Prolonged classical NF-kappaB activation prevents autophagy upon E. coli stimulation in vitro: a potential resolving mechanism of inflammation. Mediators Inflamm. 2008;2008:725854. [PMID: 18566685 PMCID: PMC2430012 DOI: 10.1155/2008/725854]

Carvedilol induces pyroptosis through NLRP3-caspase1-ASC inflammasome by nuclear migration of NF-κB in prostate cancer models

BACKGROUND

Pyroptosis is an inflammatory type of programmed cell death, and could overcome the drug-resistance induced by anti-apoptotic effect of cancers. Carvedilol (CVL), a β-adrenergic receptors antagonist, has shown anti-inflammatory response and anti-cancer effect. The aim of this study is to investigate whether pyroptosis can be activated by CVL in prostate cancer (PCa).

METHODS AND RESULTS

Datasets were used to analyze the expressions of pyroptosis-related proteins. Intracellular morphological change, cell viability, LDH and Il-1β release by cells,, and Hoechst/PI staining were used to detect the occurrence of pyroptosis. Realtime-PCR, western blot, immunofluorescence, and immunohistochemistry (IHC) were used to investigate the expressions of pyroptosis-related proteins. Datasets analyze showed the expressions of NLRP3, Caspase 1, ASC and GSDMD were all decreased in PCa comparing with normal tissues, but without prognostic significance. CVL treatment weakened the viabilities of PCa cells. Cell morphology changing, cytoplasmic vacuole formation, membrane integrity loss, LDH and IL-1β release and PI positive cells increasing were observed. NLRP3, Caspase 1, ASC, GSDMD and N-GSDMD expressions were elevated after CVL treatment, accompanied by a tendency of NF-κB transferring into nucleus. In vivo, CVL inhibited the growth of subcutaneous transplanted tumor. IHC showed CVL increased the expressions of NLRP3, ASC, and GSDMD, and decreased the expression of Ki-67 in transplanted tumor tissues.

CONCLUSION

This study demonstrated that CVL could induce pyroptosis in PCa cells through NLRP3-caspase1-ASC inflammasome by promoting nuclear translocation of NF-κB, which would lay a foundation for the application of adrenergic receptor antagonist in PCa.

Antidepressant mechanisms of ketamine's action: NF-κB in the spotlight

Ketamine recently approved for therapy of treatment-resistant depression shows a complex and not fully understood mechanism of action. Apart from its classical glutamatergic N-methyl-D-aspartate receptor antagonistic action, it is thought that anti-inflammatory properties of the drug are of clinical relevance due to the contribution of activated inflammatory mediators to the pathophysiology of depression and non-responsiveness of a group of patients to current antidepressant therapies. In a search of the mechanism underlying anti-inflammatory effects of ketamine, the nuclear factor kappa B transcription factor (NF-κB) has been proposed as a target for ketamine. The NF-κB forms precisely regulated protein signaling cascades enabling a rapid response to cellular stimuli. In the central nervous systems, NF-κB signaling appears to have pleiotropic but double-edged functions: on the one hand it participates in the regulation of processes that are crucial in the treatment of depression, such as neuroplasticity, neurogenesis or neuronal survival, on the other - in the activation of neuroinflammation and cell death. Ketamine has been found to reduce inflammation mediated by NF-κB, leading to decreased level of pro-inflammatory cytokines and other inflammatory or stress mediators. Therefore, this review presents recent data on the significance of the NF-κB cascade in the mechanism of ketamine's action and its future perspectives in designing new strategies for the treatment of depression.

Mollugin prevents CLP-induced sepsis in mice by inhibiting TAK1-NF-κB/MAPKs pathways and activating Keap1-Nrf2 pathway in macrophages

Sepsis is a life-threatening organ dysfunction associated with macrophage overactivation. Targeted therapy against macrophages is considered a promising strategy for sepsis treatment. Mollugin (MLG), a compound extracted from traditional Chinese medicine Rubia cordifolia L., possesses anti-tumor and anti-inflammatory activities. This study aimed to investigate the anti-inflammatory effects and mechanisms of MLG in macrophages and its therapeutic role in CLP-induced sepsis in mice. The results demonstrated that MLG downregulated the inflammatory response induced by LPS or tumor necrosis factor α (TNF-α) in macrophages. Mechanistically, MLG suppressed the phosphorylation of TAK1, the upstream modulator of IKKα/β and MAPKs, thereby inhibiting the pro-inflammatory signaling transduction of NF-κB and MAPKs. Additionally, MLG also activated the Nrf2 antioxidant pathway, reducing intracellular reactive oxygen species. CETSA and molecular docking analyses revealed that MLG could effectively bind to TAK1 and Keap1, which may be involved in the inhibition of TAK1- NF-κB/MAPKs and activation of Nrf2 mediated by MLG. Animal study demonstrated that MLG ameliorated inflammatory injury of lung and liver in CLP-induced sepsis mice probably by reducing the levels of pro-inflammatory cytokines. Therefore, our study suggests that bi-directional roles of MLG in improving sepsis via blocking the TAK1-NF-κB/MAPKs and activating Nrf2 pathways, indicating its potential as a promising candidate drug for sepsis treatment.

Green Synthesized Silver Nanoparticles-Mediated Cytotoxic Effect in Colorectal Cancer Cells: NF-κB Signal Induced Apoptosis Through Autophagy

Green synthesized silver nanoparticles (Ag-NPs) have demonstrated promising effects, including cytotoxicity and anticancer potential, in different cell lines. Therefore, in our previous study, Ag-NPs were synthesized from the reduction of AgNO₃ using Brassica rapa var. japonica (Bj) leaf extract as a reducing and stabilizing agent. The synthesized Ag-NPs were spherical in shape, with a size range of 15-30 nm. They had phase-centered cubic structure with strong growth inhibition potential against some bacteria. In continuation with our previous study, in the present study, we aimed to investigate the autophagy-regulated cytotoxic effect of Ag-NPs against human epithelial colorectal adenocarcinoma cells (Caco-2 cells). We found that the Bj leaf aqueous extract facilitated Brassica silver nanoparticles (Brassica Ag-NPs)-induced NF-κB mediated autophagy in Caco-2 cells. Results showed that Ag-NPs reduced cell viability of Caco-2 cells by inducing oxidative stress and DNA damage. Therefore, to understand the mechanism underlying the death-promoting activity of Ag-NPs in Caco-2 cells, western blotting was performed. Western blot analysis showed decreased expression of NFκB and increased expression of IκB, which is a sign of autophagy initiation. In addition, autophagosome formation was accelerated by the activity of p53 and light chain 3 (LC3) II. In addition, inhibition of Akt and mTOR also played a pivotal role in autophagy formation. Finally, excessive expansion of autophagy promoted apoptosis, which subsequently resulted in necrosis. These findings support a novel cell death-promoting function of autophagy by Ag-NPs in Caco-2 cells.

