Long-term intermittent theta burst stimulation enhanced hippocampus-dependent memory by regulating hippocampal theta oscillation and neurotransmitter levels in healthy rats.

Intermittent theta burst stimulation (iTBS), an updated pattern of high-frequency repetitive transcranial magnetic stimulation, is a potential candidate for improving memory. The hippocampus has been shown to be involved in the memory-enhancing effect induced by iTBS. However, it remains largely unknown whether this effect is achieved by regulating hippocampal theta oscillation and neurotransmitters gamma-aminobutyric acid (GABA) and glutamate, which are strongly related to memory. Thus, we investigated the effect of 14 days of iTBS on hippocampus-dependent memory and further explored the roles of hippocampal theta oscillation and neurotransmitters GABA and glutamate in this effect. We found that compared to sham iTBS, real iTBS enhanced hippocampus-dependent memory measured by hole-board test and object place recognition test. Further, real iTBS increased the density of c-Fos positive neurons and normalized power of theta oscillation in the dorsal hippocampus (dHip) compared to sham iTBS. Interestingly, we observed a decrease in the level of extracellular GABA and an increase in the level of extracellular glutamate in the dHip after real iTBS. Our results suggest that long-term iTBS improved hippocampus-dependent memory, which may be attributed to the enhancement of theta oscillation and altered levels of extracellular GABA and glutamate in the dHip.

Transcranial direct current stimulation of the prefrontal cortex improves depression-like behaviors in rats with Parkinson's disease.

Depression associated with Parkinson's disease (PD) seriously affects patients, and there is a lack of effective treatments. Transcranial direct current stimulation (tDCS) is increasingly used as a new non-invasive neuromodulation technique in the treatment of neuropsychiatric diseases. However, there is a paucity of research on tDCS for PD-related depression. Our study used PD model rats established with unilateral destruction of the medial forebrain bundle (MFB) to observe the modulatory effects of tDCS acting on the mPFC on depression-like behaviors. We found that tDCS acting on the mPFC improved depression-like behaviors in PD model rats by increasing sucrose intake in sucrose preference test (n = 7-10 rats/group) and shortening immobility time in forced swimming test (n = 7-8 rats/group). Meanwhile, tDCS decreased the expression of c-Fos protein (n = 8-11 rats/group) and the excitation of glutamatergic neurons (n = 6-8 rats/group) in the PrL and LHb of PD model rats. Western blots showed that tDCS decreased the overexpression of serine 845 phosphorylation site of AMPA receptor GluR1 (p-GluR1-S845) in the PrL and LHb of PD model rats (n = 8-11 rats/group), and the overexpression of p-GluR1-S831 in the LHb (n = 8-11 rats/group). The results of this study show that tDCS acting on the mPFC helps to improve PD-related depression, which involves the modulation of excitability and AMPA receptor phosphorylation on the PrL and LHb neurons.

Dose and time-dependence of acute intermittent theta-burst stimulation on hippocampus-dependent memory in parkinsonian rats.

Background: The treatment options for cognitive impairments in Parkinson's disease (PD) are limited. Repetitive transcranial magnetic stimulation has been applied in various neurological diseases. However, the effect of intermittent theta-burst stimulation (iTBS) as a more developed repetitive transcranial magnetic stimulation paradigm on cognitive dysfunction in PD remains largely unclear. Objective: Our aim was to explore the effect of acute iTBS on hippocampus-dependent memory in PD and the mechanism underlying it. Methods: Different blocks of iTBS protocols were applied to unilateral 6-hydroxidopamine-induced parkinsonian rats followed by the behavioral, electrophysiological and immunohistochemical analyses. The object-place recognition and hole-board test were used to assess hippocampus-dependent memory. Results: Sham-iTBS and 1 block-iTBS (300 stimuli) didn't alter hippocampus-dependent memory, hippocampal theta rhythm and the density of c-Fos- and parvalbumin-positive neurons in the hippocampus and medial septum. 3 block-iTBS (900 stimuli) alleviated 6-hydroxidopamine-induced memory impairments, and increased the density of hippocampal c-Fos-positive neurons at 80 min post-stimulation but not 30 min compared to sham-iTBS. Interestingly, 3 block-iTBS first decreased and then increased normalized theta power during a period of 2 h following stimulation. Moreover, 3 block-iTBS decreased the density of parvalbumin-positive neurons in the medial septum at 30 min post-stimulation compared to sham-iTBS. Conclusion: The results indicate that multiple blocks of iTBS elicit dose and time-dependent effects on hippocampus-dependent memory in PD, which may be attributed to changes in c-Fos expression and the power of theta rhythm in the hippocampus.

