Population Pharmacokinetics and Pharmacogenetics Analyses of Dasatinib in Chinese Patients with Chronic Myeloid Leukemia.

AIMS: Dasatinib, a second-generation tyrosine kinase inhibitor of BCR-ABL 1, used for first-line treatment of Philadelphia chromosome-positive chronic myeloid leukemia (CML), exhibits high pharmacokinetic (PK) variability. However, its PK data in Chinese patients with CML remains rarely reported to date. Thus, we developed a population pharmacokinetic (PPK) model of dasatinib in Chinese patients and identified the covariate that could explain the individual variability of PK for optimal individual administration. METHODS: PPK modeling for dasatinib was performed based on 754 plasma concentrations obtained from 140 CML patients and analysis of various genetic and physicochemical parameters. Modeling was performed with nonlinear mixed-effects (NLME) using Phoenix NLME. The finally developed model was evaluated using internal and external validation. Monte Carlo simulations were used to predict drug exposures at a steady state for various dosages. RESULTS: The PK of dasatinib were well described by a two-compartment with a log-additive residual error model. Patients in the current study had a relatively low estimate of CL/F (126 L/h). A significant association was found between the covariate of age and CL/F of dasatinib, which was incorporated into the final model. None of the genetic factors was confirmed as a significant covariate for dasatinib. The results of external validation with 140 samples from 36 patients were acceptable. Simulation results showed significantly higher exposures in elderly patients. CONCLUSIONS: This study's findings suggested that low-dose dasatinib would be better suited for Chinese patients, and the dosage can be appropriately reduced according to the increase of age, especially for the elderly.

Population pharmacokinetics and pharmacogenetics analyses of imatinib in Chinese patients with chronic myeloid leukemia in a real-world situation.

BACKGROUND: Imatinib is presently the first-line choice for the treatment of chronic myeloid leukemia. However, there are limited real-world data on Chinese patients to support individualized medicine. This work aims to characterize population pharmacokinetics in Chinese patients with chronic myeloid leukemia, investigate the effects of several covariates on imatinib exposure, and provide support for personalized medicine and dose reduction. METHODS: A total of 230 patients with chronic myeloid leukemia were enrolled, and 424 steady-state concentration measurements were taken to perform the population pharmacokinetic analysis and Monte Carlo simulations with Phoenix NLME software. The effects of the demographic, biological, and pharmacogenetic (ten SNP corresponding to CYP3A4, CYP3A5, ABCB1, ABCG2, SCL22A1 and POR) covariates on clearance were evaluated. RESULTS: A one-compartmental model best-described imatinib pharmacokinetics. The hemoglobin and the estimated glomerular filtration rate (< 85 mL⋅min-1⋅1.73 m2) were associated with imatinib clearance. The genetic polymorphisms related to pharmacokinetics were not found to have a significant effect on the clearance of imatinib. The final model estimates of parameters are: ka (h-1) = 0.329; Vd/F (L) = 270; CL/F (L⋅h-1) = 7.60. CONCLUSIONS: Key covariates in the study population accounting for variability in imatinib exposure are hemoglobin and the estimated glomerular filtration rate. There is some need for caution when treating patients with moderate-to-severe renal impairment and significant hemoglobin changes.

The novel function of bexarotene for neurological diseases.

Bexarotene, a retinoid X receptor (RXR) agonist, is approved by FDA to treat cutaneous T-cell lymphoma. However, it has also demonstrated promising therapeutic potential for neurological diseases such as stroke, traumatic brain injury, Parkinson's disease, and particularly Alzheimer's disease(AD). In AD, bexarotene inhibits the production and aggregation of amyloid ß (Aß), activates Liver X Receptor/RXR heterodimers to increase lipidated apolipoprotein E to remove Aß, mitigates the negative impact of Aß, regulates neuroinflammation, and ultimately improves cognitive function. For other neurological diseases, its mechanisms of action include inhibiting inflammatory responses, up-regulating microglial phagocytosis, and reducing misfolded protein aggregation, all of which aid in alleviating neurological damage. Here, we briefly discuss the characteristics, applications, and adverse effects of bexarotene, summarize its pharmacological mechanisms and therapeutic results in various neurological diseases, and elaborate on the problems encountered in preclinical research, with the aim of providing help for the further application of bexarotene in central nervous system diseases.

