Arundic acid (ONO-2506) inhibits secondary injury and improves motor function in rats with spinal cord injury

The S100B Protein: A Multifaceted Pathogenic Factor More Than a Biomarker

S100B is a calcium-binding protein mainly concentrated in astrocytes in the nervous system. Its levels in biological fluids are recognized as a reliable biomarker of active neural distress, and more recently, mounting evidence points to S100B as a Damage-Associated Molecular Pattern molecule, which, at high concentration, triggers tissue reactions to damage. S100B levels and/or distribution in the nervous tissue of patients and/or experimental models of different neural disorders, for which the protein is used as a biomarker, are directly related to the progress of the disease. In addition, in experimental models of diseases such as Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, multiple sclerosis, traumatic and vascular acute neural injury, epilepsy, and inflammatory bowel disease, alteration of S100B levels correlates with the occurrence of clinical and/or toxic parameters. In general, overexpression/administration of S100B worsens the clinical presentation, whereas deletion/inactivation of the protein contributes to the amelioration of the symptoms. Thus, the S100B protein may be proposed as a common pathogenic factor in different disorders, sharing different symptoms and etiologies but appearing to share some common pathogenic processes reasonably attributable to neuroinflammation.

ONO-2506 Can Delay Levodopa-induced Dyskinesia in the Early Stage

BACKGROUND

Levodopa-induced dyskinesia (LID) is a common motor complication of levodopa (L-DOPA) treatment for Parkinson's disease (PD). In recent years, the role of astrocytes in LID has increasingly attracted attention.

OBJECTIVE

To explore the effect of an astrocyte regulator (ONO-2506) on LID in a rat model and the potential underlying physiological mechanism.

METHODS

Unilateral LID rat models, established by administering 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle through stereotactic injection, were injected with ONO-2506 or saline into the striatum through brain catheterization and were administered L-DOPA to induce LID. Through a series of behavioral experiments, LID performance was observed. Relevant indicators were assessed through biochemical experiments.

RESULTS

In the LID model of 6-OHDA rats, ONO-2506 significantly delayed the development and reduced the degree of abnormal involuntary movement in the early stage of L-DOPA treatment and increased glial fibrillary acidic protein and glutamate transporter 1 (GLT-1) expression in the striatum compared to saline. However, there was no significant difference in the improvement in motor function between the ONO-2506 and saline groups.

CONCLUSIONS

ONO-2506 delays the emergence of L-DOPA-induced abnormal involuntary movements in the early stage of L-DOPA administration, without affecting the anti-PD effect of L-DOPA. The delaying effect of ONO-2506 on LID may be linked to the increased expression of GLT-1 in the rat striatum. Interventions targeting astrocytes and glutamate transporters are potential therapeutic strategies to delay the development of LID.

S100B Protein as a Therapeutic Target in Multiple Sclerosis: The S100B Inhibitor Arundic Acid Protects from Chronic Experimental Autoimmune Encephalomyelitis

S100B is an astrocytic protein behaving at high concentration as a damage-associated molecular pattern molecule. A direct correlation between the increased amount of S100B and inflammatory processes has been demonstrated, and in particular, the inhibitor of S100B activity pentamidine has been shown to ameliorate clinical scores and neuropathologic-biomolecular parameters in the relapsing-remitting experimental autoimmune encephalomyelitis mouse model of multiple sclerosis. This study investigates the effect of arundic acid (AA), a known inhibitor of astrocytic S100B synthesis, in the chronic experimental autoimmune encephalomyelitis, which is another mouse model of multiple sclerosis usually studied. By the daily evaluation of clinical scores and neuropathologic-molecular analysis performed in the spinal cord, we observed that the AA-treated group showed lower severity compared to the vehicle-treated mice, particularly in the early phase of disease onset. We also observed a significant reduction of astrocytosis, demyelination, immune infiltrates, proinflammatory cytokines expression and enzymatic oxidative reactivity in the AA-treated group. Overall, our results reinforce the involvement of S100B in the development of animal models of multiple sclerosis and propose AA targeting the S100B protein as a focused potential drug to be considered for multiple sclerosis treatment.

