Human trabecular meshwork cell volume regulation

Mitchell, Claire H.; Fleischhauer, Johannes; Stamer, W. Daniel; Peterson-Yantorno, K.; Civan, Mortimer M.

doi:10.1152/ajpcell.00544.2001

Cited by 63 publications

(78 citation statements)

References 28 publications

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“…As discussed elsewhere (Hamann, 2002;Mitchell et al, 2002), calcein is an unusually favorable dye in being easily loaded in the acetoxymethyl ester (AM) form, being well retained within trabecular meshwork cells, and displaying a fluorescence relatively independent of shifts in pH and Ca 2+ . Since its fluorescence is 2-3 times greater than that of other commonly used fluorophores, satisfactory signals can be generated at relatively low excitation intensity.…”

Section: Cell-volume Measurementsmentioning

confidence: 95%

“…Changes in the volume of the TM cells might modify resistance by restricting the adjacent space through which outflow could proceed (O'Donnell et al, 1995). Consistent with this reasoning, the Na + /H + -antiport inhibitor dimethylamiloride reduces both the volume of cultured human TM cells (Mitchell et al, 2002) and the IOP of living mice (Avila et al, 2002a). Alternatively, the aqueous humor outflow might be limited by passage through pores within and between the inner-wall cells of Schlemm's canal (Ethier, 2002;Johnson, 2006) and through the very leaky tight junctions between these cells (Raviola & Raviola, 1978).…”

Section: Introductionmentioning

confidence: 91%

“…In studying small numbers of ocular cells, we Mitchell et al, 2002) and others (Walker et al, 1999) previously monitored cell area as an index of cell volume, relying on indirect methods in distinguishing shrinkage from contraction Mitchell et al, 2002). Measurement of total calcein fluorescence provides a more rigorous approach to this problem.…”

Section: Cell-volume Measurementsmentioning

confidence: 99%

“…Intracellular Ca 2+ concentration was measured in confluent monolayers as previously described (Mitchell et al, 2002). Cells were seeded onto coverslips (Fisher Scientific, Pittsburgh, PA) and grown for 1-11 days to prepare confluent monolayers.…”

Section: Intracellular Ca 2+ Concentrationsmentioning

confidence: 99%

“…Data were sent to the computer, and saved. Felix software (Photon Technology International) was used to determine the ratio and calculate the Ca 2+ concentration (Mitchell et al, 2002) using the method of Grynkiewicz et al (1985).…”

Section: Intracellular Ca 2+ Concentrationsmentioning

confidence: 99%

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Cell-specific differential modulation of human trabecular meshwork cells by selective adenosine receptor agonists

Karl

Peterson-Yantorno

Civan

2007

Experimental Eye Research

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Activation of A 1 and A 2A subtype adenosine receptors (AR) likely exert opposing effects on outflow of aqueous humor, and thereby, on intraocular pressure. Selective agonists of adenosine receptor (AR) subtypes have previously been applied to trabecular meshwork (TM) and Schlemm's canal (SC) cells to identify the site(s) of differential purinergic modulation. However, the apparent changes in volume monitored by previously measuring projected cell area might have partially reflected cell contraction and relaxation. In addition, whole-cell current responses of the TM cells previously described were highly variable following application of selective A 1 , A 2A and A 3 agonists. The complexity of the electrophysiologic responses may have reflected cell heterogeneity of the populations harvested from collagenase digestion of TM explants. We now report measurements of TM-cell volume using calcein fluorescence quenching, an approach independent of contractile state. Furthermore, we have applied selective AR agonists to a uniform population of human TM cells, the hTM5 cell line. A 1 , but not A 2A or A 3 , AR agonists triggered TM-cell shrinkage. Both A 1 and A 2A AR agonists produced reproducible increases in TM-cell whole-cell currents of similar magnitude.The results suggest that previous measurements of explant-derived TM cells may have reflected a range of responses from phenotypically different cell populations, and that the opposing effects of A 1 and A 2A agonists on outflow resistance are not likely to be mediated by actions on a single population of TM cells. These opposing effects might reflect AR responses by two or more subpopulations of TM cells, by TM and SC cells or by inner-wall SC cells, alone.

