AMPK inhibitor BML-275 induces neuroprotection through decreasing cyt c and AIF expression after transient brain ischemia.

Stroke is a major public health problem with an imperative need for a more effective and tolerated therapy. Neuroprotective therapy may be an effective therapeutic intervention for stroke. The morbidity and mortality of stroke-induced secondary brain injury is mainly caused by neuronal apoptosis, which can be executed in a caspase-dependent or apoptosis inducing factor (AIF)-dependent manner. As apoptosis is an energy-dependent process with a relative time delay, abnormal energy metabolism could be a significant and fundamental pathophysiological basis of stroke. To our knowledge, convincible evidences that AMPK inhibition exerts neuroprotection in cerebral ischemia injury via anti-apoptosis remain to be investigated. Accordingly, the aims of this study were to investigate the protective effects of AMPK inhibitor BML-275 on cerebral ischemic/reperfusion (I/R) injury and to elucidate the underlying mechanisms. Cerebral ischemia was induced by transient middle cerebral artery occlusion (tMCAO) in male C57BL/6 mice. The therapeutic effects of BML-275 were evaluated by infarct sizes, neurological scores and the proportion of apoptotic neurons after 24 h of reperfusion. The cell apoptosis markers cyt c and AIF were also evaluated. The results showed that intraperitoneally administration of BML-275 alleviate the cerebral infarction, neurological deficit and neuronal apoptosis induced by MCAO. BML-275 simultaneously induces anti-apoptosis and decreases the expression of cyt c and AIF. This study supports the hypothesis that anti-apoptosis is one of potential neuroprotective strategies for the treatment of stroke.

Cyclophilin D Regulates the Nuclear Translocation of AIF, Cardiac Endothelial Cell Necroptosis and Murine Cardiac Transplant Injury.

Ischemia-reperfusion injury (IRI) is an inevitable consequence of organ transplant procedure and associated with acute and chronic organ rejection in transplantation. IRI leads to various forms of programmed cell death, which worsens tissue damage and accelerates transplant rejection. We recently demonstrated that necroptosis participates in murine cardiac microvascular endothelial cell (MVEC) death and murine cardiac transplant rejection. However, MVEC death under a more complex IRI model has not been studied. In this study, we found that simulating IRI conditions in vitro by hypoxia, reoxygenation and treatment with inflammatory cytokines induced necroptosis in MVECs. Interestingly, the apoptosis-inducing factor (AIF) translocated to the nucleus during MVEC necroptosis, which is regulated by the mitochondrial permeability molecule cyclophilin D (CypD). Furthermore, CypD deficiency in donor cardiac grafts inhibited AIF translocation and mitigated graft IRI and rejection (n = 7; p = 0.002). Our studies indicate that CypD and AIF play significant roles in MVEC necroptosis and cardiac transplant rejection following IRI. Targeting CypD and its downstream AIF may be a plausible approach to inhibit IRI-caused cardiac damage and improve transplant survival.

Bisphenol a Induces Autophagy Defects and AIF-Dependent Apoptosis via HO-1 and AMPK to Degenerate N2a Neurons.

Bisphenol A (BPA) is an environmental contaminant widely suspected to be a neurological toxicant. Epidemiological studies have demonstrated close links between BPA exposure, pathogenetic brain degeneration, and altered neurobehaviors, considering BPA a risk factor for cognitive dysfunction. However, the mechanisms of BPA resulting in neurodegeneration remain unclear. Herein, cultured N2a neurons were subjected to BPA treatment, and neurotoxicity was assessed using neuronal viability and differentiation assays. Signaling cascades related to cellular self-degradation were also evaluated. BPA decreased cell viability and axon outgrowth (e.g., by down-regulating MAP2 and GAP43), thus confirming its role as a neurotoxicant. BPA induced neurotoxicity by down-regulating Bcl-2 and initiating apoptosis and autophagy flux inhibition (featured by nuclear translocation of apoptosis-inducing factor (AIF), light chain 3B (LC3B) aggregation, and p62 accumulation). Both heme oxygenase (HO)-1 and AMP-activated protein kinase (AMPK) up-regulated/activated by BPA mediated the molecular signalings involved in apoptosis and autophagy. HO-1 inhibition or AIF silencing effectively reduced BPA-induced neuronal death. Although BPA elicited intracellular oxygen free radical production, ROS scavenger NAC exerted no effect against BPA insults. These results suggest that BPA induces N2a neurotoxicity characterized by AIF-dependent apoptosis and p62-related autophagy defects via HO-1 up-regulation and AMPK activation, thereby resulting in neuronal degeneration.