Gap junction is essential for the antidepressant effects of fluoxetine.

OBJECTIVES: Fluoxetine has been used as the first line for the therapy of depression. However, lack of therapeutic efficacy and time lag still limit the application of fluoxetine. Gap junction dysfunction is a potentially novel pathogenic mechanism for depression. To clarify the mechanism underlying these limitations, we investigated whether gap junction was related to the antidepressant effects of fluoxetine. METHODS AND KEY FINDINGS: After chronic unpredictable stress (CUS), animals showed decreases in gap junction intracellular communication (GJIC). Treatment with fluoxetine 10 mg/kg significantly improved GJIC and anhedonia of rats until six days. These results indicated that fluoxetine improved gap junction indirectly. Furthermore, to test the role of gap junction on antidepressant effects of fluoxetine, we blocked gap junction using carbenoxolone (CBX) infusion in the prefrontal cortex. CBX dampened fluoxetine-induced decrease in immobility time of mice in tail suspension test (TST). CONCLUSIONS: Our study suggested that gap junction dysfunction blocks antidepressant effects of fluoxetine, contributing to understanding the mechanism underlying the time lag of fluoxetine.

CB2 receptor activation inhibits the phagocytic function of microglia through activating ERK/AKT-Nurr1 signal pathways.

Neuroinflammation is closely related to the pathogenesis of neurodegenerative diseases. Activation of microglia, the resident immune cells in CNS, induces inflammatory responses, resulting in the release of neurotoxic molecules, which favors neuronal death and neurodegeneration. Nuclear receptor-related 1 (Nurr1) protein, one of the orphan nuclear receptor superfamilies, is an emerging target for neuroprotective therapy. In addition, the anti-inflammatory function of cannabinoid (CB) receptors has attracted increasing interest. As both CB receptors (especially CB2 receptor) and Nurr1 exist in microglia, and regulate a number of same molecular points such as NF-κB, we herein explored the interplay between the CB2 receptor and Nurr1 as well as the regulatory mechanisms in microglial cells. We showed that the application of CB2 receptor agonists JWH015 (1, 10 µM) significantly increased the nuclear Nurr1 protein in BV-2 cells and primary midbrain microglia. Overexpression of Nurr1 or application of Nurr1 agonist C-DIM12 (10 µM) significantly increased the mRNA level of CB2 receptor in BV-2 cells, suggesting that positive expression feedback existing between the CB2 receptor and Nurr1. After 2-AG and JWH015 activated the CB2 receptors, the levels of p-ERK, p-AKT, p-GSK-3ß in BV-2 cells were significantly increased. Using ERK1/2 inhibitor U0126 and PI3K/AKT inhibitor LY294002, we revealed that the amount of Nurr1 in the nucleus was upregulated through ß-arrestin2/ERK1/2 and PI3K/AKT/GSK-3ß signaling pathways. With these inhibitors, we found a cross-talk interaction between the two pathways, and the ERK1/2 signaling pathway played a more dominant regulatory role. Furthermore, we demonstrated that when the CB2 receptor was activated, the phagocytic function of BV-2 cells was significantly weakened; the activation of Nurr1 also inhibited the phagocytic function of BV-2 cells. Pretreatment with the signaling pathway inhibitors, especially U0126, reversed the inhibitory effect of 2-AG on phagocytosis, suggesting that CB2 receptor may regulate the phagocytic function of microglia by activating Nurr1. In conclusion, CB2 receptor or/and Nurr1-mediated signal pathways play instrumental roles in the progress of phagocytosis, which are expected to open up new treatment strategies for neurodegenerative diseases.

