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MBio Jun 2023Mounting evidence demonstrates that nutritional environment can alter pathogen drug sensitivity. While the rich media used for culture contains supraphysiological...
Mounting evidence demonstrates that nutritional environment can alter pathogen drug sensitivity. While the rich media used for culture contains supraphysiological nutrient concentrations, pathogens encounter a relatively restrictive environment . We assessed the effect of nutrient limitation on the protozoan parasite that causes malaria and demonstrated that short-term growth under physiologically relevant mild nutrient stress (or "metabolic priming") triggers increased tolerance of a potent antimalarial drug. We observed beneficial effects using both short-term survival assays and longer-term proliferation studies, where metabolic priming increases parasite survival to a level previously defined as resistant (>1% survival). We performed these assessments by either decreasing single nutrients that have distinct roles in metabolism or using a media formulation that simulates the human plasma environment. We determined that priming-induced tolerance was restricted to parasites that had newly invaded the host red blood cell, but the effect was not dependent on genetic background. The molecular mechanisms of this intrinsic effect mimic aspects of genetic tolerance, including translational repression and protein export. This finding suggests that regardless of the impact on survival rates, environmental stress could stimulate changes that ultimately directly contribute to drug tolerance. Because metabolic stress is likely to occur more frequently compared to the stable environment, priming-induced drug tolerance has ramifications for how results translate to studies. Improving our understanding of how pathogens adjust their metabolism to impact survival of current and future drugs is an important avenue of research to slow the evolution of resistance. There is a dire need for effective treatments against microbial pathogens. Yet, the continuing emergence of drug resistance necessitates a deeper knowledge of how pathogens respond to treatments. We have long appreciated the contribution of genetic evolution to drug resistance, but transient metabolic changes that arise in response to environmental factors are less recognized. Here, we demonstrate that short-term growth of malaria parasites in a nutrient-limiting environment triggers cellular changes that lead to better survival of drug treatment. We found that these strategies are similar to those employed by drug-tolerant parasites, which suggests that starvation "primes" parasites to survive and potentially evolve resistance. Since the environment of the human host is relatively nutrient restrictive compared to growth conditions in standard laboratory culture, this discovery highlights the important connections among nutrient levels, protective cellular pathways, and resistance evolution.
Topics: Humans; Plasmodium falciparum; Artemisinins; Malaria; Antimalarials; Drug Tolerance; Drug Resistance; Nutrients
PubMed: 37097173
DOI: 10.1128/mbio.00705-23 -
Bioanalysis Jul 2023The presence of di-/multi-meric forms of soluble target in biological samples can interfere in anti-drug antibody (ADA) assays, leading to increased background values...
The presence of di-/multi-meric forms of soluble target in biological samples can interfere in anti-drug antibody (ADA) assays, leading to increased background values and potentially false positivity. The authors investigated the use of the high ionic strength dissociation assay (HISDA) to reduce target interference in two different ADA assays. Interference caused by homodimeric FAP was successfully eliminated to enable cut point determination after applying HISDA. Biochemical experiments confirmed the dissociation of homodimeric FAP after treatment with high ionic strength conditions. HISDA is a promising approach to simultaneously achieve high drug tolerance and reduced interference by noncovalently bound dimeric target molecules in ADA assays without extensive optimization, which is particularly advantageous in routine use.
Topics: Antibodies; Drug Tolerance
PubMed: 37326333
DOI: 10.4155/bio-2023-0082 -
Antimicrobial Agents and Chemotherapy Feb 2018Tuberculosis (TB) recently became the leading infectious cause of death in adults, while attempts to shorten therapy have largely failed. Dormancy, persistence, and drug...
Tuberculosis (TB) recently became the leading infectious cause of death in adults, while attempts to shorten therapy have largely failed. Dormancy, persistence, and drug tolerance are among the factors driving the long therapy duration. Assays to measure drug susceptibility of bacteria in pulmonary lesions are needed if we are to discover new fast-acting regimens and address the global TB threat. Here we take a first step toward this goal and describe an assay developed to measure the cidal activity of anti-TB drugs against bacilli present in cavity caseum obtained from rabbits with active TB. We show that caseum bacilli are largely nonreplicating, maintain viability over the course of the assay, and exhibit extreme tolerance to many first- and second-line TB drugs. Among the drugs tested, only the rifamycins fully sterilized caseum. A similar trend of phenotypic drug resistance was observed in the hypoxia- and starvation-induced nonreplicating models, but with notable qualitative and quantitative differences: (i) caseum exhibits higher drug tolerance than nonreplicating in the Wayne and Loebel models, and (ii) pyrazinamide is cidal in caseum but has no detectable activity in these classic nonreplicating assays. Thus, caseum constitutes a unique tool to evaluate drug potency against slowly replicating or nonreplicating bacilli in their native caseous environment. Intracaseum cidal concentrations can now be related to the concentrations achieved in the necrotic foci of granulomas and cavities to establish correlations between clinical outcome and lesion-centered pharmacokinetics-pharmacodynamics (PK-PD) parameters.
