l-Carnitine protects against 1,4-benzoquinone-induced apoptosis and DNA damage by suppressing oxidative stress and promoting fatty acid oxidation in K562 cells.

Widespread occupational and environmental exposure to benzene is unavoidable and poses a public health threat. Studies of potential interventions to prevent or relieve benzene toxicity are, thus, essential. Research has shown l-carnitine (LC) has beneficial effects against various pathological processes and diseases. LC possesses antioxidant activities and participates in fatty acid oxidation (FAO). In this study, we investigated whether 1,4-benzoquinone (1,4-BQ) affects LC levels and the FAO pathway, as well as analyzed the influence of LC on the cytotoxic effects of 1,4-BQ. We found that 1,4-BQ significantly decreased LC levels and downregulated Cpt1a, Cpt2, Crat, Hadha, Acaa2, and Acadvl mRNA expression in K562 cells. Subsequent assays confirmed that 1,4-BQ decreased cell viability and increased apoptosis and caspase-3, -8, and -9 activities. It also induced obvious oxidative stress and DNA damage, including an increase in the levels of reactive oxygen species and malondialdehyde, tail DNA%, and olive tail moment. Additionally, the mitochondrial membrane potential was significantly reduced. Cotreatment with LC (500 µmol/L) relieved these alterations by reducing oxidative stress and increasing the protein expression levels of Cpt1a and Hadha, particularly in the 20 µmol/L 1,4-BQ group. Thus, our results demonstrate that 1,4-BQ causes cytotoxicity, reduces LC levels, and downregulates the FAO genes. In contrast, LC exhibits protective effects against 1,4-BQ-induced apoptosis and DNA damage by decreasing oxidative stress and promoting the FAO pathway.

PTP4A3, A Novel Target Gene of HIF-1alpha, Participates in Benzene-Induced Cell Proliferation Inhibition and Apoptosis through PI3K/AKT Pathway.

Benzene, a commonly used chemical, has been confirmed to specifically affect the hematopoietic system as well as overall human health. PTP4A3 is overexpressed in leukemia cells and is related to cell proliferation. We previously found that HIF-1alpha was involved in benzene toxicity and PTP4A3 may be the target gene of HIF-1alpha via ChIP-seq. The aim of this study is to confirm the relationship between HIF-1alpha and PTP4A3 in benzene toxicity, as well as the function of PTP4A3 on cell toxicity induced by 1,4-benzoquinone (1,4-BQ). Our results indicate that HIF-1alpha could regulate PTP4A3 with in vivo and in vitro experiments. A cell line with suppressed PTP4A3 was established to investigate the function of PTP4A3 in 1,4-BQ toxicity in vitro. The results revealed that cell proliferation inhibition was more aggravated in PTP4A3 low-expression cells than in the control cells after 1,4-BQ treatment. The relative oxygen species (ROS) significantly increased in cells with inhibited PTP4A3, while the rise was inferior to the control cells at the 20 µM 1,4-BQ group. An increase in DNA damage was seen in PTP4A3 down-regulated cells at the 10 µM 1,4-BQ group, whereas the results reversed at the concentration of 20 µM. Moreover, the apoptosis rate increased higher in down-regulated PTP4A3 cells after 1,4-BQ exposure. In addition, PI3K/AKT pathway was significantly restrained in cells with inhibited PTP4A3 after 1,4-BQ treatment. Our results indicate that HIF-1alpha may regulate PTP4A3 to be involved in benzene toxicity. Inhibition of PTP4A3 could aggravate cell proliferation suppression and apoptosis by regulating PI3K/AKT pathway after 1,4-BQ treatment.

Benzene exposure induces gut microbiota dysbiosis and metabolic disorder in mice.

The gut microbiota comprises a multispecies microbial community and is essential for maintaining health. Benzene is a widespread environmental and occupational pollutant that mainly causes blood and bone marrow abnormalities. However, the effects of benzene on gut microbiota and metabolism have not yet been investigated. In this study, C57BL/6 mice were exposed to 0, 6, 30 and 150 mg/kg benzene by subcutaneous injection for 30 days. We observed that white blood cell levels significantly decreased in the three benzene exposure groups, while red blood cell and hemoglobin levels were only changed remarkably in 30 and 150 mg/kg benzene-treated mice. The results of 16S rRNA sequencing showed that benzene exposure altered the overall structure of the gut microbial communities. In addition, significant enrichments of Actinobacteria (p < .05) at the phylum level and Helicobacter at the genus level were observed in the cecal contents and feces of mice exposed to 150 mg/kg benzene. Moreover, there was a significant negative correlation between Actinobacteria abundance and basic blood indicators, including white blood cell, red blood cell, and hemoglobin levels. Furthermore, according to LC-MS analysis, a total of 42 cecal metabolites were significantly altered by 150 mg/kg benzene. Several metabolic pathways were significantly influenced by benzene exposure, including cysteine and methionine metabolism, porphyrin and chlorophyll metabolism, steroid biosynthesis, aminoacyl-tRNA biosynthesis, and arginine and proline metabolism. In summary, this study demonstrated that benzene exposure causes dysbiosis of the gut microbiota and metabolic disorder in mice.

Prodigiosin induces apoptosis and inhibits autophagy via the extracellular signal-regulated kinase pathway in K562 cells.

