Association between sustained virological response and clinical outcomes in patients with hepatitis C infection and hepatocellular carcinoma.

BACKGROUND: Sustained viral response (SVR) improves survival for patients with hepatitis C (HCV) and hepatocellular carcinoma (HCC) after curative treatment; however, the benefit of SVR in those with active HCC with a significant competing risk of mortality is unknown. This study aimed to evaluate the association between SVR and outcomes in patients with active HCC. METHODS: The authors performed a multicenter, retrospective cohort study including consecutive adults with HCV cirrhosis and treatment-naive HCC diagnosed between 2014 and 2018. Patients were stratified into two groups: active viremia (n = 431) and SVR before HCC diagnosis (n = 135). All patients underwent nonsurgical therapy as their initial treatment and were followed until liver transplantation, last follow-up, or death. The primary outcome was incident or worsening hepatic decompensation within 6 months and the secondary outcome was overall survival. All analyses used inverse probability of treatment weights (IPTW) to account for differences between the nonrandomized cohorts. RESULTS: Post-SVR patients had significantly lower odds of hepatic decompensation compared to viremic patients (odds ratio [OR], 0.18; 95% confidence interval [CI], 0.06-0.59). Results were consistent among subgroups of patients with Child Pugh A cirrhosis (OR, 0.22; 95% CI, 0.04-0.77), Barcelona Clinic Liver Cancer stage B/C HCC (OR, 0.20; 95% CI, 0.04-0.65), and those receiving nonablative HCC therapies (OR, 0.21; 95% CI, 0.07-0.67). However, in IPTW multivariable Cox regression, SVR was not associated with improved survival (hazard ratio, 0.79; 95% CI, 0.56-1.12). CONCLUSIONS: Patients with HCV-related HCC and SVR are less likely to experience hepatic decompensation than viremic patients, suggesting patients with HCC who are undergoing nonsurgical therapies may benefit from DAA treatment.

Sexually Acquired Hepatitis C Infection in HIV-Uninfected Men Who Have Sex With Men Using Preexposure Prophylaxis Against HIV.

Sexually acquired hepatitis C virus (HCV) infections among human immunodeficiency virus (HIV)-uninfected men who have sex with men (MSM) have been rare. With the introduction of preexposure prophylaxis (PrEP) against HIV, we hypothesized that these infections would increase. Between 2013 and 2018, we diagnosed 15 likely sexually acquired HCV infections among 14 MSM using PrEP. Most (87%) were asymptomatic, detected by routine alanine transaminase (ALT) or HCV monitoring. Half reported increasing sex partners and drug use after starting PrEP; 5 reported injection of methamphetamine. Interventions are needed to prevent sexually acquired HCV infections by MSM using PrEP. Centers for Disease Control and Prevention guidelines for monitoring during PrEP should include regular ALT and HCV testing.

A bioluminescent transposon reporter-trap identifies tumor-specific microenvironment-induced promoters in Salmonella for conditional bacterial-based tumor therapy.

UNLABELLED: Salmonella specifically localize to malignant tumors in vivo, a trait potentially exploitable as a delivery system for cancer therapeutics. To characterize mechanisms and genetic responses of Salmonella during interaction with living neoplastic cells, we custom-designed a promoterless transposon reporter containing bacterial luciferase. Analysis of a library containing 7,400 independent Salmonella transposon insertion mutants in coculture with melanoma or colon carcinoma cells identified five bacterial genes specifically activated by cancer cells: adiY, yohJ, STM1787, STM1791, and STM1793. Experiments linked acidic pH, a common characteristic of the tumor microenvironment, to a strong, specific, and reversible stimulus for activation of these Salmonella genes in vitro and in vivo. Indeed, a Salmonella reporter strain encoding a luciferase transgene regulated by the STM1787 promoter, which contains a tusp motif, showed tumor-induced bioluminescence in vivo. Furthermore, Salmonella expressing Shiga toxin from the STM1787 promoter provided potent and selective antitumor activity in vitro and in vivo, showing the potential for a conditional bacterial-based tumor-specific therapeutic. SIGNIFICANCE: Salmonella, which often encounter acidic environments during classical host infection, may co-opt evolutionarily conserved pathways for tumor colonization in response to the acidic tumor microenvironment. We identified specific promoter sequences that provide a platform for targeted Salmonella-based tumor therapy in vivo.

