The antineoplastic agent anacardic 6-pentadecyl salicylic acid produces immunomodulation in vivo via the activation of MAPKs.

Anacardic 6-pentadecyl salicylic acid (6SA) is the active component of Amphipterygium adstringens, a plant used in traditional medicine for the treatment of malaria and vascular diseases and as an anti-bacterial and immune-modulatory agent. However, the effect of 6SA on the immune system remains unclear. In this study, we examined the immune-stimulatory activity of 6SA in 6-8-week-old female BALB/c mice. We found that treatment with 2 mg/kg of 6SA increased the proportions of macrophages after 7 and 14 days of treatment and of natural killer (NK) cells after 14 days of treatment in circulating blood. In lymph nodes, treatment with 6SA for 14 days increased the number of macrophages. In addition, 6SA increases in the systemic levels of pro-inflammatory cytokines such as tumour necrosis factor (TNF)-α, interleukin (IL)-2, IL-12, IL-6 and IL-1ß and of nitric oxide (NO). We observed an increase in the secretion of Granulocyte/Macrophage Colony Stimulation Factor (GM-CSF) that could explain the increase in the proportion of macrophages. Moreover, 6SA induced the classical activation of macrophages by increasing their expression of MHC-II and their production of TNF-α. These M1-polarised macrophages presented enhanced phagocytosis and NO secretion. This activation was due to induction of the phosphorylation of MAPKs such as ERK, JNK and p38 because specific inhibitors of the phosphorylation of these MAPKs reduced the 6SA-induced phagocytosis and NO and particularly, the secretion of GM-CSF in macrophages by inhibition of ERK. Despite these effects on macrophages, 6SA does not have any direct effect on the proportion of lymphocytes.

Exploring an animal model of amodiaquine-induced liver injury in rats and mice.

Amodiaquine (AQ) is associated with a relatively high incidence of idiosyncratic drug-induced liver injury (IDILI) and agranulocytosis. A previous study reported that a combination of high dose AQ and glutathione (GSH) depletion led to liver injury. However, the characteristics of this toxicity were very different from AQ-induced liver injury in humans. We developed a model of AQ-induced liver injury with characteristics similar to the injury in humans by treating mice with lower doses of AQ for several weeks. In this study we found that not only did GSH depletion not increase AQ covalent binding to hepatic proteins at this lower dose, but also it paradoxically prevented the liver injury. We extended the model to rats and found AQ treatment led to a mild delayed onset liver injury that resolved despite continued treatment with AQ. Immunohistochemistry indicated the presence of Kupffer cell activation, apoptosis and hepatocyte proliferation in the liver. There was also an increase in serum IL-2, IL-5, IL-9, IL-12, MCP-1 and TGFß, but a decrease in leptin. Coincident with the elevated serum ALT, the number of liver CD4(+) T-cells, IL-17 secreting cells and TH17/Treg cells increased at Week 3 and decreased during continued treatment. Increases in NK1.1+ cells and activated M2 macrophages were also observed during liver injury. These results suggest that the outcome of the liver injury was determined by the balance between effector and regulatory cells. Co-treatment with cyclosporin prevented AQ-induced liver injury, which supports an immune mechanism. Retinoic acid (RA), which has been reported to enhance natural killer (NK) cell activity, exacerbated AQ-induced liver injury. These results suggest that AQ-induced IDILI is immune mediated and the subsequent adaptation appears to represent immune tolerance.

Genotoxic and cytostatic effects of 6-pentadecyl salicylic anacardic acid in transformed cell lines and peripheral blood mononuclear cells.

In Mexico, as in many other countries, traditional medicine is used for the treatment of several diseases. In particular, Amphipterygium adstringens infusion is used for gastritis, gastric ulcers, and gastric cancer. Extracts from this tree have microbicidal effects against Helicobacter pylori, an important risk factor for gastric cancer development. Anacardic acids are constituents of A. adstringens, and 6-pentadecyl salicylic acid (6-PSA) is the most abundant. However, there is a lack of information regarding the effects of 6-PSA on cancer cells. Therefore, we investigated whether 6-PSA has differential effects on the induction of genotoxicity, cytostaticity, and apoptosis in normal human peripheral blood mononucleated cells (PBMCs), bone marrow polychromatic erythrocytes of Balb/c mice, and human transformed cell lines derived from both gastric cancer (AGS cells) and leukaemia (K562 cells). Treatment with 6-PSA (30-150 µM) reduced the viability of AGS and K562 cells together with a moderate, but significant, increase in the frequency of micronucleated cells and the induction of DNA breakage (Comet Assay). Moreover, 6-PSA increased the apoptosis rate in both the AGS and K562 cell lines in a caspase 8-dependent manner. In contrast, neither cytotoxicity nor genotoxicity were observed in PBMCs or bone marrow polychromatic erythrocytes of Balb/c mice after treatment with low doses of 6-PSA (0.2-2.0 mg/Kg). Instead, 6-PSA treatment resulted in the inhibition of PBMC proliferation, which was reversible after the compound was removed. Additionally, 6-PSA treatments (2-20 mg/Kg) increased the frequency of mature polychromatic erythrocytes in the bone marrow, suggesting a possible effect on the differentiation process of immune cells. The present results indicate that 6-PSA induces cytotoxicity and moderate genotoxicity, together with an increase in the apoptosis rate, in a caspase 8-dependent manner in gastric cancer cells. In contrast, a low toxicity was observed when PBMCs were exposed to 6-PSA.

