Prolactin and prolactin receptor gene polymorphisms in multiple sclerosis and systemic lupus erythematosus

The prolactin receptor: A cross-species comparison of gene structure, transcriptional regulation, tissue-specificity, and genetic variation

The conserved and multifaceted functions of prolactin (PRL) are coordinated through varied distribution and expression of its cell-surface receptor (PRLR) across a range of tissues and physiological states. The resultant heterogeneous expression of PRLR mRNA and protein across different organs and cell types supports a wide range of PRL-regulated processes including reproduction, lactation, development, and homeostasis. Genetic variation within the PRLR gene also accounts for several phenotypes impacting agricultural production and human pathology. The goal of this review is to highlight the many elements that control differential expression of the PRLR across tissues, and the various phenotypes that exist across species due to variation in the PRLR gene.

Psycho-neuro-endocrino-immunologic issues in multiple sclerosis: a critical review of clinical and therapeutic implications

Multiple sclerosis (MS) is a multifactorial, chronic, immune-mediated, and neurodegenerative disease, having a well-known hypothalamic-pituitary-adrenal (HPA) axis dysfunction. Several hormones have a great impact in the immune dysregulation, psychology, and cognitive status of patients with MS, as also in the fertility and response to treatment. In this comprehensive review, as an introduction, we mention basic data concerning MS: epidemiology, genetics, immunogenetics, epigenetics, pathophysiology, and neuroimmunology. Hormonal components of the disease cascade, mainly glucocorticoids (stress-related hormone), estrogens, prolactin and dehydroepiandrosterone (sex-related hormones), melatonin, and vitamin D, are discussed, aiming at focusing on core data regarding the impact of these hormones in MS pathophysiology, severity of the disease, correlation with comorbid mental disorders, and fertility. A great focus is given in the pre- and post-pregnancy period of MS patients, in the context of the disease-modifying treatments (DMTs) and HPA status, having in mind that there are only very limited knowledge and few papers on this specific life period of these women, having MS. All this data are presented in the main text and also in the workable tables, for the first time, suggesting targeted topics that need to be addressed in the near future.

Prolactin and autoimmunity: The hormone as an inflammatory cytokine

Nowadays, more than 80 autoimmune disorders are recognized, in which an aberrant immune response against different organs and tissues plays a crucial role. Hormonal homeostasis has great influence in achieving competent and healthy immune system function. Prolactin has a bioactive function acting as a hormone and a cytokine. It influences the immune system modulation, mainly inhibiting the negative selection of autoreactive B lymphocytes. Hyperprolactinemia has been detected in many patients with different autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, Sjögren syndrome, multiple sclerosis, autoimmune thyroid disease, systemic sclerosis, among others, and its believed to play a crucial role in disease pathogenesis. A direct correlation between prolactin levels and disease activity was not clear. Genetic factors may have a role in humans as in animal models. Dopamine agonists have proven to offer clinical benefits among autoimmune patients and represent a promising therapy to be explored. In this review, the authors attempt to provide a critical overview on the role of prolactin in the immune system, exploring its contribution to the development of autoimmune diseases.

Prolactin is Not Associated with Disability and Clinical Forms in Patients with Multiple Sclerosis

An association between prolactinemia with disability, clinical forms, and sex of patients with multiple sclerosis (MS) remains unclear. The aim of this study was to evaluate the association of prolactin with clinical forms and accumulating disability over time in patients with MS. A longitudinal study was carried out with 101 patients with relapsing-remitting MS (RRMS) and 19 with progressive forms of MS (ProgMS). The disability over time, as well as prolactin and ferritin serum levels were evaluated at baseline (T0), 8-month follow-up (T8), and 16-month follow-up. The disability at T0, T8, and T16 was higher among patients with ProgMS than those with RRMS. Prolactin and ferritin levels did not differ over time between both groups. Initially, prolactin was associated with MS disability. After introducing age and sex, the effects of prolactin on disability were no longer significant. Prolactin was associated with age and sex, whereby age was positively associated with disability. In the same way, after introducing age and sex, the effects of diagnosis on prolactin levels, as well as the association between prolactin and ferritin, were no longer significant (P = 0.563 and P = 0.599, respectively). Moreover, 21.6% of the variance in the disability was predicted by age (P < 0.001), and sex (P = 0.049), while prolactin was not significant. In conclusion, the effects of prolactin on the disability and clinical forms of MS patients may be spurious results because those correlations reflect the positive associations of age with the disability and the negative association of age with prolactin.

