Homeobox gene-encoded transcription factors in development and mature circadian function of the rodent pineal gland

Homeobox genes encode transcription factors that are widely known to control developmental processes. This is also the case in the pineal gland, a neuroendocrine brain structure devoted to nighttime synthesis of the hormone melatonin. Thus, in accordance with high prenatal gene expression, knockout studies have identified a specific set of homeobox genes that are essential for development of the pineal gland. However, as a special feature of the pineal gland, homeobox gene expression persists into adulthood, and gene product abundance exhibits 24 h circadian rhythms. Recent lines of evidence show that some homeobox genes even control expression of enzymes catalyzing melatonin synthesis. We here review current knowledge of homeobox genes in the rodent pineal gland and suggest a model for dual functions of homeobox gene-encoded transcription factors in developmental and circadian mature neuroendocrine function.

Understanding and Managing Pineal Parenchymal Tumors of Intermediate Differentiation: An In-Depth Exploration from Pathology to Adjuvant Therapies

BACKGROUND

Pineal parenchymal cell tumors constitute a rare group of primary central nervous system neoplasms (less than 1%). Their classification, especially the intermediate subtype (PPTIDs), remains challenging.

METHODS

A literature review was conducted, navigating through anatomo-pathological, radiotherapy, and neurosurgical dimensions, aiming for a holistic understanding of these tumors.

RESULTS

PPTIDs, occupying an intermediate spectrum of malignancy, reveal diverse histological patterns, mitotic activity, and distinct methylation profiles. Surgical treatment is the gold standard, but when limited to partial removal, radiotherapy becomes crucial. While surgical approaches are standardized, due to the low prevalence of the pathology and absence of randomized prospective studies, there are no shared guidelines about radiation treatment modalities.

CONCLUSION

Surgical removal remains pivotal, demanding a personalized approach based on the tumor extension. This review underscores the considerable variability in treatment approaches and reported survival rates within the existing literature, emphasizing the need for ongoing research to better define optimal therapeutic strategies and prognostic factors for PPTIDs, aiming for further and more detailed stratification among them.

Pineal cysts may promote pubertal development in girls with central precocious puberty: a single-center study from China

Introduction

Pineal cysts have long been considered a benign intracranial variation. However, in our clinical practice, it has been observed that some children with central precocious puberty (CPP) who have pineal cysts experience rapid progression in adolescent development. In recent years, there has been a significant increase in the prevalence of CPP in girls, leading to more diagnoses of CPP among children with pineal cysts. Despite this, there is no consensus regarding whether pineal cysts contribute to CPP as one of its organic factors. This study aimed to analyze the clinical characteristics of pineal cysts in children with CPP and explore the potential effects of pineal cysts on puberty development.

Methods

This single-center study retrospectively analyzed clinical data from girls aged 3 to 10 years who underwent head/pituitary magnetic resonance imaging at the Children's Hospital Affiliated to Zhengzhou University between 2019 and 2022. The study categorized the detection rates of pineal cysts based on systematic disease classification and compared the rates of cyst detection between girls diagnosed with CPP and those without CPP. Subsequently, CPP-diagnosed girls with pineal cysts were examined. Among CPP-diagnosed girls meeting the study's criteria, those with pineal cysts formed the 'cyst group,' while those without cysts were matched in a 1:1 ratio based on age and body mass index to form the 'non-cyst group.' Comparative analyses were conducted to assess the clinical characteristics between these two groups. CPP-diagnosed girls with cysts were further subdivided into three groups according to cyst size (≤5 mm, 5.1-9.9 mm, and ≥10 mm) to investigate potential differences in clinical characteristics among these subgroups. The study involved an analysis of clinical data from girls diagnosed with CPP and included imaging follow-ups to explore the progression of pineal cysts over time.

Results

Among the 23,245 girls who underwent head/pituitary magnetic resonance imaging scans, the detection rate of pineal cysts was 3.6% (837/23,245), with most cases being associated with endocrine diseases. The detection rate of pineal cysts in CPP patients was 6.4% (262/4099), which was significantly higher than the 3.0% (575/19,146) in patients without CPP. In comparison to the non-cyst group, the cyst group exhibited statistically significant increases in estradiol levels, peak luteinizing hormone (LH) levels, peak LH/follicle-stimulating hormone (FSH) ratios, uterine body length, and cervix length (P < 0.001). As cyst size increased, there were significant rises in LH peak, peak LH/FSH ratio, uterine body length, and cervical length (P < 0.01). Estradiol levels and left ovarian volume also showed an increasing trend (P < 0.05). Among girls who underwent follow-up imaging, 26.3% (5/19) exhibited an increase in cyst size.

Conclusion

Pineal cysts are relatively common in children with CPP. They may affect the pubertal development process, with larger cysts correlating to faster pubertal development. Therefore, the authors hypothesize that pineal cysts may trigger CPP in some cases, especially when the cysts are larger than 5 mm in size, as indicated by our data.

Distribution of gamma-aminobutyric acid immunoreactivity in the brain of the Siberian sturgeon (Acipenser baeri): Comparison with other fishes

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the central nervous system (CNS) of vertebrates. Immunohistochemical techniques with specific antibodies against GABA or against its synthesizing enzyme, glutamic acid decarboxylase (GAD) allowed characterizing GABAergic neurons and fibers in the CNS. However, studies on the CNS distribution of GABAergic neurons and fibers of bony fishes are scant and were done in teleost species. With the aim of understanding the early evolution of this system in bony vertebrates, we analyzed the distribution of GABA-immunoreactive (-ir) and GAD-ir neurons and fibers in the CNS of a basal ray-finned fish, the Siberian sturgeon (Chondrostei, Acipenseriformes), using immunohistochemical techniques. Our results revealed the presence and distribution of GABA/GAD-ir cells in different regions of the CNS such as olfactory bulbs, pallium and subpallium, hypothalamus, thalamus, pretectum, optic tectum, tegmentum, cerebellum, central grey, octavolateralis area, vagal lobe, rhombencephalic reticular areas, and the spinal cord. Abundant GABAergic innervation was observed in most brain regions, and GABAergic fibers were very abundant in the hypothalamic floor along the hypothalamo-hypophyseal tract and neurohypophysis. In addition, GABA-ir cerebrospinal fluid-contacting cells were observed in the alar and basal hypothalamus, saccus vasculosus, and spinal cord central canal. The distribution of GABAergic systems in the sturgeon brain shows numerous similarities to that observed in lampreys, but also to those of teleosts and tetrapods.

Exoscope-based supracerebellar infratentorial approach for a pineal meningioma in the prone position

The supracerebellar infratentorial (SCIT) approach is a well-described corridor to lesions in the quadrigeminal cistern, pineal gland, and dorsal midbrain. It can be performed in the prone or sitting position. The sitting position offers the benefit of gravity retraction of the cerebellum but comes at the expense of nonergonomic hand positioning and the potential risk of air embolism. The 3D exoscope is an alternative to the operating microscope and permits the SCIT approach in the prone position with excellent visualization. This video demonstrates exoscope-based SCIT approach for resection of a pineal meningioma in the prone position. The video can be found here: https://stream.cadmore.media/r10.3171/2023.10.FOCVID23155.

Cross-species single-cell landscape of vertebrate pineal gland

The pineal gland has evolved from a photoreceptive organ in fish to a neuroendocrine organ in mammals. This study integrated multiple daytime single-cell RNA-seq datasets from the pineal glands of zebrafish, rats, and monkeys, providing a detailed examination of the evolutionary transition at single-cell resolution. We identified key factors responsible for the anatomical and functional transformation of the pineal gland. We retrieved and integrated daytime single-cell transcriptomic datasets from the pineal glands of zebrafish, rats, and monkeys, resulting in a total of 22 431 cells after rigorous quality filtering. Comparative analysis was then conducted to elucidate the evolution of pineal cells, their photosensitivity, their role in melatonin production, and the signaling processes within the glands of these species. Our analysis identified distinct cellular compositions of the pineal gland in zebrafish, rats, and monkeys. Zebrafish photoreceptors exhibited comprehensive phototransduction gene expression, while specific genes, including transducin (Gngt1, Gnb3, and Gngt2) and phosducin (Pdc), were consistently present in mammalian pinealocytes. We found transcriptional similarities between the pineal gland and retina, underscoring shared evolutionary and functional pathways. Zebrafish displayed unique light-responsive circadian gene activity compared to rats and monkeys. Key ligand-receptor interactions were identified, especially involving MDK and PTN, influencing melatonin synthesis across species. Furthermore, we observed species-specific GPCR (G protein-coupled receptors) expressions related to melatonin synthesis and their alignment with retinal expressions. Our findings also highlighted specific transcription factors (TFs) and regulatory networks associated with pineal gland evolution and function. Our study provides a detailed analysis of the pineal gland's evolution from fish to mammals. We identified key transcriptional changes and controls that highlight the gland's functional diversity. Notably, we found significant ligand-receptor interactions influencing melatonin synthesis and demonstrated parallels between pineal and retinal expressions. These insights enhance our understanding of the pineal gland's role in phototransduction, melatonin production, and circadian rhythms in vertebrates.

