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Abbot F Clark

Publications and source records attributed to Abbot F Clark.

35 records · Page 2Linked to original sources
PubMed2005

Noninvasive measurement of rodent intraocular pressure with a rebound tonometer.

PURPOSE: The present study evaluated the applicability of a rebound tonometer in measuring intraocular pressure (IOP) in rats and mice. METHODS: The accuracy of the TonoLab rebound tonometer was determined in cannulated mouse and rat eyes. IOP was manipulated by changing reservoir height, and tonometer pressure readings were recorded by an independent observer. IOP values were recorded in conscious Wistar rats and in four different strains of mice. The effects of anesthesia on IOP were evaluated in two different strains of mice. RESULTS: The IOP readings generated by the rebound tonometer correlated very well with the actual pressure in the eye. In rats, this linear correlation had a slope of 0.96 +/- 0.05 (mean +/- SEM, n = 4) and a Y-intercept of -2.1 +/- 1.2. In mice, the slope was 0.99 +/- 0.05 (n = 3), and the Y-intercept was 0.8 +/- 1.4. Using this method, the resting IOP of conscious male Wistar rats was observed to be 18.4 +/- 0.1 mm Hg (n = 132). In mice, strain differences in IOP were detected. Baseline IOP values in Balb/c, C57-BL/6, CBA, and 11- to 12-month-old DBA/2J mice were 10.6 +/- 0.6, 13.3 +/- 0.3, 16.4 +/- 0.3, and 19.3 +/- 0.4 mm Hg (n = 12), respectively. In separated studies, anesthesia lowered IOP from 14.3 +/- 0.9 to 9.2 +/- 0.5 mm Hg (n = 8) in C57-BL/6 mice, and from 16.6 +/- 0.4 to 9.4 +/- 0.6 mm Hg (n = 10) in CBA mice. CONCLUSIONS: The rebound tonometer was easy to use and accurately measured IOP in rats and mice. This technique, together with advances in genetic and other biological studies in rodents, will be valuable in the further understanding of the etiology and pathology of glaucoma.

Anesthesia, Local↗
PubMed2004

Neurotrophin and Trk expression by cells of the human lamina cribrosa following oxygen-glucose deprivation.

BACKGROUND: Ischemia within the optic nerve head (ONH) may contribute to retinal ganglion cell (RGC) loss in primary open angle glaucoma (POAG). Ischemia has been reported to increase neurotrophin and high affinity Trk receptor expression by CNS neurons and glial cells. We have previously demonstrated neurotrophin and Trk expression within the lamina cribrosa (LC) region of the ONH. To determine if ischemia alters neurotrophin and Trk protein expression in cells from the human LC, cultured LC cells and ONH astrocytes were exposed to 48 hours of oxygen-glucose deprivation (OGD). Also cells were exposed to 48 hours of OGD followed by 24 hours of recovery in normal growth conditions. Cell number, neurotrophin and Trk receptor protein expression, neurotrophin secretion, and Trk receptor activation were examined. RESULTS: Cell number was estimated using an assay for cell metabolism following 24, 48 and 72 hours of OGD. A statistically significant decrease in LC and ONH astrocyte cell number did not occur until 72 hours of OGD, therefore cellular protein and conditioned media were collected at 48 hours OGD. Protein expression of NGF, BDNF and NT-3 by LC cells and ONH astrocytes increased following OGD, as did NGF secretion. Recovery from OGD increased BDNF protein expression in LC cells. In ONH astrocytes, recovery from OGD increased NGF protein expression, and decreased BDNF secretion. Trk A expression and activation in LC cells was increased following OGD while expression and activation of all other Trk receptors was decreased. A similar increase in Trk A expression and activation was observed in ONH astrocytes following recovery from OGD. CONCLUSIONS: In vitro conditions that mimic ischemia increase the expression and secretion of neurotrophins by cells from the ONH. Increased Trk A expression and activation in LC cells following OGD and in ONH astrocytes following recovery from OGD suggest autocrine/paracrine neurotrophin signaling could be a response to ONH ischemia in POAG. Also, the increase in NGF, BDNF and NT-3 protein expression and NGF secretion following OGD also suggest LC cells and ONH astrocytes may be a paracrine source of neurotrophins for RGCs.

