Inhibition of protein kinase (PK) Cδattenuates methamphetamine-induced dopaminergic toxicity via upregulation of phosphorylation of tyrosine hydroxylase at Ser40by modulation of protein phosphatase 2A and PKA

Network pharmacology study on the mechanism of Qiangzhifang in the treatment of panic disorder

Background

Panic disorder (PD) is a kind of mental illness characterized by the symptom of recurring panic attacks. Qiangzhifang (QZF) is a novel decoction developed by Professor Zhaojun Yan based on a unique system of syndrome differentiation and clinical experience. It has achieved remarkable results after long-term clinical practice, but its mechanism of action is still unclear. This study aims to use network pharmacology and molecular docking to explore the mechanism of QZF in the treatment of PD.

Methods

We used the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP), a literature search, and Encyclopedia of Traditional Chinese Medicine (ETCM) to find active ingredients and targets of QZF. We searched for PD targets in GeneCards, Online Mendelian Inheritance in Man (OMIM), the Comparative Toxicogenomics Database (CTD), and DrugBank. We established a PD target database, constructed a protein-protein interaction (PPI) network, and performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis in order to screen possible pathways of action and analyze the mechanism.

Results

This study identified 84 effective components of QZF, 691 potential targets, 357 PD targets, and 97 intersectional targets. Enrichment analysis using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) showed that QZF was associated with 118 biological processes (BPs), 18 cellular components (CCs), 35 molecular functions (MFs) [false discovery rate (FDR) <0.01], and 62 pathways (FDR <0.01). QZF mainly acts on its targets AKT1, FOS, and APP through active ingredients such as quercetin, β-sitosterol, 4-(4'-hydroxybenzyloxy)benzyl methyl ether, harmine, 1,7-dimethoxyxanthone, and 1-hydroxy-3,7-dimethoxyxanthone to regulate serotonin, gamma-aminobutyric acid (GABA), cyclic adenosine monophosphate (cAMP), and other signal pathways to treat PD.

Conclusions

Through network pharmacology and molecular docking technology, we predicted the possible mechanism of QZF in the treatment of PD, revealed the interaction targets and potential value of QZF, and provided a basis for its clinical application.

Protein kinase Cδ mediates methamphetamine-induced dopaminergic neurotoxicity in mice via activation of microsomal epoxide hydrolase

We previously demonstrated that activation of protein kinase Cδ (PKCδ) is critical for methamphetamine (MA)-induced dopaminergic toxicity. It was recognized that microsomal epoxide hydrolase (mEH) also induces dopaminergic neurotoxicity. It was demonstrated that inhibition of PKC modulates the expression of mEH. We investigated whether MA-induced PKCδ activation requires mEH induction in mice. MA treatment (8 mg/kg, i.p., × 4; 2 h interval) significantly enhanced the level of phosphorylated PKCδ in the striatum of wild type (WT) mice. Subsequently, treatment with MA resulted in significant increases in the expression of cleaved PKCδ and mEH. Treatment with MA resulted in enhanced interaction between PKCδ and mEH. PKCδ knockout mice exhibited significant attenuation of the enhanced mEH expression induced by MA. MA-induced hyperthermia, oxidative stress, proapoptotic potentials, and dopaminergic impairments were attenuated by PKCδ knockout or mEH knockout in mice. However, treating mEH knockout in mice with PKCδ inhibitor, rottlerin did not show any additive beneficial effects, indicating that mEH is a critical mediator of neurotoxic potential of PKCδ. Our results suggest that MA-induced PKCδ activation requires mEH induction as a downstream signaling pathway and that the modulation of the PKCδ and mEH interaction is important for the pharmacological intervention against MA-induced dopaminergic neurotoxicity.

