AS601245, a c-Jun NH2-terminal kinase (JNK) inhibitor, reduces axon/dendrite damage and cognitive deficits after global cerebral ischaemia in gerbils

JNK3 inhibitors as promising pharmaceuticals with neuroprotective properties

The intensive study and investigation of neuroprotective therapy for central nervous system (CNS) diseases is ongoing. Due to shared mechanisms of neurodegeneration, a neuroprotective approach might offer benefits across multiple neurological disorders, despite variations in symptoms or injuries. C-Jun N-terminal Kinase 3 (JNK3) is found primarily in the CNS and is involved in physiological processes such as brain development, synapse formation, and memory formation. The potential of JNK3 as a target for pharmacological development holds promise for advancing neuroprotective therapies. Developing small molecule JNK3 inhibitors into drugs with neuroprotective qualities could facilitate neuronal restoration and self-repair. This review focuses on elucidating key neuroprotective mechanisms, exploring the interplay between neurodegenerative diseases and neuroprotection, and discussing advancements in JNK3 inhibitor drug development.

Neuroprotective Effects of Tryptanthrin-6-Oxime in a Rat Model of Transient Focal Cerebral Ischemia

The activation of c-Jun N-terminal kinase (JNK) plays an important role in stroke outcomes. Tryptanthrin-6-oxime (TRYP-Ox) is reported to have high affinity for JNK and anti-inflammatory activity and may be of interest as a promising neuroprotective agent. The aim of this study was to investigate the neuroprotective effects of TRYP-Ox in a rat model of transient focal cerebral ischemia (FCI), which involved intraluminal occlusion of the left middle cerebral artery (MCA) for 1 h. Animals in the experimental group were administered intraperitoneal injections of TRYP-Ox 30 min before reperfusion and 23 and 47 h after FCI. Neurological status was assessed 4, 24, and 48 h following FCI onset. Treatment with 5 and 10 mg/kg of TRYP-Ox decreased mean scores of neurological deficits by 35-49 and 46-67% at 24 and 48 h, respectively. At these doses, TRYP-Ox decreased the infarction size by 28-31% at 48 h after FCI. TRYP-Ox (10 mg/kg) reduced the content of interleukin (IL) 1β and tumor necrosis factor (TNF) in the ischemic core area of the MCA region by 33% and 38%, respectively, and attenuated cerebral edema by 11% in the left hemisphere, which was affected by infarction, and by 6% in the right, contralateral hemisphere 24 h after FCI. TRYP-Ox reduced c-Jun phosphorylation in the MCA pool at 1 h after reperfusion. TRYP-Ox was predicted to have high blood-brain barrier permeability using various calculated descriptors and binary classification trees. Indeed, reactive oxidant production was significantly lower in the brain homogenates from rats treated with TRYP-Ox versus that in control animals. Our data suggest that the neuroprotective activity of TRYP-Ox may be due to the ability of this compound to inhibit JNK and exhibit anti-inflammatory and antioxidant activity. Thus, TRYP-Ox may be considered a promising neuroprotective agent that potentially could be used for the development of new treatment strategies in cerebral ischemia.

Transgenic Schwann cells overexpressing POU6F1 promote sciatic nerve regeneration within acellular nerve allografts

Objective.Acellular nerve allograft (ANA) is an effective surgical approach used to bridge the sciatic nerve gap. The molecular regulators of post-surgical recovery are not well-known. Here, we explored the effect of transgenic Schwann cells (SCs) overexpressing POU domain class 6, transcription factor 1 (POU6F1) on sciatic nerve regeneration within ANAs. We explored the functions of POU6F1 in nerve regeneration by using a cell model of H₂O₂-induced SCs injury and transplanting SCs overexpressing POU6F1 into ANA to repair sciatic nerve gaps.Approach.Using RNA-seq, Protein-Protein Interaction network analysis, gene ontology enrichment, and Kyoto Encyclopedia of Genes and Genomes pathway analysis, we identified a highly and differentially expressed transcription factor, POU6F1, following ANA treatment of sciatic nerve gap. Expressing a high degree of connectivity, POU6F1 was predicted to play a role in peripheral nervous system myelination.Main results.To test the role of POU6F1 in nerve regeneration after ANA, we infected SCs with adeno-associated virus-POU6F1, demonstrating that POU6F1 overexpression promotes proliferation, anti-apoptosis, and migration of SCsin vitro. We also found that POU6F1 significantly upregulated JNK1/2 and c-Jun phosphorylation and that selective JNK1/2 inhibition attenuated the effects of POU6F1 on proliferation, survival, migration, and JNK1/2 and c-Jun phosphorylation. The direct interaction of POU6F1 and activated JNK1/2 was subsequently confirmed by co-immunoprecipitation. In rat sciatic nerve injury model with a 10 mm gap, we confirmed the pattern of POU6F1 upregulation and co-localization with transplanted SCs. ANAs loaded with POU6F1-overexpressing SCs demonstrated the enhanced survival of transplanted SCs, axonal regeneration, myelination, and functional motor recovery compared to the ANA group loaded by SCs-only in line within vitrofindings.Significance.This study identifies POU6F1 as a novel regulator of post-injury sciatic nerve repair, acting through JNK/c-Jun signaling in SCs to optimize therapeutic outcomes in the ANA surgical approach.

