The study was aimed to investigate the possibility of enhancing transfection efficiency of branched polyethylenimine (BPEI) in HeLa cells by hydrophobic tail of bee venom peptide (melittin). Hydrophobic tail of melittin was synthesized and its membrane permeable activity was evaluated by hemolysis test. The peptide was mixed with BPEI and the transfection efficiency was determined in HeLa cells by using green fluorescent protein gene (GFP) as a reporter gene. The cytotoxicity of the mixture was analyzed by MTT assay at 24 hours after transfection. The results indicated that the synthesized peptide had permeable activity leading to hemolysis in both neutral and acidic solution. At optimal condition, the peptide could significantly improve the transfection efficiency of BPEI and the cytotoxicity of the mixture was lower than BPEI itself. It is concluded that hydrophobic tail of melittin may be a potential enhancer to improve transfection efficiency mediated by cationic polymers in difficult to transfect cells.
HeLa Cells ; Humans ; Hydrophobic and Hydrophilic Interactions ; Melitten ; chemistry ; genetics ; Peptides ; chemistry ; Polyethyleneimine ; pharmacology ; Transfection

OBJECTIVE: Melittin, a cell-penetrating peptide, improves the efficiency of many non-viral gene delivery vectors, yet its application in viral vectors has not been well studied. The non-pathogenic recombinant adeno-associated virus (rAAV) vector is an ideal in vivo gene delivery vector. However, its full potential will only be achieved after improvement of its transduction efficiency. To improve the transduction efficiency of rAAV2 vectors, we attempted to develop a melittin-based rAAV2 vector delivery strategy. METHODS: The melittin peptide was inserted into the rAAV2 capsid either in the loop VIII of all viral proteins (VPs) or at the N terminus of VP2. Various rAAV2-gfp or -fluc vectors were subjected to quantitative real-time polymerase chain reaction and Western blot assays to determine their titers and integrity of capsid proteins, respectively. Alternatively, the vectors based on wild-type capsid were pre-incubated with melittin, followed by transduction of cultured cells or tail vein administration of the mixture to C57BL/6 and BALB/c nude mice. In vivo bioluminescence imaging was performed to evaluate the transgene expression. RESULTS: rAAV2 vectors with melittin peptide inserted in the loop VIII of VPs had low transduction efficiency, probably due to dramatically reduced ability to bind to the target cells. Fusing the melittin peptide at the N-terminus of VP2 produced vectors without the VP2 subunit. Interestingly, among the commonly used rAAV vectors, pre-incubation of rAAV2 and rAAV6 vectors with melittin significantly enhanced their transduction efficiency in HEK293 and Huh7 cells in vitro. Melittin also had the ability to increase the rAAV2-mediated transgene expression in mouse liver in vivo. Mechanistically, melittin did not change the vector-receptor interaction. Moreover, cell counting kit-8 assays of cultured cells and serum transaminase levels indicated melittin had little cytotoxicity. CONCLUSION Pre-incubation with melittin, but not insertion of melittin into the rAAV2 capsid, significantly enhanced rAAV2-mediated transgene expression. Although further in vivo evaluations are required, this research not only expands the pharmacological potential of melittin, but also provides a new strategy to improve gene therapy mediated by rAAV vectors.
Mice ; Animals ; Humans ; Melitten/genetics* ; Dependovirus/genetics* ; Serogroup ; HEK293 Cells ; Mice, Nude ; Mice, Inbred C57BL ; Transgenes ; Genetic Vectors/genetics*

Carcinoma, Hepatocellular ; drug therapy ; Cell Line, Tumor ; Escherichia coli ; metabolism ; Green Fluorescent Proteins ; genetics ; metabolism ; pharmacology ; Humans ; Melitten ; genetics ; metabolism ; pharmacology ; Recombinant Fusion Proteins ; genetics ; metabolism ; pharmacology

In order to get new antibacterial peptide, we designed a hybrid peptide LfcinB(1-15)-Melittin(5-12), composed of 1-15 amino acid residues of bovine Lactoferricin and 5-12 amino acid residues of Melittin. According to the bias of codon utilization of Escherichia coli, We synthesized the gene encoding the hybrid peptide. We inserted the gene between the sites of Nco I and Sal I of pET-32a and obtained the recombinant expression vector for heterologous expression of LfcinB(1-15)-Melittin(5-12) in Escherichia coli. We used Escherichia coli BL21(DE3) as expression host for the recombinant plasmid. After induced by isopropyl-beta-D-thiogalactoside (IPTG) under the optimized conditions, we realized the fusion protein was successfully expressed. The fusion protein was expressed in soluble form and the level was more than 35% of the total proteins. With (His)6 x Tag, the fusion protein was easily purified by His x Bind Purification Kit. After purification, we obtained 35 mg of fusion protein from 1 L of culture medium. At last, we accomplished that the peptide LfcinB(1-15)-Melittin(5-12) was released from the fusion protein cleaved by enterokinase. The recombinant LfcinB(1-15)-Melittin(5-12) showed antimicrobial activity assayed by agar diffusion test. This is the first report on the heterologous expression of the hybrid antibacterial peptide LfcinB(1-15)-Melittin(5-12) in Escherichia coli and also provides basis for next cost-effective expression of other antimicrobial peptides in genetic engineering.
Animals ; Anti-Bacterial Agents ; biosynthesis ; Antimicrobial Cationic Peptides ; biosynthesis ; chemistry ; genetics ; Cattle ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; Lactoferrin ; biosynthesis ; genetics ; Melitten ; biosynthesis ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics

OBJECTIVETo find a new method of treating hepatocellular carcinoma with melittin by way of using the melittin gene.

