Yinghui Chen

Inhibition of p38 MAPK diminishes doxorubicin-induced drug resistance associated with P-glycoprotein in human leukemia K562 cells

Summary Background Several studies have shown that multidrug transporters, such as P-glycoprotein (PGP), are involved in cell resistance to chemotherapy and refractory epilepsy. The p38 mitogen-activated protein kinase (MAPK) signaling pathway may increase PGP activity. However, p38-mediated drug resistance associated with PGP is unclear. Here, we investigated p38-mediated doxorubicin-induced drug resistance in human leukemia K562 cells. Material/Methods The expression of PGP was detected by RT-PCR, Western blot, and immunocytochemistry. Cell viability and half-inhibitory concentrations (IC50) were determined by CCK-8 assay. The intracellular concentration of drugs was measured by HPLC. Results A doxorubicin-induced PGP overexpression cell line, K562/Dox, was generated. The p38 inhibitor SB202190 significantly decreased MDR1 mRNA expression, as well as PGP, in K562/Dox cells. The IC50 of phenytoin sodium and doxorubicin in K562/Dox cells was significantly higher than that in wild-type K562 cells, indicating the drug resistance of K562/Dox cells. During the blocking of p38 activity in the presence of SB202190, cell number was significantly reduced after the phenytoin sodium and doxorubicin treatment, and the IC50 of phenytoin sodium and doxorubicin was decreased in K562/Dox cells. HPLC showed that the intracellular levels of phenytoin sodium and doxorubicin were significantly lower in K562/Dox cells than those in K562 cells. The decrease of the intracellular level of these drugs was significantly abolished in the presence of SB202190. Conclusions Our study demonstrated that p38 is, at least in part, involved in doxorubicin-induced drug resistance. The mechanistic study of MAPK-mediated PGP and the action of SB202190 need further investigation.

Thymoquinone Alleviates the Experimental Diabetic Peripheral Neuropathy by Modulation of Inflammation

Thymoquinone has been reported to exhibit antioxidant and anti-inflammatory effects. Inflammation plays an important role in pathogenesis of diabetic peripheral neuropathy. This study investigated the effects of TQ on proliferation and apoptosis of Schwann cells exposed to high glucose conditions and electrophysiological and morphological changes of the sciatic nerve in a DPN rat model as well as relevant inflammatory mechanism. Cell proliferation and apoptosis of Schwann cells were measured using the Cell Counting Kit-8 and flow cytometry. DPN model was established in streptozotocin-induced diabetic rats. Nerve conduction velocity was measured before and after treatment. Morphologic changes were observed by H&E staining and transmission electron microscopy. COX-2, IL-1β, IL-6, and Caspase-3 expression was investigated by western blotting and Bio-Plex ProTM Assays. Finally, TQ alleviated the inhibition of Schwann cell proliferation and protected against Schwann cell apoptosis. It improved nerve conduction velocity, and alleviated the DPN-induced morphological changes and demyelination of the sciatic nerve. COX-2, IL-1β, IL-6 and Caspase-3 expression in sciatic nerve or isolated cultured Schwann cells, were also decreased by TQ. These results indicate TQ has a protective effect on peripheral nerves in a DPN rat model. The mechanism may be mediated partly by the modulation of the inflammatory reaction.

Thymoquinone attenuates brain injury via an antioxidative pathway in a status epilepticus rat model

Abstract Aim Status epilepticus (SE) results in the generation of reactive oxygen species (ROS), which contribute to seizure-induced brain injury. It is well known that oxidative stress plays a pivotal role in status epilepticus (SE). Thymoquinone (TQ) is a bioactive monomer extracted from black cumin (Nigella sativa) seed oil that has anti-inflammatory, anti-cancer, and antioxidant activity in various diseases. This study evaluated the protective effects of TQ on brain injury in a lithium-pilocarpine rat model of SE and investigated the underlying mechanism related to antioxidative pathway. Methods Electroencephalogram and Racine scale were used to value seizure severity. Passive-avoidance test was used to determine learning and memory function. Moreover, anti-oxidative activity of TQ was observed using Western blot and super oxide dismutase (SOD) activity assay. Results Latency to SE increased in the TQ-pretreated group compared with rats in the model group, while the total power was significantly lower. Seizure severity measured on the Racine scale was significantly lower in the TQ group compared with the model group. Results of behavioral experiments suggest that TQ may also have a protective effect on learning and memory function. Investigation of the protective mechanism of TQ showed that TQ-pretreatment significantly increased the expression of Nrf2, HO-1 proteins and SOD in the hippocampus. Conclusion These findings showed that TQ attenuated brain injury induced by SE via an anti-oxidative pathway.

