Ischemic Colitis Associated with Low-volume Oral Sulfate Solution for Bowel Preparation.

Ischemic colitis resulting from bowel preparation for colonoscopy is extremely rare, with only a small number of cases with polyethylene glycol having been reported. Here, we present a patient with ischemic colitis after administration of a low-volume oral sulfate solution (OSS). A 49-year-old female without any significant medical history experienced abdominal pain, vomiting, and hematochezia after ingestion of OSS. She complained of severe abdominal pain during colonoscopy, and diffuse edema, hyperemia, friability, and shallow erosions were present on the transverse, descending, and sigmoid colons. A mucosal biopsy revealed mixed lymphoid inflammatory cell infiltration with de-epithelialization, whereas an abdominal CT scan showed submucosal edema on the transverse colon. A diagnosis of ischemic colitis was made. The patient recovered with fluid and antibiotic therapy without significant sequelae. Although OSS is a clinically validated and generally safe bowel preparation agent, ischemic colitis is a rare complication that should be considered.

Moringa oleifera from Cambodia Ameliorates Oxidative Stress, Hyperglycemia, and Kidney Dysfunction in Type 2 Diabetic Mice.

Recent reports have shown the antidiabetic effect of Moringa oleifera from various parts of the world. However, M. oleifera from Cambodia has never determined. Therefore, the aim of this study was to assess the antidiabetic effect of M. oleifera extract from Cambodia. The leaf ethanolic extract contained flavonoids (31.90 mg/mL), polyphenols (53.03 mg/mL), lycopene (0.042 mg/mL), and ß-carotene (0.170 mg/mL), and possessed 2,2-diphenyl-1-picrylhydrazyl, hydrogen peroxide, and hydroxyl radical scavenging activities of 92.40, 99.25, and 83.57 TE/µM at 1 mg/mL, respectively. Db/db mice were orally administered the leaf extract (150 mg/kg/day) for 5 weeks. M. oleifera treatment significantly ameliorated the altered fasting plasma glucose (from 483 to 312 mg/dL), triglyceride (from 42.12 to 23.00 mg/dL), and low-density lipoprotein cholesterol (from 107.21 to 64.25 mg/dL) compared to control group, and increased the insulin levels from 946 ± 92 to 1678 ± 268 pg/mL. The histopathological damage and expression levels of tumor necrosis factor-alpha, interleukin (IL)-1ß, IL-6, cyclooxygenase-2, and inducible nitric oxide synthase in renal tissue decreased. These results indicate the potential antidiabetic benefits of M. oleifera ethanolic leaf extract.

Primary Retroperitoneal Mucinous Cystadenoma.

Mucinous cystadenomas and cystadenocarcinomas of the ovary are clinically and histopathologically well-established common tumors. However, primary retroperitoneal mucinous cystic tumors are extremely rare, and although their histopathogenesis is still uncertain, several theories have been proposed. Most authors suggest that they develop through mucinous metaplasia in a preexisting mesothelium-lined cyst. An accurate preoperative diagnosis of these tumors is difficult because no effective diagnostic measures have been established. Delay in diagnosis and treatment of this tumor may be fatal for the patient because of complications such as rupture, infection, and malignant transformation. We describe the case of a 31-year-old woman with abdominal pain and a palpable mass. Computed tomography of the abdomen revealed a retroperitoneal cystic mass, which was resected successfully through laparoscopy. Histopathological examination of the resected mass confirmed the diagnosis of a primary retroperitoneal mucinous cystadenoma. The patient was discharged on postoperative day 5 without any complications.

Heat-Killed Enterococcus faecalis EF-2001 Ameliorates Atopic Dermatitis in a Murine Model.

