Ciprofloxacin does not inhibit mitochondrial functions but other antibiotics do

Azithromycin alters Colony Stimulating Factor-1R (CSF-1R) expression and functional output of murine bone marrow-derived macrophages: A novel report

Antibiotic treatment may lead to side effects that require mechanistic explanation. We investigated the effect of azithromycin (AZM) treatment on bone marrow-derived macrophage (Mφ) generation, their functional output, and the subsequent effect on bacterial clearance in a mouse model of S. flexneri infection. To our fascination, AZM increased PU.1, C/EBPβ, CSF-1R/pCSF-1R expressions leading to M2-skewed in vitro BMDM generation. Altered Mφ-functions like- phagocytosis, oxidative stress generation, inflammasome-activation, cytokine release, and phenotype (pro-inflammatory-M1, anti-inflammatory-M2) even in the presence of infection were observed with AZM treatment. AZM increased CD206, egr2, arg1 (M2-marker) expression and activity while reducing CD68, inducible nitric oxide (iNOS) expression, and activity (M1-marker) in Mφs during infection. Pro-inflammatory cytokines (TNF-α, IL-12, IL-1β) were reduced and anti-inflammatory IL-10 release was augmented by AZM-treated-iMφs (aiMφs) along with decreased asc, nlrp3, aim2, nlrp1a, caspase1 expressions, and caspase3 activity signifying that aMφs/aiMφs were primed towards an anti-inflammatory phenotype. Interestingly, CSF-1R blockade increased NO, IL-12, TNF-α, IL-1β, decreased TGF-β release, and CD206 expression in aiMφs. T-cell co-stimulatory molecule cd40, cd86, and cd80 expressions were decreased in ai/aM1-Mφs and co-cultured CD8+, CD4+ T-cells had decreased proliferation, t-bet, IFN-γ, IL-17, IL-2 but increased foxp3, TGF-β, IL-4 which were rescued with CSF-1R blockade. Thus AZM affected Mφ-functions and subsequent T-cell responses independent of its antibacterial actions. This was validated in the balb/c model of S. flexneri infection. We conclude that AZM skewed BMDM generation to anti-inflammatory M2-like via increased CSF-1R expression. This warrants further investigation of AZM-induced altered-Mφ-generation during intracellular infections.

Side effects of antibiotics and perturbations of mitochondria functions

Antibiotics are one of the greatest discoveries of medicine of the past century. Despite their invaluable contribution to infectious disease, their administration could lead to side effects that in some cases are serious. The toxicity of some antibiotics is in part due to their interaction with mitochondria: these organelles derive from a bacterial ancestor and possess specific translation machinery that shares similarities with the bacterial counterpart. In other cases, the antibiotics could interfere with mitochondrial functions even if their main bacterial targets are not shared with the eukaryotic cells. The purpose of this review is to summarize the effects of antibiotics administration on mitochondrial homeostasis and the opportunity that some of these molecules could represent in cancer treatment. The importance of antimicrobial therapy is unquestionable, but the identification of interaction with eukaryotic cells and in particular with mitochondria is crucial to reduce the toxicity of these drugs and to explore other useful medical applications.

Doxycycline Treatment of Mansonella perstans-Infected Individuals Affects Immune Cell Activation and Causes Long-term T-cell Polarization

BACKGROUND

Doxycycline is used for treatment of Mansonella perstans infection. Immune modulatory effects of both M. perstans and doxycycline have been described but long-term implications on host immune response are not defined. Here we determined multiple immune parameters of M. perstans-infected individuals before and after doxycycline treatment to characterize doxycycline effects on host T-cell immunity.

METHODS

Immune characterization of doxycycline-treated M. perstans-infected individuals was performed as part of an open-label randomized clinical trial. Immune cell population phenotyping by flow cytometry and functional in vitro T-cell assays were performed at baseline, 6 months, and "long term" (18-24 months) after treatment start. Treatment efficacy, based on peripheral blood microfilaria (mf) burden, was correlated with immune parameters and effects on immune response against concomitant Mycobacterium tuberculosis infection were determined.

RESULTS

Immune population phenotyping indicated changes in functional T-cell responses after doxycycline treatment. Constitutive and superantigen-induced T-cell activation and polarization towards T-helper type (TH) 1 phenotype at baseline declined after doxycycline treatment, whereas low proportions of TH17 and TH1* cells at baseline increased significantly at follow-up. In accordance, long-term decline in antigen-specific TH1 responses against concomitant M. tuberculosis infection was seen. Notably, only TH17 and TH1* changes after 6 months and TH17 at baseline were negatively correlated with M. perstans microfilaria burden or reduction, whereas long-term changes were not associated with treatment efficacy.

CONCLUSIONS

We found long-term immune modulatory effects of doxycycline treatment leading to decreased constitutive T-cell activation, polarization towards TH17/TH1*, and impaired immune response against concomitant M. tuberculosis infection.

Activation of the integrated stress response is a vulnerability for multidrug-resistant FBXW7-deficient cells

FBXW7 is one of the most frequently mutated tumor suppressors, deficiency of which has been associated with resistance to some anticancer therapies. Through bioinformatics and genome‐wide CRISPR screens, we here reveal that FBXW7 deficiency leads to multidrug resistance (MDR). Proteomic analyses found an upregulation of mitochondrial factors as a hallmark of FBXW7 deficiency, which has been previously linked to chemotherapy resistance. Despite this increased expression of mitochondrial factors, functional analyses revealed that mitochondria are under stress, and genetic or chemical targeting of mitochondria is preferentially toxic for FBXW7‐deficient cells. Mechanistically, the toxicity of therapies targeting mitochondrial translation such as the antibiotic tigecycline relates to the activation of the integrated stress response (ISR) in a GCN2 kinase‐dependent manner. Furthermore, the discovery of additional drugs that are toxic for FBXW7‐deficient cells showed that all of them unexpectedly activate a GCN2‐dependent ISR regardless of their accepted mechanism of action. Our study reveals that while one of the most frequent mutations in cancer reduces the sensitivity to the vast majority of available therapies, it renders cells vulnerable to ISR‐activating drugs.

Tetracyclines-An Important Therapeutic Tool for Dermatologists

Tetracyclines are a group of antibiotics whose first representative was discovered over 70 years ago. Since then, they have been of great interest in dermatology. In addition to their antibacterial activity, they are able to inhibit metalloproteinases and exhibit anti-inflammatory, anti-apoptotic and antioxidant effects. The side effects have been thoroughly studied over the years, the most characteristic and important ones in daily dermatological practice being: phototoxicity, hyperpigmentation, onycholysis, photoonycholysis, induced lupus erythematosus, and idiopathic intracranial hypertension. In this article, we summarize the use of tetracyclines in infectious diseases and inflammatory dermatoses, and further discuss the instances where the efficacy and safety of tetracyclines have been highlighted over the past few years.

