Pineal Research Articles

Duplicated zebrafish (Danio rerio) inositol phosphatases inpp5ka and inpp5kb diverged in expression pattern and function

One hurdle in the development of zebrafish models of human disease is the presence of multiple zebrafish orthologs resulting from whole genome duplication in teleosts. Mutations in inositol polyphosphate 5-phosphatase K (INPP5K) lead to a syndrome characterized by variable presentation of intellectual disability, brain abnormalities, cataracts, muscle disease, and short stature. INPP5K is a phosphatase acting at position 5 of phosphoinositides to control their homeostasis and is involved in insulin signaling, cytoskeletal regulation, and protein trafficking. Previously, our group and others have replicated the human phenotypes in zebrafish knockdown models by targeting both INPP5K orthologs inpp5ka and inpp5kb. Here, we show that inpp5ka is the more closely related orthologue to human INPP5K. While both inpp5ka and inpp5kb mRNA expression levels follow a similar trend in the developing head, eyes, and tail, inpp5ka is much more abundantly expressed in these tissues than inpp5kb. In situ hybridization revealed a similar trend, also showing unique localization of inpp5kb in the pineal gland and retina indicating different transcriptional regulation. We also found that inpp5kb has lost its catalytic activity against its preferred substrate, PtdIns(4,5)P2. Since most human mutations are missense changes disrupting phosphatase activity, we propose that loss of inpp5ka alone can be targeted to recapitulate the human presentation. In addition, we show that the function of inpp5kb has diverged from inpp5ka and may play a novel role in the zebrafish.

ERKEK İNFERTİLİTESİNDE STRESİN ROLÜ VE UYGULANAN GÜNCEL MELATONİN HORMON TEDAVİLERİNİN ETKİSİNİN İNCELENMESİ

Although stress, defined as the deterioration in homeostatic mechanisms in living things due to psychological, physiological, social, and even environmental reasons, has been mentioned since the 17th century, it is frequently encountered in modern life. So much so that you can be exposed to stress anytime, from home, business life, to the street, in traffic. This situation has made stress a part of modern life. Any situation or event, such as losing a close person, workplace stress, or even living in isolation at home during the coronavirus disease (COVID-19) pandemic, can also be a source of stress. Responses that occur in the organism to the stress stimulus are for the benefit of the organism up to a certain level. However, when the duration and intensity of the stress stimulus increase, pathological conditions occur in all physiological systems. Long-term exposure to stress may cause infertility in men by causing decreases in sperm parameters such as sperm quality, sperm concentration, spermatozoid count, and sperm percentage. Various substances are being researched to reduce these adverse effects of stress on the reproductive system. Studies have shown that melatonin has antioxidant, anti-inflammatory, anti-apoptotic, and so on. It shows positive efficacy in male infertility with various mechanisms. This review it is aimed to give information on the effect of stress on the male reproductive system and the relationship between melatonin.

Melatonin and Kidney Health: From Fetal Stage to Later Life.

Melatonin, an endogenous hormone mainly released at night by the pineal gland, has multifaceted biofunctions. Emerging evidence points to melatonin having a crucial role in kidney health and disease. As the prevalence of chronic kidney disease (CKD) is still rising, a superior strategy to advance global kidney health is needed to not just treat CKD, but prevent it early on. Adult kidney disease can have its origins in early life. This review aims to evaluate the recent literature regarding melatonin's effect on kidney development, its clinical uses in the early stage of life, animal models documenting preventive applications of melatonin on offspring's kidney-related disease, and a thorough summary of therapeutic considerations concerning melatonin supplementation.

