Anlotinib affects systemic lipid metabolism and induces lipid accumulation in human lung cancer cells.

BACKGROUND: Anlotinib has demonstrated encouraging clinical outcomes in the treatment of lung cancer, soft tissue sarcoma and thyroid carcinoma. Several clinical studies have shown a relationship between anlotinib treatment and the occurrence of hyperlipidemia. The fundamental mechanisms, however, are still largely unclear. Here, the effect of anlotinib on lipid metabolism in an animal model and human cancer cells was evaluated and the role of lipid metabolism in the antitumor efficacy of anlotinib was investigated. METHODS: The C57BL/6 J mouse model as well as A549 and H460 human lung cancer cell lines were used to examine the impact of anlotinib on lipid metabolism both in vivo and in vitro. Levels of triglycerides, high-density lipoprotein, low-density lipoprotein (LDL), and total cholesterol in serum or cell samples were determined using assay kits. The expression levels of crucial genes and proteins involved in lipid metabolism were measured by quantitative RT-PCR and Western blotting. Furthermore, exogenous LDL and knockdown of low-density lipoprotein receptor (LDLR) were used in H460 cells to investigate the relevance of lipid metabolism in the anticancer efficacy of anlotinib. RESULTS: Anlotinib caused hyperlipidemia in C57BL/6 J mice, possibly by downregulating hepatic LDLR-mediated uptake of LDL cholesterol. AMP-activated protein kinase and mammalian target of rapamycin inhibition may also be involved. Additionally, anlotinib enhanced sterol response element binding protein 1/2 nuclear accumulation as well as upregulated LDLR expression in A549 and H460 cells, which may be attributable to intracellular lipid accumulation. Knockdown of LDLR reduced intracellular cholesterol content, but interestingly, anlotinib significantly improved intracellular cholesterol accumulation in LDLR-knockdown cells. Both exogenous LDL and LDLR knockdown decreased the sensitivity of cells to anlotinib. CONCLUSIONS: Anlotinib modulates host lipid metabolism through multiple pathways. Anlotinib also exerts a significant impact on lipid metabolism in cancer cells by regulating key transcription factors and metabolic enzymes. In addition, these findings suggest lipid metabolism is implicated in anlotinib sensitivity.

Metformin Potentiates the Effects of Anlotinib in NSCLC via AMPK/mTOR and ROS-Mediated Signaling Pathways.

Anlotinib is a novel multi-targeted tyrosine kinase inhibitor with activity against soft tissue sarcoma, small cell lung cancer, and non-small cell lung cancer (NSCLC). Potentiating the anticancer effect of anlotinib in combination strategies remains a clinical challenge. Metformin is an oral agent that is used as a first-line therapy for type 2 diabetes. Interesting, metformin also exerts broad anticancer effects through the activation of AMP-activated protein kinase (AMPK) and inhibition of mammalian target of rapamycin (mTOR). Here, we evaluated the possible synergistic effect of anlotinib and metformin in NSCLC cells. The results showed that metformin enhanced the antiproliferative effect of anlotinib. Moreover, anlotinib combined with metformin induced apoptosis and oxidative stress, which was associated with the activation of AMPK and inhibition of mTOR. Reactive oxygen species (ROS)- mediated p38/JNK MAPK and ERK signaling may be involved in the anticancer effects of this combination treatment. Our results show that metformin potentiates the efficacy of anlotinib in vivo by increasing the sensitivity of NSCLC cells to the drug. These data provide a potential rationale for the combination of anlotinib and metformin for the treatment of patients with NSCLC or other cancers.

Silk fibroin peptide suppresses proliferation and induces apoptosis and cell cycle arrest in human lung cancer cells.

