DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells

Blood Pb levels are associated with prostate cancer prevalence among general adult males: Linking National Cancer Registry (2002-2017) and KNHANES (2008-2017) databases of Korea

BACKGROUND

Exposure to heavy metals may increase the risk of developing prostate cancer. However, these observations are often inconsistent and not based on clinically diagnosed cases.

OBJECTIVE

To investigate the association of lead (Pb), cadmium (Cd), and mercury (Hg) exposure with clinically determined prostate cancer cases among adult males in South Korea.

METHODS

Metal biomonitoring data and cancer information from the general Korean population were extracted by linking National Cancer Center (NCC) cancer registration data (2002-2017) with Korea National Health and Nutrition Examination Survey (KNHANES) data (2008-2017). Among them, 46 prostate cancer cases (designated as 'all-prostate'), including 25 diagnosed after heavy metal measurement (designated as 'post-prostate'), and 93 matching controls were chosen. Logistic regression analysis was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) between the heavy metal levels and prostate cancer.

RESULTS

Post-prostate patients exhibited higher blood Pb levels than controls (median 3.1 μg/dL vs. 2.38 μg/dL, p = 0.01). For all-prostate cancer, the OR of prostate cancer increased by 2.04-fold for every doubling of Pb levels (95% CI = 1.08-3.87, p = 0.03). The OR was also significantly elevated when comparing the third quartile (Q3) to the lowest quartile (Q1), with ORs ranging from 3.38 to 7.95, depending on model (p < 0.05). Blood Pb levels maintained a positive association with inconsistent significance for post-prostate cancer patients. For Cd and Hg, no statistically significant association was established.

SIGNIFICANCE

By linking two national health databases for the first time, we constructed an unbiased database of prostate cancer cases and matching controls. We found that blood Pb concentrations were associated with the risk of prostate cancer in Korean men at the current level of exposure.

Renal-protective effect of Asparagus officinalis aqueous extract against lead-induced nephrotoxicity mouse model

Lead is one of the cursed substances that threaten all human life. Lead poisoning can occur through food or water contaminations and it is hard to be detected. This incognito metal accumulates over time and resides in the liver, kidneys, and brain tissues leading to serious medical conditions, affecting organ functions, causing failure, kidney tubule degeneration, and destroying neuronal development. However, known metal chelators have bad negative effects. Asparagus officinalis (AO) is a promising herb; its root extract exhibited antioxidant, antiapoptotic, protective, and immunomodulatory activities. Inspired by those reasons, this study investigated to which extent Asparagus extract affected male mice's renal toxicity caused by lead acetate (LA) and antioxidant defense system. This work screened for its nephroprotective activity in four mouse groups: negative and positive control, LA group with renal injury, and diseased but pretreated mice with AO extract (AOE). Kidney index and kidney function biomarkers were evaluated. Antioxidant activities, lipid peroxidation, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), nitric oxide (NO), and reduced glutathione (GSH) were also tested. Furthermore, inflammatory cytokine (tumor necrosis factor-α (TNF-α), interleukin-1 β (IL-1β), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)), inducible nitric oxide synthase (iNOS), renal pro-apoptotic protein (Bax), antiapoptotic protein (Bcl-2), and caspase-3 levels were evaluated. The results showed that LA administration induced oxidative stress, renal inflammation, apoptosis, and renal histopathological alteration. However, due to its antioxidant activities, AOE was found to restrain oxidative stress, therefore preventing inflammation and apoptosis. Collectively, AOE perfectly clogged lead poisoning sneaking, stopped the bad deterioration, and succeeded to protect kidney tissues from toxicity, inflammation, and apoptosis.

Metabolomics: a promising tool for deciphering metabolic impairment in heavy metal toxicities

Heavy metals are the metal compounds found in earth's crust and have densities higher than that of water. Common heavy metals include the lead, arsenic, mercury, cadmium, copper, manganese, chromium, nickel, and aluminum. Their environmental levels are consistently rising above the permissible limits and they are highly toxic as enter living systems via inhalation, ingestion, or inoculation. Prolonged exposures cause the disruption of metabolism, altered gene and/or protein expression, and dysregulated metabolite profiles. Metabolomics is a state of the art analytical tool widely used for pathomolecular inv22estigations, biomarkers, drug discovery and validation of biotransformation pathways in the fields of biomedicine, nutrition, agriculture, and industry. Here, we overview studies using metabolomics as a dynamic tool to decipher the mechanisms of metabolic impairment related to heavy metal toxicities caused by the environmental or experimental exposures in different living systems. These investigations highlight the key role of metabolomics in identifying perturbations in pathways of lipid and amino acid metabolism, with a critical role of oxidative stress in metabolic impairment. We present the conclusions with future perspectives on metabolomics applications in meeting emerging needs.

Lead induces mouse skin fibroblast apoptosis by disrupting intracellular homeostasis

Lead (Pb) is a critical industrial and environmental contaminant that can cause pathophysiological changes in several cellular and organ systems and their processes, including cell proliferation, differentiation, apoptosis, and survival. The skin is readily exposed to and damaged by Pb, but the mechanisms through which Pb damages cells are not fully understood. We examined the apoptotic properties of Pb in mouse skin fibroblast (MSF) in vitro. Treatment of fibroblasts with 40, 80, and 160 μM Pb for 24 h revealed morphological alterations, DNA damage, enhanced caspase-3, -8, and -9 activities, and apoptotic cell population. Furthermore, apoptosis was dosage (0-160 μM) and time (12-48 h) dependent. Concentrations of intracellular calcium (Ca²⁺) and reactive oxygen species were increased, and the mitochondrial membrane potential was decreased in exposed cells. Cell cycle arrest was evident at the G0/G1 phase. The Bax, Fas, caspase-3 and -8, and p53 transcript levels were increased, whereas Bcl-2 gene expression was decreased. Based on our analysis, Pb triggers MSF apoptosis bydisrupting intracellular homeostasis. Our findings enrich the knowledge about the mechanistic function of Pb-induced cytotoxicity on human skin fibroblasts and could potentially guide future Pb health risk assessments.

