JNK inhibitor protects dopaminergic neurons by reducing COX-2 expression in the MPTP mouse model of subacute Parkinson's disease

Regulation of the microglial polarization for alleviating neuroinflammation in the pathogenesis and therapeutics of major depressive disorder

Major depressive disorder (MDD), as a multimodal neuropsychiatric and neurodegenerative illness with high prevalence and disability rates, has become a burden to world health and the economy that affects millions of individuals worldwide. Neuroinflammation, an atypical immune response occurring in the brain, is currently gaining more attention due to its association with MDD. Microglia, as immune sentinels, have a vital function in regulating neuroinflammatory reactions in the immune system of the central nervous system. From the perspective of steady-state branching states, they can transition phenotypes between two extremes, namely, M1 and M2 phenotypes are pro-inflammatory and anti-inflammatory, respectively. It has an intermediate transition state characterized by different transcriptional features and the release of inflammatory mediators. The timing regulation of inflammatory cytokine release is crucial for damage control and guiding microglia back to a steady state. The dysregulation can lead to exorbitant tissue injury and neuronal mortality, and targeting the cellular signaling pathway that serves as the regulatory basis for microglia is considered an essential pathway for treating MDD. However, the specific intervention targets and mechanisms of microglial activation pathways in neuroinflammation are still unclear. Therefore, the present review summarized and discussed various signaling pathways and effective intervention targets that trigger the activation of microglia from its branching state and emphasizes the mechanism of microglia-mediated neuroinflammation associated with MDD.

c-Jun N-terminal kinase signaling in aging

Aging encompasses a wide array of detrimental effects that compromise physiological functions, elevate the risk of chronic diseases, and impair cognitive abilities. However, the precise underlying mechanisms, particularly the involvement of specific molecular regulatory proteins in the aging process, remain insufficiently understood. Emerging evidence indicates that c-Jun N-terminal kinase (JNK) serves as a potential regulator within the intricate molecular clock governing aging-related processes. JNK demonstrates the ability to diminish telomerase reverse transcriptase activity, elevate β-galactosidase activity, and induce telomere shortening, thereby contributing to immune system aging. Moreover, the circadian rhythm protein is implicated in JNK-mediated aging. Through this comprehensive review, we meticulously elucidate the intricate regulatory mechanisms orchestrated by JNK signaling in aging processes, offering unprecedented molecular insights with significant implications and highlighting potential therapeutic targets. We also explore the translational impact of targeting JNK signaling for interventions aimed at extending healthspan and promoting longevity.

Dipeptide mimetic of BDNF ameliorates motor dysfunction and striatal apoptosis in 6-OHDA-induced Parkinson's rat model: Considering Akt and MAPKs signaling

Parkinson's disease (PD) is a progressive and debilitating neurodegenerative disorder associated with motor and non-motor complaints. Dysregulation of neurotrophic factors and related signaling cascades have been reported to be common events in PD which is accompanied by dopaminergic (DA) neuron demise. However, the restoration of neurotrophic factors has several limitations. Bis-(N-monosuccinyl-L-methionyl-L-serine) heptamethylenediamide (BHME) is a dipeptide mimetic of brain-derived neurotrophic factor (BDNF) with reported anti-oxidant and neuroprotective effects in several experimental models. The current study has investigated the effect of BHME on 6-hydroxydopamine (6-OHDA)-caused motor anomalies in Wistar rats. In this regard, rats were treated daily with BHME (0.1 or 1 mg/kg) 1 h after 6-OHDA-caused damage until the twelfth day. Afterwards, motor behavior and DA neuron survival were evaluated via behavioral tests and immunohistochemistry (IHC) staining, respectively. Moreover, the activity of Akt, mitogen-activated protein kinases (MAPKs) family, and Bax/Bcl-2 ratio were evaluated by Western blotting. Our results indicated that BHME prevents motor dysfunction and DA cell death following 6-OHDA injection, and this improvement was in parallel with an enhancement in Akt activity, decrement of P38 phosphorylation, along with a reduction in Bax/Bcl-2 ratio. In conclusion, our findings indicated that BHME, as a mimetic of BDNF, can be considered for further research and is a promising therapeutic agent for PD therapy.

Discovery of Novel Indazole Chemotypes as Isoform-Selective JNK3 Inhibitors for the Treatment of Parkinson's Disease

c-Jun N-terminal kinases (JNKs) are involved in the pathogenesis of various diseases. In particular, JNK3 and not JNK1/2 is primarily expressed in the brain and plays a key role in mediating neurodegenerative diseases like Parkinson's disease (PD). Due to the sequence similarity of JNK isoforms, developing isoform-selective JNK3 inhibitors to evaluate their biological functions and therapeutic potential in PD has become a challenge. Herein, docking-based virtual screening and structure-activity relationship studies identified 25c with excellent inhibitory activity against JNK3 (IC₅₀ = 85.21 nM) and exhibited an over 100-fold isoform selectivity for JNK3 over JNK1/2 and remarkable kinase selectivity. 25c showed neuroprotective effects on in vitro and in vivo PD models by selectively inhibiting JNK3. Meanwhile, 25c showed an ideal blood-brain barrier permeability and low toxicity. Overall, this study provided a valuable molecular tool for investigating the role of JNK3 in PD and a solid foundation for developing JNK3-targeted drugs in PD treatment.

