Dysregulated claudin-5 cycling in the inner retina causes retinal pigment epithelial cell atrophy.

Age-related macular degeneration (AMD) is the leading cause of central retinal vision loss worldwide, with an estimated 1 in 10 people over the age of 55 showing early signs of the condition. There are currently no forms of therapy available for the end stage of dry AMD, geographic atrophy (GA). Here, we show that the inner blood-retina barrier (iBRB) is highly dynamic and may play a contributory role in GA development. We have discovered that the gene CLDN5, which encodes claudin-5, a tight junction protein abundantly expressed at the iBRB, is regulated by BMAL1 and the circadian clock. Persistent suppression of claudin-5 expression in mice exposed to a cholesterol-enriched diet induced striking retinal pigment epithelium (RPE) cell atrophy, and persistent targeted suppression of claudin-5 in the macular region of nonhuman primates induced RPE cell atrophy. Moreover, fundus fluorescein angiography in human and nonhuman primate subjects showed increased retinal vascular permeability in the evening compared with the morning. These findings implicate an inner retina-derived component in the early pathophysiological changes observed in AMD, and we suggest that restoring the integrity of the iBRB may represent a novel therapeutic target for the prevention and treatment of GA secondary to dry AMD.

A casein hydrolysate protects mice against high fat diet induced hyperglycemia by attenuating NLRP3 inflammasome-mediated inflammation and improving insulin signaling.

SCOPE: Activation of the nod-like receptor protein 3 (NLRP3) inflammasome is required for IL-1ß release and is a key component of obesity-induced inflammation and insulin resistance. This study hypothesized that supplementation with a casein hydrolysate (CH) would attenuate NLRP3 inflammasome mediated IL-1ß secretion in adipose tissue (AT) and improve obesity-induced insulin resistance. METHODS AND RESULTS: J774.2 macrophages were LPS primed (10 ng/mL) and stimulated with adenosine triphosphate (5 mM) to assess NLRP3 inflammasome activity. Pretreatment with CH (1 mg/mL; 48 h) reduced caspase-1 activity and decreased IL-1ß secretion from J774.2 macrophages in vitro. 3T3-L1 adipocytes cultured with conditioned media from CH-pretreated J774.2 macrophages demonstrated increased phosphorylated (p)AKT expression and improved insulin sensitivity. C57BL/6JOLaHsd mice were fed chow or high fat diet (HFD) for 12 wk ± CH resuspended in water (0.5% w/v). CH supplementation improved glucose tolerance in HFD-fed mice as determined by glucose tolerance test. CH supplementation increased insulin-stimulated pAKT protein levels in AT, liver, and muscle after HFD. Cytokine secretion was measured from AT and isolated bone marrow macrophages cultured ex vivo. CH supplementation attenuated IL-1ß, tumor necrosis factor alpha (TNF-α) and IL-6 secretion from AT and IL-1ß, IL-18, and TNF-α from bone marrow macrophages following adenosine triphosphate stimulation ex vivo. CONCLUSION: This novel CH partially protects mice against obesity-induced hyperglycemia coincident with attenuated IL-1ß secretion and improved insulin signaling.

NLRP3 Inflammasome and Pathobiology in AMD.

Age-related macular degeneration (AMD) is the leading cause of central vision loss and blindness in the elderly. It is characterized by a progressive loss of photoreceptors in the macula due to damage to the retinal pigment epithelium (RPE). Clinically, it is manifested by drusen deposition between the RPE and underlying choroid and accumulation of lipofuscin in the RPE. End-stage disease is characterized by geographic atrophy (dry AMD) or choroidal neovascularization (wet AMD). The NLRP3 inflammasome has recently been implicated in the disease pathology. Here we review the current knowledge on the involvement of this multiprotein complex and its effector cytokines interleukin-1ß (IL-1ß) and IL-18 in AMD progression. We also describe cell death mechanisms that have been proposed to underlie RPE degeneration in AMD and discuss the role of autophagy in the regulation of disease progression.

IL-18 Immunotherapy for Neovascular AMD: Tolerability and Efficacy in Nonhuman Primates.

PURPOSE: Age-related macular degeneration is the most common form of central retinal blindness in the elderly. Of the two end stages of disease, neovascular AMD-although the minority form-is the most severe. Current therapies are highly successful at controlling progression of neovascular lesions; however, a significant number of patients remain refractory to treatment and the development of alternative and additive therapies to anti-VEGFs is essential. METHODS: In order to address the translational potential of interleukin (IL)-18 for use in neovascular AMD, we initiated a nonhuman primate tolerability and efficacy study for the use of intravitreally (IVT) administered clinical grade human IL-18 (SB-485232). Cynomolgus monkeys were injected IVT with increasing doses of human IL-18 (two each at 1000, 3000, and 10,000 ng per eye). In tandem, 21 monkeys were administered nine laser burns in each eye prior to receiving IL-18 as an IVT injection at a range of doses. Fundus fluorescein angiography (FFA) was performed on days 8, 15, and 22 post injection and the development of neovascular lesions was assessed. RESULTS: We show intravitreal, mature, recombinant human IL-18 is safe and can reduce choroidal neovascular lesion development in cynomolgus monkeys. CONCLUSIONS: Based on our data comparing human IL-18 to current anti-VEGF-based therapy, clinical deployment of IL-18 for neovascular AMD has the potential to lead to a new adjuvant immunotherapy-based treatment for this severe form of central blindness.