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Leptin secreted from testicular microenvironment modulates hedgehog signaling to augment the endogenous function of Leydig cells

ABSTRACT: Although testosterone deficiency (TD) may be present in 1 out of 5 men 40 years or older, the factors responsible for TD remain largely unknown. Leydig stem cells (LSCs) differentiate into adult Leydig cells (ALC) and produce testosterone in the testes under the pulsatile control of luteinizing hormone (LH) from the pituitary gland. However, recent studies have suggested that the testicular microenvironment (TME), which is comprised of Sertoli and peritubular myoid cells (PMC), plays an instrumental role in LSC differentiation and testosterone production under the regulation of the desert hedgehog signaling pathway (DHH). It was hypothesized that TME releases paracrine factors to modulate LSC differentiation. For this purpose, cells (Sertoli, PMCs, LSCs and ALCs) were extracted from men undergoing testis biopsies for sperm retrieval and were evaluated for the paracrine factors in the presence or absence of TME (Sertoli and PMC). The results demonstrated that TME secretes leptin which induces LSC differentiation and increases T production. Leptin’s effects on LSC differentiation and T production, however, are inversely concentration-dependent: positive at low doses and negative at higher doses. Mechanistically, leptin acts on LSCs upstream of DHH; leptin-DHH regulation functions unidirectionally insofar as DHH gain or loss of function has no effects on leptin levels. Taken together, these findings identify leptin as a key paracrine factor released by cells within the TME that modulates LSC differentiation and testosterone release from mature Leydig cells, a finding with important clinical implications for TD.

ORGANISM(S): Homo sapiens

PROVIDER: GSE196702 | GEO | 2022/02/17

REPOSITORIES: GEO

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Project description:Evidence that persistent environmental pollutants may target the male reproductive system is increasing. The male reproductive system is regulated by secretion of testosterone by testicular Leydig cells, and perturbation of Leydig cells function may have ultimate consequences. 3-methylsulfonyl-DDE (3-MeSO2-DDE) is a potent adrenal toxicants formed from the persistent insecticide DDT. Although studies have revealed endocrine disruptive effect of 3-MeSO2-DDE, the underlying mechanisms at cellular level in steroidogenic Leydig cells remains to be established. The current study addresses the effect of 3-MeSO2-DDE viability, hormone production and proteome response of primary neonatal porcine Leydig cells. The AlamarBlue™ assay was used to evaluate cell viability. Solid phase radioimmunoassay was used to measure concentration of hormones produced by both unstimulated and luteinizing hormone (LH)-stimulated Leydig cells following 48 h exposure. Protein samples from Leydig cells exposed to a non-cytotoxic concentration of 3-MeSO2-DDE (10µM) were subjected to nano-LC-MS/MS and analyzed on a Q Exactive mass spectrometer and quantified using label-free quantitative algorithm. Gene Ontology (GO) and Ingenuity Pathway Analysis (IPA) were carried out for functional annotation and identification of protein interaction networks. 3-MeSO2-DDE regulated Leydig cell steroidogenesis differentially depending on cell culture condition. Whereas its effect on testosterone secretion at basal condition was stimulatory, the effect on LH-stimulated cells was inhibitory. From triplicate experiments, a total of 7540 proteins were identified in which the abundance of 87 proteins in unstimulated Leydig cells and 146 proteins in LH-stimulated Leydig cells were found to be significantly regulated in response to 3-MeSO2-DDE exposure. These proteins not only are the first reported in relation to 3-MeSO2-DDE exposure, but also display small number of proteins shared between culture conditions, suggesting the action of 3-MeSO2-DDE on several targeted pathways, including mitochondrial dysfunction, oxidative phosphorylation, EIF2-signaling, and glutathion-mediated detoxification. Further identification and characterization of these proteins and pathways may build our understanding to the molecular basis of 3-MeSO2-DDE induced endocrine disruption in Leydig cells.

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Leptin secreted from testicular microenvironment modulates hedgehog signaling to augment the endogenous function of Leydig cells

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