Inhibition of inflammatory actions of aminobisphosphonates by dichloromethylene bisphosphonate, a non-aminobisphosphonate.

1. When injected intraperitoneally into mice in doses larger than those used clinically, all the amino derivatives of bisphosphonates (aminoBPs) tested induce a variety of inflammatory reactions such as induction of histidine decarboxylase (HDC, the histamine-forming enzyme), hypertrophy of the spleen, atrophy of the thymus, hypoglycaemia, ascites and accumulation of exudate in the thorax, and an increase in the number of macrophages and/or granulocytes in the peritoneal cavity of blood. On the other hand, dichloromethylene bisphosphonate (Cl2MBP) a typical non-aminoBP, has no such inflammatory actions. In the present study, we found that this agent can suppress the inflammatory actions of aminoBPs. 2. Cl2MBP, when injected into mice before or after injection of 4-amino-1-hydroxybutylidene-1,1-bisphosphonic acid (AHBuBP; a typical aminoBP), inhibited the induction of HDC activity by AHBuBP in a dose- and time-dependent manner. The increase in HDC activity induced by AHBuBP was largely suppressed by the injection of an equimolar dose of Cl2MBP. Cl2MBP also inhibited other AHBuBP-induced inflammatory reactions, as well as the inflammatory actions of two other aminoBPs. However, Cl2MBP did not inhibit the increase in HDC activity induced by lipopolysaccharide (LPS). 3. We have previously reported that AHBuBP augments the elevation of HDC activity and the production of interleukin-1beta (IL-1beta) that are induced by LPS. These actions of AHBuBP were also inhibited by Cl2MBP. 4. Based on these results and reported actions of bisphosphonates, the mechanisms underlying the contrasting effects of aminoBPs and Cl2MBP, a non-aminoBP are discussed. The results suggest that combined administration of Cl2MBP and an aminoBP in patients might be a useful way of suppressing the inflammatory side effects of aminoBPs.