Effect of selenomethionine supplementation in food on the excretion and toxicity of arsenic exposure in female mice.

Selenium (Se) is an essential component of several major metabolic pathways and controls immune function. Arsenic (As) is a human carcinogen with immunotoxic and genotoxic activities, functioning mainly by producing oxidative stress. Due to the ability of Se to interact with As and to possibly block its toxic effects, we investigated the impact of dietary Se-methionine (Se-Met) supplementation on the toxicity of As exposure in vivo in a mouse model. Sufficient and excess levels of Se-Met (0.2 and 2 ppm, respectively) were fed to C57BL/6N female mice exposed to sodium arsenite (3, 6 and 10 mg/kg) in tap water for 9 days. We observed that As exposure increased Se-Met excretion in the urine. Se-Met supplementation increased the relative liver weight and decreased the concentration of total liver proteins in animals exposed to 10 mg/kg of As. Se-Met supplementation maintained a normal pool of glutathione in the liver and increased glutathione peroxidase concentration, although the lipoperoxidation level was increased by Se-Met even without As exposure. Se-Met supplementation helped to maintain the CD4/CD8 ratio of lymphocytes in the spleen, although it increased the proportion of B cells. Se-Met supplementation prior to As exposure increased the secretion of interleukin-4, IL-12 and interferon-γ and the stimulation index of the spleen cells in in vitro assays. Se-Met intake improved the basal immunological parameters but did not reduce the damage caused by oxidative stress after low-dose As exposure.

Retinoic acid modulates retinaldehyde dehydrogenase 1 gene expression through the induction of GADD153-C/EBPbeta interaction.

Mammalian class I aldehyde dehydrogenase (ALDH) plays an important role in the biosynthesis of the hormone retinoic acid (RA), which modulates gene expression and cell differentiation. RA has been shown to mediate control of human ALDH1 gene expression through modulation of the retinoic acid receptor alpha (RARalpha) and the CCAAT/enhancer binding protein beta (C/EBPbeta). The positive activation of these transcription factors on the ALDH1 promoter is inhibited by RA through a decrease of C/EBPbeta binding to the ALDH1 CCAAT box response element. However, the mechanism of this effect remains unknown. Here we report that the RARalpha/retinoid X receptor beta (RXRbeta) complex binds to the mouse retinaldehyde dehydrogenase 1 (Raldh1) promoter at a non-consensus RA response element (RARE) with similar affinity to that of the consensus RARE. We found that C/EBPbeta binds to a Raldh1 CCAAT box located at -82/-58bp, adjacent to the RARE. Treatment with RA increases GADD153 and GADD153-C/EBPbeta interaction resulting in a decreased cellular availability of C/EBPbeta for binding to the Raldh1 CCAAT box. These data support a model in which high RA levels inhibit Raldh1 gene expression by sequestering C/EBPbeta through its interaction to GADD153.

Non-optimal levels of dietary selenomethionine alter splenocyte response and modify oxidative stress markers in female mice.

Many studies evaluating the effects of selenium (Se) status on immunity utilize inorganic Se, although selenomethionine (Se-Met) has been suggested to be more bioavailable and less toxic. In the current study, we investigated the effects of dietary Se-Met on immune system function and cellular redox status in C57BL/6N female mice fed with low (0.02 ppm), sufficient (0.2 ppm, control group), or excess Se-Met (2 ppm) in the diet for 50 days. Low Se-Met intake reduced glutathione peroxidase (GPx) activity and glutathione concentration without modifying lipoperoxidation. While low Se-Met intake also reduced the number of B cells in the spleen, it increased mitogen-induced proliferation, IL-4 and IL-12 secretion when compared to the sufficient Se-Met intake group. In comparison to controls, excess Se-Met intake increased splenocyte proliferation and reduced B cell numbers, IL-4, and IL-12 secretion without affecting oxidative stress markers. These data suggest that Se-Met supplementation should be carefully evaluated as it many influence immune function.