Effects of aluminum chloride on sodium current, transient outward potassium current and delayed rectifier potassium current in acutely isolated rat hippocampal CA1 neurons

The History, Status, Gaps, and Future Directions of Neurotoxicology in China

BACKGROUND

Rapid economic development in China has produced serious ecological, environmental, and health problems. Neurotoxicity has been recognized as a major public health problem. The Chinese government, research institutes, and scientists conducted extensive studies concerning the source, characteristics, and mechanisms of neurotoxicants.

OBJECTIVES

This paper presents, for the first time, a comprehensive history and review of major sources of neurotoxicants, national bodies/legislation engaged, and major neurotoxicology research in China.

METHODS

Peer-reviewed research and pollution studies by Chinese scientists from 1991 to 2015 were examined. PubMed, Web of Science and Chinese National Knowledge Infrastructure (CNKI) were the major search tools.

RESULTS

The central problem is an increased exposure to neurotoxicants from air and water, food contamination, e-waste recycling, and manufacturing of household products. China formulated an institutional framework and standards system for management of major neurotoxicants. Basic and applied research was initiated, and international cooperation was achieved. The annual number of peer-reviewed neurotoxicology papers from Chinese authors increased almost 30-fold since 2001.

CONCLUSIONS

Despite extensive efforts, neurotoxicity remains a significant public health problem. This provides great challenges and opportunities. We identified 10 significant areas that require major educational, environmental, governmental, and research efforts, as well as attention to public awareness. For example, there is a need to increase efforts to utilize new in vivo and in vitro models, determine the potential neurotoxicity and mechanisms involved in newly emerging pollutants, and examine the effects and mechanisms of mixtures. In the future, we anticipate working with scientists worldwide to accomplish these goals and eliminate, prevent and treat neurotoxicity.

CITATION

Cai T, Luo W, Ruan D, Wu YJ, Fox DA, Chen J. 2016. The history, status, gaps, and future directions of neurotoxicology in China. Environ Health Perspect 124:722-732; http://dx.doi.org/10.1289/ehp.1409566.

The PI3K/Akt, p38MAPK, and JAK2/STAT3 signaling pathways mediate the protection of SO2 against acute lung injury induced by limb ischemia/reperfusion in rats

Sulfur dioxide (SO2) is naturally synthesized by glutamate-oxaloacetate transaminase (GOT) from L-cysteine in mammalian cells. We found that SO2 may have a protective effect on acute lung injury (ALI) induced by limb ischemia/reperfusion (I/R) in rats. The PI3K/Akt, p38MAPK, and JAK2/STAT3 pathways are crucial in cell signaling transduction. The present study aims to verify the role of SO2 on limb I/R-induced ALI, and investigate whether PI3K/Akt, p38MAPK, and JAK2/STAT3 pathways were involved, as well as the relationship among the three pathways; we used specific inhibitors (LY294002, SB03580, and Stattic) to block them, respectively. The experimental methods of Western, ELISA, TUNEL, etc., were used to test the results. In the I/R group, the parameters of lung injury (MDA, MPO, TUNEL, cytokines) increased significantly, but the administration of Na2SO3/NaHSO3 attenuated the damage in the lung. The Western results showed that the rat's lung exist expression of P-STAT3, P-AKT, and P-p38 proteins. After I/R, P-STAT3, P-Akt, and P-p38 proteins expression all increased. After using Na2SO3/NaHSO3, P-Akt, and P-p38 proteins expression increased, but P-STAT3 protein expression decreased. We also found a strange phenomenon; compared to the I/R + SO2 group, the administration of stattic, P-p38 protein expression showed no change, but P-Akt protein expression increased (p < 0.05). In conclusion, SO2 has a protective effect on rats with limb I/R-induced ALI. The JAK2/STAT3, PI3K/Akt, and p38MAPK pathways are likely all involved in the process, and the JAK2/STAT3 pathway may have an impact on the P13K/Akt pathway.

Effect of Homocysteine on Voltage-Gated Sodium Channel Currents in Primary Cultured Rat Caudate Nucleus Neurons and Its Modulation by 2-Arachidonylglycerol

Homocysteine (Hcy) is an important risk factor for Alzheimer's disease (AD) and other neurodegenerative diseases. Caudate nucleus (CN), the largest nucleus in the brain, is also implicated in many neurological disorders. 2-Arachidonoylglycerol (2-AG), the most abundant endogenous cannabinoid, has been shown to exhibit neuroprotective effects from many stimuli in the central nervous system (CNS). Furthermore, it has been reported that voltage-gated sodium channels (VGSCs) are the common targets of many neuronal damages and drugs. However, it is still not clear whether VGSCs are involved in the neurotoxicity of Hcy and the neuroprotective effect of 2-AG in CN neurons. In the present study, whole-cell patch clamp recording was used to invest the action of Hcy on sodium currents in primary cultured rat CN neurons and its modulation by 2-AG. The results showed that in cultured CN neurons, pathological concentration of Hcy (100 μM) significantly increased the voltage-gated sodium currents (I(Na)) and produced a hyperpolarizing shift in the activation-voltage curve of I(Na). The further data demonstrated 2-AG is capable of suppressing elevation of Hcy-induced increase in I(Na) and hyperpolarizing shift of activation curves most partly through CB1 receptor-dependent way. Our study provides a better understanding of Hcy-associated neurological disorders and suggests the therapeutic potential for 2-AG for the treatment of these diseases.

Sulfur dioxide attenuates LPS-induced acute lung injury via enhancing polymorphonuclear neutrophil apoptosis

AIM

We speculated that the enhanced apoptosis of polymorphonuclear neutrophil (PMN) might be responsible for the inhibition of PMN infiltration in the lung. This study was designed to investigate the effects of sulfur dioxide (SO(2)) on PMN apoptosis in vivo and in vitro, which may mediate the protective action of SO(2) on pulmonary diseases.