Recent reports have shown the immunomodulatory effect of heat-killed lactic acid bacteria. Atopic dermatitis (AD) is an allergic skin disease, caused by immune dysregulation among other factors. The aim of this study was to assess the effect of heat-killed Enterococcus faecalis EF-2001 (EF-2001) on AD. We established an in vivo AD model by repeated local exposure of Dermatophagoides farinae extract (DFE; house dust mite extract) and 2,4-dinitrochlorobenzene (DNCB) to the ears of mice. After oral administration of EF-2001 for four weeks, the epidermal and dermal ear thickness, mast cell infiltration, and serum immunoglobulin levels were measured. In addition, the gene expression levels of pathogenic cytokines in the ears, lymph nodes, and splenocytes were assayed. EF-2001 attenuated AD symptoms based on the ear thickness, histopathological analysis, and serum immunoglobulin levels. Moreover, EF-2001 decreased the DFE/DNCB-induced expression of various pathogenic cytokines in the ears, lymph nodes, and splenocytes. These results suggest that EF-2001 has therapeutic potential in the treatment of AD owing to its immunomodulatory effects.

Effect of Enterococcus faecalis EF-2001 on experimentally induced atopic eczema in mice.

Here, the effects of heat-killed Enterococcus faecalis EF-2001 (EF-2001) on atopic eczema (AE) were assessed. An AE model was established in vivo by repetitious topical exposure to 1-chloro-2,4-dinitrobenzene (CDNB) and dermatophagoidesfarinae extract (DFE) via application on each ear. Mice were administered EF-2001 orally for 4 weeks, dermal and epidermal ear thickness, mast cell infiltration of the ear tissue, and serum IgE and IgG2a levels were evaluated. Moreover, pathogenic cytokines levels of the ears, splenocytes, and cervical lymph nodes were determined. EF-2001 reduced AE symptoms grounded in the ear thickness, histopathological analysis, and serum IgE levels. Furthermore, EF-2001 attenuated mast cell infiltration in the ears and CDNB/DFE-induced various pathogenic cytokines levels of the ears, splenocytes and cervical lymph nodes. Thus, our data suggested that EF-2001 may have potential medicinal applications in the treatment of AE through its immunomodulatory properties.

Artemisia asiatica Nakai Attenuates the Expression of Proinflammatory Mediators in Stimulated Macrophages Through Modulation of Nuclear Factor-κB and Mitogen-Activated Protein Kinase Pathways.

The present study aimed to examine the anti-inflammatory effects and potential mechanism of action of Artemisia asiatica Nakai (A. asiatica Nakai) extract in activated murine macrophages. A. asiatica Nakai extract showed dose-dependent suppression of lipopolysaccharide (LPS)-induced nitric oxide, inducible nitric oxide synthase, and cyclooxygenase-2 activity. It also showed dose-dependent inhibition of nuclear factor-κB (NF-κB) translocation from the cytosol to the nucleus and as an inhibitor of NF-κB-alpha phosphorylation. The extract's inhibitory effects were found to be mediated through NF-κB inhibition and phosphorylation of extracellular signal-regulated kinase 1/2 and p38 in LPS-stimulated J774A.1 murine macrophages, suggesting a potential mechanism for the anti-inflammatory activity of A. asiatica Nakai. To our knowledge, this is the first report of the anti-inflammatory effects of A. asiatica Nakai on J774A.1 murine macrophages; these results may help develop functional foods possessing an anti-inflammatory activity.

Intravascular papillary endothelial hyperplasia as an aneurysm of the brachial artery.

Intravascular papillary endothelial hyperplasia (IPEH) is a benign lesion of vascular origin characterized by excessive proliferation of endothelial cells in normal blood vessels or aneurysms. A 51-year-old woman presented with a hard pulsatile mass in the left antecubital fossa. Duplex scan imaging revealed a brachial artery aneurysm with intramural thrombus. At surgery, the aneurysm was resected, and the brachio-radio-ulnar artery was bypassed with a saphenous vein graft. Histopathologic examination revealed papillary endothelial hyperplasia with features of epithelioid hemangioma. We present the first reported case of IPEH associated with a brachial artery aneurysm.

