Luteolin suppresses lipopolysaccharide‑induced cardiomyocyte hypertrophy and autophagy in vitro

Beneficial effects of flavonoids on cardiovascular diseases by influencing NLRP3 inflammasome

Cardiovascular diseases (CVDs) are a leading cause of global mortality and have a high incidence rate worldwide. The function of inflammasomes in CVDs has received a lot of attention recently, and the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome may be a new target for the prevention and treatment of CVDs. Flavonoids, which are found in food and plant extracts, inhibited inflammation in CVDs by regulating the NLRP3 inflammasome. CB-Dock was used to investigate whether 34 flavonoids from natural products acted on NLRP3 inflammasome. In brief, the PDB format of NLRP3 was selected as a protein file, and 34 flavonoids in SDF format were selected as the ligand file, and then input to CB-Dock for molecular docking. The docking results showed that epigallocatechin-3-gallate (EGCG), amentoflavone, baicalin, scutellarin, vitexin, silibinin, and puerarin had good binding affinities to NLRP3, which could be used as NLRP3 inhibitors, and aid in the discovery of lead compounds for the design and development of CVDs.

A high-throughput drug screening identifies luteolin as a therapeutic candidate for pathological cardiac hypertrophy and heart failure

Background

Pathological cardiac hypertrophy is commonly resulted from sustained pressure overload and/or metabolic disorder and eventually leads to heart failure, lacking specific drugs in clinic. Here, we aimed to identify promising anti-hypertrophic drug(s) for heart failure and related metabolic disorders by using a luciferase reporter-based high-throughput screening.

Methods

A screen of the FDA-approved compounds based on luciferase reporter was performed, with identified luteolin as a promising anti-hypertrophic drug. We systematically examined the therapeutic efficacy of luteolin on cardiac hypertrophy and heart failure in vitro and in vivo models. Transcriptome examination was performed to probe the molecular mechanisms of luteolin.

Results

Among 2,570 compounds in the library, luteolin emerged as the most robust candidate against cardiomyocyte hypertrophy. Luteolin dose-dependently blocked phenylephrine-induced cardiomyocyte hypertrophy and showed extensive cardioprotective roles in cardiomyocytes as evidenced by transcriptomics. More importantly, gastric administration of luteolin effectively ameliorated pathological cardiac hypertrophy, fibrosis, metabolic disorder, and heart failure in mice. Cross analysis of large-scale transcriptomics and drug-target interacting investigations indicated that peroxisome proliferator activated receptor γ (PPARγ) was the direct target of luteolin in the setting of pathological cardiac hypertrophy and metabolic disorders. Luteolin can directly interact with PPARγ to inhibit its ubiquitination and subsequent proteasomal degradation. Furthermore, PPARγ inhibitor and PPARγ knockdown both prevented the protective effect of luteolin against phenylephrine-induced cardiomyocyte hypertrophy in vitro.

Conclusion

Our data clearly supported that luteolin is a promising therapeutic compound for pathological cardiac hypertrophy and heart failure by directly targeting ubiquitin-proteasomal degradation of PPARγ and the related metabolic homeostasis.

Potential mechanisms of Qili Qiangxin capsule to prevent pulmonary arterial hypertension based on network pharmacology analysis in a rat model

Background

Qili Qiangxin capsule (QQC), a traditional Chinese medicine, has recently been approved to treat pulmonary arterial hypertension (PAH). However, the multi-target mechanism through which QQC acts on PAH has not been clarified. The objective of this study was to explore the pharmacological processes of QQC for treating PAH.

Methods

The rat model of PAH was established by administering monocrotaline (MCT). The impact of QQC on PAH was studied in treatment group that received QQC orally over a period of 4 weeks. The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database was searched for active compounds and QQC targets that were then identified and downloaded. Then, PAH-related targets were obtained from five databases [GeneCards, DrugBank, Online Mendelian Inheritance in Man (OMIM), Therapeutic Target Database (TTD), and PharmGKB]. The QQC targets for PAH were compiled after they had been overlapped with one another. Furthermore, the STRING network platform, the Cytoscape tool, networks of protein-protein interaction (PPI) were used, and core target analyses were carried out. Moreover, molecular docking techniques were employed in this research. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment studies of overlapping targets were carried out using the R software (version: 4.0.5; Lucent Technologies Co., Ltd., China). Finally, we verified the synergistic action mechanisms using western blotting and immunofluorescence analysis on PAH rats who were treated with or without QQC.

