Cardiac Toxicity Induced by Long-Term Environmental Levels of MC-LR Exposure in Mice.

Cyanobacterial blooms are considered a serious global environmental problem. Recent studies provided evidence for a positive association between exposure to microcystin-LR (MC-LR) and cardiotoxicity, posing a threat to human cardiovascular health. However, there are few studies on the cardiotoxic effects and mechanisms of long-term low-dose MC-LR exposure. Therefore, this study explored the long-term toxic effects and toxic mechanisms of MC-LR on the heart and provided evidence for the induction of cardiovascular disease by MC-LR. C57BL/6 mice were exposed to 0, 1, 30, 60, 90, and 120 µg/L MC-LR via drinking water for 9 months and subsequently necropsied to examine the hearts for microstructural changes using H&E and Masson staining. The results demonstrated fibrotic changes, and qPCR and Western blots showed a significant up-regulation of the markers of myocardial fibrosis, including TGF-ß1, α-SMA, COL1, and MMP9. Through the screening of signaling pathways, it was found the expression of PI3K/AKT/mTOR signaling pathway proteins was up-regulated. These data first suggested MC-LR may induce myocardial fibrosis by activating the PI3K/AKT/mTOR signaling pathway. This study explored the toxicity of microcystins to the heart and preliminarily explored the toxic mechanisms of long-term toxicity for the first time, providing a theoretical reference for preventing cardiovascular diseases caused by MC-LR.

Prevalence and associated influential factors of mental health problems among Chinese college students during different stages of COVID-19 pandemic: A systematic review.

This systematic review aims to take China as an example to determine the prevalence of mental health problems and associated influential factors of college students in different stages of the COVID-19 pandemic and provide a reference for effective intervention in the future. A systematic search was conducted on PubMed, Web of Science, Scopus, Science Direct, and Google scholar. A total of 30 articles were included. 1,477,923 Chinese college students were surveyed. In the early stage, the prevalence rates of depression, anxiety, stress, and PTSD ranged from 9.0% to 65.2%, 6.88%-41.1%, 8.53%-67.05%, and 2.7%-30.8%, respectively. Major risk factors were being a female, a medical student, isolation or quarantine, having family members or friends infected with COVID-19, and challenges of online learning. During the normalization stage, depression, anxiety, and insomnia prevalence rates ranged from 8.7% to 50.2%, 4.2%-34.6%, and 6.1%-35.0%, respectively. The main risk factors were self-quarantined after school reopening, regular taking temperature, and wearing face masks. The prevalence rates of mental health problems and associated influential factors unveiled in both stages showed that the students' mental health status was greatly affected. Therefore, a combination of efforts from the government, universities, and families or communities is highly needed to alleviate the mental health sufferings of students.

Immobilization of Microbes for Biodegradation of Microcystins: A Mini Review.

Harmful cyanobacterial blooms (HCBs) frequently occur in eutrophic freshwater ecosystems worldwide. Microcystins (MCs) are considered to be the most prominent and toxic metabolites during HCBs. MCs may be harmful to human and animal health through drinking water and recreational water. Biodegradation is eco-friendly, cost-effective and one of the most effective methods to remove MCs. Many novel MC-degrading bacteria and their potential for MCs degradation have been documented. However, it is a challenge to apply the free MC-degrading bacterial cells in natural environments due to the long-term operational instability and difficult recycling. Immobilization is the process of restricting the mobility of bacteria using carriers, which has several advantages as biocatalysts compared to free bacterial cells. Biological water treatment systems with microbial immobilization technology can potentially be utilized to treat MC-polluted wastewater. In this review article, various types of supporting materials and methods for microbial immobilization and the application of bacterial immobilization technology for the treatment of MCs-contaminated water are discussed. This article may further broaden the application of microbial immobilization technology to the bioremediation of MC-polluted environments.

