ABSTRACT
Chronic inflammatory bowel diseases (IBDs) are still waiting for improved and innovative therapeutic treatments, which can overcome the limits of the current approaches. Since IBDs affect mainly the lower tract of the intestine, a localized therapy in the colon tract will avoid most of the problems caused by systemic or poor selective therapies. Particularly promising are the advance drug delivery systems that can reach specific colon delivery, thus guaranteeing active agent release only at the site of action. This approach can meet two aims at the same time, first of all the drug will not affect healthy tissue and second a lower drug dose may be used because all the administered active agent will reach the target. To obtain a specific colon delivery we exploited the azoreductase enzymes, selectively present only in colon, by inserting an azo linker between a selected drug and a macromolecular carrier. The drug employed is mesalazine, a well know and used agent against IBDs. Poly(ethylene glycol) (PEG), of different molecular weights and structures, was used as carrier. Three different conjugates were synthesized and characterized, and the most promising one, with highest drug loading thanks to the use of diamino PEG of 4 kDa, was further investigated in vitro on mouse colonic epithelial cells (CMT-9) and in vivo on model mice with induced colitis. The data presented here demonstrate that PEG conjugation of mesalazine prevents drug release and absorption in upper intestine, after oral administration of the conjugates, and that the azo linker ensures a good drug release in the colon tract. The results in vivo take into consideration mice bodyweight gain, tissue histology and interleukin-2 beta as an index of inflammation. These parameters, all together, demonstrated the conjugate effectiveness against the controls.
Subject(s)
Colon/metabolism , Drug Delivery Systems/methods , Gastrointestinal Agents/administration & dosage , Mesalamine/administration & dosage , Polyethylene Glycols/chemistry , Administration, Oral , Animals , Cell Line , Colitis/chemically induced , Colitis/drug therapy , Colitis/metabolism , Colon/enzymology , Delayed-Action Preparations , Dextran Sulfate , Drug Carriers , Drug Evaluation, Preclinical/methods , Gastrointestinal Agents/pharmacokinetics , Male , Mesalamine/chemistry , Mesalamine/therapeutic use , Mice , Mice, Inbred BALB C , NADH, NADPH Oxidoreductases/chemistry , NADH, NADPH Oxidoreductases/metabolism , Nitroreductases , Polyethylene Glycols/therapeutic useABSTRACT
Mice were used to make a comparative study of the biological distribution of intravenous preparations of native and monomethoxypolyethylene glycol-modified superoxide dismutase isolated from bovine liver, as well as native and aldehyde dextran. The study demonstrated that the biodistribution of the native enzymes from various sources was, however, equal, but in the mouse liver there was a higher accumulation of SOD isolated from the rat liver. AD-SOD was found to have a longer half-life in the blood and in the liver of mice, in particular, while MPEG-SOD showed 10, 15, and 16 times longer in the lungs, blood and heart of the animals examined, respectively. The elevated accumulation of MPEG-SOD in some organs was used for their treatment, particularly for experimental therapy of rat myocardial ischemia. A rat model of ischemia demonstrated that the intravenous bolus administration of MPEG-SOD reduced the size of a myocardial necrotic area by 40% as compared to a 13% decrease when the other compounds were assayed. The findings suggest that the MPEG-SOD preparation is promising for decreasing reperfusion injuries of the cardiovascular system and the lungs.
Subject(s)
Myocardial Ischemia/drug therapy , Polyethylene Glycols/pharmacology , Superoxide Dismutase/drug effects , Superoxide Dismutase/therapeutic use , Animals , Cattle , Drug Evaluation, Preclinical , Iodine Radioisotopes , Liver/enzymology , Male , Mice , Mice, Inbred CBA , Myocardial Reperfusion Injury/prevention & control , Rats , Rats, Wistar , Specific Pathogen-Free Organisms , Superoxide Dismutase/isolation & purification , Superoxide Dismutase/pharmacokinetics , Tissue DistributionABSTRACT
Beef liver arginase, an enzyme potentially useful in the therapy of arginine dependent tumors or of familial hyperargininemia, was purified to homogeneity by a procedure involving a key step of hydrophobic affinity chromatography. The enzyme was extensively modified by the covalent linking of monomethoxypolyethyleneglycol molecules according to a procedure recently proposed by the Authors (Veronese et al., Appl. Biochem. Biotecnol. 11, 869, 1985) without any significant loss of activity. The derivative enzyme presents more convenient properties for a therapeutic use, as compared to the native enzyme, such an increased structural stability, a decreased digestion by proteolytic enzymes and an expanded clearance time in rats.