The involvement of oxidative stress and the TLR4/NF-κB/NLRP3 pathway in acute lung injury induced by high-altitude hypoxia

OBJECTIVE

This study investigated the effect of oxidative stress and the TLR4/NF-κB/NLRP3 pathway on the pathogenesis of acute lung injury (ALI) induced by high-altitude hypoxia.

METHODS

Rats were placed in an animal hyperbaric oxygen chamber to establish a rat model of ALI induced by high-altitude hypoxia after treatment with N-acetylcysteine (NAC; a reactive oxygen species [ROS] inhibitor) or/and MCC950 (an NLPR3 inflammasome inhibitor). After modeling, the wet-to-dry weight ratio (W/D) of rat lung tissues was calculated. In lung tissues, ROS levels were detected with immunofluorescence, the enzyme activity was tested with the kit, and the expression of TLR4/NF-κB/NLRP3 pathway-related genes and proteins was measured with western blotting and qRT-PCR. The levels of inflammatory factors in the serum were quantified with ELISA.

RESULTS

After modeling, rats showed significantly increased W/D, ROS levels, and Malondialdehyde (MDA) concentrations and markedly diminished Superoxide dismutase (SOD) and Glutathione (GSH) concentrations in lung tissues (all P < 0.01), accompanied by substantially enhanced serum levels of TNF-α, IL-6, and IL-1β, significantly reduced serum levels of IL-10, and remarkably augmented TLR4, NLRP3, p-NF-κB p65, NF-κB p65 mRNA, and Caspase-1 expression in lung tissues (all P < 0.01). Furthermore, treatment with NAC or MCC950 alone or in combination prominently lowered the W/D of lung tissues (P < 0.01), serum levels of TNF-α (P < 0.05), IL-6 (P < 0.05), and IL-1β (P < 0.01), and NF-κB p65 expression and phosphorylation (P < 0.05, P < 0.01) while significantly increasing SOD and GSH concentrations (P < 0.05, P < 0.01) and serum levels of IL-10 (P < 0.01) in modeled rats. Meanwhile, treatment of NAC alone or combined with MCC950 significantly reduced MDA concentration and ROS levels (P < 0.05, P < 0.01) in modeled rats, and treatment of MCC950 alone or combined with NAC considerably declined TLR4, NLRP3, and Caspase-1 expression in modeled rats (P < 0.05, P < 0.01).

CONCLUSION

Inhibition of oxidative stress and the TLR4/NF-κB/NLRP3 pathway can ameliorate ALI in rats exposed to high-altitude hypoxia.

Trigeminal nerve electrical stimulation attenuates early traumatic brain injury through the TLR4/NF-κB/NLRP3 signaling pathway mediated by orexin-A/OX1R system

BACKGROUND

Traumatic brain injury (TBI) is a significant contributor to global mortality and disability, and emerging evidence indicates that trigeminal nerve electrical stimulation (TNS) is a promising therapeutic intervention for neurological impairment following TBI. However, the precise mechanisms underlying the neuroprotective effects of TNS in TBI are poorly understood. Thus, the objective of this study was to investigate the potential involvement of the orexin-A (OX-A)/orexin receptor 1 (OX1R) mediated TLR4/NF-κB/NLRP3 signaling pathway in the neuroprotective effects of TNS in rats with TBI.

METHODS

Sprague-Dawley rats were randomly assigned to four groups: sham, TBI, TBI+TNS+SB334867, and TBI+TNS. TBI was induced using a modified Feeney's method, and subsequent behavioral assessments were conducted to evaluate neurological function. The trigeminal nerve trunk was isolated, and TNS was administered following the establishment of the TBI model. The levels of neuroinflammation, brain tissue damage, and proteins associated with the OX1R/TLR4/NF-κB/NLRP3 signaling pathway were assessed using hematoxylin-eosin staining, Nissl staining, western blot analysis, quantitative real-time polymerase chain reaction, and immunofluorescence techniques.

RESULTS

The findings of our study indicate that TNS effectively mitigated tissue damage, reduced brain edema, and alleviated neurological deficits in rats with TBI. Furthermore, TNS demonstrated the ability to attenuate neuroinflammation levels and inhibit the expression of proteins associated with the TLR4/NF-κB/NLRP3 signaling pathway. However, it is important to note that the aforementioned effects of TNS were reversible upon intracerebroventricular injection of an OX1R antagonist.