Role of Herbal Teas in Regulating Cellular Homeostasis and Autophagy and Their Implications in Regulating Overall Health

Tea is one of the most popular and widely consumed beverages worldwide, and possesses numerous potential health benefits. Herbal teas are well-known to contain an abundance of polyphenol antioxidants and other ingredients, thereby implicating protection and treatment against various ailments, and maintaining overall health in humans, although their mechanisms of action have not yet been fully identified. Autophagy is a conserved mechanism present in organisms that maintains basal cellular homeostasis and is essential in mediating the pathogenesis of several diseases, including cancer, type II diabetes, obesity, and Alzheimer’s disease. The increasing prevalence of these diseases, which could be attributed to the imbalance in the level of autophagy, presents a considerable challenge in the healthcare industry. Natural medicine stands as an effective, safe, and economical alternative in balancing autophagy and maintaining homeostasis. Tea is a part of the diet for many people, and it could mediate autophagy as well. Here, we aim to provide an updated overview of popular herbal teas’ health-promoting and disease healing properties and in-depth information on their relation to autophagy and its related signaling molecules. The present review sheds more light on the significance of herbal teas in regulating autophagy, thereby improving overall health.

Induction of autophagy protects human dental pulp cells from lipopolysaccharide-induced pyroptotic cell death

The NOD-like receptor protein 3/caspase-1 inflammasome can be activated in human dental pulp tissue and fibroblasts; however, the underlying mechanisms are poorly understood. In the present study, lipopolysaccharide (LPS) was used to treat dental pulp cells to establish an inflammation model. Cell viability was examined by sulforhodamine B assay. Interleukin (IL)-1β, caspase-1, microtubule-associated protein-1 light chain 3-II/I and p62 were determined by western blotting and ELISA. The phosphorylation (p-) levels of NF-κB and NF-κB inhibitor (IκB)α protein were observed by western blotting. The results demonstrated that LPS induced pyroptotic cell death in cultured dental pulp cells, which was supported by the increased levels of IL-1β, IL-18 and caspase-1. Rapamycin and 3-methyladenine (3-MA) were used to activate and inhibit autophagy, and it was observed that LPS increased autophagy and rapamycin reduced LPS-induced dental pulp cell pyroptosis. However, 3-MA aggravated LPS-induced dental pulp cell pyroptosis. In addition, LPS inhibited the expression of IκBα, but increased the expression of p-NF-κB. Compared with the LPS group, 3-MA further inhibited the expression of IκBα but promoted the expression of p-NF-κB. However, rapamycin produced the opposite results to LPS. Under LPS treatment, the NF-κB pathway inhibitor BAY11-7082 further enhanced the inhibitory effects of rapamycin, but inhibited the promoting effects of 3-MA on the protein expression levels of IL-1β and caspase-1. The results of the present study demonstrated that there is an important crosstalk between autophagy, pyroptosis and the NF-κB pathway, and that the modulation of pyroptosis in dental pulp cells may be a promising strategy to pulpitis therapy.

Aquaporin-9 is involved in the lipid-lowering activity of the nutraceutical silybin on hepatocytes through modulation of autophagy and lipid droplets composition

Hepatic steatosis is the hallmark of non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of the metabolic syndrome and insulin resistance with potential evolution towards non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Key roles of autophagy and oxidative stress in hepatic lipid accumulation and NAFLD progression are recognized. Here, we employed a rat hepatoma cell model of NAFLD progression made of FaO cells exposed to oleate/palmitate followed or not by TNFα treatment to investigate the molecular mechanisms through which silybin, a lipid-lowering nutraceutical, may improve hepatic lipid dyshomeostasis. The beneficial effect of silybin was found to involve amelioration of the fatty acids profile of lipid droplets, stimulation of the mitochondrial oxidation and upregulation of a microRNA of pivotal relevance in hepatic fat metabolism, miR-122. Silybin was also found to restore the levels of Aquaporin-9 (AQP9) and glycerol permeability while reducing the activation of the oxidative stress-dependent transcription factor NF-κB, and autophagy turnover. In conclusion, silybin was shown to have molecular effects on signaling pathways that were previously unknown and potentially protect the hepatocyte. These actions intersect TG metabolism, fat-induced autophagy and AQP9-mediated glycerol transport in hepatocytes.

Mechanism and medical implications of mammalian autophagy

Autophagy is a highly conserved catabolic process induced under various conditions of cellular stress, which prevents cell damage and promotes survival in the event of energy or nutrient shortage and responds to various cytotoxic insults. Thus, autophagy has primarily cytoprotective functions and needs to be tightly regulated to respond correctly to the different stimuli that cells experience, thereby conferring adaptation to the ever-changing environment. It is now apparent that autophagy is deregulated in the context of various human pathologies, including cancer and neurodegeneration, and its modulation has considerable potential as a therapeutic approach.

Alpha-1-Antitrypsin Enhances Primary Human Macrophage Immunity Against Non-tuberculous Mycobacteria

Rationale: The association between non-tuberculous mycobacterial lung disease and alpha-1-antitrypsin (AAT) deficiency is likely due, in part, to underlying emphysema or bronchiectasis. But there is increasing evidence that AAT itself enhances host immunity against microbial pathogens and thus deficiency could compromise host protection.

Objectives: The goal of this project is to determine if AAT could augment macrophage activity against non-tuberculous mycobacteria.

Methods: We compared the ability of monocyte-derived macrophages cultured in autologous plasma that were obtained immediately before and soon after AAT infusion—given to individuals with AAT deficiency—to control an ex vivo Mycobacterium intracellulare infection.

Measurements and Main Results: We found that compared to pre-AAT infused monocyte-derived macrophages plus plasma, macrophages, and contemporaneous plasma obtained after a session of AAT infusion were significantly better able to control M. intracellulare infection; the reduced bacterial burden was linked with greater phagosome-lysosome fusion and increased autophagosome formation/maturation, the latter due to AAT inhibition of both M. intracellulare–induced nuclear factor-kappa B activation and A20 expression. While there was a modest increase in apoptosis in the M. intracellulare-infected post-AAT infused macrophages and plasma, inhibiting caspase-3 in THP-1 cells, monocyte-derived macrophages, and alveolar macrophages unexpectedly reduced the M. intracellulare burden, indicating that apoptosis impairs macrophage control of M. intracellulare and that the host protective effects of AAT occurred despite inducing apoptosis.

Conclusion: AAT augments macrophage control of M. intracellulare infection through enhancing phagosome-lysosome fusion and autophagy.

Induction of Autophagy and Activation of SIRT-1 Deacetylation Mechanisms Mediate Neuroprotection by the Pomegranate Metabolite Urolithin A in BV2 Microglia and Differentiated 3D Human Neural Progenitor Cells

SCOPE

Urolithin A is an anti-inflammatory and neuroprotective gut-derived metabolite from ellagitannins and ellagic acid in pomegranate, berries, and nuts. The roles of SIRT-1 and autophagy in the neuroprotective activity of urolithin A are investigated.

