Neuroprotective effects of glial mediators in interactions between retinal neurons and Müller cells

Progressive retinal ganglion cell (RGC) loss underlies a number of retinal neurodegenerative disorders, which may lead to permanent vision loss. However, secreted neuroprotective factors, such as PEDF, VEGF and IL-6, which are produced by Müller cells, have been shown to promote RGC survival. Assuming that the communication of RGCs with Müller cells involves a release of glioactive substances we sought to determine whether retinal neurons are able to modulate expression levels of Müller cell-derived PEDF, VEGF and IL-6. We demonstrate elevated mRNA levels of these factors in Müller cells in co-cultures with RGCs or R28 cells when compared to homotypic Müller cell cultures. Furthermore, R28 cells were more protected from apoptosis when co-cultured with Müller cells. IL-6 and VEGF were upregulated in Müller cells under hypoxia. Both cytokines, as well as PEDF, induced an altered neuronal expression of members of the Bcl-2 family, which are central molecules in the regulation of apoptosis. These results suggest that in retinal ischemia, via own secreted mediators, RGCs can resist a potential demise by stimulating Müller cells to increase production of neuroprotective factors, which counteract RGC apoptosis.

Pigment Epithelium-Derived Factor (PEDF) Receptors Are Involved in Survival of Retinal Neurons

The demise of retinal ganglion cells (RGCs) is characteristic of diseases of the retina such as glaucoma and diabetic or ischemic retinopathies. Pigment epithelium-derived factor (PEDF) is a multifunctional secreted protein that mediates neuroprotection and inhibition of angiogenesis in the retina. We have studied expression and regulation of two of several receptors for PEDF, patatin-like phospholipase 2 gene product/PEDF-R and laminin receptor (LR), in serum-starved RGC under normoxia and hypoxia and investigated their involvement in the survival of retinal neuronal cells. We show that PEDF-R and LR are co-expressed in RGC and R28 retinal precursor cells. Expression of both receptors was enhanced in the presence of complex secretions from retinal glial (Müller) cells and upregulated by VEGF and under hypoxic conditions. PEDF-R- and LR-knocked-down cells demonstrated a markedly attenuated expression of anti-apoptotic Bcl-2 family members (Bcl-2, Bcl-xL) and neuroprotective mediators (PEDF, VEGF, BDNF) suggesting that both PEDF-R and LR mediate pro-survival effects of PEDF on RGC. While this study does not provide evidence for a differential survival-promoting influence of either PEDF-R or LR, it nevertheless highlights the importance of both PEDF receptors for the viability of retinal neurons.

In vitro drusen model - three-dimensional spheroid culture of retinal pigment epithelial cells

Age-related macular degeneration (AMD) is a leading cause of blindness in people over 50 years of age in many developed countries. Drusen are yellowish extracellular deposits beneath retinal pigment epithelium (RPE) found in aging eyes and considered as a biomarker of AMD. However, the biogenesis of drusen has not been elucidated. We reported previously that multicellular spheroids of human RPE cells constructed a well-differentiated monolayer of RPE with a Bruch's membrane. We determined that RPE spheroids exhibited drusen formation between the RPE and Bruch's membrane with expression of many drusen-associated proteins, such as amyloid β and complement components, the expression of which was altered by a challenge with oxidative stress. Artificial lipofuscin-loaded RPE spheroids yielded drusen more frequently. In the current study, we showed that drusen originates from the RPE. This culture system is an attractive tool for use as an in vitro drusen model, which might help elucidate the biogenesis of drusen and the pathogenesis of related diseases, such as AMD.

Müller Cell-Derived PEDF Mediates Neuroprotection via STAT3 Activation

Background/ Aims: This study was performed to reveal signaling pathways exploited by pigment epithelium-derived factor (PEDF) derived from retinal (glial) Müller cells to protect retinal ganglion cells (RGCs) from cell death.

METHODS

The survival of RGCs was determined in the presence of conditioned culture media (MCM) from or in co-cultures with Müller cells. The significance of PEDF-induced STAT3 activation was evaluated in viability assays and using Western blotting analyses and siRNA-transfected cells.

RESULTS

Secreted mediators of Müller cells increased survival of RGCs under normoxia or hypoxia to a similar degree as of PEDF- or IL-6-exposed cells. PEDF and MCM induced an increased STAT3 activation in RGCs and R28 cells, and neutralization of PEDF in MCM attenuated STAT3 activation. Inhibition of STAT3 reduced PEDF-promoted survival of RGCs. Similar to IL-6, PEDF induced STAT3 activation, acting in a dose-dependent manner via the PEDF receptor (PEDF-R) encoded by the PNPLA2 gene. Ablation of PEDF-R attenuated MCM-induced STAT3 activation and compromised the viability of PEDF-exposed R28 cells.

CONCLUSIONS

Müller cells are an important source of PEDF, which promotes RGC survival through STAT3 activation and, at least in part, via PEDF-R. Enhancing the secretory function of Müller cells may be useful to promote RGC survival in retinal neurodegenerative diseases.

[Protective Effects of Müller Glia Cells Towards Retinal Ganglion Cells]

INTRODUCTION

Müller glial cells carry out different tasks to warrant normal retinal functions. The aim of this study was to investigate if Müller cells also support retinal ganglion cells (RGC).

MATERIALS AND METHODS

RGC were cultured for 24 hours in the presence or absence of Müller glial cells under normoxic (20% O₂, 5% CO₂) or hypoxic (0.2% O₂, 5% CO₂, 94.8% N₂) culture conditions. The number of vital RGC and the length of the newly developed neurites were evaluated.

RESULTS

Under normoxic conditions, RGC vitality was significantly higher (p < 0.01) when cultured with Müller cells (62.85 ± 2.06%) than without (47.29 ± 2.83%). Under hypoxia, RGC vitality was significantly higher (p < 0.01) in co-cultures (41.07 ± 2.28%) than in homotypic RGC cultures (28.49 ± 2.16%). The maximum length of the newly developed neurites was found in the normoxic co-culture (90.7 ± 7.4 µm), but showed only a minor difference (p = 0.04) when compared to the normoxic homotypic RGC culture.

CONCLUSION

Müller glial cells support RGC under normoxic and hypoxic culture conditions. Length of newly developed neurites and number of surviving RGC are both parameters to evaluate cell vitality.

