Nardilysin, ADAM10, and Alzheimer's disease: of mice and men

Comprehensive analysis of bioinformatics identification TST, SQOR and NRDC is mitochondria-related biomarkers of ischemic cerebral apoplexy

Mitochondria are an important organelle affecting the occurrence and development of ischemic stroke (IS). Although the role of mitochondria in IS has been paid attention to, the relevant biomarkers have not been identified, and the targeted treatment is still lacking. To further solve these problems, in this study, we combined and standardized GSE16561 and GSE58294 datasets in the GEO database as the test set, and GSE22255 as the training set. The mitochondria-related gene set was obtained from MitoCarta3.0 for study. R language was used to screen differentially expressed genes (DEGs), and weighted gene co-expression network analysis (WGCNA) was used to obtain the intersection genes. KEGG pathway enrichment and gene ontology (GO) analysis were performed. LASSO and Logistic methods were used to determine the diagnostic markers of mitochondrial-related IS. The correlation between it and the main immune cells and immune-related factors was analysed. The ROC curve was used to determine the diagnostic efficacy. The protein co-expression network, transcription factor, and miRNA prediction, and drug prediction by cMAP were performed against these markers. Molecular docking tested the binding energy. Transmission electron microscopy was used to observe the structure and morphology of mitochondria in cerebral microvascular endothelial cells of MCAO/R rats. Biochemical kits were used to detect the levels of MDA and SOD in blood and tissues. Elisa was used to detect the changes of the above targets in blood and tissues. In this study, a total of 38 intersection genes were obtained, and a diagnostic model composed of 3 genes (TST, SQOR, NRDC) was further established. KEGG and GO analysis showed that these genes were highly related to immunity and were involved in the immune activities related to neutrophils, CD4+T cells, CD8+T cells, and macrophages. In addition, a total of 42 proteins, 601 transcription factors, and 99 miRNAs related to TST, SQOR, and NRDC were predicted, and the interaction map was constructed. cMAP predicted 5 potential small molecule drugs and molecular docking suggested that W.13 had the best binding energy. In MCAO/R rats, the mitochondria in BMECs were severely damaged and fragmented, accompanied by a decrease in SOD activity and an increase in MDA level. In addition, the levels of TST and SQOR in blood and tissues were increased, and the levels of NRDC were decreased. Our study provides new insights into further understanding of IS from a mitochondrial perspective.

Dietary Supplements and Natural Products: An Update on Their Clinical Effectiveness and Molecular Mechanisms of Action During Accelerated Biological Aging

Accelerated biological aging, which involves the gradual decline of organ or tissue functions and the distortion of physiological processes, underlies several human diseases. Away from the earlier free radical concept, telomere attrition, cellular senescence, proteostasis loss, mitochondrial dysfunction, stem cell exhaustion, and epigenetic and genomic alterations have emerged as biological hallmarks of aging. Moreover, nutrient-sensing metabolic pathways are critical to an organism's ability to sense and respond to nutrient levels. Pharmaceutical, genetic, and nutritional interventions reverting physiological declines by targeting nutrient-sensing metabolic pathways can promote healthy aging and increase lifespan. On this basis, biological aging hallmarks and nutrient-sensing dependent and independent pathways represent evolving drug targets for many age-linked diseases. Here, we discuss and update the scientific community on contemporary advances in how dietary supplements and natural products beneficially revert accelerated biological aging processes to retrograde human aging and age-dependent human diseases, both from the clinical and preclinical studies point-of-view. Overall, our review suggests that dietary/natural products increase healthspan-rather than lifespan-effectively minimizing the period of frailty at the end of life. However, real-world setting clinical trials and basic studies on dietary supplements and natural products are further required to decisively demonstrate whether dietary/natural products could promote human lifespan.

Methylomic profiling in trisomy 21 identifies cognition- and Alzheimer's disease-related dysregulation

Abstract

Background

Trisomy 21 (T21) is associated with intellectual disability that ranges from mild to profound with an average intellectual quotient of around 50. Furthermore, T21 patients have a high risk of developing Alzheimer’s disease (AD) early in life, characterized by the presence of senile plaques of amyloid protein and neurofibrillary tangles, leading to neuronal loss and cognitive decline. We postulate that epigenetic factors contribute to the observed variability in intellectual disability, as well as at the level of neurodegeneration seen in T21 individuals.

