The fibroblast growth factor receptors, FGFR-1 and FGFR-2, mediate two independent signalling pathways in human retinal pigment epithelial cells

Safety and efficacy of the pan-FGFR inhibitor erdafitinib in advanced urothelial carcinoma and other solid tumors: A systematic review and meta-analysis

Objective

This review aimed to comprehensively analyze the safety and efficacy of erdafitinib in treating advanced and metastatic urothelial carcinoma and other solid tumors.

Methods

PubMed, Embase, and ClinicalTrials.gov were searched until 10 February 2022. The safety outcome as adverse events and efficacy outcomes, including objective response rate, stable disease rates, and progressive disease rates, were selected and analyzed by comprehensive meta-analysis version 3.0 and STATA 15.0.

Results

The most common all-grade adverse events were hyperphosphatemia, dry mouth, stomatitis, diarrhea, and dysgeusia. The occurrence of ≥3 adverse events was relatively low, and stomatitis and hyponatremia were the most common. Moreover, eye disorders could not be ignored. Efficacy in urothelial carcinoma patients was obviously better than in other solid tumor patients, with a higher objective response rate (0.38 versus 0.10) and lower progressive disease rate (0.26 versus 0.68). All responses occurred in patients with fibroblast growth factor receptor (FGFR) alteration. In those patients, a specific FGFR alteration (FGFR3-TACC3) was observed to have a maximum response.

Conclusion

Erdafitinib has satisfactory clinical activity for metastatic urothelial carcinoma and other solid tumors, while the toxicity is acceptable. With more RCTs and combination therapy trials published, erdafitinib will be applied widely.

Case Report: Erdafitinib-induced Central Serous Chorioretinopathy

SIGNIFICANCE

Erdafitinib is the first fibroblast growth factor receptor inhibitor approved by the U.S. Food and Drug Administration in April 2019 for the treatment of locally advanced and unresectable or metastatic urothelial carcinoma. Central serous chorioretinopathy is a common ocular adverse effect requiring frequent monitoring with ophthalmic examination.

PURPOSE

This study aimed to increase awareness of erdafitinib-induced central serous chorioretinopathy, highlight erdafitinib dose management guidelines, and emphasize the importance of collaborating with oncologists to prevent adverse visual consequences.

CASE REPORT

An 80-year-old patient with an advanced urothelial cancer with fibroblast growth factor receptor mutations developed central serous chorioretinopathy when he was treated with daily 8 mg of erdafitinib. The erdafitinib-induced central serous chorioretinopathy resolved completely after the discontinuation of erdafitinib. He was then treated with daily 6 mg of erdafitinib and again developed central serous chorioretinopathy, which resolved completely upon discontinuation of the medication. The patient then decided to stop treatment with erdafitinib.

CONCLUSIONS

Erdafitinib, a potent tyrosine kinase receptor inhibitor of fibroblast growth factor receptors 1 to 4, demonstrates antitumor activity in advanced urothelial carcinoma with fibroblast growth factor receptor mutations with a response rate of approximately 40%. However, central serous chorioretinopathy develops in 25% of patients treated with a daily 8-mg dose of erdafitinib. Although most mild to moderate erdafitinib-induced central serous chorioretinopathies resolve with dose interruption or reduction, occasionally discontinuation of the medication is necessary. Therefore, careful coordination with oncologists is important to assess the impact of erdafitinib on vision, quality of life, and survival prognosis.

The transcriptome of peripheral blood mononuclear cells in patients with clinical subtypes of late age-related macular degeneration

Background

Peripheral blood mononuclear cells (PBMCs) are implicated in the pathogenesis of age-related macular degeneration (AMD). We here mapped the global gene transcriptome of PBMCs from patients with different clinical subtypes of late AMD.

Results

We sampled fresh venous blood from patients with geographic atrophy (GA) secondary to AMD without choroidal neovascularizations (n = 19), patients with neovascular AMD without GA (n = 38), patients with polypoidal choroidal vasculopathy (PCV) (n = 19), and aged control individuals with healthy retinae (n = 20). We isolated PBMCs, extracted RNA, and used microarray to investigate gene expression. Volcano plots identified statistically significant differentially expressed genes (P < 0.05) at a high magnitude (≥30% higher/lower) for GA (62 genes), neovascular AMD (41 genes), and PCV (41 genes). These clinical subtypes differed substantially across gene expression and the following pathways identified in enrichment analyses. In a subgroup analysis, we investigated presence vs. absence of subretinal fibrosis and found 826 differentially expressed genes (≥30% higher/lower, P < 0.05) with relation to mRNA splicing, endothelial migration, and interleukin-1 signaling.

