Decline In ATP Levels Research Articles

Rational design of an activatable dual-color fluorogenic probe for revealing the interaction of adenosine-5′-triphosphate and peroxynitrite in pyroptosis associated with acute kidney injury

ATP and ONOO- play unique roles in various biological events and exhibit notable interactions. To date, there is no available chemical tool for investigating the correlation between ATP and ONOO- concentrations in pyroptosis associated with acute kidney injury (AKI). Herein, we designed a novel dual-color near-infrared fluorescent (NIRF) probe P2 for simultaneous visualization of ATP and ONOO- both in vitro and in vivo. Unlike previously reported single-site fluorescent probes, P2 enabled concurrent imaging of ATP and ONOO- in two distinct fluorescence channels, with emission wavelengths centered at 585 and 690 nm, which greatly reduced spectral cross-talk. Employing a HK-2 pyroptosis model, a significant interaction between ATP and ONOO- was unveiled. Elevated ONOO- production was found to correlate with decreased ATP levels; conversely, an increase in ATP levels was associated with rapid ONOO- scavenging. Remarkably, P2 allowed the assessment of cellular hypoxia by monitoring ATP and ONOO- concentrations. The commercial ONOO--scavenger uric acid showcased a protective effect on HK-2 cells via inhibition of the cellular pyroptosis pathway. Furthermore, P2 was successfully employed for imaging of ATP and ONOO- in the AKI mice model. Our findings confirmed that renal ischemia-reperfusion triggered a rise in ONOO- levels, concurrent with a decline in ATP levels. Surprisingly, the cells exhibited a compensatory recovery of ATP levels as the reperfusion time was prolonged. These results suggested the newly devised P2, as a pivotal chemical tool for the simultaneous monitoring of ATP and ONOO-, might open new avenues for disease diagnosis and treatment.

Metformin-induced oxidative stress inhibits LNCaP prostate cancer cell survival.

Preclinical and clinical studies over the past several decades have indicated the potential value of metformin, a widely utilized treatment for Type 2 diabetes, in prostate cancer therapy. Notably, these studies demonstrated metformin's pleiotropic effects on several molecular and metabolic pathways, such as androgen signaling, cell cycle, and cellular bioenergetics. In this study we investigated the role of metformin in regulating intracellular redox status and cell survival in LNCaP prostate cancer cells. The cytotoxic effects of metformin with or without the presence of SBI0206965 (AMPK inhibitor) on LNCaP cells were determined using MTT and trypan blue exclusion assays. Seahorse XP extracellular analysis, Liquid Chromatography/ Mass Spectrophotometry (LC/MS), and 2,7- and Dichlorofluoresin diacetate (DCFDA) assay were used to assess the effects of metformin on cellular bioenergetics, redox status, and redox-related metabolites. mRNA expression and protein concentration of redox-related enzymes were measured using Real Time-qPCR and ELISA assay, respectively. Independently of AMP-activated protein kinase, metformin exhibited a dose- and time-dependent inhibition of LNCaP cell survival, a response mitigated by glutathione or N-acetylcysteine (ROS scavengers) treatment. Notably, these findings were concomitant with a decline in ATP levels and the inhibition of oxidative phosphorylation. The results further indicated metformin's induction of reactive oxygen species, which significantly decreased glutathione levels and the ratio of reduced to oxidized glutathione, as well as the transsulfuration metabolite, cystathionine. Consistent with an induction of oxidative stress condition, metformin increased mRNA levels of the master redox transcription factor Nrf-2 (nuclear factor erythroid-derived 2-like), as well as transsulfuration enzymes cystathionine beta-synthase and cystathionase and GSH synthesis enzymes γ-glutamylcysteine synthetase and glutathione synthetase. Our findings highlight multiple mechanisms by which metformin-induced formation of reactive oxygen species may contribute to its efficacy in prostate cancer treatment, including promotion of oxidative stress, Nrf2 activation, and modulation of redox-related pathways, leading to its anti-survival action.

Glucagon-like peptide-1 analogs activate AMP kinase leading to reversal of the Warburg metabolic switch in breast cancer cells.