Flow cytometric analysis of the graft-versus-Leukemia-effect after hematopoietic stem cell transplantation in mice

Acute Graft-versus-Host-Disease (aGvHD) is one of the major complications following allogeneic hematopoietic stem cell transplantation (HSCT). Although rather helpful, the use of conventional immunosuppressive drugs leads to general immunosuppression and is toxic. The effects of CD4(+) T-cells, in respect to the development of aGvHD, can be altered by administration of antihuman CD4 monoclonal antibodies, here MAX.16H5 IgG1 . This approach must be tested for possible interference with the Graft-versus-Leukemia-Effect (GvL). Thus, in vitro experiments were conducted, exposing P815 leukemic cells to bone marrow and splenocytes from cd4(-/-) -C57Bl/6 mice transgenic for human CD4 and HLA-DR3 (triple transgenic mice, [TTG]) as well as previously irradiated splenocytes from Balb/c(wt) mice. Using flow cytometry, the vitality of the various malignant and graft cells was analyzed over the course of 4 days. The survival rate of P815 cells did not change significantly when exposed to MAX.16H5 IgG1 , neither did the viability of the graft cells. This provides evidence that MAX.16H5 IgG1 does not impair the GvL effect in vitro. Additionally, P815-Balb/c(wt) leukemic mice were transplanted with P815(GFP) cells, bone marrow, and splenocytes from TTG mice with and without MAX.16H5 IgG1 . Without transplantation, P815(GFP) leukemic cells could be detected by flow cytometry in the liver, the bone marrow, and the spleen of recipients. The antibodies prevented aGvHD while leaving the GvL effect intact. These findings indicate no negative effect of MAX.16H5 IgG1 on the GvL effect in vitro and in vivo after HSCT in a murine model.

Thrombospondin-1 is produced by retinal glial cells and inhibits the growth of vascular endothelial cells

BACKGROUND/AIMS

By the release of antiangiogenic factors, Müller glial cells provide an angiostatic environment in the normal and ischemic retina. We determined whether Müller cells produce thrombospondin-1 (TSP-1), a known inhibitor of angiogenesis.

METHODS

Secretion of TSP-1 by cultured Müller cells was determined with ELISA. Slices of rat retinas and surgically excised retinal membranes of human subjects were immunostained against TSP-1 and the glial marker vimentin. The effects of TSP-1 on the growth of bovine retinal endothelial cells (BRECs) and activation of ERK1/2 were determined with DNA synthesis and migration assays, and Western blotting, respectively.

RESULTS

Cultured Müller cells secrete TSP-1 under normoxic and hypoxic (0.2% O2) conditions. Secretion of TSP-1 was increased in hypoxia compared to normoxia. In rat retinal slices, glial, retinal ganglion, and possibly horizontal cells were stained for TSP-1. Retinal glial cells in preretinal membranes from human subjects with nonhypoxic epiretinal gliosis (macular pucker) and proliferative diabetic retinopathy, respectively, were immunopositive for TSP-1. Exogenous TSP-1 reduced the VEGF-induced proliferation and migration of BRECs and decreased the phosphorylation level of ERK1/2 in BRECs.

CONCLUSION

The data suggest that Müller cells are one major source of TSP-1 in the normal and ischemic retina. Glia-derived TSP1 may inhibit angiogenic responses in the ischemic retina.

Enhanced survival of retinal ganglion cells is mediated by Müller glial cell-derived PEDF

The death of retinal ganglion cells (RGC) leads to visual impairment and blindness in ocular neurodegenerative diseases, primarily in glaucoma and diabetic retinopathy; hence, mechanisms that contribute to protecting RGC from ischemia/hypoxia are of great interest. We here address the role of retinal glial (Müller) cells and of pigment-epithelium-derived factor (PEDF), one of the main neuroprotectants released from the glial cells. We show that the hypoxia-induced loss in the viability of cultured purified RGC is due to apoptosis, but that the number of viable RGC increases when co-cultured with Müller glial cells suggesting that glial soluble mediators attenuate the death of RGC. When PEDF was ablated from Müller cells a significantly lower number of RGC survived in RGC-Müller cell co-cultures indicating that PEDF is a major survival factor allowing RGC to escape cell death. We further found that RGC express a PEDF receptor known as patatin-like phospholipase domain-containing protein 2 (PNPLA2) and that PEDF exposure, as well as the presence of Müller cells, leads to an activation of nuclear factor (NF)-κB in RGC. Furthermore, adding an NF-κB inhibitor (SN50) to PEDF-treated RGC cultures reduced the survival of RGC. These findings strongly suggest that NF-κB activation in RGC is critically involved in the pro-survival action of Müller-cell derived PEDF and plays an important role in maintaining neuronal survival.

Three-dimensional spheroidal culture visualization of membranogenesis of Bruch's membrane and basolateral functions of the retinal pigment epithelium

PURPOSE

Aging changes in the RPE involve lipid accumulation and membranous basal deposits onto the underlying Bruch's membrane, which may be related to AMD. Conventional in vitro cell culture is limited in its ability to observe the epithelial functions on the basal side. The purpose of this study was to develop a three-dimensional culture system to observe basolateral functions of the RPE.

METHODS

Isolated human RPE cells were cultured in a viscous medium on a rounded-bottom culture dish, resulting in spheroid formation. The appearance and size of the spheroids were assessed by light microscopy. Spheroids were fixed in 4% paraformaldehyde for immunohistochemistry or sampled for Western blotting. For transmission electron microscopy (TEM) and scanning electron microscopy (SEM), spheroids were postfixed in 1% osmium tetroxide.

RESULTS

The spheroids had a differentiated RPE monolayer with a thin elastic layer, a main layer of Bruch's membrane, on their surface and showed outward deposition of lipoproteins with apoB-100. TEM revealed widely spaced collagen, which was identified as condensation of collagen fibrils by SEM. SEM showed deposition of membranous debris and lipid particles, which have been observed in human Bruch's membrane. Western blotting showed expression of RPE differentiation markers and components of Bruch's membrane and RPE lipoproteins.

CONCLUSIONS

This model provides direct views of epithelialization processes involving elastogenesis and functions at the basolateral side such as lipoprotein deposition and may elucidate not only unknown epithelial behaviors but also the pathogenesis of RPE-related diseases.

Pigment epithelium-derived factor released by Müller glial cells exerts neuroprotective effects on retinal ganglion cells

Survival of retinal ganglion cells (RGC) is compromised in several vision-threatening disorders such as ischemic and hypertensive retinopathies and glaucoma. Pigment epithelium-derived factor (PEDF) is a naturally occurring pleiotropic secreted factor in the retina. PEDF produced by retinal glial (Müller) cells is suspected to be an essential component of neuron-glial interactions especially for RGC, as it can protect this neuronal type from ischemia-induced cell death. Here we show that PEDF treatment can directly affect RGC survival in vitro. Using Müller cell-RGC-co-cultures we observed that activity of Müller-cell derived soluble mediators can attenuate hypoxia-induced damage and RGC loss. Finally, neutralizing the activity of PEDF in glia-conditioned media partially abolished the neuroprotective effect of glia, leading to an increased neuronal death in hypoxic condition. Altogether our results suggest that PEDF is crucially involved in the neuroprotective process of reactive Müller cells towards RGC.

Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applications

Direct measurement of lung volume, i.e. functional residual capacity (FRC) has been recommended for monitoring during mechanical ventilation. Mostly due to technical reasons, FRC measurements have not become a routine monitoring tool, but promising techniques have been presented. We performed a literature search of studies with the key words 'functional residual capacity' or 'end expiratory lung volume' and summarize the physiology and patho-physiology of FRC measurements in ventilated patients, describe the existing techniques for bedside measurement, and provide an overview of the clinical questions that can be addressed using an FRC assessment. The wash-in or wash-out of a tracer gas in a multiple breath maneuver seems to be best applicable at bedside, and promising techniques for nitrogen or oxygen wash-in/wash-out with reasonable accuracy and repeatability have been presented. Studies in ventilated patients demonstrate that FRC can easily be measured at bedside during various clinical settings, including positive end-expiratory pressure optimization, endotracheal suctioning, prone position, and the weaning from mechanical ventilation. Alveolar derecruitment can easily be monitored and improvements of FRC without changes of the ventilatory setting could indicate alveolar recruitment. FRC seems to be insensitive to over-inflation of already inflated alveoli. Growing evidence suggests that FRC measurements, in combination with other parameters such as arterial oxygenation and respiratory compliance, could provide important information on the pulmonary situation in critically ill patients. Further studies are needed to define the exact role of FRC in monitoring and perhaps guiding mechanical ventilation.

Inhibition of experimental choroidal neovascularization in rats by an av-integrin antagonist

PURPOSE

Integrin alpha(v)beta3 is predominantly expressed on endothelial cells in choroidal neovascularization (CNV). We evaluated the efficacy of cyclic RGD (Arg-Gly-Asp) peptide, an alpha(v)-integrin antagonist, in a rat model of laser-induced CNV METHODS: We evaluated the effect of cyclic RGD on the adhesion and cell viability of bovine choroidal endothelial cells (BCECs) by cell counting and the trypan blue dye exclusion test. CNV was induced by laser photocoagulation in female Long Evans rats (day 0), followed by intravitreal administration of one dose of cyclic RGD of 200 (n = 9), 100 (n = 10), 50 (n = 4), or 0 microg (n = 9) on days 9 and 11. We assessed the area of CNV by fluorescein angiography and the thickness microscopically on histologic sections. Neovascular vessels were detected by an antibody against factor VIII.

RESULTS

Cyclic RGD (0.02 to 200 microg/ml) inhibited adhesion of BCECs in a dose-dependent manner without changing the cell viability (p < 0.01). In eyes treated with two injections of 200 or 100 microg of cyclic RGD peptide, the development of CNV was significantly (p < 0.01) inhibited in the area of leakage on fluorescein angiography. Histologically, the CNV membrane was observed beneath the retina and the factor VIII-positive cells and red blood cells were involved. The thickness of the lesions was significantly (p < 0.01) reduced in eyes that received 200 or 100 microg of RGD.

CONCLUSIONS

Cyclic RGD effectively inhibited CNV progression in a rat model of laser-induced CNV, suggesting that this alpha(v)-integrin antagonist may be beneficial in the treatment of CNV.

Regulation of pigment epithelium-derived factor production and release by retinal glial (Müller) cells under hypoxia

PURPOSE

To assess the regulation of pigment epithelium-derived factor (PEDF) production by retinal Müller glial cells, especially under ischemic or hypoxic conditions.

METHODS

PEDF was determined in surgically excised retinal tissue originating from patients with ischemic diabetic retinopathy and in primary guinea pig Müller cell cultures exposed to the protein synthesis inhibitor cycloheximide (CHX) and to hypoxia. PEDF production and secretion were studied by immunohistochemistry, quantitative RT-PCR, ELISA, fluorescence-activated cell sorter analysis, and Western blotting.

RESULTS

Gliotic Müller cells displayed decreased PEDF immunoreactivity in fibrovascular tissue from patients with diabetes compared with tissue from subjects with pathologic myopia. In Müller cell cultures, CHX treatment resulted in an increase, whereas mild hypoxia (2.5%-10% O(2)) induced a decrease, of PEDF mRNA and protein levels. However, strong hypoxia (0.2% O(2)) induced an upregulation of PEDF mRNA expression and resulted in only slightly reduced PEDF levels after 24 hours, detected as either a released, soluble, or cell surface-linked protein.

CONCLUSIONS

These results suggest that under certain conditions including mild hypoxia, Müller cells synthesize a protein factor that downregulates PEDF expression or its turnover. Generally, the cells appear to generate a biphasic response to hypoxia. In moderate hypoxia, PEDF is downregulated such that the VEGF-to-PEDF ratio increases (and angiogenesis is facilitated). During severe (or chronic) oxygen deficiency, however, the PEDF decline is arrested or even reversed; thus, the neurotrophic effects of PEDF remain available.

The role of alkylphosphocholines in retinal Müller glial cell proliferation

PURPOSE

Alkylphosphocholines (APCs) are investigated for their effect on Müller glial cell proliferation and F-actin stress fiber distribution in vitro.

MATERIALS AND METHODS

Müller cells were incubated with APCs (C18:1-PC and C22:1-PC) +/- fetal calf serum. Proliferation was assessed by BrdU labeling and with the tetrazolium dye-reduction assay. Toxicity was measured using the trypan blue exclusion assay. The distribution of F-actin stress fibers was determined using FITC-phalloidin staining.

RESULTS

APCs are effective inhibitors of human and rat Müller glial cell proliferation and hypoxia-induced up-regulation of F-actin stress fibers in vitro in non-toxic concentrations.

CONCLUSIONS

APCs might prevent intraretinal changes as a result of serum stimulation and hypoxia following retinal detachment.

Patient Mood and Neuropsychological Outcome After Laparoscopic and Conventional Colectomy

The study was designed to compare patients after laparoscopic and conventional colectomy with regard to early postoperative mood, cognitive function, and neurocognitive variables S100β and neuron-specific enolase (NSE). Forty-five laparoscopic and 25 open colectomies were enrolled into the prospective study. Outcome measurements were positive and negative postoperative mood (BSKE), neuropsychological tests (Trail-Making Test; word reproduction; Stroop Test), and serum biochemical parameters (S100β; NSE). Following laparoscopic procedure, patients described significantly better positive mood ( P < .05), tended to require less time in the Trail-Making Test and Stroop Test, and had lower postoperative serum concentrations of S100β compared to conventional colectomy patients ( P < .01). The current results revealed several group differences, which, in their entirety, seem to represent a more beneficial outcome after laparoscopic colonic surgery.