Neuroprotective Effects of the Lithium Salt of a Novel JNK Inhibitor in an Animal Model of Cerebral Ischemia–Reperfusion

The c-Jun N-terminal kinases (JNKs) regulate many physiological processes, including inflammatory responses, morphogenesis, cell proliferation, differentiation, survival, and cell death. Therefore, JNKs represent attractive targets for therapeutic intervention. In an effort to develop improved JNK inhibitors, we synthesized the lithium salt of 11H-indeno[1,2-b]quinoxaline-11-one oxime (IQ-1L) and evaluated its affinity for JNK and biological activity in vitro and in vivo. According to density functional theory (DFT) modeling, the Li⁺ ion stabilizes the six-membered ring with the 11H-indeno[1,2-b]quinoxaline-11-one (IQ-1) oximate better than Na⁺. Molecular docking showed that the Z isomer of the IQ-1 oximate should bind JNK1 and JNK3 better than (E)-IQ-1. Indeed, experimental analysis showed that IQ-1L exhibited higher JNK1-3 binding affinity in comparison with IQ-1S. IQ-1L also was a more effective inhibitor of lipopolysaccharide (LPS)-induced nuclear factor-κB/activating protein 1 (NF-κB/AP-1) transcriptional activity in THP-1Blue monocytes and was a potent inhibitor of proinflammatory cytokine production by MonoMac-6 monocytic cells. In addition, IQ-1L inhibited LPS-induced c-Jun phosphorylation in MonoMac-6 cells, directly confirming JNK inhibition. In a rat model of focal cerebral ischemia (FCI), intraperitoneal injections of 12 mg/kg IQ-1L led to significant neuroprotective effects, decreasing total neurological deficit scores by 28, 29, and 32% at 4, 24, and 48 h after FCI, respectively, and reducing infarct size by 52% at 48 h after FCI. The therapeutic efficacy of 12 mg/kg IQ-1L was comparable to that observed with 25 mg/kg of IQ-1S, indicating that complexation with Li⁺ improved efficacy of this compound. We conclude that IQ-1L is more effective than IQ-1S in treating cerebral ischemia injury and thus represents a promising anti-inflammatory compound.

Recent advances of small molecule JNK3 inhibitors for Alzheimer's disease

C-Jun N-terminal kinase (JNK) is a member of mitogen-activated protein kinases (MAPKs) family, with three isoforms, JNK1, JNK2 and JNK3. Alzheimer's disease (AD) is a neurological disorder and the most common type of dementia. Two well-established AD pathologies are the deposition of Aβ amyloid plaques and neurofibrillary tangles caused by Tau hyperphosphorylation. JNK3 is involved in forming amyloid Aβ and neurofibrillary tangles, suggesting that JNK3 may represent a target to develop treatments for AD. Therefore, this review will discuss the roles of JNK3 in the pathogenesis and treatment of AD, and the latest progress in the development of JNK3 inhibitors.

Neuroprotective Effects of a Novel Inhibitor of c-Jun N-Terminal Kinase in the Rat Model of Transient Focal Cerebral Ischemia

A novel specific inhibitor of c-Jun N-terminal kinase, 11H-indeno[1,2-b]quinoxalin-11-one oxime sodium salt (IQ-1S), has a high affinity to JNK3 compared to JNK1/JNK2. The aim of this work was to study the mechanisms of neuroprotective activity of IQ-1S in the models of reversible focal cerebral ischemia (FCI) in Wistar rats. The animals were administered with an intraperitoneal injection of IQ-1S (5 and 25 mg/kg) or citicoline (500 mg/kg). Administration of IQ-1S exerted a pronounced dose-dependent neuroprotective effect, not inferior to the effects of citicoline. Administration of IQ-1S at doses of 5 and 25 mg/kg reduced the infarct size by 20% and 50%, respectively, 48 h after FCI, whereas administration of citicoline reduced the infarct size by 34%. The administration of IQ-1S was associated with a faster amelioration of neurological status. Control rats showed a 2.0-fold increase in phospho-c-Jun levels in the hippocampus compared to the corresponding values in sham-operated rats 4 h after FCI. Administration of IQ-1S at a dose of 25 mg/kg reduced JNK-dependent phosphorylation of c-Jun by 20%. Our findings suggest that IQ-1S inhibits JNK enzymatic activity in the hippocampus and protects against stroke injury when administered in the therapeutic and prophylactic regimen in the rat model of FCI.

The JNK Signaling Pathway in Inflammatory Skin Disorders and Cancer

The c-Jun N-terminal kinases (JNKs), with its members JNK1, JNK2, and JNK3, is a subfamily of (MAPK) mitogen-activated protein kinases. JNK signaling regulates a wide range of cellular processes, including cell proliferation, differentiation, survival, apoptosis, and inflammation. Dysregulation of JNK pathway is associated with a wide range of immune disorders and cancer. Our objective is to provide a review of JNK proteins and their upstream regulators and downstream effector molecules in common skin disorders, including psoriasis, dermal fibrosis, scleroderma, basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma.

