Acanthoic acid suppresses lipin1/2 via TLR4 and IRAK4 signalling pathways in EtOH- and lipopolysaccharide-induced hepatic lipogenesis

IL-1 receptor-associated kinase family proteins: An overview of their role in liver disease

The interleukin-1 receptor-associated kinase (IRAK) family is a group of serine-threonine kinases that regulates various cellular processes via toll-like receptor (TLR)/interleukin-1 receptor (IL1R)-mediated signaling. The IRAK family comprises four members, including IRAK1, IRAK2, IRAK3, and IRAK4, which play an important role in the expression of various inflammatory genes, thereby contributing to the inflammatory response. IRAKs are key proteins in chronic and acute liver diseases, and recent evidence has implicated IRAK family proteins (IRAK1, IRAK3, and IRAK4) in the progression of liver-related disorders, including alcoholic liver disease, non-alcoholic steatohepatitis, hepatitis virus infection, acute liver failure, liver ischemia-reperfusion injury, and hepatocellular carcinoma. In this article, we provide a comprehensive review of the role of IRAK family proteins and their associated inflammatory signaling pathways in the pathogenesis of liver diseases. The purpose of this study is to explore whether IRAK family proteins can serve as the main target for the treatment of liver related diseases.

Synthesis and anti-liver fibrosis activity of imidazole and thiazole compounds containing amino acids

Four series of imidazoles (15a-g, 20c, and 20d) and thiazoles (18a-g, 22a, and 22b) possessing various amino acids were synthesized and evaluated for activin receptor-like kinase 5 (ALK5) inhibitory activities in an enzymatic assay. Among them, compounds 15g and 18c showed the highest inhibitory activity against ALK5, with IC50 values of 0.017 and 0.025 μM, respectively. Compounds 15g and 18c efficiently inhibited extracellular matrix (ECM) deposition in TGF-β-induced hepatic stellate cells (HSCs), and eventually suppressed HSC activation. Moreover, compound 15g showed a good pharmacokinetic (PK) profile with a favorable half-life (t1/2 = 9.14 h). The results indicated that these compounds exhibited activity targeting ALK5 and may have potential in the treatment of liver fibrosis; thus they are worthy of further study.

Mechanism and Progress of Natural Products in the Treatment of NAFLD-Related Fibrosis

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most prevalent chronic liver disorder worldwide, with liver fibrosis (LF) serving as a pivotal juncture in NAFLD progression. Natural products have demonstrated substantial antifibrotic properties, ushering in novel avenues for NAFLD treatment. This study provides a comprehensive review of the potential of natural products as antifibrotic agents, including flavonoids, polyphenol compounds, and terpenoids, with specific emphasis on the role of Baicalin in NAFLD-associated fibrosis. Mechanistically, these natural products have exhibited the capacity to target a multitude of signaling pathways, including Hedgehog, Wnt/β-catenin, TGF-β1, and NF-κB. Moreover, they can augment the activities of antioxidant enzymes, inhibit pro-fibrotic factors, and diminish fibrosis markers. In conclusion, this review underscores the considerable potential of natural products in addressing NAFLD-related liver fibrosis through multifaceted mechanisms. Nonetheless, it underscores the imperative need for further clinical investigation to authenticate their effectiveness, offering invaluable insights for future therapeutic advancements in this domain.

