Upregulation of AMPK by 4-O-methylascochlorin promotes autophagy via the HIF-1α expression

Omentin reduces venous neointimal hyperplasia in arteriovenous fistula through hypoxia-inducible factor-1 alpha inhibition

Arteriovenous fistula (AVF) failure often involves venous neointimal hyperplasia (VNH) driven by elevated hypoxia-inducible factor-1 alpha (HIF-1α) in the venous wall. Omentin, known for its anti-inflammatory and anti-hyperplasia properties, has an uncertain role in early AVF failure. This study investigates omentin's impact on VNH using a chronic renal failure (CRF) rabbit model. The CRF rabbit model of AVF received omentin-expressing adenoviral vector or control β-gal vector to assess omentin's effects on VNH. Human vascular smooth muscle cells (HVSMCs), stimulated with tumor necrosis factor-α (TNF-α), were exposed to recombinant human omentin (Rh-OMT) to study its influence on cell proliferation and migration. The AMP-activated protein kinase (AMPK) inhibitor compound C and the mammalian target of rapamycin (mTOR) activator MHY1485 were employed to explore omentin's mechanisms in VNH reduction through HIF-1α inhibition. Omentin treatment reduced VNH in CRF rabbits, concomitant with HIF-1α down-regulation and the suppression of downstream factors, including vascular endothelial growth factor and matrix metalloproteinases. Rh-OMT inhibited TNF-α-induced HVSMC proliferation and migration by modulating both cell cycle and cell adhesion proteins. Additionally, omentin reduced HIF-1α expression through the AMPK/mTOR pathway activation. Notably, the blockade of AMPK/mTOR signaling reversed omentin-mediated inhibition of VNH, cell proliferation, and migration, both in vivo and in vitro. In conclusion, omentin mitigates VNH post-AVF creation by restraining HIF-1α via AMPK/mTOR signaling. Strategies boosting circulating omentin levels may offer promise in averting AVF failure.

Hypoxia-associated autophagy flux dysregulation in human cancers

A general feature of cancer is hypoxia, determined as low oxygen levels. Low oxygen levels may cause cells to alter in ways that contribute to tumor growth and resistance to treatment. Hypoxia leads to variations in cancer cell metabolism, angiogenesis and metastasis. Furthermore, a hypoxic tumor microenvironment might induce immunosuppression. Moreover, hypoxia has the potential to impact cellular processes, such as autophagy. Autophagy refers to the catabolic process by which damaged organelles and toxic macromolecules are broken down. The abnormal activation of autophagy has been extensively recorded in human tumors and it serves as a regulator of cell growth, spread to other parts of the body, and resistance to treatment. There is a correlation between hypoxia and autophagy in human malignancies. Hypoxia can regulate the activity of AMPK, mTOR, Beclin-1, and ATGs to govern autophagy in human malignancies. Furthermore, HIF-1α, serving as an indicator of low oxygen levels, controls the process of autophagy. Hypoxia-induced autophagy has a crucial role in regulating the growth, spread, and resistance to treatment in human malignancies. Hypoxia-induced regulation of autophagy can impact other mechanisms of cell death, such as apoptosis. Chemoresistance and radioresistance have become significant challenges in recent years. Hypoxia-mediated autophagy plays a crucial role in determining the response to these therapeutic treatments.

4-O-Methylascochlorin Synergistically Enhances 5-Fluorouracil-Induced Apoptosis by Inhibiting the Wnt/β-Catenin Signaling Pathway in Colorectal Cancer Cells

