Trichosanthis Semen Suppresses Lipopolysaccharide-Induced Neuroinflammation by Regulating the NF-κB Signaling Pathway and HO-1 Expression in Microglia

The Interplay between Ferroptosis and Neuroinflammation in Central Neurological Disorders

Central neurological disorders are significant contributors to morbidity, mortality, and long-term disability globally in modern society. These encompass neurodegenerative diseases, ischemic brain diseases, traumatic brain injury, epilepsy, depression, and more. The involved pathogenesis is notably intricate and diverse. Ferroptosis and neuroinflammation play pivotal roles in elucidating the causes of cognitive impairment stemming from these diseases. Given the concurrent occurrence of ferroptosis and neuroinflammation due to metabolic shifts such as iron and ROS, as well as their critical roles in central nervous disorders, the investigation into the co-regulatory mechanism of ferroptosis and neuroinflammation has emerged as a prominent area of research. This paper delves into the mechanisms of ferroptosis and neuroinflammation in central nervous disorders, along with their interrelationship. It specifically emphasizes the core molecules within the shared pathways governing ferroptosis and neuroinflammation, including SIRT1, Nrf2, NF-κB, Cox-2, iNOS/NO·, and how different immune cells and structures contribute to cognitive dysfunction through these mechanisms. Researchers' findings suggest that ferroptosis and neuroinflammation mutually promote each other and may represent key factors in the progression of central neurological disorders. A deeper comprehension of the common pathway between cellular ferroptosis and neuroinflammation holds promise for improving symptoms and prognosis related to central neurological disorders.

Microglial TLR4/NLRP3 Inflammasome Signaling in Alzheimer's Disease

Alzheimer's disease is a pervasive neurodegenerative disease that is estimated to represent approximately 70% of dementia cases worldwide, and the molecular complexity that has been highlighted remains poorly understood. The accumulation of extracellular amyloid-β (Aβ), intracellular neurofibrillary tangles formed by tau hyperphosphorylation, and neuroinflammation are the major pathological features of Alzheimer's disease (AD). Over the years, there has been no apparent breakthrough in drug discovery based on the Aβ and tau hypotheses. Neuroinflammation has gradually become a hot spot in AD treatment research. As the primary cells of innate immunity in the central nervous system, microglia play a key role in neuroinflammation. Toll-like receptor 4 (TLR4) and nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasomes are vital molecules in neuroinflammation. In the pathological context of AD, the complex interplay between TLR4 and the NLRP3 inflammasomes in microglia influences AD pathology via neuroinflammation. In this review, the effect of the activation and inhibition of TLR4 and NLRP3 in microglia on AD pathology, as well as the cross-talk between TLR4 and the NLRP3 inflammasome, and the influence of essential molecules in the relevant signaling pathway on AD pathology, were expounded. In addition, the feasibility of these factors in representing a potential treatment option for AD has been clarified.

Trichosanthis Semen Exerts Neuroprotective Effects in Alzheimer's Disease Models by Inhibiting Amyloid-β Accumulation and Regulating the Akt and ERK Signaling Pathways

Background

Alzheimer's disease (AD), the most common form of dementia, is characterized by memory loss and the abnormal accumulation of senile plaques composed of amyloid-β (Aβ) protein. Trichosanthis Semen (TS) is a traditional herbal medicine used to treat phlegm-related conditions. While TS is recognized for various bioactivities, including anti-neuroinflammatory effects, its ability to attenuate AD remains unknown.

Objective

To evaluate the effects of TS extract (TSE) on neuronal damage, Aβ accumulation, and neuroinflammation in AD models.

Methods

Thioflavin T and western blot assays were used to assess effects on Aβ aggregation in vitro. TS was treated to PC12 cells with Aβ to assess the neuroprotective effects. Memory functions and histological brain features were investigated in TSE-treated 5×FAD transgenic mice and mice with intracerebroventricularly injected Aβ.

Results

TSE disrupted Aβ aggregation and increased the viability of cells and phosphorylation of both protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) in vitro. TSE treatment also suppressed the accumulation of Aβ plaques in the brain of 5×FAD mice, protected neuronal cells in both the subiculum and medial septum, and upregulated Akt/ERK phosphorylation in the hippocampus. Moreover, TSE ameliorated the memory decline and glial overactivation observed in 5×FAD mice. As assessing whether TS affect Aβ-induced neurotoxicity in the Aβ-injected mice, the effects of TS on memory improvement and neuroinflammatory inhibition were confirmed.

