Requirements for intracellular accumulation and release of clarithromycin and azithromycin by human phagocytes

Environmental impacts of COVID-19 treatment: Toxicological evaluation of azithromycin and hydroxychloroquine in adult zebrafish

One of the most impact issues in recent years refers to the COVID-19 pandemic, the consequences of which thousands of deaths recorded worldwide, are still inferior understood. Its impacts on the environment and aquatic biota constitute a fertile field of investigation. Thus, to predict the impact of the indiscriminate use of azithromycin (AZT) and hydroxychloroquine (HCQ) in this pandemic context, we aim to assess their toxicological risks when isolated or in combination, using zebrafish (Danio rerio) as a model system. In summary, we observed that 72 h of exposure to AZT and HCQ (alone or in binary combination, both at 2.5 μg/L) induced the reduction of total protein levels, accompanied by increased levels of thiobarbituric acid reactive substances, hydrogen peroxide, reactive oxygen species and nitrite, suggesting a REDOX imbalance and possible oxidative stress. Molecular docking analysis further supported this data by demonstrating a strong affinity of AZT and HCQ with their potential antioxidant targets (catalase and superoxide dismutase). In the protein-protein interaction network analysis, AZT showed a putative interaction with different cytochrome P450 molecules, while HCQ demonstrated interaction with caspase-3. The functional enrichment analysis also demonstrated diverse biological processes and molecular mechanisms related to the maintenance of REDOX homeostasis. Moreover, we also demonstrated an increase in the AChE activity followed by a reduction in the neuromasts of the head when zebrafish were exposed to the mixture AZT + HCQ. These data suggest a neurotoxic effect of the drugs. Altogether, our study demonstrated that short exposure to AZT, HCQ or their mixture induced physiological alterations in adult zebrafish. These effects can compromise the health of these animals, suggesting that the increase of AZT and HCQ due to COVID-19 pandemic can negatively impact freshwater ecosystems.

Therapies for neonatal encephalopathy: Targeting the latent, secondary and tertiary phases of evolving brain injury

In term and near-term neonates with neonatal encephalopathy, therapeutic hypothermia protocols are well established. The current focus is on how to improve outcomes further and the challenge is to find safe and complementary therapies that confer additional protection, regeneration or repair in addition to cooling. Following hypoxia-ischemia, brain injury evolves over three main phases (latent, secondary and tertiary), each with a different brain energy, perfusion, neurochemical and inflammatory milieu. While therapeutic hypothermia has targeted the latent and secondary phase, we now need therapies that cover the continuum of brain injury that spans hours, days, weeks and months after the initial event. Most agents have several therapeutic actions but can be broadly classified under a predominant action (e.g., free radical scavenging, anti-apoptotic, anti-inflammatory, neuroregeneration, and vascular effects). Promising early/secondary phase therapies include Allopurinol, Azithromycin, Exendin-4, Magnesium, Melatonin, Noble gases and Sildenafil. Tertiary phase agents include Erythropoietin, Stem cells and others. We review a selection of promising therapeutic agents on the translational pipeline and suggest a framework for neuroprotection and neurorestoration that targets the evolving injury.

Clarithromycin impairs tissue-resident memory and Th17 responses to macrolide-resistant Streptococcus pneumoniae infections

Abstract

The increasing prevalence of antimicrobial resistance in pathogens is a growing public health concern, with the potential to compromise the success of infectious disease treatments in the future. Particularly, the number of infections by macrolide antibiotics-resistant Streptococcus pneumoniae is increasing. We show here that Clarithromycin impairs both the frequencies and number of interleukin (IL)-17 producing T helper (Th) 17 cells within the lungs of mice infected with a macrolide-resistant S. pneumoniae serotype 15A strain. Subsequently, the tissue-resident memory CD4⁺ T cell (Trm) response to a consecutive S. pneumoniae infection was impaired. The number of lung resident IL-17⁺ CD69⁺ Trm was diminished upon Clarithromycin treatment during reinfection. Mechanistically, Clarithromycin attenuated phosphorylation of the p90-S6-kinase as part of the ERK pathway in Th17 cells. Moreover, a strong increase in the mitochondrial-mediated maximal respiratory capacity was observed, while mitochondrial protein translation and mTOR sisgnaling were unimpaired. Therefore, treatment with macrolide antibiotics may favor the spread of antimicrobial-resistant pathogens not only by applying a selection pressure but also by decreasing the natural T cell immune response. Clinical administration of macrolide antibiotics as standard therapy procedure during initial hospitalization should be reconsidered accordingly and possibly be withheld until microbial resistance is determined.