Optimization of Biodegradation Characteristics of Sphingopyxis sp. YF1 against Crude Microcystin-LR Using Response Surface Methodology.

Sphingopyxis sp. YF1 has proven to be efficient in biodegrading microcystin (MC)-leucine (L) and arginine (R) (MC-LR); however, the optimal environmental factors to biodegrade the toxin have not been investigated. In this study, the biodegrading characteristics of strain YF1 against MC-LR were assessed under diverse environmental factors, including temperature (20, 30 or 40 °C), pH (5, 7 or 9) and MC-LR concentration (1, 3 or 5 µg/mL). Data obtained from the single-factor experiment indicated that MC-LR biodegradation by strain YF1 was temperature-, pH- and MC-LR-concentration-dependent, and the maximal biodegradation rate occurred at 5 µg/mL/h. Proposing Box-Behnken Design in response surface methodology, the influence of the three environmental factors on the biodegradation efficiency of MC-LR using strain YF1 was determined. A 17-run experiment was generated and carried out, including five replications performed at the center point. The ANOVA analysis demonstrated that the model was significant, and the model prediction of MC-LR biodegradation was also validated with the experimental data. The quadratic statistical model was established to predict the interactive effects of the environmental factors on MC-LR biodegradation efficiency and to optimize the controlling parameters. The optimal conditions for MC-LR biodegradation were observed at 30 °C, pH 7 and 3 µg/mL MC-LR, with a biodegradation efficiency of 100% after 60 min. The determination of the optimal environmental factors will help to unveil the detailed biodegradation mechanism of MC-LR by strain YF1 and to apply it into the practice of eliminating MC-LR from the environment.

Under-five mortality and associated factors in southeastern Ethiopia.

BACKGROUND: In the year 2019, around 5 million children under age five died and most of the deaths happened in developing countries. Though large numbers of deaths are reported in such countries, limited availability of data poses a substantial challenge on generating reliable estimates. Hence, this study aims to assess the prevalence and factors associated with under-five mortality in southeastern Ethiopia. METHODS: A register based cross sectional study was conducted from 1st September 2014 to July 2019 in Asella teaching and referral hospital. A total of 4901 under-five age children registered on the admission and discharge book of pediatric ward with complete information were included for the analysis. Data entry and analysis were conducted using Epidata Version 7 and SPSS version 21, respectively. Descriptive statistics were used to explore the characteristics of the study participants and their condition at discharge. Adjusted Odds Ratio (AOR) with its 95% Confidence interval and P-value less than 5% was used to decide the statistically significant association. RESULTS: The prevalence of under-five mortality among admitted children in Asella Teaching and Referral hospital was 8.7% (95% CI 7.91-9.50%). Post-Neonatal and Child mortality were found to be 9.1% and 8.18%, respectively. Moreover, large numbers of death (45.2%) were seen within the first 2 days of admission. Address (AOR:1.4(1.08-1.81)), HIV status (AOR:4.64 (2.19-9.8)), severe acute malnutrition (AOR:2.82 (2.03-3.91)), hypovolemic shock (AOR:4.32 (2.31-8.1)), type I diabetes with DKA (AOR:3.53(1.34-9.29) and length of stay in the hospital for ≤2 days (AOR: 4.28 (3.09-5.95)) as well as 3-4 days (AOR: 1.48 (1.02-2.15)) were among the identified predictors. CONCLUSIONS: Though childhood mortality is swiftly decreasing, and access and utilization of health care is improving in Ethiopia, our study found large prevalence of under-five mortality, 8.7% and higher number of deaths in early days of admission. Improving the quality of service has a paramount importance in reducing the mortality and managing associated factors contributing to under-five mortality among admitted children.

Role of PI3K/Akt signaling pathway in cardiac fibrosis.

