Benzene is a well-known hematotoxic carcinogen that can cause leukemia and a variety of blood disorders. Our previous study indicated that benzene disturbs levels of metabolites in the fatty acid β-oxidation (FAO) pathway, which is crucial for the maintenance and function of hematopoietic and leukemic cells. The present research aims to investigate the effects of benzene on changes in the expression of key enzymes in the FAO pathway in male C3H/He mice. Results showed that benzene exposure caused reduced peripheral white blood cell (WBC), red blood cell (RBC), platelet (Pit) counts, and hemoglobin (Hgb) concentration. Investigation of the effects of benzene on the expression of FA transport- and β-oxidation-related enzymes showed that expression of proteins Cpt1a, Crat, Acaa2, Aldh1l2, Acadvl, Crot, Echs1, and Hadha was significantly increased. The ATP levels and mitochondrial membrane potential decreased in mice exposed to benzene. Meanwhile, reactive oxygen species (ROS), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) levels were significantly increased in the benzene group. Our results indicate that benzene induces increased expression of FA transport and β-oxidation enzymes, mitochondrial dysfunction, and oxidative stress, which may play a role in benzene-induced hematotoxicity.

Leukemias and hematopoietic disorders induced by benzene may arise from the toxicity of benzene to hematopoietic stem or progenitor cells (HS/PCs). Since there is a latency period between initial benzene exposure and the development of leukemia, subsequent impact of benzene on HS/PCs are crucial for a deeper understanding of the carcinogenicity and hematotoxicity in post-exposure stage. This study aims to explore the effects of benzene on HS/PCs and gene-expression in Wnt, Notch and Hh signaling pathways in post-exposure stage. The C3H/He mice were injected subcutaneously with benzene (0, 150, 300 mg/kg/day) for three months and were monitored for another 10 months post-exposure. The body weights were monitored, the relative organ weights, blood parameters and bone marrow smears were examined. Frequency of lineage^- sca-1⁺ c-kit⁺ (LSK) cells, capability of colony forming and expression of genes in Wnt, Notch and Hedghog (Hh) signaling pathways were also analyzed. The colony formation of the progenitor cells for BFU-E, CFU-GEMM and CFU-GM was significantly decreased with increasing benzene exposure relative to controls, while no significant difference was observed in colonies for CFU-G and CFU-M. The mRNA level of cyclin D1 was increased and Notch 1 and p53 were decreased in LSK cells in mice exposed to benzene but with no statistical significance. These results suggest that subsequent toxic effects of benzene on LSK cells and gene expression in Wnt, Notch and Hh signaling pathways persist in post-exposure stage and may play roles in benzene-induced hematotoxicity.

Currently, studies worldwide have comprehensively recognized the importance of Sphingomonadaceae bacteria and the mlrCABD gene cluster in microcystin (MC) degradation. However, knowledge about their degradation of nodularin (NOD) is still unclear. In this study, the degradation mechanism of NOD by Sphingopyxis sp. m6, an efficient MC degrader isolated from Lake Taihu, was investigated in several aspects, including degradation ability, degradation products, and potential application. The strain degraded NOD of 0.50 mg/L with a zero-order rate constant of 0.1656 mg/L/d and a half-life of 36 h. The average degradation rate of NOD was significantly influenced by the temperature, pH, and initial toxin concentrations. Moreover, four different biodegradation products, linear NOD, tetrapeptide H-Glu-Mdhb-MeAsp-Arg-OH, tripeptide H-Mdhb-MeAsp-Arg-OH, and dipeptide H-MeAsp-Arg-OH, were identified, of which the latter two are the first reported. Furthermore, the four mlr genes were upregulated during NOD degradation. The microcystinase MlrA encoded by the mlrA gene hydrolyzes the Arg-Adda bond to generate linear NOD as the first step of NOD biodegradation. Notably, recombinant MlrA showed higher degradation activity and stronger environmental adaptability than the wild strain, suggesting future applications in NOD pollution remediation. This research proposes a relatively complete NOD microbial degradation pathway, which lays a foundation for exploring the mechanisms of NOD degradation by MC-degrading bacteria.

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.

Bacterial degradation is one important Microcystin (MC) removal method in the natural environment. The traditional MC-degrading pathway was proposed based on the functions of individual recombinant Mlr enzymes and the structures of the main MC-degrading products. However, the actual MC-degrading mechanism by Mlr enzymes in wild-type bacteria remains unclear. In this study, bioinformatic analysis, heterologous expression, and knockout mutation were performed to elaborate the MC-degrading mechanism by Mlr enzymes in Sphingopyxis sp. m6. The results showed that mlr gene cluster was initially acquired by horizontal gene transfer, followed by vertical inheritance within Alphaproteobacteria. Mlr enzymes exhibit distinct subcellular localizations and possess diverse conserved catalytic domains. The enzymatic cascade MlrA/MlrB/MlrC sequentially cleaves Microcystin-LR (MC-LR) via Adda-Arg, Ala-Leu, and Adda-Glu bonds, generating characteristic intermediates (linearized MC-LR, tetrapeptide, and Adda). Notably, recombinant MlrC demonstrated dual-targeting degrading capability (linearized MC-LR and tetrapeptide), while tetrapeptide specificity in endogenous processing of Sphingopyxis sp. m6. Marker-free knockout mutants of mlr genes were first constructed in MC-degrading bacteria, unveiling that mlrA was indispensable in initial MC cleavage, whereas mlrB/mlrC/mlrD displayed functional compensation through other enzymes with similar functions. This study promotes the mechanistic understanding of MC bacterial degradation and offers a theoretical basis for a bioremediation strategy targeting cyanotoxin pollution.

Microcystins (MCs), a group of potent hepatotoxins from cyanobacterial blooms, threaten global water security due to the resistance to conventional treatment processes and multi-organ toxicity to human. This study innovatively proposed a novel sequential process combining UV irradiation with biodegradation by Sphingopyxis sp. m6 for efficient microcystin-LR (MC-LR) removal. Results revealed that sequential UV-C pretreatment followed by Sphingopyxis sp. m6 biodegradation achieved complete degradation of 1 mg/L of MC-LR within 1 h of the biological phase, drastically reducing the treatment time compared to biodegradation alone (5 h). Mechanistic investigation revealed that low-dose UV-C (50 mJ/cm²) pretreatment induced MC-LR photoisomerization consistently with previously reported Adda geometric isomers. These photoisomers, along with residual parent MC-LR, were subsequently mineralized by Sphingopyxis sp. m6. Enzymatic pathway analysis confirmed a dual-pathway degradation, where Mlr enzymes processed both the native toxin and its isomeric forms, leading to a series of linearized peptides and Adda-derived products. Critically, the process achieved efficient detoxification, as confirmed by the restoration of HepG2 cell proliferation and protein phosphatase 2A activity. Moreover, response surface methodology optimized the key parameters (31.49 °C, pH of 7.36, 0.23 mg/L) for the highest degradation efficiency. This work provides an energy- and cost-efficient strategy for MC-LR remediation and elucidates the molecular mechanism of UV-induced photoisomerization facilitating subsequent biodegradation.