Several gene programs are induced in ciprofloxacin-treated human lymphocytes as revealed by microarray analysis

A Review of Immunomodulatory Effects of Fluoroquinolones

Past researches indicate that some types of antibiotics, apart from their antimicrobial effects, have some other important effects which indirectly are exerted by modulating and regulating the immune system's mediators. Among the compounds with antimicrobial effects, fluoroquinolones (FQs) are known as synthetic antibiotics, which exhibit the property of decomposing of DNA and prevent bacterial growth by inactivating the enzymes involved in DNA twisting, including topoisomerase II (DNA gyrase) and IV. Interestingly, immune responses are indirectly modulated by FQs through suppressing pro-inflammatory cytokines, such as interleukin 1 (IL-1), IL-6, tumor necrosis factor-alpha (TNF-α), and super-inducing IL-2, which tend to increase both the growth and activity of T and B lymphocytes. In addition, they affect the development of immune responses by influencing of expression of other cytokines and mediators. This study aims to review past research on the immunomodulatory effects of FQs on the expression of cytokines, especially IL-2 and to discuss controversial investigations.

Antibiotic-induced release of small extracellular vesicles (exosomes) with surface-associated DNA

Recently, biological roles of extracellular vesicles (which include among others exosomes, microvesicles and apoptotic bodies) have attracted substantial attention in various fields of biomedicine. Here we investigated the impact of sustained exposure of cells to the fluoroquinolone antibiotic ciprofloxacin on the released extracellular vesicles. Ciprofloxacin is widely used in humans against bacterial infections as well as in cell cultures against Mycoplasma contamination. However, ciprofloxacin is an inducer of oxidative stress and mitochondrial dysfunction of mammalian cells. Unexpectedly, here we found that ciprofloxacin induced the release of both DNA (mitochondrial and chromosomal sequences) and DNA-binding proteins on the exofacial surfaces of small extracellular vesicles referred to in this paper as exosomes. Furthermore, a label-free optical biosensor analysis revealed DNA-dependent binding of exosomes to fibronectin. DNA release on the surface of exosomes was not affected any further by cellular activation or apoptosis induction. Our results reveal for the first time that prolonged low-dose ciprofloxacin exposure leads to the release of DNA associated with the external surface of exosomes.

Analysis of the membrane proteome of ciprofloxacin-resistant macrophages by stable isotope labeling with amino acids in cell culture (SILAC)

Overexpression of multidrug transporters is a well-established mechanism of resistance to chemotherapy, but other changes may be co-selected upon exposure to drugs that contribute to resistance. Using a model of J774 macrophages made resistant to the fluoroquinolone antibiotic ciprofloxacin and comparing it with the wild-type parent cell line, we performed a quantitative proteomic analysis using the stable isotope labeling with amino acids in cell culture technology coupled with liquid chromatography electrospray ionization Fourier transform tandem mass spectrometry (LC-ESI-FT-MS/MS) on 2 samples enriched in membrane proteins (fractions F1 and F2 collected from discontinuous sucrose gradient). Nine hundred proteins were identified with at least 3 unique peptides in these 2 pooled fractions among which 61 (F1) and 69 (F2) showed a significantly modified abundance among the 2 cell lines. The multidrug resistance associated protein Abcc4, known as the ciprofloxacin efflux transporter in these cells, was the most upregulated, together with Dnajc3, a protein encoded by a gene located downstream of Abcc4. The other modulated proteins are involved in transport functions, cell adhesion and cytoskeleton organization, immune response, signal transduction, and metabolism. This indicates that the antibiotic ciprofloxacin is able to trigger a pleiotropic adaptative response in macrophages that includes the overexpression of its efflux transporter.

A small molecule enhances RNA interference and promotes microRNA processing

Small interfering RNAs (siRNAs) and microRNAs (miRNAs) are sequence-specific post-transcriptional regulators of gene expression. Although major components of the RNA interference (RNAi) pathway have been identified, regulatory mechanisms for this pathway remain largely unknown. Here we demonstrate that the RNAi pathway can be modulated intracellularly by small molecules. We have developed a cell-based assay to monitor the activity of the RNAi pathway and find that the small-molecule enoxacin (Penetrex) enhances siRNA-mediated mRNA degradation and promotes the biogenesis of endogenous miRNAs. We show that this RNAi-enhancing activity depends on the trans-activation-responsive region RNA-binding protein. Our results provide a proof-of-principle demonstration that small molecules can be used to modulate the activity of the RNAi pathway. RNAi enhancers may be useful in the development of research tools and therapeutics.