METHODSThe recombinant adenoviruses carrying the melittin gene and alpha-fetoprotein (AFP) promoter (Ad-rAFP-Mel) were constructed through a bacterial homologous recombinant system. The efficiency of the adenovirus mediated gene transfer and the inhibition effect of Ad-rAFP-Mel on the proliferation of hepatocarcinoma cells were determined by X-gal staining and MTT assay respectively. The tumorigenicity of hepatocarcinoma cells transfected by Ad-rAFP-Mel and the antitumor effect of Ad-rAFP-Mel on the transplanted tumors in nude mice were detected in vivo.

RESULTSThe mRNA of the melittin gene was transcripted in HepG2 hepatocellular carcinoma cells transducted by Ad-rAFP-Mel. The efficiency of adenovirus mediated gene transfered to BEL-7402 hepatocarcinoma cells was 100% when the multiplicities of infection (MOI) of Ad-rAFP-Mel was 10 in vitro and was high in vivo as well. The inhibitive rates of Ad-rAFP-Mel and Ad-rAFP for BEL7402 cells were 66.2%+/-2.7% and 2.9%+/-2.3% (t = 30.83) by MTT assay. The inhibitive rates of Ad-CMV-Mel for BEL7402, SMMC7721 and L02 cells were 58.9%+/-9.6%, 65.9%+/-3.8%, 31.7%+/-1.2%, respectively, and those of the Ad-rAFP-Mel were 6.2%+/-2.7%, 16.1%+/-6.6%, 7.5%+/-3.3%, respectively (t = 1.27; t = 11.31, and t = 12.12, vs. Ad-CMV-Mel group in same cells). The tumorigenicity rates of hepatocarcinoma cells transfected by Ad-rAFP-Mel were decreased. A significant antineoplastic effect was detectd on transplanted tumor in nude mice by intratumoral injection of Ad-rAFP-Mel.

CONCLUSIONAd-rAFP-Mel can inhibit specifically the proliferation of AFP-producing human hepatocarcinoma cells in vitro and in vivo. It suggests that animal toxin gene can be used as an interesting antitumor gene.

Adenoviridae ; genetics ; Animals ; Carcinoma, Hepatocellular ; pathology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Gene Transfer Techniques ; Genetic Therapy ; methods ; Genetic Vectors ; genetics ; Liver Neoplasms, Experimental ; pathology ; Male ; Melitten ; biosynthesis ; genetics ; pharmacology ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Transcription, Genetic ; drug effects ; alpha-Fetoproteins ; biosynthesis ; genetics

OBJECTIVETo observe the induced apoptosis of recombinant adenovirus carrying melittin gene (Ad-rAFP-Mel) for hepatocellular carcinoma cell line (BEL-7402).

METHODSThe morphological observe, DNA electrophoresis, TUNEL and Flow cytometry assay were used to study the apoptosis of BEL-7042 cell line transfected by Ad-rAFP-Mel.

RESULTSThe morphological changes and apoptosis of BEL-7402 transfected by Ad-rAFP-Mel were confirmed with microscopy and DNA electrophoresis, TUNEL, Flow cytometry assay. The DNA ladder could be demonstrated on DNA electrophoresis in Ad-rAFP-Mel group. The apoptosis rates of BEL-7402 cells in Ad-rAFP-Mel, Ad-rAFP, and control groups were (21.5+/-2.4)%, (10.5+/-4.4)% and (3.0+/-1.4)% respectively by TUNEL assay (F = 38.0, P < 0.05) and were (7.3+/-0.5)%, (3.9+/-0.1)% and (0.8+/-0.1)% respectively by flow cytometry assay (F = 415.1, P < 0.05).

CONCLUSIONIt seems that melittin inducing apoptosis might be one of the antitumor mechanisms.

Adenoviridae ; genetics ; Apoptosis ; drug effects ; Carcinoma, Hepatocellular ; pathology ; Cell Line, Tumor ; Gene Expression ; drug effects ; Gene Silencing ; drug effects ; Genetic Therapy ; Genetic Vectors ; genetics ; Humans ; Liver Neoplasms ; pathology ; Melitten ; biosynthesis ; genetics ; pharmacology ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Transcription, Genetic ; drug effects ; Transfection