Results

The search of the TCMSP database showed that there were 11 active ingredients in QQC that treated PAH. PPI network showed that AKT1, TP53, JUN, and MAPK1 were the most important targets in the treatment of PAH. Moreover, Molecular docking techniques showed that the affinity between the bioactive compounds in QQC and their PAH targets was strong. In vivo experiments demonstrated that QQC may attenuate the progression of MCT-stimulated PAH in rats. Furthermore, the protective effect was mediated by inhibiting the PI3K/AKT pathway. The active compounds mainly included quercetin, kaempferol, formononetin, and luteolin, which had good docking scores and targeted the AKT protein.

Conclusions

QQC might activate the PI3K/AKT signaling pathway to ameliorate MCT-induced PAH. These findings support the clinical use of QQC and provide the foundation for further studies.

Inhibition of PI3K/AKT/mTOR Signalling Pathway Activates Autophagy and Suppresses Peritoneal Fibrosis in the Process of Peritoneal Dialysis

Peritoneal dialysis (PD) is an important part of replacement therapy for kidney failure. However, long-term PD treatment can cause peritoneal fibrosis. Autophagy may be involved in the pathological mechanism of peritoneal fibrosis (PF). Although autophagy is currently known to be involved in course of PF, its specific effects still lack in-depth research. In this experiment, a high-glucose (HG)-induced peritoneal fibrosis rat model was successfully established via intraperitoneal injection of HG peritoneal dialysate, and the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and the mechanistic target of rapamycin (mTOR) inhibitor rapamycin were used to treat peritoneal fibrosis rats. In addition, in vitro studies of high glucose-induced peritoneal fibrosis were performed using rat peritoneal mesothelial cells (PMCs). In vivo and in vitro experiments showed that LY294002 and rapamycin effectively inhibited the process of PF induced by high glucose. In addition, LY294002 and rapamycin were found to alleviate fibrosis by eliminating intracellular reactive oxygen species (ROS) levels, promoting the expression of the epithelial mesenchymal transdifferentiation proteins zonula occludens-1 (ZO-1) and E-cadherin, and inhibiting the expression of p-PI3K, PI3K, p-mTOR, mTOR, the fibroblast-specific proteins ferroptosis suppressor protein 1 (FSP1), and alpha-smooth muscle actin (α-SMA). Moreover, LY294002 and rapamycin promoted expression of autophagy-related proteins LC3-II/I, p62, and beclin-1. The current data indicated that inhibition of PI3K/AKT/mTOR signalling pathway activated autophagy and suppressed PF in the process of PD. Therefore, intervention in this signalling pathway may become a research goal for the prevention and treatment of PF, which has important clinical significance.

Mitoprotective Effects of a Synergistic Nutraceutical Combination: Basis for a Prevention Strategy Against Alzheimer’s Disease

Evidence to date suggests the consumption of food rich in bioactive compounds, such as polyphenols, flavonoids, omega-3 fatty acids may potentially minimize age-related cognitive decline. For neurodegenerative diseases, such as Alzheimer’s disease (AD), which do not yet have definitive treatments, the focus has shifted toward using alternative approaches, including prevention strategies rather than disease reversal. In this aspect, certain nutraceuticals have become promising compounds due to their neuroprotective properties. Moreover, the multifaceted AD pathophysiology encourages the use of multiple bioactive components that may be synergistic in their protective roles when combined. The objective of the present study was to determine mechanisms of action underlying the inhibition of Aβ_1–42-induced toxicity by a previously determined, three-compound nutraceutical combination D₅L₅U₅ for AD. In vitro experiments were carried out in human neuroblastoma BE(2)-M17 cells for levels of ROS, ATP mitophagy, and mitobiogenesis. The component compounds luteolin (LUT), DHA, and urolithin A (UA) were independently protective of mitochondria; however, the D₅L₅U₅ preceded its single constituents in all assays used. Overall, it indicated that D₅L₅U₅ had potent inhibitory effects against Aβ_1–42-induced toxicity through protecting mitochondria. These mitoprotective activities included minimizing oxidative stress, increasing ATP and inducing mitophagy and mitobiogenesis. However, this synergistic nutraceutical combination warrants further investigations in other in vitro and in vivo AD models to confirm its potential to be used as a preventative therapy for AD.

