In vitro evaluation of bevacizumab toxicity on a retinal ganglion cell line

Zoledronic Acid, Bevacizumab and Dexamethasone-Induced Apoptosis, Mitochondrial Oxidative Stress, and Calcium Signaling Are Decreased in Human Osteoblast-Like Cell Line by Selenium Treatment

Increased intracellular free calcium ion (Ca²⁺) concentration induces excessive oxidative stress and apoptosis. Medical procedures such as zoledronic acid (Zol), bevacizumab (Bev), and dexamethasone (Dex) are usually used in the treatment of bone diseases (osteoporosis, Paget's disease, etc.) and to prevent metastasis in the bone although the procedures induce osteonecrosis of the jaw through excessive production of reactive oxygen species (ROS). Recently, we observed regulator roles of selenium (Se) on apoptosis and Ca²⁺ entry through transient receptor potential vanilloid 1 (TRPV1) channels in the cancer cell lines. Therefore, Se may modulate Zol, Bev, and Dex-induced oxidative stress and apoptosis through regulation of TRPV1 channel. In the current study, we investigated the protective effects of Se on apoptosis and oxidative stress through TRPV1 in Zol, Bev, and Dex-induced osteoblast-like cell line. We used human osteoblast-like cell line (Saos-2), and the cells were divided into 12 groups as control, Zol, Bev, Dex, Se, Zol+Se, Bev+Se, Dex+Se, Zol+Dex, Zol+Dex+Se, Zol+Bev, and Zol+Bev+Se which were incubated with drugs (Zol, Bev, Dex, and Se) for 24 h. The cytosolic free Ca²⁺ concentration was increased by Zol, Bev, Dex, Zol+Bev, and Zol+Dex, although it was reduced by Se treatment. However, Zol, Bev, and Dex-induced increase in apoptosis, caspase 3, caspase 9, poly (ADP-ribose) polymerase 1 expression levels, and intracellular ROS production values in the cells were decreased by Se treatments. In conclusion, we observed that Zol, Bev, and Dex-induced apoptosis, mitochondrial oxidative stress, and calcium signaling are decreased in human osteoblast-like cell line by the Se treatment. Our findings may be relevant to the etiology and treatment of Zol, Bev, and Dex-induced osteonecrosis by Se.

Characterization of Vitreous and Aqueous Proteome in Humans With Proliferative Diabetic Retinopathy and Its Clinical Correlation

Aims:

Proliferative diabetic retinopathy (PDR) is associated with microvascular complications that cause biochemical changes in the human retina and alter the proteome of vitreous humor and aqueous humor (AH).

Methods:

Human vitreous humor and AH of PDR subjects were collected. Subjects who had surgery for epiretinal membrane or macular hole served as controls. Protein profiles were obtained and analyzed after running the samples on a liquid chromatography-mass spectrometry/mass spectrometry.

Results:

In vitreous humor, 16 unique proteins were noted in PDR patients, but not in controls. Those were associated mainly with coagulation, complement, and kallikrein-kinin systems. Under coagulation, fibrinogen and prothrombin proteins were more evident and may emphasize the importance of angiogenesis in the development of PDR. Vitreous proteins showed replicative presence in AH too. As for AH samples, we detected 10 proteins found in PDR patients, which were related to transport, coagulation, and inflammatory responses.

Conclusions:

We found 57 proteins in human vitreous and 39 proteins in AH. Identification of these proteins that are involved in various pathways will be helpful to understand diabetic retinopathy pathogenesis and to develop proteome as a biomarker for PDR.

Morphological changes in spectral domain optical coherence tomography guided bevacizumab injections in wet age-related macular degeneration, 12-months results

Purpose:

To describe retinal changes during Spectral Domain Optical Coherence Tomography (SD-OCT) guided bevacizumab treatment for neovascular age- related macular degeneration (AMD).

Settings and Design:

Single center observational study.

Materials and Methods:

We confirmed wet AMD in 47 eyes of 45 patients by fluorescein angiography and SD-OCT. After bevacizumab injection, we examined the patients at 4-week intervals. During each follow-up control, we performed SD-OCT and a complete ophthalmic examination. Criteria for reinjection were visual acuity loss of more than five ETDRS letters, and/or increase of central retinal thickness, sub-retinal fluid, intra-retinal fluid, pigment epithelium detachment. If reinjection criteria were not met, we advised the patient to return in 4 weeks’ time for the next scheduled follow-up. We used 3-dimensional SD-OCT to measure photoreceptor defects and sub-retinal fibrosis. The main efficacy endpoints were the SD-OCT measurements of the size of photoreceptor defects, the size of external membrane defects and the central retinal thickness.