Baicalein attenuates caspase-independent cells death via inhibiting PARP-1 activation and AIF nuclear translocation in cerebral ischemia/reperfusion rats.

It is reported that baicalein can activate PI3K/AKT pathway, inhibit caspase activation and reduce cerebral infarct volume in middle cerebral artery occlusion (MCAO) rats. However, a caspase-independent mechanism initiated by poly (ADP-ribose) polymerase-1 (PARP-1) activation has been reported to make more contribution to cells death after ischemic stroke. In the present study, we established a cerebral ischemia/reperfusion (I/R) rat model through middle cerebral artery occlusion following reperfusion to investigate the mechanisms of ischemic tissue recovery following baicalein treatment. The data showed that baicalein treatment at dose of 100 mg/kg for 7 days significantly inhibited the release of cytokines, activation of PARP-1, nuclear translocation of apoptosis-inducing factor (AIF) and macrophage migration inhibitory factor (MIF) in cerebral I/R rats, therefore decreased cerebral infarct volume and neurological scores. Then, we further investigated the signal transduction mechanisms of ischemic tissue protection by baicalein in vitro. Following oxygen and glucose deprivation (OGD) in SH-SY5Y cells, the mitochondrial AIF was translocated into nucleus after 12 h. The co-immunoprecipitation analysis showed that the interaction between AIF and MIF was activated by OGD and subsequently resulted in MIF nuclear translocation. Also, the baicalein inhibited apoptosis, reduced oxidative stress, protected mitochondrial function and restored mitochondrial membrane potential in OGD cells. The results obtained from both in vivo and in vitro study demonstrated the PARP-1/AIF pathway involved in mechanisms of baicalein to protect the cerebral tissues from ischemic injury.

Caspase-Independent Pathway is Related to Nilotinib Cytotoxicity in Cultured Cardiomyocytes.

BACKGROUND/AIMS: Cardiotoxicity is a predominant side-effect of nilotinib during chronic myeloid leukemia treatment. The underlying molecular mechanism remains unclear. The role of autophagy and mitochondrial signaling was investigated in nilotinib-treated cardiac H9C2 cells. METHODS: Cytotoxicity was assessed using Cell Death Detection kit. Immunoblot and immunofluorescence staining was performed, and cathepsin B and caspase3 activity was assessed in nilotinib-treated H9C2 cells with or without distinct pathway inhibitor or specific siRNA. RESULTS: Nilotinib time- and dose-dependently induced H9C2 apoptosis, which was not completely prevented by the pan caspase inhibitor z-VAD-fmk. Following nilotinib treatment, mitochondrial membrane potential decreased significantly accompanied with remarkable morphological changes. Nuclear translocation of mitochondrial apoptosis inducing factor (AIF) and increased p53 was detected in nilotinib-treated cells. AIF knockdown prevented nilotinib-induced increase of p53 and apoptosis. Additionally, increased cathepsin B activity was detected, and inhibition of cathepsin B by CA-074Me prevented nilotinib-induced apoptosis and nuclear translocation of AIF. Moreover, increased Atg5 and transition of LC3-I to LC3-II was revealed following nilotinib treatment. Increased cathepsin B activity and apoptosis by nilotinib was significantly prohibited by specific autophagy inhibitor bafilomycin A and Atg5 knockdown. CONCLUSION: Our findings demonstrate that nilotinib increases autophagy and cathepsin B activity, leading to mitochondrial AIF release and nuclear translocation, which is responsible for p53 and apoptosis induction in H9C2 cells.