Effect of ADHI on hepatic stellate cell activation and liver fibrosis in mice

The relationship between alcohol dehydrogenase (ADH) and liver fibrosis has been studied, but the mechanism of ADH involvement in liver fibrosis remains unclear. The aim of the present study was to explore the role of ADHI, the classical liver ADH, in hepatic stellate cell (HSC) activation and the effect of 4-methylpyrazole (4-MP), an ADH inhibitor, on liver fibrosis induced by carbon tetrachloride (CCl₄) in mice. The results showed that overexpression of ADHI significantly increases proliferation, migration, adhesion and invasion rates of HSC-T6 cells as compared with controls. When HSC-T6 cells were activated by ethanol, TGF-β1 or LPS, the expression of ADHI was elevated significantly (P < 0.05). Overexpression of ADHI significantly increased the levels of COL1A1 and α-SMA, markers of HSC activation. Moreover, the expression of COL1A1 and α-SMA was decreased significantly by transfection of ADHI siRNA (P < 0.01). In a liver fibrosis mouse model ADH activity increased significantly and was highest in the 3rd week. The activity of ADH in the liver was correlated with its activity in the serum (P < 0.05). 4-MP significantly decreased ADH activity and ameliorated liver injury, and ADH activity was positively correlated with the Ishak score of liver fibrosis. In conclusion, ADHI plays an important role in the activation of HSC, and inhibition of ADH ameliorates liver fibrosis in mice.

Terpenoids: Natural Compounds for Non-Alcoholic Fatty Liver Disease (NAFLD) Therapy

Natural products have been the most productive source for the development of drugs. Terpenoids are a class of natural active products with a wide range of pharmacological activities and therapeutic effects, which can be used to treat a variety of diseases. Non-alcoholic fatty liver disease (NAFLD), a common metabolic disorder worldwide, results in a health burden and economic problems. A literature search was conducted to obtain information relevant to the treatment of NAFLD with terpenoids using electronic databases, namely PubMed, Web of Science, Science Direct, and Springer, for the period 2011-2021. In total, we found 43 terpenoids used in the treatment of NAFLD. Over a dozen terpenoid compounds of natural origin were classified into five categories according to their structure: monoterpenoids, sesquiterpenoids, diterpenoids, triterpenoids, and tetraterpenoids. We found that terpenoids play a therapeutic role in NAFLD, mainly by regulating lipid metabolism disorder, insulin resistance, oxidative stress, and inflammation. The AMPK, PPARs, Nrf-2, and SIRT 1 pathways are the main targets for terpenoid treatment. Terpenoids are promising drugs and will potentially create more opportunities for the treatment of NAFLD. However, current studies are restricted to animal and cell experiments, with a lack of clinical research and systematic structure-activity relationship (SAR) studies. In the future, we should further enrich the research on the mechanism of terpenoids, and carry out SAR studies and clinical research, which will increase the likelihood of breakthrough insights in the field.

Curcumol alleviates liver fibrosis through inducing autophagy and ferroptosis in hepatic stellate cells

To explore the effect of curcumol on autophagy and ferroptosis of hepatic stellate cells, and to clarify the molecular mechanism of its anti-hepatic fibrosis. In the present study, we report that curcumol promotes the death of activated HSCs and reduces the deposition of extracellular matrix. Interestingly, curcumol treatment can trigger ferroptosis to eliminate activated HSCs characterized by iron overload, lipid ROS accumulation, glutathione depletion, and lipid peroxidation. Curcumol promotes HSC autophagy, which may be the key mechanism for its induction of ferroptosis. It is worth noting that the upregulation of nuclear receptor coactivator 4 (NCOA4) may play a key molecular mechanism. NCOA4 mediates the release of iron ions and induces the occurrence of ferroptosis. Overall, curcumol promotes autophagy in hepatic stellate cells, mediates the degradation of NCOA4 and FTH1 complexes, releases iron ions, leads to iron overload, and induces ferroptosis, which may be an important mechanism for its anti-hepatic fibrosis effect.

Acanthoic acid, unique potential pimaradiene diterpene isolated from Acanthopanax koreanum Nakai (Araliaceae): A review on its pharmacology, molecular mechanism, and structural modification

Acanthoic acid (AA) is a pimaradiene diterpene isolated from the root bark of Acanthopanax koreanum Nakai (Araliaceae) with a wide range of pharmacological activities, including anti-cancer, anti-inflammatory, anti-diabetes, liver protection, gastrointestinal protection, and cardiovascular protection. In addition, AA promotes its pharmacological effects by targeting liver X receptors (LXRs), nuclear factor-kappa B (NF-κB), Toll-Like Receptor 4 (TLR4) and IL-1 receptor-associated kinase (IRAK) signaling pathways, or AMP-activated protein kinase (AMPK) signaling pathway, etc. Also, some studies focus on the structural modification of AA to improve its pharmacological activities. The review summarizes the pharmacological activities, molecular mechanism, and the structural modification of AA, which might supply information for the development of AA in the future.

