The use of miR122 and its target sequence in adeno-associated virus-mediated trichosanthin gene therapy.

OBJECTIVE: Plant-derived cytotoxic transgene expression, such as trichosanthin (tcs), regulated by recombinant adeno-associated virus (rAAV) vector is a promising cancer gene therapy. However, the cytotoxic transgene can hamper the vector production in the rAAV producer cell line, human embryonic kidney (HEK293) cells. Here, we explored microRNA-122 (miR122) and its target sequence to limit the expression of the cytotoxic gene in the rAAV producer cells. METHODS: A miR122 target (122T) sequence was incorporated into the 3' untranslated region of the tcs cDNA sequence. The firefly luciferase (fluc) transgene was used as an appropriate control. Cell line HEK293-mir122 was generated by the lentiviral vector-mediated genome integration of the mir122 gene in parental HEK293 cells. The effects of miR122 overexpression on cell growth, transgene expression, and rAAV production were determined. RESULTS: The presence of 122T sequence significantly reduced transgene expression in the miR122-enriched Huh7 cell line (in vitro), fresh human hepatocytes (ex vivo), and mouse liver (in vivo). Also, the normal liver physiology was unaffected by delivery of 122T sequence by rAAV vectors. Compared with the parental cells, the miR122-overexpressing HEK293-mir122 cell line showed similar cell growth rate and expression of transgene without 122T, as well as the ability to produce liver-targeting rAAV vectors. Fascinatingly, the yield of rAAV vectors carrying the tcs-122T gene was increased by 77.7-fold in HEK293-mir122 cells. Moreover, the tcs-122T-containing rAAV vectors significantly reduced the proliferation of hepatocellular carcinoma cells without affecting the normal liver cells. CONCLUSION: HEK293-mir122 cells along with the 122T sequence provide a potential tool to attenuate the cytotoxic transgene expression, such as tcs, during rAAV vector production.

Protective effects of Schisandrin on high glucose-induced changes of RhoA and eNOS activity in human umbilical vein endothelial cells.

Schisandrin, derived from the Chinese medicinal herb Schisandra chinensis, has been found to confer protective effects on circulation systems. But the underlying molecular mechanisms remain unclear. The aim of this study was to investigate the effects of a high level of glucose on RhoA and eNOS activity in human umbilical vein endothelial cells(HUVECs) and how Schisandrin plays a role in mediating these effects. To find the optimal treatment time, HUVECs were cultured at a high glucose concentration (30 mM) for different lengths of time (0, 12, 24, and 48 h). Subsequently, the cells were randomized into five groups: a normal group, a high glucose group, and three high glucose groups that were given different doses (5, 10, and 20 µM) of Schisandrin. The cells were pretreated with Schisandrin for 24 h before stimulation with high glucose. The morphology of HUVECs in the various groups was assessed under a light microscope. Immunocytochemical staining was used to detect the level of p-MYPT1 expression. The levels of RhoA activity were determined using the RhoA Activation Assay Biochem Kit. The levels of eNOS activity were examined using a nitrate reduction test. The results showed that in the high glucose group, the activity of RhoA was increased and the activity of eNOS was reduced, thus decreasing the secretion of NO. However, after pretreatment with Schisandrin (10, 20 µM), the activity of RhoA was inhibited and the activity of eNOS increased, which led to an increase in NO production compared with the high glucose group. There was no evident difference between the 5 µM Schisandrin group and the high glucose group. Taken together, these findings indicate that Schisandrin can improve the function of endothelial cells by lowering the activity of RhoA/Rho kinase and raising both the activity of eNOS and the production of NO.