Andrograpanin, a compound isolated from anti-inflammatory traditional Chinese medicine Andrographis paniculata, enhances chemokine SDF-1alpha-induced leukocytes chemotaxis

Potential Plant-Based New Antiplasmodial Agent Used in Papua Island, Indonesia

Resistance to antimalarial medicine remains a threat to the global effort for malaria eradication. The World Health Organization recently reported that artemisinin partial resistance, which was defined as delayed parasite clearance, was detected in Southeast Asia, particularly in the Greater Mekong subregion, and in Africa, particularly in Rwanda and Uganda. Therefore, the discovery of a potential new drug is important to overcome emerging drug resistance. Natural products have played an important role in drug development over the centuries, including the development of antimalarial drugs, with most of it influenced by traditional use. Recent research on traditional medicine used as an antimalarial treatment on Papua Island, Indonesia, reported that 72 plant species have been used as traditional medicine, with Alstonia scholaris, Carica papaya, Andrographis paniculata, and Physalis minima as the most frequently used medicinal plants. This review aimed to highlight the current research status of these plants for potential novel antiplasmodial development. In conclusion, A. paniculata has the highest potential to be developed as an antiplasmodial, and its extract and known bioactive isolate andrographolide posed strong activity both in vitro and in vivo. A. scholaris and C. papaya also have the potential to be further investigated as both have good potential for their antiplasmodial activities in vivo. However, P. minima is a less studied medicinal plant; nevertheless, it opens the opportunity to explore the potential of this plant.

A Comprehensive Review of Andrographis paniculata (Burm. f.) Nees and Its Constituents as Potential Lead Compounds for COVID-19 Drug Discovery

The COVID-19 pandemic has intensively disrupted global health, economics, and well-being. Andrographis paniculata (Burm. f.) Nees has been used as a complementary treatment for COVID-19 in several Asian countries. This review aimed to summarize the information available regarding A. paniculata and its constituents, to provide critical points relating to its pharmacological properties, safety, and efficacy, revealing its potential to serve as a source of lead compounds for COVID-19 drug discovery. A. paniculata and its active compounds possess favorable antiviral, anti-inflammatory, immunomodulatory, and antipyretic activities that could be beneficial for COVID-19 treatment. Interestingly, recent in silico and in vitro studies have revealed that the active ingredients in A. paniculata showed promising activities against 3CLpro and its virus-specific target protein, human hACE2 protein; they also inhibit infectious virion production. Moreover, existing publications regarding randomized controlled trials demonstrated that the use of A. paniculata alone or in combination was superior to the placebo in reducing the severity of upper respiratory tract infection (URTI) manifestations, especially as part of early treatment, without serious side effects. Taken together, its chemical and biological properties, especially its antiviral activities against SARS-CoV-2, clinical trials on URTI, and the safety of A. paniculata, as discussed in this review, support the argument that A. paniculata is a promising natural source for drug discovery regarding COVID-19 post-infectious treatment, rather than prophylaxis.

Andrographolide, isolated from Andrographis paniculata, induces apoptosis in monocytic leukemia and multiple myeloma cells via augmentation of reactive oxygen species production

Background: Andrographolide (Andro) is a diterpenoid component of the plant Andrographis paniculata that is known for its anti-tumor activity against a variety of cancer cells.  

Methods: We studied the effects of Andro on the viability of the human leukemia monocytic cell line THP-1 and the human multiple myeloma cell line H929. Andro was compared with cytosine arabinoside (Ara-C) and vincristine (VCR), which are well-established therapeutics against hematopoietic tumors. The importance of reactive oxygen species (ROS) production for the toxicity of each agent was investigated by using an inhibitor of ROS production, N-acetyl-L-cysteine (NAC).   

Results:  Andro reduced the viability of THP-1 and H929 in a concentration-dependent manner. H929 viability was highly susceptible to Andro, although only slightly susceptible to Ara-C. The agents Andro, Ara-C, and VCR each induced apoptosis, as shown by cellular shrinkage, DNA fragmentation, and increases in annexin V-binding, caspase-3/7 activity, ROS production, and mitochondrial membrane depolarization. Whereas Ara-C and VCR increased the percentages of cells in the G0/G1 and G2/M phases, respectively, Andro showed little or no detectable effect on cell cycle progression. The apoptotic activities of Andro were largely suppressed by NAC, an inhibitor of ROS production, whereas NAC hardly affected the apoptotic activities of Ara-C and VCR. 