Protective role of Siberian onions against toxin-induced liver dysfunction: an insight into health-promoting effects

Siberian onions (SOs) are delicious wild vegetables. Their taste is most unique, not only like scallions but also like leeks or garlic. They also have a traditional medicinal value for anti-inflammation, anti-oxidation, and anti-pyretic analgesia, particularly facilitating hepatoprotective effects. The current study investigates the potential mechanism of SOs against toxin-induced liver dysfunction. BALB/c mice were administrated with SO or silymarin by oral gavage for one week, followed by injecting carbon tetrachloride (CCl₄) to induce hepatic fibrosis. The effect of SO against hepatic fibrosis was evaluated by examining the liver tissue for serum transaminase, oxidative stress, extracellular matrix, histological alterations, cytokine levels, and apoptosis. In vitro, HSC-T6 cells were cultured with the supernatant from Raw 264.7 cells stimulated with lipopolysaccharides, followed by SO extracts or Niclosamide (Signal Transducer and Activator of Transcription 3 (STAT3) inhibitor) at indicated time periods and doses. SO decreased serum transaminase levels and oxidative stress, and regulated the balance of ECM in CCl₄-induced mice, including α-SMA, collagen-I and TIMP-1. SO reduced the release of inflammatory factors and regulated apoptosis-associated proteins, which is related to the inhibition of STAT3 phosphorylation. Moreover, SO reduced the positive expressions of α-SMA and NLRP3 by inhibiting STAT3 phosphorylation in activated HSCs. SO could show health-promoting effects for liver dysfunction by alleviating hepatic fibrogenesis, apoptosis and inflammation in the development of hepatic fibrosis potential depending on the STAT3 signaling pathway.

Evaluation of the Mechanism of Modified Lingguizhugan Decoction in the Treatment of Nonalcoholic Fatty Liver Disease

Nonalcoholic steatohepatitis (NASH) may develop into cirrhosis and liver cancer, which imposes a great burden to individuals and society. Lingguizhugan decoction is a commonly used dampness dispelling medication in traditional Chinese medicine and is often used to treat those with phlegm and retained fluid from various causes and pathogeneses. The objective of this study was to explore the effect and mechanism of modified Lingguizhugan decoction (MLGZG) on lipid metabolism and the inflammatory response to identify a theoretical basis to promote its clinical application in NASH therapy. After treatment with MLGZG for 8 weeks, the weight of high-fat-diet (HFD)-fed NASH rats was significantly higher than that of rats in the normal group, and the weights in each dose group were significantly lower than those in the model group. The treatment groups (low, medium, and high doses) had different degrees of improvement in the changes in hepatocyte tissue structure, steatosis, and inflammatory infiltration. Compared with that in the normal group, the expression of TNF receptor-associated factor-3 (TRAF-3) and nuclear factor κB (NFκB) in the model group significantly increased to varying degrees. Compared with the NASH group, the treatment groups (low, middle, and high doses) showed modified lipid metabolism gene expression and decreased inflammatory factor expression levels. Modified Lingguizhugan decoction can improve the general condition of rats with nonalcoholic fatty liver disease by reducing the expression levels of TRAF3, NF-κB, the Toll-like receptor 4 (TLR-4) pathway, and related proteins, as well as the expression levels of lipid metabolism genes and cytokines.

Development of natural products for anti-PD-1/PD-L1 immunotherapy against cancer

ETHNOPHARMACOLOGICAL RELEVANCE

The programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) immune checkpoint is one of the most promising therapeutic targets for cancer immunotherapy, but several challenges remain in current anti-PD-1/PD-L1 therapy. Natural products, mainly derived from traditional medicine, could improve and expand anti-PD-1/PD-L1 therapy because of their advantages such as large diversity and multi-target effects.

