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1.
Ann Intern Med ; 175(11): 1543-1551, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36315944

RESUMO

BACKGROUND: In cystic fibrosis (CF), renal base excretion is impaired. Accordingly, challenged urine bicarbonate excretion may be an in vivo biomarker of cystic fibrosis transmembrane conductance regulator (CFTR) function. OBJECTIVE: To evaluate the association between challenged bicarbonate excretion and clinical characteristics at baseline, quantify the CFTR modulator drug elexacaftor/tezacaftor/ivacaftor-induced changes of challenged bicarbonate excretion after 6 months of treatment, and characterize the intraindividual variation in healthy adults. DESIGN: Prospective observational study. SETTING: Cystic fibrosis clinic, Aarhus University Hospital, Denmark. PATIENTS: Fifty adult patients with CF starting CFTR modulator therapy with elexacaftor/tezacaftor/ivacaftor between May 2020 and June 2021. MEASUREMENTS: Quantification of urine bicarbonate excretion after an acute oral sodium bicarbonate challenge before and 6 months after elexacaftor/tezacaftor/ivacaftor treatment. RESULTS: At baseline, challenged urine bicarbonate excretion was associated with several CF disease characteristics. Bicarbonate excretion was higher in patients with residual function mutations. A higher bicarbonate excretion was associated with better lung function, pancreatic sufficiency, and lower relative risk for chronic pseudomonas infections. Elexacaftor/tezacaftor/ivacaftor treatment increased bicarbonate excretion by 3.9 mmol/3 h (95% CI, 1.6 to 6.1 mmol/3 h), reaching about 70% of that seen in healthy control participants. In healthy control participants, individual bicarbonate excretion at each visit correlated with the individual mean bicarbonate excretion. The median coefficient of variation was 31%. LIMITATION: Single-center study without a placebo-controlled group. CONCLUSION: Although further studies are needed to address the performance and sensitivity of this approach, this early-stage evaluation shows that challenged urine bicarbonate excretion may offer a new, simple, and safe quantification of CFTR function and the extent of its pharmacologic improvement. Elexacaftor/tezacaftor/ivacaftor partially restores renal CFTR function in patients with CF, likely resulting in decreased risk for electrolyte disorders and metabolic alkalosis. PRIMARY FUNDING SOURCE: Innovation Fund Denmark.


Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística , Fibrose Cística , Humanos , Adulto , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/farmacologia , Fibrose Cística/tratamento farmacológico , Fibrose Cística/genética , Bicarbonatos/metabolismo , Bicarbonatos/uso terapêutico , Agonistas dos Canais de Cloreto/farmacologia , Agonistas dos Canais de Cloreto/uso terapêutico , Combinação de Medicamentos , Mutação
2.
Life Sci ; 310: 121117, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36302497

RESUMO

AIMS: The "biliary bicarbonate umbrella" is considered a critical protective mechanism of cholangiocytes against bile acid cytotoxicity. Defects in its function are closely related to various chronic cholangiopathies. Carbonic anhydrase 14 (CAR14) is an important element of normal bicarbonate homeostasis and is highly expressed in liver tissues. This study aimed to explore the effects and mechanism of CAR14 on bile acid cytotoxicity in the liver. MAIN METHODS: In vitro, alterations in the whole transcriptome after Car14 gene silencing were assessed by RNA sequencing, and the expression changes in key factors in the "biliary bicarbonate umbrella" were verified by qRT-PCR and western blotting. In vivo, 7 days after bile duct ligation in Car14 gene knockout and wild-type mice, their serum liver function indicators, liver histopathology, hepatic bile acid composition, and whole hepatic proteomic changes were investigated. KEY FINDINGS: In vitro, the transcriptional alterations induced by Car14 silencing were mainly related to transmembrane transport, including ion exchangers and ion channels that are vital in the "biliary bicarbonate umbrella" such as AE2 and CFTR. In vivo, Car14 knockout induced more severe liver dysfunction, hepatic fibrosis and bile duct lesions, and resulted in increased hepatic bile acid levels and altered bile acid compositions in BDL mice. In response, the uptake and synthesis of bile acids in the liver of Car14 knockout mice were suppressed. SIGNIFICANCE: Our data revealed that CAR14 protects the liver against bile acid toxicity, which might provide a theoretical basis for clinical strategies to prevent or treat bile duct diseases.


