Celastrol Attenuates Learning and Memory Deficits in an Alzheimer's Disease Rat Model

The neuroprotective role of celastrol on hippocampus in diabetic rats by inflammation restraint, insulin signaling adjustment, Aβ reduction and synaptic plasticity alternation

Celastrol, the primary constituent of Tripterygium wilfordii, has demonstrated neuroprotective properties in rats with dementia by reducing inflammation. A high-fat diet and streptozotocin injection were utilized to establish a diabetic rat model, which was then employed to investigate the possible protective effect of celastrol against the development of diabetes-induced learning and memory deficits. Afterwards, the experimental animals received a dose of celastrol by gavage (4 mg/kg/d). An animal study showed that celastrol enhanced insulin sensitivity and glucose tolerance in diabetic rats. In the Morris water maze test, rats with diabetes performed poorly in terms of spatial learning and memory; treatment with celastrol improved these outcomes. Additionally, administration of celastrol downregulated the expression of inflammatory-related proteins (NF-κB, IKKα, TNF-α, IL-1β, and IL-6) and greatly reduced the generation of Aβ in the diabetic hippocampus tissue. Moreover, the insulin signaling pathway-related proteins PI3K, AKT, and GSK-3β were significantly upregulated in diabetic rats after celastrol was administered. Also, celastrol prevented damage to the brain structures and increased the synthesis of synaptic proteins like PSD-95 and SYT1. In conclusion, celastrol exerts a neuroprotective effect by modulating the insulin signaling system and reducing inflammatory responses, which helps to ameliorate the cognitive impairment associated with diabetes.

Celastrol inhibits oligodendrocyte and neuron ferroptosis to promote spinal cord injury recovery

BACKGROUND

Spinal cord injury (SCI) is a traumatic injury to the central nervous system and can cause lipid peroxidation in the spinal cord. Ferroptosis, an iron-dependent programmed cell death, plays a key role in the pathophysiology progression of SCI. Celastrol, a widely used antioxidant drug, has potential therapeutic value for nervous system.

PURPOSE

To investigate whether celastrol can be a reliable candidate for ferroptosis inhibitor and the molecular mechanism of celastrol in repairing SCI by inhibiting ferroptosis.

METHODS

First, a rat SCI model was constructed, and the recovery of motor function was observed after treatment with celastrol. The regulatory effect of celastrol on ferroptosis pathway Nrf2-xCT-GPX4 was detected by Western blot and immunofluorescence. Finally, the ferroptosis model of neurons and oligodendrocytes was constructed in vitro to further verify the mechanism of inhibiting ferroptosis by celastrol.

RESULTS

Our results demonstrated that celastrol promoted the recovery of spinal cord tissue and motor function in SCI rats. Further in vitro and in vivo studies showed that celastrol significantly inhibited ferroptosis in neurons and oligodendrocytes and reduced the accumulation of ROS. Finally, we found that celastrol could inhibit ferroptosis by up-regulating the Nrf2-xCT-GPX4 axis to repair SCI.

CONCLUSION

Celastrol effectively inhibits ferroptosis after SCI by upregulating the Nrf2-xCT-GPX4 axis, reducing the production of lipid ROS, protecting the survival of neurons and oligodendrocytes, and improving the functional recovery.

Memory deficits and hippocampal cytokine expression in a rat model of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a complex behavioral disorder characterized by hyperactivity, impulsivity, inattention, and deficits in working memory and time perception. While animal models have advanced our neurobiological understanding of this condition, there are limited and inconsistent data on working and elapsed time memory function. Inflammatory signaling has been identified as a key factor in memory and cognitive impairments, but its role in ADHD remains unclear. Additionally, the disproportionate investigation of male subjects in ADHD research has contributed to a poor understanding of the disorder in females. This study sought to investigate the potential connections between memory, neuroimmunology, and ADHD in both male and female animals. Specifically, we utilized the spontaneously hypertensive rat (SHR), one of the most extensively studied animal models of ADHD. Compared to their control, the Wistar-Kyoto (WKY) rat, male SHR are reported to exhibit several behavioral phenotypes associated with ADHD, including hyperactivity, impulsivity, and poor sustained attention, along with impairments in learning and memory. As the hippocampus is a key brain region for learning and memory, we examined the behavior of male and female SHR and WKY rats in two hippocampal-dependent memory tasks. Our findings revealed that SHR have delay-dependent working memory deficits that were similar to, albeit less severe than, those seen in hippocampal-lesioned rats. We also observed impairments in elapsed time processing in female SHR, particularly in the discrimination of longer time durations. To investigate the impact of inflammatory signaling on memory in these rats, we analyzed the levels of several cytokines in the dorsal and ventral hippocampus of SHR and WKY. Although we found some sex and genotype differences, concentrations were generally similar between groups. Taken together, our results indicate that SHR exhibit deficits in spatial working memory and memory for elapsed time, as well as some differences in hippocampal cytokine concentrations. These findings contribute to a better understanding of the neurobiological basis of ADHD in both sexes and may inform future research aimed at developing effective treatments for the disorder. Nonetheless, the potential mediating role of neuroinflammation in the memory symptomatology of SHR requires further investigation.