METHODS AND RESULTS

Analyses of culture supernatants from lipopolysaccharide-stimulated BV2 microglia show that urolithin A (2.5-10 µm) produced significant reduction in the production of nitrite, tumor necrosis factor (TNF)-α and IL-6. The anti-inflammatory effect of the compound is reversed in the presence of sirtuin (SIRT)-1 and the autophagy inhibitors EX527 and chloroquine, respectively. Protein analyses reveal reduction in p65 and acetyl-p65 protein. Treatment of BV2 microglia with urolithin A results in increased SIRT-1 activity and nuclear protein, while induction of autophagy by the compound is demonstrated using autophagy fluorescent and autophagy LC3 HiBiT reporter assays. Viability assays reveal that urolithin A produces a neuroprotective effect in APPSwe-transfected ReNcell VM human neural cells, which is reversed in the presence of EX527 and chloroquine. Increase in both SIRT-1 and autophagic activities are also detected in these cells following treatment with urolithin A.

CONCLUSIONS

It has been proposed that SIRT-1 activation and induction of autophagy are involved in the neuroprotective activity of urolithin A in brain cells.

Autophagy counters LPS-mediated suppression of lysozyme

Impaired Paneth cell expression of antimicrobial protein (AMP) lysozyme is found in patients with Crohn's disease with the autophagy gene ATG16L1 risk allele, in mice with mutations in autophagy genes Atg16L1, Atg5 and Atg7, and in Irgm1 knockout mice. Defective autophagy is also associated with expansion of resident Gram-negative bacteria in the intestinal lumen. These findings suggest that autophagy may control extracellular resident microbes by governing expression of lysozyme. To test the hypothesis that autophagy may have a defensive role in host response to resident extracellular microbes, we investigated the relationship between gut microbes, autophagy, and lysozyme. RAW 264.7 macrophages were treated with fecal slurry (FS), representing the resident microbial community; lipopolysaccharide (LPS); or butyrate, representing microbial products; or a representative resident Gram-negative bacterium Desulfovibrio vulgaris (DSV). FS, LPS, and DSV inhibited lysozyme expression, whereas butyrate had no effect. Induction of autophagy by rapamycin countered this inhibition, whereas silencing of the autophagy gene Irgm1 exacerbated the inhibitory effects of LPS on lysozyme expression. LPS also inhibited lysozyme activity against DSV and autophagy reversed this effect. Our results provide a novel insight into an interaction between gut bacteria, autophagy and AMP whereby autophagy may defend the host by countering the suppression of antimicrobial protein by Gram-negative bacteria.

Autophagy dysfunction in autoinflammatory diseases

Autoinflammatory diseases (AUIDs) are a genetically heterogeneous group of rheumatic diseases characterized by episodic inflammation linked with dysregulated innate immune responses. In this review, we summarize the molecular mechanisms altered by disease-associated variants in several AUIDs, including NOD2-associated diseases, TNF receptor-associated periodic syndrome (TRAPS), familial Mediterranean fever (FMF) and hyperimmunoglobulinemia D and periodic fever syndrome (HIDS), and highlight the roles dysregulated autophagy plays in disease pathogenesis. Autophagy is a conserved eukaryotic pathway for the elimination of cellular stressors, such as misfolded proteins, damaged organelles, or intracellular microorganisms. It is now recognized that autophagy also functions to control inflammation through regulatory interactions with innate immune signaling pathways. AUID-associated genetic variants are known to directly activate inflammatory signaling pathways. Recent evidence also indicates that these variants may also cause impairment of autophagy, thus augmenting inflammatory responses indirectly. Intriguingly, these variants can impair autophagy by different mechanisms, further implicating the autophagic response pathway in AUIDs. These discoveries provide evidence that autophagy could be investigated as a new therapeutic target for AUIDs.

Phycocyanin: A Potential Drug for Cancer Treatment

Phycocyanin isolated from marine organisms has the characteristics of high efficiency and low toxicity, and it can be used as a functional food. It has been reported that phycocyanin has anti-oxidative function, anti-inflammatory activity, anti-cancer function, immune enhancement function, liver and kidney protection pharmacological effects. Thus, phycocyanin has an important development and utilization as a potential drug, and phycocyanin has become a new hot spot in the field of drug research. So far, there are more and more studies have shown that phycocyanin has the anti-cancer effect, which can block the proliferation of cancer cells and kill cancer cells. Phycocyanin exerts anti-cancer activity by blocking tumor cell cell cycle, inducing tumor cell apoptosis and autophagy, thereby phycocyanin can serve as a promising anti-cancer agent. This review discusses the therapeutic use of phycocyanin and focuses on the latest advances of phycocyanin as a promising anti-cancer drug.

Melatonin reverses H2 O2 -induced senescence in SH-SY5Y cells by enhancing autophagy via sirtuin 1 deacetylation of the RelA/p65 subunit of NF-κB

Autophagy, a degradation mechanism that plays a major role in maintaining cellular homeostasis and diminishes in aging, is considered an aging characteristic. Melatonin is an important hormone that plays a wide range of physiological functions, including the anti-aging effect, potentially via the regulation of the Sirtuin1 (SIRT1) pathway. The deacetylation ability of SIRT1 is important for controlling the function of several transcription factors, including nuclear factor kappa B (NF-ĸB). Apart from inflammation, NF-ĸB can regulate autophagy by inhibiting Beclin1, an initiator of autophagy. Although numerous studies have revealed the role of melatonin in regulating autophagy, very limited experiments have shown that melatonin can increase autophagic activity via SIRT1 in a senescent model. This study focuses on the effect of melatonin on autophagy via the deacetylation activity of SIRT1 on RelA/p65, a subunit of NF-ĸB, to determine whether melatonin can attenuate the aging condition. SH-SY5Y cells were treated with H₂ O₂ to induce the senescent state. These results demonstrated that melatonin reduced a number of beta-galactosidase (SA-βgal)-positive cells, a senescent marker. In addition, melatonin increased the protein levels of SIRT1, Beclin1, and LC3-II, a hallmark protein of autophagy, and reduced the levels of acetylated-Lys310 in the p65 subunit of NF-ĸB in SH-SY5Y cells treated with H₂ O₂ . Furthermore, in the presence of SIRT1 inhibitor, melatonin failed to increase autophagic markers. The present data indicate that melatonin enhances autophagic activity via the SIRT1 signaling pathway. Taken together, we propose that in modulating autophagy, melatonin may provide a therapeutically beneficial role in the anti-aging processes.

The bile acid receptor FXR attenuates acinar cell autophagy in chronic pancreatitis

The functional relationship between bile acid (BA) and autophagy has not been evaluated in the context of pancreatitis. Here we investigated whether BA and their nuclear farnesoid X receptor (FXR) modulate autophagy and the development of pancreatitis. FXR expression, autophagy, apoptosis and necroptosis were determined in human chronic pancreatitis (CP) tissue in vivo and in pancreatic cells lines in vitro by means of real-time PCR, immunoblots and immunofluorescence. Pancreatic cell lines exposed to the most abundant BAs glycochenodeoxycholate (GCDC) and taurocholic acid (TCA) increased the expression of nuclear FXR and diminished that of the essential autophagy-related protein ATG7. BA was also elevated in pancreatic tissues from CP patients, correlating with elevated FXR and curtailed ATG7 expression with locally reduced autophagic activity. This was accompanied by an increased manifestation of CP hallmarks including apoptosis, necroptosis, inflammation and fibrosis. The present results suggest a cascade of events in which local accumulation of BA signals via FXR to suppress autophagy in pancreatic acinar cells, thereby unleashing acinar cell apoptosis and necroptosis. Thus, BA may cause CP by suppressing autophagy and exacerbating acinar cell apoptosis and necroptosis.