Key messages

• Macrolide-resistant S. pneumoniae infection undergoes immunomodulation by Clarithromycin

• Clarithromycin treatment hinders Th17 and tissue-resident memory responses

• Macrolide antibiotics impair Th17 differentiation in vitro by ERK-pathway inhibition

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-021-02039-5.

Pharmacokinetics of Azithromycin, Levofloxacin, and Ofloxacin in Rabbit Extraocular Tissues After Ophthalmic Administration

INTRODUCTION

Azithromycin demonstrates high tissue distribution and prolonged elimination half-life. In this study, we monitored the pharmacokinetics of a single ophthalmic administration of 1% azithromycin ophthalmic solution containing polycarbophil in the extraocular tissues, including the eyelid, and compared it with that of two commercial ophthalmic products, 1.5% levofloxacin ophthalmic solution and 0.3% ofloxacin ophthalmic ointment.

METHODS

Rabbits were treated with either a single topical administration of 1% azithromycin ophthalmic solution, 1.5% levofloxacin ophthalmic solution, or 0.3% ofloxacin ophthalmic ointment. The eyelid, conjunctiva, and cornea were collected at 0.25, 0.5, 1, 2, 4, 8, and 24 h post-administration. Tissue samples were pretreated for drug concentration measurements by ultra-performance liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were determined by non-compartmental analysis.

RESULTS

Azithromycin was rapidly absorbed, and its levels remained near the observed maximum concentrations for up to 24 h post-administration in all tissue. In contrast, extraocular tissue concentrations of levofloxacin and ofloxacin decreased with time. The maximum concentrations of azithromycin, levofloxacin, and ofloxacin were 35.6, 34.1, and 55.1 µg/g in the eyelid, 44.2, 46.8, and 20.4 µg/g in the conjunctiva, and 79.9, 18.0, and 2.21 µg/g in the cornea, respectively. The values of the area under the curve from 0 to 24 h after administration of azithromycin, levofloxacin, and ofloxacin were 602, 58.5, and 267 µg·h/g in the eyelid, 837, 43.2, and 51.9 µg·h/g in the conjunctiva, and 1250, 26.4, and 5.46 µg h/g in the cornea, respectively.

CONCLUSION

The drug concentrations of azithromycin and levofloxacin were relatively comparable among the extraocular tissues following topical administration of the respective ophthalmic solutions, whereas the concentrations of ofloxacin varied following dosing of its ophthalmic ointment. The slow elimination profile in any extraocular tissue of rabbits was unique to azithromycin, and led to the demonstration of high exposures of azithromycin in all extraocular tissues after ophthalmic administration.

FUNDING

This research and Rapid Service Fees were supported by Senju Pharmaceutical Co., Ltd.

Azithromycin promotes alternatively activated macrophage phenotype in systematic lupus erythematosus via PI3K/Akt signaling pathway

Alternatively activated macrophages have been reported to be helpful to alleviate systematic lupus erythematosus (SLE), and azithromycin could serve as an immunomodulator by promoting alternatively activated macrophage phenotype. However, the effect of azithromycin in SLE and the involved mechanism remain undetermined. The aim of this study is to characterize azithromycin and the underlying mechanism contributing to SLE therapy. First, we compared monocytes from SLE patients and matched healthy donors, and found monocytes from SLE patients exhibited more CD14⁺CD86⁺ cells, impaired phagocytic activity, and elevated interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α (the classical activated phenotype), which could be blocked by azithromycin. On the contrary, there were fewer CD14⁺CD163⁺ cells in SLE patients, accompanied by decreased arginase (Arg)-1 and found in inflammatory zone (Fizz)-1 (the alternatively activated phenotype). And IL-10, the crucial immune regulatory factor secreted by alternatively activated monocytes/macrophages, also showed a decreased trend in SLE patients. In addition, all these markers were up-regulated after azithromycin treatment. Next, we used activated lymphocyte-derived-DNA to imitate SLE macrophages in vitro to investigate the possible mechanism involved. Azithromycin showed the same effect in imitated SLE macrophages, with distinct Akt phosphorylation at 30 min and 12 h. After inhibiting Akt phosphorylation by LY294002, the down-regulation of CD80, IL-1β, IL-6, and TNF-α caused by azithromycin raised again, meanwhile, the up-regulation of CD206, Arg-1, Fizz-1, and IL-10 due to azithromycin was abolished. Additionally, insulin-like growth factor 1 (IGF-1), the specific agonist of Akt, played a similar role to azithromycin in imitated SLE macrophages. Taken together, our data indicated a novel role of azithromycin in alleviating SLE by promoting alternatively activated macrophage phenotype, and the PI3K/Akt signaling pathway was involved. Our findings provide a rationale for further investigation of novel therapeutic strategy for SLE patients.