CONCLUSION

TNS may prevent brain damage and relieve neurological deficits after a TBI by inhibiting inflammation, possibly via the TLR4/NF-κB/NLRP3 signaling pathway mediated by OX-A/OX1R.

Anti-Ulcerative Colitis Effects and Active Ingredients in Ethyl Acetate Extract from Decoction of Sargentodoxa cuneata

Ulcerative colitis (UC) is an intractable disease prevalent worldwide. While ethyl acetate extract from decoction of Sargentodoxa cuneata (EAdSc) has potential anti-inflammatory activity, its effects on UC remain unknown. In this study, the constituent compounds discussed in the literature and identified by gas chromatography and mass spectrometry (GC-MS) were collected, and the blood-soluble components of EAdSc were identified by liquid chromatography-mass spectrometry. The network pharmacology analysis and molecular docking analysis were performed to explore the potential underlying mechanism and active ingredients of EAdSc against UC. Furthermore, mice with dextran sulfate sodium (DSS)-induced UC were used to study the therapeutic effects and validate the mechanism of EAdSc against UC. A total of 53 compounds from EAdSc were identified in the literature and by GC-MS, and 22 blood-soluble EAdSc components were recognized. Network pharmacology analysis revealed that multiple inflammatory signaling pathways are involved in EAdSc's anti-UC activity. Furthermore, molecular docking analysis showed that the eleutheroside A, liriodendrin, epicatechin, 2-methoxy-4-vinylphenol, catechin, androsin, coumaroyltyramine, and catechol may be active against UC through the TLR4/NF-κB/NLRP3 pathway. EAdSc reduced the disease activity, macroscopic colon damage, and histological damage indices, as well as inhibiting DSS-induced spleen enlargement and colon shortening. In addition, EAdSc decreased the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and IL-17, as well as the expression of TLR4, NF-κB p65, NLRP3, and Caspase-1 mRNA in colon tissues. These results provide insights into the anti-UC effects and underlying mechanisms of EAdSc and help elucidate the active ingredients of EAdSc in the treatment of UC.

Huangqin decoction mitigates hepatic inflammation in high-fat diet-challenged rats by inhibiting TLR4/NF-κB/NLRP3 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic hepatopathy worldwide, in which ectopic steatosis (5%) and inflammatory infiltration in the liver are the principal clinical characteristics. Huangqin decoction (HQD), a Chinese medicine formula used in the clinic for thousands of years, presents appreciable anti-inflammatory effects. Nevertheless, the role and mechanism of HQD against inflammation in NAFLD are still undefined.

AIM OF THE STUDY

The objective of this study was to evaluate the curative efficacy and unravel the involved mechanism of HQD on a high-fat diet (HFD)-induced NAFLD.

MATERIALS AND METHODS

First, HPLC was utilized to analyze the main chemical components of HQD. Then, NAFLD model was introduced by subjecting the rats to HFD for 16 weeks, and HQD (400 and 800 mg/kg) or polyene lecithin choline (PLC, 8 mg/kg) was given orally from week 8-16. Pharmacodynamic indicators including body weight, liver weight, liver index, as well as biochemical and histological parameters were assessed. As to mechanism exploration, the expressions of TLR4/NF-κB/NLRP3 pathway and molecular docking between major phytochemicals of HQD and key targets of TLR4/NF-κB/NLRP3 pathway were investigated.

RESULTS

Seven main monomeric constituents of HQD were revealed by HPLC analysis. Of note, HQD could effectively attenuate the body weight, liver weight, and liver index, rescue disorders in serum transaminases and lipid profile, correct hepatic histological abnormalities, and reduce phagocytes infiltration into the liver and pro-inflammatory cytokines release in NAFLD rats. Mechanism investigation discovered that HQD harbored inhibitory effects on TLR4/NF-κB/NLRP3 pathway-regulated liver inflammation. Further exploration found that seven phytochemicals in HQD exhibited better binding modes with TLR4/NF-κB/NLRP3 pathway, in which baicalein, baicalin and liquiritin presented the highest affinity and docking score for protein TLR4, NF-κB, and NLRP3, respectively.

CONCLUSIONS

These findings confirmed that HQD ameliorated hepatic inflammation in NAFLD rats by blocking the TLR4/NF-κB/NLRP3 pathway, with multi-components and multi-targets action pattern.

