Absence of Sigma 1 Receptor Accelerates Photoreceptor Cell Death in a Murine Model of Retinitis Pigmentosa.

Purpose: Sigma 1 Receptor (Sig1R) is a novel therapeutic target in neurodegenerative diseases, including retinal disease. Sig1R-/- mice have late-onset retinal degeneration with ganglion cell loss that worsens under stress. Whether Sig1R plays a role in maintaining other retinal neurons is unknown, but was investigated here using rd10 mice, a model of severe photoreceptor degeneration.

Analysis of MTHFR, CBS, Glutathione, Taurine, and Hydrogen Sulfide Levels in Retinas of Hyperhomocysteinemic Mice.

Purpose: Hyperhomocysteinemia (Hhcy) is implicated in certain retinal neurovascular diseases, although whether it is causative remains uncertain. In isolated ganglion cells (GCs), mild Hhcy induces profound death, whereas retinal phenotypes in Hhcy mice caused by mutations in remethylation (methylene tetrahydrofolatereductase [Mthfr+/-]) or transsulfuration pathways (cystathionine β-synthase [Cbs+/-]) demonstrate mild GC loss and mild vasculopathy. The current work investigated compensation in vivo of one pathway for the other, and, because the transsulfuration pathway yields cysteine necessary for formation of glutathione (GSH), taurine, and hydrogen sulfide (H2S), they were analyzed also.

The Role of Sigma1R in Mammalian Retina.

This review article focuses on studies of Sigma 1 Receptor (Sigma1R) and retina . It provides a brief overview of the earliest pharmacological studies performed in the late 1990s that provided evidence of the presence of Sigma1R in various ocular tissues. It then describes work from a number of labs concerning the location of Sigma1R in several retinal cell types including ganglion, Müller glia , and photoreceptors .

Activation of the molecular chaperone, sigma 1 receptor, preserves cone function in a murine model of inherited retinal degeneration.

Retinal degenerative diseases are major causes of untreatable blindness, and novel approaches to treatment are being sought actively. Here we explored the activation of a unique protein, sigma 1 receptor (Sig1R), in the treatment of PRC loss because of its multifaceted role in cellular survival. We used Pde6β(rd10) (rd10) mice, which harbor a mutation in the rod-specific phosphodiesterase gene Pde6β and lose rod and cone photoreceptor cells (PRC) within the first 6 wk of life, as a model for severe retinal degeneration.

Role of Sigma 1 Receptor in Retinal Degeneration of the Ins2Akita/+ Murine Model of Diabetic Retinopathy.

Purpose: Sigma receptor 1 (Sigma1R), a nonopioid putative molecular chaperone, has neuroprotective properties in retina. This study sought to determine whether delaying administration of (+)-pentazocine, a high-affinity Sigma1R ligand after onset of diabetes in Ins2Akita/+ diabetic mice would afford retinal neuroprotection and to determine consequences on retinal phenotype in Ins2Akita/+ diabetic mice in the absence of Sigma1R.

Methods: Ins2Akita/+ diabetic and WT mice received intraperitoneal injections of (+)-pentazocine beginning 4 or 8 weeks after onset of diabetes; eyes were harvested at 25 weeks.

Efficient Endocytic Uptake and Maturation in Drosophila Oocytes Requires Dynamitin/p50.

Dynactin is a multi-subunit complex that functions as a regulator of the Dynein motor. A central component of this complex is Dynamitin/p50 (Dmn). Dmn is required for endosome motility in mammalian cell lines.

Retinal Ganglion Cell Loss and Mild Vasculopathy in Methylene Tetrahydrofolate Reductase (Mthfr)-Deficient Mice: A Model of Mild Hyperhomocysteinemia.

Purpose: Methylenetetrahydrofolate reductase (Mthfr) is a key enzyme in homocysteine-methionine metabolism. We investigated Mthfr expression in retina and asked whether mild hyperhomocysteinemia, due to Mthfr deficiency, alters retinal neurovascular structure and function.

Methods: Expression of Mthfr was investigated at the gene and protein level using quantitative (q) RT-PCR, in situ hybridization, immunoblotting, and immunohistochemistry (IHC).

Alterations of retinal vasculature in cystathionine-Beta-synthase mutant mice, a model of hyperhomocysteinemia.

Purpose: Mice with moderate/severe hyperhomocysteinemia due to deficiency or absence of the cbs gene encoding cystathionine-beta-synthase (CBS) have marked retinal disruption, ganglion cell loss, optic nerve mitochondrial dysfunction, and ERG defects; those with mild hyperhomocysteinemia have delayed retinal morphological/functional phenotype. Excess homocysteine is a risk factor for cardiovascular diseases; however, it is not known whether excess homocysteine alters retinal vasculature.