Protective Effects of a New C-Jun N-terminal Kinase Inhibitor in the Model of Global Cerebral Ischemia in Rats

c-Jun N-terminal kinase (JNK) is activated by various brain insults and is implicated in neuronal injury triggered by reperfusion-induced oxidative stress. Some JNK inhibitors demonstrated neuroprotective potential in various models, including cerebral ischemia/reperfusion injury. The objective of the present work was to study the neuroprotective activity of a new specific JNK inhibitor, IQ-1S (11H-indeno[1,2-b]quinoxalin-11-one oxime sodium salt), in the model of global cerebral ischemia (GCI) in rats compared with citicoline (cytidine-5'-diphosphocholine), a drug approved for the treatment of acute ischemic stroke and to search for pleiotropic mechanisms of neuroprotective effects of IQ-1S. The experiments were performed in a rat model of ischemic stroke with three-vessel occlusion (model of 3VO) affecting the brachiocephalic artery, the left subclavian artery, and the left common carotid artery. After 7-min episode of GCI in rats, 25% of animals died, whereas survived animals had severe neurological deficit at days 1, 3, and 5 after GCI. At day 5 after GCI, we observing massive loss of pyramidal neurons in the hippocampal CA1 area, increase in lipid peroxidation products in the brain tissue, and decrease in local cerebral blood flow (LCBF) in the parietal cortex. Moreover, blood hyperviscosity syndrome and endothelial dysfunction were found after GCI. Administration of IQ-1S (intragastrically at a dose 50 mg/kg daily for 5 days) was associated with neuroprotective effect comparable with the effect of citicoline (intraperitoneal at a dose of 500 mg/kg, daily for 5 days).The neuroprotective effect was accompanied by a decrease in the number of animals with severe neurological deficit, an increase in the number of animals with moderate degree of neurological deficit compared with control GCI group, and an increase in the number of unaltered neurons in the hippocampal CA1 area along with a significant decrease in the number of neurons with irreversible morphological damage. In rats with IQ-1S administration, the LCBF was significantly higher (by 60%) compared with that in the GCI control. Treatment with IQ-1S also decreases blood viscosity and endothelial dysfunction. A concentration-dependent decrease (IC₅₀ = 0.8 ± 0.3 μM) of tone in isolated carotid arterial rings constricted with phenylephrine was observed after IQ-1S application in vitro. We also found that IQ-1S decreased the intensity of the lipid peroxidation in the brain tissue in rats with GCI. 2.2-Diphenyl-1-picrylhydrazyl scavenging for IQ-1S in acetonitrile and acetone exceeded the corresponding values for ionol, a known antioxidant. Overall, these results suggest that the neuroprotective properties of IQ-1S may be mediated by improvement of cerebral microcirculation due to the enhanced vasorelaxation, beneficial effects on blood viscosity, attenuation of the endothelial dysfunction, and antioxidant/antiradical IQ-1S activity.

c-Jun N-Terminal Kinases (JNKs) in Myocardial and Cerebral Ischemia/Reperfusion Injury

In this article, we review the literature regarding the role of c-Jun N-terminal kinases (JNKs) in cerebral and myocardial ischemia/reperfusion injury. Numerous studies demonstrate that JNK-mediated signaling pathways play an essential role in cerebral and myocardial ischemia/reperfusion injury. JNK-associated mechanisms are involved in preconditioning and post-conditioning of the heart and the brain. The literature and our own studies suggest that JNK inhibitors may exert cardioprotective and neuroprotective properties. The effects of modulating the JNK-depending pathways in the brain and the heart are reviewed. Cardioprotective and neuroprotective mechanisms of JNK inhibitors are discussed in detail including synthetic small molecule inhibitors (AS601245, SP600125, IQ-1S, and SR-3306), ion channel inhibitor GsMTx4, JNK-interacting proteins, inhibitors of mixed-lineage kinase (MLK) and MLK-interacting proteins, inhibitors of glutamate receptors, nitric oxide (NO) donors, and anesthetics. The role of JNKs in ischemia/reperfusion injury of the heart in diabetes mellitus is discussed in the context of comorbidities. According to reviewed literature, JNKs represent promising therapeutic targets for protection of the brain and the heart against ischemic stroke and myocardial infarction, respectively. However, different members of the JNK family exert diverse physiological properties which may not allow for systemic administration of non-specific JNK inhibitors for therapeutic purposes. Currently available candidate JNK inhibitors with high therapeutic potential are identified. The further search for selective JNK3 inhibitors remains an important task.

JNK1 inhibition by Licochalcone A leads to neuronal protection against excitotoxic insults derived of kainic acid

The mitogen-activated protein kinase family (MAPK) is an important group of enzymes involved in cellular responses to diverse external stimuli. One of the members of this family is the c-Jun-N-terminal kinase (JNK). The activation of the JNK pathway has been largely associated with the pathogenesis that occurs in epilepsy and neurodegeneration. Kainic acid (KA) administration in rodents is an experimental approach that induces status epilepticus (SE) and replicates many of the phenomenological features of human temporal lobe epilepsy (TLE). Recent studies in our group have evidenced that the absence of the JNK1 gene has neuroprotective effects against the damage induced by KA, as it occurs with the absence of JNK3. The aim of the present study was to analyse whether the pharmacological inhibition of JNK1 by Licochalcone A (Lic-A) had similar effects and if it may be considered as a new molecule for the treatment of SE. In order to achieve this objective, animals were pre-treated with Lic-A and posteriorly administered with KA as a model for TLE. In addition, a comparative study with KA was performed between wild type pre-treated with Lic-A and single knock-out transgenic mice for the Jnk1^-/- gene. Our results showed that JNK1 inhibition by Lic-A, previous to KA administration, caused a reduction in the convulsive pattern. Furthermore, it reduced phosphorylation levels of the JNK, as well as its activity. In addition, Lic-A prevented hippocampal neuronal degeneration, increased pro-survival anti-apoptotic mechanisms, reduced pro-apoptotic biomarkers, decreased cellular stress and neuroinflammatory processes. Thus, our results suggest that inhibition of the JNK1 by Lic-A has neuroprotective effects and that; it could be a new potential approach for the treatment of SE and neurodegeneration.

