EFFECTS OF INTRAVITREAL BEVACIZUMAB IN REPEATED DOSES: An Experimental Study

Evaluating the safety of intracameral bevacizumab application using oxidative stress and apoptotic parameters in corneal tissue

AIM

To investigate the possible effects of intracameral bevacizumab on oxidative stress parameters and apoptosis in corneal tissue.

METHODS

In total, 30 rats were assigned randomly into the following three groups of 10 rats each: a sham group (Group 1; n=10), a control group [Group 2; balanced salt solution (BSS) was administered at 0.01 mL; n=10], and a treatment group (Group 3; bevacizumab was administered at 0.25 mg/0.01 mL; n=10). The total antioxidant status (TAS) and the total oxidant status (TOS) in the corneal tissue and blood samples were measured, and the oxidative stress index (OSI) was calculated. Additionally, corneal tissue histopathology was evaluated for caspase-3 and -8 staining and apoptotic activity.

RESULTS

In the blood samples, the TAS, TOS, and OSI levels were not significantly different (all P>0.05). Compared with the sham and control groups, the TOS and OSI levels in the corneal tissues were significantly different in the bevacizumab group (all P<0.05). No statistically significant differences were observed between the sham and control groups (all P>0.05). However, compared with the sham and control groups, greater immunohistochemical staining for caspases-3 and -8 and an elevated level of apoptotic activity were observed in the bevacizumab group.

CONCLUSION

This study revealed that intracameral bevacizumab injections seemed to be systemically safe but may have elicited local toxic effects in the corneal tissue, as indicated by the oxidative stress parameters and histopathological evaluations.

Functional and morphological effects of systemic bevacizumab on cancer patients' eyes

PURPOSE

To evaluate the morphological and functional short-term effects of systemic bevacizumab on healthy eyes of cancer patients morphologically and functionally.

METHODS

The patients who underwent a chemotherapy regimen because of colon, lung, and breast cancer at the Department of Medical Oncology of the Gazi University School of Medicine between years 2010 and 2012 were included. All patients were administrated intravenous bevacizumab in three different dosages (5, 7.5, and 15 mg/kg per day) at 2- or 3-week intervals and a total of 6 to 18 courses in addition to regimens based on 5-fluorouracil, oxaliplatin, and irinotecan. After baseline ophthalmologic examination, patients were examined after the first course of chemotherapy and at the end of the protocol. Ophthalmologic evaluations included best-corrected visual acuity, color vision assessment, and ocular examinations with optical coherence tomography.

RESULTS

Thirty-four eyes of 17 patients were enrolled. The mean (±SD) age of the patients was 53.64 (±11.09) years and median follow-up time was 9 months (range, 4 to 18 months). Seventy-six percent of the patients were diagnosed as having colon cancer and no significant change was identified in functional assessments such as best-corrected visual acuity or color vision or in morphological examinations with optical coherence tomography (central foveal thickness and retinal nerve fiber layer thickness parameters). Patients were divided into three groups based on the dosage of systemic bevacizumab infusions, and correlation between time-dependent changes in central foveal thickness, retinal nerve fiber layer thickness, and bevacizumab dosage was investigated and no significant correlation was detected.

CONCLUSIONS

Repeated doses of systemic bevacizumab did not cause a deleterious effect on healthy eyes of cancer patients clinically, but further studies including histologic and biochemical analysis need to be conducted to reveal possible adverse effects.

Short term apoptotic activity of intravitreal bevacizumab on rabbit retina

AIM

To evaluate the safety and the short term apoptotic activity of intravitreal bevacizumab in rabbit eyes by histopathological analysis.

METHODS

Twenty-eight eyes of 14 rabbits were divided into three groups: 8 rabbits in group 1 and 3 rabbits in each of group 2 and group 3. Intravitreal bevacizumab (1.25mg/0.05mL) was applied to the right eyes of each subject in group 1 and group 2 (11 eyes) and the same volume of saline was applied to the left eyes of each subject in group 1 and group 3 (11 eyes). The left eyes in group 2 and the right eyes in group 3 were left untreated and used as control. Enucleated eyes were used for histopathologic analyses.

RESULTS

After immunohistochemical staining with caspase-3 and p53, there was no histological evidence of toxicity to the retina and the optic nerve in any of the sections that were analyzed in all three groups. In addition, vascular endothelial cells located at the retina and the optic nerve tissues in all groups showed a similar staining pattern with caspase-3 and p53.

CONCLUSION

Our study showed that intravitreal bevacizumab with the dose of 1.25mg/0.05mL caused no histological signs of toxicity or apoptotic activity on the rabbit retina.

Intravitreal bevacizumab effects on VEGF levels in distant organs: an experimental study

PURPOSE

The aim of this study was to determine the effects of single-dose intravitreal bevacizumab on the levels of vascular endothelial growth factor (VEGF) in serum and distant organs.

METHODS

Adult New Zealand albino rabbits (n = 40) were divided into experimental and control groups. Experimental rabbits received a single 0.05 ml intravitreal injection of 1.25 mg bevacizumab (Avastin) into the right eye, and control rabbits (n = 8) received no injection. Following injection, group 1 rabbits (n = 8) were sacrificed on day 1, group 2 rabbits (n = 8) on day 7, group 3 rabbits (n = 8) on day 14, and group 4 rabbits (n = 8) on day 28; control rabbits were sacrificed on day 28. After sacrifice, samples of brain, heart, liver, kidney and blood were collected. Levels of VEGF in serum and tissue were measured using enzyme-linked immunosorbent assay. The presence of bevacizumab was evaluated by immunofluorescence staining in tissues.

