Comparison between 5-aminosalicylic acid (5-ASA) and para-aminosalicylic acid (4-PAS) as potential protectors against Mn-induced neurotoxicity

Abstract

Manganese (Mn) is an essential metal for biological systems; however, occupational or clinical exposure to high levels of Mn can produce a neurological disorder called manganism. Oxidative stress and neuroinflammation play major roles in the Mn-induced neurodegeneration leading to dysfunction of the basal ganglia. We investigated the toxic effects of MnCl2 in an immortalized rat brain endothelial cell line (RBE4) and the protective effects of the radical scavenging aminosalicylic acids, 5-aminosalicylic acid (5-ASA) and 4-aminosalicylic acid (4-PAS). Mn cytotoxicity was determined with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) activity. A significant decrease in MTT reduction concomitant with increased LDH release was noted in RBE4 cells exposed for 24 h to MnCl2 (600 and 800 μM; p < 0.0001). Our results establish that compared to 4-PAS, 5-ASA has greater efficacy in protecting RBE4 cells from Mn-induced neurotoxicity after preexposure to MnCl2 800 μM (p < 0.0001).

Figure 1

The effect of 4-PAS on MTT reduction (A) and membrane integrity (B) in RBE4 cells cultured in 96-well culture plates treated for 24 h with 400, 600 or 800 μM MnCl₂ or medium alone. After 24 h RBE4 cells were treated for 45 minutes with medium or 1 or 2 mM 4-PAS in DMSO. Values of MTT (% control) (A) and LDH (% control) (B) represent mean ± SEM (n=12). ^^^ p<0.0001 significantly different from control group, *** p<0.0001,** p<0.001 significantly different from RBE4 cells exposed to the respective Mn 400, 600 and 800 μM group by one-way ANOVA followed by Bonferroni’s multiple comparison tests.

Figure 2

The effect of 5-ASA on MTT reduction (A) and membrane integrity (B) in RBE4 cells cultured in 96-well culture plates treated for 24 h with 400, 600 or 800 μM MnCl₂ or medium alone. After 24 h RBE4 cells were treated for 45 minutes with medium, or 1 or 2 mM 5-ASA in HCl. Values of MTT (% control) (A) and LDH (% control) (B) represent mean ± SEM (n=12). ^^^ p<0.0001 significantly different from control group, *** p<0.0001, ** p<0.001 significantly different from RBE4 cells exposed to the respective Mn 400, 600 and 800 μM group by one-way ANOVA followed by Bonferroni’s multiple comparison tests.