Immunosuppressive (FK506) and non-immunosuppressive (GPI1046) immunophilin ligands activate neurotrophic factors in the mouse brain

Intracerebral Xenotransplantation of GFP Mouse Bone Marrow Stromal Cells in Intact and Stroke Rat Brain: Graft Survival and Immunologic Response

The present study characterized survival and immunologic response of bone marrow stromal cells (BMSCs) following transplantation into intact and stroke brains. In the first study, intrastriatal transplantation of BMSC (60,000 in 3 μl) or vehicle was performed in normal adult Sprague-Dawley male rats that subsequently received daily cyclosporin A (CsA, 10 mg/kg, IP in 3 ml) or vehicle (olive oil, similar volume) starting on day of surgery up to 3 days posttransplantation. Animals were euthanized at 3 or 30 days posttransplantation and brains were processed either for green fluorescent protein (GFP) microscopy or flow cytometry (FACS). Both GFP epifluorescence and FACS scanning revealed GFP+ BMSCs in both groups of transplanted rats with or without CsA, although significantly increased (1.6- to 3-fold more) survival of GFP+ BMSCs was observed in the immunosuppressed animals. Further histologic examination revealed widespread dispersal of BMSCs away from the graft core accompanied by many long outgrowth processes in non-CsA-transplanted animals, whereas a very dense graft core, with cells expressing only sporadic short outgrowth processes, was observed in CsA-transplanted animals. There were no detectable GFP+ BMSCs in nontrans-planted rats that received CsA or vehicle. Immunologic response via FACS analysis revealed a decreased presence of cytotoxic cells, characterized by near complete absence of CD8+ cells, and lack of activation depicted by low CD69 expression in CsA-treated transplanted animals. In contrast, elevated levels of CD8+ cells and increased activation of CD69 expression were observed in transplanted animals that received vehicle alone. CD4+ helper cells were almost nondetectable in transplanted rats that received CsA, but also only minimally elevated in transplanted rats that received vehicle. Nontransplanted rats that received either CsA or vehicle displayed very minimal detectable levels of all three lymphocyte markers. In the second study, a new set of male Sprague-Dawley rats initially received bilateral stereotaxic intrastriatal transplantation of BMSCs and 3 days after were subjected to unilateral transient occlusion of middle cerebral artery. The animals were allowed to survive for 3 days after stroke without CsA immunosuppression. Epifluorescence microscopy revealed significantly higher (5-fold more) survival of transplanted GFP+ BMSCs in the stroke striatum compared with the intact striatum. The majority of the grafts remained within the original dorsal striatal transplant site, characterized by no obvious migration in intact striatum, but with long-distance migration along the ischemic penumbra in the stroke striatum. Moreover, FACS scanning analyses revealed low levels of immunologic response of grafted BMSCs in both stroke and intact striata. These results, taken together, suggest that xenotransplantation of mouse BMSCs into adult rats is feasible. Immunosuppression therapy can enhance xenograft survival and reduce graft-induced immunologic response; however, in the acute phase posttransplantation, BMSCs can survive in intact and stroke brain, and may even exhibit long-distance migration and increased outgrowth processes without immunosuppression.

Neuroprotective and Therapeutic Strategies against Parkinson's Disease: Recent Perspectives

Parkinsonism is a progressive motor disease that affects 1.5 million Americans and is the second most common neurodegenerative disease after Alzheimer’s. Typical neuropathological features of Parkinson’s disease (PD) include degeneration of dopaminergic neurons located in the pars compacta of the substantia nigra that project to the striatum (nigro-striatal pathway) and depositions of cytoplasmic fibrillary inclusions (Lewy bodies) which contain ubiquitin and α-synuclein. The cardinal motor signs of PD are tremors, rigidity, slow movement (bradykinesia), poor balance, and difficulty in walking (Parkinsonian gait). In addition to motor symptoms, non-motor symptoms that include autonomic and psychiatric as well as cognitive impairments are pressing issues that need to be addressed. Several different mechanisms play an important role in generation of Lewy bodies; endoplasmic reticulum (ER) stress induced unfolded proteins, neuroinflammation and eventual loss of dopaminergic neurons in the substantia nigra of mid brain in PD. Moreover, these diverse processes that result in PD make modeling of the disease and evaluation of therapeutics against this devastating disease difficult. Here, we will discuss diverse mechanisms that are involved in PD, neuroprotective and therapeutic strategies currently in clinical trial or in preclinical stages, and impart views about strategies that are promising to mitigate PD pathology.

