Geniposidic acid protects lipopolysaccharide-induced acute lung injury via the TLR4/MyD88 signaling pathway in vitro and in vivo

BACKGROUND

Acute lung injury (ALI) is a common respiratory disease and is a serious threat to human health due to the lack of effective treatment. Geniposidic acid (GPA) is an iridoid glucoside extracted from Gardeniae jasminoides Ellis and can treat inflammation-related diseases. This study aimed to investigate the regulatory functions of GPA on lipopolysaccharide (LPS)-induced ALI and its potential mechanism, providing effective strategies for the clinical treatment of ALI.

METHODS

ALI models were constructed by LPS in Sprague-Dawley rats and pulmonary epithelial cells. The function of GPA was investigated by hematoxylin-eosin staining, lung function assessment, Western blot, Masson staining, and Sirius Red staining, quantitative real-time PCR, enzyme-linked immunosorbent assay, cell counting kit-8 assay, apoptosis analysis, and immunofluorescence assays.

RESULTS

Functionally, GPA increased survival, relieved pulmonary epithelial function in response to LPS, repressed pulmonary fibrosis and inflammation caused by ALI in vivo; GPA also repressed pulmonary epithelial cell injury and inflammation induced by LPS in vitro. Mechanistically, GPA decreased the protein levels of TLR4 and MyD88 and accelerated the nuclear export of p65, suggesting that GPA repressed the activation of p65.

CONCLUSION

GPA protected LPS-induced ALI through the TLR4/MyD88 signaling pathway.

Synthesis and anti-inflammatory activity of paeonol derivatives with etherized aryl urea by regulating TLR4/MyD88 signaling pathway in RAW264.7 cell

Thirty-three novel paeonol etherized aryl urea derivatives (PEUs) were synthesized via a bromination-Williamson Ether Synthesis-deprotection-nucleophilic addition reaction sequence. The structures of PEUs were characterized by LC-MS, HRMS, ¹H NMR and ¹³C NMR spectra. The levels of nitric oxide (NO), tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages were initially employed to evaluate the anti-inflammatory effects of all compounds. Remarkably, b16 exhibited a good anti-inflammatory activity at 2.5 μm which is the same as the potency of paeonol at 20 μm. The results of mechanism research displayed that the anti-inflammatory effect of b16 was ascribed to the inhibition of the TLR4/MyD88 signaling pathway and inflammatory factors. Additionally, b16 distinctly reduced the generation of free radicals in macrophages and strikingly increased the mitochondrial membrane potential. According to the structure-activity relationships (SAR) of PEUs, the incorporation of halogens on the benzene ring and the hydrogen of phenol hydroxyl substituted by aryl urea, were beneficial to enhance the anti-inflammatory activities. Molecular docking results illustrated that the binding ability of b16 to TLR4 was stronger than that of paeonol. In summary, the novel aryl urea-derivied paeonol b16 could be a new promising candidate for the treatment of inflammation-related diseases.

[Effect of transcutaneous auricular vagus nerve stimulation on the expression of TLR4、MyD88、IL-18 protein in the prefrontal cortex of depression rats]

OBJECTIVE

To observe the effect of transcutaneous auricular vagus nerve stimulation (taVNS) on the depressive behavior in depression rats, so as to explore its mechanism underlying improvement of depression.

METHODS

A total of 24 male Sprague Dawley rats were randomly divided into normal, depression model, taVNS, tnVNS (transcutaneous auricular none-vagus nerve stimulaton) groups (n=6 in each group). The depression model was established by chronic unpredictable mild stimulation combined with solitary raising for 35 consecutive days. After 14 days modeling, transcutaneous electrostimulation (2 mA, 2 Hz/15 Hz) was applied to auricular concha or auricular margin, respectively. Each intervention was conducted for 30 minutes, once daily for 21 days. The depression-like behavior was evaluated by forced swimming immobility time and body weight. The expression levels of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and interleukin-18 (IL-18) protein in the prefrontal cortex were detected by Western blot.

RESULTS

Following modeling, the increase amount of body weight was decreased, the forced swimming immobility time and expression TLR4, MyD88 and IL-18 protein in the prefrontal cortex were increased in the model group than those in the normal group (P<0.01). Following the treatment and compared with the model group, the increase amount of body weight in the taVNS group was obviously increased (P<0.05), the swimming immobility time and the expression of TLR4, MyD88, IL-18 protein in the taVNS and tnVNS groups were significantly decreased (P<0.01).

CONCLUSION

TaVNS is able to improve depression in depression rats, which is probably related to its effect in inhibiting inflammatory response of TLR4/MyD88 signaling pathway in prefrontal cortex.

Rehabilitation training inhibits neuronal apoptosis by down-regulation of TLR4/MyD88 signaling pathway in mice with cerebral ischemic stroke

OBJECTIVE

To investigate the role of rehabilitation training and TLR4/MyD88 signaling pathway on neuronal apoptosis in mice with cerebral ischemic stroke.

