Formyl Peptide Receptor 1 Inhibits Reparative Angiogenesis and Aggravates Neuroretinal Dysfunction in Ischemic Retinopathy.

PURPOSE: Ischemic retinopathy is the major cause of vision-threatening conditions. Inflammation plays an important role in the pathogenesis of ischemic retinopathy. Formyl peptide receptor 1 (FPR1) has been reported to be implicated in the regulation of inflammatory disorders. However, the role of FPR1 in the progression of ischemic retinal injury has not been fully explained. METHODS: The activation of FPR1 was measured by real-time PCR and western blotting in the retina of OIR. The effect of FPR1 on the expression of inflammatory cytokines and relevant pro-angiogenic factors was assessed between wild-type and FPR1-deficiency OIR mice. The impact of FPR1 on retinal angiogenesis was evaluated through quantifying retinal vaso-obliteration and neovascularization between FPR1+/+ and FPR1-/- OIR mice. At last, the neuronal effect of FPR1 on the ischemic retina was investigated by ERG between wild-type and FPR1-deficient OIR mice. RESULTS: The expression of FPR1 significantly increased in the retina of OIR. Furthermore, FPR1 deficiency downregulated pro-inflammatory and pro-angiogenic factors. Ablation of FPR1 suppressed the retinal pathological neovascularization and promoted reparative revascularization, ultimately improving retinal neural function after ischemic injury. CONCLUSION: In ischemic retinopathy, FPR1 aggravates inflammation and inhibits reparative angiogenesis to exacerbate neuronal dysfunction.

Annexin A1 conveys neuroprotective function via inhibiting oxidative stress in diffuse axonal injury of rats.

Diffuse axonal injury (DAI) is a critical pathological facet of traumatic brain injury (TBI). Oxidative stress plays a significant role in the progress of DAI. Annexin A1 (AnxA1) has been demonstrated to benefit from recovery of neurofunctional outcomes after TBI. However, whether AnxA1 exhibits neuronal protective function by modulating oxidative stress in DAI remains unknown. Expression of AnxA1 was evaluated via real-time PCR and western blotting in rat brainstem after DAI. The neurological effect of AnxA1 following DAI through quantification of modified neurologic severity score (mNSS) was compared between wild-type and AnxA1-knockout rats. Brain edema and neuronal apoptosis, as well as expression of oxidative factors and inflammatory cytokines, were analyzed between wild-type and AnxA1 deficiency rats after DAI. Furthermore, mNSS, oxidative and inflammatory cytokines were assayed after timely administration of recombinant AnxA1 for DAI rats. In the brainstem of DAI, the expression of AnxA1 remarkably increased. Ablation of AnxA1 increased the mNSS score and brain water content of rats after DAI. Neuron apoptosis in the brainstem after DAI was exaggerated by AnxA1 deficiency. In addition, AnxA1 deficiency significantly upregulated the level of oxidative and inflammatory factors in the brainstem of DAI rats. Moreover, mNSS decreased by AnxA1 treatment in rats following DAI. Expression of oxidative and inflammatory molecules in rat brainstem subjected to DAI inhibited by AnxA1 administration. AnxA1 exhibited neuronal protective function in the progression of DAI mainly dependent on suppressing oxidative stress and inflammation.

Annexin A1 Promotes Reparative Angiogenesis and Ameliorates Neuronal Injury in Ischemic Retinopathy.

PURPOSE: Retinal ischemia is the main reason for vision threatening. Inflammation and aberrant angiogenesis play an important role in the pathogenesis of ischemia. Annexin A1 (ANXA1) is an endogenous protein modulating anti-inflammatory processes, and its therapeutic potential has been reported in a range of inflammatory diseases. However, the effect of ANXA1 on ischemic retinal injury has not been examined. METHODS: Expression of ANXA1 was assessed by real-time PCR and western blotting, and location of ANXA1 was evaluated by immunofluorescence staining in retina of OIR. The activation of ANXA1 was assayed in HRECs after hypoxia stimuli. The effect of ANXA1 on vascularization of OIR mouse through quantification vaso-obliteration (VO) and neovascularization (NV), as well as expression of relevant angiogenic factors and inflammatory cytokines was compared between wild type and ANXA1 deficiency mice. We also investigated the effect of ANXA1 on retinal neuronal degeneration as measured by electroretinography (ERG) and OCT. RESULTS: In retinas of OIR, the expression of ANXA1 significantly increased and located in inner retinal layers. ANXA1 was induced in HRECs after hypoxic stimuli. Furthermore, ANXA1 deficiency increased pro-angiogenic and pro-inflammatory cytokines. Ablation of ANXA1 suppressed aortic outgrowth and retinal reparative revascularization and promoted pathological NV to exacerbate retinal dysfunction after ischemia injury. CONCLUSIONS: ANXA1 inhibits angiogenic and inhibits pro-inflammatory cytokines and promotes reparative angiogenesis, thus exhibits neuronal protective function in ischemic retinopathy.