Results:

Over the 12 months study period, the percentage of scans in 3-D imaging mode showing visible defects of the junction between inner and outer segments of photoreceptors increased from 38.96 to 53.8%. The percentage of scans in 3-D imaging mode with visible sub-retinal fibrosis increased from 33 to 52% and mean central retinal thickness decreased from 333 μm (96-900 μm) to 272 μm (P = 0.011).

Conclusion:

In long-term anti- Vascular endothelial growth factor (VEGF) treatment for neovascular AMD, photoreceptor defects and fibrosis progress despite a decrease in central retinal thickness and improvements in visual acuity. We would encourage further discussion as to whether this is the natural course of the disease or a result of the treatment.

Bevacizumab treatment reduces retinal neovascularization in a mouse model of retinopathy of prematurity

AIM

To evaluate the effect of different bevacizumab concentrations on retinal neovascularization in a retinopathy of prematurity (ROP) mouse model.

METHODS

A total of 60 of C57BL/6 J mice were exposed to 75%±2% oxygen from postnatal d7 to postnatal d12. Fifteen nonexposed mice served as negative controls (group A). On d12, 30 mice (group C) were injected with 2.5 µg intravitreal bevacizumab (IVB), 30 mice (group D) were injected with 1.25 µg IVB in one eye. The contralateral eyes were injected with balanced salt solution (BSS) (control group=group B). The adenosine diphosphatase (ADPase) histochemical technique was used for retinal flat mount to assess the oxygen-induced changes of retinal vessels. Neovascularization was quantified by counting the endothelial cell proliferation on the vitreal side of the inner limiting membrane of the retina. Histological changes were examined by light microscopy. The mRNA levels of vascular endothelial growth factor (VEGF) were quantified by Real-time PCR. Western-blotting analysis was performed to examine the expression of P-VEGFR.

RESULTS

Comparing with the control group B, regular distributions and reduced tortuosity of vessels were observed in our retinal flat mounts in groups C and D. The endothelial cell count per histological section was lower in groups C (P<0.0001) and D (P<0.0001) compared with the control group B. Histological evaluation showed no retinal toxicity in any group. In all oxygen treated groups VEGF mRNA expression was significantly increased as compared to age-matched controls. No significant change in VEGF mRNA expression could be achieved in either of the treatments or the oxygen controls. The results of the Western blot were consistent with that of the Real-time PCR analysis.

CONCLUSION

An intravitreal injection of Bevacizumab is able to reduce angioproliferative retinopathy in a mouse model for oxygen-induced retinopathy.

Pharmacokinetics, pharmacodynamics and pre-clinical characteristics of ophthalmic drugs that bind VEGF

Drugs that prevent the binding of VEGF to its trans-membrane cognate receptors have revolutionized the treatment of the most important chorioretinal vascular disorders: exudative age-related macular degeneration, diabetic macular edema, and retinal vein occlusions. Pegaptanib, which binds to VEGF165 and longer isoforms, ranibizumab and bevacizumab, which bind all VEGF-A isoforms, and aflibercept, which binds VEGF-A, VEGF-B, and placental growth factor, all bind VEGF165 with high affinity. The drugs have relatively long half-lives (7 to 10 days) after intravitreal depot injections and clinical durations of action that usually exceed 4 weeks. Plasma VEGF concentrations decrease after intravitreal injections of bevacizumab and aflibercept because their systemic half-lives are extended by their Fc fragments. Extensive in vitro and in vivo testing shows that the drugs prevent VEGF-mediated activation of endothelial cells while exhibiting little evidence of toxicity. Further anti-VEGF drug development is on-going.

Structural consequences after intravitreal bevacizumab injection without increasing apoptotic cell death in a retinopathy of prematurity mouse model

PURPOSE

To evaluate the effect of different bevacizumab concentrations on retinal endothelial cell proliferation, retinal structures and apoptotic activity after intravitreal injection in a retinopathy of prematurity (ROP) mouse model.

