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Involvement of A(1) adenosine receptors in osmotic volume regulation of retinal glial cells in mice.

Wurm A, Lipp S, Pannicke T, Linnertz R, Färber K, Wiedemann P, Reichenbach A, Bringmann A - Mol. Vis. (2009)

Bottom Line: The size of Müller cell somata was recorded before and during perfusion of retinal sections and isolated Müller cells with a hypoosmolar solution.The data suggest that autocrine activation of A(1) receptors by extracellularly generated adenosine mediates the volume homeostasis of Müller cells in the murine retina.The swelling-inhibitory effect of triamcinolone is mediated by enhancement of endogenous adenosine signaling.

View Article: PubMed Central - PubMed

Affiliation: Paul Flechsig Institute of Brain Research, University of Leipzig, D-04103 Leipzig, Germany.

ABSTRACT

Purpose: Osmotic swelling of Müller glial cells has been suggested to contribute to retinal edema. We determined the role of adenosine signaling in the inhibition of Müller cell swelling in the murine retina.

Methods: The size of Müller cell somata was recorded before and during perfusion of retinal sections and isolated Müller cells with a hypoosmolar solution. Retinal tissues were freshly isolated from wild-type mice and mice deficient in A(1) adenosine receptors (A(1)AR(-/-)), or cultured as whole-mounts for three days. The potassium conductance of Müller cells was recorded in isolated cells, and retinal slices were immunostained against Kir4.1.

Results: Hypotonic exposure for 4 min induced a swelling of Müller cell bodies in retinal slices from A(1)AR(-/-) mice but not wild-type mice. Pharmacological inhibition of A(1) receptors or of the ecto-5'-nucleotidase induced hypoosmotic swelling of Müller cells from wild-type mice. Exogenous adenosine prevented the swelling of Müller cells from wild-type but not A(1)AR(-/-) mice. The antiinflammatory corticosteroid, triamcinolone acetonide, inhibited the swelling of Müller cells from wild-type mice; this effect was blocked by an antagonist of A(1) receptors. The potassium conductance of Müller cells and the Kir4.1 immunolabeling of retinal slices were not different between A(1)AR(-/-) and wild-type mice, both in freshly isolated tissues and retinal organ cultures.

Conclusions: The data suggest that autocrine activation of A(1) receptors by extracellularly generated adenosine mediates the volume homeostasis of Müller cells in the murine retina. The swelling-inhibitory effect of triamcinolone is mediated by enhancement of endogenous adenosine signaling.

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Osmotic swelling of Müller glial cells in slices of the wild-type mouse retina. A: Perfusion of slices of a freshly isolated retina with a hypoosmolar solution, containing 60% of control osmolarity, in the absence (control) and presence of 1 mM barium chloride resulted in a time-dependent swelling of Müller cell somata. The diagram displays the mean (±SEM) cross-sectional area of the somata (n=3 each). Inset images in A show original records of dye-filled Müller cell somata obtained before (left) and during (right) perfusion with the barium-containing hypoosmolar solution. Scale bars represents 5 µm. B: Hypoosmotic exposure for 4 min evoked swelling of Müller cell somata in slices of freshly isolated retinas in the presence but not absence of 1 mM barium chloride. Müller cells in slices of retinal organ cultures displayed soma swelling under both conditions. Data are mean (±SEM) soma areas (n=7–21 cells per bar) expressed in percent of the soma size recorded before hypoosmotic challenge (100%). Significant increases in the soma area: The double asterisk indicates a p<0.01 and the triple asterisk indicates a p<0.001.
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f1: Osmotic swelling of Müller glial cells in slices of the wild-type mouse retina. A: Perfusion of slices of a freshly isolated retina with a hypoosmolar solution, containing 60% of control osmolarity, in the absence (control) and presence of 1 mM barium chloride resulted in a time-dependent swelling of Müller cell somata. The diagram displays the mean (±SEM) cross-sectional area of the somata (n=3 each). Inset images in A show original records of dye-filled Müller cell somata obtained before (left) and during (right) perfusion with the barium-containing hypoosmolar solution. Scale bars represents 5 µm. B: Hypoosmotic exposure for 4 min evoked swelling of Müller cell somata in slices of freshly isolated retinas in the presence but not absence of 1 mM barium chloride. Müller cells in slices of retinal organ cultures displayed soma swelling under both conditions. Data are mean (±SEM) soma areas (n=7–21 cells per bar) expressed in percent of the soma size recorded before hypoosmotic challenge (100%). Significant increases in the soma area: The double asterisk indicates a p<0.01 and the triple asterisk indicates a p<0.001.

