Treatment of manganese and lead poisoning with sodium para-aminosalicylic acid: A contemporary update.

Sodium para-aminosalicylic acid (PAS-Na) treatment for manganese (Mn) intoxication has shown efficacy in experimental and clinical studies, giving rise to additional studies on its efficacy for lead (Pb) neurotoxicity and its associated mechanisms of neuroprotection. The difference between PAS-Na and other metal complexing agents, such as edetate calcium sodium (CaNa2-EDTA), is firstly that PAS-Na can readily pass through the blood-brain barrier (BBB), and complex and facilitate the excretion of manganese and lead. Secondly, PAS-Na has anti-inflammatory effects. Recent studies have broadened the understanding on the mechanisms associated with efficacy of PAS-Na. The latter has been shown to modulate multifarious manganese- and lead- induced neurotoxicity, via its anti-apoptotic and anti-inflammatory effects, as well as its ability to inhibit pyroptosis, and regulate abnormal autophagic processes. These observations provide novel scientific bases and new concepts for the treatment of lead, mercury, copper, thallium, as well as other toxic encephalopathies, and implicate PAS-Na as a compound with greater prospects for clinical medical application.

Effects of Manganese and Iron, Alone or in Combination, on Apoptosis in BV2 Cells.

The aim of study was to address the effects of manganese and iron, alone and in combination, on apoptosis of BV2 microglia cells, and to determine if combined exposure to these metals augments their individual toxicity. We used a murine microglial BV2 cell line. Cell cytotoxicity was analyzed by propidium iodide (PI) exclusion assay. Cell ROS production was analyzed by 2', 7'-dichlorofluorescin diacetate (DCFH-DA) probe staining. Pro-inflammatory cytokine production was monitored by ELISA. Cell apoptosis was analyzed by PE Annexin V/7-AAD staining. Mitochondrial membrane integrity was analyzed by flow cytometry. We used immunoblotting to analyze the effect of manganese, iron alone, or their combined exposure on the activation of caspase9, P53, Bax, and Bcl2 apoptosis signaling pathways. Caspase3 activity was determined using a Colorimetric. Manganese, iron, and their combined exposure for 24 h induced the activation of BV2 microglia cells and increased ROS production and the expression of the inflammatory cytokines, IL-1ß and TNF-α. And we also found that the apoptosis rate increased, mitochondrial membrane potential decreased, apoptosis-related proteins caspase9, P53, Bax, and Bcl2 expression increased, and caspase3 activity increased. Furthermore, we found that combined manganese-iron cytotoxicity was lower than that induced by manganese exposure alone. Manganese, iron alone, or their combination exposure can induce apoptosis in glial cells. Iron can reduce the toxicity of manganese, and there is an antagonistic effect between manganese and iron.

Combined exposure to manganese and iron decreases oxidative stress-induced nerve damage by increasing Nrf2/HO-1/NQO1 expression.

BACKGROUND: Manganese (Mn) and iron (Fe) are essential trace elements for humans, yet excessive exposure to Mn or Fe can accumulate in the central nervous system (CNS) and cause neurotoxicity. The purpose of this study was to investigate the effects of Mn and Fe exposure, alone or in combination, on inducing oxidative stress-induced neurological damage in rat cortical and SH-SY5Y cells, and to determine whether combined exposure to these metals increases their individual toxicity. METHODS: SH-SY5Y cells and male Sprague-Dawley rats were used to observe the effects of oxidative stress-induced neurological damage induced by exposure to manganese and iron alone or in combination. To detect the expression of anti-oxidative stress-related proteins, Nrf2, HO-1, and NQO1, and the apoptosis-related proteins, Bcl2 and Bax, and the neurological damage-related protein, α-syn. To detect reactive oxygen species generation and apoptosis. To detect the expression of the rat cortical protein Nrf2. To detect the production of proinflammatory cytokines. RESULTS: We demonstrate that juvenile developmental exposure to Mn and Fe and their combination impairs cognitive performance in rats by inducing oxidative stress causing neurodegeneration in the cortex. Mn, Fe, and their combined exposure increased the expression of ROS, Bcl2, Bax, and α-syn, activated the inflammatory factors IL-6 and IL-12, inhibited the activities of SOD and GSH, and induced oxidative stress-induced neurodegeneration both in rats and SH-SY5Y cells. Combined Mn-Fe exposure attenuated the oxidative stress induced by Mn and Fe exposure alone by increasing the expression of antioxidant factors Nrf2, HO-1, and NQO1. CONCLUSION: In both in vivo and in vitro studies, manganese and iron alone or in combination induced oxidative stress, leading to neuronal damage. In contrast, combined exposure to manganese and iron mitigated the oxidative stress induced by exposure to manganese and iron alone by increasing the expression of antioxidant factors. Therefore, studies to elucidate the main causes of toxicity and establish the molecular mechanisms of toxicity should help to develop more effective therapeutic modalities in the future.

Protective Effects of Sodium Para-Aminosalicylic Acid on Lead and Cadmium Co-Exposure in SH-SY5Y Cells.

BACKGROUND: Combined exposure to lead and cadmium is common in occupational environments. However, the effects of co-exposure to Pb-Cd on neurotoxicity have not been fully clarified. Sodium para-aminosalicylic acid (PAS-Na) has previously been shown to protect neurons from Pb-induced toxicity. This study aimed to investigate the beneficial effect of PAS-Na against co-exposure to Pb-Cd-induced neurodegeneration in SH-SY5Y cells. METHODS: The MTT assay was used to detect the effects of Pb and Cd alone, or in combination, on SH-SY5Y cell survival. The effects of Pb and Cd alone or in combination on oxidative stress were assessed by reactive oxygen species (ROS) level. Nrf2, the master switch for antioxidant responses, was detected by immunofluorescence. Protein expression levels of PI3K, Akt, p-Akt, Nrf2 and HO-1 were determined by Western blot analysis. RESULTS: MTT assay results established that the survival rate of SH-SY5Y cells was not significantly affected by exposure to 1 µmol/L lead, 0.25 µmol/L cadmium, and 1-fold Pb-Cd mixture (1 µmol/L Pb + 0.25 µmol/L Cd), while 10-fold Pb-Cd combined exposure (10 µmol/L Pb + 2.5 µmol/L Cd) significantly reduced the survival rate of SH-SY5Y cells. Combined Pb-Cd exposure significantly increased intracellular ROS levels, and N-Acetyl-L-cysteine (NAC) treatment in the 10 µmol/L Pb + 2.5 µmol/L Cd group significantly decreased ROS expression levels, attenuating the levels of oxidative stress. Protein expression of PI3K and p-Akt significantly decreased in the 10 µmol/L Pb + 2.5 µmol/L Cd group, while the expression of PI3K and p-Akt protein increased after PAS-Na intervention. Immunofluorescence analysis showed that levels of Nrf2 in the nucleus increased in the 10 µmol/L Pb + 2.5 µmol/L Cd group, along with Nrf2 protein levels, suggesting that Nrf2 was translocated from the cytoplasm into the nucleus upon combined Pb-Cd exposure. In addition, HO-1 protein expression level, a downstream gene product of Nrf2, was increased. In response to NAC intervention, HO-1 protein expression levels significantly decreased. PAS-Na had the same intervention effect as NAC. CONCLUSION: Combined exposure to Pb-Cd induced oxidative stress and cytotoxicity in SH-SY5Y cells. PAS-Na displayed antagonistic effects on neurodegenerative changes induced by combined Pb-Cd exposure; hence, it may afford a novel treatment modality for exposure to these metals.