Peculiarities of circadian regulation of the thyroid gland

Circadian rhythmicity is an autonomous period of organ cells’ functioning that is controlled by feedback mechanisms and specific genes. The thyroid gland, as a peripheral organ of the endocrine system, is subordinate to the adenohypophysis and pineal gland. Melatonin, as one of the main mediators of circadian influence, is well known for its antitumor and regulatory effects on a number of tissues, but its relationship with the hormone-producing activity of the thyroid gland has not been sufficiently studied. The purpose of the work was to analyze the current data on circadian regulation of the thyroid gland by examining evidence-based scientific publications from open databases over the past five years. Melatonin-producing pineal cells possess the homeotic genes Otx2 and Crx whose deactivation leads to a significant decrease in melatonin production by the pineal gland. In addition to pineal cells, melatonin can be synthesized by adenohypophysis-independent parafollicular cells. The effect of melatonin on thyrocytes is provided by binding to MT1 receptors and affecting the expression of thyroglobulin, RX-8, and TTF-1 (NKX2-1) genes. Under conditions of short photoperiod, melatonin inhibits the production of thyroid-stimulating hormone (TSH) β, which, in turn, acts on hypothalamic tanycytes by regulating the balance of deiodinase (Dio2/Dio3). This leads to a well-regulated seasonal control of the release of the thyroid hormone triiodothyronine. Conclusions. Circadian regulation of thyrocyte activity occurs under the influence of melatonin, which is secreted by pinealocytes and sometimes by parafollicular cells. TSH is secreted with a certain circadian periodicity under the influence of the activation of chronorhythmic genes. Hormone replacement therapy should be aimed not only at restoring the levels of pituitary hormones, but also at restoring the biological rhythm of TSH secretion. Melatonin affects the circadian work of thyrocytes, which is proven by determining the expression of the chronorhythm genes Bmal-1, Dio2, TTF-1. In thyroid pathology, there is a violation of circadian rhythms, a decrease in melatonin levels, and a decrease in the expression of Clock genes.

Modulation of Apoptosis and Autophagy by Melatonin in Juglone-Exposed Bovine Oocytes.

Melatonin, an antioxidant hormone secreted by the pineal gland, has been recognized as a regulator for numerous biological events. The deleterious effects of juglone, a polyphenolic extract of walnut trees, on embryo development has been previously reported. In the current study, we aimed to display the impact of melatonin administrated during in vitro oocyte maturation (IVM) on juglone-treated oocytes. Thus, in vitro matured oocytes were collected after 24 h post incubation with juglone in the presence or absence of melatonin. Reactive oxygen species (ROS), glutathione (GSH) content, mitochondrial distribution, and the relative abundance of mRNA transcription levels were assessed in oocytes, in addition, oocytes were in vitro fertilized to check the competency levels of oocytes to generate embryos. We found that administration of melatonin during the maturation of oocytes under juglone stress significantly improved the cleavage rate, 8-16 cell-stage embryos and day-8 blastocysts when compared to the sole juglone treatment. In addition, the fluorescence intensity of ROS increased, whereas the GSH decreased in juglone-treated oocytes compared to melatonin-juglone co-treated and untreated ones. Additionally, a significant increase in the mitochondrial aberrant pattern, the pattern that was normalized following melatonin supplementation, was observed following juglone administration. The mRNA analysis using RT-qPCR revealed a significant upregulation of autophagy and oxidative-stress-specific markers in the juglone-treated group compared to the co-treatment and control. In conclusion, the study reveals, for the first time, a protective effect of melatonin against the oxidative stress initiated following juglone treatment during the in vitro maturation of oocytes.