Growth-related effects of oxidant-induced stress on cultured RPE and choroidal endothelial cells

Mounting evidence suggests that oxidative stress caused by reactive oxygen intermediates is a significant mechanism in the pathogenesis of age-related macular degeneration (AMD). Although vascular endothelial growth factor (VEGF) and other cytokines are involved in choroidal neovascularization (CNV) it is largely unknown whether oxidative stress may predispose the eye to increased levels of proangiogenic factors. In an in vitro study we have determined viability and proliferation of both human retinal pigment epithelial (RPE) cells and bovine choroidal endothelial cells (CECs) and assessed the release of basic fibroblast growth factor (bFGF) and VEGF from RPE cells after exposing them to oxidative stress. Permanent presence of tert-butyl-hydroperoxide (tBH), a pro-oxidative stressor, in the cell cultures resulted in decreasing viability and proliferation of RPE cells and CECs. Loss of RPE cell viability was associated with activation of apoptosis by tBH in a dose-dependent manner. The antioxidant, N-acetyl-L-cysteine (NAC), and secreted soluble mediators of RPE cells were appropriate to attenuate the effects of tBH-mediated oxidative stress. RPE cells exposed to tBH were found to release increasing amounts of bFGF but not VEGF after 24h of culture, thereby supporting proliferation of CECs. These findings suggest that oxidative stress compromises the viability of RPE cells and CECs. However, increased bFGF levels concomitantly released from RPE cells may attenuate the CEC-directed effect, protect CECs from oxidative insults, and are likely to promote CNV.

Respiratory protection during high-fidelity simulated resuscitation of casualties contaminated with chemical warfare agents

Emergency room personnel are threatened by secondary poisoning when treating victims affected by chemical warfare agents. Therefore, resuscitation skills practised with respiratory protection equipment in place require evaluation. We investigated the influence of wearing air-purifying respirators on the simulated resuscitation of chemical warfare agent casualties. We studied 22 anaesthetic trainees in a simulated resuscitation scenario requiring five set tasks, either unprotected, wearing a binocular visor respirator or a panoramic visor respirator in a randomised, crossover study. Treatment times did not differ between the three groups, with mean (SD) times to complete the tasks being 122 (8) s without a mask, 126 (7) s when wearing the panoramic visor mask and 129 (8) s when wearing the binocular respirator mask. All anaesthetists preferred the panoramic visor in terms of visual orientation but 88% of them rated the binocular mask as being more comfortable. Modern respirators have a negligible effect on simulated resuscitation scenarios for victims affected by chemical warfare agents. Panoramic visor respirators allow better visual orientation for anaesthetists during simulated resuscitation.

Glycoxidized particles mimic lipofuscin accumulation in aging eyes: a new age-related macular degeneration model in rabbits

PURPOSE

The biogenesis of drusen, a hallmark of age-related macular degeneration (AMD), is still unclear. Lipofuscin, which extensively accumulates with age in RPE cells, is hardly soluble, derived in part from oxidation byproducts of the photoreceptor outer segments. The purpose of the current study is to develop a new AMD model in rabbits using glycoxidized particles as imitation lipofuscin, and determine whether accumulation of lipofuscin as insoluble material may play a role in drusen biogenesis and other pathogenesis of AMD.

METHODS

To mimic the accumulation of insoluble lipofuscin, glycoxidized microspheres (glycox-MS) were made through a glycoxidation process with albumin and glycolaldehyde, alpha-hydroxy aldehyde. As a control, microspheres made with glutaraldehyde (cMS) and soluble glycoxidized (glycox-) albumin were prepared. Each material was implanted into the subretinal space in rabbits. The implanted area was assessed by funduscopy, fluorescein angiography, histology, and transmission electron microscopy (TEM).

RESULTS

Compared with control microspheres, glycox-MS stagnated for a prolonged period in the cytoplasm of RPE cells. Eyes implanted with glycox-MS produced drusen-like deposits at a significantly higher frequency, when compared with the controls. Glycox-MS were observed at the margin of or beneath the drusen-like deposits in all cases. In some eyes with glycox-MS, late-onset sub-RPE choroidal neovascularization was observed, while control groups did not have these findings.

CONCLUSIONS

These results suggest that the accumulation of indigestible granules such as lipofuscin in RPE or subsequent depositions toward Bruch's membrane may play a role in drusen biogenesis as a trigger of inflammation or via other mechanisms. This model of AMD may be useful to elucidate drusen biogenesis and pathogenesis of AMD.

Pigment epithelium-derived factor acts as an opponent of growth-stimulatory factors in retinal glial–endothelial cell interactions

Pigment epithelium-derived factor (PEDF), a glycoprotein with pleiotropic functions, is naturally occuring in the eye and considered as crucial to prevent pathological angiogenesis. Since retinal glial (Müller) cells produce PEDF, the authors have studied its impact on glial-endothelial cellular interactions. Bovine retinal endothelial cells were cultured in the presence of culture media originating from primary Müller cells, and endothelial proliferation as well as phosphorylation of the mitogen-activated protein kinases extracellular signal-regulated kinases (ERK)-1/-2 were investigated. The concerted activity of Müller-cell derived soluble mediators attenuated endothelial proliferation and ERK-1/-2 activation, regardless of whether the Müller cells were preincubated under normoxia or hypoxia, and even though the endothelial cells were stimulated by vascular endothelial growth factor-A (VEGF). This inhibitory activity was no longer demonstrable if high levels of basic fibroblast growth factor or VEGF were supplied, suggesting that in cases of pathological neovascularization, overproduction of proangiogenic mediators overrides the "antiangiogenic background" provided by Müller cells. However, neutralizing the activity of PEDF partially restored endothelial cell proliferation and resulted in increased ERK-1/-2 activation, which is in concordance with findings demonstrating that exogenously applied PEDF is able to suppress VEGF-induced ERK-1/-2 phosphorylation. PEDF production by Müller cells is not only regulated by retinal oxygen but also by the activity of soluble factors released from retinal endothelial cells. For instance, PEDF levels were significantly elevated in glial (Müller)-endothelial cell cocultures as compared with bovine retinal endothelial cell-free Müller cell cultures. These results have implications for the pathogenesis of retinal neovascularization since the Müller cell may be regarded as a central control element which modulates retinal PEDF levels and, thus, is of critical importance for adjusting the balance between proangiogenic and antiangiogenic mediators.

Characteristics of two CD75-related cell-surface expressed antigens of human lymphocytes

The structure of cell surface carbohydrates expressed on human leukocytes is dependent on the cell's developmental stage, differentiation, and activation. Although modification of oligosaccharide side chains by sialylation is quite common, antigenic determinants on lymphocytes associated with the presence of sialoglycans are still incompletely defined. In the study presented here, monoclonal antibodies (mAbs) were used to characterize two novel but related cell surface carbohydrate antigens. One antigen, denominated as B8, is largely masked by sialyl residues on most lymphocytes, while it is detectable on the majority of B cells. Treatment with sialidase resulted in the exposure of B8 on the surface of blood cells including lymphocytes. Although the second carbohydrate antigen, C1, was sialidase-sensitive, its molecular properties and cellular distribution place it in close vicinity to B8. B8(+) as well as C1(+) lymphocytes were found predominantly in the mantle zone of secondary follicles of tonsillar tissue. These findings raised the possibility that B8 and C1 are closely related to a category of carbohydrate antigens previously classified as CDw76 (recently assigned to CD75s). MAbs directed against B8 or C1 precipitated 34, 37, 43, and 200kDa glycoproteins from tonsillar lymphocytes, indicating that identical cell surface proteins are associated with both antigens. In contrast to B8, however, the expression of C1 was increased on lymphocytes upon activation. Together the results suggest that CD75-related epitopes are distinct molecular entities which may be exposed on glycoproteins and are differently expressed on lymphocytes.

