Saez, E. (Elena)
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- Linezolid-induced lactic acidosis in two liver transplant patients with the mitochondrial DNA A2706G polymorphism(2014) Banales, J.M. (Jesús M.); Fernandez-Ros, N. (Nerea); Saez, E. (Elena); Pozo, J.L. (José Luis) del; Herrero, J.I. (José Ignacio); Yuste, J.R. (José Ramón)Mitochondrial toxicity has been recently suggested to be the underlying mechanism of long-term linezolid-associated toxicity in patients with 16S rRNA genetic polymorphisms. Here, we report for the first time two cases of lactic acidosis due to long-term linezolid exposure in liver transplant recipients who presented an A2706G mitochondrial DNA polymorphism.
- Adaptive downregulation of Cl- /HCO3 - exchange activity in rat hepatocytes under experimental obstructive cholestasis(Public Library of Science (PLoS), 2019) Banales, J.M. (Jesús M.); Miszczuk, G.S. (Gisel S.); Medina, J.F. (Juan Francisco); Saez, E. (Elena); Zucchetti, A.E. (Andrés E.); Roma, M.G. (Marcelo G.); Pisani, G.B. (Gerardo B.); Boaglio, A.C. (Andrea C.); Crocenzi, F.A. (Fernando A.)
- Bicarbonate secretion of mouse cholangiocytes involves Na(+)-HCO(3)(-) cotransport in addition to Na(+)-independent Cl(-)/HCO(3)(-) exchange(Wiley Blackwell, 2010) Banales, J.M. (Jesús M.); Oude-Elferink, R.P.J. (Ronald P.J.); Uriarte, I. (Iker); Medina, J.F. (Juan Francisco); Saez, E. (Elena); Prieto, J. (Jesús); Arenas, F. (Fabián)Bicarbonate secretion from cholangiocytes is required for appropriate adjustment of primary canalicular bile along the biliary tract. In human and rat cholangiocytes, bicarbonate secretion is mediated by anion exchanger (AE) 2, an electroneutral Na(+)-independent Cl(-)/HCO(3) (-) AE also involved in intracellular pH (pH(i)) regulation. In Ae2(a,b)-deficient mice, pH(i) is increased in lymphocytes and fibroblasts, whereas it is surprisingly normal in cholangiocytes. Here, we analyze the mechanisms for HCO(3) (-) secretion in cultured Ae2(a,b) (+/+) and Ae2(a,b) (-/-) mouse cholangiocytes by microfluorimetric measurement of pH(i) changes upon established perfusion maneuvers. Cl(-) withdrawal by isethionate-based perfusions showed that Ae2(a,b) (+/+) but not Ae2(a,b) (-/-) mouse cholangiocytes can display Cl(-)/HCO(3) (-) exchange, which is therefore entirely mediated by Ae2. Nevertheless, simultaneous withdrawal of Cl(-) and Na(+) revealed that mouse cholangiocytes possess an additional transport activity for HCO(3) (-) secretion not observed in control rat cholangiocytes. Propionate-based maneuvers indicated that this supplemental Na(+)-driven HCO(3) (-)-secreting activity is Cl(-)-independent, consistent with a Na(+)-HCO(3) (-) cotransport (NBC). NBC activity is greater in Ae2(a,b) (-/-) than Ae2(a,b) (+/+) mouse cholangiocytes, and membrane-depolarization experiments showed that it is electrogenic. Consistent with the potential role of Slc4a4/Nbc1 as the involved transporter, Ae2(a,b) (-/-) mouse cholangiocytes exhibit up-regulated expression of this electrogenic NBC carrier. Whereas Ae2-mediated Cl(-)/HCO(3) (-) exchange in Ae2(a,b) (+/+) mouse cholangiocytes is stimulated by cyclic adenosine monophosphate (cAMP) and acetylcholine, the NBC activity is down-regulated by cAMP and adenosine triphosphate (ATP) in Ae2(a,b) (-/-) mouse cholangiocytes. Polarized Ae2(a,b) (-/-) mouse cholangiocytes placed in Ussing chambers show decreased (but not abolished) cAMP-dependent Cl(-) current and increased ATP-dependent/Ca(2+)-activated Cl(-) secretion, which run in parallel with decreased cystic fibrosis transmembrane conductance regulator messenger RNA expression and increased intracellular Ca(2+) levels. Conclusion: Bicarbonate secretion in mouse cholangiocytes involves two differentially regulated activities: Ae2-mediated Cl(-)/HCO(3) (-) exchange and Na(+)-HCO(3) (-) cotransport.
