PACAP: A regulator of mammalian reproductive function

PACAP-38 and sex hormones in women with migraine: exploratory analysis of a cross-sectional, matched cohort study

BACKGROUND

Endogeneous and exogeneous sex hormones can impact the frequency and severity of migraine attacks, but the underlying mechanisms are poorly understood. In this study, we investigate the relationship between female sex hormones and Pituitary Adenylate Cyclase-Activating Polypeptide-38 (PACAP-38) concentrations in plasma of women with migraine and healthy controls, aiming to elucidate potential hormonal influences on PACAP dynamics and their relevance to migraine pathophysiology.

METHODS

This analysis is part of a cross-sectional, matched-cohort study. We recruited two groups of women with episodic migraine: one with a regular menstrual cycle (M-RMC) and another undergoing combined oral contraceptive treatment (M-COC). Additionally, we included corresponding age-matched control groups without migraine for both categories (C-RMC and C-COC). For participants with a RMC, the study visits were scheduled during the perimenstrual period (menstrual cycle day 2 ± 2) and periovulatory period (day 13 ± 2). Participants using COC were examined at day 4 ± 2 of the hormone-free interval and between day 7-14 of the hormone intake phase. During these visits, PACAP-38 concentrations in plasma were measured using a commercial Enzyme-linked-immunosorbent assay (ELISA) kit.

RESULTS

The study included 120 women, with 30 participants in each group. Women with migraine and a RMC had significantly higher PACAP-38 plasma concentrations compared to healthy controls at both study visits [day 2 ± 2: M-RMC: 2547.41 pg/ml (IQR 814.27 - 4473.48) vs. C-RMC: 1129.49 pg/ml (IQR 257.34 - 2684.88), p = 0.025; day 13 ± 2: M-RMC: 3098.89 pg/ml (IQR 1186.29 - 4379.47) vs. C-RMC: 1626.89 (IQR 383.83 - 3038.36), p = 0.028]. In contrast, PACAP-38 levels were comparable between migraine and control groups receiving COC. Women with migraine and a RMC exhibited higher PACAP-38 concentrations during menstruation compared to those using COC during the hormone-free interval.

CONCLUSION

Systemic PACAP-38 concentrations in women vary based on the presence of migraine diagnosis and their hormonal status.

Key mRNAs and lncRNAs of pituitary that affect the reproduction of FecB + + small tail han sheep

BACKGROUND

The pituitary directly regulates the reproductive process through follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Transcriptomic research on the pituitaries of ewes with different FecB (fecundity Booroola) genotypes has shown that some key genes and lncRNAs play an important role in pituitary function and sheep fecundity. Our previous study found that ewes with FecB + + genotypes (without FecB mutation) still had individuals with more than one offspring per birth. It is hoped to analyze this phenomenon from the perspective of the pituitary transcriptome.

RESULTS

The 12 Small Tail Han Sheep were equally divided into polytocous sheep in the follicular phase (PF), polytocous sheep in the luteal phase (PL), monotocous sheep in the follicular phase (MF), and monotocous sheep in the luteal phase (ML). Pituitary tissues were collected after estrus synchronous treatment for transcriptomic analysis. A total of 384 differentially expressed genes (DEGs) (182 in PF vs. MF and 202 in PL vs. ML) and 844 differentially expressed lncRNAs (DELs) (427 in PF vs. MF and 417 in PL vs. ML) were obtained from the polytocous-monotocous comparison groups in the two phases. Functional enrichment analysis showed that the DEGs in the two phases were enriched in signaling pathways known to play an important role in sheep fecundity, such as calcium ion binding and cAMP signaling pathways. A total of 1322 target relationship pairs (551 pairs in PF vs. MF and 771 pairs in PL vs. ML) were obtained for the target genes prediction of DELs, of which 29 DEL-DEG target relationship pairs (nine pairs in PF vs. MF and twenty pairs in PL vs. ML). In addition, the competing endogenous RNA (ceRNA) networks were constructed to explore the regulatory relationships of DEGs, and some important regulatory relationship pairs were obtained.