HDAC6 Triggers the ATM-Dependent DNA Damage Response To Promote PRV Replication

Pseudorabies virus (PRV) infection is modulated by various cellular host factors. In this study, we investigated the role of histone deacetylase 6 (HDAC6) in this process. We determined HDAC6 expression in vitro and performed gene knockout, pharmacological inhibition analyses, immunofluorescence assays, and statistical analyses. We found that the pharmacological and genetic inhibition of HDAC6 significantly decreased PRV replication, whereas its overexpression promoted PRV replication. Additionally, we demonstrated that PRV infection can induce the phosphorylation of histone H2AX and lead to DNA damage response (DDR), and the ataxia telangiectasia mutated (ATM) inhibitor KU55933 inhibits DDR and PRV infection. Mechanistically, the HDAC6 inhibitor tubacin and HDAC6 knockout can decrease DDR. The results of this study suggested that HDAC6 may be a crucial factor in PRV-induced ATM-dependent DDR to promote PRV replication. IMPORTANCE Pseudorabies virus (PRV) is a member of the subfamily Alphaherpesvirinae of the family Herpesviridae. PRV infection in swine can lead to high morbidity and mortality of swine, causing huge economic losses. In particular, PRV variants can cause severe damage to the nervous and respiratory systems of humans, revealing that PRV may be a potential zoonotic pathogen. Vaccines for PRV have been developed that can delay or reduce the epidemic, but they currently cannot eliminate this disease completely. Therefore, studies should investigate new targets for the prevention and control of PRV infection. In this study, we demonstrated that HDAC6 can induce ataxia telangiectasia mutated-dependent DNA damage response to foster PRV replication, indicating that HDAC6 is a therapeutic target for PRV infection.

Mechanism of herpesvirus protein kinase UL13 in immune escape and viral replication

Upon infection, the herpes viruses create a cellular environment suitable for survival, but innate immunity plays a vital role in cellular resistance to viral infection. The UL13 protein of herpesviruses is conserved among all herpesviruses and is a serine/threonine protein kinase, which plays a vital role in escaping innate immunity and promoting viral replication. On the one hand, it can target various immune signaling pathways in vivo, such as the cGAS-STING pathway and the NF-κB pathway. On the other hand, it phosphorylates regulatory many cellular and viral proteins for promoting the lytic cycle. This paper reviews the research progress of the conserved herpesvirus protein kinase UL13 in immune escape and viral replication to provide a basis for elucidating the pathogenic mechanism of herpesviruses, as well as providing insights into the potential means of immune escape and viral replication of other herpesviruses that have not yet resolved the function of it.

METTL3 inhibition reduces N6 -methyladenosine levels and prevents allogeneic CD4+ T-cell responses

Alloreactive CD4+ T cells play a central role in allograft rejection. However, the post-transcriptional regulation of the effector program in alloreactive CD4+ T cells remains unclear. N6 -methyladenosine (m6 A) RNA modification is involved in various physiological and pathological processes. Herein, we investigated whether m6 A methylation plays a role in the allogeneic T-cell effector program. m6 A levels of CD4+ T cells from spleens, draining lymph nodes and skin allografts were determined in a skin transplantation model. The effects of a METTL3 inhibitor (STM2457) on CD4+ T-cell characteristics including proliferation, cell cycle, cell apoptosis and effector differentiation were determined after stimulation of polyclonal and alloantigen-specific (TEa; CD4+ T cells specific for I-Eα52-68 ) CD4+ T cells with α-CD3/α-CD28 monoclonal antibodies and cognate CB6F1 alloantigen, respectively. We found that graft-infiltrating CD4+ T cells expressed high m6 A levels. Administration of STM2457 reduced m6 A levels, inhibited T-cell proliferation and suppressed effector differentiation of polyclonal CD4+ T cells. Alloreactive TEa cells challenged with 40 μm STM2457 exhibited deficits in T-cell proliferation and T helper type 1 cell differentiation, a cell cycle arrest in the G0 phase and elevated cell apoptosis. Moreover, these impaired T-cell responses were associated with the diminished expression levels of transcription factors Ki-67, c-Myc and T-bet. Therefore, METTL3 inhibition reduces the expression of several key transcriptional factors for the T-cell effector program and suppresses alloreactive CD4+ T-cell effector function and differentiation. Targeting m6 A-related enzymes and molecular machinery in CD4+ T cells represents an attractive therapeutic approach to prevent allograft rejection.

Vernonia amygdalina Delile Induces Apoptotic Effects of PC3 Cells: Implication in the Prevention of Prostate Cancer

Background

Prostate cancer (PCa) is one of the common cancers in males and its incidence keeps increasing globally. Approximately 81% of PCa is diagnosed during the early stage of the disease. The treatment options for prostate care include surgery, radiotherapy, and chemotherapy, but these treatments often have side effects that may lead to issues such as impotence or decreased bowel function. Our central goal is to test the apoptotic effects of Vernonia amygdalina Delile (an edible medicinal plant that is relatively inexpensive, nontoxic, and virtually without side effects) for the prevention of PCa using human adenocarcinoma (PC-3) cells as a test model.

Methods

To address our central goal, PC-3 cells were treated with Vernonia amygdalina Delile (VAD). Cell cycle arrest and cell apoptosis were evaluated by Flow Cytometry assessment. Nucleosomal DNA fragmentation was detected by agarose gel electrophoresis.

Results

Flow cytometry data showed that VAD induced cell cycle arrest at the G0/G1 checkpoint and significantly upregulated caspase-3 in treated cells compared to the control cells. Agarose gel electrophoresis resulted in the formation of DNA ladders in VAD-treated cells.