Conclusions: Andro induces ROS-dependent apoptosis in monocytic leukemia THP-1 and multiple myeloma H929 cells, underlining its potential as a therapeutic agent for treating hematopoietic tumors. The high toxicity for H929 cells, by a mechanism that is different from that of Ara-C and VCR, is encouraging for further studies on the use of Andro against multiple myeloma.

In silico studies on structural inhibition of SARS-CoV-2 main protease Mpro by major secondary metabolites of Andrographis paniculata and Cinchona officinalis

The COVID-19 infection by Novel Corona Virus (SARS-CoV-2) has become one of the largest pandemic diseases, with cumulative confirmed infections of 275,233,892 and 5,364,996 deaths to date according to World Health Organization. Due to the absence of any approved antiviral drug to treat COVID-19, its lethality is getting severe with time. The main protease of SARS-CoV-2, M^pro is considered one of the potential drug targets because of its role in processing proteins translated from viral RNA. In the present study, four of the plant metabolites, 14-deoxy-11,12-didehydroandrographolide, andrograpanin, quinine, cinchonine from two eminent medicinal plants Andrographis paniculata and Cinchona officinalis, have been evaluated against the main protease of SARS-CoV-2 through in-silico molecular docking and molecular dynamics simulation study. From the result interpretations, it is found that andrograpanin has strong binding affinities with the target protein in its active site with potential negative energies. Molecular Dynamic simulation and MMGBSA studies suggest that earlier reported N3 inhibitor and andrograpanin exhibit effective binding interactions involving identical amino acid residues with the same binding pockets of the main protease of SARS-CoV-2. Therefore, the theoretical experiment suggests that andrograpanin, could be considered the promising inhibitor against SARS-CoV-2 M^pro.

Andrographis paniculata (Burm.f.) Nees: Traditional uses, phytochemistry, pharmacological properties and quality control/quality assurance

ETHNOPHARMACOLOGICAL RELEVANCE

Andrographis paniculata (Burm.f.) Nees is a medicinal herb of the Asian countries used in many traditional medicinal systems for the treatment of diarrhea, flu, leprosy, leptospirosis, malaria, rabies, upper respiratory infections, sinusitis, syphilis, tuberculosis and HIV/AIDS etc. AIM OF THE STUDY: This review aims to provide the comprehensive, accurate and authentic information on traditional uses, phytochemistry and pharmacological properties of various extracts/fractions as well as phytocostituents of A. paniculata. In addition, this review also aims to provide advance and sensitive analytical methods along with chemical markers used in the standardization of herbal products for quality control (QC)/quality assurance (QA).

MATERIALS AND METHODS

All relevant publications were considered within the years 1983-2020. The publications were searched from Google Scholar, PubChem, Chemspider, PubMed, Elsevier, Wiley, Web of Science, China Knowledge Resource Integrated databases and ResearchGate using a combination of various relevant keywords. Besides, relevant published books and chapters were also considered those providing an overview of extant secondary literature related to traditional knowledge, phytochemistry, pharmacology and toxicity of the plant.

RESULTS AND DISCUSSION

In this review, 344 compounds, including, terpenoid lactones, flavonoids, phenolic acids, triterpenes and volatile compounds were summarized out of which more than half of the compounds have no reported pharmacological activities yet. Terpenoid lactones and flavonoids are the major bioactive classes of compounds of A. paniculata which are responsible for pharmacological activities such as anticancer and antioxidant activities, respectively. Biosynthetic pathways and active sites for target proteins of both terpenoid lactones and flavonoids were considered. Analgesic, anticancer, antidiabetic, antifertility, antiinflammatory, antimalarial, antimicrobial, antioxidant, antipyretic, antiviral, antiretroviral, antivenom, cardioprotective, hepatoprotective, immunomodulatory and neuroprotective activities have been also reported. Andrographolide is a major characteristic active principle and responsible for most of the pharmacological activities. Therefore, andrographolide has been selected as a marker for the standardization of raw and marketed herbal products by TLC, HPTLC, HPLC, GC-MS, HPLC-MS and HPLC-MS/MS methods for QC/QA.