Environmental enrichment improves declined cognition induced by prenatal inflammatory exposure in aged CD-1 mice: Role of NGPF2 and PSD-95

INTRODUCTION

Research suggests that prenatal inflammatory exposure could accelerate age-related cognitive decline that may be resulted from neuroinflammation and synaptic dysfunction during aging. Environmental enrichment (EE) may mitigate the cognitive and synaptic deficits. Neurite growth-promoting factor 2 (NGPF2) and postsynaptic density protein 95 (PSD-95) play critical roles in neuroinflammation and synaptic function, respectively.

METHODS

We examined whether this adversity and EE exposure can cause alterations in Ngpf2 and Psd-95 expression. In this study, CD-1 mice received intraperitoneal injection of lipopolysaccharide (50 μg/kg) or normal saline from gestational days 15-17. After weaning, half of the male offspring under each treatment were exposed to EE. The Morris water maze was used to assess spatial learning and memory at 3 and 15 months of age, whereas quantitative real-time polymerase chain reaction and Western blotting were used to measure hippocampal mRNA and protein levels of NGPF2 and PSD-95, respectively. Meanwhile, serum levels of IL-6, IL-1β, and TNF-α were determined by enzyme-linked immunosorbent assay.

RESULTS

The results showed that aged mice exhibited poor spatial learning and memory ability, elevated NGPF2 mRNA and protein levels, and decreased PSD-95 mRNA and protein levels relative to their young counterparts during natural aging. Embryonic inflammatory exposure accelerated age-related changes in spatial cognition, and in Ngpf2 and Psd-95 expression. Additionally, the levels of Ngpf2 and Psd-95 products were significantly positively and negatively correlated with cognitive dysfunction, respectively, particularly in prenatal inflammation-exposed aged mice. Changes in serum levels of IL-6, IL-1β, and TNF-α reflective of systemic inflammation and their correlation with cognitive decline during accelerated aging were similar to those of hippocampal NGPF2. EE exposure could partially restore the accelerated decline in age-related cognitive function and in Psd-95 expression, especially in aged mice.

DISCUSSION

Overall, the aggravated cognitive disabilities in aged mice may be related to the alterations in Ngpf2 and Psd-95 expression and in systemic state of inflammation due to prenatal inflammatory exposure, and long-term EE exposure may ameliorate this cognitive impairment by upregulating Psd-95 expression.

The therapeutic potential of triptolide and celastrol in neurological diseases

Neurological diseases are complex diseases affecting the brain and spinal cord, with numerous etiologies and pathogenesis not yet fully elucidated. Tripterygium wilfordii Hook. F. (TWHF) is a traditional Chinese medicine with a long history of medicinal use in China and is widely used to treat autoimmune and inflammatory diseases such as systemic lupus erythematosus and rheumatoid arthritis. With the rapid development of modern technology, the two main bioactive components of TWHF, triptolide and celastrol, have been found to have anti-inflammatory, immunosuppressive and anti-tumor effects and can be used in the treatment of a variety of diseases, including neurological diseases. In this paper, we summarize the preclinical studies of triptolide and celastrol in neurological diseases such as neurodegenerative diseases, brain and spinal cord injury, and epilepsy. In addition, we review the mechanisms of action of triptolide and celastrol in neurological diseases, their toxicity, related derivatives, and nanotechnology-based carrier system.

Neuroprotective Effects of Celastrol in Neurodegenerative Diseases-Unscramble Its Major Mechanisms of Action and Targets

There are rarely new therapeutic breakthroughs present for neurodegenerative diseases in the last decades. Thus, new effective drugs are urgently needed for millions of patients with neurodegenerative diseases. Celastrol, a pentacyclic triterpenoid compound, is one of the main active ingredients isolated from Tripterygium wilfordii Hook. f. that has multiple biological activities. Recently, amount evidence indicates that celastrol exerts neuroprotective effects and holds therapeutic potential to serve as a novel agent for neurodegenerative diseases. This review focuses on the therapeutic efficacy and major regulatory mechanisms of celastrol to rescue damaged neurons, restore normal cognitive and sensory motor functions in neurodegenerative diseases. Importantly, we highlight recent progress regarding identification of the drug targets of celastrol by using advanced quantitative chemical proteomics technology. Overall, this review provides novel insights into the pharmacological activities and therapeutic potential of celastrol for incurable neurodegenerative diseases.