Conclusions

We here map the global gene transcriptome of PBMCs related to clinical subtypes of late AMD and find evidence of subtype-specific immunological involvement. Our findings provide a transcriptomic insight into the systemic immunity associated with AMD.

Electronic supplementary material

The online version of this article (10.1186/s12979-019-0160-0) contains supplementary material, which is available to authorized users.

All-trans retinoic acid stimulates the secretion of TGF-β2 via the phospholipase C but not the adenylyl cyclase signaling pathway in retinal pigment epithelium cells

Background

By investigating that (i) all-trans retinoic acid (ATRA) affects human retinal pigment epithelium (RPE) in expressing and secreting transforming growth factor (TGF)-β₂ and (ii) U73122 (phospholipase C inhibitor) and SQ22536 (adenylyl cyclase inhibitor) regulate the ATRA-induced secretion of TGF-β₂ in human RPE, we sought to interpret the signaling pathway of ATRA in promoting the development of myopia.

Methods

The RPE cell line (D407) was treated with (i) ATRA (10 μM), (ii) U73122 (5–40 μM) and ATRA (10 μM), or (iii) SQ22536 (5–40 μM) and ATRA (10 μM). The control group was no-treated. After stimulated at 2, 4, 8, 16, 24, and 48 h, The expression and secretion of TGF-β₂ was detected.

Results

TGF-β2 in the cytoplasm was time-dependent increased by ATRA (p < 0.001). A time-dependent increase in the TGF-β2 protein of the supernatant was induced by ATRA (p < 0.001). U73122 (in the range of 5 to 40 μM) could suppress the secretion of TGF-β2 induced by ATRA (p < 0.001), and 40 μM U73122 could completely inhibit the up-regulated effect of 10 μM ATRA. However, SQ22536 (in the range of 5 to 40 μM) had no impact on the secretion of TGF-β₂ induced by ATRA (p > 0.05).

Conclusions

In RPE cells, ATRA stimulates the secretion of TGF-β₂ via the phospholipase C signaling pathway but not the adenylyl cyclase signaling pathway. U73122 may inhibit the promotion of ATRA in the development of myopia.

Functional Voltage-Gated Calcium Channels Are Present in Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium

Retinal pigment epithelium (RPE) performs important functions for the maintenance of photoreceptors and vision. Malfunctions within the RPE are implicated in several retinal diseases for which transplantations of stem cell‐derived RPE are promising treatment options. Their success, however, is largely dependent on the functionality of the transplanted cells. This requires correct cellular physiology, which is highly influenced by the various ion channels of RPE, including voltage‐gated Ca²⁺ (Ca_V) channels. This study investigated the localization and functionality of Ca_V channels in human embryonic stem cell (hESC)‐derived RPE. Whole‐cell patch‐clamp recordings from these cells revealed slowly inactivating L‐type currents comparable to freshly isolated mouse RPE. Some hESC‐RPE cells also carried fast transient T‐type resembling currents. These findings were confirmed by immunostainings from both hESC‐ and mouse RPE that showed the presence of the L‐type Ca²⁺ channels Ca_V1.2 and Ca_V1.3 as well as the T‐type Ca²⁺ channels Ca_V3.1 and Ca_V3.2. The localization of the major subtype, Ca_V1.3, changed during hESC‐RPE maturation co‐localizing with pericentrin to the base of the primary cilium before reaching more homogeneous membrane localization comparable to mouse RPE. Based on functional assessment, the L‐type Ca²⁺ channels participated in the regulation of vascular endothelial growth factor secretion as well as in the phagocytosis of photoreceptor outer segments in hESC‐RPE. Overall, this study demonstrates that a functional machinery of voltage‐gated Ca²⁺ channels is present in mature hESC‐RPE, which is promising for the success of transplantation therapies. stem cells translational medicine2019;8:179&15

T-cell differentiation and CD56+ levels in polypoidal choroidal vasculopathy and neovascular age-related macular degeneration

Polypoidal choroidal vasculopathy (PCV) and neovascular age-related macular degeneration (AMD) are prevalent age-related diseases characterized by exudative changes in the macula. Although they share anatomical and clinical similarities, they are also distinctly characterized by their own features, e.g. vascular abnormalities in PCV and drusen-mediated progression in neovascular AMD. PCV remains etiologically uncharacterized, and ongoing discussion is whether PCV and neovascular AMD share the same etiology or constitute two substantially different diseases. In this study, we investigated T-cell differentiation and aging profile in human patients with PCV, patients with neovascular AMD, and age-matched healthy control individuals. Fresh venous blood was prepared for flow cytometry to investigate CD4⁺ and CD8⁺ T-cell differentiation (naïve, central memory, effector memory, effector memory CD45ra⁺), loss of differentiation markers CD27 and CD28, and expression of aging marker CD56. Patients with PCV were similar to the healthy controls in all aspects. In patients with neovascular AMD we found significantly accelerated T-cell differentiation (more CD28^-CD27^- cells) and aging (more CD56⁺ cells) in the CD8⁺ T-cell compartment. These findings suggest that PCV and neovascular AMD are etiologically different in terms of T cell immunity, and that neovascular AMD is associated with T-cell immunosenescence.