Development of a Plasmid Shuttle Vector System for Genetic Manipulation of Chlamydia psittaci

The obligate intracellular bacterium Chlamydia psittaci is a known avian pathogen causing psittacosis in birds and is capable of zoonotic transmission. In human pulmonary infections, C. psittaci can cause pneumonia associated with significant mortality if inadequately diagnosed and treated. Although intracellular C. psittaci manipulates host cell organelles for its replication and survival, it has been difficult to demonstrate host-pathogen interactions in C. psittaci infection due to the lack of easy-to-handle genetic manipulation tools. Here, we show the genetic transformation of C. psittaci using a plasmid shuttle vector that contains a controllable gene induction system. The 7,553-bp plasmid p01DC12 was prepared from the nonavian C. psittaci strain 01DC12. We constructed the shuttle vector pCps-Tet-mCherry using the full sequence of p01DC12 and the 4,449-bp fragment of Chlamydia trachomatis shuttle vector pBOMB4-Tet-mCherry. pCps-Tet-mCherry includes genes encoding the green fluorescent protein (GFP), mCherry, and ampicillin resistance (AmpR). Target genes can be inserted at a multiple cloning site (MCS). Importantly, these genes can be regulated by a tetracycline-inducible (tet) promoter. Using the pCps-Tet-mCherry plasmid shuttle vector, we show the expression of GFP, as well as the induction of mCherry expression, in C. psittaci strain 02DC15, which belongs to the avian C. psittaci 6BC clade. Furthermore, we demonstrated that pCps-Tet-mCherry was stably retained in C. psittaci transformants. Thus, our C. psittaci plasmid shuttle vector system represents a novel targeted approach that enables the elucidation of host-pathogen interactions.IMPORTANCE Psittacosis, caused by avian C. psittaci, has a major economic impact in the poultry industry worldwide and represents a significant risk for zoonotic transmission to humans. In the past decade, the tools of genetic manipulation have been improved for chlamydial molecular studies. While several genetic tools have been mainly developed in Chlamydia trachomatis, a stable gene-inducible shuttle vector system has not to date been available for C. psittaci In this study, we adapted a C. trachomatis plasmid shuttle vector system to C. psittaci We constructed a C. psittaci plasmid backbone shuttle vector called pCps-Tet-mCherry. The construct expresses GFP in C. psittaci Importantly, exogeneous genes can be inserted at an MCS and are regulated by a tet promoter. The application of the pCps-Tet-mCherry shuttle vector system enables a promising new approach to investigate unknown gene functions of this pathogen.

High-throughput screening of clinically approved drugs that prime nonviral gene delivery to human Mesenchymal stem cells

Background

Human mesenchymal stem cells (hMSCs) are intensely researched for applications in cell therapeutics due to their unique properties, however, intrinsic therapeutic properties of hMSCs could be enhanced by genetic modification. Viral transduction is efficient, but suffers from safety issues. Conversely, nonviral gene delivery, while safer compared to viral, suffers from inefficiency and cytotoxicity, especially in hMSCs. To address the shortcomings of nonviral gene delivery to hMSCs, our lab has previously demonstrated that pharmacological 'priming' of hMSCs with the glucocorticoid dexamethasone can significantly increase transfection in hMSCs by modulating transfection-induced cytotoxicity. This work seeks to establish a library of transfection priming compounds for hMSCs by screening 707 FDA-approved drugs, belonging to diverse drug classes, from the NIH Clinical Collection at four concentrations for their ability to modulate nonviral gene delivery to adipose-derived hMSCs from two human donors.

Results

Microscope images of cells transfected with a fluorescent transgene were analyzed in order to identify compounds that significantly affected hMSC transfection without significant toxicity. Compound classes that increased transfection across both donors included glucocorticoids, antibiotics, and antihypertensives. Notably, clobetasol propionate, a glucocorticoid, increased transgene production 18-fold over unprimed transfection. Furthermore, compound classes that decreased transfection across both donors included flavonoids, antibiotics, and antihypertensives, with the flavonoid epigallocatechin gallate decreasing transgene production - 41-fold compared to unprimed transfection.

Conclusions

Our screen of the NCC is the first high-throughput and drug-repurposing approach to identify nonviral gene delivery priming compounds in two donors of hMSCs. Priming compounds and classes identified in this screen suggest that modulation of proliferation, mitochondrial function, and apoptosis is vital for enhancing nonviral gene delivery to hMSCs.

Mitochondria as target to inhibit proliferation and induce apoptosis of cancer cells: the effects of doxycycline and gemcitabine

Doxycycline has anti-tumour effects in a range of tumour systems. The aims of this study were to define the role mitochondria play in this process and examine the potential of doxycycline in combination with gemcitabine. We studied the adenocarcinoma cell line A549, its mitochondrial DNA-less derivative A549 ρ° and cultured fibroblasts. Treatment with doxycycline for 5 days resulted in a decrease of mitochondrial-encoded proteins, respiration and membrane potential, and an increase of reactive oxygen species in A549 cells and fibroblasts, but fibroblasts were less affected. Doxycycline slowed proliferation of A549 cells by 35%. Cellular ATP levels did not change. Doxycycline alone had no effect on apoptosis; however, in combination with gemcitabine given during the last 2 days of treatment, doxycycline increased caspase 9 and 3/7 activities, resulting in a further decrease of surviving A549 cells by 59% and of fibroblasts by 24% compared to gemcitabine treatment alone. A549 ρ° cells were not affected by doxycycline. Key effects of doxycycline observed in A549 cells, such as the decrease of mitochondrial-encoded proteins and surviving cells were also seen in the cancer cell lines COLO357 and HT29. Our results suggest that doxycycline suppresses cancer cell proliferation and primes cells for apoptosis by gemcitabine.