Phytocomponent 4-hydroxy-3-methoxycinnamaldehyde ablates T-cell activation by targeting protein kinase C-θ and its downstream pathways.

Autoreactive T-cell responses have a crucial role in the pathology and clinical course of autoimmune diseases. Therefore, controlling the activation of these cells is an important strategy for developing therapies and therapeutics. Here, we identified that 4-hydroxy-3-methoxycinnamaldehyde (4H3MC) has a therapeutic potential for T-cell activation by modulating protein kinase C-θ (PKCθ) and its downstream pathways. Pre- and post-treatment with 4H3MC prevented IL-2 release from human transformed and untransformed T cells at the micromolar concentrations without any cytotoxic effects, in fact more efficiently than its structural analogue 4-hydroxycinnamic acid-a previously reported T-cell inhibitor. In silico analysis showed that 4H3MC is a potential inhibitor of PKC isotypes, including PKCθ-a crucial PKC isotype in T cells. Consistently, 4H3MC significantly blocked PKC activity in vitro and also inhibited the phosphorylation of PKCθ in T cells. 4H3MC had no effect on TCR-mediated membrane-proximal-signalling events such as phosphorylation of Zap70. Instead, it attenuated the phosphorylation of mitogen-activated protein kinases (ERK and p38) and promoter activities of NF-κB, AP-1 and NFAT. Taken together, our results provide the evidences that 4H3MC may have curative potential as a novel immune modulator in a broad range of immunopathological disorders by modulating PKCθ activity.

A patient with eosinophilic gastroenteritis presenting with acute pancreatitis and ascites.

Eosinophilic gastroenteritis (EGE) is a rare disease characterized by focal or diffuse eosinophilic infiltration of the gastrointestinal tract, especially the stomach and duodenum. EGE has vague, nonspecific symptoms, including nausea, vomiting, abdominal pain, diarrhea, weight loss, ascites, and malabsorption. Here, we report a patient with EGE presenting with concurrent acute pancreatitis and ascites. A 68-year-old woman was admitted with abdominal pain, nausea, vomiting, and watery diarrhea. Laboratory findings revealed elevated serum titers of amylase, lipase, and peripheral blood eosinophil count. An abdominopelvic computed tomography scan showed a normal pancreas, moderate amount of ascites, and duodenal thickening. A esophagogastroduodenoscopy showed patchy erythematous mucosal lesions in the 2nd portion of the duodenum. Biopsies from the duodenum indicated eosinophilic infiltration in the lamina propria. The patient was successfully treated with prednisolone and montelukast. Despite its unusual occurrence, EGE may be considered in the differential diagnosis of unexplained acute pancreatitis, especially in a patient with duodenal edema on imaging or peripheral eosinophilia.

Aplotaxene blocks T cell activation by modulation of protein kinase C-θ-dependent pathway.

Aplotaxene, (8Z, 11Z, 14Z)-heptadeca-1, 8, 11, 14-tetraene, is one of the major components of essential oil obtained from Inula helenium root, which is used in Oriental medicine. However, the effects of aplotaxene on immunity have not been investigated. Here, we show that aplotaxene inhibits T cell activation in terms of IL-2 and CD69 expression. Aplotaxene, at a concentration that optimally inhibits IL-2 production, has little effect on apoptotic or necrotic cell death, suggesting that apoptosis is not a mechanism for aplotaxene-mediated inhibition of T cell activation. Aplotaxene affects neither superantigeninduced conjugate formation between Jurkat T cells and Raji B cells nor clustering of CD3 and LFA-1 at the immunological synapse. Aplotaxene significantly inhibits PKC-θ phosphorylation and translocation to the immunological synapse, and blocks PMA-induced T-cell receptor internalization. Furthermore, aplotaxene leads to inhibition of mitogen-activated protein kinases (JNK, ERK and p38) phosphorylation and NF-κB, NF-AT, and AP-1 promoter activities in Jurkat T cells. Taken together, our findings provide evidence for the immunosuppressive effect of aplotaxene on activated T cells through the modulation of the PKC-θ and MAPK pathways, suggesting that aplotaxene may be a novel immunotherapeutic agent for immunological diseases related to the overactivation of T cells.

