Stress and prolactin effects on bone marrow myeloid cells, serum chemokine and serum glucocorticoid levels in mice

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.

Prolactin receptor antagonism uncouples lipids from atherosclerosis susceptibility

The pituitary-derived hormone prolactin has been suggested to stimulate the development of atherosclerosis and cardiovascular disease through its effects on metabolism and inflammation. In this study, we aimed to challenge the hypothesis that inhibition of prolactin function may beneficially affect atherosclerosis burden. Hereto, atherosclerosis-susceptible LDL receptor (Ldlr) knockout mice were transplanted with bone marrow from transgenic mice expressing the pure prolactin receptor antagonist Del1-9-G129R-hPRL or their non-transgenic littermates as control. Recipient mice expressing Del1-9-G129R-hPRL exhibited a decrease in plasma cholesterol levels (-29%; P<0.05) upon feeding a Western-type diet (WTD), which could be attributed to a marked decrease (-47%; P<0.01) in the amount of cholesterol esters associated with pro-atherogenic lipoproteins VLDL/LDL. By contrast, Del1-9-G129R-hPRL-expressing mice did not display any change in the susceptibility for atherosclerosis after 12 weeks of WTD feeding. Both the absolute atherosclerotic lesion size (223 ± 33 × 10(3) μm(2) for Del1-9-G129R-hPRL vs 259 ± 32 × 10(3) μm(2) for controls) and the lesional macrophage and collagen contents were not different between the two groups of bone marrow recipients. Importantly, Del1-9-G129R-hPRL exposure increased levels of circulating neutrophils (+91%; P<0.05), lymphocytes (+55%; P<0.05), and monocytes (+43%; P<0.05), resulting in a 49% higher (P<0.01) total blood leukocyte count. In conclusion, we have shown that prolactin receptor signaling inhibition uncouples the plasma atherogenic index from atherosclerosis susceptibility in Ldlr knockout mice. Despite an associated decrease in VLDL/LDL cholesterol levels, application of the prolactin receptor antagonist Del1-9-G129R-hPRL does not alter the susceptibility for initial development of atherosclerotic lesions probably due to the parallel increase in circulating leukocyte concentrations.

No association between bone mass and prolactin levels among patients with schizophrenia

OBJECTIVE

Decreased bone mineral density has been implicated in schizophrenic patients for long years. The purpose of this study was to assess the relationship between bone mass and prolactin levels in schizophrenic patients.

METHODS

In this study, bone mass was measured using quantitative ultrasound densitometry of the calcaneus in 114 patients (49 males and 65 females). The osteosono-assessment index (OSI) was calculated as a function of the speed of sound and transmission index. Estradiol, testosterone, and prolactin levels were also measured. Factors that influenced prolactin levels and bone mass were determined via multiple linear regression analysis.

RESULTS

Among the female patients, body mass index and estradiol levels were independently and significantly associated with the OSI. Neither prolactin levels nor duration of antipsychotic treatment was associated with bone mass for either gender.

CONCLUSIONS

These findings suggest that prolactin levels do not contribute to poor bone mass, as assessed using the OSI among schizophrenic patients. However, the interpretation of our results was hampered by lack of data including differences in lifestyle and type of antipsychotic medications used in schizophrenic patients. Association between prolactin levels and low bone mineral density was not completely ruled out. Future research exploring prolactin levels and bone mineral density is warranted.

Mice treated with a benzodiazepine had an improved survival rate following Pseudomonas aeruginosa infection

Psychological stress has a high incidence after burn injury, therefore, anxiolytic drugs are often prescribed. Unfortunately, to date, no burn study has investigated the effects of anxiolytic drugs on the ability to fight infection. This study was undertaken to determine if psychological stress, anxiety-modulating drugs, or both, alter survival following an infection. On day 0, 7-week-old male C57Bl/6 mice either received a 15% full-thickness flame burn or were sham treated (anesthesia and shaved), whereas controls received no treatment. Mice received midazolam (1 mg/kg intraperitoneally) or saline daily and were stressed by exposure to rat in a guinea pig cage or placed in an empty cage for 1 hour a day, beginning on postburn day 1. For the survival experiments, mice either received bacteria after 2 or 8 consecutive days of predator exposure and drug treatment, which continued daily for 7 days after inoculation. In a separate set of experiments, after eight daily injections of midazolam, mice were given lipopolysaccharide, bacteria, or saline and were killed 12 hours later. Mice that received midazolam had improved survival rates when compared with their saline-treated counterparts, and the protective effect was more significant the more days they received the drug. For most of the cytokines, the bacteria-induced increase was significantly attenuated by midazolam as was the amount of bacteria in the liver. The protective effect seems to be independent of the drug's anxiolytic activity as there were no significant differences in survival between the predator-stressed and the nonstressed mice. The mechanisms responsible for the protective effect remain to be elucidated.