scholarly journals Modulation of mitochondrial electrical potential: a candidate mechanism for drug resistance in African trypanosomes

1997 ◽  
Vol 326 (3) ◽  
pp. 755-761 ◽  
Author(s):  
Jonathan M. WILKES ◽  
Wubet MULUGETA ◽  
Clive WELLS ◽  
Andrew S. PEREGRINE
Keyword(s):  
Drug Resistance ◽  
Drug Sensitivity ◽  
Electrical Potential ◽  
Drug Uptake ◽  
African Trypanosomes ◽  
Wide Range ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition

Bloodstream forms of four populations of the livestock pathogen Trypanosoma congolense, isolated from different natural infections, have been shown to exhibit a wide range of sensitivities to the trypanocide isometamidium chloride (Samorin®). In mice the 50% curative doses (CD50) for Samorin range from 0.007 to 20 mg/kg body weight. Uptake of isometamidium chloride demonstrated Michaelis–Menten-type kinetics in all the populations, with Km values in the range 0.35–0.87 μM, and Vmax varied from 17 to 216 pmol/min per 108 cells. The magnitude of Vmax was correlated with sensitivity to the drug. In contrast, no correlation was observed between Km values and drug sensitivity. Pulse–chase experiments indicated two compartments for accumulation of drug. The first consists of freely diffusible drug that is invariant between populations; the other consists of retained isometamidium, which is of variable magnitude between the populations and is correlated with drug sensitivity. Autoradiography and fluorescence microscopy demonstrated initial, rapid accumulation of the drug within the mitochondrion, specifically the kinetoplast. In a drug-sensitive population of T. congolense, agents affecting mitochondrial function were shown to produce dose-dependent inhibition of mitochondrial membrane potential (ΔΨmito), as measured by the accumulation of the lipophilic cations [3H]methyltriphenylphosphonium iodide or rhodamine 123. The agents also produced parallel inhibition of isometamidium uptake, suggesting an involvement of ΔΨmito in the accumulation of the drug. When characterized in each of the four populations, the spontaneous ΔΨmito was shown to be characteristic of each population and was correlated with Vmax for drug uptake and sensitivity to the drug in vitro and in vivo. We therefore conclude that in T. congolenseΔΨmito is an important determinant of the rate and accumulation of the trypanocide isometamidium chloride. Populations of this trypanosome species vary with respect to ΔΨmito, which is correlated with sensitivity to isometamidium. We suggest that when exposed to drug, the selection of such populations represents a novel mechanism of drug resistance in protozoan parasites.

scholarly journals A Biomaterial Screening Approach Reveals Microenvironmental Mechanisms of Drug Resistance

2017 ◽  
Author(s):  
Alyssa D. Schwartz ◽  
Lauren E. Barney ◽  
Lauren E. Jansen ◽  
Thuy V. Nguyen ◽  
Christopher L. Hall ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Systems Biology ◽  
Drug Screening ◽  
Drug Response ◽  
Drug Sensitivity ◽  
Mek Inhibitor ◽  
Tumor Burden ◽  
Adaptive Resistance

TOC FigureDrug response screening, gene expression, and kinome signaling were combined across biomaterial platforms to combat adaptive resistance to sorafenib.Insight BoxWe combined biomaterial platforms, drug screening, and systems biology to identify mechanisms of extracellular matrix-mediated adaptive resistance to RTK-targeted cancer therapies. Drug response was significantly varied across biomaterials with altered stiffness, dimensionality, and cell-cell contacts, and kinome reprogramming was responsible for these differences in drug sensitivity. Screening across many platforms and applying a systems biology analysis were necessary to identify MEK phosphorylation as the key factor associated with variation in drug response. This method uncovered the combination therapy of sorafenib with a MEK inhibitor, which decreased viability on and within biomaterials in vitro, but was not captured by screening on tissue culture plastic alone. This combination therapy also reduced tumor burden in vivo, and revealed a promising approach for combating adaptive drug resistance.AbstractTraditional drug screening methods lack features of the tumor microenvironment that contribute to resistance. Most studies examine cell response in a single biomaterial platform in depth, leaving a gap in understanding how extracellular signals such as stiffness, dimensionality, and cell-cell contacts act independently or are integrated within a cell to affect either drug sensitivity or resistance. This is critically important, as adaptive resistance is mediated, at least in part, by the extracellular matrix (ECM) of the tumor microenvironment. We developed an approach to screen drug responses in cells cultured on 2D and in 3D biomaterial environments to explore how key features of ECM mediate drug response. This approach uncovered that cells on 2D hydrogels and spheroids encapsulated in 3D hydrogels were less responsive to receptor tyrosine kinase (RTK)-targeting drugs sorafenib and lapatinib, but not cytotoxic drugs, compared to single cells in hydrogels and cells on plastic. We found that transcriptomic differences between these in vitro models and tumor xenografts did not reveal mechanisms of ECM-mediated resistance to sorafenib. However, a systems biology analysis of phospho-kinome data uncovered that variation in MEK phosphorylation was associated with RTK-targeted drug resistance. Using sorafenib as a model drug, we found that co-administration with a MEK inhibitor decreased ECM-mediated resistance in vitro and reduced in vivo tumor burden compared to sorafenib alone. In sum, we provide a novel strategy for identifying and overcoming ECM-mediated resistance mechanisms by performing drug screening, phospho-kinome analysis, and systems biology across multiple biomaterial environments.