Therapeutic Drug Monitoring and Individualized Medicine of Dasatinib: Focus on Clinical Pharmacokinetics and Pharmacodynamics.

Dasatinib is an oral second-generation tyrosine kinase inhibitor known to be used widely in Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). Notably, although a high pharmacokinetic variability in patients and an increased risk of pleural effusion are attendant, fixed dosing remains standard practice. Retrospective studies have suggested that dasatinib exposure may be associated with treatment response (efficacy/safety). Therapeutic drug monitoring (TDM) is gradually becoming a practical tool to achieve the goal of individualized medicine for patients receiving targeted drugs. With the help of TDM, these patients who maintain response while have minimum adverse events may achieve long-term survival. This review summaries current knowledge of the clinical pharmacokinetics variation, exposure-response relationships and analytical method for individualized dosing of dasatinib, in particular with respect to therapeutic drug monitoring. In addition, it highlights the emerging insights into several controversial issues in TDM of dasatinib, with the aim of presenting up-to-date evidence for clinical decision-making and insights for future studies.

Drp1, a potential therapeutic target for Parkinson's disease, is involved in olfactory bulb pathological alteration in the Rotenone-induced rat model.

Olfaction is often affected in parkinsonian patients and its disturbances precede the classical cognitive and locomotor dysfunction. The olfactory bulb might be the region of onset in Parkinson's disease (PD) pathogenesis, evidenced by the presence of disease-related protein aggregates and disturbed olfactory information processing. However, the underlying molecular mechanism that governs the olfactory bulb impairments remains unclear. This study was designed to investigate the relationship between olfactory bulb and inflammatory pathological alterations and the potential mechanisms. Here we found that rotenone led to typical parkinsonian symptoms and decreased tyrosine hydroxylase (TH)-positive neurons in the olfactory bulb. Additionally, increased NF-κB nuclear translocation and NLRP3 inflammasome components expressions caused by rotenone injection were observed accompanied by the activation of microglia and astrocytes in the olfactory bulb. Rotenone also triggered Drp1-mediated mitochondrial fission and this in turn caused mitochondrial damage. Furthermore, Mdivi-1(a selective Drp1 inhibitor) markedly ameliorated the morphologic disruptions of mitochondria and Drp1 translocation, inhibited the nuclear translocation of NF-κB, eventually blocked the downstream pathway of the NLRP3/caspase-1/IL-1ß axis and expression of iNOS. Overall, these findings suggest that Drp1-dependent mitochondrial fission induces NF-κB nuclear translocation and NLRP3 inflammasome activation that may further contribute to olfactory bulb disturbances.

TLR4 deficiency has a protective effect in the MPTP/probenecid mouse model of Parkinson's disease.

Parkinson's disease (PD) is a multifactorial disorder characterized by progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and the presence of Lewy bodies (LBs) consisting of misfolded α-synuclein protein. The etiology of PD is still not clear but systemic inflammation is proved to trigger and exacerbate DA neurons degeneration. Toll-like receptor 4 (TLR4) is a pattern-recognition receptor (PRR) and plays a major role in promoting the host immune. TLR4-mediated signal pathways induce the release of many inflammatory cytokines. It is reasonable to hypothesize that TLR4 is the mediator in microglia contributing to the damage of DA neurons in the SNpc. In this study, we evaluated the role of TLR4 in the chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)/probenecid mouse model. Both TLR4-deficient and wild-type (WT) mice were injected with probenecid (250 mg/kg, i.p.) followed by injection of MPTP (25 mg/kg, s.c.) every 4 days for 10 times. From D43 to D47, the behavioral performance in pole test and wire hang test was assessed. Then the mice were euthanized, and SN and striatum were dissected out for biochemical tests. We showed that compared with MPTP-treated WT mice, TLR4 deficiency significantly attenuated MPTP-induced motor deficits and TH-protein expression reduction in SNpc and striatum, suppressed MPTP-induced α-synuclein abnormality and neuroinflammation mediated through oxidative stress, glial activation, NF-κB and the NLRP3 inflammasome signaling pathways. These findings highlight the neuroprotective effect of TLR4-pathways in the chronic MPTP-induced PD mouse model.

