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

Molecular mechanisms of environmental pollutant-induced cartilage damage: from developmental disorders to osteoarthritis

The objective of the present study was to review the molecular mechanisms of the adverse effects of environmental pollutants on chondrocytes and extracellular matrix (ECM). Existing data demonstrate that both heavy metals, including cadmium (Cd), lead (Pb), and arsenic (As), as well as organic pollutants, including polychlorinated dioxins and furans (PCDD/Fs) and polychlorinated biphenyls (PCB), bisphenol A, phthalates, polycyclic aromatic hydrocarbons (PAH), pesticides, and certain other organic pollutants that target cartilage ontogeny and functioning. Overall, environmental pollutants reduce chondrocyte viability through the induction apoptosis, senescence, and inflammatory response, resulting in cell death and impaired ECM production. The effects of organic pollutants on chondrocyte development and viability were shown to be mediated by binding to the aryl hydrocarbon receptor (AhR) signaling and modulation of non-coding RNA expression. Adverse effects of pollutant exposures were observed in articular and growth plate chondrocytes. These mechanisms also damage chondrocyte precursors and subsequently hinder cartilage development. In addition, pollutant exposure was shown to impair chondrogenesis by inhibiting the expression of Sox9 and other regulators. Along with altered Runx2 signaling, these effects also contribute to impaired chondrocyte hypertrophy and chondrocyte-to-osteoblast trans-differentiation, resulting in altered endochondral ossification. Several organic pollutants including PCDD/Fs, PCBs and PAHs, were shown to induce transgenerational adverse effects on cartilage development and the resulting skeletal deformities. Despite of epidemiological evidence linking human environmental pollutant exposure to osteoarthritis or other cartilage pathologies, the data on the molecular mechanisms of adverse effects of environmental pollutant exposure on cartilage tissue were obtained from studies in laboratory rodents, fish, or cell cultures and should be carefully extrapolated to humans, although they clearly demonstrate that cartilage should be considered a putative target for environmental pollutant toxicity.

Role of intrinsic apoptosis in environmental exposure health outcomes

Environmental exposures are linked to diseases of high public health concern, including cancer, neurodegenerative disorders, and autoimmunity. These diseases are caused by excessive or insufficient cell death, prompting investigation of mechanistic links between environmental toxicants and dysregulation of cell death pathways, including apoptosis. This review describes how legacy and emerging environmental exposures target the intrinsic apoptosis pathway to potentially drive pathogenesis. Recent discoveries reveal that dynamic regulation of apoptosis may heighten the vulnerability of healthy tissues to exposures in children, and that apoptotic signaling can guide immune responses, tissue repair, and tumorigenesis. Understanding how environmental toxicants dysregulate apoptosis will uncover opportunities to deploy apoptosis-modulating agents for the treatment or prevention of exposure-linked diseases.

Human Bone Marrow-Derived Mesenchymal Stem Cell Applications in Neurodegenerative Disease Treatment and Integrated Omics Analysis for Successful Stem Cell Therapy

Neurodegenerative diseases (NDDs), which are chronic and progressive diseases, are a growing health concern. Among the therapeutic methods, stem-cell-based therapy is an attractive approach to NDD treatment owing to stem cells' characteristics such as their angiogenic ability, anti-inflammatory, paracrine, and anti-apoptotic effects, and homing ability to the damaged brain region. Human bone-marrow-derived mesenchymal stem cells (hBM-MSCs) are attractive NDD therapeutic agents owing to their widespread availability, easy attainability and in vitro manipulation and the lack of ethical issues. Ex vivo hBM-MSC expansion before transplantation is essential because of the low cell numbers in bone marrow aspirates. However, hBM-MSC quality decreases over time after detachment from culture dishes, and the ability of hBM-MSCs to differentiate after detachment from culture dishes remains poorly understood. Conventional analysis of hBM-MSCs characteristics before transplantation into the brain has several limitations. However, omics analyses provide more comprehensive molecular profiling of multifactorial biological systems. Omics and machine learning approaches can handle big data and provide more detailed characterization of hBM-MSCs. Here, we provide a brief review on the application of hBM-MSCs in the treatment of NDDs and an overview of integrated omics analysis of the quality and differentiation ability of hBM-MSCs detached from culture dishes for successful stem cell therapy.

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.

