Synaptic plasticity in hippocampal CA1 neurons and learning behavior in acute kidney injury, and estradiol replacement in ovariectomized rats

The effects of estrogens on spatial learning and memory in female rodents - A systematic review and meta-analysis

Estrogens have inconsistent effects on learning and memory in both the clinical and preclinical literature. Preclinical literature has the advantage of investigating an array of potentially important factors contributing to the varied effects of estrogens on learning and memory, with stringently controlled studies. This study set out to identify specific factors in the animal literature that influence the effects of estrogens on cognition, for possible translation back to clinical practice. The literature was screened and studies meeting strict inclusion criteria were included in the analysis. Eligible studies included female ovariectomized rodents with an adequate vehicle for the estrogen treatment, with an outcome of spatial learning and memory in the Morris water maze. Training days of the Morris water maze were used to assess acquisition of spatial learning, and the probe trial was used to evaluate spatial memory recall. Continuous outcomes were pooled using a random effects inverse variance method and reported as standardized mean differences with 95 % confidence intervals. Subgroup analyses were developed a priori to assess important factors. The overall analysis favoured treatment for the later stages of training and for the probe trial. Factors including the type of estrogen, route, schedule of administration, age of animals, timing relative to ovariectomy, and duration of treatment were all found to be important. The subgroup analyses showed that chronic treatment with 17β-estradiol, either cyclically or continuously, to young animals improved spatial recall. These results, observed in animals, can inform and guide further clinical research on hormone replacement therapy for cognitive benefits.

Patchouli alcohol as a selective estrogen receptor β agonist ameliorates AD-like pathology of APP/PS1 model mice

Clinical evidence shows that postmenpausal women are almost twice as likely to develop Alzheimer's disease (AD) as men of the same age, and estrogen is closely related to the occurrence of AD. Estrogen receptor (ER) α is mainly expressed in the mammary gland and other reproductive organs like uterus while ERβ is largely distributed in the hippocampus and cardiovascular system, suggesting that ERβ selective agonist is a valuable drug against neurodegenerative diseases with low tendency in inducing cancers of breast and other reproductive organs. In this study we identified a natural product patchouli alcohol (PTA) as a selective ERβ agonist which improved the cognitive defects in female APP/PS1 mice, and explore the underlying mechanisms. Six-month-old female APP/PS1 mice were administered PTA (20, 40 mg · kg-1 · d-1, i.g.) for 90 days. We first demonstrated that PTA bound to ERβ with a dissociation constant (KD) of 288.9 ± 35.14 nM in microscale thermophoresis. Then we showed that PTA administration dose-dependently ameliorated cognitive defects evaluated in Morris water maze and Y-maze testes. Furthermore, PTA administration reduced amyloid plaque deposition in the hippocampus by promoting microglial phagocytosis; PTA administration improved synaptic integrity through enhancing BDNF/TrkB/CREB signaling, ameliorated oxidative stress by Catalase level, and regulated Bcl-2 family proteins in the hippocampus. The therapeutic effects of PTA were also observed in vitro: PTA (5, 10, 20 μM) dose-dependently increased phagocytosis of o-FAM-Aβ42 in primary microglia and BV2 cells through enhancing ERβ/TLR4 signaling; PTA treatment ameliorated o-Aβ25-35-induced reduction of synapse-related proteins VAMP2 and PSD95 in primary neurons through enhancing ERβ/BDNF/TrkB/CREB pathways; PTA treatment alleviated o-Aβ25-35-induced oxidative stress in primary neurons through targeting ERβ and increasing Catalase expression. Together, this study has addressed the efficacy of selective ERβ agonist in the amelioration of AD and highlighted the potential of PTA as a drug lead compound against the disease.

Inhibition of the NLRP3/caspase-1 signaling cascades ameliorates ketamine-induced renal injury and pyroptosis in neonatal rats

Ketamine is a widely-used anesthetic in the field of pediatrics and obstetrics. Multiple studies have revealed that ketamine causes neurotoxicity in developing animals. However, further studies are needed to determine whether clinical doses of ketamine (20 mg/kg) are able to cause kidney damage in developing animals. Herein, we investigated the effects of continuous ketamine exposure on kidney injury and pyroptosis in seven-day-old rats. Serum renal function indicators, renal histopathological analysis, pyroptosis, as well as oxidative stress indicators, were tested. Additionally, the NLRP3 inhibitor MCC950 and the Caspase-1 inhibitor VX765 were used to evaluate the role of the NLRP3/Caspase-1 axis in ketamine-induced kidney injury among developing rats. Our findings indicate that ketamine exposure causes renal histopathological injury, increased the levels of blood urea nitrogen (BUN) and creatinine (Cre), and led to upregulation in the levels of pyroptosis. Furthermore, we found that ketamine induced an increase in levels of reactive oxygen species (ROS) and malonaldehyde (MDA), as well as a decrease in the content of glutathione (GSH) and catalase (CAT) in the kidneys of neonatal rats. Moreover, targeting NLRP3 and caspase-1 with MCC950 or VX765 improved pyroptosis and reduced renal damage after continuous ketamine exposure. In conclusion, this study suggested that continued exposure to ketamine caused kidney damage among neonatal rats and that the NLRP3/Caspase-1 axis-related pyroptosis may be involved in this process.

