Whole mitochondria genome mutational spectrum in occupationally exposed lead subjects

Aged fragmented-polypropylene microplastics induced ageing statues-dependent bioenergetic imbalance and reductive stress: In vivo and liver organoids-based in vitro study

Ageing is a nature process of microplastics that occurrs daily, and human beings are inevitably exposed to aged microplastics. However, a systematic understanding of ageing status and its toxic effect is currently still lacking. In this study, plastic cup lids-originated polypropylene (PP) microplastics were UV-photoaged until the carbonyl index (CI), a canonical indicator for plastic ageing, achieved 0.08, 0.17, 0.22 and 0.28. The adverse hepatic effect of these aged PPs (aPPs) was evaluated in Balb/c mice (75 ng/mL water, about 200 particles/day) and human-originated liver organoids (LOs, 50 particles/mL, ranged from 5.94 to 13.15 ng/mL) at low-dose equivalent to human exposure level. Low-dose of aged PP could induce hepatic reductive stress both in vitro and in vivo, by elevating the NADH/NAD+ratio in a CI-dependent manner, together with hepatoxicity (indicated by increased AST secretion and cytotoxicity), and disrupted the genes encoding the nutrients transporters and NADH subunits accompanied by the restricted ATP supply, declined mitochondrial membrane potential and mitochondrial complexI/IV activities, without significant increase in MDA levels in the liver. These changes in the liver disrupted systematic metabolism, representing a circulatory panel of increases in the lactate, triglyceride, Fgf21 levels, and decreases in the pyruvate level, linked the reductive stress to the declined body weight gain but elevated hepatic NADH contents following aPPs exposure. Additionally, assessing by the LOs, it was found that digestion drastically accelerated the ageing of aPPs and worsen the energy supply upon mitochondria, representing a "scattergun effect" induced by the formation of micro- and nano-plastics mixture toward NADH/NAD+imbalance.

Discovery of a Novel Shared Variant Among RTEL1 Gene and RTEL1-TNFRSF6B lncRNA at Chromosome 20q13.33 in Familial Progressive Myoclonus Epilepsy

Background: Progressive myoclonus epilepsy (PME) is a neurodegenerative disorder marked by recurrent seizures and progressive myoclonus. To date, based on the phenotypes and causal genes, more than 40 subtypes of PMEs have been identified, and more remain to be characterized. Our study is aimed at identifying the aberrant gene(s) possibly associated with PMEs in two siblings born to asymptomatic parents, in the absence of known genetic mutations. Methods: Clinical assessments and molecular analyses, such as the repeat expansion test for CSTB; SCA1, 2, 3, 6, and 7; whole exome sequencing (WES); and mitochondrial genome sequencing coupled with computational analysis, were performed. Results: A family-based segregation analysis of WES data was performed to identify novel genes associated with PMEs. The potassium channel, KCNH8 [c.298T>C; (p.Tyr100His)], a DNA repair gene, regulator of telomere elongation helicase 1 (RTEL1) [c.691G>T; (p.Asp231Tyr)] and long noncoding RNA, RTEL1-TNFRSF6B [chr20:62298898_G>T; NR_037882.1, hg19] were among the candidate genes that were found to be associated with PMEs. These homozygous variations in siblings belong to genes with a loss-of-function intolerant (pLI) score of ≤ 0.86, expected to be detrimental by multiple computational analyses, and were heterozygous in parents. Additionally, computational analysis and the expression of RTEL1 and RTEL1-TNFRSF6B revealed that RTEL1-TNFRSF6B may modulate RTEL1 via hsa-miR-3529-3p. In the patient with the severe phenotype, a further deleterious mutation in SLC22A17 was identified. No de novo variants specific to these probands were identified in the mitochondrial genome. Conclusions: Our study is the first to report variants in KCNH8, RTEL1, and RTEL1-TNFRSF6B among PME cases. These genes when characterized fully may shed light on pathogenicity and have the potential to be used in the diagnosis of PME.