Conclusions

These results suggest that inhibition of cancer cell growth, induction of cell cycle arrest, and apoptosis through caspase-3 activation and nucleosomal DNA fragmentation are involved in the therapeutic mechanisms of VAD as a candidate drug towards the prevention and/or treatment of PCa.

p53 as a unique target of action of cisplatin in acute leukaemia cells

Acute promyelocytic leukaemia (APL) occurs in approximately 10% of acute myeloid leukaemia patients. Arsenic trioxide (ATO) has been for APL chemotherapy, but recently several ATO-resistant cases have been reported worldwide. Cisplatin (CDDP) enhances the toxicity of ATO in ovarian, lung cancer, chronic myelogenous leukaemia, and HL-60 cells. Hence, the goal of this study was to investigate a novel target of CDDP action in APL cells, as an alternate option for the treatment of ATO-resistant APL patients. We applied biochemical, molecular, confocal microscopy and advanced gene editing (CRISPR-Cas9) techniques to elucidate the novel target of CDDP action and its functional mechanism in APL cells. Our main findings revealed that CDDP activated p53 in APL cells through stress signals catalysed by ATM and ATR protein kinases, CHK1 and CHK2 phosphorylation at Ser 345 and Thr68 residues, and downregulation and dissociation of MDM2-DAXX-HAUSP complex. Our functional studies confirmed that CDDP-induced repression of MDM2-DAXX-HAUSP complex was significantly reversed in both nutilin-3-treated KG1a and p53-knockdown NB4 cells. Our findings also showed that CDDP stimulated an increased number of promyelocytes with dense granules, activated p53 expression, and downregulated MDM2 in liver and bone marrow of APL mice. Principal conclusion of our study highlights a novel mode of action of CDDP targeting p53 expression which may provide a basis for designing new anti-leukaemic compounds for treatment of APL patients.

Up-regulation of B-cell lymphoma factor-2 expression, inhibition of oxidative stress and down-regulation of pro-inflammatory cytokines are involved in the protective effect of cabbage (Brassica oleracea) juice in lead-induced endothelial dysfunction in rats

BACKGROUND

Oxido-inflammatory stress and dysregulation of nitric oxide (NO) system has been implicated in lead toxicity. Cabbage is an antioxidant-rich household vegetable with plethora of therapeutic potentials. The present study investigated the anti-oxido-inflammatory activity of cabbage in lead-induced endothelial dysfunction.

METHODS

Twenty (20) male Wistar rats were selected into four groups (n = 5) and treated with distilled water (1 mL/100 g b.wt), lead acetate (25 mg/kg b.wt), cabbage juice (1 mL/100 g b.wt) and lead acetate (25 mg/kg b.wt) plus cabbage juice (1 mL/100 g b.wt) respectively. Treatment was done orally for 28 days, thereafter, oxidative stress (SOD, CAT, GSH, and MDA), inflammatory (TNF-α and IL-6) and apoptotic (Bcl-2) markers were assayed using standard biochemical assays as well as histoarchitectural study of the endothelium.

RESULTS

The results showed that they were significant increase in MDA, ET-1, TNF-α and IL-6 while SOD, GSH, CAT, NO and Bcl-2 protein expression were decreased in Lead exposed animals. Endothelial histoarchitecture was also altered. Following Cabbage juice treatment, MDA, ET-I, TNF-α and IL-6 were down-regulated while SOD, GSH, CAT, NO and Bcl-2 protein expression were up-regulated. Histoarchitecture was significantly recovered.

CONCLUSION

The study suggests that cabbage juice could mitigates Lead-induced endothelial dysfunction by modulating oxido-inflammatory and anti-apoptotic mediators.

DATA AVAILABILITY

All data are available upon request.

Association between lead exposure and DNA damage (genotoxicity): systematic review and meta-analysis

Studies suggest that chronic lead (Pb) exposure may induce deoxyribonucleic acid (DNA) damage. However, there is no synthesised evidence in this regard. We systematically reviewed existing literature and synthesised evidence on the association between chronic Pb exposure and markers of genotoxicity. Observational studies reporting biomarkers of DNA damage among occupationally Pb-exposed and unexposed controls were systematically searched from PubMed, Scopus and Embase databases from inception to January 2022. The markers included were micronucleus frequency (MN), chromosomal aberrations, comet assay, and 8-hydroxy-deoxyguanosine. During the execution of this review, we followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Mean differences in the biological markers of DNA damage between Pb-exposed and control groups were pooled using the random-effects model. The heterogeneity was assessed using the Cochran-Q test and I² statistic. The review included forty-five studies comparing markers of DNA damage between Pb-exposed and unexposed. The primary studies utilised buccal and/or peripheral leukocytes for evaluating the DNA damage. The pooled quantitative results revealed significantly higher DNA damage characterised by increased levels of MN and SCE frequency, chromosomal aberrations, and oxidative DNA damage (comet assay and 8-OHdG) among Pb-exposed than the unexposed. However, studies included in the review exhibited high levels of heterogeneity among the studies. Chronic Pb exposure is associated with DNA damage. However, high-quality, multicentred studies are required to strengthen present observations and further understand the Pb's role in inducing DNA damage. CRD42022286810.

