However, membrane-bound TNF is also capable of see more binding to TNF receptors and initiating a signal transduction pathway through cell–cell interactions.
At this time, a number of possible steps in transcription, translation or secretion ranging from diminished synthesis of mRNA or protein to increased destruction of either macromolecule may also be possible targets for the action of doxycycline. In this regard, preliminary data in our lab indicate that doxycycline [and even more so, 6-demethyl 6-deoxy 4-de-(dimethylamino) tetracycline (CMT-3), a chemically modified tetracycline analog that has been shown to be more potent than doxycycline, although it results in more side effects] can decrease nuclear factor-κB this website phosphorylation/activation, which could decrease cytokine and MMP expression (Gu et al., 2009). Doxycycline has been found to inhibit the protein and RNA expression of MMP-8 induced by TNF-α and phorbol myristic acetate in human rheumatoid and gingival fibroblasts (Hanemaaijer et al., 1997). Doxycycline
also inhibited type I and II collagenolytic activity in these fibroblasts (Hanemaaijer et al., 1997). Using the ECM system, we demonstrated that monocyte-derived macrophages can directly mediate ECM degradation, and doxycycline protected the ECM degradation possibly by reducing the activities and/or the levels of MMPs through reducing Fenbendazole extracellular cytokine levels. Doxycycline and nonantimicrobial tetracyclines have been shown by Golub’s group to inhibit MMP activity, connective tissue breakdown and modulate host responses. One of these compounds, CMT-3, was found to be superior to the other CMTs as an MMP inhibitor. In separate preliminary studies, we evaluated the effect of CMT-3 on the extracellular levels of the cytokines, TNF-α and IL-1β, and on MMP-9. CMT-3 (0.1 μM) inhibited 56% of the extracellular TNF-α level, while 1 and 10 μM CMT-3 reduced the extracellular levels of TNF-α by 70% and 71%, respectively (Y.
Gu, H.-M. Lee and L.M. Golub unpublished data). 0.1, 1 and 10 μM CMT-3 also reduced MMP-9 levels by 12%, 20% and 53% (data not shown). CMT-3 at different concentrations exhibited greater capacity in reducing TNF-α and MMP-9 levels, but not IL-1β levels. Future experiments will compare the potency of CMT-3 relative to doxycycline as MMP and cytokine inhibitors, especially as both subantimicrobial formulations of doxycycline or nonantibiotic CMT-3 have been tested in humans with conditions ranging from chronic inflammatory diseases such as periodontitis, rheumatoid arthritis and acne and rosacea (Ryan et al., 1996; Grenier et al., 2002; Bikowski, 2003), to a fatal lung disease (Moses et al., 2006), and a type of cancer, Kaposi’s sarcoma (Dezube et al., 2006).