Paclitaxel (Taxol)-induced NF-kappaB translocation in murine macrophages

Vitamin D Insufficiency as a Risk Factor for Paclitaxel-Induced Peripheral Neuropathy in SWOG S0221

BACKGROUND

Prior work suggests that patients with vitamin D insufficiency may have a higher risk of chemotherapy-induced peripheral neuropathy (CIPN) from paclitaxel. The objective of this study was to validate vitamin D insufficiency as a CIPN risk factor.

METHODS

We used data and samples from the prospective phase III SWOG S0221 (ClinicalTrials.gov identifier: NCT00070564) trial that compared paclitaxel-containing chemotherapy regimens for early-stage breast cancer. We quantified pretreatment 25-hydroxy-vitamin D in banked serum samples using a liquid chromatography-tandem mass spectrometry targeted assay. We tested the association between vitamin D insufficiency (≤20 ng/mL) and grade ≥3 sensory CIPN via multiple logistic regression and then adjusted for self-reported race, age, body mass index, and paclitaxel schedule (randomization to weekly or every-2-week dosing). We also tested the direct effect of vitamin D deficiency on mechanical hypersensitivity in mice randomized to a regular or vitamin D-deficient diet.

RESULTS

Of the 1,191 female patients in the analysis, 397 (33.3%) had pretreatment vitamin D insufficiency, and 195 (16.4%) developed grade ≥3 CIPN. Patients with vitamin D insufficiency had a higher incidence of grade ≥3 CIPN than those who had sufficient vitamin D (20.7% vs 14.2%; odds ratio [OR], 1.57; 95% CI, 1.14-2.15; P=.005). The association retained significance after adjusting for age and paclitaxel schedule (adjusted OR, 1.65; 95% CI, 1.18-2.30; P=.003) but not race (adjusted OR, 1.39; 95% CI, 0.98-1.97; P=.066). In the mouse experiments, the vitamin D-deficient diet caused mechanical hypersensitivity and sensitized mice to paclitaxel (both P<.05).

CONCLUSIONS

Pretreatment vitamin D insufficiency is the first validated potentially modifiable predictive biomarker of CIPN from paclitaxel. Prospective trials are needed to determine whether vitamin D supplementation prevents CIPN and improves treatment outcomes in patients with breast and other cancer types.

Chrysin attenuates paclitaxel-induced hepatorenal toxicity in rats by suppressing oxidative damage, inflammation, and apoptosis

AIMS

Paclitaxel (Pax) is a chemotherapeutic drug from the taxane family that is used in the treatment of human cancer, including ovarian, breast, and non-small cell lung carcinoma. Chrysin (CR) has antioxidant, anti-inflammatory, anti-apoptotic, anti-diabetic, and anti-carcinogenic properties, as well as hepatoprotective and renoprotective activities. In the present study, we evaluated the protective effect of CR against Pax-induced hepatorenal toxicity on inflammation, apoptosis, antioxidant levels, oxidative DNA damage, and histopathology in rats.

MATERIAL AND METHODS

Thirty-five male Sprague-Dawley rats were divided into five groups (n = 7): Group I (normal control), Group II (CR alone at a dose of 50 mg/kg), Group III (Pax at a dose of 2 mg/kg), Group IV (Pax+CR 25), and Group V (Pax+CR 50). The expressions of apoptotic (Bax and Bcl-2) and antioxidant genes (SOD1, CAT, GPx3, and GST) were evaluated using RT-PCR from paraffin sections. Caspase 3, KIM-1, NF-kB, COX-2, and 8-OHdG were also determined by immunohistochemical examination.

KEY FINDINGS

The results revealed that Pax exposure caused hepatic and renal damage in rats, which was indicated by a significant elevation of caspase 3, Bax, KIM-1, NF-kB, COX-2, and 8-OHdG. However, there was a marked downregulation in the expressions of the Bcl-2, SOD1, CAT, GPx3, and GST genes. In contrast, rats given CR in combination showed better gene expression, histological structure, and immunohistochemical staining results.

SIGNIFICANCE

Consequently, CR exhibited the ability to reduce oxidative DNA damage, exert anti-apoptotic and anti-inflammatory properties, and mitigate the toxic effects of Pax-induced hepatorenal toxicity.

Inhibiting the NF-κB pathway enhances the antitumor effect of cabazitaxel by downregulating Bcl-2 in pancreatic cancer

Optimizing the currently available treatment options for pancreatic cancer (PC) is a priority. Cabazitaxel (CTX), a semisynthetic taxane, is mainly used for treating patients with PC who are resistant to paclitaxel (PTX) or docetaxel, due its poor affinity for P-glycoprotein. However, there are only a few studies demonstrating the effect of CTX on PC. The present study aimed to investigate the efficiency and underlying mechanism of CTX in PC treatment. Cell proliferation, colony formation assay and apoptosis analysis were achieved in the two human PC cell lines AsPC-1 and BxPC-3. Drug sensitivity test was performed in BxPC-3 tumor-bearing mice. The results demonstrated that CTX had a lower half maximal inhibitory concentration compared with PTX for the inhibition of cell proliferation, both in vivo and in vitro. Furthermore, the nuclear factor-κB (NF-κB) pathway was activated following cell treatment with CTX, and NF-κB p65 overexpression attenuated CTX cytotoxicity. In addition, the combined use of the specific NF-κB inhibitor caffeic acid phenethyl ester (CAPE) with CTX significantly enhanced CTX effect, both in vivo and in vitro. Similarly, the mRNA and protein expression of B-cell lymphoma-2 was decreased in AsPC-1 and BxPC-3 cells following treatment with CTX and CAPE, suggesting that NF-κB may serve a crucial role in CTX efficiency. In conclusion, results from our previous study indicated that CTX could potentially replace PTX in the treatment of PC, and the present study demonstrated that CTX combination with an NF-κB inhibitor may be considered as a potential therapeutic option for PC, which may improve the prognosis of patients with PC.

Garcinol sensitizes breast cancer cells to Taxol through the suppression of caspase-3/iPLA2 and NF-κB/Twist1 signaling pathways in a mouse 4T1 breast tumor model

Breast cancer is a significant threat to women's health and has high incidence and mortality. Metastasis in breast cancer patients is a major cause of cancer deaths among women worldwide. Clinical experience suggests that patients with metastatic triple-negative breast cancer (TNBC) relapse quickly and often have chemotherapy resistance. Taxol (paclitaxel) is an effective chemotherapeutic agent for treating metastatic breast cancer, but Taxol at high doses can cause adverse effects and recurrent resistance. Thus, the selection of a synergistic combination therapy is recommended, which is safer and has a more significant response rate than monotherapy. In this study, our strategy is to combine a low dose of Taxol (5 mg kg^-1, i.p.) and garcinol (1 mg kg^-1, i.g.) to investigate the synergistic antitumor and anti-metastasis effects and to determine the underlying mechanisms of these effects in vivo. For the in vivo study, metastasis-specific mouse mammary carcinoma 4T1 cells were inoculated in Balb/c mice to establish an orthotopic primary tumor and spontaneous metastasis model. Tumor growth and metastases were monitored. The mechanisms of synergistic efficacies were evaluated at different signaling pathways, including proliferation, survival, and epithelial-mesenchymal transition (EMT)-regulated metastatic propensity. We demonstrated that garcinol combined with Taxol significantly increased the therapeutic efficacy when compared with either treatment alone. The synergistic antitumor and anti-metastasis effects were enhanced primarily through the induction of Taxol-stimulated G2/M phase arrest and the inhibition of caspase-3/cytosolic Ca²⁺-independent phospholipase A2 (iPLA₂) and nuclear factor-κB (NF-κB)/Twist-related protein 1 (Twist1) drive downstream events including tumor cell repopulation, survival, inflammation, angiogenesis, invasion, and EMT. Our current findings provide the first experimental evidence that a combination of a low dose of Taxol and garcinol is a promising therapeutic strategy for controlling advanced or metastatic breast cancer. Finally, our results also point to the possible role of NF-κB/Twist1 and caspase-3/iPLA₂ signaling pathways as biomarkers to predict the tumor response to treatment.

Milk-derived exosomes for oral delivery of paclitaxel

In this report milk-derived exosomes have been investigated for oral delivery of the chemotherapeutic drug paclitaxel (PAC) as an alternative to conventional i.v. therapy for improved efficacy and reduced toxicity. PAC-loaded exosomes (ExoPAC) were found to have a particle size of ~108 nm, a narrow particle size distribution (PDI ~0.190), zeta potential (~ -7 mV) and a practical loading efficiency of ~8%. Exosomes and ExoPAC exhibited excellent stability in the presence of simulated-gastrointestinal fluids, and during the storage at -80 °C. A sustained release of PAC was also observed up to 48 h in vitro using PBS (pH 6.8). Importantly, ExoPAC delivered orally showed significant tumor growth inhibition (60%; P<0.001) against human lung tumor xenografts in nude mice. Treatment with i.p. PAC at the same dose as ExoPAC, however, showed modest but statistically insignificant inhibition (31%). Moreover, ExoPAC demonstrated remarkably lower systemic and immunologic toxicities as compared to i.v. PAC.

