不同剂量熊果酸干预糖尿病小鼠视网膜病变的作用及机制研究

目的:探究不同剂量熊果酸(UA)干预糖尿病小鼠视网膜病变的作用及机制。方法:选取雄性健康C57BL/6小鼠60只,其中50只按50 mg/kg的剂量一次性往小鼠尾静脉注射新鲜配置的四氯嘧啶生理盐水溶液构建小鼠糖尿病视网膜病变模型,随机分为5组,每组10只,分别为模型组、阳性对照组(小鼠玻璃体注射3μL 40 mg/m L的曲安奈德),低剂量UA干扰组(小鼠玻璃体注射3μL剂量为0.5μg/μL的UA)、中剂量UA干扰组(小鼠玻璃体注射3μL剂量为1.0μg/μL的UA),高剂量UA干扰组(小鼠玻璃体注射3μL剂量为2.0μg/μL的UA),余下10只小鼠作为正常对照组。观察各组小鼠对胰岛素敏感性、视网膜内糖代谢情况、小鼠视网膜神经节细胞(RGCs)凋亡情况,比较各组小鼠视网膜组织中血管内皮生长因子(VEGF)、环氧化酶-2(COX-2)、基质金属蛋白酶2(MMP-2)蛋白及其mRNA的表达情况。结果:建模后,正常对照组胰岛素抵抗指数(HOMA-IR)、视网膜含糖量、葡萄糖转运体-1(GLUT-1)与葡萄糖转运体-3(GLUT-3)含量、RGCs凋亡率、视网膜组织中VEGF、COX-2、MMP-2蛋白及其mRNA的表达量低于模型组(P0.05);经干扰后,阳性对照组、不同剂量UA干扰组HOMA-IR、视网膜含糖量、GLUT-1、GLUT-3的含量、RGCs凋亡率、视网膜组织中VEGF、COX-2、MMP-2蛋白及其mRNA的表达量低于模型组(P0.05),且随UA干扰剂量的升高而降低(P0.05)。结论:UA能够降低HOMA-IR和视网膜糖代谢能力,抑制RGCs的凋亡,对VEGF、COX-2、MMP-2蛋白及其mRNA的表达具有一定的抑制作用,高剂量UA对糖尿病小鼠视网膜病预防治疗效果较好。     

Muller细胞与视网膜病变

视网膜是一薄而半透明的、具有多层结构的神经组织,位于眼球后2/3部的内侧面。向前延伸达睫状体,止于不规则边界。Muller细胞是脊椎动物视网膜内最主要的神经胶质细胞,它贯穿整个视网膜。Muller细胞对于维持神经元的完整性、代谢、内环境稳态以及信号转导等均具有重要的作用。在视网膜病变时,Muller细胞参与整个过程,并且在视网膜的各种疾病中都发现伴有Muller细胞的神经胶质增生反应。Muller细胞同时也调控视网膜病变的整个过程。Muller细胞膜上的神经递质受体、谷氨酸受体、门控电压通道、所合成分泌的营养因子及自的身增殖分化都发生改变。近年来人们对Muller细胞的认识越来越多,研究的方向也从细胞的微观结构、主要功能转变成Muller细胞对不同视网膜病变过程的参与调控。本文对视网膜Muller细胞的形态和生理功能,病理状况下Muller细胞发生的改变作一综述。     

Attenuation of retinal vascular development and neovascularization in PECAM-1-deficient mice

Platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31) is expressed on the surface of endothelial cells (EC) at high levels with important roles in angiogenesis and inflammation. However, the physiological role PECAM-1 plays during vascular development and angiogenesis remains largely unknown. Here we determined the role of PECAM-1 in the postnatal development of retinal vasculature and retinal neovascularization during oxygen-induced ischemic retinopathy (OIR) using PECAM-1-deficient (PECAM-1−/−) mice. A significant decrease in retinal vascular density was observed in PECAM-1−/− mice compared with PECAM-1+/+ mice. This was attributed to a decreased number of EC in the retinas of PECAM-1−/− mice. An increase in the rate of apoptosis was observed in retinal vessels of PECAM-1−/− mice, which was compensated, in part, by an increase in the rate of proliferation. However, the development and regression of hyaloid vasculature were not affected in the absence of PECAM-1. We did not observe a significant defect in astrocytes, the number of endothelial tip cell filopodias, and the rate of developing retinal vasculature progression in PECAM-1−/− mice. However, we observed aberrant organization of arterioles and venules, decreased secondary branching, and dilated vessels in retinal vasculature of PECAM-1−/− mice. In addition, retinal neovascularization was attenuated in PECAM-1−/− mice during OIR despite an expression of VEGF similar to that of PECAM-1+/+ mice. Mechanistically, these changes were associated with an increase in EphB4 and ephrin B2, and a decrease in eNOS, expression in retinal vasculature of PECAM-1−/− mice. These results suggest that PECAM-1 expression and its potential interactions with EphB4/ephrin B2 and eNOS are important for survival, migration, and functional organization of EC during retinal vascular development and angiogenesis.     