Association of extrapituitary prolactin promoter polymorphism with disease susceptibility and anti-RNP antibodies in Mexican patients with systemic lupus erythematosus

INTRODUCTION

Prolactin (PRL) is a 23-kDa protein that can be synthesized and secreted by pituitary and extrapituitary tissues such as immune cells due to its expression being regulated by two independent promoter regions. The promoter which is responsible for extrapituitary expression contains the single nucleotide polymorphism (SNP) -1149 G/T previously associated with autoimmune diseases in various populations. This study evaluates the relationship of PRL -1149 G/T polymorphism with PRL serum levels and clinical characteristics in systemic lupus erythematosus (SLE) patients from western Mexico.

MATERIAL AND METHODS

One hundred and sixty-three SLE patients classified according to the 1982 American College of Rheumatology (ACR) SLE classification criteria and 326 unrelated control subjects (CS), both from western Mexico, were included. The PRL -1149 G/T polymorphism was genotyped using the polymerase chain reaction restriction fragment length polymorphism technique, and both PRL serum levels and autoantibodies were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found an association between the PRL -1149 TT genotype and SLE according to the recessive genetic model (OR = 2.26, 95% CI: 1.01-5.08, p = 0.04). The TT genotype was associated with anti-RNP antibodies (p = 0.04) and with higher scores of the Mex-SLEDAI (p = 0.02). Moreover, SLE patients showed elevated PRL serum levels (12.4 ng/ml; p < 0.01), and this condition was associated with renal activity and the presence of anti-RNP antibodies.

CONCLUSIONS

PRL -1149 TT genotype is associated with susceptibility to SLE in a Mexican-Mestizo population, and high PRL serum levels are associated with anti-RNP antibodies and renal activity.

The prolactin receptor as a therapeutic target in human diseases: browsing new potential indications

INTRODUCTION

Prolactin (PRL) signaling has emerged as a relevant target in breast and prostate cancers. This has encouraged various laboratories to develop compounds targeting the PRL receptor (PRLR). As the latter is widely distributed, it is timely to address whether other conditions could also benefit from such inhibitors.

AREAS COVERED

The authors briefly overview the two classes of PRLR blockers, which involve: i) PRL-core based analogs that have been validated as competitive antagonists in various preclinical models, and ii) anti-PRLR neutralizing antibodies that are currently in clinical Phase I for advanced breast and prostate cancers. The main purpose of this review is to discuss the multiple organs/diseases that may be considered as potential targets/indications for such inhibitors. This is done in light of reports suggesting that PRLR expression/signaling is increased in disease, and/or that systemic or locally elevated PRL levels correlate with (or promote) organ pathogenesis.

EXPERT OPINION

The two immediate challenges in the field are i) to provide the scientific community with potent anti-prolactin receptor antibodies to map prolactin receptor expression in target organs, and ii) to take advantage of the availability of functionally validated PRLR blockers to establish the relevance of these potential indications in humans.

PreImplantation factor (PIF*) promotes embryotrophic and neuroprotective decidual genes: effect negated by epidermal growth factor

Background

Intimate embryo-maternal interaction is paramount for pregnancy success post-implantation. The embryo follows a specific developmental timeline starting with neural system, dependent on endogenous and decidual factors. Beyond altered genetics/epigenetics, post-natal diseases may initiate at prenatal/neonatal, post-natal period, or through a continuum. Preimplantation factor (PIF) secreted by viable embryos promotes implantation and trophoblast invasion. Synthetic PIF reverses neuroinflammation in non-pregnant models. PIF targets embryo proteins that protect against oxidative stress and protein misfolding. We report of PIF’s embryotrophic role and potential to prevent developmental disorders by regulating uterine milieu at implantation and first trimester.