Embryonic development of the chick pineal gland throughout the incubation periods

Birds have a very different pineal gland structure morphologically and cytologically. The structure of the organ shows significant changes during the incubation periods. This study, which follows the embryological development of the pineal gland and makes histomorphometric measurements of the cellular elements that make up the gland parenchyma, is a current reference for studies in these areas. These brains were taken from 24 Babcock White Leghorn chick embryos on the 10th, 13th, 16th and 21st days of incubation. At 10th embryonic day, the pineal recess was in the structure of an elongated pineal canal. Solid rosette-shaped cell clusters were transforming into round vesicles with a small lumen. These vesicles had developed into larger, oval-shaped follicles with a well-defined central lumen. On 13th day, it was observed that the number and development of follicles increased considerably. The pineal gland showed a follicular-solid structure in 16th day embryos. While the mean follicle diameter was determined as 123.46 ± 13.28 μm on the 10th embryonic day, the highest value was measured as 187.62 ± 7.37 μm on the hatching day (p < 0.05). While the mean follicle area had the lowest value in the 10th day embryos, it was determined that this value gradually increased compared to the advancing embryonic days (p < 0.05). As conclusion, it is thought that this study provides new data to the literature about pineal gland development by monitoring the histological and histomorphometric developments of chick pineal gland in different incubation periods.

Changes in Rat Adrenal Cortex and Pineal Gland in Inverted Light-Dark Cycle: A Biochemical, Histological, and Immunohistochemical Study

Poor sleep standards are common in everyday life; it is frequently linked to a rise in stress levels. The adrenal gland interacts physiologically with the pineal gland in the stress response. Pineal gland is a small endocrine organ that modulates sleep patterns. This work aimed to evaluate the inverted light-dark cycle rhythm on the histological changes within the adrenal cortex and pineal gland in adult male albino rats. Twenty adult male albino rats were equally divided into two groups: For the first control group, animals were kept on daylight-darkness for 12-12 h. The second group was kept under an inverted 12- to 12-h light-darkness cycle for 4 weeks. Adrenal sections were subjected to biochemical, histological, and immunohistochemical study. Inverted light-dark cycle group recorded a significant elevation of plasma corticosterone, tissue malondialdehyde, tumor necrosis factor-α, and interleukin-1β (IL-1β) associated with a significant reduction of catalase and superoxide dismutase. Adrenal cortex showed biochemical and histological changes. Pineal glands also showed loss of lobular architecture. A significant upregulation in activated inducible nitric oxide synthase (iNOS) and B-cell lymphoma-associated X (Bax) immunohistochemical expression was recorded in adrenal cortex associating with downregulation in B-cell lymphoma 2 (Bcl-2). It could be concluded that subchronic inverted light-dark cycle exerted direct effects on adrenal cortex and the pineal glands.

The ISL LIM-homeobox 2 transcription factor is negatively regulated by circadian adrenergic signaling to repress the expression of Aanat in pinealocytes of the rat pineal gland

Melatonin is synthesized in the pineal gland during nighttime in response to nocturnal increase in the activity of the enzyme aralkylamine N-acetyltransferase (AANAT), the transcription of which is modulated by several homeodomain transcription factors. Recent work suggests that the homeodomain transcription factor ISL LIM homeobox 2 (ISL2) is expressed in the pineal gland, but its role is currently unknown. With the purpose of identifying the mechanisms that control pineal expression of Isl2 and the possible function of Isl2 in circadian pineal biology, we report that Isl2 is specifically expressed in the pinealocytes of the rat pineal gland. Its expression exhibits a 24 h rhythm with high transcript and protein levels during the day and a trough in the second half of the night. This rhythm persists in darkness, and lesion studies reveal that it requires intact function of the suprachiasmatic nuclei, suggesting intrinsic circadian regulation. In vivo and in vitro experiments show that pineal Isl2 expression is repressed by adrenergic signaling acting via cyclic AMP; further, Isl2 is negatively regulated by the nocturnal transcription factor cone-rod homeobox. During development, pineal Isl2 expression is detectable from embryonic day 19, preceding Aanat by several days. In vitro knockdown of Isl2 is accompanied by an increase in Aanat transcript levels suggesting that ISL2 represses its daytime expression. Thus, rhythmic expression of ISL2 in pinealocytes is under the control of the suprachiasmatic nucleus acting via adrenergic signaling in the gland to repress nocturnal expression, while ISL2 itself negatively regulates daytime pineal expression of Aanat and thereby suggestively enhances the circadian rhythm in melatonin synthesis.

Indocyanine green illuminates the way to cut the tentorium in occipital transtentorial approach: technical note

BACKGROUND AND IMPORTANCE

The occipital transtentorial approach is used to address lesions at the posterior incisural space or upper cerebellum. This approach is rarely used, making standardization of the surgical procedure challenging. Here we describe the effectiveness of indocyanine green (ICG) and dye markings before tentorial incision in charting a safe and bloodless surgical trajectory for improved manoeuvrability.

CLINICAL PRESENTATION

The first case was a 40-year-old man with a residual pineal mass after chemoradiation therapy for pathologically-proven germinoma. Surgical resection was performed via left occipital craniotomy. Incision of the left cerebellar tentorium by a radiofrequency knife was preceded by visualization of the straight sinus and venous lake, which were marked with dye, enabling safe entry into the quadrigeminal cistern. Finally, total-resection of the mature teratoma was achieved. The second case was a 50-year-old man with an enhancing mass at the cerebellar vermis and left hemisphere. Left occipital craniotomy was followed by ICG administration, illuminating the straight sinus and a complex structure of dural venous channels, which were marked with dye. This visualization maximized the tentorial incision by carefully avoiding venous structures and widely exposed the upper cerebellum. Subtotal-resection of the tumor was achieved, with a diagnosis of glioblastoma.

CONCLUSION

ICG administration and dye marking are feasible and useful methods for precise identification/visualization of venous structures. They enable maximization as well as safe and appropriate tentorial incision to provide a sufficient surgical corridor for the occipital transtentorial approach.

Methadone administered to rat dams during pregnancy and lactation affects the circadian rhythms of their pups

The circadian clock is one of the most important homeostatic systems regulating the majority of physiological functions. Its proper development contributes significantly to the maintenance of health in adulthood. Methadone is recommended for the treatment of opioid use disorders during pregnancy, increasing the number of children prenatally exposed to long-acting opioids. Although early-life opioid exposure has been studied for a number of behavioral and physiological changes observed later in life, information on the relationship between the effects of methadone exposure and circadian system development is lacking. Using a rat model, we investigated the effects of prenatal and early postnatal methadone administration on the maturation of the circadian clockwork in the suprachiasmatic nucleus (SCN) and liver, the rhythm of aralkylamine N-acetyltransferase (AA-NAT) activity in the pineal gland, and gene expression in the livers of 20-day-old rats. Our data show that repeated administration of methadone to pregnant and lactating mothers has significant effect on rhythmic gene expression in the SCN and livers and on the rhythm of AA-NAT in the offspring. Similar to previous studies with morphine, the rhythm amplitudes of the clock genes in the SCN and liver were unchanged or enhanced. However, six of seven specific genes in the liver showed significant downregulation of their expression, compared to the controls in at least one experimental group. Importantly, the amplitude of the AA-NAT rhythm was significantly reduced in all methadone-treated groups. As there is a strong correlation with melatonin levels, this result could be of importance for clinical practice.

The Photoperiod-Driven Cyclical Secretion of Pineal Melatonin Regulates Seasonal Reproduction in Geese (Anser cygnoides)

The photoperiod is the predominant environmental factor that governs seasonal reproduction in animals; however, the underlying molecular regulatory mechanism has yet to be fully elucidated. Herein, Yangzhou geese (Anser cygnoides) were selected at the spring equinox (SE), summer solstice (SS), autumn equinox (AE), and winter solstice (WS), and the regulation of seasonal reproduction via the light-driven cyclical secretion of pineal melatonin was investigated. We show that there were seasonal variations in the laying rate and GSI, while the ovarian area decreased 1.5-fold from the SS to the AE. Moreover, not only did the weight and volume of the pineal gland increase with a shortened photoperiod, but the secretory activity was also enhanced. Notably, tissue distribution further revealed seasonal oscillations in melatonin receptors (Mtnrs) in the pineal gland and the hypothalamus-pituitary-gonadal (HPG) axis. The immunohistochemical staining indicated higher Mtnr levels due to the shortened photoperiod. Furthermore, the upregulation of aralkylamine N-acetyltransferase (Aanat) was observed from the SS to the AE, concurrently resulting in a downregulation of the gonadotrophin-releasing hormone (GnRH) and gonadotropins (GtHs). This trend was also evident in the secretion of hormones. These data indicate that melatonin secretion during specific seasons is indicative of alterations in the photoperiod, thereby allowing for insight into the neuroendocrine regulation of reproduction via an intrinsic molecular depiction of external photoperiodic variations.