4-O-Methyl-ascochlorin (MAC), a derivative of the prenyl-phenol antibiotic ascochlorin extracted from the fungus Ascochyta viciae, shows anticarcinogenic effects on various cancer cells. 5-Fluorouracil (5-FU) is used to treat colorectal cancer (CRC); however, its efficacy must be enhanced. In this study, we investigated the molecular mechanisms by which MAC acts synergistically with 5-FU to inhibit cell proliferation and induce apoptosis in CRC cells. MAC enhanced the cytotoxic effects of 5-FU by suppressing the Akt/mTOR/p70S6K and Wnt/β-catenin signaling pathways. It also reduced the viability of 5-FU-resistant (5-FU-R) cells. Furthermore, expression of anti-apoptosis-related proteins and cancer stem-like cell (CSC) markers by 5-FU-R cells decreased in response to MAC. Similar to MAC, the knockdown of CTNNB1 induced apoptosis and reduced expression of mRNA encoding CRC markers in 5-FU-R cells. In summary, these results suggest that MAC and other β-catenin modulators may be useful in overcoming the 5-FU resistance of CRC cells.

p53-dependent HIF-1α /autophagy mediated glycolysis to support Cr(VI)-induced cell growth and cell migration

Cr(VI) is known to be seriously toxic and carcinogenic. Hypoxia-inducible factor-1α (HIF-1α) is a crucial regulator to promote tumor development. In this study, we found that Cr(VI) significantly increased the expression of HIF-1α in A549 cells and in lung of BALB/c mice but not in HELF cells. Treatment with Lificiguat (YC-1), HIF-1α inhibitor, or CoCl2, HIF-1α inducer, could alter Cr(VI)-induced autophagy, glycolysis, and cell growth in A549 cells but not in HELF cells, validating the involvement of HIF-1α in these effects of Cr(VI) in A549 cells. Co-treatments of pcATG4B with YC-1, or siATG4B with CoCl2 demonstrated the role of HIF-1α / autophagy axis in inducing glycolysis and cell growth in A549 cells. In HELF cells, however, only autophagy but not HIF-1α played a role in inducing glycolysis. The protein level of p53 was significantly lower in A549 cells than in HELF cells. RITA, a p53 inducer, attenuated Cr(VI)-induced HIF-1α and LC3-II in A549 cells, suggesting that p53 might be the mechanism underlying the different effects of Cr(VI) on HIF-1α in A549 and HELF cells. Thus, p53-dependent HIF-1α / autophagy-mediated glycolysis plays a role in facilitating Cr(VI)-induced carcinogenesis.

An AMPK agonist suppresses the progress of colorectal cancer by regulating the polarization of TAM to M1 through inhibition of HIF-1α and mTOR signal pathway

OBJECTIVE

This study aimed to evaluate the impact of an adenosine monophosphate-activated protein kinase (AMPK) agonist, metformin (MET), on the antitumor effects of macrophages and to determine the underlying mechanism involved in the process.

MATERIALS AND METHODS

M0 macrophages were derived from phorbol-12-myristate-13-acetate-stimulated THP-1 cells.

RESULTS

The levels of tumor necrosis factor-alpha (TNF-α) and human leukocyte antigen-DR (HLA-DR) were decreased in macrophages incubated with HCT116 cells, whereas those of arginase-1 (Arg-1), CD163, and CD206 were elevated; these effects were reversed by MET. The transfection of small interfering (si) RNA abrogated the influence of MET on the expression of the M1/M2 macrophage biomarkers. MET significantly suppressed the proliferation and migration abilities of HCT116 cells incubated with M0 macrophages; these actions were reversed by siRNA transfection against AMPK. The hypoxia-inducible factor 1-alpha (HIF-1α), phosphorylated protein kinase B (p-AKT), and phosphorylated mammalian target of rapamycin (p-mTOR) levels were reduced by the introduction of MET and promoted by siRNA transfection against AMPK. In addition, the levels of HIF-1α, p-AKT, and p-mTOR suppressed by MET were markedly increased following the transfection of siRNA against AMPK.

CONCLUSION

These findings indicate that MET can repress the progression of colorectal cancer by transforming tumor-associated macrophages to the M1phenotype via inhibition of the HIF-1α and mTOR signaling pathways.