Heart failure (HF) is considered as a severe health problem worldwide, while cardiac fibrosis is one of the main driving factors for the progress of HF. Cardiac fibrosis was characterized by changes in cardiomyocytes, cardiac fibroblasts, ratio of collagen (COL) I/III, and the excessive production and deposition of extracellular matrix (ECM), thus forming a scar tissue, which leads to pathological process of cardiac structural changes and systolic as well as diastolic dysfunction. Cardiac fibrosis is a common pathological change of many advanced cardiovascular diseases including ischemic heart disease, hypertension, and HF. Accumulated studies have proven that phosphoinositol-3 kinase (PI3K)/Akt signaling pathway is involved in regulating the occurrence, progression and pathological formation of cardiac fibrosis via regulating cell survival, apoptosis, growth, cardiac contractility and even the transcription of related genes through a series of molecules including mammalian target of rapamycin (mTOR), glycogen synthase kinase 3 (GSK-3), forkhead box proteins O1/3 (FoxO1/3), and nitric oxide synthase (NOS). Thus, the review focuses on the role of PI3K/Akt signaling pathway in the cardiac fibrosis. The information reviewed here should be significant in understanding the role of PI3K/Akt in cardiac fibrosis and contribute to the design of further studies related to PI3K/Akt and the cardiac fibrotic response, as well as sought to shed light on a potential treatment for cardiac fibrosis.

Optimization of microcystin biodegradation by bacterial community YFMCD4 using response surface method.

The increasing production of microcystin-LR (MC-LR) causing animal and human health issues is found in eutrophic water bodies, marine habitats and desert environments. The health threat posed by MC-LR has led to the establishment of World Health Organization's water guideline value of 1 µg/mL. Combating this has increased the search for cost-effective approach to degrade MC-LR. The study aimed to optimize the MC-degrading environmental factors of bacterial community YFMCD4. Response surface methodology (RSM) was employed to evaluate the influence of varying temperatures, pH and initial MC-LR concentration on the biodegradation efficiency of MC-LR by bacterial community YFMCD4. The optimal MC-LR biodegradation environmental factors were found to be 30 °C, pH 7 and 2 µg/mL initial MC-LR. The biodegradation rate reached 100% after 10 h. YFMCD4 mainly consisted of genera Alacligenes, Sphingobacterium and Pseudomonas using High-throughput pyrosequencing technology. The mlrA gene encoding MlrA enzyme considered most important for MC-LR biodegradation was obtained from YFMCD4. Data demonstrated that the bacterial structure and biodegradation efficiency of YFMCD4 varied with the change of environmental factors including temperature, pH and MC-LR concentrations. RSM is considered a good method to examine the optimal biodegradation environmental conditions for MC-LR. To date, RSM and High-throughput pyrosequencing technology are employed to optimize the biodegradation conditions (30 °C, pH 7 and 2 µg/mL initial MC-LR) and analyze the structure of bacterial community for the first time.

Characterization and Mechanism of Linearized-Microcystinase Involved in Bacterial Degradation of Microcystins.

Microcystins (MCs) are extremely hazardous to the ecological environment and public health. How to control and remove MCs is an unsolved problem all over the world. Some microbes and their enzymes are thought to be effective in degrading MCs. Microcystinase can linearize microcystin-leucine-arginine (MC-LR) via a specific locus. However, linearized MC-LR is also very toxic and needs to be removed. How linearized MC-LR was metabolized by linearized-microcystinase, especially how linearized-microcystinase binds to linearized MC-LR, has not been defined. A combination of in vitro experiments and computer simulation was applied to explore the characterization and molecular mechanisms for linearized MC-LR degraded by linearized-microcystinase. The purified linearized-microcystinase was obtained by recombinant Escherichia coli overexpressing. The concentration of linearized MC-LR was detected by high-performance liquid chromatography, and linearized MC-LR degradation products were analyzed by the mass spectrometer. Homology modeling was used to predict the structure of the linearized-microcystinase. Molecular docking techniques on the computer were used to simulate the binding sites of linearized-microcystinase and linearized MC-LR. The purified linearized-microcystinase was obtained successfully. The linearized-microcystinase degraded linearized MC-LR to tetrapeptide efficiently. The second structure of linearized-microcystinase consisted of many alpha-helices, beta-strands, and colis. Linearized-microcystinase interacted the linearized MC-LR with hydrogen bond, hydrophobic interaction, electrostatic forces, and the Van der Waals force. This study firstly reveals the characterization and specific enzymatic mechanism of linearized-microcystinase for catalyzing linearized MC-LR. These findings encourage the application of MC-degrading engineering bacteria and build a great technique for MC-LR biodegradation in environmental engineering.

