RESP18 deficiency has protective effects in dopaminergic neurons in an MPTP mouse model of Parkinson's disease

Disrupted hypothalamic transcriptomics and proteomics in a mouse model of type 2 diabetes exposed to recurrent hypoglycaemia

AIMS/HYPOTHESIS

Repeated exposures to insulin-induced hypoglycaemia in people with diabetes progressively impairs the counterregulatory response (CRR) that restores normoglycaemia. This defect is characterised by reduced secretion of glucagon and other counterregulatory hormones. Evidence indicates that glucose-responsive neurons located in the hypothalamus orchestrate the CRR. Here, we aimed to identify the changes in hypothalamic gene and protein expression that underlie impaired CRR in a mouse model of defective CRR.

METHODS

High-fat-diet fed and low-dose streptozocin-treated C57BL/6N mice were exposed to one (acute hypoglycaemia [AH]) or multiple (recurrent hypoglycaemia [RH]) insulin-induced hypoglycaemic episodes and plasma glucagon levels were measured. Single-nuclei RNA-seq (snRNA-seq) data were obtained from the hypothalamus and cortex of mice exposed to AH and RH. Proteomic data were obtained from hypothalamic synaptosomal fractions.

RESULTS

The final insulin injection resulted in similar plasma glucose levels in the RH group and AH groups, but glucagon secretion was significantly lower in the RH group (AH: 94.5±9.2 ng/l [n=33]; RH: 59.0±4.8 ng/l [n=37]; p<0.001). Analysis of snRNA-seq data revealed similar proportions of hypothalamic cell subpopulations in the AH- and RH-exposed mice. Changes in transcriptional profiles were found in all cell types analysed. In neurons from RH-exposed mice, we observed a significant decrease in expression of Avp, Pmch and Pcsk1n, and the most overexpressed gene was Kcnq1ot1, as compared with AH-exposed mice. Gene ontology analysis of differentially expressed genes (DEGs) indicated a coordinated decrease in many oxidative phosphorylation genes and reduced expression of vacuolar H+- and Na+/K+-ATPases; these observations were in large part confirmed in the proteomic analysis of synaptosomal fractions. Compared with AH-exposed mice, oligodendrocytes from RH-exposed mice had major changes in gene expression that suggested reduced myelin formation. In astrocytes from RH-exposed mice, DEGs indicated reduced capacity for neurotransmitters scavenging in tripartite synapses as compared with astrocytes from AH-exposed mice. In addition, in neurons and astrocytes, multiple changes in gene expression suggested increased amyloid beta (Aβ) production and stability. The snRNA-seq analysis of the cortex showed that the adaptation to RH involved different biological processes from those seen in the hypothalamus.

CONCLUSIONS/INTERPRETATION

The present study provides a model of defective counterregulation in a mouse model of type 2 diabetes. It shows that repeated hypoglycaemic episodes induce multiple defects affecting all hypothalamic cell types and their interactions, indicative of impaired neuronal network signalling and dysegulated hypoglycaemia sensing, and displaying features of neurodegenerative diseases. It also shows that repeated hypoglycaemia leads to specific molecular adaptation in the hypothalamus when compared with the cortex.

DATA AVAILABILITY

The transcriptomic dataset is available via the GEO ( http://www.ncbi.nlm.nih.gov/geo/ ), using the accession no. GSE226277. The proteomic dataset is available via the ProteomeXchange data repository ( http://www.proteomexchange.org ), using the accession no. PXD040183.

Cordycepin improved the cognitive function through regulating adenosine A2A receptors in MPTP induced Parkinson's disease mice model

BACKGROUND

Parkinson's disease (PD), the most common neurodegenerative disorder, primarily affects dopaminergic neurons in the substantia nigra (SN). In addition to severe motor dysfunction, PD patients appear apparent cognitive impairments in the late stage. Cognitive dysfunction is accompanied by synaptic transmission damage in the hippocampus. Cordycepin has been reported to alleviate cognitive impairments in neurodegenerative diseases.

PURPOSE

The study aimed to estimate the protection roles of cordycepin on cognitive dysfunction in PD model and explore the potential mechanisms.