Long non-coding RNA NBR2 suppresses the progression of colorectal cancer by downregulating miR-19a to regulate M2 macrophage polarization

Colorectal cancer (CRC) is a malignant tumor of the gastrointestinal tract that significantly impacts the health of patients and lacks promising methods of diagnosis. Tumor-associated macrophages (TAMs) are involved in CRC progression, and their function is regulated by long non-coding RNAs (lncRNAs). The lncRNA NBR2 was recently reported as an oncogene, whose function in CRC remains uncertain. The present study aimed to investigate the biological function of lncRNA NBR2 in the progression of CRC and its underlying molecular mechanisms. Ten pairs of clinical CRC and para-carcinoma tissues were collected to determine the expression levels of lncRNA NBR2 and miR-19a, and the polarization state of TAMs. Quantitative reverse transcriptase-polymerase chain reaction was used to evaluate the expression of miR-19a, and western blotting was used to determine the expression levels of tumor necrosis factor-α, human leukocyte antigen-DR, arginase-1, CD163, CD206, interleukin-4, AMP-activated protein kinase (AMPK), p-AMPK, hypoxia-inducible factor-1α (HIF-1α), protein kinase B (AKT), p-AKT, mechanistic target of rapamycin (mTOR), and p-mTOR in TAMs. The proliferative ability of HCT-116 cells was detected using the CCK8 assay, and the migratory ability of HCT-116 cells was evaluated using the Transwell assay. The interaction between lncRNA NBR2 and miR-19a was determined using the luciferase assay. The lncRNA NBR2 was downregulated and miR-19a was highly expressed in CRC cells, accompanied by a high M2 polarization. Downregulated miR-19a promoted M1 polarization, activated AMPK, suppressed HIF-1α and AKT/mTOR signaling pathways, and promoted antitumor properties in NBR2-overexpressed TAMs, which were all reversed by the introduction of the miR-19a mimic. LncRNA NBR2 was verified to target miR-19a in macrophages according to the results of the luciferase assay. Collectively, lncRNA NBR2 may suppress the progression of CRC by downregulating miR-19a to regulate M2 macrophage polarization.

4-O-Methylascochlorin-Mediated BNIP-3 Expression Controls the Balance of Apoptosis and Autophagy in Cervical Carcinoma Cells

4-O-methylascochlorin (MAC) is a 4-fourth carbon-substituted derivative of ascochlorin, a compound extracted from a phytopathogenic fungus Ascochyta viciae. MAC induces apoptosis and autophagy in various cancer cells, but the effects of MAC on apoptosis and autophagy in cervical cancer cells, as well as how the interaction between apoptosis and autophagy mediates the cellular anticancer effects are not known. Here, we investigated that MAC induced apoptotic cell death of cervical cancer cells without regulating the cell cycle and promoted autophagy by inhibiting the phosphorylation of serine-threonine kinase B (Akt), mammalian target of rapamycin (mTOR), and 70-kDa ribosomal protein S6 kinase (p70S6K). Additional investigations suggested that Bcl-2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP-3), but not Hypoxia-inducible factor 1 alpha (HIF-1α), is a key regulator of MAC-induced apoptosis and autophagy. BNIP-3 siRNA suppressed MAC-induced increases in cleaved- poly (ADP-ribose) polymerase (PARP) and LC3II expression. The pan-caspase inhibitor Z-VAD-FMK suppressed MAC-induced cell death and enhanced MAC-induced autophagy. The autophagy inhibitor chloroquine (CQ) enhanced MAC-mediated cell death by increasing BNIP-3 expression. These results indicate that MAC induces apoptosis to promote cell death and stimulates autophagy to promote cell survival by increasing BNIP-3 expression. This study also showed that co-treatment of cells with MAC and CQ further enhanced the death of cervical cancer cells.

Unraveling the Roles of Protein Kinases in Autophagy: An Update on Small-Molecule Compounds for Targeted Therapy

Protein kinases, which catalyze the phosphorylation of proteins, are involved in several important cellular processes, such as autophagy. Of note, autophagy, originally described as a mechanism for intracellular waste disposal and recovery, has been becoming a crucial biological process closely related to many types of human diseases. More recently, the roles of protein kinases in autophagy have been gradually elucidated, and the design of small-molecule compounds to modulate targets to positively or negatively interfere with the cytoprotective autophagy or autophagy-associated cell death may provide a new clue on the current targeted therapy. Thus, in this Perspective, we focus on summarizing the different roles of protein kinases, including positive, negative, and bidirectional regulations of autophagy. Moreover, we discuss several small-molecule compounds targeting these protein kinases in human diseases, highlighting their pivotal roles in autophagy for targeted therapeutic purposes.