Methiopropamine, a methamphetamine analogue, produces neurotoxicity via dopamine receptors

Methiopropamine (MPA) is structurally categorized as a thiophene ring-based methamphetamine (MA) derivative. Although abusive potential of MPA was recognized, little is known about the neurotoxic potential of MPA up to now. We investigated whether MPA induces dopaminergic neurotoxicity, and whether MPA activates a specific dopamine receptor. Here, we observed that treatment with MPA resulted in dopaminergic neurotoxicity in a dose-dependent manner. MPA treatment potentiated oxidative parameters (i.e., increases in the level of reactive oxygen species, 4-hydroxynonenal, and protein carbonyl), M1 phenotype-related microglial activity, and pro-apoptotic property (i.e., increases in Bax- and cleaved caspase-3-expressions, while a decrease in Bcl-2-expression). Moreover, treatment with MPA resulted in significant impairments in dopaminergic parameters [i.e., changes in dopamine level, dopamine turnover rate, tyrosine hydroxylase (TH) levels, dopamine transporter (DAT) expression, and vesicular monoamine transporter-2 (VMAT-2) expression], and in behavioral deficits. Both dopamine D1 receptor antagonist SCH23390 and D2 receptor antagonist sulpiride protected from these neurotoxic consequences. Therefore, our results suggest that dopamine D1 and D2 receptors simultaneously mediate MPA-induced dopaminergic neurodegeneration in mice via oxidative burdens, microgliosis, and pro-apoptosis.

L-Tyr-Induced Phosphorylation of Tyrosine Hydroxylase at Ser40: An Alternative Route for Dopamine Synthesis and Modulation of Na+/K+-ATPase in Kidney Cells

BACKGROUND/AIMS

Dopamine (DA) is a natriuretic hormone that inhibits renal sodium reabsorption, being Angiotensin II (Ang II) its powerful counterpart. These two systems work together to maintain sodium homeostasis and consequently, the blood pressure (BP) within normal limits. We hypothesized that L-tyrosine (L-tyr) or L-dihydroxyphenylalanine (L-dopa) could inhibit the Na+/K+-ATPase activity. We also evaluated whether L-tyr treatment modulates Tyrosine Hydroxylase (TH).

METHODS

Experiments involved cultured LLCPK1 cells treated with L-tyr or L-dopa for 30 minutes a 37°C. In experiments on the effect of Dopa Descarboxylase (DDC) inhibition, cells were pre incubated for 15 minutes with 3-Hydroxybenzylhydrazine dihydrochloride (HBH), and them L-dopa was added for 30 minutes. Na+/K+-ATPase activity was quantified colorimetrically. We used immunoblotting and immunocytochemistry to identify the enzymes TH, DDC and the dopamine receptor D1R in LLCPK1 cells. TH activity was accessed by immunoblotting (increase in the phosphorylation). TH and DDC activities were also evaluated by the modulation of the Na+/K+-ATPase activity, which can be ascribed to the synthesis of dopamine.

RESULTS

LLCPK1 cells express the required machinery for DA synthesis: the enzymes TH, and (DDC) as well as its receptor D1R, were detected in control steady state cells. Cells treated with L-tyr or L-dopa showed an inhibition of the basolateral Na+/K+-ATPase activity. We can assume that DA formed in the cytoplasm from L-tyr or L-dopa led to inhibition of the Na+/K+-ATPase activity compared to control. L-tyr treatment increases TH phosphorylation at Ser40 by 100%. HBH, a specific DDC inhibitor; BCH, a LAT2 inhibitor; and Sch 23397, a specific D1R antagonist, totally suppressed the inhibition of Na+/K+-ATPase activity due to L-dopa or L-tyr administration, as indicated in the figures.

CONCLUSION

The results indicate that DA formed mainly from luminal L-tyr or L-dopa uptake by LAT2, can inhibit the Na+/K+-ATPase. In addition, our results showed for the very first time that TH activity is also significantly increased when the cells were exposed to L-tyr.

