Triptolide Modulates TREM-1 Signal Pathway to Inhibit the Inflammatory Response in Rheumatoid Arthritis

Triptolide protects against TGF-β1-induced pulmonary fibrosis by regulating FAK/calpain signaling

The present study aimed to investigate the mechanism of anti-proliferative, anti-inflammatory and anti-fibrotic effects of triptolide (TPL) on activated lung fibroblasts by regulating the focal adhesion kinase (FAK) and calpain signaling pathways. The HFL-1 human foetal lung fibroblast cell line was cultured in vitro and treated with 50 ng/ml transforming growth factor (TGF)-β1 for 48 h to establish the model of pulmonary fibrosis. Subsequently, the cells were divided into five groups, including a control, model, TPL, FAK inhibitor and calpeptin group. Subsequently, the proliferation of lung fibroblasts was detected using the Cell Counting Kit-8 assay. The concentration of interleukin (IL)-6 in the cell culture supernatant was examined by ELISA and the mRNA expression levels of collagen type I (ColI)α and ColIII in lung fibroblasts were quantified by reverse transcription-quantitative PCR. The protein levels of FAK, phosphorylated (p)-FAK, calpain 1 and calpain 2 were detected by western blot analysis. TGF-β1 induced the proliferation of lung fibroblasts, whereas TPL inhibited this proliferation in a dose-dependent manner. TPL also decreased the TGF-β1-induced production of IL-6 and reduced the upregulation of ColIα, ColIII, FAK, p-FAK, and inhibited the decrease of calpain 1 and calpain 2 induced by TGF-β1. In addition, the FAK inhibitor acted synergistically with TPL to decrease TGF-β1-induced production of IL-6 and attenuate TGF-β1-induced synthesis of ColIα and ColIII, while calpeptin had an antagonistic effect on the function of TPL. Furthermore, treatment with the FAK inhibitor and TPL markedly decreased the protein levels of FAK and p-FAK, and increased the protein expression of calpain 1 and calpain 2 in lung fibroblasts stimulated by TGF-β1 to a greater extent than TPL alone, while calpeptin had an antagonistic effect on the action of TPL. In conclusion, the present study indicated that TPL protected against TGF-β1-induced proliferation, inflammation and fibrosis by regulating the FAK and calpain signaling pathways.

Herbal compounds for rheumatoid arthritis: Literatures review and cheminformatics prediction

Rheumatoid arthritis (RA) is a systemic disease characterized by autoimmunity, joint inflammation, and cartilage destruction, which affects 0.5-1% of the population. Many compounds from herbal medicines show the potentials to treat RA. On this basis, the compounds with good pharmacokinetic behaviors and drug-likeness properties will be further studied and developed. Therefore, the herbal compounds with anti-RA activities were reviewed in this paper, and the cheminformatics tools were used to predict their drug-likeness properties and pharmacokinetic parameters. A total of 90 herbal compounds were analyzed, which were reported to be effective on RA models through anti-inflammation, chondroprotection, immunoregulation, antiangiogenesis, and antioxidation. Most of the herbal compounds have good drug-likeness properties. Most of the compounds can be an alternative and valuable source for anti-RA drug discovery.

Next-Generation Sequencing Profiles of the Methylome and Transcriptome in Peripheral Blood Mononuclear Cells of Rheumatoid Arthritis

Using next-generation sequencing to decipher methylome and transcriptome and underlying molecular mechanisms contributing to rheumatoid arthritis (RA) for improving future therapies, we performed methyl-seq and RNA-seq on peripheral blood mononuclear cells (PBMCs) from RA subjects and normal donors. Principal component analysis and hierarchical clustering revealed distinct methylation signatures in RA with methylation aberrations noted across chromosomes. Methylation alterations varied with CpG features and genic characteristics. Typically, CpG islands and CpG shores were hypermethylated and displayed the greatest methylation variance. Promoters were hypermethylated and enhancers/gene bodies were hypomethylated, with methylation variance associated with expression variance. RA genetically associated genes preferentially displayed differential methylation and differential expression or interacted with differentially methylated and differentially expressed genes. These differentially methylated and differentially expressed genes were enriched with several signaling pathways and disease categories. 10 genes (CD86, RAB20, XAF1, FOLR3, LTBR, KCNH8, DOK7, PDGFA, PITPNM2, CELSR1) with concomitantly differential methylation in enhancers/promoters/gene bodies and differential expression in B cells were validated. This integrated analysis of methylome and transcriptome identified novel epigenetic signatures associated with RA and highlighted the interaction between genetics and epigenetics in RA. These findings help our understanding of the pathogenesis of RA and advance epigenetic studies in regards to the disease.