Oxidative stress genes define two subtypes of triple-negative breast cancer with prognostic and therapeutic implications

Introduction: Oxidative stress (OS)-related genes have been confirmed to be closely related to the prognosis of triple-negative breast cancer (TNBC) patients; despite this fact, there is still a lack of TNBC subtype strategies based on this gene guidance. Here, we aimed to explore OS-related subtypes and their prognostic value in TNBC. Methods: Data from The Cancer Genome Atlas (TCGA)-TNBC and Sequence Read Archive (SRA) (SRR8518252) databases were collected, removing batch effects using a combat method before analysis. Consensus clustering analysis identified two OS subtypes (clusters A and B), with cluster A showing a better prognosis. Immune infiltration characteristics were analyzed using ESTIMATE and single-sample gene set enrichment analysis (ssGSEA) algorithms, revealing higher ImmuneScore and ESTIMATEscore in cluster A. Tumor-suppressive immune cells, human leukocyte antigen (HLA) genes, and three immune inhibitors were more prevalent in cluster A. Results: An eight-gene signature, derived from differentially expressed genes, was developed and validated as an independent risk factor for TNBC. A nomogram combining the risk score and clinical variables accurately predicted patient outcomes. Finally, we also validated the classification effect of subtypes using hub markers of each subtype in the test dataset. Conclusion: Our study reveals distinct molecular clusters based on OS-related genes to better clarify the reactive oxygen species (ROS)-mediated progression and the crosstalk between the ROS and tumor microenvironment (TME) in this heterogenetic disease, and construct a risk prognostic model which could provide more support for clinical treatment decisions.

Impacts of PFOAC8, GenXC6, and their mixtures on zebrafish developmental toxicity and gene expression provide insight about tumor-related disease

Concerns about per- and polyfluoroalkyl substances (PFASs) have grown in importance in the fields of ecotoxicology and public health. This study aims to compare the potential effects of long-chain (carbon atoms ≥ 7) and short-chain derivatives and their mixtures' exposure according to PFASs-exposed (1, 2, 5, 10, and 20 mg/L) zebrafish's (Danio rerio) toxic effects and their differential gene expression. Here, PFOA_C8, GenX_C6, and their mixtures (v/v, 1:1) could reduce embryo hatchability and increase teratogenicity and mortality. The toxicity of PFOA_C8 was higher than that of GenX_C6, and the toxicity of their mixtures was irregular. Their exposure (2 mg/L) caused zebrafish ventricular edema, malformation of the spine, blood accumulation, or developmental delay. In addition, all of them had significant differences in gene expression. PFOA_C8 exposure causes overall genetic changes, and the pathways of this transformation were autophagy and apoptosis. More importantly, in order to protect cells from PFOA_C8, GenX_C6, and their mixtures' influences, zebrafish inhibited the expression of ATPase and Ca²⁺ transport gene (atp1b2b), mitochondrial function-related regulatory genes (mt-co2, mt-co3, and mt-cyb), and tumor or carcinogenic cell proliferation genes (laptm4b and ctsbb). Overall, PFOA_C8, GenX_C6, and their mixtures' exposures will affect the gene expression effects of zebrafish embryos, indicating that PFASs may pose a potential threat to aquatic biological safety. These results showed that the relevant genes in zebrafish that were inhibited by PFASs exposure were related to tumorigenesis. Therefore, the effect of PFASs on zebrafish can be further used to study the pathogenesis of tumors.

ML390 inhibits enterovirus 71 replication by targeting de novo pyrimidine biosynthesis pathway

Enterovirus 71 (EV71), a small, single-stranded, positive-sense RNA virus belonging to the enterovirus genus in the family Picornaviridae, causes hand, foot, and mouth disease. Although EV71 seriously threatens to public health, no effective antiviral drugs are available for treating this disease. In this study, we found that ML390, a dihydroorotate dehydrogenase inhibitor, has potential anti-EV71 activity. ML390 dose-dependently inhibited EV71 replication with IC₅₀ and selectivity index values of 0.06601 μM and 156.5, respectively. Supplementation with the downstream product orotate significantly suppressed the ability of ML390 to inhibit EV71 replication. Moreover, an adequate supply of exogenous uridine and cytosine suppressed the anti-EV71 activity of ML390. Thus, the antiviral activity of ML390 is mediated by the inhibition of the pyrimidine synthesis pathway. In an EV71-infected mouse model, ML390 reduced the load of EV71 in the brain, liver, heart, spleen, front legs, and hind legs, and significantly increased the survival rate of the mice infected by EV71. ML390 shows potential for the treatment of hand, foot, and mouth disease caused by EV71 infection.

