Abstract
α-Lipoic acid (ALA) and its reduced form dihydrolipoic acid (DHLA) are endogenous dithiol compounds with significant antioxidant properties, both of which have the potential to detoxify cells. In this study, ALA (250 μM) and DHLA (50 μM) were applied to reduce metal (As, Cd, and Pb)-induced toxicity in PC12 and Caco-2 cells as simultaneous exposure. Both significantly decreased Cd (5 μM)-, As (5 μM)-, and Pb (5 μM)-induced cell death. Subsequently, both ALA and DHLA restored cell membrane integrity and intracellular glutathione (GSH) levels, which were affected by metal-induced toxicity. In addition, DHLA protected PC12 cells from metal-induced DNA damage upon co-exposure to metals. Furthermore, ALA and DHLA upregulated the expression of survival-related proteins mTOR (mammalian target of rapamycin), Akt (protein kinase B), and Nrf2 (nuclear factor erythroid 2-related factor 2) in PC12 cells, which were previously downregulated by metal exposure. In contrast, in Caco-2 cells, upon co-exposure to metals and ALA, Nrf2 was upregulated and cleaved PARP-1 (poly (ADP-ribose) polymerase-1) was downregulated. These findings suggest that ALA and DHLA can counterbalance the toxic effects of metals. The protection of ALA or DHLA against metal toxicity may be largely due to an enhancement of antioxidant defense along with reduced glutathione level, which ultimately reduces the cellular oxidative stress.
Highlights
Introduction αLipoic acid (ALA), a dithiol compound, which is often reduced enzymatically to dihydrolipoic acid (DHLA), is well known for its significant antioxidant properties.ALA and DHLA have gained interest because of their potential role in (a) free-radical scavenging, (b) metal chelation, and (c) restoring intracellular glutathione (GSH) levels against environmental pollutants, such as heavy metals [1,2,3]
Dulbecco’s modified Eagle’s medium (DMEM), ribonuclease A (RNase), ethidium bromide, and peroxidase-conjugated avidin were purchased from Sigma
Biotinylated goat anti-mouse IgG whole antibody and enhanced chemiluminescence (ECL) Western blotting detection reagent were purchased from Amersham Pharmacia Biotech (Buckinghamshire, England)
Summary
Lipoic acid (ALA), a dithiol compound, which is often reduced enzymatically to dihydrolipoic acid (DHLA), is well known for its significant antioxidant properties. ALA and DHLA have gained interest because of their potential role in (a) free-radical scavenging, (b) metal chelation, and (c) restoring intracellular glutathione (GSH) levels against environmental pollutants, such as heavy metals [1,2,3]. ALA has been used in multivitamin formulations, food supplements, antiaging formulas, and even human and pet food recipes, as an additional antioxidant compound [1,4].
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More From: International Journal of Environmental Research and Public Health
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