Expression of proinflammatory cytokines by monocytes is tightly regulated by transcription factors such as NF-κB. In this study, we show that, in LPS-stimulated human peripheral monocytes, the pentacyclic triterpenes acetyl-α-boswellic acid (AαBA) and acetyl-11-keto-β-boswellic acid (AKβBA) down-regulate the TNF-α expression. AαBA and AKβBA inhibited NF-κB signaling both in LPS-stimulated monocytes as detected by EMSA, as well as in a NF-κB-dependent luciferase gene reporter assay. By contrast, the luciferase expression driven by the IFN-stimulated response element was unaffected, implying specificity of the inhibitory effect observed. Both AαBA and AKβBA did not affect binding of recombinant p50/p65 and p50/c-Rel dimers to DNA binding sites as analyzed by surface plasmon resonance. Instead, both pentacyclic triterpenes inhibited the LPS-induced degradation of IκBα, as well as phosphorylation of p65 at Ser536 and its nuclear translocation. AαBA and AKβBA inhibited specifically the phosphorylation of recombinant IκBα and p65 by IκBα kinases (IKKs) immunoprecipitated from LPS-stimulated monocytes. In line with this, AαBA and AKβBA also bound to and inhibited the activities of active human recombinant GST-IKKα and His-IKKβ. The LPS-triggered induction of TNF-α in monocytes is dependent on IKK activity, as confirmed by IKK-specific antisense oligodeoxynucleotides. Thus, via their direct inhibitory effects on IKK, AαBA and AKβBA convey inhibition of NF-κB and subsequent down-regulation of TNF-α expression in activated human monocytes. These findings provide a molecular basis for the anti-inflammatory properties ascribed to AαBA- and AKβBA-containing drugs and suggest acetyl-boswellic acids as tools for the development of novel therapeutic interventions.

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For centuries, frankincense extracts have been commonly used in traditional medicine, and more recently, in complementary medicine. Therefore, frankincense constituents such as boswellic and lupeolic acids are of considerable therapeutic interest. Sixteen frankincense nutraceuticals were characterized by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS), revealing major differences in boswellic and lupeolic acid compositions and total contents, which varied from 0.4% to 35.7%. Frankincense nutraceuticals significantly inhibited the release of proinflammatory cytokines, such as TNF-α, IL-6, and IL-8, by LPS-stimulated peripheral blood mononuclear cells (PBMC) and whole blood. Moreover, boswellic and lupeolic acid contents correlated with TNF-α, IL-1β, IL-6, IL-8, and IL-10 inhibition. The nutraceuticals also exhibited toxicity against the human triple-negative breast cancer cell lines MDA-MB-231, MDA-MB-453, and CAL-51 in vitro. Nutraceuticals with total contents of boswellic and lupeolic acids >30% were the most active ones against MDA-MB-231 with a half maximal inhibitory concentration (IC50) ≤ 7.0 µg/mL. Moreover, a frankincense nutraceutical inhibited tumor growth and induced apoptosis in vivo in breast cancer xenografts grown on the chick chorioallantoic membrane (CAM). Among eight different boswellic and lupeolic acids tested, β-ABA exhibited the highest cytotoxicity against MDA-MB-231 with an IC50 = 5.9 µM, inhibited growth of cancer xenografts in vivo, and released proinflammatory cytokines. Its content in nutraceuticals correlated strongly with TNF-α, IL-6, and IL-8 release inhibition.

SummaryPlasmin triggers chemotaxis and NF-κBand AP-1-mediated proinflammatory gene expression in human peripheral monocytes (PM). Compared with macrophages and dendritic cells, PM express mainly the peroxisome proliferator-activated receptor (PPAR) γ and traces of PPARα as detected by semiquantitative RT-PCR and immunoblotting. The PPARγ agonist ciglitazone, but not the PPARα agonist clofibric acid, concentration-dependently inhibited the plasmin-, but not the FMLP-induced PM chemotaxis. Similarly, release of interleukin (IL)-1α, IL-1β and tumor necrosis factor (TNF)-α from plasmin-stimulated PM was concentration-dependently inhibited by ciglitazone, but not by clofibric acid, while the LPS-induced TNF-α release remained unaffected by any of both PPAR agonists. Ciglitazone activates PPARγ as shown by a novel surface plasmon resonance analysis and inhibits the plasmin-induced activation of NF-κB and AP-1. It also inhibits p38 MAPK phosphorylation essential for the plasmin-induced PM chemotaxis and gene activation. Thus, activation of PPARγ by ciglitazone may allow controling of the plasmin-mediated recruitment and activation of PM at sites of inflammation.

Triple-negative breast cancer (TNBC) is a fast growing and strong metastasizing tumor, which presents almost no cellular receptors that can be addressed by targeted therapeutics. In addition, TNBC is often characterized by high tumor grading, fast growth rates, and early metastasis. Therefore, multifunctional drug carriers allowing efficient drug delivery and bioimaging to treat and track TNBC tissue in vivo would be highly desirable. A human serum albumin-based polyethylene glycol copolymer (dcHSA-Gd-Dox) is synthesized combining multiple copies of the chemotherapeutic drug doxorubicin and gadolinium (III) (Gd(III))-based magnetic resonance imaging (MRI) contrast agent. The biodegradable albumin-based nanocarriers reveal high-contrast tumor imaging and efficient drug delivery in a preclinical TNBC xenograft model, where the xenografts are grown on the chorioallantoic membrane of fertilized chick eggs. dcHSA-Gd-Dox is injected intravenously, and the distribution of the compound is monitored by MRI and inductively coupled optical plasma emission spectrometry. dcHSA-Gd-Dox is rapidly taken up into MDA-MB-231 cells and exhibits significant cytotoxic efficacy. dcHSA-Gd-Dox combines high tissue enrichment with low systemic toxicity and high-contrast MRI rendering it an attractive nanotheranostic for TNBC.

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AA amyloidosis belongs to the group of amyloid diseases which can follow chronic inflammatory conditions of various origin. The disease is characterized by the deposition of insoluble amyloid fibrils formed by serum amyloid A1 (SAA1) leading eventually to organ failure. Macrophages are intimately involved in the fibrillogenesis as well as in the clearance of amyloid fibrils. In vivo, macrophages may occur as classically (M1) or alternatively activated (M2) macrophages. We investigate here how SAA1 might affect the macrophage phenotype and function. Gene microarray analysis revealed upregulation of 64 M1-associated genes by SAA1. M1-like polarization was further confirmed by the expression of the M1-marker MARCO, activation of the NF-κB transcription factor, and secretion of the M1-cytokines TNF-α, IL-6, and MCP-1. Additionally, we demonstrate here that M1-polarized macrophages exhibit enhanced fibrillogenic activity towards SAA1. Based on our data, we propose reconsideration of the currently used cellular amyloidosis models towards an in vitro model employing M1-polarized macrophages. Furthermore, the data suggest macrophage repolarization as potential intervention strategy in AA amyloidosis.