SREBP Plays a Regulatory Role in LH/hCG Receptor mRNA Expression in Human Granulosa-Lutein Cells

Possible Relevance of Soluble Luteinizing Hormone Receptor during Development and Adulthood in Boys and Men

Simple Summary

The reproductive hormones luteinizing hormone (LH) and human chorionic gonadotropin (hCG) are both agonists for the luteinizing hormone receptor (LHCGR) and essential for male reproduction during development and adulthood. LHCGR is expressed and stimulates testosterone production from the testicular Leydig cells. In this study, we demonstrate the presence of soluble LHCGR in blood, urine, and seminal fluid in both healthy boys and men, and patients with aberrations in sex-chromosomes. We show how circulating levels of sLHCGR are associated with pubertal development, testicular function, and semen quality and demonstrate that LHCGR is released from fetal human non-gonadal tissue. sLHCGR is released into serum by testis and other organs, which suggests possible extra-gonadal effects of LH or hCG in boys and men.

Abstract

Luteinizing hormone (LH) and human chorionic gonadotropin (hCG) are agonists for the luteinizing hormone receptor (LHCGR) which regulates male reproductive function. LHCGR may be released into body fluids. We wish to determine whether soluble LHCGR is a marker for gonadal function. Cross-sectional, longitudinal, and intervention studies on 195 healthy boys and men and 396 men with infertility, anorchia, or Klinefelter Syndrome (KS) were used to correlate LHCGR measured in serum, seminal fluid, urine, and hepatic/renal artery and vein with gonadal function. LHCGR was determined in fluids from in vitro and in vivo models of human testicular tissue and cell lines, xenograft mouse models, and human fetal kidney and adrenal glands. Western blot showed LHCGR fragments in serum and gonadal tissue of similar size using three different antibodies. The LHCGR-ELISA had no species cross-reactivity or unspecific reaction in mouse serum even after human xenografting. Instead, sLHCGR was released into the media after the culture of a human fetal kidney and adrenal glands. Serum sLHCGR decreased markedly during puberty in healthy boys (p = 0.0001). In healthy men, serum sLHCGR was inversely associated with the Inhibin B/FSH ratio (β −0.004, p = 0.027). In infertile men, seminal fluid sLHCGR was inversely associated with serum FSH (β 0.006, p = 0.009), sperm concentration (β −3.5, p = 0.003) and total sperm count (β −3.2, p = 0.007). The injection of hCG lowered sLHCGR in serum and urine of healthy men (p < 0.01). In conclusion, sLHCGR is released into body-fluids and linked with pubertal development and gonadal function. Circulating sLHCGR in anorchid men suggests that sLHCGR in serum may originate from and possibly exert actions in non-gonadal tissues. (ClinicalTrials: NTC01411527, NCT01304927, NCT03418896).

m6A mRNA methylation regulates testosterone synthesis through modulating autophagy in Leydig cells

Macroautophagy/autophagy is indispensable for testosterone synthesis in Leydig cells (LCs), and here we report a negative association between m6A modification and autophagy in LCs during testosterone synthesis. A gradual decrease of METTL14 (methyltransferase like 14) and an increase of ALKBH5 (alkB homolog 5, RNA demethylase) were observed in LCs during their differentiation from stem LCs to adult LCs. These events led to reduced mRNA methylation levels of N6-methyladenosine (m6A) and enhanced autophagy in LCs. Similar regulation of METTL14, ALKBH5, and m6A was also observed in LCs upon treatment with human chorionic gonadotropin (HsCG). Mechanistically, m6A modification promoted translation of PPM1A (protein phosphatase 1A, magnesium dependent, alpha isoform), a negative AMP-activated protein kinase (AMPK) regulator, but decreased expression of CAMKK2 (calcium/calmodulin-dependent protein kinase kinase 2, beta), a positive AMPK regulator, by reducing its RNA stability. Thus, m6A modification resulted in reduced AMPK activity and subsequent autophagy inhibition. We further demonstrated that ALKBH5 upregulation by HsCG was dependent on enhanced binding of the transcriptional factor CEBPB (CCAAT/enhancer binding protein [C/EBP], beta) and the TFEB (transcription factor EB) to its gene promoter. Moreover, HsCG treatment decreased METTL14 by reducing its stability. Collectively, this study highlights a vital role of m6A RNA methylation in the modulation of testosterone synthesis in LCs, providing insight into novel therapeutic strategies by exploiting m6A RNA methylation as targets for treating azoospermatism and oligospermatism patients with reduction in serum testosterone.Abbreviations: 3-MA: 3-methyladenine; ACTB: Actin, beta; ALKBH5: alkB homolog 5, RNA demethylase; AMPK: AMP-activated protein kinase; BafA1: bafilomycin A1; CAMKK2: calcium/calmodulin-dependent protein kinase kinase 2, beta; CEBPB: CCAAT/enhancer-binding protein (C/EBP), beta; ChIP: chromatin immunoprecipitation; FTO: fat mass and obesity associated; HsCG: human chorionic gonadotropin; HSD3B: 3β-hydroxysteroid dehydrogenase; LCs: Leydig cells; m6A: N6-methyladenosine; METTL14: methyltransferase like 14; METTL3: methyltransferase like 3; MTOR: mechanistic target of rapamycin kinase; PPM1A: protein phosphatase 1A, magnesium dependent, alpha isoform; PRKAA: 5'-AMP-activated protein kinase catalytic subunit alpha; SQSTM1: sequestosome 1; STK11/LKB1: serine/threonine kinase 11; TFEB: transcription factor EB; ULK1: unc-51-like kinase 1; WTAP: Wilms tumor 1-associating protein; YTHDF: YTH N6-methyladenosine RNA binding protein.

In Vitro Study on the Regulation of Annexin IV and VEGF by hCG in the Human Endometrium

Objective

Whether changes in vascular endothelial growth factor (VEGF) and annexin IV during implantation are regulated through the LH/hCG-R needs further research. To investigate the mechanism of hCG on the expression of annexin IV and VEGF in human endometrial cells.

Methods

Endometrial cells were isolated and identified from human specimens. The proportion of glandular and epithelial cells was analyzed. Annexin IV and VEGF were analyzed by qRT-PCR (mRNA), western blot (proteins), and immunohistochemistry (proteins). Protein location was identified by immunohistochemistry. The cells were cultured with hCG, hCG/PD98059 (a MAPK inhibitor), or no treatment (control).

Results

The proportions between the glandular epithelial cells and stromal cells at inoculation and when adding hCG were 25.8 ± 0.2% and 27.8 ± 0.04%, respectively (P > 0.05). LH/hCG-R, annexin IV, and VEGF were found in the cytoplasm of endometrial cells. After 2, 6, 12, and 24 h of hCG treatment, compared with 1 h, VEGF mRNA was increased by 1.25-fold, 3.19-fold, 4.21-fold, and 4.86-fold and annexin IV by 2.23-fold, 3.37-fold, 5.14-fold, and 5.02-fold. Compared with the control group, annexin IV mRNA and protein were increased in the hCG and hCG/PD98059 groups (mRNA/protein: 1.99-fold/1.80-fold and 2.33-fold/1.93-fold, P < 0.05). Compared with the control group, VEGF mRNA and protein were increased in the hCG group (mRNA/protein: 2.30-fold/1.86-fold), but not in the hCG/PD98059 group.

Conclusion

hCG could upregulate the mRNA and protein expression of annexin IV and VEGF. The upregulation of annexin IV by hCG could not be inhibited by PD98059, but the upregulation of VEGF by hCG could.