Auditory neuropathy spectrum disorder (ANSD) represents a variety of sensorineural deafness conditions characterized by abnormal inner hair cells and/or auditory nerve function, but with the preservation of outer hair cell function. ANSD represents up to 15% of individuals with hearing impairments. Through mutation screening, bioinformatic analysis and expression studies, we have previously identified several apoptosis-inducing factor (AIF) mitochondria-associated 1 (AIFM1) variants in ANSD families and in some other sporadic cases. Here, to elucidate the pathogenic mechanisms underlying each AIFM1 variant, we generated AIF-null cells using the clustered regularly interspersed short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system and constructed AIF-wild type (WT) and AIF-mutant (mut) (p.‍T260A, p.‍R422W, and p.‍R451Q) stable transfection cell lines. We then analyzed AIF structure, coenzyme-binding affinity, apoptosis, and other aspects. Results revealed that these variants resulted in impaired dimerization, compromising AIF function. The reduction reaction of AIF variants had proceeded slower than that of AIF-WT. The average levels of AIF dimerization in AIF variant cells were only 34.5%‍‒‍49.7% of that of AIF-WT cells, resulting in caspase-independent apoptosis. The average percentage of apoptotic cells in the variants was 12.3%‍‒‍17.9%, which was significantly higher than that (6.9%‍‒‍7.4%) in controls. However, nicotinamide adenine dinucleotide (NADH) treatment promoted the reduction of apoptosis by rescuing AIF dimerization in AIF variant cells. Our findings show that the impairment of AIF dimerization by AIFM1 variants causes apoptosis contributing to ANSD, and introduce NADH as a potential drug for ANSD treatment. Our results help elucidate the mechanisms of ANSD and may lead to the provision of novel therapies.
Humans ; Apoptosis Inducing Factor/metabolism* ; NAD/metabolism* ; Dimerization ; Apoptosis

Cardiomyocyte apoptosis leads to the functional incapacitation of myocardial plasmodium and plays an important role in the pathogenesis of heart failure transformed from compensable cardiac hypertrophy. Mitochondria are the main source of apoptosis-inducing molecule of various cells, and the role of caspartate-specific cysteinyl proteinase (caspase)-dependent mechanism has generally been accepted in the cardiomyocyte apoptosis. However, the significance of caspase-independent apoptosis-inducing factor (AIF) mechanism is not yet understood. The purpose of this study was to evaluate hypoxia-reperfusion-induced alterations of AIF mRNA and protein expressions in hypertrophic cardiomyocytes. Cardiomyocyte hypertrophy was produced by angiotensin II (0.1 mumol/L). The cells were cultured under the condition of hypoxia (95% N2 and 5% CO2; the O2 partial pressure was lower than 5 mmHg) for 8 h or 12 h (named as H8h and H12h groups, respectively), and then exposed to normal culture environment (named as H8h/R and H12h/R groups, respectively). Apoptosis was detected with Hoechst 33258 staining. The AIF mRNA and protein expressions were detected by RT-PCR and Western blot and quantified by gel scanning. The results were as follows: (1) The level of AIF mRNA expression was 0.29+/-0.08 (optical density, relative value) in the control group (hypertrophic cardiomyocytes cultured in normal environment). Compared with that in the control group, the levels of AIF mRNA expression were significantly higher in the groups of H8h and H12h (0.52+/-0.04 and 0.85+/-0.10), indicating that this effect was time-dependent. A further increase of AIF mRNA expression was observed in the groups of H8h/R (1.09+/-0.12) and H12h/R (1.41+/-0.23). (2) The level of AIF protein expression was 0.29+/-0.04 in the control group. Compared with that in the control group, the levels of AIF protein expression were significantly higher in the groups of H8h and H12h (2.07+/-0.15 and 3.12+/-0.19). The AIF protein expression was increased further in the groups of H8h/R (4.57+/-0.25) and H12h/R (5.71+/-0.27). The nuclear translocation of AIF protein was obvious only in the groups of H8h/R and H12h/R. (3) The expressions of AIF mRNA and protein were almost completely inhibited by AIF siRNA transfection. The siRNA transfection also reduced the apoptosis of hypertrophic cardiomyocytes in the groups of H8h/R and H12h/R but not in the groups of H8h and H12h. The apoptosis rate was significantly reduced by both AIF siRNA transfection and Ac-DEVD-cmk, an inhibitor of caspase-3. This reduction induced by two factors was more evident than that by one factor. (4) AIF nuclear translocation induced by hypoxia-reperfusion was not affected by inhibition of the activity of caspase-3. These data suggest that AIF plays a pivotal role in the apoptosis of hypertrophic cardiomyocytes induced by hypoxia-reperfusion.
Apoptosis ; Apoptosis Inducing Factor ; metabolism ; Cardiomegaly ; Cell Hypoxia ; Myocytes, Cardiac ; cytology ; Reperfusion Injury

OBJECTIVETo investigate the pathway and mechanism of noise exposure induced out hair cells (OHC) apoptosis.

