Glucosamine dose/concentration-effect correlation in the rat with adjuvant arthritis.

There is a debate on the dose dependency, concentration-effect, hence, the beneficial effect of glucosamine (GlcN), a widely used anti-inflammatory natural product. We investigated dose/concentration-effect relationship and determined its minimum effective dose/concentration in rats with adjuvant arthritis (AA, Mycobacterium butyricum in squalene) both as preventive and ameliorating interventions. To control already emerged arthritis, rats received oral doses of placebo or 160 mg/kg.day(-1) GlcN for 6 days. For prevention, rats were orally administered 0, 20, 40, 80, or 160 mg/kg.day(-1) GlcN commencing on the day of adjuvant injection. The arthritis index (AI), serum nitrite, and body weight were recorded. Subsequently, animals were cannulated in the right jugular veins and blood samples were collected for the determination of GlcN. GlcN ameliorated and, dose-dependently, prevented AA. It also controlled nitrite. AI was inversely correlated with GlcN dose, maximum plasma concentration, and the area under the concentration curve. Minimum effective dose was approximately 40 mg/kg.day(-1) that correspond to maximum plasma concentration of 1.37 ± 0.24 mg/L, close to 1.6 mg/L reported for pharmaceutical grades of GlcN to humans. GlcN efficacy is dose and concentration dependent. If the data extrapolated to humans, a higher than the commonly tested 1500 mg/kg dosage regimen may provide more clear treatment outcomes.

Microcalorimetric method to assess phagocytosis: macrophage-nanoparticle interactions.

This study evaluated the use of isothermal microcalorimetry (ITMC) to detect macrophage-nanoparticle interactions. Four different nanoparticle (NP) formulations were prepared: uncoated poly(isobutyl cyanoacrylate) (PIBCA), polysorbate-80-coated PIBCA, gelatin, and mannosylated gelatin NPs. Changes in NP formulations were aimed to either enhance or decrease macrophage-NP interactions via phagocytosis. Alveolar macrophages were cultured on glass slabs and inserted in the ITMC instrument. Thermal activities of the macrophages alone and after titration of 100 µL of NP suspensions were compared. The relative interactive coefficients of macrophage-NP interactions were calculated using the heat exchange observed after NP titration. Control experiments were performed using cytochalasin B (Cyto B), a known phagocytosis inhibitor. The results of NP titration showed that the total thermal activity produced by macrophages changed according to the NP formulation. Mannosylated gelatin NPs were associated with the highest heat exchange, 75.4 ± 7.5 J, and thus the highest relative interactive coefficient, 9,269 ± 630 M-1. Polysorbate-80-coated NPs were associated with the lowest heat exchange, 15.2 ± 3.4 J, and the lowest interactive coefficient, 890 ± 120 M-1. Cyto B inhibited macrophage response to NPs, indicating a connection between the thermal activity recorded and NP phagocytosis. These results are in agreement with flow cytometry results. ITMC is a valuable tool to monitor the biological responses to nano-sized dosage forms such as NPs. Since the thermal activity of macrophage-NP interactions differed according to the type of NPs used, ITMC may provide a method to better understand phagocytosis and further the development of colloidal dosage forms.