Silkworm cocoon was recorded to cure carbuncle in the Compendium of Materia Medica. Previous studies have demonstrated that the supplemental silk protein sericin exhibits anticancer activity. In the present study, we investigated the effects of silk fibroin peptide (SFP) extracted from silkworm cocoons against human lung cancer cells in vitro and in vivo and its possible anticancer mechanisms. SFP that we prepared had high content of glycine (~ 30%) and showed a molecular weight of ~ 10 kDa. Intragastric administration of SFP (30 g/kg/d) for 14 days did not affect the weights, vital signs, routine blood indices, and blood biochemical parameters in mice. MTT assay showed that SFP dose-dependently inhibited the growth of human lung cancer A549 and H460 cells in vitro with IC50 values of 9.921 and 9.083 mg/mL, respectively. SFP also dose-dependently suppressed the clonogenic activity of the two cell lines. In lung cancer H460 xenograft mice, intraperitoneal injection of SFP (200 or 500 mg/kg/d) for 40 days significantly suppressed the tumor growth, but did not induce significant changes in the body weight. We further examined the effects of SFP on cell cycle and apoptosis in H460 cells using flow cytometry, which revealed that SFP-induced cell cycle arrest at the S phase, and then promoted cell apoptosis. We demonstrated that SFP (20-50 mg/mL) dose-dependently downregulates Bcl-2 protein expression and upregulates Bax protein in H460 cells during cell apoptosis. The results suggest that SFP should be studied further as a novel therapeutic agent for the treatment of lung cancer.

Apoptosis induction in K562 human myelogenous leukaemia cells is connected to the modulation of Wnt/ß-catenin signalling by BHX, a novel pyrazoline derivative.

OBJECTIVES: The goal of this study was to explore the effects of BHX on human chronic myeloid leukaemia (CML) cells and to elucidate the underlying molecular mechanism. MATERIALS AND METHODS: CML cell line K562 cells were treated with BHX. The effects of BHX on cell proliferation, apoptosis and cell cycle were detected. Subsequently, the caspase, ATP activity, Ca2+ , ROS and mitochondrial membrane potential (MMP) levels treated with various concentrations of BHX were analysed. The variation of relevant proteins and genes was detected. Further, toxicity of BHX on peripheral blood cells, bone marrow-nucleated cells (BMNC) and organ index were investigated on mice. RESULTS: Results showed that BHX suppressed K562 cell proliferation in a dose-dependent manner and induced apoptosis and G0/G1 phase arrest. BHX induced mitochondria-mediated apoptosis, which was associated with downregulation of MMP, activation of caspase-3 and caspase-9, generation of intracellular ROS and elevation of Ca2+ in K562 cells. In treated cells, ATP levels were decreased, expression of total ß-catenin, phosphorylated ß-catenin and ß-catenin in the nucleus was decreased, and expression of cell cycle-related proteins was decreased. Further analysis revealed that BHX lowered the transcriptional level of ß-catenin. Lastly, BHX treatment significantly reduced the number of white blood cells, but had no effect on BMNC and organ index. CONCLUSIONS: These findings provide further insight into the potential use of BHX as an anti-cancer agent against human leukaemia.

Glutathione reductase mediates drug resistance in glioblastoma cells by regulating redox homeostasis.

Glutathione (GSH) and GSH-related enzymes constitute the most important defense system that protects cells from free radical, radiotherapy, and chemotherapy attacks. In this study, we aim to explore the potential role and regulatory mechanism of the GSH redox cycle in drug resistance in glioblastoma multiforme (GBM) cells. We found that temozolomide (TMZ)-resistant glioma cells displayed lower levels of endogenous reactive oxygen species and higher levels of total antioxidant capacity and GSH than sensitive cells. Moreover, the expression of glutathione reductase (GSR), the key enzyme of the GSH redox cycle, was higher in TMZ-resistant cells than in sensitive cells. Furthermore, silencing GSR in drug-resistant cells improved the sensitivity of cells to TMZ or cisplatin. Conversely, the over-expression of GSR in sensitive cells resulted in resistance to chemotherapy. In addition, the GSR enzyme partially prevented the oxidative stress caused by pro-oxidant L-buthionine -sulfoximine. The modulation of redox state by GSH or L-buthionine -sulfoximine regulated GSR-mediated drug resistance, suggesting that the action of GSR in drug resistance is associated with the modulation of redox homeostasis. Intriguingly, a trend toward shorter progress-free survival was observed among GBM patients with high GSR expression. These results indicated that GSR is involved in mediating drug resistance and is a potential target for improving GBM treatment.

BHX, a novel pyrazoline derivative, inhibits breast cancer cell invasion by reversing the epithelial-mesenchymal transition and down-regulating Wnt/ß-catenin signalling.