Methods: Cbs(+/+), cbs(+/-), and cbs(-/-) mice (age ∼3 weeks) were subjected to angiography; retinas were harvested for cryosections, flat-mount preparations, or trypsin digestion and subjected to immunofluorescence microscopy to visualize vessels using isolectin-B4, to detect angiogenesis using anti-VEGF and anti-endoglin (anti-CD105) and activated glial cells (anti-glial fibrillary acidic protein [anti-GFAP]) and to investigate the blood-retinal barrier using the tight junction markers zonula occludens-1 (ZO-1) and occludin.

Homocysteine-mediated modulation of mitochondrial dynamics in retinal ganglion cells.

Purpose: To evaluate the effect of excess homocysteine on the regulation of retinal ganglion cell mitochondrial dynamics.

Methods: Mice deficient in cystathionine-β-synthase (cbs) were used as a model of hyperhomocysteinemia. Gene and protein expression analyses of Opa1 and Fis1 were performed on cbs⁺/⁻ neural retinas.

Molecular and biochemical characterization of folate transport proteins in retinal Müller cells.

Purpose: To analyze the mechanisms of folate uptake in retinal Müller cells.

Methods: RT-PCR and Western blot analysis were performed in freshly isolated neural retina and RPE/eyecup, primary mouse Müller cells, and rMC-1 cells for the three known folate transport proteins folate receptor alpha (FRalpha), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC). Laser scanning confocal microscopy (LSCM) and immunoelectron microscopy were used to determine the subcellular location of FRalpha and PCFT in primary Müller cells.

Endogenous elevation of homocysteine induces retinal neuron death in the cystathionine-beta-synthase mutant mouse.

Purpose: To determine the effects of endogenous elevation of homocysteine on the retina using the cystathionine beta-synthase (cbs) mutant mouse.

Methods: Retinal homocysteine in cbs mutant mice was measured by high-performance liquid chromatography (HPLC). Retinal cryosections from cbs(-/-) mice and cbs(+/-) mice were examined for histologic changes by light and electron microscopy.

Expression and localization of GPR109A (PUMA-G/HM74A) mRNA and protein in mammalian retinal pigment epithelium.

Purpose: GPR109A has been identified as a G-protein-coupled receptor for niacin. beta-hydroxybutyrate (beta-HB) is a physiologic ligand for the receptor. beta-HB, the predominate ketone body in circulation, is an important energy source for neurons, including retinal neurons, under various physiologic and pathologic conditions.

Diabetes Accelerates Retinal Neuronal Cell Death In A Mouse Model of Endogenous Hyperhomocysteinemia.

Hyperhomocysteinemia has been implicated in visual dysfunction. We reported recently that mice with endogenous hyperhomocysteinemia, due to mutation of the cystathionine-β-synthase (cbs) gene, demonstrate loss of neurons in the retinal ganglion cell (RGC) layer and other retinal layers as homocysteine levels increase. Some clinical studies implicate hyperhomocysteinemia in the pathogenesis of diabetic retinopathy, which is also characterized by RGC loss.

Expression and function of system N glutamine transporters (SN1/SN2 or SNAT3/SNAT5) in retinal ganglion cells.

Purpose: Glutamine transport is essential for the glutamate-glutamine cycle, which occurs between neurons and glia. System N, consisting of SN1 (SNAT3) and SN2 (SNAT5), is the principal mediator of glutamine transport in retinal Müller cells. Mediators of glutamine transport in retinal ganglion cells were investigated.

Palisade is required in the Drosophila ovary for assembly and function of the protective vitelline membrane.

The innermost layer of the Drosophila eggshell, the vitelline membrane, provides structural support and positional information to the embryo. It is assembled in an incompletely understood manner from four major proteins to form a homogeneous, transparent extracellular matrix. Here we show that RNAi knockdown or genetic deletion of a minor constituent of this matrix, Palisade, results in structural disruptions during the initial synthesis of the vitelline membrane by somatic follicle cells surrounding the oocyte, including wide size variation among the precursor vitelline bodies and disorganization of follicle cell microvilli.

In vivo protection against retinal neurodegeneration by sigma receptor 1 ligand (+)-pentazocine.

Purpose: To evaluate the neuroprotective properties of the sigma receptor 1 (sigmaR1) ligand, (+)-pentazocine in an in vivo model of retinal neurodegeneration.