AIM OF THE STUDY

This review summarize natural products, raw extracts, and traditional medicines with pharmacological effects associated with the PD-1/PD-L1 axis, particularly PD-L1.

MATERIALS AND METHODS

Electronic literature databases, including Web of Science, PubMed, and ScienceDirect, and online drugs and chemicals databases, including DrugBank, ZINC, PubChem, STITCH, and CTD, were searched without date limitation by February 2021. 'Natural product or herb or herbal plant or traditional medicine' and 'PD-L1' and 'Cancer immunotherapy' were used as the search keywords. Among 112 articles identified in database searching, 54 articles are full text articles, reporting in silico, in vitro, in vivo and clinical trials. 68 articles included are review articles and grey literature such as thesis and congress abstracts.

RESULTS

Several natural products and traditional medicines have exhibited diverse and multi-functional effects including direct blockade of PD-1/PD-L1 interactions, modulation of PD-L1 expression, and cooperation with PD-1/PD-L1 inhibitors.

CONCLUSION

Natural products and traditional medicines can facilitate the development of more effective and acceptable diverse strategies for anti-PD-1/PD-L1 therapy, but further exploration of natural products and pharmaceutical techniques is required.

Novel roles of lipopolysaccharide and TLR4/NF-κB signaling pathway in inflammatory response to liver injury in Budd-Chiari syndrome

BACKGROUND

Budd-Chiari syndrome (BCS) is an uncommon disorder characterized by obstruction of hepatic venous outflow. To date, the exact mechanism underlying hepatic injury derived from the hepatic venous outflow obstruction in BCS remains largely unknown.

AIM

To assess the role of NF-κB-mediated inflammation in BCS-induced liver injury in humans and rats.

METHODS

A total of 180 rats were randomly assigned into nine groups, including four BCS model groups (1, 3, 6 and 12 wk), four sham-operated groups (1, 3, 6 and 12 wk), and a control group. Lipopolysaccharide (LPS) levels in each group were detected by the Tachypleus Amebocyte Lysate assay. The mRNA and protein levels of TLR4, NF-κB, tumor necrosis factor (TNF)-α, interleukin (IL)-2 and interferon (IFN)-γ were quantified. In addition, 60 patients with BCS and 30 healthy controls were enrolled, and their blood samples were analyzed.

RESULTS

Hepatic and plasma LPS levels were significantly increased in rats. The mRNA and protein expression levels of TLR4, NF-κB and inflammatory cytokines (TNF-α, IL-2 and IFN-γ) in liver tissues were significantly higher in the BCS model groups compared with the other two groups. In addition, the model groups (1, 3, 6 and 12 wk after BCS induction) showed significant differences in the levels of LPS, TLR4, NF-κB, TNF-α, IL-2 and IFN-γ. Notably, there was a significant correlation between the LPS concentrations and mRNA and protein levels of TLR4, NF-κB and inflammatory cytokines. Importantly, it was revealed that the levels of LPS, TLR4, NF-κB and inflammatory cytokines were significantly greater in chronic BCS patients than healthy controls and acute BCS patients.

CONCLUSION

LPS level is markedly elevated in BCS, in turn activating the TLR4/NF-κB signaling pathway, leading to induction of inflammatory cytokines (TNF-α, IL-2 and IFN-γ) in response to BCS-induced liver injury.

Betulin Targets Lipin1/2-Meidated P2X7 Receptor as a Therapeutic Approach to Attenuate Lipid Accumulation and Metaflammation