Analysis of structure activity relationships for LPS-mimetic activities of taxane analogs in murine macrophages

The anti-tumor agent, paclitaxel (active ingredient of Taxol®), is best recognized for its ability to bind to microtubules and to block cell division. However, it has more recently been demonstrated to mimic the varied effects of bacterial lipopolysaccharide (LPS) in murine macrophages, actions that appear to be dissociable from its well-characterized β-tubulin binding capacity. Secretion of tumor necrosis factor alpha (TNFα) and induction of TNFα gene expression were assessed in macrophages treated with paclitaxel analogs. Two structural modifications resulted in elevated TNFα mRNA and protein secretion: (i) the presence of a cyclopropane carboxylate ester at C-4 rather than an acetate; or (ii) deoxygenation of the C-7 position. Certain modifications essentially eliminated activity: derivatization of the side chain 2′ hydroxy group to form an ethyl carbonate, the presence of a benzoate at C-4 rather than an acetate, or de-acetylization to leave a free hydroxy group at the C-10 position. Substitution of the phenyl group at the 3′ carbon position of the side chain with a 2-furyl group or the presence of a 2- or 3-pyridine carboxylate moiety at C-2 rather than a benzoate also resulted in a significant reduction in TNFα. These structure—activity relationships can be distinguished from those that affect the cytotoxic effects of paclitaxel which are attributable to its microtubule binding activity.

Involvement of TLR4/MD-2 complex in species-specific lipopolysaccharide-mimetic signal transduction by Taxol

Taxol, an antitumor agent derived from a plant, mimics the action of lipopolysaccharide (LPS) in mice, but not in humans. The LPS-mimetic activity of Taxol is not observed in LPS-hyporesponsive C3H/HeJ mice which possess a point mutation in Toll-like receptor 4 (TLR4); therefore, TLR4 appears to be involved in both Taxol and LPS signaling. In addition, TLR4 was recently shown to physically associate with MD-2, a molecule that confers LPS-responsiveness on TLR4. Here we examined whether or not TLR4/MD-2 complex mediates a Taxol-induced signal by using transformants of the mouse pro-B cell line, Ba/F3, expressing mouse TLR4 alone, both mouse TLR4 and mouse MD-2, and both mouse MD-2 and mouse TLR4 lacking the cytoplasmic portion. Our results demonstrated that co-expression of mouse TLR4 and mouse MD-2 was required for Taxol responsiveness, and that the TLR4/MD-2 complex is the shared molecule in Taxol and LPS signal transduction in mice. We also found that mouse MD-2, but not human MD-2, is involved in Taxol signaling, suggesting that MD-2 is responsible for the species-specific responsiveness to Taxol.

Molecular basis for lipopolysaccharide mimetic action of Taxol™ and flavolipin

We previously reported that Taxol™, which mimics the action of LPS on murine macrophages, induces signals via mouse TLR4/MD-2, but not via human TLR4/MD-2. Here we investigated the molecular basis for this species-specific action of Taxol™. Expression of mouse MD-2 conferred both LPS and Taxol™ responsiveness on HEK293 cells expressing mouse TLR4, whereas expression of human MD-2 conferred LPS responsiveness alone, suggesting that MD-2 is responsible for the species-specificity of Taxol™ responsiveness. Furthermore, mouse MD-2 mutants, in which Gln-22 was changed to other amino acids, showed dramatically reduced ability to confer Taxol™ responsiveness, although their ability to confer LPS responsiveness was not affected. These results indicated that Gln-22 of mouse MD-2 is essential for Taxol™ signaling, but not for LPS signaling. In this study, we also found that the TLR4/MD-2 complex, together with CD14, mediated signal transduction induced by flavolipin, an amino acid-containing lipid unique to Flavobacterium meningosepticum.

Rhodobacter sphaeroides diphosphoryl lipid A inhibits interleukin-6 production in CD14-negative murine marrow stromal ST2 cells stimulated with lipopolysaccharide or paclitaxel (taxol)

Paclitaxel (taxol), a microtubule stabilizer with anticancer activity, mimics the actions of lipopolysaccharide (LPS) on murine macrophages in vitro. Recent studies have shown that the Rhodobacter sphaeroides diphosphoryl lipid A (RsDPLA) inhibits both LPS- and paclitaxel-induced activation of murine macrophages, and have suggested that LPS, RsDPLA, and paclitaxel share the same receptor site on murine macrophages. To analyze this receptor site, the present study focused on the interactions between LPS, RsDPLA and paclitaxel in the activation of ST2 cells derived from murine bone marrow stroma. The ST2 cells did not express CD14 mRNA. The cells produced IL-6 molecules and expressed IL-6 mRNA in response to LPS, but did not produce TNF and nitric oxide. Paclitaxel induced IL-6 mRNA expression in ST2 cells. RsDPLA inhibited both LPS- and paclitaxel-induced IL-6 mRNA expression in a dose-dependent manner. These results suggest that LPS, RsDPLA, and paclitaxel are recognized by the same receptor complex on ST2 cells, and that the receptor functions without membrane CD14.

Identification of CD18 as a novel Taxol binding/signaling protein in murine macrophage membranes

The anti-tumor agent, Taxol, is a potent LPS mimetic in murine macrophages, an activity that is dissociable from its well-characterized anti-mitotic activity which is mediated by microtubule hyperstabilization. A photoactivatable Taxol analog was used to identify components of a putative, shared LPS signaling apparatus in murine macrophage membranes. We report here that CD18, the β chain of the β2-integrin, Mac-1, represents a major Taxol binding protein in murine macrophages.

Atractylenolide-I sensitizes human ovarian cancer cells to paclitaxel by blocking activation of TLR4/MyD88-dependent pathway

Paclitaxel, a known TLR4 ligand, leads to activation of TLR4/MyD88-dependent pathway that mediates chemoresistance and tumor progression in epithelial ovarian carcinoma (EOC). Atractylenolide-I (AO-I), a novel TLR4-antagonizing agent, inhibits TLR4 signaling by interfering with the binding of LPS or paclitaxel to membrane TLR4 of human leukocytes. In this study, AO-I was found to attenuate paclitaxel-induced protein expression of IL-6, VEGF and survivin, and to enhance early apoptosis and growth inhibition in MyD88⁺ EOC cells; AO-I was shown to fit into the hydrophobic pocket of human MD-2 and to partially overlap with the binding site of paclitaxel by docking simulations, suggesting that AO-I may block the MD-2-mediated TLR4/MyD88-dependent paclitaxel signaling in MyD88⁺ EOC cells. Therefore, AO-I could significantly sensitize the response of MyD88⁺ EOC cells to paclitaxel by blocking MD-2-mediated TLR4/MyD88 signaling, and that AO-I-paclitaxel combination could be a promising strategy for the treatment of EOC with a functional TLR4/MyD88/NF-κB pathway.

(3S)-1,2,3,4-Tetrahydro-β-carboline-3-carboxylic acid from Cichorium endivia. L induces apoptosis of human colorectal cancer HCT-8 cells

Cichorium endivia. L, consumed either cooked or eaten raw in salads, is a popular kind of vegetable cultivated all around the World. Its components have been widely used in folk medicine in anti-inflammatory therapy. However, the anti-cancer activity of the components has never been reported. In this study, (3S)-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (1), an amino acid isolated from C. endivia. L, was found for the first time to show cytotoxic activity in colorectal cancer cell line HCT-8. Compound 1 at concentrations of 0.5–4 μM induced apoptosis of HCT-8 cells in a dose-dependent manner. The compound 1-induced apoptosis in HCT-8 cells was accompanied by the loss of mitochondrial membrane potential, the activation of caspase-3, caspase-8 and caspase-9, the up-regulation of Bax and the down-regulation of Bcl-2. In addition, compound 1 suppressed the activation of NF-κB, which acts as an inhibitor of apoptosis. Taken together, these results suggested that compound 1 could significantly induce apoptosis of HCT-8 cells through the suppression of NF-κB signaling pathway, and thus can be considered as a potential candidate for developing chemotherapeutic drugs against cancer.

