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Biomedical subjects

Cynthia L Grosskreutz

Publications and source records attributed to Cynthia L Grosskreutz.

13 recordsLinked to original sources
PubMed2006

Characterization of cytokine responses to retinal detachment in rats.

PURPOSE: Photoreceptor apoptosis is associated with retinal detachment (RD) induced photoreceptor degeneration. Previously, we demonstrated the importance of caspase activation for RD-induced photoreceptor death in a rat model of RD. However, extracellular signals that precede the activation of caspases and photoreceptor degeneration remain unclear. The aim of this study is to characterize the molecular and cellular responses that occur after RD. The expression of cytokines, chemokines, and growth factors were examined in a rat model of RD. METHODS: RD was induced in adult rats by subretinal injection of sodium hyaluronate. Retinal tissues were collected at various times (1, 3, 6, 24, and 72 h) after the induction of detachment. To screen for expressional changes in response to RD, major candidates for cytokines, chemokines, and growth factors were broadly examined by quantitative real time polymerase chain reaction (QPCR). To identify the cellular sources of the expressed genes, cells from various layers of the retina were obtained using laser capture microdissection (LCM), and their mRNAs were isolated. Protein expression was quantified by immunohistochemistry and Enzyme Linked-Immuno-Sorbent Assay (ELISA). To assess the potential of early response genes after RD to induce photoreceptor degeneration, exogenous recombinant proteins were subretinally injected and the photoreceptor cell death was assessed using a TdT-dUTP terminal nick-end labeling (TUNEL) assay at 24 h after RD. RESULTS: At 72 h after RD a significant increase in mRNA levels for tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), monocyte chemotactic protein-1 (MCP-1), and basic fibroblast growth factor (bFGF) were detected in the neural retina. LCM revealed increased expression of mRNA for bFGF and MCP-1 in all retinal layers, though bFGF was especially evident in the outer nuclear layer (ONL) and MCP-1 in the inner nuclear layer (INL). TNF-alpha was increased in the ONL and the INL, and IL-1beta was increased in the ganglion cell layer. Time course experiments showed that TNF-alpha, IL-1beta and MCP-1 increased within 1 h after RD, while bFGF was increased by 24 h. Increased protein expression for TNF-alpha, IL-1beta, and MCP-1 was demonstrated by ELISA at 6 h after RD. Immunohistochemistry showed TNF-alpha and bFGF expression in the whole retina, with IL-1beta specifically expressed in astrocytes and MCP-1 in Müller cells. Subretinal administration of MCP-1 significantly increased TUNEL-positive cells in the ONL 24 h after RD, while injection of vehicle control, TNF-alpha, or IL-1beta showed no effect. CONCLUSIONS: Retinal glial cells, including astrocytes and Müller cells, are a major source of cytokine induction after RD. The increased expression and release of MCP-1 may be an important cause of photoreceptor degeneration associated with RD. This study helps to understand the mechanisms of RD-induced photoreceptor degeneration. Our results may provide new therapeutic targets to prevent photoreceptor degeneration following RD.

Animals↗
PubMed2006

Predictability and limitations of non-invasive murine tonometry: comparison of two devices.

Our purpose was to evaluate the accuracy, reproducibility and predictive ability of two non-invasive tonometers developed for intraocular pressure (IOP) measurements in the mouse. The prototype impact-rebound tonometer (I-R) and a prototype optical interferometry tonometer (OIT) utilizing a fiberoptic pressure sensor, were compared. Enucleated eyes from C57/BL6 mice were used for the calibration. The anterior chamber was cannulated and the IOP was adjusted in increments of 5 cm of H2O (open stopcock method). A calibration curve was generated for each individual eye along with a master calibration curve for all eyes. Two operators measured the IOP. The instruments were then used in alternating order to measure the IOP in C57/BL6 and in DBA2/J animals. The same eyes were subsequently cannulated and the error of the non-invasive tonometers was determined. Both tonometers yielded almost equivalent ex vivo calibration curves with individual R2 of 0.9878 and 0.9902 respectively. Both instruments were highly reproducible. In vivo the I-R tonometer underestimated while the OIT overestimated the IOP. This error was systematic and therefore predictable. The confidence intervals of this error were determined by comparing the IOP estimates provided by each tonometer with the measurements obtained invasively by cannulation in vivo. The 95% CI of the error were 2.36 mmHg for the I-R and 2.62 mmHg for the OIT respectively. Non-invasive tonometry in the mouse is feasible. Both non-invasive instruments provide accurate and reproducible measurements with the OIT requiring calibration curves for each individual investigator.

Animals↗
PubMed2006

The course of glaucoma during pregnancy: a retrospective case series.

