Baicalin alleviates lipopolysaccharide-induced neuroglial activation and inflammatory factors activation in hippocampus of adult mice

Retinoic acid attenuates ischemic injury-induced activation of glial cells and inflammatory factors in a rat stroke model

Stroke is a leading cause of death and long-term disability which can cause oxidative damage and inflammation of the neuronal cells. Retinoic acid is an active metabolite of vitamin A that has various beneficial effects including antioxidant and anti-inflammatory effects. In this study, we investigated whether retinoic acid modulates oxidative stress and inflammatory factors in a stroke animal model. A middle cerebral artery occlusion (MCAO) was performed on adult male rats to induce focal cerebral ischemia. Retinoic acid (5 mg/kg) or vehicle was injected into the peritoneal cavity for four days before MCAO surgery. The neurobehavioral tests were carried out 24 h after MCAO and cerebral cortex tissues were collected. The cortical damage was assessed by hematoxylin-eosin staining and reactive oxygen species assay. In addition, Western blot and immunohistochemical staining were performed to investigate the activation of glial cells and inflammatory cytokines in MCAO animals. Ionized calcium-binding adapter molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) were used as markers of microglial and astrocyte activation, respectively. Tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were used as representative pro-inflammatory cytokines. Results showed that MCAO damage caused neurobehavioral defects and histopathological changes in the ischemic region and increased oxidative stress. Retinoic acid treatment reduced these changes caused by MCAO damage. We detected increases in Iba-1 and GFAP in MCAO animals treated with vehicle. However, retinoic acid alleviated increases in Iba-1 and GFAP caused by MCAO damage. Moreover, MCAO increased levels of nuclear factor-κB and pro-inflammatory cytokines, including TNF-α and IL-1β. Retinoic acid alleviated the expression of these inflammatory proteins. These findings elucidate that retinoic acid regulates microglia and astrocyte activation and modulates pro-inflammatory cytokines. Therefore, this study suggests that retinoic acid exhibits strong antioxidant and anti-inflammatory properties by reducing oxidative stress, inhibiting neuroglia cell activation, and preventing the increase of pro-inflammatory cytokines in a cerebral ischemia.

The role of astrocyte in neuroinflammation in traumatic brain injury

Traumatic brain injury (TBI), a significant contributor to mortality and morbidity worldwide, is a devastating condition characterized by initial mechanical damage followed by subsequent biochemical processes, including neuroinflammation. Astrocytes, the predominant glial cells in the central nervous system, play a vital role in maintaining brain homeostasis and supporting neuronal function. Nevertheless, in response to TBI, astrocytes undergo substantial phenotypic alternations and actively contribute to the neuroinflammatory response. This article explores the multifaceted involvement of astrocytes in neuroinflammation subsequent to TBI, with a particular emphasis on their activation, release of inflammatory mediators, modulation of the blood-brain barrier, and interactions with other immune cells. A comprehensive understanding the dynamic interplay between astrocytes and neuroinflammation in the condition of TBI can provide valuable insights into the development of innovative therapeutic approaches aimed at mitigating secondary damage and fostering neuroregeneration.

3,6'-Disinapoylsucrose alleviates the amyloid precursor protein and lipopolysaccharide induced cognitive dysfunction through upregulation of the TrkB/BDNF pathway

The aim of this study is to explore the effect and mechanism of 3,6'-disinapoylsucrose (DISS) on an Alzheimer's disease (AD) mice model induced by APPswe695 lentivirus (LV) and intraperitoneal injection of lipopolysaccharide (LPS). The results show that DISS improves cognitive ability, decreases the levels of IL-2, IL-6, IL-1β, and TNF-α, reduces the expression of NF-κB p65, and alleviates Aβ deposition and nerve cell damage. DISS can regulate tyrosine kinase B (TrkB)/brain-derived neurotrophic factor (BDNF) signaling in the hippocampus. In summary, DISS can significantly alleviate neuroinflammation, spatial learning and memory disorders in AD model mice.