CONCLUSION

According to the analysis results, we hypothesized that the pituitary first receives steroid hormone signals from the ovary and uterus and that VAV3 (Vav Guanine Nucleotide Exchange Factor 3), GABRG1 (Gamma-Aminobutyric Acid A Receptor, Gamma 1), and FNDC1 (Fibronectin Type III Domain Containing 1) played an important role in this process. Subsequently, the reproductive process was regulated by gonadotropins, and IGFBP1 (Insulin-like Growth Factor Binding Protein 1) was directly involved in this process, ultimately affecting litter size. In addition, TGIF1 (Transforming Growth Factor-Beta-Induced Factor 1) and TMEFF2 (Transmembrane Protein With EGF Like And Two Follistatin Like Domains 2) compensated for the effect of the FecB mutation and function by acting on TGF-β/SMAD signaling pathway, an important pathway for sheep reproduction. These results provided a reference for understanding the mechanism of multiple births in Small Tail Han Sheep without FecB mutation.

Temporal Changes in the Local Expression of Central Hormone-Regulating Factors in Rat Testis

Present study aimed to investigate the temporal changes in expression of some reproductive hormones in testis, originally found in hypothalamus and pituitary. Rats were sacrificed on postnatal day 23 (PND23; immature), pubertal (PND53) and PND 81 (young adult). The testicular RNAs were extracted, and semi-quantitative PCRs for gonadotropin-releasing hormone (GnRH), kisspeptin 1 (KiSS1), pituitary adenylate cyclase-activating polypeptide (PACAP), LH subunits and LH receptor were performed. Transcript levels of GnRH and KiSS1 at PND23 were significantly higher than levels of PND53 and PND81 (p <0.001). PACAP mRNA level at PND23 was significantly lower than those of PND53 and PND81 (p <0.001). The mRNA levels of both testis type and pituitary type luteinizing hormone β subunit (tLHβ and pLHβ, respectively) at PND23 were significantly lower than levels of PND53 and PND81 (p <0.001). The mRNA level of glycoprotein hormone common alpha subunit (Cgα) at PND23 was significantly lower than those of PND53 and PND81 (p <0.001). Present study revealed the intratesticular expression of KiSS1 and GnRH showed a very similar trend while the expression of PACAP in the testis showed reversed pattern. The expressions of LHβ subunits (tLHβ and pLHβ) were very low during immature stage then increased significantly during puberty and early adulthood. Our attempt to study the local role(s) of intratesticular factors will be helpful to achieve precise understanding on the testis physiology and pathology.

Gene deletion of the PACAP/VIP receptor, VPAC2R, alters glycemic responses during metabolic and psychogenic stress in adult female mice

Pituitary adenylate cyclase-activating polypeptide (PACAP) and the homologous peptide, vasoactive intestinal peptide (VIP), participate in glucose homeostasis using insulinotropic and counterregulatory processes. The role of VIP receptor 2 (VPAC2R) in these opposing actions needs further characterization. In this study, we examined the participation of VPAC2R on basal glycemia, fasted levels of glucoregulatory hormones and on glycemia responses during metabolic and psychogenic stress using gene-deleted (Vipr2-/- ) female mice. The mean basal glycemia was significantly greater in Vipr2-/- in the fed state and after an 8-h overnight fast as compared to wild-type (WT) mice. Insulin tolerance testing following a 5-h fast (morning fast, 0.38 U/kg insulin) indicated no effect of genotype. However, during a more intense metabolic challenge (8 h, ON fast, 0.25 U/kg insulin), Vipr2-/- females displayed significantly impaired insulin hypoglycemia. During immobilization stress, the hyperglycemic response and plasma epinephrine levels were significantly elevated above basal in Vipr2-/- , but not WT mice, in spite of similar stress levels of plasma corticosterone. Together, these results implicate participation of VPAC2R in upregulated counterregulatory processes influenced by enhanced sympathoexcitation. Moreover, the suppression of plasma GLP-1 levels in Vipr2-/- mice may have removed the inhibition on hepatic glucose production and the promotion of glucose disposal by GLP-1. qPCR analysis indicated deregulation of central gene markers of PACAP/VIP signaling in Vipr2-/- , upregulated medulla tyrosine hydroxylase (Th) and downregulated hypothalamic Vip transcripts. These results demonstrate a physiological role for VPAC2R in glucose metabolism, especially during insulin challenge and psychogenic stress, likely involving the participation of sympathoadrenal activity and/or metabolic hormones.