METHODSThe cochleae of control and noise exposure group were dissected. The activity of caspase 3, an important mediator of apoptosis, in OHC, was examined with carboxyfluorescein-labeled fluoromethyl ketone (FMK)-peptide inhibitors. The apoptosis inducing factor (AIF) translocation from mitochondria in OHC were further examined by immunohistology method. The nuclei were labeled with PI and the mitochondrion was labeled with Mito-tracker. Whole mount organ of Corti was prepared. Morphological and fluorescent change was observed use confocal microscope.

RESULTSIn the normal OHC, AIF is distributed where the mitochondria were located and no activated caspase 3 was observed. After the animals exposed to broadband noise at 122 dB in 4 h/day for 2 days, both apoptosis and necrosis were appeared in OHC. AIF translocated from mitochondrion to nuclei in apoptotic and necrotic OHC following noise exposure. The noise exposure triggered activation of caspase 3 in apoptic hair cells. But no caspase 3 activation appeared in necrotic OHC.

CONCLUSIONSThese findings indicated that the caspase-dependent pathway is an important pathway in noise exposure induced apoptosis. And AIF also involves OHC death pathway following noise exposure.

Animals ; Apoptosis ; Apoptosis Inducing Factor ; metabolism ; Caspase 3 ; metabolism ; Female ; Guinea Pigs ; Hair Cells, Auditory, Outer ; metabolism ; pathology ; Male ; Noise

OBJECTIVETo investigate the molecular mechanism of doxorubicin enhancement of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) inducing apoptotic effect on multiple myeloma cell line KM3.

METHODSApoptosis was studied independently through flow cytometry analysis and TUNEL staining. The expression of death receptor 5 (DR5) and nuclear factor P65 in nuclear was examined by Western blot.

RESULTSThe apoptosis ratio of KM3 cells was 20.88%, 40.03%, 57.87%, 60.82% respectively when treated with different concentration of TRAIL (10, 20, 50, 100 ng/ml) combining with doxorubicin. It is markedly higher than the group treated with TRAIL or doxorubicin alone. DR5 expression increased while P65 decreased as the doses of doxorubicin increased when KM3 cells treated with doxorubicin (0.5, 1.0, 2.0 and 4.0 microg/ml) plus 20 ng/ml TRAIL.

CONCLUSIONIncreasing the expression of DR5 and nuclear transferring of P65 are the important molecular mechanism by which doxorubicin enhances TRAIL-inducing apoptosis of KM3 cells.

Apoptosis ; drug effects ; Cell Line, Tumor ; Doxorubicin ; pharmacology ; Drug Interactions ; Humans ; Multiple Myeloma ; metabolism ; pathology ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; genetics ; metabolism ; TNF-Related Apoptosis-Inducing Ligand ; pharmacology ; Transcription Factor RelA ; genetics ; metabolism

OBJECTIVETo observe the expression of the C-terminal truncated human apoptosis-inducing factor (AIF) and its biological effect on MCF-7 cells.

METHODSPcDNA3.0-FDT-AIFδ1-480 was transfected into human breast carcinoma MCF-7 cells with lipofectamine. The expression of the truncated AIF gene was detected by Western blotting, and its effects on the biological behaviors of MCF-7 cells and on the expression of cytochrome c (cytC) were evaluated using flow cytometry, MTT assay, colony-forming assay, and mitochondrial membrane potential measurement.

RESULTSPcDNA3.0-FDT-AIFδ1-480 enhanced AIF expression in MCF-7 cells, obviously inhibited the cell proliferation, and significantly reduced the mitochondrial membrane potentials (P<0.05). Transfection of the cells with PcDNA3.0-FDT-AIFδ1-480 promoted the expression of cytC and resulted in significantly increased apoptosis of MCF-7 cells (P<0.05).

CONCLUSIONThe expression of C-terminal truncated human AIF gene can induce apoptosis of human MCF-7 cells by promoting cytC release from mitochondria.

Apoptosis ; Apoptosis Inducing Factor ; genetics ; metabolism ; Breast Neoplasms ; metabolism ; pathology ; Cell Proliferation ; Cytochromes c ; genetics ; metabolism ; Female ; Humans ; MCF-7 Cells ; Membrane Potential, Mitochondrial ; Mitochondria ; metabolism

OBJECTIVETo explore the enhanced sensitivity of leukemia cell line KG-1a to activated immune cell-mediated cytolysis after treated with resveratrol.