Caspase-independent cell death mediated by apoptosis-inducing factor (AIF) nuclear translocation is involved in ionizing radiation induced HepG2 cell death.

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world. The aim of radiotherapy is to eradicate cancer cells with ionizing radiation. Except for the caspase-dependent mechanism, several lines of evidence demonstrated that caspase-independent mechanism is directly involved in the cell death responding to irradiation. For this reason, defining the contribution of caspase-independent molecular mechanisms represents the main goal in radiotherapy. In this study, we focused on the role of apoptosis-inducing factor (AIF), the caspase-independent molecular, in ionizing radiation induced hepatocellular carcinoma cell line (HepG2) cell death. We found that ionizing radiation has no function on AIF expression in HepG2 cells, but could induce AIF release from the mitochondria and translocate into nuclei. Inhibition of AIF could reduce ionizing radiation induced HepG2 cell death. These studies strongly support a direct relationship between AIF nuclear translocation and radiation induced cell death. What's more, AIF nuclear translocation is caspase-independent manner, but not caspase-dependent manner, in this process. These new findings add a further attractive point of investigation to better define the complex interplay between caspase-independent cell death and radiation therapy.

The protection of rat retinal ganglion cells from ischemia/reperfusion injury by the inhibitory peptide of mitochondrial µ-calpain.

Intracellular Ca(2+)-dependent cysteine proteases such as calpains have been suggested as critical factors in retinal ganglion cell (RGC) death. However, it is unknown whether mitochondrial calpains are involved in RGC death. The purpose of the present study was to determine whether the inhibition of mitochondrial µ-calpain activity protects against RGC death during ischemia/reperfusion (I/R) injury. This study used a well-established rat model of experimental acute glaucoma involving I/R injury. A specific peptide inhibitor of mitochondrial µ-calpain, Tat-µCL, was topically applied to rats via eye drops three times a day for 5 days after I/R. RGC death was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The truncation of apoptosis-inducing factor (AIF) was determined by western blot analyses. Retinal morphology was determined after staining with hematoxyline and eosin. In addition, the number of Fluoro Gold-labeled RGCs in flat-mounted retinas was used to determine the percentage of surviving RGCs after I/R injury. After 1 day of I/R, RGC death was observed in the ganglion cell layer. Treatment with Tat-µCL eye drops significantly prevented the death of RGCs and the truncation of AIF. After 5 days of I/R, RGC death decreased by approximately 40%. However, Tat-µCL significantly inhibited the decrease in the retinal sections and flat-mounted retinas. The results suggested that mitochondrial µ-calpain is associated with RGC death during I/R injury via truncation of AIF. In addition, the inhibition of mitochondrial µ-calpain activity by Tat-µCL had a neuroprotective effect against I/R-induced RGC death.

Basal metabolic state governs AIF-dependent growth support in pancreatic cancer cells.

