Glial cells as mediators of protective actions of prolactin (PRL) in the CNS

Blood biomarkers of neuronal injury and astrocytic reactivity in electroconvulsive therapy

Despite electroconvulsive therapy (ECT) being recognized as an effective treatment for major depressive episodes (MDE), its application is subject to controversy due to concerns over cognitive side effects. The pathophysiology of these side effects is not well understood. Here, we examined the effects of ECT on blood-based biomarkers of neuronal injury and astrocytic reactivity. Participants with a major depressive episode (N = 99) underwent acute ECT. Blood was sampled just before (T0) and 30 min after (T1) the first ECT session, as well as just before the sixth session (T2; 48-72 h after the fifth session). Age- and sex-matched controls (N = 99) were recruited from the general population. Serum concentrations of neurofilament light chain (NfL), total tau protein, and glial fibrillary acidic protein (GFAP) were measured with ultrasensitive single-molecule array assays. Utilizing generalized least squares regression, we compared baseline (T0) biomarker concentrations against those of our control group, and calculated the shifts in serum biomarker concentrations from baseline to immediately post-first ECT session (T1), and prior to the sixth session (T2). Baseline analysis revealed that serum levels of NfL (p < 0.001) and tau (p = 0.036) were significantly elevated in ECT recipients compared with controls, whereas GFAP levels showed no significant difference. Relative to T0, serum NfL concentration neither changed at T1 (mean change 3.1%, 95%CI -0.5% to 6.7%, p = 0.088) nor at T2 (mean change -3.2%, 95%CI -7.6% to 1.5%, p = 0.18). Similarly, no change in total tau was observed (mean change 3.7%, 95%CI -11.6% to 21.7%, p = 0.65). GFAP increased from T0 to T1 (mean change 20.3%, 95%CI 14.6 to 26.3%, p < 0.001), but not from T0 to T2 (mean change -0.7%, 95%CI -5.8% to 4.8%, p = 0.82). In conclusion, our findings suggest that ECT induces a temporary increase in serum GFAP, possibly reflecting transient astrocytic activation. Importantly, we observed no indicators of neuronal damage or long-term elevation in any assessed biomarker.

Traumatic brain injury and prolactin

Traumatic brain injury (TBI) is a well-known etiologic factor for pituitary dysfunctions, with a prevalence of 15% during long-term follow-up. The most common hormonal disruption is growth hormone deficiency, followed by central adrenal insufficiency, central hypogonadism, and central hypothyroidism in varying order across studies. The prevalence of serum prolactin disturbances ranged widely from 0 to 85%. Prolactin release is mainly regulated by hypothalamic dopamine inhibition, and mediators such as TRH, serotonin, cytokines, and neurotransmitters have modulatory effects. Many factors, such as hypothalamic and/or pituitary gland injuries, as well as fluctuations in dopaminergic activity and other mediators and stress response, may cause derangements in serum prolactin levels after TBI. Although it is challenging to investigate the direct effects of TBI on serum prolactin levels due to many confounders, basal prolactin measurements and stimulation tests provide insight into the functionality of the hypothalamus and pituitary gland after TBI. Moreover, during the acute phase of TBI, prolactin levels appear to correlate with TBI severity. In contrast, in the chronic phase, hypoprolactinemia may function as an indirect indicator of pituitary dysfunction and reduced pituitary volume. Further investigations are needed to elucidate the pathophysiologic mechanisms underlying the prolactin trend following TBI, its significance, and its associations with other pituitary hormone dysfunctions. In this article, we re-evaluated our patients' TBI data regarding prolactin levels during prospective long-term follow-up, and reviewed the literature regarding the prevalence, pathophysiology, and clinical implications of serum prolactin disturbances during acute and chronic phases following TBI.