Icariside II potentiates paclitaxel-induced apoptosis in human melanoma A375 cells by inhibiting TLR4 signaling pathway

Combination therapy of paclitaxel (taxol) with natural anti-tumor agents that are capable of inhibiting survival signals may provide a rational molecular basis for novel chemotherapeutic strategies. Our previous study showed that icariside II (IS), derived from Herba Epimedii, inhibited the proliferation of melanoma cells in vivo and in vitro through the regulation of apoptosis. In this report, the combination effects of paclitaxel and IS were investigated in human melanoma A375 cells. As compared to the treatment with paclitaxel alone, the co-administration of IS and paclitaxel resulted in an enhancement of apoptosis as revealed by WST-8 and PI assays. Meanwhile, Western blot analysis showed that the co-administration of IS and paclitaxel resulted in increases of cleaved caspase-3, one of the terminal pro-apoptotic proteins. In melanoma, IL-8 and VEGF are positively correlated with disease stage and a high probability of progression. We demonstrated that treatment of A375 cells with IS in combination with paclitaxel resulted in a significant decrease in the production of IL-8 and VEGF, compared with paclitaxel alone. Recent studies suggest that TLR4-MyD88-ERK signaling may be a novel target for reversing chemoresistance to paclitaxel. Our flow cytometry and Western blot data showed that paclitaxel activated TLR4-MyD88-ERK signaling and that IS treatment could effectively inhibit this paclitaxel-induced activation of TLR4-MyD88-ERK signaling. In conclusion, this study demonstrated for the first time that IS could potentiate paclitaxel-induced apoptosis in melanoma cells. These effects were mediated, at least in part, by inhibiting the activation of the TLR4 signal transduction pathways. These findings support further preclinical evaluation of IS as a new potential anti-tumor agent.

Defining the immune response to Ehrlichia species using murine models

Pathogenic bacteria belonging to the family Anaplasmataceae include species of the genera Ehrlichia and Anaplasma. Ehrlichia chaffeensis, first known as the causative agent of human monocytic ehrlichiosis, also infects several vertebrate hosts including white-tailed deer, dogs, coyotes and goats. E. chaffeensis is transmitted from the bite of an infected hard tick, such as Amblyomma americanum. E. chaffeensis and other tick-transmitted pathogens have adapted to both the tick and vertebrate host cell environments. Although E. chaffeensis persists in both vertebrate and tick hosts for long periods of time, little is known about that process. Immunological studies will be valuable in assessing how the pathogen persists in nature in both vertebrate and invertebrate hosts. Understanding the host immune response to the pathogen originating from dual host backgrounds is also important to develop effective methods of diagnosis, control and treatment. In this paper, we provide our perspective of the current understanding of the immune response against E. chaffeensis in relation to other related Anaplasmataceae pathogens.

Nitroalkenes: synthesis, characterization, and effects on macrophage activation

Nitroalkenes derivatives of free as well as esterified unsaturated fatty acids are present in human plasma and tissue, representing novel pluripotent cell signaling mediators. Lipid nitration occurs in response to pro-inflammatory stimuli as an adaptative mechanism to downregulate inflammatory responses. This chapter first discusses the generation of nitroalkenes during macrophage activation following chemical and biological characterization. In particular, it describes procedures for (a) synthesizing and characterizing esterified (cholesteryl-nitrolinoleate, CLNO2) as well as free (nitroarachidonate, AANO2) nitroalkenes, (b) determining nitration of cholesteryl linoleic acid during macrophage activation by inflammatory stimuli, (c) examining the modulatory effects of nitroalkenes on the expression of inducible enzymes by activated macrophages, and (d) discussing the signaling pathways involved in nitroalkene-mediated anti-inflammatory actions.

Inhibition of nuclear factor-κB augments antitumor activity of adenovirus-mediated melanoma differentiation-associated gene-7 against lung cancer cells via mitogen-activated protein kinase kinase kinase 1 activation

Nuclear factor-kappaB (NF-kappaB) activation promotes cell survival and growth. Reports show that chemotherapeutic agents and cytokines that are used for cancer therapy activate NF-kappaB expression in tumor cells and its suppression enhanced the antitumor activity. We hypothesized that adenovirus-mediated overexpression of melanoma differentiation-associated gene-7/interleukin-24 (Ad-mda7/IL-24) induces NF-kappaB expression and that inhibition of this expression results in enhanced tumor cell killing. Treatment of human lung tumor (H1299 and A549) cells with Ad-mda7 resulted in NF-kappaB activation in a dose- and time-dependent manner before activation of cell death pathways. To establish that inhibition of Ad-mda7-mediated NF-kappaB activation results in enhanced tumor cell killing, H1299 cells that overexpress the dominant-negative I kappa B alpha (dnI kappa B alpha) were treated with Ad-mda7 in vitro. An enhanced growth arrest and apoptosis was observed in Ad-mda7-treated H1299-dnI kappa B alpha compared with H1299-Neo cells. This Ad-mda7-mediated enhanced killing of H1299-dnI kappa B alpha cells involved cleavage of mitogen-activated protein kinase kinase kinase 1 (MEKK1) and caspase-3 in a feedback loop mechanism. The inhibition of MEKK1 or caspase-3 cleavage in H1299-dnI kappa B alpha cells resulted in reduced Ad-mda7-mediated cell killing. In vivo, the treatment of H1299-dnI kappa B alpha s.c. tumors with Ad-mda7 resulted in increased drug sensitivity and delayed the tumor growth rate compared with Ad-mda7-treated H1299-Neo tumors. Molecular analysis of Ad-mda7-treated H1299-dnI kappa B alpha tumors showed increased MEKK1 cleavage and activation of caspase-3 compared with Ad-mda7-treated H1299-Neo tumors. Our findings thus showed that the NF-kappaB activation induced by Ad-mda7 treatment of lung cancer cells is an intrinsic survival mechanism and that the inhibition of this NF-kappaB expression results in enhanced tumor cell killing.

Induction of expression of inducible nitric oxide synthase by Taxol in murine macrophage cells

Paclitaxel (Taxol), a microtubule stabilizer with antitumor activity, mimics certain effects of lipopolysaccharide (LPS) in murine macrophages. We examined the mechanism by which Taxol regulates the expression of inducible nitric oxide synthase (iNOS) in a murine macrophage cell line. Taxol alone induced iNOS mRNA and promoter activity, but no iNOS protein or NO production. The stability of the iNOS mRNA formed in response to Taxol was lower than that formed in response to IFN-gamma or LPS, and this may have been responsible for the lack of induction of iNOS protein and NO. However, IFN-gamma synergized with Taxol by increasing iNOS mRNA stability, and upregulating levels of iNOS mRNA and protein, promoter activity, and NO production. Transfection experiments with 5'-serial deletions and site-directed mutants of the iNOS promoter revealed that the pair of upstream and downstream NF-kappaB sites was crucial for promoter activity in response to Taxol, as in the case of LPS. Electrophoretic mobility shift assays showed that both Taxol and LPS rapidly activated identical NF-kappaB complexes that could bind to the iNOS promoter. These results suggest that Taxol shares a signaling pathway for transcriptional activation of iNOS with LPS, but that the stability of the iNOS mRNA induced by Taxol is different from that induced by LPS.

In vitro hemocompatibility studies of drug-loaded poly-(L-lactic acid) fibers

Our objective was to evaluate the hemocompatibility of biodegradable stent fibers, employing a closed-loop circulation system filled with human blood. We also investigated the effects of the anti-inflammatory and anti-proliferative drugs curcumin and paclitaxel, incorporated into stent fibers. Fresh whole blood was circulated in four parallel closed-loop systems: the empty tube circuit (control) and tubes containing either a PLLA fiber coil (PLLA), a curcumin-loaded PLLA coil (C-PLLA) or a paclitaxel-loaded PLLA coil (P-PLLA). The influence of PLLA fiber, alone or loaded with drug incorporated during melt-extrusion, on leukocyte and platelet adhesion and activation was determined by flow cytometry. The effects of blood flow and fiber properties on cell deposition were assessed by scanning electron microscopy (SEM). The flow cytometry results clearly demonstrated that PLLA triggers blood cell activation at the site of deployment, as shown by increases in CD11b, CD62P and leukocyte-platelet aggregates, compared to controls. Curcumin and paclitaxel treatments both significantly reduced leukocyte and platelet activation and adhesion to PLLA fibers, as shown by flow cytometry and SEM. Activated leukocytes and platelets revealed significantly lower CD11b and CD62P receptor binding for C-PLLA compared with PLLA alone, and slightly lower for P-PLLA. Reductions in platelet-leukocyte aggregates were observed as well. In addition, there was less leukocyte and platelet adhesion to C-PLLA, compared with PLLA fiber controls, as shown by SEM. A continuous linear thrombus, composed of platelets, leukocytes, red blood cells and fibrin was occasionally detected along the line of tangency between the coil and the tube wall. Flow separation and eddying, proximal and distal to the line of tangency of coil and tube, is thought to contribute to this deposit. Curcumin was more effective than paclitaxel in reducing leukocyte and platelet activation and adhesion to PLLA stent fibers in this setting. However there was evidence of paclitaxel degeneration during melt extrusion that may have inhibited its effectiveness. Incorporation of the anti-inflammatory and anti-proliferative drug curcumin into bioresorbable stent fibers is proposed to prevent thrombosis and in-stent restenosis.