Cyclic nucleotide-regulated channels (CNG) in GtoPdb v.2023.1

Cyclic nucleotide-gated (CNG) channels are responsible for signalling in the primary sensory cells of the vertebrate visual and olfactory systems. CNG channels are voltage-independent cation channels formed as tetramers. Each subunit has 6TM, with the pore-forming domain between TM5 and TM6. CNG channels were first found in rod photoreceptors [83, 120], where light signals through rhodopsin and transducin to stimulate phosphodiesterase and reduce intracellular cyclic GMP level. This results in a closure of CNG channels and a reduced ‘dark current’. Similar channels were found in the cilia of olfactory neurons [181] and the pineal gland [71]. The cyclic nucleotides bind to a domain in the C terminus of the subunit protein: other channels directly binding cyclic nucleotides include hyperolarisation-activated, cyclic nucleotide-gated channels (HCN), ether-a-go-go and certain plant potassium channels.The HCN channels are cation channels that are activated by hyperpolarisation at voltages negative to ~-50 mV. The cyclic nucleotides cyclic AMP and cyclic GMP directly bind to the cyclic nucleotide-binding domain of HCN channels and shift their activation curves to more positive voltages, thereby enhancing channel activity. HCN channels underlie pacemaker currents found in many excitable cells including cardiac cells and neurons [65, 192]. In native cells, these currents have a variety of names, such as Ih, Iq and If. The four known HCN channels have six transmembrane domains and form tetramers. It is believed that the channels can form heteromers with each other, as has been shown for HCN1 and HCN4 [2]. High resolution structural studies of CNG and HCN channels has provided insight into the the gating processes of these channels [139, 146, 140]. A standardised nomenclature for CNG and HCN channels has been proposed by the NC-IUPHAR Subcommittee on voltage-gated ion channels [108].

Arylalkylamine N-acetyltransferase (AANAT): Blue light induction, nuclear translocation, and potential role in the survival of chicken retina neuronal cells.

In vertebrates, arylalkylamine N-acetyltransferase (AANAT; EC 2.3.1.87) is the time-keeping and key regulatory enzyme in melatonin (Mel) biosynthesis. AANAT is present in the pineal gland, retina, and other regions where it is controlled by light, cyclic adenosine monophosphate (cAMP) levels, and the molecular clock. AANAT converts serotonin to N-acetyl serotonin (NAS) and the last enzyme in the pathway, hydroxy-o-methyltransferase (HIOMT), forms Mel by NAS methylation. We have previously shown that AANAT is expressed in chicken retinal ganglion cells (RGCs) during daytime at the level of mRNA and enzyme activity. Here we investigated the presence of AANAT protein and mRNA throughout development in the chicken embryonic retina as well as AANAT expression, phosphorylation, and its sub-cellular localization in primary cultures of retinal neurons from E10 embryonic retinas exposed to blue light (BL) and controls kept in the dark (D). From embryonic days 7-10 (E7-10) AANAT mRNA and protein were visualized mainly concentrated in the forming ganglion cell layer (GCL), while from E17 through postnatal days, expression was detectable all through the different retinal cell layers. At postnatal day 10 (PN10) when animals were subjected to a 12:12 h LD cycle, AANAT was mainly expressed in the GCL and inner nuclear layer cells at noon (Zeitgeber Time (ZT 6)) and in the photoreceptor cell layer at night (ZT 21). Primary cultures of retinal neurons exhibited an induction of AANAT protein when cells were exposed to BL for 1 h as compared with D controls. After BL exposure, AANAT showed a significant change in intracellular localization from the cytoplasm to the nucleus in the BL condition, remaining in the nucleus 1-2 h in the D after BL stimulation. BL induction of nuclear AANAT was substantially inhibited when cultures were treated with the protein synthesis inhibitor cycloheximide (CHD). Furthermore, the phosphorylated form of the enzyme (pAANAT) increased after BL in nuclear fractions obtained from primary cultures as compared with D controls. Finally, the knockdown of AANAT by sh-RNA in primary cultures affected cell viability regardless of the light condition. AANAT knockdown also affected the redox balance, sh-AANAT treated cultures showing higher levels of reactive oxygen species (ROS) than in the sh-control. Our results support the idea that AANAT is a BL-sensing enzyme in the inner retina of diurnal vertebrates, undergoing phosphorylation and nuclear importation in response to BL stimulation. Moreover, it can be inferred that AANAT plays a novel role in nuclear function, cell viability, and, likely, through redox balance regulation.