The evolution of mathematical immunology

The types of mathematical models used in immunology and their scope have changed drastically in the past 10 years. Classical models were based on ordinary differential equations (ODEs), difference equations, and cellular automata. These models focused on the 'simple' dynamics obtained between a small number of reagent types (e.g. one type of receptor and one type of antigen or two T-cell populations). With the advent of high-throughput methods, genomic data, and unlimited computing power, immunological modeling shifted toward the informatics side. Many current applications of mathematical models in immunology are now focused around the concepts of high-throughput measurements and system immunology (immunomics), as well as the bioinformatics analysis of molecular immunology. The types of models have shifted from mainly ODEs of simple systems to the extensive use of Monte Carlo simulations. The transition to a more molecular and more computer-based attitude is similar to the one occurring over all the fields of complex systems analysis. An interesting additional aspect in theoretical immunology is the transition from an extreme focus on the adaptive immune system (that was considered more interesting from a theoretical point of view) to a more balanced focus taking into account the innate immune system also. We here review the origin and evolution of mathematical modeling in immunology and the contribution of such models to many important immunological concepts.

Gram-negative bacteria aggravate murine small intestinal Th1-type immunopathology following oral infection with Toxoplasma gondii

Oral infection of susceptible mice with Toxoplasma gondii results in Th1-type immunopathology in the ileum. We investigated gut flora changes during ileitis and determined contributions of gut bacteria to intestinal inflammation. Analysis of the intestinal microflora revealed that ileitis was accompanied by increasing bacterial load, decreasing species diversity, and bacterial translocation. Gram-negative bacteria identified as Escherichia coli and Bacteroides/Prevotella spp. accumulated in inflamed ileum at high concentrations. Prophylactic or therapeutic administration of ciprofloxacin and/or metronidazole ameliorated ileal immunopathology and reduced intestinal NO and IFN-gamma levels. Most strikingly, gnotobiotic mice in which cultivable gut bacteria were removed by quintuple antibiotic treatment did not develop ileitis after Toxoplasma gondii infection. A reduction in total numbers of lymphocytes was observed in the lamina propria of specific pathogen-free (SPF), but not gnotobiotic, mice upon development of ileitis. Relative numbers of CD4(+) T cells did not differ in naive vs infected gnotobiotic or SPF mice, but infected SPF mice showed a significant increase in the frequencies of activated CD4(+) T cells compared with gnotobiotic mice. Furthermore, recolonization with total gut flora, E. coli, or Bacteroides/Prevotella spp., but not Lactobacillus johnsonii, induced immunopathology in gnotobiotic mice. Animals recolonized with E. coli and/or total gut flora, but not L. johnsonii, showed elevated ileal NO and/or IFN-gamma levels. In conclusion, Gram-negative bacteria, i.e., E. coli, aggravate pathogen-induced intestinal Th1-type immunopathology. Thus, pathogen-induced acute ileitis may prove useful to study bacteria-host interactions in small intestinal inflammation and to test novel therapies based on modulation of gut flora.

Rufloxacin-induced photosensitization in yeast

The fluoroquinolone Rufloxacin (RFX) is active as specific inhibitor of bacterial gyrase. The adverse effects of the photosensitization induced by fluoroquinolones are well known. A predominant type II photosensitizing activity of Rufloxacin has already been demonstrated on simpler models (free nucleosides, calf thymus DNA), whereas a cooperative mechanism was corroborated on more complex ones (plasmid and fibroblast). The purpose of this study is to examine the drug photocytoxicity in another complex cellular model, a wild-type eukaryotic fast-growing microorganism whose cultivation is cheap and easily managed, Saccharomyces cerevisiae. This work represents the first report of the potential photogenotoxicity of Rufloxacin. Particular emphasis was given to DNA modifications caused in yeast by the formation of Rufloxacin photomediated toxic species, such as hydrogen peroxide and formaldehyde. Drug phototoxicity on yeast was evaluated by measuring DNA fragmentation (single/double strand breaks) using single cell gel electrophoresis assay and 8-OH-dGuo, a DNA photooxidation biomarker, by HPLC-ECD. Cellular sensitivity was also assessed by cell viability test. The extra- and intracellular RFX concentration (as well as its main photoproduct) was verified by HPLC-MS, whereas the cytotoxic species were evaluated by colorimetric assays. The results confirm the phototoxicity of Rufloxacin on yeast cell and are in agreement with those previously obtained with human fibroblast and with simpler models used recently, and provide a clear link between DNA photosensitization and overall phototoxicity.

Ciprofloxacin inhibits cytokine-induced nitric oxide production in human colonic epithelium

BACKGROUND

The fluoroquinolone ciprofloxacin is a broad-spectrum antibiotic that has been used in the treatment of inflammatory bowel diseases. There is evidence that quinolones have immunomodulating activities via the regulation of cytokine production.