High mobility group B1 up-regulates angiogenic and fibrogenic factors in human retinal pigment epithelial ARPE-19 cells

Hypoxia-induced retinal neovascularization plays a central role in the pathogenesis of diabetic retinopathy. This study aimed to investigate whether hypoxia leads to the release of nuclear high mobility group box 1 (HMGB1) peptides from cultured retinal pigment epithelial ARPE-19 cells, to determine the effect of HMGB1 on angiogenic cytokine production and elucidate the involved signaling pathways. A chemical hypoxia mimetic agent, cobalt chloride, induced SIRT1 downregulation, HMGB1 nucleocytoplasmic relocation and extracellular release from ARPE-19 cells, implicating its autocrine function. Resveratrol treatment significantly reduced secretion of HMGB1 from ARPE-19 cells exposed to hypoxia. Cell proliferation and cell cycle analyses demonstrated that exogenous HMGB1 caused significant growth suppression and G1 cell cycle arrest in ARPE-19 cells. Morphological observations showed that HMGB1 enhanced adhesion, but suppressed migration of ARPE-19 cells. More intriguingly, HMGB1 up-regulated expression of angiofibrogenic factors in ARPE-19 cells, including VEGF, bFGF, TGF-β2, and CTGF. Signal profiling characterization indicated that HMGB1 triggered hyperphosphorylation of Akt, p38 MAPK, and NF-κB, but not that of ERK, JNK, and Smad2, whereas inhibition of PI3K, MAPK, or NF-κB significantly attenuated the HMGB1-driven cytokine overproduction in ARPE-19 cells. Functional neutralization with anti-TLR4 and -RAGE antibodies confirmed that both receptors were involved in the cytokine overproduction. In conclusion, chemically-mimicked hypoxia induced nucleocytoplasmic relocation and release of HMGB1 peptides, which in turn up-regulated the production of angiofibrogenic factors in RPE cells, thereby contributing to the pathogenesis of hypoxia-associated diabetic retinopathies. Conversely, blockades of intraocular HMGB1 bioavailability or signal activation may prevent angiofibrogenesis in development of diabetic retinopathy.

Bis-Retinoid A2E Induces an Increase of Basic Fibroblast Growth Factor via Inhibition of Extracellular Signal-Regulated Kinases 1/2 Pathway in Retinal Pigment Epithelium Cells and Facilitates Phagocytosis

Age-related macular degeneration (ARMD) is the leading cause of vision loss in developed countries. Hallmarks of the disease are well known; indeed, this pathology is characterized by lipofuscin accumulation, is principally composed of lipid-containing residues of lysosomal digestion. The N-retinyl-N-retinylidene ethanolamine (A2E) retinoid which is thought to be a cytotoxic component for RPE is the best-characterized component of lipofuscin so far. Even if no direct correlation between A2E spatial distribution and lipofuscin fluorescence has been established in aged human RPE, modified forms or metabolites of A2E could be involved in ARMD pathology. Mitogen-activated protein kinase (MAPK) pathways have been involved in many pathologies, but not in ARMD. Therefore, we wanted to analyze the effects of A2E on MAPKs in polarized ARPE19 and isolated mouse RPE cells. We showed that long-term exposure of polarized ARPE19 cells to low A2E dose induces a strong decrease of the extracellular signal-regulated kinases' (ERK1/2) activity. In addition, we showed that A2E, via ERK1/2 decrease, induces a significant decrease of the retinal pigment epithelium-specific protein 65 kDa (RPE65) expression in ARPE19 cells and isolated mouse RPE. In the meantime, we showed that the decrease of ERK1/2 activity mediates an increase of basic fibroblast growth factor (bFGF) mRNA expression and secretion that induces an increase in phagocytosis via a paracrine effect. We suggest that the accumulation of deposits coming from outer segments (OS) could be explained by both an increase of bFGF-induced phagocytosis and by the decrease of clearance by A2E. The bFGF angiogenic protein may therefore be an attractive target to treat ARMD.