Multidrug resistance-associated protein 1 decreases the concentrations of antiepileptic drugs in cortical extracellular fluid in amygdale kindling rats.

Aim:To investigate whether multidrug resistance-associated protein 1 (MRP1) was responsible for drug resistence in refractory epilepsy in amygdale kindling rats.Methods:Rat amygdale kindling was used as a model of refractory epilepsy. The expression of MRP1 mRNA and protein in the brains was examined using RT-PCR and Western blot. MRP1-positive cells in the cortex and hippocampus were studied with immunohistochemical staining. The rats were intraperitoneally injected with phenytoin (50 mg/kg) or carbamazepine (20 mg/kg), and their concentrations in the cortical extracellular fluid were measured using microdialysis and HPLC. Probenecid, a MRP1 inhibitor (40 mmol/L, 50 μL) was administered through an inflow tube into the cortex 30 min before injection of the antiepileptic drugs.Results:The expression of MRP1 mRNA and protein was significantly up-regulated in the cortex and hippocampus in amygdale kindling rats compared with the control group. Furthermore, the number of MRP1-positive cells in the cortex and hippocampus was also significantly increased in amygdale kindling rats. Microdialysis studies showed that the concentrations of phenytoin and carbamazepine in the cortical extracellular fluid were significantly decreased in amygdale kindling rats. Pre-administration of probenecid could restore the concentrations back to their control levels.Conclusion:Up-regulation of MRP1 is responsible for the resistance of brain cells to antiepileptic drugs in the amygdale kindling rats.

Inhibition of p38 mitogen-activated protein kinase signaling reduces multidrug transporter activity and anti-epileptic drug resistance in refractory epileptic rats.

It is widely recognized that P‐glycoprotein (P‐gp) mediates drug resistance in refractory epilepsy. However, the molecular mechanism underlying the up‐regulation of P‐gp expression remains unclear. Our previous studies have demonstrated that p38 mitogen‐activated protein kinase (MAPK) regulates P‐gp expression in cultured K562 cells. However, a lack of in vivo research leaves unanswered questions regarding whether p38MAPK regulates P‐gp expression or drug resistance in refractory epilepsy. This in vivo study examined the effects of p38MAPK on the expression of P‐gp and mdr1 in the rat brain and quantified antiepileptic drug (AED) concentrations in the hippocampal extracellular fluid. In addition, the role of p38MAPK in electrical and behavioral activity in a rat epilepsy model was studied. The results indicated that p38MAPK inhibition by SB202190 reduced P‐gp expression, while increasing AED concentration in the hippocampal extracellular fluid in refractory epileptic rats. SB202190 also reduced the resistance to AEDs in drug‐resistant rats and significantly reduced the severity of seizure activity. These results suggest that p38MAPK could participate in drug resistance in refractory epilepsy through the regulation of P‐gp.

Hyperactivity and impaired attention in Gamma aminobutyric acid transporter subtype 1 gene knockout mice

Objectives Attention-deficit hyperactivity disorder (ADHD) is a common neurobehavioural disorder. It is conceivable that Gamma aminobutyric acid (GABA) neurotransmission is implicated in the pathophysiology of ADHD. This study investigated the effect of GABA transporter 1 (GAT-1) on the anxiety-like behaviours and cognitive function in knockout mice. Methods In all, 20 adult male mice were divided into two groups: wild-type (WT) group and GAT-1−/− group. The open field test, elevated O-maze (EZM) and Morris water maze were used to evaluate behavioural traits relevant to ADHD. Results Compared with WT mice, the GAT-1−/− mice travelled longer and displayed an enhanced kinematic velocity with the significant reduction of rest time in the open field test (p<0.05). The EZM showed that GAT-1−/− mice displayed a significant increase in total entries into the open sectors and the closed sectors compared with the WT mice. The WT mice showed shorter latencies after the training session (p<0.01), whereas the GAT-1−/− mice made no difference during probe test, the GAT-1−/− mice spent less time in the target quadrant (p<0.01). Conclusion Our results demonstrated that GAT-1−/− mice have phenotypes of hyperactivity, impaired sustained attention and learning deficiency, and the performance of GAT-1−/− mice is similar to ADHD symptoms. So, the study of the GAT-1−/− mice may provide new insights into the mechanisms and the discovery of novel therapeutics for the treatment of ADHD.