Melatonin – a verified remedy for jet lag? Current state of knowledge

Jet lag is a circadian rhythm disorder, affecting plane passengers travelling across multiple time zones. The severity of symptoms is strictly connected with the number of zones crossed. Common symptoms include: insomnia, difficulty concentrating attention, memory loss, anxiety, diarrhea, confusion, dizziness, headache, as well as malaise. Melatonin is a neurohormone, produced by the pineal gland. The hormone is released into the bloodstream and acts on MT1 and MT2 receptors, having the ability to induce sleep. Melatonin is therefore responsible for regulating the human biological clock and, consequently, the rhythm of sleep and wakefulness. Synthetic forms of melatonin have become a potential medication for various circadian rhythm disorders, including jet lag syndrome. Ten scientific reports were analyzed. The characteristics of the subjects, directions of the trips taken, the doses of melatonin, as well as the patterns of its administration, differed among studies. According to most of the reviewed trials, melatonin may have a beneficial effect on alleviating jet lag symptoms. The timing of intake plays a significant role – it has proven most effective when taken days before travel. However, several studies have not confirmed its effectiveness, compared to placebo. Further research seems to be inevitable to objectively reassess the effectiveness of melatonin preparations. Unambiguous determination of the melatonin dosage, the timing of its administration, the time of initiation, and the duration of the treatment would also be advisable. Nevertheless, all of the mentioned trials confirmed that the use of oral melatonin preparations, especially at low doses, turned out to be free of serious side effects.

The Role of the PAA1 Gene on Melatonin Biosynthesis in Saccharomyces cerevisiae: A Search of New Arylalkylamine N-Acetyltransferases

Recently, the presence of melatonin in fermented beverages has been correlated with yeast metabolism during alcoholic fermentation. Melatonin, originally considered a unique product of the pineal gland of vertebrates, has been also identified in a wide range of invertebrates, plants, bacteria, and fungi in the last two decades. These findings bring the challenge of studying the function of melatonin in yeasts and the mechanisms underlying its synthesis. However, the necessary information to improve the selection and production of this interesting molecule in fermented beverages is to disclose the genes involved in the metabolic pathway. So far, only one gene has been proposed as involved in melatonin production in Saccharomyces cerevisiae, PAA1, a polyamine acetyltransferase, a homolog of the vertebrate’s aralkylamine N-acetyltransferase (AANAT). In this study, we assessed the in vivo function of PAA1 by evaluating the bioconversion of the different possible substrates, such as 5-methoxytryptamine, tryptamine, and serotonin, using different protein expression platforms. Moreover, we expanded the search for new N-acetyltransferase candidates by combining a global transcriptome analysis and the use of powerful bioinformatic tools to predict similar domains to AANAT in S. cerevisiae. The AANAT activity of the candidate genes was validated by their overexpression in E. coli because, curiously, this system evidenced higher differences than the overexpression in their own host S. cerevisiae. Our results confirm that PAA1 possesses the ability to acetylate different aralkylamines, but AANAT activity does not seem to be the main acetylation activity. Moreover, we also prove that Paa1p is not the only enzyme with this AANAT activity. Our search of new genes detected HPA2 as a new arylalkylamine N-acetyltransferase in S. cerevisiae. This is the first report that clearly proves the involvement of this enzyme in AANAT activity.

Next-generation plasmids for transgenesis in zebrafish and beyond.

Transgenesis is an essential technique for any genetic model. Tol2-based transgenesis paired with Gateway-compatible vector collections has transformed zebrafish transgenesis with an accessible modular system. Here, we establish several next-generation transgenesis tools for zebrafish and other species to expand and enhance transgenic applications. To facilitate gene regulatory element testing, we generated Gateway middle entry vectors harboring the small mouse beta-globin minimal promoter coupled to several fluorophores, CreERT2 and Gal4. To extend the color spectrum for transgenic applications, we established middle entry vectors encoding the bright, blue-fluorescent protein mCerulean and mApple as an alternative red fluorophore. We present a series of p2A peptide-based 3' vectors with different fluorophores and subcellular localizations to co-label cells expressing proteins of interest. Finally, we established Tol2 destination vectors carrying the zebrafish exorh promoter driving different fluorophores as a pineal gland-specific transgenesis marker that is active before hatching and through adulthood. exorh-based reporters and transgenesis markers also drive specific pineal gland expression in the eye-less cavefish (Astyanax). Together, our vectors provide versatile reagents for transgenesis applications in zebrafish, cavefish and other models.