Cell Count↗
PubMed2004

Effect of exogenous neurotrophins on Trk receptor phosphorylation, cell proliferation, and neurotrophin secretion by cells isolated from the human lamina cribrosa.

PURPOSE: Glaucoma is the number one cause of preventable blindness in the United States. The lamina cribrosa (LC) region of the optic nerve head (ONH) is a major site of injury in glaucomatous optic neuropathy. Neurotrophins (NTs), which include NGF, BDNF, NT-3, and NT-4, are growth factors involved in the development and support of neurons and in non-neuronal interactions. Cells within the human LC express high affinity tyrosine kinase receptors (Trks) for NTs. The purpose of this study was to determine if exogenous NTs cause (a) phosphorylation of Trk receptors in LC cells and ONH astrocytes and (b) cell proliferation and/or secretion of NTs by LC cells and ONH astrocytes. METHODS: Trk phosphorylation in response to exogenous NGF, BDNF, NT-3, and NT-4 treatment was studied in LC cells and ONH astrocytes using immunoprecipitation and Western blotting. Cell number was assayed following treatment with exogenous NTs or the Trk phosphorylation inhibitor compound K-252a. Secretion of NTs following exogenous administration of NTs was determined using immunoassays. RESULTS: LC cells and ONH astrocytes express Trk receptors that are phosphorylated in response to exogenous NTs. Autocrine/paracrine signaling was also evident by Trk phosphorylation in the absence of exogenous NT treatment. ONH astrocyte cell number increased following exogenous treatment with each NT. LC cell number increased following exogenous NGF or NT-3 treatment only. Treatment with the Trk phosphorylation inhibitor K-252a decreased both LC and ONH astrocyte cell number. Exogenous NT treatment increased the secretion of NGF by LC cells and ONH astrocytes. BDNF secretion by LC cells and ONH astrocytes was decreased by exogenous NT treatment. CONCLUSIONS: LC cells and ONH astrocytes express functional Trk receptors that can be activated in response to exogenous NTs. The activation of Trk receptors expressed by LC cells and ONH astrocytes in the absence of exogenous NT treatment suggests autocrine/paracrine NT signaling may occur within the ONH. Neurotrophin signaling in LC cells and ONH astrocytes may regulate cell number and/or NT secretion within the LC region of the ONH.

Actins↗
PubMed2004

Effect of cyclical mechanical stretch and exogenous transforming growth factor-beta1 on matrix metalloproteinase-2 activity in lamina cribrosa cells from the human optic nerve head.

PURPOSE: Extensive remodeling of the lamina cribrosa extracellular matrix occurs in primary open angle glaucoma. The transforming growth factor-beta (TGF-beta) and matrix metalloproteinase (MMP) protein families are implicated in this process. The authors investigated (a). the effect of cyclical mechanical stretch on TGF-beta1 mRNA synthesis, TGF-beta1 protein secretion, MMP-2 protein activity and (b). the effect of exogenous TGF-beta1 on MMP-2 protein activity in human lamina cribrosa cells in vitro. METHODS: Primary human lamina cribrosa cells grown on flexible and rigid plates were exposed to cyclical stretch (1Hz, 15%) or static conditions for 12 and 24 hours. Cells grown on 100-mm plates were exposed to human TGF-beta1 (10 ng/ml) or vehicle (4 mM HCl/1% BSA) for 24 hours. TGF-beta1 mRNA synthesis in stretched and static cells was measured using real-time polymerase chain reaction. TGF-beta1 protein secretion in stretched and static cell media was measured using enzyme linked immunosorbent assay. Gelatin zymography measured MMP-2 activity in stretched, static, TGF-beta1- treated and vehicle-treated cell media. RESULTS: Cyclical stretch induced significant increases in TGF-beta1 mRNA synthesis after 12 hours (**P < 0.01) and TGF-beta1 protein secretion after 24 hours (*P < 0.05). Cyclical stretch significantly (*P < 0.05) increased MMP-2 activity in cell media after 24 hours. Exogenous TGF-beta 1 induced a significant (**P < 0.01) increase in cell media MMP-2 activity after 24 hours. CONCLUSIONS: These results suggest that cyclical stretch and TGF-beta1 modulate MMP-2 activity in human lamina cribrosa cells. TGF-beta 1 and MMP-2 release from lamina cribrosa cells may facilitate matrix remodeling of the optic nerve head in primary open angle glaucoma.

