Non-Native Conformational Isomers of the Catalytic Domain of PCSK9 Induce an Immune Response, Reduce Lipids and Increase LDL Receptor Levels.

PCSK9 (Proprotein convertase subtilisin/kexin type 9) increases plasma cholesterol levels by promoting LDL receptor degradation. Current antibody inhibitors block the interaction between PCSK9 and LDL receptors, significantly decrease plasma cholesterol levels, and provide beneficial clinical outcomes. To reduce the action of PCSK9 in plasma, a novel strategy that will produce a panel of non-native, conformationally-altered isomers of PCSK9 (X-PCSK9) to develop active immunotherapy targeting of native PCSK9 and inhibiting/blocking the interaction of PCSK9 with LDL receptor, thus decreasing plasma cholesterol levels is proposed. The authors used the scrambled disulfide bond technique to generate conformationally-altered isomers of the catalytic domain of mouse PCSK9. The focus was on the immune response of four X-isomers and their effects on plasma cholesterol and triglyceride levels in both C57BL/6J and Apoe-/- mice. The authors showed that the four immunogens produced significant immunogenicity against native PCSK9 to day 120 after immunization of C57BL/6J and Apoe-/- mice. This resulted in significantly decreased plasma cholesterol levels in C57BL/6J mice, and to a lesser degree in Apoe-/- mice. The X-PCSK9-B1 treated mice had increased LDL receptor mRNA and protein levels at day 120 after treatment. Thus, this study provides a new, potentially promising approach that uses long-term immunotherapy for a treatment of hypercholesterolemia.

Epithelial-to-mesenchymal transition induces cell cycle arrest and parenchymal damage in renal fibrosis.

Kidney fibrosis is marked by an epithelial-to-mesenchymal transition (EMT) of tubular epithelial cells (TECs). Here we find that, during renal fibrosis, TECs acquire a partial EMT program during which they remain associated with their basement membrane and express markers of both epithelial and mesenchymal cells. The functional consequence of the EMT program during fibrotic injury is an arrest in the G2 phase of the cell cycle and lower expression of several solute and solvent transporters in TECs. We also found that transgenic expression of either Twist1 (encoding twist family bHLH transcription factor 1, known as Twist) or Snai1 (encoding snail family zinc finger 1, known as Snail) expression is sufficient to promote prolonged TGF-ß1-induced G2 arrest of TECs, limiting the cells' potential for repair and regeneration. In mouse models of experimentally induced renal fibrosis, conditional deletion of Twist1 or Snai1 in proximal TECs resulted in inhibition of the EMT program and the maintenance of TEC integrity, while also restoring cell proliferation, dedifferentiation-associated repair and regeneration of the kidney parenchyma and attenuating interstitial fibrosis. Thus, inhibition of the EMT program in TECs during chronic renal injury represents a potential anti-fibrosis therapy.

Long-term Expression of Apolipoprotein B mRNA-specific Hammerhead Ribozyme via scAAV8.2 Vector Inhibits Atherosclerosis in Mice.

Target substrate-specific hammerhead ribozyme cleaves the specific mRNA efficiently and results in the inhibition of gene expression. In humans, overproduction of apolipoprotein B (apoB) is positively associated with premature coronary artery diseases. The goal of this study is to demonstrate that long-term reduction of apoB gene expression using hammerhead ribozyme would result in inhibition of atherosclerosis development. We designed two hammerhead ribozymes targeted at the nucleotides of apoB mRNA GUC(2326) (designated RB1) and GUA(6679) (designated RB15), and we used self-complementary adeno-associated virus 8.2 (scAAV8.2) vector to deliver these active ribozymes of RB1, RB15, combination of RB1/RB15, and an inactive hammerhead ribozyme RB15 mutant to atherosclerosis-prone LDb mice (Ldlr(-/-)Apobec1(-/-)). LDb mice lack both low density lipoproteins (LDL) receptor (Ldlr(-/-)) and apoB mRNA editing enzyme (Apobec1(-/-)) genes and develop atherosclerosis spontaneously. After the RB1, RB15, or combination of RB1/RB15 ribozymes treatment, the LDb mice had significantly decreased plasma triglyceride and apoB levels, resulting in markedly decreased of atherosclerotic lesions, Furthermore, the active ribozymes treatment decreased the levels of diacylglycerol acyltransferase 1 (Dgat1) mRNA and the levels of multiple diacylglycerol (DAG) molecular species. These results provide the first evidence that decreased apoB levels results to reduction of Dgat1 expression and triglyceride levels (TAG), which had a significant impact on the development of atherosclerosis.Molecular Therapy-Nucleic Acids (2013) 2, e125; doi:10.1038/mtna.2013.53; published online 1 October 2013.