Pb Toxicity on Gut Physiology and Microbiota.

Lead (Pb) is a toxic heavy metal, having profound threats to the global population. Multiple organs such as kidney, and liver, as well as nervous, hematologic, and reproductive systems, are commonly considered the targets of Pb toxicity. Increasing researches reported that the effects of Pb on gastrointestinal tracts are equally intensive, especially on intestinal microbiota. This review summarized Pb toxicity on gut physiology and microbiota in different animal models and in humans, of which the alterations may further have effects on other organs in host. To be more specific, Pb can impair gut barrier and increase gut permeability, which make inflammatory cytokines, immunologic factors, as well as microbial metabolites such as bile acids (BA) and short-chain fatty acids (SCFAs) enter the enterohepatic circulation easily, and finally induce multiple systematic lesion. In addition, we emphasized that probiotic treatment may be one of the feasible and effective strategies for preventing Pb toxicity.

A Review of Nephrotoxicity of Microcystins.

Cyanobacterial blooms triggered by eutrophication and climate change have become a global public health issue. The toxic metabolites microcystins (MCs) generated by cyanobacteria can accumulate in food chain and contaminate water, thus posing a potential threat to human and animals health. Studies have suggested that aside liver, the kidney may be another target organ of MCs intoxication. Therefore, this review provides various evidences on the nephrotoxicity of MCs. The review concludes that nephrotoxicity of MCs may be related to inhibition of protein phosphatases and excessive production of reactive oxygen species, cytoskeleton disruption, endoplasmic reticulum stress, DNA damage and cell apoptosis. To protect human from MCs toxic consequences, this paper also puts forward some directions for further research.

A Mini-Review on Detection Methods of Microcystins.

Cyanobacterial harmful algal blooms (CyanoHABs) produce microcystins (MCs) which are associated with animal and human hepatotoxicity. Over 270 variants of MC exist. MCs have been continually studied due of their toxic consequences. Monitoring water quality to assess the presence of MCs is of utmost importance although it is often difficult because CyanoHABs may generate multiple MC variants, and their low concentration in water. To effectively manage and control these toxins and prevent their health risks, sensitive, fast, and reliable methods capable of detecting MCs are required. This paper aims to review the three main analytical methods used to detect MCs ranging from biological (mouse bioassay), biochemical (protein phosphatase inhibition assay and enzyme linked immunosorbent assay), and chemical (high performance liquid chromatography, liquid chromatography-mass spectrometry, high performance capillary electrophoresis, and gas chromatography), as well as the newly emerging biosensor methods. In addition, the current state of these methods regarding their novel development and usage, as well as merits and limitations are presented. Finally, this paper also provides recommendations and future research directions towards method application and improvement.

Genome-Wide Analysis Reveals Genetic Potential for Aromatic Compounds Biodegradation of Sphingopyxis.