Hyperbaric oxygne tolerance in newborn mammals-hypothesis on mechanisms and outcome

Newborn mammals, compared to adults, are extremely resistant to the CNS effects of hyperbaric oxygenation (HBO) induced by excessive generation of reactive oxygen species. This tolerance to HBO may be related to either physiological responses or the chemical characteristics of the immature brain, including a low cerebral blood flow and energy metabolism and a low concentration of polyunsaturated fatty acids. In adult mammals the main protective mechanism against CNS oxygen toxicity, besides endogenous antioxidants, is a transient HBO-induced cerebral vasoconstriction. How cerebral vasculature reacts to HBO in the immature brain is not known. We present indirect evidence suggesting that HBO in newborn rats induces a persistent cerebral vasoconstriction concurrently with a severe and maintained reduction in ventilation. It is speculated that the outcome of these physiologic responses to hyperoxic exposures may be: (a) extension of tolerance to both CNS and pulmonary oxygen poisoning; (b) creation of a profound hypoxic-ischemic condition in vulnerable neural structures: and (c) impairement of the circulatory and ventilatory responses to hypoxic stimuli on return to air consequent development of a secondary hypoxic-ischemic condition. These hypothetical pre- and post-HBO events may set the stage for the development of some delayed neurological disorders, including the retinopathy of prematurity and the retardation of brain development in fetuses or prematurely-born infants subjected to oxygen therapy.     

血清Fractalkine、Apelin水平与糖尿病视网膜病变患者血糖、血脂以及病程的关系研究

目的:研究血清Fractalkine(FKN)、爱帕琳肽(Apelin)水平与糖尿病视网膜病变(DR)患者血糖、血脂以及病程的关系。方法:选取我院于2015年1月至2016年12月收治的160例糖尿病患者为研究对象,行眼底荧光造影、裂隙灯显微镜检查,按照检查结果将其区分为非增生型DR组(稳定组,43例)、背景期DR组(背景组,62例)和增殖期DR组(增殖组,55例),另外于同期选取我院40例健康体检者为健康对照组(健康组),测量4组血清FKN、Apelin、空腹血糖(FPG)、餐后2h血糖(2hPG)、糖化血红蛋白(HbA1c)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、甘油三酯(TG)和总胆固醇(TC)水平,使用Pearson相关性分析分析血清FKN、Apelin与FPG、2hPG、HbA1c、HDL-C、LDL-C、TG、TC、糖尿病病程的相关性。结果:血清FKN、Apelin水平比较:增殖组背景组稳定组健康组,各组间比较差异具有统计学意义(P0.05);血清FPG、2hPG、HbA1c、LDL-C、TG、TC水平比较:增殖组背景组稳定组健康组,各组间比较差异具有统计学意义(P0.05);血清HDL-C水平比较:健康组稳定组背景组增殖组,各组间比较差异具有统计学意义(P0.05);采用Pearson相关性分析显示,血清FKN水平与FPG、2hPG、HbA1c、LDL-C、TG、TC、糖尿病病程呈正相关性(r=0.321、0.215、0.645、0.154、0.215、0.325、0.578,P0.05),与HDL-C呈负相关性(r=-0.547,P0.05);血清Apelin水平与FPG、2hPG、HbA1c、LDL-C、TG、TC、糖尿病病程呈正相关性(r=0.245、0.574、0.951、0.357、0.357、0.159、0.546,P0.05),与HDL-C呈负相关性(r=-0.459,P0.05);糖尿病病程、HbA1c、LDL-C、HDL-C、FKN和Apelin为DR病程的相关影响因素。结论:糖尿病伴发DR患者血清FKN、Apelin水平随着病程的加重逐渐增加,且这两种因子的水平与患者血糖、血脂代谢关系密切。     

醛糖还原酶基因启动区C（-106）T多态性与糖尿病视网膜

目的：探讨醛糖还原酶（AR）基因启动区C（-106）T多态性与糖尿病视网膜病变（DR）的关系。方法：235例江苏汉族人群,其中2型糖尿病无视网膜病变组（NDR）63例,2型糖尿病伴视网膜病变组（DR）82例,正常对照组（YC）90例,用PCR-RFLP方法检测AR基因C（-106）T基因型,比较各组等位基因及基因型分布频率。结果：未发现NDR组和NC组之间AR基因C（-106）T各等位基因及基因型频率有显著差异（P分别为0．4505,0．7279）;DR组中CT及TT基因型频率均高于NC组,CC基因型频率低于NC组（P=0．0239）,DR组T等位基因频率显著高于NC组,C等位基因频率显著低于NC组（P=0．0038）。结论：AR基因启动区C（-106）T多态性与江苏汉族人群DR相关,T等位基因可能是DR的遗传危险因子。     

Blockade of TREM-1 prevents vitreoretinal neovascularization in mice with oxygen-induced retinopathy

