Dimethoxycurcumin, a metabolically stable analogue of curcumin, exhibits anti-inflammatory activities in murine and human lymphocytes

A Review of Recent Curcumin Analogues and Their Antioxidant, Anti-Inflammatory, and Anticancer Activities

Curcumin, as the main active component of turmeric (Curcuma longa), has been demonstrated with various bioactivities. However, its potential therapeutic applications are hindered by challenges such as poor solubility and bioavailability, rapid metabolism, and pan-assay interference properties. Recent advancements have aimed to overcome these limitations by developing novel curcumin analogues and modifications. This brief review critically assesses recent studies on synthesising different curcumin analogues, including metal complexes, nano particulates, and other curcumin derivatives, focused on the antioxidant, anti-inflammatory, and anticancer effects of curcumin and its modified analogues. Exploring innovative curcumin derivatives offers promising strategies to address the challenges associated with its bioavailability and efficacy and valuable insights for future research directions.

Inhibition of the thioredoxin system for radiosensitization therapy of cancer

Radiotherapy (RT) stands as a cornerstone in the clinical armamentarium against various cancers due to its proven efficacy. However, the intrinsic radiation resistance exhibited by cancer cells, coupled with the adverse effects of RT on normal tissues, often compromises its therapeutic potential and leads to unwanted side effects. This comprehensive review aims to consolidate our understanding of how radiosensitizers inhibit the thioredoxin (Trx) system in cellular contexts. Notable radiosensitizers, including gold nanoparticles (GNPs), gold triethylphosphine cyanide ([Au(SCN) (PEt3)]), auranofin, ceria nanoparticles (CONPs), curcumin and its derivatives, piperlongamide, indolequinone derivatives, micheliolide, motexafin gadolinium, and ethane selenide selenidazole derivatives (SeDs), are meticulously elucidated in terms of their applications in radiotherapy. In this review, the sensitization mechanisms and the current research progress of these radiosensitizers are discussed in detail, with the overall aim of providing valuable insights for the judicious application of Trx system inhibitors in the field of cancer radiosensitization therapy.

Mitochondrial-targeted curcumin inhibits T-cell activation via Nrf2 and inhibits graft-versus-host-disease in a mouse model

Anti-inflammatory and immune suppressive agents are required to moderate hyper-activation of lymphocytes under disease conditions or organ transplantation. However, selective disruption of mitochondrial redox has not been evaluated as a therapeutic strategy for suppression of T-cell-mediated pathologies. Using mitochondrial targeted curcumin (MitoC), we studied the effect of mitochondrial redox modulation on T-cell responses by flow cytometry, transmission electron microscopy, transcriptomics, and proteomics, and the role of Nrf2 was studied using Nrf2- /- mice. MitoC decreased mitochondrial TrxR activity, enhanced mitochondrial ROS (mROS) production, depleted mitochondrial glutathione, and suppressed activation-induced increase in mitochondrial biomass. This led to suppression of T-cell responses and metabolic reprogramming towards Treg differentiation. MitoC induced nuclear translocation and DNA binding of Nrf2, leading to upregulation of Nrf2-dependent genes and proteins. MitoC-mediated changes in mitochondrial redox and modulation of T-cell responses are abolished in Nrf2- /- mice. Restoration of mitochondrial thiols abrogated inhibition of T-cell responses. MitoC suppressed alloantigen-induced lymphoblast formation, inflammatory cytokines, morbidity, and mortality in acute graft-versus-host disease mice. Disruption of mitochondrial thiols but not mROS increase inculcates an Nrf2-dependent immune-suppressive disposition in T cells for the propitious treatment of graft-versus-host disease.

Chemosensitization of tumors via simultaneous delivery of STAT3 inhibitor and doxorubicin through HPMA copolymer-based nanotherapeutics with pH-sensitive activation