Hypothesis: JNK signaling is a therapeutic target of neurodegenerative diseases

The exact signaling leading to neurological dysfunction in neurodegenerative diseases is currently unknown. We hypothesize that the c-Jun N-terminal kinase (JNK) signaling pathway is a potential therapeutic target for neurodegenerative diseases. This postulate rests on extensive data from cell and animal experimental studies, demonstrating that JNK signaling plays a crucial role in the pathogenesis of neurodegenerative diseases. The sustained activation of JNK leads to synaptic dysfunction and even neuronal apoptosis, ultimately resulting in memory deficits and neurodegeneration. JNK phosphorylates the amyloid precursor protein and tau, ultimately resulting in the formation of extraneuronal senile plaques and intraneuronal neurofibrillary tangles. Our hypothesis could be validated by investigating the cerebral cortex of elderly chimpanzees injected with phosphorylated JNK or transgenic pig and chimpanzee models established using gene editing technology including CRISPR. This hypothesis provides clues for further understanding the molecular mechanisms of neurodegenerative diseases and the development of potential target therapeutic drugs.

A transition to degeneration triggered by oxidative stress in degenerative disorders

Although the activities of many signaling pathways are dysregulated during the progression of neurodegenerative and muscle degeneration disorders, the precise sequence of cellular events leading to degeneration has not been fully elucidated. Two kinases of particular interest, the growth-promoting Tor kinase and the energy sensor AMPK, appear to show reciprocal changes in activity during degeneration, with increased Tor activity and decreased AMPK activity reported. These changes in activity have been predicted to cause degeneration by attenuating autophagy, leading to the accumulation of unfolded protein aggregates and dysfunctional mitochondria, the consequent increased production of reactive oxygen species (ROS), and ultimately oxidative damage. Here we propose that this increased ROS production not only causes oxidative damage but also ultimately induces an oxidative stress response that reactivates the redox-sensitive AMPK and activates the redox-sensitive stress kinase JNK. Activation of these kinases reactivates autophagy. Because at this late stage, cells have become filled with dysfunctional mitochondria and protein aggregates, which are autophagy targets, this autophagy reactivation induces degeneration. The mechanism proposed here emphasizes that the process of degeneration is dynamic, that dysregulated signaling pathways change over time and can transition from deleterious to beneficial and vice versa as degeneration progresses.

Clinically Precedented Protein Kinases: Rationale for Their Use in Neurodegenerative Disease

Kinases are an intensively studied drug target class in current pharmacological research as evidenced by the large number of kinase inhibitors being assessed in clinical trials. Kinase-targeted therapies have potential for treatment of a broad array of indications including central nervous system (CNS) disorders. In addition to the many variables which contribute to identification of a successful therapeutic molecule, drug discovery for CNS-related disorders also requires significant consideration of access to the target organ and specifically crossing the blood-brain barrier (BBB). To date, only a small number of kinase inhibitors have been reported that are specifically designed to be BBB permeable, which nonetheless demonstrates the potential for success. This review considers the potential for kinase inhibitors in the context of unmet medical need for neurodegenerative disease. A subset of kinases that have been the focus of clinical investigations over a 10-year period have been identified and discussed individually. For each kinase target, the data underpinning the validity of each in the context of neurodegenerative disease is critically evaluated. Selected molecules for each kinase are identified with information on modality, binding site and CNS penetrance, if known. Current clinical development in neurodegenerative disease are summarized. Collectively, the review indicates that kinase targets with sufficient rationale warrant careful design approaches with an emphasis on improving brain penetrance and selectivity.

KMS99220 Exerts Anti-Inflammatory Effects, Activates the Nrf2 Signaling and Interferes with IKK, JNK and p38 MAPK via HO-1

Neuroinflammation is an important contributor to the pathogenesis of neurodegenerative disorders including Parkinson's disease (PD). We previously reported that our novel synthetic compound KMS99220 has a good pharmacokinetic profile, enters the brain, exerts neuroprotective effect, and inhibits NFκB activation. To further assess the utility of KMS99220 as a potential therapeutic agent for PD, we tested whether KMS99220 exerts an anti-inflammatory effect in vivo and examined the molecular mechanism mediating this phenomenon. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice, oral administration of KMS99220 attenuated microglial activation and decreased the levels of inducible nitric oxide synthase and interleukin 1 beta (IL-1b) in the nigrostriatal system. In lipopolysaccharide (LPS)-challenged BV-2 microglial cells, KMS99220 suppressed the production and expression of IL-1b. In the activated microglia, KMS99220 reduced the phosphorylation of IκB kinase, c-Jun N-terminal kinase, and p38 MAP kinase; this effect was mediated by heme oxygenase-1 (HO-1), as both gene silencing and pharmacological inhibition of HO-1 abolished the effect of KMS99220. KMS99220 induced nuclear translocation of the transcription factor Nrf2 and expression of the Nrf2 target genes including HO-1. Together with our earlier findings, our current results show that KMS99220 may be a potential therapeutic agent for neuroinflammation-related neurodegenerative diseases such as PD.

