Mesoporous silicate/carbon composites derived from dye-loaded palygorskite clay waste for efficient removal of organic contaminants

Palygorskite (Pal) is a natural abundant environment-friendly adsorbent that has shown high efficiency to decontaminate dye in water. However, the dye removal results in transformation of Pal to a very stable Maya Blue-like structure or waste Pal clay (WPal), which could not be easily regenerated by a commonly used desorption process. This paper presents a use of WPal as the precursor material to synthesize a highly-efficient mesoporous silicate/carbon composite adsorbent. The composite adsorbent has a large specific surface area (427.9 m²·g^-1), a high negative potential (-40.6 mV) and a mesoporous size (3.48 nm). This adsorbent shows almost complete removal of tetracycline (TC), crystal violet (CV) and methylene blue (MB) (initial concentration, 200 mg·L^-1) with the optimal adsorption capacities of 319.8 mg·g^-1, 244.4 mg·g^-1 and 281.7 mg·g^-1, respectively. The active -Si-O^- adsorption sites produced by the breaking of inert Si-O-Si (or M) bonds and the electrostatic interactions of negatively charged adsorbents to adsorbates play a major role in the adsorption process. Adsorption capacities of the developed composite are significantly higher than that of Pal, WPal and hydrothermally treated WPal (HWPal). Results demonstrate that the composite adsorbents have high potential in decontamination of organics in water efficiently.

KA, Su Z, Guissi NEI, Xiao Y, Zong L, Ping Q. Folate Receptor-Targeting and Reactive Oxygen Species-Responsive Liposomal Formulation of Methotrexate for Treatment of Rheumatoid Arthritis

Multifunctional nanomedicines with active targeting and stimuli-responsive drug release function utilizing pathophysiological features of the disease are regarded as an effective strategy for treatment of rheumatoid arthritis (RA). Under the inflammatory environment of RA, activated macrophages revealed increased expression of folate receptor and elevated intracellular reactive oxygen species (ROS) level. In this study, we successfully conjugated folate to polyethylene glycol 100 monostearate as film-forming material and further prepared methotrexate (MTX) and catalase (CAT) co-encapsulated liposomes, herein, shortened to FOL-MTX&CAT-L, that could actively target to activated macrophages. Thereafter, elevated intracellular hydrogen peroxide, the main source of ROS, diffused into liposomes and encapsulated CAT catalyzed the decomposition of hydrogen peroxide into oxygen and water. Continuous oxygen-generation inside liposomes would eventually disorganize its structure and release the encapsulated MTX. We characterized the in vitro drug release, cellular uptake and cytotoxicity studies as well as in vivo pharmacokinetics, biodistribution, therapeutic efficacy and safety studies of FOL-MTX&CAT-L. In vitro results revealed that FOL-MTX&CAT-L possessed sufficient ROS-sensitive drug release, displayed an improved cellular uptake through folate-mediated endocytosis and exhibited a higher cytotoxic effect on activated RAW264.7 cells. Moreover, in vivo results showed prolonged blood circulation time of PEGylated liposomes, enhanced accumulation of MTX in inflamed joints of collagen-induced arthritis (CIA) mice, reinforced therapeutic efficacy and minimal toxicity toward major organs. These results imply that FOL-MTX&CAT-L may be used as an effective nanomedicine system for RA treatment.

Heterologous expression and characterization of a novel subtilisin-like protease from a thermophilic Thermus thermophilus HB8

Subtilisins are a family of serine proteases used widely throughout the detergent, leather and food industries, with the identification and development of new enzymes holding much potential value. Thermus thermophilus HB8 was examined for serine proteases and found TTHA0724 gene. Sequence analysis of this putative serine protease placed it within the subtilisin family. To obtain active T. thermophilus HB8 subtilisins, three genes encoding prepro-subtilisin, pro-subtilisin and mature-subtilisin were cloned and expressed in Escherichia coli Transetta (DE3). Although direct expression of the mature-subtilisin gene was found to produce inactive inclusion bodies, expression of the pro-subtilisin gene resulted in active mature-subtilisin, indicating that the pro-sequence of translated pro-subtilisin underwent autoproteolysis. The resulting mature-subtilisin exhibited maximal activity between 65 and 85 °C at pH 7.5. The mature-subtilisin showed good stability, maintaining 50% activity after 48 h at 75 °C and >78% activity across the pH range 5.0-9.5. Furthermore, the mature-subtilisin demonstrated broad substrate specificity, with no requirement for the presence of metal ions which are essential for other subtilisin enzymes. Despite this Cu²⁺ was able to increase enzyme activity, while Ca²⁺ partially inhibited the activity. These properties suggest that T. thermophilus HB8 mature-subtilisin has potential value in its application in many industries.