Dynamic motile T cells highly respond to the T cell stimulation via PI3K-Akt and NF-κB pathways.

T lymphocytes (T cells) circulate from the blood into secondary lymphoid organs for immune surveillance. In this study, we hypothesized that circulating T cells are heterogeneous and can be grouped according to their differential migratory capacity in response to chemoattractants, rather than expressions of certain receptors or cytokines. We further hypothesized that, at least in part, this intrinsic difference in motility may be related to the T cell function. We established motile (m-T) and non-motile T (nm-T) cell lines based on their response to the chemokine SDF-1α. m-T cells showed more irregular and polarized morphologies than nm-T cells did. Interestingly, m-T cells produced higher levels of IL-2, a marker for T cell activation, than nm-T cells did after stimulation; however, no differences were observed in terms of surface expression of T cell receptors (TCR), adhesion molecules LFA-1 and ICAM-1, and chemokine receptor CXCR4. Both cell lines also showed similar membrane events (i.e., T cell-APC conjugation, LFA-1 accumulation at the immunological synapse, and TCR internalization). In contrast, PKC-θ, a downstream of PI3K-Akt pathway was constitutively activated in m-T cells and the activation was more prominent during T cell stimulation. Consequently, NF-κB activity was selectively upregulated in m-T cells. This study is the first, to our knowledge, to demonstrate that T cells can be subcategorized on the basis of their intrinsic migratory capacity in relation to T cell activation.

Identifying Polymorphisms in IL-31 and Their Association with Susceptibility to Asthma.

BACKGROUND: Interleukin 31 (IL-31) is a T helper type 2 effector cytokine that plays an important role in the pathogenesis of atopic and allergic diseases. IL-31 may be involved in promoting allergic inflammation and in inducing airway epithelial responses such as allergic asthma. METHODS: Single-base extension analysis was used to detect the genotypes of IL-31 single nucleotide polymorphisms (SNPs), and we compared the genotype and allele frequencies of the IL-31 SNPs between patients with asthma and healthy controls. RESULTS: There were no significant differences in the genotype and allele frequencies of the IL-31 SNPs between patients with asthma and healthy controls. Furthermore we compared the genotype and allele frequencies of IL-31 SNPs between patients with atopic asthma, those with non-atopic asthma and healthy controls. This showed that the SNPs were not associated with the susceptibility to atopic asthma. There were no significant differences in the haplotype frequencies of IL-31 SNPs between patients with asthma and healthy controls. In patients with asthma, the IL-31 SNPs were significantly correlated with total serum levels of IgE (p=0.035). CONCLUSIONS: Our results indicate that, the IL-31 SNPs may be associated with IgE production in patients with asthma.

Phytocomponent p-Hydroxycinnamic acid inhibits T-cell activation by modulation of protein kinase C-θ-dependent pathway.

The phytocomponent p-hydoxycinnamic acid (HCA) has been shown to have many beneficial effects in terms of antioxidant activity, inhibition of melanogenesis, bone resorption, and platelet activity, and stimulation of mineralization. However, effects of HCA in immune functions have not been investigated. Here, we show that HCA has a profound effect on IL-2 production in Jurkat T cells as well as in human peripheral blood leukocytes. HCA, at a concentration that optimally inhibits IL-2 production, had little effect on apoptotic or necrotic cell death of Jurkat T cells, suggesting that apoptosis is not a mechanism for HCA-induced T-cell suppression. On the contrary, HCA dramatically inhibited PKC-θ accumulation and further phosphorylation at the immunological synapse which formed at the contact site between T cells and superantigen SEE-loaded antigen presenting cells. In addition, HCA significantly inhibited ERK and p38 kinase phosphorylation in both anti-CD3/28- and PMA/A23187-stimulated T cells. Consequently, HCA inhibited both AP-1 and NF-κB promoter activities in Jurkat T cells. Collectively, our results provide evidence for the immunosuppressive effect of HCA on activated T cells, through modulation of PKC-θ pathway.