We synthesized three novel STAT3 inhibitors (S3iD1-S3iD3) possessing oxoheptanoic residue enabling linkage to HPMA copolymer carrier via a pH-sensitive hydrazone bond. HPMA copolymer conjugates bearing doxorubicin (Dox) and our STAT3 inhibitors were synthesized to evaluate the anticancer effect of Dox and STAT3 inhibitor co-delivery into tumors. S3iD1-3 and their copolymer-bound counterparts (P-S3iD1-P-S3iD3) showed considerable in vitro cytostatic activities in five mouse and human cancer cell lines with IC50 ~0.6-7.9 μM and 0.7-10.9 μM, respectively. S3iD2 and S3iD3 were confirmed to inhibit the STAT3 signaling pathway. The combination of HPMA copolymer-bound Dox (P-Dox) and P-S3iD3 at the dosage showing negligible toxicity demonstrated significant antitumor activity in B16F10 melanoma-bearing mice and completely cured 2 out of 15 mice. P-Dox alone had a significantly lower therapeutic activity with no completely cured mice. Thus, polymer conjugates bearing STAT3 inhibitors may be used for the chemosensitization of chemorefractory tumors.

Alcohol-induced liver injury in signalling pathways and curcumin's therapeutic potential

Confronting the profound public health concern of alcohol-induced liver damage calls for inventive therapeutic measures. The social, economic, and clinical ramifications are extensive and demand a comprehensive understanding. This thorough examination uncovers the complex relationship between alcohol intake and liver damage, with a special emphasis on the pivotal roles of the Toll-like receptor 4 (TLR4)/NF-κB p65 and CYP2E1/ROS/Nrf2 signalling networks. Different alcohol consumption patterns, determined by a myriad of factors, have significant implications for liver health, leading to a spectrum of adverse effects. The TLR4/NF-κB p65 pathway, a principal regulator of inflammation and immune responses, significantly contributes to various disease states when its balance is disrupted. Notably, the TLR4/MD-2-TNF-α pathway has been linked to non-alcohol related liver disease, while NF-κB activation is associated with alcohol-induced liver disease (ALD). The p65 subunit of NF-κB, primarily responsible for the release of inflammatory cytokines, hastens the progression of ALD. Breakthrough insights suggest that curcumin, a robust antioxidant and anti-inflammatory compound sourced from turmeric, effectively disrupts the TLR4/NF-κB p65 pathway. This heralds a new approach to managing alcohol-induced liver damage. Initial clinical trials support curcumin's therapeutic potential, highlighting its ability to substantially reduce liver enzyme levels. The narrative surrounding alcohol-related liver injury is gradually becoming more intricate, intertwining complex signalling networks such as TLR4/NF-κB p65 and CYP2E1/ROS/Nrf2. The protective role of curcumin against alcohol-related liver damage marks the dawn of new treatment possibilities. However, the full realisation of this promising therapeutic potential necessitates rigorous future research to definitively understand these complex mechanisms and establish curcumin's effectiveness and safety in managing alcohol-related liver disorders.

Malabaricone C, a constituent of spice Myristica malabarica, exhibits anti-inflammatory effects via modulation of cellular redox

The present study primarily focuses on the efficacy of Malabaricone C (Mal C) as an anti-inflammatory agent. Mal C inhibited mitogen-induced T-cell proliferation and cytokine secretion. Mal C significantly reduced cellular thiols in lymphocytes. N-acetyl cysteine (NAC) restored cellular thiol levels and abrogated Mal C-mediated inhibition of T-cell proliferation and cytokine secretion. Physical interaction between Mal C and NAC was evinced from HPLC and spectral analysis. Mal C treatment significantly inhibited concanavalin A-induced phosphorylation of ERK/JNK and DNA binding of NF-κB. Administration of Mal C to mice suppressed T-cell proliferation and effector functions ex vivo. Mal C treatment did not alter the homeostatic proliferation of T-cells in vivo but completely abrogated acute graft-versus-host disease (GvHD)-associated morbidity and mortality. Our studies indicate probable use of Mal C for prophylaxis and treatment of immunological disorders caused due to hyper-activation of T-cells.