Activation and blockade of 5-HT4 receptors in the dorsal hippocampus enhance working and hippocampus-dependent memories in the unilateral 6-hydroxydopamine lesioned rats.

Cognitive dysfunction is a common symptom in Parkinson's disease (PD). Serotonin4 (5-HT4) receptors are richly expressed in the dorsal hippocampus (dHIPP) and play an important role in cognitive activities. However, the mechanism underlying the role of dHIPP 5-HT4 receptors in PD-related cognitive dysfunction remains unclear. Here we found that unilateral 6-hydroxydopamine lesions of the medial forebrain bundle increased the protein expression of 5-HT4 receptors in the dHIPP, decreased hippocampal theta rhythm, and impaired working memory and hippocampus-dependent memory in the T-maze and hole-board test, respectively. Both activation and blockade of dHIPP 5-HT4 receptors (agonist BIMU8 and antagonist GR113808) improved working memory and hippocampus-dependent memory in the lesioned rats, but not in sham rats. Activation of dHIPP 5-HT4 receptors increased hippocampal theta rhythm in the lesioned rats. The neurochemical studies showed that injection of BIMU8, GR113808 or GR113808/BIMU8 in the dHIPP increased the levels of dopamine in the medial prefrontal cortex (mPFC), dHIPP and amygdala, and the level of 5-HT in the amygdala in the lesioned rats, but not in sham rats. Injection of GR113808 or GR113808/BIMU8 into the dHIPP also increased the levels of noradrenaline in the mPFC, dHIPP and amygdala only in the lesioned rats. These results suggest that activation or blockade of dHIPP 5-HT4 receptors may improve the cognitive impairments in parkinsonian rats, which may be due to the increase of hippocampal theta rhythm, up-regulated expressions of 5-HT4 receptors in the dHIPP and the changes in the levels of monoamines in the relative brain areas.

Prevalence of Dysphagia in China: An Epidemiological Survey of 5943 Participants.

OBJECTIVE: To determine the prevalence of dysphagia among an older population and patients with stroke, head and neck cancers (HNCs) or neurodegenerative diseases (NDDs) in China, to identify the factors associated with this condition, and to explore the relationship between dysphagia and nutritional status. METHODS: This study included participants 65 years and older living in the community or in nursing homes and patients who had sustained a stroke, HNC, or NDD also recruited in hospitals from 14 provinces of China. The presence of dysphagia was determined by use of a questionnaire, water swallowing test, and/or a videofluoroscopic swallowing study. Logistic regression analysis was used to assess the possible associated risk factors. Body mass index was assessed as an indicator of malnutrition. RESULTS: A total of 5943 persons met the inclusion criteria and 2341 (39.4%) were identified with dysphagia, including the following: 51.14% of patients with stroke, 34.4% in HNCs, 48.3% in NDDs, and 19.2% of otherwise healthy older adults. The elderly with comorbidity (OR = 2.90, p < 0.01) and stroke patients (OR = 2.27, p < 0.01) were significantly more likely to exhibit signs of dysphagia. Dysphagic participants were at significantly greater risk of malnutrition (OR = 1.91, p < 0.01) compared to those without dysphagia. CONCLUSION: Dysphagia is prevalent in China among older individuals and people who have suffered a stroke, HNCs, or NDDs. The prevalence of dysphagia increases steadily with increasing age and presence of comorbid disease. People with dysphagia are more likely to suffer from malnutrition.

Prevalence and risk factors of disability and anxiety in a retrospective cohort of 432 survivors of Coronavirus Disease-2019 (Covid-19) from China.

