Mithramycin A Improves Functional Recovery by Inhibiting BSCB Disruption and Hemorrhage after Spinal Cord Injury

After spinal cord injury (SCI), blood-spinal cord barrier (BSCB) disruption and progressive hemorrhage lead to secondary injury, subsequent apoptosis and/or necrosis of neurons and glia, causing permanent neurological deficits. Growing evidence indicates that mithramycin A (MA), an anti-cancer drug, has neuroprotective effects in ischemic brain injury and Huntington's disease (HD). However, the precise mechanism underlying its protective effects is largely unknown. Here, we examined the effect of MA on BSCB breakdown and hemorrhage as well as subsequent inflammation after SCI. After moderate spinal cord contusion injury at T9, MA (150 μg/kg) was immediately injected intraperitoneally (i.p.) and further injected once a day for 5 days. Our data show that MA attenuated BSCB disruption and hemorrhage, and inhibited the infiltration of neutrophils and macrophages after SCI. Consistent with these findings, the expression of inflammatory mediators was significantly alleviated by MA. MA also inhibited the expression and activation of matrix metalloprotease-9 (MMP-9) after injury, which is known to disrupt BSCB and the degradation of tight junction (TJ) proteins. In addition, the expression of sulfonylurea receptor 1 (SUR1) and transient receptor potential melastatin 4 (TRPM4), which are known to mediate hemorrhage at an early stage after SCI, was significantly blocked by MA treatment. Finally, MA inhibited apoptotic cell death and improved functional recovery after injury. Thus, our results demonstrated that MA improves functional recovery by attenuating BSCB disruption and hemorrhage through the downregulation of SUR1/TRPM4 and MMP-9 after SCI.

Cordycepin-enriched WIB-801C from Cordyceps militaris improves functional recovery by attenuating blood-spinal cord barrier disruption after spinal cord injury

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps militaris is an ingredient of traditional Chinese medicine and have been widely used for inflammatory diseases and cancer. Cordycepin is one of the major bioactive components of Cordyceps militaris, and has been known to have anti-inflammatory and anti-oxidant effects.

AIM OF THIS STUDY

In the present study, we examined whether WIB-801C, a standardized and cordycepin-enriched extract of caterpillar fungus (Cordyceps militaris), would attenuate blood-spinal cord barrier (BSCB) disruption by inhibiting matrix metalloprotease (MMP)-9 activity, leading to improvement of functional outcomes after spinal cord injury (SCI).

MATERIALS AND METHODS

Male Sprague-Dawley rats were subjected to contusive SCI using a New York University (NYU) impactor, and WIB-801C (50mg/kg) was administered at 2h and 8h after injury orally and further treated once a day for indicated time points. BSCB disruption, MMP-9 activity, blood infiltration, inflammation, neuronal apoptosis, axonal loss, demyelination, and neurological deficit were evaluated.

RESULTS

We found that WIB-801C significantly attenuated BSCB disruption by inhibiting MMP-9 expression and activation after injury. The infiltration of neutrophils at 1 d and macrophage at 5 d after SCI was also ameliorated by WIB-801C as compared with vehicle control. In addition, the expression of inflammatory cytokines and mediators such as Tnf-α, IL-1β, IL-6, Cox-2, and inos as well as chemokines such as Gro-α and Mip-2α was significantly inhibited by WIB-801C. Furthermore, WIB-801C inhibits p38MAPK activation and proNGF production in microglia after injury. These events eventually led to the inhibition of apoptotic cell death of neurons and oligodendrocytes, improved functional recovery and attenuated demyelination and axon loss after SCI.

CONCLUSION

Our results suggest that WIB-801C can be used as a therapeutic agent after SCI by attenuating BSCB disruption followed inflammation.

Jmjd3 mediates blood-spinal cord barrier disruption after spinal cord injury by regulating MMP-3 and MMP-9 expressions

The disruption of the blood-spinal cord barrier (BSCB) by matrix metalloprotease (MMP) activation is a detrimental event that leads to blood cell infiltration, inflammation, and apoptosis, thereby contributing to permanent neurological disability after spinal cord injury (SCI). However, the molecular mechanisms underlying Mmp gene regulation have not been fully elucidated. Here, we demonstrated the critical role of histone H3K27 demethylase Jmjd3 in the regulation of Mmp gene expression and BSCB disruption using in vitro cellular and in vivo animal models. We found that Jmjd3 up-regulation, in cooperation with NF-κB, after SCI is required for Mmp-3 and Mmp-9 gene expressions in injured vascular endothelial cells. In addition, Jmjd3 mRNA depletion inhibited Mmp-3 and Mmp-9 gene expressions and significantly attenuated BSCB permeability and the loss of tight junction proteins. These events further led to improved functional recovery, along with decreased hemorrhage, blood cell infiltration, inflammation, and cell death of neurons and oligodendrocytes after SCI. Thus, our findings suggest that Jmjd3 regulation may serve as a potential therapeutic intervention for preserving BSCB integrity following SCI.