Progesterone analogue protects stressed photoreceptors via bFGF-mediated calcium influx

Retinitis pigmentosa (RP) is a degenerative retinal disease leading to photoreceptor cell loss. In 2011, our group identified the synthetic progesterone 'Norgestrel' as a potential treatment for RP. Subsequent research showed Norgestrel to work through progesterone receptor membrane component 1 (PGRMC1) activation and upregulation of neuroprotective basic fibroblast growth factor (bFGF). Using trophic factor deprivation of 661W photoreceptor-like cells, we aimed to further elucidate the mechanism leading to Norgestrel-induced neuroprotection. In the present manuscript, we show by flow cytometry and live-cell immunofluorescence that Norgestrel induces an increase in cytosolic calcium in both healthy and stressed 661Ws over 24 h. Specific PGRMC1 inhibition by AG205 (1 μm) showed this rise to be PGRMC1-dependent, primarily utilizing calcium from extracellular sources, for blockade of L-type calcium channels by verapamil (50 μm) prevented a Norgestrel-induced calcium influx in stressed cells. Calcium influx was also shown to be bFGF-dependent, for siRNA knock down of bFGF prevented Norgestrel-PGRMC1 induced changes in cytosolic calcium. Notably, we demonstrate PGRMC1-activation is necessary for Norgestrel-induced bFGF upregulation. We propose that Norgestrel protects through the following pathway: binding to and activating PGRMC1 expressed on the surface of photoreceptor cells, PGRMC1 activation drives bFGF upregulation and subsequent calcium influx. Importantly, raised intracellular calcium is critical to Norgestrel's protective efficacy, for extracellular calcium chelation by EGTA abrogates the protective effects of Norgestrel on stressed 661W cells in vitro.

Pharmacology of the retinal pigment epithelium, the interface between retina and body system

The retinal pigment epithelium (RPE) is a close, interactive partner to the photoreceptors as well as an interface with the endothelium of the choroid and thus with the body's circulatory system. To fulfill these roles, the RPE communicates with neighboring tissue by secretion of a large variety of factors and is able to react to secreted factors via a plethora of transmembrane receptors. Clinically relevant local pharmacological effects are caused by anti-VEGF-A treatment in choroidal neovascularization or by carboanhydrase inhibitors reducing fluid accumulation in the macula. Being exposed to the bloodstream, the RPE reacts to systemic disease, such as diabetes or hypertension, but also to systemic pharmacological intervention, for example to hypotensive drugs acting on the renin-angiotensin-system. Sustained pharmacological treatments, in particular, cause side effects at the RPE with consequences for both RPE function and photoreceptor survival. Among these are systemic inhibition of angiotensin-converting enzyme, insulin treatment in diabetes and anti-VEGF-A therapy. Given the special anatomical and functional relationships of the RPE, pharmacological intervention targeting either the eye or the body systemically should take potential alteration of RPE and subsequently photoreceptor function into account.

Ion Channels in the Eye: Involvement in Ocular Pathologies

The eye is the sensory organ of vision. There, the retina transforms photons into electrical signals that are sent to higher brain areas to produce visual sensations. In the light path to the retina, different types of cells and tissues are involved in maintaining the transparency of avascular structures like the cornea or lens, while others, like the retinal pigment epithelium, have a critical role in the maintenance of photoreceptor function by regenerating the visual pigment. Here, we have reviewed the roles of different ion channels expressed in ocular tissues (cornea, conjunctiva and neurons innervating the ocular surface, lens, retina, retinal pigment epithelium, and the inflow and outflow systems of the aqueous humor) that are involved in ocular disease pathophysiologies and those whose deletion or pharmacological modulation leads to specific diseases of the eye. These include pathologies such as retinitis pigmentosa, macular degeneration, achromatopsia, glaucoma, cataracts, dry eye, or keratoconjunctivitis among others. Several disease-associated ion channels are potential targets for pharmacological intervention or other therapeutic approaches, thus highlighting the importance of these channels in ocular physiology and pathophysiology.

Ocular transient receptor potential channel function in health and disease

Transient receptor potential (TRP) channels sense and transduce environmental stimuli into Ca(2+) transients that in turn induce responses essential for cell function and adaptation. These non-selective channels with variable Ca(2+) selectivity are grouped into seven different subfamilies containing 28 subtypes based on differences in amino acid sequence homology. Many of these subtypes are expressed in the eye on both neuronal and non-neuronal cells where they affect a host of stress-induced regulatory responses essential for normal vision maintenance. This article reviews our current knowledge about the expression, function and regulation of TRPs in different eye tissues. We also describe how under certain conditions TRP activation can induce responses that are maladaptive to ocular function. Furthermore, the possibility of an association between TRP mutations and disease is considered. These findings contribute to evidence suggesting that drug targeting TRP channels may be of therapeutic benefit in a clinical setting. We point out issues that must be more extensively addressed before it will be possible to decide with certainty that this is a realistic endeavor. Another possible upshot of future studies is that disease process progression can be better evaluated by profiling changes in tissue specific functional TRP subtype activity as well as their gene and protein expression.