NF-κB Signalling in Glioblastoma

Nuclear factor-κB (NF-κB) is a transcription factor regulating a wide array of genes mediating numerous cellular processes such as proliferation, differentiation, motility and survival, to name a few. Aberrant activation of NF-κB is a frequent event in numerous cancers, including glioblastoma, the most common and lethal form of brain tumours of glial cell origin (collectively termed gliomas). Glioblastoma is characterized by high cellular heterogeneity, resistance to therapy and almost inevitable recurrence after surgery and treatment. NF-κB is aberrantly activated in response to a variety of stimuli in glioblastoma, where its activity has been implicated in processes ranging from maintenance of cancer stem-like cells, stimulation of cancer cell invasion, promotion of mesenchymal identity, and resistance to radiotherapy. This review examines the mechanisms of NF-κB activation in glioblastoma, the involvement of NF-κB in several mechanisms underlying glioblastoma propagation, and discusses some of the important questions of future research into the roles of NF-κB in glioblastoma.

Acanthopanax versus 3-Methyladenine Ameliorates Sodium Taurocholate-Induced Severe Acute Pancreatitis by Inhibiting the Autophagic Pathway in Rats

Objectives. To observe the therapeutic effects of Acanthopanax and 3-methyladenine against severe acute pancreatitis (SAP). Methods. Sodium taurocholate-induced SAP rats were equally randomized into a SAP group, an Acanthopanax group, and a 3-methyladenine group. Serum amylase levels were determined by ELISA; protein and mRNA expression levels of nucleus nuclear factor kappa B (NF-κB) p65, light chain 3II (LC3-II), and Beclin-1 and mRNA expression levels of Class III phosphatidylinositol 3-kinase (PI3K-III) in pancreas tissue were detected by Western blot and quantitative real-time PCR, respectively; mortality and pathological change of the pancreas were observed at 3, 12, and 24 h after operation. Results. There was no significant difference in mortality between SAP group and both treatment groups (P > 0.05). Serum amylase levels, protein, and mRNA expression levels of nucleus NF-κB p65, LC3-II, and Beclin-1 protein, mRNA expression levels of PI3K-III, and pathological score of the pancreas in both treatment groups were significantly lower than those in SAP group at 12 and 24 h after operation (P < 0.05 or 0.01). The number of autophagosomes and autophagolysosomes of pancreatic acinar cells in both treatment groups was smaller than that in SAP group at 12 and 24 h. Conclusions. Acanthopanax and 3-methyladenine had similar therapeutic effects against SAP in rats. The mechanism may be through inhibiting abnormal autophagy activation of pancreatic acinar cells.

Growth inhibitory effect of paratocarpin E, a prenylated chalcone isolated from Euphorbia humifusa Wild., by induction of autophagy and apoptosis in human breast cancer cells

Five flavones, including four flavonoids and one prenylated chalcone (paratocarpin E), were isolated from E. humifusa. and their chemical structures were established by spectroscopic analyses. We assessed the efficacy of these compounds against the growth of human breast cancer, leukemic, kidney cancer cell lines. Among them, paratocarpin E showed significant cytotoxicity against these cancer cell lines with an IC₅₀ of 19.6μM on the growth of MCF-7 cells. Paratocarpin E treatment of MCF-7 cells resulted in typical apoptotic features via increasing expression of activated caspase-8 and -9 and PARP cleavage. Moreover, paratocarpin E altered the expression of Bax and Bcl-2, leading to the release of cytochrome c from the mitochondria into the cytosol, suggesting that the mitochondria-mediated apoptosis was initiated. In addition, paratocarpin E increased the MDC-positive autophagic vacuoles, the ratio of LC3-II/LC3-I protein levels of Beclin-1, but decreased p62 expression, indicating the potent pro-autophagic effects of paratocarpin E in MCF-7 cells. Mechanistically, cell death induced by paratocarpin E is able to induce apoptosis of MCF-7 cells by activating p38 and JNK signaling pathway while inhibiting Erk pathway. Furthermore, paratocarpin E promotes the activation and nuclear translocation of NF-κB, which plays an important role in balancing paratocarpin E-mediated apoptosis and autophagy. The molecular docking study also revealed that paratocarpin E bound to Fas and NF-κB complex. These findings provide initial evidences that paratocarpin E can be used as a potential anti-cancer drug in future for breast cancer therapy.

Increased ATG5-ATG12 in hepatitis B virus-associated hepatocellular carcinoma and their role in apoptosis

AIM

To investigate autophagy-related genes, particularly ATG12, in apoptosis and cell cycle in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) and non-HBV-HCC cell lines.

METHODS

The expression of autophagy-related genes in HBV-associated hepatocellular carcinoma and non-HBV-HCC cell lines and human liver tissues was examined by quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) and western blotting. The silencing of target genes was used to examine the function of various genes in apoptosis and cell cycle progression.

RESULTS

The expression of autophagy related genes ATG5, ATG12, ATG9A and ATG4B expression was analyzed in HepG2.2.15 cells and compared with HepG2 and THLE cells. We found that ATG5 and ATG12 mRNA expression was significantly increased in HepG2.2.15 cells compared to HepG2 cells (P < 0.005). Moreover, ATG5-ATG12 protein levels were increased in tumor liver tissues compared to adjacent non-tumor tissues mainly from HCC patients with HBV infection. We also analyzed the function of ATG12 in cell apoptosis and cell cycle progression. The percentage of apoptotic cells increased by 11.4% in ATG12-silenced HepG2.2.15 cells (P < 0.005) but did not change in ATG12-silenced HepG2 cells under starvation with Earle’s balanced salt solution. However, the combination blockade of Notch signaling and ATG12 decreased the apoptotic rate of HepG2.2.15 cells from 55.6% to 50.4% (P < 0.05).

CONCLUSION

ATG12 is important for HBV-associated apoptosis and a potential drug target for HBV-HCC. Combination inhibition of ATG12/Notch signaling had no additional effect on HepG2.2.15 apoptosis.

