Humanin and Alzheimer's disease: The beginning of a new field

The neuroprotective role of Humanin in Alzheimer's disease: The molecular effects

Humanin (HN) is an endogenous micropeptide also known as a mitochondria-derived peptide. It has a neuroprotective effect against Alzheimer's disease (AD) and other neurodegenerative diseases by improving hippocampal acetylcholine and attenuating the development of oxidative stress and associated neurotoxicity. HN protects the neuron from the toxic effects of amyloid beta (Aβ). HN is regarded as a biomarker of mitochondrial stress. Interestingly, aging reduces brain expression of HN, leading to cognitive impairment and elevating the risk of neurodegeneration, including AD. However, in old subjects and AD patients, circulating HN levels increase as a compensatory mechanism to reduce neurodegeneration and mitochondrial dysfunction in AD. Conversely, other studies demonstrated a reduction in circulating HN levels in AD. These findings indicated controversial points regarding the precise mechanistic role of HN in AD. Therefore, the aim of this review was to discuss the exact role of HN in AD neuropathology and also to discuss the molecular mechanisms of HN in AD.

Discovery of a small molecule secreted clusterin enhancer that improves memory in Alzheimer's disease mice

Despite substantial research and drug discovery efforts, Alzheimer's Disease (AD) remains the sixth leading cause of death in the United States, underscoring the urgent need for novel therapeutic targets. A mutation in the clusterin (CLU) gene that hinders expression of the cyto-protective secreted isoform of clusterin (sCLU) that affects the aggregation and clearance of two key proteins implicated in AD, Aβ and tau, is the third most significant genetic risk factor for late-onset AD. Here, we present findings from our drug discovery program to identify small molecules that enhance sCLU levels and assess their impact on AD pathology and cognition in a murine model of AD. A high-throughput screening campaign identified two classes of epigenetic modulators that increase sCLU levels with subsequent medicinal chemistry efforts leading to bromodomain and extra-terminal (BET) inhibitor new chemical entities (NCEs) with enhanced potency, drug-like properties, and oral brain bioavailability. The lead candidate NCE, DDL-357, increased brain sCLU in the murine ApoE4TR-5XFAD model of AD in a subchronic study. In a follow-up chronic study in the murine 3xTg-AD model, DDL-357 reduced phospho-tau in brain and led to improvements in mouse performance and memory in the Barnes maze testing paradigm. Proteomic analysis of brain tissue from both AD models revealed changes in proteins involved in mitochondrial function and synaptic plasticity. These findings reveal the potential of sCLU enhancement as a target for therapeutic development in AD and support the continued development of the preclinical lead candidate.

Mitochondria‑derived peptides: Promising microproteins in cardiovascular diseases (Review)

Mitochondria‑derived peptides (MDPs) are a unique class of peptides encoded by short open reading frames in mitochondrial DNA, including the mitochondrial open reading frame of the 12S ribosomal RNA type‑c (MOTS‑c). Recent studies suggest that MDPs offer therapeutic benefits in various diseases, including neurodegenerative disorders and types of cancer, due to their ability to increase cellular resilience. Mitochondrial dysfunction is a key factor in the onset and progression of cardiovascular diseases (CVDs), such as atherosclerosis and heart failure, as it disrupts energy metabolism, increases oxidative stress and promotes inflammation. MDPs such as humanin and MOTS‑c have emerged as important regulators of mitochondrial health, as they show protective effects against these processes. Recent studies have shown that MDPs can restore mitochondrial function, reduce oxidative damage and alleviate inflammation, thus counteracting the pathological mechanisms that drive CVDs. Therefore, MDPs hold promise as therapeutic agents that are capable of slowing, stopping, or even reversing CVD progression and their use presents a promising strategy for future treatments. However, the clinical application of MDPs remains challenging due to their low bioavailability, poor stability and high synthesis costs. Thus, it is necessary to improve drug delivery systems to enhance the bioavailability of MDPs. Moreover, integrating basic research with clinical trials is essential to bridge the gap between experimental findings and clinical applications.

Endogenous micropeptides as potential diagnostic biomarkers and therapeutic drugs

Micropeptides, these small proteins derived from non-coding RNA, typically consist of no more than 100 amino acids in length. Despite the challenges in analysis and identification, their various critical functions within organisms cannot be overlooked. They play a significant role in maintaining energy metabolism balance, regulating the immune system, and influencing the development of tumors, which also gives them a decisive impact on the occurrence and development of various diseases. This review aims to outline the role and potential value of micropeptides, introducing their tissue classification and distribution, biological functions, and mechanisms, with a focus on their potential as diagnostic markers and therapeutic drugs.