Breast cancer (BC) is associated with type 2 diabetes mellitus (T2DM) and obesity. Glucagon-like peptide (GLP)-1 regulates post-prandial insulin secretion, satiety, and gastric emptying. Several GLP-1 analogs have been FDA-approved for the treatment of T2DM and obesity. Moreover, GLP-1 regulates various metabolic activities across different tissues by activating metabolic signaling pathways like adenosine monophosphate (AMP) activated protein kinase (AMPK), and AKT. Rewiring metabolic pathways is a recognized hallmark of cancer, regulated by several cancer-related pathways, including AKT and AMPK. As GLP-1 regulates AKT and AMPK, we hypothesized that it alters BC cells' metabolism, thus inhibiting proliferation. The effect of the GLP-1 analogs exendin-4 (Ex4) and liraglutide on viability, AMPK signaling and metabolism of BC cell lines were assessed. Viability of BC cells was evaluated using colony formation and MTT/XTT assays. Activation of AMPK and related signaling effects were evaluated using western blot. Metabolism effects were measured for glucose, lactate and ATP. Exendin-4 and liraglutide activated AMPK in a cAMP-dependent manner. Blocking Ex4-induced activation of AMPK by inhibition of AMPK restored cell viability. Interestingly, Ex4 and liraglutide reduced the levels of glycolytic metabolites and decreased ATP production, suggesting that GLP-1 analogs impair glycolysis. Notably, inhibiting AMPK reversed the decline in ATP levels, highlighting the role of AMPK in this process. These results establish a novel signaling pathway for GLP-1 in BC cells through cAMP and AMPK modulation affecting proliferation and metabolism. This study suggests that GLP-1 analogs should be considered for diabetic patients with BC.

Transcriptomic analyses of Vibrio parahaemolyticus under the phenyllactic acid stress

Phenyllactic acid (PLA) generally recognized as a natural organic acid shows against Vibrio parahaemolyticus activity. In this study, V. parahaemolyticus ATCC17802 (Vp17802) was cultured under the stress of 1/2MIC PLA, and then the antibacterial mechanisms were explored via transcriptomics. The minimum inhibitory concentration (MIC) of PLA against Vp17802 was 3.2 mg/mL, and the time-kill analysis resulted that Vp17802 was inhibited. PLA was able to destroy the bacterial membrane, leading to the leakage of intracellular substances and decline of ATP levels. The RNA-sequencing analysis results indicated that 1616 significantly differentially expressed genes were identified, among which 190 were up-regulated and 1426 were down-regulated. Down-regulation of the icd2 gene in the TCA cycle mediates blockage of tyrosine metabolic, arginine biosynthesis, and oxidative phosphorylation, causing insufficient energy supply of Vp17802. Moreover, PLA could cause amino acids, metal ions, and phosphate transporters to be blocked, affecting the acquisition of nutrients. The treatment by PLA altered the expression of genes encoding functions involved in quorum sensing, flagellar assembly, and cell chemotaxis pathway, which may be interfering with the biofilm formation in Vp17802, reducing cell motility. Overall, 1.6 mg/mL PLA inhibited the growth of Vp17802 by disrupting to uptake of nutrients, cell metabolism, and the formation of biofilms. The results suggested a new direction for exploring the activity of PLA against Vp17802 and provided a theoretical basis for bacterial pathogen control in the food industry.Key points•RNA sequencing was carried out to indicate the antibacterial mechanism of Vp17802.•The icd2 gene in the TCA cycle mediates blockage of metabolic of Vp17802.•The biofilm formation has interfered with 1.6 mg/mL PLA, which could reduce cell motility and virulence.Graphical