Members of genus Sphingopyxis are frequently found in diverse eco-environments worldwide and have been traditionally considered to play vital roles in the degradation of aromatic compounds. Over recent decades, many aromatic-degrading Sphingopyxis strains have been isolated and recorded, but little is known about their genetic nature related to aromatic compounds biodegradation. In this study, bacterial genomes of 19 Sphingopyxis strains were used for comparative analyses. Phylogeny showed an ambiguous relatedness between bacterial strains and their habitat specificity, while clustering based on Cluster of Orthologous Groups suggested the potential link of functional profile with substrate-specific traits. Pan-genome analysis revealed that 19 individuals were predicted to share 1,066 orthologous genes, indicating a high genetic homogeneity among Sphingopyxis strains. Notably, KEGG Automatic Annotation Server results suggested that most genes pertaining aromatic compounds biodegradation were predicted to be involved in benzoate, phenylalanine, and aminobenzoate metabolism. Among them, ß-ketoadipate biodegradation might be the main pathway in Sphingopyxis strains. Further inspection showed that a number of mobile genetic elements varied in Sphingopyxis genomes, and plasmid-mediated gene transfer coupled with prophage- and transposon-mediated rearrangements might play prominent roles in the evolution of bacterial genomes. Collectively, our findings presented that Sphingopyxis isolates might be the promising candidates for biodegradation of aromatic compounds in pollution sites.

A Mini Review on Microcystins and Bacterial Degradation.

Microcystins (MCs) classified as hepatotoxic and carcinogenic are the most commonly reported cyanobacterial toxins found in the environment. Microcystis sp. possessing a series of MC synthesis genes (mcyA-mcyJ) are well documented for their excessive abundance, numerous bloom occurrences and MC producing capacity. About 246 variants of MC which exert severe animal and human health hazards through the inhibition of protein phosphatases (PP1 and PP2A) have been characterized. To minimize and prevent MC health consequences, the World Health Organization proposed 1 µg/L MC guidelines for safe drinking water quality. Further the utilization of bacteria that represent a promising biological treatment approach to degrade and remove MC from water bodies without harming the environment has gained global attention. Thus the present review described toxic effects and bacterial degradation of MCs.

Child and Adolescent Mental Health Policy in Low- and Middle-Income Countries: Challenges and Lessons for Policy Development and Implementation.

Background: Child and adolescent mental health (CAMH) policy is essential for the rational development of mental health systems for children and adolescents. However, there is a universal lack of CAMH policy, especially in low- and middle-income countries (LMICs). Therefore, this review aims to identify challenges and lessons for LMICs to develop and implement CAMH policy. Methods: PubMed (1781-), MEDLINE (1950-), EMBASE (1966-), and PsycINFO (1895-) were searched from inception to December 31, 2018, for publications on CAMH policy development and/or implementation. Abstracts and main texts of articles were double screened, and extracted data were analyzed through thematic synthesis. Results: A total of 31 publications were included through the systematic review. Six major challenges were identified for CAMH policy in LMICs: (i) poor public awareness and low political willingness; (ii) stigma against mental disorders; (iii) biased culture values toward children, adolescents and CAMH, from developmental nihilism to medicalization; (iv) the lack of CAMH data and evidence, from service statistics to program evaluation; (v) the shortage of CAMH resources, including human resources, service facilities, and funding; and (vi) unintended consequence of international support, including reducing local responsibilities, planning fragmentation, and unsustainability. Six lessons to overcome challenges were summarized: (i) rethinking the concept of CAMH, (ii) encouraging a stand-alone CAMH policy and budget, (iii) involving stakeholders, (iv) reinforcing the role of research and researchers in policy process, (v) innovating the usage of human and service resources, and (vi) maximizing the positive influence of international organizations and non-governmental organizations. Conclusion: Many LMICs are still facing various challenges for their CAMH policy development and implementation. To overcome the challenges, great and long-term efforts are needed, which include great determination of from domestic and global agents, multidisciplinary innovations, and collaboration and coordination from different sectors.

A complete route for biodegradation of potentially carcinogenic cyanotoxin microcystin-LR in a novel indigenous bacterium.