Isolation of Heptadepsin, a Novel Bacterial Cyclic Depsipeptide that Inhibits Lipopolysaccharide Activity

Lipopolysaccharide (LPS) is considered to cause various inflammatory reactions. We searched among microbial secondary metabolites for compounds that could inhibit LPS-stimulated adhesion between human umbilical vein endothelial cells (HUVEC) and human myelocytic cell line HL-60 cells. In the course of our screening, we isolated a novel cyclic depsipeptide, which we named heptadepsin, from the whole culture broth of Paenibacillus sp. The addition of heptadepsin prior to LPS stimulation decreased HL-60 cell-HUVEC adhesion without showing any cytotoxicity. It also inhibited the cellular adhesion induced by lipid A, the active component of LPS, but it did not inhibit TNF-alpha or IL-1beta-induced cell adhesion. The result of surface plasmon resonance (SPR) analysis revealed that heptadepsin interacted with lipid A directly. Thus, heptadepsin, a novel naturally occurring cyclic heptadepsipeptide, was shown to inactivate LPS by direct interaction with LPS.

Molecular mechanisms of macrophage activation and deactivation by lipopolysaccharide: roles of the receptor complex

Bacterial lipopolysaccharide (LPS), the major structural component of the outer wall of Gram-negative bacteria, is a potent activator of macrophages. Activated macrophages produce a variety of inflammatory cytokines. Excessive production of cytokines in response to LPS is regarded as the cause of septic shock. On the other hand, macrophages exposed to suboptimal doses of LPS are rendered tolerant to subsequent exposure to LPS and manifest a profoundly altered response to LPS. Increasing evidence suggests that monocytic cells from patients with sepsis and septic shock survivors have characteristics of LPS tolerance. Thus, an understanding of the molecular mechanisms underlying activation and deactivation of macrophages in response to LPS is important for the development of therapeutics for septic shock and the treatment of septic shock survivors. Over the past several years, significant progress has been made in identifying and characterizing several key molecules and signal pathways involved in the regulation of macrophage functions by LPS. In this paper, we summarize the current findings of the functions of the LPS receptor complex, which is composed of CD14, Toll-like receptor 4 (TLR4), and myeloid differentiation protein-2 (MD-2), and the signal pathways of this LPS receptor complex with regard to both activation and deactivation of macrophages by LPS. In addition, recent therapeutic approaches for septic shock targeting the LPS receptor complex are described.

An angiogenic switch in macrophages involving synergy between Toll-like receptors 2, 4, 7, and 9 and adenosine A(2A) receptors

Adenosine A(2A) receptor (A(2A)R) agonists synergize with Escherichia coli (E. coli) LPS [toll-like receptor (TLR)4 agonist] to up-regulate vascular endothelial growth factor (VEGF) expression in murine macrophages. Here, we demonstrate that TLR2, TLR7, and TLR9, but not TLR3 and TLR5 agonists, also synergize with A(2A)R agonists and adenosine to up-regulate VEGF, while simultaneously strongly down-regulating TNFalpha expression. In the absence of adenosine or A(2A)R agonists, Porphyromonas gingivalis (P. gingivalis) LPS and PAM(3)CAG (TLR2 agonists), resiquimod (R848) (TLR7 agonist), and non-methylated CpG DNA (TLR9 agonist) strongly up-regulate TNFalpha expression, with no effect on VEGF. In the presence of adenosine or A(2A)R agonists, but not A(1)R agonists, TLR2, 4, 7, and 9 agonists strongly up-regulate VEGF expression, while simultaneously down-regulating TNFalpha. C57BL/10ScN (TLR4 deletion mutant) macrophages produce TNFalpha in response to TLR2, 3, 7, and 9 agonists, but not the TLR4 agonist E. coli LPS. With adenosine or A(2A)R agonists, TLR2, 7, and 9, but not TLR4 agonists, also synergistically up-regulate VEGF, while down-regulating TNFalpha expression. Polyinosinic-polycytidilic acid (poly(I:C)) (TLR3 agonist) stimulates TNFalpha expression in macrophages from both C57BL/10ScSn and C57BL/10ScN mice, but has little effect on VEGF expression in the presence of adenosine or A(2A)R agonists. R-flagellins from Serratia marcescens (S. marcescens) and Salmonella muenchen (S. muenchen) do not stimulate TNFalpha expression in either C57BL/10ScSn or C57BL10/ScN mice, and have no effect on VEGF production in the presence of adenosine or A(2A)R agonists. While adenosine and A(2A)R agonists strongly down-regulate TNFalpha protein expression induced by TLR2, 3, 4, 7, and 9 agonists, TNFalpha mRNA and NF-kappaB activation are not reduced. We propose a novel signaling pathway in murine macrophages involving synergy between TLRs 2, 4, 7, and 9 and A(2A)Rs, that up-regulates VEGF and down-regulates TNFalpha expression, thus acting as an angiogenic switch. This angiogenic switch may play an important role in ischemia when TLR agonists are present, providing an interface between innate immunity and wound healing.

Identification of mouse MD-2 residues important for forming the cell surface TLR4-MD-2 complex recognized by anti-TLR4-MD-2 antibodies, and for conferring LPS and taxol responsiveness on mouse TLR4 by alanine-scanning mutagenesis

The expression of MD-2, which associates with Toll-like receptor (TLR) 4 on the cell surface, confers LPS and LPS-mimetic Taxol responsiveness on TLR4. Alanine-scanning mutagenesis was performed to identify the mouse MD-2 residues important for conferring LPS and Taxol responsiveness on mouse TLR4, and for forming the cell surface TLR4-MD-2 complex recognized by anti-TLR4-MD-2 Ab MTS510. Single alanine mutations were introduced into mouse MD-2 (residues 17-160), and the mutants were expressed in a human cell line expressing mouse TLR4. Mouse MD-2 mutants, in which a single alanine mutation was introduced at Cys37, Leu71, Leu78, Cys95, Tyr102, Cys105, Glu111, Val113, Ile117, Pro118, Phe119, Glu136, Ile138, Leu146, Cys148, or Thr152, showed dramatically reduced ability to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510, and the mutants also showed reduced ability to confer LPS and Taxol responsiveness. In contrast, mouse MD-2 mutants, in which a single alanine mutation was introduced at Tyr34, Tyr36, Gly59, Val82, Ile85, Phe126, Pro127, Gly129, Ile153, Ile154, and His155 showed normal ability to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510, but their ability to confer LPS and Taxol responsiveness was apparently reduced. These results suggest that the ability of MD-2 to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510 is essential for conferring LPS and Taxol responsiveness on TLR4, but not sufficient. In addition, the required residues at codon numbers 34, 85, 101, 122, and 153 for the ability of mouse MD-2 to confer LPS responsiveness are partly different from those for Taxol responsiveness.

Different modes of NF-kappaB/Rel activation in pancreatic lobules

The eukaryotic transcription factor nuclear factor-kappaB (NF-kappaB)/Rel is activated by a large variety of stimuli. It has been demonstrated that NF-kappaB/Rel is induced during the course of cerulein pancreatitis. Here, we show that NF-kappaB/Rel is differentially activated in pancreatic lobules. Cerulein induces NF-kappaB/Rel via activation of IkappaB kinase (IKK), which causes degradation of IkappaBalpha but not IkappaBbeta. Tumor necrosis factor-alpha-mediated IKK activation leads to IkappaBalpha and IkappaBbeta degradation. In contrast, oxidative stress induced by H(2)O(2) activates NF-kappaB/Rel independent of IKK activation and IkappaBalpha degradation; instead IkappaBalpha is phosphorylated on tyrosine. H(2)O(2) but not cerulein-mediated NF-kappaB/Rel activation can be blocked by stabilizing microtubules with Taxol. Inhibition of tubulin polymerization with nocodazole causes NF-kappaB/Rel activation in pancreatic lobules. These results propose three different pathways of NF-kappaB/Rel activation in pancreatic acinar cells. Furthermore, these data demonstrate that microtubules play a key role in IKK-independent NF-kappaB/Rel activation following oxidative stress.