Pathogenesis-targeted, disease-modifying therapies in Parkinson disease

Parkinson disease is an inexorably progressive neurodegenerative disorder. Multiple attempts have been made to establish therapies for Parkinson disease which provide neuroprotection or disease modification-two related, but not identical, concepts. However, to date, none of these attempts have succeeded. Many challenges exist in this field of research, including a complex multisystem disorder that includes dopaminergic and non-dopaminergic features; poorly understood and clearly multifaceted disease pathogenic mechanisms; a lack of reliable animal models; an absence of effective biomarkers of disease state, progression, and target engagement; and the confounding effects of potent symptomatic therapy. In this article, we will review previous, ongoing, and potential future trials designed to alter the progressive course of the disease from the perspective of the targeted underlying pathogenic mechanisms.

Neuroimmunophilin GPI-1046 reduces ethanol consumption in part through activation of GLT1 in alcohol-preferring rats

We have previously shown that ceftriaxone, β-lactam antibiotic known to upregulate glutamate transporter 1 (GLT1), reduced ethanol intake in alcohol-preferring (P) rats. GLT1 is a glial glutamate transporter that regulates the majority of extracellular glutamate uptake. We tested in this study the effects of neuroimmunophilin GPI-1046 (3-(3-pyridyl)-1-propyl (2S)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-pyrrolidinecarboxylate), known also to upregulate GLT1 expression, in ethanol intake in P rats. Male P rats had concurrent access to free choice of 15% and 30% ethanol, water, and food for five weeks. On Week 6, P rats continued in this drinking and food regimen and they were administered either 10 or 20mg/kg GPI-1046 (i.p.), or a vehicle for five consecutive days. Body weight, ethanol intake, and water consumption were measured daily for 8 days starting on Day 1 of GPI-1046 or vehicle i.p. injections. We have also tested the effect of GPI-1046 (20mg/kg) on daily sucrose (10%) intake. The data revealed significant dose-dependent effects in the reduction of ethanol intake starting 48 h after the first treatment with GPI-1046 throughout treatment and post-treatment periods. There were also dose-dependent increases in water intake. However, GPI-1046 treatment did not affect the body weight of all animals nor sucrose intake. Importantly, GPI-1046 (20mg/kg) increased GLT1 level compared to all groups in nucleus accumbens core (NAc-core). Alternatively, GPI-1046 (10mg/kg) upregulated GLT1 level in NAc-core compared to vehicle (ethanol naïve) group. Moreover, both doses of GPI-1046 increased significantly GLT1 level in the prefrontal cortex (PFC) compared to ethanol naïve vehicle group. GPI-1046 (20mg/kg) increased GLT1 level in PFC compared to naïve control group that was exposed to water and food only. These findings demonstrated that neuroimmunophilin GPI-1046 attenuates ethanol intake in part through the upregulation of GLT1 in PFC and NAc-core.

Targets for neuroprotection in Parkinson's disease

Current therapies for Parkinson's disease significantly improve the quality of life for patients suffering from this neurodegenerative disease, yet none of the current therapies has been convincingly shown to slow or prevent the progression of disease. Much has been learned about the pathophysiology of Parkinson's disease in recent years, and these discoveries offer a variety of potential targets for protective therapy. Mechanisms implicated in the disease process include oxidative stress, mitochondrial dysfunction, protein aggregation and misfolding, inflammation, excitotoxicity, and apoptosis. At the same time, the involvement of these diverse processes makes modeling the disease and evaluation of potential treatments difficult. In addition, available clinical tools are limited in their ability to monitor the progression of the disease. In this review, we summarize the different pathogenic mechanisms implicated in Parkinson's disease and neuroprotective strategies targeting these mechanisms currently under clinical study or under preclinical development, with a view towards strategies that seem most promising.