BACKGROUND: Apoptosis-inducing factor (AIF), named for its involvement in cell death pathways, is a mitochondrial protein that regulates metabolic homeostasis. In addition to supporting the survival of healthy cells, AIF also plays a contributory role to the development of cancer through its enzymatic activity, and we have previously shown that AIF preferentially supports advanced-stage prostate cancer cells. Here we further evaluated the role of AIF in tumorigenesis by exploring its function in pancreatic cancer, a disease setting that most often presents at an advanced stage by the time of diagnosis. METHODS: A bioinformatics approach was first employed to investigate AIF mRNA transcript levels in pancreatic tumor specimens vs. normal tissues. AIF-deficient pancreatic cancer cell lines were then established via lentiviral infection. Immunoblot analysis was used to determine relative protein quantities within cells. Cell viability was measured by flow cytometry; in vitro and Matrigel™ growth/survival using Coulter™ counting and phase contrast microscopy; and glucose consumption in the absence and presence of Matrigel™ using spectrophotometric methods. RESULTS: Archival gene expression data revealed a modest elevation of AIF transcript levels in subsets of pancreatic tumor specimens, suggesting a possible role in disease progression. AIF expression was then suppressed in a panel of five pancreatic cancer cell lines that display diverse metabolic phenotypes. AIF ablation selectively crippled the growth of cells in vitro in a manner that directly correlated with the loss of mitochondrial respiratory chain subunits and altered glucose metabolism, and these effects were exacerbated in the presence of Matrigel™ substrate. This suggests a critical metabolic role for AIF to pancreatic tumorigenesis, while the spectrum of sensitivities to AIF ablation depends on basal cellular metabolic phenotypes. CONCLUSIONS: Altogether these data indicate that AIF supports the growth and survival of metabolically defined pancreatic cancer cells and that this metabolic function may derive from a novel mechanism so far undocumented in other cancer types.

Inhibition of cysteine cathepsin B and L activation in astrocytes contributes to neuroprotection against cerebral ischemia via blocking the tBid-mitochondrial apoptotic signaling pathway.

The roles of cathepsins in the ischemic astrocytic injury remain unclear. Here, we test the hypothesis that activation of cathepsin B and L contributes to the ischemic astrocyte injury via the tBid-mitochondrial apoptotic signaling pathways. In the rat models of pMCAO, CA-074Me or Clik148, a selective inhibitor of cathepsin B or cathepsin L, reduced the infarct volume, improved the neurological deficits and increased the MAP2 and GFAP levels. In OGD-induced astrocyte injury, CA-074Me or Clik148 decreased the LDH leakage and increased the GFAP levels. In the ischemic cortex or OGD-induced astrocytes injury, Clik148 or CA-074Me reversed pMCAO or OGD-induced increase in active cathepsin L or cathepsin B at 3 h or 6 h, increase in tBid, reduction in mitochondrial cytochrome-c (Cyt-c) and increase in cytoplastic Cyt-c and active caspase-3 at 12-24 h of the late stage of pMCAO or OGD. CA-074Me or Clik148 also reduced cytosolic and mitochondrial tBid, increased mitochondrial Cyt-c and decreased cytoplastic Cyt-c and active caspase-3 at 6 h of the early stage of Bid activation. CA-074Me or Clik148 blocked the pMCAO-induced release of cathepsin B or L from the lysosomes into the cytoplasm and activation of caspase-3 in ischemic astrocytes at 12 h after ischemia. Concurrent inhibition of cathepsin B and cathepsin L provided better protection on the OGD-induced astrocytic apoptosis than obtained with separate use of each inhibitor. These results suggest that inhibition of the cysteine cathepsin B and cathepsin L activation in ischemic astrocytes contributes to neuroprotection via blocking the tBid-mitochondrial apoptotic signaling pathway.

Ginsenoside Rb1 attenuates oxygen-glucose deprivation-induced apoptosis in SH-SY5Y cells via protection of mitochondria and inhibition of AIF and cytochrome c release.

To investigate the role of mitochondria in the protective effects of ginsenoside Rb1 on cellular apoptosis caused by oxygen-glucose deprivation, in this study, MTT assay, TUNEL staining, flow cytometry, immunocytochemistry and western blotting were used to examine the cellular viability, apoptosis, ROS level, mitochondrial membrane potential, and the distribution of apoptosis inducing factor, cytochrome c, Bax and Bcl-2 in nucleus, mitochondria and cytoplasm. We found that pretreatment with GRb1 improved the cellular viability damaged by OGD. Moreover, GRb1 inhibited apoptosis in SH-SY5Y cells induced by OGD. Further studies showed that the elevation of cellular reactive oxygen species levels and the reduction of mitochondrial membrane potential caused by OGD were both counteracted by GRb1. Additionally, GRb1 not only suppressed the translocation of apoptosis inducing factor into nucleus and cytochrome c into cytoplasm, but also inhibited the increase of Bax within mitochondria and alleviated the decrease of mitochondrial Bcl-2. Our study indicates that the protection of GRb1 on OGD-induced apoptosis in SH-SY5Y cells is associated with its protection on mitochondrial function and inhibition of release of AIF and cytochrome c.