The present study focused on the potential mechanism of betulin (BT), a pentacyclic triterpenoid isolated from the bark of white birch (Betula pubescens), against chronic alcohol-induced lipid accumulation and metaflammation. AML-12 and RAW 264.7 cells were administered ethanol (EtOH), lipopolysaccharide (LPS) or BT. Male C57BL/6 mice were fed Lieber-DeCarli liquid diets containing 5% EtOH for 4 weeks, followed by single EtOH gavage on the last day and simultaneous treatment with BT (20 or 50 mg/kg) by oral gavage once per day. In vitro, MTT showed that 0-25 mM EtOH and 0-25 μM BT had no toxic effect on AML-12 cells. BT could regulate sterolregulatory-element-binding protein 1 (SREBP1), lipin1/2, P2X7 receptor (P2X7r) and NOD-like receptor family, pyrin domains-containing protein 3 (NLRP3) expressions again EtOH-stimulation. Oil Red O staining also indicated that BT significantly reduced lipid accumulation in EtOH-stimulated AML-12 cells. Lipin1/2 deficiency indicated that BT might mediate lipin1/2 to regulate SREBP1 and P2X7r expression and further alleviate lipid accumulation and inflammation. In vivo, BT significantly alleviated histopathological changes, reduced serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and triglyceride (TG) levels, and regulated lipin1/2, SREBP1, peroxisome proliferator activated receptor α/γ (PPARα/γ) and PGC-1α expression compared with the EtOH group. BT reduced the secretion of inflammatory factors and blocked the P2X7r-NLRP3 signaling pathway. Collectively, BT attenuated lipid accumulation and metaflammation by regulating the lipin1/2-mediated P2X7r signaling pathway.

Allium victorialis L. Extracts Promote Activity of FXR to Ameliorate Alcoholic Liver Disease: Targeting Liver Lipid Deposition and Inflammation

Allium victorialis L. (AVL) is a traditional medicinal plant recorded in the Compendium of Materia Medica (the Ming Dynasty). In general, it is used for hemostasis, analgesia, anti-inflammation, antioxidation, and to especially facilitate hepatoprotective effect. In recent years, it has received more and more attention due to its special nutritional and medicinal value. The present study investigates the effect and potential mechanism of AVL against alcoholic liver disease (ALD). C57BL/6 mice were fed Lieber-DeCarli liquid diet containing 5% ethanol plus a single ethanol gavage (5 g/kg), and followed up with the administration of AVL or silymarin. AML12 cells were stimulated with ethanol and incubated with AVL. AVL significantly reduced serum transaminase and triglycerides in the liver and attenuated histopathological changes caused by ethanol. AVL significantly inhibited SREBP1 and its target genes, regulated lipin 1/2, increased PPARα and its target genes, and decreased PPARγ expression caused by ethanol. In addition, AVL significantly enhanced FXR, LXRs, Sirt1, and AMPK expressions compared with the EtOH group. AVL also inhibited inflammatory factors, NLRP3, and F4/80 and MPO, macrophage and neutrophil markers. In vitro, AVL significantly reduced lipid droplets, lipid metabolism enzymes, and inflammatory factors depending on FXR activation. AVL could ameliorate alcoholic steatohepatitis, lipid deposition and inflammation in ALD by targeting FXR activation.

Parthenolide, bioactive compound of Chrysanthemum parthenium L., ameliorates fibrogenesis and inflammation in hepatic fibrosis via regulating the crosstalk of TLR4 and STAT3 signaling pathway

The current study focused on the regulatory effects of parthenolide (PNL), a bioactive component derived from Chrysanthemum parthenium L., against hepatic fibrosis via regulating the crosstalk of toll-like receptor 4 (TLR4) and signal transducer and activator of transcription 3 (STAT3) in activated hepatic stellate cells (HSCs). HSCs or Raw 264.7 macrophages were activated by TGF-β or LPS for 1 hr, respectively, and then treated with PNL, CLI-095 (TLR4 inhibitor), or Niclosamide (STAT3 inhibitor) for the indicated time to detect the crosstalk of TLR4 and STAT3. PNL significantly decreased the expressions of α-SMA, collagen I, and the ratio of TIMP1 and MMP13 in TGF-β-activated HSCs. PNL significantly reduced the releases of pro-inflammatory cytokines, including IL-6, IL-1β, IL-1α, IL-18, and regulated signaling P2X7r/NLRP3 axis activation. PNL obviously induced the apoptosis of activated HSCs by regulating bcl-2 and caspases family. PNL significantly inhibited the expressions of TLR4 and STAT3, including their downstream signaling. PNL could regulate the crosstalk of TLR4 and STAT3, which were verified by their inhibitors in activated HSCs or Raw 264.7 cell macrophages. Thus, PNL could decrease the expressions of fibrosis markers, reduce the releases of inflammatory cytokines, and also induce the apoptosis of activated HSCs. In conclusion, PNL could bi-directionally inhibit TLR4 and STAT3 signaling pathway, suggesting that blocking the crosstalk of TLR4 and STAT3 might be the potential mechanism of PNL against hepatic fibrosis.