17β-Estradiol and Agonism of G-protein-Coupled Estrogen Receptor Enhance Hippocampal Memory via Different Cell-Signaling Mechanisms

The ability of 17β-estradiol (E2) to enhance hippocampal object recognition and spatial memory depends on rapid activation of extracellular signal-regulated kinase (ERK) in the dorsal hippocampus (DH). Although this activation can be mediated by the intracellular estrogen receptors ERα and ERβ, little is known about the role that the membrane estrogen receptor GPER plays in regulating ERK or E2-mediated memory formation. In this study, post-training DH infusion of the GPER agonist G-1 enhanced object recognition and spatial memory in ovariectomized female mice, whereas the GPER antagonist G-15 impaired memory, suggesting that GPER activation, like E2, promotes hippocampal memory formation. However, unlike E2, G-1 did not increase ERK phosphorylation, but instead significantly increased phosphorylation of c-Jun N-terminal kinase (JNK) in the DH. Moreover, DH infusion of the JNK inhibitor SP600125 prevented G-1 from enhancing object recognition and spatial memory, but the ERK inhibitor U0126 did not. These data suggest that GPER enhances memory via different cell-signaling mechanisms than E2. This conclusion was supported by data showing that the ability of E2 to facilitate memory and activate ERK signaling was not blocked by G-15 or SP600125, which demonstrates that the memory-enhancing effects of E2 are not dependent on JNK or GPER activation in the DH. Together, these data indicate that GPER regulates memory independently from ERα and ERβ by activating JNK signaling, rather than ERK signaling. Thus, the findings suggest that GPER in the DH may not function as an estrogen receptor to regulate object recognition and spatial memory.

SIGNIFICANCE STATEMENT

Although 17β-estradiol has long been known to regulate memory function, the molecular mechanisms underlying estrogenic memory modulation remain largely unknown. Here, we examined whether the putative membrane estrogen receptor GPER acts like the classical estrogen receptors, ERα and ERβ, to facilitate hippocampal memory in female mice. Although GPER activation did enhance object recognition and spatial memory, it did so by activating different cell-signaling mechanisms from ERα, ERβ, or 17β-estradiol. These data indicate that 17β-estradiol and GPER independently regulate hippocampal memory, and suggest that hippocampal GPER may not function as an estrogen receptor in the dorsal hippocampus. These findings are significant because they provide novel insights about the molecular mechanisms through which 17β-estradiol modulates hippocampal memory.

c-Jun NH2-terminal kinase inhibitor bentamapimod reduces induced endometriosis in baboons: an assessor-blind placebo-controlled randomized study

OBJECTIVE

To test the hypothesis that the c-Jun NH2-terminal kinase (JNK) inhibitor (JNKI) bentamapimod (AS602801/PGL5001) can reduce induced endometriosis in baboons.

DESIGN

Prospective randomized placebo-controlled study.

SETTING

Nonhuman primate research center.

ANIMAL(S)

Twenty baboons each underwent four laparoscopies. Initial screening laparoscopy (L1) was followed after one rest cycle by an endometriosis-induction laparoscopy (L2). Fifty days after L2, the baboons were randomized just before staging laparoscopy (L3). Treatment lasted for 60 days, followed by a post-treatment staging laparoscopy (L4).

INTERVENTION(S)

Randomization before a 60-day treatment in four groups: daily placebo (n = 5), daily oral administration of 20 mg/kg JNKI (n = 5), concomitant daily oral administration of 20 mg/kg JNKI and 10 mg medroxyprogesterone acetate (MPA; n = 5), or subcutaneous administration of 3 mg cetrorelix every 3 days (n = 5).

MAIN OUTCOME MEASURE(S)

Type, surface area and volume of endometriotic lesions, and revised American Society for Reproductive Medicine score and stage were recorded during L3 and L4. Menstrual cycle length and serum hormonal concentration were recorded before and after treatment.

RESULT(S)

Compared with placebo, treatment with JNKI, JNKI + PMA, or cetrorelix resulted in lower total surface area and volume of endometriotic lesions. Remodeling of red active lesions into white lesions was observed more frequently in baboons treated with JNKI + MPA than in baboons treated with JNKI only. Menstrual cycle length and serum hormonal concentration were similar between placebo and JNKI groups.

CONCLUSION(S)

JNKI alone was as effective as JNKI + MPA or cetrorelix in reducing induced endometriosis in baboons, but without severe side effects or effect on cycle length or serum reproductive hormones.