Endocranial anatomy of the early prozostrodonts (Eucynodontia: Probainognathia) and the neurosensory evolution in mammal forerunners.

Prozostrodon brasiliensis and Therioherpeton cargnini are non-mammaliaform cynodonts that lived ~233 million years ago (late Carnian, Late Triassic) in western Gondwana. They represent some of the earliest divergent members of the clade Prozostrodontia, which includes "tritheledontids", tritylodontids, "brasilodontids", and mammaliaforms (including Mammalia as crown group). Here, we studied the endocranial anatomy (cranial endocast, nerves, vessels, ducts, ear region, and nasal cavity) of these two species. Our findings suggest that during the Carnian, early prozostrodonts had a brain with well-developed olfactory bulbs, expanded cerebral hemispheres divided by the interhemispheric sulcus, and absence of an unossified zone and pineal body. The morphology of the maxillary canal represents the necessary condition for the presence of facial vibrissae. A slight decrease in encephalization is observed at the origin of the clade Prozostrodontia. This new anatomical information provides evidence for the evolution of endocranial traits of the first prozotrodonts, a Late Triassic lineage that culminated in the origin of mammals.

Abstract 4853: Evaluating the role of melatonin in thyroid cancer cell (MDA-T41) apoptosis and metabolism modulation

Abstract Melatonin, a hormone produced by the pineal gland, is typically known for its modulation of a number of physiological functions, alongside its ability to synchronize the sleep-wake rhythms. In recent years, however, its interactions with cancerous cells and role in prevention and treatment have been increasingly studied. It has been demonstrated that melatonin can improve the efficacy of chemotherapeutic drugs and directly inhibit tumorigenesis in experimental models of neoplasia. In addition, while melatonin typically displays anti-apoptotic effects in normal cells, it holds pro-apoptotic effects in cancer cells. Despite this, the mechanisms by which melatonin affects cell death and metabolism remain unclear due to the seeming difference from cell to cell. We aim to better understand the role of melatonin in regulating thyroid cancer cell apoptosis and metabolism. The MDA-T41 thyroid cancer cell line was cultured with varying quantities of melatonin. Steady volumes of staurosporine (an inductor of apoptotic cell death) were applied to cultures, and cell death levels were subsequently measured using the Realtime-Glo Annexin V Apoptosis and Necrosis assay. Our results showed that melatonin provided anti-apoptotic effects to MDA-T41 cells treated with staurosporine. Both apoptosis and necrosis were reduced by 50% in melatonin-treated cells 24 hours after staurosporine-induced cell death. Our next steps will be to evaluate the mechanisms and further signaling pathways involved in this apoptosis inhibition through Bcl-2 and p53 protein expression. Citation Format: Angela Huang, Daniel Sanches. Evaluating the role of melatonin in thyroid cancer cell (MDA-T41) apoptosis and metabolism modulation. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4853.

Abstract 5050: Case report: A 17-year-old patient developed glioblastoma secondary to intracranial germ cell tumor and was stabilized with chemoradiotherapy combined with Tumor Treating Fields

