Molecular Mechanisms Involved in the Differential Effects of Sex Steroids on the Reproduction and Infectivity of Taenia Crassiceps

Abstract

The in vitro exposure of Taenia crassiceps cysticerci to 17-beta estradiol (E2) and progesterone (P4) stimulated their reproduction and infectivity. Testosterone (T4) and dihydrotestosterone (DHT) inhibited their reproduction and reduced their motility and infectivity. E2 and P4 increased, whereas T4 and DHT reduced, the expression of parasite c-fos and c-jun and DNA synthesis. In vitro exposure of cysticerci to sex steroids before their inoculation into recipient noninfected mice resulted in large parasite loads when pretreated with E2 and P4 and in smaller loads when pretreated with T4 and DHT To determine the possible molecular mechanisms by which sex steroids affect T. crassiceps, sex steroid receptors were amplified. Taenia crassiceps expressed estrogen receptors (both alpha and beta isoforms) and androgen receptors but no P4 receptors. These results demonstrate that sex steroids act directly on parasite reproduction by binding to a classic and specific sex steroid receptor on the parasite. The differential response of cysticerci to sex steroids may also be involved in their ability to grow faster in the murine female or feminized male host. This is the first report of direct sex steroid effects on the parasite possibly through sex steroid receptors in the cysticerci.

Neuroimmunoendocrine Interactions in Murine Cysticercosis: From the Lab Bench Work to Its Possible Applications in Controlling Porcine Cysticercosis and Human Neurocysticercosis

“…For instance, it has been shown that in vitro treatment with E2 and P4 stimulates T. crassiceps reproduction. In contrast, T4 or DHT inhibit and even exert a toxic effect on the parasite (Escobedo et al, 2004). The possible molecular mechanisms by which sex-steroids affect T. crassiceps reproduction imply the presence of sex hormone receptors, since the use of tamoxifen, an anti-estrogenic compound (Escobedo et al, 2005), decreases parasite reproduction in vitro and parasite loads in vivo, as described before , we look for a estrogen receptor expressed by parasitic cells.…”

“…These mechanisms can be roughly grouped into two types: 1) evasion of the immune response by molecular mimicry or by inactivating effector immune processes (i.e, complement inhibition) (Baig et al, 2005;Laclette et al, 1989); and 2) by exploiting the host system to allow its establishment, growth or reproduction (Escobedo et al, 2004). This exploitation mechanism provides parasites with a dual benefit: first, obtaining amino acids for metabolism, and second preventing the surface-bound antibody from interfering with cytotoxic cells interacting with the parasite (Damian, 1989;Locksley, 1997).…”

“…Taeniids have evolved structures similar to the steroid and protein hormone receptors expressed in upper vertebrates, with binding properties and terminal effects similar to the hormonal metabolites synthesized by the host (Gomez et al, 2000). Such cross regulation from host to parasite has been described in at least eight parasitic infections that are caused by parasitic cestodes, like schistosomiasis (LoVerde et al, 1985), filariasis (Rajan et al, 2005), hydatid disease and murine cysticercosis (Escobedo et al, 2004).…”

“…Understanding how the host's endocrine system can favor the establishment of taeniids under certain circumstances, led us to explore the parasite's hormone receptors that might be involved, designing hormonal analogs and drugs to specifically affect the parasite (Escobedo et al, 2004). This review is focused on the literature concerning sex-steroids, adrenal steroids and other hormones and neurohormones that have been studied in regard to control parasite loads in experimental murine cysticercosis.…”

Vertebrate-Type Steroid Profile in Different Tissues of Wild and Endocrinologically Manipulated Female Brood Stocks of <i>Penaeus monodon</i>

“…A hypothetical parallelism in the endocrine functions between invertebrates and vertebrates has been suggested, although the mechanism of hormonal action and its precise role in oocyte development are not unequivocally proved in invertebrates 4 . The existence of sex steroids in many invertebrates, including coelenterates 5 , sponges 6 , helminthes 7 , annelids 8 , molluscs 9 , crustaceans 10 and echinoderms 3 has been reported. The most convincing evidence for the role of sex steroids in reproduction has been reported in molluscs 4 .…”