OBJECTIVE: To estimate the prevalence of disability and anxiety in Covid-19 survivors at discharge from hospital and analyze relative risk by exposures. DESIGN: Multi-center retrospective cohort study. SETTING: Twenty-eight hospitals located in eight provinces of China. METHODS: A total of 432 survivors with laboratory-confirmed SARS CoV-2 infection participated in this study. At discharge, we assessed instrumental activities of daily living (IADL) with Lawton's IADL scale, dependence in activities of daily living (ADL) with the Barthel Index, and anxiety with Zung's self-reported anxiety scale. Exposures included comorbidity, smoking, setting (Hubei vs. others), disease severity, symptoms, and length of hospital stay. Other risk factors considered were age, gender, and ethnicity (Han vs. Tibetan). RESULTS: Prevalence of at least one IADL problem was 36.81% (95% CI: 32.39-41.46). ADL dependence was present in 16.44% (95% CI: 13.23-20.23) and 28.70% (95% CI: 24.63-33.15) were screened positive for clinical anxiety. Adjusted risk ratio (RR) of IADL limitations (RR 2.48, 95% CI: 1.80-3.40), ADL dependence (RR 2.07, 95% CI 1.15-3.76), and probable clinical anxiety (RR 2.53, 95% CI 1.69-3.79) were consistently elevated in survivors with severe Covid-19. Age was an additional independent risk factor for IADL limitations and ADL dependence; and setting (Hubei) for IADL limitations and anxiety. Tibetan ethnicity was a protective factor for anxiety but a risk factor for IADL limitations. CONCLUSION: A significant proportion of Covid-19 survivors had disability and anxiety at discharge from hospital. Health systems need to be prepared for an additional burden resulting from rehabilitation needs of Covid-19 survivors.

Dopamine D4 receptors in the lateral habenula regulate depression-related behaviors via a pre-synaptic mechanism in experimental Parkinson's disease.

Although multiple studies report that unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta (SNc) in rats induce depressive-like behaviors and hyperactivity of the lateral habenula (LHb), effects of dopamine (DA) D4 receptors in the LHb on depressive-like behaviors are unclear. Here we found that intra-LHb injection of the different doses of D4 receptor agonist A412997 and antagonist L741742 produced the different behavioral responses in SNc sham-lesioned rats, and only the high doses of A412997 and L741742 increased the expression of depressive-like behaviors or produced antidepressant-like effects in SNc-lesioned rats. The low doses of A412997 and L741742 altered the firing rate of LHb neurons and release of DA, GABA and glutamate in the LHb via the GABAergic rostromedial tegmental nucleus (RMTg) in SNc sham-lesioned rats, but not in SNc-lesioned rats. The high doses of A412997 and L741742 also altered the firing rate and release of the transmitters in both SNc sham-lesioned and SNc-lesioned rats, whereas these effects were not involved in the RMTg. Lesions of the SNc shortened the duration of significant effects on the firing rate and release of the transmitters induced by the high doses of A412997 and L741742. These findings suggest that D4 receptors in the LHb are involved in depression-like behaviors via the pre- and post-synaptic mechanisms and depletion of DA decreases the function and/or the expression of both pre- and post-synaptic D4 receptors. This study also points to the importance of the pre-synaptic D4 receptors in the regulation of Parkinson's disease-related depression.

Activation and blockade of 5-HT6 receptor in the medial septum-diagonal band recover working memory in the hemiparkinsonian rats.

Working memory impairment is a common symptom occurred in Parkinson's disease (PD). The medial septum-diagonal band (MS-DB) complex and 5-HT6 receptor are involved in modulation of cognition. However, their roles in working memory in PD are still unknown. Here, we used behavioral, neurochemical and immunohistochemical approaches to assess the role of MS-DB 5-HT6 receptor in working memory in unilateral 6-hydroxydopamie (6-OHDA)-induced PD rats. Intra-MS-DB injection of 5-HT6 receptor agonist WAY208466 (3, 6 and 12 µg/rat) enhanced working memory and increased dopamine (DA) and noradrenaline (NA) levels in the medial prefrontal cortex (mPFC) and hippocampus in sham and 6-OHDA-lesioned rats. The dose that produced significant effect on working memory in 6-OHDA-lesioned rats was lower than that in sham rats, indicating hypersensitivity of 5-HT6 receptor after lesioning. Intra-MS-DB injection of 5-HT6 receptor antagonist SB258585 (2, 4 and 8 µg/rat) alleviated working memory deficits and increased DA level in the mPFC and hippocampus and NA level in the mPFC in 6-OHDA-lesioned rats while having no effect in sham rats, suggesting that SB258585 did not change normal cognitive status. These results suggest that activation and blockade of MS-DB 5-HT6 receptor recovered working memory in 6-OHDA-lesioned rats, which is probably related to changes in monoamine levels in the mPFC and hippocampus.

Activation and blockade of α2-adrenoceptors in the prelimbic cortex regulate anxiety-like behaviors in hemiparkinsonian rats.

