Cyclooxygenase-2 (Cox-2) and blast cells of patients with acute leukemia

Susceptibility of acute myeloid leukemia cells to ferroptosis and evasion strategies

Acute myeloid leukemia (AML) is a highly aggressive hematologic malignancy with a 5-year survival rate of less than 30%. Continuous updating of diagnostic and therapeutic strategies has not been effective in improving the clinical benefit of AML. AML cells are prone to iron metabolism imbalance due to their unique pathological characteristics, and ferroptosis is a novel cell death mode that is dominated by three cellular biological processes: iron metabolism, oxidative stress and lipid metabolism. An in-depth exploration of the unique ferroptosis mechanism in AML can provide new insights for the diagnosis and treatment of this disease. This study summarizes recent studies on ferroptosis in AML cells and suggests that the metabolic characteristics, gene mutation patterns, and dependence on mitochondria of AML cells greatly increase their susceptibility to ferroptosis. In addition, this study suggests that AML cells can establish a variety of strategies to evade ferroptosis to maintain their survival during the process of occurrence and development, and summarizes the related drugs targeting ferroptosis pathway in AML treatment, which provides development directions for the subsequent mechanism research and clinical treatment of AML.

Inhibitory effect of triamcinolone acetonide on synthesis of inflammatory mediators in the equine

Glucocorticoids (corticosteroids) are widely used anti-inflammatory agents in veterinary medical practice. These drugs are considered doping agents because they mask pain and thus, increase injury potential in equine athletes. They exhibit anti-inflammatory property by binding to glucocorticoids receptor (GR) to control the transcription of pro- and anti-inflammatory cytokines and enzymes involved in the synthesis of bioactive eicosanoids. To evaluate the role of triamcinolone acetonide (TA) on concentrations of bioactive eicosanoids in equine plasma, TA (0.04 mg/kg) was intravenously administered to horses. Before (0 h) and after TA administration, equine whole blood (EWB) samples were collected and challenged with either methanol (vehicle), calcium ionophore A-23187 (CI) or lipopolysaccharide (LPS) to stimulate ex-vivo synthesis of eicosanoids. Plasma concentrations of eicosanoids were quantified using LC-MS/MRM. Results showed that thromboxane B2 (TXB2) was not affected by TA administration when EWB was stimulated with CI. However, after LPS treatment, TXB2, PGE2, PGF2α and 15-(s)-HETE decreased during 2-8 h post-TA administration but recovered to concentrations which were not significantly different from those of pre-TA administration (0 h), after 24 h. When EWB was treated with CI, LTB4 was suppressed post-TA administration compared to 0 h. When EWB collected after TA administration was stimulated with LPS, LTB4 was not significantly different from those of 0 h. Administration of a therapeutic dose of TA (0.04 mg/kg, iv) in the horse suppressed biosynthesis of bioactive eicosanoids indicating the anti-inflammatory role of TA in the horse.

Cyclooxygenase-2 (COX-2) inhibition constrains indoleamine 2,3-dioxygenase 1 (IDO1) activity in acute myeloid leukaemia cells

Indoleamine 2,3-dioxygenase 1 (IDO1) metabolizes L-tryptophan to kynurenines (KYN), inducing T-cell suppression either directly or by altering antigen-presenting-cell function. Cyclooxygenase (COX)-2, the rate-limiting enzyme in the synthesis of prostaglandins, is over-expressed by several tumours. We aimed at determining whether COX-2 inhibitors down-regulate the IFN-g-induced expression of IDO1 in acute myeloid leukaemia (AML) cells. IFN-γ at 100 ng/mL up-regulated COX-2 and IDO1 in HL-60 AML cells, both at mRNA and protein level. The increased COX-2 and IDO1 expression correlated with heightened production of prostaglandin (PG)E₂ and kynurenines, respectively. Nimesulide, a preferential COX-2 inhibitor, down-regulated IDO1 mRNA/protein and attenuated kynurenine synthesis, suggesting that overall IDO inhibition resulted both from reduced IDO1 gene transcription and from inhibited IDO1 catalytic activity. From a functional standpoint, IFN-g-challenged HL-60 cells promoted the in vitro conversion of allogeneic CD4⁺CD25⁻ T cells into bona fide CD4⁺CD25⁺FoxP3⁺ regulatory T cells, an effect that was significantly reduced by treatment of IFN-γ-activated HL-60 cells with nimesulide. Overall, these data point to COX-2 inhibition as a potential strategy to be pursued with the aim at circumventing leukaemia-induced, IDO-mediated immune dysfunction.