METHODSThe value of 50% inhibition concentration (IC₅₀) for KG-1a by resveratrol was analyzed using trypan blue staining. Peripheral blood mononuclear cells were separated, and then activated by interleukin (IL)-2 and IL-15. The sensitivity of KG-1a treated with and without resveratrol to activated immune cell-mediated cytolysis was assayed by lactate dehydrogenase (LDH) -releasing assay. The expression of tumor necrosis factor related apoptosis inducing ligand (TRAIL) on the surface of activated immune cells and its receptors (DR4/5 and DcR1/2) on the surface of KG-1a were detected by flow cytometry.

RESULTSResveratrol could inhibit the proliferation of KG-1a and IC50 at 24 h was 25 mmol/L. At a ratio of 10:1 or 20:1 between effect and target, the cytolytic rates of treated KG-1a by activated immune cells were (55.80 ± 10.88)% and (72.31 ± 13.06)%, significantly higher than (24.96 ± 9.25)% and (37.93 ± 5.21)% of untreated KG-1a (P<0.05). The expression of DR5 on the surface of KG-1a treated with resveratrol was (9.05 ± 3.57)%, significantly higher than (3.11 ± 0.54)% of untreated KG-1a (P<0.05). Conversely, the expression of DcR1 on the surface of treated KG-1a was (13.23 ± 3.56)%, lower than (53.75 ± 10.51)% of KG-1a (P<0.05). When TRAIL pathway on the surface of activated immune cells was blocked, the cytolytic rates of treated KG-1a were (35.97 ± 6.36)% and (49.80 ± 10.68)%, significantly lower than (52.92 ± 6.98)% and (70.73 ± 9.79)% of untreated KG-1a (P<0.05) at the same ratio of effector and target.

CONCLUSIONResveratrol could enhance cytolytic sensitivity of KG-1a by activated immune cells through TRAIL pathway.

Cell Line, Tumor ; Cell Proliferation ; drug effects ; Humans ; Leukemia ; metabolism ; pathology ; Leukocytes, Mononuclear ; drug effects ; immunology ; metabolism ; Male ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; metabolism ; Receptors, Tumor Necrosis Factor, Member 10c ; metabolism ; Stilbenes ; pharmacology ; TNF-Related Apoptosis-Inducing Ligand ; metabolism

OBJECTIVETo investigate the expression differences of apoptosis-inducing factor (AIF) and caspase-3 among colorectal carcinoma, adenoma and normal mucosa, and to identify the relationship between AIF and caspase-3 expression in colorectal adenoma-carcinoma sequence.

METHODSFormalin-fixed paraffin embedded colorectal tissues from 174 cases, including 84 adenomas, 72 carcinomas, and 18 normal mucosa, were examined for expression of AIF and caspase-3 by streptavidin-peroxidase (SP) immunohistochemistry.

RESULTSThe positive rates of AIF and caspase-3 in colorectal adenoma were higher than those in normal mucosa (P <0.05). The positive rate of AIF in adenoma showed no significant difference compared to colorectal carcinoma (P >0.05). However, caspase-3 expression in adenomas was significantly higher than that in carcinoma (P <0.05). The positive rate of AIF in tubular adenoma was significantly higher than that in villous adenoma (P <0.05), while the positive expression rate of caspase-3 in the two types of adenoma showed no significant difference (P >0.05). AIF expression had no prominent correlation with the caspase-3 expression (P >0.05).

CONCLUSIONSThe dysregulation of caspase-independent pathway of apoptosis may be an early event in the development of colorectal carcinogenesis, while the dysregulation of the caspase-dependent pathway of apoptosis may be one of contributing factors of colorectal carcinogenesis. The caspase-independent pathway of apoptosis and the caspase-dependent pathway of apoptosis are two relatively independent pathways in colorectal carcinogenesis.

Adenoma ; metabolism ; pathology ; Adult ; Aged ; Apoptosis Inducing Factor ; metabolism ; Caspase 3 ; metabolism ; Colorectal Neoplasms ; metabolism ; pathology ; Female ; Humans ; Intestinal Mucosa ; metabolism ; pathology ; Middle Aged ; Young Adult

