GPBAR1 preserves neurite and synapse of dopaminergic neurons via RAD21-OPCML signaling: Role in preventing Parkinson's disease in mouse model and human patients

Cardiomyocyte-derived exosomes carrying miR-181a-5p facilitate heart-brain crosstalk and exacerbate methamphetamine dependence in rats

Background

Methamphetamine (MA) is one of the most harmful synthetic drugs, yet the mechanisms underlying its addiction and relapse remain incompletely understood. This study investigates how cardiomyocyte-derived exosomes carrying miRNAs facilitate heart-brain crosstalk and contribute to MA dependence.

Materials and methods

A conditioned place preference (CPP) model of MA dependence was established in rats. High-throughput sequencing were employed to identify candidate miRNAs in cardiac exosomes and brain tissues. Behavioral assessments, real-time PCR, nanoparticle tracking analysis, in vivo imaging, in vitro uptake assays, network pharmacology, and dual-luciferase reporter assays were used to explore the role of cardiomyocyte-derived exosomes in MA dependence.

Results

MA induced significant CPP in rats. miR-181a-5p was markedly upregulated in cardiac exosomes and brain tissue, with higher levels observed in cardiac exosomes. In vivo biodistribution showed that cardiomyocyte-derived exosomes cross the blood-brain barrier and accumulate in the brain. In vitro uptake assays demonstrated that SH-SY5Y cells internalized these exosomes, leading to increased miR-181a-5p expression. Tail vein injections of miR-181a-5p-enriched exosomes enhanced MA CPP behavior in rats. Network pharmacology revealed 108 potential targets of miR-181a-5p, enriched in processes such as steroid biosynthesis, amide metabolism, and apoptosis, involving pathways related to the endoplasmic reticulum, MAPK signaling, and amyotrophic lateral sclerosis. Molecular docking identified stable interactions between MA and 12 targets, including HSP90B1, TNF, and MAP2K1, with miR-181a-5p binding to the 3'-UTR regions of these targets. Dual-luciferase assays confirmed the negative regulation of six targets by miR-181a-5p.

Conclusion

This study reveals that cardiomyocyte-derived exosomes transport miR-181a-5p, facilitating heart-brain crosstalk and exacerbating MA CPP behavior in rats. These effects are mediated through the regulation of key brain targets, including HSP90B1, TNF, and MAP2K1, providing new insights into the molecular mechanisms of MA addiction and potential therapeutic targets.

Decoding TGR5: A comprehensive review of its impact on cerebral diseases

Currently, unraveling the enigmatic realm of drug targets for cerebral disorders poses a formidable challenge. Takeda G protein-coupled receptor 5 (TGR5), also known as G protein-coupled bile acid receptor 1, is a specific bile acid receptor. Widely distributed across various tissues, TGR5 orchestrates a myriad of biological functions encompassing inflammation, energy metabolism, fatty acid metabolism, immune responses, cellular proliferation, apoptosis, and beyond. Alongside its well-documented implications in liver diseases, obesity, type 2 diabetes, tumors, and cardiovascular diseases, a growing body of evidence accentuates the pivotal role of TGR5 in cerebral diseases. Thus, this comprehensive review aimed to scrutinize the current insights into the pathological mechanisms involving TGR5 in cerebral diseases, while contemplating its potential as a promising therapeutic target for cerebral diseases.

Double-strand-break repair protein rad21 homolog/Synaptotagmin-7 alleviates Alzheimer's disease in mice by promoting M2 polarization of microglia

Synaptotagmin-7 (SYT7) has been proposed as an innovative therapeutic strategy for treating cognitive impairment, while its contribution to Alzheimer's disease (AD) alleviation remains unclear. In this study, we investigated the role and potential mechanisms of SYT7 in AD. APP/PS1 mice were induced as an AD mouse model, and RNA-sequencing was conducted to analyze the transcriptomic differences between the brain tissues of AD mice and controls. SYT7, which was the most significantly differentially expressed gene in the RNA-sequencing, was found to be reduced in AD-like mice, and overexpression of SYT7 alleviated cognitive dysfunction and attenuated neuroinflammation and neuronal loss in the hippocampal tissues of mice with AD. Transcription factor double-strand-break repair protein rad21 homolog (RAD21) bound to the promoter of SYT7 to activate SYT7 transcription. SYT7 and RAD21 were expressed in microglia. SYT7 and RAD21 both promoted M2 polarization of microglia, while silencing of SYT7 repressed the M2 polarization of microglia in the presence of RAD21 overexpression. Overall, our results indicate that RAD21 mediated transcriptional activation of SYT7 to promote M2 polarization of microglia, thereby alleviating AD-like symptoms in mice, which might provide prospective cues for developing therapeutic strategies to improve cognitive impairment and AD course.