CONCLUSIONS

Conclusive evidence showed that the pharmacological activities reported in crude extracts and chemical markers are supporting and provides confidence in the traditional use of A. paniculata as a herbal medicine. The andrographolide could be used as a chemical marker for the QC/QA of raw and A. paniculata derived herbal products. Lactone ring in terpenoid lactone is an active site for targeted proteins. More efforts should be focused on the identification of the chemical markers from A. paniculata to provide a practical basis for QC/QA. Several aspects such as the mechanism of therapeutic potential, molecular docking technology and multi-target network pharmacology are very important for drug discovery and needed more investigation and should be considered. This compilation may be helpful in further study and QC/QA.

Diterpenoids and Flavonoids from Andrographis paniculata

Chemical investigation of the aerial parts of Andrographis paniculata resulted in isolation of nine compounds, including a new ent-labdane diterpenoid, andrographic acid methyl ester (1), a new chalcone glucoside, pashanone glucoside (5), and seven known metabolites, andrograpanin (2), andrographolide (3), andropanolide (4), andrographidine A (6), andrographidine F (7), 6-epi-8-O-acetyl-harpagide (8), and curvifloruside F (9). Their chemical structures were elucidated based on comprehensive analyses of the spectroscopic data, including NMR and MS. Among the isolated compounds, andropanolide exerted cytotoxicity toward LNCaP, HepG2, KB, MCF7, and SK-Mel2 carcinoma cells, with IC₅₀ values ranging from 31.8 to 45.9 µM. In addition, andropanolide significantly inhibited the overproduction of nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages, with an IC₅₀ value of 13.4 µM.

Phytochemistry, Pharmacology and Clinical Use of Andrographis paniculata

Andrographis paniculata (Burma f.) Wall ex Nees (Acanthaceae) is a common weed distributed throughout the tropical and subtropical regions. All parts of A. paniculata are extremely bitter in taste. This plant is well known in Siddha, Ayurvedic and traditional (tribal) systems of medicine in India. A. paniculata is used for the treatment of infectious diseases, which account for the major proportion of health problems, and which are most often used in the traditional system of medicine. The major active components of the plant are andrographiloids, which have been extensively studied in a variety of models including human clinical trials for their therapeutic effects. Moreover, A. paniculata is known to have very low toxicity in animals and humans. The plant also exhibits antifertility effects. Most of the traditional uses of the species have some scientific basis. This review is an attempt to summarize the available information on A. paniculata for further investigation.

The Contribution of Complementary and Alternative Medicine to Reduce Antibiotic Use: A Narrative Review of Health Concepts, Prevention, and Treatment Strategies

AIM

The aim of this narrative review was to explore the potential contributions of CAM to reduce antibiotic use.

METHODS

We searched PubMed, Embase, and Cochrane Database of Systematic Reviews with a specific, limited set of search terms and collected input from a group of expert CAM researchers to answer the question: What is known about the contribution of CAM health and health promotion concepts, infection prevention, and infection treatment strategies to reduce antibiotic use? Results. The worldview-related CAM health concepts enable health promotion oriented infection prevention and treatment aimed at strengthening or supporting the self-regulating ability of the human organism to cope with diseases. There is some evidence that the CAM concepts of health (promotion) are in agreement with current conceptualization of health and that doctors who practice both CAM and conventional medicine prescribe less antibiotics, although selection bias of the presented studies cannot be ruled out. There is some evidence that prevention and some treatment strategies are effective and safe. Many CAM treatment strategies are promising but overall lack high quality evidence.

CONCLUSIONS

CAM prevention and treatment strategies may contribute to reducing antibiotic use, but more rigorous research is necessary to provide high quality evidence of (cost-)effectiveness.

