Role of Epac1 in pathogenesis of diabetic retinopathy

Poster Presentations - Theme 2published_or_final_version15th Research Postgraduate Symposium, Hong Kong, China, 1-2 December 2010. In Abstract - Poster Presentations of 15th Research Postgraduate Symposium, 2010, Theme II, p. 87 Abstract no. 1

Mouse models for human diseases

Mice are increasingly being used as models for the study of various human diseases. This is primarily because among mammalian modals, they are most amenable to genetic manipulations. As we attempt to understand the molecular mechanism of diseases, it is imperative that the genes involved in the disease process be identified. One approach is to study mouse mutants with symptoms analogous to human diseases, and try to identify the genes responsible. Another approach is to manipulate the expression of genes suspected to be involved and see how they affect the disease development. This review briefly discusses the concept of manipulating gene expression by transgenic and gene knockout technology and illustrates this with how these technique are used to study the mechanism of diabetic complications.published_or_final_versio

The RhoA GTPase-activating protein DLC2 modulates RhoA activity and hyperalgesia to noxious thermal and inflammatory stimuli

Deleted in liver cancer 2 (DLC2) is a novel Rho GTPase-activating protein that regulates RhoA activity. DLC2 is ubiquitously expressed in most tissues, including the brain, spinal cord and peripheral nerves, and is thought to be involved in actin cytoskeletal reorganization. Unlike DLC1-deficient mice, DLC2-deficient mice (DLC2 -/-) are viable and without gross anatomical abnormalities. Interestingly, DLC2 -/- mice exhibit hyperalgesia to noxious thermal stimuli and inflammation-inducing chemicals, such as formalin and acetic acid. There was no difference in the structure or morphology of cutaneous or sural nerves between DLC2 +/+ and DLC2 -/- mice. However, sensory nerve conduction velocity in DLC2 -/- mice was significantly higher than that in DLC2 +/+ mice, whereas motor nerve conduction velocity was not affected. After formalin injection, DLC2 -/- mice showed increased RhoA activity in the spinal cord and an increased number of phosphorylated ERK1/2-positive cells. The inflammatory hyperalgesia in DLC2 -/- mice appeared to be mediated through the activation of RhoA and ERK1/2. Taken together, DLC2 plays a key role in pain modulation during inflammation by suppressing the activation of RhoA and ERK to prevent an exaggerated pain response, and DLC2 -/- mice provide a valuable tool for further understanding the regulation of inflammatory pain. Copyright © 2011 S. Karger AG, Basel.postprin

Practical divergent synthesis of all possible regioisomers of myo-inositol trisphosphates

open119sciescopu

Role of epac in the pathogenesis of ischemic stroke

Poster Presentations: Theme 2published_or_final_version15th Research Postgraduate Symposium, Hong Kong, China, 1-2 December 2010. In Abstract - Poste Presentations (Theme II) of 15th Research Postgraduate Symposium, 2010, p. 8

Up-regulation of aldose reductase activity in cultured mesangial cells overexpressing human aldose reductase gene is associated with increased TGF-beta1 and collagen IV expression

published_or_final_versio

Epac2-deficiency leads to more severe retinal swelling, glial reactivity and oxidative stress in transient middle cerebral artery occlusion induced ischemic retinopathy

Ischemia occurs in diabetic retinopathy with neuronal loss, edema, glial cell reactivity and oxidative stress. Epacs, consisting of Epac1 and Epac2, are cAMP mediators playing important roles in maintenance of endothelial barrier and neuronal functions. To investigate the roles of Epacs in the pathogenesis of ischemic retinopathy, transient middle cerebral artery occlusion (tMCAO) was performed on Epac1-deficient (Epac1) mice, Epac2-deficient (Epac2) mice, and their wild type counterparts (Epac1+/+ and Epac2+/+). Two-hour occlusion and 22-hour reperfusion were conducted to induce ischemia/reperfusion injury to the retina. After tMCAO, the contralateral retinae displayed similar morphology between different genotypes. Neuronal loss, retinal edema and increase in immunoreactivity for aquaporin 4 (AQP4), glial fibrillary acidic protein (GFAP), peroxiredoxin 6 (Prx6) were observed in ipsilateral retinae. Epac2 ipsilateral retinae showed more neuronal loss in retinal ganglion cell layer, increased retinal thickness and stronger immunostaining of AQP4, GFAP, and Prx6 than those of Epac2+/+. However, Epac1 ipsilateral retinae displayed similar pathology as those in Epac1+/+ mice. Our observations suggest that Epac2-deficiency led to more severe ischemic retinopathy after retinal ischemia/reperfusion injury.published_or_final_versio