Attenuation of antimicrobial activity by the human steroid hormones

Upon entering the human host, Staphylococcus aureus is exposed to endogenous steroid hormones. The interaction between S. aureus and dehydroepiandosterone (DHEA) results in an increased resistance to the host cationic defense peptide, β-1 defensin, as well as vancomycin and other antibiotics that have a positive charge. The increased resistance to vancomycin is phenotypic and appears to correlate with a DHEA-mediated alteration in cell surface architecture. DHEA-mediated cell surface changes include alterations in: cell surface charge, surface hydrophobicity, capsule production, and carotenoid production. In addition, exposure to DHEA results in decreased resistance to lysis by Triton X-100 and lysozyme, indicating activation of murien hydrolase activity. We propose that DHEA is an interspecies quorum-like signal that triggers innate phenotypic host survival strategies in S. aureus that include increased carotenoid production and increased vancomycin resistance. Furthermore, this DHEA-mediated survival system may share the cholesterol-squalene pathway shown to be statin sensitive thus, providing a potential pathway for drug targeting.

Neuroprotective Properties of a Macrolide Antibiotic in a Mouse Model of Middle Cerebral Artery Occlusion: Characterization of the Immunomodulatory Effects and Validation of the Efficacy of Intravenous Administration

Repurposing the macrolide antibiotic azithromycin has recently been suggested as a promising neuroprotective strategy for the acute treatment of ischemic stroke. Here, we aim at further characterizing the immunomodulatory properties of intraperitoneal (i.p.) administration of this drug and, more importantly, at assessing whether neuroprotection can also be achieved by the more clinically relevant intravenous (i.v.) route of administration in a mouse model of focal cerebral ischemia induced by transient (30-min) middle cerebral artery occlusion (MCAo). A single i.p. injection of azithromycin (150 mg/kg) upon reperfusion prevented ischemia-induced spleen contraction and increased the number of MAC-1-immunopositive microglia/macrophages in the ischemic hemisphere 48 h after the insult. This was paralleled by an elevation of alternatively activated phenotypes (i.e., Ym1-immunopositive M2-polarized cells) and by a reduced expression of the pro-inflammatory marker myeloperoxidase. More importantly, i.v. administration of azithromycin upon reperfusion reduced MCAo-induced infarct volume and cerebral edema to an extent comparable to that obtained via the i.p. route. Although the i.p. route is often used for research purposes, it is impractical in the clinical setting; however, i.v. administration can easily be used in ischemic stroke patients who usually have i.v. access already established on hospital admission. The neuroprotective efficacy of the clinically relevant i.v. administration of azithromycin, together with its beneficial immunomodulatory properties reported in mice subjected to transient MCAo, suggests that this macrolide antibiotic can be effectively repurposed for the acute treatment of ischemic stroke. To this end, further work is needed to validate the efficacy of azithromycin in the clinical setting.

Azithromycin protects mice against ischemic stroke injury by promoting macrophage transition towards M2 phenotype

To develop novel and effective treatments for ischemic stroke, we investigated the neuroprotective effects of the macrolide antibiotic azithromycin in a mouse model system of transient middle cerebral artery occlusion. Intraperitoneal administration of azithromycin significantly reduced blood-brain barrier damage and cerebral infiltration of myeloid cells, including neutrophils and inflammatory macrophages. These effects resulted in a dose-dependent reduction of cerebral ischemic damage, and in a remarkable amelioration of neurological deficits up to 7 days after the insult. Neuroprotection was associated with increased arginase activity in peritoneal exudate cells, which was followed by the detection of Ym1- and arginase I-immunopositive M2 macrophages in the ischemic area at 24-48 h of reperfusion. Pharmacological inhibition of peritoneal arginase activity counteracted azithromycin-induced neuroprotection, pointing to a major role for drug-induced polarization of migratory macrophages towards a protective, non-inflammatory M2 phenotype.

