Multifaceted role and regulation of neuropeptide Y in the ovary of wall lizard, Hemidactylus flaviviridis

The role of neuropeptide Y (NPY) in regulating ovarian functions has primarily been studied in mammals, while it remains meagrely explored in non-mammalian vertebrates. Our study is the first to report ovarian expression of npy and its receptor, npyr, in a reptile, Hemidactylus flaviviridis. Quantitative real-time PCR analysis demonstrated high expression of npy/npyr during early and late recrudescence, while significantly low levels were noted during regression. The study also examined role of NPY in modulating lizard ovarian functions, wherein in vitro treatment of recrudescent ovaries with NPY increased the mRNA expression of anti-apoptotic gene B-cell lymphoma 2 (bcl 2), and suppressed pro-apoptotic gene cysteine-aspartic acid protease-3 (caspase 3). NPY also stimulated cell proliferation/differentiation markers; stem cell factor (scf), receptor tyrosine kinase (c-kit), proliferating cell nuclear antigen (pcna), growth differentiation factor-9 (gdf-9), bone morphogenetic protein-15 (bmp-15), as well as gonadotropin and sex steroid receptors, follicle stimulating hormone receptor (fshr), estrogen receptor α, β (er-α, er-β), and progesterone receptor (pr). Also, NPY influenced ovarian steroidogenesis by upregulating steroidogenic acute regulatory protein (star) and cytochrome P450a family 19 (cyp19) mRNA expression. However, steroid estimation by ELISA indicates NPY-mediated differential modulation of steroidogenesis as progesterone production was elevated, while estradiol production was inhibited. Further, ovarian npy/npyr was differentially regulated by gonadotropin, sex steroids, neuropeptides, and adipokines. Expression of ligand and receptor was stimulated by 5α-dihydrotestosterone (DHT), 17β-estradiol (E₂), kisspeptin, leptin, and nesfatin-1 but inhibited by follicle stimulating hormone (FSH) and substance P. Taken together, present study provides a comprehensive picture of ovarian npy/npyr in wall lizard.