NLRP3 inflammasome pathway is involved in olfactory bulb pathological alteration induced by MPTP.

Olfactory bulb, as one of sensory organs opening to the outside, is susceptible to toxic environment and easy to deteriorate. Recent studies in Parkinson's disease (PD) patients and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys have shown that abnormal α-synuclein is accumulated in the olfactory glomeruli, suggesting that the lesions of PD are not only confined to the substantia nigra (SN) but also located in the olfactory bulb. Thus, olfactory bulb might be the region of onset in PD pathogenesis and a targeted region for diagnosis and treatment of PD. However, the relationship between olfactory bulb and pathogenesis of PD remains unclear. In the present study, we investigated the inflammatory pathological alterations in olfactory bulb and the underlying mechanisms in chronic MPTP mice. Mice were treated with MPTP/P, i.e., MPTP (25 mg/kg, s.c.) plus probenecid (250 mg/kg, i.p.) every 4 days, for ten times. The mice displayed typical parkinsonian syndrome. Then we examined their olfactory function and the pathologic changes in olfactory bulb. The mice showed obvious olfactory dysfunction in a buried pellet test. Immunohistochemical studies revealed that tyrosine hydroxylase (TH) protein levels were significantly decreased, whereas abnormal α-synuclein was significantly increased in the olfactory bulbs. Furthermore, the olfactory bulbs in MPTP/P-treated mice showed significantly increased levels of interleukin-1ß (IL-1ß), caspase-1, glial fibrillary acidic protein (GFAP), Toll receptor 4 (TLR4), phosphorylation of p65, as well as activated molecules of NOD-like receptor protein 3 (NLRP3) that were associated with neuroinflammation. Our results demonstrate that MPTP/P-caused olfactory bulb damage might be related to NLRP3-mediated inflammation.

RNAi-mediated knockdown of DJ-1 leads to mitochondrial dysfunction via Akt/GSK-3ß and JNK signaling pathways in dopaminergic neuron-like cells.

Deletions or some mutations in the gene encoding the multifunctional protein, DJ-1, have been considered to be linked with autosomal recessive early onset Parkinson's disease (PD). Current emerging evidence suggests that DJ-1 is involved in the protection against oxidative stress-induced mitochondrial damage. However, the exact molecular mechanisms underlying this are not completely clear. The aim of this study was to investigate the effects of DJ-1 on the Akt pathway, nuclear factor erythroid 2-related factor (Nrf2), and c-Jun N-terminal kinase (JNK) with regard to modulating mitochondrial function. Here we showed that knockdown of DJ-1 resulted in mitochondrial dysfunction, including a decrease in active mitochondrial mass, complex I deficits, and inhibition of cellular adenosine 5'-triphosphate (ATP) content in the dopaminergic neuron-like cells PC12 and SH-SY5Y. Additionally, loss of DJ-1 impaired Akt signaling, and reduced nuclear translocation of Nrf2, thereby inhibiting activity of Nrf2-regulated downstream antioxidant enzymes such as heme oxygenase-1 and NAD(P)H quinone oxidoreductase 1. Moreover, DJ-1 knockdown also led to a significant increase in the mitochondrial reactive oxygen species, and then promoted the activation of JNK pathways. Furthermore, oxidative stress and mitochondrial dysfunction induced by knockdown of DJ-1 were blocked by a JNK inhibitor, which confirmed the important role of JNK activation in mitochondrial dysfunction. In conclusion, the present study indicates that DJ-1 knockdown leads to mitochondrial dysfunction in dopaminergic neuron-like cells, at least in part, through suppressing the Akt/GSK3ß pathway and impairing the oxidative stress response, as well as through the subsequent increased JNK activation in dopaminergic neuron-like cells.

Nurr1: A vital participant in the TLR4-NF-κB signal pathway stimulated by α-synuclein in BV-2 cells.

