Graphene oxide quantum dots (GOQDs) induce behavioral disorders via the disturbance of kynurenine pathway in zebrafish larvae.

The emergence of graphene quantum dots (GQDs) expands the use of graphene derivatives in nanomedicine for its direct therapeutic applications in treating neurodegeneration, inflammation, metabolic dysfunction, and among others. Nevertheless, the biosafety assessment of GQDs remains deficient mostly because of the diverse surface characteristics of the nanoparticles. Our prior work demonstrated that GQDs can induce strong thigmotactic effects in zebrafish larvae over a wide range of concentrations, yet the underlying metabolic mechanisms remain largely unknown. In this study, we conducted a further exploration about graphene oxide quantum dots (GOQDs) for its potential neurotoxic effect on the behaviors of zebrafish larvae by combining neurotransmitter-targeted metabolomics with locomotion analysis. After continuous exposure to a concentration gradient of GOQDs (12.5 - 25 - 50 - 100 - 200 µg/mL) for 7 days, the thigmotactic activities of zebrafish larvae were observed across all exposure concentrations relative to the control group, while the basal locomotor activities, including distance moved and average velocity, were significantly changed by low concentrations of GOQDs. Targeted metabolomics was performed using zebrafish larvae at 7 days post-fertilization (dpf) that were exposed to 12.5 and 200 µg/mL, both of which were found to perturb the kynurenine pathway by regulating the levels of kynurenine, 3-hydroxyanthranilic acid (3-HAA), and quinolinic acid (QA). Furthermore, the thigmotaxis of larval fish induced by GOQDs during exposure could be counteracted by supplementing Ro-61-8048, an agonist acting on kynurenine 3-monooxygenase (KMO). In conclusion, our study establishes the involvement of the kynurenine pathway in GOQDs-induced thigmotaxis, which is independent of the transcriptional modulation of glutamate receptor families.

Graphene quantum dots (GQDs) induce thigmotactic effect in zebrafish larvae via modulating key genes and metabolites related to synaptic plasticity.

Graphene quantum dots (GQDs) recently gain much attention for its medicinal values in treating diseases such as neurodegeneration and inflammations. However, owing to the high permeability of GQDs across the blood-brain barrier, whether its retention in the central nervous system (CNS) perturbs neurobehaviors remains less reported. In the study, the locomotion of zebrafish larvae (Danio rerio) was fully evaluated when administrated by two GQDs in a concentration gradient, respectively as reduced-GQDs (R-GQDs): 150, 300, 600, 1200, and 2400 g/L, and graphene oxide QDs (GOQDs): 60, 120, 240, 480, and 960 g/L. After exposure, the larvae were kept for locomotion analysis within one week's depuration. Substantial data showed that the basal locomotor activity of zebrafish larvae was not significantly changed by both two GQDs at low concentrations while weakened greatly with the increase of concentrations, and the total ATP levels of zebrafish larvae were also found to decrease significantly when exposed to the highest concentrations of GQDs. Next, the thigmotactic effect was observed to be remarkably induced in larvae by both two GQDs at any concentrations during exposure, and remained strong in larvae treated by high concentrations of R-GQDs after 7 days' depuration. To be noted, we found that GQDs affected the synaptic plasticity via downregulating the mRNA levels of NMDA and AMPA receptor family members as well as the total glutamine levels in zebrafish larvae. Together, our study presented robust data underlying the locomotor abnormalities aroused by GQDs in zebrafish larvae and indicated the potential adverse effects of GQDs on synaptic plasticity.

In vivo toxicity assessment of four types of graphene quantum dots (GQDs) using mRNA sequencing.