Methods

PIF’s effect on human implantation (human endometrial stromal cells (HESC)) and first-trimester decidua cultures (FTDC) was examined, by global gene expression (Affymetrix), disease-biomarkers ranking (GeneGo), neuro-specific genes (Ingenuity) and proteins (mass-spectrometry). PIF co-cultured epidermal growth factor (EGF) in both HESC and FTDC (Affymetrix) was evaluated.

Results

In HESC, PIF promotes neural differentiation and transmission genes (TLX2, EPHA10) while inhibiting retinoic acid receptor gene, which arrests growth. PIF promotes axon guidance and downregulates EGF-dependent neuroregulin signaling. In FTDC, PIF promotes bone morphogenetic protein pathway (SMAD1, 53-fold) and axonal guidance genes (EPH5) while inhibiting PPP2R2C, negative cell-growth regulator, involved in Alzheimer’s and amyotrophic lateral sclerosis. In HESC, PIF affects angiotensin via beta-arrestin, transforming growth factor-beta (TGF-β), notch, BMP, and wingless-int (WNT) signaling pathways that promote neurogenesis involved in childhood neurodevelopmental diseases—autism and also affected epithelial-mesenchymal transition involved in neuromuscular disorders. In FTDC, PIF upregulates neural development and hormone signaling, while downregulating genes protecting against xenobiotic response leading to connective tissue disorders.

In both HESC and FTDC, PIF affects neural development and transmission pathways. In HESC interactome, PIF promotes FUS gene, which controls genome integrity, while in FTDC, PIF upregulates STAT3 critical transcription signal. EGF abolished PIF’s effect on HESC, decreasing metalloproteinase and prolactin receptor genes, thereby interfering with decidualization, while in FTDC, EGF co-cultured with PIF reduced ZHX2, gene that regulates neural AFP secretion.

Conclusions

PIF promotes decidual trophic genes and proteins to regulate neural development. By regulating the uterine milieu, PIF may decrease embryo vulnerability to post-natal neurodevelopmental disorders. Examination of PIF-based intervention strategies used during embryogenesis to improve pregnancy prognosis and reduce post-natal vulnerability is clearly in order.

Prolactin promoter polymorphism (-1149 G/T) is associated with anti-DNA antibodies in Mexican patients with systemic lupus erythematosus

Prolactin (PRL) is a 23-kDa protein hormone that is synthesized mainly by the anterior pituitary gland. However, PRL can also be synthesized and secreted by extrapituitary tissues, particularly immune cells. A biallelic polymorphism (-1149 G/T) in the prolactin promoter has been shown to be functionally important, as modulation of prolactin expression has been associated with SLE in some populations. We have performed an association study using Mexican patients with SLE. We used qPCR to determine the SNP allele and genotype frequencies. We did not find statistically significant differences in allele and genotype frequencies between patients and healthy controls. However, we found a statistically significant association between the G allele and the presence of anti-dsDNA antibodies in serum (Allele frequency (G): P = 0.005; Genotyping frequency (GG): P = 0.001, OR = 7.8, 95% CI 3.59-27.1). Our data demonstrate that the prolactin promoter polymorphism -1149 G/T does not significantly contribute to SLE disease susceptibility but does predispose carriers to other immunological changes.