Parkinson's disease (PD) is a multi-factorial neurodegenerative disease. Abnormal α-synuclein protein aggregate and sustained microglia activation contribute to the pathogenic processes of PD. However, the relationship between α-synuclein and microglia-mediated neuroinflammation remains unclear. We purified α-synuclein after overexpression in Escherichia coli and then used it to stimulate BV-2 cells or primary microglia cells from wild type or toll-like receptor 4 (TLR4)-defective mice. Enzyme linked immunosorbent assay (ELISA) and real-time PCR results confirmed that α-synuclein could enhance the production of tumor necrosis factor α (TNF-α) through TLR4 activation. Western blotting results confirmed the involvement of the TLR4/PI3K/AKT/GSK3ß signal pathway in the inflammatory response. Nuclear factor kappa B (NF-κB) could translocate to the nucleus, promoting the expression of TNF-α when stimulated by α-synuclein in BV-2 cells. Nurr1 suppressed the production of TNF-α via interaction with NF-κB/p65 and inhibiting its nuclear translocation. In addition, both NF-κB and Nurr1 appeared to be regulated by the TLR4-mediated signal pathway. Our work demonstrated that TLR4 recognized α-synuclein and activated downstream signaling mechanisms leading to the release of pro-inflammatory mediators that are contra-balanced by Nurr1 expression. In conclusion, Nurr1 is a novel participant in the neuroinflammation stimulated by α-synuclein, thus the regulation of Nurr1 may be a novel neuroprotective target for PD treatment.

Prion-like propagation of α-synuclein in the gut-brain axis.

Parkinson's disease (PD) is a progressive degenerative disease of the nervous system, which is characterized by movement disorders, such as static tremor, rigidity, and bradykinesia in advanced patients. Gastrointestinal (GI) dysfunction, such as gastric dysmotility, constipation, and anorectic dysfunction, is common non-motor symptom in the early stage of PD. The progression of PD includes the degenerative loss of dopaminergic (DA) neurons and aggregation of α-synuclein in the substantia nigra (SN). Interestingly, both of them are also present in the enteric nervous system (ENS) of PD patients. In this review, we describe the relationship between non-motor symptoms particularly GI dysfunction and the pathogenesis of PD, aiming to show the powerful evidences about the prion-like propagation of α-synuclein and support the hypothesis of gut-brain axis in PD. We then summarize the mechanism of the gut-brain axis and confirm α-synuclein as a potential target for drug design or new clinical treatment.

Anti-neuroinflammatory effects of 20C from Gastrodia elata via regulating autophagy in LPS-activated BV-2 cells through MAPKs and TLR4/Akt/mTOR signaling pathways.

20C, a novel bibenzyl compound, is isolated from Gastrodia elata. In our previous study, 20C showed protective effects on tunicamycin-induced endoplasmic reticulum stress, rotenone-induced apoptosis and rotenone-induced oxidative damage. However, the anti-neuroinflammatory effect of 20C is still with limited acquaintance. The objective of this study was to confirm the anti-neuroinflammatory effect of 20C on Lipopolysaccharide (LPS)-activated BV-2 cells and further elucidated the underlying molecular mechanisms. In this study, 20C significantly attenuated the protein levels of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and interleukin (IL)-1ß, and secretion of nitric oxide (NO) and tumor necrosis factor (TNF)-α induced by Lipopolysaccharide (LPS) in BV-2 cells. Moreover, 20C up-regulated the levels of autophagy-related proteins in LPS-activated BV-2 cells. The requirement of mitogen-activated protein kinases (MAPKs) has been well documented for regulating the process of autophagy. Both 20C and rapamycin enhanced autophagy by suppressing the phosphorylation of MAPKs signaling pathway. Furthermore, 20C treatment significantly inhibited the levels of toll like receptor 4 (TLR4), phosphorylated-protein kinase B (Akt) and phosphorylated-mechanistic target of rapamycin (mTOR), indicating blocking TLR4/Akt/mTOR might be an underlying basis for the anti-inflammatory effect of 20C. These findings suggest that 20C has therapeutic potential for treating neurodegenerative diseases in the future.