Anti-inflammatory actions of β-funaltrexamine in a mouse model of lipopolysaccharide-induced inflammation

Neuroinflammation is involved in a wide range of brain disorders, thus there is great interest in identifying novel anti-inflammatory agents to include in therapeutic strategies. Our previous in vitro studies revealed that beta-funaltrexamine (β-FNA), a well-characterized selective mu-opioid receptor (MOR) antagonist, inhibits inflammatory signaling in human astroglial cells, albeit through an apparent MOR-independent mechanism. We also previously determined that lipopolysaccharide (LPS)-induced sickness behavior and neuroinflammation in mice are prevented by pretreatment with β-FNA. Herein we investigated the temporal importance of β-FNA treatment in this pre-clinical model of LPS-induced neuroinflammation. Adult, male C57BL/6J mice were administered an i.p. injection of LPS followed by treatment (i.p. injection) with β-FNA immediately or 4 h post-LPS. Sickness behavior was assessed using an open-field test, followed by assessment of inflammatory signaling in the brain, spleen, and plasma. Levels of inflammatory chemokines/cytokines (interferon γ-induced protein, CXCL10; monocyte chemotactic protein 1, CCL2; and interleukin-6, IL-6) in tissues were measured using an enzyme-linked immunosorbent assay and nuclear factor-kappa B (NFκB), p38 mitogen activated kinase (p38 MAPK), and glial fibrillary acidic protein (GFAP) expression were measured by western blot. LPS-induced sickness behavior and chemokine expression were inhibited more effectively when β-FNA treatment occurred immediately after LPS administration, as opposed to 4 h post-LPS; and β-FNA-mediated effects were time-dependent as evidenced by inhibition at 24 h, but not at 8 h. The inhibitory effects of β-FNA on chemokine expression were more evident in the brain versus the spleen or plasma. LPS-induced NFκB-p65 and p38 MAPK expression in the brain and spleen were inhibited at 8 and 24 h post-LPS. These findings extend our understanding of the anti-inflammatory effects of β-FNA and warrant further investigation into its therapeutic potential.

Beneficial effects of natural flavonoids on neuroinflammation

Neuroinflammation is the fundamental immune response against multiple factors in the central nervous system and is characterized by the production of inflammatory mediators, activated microglia and astrocytes, and the recruitment of innate and adaptive immune cells to inflammatory sites, that contributes to the pathological process of related brain diseases, such as Alzheimer’s disease, Parkinson’s disease, depression, and stroke. Flavonoids, as a species of important natural compounds, have been widely revealed to alleviate neuroinflammation by inhibiting the production of pro-inflammatory mediators, elevating the secretion of anti-inflammatory factors, and modulating the polarization of microglia and astrocyte, mainly via suppressing the activation of NLRP3 inflammasome, as well as NF-κB, MAPK, and JAK/STAT pathways, promoting Nrf2, AMPK, BDNF/CREB, Wnt/β-Catenin, PI3k/Akt signals and SIRT1-mediated HMGB1 deacetylation. This review will provide the latest and comprehensive knowledge on the therapeutic benefits and mechanisms of natural flavonoids in neuroinflammation, and the natural flavonoids might be developed into food supplements or lead compounds for neuroinflammation-associated brain disorders.

Protective and therapeutic effects of Scutellaria baicalensis and its main active ingredients baicalin and baicalein against natural toxicities and physical hazards: a review of mechanisms

OBJECTIVES

Scutellaria baicalensis (SB) has been traditionally used to combat a variety of conditions ranging from ischemic heart disease to cancer. The protective effects of SB are due to the action of two main flavonoids baicalin (BA) and baicalein (BE). This paper aimed to provide a narrative review of the protective and antidotal effects of SB and its main constituents against natural toxicities and physical hazards.

EVIDENCE ACQUISITION

Scientific databases Medline, Scopus, and Web of Science were thoroughly searched, based on different keywords for in vivo, in vitro and clinical studies which reported protective or therapeutic effects of SB or its constituents in natural and physical toxicities.