Phycocyanin Inhibits Tumorigenic Potential of Pancreatic Cancer Cells: Role of Apoptosis and Autophagy

Pancreatic adenocarcinoma (PDA) is one of the most lethal human malignancies, and unresponsive to current chemotherapies. Here we investigate the therapeutic potential of phycocyanin as an anti-PDA agent in vivo and in vitro. Phycocyanin, a natural product purified from Spirulina, effectively inhibits the pancreatic cancer cell proliferation in vitro and xenograft tumor growth in vivo. Phycocyanin induces G2/M cell cycle arrest, apoptotic and autophagic cell death in PANC-1 cells. Inhibition of autophagy by targeting Beclin 1 using siRNA significantly suppresses cell growth inhibition and death induced by phycocyanin, whereas inhibition of both autophagy and apoptosis rescues phycocyanin-mediated cell death. Mechanistically, cell death induced by phycocyanin is the result of cross-talk among the MAPK, Akt/mTOR/p70S6K and NF-κB pathways. Phycocyanin is able to induce apoptosis of PANC-1 cell by activating p38 and JNK signaling pathways while inhibiting Erk pathway. On the other hand, phycocyanin promotes autophagic cell death by inhibiting PI3/Akt/mTOR signaling pathways. Furthermore, phycocyanin promotes the activation and nuclear translocation of NF-κB, which plays an important role in balancing phycocyanin-mediated apoptosis and autosis. In conclusion, our studies demonstrate that phycocyanin exerts anti-pancreatic cancer activity by inducing apoptotic and autophagic cell death, thereby identifying phycocyanin as a promising anti-pancreatic cancer agent.

Inhibition of caspase-9 aggravates acute liver injury through suppression of cytoprotective autophagy

Acute liver disease is characterized by inflammation, oxidative stress and necrosis, which can greatly influence the long term clinical outcome and lead to liver failure or cancer. Here, we initially demonstrated the beneficial role of caspase-9-dependent autophagy in acute liver injury. Treatment with caspase-9 inhibitor z-LEHD-FMK in HepG2 cells, AML12 cells and C57BL/b6N mice exacerbated CCl₄-induced acute hepatocellular damage, and also down-regulated autophagy markers expression levels, indicating that caspase-9 inhibition may aggravate acute liver damage by suppressing cytoprotective autophagy. CCl₄ was used as an acute liver injury inducer which caused oxidative stress and apoptosis through up-regulation of HIF-1α, as well as triggered hepatic inflammation and necroptosis via TLR4/NF-κB pathway. Caspase-9 Thr125 site was firstly phosphorylated by ERK1/2 which subsequently activated the cytoprotective autophagy process to attenuate acute CCl₄ injury. Caspase-9 inhibition further aggravated hepatic necroptosis through NF-κB expression, leading to increased pro-inflammatory mediators levels, suggesting a protective role of caspase-9-dependent autophagy in the inflammatory process as well as its possibility being a new therapeutic target for the treatment of acute liver injury.

NF-κB signaling as a driver of ageing

NF-κB signaling exerts essential roles in immunity and cellular stress responses, regulating many functions related with organism innate defense. Besides, NF-κB altered signaling has been causally linked to ageing and diverse pathological conditions. We discuss herein the functional involvement of this signaling pathway in ageing, visiting recent experimental evidence about NF-κB activation in this complex process, its functional consequences and the novel biological functions raised from these works. Moreover, we discuss ageing intervention strategies based on NF-κB inhibition, which have demonstrated to be effective at delaying and even reverting different ageing manifestations in human and mouse models of both normal and accelerated ageing. Altogether, the current evidence supports that NF-κB activation constitutes a driving force of the ageing process and a preferential target for rejuvenation-aimed approaches.

Anti-osteoclastogenic activity of isoliquiritigenin via inhibition of NF-κB-dependent autophagic pathway

Previous studies, including those from our laboratory, have demonstrated that the natural flavonoid isoliquiritigenin (ISL) is a promising agent for bone destructive diseases. However, the mechanisms underlying its anti-osteoclastogenic effects are still far from clear. Here, we evaluated the potential alterations of autophagy and nuclear factor-κB (NF-κB) during anti-osteoclastogenic effects by ISL in vitro and in vivo. We observed that ISL inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and suppressed autophagic microtubule-associated protein light chain 3 (LC3)-II and Beclin 1 accumulation. ISL treatment resulted in the interruption of several specific features for autophagy in osteoclast precursors, including acidic vesicular organelle formation, LC3-II accumulation, and appearance of autophagic vacuoles. The RANKL-stimulated expression levels of autophagy-related genes and proteins also diminished in ISL-treated osteoclast precursors. The reactivation of autophagy by rapamycin almost reversed the ISL-elicited anti-osteoclastogenic effects. Interestingly, ISL inhibited the RANKL-stimulated NF-κB expression and nuclear translocation, whereas the NF-κB inhibitor Bay 11-7082 markedly suppressed the RANKL-induced autophagic activation. Consistent with the in vitro results, the administration of ISL could attenuate osteoclastogenic cathepsin K, autophagic LC3, and NF-κB expression to protect against inflammatory calvarial bone erosion in vivo. Our findings highlight the inhibition of NF-κB-dependent autophagy as an important mechanism of ISL-mediated anti-osteoclastogenic activity.

Maternal immunity and pregnancy outcome: focus on preconception and autophagy

Modulation of the maternal immune system before conception has a major role in determining subsequent pregnancy outcome. However, this has been a neglected area of investigation. There is a correlation between the length of time a woman is exposed to semen from her male partner and the development of regulatory T cells that limit a maternal antifetal immune response. Similarly, the composition of the vaginal microbiota influences the capacity of microorganisms to bypass the cervical barrier and colonize the uterus before pregnancy. The extent that this preconception colonization influences pre- and post-implantation gestational events depends on the types of microbes present, the genetic make-up of the mother and environmental influences on the magnitude and direction of her immune responses. Prepregnancy uterine and placental colonization with commensal bacteria may be beneficial to the fetus and newborn by generating tolerance to organisms that enhance postnatal well-being. Efforts to prevent or stop the progression of premature myometrial contractions have been limited because of an incomplete understanding of the mechanism(s) that trigger this occurrence. Based on recent studies of autophagy during gestation and parturition, inhibition of autophagy in myometrial cells may be the critical factor leading to a sequence of events culminating in induction of myometrial contractions either prematurely or at term.

Regulation of autophagy by the nuclear factor κB signaling pathway in the hippocampus of rats with sepsis

BACKGROUND

Sepsis with brain dysfunction has contributed to an increase risk of morbidity and mortality. In its pathophysiology, both autophagy and nuclear factor κB (NF-κB) have been suggested to play important roles. Based on the fact that crosstalk between autophagy and NF-κB, two stress-response signaling pathways, has been detected in other pathophysiological processes, this study was undertaken to explore the process of autophagy in the hippocampus of septic rats and the role NF-κB plays in the regulation of autophagy during the process.

METHODS

Cecal ligation and puncture (CLP) or a sham operation was conducted on male Wistar rats. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of the NF-κB signaling pathway, or a vehicle control, was used to treat with the rats 2 h before the CLP operation. Hematoxylin-eosin staining and biological signal recording was used to measure the morphological and physiological signs of hippocampal dysfunction. An electron microscope was used to observe autophagosome formation and lysosome activation in the hippocampus after CLP. Western blotting and immune histochemistry were used to detect the hippocampus levels of NF-κB and essential proteins involved in formation of the autophagosome (microtubule-associated protein light chain 3 (LC3), Beclin1, Lamp-1, and Rab7).