A genome-wide analysis of targets of macrolide antibiotics in mammalian cells

Macrolide antibiotics, such as erythromycin and josamycin, are natural polyketide products harboring 14- to 16-membered macrocyclic lactone rings to which various sugars are attached. These antibiotics are used extensively in the clinic because of their ability to inhibit bacterial protein synthesis. More recently, some macrolides have been shown to also possess anti-inflammatory and other therapeutic activities in mammalian cells. To better understand the targets and effects of this drug class in mammalian cells, we used a genome-wide shRNA screen in K562 cancer cells to identify genes that modulate cellular sensitivity to josamycin. Among the most sensitizing hits were proteins involved in mitochondrial translation and the mitochondrial unfolded protein response, glycolysis, and the mitogen-activated protein kinase signaling cascade. Further analysis revealed that cells treated with josamycin or other antibacterial agents exhibited impaired oxidative phosphorylation and metabolic shifts to glycolysis. Interestingly, we observed that knockdown of the mitogen-activated protein kinase kinase kinase 4 (MAP3K4) gene, which contributes to p38 mitogen-activated protein kinase signaling, sensitized cells only to josamycin but not to other antibacterial agents. There is a growing interest in better characterizing the therapeutic effects and toxicities of antibiotics in mammalian cells to guide new applications in both cellular and clinical studies. To our knowledge, this is the first report of an unbiased genome-wide screen to investigate the effects of a clinically used antibiotic on human cells.

The adverse effect of gentamicin on cell metabolism in three cultured mammary cell lines: "Are cell culture data skewed?"

Many cells are cultured in media that contains an antibiotic to prevent bacterial contamination. Mycoplasma and other bacterial contamination is a serious problem for those involved in cell culture. Antibiotics in the media helps prevent this contamination and make life easier for the investigators; as performing cell culture experiments in antibiotic free media is difficult and requires vigorous sterile technique. There are many reports of antibiotics causing mitochondrial damage. In this study, we tested the effect of gentamicin in culture media on human mammary epithelial MCF-12A and breast cancer MCF-7 and MDA-MB-231 cell lines by real time PCR, immunofluorescent microscopy, lactate assay, DNA damage assay. We found that the addition of gentamicin in media upregulated the gene expression of hypoxia inducer factor 1 alpha (HIF1a), glycolytic enzymes and glucose transporters, compared to the cells cultured in gentamicin free media. Gentamicin also increased the lactate production and inhibited mitochondrial membrane potential of the cell lines. Furthermore, the antibiotics in media induced mitochondrial reactive oxygen species causing DNA damage. We found an increase of 8-hydroxy-2'-deoxyguanosine a product of DNA oxidative damage in the media of MCF-12A, MCF-7 and MDA-MB-231 cell lines. These results showed that normal epithelial and breast cancer cells cultured in the media with gentamicin had increased HIF1a, aerobic glycolysis and DNA oxidative damage. If we use these unhealthy cells in the experiment, all data will be different, compared to cells grown in gentamicin free media. We have studied the detrimental effects of three antibiotics on mitochondrial function in the untransformed MCF-12A human mammary cell line and two human mammary cancer cell lines, MCF-7 and MB-MDA-231. The metabolic changes in all cell lines were dramatically different between those in antibiotic free media versus antibiotic containing media. There was a marked difference in gene expression of glycolytic enzymes, reactive oxygen species production and effects on membrane potential. Ironically, our first studies were done in media containing gentamicin, and repeated studies were done in gentamicin free media. The results were very different. The purpose of this report is to emphasize that metabolic cell culture data may be inaccurate because experiments were performed in cell culture media containing antibiotics. We will present evidence to support this theory.

Minocycline Inhibits Candida albicans Budded-to-Hyphal-Form Transition and Biofilm Formation

Candida albicans frequently causes bloodstream infections; its budded-to-hyphalform transition (BHT) and biofilm formation are major contributors to virulence. During an analysis of antibacterial compounds that inhibit C. albicans BHT, we found that the tetracycline derivative minocycline inhibited BHT and subsequent biofilm formation. Minocycline decreased expression of hypha-specific genes HWP1 and ECE1, and adhesion factor gene ALS3 of C. albicans. In addition, minocycline decreased cell surface hydrophobicity and the extracellular β-glucan level in biofilms. Minocycline has been widely used for catheter antibiotic lock therapy to prevent bacterial infection; this compound may also be prophylactically effective against Candida infection.

Impacts of Antibiotic and Bacteriophage Treatments on the Gut-Symbiont-Associated Blissus insularis (Hemiptera: Blissidae)

The Southern chinch bug, Blissus insularis, possesses specialized midgut crypts that harbor dense populations of the exocellular symbiont Burkholderia. Oral administration of antibiotics suppressed the gut symbionts in B. insularis and negatively impacted insect host fitness, as reflected by retarded development, smaller body size, and higher susceptibility to an insecticide, bifenthrin. Considering that the antibiotics probably had non-lethal but toxic effects on host fitness, attempts were conducted to reduce gut symbionts using bacteriophage treatment. Soil-lytic phages active against the cultures of specific Burkholderia ribotypes were successfully isolated using a soil enrichment protocol. Characterization of the BiBurk16MC_R phage determined its specificity to the Bi16MC_R_vitro ribotype and placed it within the family Podoviridae. Oral administration of phages to fifth-instar B. insularis, inoculated with Bi16MC_R_vitro as neonates had no deleterious effects on host fitness. However, the ingested phages failed to impact the crypt-associated Burkholderia. The observed inactivity of the phage was likely due to the blockage of the connection between the anterior and posterior midgut regions. These findings suggest that the initial colonization by Burkholderia programs the ontogeny of the midgut, providing a sheltered residence protected from microbial antagonists.

Doxycycline down-regulates DNA-PK and radiosensitizes tumor initiating cells: Implications for more effective radiation therapy

