OBJECTIVE: To explore the expression patterns, prognostic implications, and biological role of leukotriene B4 receptor (LTB4R) in patients with acute myeloid leukemia (AML). METHODS: We collected the data of mRNA expression levels and clinical information of patients with AML from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database for mRNA expression analyses, survival analyses, Cox regression analyses and correlation analyses using R studio to assess the expression patterns and prognostic value of LTB4R. The correlation of LTB4R expression levels with clinical characteristics of the patients were analyzed using UALCAN. The co-expressed genes LTB4R were screened from Linkedomics and subjected to functional enrichment analysis. A protein-protein interaction network was constructed using STRING. GSEA analyses of the differentially expressed genes (DEGs) were performed based on datasets from TCGA-LAML stratified by LTB4R expression level. We also collected peripheral blood mononuclear cells (PBMCs) from AML patients and healthy donors for examination of the mRNA expression levels of LTB4R and immune checkpoint genes using qRT-PCR. We also examined serum LTB4R protein levels in the patients using ELISA. RESULTS: The mRNA expression level of LTB4R was significantly increased in AML patients (4.898±1.220 vs 2.252±0.215, P < 0.001), and an elevated LTB4R expression level was correlated with a poor overall survival (OS) of the patients (P=0.004, HR=1.74). LTB4R was identified as an independent prognostic factor for OS (P=0.019, HR=1.66) and was associated with FAB subtypes, cytogenetic risk, karyotype abnormalities and NPM1 mutations. The co- expressed genes of LTB4R were enriched in the functional pathways closely associated with AML leukemogenesis, including neutrophil inflammation, lymphocyte activation, signal transduction, and metabolism. The DEGs were enriched in differentiation, activation of immune cells, and cytokine signaling. Examination of the clinical serum samples also demonstrated significantly increased expressions of LTB4R mRNA (P=0.044) and protein (P=0.008) in AML patients, and LTB4R mRNA expression was positively correlated with the expression of the immune checkpoint HAVCR2 (r= 0.466, P=0.040). CONCLUSION LTB4R can serve as a novel biomarker and independent prognostic indicator of AML and its expression patterns provide insights into the crosstalk of leukemogenesis signaling pathways involving tumor immunity and metabolism.
Humans ; Leukemia, Myeloid, Acute/metabolism* ; Leukocytes, Mononuclear/metabolism* ; Prognosis ; RNA, Messenger/metabolism* ; Receptors, Leukotriene B4/genetics*

Leukotriene B4(LTB4), derived from arachidonic acid, is a potent chemotactic agent and activating factor for hematopoietic cells. In addition to host defense in vivo, several eicosanoids have been reported to be involved in stem cell differentiation or proliferation. In this study, we investigated the effect of LTB4 on human cord blood CD34+ hematopoietic stem cells (HSCs). LTB4 was shown to induce proliferation of HSC and exert anti-apoptotic effect on the stem cells. Blockade of interaction between LTB4 and its receptor enhanced self-renewal of the stem cells. Effect of LTB4 on differentiation of CD34+ HSCs were confirmed by clonogenic assays, and induction of the expression of BLT2 (the low- affinity LTB4 receptor), during the ex vivo expansion was confirmed by reverse transcription-PCR. Our results suggest that LTB4-BLT2 interaction is involved in the cytokine-induced differentiation and ex vivo expansion of hematopoietic stem cells.
Antigens, CD34/metabolism ; Apoptosis/drug effects ; Cell Differentiation/drug effects ; Cell Proliferation/drug effects ; Fetal Blood/cytology/drug effects ; Hematopoietic Stem Cells/*drug effects/metabolism ; Humans ; Leukotriene B4/*pharmacology ; Receptors, Leukotriene B4/genetics/metabolism ; Research Support, Non-U.S. Gov't ; Reverse Transcriptase Polymerase Chain Reaction ; *Signal Transduction

The incidence rates of urinary bladder cancer continue to rise yearly, and thus new therapeutic approaches and early diagnostic markers for bladder cancer are urgently needed. Thus, identifying the key mediators and molecular mechanisms responsible for the survival of bladder cancer has valuable implications for the development of therapy. In this study, the role of BLT2, a receptor for leukotriene B4 (LTB4) and 12(S)-hydroxyeicosatetraenoic acid (HETE), in the survival of bladder cancer 253J-BV cells was investigated. We found that the expression of BLT2 is highly elevated in bladder cancer cells. Also, we observed that blockade of BLT2 with an antagonist or BLT2 siRNA resulted in cell cycle arrest and apoptotic cell death, suggesting a role of BLT2 in the survival of human bladder cancer 253J-BV cells. Further experiments aimed at elucidating the mechanism by which BLT2 mediates survival revealed that enhanced level of reactive oxygen species (ROS) are generated via a BLT2-dependent up-regulation of NADPH oxidase members NOX1 and NOX4. Additionally, we observed that inhibition of ROS generation by either NOX1/4 siRNAs or treatment with an ROS-scavenging agent results in apoptotic cell death in 253J-BV bladder cancer cells. These results demonstrated that a 'BLT2-NOX1/4-ROS' cascade plays a role in the survival of this aggressive bladder cancer cells, thus pointing to BLT2 as a potential target for anti-bladder cancer therapy.
*Apoptosis ; Blotting, Western ; Cell Proliferation ; Cells, Cultured ; Gene Expression Regulation, Neoplastic/*physiology ; Humans ; Leukotriene Antagonists/pharmacology ; NADPH Oxidase/antagonists & inhibitors/genetics/metabolism ; Phosphorylation ; RNA, Messenger/genetics ; RNA, Small Interfering/genetics ; Reactive Oxygen Species/*metabolism ; Receptors, Leukotriene B4/antagonists & inhibitors/*genetics ; Reverse Transcriptase Polymerase Chain Reaction ; Signal Transduction ; Tetrazoles/pharmacology ; Up-Regulation ; Urinary Bladder Neoplasms/*genetics/mortality