The novel pyrazoline derivative, BHX, has recently been shown to exhibit potent anti-tumour activity by blocking the Wnt/ß-catenin signalling pathway. However, its effect on breast cancer growth and invasion are unknown. Our results show that BHX suppresses MDA-MB-231 cell viability and colony formation in a dose-dependent manner, and induces apoptosis and G0/G1 phase arrest. BHX-treated breast cancer cells showed morphological characteristics of cells undergoing apoptosis. Furthermore, BHX inhibited cell migration and invasion, which was associated with increased E-cadherin mRNA and protein expression, and down-regulation of SNAIL and vimentin. In addition, BHX induced the generation of intracellular ROS and decreased ß-catenin protein and mRNA expression. We used a mouse xenograft model to investigate the effects of BHX in vivo, where the growth of MDA-MB-231 xenografted tumours was suppressed in nude mice treated continuously with BHX for 21 days. Finally, the rat plasma concentration of BHX was measured by ultra-performance liquid-chromatography tandem mass spectrometry and the pharmacokinetic parameters of BHX were processed by non-compartmental analysis. In conclusion, BHX merits further study as a novel therapeutic small molecule for the treatment of breast cancer.

BHX Inhibits the Wnt Signaling Pathway by Suppressing ß-catenin Transcription in the Nucleus.

BHX (N-(4-hydroxybenzyl)-1,3,4-triphenyl-4,5-dihydro-1H-pyrazole-5-carboxamide), a Wnt signaling pathway inhibitor, effectively inhibits tumor cell growth, but the underlying mechanism is unclear. Thus, we aim to investigate the effects and associated mechanism of BHX action on A549 and MCF-7 cell lines. In our study, MTT(3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide) and xenograft model assay indicated that cell growth was inhibited by BHX at a range of concentrations in vitro and in vivo. The expression of ß-catenin and Wnt signaling pathway downstream target genes were decreased evidently under BHX treatment. Flow cytometry also revealed that BHX treatment significantly induced G1 arrest. Further analysis showed that BHX lowered the transcriptional level of ß-catenin. In conclusion, BHX inhibited the nuclear synthesis of ß-catenin, thereby suppressing the Wnt signaling pathway and further inhibiting tumor growth and proliferation.

Ursolic acid attenuates temozolomide resistance in glioblastoma cells by downregulating O(6)-methylguanine-DNA methyltransferase (MGMT) expression.

The DNA-alkylating agent temozolomide (TMZ) is an effective chemotherapeutic agent against malignant glioma, including glioblastoma multiforme (GBM). However, the clinical efficacy of TMZ is limited in many patients because of O(6)-methylguanine-DNA methyltransferase (MGMT)-driven resistance. Thus, new strategies to overcome TMZ resistance are urgently needed. Ursolic acid (UA) is a naturally derived pentacyclic triterpene acid that exerts broad anticancer effects, and shows capability to cross the blood-brain barrier. In this study, we evaluated the possible synergistic effect of TMZ and UA in resistant GBM cell lines. The results showed that UA prevented the proliferation of resistant GBM cells in a concentration-dependent manner. Compared with TMZ or UA treatment alone, the combination treatment of TMZ and UA synergistically enhanced cytotoxicity and senescence in TMZ-resistant GBM cells. This effect was correlated with the downregulation of MGMT. Moreover, experimental results with an in vivo mouse xenograft model showed that the combination treatment of UA and TMZ reduced tumor volumes by depleting MGMT. Therefore, UA as both a monotherapy and a resensitizer, might be a candidate agent for patients with refractory malignant gliomas.

Regulation of cell transformation by Rb-controlled redox homeostasis.

Rb is a tumor suppressor, and regulates various biological progresses, such as cell proliferation, development, metabolism and cell death. In the current study, we show that Rb knockout in 3T3 cells leads to oxidative redox state and low mitochondrial membrane potential by regulating mitochondrial activity. Our results indicate that Rb plays an important role in controlling redox homeostasis. More importantly, the functions of Rb in modulating cell proliferation, death and transformation are, at least in part, mediated by its controlling cellular redox state. In addition, our results also suggest that the cellular redox state possibly determines various biological activities, including cell survival, death and transformation, where Rb is functioning as a regulator of redox homeostasis.

Synthesis, characterization, and evaluation of a novel inhibitor of WNT/ß-catenin signaling pathway.