17β-estradiol inhibits MMP-9 and SUR1/TrpM4 expression and activation and thereby attenuates BSCB disruption/hemorrhage after spinal cord injury in male rats

Blood-spinal cord barrier (BSCB) disruption and progressive hemorrhage after spinal cord injury (SCI) lead to secondary injury and the subsequent apoptosis and/or necrosis of neuron and glia, causing permanent neurological deficits. In this study, we examined the effect of 17β-estradiol (E2) on BSCB breakdown and hemorrhage as well as subsequent inflammation after SCI. After a moderate contusion injury at the 9th thoracic segment of spinal cord, E2 (300 μg/kg) was administered by iv injection immediately after SCI, and the same dose of E2 was then administered 6 and 24 hours after injury. Our data show that E2 attenuated BSCB permeability and hemorrhage and reduced the infiltration of neutrophils and macorphages after SCI. Consistent with this finding, the expression of inflammatory mediators was significantly reduced by E2. Furthermore, E2 treatment significantly inhibited the expression of sulfonylurea receptor 1 and transient receptor potential melastatin 4 after injury, which are known to mediate hemorrhage at an early stage after SCI. Moreover, the expression and activation of matrix metalloprotease-9 after injury, which is known to disrupt BSCB, and the degradation of tight junction proteins, such as zona occludens-1 and occludin, were significantly inhibited by E2 treatment. Furthermore, the protective effects of E2 on BSCB disruption and functional improvement were abolished by an estrogen receptor antagonist, ICI 182780 (3 mg/kg). Thus, our study provides evidence that the neuroprotective effect of E2 after SCI is, in part, mediated by inhibiting BSCB disruption and hemorrhage through the down-regulation of sulfonylurea receptor 1/transient receptor potential melastatin 4 and matrix metalloprotease-9, which is dependent on estrogen receptor.

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.

Valproic acid attenuates blood-spinal cord barrier disruption by inhibiting matrix metalloprotease-9 activity and improves functional recovery after spinal cord injury

The disruption of blood-spinal cord barrier (BSCB) after spinal cord injury (SCI) elicits an intensive local inflammation by the infiltration of blood cells such as neutrophils and macrophages, leading to cell death and permanent neurological disability. SCI activates matrix metalloprotease-9 (MMP-9), which is known to induce BSCB disruption. Here, we examined whether valproic acid (VPA), a histone deacetylase inhibitor, would attenuate BSCB disruption by inhibiting MMP-9 activity, leading to improvement of functional outcome after SCI. After moderate spinal cord contusion injury at T9, VPA (300 mg/kg) were immediately injected subcutaneously and further injected every 12 h for 5 days. Our data show that VPA inhibited MMP-9 activity after injury, and attenuated BSCB permeability and degradation of tight junction molecules such as occludin and ZO-1. In addition, VPA reduced the expression of inflammatory mediators including tumor necrosis factor-α. Furthermore, VPA increased the levels of acetylated histone 3, pAkt, and heat-shock protein 27 and 70, which have anti-apoptotic functions after SCI. Finally, VPA inhibited apoptotic cell death and caspase 3 activation, reduced the lesion volume and improved functional recovery after injury. Thus, our results demonstrated that VPA improves functional recovery by attenuating BSCB disruption via inhibition of MMP-9 activity after SCI.

Cloning of a cDNA encoding cathepsin D from salamander, Hynobius leechii, and its expression in the limb regenerates

Cathepsin D is a major lysosomal aspartic proteinase participating in the degradation or modification of intra- and extracellular matrix molecules, and its activity is known to increase in the process of tissue reorganization during the early phase of salamander limb regeneration. Here, we report the cloning of a salamander cathepsin D cDNA from Hynobius leechii and its expression profile in normal and retinoic acid (RA) treated limb regenerates. The gene expression of cathepsin D increased notably during the dedifferentiation stage and decreased gradually thereafter. Furthermore, RA that enhances dedifferentiation of regenerating salamander limb caused the elevation of cathepsin D expression both in terms of level and duration. These results suggest that cathepsin D plays important role(s) in the dedifferentiation process, and enhancement of cathepsin D expression might be closely related to RA-evoked pattern duplication.