RESULTS

Compared with sham-operated rats, the CLP rats showed decreasing mean arterial pressure (MAP), increasing heart rate (HR), and pathological histological changes. CLP rats exhibited not only increased vacuolization through electron micrographs but also increased LC3-II, decreased Beclin1, LAMP-1, and Rab7 through the immunofluorescence and Western blot. However, PDTC + CLP rats revealed that inhibition of the NF-κB signal axis by PDTC increased the levels of LC3-II, Beclin1, LAMP-1, and Rab7 and improved physiological function including blood pressure and heart rate.

CONCLUSIONS

The autophagy process during the hippocampus of CLP rats might be blocked by the activation of NF-κB signaling pathway. Inhibition of NF-κB signaling pathway could enhance the completion of autophagy with a neuroprotective function in septic brains.

Melatonin regulates aging and neurodegeneration through energy metabolism, epigenetics, autophagy and circadian rhythm pathways

Brain aging is linked to certain types of neurodegenerative diseases and identifying new therapeutic targets has become critical. Melatonin, a pineal hormone, associates with molecules and signaling pathways that sense and influence energy metabolism, autophagy, and circadian rhythms, including insulin-like growth factor 1 (IGF-1), Forkhead box O (FoxOs), sirtuins and mammalian target of rapamycin (mTOR) signaling pathways. This review summarizes the current understanding of how melatonin, together with molecular, cellular and systemic energy metabolisms, regulates epigenetic processes in the neurons. This information will lead to a greater understanding of molecular epigenetic aging of the brain and anti-aging mechanisms to increase lifespan under healthy conditions.

NF-κB activation was involved in reactive oxygen species-mediated apoptosis and autophagy in 1-oxoeudesm-11(13)-eno-12,8α-lactone-treated human lung cancer cells

1-oxoeudesm-11(13)-eno-12,8α-lactone (OEL), a novel eudesmane-type sesquiterpene compound, has been shown to inhibit the growth of some cancer cell lines and induce significant apoptosis. Here, we investigated the anti-cancer activities of OEL in human lung cancer cells. Our studies demonstrated that OEL induced both apoptosis and autophagy in A549 and H460 cells. OEL-induced autophagy was assessed by appearance of autophagic vacuoles, formation of acidic vesicular organelles, conversion of LC3-I to LC3-II, recruitment of LC3-II to the autophagosomes, and activation of autophagy genes. Furthermore, administration of autophagic inhibitor 3-methyladenine augments OEL-induced apoptotic cell death. The induction of autophagy and apoptosis by OEL links to NF-κB activation and the generation of reactive oxygen species (ROS). Interruption of NF-κB activation by specific inhibitor promotes apoptosis, but decreases autophagy. ROS antioxidants (N-acetylcysteine) attenuated both OEL-induced autophagy and apoptosis. Further experiments confirmed that OEL-induced activation of ROS was increased by NF-κB inhibitor whereas NF-κB activation was not affected by ROS inhibition. These findings suggest that OEL-elicited autophagic response plays a protective role that impedes cell death, and inhibition of autophagy could be an adjunctive strategy for enhancing the chemotherapeutic effect of OEL as an antitumor agent.

Regulation of autophagy by stress-responsive transcription factors

Autophagy is an evolutionarily conserved process that promotes the lysosomal degradation of intracellular components including organelles and portions of the cytoplasm. Besides operating as a quality control mechanism in steady-state conditions, autophagy is upregulated in response to a variety of homeostatic perturbations. In this setting, autophagy mediates prominent cytoprotective effects as it sustains energetic homeostasis and contributes to the removal of cytotoxic stimuli, thus orchestrating a cell-wide, multipronged adaptive response to stress. In line with the critical role of autophagy in health and disease, defects in the autophagic machinery as well as in autophagy-regulatory signaling pathways have been associated with multiple human pathologies, including neurodegenerative disorders, autoimmune conditions and cancer. Accumulating evidence indicates that the autophagic response to stress may proceed in two phases. Thus, a rapid increase in the autophagic flux, which occurs within minutes or hours of exposure to stressful conditions and is entirely mediated by post-translational protein modifications, is generally followed by a delayed and protracted autophagic response that relies on the activation of specific transcriptional programs. Stress-responsive transcription factors including p53, NF-κB and STAT3 have recently been shown to play a major role in the regulation of both these phases of the autophagic response. Here, we will discuss the molecular mechanisms whereby autophagy is orchestrated by stress-responsive transcription factors.

NF-κB-mediated induction of autophagy in cardiac ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury severely attenuates the benefit of revascularization after acute myocardial infarction, in which transcription factor NF-κB plays an important role. Recently, there is increasing evidence to suggest that autophagy is involved in this process. We sought to define the role of NF-κB in the induction of autophagy during cardiac I/R injury. The left circumflex coronary arteries of New Zealand white rabbits were ligated for 1.5h, followed by reperfusion for 1h to induce I/R injury. Production of reactive oxygen species (ROS) was detected in myocardial injury area following I/R injury. Furthermore, the results indicated that the cardiac area at risk (AAR) for ischemia has the most abundant expression of Beclin 1 in parallel to p65 expression after cardiac I/R injury. Inhibition of NF-κB significantly attenuated Beclin 1 expression and autophagy in the AAR, which was associated with a marked reduction in the extent of the AAR. Our data thus suggests that I/R injury promotes NF-κB activity, in response to ROS, to aggravate myocardial injury through the activation of Beclin 1-mediated autophagy.

Pathogen-induced autophagy signaling in innate immunity

Innate immunity induces rapid responses to fight invading pathogens. To eliminate intracellular bacteria or viruses, innate cellular responses lead to the production of nuclear factor-κB-dependent inflammatory cytokines, inflammasome activation, type I interferon synthesis, and/or eventually death of the infected cells. Autophagy emerged as another component of innate immunity, as it offers an immediate autonomous cell defense mechanism by degrading intracellular pathogens. In addition, autophagy participates in the regulation of immune and inflammatory cell responses. Instead of providing a comprehensive status of the art that has already been addressed elsewhere, we chose to highlight some recent issues brought up in the field.

TBK1 kinase addiction in lung cancer cells is mediated via autophagy of Tax1bp1/Ndp52 and non-canonical NF-κB signalling

K-Ras dependent non-small cell lung cancer (NSCLC) cells are 'addicted' to basal autophagy that reprograms cellular metabolism in a lysosomal-sensitive manner. Here we demonstrate that the xenophagy-associated kinase TBK1 drives basal autophagy, consistent with its known requirement in K-Ras-dependent NSCLC proliferation. Furthermore, basal autophagy in this context is characterised by sequestration of the xenophagy cargo receptor Ndp52 and its paralogue Tax1bp1, which we demonstrate here to be a bona fide cargo receptor. Autophagy of these cargo receptors promotes non-canonical NF-κB signalling. We propose that this TBK1-dependent mechanism for NF-κB signalling contributes to autophagy addiction in K-Ras driven NSCLC.