Role and neural regulation of clock genes in the rat pineal gland: Clock modulates amplitude of rhythmic expression of Aanat encoding the melatonin-producing enzyme

Circadian clock gene expression in the suprachiasmatic nucleus (SCN) controls 24h rhythms in body functions, but clock genes are also expressed in extra-hypothalamic tissues, including the melatonin-producing pineal gland. The nocturnal increase in pineal melatonin synthesis is a hallmark in circadian biology, but the role of local clock gene oscillations in the mammalian pineal gland is unknown. The aim of this work is to determine the role of clock genes in endocrine function of the pineal gland with focus on the Aanat transcript encoding the rhythm-generating enzyme of melatonin synthesis. Using the rat as a model, we here established 24h expression patterns of clock genes in the pineal gland in vivo. Lesion studies showed that rhythmic clock gene expression in the pineal gland to a large extent depends on the SCN; further, clock gene rhythms could be reestablished in cultured pineal cells synchronized by rhythmic stimulation with norepinephrine in 12 h pulses, suggesting that pineal cells house a slave oscillator controlled by adrenergic signaling in the gland. Histological analyses showed that clock genes are expressed in pinealocytes and co-localize with Aanat transcripts, thus potentially enabling clock gene products to control cellular melatonin production. To test this, cultured pineal cells were transfected using small interfering RNA to knock down clock gene expression. While successful knockdown of Per1 had a minor effect on Aanat, Clock knockdown produced a marked overexpression of Aanat in the pinealocytes. Our study suggests that SCN-dependent rhythmic Clock gene expression in the pinealocytes regulates the daily profile of Aanat expression. This article is protected by copyright. All rights reserved.

Pineal Abnormalities in Psychosis and Mood Disorders: A Systematic Review

The pineal gland (PG) is a small interhemispheric brain structure that influences human physiology in many ways, most importantly via secretion of the hormone melatonin which is known to regulate sleep and wakefulness. Here, we systematically reviewed existing neuroimaging studies of PG structure, and/or melatonin release (MLT) in psychosis and mood disorders. Medline, PubMed, and Web of Science databases were searched (on 3 February 2023), yielding 36 studies (8 PG volume, 24 MLT). The findings showed smaller-than-normal PG volume in people with schizophrenia, regardless of symptom severity and illness stage; and smaller-than-normal PG volume in major depression, with some indication of this being present only in certain subgroups, or in those with high scores on the 'loss of interest' symptom. There was considerable evidence of lower-than-normal MLT as well as aberrant MLT secretion pattern in schizophrenia. A similar picture, though less consistent than that seen in schizophrenia, emerged in major depression and bipolar disorder, with some evidence of a transient lowering of MLT following the initiation of certain antidepressants in drug-withdrawn patients. Overall, PG and MLT aberrations appear to represent transdiagnostic biomarkers for psychosis and mood disorders, but further work is needed to establish their clinical correlates and treatment implications.

Large pineal parenchymal tumor of intermediate differentiation causing compression with resultant obstructive hydrocephalus: a case report

The epithalamus region contains the tiny, functionally endocrine pineal gland, which has the shape of a pinecone. Less than 1% of adult primary intracranial malignancies are pineal parenchymal tumors, which are incredibly uncommon brain tumors. A rare variety of pineal parenchymal tumors are those with intermediate differentiation. These tumors, whose namesake refers to a malignant pineal parenchymal tumor, are intermediate between pineoblastomas and pineocytomas (a benign pineal parenchymal tumor).

Case Presentation

A female patient, age 13, who had been experiencing terrible headaches on and off for a month, went to the emergency room. Along with the headache, she experienced nausea, vomiting, dizziness, and blurred eyesight. A nonenhanced computed tomography scan was used for the initial brain neuroimaging, which showed a hypodense mass posterior to the midbrain and superior to the cerebellum. A heterogeneous bulk was visible on MRI.

Clinical Outcome

The headache, vertigo, visual disturbance, nausea, and vomiting have all improved, according to the patient. Both postoperative MRIs with and without contrast revealed the resolution of the obstructive hydrocephalus and the absence of any residual enhancing mass. The patient was followed up for 2 months without any complications or adverse events.

Conclusion

One should carefully investigate a headache as the early symptom of many illnesses and rule out any other potential causes. This would therefore enable us to create a management structure for such a very unusual malignancy.

Long-Term Survival of Patients With Glioblastoma of the Pineal Gland: A ChatGPT-Assisted, Updated Case of a Multimodal Treatment Strategy Resulting in Extremely Long Overall Survival at a Site With Historically Poor Outcomes

We present an updated case report of a patient with glioblastoma isolated to the pineal gland with an overall survival greater than five years and no progression of focal central nervous system (CNS) deficits since initial presentation. The patient underwent radiotherapy up to 60 Gy with concurrent and adjuvant temozolomide with the use of non-standard treatment volumes that included the ventricular system. The utilization of ventricular irradiation as well as the addition of bevacizumab at disease recurrence may have encouraged this unusually long survival by preventing/delaying leptomeningeal spread. We also present an updated review of the literature, which shows a median survival of six months, reinforcing the patients atypical disease trajectory. Finally, we utilize OpenAI's language model ChatGPT to aid in synthesizing this manuscript. In doing so, we demonstrate that ChatGPT is apt at creating concise summaries of relevant literature and topic subjects, however its output is often repetitive with similar sentence/paragraph structure, less than ideal grammar and poor syntax requiring editing. Thus, in its current iteration, ChatGPT is a helpful aid that cuts down on the time spent in data acquisition and processing but is not a replacement for human input in the creation of quality medical literature.

Retinoic Acid Signalling in the Pineal Gland Is Conserved across Mammalian Species and Its Transcriptional Activity Is Inhibited by Melatonin

The pineal gland is integral to the circadian timing system due to its role in nightly melatonin production. Retinoic acid (RA) is a potent regulator of gene transcription and has previously been found to exhibit diurnal changes in synthesis and signalling in the rat pineal gland. This study investigated the potential for the interaction of these two systems. PCR was used to study gene expression in mouse and human pineal glands, ex-vivo organotypic cultured rat pineal gland and cell lines. The mouse and human pineal glands were both found to express the necessary components required for RA signalling. RA influences the circadian clock in the brain, therefore the short-term effect of RA on clock gene expression was determined in ex vivo rat pineal glands but was not found to rapidly regulate Per1, Per2, Bmal1, or Cry1. The interaction between RA and melatonin was also investigated and, unexpectedly, melatonin was found to suppress the induction of gene transcription by RA. This study demonstrates that pineal expression of the RA signalling system is conserved across mammalian species. There is no short-term regulation of the circadian clock but an inhibitory effect of melatonin on RA transcriptional activity was demonstrated, suggesting that there may be functional cross-talk between these systems.

Melatonin: Both a Messenger of Darkness and a Participant in the Cellular Actions of Non-Visible Solar Radiation of Near Infrared Light

Throughout the history of melatonin research, almost exclusive focus has been on nocturnally-generated pineal melatonin production, which accounts for its circadian rhythm in the blood and cerebrospinal fluid; these light/dark melatonin cycles drive the daily and seasonal photoperiodic alterations in organismal physiology. Because pineal melatonin is produced and secreted primarily at night, it is referred to as the chemical expression of darkness. The importance of the other sources of melatonin has almost been ignored. Based on current evidence, there are at least four sources of melatonin in vertebrates that contribute to the whole-body melatonin pool. These include melatonin produced by (1) the pineal gland; (2) extrapineal cells, tissues, and organs; (3) the microbiota of the skin, mouth, nose, digestive tract, and vagina as well as (4) melatonin present in the diet. These multiple sources of melatonin exhibit differentially regulated mechanisms for its synthesis. Visible light striking the retina or an intense physical stimulus can suppress nocturnal pineal melatonin levels; in contrast, there are examples where extrapineal melatonin levels are increased during heavy exercise in daylight, which contains the whole range of NIR radiation. The cumulative impact of all cells producing augmented extrapineal melatonin is sufficient to elevate sweat concentrations, and potentially, if the exposure is sustained, to also increasing the circulating values. The transient increases in sweat and plasma melatonin support the premise that extrapineal melatonin has a production capacity that exceeds by far what can be produced by the pineal gland, and is used to maintain intercellular homeostasis and responds to rapid changes in ROS density. The potential regulatory mechanisms of near infrared light (NIR) on melatonin synthesis are discussed in detail herein. Combined with the discovery of high levels of melanopsin in most fat cells and their response to light further calls into question pineal centric theories. While the regulatory processes related to microbiota-derived melatonin are currently unknown, there does seem to be crosstalk between melatonin derived from the host and that originating from microbiota.