METHODS

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was used to establish the PD model in vivo and in vitro experiments. In the in vivo experiments, the C57BL / 6 mice were intraperitoneally injected with MPTP and intragastric administration with cordycepin. Open field test (OFT) was used to estimate the exercise ability. Spontaneous alternation behavioral (SAB) and morris water maze (MWM) tests were used to evaluate the learning and memory abilities. The hippocampal slices from C57BL / 6 and Kunming mice in the in vitro experiments were used to record field excitatory postsynaptic potential (fEPSP) by electrophysiological methods. Western blotting was used to examine the level of tyrosine hydroxylase (TH) in the in vivo experiments and the levels of adenosine A₁ and A_2A receptors (A₁R and A_2AR) in the in vitro experiments, respectively. The drugs of MPTP, cordycepin, DPCPX and SCH58261 were perfused through dissolving in artificial cerebrospinal fluid.

RESULTS

Cordycepin could significantly reduce the impairments on motor, exploration, spatial learning and memory induce by MPTP. MPTP reduced the amplitude of LTP in hippocampal CA1 area but cordycepin could improve LTP amplitudes. Cordycepin at dosage of 20 mg/kg also increased the TH level in SN. In the in vitro experiments, MPTP inhibited synaptic transmission in hippocampal Schaffer-CA1 pathway with a dose-dependent relationship, while cordycepin could reverse the inhibition of synaptic transmission. Furthermore, the roles of cordycepin on synaptic transmission could been attenuated in the presence of the antagonists of A₁R and A_2AR, DPCPX and SCH58261, respectively. Interestingly, the level of A_2AR rather than A₁R in hippocampus was significantly decreased in the cordycepin group as compared to the control.

CONCLUSION

The present study has showed that cordycepin could improve cognitive function in the PD model induced by MPTP through regulating the adenosine A_2A receptors. These findings were helpful to provide a new strategy for the dementia caused by Parkinson's disease.

mRNA and lncRNA co-expression network in mice of acute intracerebral hemorrhage

Background

Intracerebral hemorrhage (ICH) is a severe subtype of stroke lacking effective pharmacological targets. Long noncoding RNA (lncRNA) has been confirmed to participate in the pathophysiological progress of various neurological disorders. However, how lncRNA affects ICH outcomes in the acute phase is not completely clear. In this study, we aimed to reveal the relationship of lncRNA-miRNA-mRNA following ICH.

Method

We conducted the autologous blood injection ICH model and extracted total RNAs on day 7. Microarray scanning was used to obtain mRNA and lncRNA profiles, which were validated by RT-qPCR. GO/KEGG analysis of differentially expressed mRNAs was performed using the Metascape platform. We calculated the Pearson correlation coefficients (PCCs) of lncRNA-mRNA for co-expression network construction. A competitive endogenous (Ce-RNA) network was established based on DIANALncBase and miRDB database. Finally, the Ce-RNA network was visualized and analyzed by Cytoscape.

Results

In total, 570 differentially expressed mRNAs and 313 differentially expressed lncRNAs were identified (FC ≥ 2 and value of p <0.05). The function of differentially expressed mRNAs was mainly enriched in immune response, inflammation, apoptosis, ferroptosis, and other typical pathways. The lncRNA-mRNA co-expression network contained 57 nodes (21 lncRNAs and 36 mRNAs) and 38 lncRNA-mRNA pairs. The ce-RNA network was generated with 303 nodes (29 lncRNAs, 163 mRNAs, and 111 miRNAs) and 906 edges. Three hub clusters were selected to indicate the most significant lncRNA-miRNA-mRNA interactions.

Conclusion

Our study suggests that the top differentially expressed RNA molecules may be the biomarker of acute ICH. Furthermore, the hub lncRNA-mRNA pairs and lncRNA-miRNA-mRNA correlations may provide new clues for ICH treatment.

Aire and Fezf2, two regulators in medullary thymic epithelial cells, control autoimmune diseases by regulating TSAs: Partner or complementer?