Inhibition of glutathione S-transferase-pi triggers c-jun N-terminal kinase-dependent neuronal death in Zn-induced Parkinsonism

Oxidative stress is recognized as one of the major wrongdoers in Parkinson's disease (PD) while glutathione S-transferase (GST), an endogenous antioxidant, protects from oxidative stress-induced neurodegeneration. Despite GST-pi (GST-π) encounters the toxic manifestations in PD, its role in zinc (Zn)-induced nigrostriatal dopaminergic neurodegeneration remains elusive. The study aimed to explore the role of GST-π in Zn-induced Parkinsonism and its underlying molecular mechanism. Male Wistar rats were treated intraperitoneally with zinc (zinc sulfate), twice a week, for 2-12 weeks. GST-π inducer, benzyl isothiocyanate (BITC) was also administered in a few sets of experiments along with respective vehicle. Catalytic activity and expression of GST-π protein, total GST activity, neurobehavioral indexes, striatal dopamine and its metabolites, nigral tyrosine hydroxylase (TH)-positive neurons and expression of TH and B-cell lymphoma-2 (Bcl-2) proteins were reduced in Zn-treated rats. Conversely, oxidative stress indicators, c-jun N-terminal kinase (JNK) activation, c-jun phosphorylation, cytochrome c release, Bcl-2-associated X protein (Bax) translocation, and procaspase 3/9 to caspase 3/9 conversion were significantly increased in Zn-exposed rats. BITC ameliorated GST-π activity/expression and normalized Zn-induced changes in neurodegenerative indicators, oxidative stress, JNK activation, c-jun phosphorylation and apoptotic indexes. The results demonstrate that Zn inhibits GST-π expression leading to increased oxidative stress and JNK activation, which induce apoptosis thereby degeneration of the nigrostriatal dopaminergic neurons.

Effect of Zishenpingchan granule prepared from Chinese medicinal substances on the c-Jun N-terminal protein kinase pathway in mice with Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

OBJECTIVE

To investigate the regulatory mechanism of the c-Jun N-terminal protein kinase (JNK) signaling pathway in substantia nigra (SN) dopaminergic neurons inflammation and apoptosis, and the neuroprotective effect of Zishenpingchan granules in mice with Parkinson's disease (PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

METHODS

PD model mice were established by intraperitoneally injecting MPTP. Sixty mice were divided into a model group, Traditional Chinese Medicine (TCM) group and control group. The mice of the TCM group were administered Zishenpingchan granules 7 days before PD induction. Seven days after PD induction, we examined locomotor activity, and performed the rotarod test and swimming test, to evaluate limb movement function. Furthermore, we used immunohistochemistry and western blotting to examine the expression of tyrosine hydroxylase (TH), cyclooxygenase-2 (Cox-2), caspase-3 and p-JNK. The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method was used to examine neuron apoptosis in the SN.

RESULTS

Compared with the control group, the mean score of locomotor activity, rotarod test and swimming test was significantly lower in the model group (P < 0.05); the TH-positive neuron expression was significantly decreased in the SN pars compacta (SNpc); the protein expression levels of Cox-2, caspase-3 and p-JNK was obviously increased; and the number of TUNEL-positive neurons in the SN was increased (P < 0.01). Compared with the model group, the mean score of neurobehavioral tests in the TCM group was obviously higher, the loss of TH-positive neurons ignificantly decreased, the protein expression levels of Cox-2, caspase-3 and p-JNK obviously decreased, and the number of TUNEL- positive neurons in the SN clearly decreased (P < 0.01).

CONCLUSION

The JNK pathway plays an important role in the regulation of inflammation and apoptosis in nigral cells in PD mice. TCM can suppress the over-activation of the JNK pathway in the SN, and alleviate the inflammatory response in nigral cells and dopaminergic neuron apoptosis in PD mice.

Dual Kinase Inhibition Affords Extended in vitro Neuroprotection in Amyloid-β Toxicity

In Alzheimer's disease (AD), the amyloid cascade hypothesis proposes that amyloid-beta (Aβ) neurotoxicity leads to neuroinflammation, synaptic loss, and neuronal degeneration. In AD patients, anti-amyloid immunotherapies did not succeed because they were possibly administered late in AD progression. Modulating new targets associated with Aβ toxicity, such as PKR (double-stranded RNA dependent kinase), and JNK (c-Jun N-terminal kinase) is a major goal for neuroprotection. These two pro-apoptotic kinases are activated in AD brains and involved in Aβ production, tau phosphorylation, neuroinflammation, and neuronal death. In HEK cells transfected with siRNA directed against PKR, and in PKR knockout (PKR-/-) mice neurons, we showed that PKR triggers JNK activation. Aβ-induced neuronal apoptosis, measured by cleaved PARP (Poly ADP-ribose polymerase) and cleaved caspase 3 levels, was reduced in PKR-/- neurons. Two selective JNK inhibitory peptides also produced a striking reduction of Aβ toxicity. Finally, the dual inhibition of PKR and JNK nearly abolished Aβ toxicity in primary cultured neurons. These results reveal that dual kinase inhibition can afford neuroprotection and this approach is worth being tested in in vivo AD and oxidative stress models.

Neuroprotection of Cilostazol against ischemia/reperfusion-induced cognitive deficits through inhibiting JNK3/caspase-3 by enhancing Akt1

Cilostazol(CTL) is a phosphodiesterase inhibitor, which has been widely used as anti-platelet agent. It also has preventive effects on various central nervous system (CNS) diseases, including ischemic stroke, Parkinson's disease and Alzheimer disease. However, the molecular mechanism underlying the protective effects of CTL is still unclear, and whether CTL can prevent I/R induced cognitive deficit has not been reported. Transient global brain ischemia was induced by 4-vessel occlusion in adult male Sprague-Dawley rats. The open field tasks and Morris water maze were used to assess the effect of CTL on anxiety-like behavioral and cognitive impairment after I/R. Western blotting were performed to examine the expression of related proteins, and HE-staining was used to detect the percentage of neuronal death in the hippocampal CA1 region. Here we found that CTL significantly improved cognitive deficits and the behavior of rats in Morris water maze and open field tasks (P<0.05). HE staining results showed that CTL could significantly protect CA1 neurons against cerebral I/R (P<0.05). Additionally, Akt1 phosphorylation levels were evidently up-regulated (P<0.05), while the activation of JNK3, which is an important contributor to I/R-induced neuron apoptosis, was reduced by CTL after I/R (P<0.05), and caspase-3 levels were also decreased by CTL treatment. Furthermore, all of CTL's protective effects were reversed by LY294002, which is a PI3K/Akt1 inhibitor. Taken together, our results suggest that CTL could protect hippocampal neurons and ameliorate the impairment of learning/memory abilities and locomotor/ exploratory activities in ischemic stroke via a PI3K-Akt1/JNK3/caspase-3 dependent mechanism.