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) induces apoptosis selectively in cancer cells while sparing normal cells. However, many cancer cells are resistant to TRAIL-induced cell death. Here, we report that paxilline, an indole alkaloid from Penicillium paxilli, can sensitize various glioma cells to TRAIL-mediated apoptosis. While treatment with TRAIL alone caused partial processing of caspase-3 to its p20 intermediate in TRAIL-resistant glioma cell lines, co-treatment with TRAIL and subtoxic doses of paxilline caused complete processing of caspase-3 into its active subunits. Paxilline treatment markedly upregulated DR5, a receptor of TRAIL, through a CHOP/GADD153-mediated process. In addition, paxilline treatment markedly downregulated the protein levels of the short form of the cellular FLICE-inhibitory protein (c-FLIPS) and the caspase inhibitor, survivin, through proteasome-mediated degradation. Taken together, these results show that paxilline effectively sensitizes glioma cells to TRAIL-mediated apoptosis by modulating multiple components of the death receptor-mediated apoptotic pathway. Interestingly, paxilline/TRAIL co-treatment did not induce apoptosis in normal astrocytes, nor did it affect the protein levels of CHOP, DR5 or survivin in these cells. Thus, combined treatment regimens involving paxilline and TRAIL may offer an attractive strategy for safely treating resistant gliomas.
Antineoplastic Agents/*pharmacology ; Apoptosis/*drug effects ; Astrocytes/metabolism ; CASP8 and FADD-Like Apoptosis Regulating Protein/genetics/*metabolism ; Caspase 3/metabolism ; Cell Line, Tumor ; Drug Discovery ; Flow Cytometry ; Glioma/*metabolism/pathology ; Humans ; Indoles/*pharmacology ; Inhibitor of Apoptosis Proteins/metabolism ; RNA, Small Interfering ; Receptors, TNF-Related Apoptosis-Inducing Ligand/genetics/metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; TNF-Related Apoptosis-Inducing Ligand/metabolism/*pharmacology ; Transcription Factor CHOP/analysis

OBJECTIVETo clone and identify novel proteins binding to the death domain of the death receptor 4 (DR4).

METHODSThe yeast two-hybrid system was used for this study. Automatic sequencing was carried out for DNA sequencing. The sequence homology and the functional domains were analyzed by BLAST and the ScanProsite Tool softwares, respectively. Co-immunoprecipitate method was used to confirm human formyl peptide receptor-like 1 (FPRL1) binding specifically with DR4CD (the cytoplasmic domain of DR4) in HEK293T cells.

RESULTSTwo positive clones, named as pADB1 and pADB2, were obtained. BLAST searching showed that the homology of the insert sequence of pADB1 with the mRNA of FPRL1 was 97%. The insert of pADB2 shared no homology with any known peptides in GeneBank. Co-immunoprecipitate analysis further confirmed that FPRL1 could bind to DR4CD in vivo specifically.

CONCLUSIONSFPRL1 may associate with DR4CD in vivo specifically. The functional studies of FPRL1 in signaling pathway mediated by TNF-related apoptosis inducing ligand (TRAIL) are in active progress in our laboratory.

Amino Acid Sequence ; Apoptosis ; Apoptosis Regulatory Proteins ; Base Sequence ; Carrier Proteins ; biosynthesis ; genetics ; Cloning, Molecular ; Humans ; Membrane Glycoproteins ; metabolism ; Molecular Sequence Data ; Protein Structure, Tertiary ; Receptors, Formyl Peptide ; metabolism ; Receptors, Lipoxin ; metabolism ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; Receptors, Tumor Necrosis Factor ; genetics ; metabolism ; Signal Transduction ; TNF-Related Apoptosis-Inducing Ligand ; Tumor Necrosis Factor-alpha ; metabolism

OBJECTIVETo investigate the correlation between sensitivity to tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and expression level of death receptor 5 (DR5) on tumor cell surface.

METHODSAnti-DR5 mAb was used to detect expression level of DR5 on surface of tumor cells by flow cytometry. Sensitivity to apoptosis induced by TRAIL was determined by TRAIL apoptosis kit. The correlation between expression level of DR5 and sensitivity to TRAIL was analyzed.

RESULTSThe expression of DR5 on surface of tumor cells was approximately 97.9% in U937 cells, 95.1% in Jurkat cells, 93.8% in SW480 cells, 86.2% in HCT116 cells, 64.2% in HL-60 cells, 46.6% in HeLa cells and 13.1% in K562 cells, respectively. The apoptosis rate induced by TRAIL was 72.6% in U937 cells, 85.2% in Jurkat cells, 78.6% in SW480 cells, 70.2% in HCT116 cells, 60.1% in HL-60 cells, 45.4% in HeLa cells and 12.3% in K562 cells, respectively. There was a significant positive correlation between the expression level of DR5 with TRAIL-inducing apoptosis (r = 0.997, P < 0.001).

CONCLUSIONTRAIL-inducing apoptosis is related to the expression level of DR5 on surface of tumor cells. The results confirm the importance of DR5 expression for induction of apoptosis by TRAIL.

Antibodies, Monoclonal ; immunology ; Apoptosis ; drug effects ; Apoptosis Regulatory Proteins ; metabolism ; pharmacology ; Cell Line, Tumor ; Humans ; Jurkat Cells ; Membrane Glycoproteins ; metabolism ; pharmacology ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; Receptors, Tumor Necrosis Factor ; immunology ; metabolism ; TNF-Related Apoptosis-Inducing Ligand ; Tumor Necrosis Factor-alpha ; metabolism ; pharmacology ; U937 Cells