Antineovascular agents in the treatment of eye diseases

Neovascularization is a common and potentially visually threatening complication of eye diseases such as diabetic retinopathy (DR) and age-related macular degeneration (AMD). An antiangiogenic therapy is aimed at inhibiting the growth of new blood vessels and should prevent onset or progression of neovascularization. Accumulated evidence indicates that growth factors, endothelial cell surface receptors, and extracellular matrix (ECM) proteins are major mediators of neovascularization and appealing targets for pharmacotherapeutical intervention. Vascular endothelial growth factor (VEGF) plays a critical role in the pathogenesis of retinal neovascularization (in linking tissue ischemia to angiogenesis), and is likely to contribute also significantly to choroidal neovascularization (CNV). Several antineovascular agents antagonize the function of VEGF, by blocking its proangiogenic activity. Indeed, VEGF targeting or disruption of VEGF signalling is the most effective strategy known so far in the pharmacological treatment of ocular neovascularization. Other compounds such as pigment epithelium-derived factor (PEDF) either aim at balancing the levels of pro-angiogenic and angiostatic molecules, target inflammation (cyclooxygenase inhibitors, steroids) or comprise modifiers of the ECM such as inhibitors of matrix metalloproteinases (MMPs) and agents that block the action of integrins. Vascular targeting agents (combretastatin) promote removal of newly formed vessels. This review provides an update on recent investigations directed at the pharmacotherapeutical management of ocular neovascular diseases, placing special emphasis on the underlying target molecules and relevant intracellular signalling pathways.

The Na+/H+ exchange inhibitor cariporide is washed out of the myocardium by crystalloid cardioplegia

BACKGROUND

Inhibition of the Na (+)/H (+) exchanger (NHE) is cardioprotective, but dosage and timing of NHE-inhibitors are critical for their efficacy. We studied the effect of a new dosing regime of the NHE-inhibitor cariporide on myocardial function and damage after cardioplegic arrest (CPA) and determined its myocardial and serum concentrations.

METHODS

3 pigs received a bolus of 180 mg cariporide intravenously (i. v.) and were sacrificed shortly thereafter to allow measurement of the myocardial concentrations of cariporide. Subsequently, 10 pigs were randomized to receive either i. v. cariporide (bolus followed by an infusion of 40 mg/h) or placebo. Cardiopulmonary bypass was initiated, and the heart was arrested for 60 minutes by infusion of St. Thomas Hospital solution. Left ventricular (LV) function was studied using microsonometry. Myocardial damage was assessed by troponin T. Serum concentrations of cariporide were measured throughout the study, and myocardial concentrations were measured before the end of CPA and 180 minutes thereafter.

RESULTS

Cariporide was present in all myocardial specimens (median: 1.4 ng/mg) studied previously. In the main study, LV function or myocardial damage did not differ significantly between the groups at any time point. Stable serum cariporide concentrations were achieved (3.4 +/- 0.5 microg/ml). Cariporide was detectable in only one of the myocardial biopsies obtained before the end of CPA, but 180 minutes thereafter, the myocardial cariporide concentration was 2.5 +/- 0.3 ng/mg.

CONCLUSION

We observed no effect of i. v. cariporide on LV function or myocardial damage after cardioplegic arrest. Our data suggest that cariporide is washed out of the myocardium by repeated application of crystalloid cardioplegia. Thus, the mode of delivery also appears to be critical for cardioprotection with NHE-inhibitors.

Characteristics of iris and retinal pigment epithelial cells cultured on collagen type I membranes

PURPOSE

Transplantation of pigment epithelial cells is a promising treatment modality to repair retinal damage in age-related macular degeneration. For this purpose, it is necessary to establish cell culture techniques that allow acquisition of proper functional and morphological characteristics by the cells to be transplanted.

METHODS

Primary retinal pigment epithelial (RPE) and iris pigment epithelial (IPE) cells grown to confluence on collagen membranes were examined for morphology, adhesion, proliferation, apoptosis, as well as viability after ex vivo transplantation.

RESULTS

Pigment epithelial cells adhere, proliferate, form monolayers, acquire differentiated properties, and remain viable during transplantation to the subretinal space.

CONCLUSIONS

Pigment epithelial cells cultured on collagen membranes acquire differentiated characteristics and are amenable to be transplanted as cell monolayers.

Effects of candesartan and enalaprilat on the organ-specific microvascular permeability during haemorrhagic shock in rats

BACKGROUND

To counteract the contribution of angiotensin II to shock-induced ischaemic organ damage pharmacologic blockade of the renin-angiotensin-system (RAS) is currently under investigation. To evaluate potential side-effects of RAS blockade regarding capillary leak, we studied alterations in microvascular permeability in various organs during haemorrhagic shock (HS) in rats pretreated with candesartan (AT(1)-receptor antagonism) or enalaprilat (ACE-inhibition).

METHODS

Thirty-eight instrumented and anaesthetized animals received either candesartan, enalaprilat or placebo. Within each of the three groups 6-7 animals were exposed to HS and 6 animals of each group served as normovolaemic controls. After 30 min of shock, 50 mg kg(-1) Evans blue (EB) was injected i.v. followed by a distribution period of 20 min. Exsanguination was performed with saline, before harvesting organs to quantify albumin-bound EB extravasation.

RESULTS

To reduce cardiac output from 37.5 (1.3) to 20.4 (1.1) ml min(-1) [mean (SEM)] in the shock groups, withdrawal of 4.0 (0.25) ml [mean (SEM)] blood was necessary. Simultaneously mean arterial pressure decreased from 77.5 (3.2) to 36.1 (2) mm Hg. Serum lactate increased significantly from 1.3 (0.1) to 3.5 (0.24) mmol litre(-1). Treatment with candesartan increased EB extravasation in the kidney in normovolaemic controls. Specific AT(1) and ACE-blockade before acute non-resuscitated HS significantly increased EB extravasation in the rat ileum by 53 and 66%, respectively.

CONCLUSION

This observation of increased microvascular albumin extravasation should be borne in mind for any interventional use of candesartan or enalaprilat during circulatory stress.