Association of RDoC dimensions with post mortem brain transcriptional profiles in Alzheimer's disease

INTRODUCTION

Neuropsychiatric symptoms are common in people with Alzheimer's disease (AD) across all severity stages. Their heterogeneous presentation and variable temporal association with cognitive decline suggest shared and distinct biological mechanisms. We hypothesized that specific patterns of gene expression associate with distinct National Institute of Mental Health Research Domain Criteria (RDoC) domains in AD.

METHODS

Post-mortem bulk RNA sequencing of the insula and anterior cingulate cortex from 60 brain donors, representing the spectrum of canonical Alzheimer's disease neuropathology, was combined with natural language processing approaches based on the RDoC Clinical Domains to uncover transcriptomic patterns linked to disease progression.

RESULTS

Distinct sets of >100 genes (P false discovery rate < 0.05) were specifically associated with at least one clinical domain (cognitive, social, negative, positive, arousal). In addition, dysregulation of immune response pathways was shared across domains and brain regions.

DISCUSSION

Our findings provide evidence for distinct transcriptional profiles associated with RDoC domains suggesting that each dimension is characterized by sets of genes providing insight into the underlying mechanisms.

Highlights

Post mortem brain tissue investigations are critically important for Alzheimer's disease (AD) research.Neuropsychiatric symptoms in AD are common and an important aspect of AD.Categorical phenotypes are commonly used, but insufficiently describe the heterogenous presentation of AD.Using natural language processing (NLP) of post mortem brain donor health records provides insight into dimensional phenotypes of AD.We provide evidence for distinct RNA expression profiles associated with NLP-derived Research Domain Criteria clinical domain scores.

Potential Role of High-Intensity Interval Training-Induced Increase in Humanin Levels for the Management of Type 2 Diabetes

This study investigated the effect of 8 weeks of high-intensity interval training (HIIT) on oxidative stress, inflammation, and apoptosis in rats with type 2 diabetes (T2D), focusing on the role of the Humanin (HN). In this study, 28 male Wistar rats were assigned to one of four groups: healthy control (CO), diabetes control (T2D), exercise (EX), and diabetes + exercise (T2D + EX). After diabetes induction (2-month high-fat diet and injection of 35 mg/kg streptozotocin), the animals in the EX and T2D + EX groups underwent an 8-week HIIT protocol (4-10, interval of 80%-100% of maximum speed). HOMA-IR, fasting blood glucose, and HN levels were measured in the serum. The expression of HN, Bax, Bcl-2, CAT, GPx, MDA, TNFα, and IL-10 was measured in the soleus muscle. Our results showed that the serum level of HN and the muscle levels of IL-10, SOD, CAT, and Bax were higher in the T2D + EX group than in the T2D group. However, the HOMA-IR index and the muscle levels of MDA, TNFα, and Bcl-2 were lower in the T2D + EX group than in the T2D group. Muscle levels of HN and GPx showed no significant difference between the T2D + EX and T2D groups. The result of Pearson analysis showed a significant correlation between HN and MDA, SOD, Bax and Bcl-2. This study provides evidence that there is a correlation between serum Humanin levels and HIIT. HIIT benefits T2D rats by reducing inflammation and oxidative stress. Given Humanin's established involvement in inflammation and oxidative stress, it is possible that the benefits of HIIT on T2D rats are mediated by humanin.

[Gly14]-Humanin ameliorates high glucose-induced endothelial senescence via SIRT6

High glucose (HG) induced endothelial senescence is related to endothelial dysfunction and cardiovascular complications in diabetic patients. Humanin, a member of mitochondrial derived peptides (MDPs), is thought to contribute to aging-related cardiovascular protection. The goal of the study is to explore the pathogenesis of HG-induced endothelial senescence and potential anti-senescent effects of Humanin. Human umbilical vein endothelial cells (HUVECs) were exposed to glucose to induce senescence, determined by β-galactosidase staining and the expressions of p21, p53, and p16. A clinically relevant dose of HG (15 mM, HG) induced endothelial senescence after 72 h incubation without elevated apoptosis. HG-induced senescence was attributed to the induction of reactive oxygen species (ROS) caused by SIRT6 downregulation, as ROS inhibitor N-acetyl cysteine blocked HG-induced senescence, while inactivation of SIRT6 increased ROS levels and promoted senescence. Strikingly. pretreatment with [Gly14]-Humanin (HNG) antagonized the downregulation of SIRT6 in response to HG and alleviated ROS production and cell senescence. HG-induced reduction of SIRT6 results in ROS overproduction and endothelial senescence. Humanin protects against HG-induced endothelial senescence via SIRT6. This study provides new directions for biological products related to Humanin to be a potential candidate for the prevention of vascular aging in diabetes.

