Studying the effects of lead on DNA fragmentation and proapoptotic bax and antiapoptotic bcl-2 protein expression in PC12 cells

Maternal lead exposure induces sex-dependent cerebellar glial alterations and repetitive behaviors

Lead (Pb) is one of the most prevalent heavy metals we encounter daily. Although there are many reports regarding their toxic effects on humans, the effects of exposure to low lead concentrations throughout the pregnancy period on the offspring are not fully elucidated yet. This study aimed to investigate the cellular mechanisms that occur in response to lead exposure. To this end, we administered lead-containing water to pregnant mice from the day of conception till delivery or till day 28 postnatally. Furthermore, we performed neurodevelopmental disorder-related behavior tests and RNA-sequencing analysis. We used both genders for all experiments because neurodevelopmental disorders usually show several sex-dependent differences. The results revealed increased levels of gliosis in the cerebella of lead-exposed pups compared to those in littermates belonging to the control group. Additionally, we observed altered behaviors of male mice in the autism spectrum disorder-related tests. RNA-sequencing results revealed changes in gamma-aminobutyric acid (GABA) signaling in the lead-exposed mouse model. Specifically, the lead-exposed male mice showed decreased monoamine oxidase B and increased levels of diamine oxidase enzyme, which is related to the synthesis of GABA in astrocytes. These findings demonstrate sex-dependent basal developmental changes in glial cells and an increased prevalence of autistic-like behaviors in the young pups of mothers exposed to lead during pregnancy.

Conditioned Medium of Adipose-Derived Mesenchymal Stem Cells as a Promising Candidate to Protect High Glucose-Induced Injury in Cultured C28I2 Chondrocytes

Purpose: The aim of this study was to evaluate the protective effect of conditioned medium derived from human adipose mesenchymal stem cells (CM-hADSCs) on C28I2 chondrocytes against oxidative stress and mitochondrial apoptosis induced by high glucose (HG).

Methods: C28I2 cells were pre-treated with CM-hADSCs for 24 hours followed by HG exposure (75 mM) for 48 hours. MTT assay was used to assess the cell viability. Reactive oxygen species (ROS) and lipid peroxidation were determined by 2,7-dichlorofluorescein diacetate (DCFHDA) and thiobarbituric acid reactive substances (TBARS) assays, respectively. Expressions of glutathione peroxidase 3 (GPX 3), heme oxygenase-1 (HO-1), and NAD(P)H quinone dehydrogenase 1 (NQO1) were analyzed by RT-PCR. Finally, western blot analysis was used to measure Bax, Bcl-2, cleaved caspase-3, and Nrf-2 expression at protein levels.

Results: CM-hADSCs pretreatment mitigated the cytotoxic effect of HG on C28I2 viability. Treatment also markedly reduced the levels of ROS, lipid peroxidation, and augmented the expression of HO-1, NQO1, and GPx3 genes in HG-exposed group. CM-ADSCs enhanced Nrf-2 protein expression and reduced mitochondrial apoptosis through reducing Bax/Bcl-2 ratio and Caspase-3 activation.

Conclusion: MSCs, probably through its paracrine effects, declined the deleterious effect of HG on chondrocytes. Hence, therapies based on MSCs secretomes appear to be a promising therapeutic approaches to prevent joint complications in diabetic patients.

Investigating The Alterations of Oxidative Stress Status, Antioxidant Defense Mechanisms, MAP Kinase and Mitochondrial Apoptotic Pathway in Adipose-Derived Mesenchymal Stem Cells from STZ Diabetic Rats

Objective

This study aimed to investigate the reliability of diabetic adipose-derived stem cells (ADSCs) for autologous cell-based therapies by exploring the functionality of signalling pathways involved in regulating oxidative stress and apoptosis.

