Limits...
TRPV4 channel is involved in the coupling of fluid viscosity changes to epithelial ciliary activity.

Andrade YN, Fernandes J, Vázquez E, Fernández-Fernández JM, Arniges M, Sánchez TM, Villalón M, Valverde MA - J. Cell Biol. (2005)

Bottom Line: This mechanical activation is prevented in native ciliated cells loaded with a TRPV4 antibody.Application of the TRPV4 synthetic ligand 4alpha-phorbol 12,13-didecanoate increased cationic currents, intracellular Ca(2+), and the CBF in the absence of a viscous load.Therefore, TRPV4 emerges as a candidate to participate in the coupling of fluid viscosity changes to the generation of the Ca(2+) signal required for the autoregulation of CBF.

View Article: PubMed Central - PubMed

Affiliation: Grup de Fisiologia Cellular i Molecular, Unitat de Senyalització Cellular, Universitat Pompeu Fabra, Barcelona 08003, Spain.

ABSTRACT
Autoregulation of the ciliary beat frequency (CBF) has been proposed as the mechanism used by epithelial ciliated cells to maintain the CBF and prevent the collapse of mucociliary transport under conditions of varying mucus viscosity. Despite the relevance of this regulatory response to the pathophysiology of airways and reproductive tract, the underlying cellular and molecular aspects remain unknown. Hamster oviductal ciliated cells express the transient receptor potential vanilloid 4 (TRPV4) channel, which is activated by increased viscous load involving a phospholipase A(2)-dependent pathway. TRPV4-transfected HeLa cells also increased their cationic currents in response to high viscous load. This mechanical activation is prevented in native ciliated cells loaded with a TRPV4 antibody. Application of the TRPV4 synthetic ligand 4alpha-phorbol 12,13-didecanoate increased cationic currents, intracellular Ca(2+), and the CBF in the absence of a viscous load. Therefore, TRPV4 emerges as a candidate to participate in the coupling of fluid viscosity changes to the generation of the Ca(2+) signal required for the autoregulation of CBF.

Show MeSH

Related in: MedlinePlus

PLA2-dependent activation of TRPV4 under high viscous conditions. (a) Whole-cell currents recorded in a cell dialyzed with NMDG-Cl solutions and bathed consecutively in control solutions, 100 μM pBPB, 20% dextran + pBPB, and 1 μM 4αPDD. Basal current levels recovered after washout. (b) Average current density measured at −100 mV and +100 mV with NMDG-Cl–containing pipette solutions and Ca2+-free bathing solution under the following conditions: control (n = 16), 20% dextran (n = 16), pBPB (n = 12), and pBPB + 20% dextran (n = 12). *, P < 0.05, compared with control. (c) CBF recorded at steady-state conditions (15–25 min) under control (1 cP) and 20% dextran solutions (73 cP) in the absence or presence of 50 μM AACOCF3. Results are the mean ± SEM of 5–10 separate cultures. Significant differences (P < 0.05) between groups are marked with different letters.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2171792&req=5

fig5: PLA2-dependent activation of TRPV4 under high viscous conditions. (a) Whole-cell currents recorded in a cell dialyzed with NMDG-Cl solutions and bathed consecutively in control solutions, 100 μM pBPB, 20% dextran + pBPB, and 1 μM 4αPDD. Basal current levels recovered after washout. (b) Average current density measured at −100 mV and +100 mV with NMDG-Cl–containing pipette solutions and Ca2+-free bathing solution under the following conditions: control (n = 16), 20% dextran (n = 16), pBPB (n = 12), and pBPB + 20% dextran (n = 12). *, P < 0.05, compared with control. (c) CBF recorded at steady-state conditions (15–25 min) under control (1 cP) and 20% dextran solutions (73 cP) in the absence or presence of 50 μM AACOCF3. Results are the mean ± SEM of 5–10 separate cultures. Significant differences (P < 0.05) between groups are marked with different letters.

Mentions: Cell swelling-dependent activation of TRPV4 requires the PLA2-mediated release of arachidonic acid (Vriens et al., 2004), suggesting that the TRPV4 channel is not an osmosensor per se, but a key element in the transduction of osmotic changes into Ca2+ signals. Both cell swelling and mechanical stress activate PLA2 and the formation of arachidonic acid (Lehtonen and Kinnunen, 1995; Pedersen et al., 2000). Therefore, we evaluated whether or not activation of the TRPV4-like current by 20% dextran solutions might also depend on the activity of PLA2 (Fig. 5). Currents were recorded with N-methyl-d-glucamine (NMDG) intracellular solutions, favoring the presence of inward currents. Incubation of single ciliated cells with the PLA2 inhibitor 4-bromophenacyl bromide (pBPB; 100 μM) prevented the activation of TRPV4-like currents under high viscosity conditions (Fig. 5, a and b) but did not affect current activation by 4αPDD (Fig. 5 a). These results are in accordance with previous observations reporting that swelling- and 4αPDD-induced activation of TRPV4 use distinct pathways (Arniges et al., 2004; Vriens et al., 2004). Moreover, inhibition of PLA2 activity with arachidonyl trifluoromethyl ketone (AACOCF3; 50 μM) also prevented the cilia autoregulatory response. In the presence of AACOCF3, the CBF in response to 20% dextran solutions (73 cP) dropped to 44% of the basal value (Fig. 5 c), similar to the CBF reduction observed in the absence of Ca2+ or in the presence of Gd3+ (Fig. 1 d).