Attention-deficit/hyperactivity disorder symptoms in offspring of mothers with impaired serotonin production.

CONTEXT: Exposure to adverse events during prenatal and postnatal development, as well as serotonin deficiency, have been implicated in disturbances of mood and impulsivity, but the underlying mechanisms are unknown. OBJECTIVE: To investigate the long-term effects of an impaired serotonin synthesis on the developing human brain, we studied the effects of nonsynonymous mutations affecting tryptophan hydroxylase (TPH) enzymes responsible for serotonin production in maternal reproductive tissues (TPH1) and the brain (TPH2). DESIGN: Family-based case-control and functional studies of candidate genes. SETTING: Adult outpatients with attention-deficit/hyperactivity disorder (ADHD), their family members, and random control subjects were recruited across Norway. PARTICIPANTS: Nine pedigrees with TPH1 and TPH2 mutation carriers were identified among 459 patients with ADHD and 187 controls. The TPH genes were then sequenced in 97 additional family members, and information about psychiatric diagnoses and symptoms was obtained from 606 controls, the 459 patients, and their relatives. MAIN OUTCOME MEASURES: The effects of maternal vs paternal TPH1 mutations compared in all families. RESULTS: Nine different TPH1 and TPH2 mutations were found by sequencing in 646 individuals (1.0% and 0.2% allele frequency, respectively). In vitro studies showed that 8 TPH mutants had significantly impaired enzyme function. Family analysis of 38 TPH1 mutation carriers and 41 of their offspring revealed that offspring of mothers carrying TPH1 mutations reported 1.5- to 2.5-times-higher ADHD scores and related symptoms during childhood and as adults than did controls (P < 10(-6)) or offspring of fathers with the corresponding TPH1 mutations (P < .001). CONCLUSIONS: Impaired maternal serotonin production may have long-term consequences for brain development and increase the risk of ADHD-related symptoms and behavior in offspring. Replication studies are required to form conclusions about the clinical implications of mutations affecting serotonin biosynthesis.

Effect of pharmacological chaperones on brain tyrosine hydroxylase and tryptophan hydroxylase 2.

Phenylalanine hydroxylase (PAH), tyrosine hydroxylase (TH) and the tryptophan hydroxylases (TPH1 and TPH2) are structurally and functionally related enzymes that share a number of ligands, such as amino acid substrates, pterin cofactors and inhibitors. We have recently identified four compounds (I-IV) with pharmacological chaperone effect for PAH and phenylketonuria mutants (Pey et al. (2008) J. Clin. Invest. 118, 2858-2867). We have now investigated the effect of these compounds on the brain enzymes TH and TPH2, comparative to hepatic PAH. As assayed by differential scanning fluorimetry each of the purified human PAH, TH and TPH2 was differently stabilized by the compounds and only 3-amino-2-benzyl-7-nitro-4-(2-quinolyl)-1,2-dihydroisoquinolin-1-one (compound III) stabilized the three enzymes. We also investigated the effect of compounds II-IV in wild-type mice upon oral loading with 5 mg/kg/day. Significant effects were obtained by treatment with compound III - which increased total TH activity in mouse brain extracts by 100% but had no measurable effects either on TPH activity nor on monoamine neurotransmitter metabolites dopamine, dihydroxyphenylacetic acid, homovanillic acid, serotonin and 5-hydroxyindolacetic acid - and with 5,6-dimethyl-3-(4-methyl-2-pyridinyl)-2-thioxo-2,3-dihydrothieno[2,3-d]pyrimidin-4(1H)-one (compound IV) - which led to a 10-30% decrease of these metabolites. Our results indicate that pharmacological chaperones aiming the stabilization of one of the aromatic amino acid hydroxylases should be tested on other members of the enzyme family. Moreover, compound III stabilizes in vitro the human TH mutant R202H, associated to autosomal recessive L-DOPA-responsive dystonia, revealing the potential of pharmacological chaperones for the treatment of disorders associated with TH misfolding.

Functional properties of missense variants of human tryptophan hydroxylase 2.

