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Waking action of ursodeoxycholic acid (UDCA) involves histamine and GABAA receptor block.

Yanovsky Y, Schubring SR, Yao Q, Zhao Y, Li S, May A, Haas HL, Lin JS, Sergeeva OA - PLoS ONE (2012)

Bottom Line: In cultured hypothalamic neurons UDCA did not affect firing rate but synchronized the firing, an effect abolished by the GABA(A)R antagonist gabazine.The mutation α1Q241L, which abolishes GABA(A)R potentiation by several neurosteroids, had no effect on GABA(A)R inhibition by UDCA.In conclusion, UDCA enhances alertness through disinhibition, at least partially of the histaminergic system via GABA(A) receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Medical Faculty, Heinrich-Heine-University, Dusseldorf, Germany.

ABSTRACT
Since ancient times ursodeoxycholic acid (UDCA), a constituent of bile, is used against gallstone formation and cholestasis. A neuroprotective action of UDCA was demonstrated recently in models of Alzheimer's disease and retinal degeneration. The mechanisms of UDCA action in the nervous system are poorly understood. We show now that UDCA promotes wakefulness during the active period of the day, lacking this activity in histamine-deficient mice. In cultured hypothalamic neurons UDCA did not affect firing rate but synchronized the firing, an effect abolished by the GABA(A)R antagonist gabazine. In histaminergic neurons recorded in slices UDCA reduced amplitude and duration of spontaneous and evoked IPSCs. In acutely isolated histaminergic neurons UDCA inhibited GABA-evoked currents and sIPSCs starting at 10 µM (IC(50) = 70 µM) and did not affect NMDA- and AMPA-receptor mediated currents at 100 µM. Recombinant GABA(A) receptors composed of α1, β1-3 and γ2L subunits expressed in HEK293 cells displayed a sensitivity to UDCA similar to that of native GABA(A) receptors. The mutation α1V256S, known to reduce the inhibitory action of pregnenolone sulphate, reduced the potency of UDCA. The mutation α1Q241L, which abolishes GABA(A)R potentiation by several neurosteroids, had no effect on GABA(A)R inhibition by UDCA. In conclusion, UDCA enhances alertness through disinhibition, at least partially of the histaminergic system via GABA(A) receptors.

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Impairment of GABAAR-block by UDCA in the mutant α1V256S- but not α1Q241L-containing receptors.A. GABA-evoked currents, in response to maximal concentrations and concentrations around EC25, and their inhibition by pregnenolone sulphate (PS) or UDCA 100 µM. B. GABA dose-response curves constructed for the plateau amplitudes measured for control: immediately before UDCA application, which started 15–25 s after the beginning of the GABA application; and for the amplitude of blocked current: at the beginning of UDCA application (first point at a steady-state level). The inhibition of maximal GABA-responses by UDCA is significantly smaller in WT (47±3% of control, n = 7) and mutant α1Q241L receptors (54±2% of control, n = 5, no difference with WT) than in the mutant α1V256S receptors (87±1% of control, n = 5; p = 0.0047 vs WT). UDCA does not significantly modify the EC50 and nH values for GABA in the WT (6±1 µM; 1.2±0.2 versus 5.1±0.5 µM; 1.4±0.1 in control), in the mutant α1Q241L (11.5±1.2 µM; 2.0±0.4 versus 9.8±0.7 µM; 1.9±0.2 in control) and α1V256S (1.5±0.07 µM; 1.6±0.1 versus 0.83±0.03 µM; 1.5±0.06 in control) receptors. C. GABA dose-response curves constructed from peak current amplitude values normalized on maximal GABA-evoked current for the WT (EC50 = 8±0.5 µM; nH = 1.2±0.1; n = 8), α1V256S (EC50 = 0.9±0.03 µM; nH = 1.5±0.06; n = 5) and α1Q241L (EC50 = 20±1 µM; nH = 1.4±0.1; n = 5) receptors of α1β2γ2L-composition expressed in HEK293 cells.
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pone-0042512-g007: Impairment of GABAAR-block by UDCA in the mutant α1V256S- but not α1Q241L-containing receptors.A. GABA-evoked currents, in response to maximal concentrations and concentrations around EC25, and their inhibition by pregnenolone sulphate (PS) or UDCA 100 µM. B. GABA dose-response curves constructed for the plateau amplitudes measured for control: immediately before UDCA application, which started 15–25 s after the beginning of the GABA application; and for the amplitude of blocked current: at the beginning of UDCA application (first point at a steady-state level). The inhibition of maximal GABA-responses by UDCA is significantly smaller in WT (47±3% of control, n = 7) and mutant α1Q241L receptors (54±2% of control, n = 5, no difference with WT) than in the mutant α1V256S receptors (87±1% of control, n = 5; p = 0.0047 vs WT). UDCA does not significantly modify the EC50 and nH values for GABA in the WT (6±1 µM; 1.2±0.2 versus 5.1±0.5 µM; 1.4±0.1 in control), in the mutant α1Q241L (11.5±1.2 µM; 2.0±0.4 versus 9.8±0.7 µM; 1.9±0.2 in control) and α1V256S (1.5±0.07 µM; 1.6±0.1 versus 0.83±0.03 µM; 1.5±0.06 in control) receptors. C. GABA dose-response curves constructed from peak current amplitude values normalized on maximal GABA-evoked current for the WT (EC50 = 8±0.5 µM; nH = 1.2±0.1; n = 8), α1V256S (EC50 = 0.9±0.03 µM; nH = 1.5±0.06; n = 5) and α1Q241L (EC50 = 20±1 µM; nH = 1.4±0.1; n = 5) receptors of α1β2γ2L-composition expressed in HEK293 cells.

