Preparation and evaluation of a new releasable PEGylated tumor necrosis factor-α(TNF-α) conjugate for therapeutic application

To design a releasable PEGylated TNF-α(rPEG-TNF-α ), a cathepsin B-sensitive dipeptide (Val-Cit moiety) was inserted into conventional PEG-modified TNF- (PEG-TNF- ), facilitating its clinical use for anti-tumor therapy. Comparative pharmaco- kinetic and pharmacodynamic studies showed that the half-lives of both PEGylated forms of TNF-α were ~60-fold greater than that of unmodified TNF-α . In addition, the in vitro bioactivity of rPEG-TNF-α was greater than that of PEG-TNF-α with the same degree of PEG modification. Release of TNF-α from rPEG-TNF-α in vitro was dependent on the presence of cathepsin B and was inhibited by a cathepsin B inhibitor. Despite the potent cytotoxicity of unmodified TNF-α against normal cells, its PEGylated forms at higher TNF-α concentrations showed low cytotoxic activity against these cells. In contrast, both forms of PEGylated TNF-α showed potent cytotoxic activity against the B16 and L929 cell lines, with rPEG-TNF-α being 5- and 9- fold more potent, respectively, than PEG-TNF-α . Moreover, rPEG-TNF-α was a more potent in vivo antitumor agent than PEG-TNF-α .     

Effect of environmental stresses and high hydrostatic pressure on the Antibiotic susceptibility of pathogenic Vibrio parahaemolyticus

The aim of the present study was to determine the effect of environmental stresses (temperature, pH, osmotic pressure, high hydrostatic pressure (HHP)) on the antibiotic susceptibility of 12 different pathogenic Vibrio parahaemolyticus isolates. Isolates were subjected to growth at (30 ℃and 37 ℃), an osmotic pressure of (1% and 6% NaCl), a media at pH (6.0 and 9.0) and three different HHP treatment (180, 250, 300 MPa). The minimal inhibitory concentrations (MICs) of tested antibiotics used against unstressed (control), stressed or post-stressed isolates were determined using the broth microdilution method. The study found that incubation under increased salt (6%), reduced salt (1%) and increased pH (9.0) conditions were commonly associated with increased antibiotic resistance. Incubation at 30 ℃ temperature, reduced pH (6.0) and HHP treatment were commonly associated with decreased antibiotic resistance. Besides, both ciprofloxacin and cefotaxime kept a constant MIC during almost all stress challenges. Thus our data demonstrate that exposure of V. parahaemolyticus to some stress conditions may contribute on the rapid development of antibiotic resistance in this food borne pathogen.