Rajendra S. Apte

Macrophages Inhibit Neovascularization in a Murine Model of Age-Related Macular Degeneration

Background Age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 y of age in at least three continents. Choroidal neovascularization (CNV) is the process by which abnormal blood vessels develop underneath the retina. CNV develops in 10% of patients with AMD but accounts for up to 90% of the blindness from AMD. Although the precise etiology of CNV in AMD remains unknown, the macrophage component of the inflammatory response, which has been shown to promote tumor growth and support atherosclerotic plaque formation, is thought to stimulate aberrant angiogenesis in blinding eye diseases. The current theory is that macrophage infiltration promotes the development of neovascularization in CNV. Methods and Findings We examined the role of macrophages in a mouse model of CNV. IL-10 −/− mice, which have increased inflammation in response to diverse stimuli, have significantly reduced CNV with increased macrophage infiltrates compared to wild type. Prevention of macrophage entry into the eye promoted neovascularization while direct injection of macrophages significantly inhibited CNV. Inhibition by macrophages was mediated by the TNF family death molecule Fas ligand (CD95-ligand). Conclusions Immune vascular interactions can be highly complex. Normal macrophage function is critical in controlling pathologic neovascularization in the eye. IL-10 regulates macrophage activity in the eye and is an attractive therapeutic target in order to suppress or inhibit CNV in AMD that can otherwise lead to blindness.

Senescence regulates macrophage activation and angiogenic fate at sites of tissue injury in mice

Abnormal angiogenesis plays a key role in diseases of aging such as heart disease, certain cancers, and eye diseases including age-related macular degeneration. Macrophages have been shown previously to be both anti- and proangiogenic, and their role in regulating angiogenesis at sites of tissue injury is critical and complex. In this study, we analyzed cytokine gene expression patterns of mouse macrophages by real-time quantitative PCR and tested the functional effects of senescence on gene expression and macrophage polarization. Following laser injury to the retina, IL-10 was upregulated and Fas ligand (FasL), IL-12, and TNF-alpha were downregulated in ocular macrophages of old mice (>18 months of age). Downregulation of FasL on macrophages led to a loss of the antiangiogenic phenotype, as evidenced by the inability of these macrophages to inhibit vascular endothelial cells. Our results demonstrate that senescence, FasL, and IL-10 are key determinants of macrophage function that alter the growth of abnormal postdevelopmental blood vessels in disease processes including blinding eye disease.

Zika Virus Infection in Mice Causes Panuveitis with Shedding of Virus in Tears.

Zika virus (ZIKV) is an emerging flavivirus that causes congenital abnormalities and Guillain-Barré syndrome. ZIKV infection also results in severe eye disease characterized by optic neuritis, chorioretinal atrophy, and blindness in newborns and conjunctivitis and uveitis in adults. We evaluated ZIKV infection of the eye by using recently developed mouse models of pathogenesis. ZIKV-inoculated mice developed conjunctivitis, panuveitis, and infection of the cornea, iris, optic nerve, and ganglion and bipolar cells in the retina. This phenotype was independent of the entry receptors Axl or Mertk, given that Axl(-/-), Mertk(-/-), and Axl(-/-)Mertk(-/-) double knockout mice sustained levels of infection similar to those of control animals. We also detected abundant viral RNA in tears, suggesting that virus might be secreted from lacrimal glands or shed from the cornea. This model provides a foundation for studying ZIKV-induced ocular disease, defining mechanisms of viral persistence, and developing therapeutic approaches for viral infections of the eye.

Interleukin-10 Promotes Pathological Angiogenesis by Regulating Macrophage Response to Hypoxia during Development

Aberrant angiogenesis in the eye is the most common cause of blindness. The current study examined the role of interleukin-10 (IL-10) in ischemia-induced pathological angiogenesis called neovascularization during postnatal development. IL-10 deficiency resulted in significantly reduced pathological retinal angiogenesis. In contrast to the choroicapillaris where IL-10 interferes with macrophage influx, IL-10 did not prevent anti-angiogenic macrophages from migrating to the retina in response to hypoxia. Instead, IL-10 promoted retinal angiogenesis by altering macrophage angiogenic function, as macrophages from wild-type mice demonstrated increased vascular endothelial growth factor (VEGF) and nitric oxide (NO) compared to IL-10 deficient macrophages. IL-10 appears to directly affect macrophage responsiveness to hypoxia, as macrophages responded to hypoxia with increased levels of IL-10 and STAT3 phosphorylation as opposed to IL-10 deficient macrophages. Also, IL-10 deficient macrophages inhibited the proliferation of vascular endothelial cells in response to hypoxia while wild-type macrophages failed to do so. These findings suggest that hypoxia guides macrophage behavior to a pro-angiogenic phenotype via IL-10 activated pathways.

Association of complement factor H and LOC387715 genotypes with response of exudative age-related macular degeneration to photodynamic therapy

AimTo determine whether there is an association between complement factor H (CFH) or LOC387715 genotypes and response to treatment with photodynamic therapy (PDT) for exudative age-related macular degeneration (AMD).MethodsSixty-nine patients being treated for neovascular AMD with PDT were genotyped for the CFH Y402H and LOC387715 A69S polymorphisms by allele-specific digestion of PCR products. AMD phenotypes were characterized by clinical examination, fundus photography, and fluorescein angiography.ResultsAdjusting for age, pre-PDT visual acuity (VA), and lesion type, mean VA after PDT was significantly worse for the CFH TT genotype than for the TC or CC genotypes (P=0.05). Post-PDT VA was significantly worse for the CFH TT genotype in the subgroup of patients with predominantly classic choroidal neovascular lesions (P=0.04), but not for the patients with occult lesions (P=0.22). For the LOC387715 A69S variant, there was no significant difference among the genotypes in response to PDT therapy.ConclusionsThe CFH Y402H variant was associated with a response to PDT treatment in this study. Patients with the CFH TT genotype fared significantly worse with PDT than did those with the CFH TC and CC genotypes, suggesting a potential relationship between CFH genotype and response to PDT.

