Diethylcarbamazine (DEC) Does Not Induce Nitric Oxide (NO) Synthesis

Abstract

Rajan, T. V., Shultz, L. D., Babu, S., Doukas, J., Greiner, D., and Porte, P. 1998. Diethylcarbamazine (DEC) does not induce nitric oxide (NO) synthesis.Experimental Parasitology88, 217–222. Diethylcarbomazine (DEC) was discovered in 1947 as a potent therapeutic agent in lymphatic filariasis and has been a mainstay of antifilarial therapy over the past five decades (R. I. Hewitt,et al., 1947,Journal of Laboratory and Clinical Medicine32, 1304–1313). Several hundred million doses of this drug have been administered to people. Despite its widespread and successful use over this prolonged time scale, its mechanism of action remains obscure (R. M. Maizels and D. A. Denham, 1992,Parasitology105Suppl. 549–560). Numerous studies suggest that DEC has no direct effect on the parasite (F. Hawking and W. Laurie, 1949,Lancet2, 146–147) and that it exerts its action by stimulating host immune defense mechanisms (F. Hawkinget al., 1948,Lancet2, 730–731), or by activating host platelets to become microfilaricidal (J. Y. Cesbronet al., 1987,Nature325(6104) 533–536). Recent data from two different laboratories suggest that NO may be involved in host defense against filarial parasites (T. V. Rajanet al., 1996,Infection and Immunity64(8), 3351–3353; M. J. Tayloret al., 1996,Parasitology112, 315–322). We investigated whether DEC stimulates the production of NO from murine macrophages or rat endothelial cells. DEC did not stimulate the synthesis or secretion of NO from either, nor did it synergize with interferon-gamma or tumor necrosis factor-alpha in the induction of inducible NO synthase (iNOS). In addition, there was no consistent increase in the output of inorganic nitrate, the end product of NO metabolism, in the urines of rats treated with DEC. These data suggest that DEC does not achieve its therapeutic efficacy through the induction of host iNOS.