Cell Culture Techniques↗
PubMed2003

Cells of the human optic nerve head express glial cell line-derived neurotrophic factor (GDNF) and the GDNF receptor complex.

PURPOSE: Glial cell-line derived neurotrophic factor (GDNF) is a distant member of the TGFbeta family of growth factors and has wide ranging effects within the central nervous system. In the present study we profile the expression of GDNF and its receptor complex (Ret and GFRalpha-1) in cells isolated from the human optic nerve head (ONH). METHODS: Lamina cribrosa (LC) cells and ONH astrocytes were used from normal donors of various ages. Total RNA was isolated and subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) to examine mRNA expression of GDNF, Ret, and GFRalpha-1. Western immunoblotting and immunohistochemistry was used to study protein expression of GDNF and GDNF receptor complex proteins in cultured ONH cells. An immunoassay system (ELISA) was used to examine secretion of GDNF by ONH cells. Cell proliferation was examined following exogenous administration of GDNF. RESULTS: Lamina cribrosa cells, ONH astrocytes, and LC tissues expressed messenger RNA for GDNF, Ret and GFRalpha-1. Lamina cribrosa cells and ONH astrocytes also expressed protein for GDNF, Ret, and GFRalpha-1. Secretion of GDNF by either cell type was not detected. Exogenous GDNF caused a significant increase in cell proliferation of LC cells but not ONH astrocytes. CONCLUSIONS: Cells from the human lamina cribrosa express mRNA and protein for GDNF and its receptor complex. LC cells proliferate in response to exogenous GDNF. The potential for autocrine and/or paracrine GDNF signaling thus exists within the lamina cribrosa, a tissue involved in glaucoma pathogenesis.

Adolescent↗
PubMed2003

Characterization of rabbit myocilin: Implications for human myocilin glycosylation and signal peptide usage.

BACKGROUND: Mutations in the gene encoding human myocilin (MYOC) have been shown to cause juvenile- and adult-onset glaucoma. In addition, myocilin has been associated with glucocorticoid-induced ocular hypertension and steroid-induced glaucoma. To better understand the role myocilin plays in steroid-induced glaucoma and open-angle glaucoma, we examined rabbit myocilin for use in the rabbit animal model of steroid-induced glaucoma. RESULTS: We have cloned the rabbit ortholog of human MYOC. Rabbit MYOC consists of three exons and an open reading frame encoding a 490 amino acid, 54,882-Da protein, which is 14 amino acids shorter at the N-terminus than human myocilin but 84% identical overall. Rabbit myocilin migrates as a single electrophoretic band, vs. double-banded human myocilin, by SDS-PAGE/immunoblot analysis. We determined that the differential migration exhibited is due to an N-glycosylation site that is present in human (Asn57), monkey and mouse myocilin but absent in rabbit (Ser43), rat and bovine myocilin. Rabbit myocilin is secreted in vitro in trabecular meshwork cell culture and in vivo in aqueous humor. Secretion of human myocilin is shown to be dependent on the signal peptide and independent of the extra 14 amino acids not found in rabbit myocilin. Many of the amino acids in myocilin that are mutated in glaucoma patients are conserved across species. CONCLUSION: We have cloned the rabbit MYOC cDNA and determined that rabbit myocilin is secreted but not N-linked glycosylated. Knowledge of the rabbit MYOC cDNA sequence will facilitate future studies in the rabbit animal model examining the role of myocilin in steroid-induced glaucoma and the gain-of-function hypothesis in open-angle glaucoma.

