Antimicrobial peptide melittin against Xanthomonas oryzae pv. oryzae, the bacterial leaf blight pathogen in rice.

Xanthomonas oryzae pv. oryzae is a destructive bacterial disease of rice, and the development of an environmentally safe bactericide is urgently needed. Antimicrobial peptides, as antibacterial sources, may play important roles in bactericide development. In the present study, we found that the antimicrobial peptide melittin had the desired antibacterial activity against X. oryzae pv. oryzae. The antibacterial mechanism was investigated by examining its effects on cell membranes, energy metabolism, and nucleic acid, and protein synthesis. The antibacterial effects arose from its ability to interact with the bacterial cell wall and disrupt the cytoplasmic membrane by making holes and channels, resulting in the leakage of the cytoplasmic content. Additionally, melittin is able to permeabilize bacterial membranes and reach the cytoplasm, indicating that there are multiple mechanisms of antimicrobial action. DNA/RNA binding assay suggests that melittin may inhibit macromolecular biosynthesis by binding intracellular targets, such as DNA or RNA, and that those two modes eventually lead to bacterial cell death. Melittin can inhibit X. oryzae pv. oryzae from spreading, alleviating the disease symptoms, which indicated that melittin may have potential applications in plant protection.

Covalently dimerized Camelidae antihuman TNFa single-domain antibodies expressed in yeast Pichia pastoris show superior neutralizing activity.

Antagonists of tumor necrosis factor alpha (TNFa) have revolutionized the treatment of selected inflammatory diseases. Recombination Camelidae variable heavy-chain domain-only TNFa antibodies (anti-TNF-VHH) have been developed to antagonize the action of human and murine TNFa. Here, we describe a strategy to obtain functional covalent dimer anti-TNF-VHH molecules with the C-terminal fusion of human IgG1 Fc domain named anti-TNF-VHH-Fc. The resulting fusion proteins were separately expressed by use of the pET28a vector in Escherichia coli ((Ec)) strain BL21 and the pPICZaA vector in Pichia pastoris ((Pp)) strain GS115, then purified by protein A affinity resin. Fc-engineered anti-(Ec)TNF-VHH-Fc was about 40 kDa and anti-(Pp)TNF-VHH-Fc was about 43 kDa. Monomeric VHH was also cloned and expressed in E. coli strain BL21, with the molecular weight of about 18 kDa. Enzyme-linked immunosorbent assay and L929 cell cytotoxicity assay demonstrated that the fusion protein anti-(Pp)TNF-VHH-Fc blocked TNFa activity more effectively than either anti-(Ec)TNF-VHH-Fc or monomeric anti-(Ec)TNF-VHH protein. We suggest that efficient disulfide bond formation using the P. pastoris expression system improves the covalent dimer anti-TNF-VHH-Fc neutralizing activity.

Novel peptide myristoly-CM4 induces selective cytotoxicity in leukemia K562/MDR and Jurkat cells by necrosis and/or apoptosis pathway.

Purpose: There is an urgent need for the development of novel, effective, and less toxic drugs to treat leukemia. Antimicrobial peptides (AMPs) have received much more attention as alternative chemotherapeutic agents. This study aimed to examined the cytotoxicity of a novel AMP myristoly-CM4 against chronic myeloid leukemia cells (K562/MDR) and acute lymphocytic leukemia cells (Jurkat), and further investigated its selectivity to clarify the cytotoxic mechanism. Materials and methods: In this study, the cytotoxicity and selectivity of myristoly-CM4 against K562/MDR and Jurkat cells were assessed in vitro, and the anticancer mechanism responsible for its cytotoxicity and selectivity was further investigated. Results: Myristoly-CM4 was cytotoxic to these leukemia cell lines (IC50 2-4 µM) and was less cytotoxic to normal cells (HEK-293, L02 cells, peripheral blood mononuclear cells, and erythrocytes). Myristoyl-CM4 had stronger affinity to K562/MDR and Jurkat cells than to normal cells, while the contents of phosphatidylserine and sialic acids on the cell surfaces of K562/MDR and Jurkat cells were significantly higher than that of HEK293 cells. The myristoyl group effectively mediated the internalization of myristoyl-CM4 to leukemia cells. After internalization, myristoyl-CM4 could target mitochondria and affected mitochondrial function, including disruption of Δψm, increasing the accumulation of ROS, increasing the Bax/Bcl-2 ratio, activating caspase 9 and 3, and PARP to induce mitochondria-dependent apoptosis in both K562/MDR and Jurkat cells. Myristoyl-CM4 also induced K562/MDR cell necrosis by directive membrane disruption, and significantly decreased the level of P-glycoprotein in K562/MDR cells. Conclusion: These results suggested that myristoyl-CM4 showed selective cytotoxicity to leukemia K562/MDR and Jurkat cells by apoptosis and/or necrosis pathway. Myristoyl-CM4, thus, appears to be a promising candidate for leukemia treatment, including multidrug-resistant leukemia.

Equine adipose-derived stem cell (ASC) expresses BAFF and its receptors, which may be associated with the differentiation process of ASC towards adipocyte.

B cell activating factor (BAFF) and its receptors were regarded as elements of the immune system, regulating the fate of B cell. In recent years, these molecules were identified in a number of normal and pathological tissues, expanding their potential functions beyond the immune system. In this study, on the basis of molecular clone and prokaryotic expression of equine BAFF, we reported that equine adipose-derived stem cell (ASC) expressed BAFF and its receptors, which exhibited the increased expression during ASC adipogenic differentiation in vitro. Moreover, with the addition of recombinant protein His6-sBAFF, an increased differentiation of equine ASC towards adipocyte was detected. These results suggested that BAFF and its receptors might be associated with the differentiation process of ASC towards adipocyte in horse.

Role of glycosylation in the anticancer activity of antibacterial peptides against breast cancer cells.

Antibacterial peptides (ABPs) with cancer-selective toxicity have received much more attention as alternative chemotherapeutic agents in recent years. However, the basis of their anticancer activity remains unclear. The modification of cell surface glycosylation is a characteristic of cancer cells. The present study investigated the effect of glycosylation, in particular sialic acid, on the anticancer activity of ABPs. We showed that aurein 1.2, buforin IIb and BMAP-28m exhibited selective cytotoxicity toward MX-1 and MCF-7 breast cancer cells. The binding activity, cytotoxicity and apoptotic activity of ABPs were enhanced by the presence of O-, N-glycoproteins, gangliosides and sialic acid on the surface of breast cancer cells. Among N-, O-glycoproteins and ganglioside, O-glycoproteins almost had the strongest effect on the binding and cytotoxicity of the three peptides. Further, up-regulation of hST6Gal1 in CHO-K1 cells enhanced the susceptibility of cells to these peptides. Finally, the growth of MX-1 xenograft tumors in mice was significantly suppressed by buforin IIb treatment, which was associated with induction of apoptosis and inhibition of vascularization. These data demonstrate that the three peptides bind to breast cancer cells via an interaction with surface O-, N-glycoproteins and gangliosides. Sialic acids act as key glycan binding sites for cationic ABP binding to glycoproteins and gangliosides. Therefore, glycosylation in breast cancer cells plays an important role in the anticancer activity of ABPs, which may partly explain their cancer-selective toxicity. Anticancer ABPs with cancer-selective cytotoxicity will be promising candidates for anticancer therapy in the future.