GM1 Ameliorates Lead-Induced Cognitive Deficits and Brain Damage Through Activating the SIRT1/CREB/BDNF Pathway in the Developing Male Rat Hippocampus

Developmental lead (Pb) exposure involves various serious consequences, especially leading to neurotoxicity. In this study, we examined the possible role of monosialoganglioside (GM1) in lead-induced nervous impairment in the developing rat. Newborn male Sprague-Dawley rat pups were exposed to lead from birth for 30 days and then subjected to GM1 administration (0.4, 2, or 10 mg/kg; i.p.) or 0.9% saline. The results showed that developmental lead exposure significantly impaired spatial learning and memory in the Morris water maze test, reduced GM1 content, induced oxidative stress, and weakened the antioxidative systems in the hippocampus. However, co-treatment with GM1 reversed these effects. Moreover, GM1 counteracted lead-induced apoptosis by decreasing the expression of Bax, cleaved caspase-3, and by increasing the level of Bcl-2 in a dose-dependent manner. Furthermore, we found that GM1 upregulated the expression of SIRT1, CREB phosphorylation, and BDNF, which underlie learning and memory in the lead-treated developing rat hippocampus. In conclusion, our study demonstrated that GM1 exerts a protective effect on lead-induced cognitive deficits via antioxidant activity, preventing apoptosis, and activating SIRT1/CREB/BDNF in the developing rat hippocampus, implying a novel potential assistant therapy for lead poisoning.

The effects of lead on the development of somites in chick embryos (Gallus gallus domesticus) under in vitro conditions: a histological study

Lead (Pb) is one of the most abundant toxic metals in the environment that can cause a variety of harmful effects. During embryonic development of vertebrates, somites are temporary organs that give rise to skeletal muscle, cartilage, tendon, endothelial cells, and dermis. In this study, we investigated the effects of lead on the development of somites and their derivatives in chick embryos under in vitro conditions. For this propose, fertilized eggs of Gallus gallus domesticus were incubated until they reached the stage of 15-20 somites. The somites and notochord were isolated and treated with different concentrations of lead acetate (500, 1000, 2000, and 4000 ng ml-1) for 72 h. Our results indicated that high concentrations of lead reduced the nucleus diameter, reduced the synthesis of collagen, inhibited the formation of the cartilage matrix in somite cells, and disturbed the formation and order of myotubes. In conclusion, the results of the current study for the first time indicated the disturbing effects of lead on the development of somites in the chick embryo. Our results revealed that lead disturbed the development of somites in the chick embryo, which suggested that at high concentrations it can cause a serious mortal danger to life.

2,5-hexanedione induces bone marrow mesenchymal stem cell apoptosis via inhibition of Akt/Bad signal pathway

2,5-Hexanedione (HD) is an important bioactive metabolite of n-hexane and mediates the neurotoxicity of parent compound. Studies show that HD induces apoptotic death of neural progenitor cells. However, its underlying mechanism remains unknown. Mesenchymal stem cells (MSCs) are multipotential stem cells with the ability to differentiate into various cell types and have been used as cell model for studying the toxic effects of chemicals on stem cells. In this study, we exposed rat bone marrow MSCs to 0, 10, 20, and 40 mM HD in vitro. Apoptosis and disruption of mitochondrial transmembrane potential were estimated by immunochemistry staining. The expression of Akt, Bad, phosphorylated Akt (p-Akt), and Bad (p-Bad) as well as cytochrome c in mitochondria and cytosol were examined by Western blot. Moreover, caspase 3 activity, viability, and death of cells were measured by spectrophotometry. Our results showed that HD induced cell apoptosis and increased caspase 3 activity. HD down-regulated the expression levels of p-Akt, p-Bad and induced MMP depolarization, followed by cytochrome c release. Moreover, HD led to a concentration-dependent increase in the MSCs death, which was relative to MSCs apoptosis. However, these toxic effects of HD on the MSCs were significantly mitigated in the presence of IGF, which could activate PI3 K/Akt pathway. These results indicated that HD induced mitochondria-mediated apoptosis in the MSCs via inhibiting Akt/Bad signaling pathway and apoptotic death of MSCs via the signaling pathway. These results might provide some clues for studying further the mechanisms of HD-induced stem cell apoptosis and adverse effect on neurogenesis.