[Effect of Erjing Pills on alleviating neuroinflammation of AD rats based on TLR4/NF-κB/NLRP3 pathway and its mechanism]

This paper aimed to study the effect of Erjing Pills on the improvement of neuroinflammation of rats with Alzheimer's di-sease(AD) induced by the combination of D-galactose and Aβ_(25-35) and its mechanism. SD rats were randomly divided into a sham group, a model control group, a positive drug group(donepezil, 1 mg·kg~(-1)), an Erjing Pills high-dose group(9.0 g·kg~(-1)), and an Erjing Pills low-dose group(4.5 g·kg~(-1)), with 14 rats each group. To establish the rat model of AD, Erjing Pills were intragastrically administrated to rats for 5 weeks after 2 weeks of D-galactose injection. D-galactose was intraperitoneally injected into rats for 3 weeks, and then Aβ_(25-35) was injected into the bilateral hippocampus. The new object recognition test was used to evaluate the learning and memory ability of rats after 4 weeks of intragastric administration. Tissues were acquired 24 h after the last administration. The immunofluorescence method was used to detect the activation of microglia in the brain tissue of rats. The positive expressions of Aβ_(1-42) and phosphory protein Tau~(404)(p-Tau~(404)) in the CA1 area of the hippocampus were detected by immunohistochemistry. The levels of inflammatory factors interleukin-1β(IL-1β), tumor necrosis factor-α(TNF-α), and interleukin-6(IL-6) in the brain tissue were determined by enzyme-linked immunosorbent assay(ELISA). Toll-like receptor 4(TLR4)/nuclear factor kappa B(NF-κB)/nucleotide-binding oligomerization domain-like receptors 3(NLRP3) pathway-associated proteins in the brain tissue were determined by Western blot. The results showed that as compared with the sham group, the new object recognition index of rats in the model control group decreased significantly, the deposition of Aβ_(1-42) and p-Tau~(404) positive protein in the hippocampus increased significantly, and the levels of microglia activation increased significantly in the dentate gyrus. The levels of IL-1β, TNF-α, and IL-6 in the hippocampus of the model control group increased significantly, and the expression levels of TLR4, p-NF-κB p65/NF-κB p65, p-IκBα/IκBα, and NLRP3 proteins in the hippocampus increased significantly. Compared with the model control group, the Erjing Pill groups enhanced the new object recognition index of rats, decreased the deposition of Aβ_(1-42) and the expression of p-Tau~(404) positive protein in the hippocampus, inhibited the activation of microglia in the dentate gyrus, reduced the levels of inflammatory factors IL-1β, TNF-α, and IL-6 in the hippocampus, and down-regulated the expression levels of TLR4, p-NF-κB P65/NF-κB P65, p-IκBα/IκBα, and NLRP3 proteins in the hippocampus. In conclusion, Erjing Pills can improve the learning and memory ability of the rat model of AD presumably by improving the activation of microglia, reducing the expression levels of neuroinflammatory factors IL-1β, TNF-α, and IL-6, inhibiting the TLR4/NF-κB/NLRP3 neuroinflammation pathway, and decreasing hippocampal deposition of Aβ and expression of p-Tau, thereby restoring the hippocampal morphological structure.

[Effect of electroacupuncture on cognitive impairment in APP/PS1 mice based on TLR4/NF-κB/NLRP3 pathway]

OBJECTIVE

To observe the effect of electroacupuncture (EA) on the expressions of tight junction related proteins Claudin-5, ZO-1 in the colon and hippocampus, Toll-like receptor 4/nuclear factor-kappa B/NOD-like receptor protein 3 (TLR4/NF-κB/NLRP3) pathway in the hippocampus of APP/PS1 mice, so as to explore its mechanisms underlying improvement of cognitive impairment.

METHODS

Eighteen 5-month-old male APP/PS1 mice were equally randomized into model and EA groups,and nine 5-month-old male C57BL/6 mice were used as the normal control. EA(2 Hz, 1 mA) was applied to "Baihui" (GV20), "Dachangshu" (BL25) and "Zusanli" (ST36) for 15 min, once daily, 5 days a week for 5 weeks. The Morris water maze swimming test was used to evaluate the mice's cognitive impairment. Nissl staining was used to observe the pathological morphology of hippocampus. The expression of amyloid β-peptide (Aβ) in brain tissue was detect by immunohistochemistry; the contents of lipopolysaccharide (LPS) in colon, serum and hippocampus were detected by ELISA; the expression levels of Claudin-5, ZO-1 in colon and hippocampus, and TLR4/NF-κB/NLRP3 pathway related proteins in hippocampus were detected by Western blot.