Bentamapimod (JNK Inhibitor AS602801) Induces Regression of Endometriotic Lesions in Animal Models

Endometriosis is an estrogen (ER)-dependent gynecological disease caused by the growth of endometrial tissue at extrauterine sites. Current endocrine therapies address the estrogenic aspect of disease and offer some relief from pain but are associated with significant side effects. Immune dysfunction is also widely believed to be an underlying contributor to the pathogenesis of this disease. This study evaluated an inhibitor of c-Jun N-terminal kinase, bentamapimod (AS602801), which interrupts immune pathways, in 2 rodent endometriosis models. Treatment of nude mice bearing xenografts biopsied from women with endometriosis (BWE) with 30 mg/kg AS602801 caused 29% regression of lesion. Medroxyprogesterone acetate (MPA) or progesterone (PR) alone did not cause regression of BWE lesions, but combining 10 mg/kg AS602801 with MPA caused 38% lesion regression. In human endometrial organ cultures (from healthy women), treatment with AS602801 or MPA reduced matrix metalloproteinase-3 (MMP-3) release into culture medium. In organ cultures established with BWE, PR or MPA failed to inhibit MMP-3 secretion, whereas AS602801 alone or MPA + AS602801 suppressed MMP-3 production. In an autologous rat endometriosis model, AS602801 caused 48% regression of lesions compared to GnRH antagonist Antide (84%). AS602801 reduced inflammatory cytokines in endometriotic lesions, while levels of cytokines in ipsilateral horns were unaffected. Furthermore, AS602801 enhanced natural killer cell activity, without apparent negative effects on uterus. These results indicate that bentamapimod induced regression of endometriotic lesions in endometriosis rodent animal models without suppressing ER action. c-Jun N-terminal kinase inhibition mediated a comprehensive reduction in cytokine secretion and moreover was able to overcome PR resistance.

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.

Ras family small GTPase-mediated neuroprotective signaling in stroke

Selective neuronal cell death is one of the major causes of neuronal damage following stroke, and cerebral cells naturally mobilize diverse survival signaling pathways to protect against ischemia. Importantly, therapeutic strategies designed to improve endogenous anti-apoptotic signaling appear to hold great promise in stroke treatment. While a variety of complex mechanisms have been implicated in the pathogenesis of stroke, the overall mechanisms governing the balance between cell survival and death are not well-defined. Ras family small GTPases are activated following ischemic insults, and in turn, serve as intrinsic switches to regulate neuronal survival and regeneration. Their ability to integrate diverse intracellular signal transduction pathways makes them critical regulators and potential therapeutic targets for neuronal recovery after stroke. This article highlights the contribution of Ras family GTPases to neuroprotective signaling cascades, including mitogen-activated protein kinase (MAPK) family protein kinase- and AKT/PKB-dependent signaling pathways as well as the regulation of cAMP response element binding (CREB), Forkhead box O (FoxO) and hypoxiainducible factor 1(HIF1) transcription factors, in stroke.

Kinase control prevents HIV-1 reactivation in spite of high levels of induced NF-κB activity

Despite its clinical importance, the molecular biology of HIV-1 latency control is at best partially understood, and the literature remains conflicting. The most recent description that latent HIV-1 is integrated into actively expressed host genes has further confounded the situation. This lack of molecular understanding complicates our efforts to identify therapeutic compounds or strategies that could reactivate latent HIV-1 infection in patients, a prerequisite for the eradication of HIV-1 infection. Currently, many therapeutic development efforts operate under the assumption that a restrictive histone code could govern latent infection and that either dissipation of the histone-based restrictions or NF-κB activation could be sufficient to trigger HIV-1 reactivation. We here present data that suggest an additional, higher level of molecular control. During a high-content drug screening effort, we identified AS601245 as a potent inhibitor of HIV-1 reactivation in latently infected primary T cells and T cell lines. In either system, AS601245 inhibited HIV-1 reactivation despite high levels of induced NF-κB activation. This finding suggests the presence of a gatekeeper kinase activity that controls latent HIV-1 infection even in the presence of high levels of NF-κB activity. Potential therapeutic stimuli that do not target this gatekeeper kinase will likely fail to trigger efficient system-wide HIV-1 reactivation.

JNK regulates FoxO-dependent autophagy in neurons

The cJun N-terminal kinase (JNK) signal transduction pathway is implicated in the regulation of neuronal function. JNK is encoded by three genes that play partially redundant roles. Here we report the creation of mice with targeted ablation of all three Jnk genes in neurons. Compound JNK-deficient neurons are dependent on autophagy for survival. This autophagic response is caused by FoxO-induced expression of Bnip3 that displaces the autophagic effector Beclin-1 from inactive Bcl-XL complexes. These data identify JNK as a potent negative regulator of FoxO-dependent autophagy in neurons.

Protective effects of SP600125 on renal ischemia-reperfusion injury in rats

BACKGROUND

Ischemia/reperfusion injury (IRI) has a negative effect on renal allograft survival. Using a rat model of kidney IRI in this study, we investigated the overall effect of selective c-Jun N-terminal kinase (JNK) inhibitor SP600125 on renal IRI events.

METHODS

All 45 Fisher rats were anesthetized and renal IRI model was established by 45 min clamp of bilateral renal pedicles and 24 h reperfusion. Vehicle solution or SP600125 solution was intraperitoneally injected 45 min before ischemia, respectively. Analysis of renal histology, function, reactive oxygen species (ROS) expression, JNK phosphorylation status, as well as intra-renal pro-inflammatory cytokines expression was evaluated in this study.