Topics: Animals; Antitubercular Agents; Drug Tolerance; Mycobacterium tuberculosis; Pyrazinamide; Rabbits; Rifamycins; Tuberculosis
PubMed: 29203492
DOI: 10.1128/AAC.02266-17 -
Molecular Pain May 2015Chronic pain is a major public health problem with limited treatment options. Opioids remain a routine treatment for chronic pain, but extended exposure to opioid... (Review)
Review
Chronic pain is a major public health problem with limited treatment options. Opioids remain a routine treatment for chronic pain, but extended exposure to opioid therapy can produce opioid tolerance and hyperalgesia. Although the mechanisms underlying chronic pain, opioid-induced tolerance, and opioid-induced hyperalgesia remain to be uncovered, mammalian target of rapamycin (mTOR) is involved in these disorders. The mTOR complex 1 and its triggered protein translation are required for the initiation and maintenance of chronic pain (including cancer pain) and opioid-induced tolerance/hyperalgesia. Given that mTOR inhibitors are FDA-approved drugs and an mTOR inhibitor is approved for the treatment of several cancers, these findings suggest that mTOR inhibitors will likely have multiple clinical benefits, including anticancer, antinociception/anti-cancer pain, and antitolerance/hyperalgesia. This paper compares the role of mTOR complex 1 in chronic pain, opioid-induced tolerance, and opioid-induced hyperalgesia.
Topics: Analgesics, Opioid; Animals; Chronic Pain; Drug Tolerance; Humans; Hyperalgesia; Pain Threshold; TOR Serine-Threonine Kinases
PubMed: 26024835
DOI: 10.1186/s12990-015-0030-5 -
Biochemical Pharmacology Apr 2019Although many drugs/treatments are now available for most diseases, too often, resistance to these treatments impedes complete therapeutic success. Acquired resistance... (Review)
Review
Although many drugs/treatments are now available for most diseases, too often, resistance to these treatments impedes complete therapeutic success. Acquired resistance is a major problem in many pathologies but it is an acute one in cancers and infections. This is probably because these diseases often require long durations of treatment, which ascribe to the selection of resistant cells. However, the actual mechanisms implicated in the selection process are still under debate. It is becoming increasingly clear that resistance is associated with the heterogeneity of cancer cells or micro-organisms and that multiple mechanisms underlie the emergence of drug-resistant subpopulations. Recently, it has been suggested that a subpopulation of drug tolerant cells present in cancer populations and called "persisters" play a major role in this resistance. Recent studies have shown that microorganisms share similar properties. Still, how persister/tolerant cells intervene in the development of resistance is not completely elucidated but seems to be related to epigenetic changes in treated cells and the capacity of persisters to modulate and/or highjack their microenvironment. Due to the complexity of this process, the input from mathematicians, as well as new methods of bioinformatics and statistics, is necessary to fully comprehend the acquisition of resistance/tolerance deriving from and leading to the heterogeneous cell populations. The present review will give a brief overview of the most recent data available on drug tolerant cells in cancers and their similarities with microorganisms.