Therapeutic Effect of Modulating TREM-1 via Anti-inflammation and Autophagy in Parkinson's Disease

Parkinson’s disease (PD) is one of the most common age-related neurodegenerative diseases, and neuroinflammation has been identified as one of its key pathological characteristics. Triggering receptors expressed on myeloid cells-1 (TREM-1) amplify the inflammatory response and play a role in sepsis and cancer. Recent studies have demonstrated that the attenuation of TREM-1 activity produces cytoprotective and anti-inflammatory effects in macrophages. However, no study has examined the role of TREM-1 in neurodegeneration. We showed that LP17, a synthetic peptide blocker of TREM-1, significantly inhibited the lipopolysaccharide (LPS)-induced upregulation of proinflammatory cascades of inducible nitric oxide synthase (iNOS), cyclooxygenase-2, and nuclear factor-kappa B. Moreover, LP17 enhanced the LPS-induced upregulation of autophagy-related proteins such as light chain-3 and histone deacetylase-6. We also knocked down TREM-1 expression in a BV2 cell model to further confirm the role of TREM-1. LP17 inhibited 6-hydroxydopamine-induced locomotor deficit and iNOS messenger RNA expression in zebrafish. We also observed therapeutic effects of LP17 administration in 6-hydroxydopamine-induced PD syndrome using a rat model. These data suggest that the attenuation of TREM-1 could ameliorate neuroinflammatory responses in PD and that this neuroprotective effect might occur via the activation of autophagy and anti-inflammatory pathways.

Triptolide Improves Cognitive Dysfunction in Rats with Vascular Dementia by Activating the SIRT1/PGC-1α Signaling Pathway

Tripterygium Wilfordii Hook F has been exploited as a treatment for several diseases due to its neuroprotective, anti-tumor, and anti-inflammatory effects. Triptolide is one of its key bioactive compounds. Currently, the role of triptolide in cognitive dysfunction remains unclear. Here, the role of triptolide on cognitive dysfunction was investigated using chronic cerebral hypoperfusion-induced vascular dementia (VD) rat model. SD rats were administrated with Triptolide (5 μg/kg) for 6 weeks after undergoing permanent bilateral common carotid artery occlusion. The results show that triptolide treatment conferred neuroprotective effects in VD rats. Intraperitoneal injection of triptolide attenuated oxidative stress, learning and memory deficits, and neuronal apoptosis in the hippocampi. Moreover, triptolide enhanced the expression of SIRT1, PGC-1α, ZO-1, Claudin-5, and decreased the serum levels of NSE and S100B significantly. It also improved CCH-induced learning and memory deficits, and this is attributed to its capacity to promote SIRT1/PGC-1α signaling, confer antioxidant effects, and inhibit neuronal apoptosis. These findings indicate that triptolide may be an effective therapeutic agent for vascular cognitive dysfunction.

Triptolide exerts an anti-tumor effect on non‑small cell lung cancer cells by inhibiting activation of the IL‑6/STAT3 axis

Lung cancer is the leading cause of cancer‑associated mortality and current treatments are not sufficiently effective. Numerous studies have revealed that triptolide (TP), a classical traditional Chinese medicine compound widely used as an anti‑inflammatory and antirheumatic drug, also has an antitumor effect. This effect is hypothesized to be mediated by multiple pathways, with signal transducer and activator of transcription 3 (STAT3) possibly one of them. Evidence indicates that STAT3 participates in the initiation and progression of lung cancer during cell proliferation, apoptosis and migration; however, whether and how TP affects STAT3 and its targets remain unclear. In this study, the potential role of TP in the proliferation, apoptosis, and migration of non‑small cell lung cancer cell lines was investigated and evaluated the impact of TP on the interleukin‑6 (IL‑6)/STAT3 axis. The results showed that TP inhibited cell proliferation and migration and induced apoptosis. TP decreased the phosphorylation of STAT3, inhibited STAT3 translocation into the nucleus, and reduced the expression of STAT3 target genes involved in cell survival, apoptosis and migration, e.g. C‑myc, BCL‑2, myeloid cell leukemia‑1 (MCL‑1), and matrix metallopeptidase 9 (MMP‑9). Additionally, IL‑6‑induced activation of STAT3 target genes (e.g. MCL‑1 and BCL‑2) was attenuated by TP and homoharringtonine. In conclusion, the effect of TP on STAT3 signaling points to a promising strategy for drug development.