Fatty acid-binding protein 4 silencing protects against lipopolysaccharide-induced cardiomyocyte hypertrophy and apoptosis by inhibiting the Toll-like receptor 4-nuclear factor-κB pathway

Objective

To explore the effects and potential mechanisms of fatty acid-binding protein 4 (FABP4) in a lipopolysaccharide (LPS)-induced in vitro septic cardiomyopathy model.

Methods

Rat cardiomyocyte H9c2 cells were transfected with small interfering RNA (siRNA) against FABP4 (siFABP4), then induced with LPS. The following parameters were measured: cell viability, lactate dehydrogenase release, cardiac hypertrophy and related marker expression, apoptosis, inflammatory cytokine release and expression, and the activation of Toll-like receptor 4 (TLR4) and nuclear factor-κB (NF-κB) pathways.

Results

LPS increased the mRNA and protein expression of FABP4 in H9c2 cells. FABP4 silencing by siFABP4 significantly inhibited LPS-induced cardiac hypertrophy and reduced the mRNA expression of the myocardial hypertrophy markers atrial natriuretic peptide and brain natriuretic peptide. siFABP4 also attenuated LPS-induced increase in TUNEL-positive apoptotic cells, caspase-3 and caspase-9 activities, and the release and expression of proinflammatory cytokines. Mechanistically, we found that FABP4 silencing inhibited the mRNA and protein expression of TLR4 and suppressed the NF-kappa B signaling pathway, as evidenced by reduced nuclear NF-κB p65 and increased cytoplasmic I-κBα expression in LPS-stimulated H9c2 cells.

Conclusion

FABP4 silencing reduces LPS-induced cardiomyocyte hypertrophy and apoptosis by down-regulating the TLR4/NF-κB axis.

[Role of autophagy in lipopolysaccharide-induced apoptosis of odontoblasts]

OBJECTIVE

To investigate the role of autophagy in lipopolysaccharide (LPS)-induced apoptosis of murine odontoblasts.

METHODS

Murine odontoblasts (mDPC-23 cells) were treated with 5 μg/mL LPS for 6, 12 and 24 h, and the changes in cell viability was examined using CCK8 kit and cell apoptosis was detected by TUNEL staining. The changes in the protein levels of LC3, Beclin1, Atg5, AKT, p-AKT, mTOR and p-mTOR were detected using Western blotting. The effect of 3-MA treatment for 24 h on LPS-induced apoptosis of mDPC-23 cells was evaluated by detecting the expressions of apoptosis-related proteins caspase-3 and Bax using Western blotting.

RESULTS

Stimulation with LPS for 6 and 12 h did not cause significant changes in the proliferation or apoptosis of mDPC-23 cells, but LPS treatment for 24 h significantly suppressed cell proliferation (P < 0.05) and promoted cell apoptosis as shown by TUNEL assay (P < 0.05). Stimulation with LPS for 24 significantly increased the expression levels of LC3, Beclin1 and Atg5, decreased the expressions of p-AKT and p-mTOR (P < 0.05), and obviously upregulated the expressions of caspase-3 and Bax (P < 0.05). Treatment with 3-MA markedly lowered caspase-3 and Bax protein expressions in LPS-stimulated cells (P < 0.05).

CONCLUSIONS

LPS stimulation induces autophagy to promote apoptosis of mDPC-23 cells, and suppression of autophagy attenuates LPS-induced apoptosis. Autophagy may play an important role in the injury of inflamed pulp tissues.