The role of adenosine monophosphate-activated protein kinase inhibition in apoptosis and autophagy induction in tumor cell lines

U ovoj doktorskoj disertaciji ispitivan je uticaj inhibicije intracelularnog energetskog senzora protein kinaze aktivirane adenozin-monofosfatom (AMPK) na indukciju apoptoze i autofagije u tumorskim ćelija. Farmakološki inhibitor AMPK dorzomorfin indukovao je G2/M blokadu ćelijskog ciklusa, praćen apoptozom koju karakteriše aktivacija kaspaza, eksternalizacija fosfatidilserina i fragmentacija DNK u U251 humanim i C6 pacovskim ćelijama glioma, dok na vijabilitet primarnih pacovskih astrocita i ćelija mišjeg melanoma B16 nije imao uticaja. Mehanizam indukcije apoptoze dorzomorfinom bio je posredovan stimulacijom produkcije reaktivnih vrsta kiseonika i inhibicijom ekspresije antiapoptotskog Bcl-2 proteina. Dorzomorfin je inhibirao fosforilaciju i enzimatsku aktivnost AMPK, što je za posledicu imalo smanjenje fosforilacije njenog supstrata acetil-CoA karboksilaze. Aktivatori AMPK metformin i AICAR delimično su neutralisali blokadu ćelijskog ciklusa, oksidativni stres i apoptozu indukovanu dorzomorfinom. Mala interferirajuća RNK (siRNK) koja sprečava ekspresiju humanog AMPK enzima je poput dorzomorfina zaustavila proliferaciju ćelija u G2/M fazi ćelijskog ciklusa, ali nije izazvala oksidativni stres i apoptozu u U251 ćelijama. Dakle, inhibicija AMPK je neophodna, ali ne i dovoljna za indukciju apotpoze dorzomorfinom u ćelijama glioma. U ovoj studiji takođe je pokazano da dorzomorfin indukuje autofagiju u ćelijama kancera. Indukcija autofagije u U251 ćelijama detektovana je fluorescentnim bojenjem unutarćelijskih kiselih vezikula akridin oranžom, indukcijom beklina-1, degradacijom p62 proteina i konverzijom LC3-I u formu asociranu sa autofagozomima LC3-II u odsustvu i prisustvu proteolitičkih inhibitora...In this doctoral dissertation the effect of intracellular energy sensor AMP-activated protein kinase (AMPK) inhibition on induction of apoptosis and autophagy in tumor cells was investigated. Pharmacological AMPK inhibitor dorsomorphin caused G2/M cell cycle block, accompanied by apoptotic cell death characterized by caspase activation, phosphatidylserine exposure and DNA fragmentation in U251 human and C6 rat glioma cells, while it had no effect on viability of primary rat astrocytes and B16 mouse melanoma cells. The mechanisms underlying the pro-apoptotic action of dorsomorphin involved induction of oxidative stress and down-regulation of antiapoptotic molecule Bcl-2. Dorsomorphin diminished AMPK phosphorylation and enzymatic activity, resulting in reduced phosphorylation of its target acetyl CoA carboxylase. AMPK activators metformin and AICAR partly prevented the cell cycle block, oxidative stress and apoptosis induced by dorsomorphin. The small interfering RNA (siRNA) targeting of human AMPK mimicked dorsomorphin-induced G2/M cell cycle arrest, but failed to induce oxidative stress and apoptosis in U251 glioma cells. Therefore, AMPK inhibition is required, but not sufficient for dorsomorphin-mediated apoptotic death of glioma cells. In this study, it was also reported that dorsomorphin can induce autophagy in cancer cells. The induction of autophagy in U251 human glioma cell line was demonstrated by acridine orange staining of intracellular acidic vesicles, Beclin 1 induction, p62 decrease and conversion of LC3-I to autophagosome-associated LC3-II in the absence and presence of proteolysis inhibitors. The presence of autophagosome like vesicles was confirmed by transmission electron microscopy. Dorsomorphin-mediated inhibition of AMPK and Raptor in U251 cells was associated with paradoxical decrease in phosphorylation of AMPK/Raptor-repressed mTOR, a major negative regulator of autophagy, and its downstream target p70S6K..