Potential mechanisms of Shenmai injection against POCD based on network pharmacology and molecular docking

BACKGROUND

As the population ages, the number of patients with postoperative cognitive dysfunction increases. This study aims to investigate the mechanisms of Shenmai injection as a therapeutic strategy for postoperative cognitive dysfunction using a network pharmacology approach.

METHODS

Shenmai injection and its targets were retrieved from the Traditional Chinese Medicine Systems Pharmacology database. Postoperative cognitive dysfunction-associated protein targets were identified using the GeneCards and DisGeNET databases. Subsequently, a protein-protein interaction network was constructed using the String database. For treating postoperative cognitive dysfunction, the core targets of Shenmai injection were identified through topological analysis, followed by the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses performed for annotation. Molecular docking was performed on the screened core targets and components.

RESULTS

One hundred and eighty-two related targets of Shenmai injection in treating postoperative cognitive dysfunction were identified. Eleven active ingredients in Shenmai injection were detected to have a close connection with postoperative cognitive dysfunction-related targets. Additionally, Gene Ontology analysis revealed 10 biological processes, 10 cellular components and 10 molecular functions. The Kyoto Encyclopedia of Genes and Genomes analysis identified 20 signaling pathways. The docking results indicated five active ingredients from Shenmai injection can fit in the binding pockets of all three candidate targets.

CONCLUSIONS

Thus, the present work systematically explored the anti-postoperative cognitive dysfunction mechanism of potential targets and signaling pathways of Shenmai injection. These results provide an important reference for subsequent basic research on postoperative cognitive dysfunction.

Sex differences in bipolar disorder: The dorsolateral prefrontal cortex as an etiopathogenic region

Bipolar disorder (BD) is worldwide a prevalent mental illness and a leading risk factor for suicide. Over the past three decades, it has been discovered that sex differences exist throughout the entire panorama of BD, but the etiologic regions and mechanisms that generate such differences remain poorly characterized. Available evidence indicates that the dorsolateral prefrontal cortex (DLPFC), a critical region that controls higher-order cognitive processing and mood, exhibits biological disparities between male and female patients with psychiatric disorders, which are highly correlated with the co-occurrence of psychotic symptoms. This review addresses the sex differences in BD concerning epidemiology, cognitive impairments, clinical manifestations, neuroimaging, and laboratory abnormalities. It also provides strong evidence linking DLPFC to the etiopathogenesis of these sex differences. We emphasize the importance of identifying gene signatures using human brain transcriptomics, which can depict sexually different variations, explain sex-biased symptomatic features, and provide novel targets for sex-specific therapeutics.

Alterations in the Serum Proteome Following Electroconvulsive Therapy for a Major Depressive Episode: A Longitudinal Multicenter Study

Background

Electroconvulsive therapy (ECT) is the most effective treatment for severe depression, but the biological changes induced by ECT remain poorly understood.

Methods

This study investigated alterations in blood serum proteins in 309 patients receiving ECT for a major depressive episode. We analyzed 201 proteins in samples collected at 3 time points (T): just before the first ECT treatment session (T0), within 30 minutes after the first ECT session (T1), and just before the sixth ECT session (T2).

Results

Using statistical models to account for repeated sampling, we identified 152 and 70 significantly (<5% false discovery rate) altered proteins at T1 and T2, respectively. The most pronounced alterations at T1 were transiently increased levels of prolactin, myoglobin, and kallikrein-6. However, most proteins had decreased levels at T1, with the largest effects observed for pro-epidermal growth factor, proto-oncogene tyrosine-protein kinase Src, tumor necrosis factor ligand superfamily member 14, sulfotransferase 1A1, early activation antigen CD69, and CD40 ligand. The change of several acutely altered proteins correlated with electric current and pulse frequency in a dose-response-like manner. Over a 5-session course of ECT, some acutely altered levels were sustained while others increased, e.g., serine protease 8 and chitinase-3-like protein 1. None of the studied protein biomarkers were associated with clinical response to ECT.