scholarly journals Inhibition of duck hepatitis B virus replication by 2',3'-dideoxy-3'-fluoroguanosine in vitro and in vivo.

1996 ◽  
Vol 40 (3) ◽  
pp. 792-794 ◽  
Author(s):  
P Hafkemeyer ◽  
A Keppler-Hafkemeyer ◽  
M A al Haya ◽  
M von Janta-Lipinski ◽  
E Matthes ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Strong Inhibitor ◽  
Duck Hepatitis B Virus ◽  
Duck Hepatitis ◽  
B Virus ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition

The antiviral activity of 2',3'-dideoxy-3'-fluoroguanosine (FdG) or its triphosphate was evaluated in the duck hepatitis B virus (DHBV) system in vitro and in vivo. In primary DHBV-infected hepatocytes FdG results in a dose-dependent inhibition of viral replication with a nearly complete inhibition at a concentration of 1 microM. Also in vivo, FdG treatment of DHBV-infected ducklings reduces DHBV DNA replication by more than 90%. These data demonstrate that FdG is a strong inhibitor of DHBV replication in vitro and in vivo.

Triazolylthioacetamides Confer Inhibitory Efficacy against Metallo-β-Lactamase IMP-1

2020 ◽  
Vol 17 ◽  
Author(s):  
Yue-Juan Zhang ◽  
Le Zhai ◽  
Yi Wan ◽  
Ke-Wu Yang
Keyword(s):  
Antibiotic Resistance ◽  
Antimicrobial Activities ◽  
Docking Studies ◽  
Titration Calorimetry ◽  
Global Public Health ◽  
Inhibition Activity ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition

Background: : The appearance of antibiotic resistance caused by metallo-β-lactamases (MβLs) is a global public health threat. Developing MβLs inhibitor is an effective way to overcome antibiotic resistance. Recently, azolylthioacetamides were reported to be promising MβLs inhibitors. Methods:: Triazolylthioacetamides were synthesized and tested for inhibition activity against the purified MβL IMP-1. Antimicrobial activities of these inhibitors in combination with cefazolin were evaluated. Isothermal titration calorimetry (ITC) was employed to characterize the binding of the inhibitor to IMP-1, and their action mechanism was studied by molecular docking. Results and Discussion: : Twenty compounds exhibited specific inhibitory activity against IMP-1 with an IC50 value in the range of 3.1-62.5 μM. Eight of the compounds can restore the antibacterial efficacy of cefazolin against E. coli BL21 strain producing IMP-1 by 2-4 fold. ITC monitoring showed that 1c exhibited dose-dependent inhibition on IMP-1. Docking studies revealed that the triazole group in 1c and 2d played an essential role in the inhibition activity. Cytotoxicity assay showed that 1c and 2d have low toxicity in L929 mouse fibroblastic cells. Conclusion: : The triazolylthioacetamides are efficient inhibitors of IMP-1 in vitro and in vivo.

scholarly journals Liposomal Curcumin Targeting Endometrial Cancer Through the NF-κB Pathway