Amino Acid Sequence↗
PubMed2003

Ophthalmic drug discovery.

Millions of people suffer from a wide variety of ocular diseases, many of which lead to irreversible blindness. The leading causes of irreversible blindness in the elderly--age-related macular degeneration and glaucoma--will continue to effect more individuals as the worldwide population continues to age. Although there are therapies for treating glaucoma, as well as ongoing clinical trials of treatments for age-related macular degeneration, there still is a great need for more efficacious treatments that halt or even reverse ocular diseases. The eye has special attributes that allow local drug delivery and non-invasive clinical assessment of disease, but it is also a highly complex and unique organ, which makes understanding disease pathogenesis and ocular drug discovery challenging. As we learn more about the cellular mechanisms involved in age-related macular degeneration and glaucoma, potentially, new drug targets will emerge. This review provides insight into some of the new approaches to therapy.

Animals↗
PubMed2003

Expression of matrix metalloproteinases and their inhibitors in human trabecular meshwork cells.

PURPOSE: Matrix metalloproteinases (MMPs) are involved in trabecular meshwork (TM) extracellular matrix metabolism and have been shown to increase aqueous outflow facility. The purpose of this study was to characterize effects of cytokines, a phorbol ester, and prostanoids on the expression of MMP-1, -2, -3, and -9 and tissue inhibitors of metalloproteinases (TIMP)-1 and -2 in cultured human TM cells. METHODS: Five human TM cell strains were treated with selected compounds. Levels of proMMPs and TIMPs in cell media were quantified by ELISA. MMP-3 activity was assayed by casein zymography. RESULTS: All human TM cell strains produced detectable basal amounts of proMMPs and TIMPs. 12-O-tetradecanoyl-phorbol-13-acetate was effective in increasing the levels of proMMP-1, -3, and -9 and TIMP-1. Its effect on proMMP-1 was concentration-dependent with an EC(50) of 2 to 3 nM. Interleukin (IL)-1alpha did not affect levels of proMMP-1 and -2 or the TIMPs, but was most efficacious in increasing proMMP-3 production with an EC(50) of 0.5 ng/mL. The IL-1alpha-induced upregulation of proMMP-3 correlated with an increase in MMP-3 activity. Tumor necrosis factor-alpha activated proMMP-3 production in some but not all cell strains. Platelet-derived growth factor-BB was generally ineffective in modulating MMP and TIMP levels. Prostaglandins E(2) and F(2alpha) at 10 micro M did not affect levels of proMMP-1 or -3. CONCLUSIONS: The expression of the different MMPs and TIMPs in human TM cells was independently regulated. Production of MMP-3 was maximally activated by IL-1alpha. The IL-1alpha-stimulated expression of MMP-3 provides a probable mechanism for IL-1alpha-enhanced aqueous outflow.

Adolescent↗
PubMed2003

Involvement of AP-1 in interleukin-1alpha-stimulated MMP-3 expression in human trabecular meshwork cells.

