TOXICITY OF STATINS ON NEURONAL CELLS: POSSIBLE REVERSIBILITY BY MITO-Q

Abstract

Statins are among the most commonly prescribed drugs to patients with cardiovascular events. They are cholesterol-lowering drugs that competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in the mevalonate pathway. They exhibit a pleiotropic role in different tissues and body organs. On the other hand, statin toxicity involves renal, liver, muscle, and neurological events. Studies however on its neurotherapeutic effects have been controversial being neuroprotective in some and neurodegenerative in others. In addition to their hypocholesterolemic effects, statins decrease downstream biomolecules of important cellular functions such as isoprenoids, and ubiquinone. In this study, we compared the direct effect of 5 different statins on 2 neuronal cell lines: rat PC12 and human SH-SY5Y. The following statins were used in this study: one natural product mevastatin and 4-synthetic (atorvastatin, rosuvastatin, pitavastatin, and fluvastatin). The viability of statin-treated (1-15 μM; 24 and 48 hours) cells was evaluated using (trypan blue exclusion/MTT assays). Changes in reactive oxygen species and ATP levels in treated cells were determined using NBT and luciferase assays respectively. The possible protective effect of pre-/ or co-MitoQ treatment with statins was investigated. The level of cholesterol and the direct inhibitory effect of statins on purified HMG-CoA reductase activity was determined. Compared to SH-SY5Y, PC12 was insensitive to statins, hence we opted to limit the study to human cells treated with statins, for 24 and 48 hours at a concentration lower than the estimated IC50. We report in the statin-treated SH-SY5Y a significant dose and time-dependent a) decrease in viability (85-90% at 48hrs); b) increase in ROS (50-75%); and c) a decrease in ATP (60%-99%). MitoQ pre- and co-treatment with statins exhibited no protective effect. Catalase also did not prevent or protect against cell death. Preliminary determination of cholesterol level showed an increase in statin-treated cells that may result from induced LDL receptors expression favoring cholesterol uptake, in response to HMG-CoA reductase inhibition. Statins’ neurotoxicity in-vitro is not limited to the inhibition of HMG-CoA reductase enzyme, but to statin-related factors including differences in their physicochemical properties, size, and hydrophobicity. The sensitivity of SH-SY5Y cells to the different 3 statins varied with lipophilicity in the following order with the most potent being fluvastatin> pitavastatin> atorvastatin > rosuvastatin the least effective. The structural differences of the various statins supported the difference in the pharmacokinetic response of these drugs on SH-SY5Y neuronal cells. While most of the literature claim indirect and direct protective effect for statins, we hereby show a toxic effect on statin-treated (48 hours) human neuronal cells. These findings may underlie some of the reported side effects in patients on statins such as dementia, cognitive decline, and Alzheimer’s disease.