A novel peripherin gene (PRPH) mutation identified in one sporadic amyotrophic lateral sclerosis patient

Motor neurons in amyotrophic lateral sclerosis (ALS) are characterized by the presence of inclusion bodies composed of intermediate filament (IF) proteins. Peripherin protein is as components of these inclusions and rare mutations in peripherin gene (PRPH) were identified in sporadic ALS cases. The aim of this study was to further define the spectrum of PRPH mutations in a cohort of 122 Italian ALS patients. We screened the coding sequence, the exon/intron boundaries, and the 5'-3' un-translated regions (UTRs) in 122 ALS patients. Eighteen sequence variations were detected. Seven variants were not identified in a panel of at least 245 matched controls, including 2 missense variations, namely p.R133P and p.D141Y, each identified in one heterozygous patient. p.R133P was newly identified whereas p.D141Y was previously described in one homozygous sporadic ALS patient. These 2 variants were predicted to have a deleterious effect on protein structure or function. This work contributes to determine the role of PRPH gene variants in ALS. Further studies are necessary to define the mechanisms through which the mutant peripherin could cause ALS phenotype.

The PRL -1149 G/T polymorphism and rheumatoid arthritis susceptibility

OBJECTIVE

Previous studies have demonstrated that the PRL -1149 T (minor) allele decreases prolactin expression and may be associated with autoimmune disease. The aim of this study was to determine the role of the PRL -1149 G/T polymorphism (rs1341239) in rheumatoid arthritis (RA) susceptibility.

METHODS

We examined the association between PRL -1149 G/T and RA risk in 4 separate study populations, consisting of a total of 3,405 RA cases and 4,111 controls of self-reported white European ancestry. Samples were genotyped using 1 of 3 genotyping platforms, and strict quality control metrics were applied. We tested for association using a 2-tailed Cochran-Mantel-Haenszel additive, fixed-effects model.

RESULTS

In the individual populations, odds ratios (ORs) for an association between PRL -1149 T and RA risk ranged from 0.80 to 0.97. In a joint meta-analysis across all 4 populations, the OR for an association between PRL -1149 T and RA risk was 0.90 (95% confidence interval 0.84-0.96, P=0.001).

CONCLUSION

Our findings indicate a possible association between the PRL -1149 T allele and decreased RA risk. The effect size is small but similar to ORs for other genetic polymorphisms associated with complex traits, including RA.

DNA polymorphism of 5' flanking region of prolactin gene and its association with litter size in sheep

A single nucleotide polymorphism of 5' flanking region of the prolactin gene was investigated in both high prolificacy breeds (Small Tail Han and Hu sheep) and low prolificacy breeds (Dorset and Suffolk sheep) using polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP). The results indicated that two genotypes (AA and AB) were detected in Small Tail Han sheep (n = 239), only one genotype (AA) was detected in Hu (n = 40), Dorset (n = 50) and Suffolk sheep (n = 39). The mutant homozygous genotype (BB) was not detected in four sheep breeds. In Small Tail Han sheep (n = 239), the frequency of genotypes AA and AB was 0.91 and 0.09, the frequency of the A and B alleles was 0.95 and 0.05, respectively. The fitness tests showed that the Small Tail Han sheep population was in Hardy-Weinberg equilibrium. Sequencing revealed a mutation (G-->T) at the position 63 bp of the 5' flanking region of prolactin gene in AB genotype compared with AA genotype in Small Tail Han sheep. The Small Tail Han ewes with AB genotype had 0.83 (p < 0.05) lambs more than those with AA genotype. These results preliminarily showed that the prolactin locus is either a major gene that influences the high prolificacy in Small Tail Han sheep or is in close linkage with such a gene.

SOD1 gene mutations in Italian patients with Sporadic Amyotrophic Lateral Sclerosis (ALS)

Mutations in the SOD1 gene exons and exon/intron boundaries were searched in 66 sporadic and 4 familial Italian ALS cases consecutively referred to our centre from different Italian regions. A mutation was found in three sporadic cases (4.5%): a new nonsense mutation in exon 5 (K136X) in a patient with a rapid and severe disease course and two previously described missense nucleotide substitutions (N65S and A95T) in two patients with a mild disease course. Comparison of the clinical characteristics with previously reported patients carrying the same or similar mutations showed a remarkable genotype-phenotype correlation. No association was found with intronic sequence variations by comparing their frequency in the patients and in 181 matched controls.

