Dose-dependent effects of chronic lead toxicity in vivo: Focusing on trace elements and gut microbiota

Lead toxicity mitigation effect of a Lactiplantibacillus plantarum-chondroitin sulfate complex revealed by microbiome and metabolomic analyses

Lead (Pb) is a highly toxic metal with no physiological function in humans, accumulates in the body through food intake, and causes gut microbiome disorders and other hazards. In the present study, we examined the efficacy of a combination of chondroitin sulfate and Lactiplantibacillus plantarum CCFM8661 (CCFM8661 + CS) on tissue Pb accumulation and pathological damage to the liver and kidneys, gut microbiota, and fecal metabolites in Pb-exposed mice. Oral administration of CCFM8661 + CS to Pb-exposed mice reduced Pb accumulation in the liver, kidney, and bone tissues (from 3.70, 14.11 and 121.20 mg g-1 wet tissue to 2.26, 8.72 and 65.57 mg g-1 wet tissue, respectively) and increased total antioxidant capacity, superoxide dismutase, and glutathione in the liver and kidneys. Additionally, gut microbiome analysis showed that CCFM8661 + CS intervention attenuated Pb-induced perturbation in gut microbiota, altering the abundance of bacteria such as Faecalibaculum, Ruminococcaceae UCG 014, Anaerostipes, and Enterorhabdus. Untargeted metabolomics analyses showed that CCFM8661 + CS significantly increased cinnamoylglycine, hippuric acid, and equol (to 31.24, 28.77 and 20.13 times the baseline, respectively) and decreased guanine and 4-coumaric acid (0.30 and 0.09 times the baseline, respectively) in the feces, affecting pathways such as purine and amino acid metabolism. Further analyses showed that promoting Pb excretion and restoring the Pb-impaired gut microbiome and its metabolism may be important contributors to CCFM8661 + CS alleviation of Pb toxicity.

The correlation between single and mixed trace elements exposure in systemic lupus erythematosus: A case-control study

BACKGROUND

Recent studies have shown an association between trace elements and systemic lupus erythematosus (SLE), but the relationship between trace elements and SLE is still unclear. This study aims to determine the distribution of plasma trace elements in newly diagnosed SLE patients and the association between these essential and toxic element mixtures and SLE.

METHODS

In total, 110 SLE patients and 110 healthy controls were included. Blood samples were collected. 15 plasma trace elements were quantified using an inductively coupled plasma mass spectrometer (ICP-MS). Multivariate logistic regression, restricted cubic spline (RCS), weighted quantile sum (WQS) regression, quantile g-computation (qgcomp), and Bayesian kernel machine regression (BKMR) are used to analyze the association between single and mixed exposure of elements and SLE.

RESULTS

The logistic regression model shows that, plasma lithium (Li) [OR (95 % CI): 1.963 (1.49-2.586)], vanadium (V) [OR (95 % CI): 2.617(1.645-4.166)] and lead (Pb) [OR (95 % CI): 1.603(1.197-2.145)] were positively correlated with SLE, while selenium (Se) [OR (95 % CI): 0.055(0.019-0.157)] and barium (Ba) [OR (95 % CI): 0.792(0.656-0.957)] had been identified as protective factors for SLE. RCS results showed a non-linear correlation between the elements Li, V, Ni, copper, Se, rubidium and SLE. In addition, WQS regression, qgcomp, and BKMR models consistently revealed significant positive effects of plasma Li and Pb on SLE, as well as significant negative effects of plasma Se.

CONCLUSIONS

Exposure to heavy metals such as Li and Pb is significantly positively correlated with SLE, but Se may be protective factors for SLE. In addition, there is a nonlinear correlation between the elements Li and Se and SLE, and there are complex interactions between the elements. In the future, larger populations and prospective studies are needed to confirm these associations.