Aqueous Extract of Allium sativum (Linn.) Bulbs Ameliorated Pituitary-Testicular Injury and Dysfunction in Wistar Rats with Pb-Induced Reproductive Disturbances

AIM

To determine the effects of aqueous extract of Allium sativum bulbs (AEASAB) on pituitary-testicular injury and dysfunction in Wistar rats with lead-induced reproductive disturbances.

MATERIALS AND METHODS

Male Wistar rats were divided into 7 groups such that the control group received propylene glycol at 0.2 ml/100 g intraperitoneally for 10 consecutive days, the toxic group received lead (Pb) alone at 15 mg/kg/day via intraperitoneal route for 10 days while the treatment groups were pretreated with lead as the toxic group after which they received graded doses of the extract at 50, 100 and 200 mg/kg/day via oral route for 28 days.

RESULTS

Pb administration induced significant deleterious alterations in the antioxidant status of the brain and testis, sperm characterization (counts, motility and viability) as well as reproductive hormones (FSH, LH and testosterone) of exposed rats (p < 0.05). These were significantly reversed in the AEASAB-treated groups (p < 0.05). Also, there was marked improvement in the Pb-induced vascular congestion and cellular loss in the pituitary while the observed Pb-induced severe testicular vacuolation was significantly reversed in the representative photomicrographs, following administration of the extract.

CONCLUSION

AEASAB treatment ameliorated the pituitary-testicular injury and dysfunction in Wistar rats with Pb-Induced reproductive disturbances.

2,5-hexanedione induced apoptosis in mesenchymal stem cells from rat bone marrow via mitochondria-dependent caspase-3 pathway

2,5-hexanedione (HD) induces apoptosis of nerve cells. However,the mechanism of HD-induced apoptosis remains unknown. Mesenchymal stem cells (MSCs) are multipotential stem cells with the ability to differentiate into various cell types. This study is designed to investigate the apoptosis induced by HD in rat bone marrow MSCs (BMSCs) and the related underlying mechanisms. The fifth generation of MSCs was treated with 0, 10, 20 and 40 mM HD respectively. The viability of BMSCs was observed by MTT. Apoptosis were estimated by Hoechst 33342 staining and TUNEL assay. The disruption of mitochondrial transmembrane potential (MMP) was examined by JC-1 staining. Moreover, the expression of Bax and Bcl-2, cytochrome c release, and caspase-3 activity were determined by real-time RT-PCR, Western blot and Spectrophotometry. Our results showed that HD induced apoptosis in MSCs in a dose dependent manner. Moreover, HD downregulated the Bcl-2 expression,upregulated the Bax expression and the Bax/Bcl-2 ratio, promoted the disruption of MMP, induced the release of cytochrome c from mitochondria to cytosol, and increased the activity of caspase-3 in MSCs. These results indicate that HD induces apoptosis in MSCs and the activated mitochondria-dependent caspase-3 pathway may be involved in the HD-induced apoptosis.

Lead exposure is a risk for worsening bone mineral density in middle-aged male workers

OBJECTIVE

Lead exposure linked to osteoporosis in women. However, there is no direct evidence whether lead exposure has effects on bone metabolism in middle-aged male subjects. Therefore, the present study investigated the relationship between bone mineral densitometry measurements, bone markers, endocrine hormones and blood lead levels.

MATERIAL AND METHODS

The present study included lead exposure patients (n: 30) and control subjects (n: 32). We recorded information on patient demographics and risk factors of osteoporosis. Blood lead levels were evaluated using Varian AA 240Z atomic absorption spectrophotometry. Bone mineral density measurements were measured using dual-energy X-ray absorptiometry.

RESULTS

Each lumbar T and Z scores in the lead exposure group were lower than the control group. There were no significant differences in femur neck and femur total T and Z scores between two groups. Blood lead levels were also negatively correlated with lumbar 2-4 T score, total lumbar T score, lumbar 2-4 Z score and total lumbar Z score. Urinary hydroxyproline and urinary deoxypyridinoline levels in the lead exposure group were significantly higher compared to controls. Blood lead levels were strong, positively correlated with urinary deoxypyridinoline. Endocrine hormone levels and 1,25-dihydroxy-vitamin D3 levels were comparable between lead exposure and control group.

CONCLUSION

Lead exposure in male workers is an important factor for deterioration in bone mineral density. We should be screening blood lead levels and history of lead exposure in male osteoporosis.