Occupational lead exposure on genome-wide DNA methylation and DNA damage

Lead (Pb) exposure can induce DNA damage and alter DNA methylation but their inter-relationships have not been adequately determined. Our overall aims were to explore such relationships and to evaluate underlying epigenetic mechanisms of Pb-induced genotoxicity in Chinese workers. Blood Pb levels (BLLs) were determined and used as individual's Pb-exposure dose and the Comet assay (i.e., % tail DNA) was conducted to evaluate DNA damage. In the screening assay, 850 K BeadChip sequencing was performed on peripheral blood from 10 controls (BLLs ≤100 μg/L) and 20 exposed workers (i.e., 10 DNA-damaged and 10 DNA-undamaged workers). Using the technique, differentially methylated positions (DMPs) between the controls and the exposed workers were identified. In addition, DMPs were identified between the DNA-undamaged and DNA-damaged workers (% tail DNA >2.14%). In our validation assay, methylation levels of four candidate genes were measured by pyrosequencing in an independent sample set (n = 305), including RRAGC (Ras related GTP binding C), USP1 (Ubiquitin specific protease 1), COPS7B (COP9 signalosome subunit 7 B) and CHEK1 (Checkpoint kinase 1). The result of comparisons between the controls and the Pb-exposed workers show that DMPs were significantly enriched in genes related to nerve conduction and cell cycle. Between DNA-damaged group and DNA-undamaged group, differentially methylated genes were enriched in the pathways related to cell cycle and DNA integrity checkpoints. Additionally, methylation levels of RRAGC and USP1 were negatively associated with BLLs (P < 0.05), and the former mediated 19.40% of the effect of Pb on the % tail DNA. These findings collectively indicated that Pb-induced DNA damage was closely related to methylation of genes in cell cycle regulation, and methylation levels of RRAGC were involved in Pb-induced genotoxicity.

Metals Bioaccumulation in 15 Commonly Consumed Fishes from the Lower Meghna River and Adjacent Areas of Bangladesh and Associated Human Health Hazards

The lower Meghna River, the easternmost part of the Ganges Delta, faces severe anthropogenic perturbations as it receives a huge discharge and industrial effluents. To measure the metal concentrations and human health hazards, edible tissues of 15 commercially important fish species were collected from the local fish markets and the lower Meghna River, Bangladesh. Trace and heavy metals such as Pb, Cr, Cu, Zn, Mn, Fe, Hg, Ni, Ca, Co, Se, Rb, Sr, and As were detected using the Energy Dispersive X-ray Fluorescence (EDXRF) method. The hierarchy of mean metal concentrations obtained was: Fe (162.198 mg/kg) > Zn (113.326 mg/kg) > Ca (87.828 mg/kg) > Sr (75.139 mg/kg) > Cu (36.438 mg/kg) > Se (9.087 mg/kg) > Cr (7.336 mg/kg) > Mn (6.637 mg/kg) > Co (3.474 mg/kg) > Rb (1.912 mg/kg) > Hg (1.657 mg/kg) > Ni (1.467 mg/kg) > Pb (0.521 mg/kg) > As (BDL). Based on the metal concentration obtained, the carnivorous species contained more metals than omnivores and herbivores. Similarly, the euryhaline and benthic feeder fishes had more metals than the stenohalines and demersal fishes. The metal pollution index (MPI) suggested that the highly consumed fish species Tilapia (Oreochromis mossambicus) and Rui (Labeo rohita) accumulated higher metals than other fishes. Both the Targeted Hazard Quotient (THQ) and Hazard Index (HI) values for adult and child consumers were <1, indicating that consumers would not experience the non-carcinogenic health effects. Although children were more susceptible than adults, carcinogenic risk (CR) exposure of Cr for all the consumers was found in the acceptable range (10−6 to 10−4), but the CR exposure of Pb was negligible for all the consumers. The correlation, principal component analysis (PCA), and cluster analysis were conducted to identify the sources of metals identified from the fish tissue. The results indicated that the probable sources of the pollutants were anthropogenic, arising from agricultural activities, electroplating materials, and lubricants used near the study area. However, the present study showed a different metal concentration in the samples at different levels but within the threshold levels non-carcinogenic and carcinogenic health risks; hence, the fishes of the area, in general, are safe for human consumption.

Pseudorabies virus kinase UL13 phosphorylates H2AX to foster viral replication

The DNA damage response (DDR) pathway is critical for maintaining genomic integrity and sustaining organismal development. Viruses can either utilize or circumvent the DDR to facilitate their replication. Pseudorabies virus (PRV) infection was shown to induce apoptosis via stimulating DDR. However, the underlying mechanisms have not been fully explored to date. This study showed that PRV infection robustly activates the ATM and DNA-PK signaling pathways shortly after infection. However, inhibition of ATM, but not DNA-PK, could dampen PRV replication in cells. Importantly, we found that PRV-encoded serine/threonine kinase UL13 interacts with and subsequently phosphorylates H2AX. Furthermore, we found that UL13 deletion largely attenuates PRV neuroinvasiveness and virulence in vivo. In addtion, we showed that UL13 contributes to H2AX phosphorylation upon PRV infection both in vitro and in vivo, but does not affect ATM phosphorylation. Finally, we showed that knockdown of H2AX reduces PRV replication, while this reduction can be further enhanced by deletion of UL13. Taken together, we conclude that PRV-encoded kinase UL13 regulates DNA damage marker γH2AX and UL13-mediated H2AX phosphorylation plays a pivotal role in efficient PRV replication and progeny production.

Protective Effect of Chlorogenic Acid and Its Analogues on Lead-Induced Developmental Neurotoxicity Through Modulating Oxidative Stress and Autophagy

Lead (Pb) is among the deleterious heavy metal and has caused global health concerns due to its tendency to cause a detrimental effect on the development of the central nervous system (CNS). Despite being a serious health concern, treatment of Pb poisoning is not yet available, reflecting the pressing need for compounds that can relieve Pb-induced toxicity, especially neurotoxicity. In the quest of exploring protective strategies against Pb-induced developmental neurotoxicity, compounds from natural resources have gained increased attention. Chlorogenic acid (CGA) and its analogues neochlorogenic acid (NCGA) and cryptochlorogenic acid (CCGA) are the important phenolic compounds widely distributed in plants. Herein, utilizing zebrafish as a model organism, we modeled Pb-induced developmental neurotoxicity and investigated the protective effect of CGA, NCGA, and CCGA co-treatment. In zebrafish, Pb exposure (1,000 μg/L) for 5 days causes developmental malformation, loss of dopaminergic (DA) neurons, and brain vasculature, as well as disrupted neuron differentiation in the CNS. Additionally, Pb-treated zebrafish exhibited abnormal locomotion. Notably, co-treatment with CGA (100 µM), NCGA (100 µM), and CCGA (50 µM) alleviated these developmental malformation and neurotoxicity induced by Pb. Further underlying mechanism investigation revealed that these dietary phenolic acid compounds may ameliorate Pb-induced oxidative stress and autophagy in zebrafish, therefore protecting against Pb-induced developmental neurotoxicity. In general, our study indicates that CGA, NCGA, and CCGA could be promising agents for treating neurotoxicity induced by Pb, and CCGA shows the strongest detoxifying activity.