The Role of Mitochondria in Ozone Therapy

Inhaled ozone can react with the biomolecules present in the epithelial lining fluid, causing the depletion of antioxidants. It can react with the surfactant polyunsaturated fatty acids (PUFA) present at the air-ELF interface to form several reactive oxygen species (ROS). High ozone exposure resulted in sustained ventricular tachycardia in male and female rats. Ozone can induce oxidative stress, alter some inflammatory factors in tissue, and induce mitochondria-dependent apoptosis. It is not surprising that the mitochondria could be putatively affected by ozone as this organelle is highly sensitive to oxidative stress. Exposure of blood to a few micrograms of ozone was shown to cause a decrease in mitochondrial function and energy metabolism, as it caused a decline in ATP levels and an increase in the NADH/NAD+ ratio. It was also found that cytochrome-c-oxidase was almost wholly inhibited under these conditions. However, in a specific range of concentrations, ozone can induce a beneficial modulation in the anti-inflammatory and antioxidant systems. Some of the biological responses induced by ozone may be potentially suitable to become an active part of the various mechanisms of metabolic regulation, with positive effects on several pathologies. The therapeutic efficacy of ozone therapy may result from controlled and moderate oxidative stress produced by ozone’s reactions with various biological components. Although there is not enough data, there are indications that ozone may induce good responses in mitochondria.

KUS121 attenuates the progression of monosodium iodoacetate-induced osteoarthritis in rats

Currently there is no effective treatment available for osteoarthritis (OA). We have recently developed Kyoto University Substances (KUSs), ATPase inhibitors specific for valosin-containing protein (VCP), as a novel class of medicine for cellular protection. KUSs suppressed intracellular ATP depletion, endoplasmic reticulum (ER) stress, and cell death. In this study, we investigated the effects of KUS121 on chondrocyte cell death. In cultured chondrocytes differentiated from ATDC5 cells, KUS121 suppressed the decline in ATP levels and apoptotic cell death under stress conditions induced by TNFα. KUS121 ameliorated TNFα-induced reduction of gene expression in chondrocytes, such as Sox9 and Col2α. KUS121 also suppressed ER stress and cell death in chondrocytes under tunicamycin load. Furthermore, intraperitoneal administration of KUS121 in vivo suppressed chondrocyte loss and proteoglycan reduction in knee joints of a monosodium iodoacetate-induced OA rat model. Moreover, intra-articular administration of KUS121 more prominently reduced the apoptosis of the affected chondrocytes. These results demonstrate that KUS121 protects chondrocytes from stress-induced cell death in vitro and in vivo, and indicate that KUS121 is a promising novel therapeutic agent to prevent the progression of OA.

The mitochondria-targeted hydrogen sulfide donor AP39 improves health and mitochondrial function in a C. elegans primary mitochondrial disease model.

Primary mitochondrial diseases (PMD) are inherited diseases that cause dysfunctional mitochondrial oxidative phosphorylation, leading to diverse multisystem diseases and substantially impaired quality of life. PMD treatment currently comprises symptom management, with an unmet need for therapies targeting the causative mitochondrial defects. Molecules which selective target mitochondria have been proposed as potential treatment options in PMD but have met with limited success. We have previously shown in animal models that mitochondrial dysfunction caused by the disease process could be prevented and/or reversed by selective targeting of the "gasotransmitter" hydrogen sulfide (H2 S) to mitochondria using a novel compound, AP39. Therefore, in this study we investigated whether AP39 could also restore mitochondrial function in PMD models where mitochondrial dysfunction was the cause of the disease pathology using C. elegans. We characterised several PMD mutant C. elegans strains for reduced survival, movement and impaired cellular bioenergetics and treated each with AP39. In animals with widespread electron transport chain deficiency (gfm-1[ok3372]), AP39 (100 nM) restored ATP levels, but had no effect on survival or movement. However, in a complex I mutant (nuo-4[ok2533]), a Leigh syndrome orthologue, AP39 significantly reversed the decline in ATP levels, preserved mitochondrial membrane potential and increased movement and survival. For the first time, this study provides proof-of-principle evidence suggesting that selective targeting of mitochondria with H2 S could represent a novel drug discovery approach to delay, prevent and possibly reverse mitochondrial decline in PMD and related disorders.

