of SLC4A4 expression might promote drug response to Anti-EGFR_therapy, Aflibercept drug response. Based on the SLC4A4/immunization-related DEGs, we constructed RiskScore to assess the prognosis of CRC, which showed excellent predictive effect and robustness. RiskScore showed a trend of negative correlation with SLC4A4, which was consistent with the trend of the effect of SLC4A4 on CRC survival. Besides, RiskScore could also be useful for predicting patient prognosis. Finally, we constructed a nomogram for predicting CRC survival based on metrics with independent prognostic value (Age, M stage, Stage, RiskScore), which showed potential clinical value. CONCLUSION: Overall, upregulation of SLC4A4 expression promoted an inflammatory tumor microenvironment in CRC, and RiskScore predicted therapeutic expectancy. SLC4A4 could be a potentially clinically valuable target for CRC therapy.

RESUMEN

The copious metabolic acid production and -extrusion by cancer cells render poorly vascularized regions of solid tumors highly acidic. A growing list of proton - and bicarbonate transporters has been suggested to contribute to net acid extrusion from cancer cells, and/or been shown to be dysregulated and favor malignant development in various cancers. The great majority of these roles have been studied at the level of the cancer cells. However, recent advances in understanding of the cellular and physicochemical heterogeneity of solid tumors both enable and necessitate a reexamination of the regulation and roles of acid-base transporters in such malignancies. This review will briefly summarize the state-of-the-art, with a focus on the SLC9A and SLC4A families, for which most evidence is available. This is followed by a discussion of key concepts and open questions arising from recent insights and of the challenges that need to be tackled to address them. Finally, opportunities and challenges in therapeutic targeting of the acid-base transportome in cancers will be addressed.

Asunto(s)

Neoplasias , Humanos , Concentración de Iones de Hidrógeno , Neoplasias/metabolismo , Proteínas de Transporte de Membrana , Protones

RESUMEN

Hereditary spherocytosis (HS) is the most common hereditary hemolytic disorder induced by red blood cell (RBC) membrane defect. This study was undertaken to determine mutations in genes associated with RBC membrane defect in patients with HS such as α-spectrin gene (SPTA1), ß-spectrin gene (SPTB), ankyrin gene (ANK1), band 3 anion transport gene (SLC4A1) and erythrocyte membrane protein band 4.1 gene (EPB41). Blood samples were collected from 23 unrelated patients with HS. Patients were diagnosed according to the guidelines from the British Society for Hematology. All hematological examinations for the determination of RBC abnormalities and osmotic fragility tests were conducted. Genomic DNA were extracted from peripheral blood cells and coding exons of known genes for hereditary spherocytosis were enriched using Roche/KAPA sequence capture technology and sequenced on an Illumina system via next-generation sequencing (NGS). The data showed that most of the HS patients confirmed splenomegaly and showed elevated reticulocytes and abnormal bilirubin values. NGS analysis identified the heterozygous variant c.5501G > A in the exon 39 of SPTA1 gene, resulted in a Trp1834*, which leads to a premature stop codon and subsequent mRNA degradation (nonsense- mediated decay) or truncation in α spectrin. Moreover, our data also revealed conventional mutations in genes SPTB, ANK, SLC4A1 and EBP41 in severe patients of HS. In short, this is the first report that determined a novel mutation c.5501G > A in SPTA1 gene in the Saudi population. To the best of our knowledge, this variant c.5501G > A has not been described in global literature so far. This novel mutation in SPTA1 gene is unique in the Saudi population.