Reversal of multidrug resistance in breast cancer cells by a combination of ursolic acid with doxorubicin

Multidrug resistance (MDR) has seriously affected or hindered the effect of chemotherapy. Ursolic acid (UA) as a natural compound exhibits a number of potential biological effects including antitumor. Searching for the reversal agents from the natural products has been an effective strategy recently applied in overcoming the MDR. So in this study, the reversal effect of UA on the MDR and involved mechanisms were investigated via a multidrug-resistant MCF-7/ADR cells model and ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analytical methods. The synergistic effects were yielded by the combination of UA and Dox based on the investigation of the intracellular accumulation, the P-glycoprotein (P-gp) mediated transport, the energy metabolism including glycolysis, tricarboxylic acid (TCA) cycle, and glutamine metabolism as well as related amino acid metabolism. Obtained results showed that the UA could increase amount of doxorubicin (Dox) entering the cell to accumulate in nuclei, decrease the efflux ratio of digoxin comparable to the effects of the known inhibitor verapamil by acting as a P-gp substrate, decrease the content of intracellular alanine, lactate, pyruvate, glucose, α-ketoglutarate, glutamate, glutamine, aspartate, serine, and glycine. Taken together, inhibition of P-gp function and disruption of the metabolism of energy and related amino acids could be the key mechanisms by which UA could reverse the MDR. The findings also indicated that UA could be a potential alternative adjuvant antitumour herbal medicine to resensitize cells with MDR to chemotherapeutic agents.

From waste hot-pot oil as carbon precursor to development of recyclable attapulgite/carbon composites for wastewater treatment

The utilization of waste products as valuable materials was a technical imperative for waste management. In this study, the cost-effective attapulgite/carbon (APT/C) composite was developed for wastewater treatment using waste hot-pot oil as a carbon precursor through a facile one-step calcination process. The APT/C composite prepared at 300°C exhibited the excellent adsorption capacity and rapid equilibrium rate over a broad pH range for the removal of various pollutants. More importantly, the removal ratios of the composites toward Methyl Violet and tetracycline still remained 77.6% and 60.2% of the initial adsorption capacity after ten adsorption-regeneration cycles via a facile thermal regeneration strategy, respectively. Beyond all doubt, this research provided a feasible and economical way for the sustainable utilization of waste hot-pot oil in wastewater treatment, achieving the concept of disposal waste with waste and recycling.

Liquid extraction surface analysis nanospray electrospray ionization based lipidomics for in situ analysis of tumor cells with multidrug resistance

RATIONALE

Multidrug resistance (MDR) occurs frequently and is a major challenge in tumor treatment. The lipid composition in the cell membrane and the redox balance are closely associated with the development of MDR. Liquid extraction surface analysis in combination with mass spectrometry (LESA-MS) has the characteristics of minimal sample preparation, rapid analysis, high sensitivity and high throughput, and has obtained wide applications.

METHODS

LESA-MS was employed to in situ determine the lipids and other specific metabolites of intact MCF-7/ADR cells (adriamycin-resistant breast cancer cells) and its parental MCF-7/S cells grown on a glass slide. In situ atomic force microscopy was used to observe the morphology of tumor cells before and after extraction. Multivariate statistical analysis was used to investigate the potential lipid biomarkers correlated with the MDR. Moreover, the cell membrane fluidity and potential were determined.

RESULTS

The changes in the level of the lipids were closely correlated with the multidrug resistance of MCF-7/S cells. Moreover, lower cell membrane fluidity and higher cell membrane potential were observed and thus demonstrated the changes in the cell membrane induced by multidrug resistance. Also, the ratios of GSH/GSSG, ATP/ADP and ATP/AMP were significantly higher in MCF-7/ADR cells relative to MCF-7/S cells.

CONCLUSIONS

Lower cell membrane fluidity and higher cell membrane potential caused by the changes in lipid compositions, enhanced anti-oxidative ability and energy generation were involved in the development of the MDR. The specific alterations identified in this study may provide more information for overcoming MDR.