Methods: Spontaneously diabetic Ins2(Akita/+) and wild-type mice received intraperitoneal injections of (+)-pentazocine for 22 weeks beginning at diabetes onset. Retinal mRNA and protein were analyzed by RT-PCR and Western blot analysis.

Hepcidin expression in mouse retina and its regulation via lipopolysaccharide/Toll-like receptor-4 pathway independent of Hfe.

Hepcidin is a hormone central to the regulation of iron homeostasis in the body. It is believed to be produced exclusively by the liver. Ferroportin, an iron exporter, is the receptor for hepcidin.

Serine racemase expression and D-serine content are developmentally regulated in neuronal ganglion cells of the retina.

D-Serine, the endogenous ligand for the glycine modulatory binding site of the NMDA receptor, and serine racemase, the enzyme that converts L-serine to D-serine, have been reported in vertebrate retina; initial reports suggested that localization was restricted to Müller glial cells. Recent reports, in which D-serine and serine racemase were detected in neurons of the brain, prompted the present investigation of neuronal expression of D-serine and serine racemase in retina and whether expression patterns were developmentally regulated. RT-PCR, in situ hybridization, western blotting, immunohistochemistry, and immunocytochemical methods were used to localize D-serine and serine racemase in intact retina obtained from 1 to 3 day, 3 week, and 18 week mouse retinas and in primary ganglion cells harvested by immunopanning from neonatal mouse retina.

Spontaneous development of intestinal and colonic atrophy and inflammation in the carnitine-deficient jvs (OCTN2(-/-)) mice.

Carnitine is essential for transport of long-chain fatty acids into mitochondria for their subsequent beta-oxidation, but its role in the gastrointestinal tract has not been well described. Recently several genetic epidemiologic studies have shown strong association between mutations in carnitine transporter genes OCTN1 and OCTN2 and a propensity to develop Crohn's disease. This study aims to investigate role of carnitine and beta-oxidation in the GI tract.

Expression of the sodium-coupled monocarboxylate transporters SMCT1 (SLC5A8) and SMCT2 (SLC5A12) in retina.

Purpose: Monocarboxylates are primary energy substrates in the retina. Recently, the authors identified two sodium-coupled monocarboxylate transporters (SMCTs), SMCT1 (a high-affinity transporter) and SMCT2 (a low-affinity transporter). Expression of SMCT1 and SMCT2 has been studied in several tissues; however, little is known about their expression in retina.

Transport of nicotinate and structurally related compounds by human SMCT1 (SLC5A8) and its relevance to drug transport in the mammalian intestinal tract.

Unlabelled: PURPOSE. To examine the involvement of human SMCT1, a Na+-coupled transporter for short-chain fatty acids, in the transport of nicotinate/structural analogs and monocarboxylate drugs, and to analyze its expression in mouse intestinal tract.

Materials And Methods: We expressed human SMCT1 in X.

Expression and polarized localization of the hemochromatosis gene product HFE in retinal pigment epithelium.

Purpose: Hereditary hemochromatosis is an autosomal recessive disorder of iron overload leading to oxidative stress. Mutations in HFE are responsible for approximately 90% of cases of this disease. HFE is the principal regulator of iron homeostasis, and the process involves interaction with transferrin receptor (TfR)-1, transferrin receptor (TfR)-2, and beta2-microglobulin (beta2M).

c/ebpdelta Null mouse as a model for the double knock-out of slc5a8 and slc5a12 in kidney.

slc5a8 and slc5a12 represent the high affinity and low affinity Na+/lactate co-transporters, respectively, in the kidney. Here we show that these transporters are expressed in the apical membrane of the proximal tubular cells in mouse kidney, indicating that these transporters are likely to mediate the first step in the renal reabsorption of lactate. Interestingly, the renal expression of both transporters is almost completely ablated in mice homozygous for the deletion of the transcription factor c/ebpdelta.

Infection of retinal neurons during murine cytomegalovirus retinitis.

Purpose: Previous results suggest that retinal neurons are infected early during murine cytomegalovirus (MCMV) infection of the inner retina. The purposes of this study were to identify which retinal neurons are infected and to determine the routes by which MCMV spreads in the retina.

Methods: Immunosuppressed (IS) BALB/c mice were inoculated with 5 x 10(3) PFU of MCMV (k181) through the supraciliary route.

Death of retinal neurons in streptozotocin-induced diabetic mice.

Purpose: Neuronal cell death has been reported in retinas of humans with diabetic retinopathy and in diabetic rat models. Little is known about neuronal cell death in mouse models of diabetic retinopathy. This study was designed to determine whether neurons are lost in diabetic mouse retinas and whether the loss involves an apoptotic process.