At present, whether α2-adrenoceptors in the prelimbic cortex (PrL) are involved in Parkinson's disease-related anxiety is unclear. We examined the effects of PrL α2-adrenoceptors on anxiety-like behaviors in rats with unilateral 6-hydroxydopamine lesions of the medial forebrain bundle. Compared to the sham operation, the lesion induced anxiety-like responses as measured by the open field test and elevated plus-maze test. Intra-PrL injection of the α2-adrenoceptor agonist clonidine (1.25, 2.5 or 5 µg/rat) produced anxiolytic effects in sham-operated and lesioned rats. Furthermore, intra-PrL injection of the α2-adrenoceptor antagonist idazoxan (1, 2 or 4 µg/rat) induced anxiogenic effects in two groups of rats. The effective doses produced by clonidine and idazoxan in lesioned rats were higher than those in sham-operated rats. Neurochemical results showed that intra-PrL injection of clonidine (5 µg/rat) or idazoxan (4 µg/rat) decreased or increased dopamine (DA) and noradrenaline (NA) and serotonin (5-HT) levels in the medial prefrontal cortex (mPFC) and amygdala in sham-operated and lesioned rats, respectively. These results suggest that α2-adrenoceptors in the PrL are involved in the regulation of anxiety-like behaviors, which is attributable to changes in DA, NA and 5-HT levels in the mPFC and amygdala after activation and blockade of α2-adrenoceptors.

Alpha-synuclein induces microglial migration via PKM2-dependent glycolysis.

After spinal cord injury, microglial cells are activated and converted to an M1 phenotype. Emerging evidence supports the hypothesis that glucose reprogramming accompanies microglial activation. What contributes to the activation of microglia and glucose reprogramming, however, remains unclear. In the current study, we investigated the role and underlying mechanism of a-synuclein in regulating the aerobic glycolysis in microglia. We found that a-synuclein contributed to the reprogramming of glucose metabolism in microglia by promoting glycolysis and inhibiting mitochondrial biogenesis and oxidative phosphorylation. Further studies demonstrated that pyruvate kinase M2 (PKM2), a rate-limiting enzyme in glycolysis, mediated glucose reprogramming regulated by a-synuclein. A co-immunoprecipitation assay and Western blot assay demonstrated that a-synuclein interacted with PKM2. Further studies demonstrated that knockdown of PKM2 in a-synuclein-exposed microglia markedly reduced glycolysis and lactate production. Additionally, a-synuclein exposure promoted migration abilities in glucose-cultured microglia, whereas migration ability was suppressed in PKM2 knockdown microglia. Additionally, the PKM2 activator TEPP-46 promoted migration ability in a-synuclein-treated microglia, compared to treatment with a-synuclein alone. In conclusion, we demonstrate a PKM2-dependent glycolysis of a-synuclein in microglial.

High expression of Kruppel-like factor 4 as a predictor of poor prognosis for cervical cancer patient response to radiotherapy.

PURPOSE: The aim of this study was to explore the associations of Kruppel-like factor 4 expression with sensitivity to radiation therapy in locally advanced cervical squamous cell carcinoma patients. METHODS: The records of 117 locally advanced cervical squamous cell carcinoma patients were retrospectively reviewed, and Kruppel-like factor 4 expression in cervical carcinoma tissues was examined by immunohistochemical staining. The associations of Kruppel-like factor 4 expression with clinicopathological parameters were analyzed. Survival time was analyzed using Kaplan-Meier analysis and a Cox regression model. RESULTS: Patients being resistant to radiation therapy were associated with advanced International Federation of Gynecology and Obstetrics stage, tumor diameter (>4 cm), and poor differentiation grade. The high Kruppel-like factor 4 expression level was significantly related to resistance to radiation therapy, including radiation therapy non-response, local recurrence, and distant metastasis. The high Kruppel-like factor 4 expression level was also significantly related to the advanced International Federation of Gynecology and Obstetrics stage and poor differentiation grade. Kaplan-Meier analysis indicates that locally advanced cervical squamous cell carcinoma patients with high Kruppel-like factor 4 expression showed worse progression-free survival and overall survival. Univariate and multivariate Cox regression model analyses suggest that the high Kruppel-like factor 4 expression was one of the high-risk factors associated with poor prognosis in locally advanced cervical squamous cell carcinoma patients after radiation therapy. CONCLUSION: Our results suggest that the high Kruppel-like factor 4 expression can be used as a novel biomarker to predict radiation therapy resistance and poor prognosis for locally advanced cervical squamous cell carcinoma.

Α-synuclein induces microglial cell migration through stimulating HIF-1α accumulation.