2018 ◽  
Vol 48 (2) ◽  
pp. 569-582 ◽  
Author(s):  
Hanzi Xu ◽  
Zhen Gong ◽  
Siying Zhou ◽  
Sujin Yang ◽  
Dandan Wang ◽  
...  
Keyword(s):  
Cell Motility ◽  
Tumor Model ◽  
Pcr Analysis ◽  
Therapeutic Effects ◽  
Zebrafish Model ◽  
Inhibition Of Proliferation ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition

Background/Aims: Emerging evidence suggests that curcumin possesses chemopreventive properties against various cancers. However, its poor bioavailability limits its clinical application. In this study, we aimed to utilize encapsulation in liposomes (Lipo) as a strategy for the clinical administration of curcumin for endometrial carcinoma (EC). Methods: Curcumin was encapsulated in a liposomal delivery system to prepare a formulation of liposomal curcumin (LC). EC cell lines Ishikawa and HEC-1 were treated with the compound and cell proliferation was measured using MTT assay. Hoechst 33258 staining assay and flow cytometry were used to detect apoptosis of the cells. Wound healing and cell invasion assays were employed to monitor cell motility. Underlying target signaling, such as NF-κB, caspases, and MMPs, were further studied via qRT-PCR and western blot. Thereafter, a zebrafish model was used to assess the toxicity of LC. Finally, a zebrafish transplantation tumor model of EC was grown and treated with LC. Tumors were monitored and harvested to study the expression of NF-κB. Results: The formation of LC was successfully developed with excellent purity and physical properties. In vitro, LC resulted in dose-dependent inhibition of proliferation, induction of apoptosis, and suppression of Ishikawa and HEC-1 cell motility. LC treatment also suppressed the activation and/or expression of NF-κB, caspase-3, and MMP-9. No demonstrable toxicity was found in the zebrafish model and tumors were suppressed after treatment with LC. PCR analysis also showed down-regulated expression of NF-κB. Conclusions: LC was successfully prepared and played biological roles against EC probably through negative regulation of the NF-κB pathway in vitro and in vivo, which demonstrates its potential therapeutic effects in EC.

scholarly journals Flavonoid Library Screening Reveals Kaempferol as a Potential Antiviral Agent Against African Swine Fever Virus

2021 ◽  
Vol 12 ◽  
Author(s):  
Erik Arabyan ◽  
Astghik Hakobyan ◽  
Tamara Hakobyan ◽  
Rafaella Grigoryan ◽  
Roza Izmailyan ◽  
...  
Keyword(s):  
African Swine Fever Virus ◽  
Screening Method ◽  
African Swine Fever ◽  
Vero Cells ◽  
Fever Virus ◽  
Wide Range ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Dose Dependent

Naturally occurring plant flavonoids are a promising class of antiviral agents to inhibit African swine fever virus (ASFV), which causes highly fatal disease in pigs and is a major threat to the swine industry. Currently known flavonoids with anti-ASFV activity demonstrate a wide range of antiviral mechanisms, which motivates exploration of new antiviral candidates within this class. The objective of this study was to determine whether other flavonoids may significantly inhibit ASFV infection in vitro. We performed a cell-based library screen of 90 flavonoids. Our screening method allowed us to track the development of virus-induced cytopathic effect by MTT in the presence of tested flavonoids. This screening method was shown to be robust for hit identification, with an average Z-factor of 0.683. We identified nine compounds that inhibit ASFV Ba71V strain in Vero cells. Among them, kaempferol was the most potent and exhibited dose-dependent inhibition, which occurred through a virostatic effect. Time-of-addition studies revealed that kaempferol acts on the entry and post-entry stages of the ASFV replication cycle and impairs viral protein and DNA synthesis. It was further identified that kaempferol induces autophagy in ASFV-infected Vero cells, which is related to its antiviral activity and could be partially abrogated by the addition of an autophagy inhibitor. Kaempferol also exhibited dose-dependent inhibition of a highly virulent ASFV Arm/07 isolate in porcine macrophages. Together, these findings support that kaempferol is a promising anti-ASFV agent and has a distinct antiviral mechanism compared to other anti-ASFV flavonoids.