Transcriptional and translational-uncoupling in regulation of the CXCL12 and its receptors CXCR4, 7 in THP-1 monocytes and macrophages

INTRODUCTION

The chemokine CXCL12 and its receptors CXCR4 and 7 play crucial roles in the immune system. In the present study, regulation of this pathway was further examined using the in-vitro model of undifferentiated human THP-1 monocytes (u-THP-1) and phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 macrophages (d-THP-1), to assess the effects of differentiation and the TLR4 ligand lipopolysaccharide (LPS) on the pathway.

METHODS/RESULTS

Differentiation did not affect the CXCR4, 7 mRNA levels. Interestingly, the CXCL12 and CXCR7 proteins but not CXCR4 were found to be up-regulated during differentiation. LPS, through CD14-dependent pathway, induced CXCL12 and CXCR4, 7 mRNA levels to a greater magnitude in d- than u-THP-1. The induction effect on CXCL12 stimulated by LPS was confirmed using ELISA. Increased migration of u-THP-1 was observed using conditioned medium from LPS-treated d-THP-1. Additionally, d-THP-1, although expressed higher CXCR7 protein levels, failed to migrate toward CXCL12. In contrast, LPS did not affect CXCR4, 7 protein levels.

CONCLUSION

Hence, this study indicated that CXCL12, CXCR4, and CXCR7 were differentially expressed and regulated in u-THP-1 and d-THP-1 cells in response to external stimuli. Importantly, we reported here a novel observation that uncoupling exists between transcriptional and translational regulation of CXCR4, 7 expressions by differentiation and TLR stimuli.

Attenuation of Innate Immunity by Andrographolide Derivatives Through NF-κB Signaling Pathway

Andrographolide derivatives or analogs exhibit potent anti-inflammatory effects in several disease models through NF-κB activity. In this study, we synthesized different andrographolide derivatives and investigated their effects on the toll-like receptor (TLR)-induced production of pro-inflammatory cytokines. Among these compounds, 3b, 5a, and 5b inhibited both TNF-α/NF-κB and TLR4/NF-κB signaling pathways. Treatment with compounds 3b, 5a, and 5b and their structural analogs, 3a and 6b, suppressed the expression of pro-inflammatory cytokines upon the activation of TLR3 and TLR4 ligands. Compounds 3b and 5a, but not 3a, 5b, or 6b, inhibited the nuclear translocation of the NF-κB p65 subunit. Treatment with compounds 3b, 5a, 3a, 5b, and 6b attenuated the phosphorylation of p65 and IκBα. Compounds 6b suppressed the expression of the NF-κB p65 subunit. However, these compounds, except for 5b, did not affect the TLR9-induced NF-κB-independent production of the pro-inflammatory cytokines, TNF-α, and IFN-β. Compound 3b potentially protected mice from LPS-induced acute pulmonary inflammation through the inhibition of p65 phosphorylation and the decrease of serum pro-inflammatory cytokines and chemokine. Our study revealed a functional structure–activity relationship between andrographolide derivatives and innate immunity. We identified compound 3b as a potent immune suppressive agent with the potential to protect acute pulmonary infection.

Preliminary results of a non-invasive method to measure tumor size and distribution in vivo

Molecular imaging of reporter gene expression in cancer cells can provide rapid, sensitive and non-invasive monitoring of tumor behavior. The aim of the present study was to establish a non-invasive method to measure tumor size and distribution in vivo. Briefly, H-Ras-transformed cells were stably transfected with a plasmid containing the luciferase gene (Luc), designated as Ras/Luc. Ras/Luc cells were injected into the back or tail vein of nude BALB/cAnN-Foxn1nu/CrlNarl mice (age, 6-8 weeks). Mice were subsequently administered D-luciferin via intra-peritoneal injection, prior to image acquisition. Photons emitted from the mice were detected via an imaging system. Tumor size and distribution in vivo were quantified as photons/second. Andrographolide has demonstrated radiosensitization in previous in vitro and in vivo studies. In the present study, the potential effects of andrographolide cancer metastasis were investigated further, using an imaging system. Preliminary results of andrographolide combined with radiation indicated the inhibition of cancer metastasis. The present mechanistic study of andrographolide-mediated effects demonstrated that activated extracellular signal regulated kinase protein and H₂O₂ production levels were significantly increased by andrographolide. In summary, the present study established a non-invasive method to measure tumor size and distribution in vivo and indicated that andrographolide may be a potential therapeutic strategy in cancer therapy.

