Differential effects of non-steroidal anti-inflammatory drugs on mitochondrial dysfunction during oxidative stress

We investigated the effects of several non-steroidal anti-inflammatory drugs on swelling related properties of mitochondria, with an emphasis on compounds that are marketed and utilized topically in the eye (nepafenac, ketorolac, diclofenac, bromfenac), and compared these to the effects of amfenac (a metabolite of nepafenac) and to celecoxib (active principle of Celebrex). With the exception of the last compound, none of the drugs promote swelling of normal mitochondria that are well energized by succinate oxidation. However, swelling is seen when the mitochondria are under an oxidative stress due to the presence of t-butylhydroperoxide. When used at 200 μM the order of potency is celecoxib > bromfenac > diclofenac > ketorolac > amfenac > nepafenac ≈ 0. Again with the exception of celecoxib, this swelling is not seen when mitochondria are depleted of endogenous Ca2+ and is accelerated when exogenous Ca2+ is provided. Sr2+ does not substitute for exogenous Ca2+ and prevents swelling in the presence of endogenous Ca2+ only. The same is true for ruthenium red (inhibitor of the Ca2+ uniporter), for cyclosporin A (inhibitor of the mitochondrial permeability transition), and for a 3.4 kDa polyethylene glycol (polymer that cancels the force which drives swelling following the permeability transition). It is concluded that several non-steroidal anti-inflammatory drugs promote the mitochondrial permeability transition under conditions of oxidative stress and in a Ca2+ dependent fashion, whereas celecoxib functions by another mechanism. Potency of those compounds that promote the transition varies widely with bromfenac being the most potent and nepafenac having almost no effect. The mitochondrial dysfunction which is caused by the transition may underlie side effects that are produced by some of these compounds.