Altered genome-wide hippocampal gene expression profiles following early life lead exposure and their potential for reversal by environmental enrichment

Early life lead (Pb) exposure is detrimental to neurobehavioral development. The quality of the environment can modify negative influences from Pb exposure, impacting the developmental trajectory following Pb exposure. Little is known about the molecular underpinnings in the brain of the interaction between Pb and the quality of the environment. We examined relationships between early life Pb exposure and living in an enriched versus a non-enriched postnatal environment on genome-wide transcription profiles in hippocampus CA1. RNA-seq identified differences in the transcriptome of enriched vs. non-enriched Pb-exposed animals. Most of the gene expression changes associated with Pb exposure were reversed by enrichment. This was also true for changes in upstream regulators, splicing events and long noncoding RNAs. Non-enriched rats also had memory impairments; enriched rats had no deficits. The results demonstrate that an enriched environment has a profound impact on behavior and the Pb-modified CA1 transcriptome. These findings show the potential for interactions between Pb exposure and the environment to result in significant transcriptional changes in the brain and, to the extent that this may occur in Pb-exposed children, could influence neuropsychological/educational outcomes, underscoring the importance for early intervention and environmental enrichment for Pb-exposed children.

Mitochondrial DNA Mutagenesis: Feature of and Biomarker for Environmental Exposures and Aging

PURPOSE OF REVIEW

Mitochondrial dysfunction is a hallmark of aging. Mitochondrial genome (mtDNA) instability contributes to mitochondrial dysfunction, and mtDNA mutagenesis may contribute to aging. However, the origin of mtDNA mutations remains somewhat controversial. The goals of this review are to introduce and review recent literature on mtDNA mutagenesis and aging, address recent animal and epidemiological evidence for the effects of chemicals on mtDNA damage and mutagenesis, propose hypotheses regarding the contribution of environmental toxicant exposure to mtDNA mutagenesis in the context of aging, and suggest future directions and approaches for environmental health researchers.

RECENT FINDINGS

Stressors such as pollutants, pharmaceuticals, and ultraviolet radiation can damage the mitochondrial genome or disrupt mtDNA replication, repair, and organelle homeostatic processes, potentially influencing the rate of accumulation of mtDNA mutations. Accelerated mtDNA mutagenesis could contribute to aging, diseases of aging, and sensitize individuals with pathogenic mtDNA variants to stressors. We propose three potential mechanisms of toxicant-induced effects on mtDNA mutagenesis over lifespan: (1) increased de novo mtDNA mutations, (2) altered frequencies of mtDNA mutations, or (3) both. There are remarkably few studies that have investigated the impact of environmental chemical exposures on mtDNA instability and mutagenesis, and even fewer in the context of aging. More studies are warranted because people are exposed to tens of thousands of chemicals, and are living longer. Finally, we suggest that toxicant-induced mtDNA damage and mutational signatures may be a sensitive biomarker for some exposures.

Health repercussions of environmental exposure to lead: Methylation perspective

Lead (Pb) exposure has been a major public health concern for a long time now due to its permanent adverse effects on the human body. The process of lead toxicity has still not been fully understood, but recent advances in Omics technology have enabled researchers to evaluate lead-mediated alterations at the epigenome-wide level. DNA methylation is one of the widely studied and well-understood epigenetic modifications. Pb has demonstrated its ability to induce not just acute deleterious health consequences but also alters the epi-genome such that the disease manifestation happens much later in life as supported by Barkers Hypothesis of the developmental origin of health and diseases. Furthermore, these alterations are passed on to the next generation. Based on previous in-vivo, in-vitro, and human studies, this review provides an insight into the role of Pb in the development of several human disorders.