Therapeutic potential of AMPK signaling targeting in lung cancer: Advances, challenges and future prospects

Lung cancer (LC) is a leading cause of death worldwide with high mortality and morbidity. A wide variety of risk factors are considered for LC development such as smoking, air pollution and family history. It appears that genetic and epigenetic factors are also potential players in LC development and progression. AMP-activated protein kinase (AMPK) is a signaling pathway with vital function in inducing energy balance and homeostasis. An increase in AMP:ATP and ADP:ATP ratio leads to activation of AMPK signaling by upstream mediators such as LKB1 and CamKK. Dysregulation of AMPK signaling is a common finding in different cancers, particularly LC. AMPK activation can significantly enhance LC metastasis via EMT induction. Upstream mediators such as PLAG1, IMPAD1, and TUFM can regulate AMPK-mediated metastasis. AMPK activation can promote proliferation and survival of LC cells via glycolysis induction. In suppressing LC progression, anti-tumor compounds including metformin, ginsenosides, casticin and duloxetine dually induce/inhibit AMPK signaling. This is due to double-edged sword role of AMPK signaling in LC cells. Furthermore, AMPK signaling can regulate response of LC cells to chemotherapy and radiotherapy that are discussed in the current review.

Mitofusin-2 boosts innate immunity through the maintenance of aerobic glycolysis and activation of xenophagy in mice

Mitochondrial function and innate immunity are intimately linked; however, the mechanisms how mitochondrion-shaping proteins regulate innate host defense remains largely unknown. Herein we show that mitofusin-2 (MFN2), a mitochondrial fusion protein, promotes innate host defense through the maintenance of aerobic glycolysis and xenophagy via hypoxia-inducible factor (HIF)-1α during intracellular bacterial infection. Myeloid-specific MFN2 deficiency in mice impaired the antimicrobial and inflammatory responses against mycobacterial and listerial infection. Mechanistically, MFN2 was required for the enhancement of inflammatory signaling through optimal induction of aerobic glycolysis via HIF-1α, which is activated by mitochondrial respiratory chain complex I and reactive oxygen species, in macrophages. MFN2 did not impact mitophagy during infection; however, it promoted xenophagy activation through HIF-1α. In addition, MFN2 interacted with the late endosomal protein Rab7, to facilitate xenophagy during mycobacterial infection. Our findings reveal the mechanistic regulations by which MFN2 tailors the innate host defense through coordinated control of immunometabolism and xenophagy via HIF-1α during bacterial infection.

Optimal vacuum erectile device therapy regimen for penile rehabilitation in a bilateral cavernous nerve crush rat model

BACKGROUND

Vacuum erectile device (VED) therapy has been widely used in penile rehabilitation after radical prostatectomy; however, there is no consensus on the best regimen.

OBJECTIVES

To explore an optimal VED therapy regimen in bilateral cavernous nerve crush (BCNC) rat model.

MATERIALS AND METHODS

Adult male rats were used to measure the effects of different durations (1-30 min) of VED treatment on penile length, penile blood gas analysis, and adverse effects. Forty-eight adult male rats were randomly divided into Sham, BCNC, and VED treatment groups (2-3-2-3 min, 4-3-3 min, 5-5 min, and 10 min). Penile length, erectile function, and side effects were detected after VED treatment. Histopathological staining and Western blotting were performed to explore the cellular and molecular changes.