Mentions: The swelling of Müller cell somata was investigated by perfusion of freshly isolated retinal slices with a hypoosmolar solution (containing 60% of control osmolarity). Under isotonic conditions, the absolute soma areas of Müller cells from wild-type and knockout animals were not different (wild-type: 49.6±1.7 µm2, n=48; A1AR−/−: 45.8±1.3 µm2, n=60; p>0.05). Hypotonic exposure for 4 min did not evoke a significant swelling of glial cell bodies in freshly isolated retinal slices from wild-type mice (Figures 1A,B). The increase in the size of glial cell bodies was significantly (p<0.01) stronger and faster when 1 mM barium chloride was jointly applied with the hypoosmolar solution (Figures 1A,B). Barium ions are known to block the principal potassium conductance of Müller cells mediated by inwardly rectifying potassium (Kir) channels [28,29]. As shown recently, Müller cells in slices of retinal organ cultures of the rat display a decrease in their Kir currents which is associated with an induction of cellular swelling under hypotonic conditions [25]. We found that Müller cells in organ cultures of the wild-type mouse retina displayed a swelling of their cell bodies under hypoosmotic conditions in the absence and presence of barium ions (Figure 1B). The swelling in the absence of barium suggests that retina culturing alters the volume regulation mechanisms of Müller cells.


Involvement of A(1) adenosine receptors in osmotic volume regulation of retinal glial cells in mice.

Wurm A, Lipp S, Pannicke T, Linnertz R, Färber K, Wiedemann P, Reichenbach A, Bringmann A - Mol. Vis. (2009)

Osmotic swelling of Müller glial cells in slices of the wild-type mouse retina. A: Perfusion of slices of a freshly isolated retina with a hypoosmolar solution, containing 60% of control osmolarity, in the absence (control) and presence of 1 mM barium chloride resulted in a time-dependent swelling of Müller cell somata. The diagram displays the mean (±SEM) cross-sectional area of the somata (n=3 each). Inset images in A show original records of dye-filled Müller cell somata obtained before (left) and during (right) perfusion with the barium-containing hypoosmolar solution. Scale bars represents 5 µm. B: Hypoosmotic exposure for 4 min evoked swelling of Müller cell somata in slices of freshly isolated retinas in the presence but not absence of 1 mM barium chloride. Müller cells in slices of retinal organ cultures displayed soma swelling under both conditions. Data are mean (±SEM) soma areas (n=7–21 cells per bar) expressed in percent of the soma size recorded before hypoosmotic challenge (100%). Significant increases in the soma area: The double asterisk indicates a p<0.01 and the triple asterisk indicates a p<0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2743807&req=5