Assuntos
Ácidos e Sais Biliares , Anidrases Carbônicas , Camundongos , Animais , Ácidos e Sais Biliares/metabolismo , Bicarbonatos/metabolismo , Proteômica , Fígado/metabolismo , Ductos Biliares/metabolismo , Anidrases Carbônicas/genética
3.
PLoS One ; 17(10): e0276397, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36264955

RESUMO

INTRODUCTION: Cystic fibrosis transmembrane conductance regulator (CFTR) plays a central role in pancreatic ductal fluid secretion by mediating Cl- and HCO3- ion transport across the apical membrane. Severe CFTR mutations that diminish chloride conductance cause cystic fibrosis (CF) if both alleles are affected, whereas heterozygous carrier status increases risk for chronic pancreatitis (CP). It has been proposed that a subset of CFTR variants characterized by a selective bicarbonate conductance defect (CFTRBD) may be associated with CP but not CF. However, a rigorous genetic analysis of the presumed association has been lacking. AIMS: To investigate the role of heterozygous CFTRBD variants in CP by meta-analysis of published case-control studies. MATERIALS AND METHODS: A systematic search was conducted in the MEDLINE, Embase, Scopus, and CENTRAL databases for published studies that reported the CFTRBD variants p.R74Q, p.R75Q, p.R117H, p.R170H, p.L967S, p.L997F, p.D1152H, p.S1235R, and p.D1270N in CP patients and controls. RESULTS: Twenty-two studies were eligible for quantitative synthesis. Combined analysis of the 9 CFTRBD variants indicated enrichment in CP patients versus controls (OR = 2.31, 95% CI = 1.17-4.56). Individual analysis of CFTRBD variants revealed no association of p.R75Q with CP (OR = 1.12, 95% CI = 0.89-1.40), whereas variants p.R117H and p.L967S were significantly overrepresented in cases relative to controls (OR = 3.16, 95% CI = 1.94-5.14, and OR = 3.88, 95% CI = 1.32-11.47, respectively). The remaining 6 low-frequency variants gave inconclusive results when analyzed individually, however, their pooled analysis indicated association with CP (OR = 2.08, 95% CI = 1.38-3.13). CONCLUSION: Heterozygous CFTRBD variants, with the exception of p.R75Q, increase CP risk about 2-4-fold.


Assuntos
Fibrose Cística , Pancreatite Crônica , Humanos , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Bicarbonatos/metabolismo , Cloretos , Pancreatite Crônica/genética , Fibrose Cística/genética , Mutação
4.
Clin Liver Dis ; 26(4): 583-611, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36270718

RESUMO

Primary biliary cholangitis (PBC) is an autoimmune liver disease with a female predisposition and selective destruction of intrahepatic small bile ducts leading to nonsuppurative destructive cholangitis. It is characterized by seropositivity of antimitochondrial antibodies or PBC-specific antinuclear antibodies, progressive cholestasis, and typical liver histologic manifestations. Destruction of the protective bicarbonate-rich umbrella is attributed to the decreased expression of membrane transporters in biliary epithelial cells (BECs), leading to the accumulation of hydrophobic bile acids and sensitizing BECs to apoptosis. A recent X-wide association study reveals a novel risk locus on the X chromosome, which reiterates the importance of Treg cells.


Assuntos
Colangite , Cirrose Hepática Biliar , Feminino , Humanos , Cirrose Hepática Biliar/metabolismo , Ductos Biliares , Bicarbonatos/metabolismo , Anticorpos Antinucleares , Ácidos e Sais Biliares/metabolismo , Proteínas de Membrana Transportadoras/metabolismo
5.
Int J Mol Sci ; 23(19)2022 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-36232697

RESUMO

Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a plasma membrane protein expressed on the apical surface of secretory epithelia of the airways. In the airways, defective or absent function of the CFTR protein determines abnormalities of chloride and bicarbonate secretion and, in general, of the transepithelial homeostasis that lead to alterations of airway surface liquid (ASL) composition and properties. The reduction of ASL volume impairs ciliary beating with the consequent accumulation of a sticky mucus. This situation prevents normal mucociliary clearance, favoring the survival and proliferation of bacteria and contributing to the genesis of the CF pulmonary disease. We explored the potential of some CFTR modulators, namely ivacaftor, tezacaftor, elexacaftor and their combination KaftrioTM, capable of partially recovering the basic defects of the CFTR protein, to ameliorate the transepithelial fluid transport and the viscoelastic properties of the mucus when used singly or in combination. Primary human bronchial epithelial cells obtained from CF and non-CF patients were differentiated into a mucociliated epithelia in order to assess the effects of correctors tezacaftor, elexacaftor and their combination with potentiator ivacaftor on the key properties of ASL, such as fluid reabsorption, viscosity, protein content and pH. The treatment of airway epithelia bearing the deletion of a phenylalanine at position 508 (F508del) in the CFTR gene with tezacaftor and elexacaftor significantly improved the pericilial fluid composition, reducing the fluid reabsorption, correcting the ASL pH and reducing the viscosity of the mucus. KaftrioTM was more effective than single modulators in improving all the evaluated parameters, demonstrating once more that this combination recently approved for patients 6 years and older with cystic fibrosis who have at least one F508del mutation in the CFTR gene represents a valuable tool to defeat CF.


Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística , Fibrose Cística , Aminofenóis , Benzodioxóis/farmacologia , Bicarbonatos/metabolismo , Cloretos/metabolismo , Fibrose Cística/tratamento farmacológico , Fibrose Cística/genética , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Humanos , Mutação , Fenilalanina/genética , Quinolonas
6.
Int J Mol Sci ; 23(20)2022 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-36293229

RESUMO

Cystic fibrosis is a genetic disease caused by mutation of the CFTR gene, which encodes a chloride and bicarbonate transporter in epithelial cells. Due to the vast range of geno- and phenotypes, it is difficult to find causative treatments; however, small-molecule therapeutics have been clinically approved in the last decade. Still, the search for novel therapeutics is ongoing, and thousands of compounds are being tested in different assays, often leaving their mechanism of action unknown. Here, we bring together a CFTR-specific compound database (CandActCFTR) and systems biology model (CFTR Lifecycle Map) to identify the targets of the most promising compounds. We use a dual inverse screening approach, where we employ target- and ligand-based methods to suggest targets of 309 active compounds in the database amongst 90 protein targets from the systems biology model. Overall, we identified 1038 potential target-compound pairings and were able to suggest targets for all 309 active compounds in the database.


Assuntos
Fibrose Cística , Humanos , Fibrose Cística/tratamento farmacológico , Fibrose Cística/genética , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Cloretos/metabolismo , Ligantes , Bicarbonatos/metabolismo , Mutação , Preparações Farmacêuticas
7.
FASEB J ; 36(11): e22534, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36183361

RESUMO

The solute carrier 26 family member A9 (SLC26A9) is an epithelial anion transporter that is assumed to contribute to airway chloride secretion and surface hydration. Whether SLC26A9 or CFTR is responsible for airway Cl- transport under basal conditions is still unclear, due to the lack of a specific inhibitor for SLC26A9. In the present study, we report a novel potent and specific inhibitor for SLC26A9, identified by screening of a drug-like molecule library and subsequent chemical modifications. The most potent compound S9-A13 inhibited SLC26A9 with an IC50 of 90.9 ± 13.4 nM. S9-A13 did not inhibit other members of the SLC26 family and had no effects on Cl- channels such as CFTR, TMEM16A, or VRAC. S9-A13 inhibited SLC26A9 Cl- currents in cells that lack expression of CFTR. It also inhibited proton secretion by HGT-1 human gastric cells. In contrast, S9-A13 had minimal effects on ion transport in human airway epithelia and mouse trachea, despite clear expression of SLC26A9 in the apical membrane of ciliated cells. In both tissues, basal and stimulated Cl- secretion was due to CFTR, while acidification of airway surface liquid by S9-A13 suggests a role of SLC26A9 for airway bicarbonate secretion.


Assuntos
Cloretos , Regulador de Condutância Transmembrana em Fibrose Cística , Animais , Antiporters/metabolismo , Bicarbonatos/metabolismo , Cloretos/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Células Epiteliais/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Camundongos , Prótons , Transportadores de Sulfato/genética , Transportadores de Sulfato/metabolismo
8.
Mol Cell ; 82(17): 3121-3123, 2022 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-36055205

RESUMO

In this issue of Molecular Cell, Ali et al. (2022) show that bicarbonate uptake by SLC4A7 fuels de novo nucleotide synthesis and cell proliferation and is regulated by mTORC1.


Assuntos
Bicarbonatos , Simportadores de Sódio-Bicarbonato , Bicarbonatos/metabolismo , Proliferação de Células , Alvo Mecanístico do Complexo 1 de Rapamicina/genética , Nucleotídeos
9.
J Comp Physiol B ; 192(6): 713-725, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36098803

RESUMO

Pacific hagfish (Eptatretus stoutii) are marine scavengers and feed on decaying animal carrion by burrowing their bodies inside rotten carcasses where they are exposed to several threatening environmental stressors, including hypercapnia (high partial pressures of CO2). Hagfish possess a remarkable capacity to tolerate hypercapnia, and their ability to recover from acid-base disturbances is well known. To deal with the metabolic acidosis resulting from exposure to high CO2, hagfish can mount a rapid elevation of plasma HCO3- concentration (hypercarbia). Once PCO2 is restored, hagfish quickly excrete their HCO3- load, a process that likely involves the enzyme carbonic anhydrase (CA), which catalyzes HCO3- dehydration into CO2 at the hagfish gills. We aimed to characterize the role of branchial CA in CO2/HCO3- clearance from the plasma at the gills of E. stoutii, under control and high PCO2 (hypercapnic) exposure conditions. We assessed the relative contributions of plasma accessible versus intracellular (cytosolic) CA to gill HCO3- excretion by measuring in situ [14C]-HCO3- fluxes. To accomplish this, we employed a novel surgical technique of individual gill pouch arterial perfusion combined with perifusion of the gill afferent to efferent water ducts. [14C]-HCO3- efflux was measured at the gills of fish exposed to control, hypercapnic (48 h) and recovery from hypercapnia conditions (6 h), in the presence of two well-known pharmacological inhibitors of CA, the membrane impermeant C18 (targets membrane bound, plasma accessible CA) and membrane-permeant acetazolamide, which targets all forms of CA, including extracellular and intracellular cytosolic CAs. C18 did not affect HCO3- flux in control fish, whereas acetazolamide resulted in a significant reduction of 72%. In hypercapnic fish, HCO3- fluxes were much higher and perfusion with acetazolamide caused a reduction of HCO3- flux by 38%. The same pattern was observed for fish in recovery, where in all three experimental conditions, there was no significant inhibition of plasma-accessible CA. We also observed no change in CA enzyme activity (measured in vitro) in any of the experimental PCO2 conditions. In summary, our data suggests that there are additional pathways for HCO3- excretion at the gills of hagfish that are independent of plasma-accessible CA.