N-Linked Glycosylation Is Not Essential for Sodium Taurocholate Cotransporting Polypeptide To Mediate Hepatitis B Virus Infection In Vitro

Sodium taurocholate cotransporting polypeptide (NTCP) has been identified as a hepatitis B virus (HBV) receptor, and its overexpression in HepG2 cell lines leads to efficient secretion of hepatitis B e antigen (HBeAg) following challenge with a large dose of cell culture-derived HBV (cHBV) particles. However, NTCP-reconstituted HepG2 cells are inefficiently infected by patient serum-derived HBV (sHBV) and release very little hepatitis B surface antigen (HBsAg) following cHBV infection, unlike differentiated HepaRG cells, which are naturally susceptible to both cHBV and sHBV particles. Here, we investigated whether NTCP could explain the different behaviors of the two cell types. Endogenous NTCP protein from differentiated HepaRG cells was unglycosylated despite wild-type coding sequence. HepaRG cells stably transfected with an epitope-tagged NTCP expression construct displayed higher sHBV but not cHBV susceptibility than cells transfected with the null mutant. Tagged NTCP introduced to both HepG2 and HepaRG cells was glycosylated, with N5 and N11 being sites of N-linked glycosylation. Mutating N5, N11, or both did not alter cell surface availability of NTCP or its subcellular localization, with both the singly glycosylated and nonglycosylated forms still capable of mediating cHBV infection in HepG2 cells. In conclusion, nonglycosylated NTCP is expressed by differentiated HepaRG cells and capable of mediating cHBV infection in HepG2 cells, but it cannot explain differential susceptibility of HepaRG and HepG2/NTCP cells to cHBV versus sHBV infection and different HBsAg/HBeAg ratios following cHBV infection. The responsible host factor(s) remains to be identified.IMPORTANCE HBV can infect differentiated HepaRG cells and also HepG2 cells overexpressing NTCP, the currently accepted HBV receptor. However, HepG2/NTCP cells remain poorly susceptible to patient serum-derived HBV particles and release very little hepatitis B surface antigen following infection by cell culture-derived HBV. We found differentiated HepaRG cells expressed nonglycosylated NTCP despite a wild-type coding sequence. NTCP introduced to HepG2 cells was glycosylated at two N-linked glycosylation sites, but mutating either or both sites failed to prevent infection by cell culture-derived HBV or to confer susceptibility to serum-derived HBV. Overexpressing NTCP in HepRG cells did not increase infection by cell culture-derived HBV or distort the ratio between the two viral antigens. These findings suggest that host factors unique to HepaRG cells are required for efficient infection by serum-derived HBV, and factors other than NTCP contribute to balanced viral antigen production following infection by cell culture-derived HBV.

Targeted delivery of antigen to intestinal dendritic cells induces oral tolerance and prevents autoimmune diabetes in NOD mice

AIMS/HYPOTHESIS

The intestinal immune system is an ideal target to induce immune tolerance physiologically. However, the efficiency of oral protein antigen delivery is limited by degradation of the antigen in the gastrointestinal tract and poor uptake by antigen-presenting cells. Gut dendritic cells (DCs) are professional antigen-presenting cells that are prone to inducing antigen-specific immune tolerance. In this study, we delivered the antigen heat shock protein 65-6×P277 (H6P) directly to the gut DCs of NOD mice through oral vaccination with H6P-loaded targeting nanoparticles (NPs), and investigated the ability of this antigen to induce immune tolerance to prevent autoimmune diabetes in NOD mice.

METHODS

A targeting NP delivery system was developed to encapsulate H6P, and the ability of this system to protect and facilitate H6P delivery to gut DCs was assessed. NOD mice were immunised with H6P-loaded targeting NPs orally once a week for 7 weeks and the onset of diabetes was assessed by monitoring blood glucose levels.

RESULTS

H6P-loaded targeting NPs protected the encapsulated H6P from degradation in the gastrointestinal tract environment and significantly increased the uptake of H6P by DCs in the gut Peyer's patches (4.1 times higher uptake compared with the control H6P solution group). Oral vaccination with H6P-loaded targeting NPs induced antigen-specific T cell tolerance and prevented diabetes in 100% of NOD mice. Immune deviation (T helper [Th]1 to Th2) and CD4⁺CD25⁺FOXP3⁺ regulatory T cells were found to participate in the induction of immune tolerance.