Impact of endostatin on bFGF-induced proliferation, migration, and matrix metalloproteinase-2 expression/secretion of bovine choroidal endothelial cells

PURPOSE

To investigate the potential role of endostatin, an endogenous angiogenesis inhibitor, in the prevention of choroidal angiogenesis-related disorders.

METHODS

Bovine choroidal endothelial cells (CEC) were cultured and treated with basic fibroblast growth factor (bFGF) alone or combined with endostatin at concentrations ranging from 0.1 to 10 microg/ml. The proliferation and migration of CECs were evaluated by using 3, (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay and modified Boyden chamber assay, respectively. For evaluating expression and secretion of matrix metalloproteinase-2 (MMP-2), CEC-conditioned media were subjected to zymography and/or Western blot analysis, and the cells were used for semiquantitative reverse transcription polymerase chain reaction (RT-PCR) analysis.

RESULTS

Endostatin did not inhibit bFGF-induced or nonstimulated CEC proliferation (p > 0.05). The bFGF-induced migration was significantly inhibited by endostatin at concentrations of 1 and 10 microg/ml (p < 0.05). The bFGF-upregulated expression of mRNA in CECs and the secretion of MMP-2 protein of CECs were both suppressed by endostatin.

CONCLUSIONS

Inhibitory effect of endostatin on expression and secretion of MMP-2 and cell migration, but not on proliferation of CECs, could respond to its therapeutic action for choroidal neovascularization-dependent disorders.

PEDF derived from glial Müller cells: a possible regulator of retinal angiogenesis

A precise balance between stimulators and inhibitors of angiogenesis, such as vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF), respectively, is essential for angiogenic homeostasis in ocular tissues. Retinal hypoxia is accompanied by some pathological conditions that may promote intraocular neovascularization. Here we demonstrate that retinal glial (Müller) cells express and release pigment epithelium-derived factor (PEDF). Decreasing oxygen concentrations cause strong attenuation of PEDF release resulting in enhanced VEGF/PEDF ratios. Exposure of Müller cells to VEGF suppressed PEDF release in a dose-dependent manner. This may represent a novel mechanism of ocular angiogenic homeostasis sufficient in the control of PEDF levels during normoxia or mild hypoxia but supplemented by other (hitherto unknown) mechanisms in cases of strong hypoxia. In spite of the enhanced VEGF/PEDF ratios resulting from hypoxia, conditioned media of Müller cells failed to stimulate additional proliferation of retinal endothelial cells. These findings suggest that in the ischemic retina, Müller cells generate a permissive condition for angiogenesis by secreting more VEGF and less PEDF, but the onset of retinal endothelial cell proliferation requires another triggering signal that remains to be identified.

Angiogenesis-related factors derived from retinal glial (Müller) cells in hypoxia

Retinal glial (Müller) cells may play a major role in vascular eye diseases as they secrete vascular endothelial growth factor (VEGF), a hypoxia-induced angiogenic cytokine. They also release significant amounts of the anti-angiogenic factors, transforming growth factor (TGF)-beta2, pigment epithelium derived factor (PEDF), and thrombospondin-1 (TSP-1). Exposure of human (MIO-M1) and guinea-pig Müller cells to hypoxia resulted in a decreased release of TGF-beta2 and PEDF but in an elevated secretion of TSP-1. When retinal endothelial cells were exposed to VEGF/anti-angiogenic factor ratios mimicking those found in culture media of Müller cells under normoxia or hypoxia, their proliferation was significantly inhibited by TGF-beta2, PEDF or TSP-1. Thus Müller cells may provide a permanent anti-proliferative condition for retinal endothelial cells.

Molecular cloning of bovine CD97: an EGF-TM7 molecule expressed as isoforms

CD97, a cell surface molecule on immune cells with potential adhesive function, is a member of the epidermal growth factor seven-span transmembrane (EGF-TM7) family. We have cloned and characterized bovine CD97 and determined its expression in various cells and tissues. Based on sequence alignment with human genomic DNA, as well as human cDNA sequences encoding various CD97 isoforms, we predict that bovine CD97 mRNA occurs in four splice variants. The encoded CD97 isoforms (800, 751, 756, and 707 amino acids in length) contain different numbers of EGF-like modules, a stalk region, and a TM7 domain with a cytoplasmic tail. RT-PCR demonstrated expression of CD97 mRNA in leukocytes and several other tissues. In each cell type, CD97 mRNA encoding the shortest isoform, CD97 (EGF 1,2,5), was detected at the highest level, which was consistent with the cell surface expression of a 90-kDa polypeptide precipitated from lysates of peripheral blood mononuclear cells.

Retinal Endothelial Angiogenic Activity: Effects of Hypoxia and Glial (Müller) Cells

OBJECTIVE

To explore the impact of retinal glial (Müller) cells on survival and neovascularization-related activities of cultured retinal endothelial cells under normoxic and hypoxic conditions.

METHODS

Bovine retinal endothelial cells (BRECs) were cultured under normoxia or hypoxia (0.5% O2) either alone, together with the human Müller cell line MIO-M1, or in normoxia- or hypoxia-conditioned media of MIO-M1 cells. Cell number, proliferation, apoptotic cell death, and migration of BRECs were determined.

RESULTS

Exposure of BRECs to hypoxia for 24 h decreased the number of adherent cells and the proliferation rate, but increased apoptosis and cell migration. Increased apoptosis and decreased proliferation of the BRECs occurred also in the presence of conditioned media of MIO-M1 cells. Under normoxic conditions, co-culture with MIO-M1 cells resulted in increased proliferation, but decreased apoptosis and migration rates of BRECs. Under hypoxic conditions, the Müller cells released elevated amounts of VEGF but their presence decreased proliferation, apoptosis and the migration rates of BRECs.

CONCLUSIONS

Hypoxia inhibits the proliferation of retinal endothelial cells. Müller cells release soluble mediators that enhance this hypoxia-mediated effect but, under certain conditions (i.e., in co-culture), may protect retinal endothelial cells from apoptosis, thus supporting their survival. Altogether the findings indicate that the key signal necessary to trigger retinal endothelial proliferation under hypoxia remains to be determined.

Clinical biochemical tissue monitoring during ischaemia and reperfusion in major vascular surgery

BACKGROUND

Major vascular surgery with aortic cross-clamping is associated with temporary ischaemia of the lower limb due to lack of tissue blood flow. The present study was designed to determine if the short-term changes in cellular metabolism occurring during this situation can be detected by subcutaneous microdialysis. It was also hoped to ascertain if this new technique is useful in the continuous bedside monitoring of metabolism during aortic surgery.

METHODS

In a controlled clinical study 20 patients undergoing elective aortic surgery were monitored using microdialysis probes that were inserted in the subcutaneous tissue of the left lower limb and a non-ischaemic region (shoulder). Interstitial fluid was obtained and the concentrations of glucose and lactate during lower limb ischaemia and during reperfusion were measured and compared with concentrations observed in fluid obtained from the non-ischaemic control tissue.

