Identification and quantification of sea lamprey gonadotropin-releasing hormones by electrospray ionization tandem mass spectrometry

Recent advances in mass spectrometry analysis of neuropeptides

Due to their involvement in numerous biochemical pathways, neuropeptides have been the focus of many recent research studies. Unfortunately, classic analytical methods, such as western blots and enzyme-linked immunosorbent assays, are extremely limited in terms of global investigations, leading researchers to search for more advanced techniques capable of probing the entire neuropeptidome of an organism. With recent technological advances, mass spectrometry (MS) has provided methodology to gain global knowledge of a neuropeptidome on a spatial, temporal, and quantitative level. This review will cover key considerations for the analysis of neuropeptides by MS, including sample preparation strategies, instrumental advances for identification, structural characterization, and imaging; insightful functional studies; and newly developed absolute and relative quantitation strategies. While many discoveries have been made with MS, the methodology is still in its infancy. Many of the current challenges and areas that need development will also be highlighted in this review.

Quantitation of endogenous GnRH by validated nano-HPLC-HRMS method: a pilot study on ewe plasma

Gonadotropin-releasing hormone isoform I (GnRH), a neuro-deca-peptide, plays a fundamental role in development and maintenance of the reproductive system in vertebrates. The anomalous release of GnRH is observed in reproductive disorder such as hypogonadotropic hypogonadism, polycystic ovary syndrome (PCOS), or following prenatal exposure to elevated androgen levels. Quantitation of GnRH plasma levels could help to diagnose and better understand these pathologies. Here, a validated nano-high-performance liquid chromatography–high-resolution mass spectrometry (HPLC-HRMS) method to quantify GnRH in ewe plasma samples is presented. Protein precipitation and solid-phase extraction (SPE) pre-treatment steps were required to purify and enrich GnRH and internal standard (lamprey-luteinizing hormone-releasing hormone-III, l-LHRH-III). For the validation process, a surrogate matrix approach was chosen following the International Council for Harmonisation (ICH) and FDA guidelines. Before the validation study, the validation model using the surrogate matrix was compared with those using a real matrix such as human plasma. All the tested parameters were analogous confirming the use of the surrogate matrix as a standard calibration medium. From the validation study, limit of detection (LOD) and limit of quantitation (LOQ) values of 0.008 and 0.024 ng/mL were obtained, respectively. Selectivity, accuracy, precision, recovery, and matrix effect were assessed with quality control samples in human plasma and all values were acceptable. Sixteen samples belonging to healthy and prenatal androgen (PNA) exposed ewes were collected and analyzed, and the GnRH levels ranged between 0.05 and 3.26 ng/mL. The nano-HPLC-HRMS developed here was successful in measuring GnRH, representing therefore a suitable technique to quantify GnRH in ewe plasma and to detect it in other matrices and species.

Role of elasmobranchs and holocephalans in understanding peptide evolution in the vertebrates: Lessons learned from gonadotropin releasing hormone (GnRH) and corticotropin releasing factor (CRF) phylogenies

The cartilaginous fishes (Class Chondrichthyes) comprise two morphologically distinct subclasses; Elasmobranchii and Holocephali. Evidence indicates early divergence of these subclasses, suggesting monophyly of their lineage. However, such a phylogenetic understanding is not yet developed within two highly conserved peptide lineages, GnRH and CRF. Various GnRH forms exist across the Chondrichthyes. Although 4-7 immunoreactive forms have been described in Elasmobranchii, only one has been elucidated in Holocephali. In contrast, Chondrichthyan CRF phylogeny follows a pattern more consistent with vertebrate evolution. For example, three forms are expressed within the lamprey, with similar peptides present within the genome of the Callorhinchus milii, a holocephalan. Although these findings are consistent with recent evidence regarding the phylogenetic age of Chondrichthyan lineages, CRF evolution in vertebrates remains elusive. Assuming that the Elasmobranchii and Holocephali are part of a monocladistic clade within the Chondrichthyes, we interpret the findings of GnRH and CRF to be products of their respective lineages.

Elevated prenatal anti-Müllerian hormone reprograms the fetus and induces polycystic ovary syndrome in adulthood

Polycystic ovary syndrome (PCOS) is the main cause of female infertility worldwide and corresponds with a high degree of comorbidities and economic burden. How PCOS is passed on from one generation to the next is not clear, but it may be a developmental condition. Most women with PCOS exhibit higher levels of circulating luteinizing hormone, suggestive of heightened gonadotropin-releasing hormone (GnRH) release, and Anti-Müllerian Hormone (AMH) as compared to healthy women. Excess AMH in utero may affect the development of the female fetus. However, as AMH levels drop during pregnancy in women with normal fertility it was unclear if their levels were also elevated in pregnant women with PCOS. Here, we measured AMH in a cohort of pregnant women with PCOS and control women and found that AMH is significantly more elevated in the former group versus the latter. To determine if the elevation of AMH during pregnancy in women with PCOS is a bystander effect or a driver of the condition in the offspring, we modelled our clinical findings by treating pregnant mice with AMH and followed the neuroendocrine phenotype of their female progeny postnatally. This treatment resulted in maternal neuroendocrine-driven testosterone excess and diminished placental metabolism of testosterone to estradiol, resulting in a masculinization of the exposed female fetus and a PCOS-like reproductive and neuroendocrine phenotype in adulthood. We found that the affected females had persistently hyperactivated GnRH neurons and that GnRH antagonist treatment in the adult female offspring restored their neuroendocrine phenotype to a normal state. These findings highlight a critical role for excess prenatal AMH exposure and subsequent aberrant GnRH receptor signaling in the neuroendocrine dysfunctions of PCOS, while offering a new potential therapeutic avenue to treat the condition during adulthood.

Application of liquid chromatography-tandem mass spectrometry in quantitative bioanalyses of organic molecules in aquatic environment and organisms

Analytical methods using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of metabolites or contaminants (or both) in various tissues of aquatic organisms and in the aquatic environment have received increasing attention in the last few years. This review discusses the findings relevant to such procedures published between 2005 and 2015. The aim is to evaluate the advantages, restrictions, and performances of the procedures from sample preparation to mass spectrometry measurement. To support these discussions, a general knowledge on LC-MS/MS is also provided.