DNA-PK is an enzyme that is required for proper DNA-repair and is thought to confer radio-resistance in cancer cells. As a consequence, it is a high-profile validated target for new pharmaceutical development. However, no FDA-approved DNA-PK inhibitors have emerged, despite many years of drug discovery and lead optimization. This is largely because existing DNA-PK inhibitors suffer from poor pharmacokinetics. They are not well absorbed and/or are unstable, with a short plasma half-life. Here, we identified the first FDA-approved DNA-PK inhibitor by "chemical proteomics". In an effort to understand how doxycycline targets cancer stem-like cells (CSCs), we serendipitously discovered that doxycycline reduces DNA-PK protein expression by nearly 15-fold (> 90%). In accordance with these observations, we show that doxycycline functionally radio-sensitizes breast CSCs, by up to 4.5-fold. Moreover, we demonstrate that DNA-PK is highly over-expressed in both MCF7- and T47D-derived mammospheres. Interestingly, genetic or pharmacological inhibition of DNA-PK in MCF7 cells is sufficient to functionally block mammosphere formation. Thus, it appears that active DNA-repair is required for the clonal expansion of CSCs. Mechanistically, doxycycline treatment dramatically reduced the oxidative mitochondrial capacity and the glycolytic activity of cancer cells, consistent with previous studies linking DNA-PK expression to the proper maintenance of mitochondrial DNA integrity and copy number. Using a luciferase-based assay, we observed that doxycycline treatment quantitatively reduces the anti-oxidant response (NRF1/2) and effectively blocks signaling along multiple independent pathways normally associated with stem cells, including STAT1/3, Sonic Hedgehog (Shh), Notch, WNT and TGF-beta signaling. In conclusion, we propose that the efficacy of doxycycline as a DNA-PK inhibitor should be tested in Phase-II clinical trials, in combination with radio-therapy. Doxycycline has excellent pharmacokinetics, with nearly 100% oral absorption and a long serum half-life (18-22 hours), at a standard dose of 200-mg per day. In further support of this idea, we show that doxycycline effectively inhibits the mammosphere-forming activity of primary breast cancer samples, derived from metastatic disease sites (pleural effusions or ascites fluid). Our results also have possible implications for the radio-therapy of brain tumors and/or brain metastases, as doxycycline is known to effectively cross the blood-brain barrier. Further studies will be needed to determine if other tetracycline family members also confer radio-sensitivity.

The Zinc Finger Protein Mig1 Regulates Mitochondrial Function and Azole Drug Susceptibility in the Pathogenic Fungus Cryptococcus neoformans

Fungal pathogens of humans are difficult to treat, and there is a pressing need to identify new targets for antifungal drugs and to obtain a detailed understanding of fungal proliferation in vertebrate hosts. In this study, we examined the roles of the regulatory proteins Mig1 and HapX in mitochondrial function and antifungal drug susceptibility in the fungus Cryptococcus neoformans. This pathogen is a particular threat to the large population of individuals infected with human immunodeficiency virus (HIV). Our analysis revealed regulatory interactions between Mig1 and HapX, and a role for Mig1 in mitochondrial functions, including respiration, tolerance for reactive oxygen species, and expression of genes for iron consumption and iron acquisition functions. Importantly, loss of Mig1 increased susceptibility to the antifungal drug fluconazole, which is commonly used to treat cryptococcal disease. These studies highlight an association between mitochondrial dysfunction and drug susceptibility that may provide new targets for the development of antifungal drugs.

The opportunistic pathogen Cryptococcus neoformans causes fungal meningoencephalitis in immunocompromised individuals. In previous studies, we found that the Hap complex in this pathogen represses genes encoding mitochondrial respiratory functions and tricarboxylic acid (TCA) cycle components under low-iron conditions. The orthologous Hap2/3/4/5 complex in Saccharomyces cerevisiae exerts a regulatory influence on mitochondrial functions, and Hap4 is subject to glucose repression via the carbon catabolite repressor Mig1. In this study, we explored the regulatory link between a candidate ortholog of the Mig1 protein and the HapX component of the Hap complex in C. neoformans. This analysis revealed repression of MIG1 by HapX and activation of HAPX by Mig1 under low-iron conditions and Mig1 regulation of mitochondrial functions, including respiration, tolerance for reactive oxygen species, and expression of genes for iron consumption and iron acquisition functions. Consistently with these regulatory functions, a mig1Δ mutant had impaired growth on inhibitors of mitochondrial respiration and inducers of ROS. Furthermore, deletion of MIG1 provoked a dysregulation in nutrient sensing via the TOR pathway and impacted the pathway for cell wall remodeling. Importantly, loss of Mig1 increased susceptibility to fluconazole, thus further establishing a link between azole antifungal drugs and mitochondrial function. Mig1 and HapX were also required together for survival in macrophages, but Mig1 alone had a minimal impact on virulence in mice. Overall, these studies provide novel insights into a HapX/Mig1 regulatory network and reinforce an association between mitochondrial dysfunction and drug susceptibility that may provide new targets for the development of antifungal drugs.

IMPORTANCE Fungal pathogens of humans are difficult to treat, and there is a pressing need to identify new targets for antifungal drugs and to obtain a detailed understanding of fungal proliferation in vertebrate hosts. In this study, we examined the roles of the regulatory proteins Mig1 and HapX in mitochondrial function and antifungal drug susceptibility in the fungus Cryptococcus neoformans. This pathogen is a particular threat to the large population of individuals infected with human immunodeficiency virus (HIV). Our analysis revealed regulatory interactions between Mig1 and HapX, and a role for Mig1 in mitochondrial functions, including respiration, tolerance for reactive oxygen species, and expression of genes for iron consumption and iron acquisition functions. Importantly, loss of Mig1 increased susceptibility to the antifungal drug fluconazole, which is commonly used to treat cryptococcal disease. These studies highlight an association between mitochondrial dysfunction and drug susceptibility that may provide new targets for the development of antifungal drugs.

Causes of upregulation of glycolysis in lymphocytes upon stimulation. A comparison with other cell types

In this review, we revisit the metabolic shift from respiration to glycolysis in lymphocytes upon activation, which is known as the Warburg effect in tumour cells. We compare the situation in lymphocytes with those in several other cell types, such as muscle cells, Kupffer cells, microglia cells, astrocytes, stem cells, tumour cells and various unicellular organisms (e.g. yeasts). We critically discuss and compare several explanations put forward in the literature for the observation that proliferating cells adopt this apparently less efficient pathway: hypoxia, poisoning of competitors by end products, higher ATP production rate, higher precursor supply, regulatory effects, and avoiding harmful effects (e.g. by reactive oxygen species). We conclude that in the case of lymphocytes, increased ATP production rate and precursor supply are the main advantages of upregulating glycolysis.

Doxycycline alters metabolism and proliferation of human cell lines

The tetracycline antibiotics are widely used in biomedical research as mediators of inducible gene expression systems. Despite many known effects of tetracyclines on mammalian cells–including inhibition of the mitochondrial ribosome–there have been few reports on potential off-target effects at concentrations commonly used in inducible systems. Here, we report that in human cell lines, commonly used concentrations of doxycycline change gene expression patterns and concomitantly shift metabolism towards a more glycolytic phenotype, evidenced by increased lactate secretion and reduced oxygen consumption. We also show that these concentrations are sufficient to slow proliferation. These findings suggest that researchers using doxycycline in inducible expression systems should design appropriate controls to account for potential confounding effects of the drug on cellular metabolism.

