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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.

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Effect of viscous loading on CBF. (a) Time course of CBF changes in hamster oviduct ciliated cells exposed to 5% (4.8 cP), 12% (21.5 cP), 20% (73 cP), and 30% (200 cP) dextran solutions. (b) Effect of viscous load on the CBF recorded after 20-min exposure to increased viscosity. CBF recorded at steady-state conditions (15–25 min) after exposure to 4.8 (c) or 73 cP (d) in the absence of extracellular Ca2+ or in the presence of 100 μM Gd3+. Results are the mean ± SEM of 5–10 separate cultures. Significant differences (P < 0.05) between groups are marked with different letters.
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fig1: Effect of viscous loading on CBF. (a) Time course of CBF changes in hamster oviduct ciliated cells exposed to 5% (4.8 cP), 12% (21.5 cP), 20% (73 cP), and 30% (200 cP) dextran solutions. (b) Effect of viscous load on the CBF recorded after 20-min exposure to increased viscosity. CBF recorded at steady-state conditions (15–25 min) after exposure to 4.8 (c) or 73 cP (d) in the absence of extracellular Ca2+ or in the presence of 100 μM Gd3+. Results are the mean ± SEM of 5–10 separate cultures. Significant differences (P < 0.05) between groups are marked with different letters.

Mentions: Exposure of primary cultures of hamster oviductal ciliated cells to increased viscous loading reduced the CBF, reaching a new stable value within the first 10 min (Fig. 1 a). The CBF dropped ∼35% within the range of 2–37 cP (2–15% dextran solutions), but no further decrease was observed at higher viscosities in the range of 37–200 cP (15–30% dextran solutions; Fig. 1 b). These results indicate that mucus transporting ciliated cells are capable of maintaining their CBF in high viscosity conditions and suggest the presence of an autoregulatory mechanism that allows ciliated epithelia to adjust their CBF to varying viscous loads without collapsing mucus transport. The signal coupling changes in mechanical load (fluid viscosity) to the autoregulation of CBF is still unknown, although early works pointed to the influx of Ca2+ into the cells as a probable candidate (Johnson et al., 1991). We tested the Ca2+ hypothesis by measuring CBF in ciliated cells exposed to either 5% (4.8 cP) or 20% dextran solutions (73 cP, viscosity value within the range where autoregulation of the CBF occurred) in the absence of extracellular Ca2+ or in the presence of 100 μM Gd3+, a blocker of mechanosensitive cation channels (Yang and Sachs, 1989). Fig. 1 c shows that neither the absence of extracellular Ca2+ or the presence of Gd3+ modified the CBF at low viscosity conditions but determined a marked reduction of the CBF at high viscous loads (73 cP; Fig. 1 d). These results suggested that the autoregulation of CBF at high viscous loads required the entry of Ca2+ into the ciliated cell, a process that apparently does not play a crucial role in the establishment of the steady-state CBF at lower viscosities.


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)

Effect of viscous loading on CBF. (a) Time course of CBF changes in hamster oviduct ciliated cells exposed to 5% (4.8 cP), 12% (21.5 cP), 20% (73 cP), and 30% (200 cP) dextran solutions. (b) Effect of viscous load on the CBF recorded after 20-min exposure to increased viscosity. CBF recorded at steady-state conditions (15–25 min) after exposure to 4.8 (c) or 73 cP (d) in the absence of extracellular Ca2+ or in the presence of 100 μM Gd3+. 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

fig1: Effect of viscous loading on CBF. (a) Time course of CBF changes in hamster oviduct ciliated cells exposed to 5% (4.8 cP), 12% (21.5 cP), 20% (73 cP), and 30% (200 cP) dextran solutions. (b) Effect of viscous load on the CBF recorded after 20-min exposure to increased viscosity. CBF recorded at steady-state conditions (15–25 min) after exposure to 4.8 (c) or 73 cP (d) in the absence of extracellular Ca2+ or in the presence of 100 μM Gd3+. Results are the mean ± SEM of 5–10 separate cultures. Significant differences (P < 0.05) between groups are marked with different letters.
Mentions: Exposure of primary cultures of hamster oviductal ciliated cells to increased viscous loading reduced the CBF, reaching a new stable value within the first 10 min (Fig. 1 a). The CBF dropped ∼35% within the range of 2–37 cP (2–15% dextran solutions), but no further decrease was observed at higher viscosities in the range of 37–200 cP (15–30% dextran solutions; Fig. 1 b). These results indicate that mucus transporting ciliated cells are capable of maintaining their CBF in high viscosity conditions and suggest the presence of an autoregulatory mechanism that allows ciliated epithelia to adjust their CBF to varying viscous loads without collapsing mucus transport. The signal coupling changes in mechanical load (fluid viscosity) to the autoregulation of CBF is still unknown, although early works pointed to the influx of Ca2+ into the cells as a probable candidate (Johnson et al., 1991). We tested the Ca2+ hypothesis by measuring CBF in ciliated cells exposed to either 5% (4.8 cP) or 20% dextran solutions (73 cP, viscosity value within the range where autoregulation of the CBF occurred) in the absence of extracellular Ca2+ or in the presence of 100 μM Gd3+, a blocker of mechanosensitive cation channels (Yang and Sachs, 1989). Fig. 1 c shows that neither the absence of extracellular Ca2+ or the presence of Gd3+ modified the CBF at low viscosity conditions but determined a marked reduction of the CBF at high viscous loads (73 cP; Fig. 1 d). These results suggested that the autoregulation of CBF at high viscous loads required the entry of Ca2+ into the ciliated cell, a process that apparently does not play a crucial role in the establishment of the steady-state CBF at lower viscosities.

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