Role of protein kinase Cδ in dopaminergic neurotoxic events

The pro-apoptotic role of Protein kinase Cδ (PKCδ), a member of the novel PKC subfamily, has been well-documented in various pathological conditions. In the central nervous system, the possible role of PKCδ has been studied, mainly in the condition of dopaminergic loss. It has been suggested that the phosphorylation of PKCδ at tyrosine 311 residue (Tyr³¹¹) by redox-sensitive Src family kinases (SFKs) is critical for the caspase-3-mediated proteolytic cleavage, which produces the constitutively active cleaved form of PKCδ. Mitochondrial translocation of cleaved PKCδ has been suggested to facilitate mitochondria-derived apoptosis and oxidative burdens. Moreover, it has been suggested that PKCδ contribute to neuroinflammation through the transformation of microglia into the pro-inflammatory M1 phenotype and the assembly of membrane NADPH oxidase in dopaminergic impairments. Interestingly, mitochondrial respiratory chain inhibitors or neuroinflammogens have shown to induce PKCδ activation in dopaminergic systems. Thus, PKCδ activation may be one of the pivotal causes of neuropathologic events, and could amplify these processes further in a positive feedback manner. Furthermore, PKCδ may play an intermediary role in connecting each neuropathologic event. This review affords insight into the role of PKCδ in various dopaminergic neurotoxic models, which could provide a potential target for mitigating dopaminergic neurotoxicity.

Exposure to far-infrared ray attenuates methamphetamine-induced impairment in recognition memory through inhibition of protein kinase C δ in male mice: Comparison with the antipsychotic clozapine

We have previously demonstrated that repeated treatment with methamphetamine (MA) results in a recognition memory impairment via upregulation of protein kinase C (PKC) δ and downregulation of the glutathione peroxidase-1 (GPx-1)-dependent antioxidant system. We also demonstrated that far-infrared ray (FIR) attenuates acute restraint stress via induction of the GPx-1 gene. Herein, we investigated whether exposure to FIR modulates MA-induced recognition memory impairment in male mice, and whether cognitive potentials mediated by FIR require modulation of the PKCδ gene, extracellular signal-regulated kinase (ERK) 1/2, and glutathione-dependent system. Repeated treatment with MA significantly increased PKCδ expression and its phosphorylation out of PKC isoenzymes (i.e., PKCα, PKCβI, PKCβII, PKCζ, and PKCδ expression) in the prefrontal cortex of mice. Exposure to FIR significantly attenuated MA-induced increase in phospho-PKCδ and decrease in phospho-ERK 1/2. In addition, FIR further facilitated the nuclear factor E2-related factor 2 (Nrf2)-dependent glutathione synthetic system. Moreover, L-buthionine-(S, R)-sulfoximine, an inhibitor of glutathione synthesis, counteracted the FIR-mediated phospho-ERK 1/2 induction and memory-enhancing activity against MA insult. More important, positive effects of FIR are comparable to those of genetic depletion of PKCδ or the antipsychotic clozapine. Our results indicate that FIR protects against MA-induced memory impairment via activations of the Nrf2-dependent glutathione synthetic system, and ERK 1/2 signaling by inhibition of the PKCδ gene.

Melatonin as a mitochondrial protector in neurodegenerative diseases

Mitochondria are crucial organelles as their role in cellular energy production of eukaryotes. Because the brain cells demand high energy for maintaining their normal activities, disturbances in mitochondrial physiology may lead to neuropathological events underlying neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease and Huntington's disease. Melatonin is an endogenous compound with a variety of physiological roles. In addition, it possesses potent antioxidant properties which effectively play protective roles in several pathological conditions. Several lines of evidence also reveal roles of melatonin in mitochondrial protection, which could prevent development and progression of neurodegeneration. Since the mitochondrial dysfunction is a primary event in neurodegeneration, the neuroprotection afforded by melatonin is thereby more effective in early stages of the diseases. This article reviews mechanisms which melatonin exerts its protective roles on mitochondria as a potential therapeutic strategy against neurodegenerative disorders.