PURPOSE: Stromelysin-1 (MMP-3) degrades extracellular matrix and increases aqueous outflow. In the trabecular meshwork (TM), interleukin (IL)-1alpha is a potent inducer of MMP-3 expression. In different cells, IL-1alpha activates different signaling pathways, such as nuclear factor (NF)-kappaB-mediated protein expression, the phospholipase A(2) (PLA(2))-activated arachidonate cascade, and activator protein (AP)-1-associated transcription. In the present study, pharmacological tools were used to delineate the signaling mechanism involved in the effect of IL-1alpha on MMP-3 production in human TM cells compared with other ocular cells. METHODS: Human TM and three other ocular cells (ciliary muscle, corneoscleral fibroblast, and lamina cribrosa) were cultured in 24-well plates in the presence or absence of IL-1alpha, with or without specific inhibitors of selected signaling pathways. Secreted proMMP-3 was quantified by ELISA, and MMP-3 activity was assayed by casein zymography. RESULTS: IL-1alpha (5 ng/mL) increased proMMP-3 levels in human TM cells to 10- to 38-fold of control (P < 0.001). The effect of IL-1alpha was blocked by Gö6976, a protein kinase C micro (PKC micro ) inhibitor; PD98059, a mitogen-activated protein kinase kinase (MEK) inhibitor; SB202190, a p38 inhibitor; and SR11302, an AP-1 inhibitor; but not by inhibitors of casein kinase II, NFkappaB, PLA(2), phospholipase D (PLD), cyclooxygenases, lipoxygenase, or sphingomyelinase. SR11302 did not inhibit the effect of IL-1alpha on MMP-3 production in the other ocular cells tested. CONCLUSIONS: Based on the pharmacological effects of the inhibitors, the data indicate that activation of PKC micro, MEK, and p38 leading to the activation of AP-1 is critical to the IL-1alpha-stimulated upregulation of MMP-3 in human TM cells. Therefore, it is likely that compounds that activate the AP-1 pathway would upregulate the production of MMP-3 and improve aqueous outflow.

Adolescent↗
PubMed2003

Aqueous outflow-enhancing effect of tert-butylhydroquinone: involvement of AP-1 activation and MMP-3 expression.

PURPOSE: To test the effect of stimulators of activator protein (AP)-1, on expression of stromelysin (MMP-3) in human TM cells and on aqueous outflow in perfused human anterior segments. METHODS: Change in MMP-3 expression was determined by immunoassay of proMMP-3 levels in the media of cultured human TM cells. Anterior segments of human donor eyes with or without glaucoma were perfused with vehicle or the AP-1 stimulator tert-butylhydroquinone (tBHQ). The outflow rates or intraocular pressure (IOP), and proMMP-3 levels in the perfusate were monitored. RESULTS: AP-1 stimulators, such as beta-naphthoflavone, 3-methylcholanthrene, and tBHQ, significantly upregulated (2-4-fold) TM cell expression of MMP-3. The stimulatory effect of tBHQ was concentration dependent, with an EC(50) of approximately 3 micro M, and was blocked by concomitant treatment with 100 nM SR11302, which sequesters AP-1. When nonglaucomatous human eyes were perfused with tBHQ (10 micro M), both outflow rates and perfusate proMMP-3 level increased significantly within the first 24 hours. The outflow effect of tBHQ was suppressed when SR11302 (100 nM) was added in the perfusate. tBHQ also lowered the IOP by more than 40% in perfused glaucomatous eyes. CONCLUSIONS: An AP-1 activator, tBHQ, upregulated expression of MMP-3 in cultured human TM cells and perfused human eyes and enhanced outflow ex vivo. These effects were blocked by sequestering AP-1, suggesting that activation of AP-1 can lead to increased MMP-3 production in the TM, which in turn improves outflow facility. This unique mechanism may provide a novel therapy for glaucoma.

Anterior Eye Segment↗
PubMed2003

Interactions of endothelin-1 with dexamethasone in primary cultured human trabecular meshwork cells.