GQDs show great potential in drug carriers, bioimaging, biosensors, theranostics, and are recently reported as promising therapeutic agents to treat amyloid-related diseases such as Parkinson's disease and inflammations such as colitis. However, current toxicity data about GQDs based on in vivo toxicity assessments remain scarce. In the study, we examined the mRNA expression changes of zebrafish embryos exposed to four types of GQDs, including raw graphene quantum dots (R-GQDs), graphene oxide quantum dots (GOQDs), carboxyl GQDs (C-GQDs), and aminated GQDs (A-GQDs). Firstly, we treated embryos with the four GQDs at three concentrations (50, 100, and 200 µg/mL), and found that only A-GQDs caused embryonic developmental arrest at 100 and 200 µg/mL with significantly decreased survival rates and heartbeat rates, as well as the elevated malformation rates. Next, we analyzed the mRNA sequencing data acquired from zebrafish embryos exposed to the four GQDs for 7 days at 100 µg/mL, and found that all GQDs can act on potassium (K+) and calcium (Ca2+) channels, and spliceosomes with varying degrees of regulatory effects. Compared to other GQDs, A-GQDs can strongly perturb the anticoagulant protein C (PC) pathway via activating most genes associated with complement and coagulation system, cell adhesion molecules (CAMs), and MAPK. In conclusion, this study provided substantial transcriptomic data underlying the common signaling pathways induced by various types of GQDs and pointed out the specific toxicity of A-GQDs on hemostatic system.

Molecular basis of neurophysiological and antioxidant roles of Szechuan pepper.

The balance between anti- and pro-oxidant activities is of great important to maintain the biochemical and physiological homeostasis in the human body. Developing new therapeutic strategies to reduce health risks caused by free radicals has always been research focus over the past decades. Szechuan pepper, a characteristic pungent-flavored spice in Sichuanese cuisine, recently attracts the attention of researchers for its widespread therapeutic effects on acute and chronic diseases. The plant produces the innocuous 'tingling and numbing' sensations across the oral cavity by stirring specific neuron types, which are mechanically distinct from those excited by capsaicin. Furthermore, the extracts or the compounds of Szechuan pepper are biochemically proven to possess strong antioxidant activities that could scavenge free radicals and inhibit overactive peroxidase system in pathological models. Herein, the review emphasizes the molecular basis underlying the neurophysiological and antioxidant activities of the plant by a comprehensive analysis of various signaling pathways in disease models treated by Szechuan pepper. Further, we performed a broadening analysis to unearth potential signaling pathways associated with the antioxidant roles of the plant.

Bioinformatics analysis reveals different gene expression patterns in the annulus fibrosis and nucleus pulpous during intervertebral disc degeneration.

Degeneration of the intervertebral disc (IVD), which consists of the annulus fibrosus (AF) and nucleus pulposus (NP), is a multifactorial physiological process associated with lower back pain. Despite decades of research, the knowledge of the underlying molecular mechanisms of IVD degeneration (IDD) has remained limited. The present study aimed to reveal the differential gene expression patterns in AF and NP during the process of IDD and to identify key biomarkers contributing to these differences. The microarray dataset GSE70362 containing 24 AF and 24 NP samples was retrieved from the Gene Expression Omnibus database. Of these, 8 healthy samples were discarded. GeneSpring11.5 software was employed to identify differentially expressed genes (DEGs). Metascape online tools were used to perform enrichment analyses. Finally, the DEGs were mapped with the Search Tool for the Retrieval of Interacting Genes, and a protein-protein interaction (PPI) network was constructed in Cytoscape software. A total of 87 DEGs were identified. Gene ontology enrichment revealed that these DEGs were mainly involved in the inflammatory response, the extracellular matrix and RNA polymerase II transcription factor activity. Pathway enrichment revealed that the DEGs were mainly involved in the transforming growth factor (TGF-ß) and estrogen signaling pathways. Matrix metalloproteinase (MMP)1 and interleukin (IL)6 were included in the genes enriched in rheumatoid arthritis, whereas bone morphogenetic protein (BMP)2 and thrombospondin 1 (THBS1) were among the genes enriched in the TGF-ß signaling pathway. In the PPI network, IL6 was identified as the central gene. In conclusion, as MMP1 has been demonstrated degrade collagen III at higher rates compared with other types of collagen (which is at a higher quantity in AF than NP), collagen types may be in different distribution patterns, which may contribute to the upregulation of MMP1 in AF. Differences in the expression of BMP2, ESR1 and THBS1 may explain for the pathological differences between AF and NP. IL6 may have a key role in different degeneration processes in AF and NP.