METHODS

Mice were randomized into six groups, which were normal group (healthy mice, n=20), control group (sham surgery, n=20), model group (middle cerebral artery occlusion (MCAO) model, n=20), training (MCAO model, continuous rehabilitation training for 4 weeks, n=20), TAK-242 group (MCAO model, TL R4 inhibitor TAK-242, n=20), and TAK-242 + Training group (MCAO model, TLR4 inhibitor TAK-242 + rehabilitation training, n=20).

RESULTS

Neurobehavioral assessment was performed, and cerebral infarction area of mice was detected by triphenyl tetrazolium chloride staining. Compared with the normal group, no significant differences in all indicators were found in the control group (all P>0.05), while the other groups had higher neurological function scores, cerebral infarction area, neuronal apoptosis rate, increased expressions of TLR4, MyD88, Bax, NF-κB, TNF-α, Caspase-3, IL-1βA and decreased mRNA and protein expressions of Bcl-2 (all P<0.05).

CONCLUSION

Rehabilitation training can effectively reduce the apoptosis of hippocampal neurons in mice with ischemic stroke by inhibiting the TLR4/MyD88 signaling pathway.

Anti-inflammatory and Regulatory Effects of Huanglian Jiedu Decoction on Lipid Homeostasis and the TLR4/MyD88 Signaling Pathway in LPS-Induced Zebrafish

Huanglian Jiedu decoction (HLJDD) has been used in the clinical treatment of inflammatory conditions. To clarify the mechanism of its comprehensive anti-inflammatory activities, the correlation between lipid homeostasis and the TLR4/MyD88 signaling pathway in zebrafish was established in the present study. In the lipopolysaccharide (LPS)-induced inflammation in zebrafish model, RT-PCR assays of five inflammatory cytokines and six targeted proteins were measured. Lipidomics analysis was conducted to identify potential lipid markers. HLJDD displayed strong efficacies, with a 61% anti-inflammatory rate at a concentration of 50 μg/mL. The activation of TLR4/MyD88 played an essential role in the inflammatory process. All protein indexes in the HLJDD group exhibited a tendency to reverse back to normal levels. Moreover, 79 potential pathological lipid biomarkers were identified. Compared with the model group, 61 therapeutic lipid biomarkers were detected in HLJDD group. Most perturbations of lipids were ameliorated by HLJDD, mainly through the glycerophospholipid metabolic pathway. In the visual network study, the corresponding lipoproteins such as PLA2, SGMS, and SMDP were observed as important intermediates between lipid homeostasis and the TLR4/MyD88 signaling pathway.

Effect of TLR4/MyD88 signaling pathway on sepsis-associated acute respiratory distress syndrome in rats, via regulation of macrophage activation and inflammatory response

The present study aimed to investigate the effects of the Toll-like receptor (TLR)4/myeloid differentiation primary response (MyD)88 signaling pathway on sepsis-associated acute respiratory distress syndrome (ARDS) in rats, and the involvement of macrophage activation and the inflammatory response. A total of 36 specific pathogen-free male Sprague-Dawley rats were selected to establish the rat model of sepsis-associated ARDS using cecal ligation and puncture (CLP). Rats were assigned into the Ab (anti-TLR4 monoclonal antibody)-CLP, CLP and Sham groups. Arterial partial pressure of oxygen (P_aO₂) was detected using blood gas analysis. Bronchoalveolar lavage fluid (BALF) and alveolar macrophages were collected. The pathological structure of lung tissue was observed following hematoxylin-eosin staining. The ultrastructural alterations of alveolar epithelial cells were observed under transmission electron microscope. The ratios of wet/dry weight of lung tissue and total protein content in BALF were measured. The concentration of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in BALF and peripheral blood was determined by enzyme-linked immunosorbent assay. The TLR4, TLR9, MyD88 and nuclear factor (NF)-κΒ mRNA and protein expression levels in alveolar macrophages were measured by reverse transcription-quantitative polymerase chain reaction and western blotting. Compared with the Sham group, the rats in the CLP group demonstrated significantly increased respiratory frequency, lung permeability, lung edema, inflammatory infiltration, TNF-α and IL-1β expression levels in BALF and peripheral blood and TLR4, TLR9, MyD88 and NF-κΒ expression levels in macrophages, however decreased arterial P_aO₂. Following pretreatment with anti-TLR4 monoclonal antibody, rats exhibited decreased lung injury, inflammatory infiltration, lung edema, TNF-α and IL-1β expressions in BALF and peripheral blood, and TLR4, TLR9, MyD88 and NF-κΒ expression levels in macrophages, with increased arterial P_aO₂. These results suggested that the inhibition of TLR4/MyD88 signaling pathway may relieve sepsis-associated ARDS in rats through regulating macrophage activation and the inflammatory response.