The Pharmacokinetics of Recombinant Human Erythropoietin in Balkan Endemic Nephropathy Patients

Background: Balkan endemic nephropathy (BEN) hemodialysis patients require a higher dose of recombinant human erythropoietin for maintaining target hemoglobin level than patients with other kidney diseases. Objectives: Comparison of the pharmacokinetics of beta-erythropoietin given subcutaneously to hemodialysis patients with BEN or other kidney diseases (non-BEN). Methods: Recombinant human erythropoietin (75U/kg) was administered subcutaneously to 10 BEN and 14 non-BEN hemodialysis patients. The predose plasma level of erythropoietin (Epo) was subtracted from all postdose levels. The relevant pharmacokinetic parameters were calculated after noncompartmental pharmacokinetic analysis using Kinetica software (Thermo Scientific, ver.5.0). Results: Although basal plasma Epo concentration was similar in BEN (20.1 +/- 10.3U/L) and non-BEN (15.1 +/- 8.1U/L; p=.1964) patients, there were significant differences between the groups for elimination rate constant (0.016 +/- 0.006 vs 0.026 +/- 0.011 hr(-1); p=.020) and elimination half-life (50.24 +/- 19.12 vs 33.79 +/- 18.91 hr, p=.048). These differences remained significant after adjustment for patient characteristics (age, sex, hennodialysis duration, ferritin, PTH and ACEI use). No significant differences between groups were found in maximal Epo concentration, time to maximum Epo concentration, area under the curve from time of dosing extrapolated to infinity, clearance, mean residence time of Epo between groups both before and after adjustment. Conclusion: Pharmacokinetic analysis of beta-erythropoietin detected a significantly longer elimination half-life in BEN than in non BEN patients. This finding needs to be confirmed in a well-controlled study with a larger sample size

Autophagy receptor p62 regulates SARS-CoV-2-induced inflammation in COVID-19

Introduction: Since the interaction between autophagy and virus-induced inflammation is complex, we investigated the interplay between autophagy and inflammation in COVID-19 patients and THP-1 cells expressing SARS-Cov2 proteins NSP5 and ORF3a. Methods: Autophagy markers in blood from 19 control subjects and 26 COVID-19 patients at hospital admission and one week later were measured by ELISA, while cytokine levels were examined by flow cytometric bead immunoassay. The level of p62 in cells and its concentration in cell culture supernatants was measured by immunoblot/ELISA. The mRNA levels of proinflammatory cytokines were measured by RT-qPCR. Results: IFN-α, TNF, IL-6, IL-8, IL-17, IL-33, and IFN-γ were elevated in COVID-19 patients at both time points, whereas IL-10 and IL-1β were elevated at admission and one week later, respectively. Autophagy markers LC3 and ATG5 were unchanged in COVID-19. The concentration of autophagic cargo receptor p62 was significantly lower and positively correlated with TNF, IL-10, IL-17, and IL-33 at hospital admission,returning to normal levels after one week. The expression of SARS-CoV-2 proteins NSP5 or ORF3a in THP-1 cells caused an autophagy-independent decrease/autophagy-inhibition-dependent increase of intracellular and secreted p62. This was associated with an NSP5-mediated decrease in TNF/IL-10 mRNA and an ORF3a-mediated increase in TNF/IL-1β/IL-6/IL-10/IL-33 mRNA levels. A genetic knockdown of p62 mimicked the immunosuppressive effect of NSP5, while a p62 increase in autophagy-deficient cells mirrored the immunostimulatory action of ORF3a. Conclusion: The autophagy receptor p62 is reduced in acute COVID-19, and the balance between autophagy-independent decrease and autophagy blockade-dependent increase of p62 levels could affect SARS-CoV-induced inflammation

Compound C induces protective autophagy in cancer cells through AMPK inhibition-independent blockade of Akt/mTOR pathway

