Upregulation of hepatic prolactin receptor gene expression by 17beta-estradiol following trauma-hemorrhage

The effects of novel and newly approved antipsychotics on serum prolactin levels: a comprehensive review

Since the 1970s, clinicians have increasingly become more familiar with hyperprolactinemia (HPRL) as a common adverse effect of antipsychotic medication, which remains the cornerstone of pharmacological treatment for patients with schizophrenia. Although treatment with second-generation antipsychotics (SGAs) as a group is, compared with use of the first-generation antipsychotics, associated with lower prolactin (PRL) plasma levels, the detailed effects on plasma PRL levels for each of these compounds in reports often remain incomplete or inaccurate. Moreover, at this moment, no review has been published about the effect of the newly approved antipsychotics asenapine, iloperidone and lurasidone on PRL levels. The objective of this review is to describe PRL physiology; PRL measurement; diagnosis, causes, consequences and mechanisms of HPRL; incidence figures of (new-onset) HPRL with SGAs and newly approved antipsychotics in adolescent and adult patients; and revisit lingering questions regarding this hormone. A literature search, using the MEDLINE database (1966-December 2013), was conducted to identify relevant publications to report on the state of the art of HPRL and to summarize the available evidence with respect to the propensity of the SGAs and the newly approved antipsychotics to elevate PRL levels. Our review shows that although HPRL usually is defined as a sustained level of PRL above the laboratory upper limit of normal, limit values show some degree of variability in clinical reports, making the interpretation and comparison of data across studies difficult. Moreover, many reports do not provide much or any data detailing the measurement of PRL. Although the highest rates of HPRL are consistently reported in association with amisulpride, risperidone and paliperidone, while aripiprazole and quetiapine have the most favorable profile with respect to this outcome, all SGAs can induce PRL elevations, especially at the beginning of treatment, and have the potential to cause new-onset HPRL. Considering the PRL-elevating propensity of the newly approved antipsychotics, evidence seems to indicate these agents have a PRL profile comparable to that of clozapine (asenapine and iloperidone), ziprasidone and olanzapine (lurasidone). PRL elevations with antipsychotic medication generally are dose dependant. However, antipsychotics having a high potential for PRL elevation (amisulpride, risperidone and paliperidone) can have a profound impact on PRL levels even at relatively low doses, while PRL levels with antipsychotics having a minimal effect on PRL, in most cases, can remain unchanged (quetiapine) or reduce (aripiprazole) over all dosages. Although tolerance and decreases in PRL values after long-term administration of PRL-elevating antipsychotics can occur, the elevations, in most cases, remain above the upper limit of normal. PRL profiles of antipsychotics in children and adolescents seem to be the same as in adults. The hyperprolactinemic effects of antipsychotic medication are mostly correlated with their affinity for dopamine D2 receptors at the level of the anterior pituitary lactotrophs (and probably other neurotransmitter mechanisms) and their blood-brain barrier penetrating capability. Even though antipsychotics are the most common cause of pharmacologically induced HPRL, recent research has shown that HPRL can be pre-existing in a substantial portion of antipsychotic-naïve patients with first-episode psychosis or at-risk mental state.

Estrogen: a novel therapeutic adjunct for the treatment of trauma-hemorrhage-induced immunological alterations

Trauma-hemorrhage leads to prolonged immune suppression, sepsis, and multiple organ failure. The condition affects all compartments of the immune system, and extensive studies have been carried out elucidating the immunological events following trauma-hemorrhage. The immune alteration observed following trauma-hemorrhage is gender dependent in both animal models and humans, though some studies in humans are contradictory. Within 30 min after trauma-hemorrhage, splenic and peritoneal macrophages, as well as T-cell function, are depressed in male animals, but not in proestrus females. Studies have also shown that the mortality [corrected] rate and the induction of subsequent sepsis following trauma-hemorrhage are significantly higher in males and ovariectomized females compared with proestrus females. These and other investigations show that sex hormones form the basis of this gender dichotomy, and administration of estrogen can ameliorate the immune depression and increase the survival rate after trauma-hemorrhage. This review specifically elaborates the studies carried out thus far demonstrating immunological alteration after trauma-hemorrhage and its modulation by estrogen. Also, estrogen was shown to produce its salutary effects through nuclear as well as extranuclear receptors. Estrogen rapidly activates several protein kinases and phosphatases, as well as the release of calcium in different cell types. The results of the studies exemplify the promise of estrogen as a therapeutic adjunct in treating adverse pathophysiological conditions following trauma-hemorrhage.

Prolactin receptors in rat cholangiocytes: regulation of level and isoform ratio is sex independent

The presence of prolactin receptor and peculiarities of its isoform expression in bile duct cells (cholangiocytes) differentially isolated from rat liver under different conditions were investigated in the present study. Normal cholangiocytes express prolactin receptor at relatively low level comparable to those of some prolactin-dependent tissues. Long receptor isoform is predominant in cholangiocytes but not in hepatocytes. The prolactin receptor level increases significantly under obstructive cholestasis due to evaluation of long and appearance of short isoforms. In rat cholangiocytes, unlike other tissues, the main positive regulators of prolactin receptor expression are cholestasis-induced factors instead of sex hormone and prolactin levels. Long isoform is predominant and induced primarily by cholestasis-induced factors.

Tissue-specific gene expression of prolactin receptor in the acute-phase response induced by lipopolysaccharides

Acute inflammation can elicit a defense reaction known as the acute-phase response (APR) that is crucial for reestablishing homeostasis in the host. The role for prolactin (PRL) as an immunomodulatory factor maintaining homeostasis under conditions of stress has been proposed; however, its function during the APR remains unclear. Previously, it was shown that proinflammatory cytokines characteristic of the APR (TNF-alpha, IL-1beta, and IFNgamma) induced the expression of the PRL receptor (PRLR) by pulmonary fibroblasts in vitro. Here, we investigated the in vivo expression of PRLR during lipopolysaccharide (LPS)-induced APR in various tissues of the mouse. We show that PRLR mRNA and protein levels were downregulated in hepatic tissues after intraperitoneal LPS injection. Downregulation of PRLR in the liver was confirmed by immunohistochemistry. A suppressive effect on mRNA expression was also observed in prostate, seminal vesicle, kidney, heart, and lung tissues. However, PRLR mRNA levels were increased in the thymus, and no changes were observed in the spleen. The proportion of transcripts for the different receptor isoforms (long, S1, S2, and S3) in liver and thymus was not altered by LPS injection. These findings suggest a complex tissue-specific regulation of PRLR expression in the context of the APR.