Fluoxetine prevents oligodendrocyte cell death by inhibiting microglia activation after spinal cord injury.

Oligodendrocyte cell death and axon demyelination after spinal cord injury (SCI) are known to be important secondary injuries contributing to permanent neurological disability. Thus, blocking oligodendrocyte cell death should be considered for therapeutic intervention after SCI. Here, we demonstrated that fluoxetine, an antidepressant drug, alleviates oligodendrocyte cell death by inhibiting microglia activation after SCI. After injury at the T9 level with a Precision Systems and Instrumentation (Lexington, KY) device, fluoxetine (10 mg/kg, intraperitoneal) was administered once a day for the indicated time points. Immunostaining with CD11b (OX-42) antibody and quantification analysis showed that microglia activation was significantly inhibited by fluoxetine at 5 days after injury. Fluoxetine also significantly inhibited activation of p38 mitogen-activated protein kinase (p38-MAPK) and expression of pro-nerve growth factor (pro-NGF), which is known to mediate oligodendrocyte cell death through the p75 neurotrophin receptor after SCI. In addition, fluoxetine attenuated activation of Ras homolog gene family member A and decreased the level of phosphorylated c-Jun and, ultimately, alleviated caspase-3 activation and significantly reduced cell death of oligodendrocytes at 5 days after SCI. Further, the decrease of myelin basic protein, myelin loss, and axon loss in white matter was also significantly blocked by fluoxetine, as compared to vehicle control. These results suggest that fluoxetine inhibits oligodendrocyte cell death by inhibiting microglia activation and p38-MAPK activation, followed by pro-NGF production after SCI, and provide a potential usage of fluoxetine for a therapeutic agent after acute SCI in humans.

Fluoxetine inhibits transient global ischemia-induced hippocampal neuronal death and memory impairment by preventing blood-brain barrier disruption.

Ischemia induces blood-brain barrier (BBB) disruption by matrix metalloproteases (MMPs) activation, leading to neuronal cell death. Here, we show that fluoxetine inhibits apoptotic cell death of hippocampal neuron and memory impairment by blocking BBB disruption after transient global ischemia. Fluoxetine treatment (10 mg/kg) after global ischemia significantly inhibited mRNA expression of MMP-2 and -9 and reduced MMP-9 activity. By Evan blue assay, fluoxetine reduced ischemia-induced BBB permeability. In parallel, fluoxetine significantly attenuated the loss of occludin and laminin in the hippocampal area after ischemia. By immunostaining with occludin antibody, fluoxetine preserved the integrity of vascular networks, especially in hippocampal areas after injury. Fluoxetine also prevented the infiltration of macrophages and inhibited the mRNA expression of inflammatory mediators after injury. In addition, the activation of microglia and astrocyte in hippocampal regions was significantly attenuated by fluoxetine. Finally, fluoxetine reduced apoptotic cell death of hippocampal neurons as well as vascular endothelial cell death and improved learning and memory. Thus, our study suggests that the neuroprotective effect of fluoxetine is likely mediated by blocking MMP activation followed BBB disruption after transient global ischemia, and the drug may represent a potential therapeutic agent for preserving BBB integrity following ischemic brain injury in humans.

Valproic acid protects motor neuron death by inhibiting oxidative stress and endoplasmic reticulum stress-mediated cytochrome C release after spinal cord injury.

Both oxidative stress and endoplasmic reticulum (ER) stress are known to contribute to secondary injury, ultimately leading to cell death after spinal cord injury (SCI). Here, we showed that valproic acid (VPA) reduced cell death of motor neurons by inhibiting cytochrome c release mediated by oxidative stress and ER stress after SCI. After SCI, rats were immediately injected with VPA (300 mg/kg) subcutaneously and further injected every 12 h for an indicated time period. Motor neuron cell death at an early time after SCI was significantly attenuated by VPA treatment. Superoxide anion (O2-) production and inducible NO synthase (iNOS) expression linked to oxidative stress was increased after injury, which was inhibited by VPA. In addition, VPA inhibited c-Jun N-terminal kinase (JNK) activation, which was activated and peaked at an early time after SCI. Furthermore, JNK activation and c-Jun phosphorylation were inhibited by a broad-spectrum reactive oxygen species (ROS) scavenger, Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), indicating that ROS including O2- increased after SCI probably contribute to JNK activation. VPA also inhibited cytochrome c release and caspase-9 activation, which was significantly inhibited by SP600125, a JNK inhibitor. The levels of phosphorylated Bim and Mcl-1, which are known as downstream targets of JNK, were significantly reduced by SP600125. On the other hand, VPA treatment inhibited ER stress-induced caspase-12 activation, which is activated in motor neurons after SCI. In addition, VPA increased the Bcl-2/Bax ratio and inhibited CHOP expression. Taken together, our results suggest that cell death of motor neurons after SCI is mediated through oxidative stress and ER stress-mediated cytochrome c release and VPA-inhibited cytochrome c release by attenuating ROS-induced JNK activation followed by Mcl-1 and Bim phosphorylation and ER stress-coupled CHOP expression.