Assuntos
Anidrases Carbônicas , Feiticeiras (Peixe) , Acetazolamida/farmacologia , Animais , Bicarbonatos/metabolismo , Dióxido de Carbono/metabolismo , Anidrases Carbônicas/metabolismo , Brânquias/metabolismo , Feiticeiras (Peixe)/fisiologia , Hipercapnia , Água/metabolismo
10.
Proc Natl Acad Sci U S A ; 119(40): e2203904119, 2022 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-36161891

RESUMO

Many calcifying organisms utilize metabolic CO2 to generate CaCO3 minerals to harden their shells and skeletons. Carbonic anhydrases are evolutionary ancient enzymes that have been proposed to play a key role in the calcification process, with the underlying mechanisms being little understood. Here, we used the calcifying primary mesenchyme cells (PMCs) of sea urchin larva to study the role of cytosolic (iCAs) and extracellular carbonic anhydrases (eCAs) in the cellular carbon concentration mechanism (CCM). Molecular analyses identified iCAs and eCAs in PMCs and highlight the prominent expression of a glycosylphosphatidylinositol-anchored membrane-bound CA (Cara7). Intracellular pH recordings in combination with CO2 pulse experiments demonstrated iCA activity in PMCs. iCA activity measurements, together with pharmacological approaches, revealed an opposing contribution of iCAs and eCAs on the CCM. H+-selective electrodes were used to demonstrate eCA-catalyzed CO2 hydration rates at the cell surface. Knockdown of Cara7 reduced extracellular CO2 hydration rates accompanied by impaired formation of specific skeletal segments. Finally, reduced pHi regulatory capacities during inhibition and knockdown of Cara7 underscore a role of this eCA in cellular HCO3- uptake. This work reveals the function of CAs in the cellular CCM of a marine calcifying animal. Extracellular hydration of metabolic CO2 by Cara7 coupled to HCO3- uptake mechanisms mitigates the loss of carbon and reduces the cellular proton load during the mineralization process. The findings of this work provide insights into the cellular mechanisms of an ancient biological process that is capable of utilizing CO2 to generate a versatile construction material.


Assuntos
Calcificação Fisiológica , Dióxido de Carbono , Carbono , Inibidores da Anidrase Carbônica , Anidrases Carbônicas , Ouriços-do-Mar , Animais , Bicarbonatos/metabolismo , Carbono/metabolismo , Dióxido de Carbono/metabolismo , Inibidores da Anidrase Carbônica/farmacologia , Anidrases Carbônicas/genética , Anidrases Carbônicas/metabolismo , Glicosilfosfatidilinositóis , Concentração de Íons de Hidrogênio , Prótons , Ouriços-do-Mar/enzimologia
11.
Bioresour Technol ; 363: 127921, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36089131

RESUMO

In order to improve the potential of cyanobacterial cell factories, Synechococcus sp. PCC7002 was engineered as 'one cell-two wells bio-refinery', for ethylene ('heterologous' hydrocarbon) and carotenoids ('natural' metabolites) production, and demonstrating its outdoor performance. Although the cultures showed better production outdoor, they experienced multiple collapses during scale-up. Hence, flux balance analysis was performed which predicted higher ethylene production with increase in carbon input under outdoor light conditions. Furthermore, FBA predicted that ethylene production will not increase beyond a threshold carbon input flux, owing to limitations on ribulose-1,5-bisphosphate regeneration. Hence, a bicarbonate-supplementation strategy was devised. Cultures grown outdoor at optimal bicarbonate concentration (20 g/L) resulted in improved growth (0.141/h) and ethylene productivity (1.88 mL/L.h) for > 10 days, with enhanced carotenoid titres (40.4 mg/L). In a 100 L air-lift photo-bioreactor; cultures exhibited efficient ethylene (2.464 mL/L.h) and biomass (0.3 g/L.d) productivities, and carotenoids titres (64.4 mg/L), establishing a significant step towards commercialization.


