Conotoxin MVIIA improves cell viability and antioxidant system after spinal cord injury in rats

Abstract

This study evaluates whether intrathecal MVIIA injection after spinal cord injury (SCI) elicits neuroprotective effects. The test rats were randomly distributed into six groups— sham, placebo, MVIIA 2.5 μM, MVIIA 5 μM, MVIIA 10 μM, and MVIIA 20 μM—and were administered the treatment four hours after SCI. After the optimal MVIIA dose (MVIIA 10 μM) was defined, the best time for application, one or four hours, was analyzed. Locomotor hind limb function and side effects were assessed. Forty-eight hours after the injury and immediately after euthanasia, spinal cord segments were removed from the test rats. Cell viability, reactive oxygen species, lipid peroxidation, and glutamate release were investigated. To examine the MVIIA mechanism of action, the gene expressions of pro-apoptotic (Bax, nNOS, and caspase-3, -8, -9, -12) and anti-apoptotic (Bcl-xl) factors in the spinal cord tissue samples were determined by real-time PCR, and the activities of antioxidant enzymes were also investigated. Application of intrathecal MVIIA 10 μM four hours after SCI prompted a neuroprotective effect: neuronal death decreased (22.46%), oxidative stress diminished, pro-apoptotic factors (Bax, nNOS, and caspase-3, -8) were expressed to a lesser extent, and mitochondrial viability as well as anti-apoptotic factor (Bcl-xl) expression increased. These results suggested that MVIIA provided neuroprotection through antioxidant effects. Indeed, superoxide dismutase (188.41%), and glutathione peroxidase (199.96%), reductase (193.86%), and transferase (175.93%) expressions increased. Therefore, intrathecal MVIIA (MVIIA 10 μM, 4 h) application has neuroprotective potential, and the possible mechanisms are related to antioxidant agent modulation and to intrinsic and extrinsic apoptotic pathways.

Omega-conotoxin MVIIA reduces neuropathic pain after spinal cord injury by inhibiting N-type voltage-dependent calcium channels on spinal dorsal horn

“…Recently, a human clinical study using ziconotide, N-type voltage-dependent calcium-channel blockers: MVIIA, in patients with SCI-induced pain reported a decrease in pain ( Brinzeu et al, 2019 ); however, the effects and mechanisms of MVIIA on SCI-induced pain are still fully unknown. For example, a behavioral study using animal models investigated the effect of MVIIA administration 3 weeks after SCI on neuropathic pain ( Hama and Sagen, 2009 ), while another study investigated the cell viability, including mitochondrial viability or cell death value ( Oliveira et al, 2018 ). Therefore, the direct spinal analgesic effect and spinal cellular mechanisms of MVIIA were not investigated, especially when administered in the acute phase after SCI, on neuropathic pain.…”

“…Analgesic studies have demonstrated that MVIIA concentrations of 3–200 μM effectively block N-type voltage-dependent calcium channels ( Oliveira et al, 2018 ). The incidence of side effects limited the use of higher MVIIA concentrations; side effects become more intense and more frequent at higher MVIIA doses ( Souza et al, 2008 ; Oliveira et al, 2018 ).…”

“…Analgesic studies have demonstrated that MVIIA concentrations of 3–200 μM effectively block N-type voltage-dependent calcium channels ( Oliveira et al, 2018 ). The incidence of side effects limited the use of higher MVIIA concentrations; side effects become more intense and more frequent at higher MVIIA doses ( Souza et al, 2008 ; Oliveira et al, 2018 ). Doses greater than the maximum recommended dose exaggerate pharmacological effects (ataxia, nystagmus, dizziness, stupor, unresponsiveness, spinal myoclonus, confusion, sedation, hypotension, word-finding difficulties, garbled speech, nausea, and vomiting); however, Hama and Sagen reported that MVIIA at a dose of 5 μM did not cause complications ( Hama and Sagen, 2009 ).…”

Neurotoxins Acting at Synaptic Sites: A Brief Review on Mechanisms and Clinical Applications

“…Studies have reported that Prialt™ has neuroprotective potential after spinal cord injury (SCI), which suggests it may be a good alternative treatment for acute SCI [ 178 ]. After SCI, secondary neuronal death happens due to the glutamate-mediated excitotoxicity, leading to excessive intracellular calcium, mitochondrial dysfunction, acidosis, and the overproduction of free radicals [ 280 , 281 , 282 , 283 , 284 , 285 , 286 ].…”

“…This condition can be prevented by Prialt™ via inhibiting the release of glutamate [ 287 , 288 ] and calcium influx [ 276 ] and protecting mitochondria from traumatic brain injury [ 289 , 290 , 291 ]. Moreover, Prialt™ can reduce the expression of nNOS to inhibit apoptosis [ 178 ]. Furthermore, a recent article has reported a novel ω-conotoxin Bu8 with five amino acid residues and three disulfide bonds synthesized by Conus Bullatus.…”