A novel cyano derivative of 11-keto-ß-boswellic acid causes apoptotic death by disrupting PI3K/AKT/Hsp-90 cascade, mitochondrial integrity, and other cell survival signaling events in HL-60 cells.

Intervention of apoptosis is a promising strategy for discovery of novel anti-cancer therapeutics. In this study, we examined the ability of a novel cyano derivative of 11-keto-ß-boswellic acid, that is, butyl 2-cyano-3,11-dioxours-1,12-dien-24-oate (BCDD) to induce apoptosis in cancer cells. BCDD inhibited cell proliferation with 48 h IC(50) of 0.67 µM in HL-60, 1 µM in Molt4, and 1.5 µM in THP1 cells. The mechanism of cell death was investigated in HL-60 cells where it caused apoptosis by acting against several potential apoptosis suppressive targets. It inhibited phosphatidylinositol-3-kinase (PI3K)/AKT activity, NF-κB, Hsp-90, and survivin which may enhance the sensitivity of cells to apoptosis. Also, BCDD decreased the activity of Bid and Bax in cytosol, caused ΔΨ(mt) loss, releasing pro-apoptotic cytochrome c, SMAC/DIABLO leading to caspase-9-mediated down stream activation of caspase-3, ICAD, and PARP1 cleavage. Translocation of apoptotis-inducing factor (AIF) from mitochondria to the nucleus indicated some caspases-independent apoptosis. Though it upregulated DR-5 and caspase-8, the caspase inhibitor yet had no effect on apoptosis as against 75% inhibition by caspase-9 inhibitor. Attempts were made to examine any acclaimed role of AIF in the activation of caspase-8 using siRNA where it had no effect on caspase-8 activity while the Bax-siRNA inhibited caspase-3 activation suggesting predominance of intrinsic signaling. Our studies thus demonstrated that BCDD exerts multi-focal action in cancer cells while it required 10-fold higher the concentration to produce cytotoxicity in normal human PBMC and gingival cell line, and therefore, may find usefulness in the management of human leukemia.

[Cycloferon: mechanism of action, functions and application].

In recent years, both interferons and inductors of endogenous interferon production find increasing use in clinical practice. The latter agents are characterized by high antiviral and immunomodulatory activity in the absence of serious side effects, which makes it possible to prescribe long courses if necessary. One of the most frequently used interferon inductors is cycloferon. Diverse effects of cycloferon on biochemical and cellular cascades (including induction of alpha- and beta-interferon, inhibition ofproapoptotic factors such as tumor necrosis factor and interleukin 1-beta) suggest that it also takes active part in the regulation of apoptosis, one of the most important processes of cell activity that opens up new prospects for the therapeutic use of cycloferon.

Flagellin administration protects gut mucosal tissue from irradiation-induced apoptosis via MKP-7 activity.