Crosstalk between gut-brain axis: unveiling the mysteries of gut ROS in progression of Parkinson's disease

"Path to a good mood lies through the gut." This statement seems to imply that it has long been believed that the gut is connected with the brain. Research has shown that eating food activates the reward system and releases dopamine (DA), establishing a link between the peripheral and central nervous system. At the same time, researchers also trust that the gut is involved in the onset of many diseases, including Parkinson's disease (PD), in which gastrointestinal dysfunction is considered a prevalent symptom. Reports suggest that PD starts from the gut and reaches the brain via the vagus nerve. Recent studies have revealed an intriguing interaction between the gut and brain, which links gut dysbiosis to the etiology of PD. This review aims to explore the mechanistic pathway how reactive oxygen species (ROS) generation in the gut affects the makeup and operation of the dopamine circuitry in the brain. Our primary concern is ROS generation in the gut, which disrupts the gut microbiome (GM), causing α-synuclein accumulation and inflammation. This trio contributes to the loss of DA neurons in the brain, resulting in PD development. This review also compiles pre-clinical and clinical studies on antioxidants, demonstrating that antioxidants reduce ROS and increase DA levels. Collectively, the study highlights the necessity of comprehending the gut-brain axis for unraveling the riddles of PD pathogenesis and considering new therapeutic approaches.

Could the gut microbiota be capable of making individuals more or less susceptible to environmental toxicants?

Environmental toxicants are chemical substances capable to impair environmental quality and exert adverse effects on humans and other animals. The main routes of exposure to these pollutants are through the respiratory tract, skin, and oral ingestion. When ingested orally, they will encounter trillions of microorganisms that live in a community - the gut microbiota (GM). While pollutants can disrupt the GM balance, GM plays an essential role in the metabolism and bioavailability of these chemical compounds. Under physiological conditions, strategies used by the GM for metabolism and/or excretion of xenobiotics include reductive and hydrolytic transformations, lyase and functional group transfer reactions, and enzyme-mediated functional transformations. Simultaneously, the host performs metabolic processes based mainly on conjugation, oxidation, and hydrolysis reactions. Thus, due to the broad variety of bacterial enzymes present in GM, the repertoire of microbial transformations of chemicals is considered a key component of the machinery involved in the metabolism of pollutants in humans and other mammals. Among pollutants, metals deserve special attention once contamination by metals is a worldwide problem, and their adverse effects can be observed even at very low concentrations due to their toxic properties. In this review, bidirectional interaction between lead, arsenic, cadmium, and mercury and the host organism and its GM will be discussed given the most recent literature, presenting an analysis of the ability of GM to alter the host organism's susceptibility to the toxic effects of heavy metals, as well as evaluating the extent to which interventions targeting the microbiota could be potential initiatives to mitigate the adverse effects resulting from poisoning by heavy metals. This study is the first to highlight the overlap between some of the bacteria found to be altered by metal exposure and the bacteria that also aid the host organism in the metabolism of these metals. This could be a key factor to determine the beneficial species able to minimize the toxicity of metals in future therapeutic approaches.

Effect of Lactiplantibacillus plantarum CCFM8661 on serum metabolites and gut microbiota in a lead-exposed population

In this study, we investigated the impact of Lactiplantibacillus plantarum (L. plantarum) CCFM8661 on the gut microbiota, and the serum and fecal metabolomes in lead (Pb)-exposed individuals. The volunteers recruited for this study were divided into two treatment groups, (i) the placebo (control) and (ii) the L. plantarum CCFM8661 treatment groups. The analysis revealed that probiotic intervention reversed some of the changes in Pb exposure-induced intestinal bacterial abundance, including the abundance of Parabacteroides, Bacteroides, Clostridiaceae, and Erysipelotrichaceae. An analysis of the fecal metabolome identified 26 differential metabolites involved in purine metabolism, unsaturated fatty acid metabolism, and other pathways. Serum metabolite analysis showed that L. plantarum CCFM8661 treatment altered the serum metabolite levels of various metabolic pathways, such as the glycerophospholipid, amino acid, and glutathione metabolism pathways. These results suggest that L. plantarum CCFM8661 may have beneficial effects on Pb-exposed populations by modulating the gut microbiota, host serum metabolism, and the metabolism of the gut microbiota.