RESULTS

Prolongation of the duration of VED treatment significantly decreased the penile oxygen saturation, partial oxygen pressure, and arterial blood ratio (P < 0.05). Compared with the BCNC group, all VED treatment regimens partially reversed BCNC-induced penile shortening and erectile dysfunction (P < 0.0001), with the 4-3-3-min and 5-5-min treatment groups exhibiting more significant improvement than the 10-min and 2-3-2-3-min treatment groups (P < 0.0001). The mechanism may be related to the up-regulation of the smooth muscle cell/collagen ratio, endothelial nitric oxide synthase, and α-smooth muscle actin (all P < 0.0001); and the down-regulation of hypoxia-inducible factor-1α, transforming growth factor-β1, and apoptosis (all P < 0.0001). The incidence of adverse effects in the 2-3-2-3-min treatment group was the highest.

DISCUSSION

The commonly used VED therapy regimens maintained erectile function and penile length of BCNC rat by relieving hypoxia and fibrosis, and no further benefits were observed with increased treatment frequency or prolonged treatment duration.

CONCLUSION

Two consecutive 5-min treatments with a short interval is the optimal VED therapy regimen for penile rehabilitation in BCNC rat model.

Protective impact of Spirulina platensis against γ-irradiation and thioacetamide-induced nephrotoxicity in rats mediated by regulation of micro-RNA 1 and micro-RNA 146a

Chronic kidney disease develops popular and medical health problems, especially in developing countries. The objective of this study is to investigate the protective mechanism of Spirulina platensis against γ-irradiation (R) and/or thioacetamide (TAA)-induced nephrotoxicity in rats. Rats intoxicated with R or TAA showed alterations in kidney function markers (urea, creatinine, albumin, and total protein contents), oxidative stress markers (malondialdehyde, reduced glutathione), antioxidant enzymes (superoxide dismutase, catalase), and several inflammatory markers (including, the high-sensitivity C-reactive protein, hypoxia-inducible factor-1 alpha, tumor necrosis factor-alpha, interferon-gamma, some interleukins, and nuclear factor-kappa B). Rats also acquired apoptosis, evinced by high caspase-3 efficacy. This nephrotoxicity mediated by upregulation of the messenger RNA (mRNA) gene expression of the autophagy markers: Beclin-1, microtubule-associated protein LC3, p62 binding protein, immunoglobulin G receptor Fcγ receptor (FcγR), micro-RNA-1 (miR-1), protein expression of phospho-adenosine monophosphate-activated protein kinase, and phospho-mammalian target of rapamycin, along with downregulation of miR-146a mRNA gene expression and alteration of calcium and iron levels. The combined treatment R/TAA enhanced the observed oxidative stress, inflammation, apoptosis, and autophagy that mediated by higher upregulation of miR-1 and downregulation of miR-146a mRNA gene expression. Spirulina platensis administration exhibited a nephroprotective impact on R, TAA, and R/TAA toxicities via regulating miR-1 and miR-146a mRNA gene expression that monitored adenosine monophosphate-activated protein kinase/mammalian target of rapamycin signaling.

Deoxypodophyllotoxin Inhibits Non-Small Cell Lung Cancer Cell Growth by Reducing HIF-1α-Mediated Glycolysis

Cancer cell proliferation is a metabolically demanding process that requires high rate of glycolysis to support anabolic growth. Deoxypodophyllotoxin (DPT) is a natural flavonolignan with various pharmacological activities, including antitumor effect. However, whether DPT affects the metabolic reprogramming of cancer cells is unknown. The purpose of this study is to investigate the role of DPT on non-small cell lung cancer (NSCLC) and to explore whether HIF-1α-mediated glycolysis is involved in its mechanism of action.The level of HIF-1α mRNA and protein in NSCLC cells following DPT treatment was detected using qRT-PCR and western blotting, respectively. Cell Counting Kit-8 (CCK-8) and caspase-3 activity assays were performed to analyze cell proliferation and apoptosis. The underlying molecular mechanism was identified by dual luciferase assay, Western blotting, qRT-PCR, glucose consumption, lactate production, and immunoprecipitation. A murine NSCLC model was used to clarify the effect of DPT treatment on tumor cell proliferation. Our findings showed that DPT treatment inhibited NSCLC cell growth in a dose- and time-dependent manner. Further analysis suggested that DPT treatment inhibited HIF-1α signaling pathway by Parkin-mediated protein degradation in NSCLC cells. DPT treatment significantly decreased glucose consumption and lactate production. In addition, DPT treatment reduced the expression of HIF-1α target genes, including GLUT1, HK2 and LDHA, resulting in reduction in glycolysis. We further revealed that DPT-induced cell growth inhibition and increased glucose and lactate levels could be reversed by overexpressing HIF-1α. Additionally, we found that DPT repressed NSCLC growth and GLUT1, HK2 and LDHA expression in vivo. Overall, this study suggested that DPT inhibited NSCLC growth by preventing HIF-1α-mediated glycolysis.