Sex-specific metabolic and functional differences in human umbilical vein endothelial cells from twin pairs

Background and aimsGonadal hormones are mainly thought to account for sex and gender differences in the incidence, clinical manifestation and therapy of many cardiovascular diseases. However, intrinsic sex differences at the cellular level are mostly overlooked. Here, we assessed sex-specific metabolic and functional differences between male and female human umbilical vein endothelial cells (HUVECs). MethodsCellular metabolism was investigated by bioenergetic studies (Seahorse Analyser) and a metabolomic approach. Protein levels were determined by Western blots and proteome analysis. Vascular endothelial growth factor (VEGF)-stimulated cellular migration was assessed by gap closure. HUVECs from dizygotic twin pairs were used for most experiments. ResultsNo sex differences were observed in untreated cells. However, sexual dimorphisms appeared after stressing the cells by serum starvation and treatment with VEGF. Under both conditions, female cells had higher intracellular ATP and metabolite levels. A significant decline in ATP levels was observed in male cells after serum starvation. After VEGF, the ratio of glycolysis/mitochondrial respiration was higher in female cells and migration was more pronounced. ConclusionsThese results point to an increased stress tolerance of female cells. We therefore propose that female cells have an energetic advantage over male cells under conditions of diminished nutrient supply. A more favourable energy balance of female HUVECs after serum starvation and VEGF could potentially explain their stronger migratory capacity.

α-Synuclein induced mitochondrial dysfunction via cytochrome c oxidase subunit 2 in SH-SY5Y cells

The transfer of misfolded α-Synuclein (α-Syn) from cell to cell as a prion protein is important in α-Synucleinopathies. Extraneous α-Syn induces apoptosis of dopaminergic neurons by causing mitochondrial dysfunction. However, the mechanism by which α-Syn disrupts the mitochondrial function is still unclear. In the present study, we used a gene microarray and western blotting analysis to show that the expression of mitochondrially encoded cytochrome c oxidase subunit 2 (MT-CO2, COXII) increased significantly in SH-SY5Y cells stimulated by α-Syn for 24 h. Furthermore, the decline in ATP levels, the decreased mitochondrial membrane potential, and the enhanced reactive oxygen species in cells treated by α-Syn was reversed by inhibiting MT-CO2 gene expression. Subsequently, we observed that upregulation of MT-CO2 contributed to the release of cytochrome c and altered the levels of certain mitochondria-localized proteins, such as BCL2 family proteins. Therefore, we hypothesized that after being transferred into dopaminergic neurons, α-Syn injures mitochondria via activating MT-CO2. Our results suggested the initial step of the process by which α-Syn injures dopaminergic neurons and provides new therapeutic targets for α-Syn associated neurodegenerative disorders.

Interaction of mitochondrial fission factor with dynamin related protein 1 governs physiological mitochondrial function in vivo

Mitochondria form a dynamic network governed by a balance between opposing fission and fusion processes. Because excessive mitochondrial fission correlates with numerous pathologies, including neurodegeneration, the mechanism governing fission has become an attractive therapeutic strategy. However, targeting fission is a double-edged sword as physiological fission is necessary for mitochondrial function. Fission is trigged by Drp1 anchoring to adaptors tethered to the outer mitochondrial membrane. We designed peptide P259 that distinguishes physiological from pathological fission by specifically inhibiting Drp1′s interaction with the Mff adaptor. Treatment of cells with P259 elongated mitochondria and disrupted mitochondrial function and motility. Sustained in vivo treatment caused a decline in ATP levels and altered mitochondrial structure in the brain, resulting in behavioral deficits in wild-type mice and a shorter lifespan in a mouse model of Huntington’s disease. Therefore, the Mff-Drp1 interaction is critical for physiological mitochondrial fission, motility, and function in vitro and in vivo. Tools, such as P259, that differentiate physiological from pathological fission will enable the examination of context-dependent roles of Drp1 and the suitability of mitochondrial fission as a target for drug development.