Novel Complement Modulators for Paroxysmal Nocturnal Hemoglobinuria: Peptide and Protein Inhibitors of C3 Convertase Prevent Both Surface C3 Deposition and Subsequent Hemolysis of Affected Erythrocytes in Vitro

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 370-370
Author(s):  
Antonio M. Risitano ◽  
Patrizia Ricci ◽  
Caterina Pascariello ◽  
Maddalena Raia ◽  
Christoph Q Schmidt ◽  
...  
Keyword(s):  
Paroxysmal Nocturnal Hemoglobinuria ◽  
Alternative Pathway ◽  
Complement Cascade ◽  
Intravascular Hemolysis ◽  
Complement Inhibitors ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Dose Dependent

Abstract Abstract 370 Paroxysmal nocturnal hemoglobinuria (PNH) is a complex hematological disorder characterized by the expansion of blood cells deficient in the surface complement inhibitors CD55 and CD59; affected erythrocytes suffer from uncontrolled complement activation on their surface, and subsequent membrane attack complex (MAC)-mediated intravascular hemolysis. The anti-C5 antibody eculizumab has proven effective in controlling intravascular hemolysis in vivo, leading to remarkable clinical benefit in almost all PNH patients. Yet, we have demonstrated that persistent C3 activation occurring during eculizumab treatment may lead to progressive C3 deposition on affected erythrocyte and subsequent C3-mediated extravascular hemolysis, possibly limiting the hematological benefit of anti-C5 treatment (Risitano et al, Blood 2009). Thus, upstream inhibition of the complement cascade seems an appropriate strategy to improve the results of current anti-complement treatment; indeed, we have recently documented that the CD21/factor H (FH) fusion protein TT30 efficiently prevents both hemolysis and C3 deposition of PNH erythrocytes (Risitano et al, Blood 2012). Here we used the same in vitro model to evaluate two novel complement inhibitors that both act at the level of C3 convertases. Cp30 is an analog of the peptidic inhibitor compstatin, which is a 13-residue disulphide-bridged peptide that selectively binds to C3 and its activate fragment C3b. Compstatin and its analogues thereby prevent the initiation, amplification and terminal damage of the complement cascade via all its major pathways (classical, alternative, and mannose/lectin). Cp30 is one of the analogues developed to increase potency and stability of compstatin. Mini-FH, on the other hand, is an engineered 43kDa protein that combines the regulatory and surface-recognition activities of FH while showing increased affinity for the opsonins C3b, iC3b and C3d. Indeed, mini-FH retained both convertase decay acceleration and cofactor activities typical of endogenous human FH, resulting in a potent and selective inhibition of activation and amplification of the complement alternative pathway, without affecting the classical and the mannose/lectin pathway. Erythrocytes from PNH patients were washed and incubated in ABO-matched sera and exposed to pH-lowering to activate the alternative pathway, both in absence and presence of Cp30, mini-FH, and appropriate controls. Assessment of hemolysis and of C3 activation and deposition on PNH erythrocytes was performed by flow cytometry analyses of erythrocytes using anti-C3 and anti-CD59 antibodies, as previously described (Risitano et al Blood 2012). In absence of inhibitors, >90% of PNH erythrocytes lysed within 24 hours of incubation. Cp30 demonstrated a dose-dependent inhibition of hemolysis, with an IC50 of 4 μM and full inhibition at 8 μM. Cp30 also prevented deposition of any C3 fragment on the surface of surviving PNH erythrocyte. Similarly, mini-FH also showed dose-dependent inhibition of hemolysis, with an IC50 of 0.05 μM and full inhibition at 0.1 μM. Notably, both full-length fH and fH SCR1-4 were much less efficient in preventing hemolysis and C3 deposition (IC50 ∼ 0.5 μM; full inhibition >1 μM), supporting the higher potency of the engineered protein mini-FH. As expected, mini-FH also prevented surface deposition of C3 fragments on PNH erythrocytes. In conclusion, we confirm that inhibition of early phases of complement activation efficiently prevents hemolysis of PNH erythrocytes and their opsonization with C3 fragments in vitro. This effect may be obtained using either broad or pathway-specific inhibitors of C3 convertase, namely Cp30 and mini-FH, respectively. Thus, both strategies promise to prevent in vivo both MAC-mediated intravascular and C3-mediated extravascular hemolysis; however, according to their effect on specific complement pathways, they likely entail distinct patterns of potential risks. Our study provides the rationale for future translational plans to investigate the risk-to-benefit of these novel complement modulators in PNH. Disclosures: Risitano: Alexion: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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