Investigation of gene expression profiles in a rat adjuvant arthritis model suggests an effective role of triptolide via PI3K-AKT signaling

Rheumatoid arthritis (RA) is a common systemic autoimmune disease mainly involving the formation of a synovial pannus, for which no effective treatment is available. In order to study the molecular biological mechanisms underlying the inhibition of RA synovial pannus by triptolide, differentially expressed genes in synovial tissues from an adjuvant arthritis (AA) rat model with and without triptolide treatment were detected in an mRNA microarray profile produced by Agilent Technologies and verified by reverse transcription-quantitative polymerase chain reaction analysis (RT-qPCR). An AA model was established by subcutaneously injecting 0.1 ml Freund's complete adjuvant daily for 18 days and scored by arthritis index assessment. Subsequently, triptolide (0.4 mg/kg) or an equivalent amount of saline was administered daily for 14 days. At the end of the experiment, synovial tissues were obtained from the ankle joints of the rats' hind legs. Total RNA was extracted and purified, and microarray hybridization was used to obtain the gene expression profile for RA with and without triptolide treatment. A total of 48 genes were identified to be differentially expressed between the treatment and model groups, including 32 upregulated and 16 downregulated genes. The possible signaling pathways associated with the effect of triptolide were investigated by Gene Ontology and pathway analysis, revealing that the phosphoinositide-3 kinase (PI3K)/AKT signaling pathway has a key role in the proliferation and apoptosis of synovial cells in RA joints. Reverse transcription-quantitative polymerase chain reaction analysis was applied to confirm the aberrant expression of key mRNAs and revealed that vascular endothelial growth factor (VEGF) A and C1q and tumor necrosis factor related protein 3 (C1QTNF3) were downregulated in the treatment group compared with the model group (P<0.05). In conclusion, triptolide may exert its effects against RA via the PI3K/AKT pathway and has an inhibitory effect on the expression of VEGFA and C1QTNF3, thus are potentially associated with the occurrence and development of RA.

The triptolide-induced apoptosis of osteoclast precursor by degradation of cIAP2 and treatment of rheumatoid arthritis of TNF-transgenic mice

This study aims to discuss the effect of triptolide (TPL) on rheumatoid arthritis (RA) and the mechanism related to osteoclast precursor (OCP) and osteoclast (OC). TNF-transgenic RA mice were treated with different doses of TPL by gavage. After the administration was finished, the curative effects were evaluated and compared, and the OCP apoptosis rates, the OC number, and the OC differentiation ability in vitro were detected. Finally, splenocytes of wild-type mice were cultured in vitro and induced to differentiate into OCP, and the cell apoptosis rate, cIAP2, and apoptotic effectors expression level were detected after cIAP2 overexpression and TPL administration. After TPL administration, the RA symptoms in the TPL groups were all better, the apoptosis rate of OCP was higher, and the amount of OC in vitro were lower than that in the control group (all P < 0.05), and all of the changes in the high-dose group were more obvious than the low-dose group. In splenocytes cells cultured in vitro, cIAP2 overexpression could decrease the apoptosis rate of OCPs and increase the OC number, and TPL treatment could down-regulate the cIAP2 and promote OCP apoptosis and OC reduction. In conclusion, TPL could induce OCP apoptosis and inhibit OC formation to effectively treat RA by mediating cIAP2 degradation.

Retrospective analysis of tacrolimus combined with Tripterygium wilfordii polyglycoside for treating idiopathic membranous nephropathy

BACKGROUND

Idiopathic membranous nephropathy (IMN) is one of the most common adult nephrotic syndromes. Some patients with this disorder require immunosuppressive therapy. This retrospective case series was performed to assess the effects of tacrolimus (TAC) combined with Tripterygium wilfordii polyglycoside (TWG) in treating IMN.

METHODS

From January 2015 to August 2016, kidney-biopsy-proven IMN patients treated with TAC in the Chinese PLA General Hospital were screened. Data were retrieved from the patients' medical records. The first efficacy evaluation index was remission rate (complete remission and partial remission), and the secondary efficacy evaluation indices included relapse rate, proteinuria, serum albumin and estimated glomerular filtration rate (eGFR). Adverse events were also assessed.

RESULTS

The included patients' treatments were tacrolimus monotherapy (TAC group, n = 33), tacrolimus combined with methylprednisolone (MP) (TAC + MP group, n = 24) and tacrolimus combined with Tripterygium wilfordii polyglycoside (TAC + TWG group, n = 21). The remission rates of the TAC, TAC + MP, and TAC + TWG groups in the 10th month were 54.5, 62.5, and 85.7%, respectively (TAC + TWG group vs TAC group, P = 0.037, TAC + TWG group vs TAC + MP group, P = 0.125). Moreover, the complete remission rates of the TAC, TAC + MP, and TAC + TWG groups in the 10th month were 21.2, 20.8, and 57.1%, respectively (TAC + TWG group vs TAC group, P = 0.007, TAC + TWG group vs TAC + MP group, P = 0.012). Compared with the TAC group, the TAC + TWG group had a higher remission rate during these ten months (log-rank, P = 0.005). Compared with the TAC and TAC + MP groups, the TAC + TWG group had a higher complete remission rate (log-rank, P = 0.019 and log-rank, P = 0.005, respectively).