MATERIALS AND METHODS

We investigated the effect of ciprofloxacin on the nitric oxide (NO) production by colonic epithelium. HT-29 cells and colonic biopsies from patients (n = 4) with ulcerative colitis (UC) and normal controls (n = 4) were cultured with various concentrations of ciprofloxacin (10-100 microg mL(-1)) in the presence and absence of pro-inflammatory cytokines. The production of NO was measured in culture supernatants with a spectrophotometric method and inducible nitric oxide synthase (iNOS) mRNA expression was examined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Ciprofloxacin did not have any effect on the basal NO production by HT-29 cells. In contrast, ciprofloxacin significantly (P < 0.001) inhibited the pro-inflammatory cytokines (interleukin-1alpha + tumour necrosis factor-alpha + interferon-gamma)-induced NO production in HT-29, in a concentration-dependent manner, via the inhibition of the cytokine-induced iNOS mRNA expression. Wortmannin produced a concentration related reversal of the inhibitory effect of ciprofloxacin at both iNOS mRNA expression and NO production in HT-29 cells. A similar inhibitory effect of ciprofloxacin on the cytokine-induced NO production and iNOS mRNA expression was detected in vitro in cultures of normal colonic tissue. In addition, ciprofloxacin significantly inhibited the NO production and iNOS mRNA expression in cultures of colonic tissue from ulcerative colitis patients, in a concentration-dependent manner.

CONCLUSIONS

These data suggest that ciprofloxacin, in addition to its antimicrobial role, might have an immunoregulatory effect on intestinal inflammation, via the modulation of inflammatory mediators.

Calcium signals are affected by ciprofloxacin as a consequence of reduction of mitochondrial DNA content in Jurkat cells

The effects of ciprofloxacin on mitochondrial DNA (mtDNA) content, oxygen consumption, mitochondrial membrane potential, cellular ATP formation, and capacitative Ca(2+) entry into Jurkat cells were investigated. In cells incubated for several days with 25 mug/ml ciprofloxacin, a 60% reduction of mtDNA content, inhibition of the respiratory chain, and a significant decrease in mitochondrial membrane potential were observed. These changes led to a decrease in the calcium buffering capacity of mitochondria which, in turn, resulted in a gradual inhibition of the capacitative Ca(2+) entry. On days 4, 7, and 11 of incubation with ciprofloxacin, the initial rates of Ca(2+) entry were reduced by 33%, 50%, and 50%, respectively. Ciprofloxacin caused a transient decrease in the cellular capability for ATP formation. In cells incubated for 15 min with glucose, pyruvate, and glutamine as exogenous fuel, ciprofloxacin reduced ATP content by 16% and 35% on days 4 and 7, respectively, of incubation with the drug. However, on day 11 of incubation with ciprofloxacin, a recovery of cellular ATP formation was observed. In conclusion, long-term exposure of Jurkat cells to ciprofloxacin at a concentration of 25 mug/ml seriously affects cellular energy metabolism and calcium homeostasis.

Cellular accumulation and activity of quinolones in ciprofloxacin-resistant J774 macrophages

Ciprofloxacin is the substrate for a multidrug resistance-related protein (MRP)-like multidrug transporter in J774 mouse macrophages, which also modestly affects levofloxacin but only marginally affects garenoxacin and moxifloxacin (J.-M. Michot et al., Antimicrob. Agents Chemother. 49:2429-2437, 2005). Two clones of ciprofloxacin-resistant cells were obtained by a stepwise increase in drug concentration (from 34 to 51 to 68 mg/liter) in the culture fluid. Compared to wild-type cells, ciprofloxacin-resistant cells showed (i) a markedly reduced ciprofloxacin accumulation (12% of control) and (ii) a two- to threefold lower sensitivity to the enhancing effect exerted by MRP-inhibitors (probenecid and MK571) on ciprofloxacin accumulation or by ciprofloxacin itself. ATP-depletion brought ciprofloxacin accumulation to similarly high levels in both wild-type and ciprofloxacin-resistant cells. Garenoxacin and moxifloxacin accumulation remained unaffected, and levofloxacin showed an intermediate behavior. DNA and protein synthesis were not impaired in ciprofloxacin-resistant cells for ciprofloxacin concentrations up to 100 mg/liter (approximately 85 and 55% inhibition, respectively, in wild-type cells). In Listeria monocytogenes-infected ciprofloxacin-resistant cells, 12-fold higher extracellular concentrations of ciprofloxacin were needed to show a bacteriostatic effect in comparison with wild-type cells. The data suggest that the resistance mechanism is mediated by an overexpression and/or increased activity of the MRP-like ciprofloxacin transporter expressed at a basal level in wild-type J774 macrophages, which modulates both the intracellular pharmacokinetics and activity of ciprofloxacin.