Effect of PACAP on Heat Exposure

Heat stroke is a life-threatening illness caused by exposure to high ambient temperatures and relative humidity. The incidence of heat stroke is expected to increase due to climate change. Although pituitary adenylate cyclase-activating polypeptide (PACAP) has been implicated in thermoregulation, the role of PACAP on heat stress remains unclear. PACAP knockout (KO) and wild-type ICR mice were subjected to heat exposure at an ambient temperature of 36 °C and relative humidity of 99% for 30-150 min. After heat exposure, the PACAP KO mice had a greater survival rate and maintained a lower body temperature than the wild-type mice. Moreover, the gene expression and immunoreaction of c-Fos in the ventromedially preoptic area of the hypothalamus, which is known to harbor temperature-sensitive neurons, were significantly lower in PACAP KO mice than those in wild-type mice. In addition, differences were observed in the brown adipose tissue, the primary site of heat production, between PACAP KO and wild-type mice. These results suggest that PACAP KO mice are resistant to heat exposure. The heat production mechanism differs between PACAP KO and wild-type mice.

Discovering a trans-omics biomarker signature that predisposes high risk diabetic patients to diabetic kidney disease

Diabetic kidney disease is the leading cause of end-stage kidney disease worldwide; however, the integration of high-dimensional trans-omics data to predict this diabetic complication is rare. We develop artificial intelligence (AI)-assisted models using machine learning algorithms to identify a biomarker signature that predisposes high risk patients with diabetes mellitus (DM) to diabetic kidney disease based on clinical information, untargeted metabolomics, targeted lipidomics and genome-wide single nucleotide polymorphism (SNP) datasets. This involves 618 individuals who are split into training and testing cohorts of 557 and 61 subjects, respectively. Three models are developed. In model 1, the top 20 features selected by AI give an accuracy rate of 0.83 and an area under curve (AUC) of 0.89 when differentiating DM and non-DM individuals. In model 2, among DM patients, a biomarker signature of 10 AI-selected features gives an accuracy rate of 0.70 and an AUC of 0.76 when identifying subjects at high risk of renal impairment. In model 3, among non-DM patients, a biomarker signature of 25 AI-selected features gives an accuracy rate of 0.82 and an AUC of 0.76 when pinpointing subjects at high risk of chronic kidney disease. In addition, the performance of the three models is rigorously verified using an independent validation cohort. Intriguingly, analysis of the protein-protein interaction network of the genes containing the identified SNPs (RPTOR, CLPTM1L, ALDH1L1, LY6D, PCDH9, B3GNTL1, CDS1, ADCYAP and FAM53A) reveals that, at the molecular level, there seems to be interconnected factors that have an effect on the progression of renal impairment among DM patients. In conclusion, our findings reveal the potential of employing machine learning algorithms to augment traditional methods and our findings suggest what molecular mechanisms may underlie the complex interaction between DM and chronic kidney disease. Moreover, the development of our AI-assisted models will improve precision when diagnosing renal impairment in predisposed patients, both DM and non-DM. Finally, a large prospective cohort study is needed to validate the clinical utility and mechanistic implications of these biomarker signatures.