Activation of Lxrr Causes Metabolic Reprogramming and Sensitizes Solid Tumors to Bcl-xL Inhibition Mediated Apoptosis

Liver-X-receptor agonists (LXR) have been shown to bear anti-tumor activity. However, their efficacy is limited and therefore additional strategies to further enhance their anti-cancer activity are warranted. By uncovering novel and unexpected mechanisms through transcriptome and gene set enrichment analysis coupled with global untargeted metabolite screening, we show that LXR agonists, LXR623 and GW3965, enhance the anti-proliferative effects of clinically validated as well as novel selective BH3-mimetics in solid tumor malignancies, including glioblastoma, colon carcinoma, melanoma and triple-receptor negative breast cancer. LXR agonists and ABT263 acted in a synergistic fashion to reduce proliferation of cancer cells, which was predominantly mediated by enhanced apoptosis. Inhibition of Bcl-xL was most relevant for the combination treatment to exert its effects. Extracellular flux analysis revealed that activation of LXRβ resulted in reprogramming of tumor cell metabolism, leading to suppression of mitochondrial respiration, which occurred independent of cholesterol. Instead, LXR activation engages in a transcriptional program to suppress mitochondrial metabolism. In turn, this leads to a subsequent decline in ATP levels, culminating in endoplasmic reticulum stress with upregulation of pro-apoptotic Noxa in an ATF4 dependent manner. Consistently, siRNA mediated suppression of Noxa rescued from the combination treatment of BH3-mimetics and LXR agonists. In conventional and patient-derived xenograft models of colon carcinoma, melanoma and glioblastoma, the combination treatment of ABT263 and LXR agonists reduced tumor sizes significantly stronger than single treatments. Therefore, the combination treatment of LXR agonists and BH3-mimetics might be a viable efficacious treatment approach for solid malignancies.

Pinocembrin Provides Mitochondrial Protection by the Activation of the Erk1/2-Nrf2 Signaling Pathway in SH-SY5Y Neuroblastoma Cells Exposed to Paraquat.

Pinocembrin (PB; 5,7-dihydroxyflavanone; C15H12O4) is a flavonoid found in propolis and exerts antioxidant, anti-inflammatory, and antimicrobial effects. Furthermore, PB has been studied as a neuroprotective agent. However, it remains to be understood whether and how PB would induce mitochondrial protection in mammalian cells. Therefore, we investigated here the mechanism involved in the protective effects elicited by PB in paraquat (PQ; 100μM)-treated SH-SY5Y neuroblastoma cells. PB (25μM) pretreatment (for 4h) downregulated the levels of Bcl-2-associated X protein (Bax), blocked the release of cytochrome c to the cytosol, and inhibited the PQ-induced activation of caspase-9 and caspase-3. Besides, PB prevented mitochondrial dysfunction by suppressing the PQ-elicited inhibition of complexes I and V. Moreover, PB abrogated the loss of mitochondrial membrane potential (MMP) and the decline in ATP levels in the cells exposed to PQ. PB exerted antioxidant effects on mitochondria by decreasing the levels of redox impairment markers in mitochondrial membranes. Importantly, PB enhanced the levels of mitochondrial reduced glutathione (GSH). Upregulation of enzymes involved in the synthesis of GSH was seen in the cells exposed to PB. PB afforded mitochondrial protection by activating the extracellular signal-regulated kinase/nuclear factor erythroid 2-related factor 2 (Erk1/2-Nrf2) axis, since inhibition of Erk1/2 or silencing of Nrf2 abrogated these effects. Therefore, PB exerted mitochondrial and cellular protection by an Erk1/2-Nrf2-dependent mechanism.

Abstract 606: Similar 3D pharmacodynamic (3D-PD) responses of human tumor spheroids and xenografts to topoisomerase 1 inhibitor-induced DNA damage