RESULTS

Numerous studies have reported that treatment with BE, BA, or total SB extract prevents or counteracts the detrimental toxic effects of various natural compounds and physical hazards. The toxic agents include mycotoxins, lipopolysaccharide, multiple plants and animal-derived substances as well as physical factors which negatively affected vital organs such as CNS, liver, kidneys, lung and heart. Increasing the expression of radical scavenging enzymes and glutathione content as well as inhibition of pro-inflammatory cytokines and pro-apoptotic mediators were important mechanisms of action.

CONCLUSION

Different studies on the Chinese skullcap have exhibited that its total root extract, BA or BE can act as potential antidotes or protective agents against the damage induced by natural toxins and physical factors by alleviating oxidative stress and inflammation. However, the scarcity of high-quality clinical evidence means that further clinical studies are required to reach a more definitive conclusion.

Baicalein Exerts Therapeutic Effects against Endotoxin-Induced Depression-like Behavior in Mice by Decreasing Inflammatory Cytokines and Increasing Brain-Derived Neurotrophic Factor Levels

Inflammation plays an important role in the pathophysiology of depression. This study aims to elucidate the antidepressant effect of baicalein, an anti-inflammatory component of a traditional Chinese herbal medicine (Scutellaria baicalensis), on lipopolysaccharide (LPS)-induced depression-like behavior in mice, and to investigate the underlying mechanisms. In vitro, baicalein exhibited antioxidant activity and protected macrophages from LPS-induced damage. The results of the tail suspension test and forced swimming test (tests for despair potential in mice) showed the antidepressant effect of baicalein on LPS-treated mice. It also substantially decreased the production of pro-inflammatory cytokines, including IL-6, TNF-α, MCP-1, and eotaxin, elicited by LPS in the plasma. Baicalein downregulated NF-κB-p65 and iNOS protein levels in the hippocampus, demonstrated its ability to mitigate neuroinflammation. Additionally, baicalein increased the levels of the mature brain-derived neurotrophic factor (mBDNF) in the hippocampus of LPS-treated mice, and elevated the ratio of mBDNF/proBDNF, which regulates neuronal survival and synaptic plasticity. Baicalein also promoted the expression of CREB, which plays a role in a variety of signaling pathways. In summary, the findings of this study demonstrate that the administration of baicalein can attenuate LPS-induced depression-like behavior by suppressing neuroinflammation and inflammation induced by the peripheral immune response.

Neuroprotective and anti-inflammatory effect of pectolinarigenin, a flavonoid from Amazonian Aegiphila integrifolia (Jacq.), against lipopolysaccharide-induced inflammation in astrocytes via NFκB and MAPK pathways

Neurodegenerative diseases affect millions of people worldwide. Regardless of the underlying cause, neuroinflammation is the greatest risk factor for developing any of these disorders. Pectolinarigenin (PNG) is an active flavonoid with several biological properties, anti-metastatic and anti-inflammatory activity. This study investigate the biological effects of PNG in macrophage and astrocyte cultures, with focus on elucidating the molecular mechanisms involved in the PNG activity. J774A.1 murine macrophage or cerebral cortex primary astrocytes primary cultures were treated with different concentration of PNG (1-160 μM) and the inflammatory process was stimulated by LPS (1 μg/ml) and the effect of PNG in different inflammatory markers were determined. PNG did not affect astrocyte or macrophage viability. Moreover, this flavonoid reduced NO• release in macrophages, attenuated astrocyte activation by preventing the overexpression of glial fibrillary acidic protein, and decreased the release of inflammatory mediators, IL-1β and IL-6 induced by LPS by the glial cell, as well as enhanced basal levels of IL-10. In addition, PNG suppressed NFκB, p38MAPK and ERK1/2 phosphorylation in astrocytes culture induced by LPS. The results show clear evidence that this novel flavonoid protects astrocytes against LPS-induced inflammatory toxicity. In conclusion, PNG presents neuroprotective and anti-inflammatory property through the inhibition of inflammatory signaling pathways.