Synthesis and Evaluation of Chiral Rhodanine Derivatives Bearing Quinoxalinyl Imidazole Moiety as ALK5 Inhibitors

BACKGROUND

TGF-β signaling pathway inhibition is considered an effective way to prevent the development of several diseases. In the design and synthesis of TGF-β inhibitors, a rhodanine compound containing a quinoxalinyl imidazole moiety was found to have strong antimicrobial activity.

OBJECTIVE

The purpose of this work was to investigate the antimicrobial activity of other chiral rhodanine TGF-β inhibitors synthesized.

METHODS

Two series of 3-substituted-5-((5-(6-methylpyridin-2-yl)-4-(quinoxalinyl-6-yl)- 1H-imidazol-2-yl)methylene)-2-thioxothiazolin-4-ones (12a-h and 13a-e) were synthesized and evaluated for their ALK5 inhibitory and antimicrobial activity. The structures were confirmed by their 1H NMR, 13C NMR, and HRMS spectra. All the synthesized compounds were screened against Gram-positive strains, Gram-negative strains, and fungi.

RESULTS

Among the synthesized compounds, compound 12h showed the highest activity (IC50 = 0.416 μM) against ALK5 kinase. Compound 12h exhibited a good selectivity index of > 24 against p38α MAP kinase and was 6.0-fold more selective than the clinical candidate, compound 2 (LY-2157299). Nearly all the compounds displayed high selectivity toward both Gram-positive and Gram-negative bacteria. They also showed similar or 2.0-fold greater antifungal activity (minimum inhibitory concentration [MIC] = 0.5 µg/mL) compared with the positive control compounds Gatifloxacin (MIC = 0.5 µg/mL) and fluconazole (MIC = 1 µg/mL).

CONCLUSION

The findings suggest that the synthesized rhodanine compounds have good ALK5 inhibitory activity and can be used for further research and development as potential antifungal drugs.

The Impact of Acute or Chronic Alcohol Intake on the NF-κB Signaling Pathway in Alcohol-Related Liver Disease

Ethanol misuse is frequently associated with a multitude of profound medical conditions, contributing to health-, individual- and social-related damage. A particularly dangerous threat from this classification is coined as alcoholic liver disease (ALD), a liver condition caused by prolonged alcohol overconsumption, involving several pathological stages induced by alcohol metabolic byproducts and sustained cellular intoxication. Molecular, pathological mechanisms of ALD principally root in the innate immunity system and are especially associated with enhanced functionality of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. NF-κB is an interesting and convoluted DNA transcription regulator, promoting both anti-inflammatory and pro-inflammatory gene expression. Thus, the abundancy of studies in recent years underlines the importance of NF-κB in inflammatory responses and the mechanistic stimulation of inner molecular motifs within the factor components. Hereby, in the following review, we would like to put emphasis on the correlation between the NF-κB inflammation signaling pathway and ALD progression. We will provide the reader with the current knowledge regarding the chronic and acute alcohol consumption patterns, the molecular mechanisms of ALD development, the involvement of the NF-κB pathway and its enzymatic regulators. Therefore, we review various experimental in vitro and in vivo studies regarding the research on ALD, including the recent active compound treatments and the genetic modification approach. Furthermore, our investigation covers a few human studies.