TRPV4 channel is involved in the coupling of fluid viscosity changes to epithelial ciliary activity.

Andrade YN, Fernandes J, Vázquez E, Fernández-Fernández JM, Arniges M, Sánchez TM, Villalón M, Valverde MA - J. Cell Biol. (2005)

PLA2-dependent activation of TRPV4 under high viscous conditions. (a) Whole-cell currents recorded in a cell dialyzed with NMDG-Cl solutions and bathed consecutively in control solutions, 100 μM pBPB, 20% dextran + pBPB, and 1 μM 4αPDD. Basal current levels recovered after washout. (b) Average current density measured at −100 mV and +100 mV with NMDG-Cl–containing pipette solutions and Ca2+-free bathing solution under the following conditions: control (n = 16), 20% dextran (n = 16), pBPB (n = 12), and pBPB + 20% dextran (n = 12). *, P < 0.05, compared with control. (c) CBF recorded at steady-state conditions (15–25 min) under control (1 cP) and 20% dextran solutions (73 cP) in the absence or presence of 50 μM AACOCF3. Results are the mean ± SEM of 5–10 separate cultures. Significant differences (P < 0.05) between groups are marked with different letters.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171792&req=5

fig5: PLA2-dependent activation of TRPV4 under high viscous conditions. (a) Whole-cell currents recorded in a cell dialyzed with NMDG-Cl solutions and bathed consecutively in control solutions, 100 μM pBPB, 20% dextran + pBPB, and 1 μM 4αPDD. Basal current levels recovered after washout. (b) Average current density measured at −100 mV and +100 mV with NMDG-Cl–containing pipette solutions and Ca2+-free bathing solution under the following conditions: control (n = 16), 20% dextran (n = 16), pBPB (n = 12), and pBPB + 20% dextran (n = 12). *, P < 0.05, compared with control. (c) CBF recorded at steady-state conditions (15–25 min) under control (1 cP) and 20% dextran solutions (73 cP) in the absence or presence of 50 μM AACOCF3. Results are the mean ± SEM of 5–10 separate cultures. Significant differences (P < 0.05) between groups are marked with different letters.
Mentions: Cell swelling-dependent activation of TRPV4 requires the PLA2-mediated release of arachidonic acid (Vriens et al., 2004), suggesting that the TRPV4 channel is not an osmosensor per se, but a key element in the transduction of osmotic changes into Ca2+ signals. Both cell swelling and mechanical stress activate PLA2 and the formation of arachidonic acid (Lehtonen and Kinnunen, 1995; Pedersen et al., 2000). Therefore, we evaluated whether or not activation of the TRPV4-like current by 20% dextran solutions might also depend on the activity of PLA2 (Fig. 5). Currents were recorded with N-methyl-d-glucamine (NMDG) intracellular solutions, favoring the presence of inward currents. Incubation of single ciliated cells with the PLA2 inhibitor 4-bromophenacyl bromide (pBPB; 100 μM) prevented the activation of TRPV4-like currents under high viscosity conditions (Fig. 5, a and b) but did not affect current activation by 4αPDD (Fig. 5 a). These results are in accordance with previous observations reporting that swelling- and 4αPDD-induced activation of TRPV4 use distinct pathways (Arniges et al., 2004; Vriens et al., 2004). Moreover, inhibition of PLA2 activity with arachidonyl trifluoromethyl ketone (AACOCF3; 50 μM) also prevented the cilia autoregulatory response. In the presence of AACOCF3, the CBF in response to 20% dextran solutions (73 cP) dropped to 44% of the basal value (Fig. 5 c), similar to the CBF reduction observed in the absence of Ca2+ or in the presence of Gd3+ (Fig. 1 d).

Bottom Line: This mechanical activation is prevented in native ciliated cells loaded with a TRPV4 antibody.Application of the TRPV4 synthetic ligand 4alpha-phorbol 12,13-didecanoate increased cationic currents, intracellular Ca(2+), and the CBF in the absence of a viscous load.Therefore, TRPV4 emerges as a candidate to participate in the coupling of fluid viscosity changes to the generation of the Ca(2+) signal required for the autoregulation of CBF.

View Article: PubMed Central - PubMed

Affiliation: Grup de Fisiologia Cellular i Molecular, Unitat de Senyalització Cellular, Universitat Pompeu Fabra, Barcelona 08003, Spain.

ABSTRACT
Autoregulation of the ciliary beat frequency (CBF) has been proposed as the mechanism used by epithelial ciliated cells to maintain the CBF and prevent the collapse of mucociliary transport under conditions of varying mucus viscosity. Despite the relevance of this regulatory response to the pathophysiology of airways and reproductive tract, the underlying cellular and molecular aspects remain unknown. Hamster oviductal ciliated cells express the transient receptor potential vanilloid 4 (TRPV4) channel, which is activated by increased viscous load involving a phospholipase A(2)-dependent pathway. TRPV4-transfected HeLa cells also increased their cationic currents in response to high viscous load. This mechanical activation is prevented in native ciliated cells loaded with a TRPV4 antibody. Application of the TRPV4 synthetic ligand 4alpha-phorbol 12,13-didecanoate increased cationic currents, intracellular Ca(2+), and the CBF in the absence of a viscous load. Therefore, TRPV4 emerges as a candidate to participate in the coupling of fluid viscosity changes to the generation of the Ca(2+) signal required for the autoregulation of CBF.

Show MeSH
Related in: MedlinePlus