A new face for old antibiotics: tetracyclines in treatment of amyloidoses

The use of tetracyclines has declined because of the appearance of resistant bacterial strains. However, the indications of nonantimicrobial activities of these drugs have considerably raised interest and triggered clinical trials for a number of different pathologies. About 10 years ago we first reported that tetracyclines inhibited the aggregation of prion protein fragments and Alzheimer's β peptides, destabilizing their aggregates and promoting their degradation by proteases. On the basis of these observations, the antiamyloidogenic effects of tetracyclines on a variety of amyloidogenic proteins were studied and confirmed by independent research groups. In this review we comment on the data available on their antiamyloidogenic activity in preclinical and clinical studies. We also put forward that the beneficial effects of these drugs are a result of a peculiar pleiotropic action, comprising their interaction with oligomers and disruption of fibrils, as well as their antioxidant, anti-inflammatory, antiapoptotic, and matrix metalloproteinase inhibitory activities.

Adverse effects of antimicrobials via predictable or idiosyncratic inhibition of host mitochondrial components

This minireview explores mitochondria as a site for antibiotic-host interactions that lead to pathophysiologic responses manifested as nonantibacterial side effects. Mitochondrion-based side effects are possibly related to the notion that these organelles are archaic bacterial ancestors or commandeered remnants that have co-evolved in eukaryotic cells; thus, this minireview focuses on mitochondrial damage that may be analogous to the antibacterial effects of the drugs. Special attention is devoted to aminoglycosides, chloramphenicol, and fluoroquinolones and their respective single side effects related to mitochondrial disturbances. Linezolid/oxazolidinone multisystemic toxicity is also discussed. Aminoglycosides and oxazolidinones are inhibitors of bacterial ribosomes, and some of their side effects appear to be based on direct inhibition of mitochondrial ribosomes. Chloramphenicol and fluoroquinolones target bacterial ribosomes and gyrases/topoisomerases, respectively, both of which are present in mitochondria. However, the side effects of chloramphenicol and the fluoroquinolones appear to be based on idiosyncratic damage to host mitochondria. Nonetheless, it appears that mitochondrion-associated side effects are a potential aspect of antibiotics whose targets are shared by prokaryotes and mitochondria-an important consideration for future drug design.

Oxidized mitochondrial DNA activates the NLRP3 inflammasome during apoptosis

We report that in the presence of signal 1 (NF-κB), the NLRP3 inflammasome was activated by mitochondrial apoptotic signaling that licensed production of interleukin-1β (IL-1β). NLRP3 secondary signal activators such as ATP induced mitochondrial dysfunction and apoptosis, resulting in release of oxidized mitochondrial DNA (mtDNA) into the cytosol, where it bound to and activated the NLRP3 inflammasome. The antiapoptotic protein Bcl-2 inversely regulated mitochondrial dysfunction and NLRP3 inflammasome activation. Mitochondrial DNA directly induced NLRP3 inflammasome activation, because macrophages lacking mtDNA had severely attenuated IL-1β production, yet still underwent apoptosis. Both binding of oxidized mtDNA to the NLRP3 inflammasome and IL-1β secretion could be competitively inhibited by the oxidized nucleoside 8-OH-dG. Thus, our data reveal that oxidized mtDNA released during programmed cell death causes activation of the NLRP3 inflammasome. These results provide a missing link between apoptosis and inflammasome activation, via binding of cytosolic oxidized mtDNA to the NLRP3 inflammasome.

Mitochondrial dysfunction and biogenesis: do ICU patients die from mitochondrial failure?

Mitochondrial functions include production of energy, activation of programmed cell death, and a number of cell specific tasks, e.g., cell signaling, control of Ca²⁺ metabolism, and synthesis of a number of important biomolecules. As proper mitochondrial function is critical for normal performance and survival of cells, mitochondrial dysfunction often leads to pathological conditions resulting in various human diseases. Recently mitochondrial dysfunction has been linked to multiple organ failure (MOF) often leading to the death of critical care patients. However, there are two main reasons why this insight did not generate an adequate resonance in clinical settings. First, most data regarding mitochondrial dysfunction in organs susceptible to failure in critical care diseases (liver, kidney, heart, lung, intestine, brain) were collected using animal models. Second, there is no clear therapeutic strategy how acquired mitochondrial dysfunction can be improved. Only the benefit of such therapies will confirm the critical role of mitochondrial dysfunction in clinical settings. Here we summarized data on mitochondrial dysfunction obtained in diverse experimental systems, which are related to conditions seen in intensive care unit (ICU) patients. Particular attention is given to mechanisms that cause cell death and organ dysfunction and to prospective therapeutic strategies, directed to recover mitochondrial function. Collectively the data discussed in this review suggest that appropriate diagnosis and specific treatment of mitochondrial dysfunction in ICU patients may significantly improve the clinical outcome.

Isolation and characterisation of bacterial colonies from seeds and in vitro cultures of Fraxinus spp. from Italian sites

Culturable bacteria were isolated from seeds, embryos and contaminated in vitro cultures of ash (Fraxinus excelsior L., F. ornus L. and F. angustifolia L.) and were identified using morphological and molecular analyses. Fourteen morphologically distinct isolates were recovered from seeds of Fraxinus spp. 16S rDNA sequencing categorised these isolates into ten separate genera. Three strains isolated from contaminated in vitro cultures, Pantoea agglomerans, Staphylococcus succinus and Aerococcus viridans, were used for comparative analysis with isolates from seeds. Antibiotic sensitivity testing of the isolated contaminants, including phytotoxicity of antibiotics on in vitro cultures of ash, was also investigated. Phytotoxic effects on explants immersed in ampicillin or cultured on medium containing ampicillin were negligible, however tetracycline, either alone or in combination with other antibiotics, had phytotoxic effects. We conclude that ampicillin is a suitable antibiotic to limit the growth of contaminating bacteria during the in vitro culture of ash.

Survival in critical illness is associated with early activation of mitochondrial biogenesis

RATIONALE

We previously reported outcome-associated decreases in muscle energetic status and mitochondrial dysfunction in septic patients with multiorgan failure. We postulate that survivors have a greater ability to maintain or recover normal mitochondrial functionality.

OBJECTIVES

To determine whether mitochondrial biogenesis, the process promoting mitochondrial capacity, is affected in critically ill patients.

METHODS

Muscle biopsies were taken from 16 critically ill patients recently admitted to intensive care (average 1-2 d) and from 10 healthy, age-matched patients undergoing elective hip surgery.