Eupatilin exhibits a novel anti-tumor activity through the induction of cell cycle arrest and differentiation of gastric carcinoma AGS cells.

In many cases, the process of cancer cell differentiation is associated with the programmed cell death. In the present study, interestingly, we found that eupatilin, one of the pharmacologically active ingredients of Artemisia asiatica that has been reported to induce apoptosis in human gastric cancer AGS cells, also triggers differentiation of these cells. Treatment of AGS cells with eupatilin induced cell cycle arrest at the G(1) phase with the concomitant induction of p21(cip1), a cell cycle inhibitor. This led us to test whether eupatilin may trigger AGS cells to differentiate into the matured phenotypes of epithelial cells and this phenomenon may be coupled to the apoptosis. Eupatilin induced changes of AGS cells to a more flattened morphology with increased cell size, granularity, and mitochondrial mass. It also markedly induced trefoil factor 1 (TFF1), a gene responsible for the gastrointestinal cell differentiation. Eupatilin dramatically induced redistribution of tight junction proteins such as occludin and ZO-1, and F-actin at the junctional region between cells. It also induced phosphorylation of extracellular signal-regulated kinase 2 and p38 kinase. Blockade of ERK signaling by PD098059 or the dominant-negative ERK2 significantly reduced eupatilin-induced TFF1 and p21 expression as well as ZO-1 redistribution, indicating that ERK cascades may mediate eupatilin-induced AGS cell differentiation. Collectively, our results suggest that eupatilin acts as a novel anti-tumor agent by inducing differentiation of gastrointestinal cancer cells rather than its direct role in inducing apoptotic cell death.

Ammonium glycyrrhizinate protects gastric epithelial cells from hydrogen peroxide-induced cell death.

Glycyrrhiza uralensis has a potential for preventing or ameliorating gastric mucosal ulceration. To understand the molecular mechanism about the medicinal effect of G. uralensis, we isolated four single compounds from G. uralensis and one related compound and screened for the cellular protective effect against H(2)O(2)-induced damage in gastric epithelial AGS cells. Interestingly, we found that ammonium glycyrrhizinate (AG) prepared from glycyrrhizin dramatically protects AGS cells from H(2)O(2)-induced damage as measured by the integrity of actin cytoskeleton. AG also inhibited FeSO(4)-induced reactive oxygen radicals in a dose-dependent manner, suggesting the role for AG as a free radical scavenger. To better understand the protective role of AG at the transcriptional level, we performed genome-wide expression profiling using high-density oligonucleotide microarrays, followed by validation using RT-PCR. Among the 33,096 genes that were screened in the microarray, 936 genes were found to be differentially expressed in a statistically significant manner in the presence or absence of H(2)O(2) and AG. Among the 936 genes, 51 genes were differentially expressed at least 3-fold in response to the H(2)O(2) treatment. AG blocked the expression of genes related to apoptotic cell death (GDF15, ATF3, TNFRSF10A, NALP1) or oxidative stress path-ways (HMOX1) which was elevated in response to H(2)O(2) treatment, suggesting a potential protective role for AG in oxidative stress-induced cell death. Collectively, current results demonstrate that AG is a novel antioxidant that could be effective for the treatment of gastric diseases related to the oxidative stress-induced mucosal damage.

Induction and localization of NOD2 protein in human endothelial cells.