RESULTS

After IRI, the levels of blood urea nitrogen, creatinine, tissue malondialdehyde, TNF-α, IL-1β, IL-6 were all elevated significantly, while superoxide dismutase, catalase activity were decreased. Histologic findings showed severe devastating lesions and increased rodent cell apoptosis; SP600125 effectively improved morphologic features, reversed above-mentioned parameters, and significantly attenuated c-Jun phosphorylation, as well as intra-renal pro-inflammatory cytokines expression compared with vehicle-treated group.

CONCLUSION

These data demonstrate that inhibition of c-Jun with SP600125 is capable of attenuating renal IRI, which might be a novel therapy target.

Synthesis and SAR of novel quinazolines as potent and brain-penetrant c-jun N-terminal kinase (JNK) inhibitors

Quinazoline 3 was discovered as a novel c-jun N-terminal kinase (JNK) inhibitor with good brain penetration and pharmacokinetic (PK) properties. A number of analogs which were potent both in the biochemical and cellular assays were discovered. Quinazoline 13a was found to be a potent JNK3 inhibitor (IC(50)=40 nM), with >500-fold selectivity over p38, and had good PK and brain penetration properties. With these properties, 13a is considered a potential candidate for in vivo evaluation.

2-Phenyl-5-(pyrrolidin-1-yl)-1-(3,4,5-trimethoxybenzyl)-1H-benzimidazole, a benzimidazole derivative, inhibits growth of human prostate cancer cells by affecting tubulin and c-Jun N-terminal kinase

BACKGROUND AND PURPOSE

The c-Jun N-terminal kinase (JNK) and tubulin are, frequently, targets for developing anti-cancer drugs. A major obstacle to successful development is P-glycoprotein (P-gp)-mediated resistance. Here, we have assessed a compound that inhibited growth of cancer cells, for effects on JNK and tubulin and as a substrate for P-gp.

EXPERIMENTAL APPROACH

Several pharmacological and biochemical assays were used to characterize signalling pathways of 2-phenyl-5-(pyrrolidin-1-yl)-1-(3,4,5-trimethoxybenzyl)-1H-benzimidazole (PPTMB), a benzimidazole analogue, in prostate cancer cells.

KEY RESULTS

PPTMB inhibited proliferation of several human prostate cancer cell lines. It displayed similar activity against a P-gp-rich cell line, indicating that PPTMB was not a substrate for P-gp. PPTMB induced G2/M arrest of the cell cycle and subsequent apoptosis, using flow cytometry. Tubulin polymerization assays and Western blot analysis showed that PPTMB directly acted on tubulin and caused disruption of microtubule dynamics, inducing mitotic arrest and sustained high levels of cyclin B1 expression and Cdk1 activation. Subsequently, mitochondria-related apoptotic cascades were induced, including Bcl-2 and Bcl-xL phosphorylation, Mcl-1 down-regulation, truncated Bad formation and activation of caspase-9 and -3. PPTMB stimulated JNK phosphorylation at Thr(183)/Tyr(185). SP600125, a specific JNK inhibitor, significantly inhibited apoptotic signalling, indicating that JNK plays a key role in PPTMB action. PPTMB showed a 10-fold higher potency against prostate cancer cells than normal prostate cells.

CONCLUSIONS AND IMPLICATIONS

PPTMB is an effective anti-cancer agent. It disrupted microtubule dynamics, leading to mitotic arrest of the cell cycle and JNK activation, which in turn stimulated the mitochondria-related apoptotic cascades in prostate cancer cells.

Experimental models of vascular dementia and vascular cognitive impairment: a systematic review

Vascular cognitive impairment (VCI) encompasses vascular dementia and is the second most common cause of dementing illness after Alzheimer's disease. The main causes of VCI are: cerebral small vessel disease; multi-infarct dementia; strategic infarct (i.e. located in a functionally-critical brain area); haemorrhage/microbleed; angiopathy (including cerebral amyloid angiopathy); severe hypoperfusion (e.g. cardiac arrhythmia); and hereditary vasculopathy (e.g. cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, CADASIL). In this systematic analysis, we aimed to relate cognitive and neuropathological features of experimental models to clinical VCI. We extracted data from 107 studies covering 16 models. These included: brief global ischaemic insults (in rats, mice or gerbils); chronic global hypoperfusion (rats, mice, gerbils); chronic hypertension (in primates or stroke-prone, spontaneously-hypertensive rats); multiple ischaemic lesions because of intra-vascular emboli (in rodents, rabbits or primates); strategic ischaemic lesions (in rats or mini-pigs); generalised vasculopathies, because of mutant Notch3, hyperhomocysteinaemia, experimental diabetes mellitus or lack of cerebral vasodilator M(5) receptors (rats or mice). Most cognitive testing showed deficits in working and reference memory. The lesions observed were microinfarcts, diffuse white matter lesions, hippocampal neuronal death, focal ischaemic lesions and micro-haemorrhages. The most-used model was bilateral carotid artery occlusion in rats, leading to chronic hypoperfusion and white matter injury.