METHODS

A total of 35 of C57BL/J6 mice were exposed to 75±2% oxygen from postnatal day 7 to postnatal day 12. On day 12, 10 mice (group C) were injected with 2.5 μg intravitreal bevacizumab (IVB), 11 mice (group D) were injected with 1.25 μg IVB, and 14 mice (group E) were injected with 0.625 μg IVB in one eye. The contralateral eyes were injected with isotonic saline (control group=group B). Four nonexposed mice served as negative controls (group A). Neovascularization was quantified by counting the endothelial cell proliferation on the vitreal side of the inner limiting membrane of the retina. Histological and ultrastructural changes were examined by light and electron microscopy. Terminal deoxynucleotidyl transferase deoxy-UTP-nick end labelling (TUNEL) was used to detect apoptosis.

RESULTS

The endothelial cell count per histological section was lower in groups C (p<0.0001), D (p<0.0001) and E (p<0.0001) compared with the control group B. Histological evaluation showed no retinal toxicity in any group. Electron microscopy revealed hyperoxia-induced mitochondrial dysmorphology in group B. Mitochondrial dysmorphology displayed dose-dependent gradual increase in IVB-injected eyes. Intravitreal bevacizumab induced no significant increase in apoptotic cell death.

CONCLUSION

Bevacizumab suppresses endothelial cell proliferation in a ROP mouse model. In addition to hyperoxia-induced mitochondrial dysmorphology of C57BL/J6 retina, morphological findings implicate further mitochondrial vulnerability because of bevacizumab without increase in apoptotic cell death.

Reduced occurrence of programmed cell death and gliosis in the retinas of juvenile rabbits after shortterm treatment with intravitreous bevacizumab

OBJECTIVE

Bevacizumab has been widely used as a vascular endothelial growth factor antagonist in the treatment of retinal vasoproliferative disorders in adults and, more recently, in infants with retinopathy of prematurity. Recently, it has been proposed that vascular endothelial growth factor acts as a protective factor for neurons and glial cells, particularly in developing nervous tissue. The purpose of this study was to investigate the effects of bevacizumab on the developing retinas of juvenile rabbits.

METHODS

Juvenile rabbits received bevacizumab intravitreously in one eye; the other eye acted as an untreated control. Slit-lamp and fundoscopic examinations were performed both prior to and seven days after treatment. At the same time, retina samples were analyzed using immunohistochemistry to detect autophagy and apoptosis as well as proliferation and glial reactivity. Morphometric analyses were performed, and the data were analyzed using the Mann-Whitney U test.

RESULTS

No clinical abnormalities were observed in either treated or untreated eyes. However, immunohistochemical analyses revealed a reduction in the occurrence of programmed cell death and increases in both proliferation and reactivity in the bevacizumab-treated group compared with the untreated group.

CONCLUSIONS

Bevacizumab appears to alter programmed cell death patterns and promote gliosis in the developing retinas of rabbits; therefore, it should be used with caution in developing eyes.

Preclinical aspects of anti-VEGF agents for the treatment of wet AMD: ranibizumab and bevacizumab

Three anti-vascular endothelial growth factor (VEGF) therapies are currently used for the treatment of patients with wet age-related macular degeneration (AMD): pegaptanib, ranibizumab, and bevacizumab. Ranibizumab is an antibody fragment approved for the treatment of wet AMD. Bevacizumab is a full-length antibody registered for use in oncology but unlicensed for wet AMD. However, it is used off-label worldwide not only for wet AMD but also for various other ocular diseases associated with macular edema and abnormal vessel growth. We consider aspects of ranibizumab and bevacizumab in relation to their molecular characteristics, in vitro and in vivo properties, and preclinical safety data. Before 2009, most studies described the short-term toxicity of bevacizumab in multiple cell types of the eye. Since 2009, an increasing number of studies have compared the properties of ranibizumab and bevacizumab and investigated their impact on retinal cell functioning. Compared with bevacizumab, ranibizumab neutralizes VEGF better at low concentrations, maintains efficacy for longer, and has a higher retinal penetration and potency. Studies in animals demonstrate ranibizumab to be better localized to the injected eye, whereas bevacizumab appears to have a greater effect in the fellow eye. In humans, a localized and systemic effect has been reported for both molecules. In conclusion, overlapping yet distinct pharmacological properties of ranibizumab and bevacizumab indicate that safety or efficacy data from one cannot be extrapolated to the other.