CONCLUSION

This retrospective study showed that TAC combined with TWG may be effective for treating IMN. Further randomized controlled trials (RCTs) are needed to assess the efficacy and safety of TAC combined with TWG.

Hei-Gu-Teng Zhuifenghuoluo Granule Modulates IL-12 Signal Pathway to Inhibit the Inflammatory Response in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a type of chronic systemic inflammatory disease; it has a very complicated pathogenesis, and multiple pathological changes are implicated. Traditional Chinese medicine (TCM) like Tripterygium wilfordii Hook. F. or Sinomenium acutum (Thunb.) Rehd et Wils. has been extensively used for centuries in the treatment of arthritic diseases and been reported effective for relieving the severity of RA. Hei-Gu-Teng Zhuifenghuoluo granule (HGT) which contains Periploca forrestii Schltr., Sinomenium acutum (Thunb.) Rehd et Wils., and Lysimachia paridiformis Franch. var. stenophylla Franch. was a representative natural rattan herb formula for the treatment of RA in China, but the mechanism has not been elucidated. This study aimed at exploring the mechanism of HGT on RA using the bioinformatics analysis with in vivo and in vitro experiment validation. The potential action mechanism was first investigated by bioinformatics analysis via Ingenuity Pathway Analysis (IPA) software. After that, we use experimental validation such as collagen-induced arthritis (CIA) mice model in vivo and U937 cell model in vitro. The bioinformatics results suggested that HGT may have anti-inflammatory characteristic on RA and IL-12 signaling pathway could be the potential key trigger. In vivo experiments demonstrated that HGT ameliorated the symptoms in CIA mice and decreased the production of inflammatory cytokines in both mice ankle joints and serum. Furthermore, HGT effectively inhibited the activation of IL-12R and STAT4 on IL-12 signaling pathway. In vitro experiments showed that HGT inhibited the production of IL-12R and STAT4 induced by IL-12 in lipopolysaccharide- (LPS-) stimulated U937 cells. Moreover, IL-12R knockdown was able to interfere with the inhibition effects of HGT on the production of these cytokines. Our results confirmed the anti-inflammatory property of HGT, which was attributed to its inhibition on IL-12 signaling pathway.

Identification of peculiar gene expression profile in peripheral blood mononuclear cells (PBMC) of celiac patients on gluten free diet

Celiac disease (CD) is a systemic disorder characterized by an immune-mediated reaction to gluten and a wide spectrum of clinical manifestations. Currently, the main treatment of CD is represented by adherence to a gluten-free diet (GFD) which determines the resolution of symptoms, and the normalization of the serology and of the duodenal villous atrophy. In the present study, we aimed to identify changes in gene expression in peripheral blood mononuclear cells (PBMCs) of celiac patients on GFD for at least 2 years, in order to identify novel disease biomarkers and candidate targets for putative therapeutic approaches. Microarray analysis was performed on PBMCs from 17 celiac patients on long-term GFD and 20 healthy controls. We identified 517 annotated genes that were significantly modulated between celiac patients and controls. Significant biological pathways were functionally clustered using the Core Function of Ingenuity System Pathway Analysis (IPA). Intriguingly, despite being on a GFD, celiac patients exhibited a peculiar PBMC profile characterized by an aberrant expression of genes involved in the regulation of immunity, inflammatory response, metabolism, and cell proliferation. Random forest algorithm was then used to validate the prediction ability of core genes as classifiers of the "celiac status". In conclusion, our study identified a characteristic PBMCs signature profile in clinically asymptomatic celiac patient.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.

The Effect of Triptolide in Rheumatoid Arthritis: From Basic Research towards Clinical Translation

Triptolide (TP), a major extract of the herb Tripterygium wilfordii Hook F (TWHF), has been shown to exert potent pharmacological effects, especially an immunosuppressive effect in the treatment of rheumatoid arthritis (RA). However, its multiorgan toxicity prevents it from being widely used in clinical practice. Recently, several attempts are being performed to reduce TP toxicity. In this review, recent progress in the use of TP for RA, including its pharmacological effects and toxicity, is summarized. Meanwhile, strategies relying on chemical structural modifications, innovative delivery systems, and drug combinations to alleviate the disadvantages of TP are also reviewed. Furthermore, we also discuss the challenges and perspectives in their clinical translation.