Tryptophan hydroxylase 2 (TPH2) catalyzes the rate-limiting step in serotonin biosynthesis in the nervous system. Several variants of human TPH2 have been reported to be associated with a spectrum of neuropsychiatric disorders such as unipolar major depression, bipolar disorder, suicidality, and attention-deficit/hyperactivity disorder (ADHD). We used three different expression systems: rabbit reticulocyte lysate, Escherichia coli, and human embryonic kidney cells, to identify functional effects of all human TPH2 missense variants reported to date. The properties of mutants affecting the regulatory domain, that is, p.Leu36Val, p.Leu36Pro, p.Ser41Tyr, and p.Arg55Cys, were indistinguishable from the wild-type (WT). Moderate loss-of-function effects were observed for mutants in the catalytic and oligomerization domains, that is, p.Pro206Ser, p.Ala328Val, p.Arg441His, and p.Asp479Glu, which were manifested via stability and solubility effects, whereas p.Arg303Trp had severely reduced solubility and was completely inactive. All variants were tested as substrates for protein kinase A and were found to have similar phosphorylation stoichiometries. A standardized assay protocol as described here for activity and solubility screening should also be useful for determining properties of other TPH2 variants that will be discovered in the future.

Activation and stabilization of human tryptophan hydroxylase 2 by phosphorylation and 14-3-3 binding.

TPH (tryptophan hydroxylase) catalyses the rate-limiting step in the synthesis of serotonin, and exists in two isoforms: TPH1, mainly found in peripheral tissues and the pineal body, and TPH2, a neuronal form. In the present study human TPH2 was expressed in Escherichia coli and in HEK (human embryonic kidney)-293 cells and phosphorylated using several different mammalian protein kinases. TPH2 was rapidly phosphorylated to a stoichiometry of 2 mol of phosphate/mol of subunit by PKA (protein kinase A), but only to a stoichiometry of 0.2 by Ca(2+)/calmodulin dependent protein kinase II. Both kinases phosphorylated Ser(19), but PKA also phosphorylated Ser(104), as determined by MS, phosphospecific antibodies and site-directed mutagenesis of several possible phosphorylation sites, i.e. Ser(19), Ser(99), Ser(104) and Ser(306). On average, purified TPH2 WT (wild-type) was activated by 30% after PKA phosphorylation and studies of the mutant enzymes showed that enzyme activation was mainly due to phosphorylation at Ser(19). This site was phosphorylated to a stoichiometry of up to 50% in HEK-293 cells expressing TPH2, and the enzyme activity and phosphorylation stoichiometry was further increased upon treatment with forskolin. Purified PKA-phosphorylated TPH2 bound to the 14-3-3 proteins gamma, epsilon and BMH1 with high affinity, causing a further increase in enzyme stability and activity. This indicates that 14-3-3 proteins could play a role in consolidating and strengthening the effects of phosphorylation on TPH2 and that they may be important for the regulation of serotonin function in the nervous system.

Brain-specific tryptophan hydroxylase 2 (TPH2): a functional Pro206Ser substitution and variation in the 5'-region are associated with bipolar affective disorder.

The neurotransmitter serotonin [5-hydroxytryptamine (5-HT)] controls a broad range of biological functions that are disturbed in affective disorder. In the brain, 5-HT production is controlled by tryptophan hydroxylase 2 (TPH2). In order to assess the possible contribution of TPH2 genetic variability to the aetiology of bipolar affective disorder (BPAD), we systematically investigated common and rare genetic variation in the TPH2 gene through a sequential sequencing and SNP-based genotyping approach. Our study sample comprised two cohorts of BPAD from Germany and Russia, totalling 883 patients and 1300 controls. SNPs located in a haplotype block covering the 5' region of the gene as well as a rare, non-synonymous SNP, resulting in a Pro206Ser substitution, showed significant association with bipolar disorder. The odds ratio for the minor allele in the pooled sample was 1.5 (95% CI 1.2-1.9) for rs11178997 (in the 5'-associated haplotype block) and 4.8 (95% CI 1.6-14.8) for rs17110563 encoding the Pro206Ser substitution. Examination of the functional effects of TPH2 Pro206Ser provided evidence for a reduced thermal stability and solubility of the mutated enzyme, suggesting reduced 5-HT production in the brain as a pathophysiological mechanism in BPAD.

Stably integrated luxCDABE for assessment of Salmonella invasion kinetics.