Heterozygous overexpression of preproendothelin-1 in endothelial cells enhances thromboxane-prostanoid receptor-induced contractions in the renal artery of obese mice

Session 3: Renal Diseases: O-5Circulating levels of the endothelium-derived peptide endothelin-1 (ET-1) are elevated in human obesity, and ET-1 mediated vascular tone is increased. The renal artery is important in controlling intrarenal blood # ow and is highly sensitive to ET-1. Whether or not ET-1 affects renal artery tone in obesity is unknown. To investigate the role of endogenous ET-1, a mouse model with tie-1 promoter-driven endothelium-restricted heterozygous overexpression of preproendothelin-1 was used (TET+/-). Obesity was induced in TET+/- and WT littermates by feeding a high fat diet ...postprin

Selective over-expression of endothelin-1 in endothelial cells exacerbates inner retinal edema and neuronal death in ischemic retina

The level of endothelin-1 (ET-1), a potent vasoconstrictor, was associated with retinopathy under ischemia. The effects of endothelial endothelin-1 (ET-1) over-expression in a transgenic mouse model using Tie-1 promoter (TET-1 mice) on pathophysiological changes of retinal ischemia were investigated by intraluminal insertion of a microfilament up to middle cerebral artery (MCA) to transiently block the ophthalmic artery. Two-hour occlusion and twenty-two-hour reperfusion were performed in homozygous (Hm) TET-1 mice and their non-transgenic (NTg) littermates. Presence of pyknotic nuclei in ganglion cell layer (GCL) was investigated in paraffin sections of ipsilateral (ischemic) and contralateral (non-ischemic) retinae, followed by measurement of the thickness of inner retinal layer. Moreover, immunocytochemistry of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS) and aquaporin-4 (AQP4) peptides on retinal sections were performed to study glial cell reactivity, glutamate metabolism and water accumulation, respectively after retinal ischemia. Similar morphology was observed in the contralateral retinae of NTg and Hm TET-1 mice, whereas ipsilateral retina of NTg mice showed slight structural and cellular changes compared with the corresponding contralateral retina. Ipsilateral retinae of Hm TET-1 mice showed more significant changes when compared with ipsilateral retina of NTg mice, including more prominent cell death in GCL characterized by the presence of pyknotic nuclei, elevated GS immunoreactivity in Müller cell bodies and processes, increased AQP-4 immunoreactivity in Müller cell processes, and increased inner retinal thickness. Thus, over-expression of endothelial ET-1 in TET-1 mice may contribute to increased glutamate-induced neurotoxicity on neuronal cells and water accumulation in inner retina leading to edema. © 2011 Cheung et al.published_or_final_versio

Aldose reductase deficiency protects the retinal neurons in a mouse model of retinopathy of prematurity

Poster Presentation: P64PURPOSE: Retinopathy of prematurity (ROP) is a common retinal disease occurred in premature babies. It is found to be related to oxidative stress while dysfunction of the neural retina has also been documented. We previously showed that genetic deletion or pharmacological inhibition of aldose reductase (AR), a rate- limiting enzyme in the polyol pathway, prevented ischemia-induced retinal ganglion cell (RGC) loss and oxidative stress. Here, we assessed the effects of AR deletion on retinal neurons using a mouse model of ROP. METHODS: Seven-day-old mouse pups were exposed to 75% oxygen for five days and returned to room air. The pathological neuronal changes were examined and compared between wild-type (WT) and AR-deficient retinae on P14 and P17 (P, postnatal). Retinal thickness was measured and immunohistochemistry for calbindin, calretinin, PKCα, Tuj1, glial fibrillary acidic protein (GFAP), nitrotyrosine (NT), as well as poly(ADP-ribose) (PAR) was performed. RESULTS: After hyperoxia exposure, significantly reduced inner nuclear layer (INL) and inner plexiform layer (IPL) thickness were found in both genotypes. The intensity of calbindin staining for horizontal cells in INL was reduced in the WT retinae but not in AR-deficient retinae. In addition, significant reduction was found in calretinin-positive amacrine cell bodies in central INL especially in WT retinae. Serious distortion was also observed in the three calretinin-positive strata along IPL in the WT retinae but not AR-deficient retinae on P17. Moreover, increased GFAP intensity across IPL indicating Müller cell processes was observed in AR-deficient retinae on P14 and in WT retinae on P17. Furthermore, increased NT immunoreactivity in INL and nuclear or para-nuclear PAR staining along GCL were observed in WT retina while these changes were not apparent in AR-deficient retina. CONCLUSION: Our observations demonstrated morphological changes of retinal neurons in the mouse model of ROP and indicated that AR deficiency showed neuronal protection in the retina, possibly through modulating glial responses and reducing oxidative stress.postprin