MEASUREMENTS AND MAIN RESULTS

Survival, mitochondrial morphology, mitochondrial protein content and enzyme activity, mitochondrial biogenesis factor mRNA, microarray analysis, and phosphorylated (energy) metabolites were determined. Ten of 16 critically ill patients survived intensive care. Mitochondrial size increased with worsening outcome, suggestive of swelling. Respiratory protein subunits and transcripts were depleted in critically ill patients and to a greater extent in nonsurvivors. The mRNA content of peroxisome proliferator-activated receptor γ coactivator 1-α (transcriptional coactivator of mitochondrial biogenesis) was only elevated in survivors, as was the mitochondrial oxidative stress protein manganese superoxide dismutase. Eventual survivors demonstrated elevated muscle ATP and a decreased phosphocreatine/ATP ratio.

CONCLUSIONS

Eventual survivors responded early to critical illness with mitochondrial biogenesis and antioxidant defense responses. These responses may partially counteract mitochondrial protein depletion, helping to maintain functionality and energetic status. Impaired responses, as suggested in nonsurvivors, could increase susceptibility to mitochondrial damage and cellular energetic failure or impede the ability to recover normal function. Clinical trial registered with clinical trials.gov (NCT00187824).

Is MOF an outcome parameter or a transient, adaptive state in critical illness?

PURPOSE OF REVIEW

The term 'multiorgan failure' (MOF) carries the negative connotation of major homeostatic breakdown and severe malfunction. However, this traditional paradigm may not be necessarily accurate. This review will investigate the rationale for no longer considering MOF to be simply a 'failed' pathophysiological state.

RECENT FINDINGS

Multiorgan failure is characterized by a hypometabolic, immunodepressed state with clinical and biochemical evidence of decreased functioning of the body's organ systems. Notwithstanding these findings, evidence for cell death is scarce and organ recovery is frequently the rule in surviving patients without pre-existing organ disease. Decreased mitochondrial activity appears to play a key role in the processes underlying MOF, both as a victim and a player. Reduced ATP production will compromise normal metabolic functioning. To protect itself from dying, the cell may adapt by decreasing its metabolic rate, and this is clinically manifest as organ dysfunction. Mitochondrial modulation may thus represent an important therapeutic target.

SUMMARY

The concept of MOF could be revisited as a transient state of metabolic shutdown analogous to hibernation. Avoiding the detrimental effects of inappropriate and counter-adaptive iatrogenic interventions is an important cornerstone of therapeutic management.

Interactions of doxycycline with chemotherapeutic agents in human breast adenocarcinoma MDA-MB-231 cells

Commonly used chemotherapeutic agents for breast cancer treatment include cisplatin, doxorubicin, and paclitaxel. Unfortunately, these effective antiproliferative agents are limited by their toxicities. Previously, we have shown that doxycycline can substantially reduce tumor burden in an animal model of breast cancer bone metastasis. The purpose of this study was to examine the effect of doxycycline in combination with chemotherapy. Human breast adenocarcinoma MDA-MB-231 cells were treated in vitro with each drug individually and in combination with doxycycline. Cell survival was determined using the clonogenic survival assay. Doxycycline in combination with doxorubicin or paclitaxel yielded therapeutic antagonism at all effect levels. Combinatory treatment with cisplatin, however, yielded a biphasic interaction, at low combinatorial doses, the effect was quantified as nearly additive, whereas higher doxycycline-cisplatin doses yielding greater than 50% cell inhibition resulted in synergistic effects. Cell cycle profiles were determined and showed that treatment with doxycycline, cisplatin, and doxorubicin resulted in G1-phase, S-phase, and G2/M-phase arrests, respectively. Upon addition of doxycycline to doxorubicin, the G2/M-arrest characteristic of doxorubicin-only treatment was abrogated, which may account for the observed antagonism. Cells treated with doxycycline and cisplatin showed a further increase in S-phase arrest, also observed with cisplatin alone, which may be responsible for the additive and synergistic effects on cell survival. We clearly show that doxycycline in combination with paclitaxel or doxorubicin treatment resulted in antagonism; however, combining doxycycline with cisplatin led to synergistic interactions at higher effect levels. The increased potency of cisplatin may warrant dose reduction and thus decrease toxicity in vivo.

Ciprofloxacin decreases survival in HT-29 cells via the induction of TGF-beta1 secretion and enhances the anti-proliferative effect of 5-fluorouracil

BACKGROUND AND PURPOSE

Fluoroquinolones are potent anti-microbial agents with multiple effects on host cells and tissues. Previous studies have highlighted their pro-apoptotic effect on human cancer cells and an immunoregulatory role in animal models of inflammatory bowel disease. We examined the effect of ciprofloxacin on proliferation, cell cycle and apoptosis of HT-29 cells, a human colonic epithelial cell line sensitive to transforming growth factor (TGF)-beta1-mediated growth inhibition and its role in TGF-beta1 production. We also examined the effect of ciprofloxacin on proliferation of HT-29 cells in combination with 5-fluorouracil (5-FU), a well-established pro-apoptotic agent.

EXPERIMENTAL APPROACH

Using subconfluent cultures of HT-29 and Caco-2 cells, we studied the effect of ciprofloxacin, TGF-beta1 and 5-FU on proliferation, apoptosis, necrosis and cell cycle. The effect of ciprofloxacin on TGF-beta1 mRNA expression and production was studied in RNA extracts and cell culture supernatants respectively, using confluent cultures.

KEY RESULTS

Ciprofloxacin decreased proliferation of HT-29 cells in a concentration- and time-dependent manner. This was mediated by accumulation of HT-29 cells into the S-phase but without any effect on apoptosis or necrosis. Additionally, ciprofloxacin enhanced the antiproliferative effect of 5-FU. Interestingly, ciprofloxacin was found to up-regulate TGF-beta1 production by HT-29 cells and its anti-proliferative effect was abolished when TGF-beta1 was blocked. Confirming this mechanism further, ciprofloxacin had no effect on Caco-2, a human colonic epithelial cell line that lacks functional TGF-beta1 receptors.

CONCLUSIONS AND IMPLICATIONS

We demonstrate a novel anti-proliferative and immunoregulatory effect of ciprofloxacin on human intestinal epithelial cells mediated via TGF-beta1.