Dimethoxycurcumin Acidifies Endolysosomes and Inhibits SARS-CoV-2 Entry

The pandemic of coronavirus disease 2019 (COVID-19) caused by infection by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) continues to take a huge toll on global health. Although improving, currently there are only limited therapies against SARS-CoV-2. Curcumin, a natural polyphenol, exerts antiviral effects against a wide variety of viruses and can inhibit SARS-CoV-2 entry. However, undesirable physicochemical and pharmacokinetic properties of curcumin limit its clinical application. Here, we determined the effects of dimethoxycurcumin (DiMC), a methylated analog of curcumin with improved bioavailability, on the entry of SARS-CoV-2. DiMC blocked entry of pseudo-SARS-CoV-2 into Calu-3 human non-small cell lung adenocarcinoma cells and Vero E6 green monkey kidney epithelial cells. Mechanistically, DiMC acidified lysosomes, enhanced lysosome degradation capabilities, and promoted lysosome degradation of angiotensin converting enzyme 2 (ACE2), a major receptor for SARS-CoV-2 entry, as well as pseudo-SARS-CoV-2 and the SARS-CoV-2 S1 protein. Furthermore, other lysosome acidifying agents, including the TRPML1 agonist ML-SA1 and the BK channel activator NS1619, also blocked the entry of pseudo-SARS-CoV-2. Thus, the anti-SARS-CoV-2 potential of DiMC and lysosome acidifying agents might be explored further as possible effective therapeutic strategies against COVID-19.

Complex polymeric nanomicelles co-delivering doxorubicin and dimethoxycurcumin for cancer chemotherapy

Combinational therapy is a new trend in medical sciences to achieve a maximum therapeutic response of the drugs with a comparatively low incidence of severe adverse effects. To overcome the challenges of conventional formulations for cancer chemotherapy, a polymer-based complex nanomicellar system, namely CPM-DD, was developed co-delivering the anti-cancer agent doxorubicin (DOX) and potent antioxidant dimethoxycurcumin (DiMC). The optimal mass ratio of DOX/DiMC in CPM-DD was determined as 1:6 due to the synergistic antiproliferative effect from in vitro cytotoxicity assay, while the biocompatible diblock copolymer of mPEG2000-PLA5000 was selected for drug entrapment at an optimal feeding ratio of 9:1 to both drugs together. The uniform particles of CPM-DD with suitable particle size (∼30 nm) and stable drug loading content (>9%) could be reliably obtained by self-assembly with the encapsulation yield up to 95%. Molecular dynamics simulation revealed the interaction mechanism responsible for forming these complex nanomicelles. The acid-base interaction between two drugs would significantly improve their binding with the copolymer, thus leading to good colloidal stability and controlled drug release characteristics of CPM-DD. Systematic evaluation based on the MCF-7 breast tumor-bearing nude mice model further demonstrated the characteristics of tissue biodistribution of both drugs delivered by CPM-DD, which were closely related to the drug loading pattern and greatly responsible for the improved anti-cancer potency and attenuated toxicity of this complex formulation. Therefore, all the findings indicated that CPM-DD would be a good alternative to the conventional formulations of DOX and worthy of clinical application for cancer chemotherapy.

The Anti-Cancer Effect of Four Curcumin Analogues on Human Glioma Cells

Purpose

Glioblastoma multiforme (GBM) is the primary aggressive malignancy of the brain with poor outcome. Curcumin analogues are polyphenolic compounds as the bioactive substances extracted from turmeric. This study aims to investigate the anti-cancer effects of four curcumin analogues. Furthermore, the molecular mechanisms of dimethoxycurcumin in human gliomas were analyzed by Western blot.

Materials and Methods

Human LN229 and GBM8401 glioma cells were treated by four curcumin analogues with different number of methoxy groups. The cell viability, cell cycle, apoptosis, proliferation and ROS production of human gliomas were analyzed by flow cytometry. Moreover, the effects of four curcumin analogues on tumorigenesis of gliomas were conducted by wound healing assay and colony formation assay. Furthermore, the molecular mechanisms of dimethoxycurcumin in human gliomas were analyzed by Western blot.

Results

Our data showed that four different curcumin analogues including curcumin, bisdemethoxycurcumin, demethoxycurcumin, and dimethoxycurcumin promote sub-G1 phase, G2/M arrest, apoptosis, and ROS production in human glioma cells. Moreover, dimethoxycurcumin suppressed cell viability, migration, and colony formation, induction of sub-G1, G2/M arrest, apoptosis, and ROS production in glioma cells. Moreover, the mechanism of dimethoxycurcumin is ROS production to increase LC3B-II expression to induce autophagy. Furthermore, dimethoxycurcumin suppressed apoptotic marker, BCL-2 to promote apoptosis in LN229 and GBM8401 glioma cells.

Conclusion

Our study found that dimethoxycurcumin induced apoptosis, autophagy, ROS production and suppressed cell viability in human gliomas. Dimethoxycurcumin might be a potential therapeutic candidate in human glioma cells.

