Nitric oxide synthase in filariae: Demonstration of nitric oxide production by embryos in Brugia malayi and Acanthocheilonema viteae

The radical gas nitric oxide (NO) is synthesized by nitric oxide synthase ( NOS) from (L)-arginine and molecular oxygen. Nitric oxide is an important s ignaling molecule in invertebrate and vertebrate systems. Previously we hav e shown that NOS is localized to more tissues in Brugia malayi than has bee n reported in Ascaris suum. In this paper, we analyze the distribution of N OS in Acanthocheilonema viteae, a filarial nematode that differs from B. ma layi in that A. viteae females release microfilariac without a sheath. A. v iteae is also one of a few filarial parasites without the Wolbachia intrace llular endosymbiont. By use of a specific antibody, NOS was demonstrated in extracts of A. viteae and Dirofilaria immitis. The localization pattern of NOS in A. viteae was similar to that seen in B. malayi, with the enzyme lo calized to the body wall muscles of both sexes, developing spermatozoa, int rauterine specific for nitric oxide, the embryos of B. malayi and A. viteae were demonstrated to produce NO ex utero. The near identical staining patt erns seen in A. viteae and B. malayi argue that NO is not produced by Wolba chia, nor is it produced by the nematodes in response to the infection. Loc alization of NOS to the sperm of filarial nematodes suggests a role for NO during fertilization as has been described for sea urchin and ascidian fert ilization. Demonstration of the activity of embryonic NOS supports our earl ier hypothesis that NO is a signaling molecule during embryogenesis in fila rial nematodes. (C) 2001 Academic Press.