Dendrimer-Triamcinolone Acetonide Reduces Neuroinflammation, Pathological Angiogenesis, and Neuroretinal Dysfunction in Ischemic Retinopathy.

Diabetic retinopathy (DR) is the leading cause of blindness in working-age adults. Severe visual loss in DR is primarily due to proliferative diabetic retinopathy, characterized by pathologic preretinal angiogenesis driven by retinal ischemia. Microglia, the resident immune cells of the retina, have emerged as a potentially important regulator of pathologic retinal angiogenesis. Corticosteroids including triamcinolone acetonide (TA), known for their antiangiogenic effects, are used in treating retinal diseases, but their use is significantly limited by side effects including cataracts and glaucoma. Generation-4 hydroxyl polyamidoamine dendrimer nanoparticles are utilized to deliver TA to activated microglia in the ischemic retina in a mouse model of oxygen-induced retinopathy (OIR). Following intravitreal injection, dendrimer-conjugated TA (D-TA) exhibits selective localization and sustained retention in activated microglia in disease-associated areas of the retina. D-TA, but not free TA, suppresses inflammatory cytokine production, microglial activation, and preretinal neovascularization in OIR. In addition, D-TA, but not free TA, ameliorates OIR-induced neuroretinal and visual dysfunction. These results indicate that activated microglia are a promising therapeutic target for retinal angiogenesis and neuroprotection in ischemic retinal diseases. Furthermore, dendrimer-based targeted therapy and specifically D-TA constitute a promising treatment approach for DR, offering increased and sustained drug efficacy with reduced side effects.

Inhibition of the Keap1-Nrf2 protein-protein interaction protects retinal cells and ameliorates retinal ischemia-reperfusion injury.

The Nrf2-Keap1 pathway regulates transcription of a wide array of antioxidant and cytoprotective genes and offers critical protection against oxidative stress. This pathway has demonstrated benefit for a variety of retinal conditions. Retinal ischemia plays a pivotal role in many vision threatening diseases. Retinal vascular endothelial cells are an important participant in ischemic injury. In this setting, Nrf2 provides a protective pathway via amelioration of oxidative stress and inflammation. In this study, we investigated a potent small molecule inhibitor of the Nrf2-Keap1 protein-protein interaction (PPI), CPUY192018, for its therapeutic potential in retinal cells and retinal ischemia-reperfusion injury. In human retinal endothelial cells (HREC), treatment with CPUY192018 increased Nrf2 protein levels and nuclear translocation, stimulated Nrf2-ARE-induced transcriptional capacity, and induced Nrf2 target gene expression. Furthermore, CPUY192018 protected HREC against oxidative stress and inflammatory activation. CPUY192018 also activated Nrf2 and suppressed inflammatory response in macrophages. In the retinal ischemia-reperfusion (I/R) model, administration of CPUY192018 induced Nrf2 target gene activation in the retina. Both systemic and topical treatment with CPUY192018 rescued visual function after ischemia-reperfusion injury. Taken together, these findings indicate that small molecule Keap1-Nrf2 PPI inhibitors can activate the Nrf2 pathway in the retina and provide protection against retinal ischemic and inflammatory injury, suggesting Keap1-Nrf2 PPI inhibition in the treatment of retinal conditions.

Effects of Interleukin-6 on posterior capsular opacification.

The purpose of this work was to determine the effects of interleukin-6 (IL-6) on the development of posterior capsular opacification (PCO) in vitro and in vivo. Western blot and real-time PCR were used to test the IL-6-induced epithelial-mesenchymal transition (EMT) marker α-smooth muscle actin (α-SMA), the extracellular matrix (ECM) markers fibronectin (Fn) and type I collagen (COL-1), transforming growth factor ß2 (TGF-ß2), and the activation and role of the JAK/STAT3 signaling pathway in human lens epithelial cells (HLECs). Immunocytofluorescence staining was performed to detect gp130 and IL-6Rα expression in HLECs. Rat PCO models were then established to examine the impact of STAT3 knockdown by shRNA adeno-associated virus on PCO development, and immunohistochemical staining was performed to detect the expression of Fn in the anterior and posterior capsule in vivo. We found that IL-6 promotes the expression of Fn, COL-1, TGF-ß2, p-JAK2 and p-STAT3 in HLECs but exerts little effect on α-SMA. The JAK/STAT3 inhibitor WP1066 effectively suppressed the IL-6-induced expression of Fn and COL-1 in lens epithelial cells. STAT3 knockdown effectively inhibited the development of PCO in rats and significantly reduced the expression of Fn in the anterior and posterior capsule. These data suggest that IL-6 contributes to the development of PCO by promoting TGF-ß2 activation and ECM synthesis through a JAK/STAT3 signaling-dependent mechanism. Furthermore, inhibiting JAK/STAT3 signaling effectively impairs both PCO development in rats and ECM synthesis in the lens capsule.