Yupingfeng San Inhibits NLRP3 Inflammasome to Attenuate the Inflammatory Response in Asthma Mice

Yupingfeng San (YPFS) is a representative Traditional Chinese Medicine (TCM) formula with accepted therapeutic effect on Asthma. However, its action mechanism is still obscure. In this study, we used network pharmacology to explore potential mechanism of YPFS on asthma. Nucleotide-binding oligomerization domain (NOD)-like receptor pathway was shown to be the top one shared signaling pathway associated with both YPFS and asthma. In addition, NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome was treated as target protein in the process of YPFS regulating asthma. Further, experimental validation was done by using LPS-stimulated U937 cells and ovalbumin (OVA)-sensitized BALB/c mice model. In vitro experiments showed that YPFS significantly decreased the production of TNF-α and IL-6, as well as both mRNA and protein levels of IL-1β, NLRP3, Caspase-1 and ASC in LPS-stimulated U937 cells. In vivo experiment indicated that YPFS treatment not only attenuated the clinical symptoms, but also reduced inflammatory cell infiltration, mucus secretion and MUC5AC production in lung tissue of asthmatic mice. Moreover, YPFS treatment remarkably decreased the mRNA and protein levels of IL-1β, NLRP3, Caspase-1 and ASC in lung tissue of asthmatic mice. In conclusion, these results demonstrated that YPFS could inhibit NLRP3 inflammasome components to attenuate the inflammatory response in asthma.

Critical Role of Hepatic Cyp450s in the Testis-Specific Toxicity of (5R)-5-Hydroxytriptolide in C57BL/6 Mice

Low solubility, tissue accumulation, and toxicity are chief obstacles to developing triptolide derivatives, so a better understanding of the pharmacokinetics and toxicity of triptolide derivatives will help with these limitations. To address this, we studied pharmacokinetics and toxicity of (5R)-5-hydroxytriptolide (LLDT-8), a novel triptolide derivative immunosuppressant in a conditional knockout (KO) mouse model with liver-specific deletion of CYP450 reductase. Compared to wild type (WT) mice, after LLDT-8 treatment, KO mice suffered severe testicular toxicity (decreased testicular weight, spermatocytes apoptosis) unlike WT mice. Moreover, KO mice had greater LLDT-8 exposure as confirmed with elevated AUC and Cmax, increased drug half-life, and greater tissue distribution. γ-H2AX, a marker of meiosis process, its localization and protein level in testis showed a distinct meiosis block induced by LLDT-8. RNA polymerase II (Pol II), an essential factor for RNA storage and synapsis in spermatogenesis, decreased in testes of KO mice after LLDT-8 treatment. Germ-cell line based assays confirmed that LLDT-8 selectively inhibited Pol II in spermatocyte-like cells. Importantly, the analysis of androgen receptor (AR) related genes showed that LLDT-8 did not change AR-related signaling in testes. Thus, hepatic CYP450s were responsible for in vivo metabolism and clearance of LLDT-8 and aggravated testicular injury may be due to increased LLDT-8 exposure in testis and subsequent Pol II reduction.

Effect of Triggering Receptor Expressed on Myeloid Cells 1 (TREM-1) Blockade in Rats with Cecal Ligation and Puncture (CLP)-Induced Sepsis

Background

Blocking of TREM-1 signaling improves survival of mice with sepsis induced by Pseudomonas aeruginosa. However, whether TREM-1 blockade has beneficial effects in polymicrobial sepsis is poorly understood. Here, we aimed to investigate the effect of modulation of the TREM-1 pathway in rats with polymicrobial sepsis induced by cecal ligation and puncture (CLP).

Material/Methods

Normal Sprague-Dawley (SD) rats with sepsis induced by CLP were allocated randomly to received scramble peptide or LP17 via the jugular vein. Serum level of sTREM-1, IL6, TNF-α, and IL-1β were detected by ELISA assay. The mRNA and protein levels of JAK2 and STAT3 were detected by real-time PCR and Western blot analysis.

Results

STREM-1 concentration was greatly and progressively increased in rats with CLP-induced sepsis, and the increase was attenuated by TREM-1 inhibitory peptide LP17. More than 60% survival was observed in rats at the experiment endpoint after LP17 treatment. TREM-1 blockade also attenuated the increased level of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β, and thus attenuated systematic and distant inflammatory responses. Furthermore, TREM-1 blockade significantly attenuated the increased levels of pJAK2 and pSTAT3.

Conclusions

TREM-1 blockade by the use of an inhibitory peptide LP17 could prolong survival of rats with polymicrobial sepsis and attenuate systematic inflammatory responses through the JAK2/STAT3 signaling pathway. Our results suggest that modulation of TREM-1 by a synthetic peptide might be a potential therapeutic option for polymicrobial sepsis.