Materials and Methods

In this experimental study, ADSCs were isolated from streptozotocin (STZ)-induced diabetic rats (dADSCs) and normal rats (nADSCs). The colonies derived from dADSCs and nADSCs were compared by colony-forming unit (CFU) assay. Reactive oxygen species (ROS) formation and total antioxidant power (TAP) were also measured. Furthermore, the expression of antioxidant enzymes, including catalase (Cat), superoxide dismutase (Sod)-1 and -3, glutathione peroxidase (Gpx)-1, -3 and -4 was measured at mRNA level by semi-quantitative reverse transcriptase polymerase chain reaction assay. The expression of Bax, Bcl2, caspase-3, total and phosphorylated c-Jun N-terminal kinase (JNK) and P38 Mitogen-Activated Protein Kinase (MAPK) at protein level was analyzed by western blotting.

Results

The results of this study indicated that viability and plating efficiency of dADSCs were significantly lower than those of nADSCs. ROS generation and TAP level were respectively higher and lower in dADSCs. The gene expression of antioxidant enzymes, including Cat, Sod-1, Gpx-3 and Gpx-4 in dADSCs was significantly greater than that in nADSCs. However, Sod-3 and Gpx-1 mRNA levels were decreased in dADSCs. Moreover, Bax/Bcl-2 protein ratio, caspase-3 protein expression and phosphorylation of JNK and P38 proteins were increased in dADSCs compared to nADSCs.

Conclusion

Taken together, diabetes might impair the cellular functions of dADSCs as candidates for autologous cell- based therapies. This impairment seems to be mediated by JNK, P38 MAPKs, and mitochondria pathway of apoptosis and partly by disruption of antioxidant capacity.

Neuroprotective effect of CPCGI on Alzheimer's disease and its mechanism

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder causing progressive memory loss and cognitive impairment. The aberrant accumulation of amyloid‑β (Aβ) and neuroinflammation are two major events in AD. Aβ‑induced neurotoxicity and oxidative stress are also involved in the pathogenesis of AD. The purpose of the current study was to investigate the effect of compound porcine cerebroside and ganglioside injection (CPCGI) on the progression of AD, and to explore the molecular mechanism. In vivo and in vitro models of AD were established and treated with CPCGI. Aβ40 and Aβ42 protein levels were detected using western blotting. Production of pro‑inflammatory factors [tumor necrosis factor (TNF)‑α and interleukin (IL)‑1β] and oxidative stress markers [malondialdehyde (MDA), superoxide dismutase (SOD)] and reactive oxygen species (ROS) production were determined. Cell viability and apoptosis were detected using 3‑(4,5‑dimethyl‑2‑thiazolyl)‑2,5‑​diphenyl‑2‑H‑tetrazolium bromide assay and flow cytometry analysis respectively. Results demonstrated that CPCGI administration reduced Aβ40 and Aβ42 accumulation, and inhibited inflammatory response and oxidative stress in the in vivo rat model of AD, evidenced by decreased Aβ40 and Aβ42 protein expression, reduced levels of TNF‑α and IL‑1β, reduced MDA content, enhanced SOD activity, and reduced ROS level. It was found that CPCGI enhanced cell viability and reduced cell apoptosis of Aβ25‑35 induced PC12 cells. In addition, the mitogen‑activated protein kinase/NF‑κB pathway was involved in the protective effect of CPCGI on AD. Taken together, the data demonstrated that CPCGI exerted a protective effect on AD by reducing Aβ accumulation, inhibiting inflammatory response and oxidative stress, In addition to preventing neuronal apoptosis.