Abstract Background: Germ Cell Tumor (GCT) is a rare intracranial tumor occurring in children and young adults. Some patients with GCT are curable with radiotherapy and chemotherapy. Due to long-term survival, the tumor secondary to radiotherapy is of concern. The treatment of the secondary tumor is less elaborated and worth exploring. Case Presentation: Here we report a patient with GCT who developed radiotherapy-induced glioblastoma. He was diagnosed as pineal gland GCT at the age of 12. Afterwards, he underwent a set of treatments, including chemotherapy, radiotherapy, and surgery. Unfortunately, after 5 years of tumor-free survival, he developed an intracranial mass involved the right thalamus and brainstem, around pineal region. The GCT recurrence was firstly considered, however, the failure of 7 cycles of chemotherapy drew attention. Then brain biopsy underwent by ROSA robot showed high-grade glioma. Next Generation Sequencing showed IDH-wildtype, MGMT methylation, CDKN2A/B homozygous deletion, EGFR amplification, the +7/−10 signature, which supported the diagnosis of glioblastoma. Resection operation is not applicable for this patient as the involvement of thalamus and brainstem. Considering the difficulty of treatment and poor prognosis of glioblastoma, re-radiotherapy is a feasible choice. Chemoradiotherapy with Tumor Treating Fields (TTFields) is a innovative try for secondary glioblastoma in a 17-year-old patient. After the combination therapy, the intracranial mass went regression and the patient has lived for more than 1 years. Conclusions: For the patients with brain tumor who anticipate long-term survival, the secondary tumor after radiotherapy is of concern. Secondary Glioblastoma is rare and difficult to treat. Chemoradiotherapy with TTFields is a feasible and safe treatment option for some patients, but we need more evidence to support. Citation Format: Shaoqun Li, Mingyao Lai, Hainan Li, Juan Li, Jiangfen Zhou, Qingjun Hu, Minting Ye, Ruyu Ai, Junqiao Zhu, Lijun Huang, Linbo Cai. Case report: A 17-year-old patient developed glioblastoma secondary to intracranial germ cell tumor and was stabilized with chemoradiotherapy combined with Tumor Treating Fields. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5050.

Study of the Histomorphology of Human Pineal Gland

Introduction: Histologically, the pineal gland shows pinealocytes, glial cells, and sometimes calcific concretions. Age-related changes in these three components have been reported by various workers. However, a statistically significant difference between the two sexes has not been found. This study was conducted to find out morphological and histological changes in human pineal gland in relation to advancing age and in relation to gender. Methodology: Forty pineal glands were taken for the study. The pineal glands were fixed in 10% formol saline and processed. Slides for microanatomical study were prepared and observed under microscope. Results: The size of the pinealocytes, size of their nuclei, and number of glial cells increased with age, but it was not significant. The number of pinealocytes decreased with age (P = 0.02). The size of the calcific concretions increased with age (P = 0.02). The difference in size of pinealocytes, nuclei of the pinealocytes, and the number of pinealocytes between genders was not significant. The difference in the number of glial cells between genders was significant (P = 0.03). The difference in the number of concentric lamellated type of calcific concretions between genders was significant (P = 0.03). Conclusion: A histological study of pineal gland in human is an area of interest for anatomists, radiologists, and neurologists. This study has paved a way for us for further research using immunohistochemistry and electron microscopy.

Potential therapeutic role of melatonin in hepatobiliary diseases: current evidence and clinical observations.

Melatonin (MEL) is produced and secreted by the pineal gland as well as the small intestine, liver, retina, lymphocytes, and melanocytes in the skin in both experimental animals as well as in humans. While pineal and retinas MEL is closely related to the light/dark cycle, the production of MEL by other so called extrapineal tissues is independent of such circadian rhythm. Among the primary mechanisms of action of MEL in humans, the most important are interaction of MEL with specific receptors (M1, M2, M3) and the MEL 'scavenging' activity against the formation of free oxygen metabolites as a result of MEL's ability to transfer free electrons and stimulation of the expression of redox reaction enzymes. In addition, MEL binds to intracellular proteins such as calmodulin, thereby affecting the course of cell cycle, and it has been shown to activate of nuclear receptors belonging to the retinoid orphan receptors/retinoid Z receptors (ROR/RZR) subfamily. MEL exerts regulatory effects on the master clock regulating diurnal rhythms. This updated review presents current view on the synthesis and metabolism of MEL and the growing body of experimental evidence transferable to the practical medicine supporting a pleiotropic molecule beneficial effects on the health including protection against various organ abnormalities, including internal organs such as the liver. Although the beneficial effects of MEL in various types of liver damage have been well documented in experimental studies, there are relatively few studies on liver dysfunction in humans. Considering the worldwide obesity pandemic often associated with the occurrence of steatohepatitis and cirrhosis, the beneficial effects of MEL in liver pathology should be proven in randomized trials involving patients presenting with hepatic disorders.