RESULTS

Compared with the normal group, the escape latency of the mice in the model group was prolonged from the 3^rd day (P<0.05, P<0.01), the number of crossing the platform and the percentage of target quadrant residence time were significantly decreased (P<0.01), and the contents of LPS in colon, serum and hippocampus were significantly increased (P<0.01), the expression levels of TLR4, NF-κB p65, NLRP3, Caspase-1, interleukin (IL)-1β and tumor necrosis factor (TNF)-α in hippocampus and Aβ in brain tissue were significantly increased (P<0.01), while the expression levels of Claudin-5, ZO-1 in colon and hippocampus were significantly decreased (P<0.01). Compared with the model group, the escape latency of mice in the EA group was shortened from the 4th day (P<0.05, P<0.01), the number of crossing the platform and the percentage of target quadrant residence time were increased (P<0.01, P<0.05), and the contents of LPS in serum and hippocampus were decreased (P<0.05), and the expression levels of TLR4, NF-κB p65, Caspase-1, NLRP3, IL-1β, TNF-α in hippocampus and Aβ in brain tissue were significantly decreased (P<0.05, P<0.01), while the expression levels of Claudin-5, ZO-1 in colon and hippocampus were significantly increased (P<0.05, P<0.01). Outcomes of Nissl staining showed dispersed arrangement of neurons with nuclear pyknosis or hyperchromasia in the hippocampus, and a decreased number of cell layers in the model group, which was relatively milder in the EA group.

CONCLUSION

EA may improve the cognitive impairment of APP/PS1 mice by up-regulating the expression of Claudin-5 and ZO-1, reducing the transposition of gut-derived LPS to the central nervous system, inhibiting the over-activation of TLR4/NF-κB/NLRP3 pathway, and alleviating the inflammatory reaction of the central nervous system.

Daphnes Cortex and its licorice-processed products suppress inflammation via the TLR4/NF-κB/NLRP3 signaling pathway and regulation of the metabolic profile in the treatment of rheumatoid arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Daphnes Cortex (Daphne Giraldii Nitsche, DGN) is a popular traditional Chinese herbal medicine for traumatic injuries and rheumatoid arthritis (RA) in the Shaanxi and Gansu provinces of China. Due to skin irritation caused by raw DGN (RDGN), licorice-processed DGN products are usually used in clinical practice. However, the efficacy and mechanisms of action between DGN and its licorice-processed DGN products in treating RA have not been compared.

AIMS

This study compared the efficacy and elucidated the mechanisms in vitro and in vivo between RDGN and its licorice-processed DGN products in treating RA.

MATERIALS AND METHODS

A collagen-induced RA rat model was established, and treated with different doses of RDGN and its licorice-processed DGN products for 4 weeks to explore the therapeutic effects. The anti-inflammatory effects were assessed in RAW 264.7 macrophages stimulated by lipopolysaccharide (LPS). Analyses of the differential quality markers (DQMs) between DGN and its licorice-processed DGN products using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry, and non-targeted metabolomics analyses of rat synovial tissues were used to systematically explore correlations between DGN processing and its efficacy.

RESULTS

Licorice-processed DGN products significantly ameliorated RA symptoms in CIA rats. Licorice-processed DGN products also regulated inflammatory cytokines, matrix metalloproteinases, and vascular endothelial growth factor in the serum and cell supernatants. Licorice-processed DGN products significantly inhibited Toll-like receptor 4/nuclear factor kappa B/NOD-like receptor family, pyrin domain containing 3 (TLR4/NF-κB/NLRP3) signaling in CIA rats and LPS-induced RAW264.7 cells. The DQMs between RDGN and its licorice-processed DGN products were identified, most of which were amino acids or energy-related metabolites present in licorice-processed DGN products. Correlations between DQMs with differential metabolites and differential metabolic pathways were established.

CONCLUSIONS

Licorice-processed DGN products displayed better anti-inflammatory effects via the TLR4/NF-κB/NLRP3 signaling pathway on CIA rats and LPS-induced RAW264.7 cells, and regulation of the metabolic profile in treating RA.