OBJECTIVE: To better understand the course of glaucoma during pregnancy in women with preexisting disease. METHODS: Retrospective case series of 28 eyes of 15 women with glaucoma followed up during pregnancy. Data were analyzed for age, race/ethnicity, medications, glaucoma type, intraocular pressure (IOP), and visual fields before, during, and after pregnancy. RESULTS: In 16 (57.1%) of 28 eyes, IOP was stable during pregnancy, with no progression of visual field loss. In 5 eyes (17.9%), visual field loss progressed during pregnancy, while IOP remained stable or increased. In 5 eyes (17.9%), IOP increased during pregnancy, but there was no progression of visual field loss. In 2 eyes (7.1%), data were inconclusive because of medication noncompliance and preexisting severe visual field loss. Glaucoma medications were used by 13 of 15 patients to control glaucoma during pregnancy. The classes of medications used most frequently were beta-blockers, alpha2-adrenergic agents, cholinergic agents, and topical carbonic anhydrase inhibitors. CONCLUSIONS: The course of glaucoma during pregnancy is variable, and women must be monitored closely during pregnancy. Medications may be necessary to control IOP and to prevent vision loss during pregnancy.

Adult↗
PubMed2006

Downregulation of Thy1 in retinal ganglion cells in experimental glaucoma.

PURPOSE: Thy1 is a surface glycoprotein uniquely expressed in retinal ganglion cells (RGCs) in retina. The aim of this study was to investigate the expression change of Thy1 in a model of experimental glaucoma. METHODS: The change of protein and mRNA levels of Thy1 in the retina were studied using stereological counts of back-labeled RGCs, Western blot analysis, immunohistochemistry, and laser capture microdissection (LCM) of RGCs with quantitative PCR analysis of mRNA in a model of experimental glaucoma. LCM after optic nerve crush was also performed to evaluate Thy1 mRNA levels after a different injury. RESULTS: After 10 days of elevated IOP, there was a 34% loss of RGC number, Thy1 protein decreased 60% in eyes with elevated intraocular pressure (IOP), and Thy1 mRNA levels decreased 51% in RGCs. Both protein and mRNA level change of Thy1 is to a much greater extent than RGC number loss. CONCLUSIONS: The current results confirm that Thy 1 mRNA levels do not reflect the number of RGCs present and extend this to include a parallel decrease in Thy1 protein levels. These results suggest that Thy1 serves as an early marker of RGC stress, but not a marker of RGC loss, in models of retinal damage.

Animals↗
PubMed2005

Calcineurin cleavage is triggered by elevated intraocular pressure, and calcineurin inhibition blocks retinal ganglion cell death in experimental glaucoma.

Increased intraocular pressure (IOP) leads, by an unknown mechanism, to apoptotic retinal ganglion cell (RGC) death in glaucoma. We now report cleavage of the autoinhibitory domain of the protein phosphatase calcineurin (CaN) in two rodent models of increased IOP. Cleaved CaN was not detected in rat or mouse eyes with normal IOP. In in vitro systems, this constitutively active cleaved form of CaN has been reported to lead to apoptosis via dephosphorylation of the proapoptotic Bcl-2 family member, Bad. In a rat model of glaucoma, we similarly detect increased Bad dephosphorylation, increased cytoplasmic cytochrome c (cyt c), and RGC death. Oral treatment of rats with increased IOP with the CaN inhibitor FK506 led to a reduction in Bad dephosphorylation and cyt c release. In accord with these biochemical results, we observed a marked increase in both RGC survival and optic nerve preservation. These data are consistent with a CaN-mediated mechanism of increased IOP toxicity. CaN cleavage was not observed at any time after optic nerve crush, suggesting that axon damage alone is insufficient to trigger cleavage. These findings implicate this mechanism of CaN activation in a chronic neurodegenerative disease. These data demonstrate that increased IOP leads to the initiation of a CaN-mediated mitochondrial apoptotic pathway in glaucoma and support neuroprotective strategies for this blinding disease.

Analysis of Variance↗
PubMed2005

FK506 blocks activation of the intrinsic caspase cascade after optic nerve crush.

Retinal ganglion cells die by apoptosis after optic nerve crush. FK506 has been shown to be neuroprotective in this model but the mechanism(s) by which it exerts these actions remains unknown. We and others have shown that caspase 9 is cleaved in the retina in other injury models and we hypothesized that the neuroprotection observed with FK506 was mediated by interference with caspase 9 activation. The present study examined the cellular localization of caspase 9 cleavage after intraorbital optic nerve crush in rats, the time course of caspase 9 cleavage after optic nerve crush and the ability of orally administered FK506 to block caspase 9 cleavage after optic nerve crush. We show by immunohistochemistry that cleaved caspase 9 is present in retinal ganglion cells (identified by prior backlabelling) after optic nerve crush. Immunoblot analysis showed that caspase 9 cleavage is significantly elevated 5 and 8 days after optic nerve crush. We show that orally administered FK506 reaches the retina and is pharmacologically active in retinal tissue. Furthermore, the oral administration of FK506 5 mg kg(-1) day(-1) blocks the cleavage of caspase 9 at both time points. These data suggest that caspase 9 activation may play an important role in retinal ganglion cell death following optic nerve crush and that the neuroprotection seen with FK506 may be mediated by interfering with the activation of caspase 9.