RESUMEN

Regulation of intracellular pH (pHi) is an important homeostatic function of cells. There are three major pHi regulatory mechanisms: the HCO3-/Cl- exchanger (AE), which alleviates alkalosis, and the Na+/H+ exchanger (NHE) and Na+,HCO3-/Cl- exchanger (NDBCE), both of which counteract acidosis. NHE activity, which is high at the germinal vesicle stage of oocyte, is inhibited during meiotic maturation, while this inhibition is abolished when the oocyte reaches the pronuclear (PN) stage of the zygote. On the other hand, we have previously found that NDBCE performs complementary regulation against acidosis during meiotic maturation. Additionally, we found that AE activity, which is a defense mechanism against alkalosis, gradually decreases during preimplantation period of embryonic development. Considering that NHE activity is inhibited during meiotic maturation and AE activity gradually decreases during embryonic development stages, we investigated whether NHE and NDBCE activities, both of which act against acidosis, functionally change from the PN zygote to the blastocyst stage of the embryo and identified these pH-regulating proteins at the molecular level in mice of the Balb/c strain. PN zygotes, two-cell (2-c), four-cell (4-c), morula and blastocyst stage embryos were obtained from 5-8-week-old, sexually mature female Balb/c mice by using the classical superovulation procedure. pHi was recorded by using the microspectrofluorometric technique on zygotes and embryos simultaneously loaded with the pH-sensitive fluorophore, 2',7'-Bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The activities of NHE and NDBCE were determined from the recovery curve of induced-acidosis in bicarbonate-free and bicarbonate-containing media, respectively. Specific inhibitors such as cariporide (1 µM), S3226 (1 and 10 µM), EIPA (1, 5, and 25 µM), and amiloride (1 mM) were used to functionally identify NHE isoforms, and the nonspecific inhibitor 4,4'-diisocyanatostilbene-2,2' disulphonic acid, disodium salt (DIDS) was used to confirm NDBCE activity. The isoforms of the pHi-regulatory proteins were also identified by molecular biology using real-time PCR. We found that NHE activity was high at all embryonic stages, and differences between stages were not significant. Functional and molecular findings indicated that isoforms of NHE 1 and 5 are present in the blastocyst, whereas isoforms of NHE 1, 3, and 4 are functional at earlier embryonic stages. Although the contribution of NDBCE activity to recovery from induced-acidosis was detected at all embryonic stages, it was significant only in the PN zygote and the 2-c embryo. This finding was confirmed by molecular analysis, which detected the expression of SLC4A8 encoding NDBCE at all embryonic stages. In conclusion, NHE is an active and important defense mechanism against acidosis and is encoded by at least two protein isoforms in all stages of the Balb/c strain of mice. NDBCE has a supportive function in all embryonic stages, especially in the PN zygote and the 2-c embryo. Preimplantation stage embryos have effective mechanisms to defend against acidosis in response to their metabolic end products (increased acid load) and the acidic environment in utero.

Asunto(s)

Acidosis , Alcalosis , Enfermedades de los Roedores , Embarazo , Ratones , Femenino , Animales , Concentración de Iones de Hidrógeno , Antiportadores de Cloruro-Bicarbonato/fisiología , Ratones Endogámicos BALB C , Acidosis/veterinaria , Intercambiadores de Sodio-Hidrógeno/metabolismo , Alcalosis/veterinaria , Isoformas de Proteínas/metabolismo , Mecanismos de Defensa

RESUMEN

The kidney plays a crucial role in acid-base homeostasis. In the distal nephron, α-intercalated cells contribute to urinary acid (H+) secretion and ß-intercalated cells accomplish urinary base (HCO3-) secretion. ß-intercalated cells regulate the acid base status through modulation of the apical Cl-/HCO3- exchanger pendrin (SLC26A4) activity. In this review, we summarize and discuss our current knowledge of the physiological role of the renal transporter AE4 (SLC4A9). The AE4, as cation-dependent Cl-/HCO3- exchanger, is exclusively expressed in the basolateral membrane of ß-intercalated cells and is essential for the sensing of metabolic acid-base disturbances in mice, but not for renal sodium reabsorption and plasma volume control. Potential intracellular signaling pathways are discussed that might link basolateral acid-base sensing through the AE4 to apical pendrin activity.

Asunto(s)

Túbulos Renales Colectores , Animales , Ratones , Antiportadores de Cloruro-Bicarbonato/metabolismo , Riñón/metabolismo , Túbulos Renales Colectores/metabolismo

RESUMEN

PURPOSE: SLC4A10 encodes a plasma membrane-bound transporter, which mediates Na+-dependent HCO3- import, thus mediating net acid extrusion. Slc4a10 knockout mice show collapsed brain ventricles, an increased seizure threshold, mild behavioral abnormalities, impaired vision, and deafness. METHODS: Utilizing exome/genome sequencing in families with undiagnosed neurodevelopmental disorders and international data sharing, 11 patients from 6 independent families with biallelic variants in SLC4A10 were identified. Clinico-radiological and dysmorphology assessments were conducted. A minigene assay, localization studies, intracellular pH recordings, and protein modeling were performed to study the possible functional consequences of the variant alleles. RESULTS: The families harbor 8 segregating ultra-rare biallelic SLC4A10 variants (7 missense and 1 splicing). Phenotypically, patients present with global developmental delay/intellectual disability and central hypotonia, accompanied by variable speech delay, microcephaly, cerebellar ataxia, facial dysmorphism, and infrequently, epilepsy. Neuroimaging features range from some non-specific to distinct neuroradiological findings, including slit ventricles and a peculiar form of bilateral curvilinear nodular heterotopia. In silico analyses showed 6 of 7 missense variants affect evolutionarily conserved residues. Functional analyses supported the pathogenicity of 4 of 7 missense variants. CONCLUSION: We provide evidence that pathogenic biallelic SLC4A10 variants can lead to neurodevelopmental disorders characterized by variable abnormalities of the central nervous system, including altered brain ventricles, thus resembling several features observed in knockout mice.