Serum nickel is associated with craniosynostosis risk: Evidence from humans and mice

BACKGROUND

To date, few studies have explored the effects of exposure to metal mixtures on adverse developmental outcomes, and no reported studies have linked metal exposure to craniosynostosis (CS). The purpose of this study is to investigate the association between metal exposure and the risk of CS by conducting epidemiological and experimental studies.

METHODS

Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure the concentrations of 6 metals (chromium [Cr], nickel [Ni], tin [Sn], arsenic [As], thallium [Tl], and lead [Pb]) in serum samples from 174 CS patients and 85 control individuals. Non-syndromic patients with isolated sagittal suture closure were selected as the case group, and healthy children matched by sex and age were selected as controls. Bayesian kernel machine regression (BKMR) models were used to account for joint metal effects. Multiple logistic regression analysis was used to explore the association between metal concentration and CS occurrence, with adjustment for potential confounders. During pregnancy, mice were exposed to Ni (0, 0.05, or 0.1 g/kg/day) until weaning, and the widths of the sutures and shapes of the skull were analysed by micro-CT 3D imaging and histological analysis. MC3T3-E1 cells were treated with Ni (0, 0.005, or 0.05 μg/mL) for 72 h. Alkaline phosphate (ALP) staining and Alizarin red staining were performed to observe the development of osteoblasts. The expression levels of osteoblast-related genes were also detected.

RESULTS

A positive association between the metal mixture and CS risk was observed based on population data; the Ni group had the highest conditional posterior inclusion probability (PIP), at 0.8416, and in the fully adjusted model, the highest Ni exposure level had a more significant association with CS (coefficient = 2.65, 95% CI: 0.29, 5.02) than the lowest Ni exposure level. The mean widths of the sagittal sutures in mice were 8.8 ± 0.6 mm in the control group, 8.0 ± 0.8 mm in the 0.05 g/kg/day group and 6.8 ± 0.4 mm in the 0.1 g/kg/day group. After Ni exposure, ALP gene expression in skull tissue was increased, and ALP activity was increased in MC3T3-E1 cells. Moreover, increased collagen content in mouse skull sections and elevated osteocalcin (OCN) expression in MC3T3-E1 cells were observed in the Ni-treated groups compared to the control group.

CONCLUSIONS

This study is the first to provide evidence that increased serum Ni was associated with an increased risk of CS. Early life exposure to Ni promoted osteogenesis during skull growth, which may contribute to the development of CS.

4-O-methylascochlorin attenuates inflammatory responses induced by lipopolysaccharide in RAW 264.7 macrophages

