Treatment of acute cerebral ischemia using animal models: a meta-analysis

Comparative Investigation of Raw and Processed Radix Polygoni Multiflori on the Treatment of Vascular Dementia by Liquid Chromatograph-Mass Spectrometry Based Metabolomic Approach

Radix Polygoni Multiflori (PM) is a well-known nootropic used in traditional Chinese medicine (TCM). Considering the efficacy and application discrepancy between raw (RPM) and processed PM (PPM), the similarities and differences between them in the treatment of vascular dementia (VaD) is intriguing. In this study, a VaD rat model was constructed by 2-vessel occlusion (2-VO). During 28 days of treatment, plasma was collected on days 7, 14, 21, and 28 after the start of dosing and the metabolic profile was analyzed by HPLC-MS/MS-based metabolomics. The Morris Water Maze Test, hematoxylin-eosin and Nissl staining, and biochemical analysis were used to assess cognitive function, pathogenic alterations and oxidative stress, respectively. RPM and PPM effectivelyreducedthe 2VO-induced cognitive impairment and mitigated histological alterations in hippocampus tissue. The 2-VO model significantly elevated MDA level and decreased SOD activity and GSH level, indicating severe oxidative stress, which could also be attenuated by RPM and PPM treatment. RPM outperformed PPM in decreasing MDA levels while PPM outperformed RPM in increasing GSH levels. Differential metabolites were subjected to Metabolite Set Enrichment Analysis (MSEA) and genes corresponding to proteins having interactions with metabolites were further annotated with Gene Ontology (GO). Both RPM and PPM ameliorated VaD-relevant vitamin B6 metabolism, pentose phosphate pathways, and taurine and hypotaurine metabolism. In addition, the metabolism of cysteine and methionine was regulated only by RPM, and riboflavin metabolism was modulated only by PPM. The results suggested that raw and processed PM had comparable efficacy in the treatment of VaD but also with some mechanistic differenece.

Preclinical animal studies in ischemic stroke: Challenges and some solutions

Despite the impressive efficacies demonstrated in preclinical research, hundreds of potentially neuroprotective drugs have failed to provide effective neuroprotection for ischemic stroke in human clinical trials. Lack of a powerful animal model for human ischemic stroke could be a major reason for the failure to develop successful neuroprotective drugs for ischemic stroke. This review recapitulates the available cerebral ischemia animal models, provides an anatomical comparison of the circle of Willis of each species, and describes the functional assessment tests used in these ischemic stroke models. The distinct differences between human ischemic stroke and experimental stroke in available animal models is explored. Innovative animal models more closely resembling human strokes, better techniques in functional outcome assessment and better experimental designs generating clearer and stronger evidence may help realise the development of truly neuroprotective drugs that will benefit human ischemic stroke patients. This may involve use of newer molecules or revisiting earlier studies with new experimental designs. Translation of any resultant successes may then be tested in human clinical trials with greater confidence and optimism.

Astrocyte-derived exosome-transported microRNA-34c is neuroprotective against cerebral ischemia/reperfusion injury via TLR7 and the NF-κB/MAPK pathways

Exosomes and microRNAs (miRs) are critical in reducing ischemia/reperfusion (I/R) injury, but the mechanism of astrocyte-derived exosome (ATC-Exo)-transported miR-34c in cerebral I/R injury is unclear. A rat model of cerebral I/R injury was established in this study, and the rats were injected with ATC-Exos. An oxygen glucose deprivation/reperfusion (OGD/R) model in N2a cells was utilized to mimic cerebral I/R injury in vitro, and the effects of ATC-Exo-transported miR-34c on the biological episodes of OGD/R-stimulated N2a cells were evaluated. The downstream gene and pathway of miR-34c were verified, and a rescue experiment of the pathway was performed. Consequently, we found that I/R damaged neurons, and ATC-Exo-transported miR-34c alleviated the neuronal injury caused by I/R. In addition, ATC-Exo-transported miR-34c promoted proliferation and inhibited apoptosis in OGD/R-stimulated N2a cells. miR-34c targeted Toll-like receptor 7 (TLR7) and downregulated the NF-κB/MAPK axis. Treatment with NF-κB- or MAPK-specific inhibitors partially restored the impaired protection against I/R that was caused by ATC-Exos with low expression of miR-34c. Overall, ATC-Exo-transported miR-34c targets TLR7 to downregulate the NF-κB/MAPK axis and relieve neurological damage induced by I/R. This study may offer novel insight for the treatment of cerebral I/R injury.

Structure modeling of γ-aminobutyric acid transporters - Molecular basics of ligand selectivity

γ-Aminobutyric acid transporters are responsible for regulating the GABA level in the synaptic cleft. In this way, they affect GABA-ergic transmission which is important for the proper functioning of the central nervous system. The exact structure of GABA transporters is still unknown, which hinders the design of new, potent and selective inhibitors. For these reasons, we decided to create models of all types of human gamma-aminobutyric acid transporters. They were built based on crystal structures of related proteins from the SLC6 family using homology modeling methods. The reliability of the received models has been confirmed by a number of tools assessing the quality of protein models. To determine the ligand binding mode and indicate the amino acids responsible for selectivity, docking studies and molecular dynamics simulations were performed. The amino acids lining the bottom of the main binding site have a major impact on the selective ligand binding. In addition, an important element is the non-helical fragment of the transmembrane domain 10, and several amino acids within the vestibule of the transporters, which affect its volume. To check whether obtained models are suitable to distinguish active compounds from inactive ones, enrichment plots were prepared. Results suggest that our models may be useful in the search for new inhibitors of GABA transporters of the desired selectivity.

γ-Aminobutyric acid transporters as relevant biological target: Their function, structure, inhibitors and role in the therapy of different diseases

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the nervous system. It plays a crucial role in many physiological processes. Upon release from the presynaptic element, it is removed from the synaptic cleft by reuptake due to the action of GABA transporters (GATs). GATs belong to a large SLC6 protein family whose characteristic feature is sodium-dependent relocation of neurotransmitters through the cell membrane. GABA transporters are characterized in many contexts, but their spatial structure is not fully known. They are divided into four types, which differ in occurrence and role. Herein, the special attention was paid to these transporting proteins. This comprehensive review presents the current knowledge about GABA transporters. Their distribution in the body, physiological functions and possible utilization in the therapy of different diseases were fully discussed. The important structural features were described based on published data, including sequence analysis, mutagenesis studies, and comparison with known SLC6 transporters for leucine (LeuT), dopamine (DAT) and serotonin (SERT). Moreover, the most important inhibitors of GABA transporters of various basic scaffolds, diverse selectivity and potency were presented.