Microglial cell migration and infiltration plays a critical role in spinal cord injury after thoracoabdominal aortic surgery. In our previous study, α-synuclein, a presynaptic protein was shown to be released from injured neurons and cause microglial cell activation. Here, we aimed to explore the effect of α-synuclein on microglial cell migration. Primary microglial cells were isolated from Sprague-Dawley rats and then exposed different doses (0.2, 0.4, and 0.6 µM) of α-synuclein oligomers. The mRNA and protein levels of HIF-1α were then analyzed by qRT-PCR and Western blot. Cell migration was examined by a 96-well Boyden chamber. Moreover, toll-like receptor (TLR) 2-expression as well as TLR7/8-expression was inhibited by specific siRNA transfection. HIF-1α was overexpressed by Ad-HIF-1α transfection. In the results, α-synuclein was found to stimulate HIF-1α accumulation in microglial cells in a dose-dependent manner. Silencing HIF-1α expression dampened α-synuclein induced microglial cell migration. Furthermore, blockade of TLR7/8 expression but not TLR2 expression reduced HIF-1α accumulation in microglial cells. In addition, overexpressed HIF-1α, along with Src, prompted caveolin-1 expression and phosphorylation, as well as migration in microglial cells. Α-synuclein acts via TLR7/8 and enhances HIF-1α expression, which might play a regulatory role in microglial cell migration. © 2017 Wiley Periodicals, Inc.

The response of juxtacellular labeled GABA interneurons in the basolateral amygdaloid nucleus anterior part to 5-HT2A/2C receptor activation is decreased in rats with 6-hydroxydopamine lesions.

Here we report that juxtacellular labeled GABA interneurons in the basolateral amygdaloid nucleus anterior part (BLA) of rats with 6-hydroxydopamine lesions of the substantia nigra pars compacta (SNc) showed a more burst-firing pattern, while having no change in the firing rate. In sham-operated and the lesioned rats, systemic administration of 5-HT(2A/2C) receptor agonist DOI produced excitation, inhibition and unchanged in the firing rate of the interneurons, and the mean response of DOI was excitatory. However, cumulative dose producing excitation in the lesioned rats was higher than that of sham-operated rats. The local administration of DOI in the BLA also produced three types of responses in two groups of rats. Furthermore, the local administration of DOI excited the interneurons in sham-operated rats, whereas the mean firing rate of the interneurons in the lesioned rats was not affected at the same dose. The excitatory effect of the majority of the interneurons after systemic and local administration of DOI was not reversed by the selective 5-HT(2C) receptor antagonist SB242084, and the inhibitory effect of DOI in all the interneurons examined was reversed by GABA(A) receptor antagonist picrotoxinin. The SNc lesion in rats did not change the density of GAD67/5-HT(2A) receptor co-expressing neurons in the BLA. These results indicate that the SNc lesion changes the firing activity of BLA GABA interneurons. Moreover, DOI regulated the firing activity of the interneurons mainly through activation of 5-HT(2A) receptor, and the lesion led to a decreased response of the interneurons to DOI, which attributes to dysfunction of 5-HT(2A) receptor on these interneurons.

Osthole protects lipopolysaccharide-induced acute lung injury in mice by preventing down-regulation of angiotensin-converting enzyme 2.

The renin-angiotensin-aldosterone system (RAAS) plays an important role in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Angiotensin converting enzyme 2 (ACE2) plays a protective role in acute lung injury. Osthole, a natural coumarin derivative extracted from traditional Chinese medicines, is known to have anti-inflammatory effect, but the effect of osthole on the ALI is largely unknown. The aim of this study is to explore whether and by what mechanisms osthole protects lipopolysaccharide(LPS)-induced acute lung injury. Herein, we found that osthole had a beneficial effect on LPS-induced ALI in mice. As revealed by survival study, pretreatment with high doses of osthole reduced the mortality of mice from ALI. Osthole pretreatment significantly improved LPS-induced lung pathological changes, reduced lung wet/dry weight ratios and total protein in BALF. Osthole also inhibited the release of inflammatory mediators TNF-α and IL-6. Meanwhile, osthole markedly prevented the loss of ACE2 and Ang1-7 in lung tissue of ALI mice. ACE2 inhibitor blocked the protective effect of osthole in NR 8383 cell lines. Taken together, our study showed that osthole improved survival rate and attenuated LPS-induced ALI and ACE2 may play a role in it.

Gene expression changes in the pituitary gland of rats exposed to electromagnetic pulses.

