Cyclooxygenases (COX-1 and COX-2) catalyze the conversion of arachidonic acid (AA) into PGH2 that is further metabolized by terminal prostaglandin (PG) synthases into biologically active PGs, for example, prostaglandin E2 (PGE2), prostacyclin I2 (PGI2), thromboxane A2 (TXA2), prostaglandin D2 (PGD2), and prostaglandin F2 alpha (PGF2α). Among them, PGE2 is a widely distributed PG in the human body, and an important mediator of inflammatory processes. The successful modulation of this PG provides a beneficial strategy for the potential anti-inflammatory therapy. For instance, nonsteroidal anti-inflammatory agents (NSAIDs), both classical nonselective (cNSAIDs) and the selective COX-2 inhibitors (coxibs) attenuate the generation of PGH2 from AA that in turn reduces the synthesis of PGE2 and modifies the inflammatory conditions. However, the long-term use of these agents causes severe side effects due to the nonselective inhibition of other PGs, such as PGI2 and TXA2, etc. Microsomal prostaglandin E2 synthase-1 (mPGES-1), a downstream PG synthase, specifically catalyzes the biosynthesis of COX-2-derived PGE2 from PGH2, and describes itself as a valuable therapeutic target for the treatment of acute and chronic inflammatory disease conditions. Therefore, the small molecule inhibitors of mPGES-1 would serve as a beneficial anti-inflammatory therapy, with reduced side effects that are usually associated with the nonselective inhibition of PG biosynthesis.

Previous studies of the round goby (Neogobius melanostomus Pallas, 1814), an invasive fish species in the Laurentian Great Lakes of North America, have shown that this species has the ability to both synthesize and smell steroids that have a 5 beta-reduced and 3 alpha-hydroxyl (5 beta,3 alpha) configuration. An enzyme-linked immunoassay (EIA) for 3 alpha-hydroxy-5 beta-androstane-11,17-dione (11-O-ETIO) has been used to show a substantial rise in the rate of release of immunoreactive compounds into the water when males are injected with salmon gonadotropin releasing hormone analogue. Similar increases were noted for 11-ketotestosterone and 17,20 beta-dihydroxypregn-4-en-3-one. Partitioning of the extracts between diethyl ether and water showed the presence of both free and conjugated immunoreactive 11-O-ETIO. Only conjugated immunoreactivity was found in urine (implying that free steroid is released via the gills). The identity of the conjugates was probed by using HPLC, EIA, and mass spectrometry and removal of sulfate and glucosiduronate groups. Immunoreactivity in the conjugated fraction was found to be due mainly to 3 alpha,17beta-dihydroxy-5 beta-androstan-11-one 17-sulfate. However, the evidence was also strong for the presence in water extracts of substantial amounts of 3 alpha-hydroxy-5 beta-androstane-11,17-dione 3-glucosiduronate (which could be detected only by EIA after removal of the glucosiduronate group with beta-glucuronidase). There were also small amounts of 3 alpha-hydroxy-5 beta-androstane-11,17-dione 3-sulfate and 3 alpha,17beta-dihydroxy-5 beta-androstan-11-one 17-glucosiduronate. These studies give some idea of the types, amounts, and ratios of 11-O-ETIO derivatives that are released by reproductive N. melanostomus and will aid further research into the putative pheromonal roles of 5 beta,3 alpha-reduced androgens in this species.

The round goby (Neogobius melanostomus) is an invasive fish in the Laurentian Great Lakes and beyond. Pheromones appear to be important for their reproductive success, as females are attracted to water in which reproductive males have resided ("conditioned water"). Previous investigation has shown conjugated and unconjugated forms of 3␣-hydroxy- are released in the urine of these males. The goal of this study was to determine if the urine of reproductive males and fractionated extracts attract females. We found that reproductively active females were attracted to male urine and to isolates of male-conditioned water that contained conjugated 11-O-ETIO. The fractionated preparation that corresponded to unconjugated 11-O-ETIO (i.e., "free" steroid released via the gills of males) was not attractive to reproductive females, but curiously, it was attractive to nonreproductive females. Olfactory sensory deprivation confirmed that the behavioural responses were mediated by olfaction. These findings take us closer towards identifying the pheromone(s) that attract female gobies and, therefore, closer to having a method to limit this species' damaging invasion.Résumé : Le gobie à taches noires (Neogobius melanostomus) est un poisson envahissant dans les Grands Lacs laurentiens et au-delà . Les phérormones semblent être un facteur important en ce qui concerne leur succès de reproduction, les femelles étant attirées par l'eau dans laquelle ont résidé des mâles reproducteurs (« eau conditionnée »). Une étude précédente a démontré que des formes conjuguées et non conjuguées de la 3␣-hydroxy-5␤-androstane-11,17-dione (11-oxo-étiocholanolone; 11-O-ETIO) sont libérées dans l'urine de ces mâles. Le but de l'étude était de déterminer si l'urine de mâles reproducteurs et des extraits fractionnés attiraient les femelles. Nous avons constaté que les femelles reproductrices étaient attirées par l'urine des mâles et des isolats d'eau conditionnée par ces derniers contenant de la 11-O-ETIO conjuguée. La préparation fractionnée qui correspondait à la 11-O-ETIO non conjuguée (c.-à -d. stéroïde « libre » libéré par les branchies des mâles) n'attirait pas les femelles reproductrices bien que, fait surprenant, elle ait attiré les femelles non reproductrices. La privation olfactive a confirmé que les réponses comportementales étaient modulées par l'olfaction. Ces résultats sont un pas de plus vers l'identification de la ou des phéror-mones qui attirent les gobies et ainsi, vers la mise au point d'une méthode permettant de limiter l'invasion de cette espèce dommageable. [Traduit par la Rédaction]

The round goby, Neogobius melanostomus, is a highly successful invasive species in the Laurentian Great Lakes. Previous behavioral studies implied that females are attracted by pheromones to the nests of reproductive males, and that males release putative steroidal pheromones--unconjugated as well as conjugated forms of 3α-hydroxy-5β-androstane-11,17-dione (11-O-ETIO)-following stimulation of the hypothalamic--gonadal axis with salmon gonadotropin releasing hormone analog (sGnRHa). In this study, we tested the olfactory system of females in response to extracts containing these released steroids. We compared electrical field potential responses from the olfactory epithelium (electro-olfactogram, EOG) of non-reproductive females to methanol extracts of water that previously held males, collected before and after injection of the males with sGnRHa or saline. The females showed increased EOG responses to the post-injection extracts when males were treated with sGnRHa but not saline. This finding provides further evidence for interactions between male and female N. melanostomus via steroidal reproductive pheromones.