Retinal pigment epithelial tears in ranibizumab-treated eyes.

Purpose: To report the incidence of retinal pigment epithelial (RPE) tears in patients treated with ranibizumab therapy for choroidal neovascularization due to age-related macular degeneration. Design: Interventional case series. Methods: One hundred sixty-four eyes from a large clinical practice were retrospectively reviewed for number of injections and the presence or absence of a fibrovascular retinal pigment epithelial detachment. Main outcome measures were occurrence of RPE tears, and timing of tears following the last injection. Results: Patients were observed for an average of 11 months. A single patient (0.61%) experienced an RPE tear and this occurred after the first injection. In eyes with a fibrovascular retinal pigment epithelial detachment the incidence was 5%. Lesions containing a fibrovascular retinal pigment epithelial detachment tended to be larger (4.5 versus 3.8 Macular Photocoagulation Study Disc Areas), but this was not statistically significant. (P = 0.63). However, these lesions required more injections on average (P = 0.05). Conclusion: The incidence of RPE tears associated with ranibizumab therapy is low and may result from a predisposition rather than an effect of treatment. Even so, patients undergoing ranibizumab therapy should be counseled regarding this possible complication.

Intravitreal Bevacizumab for Choroidal Neovascularization in Ocular Histoplasmosis

PURPOSE To define the role of intravitreal bevacizumab in individuals with choroidal neovascularization (CNV) resulting from Ocular Histoplasmosis syndrome (OHS). DESIGN Retrospective chart review of a surgical therapy. METHODS We reviewed the course of 28 eyes of 28 patients who underwent intravitreal injection of bevacizumab for treatment of CNV secondary to OHS. Outcome was measured by pretreatment and posttreatment visual acuity (VA). RESULTS The average pretreatment logarithm of the minimum angle of resolution (logMAR) VA was 0.65 (Snellen equivalent of 20/88). Mean follow-up was 22.43 weeks with an average of 1.8 intravitreal injections. Average final logMAR VA was 0.43 (Snellen equivalent of 20/54). Twenty eyes (71%) experienced an increase in central VA, whereas four eyes (14%) were unchanged and four eyes (14%) experienced a decrease in vision. CONCLUSIONS Intravitreal bevacizumab may improve or stabilize VA in a significant majority of patients with neovascular complications of OHS (24 eyes [85.7%] in our study population).

Effect of senescence on macrophage polarization and angiogenesis.

There is mounting evidence that as the immune system ages, a progressive deterioration in normal function occurs. Termed immunosenescence, aging impacts both the innate and adaptive immune responses. This review discusses the age-related alterations in the innate immune system, with a specific focus on macrophages. The downstream effect of altered macrophage function on aberrant angiogenesis in the pathophysiology of age-related eye disease is also discussed.

A systematic review of as needed versus treat and extend ranibizumab or bevacizumab treatment regimens for neovascular age-related macular degeneration

Purpose To evaluate the relative efficacy of as needed versus treat and extend regimen for the treatment of neovascular age-related macular degeneration (AMD). Methods We conducted a systematic review of studies that evaluated the efficacy of as needed or treat and extend regimen for neovascular AMD by searching multiple databases up to December 2013. Included studies were selected based on study duration of no less than 12 months, availability of outcome data, treatment protocol for as needed groups or pro re nata (PRN) receiving bevacizumab or ranibizumab, and all studies with treat extend protocols following the ‘inject and extend’ regimen. The outcome data were pooled and analysed. Results 1046 peer reviewed articles meeting our initial search criteria were returned. After further review by two independent reviewers, 8 studies meeting treat and extend protocol and 62 studies meeting PRN protocol were included. The mean improvement in visual acuity in the PRN group was 5.4 ETDRS letters compared with 10.4 ETDRS letters in the treat and extend group. The PRN group received an average of 5.60 injections at 1 year compared with 8.09 in the treat and extend group. Central retinal thickness improved on average by 100.32 µ in the PRN group compared with 87.7 µ in the treat and extend group. Conclusions Though our study suggests superiority of the treat and extend regimen to PRN treatment in a 12-month period, this review demonstrates the need for randomised clinical trials to confirm our findings and to evaluate long-term efficacy outcomes with these regimens compared with monthly therapy.

Resveratrol regulates pathologic angiogenesis by a eukaryotic elongation factor-2 kinase-regulated pathway.

Abnormal angiogenesis is central to the pathophysiology of diverse disease processes including cancers, ischemic and atherosclerotic heart disease, and visually debilitating eye disease. Resveratrol is a naturally occurring phytoalexin that has been demonstrated to ameliorate and decelerate the aging process as well as blunt end organ damage from obesity. These effects of resveratrol are largely mediated by members of the sirtuin family of proteins. We demonstrate that resveratrol can inhibit pathological angiogenesis in vivo and in vitro by a sirtuin-independent pathway. Resveratrol inhibits the proliferation and migration of vascular endothelial cells by activating eukaryotic elongation factor-2 kinase. The active kinase in turn phosphorylates and inactivates elongation factor-2, a key mediator of ribosomal transfer and protein translation. Functional inhibition of the kinase by gene deletion in vivo or RNA as well as pharmacological inhibition in vitro is able to completely reverse the effects of resveratrol on blood vessel growth. These studies have identified a novel and critical pathway that promotes aberrant vascular proliferation and one that is amenable to modulation by pharmacological means. In addition, these results have uncovered a sirtuin-independent pathway by which resveratrol regulates angiogenesis.