Paclitaxel (Taxol) attenuates clinical disease in a spontaneously demyelinating transgenic mouse and induces remyelination

Treatment with paclitaxel by four intraperitoneal injections (20 mg/kg) 1 week apart attenuated clinical signs in a spontaneously demyelinating model, if given with onset of clinical signs. If given at 2 months of age (1 month prior to clinical signs), disease was almost completely prevented The astrogliosis, prominent in our model, was reversed by paditaxel as determined by astrocyte counts and quantitation of GFAP. Electron microscopic examination of affected regions at 2.5 months demonstrated that the myelin was generally normal. By 4 months of age, demyelination was common in the superior cerebellar peduncle, maximal at 6 months, but continued to 8 months. In addition to myelin vacuolation and nude axons, the presence of many thin myelin sheaths suggested remyelination or partial demyelination. Although no evidence of oligodendrocyte loss was seen, nuclear changes were observed. To substantiate that remyelination was occurring, we measured MBP (18.5 kDa), MBP-exon II, Golli-MBP, TP8, Golli-MBP-J37, platelet-derived growth factor alpha (PDGFR alpha) and sonic hedgehog (SHH). Of these TP8, PDGFR alpha and SHH were up-regulated in the untreated transgenic. After paditaxel treatment, MBP-Exon II, TP8, PDGFR alpha and SHH were further up-regulated. We concluded that some of the effects of paditaxel were to stimulate proteins involved in early myelinating events possibly via a signal transduction mechanism.

Bacterial peptidoglycan binds to tubulin

A search for cellular binding proteins for peptidoglycan (PGN), a CD14- and TLR2-dependent macrophage activator from Gram-positive bacteria, using PGN-affinity chromatography and N-terminal micro-sequencing, revealed that tubulin was a major PGN-binding protein in mouse macrophages. Tubulin also co-eluted with PGN from anti-PGN vancomycin affinity column and bound to PGN coupled to agarose. Tubulin-PGN binding was preferential under the conditions that promote tubulin polymerization, required macromolecular PGN, was competitively inhibited by soluble PGN and tubulin, did not require microtubule-associated proteins, and had an affinity of 100-150 nM. By contrast, binding of tubulin to lipopolysaccharide (LPS) had 2-3 times lower affinity, faster kinetics of binding, and showed positive cooperativity. PGN enhanced tubulin polymerization in the presence of 4 M glycerol, but in the absence of glycerol, both PGN and LPS decreased microtubule polymerization. These results indicate that tubulin is a major PGN-binding protein and that PGN modulates tubulin polymerization.

NF-kappaB/RelA transactivation is required for atypical protein kinase C iota-mediated cell survival

In chronic myelogenous leukemia (CML), the oncogene bcr-abl encodes a dysregulated tyrosine kinase that inhibits apoptosis. We showed previously that human erythroleukemia K562 cells are resistant to antineoplastic drug (taxol)-induced apoptosis through the atypical protein kinase C iota isozyme (PKC iota), a kinase downstream of Bcr-Abl. The mechanism(s) by which PKC iota mediates cell survival to taxol is unknown. Here we demonstrate that PKC iota requires the transcription factor nuclear factor-kappaB (NF-kappaB) to confer cell survival. At apoptosis-inducing concentrations, taxol weakly induces IkappaB(alpha) proteolysis and NF-kappaB translocation in K562 cells, but potently induces its transcriptional activity. Inhibition of NF-kappaB activity (by blocking IkappaB(alpha) degradation) significantly sensitizes cells to taxol-induced apoptosis. Likewise, K562 cells expressing antisense PKC iota mRNA or kinase dead PKC iota (PKC iota-KD) are sensitized to taxol; these cells are rescued from apoptosis by NF-kappaB overexpression. Expression of constitutively active PKC iota (PKC iota-CA) upregulates NF-kappaB transactivation and rescues cells from apoptosis in the absence of Bcr-Abl tyrosine kinase activity. Using a chimeric GAL4-RelA transactivator, we find that taxol potently activates GAL4-RelA-dependent transcription. This activation was further upregulated by expression of PKC iota-CA and inhibited by expression of PKC iota-KD. Our results indicate that RelA transactivation is an important downstream target of the PKC iota-mediated Bcr-Abl signaling pathway and is required for resistance to taxol-induced apoptosis.

Induction of proinflammatory and chemokine genes by lipopolysaccharide and paclitaxel (Taxol) in murine and human breast cancer cell lines

In murine macrophages, the anti-tumor agent, paclitaxel, induces expression of a wide variety of inflammatory and anti-inflammatory genes, and causes cytokine secretion via signaling pathways that overlap with those engaged by lipopolysaccharide (LPS), the endotoxic component of Gram-negative bacteria. Using semi-quantitative RT-PCR for detection of gene expression, coupled with ELISA for the detection of secreted gene products, we analyzed the responsiveness of an extensive panel of cytokine and non-cytokine genes to induction by paclitaxel and LPS in the murine DA-3 breast cancer line. A subset of the genes examined (e.g., G-CSF, MIP-2, iNOS, and IL-1 beta, and GM-CSF) was upregulated >3-20-fold by both LPS and paclitaxel in the DA-3 cell line, while IP-10 mRNA was induced by paclitaxel, but not by LPS. In the human MDA-MB-231 breast cancer cell line, LPS also increased mRNA levels for both GM-CSF and IP-10 significantly, while, paclitaxel increased IP-10 mRNA levels with delayed kinetics and failed to induce GM-CSF mRNA. Co-cultures of murine breast cancer cells and macrophages, stimulated with IFN-gamma plus either paclitaxel or LPS, resulted in augmented release of nitric oxide. As both GM-CSF and IP-10 have been implicated in tumor rejection in vivo through either indirect actions on the host immune system or by inhibiting tumor angiogenesis, our data strengthen the hypothesis that tumor cell-derived inflammatory mediators may, in part, underlie the anti-tumor efficacy of paclitaxel in breast cancer.

The role of ERK 1/2 and p38 MAP-kinase pathways in taxol-induced apoptosis in human ovarian carcinoma cells

Taxol is an anticancer agent of natural origin with significant activity against a number of human cancers including ovarian and breast carcinomas. Its cytotoxic activity has been attributed to its ability to stabilize microtubules and to promote microtubule assembly. Recently it has become clearer that Taxol has additional activities including effects in cell signaling and gene expression. We have shown previously that Taxol activates ERK 1/2 MAP-kinases and results in the formation of GRB2/SHC complexes in murine macrophage-like RAW 267.4 cells. Here we demonstrate that Taxol activates ERK 1/2 and p38 MAP-kinases in human ovarian carcinoma cells with distinct kinetics. Activation of ERK1/2 has been observed at low concentrations of Taxol (1-100 nM) within 0.5-6 h, whereas longer exposure(24 h) to nanomolar concentrations of Taxol resulted in an abrogation of the ERK1/2 phosphorylation/activation. Higher concentrations (1-10 microM) resulted in a sharp inhibition of ERK1/2 activity. p38 kinase was activated by high concentrations (1-10 microM) of Taxol within 2 h and remained active for more than 24 h. The kinetic studies showed that these effects of Taxol coincided with an inhibition of proliferation, and the onset of apoptosis. The appearance of the fragmented chromatin visualized by DAPI staining, and DNA fragments seen on an agarose gel, coincided with the decrease in ERK1/2 activation and concomitant increase of the level of active p38 MAPK. The inhibitor PD98059 abrogated ERK 1/2 activation and increased the cytotoxic effect of Taxol. An inhibitor of p38 kinase, SB203580, protected the cells partially from Taxol and, unexpectedly, activated ERK 1/2 kinases. We conclude that the alternative use of ERK1/2 and p38 MAP-kinase pathways may be necessary for the transition from proliferation state to Taxol-induced apoptosisin human ovarian carcinoma cells.

Inhibition of the NF-kappa B transcription factor increases Bax expression in cancer cell lines

The NF-kappa B transcription factor has been shown to inhibit apoptosis in several experimental systems. We therefore investigated whether the expression of the Bax proapoptotic protein could be influenced by NF-kappa B activity. Increased Bax protein expression was detected in HCT116, OVCAR-3 and MCF7 cells stably expressing a mutated unresponsive I kappa B-alpha inhibitory protein that blocks NF-kappa B activity. Northern blots showed that bax mRNA expression was increased as a consequence of mutated I kappa B-alpha expression in HCT116 cells. A careful examination of the human bax gene promoter sequence showed three putative binding sites for NF-kappa B, and the kappa B2 site at position -687 could indeed bind NF-kappa B complexes in vitro. Transient transfection of a bax promoter luciferase construct in HCT116 cells showed that NF-kappa B proteins could partially inhibit the transactivation of the bax promoter by p53. Mutations or deletions of the kappa B sites, including kappa B2, indicated that this NF-kappa B-dependent inhibitory effect did not require NF-kappa B DNA-binding, and was thus an indirect effect. However, cotransfection of expression vectors for several known cofactors failed to identify a competition between p53 and NF-kappa B for a transcription coactivator. Our findings thus demonstrate for the first time that NF-kappa B regulates, through an indirect pathway, the bax gene expression.

