After confirming the overexpression of miRNAs (data not shown), we investigated their effect on FAS-induced apoptosis in hepatocytes. By cell counting,

we found that miR-221 inhibited Jo2-induced cell death most prominently in comparison to other miRNAs (Fig. 2A). We therefore focused on miR-221 for further analyses. WST assay also revealed that miR-221 overexpression followed by Jo2-treatment led to an increase in cell survival, whereas inhibition of miR-221 decreased cell survival (Fig. 2B). In order to determine whether increased hepatocyte survival was due to inhibition of apoptosis we measured the activity of caspase-3/7. buy Ivacaftor We found decreased caspase-3/7 activity in hepatocytes transfected with miR-221 mimic, whereas increased caspase-3/7 activity was seen in hepatocytes transfected with miR-221 inhibitor (Fig. 2C). Together, cell viability assay and caspase-3/7 assay provide evidence that miR-221 protects cultured hepatocytes from Jo2-induced apoptosis. We then addressed the question whether overexpression of miR-221 can rescue the observed high sensitivity of shDGCR8 cells to FAS-induced apoptosis. To this end, we transfected shDGCR8 cells with miR-221 mimic followed by FAS-induced apoptosis. By Annexin V staining and caspase-3/7 assay we found that shDGCR8 cells transfected with mimics of miR-221

had reduced apoptosis (Fig. 2D,E). Therefore, miR-221 can partially rescue cells from FAS-induced apoptosis and hence ABT-199 nmr partially compensate for global loss of miRNAs in shDGCR8 cells. Next we sought to investigate whether overexpression of miR-221 can protect mice from FAS-induced fulminant liver failure. To overexpress miRNAs in vivo, we used AAV8. AAV8 has been shown to transduce up to 100% hepatocytes when injected intravenously in mice.25 Moreover, a successful

miRNA delivery by AAV8 and regression of tumors has recently been shown in a mouse model of hepatocellular carcinoma.26 We therefore prepared AAV8-Ttr-miR-221 vector expressing miR-221 under the control of a hepatocyte-specific transthyretin Pyruvate dehydrogenase lipoamide kinase isozyme 1 (Ttr) promoter and an AAV8-Ttr-Cre (control) vector expressing Cre recombinase (Fig. 3A). In vivo hepatocyte transduction efficiency was assessed by injecting 1 × 1011 viral particles of AAV8-Ttr-Cre vectors into the tail vein of ROSA26 reporter mice,27 which contains a floxed stop codon upstream of the β-galactosidase reporter gene. Efficient hepatocyte transduction was confirmed by X-gal staining (Fig. 3B). We then injected 1 × 1011 viral particles of either AAV8-Ttr-Cre or AAV8-Ttr-miR-221 vector intravenously into BALB/c mice. AAV8-injected mice showed normal histology (Fig. 3B) and normal levels of transaminases (data not shown). Four days after AAV8 injection, we detected 8-fold higher expression of miR-221 in purified hepatocytes from mice injected with AAV8-Ttr-miR-221 compared to control hepatocytes from AAV8-Ttr-Cre-injected mice (Fig. 3C).