Rab27a GTPase modulates L-type Ca2+ channel function via interaction with the II-III linker of CaV1.3 subunit

In a variety of cells, secretory processes require the activation of both Rab27a and L-type channels of the Ca(V)1.3 subtype. In the retinal pigment epithelium (RPE), Rab27a and Ca(V)1.3 channels regulate growth-factor secretion towards its basolateral side. Analysis of murine retina sections revealed a co-localization of both Rab27a and Ca(V)1.3 at the basolateral membrane of the RPE. Heterologously expressed Ca(V)1.3/β3/α2δ1 channels showed negatively shifted voltage-dependence and decreased current density of about 70% when co-expressed with Rab27a. However, co-localization analysis using α(5)β(1) integrin as a membrane marker revealed that Rab27a co-expression reduced the surface expression of Ca(V)1.3 only about 10%. Physical binding of heterologously expressed Rab27a with Ca(V)1.3 channels was shown by co-localization in immunocytochemistry as well as co-immunoprecipitation which was abolished after deletion of a MyRIP-homologous amino acid sequence at the II-III linker of the Ca(V)1.3 subunit. Rab27a over-expression in ARPE-19 cells positively shifted the voltage dependence, decreased current density of endogenous Ca(V)1.3 channels and reduced VEGF-A secretion. We show the first evidence of a direct functional modulation of an ion channel by Rab27a suggesting a new mechanism of Rab and ion channel interaction in the control of VEGF-A secretion in the RPE.

Bevacizumab modulates the process of fibrosis in vitro

BACKGROUND

Fibrosis is the most common side effect after anti-vascular epithelial growth factor (VEGF) therapy (intravitreal bevacizumab) for retinal or choroidal neovascularization. This study was to investigate the efficacy of bevacizumab on the expressions of fibrosis-related cytokines in human umbilical vein endothelial cells (HUVECs) in vitro.

METHODS

Cultured HUVECs were divided into groups of controls (group 1), hypoxia (group 2) and hypoxia combined with bevacizumab (group 3). No treatment was given in group 1. In group 2, cobalt(II) chloride (CoCl₂) (200 μm) was added to the medium. In group 3, in addition to CoCl₂, bevacizumab was mixed in the medium, with a final concentration of 0.25 mg/mL, roughly equal to the concentration used clinically. The expressions of connective tissue growth factor (CTGF), transforming growth factor-β₂ (TGF-β₂) and basic fibroblast growth factor-2 (bFGF-2) were evaluated by SYBR green real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay at 6 h, 12 h, 24 h and 48 h. Matrix metalloproteinases (MMP)-2 was detected by SYBR green real-time PCR and Western blotting at each time point.

RESULTS

Both messenger RNA and protein levels of CTGF, bFGF, TGF-β₂ and MMP-2 in group 2 were higher than group 1 (P < 0.05). In group 3, the expressions of CTGF, bFGF, TGF-β₂ and MMP-2 were upregulated compared with group 2 (P < 0.05).

CONCLUSIONS

Bevacizumab at clinical doses can exert pro-fibrotic effects on HUVECs by upregulating the expressions of CTGF, bFGF, TGF-β₂ and MMP-2. This may be involved in fibrosis after anti-VEGF therapy.

Trophic factors in the pathogenesis and therapy for retinal degenerative diseases

Trophic factors are endogenously secreted proteins that act in an autocrine and/or paracrine fashion to affect vital cellular processes such as proliferation, differentiation, and regeneration, thereby maintaining overall cell homeostasis. In the eye, the major contributors of these molecules are the retinal pigment epithelial (RPE) and Müller cells. The primary paracrine targets of these secreted proteins include the photoreceptors and choriocapillaris. Retinal degenerative diseases such as age-related macular degeneration and retinitis pigmentosa are characterized by aberrant function and/or eventual death of RPE cells, photoreceptors, choriocapillaris, and other retinal cells. We discuss results of in vitro and in vivo animal studies in which candidate trophic factors, either singly or in combination, were used in an attempt to ameliorate photoreceptor and/or retinal degeneration. We also examine current trophic factor therapies as they relate to the treatment of retinal degenerative diseases in clinical studies.

Pro-inflammatory and anti-angiogenic effects of bisphosphonates on human cultured retinal pigment epithelial cells

AIM

Bisphosphonates have been shown to induce ocular inflammatory diseases such as uveitis and scleritis, while being protective against angiogenic diseases like neovascular age-related macular degeneration (AMD). Therefore, we studied the effects of bisphosphonates on primary culture of human fetal retinal pigment epithelium (hRPE), a cell type known to secrete both inflammatory and angiogenic factors. Alendronate and etidronate were selected for this experiment as they are members of the two structurally different classes of bisphosphonates.

