Spinal cord injury (SCI) is a condition producing irreversible damage to the neurological function. Among the leading mechanisms associated to cell death after SCI, excitotoxicity, oxidative stress, inflammatory response and apoptosis are considered potential targets to prevent tissue damage. We recently reported that dapsone an anti-inflammatory drug, decreases the activity of myeloperoxidase, lipid peroxidation, improve neurological function and increase the amount of spared tissue after SCI in rats. In this study, we characterized the anti-apoptotic effect of dapsone administered at 12.5 mg/kg/24 h dose, starting at 3 and 5 h after SCI. We monitored the activity of caspases-8, 9, and 3 and quantitated Annexin V and TUNEL positive cells in the core of the lesion. Results showed increased activities of caspase-8, 9 and 3 at 72 h by SCI to reach increments of 69, 143 and 293 %, respectively, as compared to sham group. Meanwhile, dapsone, administered at 3 and 5 after SCI, reduced caspase-8 activity by 36 and 44 % respectively, whereas the activity of caspase-9 was diminished by 37 %. Likewise, the activity of caspase-3 showed a decrease of 38 %. Finally, both Annexin V and TUNEL-positive cells were significantly reduced by DDS as compared to untreated SCI animals. Results showed that dapsone exerted anti-apoptotic effect after SCI.

After spinal cord injury (SCI), some self-destructive mechanisms start leading to irreversible neurological deficits. It is known that oxidative stress and apoptosis play a major role in increasing damage after SCI. Metallothioneins I and II (MT) are endogenous peptides with known antioxidant, neuroprotective capacities. Taking advantage of those capacities, we administered exogenous MT to rats after SCI in order to evaluate the protective effects of MT on the production of reactive oxygen species (ROS) and lipid peroxidation (LP), as markers of oxidative stress. The activities of caspases-9 and -3 and the number of annexin V and TUNEL-positive cells in the spinal cord tissue were also measured as markers of apoptosis. Rats were subjected to either sham surgery or SCI and received vehicle or two doses of MT (10 μg per rat) at 2 and 8 h after surgical procedure. The results showed a significant increase in levels of MT protein by effect of SCI and SCI plus treatment at 12 h, while at 24 h an increase of MT was observed only in the injury plus treatment group (p < 0.05). ROS production was decreased by effect of MT in lesioned tissue; likewise, we observed diminished LP levels by MT effect both in the sham group and in the group with SCI. Also, the results showed an increase in the activity of caspase-9 due to SCI, without changes by effect of MT, as compared to the sham group. Caspase-3 activity was increased by SCI, and again, MT treatment reduced this effect only at 24 h after injury. Finally, the results of the number of cells positive to annexin V and TUNEL showed a reduction due to MT treatment both at 24 and 72 h after the injury. With the findings of this work, we conclude that exogenously administered MT has antioxidant and antiapoptotic effects after SCI.

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