Analysis of bioactive eicosanoids in equine plasma by stable isotope dilution reversed-phase liquid chromatography/multiple reaction monitoring mass spectrometry

Oxidative metabolites of arachidonic acid (AA) are implicated in inflammation. Thus, we evaluated cycloxygenases (COXs) and lipoxygenases (LOs) mediated metabolism of AA to eicosanoids in equine plasma. Eicosanoids were extracted from plasma by two liquid-liquid extraction (LLE) steps; first was by chloroform/isopropanol and second by methyl-tert-butyl ether. For identification and quantification of 25 eicosanoids, a highly specific, selective and sensitive stable isotope dilution liquid chromatography (LC) multiple reaction monitoring (MRM) mass spectrometric (MS) method was developed. To avoid artifact formation of eicosanoids, deferoxamine was added to plasma to chelate residual transition metal ions. The calibration curve showed excellent linearity within 0.1 to 10 ng/mL. Slopes of the calibration curves generated by adding known quantities of eicosanoids in plasma were higher than those prepared in methanol/mobile phase A. Addition of deferoxamine decreased the slope of calibration curves generated using plasma. Limit of detection (LOD) was 1-10 pg on-column for 25 different eicosanoids. Inter-day accuracy was 86-111%, whereas intra-day accuracy was from 88-110%, and precision did not exceed 15% for all quality control (QC) samples. To evaluate the formation of eicosanoids, AA was exogenously added or endogenous AA was released from esterified lipids by calcium ionophore (CI) A23187 treatment of equine whole blood. Pre-treatment of equine whole blood with dexamethasone (DEX) significantly inhibited AA or CI A23187- mediated formation of eicosanoids. The validated method is now employed in studies undertaken to better understand the mechanism of action and pharmacokinetics/pharmacodynamics of eicosanoids after administration of glucocorticoids to horses. This method is reliably reproducible.

Cyclooxygenase-2 in oncogenesis

Compelling experimental and clinical evidence supports the notion that cyclooxygenase-2, the inducible isoform of cyclooxygenase, plays a crucial role in oncogenesis. Clinical and epidemiological data indicate that aberrant regulation of cyclooxygenase-2 in certain solid tumors and hematological malignancies is associated with adverse clinical outcome. Moreover, findings extrapolated from experimental studies in cultured tumor cells and animal tumor models indicate that cyclooxygenase-2 critically influences all stages of tumor development from tumor initiation to tumor progression. Cyclooxygenase-2 elicits cell-autonomous effects on tumor cells resulting in stimulation of growth, increased cell survival, enhanced tumor cell invasiveness, stimulation of neovascularization, and tumor evasion from the host immune system. Additionally, the oncogenic effects of cyclooxygenase-2 stem from its unique ability to impact tumor cell surroundings and create a proinflammatory environment conducive for tumor development, growth and progression. The initial enthusiasm generated by the availability of cyclooxygenase-2 selective inhibitors for cancer prevention and therapy has been lessened by the severe cardiovascular adverse side effects associated with their long-term use, as well as by the mixed results of recent clinical trials evaluating the efficacy of cyclooxygenase-2 inhibitors in adjuvant chemotherapy. Therefore, our ability to efficiently target the oncogenic effects of cyclooxygenase-2 for therapeutic and preventive purposes strictly depends on a better understanding of the spatial and temporal aspects of its activation in tumor cells along with a clearer elucidation of the signaling networks whereby cyclooxygenase-2 affects tumor cells and their interactions with the tumor microenvironment. This knowledge has the potential of leading to the identification of novel cyclooxygenase-2-dependent molecular and signaling networks that can be exploited to improve cancer prevention and therapy.

Lipid mediators and human leukemic blasts

Some of the most potent inflammatory mediators share a lipid origin. They regulate a wide spectrum of cellular processes including cell proliferation and apoptosis. However, the precise roles and ways (if any) in which these compounds impact the growth and apoptosis of leukemic blasts remain incompletely resolved. In spite of this, significant advances have been recently made. Here we briefly review the current knowledge about the production of lipid mediators (prostaglandins, leukotrienes, platelet-activating factor) by leukemic blasts, the enzymatic activities (phospholipase A₂, cyclooxygenases, lipoxygenases) involved in their productions and their effects (through specific membrane bound receptors) on the growth, and apoptosis of leukemic blasts.

The role of non-steroidal anti-inflammatory drugs in the risk of development and treatment of hematologic malignancies

Non-steroidal anti-inflammatory drugs (NSAIDs) comprise the group of structurally diverse but similarly acting compounds that are used for relieving signs and symptoms of inflammation, especially in treatment of rheumatic diseases. Recent reports suggested potential association between regular use of NSAIDs and the risk of development of hematological malignancies. However, the data distinctly differ depending on type of NSAID used, period of its administration and type of malignancy. Regular use of aspirin and other NSAIDs was shown to correlate with reduced risk of lymphoid malignancies. Frequent use of aspirin was found to be associated with decreased risk of acute leukemia (AL) development. In contrast, correlation between long-term acetaminophen usage and increased incidence of AL and multiple myeloma (MM) was indicated. On the other hand, NSAIDs were found to exert anti-cancer effects, inhibiting proliferation and invasive growth or inducing cell apoptosis in several tumors, including hematologic malignancies. One of those agents, non-cyclooxygenase 2-inhibiting R-enantiomer of etodolac (SDX-101), exerts cytotoxic effects against chronic lymphocytic leukemia (CLL) and MM cells, and is currently investigated in phase II clinical trial in CLL. The indole-pyran analogue of SDX-101, SDX-308 (CEP-18082), showed more potent cytotoxicity than SDX-101 against MM cells and inhibited osteoclast formation and activity of mature osteoclasts. Thus, SDX-308 may be an ideal agent for bone disease in MM and related diseases. Another analogue of SDX-101, SDX-309, showed also significant anti-tumor activity in first preclinical studies. The potential role of NSAIDs in prevention and treatment of hematologic malignancies is the subject of this review.