(melle-4)cyclosporin and Spinal-Cord-Injuries

Mitochondrial homeostasis is essential for maintaining cellular function and survival in the central nervous system (CNS). Mitochondrial function is significantly compromised after spinal cord injury (SCI) and is associated with accumulation of high levels of calcium, increased production of free radicals, oxidative damage, and eventually mitochondrial permeability transition (mPT). The formation of the mPT pore (mPTP) and subsequent mPT state are considered to be end stage events in the decline of mitochondrial integrity, and strategies that inhibit mPT can limit mitochondrial demise. Cyclosporine A (CsA) is thought to inhibit mPT by binding to cyclophilin D and has been shown to be effective in models of CNS injury. CsA, however, also inhibits calcineurin, which is responsible for its immunosuppressive properties. In the present study, we conducted a dose-response examination of NIM811, a nonimmunosuppressive CsA analog, on recovery of function and tissue sparing in a rat model of moderate to severe SCI. The results of our experiments revealed that NIM811 (10 mg/kg) significantly improved open field locomotor performance, while the two higher doses tested (20 and 40 mg/kg) significantly improved return of reflexive bladder control and significantly decreased the rostral-caudal extent of the lesion. Taken together, these results demonstrate the ability of NIM811 to improve recovery of function in SCI and support the role of protecting mitochondrial function as a potential therapeutic target.

Topics: Animals; Cyclosporine; Dose-Response Relationship, Drug; Female; Neuroprotective Agents; Random Allocation; Rats; Rats, Long-Evans; Recovery of Function; Spinal Cord Injuries

Trauma to the spinal cord causes a cascade of secondary events, such as mitochondrial dysfunction, which disrupts cellular functions and ultimately leads to cell death. Cyclosporin A (CsA) is a potent immunosuppressant that promotes mitochondrial function by inhibiting mitochondrial permeability transition (mPT). Clinical trials examining CsA in traumatic brain injury are currently under-way, but CsA is potentially neurotoxic. NIM811 is a non-immunosuppressive CsA derivative that inhibits mPT at nanomolar concentrations and with significantly less cytotoxicity than CsA. In the present study, we investigated the effects of NIM811 treatment on mitochondrial bioenergetics and the production of reactive oxygen species following spinal cord injury (SCI) in rats. Rats were pretreated with NIM811 or vehicle, and after 15 min the rats received a "mild/moderate" spinal cord contusion. After 24 h, the spinal cords were rapidly removed and synaptosomal mitochondria were isolated. NIM811 pretreatment significantly improved mitochondrial respiratory control ratios, and the maximal electron transport capacity of complex I and II, as well as their ATP-producing capacity. Consistent with the improvements in mitochondrial function, NIM811 pretreatment significantly decreased free radical production in isolated mitochondria. These studies are the first to demonstrate the therapeutic potential of CsA derivatives in a model of SCI, and support the need for continued investigation of compounds like NIM811 as an acute treatment for human SCI.

Topics: Animals; Biomechanical Phenomena; Chromatography, High Pressure Liquid; Contusions; Cyclosporine; Female; Mass Spectrometry; Mitochondria; Oxygen Consumption; Rats; Rats, Long-Evans; Reactive Oxygen Species; Spinal Cord Injuries; Synapses

Cyclosporin A (CsA) is a potent immunosuppressive drug shown to inhibit mitochondrial permeability transition (mPT). Although the therapeutic efficacy of CsA in traumatic brain injury is being investigated, CsA is highly neurotoxic and any neuroprotective effect in models of spinal cord injury (SCI) is unclear. NIM811 is a non-immunosuppressive CsA derivative that inhibits mPT, and is significantly less cytotoxic than CsA. Presently, we investigated the effects of NIM811 post-treatment on indices of apoptosis, lesion size, and tissue sparing at acute time-points following SCI. Adult rats received a "mild/moderate" contusion to the spinal cord, and were administered either 20 mg/kg NIM811 or vehicle by oral gavage 15 min later. One group of rats was euthanized at 1, 4, or 24 h post-injury, and the cytosolic levels of cytochrome c and fragmented DNA in the spinal cord were quantified. The remaining rats received an additional dose of NIM811 or vehicle at 24 h post-injury, and were euthanized on day 7 for morphometric assessments of the lesion and tissue spared. Control groups included rats that received sham surgery or no surgery. The results revealed that NIM811 post-treatment reduced the cytosolic levels of cytochrome c and fragmented DNA during the first 24 h following SCI. NIM811 also reduced the volume of the lesion, and enhanced the volumes of spared gray and white matter at 7 days post-injury. Together, these findings suggest that NIM811 treatment promoted tissue survival following SCI, in part, through inhibition of apoptotic mechanisms. This is the first study to demonstrate the therapeutic potential of NIM811 post-treatment in a model of acute SCI, and supports the need for continued investigation into NIM811 as a neuroprotective treatment for human SCI.

Topics: Animals; Apoptosis; Cyclosporine; Cytochromes c; Cytosol; DNA Fragmentation; Enzyme-Linked Immunosorbent Assay; Female; Image Processing, Computer-Assisted; Neuroprotective Agents; Rats; Rats, Long-Evans; Spinal Cord Injuries; Time