Context-Dependent Regulation of Autophagy by IKK-NF-κB Signaling: Impact on the Aging Process

The NF-κB signaling system and the autophagic degradation pathway are crucial cellular survival mechanisms, both being well conserved during evolution. Emerging studies have indicated that the IKK/NF-κB signaling axis regulates autophagy in a context-dependent manner. IKK complex and NF-κB can enhance the expression of Beclin 1 and other autophagy-related proteins and stimulate autophagy whereas as a feedback response, autophagy can degrade IKK components. Moreover, NF-κB signaling activates the expression of autophagy inhibitors (e.g., A20 and Bcl-2/xL) and represses the activators of autophagy (BNIP3, JNK1, and ROS). Several studies have indicated that NF-κB signaling is enhanced both during aging and cellular senescence, inducing a proinflammatory phenotype. The aging process is also associated with a decline in autophagic degradation. It seems that the activity of Beclin 1 initiation complex could be impaired with aging, since the expression of Beclin 1 decreases as does the activity of type III PI3K. On the other hand, the expression of inhibitory Bcl-2/xL proteins increases with aging. We will review the recent literature on the control mechanisms of autophagy through IKK/NF-κB signaling and emphasize that NF-κB signaling could be a potent repressor of autophagy with ageing.

Autophagy regulation by the nuclear factor κB signal axis in acute pancreatitis

OBJECTIVES

The objective of the study was to investigate the significance of LC3 and beclin 1 in the pancreas of rat after acute necrotizing pancreatitis (ANP) and whether nuclear factor κB (NF-κB) signal regulates autophagy during sodium taurocholate-induced ANP.

METHODS

Acute necrotizing pancreatitis was induced in rat by sodium taurocholate injection in the pancreaticobiliary duct. Pyrrolidine dithiocarbamate was administrated before the injection of sodium taurocholate. Then, serum amylase activity, trypsinogen activation peptide and tumor necrosis factor α, and morphological signs of pancreatitis were measured. The formation of autophagosome and the activation of lysosome were observed in the pancreas after ANP by using electron microscope. Meanwhile, the pancreatic levels of NF-κB and essential proteins involved in formation of the autophagosome (LC3 and beclin 1) were assessed by Western blotting and immunohistochemistry.

RESULTS

Sodium taurocholate increased serum amylase, trypsinogen activation peptide, tumor necrosis factor α, and pancreatic NF-κB levels compared with sham-operated rats and increased the levels of LC3-II and beclin 1. Inhibition of the NF-κB signal axis with pyrrolidine dithiocarbamate reduced serum amylase, blocked pancreatic NF-κB activation, and reduced the levels of LC3-II and beclin 1.

CONCLUSIONS

Nuclear factor κB pathway activation stimulates autophagy during induction of ANP. Targeted inhibition of the NF-κB pathway may provide novel therapeutic strategies for reducing the severity of ANP.

Autophagy: cellular defense to excessive inflammation

Autophagy can orchestrate a variety of cellular responses to dangerous stimuli. Our understanding of the physiologic roles of autophagy has recently expanded; in addition to its other roles, autophagy now appears to play an essential role in regulating inflammatory responses. This review describes recent findings concerning the roles and mechanisms of autophagy in controlling excessive inflammation.

The complex interplay between autophagy and NF-κB signaling pathways in cancer cells

Tight regulation of both the NF-κB pathway and the autophagy process is necessary for maintenance of cellular homeostasis. Deregulation of both pathways is frequently observed in cancer cells and is associated with tumorigenesis and tumor cell resistance to cancer therapies. Autophagy is involved in several cellular functions regulated by NF-κB including cell survival, differentiation, senescence, inflammation, and immunity. On a molecular level, autophagy and NF-κB share common upstream signals and regulators and can control each other through positive or negative feedback loops, thus ensuring homeostatic responses. Here, we summarize and discuss the most recent discoveries that shed new light on the complex interplay between autophagy and NF-κB signaling pathways; this certainly has functional relevance in tumorigenesis and tumor responses to therapy.

Vitamin D, vitamin D receptor, and macroautophagy in inflammation and infection

Vitamin D is involved in mineral and bone homeostasis, immune responses, anti-inflammation, anti-infection, and cancer prevention. Vitamin D receptor (VDR) is a nuclear receptor that mediates most biological functions of 1,25(OH)(2)D(3) or vitamin D(3), the active form of vitamin D. Recently, vitamin D(3)-induced autophagy has been reported. Autophagy is a lysosome-mediated catabolic pathway classified into three different types: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy contributes to anti-aging, antimicrobial defense, and tumor suppression. The functions of autophagy overlap remarkably with those of vitamin D/VDR signaling. This review focuses on vitamin D(3), VDR, and macroautophagy in inflammation and infection. We place emphasis on the regulatory roles of vitamin D(3) on autophagy at different steps, including induction, nucleation, elongation to maturation, and degradation. We summarize the known molecular mechanisms of vitamin D/VDR signaling on autophagy homeostasis. The potential application of the insights gleaned from these research findings to anti-inflammation and anti-infection is also discussed.

Jun proteins are starvation-regulated inhibitors of autophagy

The growing number of biological functions affected by autophagy ascribes a special significance to identification of factors regulating it. The activator protein-1 (AP-1) transcription factors are involved in most aspects of cellular proliferation, death, or survival, yet no information regarding their involvement in autophagy is available. Here, we show that the AP-1 proteins JunB and c-Jun, but not JunD, c-Fos, or Fra-1, inhibit autophagy. JunB inhibits autophagy induced by starvation, overexpression of a short form of ARF (smARF), a potent inducer of autophagy, or even after rapamycin treatment. In agreement, acute repression of JunB expression, by JunB knockdown, potently induces autophagy. As expected from autophagy-inhibiting proteins, Jun B and c-Jun expression is reduced by starvation. Decrease in JunB mRNA expression and posttranscriptional events downregulate JunB protein expression after starvation. The inhibition of autophagy by JunB is not mediated by mammalian target of rapamycin (mTOR) regulation, as it occurs also in the absence of mTOR activity, and autophagy induced by JunB knockdown is not correlated with changes in mTOR activity. Nevertheless, the transcriptional activities of c-Jun and JunB are required for autophagy inhibition, and JunB incapable of heterodimerizing is a less effective inhibitor of autophagy. Most importantly, inhibition of autophagy in starved HeLa cells by JunB enhances apoptotic cell death. We suggest that JunB and c-Jun are regulators of autophagy whose expression responds to autophagy-inducing signals.

Functional genomic analysis of peripheral blood during early acute renal allograft rejection

BACKGROUND

Acute graft rejection is an important clinical problem in renal transplantation and an adverse predictor for long-term graft survival. Peripheral blood biomarkers that provide evidence of early graft rejection may offer an important option for posttransplant monitoring, optimize the utility of graft biopsy, and permit timely and effective therapeutic intervention to minimize the graft damage.