CONCLUSIONS/INTERPRETATION

In this study, we successfully induced antigen-specific T cell tolerance and prevented the onset of diabetes in NOD mice. To our knowledge, this is the first attempt at delivering antigen to gut DCs using targeting NPs to induce T cell tolerance.

A multifunctional nanoparticle constructed with a detachable albumin outer shell and a redox-sensitive inner core for efficient siRNA delivery to hepatocellular carcinoma cells

Successful delivery of small interfering RNA (siRNA) into the cytoplasm of target cells relies on biocompatible and efficient vectors. In this study, a novel multifunctional core/shell nanoparticle [CS-SS-9R/BSA-c(RGDyK)] was developed to effectively deliver siVEGF to hepatocellular carcinoma cells (Bel-7402 cells). To improve the gene payload and transfection efficiency, a positively charged inner core (CS-SS-9R) was constructed by grafting nona-arginine (9R) onto chitosan (CS) using disulphide bonds. The negatively charged outer shell [BSA-c(RGDyK)] assembled on the surface of the inner core by electrostatic forces that shielded high cationic charges and provided improved targeting. The protein outer shell gradually detached from the inner core in the acidic lysosomal environment, leaving the cationic inner core exposed in order to escape from lysosomes. The nanoparticles were capable of delivering siVEGF into Bel-7402 cells via integrin receptor-mediated endocytosis. Successful lysosomal escape of the inner core and the rapid release of siVEGF into the cytoplasm resulted in a 78.9% decrease in VEGF expression and 81.2% inhibition of tumour cell proliferation. In conclusion, this nanoparticle is responsive to the intracellular environment and accurately delivered siRNA into the cytoplasm, providing a safe and highly efficient gene delivery strategy for cancer therapy.

Cell metabolomics reveals the neurotoxicity mechanism of cadmium in PC12 cells

The heavy metals such as cadmium (Cd) can induce neurotoxicity. Extensive studies about the effects of Cd on human health have been reported, however, a systematic investigation on the molecular mechanisms of the effects of Cd on central nervous system is still needed. In this paper, the neuronal PC-12 cells were treated with a series of concentrations of CdCl₂ for 48h. Then the cytotoxicity was evaluated by MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay. The IC₁₅ value (15% inhibiting concentration) was selected for further mechanism studies. After PC-12 cells incubated with CdCl₂ at a dose of IC₁₅ for 48h, the intracellular and extracellular metabolites were profiled using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS)-based cell metabolomics approach. As found, the effects of the heavy metal Cd produced on the PC-12 cell viability were dose-dependent. The metabolic changes were involved in the glycolysis and gluconeogenesis, biopterin metabolism, tryptophan metabolism, tyrosine metabolism, glycerophospholipid metabolism, and fatty acids beta-oxidation. These could cause the perturbation of cell membrane, redox balance, energy supply, cellular detoxification, further affecting the cellular proliferation and apoptosis and other cellular activities.

Metabolomics analysis of multidrug-resistant breast cancer cellsin vitrousing methyl-tert-butyl ether method

MTBE-based cellular lipidomics to investigate the mechanisms of multidrug resistance of breast cancer.

Dendritic Cells Targeting and pH-Responsive Multi-layered Nanocomplexes for Smart Delivery of DNA Vaccines

Specific and effective delivery of DNA vaccines into dendritic cells (DCs) to express antigens is a precondition for induction of immune responses. Construction of a new DNA vaccine delivery system with the ability of programmed gene transfection may achieve this objective. In this study, we successfully integrated dendritic lipopeptide, charge-reversible polymer, and APC-targeted material into DNA vaccine delivery system through layer-by-layer (LBL) assembly. By the means of adjusting the weight ratios and concentration ratios of components, stable complexes were formulated with a particle size of 256.8 ± 10.7 nm and zeta potential of 25.1 ± 2.3 mV. Moreover, this DNA vaccine delivery system could achieve specific delivery into DCs, high transfection efficiency and low cytotoxicity, holding great promise for immunotherapy.