Seasonal changes in the expression of PACAP, VPAC1, VPAC2, PAC1 and testicular activity in the testis of the muskrat (<em>Ondatra zibethicus</em>)

Pituitary adenylate cyclase-activating polypeptide (PACAP) plays an important role in the steroidogenesis and spermatogenesis in the testis through its receptors PAC1, VPAC1, and VPAC2. In this study, we investigated the seasonal expressions of PACAP, PAC1, VPAC1, VPAC2, luteinizing hormone receptor (LHR), follicle stimulating hormone receptor (FSHR), steroidogenic acute regulatory protein (StAR), 3β-hydroxysteroid dehydrogenase (3β-HSD), and CYP17A1 in the testis of the male muskrat during the breeding season and the non-breeding season. Histologically, we found the presence of Leydig cells, Sertoli cells and all kinds of germ cells in the testis during the breeding season but only Leydig cells, Sertoli cells, spermatogonia and primary spermatocyte during the non-breeding season. The immunohistochemical localizations of PACAP and VPAC1 were identified in the Leydig cells, spermatogonia and spermatozoa during the breeding season while only in Leydig cells and spermatogonia during the non-breeding season, and PAC1 and VPAC2 were localized in the Leydig cells in both seasons, in which LHR, StAR, 3β-HSD and CYP17A1 were also expressed. Meanwhile, protein and mRNA expression levels of PACAP, PAC1, VPAC1, VPAC2, LHR, FSHR, StAR, 3β-HSD and CYP17A1 in the testis during the breeding season were significantly higher than those during the non-breeding season. These results suggested that PACAP may involve in the regulation of, steroidogenesis and spermatogenesis via an endocrine, autocrine or paracrine manner in the testis of the muskrat.

Effects of Pituitary Adenylate Cyclase Activating Polypeptide on Cell Death

Pituitary adenylate cyclase activating polypeptide (PACAP) was first isolated as a hypothalamic peptide based on its efficacy to increase adenylate cyclase (AC) activity. It has a widespread distribution throughout the body including the nervous system and peripheral organs, where PACAP exerts protective effects both in vivo and in vitro through its anti-apoptotic, anti-inflammatory, and antioxidant functions. The aim of the present paper was to review the currently available literature regarding the effects of PACAP on cell death in vitro in neural and non-neural cells. Among others, its effect on apoptosis can be detected in cerebellar granule cells against different toxic stimuli. Different neural cell types from the cerebral cortex are also prevented from cell death. PACAP also shows effects on cell death in cells belonging to the peripheral nervous system and protects both neural and non-neural cells of sensory organs. In addition, cell survival-promoting effect can be observed in different peripheral organ systems including cardiovascular, immune, respiratory, gastrointestinal, urinary, and reproductive systems. The studies summarized here indicate its noteworthy effect on cell death in different in vitro models, suggesting PACAP’s potential therapeutic usage in several pathological conditions.

Shorebirds' Longer Migratory Distances Are Associated With Larger ADCYAP1 Microsatellites and Greater Morphological Complexity of Hippocampal Astrocytes

For the epic journey of autumn migration, long-distance migratory birds use innate and learned information and follow strict schedules imposed by genetic and epigenetic mechanisms, the details of which remain largely unknown. In addition, bird migration requires integrated action of different multisensory systems for learning and memory, and the hippocampus appears to be the integration center for this task. In previous studies we found that contrasting long-distance migratory flights differentially affected the morphological complexity of two types of hippocampus astrocytes. Recently, a significant association was found between the latitude of the reproductive site and the size of the ADCYAP1 allele in long distance migratory birds. We tested for correlations between astrocyte morphological complexity, migratory distances, and size of the ADCYAP1 allele in three long-distance migrant species of shorebird and one non-migrant. Significant differences among species were found in the number and morphological complexity of the astrocytes, as well as in the size of the microsatellites of the ADCYAP1 gene. We found significant associations between the size of the ADCYAP1 microsatellites, the migratory distances, and the degree of morphological complexity of the astrocytes. We suggest that associations between astrocyte number and morphological complexity, ADCYAP1 microsatellite size, and migratory behavior may be part of the adaptive response to the migratory process of shorebirds.