Protein Kinases and Parkinson's Disease

Currently, the lack of new drug candidates for the treatment of major neurological disorders such as Parkinson’s disease has intensified the search for drugs that can be repurposed or repositioned for such treatment. Typically, the search focuses on drugs that have been approved and are used clinically for other indications. Kinase inhibitors represent a family of popular molecules for the treatment and prevention of various cancers, and have emerged as strong candidates for such repurposing because numerous serine/threonine and tyrosine kinases have been implicated in the pathobiology of Parkinson’s disease. This review focuses on various kinase-dependent pathways associated with the expression of Parkinson’s disease pathology, and evaluates how inhibitors of these pathways might play a major role as effective therapeutic molecules.

Heroin activates ATF3 and CytC via c-Jun N-terminal kinase pathways to mediate neuronal apoptosis

Background

Drug abuse and addiction has become a major public health problem that impacts all societies. The use of heroin may cause spongiform leukoencephalopathy (SLE).

Material/Methods

Cerebellar granule cells were derived from 7-day-old Sprague-Dawley rat pups.

Neurons were dissociated from freshly dissected cerebella by mechanical disruption in the presence of 0.125% trypsin and DNaseI and then seeded at a density of 4×10⁶ cells/ml in Dulbecco’s modified Eagle’s medium/nutrient mixture F-12 ham’s containing 10% fetal bovine serum and Arc-C(sigma) at concentrations to inhibit glial cell growth inoculated into 6-well plates and a small dish.

Results

We found that heroin induces the apoptosis of primary cultured cerebellar granule cells (CGCS) and that the c-Jun N-terminal kinase (JNK) pathway was activated under heroin treatment and stimulated obvious increases in the levels of C-jun, Cytc, and ATF3mRNA. CYTC and ATF3 were identified as candidate targets of the JNK/c-Jun pathway in this process because the specificity inhibitors SP600125 of JNK/C-jun pathways reduced the levels of C-jun, Cytc, and ATF3mRNA. The results suggested that SP600125 of JNK/C-jun can inhibit heroin-induced apoptosis of neurons.

Conclusions

The present study analyzes our understanding of the critical role of the JNK pathway in the process of neuronal apoptosis induced by heroin, and suggests a new and effective strategy to treat SLE.

Inflammatory response in Parkinson's disease (Review)

Parkinson's disease (PD) is one of the most common age‑related neurodegenerative diseases, which results from a number of environmental and inherited factors. PD is characterized by the slow progressive degeneration of dopaminergic (DA) neurons in the substantia nigra. The nigrostriatal DA neurons are particularly vulnerable to inflammatory attack. Neuroinflammation is an important contributor to the pathogenesis of age‑related neurodegenerative disorders, such as PD, and as such anti‑inflammatory agents are becoming a novel therapeutic focus. This review will discuss the current knowledge regarding inflammation and review the roles of intracellular inflammatory signaling pathways, which are specific inflammatory mediators in PD. Finally, possible therapeutic strategies are proposed, which may downregulate inflammatory processes and inhibit the progression of PD.

Valproic acid protects neurons and promotes neuronal regeneration after brachial plexus avulsion

Valproic acid has been shown to exert neuroprotective effects and promote neurite outgrowth in several peripheral nerve injury models. However, whether valproic acid can exert its beneficial effect on neurons after brachial plexus avulsion injury is currently unknown. In this study, brachial plexus root avulsion models, established in Wistar rats, were administered daily with valproic acid dissolved in drinking water (300 mg/kg) or normal water. On days 1, 2, 3, 7, 14 and 28 after avulsion injury, tissues of the C5-T1 spinal cord segments of the avulsion injured side were harvested to investigate the expression of Bcl-2, c-Jun and growth associated protein 43 by real-time PCR and western blot assay. Results showed that valproic acid significantly increased the expression of Bcl-2 and growth associated protein 43, and reduced the c-Jun expression after brachial plexus avulsion. Our findings indicate that valproic acid can protect neurons in the spinal cord and enhance neuronal regeneration following brachial plexus root avulsion.