Ginger (Zingiber officinale Roscoe) in the Prevention of Ageing and Degenerative Diseases: Review of Current Evidence

Currently, the age of the population is increasing as a result of increased life expectancy. Ageing is defined as the progressive loss of physiological integrity, which can be characterized by functional impairment and high vulnerability to various types of diseases, such as diabetes, hypertension, Alzheimer's disease (AD), Parkinson's disease (PD), and atherosclerosis. Numerous studies have reported that the presence of oxidative stress and inflammation contributes to the development of these diseases. In general, oxidative stress could induce proinflammatory cytokines and reduce cellular antioxidant capacity. Increased oxidative stress levels beyond the production of antioxidant agents cause oxidative damage to biological molecules, including DNA, protein, and carbohydrates, which affects normal cell signalling, cell growth, differentiation, and apoptosis and leads to disease pathogenesis. Since oxidative stress and inflammation contribute to these diseases, ginger (Zingiber officinale Roscoe) is one of the potential herbs that can be used to reduce the level of oxidative stress and inflammation. Ginger consists of two major active components, 6-gingerol and 6-shogaol, which are essential for preventing oxidative stress and inflammation. Thus, this paper will review the effects of ginger on ageing and degenerative diseases, including AD, PD, type 2 diabetes mellitus (DM), hypertension, and osteoarthritis.

Differential response to lead toxicity in rat primary microglia and astrocytes

Lead (Pb) is one of the most widely studied occupational and environmental toxins. Chronic exposure to Pb affects neural function in the central nervous system (CNS). Glial cells in the CNS, such as microglia and astrocytes, respond differently to Pb-induced toxicity. However, the underlying mechanism has not yet been identified. We measured the cell viability and intracellular Pb uptake in rat primary microglia and astrocytes using the CCK-8 assay and inductively coupled plasma mass spectrometry, and found that Pb decreased microglial viability at lower dosages than in astrocytes, while Pb uptake was greater in astrocytes. Pb-induced oxidative stress in microglia results in increased production of reactive oxygen species, down-regulation of glutathione, and enhanced Nrf2 protein expression, while there was no obvious change in astrocytes. The role of Nrf2 in Pb-induced oxidative stress has also been confirmed in primary microglia with the use of Nrf2 small interfering RNA and an Nrf2 agonist. These data indicate that primary microglia were more sensitive to Pb exposure than astrocytes, which is associated with an obvious oxidative stress response and up-regulation of Nrf2 might be involved in this process.

t-BHQ Provides Protection against Lead Neurotoxicity via Nrf2/HO-1 Pathway

The neurotoxicity of lead has been well established, and oxidative stress is strongly associated with lead-induced neurotoxicity. Nrf2 is important for protection against oxidative stress in many disease models. We applied t-BHQ, which is an Nrf2 activator, to investigate the possible role of Nrf2 in the protection against lead neurotoxicity. t-BHQ significantly attenuated the oxidative stress in developmental rats by decreasing MDA level, as well as by increasing SOD activity and GSH content, in the hippocampus and frontal cortex. Furthermore, neuronal apoptosis was detected by Nissl staining, and Bax expression was inhibited in the t-BHQ-treated group. Results showed that t-BHQ suppressed ROS production and caspase 3/7 activity but increased intracellular GSH content, in SH-SY5Y cells under lead exposure. Moreover, in vivo and in vitro, t-BHQ enhanced the nuclear translocation of Nrf2 and binding to ARE areas but did not induce Nrf2 transcription. These phenomena were confirmed using RT-PCR, EMSA, Western blot, and immunofluorescence analyses. Subsequent upregulation of the expression of HO-1, NQO1, and GCLC was observed. However, knockdown of Nrf2 or HO-1 adversely affected the protective effects of t-BHQ against lead toxicity in SH-SY5Y cells. Thus, t-BHQ can protect against lead neurotoxicity, depending on the Nrf2/HO-1 pathway.

Cytotoxic, genotoxic, and neurotoxic effects of Mg, Pb, and Fe on pheochromocytoma (PC-12) cells