Animals↗
PubMed2005

Transcriptional up-regulation and activation of initiating caspases in experimental glaucoma.

In glaucoma, retinal ganglion cells (RGCs) die by apoptosis, generally attributed to an elevated intraocular pressure (IOP). We now describe the impact of elevated IOP in the rat on expression of caspase 8 and caspase 9, initiators of the extrinsic and intrinsic caspase cascades, respectively. Activation of both caspases was demonstrated by the presence of cleaved forms of the caspases and the detection of cleaved Bid and PARP, downstream consequences of caspase activation. Surprisingly, the absolute level of procaspase 9 was also elevated after 10 days of increased IOP. To examine the cause of increased levels of the procaspase, we used laser capture microdissection to capture Fluorogold back-labeled RGCs and real-time polymerase chain reaction to measure mRNA changes of initiating caspases. The mRNA levels of both caspase 8 and caspase 9 were increased specifically in RGCs. These data suggest that elevated IOP activates a transcriptional up-regulation and activation of initiating caspases in RGCs and triggers apoptosis through both extrinsic and intrinsic caspase cascades.

Animals↗
PubMed2003

Cataract formation after initial trabeculectomy in young patients.

OBJECTIVE: To evaluate the risk of cataract formation in young patients after initial trabeculectomy. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Thirty-four eyes from 27 patients undergoing initial trabeculectomy at the Glaucoma Consultation Service, Massachusetts Eye and Ear Infirmary (mean age, 43.7 years; range, 12-54 years). INTERVENTION: Follow-up averaged 42.6 months (range, 11-90 months). METHODS: Lens status was observed before surgery and at 3 months; 6 months; and 1, 2, 3, 4, 5, and 6 years after initial trabeculectomy. MAIN OUTCOME MEASURE: The main outcome measure was defined as cataract extraction for visually significant lenticular opacifications that developed after trabeculectomy. RESULTS: The rate of cataract extraction after initial trabeculectomy was 24% (n = 8). The average time from trabeculectomy to cataract extraction was 26 months (range, 5-58 months). Progression of lenticular opacities occurred throughout the follow-up period. There was no increased rate of cataract formation in subjects with uveitic and steroid-induced glaucoma when compared with all other types of glaucoma. In the patients with both eyes in the study, the first eye was a predictor of cataract progression in the fellow eye. CONCLUSIONS: Cataract is a common complication after trabeculectomy in young patients. The 24% rate of cataract extraction after trabeculectomy reported in this study is a significant risk of which young patients contemplating surgery should be aware.

Adolescent↗
PubMed2002

Glaucomatous optic neuropathy: mechanisms of disease.

The optic neuropathy of glaucoma appears to be multifactorial in etiology. Both mechanical and vasogenic theories remain viable explanations for the observed nerve damage and the destructive effect of trophic withdrawal could be espoused by either theory. Each theory feeds into the final common pathway of cell death; even the immune system may kill cells in glaucoma by apoptosis. This knowledge has led to the hope that glaucomatous nerve damage can be curtailed or even prevented with the use of neuroprotective agents. Indeed, there are many intriguing new therapeutic possibilities on the horizon. Until evidence from clinical trials demonstrates the effectiveness of these agents however, control of IOP will remain the mainstay of treatment for glaucoma.

Glaucoma, Open-Angle↗
PubMed2002

Activation of caspase 9 in a rat model of experimental glaucoma.

PURPOSE: We investigated retinal ganglion cell (RGC) death and activation of caspase 9 in rats with experimental glaucoma. METHODS: Elevated intraocular pressure (IOP) was induced in rats using the Morrison model. Surviving backlabeled RGC were counted and TUNEL staining detected apoptosis. Procaspase 9 expression and activated caspase 9 were studied by immunoblot and immunohistochemistry. RESULTS: IOP correlated with surviving RGC. TUNEL-positive RGC were observed in animals with elevated IOP. Procaspase 9 levels increased with IOP intensity. Cleaved caspase 9 was detected by immunoblot only in rats with peak IOP above 35 mm Hg for > or =6 days. Cleaved caspase 9 staining was seen only in the ganglion cell layer of retinas from rats with peak IOP > or =32 mm Hg. CONCLUSIONS: RGC loss is correlated with IOP in experimental glaucoma. These results support activation of caspase 9, the intrinsic caspase cascade, in RGC death in experimental glaucoma.

Animals↗