Driving GDNF expression: the green and the red traffic lights

Glial cell line-derived neurotrophic factor (GDNF) is widely recognized as a potent survival factor for dopaminergic neurons of the nigrostriatal pathway that degenerate in Parkinson's disease (PD). In animal models of PD, GDNF delivery to the striatum or the substantia nigra protects dopaminergic neurons against subsequent toxin-induced injury and rescues previously damaged neurons, promoting recovery of the motor function. Thus, GDNF was proposed as a potential therapy to PD aimed at slowing down, halting or reversing neurodegeneration, an issue addressed in previous reviews. However, the use of GDNF as a therapeutic agent for PD is hampered by the difficulty in delivering it to the brain. Another potential strategy is to stimulate the endogenous expression of GDNF, but in order to do that we need to understand how GDNF expression is regulated. The aim of this review is to do a comprehensive analysis of the state of the art on the control of endogenous GDNF expression in the nervous system, focusing mainly on the nigrostriatal pathway. We address the control of GDNF expression during development, in the adult brain and after injury, and how damaged neurons signal glial cells to up-regulate GDNF. Pharmacological agents or natural molecules that increase GDNF expression and show neuroprotective activity in animal models of PD are reviewed. We also provide an integrated overview of the signalling pathways linking receptors for these molecules to the induction of GDNF gene, which might also become targets for neuroprotective therapies in PD.

Promotion of nerve regeneration in peripheral nerve by short-course FK506 after end-to-side neurorrhaphy

BACKGROUND/AIMS

To discuss the feasibility of peripheral nerve injury treated by end-to-side neurorrhaphy in clinic and to evaluate the effect of short-course FK506 on promoting nerve regeneration after end-to-side neurorrhaphy.

METHODS

Thirty adult male Sprague Dawley rats were randomly divided into 3 groups: Group A, 10 rats received end-to-end anastomosis; Group B, 10 rats received end-to-side neurorrhaphy; Group C, 10 rats received the same operation as Group B. After operation, rats in Groups B and C received muscle injection with saline water (1 mg/kg x d(-1)) and FK506 (1 mg/kg x d(-1)), respectively, both for 4 wk. Histological and morphological examinations were performed 12 wk after the operation. In the 2nd, 4th, 6th, 8th, and 12th wk after operation, function recovery analysis was performed.

RESULTS

The results of histological and immunochemistry study (the total number of Schwann cells and the axon numbers at the distal stump of the peroneal nerve, wet weight of extensor digitorum longus muscle) suggested that there were significant differences between Group B (saline water group) and Group C (FK506 group) (P < 0.05), also between Group A (end-to-end group) and Group C (P < 0.05). There were statistically significant differences in function recovery (peroneal functional index and sciatic functional index) between Groups B and C (P < 0.05) and also between Groups A and C (P < 0.05).

CONCLUSION

End-to-side repair combined with FK506 has a potential for application in selected cases of peripheral nerve injury in clinic.

Neuroprotective therapy in Parkinson disease

During the past decade, there has been a remarkable progress in our understanding of the biology of Parkinson disease (PD), which has been translated into searching for novel therapy for PD. Much focus is shifted from the development of drugs that only relieve PD symptoms to new generation of remedies that can potentially protect dopaminergic neurons and modify the disease course. Several novel therapeutic approaches have been tested in preclinical experiments and in clinical trials, including molecules targeting on genes involved in the pathogenesis of the disease, neurotrophic factors critical for dopaminergic neuron survival and function, new generation of dopamine receptor agonists that may possess neuroprotective effects, and agents of antioxidation, antiinflammation, and antiapoptosis. The results of these studies will shed new light to our hope that PD can be cured in the future.

Modeling and synthesis of non-cyclic derivatives of GPI-1046 as potential FKBP ligands with neurotrophic properties

Prompted by the therapeutic potential of the neuroimmunophilin FK506-binding protein (FKBP) ligand, GPI-1046, in the treatment of nerve injuries and neurodegenerative diseases, a novel series of non-cyclic derivatives of GPI-1046 were designed and synthesized. Computer modeling analysis revealed that these relatively linear derivatives could energy-favorably bind to FKBP12 with an analogous binding mode to GPI-1046. The neurotrophic activity of the target compounds was assessed in chick dorsal root ganglion (DRG) cultures. As a result, 6 out of 11 test compounds at either or both concentrations of 1 pM and 100 pM significantly promoted neurite outgrowth in DRGs in the presence of 0.15 ng/ml nerve growth factor (NGF). Compound 5c at 100 pM exhibited the greatest neurotrophic effect in promoting both the number and length of neurite processes. However, in the absence of exogenously added NGF, all test compounds, including GPI-1046, failed to afford any positive effect on DRGs. This study suggests the intriguing potential of these compounds for further investigation.