In the present study, we report that compound C, an inhibitor of a key intracellular energy sensor AMP-activated protein kinase (AMPK), can induce autophagy in cancer cells. The induction of autophagy in U251 human glioma cell line was demonstrated by acridine orange staining of intracellular acidic vesicles, Beclin 1 induction, p62 decrease and conversion of LC3-I to autophagosome-associated LC3-II in the presence of proteolysis inhibitors. The presence of autophagosome-like vesicles was confirmed by transmission electron microscopy. Compound C-mediated inhibition of AMPK and raptor in U251 cells was associated with paradoxical decrease in phosphorylation of AMPK/raptor-repressed mTOR, a major negative regulator of autophagy, and its downstream target p70S6K. The phosphorylation of an mTOR activator Akt and the PI3K-activating kinase Src was also impaired in compound C-treated cells. The siRNA-mediated AMPK silencing did not reduce the activity of the Akt/mTOR/p70S6K pathway and AMPK activators metformin and AICAR failed to block compound C-induced autophagy. Autophagy inhibitors bafilomycin and chloroquine significantly increased the cytotoxicity of compound C towards U251 cells, as confirmed by increase in lactate dehydrogenase release, DNA fragmentation and caspase-3 activation. Similar effects of compound C were also observed in C6 rat glioma, L929 mouse fibrosarcoma and B16 mouse melanoma cell lines. Since compound C has previously been reported to suppress AMPK-dependent autophagy in different cell types, our findings suggest that the effects of compound C on autophagy might be dose-, cell type- and/or context-dependent. By demonstrating the ability of compound C to induce autophagic response in cancer cells via AMPK inhibition-independent downregulation of Akt/mTOR pathway, our results warrant caution when using compound C to inhibit AMPK-dependent cellular responses, but also support further exploration of compound C and related molecules as potential anticancer agents.Ministry of Science and Technological Development of the Republic of Serbia [145073, 145058

Inhibition of AMPK-dependent autophagy enhances in vitro antiglioma effect of simvastatin

The role of autophagy, a process in which the cell self-digests its own components, was investigated in glioma cell death induced by the hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase-inhibiting drug simvastatin. Induction of autophagy and activation of autophagy-regulating signalling pathways were analyzed by immunoblotting. Flow cytometry/fluorescent microscopy was used to assess autophagy-associated intracellular acidification and apoptotic markers (phosphatidylserine exposure, DNA fragmentation and caspase activation). Cell viability was determined by crystal violet, MTT or LDH release assay. Simvastatin treatment of U251 and C6 glioma cell lines caused the appearance of autophagolysosome-like intracytoplasmic acidic vesicles. The induction of autophagy in U251 cells was confirmed by the upregulation of autophagosome-associated LC3-II and pro-autophagic beclin-1, as well as by the downregulation of the selective autophagic target p62. Simvastatin induced the activation of AMP-activated protein kinase (AMPK) and its target Raptor, while simultaneously downregulating activation of Akt. Mammalian target of rapamycin (mTOR). a major AMPK/Akt downstream target and a major negative autophagy regulator, and its substrate p70 S6 kinase 1 were also inhibited by simvastatin. Mevalonate, the product of HMG-CoA reductase enzymatic activity, AMPK siRNA or pharmacological inactivation of AMPK with compound C suppressed, while the inhibitors of Akt (10-DEBC hydrochloride) and mTOR (rapamycin) mimicked autophagy induction by simvastatin. Inhibition of autophagy with bafilomycin A1, 3-methyladenine and LC3 beta shRNA, as well as AMPK inhibition with compound C or AMPK siRNA, markedly increased apoptotic death of simvastatin-treated U251 cells. These data suggest that inhibition of AMPK-depenclent autophagic response might sensitize glioma cells to statin-induced apoptotic death. (C) 2011 Elsevier Ltd. All rights reserved.Ministry of Science and Technological Development of the Republic of Serbia [41025, 173053

AMP-activated protein kinase-dependent and -independent mechanisms underlying in vitro antiglioma action of compound C