Azithromycin suppresses CD4(+) T-cell activation by direct modulation of mTOR activity

Advanced macrolides, such as azithromycin (AZM) or clarithromycin (CLM), are antibiotics with immunomodulatory properties. Here we have sought to evaluate their in vitro influence on the activation of CD4(+) T-cells. Isolated CD4(+) T-cells were stimulated with agonistic anti-CD3/anti-CD28 monoclonal antibodies in the presence of 0.6 mg/L, 2.5 mg/L, 10 mg/L or 40 mg/L AZM or CLM. Cell proliferation, cytokine level in supernatants and cell viability was assessed. Intracellular signaling pathways were evaluated using reporter cell lines, FACS analysis, immunoblotting and in vitro kinase assays. AZM inhibited cell proliferation rate and cytokine secretion of CD4(+) T-cells in a dose-dependent manner. Similarly, high concentrations of CLM (40 mg/L) also suppressed these T-cell functions. Analysis of molecular signaling pathways revealed that exposure to AZM reduced the phosphorylation of the S6 ribosomal protein, a downstream target of mTOR. This effect was also observed at 40 mg/L CLM. In vitro kinase studies using recombinant mTOR showed that AZM inhibited mTOR activity. In contrast to rapamycin, this inhibition was independent of FKBP12. We show for the first time that AZM and to a lesser extent CLM act as immunosuppressive agents on CD4(+) T-cells by inhibiting mTOR activity. Our results might have implications for the clinical use of macrolides.

Macrolactonolides: a novel class of anti-inflammatory compounds

A new concept in design of safe glucocorticoid therapy was introduced by conjugating potent glucocorticoid steroids with macrolides (macrolactonolides). These compounds were synthesized from various steroid 17β-carboxylic acids and 9a-N-(3-aminoalkyl) derivatives of 9-deokso-9a-aza-9a-homoeritromicin A and 3-descladinosyl-9-deokso-9a-aza-9a-homoeritromicin A using stable alkyl chain. Combining property of macrolides to preferentially accumulate in immune cells, especially in phagocyte cells, with anti-inflammatory activity of classic steroids, we designed molecules which showed good anti-inflammatory activity in ovalbumin (OVA) induced asthma in rats. The synthesis, in vitro and in vivo anti-inflammatory activity of this novel class of compounds are described.

Evaluation of subgingivally delivered 0.5% clarithromycin as an adjunct to nonsurgical mechanotherapy in the management of chronic periodontitis: a short-term double blinded randomized control trial

OBJECTIVE

As the risk involved with systemic antimicrobials (high doses, microbial resistance, adverse reactions, etc.) restricts their use and local delivery of antimicrobials into periodontal pockets improves periodontal health, this study was designed to investigate the effects of subgingivally delivered clarithromycin (CLM; 0.5%) as an adjunct to nonsurgical mechanotherapy in chronic periodontitis subjects.

METHODS

Ninety-eight patients were categorized into two treatment groups: scaling and root planing (SRP) plus 0.5% CLM (test; group 1) and SRP plus placebo (control; group 2). Clinical parameters included gingival index (GI), sulcus bleeding index (SBI), plaque index (PI), probing depth (PD), and periodontal attachment level (PAL), recorded at 4, 8 and 12 weeks. The concentration of 0.5% CLM in gingival fluid was estimated by reverse-phase high pressure liquid chromatography. anova, the chi-square test and the Scatterthwaite test were used for statistical analysis.

RESULTS

Patients treated with SRP + CLM showed enhanced reductions in GI, SBI, and PD, and gains in PAL (P < 0.001) over time, as compared with the placebo group. However, no statistically significant differences were noted for PI. The mean concentration of CLM was detected in gingival crevicular fluid for up to 7 weeks, fulfilling the conditions for a controlled-release device.

CONCLUSION

Adjunctive use of 0.5% CLM as a controlled drug delivery system enhanced the clinical outcome up to 3 months.

Distribution of systemic clarithromycin to gingiva

BACKGROUND

Aggressive and recurrent forms of periodontitis are associated with infections by Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) and Porphyromonas gingivalis. Because these pathogens invade tissue, they are difficult to eliminate by root planing alone. The use of systemic antibiotics in conjunction with root planing significantly enhances clinical and microbiologic treatment outcomes. Although it is not widely prescribed by periodontists, clarithromycin is potentially useful because it is taken up by host cells and has favorable antimicrobial activity.

METHODS

Experimental gingivitis was induced in eight healthy subjects at one randomly selected maxillary posterior site. The contralateral maxillary site served as the healthy control. Thereafter, subjects were administered six doses of clarithromycin, 500 mg, every 12 hours. Blood was then drawn, and samples of gingiva were harvested from both sites. The samples were extracted, and clarithromycin content was analyzed by liquid chromatography.

RESULTS

Mean clarithromycin concentrations in healthy control and inflamed gingiva (2.4 and 3.0 microg/g, respectively) were significantly higher than in serum (0.5 microg/ml; P <0.05). Clarithromycin levels at control and gingivitis sites were higher than serum by 5.7- and 7.0-fold, respectively (difference between sites was significant; P = 0.02). At control sites, a significant decrease in gingival crevicular fluid flow rate was evident at the conclusion of the clarithromycin regimen (P = 0.018).