Mentions: The actions of BS on native and recombinant GABAA receptors expressed in HEK 293 cells appear kinetically similar to those observed in the presence of inhibitory neurosteroids, e.g., pregnenolone sulphate, which enhances the apparent rate of desensitization and, under some experimental conditions, reduces the peak amplitude [27]. A previous study showed that a mutation to the 2′residue in the α-subunit M2 transmembrane domain (α1V256S) strongly reduces inhibition by neurosteroids [28]. Here, we tested the effect of the α1V256S mutation on GABAAR inhibition by UDCA. In wild-type receptors, the UDCA-inhibition did not depend on the GABA concentration (Fig. 7A): at all GABA concentrations tested UDCA (100 µM) inhibited control GABA responses to the same extent. The relative amplitude of maximal GABA-responses was reduced by UDCA in the mutant α1V256S receptors to 87±1% of control (n = 5), differing significantly from wild type receptors (47±3% of control, n = 7, p<0.005, Fig. 7A, B). Pregnenolone sulphate (10 µM) inhibited the steady-state amplitude of maximal GABA-currents to 11±3% of control in WT and to 82±6% of control in mutated α1V256Sβ2γ2L receptors (p<0.001)(Fig. 7A). UDCA's blocking potency was significantly reduced (p<0.01) in the mutant α1V256S receptors (IC50 = 330±41 µM (n = 4) vs 84.7±11.3 µM (n = 5) in WT). UDCA did not significantly modify the GABA EC50 and nH values in the WT and α1V256S receptors (Fig. 7B).


Waking action of ursodeoxycholic acid (UDCA) involves histamine and GABAA receptor block.

Yanovsky Y, Schubring SR, Yao Q, Zhao Y, Li S, May A, Haas HL, Lin JS, Sergeeva OA - PLoS ONE (2012)

Impairment of GABAAR-block by UDCA in the mutant α1V256S- but not α1Q241L-containing receptors.A. GABA-evoked currents, in response to maximal concentrations and concentrations around EC25, and their inhibition by pregnenolone sulphate (PS) or UDCA 100 µM. B. GABA dose-response curves constructed for the plateau amplitudes measured for control: immediately before UDCA application, which started 15–25 s after the beginning of the GABA application; and for the amplitude of blocked current: at the beginning of UDCA application (first point at a steady-state level). The inhibition of maximal GABA-responses by UDCA is significantly smaller in WT (47±3% of control, n = 7) and mutant α1Q241L receptors (54±2% of control, n = 5, no difference with WT) than in the mutant α1V256S receptors (87±1% of control, n = 5; p = 0.0047 vs WT). UDCA does not significantly modify the EC50 and nH values for GABA in the WT (6±1 µM; 1.2±0.2 versus 5.1±0.5 µM; 1.4±0.1 in control), in the mutant α1Q241L (11.5±1.2 µM; 2.0±0.4 versus 9.8±0.7 µM; 1.9±0.2 in control) and α1V256S (1.5±0.07 µM; 1.6±0.1 versus 0.83±0.03 µM; 1.5±0.06 in control) receptors. C. GABA dose-response curves constructed from peak current amplitude values normalized on maximal GABA-evoked current for the WT (EC50 = 8±0.5 µM; nH = 1.2±0.1; n = 8), α1V256S (EC50 = 0.9±0.03 µM; nH = 1.5±0.06; n = 5) and α1Q241L (EC50 = 20±1 µM; nH = 1.4±0.1; n = 5) receptors of α1β2γ2L-composition expressed in HEK293 cells.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3412845&req=5