The Involvement of Lactic Acid Bacteria and Their Exopolysaccharides in the Biosorption and Detoxication of Heavy Metals in the Gut

Heavy metal pollution has become one of the most important global environmental issues. The human health risk posed by heavy metals encountered through the food chain and occupational and environmental exposure is increasing, resulting in a series of serious diseases. Ingested heavy metals might disturb the function of the gut barrier and cause toxicity to organs or tissues in other sites of the body. Probiotics, including some lactic acid bacteria (LAB), can be used as an alternative strategy to detoxify heavy metals in the host body due to their safety and effectiveness. Exopolysaccharides (EPS) produced by LAB possess varied chemical structures and functional properties and take part in the adsorption of heavy metals via keeping the producing cells vigorous. The main objective of this paper was to summarize the roles of LAB and their EPS in the adsorption and detoxification of heavy metals in the gut. Accumulated evidence has demonstrated that microbial EPS play a pivotal role in heavy metal biosorption. Specifically, EPS-producing LAB have been reported to show superior absorption, tolerance, and efficient abatement of the toxicity of heavy metals in vitro and/or in vivo to non-EPS-producing species. The mechanisms underlying EPS-metal binding are mainly related to the negatively charged acidic groups and unique steric structure on the surface of EPS. However, whether the enriched heavy metals on the bacterial cell surface increase toxicity to local mammal cells or tissues in the intestine and whether they are released during excretion remain to be elucidated.

Lead exposure disturbs ATP7B-mediated copper export from brain barrier cells by inhibiting XIAP-regulated COMMD1 protein degradation

The brain barrier is an important structure for metal ion homeostasis. According to studies, lead (Pb) exposure disrupts the transportation of copper (Cu) through the brain barrier, which may cause impairment of the nervous system; however, the specific mechanism is unknown. The previous studies suggested the X-linked inhibitor of apoptosis (XIAP) is a sensor for cellular Cu level which mediate the degradation of the MURR1 domain-containing 1 (COMMD1) protein. XIAP/COMMD1 axis was thought to be an important regulator in Cu metabolism maintenance. In this study, the role of XIAP-regulated COMMD1 protein degradation in Pb-induced Cu disorders in brain barrier cells was investigated. Pb exposure significantly increased Cu levels in both cell types, according to atomic absorption technology testing. Western blotting and reverse transcription PCR (RT-PCR) showed that COMMD1 protein levels were significantly increased, whereas XIAP, ATP7A, and ATP7B protein levels were significantly decreased. However, there were no significant effects at the messenger RNA (mRNA) level (XIAP, ATP7A, and ATP7B). Pb-induced Cu accumulation and ATP7B expression were reduced when COMMD1 was knocked down by transient small interfering RNA (siRNA) transfection. In addition, transient plasmid transfection of XIAP before Pb exposure reduced Pb-induced Cu accumulation, increased COMMD1 protein levels, and decreased ATP7B levels. In conclusion, Pb exposure can reduce XIAP protein expression, increase COMMD1 protein levels, and specifically decrease ATP7B protein levels, resulting in Cu accumulation in brain barrier cells.

Emblica officinalis mitigates intestinal toxicity of mice by modulating gut microbiota in lead exposure

Lead (Pb) contamination has been affecting public health for decades. As a plant-derived medicine, the safety and effectiveness of Emblica officinalis (E. officinalis) fruit extract has been emphasized. The current study focused on mitigating the adverse effects of lead (Pb) exposure in reducing its toxicity worldwide. According to our findings, E. officinalis significantly improved weight loss and colon length shortening (p < 0.05 or p < 0.01). The data of colon histopathology and serum levels of inflammatory cytokines indicated a positive impact to the colonic tissue and inflammatory cell infiltration in a dose-dependent manner. Moreover, we confirmed the expression level improvement of tight junction proteins (TJPs), including ZO-1, Claudin-1, and Occludin. Furthermore, we found that the abundance of some commensal species necessary for maintaining homeostasis and other beneficial function decreased in Pb exposure model, while a remarkable reversion impact was noticed on the intestinal microbiome composition in the treatment group. These findings were consistent with our speculations that E. officinalis could mitigate the adverse effects caused by Pb in alleviating intestinal tissue damage, intestinal barrier disruption, and inflammation. Meanwhile, the variations in gut microbiota might drive the fulfilling current impact. Hence, the present study could provide the theoretical basis for mitigating intestinal toxicity induced by Pb exposure with the help of E. officinalis.