Paclitaxel-induced immune suppression is associated with NF-kappaB activation via conventional PKC isotypes in lipopolysaccharide-stimulated 70Z/3 pre-B lymphocyte tumor cells

Paclitaxel, a potent antitumor agent, has been shown to be lipopolysaccharide (LPS) mimetic in mice, stimulating signaling pathways and gene expression indistinguishably from LPS. In the present study, we showed the intracellular signaling pathway of paclitaxel-induced nuclear factor-kappaB (NF-kappaB) activation and its suppressive effect on LPS-induced signaling in murine 70Z/3 pre-B cells. Stimulation of 70Z/3 cells with LPS for 30 min caused activation of NF-kappaB in the nuclei by detection of DNA-protein binding specific to NF-kappaB. Similarly, paclitaxel also produced a marked and dose-related NF-kappaB activation. However, pretreatment of cells with 10 microM paclitaxel for 18 h resulted in complete inhibition of LPS-mediated NF-kappaB activation. Interestingly, the activity of IkappaB kinase (IKK-beta), which plays an essential role in NF-kappaB activation through IkappaB phosphorylation, was largely enhanced in paclitaxel-treated cells, detected as IkappaBalpha phosphorylation. Because protein kinase C (PKC) is implicated in the activation of NF-kappaB via IKK-beta, the effect of paclitaxel on PKC activation was also measured. It was shown that NF-kappaB nuclear translocation and DNA binding in response to paclitaxel was completely blocked by the conventional PKC inhibitor, Gö 6976. Moreover, immunoblotting analysis with paclitaxel-treated cell extract demonstrated that the conventional PKC isotype PKC-alpha was found to be involved in the regulation of paclitaxel-induced NF-kappaB activation, as determined by electrophoretic mobility shift of PKC. Therefore, these data suggest that paclitaxel may activate IKK-beta via conventional PKC isotypes, resulting in NF-kappaB activation and, finally, desensitization of LPS-inducible signaling pathway in 70Z/3 pre-B cells.

Cutting edge: Gln22 of mouse MD-2 is essential for species-specific lipopolysaccharide mimetic action of taxol

MD-2 associates with the extracellular domain of Toll-like receptor 4 (TLR4) and greatly enhances LPS signaling via TLR4. Taxol, which mimics the action of LPS on murine macrophages, induces signals via mouse TLR4-MD-2, but not via human TLR4-MD-2. Here we investigated the molecular basis for this species-specific action of Taxol. Expression of mouse MD-2 conferred both LPS and Taxol responsiveness on human embryonic kidney 293 cells expressing mouse TLR4, whereas expression of human MD-2 conferred LPS responsiveness alone, suggesting that MD-2 is responsible for the species-specificity as to Taxol responsiveness. Furthermore, mouse MD-2 mutants, in which Gln(22) was changed to other amino acids, showed dramatically reduced ability to confer Taxol responsiveness, although their ability to confer LPS responsiveness was not affected. These results indicated that Gln(22) of mouse MD-2 is essential for Taxol signaling but not for LPS signaling.

CD11b/CD18 acts in concert with CD14 and Toll-like receptor (TLR) 4 to elicit full lipopolysaccharide and taxol-inducible gene expression

Overproduction of inflammatory mediators by macrophages in response to Gram-negative LPS has been implicated in septic shock. Recent reports indicate that three membrane-associated proteins, CD14, CD11b/CD18, and Toll-like receptor (TLR) 4, may serve as LPS recognition and/or signaling receptors in murine macrophages. Therefore, the relative contribution of these proteins in the induction of cyclooxygenase 2 (COX-2), IL-12 p35, IL-12 p40, TNF-alpha, IFN-inducible protein (IP)-10, and IFN consensus sequence binding protein (ICSBP) genes in response to LPS or the LPS-mimetic, Taxol, was examined using macrophages derived from mice deficient for these membrane-associated proteins. The panel of genes selected reflects diverse macrophage effector functions that contribute to the pathogenesis of septic shock. Induction of the entire panel of genes in response to low concentrations of LPS or Taxol requires the participation of both CD14 and TLR4, whereas high concentrations of LPS or Taxol elicit the expression of a subset of LPS-inducible genes in the absence of CD14. In contrast, for optimal induction of COX-2, IL-12 p35, and IL-12 p40 genes by low concentrations of LPS or by all concentrations of Taxol, CD11b/CD18 was also required. Mitigated induction of COX-2, IL-12 p35, and IL-12 p40 gene expression by CD11b/CD18-deficient macrophages correlated with a marked inhibition of NF-kappa B nuclear translocation and mitogen-activated protein kinase (MAPK) activation in response to Taxol and of NF-kappa B nuclear translocation in response to LPS. These findings suggest that for expression of a full repertoire of LPS-/Taxol-inducible genes, CD14, TLR4, and CD11b/CD18 must be coordinately engaged to deliver optimal signaling to the macrophage.

Effect of a synthetic lipid immunomodulator on the regulation of the transcription factor NF-kappaB

Macrophage activation plays a central role in host defense against a variety of pathogens via inducible messengers. The transcription factor NF-kappaB controls the synthesis of cytokines involved in immune responses. In quiescent cells, NF-kappaB is located in the cytosol bound to an inhibitor IkappaB. Upon appropriate signal, NF-KB translocates to the nucleus and binds to DNA. The present study investigated the involvement of an immunomodulator, (diHDA-glycerol) on the NF-kappaB/IkappaB complex. Results were compared to those obtained with lipopolysaccharide (LPS) as a major virulence factor in bacterial sepsis. Data showed that exposure of J774.1 cells either to LPS or diHDA-glycerol substantially increased with time the nuclear levels of NF-kappaB complexes. Antibodies to various NF-kappaB proteins supershifted p50, p65 and to a lesser extent c-rel. Western blot analyses showed a rapid cytosolic IkappaB-alpha turn over following LPS exposure in contrast to diHDA-glycerol treatment. Further experiments investigated the involvement of protein kinase C (PKC) by using two inhibitors, staurosporine and H7. Pretreatment of J774.1 with either inhibitor prior to diHDA-glycerol or LPS exposure decreased NF-kappaB activation. Our results indicate that diHDA-glycerol was acting on NF-kappaB through IkappaB regulative mechanisms differing from those used by LPS. DiHDA-glycerol is likely acting on many other transcription factors targeting distinct genes implied in up regulation of the immune system.

Paclitaxel causes mouse splenic lymphocytes to a state hyporesponsive to lipopolysaccharide stimulation

Multiple immune system actions have been ascribed to paclitaxel (taxol), a novel anticancer drug, including the capacity to induce macrophage antitumor cytotoxic molecule production. In the present studies, we demonstrated that paclitaxel produced a selective inhibition of lipopolysaccharide (LPS)-induced B cell proliferation. Similarly, in vitro polyclonal antibody-forming cell responses also were found to be inhibited by paclitaxel. Conversely, paclitaxel exhibited no inhibitory effects on concanavalin A (Con A)-induced T cell proliferation. To study the pathway leading to paclitaxel-induced immunosuppression, we analyzed Raf-1/ERK and JNK/p38 MAPK pathways, both of which have been reported to be involved in LPS signaling. Our results indicate that taxol treatment inhibits Raf-1 kinase activation while having no effect on ERK activation suggesting that ERK activation is distinct from upstream Raf-1 kinase in taxol-induced immunomodulation. Furthermore, paclitaxel pretreatment caused down-regulation of stress-activated MAPKs, JNK and p38 MAPK in lipopolysaccharide (LPS)-stimulated mouse splenic lymphocytes, demonstrating that spleen cells are induced to a state hyporesponsive to LPS stimulation by pre-exposing them to paclitaxel. Taken together, these results suggest that down-regulation of JNK/p38 MAP kinase may contribute to paclitaxel-induced immunosuppression in mouse splenic lymphocytes.

Mouse toll-like receptor 4.MD-2 complex mediates lipopolysaccharide-mimetic signal transduction by Taxol

Taxol, an antitumor agent derived from a plant, mimics the action of lipopolysaccharide (LPS) in mice but not in humans. Although Taxol is structurally unrelated to LPS, Taxol and LPS are presumed to share a receptor or signaling molecule. The LPS-mimetic activity of Taxol is not observed in LPS-hyporesponsive C3H/HeJ mice, which possess a point mutation in Toll-like receptor 4 (TLR4); therefore, TLR4 appears to be involved in both Taxol and LPS signaling. In addition, TLR4 was recently shown to physically associate with MD-2, a molecule that confers LPS responsiveness on TLR4. To determine whether TLR4.MD-2 complex mediates a Taxol-induced signal, we constructed transformants of the mouse pro-B cell line, Ba/F3, expressing mouse TLR4 alone, both mouse TLR4 and mouse MD-2, and both mouse MD-2 and mouse TLR4 lacking the cytoplasmic portion, and then examined whether Taxol induced NFkappaB activation in these transfectants. Noticeable NFkappaB activation by Taxol was detected in Ba/F3 expressing mouse TLR4 and mouse MD-2 but not in the other transfectants. Coexpression of human TLR4 and human MD-2 did not confer Taxol responsiveness on Ba/F3 cells, suggesting that the TLR4. MD-2 complex is responsible for the species specificity with respect to Taxol responsiveness. Furthermore, Taxol-induced NFkappaB activation via TLR4.MD-2 was blocked by an LPS antagonist that blocks LPS-induced NFkappaB activation via TLR4.MD-2. These results demonstrated that coexpression of mouse TLR4 and mouse MD-2 is required for Taxol responsiveness and that the TLR4.MD-2 complex is the shared molecule in Taxol and LPS signal transduction in mice.