BACKGROUND AND AIMS: Radiotherapy for neoplastic disease is associated with significant adverse enteric effects associated with excessive cell death. Ionising radiation induces cell death by a mechanism that is dependent on JNK (c-jun N-terminal kinase) pathway signalling. Additionally, it is known that cells exposed to extracellular bacterial products such as flagellin, pleiotropically activate a number of innate immune pathways, including that of JNK. The JNK pathway controls its own activity by inducing the transcription of mitogen-activated protein kinase phosphatase-7 (MKP-7) which directly targets phosphorylated JNK, thus functioning as a negative feedback loop. Previously, it has been shown that flagellin limits ionising radiation-induced mortality in mice, but the cellular mechanism of protection remained unknown. METHODS: Wild-type C57BL/6 or tlr5(-/-) C57BL/6 were injected with flagellin 2 h before exposure to irradiation, and their intestines were examined for apoptosis. Candidate proteins mediating cytoprotection from irradiation were identified by expression profiling. One of these candidates, MKP-7, was cloned and packaged into adenovirus particles, used to infect cultured cells, and examined for the extent to which its activity reduced cellular apoptosis by flow cytometry or immunoblot analysis. RESULTS: Flagellin pretreatment protected mice from radiation-induced intestinal mucosal injury and apoptosis via a Toll-like receptor 5 (TLR5)-dependent mechanism. Expression profiling of flagellin-treated mice showed upregulation of MKP-7, an inducible repressor of the JNK pathway. MKP-7 expression reached a maximum at 2 h after flagellin treatment, coinciding with suppression of phosphorylated JNK and JNK pathway inhibition. Furthermore, constitutive MKP-7 expression protected cultured cells from radiation-induced apoptosis. CONCLUSIONS: Flagellin is a promising adjuvant for suppressing ionising radiation-induced injury. MKP-7 activity exhibits cytoprotective effects, and is thus a candidate cellular molecule for limiting the damaging effect of radiotherapy on the gastreointestinal system.

Apoptosis-inducing factor mediates dopaminergic cell death in response to LPS-induced inflammatory stimulus: evidence in Parkinson's disease patients.

We show that intranigral lipopolysaccharide (LPS) injection, which provokes specific degeneration of DA neurons, induced caspase-3 activation in the rat ventral mesencephalon, which was mostly associated with glial cells. In contrast, nigral DA neurons exhibited AIF nuclear translocation in response to LPS. A significant decrease of the Bcl-2/Bax ratio in nigral tissue after LPS injection was observed. We next developed an in vitro co-culture system with the microglial BV2 and the DA neuronal MN9D murine cell lines. The silencing of caspase-3 or AIF by small interfering RNAs exclusively in the DA MN9D cells demonstrated the key role of AIF in the LPS-induced death of DA cells. In vivo chemical inhibition of caspases and poly(ADP-ribose)polymerase-1, an upstream regulator of AIF release and calpain, proved the central role of the AIF-dependent pathway in LPS-induced nigral DA cell death. We also observed nuclear translocation of AIF in the ventral mesencephalon of Parkinson's disease subjects.

Visible light may directly induce nuclear DNA damage triggering the death pathway in RGC-5 cells.

PURPOSE: Visible light has been previously demonstrated to induce retinal ganglion cell (RGC)-5 cell death through the mitochondrial pathway. The present study was designed to determine whether visible light might also directly trigger the death pathway by damaging nuclear DNA. METHODS: RGC-5 cells were exposed to various intensities and durations of visible light exposure. Cell viability and death were monitored with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and propidium iodide staining. Nuclear DNA damage caused by light was determined with the plasmid assay, genome DNA assay, and in situ terminal deoxynucleotidyl transferase dUTP nick end labeling. The subsequent activation of nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) was measured with western blot, and PARP-1's role in the death pathway was assessed by using specific inhibitors. Poly (ADP-ribose) glycohydrolase and apoptosis-inducing factor (AIF) inhibitors were used to show their influence on light-induced cell death. Calcium influx was examined with the fura-2 assay and calcium channel blocker. RESULTS: We found that visible light induced RGC-5 cell death in a time- and intensity-dependent manner. After the light intensity was increased to 2,600 lx, activation of the death pathway in RGC-5 cells was clearly observed by detecting double-strand DNA breaks and nuclear DNA damage in vitro. Nuclear enzyme PARP-1 was promptly activated after exposure to 2,600 lx of light for 2 days, and specific inhibitors of PARP-1 had significant neuroprotective effects. The poly(ADP-ribose) glycohydrolase inhibitor tannic acid and AIF inhibitor N-phenylmaleimide partially protected RGC-5 cells from light injury. A massive calcium influx was detected after 2 days of light exposure, and a calcium channel blocker partially protected cells against light injury. CONCLUSIONS: These results suggest that visible light exposure may directly cause nuclear DNA damage, which consequently activates PARP-1. In addition, RGC-5 cells damaged by 2,600 lx of light exposure can be used as an appropriate cell death model for screening neuroprotective drugs, since this treatment induced remarkable cell death within 2 days. Moreover, these results show that 2,600 lx of light exposure provides a more apparent activation of the death pathway than 1,000 lx of light exposure, which was used in a previous study.

