In vitro and in vivo evaluation of a pH-, microbiota- and time-based oral delivery platform for colonic release.

Several formulation strategies have been proposed for oral colon delivery, particularly for the therapy of inflammatory bowel disease (IBD). However, targeting the large intestine remains a challenging goal. The aim of this study was to develop and evaluate a novel type of drug delivery system, which is based on multiple drug release triggers for reliable performance. The system consists of: (i) a drug core, (ii) an inner swellable low-viscosity hydroxypropyl methylcellulose (HPMC) layer, and (iii) an outer film coating based on a Eudragit® S:high-methoxyl (HM) pectin (7:3 w/w) blend, optionally containing chitosan. Convex immediate release tablets (2 or 4 mm in diameter) containing paracetamol or 5-aminosalicylic acid (5-ASA) were coated in a fluid bed. The double-coated tablets exhibited pulsatile release profiles when changing the release medium from 0.1 N HCl to phosphate buffer pH 7.4. Also, drug release was faster in simulated colonic fluid (SCF) in the presence of fecal bacteria from IBD patients compared to control culture medium from tablets with outer Eudragit® S: HM pectin: chitosan coatings. The latter systems showed promising results in the control of the progression of colitis and alteration of the microbiota in a preliminary rat study.

The schistosome glutathione S-transferase P28GST, a unique helminth protein, prevents intestinal inflammation in experimental colitis through a Th2-type response with mucosal eosinophils.

Intestinal helminth parasites are potent inducers of T helper type 2 (Th2) response and have a regulatory role, notably on intestinal inflammation. As infection with schistosomes is unlikely to provide a reliable treatment of inflammatory bowel diseases, we have investigated the beneficial effect of a schistosome enzymatic protein, the 28-kDa glutathione S-transferase (P28GST), on the modulation of disease activity and immune responses in experimental colitis. Our results showed that immunization with recombinant P28GST is at least as efficient as established schistosome infection to reduce colitis lesions and expression of pro-inflammatory cytokines. Considering underlying mechanisms, the decrease of inflammatory parameters was associated with the polarization of the immune system toward a Th2 profile, with local and systemic increases of interleukin (IL)-13 and IL-5. Dense eosinophil infiltration was observed in the colons of P28GST-immunized rats and mice. Depletion of eosinophils by treatment with an anti-Siglec-F monoclonal antibody and use of IL-5-deficient mice led to the loss of therapeutic effect, suggesting the crucial role for eosinophils in colitis prevention by P28GST. These findings reveal that immunization with P28GST, a unique recombinant schistosome enzyme, ameliorates intestinal inflammation through eosinophil-dependent modulation of harmful type 1 responses, representing a new immuno-regulatory strategy against inflammatory bowel diseases.

Effects of oxysterols on arachidonic acid metabolism and prostacyclin synthesis in bovine aortic smooth muscle cells in culture.

Previous studies have shown that oxysterols could induce arterial damage in animals and manifest potent toxicity in cultured cells. Bovine aortic smooth muscle cells in culture were used to study the effects of several cholesterol oxides on arachidonic acid (AA) metabolism. Using two different methods, i.e. radioactive labeling of cells with 14C-AA and radioimmunoassay of 6kPGF1 alpha, the stable metabolite of Prostacyclin (PGI2), we observed various effects depending on the substance. Oxysterols oxidised on the rings were able to inhibit AA metabolism only at high doses, toxic to the cells, presumably through a non specific lytic mechanism. Oxysterols oxidised on the side chain induced an inhibition of the overall arachidonate conversion and PGI2 synthesis at low doses, below the range of cytotoxicity. This inhibition was noted both on the basal and stimulated metabolism. Mechanisms involved in such actions are still to be determined.

Effect of systemic and orally administered iota-carrageenan on ovalbumin-specific antibody response in the rat.

Iota-carrageenans are high molecular weight polygalactans commonly used in the food industry. Their immunomodulating effects were examined on the reaginic and IgG ovalbumin-specific responses after systemic or oral administration to Brown Norway rats. Intraperitoneal injection of ovalbumin with either iota-carrageenan or alum induced both a reaginic and IgG response. Reaginic antibodies were detected in the primary response with alum, but only in the secondary response with iota-carrageenan. Oral tolerance to ovalbumin was similarly induced whether the protein was given alone or admixed in solution with iota-carrageenan. These results confirmed the systemic adjuvant action of iota-carrageenan described earlier, and showed that this effect did not take place when orally administered.