RESULTS

Positive bevacizumab immunoreactivity was observed in brain, heart and kidney. Serum VEGF levels significantly decreased in groups 3 and 4 compared with controls (p < 0.05). Liver VEGF levels significantly decreased in group 3 compared with controls (p < 0.05).

CONCLUSIONS

Intravitreal bevacizumab not only may escape from the blood-retinal barrier and enter the general circulation, but also may be disseminated to distant organs. Our study demonstrates that a single dose of intravitreally injected bevacizumab decreases VEGF levels in serum and liver.

Effects of multiple intravitreal anti-VEGF injections on retinal nerve fiber layer and intraocular pressure: a comparative clinical study

AIM

To determine the effect of multiple injections of ranibizumab or bevacizumab on retinal nerve fiber layer (RNFL) and intraocular pressure (IOP) in patients with age-related macular degeneration (AMD).

METHODS

This retrospective study includes 35 eyes of 35 patients treated with intravitreal bevacizumab (IVB, 1.25mg/0.05mL) and 30 eyes of 30 patients with intravitreal ranibizumab (IVR, 0.5mg/0.05mL) who had Fast RNFL analysis (Stratus™); IOP measurements were taken 30 minutes and 24 hours after each injection.

RESULTS

The mean ages were 68.0±7.5 and 69.1±7.7 years in the IVR and IVB groups, respectively (P=0.55). They underwent (6.3±1.9) and (5.1±1.3) injections (P=0.07) over (13.6±2.1) and (14.05±2.6) months (P=0.45) in the IVR and IVB groups, respectively. Changes in overall and temporal RNFL thickness in IVR-treated eyes (105.3±6.9µm and 74.4±11.2µm) were not different from those in untreated eyes in the IVR group (104.6± 8.4µm and 75.1±12.6µm) (P=0.57 and P=0.41, respectively). Similarly, overall and temporal RNFL thickness in IVB-treated eyes (105.8±8.1µm and 74.5±11.8µm) were not different from those in untreated eyes in the IVB group (104.6±8µm and 74.8±12.9µm) (P=0.42 and P=0.80, respectively). The frequencies of IOP rise (P=0.60) and changes in RNFL thickness from baseline (P=0.16) were comparable between groups.

CONCLUSION

Repeated intravitreal injection of ranibizumab or bevacizumab does not seem have adverse effects on RNFL thickness or IOP in wet AMD patients.

Coenzyme Q10 protects retinal cells from apoptosis induced by radiation in vitro and in vivo

The key pathogenetic event of many retinopathies is apoptosis of retinal cells. Our previous studies have demonstrated that Coenzyme Q10 (CoQ10) prevents apoptosis of corneal keratocytes both in vitro and in vivo, by virtue of its ability to inhibit mitochondrial depolarization, independently of its free radical scavenger role. The aim of this study was to evaluate whether CoQ10 can protect cultured retinal cells and the retinas of rats from radiation-induced apoptosis, if instilled as eye drops in the cornea. In vitro experiments were carried out on cultured ARPE-19 or RGC-5 cells pretreated with CoQ10 before eliciting apoptosis by UV- and γ-radiation, chemical hypoxia (Antimycin A) and serum starvation. Cell viability was evaluated by light microscopy and fluorescence activated cell sorting analysis. Apoptotic events were scored by time-lapse videomicroscopy. Mitochondrial permeability transition was evaluated by JC-1. The anti-apoptotic effectiveness of CoQ10 in retina was also evaluated by an in situ end-labeling assay in Wistar albino rats treated with CoQ10 eye drops prior to UV irradiation of the eye. CoQ10 substantially increased cell viability and lowered retinal cell apoptosis in response both to UV- and γ-radiation and to chemical hypoxia or serum starvation by inhibiting mitochondrion depolarization. In the rat, CoQ10, even when applied as eye drops on the cornea, protected all retina layers from UVR-induced apoptosis. The ability of CoQ10 to protect retinal cells from radiation-induced apoptosis following its instillation on the cornea suggests the possibility for CoQ10 eye drops to become a future therapeutic countermeasure for radiation-induced retinal lesions.

Oxidation and age-related macular degeneration: insights from molecular biology

Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world. It is a multifactorial disease, and current therapy predominantly limits damage only when it has already occurred. The macula is a source of high metabolic activity, and is therefore exposed to correspondingly high levels of reactive oxygen species (ROS). With age, the balance between production of ROS and local antioxidant levels is shifted, and damage ensues. Systemic ROS and antioxidant levels in AMD reflect these local processes. Genetic studies investigating mutations in antioxidant genes in AMD are inconclusive and further studies are indicated, especially to determine the role of mitochondria. Oral antioxidant supplements could be beneficial, and diet modification may help. Future treatments might either increase antioxidant capacity or reduce the production of ROS, using methods such as genetic manipulation. This article reviews the role of oxidative stress in AMD and the potential therapies that might have a role in preventing the blindness resulting from this disease.