Inhibitory effect of Triperygium wilfordii polyglucoside on dipeptidyl peptidase I in vivo and in vitro

BACKGROUD

Dipeptidyl peptidase I (DPPI), a lysosomal cysteine protease is derived from granule immune cells including mast cell, neutrophils, and toxicity T cells. DPPI can activate serine proteases by removal of dipeptides from N-termini of the pro-proteases, resulting in granule immune cells activation which involved in physiological or pathological responses. Triperygium Wilfordii Polyglucoside (TWP) is one of the traditional Chinese medicines, and commonly used in rheumatoid arthritis (RA) treatment. The present study intended to evaluate the effects of TWP on DPPI activity.

METHODS

In vivo and in vitro studies were carried out to investigate the functions of TWP or triptolide (TP) on DPPI activities in serum, tissues of CIA rats. Rats were divided into five groups randomly: normal group, untreated CIA rat group, TWP treatment CIA groups (the low dose 2.5mg/100g body-weight and high dose 5mg/100g body-weight), and TP treatment CIA group (4μg/100g body-weight). Arthritis development was monitored visually, and joint pathology was examined radiologically. Total protein concentrations in synovial fluids (SFs) were determined by BCA method. Serums and tissue homogenates from CIA rats were collected and DPPI activities were detected using fluorescence substrate GF-AFC. The in vitro interactions between DPPI in serums or in tissue homogenates and TWP or TP were assessed.

RESULTS

TWP-treated CIA rats showed a significant improvement in bone erosion. TWP significantly suppressed paw swelling and total protein concentration in the SFs of CIA rats compared with untreated CIA rats. The elevated activities of DPPI in serums or tissues of CIA rats were significantly inhibited by TWP, but not by TP in vivo. The inhibitory effects of TWP on DPPI activities were also confirm by in vitro study.

CONCLUSION

One of the therapeutic functions of TWP in RA treatment could be inhibiting DPPI activity in serums and synovial tissue produced during RA development, and then reducing inflammatory serine proteases activities and further recovering CIA rats from RA symptoms.

Atomic Force Microscopy Study of the Anti-inflammatory Effects of Triptolide on Rheumatoid Arthritis Fibroblast-like Synoviocytes

High-resolution atomic force microscopy (AFM) was used for the in situ evaluation of the anti-inflammatory effects of triptolide on rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) to understand the anti-RA effects of triptolide, based on the morphological and biophysical changes observed in RA-FLS. RA-FLS have been reported to play a primary role in inflammatory bone destruction during the development of RA and thus are regarded as an important target for RA treatment. Triptolide pretreatment significantly inhibited tumor necrosis factor-α-induced expression of the interleukin (IL)-1β, IL-6, and IL-8 genes in MH7A cells. Using AFM, we showed that triptolide-induced morphological damage in MH7A cells by inducing significant ultrastructure changes in the membrane, which were closely related to triptolide-induced apoptosis in MH7A cells. Using force measurements determined with AFM, triptolide was shown to increase the stiffness of MH7A cells. These findings not only revealed the strong anti-inflammatory effects of triptolide on RA-FLS, highlighting triptolide as a potential anti-RA agent, but also revealed the possible use of AFM for studying anti-inflammatory responses in RA-FLS, which we expect to be developed into a potential tool for anti-RA drug studies in RA-FLS.

TREM-1 and its potential ligands in non-infectious diseases: from biology to clinical perspectives

Triggering receptor expressed on myeloid cells-1 (TREM-1) is expressed on the majority of innate immune cells and to a lesser extent on parenchymal cells. Upon activation, TREM-1 can directly amplify an inflammatory response. Although it was initially demonstrated that TREM-1 was predominantly associated with infectious diseases, recent evidences shed new light into its role in sterile inflammatory diseases. Indeed, TREM-1 receptor and its signaling pathways contribute to the pathology of several non-infectious acute and chronic inflammatory diseases, including atherosclerosis, ischemia reperfusion-induced tissue injury, colitis, fibrosis and cancer. This review, aims to give an extensive overview of TREM-1 in non-infectious diseases, with the focus on the therapeutic potential of TREM-1 intervention strategies herein. In addition, we provide the reader with a functional enrichment analysis of TREM-1 signaling pathway and potential TREM-1 ligands in these diseases, obtained via in silico approach. We discuss pre-clinical studies which show that TREM-1 inhibition, via synthetic soluble TREM-1 protein mimickers, is effective in treating (preventing) specific inflammatory disorders, without significant effects on antibacterial response. Further research aimed at identifying specific TREM-1 ligands, in different inflammatory disorders, is required to further unravel the role of this receptor, and explore new avenues to modulate its function.