RESULTS

Circulatory occlusion caused an immediate and significant decrease in the glucose/lactate ratio from 3.1+/-1.3 to 0.48+/-0.5 (P<0.05) that returned to preocclusion values within 2 h of commencing reperfusion.

CONCLUSION

We suggest that microdialysis may be used both to assess acute changes in tissue metabolism during ischaemic periods and also to act as an additional tool for the detection of peri-operative acute variations in limb blood flow.

[Microdialysis as a procedure for evaluating intestinal hypoxia--an animal experiment approach]

Usual ICU monitoring of patients with abdominal pathology provides no detailed information about hepatosplanchnic haemodynamics or intestinal metabolism. In our animal experiment, the effects of systemic hypoxia on microdialysis measurements of the peritoneum in comparison with the ischiocrural muscle as reference were investigated in 7 rats. The parameter of interest was the course of glucose metabolism reflecting sympathoadrenergic activity during the experiment. Measurements were obtained at timed intervals at baseline, under hypoxia, and during reoxygenation. After induction of systemic hypoxia, the peritoneal microdialysis showed significantly higher levels of glucose in comparison with the ischiocrural muscle. The results indicate hypermetabolic activity or a hypersympathetic response of the bowel in response to hypoxic stress. In the clinical setting, the bowel has an important role in the development of multiorgan failure. Microdialysis may therefore be an interesting tool for the early detection of hypoxic metabolism during and after abdominal procedures.

High CXCR3 expression in synovial mast cells associated with CXCL9 and CXCL10 expression in inflammatory synovial tissues of patients with rheumatoid arthritis

To improve our knowledge on the pathophysiology of rheumatoid arthritis (RA), we investigated gene expression patterns in synovial tissue from RA and osteoarthritis (OA) patients. DNA oligonucleotide microarray analysis was employed to identify differentially expressed genes in synovial tissue from pathologically classified tissue samples from RA (n = 20) and OA patients (n = 10). From 7131 gene sets displayed on the microarray chip, 101 genes were found to be upregulated and 300 genes to be downregulated in RA as compared with OA. Semiquantitative reverse-transcription polymerase chain reaction, Western blotting and immunohistochemistry were used to validate microarray expression levels. These experiments revealed that Cys-X-Cys receptor (CXCR)1, CXCR2 and CXCR3 mRNAs, as well as Cys-X-Cys ligand (CXCL)9 (monokine induced by IFN-gamma) and CXCL10 (IFN-gamma inducible protein 10) mRNAs, were significantly upregulated in RA as compared with OA disease. Elevated protein levels in RA synovial tissue were detected for CXCR1 and CXCR3 by Western blotting. Using immunohistochemistry, CXCR3 protein was found to be preferentially expressed on mast cells within synovial tissue from RA patients. These findings suggest that substantial expression of CXCR3 protein on mast cells within synovial tissue from RA patients plays a significant role in the pathophysiology of RA, accompanied by elevated levels of the chemokines CXCL9 and CXCL10. Mature mast cells are likely to contribute to and sustain the inflamed state in arthritic lesions (e.g. by production of inflammatory mediators such as histamine, proteinases, arachidonic acid metabolites and cytokines). Thus, the mast cell could become a potential target in therapeutic intervention.

Advanced glycation end products induce choroidal endothelial cell proliferation, matrix metalloproteinase-2 and VEGF upregulation in vitro

BACKGROUND

Advanced glycation end products (AGEs) are considered to be important modulators of angiogenesis and accumulate in choroidal neovascularization (CNV). Their effects regarding cells involved in proliferation of CNV [retinal pigment epithelial (RPE) cells, Müller cells and choroidal endothelial cells (CECs)] were investigated. Furthermore, the effects of AGEs on expression of matrix metalloproteinase-2 (MMP-2) and vascular endothelial growth factor (VEGF) by CECs were explored.

METHODS

RPE cells, CECs and Müller cells were exposed to AGEs (10 microg/ml, 50 microg/ml and 100 microg/ml) for a time course of three days in their desired medium and proliferation was estimated by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. MMP-2 expression of AGE-stimulated CECs was determined by zymography and reverse-transcription polymerase chain reaction (RT-PCR) after 36 h of exposure. Furthermore, VEGF expression of AGE-stimulated CECs (50 microg/ml and 100 microg/ml) was determined by RT-PCR after an exposure time of 36 h.

RESULTS

AGEs in a concentration of 50 microg/ml and 100 microg/ml increased the proliferation of CECs (41% vs 46.1%; P<0.005). No AGE effect on RPE cell and Müller cell proliferation was seen. AGEs in all concentrations used upregulated the VEGF mRNA expression of CECs. Zymography and RT-PCR demonstrated the upregulation of MMP-2 by CECs after AGE exposure.

CONCLUSION

AGEs stimulate CEC proliferation, MMP-2 secretion and VEGF upregulation and may be important promoters of CNV formation in exudative AMD in vivo.

Influence of adenoviral vector on expression of angiogenesis regulating factors in non-small cell lung cancer cell lines

Gene therapy to suppress the neovascularization of solid tumors may prove to be an effective strategy in cancer therapy. Recombinant adenovirus (Ad) vectors are currently the most widely used vectors for gene transfer. In this study, we examined the expression of angiogenesis-regulating factors in tumor cells infected with the Ad vector. These cells showed upregulation of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) transcription, and a higher protein level of intracellular bFGF and increased VEGF secretion. In addition, we observed an increase of angiostatin-generating activity in the supernatants of infected tumor cells. Supernatants of Ad vector-infected cells did not stimulate endothelial cell proliferation, and inhibited their migration. These results indicate that infection of tumor cells with the Ad vector results in an increase expression of angiogenesis-regulating factors, but does not by itself activate angiogenesis.

Modulation of matrix metalloproteinase and TIMP-1 expression by cytokines in human RPE cells

PURPOSE

The balance between matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) is crucial for homeostasis of ocular extracellular matrices. To assess altered MMP activity as a determinant in the migration of human retinal pigment epithelial (RPE) cells, expression characteristics of several MMPs and TIMP-1 in RPE cell cultures were investigated.

METHODS

Expression studies were performed with RT-PCR, ELISA, and immunofluorescence analysis. Secretion of MMP-2 was demonstrated by zymography. Migration of cytokine-stimulated RPE cells was evaluated with microporous membranes of permeable chambers.

RESULTS

MMP-1, -2, -3, and -9; MT2-MMP; and TIMP-1 were expressed in cultured RPE cells. MMP-2 was detected on the cell surface and in secreted inactive and active forms. TGF-beta(2), IL-1beta, and TNF-alpha enhanced secretion of MMP-1, -2, and -3. TGF-beta(2) also stimulated MT2-MMP cell surface expression and release of TIMP-1. The mRNA levels of MMP-1, -2, and -3 and TIMP-1 were markedly increased by TNF-alpha and TGF-beta(2). MMP-2 mRNA levels were also upregulated by PDGF-BB. Migration of RPE cells stimulated by TGF-beta(2) or PDGF-BB was inhibited in presence of a synthetic MMP inhibitor.

