A preliminary in vitro and in vivo study of the effects of new anthraquinones on neutrophils and bone remodeling

Osteolysis, that is, progressive periprosthetic bone loss, is responsible for approximately 70% of aseptic loosening and implant failure. Usually, it is due to a granulomatous reaction wear-induced, leading to macrophage and osteoclast-mediated bone resorption. At present, there is no established prophylaxis or treatment for this process. For this purpose, as a preliminary investigation, we aimed to study the effects in two directions, inhibition of proinflammatory signals, and bone remodeling activity, of two newly synthesized anthraquinone molecules [NN'-Diethylamino2,6-anthraquinone-disulfonamide (GR375) and N,N'-(pethoxyphenyl)-2,6-anthraquinone-disulfon amide (GR377)]. Among the pro-inflammatory signals, the ability of the two anthraquinones to interfere with the production of superoxide anion (O-2(-)), which was assumed as a marker of reactive oxygen species (ROS), was evaluated in an in vitro cell model by testing phagocytes, such as human neutrophils, challenged by the chemotactic agent N-formylmethionyl-leucyl-phenylalanine (FMLP). Both compounds inhibited O-2(-) production, in a dose-dependent way, without exerting scavenger effects. An in vivo model was applied to investigate their effect on bone remodeling. Fifty-four female Wistar rats were divided into eight groups of six animals each, and a 4-week treatment was applied in two phases. A 25 mg/kg/os dose in the first phase and 12.5-6.25mg/kg/os doses in the second one were employed. The tibia trabecular bone at the secondary spongiosa level was analyzed, and trabecular bone volume (%TBV), trabecular thickness (TbTh), and apatite lattice parameters were measured. At the highest doses of GR375 and GR377 the %TBV and the TbTh increased by 33.2, 34.6%, and 3.6 and 9.1%, respectively, whereas crystallographic parameters were not significantly different from the untreated group. Our results suggest a simultaneous antiinflammatory and antiosteoclastic activity of both drugs that encourages to perform further research. If it will be confirmed, they could be proposed in a variety of bone diseases, in particular, when acute inflammation is associated to osteolytic processes and, eventually, in the prevention and treatment of periprosthetic osteolysis. (c) 2005 Wiley Periodicals, Inc.