Abstract Three-dimensional (3D) cultures have been proposed as higher fidelity models of in vivo tumors than 2D cultures. To determine whether this idea extends to drug pharmacodynamics, we examined whether 3D cultures of the human melanoma line A375 (grown as tumor spheroids) could replicate the timing and magnitude of the nuclear γH2AX response to the topoisomerase 1 inhibitor, topotecan observed in A375 tumor xenografts (Kinders et al, Clin Can Res 2010). The appearance of γH2AX-positive nuclear foci has been used as a biomarker for drug- and radiation-induced double-strand breaks in DNA; we reported previously that treatment of nu/nu mice harboring A375 xenografts with a single-dose of topotecan induced nuclear γH2AX foci in a dose- and time-dependent manner, which peaked 4 hours after drug administration. A375 spheroids were generated by seeding cells into ULA U-bottom plates; 4 hours of exposure to 0.1 μM topotecan elicited a γH2AX signal in these 3D cultures while cell viability and intracellular ATP levels remained unchanged, indicating a DNA damage repair response at the maximally tolerated topotecan concentration for human hematopoietic cells (Erickson-Miller et al, Can Chemo Pharmacol 2009). Extending drug exposure to 24 hours caused substantial loss of viable cells (calcein AM+) and 50% decline in ATP levels but no further increase in γH2AX. In contrast, the HT29 tumor line was refractory to topotecan in vivo, and exposing 3D cultures of HT-29 spheroids to 0.1 μM topotecan for 24 hours elicited a strong nuclear γH2AX biomarker response in only a small fraction of cells at the surface of the spheroids. Longer exposure durations or supra-pharmacological concentrations (1 μM) of topotecan were required to achieve a strong nuclear γH2AX response in HT-29 spheroids. These results support the hypothesis that the 3D pharmacodynamics (PD) of drug response is similar to PD drug response in vivo for the camptothecin class of topoisomerase 1 inhibitors. Funded by NCI Contract No. HHSN261200800001E. Citation Format: David M. Evans, Rene Delosh, Julie Laudeman, Chad Ogle, Russell Reinhart, Michael Selby, Silvers Thomas, Robert Kinders, Tony Navas, Scott Lawrence, Anne Monks, Annamaria Rapisarda, Ralph E. Parchment, James H. Doroshow, Beverly Teicher. Similar 3D pharmacodynamic (3D-PD) responses of human tumor spheroids and xenografts to topoisomerase 1 inhibitor-induced DNA damage. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 606.

Sestrin2 is induced by glucose starvation via the unfolded protein response and protects cells from non-canonical necroptotic cell death.

Sestrin2 is a member of a family of stress responsive proteins, which controls cell viability via antioxidant activity and regulation of the mammalian target of rapamycin protein kinase (mTOR). Sestrin2 is induced by different stress insults, which diminish ATP production and induce energetic stress in the cells. Glucose is a critical substrate for ATP production utilized via glycolysis and mitochondrial respiration as well as for glycosylation of newly synthesized proteins in the endoplasmic reticulum (ER) and Golgi. Thus, glucose starvation causes both energy deficiency and activation of ER stress followed by the unfolding protein response (UPR). Here, we show that UPR induces Sestrin2 via ATF4 and NRF2 transcription factors and demonstrate that Sestrin2 protects cells from glucose starvation-induced cell death. Sestrin2 inactivation sensitizes cells to necroptotic cell death that is associated with a decline in ATP levels and can be suppressed by Necrostatin 7. We propose that Sestrin2 protects cells from glucose starvation-induced cell death via regulation of mitochondrial homeostasis.

Testosterone Replacement Modulates Cardiac Metabolic Remodeling after Myocardial Infarction by Upregulating PPARα.

Despite the importance of testosterone as a metabolic hormone, its effects on myocardial metabolism in the ischemic heart remain unclear. Myocardial ischemia leads to metabolic remodeling, ultimately resulting in ATP deficiency and cardiac dysfunction. In the present study, the effects of testosterone replacement on the ischemic heart were assessed in a castrated rat myocardial infarction model established by ligating the left anterior descending coronary artery 2 weeks after castration. The results of real-time PCR and Western blot analyses showed that peroxisome proliferator-activated receptor α (PPARα) decreased in the ischemic myocardium of castrated rats, compared with the sham-castration group, and the mRNA expression of genes involved in fatty acid metabolism (the fatty acid translocase CD36, carnitine palmitoyltransferase I, and medium-chain acyl-CoA dehydrogenase) and glucose transporter-4 also decreased. A decline in ATP levels in the castrated rats was accompanied by increased cardiomyocyte apoptosis and fibrosis and impaired cardiac function, compared with the sham-castration group, and these detrimental effects were reversed by testosterone replacement. Taken together, our findings suggest that testosterone can modulate myocardial metabolic remodeling by upregulating PPARα after myocardial infarction, exerting a protective effect on cardiac function.