Andrographis paniculata (Burm. f.) Wall. ex Nees: a review of ethnobotany, phytochemistry, and pharmacology

As aboriginal sources of medications, medicinal plants are used from the ancient times. Andrographis paniculata is one of the highly used potential medicinal plants in the world. This plant is traditionally used for the treatment of common cold, diarrhoea, fever due to several infective cause, jaundice, as a health tonic for the liver and cardiovascular health, and as an antioxidant. It is also used to improve sexual dysfunctions and serve as a contraceptive. All parts of this plant are used to extract the active phytochemicals, but the compositions of phytoconstituents widely differ from one part to another and with place, season, and time of harvest. Our extensive data mining of the phytoconstituents revealed more than 55 ent-labdane diterpenoids, 30 flavonoids, 8 quinic acids, 4 xanthones, and 5 rare noriridoids. In this review, we selected only those compounds that pharmacology has already reported. Finally we focused on around 46 compounds for further discussion. We also discussed ethnobotany of this plant briefly. Recommendations addressing extraction process, tissue culture, and adventitious rooting techniques and propagation under abiotic stress conditions for improvement of phytoconstituents are discussed concisely in this paper. Further study areas on pharmacology are also proposed where needed.

Bioactive diterpenoids and flavonoids from the aerial parts of Scoparia dulcis

Six new diterpenoids, 4-epi-7α-O-acetylscoparic acid A (1), 7α-hydroxyscopadiol (2), 7α-O-acetyl-8,17β-epoxyscoparic acid A (3), neo-dulcinol (4), dulcinodal-13-one (5), and 4-epi-7α-hydroxydulcinodal-13-one (6), and a new flavonoid, dillenetin 3-O-(6″-O-p-coumaroyl)-β-D-glucopyranoside (10), along with 12 known compounds, were isolated from the aerial parts of Scoparia dulcis. The 7S absolute configuration of the new diterpenoids 1-4 and 6 was deduced by comparing their NOESY spectra with that of a known compound, (7S)-4-epi-7-hydroxyscoparic acid A (7), which was determined by the modified Mosher's method. The flavonoids scutellarein (11), hispidulin (12), apigenin (15), and luteolin (16) and the terpenoids 4-epi-scopadulcic acid B (9) and betulinic acid (19) showed more potent α-glucosidase inhibitory effects (with IC50 values in the range 13.7-132.5 μM) than the positive control, acarbose. In addition, compounds 1, 11, 12, 15, 16, and acerosin (17) exhibited peroxisome proliferator-activated receptor gamma (PPAR-γ) agonistic activity, with EC50 values ranging from 0.9 to 24.9 μM.

Isolation and identification of bioactive compounds in Andrographis paniculata (Chuanxinlian)

Andrographis paniculata (Burm. f.) Nees (Acanthaceae) is a medicinal plant used in many countries. Its major constituents are diterpenoids, flavonoids and polyphenols. Among the single compounds extracted from A. paniculata, andrographolide is the major one in terms of bioactive properties and abundance. Among the andrographolide analogues, 14-deoxy-11,12-didehydroandrographolide is immunostimulatory, anti-infective and anti-atherosclerotic; neoandrographolide is anti-inflammatory, anti-infective and anti-hepatotoxic; 14-deoxyandrographolide is immunomodulatory and anti-atherosclerotic. Among the less abundant compounds from A. paniculata, andrograpanin is both anti-inflammatory and anti-infective; 14-deoxy-14,15-dehydroandrographolide is anti-inflammatory; isoandrographolide, 3,19-isopropylideneandrographolide and 14-acetylandrographolide are tumor suppressive; arabinogalactan proteins are anti-hepatotoxic. The four flavonoids from A. paniculata, namely 7-O-methylwogonin, apigenin, onysilin and 3,4-dicaffeoylquinic acid are anti-atherosclerotic.