f1: Osmotic swelling of Müller glial cells in slices of the wild-type mouse retina. A: Perfusion of slices of a freshly isolated retina with a hypoosmolar solution, containing 60% of control osmolarity, in the absence (control) and presence of 1 mM barium chloride resulted in a time-dependent swelling of Müller cell somata. The diagram displays the mean (±SEM) cross-sectional area of the somata (n=3 each). Inset images in A show original records of dye-filled Müller cell somata obtained before (left) and during (right) perfusion with the barium-containing hypoosmolar solution. Scale bars represents 5 µm. B: Hypoosmotic exposure for 4 min evoked swelling of Müller cell somata in slices of freshly isolated retinas in the presence but not absence of 1 mM barium chloride. Müller cells in slices of retinal organ cultures displayed soma swelling under both conditions. Data are mean (±SEM) soma areas (n=7–21 cells per bar) expressed in percent of the soma size recorded before hypoosmotic challenge (100%). Significant increases in the soma area: The double asterisk indicates a p<0.01 and the triple asterisk indicates a p<0.001.
Mentions: The swelling of Müller cell somata was investigated by perfusion of freshly isolated retinal slices with a hypoosmolar solution (containing 60% of control osmolarity). Under isotonic conditions, the absolute soma areas of Müller cells from wild-type and knockout animals were not different (wild-type: 49.6±1.7 µm2, n=48; A1AR−/−: 45.8±1.3 µm2, n=60; p>0.05). Hypotonic exposure for 4 min did not evoke a significant swelling of glial cell bodies in freshly isolated retinal slices from wild-type mice (Figures 1A,B). The increase in the size of glial cell bodies was significantly (p<0.01) stronger and faster when 1 mM barium chloride was jointly applied with the hypoosmolar solution (Figures 1A,B). Barium ions are known to block the principal potassium conductance of Müller cells mediated by inwardly rectifying potassium (Kir) channels [28,29]. As shown recently, Müller cells in slices of retinal organ cultures of the rat display a decrease in their Kir currents which is associated with an induction of cellular swelling under hypotonic conditions [25]. We found that Müller cells in organ cultures of the wild-type mouse retina displayed a swelling of their cell bodies under hypoosmotic conditions in the absence and presence of barium ions (Figure 1B). The swelling in the absence of barium suggests that retina culturing alters the volume regulation mechanisms of Müller cells.

Bottom Line: The size of Müller cell somata was recorded before and during perfusion of retinal sections and isolated Müller cells with a hypoosmolar solution.The data suggest that autocrine activation of A(1) receptors by extracellularly generated adenosine mediates the volume homeostasis of Müller cells in the murine retina.The swelling-inhibitory effect of triamcinolone is mediated by enhancement of endogenous adenosine signaling.

View Article: PubMed Central - PubMed

Affiliation: Paul Flechsig Institute of Brain Research, University of Leipzig, D-04103 Leipzig, Germany.

ABSTRACT

Purpose: Osmotic swelling of Müller glial cells has been suggested to contribute to retinal edema. We determined the role of adenosine signaling in the inhibition of Müller cell swelling in the murine retina.

Methods: The size of Müller cell somata was recorded before and during perfusion of retinal sections and isolated Müller cells with a hypoosmolar solution. Retinal tissues were freshly isolated from wild-type mice and mice deficient in A(1) adenosine receptors (A(1)AR(-/-)), or cultured as whole-mounts for three days. The potassium conductance of Müller cells was recorded in isolated cells, and retinal slices were immunostained against Kir4.1.

Results: Hypotonic exposure for 4 min induced a swelling of Müller cell bodies in retinal slices from A(1)AR(-/-) mice but not wild-type mice. Pharmacological inhibition of A(1) receptors or of the ecto-5'-nucleotidase induced hypoosmotic swelling of Müller cells from wild-type mice. Exogenous adenosine prevented the swelling of Müller cells from wild-type but not A(1)AR(-/-) mice. The antiinflammatory corticosteroid, triamcinolone acetonide, inhibited the swelling of Müller cells from wild-type mice; this effect was blocked by an antagonist of A(1) receptors. The potassium conductance of Müller cells and the Kir4.1 immunolabeling of retinal slices were not different between A(1)AR(-/-) and wild-type mice, both in freshly isolated tissues and retinal organ cultures.

Conclusions: The data suggest that autocrine activation of A(1) receptors by extracellularly generated adenosine mediates the volume homeostasis of Müller cells in the murine retina. The swelling-inhibitory effect of triamcinolone is mediated by enhancement of endogenous adenosine signaling.

Show MeSH
Related in: MedlinePlus