Loss of MAP function leads to hippocampal synapse loss and deficits in the Morris Water Maze with aging

Hyperphosphorylation and accumulation of tau aggregates are prominent features in tauopathies, including Alzheimer's disease, but the impact of loss of tau function on synaptic and cognitive deficits remains poorly understood. We report that old (19-20 months; OKO) but not middle-aged (8-9 months; MKO) tau knock-out mice develop Morris Water Maze (MWM) deficits and loss of hippocampal acetylated α-tubulin and excitatory synaptic proteins. Mild motor deficits and reduction in tyrosine hydroxylase (TH) in the substantia nigra were present by middle age, but did not affect MWM performance, whereas OKO mice showed MWM deficits paralleling hippocampal deficits. Deletion of tau, a microtubule-associated protein (MAP), resulted in increased levels of MAP1A, MAP1B, and MAP2 in MKO, followed by loss of MAP2 and MAP1B in OKO. Hippocampal synaptic deficits in OKO mice were partially corrected with dietary supplementation with docosahexaenoic acid (DHA) and both MWM and synaptic deficits were fully corrected by combining DHA with α-lipoic acid (ALA), which also prevented TH loss. DHA or DHA/ALA restored phosphorylated and total GSK3β and attenuated hyperactivation of the tau C-Jun N-terminal kinases (JNKs) while increasing MAP1B, dephosphorylated (active) MAP2, and acetylated α-tubulin, suggesting improved microtubule stability and maintenance of active compensatory MAPs. Our results implicate the loss of MAP function in age-associated hippocampal deficits and identify a safe dietary intervention, rescuing both MAP function and TH in OKO mice. Therefore, in addition to microtubule-stabilizing therapeutic drugs, preserving or restoring compensatory MAP function may be a useful new prevention strategy.

Parkinson's disease-implicated kinases in the brain; insights into disease pathogenesis

Substantial evidence implicates abnormal protein kinase function in various aspects of Parkinson’s disease (PD) etiology. Elevated phosphorylation of the PD-defining pathological protein, α-synuclein, correlates with its aggregation and toxic accumulation in neurons, whilst genetic missense mutations in the kinases PTEN-induced putative kinase 1 and leucine-rich repeat kinase 2, increase susceptibility to PD. Experimental evidence also links kinases of the phosphoinositide 3-kinase and mitogen-activated protein kinase signaling pathways, amongst others, to PD. Understanding how the levels or activities of these enzymes or their substrates change in brain tissue in relation to pathological states can provide insight into disease pathogenesis. Moreover, understanding when and where kinase dysfunction occurs is important as modulation of some of these signaling pathways can potentially lead to PD therapeutics. This review will summarize what is currently known in regard to the expression of these PD-implicated kinases in pathological human postmortem brain tissue.

The JNK inhibitor, SP600125, potentiates the glial response and cell death induced by methamphetamine in the mouse striatum

This study investigates the effect of the selective Jun NH2-terminal kinase 1/2 (JNK1/2) inhibitor, (SP600125) on the striatal dopamine nerve terminal loss and on the increased interleukin-15 (IL-15) expression and glial response induced by methamphetamine (METH). Mice were given repeated low doses of METH (4 mg/kg, i.p., three times separated by 3 h) and killed 24 h or 7 d after the last dose. SP600125 (30 mg/kg, i.p) was administered 30 min before the last METH injection. Results indicate that METH produced dopaminergic axonal neurotoxicity reflected as a marked decrease in the striatal density of tyrosine hydroxylase-immunoreactive (TH-ir) fibres and dopamine transporter-immunoreactivity (DAT-ir) 24 h after dosing. These effects were not modified by SP600125. This compound also failed to prevent the long-term loss of dopamine levels and DAT observed 7 d following METH injection. Nevertheless, SP600125 potentiated METH-induced striatal cell loss reflected by an increase in Fluoro-Jade immunostaining, cleaved capase-3 immunoreactivity and the number of terminal deoxyncleotidyl transferase-mediated dUTP nick end labelling (TUNEL) positive cells. In line with a deleterious effect of JNK1/2 inhibition, SP600125 increased the astroglial and microglial response induced by METH and interfered with drug-induced IL-15 expression. Together these data indicate that, not only does SP600125 fail to protect against the dopaminergic damage induced by METH but also, in fact, it potentiates the glial response and the non-dopaminergic striatal cell loss caused by the drug.

The specific, reversible JNK inhibitor SP600125 improves survivability and attenuates neuronal cell death in experimental cerebral malaria (ECM)

Cerebral malaria (CM) is the most severe complication of Plasmodium falciparum in humans and major cause of death. SP600125 is a specific, small molecule inhibitor of JNK that prevents the phosphorylation of c-Jun and blocks the expression of proinflammatory cytokines and attenuates neuronal apoptosis in several neurodegenerative disorders. We evaluated the effect of SP600125 treatment on the survival of Plasmodium berghei ANKA (PbA)-infected C57BL/6J mice. Administration of SP600125 improved survival in PbA-infected C57BL6J mice but has no effect on parasitemia. Further, SP600125 administration resulted in attenuation of neuronal cell death along with inhibition of proinflammatory mediators TNF-α and COX-2 and proapoptotic mediators p-c-Jun and active caspase 3 in PbA-infected mice. The promising findings of this study make SP600125 a potential agent for supportive therapy to alleviate inflammation and neuronal cell death associated with CM.

JNK and p38 MAPK regulate oxidative stress and the inflammatory response in chlorpyrifos-induced apoptosis

To investigate mechanisms of neuronal cell death in response to chlorpyrifos (CPF), a pesticide, we evaluated the regulation of ROS and COX-2 in human neuroblastoma SH-SY5Y cells treated with CPF. CPF treatment produced cytotoxic effects that appeared to involve an increase in ROS. In addition, CPF treatment activated MAPK pathways including JNK, ERK1/2, and p38 MAPK, and MAPK inhibitors abolished the cytotoxicity and reduced ROS generation. Our data demonstrate that CPF induced apoptosis involving MAPK activation through ROS production. Furthermore, after the CPF treatment, COX-2 expression increased. Interestingly, JNK and p38 MAPK inhibitors attenuated the CPF-induced COX-2 expression while an ERK1/2 inhibitor did not. These findings suggest that pathways involving JNK and p38 MAPK, but not ERK1/2, mediated apoptosis and are involved in the inflammatory response. In conclusion, the JNK and p38 MAPK pathways might be critical mediators in CPF-induced neuronal apoptosis by both generating ROS and up-regulating COX-2.