PURPOSE: Concentrations of aqueous humor endothelin (ET)-1 are increased in patients with primary open-angle glaucoma (POAG) as well as in animal models of glaucoma. Glucocorticoids have also been associated with glaucoma, in that topical administration of glucocorticoids can increase intraocular pressure by increasing outflow resistance in the trabecular meshwork (TM) in some individuals. Recent research has shown that dexamethasone (Dex), a synthetic glucocorticoid, can increase the release of ET-1 from human nonpigmented ciliary epithelial (HNPE) cells, a source of aqueous ET-1. In the present study, the downstream interaction of ET-1 with Dex in target TM cells, an action that may alter outflow resistance, was investigated. METHODS: A normal primary human TM (NTM) cell line and a TM cell line derived from a glaucomatous eye (GTM) were used. The cells were treated with vehicle or Dex. The mRNA levels of prepro-ET-1, endothelin receptor A (ET(A)), and endothelin receptor B (ET(B)) were measured by quantitative RT-PCR (QPCR). The protein expression of ET(A) and ET(B) receptors were investigated by Western blot analysis using polyclonal anti-ET(A) and anti-ET(B) antibodies, respectively, on plasma membrane fractions. Intracellular Ca(2+) ([Ca(2+)](i)) mobilization mediated by ET-1 was measured using the Fura-2 AM fluorescent probe technique as an index of ET receptor function. ET-1-stimulated nitric oxide (NO) release was measured using a Griess colorimetric NO synthase assay kit. RESULTS: Both NTM and GTM cultured cells expressed prepro-ET-1 mRNA less abundantly than did HNPE cells, and Dex treatment had no effect on the mRNA expression of the ET-1 gene. TM cells expressed mRNA of ET(A) receptors as detected by QPCR, whereas the ET(B) message was not clearly delineated. Western blot analysis showed that both ET(A) and ET(B) receptor proteins were present. The ET(A) receptor was linked to calcium mobilization as ET-1 produced an increase in intracellular calcium release, and this increase was blocked with a selective ET(A) receptor antagonist. Dex failed to induce any change in the expression of the ET(A) receptor in both NTM and GTM cells, and this was supported by the absence of a Dex effect on the ET-1-induced calcium response. However, Dex treatment diminished ET(B) receptor protein expression and produced a decrease in ET-1-stimulated release of NO, a response mediated by ET(B) receptors in TM cells. CONCLUSIONS: The Dex-induced increase in ET-1 released by HNPE cells coupled to the downstream Dex-induced specific suppression of ET(B) receptor protein expression and declines in ET-1-mediated increase in NO released by TM cells could increase contraction and decrease relaxation of the TM and contribute to the declines in conventional aqueous humor outflow and increases in intraocular pressure that occur with glucocorticoids.

Aged↗
PubMed2002

Expression of bone morphogenetic proteins (BMP), BMP receptors, and BMP associated proteins in human trabecular meshwork and optic nerve head cells and tissues.

PURPOSE: Bone morphogenetic proteins (BMPs) are multi-functional cytokines that have wide ranging effects on a variety of cells and tissues. In the present study, we profile the expression of BMPs, BMP receptors, and BMP associated proteins in the human trabecular meshwork (TM) and optic nerve head (ONH), two tissues involved in glaucoma pathogenesis. METHODS: Total RNA was isolated and subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) to examine the expression of BMP, BMP receptor, and BMP associated proteins in tissues and cultured cells from the human TM and ONH (ONH astrocytes and lamina cribrosa cells). Western immunoblotting was used to study the expression of BMP and BMP receptor proteins in cultured human TM and ONH cells. RESULTS: Both TM and ONH cells and tissues expressed mRNAs for BMP2, BMP4, BMP5, BMP7, BMP-RIA, BMP-RIB, BMP-RII, DRM (gremlin), follistatin, chordin and NMA (BAMBI). The proteins for BMP2, BMP4, BMP5, BMP7, and all three BMP receptors were expressed in cultured human TM and ONH cells. CONCLUSIONS: Members of the BMP family of genes, including BMPs, BMP receptors, and inhibitory BMP associated proteins are expressed in the human TM and ONH. These molecules may be involved in the normal formation and function of these tissues. Altered expression of members of this gene family may lead to functional changes in the TM and ONH. These genes and their respective signaling pathways merit further research to examine their possible role in glaucoma.

Aged↗
PubMed2002

Advances in glaucoma therapeutics.