Exploring differentially expressed genes in hypothalamic, pars tuberalis and pineal gland transcriptomes in different sexual behavior phenotypes in rams using RNA-Seq

Reproductive seasonality is a limiting factor in sheep production. Sexual behavior is a key element in reproductive efficiency, and this function is regulated by the hypothalamus-pituitary-gonadal (HPG) axis. To understand the mechanisms of sexual behavior, transcriptomic sequencing technology was used to identify differentially expressed genes (DEGs) in the hypothalamus (HT), pars tuberalis (PT) and pineal gland (PG) in Rasa Aragonesa rams with different sexual behavior. Bioinformatics analysis of the 16,401 identified genes by RNA-Seq revealed 103 and 12 DEGs in the HT and the PG, respectively, at a false discovery rate (FDR) of 5% with an absolute value of expression ≥ 1 (log2FC). However, no DEGs were found in the PT. Functional annotation and pathway enrichment analysis showed that DEGs of HT were enriched mainly in neuroactive ligand-receptor interactions and signaling pathways, including notable candidate genes such as MTNR1A, CHRNA2, FSHB, LHB, GNRHR, AVP, PRL, PDYN, CGA, GABRD, and TSHB, which play a crucial role in sexual behavior. The GnRH and cAMP signaling pathways were also highlighted. In addition, gene set enrichment analysis (GSEA) identified potential pathways, dominated mainly by biological process category, that could be responsible for the differences in sexual behavior observed in rams. The intracellular protein transport and pattern specification process were enriched within the PT and the transcription factor binding and protein ubiquitination pathways for the PG. Thus, these pathways together may play an important role in the regulation of the sexual behavior in Rasa Aragonesa rams through the hypothalamic-pituitary-gonadal axis. The validation of 5 DEGs using reverse transcription quantitative polymerase chain reaction (RT-qPCR) showed expression patterns like the found with RNA-Seq. Overall, these results contribute to understanding the genomic basis of sexual behavior in rams. Our study demonstrates that multiple networks and pathways orchestrate sexual behavior in sheep.

Digital histological morphometry of the human pineal gland in a postmortem study, with endocrine and neurological clinical implications

The pineal gland is a small-sized, photo neuroendocrine organ in the midline of the brain that synthesises and secretes melatonin and serotonin. Chords and islands of pinealocytes constitute the secretory parenchyma, while glial tissue and calcifications represent degenerative changes. This study examined human postmortem pineal glands to microscopically assess morphological changes possibly associated with clinical data, by using digital techniques. A retrospective autopsy study has been performed on 72 paediatric and adult autopsy cases. The glands have been processed for histological analysis and immunohistochemical staining with synaptophysin (SYN), neuron-specific enolase (NSE), and neurofilament (NF). Slides were digitally scanned. Morphometric data were obtained using CaseViewer and ImageJ. The comorbidities used for correlation with morphometric data were obesity, type 2 diabetes, adrenal gland adenoma, goitre, chronic pancreatitis, arterial hypertension, and mixed dementia. Thirty-three females and 39 males were included in the study. Increased secretory parenchyma was found in patients with chronic pancreatitis, arterial hypertension, and adrenal gland adenoma. Reduced activity was found in patients with type 2 diabetes, obesity, advanced pineal calcification, mixed dementia, and old age. There were no changes associated with goitre, cachexia, or Willis's polygon atherosclerosis. No significant differences between gender were found. The activity of the pineal gland can be assessed by quantitative immunohistochemistry of neuroendocrine and structural pinealocyte markers and observation of glial tissue and calcifications. There is a need for further research to evaluate the clinical impact of these morphological changes on the neuroendocrine systems, with clinical implications in endocrinology, neurology, and even psychiatry. Digital techniques offer a more exact analysis of histological data.

Microglia in Circumventricular Organs: The Pineal Gland Example

The circumventricular organs (CVOs) are unique areas within the central nervous system. They serve as a portal for the rest of the body and, as such, lack a blood-brain barrier. Microglia are the primary resident immune cells of the brain parenchyma. Within the CVOs, microglial cells find themselves continuously challenged and stimulated by local and systemic stimuli, even under steady-state conditions. Therefore, CVO microglia in their typical state often resemble the activated microglial forms found elsewhere in the brain as they are responding to pathological conditions or other stressors. In this review, I focus on the dynamics of CVO microglia, using the pineal gland as a specific CVO example. Data related to microglia heterogeneity in both homeostatic and unhealthy environments are presented and discussed, including those recently generated by using advanced single-cell and single-nucleus technology. Finally, perspectives in the CVO microglia field are also included.Summary StatementMicroglia in circumventricular organs (CVOs) continuously adapt to react differentially to the diverse challenges they face. Herein, I discuss microglia heterogeneity in CVOs, including pineal gland. Further studies are needed to better understand microglia dynamics in these unique brain areas. .

Physiological and pharmacological perspectives of melatonin

The pineal gland is a interface between light-dark cycle and shows neuro-endocrine functions. Melatonin is the primary hormone of pineal gland, secreted at night. The night-time melatonin peak regulates the physiological functions at dark. Melatonin has several unique features as it synchronises internal rhythm with daily and seasonal variations, regulates circadian rhythm and sleep-wake cycle. Physiologically melatonin involves in detoxification of free radicals, immune functions, neuro-protection, oncostatic effects, cardiovascular functions, reproduction, and foetal development. The precise functions of melatonin are exhibited by specific receptors. In relation to pathophysiology, impaired melatonin secretion promotes sleep disorder, cancer progression, type-2 diabetes, and neurodegenerative diseases. Several reports have highlighted the therapeutic benefits of melatonin specially related to cancer protection, sleep disorder, psychiatric disorders, and jet lag problems. This review will touch the most of the area of melatonin-oriented health impacts and its therapeutic aspects.

Melatonin Modulation of Radiation-Induced Molecular Changes in MCF-7 Human Breast Cancer Cells

Radiation therapy is an important component of cancer treatment scheduled for cancer patients, although it can cause numerous deleterious effects. The use of adjuvant molecules aims to limit the damage in normal surrounding tissues and enhance the effects of radiation therapy, either killing tumor cells or slowing down their growth. Melatonin, an indoleamine released by the pineal gland, behaves as a radiosensitizer in breast cancer, since it enhances the therapeutic effects of ionizing radiation and mitigates side effects on normal cells. However, the molecular mechanisms through which melatonin modulates the molecular changes triggered by radiotherapy remain mostly unknown. Here, we report that melatonin potentiated the anti-proliferative effect of radiation in MCF-7 cells. Treatment with ionizing radiation induced changes in the expression of many genes. Out of a total of 25 genes altered by radiation, melatonin potentiated changes in 13 of them, whereas the effect was reverted in another 10 cases. Among them, melatonin elevated the levels of PTEN and NME1, and decreased the levels of SNAI2, ERBB2, AKT, SERPINE1, SFN, PLAU, ATM and N3RC1. We also analyzed the expression of several microRNAs and found that melatonin enhanced the effect of radiation on the levels of miR-20a, miR-19a, miR-93, miR-20b and miR-29a. Rather surprisingly, radiation induced miR-17, miR-141 and miR-15a but melatonin treatment prior to radiation counteracted this stimulatory effect. Radiation alone enhanced the expression of the cancer suppressor miR-34a, and melatonin strongly stimulated this effect. Melatonin further enhanced the radiation-mediated inhibition of Akt. Finally, in an in vivo assay, melatonin restrained new vascularization in combination with ionizing radiation. Our results confirm that melatonin blocks many of the undesirable effects of ionizing radiation in MCF-7 cells and enhances changes that lead to optimized treatment results. This article highlights the effectiveness of melatonin as both a radiosensitizer and a radioprotector in breast cancer. Melatonin is an effective adjuvant molecule to radiotherapy, promoting anti-cancer therapeutic effects in cancer treatment. Melatonin modulates molecular pathways altered by radiation, and its use in clinic might lead to improved therapeutic outcomes by enhancing the sensitivity of cancerous cells to radiation and, in general, reversing their resistance toward currently applied therapeutic modalities.

GnRH and the photoperiodic control of seasonal reproduction: Delegating the task to kisspeptin and RFRP-3

Synchronization of mammalian breeding activity to the annual change of photoperiod and environmental conditions is of the utmost importance for individual survival and species perpetuation. Subsequent to the early 1960s, when the central role of melatonin in this adaptive process was demonstrated, our comprehension of the mechanisms through which light regulates gonadal activity has increased considerably. The current model for the photoperiodic neuroendocrine system points to pivotal roles for the melatonin-sensitive pars tuberalis (PT) and its seasonally-regulated production of thyroid-stimulating hormone (TSH), as well as for TSH-sensitive hypothalamic tanycytes, radial glia-like cells located in the basal part of the third ventricle. Tanycytes respond to TSH through increased expression of thyroid hormone (TH) deiodinase 2 (Dio2), which leads to heightened production of intrahypothalamic triiodothyronine (T3) during longer days of spring and summer. There is strong evidence that this local, long-day driven, increase in T3 links melatonin input at the PT to gonadotropin-releasing hormone (GnRH) output, to align breeding with the seasons. The mechanism(s) through which T3 impinges upon GnRH remain(s) unclear. However, two distinct neuronal populations of the medio-basal hypothalamus, which express the (Arg)(Phe)-amide peptides kisspeptin and RFamide-related peptide-3, appear to be well-positioned to relay this seasonal T3 message towards GnRH neurons. Here, we summarize our current understanding of the cellular, molecular and neuroendocrine players, which keep track of photoperiod and ultimately govern GnRH output and seasonal breeding.