Mercury Chloride but Not Lead Acetate Causes Apoptotic Cell Death in Human Lung Fibroblast MRC5 Cells via Regulation of Cell Cycle Progression

Heavy metals are important for various biological systems, but, in excess, they pose a serious risk to human health. Heavy metals are commonly used in consumer and industrial products. Despite the increasing evidence on the adverse effects of heavy metals, the detailed mechanisms underlying their action on lung cancer progression are still poorly understood. In the present study, we investigated whether heavy metals (mercury chloride and lead acetate) affect cell viability, cell cycle, and apoptotic cell death in human lung fibroblast MRC5 cells. The results showed that mercury chloride arrested the sub-G₁ and G₂/M phases by inducing cyclin B1 expression. In addition, the exposure to mercury chloride increased apoptosis through the activation of caspase-3. However, lead had no cytotoxic effects on human lung fibroblast MRC5 cells at low concentration. These findings demonstrated that mercury chloride affects the cytotoxicity of MRC5 cells by increasing cell cycle progression and apoptotic cell death.

Lead (Pb) Accumulation in Human THP-1 Monocytes/Macrophages In Vitro and the Influence on Cell Apoptosis

In this study, we investigated the ability of THP-1 monocytes and macrophages to accumulate lead (Pb) in vitro, relative to Pb concentration and length of exposure. Moreover, we also evaluated the effect of Pb accumulation on cell viability and apoptosis. THP-1 monocytes and macrophages were cultured in the presence of Pb at 1.25 μg/dL, 2.5 μg/dL, 5 μg/dL, and 10 μg/dL. Pb accumulation was examined by inductively coupled plasma and confocal microscopy. The influence of Pb on cell viability, apoptosis, and necrosis was assessed using flow cytometry. The results showed that Pb was toxic to THP-1 monocytes/macrophages even at very low environmental concentrations. Despite the use of low concentrations, both monocytes and macrophages showed dose-dependent and time-dependent decreases in viability, with a simultaneous increase in the percentage of early and late apoptotic cells. Macrophages reacted more strongly to Pb than monocytes. When exposed to the same Pb concentrations, they showed lower viability and a higher percentage of necrotic cells. The incubation time positively correlated with Pb accumulation in a dose-dependent manner. The obtained results indicate that environmental exposure to low Pb concentrations may significantly impair the function of macrophages, with the increased number of apoptotic cells potentially contributing to the development of many pathologies in the brain and whole body.

Circulating lead modifies hexavalent chromium-induced genetic damage in a chromate-exposed population: An epidemiological study

Chromium (Cr) can coexist with other heavy metals in the blood of chronically chromate-exposed individuals. However, few studies have explored the health impacts of other hazardous metals after exposure to hexavalent chromium [Cr(VI)]. This study aimed to assess the modification effects of blood lead (Pb) on the genetic damage induced by Cr(VI). During 2010-2019, 1000 blood samples were collected from 455 workers exposed to chromate and 545 workers not exposed to chromate from the same factory with similar labor intensity. The levels of Cr and Pb were measured in whole blood samples. Micronucleus frequency (MNF) and urinary 8-hydroxydeoxyguanosine (8-OHdG) were measured to reflect different types of genetic damage. Multivariate linear regression analyses were performed to evaluate the associations between hazardous metals and the modification effects of Pb on genetic damage. The geometric mean levels of Cr and Pb in the exposure group were significantly higher than those in the control group [Cr: 6.42 (6.08- 6.79) vs. 1.29 (1.22- 1.36) μg/L; Pb: 38.82 (37.22- 40.50) vs. 34.47 (33.15- 35.85) μg/L]. The geometric means of urinary 8-OHdG and MNF in exposure group were 4.00 (3.64- 4.40) μg/g and 5.40 (4.89- 5.97) ‰, respectively, significantly higher than the 3.20 (2.94- 3.48) μg/g and 4.57 (4.15- 5.03) ‰, respectively, in control group. log₂Cr was independently and positively associated with urinary 8-OHdG (β_-adjusted = 0.143, 95% CI: 0.082- 0.204) and MNF (β_-adjusted = 0.303, 95%CI: 0.020- 0.587). With the change in circulating Pb levels, the types of genetic damage induced by Cr(VI) were different. At low levels of circulating Pb (<30.80 μg/L), chromate mainly caused changes in 8-OHdG, while at high circulating Pb levels (≥44.88 μg/L), chromate induced alterations in MNF. The findings suggested that chromate exposure could cause multiple types of genetic damage, and circulating Pb might modify the association between circulating Cr and the form of genetic damage.