A study on the effect of JNK inhibitor, SP600125, on the disruption of blood-brain barrier induced by methamphetamine

Methamphetamine (METH) is a widely consumed drug with high abuse potential. Studies in animals have shown that the drug produces dopaminergic neurotoxicity following both single high-dose and repeated low-dose administration. In addition, METH produces an increase in matrix metalloproteinase expression and loss of BBB integrity. We have examined the effect of repeated low-dose METH on MMP-9/2 expression and activity and laminin expression and the role of MMPs and JNK 1/2 phosphorylation on the changes induced by the drug in BBB integrity. Mice were given METH (4 mg/kg, i.p., three times separated by 3 h) and killed at different times after the last dose. Striatal MMP-9/2 activity was determined by zymography and expression of MMPs, laminin and phosphorylated JNK 1/2 was determined by western blot. BBB integrity was determined by IgG immunoreactivity. SP600125 and BB-94 were used to inhibit JNK and MMPs respectively. METH increased striatal MMP-9 expression and activity, IgG immunoreactivity and p-JNK 1/2 expression and decreased laminin expression. Increased IgG immunoreactivity colocalized with areas of greater MMP-9 activity. JNK inhibition prevented METH-induced changes in MMP-9 activity, laminin degradation and BBB leakage. BB-94 also prevented laminin degradation and BBB leakage. The decrease in BBB integrity induced by METH is mediated by the JNK pathway which activates MMP-9 causing degradation of laminin and BBB leakage.

Role of the JNK pathway in human diseases

The c-Jun-NH(2)-terminal kinase (JNK) signaling pathway plays a critical role in regulating cell fate, being implicated in a multitude of diseases ranging from cancer to neurological and immunological/inflammatory conditions. Not surprisingly, therefore, it has been sought after for therapeutic intervention, and its inhibition has been shown to ameliorate many pathological conditions in experimental systems, paving the way for initial clinical trials. However, the fundamental problem in fully harnessing the potential provided by the JNK pathway has been the lack of specificity, due to the multiple JNK forms that are involved in multiple cellular processes in various cell types. Moreover, lack of sufficient knowledge of all JNK-interacting proteins and substrates has also hindered progress. This review will therefore focus on the role of the JNKs in human diseases and appraise the efforts to inhibit JNK signaling to ameliorate disease conditions, assessing potential challenges and providing insights into possible future directions to efficiently target this pathway for therapeutic use.

Targeting JNK for therapeutic depletion of stem-like glioblastoma cells

Control of the stem-like tumour cell population is considered key to realizing the long-term survival of patients with glioblastoma, one of the most devastating human malignancies. To date, possible therapeutic targets and targeting methods have been described, but none has yet proven to target stem-like glioblastoma cells in the brain to the extent necessary to provide a survival benefit. Here we show that targeting JNK in vivo, the activity of which is required for the maintenance of stem-like glioblastoma cells, via transient, systemic administration of a small-molecule JNK inhibitor depletes the self-renewing and tumour-initiating populations within established tumours, inhibits tumour formation by stem-like glioblastoma cells in the brain, and provide substantial survival benefit without evidence of adverse events. Our findings not only implicate JNK in the maintenance of stem-like glioblastoma cells but also demonstrate that JNK is a viable, clinically relevant therapeutic target in the control of stem-like glioblastoma cells.

Reactive oxygen species regulated mitochondria-mediated apoptosis in PC12 cells exposed to chlorpyrifos

Reactive oxidative species (ROS) generated by environmental toxicants including pesticides could be one of the factors underlying the neuronal cell damage in neurodegenerative diseases. In this study we found that chlorpyrifos (CPF) induced apoptosis in dopaminergic neuronal components of PC12 cells as demonstrated by the activation of caspases and nuclear condensation. Furthermore, CPF also reduced the tyrosine hydroxylase-positive immunoreactivity in substantia nigra of the rat. In addition, CPF induced inhibition of mitochondrial complex I activity. Importantly, N-acetyl cysteine (NAC) treatment effectively blocked apoptosis via the caspase-9 and caspase-3 pathways while NAC attenuated the inhibition of mitochondrial complex I activity as well as the oxidative metabolism of dopamine (DA). These results demonstrated that CPF-induced apoptosis was involved in mitochondrial dysfunction through the production of ROS. In the response of cellular antioxidant systems to CPF, we found that CPF treatment increased HO-1 expression while the expression of CuZnSOD and MnSOD was reduced. In addition, we found that CPF treatment activated MAPK pathways, including ERK 1/2, the JNK, and the p38 MAP kinase in a time-dependent manner. NAC treatment abolished MAPK phosphorylation caused by CPF, indicating that ROS are upstream signals of MAPK. Interestingly, MAPK inhibitors abolished cytotoxicity and reduced ROS generation by CPF treatment. Our results demonstrate that CPF induced neuronal cell death in part through MAPK activation via ROS generation, suggesting its potential to generate oxidative stress via mitochondrial damage and its involvement in oxidative stress-related neurodegenerative disease.