Soluble Epoxide Hydrolase Inhibitor Suppresses the Expression of Triggering Receptor Expressed on Myeloid Cells-1 by Inhibiting NF-kB Activation in Murine Macrophage

Triggering receptors expressed on myeloid cell-1 (TREM-1) is a superimmunoglobulin receptor expressed on myeloid cells. TREM-1 amplifies the inflammatory response. Epoxyeicosatrienoic acids (EETs), the metabolites of arachidonic acid derived from the cytochrome P450 enzyme, have anti-inflammatory properties. However, the effects of EETs on TREM-1 expression under inflammatory stimulation remain unclear. Therefore, inhibition of soluble epoxide hydrolase (sEH) with a highly selective inhibitor [1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea, TPPU] was used to stabilize EETs. LPS was intratracheally injected into mice to induce pulmonary inflammation, after TPPU treatment for 3 h. Histological examination showed TPPU treatment-alleviated LPS-induced pulmonary inflammation. TPPU decreased TREM-1 expression, but not DAP12 or MyD88 expression. Murine peritoneal macrophages were challenged with LPS in vitro. We found that TPPU reduced LPS-induced TREM-1 expression in a dose-dependent manner, but not DAP12 or MyD88 expression. TPPU also decreased downstream signal from TREM-1, reducing pro-inflammatory cytokine TNF-α and IL-1β mRNA expression. Furthermore, TPPU treatment inhibited IkB degradation in vivo and in vitro. Our results indicate that the inhibition of sEH suppresses LPS-induced TREM-1 expression and inflammation via inhibiting NF-kB activation in murine macrophage.

Triptolide attenuates pressure overload-induced myocardial remodeling in mice via the inhibition of NLRP3 inflammasome expression

Triptolide is the predominant active component of the Chinese herb Tripterygium wilfordii Hook F (TwHF) that has been widely used to treat several chronic inflammatory diseases due to its immunosuppressive, anti-inflammatory, and anti-proliferative properties. In the present study, we elucidated the cardioprotective effects of triptolide against cardiac dysfunction and myocardial remodeling in chronic pressure-overloaded hearts. Furthermore, the potential mechanisms of triptolide were investigated. For this purpose, C57/BL6 mice were anesthetized and subjected to transverse aortic constriction (TAC) or sham operation. Six weeks after the operation, all mice were randomly divided into 4 groups: sham-operated with vehicle group, TAC with vehicle group, and TAC with triptolide (20 or 100 μg/kg/day intraperitoneal injection) groups. Our data showed that the levels of NLRP3 inflammasome were significantly increased in the TAC group and were associated with increased inflammatory mediators and profibrotic factor production, resulting in myocardial fibrosis, cardiomyocyte hypertrophy, and impaired cardiac function. Triptolide treatment attenuated TAC-induced myocardial remodeling, improved cardiac diastolic and systolic function, inhibited the NLRP3 inflammasome and downstream inflammatory mediators (IL-1β, IL-18, MCP-1, VCAM-1), activated the profibrotic TGF-β1 pathway, and suppressed macrophage infiltration in a dose-dependent manner. Our study demonstrated that the protective effect of triptolide against pressure overload in the heart may act by inhibiting the NLRP3 inflammasome-induced inflammatory response and activating the profibrotic pathway.

Blocking triggering receptor expressed on myeloid cells-1 attenuates lipopolysaccharide-induced acute lung injury via inhibiting NLRP3 inflammasome activation

Acute lung injury (ALI) is associated with high mortality and uncontrolled inflammation plays a critical role in ALI. TREM-1 is an amplifier of inflammatory response, and is involved in the pathogenesis of many infectious diseases. NLRP3 inflammasome is a member of NLRs family that contributes to ALI. However, the effect of TREM-1 on NLRP3 inflammasome and ALI is still unknown. This study aimed to determine the effect of TREM-1 modulation on LPS-induced ALI and activation of the NLRP3 inflammasome. We showed that LR12, a TREM-1 antagonist peptide, significantly improved survival of mice after lethal doses of LPS. LR12 also attenuated inflammation and lung tissue damage by reducing histopathologic changes, infiltration of the macrophage and neutrophil into the lung, and production of the pro-inflammatory cytokine, and oxidative stress. LR12 decreased expression of the NLRP3, pro-caspase-1 and pro-IL-1β, and inhibited priming of the NLRP3 inflammasome by inhibiting NF-κB. LR12 also reduced the expression of NLRP3 and caspase-1 p10 protein, and secretion of the IL-1β, inhibited activation of the NLRP3 inflammasome by decreasing ROS. For the first time, these data show that TREM-1 aggravates inflammation in ALI by activating NLRP3 inflammasome, and blocking TREM-1 may be a potential therapeutic approach for ALI.

