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Lymphocyte trafficking out of secondary lymphoid organs is regulated by concentration gradient-dependent interactions between the membrane-derived lysophospholipid signaling molecule sphingosine 1-phosphate (S1P) and the G-protein-coupled receptor, S1P 1 Etrasimod is a novel, next-generation, small-molecule, oral S1P receptor modulator in clinical development for the treatment of immune-mediated inflammatory disorders, including ulcerative colitis. In preclinical pharmacology studies, etrasimod was a full agonist of recombinant human (6.1 nM EC 50 ), mouse (3.65 nM EC 50 ), dog (4.19 nM EC 50 ), and monkey (8.7 nM EC 50 ) S1P 1 receptors, and a partial agonist of human S1P 4 (147 nM EC 50 ) and S1P 5 (24.4 nM EC 50 ), with relative efficacies of 63% and 73% of S1P response, respectively; whereas neither agonist nor antagonist activity was observed for human S1P 2 or S1P 3 A dose-dependent relationship was observed for etrasimod plasma concentration and lymphocyte count in mice, and chronic treatment with etrasimod resulted in attenuation of inflammation in a CD4 + CD45RB high T-cell transfer mouse model of colitis., (Copyright © 2019 by The American Society for Pharmacology and Experimental Therapeutics.)

Regulation of cellular metabolism by the citric acid cycle occurs in the mitochondria. However, the citric acid cycle intermediate succinate was shown recently to be a ligand for the G-protein-coupled receptor GPR91. Here, we describe a role for succinate and its receptor in the stimulation of hematopoietic progenitor cell (HPC) growth. GPR91 mRNA and protein expression were detected in human bone marrow CD34+ progenitor cells, as well as in erythroid and megakaryocyte cultures and the erythroleukemic cell line TF-1. Treatment of these cell cultures with succinate resulted in increased proliferation rates. The proliferation response of TF-1 cells was pertussis toxin (PTX)-sensitive, suggesting a role for Gi signaling. Proliferation was also blocked when TF-1 cells were transfected with small interfering RNA specific for GPR91. Succinate stimulated activation of the Erk MAPK pathway and inositol phosphate accumulation in a PTX-sensitive manner. Pretreatment of TF-1 cells with the Erk1/2 kinase (MEK) inhibitor PD98059 blocked the proliferation response. Succinate treatment additionally protected TF-1 cells from cell death induced by serum deprivation. Finally, in vivo administration of succinate was found to elevate the levels of hemoglobin, platelets, and neutrophils in a mouse model of chemotherapy-induced myelosuppression. These results suggest that succinate-GPR91 signaling is capable of promoting HPC development.

Plasmid DNA condensed by polylysine enhanced cationic-liposome-mediated transfection of Hep G2 cells. The luciferase expression plasmid pCMVL was complexed with the polycation poly-L-lysine and mixed with liposomes that contained a 1:1 molar ratio of the cationic lipid 1,2-dioleoyloxy-3-trimethyl-ammoniumpropane, with the neutral phospholipid 1,2-di-(cis-9-octadecenoyl)-sn-glycero-3-phosphoethanolamine. Polylysine enhanced cationic-liposome-mediated transfection of the hepatoblastoma cell line Hep G2 9-fold compared with pCMVL complexed alone with liposomes. The ratio of cationic to anionic charge of the polylysine-pCMVL complexes, and the quantity of cationic liposomes, are important determinants for optimal transfection of Hep G2 cells.

Vascular endothelial growth factor was infused into rat carotid arteries for 3 minutes immediately after endothelial denudation by balloon injury. Endothelial proliferation was determined by immunohistochemical labelling of proliferating cell nuclear antigen using Häutchen preparations. The proliferation index, or number of proliferating cells/total cells, measured at 25.5 or 30 hours was markedly increased after infusion of vascular endothelial growth factor. In addition, the total number of proliferating cells increased with increasing doses up to 100 micrograms total dose per infusion. These data indicate that infusion of vascular endothelial growth factor increases endothelial cell proliferation after mechanical denudation injury of the vascular wall.

The liver is an attractive target tissue for gene therapy. Current approaches for hepatic gene delivery include retroviral and adenoviral vectors, liposome/DNA, and peptide/DNA complexes. This study describes a technique for direct injection of DNA into liver that led to significant gene expression. Gene expression was characterized in both rats and cats following injection of plasmid DNA encoding several different proteins. Luciferase activity was measured after injection of plasmid DNA encoding the luciferase gene (pCMVL), beta-galactosidase (beta-Gal) activity was evaluated in situ using plasmid DNA encoding Lac Z (pCMV beta), and serum concentration of secreted human alpha-1-antitrypsin was measured following injection of plasmid DNA encoding this protein (pRC/CMV-sHAT). Several variables, including injection technique, DNA dose, and DNA diluent, were investigated. Direct injection of pCMVL resulted in maximal luciferase expression at 24-48 hr. beta-Gal staining demonstrated that the majority of transfected hepatocytes were located near the injection site. Significant concentrations of human alpha-1-antitrypsin were detected in the serum of animals injected with pRC/CMV-sHAT. These findings demonstrate the general principle that direct injection of plasmid DNA into liver can lead to significant gene expression.