Conclusions

We report experimental data on alterations in the circulating proteome triggered by ECT in a clinical setting. The findings implicate hormonal signaling, immune response, apoptotic processes, and more. None of the findings were associated with clinical response to ECT.

Multiparity Differentially Affects Specific Aspects of the Acute Neuroinflammatory Response to Traumatic Brain Injury in Female Mice

Pregnancy is associated with profound acute and long-term physiological changes, but the effects of such changes on brain injury outcomes are unclear. Here, we examined the effects of previous pregnancy and maternal experience (parity) on acute neuroinflammatory responses to lateral fluid percussion injury (FPI), a well-defined experimental traumatic brain injury (TBI) paradigm. Multiparous (2-3 pregnancies and motherhood experiences) and age-matched nulliparous (no previous pregnancy or motherhood experience) female mice received either FPI or sham injury and were euthanized 3 days post-injury (DPI). Increased cortical Iba1, GFAP, and CD68 immunolabeling was observed following TBI independent of parity and microglia morphology did not differ between TBI groups. However, multiparous females had fewer CD45⁺ cells near the site of injury compared to nulliparous females, which was associated with preserved aquaporin-4 polarization, suggesting that parity may influence leukocyte recruitment to the site of injury and maintenance of blood brain barrier permeability following TBI. Additionally, relative cortical Il6 gene expression following TBI was dependent on parity such that TBI increased Il6 expression in nulliparous, but not multiparous, mice. Together, this work suggests that reproductive history may influence acute neuroinflammatory outcomes following TBI in females.

Prolactin at moderately increased levels confers a neuroprotective effect in non-secreting pituitary macroadenomas

Context

Prolactin, a hormone synthesized by the anterior pituitary gland demonstrates promise as a neuroprotective agent, however, its role in humans and in vivo during injury is not fully understood.

Objective

To investigate whether elevated levels of prolactin attenuate injury to the retinal nerve fiber layer (RNFL) following compression of the optic chiasm in patients with a prolactin secreting pituitary macroadenoma (i.e., prolactinoma).

Design setting and participants

A retrospective cross-sectional study of all pituitary macroadenoma patients treated at a single institution between 2009 and 2019.

Main outcome measure(s)

Primary outcome measures included RNFL thickness, mean deviation, and prolactin levels for both prolactin-secreting and non-secreting pituitary macroadenoma patients.

Results

Sixty-six patients met inclusion criteria for this study (14 prolactin-secreting and 52 non-secreting macroadenoma patients). Of 52 non-secreting macroadenoma patients, 12 had moderate elevation of prolactin secondary to stalk effect. Patients with moderate elevation in prolactin demonstrated increased RNFL thickness compared to patients with normal prolactin levels (p < 0.01). Additionally, a significant positive relation between increasing levels of prolactin and RNFL thickness was identified in patients with moderate prolactin elevation (R = 0.51, p-value = 0.035). No significant difference was identified between prolactinoma patients and those with normal prolactin levels.

Conclusions

Moderately increased serum prolactin is associated with increased RNFL thickness when compared to controls. These associations are lost when serum prolactin is < 30 ng/ml or elevated in prolactinomas. This suggests a neuroprotective effect of prolactin at moderately increased levels in preserving retinal function during optic chiasm compression.

Recombinant human erythropoietin upregulates PPARγ through the PI3K/Akt pathway to protect neurons in rats subjected to oxidative stress

