The Neuroprotective Effect of CoEnzymeQ10 in Experimental Glaucoma is Mediated Through Mitochondrial Mechanisms

Abstract

Purpose: : We have shown that topical CoEnzyme Q10 (CoQ10) is neuroprotective in experimental glaucoma, by significantly inhibiting the development of RGC apoptosis. In this study, we investigated possible mechanisms by which this occurred by studying effects of CoQ10 on known mitochondrial-related apoptosis proteins: phosphorylated Akt (p-Akt) and Adenin Nucleotide Translocase (ANT).

Methods: : CoQ10 was assessed in our established chronic ocular hypertension (OHT) rat model with DARC imaging at 3 weeks after IOP elevation. Animals were randomly assigned to treatment with control ( n=10) or CoQ10 0.1% eyedrops (n=10) (Visufarma srl, Italy) 30 minutes before, and 1 hour and 1 week after IOP elevation. Histological analysis was performed on sequential 5 µm thick paraffin sections from enucleated eyes , using the following antibodies: pAkt (1:100), Cytochrome c (1:100) and ANT (1:1000) . Immunostaining was assessed using a grading system we have previously established. Statistical analysis was performed using the Student’s t test one tail.

Results: : Histology confirmed that CoQ10 0.1% topically administered significantly inhibit the development of RGC apoptosis at 3 weeks in the OHT model (95.6% reduction RGC apoptosis compared to control, p<0.05). Both ANT and pAkt were expressed in the RGC layer in OHT control and treated eyes. CoQ10 treatment was associated with a significant reduction (P<0.05) in the level of ANT (2.50 ± 0.22 (control) v 1.83 ± 0.21 (CoQ10)). In contrast, pAkt expression was elevated in CoQ10-treated eyes (1.56 ± 0.50 (control) v 1.31 ± 0.31 (CoQ10)), but this did not reach statistical significance.

Conclusions: : Both pAkT and ANT are associated with apoptosis - PAkt phosphorylates Bad, interfering with mitochondrial cytochrome C release and caspase signalling, whereas ANT regulates the opening of mitochondrial permeability transition pore (PTP). The increased expression of pAkt suggests a limited role in CoQ10-associated RGC apoptosis protection. However, our results strongly suggest that the mechanism for CoQ10 0.1% being neuroprotective of RGCs in glaucoma is mediated through the inhibition of the opening of the mitochondrial PTP.

Keywords: neuroprotection • apoptosis/cell death • mitochondria