Genetic ablation of the Bsx homeodomain transcription factor in zebrafish: Impact on mature pineal gland morphology and circadian behavior

The pineal gland is a neuroendocrine structure in the brain, which produces and secretes the hormone melatonin at nighttime and is considered a key element in the circadian clock system. Early morphogenesis of the gland is controlled by a number of transcription factors, some of which remain active in adult life. One of these is the brain-specific homeobox (Bsx), a highly conserved homeodomain transcription factor with a developmental role in the pineal gland of several species, including zebrafish, and regulatory roles in mature pinealocytes of the rat. To determine the role of Bsx in circadian biology, we here examined the effects of a bsx loss-of-function mutation on the pineal gland in adult zebrafish and on behavioral circadian rhythms in larvae. In pineal cell type-specific Gfp/Egfp reporter zebrafish lines, we did not detect fluorescence signals in the pineal area of homozygous (bsx^-/- ) mutants. Interestingly, a nonpigmented area on the dorsal surface of the head above the gland, known as the pineal window, was pigmented in the homozygous mutants. Furthermore, a structure corresponding to the pineal gland was not detectable in the midline of the adult brain in histological sections analyzed by Nissl staining and S-antigen immunohistochemistry. Moreover, the levels of pineal transcripts were greatly reduced in bsx^-/- mutants, as revealed by quantitative real-time polymerase chain reaction analysis. Notably, analysis of locomotor activity at the larval stage revealed altered circadian rhythmicity in the bsx mutants with periods and phases similar to wildtype, but severely reduced amplitudes in locomotor activity patterns. Thus, Bsx is essential for full development of the pineal gland, with its absence resulting in a phenotype of morphological pineal gland ablation and disrupted circadian behavior.

Profiling Temporal Changes of the Pineal Transcriptomes at Single Cell Level Upon Neonatal HIBD

Neonatal hypoxic-ischemic brain damage (HIBD) often results in various neurological deficits. Among them, a common, yet often neglected, symptom is circadian rhythm disorders. Previous studies revealed that the occurrence of cysts in the pineal gland, an organ known to regulate circadian rhythm, is associated with circadian problems in children with HIBD. However, the underlying mechanisms of pineal dependent dysfunctions post HIBD remain largely elusive. Here, by performing 10x single cell RNA sequencing, we firstly molecularly identified distinct pineal cell types and explored their transcriptome changes at single cell level at 24 and 72 h post neonatal HIBD. Bioinformatic analysis of cell prioritization showed that both subtypes of pinealocytes, the predominant component of the pineal gland, were mostly affected. We then went further to investigate how distinct pineal cell types responded to neonatal HIBD. Within pinealocytes, we revealed a molecularly defined β to α subtype conversion induced by neonatal HIBD. Within astrocytes, we discovered that all three subtypes responded to neonatal HIBD, with differential expression of reactive astrocytes markers. Two subtypes of microglia cells were both activated by HIBD, marked by up-regulation of Ccl3. Notably, microglia cells showed substantial reduction at 72 h post HIBD. Further investigation revealed that pyroptosis preferentially occurred in pineal microglia through NLRP3-Caspase-1-GSDMD signaling pathway. Taken together, our results delineated temporal changes of molecular and cellular events occurring in the pineal gland following neonatal HIBD. By revealing pyroptosis in the pineal gland, our study also provided potential therapeutic targets for preventing extravasation of pineal pathology and thus improving circadian rhythm dysfunction in neonates with HIBD.

Pineal germinoma in a young adult: A case report

BACKGROUND

Intracranial germinomas (GN) are rare cancers that primarily affect children, making them rarer still in adults. Standard treatment for this neoplasm includes neoadjuvant chemotherapy (NC) followed by radiotherapy (RT) or RT at a higher dose and larger field. These recommendations are based on studies focused mostly on children; it is currently unclear whether this treatment is applicable to adults.

CASE

We present a case of a 23-year-old adult male with no underlying pathologies, drug allergies, or family history of cancer, who presented for medical evaluation with blurred vision, diplopia, forgetfulness, and weight loss starting 3-4 months before the evaluation. Clinical examination indicated Parinaud's Syndrome. Magnetic resonance imaging (MRI) and computed tomography (CT) revealed a pineal tumor with ependymal dissemination in both lateral ventricles, which was causing obstructive hydrocephalus. The patient had surgery consisting of ventriculostomy, Holter shunt insertion, cisternal ventricular intubation, and cisterna magna anastomosis to improve ventricular drainage. Pathology confirmed pineal germinoma. Cerebrospinal fluid cytology and MRI of the axis were negative. Four cycles of NC were given to the patient (carboplatin, etoposide, and ifosfamide), with reduced dosage. Once a partial volumetric response was confirmed, whole-ventricular radiotherapy (WVR) was initiated with a total tumor bed dose of 45 Gy over 25 sessions in 5 weeks. Optimum clinical results were observed, and no short-term (<90 day) radiation toxicity was observed. The patient was able to resume his normal activities soon after treatment. Follow-ups over 2 years post-surgery indicated continued control of the lesion and absence of symptoms except for mild diplopia.

CONCLUSION

Although this is a case report, these data suggest that a reduced NC course and WVR may effectively treat adult GN. This protocol likely decreases the risk of undesirable NC and RT secondary effects, while providing excellent local control; however, using a narrower RT field is not recommended.

Anatomical and histological investigation of the pineal gland in the lake van fish (Alburnus tarichi (Güldenstädt, 1814))

The pineal gland and melatonin secreted from the gland regulate the biological clock and adaptation to seasonal changes, glucose balance, nutrition and locomotor activities. In this study, the pineal gland of the Lake Van fish was examined anatomically and histologically. The melatonin level secreted from the pineal gland was determined in fish plasma sampled from both lakes and streams during reproduction migration. The pineal gland in the Lake Van fish, as in other teleost fish, is located in the head, under the translucent pineal window, which does not contain many pigment cells. The gland consists of pineal vesicle and pineal stalk parts on the dorsal sac in the Lake Van fish. It was determined that the pineal gland showed good vascularity. The presence of pinealocytes and different types of cells in the pineal organ was determined histologically. Pinealocytes were intensely localized in the lumen of the pineal vesicle. The plasma melatonin level increased in fish passing from lake to stream for reproductive migration.

Adult Primary Pineal Alveolar Rhabdomyosarcoma with FOXO1 Gene Rearrangement and OLIG2 Expression: A Rare Case Report and Literature Review

Alveolar rhabdomyosarcoma is a common malignant soft tissue tumor in child and adolescents. Intracranial alveolar rhabdomyosarcoma in adults is rare, especially in the pineal region. We present a case of primary alveolar rhabdomyosarcoma of the pineal gland in a 36-year-old Chinese male with a chief complaint of dizziness, headache and a loss of balance when walking. Imaging identified a space-occupying mass in the pineal region with obstructive hydrocephalus. An endoscopic-assisted pineal mass resection was performed. Pathology revealed a solid, sheet-like growth of medium-sized, round or oval cells with map-like necrosis and some rhabdomyoblasts. The tumor cells were diffusely positive for desmin, myogenin, MyoD1, ALK, and OLIG2. Fluorescence in situ hybridization (FISH) detected FOXO1 gene rearrangement. This rare case is presented to expand the knowledge of pineal gland tumors and alert us to pay attention to the differential diagnosis of OLIG2-positive round-cell tumors of the central nervous system.

Pineal gland hypermetabolic involvement without central nervous system symptoms in a pediatric patient with primary nodular sclerosis subtype classical Hodgkin Lymphoma

This case report presents the first reported pediatric case of primary classical nodular sclerosing Hodgkin Lymphoma (HL) with pineal gland involvement, presenting without CNS symptoms, which completely resolved after 2 cycles of chemotherapy. The 12 year-old male first presented with a right inguinal mass and external iliac lymphadenopathy accompanied by B symptoms. He was diagnosed with stage IV B classical HL, and as part of the staging work-up, a full-body PET/CT scan was performed. In addition to the right inguinal mass, the PET/CT demonstrated increased FDG uptake at the pineal gland along with level II lymph nodes. The patient was treated with ABVE-PC chemotherapy (Doxorubicin, Bleomycin, Vincristine, Etoposide, Prednisone, and Cyclophosphamide) as per standard arm of AHOD1331 COG protocol for newly diagnosed high-risk HL patients, which resolved the pineal mass after 2 cycles without requiring radiation therapy. Following 5 cycles, a full-body PET/CT showed no brain or neck activity, along with decreased size and activity of the right groin mass. To our knowledge, there are no other documented cases of primary HL with specific pineal involvement, and no cases that lack CNS symptoms altogether like this one did. Additionally, this is the third published pediatric case of primary CNS-HL, both of the previous cases were treated with radiotherapy and presented with CNS symptoms. Thus, this case demonstrates the importance of ordering a full-body PET/CT as part of the initial HL work-up and provides evidence that chemotherapy alone is a treatment option for some patients with primary intracranial HL.

Asynchronous pineoblastoma is more likely after early diagnosis of retinoblastoma: a meta-analysis

Purpose

To determine the risk of patients with an early diagnosis of heritable retinoblastoma being diagnosed with TRb (or pineoblastoma) asynchronously in a later stage and its effect on screening.