Spatiotemporally resolved metabolomics and isotope tracing reveal CNS drug targets.

Deconvolution of potential drug targets of the central nervous system (CNS) is particularly challenging because of the complicated structure and function of the brain. Here, a spatiotemporally resolved metabolomics and isotope tracing strategy was proposed and demonstrated to be powerful for deconvoluting and localizing potential targets of CNS drugs by using ambient mass spectrometry imaging. This strategy can map various substances including exogenous drugs, isotopically labeled metabolites, and various types of endogenous metabolites in the brain tissue sections to illustrate their microregional distribution pattern in the brain and locate drug action-related metabolic nodes and pathways. The strategy revealed that the sedative-hypnotic drug candidate YZG-331 was prominently distributed in the pineal gland and entered the thalamus and hypothalamus in relatively small amounts, and can increase glutamate decarboxylase activity to elevate γ-aminobutyric acid (GABA) levels in the hypothalamus, agonize organic cation transporter 3 to release extracellular histamine into peripheral circulation. These findings emphasize the promising capability of spatiotemporally resolved metabolomics and isotope tracing to help elucidate the multiple targets and the mechanisms of action of CNS drugs.

Age, and non-age-related cytoarchitectural changes in the brain of some Nigerian cattle

Brain is the most vulnerable organ in the body to the ageing processes which operates at variable levels between organs and species. In this study we examine brains histopathologically for architectural changes in four Nigerian cattle breeds. Brains from 246 cattle (Bunaji=80, Muturu=78, Rahaji=62 and Sokoto Gudali=26), aged 1–≥12years were examined at 8 different neuroanatomical locations. All the cattle used were obtained from Abattoir in Ibadan, Nigeria. They were examined at ante-mortem and those without clinical signs suggestive of neurological disease were sampled. Major changes observed were intracellular accumulation of substances (61.4%), neuronal and or axonal degenerations and loss (51.6%), perivascular cuffing (50.0%), extracellular accumulation of substances (29.7%), hypercellularity (19.1%) and spongy state (0.4%), malacia (0.0%), demyelination (0.0%) in 233 cattle. Intraneuronal vacuolations (35%), lipofuscin accumulation (42%), axonal spheroids (50%), inflammatory changes (50%), and brain sand (22%). Although perivascular cuffing was high, there was low incidence of lymphocytic infiltration in the pineal gland in both sexes. Intracellular accumulation of substances, neuronal and or axonal degenerations and loss, and extracellular accumulation of substances display levels of significant changes with age (p<0.0001). Changes starts at the age of 2 years in life in these breeds of cattle due probably to the adverse stress exerted by the tropical climate. The description of histological findings in the brain of symptomless cattle in the present study provides a useful background for diagnostic bovine neuropathology in the tropics.

Melatonin suppresses sympathetic vasomotor tone through enhancing GABAA receptor activity in the hypothalamus.

