Multidrug resistance (MDR) of tumor cells attenuates the efficacy of anticancer drugs and has become the main reason for chemotherapy failure. It is indispensable to establish an effective way to reverse multidrug resistance. Our previous work has shown that downregulation of the ERK/MAPK signaling pathway activity can reverse the drug resistance of resistant cells. Furthermore, the effect of signal transduction is strongly associated with lipid rafts. The drug resistance is reversed successfully after lipid rafts are destroyed by heptakis(2,6-di-O-methyl)-β-cyclodextrin (MβCD). However, reversal of the drug resistance is not associated with downregulation of ERK1/2 expression. Cell membrane permeability may increase when lipid rafts are destroyed by MβCD, causing the reversal of drug resistance due to an increased drug accumulation in cytoplasm. To minimize the influence of MβCD on the cell membrane structure, we selected flotillin, a marker protein of lipid rafts, as the target molecule to further investigate the mechanism of changes in drug resistance after destruction of lipid rafts. The effect of flotillin on the reversal of drug resistance was examined using RNA interference (RNAi) in a retroviral system in human drug resistant strains of colorectal cancer cell line HCT-15. The results demonstrate that flotillin-1 downregulation by RNAi (Flot1-RNAi) reduced the drug resistance, caused cell cycle arrest and decreased the expression of ERK1/2; however, apoptosis was not significantly affected. Knockdown of flotillin-2 by RNAi (Flot2-RNAi) had effects similar to those of Flot1-RNAi except that the effects on ERK1/2 expression and apoptosis were different. Screening of multiple pathways indicated that the PI3K/Akt signaling pathway was closely related. This experiment demonstrates an association between PI3K and drug resistance through the activation of PI3K and suggests that PI3K may play a key role during the development of resistance in CRC. The results reveal that the levels of IRS-1 and PI3K proteins in the Flot1-RNAi and Flot2-RNAi groups were significantly downregulated. Knockdown of flotillins by RNAi reduced the resistance of HCT-15/ADM cells; and the results on Akt pathway indicate a decrease in resistance after lipid raft destruction. These data confirm that knockdown of flotillin reduces the resistance of HCT-15/ADM cells and the mechanism may be relevant to the PI3K/Akt pathway. Additionally, flotillin may be used as a potential target for chemotherapy in the treatment of colorectal cancer.
Background: Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system characterized by severe white matter demyelination. Because of its complex pathogenesis, there is no definite cure for MS. Experimental autoimmune encephalomyelitis (EAE) is an ideal animal model for the study of MS. Arsenic trioxide (ATO) is an ancient Chinese medicine used for its therapeutic properties with several autoimmune diseases. It is also used to inhibit acute immune rejection due to its anti-inflammatory and immunosuppressive properties. However, it is unclear whether ATO has a therapeutic effect on EAE, and the underlying mechanisms have not yet been clearly elucidated. In this study, we attempted to assess whether ATO could be used to ameliorate EAE in mice. Methods: ATO (0.5 mg/kg/day) was administered intraperitoneally to EAE mice 10 days post-immunization for 8 days. On day 22 post-immunization, the spinal cord, spleen, and blood were collected to analyze demyelination, inflammation, microglia activation, and the proportion of CD4 + T cells. In vitro, for mechanistic studies, CD4 + T cells were sorted from the spleen of naïve C57BL/6 mice and treated with ATO and then used for an apoptosis assay, JC-1 staining, imaging under a transmission electron microscope, and western blotting. Results: ATO delayed the onset of EAE and alleviated the severity of EAE in mice. Treatment with ATO also attenuated demyelination, alleviated inflammation, reduced microglia activation, and decreased the expression levels of IL-2, IFN-γ, IL-1β, IL-6, and TNF-α in EAE mice. Moreover, the number and proportion of CD4 + T cells in the spinal cord, spleen, and peripheral blood were reduced in ATO-treated EAE mice. Finally, ATO induced CD4 + T cell apoptosis via the mitochondrial pathway both in vitro and in vivo. Additionally, the administration of ATO had no adverse effect on the heart, liver, or kidney function, nor did it induce apoptosis in the spinal cord. Conclusions: Overall, our findings indicated that ATO plays a protective role in the initiation and progression of EAE and has the potential to be a novel drug in the treatment of MS.