Growing role of S100B protein as a putative therapeutic target for neurological- and nonneurological-disorders

S100B is a calcium-binding protein mainly expressed by astrocytes, but also localized in other definite neural and extra-neural cell types. While its presence in biological fluids is widely recognized as a reliable biomarker of active injury, growing evidence now indicates that high levels of S100B are suggestive of pathogenic processes in different neural, but also extra-neural, disorders. Indeed, modulation of S100B levels correlates with the occurrence of clinical and/or toxic parameters in experimental models of diseases such as Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, muscular dystrophy, multiple sclerosis, acute neural injury, inflammatory bowel disease, uveal and retinal disorders, obesity, diabetes and cancer, thus directly linking the levels of S100B to pathogenic mechanisms. In general, deletion/inactivation of the protein causes the improvement of the disease, whereas its over-expression/administration induces a worse clinical presentation. This scenario reasonably proposes S100B as a common therapeutic target for several different disorders, also offering new clues to individuate possible unexpected connections among these diseases.

Arundic acid (ONO-2526) inhibits stimulated-S100B secretion in inflammatory conditions

Astrocytes respond to injury by modifying the expression profile of several proteins, including the S100 calcium-binding protein B (S100B), assumed to be a marker as well as a mediator of brain injury. AA is an inhibitor of S100B synthesis and plays a protective role in different models of brain injury, as decreases in S100B expression cause decreases in extracellular S100B. However, S100B mRNA expression, S100B protein content and S100B secretion do not always occur in association; as such, we herein investigated the effect of AA on S100B secretion, using different approaches with three stimulating conditions for S100B secretion, namely, low potassium medium, TNF-α (in hippocampal slices) and LPS exposure (in astrocyte cultures). Our data indicate that AA directly affects S100B secretion, indicating that the extracellular levels of this astroglial protein may be mediating the action of this compound. More importantly, AA had no effect on basal S100B secretion, but inhibited stimulated S100B secretion (stimulated either by the proinflammatory molecules, LPS or TNF-α, or by low potassium medium). Data from hippocampal slices that were directly exposed to AA, or from animals that received the acid by intracerebroventricular infusion, contribute to understanding its neuroprotective effect.

Arundic Acid (ONO-2506), an Inhibitor of S100B Protein Synthesis, Prevents Neurological Deficits and Brain Tissue Damage Following Intracerebral Hemorrhage in Male Wistar Rats

Stroke is one of the leading causes of mortality and neurological morbidity. Intracerebral hemorrhage (ICH) has the poorest prognosis among all stroke subtypes and no treatment has been effective in improving outcomes. Following ICH, the observed high levels of S100B protein have been associated with worsening of injury and neurological deficits. Arundic acid (AA) exerts neuroprotective effects through inhibition of astrocytic synthesis of S100B in some models of experimental brain injury; however, it has not been studied in ICH. The aim of this study was to evaluate the effects of intracerebroventricular (ICV) administration of AA in male Wistar rats submitted to ICH model assessing the following variables: reactive astrogliosis, S100B levels, antioxidant defenses, cell death, lesion extension and neurological function. Firstly, AA was injected at different doses (0.02, 0.2, 2 and 20 μg/μl) in the left lateral ventricle in order to observe which dose would decrease GFAP and S100B striatal levels in non-injured rats. Following determination of the effective dose, ICH damage was induced by IV-S collagenase intrastrial injection and 2 μg/μl AA was injected through ICV route immediately before injury. AA treatment prevented ICH-induced neurological deficits and tissue damage, inhibited excessive astrocytic activation and cellular apoptosis, reduced peripheral and central S100B levels (in striatum, serum and cerebrospinal fluid), improved neuronal survival and enhanced the antioxidant defences after injury. Altogether, these results suggest that S100B is a viable target for treating ICH and highlight AA as an interesting strategy for improving neurological outcome after experimental brain hemorrhage.

Administration of ONO-2506 suppresses neuropathic pain after spinal cord injury by inhibition of astrocytic activation

BACKGROUND CONTEXT

Spinal cord injury (SCI) results in not only motor dysfunction but also chronic neuropathic pain. Allodynia, an abnormal sensation that evokes pain against non-noxious stimuli, is a major symptom of post-SCI neuropathic pain. Astrocytic activation is a cause of post-SCI neuropathic pain and is considered a key treatment target. However, no effective treatment for these problems is available to date. ONO-2506 is a novel agent that suppresses astrocytic activation by inhibition of S100B production from astrocytes. Recently, it has been demonstrated that ONO-2506 inhibits secondary injury and improves motor function after SCI.

PURPOSE

This study aimed to investigate the effect of ONO-2506 on post-SCI neuropathic pain.

STUDY DESIGN

Animal study of a rat model of spinal cord contusion.