Microcystin-leucine-arginine (MC-LR), a cyclic potentially carcinogenic hepatotoxin, occurs frequently in aquatic habitats worldwide and seriously threatens ecosystem and public health. Limited effectiveness of physicochemical treatments to remove MC-LR from drinking water has led to a search for alternative cost-effective and environment friendly biodegradation strategies. Obtaining MC-degrading bacteria and understanding their MC-degrading mechanisms are outstanding challenges. Here, a novel indigenous bacterium named Sphingopyxis sp. YF1 with a high efficient capacity for MC-degradation was successfully isolated from eutrophic Lake Taihu. Through integrating mass spectrometer and multi-omics analyses accompanied by functional verification of certain genes and proteins, a complete MC-degradation pathway was firstly identified, in which MC-LR was sequentially degraded into linearized MC-LR, tetrapeptide, Adda, phenylacetic acid, and finally potential product CO2. Some specific proteins such as microcystinase, linearized-microcystinase, tetrapeptidease and PAAase responsible for this pathway were identified. This study pioneeringly demonstrated that MC-LR can be completely degraded through natural remediation processes and revealed a significant potential for MC-LR biodegradation in both natural environment and engineered systems.

Simultaneous Microcystis algicidal and microcystin synthesis inhibition by a red pigment prodigiosin.

Microcystis blooms and their secondary metabolites microcystins (MCs) occurred all over the world, which have damaged aquatic ecosystems and threatened public health. Techniques to reduce the Microcystis blooms and MCs are urgently needed. This study aimed to investigate the algicidal and inhibitory mechanisms of a red pigment prodigiosin (PG) against the growth and MC-producing abilities of Microcystis aeruginosa (M. aeruginosa). The numbers of Microcystis cells were counted under microscope. The expression of microcystin synthase B gene (mcyB) and concentrations of MCs were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme linked immunosorbent assay (ELISA) methods, respectively. The inhibitory effects of PG against M. aeruginosa strain FACHB 905 with 50% algicidal concentration (LC50) at 120 h was 0.12 µg/mL. When M. aeruginosa cells exposed to 0.08 µg/mL, 0.16 µg/mL, 0.32 µg/mL PG, the expression of mcyB of M. aeruginosa was down-regulated 4.36, 8.16 and 18.51 times lower than that of the control at 120 h. The concentrations of total MC (TMC) also were 1.66, 1.72 and 5.75 times lower than that of the control at 120 h. PG had high algicidal effects against M. aeruginosa, with the activities of superoxide dismutase (SOD) initially increased and then decreased after 72 h, the contents of malondialdehyde (MDA) increase, the expression of mcyB gene down-regulation, and MCs synthesis inhibition. This study was first to report the PG can simultaneously lyse Microcystis cells, down-regulate of mcyB expression and inhibit MCs production effectively probably due to oxidative stress, which indicated PG poses a great potential for regulating Microcystis blooms and MCs pollution in the environment.

A Review of Cardiovascular Toxicity of Microcystins.

The mortality rate of cardiovascular diseases (CVD) in China is on the rise. The increasing burden of CVD in China has become a major public health problem. Cyanobacterial blooms have been recently considered a global environmental concern. Microcystins (MCs) are the secondary products of cyanobacteria metabolism and the most harmful cyanotoxin found in water bodies. Recent studies provide strong evidence of positive associations between MC exposure and cardiotoxicity, representing a threat to human cardiovascular health. This review focuses on the effects of MCs on the cardiovascular system and provides some evidence that CVD could be induced by MCs. We summarized the current knowledge of the cardiovascular toxicity of MCs, with regard to direct cardiovascular toxicity and indirect cardiovascular toxicity. Toxicity of MCs is mainly governed by the increasing level of reactive oxygen species (ROS), oxidative stress in mitochondria and endoplasmic reticulum, the inhibition activities of serine/threonine protein phosphatase 1 (PP1) and 2A (PP2A) and the destruction of cytoskeletons, which finally induce the occurrence of CVD. To protect human health from the threat of MCs, this paper also puts forward some directions for further research.