Metals such as lead (Pb), magnesium (Mg), and iron (Fe) are ubiquitous in the environment as a result of natural occurrence and anthropogenic activities. Although Mg, Fe, and others are considered essential elements, high level of exposure has been associated with severe adverse health effects including cardiovascular, hematological, nephrotoxic, hepatotoxic, and neurologic abnormalities in humans. In the present study we hypothesized that Mg, Pb, and Fe are cytotoxic, genotoxic and neurotoxic, and their toxicity is mediated through oxidative stress and alteration in protein expression. To test the hypothesis, we used the pheochromocytoma (PC-12) cell line as a neuro cell model and performed the LDH assay for cell viability, Comet assay for DNA damage, Western blot for oxidative stress, and HPLC-MS to assess the concentration levels of neurological biomarkers such as glutamate, dopamine (DA), and 3-methoxytyramine (3-MT). The results of this study clearly show that Mg, Pb, and Fe, respectively in the form of MgSO4 , Pb(NO3 )2 , FeCl2 , and FeCl3 induce cytotoxicity, oxidative stress, and genotoxicity in PC-12 cells. In addition, exposure to these metallic compounds caused significant changes in the concentration levels of glutamate, dopamine, and 3-MT in PC-12 cells. Taken together the findings suggest that MgSO4 , Pb(NO3 )2 , FeCl2 , and FeCl3 have the potential to induce substantial toxicity to PC-12 cells.

Puerarin induces the upregulation of glutathione levels and nuclear translocation of Nrf2 through PI3K/Akt/GSK-3β signaling events in PC12 cells exposed to lead

Oxidative stress is thought to be involved in lead-induced toxicity, especially affecting the brain. We reported previously that puerarin possesses antioxidative properties in the nervous system. Therefore, the aim of the present study was to test the hypothesis that puerarin inhibits lead acetate-induced oxidative stress in PC12 cells by interrupting phosphatidylinositol-3 kinase (PI3K)/Akt signaling through increasing glutathione (GSH) synthesis. Our results showed that puerarin attenuates oxidative stress in a concentration-dependent manner in PC12 cells exposed to lead acetate demonstrated by scavenging reactive oxygen species (ROS) and reducing lipid peroxidation (LPO). Treatment with puerarin significantly up-regulates glutamate cysteine ligase catalytic subunit (GCLc) expression both at its mRNA and protein levels, but not glutamate cysteine ligase modifier (GCLm) subunit, accompanying the elevation of cellular glutathione level. The increased nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2) was not because of increased transcription of Nrf2 as Nrf2 transcript levels did not change after puerarin treatment. The effects of puerarin could be partially blocked by pharmacologic inhibition of PI3K and the glycogen synthase kinase 3β (GSK-3β) pathways with LY294002 and LiCl, respectively. On the other hand, puerarin treatment promoted Akt and GSK-3β phosphorylation in PC12 cells exposed to lead acetate. Moreover, puerarin failed to modulate the phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), p-c-Jun N-terminal kinases (JNK), and p-p38 mitogen-activated protein kinase (MAPK) demonstrating some specificity for its action on the PI3K/GSK-3β pathway. These findings suggest that puerarin as a phytoestrogen might be an attractive agent for prevention and treatment of chronic diseases related to lead neurotoxicity.

Perinatal exposure to lead induces morphological, ultrastructural and molecular alterations in the hippocampus

The aim of this paper is to examine if pre- and neonatal exposure to lead (Pb) may intensify or inhibit apoptosis or necroptosis in the developing rat brain. Pregnant experimental females received 0.1% lead acetate (PbAc) in drinking water from the first day of gestation until weaning of the offspring; the control group received distilled water. During the feeding of pups, mothers from the experimental group were still receiving PbAc. Pups were weaned at postnatal day 21 and the young rats of both groups then received only distilled water until postnatal day 28. This treatment protocol resulted in a concentration of Pb in rat offspring whole blood (Pb-B) below the threshold of 10 μg/dL, considered safe for humans.We studied Casp-3 activity and expression, AIF nuclear translocation, DNA fragmentation, as well as Bax, Bcl-2 mRNA and protein expression as well as BDNF concentration in selected structures of the rat brain: forebrain cortex (FC), cerebellum (C) and hippocampus (H). The microscopic examinations showed alterations in hippocampal neurons.Our data shows that pre- and neonatal exposure of rats to Pb, leading to Pb-B below 10 μg/dL, can decrease the number of hippocampus neurons, occurring concomitantly with ultrastructural alterations in this region. We observed no morphological or molecular features of severe apoptosis or necrosis (no active Casp-3 and AIF translocation to nucleus) in young brains, despite the reduced levels of BDNF. The potential protective factor against apoptosis was probably the decreased Bax/Bcl-2 ratio, which requires further investigation. Our findings contribute to further understanding of the mechanisms underlying Pb neurotoxicity and cognition impairment in a Pb-exposed developing brain.