BACKGROUND: Wnt/ß-catenin signaling is a highly conserved pathway in organism evolution and is important in many biological processes. Overactivation of Wnt/ß-catenin signaling is closely related to tumor development and progression. To identify potent small molecules that can fight aberrant Wnt/ß-catenin-mediated cancer, we synthesized a novel pyrazoline derivative (N-(4-hydroxybenzyl)-1,3,4-triphenyl-4,5-dihydro-1H-pyrazole-5-carboxamide, BHX) to block Wnt signaling, and determined the absolute configuration of its precursor (ethyl 1,3,4-triphenyl-4,5-dihydro-1H-pyrazole-5-carboxylate). We then evaluated the inhibitory effect of BHX in vitro and in vivo. RESULTS: Cell proliferation was assessed in three human cancer cell lines (A549, HT29, and MGC803) in the presence and absence of BHX using MTS assays. BHX effectively inhibited A549, HT29, and MGC803 cell proliferation with IC50 of 5.43 ± 1.99, 6.95 ± 0.24, and 7.62 ± 1.31 µM, respectively. BHX significantly induced apoptosis and G1 phase arrest in A549 and MGC803 cells. The ß-catenin protein level was markedly reduced in A549 and MGC803 cells under BHX treatment. The inhibitory effect of BHX in vivo was investigated using a mouse xenograft model. A549 xenograft growth was suppressed by 50.96% in nude mice treated continuously with 100 mg/kg BHX for 21 d. Weight remained almost unchanged, which indicates the low toxicity of the compound. CONCLUSIONS: Our data suggest that BHX is a new drug candidate for cancer treatment because of its potent effect on the Wnt/ß-catenin pathway and low toxicity.

A phase I pharmacokinetic study of ursolic acid nanoliposomes in healthy volunteers and patients with advanced solid tumors.

BACKGROUND: Ursolic acid is a promising anticancer agent. The current study aims to evaluate the single- and multiple-dose pharmacokinetics (PK) as well as the safety of ursolic acid nanoliposomes (UANL) in healthy volunteers and in patients with advanced solid tumors. METHODS: Twenty-four healthy volunteers in the single-dose PK study were divided into three different groups, which received 37, 74, and 98 mg/m(2) of UANL. Eight patients in the multiple-dose PK study were administered with 74 mg/m(2) of UANL daily for 14 days. The UA plasma concentrations were determined using ultra-performance liquid chromatograph-tandem mass spectrometry. RESULTS: The plasma concentration profiles of all subjects were characterized by a biexponential decline after infusion. The mean peak plasma concentration (C(max)) increased linearly as a function of the dose (r = 0.999). The mean area under the plasma concentration-time curve (AUC) from 0 to 16 hours also increased proportionally with dose escalation (r = 0.998). However, the clearance was constant over the specific dose interval. In the multiple-dose PK study, the trough and average concentrations remained low. The mean AUC, half-life, C(max), time to C(max), and the volume of distribution on the first day were similar to those on the last day. All subjects tolerated the treatments well. Most UANL-associated adverse events varied from mild to moderate. CONCLUSIONS: UANL exhibits relatively linear PK behavior with dose levels from 37 mg/m(2) to 98 mg/m(2). No drug accumulation was observed with repeated doses of UANL. The intravenous infusion of UANL was well tolerated by healthy volunteers and patients with advanced tumors.

Pharmacokinetic characteristics of vincristine sulfate liposomes in patients with advanced solid tumors.

AIM: To evaluate the single- and multiple-dose pharmacokinetics of vincristine sulfate liposomes (VSLI) in patients with advanced solid tumors. METHODS: In single-dose pharmacokinetic study, 16 patients were administered VSLI (1.5, 2.0, or 2.3 mg·m(-2)) through intravenous infusion. Another 6 patients receiving vincristine sulfate (VCR, 2.0 mg) were taken as the control. In multiple-dose pharmacokinetic study, 12 patients were administered VSLI (1.5 or 1.8 mg·m(-2)) through intravenous infusion weekly for 4 consecutive weeks. The plasma concentration of VSLI was determined using the liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. RESULTS: After intravenous infusion of the single dose of VSLI, the plasma concentrations were characterized by bi-exponential decline curves. No statistically significant differences were observed between the main pharmacokinetic parameters in the 3 dose groups. Compared with the patients receiving VCR, the patients treated with VSLI displayed an increase in the area under the plasma concentration vs time curve (AUC), and a decrease in plasma clearance rates. On the 4th cycle in the multiple-dose study, the plasma concentration of VCR in all subjects prior to the weekly administration was below the lower limit of quantification (LLOQ). The calculated pharmacokinetic parameters from the subjects in the multiple- and single-dose (1.5 mg·m(-2)) groups had no significant differences. Although the administration of liposomal VCR may significantly elevate the plasma concentration of VCR, VSLI-associated adverse events were similar to those associated with conventional VCR. CONCLUSION: VSLI exhibits a lower clearance and a higher AUC compared with conventional VCR. No accumulation was observed in patients exposed to VSLI for 4 consecutive weeks. VSLI was generally tolerated in the subjects. The phase II dose of VSLI may be recommended as 4 doses of 1.5 mg·m(-2) for treatment of patients with advanced solid tumors.

