ABSTRACT
Amphiphilic graft copolymer consisting of poly(γ-glutamic acid) (γ-PGA) as the hydrophilic backbone and L-phenylalanine ethyl ester (Phe) as the hydrophobic side chain is an important biodegradable polymer with great potential in medical applications. In this research, we established analytical methods for the characterization and quality control of γ-PGA-graft-Phe (γ-PGA-Phe), which forms nanoparticles in aqueous solution, as a deployment platform in practical applications for vaccine adjuvants. The SEC-RI/MALS system, which uses size exclusion chromatography (SEC) coupled with a multi_angle light scattering (MALS) detector and refractive index (RI) detector, was developed to evaluate the characteristics of various types of polymers. By this method, it was indicated that absolute molecular weight (MW) should be used to measure the branch polymer. A gradient reversed phase HPLC (RP-HPLC) method was developed for the content of γ-PGA-Phe and the impurity levels to control product quality and safety. This quantitative approach could become key elements for identifying and characterizing γ-PGA-Phe. In addition, the degradation mechanism of γ-PGA-Phe was also identified as cleavage of main-chain of γ-PGA-Phe based on the stability study of γ-PGA-Phe in buffer solution with various pH values. The analytical developments described above will be important for use in both characterization and formulation design of biopolymers. Nanoparticles (NPs) composed of well-characterized biodegradable γ-PGA-Phe are expected to have a variety of potential clinical applications such as their use as drug and vaccine carriers.
Subject(s)
Absorbable Implants , Adjuvants, Immunologic/chemistry , Drug Carriers , Nanoparticles , Nanotechnology , Polyglutamic Acid/analogs & derivatives , Technology, Pharmaceutical/methods , Buffers , Chromatography, Gel , Chromatography, High Pressure Liquid , Chromatography, Reverse-Phase , Dynamic Light Scattering , Humidity , Hydrogen-Ion Concentration , Nanotechnology/standards , Polyglutamic Acid/chemistry , Quality Control , Technology, Pharmaceutical/standards , Temperature , Time FactorsABSTRACT
Human ATP-binding cassette (ABC) transporter ABCC2 (cMOAT/MRP2) plays a crucial role in the hepatobiliary transport of sulfate-, glucuronide-, and glutathione-conjugated metabolites as well as a variety of amphiphilic organic anions derived from hepatic metabolism. Molecular mechanisms underlying the induction of this hepatic ABC transporter are of great interest to understand the transport-metabolism interplay in vivo. In the present study, to gain insight into the mechanism of ABCC2 induction, we tested a total of 46 structurally diverse compounds, including nuclear receptor ligands, antibiotics, bile salts, phytochemicals, and anticancer drugs. Among them, we found that LXRalpha ligands, i.e., T0901317, paxilline, and 22(R)-hydroxycholesterol, acted potently to induce the expression of ABCC2 at both mRNA and protein levels in human hepatocellular carcinoma HepG2 cells. The ABCC2 induction by T0901317 was dose- and time-dependent, where the induction pattern of ABCC2 was very similar to that of ABCG1, one of the target genes of LXRalpha. The ABCC2 induction by T0901317 was more strongly elicited when the LXRalpha gene was transiently transfected into HepG2 cells. In contrast, ABCC2 induction by T0901317 was attenuated by transient transfection of a dominant negative LXRalpha variant, suggesting that LXRalpha is involved in ABCC2 induction. Interestingly, RXR, a heterodimer partner of LXRalpha, affected the mRNA levels of ABCC2 and ABCG1 differently. ABCC2 induction by T0901317 was enhanced by RXR siRNA treatment, whereas ABCG1 induction was suppressed by the same treatment. This is the first report demonstrating that LXRalpha is potentially involved in ABCC2 induction.