A new diterpene from the leaves of Andrographis paniculata Nees

Phytochemical investigation of the ethanol extract of the leaves of Andrographis paniculata yielded one novel diterpene (13R, 14R) 3, 13, 14, 19-tetrahydroxy-ent-labda-8 (17), 11-dien-16, 15-olide 1 which has an uncommon cis-diol groups in the lactone moiety, and 3, 19-isopropylidene-14-deoxy-ent-labda-8 (17), 13-dien-16, 15-olide 2, probably an artifact diterpene, together with eight known diterpenoids 3-10. The structures of these compounds were determined on the basis of spectral methods. The structure and stereochemistry of 1 was confirmed by X-ray crystallographic analyses.

CXCR4+FOXP3+CD25+ Lymphocytes Accumulate in CXCL12-Expressing Malignant Pleural Mesothelioma

CXCL12 is a chemokine that binds to a G-protein-coupled receptor (CXCR4). CXCL12 is expressed in various tumors and is considered as playing an important role in tumor growth and invasion. The aim of this study is to investigate the expression of CXCL12 in human malignant mesothelioma (MM), the chemotactic effect of CXCL12 derived from MM, and the expression of CXCR4 in MM tissues in relation to regulatory T cells. CXCL12 expression was examined by immunostaining of tissue specimens from malignant pleural mesothelioma (MPM) and malignant peritoneal mesothelioma (MPEM). The MM group comprised 6 patients (4 men/2 women, MPM=4, MPEM=2, aged 56.0 ± 12.4 years) and the control (non-mesothelioma) group also had 6 patients (4 men/2 women aged 65.0 ± 6.7 years). CXCL12 mRNA expression was also examined by RT-PCR in MPM cell lines (H28, H2052, and H2058), while CXCR4 mRNA expression was examined by in situ hybridization in MPM tissue. CXCL12 was expressed in the cytoplasm of MM cells from all patients, but was not expressed in the control group. H2052 and H2058 cells expressed CXCL12 mRNA, but H28 cells did not. CXCL12 in MM tissue homogenate supernatant had a chemotactic effect on CXCR4-expressing THP-1 cells. CXCR4 mRNA was expressed by a part of LCA+CD3+ Foxp3+CD25+ T cells that were located adjacent to the border of CXCL12-expressing epithelioid MPM. These findings suggest that CXCL12 contributed to tumor-related inflammation by inducing the accumulation of CXCR4-expressing cells with regulatory T cell markers around MM.

Cytotoxic constituents from Andrographis paniculata induce cell cycle arrest in jurkat cells

Herbal medicines are now attracting attention as potential sources of anticancer agents. Andrographis paniculata is a traditionally used anticancer herb in Indian and Chinese herbal medicine. Phytochemical investigation of the ethanol extract of the aerial parts of this herb resulted in the isolation of 14 compounds including flavonoids and labdane diterpenoids. This is the first isolation of compound 6 from a natural source, and the aerial parts of A. paniculata are a rich source for the molecule andrographolide (9, 1.375%, w/w). The structures of the isolated compounds were established by means of spectral data. The cytotoxic activities of these isolates were evaluated against Jurkat, PC-3, HepG2 and Colon 205 tumor cells, and normal cells PBMCs. The bioactivity assays showed that metabolites 1-4 and 6-8 exhibited moderate cytotoxic activity against Jurkat, PC-3 and Colon 205 cell lines, where compound 6 had IC(50) values of 0.05, 0.07 and 0.05 mm, respectively. Further, among these effective compounds, 3 and 6 selectively blocked the cell cycle progression at G0/G1, while 1, 2, 4, 7 and 8 blocked the same at G2/M phase of the Jurkat cell line. This is the first cell cycle analysis for the above mentioned isolates on the Jurkat cells. Therefore, these plant-derived compounds may play a role in the prevention and/or management of cancer.