Conclusions

TSE disrupted Aβ aggregation, protected neurons against Aβ-induced toxicity, and suppressed neuroinflammation, suggesting that it can suppress the development of AD.

Role of NRF2 in Colorectal Cancer Prevention and Treatment

Nuclear factor erythroid 2-related factor 2 (NRF2) is a basic leucine zipper protein that participates in a complex regulatory network in the body. The activation of NRF2 can prevent and treat colorectal cancer (CRC). A variety of natural compounds can activate NRF2 to inhibit oxidative stress and inflammation to prevent the occurrence and development of CRC, inhibit the proliferation of CRC cells and induce their apoptosis. However, some studies have also shown that it also has negative effects on CRC, such as overexpression of NRF2 can promote the growth of colorectal tumors and increase the drug resistance of chemotherapeutic drugs such as 5-fluorouracil and oxaliplatin. Therefore, inhibition of NRF2 can also be helpful in the treatment of CRC. In this study, we analyze the current research progress of NRF2 in CRC from various aspects to provide new ideas for prevention and treatment based on the NRF2 signaling pathway in CRC.

Trichosanthis Semen and Zingiberis Rhizoma Mixture Ameliorates Lipopolysaccharide-Induced Memory Dysfunction by Inhibiting Neuroinflammation

Neuroinflammation, a key pathological contributor to various neurodegenerative diseases, is mediated by microglial activation and subsequent secretion of inflammatory cytokines via the mitogen-activated protein kinase (MAPK) signaling pathway. Moreover, neuroinflammation leads to synaptic loss and memory impairment. This study investigated the inhibitory effects of PNP001, a mixture of Trichosanthis Semen and Zingiberis Rhizoma in a ratio of 3:1, on neuroinflammation and neurological deficits induced by lipopolysaccharide (LPS). For the in vitro study, PNP001 was administered in LPS-stimulated BV2 microglial cells, and reduced the pro-inflammatory mediators, such as nitric oxide, inducible nitric oxide synthase, and cyclooxygenase-2 by downregulating MAPK signaling. For the in vivo study, ICR mice were orally administered PNP001 for 18 consecutive days, and concurrently treated with LPS (1 mg/kg, i.p.) for 10 days, beginning on the 4th day of PNP001 administration. The remarkably decreased number of activated microglial cells and increased expression of pre- and post-synaptic proteins were observed more in the hippocampus of the PNP001 administered groups than in the LPS-treated group. Furthermore, daily PNP001 administration significantly attenuated long-term memory decline compared with the LPS-treated group. Our study demonstrated that PNP001 inhibits LPS-induced neuroinflammation and its associated memory dysfunction by alleviating microglial activation and synaptic loss.

Suppressive Effect of Tetrahydrocurcumin on Pseudomonas aeruginosa Lipopolysaccharide-Induced Inflammation by Suppressing JAK/STAT and Nrf2/HO-1 Pathways in Microglial Cells

Brain inflammation, a pathological feature of neurodegenerative disorders, exhibits elevated microglial activity and increased levels of inflammatory factors. The present study was aimed at assessing the anti-inflammatory response of tetrahydrocurcumin (THC), the primary hydrogenated metabolite of curcumin, which was applied to treat Pseudomonas aeruginosa (P.a.) lipopolysaccharide- (LPS-) stimulated BV2 microglial cells. THC reduced P.a. LPS–induced mortality and the production of inflammatory mediators IL-6, TNF-α, MIP-2, IP-10, and nitrite. A further investigation revealed that THC decreased these inflammatory cytokines synergistically with JAK/STAT signaling inhibitors. THC also increased Nrf2/HO-1 signaling transduction which inhibits iNOS/COX-2/pNFκB cascades. Additionally, the presence of the HO-1 inhibitor Snpp increased the levels of IP-10, IL-6, and nitrite while THC treatment reduced those inflammatory factors in P.a. LPS–stimulated BV2 cells. In summary, we demonstrated that THC exhibits anti-inflammatory activities in P.a. LPS-induced inflammation in brain microglial cells by inhibiting STAT1/3-dependent NF-κB activation and inducing Nrf2-mediated HO-1 expression.