A phase I pharmacokinetics study of 9-nitrocamptothecin in patients with advanced solid tumors.

PURPOSE: 9-Nitrocamptothecin (9-NC) is a novel orally administered camptothecin analog. The purpose of this study is to evaluate the pharmacokinetics and safety of 9-nitrocamptothecin in patients with advanced solid tumors. METHODS: The 23 patients for a single-dose pharmacokinetic experiment were divided into 3 dosing cohorts. The dosage of 9-nitrocamptothecin capsule was 1.25, 1.5 and 1.75 mg/m(2), respectively. The 8 patients for a multiple-dose pharmacokinetic study were orally administered 9-nitrocamptothecin 1.5 mg/m(2) for 5 consecutive days. Determination of the plasma concentration of 9-nitrocamptothecin was performed by high-performance liquid chromatography-ultraviolet detector technique, and determination of plasma concentration of 9-aminocamptothecin was performed by high-performance liquid chromatography-fluorescence detector technique. RESULTS: In the single-dose pharmacokinetic study, the mean ± SD 9-nitrocamptothecin C(max) were 94.49 ± 41.38, 115.56 ± 63.27 and 147.57 ± 38.19 ng/mL; AUC(0-36) were 877.14 ± 360.90, 961.33 ± 403.58 and 1,189.75 ± 405.80 ng h/mL, respectively; the mean ± SD 9-aminocamptothecin C(max) were 12.85 ± 6.46, 10.72 ± 6.58 and 28.74 ± 31.94 ng/mL; AUC(0-36) were 157.61 ± 111.61, 88.71 ± 39.51 and 173.52 ± 122.19 ng h/mL, respectively. In the multiple-dose pharmacokinetic study, the mean ± SD 9-nitrocamptothecin AUC(ss) was 907.04 ± 736.47 ng h/mL, C(max) was 85.98 ± 47.52 ng/mL, C(min) was 18.91 ± 22.50 ng/mL, C(av) was 37.79 ± 30.69 ng/mL, DF was 2.16 ± 0.87; the mean ± SD 9-aminocamptothecin AUC(ss) was 442.73 ± 308.39 ng h/mL, C(max) was 34.83 ± 18.31 ng/mL, C(min) was 10.32 ± 6.95 ng/mL, C(av) was 18.45 ± 12.85 ng/mL, DF was 1.34 ± 0.42. Comparing single-dose 1.5 mg/m(2) group with multiple-dose 1.5 mg/m(2) group, no significant difference was observed in 9-NC pharmacokinetic parameters, but with respect to the metabolite, significant differences were observed in C(max) and AUC. The toxicity of 9-NC varied from mild to moderate. No grade 3 or grade 4 toxicity was observed during the study. There was 2- to 13-fold variabilities in 9-NC and 9-AC exposure among different patients for any given dose of 9-NC. CONCLUSIONS: All participants had good tolerance throughout the study. 9-NC and 9-AC exposure did not increase proportionally to the dose ranging from 1.25 to 1.75 mg/m(2). After 5-day continuous administration, accumulation was observed in the metabolite 9-AC, but not in 9-NC.

Pharmacokinetics of panaxatrol disuccinate sodium, a novel anti-cancer drug from Panax notoginseng, in healthy volunteers and patients with advanced solid tumors.

