Spontaneous, transient adenosine release is not enhanced in the CA1 region of hippocampus during severe ischemia models

Hippocampal-derived extracellular vesicle synergistically deliver active adenosine hippocampus targeting to promote cognitive recovery after stroke

Ischemic stroke is a neurological disease that leads to brain damage and severe cognitive impairment. In this study, extracellular vesicles(Ev) derived from mouse hippocampal cells (HT22) were used as carriers, and adenosine (Ad) was encapsulated to construct Ev-Ad to target the damaged hippocampus. The results showed that, Ev-Ad had significant antioxidant effect and inhibited apoptosis. In vivo, Ev-Ad reduced cell death and reversed inflammation in hippocampus of ischemic mice, and improved long-term memory and learning impairment by regulating the expression of the A1 receptor and the A2A receptor in the CA1 region. Thus, the developmental approach based on natural carriers that encapsulating Ad not only successfully restored nerves after ischemic stroke, but also improved cognitive impairment in the later stage of ischemic stroke convalescence. The development and design of therapeutic drugs provides a new concept and method for the treatment of cognitive impairment in the convalescent phase after ischemic stroke.

Dynamic and Rapid Detection of Guanosine during Ischemia

Guanosine acts in both neuroprotective and neurosignaling pathways in the central nervous system; in this paper, we present the first fast voltammetric measurements of endogenous guanosine release during pre- and post-ischemic conditions. We discuss the metric of our measurements via analysis of event concentration, duration, and interevent time of rapid guanosine release. We observe changes across all three metrics from our normoxic to ischemic conditions. Pharmacological studies were performed to confirm that guanosine release is a calcium-dependent process and that the signaling observed is purinergic. Finally, we show the validity of our ischemic model via staining and fluorescent imaging. Overall, this paper sets the tone for rapid monitoring of guanosine and provides a platform to investigate the extent to which guanosine accumulates at the site of brain injury, i.e., ischemia.

Chrysin protects against cerebral ischemia-reperfusion injury in hippocampus via restraining oxidative stress and transition elements

Chrysin is a natural flavonoid compound that has antioxidant and neuroprotective effects. Cerebral ischemia reperfusion (CIR) is closely connected with increased oxidative stress in the hippocampal CA1 region and homeostasis disorder of transition elements such as iron (Fe), copper (Cu) and zinc (Zn). This exploration was conducted to elucidate the antioxidant and neuroprotective effects of chrysin based on transient middle cerebral artery occlusion (tMCAO) in rats. Experimentally, sham group, model group, chrysin (50.0 mg/kg) group, Ginaton (21.6 mg/kg) group, Dimethyloxallyl Glycine (DMOG, 20.0 mg/kg) + chrysin group and DMOG group were devised. The rats in each group were performed to behavioral evaluation, histological staining, biochemical kit detection, and molecular biological detection. The results indicated that chrysin restrained oxidative stress and the rise of transition element levels, and regulated transition element transporter levels in tMCAO rats. DMOG activated hypoxia-inducible factor-1 subunit alpha (HIF-1α), reversed the antioxidant and neuroprotective effects of chrysin, and increased transition element levels. In a word, our findings emphasize that chrysin plays a critical role in protecting CIR injury via inhibiting HIF-1α against enhancive oxidative stress and raised transition metal levels.

Efficacy of acupuncture in animal models of vascular dementia: A systematic review and network meta-analysis

Background and purpose

Acupuncture is widely used in clinical practice for the treatment of vascular diseases. However, the protocol, efficacy, and mechanism of acupuncture in animal models of vascular dementia are still controversial. Based on the above problems, we initiated this comprehensive study.

Methods

To analyze the literatures included in this study, 4 databases were searched and the SYRCLE's Risk of bias tool was employed. To perform the subgroup analysis of different acupuncture methods and the Review Manager 5.3 was applied. Meanwhile, the pairwise and network meta-analysis were conducted using Addis 1.16.8. The outcomes included escape latency, number of crossings, time spent in the target quadrant, and swimming speed.