SuhB Regulates the Motile-Sessile Switch in Pseudomonas aeruginosa through the Gac/Rsm Pathway and c-di-GMP Signaling

Many Pseudomonas aeruginosa virulence traits that contribute to human infections are accepted as being associated with its environmental lifestyle. Therefore, identifying the molecular mechanisms that govern the lifestyle choice is of high significance. We previously reported that a mutation in suhB results in a decrease in swimming motility and increased biofilm formation compared to the wild-type strain. Yet, little is known about how this occurs. In this study, we demonstrated that SuhB inversely regulates motility and biofilm formation through the GacA-RsmY/Z-RsmA cascade. Mutations in gacA or the two small RNAs rsmY/rsmZ, or overproduction of the RsmA protein essentially rescued the motility defect of the suhB mutant. Additionally, we identified a c-di-GMP mediated mechanism for SuhB regulation of motility and biofilm formation. We showed that the ΔsuhB mutant displayed elevated levels of c-di-GMP, and the ΔsuhB motility and biofilm phenotypes could be switched by artificially decreasing c-di-GMP levels. Further experiments led to the identification of the diguanylate cyclase GcbA responsible for regulating the c-di-GMP concentration in ΔsuhB and hence the switch between planktonic and surface-associated growth. Together, our results demonstrate a novel mechanism for SuhB regulation of the lifestyle transition via the Gac/Rsm and c-di-GMP signaling networks in P. aeruginosa.

Fabrication of CMC-g-PAM Superporous Polymer Monoliths via Eco-Friendly Pickering-MIPEs for Superior Adsorption of Methyl Violet and Methylene Blue

A series of superporous carboxymethylcellulose-graft-poly(acrylamide)/palygorskite (CMC-g-PAM/Pal) polymer monoliths presenting interconnected pore structure and excellent adsorption properties were prepared by one-step free-radical grafting polymerization reaction of CMC and acrylamide (AM) in the oil-in-water (O/W) Pickering-medium internal phase emulsions (Pickering-MIPEs) composed of non-toxic edible oil as a dispersion phase and natural Pal nanorods as stabilizers. The effects of Pal dosage, AM dosage, and co-surfactant Tween-20 (T-20) on the pore structures of the monoliths were studied. It was revealed that the well-defined pores were formed when the dosages of Pal and T-20 are 9–14 and 3%, respectively. The porous monolith can rapidly adsorb 1,585 mg/g of methyl violet (MV) and 1,625 mg/g of methylene blue (MB). After the monolith was regenerated by adsorption-desorption process for five times, the adsorption capacities still reached 92.1% (for MV) and 93.5% (for MB) of the initial maximum adsorption capacities. The adsorption process was fitted with Langmuir adsorption isotherm model and pseudo-second-order adsorption kinetic model very well, which indicate that mono-layer chemical adsorption mainly contribute to the high-capacity adsorption for dyes. The superporous polymer monolith prepared from eco-friendly Pickering-MIPEs shows good adsorption capacity and fast adsorption rate, which is potential adsorbent for the decontamination of dye-containing wastewater.

A rationally designed peptide IA-2-P2 against type 1 diabetes in streptozotocin-induced diabetic mice

Recent studies have investigated the potential of type 1 diabetes mellitus-related autoantigens, such as heat shock protein 60, to induce immunological tolerance or to suppress the immune response. A functional 24-residue peptide derived from heat shock protein 60 (P277) has shown anti-type 1 diabetes mellitus potential in experimental animals and in clinical studies, but it also carries a potential atherogenic effect. In this study, we have modified P277 to retain an anti-type 1 diabetes mellitus effect and minimize the atherogenic potential by replacing the P277 B epitope with another diabetes-associated autoantigen, insulinoma antigen-2 (IA-2), to create the fusion peptide IA-2-P2. In streptozotocin-induced diabetic C57BL/6J mice, the IA-2-P2 peptide displayed similar anti-diabetic effects to the control P277 peptide. Also, the IA-2-P2 peptide did not show atherogenic activity in a rabbit model. Our findings indicate the potential of IA-2-P2 as a promising vaccine against type 1 diabetes mellitus.