The expression of tissue-specific antigens (TSAs) in medullary thymic epithelial cells (mTECs) is believed to be responsible for the elimination of autoreactive T cells, a critical process in the maintenance of central immune tolerance. The transcription factor autoimmune regulator (Aire) and FEZ family zinc finger 2(Fezf2) play an essential role in driving the expression of TSAs in mTECs, while their deficiency in humans and mice causes a range of autoimmune manifestations, such as type 1 diabetes, Sjögren’s syndrome and rheumatoid arthritis. However, because of their regulatory mechanisms, the expression profile of TSAs and their relationship with special autoimmune diseases are still in dispute. In this review, we compare the roles of Aire and Fezf2 in regulating TSAs, with an emphasis on their molecular mechanisms in autoimmune diseases, which provides the foundation for devising improved diagnostic and therapeutic approaches for patients.

Deficiency of miR-29b2/c leads to accelerated aging and neuroprotection in MPTP-induced Parkinson's disease mice

Studies reveal a linkage of miR-29s in aging and Parkinson's disease (PD). Here we show that the serum levels of miR-29s in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice exhibited dynamic changes. The role of miR-29b2/c in aging and PD was studied utilizing miR-29b2/c gene knockout mice (miR-29b2/c KO). miR-29b2/c KO mice were characterized by a markedly lighter weight, kyphosis, muscle weakness and abnormal gait, when compared with wild-type (WT) mice. The WT also developed apparent dermis thickening and adipose tissue reduction. However, deficiency of miR-29b2/c alleviated MPTP-induced damages of the dopaminergic system and glial activation in the nigrostriatal pathway and consequently improved the motor function of MPTP-treated KO mice. Knockout of miR-29b2/c inhibited the expression of inflammatory factors in 1-methyl-4-phenylpyridinium (MPP⁺)-treated primary cultures of mixed glia, primary astrocytes, or LPS-treated primary microglia. Moreover, miR-29b2/c deficiency enhanced the activity of AMPK but repressed the NF-κB p65 signaling in glial cells. Our results show that miR-29b2/c KO mice display the progeria-like phenotype. Less activated glial cells and repressed neuroinflammation might bring forth dopaminergic neuroprotection in miR-29b2/c KO mice. Conclusively, miR-29b2/c is involved in the regulation of aging and plays a detrimental role in Parkinson's disease.

Regulated Endocrine-Specific Protein-18, an Emerging Endocrine Protein in Physiology: A Literature Review

Regulated endocrine-specific protein-18 (RESP18), a novel 18-kDa protein, was first identified in neuroendocrine tissue. Subsequent studies showed that Resp18 is expressed in the adrenal medulla, brain, pancreas, pituitary, retina, stomach, superior cervical ganglion, testis, and thyroid and also circulates in the plasma. Resp18 has partial homology with the islet cell antigen 512, also known as protein tyrosine phosphatase, receptor type N (PTPRN), but does not have phosphatase activity. Resp18 might serve as an intracellular signal; however, its function is unclear. It is regulated by dopamine, glucocorticoids, and insulin. We recently reported that the targeted disruption of the Resp18 locus in Dahl salt-sensitive rats increased their blood pressure and caused renal injury. The aim of the present review was to provide a comprehensive summary of the reported data currently available, especially the expression and proposed organ-specific function of Resp18.

The pretreatment of chronic restraint stress exerts little impact on the progression of heart failure in mice

Stress is a potent risk factor for depression. Chronic stress can exacerbate and induce symptoms of depression. Clinical studies suggested that depressive patients are more likely to develop coronary artery diseases. However, the causal relationship between depression and heart failure progression remains unclear. In this study, we aimed to explore the relevance between stress and heart failure (HF) in a mouse model subjected to chronic restraint stress and left anterior descending coronary artery (LAD) ligation. Mice were restrained for 3 h daily for 21 days and the processes were repeated once 3 months later. After the repeated chronic restraint stress, mice showed dramatically increased immobility time in the forced swim test, indicating a state of despair. Restrained and control mice were further subjected to LAD ligation surgery. Echocardiography was conducted 1 week, 2 weeks, and 1 month afterward. LAD-operated mice showed a significant decrease in the values of left ventricular ejection fraction (LVEF), and there was no difference in the LVEF values between the restrained and control mice. Relevant gene expression, neurotransmitter system, glial activation, and morphology of the heart-brain axis were comprehensively evaluated. We found no overall differences between the restrained and control mice with HF. Our results revealed that the repeated chronic restraint stress may have little effects on the progression of heart failure.