Dimethoxycurcumin reduces proliferation and induces apoptosis in renal tumor cells more efficiently than demethoxycurcumin and curcumin

Curcumin (Cur), is a pigment with antiproliferative activity but has some pharmacokinetic limitations, which led researchers to look for more effective structure analogs. This work investigated the effects of Cur and compared them with the two analogs, demethoxycurcumin (DeMC) and dimethoxycurcumin (DiMC), to elucidate their mechanisms of action. The cytotoxic, antiproliferative, and genotoxic effects these compounds were correlated based on gene expression analysis in the human renal adenocarcinoma cells (786-O). Cur decreased CYP2D6 expression and exhibited cytotoxic effects, such as inducing monopolar spindle formation and mitotic arrest mediated by the increase in CDKN1A (p21) mRNA. This dysregulation induced cell death through a caspase-independent pathway but was mediated by decrease in MTOR and BCL2 mRNA expression, suggesting that apoptosis occurred by autophagy. DeMC and DiMC had similar effects in that they induced monopolar spindle and mitotic arrest, were genotoxic, and activated GADD45A, an important molecule in repair mechanisms, and CDKN1A. However, the induction of apoptosis by DeMC was delayed and regulated by the decrease of antiapoptotic mRNA BCL.XL and subsequent activation of caspase 9 and caspase 3/7. DiMC treatment increased the expression of CYP1A2, CYP2C19, and CYP3A4 and exhibited higher cytotoxicity compared with other compounds. It induced apoptosis by increasing mRNA expression of BBC3, MYC, and CASP7 and activation of caspase 9 and caspase 3/7. These data revealed that different gene regulation processes are involved in cell death induced by Cur, DeMC, and DiMC. All three can be considered as promising chemotherapy candidates, with DiMC showing the greatest potency.

Curcumin: a phytochemical modulator of estrogens and androgens in tumors of the reproductive system

Curcumin (Cur) is an active derivative extracted from turmeric which exerts a wide range of interactions with biomolecules through complex signaling pathways. Cur has been extensively shown to possess potential antitumor properties. In addition, there is growing body of evidence suggesting that Cur may exert potential anti-estrogen and anti-androgen activity. In vitro and in vivo studies suggest that anticancer properties of Cur against tumors affecting the reproductive system in females and males may be underlied by the Cur-mediated inhibition of androgen and estrogen signaling pathways. In this review we examine various studies assessing the crosstalk between Cur and both androgen and estrogen hormonal activity. Also, we discuss the potential chemopreventive and antitumor role of Cur in the most prevalent cancers affecting the reproductive system in females and males.

Protective effects of curcumin against chronic alcohol-induced liver injury in mice through modulating mitochondrial dysfunction and inhibiting endoplasmic reticulum stress

Background

Curcumin is a major active ingredient extracted from powdered dry rhizome of Curcuma longa. In Ayurveda and traditional Chinese medicine, it has been used as a hepatoprotective agent for centuries. However, the underlying mechanisms are not clear.

Objective

The present study is to investigate the hepatoprotective effects of curcumin in chronic alcohol-induced liver injury and explore its mechanism.

Design

Alcohol-exposed Balb/c mice were treated with curcumin (75 and 150 mg/kg) once per day for 8 weeks. Tissue from individual was fixed with formaldehyde for pathological examination. The activities of mitochondrial antioxidant enzymes, Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺Mg²⁺-ATPase, were determined. The level of mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (MPTP) opening was also determined. The expression of PGC-1α, NRF1, Mn-SOD, GRP78, PERK, IRE1α, nuclear NF-κB, and phosphorylated IκBα was quantified by western blot. The contents of TNF-α, IL-1β, and IL-6 in the liver were measured using the ELISA method.

Results

Curcumin significantly promoted hepatic mitochondrial function by reducing the opening of MPTP, thus increasing the MMP, promoting the activity of Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺/Mg²⁺-ATPase, and attenuating oxidative stress. Curcumin upregulated the expression of PGC-1α, NRF1, and Mn-SOD, and downregulated the expression of GRP78, PERK, and IRE1α in hepatic tissue. Curcumin also attenuated inflammation by inhibiting the IκBα–NF-κB pathway, which reduced the production of TNF, IL-1β, and IL-6.