Asunto(s)

Discapacidad Intelectual , Trastornos del Neurodesarrollo , Animales , Humanos , Ratones , Bicarbonatos/metabolismo , Antiportadores de Cloruro-Bicarbonato/metabolismo , Discapacidad Intelectual/genética , Proteínas de Transporte de Membrana , Ratones Noqueados , Trastornos del Neurodesarrollo/genética , Sodio/metabolismo , Bicarbonato de Sodio/metabolismo , Simportadores de Sodio-Bicarbonato/genética

RESUMEN

Congenital defects of the erythrocyte membrane are common in northern Europe and all over the world. The resulting diseases, for example, hereditary spherocytosis (HS), are often underdiagnosed, partly due to their sometimes mild and asymptomatic courses. In addition to a broad clinical spectrum, this is also due to the occasionally complex diagnostics that are not available to every patient. To test whether next-generation sequencing (NGS) could replace time-consuming spherocytosis-specific functional tests, 22 consecutive patients with suspected red cell membranopathy underwent functional blood tests. We were able to identify the causative genetic defect in all patients with suspected HS who underwent genetic testing (n = 17). The sensitivity of the NGS approach, which tests five genes (ANK1 (gene product: ankyrin1), EPB42 (erythrocyte membrane protein band4.2), SLC4A1 (band3), SPTA1 (α-spectrin), and SPTB (ß-spectrin)), was 100% (95% confidence interval: 81.5-100.0%). The major advantage of genetic testing in the paediatric setting is the small amount of blood required (<200 µL), and compared to functional assays, sample stability is not an issue. The combination of medical history, basic laboratory parameters, and an NGS panel with five genes is sufficient for diagnosis in most cases. Only in rare cases, a more comprehensive functional screening is required.

Asunto(s)

Ancirinas , Esferocitosis Hereditaria , Humanos , Niño , Ancirinas/genética , Ancirinas/metabolismo , Mutación , Esferocitosis Hereditaria/diagnóstico , Esferocitosis Hereditaria/genética , Espectrina/genética , Espectrina/metabolismo , Proteínas del Citoesqueleto/genética , Secuenciación de Nucleótidos de Alto Rendimiento

RESUMEN

SLC4A4 variants are the etiologies of inherited proximal renal tubular acidosis (pRTA), which results in metabolic acidosis, hypokalemia, glaucoma, band keratopathy, and cataract. This study aims to characterize SLC4A4 variant and uniparental isodisomy of chromosome 4 in a patient, and analyse the functional characterization of SLC4A4 variants. This study analyzed renal tubular acidosis disease genes by whole exome sequencing (WES). H3M2 algorithm was used to analyze the run of homozygosity region in chromosomal regions in trio-WES data. The pathogenicity analysis of variants was performed using bioinformatics tools. Additionally, protein stability was analyzed by cycloheximide chase assay. Whole-cell patch clamping was used to examine the electrophysiological properties of NBCe1-A. A novel homozygous SLC4A4 variant was identified in the patient: a missense variant c.496C > T, p. Arg166Trp (NM_003759.4). But the father was heterozygous variant carrier, and the mother did not detect the variant. The H3M2 and UPDio algorithm revealed paternal uniparental isodisomy on chromosome 4 in the patient. SIFT, Poly Phen-2, FATHMM and Mutant Taster showed that the variant might be pathogenic. The tertiary structure analysis showed that the variant could cause structural damage to NBCe1 protein. Foldx results showed that the protein stability of the variant was slightly reduced. Cycloheximide chase assay demonstrated that the variant affects protein stability. The result of electrophysiological studies showed that the variant altered Na+/HCO3- cotransport activity of protein. In conclusion, the study is the first to report a pRTA patient with Arg166Trp variant with UPiD (4) pat and analyze the function of Arg166Trp variant.

Asunto(s)

Arritmias Cardíacas , Síndrome de QT Prolongado , Humanos , Electrocardiografía