Microproteins encoded by short open reading frames: Vital regulators in neurological diseases

Short open reading frames (sORFs) are frequently overlooked because of their historical classification as non-coding elements or dismissed as "transcriptional noise". However, advanced genomic and proteomic technologies have allowed for screening and validating sORFs-encoded peptides, revealing their fundamental regulatory roles in cellular processes and sparking a growing interest in microprotein biology. In neuroscience, microproteins serve as neurotransmitters in signal transmission and regulate metabolism and emotions, exerting pivotal effects on neurological conditions such as nerve injury, neurogenic tumors, inflammation, and neurodegenerative diseases. This review summarizes the origins, characteristics, classifications, and functions of microproteins, focusing on their molecular mechanisms in neurological disorders. Potential applications, future perspectives, and challenges are discussed.

Comparison of the Mitophagy and Apoptosis Related Gene Expressions in Waste Embryo Culture Medium of Female Infertility Types

Mitochondria is an important organelle for the oocyte-to-embryo transition in the early embryonic development period. The oocyte uses mitochondria functionally and its mitochondrial DNA (mtDNA) content as the main energy source in the embryo development at the preimplantation stage. The aim of this study is to compare mitophagic, apoptotic and humanin gene expressions from the culture medium fluid in which embryos are developed and monitored among normoresponder (NOR), polycystic ovary syndrome (PCOS), young and older patients with poor ovarian reserve (POR). The study groups consisted of infertile patients who applied to the Bahçeci Umut IVF Center as NOR (Control), PCOS, POR-Advanced (POR-A) and POR-Young (POR-Y). After the isolation of total RNA from the collected samples, MFN1, MFN2, PINK1, PARKIN, SMN1, SMN2, p53 and Humanin gene expressions were determined by Real Time-PCR. The average age of only the POR-A was determined to be higher than the NOR (p < 0.001). The MFN1, SMN2 (p < 0.05), Humanin and p53 gene expressions (p < 0.001) increased, while PINK1 gene expression decreased (p < 0.05), in the POR-Y compared to the NOR. A decrease in MFN2, PARKIN (p < 0.05) and PINK1 gene expressions was determined in the PCOS compared to the NOR (p < 0.001). Furthermore, a decrease was observed in MFN2, PINK1 (p < 0.001) and Humanin gene expressions compared to the NOR (p < 0.05). The current data are the first in the literature determining the apoptotic and mitophagic status of the oocyte. The current results prove that waste embryo culture fluid may provide a non-invasive profile for important cellular parameters such as mitochondrial dysfunction in female infertility. The evaluation of significant cellular parameters can be performed much earlier without any intervention into the embryo.

Mitochondrial-derived peptides in cardiovascular disease: Novel insights and therapeutic opportunities

BACKGROUND

Mitochondria-derived peptides (MDPs) represent a recently discovered family of peptides encoded by short open reading frames (ORFs) found within mitochondrial genes. This group includes notable members including humanin (HN), mitochondrial ORF of the 12S rDNA type-c (MOTS-c), and small humanin-like peptides 1-6 (SHLP1-6). MDPs assume pivotal roles in the regulation of diverse cellular processes, encompassing apoptosis, inflammation, and oxidative stress, which are all essential for sustaining cellular viability and normal physiological functions. Their emerging significance extends beyond this, prompting a deeper exploration into their multifaceted roles and potential applications.