METHODS

In this feasibility study (n=58), we have used gene expression profiling in a case-control design to compare whole blood samples between normal subjects (n=20) and patients with (n=11) or without (n=22) biopsy-confirmed acute rejection (BCAR) or borderline changes (n=5).

RESULTS

A total of 183 probe sets representing 160 genes were differentially expressed (false discovery rate [FDR] <0.01) between subjects with or without BCAR, from which linear discriminant analysis and cross-validation identified an initial gene signature of 24 probe sets, and a more refined set of 11 probe sets found to classify subject samples correctly. Cross-validation suggested an out-of-sample sensitivity of 73% and specificity of 91% for identification of samples with or without BCAR. An increase in classifier gene expression correlated closely with acute rejection during the first 3 months posttransplant. Biological evaluation indicated that the differentially expressed genes encompassed processes related to immune response, signal transduction, and cytoskeletal reorganization.

CONCLUSION

Preliminary evidence indicates that gene expression in the peripheral blood may yield a relevant measure for the occurrence of BCAR and offer a potential tool for immunologic monitoring. These results now require confirmation in a larger cohort.

The IKK complex contributes to the induction of autophagy

In response to stress, cells start transcriptional and transcription-independent programs that can lead to adaptation or death. Here, we show that multiple inducers of autophagy, including nutrient depletion, trigger the activation of the IKK (IkappaB kinase) complex that is best known for its essential role in the activation of the transcription factor NF-kappaB by stress. Constitutively active IKK subunits stimulated autophagy and transduced multiple signals that operate in starvation-induced autophagy, including the phosphorylation of AMPK and JNK1. Genetic inhibition of the nuclear translocation of NF-kappaB or ablation of the p65/RelA NF-kappaB subunit failed to suppress IKK-induced autophagy, indicating that IKK can promote the autophagic pathway in an NF-kappaB-independent manner. In murine and human cells, knockout and/or knockdown of IKK subunits (but not that of p65) prevented the induction of autophagy in response to multiple stimuli. Moreover, the knockout of IKK-beta suppressed the activation of autophagy by food deprivation or rapamycin injections in vivo, in mice. Altogether, these results indicate that IKK has a cardinal role in the stimulation of autophagy by physiological and pharmacological stimuli.

Autophagy and pattern recognition receptors in innate immunity

Autophagy is a physiologically and immunologically controlled intracellular homeostatic pathway that sequesters and degrades cytoplasmic targets including macromolecular aggregates, cellular organelles such as mitochondria, and whole microbes or their products. Recent advances show that autophagy plays a role in innate immunity in several ways: (i) direct elimination of intracellular microbes by digestion in autolysosomes, (ii) delivery of cytosolic microbial products to pattern recognition receptors (PRRs) in a process referred to as topological inversion, and (iii) as an anti-microbial effector of Toll-like receptors and other PRR signaling. Autophagy eliminates pathogens in vitro and in vivo but, when aberrant due to mutations, contributes to human inflammatory disorders such as Crohn's disease. In this review, we examine these relationships and propose that autophagy is one of the most ancient innate immune defenses that has possibly evolved at the time of alpha-protobacteria-pre-eukaryote relationships, leading up to modern eukaryotic cell-mitochondrial symbiosis, and that during the metazoan evolution, additional layers of immunological regulation have been superimposed and integrated with this primordial innate immunity mechanism.

NF-kappab facilitates oridonin-induced apoptosis and autophagy in HT1080 cells through a p53-mediated pathway

In this study, we investigated the molecular mechanisms involving in oridonin-induced apoptosis and autophagy. We found that apoptosis and autophagy were simultaneously induced by oridonin time-dependently in HT1080 cells, and inhibition of autophagy by 3MA decreased oridonin-induced apoptosis, indicating that they act in synergy to mediate cell death. In addition, treatment with oridonin caused an increase in NF-kappaB and p53 activities in a time-dependent manner. Inhibition of NF-kappaB or p53 activation by its specific inhibitor PDTC or pifithrin-alpha respectively, significantly reduced both oridonin-induced apoptosis and autophagy accompanied by the decrease in Beclin 1 and LC3 levels. Further experiments confirmed that oridonin-induced p53 activation was reduced by the NF-kappaB inhibitor whereas the activation of NF-kappaB was not affected by p53 inhibition. Taken together, these results demonstrate that NF-kappaB promotes oridonin-induced apoptotic and autophagic cell death through regulating p53 activation in HT1080 cells.

When apoptosis meets autophagy: deciding cell fate after trauma and sepsis

Apoptotic cell death is considered to be an underlying mechanism in immunosuppression and multiple organ dysfunction after trauma-hemorrhage and sepsis. Although studied intensively over the last decade, the role of other cell death mechanisms under similar pathophysiological conditions has remained elusive. Recently, autophagy has emerged as an important mediator of programmed cell death pathways. Here, we review recent advances in our understanding of apoptosis and autophagy and the crosstalk between these processes. We explore the coexistence of these two processes and the effects of autophagy on apoptosis after trauma-hemorrhage and sepsis. The inter-relationship between autophagy and apoptosis might unveil novel therapeutic approaches for the detection and treatment of trauma-hemorrhage and sepsis.

Autophagy in immunity against mycobacterium tuberculosis: a model system to dissect immunological roles of autophagy

The recognition of autophagy as an immune mechanism has been affirmed in recent years. One of the model systems that has helped in the development of our current understanding of how autophagy and more traditional immunity systems cooperate in defense against intracellular pathogens is macrophage infection with Mycobacterium tuberculosis. M. tuberculosis is a highly significant human pathogen that latently infects billions of people and causes active disease in millions of patients worldwide. The ability of the tubercle bacillus to persist in human populations rests upon its macrophage parasitism. One of the initial reports on the ability of autophagy to act as a cell-autonomous innate immunity mechanism capable of eliminating intracellular bacteria was on M. tuberculosis. This model system has further contributed to the recognition of multiple connections between conventional immune regulators and autophagy. In this chapter, we will review how these studies have helped to establish the following principles: (1) autophagy functions as an innate defense mechanism against intracellular microbes; (2) autophagy is under the control of pattern recognition receptors (PRR) such as Toll-like receptors (TLR), and it acts as one of the immunological output effectors of PRR and TLR signaling; (3) autophagy is one of the effector functions associated with the immunity-regulated GTPases, which were initially characterized as molecules involved in cell-autonomous defense, but whose mechanism of function was unknown until recently; (4) autophagy is an immune effector of Th1/Th2 T cell response polarization-autophagy is activated by Th1 cytokines (which act in defense against intracellular pathogens) and is inhibited by Th2 cytokines (which make cells accessible to intracellular pathogens). Collectively, the studies employing the M. tuberculosis autophagy model system have contributed to the development of a more comprehensive view of autophagy as an immunological process. This work and related studies by others have led us to propose a model of how autophagy, an ancient innate immunity defense, became integrated over the course of evolution with other immune mechanisms of ever-increasing complexity.