Assuntos
Bicarbonatos , Synechococcus , Bicarbonatos/metabolismo , Carbono/metabolismo , Carotenoides/metabolismo , Etilenos/metabolismo , Synechococcus/metabolismo
12.
Int J Mol Sci ; 23(17)2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36077461

RESUMO

The progression of nonalcoholic fatty liver disease (NAFLD) is associated with alterations of the gut-liver axis. The activation of toll-like receptor 4 (TLR4) pathways by endotoxins, such as lipopolysaccharide (LPS), contributes to liver injury. The aim of the present study was to evaluate the possible beneficial effects of a calcium-sulphate-bicarbonate natural mineral water on the gut-liver axis by evaluating liver and terminal ileum histopathology in a murine model of NAFLD. NAFLD was induced in mice by administrating a methionine-choline-deficient (MCD) diet. The following experimental groups were evaluated: controls (N = 10); MCD+Tap water (MCD; N = 10); MCD+Calcium-sulphate-bicarbonate water (MCD/Wcsb; N = 10). Mice were euthanised after 4 and 8 weeks. Liver and terminal ileum samples were collected. Samples were studied by histomorphology, immunohistochemistry, and immunofluorescence. In mice subjected to the MCD diet, treatment with mineral water improved inflammation and fibrosis, and was associated with a reduced number of activated hepatic stellate cells when compared to MCD mice not treated with mineral water. Moreover, MCD/Wcsb mice showed lower liver LPS localization and less activation of TLR4 pathways compared to the MCD. Finally, Wcsb treatment was associated with improved histopathology and higher occludin positivity in intestinal mucosa. In conclusion, calcium-sulphate-bicarbonate water may exert modulatory activity on the gut-liver axis in MCD mice, suggesting potential beneficial effects on NAFLD.


Assuntos
Deficiência de Colina , Águas Minerais , Hepatopatia Gordurosa não Alcoólica , Animais , Bicarbonatos/metabolismo , Cálcio/metabolismo , Sulfato de Cálcio , Colina/metabolismo , Deficiência de Colina/complicações , Deficiência de Colina/metabolismo , Modelos Animais de Doenças , Lipopolissacarídeos/metabolismo , Fígado/metabolismo , Metionina/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Hepatopatia Gordurosa não Alcoólica/metabolismo , Sulfatos/metabolismo , Receptor 4 Toll-Like/metabolismo
13.
J Bacteriol ; 204(9): e0020022, 2022 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-36043862

RESUMO

It was previously demonstrated that anthrax toxin activator (AtxA) binds directly to the σA-like promoter region of pagA (encoding protective antigen, PA) immediately upstream of the RNA polymerase binding site. In this study, using electrophoretic mobility shift assays and in vivo analyses, we identified AtxA-binding sites in the promoter regions of the lef and cya genes (encoding lethal and edema factors, respectively) and of two Bacillus anthracis small RNAs (XrrA and XrrB). Activities of all four newly studied promoters were enhanced in the presence of CO2/bicarbonate and AtxA, as previously seen for the pagA promoter. Notably, the cya promoter was less activated by AtxA and CO2/bicarbonate conditions. The putative promoter of a recently described third small RNA, XrrC, showed a negligible response to AtxA and CO2/bicarbonate. RNA polymerase binding sites of the newly studied promoters show no consensus and differ from the σA-like promoter region of pagA. In silico analysis of the probable AtxA binding sites in the studied promoters revealed several palindromes. All the analyzed palindromes showed very little overlap with the σA-like pagA promoter. It remains unclear as to how AtxA and DNA-dependent RNA-polymerase identify such diverse DNA-sequences and differentially regulate promoter activation of the studied genes. IMPORTANCE Anthrax toxin activator (AtxA) is the major virulence regulator of Bacillus anthracis, the causative agent of anthrax. Understanding AtxA's mechanism of regulation could facilitate the development of therapeutics for B. anthracis infection. We provide evidence that AtxA binds to the promoters of the cya, lef, xrrA, and xrrB genes. In vivo assays confirmed the activities of all four promoters were enhanced in the presence of AtxA and CO2/bicarbonate, as previously seen for the pagA promoter. The cya and lef genes encode important toxin components. The xrrA and xrrB genes encode sRNAs with a suggested function as cell physiology regulators. Our data provides further evidence for the direct regulatory role of AtxA that was previously shown with the pagA promoter.


