Qinli Zhang

Aluminum Impairs Rat Neural Cell Mitochondria In Vitro

Exposure to aluminum has been reported to lead to neurotoxicity. Mitochondria are important organelles involved in maintaining cell function. This study investigates the effect of aluminum on mitochondria in rat neural cells. The ultrastructure of mitochondria was observed, and the cell death rate (CDR), reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and 3-[4,5demethyl-2-thiazalyl]-2,-5diphenyl-2H-tetrazolium bromide (MTT) were measured to investigate the effect of aluminum on the mitochondrial structure and its function in neural cells. Results observed from the mitochondrial ultrastructure show that aluminum may impair the mitochondrial membrane and cristae. Increased CDR, enhanced ROS, decreased MMP, and decreased enzyme activity in mitochondria were observed in the Al-exposed neurons (100 – 500 μM). The present study demonstrates that alteration in the mitochondrial structure and function plays an important role in neurotoxic mechanisms induced by aluminum.

The relationship between Bcl-2 gene expression and learning & memory impairment in chronic aluminum-exposed rats

Aluminum (AI), a known neurotoxin, has been implicated in Alzheimer’s Disease (AD), Amyotrophic Lateral Selerosis (ALS), Parkinsonism Dementia Complex, etc., and it causes extensive damage to the nervous system, including the impairment of learning and memory. However, to date, the mechanism of Al neurotoxicity has not been fully elucidated. Neuronal apoptosis has become a focus of interest, as it has been reported to play a key role in the impairment of learning and memory processes (Thompson,Science 267:1456, 1995). The Bcl-2 gene acts as an important effector for inhibiting apoptosis. In the present study we observe neuronal apoptosis in association with learning and memory impairment, as well as regional brain alterations in Bcl-2 expression in rats chronically exposed to Al. The chronic Al-intoxicated model was established by i.p. injection of AlCl3 in adult Sprague Dawley rats for 3 successive days, with one-day intervals, for 60 days. After exposure, the step-down test was performed to examine the behavioral reaction of the rats. Neuronal apoptosis and Bcl-2 protein expression in different regions of rat brain were then assessed by an immunohistochemical method. In the step-down test, the latency of Al-exposed rats was significantly lower than that of controls. Also, the number of performance errors in 5 minutes of exposure was significantly higher than that of controls. Neuronal apoptosis was extensive in the brain of Al-exposed groups, and the expressions of Bcl-2 protein in frontal cortex, cerebellum and hippocampus of Al-exposed rats was stronger. In conclusion, chronic Al-exposure in rats is associated with neuronal apoptosis in brain, and impaired learning and memory. Augmented Bcl-2 protein expression may be a stimulated compensatory mechanism.

APP/PS1 transgenic mice treated with aluminum: an update of Alzheimer's disease model.

There is still no animal model available that can mimic all the cognitive, behavioral, biochemical, and histopathological abnormalities observed in patients with Alzheimers disease (AD). We undertook to consider the interaction between genetic factors, including amyloid precursor protein (APP) and presenilin-1 (PS1), and environmental factors, such as Aluminum (Al) in determining susceptibility outcomes when studying the pathogenesis of AD. In this article, we provide an AD model in APP/PS1 transgenic mice triggered by Al. The animal model was established via intracerebral ventricular microinjection of aluminum chloride once a day for 5 days in APP/PS1 transgenic mice. Twenty wild type (WT) mice and 20 APP/PS1 transgenic (TG) mice were separately divided into 2 groups (control and Al group), and a stainless steel injector with stopper was used for microinjection into the left-lateral cerebral ventricle of each mouse. The Morris water maze task was used to evaluate behavioral function of learning and memory ability on the 20th day after the last injection. This AD models brain was analyzed by: (1) amyloid β immunohistochemical staining; (2) Tunnel staining; (3) apoptotic rates; (4) caspase-3 gene expression. Here, decrease of cognitive ability and neural cells loss were shown in APP/PS1 transgenic mice exposed to Al, which were more extensive than those in APP/PS1 TG alone and WT mice exposed to Al alone. These findings indicate that there is a close relationship between over-expression of APP and PS1 genes and Al overload. It is also suggested that APP/PS1 TG mice exposed to Al have potential value for improving AD models.