- Bicarbonate-rich choleresis induced by secretin in normal rat is taurocholate-dependent and involves AE2 anion exchanger(Wiley Blackwell, 2006) Banales, J.M. (Jesús M.); Uriarte, I. (Iker); Medina, J.F. (Juan Francisco); Saez, E. (Elena); Rodriguez-Ortigosa, C.M. (Carlos M.); Prieto, J. (Jesús); Arenas, F. (Fabián); Doctor, R.B. (R. Brian)Canalicular bile is modified along bile ducts through reabsorptive and secretory processes regulated by nerves, bile salts, and hormones such as secretin. Secretin stimulates ductular cystic fibrosis transmembrane conductance regulator (CFTR)-dependent Cl- efflux and subsequent biliary HCO3- secretion, possibly via Cl-/HCO3- anion exchange (AE). However, the contribution of secretin to bile regulation in the normal rat, the significance of choleretic bile salts in secretin effects, and the role of Cl-/HCO3- exchange in secretin-stimulated HCO3- secretion all remain unclear. Here, secretin was administered to normal rats with maintained bile acid pool via continuous taurocholate infusion. Bile flow and biliary HCO3- and Cl- excretion were monitored following intrabiliary retrograde fluxes of saline solutions with and without the Cl- channel inhibitor 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) or the Cl-/HCO3- exchange inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). Secretin increased bile flow and biliary excretion of HCO3- and Cl-. Interestingly, secretin effects were not observed in the absence of taurocholate. Whereas secretin effects were all blocked by intrabiliary NPPB, DIDS only inhibited secretin-induced increases in bile flow and HCO3- excretion but not the increased Cl- excretion, revealing a role of biliary Cl-/HCO3- exchange in secretin-induced, bicarbonate-rich choleresis in normal rats. Finally, small hairpin RNA adenoviral constructs were used to demonstrate the involvement of the Na+-independent anion exchanger 2 (AE2) through gene silencing in normal rat cholangiocytes. AE2 gene silencing caused a marked inhibition of unstimulated and secretin-stimulated Cl-/HCO3- exchange. In conclusion, maintenance of the bile acid pool is crucial for secretin to induce bicarbonate-rich choleresis in the normal rat and that this occurs via a chloride-bicarbonate exchange process consistent with AE2 function.
- Promoter hypermethylation of the AE2/SLC4A2 gene in PBC(Elsevier, 2019) Medina, J.F. (Juan Francisco); Saez, E. (Elena); Melero, S. (Saida); Prieto, J. (Jesús); Arenas, F. (Fabián); Parés, A. (Albert); Hervias, I. (Isabel)Primary biliary cholangitis (PBC) is a chronic immuneassociated cholestatic liver disease with unclear complex/multifactorial etiopathogenesis affecting mostly middle-aged women. Patients with PBC exhibit reduced expression of the AE2/SLC4A2 gene. Herein, we found that AE2 promoter regions are hypermethylated in the liver and peripheral blood mononuclear cells of patients with PBC. This increased methylation is associated with downregulated AE2-gene expression, which might contribute to the pathogenesis of PBC. Therefore, novel epigenetic targets may improve treatment in patients with PBC who respond poorly to current pharmacological therapies.
- Inefficient chronic activation of parietal cells in Ae2a,b-/-(Elsevier, 2006-07-01) Oude-Elferink, R.P.J. (Ronald P.J.); Mardones, P. (Pablo); Salas, J.T. (January T.); Kunne, C. (Cindy); Medina, J.F. (Juan Francisco); Saez, E. (Elena); Burrell, M.A. (María Ángela); Prieto, J. (Jesús); Looije, N. (Norbert); Recalde, S. (Sergio); Martinez-Anso, E. (Eduardo)In parietal cells, basolateral Ae2 C1 /HCO3 exchanger (S1c4a2) appears to compensate for luminal H pumping while providing C1 for apical secretion. In mouse and rat, mRNA variants Ae2a, Ae2b1, Ae2b2, and Ae2c2 are all found in most tissues (altough the latter at very low levels), whereas Ae2c1 is restricted to the stomach. We studied the acid secretory function of gastric mucosa in mice with targeted disruption of Ae2a, Ae2b1, and Ae2b2 (but not Ae2c) isoforms. In the oxyntic mucosa of Ae2a,b−/− mice, total Ae2 protein was nearly undetectable, indicating low gastric expression of the Ae2c isoforms. In Ae2a,b−/− mice basal acid secretion was normal, whereas carbachol/histamine-stimulated acid secretion was impaired by 70%. These animals showed increased serum gastrin levels and hyperplasia of G cells. Immunohistochemistry and electron microscopy revealed baseline activation of parietal cells with fusion of intracellular H+/K+-ATPase-containing vesicles with the apical membrane and degenerative changes (but not substantial apoptosis) in a subpopulation of these cells. Increased expression of proliferating cell nuclear antigen in the oxyntic glands suggested enhanced Ae2a,b−/− parietal cell turnover. These data reveal a critical role of Ae2a-Ae2b1-Ae2b2 isoforms in stimulated gastric acid secretion whereas residual Ae2c isoforms could account to a limited extent for basal acid secretion.