Elucidation of mechanisms underlying the protective effects of olive leaf extract against lead-induced neurotoxicity in Wistar rats

Recently, we identified that olive leaf extract (OLE) prevents lead (Pb)-induced abnormalities in behavior and neurotransmitters production in chronic Pb exposure in rats. The aim of the present study was to provide additional evidence that OLE acts as an anti-apoptotic, anti-inflammatory, and antioxidant mediator in Pb exposed rats. 4-weeks old Wistar rats were exposed or not to 250 mg/l Pb for 13-weeks and then exposed to tap water containing or not 0.1% OLE for additional 2-weeks. Atomic absorption spectrophotometry showed significantly elevated Pb levels in the hippocampus and serum and reaches 5 and 42 µg/mg tissue, respectively. In the hippocampus, the examination of markers of apoptosis and inflammation revealed an increase in caspase-3 activity and DNA fragmentation as well as tumor necrosis factor alpha, interleukin-1 beta and prostaglandin E2 in Pb-exposed rats. In addition, our findings showed that Pb induced 4-hydroxynonenal production and inhibited antioxidant-related enzyme activity, such as glutathione-S-transferase as wells as energy metabolism-related enzyme activity, such as NADP-isocitrate dehydrogenase and glucose transporter. Upon examination of signaling pathways involved in apoptosis process, we found that Pb induced p38 mitogen activated protein kinase (MAPK) and Akt phosphorylation, but in contrast, inhibited that of ERK(1/2). Interestingly, OLE administration diminished tissue Pb deposition and prevented all Pb effects. In the frontal cortex, our data also showed that OLE-abolished Pb-induced caspase-3 activity and DNA fragmentation. Collectively, these data support the use of OLE by traditional medicine to counter Pb neurotoxicity.

Effects of flaxseed oil on lead acetate-induced neurotoxicity in rats

It is well known that chronic exposure to lead (Pb(+2)) alters a variety of behavioral tasks in rats and mice. Here, we investigated the effect of flaxseed oil (1,000 mg/kg) on lead acetate (20 mg/kg)-induced brain oxidative stress and neurotoxicity in rats. The levels of Pb(+2), lipid peroxidation, nitric oxide (NO), and reduced glutathione (GSH) and the activity of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione-S-transferase (GST), and glutathione peroxidase (GPx) were determined in adult male albino rats. The level of Pb(+2) was markedly elevated in brain and blood of rats. This leads to enhancement of lipid peroxidation and NO production in brain with concomitant reduction in GSH, CAT, SOD, GR, GST, and GPx activities. These findings were associated with DNA fragmentation. In addition, lead acetate induced brain injury as indicated by histopathological changes of the brain. Treatment of rats with flaxseed oil resulted in marked improvement in most of the studied parameters as well as histopathological features. These findings suggest to the conclusion that flaxseed oil significantly decreased the adverse harmful effects of lead acetate exposure on the brain as well as Pb(+2)-induced oxidative stress.

Lead acetate induces cell apoptosis and promotes caspase-3 expression in human liver cell line L-02

AIM: To investigate the impact of lead acetate on cell apoptosis and caspase-3 expression in human liver cell line L-02.

METHODS: After L-02 cells were treated with different concentrations (0, 2.5, 40, 100, 200, 400 μmol/L) of lead acetate for 24 or 48 h, the proliferation of L-02 cells was assayed by MTT assay; cell morphological changes were observed after Hoechest33258 staining; and the expression of caspase-3 mRNA and protein was determined by RT-PCR and Western blot.