Materials and Methods

A genome-wide DNA methylation study was performed using Illumina Infinium® MethylationEPIC BeadChips on whole blood DNA of 3 male T21 patients with low IQ, 8 T21 patients with high IQ (4 males and 4 females), and 21 age- and sex-matched control samples (12 males and 9 females) in order to determine whether DNA methylation alterations could help explain variation in cognitive impairment between individuals with T21. In view of the increased risk of developing AD in T21 individuals, we additionally investigated the T21-associated sites in published blood DNA methylation data from the AgeCoDe cohort (German study on Ageing, Cognition, and Dementia). AgeCoDe represents a prospective longitudinal study including non-demented individuals at baseline of which a part develops AD dementia at follow-up.

Results

Two thousand seven hundred sixteen differentially methylated sites and regions discriminating T21 and healthy individuals were identified. In the T21 high and low IQ comparison, a single CpG located in the promoter of PELI1 was differentially methylated after multiple testing adjustment. For the same contrast, 69 differentially methylated regions were identified. Performing a targeted association analysis for the significant T21-associated CpG sites in the AgeCoDe cohort, we found that 9 showed significant methylation differences related to AD dementia, including one in the ADAM10 gene. This gene has previously been shown to play a role in the prevention of amyloid plaque formation in the brain.

Conclusion

The differentially methylated regions may help understand the interaction between methylation alterations and cognitive function. In addition, ADAM10 might be a valuable blood-based biomarker for at least the early detection of AD.

Clinical determination of serum nardilysin levels in predicting 30-day mortality among adults with malignant cerebral infarction

BACKGROUND

Nardilysin, a kind of metalloendopeptidase, plays an important role in numerous inflammatory diseases. Malignant cerebral infarction (Glasgow coma scale score of <9) is associated with a high mortality risk. Here, we intended to investigate the relationship between serum nardilysin levels and prognosis of patients with malignant cerebral infarction.

METHODS

Serum nardilysin concentrations were quantified at malignant cerebral infarction diagnosis moment in 105 patients and at study entrance in 105 healthy controls. Association of nardilysin concentrations with 30-day mortality and overall survival was estimated using multivariate analyses.

RESULTS

The patients exhibited substantially increased serum nardilysin concentrations, as compared to the controls. Nardilysin concentrations were in pronounced correlation with Glasgow coma scale scores and serum C-reactive protein concentrations. Serum nardilysin was independently predictive of 30-day mortality and overall survival. Under receiver operating characteristic curve, its high discriminatory ability was found.

CONCLUSIONS

Rising serum nardilysin concentrations following malignant cerebral infarction are strongly related to stroke severity, inflammatory extent and a higher risk of mortality, substantializing serum nardilysin as a potential prognostic biomarker for malignant cerebral infarction.

Serotoninergic antidepressants positively affect platelet ADAM10 expression in patients with Alzheimer's disease

BACKGROUND

Studies have demonstrated a decreased platelet ADAM10 expression in patients with Alzheimer's Disease (AD), classifying this protein as a blood-based AD biomarker. About 50% of the patients with AD are diagnosed with depression, which is commonly treated with tricyclic and tetracyclic antidepressants, monoaminoxidade (MAO) inhibitors and, more preferably, with selective serotonin reuptake inhibitors (SSRIs). Considering that a large proportion of patients with AD takes antidepressant medications during the course of the disease we investigated the influence of this medication on the expression of platelet ADAM10, which is considered the main α-secretase preventing beta-amyloid (βA) formation.

METHODS

Blood was collected for protein extraction from platelets. ADAM10 was analyzed by using western blotting and reactive bands were measured using β-actin as endogenous control.

RESULTS

Platelet ADAM10 protein expression in patients with AD was positively influenced by serotoninergic medication.

CONCLUSION

More studies on the positive effects of serotonergic antidepressants on ADAM10 platelet expression should be performed in order to understand its biological mechanisms and to verify whether these effects are reflected in the central nervous system. This work represents an important advance for the study of AD biomarkers, as well as for more effective pharmacological treatment of patients with AD and associated depression.

Ultrastructural localization and distribution of Nardilysin in mammalian male germ cells

Background

NRD convertase, also termed Nardilysin, is a Zn⁺⁺ metalloendopeptidase that specifically cleaves the N-terminus of arginine and lysine residues into dibasic moieties. Although this enzyme was found located within the testis, its function in male reproduction is largely unknown. In addition, the precise distribution of this enzyme within germ cells remains to be determined.