Inflammation is implicated in various diseases, such as inflammatory bowel disease and cancer. Ascochlorin (ASC) and its derivatives have been shown to modulate inflammatory responses in many previous studies. However, the effects of 4-O-methylascochlorin (MAC), one of the ASC derivatives, on inflammatory responses have yet to be reported. In addition, the consequences of chemical modification of ASC on protein signaling and immunity have yet to be fully understood. The fourth carbon in MAC is methylated, which may result in modulation of immune response differently compared with ASC. Hence, we have investigated the role of MAC in inflammatory response induced by lipopolysaccharide in murine macrophage cells. Here, we found that MAC treatment decreased the inflammatory response by murine macrophages. When murine macrophages were treated with MAC, the transcription and translation of various pro-inflammatory indicators such as iNOS and COX-2 decreased. In addition, the ELISA results showed that the expression of TNF-α, IL-6, and IL-1β, which are pro-inflammatory cytokines, was successfully decreased by MAC. Such effects of MAC appear to be mediated via downregulation of MAPK signaling and the transactivational activity of NF-κB. Lipopolysaccharide upregulates MAPK protein phosphorylation and NF-κB translocation, which in turn enhances the transactivation of genes related to NF-κB. Such results of lipopolysaccharide were attenuated by MAC. Collectively, our results indicate that MAC alleviated the inflammatory responses induced by lipopolysaccharide in murine macrophages successfully by modulating MAPK signaling pathway and NF-κB-related genes. This study shows that MAC, similar to other ASC derivatives, can potentially be used therapeutically to reduce the harmful damage induced by prolonged inflammation. In addition, the structural differences between ASC and its derivatives as well as their effect on intracellular signaling will also be discussed.

BNIP3 in Lung Cancer: To Kill or Rescue?

Simple Summary

Bcl-2/adenovirus E1B 19kDa interacting protein 3 (BNIP3) is a pro-apoptotic BH3-only protein of the Bcl-2 family. Its function in various biological processes was described. Although potential involvement of BNIP3 in cancer progression has been discussed in many review articles, its specific role in lung cancer is still unclear. In this review, we shed light on the BNIP3‘s role in different types of cancer in general and lung cancer, in particular, as well as suggested its potential for targeting therapy of lung cancer.

Abstract

Bcl-2/adenovirus E1B 19kDa interacting protein 3 (BNIP3) is a pro-apoptotic BH3-only protein of the Bcl-2 family. Initially, BNIP3 was described as one of the mediators of hypoxia-induced apoptotic cell death in cardiac myocytes and neurons. Besides apoptosis, BNIP3 plays a crucial role in autophagy, metabolic pathways, and metastasis-related processes in different tumor types. Lung cancer is one of the most aggressive types of cancer, which is often diagnosed at an advanced stage. Therefore, there is still urgent demand for reliable biochemical markers for lung cancer and its efficient treatment. Mitochondria functioning and mitochondrial proteins, including BNIP3, have a strong impact on lung cancer development and progression. Here, we summarized current knowledge about the BNIP3 gene and protein features and their role in cancer progression, especially in lung cancer in order to develop new therapeutic approaches associated with BNIP3.

Activation of AMPK under Hypoxia: Many Roads Leading to Rome

AMP-activated protein kinase (AMPK) is known as a pivotal cellular energy sensor, mediating the adaptation to low energy levels by deactivating anabolic processes and activating catabolic processes in order to restore the cellular ATP supply when the cellular AMP/ATP ratio is increased. Besides this well-known role, it has also been shown to exert protective effects under hypoxia. While an insufficient supply with oxygen might easily deplete cellular energy levels, i.e., ATP concentration, manifold other mechanisms have been suggested and are heavily disputed regarding the activation of AMPK under hypoxia independently from cellular AMP concentrations. However, an activation of AMPK preceding energy depletion could induce a timely adaptation reaction preventing more serious damage. A connection between AMPK and the master regulator of hypoxic adaptation via gene transcription, hypoxia-inducible factor (HIF), has also been taken into account, orchestrating their concerted protective action. This review will summarize the current knowledge on mechanisms of AMPK activation under hypoxia and its interrelationship with HIF.

Alpha7 Nicotinic Acetylcholine Receptor Alleviates Inflammatory Bowel Disease Through Induction of AMPK-mTOR-p70S6K-Mediated Autophagy