12(S)-Hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT) is an enzymatic product of prostaglandin H2 (PGH2) derived from cyclooxygenase (COX)-mediated arachidonic acid metabolism. Despite the high level of 12-HHT present in tissues and bodily fluids, its precise function remains largely unknown. In this study, we found that 12-HHT treatment in HaCaT cells remarkably down-regulated the ultraviolet B (UVB) irradiation-induced synthesis of interleukin-6 (IL-6), a pro-inflammatory cytokine associated with cutaneous inflammation. In an approach to identify the down-stream signaling mechanism by which 12-HHT down-regulates UVB-induced IL-6 synthesis in keratinocytes, we observed that 12-HHT inhibits the UVB-stimulated activation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-kappaB). In addition, we found that 12-HHT markedly up-regulates MAPK phosphatase-1 (MKP-1), a critical negative regulator of p38 MAPK. When MKP-1 was suppressed by siRNA knock-down, the 12-HHT-mediated inhibitory effects on the UVB-stimulated activation of p38 MAPK and NF-kappaB, as well as the production of IL-6, were attenuated in HaCaT cells. Taken together, our results suggest that 12-HHT exerts anti-inflammatory effect via up-regulation of MKP-1, which negatively regulates p38 MAPK and NF-kappaB, thus attenuating IL-6 production in UVB-irradiated HaCaT cells. Considering the critical role of IL-6 in cutaneous inflammation, our findings provide the basis for the application of 12-HHT as a potential anti-inflammatory therapeutic agent in UV-induced skin diseases.
Anti-Inflammatory Agents, Non-Steroidal/pharmacology ; Cell Line ; Dual Specificity Phosphatase 1/biosynthesis/genetics ; Enzyme Activation ; Fatty Acids, Unsaturated/*pharmacology ; Humans ; Interleukin-6/*biosynthesis ; Keratinocytes/*metabolism/radiation effects ; NF-kappa B/metabolism ; RNA Interference ; RNA, Small Interfering ; Receptors, Leukotriene B4/genetics ; Signal Transduction/drug effects ; Skin Diseases/drug therapy ; *Ultraviolet Rays ; Up-Regulation ; p38 Mitogen-Activated Protein Kinases/metabolism

A variety of benzylidenethiazole analogs have been demonstrated to inhibit 5-lipoxygenase (5-LOX). Here we report the anti-atherogenic potential of 5-(4-hydroxy-2,3,5-trimethylbenzylidene) thiazolidin-2,4-dione (HMB-TZD), a benzylidenethiazole analog, and its potential mechanism of action in LDL receptor-deficient (Ldlr-/-) mice. HMB-TZD Treatment reduced leukotriene B4 (LTB4) production significantly in RAW264.7 macrophages and SVEC4-10 endothelial cells. Macrophages or endothelial cells pre-incubated with HMB-TZD for 2 h and then stimulated with lipopolysaccharide or tumor necrosis factor-alpha (TNF-alpha) displayed reduced cytokine production. Also, HMB-TZD reduced cell migration and adhesion in accordance with decreased proinflammatory molecule production in vitro and ex vivo. HMB-TZD treatment of 8-week-old male Ldlr-/- mice resulted in significantly reduced atherosclerotic lesions without a change to plasma lipid profiles. Moreover, aortic expression of pro-atherogenic molecules involved in the recruitment of monocytes to the aortic wall, including TNF-alpha , MCP-1, and VCAM-1, was downregulated. HMB-TZD also reduced macrophage infiltration into atherosclerotic lesions. In conclusion, HMB-TZD ameliorates atherosclerotic lesion formation possibly by reducing the expression of proinflammatory molecules and monocyte/macrophage recruitment to the lesion. These results suggest that HMB-TZD, and benzylidenethiazole analogs in general, may have therapeutic potential as treatments for atherosclerosis.
Animals ; Atherosclerosis/*drug therapy ; Cell Adhesion/drug effects ; Cell Line ; Cell Movement/drug effects ; Chemokine CCL2/metabolism ; Dinoprostone/metabolism ; Enzyme-Linked Immunosorbent Assay ; Humans ; Leukotriene B4/metabolism ; Macrophages/cytology/drug effects ; Male ; Mice ; Monocytes/cytology/*drug effects ; Random Allocation ; Receptors, LDL/deficiency/genetics ; Thiazolidinediones/*therapeutic use ; Tumor Necrosis Factor-alpha/pharmacology