Cytotoxic and Genotoxic effects of Arsenic and Lead on Human Adipose Derived Mesenchymal Stem Cells (AMSCs)

Arsenic and lead, known to have genotoxic and mutagenic effects, are ubiquitously distributed in the environment. The presence of arsenic in drinking water has been a serious health problem in many countries. Human exposure to these metals has also increased due to rapid industrialization and their use in formulation of many products. Liposuction material is a rich source of stem cells. In the present study cytotoxic and genotoxic effects of these metals were tested on adipose derived mesenchymal stem cells (AMSCs). Cells were exposed to 1-10 μg/ml and 10-100 μg/ml concentration of arsenic and lead, respectively, for 6, 12, 24 and 48 h. The cytotoxic effects were measured by neutral red uptake assay, while the genotoxic effects were tested by comet assay. The growth of cells decreased with increasing concentration and the duration of exposure to arsenic. Even the morphology of cells was changed; they became round at 10 μg /ml of arsenic. The cell growth was also decreased after exposure to lead, though it proved to be less toxic when cells were exposed for longer duration. The cell morphology remained unchanged. DNA damage was observed in the metal treated cells. Different parameters of comet assay were investigated for control and treated cells which indicated more DNA damage in arsenic treated cells compared to that of lead. Intact nuclei were observed in control cells. Present study clearly demonstrates that both arsenic and lead have cytotoxic and genotoxic effects on AMSCs, though arsenic compared to lead has more deleterious effects on AMSCs.

Investigation of 1-(4-morpholinophenyl)-3-(4-fluorophenyl)-propenone and 1-(4-morpholinophenyl)-3-(3-fluorophenyl)-propenone as new apoptosis inducers on Spodoptera frugiperda (Sf9) cells

The objective of this study was to examine the toxicity of 1-(4-morpholinophenyl)-3-(4-fluorophenyl)-propenone (A) and 1-(4-morpholinophenyl)-3-(3-fluorophenyl)-propenone (B) on Spodoptera frugiperda (Sf9) cells and the mechanism of the toxicity. By cell-based thiazolyl blue tetrazolium bromide (MTT) assay, we found that the IC(50) were 35.45 μM for A and 31.97 μM for B respectively. Formation of apoptotic bodies was observed at 24 h in the treated cells. There was a significant increase of DNA ladders in the treated Sf9 cells compared to controls. In the presence of 50 μM compound A and B for 24 h, ATP content of Sf9 cells reduced by approximately 50%. Compared to the controls, the significant over-expression of caspase-3 in treated cells was measured by caspase-3 activity kit, and the loss of mitochondrial membrane potential (ΔΨm) was detected in apoptosis cells. The results suggested that the two compounds could be identified as new potent cell apoptosis inducers.

Decreased blood lead levels after calcitriol treatment in hemodialysis patients with secondary hyperparathyroidism

OBJECTIVE

Secondary hyperparathyroidism (SHP) is characterized by high bone turnover, which may, in turn, result in increased release of lead from bone stores. This study investigated the effects of intravenous calcitriol on blood lead (BL) levels in patients with SHP.

METHODS

Intravenous calcitriol therapy was administered for 16 wk to 28 patients who were on maintenance hemodialysis (HD) and had intact parathyroid hormone (iPTH) plasma levels of >300 pg/mL. Blood was drawn at baseline and every 4 wk for 16 wk to determine the levels of iPTH; bone remodeling markers, including bone-specific alkaline phosphatase (bAP) and type 5b tartrate-resistant acid phosphatase (TRAP); and BL.

RESULTS

Of the 28 patients, 25 responded to calcitriol therapy; they exhibited significant decrements in serum iPTH levels by the end of 4 wk of therapy and thereafter. After 16 wk of therapy, these patients had significant reductions in serum iPTH levels (p<0.01) and significant and parallel decreases in the levels of bAP (p<0.01), TRAP (p<0.01), and BL (p<0.01). Further analysis showed a significant positive correlation between the levels of BL and serum iPTH (r=0.34, p<0.01) and BL and serum TRAP (r=0.22, p<0.05). However, there was no significant correlation between the levels of BL and serum bAP.

CONCLUSION

Elevated levels of BL and serum bone remodeling markers, which are common features of SHP, can be effectively suppressed by calcitriol therapy. This indicates that hyperparathyroidism not only accelerates bone remodeling but may also enhance bone lead mobilization in patients on maintenance HD.

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.