Methods

We updated the search (PubMed and Embase) for published literature as performed by our research group in 2014 and 2019. Trilateral retinoblastoma (TRb) patients were eligible for inclusion if identifiable as unique and the age at which TRb was diagnosed was available. The search yielded 97 new studies. Three new studies and eight new patients were included. Combined with 189 patients from the previous meta‐analysis, the database included 197 patients. The main outcome was the percentage of asynchronous TRb in patients diagnosed before and after preset age thresholds of 6 and 12 months of age at retinoblastoma diagnosis.

Results

Seventy‐nine per cent of patients with pineoblastoma are diagnosed with retinoblastoma before the age of 12 months. However, baseline MRI screening at time of retinoblastoma diagnosis fails to detect the later diagnosed pineal TRb in 89% of patients. We modelled that an additional MRI performed at the age of 29 months picks up 53% of pineoblastomas in an asymptomatic phase. The detection rate increased to 72%, 87% and 92%, respectively, with 2, 3 and 4 additional MRIs.

Conclusions

An MRI of the brain in heritable retinoblastoma before the age of 12 months misses most pineoblastomas, while retinoblastomas are diagnosed most often before the age of 12 months. Optimally timed additional MRI scans of the brain can increase the asymptomatic detection rate of pineoblastoma.

Epidemiology, Management, and Long-Term Survival Outcomes of Intracranial Typical Site Germinomas: An Analysis of the Surveillance, Epidemiology, and End-Results (SEER) Database

BACKGROUND

The correlations of epidemiological characteristics and clinical outcomes with different tumor sites in patients with intracranial typical site germinomas (ICTSGs) have not yet been well established. We analyzed ICTSGs using a multicenter database, focusing on its demographic, management patterns, and long-term survival outcomes.

METHODS

Patients diagnosed with ICTSGs were selected from the Surveillance, Epidemiology, and End-Results (SEER) database. Demographic information and management patterns of ICTSGs were extracted for data analysis stratified by different tumor sites. Kaplan-Meier curves were used to evaluate the survival outcome stratified by treatment, tumor site and tumor size.

RESULTS

Among the 327 patients enrolled in the study, 16.21% had tumors located in the suprasellar region and 83.79% in the pineal region. The proportion of males was significantly higher among pineal germinomas (94.16 vs 66.04%; P < .001). Smaller tumors (<24 mm) were more common in the suprasellar region (37.74 vs 18.87%; P < .001). A higher percentage of patients with suprasellar germinomas underwent surgery. Radiotherapy (RT) and chemotherapy (CT) was, respectively, administered to 82.97 and 60.61% of patients during the treatment period, with no significant difference between suprasellar and pineal germinomas. CT plus RT was the most common treatment modality for both pituitary (30.19%) and pineal (33.94%) germinomas. Both RT and CT were associated with improved long-term survival. No survival difference was observed between suprasellar and pineal germinomas.

CONCLUSIONS

Despite significant differences in epidemiology and management, pineal and suprasellar germinomas had a similar long-term clinical outcome.

AAV vectors accumulate in the pineal gland after injections into the brain or spinal cord

AAV vectors are being used extensively for gene-modifying therapies for neurological disorders. Here, we report the surprising discovery that injections of different AAVs into the brain, spinal cord, or cerebrospinal fluid (CSF) lead to robust transduction of cells in the pineal gland. We document transduction of cells in the pineal gland following focal injections of AAV2/9-shPTEN-zsGreen into the sensorimotor or hippocampus of rats and injections of AAV2/Cre into the spinal cord of transgenic mice with a stop-flox tdT reporter. Pineal transduction was evident even when AAV2/Cre injections were made into the lumbar spinal cord many millimeters distant from the pineal gland. Immunostaining with antibodies for cell types in the pineal gland revealed that pinealocytes were transduced. Pineal transduction was also observed with intracerebroventricular (i.c.v.) injections of AAV2/9-shPTEN-zsGreen, suggesting that pineal transduction following focal injections of AAV into CNS parenchyma may be caused by diffusion of the vector from the injection sites into the CSF and then accumulation in the pineal gland. Together, these findings suggest the need for vigilance for functional consequences and possible adverse effects of off-target accumulation of therapeutic AAVs in the pineal gland and AAV-driven expression of therapeutic cargos in pinealocytes.

Incidence, Prognostic Factors, and Survival Trend in Pineal Gland Tumors: A Population-Based Analysis

Introduction

Pineal gland tumors are exceedingly rare and account for 0.4-1.0% of brain neoplasms. Their rarity has confounded a clear understanding of the prognostic factors and standards of care for these neoplasms. In this study, we aimed to investigate the incidence, prognostic indicators, and survival trend of tumors emanating from the pineal gland.

Methods

We accessed the Surveillance, Epidemiology, End Results (SEER) Program for pineal gland tumors from 1975-2016. A multivariate Cox regression model was used to investigate the impact of clinicopathological parameters on all-cause mortality. For survival trend analysis, we employed the Kaplan Meier curve and pairwise comparisons to examine the trend.

Results

We found 1,792 and 310,003 pineal gland and brain neoplasms during 1975-2016 resulting in an incidence of 0.6%. In the multivariate Cox proportional hazards model, older age, male gender, non-germ cell tumor, and receipt of chemotherapy were significantly associated with poor survival (p < 0.001). The extent of resection and radiotherapy administration did not produce survival advantages. Our result also highlighted an increased survival of pineal gland tumors over the years.

Conclusion

Our study investigated the prognostic factors that influenced survival in patients with pineal gland tumors. Chemotherapy use adversely affected patient outcomes and should be considered carefully in specific circumstances to avoid its harmful effects. These findings provide important evidence to improve current standards of care for this rare group of tumors. The survival of pineal tumors has improved over time reflecting improvements in current practice.

Serotonin modulates melatonin synthesis as an autocrine neurotransmitter in the pineal gland

The pineal gland secretes melatonin principally at night. Regulated by norepinephrine released from sympathetic nerve terminals, adrenergic receptors on pinealocytes activate aralkylamine N-acetyltransferase that converts 5-hydroxytryptamine (5-HT, serotonin) to N-acetylserotonin, the precursor of melatonin. Previous studies from our group and others reveal significant constitutive secretion of 5-HT from pinealocytes. Here, using mass spectrometry, we demonstrated that the 5-HT is secreted primarily via a decynium-22-sensitive equilibrative plasma membrane monoamine transporter instead of by typical exocytotic quantal secretion. Activation of the endogenous 5-HT receptors on pinealocytes evoked an intracellular Ca²⁺ rise that was blocked by RS-102221, an antagonist of 5-HT_2C receptors. Applied 5-HT did not evoke melatonin secretion by itself, but it did potentiate melatonin secretion evoked by submaximal norepinephrine. In addition, RS-102221 reduced the norepinephrine-induced melatonin secretion in strips of pineal gland, even when no exogenous 5-HT was added, suggesting that the 5-HT that is constitutively released from pinealocytes accumulates enough in the tissue to act as an autocrine feedback signal sensitizing melatonin release.

The Circadian Rhythms of STAT3 in the Rat Pineal Gland and Its Involvement in Arylalkylamine-N-Acetyltransferase Regulation

In rodents, the melatonin production by the pineal gland is controlled through adrenergic signaling from the suprachiasmatic nuclei and regulation of the principal enzyme in its synthesis, arylalkylamine-N-acetyltransferase (AANAT). In the present study, we identified increased isoprenaline-induced aa-nat expression and nocturnal AANAT activity in the pineal glands in response to the silencing of the signal transducer and activator of transcription 3 (STAT3) with siRNA or STAT3 inhibitors WP1066 and AZD1480. This AANAT activity enhancement in vivo did not interfere with light-induced AANAT suppression. Systemic or in vitro lipopolysaccharide (LPS) administration markedly increased Stat3 expression and STAT3 phosphorylation, but it did not significantly affect AANAT expression or activity. Simultaneous LPS administration and Stat3 silencing enhanced the aa-nat transcription and AANAT activity to a similar extent as Stat3 inhibition without LPS co-administration. Furthermore, we describe the circadian rhythmicity in Stat3 expression and the phosphorylated form of STAT3 protein in the rat pineal gland. Our data suggest that the higher nocturnal endogenous level of STAT3 in the pineal gland decelerates or hampers the process of NA-induced AANAT activation or affects the AANAT enzyme stability.

The role of homeobox gene-encoded transcription factors in regulation of phototransduction: Implementing the primary pinealocyte culture as a photoreceptor model

Homeobox genes encode transcription factors controlling development; however, a number of homeobox genes are expressed postnatally specifically in melatonin-producing pinealocytes of the pineal gland and photoreceptors of the retina along with transcripts devoted to melatonin synthesis and phototransduction. Homeobox genes regulate melatonin synthesis in pinealocytes, but some homeobox genes also seem to be involved in regulation of retinal phototransduction. Due to the lack of photoreceptor models, we here introduce the rat pinealocyte culture as an in vitro model for studying retinal phototransduction. Systematic qPCR analyses were performed on the rat retina and pineal gland in 24 hour in vivo series and on primary cultures of rat pinealocytes: All homeobox genes and melatonin synthesis components, as well as nine out of ten phototransduction genes, were readily detectable in all three experimental settings, confirming molecular similarity between cultured pinealocytes and in vivo retinal tissue. 24 hours circadian expression was mostly confined to transcripts in the pineal gland, including a novel rhythm in arrestin (Sag). Individual knockdown of the homeobox genes orthodenticle homeobox 2 (Otx2), cone-rod homeobox (Crx) and LIM homeobox 4 (Lhx4) in pinealocyte culture using siRNA resulted in specific downregulation of transcripts representing all levels of phototransduction; thus, all phototransduction genes studied in culture were affected by one or several siRNA treatments. Histological colocalization of homeobox and phototransduction transcripts in the rat retinal photoreceptor was confirmed by RNAscope in situ hybridization, thus suggesting that homeobox gene-encoded transcription factors control postnatal expression of phototransduction genes in the retinal photoreceptor.