Alpha7 nicotinic acetylcholine receptor (α7nAChR) has been reported to be protective in several kinds of disorders through inflammatory suppression. Here, we investigated the role of α7nAChR in inflammatory bowel disease (IBD) on α7nAChR deficient mice (α7nAChR^-/-) and the wild-type mice (α7nAChR^+/+). Three percent dextran sulfate sodium (DSS) was used for the creation of IBD mice model and lipopolysaccharides (LPS)/DSS as an inflammatory stressor in murine bone marrow-derived macrophages (BMDMs). The severity of IBD was determined and HE staining as well as enzyme-linked immunosorbent assay (ELISA) and real-time PCR were used to detect the level of inflammatory activation. Western blot was used to determine the levels of autophagy-related proteins. Transmission electron microscopy and mRFP-GFP-LC3 plasmid were applied to determine the levels of autophagy. We demonstrated that deficiency in α7nAChR produced a detrimental effect on IBD severity and inflammatory reaction in DSS-induced colitis models. Those effects were led to via autophagy dysfunction. α7nAChR deficiency attenuated the protective and anti-inflammatory effect of autophagy inducer in IBD mice and BMDMs challenged with LPS/DSS. The alleviative effect of activating α7nAChR was attenuated through inhibiting adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-mediated signaling. In conclusion, α7nAChR contributes to alleviate IBD through the induction of AMPK-mammalian target of rapamycin rabbit (mTOR)-p70 ribosomal protein S6 kinase (p70S6K)-mediated autophagy, thus providing a novel target for the treatment of IBD.

4-O-methylascochlorin stabilizes hypoxia-inducible factor-1 in a manner different from hydroxylase inhibition by iron chelating or substrate competition

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that plays essential roles in human diseases including cancer. The synthetic ascochlorin derivative 4-O-methylascochlorin stabilizes HIF-1α protein, and activates its transcriptional activity, resulting to induce gene expression of its downstream targets such as VEGF and GLUT-1. Here, we quantified protein level of HIF-1α in human osteosarcoma U2OS cells treated with ascochlorin-related compounds and typical HIF-1α stabilizers to characterize properties of HIF-1α stabilization by 4-O-methylascochlorin. Structure-activity relationship studies suggested that the aromatic moiety and hydrophobic substitution of the 4'-hydroxyl group are important for HIF-1α stabilization by ascochlorin-related compounds. 4-O-Methylascochlorin-induced HIF-1α stabilization was suppressed by ascorbic acid and compound C, but not by Fe(II), whereas ascorbic acid only suppressed HIF-1α stabilization by dimethyloxaloylglycine, an analog of the HIF-1 hydroxylase substrate. Fe(II) completely suppressed iron chelator-induced stabilization. These results suggest that ascochlorin-related compounds stabilize HIF-1α in a manner distinct from iron chelating or substrate competition.

Upregulation of AMPK by 4-O-methylascochlorin promotes autophagy via the HIF-1α expression

4‐O‐methylascochlorin (MAC) is a derivative of ascochlorin, a prenyl‐phenol compound antibiotic isolated from the fungus Ascochyta viciae. MAC induces caspase/poly (ADP‐ribose) polymerase‐mediated apoptosis in leukemia cells. However, the effects of MAC on autophagy in cancer cells and the underlying molecular mechanisms remain unknown. Here, we show that MAC induces autophagy in lung cancer cells. MAC significantly induced the expression of autophagy marker proteins including LC3‐II, Beclin1, and ATG7. MAC promoted AMP‐activated protein kinase (AMPK) phosphorylation and inhibited the phosphorylation of mammalian target of rapamycin (mTOR) and its downstream signalling proteins P70S6K and 4EBP1. The AMPK activator AICAR upregulated LC3‐II expression through the AMPK/mTOR pathway similar to the effects of MAC. MAC‐induced LC3‐II protein expression was slightly reduced in AMPK siRNA transfected cells. MAC upregulated hypoxia‐inducible factor‐1α (HIF‐1α) and BNIP3, which are HIF‐1α‐dependent autophagic proteins. Treatment with CoCl₂, which mimics hypoxia, induced autophagy similar to the effect of MAC. The HIF‐1α inhibitor YC‐1 and HIF‐1α siRNA inhibited the MAC‐induced upregulation of LC3‐II and BNIP3. These results suggest that MAC induces autophagy via the AMPK/mTOR signalling pathway and by upregulating HIF‐1α and BNIP3 protein expression in lung cancer cells.