Luteolin and gefitinib regulation of EGF signaling pathway and cell cycle pathway genes in PC-3 human prostate cancer cells

cRNA microarray and real-time PCR (qPCR) studies from our lab identified five Cell Cycle Pathway (CCP) genes (CCNA2, CCNE2, CDC25A, CDKN1B, and PLK-1) as targets for luteolin in PC-3 prostate cancer cells [Shoulars et al., J. Steroid Biochem. Mol. Biol. 118 (2010) 41-50]. In this paper, Ingenuity Pathway Analysis of the microarray data identified 7 luteolin-regulated genes (EGFR, c-Fos, SOS, GRB2, JNK1, MKK4 and RasGAP) in the Epidermal Growth Factor Signaling Pathway (EGFSP) potentially involved in luteolin regulation of CCP genes and cell proliferation. To address these possibilities, we compared the response profiles (RNA and protein) of these EGFSP and CCP genes to luteolin and gefitinib by real-time PCR (qPCR) and Western blot analyses. Luteolin and gefitinib are known antagonists of EGFR-associated tyrosine protein kinase. Thus, the response profiles of EGFR regulated EGFSP or CCP genes should be very similar if genes in both pathways are controlled through this common mechanism of action. Treatment of PC-3 cell with luteolin for 24h caused a 4-fold stimulation of c-Fos gene expression, significant inhibition (p<0.001) of the CCP genes and G2/M arrest. Treatment of PC-3 cells with gefitinib also inhibited most of the CCP genes in a fashion similar to that of luteolin, however, the EGFR antagonist inhibited c-Fos gene expression, stimulated CDKN1B (p27) and arrested the cells in G0/G1. Thus, although the response patterns of most of the CCP genes to luteolin or gefitinib were similar, the effects of the two compounds on EGFSP gene expression and cell cycle arrest were clearly different. Combination studies revealed that the response of EGFSP genes to luteolin was not affected by gefitinib, even though the two compounds were additive with respect to their abilities to inhibit CCNA2, CCNE2, CDC25A and PCNA. These findings suggest that luteolin and gefitinib regulate CCP gene expression through a common mechanism involving EGFR-associated tyrosine kinase. Conversely, luteolin regulates PC-3 cell proliferation through an EGFR-tyrosine kinase independent mechanism(s), likely involving the epigenetic control of gene EGFSP gene expression through histone H4 binding interactions resulting in the upregulation of c-Fos and p21 gene expression.

Evaluation of differential toxicity of varying doses of bevacizumab on retinal ganglion cells, retinal pigment epithelial cells, and vascular endothelial growth factor-enriched choroidal endothelial cells

PURPOSE

To evaluate in vitro the effects of bevacizumab, an anti-vascular endothelial growth factor (VEGF) antibody, on retinal pigment epithelial cells (RPE) and retinal ganglion cells (RGC), at doses that were inhibitory to VEGF-enriched choroidal endothelial cells (CEC).

METHODS

Monkey CEC (RF6A), human RPE cells (ARPE-19), and rat RGC (RGC-5) were exposed for 24 h to increasing doses of bevacizumab. Cell numbers were quantified with WST-1 assay. Cell death was assessed using propidium iodide (PI) staining via flow cytometry and fluorescent microscopy.

RESULTS

Bevacizumab was inhibitory to RF6A at 2.0 mg/mL (P < 0.005). No effect on cell viability was noted on ARPE-19 and RGC-5 cell lines at this particular dose of bevacizumab. These results were supported by fluorescent microscopy of PI-stained cells.

CONCLUSIONS

VEGF-stimulated proliferation of CEC was inhibited by bevacizumab. Bevacizumab was not cytotoxic to human RPE and rat RGC in vitro at a dose that is inhibitory to monkey CEC.

Prediction of diabetic retinopathy: role of oxidative stress and relevance of apoptotic biomarkers

Diabetic retinopathy (DR) is the foremost cause of blindness in working-aged worldwide; it is characterized by vascular and neuronal degeneration. Features of DR include leukocyte adhesion, increased vascular permeability, neovascularization and neuronal cell death. Early diagnosis and intervention are important to prevent or at least ameliorate the development of DR. Recent reports indicate that pathophysiological mechanisms leading to diabetic retinopathy include oxidative stress and retinal cell death cascades. Circulating biomarkers of oxidative stress such as malondialdehyde (MDA), thiobarbituric acid reacting substances (TBARS), conjugated diene (CD), advanced oxidation protein products (AOPP), protein carbonyl, 8-hydroxydeoxyguanosin (8-OHdG), nitrotyrosine, and F(2) isoprostanes and pro-apoptosis molecules (caspase-3, Fas, and Bax) are associated with increased susceptibility to develop DR in diabetic subjects. Thus, identification of oxidative stress and cell death biomarkers in diabetic patients could be in favor of predicting, diagnosis, and prevention of DR, and to target for novel therapeutic interventions.