METHODS

Primary cultures of hRPE were serum-starved for 24 h and then treated for 24 h with alendronate (0.0001, 0.1, 100 µM) or etidronate (0.01, 1 µM). Cell viability was measured using the MTT assay. Investigation of secreted cytokines induced by bisphosphonates was performed using a human cytokine 29-Plex Panel (Bio-Plex) array and the results were analysed with an analysis of variance (ANOVA).

RESULTS

Etidronate, at the lower concentration, significantly increased the expression of interleukin (IL)-6 (p=0.03) and IL-8 (p=0.04). At the higher concentration, etidronate significantly decreased the expression of granulocyte macrophage colony-stimulating factor (p=0.02) and basic fibroblast growth factor (bFGF) (p=0.02). Alendronate, at the highest concentration, significantly increased the expression of IL-8 (p=0.02) and decreased the expression of eotaxin (p=0.02). Alendronate also significantly decreased the expression of bFGF at all concentrations (p<0.05) and demonstrated a trend towards decreasing vascular endothelial growth factor expression at low concentration.

CONCLUSIONS

Alendronate and etidronate display dose dependent effects in hRPE cells. Alendronate and etidronate administration resulted in concentration dependent elevations in inflammatory cytokines. Furthermore, alendronate and etidronate administration resulted in reduced expression of a number of angiogenic factors. These findings may explain the increased incidence of ocular inflammation as well as the therapeutic effect on neovascular AMD which have been described with bisphosphonates.

Directional protein secretion by the retinal pigment epithelium: roles in retinal health and the development of age-related macular degeneration

The structural and functional integrity of the retinal pigment epithelium (RPE) is fundamental for maintaining the function of the neuroretina. These specialized cells form a polarized monolayer that acts as the retinal–blood barrier, separating two distinct environments with highly specialized functions: photoreceptors of the neuroretina at the apical side and Bruch's membrane/highly vascularized choriocapillaris at the basal side. The polarized nature of the RPE is essential for the health of these two regions, not only in nutrient and waste transport but also in the synthesis and directional secretion of proteins required in maintaining retinal homoeostasis and function. Although multiple malfunctions within the RPE cells have been associated with development of age-related macular degeneration (AMD), the leading cause of legal blindness, clear causative processes have not yet been conclusively characterized at the molecular and cellular level. This article focuses on the involvement of directionally secreted RPE proteins in normal functioning of the retina and on the potential association of incorrect RPE protein secretion with development of AMD. Understanding the importance of RPE polarity and the correct secretion of essential structural and regulatory components emerge as critical factors for the development of novel therapeutic strategies targeting AMD.

NCAM function in the adult brain: lessons from mimetic peptides and therapeutic potential

Neural cell adhesion molecules (NCAMs) are complexes of transmembranal proteins critical for cell-cell interactions. Initially recognized as key players in the orchestration of developmental processes involving cell migration, cell survival, axon guidance, and synaptic targeting, they have been shown to retain these functions in the mature adult brain, in relation to plastic processes and cognitive abilities. NCAMs are able to interact among themselves (homophilic binding) as well as with other molecules (heterophilic binding). Furthermore, they are the sole molecule of the central nervous system undergoing polysialylation. Most interestingly polysialylated and non-polysialylated NCAMs display opposite properties. The precise contributions each of these characteristics brings in the regulations of synaptic and cellular plasticity in relation to cognitive processes in the adult brain are not yet fully understood. With the aim of deciphering the specific involvement of each interaction, recent developments led to the generation of NCAM mimetic peptides that recapitulate identified binding properties of NCAM. The present review focuses on the information such advances have provided in the understanding of NCAM contribution to cognitive function.

Basic fibroblast growth factor protects C17.2 cells from radiation-induced injury through ERK1/2

AIMS

To establish a radiation-induced neural injury model using C17.2 neural stem cells (NSCs) and to investigate whether basic fibroblast growth factor (bFGF) can protect the radiation-induced injury of C17.2 NSCs. Furthermore, we aim to identify the possible mechanisms involved in this model.

METHODS

C17.2 NSCs received a single exposure (3, 6, and 9 Gy, respectively) at a dose rate of 300 cGy/min with a control group receiving 0 Gy. Different concentrations of bFGF were added for 24 h, 5 min postirradiation. The MTS assay and flow cytometry were used to detect cytotoxicity and apoptosis. Expression of FGFR1, ERK1/2, and p-ERK1/2 proteins was detected with or without U0126 was pretreated prior to C17.2 NSCs receiving irradiation.