Glaucoma is a major cause of irreversible blindness in the world. The prevalence of glaucomatous loss in vision will continue to grow as our populations age. Ocular hypertension is a major risk factor for the development of glaucoma and current glaucoma therapy is directed at lowering intraocular pressure. Several new ocular hypotensive agents have been introduced in the past several years providing a variety of treatment options. In addition, various classes of neuroprotective agents demonstrating activity in a wide variety of animal models have been proposed as potential new glaucoma therapeutics. Although these approaches will slow the progression of vision loss, they do not directly intervene in the disease process(es). Advances have been made attempting to understand the pathogenic pathways involved in glaucomatous damage to the eye and in methods to clinically measure glaucoma damage. An increased understanding of the pathophysiology of glaucoma will lead to the development of new therapeutic agents that intervene and perhaps even reverse glaucomatous damage to the eye. There also is a need to develop new methods to clinically measure glaucoma damage because, currently, considerable damage occurs before glaucoma is diagnosed and glaucoma remains underdiagnosed in the general population.

Journal Article↗
PubMed2002

Human optic nerve head astrocytes as a target for endothelin-1.

PURPOSE: To determine whether human optic nerve head astrocytes (hONAs) are target cells for the actions of endothelin (ET)-1, a potent vasoactive peptide, by causing astrocyte proliferation, as occurs in glaucomatous optic nerve heads. ET-1 levels are elevated in glaucomatous eyes, and administration of ET-1 to the retina causes glial activation and optic nerve damage in animal models in a manner similar to that observed in glaucoma. METHODS: Well-characterized hONAs were used in this study. Cell proliferation of hONAs was assessed, after ET-1 treatment under serum-free culture conditions, with both a formazan assay and [3H]thymidine uptake. ET receptor involvement for cell proliferation was determined with BQ788 (an ETB antagonist), BQ610 (an ETA antagonist), PD142893 (an ET(A/B) mixed antagonist), and sarafotoxin 6C (S6C; an ET(B) agonist). ET-1-induced intracellular calcium ([Ca2+]i) in hONAs was measured by fura-2 imaging. RT-PCR was used to determine whether hONAs express mRNA for preproET-1, ET(A), and ET(B) receptors. RESULTS: ET-1 (10 and 100 nM) caused a time-dependent proliferation of hONAs, which was completely blocked by PD142893, as detected by two different cell proliferation assays. The effects of ET-1 were blocked by BQ788 and were also mimicked by S6C, indicative of the involvement of ET(B) receptor activation. ET-1-induced elevation in [Ca2+]i, and cell proliferation were both blocked completely by the ET(A) antagonist BQ610, suggesting ET(A) receptor involvement. The hONAs expressed mRNA for ET(A) and ET(B) receptors as well as preproET-1, suggesting that these cells may also be a source for ET-1 in the optic nerve head. CONCLUSIONS: ET-1 induces astroglial proliferation in cultured human optic nerve head astrocytes through ET(A/B) receptor activation. This is similar to the proliferation of ET-1 in brain astrocytes. These findings suggest that ET-1, which is elevated in glaucoma, could cause proliferation of ONAs in the optic nerve head.

Aged↗
PubMedDate not supplied

Inherited glaucoma in DBA/2J mice: pertinent disease features for studying the neurodegeneration.

The glaucomas are neurodegenerative diseases involving death of retinal ganglion cells and optic nerve head excavation. A major risk factor for this neurodegeneration is a harmfully elevated intraocular pressure (IOP). Human glaucomas are typically complex, progressive diseases that are prevalent in the elderly. Family history and genetic factors are clearly important in human glaucoma. Mouse studies have proven helpful for investigating the genetic and mechanistic basis of complex diseases. We previously reported inherited, age-related progressive glaucoma in DBA/2J mice. Here, we report our updated findings from studying the disease in a large number of DBA/2J mice. The period when mice have elevated IOP extends from 6 months to 16 months, with 8-9 months representing an important transition to high IOP for many mice. Optic nerve degeneration follows IOP elevation, with the majority of optic nerves being severely damaged by 12 months of age. This information should help with the design of experiments, and we present the data in a manner that will be useful for future studies of retinal ganglion cell degeneration and optic neuropathy.

Animals↗