RESULTS: Compared to the normal control group, the proliferation of L-02 cells was significantly inhibited after treatment with different concentrations of lead acetate for 24 or 48 h (24 h: 0.4678 ± 0.0438, 0.4686 ± 0.0733, 0.4500 ± 0.0712, 0.4244 ± 0.0407, 0.3998 ± 0.0499 vs 0.5234 ± 0.0589; 48 h: 0.4290 ± 0.0607, 0.4184 ± 0.0296, 0.4032 ± 0.0499, 0.3856 ± 0.0386, 0.3750 ± 0.0149 vs 0.5300 ± 0.0397, all P < 0.05 or 0.01). Significant morphological changes were noted in cells treated with lead acetate for 48 h. Compared to the normal control group, the levels of caspase-3 mRNA increased significantly in a dose-dependent manner in L-02 cells treated with lead acetate (1.0912 ± 0.0769, 1.2874 ± 0.144, 1.4536 ± 0.1046, 1.6986 ± 0.1371, 1.9882 ± 0.0925 vs 0.8438 ± 0.0933, all P < 0.01). Additionally, the expression levels of caspase-3 protein also significantly increased after treatment with lead acetate.

CONCLUSION: Lead acetate inhibits proliferation and induces apoptosis of L-02 cells possibly via a mechanism associated with the activation of caspase-3.

Investigating the effect of lead acetate on rat bone marrow-derived mesenchymal stem cells toxicity: role of apoptosis

Lead exposure continues to be a significant public health problem. Osteoporosis, inhibition of fracture healing, and cartilage functional impairment have been reported from lead exposure. Mesenchymal stem cells (MSCs) are a bone marrow population of cells with the ability to differentiate into various cell types, particularly osteocytes and chondrocytes. Despite intensive investigation on the effect of lead poisoning on various cell types, there is very little if any report on the effect of lead on MSCs. The aim of this study, therefore, was to investigate the effect of lead acetate on rat bone marrow derived MSCs toxicity and its mechanism by examining the role of pro- and anti-apoptotic proteins in this process. It was revealed that lead acetate could induce cell death in a dose-dependent manner using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium (MTT) assay. Compared to controls, the significant over-expression of pro-apoptotic proteins, including Bax, caspases-9, -3, and p53, with no significant change in anti-apoptotic Bcl(2) protein were obtained in lead-treated cells using western blotting analysis. There was a significant increase in DNA fragmentation in treated MSCs compared to controls using flow-cytometry. Finally, it might be concluded that lead acetate could induce cell toxicity and apoptosis in MSCs, causing instability in mitochondria and in turn activation of the intrinsic pathway including over-expression of Bax, caspase 9 and caspase 3, leading to DNA damage and activation of P53.

Effect of chronic lead exposure on pro-apoptotic Bax and anti-apoptotic Bcl-2 protein expression in rat hippocampus in vivo

Despite reduction in environmental lead, chronic lead exposure still possess a public health hazard, particularly in children, with devastating effects on developing CNS. To investigate the mechanism of this neurotoxicity, young and adult rats were used to study whether exposure to 500 ppm concentrations of lead could induce apoptosis in hippocampus. 2-4 and 12-14-week-old rats received lead acetate in concentration of 500 ppm for 40 days. Control animals received deionized distilled water. In lead-treated groups, the blood lead levels were increased by 3-4 folds. Light and electron microscopical study of hippocampus revealed increased apoptotic cells. Western blot analysis of Bax and Bcl-2 (pro- and anti-apoptotic gene products, respectively) indicated higher expression of Bax protein and no significant change in bcl-2 expression and accordingly increased the Bax/Bcl-2 ratio compared to control group, confirming the histological study. In conclusion, these data suggest that neurotoxicity of chronic lead exposure in hippocampus in vivo may partly be due to facilitation of apoptosis.