Prodigiosin contains a tripyrrole skeleton and shows impressive anticancer potential in multiple cell lines. Numerous studies have been conducted on prodigiosin-induced apoptosis and the related mechanisms. However, few reports have considered the effects of prodigiosin on autophagy and the relationship between apoptosis and autophagy. Here, we examined whether prodigiosin affected apoptosis and autophagy through the extracellular signal-regulated (ERK) signaling pathway in K562 cells, employing cell proliferation, flow cytometry, caspase activity, and western blot analyses. Inhibition of the ERK signaling pathway with PD184352 was conducted to verify the role of this pathway on prodigiosin-mediated processes. Our findings revealed that prodigiosin inhibited the proliferation of K562 cells, increased reactive oxygen species (ROS), induced apoptosis and inhibited autophagy in K562 cells. Additionally, the ROS scavenger, N-Acetyl-L-cysteine (NAC), partially prevented prodigiosin-induced apoptosis but did not reduce prodigiosin-inhibited autophagy in K562 cells. Furthermore, prodigiosin treatment in K562 cells reduced the phosphorylation of c-Jun N-terminal kinases (JNKs) and P38, and activated ERK signaling pathway. When ERK1/2 phosphorylation was blocked by PD184352, prodigiosin-induced apoptosis and the inhibition of autophagy decreased significantly. Taken together, these results demonstrated that the ERK signaling pathway was involved in prodigiosin-induced apoptosis and prodigiosin-inhibited autophagy.

Overexpression of HIF-1a could partially protect K562 cells from 1,4-benzoquinone induced toxicity by inhibiting ROS, apoptosis and enhancing glycolysis.

Benzene is an environmental contaminant which causes hematological diseases. Previously, hypoxia inducible factor-1a (HIF-1a) was found to be involved in benzene-induced hematotoxicity. This study aims to explore whether overexpression of HIF-1a in K562 cell line could influence the toxicity caused by 1,4-BQ. HIF-1a overexpression K562 cell line was constructed with a lentiviral vector. Results showed that HIF-1a was significantly elevated in control K562 cells and HIF-1a overexpression cells exposed to 1,4-BQ. Compared with 1,4-BQ exposed control cells, HIF-1a overexpression blocked cell cycle at G2/M phase, remarkably reduced apoptosis and ROS level. And HIF-1a overexpression caused downregulation of Nox4 and upregulation of Bcl-2. In addition, the lactic acid (LD)/pyruvic acid (PA) ratio was significantly higher in HIF-1a overexpression cells than that in control cells at the same 1,4-BQ dose. Furthermore, significant increases in Glut1, Ldha, Pkm2, Pgk1, Pdk1, Pfkl, Pfkfb3 protein levels was also observed in HIF-1a overexpression cells. Overall, our results indicated that HIF-1a overexpression could alleviate ROS and apoptosis caused by 1,4-BQ through targeting Nox4, Bcl-2 and key enzymes in glycolysis.

Global Identification of HIF-1α Target Genes in Benzene Poisoning Mouse Bone Marrow Cells.

Benzene is a hematopoietic toxicant, and hematopoietic cells in bone marrow (BM) are one of the main targets for its action, especially hematopoietic stem cells (HSCs). Hypoxia-inducible factor-1α (HIF-1α) is associated with the metabolism and physiological functions of HSCs. We previously found that the mechanism of regulation of HIF-1α is involved in benzene-induced hematopoietic toxicity. In this study, chromatin immunoprecipitation sequencing (ChIP-Seq) technologies were used to analyze the genome-wide binding spectrum of HIF-1α in mouse BM cells, and specific HIF-1α target genes and pathways associated with benzene toxicity were screened and validated. By application of the ChIP-Seq technique, we identified target genes HIF-1α directly binds to and regulates. Forty-two differentially down-regulated genes containing the HIF-1α specific binding site hypoxia response element (HRE) were found, of which 25 genes were with biological function. Moreover, the enrichment analysis of signal pathways indicated that these genes were significantly enriched in the Jak-STAT signaling pathway, Natural killer cell mediated cytotoxicity, the Fc epsilon RI signaling pathway, Pyrimidine metabolism, the T cell receptor signaling pathway, and Transcriptional misregulation in cancer. After verification, 11 genes involved in HSC self-renewal, cell cycle, differentiation, and apoptosis pathways were found to be significantly reduced, and may participate in benzene-induced hematotoxicity. Our study provides a new academic clue for the mechanism of benzene hematotoxicity.

Plasma metabonomics investigation reveals involvement of fatty acid oxidation in hematotoxicity in Chinese benzene-exposed workers with low white blood cell count.

Benzene is an environmental and occupational contaminant. Health hazards associated with occupational benzene exposure is a major public health problem in China. In this study, we analyzed metabolite profiles among plasma samples collected from benzene-exposed workers with low white blood cell count (BLWs) and healthy controls using high-performance liquid chromatography-time-of-flight mass spectrometry. To screen potential benzene hematotoxicity biomarkers and metabolic pathways, principal component analysis was used to examine metabolite profile changes in plasma samples. The alterations in fatty acid oxidation (FAO) pathway were consistent with our previous findings in a mouse model; hence, two key genes were selected and verified in WBC samples. A total of nine identified metabolites were significantly changed in BLWs, which were involved in glutathione metabolism, porphyrin metabolism, lipid metabolism pathway, and FAO metabolism. Furthermore, compared with healthy controls, the mRNA expressions of carnitine acyltransferase (CRAT) and ACADVL were significantly increased in BLWs. Particularly, WBC counts was negatively correlated with the expression of AVADVL in BLWs. These aberrant metabolites could act as potential biomarkers for benzene hematotoxicity. In addition, fatty acid oxidation pathway may play a critical role in the development of hematotoxicity caused by benzene.