Cytokines IL-1beta, IL-2, IL-6, IL-8, MCP-1, GM-CSF and TNFalpha in patients with epithelial ovarian cancer and their relationship to treatment with paclitaxel

In vitro work suggests that cytokines may be important modulators of the cytotoxic effects of paclitaxel and subsequent drug resistance. This has been investigated in vivo in patients with ovarian cancer by ELISA. There was consistently elevated expression of IL-6 and IL-8 but not MCP-1, IL-1beta, IL-2, GM-CSF or TNFalpha. Peritoneal fluid concentrations of IL-6, IL-8 and MCP-1 were two to three logs greater than serum concentrations. Elevated concentrations of IL-6 correlated with a poor final outcome (P = 0.039), and increased IL-6 and IL-8 correlated with a poor initial response to chemotherapy (P = 0.041 and P = 0.041, respectively). There was a relatively clear pattern of change in all three cytokines. In serum, IL-6, IL-8 and MCP-1 decreased with the administration of steroids prior to paclitaxel, and increased in the 24 h after paclitaxel. Postoperative drainage fluid was relatively acellular, preventing flow-cytometric analysis of epithelial cells for apoptosis, but suggested activation of T cells by paclitaxel. IL-6 and IL-8 appear to be of prognostic importance in epithelial ovarian cancer. Treatment with paclitaxel is associated with an increase in expression of a limited number of cytokines in patients with ovarian cancer, notably IL-6, IL-8 and MCP-1.

Use of a Photoactivatable Taxol Analogue to Identify Unique Cellular Targets in Murine Macrophages: Identification of Murine CD18 as a Major Taxol-Binding Protein and a Role for Mac-1 in Taxol-Induced Gene Expression

Taxol, a potent antitumor agent that binds β-tubulin and promotes microtubule assembly, results in mitotic arrest at the G2/M phase of the cell cycle. More recently, Taxol was shown to be a potent LPS mimetic in murine, but not in human macrophages, stimulating signaling pathways and gene expression indistinguishably from LPS. Although structurally unrelated to LPS, Taxol’s LPS-mimetic activities are blocked by inactive structural analogues of LPS, indicating that despite the species-restricted effects of Taxol, LPS and Taxol share a common receptor/signaling complex that might be important in LPS-induced human diseases. To identify components of the putatively shared Taxol/LPS receptor, a novel, photoactivatable Taxol analogue was employed to identify unique Taxol-binding proteins in murine macrophage membranes. Seven major Taxol-binding proteins, ranging from ∼50 to 200 kDa, were detected. Although photoactivatable Taxol analogue failed to bind to CD14, the prominent Taxol-binding protein was identified as CD18, the ∼96-kDa common component of the β2 integrin family. This finding was supported by the concomitant failure of macrophage membranes from Mac-1 knockout mice to express immunoreactive CD18 and the major Taxol-binding protein. In addition, Taxol-induced IL-12 p40 mRNA was markedly reduced in Mac-1 knockout macrophages and anti-Mac-1 Ab blocked secretion of IL-12 p70 in Taxol- and LPS-stimulated macrophages. Since CD18 has been described as a participant in LPS-induced binding and signal transduction, these data support the hypothesis that the interaction of murine CD18 with Taxol is involved in its proinflammatory activity.

Lipopolysaccharide tolerance in murine peritoneal macrophages induces downregulation of the lipopolysaccharide signal transduction pathway through mitogen-activated protein kinase and nuclear factor-kappaB cascades, but not lipopolysaccharide-incorporation steps

Endotoxin/lipopolysaccharide (LPS) tolerance, a hyporesponsive state to endotoxin or LPS stimulation, was induced in murine peritoneal macrophages by previous exposure of macrophages to LPS. Expression of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 mRNA in response to LPS stimulation was suppressed in LPS-tolerant macrophages. Tyrosine phosphorylations in response to LPS of 40-45-kDa proteins in non-tolerant macrophages were also suppressed in LPS-tolerant macrophages. These proteins corresponded to two members of the mitogen-activated protein kinase (MAPK) family, ERK and p38. In addition to these proteins, another MAPK family protein, JNK, was also suppressed in LPS-tolerant macrophages. Activation of Raf-1, located in the upstream portion of ERK cascades, was also suppressed by LPS-tolerance induction. These suppressions in LPS-tolerant macrophages were exhibited against stimulation by an LPS agonist like taxol, but not towards stimulation by an unrelated activator like phorbol ester (PMA). Activation of the transcription factor NF-kappaB, which is supposed to be one of the components of another important pathway for transduction of LPS-stimulated cytokine producing signals, was strongly suppressed and degradation of IkappaB, an inhibitor of NF-kappaB, was also severely diminished in LPS-tolerant macrophages. Although a monosaccharide lipid A analog, GLA-58, was able to stimulate macrophages to activate ERK proteins without cytokine production, pretreatment of macrophages with this compound suppressed both LPS-stimulated activation of ERK and cytokine production. Furthermore, downregulation of LPS-uptake in LPS-tolerant macrophages was not observed. Based on all these findings, LPS tolerance might be caused by the previous activation of some components on LPS-signaling pathways. This may then induce a refractory state in key LPS-signal transducer molecules located downstream of the cell membrane LPS receptor and upstream of the branching point in intracellular cascades for activation of MAPK and NF-kappaB, probably in some initial steps of intracellular signaling.

Cutting Edge: Functional Characterization of the Effect of the C3H/HeJ Defect in Mice that Lack an Lps n Gene: In Vivo Evidence for a Dominant Negative Mutation

A point mutation in the Tlr4 gene, which encodes Toll-like receptor 4, has recently been proposed to underlie LPS hyporesponsiveness in C3H/HeJ mice (Lpsd). The data presented herein demonstrate that F1 progeny from crosses between mice that carry a ∼9-cM deletion of chromosome 4 (including deletion of LpsTlr4) and C3H/HeJ mice (i.e., Lps0 × Lpsd F1 mice) exhibit a pattern of LPS sensitivity, measured by TNF activity, that is indistinguishable from that exhibited by Lpsn × Lpsd F1 progeny and whose average response is “intermediate” to parental responses. Thus, these data provide clear functional support for the hypothesis that the C3H/HeJ defect exerts a dominant negative effect on LPS sensitivity; however, expression of a normal Toll-like receptor 4 molecule is apparently not required.

Effect of Taxol and Taxotere on Gene Expression in Macrophages: Induction of the Prostaglandin H Synthase-2 Isoenzyme

Induction of genes encoding cytokines or other, unidentified proteins may contribute to the pharmacological effects of taxol. We hypothesized that prostaglandin H synthase-2 (PGHS-2) was one of the unidentified genes induced by taxol. Taxol alone or taxol plus IFN-γ increased PGE2 formation, PGHS-2 protein expression, and PGHS-2 mRNA expression in RAW 264.7 murine macrophages. The kinetics for mRNA induction, protein expression, and catalysis were self-consistent. A selective inhibitor of PGHS-2 blocked PGE2 formation by cells incubated with taxol; a selective inhibitor of PGHS-1 had no effect. A glucocorticoid blocked the induction of mRNA, the expression of PGHS-2 protein, and the formation of PGE2. Neither taxol alone nor taxol plus IFN-γ altered the expression of the PGHS-1 isoenzyme in RAW 264.7 cells. Taxotere, an analogue that stabilizes microtubules as potently as taxol, did not alter the expression of PGHS-2, implying that its induction in RAW 264.7 murine macrophages did not originate from microtubule stabilization. Taxol and taxotere each induced PGHS-2 expression in human monocytes suspended in 10% human serum. However, human monocytes suspended in 10% bovine serum responded only to LPS, not to taxol or taxotere, implying that they act independently of the LPS-mimetic process that is prominent in mice. Taxol induced PGHS-2 in human and murine monocytes via a p38 mitogen-associated protein kinase pathway. The inclusion of PGHS-2 among the early response genes induced in leukocytes may be relevant to the beneficial and adverse effects encountered during taxol administration.