Sex hormones and SLE: influencing the fate of autoreactive B cells

The prevalence of systemic lupus erythematosus (SLE) is far higher in females than in males and numerous investigations to understand this gender bias have been conducted. While it is plausible that some sex-linked genes may contribute to the genetic predisposition for the disease, other likely culprits are the sex hormones estrogen and prolactin. In this chapter we review studies that have addressed the influence of sex hormones in SLE activity and discuss the recent data established in a BALB/c mouse transgenic for the heavy chain of an anti-DNA antibody. These mice are prone to develop lupus following exposure to exogenous sex hormones. We describe how estrogen and prolactin influence B cell maturation and selection, permitting B cells to mature to immunocompetence. Finally, we discuss the relevance and implications of these data for human disease.

Spotlight on the role of hormonal factors in the emergence of autoreactive B-lymphocytes

Pathogenic autoimmunity requires a combination of inherited and acquired factors. In as much as hormones influence the sexual dimorphism of the immune system, it is possible that they can initiate or accelerate an autoimmune process, and contribute to gender-biased autoimmune disorders. Not only natural hormones, but also endocrine disruptors, such as environmental estrogens, may act in conjunction with other factors to override immune tolerance to self-antigens. In lupus, murine and human studies demonstrate that female sex hormones are implicated in disease pathogenesis. In the B cell compartment, both prolactin and estrogen are immunomodulators that affect maturation, selection and antibody secretion. Their impact may be based on their capacity to allow autoreactive B cells to escape the normal mechanisms of tolerance and to accumulate in sufficient numbers to cause clinically apparent disease. Both hormones lead to the survival and activation of autoreactive B cells, but they skew B cell maturation towards different directions, with prolactin inducing T cell-dependent autoreactive follicular B cells and estrogen eliciting T cell-independent autoreactive marginal zone B cells. Differential modulation of the cytokine milieu by hormones may also affect the development and activation of specific mature B cell subsets. This novel insight suggests that targeted manipulation of these pathways may represent a promising avenue in the treatment of lupus and other gender-biased autoimmune diseases.

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Genetics of systemic lupus erythematosus: how far have we come?

There are two primary mechanisms for studying the genetic forces at work in systemic lupus erythematosus (SLE). Several groups have collected large numbers of pedigrees in which multiple family members have SLE for use in linkage studies. These linkage studies serve to isolate areas of the genome in which susceptibility genes lie. Other groups have taken a more direct approach of investigating genes that might contribute to disease pathogenesis in sets of lupus subjects and matched controls. These association studies are accumulating in greater numbers as the technology to determine the genotype at a given locus becomes more accessible. This article discusses the results of both types of studies.

Prolactin as a modulator of B cell function: implications for SLE

Prolactin is not only a lactigenic hormone but also an immunomodulator involved in lymphocyte survival, activation and proliferation. There is increasing data implicating prolactin in autoimmunity, and specifically in SLE. Increased serum prolactin levels have been reported in lupus patients of both genders, and have been associated with accelerated disease expression and early mortality in lupus-prone mice. Furthermore, suppression of prolactin secretion with bromocriptine provides beneficial effects in murine lupus, and perhaps in some SLE patients as well. Treatment with prolactin that causes mild to moderate hyperprolactinemia, similar to that present in SLE patients, breaks tolerance and induces a lupus-like illness in non-spontaneously autoimmune mice with a susceptible genetic background. These immuno stimulatory effects of prolactin are mediated by a decrease in negative selection and the maturation of autoreactive B cells to the follicular subset. Consistent with the fact that follicular B cells are T cell dependent, CD4+ T cells are necessary for the prolactin-mediated break down of B cell tolerance. In mice, the effects of prolactin on the immune system are genetically determined, suggesting that only a subset of SLE patients are likely to have a prolactin-responsive disease. The manipulation of serum prolactin or, even more specifically, follicular B cells that are susceptible to the immuno stimulatory effects of prolactin, may provide novel therapeutic options for those SLE patients with a prolactin-modulated disease.