RESULTS

C17.2 NSCs showed a dose-dependent cell death as the dose of radiation was increased. Additionally, the rate of apoptosis in the C17.2 NSCs reached 31.2 ± 1.23% in the 6 Gy irradiation group, which was the most significant when compared to the other irradiation treated groups. bFGF showed protective effect on cell apoptosis in a dose-dependent manner. The mean percentage of apoptotic cells decreased to 7.83 ± 1.75% when 100 ng/mL bFGF was given. Furthermore, U0126 could block the protective effect of bFGF by inhibiting the phosphorylation of ERK1/2.

CONCLUSIONS

An in vitro cellular model of radiation-induced apoptosis of NSCs, in C17.2 NSCs, was developed successfully. Additionally, bFGF can protect neurons from radiation injury in vitro via the ERK1/2 signal transduction pathway.

Neural cell adhesion molecule differentially interacts with isoforms of the fibroblast growth factor receptor

The fibroblast growth factor receptor (FGFR) can be activated through direct interactions with various fibroblast growth factors or through a number of cell adhesion molecules, including the neural cell adhesion molecule (NCAM). We produced recombinant proteins comprising the ligand-binding immunoglobulin-like modules 2 and 3 of FGFR1b, FGFR1c, FGFR2b, FGFR2c, FGFR3b, FGFR3c, and FGFR4, and found that all FGFR isoforms, except for FGFR4, interacted with NCAM. The binding affinity of NCAM-FGFR interactions was considerably higher for splice variant 'b' than for splice variant 'c'. We suggest that the expression pattern of various FGFR isoforms determines the cell context-specific effects of NCAM signaling through FGFR.

HTRA1 in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of severe visual impairment and irreversible blindness in most developed countries, affecting more than 50 million of elderly people worldwide. Current treatments, such as intravitreal injection of antiangiogenic agents, mitigate the effect of advanced AMD but cannot completely cure the disease. Comprehensive understanding of the AMD pathological mechanisms is important for the development of new therapies. Previously, we identified a single-nucleotide polymorphism (rs11200638) in the promoter region of the high temperature requirement factor A1 (HTRA1) gene on chromosome 10q26 to be associated with exudative AMD. In further biological studies, we have provided evidence that HTRA1 could be a potential disease-causing gene within the 10q26 locus. In this review, we summarize the pathology of AMD and the molecular function of the HtrA1 protein. Also evaluated are the genetic effects of HTRA1 polymorphism on AMD in different populations and interactions with other AMD-associated genes, especially with the complement factor H (CFH) gene, which was identified for nonexudative AMD. The biological roles of HtrA1 are exhaustively examined on its contribution to the multifactorial pathogenic mechanism of AMD. Although HtrA1 should play a part in AMD pathogenesis, a host of other genetic and environmental factors, known and unknown, is involved and warrants intensive future research.

Mediators of ocular angiogenesis

Angiogenesis is the formation of new blood vessels from pre-existing vasculature. Pathologic angiogenesis in the eye can lead to severe visual impairment. In our review, we discuss the roles of both pro-angiogenic and anti-angiogenic molecular players in corneal angiogenesis, proliferative diabetic retinopathy, exudative macular degeneration and retinopathy of prematurity, highlighting novel targets that have emerged over the past decade.

Building a fly eye: terminal differentiation events of the retina, corneal lens, and pigmented epithelia

In the past, vast differences in ocular structure, development, and physiology throughout the animal kingdom led to the widely accepted notion that eyes are polyphyletic, that is, they have independently arisen multiple times during evolution. Despite the dissimilarity between vertebrate and invertebrate eyes, it is becoming increasingly evident that the development of the eye in both groups shares more similarity at the genetic level than was previously assumed, forcing a reexamination of eye evolution. Understanding the molecular underpinnings of cell type specification during Drosophila eye development has been a focus of research for many labs over the past 25 years, and many of these findings are nicely reviewed in Chapters 1 and 4. A somewhat less explored area of research, however, considers how these cells, once specified, develop into functional ocular structures. This review aims to summarize the current knowledge related to the terminal differentiation events of the retina, corneal lens, and pigmented epithelia in the fly eye. In addition, we discuss emerging evidence that the different functional components of the fly eye share developmental pathways and functions with the vertebrate eye.