PAK5-mediated AIF phosphorylation inhibits its nuclear translocation and promotes breast cancer tumorigenesis.

Although p21 activated kinase 5 (PAK5) is related to the progression of multiple cancers, its biological function in breast cancer remains unclear. Apoptosis-inducing factor (AIF) is a vital apoptosis factor in mitochondria, which can be released from mitochondria and enter the nucleus, causing caspase-independent apoptosis. In this study, we reveal that PAK5 inhibits apoptosis by preventing the nuclear translocation of AIF. PAK5 inhibits the release of AIF from mitochondria in breast cancer cells by decreasing the mitochondria membrane permeability and increasing the membrane potential. Furthermore, PAK5 phosphorylates AIF at Thr281 site to inhibit the formation of AIF/importin α3 complex, leading to decrease AIF nuclear translocation. Functionally, we demonstrate that PAK5-mediated AIF phosphorylation promotes the proliferation of breast cancer cells and accelerates the growth of breast cancer in vivo. Significantly, PAK5 and AIF expression in breast cancer are positively correlated with poor patient prognosis. PAK5 expression is negatively correlated with AIF nuclear translocation. These results suggest that PAK5-AIF signaling pathway may play an essential role in mammary tumorigenesis, providing a new therapeutic target for the treatment of breast cancer.

C9orf72 regulates energy homeostasis by stabilizing mitochondrial complex I assembly.

The haploinsufficiency of C9orf72 is implicated in the most common forms of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), but the full spectrum of C9orf72 functions remains to be established. Here, we report that C9orf72 is a mitochondrial inner-membrane-associated protein regulating cellular energy homeostasis via its critical role in the control of oxidative phosphorylation (OXPHOS). The translocation of C9orf72 from the cytosol to the inter-membrane space is mediated by the redox-sensitive AIFM1/CHCHD4 pathway. In mitochondria, C9orf72 specifically stabilizes translocase of inner mitochondrial membrane domain containing 1 (TIMMDC1), a crucial factor for the assembly of OXPHOS complex I. C9orf72 directly recruits the prohibitin complex to inhibit the m-AAA protease-dependent degradation of TIMMDC1. The mitochondrial complex I function is impaired in C9orf72-linked ALS/FTD patient-derived neurons. These results reveal a previously unknown function of C9orf72 in mitochondria and suggest that defective energy metabolism may underlie the pathogenesis of relevant diseases.

Inhibiting the interaction between apoptosis-inducing factor and cyclophilin A prevents brain injury in neonatal mice after hypoxia-ischemia.

The interaction between apoptosis-inducing factor (AIF) and cyclophilin A (CypA) has been shown to contribute to caspase-independent apoptosis. Blocking the AIF/CypA interaction protects against glutamate-induced neuronal cell death in vitro, and the purpose of this study was to determine the in vivo effect of an AIF/CypA interaction blocking peptide (AIF(370-394)-TAT) on neonatal mouse brain injury after hypoxia-ischemia (HI). The pups were treated with AIF (370-394)-TAT peptide intranasally prior to HI. Brain injury was significantly reduced at 72 h after HI in the AIF(370-394)-TAT peptide treatment group compared to vehicle-only treatment for both the gray matter and the subcortical white matter, and the neuroprotection was more pronounced in males than in females. Neuronal cell death was evaluated in males at 8 h and 24 h post-HI, and it was decreased significantly in the CA1 region of the hippocampus and the nucleus habenularis region after AIF(370-394)-TAT treatment. Caspase-independent apoptosis was decreased in the cortex, striatum, and nucleus habenularis after AIF(370-394)-TAT treatment, but no significant change was found on caspase-dependent apoptosis as indicated by the number of active caspase-3-labeled cells. Further analysis showed that both AIF and CypA nuclear accumulation were decreased after treatment with the AIF(370-394)-TAT peptide. These results suggest that AIF(370-394)-TAT inhibited AIF/CypA translocation to the nucleus and reduced HI-induced caspase-independent apoptosis and brain injury in young male mice, suggesting that blocking AIF/CypA might be a potential therapeutic target for neonatal brain injury.