Assuntos
Bacillus anthracis , Antígenos de Bactérias/metabolismo , Bacillus anthracis/metabolismo , Proteínas de Bactérias/metabolismo , Bicarbonatos/metabolismo , Dióxido de Carbono/metabolismo , DNA/metabolismo , RNA Polimerases Dirigidas por DNA/metabolismo , Regulação Bacteriana da Expressão Gênica , Regiões Promotoras Genéticas , RNA/metabolismo
14.
PLoS One ; 17(8): e0273208, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36006975

RESUMO

The sympathetic nervous system is highly involved in the regulation of gastrointestinal functions such as luminal alkalinisation and fluid absorption. However, the exact mechanisms are not clear. This study aimed to delineate how α2-adrenergic receptor stimulation reduces duodenal luminal alkalinisation and induces net fluid absorption. This was tested by perfusing the duodenum of anesthetized rats with isotonic solutions devoid of Cl- and/or Na+, in the absence and presence of the α2-adrenoceptor agonist clonidine. The clonidine was also studied in rats treated with dimethylamiloride (a Na+/H+ exchange inhibitor), vasoactive intestinal peptide, and the nicotinic receptor antagonist hexamethonium. Clonidine reduced luminal alkalinisation and induced net fluid absorption. The Cl--free solution decreased luminal alkalinisation and abolished net fluid absorption, but did not prevent clonidine from doing so. Both the Na+-free solution and luminal dimethylamiloride increased luminal alkalinisation and abolished net fluid absorption, effects counteracted by clonidine. The NaCl-free solution (D-mannitol) did not affect luminal alkalinisation, but reduced net fluid absorption. Clonidine reduced luminal alkalinisation and induced net fluid absorption in rats perfused luminally with mannitol. However, clonidine did not affect the vasoactive intestinal peptide-induced increase in luminal alkalinisation or fluid secretion. Pre-treatment with hexamethonium abolished the effects of clonidine on luminal alkalinisation and net fluid flux. In summary, our in vivo experiments showed that clonidine-induced reduction in luminal alkalinisation and induction of net fluid absorption was unrelated to luminal Na+ and Cl-, or to apical Na+/H+ or Cl-/HCO3- exchangers. Instead, clonidine seems to exert its effects via suppression of nicotinic receptor-activated acetylcholine secretomotor neurons.


Assuntos
Bicarbonatos , Receptores Nicotínicos , Animais , Bicarbonatos/metabolismo , Clonidina/farmacologia , Duodeno/metabolismo , Hexametônio/farmacologia , Manitol/farmacologia , Ratos , Receptores Adrenérgicos , Sódio/metabolismo , Peptídeo Intestinal Vasoativo/farmacologia
15.
Hepatol Commun ; 6(10): 2748-2764, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35852334

RESUMO

Fluid and bicarbonate secretion is a principal function of cholangiocytes, and impaired secretion results in cholestasis. Cholangiocyte secretion depends on peri-apical expression of the type 3 inositol trisphosphate receptor (ITPR3), and loss of this intracellular Ca2+ release channel is a final common event in most cholangiopathies. Here we investigated the mechanism by which ITPR3 localizes to the apical region to regulate secretion. Isolated bile duct units, primary mouse cholangiocytes, and polarized Madin-Darby canine kidney (MDCK) cells were examined using a combination of biochemical and fluorescence microscopy techniques to investigate the mechanism of ITPR3 targeting to the apical region. Apical localization of ITPR3 depended on the presence of intact lipid rafts as well as interactions with both caveolin 1 (CAV1) and myosin heavy chain 9 (MYH9). Chemical disruption of lipid rafts or knockdown of CAV1 or MYH9 redistributed ITPR3 away from the apical region. MYH9 interacted with the five c-terminal amino acids of the ITPR3 peptide. Disruption of lipid rafts impaired Ca2+ signaling, and absence of CAV1 impaired both Ca2+ signaling and fluid secretion. Conclusion: A cooperative mechanism involving MYH9, CAV1, and apical lipid rafts localize ITPR3 to the apical region to regulate Ca2+ signaling and secretion in cholangiocytes.


Assuntos
Sinalização do Cálcio , Caveolina 1 , Aminoácidos/metabolismo , Animais , Bicarbonatos/metabolismo , Sinalização do Cálcio/fisiologia , Caveolina 1/genética , Cães , Inositol , Receptores de Inositol 1,4,5-Trifosfato/genética , Camundongos , Cadeias Pesadas de Miosina/genética
16.
Curr Opin Nephrol Hypertens ; 31(5): 479-485, 2022 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-35894283