AIM: To evaluate single-dose and multiple-dose pharmacokinetics of panaxatrol disuccinate sodium in healthy volunteers and patients with advanced solid tumors. METHODS: In the single-dose pharmacokinetic study, 27 healthy volunteers received panaxatrol disuccinate sodium in three doses (70, 100, and 140 mg·m⁻²). In the multiple-dose pharmacokinetic study, Panaxatrol disuccinate sodium was administered to 8 patients at 100 mg·m⁻² daily in a 30-day continuous intravenous injection. Determination of the panaxatrol disuccinate sodium plasma concentration was performed by an LC-MS method. The pharmacokinetic analysis system - Drug and Statistics (DAS) - was applied to assess plasma panaxatrol disuccinate sodium concentration-time data. RESULTS: After a single intravenous dose of 70, 100, or 140 mg·m⁻² was administered to subjects, panaxatrol disuccinate sodium distributed broadly, and the plasma concentration of panaxatrol disuccinate sodium declined rapidly. No significant differences were observed in the main pharmacokinetic parameters among the three dosing groups, including AUC(0-t), MRT(0-t), VRT(0-t), t(1/2Z), CL(z/F), V(z/F), and C0 (P>0.05). In the multiple-dose pharmacokinetic study, the mean steady-state peak concentration (C(max)), trough concentration (C(min)), average concentration (C(av)), mean steady state AUC (AUC(ss)) and the degree of fluctuation were 13.96±15.48 mg·L⁻¹, 0.18±0.29 mg·L⁻¹, 0.15±0.29 mg·L⁻¹, 3.58±6.94 mg·L⁻¹·h, and 148.00±117.18, respectively. At any given dose of panaxatrol disuccinate sodium, interindividual variability in the pharmacokinetic parameters was obvious. CONCLUSION: The effect of the dose level on single-dose pharmacokinetics of panaxatrol disuccinate sodium was not significant. No accumulation was observed with exposure to 100 mg·m⁻² panaxatrol disuccinate sodium in the 30-day continuous intravenous injection. All subjects were evaluated for tolerability throughout the study. Thus, the phase II dose of panaxatrol disuccinate sodium may be considered to be 100 mg·m⁻² for a 30-day continuous intravenous injection to treat patients with advanced solid tumors.

[Effect of TTRAP expression on apoptosis induced by hydroquinone in HL-60 cells in vitro.].

OBJECTIVE: To study the effect of TTRAP expression on apoptosis induced by hydroquinone in HL-60 cells in vitro, and explore the relationship between TTRAP expression and the apoptosis. METHODS: Apoptotic and necrotic rate was examined by flow cytometer with Anti-AnnexinV/FITC Plus PI staining. The mRNA expression of TTRAP was detected by RT-PCR. The differences in different treated groups were compared. RESULTS: After different concentrations of hydroquinone to the cells for 0, 4, 8, 12 h culture, were added, the cell apoptotic rate in different concentrations of hydroquinone groups was significantly higher than that in blank control groups. The optimal concentration of hydroquinone was 200 micromol/L, lasting for 8 h. When it was 250 micromol/L, the necrotic rate increased significantly. The apoptosis induced by hydroquinone was associated with the culture time at the concentration of 200 micromol/L, and the peak apoptotic time was 8 h. Then the apoptotic rate decreased and necrotic rate increased. Furthermore, with the concentrations of hydroquinone increased and time lasted for 8 h, the apoptotic rate of cells increased, the amount of TTRAP expression in the mRNA level also increased accordingly. When the concentrations of hydroquinone was above 250 micromol/L, necrotic rate increased sharply, and the amount of TTRAP expression decreased. CONCLUSION: Hydroquinone could induce apoptosis of HL-60 cells. The up-regulation of TTRAP expression may promote hydroquinone to induce HL-60 cells to go into apoptosis in vitro with dose-effect and time-effect relationship.

[Redox modulation of large conductance calcium-activated potassium channels in rat cultured trigeminal ganglion neurons].

AIM: To observe redox modulation of ion channel in trigeminal ganglion neurons by oxidants and reducing agents. METHODS: The effects of oxidants and reducing agents on maxi-conductance calcium-activated potassium channel in cultured rat trigeminal ganglion neurons by using whole-cell patch-clamp technique. RESULTS: Methionine-specific oxidant chloramine-T (Ch-T) 1 mmol/L slightly increased the current amplitude and this enhancement did not antagonized by DTT. In contrast, cysteine-specific reagent 5, 5'-dithio-bis(2-nitrobenzoic acid) (DTNB) 500 micromol/L significantly decreased current amplitude of BK(Ca) channels. The effect was reversed by the reducing agent 2 mmol/L 1, 4-dithio-DL-threitol (DTT). CONCLUSION: Reactive oxygen species were definitely involved in regulation of native neuronal function via redox modulation of BK(Ca) channels, which are suggested to play compensatory roles under oxidative stress-related conditions.