Knockdown of TREM-1 suppresses IL-1β-induced chondrocyte injury via inhibiting the NF-κB pathway

Triggering receptor expressed on myeloid cells 1 (TREM-1) is a recently discovered molecule that modulates inflammatory responses. This study aimed to investigate the specific function of TREM-1 in chondrocytes and its association with the pathophysiology of osteoarthritis (OA). We observed upregulation of TREM-1 in OA cartilage compared to normal tissues. Knockdown of TREM-1 suppressed interleukin 1 beta (IL-1β)-induced extracellular matrix (ECM) metabolic imbalance, pro-inflammatory cytokine production, decrease in cell viability and apoptosis. Mechanistic analyses further revealed that IL-1β-induced activation of the NF-κB pathway is suppressed upon TREM-1 knockdown, similar to the effect of pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-κB. TREM-1 expression was consistently increased in a mouse OA model in vivo, and its silencing led to inhibition of matrix metallopeptidase-13 (MMP-13) production, increased collagen type II synthesis and decreased NF-κB signaling. Our data collectively suggest that TREM-1 plays a critical in OA development through regulation of NF-κB signaling. Pharmacological inhibition of TREM-1 may therefore present an effective novel therapeutic approach for OA.

Triptolide Upregulates Myocardial Forkhead Helix Transcription Factor p3 Expression and Attenuates Cardiac Hypertrophy

The forkhead/winged helix transcription factor (Fox) p3 can regulate the expression of various genes, and it has been reported that the transfer of Foxp3-positive T cells could ameliorate cardiac hypertrophy and fibrosis. Triptolide (TP) can elevate the expression of Foxp3, but its effects on cardiac hypertrophy remain unclear. In the present study, neonatal rat ventricular myocytes (NRVM) were isolated and stimulated with angiotensin II (1 μmol/L) to induce hypertrophic response. The expression of Foxp3 in NRVM was observed by using immunofluorescence assay. Fifty mice were randomly divided into five groups and received vehicle (control), isoproterenol (Iso, 5 mg/kg, s.c.), one of three doses of TP (10, 30, or 90 μg/kg, i.p.) for 14 days, respectively. The pathological morphology changes were observed after Hematoxylin and eosin, lectin and Masson's trichrome staining. The levels of serum brain natriuretic peptide (BNP) and troponin I were determined by enzyme-linked immunosorbent assay and chemiluminescence, respectively. The mRNA and protein expressions of α- myosin heavy chain (MHC), β-MHC and Foxp3 were determined using real-time PCR and immunohistochemistry, respectively. It was shown that TP (1, 3, 10 μg/L) treatment significantly decreased cell size, mRNA and protein expression of β-MHC, and upregulated Foxp3 expression in NRVM. TP also decreased heart weight index, left ventricular weight index and, improved myocardial injury and fibrosis; and decreased the cross-scetional area of the myocardium, serum cardiac troponin and BNP. Additionally, TP markedly reduced the mRNA and protein expression of myocardial β-MHC and elevated the mRNA and protein expression of α-MHC and Foxp3 in a dose-dependent manner. In conclusion, TP can effectively ameliorate myocardial damage and inhibit cardiac hypertrophy, which is at least partly related to the elevation of Foxp3 expression in cardiomyocytes.

Triptolide inhibits the migration and invasion of rheumatoid fibroblast-like synoviocytes by blocking the activation of the JNK MAPK pathway

Triptolide, a primary active ingredient extracted from a traditional Chinese herb, Tripterygium wilfordii Hook F, has been demonstrated to have a positive therapeutic effect on patients with rheumatoid arthritis (RA); however, its mechanism of action against RA is not well established. Therefore, in the present study, we observed the effect of triptolide on the aggressive behavior of RA fibroblast-like synoviocytes (RA FLSs), and we explored its underlying signal mechanisms. We found that triptolide treatment significantly reduced the migratory and invasive capacities of RA FLSs in vitro. We also demonstrated that the invasion of RA FLSs into the cartilage, evaluated in the severe combined immunodeficiency (SCID) mouse co-implantation model, was attenuated by treatment with triptolide in vivo. Additionally, the immunofluorescence results showed that triptolide treatment decreased the polymerization of F-actin and the activation of matrix metalloproteinase 9 (MMP-9). To gain insight into the molecular signal mechanisms, we determined the effect of triptolide on the activation of MAPK signal pathways. Our results indicate that triptolide treatment reduced the TNF-α-induced expression of phosphorylated JNK, but did not affect the expression of phosphorylated p38 and ERK. A JNK-specific inhibitor decreased the migration of RA FLSs. We also observed that triptolide administration improved clinical arthritic conditions and joint destruction in mice with collagen-induced arthritis (CIA). Thus, our findings suggest that the therapeutic effects of triptolide on RA might be, in part, due to its contribution to the aggressive behavior of RA FLSs.