CONCLUSIONS

Proinflammatory cytokines and TGF-beta(2) play an important role in the upregulation of expression of MMP-1, -2, and -3 in RPE cells and account for a directional shift in the balance between MMPs and TIMPs. Facilitation of RPE cell migration stimulated by cytokines (i.e., TGF-beta(2) or PDGF-BB) in ocular diseases may be due to increased release of MMPs, in the presence of comparatively lower levels of their inhibitors.

Correlation between expression of selectins and migration of eosinophils into the bovine ovary during the periovulatory period

Leukocytes enter specific ovarian areas at a precisely defined moment, influencing cyclically changing structures such as follicles and corpora lutea. As yet, no studies have been published on the trafficking mechanisms involving the interaction between adhesion molecules on endothelial cells (ECs) and those on leukocytes. First, antibodies against human adhesion molecules were examined by flow cytometry with the aim of identifying the same bovine antigen. Western blot analysis and immunoprecipitation revealed that the molecules had the same molecular weight as their human counterparts. Afterwards, we investigated the distribution of these antigens in various ovarian stages using immunohistology. Among the molecules, P-selectin (CD62P) and L-selectin (CD62L) showed stage-dependent expression, and were thus examined further. In the preovulatory follicle, microvascular ECs were negative for CD62P. Few of the leukocytes expressed CD62L. In a freshly ruptured follicle, CD62P expression was found in the dilated vessels of the former thecal layer. Simultaneously, a large proportion of the rapidly increased numbers of leukocytes, mainly eosinophils, located around the microvessels of the outer thecal layer expressed CD62L. In the early corpus luteum development stage, CD62L showed peak expression with 70%-80% positive cells compared to leukocytes. In the secretory stage, the septal venules showed a consistent, but now weak, staining for CD62P. Few leukocytes expressed CD62L. During regression, the total number of leukocytes, now representing macrophages, increased significantly, but the proportion of CD62L-positive cells remained constant. In summary, we found a strong correlation of CD62P expression on activated ECs and the appearance of CD62L-positive leukocytes in the early corpus luteum development stage, suggesting the participation of both selectins in the migration of eosinophils under physiological conditions.

Inhibitory effects of triamcinolone acetonide on bFGF-induced migration and tube formation in choroidal microvascular endothelial cells

BACKGROUND

Angiostatic drugs might provide desirable modulation of choroidal angiogenesis-related diseases, including histoplasmosis and the exudative form of age-related macular degeneration. However, the precise effects of this class of compounds in the choroidal neovascularization are still unclear. In the present study, we investigated the effects of triamcinolone acetonide (TA), an angiostatic steroid, on choroidal angiogenesis in vitro.

METHODS

Bovine choroidal endothelial cells (CEC), which are the critical cellular component of choroidal angiogenesis in vivo, were isolated with Lycopersicon esculentum agglutinin-coated Dynabeads and cultured in EGM medium. CEC were treated with basic fibroblast growth factor (bFGF) and TA at various concentrations ranging from 50 to 300 mg/l. The capacities for CEC migration and tube formation were evaluated with the modified Boyden chamber and the Vitrogen collagen assay, respectively. The activities of matrix metalloproteinases (MMP)-2 and -9 were examined using gelatin zymography.

RESULTS

The stimulation of CEC with 50 ng/ml bFGF resulted in an increase of about 100% in migration activity (P<0.01). Preincubation of CEC with TA at the indicated concentrations for 20 min inhibited the bFGF-stimulated migration in a dose-dependent manner (P<0.01). After 5 days, the bFGF-stimulated tube formation in CEC was inhibited by TA at the concentrations 100, 150 and 300 mg/l (P<0.01). Gelatin zymography of the culture media of CEC showed that the bFGF-induced activation of MMP-2 was attenuated by 300 mg/l TA (P<0.05).

CONCLUSION

Downregulation of the activation of MMPs in CEC could be one of the mechanisms by which angiostatic steroids inhibit choroidal angiogenesis.

Hypoxia: modulation of endothelial cell proliferation by soluble factors released by retinal cells

A devastating complication of ischemic retinopathies is retinal neovascularization. We studied the impact on retinal endothelial cell proliferation of soluble factors released from cultured retinal glial (Müller) cells and from retinal explant cultures. Hypoxia strongly stimulated VEGF release by all types of cultures but endothelial cell growth was not further increased by the corresponding conditioned media if compared to supernatants obtained under normoxia. When the final concentration of the hypoxia-conditioned media was adjusted to the VEGF level of normoxia-conditioned media, they even inhibited endothelial cell proliferation. Inhibition may be exerted by TGF-beta 2 but TGF-beta 2 mRNA and protein expression in Müller cells were found to be down-regulated under hypoxia. We conclude that retinal endothelial cell proliferation is controlled by the balance of the amount and/or efficacy of several stimulatory and inhibitory factors.

Blood levels of atrial natriuretic peptide, endothelin, cortisol and ACTH in patients undergoing coronary artery bypass grafting surgery with cardiopulmonary bypass

Previous studies demonstrated a biphasic time course with post-operative dissociation of blood levels of cortisol and ACTH in patients undergoing major surgery and critically ill patients. A possible role of endothelin and atrial natriuretic peptide (ANP) in the dissociation of concentrations of cortisol and ACTH in critically ill patients has been suggested. In the present study, we investigated the perioperative course of blood levels of endothelin, ANP, ACTH, and cortisol in 13 male patients undergoing cardiac surgery with cardiopulmonary bypass (CPB): group 1 consisted of 7 patients with an uneventful perioperative period and group 2 consisted of 6 patients with perioperative complications. Blood samples were taken pre-[T1], intra-[T2], post-operatively (on the day of surgery) [T3], as well as on the first [T4] and second [T5] post-operative days. Blood samples of endothelin, ANP, cortisol, and ACTH were measured using commercially available immunoassays. Perioperatively, a biphasic time course with post-operative dissociation of ACTH and cortisol concentrations was observed in all patients studied. Intraoperatively, during CPB, the highest levels of endothelin were found. Perioperatively, ANP and endothelin levels were elevated compared to pre-operative values up to the second post-operative day. On the second post-operative day, ANP concentrations were significantly higher in patients with complications in the perioperative period compared to those with an uneventful perioperative period. Our results suggest that: 1) plasma levels of ANP increased in patients with perioperative complications; 2) plasma levels of ANP may have prognostic value for patients undergoing cardiac surgery; and 3) the dissociation of ACTH and cortisol cannot solely be explained by the increase in endothelin-1 and ANP concentrations observed in patients undergoing major surgery.