Topics: Animals; Antineoplastic Agents; Drug Delivery Systems; Drug Resistance, Neoplasm; Drug Tolerance; Humans; Neoplasms; Tumor Microenvironment
PubMed: 30414937
DOI: 10.1016/j.bcp.2018.11.004 -
International Review of Neurobiology 2016The etiology of diabetic peripheral neuropathy (DPN) involves an interrelated series of metabolic and vascular insults that ultimately contribute to sensory neuron... (Review)
Review
The etiology of diabetic peripheral neuropathy (DPN) involves an interrelated series of metabolic and vascular insults that ultimately contribute to sensory neuron degeneration. In the quest to pharmacologically manage DPN, small-molecule inhibitors have targeted proteins and pathways regarded as "diabetes specific" as well as others whose activity are altered in numerous disease states. These efforts have not yielded any significant therapies, due in part to the complicating issue that the biochemical contribution of these targets/pathways to the progression of DPN does not occur with temporal and/or biochemical uniformity between individuals. In a complex, chronic neurodegenerative disease such as DPN, it is increasingly appreciated that effective disease management may not necessarily require targeting a pathway or protein considered to contribute to disease progression. Alternatively, it may prove sufficiently beneficial to pharmacologically enhance the activity of endogenous cytoprotective pathways to aid neuronal tolerance to and recovery from glucotoxic stress. In pursuing this paradigm shift, we have shown that modulating the activity and expression of molecular chaperones such as heat shock protein 70 (Hsp70) may provide translational potential for the effective medical management of insensate DPN. Considerable evidence supports that modulating Hsp70 has beneficial effects in improving inflammation, oxidative stress, and glucose sensitivity. Given the emerging potential of modulating Hsp70 to manage DPN, the current review discusses efforts to characterize the cytoprotective effects of this protein and the benefits and limitations that may arise in drug development efforts that exploit its cytoprotective activity.
Topics: Animals; Diabetic Neuropathies; Drug Tolerance; Glucose; Humans; Molecular Chaperones; Neurodegenerative Diseases; Oxidative Stress; Sensory Receptor Cells
PubMed: 27133150
DOI: 10.1016/bs.irn.2016.03.001 -
Proceedings of the National Academy of... Jul 2019Understanding the evolution of microorganisms under antibiotic treatments is a burning issue. Typically, several resistance mutations can accumulate under antibiotic...
Understanding the evolution of microorganisms under antibiotic treatments is a burning issue. Typically, several resistance mutations can accumulate under antibiotic treatment, and the way in which resistance mutations interact, i.e., epistasis, has been extensively studied. We recently showed that the evolution of antibiotic resistance in is facilitated by the early appearance of tolerance mutations. In contrast to resistance, which reduces the effectiveness of the drug concentration, tolerance increases resilience to antibiotic treatment duration in a nonspecific way, for example when bacteria transiently arrest their growth. Both result in increased survival under antibiotics, but the interaction between resistance and tolerance mutations has not been studied. Here, we extend our analysis to include the evolution of a different type of tolerance and a different antibiotic class and measure experimentally the epistasis between tolerance and resistance mutations. We derive the expected model for the effect of tolerance and resistance mutations on the dynamics of survival under antibiotic treatment. We find that the interaction between resistance and tolerance mutations is synergistic in strains evolved under intermittent antibiotic treatment. We extend our analysis to mutations that result in antibiotic persistence, i.e., to tolerance that is conferred only on a subpopulation of cells. We show that even when this population heterogeneity is included in our analysis, a synergistic interaction between antibiotic persistence and resistance mutations remains. We expect our general framework for the epistasis in killing conditions to be relevant for other systems as well, such as bacteria exposed to phages or cancer cells under treatment.
Topics: Anti-Bacterial Agents; Drug Resistance, Bacterial; Drug Tolerance; Epistasis, Genetic; Escherichia coli; Evolution, Molecular; Gene Expression Regulation, Bacterial; Microbial Sensitivity Tests; Models, Genetic; Mutation
PubMed: 31262806
DOI: 10.1073/pnas.1906169116 -
Molecular Oncology Apr 2023Targeted therapies have become a mainstay in the treatment of cancer, but their long-term efficacy is compromised by acquired drug resistance. Acquired therapy... (Review)
Review
Targeted therapies have become a mainstay in the treatment of cancer, but their long-term efficacy is compromised by acquired drug resistance. Acquired therapy resistance develops via two phases-first through adaptive development of nongenetic drug tolerance, which is followed by stable resistance through the acquisition of genetic mutations. Drug tolerance has been described in practically all clinical cancer treatment contexts, and detectable drug-tolerant tumors are highly associated with treatment relapse and poor survival. Thereby, novel therapeutic strategies are needed to overcome cancer therapy tolerance. Recent studies have identified a critical role of mitochondrial mechanisms in defining cancer cell sensitivity to targeted therapies and the surprising effects of established cancer therapies on mitochondria. Here, these recent studies are reviewed emphasizing an emerging concept of triplet therapies including three compounds targeting different cancer cell vulnerabilities but including at least one compound that targets the mitochondria. These mitochondria-targeting triplet therapies have very promising preclinical effects in overcoming cancer therapy tolerance. Potential strategies of how to overcome challenges in the clinical translation of mitochondria-targeting triplet therapies are also discussed.