Salmonella Typhimurium is a common cause of gastroenteritis in humans and also localizes to neoplastic tumors in animals. Invasion of specific eukaryotic cells is a key mechanism of Salmonella interactions with host tissues. Early stages of gastrointestinal cell invasion are mediated by a Salmonella type III secretion system, powered by the adenosine triphosphatase invC. The aim of this work was to characterize the invC dependence of invasion kinetics into disparate eukaryotic cells traditionally used as models of gut epithelium or neoplasms. Thus, a nondestructive real-time assay was developed to report eukaryotic cell invasion kinetics using lux+ Salmonella that contain chromosomally integrated luxCDABE genes. Bioluminescence-based invasion assays using lux+ Salmonella exhibited inoculum dose-response correlation, distinguished invasion-competent from invasion-incompetent Salmonella, and discriminated relative Salmonella invasiveness in accordance with environmental conditions that induce invasion gene expression. In standard gentamicin protection assays, bioluminescence from lux+ Salmonella correlated with recovery of colony-forming units of internalized bacteria and could be visualized by bioluminescence microscopy. Furthermore, this assay distinguished invasion-competent from invasion-incompetent bacteria independent of gentamicin treatment in real time. Bioluminescence reported Salmonella invasion of disparate eukaryotic cell lines, including neoplastic melanoma, colon adenocarcinoma, and glioma cell lines used in animal models of malignancy. In each case, Salmonella invasion of eukaryotic cells was invC dependent.

Selectivity and affinity determinants for ligand binding to the aromatic amino acid hydroxylases.

Hydroxylation of the aromatic amino acids phenylalanine, tyrosine and tryptophan is carried out by a family of non-heme iron and tetrahydrobiopterin (BH4) dependent enzymes, i.e. the aromatic amino acid hydroxylases (AAHs). The reactions catalyzed by these enzymes are important for biomedicine and their mutant forms in humans are associated with phenylketonuria (phenylalanine hydroxylase), Parkinson's disease and DOPA-responsive dystonia (tyrosine hydroxylase), and possibly neuropsychiatric and gastrointestinal disorders (tryptophan hydroxylase 1 and 2). We attempt to rationalize current knowledge about substrate and inhibitor specificity based on the three-dimensional structures of the enzymes and their complexes with substrates, cofactors and inhibitors. In addition, further insights on the selectivity and affinity determinants for ligand binding in the AAHs were obtained from molecular interaction field (MIF) analysis. We applied this computational structural approach to a rational analysis of structural differences at the active sites of the enzymes, a strategy that can help in the design of novel selective ligands for each AAH.

Characterization of wild-type and mutant forms of human tryptophan hydroxylase 2.

Tryptophan hydroxylase (TPH) catalyses the rate-limiting step in the biosynthesis of serotonin. In vertebrates, the homologous genes tph1 and tph2 encode two different enzymes with distinct patterns of expression, enzyme kinetics and regulation. Variants of TPH2 have recently reported to be associated with reduced serotonin production and behavioural alterations in man and mice. We have produced the human forms of these enzymes in Esherichia coli and in human embryonic kidney cell lines (HEK293) and examined the effects of mutations on their heterologous expression levels, solubility, thermal stability, secondary structure, and catalytic properties. Pure human TPH2 P449R (corresponds to mouse P447R) had comparable catalytic activity (V(max)) and solubility relative to the wild type, but had decreased thermal stability; whereas human TPH2 R441H had decreased activity, solubility and stability. Thus, we consider the variations in kinetic values between wild-type and TPH2 mutants to be of secondary importance to their effects on protein stability and solubility. These findings provide potential molecular explanations for disorders related to the central serotonergic system, such as depression or suicidal behaviour.

Different properties of the central and peripheral forms of human tryptophan hydroxylase.

Tryptophan hydroxylase (TPH) catalyses the rate-limiting reaction in the biosynthesis of serotonin. In humans, two different TPH genes exist, located on chromosomes 11 and 12, respectively, and encoding two enzymes (TPH1 and TPH2) with an overall sequence identity of 71%. We have expressed both enzymes as various fusion proteins in Escherichia coli and using an in vitro transcription/translation system, and compared their solubility and kinetic properties. TPH2 is more soluble than TPH1, has a higher molecular weight and different kinetic properties, including a lower catalytic efficiency towards phenylalanine than TPH1. Both enzymes are phosphorylated by cAMP-dependent protein kinase A. TPH2 was phosphorylated at Ser19, a phosphorylation site not present in TPH1. The differences between TPH1 and TPH2 have important implications for the regulation of serotonin production in the brain and the periphery and may provide an explanation for some of the diverging results reported for TPH from different sources in the past.