Sequence analysis and functional characterization of full-length hepatitis B virus genomes from Korean cirrhotic patients with or without liver cancer

This study aimed to identify and characterize mutations in the hepatitis B virus (HBV) genome associated with advanced liver diseases. The 3.2-kb HBV genome of the C2 subgenotype was amplified from sera of 18 cirrhotic Korean patients with (10) or without (8) hepatocellular carcinoma (HCC), and two clones per patient were characterized by transient transfection experiments in human hepatoma cells. While A1762T/G1764A core promoter mutations were highly prevalent in both groups, the G1896A precore mutation to abolish hepatitis B e antigen (HBeAg) expression was more common in HCC clones (55% vs. 20%). High replication capacity was mostly found in HCC clones and associated with core promoter mutations, whereas more non-HCC clones harbored a nonfunctional core gene (34% vs. 8%). Large in-frame deletions in the preS region were found in 60% of HCC clones and 38% of non-HCC clones. They removed the first 11 residues of large envelope protein or impaired small envelope protein expression, or deleted a neutralizing epitope in the preS2 domain. Additional point mutations prevented middle envelope protein expression, or caused nonsense mutations in the preS or S region to truncate large and/or small envelope protein. Consequently, many clones were unable to express or secrete hepatitis B surface antigen (HBsAg). In conclusion, mutations associated with the advanced stage of chronic HBV infection are complex and diverse. Host immune pressure most likely selected for mutations in the HBV genome to abolish or reduce HBeAg or HBsAg production, to enhance genome replication, or to escape neutralizing antibodies. Some of these mutations may contribute to liver cirrhosis or HCC development.

The Envelope Gene of Hepatitis B Virus Is Implicated in Both Differential Virion Secretion and Genome Replication Capacities between Genotype B and Genotype C Isolates

Chronic infection by hepatitis B virus (HBV) genotype C is associated with a prolonged replicative phase and an increased risk of liver cancer, compared with genotype B infection. We previously found lower replication capacity but more efficient virion secretion by genotype C than genotype B isolates. Virion secretion requires interaction between core particles and ENVELOPE proteins. In the present study, chimeric constructs between genotype B and genotype C clones were generated to identify the structural basis for differential virion secretion. In addition to dimeric constructs, we also employed 1.1mer constructs, where the cytomegalovirus (CMV) promoter drove pregenomic RNA transcription. Through transient transfection experiments in Huh7 cells, we found that exchanging the entire envelope gene or just its S region could enhance virion secretion by genotype B clones while diminishing virion secretion by genotype C. Site-directed mutagenesis established the contribution of genotype-specific divergence at codons 108 and 115 in the preS1 region, as well as codon 126 in the S region, to differential virion secretion. Surprisingly, exchanging the envelope gene or just its S region, but not the core gene or 3′ S region, could markedly increase intracellular replicative DNA for genotype C clones but diminish that for genotype B, although the underlying mechanism remains to be clarified.

Targeted delivery of doxorubicin by nano-loaded mesenchymal stem cells for lung melanoma metastases therapy

Poor antigenic presentation of tumor tissues and a lack of specific targets currently limit the success of nanoparticle delivery system. Cellular carrier technique has been recently explored extensively as a substitutive or supplement for traditional targeting delivery system. Here, we demonstrate the usage of mesenchymal stem cells (MSCs) loaded with doxorubicin containing polymer nanoparticles in pulmonary melanoma metastases therapy, as a modified technique of targeted delivery system. The characterizations of prepared nanoparticles and MSCs sensitivity to DOX and PLGA-DOX were measured. In vitro tumor tropism, and in vivo distributions of nanoparticles loaded MSCs were also investigated. The findings have demonstrated that, the modified system not only integrates the controlled-release property of nanoparticles but also exhibits tumor tropism and penetrative characteristics of MSCs. Furthermore, the in vitro and in vivo anti-tumor study has demonstrated that drug loaded MSCs had potent efficacy in lung melanoma metastases treatment.

Differential regulation of hepatitis B virus core protein expression and genome replication by a small upstream open reading frame and naturally occurring mutations in the precore region

Hepatitis B virus (HBV) transcribes two subsets of 3.5-kb RNAs: precore RNA for hepatitis B e antigen (HBeAg) expression, and pregenomic RNA for core and P protein translation as well as genome replication. HBeAg expression could be prevented by mutations in the precore region, while an upstream open reading frame (uORF) has been proposed as a negative regulator of core protein translation. We employed replication competent HBV DNA constructs and transient transfection experiments in Huh7 cells to verify the uORF effect and to explore the alternative function of precore RNA. Optimized Kozak sequence for the uORF or extra ATG codons as present in some HBV genotypes reduced core protein expression. G1896A nonsense mutation promoted more efficient core protein expression than mutated precore ATG, while a +1 frameshift mutation was ineffective. In conclusion, various HBeAg-negative precore mutations and mutations affecting uORF differentially regulate core protein expression and genome replication.