Effects of Benzo[a]pyrene on Autonomic Nervous System of Coke Oven Workers

Effects of Benzo[a]pyrene on Autonomic Nervous System of Coke Oven Workers: Hong‐Mei Zhang, et al. Department of Occupational Health, School of Public Health, Shanxi Medical University, China—Objectives are to investigate the effects of benzo[a]pyrene (B[a]P) on the autonomic nervous system of coke oven workers. One hundred eightyfour coke oven workers were divided into 3 groups according to their working sites (coke oven bottom group, coke oven side group and coke oven top group), and 93 referents were recruited. B[a]P monitored by air sampling pumps as well as urinary 1‐hydroxypyrene (1‐OH‐Py) was determined by high performance liquid chromatograph with a fluorescence detector (HPLCFD). The autonomic nervous system (ANS) function was determined by 4 tests: Valsalva Manoeuvre heart rate variation (HR‐V), variation of heart rate when breathing deeply (HR‐DB), variation of heart rate when instantly standing up (HR‐IS, including RR30:15 and RRmax:min) and variation of blood pressure when instantly standing up (BP‐IS). The B[a]P mean concentrations in coke oven bottom, coke oven side and coke oven top were 19, 185 and 1,623 ng/m3, respectively. The levels of urinary 1‐OH‐Py were markedly higher in the 3 exposed groups than that in the referent group (p<0.01). No significant difference was found in each group between smokers and nonsmokers (p>0.05). Compared with referents, HR‐V decreased significantly in coke oven workers (p<0.01), representing modulation of parasympathetic nervous function. However, no statistical differences were found in HR‐DB, RR30:15, RRmax:min and BP‐IS between the exposed groups and the control group (p>0.05). HR‐V decreased with the increment of 1‐OH‐Py (p<0.05), and results of multiple linear stepwise regression demonstrated that external exposure level and duration of education entered the HR‐V model; age was a significant factor of HR‐DB and RRmax:min, but no variable was involved in RR30:15 and BP‐IS regression. Benzo[a]pyrene affects the autonomic nervous function of coke oven workers mainly by down‐regulating the parasympathetic nervous function.

Is necroptosis a death pathway in aluminum-induced neuroblastoma cell demise?

Besides being an aggravating factor secondary to major physiological alterations in degenerative diseases, aluminum has also been considered as a risk factor in the etiology. Although many in vivo and in vitro data are in favor of apoptosis and necrosis being involved in Al induced neurodegenerative processes, there is considerable evidence that very complex events may contribute to neural cell death. Necroptosis, a novel cell death pathway, was recently reported to contribute to ischemia brain injury. It is different from, but associated with, apoptosis and necrosis, the two common major pathways of cell demise. In the present study, SH-SY5Y cells were put under stress by Al, a potential degenerative cell death inducer. Nec-1, a specific inhibitor, was used to identify necroptosis. The characteristics observed in Nec-1 and Al treated SH-SY5Y cells showed that necrotic morphological changes were reduced, and a sharp decrease of necrotic rate was detected. Besides, there were Al-induced mitochondria membrane potential decreasing, reactive oxygen species remaining, and autophagosomes declining. The mechanism of Nec-1s effect on cell death may be related to caspases pathways. To our best knowledge, this is the pioneer report on necroptosis in mixed human neural cell death pathways, which might offer a novel therapeutic target for neurodegenerative diseases, and an extended window for neuroprotection.

How Do Rat Cortical Cells Cultured with Aluminum Die: Necrosis or Apoptosis?

Aluminum (Al) exposure has been implicated as the cause of neural cells loss in several neurodegenerative diseases. Therefore, defining the mechanism of neural cell death in Al toxicity and degenerative diseases might lead to the development of therapeutic agents which promote neural cell survival. Furthermore, knowledge of cell death pathways might facilitate the discovery of treatments for neurodegeneration. However, the death mode of neural cells triggered by Al has not been firmly established. The present study focuses on understanding the pathway of cells death in cultured cortical cells treated with Al. Primary neurons cultured alone, astrocytes cultured alone, and neuron/astrocyte co-cultures obtained from newborn rats were incubated with Al at the concentrations of 0, 0.5,1.0, or 2.0 mM for 72 h. Morphological changes were observed with an inverted phase microscope, a fluorescent microscope, and an electron microscope. Simultaneously, the rate of apoptosis was quantified with flow cytometry. Morphological characteristics of apoptosis such as cell shrinkage, aggregation and fragmentation of chromatin, membrane buds, and formation of membrane-bound apoptotic bodies were observed in Al-treated neurons, while none of these characteristics were found in Al-treated astrocytes. Quantitative results of apoptotic rates detected with flow cytometry indicated a typical apoptosis progression in neurons at various dosages. A concentration-dependent relationship between Al concentration and apoptotic rates confirmed that apoptosis is the prominent cause of cell death in primary cultured neurons, even at a concentration lower than 2 mM. Both necrosis and apoptosis are evident in neuron/astrocyte co-cultures, but the intensity of apoptosis is much less compared with that of neurons, suggesting that astrocytes may be especially important for neuronal survival in the presence of Al.