Conclusion

Curcumin attenuates alcohol-induced liver injury via improving mitochondrial function and attenuating endoplasmic reticulum stress and inflammation. This study provides strong evidence for the beneficial effects of curcumin in the treatment of chronic alcohol-induced liver injury.

Ginger Oleoresin Alleviated γ-Ray Irradiation-Induced Reactive Oxygen Species via the Nrf2 Protective Response in Human Mesenchymal Stem Cells

Unplanned exposure to radiation can cause side effects on high-risk individuals; meanwhile, radiotherapies can also cause injury on normal cells and tissues surrounding the tumor. Besides the direct radiation damage, most of the ionizing radiation- (IR-) induced injuries were caused by generation of reactive oxygen species (ROS). Human mesenchymal stem cells (hMSCs), which possess self-renew and multilineage differentiation capabilities, are a critical population of cells to participate in the regeneration of IR-damaged tissues. Therefore, it is imperative to search effective radioprotectors for hMSCs. This study was to demonstrate whether natural source ginger oleoresin would mitigate IR-induced injuries in human mesenchymal stem cells (hMSCs). We demonstrated that ginger oleoresin could significantly reduce IR-induced cytotoxicity, ROS generation, and DNA strand breaks. In addition, the ROS-scavenging mechanism of ginger oleoresin was also investigated. The results showed that ginger oleoresin could induce the translocation of Nrf2 to cell nucleus and activate the expression of cytoprotective genes encoding for HO-1 and NQO-1. It suggests that ginger oleoresin has a potential role of being an effective antioxidant and radioprotective agent.

Biological and pharmacological evaluation of dimethoxycurcumin: A metabolically stable curcumin analogue with a promising therapeutic potential

Dimethoxycurcumin (DiMC) is a synthetic analog of curcumin with superior inter-related pro-oxidant and anti-cancer activity, and metabolic stability. Numerous studies have shown that DiMC reserves the biologically beneficial features, including anti-inflammatory, anti-carcinogenic, and cytoprotective properties, almost to the same extent as curcumin exhibits. DiMC lacks the phenolic-OH groups as opposed to curcumin, dimethoxycurcumin, and bis-demethoxycurcumin that all vary in the number of methoxy groups per molecule, and has drawn the attentions of researchers who attempted to discover the structure-activity relationship (SAR) of curcumin. In this regard, tetrahydrocurcumin (THC), the reduced and biologically inert metabolite of curcumin, denotes the significance of the conjugated α,β diketone moiety for the curcumin activity. DiMC exerts unique molecular activities compared to curcumin, including induction of androgen receptor (AR) degradation and suppression of the transcription factor activator protein-1 (AP-1). The enhanced AR degradation on DiMC treatment suggests it as a novel anticancer agent against resistant tumors with androgenic etiology. Further, DiMC might be a potential treatment for acne vulgaris. DiMC induces epigenetic alteration more effectively than curcumin, although both showed no direct DNA hypomethylating activity. Given the metabolic stability, nanoparticulation of DiMC is more promising for in vivo effectiveness. However, studies in this regard are still in its infancy. In the current review, we portray the various molecular and biological functions of DiMC reported so far. Whenever possible, the efficiency is compared with curcumin and the reasons for DiMC being more metabolically stable are elaborated. We also provide future perspective investigations with respect to varying DiMC-nanoparticles.

Development of resveratrol-curcumin hybrids as potential therapeutic agents for inflammatory lung diseases

Acute lung injury (ALI) is a major cause of acute respiratory failure in critically-ill patients. Resveratrol and curcumin are proven to have potent anti-inflammatory efficacy, but their clinical application is limited by their metabolic instability. Here, a series of resveratrol and the Mono-carbonyl analogs of curcumin (MCAs) hybrids were designed and synthesized by efficient aldol construction strategy, and then screened for anti-inflammatory activities in vitro and in vivo. The results showed that the majority of analogs effectively inhibited the LPS-induced production of IL-6 and TNF-α. Five analogs, a9, a18, a19, a20 and a24 exhibited excellent anti-inflammatory activity in a dose-dependent manner along with low toxicity in vitro. Structure activity relationship study revealed that the electron-withdrawing groups at meta-position and methoxyl group (OCH₃) at the para position of the phenyl ring were important for anti-inflammatory activities. The most promising compound a18 decreased LPS induced TNF-α, IL-6, IL-12, and IL-33 mRNA expression. Additionally, a18 significantly protected against LPS-induced acute lung injury in the in vivo mouse model. The research of resveratrol and MCAs hybrids could bring insight into the treatment of inflammatory diseases and compound a18 may serve as a lead compound for the development of anti-ALI agents.