CONCLUSIONS

Clarithromycin can attain higher levels in gingiva than serum and reach higher levels in inflamed gingiva than in healthy gingiva. Its distribution profile seems to be suitable for the treatment of periodontitis. The reduction in crevicular fluid flow at control sites suggested that clarithromycin may produce anti-inflammatory effects.

Erythromycin derivatives inhibit HIV-1 replication in macrophages through modulation of MAPK activity to induce small isoforms of C/EBPbeta

Macrophages (MPhis) are a major source of HIV-1 especially in patients with tuberculosis. There are MPhis that are permissive and those that restrict HIV-1. Regulation of hematopoietic cell kinase (Hck) activity and selective expression of CCAAT enhancer binding protein beta (C/EBPbeta) isoforms greatly contribute to determine distinct susceptibility of MPhis to HIV-1. Resistance is attributable to reduced expression of Hck and augmented expression of an inhibitory small isoform of C/EBPbeta. Derivatives of erythromycin A (EMA) EM201 and EM703 inhibit the replication of HIV-1 in tissue MPhis, at posttranscriptional and translational levels. We demonstrate that EM201 and EM703 convert tissue MPhis from HIV-1 susceptible to HIV-1 resistant through down-regulation of Hck and induction of small isoforms of C/EBPbeta. These drugs inhibit p38MAPK activation which is expressed only in susceptible tissue MPhis. Activated CD4(+)T cells stimulate the viral replication in HIV-1 resistant MPhis through down-regulation of small isoforms of C/EBPbeta via activation of ERK1/2. EM201 and EM703 can inhibit the MAPK activation and inhibit the burst of viral replication produced when CD4(+)T cells and MPhis interact. These EM derivatives may be highly beneficial for repression of residual HIV-1 in the lymphoreticular system of HIV-1-infected patients and offer great promise for the creation of new anti-HIV drugs for the future treatment of AIDS patients.

Pharmacokinetics of single- and multiple-dose oral clarithromycin in soft tissues determined by microdialysis

The antimicrobial spectrum of clarithromycin renders this antibiotic a frequently used option in the treatment of skin and soft-tissue infections. In most cases, these infections are caused by extracellularly proliferating microorganisms. Thus, clarithromycin concentrations achieved in the interstitial space are considered particularly important for clinical efficacy. In the present study, clarithromycin concentrations in plasma and interstitial-space fluid of subcutaneous adipose tissue and skeletal muscle of six healthy male volunteers were assessed by means of the microdialysis technique after oral single-dose administration of 250 mg and multiple doses of 500 mg of clarithromycin twice a day (b.i.d.). The ratios of the area under the concentration-time curve of free clarithromycin from 0 to 24 h calculated for a single dose of 250 mg (fAUC(0-24)) in interstitial-space fluid to the fAUC(0-24) in plasma were 0.29 +/- 0.17 and 0.42 +/- 0.18 for subcutis and skeletal muscle, respectively. For 500 mg of clarithromycin at the steady state (3 to 5 days of intake twice daily), the fAUC(0-24(b.i.d.)) ratios at the steady state were 0.39 +/- 0.04 and 0.41 +/- 0.19 for subcutis and skeletal muscle, respectively. The half-life was around 2 h after a single dose but increased to approximately 4 h in plasma and tissues after repetitive clarithromycin administration. Based on subsequently performed pharmacokinetic-pharmacodynamic calculations, a dosing regimen of 500 mg b.i.d. may be ineffective in the treatment of soft-tissue infections caused by pathogens with a drug MIC higher than 0.125 mg/liter.

Pulmonary disposition of erythromycin, azithromycin, and clarithromycin in foals

The objectives of the present study were to determine and compare the pulmonary disposition of azithromycin, clarithromycin, and erythromycin in foals. A single dose (10 mg/kg) of azithromycin, clarithromycin, or erythromycin was administered intragastrically to six healthy 1- to 3-month-old foals using an orthogonal design. Activity of the drugs was measured in serum, pulmonary epithelial lining fluid (PELF), and bronchoalveolar lavage (BAL) cells by use of a microbiologic assay. Peak drug activity in PELF was significantly higher in foals treated with clarithromycin (48.96+/-13.26 microg/mL) than in foals treated with azithromycin (10.00+/-7.46 microg/mL). Quantifiable erythromycin activity in PELF was only found in two of six foals. Peak drug activity in BAL cells was not significantly different between azithromycin (49.92+/-26.94 microg/mL) and clarithromycin (74.20+/-45.80 microg/mL) but activity for both drugs was significantly higher than that of erythromycin (1.02+/-1.11 microg/mL). Terminal half-life of azithromycin in serum (25.7+/-15.4 h), PELF (34.8+/-30.9 h), and BAL cells (54.4+/-17.5 h) was significantly longer than that of both clarithromycin and erythromycin. Peak azithromycin and clarithromycin activity was significantly higher in BAL cells, followed by PELF, and serum. In contrast, peak erythromycin activity in BAL cells was not significantly different from that of serum.