Results

Forty-two studies with a total of 1,486 animals were included in this meta-analysis. According to the results from subgroup analysis, GV20 + ST36 (Baihui + bilateral Zusanli) combined with 14-day manual acupuncture can obtain best improvement of the rats cognitive function among all acupuncture regimens (MD: -23.41; 95%CI: -26.66, -20.15; I2 = 0%; P < 0.001). The heterogeneity of other acupuncture treatments was significantly higher than that of GV20 + ST36, because the treatment courses were not uniform. Pair-wise and network comparisons are highly consistent. The major results of the network meta-analysis were as follows, In comparison to the impaired group, the acupuncture group showed significantly reduced escape latency (MD: -25.87; 95%CI: -30.75, -21.12), increased number of original platform crossings (MD: 2.63; 95%CI: 1.94, 3.34) and time spent in the target quadrant (MD: 7.88; 95%CI: 4.25, 11.44). The overall results of the network meta-analysis are as follows: the normal and sham-operated groups performed the best, followed by medicine and acupuncture, while no effect was found in the impaired group treated with non-acupoint and palliative.

Conclusions

Acupuncture significantly improves cognitive function in rats with vascular dementia. Compared to other acupuncture plans, (GV20 + ST36, MA) and 14 -day manual acupuncture can be used to obtain better results. The main mechanism of acupuncture in the treatment of vascular dementia is reduced oxidative stress, neuronal inflammation, and apoptosis, as well as the increased synaptic plasticity and neurotransmitters.

Systematic review registration

https://inplasy.com/inplasy-2021-11-0036/, identifier: INPLASY2021110036.

Dual-Channel Electrochemical Measurements Reveal Rapid Adenosine is Localized in Brain Slices

Rapid adenosine signaling has been detected spontaneously or after mechanical stimulation in the brain, providing rapid neuromodulation in a local area. To measure rapid adenosine signaling, a single carbon-fiber microelectrode has traditionally been used, which limits spatial resolution and an understanding of regional coordination. In this study, we utilized dual-channel fast-scan cyclic voltammetry to measure the spontaneous or mechanically stimulated adenosine release at two electrodes placed at different spacings in hippocampal CA1 mouse brain slices. For mechanically stimulated adenosine release, adenosine can be detected up to 150 μm away from where it was stimulated, although the signal is smaller and delayed. While spontaneous adenosine transients were detected at both electrodes, only 10 percent of the events were detected concurrently, and that number was similar at 50 and 200 μm electrode spacings. Thus, most adenosine transients were not caused by the widespread coordination of release. There was no evidence of diffusion of spontaneous transients to a second electrode 50-200 μm away. This study shows that spontaneous adenosine events are very localized and thus provide only local neuromodulation. Injury, such as mechanical stimulation, allows adenosine to diffuse farther, but the neuroprotective effects are still regional. These results provide a better understanding of the spatial and temporal profiles of adenosine available to act at receptors, which is crucial for future studies that design neuroprotective treatments based on rapid adenosine signaling.

Does the inability of CA1 area to respond to ischemia with early rapid adenosine release contribute to hippocampal vulnerability?: An Editorial Highlight for "Spontaneous, transient adenosine release is not enhanced in the CA1 region of hippocampus during severe ischemia models"

This Editorial highlights a remarkable study in the current issue of the Journal of Neurochemistry in which Ganesana & Venton (2021) report new data showing that brain ischemia does not elicit transient adenosine release in the CA1 hippocampal area. Using fast-scan cyclic voltammetry at a carbon-fiber microelectrode implanted in the CA1 subfield of the hippocampus, it was shown that none of three different ischemia/reperfusion models could increase spontaneous, transient adenosine release, and more severe models even suppressed this presumably neuroprotective release. Since the authors have previously shown that in the caudate putamen, ischemia increased the frequency of spontaneous adenosine release (Ganesana & Venton, 2018), the new data may disclose a mechanism underlying important regional differences in rapid neuroprotective adenosine signaling. The phenomenon of selective susceptibility of the hippocampus to ischemia/hypoxia is well-documented, and the reported failure of its CA1 area to respond to ischemia by rapid adenosine release may be indicative of an insufficiency of this neuroprotective mechanism contributing to hippocampal vulnerability.