l-817818 and Disease-Models--Animal

Somatostatin plays important roles in modulating neuronal functions by activating the five specific G-protein coupled receptors (sst1-sst5). Previous studies have demonstrated that sst5 were expressed in retinal ganglion cells (RGCs) and sst5 agonist attenuated the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid-induced retinal neurotoxicity. In this study, we investigated effects and underlying mechanisms of the sst5 agonist L-817,818 on RGC injury induced by elevated intraocular pressure (COH) in experimental glaucoma. Our results showed that intraperitoneal administration of L-817,818 significantly reduced RGC loss and decreased the number of terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL)-positive RGCs in COH retinas, suggesting that L-817,818 may attenuate RGC apoptosis. Consistently, in COH retinas with L-817,818 administration, both the down-regulated mRNA and protein levels of anti-apoptotic Bcl-2 and the up-regulated mRNA and protein levels of pro-apoptotic Bax were partially reversed. L-817,818 administration downregulated the expression of apoptosis-related proteins caspase-9 and caspase-3 in COH retinas. In addition, L-817,818 administration reduced the concentrations of reactive oxygen species/reactive nitrogen species and malondialdehyde, and ameliorated the functions of mitochondrial respiratory chain complex (MRCC). Our results imply that administration of the sst5 agonist L-817,818 reduces RGC loss in COH rats through decreasing RGC apoptosis, which is mediated by regulating Bcl-2/Bax balance, reducing oxidative stress and rescuing activities of MRCC. Activation of sst5 may provide neuroprotective roles for RGCs in glaucoma.

Topics: Amides; Animals; Apoptosis; bcl-2-Associated X Protein; Cell Survival; Disease Models, Animal; Glaucoma; Hydrogen Peroxide; In Situ Nick-End Labeling; Injections, Intraperitoneal; Male; Malondialdehyde; Naphthalenes; Neuroprotective Agents; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Real-Time Polymerase Chain Reaction; Receptors, Somatostatin; Retinal Ganglion Cells; RNA, Messenger; Superoxide Dismutase

Somatostatin receptor 5 (SSTR5) is involved in intestinal barrier protection during colitis through modulating tight junction (TJ) proteins, but the mechanisms of SSTR5 in TJ regulation are largely unknown. Therefore, the present study was designed to illuminate how SSTR5 modulated intestinal barrier function and TJ proteins. In this study, activation of SSTR5 by its special agonist L817,818 effectively ameliorated impaired intestinal barrier function in TNF-α-pretreated cells and mice with colitis. Restoration of intestinal barrier function was dependent on upregulation of claudin-4 and ZO-1. Suppression of SSTR5 signaling through specific siRNA or the antagonist BIM23056 markedly exacerbated TNF-α-induced claudin-4 and ZO-1 damage. L817,818 treatment markedly suppressed TNF-α-induced NF-κB p65 phosphorylation, myosin light chain kinase (MLCK) upregulation and myosin light chain (MLC) phosphorylation. Exposure to a NF-κB inhibitor (QNZ) or MLCK inhibitor (ML-7) effectively inhibited compromised claudin-4 and ZO-1 induced by BIM23056/TNF-α. These observations indicate that activation of SSTR5 protects intestinal barrier function by upregulating claudin-4 and ZO-1 expression, which is mediated by NF-κB-MLCK-MLC signaling. Taken together, our findings suggest that SSTR5 might represent a promising target for colitis therapy.

Topics: Amides; Animals; Caco-2 Cells; Claudin-4; Colitis; Disease Models, Animal; Gene Expression Regulation; HT29 Cells; Humans; Mice; Naphthalenes; Oligopeptides; Receptors, Somatostatin; Signal Transduction; Tumor Necrosis Factor-alpha; Zonula Occludens-1 Protein

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

In a recent study, we employed an in vivo model of retinal excitotoxicity to investigate the neuroprotective effect of somatostatinergic agents. Intravitreal administration of somatostatin and sst(2) selective agonists protected the retina from (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid hydrobromide (AMPA) induced excitotoxicity. The sst(1) and sst(4) selective ligands had no effect (Kiagiadaki and Thermos, 2008). The presence of sst(5) receptors in rat retina was only recently reported (Ke and Zhong, 2007). Synthetic agonists that activate sst(2) receptors also bind with high affinity to the sst(5) subtype. In the present study the putative neuroprotective effects of sst(5) receptor activation were investigated. Adult female and male Sprague-Dawley (250-350g) rats were employed. Groups of animals received intravitreally PBS (50mM) or AMPA (42 nmol/eye) alone or in combination with L-817,818 (sst(5), 10(-5), 10(-4)M). To exclude neuroprotective effects via the activation of sst(2) receptors, L-817,818 (10(-4)M) was coinjected with the sst(2) antagonist CYN-154806 (10(-4)M). Immunohistochemistry (IHC) studies using the anti-retinal marker choline acetyltransferase (ChAT) and TUNEL staining were employed to examine retinal cell loss and protection. IHC and Western blot analysis were also employed to assess whether the sst(5) receptors are viable in the AMPA treated tissue as compared to control retina. sst(5) receptors were not affected by AMPA. L-817,818 protected the retina from the AMPA insult in the dose of 10(-4)M, while CYN-154806 (10(-4)M) had no effect on the sst(5) neuroprotection. TUNEL staining confirmed the AMPA-induced retinal toxicity and the L-817,818 neuroprotection. These results demonstrate for the first time that sst(5) receptors are functional in the retina, and that sst(5) analogs administered intravitreally protect the retina from excitotoxicity. Further studies are essential to ascertain the therapeutic relevance of these results.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Amides; Animals; Cell Death; Choline O-Acetyltransferase; Disease Models, Animal; Excitatory Amino Acid Agonists; Female; Gene Expression Regulation; In Situ Nick-End Labeling; Male; Naphthalenes; Neuroprotective Agents; Neurotoxicity Syndromes; Oligopeptides; Rats; Rats, Sprague-Dawley; Receptors, Somatostatin; Retina