Andrograpanin, isolated from Andrographis paniculata, exhibits anti-inflammatory property in lipopolysaccharide-induced macrophage cells through down-regulating the p38 MAPKs signaling pathways

Andrographis paniculata Nees is an official herbal medicine for treatment of infection and inflammation in China. Andrograpanin, the one of diterpene lactones in A. paniculata, is a hydrolysate from neoandrographolide in vivo and in vitro. The goal of the present study was to investigate andrograpanin which effects on over production of nitric oxide (NO) and pro-inflammatory cytokines (TNF-alpha, IL-6 and IL-12p70) and the key signaling pathways involved in lipopolysaccharide (LPS)-activated macrophage cells. The results showed that NO and all three pro-inflammatory cytokines were inhibited by andrograpanin (15-90 microM) in a dose-dependent manner. The RT-PCR and western blotting assays showed that andrograpanin inhibited productions of NO and pro-inflammatory cytokines through down-regulating iNOS and pro-inflammatory cytokines gene expression levels. Further studies suggested that down-regulation of p38 mitogen-activated protein kinase (MAPKs) signaling pathways were involved in the anti-inflammatory activities of andrograpanin. This study provided evidences that andrograpanin might be useful as a potential anti-inflammatory leading compound for inflammatory drug development.

Plectin regulates the signaling and trafficking of the HIV-1 co-receptor CXCR4 and plays a role in HIV-1 infection

The CXC chemokine CXCL12 and its cognate receptor CXCR4 play an important role in inflammation, human immunodeficiency virus (HIV) infection and cancer metastasis. The signal transduction and intracellular trafficking of CXCR4 are involved in these functions, but the underlying mechanisms remain incompletely understood. In the present study, we demonstrated that the CXCR4 formed a complex with the cytolinker protein plectin in a ligand-dependent manner in HEK293 cells stably expressing CXCR4. The glutathione-S-transferase (GST)-CXCR4 C-terminal fusion proteins co-precipitated with the full-length and the N-terminal fragments of plectin isoform 1 but not with the N-terminal deletion mutants of plectin isoform 1, thereby suggesting an interaction between the N-terminus of plectin and the C-terminus of CXCR4. This interaction was confirmed by confocal microscopic reconstructions showing co-distribution of these two proteins in the internal vesicles after ligand-induced internalization of CXCR4 in HEK293 cells stably expressing CXCR4. Knockdown of plectin with RNA interference (RNAi) significantly inhibited ligand-dependent CXCR4 internalization and attenuated CXCR4-mediated intracellular calcium mobilization and activation of extracellular signal regulated kinase 1/2 (ERK1/2). CXCL12-induced chemotaxis of HEK293 cells stably expressing CXCR4 and of Jurkat T cells was inhibited by the plectin RNAi. Moreover, CXCR4 tropic HIV-1 infection in MAGI (HeLa-CD4-LTR-Gal) cells was inhibited by the RNAi of plectin. Thus, plectin appears to interact with CXCR4 and plays an important role in CXCR4 signaling and trafficking and HIV-1 infection.

The 73-kDa heat shock cognate protein is a CXCR4 binding protein that regulates the receptor endocytosis and the receptor-mediated chemotaxis

The CXCR4 chemokine receptor is a G protein-coupled receptor that plays an important role in leukocyte homing, cancer metastasis, and human immunodeficiency virus infection. In response to ligand stimulation, chemokine receptors undergo endocytosis through clathrin-coated vesicle (CCV). Uncoating of CCV, a process involving heat shock cognate protein and several other proteins, is critical for fusion of CCV to endosomal compartments. The present study demonstrated that CXCR4 was associated with the 73-kDa heat shock cognate protein (Hsc73) in human embryonic kidney 293 cells in response to ligand stimulation. Truncation of the carboxyl terminal domain of CXCR4 reduced the association with Hsc73 and a glutathione S-transferase-CXCR4 carboxyl terminal fusion protein associated with Hsc73 in vitro, suggesting involvement of the carboxyl terminal domain of the receptor in the interaction. In response to ligand stimulation, CXCR4 underwent internalization and colocalization with Hsc73, but the receptor endocytosis was blocked by knockdown of Hsc73 with RNA interference. Moreover, Hsc73 knockdown significantly reduced the CXCR4-mediated chemotaxis of U87 glioma cell lines. These findings suggest that Hsc73 plays a role in chemokine receptor trafficking and the receptor-mediated chemotaxis.