1,4-Naphthoquinone, a pro-oxidant, ameliorated radiation induced gastro-intestinal injury through perturbation of cellular redox and activation of Nrf2 pathway

Detrimental effects of ionizing radiation (IR) are observed at the doses above 1 Gy. Treatment modalities are available up to doses of 6 Gy including bonemarrow transplantation and administration of antibiotics. However, exposure to IR doses above 8 Gy results in gastro-intestinal (GI) syndrome characterised by denudated villi, apoptosis of crypt cells and elevated inflammatory responses. Multiple strategies have been employed to investigate novel agents to protect against IR induced injury. Since cellular redox homeostasis plays a pivotal role in deciding the cell fate, present study was undertaken to explore the potential of 1,4-naphthoquinone (NQ), a pro-oxidant, to ameliorate IR induced GI syndrome. NQ protected INT 407 cells against IR induced cell death of intestinal epithelial cells in vitro. NQ induced perturbation in cellular redox status and induced the activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. Thiol antioxidant and inhibitors of Nrf2 pathway abrogated the radioprotection offered by NQ. Further, knocking down Nrf2 rescind the NQ mediated protection against IR induced cell death. In conclusion, NQ protects against IR radiation induced GI syndrome in vitro by perturbing cellular redox and activating Nrf2 pathway. This is the first report highlighting the potential of a pro-oxidant to ameliorate IR induced GI injury.

Curcumin attenuates chronic ethanol-induced liver injury by inhibition of oxidative stress via mitogen-activated protein kinase/nuclear factor E2-related factor 2 pathway in mice

OBJECTIVE

This study aimed to investigate the protective effect of curcumin on chronic ethanol-induced liver injury in mice and to explore its underlying mechanisms.

MATERIALS AND METHODS

Ethanol-exposed Balb/c mice were simultaneously treated with curcumin for 6 weeks. Liver injury was evaluated by biochemical and histopathological examination. Lipid peroxidation and anti-oxidant activities were measured by spectrophotometric method. Anti-oxidative genes expression such as NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), and superoxide dismutase (SOD) were determined by real-time polymerase chain reaction. The nuclear factor E2-related factor 2 (Nrf2) and the phosphorylation states of specific proteins central to intracellular signaling cascades were measured by western blotting.

RESULTS

Curcumin treatment protected liver from chronic ethanol-induced injury through reducing serum alanine aminotransferase and aspartate aminotransferase activities, improving liver histological architecture, and reversing lipid disorders indicated by decrease of triglyceride, total cholesterol and low-density lipoprotein-cholesterol levels and increase of High-density lipoprotein-cholesterol levels. Meanwhile, curcumin administration attenuated oxidative stress via up-regulating SOD and glutathione peroxidase activities, leading to a reduction of lipid hydroperoxide production. In addition, curcumin increased Nrf2 activation and anti-oxidative genes expressions such as NQO1, HO-1, and SOD through inducing extracellular signal-regulated kinase (ERK) and p38 phosphorylation.

CONCLUSION

Our data suggested that curcumin protected the liver from chronic-ethanol induced injury through attenuating oxidative stress, at least partially, through ERK/p38/Nrf2-mediated anti-oxidant signaling pathways.

Prediction of the anti-inflammatory mechanisms of curcumin by module-based protein interaction network analysis

Curcumin, the medically active component from Curcuma longa (Turmeric), is widely used to treat inflammatory diseases. Protein interaction network (PIN) analysis was used to predict its mechanisms of molecular action. Targets of curcumin were obtained based on ChEMBL and STITCH databases. Protein–protein interactions (PPIs) were extracted from the String database. The PIN of curcumin was constructed by Cytoscape and the function modules identified by gene ontology (GO) enrichment analysis based on molecular complex detection (MCODE). A PIN of curcumin with 482 nodes and 1688 interactions was constructed, which has scale-free, small world and modular properties. Based on analysis of these function modules, the mechanism of curcumin is proposed. Two modules were found to be intimately associated with inflammation. With function modules analysis, the anti-inflammatory effects of curcumin were related to SMAD, ERG and mediation by the TLR family. TLR9 may be a potential target of curcumin to treat inflammation.