Down-regulation of the apoptosis-inducing factor or Bcl-2 inhibitor of transcription by RNA interference can alleviate TAp63gamma-induced apoptosis in esophageal squamous carcinoma EC9706 cells.

In this communication, the roles of apoptosis-inducing factor (AIF) and Bcl-2 inhibitor of transcription (Bit1) in TAp63gamma-induced apoptosis were investigated in human esophageal squamous cancer EC9706 cells. Positive RNA and protein expressions of AIF and Bit1 in these cells were verified. However, no TAp63gamma could be detected. Transfection of expression vector pcDNA3.1-TAp63gamma into EC9706 resulted in TAp63gamma expression, and peak level apoptosis was observed 24 h after the transfection disclosed by DNA fragmentation assay. In addition, it was found with Western blot that AIF and Bit1 were released into cytosol from mitochondria, and AIF was further translocated into nucleus, during the stage of TAp63gamma-induced cell apoptosis. Down-regulation of either AIF or Bit1 by RNA interference could, however, alleviate TAp63gamma-induced cell apoptosis. In conclusion, TAp63gamma could induce apoptosis in human esophageal squamous cancer EC9706 cells, through at least releasing AIF and Bit1 from mitochindria into cytosol and nucleus, where apoptotic cascade takes place. These findings indicate that mitochondria-released proapoptotic proteins, AIF and Bit1, are important factors in a TAp63gamma-induced EC9706 cell apoptosis pathway.

Cell adhesion to fibronectin induces mitomycin C resistance in bladder cancer cells.

OBJECTIVE: To investigate whether cell adhesion to fibronectin induces drug resistance in human bladder cancer cells, and to study the survival signalling pathway in cell adhesion to fibronectin-mediated chemotherapy resistance in vitro. MATERIALS AND METHODS: T24 cells (human bladder cancer cell lines) were pre-coated with fibronectin, and treated with mitomycin C (MMC) and the specific phosphoinositide-3 kinase (PI3-K) inhibitor LY294002. The apoptosis and cell cycles were analysed. The activity of the caspase-8, -9 and apoptosis-inducing factor (AIF) apoptosis pathways were assessed using colorimetric assay, immunofluorescence, Western blot and flow cytometry. The expression of glycogen synthase kinase-3beta (GSK-3beta) and cyclin D1, as the key regulator of G1/S phase transition, were determined by Western blot. The expression of PI3-K, Akt, phospho-Akt and beta1-integrin were also examined by Western blot. RESULTS: Apoptosis induced by MMC was significantly resisted by fibronectin adhesion in T24 cells, and this effect was through inhibition of the caspase-9 and AIF apoptosis pathways, but not the caspase-8 pathway. Fibronectin antagonized MMC-induced G0/G1-phase arrest by inactivating GSK-3beta to stabilize cyclin D1 expression in T24 cells. Furthermore, fibronectin-mediated protection of T24 cells was dependent on the activity of the PI3-K/Akt signalling pathway, and the protection could be abolished by the PI3-K inhibitor LY294002. CONCLUSIONS: Fibronectin-mediated PI3-K/Akt activation protects T24 cells from MMC-induced cell death through inhibition of both caspase-9 and AIF-mediated apoptosis and GSK-3beta/cyclin D1 involved G0/G1-phase arrest.