A multiplexed proteomics approach to differentiate neurite outgrowth patterns

We report here a method for proteomics pattern discovery by utilizing a self-organizing map approach to analyze data obtained from a novel multiplex iTRAQ proteomics method. Through the application of this technique, we were able to delineate the early molecular events preceding dorsal root ganglia neurite outgrowth induced by either nerve growth factor (NGF) or an immunophilin ligand, JNJ460. Following pattern analysis we discovered that each neurotrophic agent promoted mostly distinct increases in protein expression with few overlapping patterns. In the NGF-treated group, proteins possessing "biosynthesis function" (p < 0.002) and "ribosome localization" (p < 0.0003) were increased, while proteins promoting "organogenesis" (p < 0.004) and related "signal transduction" (p < 0.008) functions were notably increased in the JNJ460-treated group. This study suggests that the properties of neurite outgrowth triggered by NGF and JNJ460 can be distinguished at the proteome level. Multiplexed proteomics analysis, along with pattern discovery bioinformatics tools, has the capability to differentiate subtle neuroproteomics patterns.

FK506-Binding Protein Ligands: Structure-Based Design, Synthesis, and Neurotrophic/Neuroprotective Properties of Substituted 5,5-Dimethyl-2-(4-thiazolidine)carboxylates

Structure-based design and discovery of novel neuroimmunophilin FK506-binding protein (FKBP) ligands were pursued in the present study. The binding mode of the known FKBP ligand 1 (3-(3-pyridyl)-1-propyl (2S)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-pyrrolidinecarboxylate) in complex with FKBP12 was investigated using LUDI simulation and upon which a novel scaffold structure predicted to possess improved binding affinity was designed. A virtual combinatorial library composed of diverse combinations of two substituted groups was constructed using Project Library, followed by an automated screening of the library against the ligand binding site on FKBP52 using DOCK. Forty-three candidate compounds that displayed favorable binding with the receptor were identified and synthesized. The neurotrophic activity of the candidate compounds was evaluated on chick dorsal root ganglion cultures in vitro. As a result, 15 compounds exhibited positive effects on ganglion neurite outgrowth in the presence of 0.15 ng/mL NGF, among which 7 compounds at testing concentrations of 1 pM and 100 pM showed greater efficacy than 1 at 100 pM. Compound 18 (3-(3-pyridyl)-1-propyl (2S)-5,5-dimethyl-1-(3,3-dimethyl-1,2-dioxobutyl)-2-(4-thiazolidine)carboxylate) afforded the most potent effect in promoting the processes of neurite outgrowth and which was in a concentration-dependent manner from 1 pM to 100 pM. Half-maximal effect occurred at about 10 pM. Moreover, 18 at a dosage of 10 mg/kg was found to be significantly neuroprotective in a mouse peripheral sympathetic nerve injury model induced by 8 mg/kg 6-hydroxydopamine. This study further suggests the clinical potential of novel FKBP ligands as a new therapeutic approach in the treatment of neurodegenerative disorders, such as Parkinson's disease.

An analog of a dipeptide-like structure of FK506 increases glial cell line-derived neurotrophic factor expression through cAMP response element-binding protein activated by heat shock protein 90/Akt signaling pathway