Inflammation and brain injury: acute cerebral ischaemia, peripheral and central inflammation

Inflammation is a classical host defence response to infection and injury that has many beneficial effects. However, inappropriate (in time, place and magnitude) inflammation is increasingly implicated in diverse disease states, now including cancer, diabetes, obesity, atherosclerosis, heart disease and, most relevant here, CNS disease. A growing literature shows strong correlations between inflammatory status and the risk of cerebral ischaemia (CI, most commonly stroke), as well as with outcome from an ischaemic event. Intervention studies to demonstrate a causal link between inflammation and CI (or its consequences) are limited but are beginning to emerge, while experimental studies of CI have provided direct evidence that key inflammatory mediators (cytokines, chemokines and inflammatory cells) contribute directly to ischaemic brain injury. However, it remains to be determined what the relative importance of systemic (largely peripheral) versus CNS inflammation is in CI. Animal models in which CI is driven by a CNS intervention may not accurately reflect the clinical condition; stroke being typically induced by atherosclerosis or cardiac dysfunction, and hence current experimental paradigms may underestimate the contribution of peripheral inflammation. Experimental studies have already identified a number of potential anti-inflammatory therapeutic interventions that may limit ischaemic brain damage, some of which have been tested in early clinical trials with potentially promising results. However, a greater understanding of the contribution of inflammation to CI is still required, and this review highlights some of the key mechanism that may offer future therapeutic targets.

Basal c-Jun NH2-terminal protein kinase activity is essential for survival and proliferation of T-cell acute lymphoblastic leukemia cells

Hyperactivation of c-Jun NH2-terminal protein kinase (JNK) has been found in various malignant lymphocytes and inhibition of JNK activity leads to cell cycle arrest and apoptosis. However, the role of JNK activity in the oncogenic growth of T-cell acute lymphoblastic leukemia (T-ALL) cells remains largely unknown. Here, we report that treatment of T-ALL cells with JNK inhibitors led to cell cycle arrest and apoptosis and increased sensitivity to Fas-mediated apoptosis, whereas weak ectopic expression of MKK7-JNK1 fusion protein, which shows constitutive JNK activity, in T-ALL cells resulted in accelerated cell cycle progression and resistance to Fas-mediated apoptosis. The protein levels of c-Myc and Bcl-2 were reduced in the presence of JNK inhibitors but were enhanced with MKK7-JNK1. Small interfering RNA against JNK1, but not JNK2, exhibited similar effects to JNK inhibitors. These findings suggest that targeting JNK, especially JNK1 isoform, may have some important therapeutic implications in the treatment of T-ALL. Further exploration revealed that JNK protein and basal JNK activity in T-ALL cells showed aberrant subcellular localization, but no hyperactivation of JNK was observed. Thus, our work suggests that there might be novel mechanism(s) other than hyperactivation underlying the protumorigenic role of JNK activity.

Synthesis, biological evaluation, X-ray structure, and pharmacokinetics of aminopyrimidine c-jun-N-terminal kinase (JNK) inhibitors

Given the significant body of data supporting an essential role for c-jun-N-terminal kinase (JNK) in neurodegenerative disorders, we set out to develop highly selective JNK inhibitors with good cell potency and good brain penetration properties. The structure-activity relationships (SAR) around a series of aminopyrimidines were evaluated utilizing biochemical and cell-based assays to measure JNK inhibition and brain penetration in mice. Microsomal stability in three species, P450 inhibition, inhibition of generation of reactive oxygen species (ROS), and pharmacokinetics in rats were also measured. Compounds 9g, 9i, 9j, and 9l had greater than 135-fold selectivity over p38, and cell-based IC(50) values < 100 nM. Moreover, compound 9l showed an IC(50) = 0.8 nM for inhibition of ROS and had good pharmacokinetic properties in rats along with a brain-to-plasma ratio of 0.75. These results suggest that biaryl substituted aminopyrimidines represented by compound 9l may serve as the first small molecule inhibitors to test efficacy of JNK inhibitors in neurodegenerative disorders.

Targeting protein kinases in central nervous system disorders

Protein kinases are a growing drug target class in disorders in peripheral tissues, but the development of kinase-targeted therapies for central nervous system (CNS) diseases remains a challenge, largely owing to issues associated specifically with CNS drug discovery. However, several candidate therapeutics that target CNS protein kinases are now in various stages of preclinical and clinical development. We review candidate compounds and discuss selected CNS protein kinases that are emerging as important therapeutic targets. In addition, we analyse trends in small-molecule properties that correlate with key challenges in CNS drug discovery, such as blood-brain barrier penetrance and cytochrome P450-mediated metabolism, and discuss the potential of future approaches that will integrate molecular-fragment expansion with pharmacoinformatics to address these challenges.

The c-Jun N-terminal kinase (JNK) inhibitor XG-102 enhances the neuroprotection of hyperbaric oxygen after cerebral ischaemia in adult rats

AIM

Both hyperbaric oxygenation (HBO) and inhibition of the c-Jun N-terminal kinases (JNKs) by the peptide inhibitor XG-102 (D-JNKI-1) are efficient protective strategies against ischaemia-induced neurodegeneration. The present study investigated whether the combination of HBO and JNK inhibitor, XG-102, provides additive neuroprotection against cerebral ischaemia.

METHODS

Rat middle cerebral artery was occluded (MCAO) for 90 min. XG-102 [2 mg/kg, intraperitoneally] or HBO (3 ATA, 60 min) was applied 3 h after the onset of MCAO. For the combination treatment, HBO was started 10 min after the injection of XG-102. Twenty-four hours after MCAO, the infarct area, the neurological score and the immunohistochemistry staining in brain slices for cleaved-PARP, transferase-mediated biotinylated UTP nick end labelling, c-Jun and phosphorylated (activated) c-Jun were observed.