METHODS

A total of 22 male Sprague-Dawley rats aged 6 weeks were used. Incomplete SCI was created at T10 level. Animals were divided into two groups: Saline group and ONO-2506 group. Nine animals in each group were finally included for this study. Intraperitoneal administration of ONO-2506 (20 mg/kg) or saline was continued daily for 1 week following SCI. Recovery of hind limb motor function was assessed using the Basso, Beattie, and Bresnahan (BBB) score. Mechanical and thermal allodynia of hind paws were evaluated by the withdrawal threshold using a von Frey filament and the withdrawal latency using the plantar test device. At 6 weeks after SCI, sagittal sections at the injured site and axial sections at L 4/5 were evaluated by fluorescent immunohistochemistry staining using S100B and glial fibrillary acidic protein (GFAP) antibodies.

RESULTS

The improvement course of BBB scores was similar between the two groups. However, the withdrawal thresholds for mechanical stimuli and the withdrawal latency for thermal stimuli were significantly higher in the ONO-2506 group than in the Saline group over 6 weeks after SCI. The histologic assessments at the injured site demonstrated a significant reduction in the cross-sectional area of the cysts and a high fluorescence intensity area of S100B and GFAP in the ONO-2506 group. By correlation analysis, a high absolute value of the correlation coefficient was confirmed between the intensity of S100B expression at the injured site and the allodynia severity.

CONCLUSION

Administration of ONO-2506 attenuated post-SCI neuropathic pain in a rat model of incomplete SCI. Histologic results support that the inhibition of S100B production and subsequent suppression of astrocytic activation contributed to the reduction in neuropathic pain.

Arundic Acid Prevents Developmental Upregulation of S100B Expression and Inhibits Enteric Glial Development

S100B is expressed in various types of glial cells and is involved in regulating many aspects of their function. However, little is known about its role during nervous system development. In this study, we investigated the effect of inhibiting the onset of S100B synthesis in the development of the enteric nervous system, a network of neurons and glia located in the wall of the gut that is vital for control of gastrointestinal function. Intact gut explants were taken from embryonic day (E)13.5 mice, the day before the first immunohistochemical detection of S100B, and cultured in the presence of arundic acid, an inhibitor of S100B synthesis, for 48 h. The effects on Sox10-immunoreactive enteric neural crest progenitors and Hu-immunoreactive enteric neurons were then analyzed. Culture in arundic acid reduced the proportion of Sox10+ cells and decreased cell proliferation. There was no change in the density of Hu+ enteric neurons, however, a small population of cells exhibited atypical co-expression of both Sox10 and Hu, which was not observed in control cultures. Addition of exogenous S100B to the cultures did not change Sox10+ cell numbers. Overall, our data suggest that cell-intrinsic intracellular S100B is important for maintaining Sox10 and proliferation of the developing enteric glial lineage.

Intracerebroventricular application of S100B selectively impairs pial arteriolar dilating function in rats

S100B is an astrocyte-derived protein that can act through the receptor for advanced glycation endproducts (RAGE) to mediate either "trophic" or "toxic" responses. Its levels increase in many neurological conditions with associated microvascular dysregulation, such as subarachnoid hemorrhage (SAH) and traumatic brain injury. The role of S100B in the pathogenesis of microvasculopathy has not been addressed. This study was designed to examine whether S100B alters pial arteriolar vasodilating function. Rats were randomized to receive (1) artificial cerebrospinal fluid (aCSF), (2) exogenous S100B, and (3) exogenous S100B+the decoy soluble RAGE (sRAGE). S100B was infused intracerebroventricularly (icv) using an osmotic pump and its levels in the CSF were adjusted to achieve a concentration similar to what we observed in SAH. After 48 h of continuous icv infusion, a cranial window/intravital microscopy was applied to animals for evaluation of pial arteriolar dilating responses to sciatic nerve stimulation (SNS), hypercapnia, and topical suffusion of vasodilators including acetylcholine (ACh), s-nitroso-N-acetyl penicillamine (SNAP), or adenosine (ADO). Pial arteriolar dilating responses were calculated as the percentage change of arteriolar diameter in relation to baseline. The continuous S100B infusion for 48 h was associated with reduced responses to the neuronal-dependent vasodilator SNS (p<0.05) and the endothelial-dependent vasodilator ACh (p<0.05), compared to controls. The inhibitory effects of S100B were prevented by sRAGE. On the other hand, S100B did not alter the responses elicited by vascular smooth muscle cell-dependent vasodilators, namely hypercapnia, SNAP, or ADO. These findings indicate that S100B regulates neuronal and endothelial dependent cerebral arteriolar dilation and suggest that this phenomenon is mediated through RAGE-associated pathways.