Background: Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system characterized by severe demyelination of white matter. There is no definite cure for MS owing to its complex pathogenesis. Experimental autoimmune encephalomyelitis (EAE) is an ideal animal model for the study of MS. Arsenic trioxide (ATO) is an ancient Chinese medicine used for its therapeutic properties for several autoimmune diseases. It is also used to inhibit acute immune rejection due to its anti-inflammatory and immunosuppressive properties. However, it is unclear whether ATO has a therapeutic effect on EAE, and the underlying mechanisms have not been clearly elucidated. In this study, we attempted to explore the possibility of using ATO to ameliorate EAE in mice.Methods: ATO (0.5 mg/kg/day) was administered intraperitoneally to EAE mice 10 days post-immunization for 8 days. On day 22 post-immunization, the spinal cord, spleen, and blood were collected to analyze demyelination, inflammation, microglia activation, and proportion of CD4+ T cells. In vitro, for mechanistic studies, CD4+ T cells were sorted from the spleen of naïve C57BL/6 mice and treated with ATO and then used for apoptosis assay, JC-1 staining, transmission electron microscope, and western blotting.Results: ATO delayed the onset of EAE and alleviated the severity of EAE in mice. Treatment with ATO also attenuated demyelination, alleviated inflammation, reduced microglia activation and decreased the expression of IL-2, IFN-γ, IL-1β, IL-6, and TNF-α in EAE mice. Moreover, the number and proportion of CD4+ T cells in the spinal cord, spleen, and peripheral blood were reduced in ATO-treated EAE mice. Finally, ATO induced CD4+ T cells apoptosis through the mitochondrial pathway both in vitro and in vivo. Additionally, the administration of ATO had no adverse effect on the heart, liver, and kidney function and did not induce apoptosis in the spinal cord.Conclusions: Overall, our findings indicated that ATO plays a protective role in the initiation and progression of EAE and has the potential to be a novel drug in the treatment of MS.
Background: Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system characterized by severe white matter demyelination. Because of its complex pathogenesis, there is no definite cure for MS. Experimental autoimmune encephalomyelitis (EAE) is an ideal animal model for the study of MS. Arsenic trioxide (ATO) is an ancient Chinese medicine used for its therapeutic properties with several autoimmune diseases. It is also used to inhibit acute immune rejection due to its anti-inflammatory and immunosuppressive properties. However, it is unclear whether ATO has a therapeutic effect on EAE, and the underlying mechanisms have not yet been clearly elucidated. In this study, we attempted to assess whether ATO could be used to ameliorate EAE in mice.Methods: ATO (0.5 mg/kg/day) was administered intraperitoneally to EAE mice 10 days post-immunization for 8 days. On day 22 post-immunization, the spinal cord, spleen, and blood were collected to analyze demyelination, inflammation, microglia activation, and the proportion of CD4+ T cells. In vitro, for mechanistic studies, CD4+ T cells were sorted from the spleen of naïve C57BL/6 mice and treated with ATO and then used for an apoptosis assay, JC-1 staining, imaging under a transmission electron microscope, and western blotting.Results: ATO delayed the onset of EAE and alleviated the severity of EAE in mice. Treatment with ATO also attenuated demyelination, alleviated inflammation, reduced microglia activation and decreased the expression levels of IL-2, IFN-γ, IL-1β, IL-6, and TNF-α in EAE mice. Moreover, the number and proportion of CD4+ T cells in the spinal cord, spleen, and peripheral blood were reduced in ATO-treated EAE mice. Finally, ATO induced CD4+ T cell apoptosis via the mitochondrial pathway both in vitro and in vivo. Additionally, the administration of ATO had no adverse effect on the heart, liver, or kidney function, nor did it induce apoptosis in the spinal cord.Conclusions: Overall, our findings indicated that ATO plays a protective role in the initiation and progression of EAE and has the potential to be a novel drug in the treatment of MS.
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