Induction of adrenomedullin mRNA and protein by lipopolysaccharide and paclitaxel (Taxol) in murine macrophages

Lipopolysaccharide (LPS), a potent inflammatory stimulus derived from the outer membrane of gram-negative bacteria, has been implicated in septic shock. Plasma levels of adrenomedullin (AM), a potent vasorelaxant, are increased in septic shock and possibly contribute to the characteristic hypotension. As macrophages play a central role in the host response to LPS, we studied AM production by LPS-stimulated macrophages. When peritoneal exudate macrophages from C3H/OuJ mice were treated with protein-free LPS (100 ng/ml) or the LPS mimetic paclitaxel (Taxol; 35 microM), an approximately 10-fold increase in steady-state AM mRNA levels was observed, which peaked between 2 and 4 h. A three- to fourfold maximum increase in the levels of immunoreactive AM protein was detected after 6 to 8 h of stimulation. While LPS-hyporesponsive C3H/HeJ macrophages failed to respond to protein-free LPS with an increase in steady-state AM mRNA levels, increased levels were observed after stimulation of these cells with a protein-rich (butanol-extracted) LPS preparation. In addition, increased AM mRNA was observed following treatment of either C3H/OuJ or C3H/HeJ macrophages with soluble Toxoplasma gondii tachyzoite antigen or the synthetic flavone analog 5, 6-dimethylxanthenone-4-acetic acid. Gamma interferon also stimulated C3H/OuJ macrophages to express increased AM mRNA levels yet was inhibitory in the presence of LPS or paclitaxel. In vivo, mice challenged intraperitoneally with 25 microg of LPS exhibited increased AM mRNA levels in the lungs, liver, and spleen; the greatest increase (>50-fold) was observed in the liver and lungs. Thus, AM is produced, by murine macrophages, and furthermore, LPS induces AM mRNA in vivo in a number of tissues. These data support a possible role for AM in the pathophysiology of sepsis and septic shock.

Paclitaxel (Taxol)-induced killing of Leishmania major in murine macrophages

The antitumor drug paclitaxel (Taxol) has been demonstrated to be a lipopolysaccharide mimetic in murine macrophages. In this study, the capacity of paclitaxel to activate macrophages to become microbicidal for Leishmania major was examined. Paclitaxel and gamma interferon synergized to kill intracellular L. major in Lpsn, but not Lpsd, macrophages by a nitric oxide (NO.)-dependent mechanism.

Glucocorticoid-induced apoptosis and regulation of NF-kappaB activity in human leukemic T cells

Glucocorticoid-induced apoptosis was investigated in glucocorticoid-sensitive 6TG1.1 and resistant ICR27TK.3 human leukemic T cells. Following glucocorticoid treatment of 6TG1.1 cells, chromatin fragmentation was observed after a delay of 24 h. Fragmentation was not observed in ICR27TK.3 cells containing mutant glucocorticoid receptors (L753F) that are activation-deficient but retain the ability to repress AP-1 activity. Nor was fragmentation observed after treatment with RU38486, indicating that repression of AP-1 activity is not involved. As described in other systems, fragmentation required ongoing protein synthesis. However, inhibition of protein synthesis with cycloheximide anytime during the first 18 h of steroid treatment was as effective in blocking chromatin fragmentation as inhibition for the entire period, suggesting that synthesis of a component with a rapid turnover rate is required. Dexamethasone treatment completely blocked 12-O-tetradecanoylphorbol 13-acetate induction of nuclear factor-kappaB (NF-kappaB) activity and elicited an increase in the amount of immunoreactive IkappaB alpha in sensitive 6TG1.1 cells but not in resistant ICR27TK.3 cells. In addition, mild detergent treatment of cell extracts indicated that a substantial amount of cytoplasmic NF-kappaB is complexed with IkappaB alpha or some other inhibitory factor. These results suggest that induction of a labile inhibitory factor such as IkappaB alpha may contribute to glucocorticoid-induced apoptosis.

Taxane-mediated gene induction is independent of microtubule stabilization: induction of transcription regulators and enzymes that modulate inflammation and apoptosis

Pharmacological traits of the antineoplastic agent taxol may originate in part from its effects on gene expression and not simply from its effects on microtubule assembly. This prompts three questions. First, how extensive is gene induction by taxol? Second, is gene induction confined to taxol itself, or does it occur with other taxane analogs? Third, do the functions of any induced genes correspond with known attributes of taxol or taxane analogs? We report that taxol induces numerous early-response genes, not just cytokine genes. Previously unidentified taxol-induced genes include genes coding transcription factors with tumor suppressor effects (krox-24) and enzymes that govern proliferation, apoptosis, and inflammation (2'5'-oligoadenylate synthase, cyclooxygenase-2, and an IkappaB kinase termed chuk). Taxotere, a potent analog of taxol, did not induce any of these genes, implying that taxol modulates gene expression by a mechanism that is distinct from microtubule stabilization and cell cycle arrest. Other taxane analogs induce some of the same genes as taxol, indicating that this process is not unique to taxol. Functional changes coincided with changes in gene expression. For instance, induction of tumor necrosis factor alpha (TNFalpha) accentuated apoptosis in cells treated with taxol compared with corresponding cells treated with taxotere. The functions of several induced genes (e.g., krox-24 and cyclooxygenase-2) are self-consistent with beneficial and adverse effects encountered during taxol administration. These results may be relevant to the safe and effective use of taxol or its analogs in oncology and other areas of medicine.

Lipopolysaccharide (LPS)-induced IL-6 production by embryonic fibroblasts isolated and cloned from LPS-responsive and LPS-hyporesponsive mice

Fibroblasts participate in inflammatory processes and non-specific immunity by producing cytokines and mediators in response to bacterial lipopolysaccharide (LPS). The detailed mechanism of LPS-induced cytokine production by fibroblasts has not been sufficiently studied. We isolated murine embryonic fibroblasts (MEF) from LPS-responsive C3H/HeN mice and LPS-hyporesponsive C3H/HeJ mice and established MEF cell lines and MEF clones. Primarily cultured MEF, MEF cell lines and MEF clones from C3H/HeN mice (MEF.He) expressed interleukin (IL)-6 mRNA and produced IL-6 molecules in response to even a very low dose (1 ng/ml) of LPS. By contrast, those from C3H/HeJ mice (MEF.HeJ) neither expressed IL-6 mRNA nor produced IL-6 in response to 1 ng of LPS per ml, although they expressed IL-6 mRNA and produced IL-6 in response to high doses (more than 100 ng/ml) of LPS. The MEF.He clone, but not the MEF.HeJ clone, expressed IL-6 mRNA in response to taxol or ceramide, whereas MEF.HeJ clones as well as the MEF.He clone expressed IL-6 mRNA in response to IL-1alpha. These results indicate that in the responses to LPS, taxol and ceramide, MEF retain the same reactivity as that of the mouse strains from which the MEF were derived, and LPS shares the IL-6 signal transduction pathway with taxol and ceramide, but not with IL-1. CD14 is not relevant to the LPS-induced IL-6 production by MEF, since cloned MEF.He and MEF.HeJ were shown not to express CD14 mRNA by Northern blot analysis. No difference in LPS-specific binding capacity was shown between the MEF.He and MEF.HeJ clones. This finding, together with the fact that hyporesponsiveness of MEF.HeJ to LPS was shown at the level of IL-6 mRNA expression, suggests that the defect in the LPS-induced IL-6 signal transduction pathway in MEF from C3H/HeJ mice is probably located at some site after the LPS-recognition site on the cell surface and before transcription of the IL-6 gene.

Identification of tumor-specific paclitaxel (Taxol)-responsive regulatory elements in the interleukin-8 promoter

Paclitaxel (Taxol) is a novel chemotherapeutic drug that is effective against breast and ovarian cancers. Although the primary target of paclitaxel is microtubules, its efficacy exceeds that of conventional microtubule-disrupting agents, suggesting that it may have additional cellular effects. Previously, we demonstrated that paclitaxel can induce interleukin-8 (IL-8) gene expression at the transcriptional level in subsets of human ovarian cancer lines. In this as well as the previous report, we present evidence that this ability is not linked to the lipopolysaccharide pathway of IL-8 gene induction. The present study identifies the cis-acting elements and trans-acting factors involved in this induction by transfecting DNA constructs containing the 5'-flanking region of the IL-8 gene linked to the chloramphenicol acetyltransferase reporter gene into paclitaxel-responsive and nonresponsive ovarian cancer cells (responsiveness refers to the IL-8 response). Paclitaxel only activated the IL-8 promoter in responsive cells. The AP-1 and NF-kappaB binding sites in the IL-8 promoter are required for activation by paclitaxel; in contrast, a C/EBP site required for IL-8 promoter activation in other cell types is not involved. Gel shift assays demonstrate that paclitaxel causes a marked increase in protein binding to the NF-kappaB and AP-1 consensus binding sequences in the paclitaxel-responsive ovarian cells, but not the nonresponsive cells. The induction of NF-kappaB and AP-1 binding is reduced by the addition of protein kinase C inhibitors and cyclic AMP effector, respectively. These results demonstrate a molecular mechanism for cell-specific paclitaxel-induced IL-8 gene expression which may have clinical relevance.