In vitro cell experiments have suggested that recombinant human erythropoietin (rhEPO) and peroxisome proliferator activated receptor γ (PPARγ) activation exert protective effects on neurons. This study observed the learning and memory ability, antioxidant capacity and the ratio of apoptotic cells after rhEPO intervention and investigated the relationship among rhEPO, PI3K/Akt and PPARγ in the anti-neural oxidative stress injury process in vivo. The results showed that rhEPO significantly improved the learning and memory abilities of rats subjected to oxidative stress, enhanced the antioxidant capacity of cells, and reduced neuronal apoptosis. Then, the PI3K/Akt and PPARγ pathways were inhibited, and TUNEL staining were used to observe the changes in the effect of rhEPO. After the PI3K/Akt and PPARγ pathways were inhibited, the effect of rhEPO on rats subjected to oxidative stress was significantly weakened, suggesting that both the PI3K/Akt and PPARγ pathways are involved in the process by which rhEPO protects neurons. Finally, Western blotting and immunofluorescence staining were used to observe the changes in PI3K/Akt and PPARγ signalling proteins in the neurons after the rhEPO intervention and to explore the relationship among the three. The results showed that rhEPO significantly increased the levels of the p-Akt and PPARγ proteins and the level of the PPARγ protein in the nucleus, indicating that the PI3K/Akt pathway was located upstream of and regulates PPARγ. In conclusion, this study suggested that rhEPO activates the PI3K/Akt to upregulate PPARγ, enhance the cellular antioxidant capacity, and protect neurons in rats subjected to oxidative stress.

Empty Sella Syndrome as a Window Into the Neuroprotective Effects of Prolactin

Background: The goal of this study was to relate diffusion MR measures of white matter integrity of the retinofugal visual pathway with prolactin levels in a patient with downward herniation of the optic chiasm secondary to medical treatment of a prolactinoma. Methods: A 36-year-old woman with a prolactinoma presented with progressive bilateral visual field defects 9 years after initial diagnosis and medical treatment. She was diagnosed with empty-sella syndrome and instructed to stop cabergoline. Hormone testing was conducted in tandem with routine clinical evaluations over 1 year and the patient was followed with diffusion magnetic resonance imaging (dMRI), optical coherence tomography (OCT), and automated perimetry at three time points. Five healthy controls underwent a complementary battery of clinical and neuroimaging tests at a single time point. Results: Shortly after discontinuing cabergoline, diffusion metrics in the optic tracts were within the range of values observed in healthy controls. However, following a brief period where the patient resumed cabergoline (of her own volition), there was a decrease in serum prolactin with a corresponding decrease in visual ability and increase in radial diffusivity (p < 0.001). Those measures again returned to their baseline ranges after discontinuing cabergoline a second time. Conclusions: These results demonstrate the sensitivity of dMRI to detect rapid and functionally significant microstructural changes in white matter tracts secondary to alterations in serum prolactin levels. The inverse relations between prolactin and measures of white matter integrity and visual function are consistent with the hypothesis that prolactin can play a neuroprotective role in the injured nervous system.

Decoding signaling pathways involved in prolactin-induced neuroprotection: A review

It has been well recognized that prolactin (PRL), a pleiotropic hormone, has many functions in the brain, such as maternal behavior, neurogenesis, and neuronal plasticity, among others. Recently, it has been reported to have a significant role in neuroprotection against excitotoxicity. Glutamate excitotoxicity is a common alteration in many neurological and neurodegenerative diseases, leading to neuronal death. In this sense, several efforts have been made to decrease the progression of these pathologies. Despite various reports of PRL's neuroprotective effect against excitotoxicity, the signaling pathways that underlie this mechanism remain unclear. This review aims to describe the most recent and relevant studies on the molecular signaling pathways, particularly, PI3K/AKT, NF-κB, and JAK2/STAT5, which are currently under investigation and might be implicated in the molecular mechanisms that explain the PRL effects against excitotoxicity and neuroprotection. Remarkable neuroprotective effects of PRL might be useful in the treatment of some neurological diseases.