Amyloidogenic proteins associated with neurodegenerative diseases activate the NLRP3 inflammasome.

Neuroinflammation has been shown as an essential factor in the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, and Multiple Sclerosis. Furthermore, activated microglia and increased pro-inflammatory cytokines are the major hallmarks in neurodegenerative diseases. A multimolecular complex named as inflammasome is involved in the process of inflammatory response, which can activate inflammatory caspases, leading to the cleavage and secretion of inflammatory cytokines, and finally generates a potent inflammatory response. In neurodegenerative diseases, it has been widely assumed that some types of amyloid proteins might be the triggers to activate the NLRP3 inflammasome. In this review, we summarize the current researches about the role of NLRP3 inflammasome, by reviewing the main studies in vitro and in vivo experiments and discuss the potential for new therapeutic interventions in neurodegenerative diseases.

Virtual Screening against Phosphoglycerate Kinase 1 in Quest of Novel Apoptosis Inhibitors.

Inhibition of apoptosis is a potential therapy to treat human diseases such as neurodegenerative disorders (e.g., Parkinson's disease), stroke, and sepsis. Due to the lack of druggable targets, it remains a major challenge to discover apoptosis inhibitors. The recent repositioning of a marketed drug (i.e., terazosin) as an anti-apoptotic agent uncovered a novel target (i.e., human phosphoglycerate kinase 1 (hPgk1)). In this study, we developed a virtual screening (VS) pipeline based on the X-ray structure of Pgk1/terazosin complex and applied it to a screening campaign for potential anti-apoptotic agents. The hierarchical filters in the pipeline (i.e., similarity search, a pharmacophore model, a shape-based model, and molecular docking) rendered 13 potential hits from Specs chemical library. By using PC12 cells (exposed to rotenone) as a cell model for bioassay, we first identified that AK-918/42829299, AN-465/41520984, and AT-051/43421517 were able to protect PC12 cells from rotenone-induced cell death. Molecular docking suggested these hit compounds were likely to bind to hPgk1 in a similar mode to terazosin. In summary, we not only present a versatile VS pipeline for potential apoptosis inhibitors discovery, but also provide three novel-scaffold hit compounds that are worthy of further development and biological study.

DJ-1 regulating PI3K-Nrf2 signaling plays a significant role in bibenzyl compound 20C-mediated neuroprotection against rotenone-induced oxidative insult.

Oxidative stress is thought to be involved in the development of Parkinson's disease (PD). We previously reported that 20C, a bibenzyl compound isolated from Gastrodia elata, possesses antioxidative properties, but its in-depth molecular mechanisms against rotenone-induced neurotoxicity remains unknown. Recent studies indicate that without intact DJ-1, nuclear factor erythroid 2-related factor (Nrf2) protein becomes unstable, and the activity of Nrf2-mediated downstream antioxidant enzymes are thereby suppressed. In this study, we showed that 20C clearly protected PC12 and SH-SY5Y cells against rotenone-induced oxidative injury. Furthermore, 20C markedly up-regulated the levels of DJ-1, which in turn activated phosphoinositide-3-kinase (PI3K)/Akt signaling and inhibited glycogen synthase kinase 3ß (GSK3ß) activation, eventually promoted the nuclear translocation of Nrf2 and induced the expression of hemeoxygenase-1 (HO-1). The antioxidant effects of 20C could be partially blocked by ShRNA-mediated knockdown of DJ-1 and inhibition of the PI3K/Akt pathways with Akt1/2 kinase inhibitor, respectively. Conclusively, our findings confirm that DJ-1 is necessary for 20C-mediated protection against rotenone-induced oxidative damage, at least in part, by activating PI3K/Akt signaling, and subsequently enhancing the nuclear accumulation of Nrf2. The findings from our investigation suggest that 20C should be developed as a novel candidate for alleviating the consequences of PD in the future.