Deletion of Gαq/11 or Gαs Proteins in Gonadotropes Differentially Affects Gonadotropin Production and Secretion in Mice

Gonadotropin-releasing hormone (GnRH) regulates gonadal function via its stimulatory effects on gonadotropin production by pituitary gonadotrope cells. GnRH is released from the hypothalamus in pulses and GnRH pulse frequency differentially regulates follicle-stimulating hormone (FSH) and luteinizing hormone (LH) synthesis and secretion. The GnRH receptor (GnRHR) is a G protein-coupled receptor that canonically activates Gα q/11-dependent signaling on ligand binding. However, the receptor can also couple to Gα s and in vitro data suggest that toggling between different G proteins may contribute to GnRH pulse frequency decoding. For example, as we show here, knockdown of Gα s impairs GnRH-stimulated FSH synthesis at low- but not high-pulse frequency in a model gonadotrope-derived cell line. We next used a Cre-lox conditional knockout approach to interrogate the relative roles of Gα q/11 and Gα s proteins in gonadotrope function in mice. Gonadotrope-specific Gα q/11 knockouts exhibit hypogonadotropic hypogonadism and infertility, akin to the phenotypes seen in GnRH- or GnRHR-deficient mice. In contrast, under standard conditions, gonadotrope-specific Gα s knockouts produce gonadotropins at normal levels and are fertile. However, the LH surge amplitude is blunted in Gα s knockout females and postgonadectomy increases in FSH and LH are reduced both in males and females. These data suggest that GnRH may signal principally via Gα q/11 to stimulate gonadotropin production, but that Gα s plays important roles in gonadotrope function in vivo when GnRH secretion is enhanced.

Stereology of gonadotropin-releasing hormone and kisspeptin neurons in PACAP gene-deficient female mice

The hypothalamic gonadotropin-releasing hormone (GnRH)-kisspeptin neuronal network regulates fertility in all mammals. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide isolated from the hypothalamus that is involved in the regulation of several releasing hormones and trop hormones. It is well-known that PACAP influences fertility at central and peripheral levels. However, the effects of PACAP on GnRH and kisspeptin neurons are not well understood. The present study investigated the integrity of the estrous cycle in PACAP-knockout (KO) mice. The number and immunoreactivity of GnRH (GnRH-ir) neurons in wild-type (WT) and PACAP KO female mice were determined using immunohistochemistry. In addition, the number of kisspeptin neurons was measured by counting kisspeptin mRNA-positive cells in the rostral periventricular region of the third ventricle (RP3V) and arcuate nucleus (ARC) using the RNAscope technique. Finally, the mRNA and protein expression of estrogen receptor alpha (ERα) was also examined. Our data showed that the number of complete cycles decreased, and the length of each cycle was longer in PACAP KO mice. Furthermore, the PACAP KO mice experienced longer periods of diestrus and spent significantly less time in estrus. There was no difference in GnRH-ir or number of GnRH neurons. In contrast, the number of kisspeptin neurons was decreased in the ARC, but not in the R3PV, in PACAP KO mice compared to WT littermates. Furthermore, ERα mRNA and protein expression was decreased in the ARC, whereas in the R3PV region, ERα mRNA levels were elevated. Our results demonstrate that embryonic deletion of PACAP significantly changes the structure and presumably the function of the GnRH-kisspeptin neuronal network, influencing fertility.