Methods

To answer these questions, we developed an immuno-gold electron microscopy analysis to detect Nardilysin at ultrastructural level in mice. In addition, we performed a quantitative analysis of these gold particles to statistically estimate the distribution of Nardilysin in the different subcellular compartments of differentiating late spermatids/spermatozoa.

Results

Expression of Nardilysin in wild-type mice was restricted to germ cells and markedly increased during the last steps of spermiogenesis. In elongated spermatids, we found the enzyme mainly localized in the cytoplasm, more precisely associated with two microtubular structures, the manchette and the axoneme. No labelling was detected over the membranous organelles of the spermatids. To test whether this localization is dependent of the functional microtubules organization of the flagella, we analysed the localization into a specific mouse mutant ebo/ebo (ébouriffé) known to be sterile due to an impairment of the final organization of the flagellum. In the ebo/ebo, the enzyme was still localized over the microtubules of the axoneme and over the isolated cytoplasmic microtubules doublets. Quantification of gold particles in wild-type and mutant flagella revealed the specific association of the enzyme within the microtubular area of the axoneme.

Conclusions

The strong and specific accumulation of Nardilysin in the manchette and axoneme suggests that the enzyme probably contributes either to the establishment of these specific microtubular structures and/or to their functional properties.

Solution structure of a DNA quadruplex containing ALS and FTD related GGGGCC repeat stabilized by 8-bromodeoxyguanosine substitution

A prolonged expansion of GGGGCC repeat within non-coding region of C9orf72 gene has been identified as the most common cause of familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), which are devastating neurodegenerative disorders. Formation of unusual secondary structures within expanded GGGGCC repeat, including DNA and RNA G-quadruplexes and R-loops was proposed to drive ALS and FTD pathogenesis. Initial NMR investigation on DNA oligonucleotides with four repeat units as the shortest model with the ability to form an unimolecular G-quadruplex indicated their folding into multiple G-quadruplex structures in the presence of K⁺ ions. Single dG to 8Br-dG substitution at position 21 in oligonucleotide d[(G₄C₂)₃G₄] and careful optimization of folding conditions enabled formation of mostly a single G-quadruplex species, which enabled determination of a high-resolution structure with NMR. G-quadruplex structure adopted by d[(G₄C₂)₃GG^BrGG] is composed of four G-quartets, which are connected by three edgewise C-C loops. All four strands adopt antiparallel orientation to one another and have alternating syn-anti progression of glycosidic conformation of guanine residues. One of the cytosines in every loop is stacked upon the G-quartet contributing to a very compact and stable structure.

Loss of hfe function reverses impaired recognition memory caused by olfactory manganese exposure in mice

Excessive manganese (Mn) in the brain promotes a variety of abnormal behaviors, including memory deficits, decreased motor skills and psychotic behavior resembling Parkinson’s disease. Hereditary hemochromatosis (HH) is a prevalent genetic iron overload disorder worldwide. Dysfunction in HFE gene is the major cause of HH. Our previous study has demonstrated that olfactory Mn uptake is altered by HFE deficiency, suggesting that loss of HFE function could alter manganese-associated neurotoxicity. To test this hypothesis, Hfe-knockout (Hfe^−/−) and wild-type (Hfe^+/+) mice mice were intranasally-instilled with manganese chloride (MnCl₂ 5 mg/kg) or water daily for 3 weeks and examined for memory function. Olfactory Mn diminished both short-term recognition and spatial memory in Hfe^+/+ mice, as examined by novel object recognition task and Barnes maze test, respectively. Interestingly, Hfe^−/− mice did not show impaired recognition memory caused by Mn exposure, suggesting a potential protective effect of Hfe deficiency against Mn-induced memory deficits. Since many of the neurotoxic effects of manganese are thought to result from increased oxidative stress, we quantified activities of anti-oxidant enzymes in the prefrontal cortex (PFC). Mn instillation decreased superoxide dismutase 1 (SOD1) activity in Hfe^+/+ mice, but not in Hfe^−/− mice. In addition, Hfe deficiency up-regulated SOD1 and glutathione peroxidase activities. These results suggest a beneficial role of Hfe deficiency in attenuating Mn-induced oxidative stress in the PFC. Furthermore, Mn exposure reduced nicotinic acetylcholine receptor levels in the PFC, indicating that blunted acetylcholine signaling could contribute to impaired memory associated with intranasal manganese. Together, our model suggests that disrupted cholinergic system in the brain is involved in airborne Mn-induced memory deficits and loss of HFE function could in part prevent memory loss via a potential up-regulation of anti-oxidant enzymes in the PFC.