Influence on mitochondria and cytotoxicity of different antibiotics administered in high concentrations on primary human osteoblasts and cell lines

Osteomyelitis, osteitis, spondylodiscitis, septic arthritis, and prosthetic joint infections still represent the worst complications of orthopedic surgery and traumatology. Successful treatment requires, besides surgical débridement, long-term systemic and high-concentration local antibiotic therapy, with possible local antibiotic concentrations of 100 microg/ml and more. In this study, we investigated the effect of 20 different antibiotics on primary human osteoblasts (PHO), the osteosarcoma cell line MG63, and the epithelial cell line HeLa. High concentrations of fluoroquinolones, macrolides, clindamycin, chloramphenicol, rifampin, tetracycline, and linezolid during 48 h of incubation inhibited proliferation and metabolic activity, whereas aminoglycosides and inhibitors of bacterial cell wall synthesis did not. Twenty percent inhibitory concentrations for proliferation of PHO were determined as 20 to 40 microg/ml for macrolides, clindamycin, and rifampin, 60 to 80 microg/ml for chloramphenicol, tetracylin, and fluoroquinolones, and 240 microg/ml for linezolid. The proliferation of the cell lines was always less inhibited. We established the measurement of extracellular lactate concentration as an indicator of glycolysis using inhibitors of the respiratory chain (antimycin A, rotenone, and sodium azide) and glycolysis (iodoacetic acid) as reference compounds, whereas inhibition of the respiratory chain increased and inhibition of glycolysis decreased lactate production. The measurement of extracellular lactate concentration revealed that fluoroquinolones, macrolides, clindamycin, rifampin, tetracycline, and especially chloramphenicol and linezolid impaired mitochondrial energetics in high concentrations. This explains partly the observed inhibition of metabolic activity and proliferation in our experiments. Because of differences in the energy metabolism, PHO provided a more sensitive model for orthopedic antibiotic usage than stable cell lines.

Inhibition of mammalian mitochondrial protein synthesis by oxazolidinones

The effects of a variety of oxazolidinones, with different antibacterial potencies, including linezolid, on mitochondrial protein synthesis were determined in intact mitochondria isolated from rat heart and liver and rabbit heart and bone marrow. The results demonstrate that a general feature of the oxazolidinone class of antibiotics is the inhibition of mammalian mitochondrial protein synthesis. Inhibition was similar in mitochondria from all tissues studied. Further, oxazolidinones that were very potent as antibiotics were uniformly potent in inhibiting mitochondrial protein synthesis. These results were compared to the inhibitory profiles of other antibiotics that function by inhibiting bacterial protein synthesis. Of these, chloramphenicol and tetracycline were significant inhibitors of mammalian mitochondrial protein synthesis while the macrolides, lincosamides, and aminoglycosides were not. Development of future antibiotics from the oxazolidinone class will have to evaluate potential mitochondrial toxicity.

Treating critical illness: the importance of first doing no harm

Singer and Glynne present evidence to suggest that the short- term benefits of many interventions for treating critical illness may camouflage an underlying tendency to cause harm.

Immunomodulating activity of quinolones: review

Fluorinated quinolones exert their bactericidal activity by inhibiting bacterial type II topoisomerases. At therapeutic concentrations, quinolones superinduce interleukin-2 (IL-2) and interferon-gamma production by mitogen-activated human peripheral blood T lymphocytes. At the molecular level, a stronger activation of the nuclear factor AP-1 ('activator protein-1') is observed in cells incubated with ciprofloxacin, resulting in enhanced cytokine gene transcription. Several cytokine and immediate early (e.g., c-fos and c-jun) mRNAs are upregulated by ciprofloxacin, possibly reflecting a mammalian stress response. In cultures with murine splenocytes, quinolones enhance IL-3 and granulocyte-macrophage colony stimulating factor (GM-CSF) synthesis. The stimulation of these hematopoietic growth factors prolongs survival of mice with depressed bone marrow and prevents experimental antiphospholipid syndrome (APS). In contrast, quinolones inhibit both human and mouse monocytic IL-1 and TNF-alpha synthesis, an effect that is beneficial in rat experimental type II collagen induced arthritis and LPS-induced septic chock in mice. The intriguing immunomodulatory activities of fluoroquinolones warrant future investigations with new tailored derivatives.

Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistance

Tetracyclines were discovered in the 1940s and exhibited activity against a wide range of microorganisms including gram-positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and protozoan parasites. They are inexpensive antibiotics, which have been used extensively in the prophlylaxis and therapy of human and animal infections and also at subtherapeutic levels in animal feed as growth promoters. The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953. Tetracycline resistance now occurs in an increasing number of pathogenic, opportunistic, and commensal bacteria. The presence of tetracycline-resistant pathogens limits the use of these agents in treatment of disease. Tetracycline resistance is often due to the acquisition of new genes, which code for energy-dependent efflux of tetracyclines or for a protein that protects bacterial ribosomes from the action of tetracyclines. Many of these genes are associated with mobile plasmids or transposons and can be distinguished from each other using molecular methods including DNA-DNA hybridization with oligonucleotide probes and DNA sequencing. A limited number of bacteria acquire resistance by mutations, which alter the permeability of the outer membrane porins and/or lipopolysaccharides in the outer membrane, change the regulation of innate efflux systems, or alter the 16S rRNA. New tetracycline derivatives are being examined, although their role in treatment is not clear. Changing the use of tetracyclines in human and animal health as well as in food production is needed if we are to continue to use this class of broad-spectrum antimicrobials through the present century.

Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistance

Tetracyclines were discovered in the 1940s and exhibited activity against a wide range of microorganisms including gram-positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and protozoan parasites. They are inexpensive antibiotics, which have been used extensively in the prophlylaxis and therapy of human and animal infections and also at subtherapeutic levels in animal feed as growth promoters. The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953. Tetracycline resistance now occurs in an increasing number of pathogenic, opportunistic, and commensal bacteria. The presence of tetracycline-resistant pathogens limits the use of these agents in treatment of disease. Tetracycline resistance is often due to the acquisition of new genes, which code for energy-dependent efflux of tetracyclines or for a protein that protects bacterial ribosomes from the action of tetracyclines. Many of these genes are associated with mobile plasmids or transposons and can be distinguished from each other using molecular methods including DNA-DNA hybridization with oligonucleotide probes and DNA sequencing. A limited number of bacteria acquire resistance by mutations, which alter the permeability of the outer membrane porins and/or lipopolysaccharides in the outer membrane, change the regulation of innate efflux systems, or alter the 16S rRNA. New tetracycline derivatives are being examined, although their role in treatment is not clear. Changing the use of tetracyclines in human and animal health as well as in food production is needed if we are to continue to use this class of broad-spectrum antimicrobials through the present century.