Electroacupuncture Upregulates SIRT1-Dependent PGC-1α Expression in SAMP8 Mice.

BackgroundAbnormalities of brain energy metabolism are involved in Alzheimer disease (AD). Sirtuin 1 (SIRT1) is a class III histone deacetylase and activates peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α), which enhances mitochondrial biogenesis and energy homeostasis. Electroacupuncture (EA) has been reported to improve brain energy metabolism in AD. However, the effect of EA on SIRT1 and PGC-1α in AD remains unclear.Material/MethodsATP levels were measured using assay kits in the hippocampus and frontal cortex of senescence-accelerated mouse prone 8 (SAMP8) mice. Western blotting analysis and quantitative real-time RT-PCR were performed to measure the expression of SIRT1 and PGC-1α in the hippocampus of SAMP8 mice. PGC-1α acetylation was analyzed using immunoprecipitation.ResultsCompared with senescence-accelerated resistant mice 1 (SAMR1) mice, SAMP8 mice had a decline in ATP levels and the expression of SIRT1 and PGC-1α. EA treatment improved ATP levels, upregulated the expression of SIRT1 and PGC-1α, and decreased PGC-1α acetylation.ConclusionsThese data suggest that EA improved brain energy metabolism, potentially associated with the upregulation of SIRT1-dependent PGC-1α expression.

Silibinin, a natural flavonoid, induces autophagy via ROS-dependent mitochondrial dysfunction and loss of ATP involving BNIP3 in human MCF7 breast cancer cells.

Silibinin, derived from the milk thistle plant (Silybum marianum), has anticancer and chemopreventive properties. Silibinin has been reported to inhibit the growth of various types of cancer cells. However, the mechanisms by which silibinin exerts an anticancer effect are poorly defined. The present study aimed to investigate whether silibinin-induced cell death might be attributed to autophagy and the underlying mechanisms in human MCF7 breast cancer cells. Our results showed that silibinin-induced cell death was greatly abrogated by two specific autophagy inhibitors, 3-methyladenine (3-MA) and bafilomycin-A1 (Baf-A1). In addition, silibinin triggered the conversion of light chain 3 (LC3)-I to LC3-II, promoted the upregulation of Atg12-Atg5 formation, increased Beclin-1 expression, and decreased the Bcl-2 level. Moreover, we noted elevated reactive oxygen species (ROS) generation, concomitant with the dissipation of mitochondrial transmembrane potential (ΔΨm) and a drastic decline in ATP levels following silibinin treatment, which were effectively prevented by the antioxidants, N-acetylcysteine and ascorbic acid. Silibinin stimulated the expression of Bcl-2 adenovirus E1B 19-kDa-interacting protein 3 (BNIP3), a pro-death Bcl-2 family member, and silencing of BNIP3 greatly inhibited silibinin-induced cell death, decreased ROS production, and sustained ΔΨm and ATP levels. Taken together, these findings revealed that silibinin induced autophagic cell death through ROS-dependent mitochondrial dysfunction and ATP depletion involving BNIP3 in MCF7 cells.

NADPH oxidase 2-dependent oxidative stress, mitochondrial damage and apoptosis in the ventral cochlear nucleus of d-galactose-induced aging rats