Protective Effects of Thymoquinone Against Convulsant Activity Induced by Lithium-Pilocarpine in a model of Status Epilepticus

Inflammation plays a pivotal role in status epilepticus (SE). Thymoquinone (TQ) is a bioactive monomer extracted from black seed (Nigella sativa) oil, which has anti-inflammatory properties in the context of various diseases. This study explored the protective effects of TQ in SE and used a lithium-pilocarpine model of SE to investigate the underlying mechanism, which was related to inflammation mediated by the NF-κB signaling pathway. In the present study, latency to SE increased in the TQ-pretreated group compared with the SE group, and the incidence of SE was significantly reduced. The seizure severity score measured on the Racine scale was significantly decreased in the TQ group compared with the SE group. Moreover, the results of the behavioral tests suggested that TQ may also have a protective effect on learning and memory functions. Finally, we further investigated the protective mechanism of TQ. The results showed that TQ-pretreatment significantly downregulated the protein levels of COX-2 and TNF-α in the brain, in a manner mediated by the NF-κB signaling pathway. These findings demonstrate that TQ attenuates convulsant activity via an anti- inflammation signaling pathway in a model of SE.

Beneficial effect of tetrandrine on refractory epilepsy via suppressing P-glycoprotein.

Patients with refractory epilepsy are resistance to antiepileptic drugs (AEDs). The mechanisms of drug resistance are varied, but one of them is the overexpression of multidrug transporters, such as P-glycoprotein (P-gp), in the brain. Tetrandrine (TTD) is a bis-benzylisoquinoline alkaloid isolated from the root of Stephania tetrandra (S, Moore) and is found to have a favorable effect against multidrug resistance (MDR) in chemotherapy. However, whether TTD affects AEDs in refractory epilepsy is unknown. In this study, we investigated the change in AED treatment efficacy in doxorubicin-induced drug resistant cells after TTD administration. We also examined the effect of TTD on seizure behaviors in the refractory epileptic rats, specifically the expression of MDR1 mRNA and P-gp protein in the cortex and hippocampus of the refractory epileptic rats. Our results demonstrated that TTD decreased cell resistance to phenytoin and valproate. TTD decreased seizure rate and increased the treatment efficacy of AEDs by reducing the expression of P-gp at mRNA and protein levels in vivo. These data support the use of TTD as an adjuvant drug for treating refractory epilepsy.

Involvement of microRNA-146a in diabetic peripheral neuropathy through the regulation of inflammation

Purpose Recent evidence has shown the involvement of inflammation in the development of diabetic peripheral neuropathy (DPN). MicroRNA-146a (miR-146a) is closely involved in the inflammatory response. However, the role of miR-146a in the inflammatory reaction in DPN has not been clarified. This study was designed to explore the role of miR-146a in the regulation of inflammatory responses in DPN. Methods Rats were randomly divided into three groups (n=6 per group): control group, type 2 diabetes mellitus (T2DM) group and DPN group. T2DM and DPN rats were intraperitoneally injected with streptozotocin. Sciatic nerve conduction velocity (NCV) was determined at the 6th week and the 12th week in each group. The expression of microRNAs was detected by quantitative real-time polymerase chain reaction in three sciatic nerves for each group of rats. Expression of inflammatory cytokines in nerve tissues and plasma was measured by Western blot and Bio-Plex Pro™ assays. Results The NCV and expression levels of miR-146a in the DPN group were significantly decreased (P<0.01) compared to the other two groups. Expression of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in the DPN group was significantly increased compared with the control and T2DM groups (P<0.01). Pearson’s correlation analysis showed that the expression level of miR-146a was negatively correlated with the levels of IL-1β, TNF-α and NF-κB. Conclusion miR-146a is involved in the pathogenesis of DPN, and its expression level is closely related to the inflammatory responses that aggravate sciatic nerve injuries.

Involvement of p38 MAPK in the Drug Resistance of Refractory Epilepsy Through the Regulation Multidrug Resistance- Associated Protein 1

Increased expression of multidrug-resistance associated protein 1 in brain tissue has been reported which lead to multidrug resistance of refractory epilepsy. However, the mechanism of up-regulated expression is still unclear. In our previous study, we have found that the MAPK signaling pathway mediated the expression of P-glycoprotein. So in this study, we used a rat model of refractory epilepsy to examine whether p38 MAPK affect the expression of MRP1 and the concentrations of AEDs in the brain. The expression of MRP1 and p38 MAPK was detected by immunofluorescence, Western-blot and real time-PCR, while the concentration of AEDs was measured by microdialysis and HPLC. The result showed that SB202190, the specific inhibitor of p38 MAPK, could down-regulate the expression of MRP1, while increase the concentrations of valproate and lamotrigine in hippocampus extracellular fluid of refractory epileptic rat. We demonstrate that p38 MAPK signaling pathway may be involved in drug resistance of refractory epilepsy by regulating MRP1.