Hepatoprotective effect of Moringa oleifera leaves aquatic extract against lead acetate-induced liver injury in male Wistar rats

Current research was performed to explore the hepatoprotective potential of Moringa oleifera leaves extract on lead acetate-induced hepatic injury. Twenty-four male Wistar rats were divided equally into 4 groups. The first group was control, while the second, third, and fourth groups were given 200 mg/kg aqueous Moringa extract only, 100 mg/kg lead only, and 100 mg/kg lead plus 200 mg/kg aqueous Moringa leaves extract, respectively, via oral gavage for 4 weeks. Weight gain and feed efficiency ratio were recorded. Serum lipid profiles, liver enzyme activities, and proteins beside hepatic superoxide dismutase activity, reduced glutathione, tumor necrosis factor alpha (TNF-α), and deoxyribonucleic acid fragmentation were assessed. Liver histopathological examination and nuclear factor kappa B (NF-kB) immunohistochemistry were performed. Administration of lead lowered (P < 0.05) weight gain, feed efficiency ratio, and perturbed lipid profile than control. Lead increased liver enzyme activities and TNF-α, while reduced serum proteins and hepatic antioxidant markers compared to control. Lead aggravated hepatic DNA fragmentation beside the presence of histopathological lesions. Co-administration of aqueous Moringa extract with lead significantly alleviated lead-induced adverse effects. The administration of aqueous Moringa extract with its antioxidant significantly restored the lead perturbations through reduction of oxidative stress-induced DNA damage via amelioration of NF-kB and TNF-α which kept hepatocyte integrity and reduced serum hepatic enzyme activities.

Protective Effects of Smilax glabra Roxb. Against Lead-Induced Renal Oxidative Stress, Inflammation and Apoptosis in Weaning Rats and HEK-293 Cells

Lead (Pb) is an important environmental pollutant. Oxidative stress and the inflammatory response have been postulated as mechanisms involved in lead-induced renal damage. Smilax glabra Roxb. has been used for treatment of heavy-metal poisoning in China for 500 years. We investigated S. glabra flavonoids extract (SGF) could attenuate lead acetate-induced nephrotoxicity in weaning rats and human embryonic kidney (HEK)-293 cells, and investigated the possible mechanisms. Compared with Pb exposed group of weaning rats, SGF could significantly promote lead excretion in the blood and kidney, and increase the content of the renal-function indicators blood urea nitrogen, serum uric acid, and serum creatinine. SGF could improve the glomerular filtration rate (GFR) and histologic changes in the kidneys of weaning rats exposed to Pb. SGF could also reduce lead-induced cytotoxicity, improve DNA damage-induced apoptosis and cleaved caspase-3-mediated apoptosis in HEK-293 cells stimulated with Pb. SGF significantly increased the activity of the antioxidant enzymes superoxide dismutase, glutathione peroxidase and catalase, and decreased excessive release of reactive oxygen species (ROS) and malondialdehyde in the kidneys of the weaning rats and in HEK-293 cells. The antioxidant mechanism of SGF related to activation of the Kelch-like ECH-associated protein 1/nuclear-factor-E2-related factor 2/hemeoxygenase-1(Keap1/Nrf2/HO-1) pathway. SGF could inhibit secretion of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α induced by Pb in vivo and in vitro. The anti-inflammatory mechanism of SGF related to inhibition of ROS and pro-inflammatory cytokines triggered the nuclear factor-kappa B (NF-κB) pathway through blockade of inhibitors of I-κB degradation, phosphorylation of NF-κB p65, and nuclear translocation of p65. Our findings indicate that SGF could be a natural antioxidant and anti-inflammatory agent for treating lead-induced nephrotoxicity.

Regulation of Nrf2 and NF-κB during lead toxicity in bovine granulosa cells

Lead (Pb), one of the pervasive and protracted environmental heavy metals, is believed to affect the female reproductive system in many species. The Nrf2 and NF-κB are the two key transcriptional factors regulating cellular redox status and response against stress and inflammation respectively, showing an interaction between each other. The aim of this study is to investigate the effect of Pb on bovine granulosa cells (GCs) and its association with the regulation of Nrf2 and NF-κB pathways. For this, bovine GCs were cultured in vitro and exposed to different doses of Pb for 2 h. Cellular response to Pb insult was investigated 24 h post treatment. Results showed that exposure of GCs to Pb-induced ROS accumulation and protein carbonylation. Additionally, GCs exhibited reduction in cell viability and decrease in the expression of cell proliferation marker genes (CCND2 and PCNA). This was accompanied by cell cycle arrest at G0/G1 phase. Moreover, Pb downregulated both Nrf2 and NF-κB and their downstream genes. Lead increased the expression of endoplasmic reticulum (ER) stress marker genes (GRP78 and CHOP) and the proapoptotic gene (caspase-3) while the antiapoptotic gene (BCL-2) was reduced. Our findings suggest that Pb-driven oxidative stress affected GCs proliferation, enhances ER stress, induces cell cycle arrest and mediates apoptosis probably via disruption of Nrf2/NF-κB cross-talk. However, further functional analysis is required to explain different aspects of Nrf2 and NF-κB interactions under metal challenge.

BIRC5 Gene Disruption via CRISPR/Cas9n Platform Suppress Acute Myelocytic Leukemia Progression

Background

Acute myelocytic leukemia (AML) is a clonal malignancy resulting from the accumulation of genetic abnormalities in the cells. Human baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5), encodes survivin, is one of only a handful of genes that is differentially over-expressed in numerous malignant diseases including AML.

Methods

The BIRC5 was silenced permanently in two AML cell lines, HL‑60 and KG-1, via the CRISPR/Cas9n system. After transfection of CRISPR constructs, genomic DNA was extracted and amplified to assess mutation detection. To evaluate BIRC5 gene expression, quantitative real-time PCR was performed. Also, MTT cell viability and Annexin‑V/propidium iodide flowcytometric staining were performed, and the data were analyzed using the Kolmogorov-Smirnov, Levene's, and ANOVA tests.

Results

The results indicated that Cas9n and its sgRNAs successfully triggered site-specific cleavage and mutation in the BIRC5 gene locus. Moreover, suppression of BIRC5 resulted in the reduction of cell viability, and induction of apoptosis and necrosis in HL60 and KG1 suggested that the permanent suppression of BIRC5 remarkably dropped the gene expression and cells viability.

Conclusion

This study reinforces the idea that BIRC5 disruption via Cas9n:sgRNAs has favorable effects on the AML clinical outcome. It thereby can be a promising candidate in a variety of leukemia treatments.