TGR5-mediated lateral hypothalamus-dCA3-dorsolateral septum circuit regulates depressive-like behavior in male mice

Although bile acids play a notable role in depression, the pathological significance of the bile acid TGR5 membrane-type receptor in this disorder remains elusive. Using depression models of chronic social defeat stress and chronic restraint stress in male mice, we found that TGR5 in the lateral hypothalamic area (LHA) predominantly decreased in GABAergic neurons, the excitability of which increased in depressive-like mice. Upregulation of TGR5 or inhibition of GABAergic excitability in LHA markedly alleviated depressive-like behavior, whereas down-regulation of TGR5 or enhancement of GABAergic excitability facilitated stress-induced depressive-like behavior. TGR5 also bidirectionally regulated excitability of LHA GABAergic neurons via extracellular regulated protein kinases-dependent Kv4.2 channels. Notably, LHA GABAergic neurons specifically innervated dorsal CA3 (dCA3) CaMKIIα neurons for mediation of depressive-like behavior. LHA GABAergic TGR5 exerted antidepressant-like effects by disinhibiting dCA3 CaMKIIα neurons projecting to the dorsolateral septum (DLS). These findings advance our understanding of TGR5 and the LHAGABA→dCA3CaMKIIα→DLSGABA circuit for the development of potential therapeutic strategies in depression.

Endogenous opiates and behavior: 2022

This paper is the forty-fifth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2022 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Ursodeoxycholic acid induces sarcopenia associated with decreased protein synthesis and autophagic flux

BACKGROUND

Skeletal muscle generates force and movements and maintains posture. Under pathological conditions, muscle fibers suffer an imbalance in protein synthesis/degradation. This event causes muscle mass loss and decreased strength and muscle function, a syndrome known as sarcopenia. Recently, our laboratory described secondary sarcopenia in a chronic cholestatic liver disease (CCLD) mouse model. Interestingly, the administration of ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is an effective therapy for cholestatic hepatic alterations. However, the effect of UDCA on skeletal muscle mass and functionality has never been evaluated, nor the possible involved mechanisms.

METHODS

We assessed the ability of UDCA to generate sarcopenia in C57BL6 mice and develop a sarcopenic-like phenotype in C₂C₁₂ myotubes and isolated muscle fibers. In mice, we measured muscle strength by a grip strength test, muscle mass by bioimpedance and mass for specific muscles, and physical function by a treadmill test. We also detected the fiber's diameter and content of sarcomeric proteins. In C₂C₁₂ myotubes and/or isolated muscle fibers, we determined the diameter and troponin I level to validate the cellular effect. Moreover, to evaluate possible mechanisms, we detected puromycin incorporation, p70S6K, and 4EBP1 to evaluate protein synthesis and ULK1, LC3 I, and II protein levels to determine autophagic flux. The mitophagosome-like structures were detected by transmission electron microscopy.

RESULTS

UDCA induced sarcopenia in healthy mice, evidenced by decreased strength, muscle mass, and physical function, with a decline in the fiber's diameter and the troponin I protein levels. In the C₂C₁₂ myotubes, we observed that UDCA caused a reduction in the diameter and content of MHC, troponin I, puromycin incorporation, and phosphorylated forms of p70S6K and 4EBP1. Further, we detected increased levels of phosphorylated ULK1, the LC3II/LC3I ratio, and the number of mitophagosome-like structures. These data suggest that UDCA induces a sarcopenic-like phenotype with decreased protein synthesis and autophagic flux.

CONCLUSIONS

Our results indicate that UDCA induces sarcopenia in mice and sarcopenic-like features in C₂C₁₂ myotubes and/or isolated muscle fibers concomitantly with decreased protein synthesis and alterations in autophagic flux.

Fucoidan from Fucus vesiculosus prevents the loss of dopaminergic neurons by alleviating mitochondrial dysfunction through targeting ATP5F1a

Parkinson's disease is a neurodegenerative disease that is characterized by the loss of dopaminergic neurons. Fucoidan, which has emerged as a neuroprotective agent, is a marine-origin sulfated polysaccharide enriched in brown algae and sea cucumbers. However, variations in structural characteristics exist among fucoidans derived from different sources, resulting in a wide spectrum of biological effects. It is urgent to find the fucoidan with the strongest neuroprotective effect, and the mechanism needs to be further explored. We isolated and purified four different fucoidan species with different chemical structures and found that Type II fucoidan from Fucus vesiculosus (FvF) significantly improved mitochondrial dysfunction, prevented neuronal apoptosis, reduced dopaminergic neuron loss, and improved motor deficits in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. Further mechanistic investigation revealed that the ATP5F1a protein is a key target responsible for alleviating mitochondrial dysfunction of FvF to exert neuroprotective effects. This study highlights the favorable properties of FvF for neuroprotection, making FvF a promising candidate for the treatment of PD.