Iron overload adversely effects bone marrow haematogenesis via SIRT-SOD2-mROS in a process ameliorated by curcumin.

BACKGROUND: Iron overload, which is common in patients with haematological disorders, is known to have a suppressive effect on haematogenesis. However, the mechanism for this effect is still unclear. The antioxidant curcumin has been reported to protect against iron overload-induced bone marrow damage through an as-yet-unknown mechanism. METHODS: We established iron overload cell and mouse models. Mitochondrial reactive oxygen species (mROS) levels, autophagy levels and the SIRT3/SOD2 pathway were examined in the models and in the bone marrow of patients with iron overload. RESULTS: Iron overload was shown to depress haematogenesis and induce mitochondrion-derived superoxide anion-dependent autophagic cell death. Iron loading decreased SIRT3 protein expression, promoted an increase in SOD2, and led to the elevation of mROS. Overexpression of SIRT3 reversed these effects. Curcumin treatment ameliorated peripheral blood cells generation, enhanced SIRT3 activity, decreased SOD2 acetylation, inhibited mROS production, and suppressed iron loading-induced autophagy. CONCLUSIONS: Our results suggest that curcumin exerts a protective effect on bone marrow by reducing mROS-stimulated autophagic cell death in a manner dependent on the SIRT3/SOD2 pathway.

Benzene induces haematotoxicity by promoting deacetylation and autophagy.

Chronic exposure to benzene is known to be associated with haematotoxicity and the development of aplastic anaemia and leukaemia. However, the mechanism underlying benzene-induced haematotoxicity, especially at low concentrations of chronic benzene exposure has not been well-elucidated. Here, we found that increased autophagy and decreased acetylation occurred in bone marrow mononuclear cells (BMMNCs) isolated from patients with chronic benzene exposure. We further showed in vitro that benzene metabolite, hydroquinone (HQ) could directly induce autophagy without apoptosis in BMMNCs and CD34+ cells. This was mediated by reduction in acetylation of autophagy components through inhibiting the activity of acetyltransferase, p300. Furthermore, elevation of p300 expression by Momordica Antiviral Protein 30 Kd (MAP30) or chloroquine reduced HQ-induced autophagy. We further demonstrated that in vivo, MAP30 and chloroquine reversed benzene-induced autophagy and haematotoxicity in a mouse model. Taken together, these findings highlight increased autophagy as a novel mechanism for benzene-induced haematotoxicity and provide potential strategies to reverse this process for therapeutic benefits.

Benzene metabolite hydroquinone induces apoptosis of bone marrow mononuclear cells through inhibition of ß-catenin signaling.

The Akt/glycogen synthase kinase-3ß (GSK-3ß)/ß-catenin signaling pathway has been shown to play an important role in hematopoiesis, and hematopoietic cells are sensitive targets for benzene-induced hematotoxicity. We therefore hypothesized that dysregulation of the Akt/GSK-3ß/ß-catenin signaling was associated with benzene-induced hematotoxicity. Here, we showed that hydroquinone (HQ), a major metabolite of benzene in humans, significantly inhibited cell viability and colony formation while inducing apoptosis of human bone marrow mononuclear cells in vitro. Interestingly, we found that HQ inhibited the Akt affected ß-catenin signaling by activation of GSK-3ß, resulting in downregulation of ß-catenin and its targets Cyclin D1 and Survivin. HQ blocked nuclear translocation of ß-catenin and lymphoid enhancer-binding factor 1 (LEF-1), and importantly, HQ also reduced the interaction of ß-catenin and LEF-1 in the nucleus. As expected, blockage of GSK-3ß activity with a GSK-3ß inhibitor lithium chloride (LiCl) or activation of Akt signaling with an Akt agonist insulin-like growth factor-1 (IGF-1) could inhibit HQ-induced activation of GSK-3ß as well as hematotoxicity. Taken together, our results suggest that HQ-induced hematotoxicity in bone marrow mononuclear cells is associated with dysregulation of Akt/GSK-3ß/ß-catenin signaling due to the dissociation of ß-catenin/LEF-1 complex, and LiCl and IGF-1 may be two potential agents to ameliorate HQ-induced hematotoxicity.

Histone Deacetylase Inhibitors Trichostatin A and MCP30 Relieve Benzene-Induced Hematotoxicity via Restoring Topoisomerase IIα.