Glial cell line-derived neurotrophic factor (GDNF) is an important neurotrophic factor that has therapeutic implications for neurodegenerative disorders. We previously showed that leucine-isoleucine (Leu-Ile), an analog of a dipeptide-like structure of FK506 (tacrolimus), induces GDNF expression both in vivo and in vitro. In this investigation, we sought to clarify the cellular mechanisms underlying the GDNF-inducing effect of this dipeptide. Leu-Ile transport was investigated using fluorescein isothiocyanate-Leu-Ile in cultured neurons, and the results showed the transmembrane mobility of this dipeptide. By liquid chromatography-mass spectrometry and quartz crystal microbalance assay, we identified heat shock cognate protein 70 as a protein binding specifically to Leu-Ile, and molecular modeling showed that the ATPase domain is the predicted binding site. Leu-Ile stimulated Akt phosphorylation, which was attenuated significantly by heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA). Moreover, enhanced interaction between phosphorylated Akt and Hsp90 was detected by immunoprecipitation. Leu-Ile elicited an increase in cAMP response element binding protein (CREB) phosphorylation, which was inhibited by GA, indicating that CREB is a downstream target of Hsp90/Akt signaling. Leu-Ile elevated the levels of GDNF mRNA and protein expression, whereas inhibition of CREB blocked such effects. Leu-Ile promoted the binding activity of phosphorylated CREB with cAMP response element. These findings show that CREB plays a key role in transcriptional regulation of GDNF expression induced by Leu-Ile. In conclusion, Leu-Ile activates Hsp90/Akt/CREB signaling, which contributes to the upregulation of GDNF expression. It may represent a novel lead compound for the treatment of dopaminergic neurons or motoneuron diseases.

Immunosuppression with either cyclosporine a or FK506 supports survival of transplanted fibroblasts and promotes growth of host axons into the transplant after spinal cord injury

Fibroblasts that have been genetically modified to secrete neurotrophins can stimulate axonal regeneration, rescue injured neurons, and improve function when grafted into a spinal cord injury site. These grafts are usually allografts that require immunosuppression to prevent rejection. In this study, we compared the effects of two immunophilin-ligands (cyclosporine A [CsA] and FK506) that are used clinically to prevent transplant rejection on protection of grafted fibroblasts. As there are risks associated with prolonged immunosuppression, we compared the effects of 2 or 8 weeks of administration of these drugs, in combination with our standard methylprednisolone protocol, in animals that survived for 8 weeks, to determine whether a shorter course of immunosuppression would be effective. Outcome measures included fibroblast survival, infiltration of activated macrophages and microglia into the graft, final lesion size, and growth of host axons into the graft. The graft consisted of a Vitrogen matrix into which fibroblasts were suspended; the graft was placed into a C3/C4 lateral funiculus lesion. The fibroblasts were isolated from a transgenic strain of Fischer rats that produce the marker alkaline phosphatase (Fb/AP). This enabled us to track the grafted fibroblasts and to evaluate the extent of their survival. The grafted matrix filled the lesion cavity. The density of fibroblasts within the matrix differed according to treatment. Fibroblast survival was most robust in animals that received 8 weeks of immunophilin-ligand treatment. FK506 supported greater Fb/AP survival than CsA. ED-1 immunostaining for activated microglia and macrophages showed an inverse correlation between AP immunoreactivity and the density of immune cells within the graft. Thus, prolonged administration of either FK506 or CsA was necessary for maximal fibroblast survival and for limiting the macrophage invasion of the graft. None of the FK506 or CsA protocols modified the size of the lesion, indicating that these immunophilin-ligands had little effect on secondary enlargement of the lesion and therefore little neuroprotective effect. Because immunophilin-ligands have been shown to be neurotrophic, we used RT-97 immunostaining for neurofilaments and calcitonin gene related protein (CGRP) staining for dorsal root axons to visualize axons that grew into the graft. Some axons grew into the matrix even in the absence of immunophilin-ligand treatment, suggesting that the Vitrogen matrix itself is permissive, but all of the immunophilin-ligand protocols were much more effective in eliciting axonal growth. Growth of axons into the transplants was equally increased by drug treatment for 2 or 8 weeks. Thus, both treatments improved fibroblast survival, diminished immune cell invasion, and promoted axonal growth, and a 2-week course of treatment with either immunophilin-ligand was as effective as 8 weeks in stimulating axonal growth.

Shedding light into the role of BDNF in the pharmacotherapy of Parkinson's disease

Parkinson's disease (PD) is a chronic, neurodegenerative disease with a 1% incidence in the population over 55 years of age. Movement impairments represent undoubtedly the hallmark of the disorder; however, extensive evidence implicates cognitive deficits as concomitant peculiar features. Brain-derived neurotrophic factor (BDNF) colocalizes with dopamine neurons in the substantia nigra, where dopaminergic cell bodies are located, and it has recently garnered attention as a molecule crucial for cognition, a function that is also compromised in PD patients. Thus, due to its colocalization with dopaminergic neurons and its role in cognition, BDNF might possess a dual role in PD, both as a neuroprotective molecule, since its inhibition leads to loss of nigral dopaminergic neurons, and as a neuromodulator, as its enhanced expression ameliorates cognitive processes. In this review, we discuss the mechanism of action of established as well as novel drugs for PD with a particular emphasis to those interfering with BDNF biosynthesis.

