Characterization of the hepatic prolactin receptors induced by chronic iron deficiency and neuroleptics

Prolactin Drives Iron Release from Macrophages and Uptake in Mammary Cancer Cells through CD44

Iron is an essential element for human health. In humans, dysregulated iron homeostasis can result in a variety of disorders and the development of cancers. Enhanced uptake, redistribution, and retention of iron in cancer cells have been suggested as an "iron addiction" pattern in cancer cells. This increased iron in cancer cells positively correlates with rapid tumor growth and the epithelial-to-mesenchymal transition, which forms the basis for tumor metastasis. However, the source of iron and the mechanisms cancer cells adopt to actively acquire iron is not well understood. In the present study, we report, for the first time, that the peptide hormone, prolactin, exhibits a novel function in regulating iron distribution, on top of its well-known pro-lactating role. When stimulated by prolactin, breast cancer cells increase CD44, a surface receptor mediating the endocytosis of hyaluronate-bound iron, resulting in the accumulation of iron in cancer cells. In contrast, macrophages, when treated by prolactin, express more ferroportin, the only iron exporter in cells, giving rise to net iron output. Interestingly, when co-culturing macrophages with pre-stained labile iron pools and cancer cells without any iron staining, in an iron free condition, we demonstrate direct iron flow from macrophages to cancer cells. As macrophages are one of the major iron-storage cells and it is known that macrophages infiltrate tumors and facilitate their progression, our work therefore presents a novel regulatory role of prolactin to drive iron flow, which provides new information on fine-tuning immune responses in tumor microenvironment and could potentially benefit the development of novel therapeutics.

The Unexplored Crossroads of the Female Athlete Triad and Iron Deficiency: A Narrative Review

Despite the severity and prevalence of iron deficiency in exercising women, few published reports have explored how iron deficiency interacts with another prevalent and severe condition in exercising women: the 'female athlete triad.' This review aims to describe how iron deficiency may interact with each component of the female athlete triad, that is, energy status, reproductive function, and bone health. The effects of iron deficiency on energy status are discussed in regards to thyroid function, metabolic fuel availability, eating behaviors, and energy expenditure. The interactions between iron deficiency and reproductive function are explored by discussing the potentially impaired fertility and hyperprolactinemia due to iron deficiency and the alterations in iron metabolism due to menstrual blood loss and estrogen exposure. The interaction of iron deficiency with bone health may occur via dysregulation of the growth hormone/insulin-like growth factor-1 axis, hypoxia, and hypothyroidism. Based on these discussions, several future directions for research are presented.

Iron deficiency: Differential effects on monoamine transporters

In this study, we extend previous work on iron deficiency and dopamine (DA) transporters to include an examination of central serotonin (5-HT) and noradrenergic (NE) transporters. Rats were fed either iron deficient (ID) or iron adequate (CN) diets from weaning until adulthood. In males, an additional group of iron deficient animals (IR) were given iron supplementation. DA, 5-HT, and NE transporter binding was done in situ on thin sections. ID males, but not females, decreased DA transporter binding in the nucleus accumbens, caudate putamen and substantia nigra by 20-40%. ID males also had a 20-30% reduction in 5-HT transporter binding in several areas (nucleus accumbens, olfactory tubercle, colliculus) while in ID females there was 15-25% increased serotonin transporter binding in the olfactory tubercle, zona incerta, anteroventral thalamic nucleus and vestibular nucleus. Iron deficiency reduced 3H-nisoxetine binding to the NE transporter in locus ceruleus and anteroventral thalamic nucleus in males but not females. Only some of the changes observed in DA, serotonin and NE transporter binding were reversible by iron supplementation. These findings show that iron deficiency affects monoamine systems related to homeostasis and in most cases males appear to be more vulnerable than females.

Iron deficiency in pediatric patients in long-term risperidone treatment

OBJECTIVE

Atypical antipsychotics, increasingly used in children and adolescents, modulate brain dopamine. Iron plays a critical role in dopaminergic signaling. Therefore, we explored whether body iron status is related to psychiatric symptom severity, treatment response, and tolerability following extended antipsychotic therapy.

METHODS

Between November 2005 and August 2009, medically healthy 7-17-year-old risperidone-treated participants enrolled in a cross-sectional study examining the long-term safety of this antipsychotic. Anthropometric measurements were obtained. Psychiatric symptom severity and dietary intake were assessed. Serum ferritin, transferrin receptor, and prolactin concentrations were measured. Linear multivariable regression analysis tested the association among body iron, symptom severity, the dose of risperidone and psychostimulants, and serum prolactin concentration.

RESULTS

The sample consisted of 115 patients (87% males) with a mean (±SD) age of 11.6 (±2.8) years. The majority had externalizing disorders, and they had taken risperidone for 2.4 (±1.7) years. Body iron was low, with 45% having iron depletion and 14% having iron deficiency. Iron status was inversely associated with weight gain during risperidone treatment and with interleukin-6. Body iron was neither associated with psychiatric symptom severity nor with the daily dose of risperidone and psychostimulants. It was, however, inversely associated with prolactin concentration, which was nearly 50% higher in the iron-deficient group.