METHODS

Acute lung injury (ALI) was induced by intratracheally instillation of lipopolysaccharide (LPS, 100 μg/100 g, in 200 μL saline) in adult male SD rats. SO(2) solution (25 μmol/kg) was administered intraperitoneally 30 min before LPS treatment. The rats were killed 6 h after LPS treatment. Lung tissues were collected for histopathologic study and SO(2) concentration assay. Bronchoalveolar lavage fluid (BALF) was collected for the measurement of PMN apoptosis. For in vitro experiments, rat peripheral blood PMNs were cultured and treated with LPS (30 mg/L) and SO(2) (10, 20 and 30 μmol/L) for 6 h, and apoptosis-related protein expression was detected by Western blotting, and apoptosis rate was measured with flow cytometry.

RESULTS

LPS treatment significantly reduced the SO(2) concentrations in the lung tissue and peripheral blood, as compared with the control group. Pretreatment with SO(2) prevented LPS-induced reduction of the SO(2) concentration in the lung tissue and peripheral blood. LPS treatment significantly reduced PMN apoptosis both in vivo and in vitro, which could be prevented by the pretreatment with SO(2). The protein levels of Caspase-3 and Bax was significantly increased, but Bcl-2 was decreased by the pretreatment with SO(2), as compared with LPS administration alone.

CONCLUSION

SO(2) plays an important role as the modulator of PMN apoptosis during LPS-induced ALI, which might be one of the mechanisms underlying the protective action of SO(2) on pulmonary diseases.

Aluminium sulphate exposure increases oxidative stress and suppresses brain development in Ross broiler chicks

Background

Aluminium (Al) is known to have neurotoxic effects that can result in oxidative damage to a range of cellular biomolecules. These effects appear to be of significance in the developmental stages of the brain. We therefore investigated the oxidative and histopathological damage induced by Al during growth and development of the chick brain.

Material/Methods

We used a chick embryonic development model, with Al treatment of 500 μg Al sulphate in 0.1 ml saline injected into the egg air chambers at the beginning of their incubation period. The effects on chick-brain growth and development were then assessed at term (day 21). Determination of malondialdehyde and glutathione levels were used as relevant biological measures for increased oxidative stress in terms of lipid peroxidation and biochemical oxidative damage, respectively. Furthermore, we also monitored neuronal degeneration as estimated stereologically using the Cavalieri brain volume estimation tool.

Results

This Al treatment showed significantly increased MDA levels and decreased GSH levels, as indicators of increased biochemical oxidative damage. This was accompanied by significantly decreased brain volume, as a measure of neuronal degeneration during brain development in this chick embryonic development model.

Conclusions

Exposure to Al during chick embryonic development results in increased oxidative stress in the brain that is accompanied by neuronal degeneration.

Potentiation of the nicotinic acetylcholine receptor by aluminum in mammalian neurons

Aluminum (Al(3+)), a known neurotoxic substance, has long been implicated in the pathogenesis of Alzheimer's disease and other neurodegenerative diseases. Al(3+) targets many ligand-gated and voltage-gated ion channels and modulates their functions. In the present study, the actions of Al(3+) on the nicotinic acetylcholine receptor (nAChR) were investigated by whole-cell patch clamp technique in acutely isolated rat trigeminal ganglion neurons. We observed that Al(3+) potentiated nicotine-evoked inward currents in a concentration-dependent manner (10-1000 microM). The effects of Al(3+) on nicotine-evoked currents were voltage independent. Al(3+) appeared to increase the affinity of nicotine to nAChR but not the efficacy. Al(3+) reduced the agonist concentration producing a half-maximal response (EC(50)) for nicotine from 74.4+/-1.9 microM to 32.9+/-2.6 microM, but did not alter the threshold nor maximal response. On the contrary, another trivalent cation, Ga(3+), had little effect on nicotine-evoked currents. The present results indicated that Al(3+) enhanced the function of nAChR and this potentiation might underlie the neurological alteration induced by Al(3+).

Prenatal stress on the kinetic properties of Ca2+ and K+ channels in offspring hippocampal CA3 pyramidal neurons

Prenatal stress is known to cause neuronal loss and oxidative damage in the hippocampus of offspring rats. To further understand the mechanisms, the present study was undertaken to investigate the effects of prenatal stress on the kinetic properties of high-voltage-activated (HVA) Ca(2+) and K(+) channels in freshly isolated hippocampal CA3 pyramidal neurons of offspring rats. Pregnant rats in the prenatal stress group were exposed to restraint stress on days 14-20 of pregnancy three times daily for 45 min. The patch clamp technique was employed to record HVA Ca(2+) and K(+) channel currents. Prenatal stress significantly increased HVA Ca(2+) channel disturbance including the maximal average HVA calcium peak current amplitude (-576.52+/-7.03 pA in control group and -702.05+/-6.82 pA in prenatal stress group, p<0.01), the maximal average HVA Ca(2+) current density (-40.89+/-0.31 pA/pF in control group and -49.44+/-0.37 pA/pF in prenatal stress group, p<0.01), and the maximal average integral current of the HVA Ca(2+) channel (106.81+/-4.20 nA ms in control group and 133.49+/-4.59 nA ms in prenatal stress group, p<0.01). The current-voltage relationship and conductance--voltage relationship of HVA Ca(2+) channels and potassium channels in offspring CA3 neurons were not affected by prenatal stress. These data suggest that exposure of animals to stressful experience during pregnancy can exert effects on calcium ion channels of offspring hippocampal neurons and that the calcium channel disturbance may play a role in prenatal stress-induced neuronal loss and oxidative damage in offspring brain.