Effects of Salinomycin and Deferiprone on Lead-Induced Changes in the Mouse Brain

Lead (Pb) is a highly toxic heavy metal that has deleterious effects on the central nervous system. This study aimed to investigate the effects of salinomycin (Sal) and deferiprone (DFP) on brain morphology and on the content of some essential elements in Pb-exposed mice. Adult male Institute of Cancer Research (ICR) mice were exposed to a daily dose of 80 mg/kg body weight ( b.w.) Pb(II) nitrate for 14 days and subsequently treated with Sal (16 mg/kg b.w.) or DFP (19 mg/kg b.w.) for another 14 days. At the end of the experimental protocol, the brains were processed for histological and inductively coupled plasma mass spectrometry (ICP-MS) analyses. Pb exposure resulted in a 50-fold increase in Pb concentration, compared with controls. Magnesium (Mg) and phosphorus (P) were also significantly increased by 22.22% and 17.92%, respectively. The histological analysis of Pb-exposed mice revealed brain pathological changes with features of neuronal necrosis. Brain Pb level remained significantly elevated in Sal- and DFP-administered groups (37-fold and 50-fold, respectively), compared with untreated controls. Treatment with Sal significantly reduced Mg and P concentrations by 22.56% and 18.38%, respectively, compared with the Pb-exposed group. Administration of Sal and DFP ameliorated brain injury in Pb-exposed mice and improved histological features. The results suggest the potential application of Sal and DFP for treatment of Pb-induced neurotoxicity.

Adverse health effects of emerging contaminants on inflammatory bowel disease

Inflammatory bowel disease (IBD) is becoming increasingly prevalent with the improvement of people's living standards in recent years, especially in urban areas. The emerging environmental contaminant is a newly-proposed concept in the progress of industrialization and modernization, referring to synthetic chemicals that were not noticed or researched before, which may lead to many chronic diseases, including IBD. The emerging contaminants mainly include microplastics, endocrine-disrupting chemicals, chemical herbicides, heavy metals, and persisting organic pollutants. In this review, we summarize the adverse health effect of these emerging contaminants on humans and their relationships with IBD. Therefore, we can better understand the impact of these new emerging contaminants on IBD, minimize their exposures, and lower the future incidence of IBD.

Chronic lead exposure exacerbates hepatic glucolipid metabolism disorder and gut microbiota dysbiosis in high-fat-diet mice

Lead (Pb) and obesity are co-occurring risk factors for metabolic disorders. However, there is still a lack of study on the combined effects of both stressors on metabolism. C57BL/6J mice were exposed to 200 mg/L Pb or/and HFD for 24 weeks and were used to investigate the effects and underlying mechanisms of chronic Pb exposure on obese mice. The results showed that Pb significantly increased body weight, visceral obesity, fasting blood glucose levels, and insulin resistance, and aggravated liver damage, hepatic lipid accumulation and steatosis in HFD-fed mice. Further analysis showed that Pb significantly inhibited insulin signaling pathway PI3K/AKT and fatty acid β-oxidation, and accelerated fatty acid synthesis. Moreover, Pb exacerbated HFD-induced disruption of gut microbiota homeostasis, manifested by increased proportions of pathogenic genera such as Desulfovibrio, Alistipes and Helicobacter, and decreased proportions of beneficial microbes Akkermansia and Barnesiella, which were negatively associated with obesity. These results indicated that Pb exposure exacerbated the disruption of liver glucolipid metabolism in HFD mice possibly by disrupting gut microbiota.