Melatonin: A regulator of the interplay between FoxO1, miR96, and miR215 signaling to diminish the growth, survival, and metastasis of murine adenocarcinoma

Melatonin (Mel.), also known as the magic hormone, is a nocturnally secreted hormone orchestrates the clearance of free radicals that have been built up and cumulated during day. This study aims to detect the impact of pineal gland removal on the incidence of tumor development and to assess the signaling pathways via which exogenous melatonin counteract cancer growth. This goal has been achieved by novel approach for pineal destruction using dental micromotor which validated by melatonin downregulation in blood plasma. Mice were injected sub-cutenously with Ehrlich cells to develop solid tumor as a murine model of breast cancer. The increase at tumor markers carcino embryonic antigen, TNFα, and nuclear factor kappa-light-chain-enhancer of activated B cells was over countered by exogenous melatonin supplementation (20 mg/kg) daily for 1 month. The anticancer effects of melatonin were significantly mediated by scavenging H₂ O₂ and NO and diminishing of lipid peroxidation marker malondialdehyde. The real-time polymerase chain Rx analyses indicated a significant effect of Melatonin in upregulating the expression of miR215, fork head box protein O1 (foxO1), and downregulation of miR96. Flowcytometric analyses indicated a significant effect of melatonin on induction of cell cycle arrest at G1 phase which was further confirmed by Ki67 downregulation. Immunohistochemical analyses indicated the role of melatonin in upregulating P53-dependent apoptosis and downregulating CD44 signaling for survivin, matrix metallo-protein kinase 2, and vascular endothelial growth factor to inhibit cell survival and metastasis. In conclusion, this study sheds the light on M./P53/miR215/CD44 with an emphasis on M./miR96//foxO1 signaling cascades, as a novel pathway of melatonin signaling in adenocarcinoma to diminish cancer cell growth, survival and metastasis.

DESCARTES and his project of a fantasized brain

Interest in anatomy dates from the earliest times. Such knowledge was acquired through dissections of animals and human corpses by many researchers. The macroscopic anatomy of the varied structures of the brain were identified over the centuries, and the predominating solid substance was seen as amorphous, and devoid of any specific function, until the Renaissance. René Descartes, a personage with a brilliant and creative mind, conceived the brain, its structure and function, in a distinct manner to what was known at his time. He valued the solid matter and gave it, for the first time, a theoretical minute structure, related to a presumptive function based on the presence of the pineal gland and the animal spirits, underlying cognitive, sensory and motor activities. Such structural view was endorsed, in a given sense, by the microscopic findings of Marcello Malpighi, which begun to change the understanding of the nervous system.

A hypothetical role for autophagy during the day/night rhythm-regulated melatonin synthesis in the rat pineal gland

Melatonin is a highly conserved molecule that regulates day/night rhythms; it is associated with sleep improvement, reactive oxygen species (ROS) scavenging, anti-aging effects, and seasonal and circadian rhythms and has been a hot topic of research for decades. Using single-cell RNA sequencing, a recent study describes a single-cell transcriptome atlas for the rat pineal gland. Based on a more comprehensive analysis of the retrieved data (Mays et al., PLoS One, 2018, 13, e0205883), results from the current study unveiled the underappreciated gene regulatory network behind different cell populations in the pineal gland. More importantly, our study here characterized, for the first time, the day/night activation of autophagy flux in the rat pineal gland, indicating a potential role of autophagy in regulating melatonin synthesis in the rat pineal gland. These findings emphasized a hypothetical role of day/night autophagy in linking the biological clock with melatonin synthesis. Furthermore, ultrastructure analysis of pinealocytes provided fascinating insights into differences in their intracellular structure between daytime and nighttime. In addition, we also provide a preliminary description of cell-cell communication in the rat pineal gland. In summary, the current study unveils the day/night regulation of autophagy in the rat pineal gland, raising a potential role of autophagy in day/night-regulated melatonin synthesis.

Pineal region tumors: pathophysiological mechanisms of presenting symptoms

Pineal region tumors (PRTs) affect all ages, with a remarkable proportion of cases occurring in children. They are mainly classified into three categories, namely germ cell tumors (GCTs), pineal parenchymal tumors (PPTs), and other tumors such as gliomas and tumors of the surrounding structures. The purpose of this article is to review the current literature regarding pathophysiological mechanisms of the presenting clinical features of patients with PRT. The usual presentation of PRTs is the symptoms of obstructive hydrocephalus and intracranial hypertension, such as headache and vomiting. However, there is a remarkable spectrum of clinical findings that can be caused by such lesions. These include ophthalmologic and endocrinologic disturbances, motor and sensory abnormalities, and cognitive and psychiatric symptoms. The unique anatomic location of the pineal gland, which is close to many vital brain structures, is crucial for the explanation of most of those findings. In rare cases, manifestations of intracranial bleeding may be the presenting feature of a PRT. Tumor histology and patient's age can affect the clinical presentation. Hydrocephalus is the most common clinical syndrome of a PRT because of the location of the pineal gland. Presenting symptoms also include ophthalmologic, endocrinologic, motor, sensory, cognitive, and psychiatric symptoms. Clinicians should be aware of the initial symptoms of PRTs, including the misleading ones, in order to avoid delay in the diagnosis and management of these life-threatening lesions.

Norepinephrine Is a Major Regulator of Pineal Gland Secretory Activity in the Domestic Goose (Anser anser)

This study determined the effect of norepinephrine and light exposure on melatonin secretion in goose pineal explants. Additionally, it investigated changes in the content of norepinephrine, dopamine, and their metabolites [3,4-dihydroxyphenylacetic acid; vanillylmandelic acid (VMA); homovanillic acid] in goose pineal glands in vivo under 12 h of light and 12 h of darkness (LD), a reversed cycle (DL), constant light (LL), and constant darkness (DD). In vitro content of melatonin was measured by radioimmunoassay; contents of catecholamines and their metabolites were measured by high-performance liquid chromatography. Exposure of pineal explants to LD or DL established rhythmic melatonin secretion; this rhythm was much better entrained with norepinephrine exposure during photophase than without it. When the explants were kept in LL or DD, the rhythm was abolished, unless NE was administered during natural scotophase of a daily cycle. In vivo, norepinephrine and dopamine levels did not display rhythmic changes, but their respective metabolites, HMV and VMA, displayed well-entrained diurnal rhythms. These results indicate that norepinephrine and sympathetic innervation play key roles in regulation of pineal secretory activity in geese, and that pineal levels of VMA and HMV provide precise information about the activity of sympathetic nerve fibers in goose pineal glands.

Exploratory assessment of pineal gland volume, composition, and urinary 6-sulfatoxymelatonin levels on prostate cancer risk

INTRODUCTION

Melatonin levels are partially driven by the parenchyma volume of the pineal gland. Low urinary levels of 6-sulfatoxymelatonin have been associated with increased risk of advanced prostate cancer, but the relationship between pineal gland volume and composition and prostate cancer risk has not been examined.

MATERIALS AND METHODS

We utilized data from 864 men from the AGES-Reykjavik Study with complete pineal gland volumes and urinary 6-sulfatoxymelatonin measurements. Pineal parenchyma, calcification, and cyst volumes were calculated from brain magnetic resonance imaging. Levels of 6-sulfatoxymelatonin were assayed from prediagnostic urine samples. We calculated Pearson correlation coefficients between parenchyma volume and urinary 6-sulfatoxymelatonin levels. We used Cox proportional hazards regression to calculate multivariable hazard ratios (HRs) and 95% confidence intervals (95% CIs) comparing prostate cancer risk across parenchyma volume tertiles and across categories factoring in parenchyma volume, gland composition, and urinary 6-sulfatoxymelatonin level.

RESULTS

Parenchyma volume was moderately correlated with urinary 6-sulfatoxymelatonin level (r = .24; p < .01). There was no statistically significant association between parenchyma volume tertile and prostate cancer risk. Men with high parenchyma volume, pineal cysts and calcifications, and low urinary 6-sulfatoxymelatonin levels had almost twice the risk of total prostate cancer as men with low parenchyma volume, no pineal calcifications or cysts, and low urinary 6-sulfatoxymelatonin levels (HR: 1.98; 95% CI: 1.02, 3.84; p: .04).

CONCLUSIONS

Although parenchyma volume is not associated with prostate cancer risk, pineal gland composition and other circadian dynamics may influence risk for prostate cancer. Additional studies are needed to examine the interplay of pineal gland volume, composition, and melatonin levels on prostate cancer risk.