The IgD-binding domain of the Moraxella IgD-binding protein MID (MID962-1200) activates human B cells in the presence of T cell cytokines

Moraxella catarrhalis immunoglobulin D (IgD)-binding protein (MID) is an outer membrane protein with specific affinity for soluble and cell-bound human IgD. Here, we demonstrate that mutated M. catarrhalis strains devoid of MID show a 75% decreased activation of human B cells as compared with wild-type bacteria. In contrast to MID-expressing Moraxella, the MID-deficient Moraxella mutants did not bind to human CD19+ IgD+ B cells. The smallest MID fragment with preserved IgD-binding capacity comprises 238 amino acids (MID(962-1200)). To prove the specificity of MID(962-1200) for IgD, a Chinese hamster ovary (CHO) cell line expressing membrane-anchored human IgD was manufactured. MID(962-1200) bound strongly to the recombinant IgD on CHO cells. Moreover, MID(962-1200) stimulated peripheral blood lymphocyte (PBL) proliferation 5- and 15-fold at 0.1 and 1.0 microg/ml, respectively. This activation could be blocked completely by antibodies directed against the CD40 ligand (CD154). MID(962-1200) also activated purified B cells in the presence of interleukin (IL)-2 or IL-4. An increased IL-6 production was seen after stimulation with MID(962-1200), as revealed by a human cytokine protein array. MID(962-1200) fused to green fluorescent protein (GFP) bound to human B cells and activated PBL to the same degree as MID(962-1200). Taken together, MID is the only IgD-binding protein in Moraxella. Furthermore, the novel T cell-independent antigen MID(962-1200) may, together with MID(962-1200)-GFP, be considered as promising reagents in the study of IgD-dependent B cell activation.

Rufloxacin induced photosensitization in bio-models of increasing complexity

Rufloxacin belongs to the class of fluoroquinolones that act mainly as specific inhibitors of bacterial Topoisomerase II. These drugs are widely known to be involved in various diseases ranging from cutaneous reactions to aging. The type II photosensitizing activity of Rufloxacin has been already demonstrated on calf thymus DNA and free nucleosides. The aim of this study is to examine in control untreated and UVA irradiated human fibroblasts the modifications on DNA status induced by Rufloxacin added in the culture medium. This allows to investigate the photosensitizing activity of Rufloxacin in a more complex cell model. Fibroblasts, either in the presence or in the absence of Rufloxacin, were exposed to UVA irradiation for different times. An experimental protocol was followed in order to evaluate the amount of single-strand breaks (SSB) and double-strand breaks (DSB) DNA fragmentation by comet assay, and plasmid photocleavage. The presence of oxidized bases was also evaluated using the 8-OH-dGuo test. The comet assay test was also employed to assess cellular repair capacity. The intracellular drug concentration was verified by HPLC-MS. The results confirming the role of Rufloxacin as photosensitizer were: (i) a time-dependent increase in DNA fragmentation when fibroblasts were irradiated in the presence of Rufloxacin; (ii) the efficiency of the cellular repair machinery to be exhaustive after 2 h (whereas no correlation between irradiation time and DNA damage repair was observed with a higher level of DNA fragmentation after shorter irradiation times); (iii) the increased number of cells exhibiting high DNA fragmentation, seen as comets with long tails, was not accompanied by a similar large extent of oxidised DNA base formation, as measured by 8-OH-dGuo analysis; (iv) the double helix SSB, formed in plasmid photosensitization, agreed with the comet assay results, pointing out a good correlation among the cell system and the simpler models used.

Bone marrow stromal cells, preadipocytes, and dermal fibroblasts promote epidermal regeneration in their distinctive fashions

Mesenchymal cell types, under mesenchymal-epithelial interaction, are involved in tissue regeneration. Here we show that bone marrow stromal cells (BMSCs), subcutaneous preadipocytes, and dermal fibroblasts distinctively caused keratinocytes to promote epidermal regeneration, using a skin reconstruction model by their coculture with keratinocytes. Three mesenchymal cell types promoted the survival, growth, and differentiation of keratinocytes, whereas BMSCs and preadipocytes inhibited their apoptosis. BMSCs and preadipocytes induced keratinocytes to reorganize rete ridge- and epidermal ridge-like structures, respectively. Keratinocytes with fibroblasts or BMSCs expressed the greatest amount of interleukin (IL)-1alpha protein, which is critical for mesenchymal-epithelial cross-talk in skin. Keratinocytes with or without three mesenchymal supports displayed another cross-talk molecule, c-Jun protein. Without direct mesenchymal-epithelial contact, the rete ridge- and epidermal ridge-like structures were not replicated, whereas the other phenomena noted above were. DNA microarray analysis showed that the mesenchymal-epithelial interaction affected various gene expressions of keratinocytes and mesenchymal cell types. Our results suggest that not only skin-localized fibroblasts and preadipocytes but also BMSCs accelerate epidermal regeneration in complexes and that direct contact between keratinocytes and BMSCs or preadipocytes is required for the skin-specific morphogenesis above, through mechanisms that differ from the IL-1alpha/c-Jun pathway.