Pulmonary disposition of tilmicosin in foals and in vitro activity against Rhodococcus equi and other common equine bacterial pathogens

The objectives of this study were to determine the serum and pulmonary disposition of tilmicosin in foals and to investigate the in vitro activity of the drug against Rhodococcus equi and other common bacterial pathogens of horses. A single dose of a new fatty acid salt formulation of tilmicosin (10 mg/kg of body weight) was administered to seven healthy 5- to 8-week-old foals by the intramuscular route. Concentrations of tilmicosin were measured in serum, lung tissue, pulmonary epithelial lining fluid (PELF), bronchoalveolar lavage (BAL) cells, and blood neutrophils. Mean peak tilmicosin concentrations were significantly different between sampling sites with highest concentrations measured in blood neutrophils (66.01+/-15.97 microg/mL) followed by BAL cells (20.1+/-5.1 microg/mL), PELF (2.91+/-1.15 microg/mL), lung tissue (1.90+/-0.65 microg/mL), and serum (0.19+/-0.09 microg/mL). Harmonic mean terminal half-life in lung tissue (193.3 h) was significantly longer than that of PELF (73.3 h), bronchoalveolar cells (62.2 h), neutrophils (47.9 h), and serum (18.4 h). The MIC90 of 56 R. equi isolates was 32 microg/mL. Tilmicosin was active in vitro against most streptococci, Staphylococcus spp., Actinobacillus spp., and Pasteurella spp. The drug was not active against Enterococcus spp., Pseudomonas spp., and Enterobacteriaceae.

Pharmacokinetics of clarithromycin and concentrations in body fluids and bronchoalveolar cells of foals

OBJECTIVE

To determine pharmacokinetics of clarithromycin and concentrations in body fluids and bronchoalveolar (BAL) cells of foals.

ANIMALS

6 healthy 2-to 3-week-old foals.

PROCEDURES

In a crossover design, clarithromycin (7.5 mg/kg) was administered to each foal via IV and intragastric (IG) routes. After the initial IG administration, 5 additional doses were administered IG at 12-hour intervals. Concentrations of clarithromycin and its 14-hydroxy metabolite were measured in serum by use of high-performance liquid chromatography. A microbiologic assay was used to measure clarithromycin activity in serum, urine, peritoneal fluid, synovial fluid, CSF, pulmonary epithelial lining fluid (PELF), and BAL cells.

RESULTS

After IV administration, elimination half-life (5.4 hours) and mean +/- SD body clearance (1.27 +/- 0.25 L/h/kg) and apparent volume of distribution at steady state (10.4 +/- 2.1 L/kg) were determined for clarithromycin. The metabolite was detected in all 6 foals by 1 hour after clarithromycin administration. Oral bioavailability of clarithromycin was 57.3 +/- 12.0%. Maximum serum concentration of clarithromycin after multiple IG administrations was 0.88 +/- 0.19 microg/mL. After IG administration of multiple doses, clarithromycin concentrations in peritoneal fluid, CSF, and synovial fluid were similar to or lower than concentrations in serum, whereas concentrations in urine, PELF, and BAL cells were significantly higher than concentrations in serum.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration of clarithromycin at 7.5 mg/kg every 12 hours maintains concentrations in serum, PELF, and BAL cells that are higher than the minimum inhibitory concentration (0.12 microg/mL) for Rhodococcus equiisolates for the entire 12-hour dosing interval.

Exploring the mechanisms of macrolides in cystic fibrosis

Several studies have reported clinical improvements in cystic fibrosis (CF) patients on macrolide antibiotics although the mechanism of action remains unclear. We conducted an open-label study of azithromycin (500 mg daily for 2 weeks) in 9 adult CF patients to explore 3 possible mechanisms: up-regulation of the multi-drug resistance (MDR) or cystic fibrosis transmembrane regulator (CFTR) proteins, correction of epithelial ion transport and reduced bacterial adherence. End-points included nasal potential difference (PD) measurements, nasal epithelial MDR and CFTR mRNA levels and Pseudomonas aeruginosa adherence to nasal epithelium. Forced expiratory volume in the 1st second (FEV(1)) increased significantly after 2 weeks of azithromycin (pre- 41.1 [5.0]%; post- 44.6 [5.8]%; P<0.05), although improvements in forced vital capacity (FVC) did not reach significance (pre- 61.3 [4.0]%; post- 67.1 [5.4]%, NS). Before treatment all subjects had nasal PD measurements characteristic of CF. Treatment led to no significant group differences in any measures of either sodium absorption or chloride secretion. Neither CFTR nor MDR mRNA levels had altered significantly and the adherence of P. aeruginosa did not decrease. We conclude that these are unlikely to be significant contributing mechanisms accounting for the consistent beneficial results observed in clinical trials of macrolides in CF.