The antagonistic effect of Se on the Pb-weakening formation of neutrophil extracellular traps in chicken neutrophils

Neutrophils represent an important part of the body's innate immunity and can resist the invasion of pathogenic microorganisms by releasing neutrophil extracellular traps (NETs). In this study, we investigated the toxic effects of lead (Pb) on the release of NETs, the antagonism of selenium (Se) on Pb toxicity and the potential molecular mechanisms. Our model was an in vitro exposure model for the addition of Se, Pb or both in the culture medium and was based on the separation of neutrophils from the peripheral blood of healthy chickens. Phorbol-myristate-acetate (PMA) was used as a stimulant. The scanning electron microscopy and fluorescence microscopy results showed that Pb weakened the PMA-induced formation of NETs. Exposure to Pb reduced the expression of the extracellular regulated protein kinase (ERK) pathway and the respiratory burst. Exposure to Pb also attenuated the release of Ca²⁺ in the endoplasmic reticulum mediated by the inositol 1,4,5-trisphosphate receptor (IP3R). These are two ways by which Pb decreases the formation of NETs. Pb also attenuates the expression levels of myeloperoxidase (MPO) and neutrophil elastase (NE), and attenuates histone removal by affecting the expression of different protein kinase C (PKC) isoforms. In contrast, Se can reduce the toxic damage caused by Pb. These results indicate that exposure to Pb decreases the formation of NETs, while Se can antagonize the toxicity of Pb to allow the formation of NETs.

Synergistic effects of Pb and repeated heat pulse on developmental neurotoxicity in zebrafish

Pollutant discharges to the aquatic environment often contain multiple environmental stressors, affecting aquatic organisms. To mimic the discharges from nuclear and industry facilities, the combined effects of two independent types of stressors, heavy metal Pb and repeated heat pulse were addressed in this study. We investigated the developmental toxicity of combined treatment, especially its toxic effects on zebrafish neurodevelopment. The normal embryos at 4 hpf were exposed to 0.2 mM of Pb dissolved in the bathing medium with different temperatures (30, 32, and 34 °C) and then maintained in an incubator at 28 °C. After performing above treatment once every 24 h for 6 days, we found that combined treatment significantly affected neural development, including loss of dopaminergic (DA) neurons and brain vasculature, disruption of locomotor activity and neurodevelopmental genes expression in a temperature-dependent manner as compared to the Pb alone exposure group, indicating that repeated heat pulse enhances these negative impacts induced by Pb. In contrast, no apparent toxicity was observed in repeated heat pulse alone groups, suggesting that Pb treatment reduces thermal tolerance in zebrafish, which emphasized the importance to evaluate synergistic effects of Pb and repeated heat pulse. Moreover, repeated heat pulse aggravated Pb-induced apoptosis in the zebrafish brain. Further study of the underlying mechanism suggested that Caspase 3 regulated apoptosis was involved in this process. Taken together, our findings shed light on the full understanding of toxic effects of discharges from industrial applications on living organisms and its environmental impact.

State of the science review of the health effects of inorganic arsenic: Perspectives for future research

Human exposure to inorganic arsenic (iAs) is a global health issue. Although there is strong evidence for iAs-induced toxicity at higher levels of exposure, many epidemiological studies evaluating its effects at low exposure levels have reported mixed results. We comprehensively reviewed the literature and evaluated the scientific knowledge on human exposure to arsenic, mechanisms of action, systemic and carcinogenic effects, risk characterization, and regulatory guidelines. We identified areas where additional research is needed. These priority areas include: (1) further development of animal models of iAs carcinogenicity to identify molecular events involved in iAs carcinogenicity; (2) characterization of underlying mechanisms of iAs toxicity; (3) assessment of gender-specific susceptibilities and other factors that modulate arsenic metabolism; (4) sufficiently powered epidemiological studies to ascertain relationship between iAs exposure and reproductive/developmental effects; (5) evaluation of genetic/epigenetic determinants of iAs effects in children; and (6) epidemiological studies of people chronically exposed to low iAs concentrations.

Combination of Mitochondrial and Plasma Membrane Citrate Transporter Inhibitors Inhibits De Novo Lipogenesis Pathway and Triggers Apoptosis in Hepatocellular Carcinoma Cells

Increased expression levels of both mitochondrial citrate transporter (CTP) and plasma membrane citrate transporter (PMCT) proteins have been found in various cancers. The transported citrates by these two transporter proteins provide acetyl-CoA precursors for the de novo lipogenesis (DNL) pathway to support a high rate of cancer cell viability and development. Inhibition of the DNL pathway promotes cancer cell apoptosis without apparent cytotoxic to normal cells, leading to the representation of selective and powerful targets for cancer therapy. The present study demonstrates that treatments with CTP inhibitor (CTPi), PMCT inhibitor (PMCTi), and the combination of CTPi and PMCTi resulted in decreased cell viability in two hepatocellular carcinoma cell lines (HepG2 and HuH-7). Treatment with citrate transporter inhibitors caused a greater cytotoxic effect in HepG2 cells than in HuH-7 cells. A lower concentration of combined CTPi and PMCTi promotes cytotoxic effect compared with either of a single compound. An increased cell apoptosis and an induced cell cycle arrest in both cell lines were reported after administration of the combined inhibitors. A combination treatment exhibits an enhanced apoptosis through decreased intracellular citrate levels, which consequently cause inhibition of fatty acid production in HepG2 cells. Apoptosis induction through the mitochondrial-dependent pathway was found as a consequence of suppressed carnitine palmitoyl transferase-1 (CPT-1) activity and enhanced ROS generation by combined CTPi and PMCTi treatment. We showed that accumulation of malonyl-CoA did not correlate with decreasing CPT-1 activity. The present study showed that elevated ROS levels served as an inhibition on Bcl-2 activity that is at least in part responsible for apoptosis. Moreover, inhibition of the citrate transporter is selectively cytotoxic to HepG2 cells but not in primary human hepatocytes, supporting citrate-mediating fatty acid synthesis as a promising cancer therapy.