AIM OF REVIEW

This review aims to comprehensively explore the biogenesis, various types, and diverse functions of MDPs. It seeks to elucidate the central roles and underlying mechanisms by which MDPs participate in the onset and development of cardiovascular diseases (CVDs), bridging the connections between cell apoptosis, inflammation, and oxidative stress. Furthermore, the review highlights recent advancements in clinical research related to the utilization of MDPs in CVD diagnosis and treatment.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MDPs levels are diminished with aging and in the presence of CVDs, rendering them potential new indicators for the diagnosis of CVDs. Also, MDPs may represent a novel and promising strategy for CVD therapy. In this review, we delve into the biogenesis, various types, and diverse functions of MDPs. We aim to shed light on the pivotal roles and the underlying mechanisms through which MDPs contribute to the onset and advancement of CVDs connecting cell apoptosis, inflammation, and oxidative stress. We also provide insights into the current advancements in clinical research related to the utilization of MDPs in the treatment of CVDs. This review may provide valuable information with MDPs for CVD diagnosis and treatment.

Noncanonical microprotein regulation of immunity

The immune system is highly regulated but, when dysregulated, suboptimal protective or overly robust immune responses can lead to immune-mediated disorders. The genetic and molecular mechanisms of immune regulation are incompletely understood, impeding the development of more precise diagnostics and therapeutics for immune-mediated disorders. Recently, thousands of previously unrecognized noncanonical microprotein genes encoded by small open reading frames have been identified. Many of these microproteins perform critical functions, often in a cell- and context-specific manner. Several microproteins are now known to regulate immunity; however, the vast majority are uncharacterized. Therefore, illuminating what is often referred to as the "dark proteome," may present opportunities to tune immune responses more precisely. Here, we review noncanonical microprotein biology, highlight recently discovered examples regulating immunity, and discuss the potential and challenges of modulating dysregulated immune responses by targeting microproteins.

Mitochondrial dysfunction is associated with cognitive impairment in adults with OSA without dementia

STUDY OBJECTIVES

Increased reactive oxygen species associated with loss of mitochondrial function affect synaptic activity, which is an important mechanism underlying cognitive decline. This study assesses the role of mitochondrial proteins in neuron-derived exosomes (NDEs) on cognitive impairment in patients with obstructive sleep apnea (OSA) without dementia.

METHODS

Analyses were conducted in 268 study participants with complete polysomnography data, cognitive tests, and important clinical data available. NDEs were isolated immunochemically for enzyme-linked immunosorbent assay quantification of mitochondrial proteins, i.e., humanin and mitochondrial open reading frame of the 12S rRNA-c (MOTS-c), and synaptic protein, i.e., neurogranin (NRGN). A mediation analysis of the relationship between sleep parameters and cognition was performed using humanin, MOTS-c, and NRGN values as a mediating factor. Twenty-two patients with moderate to severe OSA who received CPAP therapy were followed up, and humanin, MOTS-c and NRGN levels were reassessed after 1 year of treatment.

RESULTS

All participants were divided into the OSA + MCI group (n = 91), OSA-MCI group (n = 89), MCI group (MCI without OSA) (n = 38) and control group (normal cognitive state without OSA) (n = 50). The mean CD63-normalized NDE levels of humanin, MOTS-c, and NRGN in the OSA + MCI group were higher than those in the OSA-MCI and control groups. The NDE levels of humanin, MOTS-c, and NRGN in the MCI group were lower than those in controls. The odds of cognitive impairment in patients with OSA were higher with higher NDE levels of humanin, MOTS-c, and NRGN (odds ratio (OR): 2.100, 95 % confidence interval (CI): 1.646-2.679, P < 0.001; OR: 5.453, 95 % CI: 3.112-9.556, P < 0.001; OR: 3.115, 95 % CI: 2.163-4.484, P < 0.001). The impaired cognitive performance was associated with higher NDE levels of humanin (β: 0.505, SE: 0.048, P < 0.001), MOTS-c (β: 0.580, SE: 0.001, P < 0.001), and NRGN (β: 0.585, SE: 0.553, P < 0.001). The relationship between sleep parameters (mean SaO2 and T90) and MoCA scores was mediated by the NDE levels of humanin, MOTS-c, and NRGN with the proportion of mediation varying from 35.33 % to 149.07 %. Receiver operating characteristic curve revealed an area under the curve of 0.905 for humanin, 0.873 for MOTS-c, and 0.934 for NRGN to predict MCI in OSA patients without dementia. Increased humanin, MOTS-c, and NRGN levels significantly decreased after CPAP treatment.

