Comprehensive analysis of aflatoxin B1 biosynthesis in Aspergillus flavus via transcriptome-wide m6A methylome response to cycloleucine

Aspergillus flavus and its toxic aflatoxins secondary metabolites contaminate food and grains, posing a severe threat to human health and leading to liver cancer. Here, we demonstrated that cycloleucine blocked aflatoxin B1 synthesis by inhibiting N6-methyladenosine (m6A) methylation modification of messenger RNA (mRNA). m6A Methylation Immunoprecipitation Sequencing (m6A MeRIP-Seq)-based comprehensive transcriptome-wide m6A profiling identified 102 differentially expressed genes that underwent m6A modification, of which 22 hypermethylated genes were downregulated and 49 hypomethylated genes were upregulated, suggesting a negative correlation between m6A methylation and gene expression. Notably, cycloleucine inhibited aflatoxin B1 production via multiple targets. The m6A sites of several key genes involved in the aflatoxin B1 biosynthesis pathway were significantly enriched in the coding sequence and around the stop codon, resulting in their downregulation. Furthermore, m6A methylation on genes related to the aflatoxin B1 biosynthesis pathway led to reduced mRNA stability. Cycloleucine inhibition of aflatoxin B1 production highlights its potential as an agent for removing mycotoxins in environmental pollution. ENVIRONMENTAL IMPLICATION: Aflatoxins, highly carcinogenic secondary metabolites produced by Aspergillus flavus, frequently contaminate crops such as peanut, corn, wheat and sesame leading to irreversible loss in the quality and yield of agricultural products and posing serious threats to food safety. Aflatoxins has also been linked to developmental delays and liver cancer in humans. In our study, 'monitoring aflatoxin concentrations and its bioaccumulation in organisms' has been conducted. The results demonstrated that aflatoxin production in A. flavus was completely blocked after cycloleucine treatment. Additionally, we demonstrated that inhibition of aflatoxin was linked to N6-methyladenosine methylation of multiple genes in aflatoxin biosynthesis pathway.

Cycloleucine negatively regulates porcine oocyte maturation and embryo development by modulating N6-methyladenosine and histone modifications

Maturation of oocytes and early embryo development are regulated precisely by numerous factors at transcriptional and posttranslational levels through precise mechanisms. N6-methyladenosine (m⁶A) is the most common modification in mRNA which regulates RNA metabolism and gene expression. However, the role of RNA m⁶A on porcine oocyte maturation and early embryogenesis is largely unknown. Here, we found that oocytes treated with cycloleucine (CL), an RNA m⁶A inhibitor, express impaired cumulus expansion, increased production of reactive oxygen species (ROS) in the mitochondria, and delayed maturation of oocytes by disrupting spindle organization and chromosome alignment. Also, CL halted the development of embryos at the 4-cell stage and resulted in low-quality blastocysts. Furthermore, CL treatment decreased the RNA m⁶A, H3K4me3, and H3K9me3 levels, but increased the acetylation level of H4K16 during parthenogenetic embryonic development in pigs. Single-cell RNA-seq (scRNA-seq) analysis further revealed that CL treatment dramatically up-regulated the expression of metabolism-related genes (SLC16A1, and MAIG3 etc.) and maternal related genes, including BTG4, WEE2, and BMP15 among others, at the blastocyst stage. Taken together, inhibition of RNA m⁶A by CL impaired meiosis of oocytes and early embryonic development of porcine via RNA m⁶A methylation, histone modifications, and altering the expression of metabolism-related genes in blastocysts.

Effects of Cycloleucine in the Nucleus Accumbens Septi on the Elevated plus Maze Test in Rats

INTRODUCTION

In recent years, an important number of studies have emphasized the psychopharmacological actions of cycloleucine (1-aminocyclopentanecarboxylic acid) acting on the NR1 subunit (glycine allosteric site) of NMDA (N-methyl-D-aspartic acid) receptor. We studied the effects of its injection in an anxiety test.

METHODS

The elevated plus maze test was used. Male rats bilaterally cannulated into the nucleus accumbens septi (NAS) were employed. Rats were divided into 5 groups that received either 1 µL injections of saline or cycloleucine (0.5, 1, 2, or 4 µg) 15 min before testing.

RESULTS

Time spent in the open arm was significantly increased by cycloleucine treatment with all doses (1 and 2 µg, p < 0.05; 0.5 and 4 µg, p < 0.01), like number of extreme arrivals (0.5 and 1 µg, p < 0.05; 2 µg, p < 0.01; and 4 µg, p < 0.001). Open arm entries were increased by the highest dose only (4 µg, p < 0.01).

DISCUSSION/CONCLUSION

Present results show no difference between all doses in the time spent in the open arm, suggesting an indirect, noncompetitive action of the drug. The increase in extreme arrivals and open arm entries suggests a dose influence in these parameters. We conclude that cycloleucine influence on the NMDA receptors within NAS leads to anxiolytic-like effects and behavioral disinhibition, which once more confirms the involvement of NAS in anxiety processing.