Identifying the heat resistant genes by multi-tissue transcriptome sequencing analysis in Turpan Black sheep

Heat stress not only affects the physical condition but also affects reproductive performance in sheep. A thorough understanding of the molecular and physiological mechanisms underlying heat stress would certainly improve livestock productivity and provide genetic evaluation ways for heat resistant breeds selection. In this study, 85 Turpan Black sheep, a breed exhibited excellent heat resistance from long-term artificial selection, and 85 heat sensitive Kazakh sheep in Turpan basin were tested for physiological and reproductive performance from July to August in summer. The results showed that the estrus rate was significantly higher in Turpan Black sheep (P < 0.05), while the heart rate and respiratory rate of Turpan Black sheep are significantly lower than that of Kazakh sheep (P < 0.05). Furthermore, to clarify genes participated in heat stress response, the pituitary, ovarian and hepatic tissues from three Turpan Black sheep and three Kazakh sheep were subjected to RNA-seq. The results indicated that 32, 49 and 69 genes were up-regulated, and 39, 60 and 145 genes were down-regulated in pituitary, ovarian and hepatic tissues in Turpan Black sheep compared with that of the Kazakh sheep, respectively. KEGG and gene set enrichment analysis showed that the differentially expressed genes were mainly involved in signal transduction pathways. In particular, the differentially expressed genes in hepar were enriched in the energy metabolism pathway, while the differentially expressed genes in ovarian tissue were enriched in the ovarium steroidogenesis pathway. In conclusion, our results implied that the pituitary-ovary axis might include hepar as downstream targeted organism in heat resistant regulation. Under heat stress, the signals released from pituitary would impact steroidogenesis in ovary, and further alter energy metabolism in hepar. As we know, this is the first comparative study to investigate the gene expression in multi-tissue in sheep under heat stress.

Estrogen mediates sex differences in preoptic neuropeptide and pituitary hormone production in medaka

The preoptic area (POA) is one of the most evolutionarily conserved regions of the vertebrate brain and contains subsets of neuropeptide-expressing neurons. Here we found in the teleost medaka that two neuropeptides belonging to the secretin family, pituitary adenylate cyclase-activating polypeptide (Pacap) and vasoactive intestinal peptide (Vip), exhibit opposite patterns of sexually dimorphic expression in the same population of POA neurons that project to the anterior pituitary: Pacap is male-biased, whereas Vip is female-biased. Estrogen secreted by the ovary in adulthood was found to attenuate Pacap expression and, conversely, stimulate Vip expression in the female POA, thereby establishing and maintaining their opposite sexual dimorphism. Pituitary organ culture experiments demonstrated that both Pacap and Vip can markedly alter the expression of various anterior pituitary hormones. Collectively, these findings show that males and females use alternative preoptic neuropeptides to regulate anterior pituitary hormones as a result of their different estrogen milieu.

Mouse Models of Human Proprotein Convertase Insufficiency

The kexin-like proprotein convertases perform the initial proteolytic cleavages that ultimately generate a variety of different mature peptide and proteins, ranging from brain neuropeptides to endocrine peptide hormones, to structural proteins, among others. In this review, we present a general introduction to proprotein convertase structure and biochemistry, followed by a comprehensive discussion of each member of the kexin-like subfamily of proprotein convertases. We summarize current knowledge of human proprotein convertase insufficiency syndromes, including genome-wide analyses of convertase polymorphisms, and compare these to convertase null and mutant mouse models. These mouse models have illuminated our understanding of the roles specific convertases play in human disease and have led to the identification of convertase-specific substrates; for example, the identification of procorin as a specific PACE4 substrate in the heart. We also discuss the limitations of mouse null models in interpreting human disease, such as differential precursor cleavage due to species-specific sequence differences, and the challenges presented by functional redundancy among convertases in attempting to assign specific cleavages and/or physiological roles. However, in most cases, knockout mouse models have added substantively both to our knowledge of diseases caused by human proprotein convertase insufficiency and to our appreciation of their normal physiological roles, as clearly seen in the case of the furin, proprotein convertase 1/3, and proprotein convertase 5/6 mouse models. The creation of more sophisticated mouse models with tissue- or temporally-restricted expression of specific convertases will improve our understanding of human proprotein convertase insufficiency and potentially provide support for the emerging concept of therapeutic inhibition of convertases.