L-Dopa decarboxylase modulates autophagy in hepatocytes and is implicated in dengue virus-caused inhibition of autophagy completion.

The enzyme L-Dopa Decarboxylase (DDC) synthesizes the catecholamine dopamine and the indolamine serotonin. Apart from its role in the brain as a neurotransmitter biosynthetic enzyme, DDC has been detected also in the liver and other peripheral organs, where it is implicated in cell proliferation, apoptosis, and host-virus interactions. Dengue virus (DENV) suppresses DDC expression at the later stages of infection, during which DENV also inhibits autophagosome-lysosome fusion. As dopamine affects autophagy in neuronal cells, we investigated the possible association of DDC with autophagy in human hepatocytes and examined whether DDC mediates the relationship between DENV infection and autophagy. We performed DDC silencing/overexpression and evaluated autophagic markers upon induction of autophagy, or suppression of autophagosome-lysosome fusion. Our results showed that DDC favored the autophagic process, at least in part, through its biosynthetic function, while knockdown of DDC or inhibition of DDC enzymatic activity prevented autophagy completion. In turn, autophagy induction upregulated DDC, while autophagy reduction by chemical or genetic (ATG14L knockout) ways caused the opposite effect. This study also implicated DDC with the cellular energetic status, as DDC silencing reduced the oxidative phosphorylation activity of the cell. We also report that upon DDC silencing, the repressive effect of DENV on the completion of autophagy was enhanced, and the inhibition of autolysosome formation did not exert an additive effect on viral proliferation. These data unravel a novel role of DDC in the autophagic process and suggest that DENV downregulates DDC expression to inhibit the completion of autophagy, reinforcing the importance of this protein in viral infections.

Association of Hepatitis C Virus Replication with the Catecholamine Biosynthetic Pathway.

A bidirectional negative relationship between Hepatitis C virus (HCV) replication and gene expression of the catecholamine biosynthetic enzyme L-Dopa decarboxylase (DDC) was previously shown in the liver and attributed at least to an association of DDC with phosphatidylinositol 3-kinase (PI3K). Here, we report that the biosynthesis and uptake of catecholamines restrict HCV replication in hepatocytes, while HCV has developed ways to reduce catecholamine production. By employing gene silencing, chemical inhibition or induction of the catecholamine biosynthetic and metabolic enzymes and transporters, and by applying the substrates or the products of the respective enzymes, we unravel the role of the different steps of the pathway in viral infection. We also provide evidence that the effect of catecholamines on HCV is strongly related with oxidative stress that is generated by their autoxidation in the cytosol, while antioxidants or treatments that lower cytosolic catecholamine levels positively affect the virus. To counteract the effect of catecholamines, HCV, apart from the already reported effects on DDC, causes the down-regulation of tyrosine hydroxylase that encodes the rate-limiting enzyme of catecholamine biosynthesis and suppresses dopamine beta-hydroxylase mRNA and protein amounts, while increasing the catecholamine degradation enzyme monoamine oxidase. Moreover, the NS4B viral protein is implicated in the effect of HCV on the ratio of the ~50 kDa DDC monomer and a ~120 kDa DDC complex, while the NS5A protein has a negative effect on total DDC protein levels.

Aortic root replacement: comparison of clinical outcome between different surgical techniques.

OBJECTIVES: To examine the influence of different surgical procedures on clinical outcome in patients undergoing aortic root replacement for ascending aorta aneurysm (AAA) with or without concomitant aortic valve regurgitation (AR). METHODS: Between 2000 and 2011, a total of 370 patients (mean age 52 ± 17 years) underwent aortic root replacement. Patients were retrospectively assigned to three groups according to the surgical procedures: valve-sparing root replacement (VSRR) (Group A; n = 178), Bentall procedure with a biological conduit (Group B; n = 91) and with a mechanical conduit (Group C; n = 101). All patients were studied with clinical assessment and echocardiography during a mean follow-up time of 4.3 years. RESULTS: Estimated 5-year survival probability rates for Groups A, B and C were 95.2 ± 1.8, 80.9 ± 4.4 and 79.3 ± 4.5%, respectively (P < 0.01; log-rank). Estimated 5-year survival probability rates for patients who had undergone elective operations for Groups A, B and C were 96.1 ± 1.8, 88.9 ± 4.4 and 82.3 ± 4.9%, respectively (P = 0.02; log-rank). Actuarial overall 5-year freedom from valve-related reoperations was 94.3 ± 1.9%, without being significantly different between groups (P = 0.13; log-rank). Estimated 5-year probability rates for freedom from major bleeding events for Groups A, B and C were 99.3 ± 0.7, 100 and 93.0 ± 3.4%, respectively (P = 0.03; log-rank). Actuarial overall 5-year freedom from thromboembolism and endocarditis were 93.6 ± 0.2% (P = 0.53; log-rank) and 96.1 ± 1.5% (P = 0.46; log-rank), respectively, without significant differences between groups. CONCLUSIONS: The data from the present study support the VSRR strategy in patients undergoing aortic root replacement. Furthermore, if Bentall operation is unavoidable, biological valved conduit should be preferred in order to avoid late bleeding complications.