NOD2 is mainly expressed in human monocytes/macrophages and intestinal epithelial cells and has been speculated to play in gut physiology. However, whether NOD2 is expressed in vascular endothelium is not currently determined. Human umbilical vascular endothelial cells (HUVECs) minimally expressed NOD2 gene, whereas stimulation of HUVEC with bacterial LPS, IL-1beta, or TNF-alpha resulted in significant up-regulation of NOD2. NOD2 protein was mostly localized in the cytoplasm. Overexpression of wild-type NOD2 (WT-NOD2) gene induced NF-kappaB-dependent transcriptional activity and this activity was further increased by muramyl dipeptide (MDP). Otherwise, down-regulation of WT-NOD2 gene by antisense NOD2 abolished NF-kappaB-dependent transcriptional activity mediated by either WT-NOD2 itself or MDP. Since vascular endothelial cells, like macrophages and epithelial cells, are critical targets for the circulating bacterial molecules such as MDP, collectively, the results presented here suggest that NOD2 may play an important role in recognizing structural patterns of bacterial pathogen in the endothelium.

Increased expression of MIP-3alpha/CCL20 in peripheral blood mononuclear cells from patients with ulcerative colitis and its down-regulation by sulfasalazine and glucocorticoid treatment.

UNLABELLED: CCL20 expression is known to increase in the mucosal tissues of inflammatory bowel diseases (IBDs). Moreover, the discovery of Nod2 as the IBD1 susceptibility gene has underscored the significance of blood mononuclear cells in IBD pathogenesis. METHODS: This study addresses whether CCL20 expression is similarly altered in peripheral blood mononuclear cells (PBMCs) of patients with ulcerative colitis (UC), a major type of IBD in Korea. RESULTS: Expression of CCL20 was significantly up-regulated in the PBMCs of patients with UC compared with those of normal healthy controls. Interestingly, untreated UC groups expressed higher levels of CCL20 mRNA than either treated UC or normal control groups, suggesting that CCL20 could be modulated by anti-inflammatory drugs. Accordingly, a strong association between CCL20 levels and disease activity index was observed. Supporting these findings, results from a 3-month follow-up study revealed that the UC groups treated with 5-aminosalicylic acid and glucocorticoid exhibited dramatic decreases of CCL20 mRNA in PBMCs, accompanied by ameliorated disease states. Moreover, tumor necrosis factor-alpha- or interleukin-1beta-induced CCL20 secretion was greatly diminished by 5-aminosalicylic acid and/or glucocorticoid treatment of human intestinal epithelial HT-29 cells. Of note, CCR6 cell populations were significantly reduced in the blood of severe patients with UC compared with normal controls, whereas no significant changes in CCR6 cell populations were observed in the blood of patients with mild UC or acute colitis. CONCLUSIONS: Collectively, these findings suggest that CCL20 expression in blood mononuclear cells is associated with altered immune and inflammatory responses in patients with UC.

Combined action of extracellular signal-regulated kinase and p38 kinase rescues Molt4 T cells from nitric oxide-induced apoptotic and necrotic cell death.

The mechanisms that regulate nitric oxide (NO)-induced apoptosis, especially in T cell apoptosis, are largely uncharacterized. Here, we report that protection from NO-induced cell death by phorbol 12-myristate 13-acetate (PMA) is dependent on both p38 and extracellular signal-regulated kinase (ERK) activation. Exposure of Molt4 cells to NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) induced both apoptotic and necrotic modes of cell death along with a sustained increase in p38 kinase phosphorylation. However, the p38 inhibitor SB202190 only slightly protected Molt4 cells from NO toxicity. In contrast, PMA rapidly phosphorylated both p38 kinase and ERK, and the phosphorylation statuses were not altered in the presence of SNAP. Interestingly, although each mitogen-activated protein kinase (MAPK) inhibitor by itself had only a modest effect, the combination of inhibitors for both MAPKs almost completely abolished the protective effect of PMA. Furthermore, dominant negative or catalytically inactive variants that modulate p38 and ERK mimicked the effects of MAPK inhibitors. We located the action of p38 and ERK upstream of the p53/mitochondrial membrane potential loss and caspases cascade. Together, these findings suggest that the PMA-induced activations of ERK and p38 kinase are parallel events that are both required for inhibition of NO-induced death of Molt4 cells.

