Morphine is a potent analgesic opioid used extensively for pain treatment. During the
last decade, global consumption grew more than 4-fold. However, molecular mechanisms
elicited by morphine are not totally understood. Thus, a growing literature indicates
that there are additional actions to the analgesic effect. Previous studies about
morphine and oxidative stress are controversial and used concentrations outside the
range of clinical practice. Therefore, in this study, we hypothesized that a
therapeutic concentration of morphine (1 μM) would show a protective effect in a
traditional model of oxidative stress. We exposed the C6 glioma cell line to hydrogen
peroxide (H2O2) and/or morphine for 24 h and evaluated cell
viability, lipid peroxidation, and levels of sulfhydryl groups (an indicator of the
redox state of the cell). Morphine did not prevent the decrease in cell viability
provoked by H2O2 but partially prevented lipid peroxidation
caused by 0.0025% H2O2 (a concentration allowing more than 90%
cell viability). Interestingly, this opioid did not alter the increased levels of
sulfhydryl groups produced by exposure to 0.0025% H2O2, opening
the possibility that alternative molecular mechanisms (a direct scavenging activity
or the inhibition of NAPDH oxidase) may explain the protective effect registered in
the lipid peroxidation assay. Our results demonstrate, for the first time, that
morphine in usual analgesic doses may contribute to minimizing oxidative stress in
cells of glial origin. This study supports the importance of employing concentrations
similar to those used in clinical practice for a better approximation between
experimental models and the clinical setting.