Hybrid curcumin compounds: a new strategy for cancer treatment

Cancer is a multifactorial disease that requires treatments able to target multiple intracellular components and signaling pathways. The natural compound, curcumin, was already described as a promising anticancer agent due to its multipotent properties and huge amount of molecular targets in vitro. Its translation to the clinic is, however, limited by its reduced solubility and bioavailability in patients. In order to overcome these pharmacokinetic deficits of curcumin, several strategies, such as the design of synthetic analogs, the combination with specific adjuvants or nano-formulations, have been developed. By taking into account the risk-benefit profile of drug combinations, as well as the knowledge about curcumin's structure-activity relationship, a new concept for the combination of curcumin with scaffolds from different natural products or components has emerged. The concept of a hybrid curcumin molecule is based on the incorporation or combination of curcumin with specific antibodies, adjuvants or other natural products already used or not in conventional chemotherapy, in one single molecule. The high diversity of such conjugations enhances the selectivity and inherent biological activities and properties, as well as the efficacy of the parental compound, with particular emphasis on improving the efficacy of curcumin for future clinical treatments.

Mitigation of radiation-induced hematopoietic injury via regulation of cellular MAPK/phosphatase levels and increasing hematopoietic stem cells

Here we describe a novel strategy for mitigation of ionizing radiation-induced hematopoietic syndrome by suppressing the activity of MKP3, resulting in ERK activation and enhanced abundance of hematopoietic stem cells, using the antioxidant flavonoid baicalein (5,6,7-trihydroxyflavone). It offered complete protection to mouse splenic lymphocytes against radiation-induced cell death. Inhibitors of ERK and Nrf-2 could significantly abrogate baicalein-mediated radioprotection in lymphocytes. Baicalein inhibited phosphatase MKP3 and thereby enhanced phosphorylation of ERK and its downstream proteins such as Elk and Nrf-2. It also increased the nuclear levels of Nrf-2 and the mRNA levels of its dependent genes. Importantly, baicalein administration to mice before radiation exposure led to significant recovery of loss of bone marrow cellularity and also inhibited cell death. Administration of baicalein increased the hematopoietic stem cell frequency as measured by side-population assay and also by antibody staining. Further, baicalein offered significant protection against whole-body irradiation (WBI; 7.5Gy)-induced mortality in mice. Interestingly, we found that baicalein works by activating the same target molecules ERK and Nrf-2 both in vitro and in vivo. Finally, administration of all-trans-retinoic acid (inhibitor of Nrf-2) significantly abrogated baicalein-mediated protection against WBI-induced mortality in mice. Thus, in contrast to the generalized conception of antioxidants acting as radioprotectors, we provide a rationale that antioxidants exhibit pleiotropic effects through the activation of multiple cellular signaling pathways.

Synthesis and biological evaluation of allylated and prenylated mono-carbonyl analogs of curcumin as anti-inflammatory agents

Curcumin has been shown to possess anti-inflammatory activities but has been limited for its low stability and poor bioavailability. We have previously reported four series of 5-carbon linker-containing mono-carbonyl analogs of curcumin (MACs). In continuation of our ongoing research, we designed and synthesized 33 novel allylated or prenylated MACs here, and evaluated their anti-inflammatory effects in RAW 264.7 macrophages. A majority of them effectively inhibited the LPS-induced expression of TNF-α and IL-6, especially IL-6. The preliminary SAR and quantitative SAR analysis were conducted. Compound 14q is the most potent analog among them, and exhibits significant protection against LPS-induced death in septic mice. Together, these data present a series of new analogs of curcumin as promising anti-inflammatory agents.