Cognitive Disorders and Tau-Protein Expression Among Retired Aluminum Smelting Workers

Objectives: To analyze cognitive functions and tau-protein expression in peripheral blood lymphocytes of retired aluminum (Al)-exposed workers. Methods: A total of 66 retired Al potroom workers and 70 unexposed controls were investigated. The cognitive functions were assessed with the Mini-Mental State Examination. The tau-protein expression in peripheral blood lymphocyte was analyzed with Western blot. Results: The cognitive functions of the exposed group were significantly decreased. Twelve mild cognitive impairment cases in the exposed group and four mild cognitive impairment cases in the control group were diagnosed. Significantly higher p-tau181 and p-tau231 levels were detected in the Al-exposed workers than in the control group. Conclusions: The study suggests that long-term exposure to Al may cause cognitive disorders and that p-tau181 and p-tau231 might be useful indicators for monitoring cognitive decline in Al-exposed workers.

Caspase-3 short hairpin RNAs: a potential therapeutic agent in neurodegeneration of aluminum-exposed animal model.

There is abundant evidence supporting the role of caspases in the development of neurodegenerative disease, including Alzheimers disease (AD). Therefore, regulating the activity of caspases has been considered as a therapeutic target. However, all the efforts on AD therapy using pan-caspase inhibitors have failed because of uncontrolled adverse effects. Alternatively, the specific knockdown of caspase-3 gene through RNA interference (RNAi) could serve as a future potential therapeutic strategy. The aim of the present study is to down-regulate the expression of caspase-3 gene using lentiviral vector-mediated caspase-3 short hairpin RNA (LV-Caspase-3 shRNA). The effect of LV-Caspase-3 shRNA on apoptosis induced by aluminum (Al) was investigated in primary cultured cortical neurons and validated in C57BL/6J mice. The results indicated an increase in apoptosis and caspase-3 expression in primary cultured neurons and the cortex ofmice exposed to Al, which could be down-regulated by LV-Caspase-3 shRNA. Furthermore, LV-Caspase-3 shRNA reduced neural cell death and improved learning and memory in C57BL/6J mice treated with Al. Our results suggest that LV-caspase-3 shRNA is a potential therapeutic agent to prevent neurodegeneration and cognitive dysfunction in aluminum- exposed animal models. The findings provide a rational gene therapy strategy for AD.

The Relationship Between Cognitive Impairment and Global DNA Methylation Decrease Among Aluminum Potroom Workers.

Objective: To investigate the relationship between cognitive impairment and global DNA methylation in aluminum (Al) potroom workers. Methods: A total of 366 Al-exposed workers were investigated, and their cognitive functions were assessed with the Mini-Mental State Examination (MMSE). Aluminum in serum was quantified using graphite furnace atomic absorption spectrometry. Global DNA methylation was analyzed in whole blood using an enzyme-linked immunosorbent assay–like reaction. Results: Mini-Mental State Examination scores and global DNA methylation decreased with the increase of serum Al concentration. Forty-three mild cognitive impairment (MCI) people were diagnosed. Global DNA methylation of the MCI was lower than the non-MCI. Multiple logistic analysis showed that the Al-exposed workers had lower global DNA methylation and higher serum Al concentration and were at the higher risk of MCI. Conclusions: Long-term exposure to Al may cause MCI. Mild cognitive impairment was significantly associated with global DNA methylation in blood.

Therapeutic potential of BAK gene silencing in aluminum induced neural cell degeneration

Previous studies have demonstrated robust BAK gene silencing via RNA interference (RNAi). To investigate whether BAK RNAi may serve as a co-therapeutic agent in neural cell death, we herein established a cell degeneration model using a human neuroblastoma cell line (SH-SY5Y) treated by aluminum (Al). Combining cell viability assays and expression analyses by QRT (quantitative real-time)-PCR and immunocytochemistry, we selected and validated the optimal small interfering RNA (siRNA) from three candidate siRNAs for the BAK gene. Our data identified siRNA1 as the most effective siRNA; the optimal concentration of the transfection agent was 10nM and the optimal incubation period was 24h. The transfection and knockdown efficiency was 93% and 58%, respectively, which closely correlated with the BAK protein expression. SH-SY5Y cells with BAK knockdown showed a clear resistance against cell death and Al-induced apoptosis. These results indicate that genetic inactivation of BAK could be an effective strategy in delaying the onset of apoptosis in Al-treated cells, and exemplify the therapeutic potential of RNAi-based methods for the treatment of neural cell degeneration.