Fringe forms a complex with Notch

The Fringe protein of Drosophila and its vertebrate homologues function in boundary determination during pattern formation. Fringe has been proposed to inhibit Serrate-Notch signalling but to potentiate Delta-Notch signalling. Here we show that Fringe and Notch form a complex through both the Lin-Notch repeats and the epidermal growth factor repeats 22-36 (EGF22-36) of Notch when they are co-expressed. The Abruptex59b (Ax59b) and AxM1 mutations, which are caused by missense mutations in EGF repeats 24 and 25, respectively, abolish the Fringe-Notch interaction through EGF22-36, whereas the l(1)N(B) mutation in the third Lin-Notch repeat of Notch abolishes the interaction through Lin-Notch repeats. Ax mutations also greatly affect the Notch response to ectopic Fringe in vivo. Results from in vitro protein mixing experiments and subcellular colocalization experiments indicate that the Fringe-Notch complex may form before their secretion. These findings explain how Fringe acts cell-autonomously to modulate the ligand preference of Notch and why the Fringe-Notch relationship is conserved between phyla and in the development of very diverse structures.

Upregulation of cathepsin D expression in the dedifferentiating salamander limb regenerates and enhancement of its expression by retinoic acid

In the regenerating urodele limb, catheptic activity has been known to be present in the stump tissue undergoing histolysis, and it has been implicated in the modification of some intracellular and extracellular matrix molecules. In this study, we compared spatial and temporal gene expression profiles of cathepsin D in normal, retinoic acid-treated, or denervated larval limb regenerates of Hynobius leechii and compared cathepsin D activities between normal and retinoic acid-treated limb regenerates. The results showed that the expression of cathepsin D increased markedly in the vicinity of an amputation site under the wound epidermis at dedifferentiation stage, whereas the expression level of cathepsin D was low in the denervated limb. With retinoic acid treatment, the expression of cathepsin D was elevated in terms of both level and duration. In addition, the profile of cathepsin D activity coincided well with the expression profile of cathepsin D in normal and retinoic acid-treated limb regenerates. These results suggest that the increase of cathepsin D activity during the dedifferentiation period is due to the upregulation of cathepsin D transcription, and nerve factors are involved in this process. Furthermore, retinoic acid appears to upregulate cathepsin D expression, which might be linked to the enhanced dedifferentiation in the retinoic acid-treated limb regenerates.

Pattern duplication by retinoic acid treatment in the regenerating limbs of Korean salamander larvae, Hynobius leechii, correlates well with the extent of dedifferentiation

In the regenerating limbs of Korean salamanders, Hynobius leechii, retinoic acid (RA) induces duplication of skeletal structures in the proximodistal (PD) axis and often in the transverse axes. In the present study, the stage-dependent effects of RA for the duplication of limb skeletal structures at two amputation levels, the distal stylopodium and the distal zeugopodium, were studied using larval limbs of Korean salamanders. The results showed that the mean level of proximalization (MLP) by RA treatment increased during the stages of dedifferentiation and early bud formation while the MLP declined thereafter in both amputation levels. The decline of the MLP at the later stages of regeneration was due to the high frequency of hypomorphic regeneration or blocked regeneration. When the effects of RA treatment at two amputation levels were compared, the overall trends were similar but the actual timing was delayed for 2-4 days in the proximal level of amputation. Furthermore, the peak level of proximalization was achieved earlier and the peak level remained longer in the distal stylopodial level of amputation compared to the distal zeugopodial level of amputation. Since the histological observations revealed that the dedifferentiation period was also extended up to 2-4 days in the proximal level of amputation, the acid phosphatase activity during the course of regeneration was measured to look for a quantitative relationship between the enzyme activity and the states of dedifferentiation. The results show that the level and the duration of acid phosphatase activity in the upper arm regenerates are both higher and longer than those in the lower arm regenerates. Furthermore, RA treatment caused an increase in acid phosphatase activity. Thus our results suggest that the state of dedifferentiation might be closely linked to the extent of proximalization of regenerating limbs by RA treatment.