CONCLUSIONS

Iron depletion and deficiency are prevalent in children and adolescents chronically treated with risperidone. Iron deficiency accentuates the antipsychotic-induced elevation in prolactin. Future studies should confirm this finding and investigate the potential benefit of iron supplementation in antipsychotic-treated patients.

Long-term neuroendocrine effects of iron-deficiency anemia in infancy

INTRODUCTION

Iron-deficiency anemia (IDA) is recognized to have long-lasting effects on neurodevelopment, but there is little research on neuroendocrine systems.

METHODS

This study examined the effects of IDA in early or later infancy on plasma cortisol and prolactin stress-response patterns for 1 h after a venipuncture and catheter placement in 10-y-old healthy Chilean children. Children identified with IDA at 6 mo (IDA-6; n = 13) or 12 mo (IDA-12; n = 24) and who were iron sufficient (IS) at other infancy time points were compared to children who were IS at all time points during infancy (n = 23). All children received at least 6 mo of oral iron treatment in infancy.

RESULTS

At 10 y of age, IDA-6 and IDA-12 children demonstrated altered cortisol response patterns; both showed a more immediate decline and IDA-12 children showed a blunted curvature as compared to IS children. IDA-12 children showed significantly lower cortisol levels at 30 and 45 min after venipuncture and catheter placement than did IS children. There were no significant differences for stress-responsive plasma prolactin patterns between groups.

DISCUSSION

The results indicate that having IDA during infancy is associated with long-term neuroendocrine effects on stress-responsive cortisol patterns.

Early iron deficiency has brain and behavior effects consistent with dopaminergic dysfunction

To honor the late John Beard's many contributions regarding iron and dopamine biology, this review focuses on recent human studies that test specific hypotheses about effects of early iron deficiency on dopamine system functioning. Short- and long-term alterations associated with iron deficiency in infancy can be related to major dopamine pathways (mesocortical, mesolimbic, nigrostriatal, tuberohypophyseal). Children and young adults who had iron deficiency anemia in infancy show poorer inhibitory control and executive functioning as assessed by neurocognitive tasks where pharmacologic and neuroimaging studies implicate frontal-striatal circuits and the mesocortical dopamine pathway. Alterations in the mesolimbic pathway, where dopamine plays a major role in behavioral activation and inhibition, positive affect, and inherent reward, may help explain altered social-emotional behavior in iron-deficient infants, specifically wariness and hesitance, lack of positive affect, diminished social engagement, etc. Poorer motor sequencing and bimanual coordination and lower spontaneous eye blink rate in iron-deficient anemic infants are consistent with impaired function in the nigrostriatal pathway. Short- and long-term changes in serum prolactin point to dopamine dysfunction in the tuberohypophyseal pathway. These hypothesis-driven findings support the adverse effects of early iron deficiency on dopamine biology. Iron deficiency also has other effects, specifically on other neurotransmitters, myelination, dendritogenesis, neurometabolism in hippocampus and striatum, gene and protein profiles, and associated behaviors. The persistence of poorer cognitive, motor, affective, and sensory system functioning highlights the need to prevent iron deficiency in infancy and to find interventions that lessen the long-term effects of this widespread nutrient disorder.

Iron deficiency in infancy predicts altered serum prolactin response 10 years later

Serum prolactin may reflect CNS dopaminergic function. Because iron deficiency (ID) alters brain dopamine in rats, serum prolactin levels were previously investigated in infants with varied iron status. High serum prolactin levels correlated with behaviors typical of chronic ID. The objective of this study was to determine the effect of infant iron status on serum prolactin levels after a stressor in early adolescence. One hundred fifty-nine of 191 children enrolled in infancy (chronic ID, n = 46; good iron comparison group, n = 113) had serum prolactin measurements after catheter placement at 11-14 y of age. Serum prolactin levels were compared by sex, pubertal status and infant iron status and the pattern of change over time was compared by infant iron status controlling for pubertal stage and background factors. Males and less mature adolescents had lower serum prolactin concentrations than females and more mature adolescents. Controlling for these factors, the serum prolactin response pattern differed significantly by infant iron status. Serum prolactin declined earlier for the chronic ID group. In conclusion, an altered serum prolactin response pattern was observed 10 y after chronic ID in infancy and may suggest a long-lasting effect of ID on the regulation of prolactin.

Serum prolactin levels and behavior in infants

This study examined the relationship between serum prolactin levels and behavior in infants and toddlers who experienced two potentially stressful experiences (developmental testing and venipuncture). Serum prolactin levels showed considerable consistency over a 3-month period (r = 0.64 between study entry and three months, p < 0.001, n = 50). There was also stability in having either a normal or a high value (> or = 25 ng/ml). Among children who had a normal value on initial testing, 97% also has a normal value after 3 months; 55% of those with initial high values continued to have high values (chi 2 = 19.26, p < 0.001). Children with high serum prolactin levels were more likely to be rated as unusually hesitant and unhappy during developmental testing. Overall, 53% of the children with serum prolactin levels > or = 25 ng/ml were considered abnormal in affect, compared to 20% of those with lower serum prolactin values (total n = 138, chi 2 = 13.56, p < 0.001). These results suggest that, even in early life, serum prolactin levels may reflect characteristic individual behavioral and neuroendocrine responses to stress.