Topics: Humans; Drug Tolerance; Mitochondria; Neoplasms
PubMed: 36852624
DOI: 10.1002/1878-0261.13406 -
Antimicrobial Agents and Chemotherapy Apr 2022Aspergillus terreus is an opportunistic causative agent of invasive aspergillosis and, in most cases, it is refractory to amphotericin B (AMB) therapy. Notably,...
Aspergillus terreus is an opportunistic causative agent of invasive aspergillosis and, in most cases, it is refractory to amphotericin B (AMB) therapy. Notably, AMB-susceptible Aspergillus terreus (s.s.) representatives exist which are also associated with poor clinical outcomes. Such findings may be attributable to drug tolerance, which is not detectable by antifungal susceptibility testing. Here, we tested antifungal susceptibility (AFST) and the fungicidal activity of AMB against 100 clinical isolates of A. terreus species complex in RPMI 1640 and antibiotic medium 3 (AM3). MICs ranged from 0.5 to 16 μg/mL for RPMI 1640 and from 1 to >16 mg/L for AM3. AMB showed medium-dependent activity, with fungicidal effects only in antibiotic medium 3, not in RPMI 1640. Furthermore, the presence of AMB-tolerant phenotypes of A. terreus has been examined by assessing the minimum duration for killing 99% of the population (MDK99) and evaluating the data obtained in a Galleria mellonella infection model. A time-kill curve analysis revealed that A. terreus with AMB MICs of ≤1 mg/L (susceptible range) displayed AMB-tolerant phenotypes, exhibiting MDK99s at 18 and 36 h, respectively. Survival rates of infected G. mellonella highlighted that AMB was effective against susceptible A. terreus isolates, but not against tolerant or resistant isolates. Our analysis reveals that A. terreus isolates which are defined as susceptible based on MIC may comprise tolerant phenotypes, which may, in turn, explain the worse outcome of AMB therapy for phenotypically susceptible isolates.
Topics: Amphotericin B; Anti-Bacterial Agents; Antifungal Agents; Aspergillus; Drug Resistance, Fungal; Drug Tolerance; Microbial Sensitivity Tests
PubMed: 35254091
DOI: 10.1128/aac.02274-21 -
The Journal of Pharmacology and... Dec 2014The serotonin 5-hydroxytryptamine 2A (5-HT2A) receptor is a potential therapeutic target to a host of neuropsychiatric conditions, but agonist actions at this site are...
The serotonin 5-hydroxytryptamine 2A (5-HT2A) receptor is a potential therapeutic target to a host of neuropsychiatric conditions, but agonist actions at this site are linked to abuse-related hallucinogenic effects that may limit therapeutic efficacy of chronic drug administration. Tolerance to some effects of hallucinogens has been observed in humans and laboratory animals, but the understanding of tolerance and cross-tolerance between distinct structural classes of hallucinogens is limited. Here, we used the drug-elicited head twitch response (HTR) in mice to assess the development of tolerance and cross-tolerance with two phenethylamine-derived [DOI (2,5-dimethoxy-4-iodoamphetamine) and 2C-T-7 (2,5-dimethoxy-4-propylthiophenethylamine)] and two tryptamine-derived [DPT (N,N-dipropyltryptamine) and DIPT (N,N-diisopropyltryptamine)] drugs with agonist affinity for 5-HT2A receptors. Tolerance developed to HTR elicited by daily DOI or 2C-T-7, but not to HTR elicited by DPT or DIPT. DOI-elicited tolerance was not surmountable with dose, and a similar insurmountable cross-tolerance was evident when DOI-tolerant mice were tested with various doses of 2C-T-7 or DPT. These studies suggest that the use of phenethylamine-derived hallucinogens as therapeutic agents may be limited not only by their abuse potential, but also by the rapid development of tolerance that would likely be maintained even if a patient were switched to a different 5-HT2A agonist medication from a distinct structural class. However, these experiments also imply that tryptamine-derived hallucinogens might have a reduced potential for tolerance development, compared with phenethylamine-derived 5-HT2A agonists, and might therefore be more suitable for chronic administration in a therapeutic context.
Topics: Animals; Dose-Response Relationship, Drug; Drug Tolerance; Hallucinogens; Head Movements; Male; Mice; Phenethylamines; Random Allocation; Serotonin 5-HT2 Receptor Agonists; Tryptamines
PubMed: 25271256
DOI: 10.1124/jpet.114.219337