OBJECTIVE: We examined alterations in the expression of tumorigenesis-related genes in the pituitary gland of rats exposed to electromagnetic pulses (EMP). METHODS: The global gene expression profiles of the pituitary gland in EMP-exposed and control groups were detected by cDNA microarray analysis. We then validated and further investigated the reduced expression of two tumorigenesis-related genes, Pten, and Jund, by assessing their mRNA and protein expression by quantitative real-time-PCR, western blotting, and immunohistochemistry in the pituitary gland of rats 6 months after exposure to EMP. RESULTS: EMP exposure induced genome-wide gene expression changes in the rat pituitary gland. There was decreased expression of the Pten and Jund mRNAs and proteins in EMP-exposed rats compared with in unexposed control animals. CONCLUSION: EMP exposure alters the expression of tumorigenesis-related genes in the pituitary gland. These tumorigenesis-related genes are potentially involved in the development of pituitary gland tumors in rats.

Tert-butyl-2(4,5-dihydrogen-4,4,5,5-tetramethyl-3-O-1H-imidazole-3-cationic-1-oxyl-2-pyrrolidine-1-carboxylic ester displays novel cytotoxicity through reactive oxygen species-mediated oxidative damage in MCF-7 and MDA-MB-231 cells.

The cytotoxicity of a new nitroxyl nitroxide radical, tert-butyl-2 (4,5-dihydrogen-4,4,5,5-tetramethyl-3-O-1H-imidazole-3-cationic-1-oxyl-2-pyrrolidine-1-carboxylic ester (L-NNP) was examined in MCF-7 and MDA-MB-231 cells. L-NNP treatment resulted in a significant growth inhibition in MCF-7 and MDA-MB-231 cells. Compared with control, 10, 30, and 50µg/ml L-NNP treatments for 48h induced significant cell and nuclei swelling, and organelle distension. The marked cell death was seen in a concentration- and time-dependant manner in L-NNP treated groups. The L-NNP treated group displayed a concentration-dependant increase in DNA double strand damage compared to the control and the 1Gy γ-rays exposure groups. These results suggest that L-NNP could result in more lethal genotoxicity than 1Gy γ-radiation. Based on mitochondrial alteration (membrane potential loss and SDH activity descend), DNA damage, an increase in MDA production, and GSH-PX inactivation, we predicate that L-NNP induces lipid oxidation and oxidative damage in MCF-7 and MDA-MB-231 cells. Since L-NNP initiated a significant increase in reactive oxygen species, which could largely be inhibited by NAC pretreatment, the overall data strongly suggest that the mechanism of cytotoxicity of L-NNP was its ability to act as a strong free radical, and significantly increase intracellular reactive oxygen species production. This led to intracellular oxidative damage, and antioxidant enzyme inactivation, resulting in cell death. We hypothesize that the greater cytotoxicity of L-NNP in MDA-MB-231 cells than in MCF-7 cells might be due to more ROS production in MDA-MB-231 cells, leading to more oxidative damage.

[Change of oxygen free radical in reversing multidrug-resistance of human leukemic cell line HL-60/ADM by cyclosporin A].

This study was aimed to evaluate the reversed effects of cyclosporin A (CsA) on multidrug resistance (MDR) of human leukemic cell line HL-60/ADM, and to investigate the relationship of the oxygen free radical content between HL-60/ADM cells and the reversed HL-60/ADM cells (HL-60/ADM + CsA). The cytotoxicity and the reversed effects of CsA on multidrug resistance of human leukemic cell line HL-60/ADM were studied by MTT, flow cytometry (FCM) and immunohistochemical assay; the oxygen free radical for HL-60/ADM and HL-60/ADM + CsA cell lines were detected by colorimetric method. The results showed that the CsA less than 4 microg/ml had no significant cytotoxicity on HL-60/ADM, while the cytotoxicity was rised with CsA concentration increasing; And CsA (4 microg/ml) combined with ADM (1 microg/ml) could obviously restrain the growth of HL-60/ADM cells (p < 0.001). The P-gp expression of HL-60/ADM decreased obviously after exposure to CsA (4 microg/ml) for 72 hours, at the same cell conditions, MDA concentration of the reversed groups (HL-60/ADM + CsA cells) was higher than that of the control groups (HL-60/ADM cells) (p < 0.05), while the levels of SOD and GSH in the reversed groups were significantly lower than that in control groups (p < 0.001). It is concluded that MDR of HL-60/ADM can be reversed effectively by low dose of CsA, the level of oxygen free radical increases and the activity of antioxidants decreases in the reversed cells. Oxygen free radicals may be involved in this reverse process, which thereby lead to the cell death.