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Section: Cell-volume Measurementsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 91%

Section: Cell-volume Measurementsmentioning

confidence: 99%

Section: Intracellular Ca 2+ Concentrationsmentioning

confidence: 99%

Section: Intracellular Ca 2+ Concentrationsmentioning

confidence: 99%

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Cell-specific differential modulation of human trabecular meshwork cells by selective adenosine receptor agonists

Karl

Peterson-Yantorno

Civan

2007

Experimental Eye Research

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Differential Expression Profile Prioritization of Positional Candidate Glaucoma Genes

et al. 2007

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To develop and apply a model for prioritization of candidate glaucoma genes. Methods: This Affymetrix GeneChip (Affymetrix, Santa Clara, Calif) study of gene expression in primary culture human trabecular meshwork cells uses a positional differential expression profile model for prioritization of candidate genes within the GLC1C genetic inclusion interval. Results: Sixteen genes were expressed under all conditions within the GLC1C interval. TMEM22 was the only gene within the interval with differential expression in the same direction under both conditions tested. Two genes, ATP1B3 and COPB2, are of interest in the context of a protein-misfolding model for candidate selection. SLC25A36, PCCB, and FNDC6 are of lesser interest because of moderate expression and changes in expression. Transcription factor ZBTB38 emerges as an interesting candidate gene because of the overall expression level, differential expression, and function. Conclusions: Only 1 gene in the GLC1C interval fits our model for differential expression under multiple glaucoma risk conditions. The use of multiple prioritization models resulted in filtering 7 candidate genes of higher interest out of the 41 known genes in the region. Clinical Relevance: This study identified a small subset of genes that are most likely to harbor mutations that cause glaucoma linked to GLC1C.

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Mechanosensitive release of adenosine 5′‐triphosphate through pannexin channels and mechanosensitive upregulation of pannexin channels in optic nerve head astrocytes: A mechanism for purinergic involvement in chronic strain

Beckel

Argall

Lim

et al. 2014

Glia

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140

153

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As ATP released from astrocytes can modulate many neural signaling systems, the triggers of and pathways for this ATP release are important. Here, the ability of mechanical strain to trigger ATP release through pannexin channels, and the effects of sustained strain on pannexin expression, were examined in rat optic nerve head astrocytes. Astrocytes released ATP when subjected to 5% equibiaxial strain or to hypotonic swelling. While astrocytes expressed mRNA for pannexins 1–3, connexin 43 and VNUT, pharmacological analysis suggested a predominant role for pannexins in mechanosensitive ATP release, with Rho kinases contributing. Astrocytes from panx1−/− mice had reduced baseline and stimulated levels of extracellular ATP, confirming the role for pannexins. Swelling astrocytes triggered a regulatory volume decrease that was inhibited by apyrase or probenecid. The swelling–induced rise in calcium was inhibited by P2X7 receptor antagonists A438079 and AZ10606120, in addition to apyrase and carbenoxelone. Extended stretch of astrocytes in vitro upregulated expression of panx1 and panx2 mRNA. A similar upregulation was observed in vivo in optic nerve head tissue from the Tg-MYOCY437H mouse model of chronic glaucoma; genes for panx1, panx2 and panx3 were increased while immunohistochemistry confirmed increased expression of pannexin 1 protein. In summary, astrocytes released ATP in response to mechanical strain, with pannexin 1 the predominant efflux pathway. Sustained strain upregulated pannexins in vitro and in vivo. Together these findings provide a mechanism by which extracellular ATP remains elevated under chronic mechanical strain, as found in the optic nerve head of patients with glaucoma.

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Human trabecular meshwork cell volume regulation

Cited by 63 publications

References 28 publications

Cell-specific differential modulation of human trabecular meshwork cells by selective adenosine receptor agonists

Cell-specific differential modulation of human trabecular meshwork cells by selective adenosine receptor agonists

Differential Expression Profile Prioritization of Positional Candidate Glaucoma Genes

Mechanosensitive release of adenosine 5′‐triphosphate through pannexin channels and mechanosensitive upregulation of pannexin channels in optic nerve head astrocytes: A mechanism for purinergic involvement in chronic strain

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