RESUMO

PURPOSE OF REVIEW: Kir5.1 interacts with Kir4.2 in proximal tubule and with Kir4.1 in distal convoluted tubule (DCT), connecting tubule (CNT) and cortical collecting duct (CCD) to form basolateral-K+-channels. Kir4.2/Kir5.1 and Kir4.1/Kir5.1 play an important role in regulating Na+/HCO3--transport of the proximal tubule and Na+/K+ -transport in the DCT/CNT/CCD. The main focus of this review is to provide an overview of the recent development in the field regarding the role of Kir5.1 regulating renal electrolyte transport in the proximal tubule and DCT. RECENT FINDINGS: Loss-of-function-mutations of KCNJ16 cause a new form of tubulopathy, characterized by hypokalaemia, Na+-wasting, acid-base-imbalance and metabolic-acidosis. Abnormal bicarbonate transport induced by loss-of-function of KCNJ16-mutants is recapitulated in Kir4.2-knockout-(Kir4.2 KO) mice. Deletion of Kir5.1 also abolishes the effect of dietary Na+ and K+-intakes on the basolateral membrane voltage and NCC expression/activity. Long-term high-salt intake or high-K+-intake causes hyperkalaemic in Kir5.1-deficient mice. SUMMARY: Kir4.2/Kir5.1 activity in the proximal tubule plays a key role in regulating Na+, K+ and bicarbonate-transport through regulating electrogenic-Na+-bicarbonate-cotransporter-(NBCe1) and type 3-Na+/H+-exchanger-(NHE3). Kir4.1/Kir5.1 activity of the DCT plays a critical role in mediating the effect of dietary-K+ and Na+-intakes on NCC activity/expression. As NCC determines the Na+ delivery rate to the aldosterone-sensitive distal nephron (ASDN), defective regulation of NCC during high-salt and high-K+ compromises renal K+ excretion and K+ homeostasis.


Assuntos
Canais de Potássio Corretores do Fluxo de Internalização , Animais , Bicarbonatos/metabolismo , Humanos , Transporte de Íons/fisiologia , Túbulos Renais/metabolismo , Túbulos Renais Distais/metabolismo , Camundongos , Canais de Potássio Corretores do Fluxo de Internalização/genética , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Sódio/metabolismo
17.
Oncogene ; 41(31): 3886-3897, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35780182

RESUMO

We previously found that lactic acidosis in the tumor environment was permissive to cancer cell surviving under glucose deprivation and demonstrated that neutralizing lactic acidosis restored cancer cell susceptibility to glucose deprivation. We then reported that alternate infusion of bicarbonate and anticancer agent into tumors via tumor feeding artery markedly enhanced the efficacy of transarterial chemoembolization (TACE) in the local control of hepatocellular carcinoma (HCC). Here we sought to further investigate the mechanism by which bicarbonate enhances the anticancer activity of TACE. We propose that interfering cellular pH by bicarbonate could induce a cascade of molecular events leading to cancer cell death. Alkalizing cellular pH by bicarbonate decreased pH gradient (ΔpH), membrane potential (ΔΨm), and proton motive force (Δp) across the inner membrane of mitochondria; disruption of oxidative phosphorylation (OXPHOS) due to collapsed Δp led to a significant increase in adenosine monophosphate (AMP), which activated the classical AMPK-mediated autophagy. Meanwhile, the autophagic flux was ultimately blocked by increased cellular pH, reduced OXPHOS, and inhibition of lysosomal proton pump in alkalized lysosome. Bicarbonate also induced persistent mitochondrial permeability (MPT) and damaged mitochondria. Collectively, this study reveals that interfering cellular pH may provide a valuable approach to treat cancer.


Assuntos
Acidose Láctica , Carcinoma Hepatocelular , Quimioembolização Terapêutica , Neoplasias Hepáticas , Acidose Láctica/metabolismo , Autofagia , Bicarbonatos/metabolismo , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/terapia , Morte Celular , Glucose/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Neoplasias Hepáticas/metabolismo , Mitocôndrias/metabolismo
18.
Int J Mol Sci ; 23(11)2022 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-35683013

RESUMO

Alkalinization of sperm cytosol is essential for plasma membrane hyperpolarization, hyperactivation of motility, and acrosomal exocytosis during sperm capacitation in mammals. The plasma membrane of sperm cells contains different ion channels implicated in the increase of internal pH (pHi) by favoring either bicarbonate entrance or proton efflux. Bicarbonate transporters belong to the solute carrier families 4 (SLC4) and 26 (SLC26) and are currently grouped into Na+/HCO3- transporters and Cl-/HCO3- exchangers. Na+/HCO3- transporters are reported to be essential for the initial and fast entrance of HCO3- that triggers sperm capacitation, whereas Cl-/HCO3- exchangers are responsible for the sustained HCO3- entrance which orchestrates the sequence of changes associated with sperm capacitation. Proton efflux is required for the fast alkalinization of capacitated sperm cells and the activation of pH-dependent proteins; according to the species, this transport can be mediated by Na+/H+ exchangers (NHE) belonging to the SLC9 family and/or voltage-gated proton channels (HVCN1). Herein, we discuss the involvement of each of these channels in sperm capacitation and the acrosome reaction.