Inhibitory effects of the quinolone antibiotics trovafloxacin, ciprofloxacin, and levofloxacin on osteoblastic cells in vitro

We studied the inhibitory effects of the fluoroquinolones levofloxacin, ciprofloxacin, and trovafloxacin on growth and extracellular matrix mineralization in MC3T3-E1 osteoblast-like cell cultures. Levofloxacin had the least inhibitory effect on cell growth, with a 50% inhibitory concentration of approximately 80 microg/ml at 48 and 72 hours. Ciprofloxacin had an intermediate degree of inhibition, with a 50% inhibitory concentration of 40 microg/ml at 48 and 72 hours. Trovafloxacin exerted a profound inhibitory effect on cell growth, with a 50% inhibitory concentration of 0.5 microg/ml, lower than clinically achievable serum levels. The decreased cell counts with up to 2.5 microg/ml of trovafloxacin and with up to 40 microg/ml of ciprofloxacin were not associated with decreased rates of 5-bromo-2'-deoxyuridine incorporation per cell. Alatrovafloxacin, the L-alanyl-l-alanine prodrug of trovafloxacin, exerted effects on proliferation and 5-bromo-2'-deoxyuridine incorporation similar to those of the parent compound. The quinolones evaluated also inhibited extracellular matrix mineralization by MC3T3-E1 cells. Treatment of confluent cultures with trovafloxacin, ciprofloxacin, or levofloxacin resulted in strong inhibition of calcium deposition, as determined on day 14 by alizarin red staining and biochemical analysis. The effect was apparent with 2.5-5 microg/ml of each of the three antibiotics tested and progressively increased to more than a 90% decline in the calcium/protein ratio with 20-40 microg/ml antibiotic concentration. Further in vivo studies are advocated to evaluate the relevance of the in vitro cytotoxicity reported here to bone healing in orthopaedic patients.

Tetracycline reduces fluoroquinolones-induced bleaching of Euglena gracilis

Inhibitory activity of tetracycline against ofloxacin- and fleroxacin-induced bleaching of green and etiolated Euglena gracilis was examined. Tetracycline hydrochloride in concentrations of 83-2079 microM in the light partially inhibited the bleaching activity of 83 microM ofloxacin and of 162 microM fleroxacin. In the dark, the TC inhibition of the fluoroquinolones-induced bleaching activity was most obvious, the white colony counts were all decreased. The total inhibition of bleaching was observed in 43 microM ofloxacin and 81 microM fleroxacin both in light and darkness. Cell growth was not significantly influenced by ofloxacin, fleroxacin and tetracycline in the light or darkness. Cell growth was not significantly influenced by ofloxacin, fleroxacin and tetracycline in the light or darkness. Inhibition of ofloxacin-induced Euglena bleaching by tetracycline was more effective in etiolated cells. TC at 0-416 microM did not influence the growth of ofloxacin (2.15 microM)-induced Salmonella typhimurium revertants.

Enhancement of the immunosuppressive effect of cyclosporin A by ciprofloxacin in a rat cardiac allograft transplantation model

Ciprofloxacin hyperinduces interleukin-2 production in stimulated human and mouse lymphocytes. In this study, an enhanced and prolonged interleukin-2 response was also detected in polyclonally stimulated rat splenocytes in the presence of ciprofloxacin (5-80 micrograms/ml) compared to control cells without any antibiotic. Ciprofloxacin was able to counteract the immunosuppressive effect of 10 ng/ml cyclosporin A (CyA) but did not interfere with higher CyA concentrations. In parallel, ciprofloxacin did not influence thymidine uptake in mixed lymphocyte reactions in the presence of CyA. To obtain an in vivo application of these findings, graft survival was studied by performing rat cardiac allograft transplantations in the presence or absence of CyA. Brown Norway rats served as donors and Wistar Furth rats as recipients. Ciprofloxacin was injected intraperitoneally either at a high-dose regimen (240 mg/kg per 24 h) into rats every 8th h starting 1 day before transplantation until day 21 or graft loss, or it was injected at a low and clinically relevant dose regimen (45 mg/kg per 24 h) until day 9. CyA was administered orally (10 mg/kg per 24 h) from day 1 through day 9. Ciprofloxacin given alone at a high-dose regimen resulted in a median graft survival of 14.8 days, which was significantly longer than graft survival in rats without treatment (median 8.0 days). A low-dose regimen of ciprofloxacin alone did not affect graft survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytofluorometric analysis of chondrotoxicity of fluoroquinolone antimicrobial agents

To better understand quinolone-related arthropathy, we conceived an experimental ex vivo model using cell cultures of articular chondrocytes issued from pretreated New Zealand White rabbits (NZW). Juvenile (4- to 5-week-old) NZW were orally dosed with ofloxacin or pefloxacin (300 mg/kg of body weight for 1 day) or with pefloxacin (300 mg/kg for 7 days). Adult (5-month-old) NZW were treated with pefloxacin (300 mg/kg for 1 day). Chondrocytes were enzymatically recovered from cartilage and were analyzed by cytofluorometry using 2',7'-dichlorofluorescein diacetate (DCFH-DA) and dihydrorhodamine 123 (DHR), reflecting cellular respiratory-burst activity, and rhodamine 123 (Rh123) and 10-N-nonyl-acridine orange (NAO), specific for the mitochondrial activity and mass, respectively. A significant increase in the respiratory burst was detected by DCFH-DA and DHR in all treated groups of young animals, compared with untreated control groups. No significant increase of respiratory burst was noted in older treated rabbits. The 7-day treatment resulted in a decrease in mitochondrial uptake of Rh123 and an increase in NAO uptake. Fluoroquinolone arthrotoxicity seems to involve in its early phase the respiratory burst of immature articular chondrocytes.

Selective enhancement of synthesis of interleukin-2 in lymphocytes in the presence of ciprofloxacin

A study was performed to verify the effect of ciprofloxacin on the production of interleukin-2 and other cytokines in cultures of human peripheral lymphocytes. In the presence of ciprofloxacin, lymphocytes demonstrated increased synthesis of interleukin-2 (100-fold, 7-fold and 1.5-fold increase at ciprofloxacin concentrations of 80, 20 and 5 micrograms/ml respectively), as measured by radioimmunoassay. Synthesis of other cytokines from T lymphocytes, gamma-interferon, lymphotoxin and granulocyte-macrophage colony stimulating factor as well as interleukin-1 and tumour necrosis factor from monocytes was not increased, but inhibited at a ciprofloxacin concentration of 80 micrograms/ml. Thus the effect of ciprofloxacin resulting in enhanced synthesis of interleukin-2 seems to be specific.