We investigated the effect of compound C, a well-known inhibitor of the intracellular energy sensor AMP-activated protein kinase (AMPK), on proliferation and viability of human U251 and rat C6 glioma cell lines. Compound C caused G(2)/M cell cycle block, accompanied by apoptotic glioma cell death characterized by caspase activation, phosphatidylserine exposure and DNA fragmentation. The mechanisms underlying the pro-apoptotic action of compound C involved induction of oxidative stress and downregulation of antiapoptotic molecule Bcl-2, while no alteration of pro-apoptotic Bax was observed. Compound C diminished AMPK phosphorylation and enzymatic activity, resulting in reduced phosphorylation of its target acetyl CoA carboxylase. AMPK activators metformin and AICAR partly prevented the cell cycle block, oxidative stress and apoptosis induced by compound C. The small interfering RNA (siRNA) targeting of human AMPK mimicked compound C-induced G(2)/M cell cycle arrest, but failed to induce oxidative stress and apoptosis in U251 glioma cells. In conclusion, our data indicate that AMPK inhibition is required, but not sufficient for compound C-mediated apoptotic death of glioma cells. (c) 2009 Elsevier Inc. All rights reserved.Ministry of Science of the Republic of Serbia [145073, 145067, 143030

Inhibition of AMPK-dependent autophagy enhances in vitro antiglioma effect of simvastatin

The role of autophagy, a process in which the cell self-digests its own components, was investigated in glioma cell death induced by the hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase-inhibiting drug simvastatin. Induction of autophagy and activation of autophagy-regulating signalling pathways were analyzed by immunoblotting. Flow cytometry/fluorescent microscopy was used to assess autophagy-associated intracellular acidification and apoptotic markers (phosphatidylserine exposure, DNA fragmentation and caspase activation). Cell viability was determined by crystal violet, MTT or LDH release assay. Simvastatin treatment of U251 and C6 glioma cell lines caused the appearance of autophagolysosome-like intracytoplasmic acidic vesicles. The induction of autophagy in U251 cells was confirmed by the upregulation of autophagosome-associated LC3-II and pro-autophagic beclin-1, as well as by the downregulation of the selective autophagic target p62. Simvastatin induced the activation of AMP-activated protein kinase (AMPK) and its target Raptor, while simultaneously downregulating activation of Akt. Mammalian target of rapamycin (mTOR). a major AMPK/Akt downstream target and a major negative autophagy regulator, and its substrate p70 S6 kinase 1 were also inhibited by simvastatin. Mevalonate, the product of HMG-CoA reductase enzymatic activity, AMPK siRNA or pharmacological inactivation of AMPK with compound C suppressed, while the inhibitors of Akt (10-DEBC hydrochloride) and mTOR (rapamycin) mimicked autophagy induction by simvastatin. Inhibition of autophagy with bafilomycin A1, 3-methyladenine and LC3 beta shRNA, as well as AMPK inhibition with compound C or AMPK siRNA, markedly increased apoptotic death of simvastatin-treated U251 cells. These data suggest that inhibition of AMPK-depenclent autophagic response might sensitize glioma cells to statin-induced apoptotic death. (C) 2011 Elsevier Ltd. All rights reserved.Ministry of Science and Technological Development of the Republic of Serbia [41025, 173053

The protection of cells from nitric oxide-mediated apoptotic death by mechanochemically synthesized fullerene (C-60) nanoparticles

The influence of fullerene (C-60) nanoparticles on the cytotoxicity of a highly reactive free radical nitric oxide (NO) was investigated. Fullerene nanoparticles were prepared by mechanochemically assisted complexation with anionic surfactant sodium dodecyl sulfate, macrocyclic oligosaccharide gamma-cyclodextrin or the copolymer ethylene vinyl acetate-ethylene vinyl versatate. C-60 nanoparticles were characterized by UV-vis and atomic force microscopy. While readily internalized by mouse L929 fibroblasts, C-60 nanoparticles were not cytotoxic. Moreover, they partially protected L929 cells from the cytotoxic effect of NO-releasing compounds sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP), S-nitrosoglutathione (GSNO) and 3-morpholino-sydnonimine (SIN-1). C-60 nanoparticles reduced SNP-induced apoptotic cell death by preventing mitochondrial depolarization, caspase activation, cell membrane phosphatidylserine exposure and DNA fragmentation. The protective action of C-60 nanoparticles was not exerted via direct interaction with NO, but through neutralization of mitochondria-produced superoxide radical in NO-treated cells, as demonstrated by using different redox-sensitive reporter fluorochromes. These data suggest that C-60 complexes with appropriate host molecules might be plausible candidates for preventing NO-mediated cell injury in inflammatory/autoimmune disorders. (C) 2009 Elsevier Ltd. All rights reserved.Ministry of Science of the Republic of Serbia [145073