Assuntos
Bicarbonatos , Capacitação Espermática , Reação Acrossômica , Animais , Bicarbonatos/metabolismo , Masculino , Mamíferos/metabolismo , Prótons , Sódio/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Capacitação Espermática/fisiologia , Espermatozoides/metabolismo
19.
Microb Cell Fact ; 21(1): 102, 2022 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-35643577

RESUMO

BACKGROUND: The microbial production of succinic acid (SA) from renewable carbon sources via the reverse TCA (rTCA) pathway is a process potentially accompanied by net-fixation of carbon dioxide (CO2). Among reduced carbon sources, glycerol is particularly attractive since it allows a nearly twofold higher CO2-fixation yield compared to sugars. Recently, we described an engineered Saccharomyces cerevisiae strain which allowed SA production in synthetic glycerol medium with a maximum yield of 0.23 Cmol Cmol-1. The results of that previous study suggested that the glyoxylate cycle considerably contributed to SA accumulation in the respective strain. The current study aimed at improving the flux into the rTCA pathway accompanied by a higher CO2-fixation and SA yield. RESULTS: By changing the design of the expression cassettes for the rTCA pathway, overexpressing PYC2, and adding CaCO3 to the batch fermentations, an SA yield on glycerol of 0.63 Cmol Cmol-1 was achieved (i.e. 47.1% of the theoretical maximum). The modifications in this 2nd-generation SA producer improved the maximum biomass-specific glycerol consumption rate by a factor of nearly four compared to the isogenic baseline strain solely equipped with the dihydroxyacetone (DHA) pathway for glycerol catabolism. The data also suggest that the glyoxylate cycle did not contribute to the SA production in the new strain. Cultivation conditions which directly or indirectly increased the concentration of bicarbonate, led to an accumulation of malate in addition to the predominant product SA (ca. 0.1 Cmol Cmol-1 at the time point when SA yield was highest). Off-gas analysis in controlled bioreactors with CO2-enriched gas-phase indicated that CO2 was fixed during the SA production phase. CONCLUSIONS: The data strongly suggest that a major part of dicarboxylic acids in our 2nd-generation SA-producer was formed via the rTCA pathway enabling a net fixation of CO2. The greatly increased capacity of the rTCA pathway obviously allowed successful competition with other pathways for the common precursor pyruvate. The overexpression of PYC2 and the increased availability of bicarbonate, the co-substrate for the PYC reaction, further strengthened this capacity. The achievements are encouraging to invest in future efforts establishing a process for SA production from (crude) glycerol and CO2.


Assuntos
Saccharomyces cerevisiae , Ácido Succínico , Bicarbonatos/metabolismo , Dióxido de Carbono/metabolismo , Meios de Cultura/metabolismo , Glicerol/metabolismo , Glioxilatos/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Ácido Succínico/metabolismo
20.
Gen Comp Endocrinol ; 326: 114073, 2022 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-35697316

RESUMO

The present study aimed to clarify the effects of neurotensin and xenin on pancreatic exocrine secretion in conscious sheep and their mechanism of actions. The animals were equipped with two silastic cannulae in the common bile duct to separately collect pancreatic fluid and bile, and a silastic cannula in the proximal duodenum to continuously return the mixed fluids. NT and xenin were intravenously injected at range of 0.01-3.0 nmol/kg during the phase I of duodenal migrating motor complex. A single intravenous NT injection significantly and dose-dependently increased pancreatic fluid, protein, and bicarbonate outputs. The effect of NT at 1 nmol/kg was completely inhibited by a background intravenous infusion of atropine methyl nitrate at a dose of 10 nmol/kg/min, however, the effect was not altered by a prior injection of the neurotensin receptor subtype (NTR)-1 antagonist SR 48692 at 60 nmol/kg. Moreover, a single intravenous xenin-25 injection significantly and dose-dependently increased pancreatic fluid and protein output, whereas the effect of xenin-25 did not clearly show dose-dependence. The prior SR 48692 injection at 30 nmol/kg did not significantly alter the effects of xenin-25 at 0.3 nmol/kg, while the atropine infusion significantly inhibited the increase in fluid secretion. Under the atropine infusion, xenin-25 at 0.3 nmol/kg did not increase protein and bicarbonate outputs, whereas the inhibitory effect of the atropine was not significant compared to that of the single injection of xenin-25. A single intravenous injection of NTR-2 agonist levocabastine at 0.1-3 nmol/kg did not alter pancreatic exocrine secretion. These results suggest that both NT and xenin-25 effectively stimulates pancreatic exocrine secretion through the peripheral cholinergic system in sheep and that NTR-2 is not involved in the regulation of pancreatic exocrine secretion, however, we did not precisely determine the role of NTR-1 in the actions of both the peptides on pancreatic exocrine secretion.


Assuntos
Bicarbonatos , Neurotensina , Animais , Atropina/farmacologia , Bicarbonatos/metabolismo , Bicarbonatos/farmacologia , Colinérgicos/metabolismo , Colinérgicos/farmacologia , Neurotensina/metabolismo , Neurotensina/farmacologia , Pâncreas/metabolismo , Proteínas/metabolismo , Ovinos
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