Impact of stereochemistry on the biological activity of novel oleandomycin derivatives.

A set of 8-methylene-, 8-methyl-, and 8-methyl-9-dihydro-oleandomycin derivatives having different combinations of stereochemistries at positions C-8 and/or C-9 have been prepared in a chemoselective and stereoselective manner and tested in vitro for antibacterial activity and inhibition of IL-6 production. Configurations of the stereocenters at C-8 and C-9 were determined using 2D NMR techniques. We have shown that change of stereochemistry at these positions can exert a major influence on antibacterial activity as well as IL-6 inhibition, providing novel macrolide derivatives with diminished antibacterial and potent anti-inflammatory activity. In addition, the anti-inflammatory activity observed in vitro was confirmed in an in vivo model of lipopolysaccharide-induced inflammation.

Azithromycin inhibits macrophage interleukin-1ß production through inhibition of activator protein-1 in lipopolysaccharide-induced murine pulmonary neutrophilia.

Macrolide antibiotics, including azithromycin, also possess anti-inflammatory properties. However, the molecular mechanism(s) of activity as well as the target cells for their action have not been unambiguously identified as yet. In this study, the effects of azithromycin on lipopolysaccharide (LPS)-induced pulmonary neutrophilia were investigated in mice. Using immunohistochemistry, mRNA and specific protein assays, we confirmed that azithromycin ameliorates LPS-induced pulmonary neutrophilia by inhibiting interleukin-1ß (IL-1ß) expression and production selectively in alveolar macrophages as well as in LPS-stimulated J774.2 macrophage-derived cells in vitro. Inhibition by azithromycin of neutrophilia and IL-1ß was accompanied by prevention of nuclear expression of activator protein-1 (AP-1) in both alveolar macrophages and J774.2 cells. The macrolide did not alter nuclear factor kappa B (NF-κB) or extracellular signal-regulated kinase 1/2 (ERK1/2) expression, activation or localization in LPS-stimulated lungs or in J774.2 cells. In conclusion, we have shown that inhibition of LPS-induced pulmonary neutrophilia and IL-1ß concentrations in lung tissue following azithromycin treatment is mediated through effects on alveolar macrophages. In addition, we have shown for the first time, in an in vivo model, that azithromycin inhibits AP-1 activation in alveolar macrophages, an action confirmed on J774.2 cells in vitro.

Differential evaluation of excisional non-occluded wound healing in db/db mice.

The full-thickness wound in the genetically diabetic (db/db) mouse is a commonly used model of impaired wound healing. We investigated delayed healing of non-occluded, excisional, full-thickness, dermal wounds in db/db mice in comparison to their normal littermate controls and refined methods for monitoring skin wound re-epithelialization, contraction, granulation tissue formation, and inflammation. We have confirmed with a computer-assisted planimetry method the results of previous studies showing that healing of non-occluded full excision wounds in db/db mice does not occur by contraction as much as in healthy mice. In addition, we have developed separate histological methods for the assessment of re-epithelialization, contraction, granulation tissue (mature, immature, fibrosis), and inflammation (lipogranulomas, secondary, nonspecific). Using a new approach to histological assessment, we have shown that wound closure in db/db mice is delayed owing to: (1) delayed granulation tissue maturation; (2) ''laced,'' widely distributed granulation tissue around fat lobules; and (3) obstruction by lipogranulomas, whereas the rate of re-epithelialization seems to be the same as in C57Bl/6 mice. This methodology should permit a more precise differentiation of effects of novel therapeutic agents on the wound healing process in db/db mice.