Dysfunction of histone acetylation inhibits topoisomerase IIα (Topo IIα), which is implicated in benzene-induced hematotoxicity in patients with chronic benzene exposure. Whether histone deacetylase (HDAC) inhibitors can relieve benzene-induced hematotoxicity remains unclear. Here we showed that hydroquinone, a main metabolite of benzene, increased the HDAC activity, decreased the Topo IIα expression and induced apoptosis in human bone marrow mononuclear cells in vitro, and treatment with two HDAC inhibitors, namely trichostatin A (TSA) or a mixture of ribosome-inactivating proteins MCP30, almost completely reversed these effects. We further established a benzene poisoning murine model by inhaling benzene vapor in a container and found that benzene poisoning decreased the expression and activity of Topo IIα, and impaired acetylation of histone H4 and H3. The analysis of regulatory factors of Topo IIα promoter found that benzene poisoning decreased the mRNA levels of SP1 and C-MYB, and increased the mRNA level of SP3. Both TSA and MCP30 significantly enhanced the acetylation of histone H3 and H4 in Topo IIα promoter and increased the expression and activity of Topo IIα in benzene poisoning mice, which contributed to relieve the symptoms of hematotoxicity. Thus, treatment with HDAC inhibitors represents an attractive approach to reduce benzene-induced hematotoxicity.

MAP30 inhibits autophagy through enhancing acetyltransferase p300 and induces apoptosis in acute myeloid leukemia cells.

Momordica anti-human immunodeficiency virus protein of 30 kDa (MAP30) has been shown to exhibit potent antitumor activities against several solid tumors. In the present investigation we demonstrated that MAP30 significantly inhibited the proliferation of acute myeloid leukemia (AML) HL-60 and THP-1 cell lines and patient AML cells through autophagy inhibition and apoptosis induction. Intriguingly, MAP30-induced cell death and apoptosis were partially rescued in combination with an autophagy activator rapamycin, and aggravated in combination with an autophagy inhibitor bafilomycin A1 in HL-60 cells, suggesting that autophagy is a pro-survival signal and its inhibition contributes to the induction of apoptosis in MAP30­induced cell death. Further mechanism analysis demonstrated that MAP30 enhanced p300, and C646, a selective inhibitor of p300, markedly promoted autophagy and partially rescued the MAP30-induced cell death in HL-60 cells and patient AML cells. Collectively, our findings suggest that apoptosis and autophagy act cooperatively to elicit MAP30-induced cell death and MAP30 may be a potential antitumor drug candidate against AML.

[Histone acetylation modification of topoisomerase enzyme â ¡α promoter regulation factors in patients with chronic benzene poisoning].

OBJECTIVE: To investigate histone acetylation modification of topoisomerase enzyme Ⅱα (TOPOⅡα) promoter regulation factors in patients with chronic benzene poisoning, to explore the possible regulatory mechanism of TOPOⅡα involved in toxicity of chronic benzene poisoning; METHODS: The bone marrow samples were from 25 chronic benzene poisoning cases and 25 controls. The Chromatin Immunoprecipitation (ChIP) assay was carried out to study the possible mechanism of TOPOⅡα promoter regulation factors expression changes. TOPOⅡα promoter regulation factors mRNA were detected by RT-PCR technique. RESULTS: (1) Compared with the control, the histone H4 acetylation, histone H3 acetylation level of TOPOⅡα promoter regulation factors SP1, ATF-2, SP3, NF-YA, P53, C-MYB, ICBP90, NF-M in chronic benzene poisoning patients decreased, with the significant difference (P<0.05) , except for C-JUN (P>0.05) ; (2) The mRNA expression of TOPOⅡαpromoter regulation factors SP1, NF-YA, C-MYB, C-JUN and NF-M were significantly lower than in the control with the significant difference (P<0.05) , while the expression of SP3、P53 mRNA increased (P<0.05) , ATF-2、ICBP90 mRNA wasn't changed (P>0.05) . CONCLUSION: (1) Chronic benzene poisoning TOPO Ⅱα promoter regulation factors histone modification changes accompanied with mRNA level changed. (2) Histone acetylation modification of topoisomerase enzyme Ⅱα promoter regulation factors takes important role in the benezen's Hematopoietic toxicity.