Tetrahydrobiopterin binding to aromatic amino acid hydroxylases. Ligand recognition and specificity.

The three aromatic amino acid hydroxylases (phenylalanine, tyrosine, and tryptophan hydroxylase) and nitric oxide synthase (NOS) all utilize (6R)-l-erythro-5,6,7,8-tetrahydrobiopterin (BH(4)) as cofactor. The pterin binding site in the three hydroxylases is well conserved and different from the binding site in NOS. The structures of phenylalanine hydroxylase (PAH) and of NOS in complex with BH(4) are still the only crystal structures available for the reduced cofactor-enzyme complexes. We have studied the enzyme-bound and free conformations of BH(4) by NMR spectroscopy and molecular docking into the active site of the three hydroxylases, using endothelial NOS as a comparative probe. We have found that the dihydroxypropyl side chain of BH(4) adopts different conformations depending on which hydroxylase it interacts with. All the bound conformations are different from that of BH(4) free in solution at neutral pH. The different bound conformations appear to result from specific interactions with nonconserved amino acids at the BH(4) binding sites of the hydroxylases, notably the stretch 248-251 (numeration in PAH) and the residue corresponding to Ala322 in PAH, i.e., Ser in TH and Ala in TPH. On the basis of analysis of molecular interaction fields, we discuss the selectivity determinants for each hydroxylase and explain the high-affinity inhibitory effect of 7-tetrahydrobiopterin specifically for PAH.

Disruption of type III secretion in Salmonella enterica serovar Typhimurium by external guide sequences.

The type III secretion system involved in Salmonella enterica serovar Typhimurium invasion of host cells has been disrupted using inducibly expressed oligonucleotide external guide sequences (EGSs) complementary to invB or invC mRNA. These EGSs direct single site cleavage in these mRNAs by endogenous RNase P, and their expression in Salmonella results in invC mRNA and InvC protein depletion, decreased type III secretion and interference with host cell invasion. Comparison of these effects with those from studies of Salmonella invB and invC mutants suggests that invB EGSs have polar effects on invC mRNA.

Expression and purification of human tryptophan hydroxylase from Escherichia coli and Pichia pastoris.

Tryptophan hydroxylase (TPH) from several mammalian species has previously been cloned and expressed in bacteria. However, due to the instability of wild type TPH, most successful attempts have been limited to the truncated forms of this enzyme. We have expressed full-length human TPH in large amounts in Escherichia coli and Pichia pastoris and purified the enzyme using new purification protocols. When expressed as a fusion protein in E. coli, the maltose-binding protein-TPH (MBP-TPH) fusion protein was more soluble than native TPH and the other fusion proteins and had a 3-fold higher specific activity than the His-Patch-thioredoxin-TPH and 6xHis-TPH fusion proteins. The purified MBP-TPH had a V(max) of 296 nmol/min/mg and a K(m) for L-tryptophan of 7.5+/-0.7 microM, compared to 18+/-5 microM for the partially purified enzyme from P. pastoris. To overcome the unfavorable properties of TPH, the stabilizing effect of different agents was investigated. Both tryptophan and glycerol had a stabilizing effect, whereas dithiothreitol, (6R)-5,6,7,8,-tetrahydrobiopterin, and Fe(2+) inactivated the enzyme. Irrespective of expression conditions, both native TPH expressed in bacteria or yeast, or TPH fusion proteins expressed in bacteria exhibited a strong tendency to aggregate and precipitate during purification, indicating that this is an intrinsic property of this enzyme. This supports previous observations that the enzyme in vivo may be stabilized by additional interactions.

Tightly regulated gene expression system in Salmonella enterica serovar Typhimurium.

A new Salmonella enterica serovar Typhimurium strain has been constructed to facilitate tightly regulated gene expression. Arabinose-inducible and glucose-repressible expression of a T7 RNA polymerase gene that has been integrated with an adjacent araC-P(BAD) control element into the bacterial chromosome allows dynamic control of T7 promoter-driven RNA transcription.