Involvement of ERK-Nrf-2 signaling in ionizing radiation induced cell death in normal and tumor cells

Prolonged oxidative stress favors tumorigenic environment and inflammation. Oxidative stress may trigger redox adaptation mechanism(s) in tumor cells but not normal cells. This may increase levels of intracellular antioxidants and establish a new redox homeostasis. Nrf-2, a master regulator of battery of antioxidant genes is constitutively activated in many tumor cells. Here we show that, murine T cell lymphoma EL-4 cells show constitutive and inducible radioresistance via activation of Nrf-2/ERK pathway. EL-4 cells contained lower levels of ROS than their normal counterpart murine splenic lymphocytes. In response to radiation, the thiol redox circuits, GSH and thioredoxin were modified in EL-4 cells. Pharmacological inhibitors of ERK and Nrf-2 significantly enhanced radiosensitivity and reduced clonogenic potential of EL-4 cells. Unirradiated lymphoma cells showed nuclear accumulation of Nrf-2, upregulation of its dependent genes and protein levels. Interestingly, MEK inhibitor abrogated its nuclear translocation suggesting role of ERK in basal and radiation induced Nrf-2 activation in tumor cells. Double knockdown of ERK and Nrf-2 resulted in higher sensitivity to radiation induced cell death as compared to individual knockdown cells. Importantly, NF-kB which is reported to be constitutively active in many tumors was not present at basal levels in EL-4 cells and its inhibition did not influence radiosensitivity of EL-4 cells. Thus our results reveal that, tumor cells which are subjected to heightened oxidative stress employ master regulator cellular redox homeostasis Nrf-2 for prevention of radiation induced cell death. Our study reveals the molecular basis of tumor radioresistance and highlights role of Nrf-2 and ERK.

Schisandrin B exhibits anti-inflammatory activity through modulation of the redox-sensitive transcription factors Nrf2 and NF-κB

Schisandrin B (SB), a dibenzocyclooctadiene derivative isolated from Schisandra chinensis and used commonly in traditional Chinese medicine for the treatment of hepatitis and myocardial disorders, has been recently shown to modulate cellular redox balance. Since we have shown that cellular redox plays an important role in the modulation of immune responses, the present studies were undertaken to study the effects of SB on activation and effector functions of lymphocytes. SB altered the redox status of lymphocytes by enhancing the basal reactive oxygen species levels and altering the GSH/GSSG ratio in lymphocytes. It also induced nuclear translocation of redox sensitive transcription factor Nrf2 and increased the transcription of its dependent genes. SB inhibited mitogen-induced proliferation and cytokine secretion by lymphocytes. SB also significantly inhibited mitogen-induced upregulation of T cell costimulatory molecules and activation markers. It was observed that SB inhibited mitogen-induced phosphorylation of c-Raf, MEK, ERK, JNK, and p38. It suppressed IκBα degradation and nuclear translocation of NF-κB in activated lymphocytes. Anti-inflammatory effects of SB were significantly abrogated by the inhibitors of Nrf2 and HO-1, suggesting the involvement of this pathway. Similar anti-inflammatory effects of SB on lymphocyte proliferation and cytokine secretion were also observed in vivo. To our knowledge, this is the first report showing that the anti-inflammatory effects of SB are mediated via modulation of Nrf2 and NF-κB in lymphocytes.

Curcumin inhibits protein phosphatases 2A and 5, leading to activation of mitogen-activated protein kinases and death in tumor cells

Curcumin can induce p53-independent apoptosis. However, the underlying mechanism remains to be defined. Here, we show that curcumin-induced apoptosis in a panel of tumor cells with mutant p53. Curcumin rapidly induced activation of the mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase 1/2 (Erk1/2) and c-Jun N-terminal kinase (JNK). Inhibition of JNK (with SP600125) or Erk1/2 (with U0126) partially prevented curcumin-induced cell death in the cells. Similarly, expression of dominant negative c-Jun or downregulation of Erk1/2 in part attenuated curcumin-induced cell death. It appears that curcumin-induced activation of MAPKs and apoptosis was due to induction of reactive oxygen species (ROS), as pretreatment with N-acetyl-L-cysteine, a ROS scavenger, blocked these events. Furthermore, we found that curcumin-induced activation of MAPK pathways was related to inhibition of the serine/threonine protein phosphatases 2A (PP2A) and 5 (PP5). Overexpression of PP2A or PP5 partially prevented curcumin-induced activation of JNK and Erk1/2 phosphorylation as well as cell death. The results suggest that curcumin induction of ROS activates MAPKs, at least partially by inhibiting PP2A and PP5, thereby leading to p53-independent apoptosis in tumor cells.