Associations of blood lead levels with multiple genotoxic biomarkers among workers in China: A population-based study

Carcinogenic effects from low doses of lead (Pb) exposure to populations have been suspected but not concluded. Therefore, a large-scale cross-sectional study was conducted by us to investigate genotoxic effects from Pb exposure during 2016-2018 in North China. Blood lead levels (BLLs) and cumulative blood lead levels (CBLLs) were measured. Multiple relevant biomarkers were used to assess genotoxicity of Pb: mitochondrial DNA copy number (mtDNAcn, n = 871), Comet Tail Intensity (n = 872), γ-H2AX (n = 345), relative telomere length (rTL, n = 757), micronuclei (MN, n = 934) and phosphatidylinositol glycan class A mutation (PIG-A, n = 362). The BLL data show right-skewed distribution, with increase of the median (P25, P75) from 17.4 (8.9, 26.4) μg/dl in 2016 to 18.5 (10.5, 27.2) μg/dl in 2017, and to 20.8 (11.3, 31.0) μg/dl in 2018. Multivariate regression analyses show that mtDNAcn was non-linearly associated with BLLs or CBLLs, i.e. decreased at low levels but increased at the higher levels. Comet and Micronuclei data show positive dose-response relationships with BLLs as well as CBLLs. γ-H2AX data show an overall increased trend with BLLs while rTL data show a shortening trend. No associations were found for PIG-A mutation with Pb exposure. Our findings indicate that current low dose exposure to Pb can still cause health hazards to occupational populations, and the mechanism may be via the induction of DNA & chromosome damage rather than via the mutagenesis pathway.

Lead exposure induces metabolic reprogramming in rat models

Lead is a toxin of great public health concern affecting the young and aging population. Several factors such as age, gender, lifestyle, dose, and genetic makeup result in interindividual variations to lead toxicity mainly due to variations in metabolic consequences. Hence, the present study aimed to examine dose-dependent lead-induced systemic changes in metabolism using rat model by administering specific doses of lead such as 10 (low lead; L-Pb), 50 (moderate lead; M-Pb), and 100 mg/kg (high lead; H-Pb) body weight for a period of one month. Biochemical and haematological analysis revealed that H-Pb was associated with low body weight and feed efficiency, low total protein levels (p ≤ 0.05), high blood lead (Pb-B) levels (p ≤ 0.001), low ALAD (δ-aminolevulinate dehydratase) activity (p ≤ 0.0001), high creatinine (p ≤ 0.0001) and blood urea nitrogen (BUN) (p ≤ 0.01) levels, elevated RBC and WBC counts, reduced haemoglobin and blood cell indices compared to control. Spatial learning and memory test revealed that H-Pb exposed animals presented high latency to the target quadrant and escape platform compared to other groups indicating H-Pb alters cognition function in rats. Histopathological changes were observed in liver and kidney as they are the main target organs of lead toxicity. LC-MS analysis further revealed that Butyryl-L-carnitine (p ≤ 0.01) and Ganglioside GD2 (d18:0/20:0) (p ≤ 0.05) levels were significantly reduced in H-Pb group compared to all groups. Further, pathway enrichment analysis revealed abundance and significantly modulated metabolites associated with oxidative stress pathways. The present study is the first in vivo model of dose-dependent lead exposure for serum metabolite profiling.

Placental mitochondrial DNA mutations and copy numbers in intrauterine growth restricted (IUGR) pregnancy

Intrauterine Growth Restriction (IUGR) is a common and significant complication that arises during pregnancy wherein the fetus fails to attain its full growth potential. Mitochondria being one of the primary sources of energy, plays an important role in placentation and fetal development. In IUGR pregnancy, increased oxidative stress due to inadequate oxygen and nutrient supply could possibly alter mitochondrial functions and homeostasis. In this study, we evaluated the biochemical and molecular changes in mitochondria as biosignature for early and better characterization of IUGR pregnancies. We identified significant increase in mtDNA copy number in both IUGR (p = 0.0001) and Small for Gestational Age (SGA) but healthy (p = 0.0005) placental samples when compared to control. Whole mitochondrial genome sequencing identified novel mutations in both coding and non-coding regions of mtDNA in multiple IUGR placental samples. Sirtuin-3 (Sirt3) protein expression was significantly downregulated (p = 0.027) in IUGR placenta but there was no significant difference in Nrf1 expression in IUGR when compared to control group. Our study provides an evidence for altered mitochondrial homeostasis and paves a way towards interrogating mitochondrial abnormalities in IUGR pregnancies.