Introduction: Melatonin (5-methoxy-N-acetyl-tryptamine) is a circadian hormone synthesized and secreted by the pineal gland. In addition to regulating circadian rhythms of many physiological functions, melatonin is involved in regulating autonomic nervous function and blood pressure. Hypothalamus paraventricular nucleus (PVN), receiving melatonin projections from the superchiasmatic nucleus, is a critical brain region to regulate neuroendocrine and cardiovascular function. Here, we determined the synaptic mechanisms involved in the effect of melatonin on the sympathetic outflow and blood pressure. Methods and Results: Microinjection of melatonin into the PVN produced a depressor effect and decreased renal sympathetic nerve activity (RSNA). While microinjection of luzindole, a non-selective melatonin receptor antagonist, into the PVN did not change melatonin-induced sympathoinhibition, GABAA receptor antagonist bicuculline eliminated melatonin-induced sympathoinhibition. Furthermore, melatonin decreased firing rate of retrogradely labeled PVN neurons which project to the rostral ventrolateral medulla (RVLM), an effect was not altered by luzindole but eliminated by bicuculline. Melatonin significantly increased the amplitude of spontaneous and evoked GABAergic inhibitory synaptic currents, as well as GABA-induced currents. Conclusion: These data suggest that melatonin in the PVN suppresses sympathetic vasomotor tone through enhancing GABAA receptor activity. This study provides novel information for understanding the cellular mechanisms involved in the effect of melatonin on regulating blood pressure and sympathetic output.

Expression of the melatonergic system during meiotic maturation of cynomolgus monkey cumulus-oocyte complexes.

Melatonin is a multifunctional hormone synthesized in the pineal gland and peripheral reproductive tissues that regulates many biological processes. There is increasing evidence for a role of melatonin in oocyte maturation and embryonic development in various mammals. However, no study has reported evidence for the existence of melatonergic system, such as melatonin synthesis enzymes, melatonin membrane receptors, or melatonin binding sites in non-human primate cumulus-oocyte complexes (COCs). Reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry were performed to detect transcripts and proteins of the rate-limiting enzyme in melatonin synthesis (arylalkylamine N-acetyltransferase, AANAT), melatonin membrane receptors (MT1 and MT2), and a melatonin binding site (NRH: quinone oxidoreductase 2, NQO2) in cynomolgus monkey COCs. RT-PCR analyses revealed the presence of AANAT, MT1, MT2, and NQO2 transcripts in granulosa cells, germinal vesicle (GV)- and metaphase II (MII)-stage cumulus cells, and oocytes. Immunocytochemistry revealed the presence of AANAT, MT1, MT2, and NQO2 proteins in GV- and MII-stage COCs. Our results provide the first evidence for the existence of the rate-limiting enzyme required for melatonin synthesis, melatonin membrane receptors, and a melatonin binding site in non-human primate COCs.

Melatonin and vitamin D, two sides of the same coin, better to land on its edge to improve multiple sclerosis

Previous studies revealed a latitudinal gradient of multiple sclerosis (MS) prevalence, increasing by moving from the equator to the poles. The duration and quality of an individual’s exposure to sunlight vary with latitude. Skin exposure to sunlight activates vitamin D synthesis, while light absence, as perceived by the eyes, activates melatonin synthesis in the pineal gland. Vitamin D or melatonin deficiency/insufficiency or overdose can occur at any latitude due to specific lifestyles and diets. Moving away from the equator, especially beyond 37°, decreases vitamin D while raising melatonin. Furthermore, melatonin synthesis increases in cold habitats like northern countries. Since melatonin's beneficial role was shown in MS, it is expected that northern countries whose individuals have higher endogenous melatonin should show a lower MS prevalence; however, these are ranked with the highest scores. In addition, countries like the United States and Canada have uncontrolled over-the-counter usage. In high latitudes, vitamin D deficiency and a higher MS prevalence persist even though vitamin D is typically compensated for by supplementation and not sunlight. Recently, we found that prolonged darkness increased MS melatonin levels, mimicking the long-term increase in northern countries. This caused a reduction in cortisol and increased infiltration, inflammation, and demyelination, which were all rescued by constant light therapy. In this review, we explain melatonin and vitamin D's possible roles in MS prevalence. The possible causes in northern countries are then discussed. Finally, we suggest strategies to treat MS by manipulating vitamin D and melatonin, preferably with sunlight or darkness, not supplements.