Identification and characterization of a novel indigenous algicidal bacterium Chryseobacterium species against Microcystis aeruginosa.

Harmful Microcystis aeruginosa blooms occurred frequently in many eutrophic lakes and rivers with resultant serious global environmental consequences. Algicidal bacteria may play an important role in inhibiting the growth of Microcystis aeruginosa and are considered as an effective method for preventing the appearance of blooms. In order to counteract the harmful effects of Microcystis aeruginosa, a critical step is to identify, isolate and characterize indigenous algicidal bacteria. This study aimed to isolate a novel indigenous algicidal bacterium identified as Chryseobacterium species based upon its 16S rDNA sequence analysis, and determine whether this bacterium was effective in lysing Microcystis aeruginosa FACHB 905. The influence of environmental factors including temperature, pH, quantity of Chryseobacterium species as well as Microcystis aeruginosa concentration were examined with respect to algae-lysing properties of this bacterial strain. Data demonstrated that the highest algae-lysing activity of 80% against Microcystis aeruginosa FACHB 905 occurred within 72 hr. In addition, the algae-lysing activities of Chryseobacterium species cells were significantly higher than those of cell-free supernatant. In conclusion, data showed the algicidal bacterium Chryseobacterium species exhibited potent Microcystis aeruginosa-lysing activities and attacked Microcystis aeruginosa directly suggesting this algicidal bacterium may be potentially useful for reducing the number of harmful Microcystis aeruginosa blooms.

Effects of Microcystin-LR on the Microstructure and Inflammation-Related Factors of Jejunum in Mice.

The increasing cyanobacterial blooms have recently been considered a severe environmental problem. Microcystin-leucine arginine (MC-LR) is one of the secondary products of cyanobacteria metabolism and most harmful cyanotoxins found in water bodies. Studies show MC-LR negatively affects various human organs when exposed to it. The phenotype of the jejunal chronic toxicity induced by MC-LR has not been well described. The aim of this paper was to investigate the effects of MC-LR on the jejunal microstructure and expression level of inflammatory-related factors in jejunum. Mice were treated with different doses (1, 30, 60, 90 and 120 µg/L) of MC-LR for six months. The microstructure and mRNA expression levels of inflammation-related factors in jejunum were analyzed. Results showed that the microstructure of the jejunum was destroyed and expression levels of inflammation-related factors interleukin (IL)-1ß, interleukin (IL)-8, tumor necrosis factor alpha, transforming growth factor-ß1 and interleukin (IL)-10 were altered at different MC-LR concentrations. To the best of our knowledge, this is the first study that mice were exposed to a high dose of MC-LR for six months. Our data demonstrated MC-LR had the potential to cause intestinal toxicity by destroying the microstructure of the jejunum and inducing an inflammatory response in mice, which provided new insight into understanding the prevention and diagnosis of the intestinal diseases caused by MC-LR.

Exposure routes and health effects of heavy metals on children.

Heavy metals are naturally existing elements that have relatively high atomic weight and a minimum density five times the density of water. Heavy metals have extensive applications in industries, homes, agriculture and medicine, leading to their wide distribution in the environment. Most heavy metals are reported to be highly toxic. They also have numerous exposure routes, including ingestion, inhalation, and dermal absorption, subsequently inducing some health effects resulting from human and heavy metals contact. The implications of heavy metals with regards to children's health have been noted to be more severe compared to adults. The element's harmful consequences on children health include mental retardation, neurocognitive disorders, behavioral disorders, respiratory problems, cancer and cardiovascular diseases. Much attention should be given to heavy metals because of their high toxicity potential, widespread use, and prevalence. This review therefore examines the exposure routes and health effects of mercury (Hg), lead (Pb), chromium (Cr), cadmium (Cd), and barium (Ba) on children. In addition, their toxic mechanisms are elucidated.