Iron chelator triggers inflammatory signals in human intestinal epithelial cells: involvement of p38 and extracellular signal-regulated kinase signaling pathways.

Competition for cellular iron (Fe) is a vital component of the interaction between host and pathogen. Most bacteria have an obligate requirement for Fe to sustain infection, growth, and survival in host. To obtain iron required for growth, many bacteria secrete iron chelators (siderophores). This study was undertaken to test whether a bacterial siderophore, deferoxamine (DFO), could trigger inflammatory signals in human intestinal epithelial cells as a single stimulus. Incubation of human intestinal epithelial HT-29 cells with DFO increased the expression of IL-8 mRNA, as well as the release of IL-8 protein. The signal transduction study revealed that both p38 and extracellular signal-regulated kinase-1/2 were significantly activated in response to DFO. Accordingly, the selective inhibitors for both kinases, either alone or in combination, completely abolished DFO-induced IL-8 secretion, indicating an importance of mitogen-activated protein kinases pathway. These proinflammatory effects of DFO were, in large part, mediated by activation of Na(+)/H(+) exchangers, because selective blockade of Na(+)/H(+) exchangers prevented the DFO-induced IL-8 production. Interestingly, however, DFO neither induced NF-kappaB activation by itself nor affected IL-1beta- or TNF-alpha-mediated NF-kappaB activation, suggesting a NF-kappaB-independent mechanism in DFO-induced IL-8 production. Global gene expression profiling revealed that DFO significantly up-regulates inflammation-related genes including proinflammatory genes, and that many of those genes are down-modulated by the selective mitogen-activated protein kinase inhibitors. Collectively, these results demonstrate that, in addition to bacterial products or cell wall components, direct chelation of host Fe by infected bacteria may also contribute to the evocation of host inflammatory responses.

Soluble factor from murine bladder tumor-2 cell elevates nitric oxide production in macrophages and enhances the taxol-mediated macrophage cytotoxicity on tumor cells.

The therapeutic mechanism of taxol is believed to reside primarily in its ability to stabilize microtubules and prevent cell progression through mitosis. Taxol also can activate macrophage-mediated antitumor mechanism through a nitric oxide (NO)-dependent pathway. To address whether any mechanisms account for superficial urinary bladder tumor cell killing, we evaluated the effects of taxol on the growth and viability of murine bladder tumor-2 (MBT-2) cells in vitro, both in the absence and presence of murine macrophages. In addition, we evaluated whether a soluble factor generated from MBT-2 cells could modulate the antitumor activity of the taxol-activated macrophages. Although taxol inhibited the growth of MBT-2 cells, it did not kill the tumor cells. However, preincubation of macrophages with taxol significantly decreased the viability of MBT-2 cells. Secretion of NO correlated with MBT-2 cell killing, and the activated macrophages failed to kill tumor cell targets in the presence of NG-monomethyl-L-arginine, a competitive inhibitor of NO synthase. By the co-culture of macrophages and MBT-2 cells, untreated macrophages also released modest amount of NO and this was synergistically augmented by the treatment with taxol, indicating that MBT-2 tumor cells released some unknown factor that activated the macrophages and enhanced NO production. We named this factor the tumor-derived macrophage activating factor (TMAF). The TMAF-mediated activation of macrophages to enhance the NO production was not blocked by treatment of macrophages with oxidized low-density lipoprotein (Ox-LDL), implying that the scavenger receptor of macrophages is not involved. Sodium nitroprusside (SNP), an NO donor given to the MBT-2 cells, increased the activities of c-Jun N-terminal kinase and caspase-3 in MBT-2 cells and associated with nucleosomal fragmentation or apoptosis, whereas taxol had no direct effect on these parameters. Collectively, our results strongly suggest that taxol kills the murine bladder tumor cells through indirect activation of macrophages via NO-dependent apoptosis, instead of its better-known role as the direct antimitotic action. Our results further demonstrate that TMAF acts in synergy with taxol to activate the macrophages to elicit enhanced tumor cell killing ability.