Kinases and kinase signaling pathways: potential therapeutic targets in Parkinson's disease

Complex molecular mechanisms underlying the pathogenesis of Parkinson's disease (PD) are gradually being elucidated. Accumulating genetic evidence implicates dysfunction of kinase activities and phosphorylation pathways in the pathogenesis of PD. Causative and risk gene products associated with PD include protein kinases (such as PINK1, LRRK2 and GAK) and proteins related phosphorylation signaling pathways (such as SNCA, DJ-1). PINK1, LRRK2 and several PD gene products have been associated with mitogen-activated protein (MAP) and protein kinase B (AKT) kinase signaling pathways. C-Jun N-terminal kinase (JNK), extracellular signal-regulated kinases (ERK) and p38, signaling pathways downstream of MAP, are particularly important in PD. JNK and p38 play an integral role in neuronal death. Targeting JNK or p38 signaling may offer an effective therapy for PD. Inhibitors of the ERK signaling pathway, which plays an important role in the development of l-DOPA-induced dyskinesia (LID), have been shown to attenuate this condition in animal models. In this review, we summarize experimental evidence gathered over the last decade on the role of PINK1, LRRK2 and GAK and their related phosphorylation signaling pathways (JNK, ERK, p38 and PI3K/AKT) in PD. It is speculated that improvement or modulation of these signaling pathways will reveal potential therapeutic targets for attenuation of the cardinal symptoms and motor complications in patients with PD in the future.

Heat shock protein 72 inhibits c-Jun N-terminal kinase 3 signaling pathway via Akt1 during cerebral ischemia

Although recent researches show that Heat Shock Protein 72 (HSP72) plays an important role in neuronal survival, little knowledge is known about the precise mechanisms during cerebral ischemia/reperfusion (I/R). Our present study investigated the neuroprotective mechanisms of HSP72 against ischemic brain injury induced by cerebral I/R. Mild heat shock pretreatment was employed to induce the overexpression of HSP72 by immersing rats into the water bath at 42°C for 20 min before cerebral I/R. HSP72 antisense oligodeoxynucleotides (ODNs) were used to inhibit HSP72 expression by intracerebroventricular infusion once per day for 3 days before cerebral I/R animal model was induced by four-vessel occlusion for 15 min transient ischemia and then reperfused for various time in Sprague-Dawley rats. Immunoprecipitation and immunoblotting were used to detect the expression of the related proteins. HE-staining and TUNEL-staining were carried out to examine the neuronal death of hippocampal CA1 region. Results showed that mild heat shock could increase the phosphorylation of protein kinase B (Akt), inhibit the assembly of MLK3-MKK7-JNK3 signaling module, diminish the phosphorylation of JNK3 and c-Jun, and decrease the activation of caspase-3. Furthermore, mild heat shock could significantly protect neurons against cerebral I/R. Whereas, all of the aforementioned effects of mild heat shock were reversed by HSP72 antisense ODNs. In summary, our results imply that Akt1 activation is involved in the neuroprotection of HSP72 against ischemic brain injury via suppressing JNK3 signaling pathway and provide a new experimental foundation for stroke therapy.

SP600125 inhibits Orthopoxviruses replication in a JNK1/2 -independent manner: Implication as a potential antipoxviral

The pharmacological inhibitor SP600125 [anthra(1,9-cd)pyrazol-6(2H)-one 1,9-pyrazoloanthrone] has been largely employed as a c-JUN N-terminal kinase (JNK1/2) inhibitor. In this study, we evaluated whether pretreatment with SP600125 was able to prevent Orthopoxviruses Vaccinia virus (VACV), Cowpox virus (CPXV) and modified Vaccinia virus Ankara (MVA) replication. We found that incubation with SP600125 not only blocked virus-stimulated JNK phosphorylation, but also, significantly reduced virus production. We observed 1-3 log decline in viral yield depending on the cell line infected (A31, BSC-40 or BHK-21). The reduction in viral yield correlated with a dramatic impact on virus morphogenesis progress, intracellular mature viruses (IMV) were barely detected. Despite the fact that SP600125 can act as an efficient anti-orthopoxviral compound, we also provide evidence that this antiviral effect is not specifically exerted through JNK1/2 inhibition. This conclusion is supported by the fact that viral titers measured after infections of JNK1/2 knockout cells were not altered as compared to those of wild-type cells. In contrast, a decline in viral titers was verified when the infection of KO cells was carried out in the presence of the pharmacological inhibitor. SP600125 has been the focus of recent studies that have evaluated its action on diverse viral infections including DNA viruses. Our data support the notion that SP600125 can be regarded as a potential antipoxviral compound.

Phosphatidylinositol 3-kinase/Akt signaling pathway mediates acupuncture-induced dopaminergic neuron protection and motor function improvement in a mouse model of Parkinson's disease

It has been reported that acupuncture treatment reduced dopaminergic neuron degeneration in Parkinson's disease (PD) models. However, the mechanistic pathways underlying, such neuroprotection, are poorly understood. Here, we investigated the effects and the underlying mechanism of acupuncture in a mouse model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). First, we observed that MPTP-induced impairment of Akt activation, but not MPTP-induced c-Jun activation, was effectively restored by acupuncture treatment in the substantia nigra. Furthermore, we demonstrated for the first time that the brain-specific blockade of phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, by intranasal administration of LY294002, a specific inhibitor of PI3K/Akt signaling pathway, significantly blocked acupuncture-induced dopaminergic neuron protection and motor function improvement. Our results provide evidence that PI3K/Akt signaling pathway may play a central role in the mechanism underlying acupuncture-induced benefits in Parkinsonian mice.