CONCLUSIONS

Mitochondrial dysfunction is implicated in cognitive impairment in OSA patients without dementia, and mainly mediates the association between intermittent hypoxia and cognitive impairment in adults with OSA without dementia. Mitochondrial dysfunction can be partially reversible by CPAP treatment. Mitochondrial proteins can be used as markers of cognitive impairment in patients with OSA.

Single cell transcriptomics of cerebrospinal fluid cells from patients with recent-onset narcolepsy

Narcolepsy is a rare cause of hypersomnolence and may be associated or not with cataplexy, i.e. sudden muscle weakness. These forms are designated narcolepsy-type 1 (NT1) and -type 2 (NT2), respectively. Notable characteristics of narcolepsy are that most patients carry the HLA-DQB1*06:02 allele and NT1-patients have strongly decreased levels of hypocretin-1 (synonym orexin-A) in the cerebrospinal fluid (CSF). The pathogenesis of narcolepsy is still not completely understood but the strong HLA-bias and increased frequencies of CD4+ T cells reactive to hypocretin in the peripheral blood suggest autoimmune processes in the hypothalamus. Here we analyzed the transcriptomes of CSF-cells from twelve NT1 and two NT2 patients by single cell RNAseq (scRNAseq). As controls, we used CSF cells from patients with multiple sclerosis, radiologically isolated syndrome, and idiopathic intracranial hypertension. From 27,255 CSF cells, we identified 20 clusters of different cell types and found significant differences in three CD4+ T cell and one monocyte clusters between narcolepsy and multiple sclerosis patients. Over 1000 genes were differentially regulated between patients with NT1 and other diseases. Surprisingly, the most strongly upregulated genes in narcolepsy patients as compared to controls were coding for the genome-encoded MTRNR2L12 and MTRNR2L8 peptides, which are homologous to the mitochondria-encoded HUMANIN peptide that is known playing a role in other neurological diseases including Alzheimer's disease.

Small but mighty: the rise of microprotein biology in neuroscience

The mammalian central nervous system coordinates a network of signaling pathways and cellular interactions, which enable a myriad of complex cognitive and physiological functions. While traditional efforts to understand the molecular basis of brain function have focused on well-characterized proteins, recent advances in high-throughput translatome profiling have revealed a staggering number of proteins translated from non-canonical open reading frames (ncORFs) such as 5' and 3' untranslated regions of annotated proteins, out-of-frame internal ORFs, and previously annotated non-coding RNAs. Of note, microproteins < 100 amino acids (AA) that are translated from such ncORFs have often been neglected due to computational and biochemical challenges. Thousands of putative microproteins have been identified in cell lines and tissues including the brain, with some serving critical biological functions. In this perspective, we highlight the recent discovery of microproteins in the brain and describe several hypotheses that have emerged concerning microprotein function in the developing and mature nervous system.

Mitochondrial-derived peptides: Antidiabetic functions and evolutionary perspectives

Mitochondrial-derived peptides (MDPs) are a novel class of bioactive microproteins encoded by short open-reading frames (sORF) in mitochondrial DNA (mtDNA). Currently, three types of MDPs have been identified: Humanin (HN), MOTS-c (Mitochondrial ORF within Twelve S rRNA type-c), and SHLP1-6 (small Humanin-like peptide, 1 to 6). The 12 S ribosomal RNA (MT-RNR1) gene harbors the sequence for MOTS-c, whereas HN and SHLP1-6 are encoded by the 16 S ribosomal RNA (MT-RNR2) gene. Special genetic codes are used in mtDNA as compared to nuclear DNA: (i) ATA and ATT are used as start codons in addition to the standard start codon ATG; (ii) AGA and AGG are used as stop codons instead of coding for arginine; (iii) the standard stop codon UGA is used to code for tryptophan. While HN, SHLP6, and MOTS-c are encoded by the H (heavy owing to high guanine + thymine base composition)-strand of the mtDNA, SHLP1-5 are encoded by the L (light owing to less guanine + thymine base composition)-strand. MDPs attenuate disease pathology including Type 1 diabetes (T1D), Type 2 diabetes (T2D), gestational diabetes, Alzheimer's disease (AD), cardiovascular diseases, prostate cancer, and macular degeneration. The current review will focus on the MDP regulation of T2D, T1D, and gestational diabetes along with an emphasis on the evolutionary pressures for conservation of the amino acid sequences of MDPs.