In pathological retinal neovascularization (RNV) disorders, the retina is infiltrated by activated leukocytes and macrophages. Triggering receptor expressed on myeloid cells 1 (TREM-1), an inflammation amplifier, activates monocytes and macrophages and plays an important role in cancer, autoimmune and other inflammation-associated disorders. Hypoxia-inducible TREM-1 is involved in cancer angiogenesis but its role in RNV remains unclear. Here, to close this gap, we evaluated the role of TREM-1 in RNV using a mouse model of oxygen-induced retinopathy (OIR). We found that hypoxia induced overexpression of TREM-1 in the OIR retinas compared to that of the room air group. TREM-1 was observed specifically in areas of pathological RNV, largely colocalizing with macrophage colony-stimulating factor (M-CSF) and CD45- and Iba-1-positive cells. TREM-1 blockade using systemically administered first-in-class ligand-independent TREM-1 inhibitory peptides rationally designed using the signaling chain homooligomerization (SCHOOL) strategy significantly (up to 95%) reduced vitreoretinal neovascularization. The peptides were well-tolerated when formulated into lipopeptide complexes for peptide half-life extension and targeted delivery. TREM-1 inhibition substantially downregulated retinal protein levels of TREM-1 and M-CSF suggesting that TREM-1-dependent suppression of pathological angiogenesis involves M-CSF. Targeting TREM-1 using TREM-1-specific SCHOOL peptide inhibitors represents a novel strategy to treat retinal diseases that are accompanied by neovascularization including retinopathy of prematurity.     

Translocation of H-Ras and its implications in the development of diabetic retinopathy

H-Ras, a small molecular weight G-protein, undergoes post-translational modifications enabling its translocation from cytosol to the membrane. Hyperglycemia increases apoptosis of retinal capillary cells via activation of H-Ras, which can be ameliorated by farnesylation inhibitors. Our aim is to investigate the mechanism of retinal H-Ras activation in diabetes. H-Ras and Raf-1 were quantified in the retinal membrane and cytosol fractions obtained from streptozotocin-induced diabetes rats, and the role of post-translation modification was determined by investigating the effect of simvastatin on diabetes-induced alterations. The effect of H-Ras-siRNA on membrane translocation and apoptosis was also determined in bovine retinal endothelial cells (BRECs). Diabetes increased expressions of H-Ras and Raf-1 in the retinal membranes, and simvastatin prevented such translocation. Glucose-exposure of BRECs increased membrane H-Ras expression and H-Ras-siRNA prevented this translocation, and also decreased their apoptosis. Thus, membrane translocation of H-Ras is a plausible mechanism responsible for accelerated apoptosis of retinal capillary cells in diabetes.     

The “flip-flop” of aldose reductase gene in diabetic retinopathy and nephropathy

Retinopathy and nephropathy - current view

The Kumamoto and UKPDS studies of type-2 diabetes demonstrated that high glucose mean faster worsening for both diabetic retinopathy and nephropathy. However, why so many type-2 diabetics develop nephropathy but no retinopathy? Why so many type-2 diabetics have severe retinopathy and little or no nephropathy? The answer may be genetic susceptibility.

Hypothesis: the “flip-flop” effect of aldose reductase gene

When the CC genotype (high aldose reductase expression) of the (−106) polymorphism of the aldose reductase gene was linked to enhanced retinal susceptibility to hyperglycemia, it was expected that it would also accelerate nephropathy. As the case was the opposite, we now hypothesize that in the kidney, higher aldose reductase activity reduces susceptibility to hyperglycaemia by means of shifting glucose away from the synthesis of Transforming Growth Factor-Beta (TGF-β), a stimulator of mesangial expansion - the landmark of diabetic nephropathy. As the CT & TT genotypes (lower expression of aldose reductase) have effects that are the opposite of those of CC genotype, i.e. retinopathy-protection & nephropathy proneness, we have coined the term “flip-flop”, an acronym taken from electronics, meaning a system that is bi-stable.

If the “flip-flop” was confirmed - what then?

Those diabetics who are retinopathy-protected & nephropathy-prone (CT & TT), should not be given aldose reductase inhibitors (which could worsen nephropathy) but the new breed of TGF-β inhibitors. This might be a first step towards “genetic individualization of diabetes therapy”.     

Regulation of the excitatory amino acid transporter EAAT5 by the serum and glucocorticoid dependent kinases SGK1 and SGK3

In the mammalian retina, glutamate re-uptake is mediated by the sodium dependent cotransport systems EAAT1-5 thus terminating neuronal excitation and preventing neuroexcitotoxicity. In retinal amacrine and ganglion cells, EAAT5 is colocalized with the serum and glucocorticoid inducible kinase SGK1, a serine/threonine kinase known to regulate transport. The study explored the possible regulation of EAAT5 by SGK1, its isoform SGK3, and the closely related protein kinase B. EAAT5 was coexpressed in Xenopus laevis oocytes with or without the respective kinases. Transport activity was quantified by electrophysiology and cell surface expression was determined by chemiluminescence. Both EAAT5 mediated currents and EAAT5 protein abundance at the cell surface were increased by a factor of 1.5-2 upon coexpression of SGK1 or SGK3 but not following coexpression of PKB. In conclusion, the kinases SGK1 and SGK3 increase EAAT5 activity by increasing cell surface abundance of the carrier.