Hepatoprotective efficacy of Spirulina platensis against lead-induced oxidative stress and genotoxicity in catfish; Clarias gariepinus

Lead (Pb) is a toxic environmental pollutant that induces a broad range of biochemical and physiological hazards in living organisms. We investigated the possible hepatoprotective effects of Spirulina platensis (SP) in counteracting the Pb-induced oxidative damage. Ninety-six adult African catfish were allocated into four equal groups. The 1st group (control) fed basal diet while the 2nd group (Pb-treated) fed on basal diet and exposed to 1mg Pb(NO₃)₂/L. The 3rd and 4th groups fed SP-supplemented basal diets at levels of 0.25% and 0.5%, respectively and exposed to Pb. Serum samples were used to analyze hepatic function biomarkers, electrolytes, and oxidant and antioxidant status. Lipid peroxidation and DNA fragmentation were determined in the liver tissues. Pb exposure induced hepatic dysfunction, electrolytes (Na⁺, K⁺, Ca⁺², and Cl^-) imbalance, as well a significant decrease in GSH content, and LDH, AChE, SOD, CAT and GST enzymes activity. SP supplementation reverted these biochemical and genetic alterations close to control levels. This amelioration was higher with 0.5% SP and at the 4th week of exposure, showing concentration- and time-dependency. Thus, the current study suggests that SP could protect the catfish liver against lead-induced injury by scavenging ROS, sustaining the antioxidant status and diminishing DNA oxidative damage. The dietary inclusion of SP can be used as a promising protective agent to counteract oxidative stress-mediated diseases and toxicities.

Genotoxicity of two heavy metal compounds: lead nitrate and cobalt chloride in Polychaete Perinereis cultrifera

The present study explores the in vivo and in vitro genotoxic effects of lead nitrate, [Pb(NO₃)₂] a recognized environmental pollutant and cobalt chloride (CoCl₂), an emerging environmental pollutant in polychaete Perinereis cultrifera using comet assay. Despite widespread occurrence and extensive industrial applications, no previous published reports on genotoxicity of these compounds are available in polychaete as detected by comet assay. Polychaetes were exposed in vivo to Pb(NO₃)₂ (0, 100, 500, and 1000 μg/l) and CoCl₂ (0, 100, 300, and 500 μg/l) for 5 days. At 100 μg/l Pb(NO₃)₂ concentration, tail DNA (TDNA) values in coelomocytes were increase by 1.16, 1.43, and 1.55-fold after day 1, day 3, and day 5, whereas, OTM showed 1.12, 2.33, and 2.10-fold increase in in vivo. Pb(NO₃)₂ showed a concentration and time-dependent genotoxicity whereas CoCl₂ showed a concentration-dependent genotoxicity in in vivo. A concentration-dependent increase in DNA damage was observed in in vitro studies for Pb(NO₃)₂ and CoCl₂. DNA damage at 500 μg/L showed almost threefold increase in TDNA and approximately fourfold increase in OTM as compared to control in in vitro. Our studies suggest that Pb(NO₃)₂ and CoCl₂ have potential to cause genotoxic damage, with Pb(NO₃)₂ being more genotoxic in polychaete and should be used more carefully in industrial and other activities. Graphical abstract.

Nickel-Refining Fumes Induced DNA Damage and Apoptosis of NIH/3T3 Cells via Oxidative Stress

Although there have been numerous studies examining the toxicity and carcinogenicity of nickel compounds in humans and animals, its molecular mechanisms of action are not fully elucidated. In our research, NIH/3T3 cells were exposed to nickel-refining fumes at the concentrations of 0, 6.25, 12.50, 25, 50 and 100 μg/mL for 24 h. Cell viability, cell apoptosis, reactive oxygen species (ROS) level, lactate dehydrogenase (LDH) assay, the level of glutathione (GSH), activities of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) level were detected. The exposure of NIH/3T3 cells to nickel-refining fumes significantly reduced cell viability and induced cell apoptotic death in a dose-dependent manner. Nickel-refining fumes significantly increased ROS levels and induced DNA damage. Nickel-refining fumes may induce the changes in the state of ROS, which may eventually initiate oxidative stress, DNA damage and apoptosis of NIH/3T3 cells.

Indigofera oblongifolia mitigates lead-acetate-induced kidney damage and apoptosis in a rat model

This study was conducted to appraise the protective effect of Indigofera oblongifolia leaf extract on lead acetate (PbAc)-induced nephrotoxicity in rats. PbAc was intraperitoneally injected at a dose of 20 mg/kg body weight for 5 days, either alone or together with the methanol extract of I. oblongifolia (100 mg/kg). Kidney lead (Pb) concentration; oxidative stress markers including lipid peroxidation, nitrite/nitrate, and glutathione (GSH); and antioxidant enzyme activities, namely superoxide dismutase, catalase, GSH peroxidase, and GSH reductase were all determined. The PbAc injection elicited a marked elevation in Pb concentration, lipid peroxidation, and nitrite/nitrate, with a concomitant depletion in GSH content compared with the control and a remarkable decrease in antioxidant enzymes. Oxidant/antioxidant imbalance, Pb accumulation, and histological changes in the kidneys were successfully prevented by the pre-administration of I. oblongifolia extract. In addition, the elevated expression of proapoptotic protein, Bax, in the kidneys of the PbAc-injected rats was reduced as a result of I. oblongifolia pre-administration, while the hitherto reduced expression of the anti-apoptotic protein Bcl-2 was elevated. Based on the current findings, it can be concluded that I. oblongifolia successfully minimizes the deleterious effects in kidney function and histological coherence associated with nephrotoxicity by strengthening the antioxidant defense system, suppressing oxidative stress, and mitigating apoptosis.