Humanin ameliorates TBI-related cognitive impairment by attenuating mitochondrial dysfunction and inflammation

Traumatic brain injury (TBI) often results in a reduction of the capacity of cells to sustain energy demands, thus, compromising neuronal function and plasticity. Here we show that the mitochondrial activator humanin (HN) counteracts a TBI-related reduction in mitochondrial bioenergetics, including oxygen consumption rate. HN normalized the disruptive action of TBI on memory function, and restored levels of synaptic proteins (synapsin 1 and p-CREB). HN also counteracted TBI-related elevations of pro-inflammatory cytokines in plasma (TNF-α, INF-y, IL 17, IL 5, MCP 5, GCSF, RANNETS, sTNFRI) as well as in the hippocampus (gp-130 and p-STAT3). Gp-130 is an integral part of cytokine receptor impinging on STAT3 (Tyr-705) signaling. Furthermore, HN reduced astrocyte proliferation in TBI. The overall evidence suggests that HN plays an integral role in normalizing fundamental aspects of TBI pathology which are central to energy balance, brain function, and plasticity.

Neuroprotective Action of Humanin and Humanin Analogues: Research Findings and Perspectives

Humanin is a 24-mer peptide first reported in the early 2000s as a new neuroprotective/cytoprotective factor rescuing neuronal cells from death induced by various Alzheimer's disease-associated insults. Nowadays it is known that humanin belongs to the novel class of the so-called mitochondrial-derived peptides (which are encoded by mitochondrial DNA) and has been shown to exert beneficial cytoprotective effects in a series of in vitro and/or in vivo experimental models of human diseases, including not only neurodegenerative disorders but other human diseases as well (e.g., age-related macular degeneration, cardiovascular diseases, or diabetes mellitus). This review article is focused on the presentation of recent in vitro and in vivo research results associated with the neuroprotective action of humanin as well as of various, mainly synthetic, analogues of the peptide; moreover, the main mode(s)/mechanism(s) through which humanin and humanin analogues may exert in vitro and in vivo regarding neuroprotection have been reported. The prospects of humanin and humanin analogues to be further investigated in the frame of future research endeavors against neurodegenerative/neural diseases have also been briefly discussed.

Amylin and Secretases in the Pathology and Treatment of Alzheimer's Disease

Alzheimer's disease remains a prevailing neurodegenerative condition which has an array physical, emotional, and financial consequences to patients and society. In the past decade, there has been a greater degree of investigation on therapeutic small peptides. This group of biomolecules have a profile of fundamentally sound characteristics which make them an intriguing area for drug development. Among these biomolecules, there are four modulatory mechanisms of interest in this review: alpha-, beta-, gamma-secretases, and amylin. These protease-based biomolecules all have a contributory role in the amyloid cascade hypothesis. Moreover, the involvement of various biochemical pathways intertwines these peptides to have shared regulators (i.e., retinoids). Further clinical and translational investigation must occur to gain a greater understanding of its potential application in patient care. The aim of this narrative review is to evaluate the contemporary literature on these protease biomolecule modulators and determine its utility in the treatment of Alzheimer's disease.

Humanin derivative, HNG, enhances neurotransmitter release

BACKGROUND

Humanin (HN) is an endogenous 24-residue peptide that was first identified as a protective factor against neuronal death in Alzheimer's disease (AD). We previously demonstrated that the highly potent HN derivative HNG (HN with substitution of Gly for Ser14) ameliorated cognitive impairment in AD mouse models. Despite the accumulating evidence on the antagonizing effects of HN against cognitive deficits, the mechanisms behind these effects remain to be elucidated.

METHODS

The extracellular fluid in the hippocampus of wild-type young mice was collected by microdialysis and the amounts of neurotransmitters were measured. The kinetic analysis of exocytosis was performed by amperometry using neuroendocrine cells.

RESULTS

The hippocampal acetylcholine (ACh) levels were increased by intraperitoneal injection of HNG. HNG did not affect the physical activities of the mice but modestly improved their object memory. In a neuronal cell model, rat pheochromocytoma PC12 cells, HNG enhanced ACh-induced dopamine release. HNG increased ACh-induced secretory events and vesicular quantal size in primary neuroendocrine cells.

CONCLUSIONS

These findings suggest that HN directly enhances regulated exocytosis in neurons, which can contribute to the improvement of cognitive functions.

GENERAL SIGNIFICANCE

The regulator of exocytosis is a novel physiological role of HN, which provides a molecular clue for HN's effects on brain functions under health and disease.