A role for schwann cells in the neuroregenerative effects of a non-immunosuppressive fk506 derivative, jnj460

FK506 and its non-immunosuppressive derivatives represent a class of pharmacological agents referred to as immunophilin ligands that have been reported to promote neuroregeneration and survival in several experimental models; however their cellular and molecular mechanisms of action have not been well established. Here we characterize a new immunophilin ligand that interacts with both FK506 binding protein 12 (FKBP12) and FKBP52, and demonstrate that JNJ460 induces neurite outgrowth from freshly explanted dorsal root ganglia (DRG) in a Schwann cell-dependent manner. Purified cultures of neurons fail to respond to these drugs, but cultures containing Schwann cells and neurons respond with neurite outgrowth, as do neurons grown in conditioned medium from JNJ460-treated Schwann cells. Using microarray analysis and a transcription reporter assay, we show that JNJ460 induces a series of transcriptional changes that occur in a temporal cascade. Among the Schwann cell-expressed genes upregulated following JNJ460 treatment is the POU transcription factor SCIP, which has been shown to regulate Schwann cell gene transcription and differentiation. JNJ460 potentiated transforming growth factor beta (TGF-beta)-induced transcriptional activation and SCIP induction in Schwann cells, by altering the interaction between FKBP12 and the TGF-beta type I receptor, TbetaR1. Finally, to test whether JNJ460 enhances neurite regeneration in vivo, we treated animals with JNJ460 for 30 days following mechanical transection of the sciatic nerve and demonstrated myelin and axonal hypertrophy at the ultrastructural level. Collectively, these data suggest that Schwann cells play an important role in the biological effects of immunophilin ligands by affecting neuron-glial signaling during regeneration.

SUMMARY

The cellular and molecular mechanisms responsible for the regenerative effects of immunophilin ligands are not well understood. Here we show that the neuritogenic effects of JNJ460 in a DRG model depend on interactions between neurons and Schwann cells. Treatment of purified Schwann cells with JNJ460 alters Schwann cell gene expression, and promotes the generation of factors that act on neurons. These data indicate that Schwann cells play an important role in the actions of immunophilin ligands.

Neuroimmunophilins: A novel drug therapy for the reversal of neurodegenerative disease?

Neuroimmunophilin ligands (NILs) are drugs derived from the immunosuppressant FK506 (tacrolimus) that have been shown to have variable efficacy in reversing neuronal degeneration and preventing cell death. In a wide range of animal models mimicking Parkinson's disease, dementia and even surgical nerve damage they induce re-sprouting, are neurotrophic or prevent nerve damage. The neurotrophic mechanism of action of these compounds is not known and may be dependent on the type of damage and genetic variability at the species or cellular level. Some evidence suggests that NILs may act through a family of proteins called FK506 binding proteins, some of which may regulate steroid hormone receptors. Other evidence suggests that NILs may protect neurons by upregulating the antioxidant glutathione and stimulating nerve regrowth by inducing the production of neurotrophic factors. Initial clinical trials have had mixed success. In one, patients with moderately severe Parkinson's disease showed no overall improvement in fine motor skills following 6 months of treatment by the neuroimmunophilin GPI 1485. But these patients did exhibit decreased loss of dopaminergic nerve terminals with a low dose of GPI 1485 and in fact some increase in dopaminergic terminals within 6 months of the higher dose of GPI 1485 drug treatment. As a result, a second phase II clinical trial using a patient population with less severe degeneration has been initiated concurrent with an investigation of GPI 1485 and other neuroprotective therapies funded by the National Institute of Neurological Disorders and Stroke. Another clinical trial ongoing at this time is exploring the use of a neuroimmunophilin ligand to prevent nerve degeneration and erectile dysfunction resulting from prostatectomy. In summary, neuroimmunophilins show promise to reverse some forms of neurodegeneration but exact factors that predict outcome have not been identified.