Listeria monocytogenes-infected bone marrow myeloid cells promote bacterial invasion of the central nervous system

Listeria monocytogenes is a facultative intracellular pathogen that is able to invade the central nervous system causing meningoencephalitis and brain abscesses. The mechanisms allowing bacteria to cross the blood-brain barrier are poorly understood. In this work, we used an experimental model of acute listeriosis in the mouse inducing a reproducible invasion of the central nervous system. At the early phase of infection, we find that bacteria invade and rapidly grow in bone marrow cells identified as bone marrow myelomonocytic cells expressing the phenotype CD31pos:Ly-6Cpos:CD11b(pos):LY-6Glow. We demonstrate that central nervous system invasion is facilitated by injecting L. monocytogenes-infected bone marrow cells in comparison with free bacteria or infected spleen cells. In mice transplanted with bone marrow cells from transgenic donor mice expressing the green fluorescent protein (GFP), we show that infected myeloid GFP+ cells adhere to activated brain endothelial cells, accumulate in brain vessels and participate to the pathogenesis of meningoencephalitis and brain abscesses. Our results demonstrate that bone marrow, the main haematopoietic tissue, is a previously unrecognized reservoir of L. monocytogenes-infected myeloid cells, which can play a crucial role in the pathophysiology of meningoencephalitis by releasing infected cells into the circulation that ultimately invade the central nervous system.

Disposition and intracellular levels of moxifloxacin in human THP-1 monocytes in unstimulated and stimulated conditions

Moxifloxacin uptake by human THP-1 monocytes was passive and initially linear and reached equilibrium after approximately 4 h. High intracellular concentrations were achieved and intracellular/extracellular [I/E] ratios were between 1925 and 4575 for the lowest concentration of 0.004 microg/ml at pH 7.4 and 6.9. The uptake of moxifloxacin was reduced by sodium fluoride, -azide, -cyanide, low temperature and low pH. However, the uptake was not affected by any of the ion channel blockers. Adenosine demonstrated marginal competition with moxifloxacin for uptake suggesting a nucleoside transporter may be involved. The sodium-ATPase pump when blocked, also retarded moxifloxacin uptake at 2 and 4 h. This I/E ratio was high compared with other macrolides and indicateed that the monocyte may contain sufficient moxifloxacin levels to conduct the antibiotic throughout systemic circulation to infection sites. Efflux from THP-monocytes was essentially complete after 2 h indicating no long term sequestering of the antibiotic occurred. Disposition of the antibiotic within the THP-1 monocytes showed large amounts present in the nucleus and cytoplasm in stimulated and unstimulated cells. Increased amounts of the drug were found in the THP-1 monocytes as well as the endoplasmic reticulum and the isolated phagosomes after stimulation by zymogen A, Staphylococcus aureus or Streptococcus pneumoniae.

Disposition and intracellular activity of azithromycin in human THP-1 acute monocytes

Uptake of [14C]-azithromycin into THP-1 human monocytes was determined at pH 7.4, 6.8 or 5.5 over 4-log antibiotic concentrations for 24 h under a number of conditions. Stimulation of cells was with bacteria, latex beads, lipopolysaccharide (LPS), or zymogen A. Subcellular organelle disposition was determined after isolation by ultracentrifugation or sucrose gradients. Hydrolytic enzyme activities and mediators of intracellular inflammation (IL-1, IL-6, IL-8, and TNFalpha) were assessed. Azithromycin uptake into human THP-1 monocytes was initially linear achieving approximately 2% of the extracellular concentration. At pH 7.4, uptake was both passive- and carrier-mediated, but as the pH became more acidic, the uptake was exclusively passive. The intracellular concentration was not pH-dependent over 24 h. Uptake was dependent upon temperature but not the presence of foetal calf serum. Intracellular disposition in zymogen A-stimulated and unstimulated cells was throughout all compartments of the cell, but was higher in the nucleus and cell sap. Phagosomes of stimulated cells contained higher level of the antibiotic. Efflux from THP-1 monocytes was complete between 3 and 4 h. After 1 h treatment with zymogen A, THP-1 monocytes demonstrated an increase in intracellular acidity, protein kinase C, SOD and NAG activities, and NO, H(2)O(2), TNFalpha and IL-1 release over the 1st h. After 2-4 h the pH became alkaline, activities of NADPH reductase, NAG and cathepsin were reduced, and the release of NO, H(2)O(2), TNFalpha and IL-6 were suppressed. Protein synthesis and killing of the bacteria was evident in bacteria kept in monocyte-free medium and those phagocytized by the THP-1 monocytes moderately at 2 h, but more significantly at 24 h. The early killing of the bacteria appears to be a cidal mechanism whereas later, a standard bacteriostatic mechanism was evident. Nevertheless, suppression of these chemical mediators and hydrolytic enzyme activities would reduce the infection and the spread to adjacent areas.

