FMRP Mediates Chronic Ethanol-Induced Changes in NMDA, Kv4.2, and KChIP3 Expression in the Hippocampus

BACKGROUND

Exposure to chronic ethanol (EtOH) results in changes in the expression of proteins that regulate neuronal excitability. This study examined whether chronic EtOH alters the hippocampal expression and function of fragile X mental retardation protein (FMRP) and the role of FMRP in the modulation of chronic EtOH-induced changes in the expression of NMDA receptors and Kv4.2 channels.

METHODS

For in vivo studies, C57BL/6J mice underwent a chronic intermittent EtOH (CIE) vapor exposure procedure. After CIE, hippocampal tissue was collected and subjected to immunoblot blot analysis of NMDA receptor subunits (GluN1, GluN2B), Kv4.2, and its accessory protein KChIP3. For in vitro studies, hippocampal slice cultures were exposed to 75 mM EtOH for 8 days. Following EtOH exposure, mRNAs bound to FMRP was measured. In a separate set of studies, cultures were exposed to an inhibitor of S6K1 (PF-4708671 [PF], 6 μM) in order to assess whether EtOH-induced homeostatic changes in protein expression depend upon changes in FMRP activity.

RESULTS

Immunoblot blot analysis revealed increases in GluN1 and GluN2B but reductions in Kv4.2 and KChIP3. Analysis of mRNAs bound to FMRP revealed a similar bidirectional change observed as reduction of GluN2B and increase in Kv4.2 and KChIP3 mRNA transcripts. Analysis of FMRP further revealed that while chronic EtOH did not alter the expression of FMRP, it significantly increased phosphorylation of FMRP at the S499 residue that is known to critically regulate its activity. Inhibition of S6K1 prevented the chronic EtOH-induced increase in phospho-FMRP and changes in NMDA subunits, Kv4.2, and KChIP3. In contrast, PF had no effect in the absence of alcohol, indicating it was specific for the chronic EtOH-induced changes.

CONCLUSIONS

These findings demonstrate that chronic EtOH exposure enhances translational control of plasticity-related proteins by FMRP, and that S6K1 and FMRP activities are required for expression of chronic EtOH-induced homeostatic plasticity at glutamatergic synapses in the hippocampus.

Pendrin modulates ENaC function by changing luminal HCO3-

The epithelial Na(+) channel, ENaC, and the Cl(-)/HCO(3)(-) exchanger, pendrin, mediate NaCl absorption within the cortical collecting duct and the connecting tubule. Although pendrin and ENaC localize to different cell types, ENaC subunit abundance and activity are lower in aldosterone-treated pendrin-null mice relative to wild-type mice. Because pendrin mediates HCO(3)(-) secretion, we asked if increasing distal delivery of HCO(3)(-) through a pendrin-independent mechanism "rescues" ENaC function in pendrin-null mice. We gave aldosterone and NaHCO(3) to increase pendrin-dependent HCO(3)(-) secretion within the connecting tubule and cortical collecting duct, or gave aldosterone and NaHCO(3) plus acetazolamide to increase luminal HCO(3)(-) concentration, [HCO(3)(-)], independent of pendrin. Following treatment with aldosterone and NaHCO(3), pendrin-null mice had lower urinary pH and [HCO(3)(-)] as well as lower renal ENaC abundance and function than wild-type mice. With the addition of acetazolamide, however, acid-base balance as well as ENaC subunit abundance and function was similar in pendrin-null and wild-type mice. We explored whether [HCO(3)(-)] directly alters ENaC abundance and function in cultured mouse principal cells (mpkCCD). Amiloride-sensitive current and ENaC abundance rose with increased [HCO(3)(-)] on the apical or the basolateral side, independent of the substituting anion. However, ENaC was more sensitive to changes in [HCO(3)(-)] on the basolateral side of the monolayer. Moreover, increasing [HCO(3)(-)] on the apical and basolateral side of Xenopus kidney cells increased both ENaC channel density and channel activity. We conclude that pendrin modulates ENaC abundance and function, at least in part by increasing luminal [HCO(3)(-)] and/or pH.