Aging has been associated with oxidative stress and the accumulation of mitochondrial DNA (mtDNA) mutation. The previous study has established a mimetic rat model of aging using d-galactose (d-gal) and revealed that chronic injection of d-gal can increase NADPH oxidase (NOX)-dependent oxidative stress, mitochondrial damage and apoptosis in the peripheral auditory system. However, the effects of NOXs in the central auditory system (CAS) were still obscure. The current study was designed to investigate potential causative mechanisms of central presbycusis by using the d-gal-induced aging rats. We found that the levels of H2O2 and the expression of NADPH oxidase 2 (NOX2) and its corresponding subunits P22phox, P47phox and P67phox were greatly increased in the ventral cochlear nucleus (VCN) of d-gal-treated rats as compared with controls. And, the levels of a typical biomarker of oxidative stress, 8-hydroxy-2-deoxyguanosine (8-OHdG), and the accumulation of mtDNA common deletion (CD) were also increased in the VCN of d-gal-treated rats as compared with controls. Moreover, the damage of mitochondrial ultrastructure, a decline in ATP levels, the loss of mitochondrial membrane potential (MMP), an increase in the amount of cytochrome c (cyt c) translocated to the cytoplasm and caspase-3 activation were observed in the VCN induced by d-gal. In addition, we also found that the terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end-labeling (TUNEL)-positive cells in the VCN were increased in d-gal-treated rats. Taken together, these findings suggest that NOX2-dependent oxidative stress may contribute to mitochondrial damage and activate a caspase-3-dependent apoptosis pathway in the CAS during aging. This study also provides new insights into the development of presbycusis.

Cellular Metabolic Regulators

The Toll-like receptor 4 (TLR4) ligand endotoxin triggers robust systemic inflammatory responses in humans at doses equal to or greater than 1 ng/kg. In this study, we tested the hypothesis that evidence of TLR4-induced responses would be detectable in leukocytes challenged with endotoxin doses that are below the threshold needed to trigger a characteristic systemic inflammatory phenotype in humans. Subjects were challenged with endotoxin at 1, 0.5, or 0.1 ng/kg (n = 5 per dose). Systemic responses were monitored for 24 hours. Blood samples, collected at designated intervals, were used to determine plasma cytokines levels, total and differential leukocyte counts, expression of leukocyte cell surface receptors, and changes in the leukocyte transcriptome. Western blotting was used to determine changes in leukocyte protein expression. We found that in vivo endotoxin at doses below 1.0 ng/kg triggers weak and variable responses in humans. In marked contrast, we show that endotoxin at a concentration as low as 0.1 ng/kg triggers a transient decline in cellular ATP levels in leukocytes. This is associated with the appearance of a unique protein expression signature in leukocytes. The protein expression signature includes 3 prominent features: (i) AMP-activated protein kinase subunit α (AMPKα) degradation, (ii) increased hypoxia inducible factor-1 (HIF-1) α expression, and (iii) autophagy, collectively indicative of a regulated metabolic response. An indistinguishable response phenotype was observed in human leukocytes treated with endotoxin in vitro. These data demonstrate for the first time in humans that a TLR4 ligand concentration that is below the threshold needed to trigger clinically evident systemic inflammatory manifestations initiates a transient decline in ATP levels, AMPKα degradation, HIF-1α expression, and autophagy in leukocytes. This establishes that low-grade TLR4 activation exerts control over leukocyte metabolism in the absence of systemic inflammatory indicators.

Pyrroloquinoline Quinone Induces Cancer Cell Apoptosis via Mitochondrial-Dependent Pathway and Down-Regulating Cellular Bcl-2 Protein Expression.

Pyrroloquinoline quinone (PQQ) has been reported as a promising agent that might contribute to tumor cell apoptosis and death, yet little is known on its mechanisms. In current study, the effect of PQQ on cell proliferation and mitochondrial-dependent apoptosis were examined in 3 solid tumor cell lines (A549, Neuro-2A and HCC-LM3). PQQ treatment at low to medium dosage exhibited potent anti-tumor activity on A549 and Neuro-2A cells, while had comparably minimal impact on the viabilities of 2 human normal cell lines (HRPTEpiC and HUVEC). The apoptosis of the 3 tumor cell lines induced by PQQ were increased in a concentration-dependent manner, which might be attributed to the accumulation of intracellular reactive oxygen species (ROS), decline in ATP levels and dissipation of mitochondrial membrane potential (MMP), in conjunction with down-regulation of Bcl-2 protein expression, up-regulation of activated caspase-3, and disturbed phosphorylated MAPK protein levels. PQQ induced tumor cells apoptosis was significantly alleviated by pan-caspase inhibitor Z-VAD-FMK. The present work highlights the potential capability of PQQ as an anti-tumor agent with low toxicity towards normal cells through activating mitochondrial-dependent apoptosis pathways, and warrants its development for cancer therapy.