pone-0042512-g007: Impairment of GABAAR-block by UDCA in the mutant α1V256S- but not α1Q241L-containing receptors.A. GABA-evoked currents, in response to maximal concentrations and concentrations around EC25, and their inhibition by pregnenolone sulphate (PS) or UDCA 100 µM. B. GABA dose-response curves constructed for the plateau amplitudes measured for control: immediately before UDCA application, which started 15–25 s after the beginning of the GABA application; and for the amplitude of blocked current: at the beginning of UDCA application (first point at a steady-state level). The inhibition of maximal GABA-responses by UDCA is significantly smaller in WT (47±3% of control, n = 7) and mutant α1Q241L receptors (54±2% of control, n = 5, no difference with WT) than in the mutant α1V256S receptors (87±1% of control, n = 5; p = 0.0047 vs WT). UDCA does not significantly modify the EC50 and nH values for GABA in the WT (6±1 µM; 1.2±0.2 versus 5.1±0.5 µM; 1.4±0.1 in control), in the mutant α1Q241L (11.5±1.2 µM; 2.0±0.4 versus 9.8±0.7 µM; 1.9±0.2 in control) and α1V256S (1.5±0.07 µM; 1.6±0.1 versus 0.83±0.03 µM; 1.5±0.06 in control) receptors. C. GABA dose-response curves constructed from peak current amplitude values normalized on maximal GABA-evoked current for the WT (EC50 = 8±0.5 µM; nH = 1.2±0.1; n = 8), α1V256S (EC50 = 0.9±0.03 µM; nH = 1.5±0.06; n = 5) and α1Q241L (EC50 = 20±1 µM; nH = 1.4±0.1; n = 5) receptors of α1β2γ2L-composition expressed in HEK293 cells.
Mentions: The actions of BS on native and recombinant GABAA receptors expressed in HEK 293 cells appear kinetically similar to those observed in the presence of inhibitory neurosteroids, e.g., pregnenolone sulphate, which enhances the apparent rate of desensitization and, under some experimental conditions, reduces the peak amplitude [27]. A previous study showed that a mutation to the 2′residue in the α-subunit M2 transmembrane domain (α1V256S) strongly reduces inhibition by neurosteroids [28]. Here, we tested the effect of the α1V256S mutation on GABAAR inhibition by UDCA. In wild-type receptors, the UDCA-inhibition did not depend on the GABA concentration (Fig. 7A): at all GABA concentrations tested UDCA (100 µM) inhibited control GABA responses to the same extent. The relative amplitude of maximal GABA-responses was reduced by UDCA in the mutant α1V256S receptors to 87±1% of control (n = 5), differing significantly from wild type receptors (47±3% of control, n = 7, p<0.005, Fig. 7A, B). Pregnenolone sulphate (10 µM) inhibited the steady-state amplitude of maximal GABA-currents to 11±3% of control in WT and to 82±6% of control in mutated α1V256Sβ2γ2L receptors (p<0.001)(Fig. 7A). UDCA's blocking potency was significantly reduced (p<0.01) in the mutant α1V256S receptors (IC50 = 330±41 µM (n = 4) vs 84.7±11.3 µM (n = 5) in WT). UDCA did not significantly modify the GABA EC50 and nH values in the WT and α1V256S receptors (Fig. 7B).

Bottom Line: In cultured hypothalamic neurons UDCA did not affect firing rate but synchronized the firing, an effect abolished by the GABA(A)R antagonist gabazine.The mutation α1Q241L, which abolishes GABA(A)R potentiation by several neurosteroids, had no effect on GABA(A)R inhibition by UDCA.In conclusion, UDCA enhances alertness through disinhibition, at least partially of the histaminergic system via GABA(A) receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Medical Faculty, Heinrich-Heine-University, Dusseldorf, Germany.

ABSTRACT
Since ancient times ursodeoxycholic acid (UDCA), a constituent of bile, is used against gallstone formation and cholestasis. A neuroprotective action of UDCA was demonstrated recently in models of Alzheimer's disease and retinal degeneration. The mechanisms of UDCA action in the nervous system are poorly understood. We show now that UDCA promotes wakefulness during the active period of the day, lacking this activity in histamine-deficient mice. In cultured hypothalamic neurons UDCA did not affect firing rate but synchronized the firing, an effect abolished by the GABA(A)R antagonist gabazine. In histaminergic neurons recorded in slices UDCA reduced amplitude and duration of spontaneous and evoked IPSCs. In acutely isolated histaminergic neurons UDCA inhibited GABA-evoked currents and sIPSCs starting at 10 µM (IC(50) = 70 µM) and did not affect NMDA- and AMPA-receptor mediated currents at 100 µM. Recombinant GABA(A) receptors composed of α1, β1-3 and γ2L subunits expressed in HEK293 cells displayed a sensitivity to UDCA similar to that of native GABA(A) receptors. The mutation α1V256S, known to reduce the inhibitory action of pregnenolone sulphate, reduced the potency of UDCA. The mutation α1Q241L, which abolishes GABA(A)R potentiation by several neurosteroids, had no effect on GABA(A)R inhibition by UDCA. In conclusion, UDCA enhances alertness through disinhibition, at least partially of the histaminergic system via GABA(A) receptors.

Show MeSH
Related in: MedlinePlus