Interferon-γ plays a role in paraquat-induced neurodegeneration involving oxidative and proinflammatory pathways

Exposure to environmental contaminants, particularly pesticides, may be an important etiological factor in Parkinson's disease (PD); and evidence suggests a role for microglia-dependent inflammatory and oxidative processes in nigrostriatal pathology induced by such toxins. Yet, the events mediating microglial activation and their effects are not fully known. To this end, we hypothesized that the proinflammatory cytokine, interferon-gamma (IFN-γ), may be a prime factor in the pathogenesis of PD, given its critical role in regulating microglial responses to pathogens. Indeed, the present investigation demonstrated that genetic deletion of IFN-γ protected substantia nigra pars compacta (SNc) dopamine (DA) neurons from the toxic effects of the pesticide, paraquat, and normalized changes in inflammatory and oxidative factors within this brain region. Specifically, IFN-γ knockout prevented the paraquat-induced morphological signs of microglial activation and expression of key nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, while also preventing time-dependent changes in proinflammatory enzymes (inducible nitric oxide synthase [iNOS], cyclooxygenase-2 [COX-2]), cytokines (interleukin-1β [IL-1β], tumor necrosis factor-α [TNF-α]), and signaling factors (c-Jun N-terminal kinase [JNK], p38 MAP kinase [p38], Signal transducer and activator of transcription-1 [STAT1], nuclear factor kappa B [NF-κB]). Moreover, paraquat transiently suppressed substantia nigra pars compacta expression of trophic and proneuroplastic factors (cyclic-AMP response element binding protein [CREB], brain-derived neurotrophic factor [BDNF]), and IFN-γ deficiency again reversed these effects. These data suggest that IFN-γ is important for paraquat-induced neurodegeneration and the accompanying oxidative, inflammatory, and trophic changes that characterize the response to the toxin. Targeting IFN-γ could thus have therapeutic implications for PD and other neurodegenerative conditions that involve multiple inflammatory pathways.

Possible role of propofol's cyclooxygenase-inhibiting property in alleviating dopaminergic neuronal loss in the substantia nigra in an MPTP-induced murine model of Parkinson's disease

Propofol is an intravenous anesthetic widely used for sedation and general anesthesia. We investigated the effect of propofol on prostanoid production by activated microglia. Primary microglial culture was obtained from the brains of neonatal C57BL/6 mice. The microglia were stimulated with lipopolysaccharide (LPS) in the presence of propofol. Propofol suppressed the LPS-induced production of prostaglandin E(2) and thromboxane B(2). Cyclooxygenase (COX) protein expression and arachidonic acid release were not affected by propofol, while COX enzyme activity was significantly inhibited by propofol. The COX-inhibiting activity was also observed with purified enzymes, with COX-2 inhibition being significantly greater than COX-1 inhibition. Next, we studied whether the COX-inhibiting activity of propofol resulted in dopaminergic neuroprotection in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) murine model of Parkinson's disease, in which COX inhibitors, such as non-steroidal anti-inflammatory drugs, are reported to be neuroprotective. C57BL/6 mice received intraperitoneal injections of MPTP with or without propofol treatment, and the dopaminergic neurons in the substantia nigra pars compacta (SNpc) were examined immunohistochemically by observing the tyrosine hydroxylase-positive cells. The number of dopaminergic neurons in the SNpc was significantly reduced by MPTP treatment, while the MPTP-induced neuronal loss was minimal upon treatment with propofol or the selective COX-2 inhibitor, NS-398. These results indicate that propofol might be beneficial in mitigating MPTP-induced dopaminergic neurons, possibly via its COX-inhibiting activity.

Inflammatory mechanisms of neurodegeneration in toxin-based models of Parkinson's disease

Parkinson's disease (PD) has been associated with exposure to a variety of environmental agents, including pesticides, heavy metals, and organic pollutants; and inflammatory processes appear to constitute a common mechanistic link among these insults. Indeed, toxin exposure has been repeatedly demonstrated to induce the release of oxidative and inflammatory factors from immunocompetent microglia, leading to damage and death of midbrain dopamine (DA) neurons. In particular, proinflammatory cytokines such as tumor necrosis factor-α and interferon-γ, which are produced locally within the brain by microglia, have been implicated in the loss of DA neurons in toxin-based models of PD; and mounting evidence suggests a contributory role of the inflammatory enzyme, cyclooxygenase-2. Likewise, immune-activating bacterial and viral agents were reported to have neurodegenerative effects themselves and to augment the deleterious impact of chemical toxins upon DA neurons. The present paper will focus upon the evidence linking microglia and their inflammatory processes to the death of DA neurons following toxin exposure. Particular attention will be devoted to the possibility that environmental toxins can activate microglia, resulting in these cells adopting a “sensitized” state that favors the production of proinflammatory cytokines and damaging oxidative radicals.

Diverse methyl sulfone-containing benzo[b]thiophene library via iodocyclization and palladium-catalyzed coupling

Parallel solution-phase methods for the synthesis of a 72-membered benzo[b]thiophene library are reported. Medicinally interesting, drug-like, methyl sulfone-substituted benzo[b]thiophenes have been prepared by the palladium-catalyzed substitution of 3-iodobenzo[b]thiophenes by Suzuki-Miyaura, Sonogashira, Heck, carboalkoxylation, and aminocarbonylation chemistry. The key intermediates for library generation, methyl sulfone-containing 3-iodobenzo[b]thiophenes, are readily prepared by iodocyclization and oxidation methodologies from readily available alkynes.