RESULTS

XG-102 or HBO alone reduced the total infarct area by 43% and 63%, respectively. The combination diminished total infarct area by 78%, improved the neurological function and reduced brain oedema. Co-application of HBO and XG-102 also significantly reduced the cleavage of PARP, by 96% and 91% in cortical penumbra and ischaemic core, respectively. Moreover, cotreatment significantly attenuated the number of cells labelled with transferase-mediated biotinylated UTP nick end labelling and phosphorylated c-Jun.

CONCLUSION

Our study demonstrates that HBO reinforces the efficiency of neuroprotective drugs such as XG-102 and vice versa. Both treatments, physical HBO and pharmacological XG-102, are already in phase I/II studies and promising strategies for clinical use.

Increased operant responding for ethanol in male C57BL/6J mice: specific regulation by the ERK1/2, but not JNK, MAP kinase pathway

RATIONALE

Extracellular signal-regulated protein kinase (ERK(1/2)) is a member of the mitogen-activated protein kinase (MAPK) signaling pathway and a key molecular target for ethanol (EtOH) and other drugs of abuse.

OBJECTIVE

The aim of the study was to assess the role of two MAPK pathways, ERK(1/2) and c-Jun N-terminal kinase (JNK), on the modulation of EtOH and sucrose self-administration.

MATERIALS AND METHODS

C57BL/6J mice were trained to lever press on a fixed-ratio 4 schedule with 9% EtOH/2% sucrose, or 2% sucrose, as the reinforcer. In experiments 1 and 2, mice were injected with the MEK(1/2) inhibitor SL 327 (0-100 mg/kg) and the JNK inhibitor AS 6012452 (0-56 mg/kg) prior to self-administration. In experiment 3, SL 327 (0-100 mg/kg) was administered prior to performance on a progressive ratio (PR) schedule of EtOH reinforcement. In experiment 4, SL 327 and AS 601245 were injected 2 h before a locomotor test.

RESULTS

SL 327 (30 mg/kg) significantly increased EtOH self-administration without affecting locomotion. Higher doses of SL 327 and AS 601245 reduced EtOH-reinforced responding and locomotor activity. Reductions of both ligands on sucrose self-administration were due to decreases in motor activity. SL 327 pretreatment had no effect on PR responding.

CONCLUSIONS

ERK(1/2) activity is more directly involved in modulating the reinforcing properties of EtOH than JNK activity due to its selective potentiation of EtOH-reinforced responding. The specificity of this effect to EtOH self-administration, rather than sucrose self-administration, suggests that the mechanism by which ERK(1/2) increases EtOH-reinforced responding does not generalize to all reinforcing solutions and is not due to increased motivation to consume EtOH.

Role of Rac1 GTPase in JNK signaling and delayed neuronal cell death following global cerebral ischemia

The overall goal of this study was to determine the role of Rac1 in POSH/MLK/JNK signaling and delayed neuronal cell death following cerebral ischemia. Temporal studies revealed that Rac1 GTPase activation was significantly elevated in hippocampus CA1 at 10 min to 72 h after cerebral ischemia reperfusion, with peak levels 30 min to 6 h after reperfusion. Total Rac1 protein levels were not significantly changed following cerebral ischemia. Rac1 has been shown to interact with POSH (plenty of SH3s), a scaffold protein that binds to and regulates MLK3 and JNK activation. Co-immunoprecipitation (Co-IP) studies revealed that POSH-Rac1-MLK3 complex formation displayed a significant and prolonged elevation after reperfusion, with a correlative increase in phosphorylation/activation of MLK3 as compared to sham controls. Intracerebroventricular administration of Rac1 antisense oligonucleotides (AS-ODNs) significantly attenuated Rac1 levels and Rac1 activation at 30 min after reperfusion, with a correlated significant attenuation of POSH-MLK3-Rac1 complex formation and MLK3 activation in hippocampus CA1. Infusion of Rac1 AS-ODNs also significantly attenuated post-ischemic activation of JNK, downstream of MLK3, and strongly protected the hippocampus CA1 from ischemic damage. Missense oligos had no effect on any of the parameters measured. The Rac1 AS-ODNs results were further confirmed by administration of a Rac1 inhibitor (NSC23766), which markedly attenuated activation of Rac1 and JNK, and significantly attenuated apoptotic delayed neuronal cell death following cerebral ischemia. As a whole, these studies demonstrate an important role for Rac1 in activation of the prodeath MLK3-JNK kinase signaling pathway and delayed neuronal cell death following cerebral ischemia.

c-Jun N-Terminal Kinase Signaling Inhibitors Under Development

Targeting protein kinases has been active area in drug discovery. The c-Jun N-terminal kinases (JNKs) have also been target for development of novel therapy in various diseases, since the roles of JNK signaling in pathological conditions were revealed in studies using jnk-deficient mice. Small molecule inhibitors and peptide inhibitors are identified for therapeutic intervention of JNK signaling pathway. SP-600125, an anthrapyrazole small molecule inhibitor for JNK with high potency and selectivity has been widely used for dissecting JNK signaling pathway. CC-401 is the first JNK inhibitor that went into clinical trial for inflammation and leukemia. Inhibitor for mixed lineage kinase (MLK), CEP-1347 also negatively regulates JNK signaling, and tried for potential use in Parkinson's disease. Cell-permeable peptide inhibitor D-JNKI-1 is being developed for the treatment of hearing loss. The current status of these JNK inhibitors and safety issue is discussed in the minireview.