Recombinant Human Growth Hormone Activates Neuroprotective Growth Factors in Hypoxic Brain Injury in Neonatal Mice

Perinatal hypoxia severely disrupts cerebral metabolic and maturational programs beyond apoptotic cell death. Antiapoptotic treatments such as erythropoietin are suggested to improve outcomes in hypoxic brain injury; however, the results are controversial. We analyzed the neuroprotective effects of recombinant human growth hormone (rhGH) on regenerative mechanisms in the hypoxic developing mouse brain in comparison to controls. Using an established model of neonatal acute hypoxia (8% O2, 6 hours), P7 mice were treated intraperitoneally with rhGH (4000 µg/kg) 0, 12, and 24 hours after hypoxic exposure. After a regeneration period of 48 hours, expression of hypoxia-inducible neurotrophic factors (erythropoietin [EPO], vascular endothelial growth factor A [VEGF-A], insulin-like growth factors 1 and 2 [IGF-1/-2], IGF binding proteins) and proinflammatory markers was analyzed. In vitro experiments were performed using primary mouse cortical neurons (E14, DIV6). rhGH increased neuronal gene expression of EPO, IGF-1, and VEGF (P < .05) in vitro and diminished apoptosis of hypoxic neurons in a dose-dependent manner. In the developing brain, rhGH treatment led to a notable reduction of apoptosis in the subventricular zone and hippocampus (P < .05), abolished hypoxia-induced downregulation of IGF-1/IGF-2 expression (P < .05), and led to a significant accumulation of endogenous EPO protein and anti-inflammatory effects through modulation of interleukin-1β and tumor necrosis factor α signaling as well as upregulation of cerebral phosphorylated extracellularly regulated kinase 1/2 levels (ERK1/2). Indicating stabilizing effects on the blood-brain barrier (BBB), rhGH significantly modified cerebrovascular occludin expression. Thus, we conclude that rhGH mediates neuroprotective effects by the activation of endogenous neurotrophic growth factors and BBB stabilization. In addition, the modification of ERK1/2 pathways is involved in neuroprotective actions of rhGH. The present study adds further evidence that pharmacologic activation of neurotrophic growth factors may be a promising target for neonatal neuroprotection.

The role of prolactin in central nervous system inflammation

Prolactin has been shown to favor both the activation and suppression of the microglia and astrocytes, as well as the release of inflammatory and anti-inflammatory cytokines. Prolactin has also been associated with neuronal damage in diseases such as multiple sclerosis, epilepsy, and in experimental models of these diseases. However, studies show that prolactin has neuroprotective effects in conditions of neuronal damage and inflammation and may be used as neuroprotector factor. In this review, we first discuss general information about prolactin, then we summarize recent findings of prolactin function in inflammatory and anti-inflammatory processes and factors involved in the possible dual role of prolactin are described. Finally, we review the function of prolactin specifically in the central nervous system and how it promotes a neuroprotective effect, or that of neuronal damage, particularly in experimental autoimmune encephalomyelitis and during excitotoxicity. The overall studies indicated that prolactin may be a promising molecule for the treatment of some neurological diseases.

The protective effects of prolactin on brain injury

AIMS

Brain injuries based on their causes are divided into two categories, TBI and NTBI. TBI is caused by damages such as head injury, but non-physical injury causes NTBI. Prolactin is one of the blood factors that increase during brain injury. It has been assumed to play a regenerative role in post-injury recovery.

MATERIALS AND METHODS

In this review, various valid papers from electronic sources (including Web of Science, Scopus, PubMed, SID, Google Scholar, and ISI databases) used, which in them the protective effect of prolactin on brain injury investigated.

KEY FINDINGS

Inflammation following brain injury with the production of pro-inflammatory cytokines in the affected area can even lead to excitotoxicity and cell death in the damaged area. Medical brain damage treatments are long-term, and can have several side effects. Therefore, it is better to consider medication treatments that have fewer side effects and greater efficacy. Research suggests that prolactin has numerous regenerative effects on brain injury, and prevents cell death. Prolactin is one of the hormones produced in the body; therefore it has fewer side effects and may be more effective because it increases during brain injury.

SIGNIFICANCE

Prolactin can be used peripherally and centrally, and exerts its neuro regenerative effects against further damage post-TBI and NTBI.