Scoparone alleviates hepatic fibrosis by inhibiting the TLR-4/NF-κB pathway

The aim of this study was to investigate the role of scoparone (SCO) in hepatic fibrosis. For this, we conducted in vivo and in vitro experiments. In vivo rats that were divided into six groups, control, carbon tetrachloride, and colchicine, as well as SCO groups, SCO50, SCO100, and SCO200 treated with 50, 100, and 200 mg/kg SCO doses, respectively. Furthermore, SCO was shown to inhibit Toll-like receptor-4 (TLR-4)/nuclear factor kappa-B (NF-κB; TLR-4/NF-κB) signals by inhibiting TLR-4, which in turn downregulates the expression of MyD88, promotes NF-κB inhibitor-α, NF-κB inhibitor-β, and NF-κB inhibitor-ε activation, while inhibiting NF-κB inhibitor-ζ. Subsequently, the decrease of phosphorylation of nuclear factor-κB levels leads to the downregulation of the downstream inflammatory factors' tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and IL-1 beta, thus weakening hepatic fibrosis. Notably, the SCO200 treated group presented the most significant improvement. Hence, we conclude that SCO alleviates hepatic fibrosis by inhibiting TLR-4/NF-κB signals.

The effects of estradiol on inflammatory and endothelial dysfunction in rats with preeclampsia

Preeclampsia (PE), a hypertensive disorder during pregnancy, has adverse effects to both the mother and the fetus. Maternal inflammatory and vascular endothelial dysfunction are important factors in the pathogenesis of PE. The present study aimed to investigate the effects of estradiol (E2) on inflammatory and endothelial dysfunction in an N (omega)-nitro-L-arginine methyl ester (L-NAME)-induced rat model of PE. Adult pregnant female Sprague-Dawley rats were divided into four equal groups between days 7 and 11 of gestation and treated as follows: i) Pregnant rats receiving daily intraperitoneal (i.p.) injections of equal volume of 0.9% normal saline (NS) (Control group, n=12); ii) pregnant rats receiving daily i.p. injections of L-NAME at 50 mg/kg (L-NAME group, n=12); iii) pregnant rats receiving a daily i.p. injection of 50 mg/kg L-NAME and NS from day 11 (L-NAME + NS group, n=12); and iv) pregnant rats receiving daily i.p. injections of 50 mg/kg L-NAME and 100 µg/kg/day E2 from day 11 (L-NAME + E2 group, n=12). On day 21, blood pressure (BP) and the level of 24-h urine protein in the maternal rats, fetal weight and percentage of stillbirths following a cesarean section were recorded. The activities of nitric oxide (NO) and inducible NO synthase (iNOS), the levels of inflammatory cytokines [interleukin (IL)-1β, IL-6, interferon-γ and monocyte chemoattractant protein-1], adherence factors (CD49d, intracellular adhesion molecule 1 and lymphocyte function-associated antigen-1) and uterine angiogenic status (Fms-like tyrosine kinase-1, vascular cell adhesion molecule and matrix metalloproteinase 2/9) were also assessed. In addition, the histopathology of the placenta, the expression of estrogen receptor α 36 (ERα36), ERα, ERβ and G protein-coupled ER, as well as the activation of the toll-like receptor 4 (TLR4) signaling pathway (TLR4, myeloid differentiation primary response 88, IL-1 receptor-associated kinase 4 and tumor necrosis factor receptor-associated factor 6) were evaluated by H&E staining, immunofluorescence and western blot assays. Treatment with L-NAME increased the BP, urine protein and rate of stillbirths and suppressed fetal weight compared with those in the control group. The L-NAME-induced effects were attenuated by the administration of E2. In addition, the administration of E2 decreased inflammation and NO levels and altered the uterine angiogenic status. The histological analysis of PE rat placenta in the E2-treated group confirmed the effects on biochemical parameters. Of note, E2 treatment significantly suppressed the TLR4 signaling pathway. In the rat model of PE, adverse outcomes including BP, fetal rat weight and proteinuria, high neonatal death rate, inflammatory response, oxidative stress and endothelial dysfunction were attenuated by exogenous E2 administration, which may present a novel approach for the clinical treatment of PE.