Reduced ENaC protein abundance contributes to the lower blood pressure observed in pendrin-null mice

Pendrin (encoded by Pds, Slc26a4) is a Cl(-)/HCO(3)(-) exchanger expressed in the apical regions of type B and non-A, non-B intercalated cells of kidney and mediates renal Cl(-) absorption, particularly when upregulated. Aldosterone increases blood pressure by increasing absorption of both Na(+) and Cl(-) through increased protein abundance and function of Na(+) transporters, such as the epithelial Na(+) channel (ENaC) and the Na(+)-Cl(-) cotransporter (NCC), as well as Cl(-) transporters, such as pendrin. Because aldosterone analogs do not increase blood pressure in Slc26a4(-/-) mice, we asked whether Na(+) excretion and Na(+) transporter protein abundance are altered in kidneys from these mutant mice. Thus wild-type and Slc26a4-null mice were given a NaCl-replete, a NaCl-restricted, or NaCl-replete diet and aldosterone or aldosterone analogs. Abundance of the major renal Na(+) transporters was examined with immunoblots and immunohistochemistry. Slc26a4-null mice showed an impaired ability to conserve Na(+) during dietary NaCl restriction. Under treatment conditions in which circulating aldosterone is increased, alpha-, beta-, and 85-kDa gamma-ENaC subunit protein abundances were reduced 15-35%, whereas abundance of the 70-kDa fragment of gamma-ENaC was reduced approximately 70% in Slc26a4-null relative to wild-type mice. Moreover, ENaC-dependent changes in transepithelial voltage were much lower in cortical collecting ducts from Slc26a4-null than from wild-type mice. Thus, in kidney, ENaC protein abundance and function are modulated by pendrin or through a pendrin-dependent downstream event. The reduced ENaC protein abundance and function observed in Slc26a4-null mice contribute to their lower blood pressure and reduced ability to conserve Na(+) during NaCl restriction.

Minimal standard terminology for digestive endoscopy: results of prospective testing and validation in the GASTER project

BACKGROUND AND STUDY AIMS

Standardization of the endoscopic report is a key issue for future research in the field of digestive endoscopy. The Minimal Standard Terminology (MST) has been proposed by the European Society for Gastrointestinal Endoscopy (ESGE) as a structured language for production of computerized endoscopic reports. The aim of this study was to validate version 1.0 of this terminology prospectively, by collecting cases in a multicenter, multilingual trial.

METHODS

Endoscopic cases (esophagogastroduodenoscopy [EGD], colonoscopy, endoscopic retrograde cholangiopancreatography [ERCP]) were prospectively collected in nine university hospitals in Europe, using the same software. Reports were produced in the local language, but the software allowed comparison of reports between languages, and global analysis of the database. Outcome measures were the adequacy of terms proposed in the MST to describe "reasons for performing an endoscopy", "findings", and "endoscopic diagnoses", frequency of use and content of free-text fields, and types of lesions described.

RESULTS

A total of 6,232 reports were analyzed, including 3,447 gastroscopies, 1,743 colonoscopies, and 1,042 ERCPs. Overall, terms originally contained in the MST were adequate to describe fully 91.0% of all examinations where "reasons for endoscopy" were described, 99.5 % of examinations where "findings" were described, 95.8% of all examinations containing descriptions of "endoscopic diagnosis", 98.9% of examinations containing descriptions of "additional diagnostic procedures", and 94.8 % of examinations containing descriptions of "additional therapeutic procedures". Free-text fields were only used in the other cases (less than 5% of cases in average).

CONCLUSIONS

The MST appeared adequate to cover a large part of routine endoscopy reports, and could thus be used as a tool for standardization of endoscopic reports in clinical practice. The latter could be significantly improved by the use of a structured and standardized terminology for the production of endoscopic reports.

Adrenal gland function in dogs given methylprednisolone

Serum cortisol (hydrocortisone) was measured by radioimmunoassay in dogs given methylprednisolone (MP) orally or methylprednisolone acetate (MPA) IM. The MP was given on a daily and on an alternate-day basis to different treatment groups and the MPA was administered weekly. Samples of blood were obtained twice a week over a 9-week treatment period for serum cortisol determination, and the adrenal gland response to ACTH was assessed on posttreatment days 1, 3, 5, and 7. Administration of MP on an alternate or daily basis caused a slight but significant (P < 0.05) depression in mean resting cortisol values over time. The MPA administration caused a severe depression of resting serum cortisol values. In response to ACTH, cortisol values invariably increased sharply in nontreated control dogs and in those dogs given MP on an alternate-day basis. Dogs given MP daily had a depressed response to ACTH. The MPA treatment resulted in adrenal cortices that were unresponsive to ACTH. Dogs given MPA, but not challenge exposed with ACTH, had markedly lowered cortisol values for at least 2 weeks after cessation of treatment. Consequently, a difference between daily- and alternate-day MP administration was detected after ACTH challenge exposure; MPA administration inhibited adrenal cortisol secretion for at least the duration of the experiment.