Purification and identification of 25-hydroxycholesterol in a reptile: Seasonal variation and hormonal regulation

Ovarian nesfatin-1 in Hemidactylus flaviviridis: Reproductive phase-dependent expression, role and hormonal regulation

Nesfatin-1 has recently emerged as a modulator of ovarian functions in mammals. Studies in non-mammalian vertebrates, though limited and majorly restricted to fishes, have evidenced a role of this peptide in the regulation of ovarian steroidogenesis and oocyte maturation. Interestingly, nesfatin-1 remains completely unexplored in reptiles. Therefore, the present study aimed to identify nesfatin-1 and elucidate its role and regulation in the ovary of Hemidactylus flaviviridis. Ovarian expression of nucb2/nesfatin-1 was highest during late recrudescence and breeding while it was lowest during regression. Follicular stage-dependent expression analysis showed significantly high expression of nucb2/nesfatin-1 in previtellogenic follicles. Further, in vitro treatment of recrudescent wall lizard ovaries with nesfatin-1 resulted in increased expression of anti-apoptotic gene, bcl-2, along with a concomitant decline in the pro-apoptotic gene, caspase-3. In addition, proliferation/differentiation markers like scf, c-kit, pcna, and bmp-15 were stimulated in ovaries incubated with the peptide. Ovarian steroidogenesis was also positively influenced by nesfatin-1 as treatment with the peptide resulted in heightened star expression as well as increased estradiol and progesterone production. Also, all concentrations of nesfatin-1 stimulated glucose uptake and metabolism in wall lizard ovary. Our observations provide the first evidence of ovarian functions of nesfatin-1 in a reptile. Further, ovarian nucb2/nesfatin-1 was differentially regulated by gonadotropin and sex steroids wherein its expression was stimulated by dihydrotestosterone (DHT) and 17β-estradiol (E2) but inhibited by follicle-stimulating hormone (FSH). In summary, this is the first report of the presence, reproductive stage-dependent expression, role, and regulation of ovarian nucb2/nesfatin-1 in H. flaviviridis.

Nesfatin-1 in a reptile: its role and hormonal regulation in wall lizard testis

Nesfatin-1 is a pleiotropic hormone implicated in various physiological functions including reproduction. Studies though limited, have established an important role of the peptide in regulation of testicular functions in mammals and fishes. However, role of nesfatin-1 in regulation of spermatogenesis and testicular steroidogenesis remains completely unexplored in reptiles. Therefore, present study aimed to develop an insight into reproductive phase-dependent testicular expression, function and regulation of nucb2/nesfatin-1 in a reptile, Hemidactylus flaviviridis. Expression of nucb2/nesfatin-1 in testis of wall lizard varied significantly depending upon reproductive phase, being highest in the active phase while lowest during regressed phase. Further, in vitro treatment of wall lizard testis with nesfatin-1 showed a concentration- and time-dependent stimulatory effect of the peptide on expression of cell proliferation and differentiation markers like scf, c-kit and pcna suggesting a spermatogenic role of nesfatin-1 in wall lizard. Also, nesfatin-1 stimulated the anti-apoptotic marker, bcl-2 while inhibited the apoptotic marker, caspase-3, suggesting its role as an inhibitor of apoptosis of testicular cells. Further, treatment with nesfatin-1 resulted in significantly higher expression of star along with a concomitant increase in testosterone production by the lizard testis. The present study also demonstrates hormonal regulation of testicular nucb2/nesfatin-1 wherein follicle-stimulating hormone (FSH) inhibited while sex steroids like dihydrotestosterone (DHT) and 17β-estradiol-3-benzoate (E2) stimulated the mRNA expression of nesfatin-1. Observations from the current study for the first time provide comprehensive evidence of spermatogenic and steroidogenic role of nesfatin-1 as well as its hormonal regulation in the testis of a reptile, H. flaviviridis.

Testicular 25-hydroxycholesterol: An alternate substrate for steroidogenesis in reptiles

The current study in wall lizards Hemidactylus flaviviridis was designed to ascertain that Leydig cells utilize testicular macrophage-derived 25-hydroxycholesterol (25-HC) for steroidogenesis. Leydig cells (LC) collected from regressed testes when incubated with 25-HC that was obtained from HPLC-eluted fraction of testicular macrophage-conditioned medium (TMCM), lyophilized and reconstituted in culture medium (0.5 µg/ml/well), produced considerably higher amount of testosterone. A similar observation was made when Leydig cells were incubated with varying concentrations of commercial 25-HC. Testosterone production by LC increased in a concentration-dependent manner. Taken together, it is evident that LC utilize 25-HC as a substrate for testosterone biosynthesis. To examine the gonadotropic regulation of steroid biosynthesis utilizing 25-HC as substrate, ovine follicle-stimulating hormone (FSH) that regulates both the testicular functions in lizards was used. Leydig cells were incubated with combinations of FSH and 25-HC as follows: 0 h FSH + 12 h 25-HC, 0 h 25-HC + 12 h FSH. As compared to respective controls, a marked increase in testosterone production was observed in response to FSH indicating that gonadotropin up-regulates uptake of 25-HC as a substrate for testosterone biosynthesis.

Macrophage Migration Inhibitory Factor Promotes Chemotaxis of Astrocytes through Regulation of Cholesterol 25-Hydroxylase Following Rat Spinal Cord Injury

Oxysterol derived from cholesterol metabolism is involved in the inflammatory activation, and consequently in development of major chronic diseases. Multiple cytokines have been found to induce the expression of cholesterol metabolism-related enzymes. Several studies have shown that the protein level of cholesterol-25-hydroxylase (CH25H) is remarkably increased in response to injury of central nervous system (CNS), but little is known about the mechanisms of cytokine-induced expression of CH25H in specific cell types, and the resultant effects. In the present study, we demonstrated that ch25h expression was significantly upregulated in the astrocytes of rat injured spinal cord, in parallel with those of MIF. Administration of MIF inhibitor 4-IPP in the lesion sites attenuated injury-induced ch25h expression. MIF facilitated ch25h expression of astrocytes through interaction with CD74 membrane receptor, which in turn promoted production of chemokines, as identified by transcriptome profiles. MIF-induced release of oxysterol 25-hydroxycholesterol (25-HC) from astrocytes affects cell migration, but inhibited cell viability in dose-dependent manner, suggesting that MIF aggravates progressive neuropathology through regulation of cholesterol metabolism following CNS injury. These results have provided a novel mechanism and a potential therapeutic strategy for injured CNS.