A Probabilistic Atlas of the Pineal Gland in the Standard Space

Pineal gland (PG) is a structure located in the midline of the brain, and is considered as a main part of the epithalamus. There are numerous reports on the facilitatory role of this area for brain function; hormone secretion and its role in sleep cycle are the major reports. However, reports are rarely available on the direct role of this structure in brain cognition and in information processing. A suggestion for the limited number of such studies is the lack of a standard atlas for the PG; none of the available MRI templates and atlases has provided parcellations for this structure. In this study, we used the three-dimensional (3D) T1-weighted MRI data of 152 healthy young volunteers, and provided a probabilistic map of the PG in the standard Montreal Neurologic Institute (MNI) space. The methods included collecting the data using a 64-channel head coil on a 3-Tesla Prisma MRI Scanner, manual delineation of the PG by two experts, and robust template and atlas construction algorithms. This atlas is freely accessible, and we hope importing this atlas in the well-known neuroimaging software packages would help to identify other probable roles of the PG in brain function. It could also be used to study pineal cysts, for volumetric analyses, and to test any associations between the cognitive abilities of the human and the structure of the PG.

An Elderly Man Suffers a Renal Cell Carcinoma Metastasis in the Pineal Gland: Lessons Learned and Ethical Considerations

Metastases to the pineal gland are rare and reported cases have consisted mainly of lung and gastrointestinal primary malignancies. Here we report the third case in the literature of pineal gland metastasis from renal cell carcinoma.

A 69-year-old man, status post excision of right renal cell carcinoma 20 years ago, presented with a one-month history of urinary incontinence. Images revealed a solitary mass in the pineal region with obstructive hydrocephalus. Endoscopic third ventriculostomy (ETV) and biopsy of pineal mass were performed. The histological diagnosis of the biopsy was inconclusive. The patient was scheduled for a follow-up and readmission for a repeat biopsy, however, was lost to follow-up. No attempts were made by the hospital team or patient relations department to contact him. Eventually, the patient presented after 18 months to the emergency room (ER) with confusion, forgetfulness, gait disturbance, weakness of lower extremities, and vision loss due to enlarged pineal mass. Another ETV and biopsy were performed. The histological findings were compatible with metastasis from renal cell carcinoma. The patient died after three months due to rapid general deterioration in his condition.

The lessons that have been learned from this case are: 1) Metastatic tumor should be considered in the differential diagnosis of pineal region tumors, particularly in elderly patients and with a known history of malignancy; 2) If the first biopsy is inconclusive, a rapid plan and a strict follow-up for a repeat biopsy should be made; 3) Elderly patients should have special care; they should be well informed about their condition and should be contacted regularly to ensure that they receive the optimal management plan.

Pinealectomy and gonadectomy modulate amplitude, but not photoperiodic modulation of Clock gene expression in the Syrian hamster suprachiasmatic nuclei

The duration of daytime light phase (photoperiod) controls reproduction in seasonal mammals. Syrian hamsters are sexually active when exposed to long photoperiod, while gonadal atrophy is observed after exposure to short photoperiod. The photorefractory period, or photorefractoriness, is a particular state of spontaneous recrudescence of sexual activity that occurs after a long-term exposure to short photoperiod. Expression of core clock genes in the master circadian clock contained in the suprachiasmatic nuclei depends on photoperiodic conditions. Interestingly, the expression of the Clock gene is also modified in photorefractory Syrian hamsters. Since melatonin and testosterone levels in seasonal species are dependent on photoperiod, photoperiodic variations of Clock mRNA levels in the suprachiasmatic clock could be a consequence of these hormonal changes. To test this hypothesis, we analysed the effects of pinealectomy on Clock mRNA changes due to long to short photoperiod transition and of gonadectomy on Clock mRNA levels in photorefractory period. Our data show that the suprachiasmatic integration of the short photoperiod (assessed by a rhythmic expression profile of Clock) is independent of the presence of melatonin. Furthermore, constitutively low expression of Clock observed during the photorefractory period does not require the presence of either melatonin or testosterone. However, we show that both hormones provide positive feedback on average levels of Clock expression. Thus, our data support the hypothesis that daily variations of Clock levels in the suprachiasmatic nuclei are influenced by photoperiodic changes and the time spent in short photoperiod, independently of seasonal modifications of melatonin or testosterone levels.

Melatonin in Cancer Treatment: Current Knowledge and Future Opportunities

Melatonin is a pleotropic molecule with numerous biological activities. Epidemiological and experimental studies have documented that melatonin could inhibit different types of cancer in vitro and in vivo. Results showed the involvement of melatonin in different anticancer mechanisms including apoptosis induction, cell proliferation inhibition, reduction in tumor growth and metastases, reduction in the side effects associated with chemotherapy and radiotherapy, decreasing drug resistance in cancer therapy, and augmentation of the therapeutic effects of conventional anticancer therapies. Clinical trials revealed that melatonin is an effective adjuvant drug to all conventional therapies. This review summarized melatonin biosynthesis, availability from natural sources, metabolism, bioavailability, anticancer mechanisms of melatonin, its use in clinical trials, and pharmaceutical formulation. Studies discussed in this review will provide a solid foundation for researchers and physicians to design and develop new therapies to treat and prevent cancer using melatonin.

Is there any relationship between autism and pineal gland volume?

Purpose

Abnormalities in melatonin physiology and circadian rhythm are detected in patients with autism. Melatonin is produced predominantly in the pineal gland and the amount of melatonin released is proportional to the pineal gland volume. This study aimed to examine whether the pineal gland volume in children with autism is different from that in healthy children.

Material and methods

Brain magnetic resonance images (MRI) of 120 paediatric patients with autism and 82 control paediatric subjects were examined; pineal parenchymal volume (PPV), pineal cyst rate (PCR), and total pineal gland volume (TPGV) were measured using a multimodality viewer (MMV), but only the TPGVs were measured using a tumour tracking (TT) method. Measurements were taken by 2 separate radiologists.

Results

In patients with autism, the PPV and TPGV according to MMV, and the TPGV according to TT were significantly lower, and the PCR was significantly higher. Moreover, the ratio of PPV to TPGV was significantly lower in the autism patient group. In both groups, the TPGVs were significantly lower in the autism patient group than the controls among all age groups.

Conclusions

Our study was the first to examine TPGVs in detail in paediatric patients with autism using 2 different methods. Low PPV-TPGV and high PCR have been observed in autism. This study also provides comparable reference values for pineal gland size in healthy children or autistic children aged 2-17 years. These results show promising potential for further research to understand the relationship between autism pathogenesis and the pineal gland.

Age-Related Changes of the Pineal Gland in Humans: A Digital Anatomo-Histological Morphometric Study on Autopsy Cases with Comparison to Predigital-Era Studies

Background and objectives: The pineal gland is a photoneuroendocrine organ in the midline of the brain, responsible primarily for melatonin synthesis. It is composed mainly of pinealocytes and glial tissue. This study examined human postmortem pineal glands to microscopically assess age-related changes using digital techniques, and offers a perspective on evolutionary tendencies compared to the past. Materials and Methods: A retrospective autopsy study has been performed on 72 pediatric and adult autopsy cases. The glands have been processed for histological analysis and immunohistochemical staining with glial fibrillary acidic protein (GFAP). Slides were assessed under polarized light and digitally scanned. Morphometric data were obtained using CaseViewer and ImageJ. Results: Thirty-three females and 39 males were included in the study, grouped under three age groups: 0–25, 46–65, and 66–96 years of age. The peak gland volume was found within the 46–65 age group, the overall mean volume was 519 mm³, the main architectural types were lobular and insular, and the mean percentage of pineal calcification was 15% of the gland, peaking within the 66–96 age group, with a predominantly globular shape. Glial cysts were found in 20.8% of cases. The intensity of GFAP stain was maximal in the pediatric age group, but the extent of glial tissue was much larger in elderly patients. Discussion: The degenerative process of the pineal gland can be quantified by measuring normal parenchyma, calcifications, glial tissue, and glial cysts. Morphometric differences have been observed and compared to a similar studies performed in the published literature. The current study, unfortunately, lacks a 26–45 age group. Digital techniques seemed to offer a more exact analysis, but returned similar results to studies performed over 40 years ago, therefore offering important information on evolutionary tendencies. Conclusions: Increase in glial tissue, calcifications, and glial cysts have a defining role as age-related changes in the pineal gland.

Mass-spectrometry analysis of the human pineal proteome during night and day and in autism

The human pineal gland regulates day-night dynamics of multiple physiological processes, especially through the secretion of melatonin. Using mass-spectrometry-based proteomics and dedicated analysis tools, we identify proteins in the human pineal gland and analyze systematically their variation throughout the day and compare these changes in the pineal proteome between control specimens and donors diagnosed with autism. Results reveal diverse regulated clusters of proteins with, among others, catabolic carbohydrate process and cytoplasmic membrane-bounded vesicle-related proteins differing between day and night and/or control versus autism pineal glands. These data show novel and unexpected processes happening in the human pineal gland during the day/night rhythm as well as specific differences between autism donor pineal glands and those from controls.