Differences in the temporal expression of regulatory growth factors during choroidal neovascular development

Although the roles of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hepatocyte growth factor (HGF) in pathologic neovascularization have been well characterized in certain tissues, their particular functions and expression patterns in choroidal neovascularization (CNV) have not been clearly established. After localized laser trauma to Bruch's membrane to induce CNV development, the temporal changes in mRNA and protein expression of these 3 cytokines were documented and compared histologically to areas of immunofluorescence, the proliferation of endothelial cells, neovascular development, and temporal changes in vascular permeability. Changes in mRNA and protein levels of bFGF and HGF occurred quickly and reached peak expression within hours. This activity corresponded in time to intense and localized immunofluorescence for these cytokines within the choriocapillaris within laser lesion sites. During this same initial time period, mRNA upregulation of VEGF occurred, primarily within the neural retina and this expression corresponded to intense immunolabeling of Müller cells immediately adjacent to the lesion sites. By 3 days after lasering, increased VEGF(164) protein expression was measurable, whereas early neovascular development histologically corresponded to HGF and bFGF mRNA expansion into the developing choroidal neovascular membrane (CNVM). At 7 days, CNV expansion, maturation, and increased vascular permeability corresponded to peak VEGF mRNA and protein expression and to immunofluorescence of the CNVM. Differences also occurred in the expression of precursor and activated isoforms of these cytokines in the retinal pigment epithelium/choroid as compared to those in the retina. These molecular and immunocytochemical results suggest that bFGF and HGF may be important as initial regulators neovascularization in this CNV model; whereas VEGF may be important during later phases of angiogenesis and neovascular hyperpermeability.

Geldanamycin, a HSP90 inhibitor, attenuates the hypoxia-induced vascular endothelial growth factor expression in retinal pigment epithelium cells in vitro

Hypoxia is the most common factor contributing to the pathogenesis of choroidal neovascularization, which is the major cause for blindness and occurs in proliferative diabetic retinopathy and age-related macular degeneration. The purpose of this study is to investigate the role of retinal pigment epithelial (RPE) cells in the regulation of subretinal neovascularization under hypoxia and the possible function of a heat shock protein 90 (HSP90) inhibitor, geldanamycin (GA), in the regulation of VEGF expression. An in vitro hypoxic experimental model was used to mimic the ischemic microenvironment of RPE cells. The cell growth was measured by proliferation assay and the morphological observation was documented by microscope. The gene expression of VEGF, hsp70, hsp90alpha and hsp90beta were measured using semi-quantitative RT-PCR. The VEGF release from RPE cells were detected by ELISA. No alteration in growth rate and cell morphology under 1% O(2) condition for 24h was noticed. The proangiogenic growth factor VEGF, but not bFGF, released from hypoxia-treated cells were significantly higher than those of normoxic controls. A similar tendency of VEGF(165) isoform gene expression, detected by RT-PCR, was noticed in hypoxia-treated cells. Heat shock pretreatment elevated hsp70 and VEGF(165) gene expression and augmented the hypoxia-induced VEGF gene expression and protein release. Pretreatment with GA can significantly suppress the hypoxia-induced VEGF gene expression in and peptide release from RPE cells. These in vitro findings suggest that HSP90 inhibitors could be considered as novel anti-angiogenesis agents for diseases with intraocular neovascularization.

Growth hormone, VEGF and FGF: involvement in rheumatoid arthritis

Adult rheumatoid arthritis (RA), a systemic autoimmune disorder of unknown etiology, is characterized by dysfunctional cellular and humoral immunity, enhanced migration and attachment of peripheral macrophages and pro-inflammatory leukocytes to the synovium and articular cartilage of diarthrodial joints. The progressive destruction of cartilage and bone in RA is a result of elevated pro-inflammatory cytokine gene expression, synovial neovascularization, proteinase-mediated dissolution of articular cartilage matrix and osteoclast-mediated subchondral bone resorption. Juvenile chronic arthritis (JCA) is disease with manifestations similar to adult RA that occurs in childhood. JCA usually causes precocious joint destruction and often also presents with evidence of growth plate anomalies and reduced stature. Three proteins play an integral role in both adult RA and JCA. These are somatotropin (also called pituitary growth hormone (GH)), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). GH is responsible for regulating long bone growth and skeletal maturation through its capacity to stimulate insulin-like growth factor-I (IGF-1) synthesis by hepatocytes. Mechanisms responsible for growth plate disturbances and short stature in children with JCA include deficient GH production, GH-insensitivity resulting from defects in the GH receptor, suppressed IGF-1 synthesis or neutralization of IGF-1 action by IGF-1 binding proteins (IGFBPs). In addition, GH has also been implicated in perpetuating inflammation and pain in adult RA. VEGF has been shown to be the critical angiogenesis factor responsible for vascular proliferation and blood vessel invasion of the synovial lining membrane in RA. Acidic FGF (FGF-1) and basic FGF (FGF-2) have also been implicated in aberrant synoviocyte proliferation (i.e. synovial hyperplasia) and apoptosis resistance in adult RA.