Synaptic plasticity and cognitive impairment consequences to acute kidney injury: Protective role of ellagic acid

Objectives

The goal of the current experiment was to define the efficacy and underlying molecular mechanisms of Ellagic acid (EA) on acute kidney injury (AKI) induced impairment in cognitive and synaptic plasticity in rats.

Materials and Methods

Administration of 8 ml/kg glycerol (intramuscular) was used to establish the AKI model. Injured animals were treated by EA (25, 50, and 100 mg/kg, daily, gavage) for 14 consecutive days. To approve the renal injuries and the effects of EA on AKI, creatinine values in serum and urea nitrogen (BUN) values in blood were measured. Cognitive performance was investigated using the Morris water maze test. In vivo long-term potentiation (LTP) was recorded from the hippocampus. Then, the level of IL-10β and TNF-α levels were measured using ELISA kits. The integrity index of the Blood-brain barrier (BBB) was assessed by extravasation of Evans blue dye into the brain.

Results

Glycerol injection increased blood urea nitrogen (BUN) and serum creatinine (Scr) levels significantly in the AKI group, and EA treatment resulted in a significant reduction in BUN levels in all concentration groups. Also, a significant reduction in the cerebral EBD concentrations was demonstrated in EA treatment rats. Moreover, the indexes of brain electrophysiology, spatial learning, and memory were improved in the EA administrated group compared with the AKI rats.

Conclusion

The current experiment demonstrated the efficacy of EA in hippocampal complication and cognitive dysfunction secondary to AKI via alleviating the inflammation.

Surface Nanosieving Polyether Sulfone Particles with Graphene Oxide Encapsulation for the Negative Isolation toward Extracellular Vesicles

Extracellular vesicles (EVs) contain specific biomarkers for disease diagnosis. Current EV isolation methods are hampered in important biological applications due to their low recovery and purity. Herein, we first present a novel EV negative isolation strategy based on surface nanosieving polyether sulfone particles with graphene oxide encapsulation (SNAPs) by which the coexisting proteins are irreversibly adsorbed by graphene oxide (GO) inside the particles, while EVs with large sizes are excluded from the outside due to the well-defined surface pore sizes (10-40 nm). By this method, the purity of the isolated EVs from urine could be achieved 4.91 ± 1.01e¹⁰ particles/μg, 40.9-234 times higher than those obtained by the ultracentrifugation (UC), size-exclusion chromatography (SEC), and PEG-based precipitation. In addition, recovery ranging from 90.4 to 93.8% could be obtained with excellent reproducibility (RSD < 6%). This was 1.8-4.3 times higher than those obtained via SEC and UC, comparable to that obtained by PEG-based precipitation. Taking advantage of this strategy, we further isolated urinary EVs from IgA nephropathy (IgAN) patients and healthy donors for comparative proteome analysis, by which significantly regulated EV proteins were found to distinguish IgAN patients from healthy donors. All of the results indicated that our strategy would provide a new avenue for highly efficient EV isolation to enable many important clinical applications.

Electrophysiological and inflammatory changes of CA1 area in male rats exposed to acute kidney injury: Neuroprotective effects of erythropoietin

The high mortality rate associated with acute kidney injury (AKI) is commonly due to progressive, inflammatory multiple organ dysfunction, which often involves neurological complications. The AKI-stimulated mechanisms leading to brain dysfunction are not well understood, which hinders development of new therapeutic avenues to minimize AKI-mediated neural effects. The hippocampal CA1 area is a particularly vulnerable region during AKI but the electrophysiological and inflammatory mechanisms involved in this vulnerability remain largely unknown. Here, we used immunohistochemistry to quantitatively investigate the number of astrocytes expressing glial fibrillary acidic protein (GFAP) as an indicator of inflammation, and whole cell patch clamp to evaluate electrophysiological changes in CA1 at different time points following induction of bilateral renal ischemia (BRI) in male Wistar rats. Further we evaluated the effectiveness of erythropoietin (EPO, 1000 U/kg i.p.) in mitigating BRI-associated changes. Plasma concentrations of blood urea nitrogen (BUN) were significantly enhanced at 24 h, 72 h and 1 week, and creatinine (Cr) was increased at 24 h after reperfusion, which were changes reduced by EPO. BRI led to an increase in CA1 GFAP-positive cells 24 h and 72 h, but not 1 week, after reperfusion, and EPO reversed this effect of BRI at 24 h. Additionally, BRI caused an increase in the peak amplitude and coefficient of variation of CA1 pyramidal neuronal action potentials, which were changes not seen in presence of EPO. When taken together, altered neuronal electrophysiological properties and astrogliosis could contribute to the neurological complications induced by AKI, and EPO offers hope as a potential neuroprotective agent.