Pharmacokinetic considerations in the treatment of inflammatory bowel disease

This review describes the pharmacokinetics of the major drugs used for the treatment of inflammatory bowel disease. This information can be helpful for the selection of a particular agent and offers guidance for effective and well tolerated regimens. The corticosteroids have a short elimination half-life (t1/2beta) of 1.5 to 4 hours, but their biological half-lives are much longer (12 to 36 hours). Most are moderate or high clearance drugs that are hepatically eliminated, primarily by cytochrome P450 (CYP) 3A4-mediated metabolism. Prednisone and budesonide undergo presystemic elimination. Any disease state or comedication affecting CYP3A4 activity should be taken into account when prescribing corticosteroids. Depending on the preparation used, 10 to 50% of an oral or rectal dose of mesalazine is absorbed. Rapid acetylation in the intestinal wall and liver (t1/2beta 0.5 to 2 hours) and transport probably by P-glycoprotein affect mucosal concentrations of mesalazine, which apparently determine clinical response. Any clinical condition influencing the release and topical availability of mesalazine might modify its therapeutic potential. Metronidazole has high (approximately 90%) oral bioavailability, with hepatic elimination characterised by a t1/2beta of 6 to 10 hours and a total clearance of about 4 L/h/kg. Ciprofloxacin is largely excreted unchanged both renally (about 45% of dose) and extrarenally (25%), with a relatively short t1/2beta (3.5 to 7 hours). Thus, renal function affects the systemic availability of ciprofloxacin. Both mercaptopurine and its prodrug azathioprine are metabolised to active compounds (6-thioguanine nucleotides; 6-TGN) by hypoxanthine-guanine phosphoribosyltransferase and to inactive metabolites by the polymorphically expressed thiopurine S-methyltransferase (TPMT) and xanthine oxidase. Patients with low TPMT activity have a higher risk of developing haemopoietic toxicity. Both mercaptopurine and azathioprine have a short t1/2beta (1 to 2 hours), but the t1/2beta of 6-TGN ranges from 3 to 13 days. Therapeutic response seems to be related to 6-TGN concentration. Almost complete bioavailability has been observed after intramuscular and subcutaneous administration of methotrexate, which is predominantly (85%) excreted as unchanged drug with a t1/2beta of up to 50 hours. Thus, renal function is the major determinant for disposition of methotrexate. Cyclosporin is slowly and incompletely absorbed. It is extensively metabolised by CYP3A4/5 in the liver and intestine (median t1/2beta and clearance 7.9 hours and 0.46 L/h/kg, respectively), and inhibitors and inducers of CYP3A4 can modify response and toxicity. Infliximab is predominantly distributed to the vascular compartment and eliminated with a t1/2beta between 10 and 14 days. No accumulation was observed when it was administered at intervals of 4 or 8 weeks. Methotrexate may reduce the clearance of infliximab from serum.

Characteristics and mechanisms of azithromycin accumulation and efflux in human polymorphonuclear leukocytes

Azithromycin achieves prolonged, high tissue concentrations in spite of low serum levels and obviously must be active at tissue sites of infection to be effective. These unique features prompted us to evaluate the interactions of azithromycin and human polymorphonuclear leukocytes (PMN). Uptake of radiolabeled antibiotic by PMN was determined by a velocity-gradient centrifugation technique and expressed as the ratio of cellular to extracellular drug concentration (C/E). Azithromycin was massively accumulated by human PMN (C/E=387.2 at 2 h). Uptake was not influenced by inhibitors of cellular metabolism, but phagocytosis slightly inhibited the entry of azithromycin into PMN. After removal of extracellular drug, the release (efflux) of azithromycin from PMN was extremely slow. Agents which neutralize lysosomal pH, preventing protonation and trapping of azithromycin, markedly increased antibiotic efflux. Active concentration and prolonged retention of azithromycin by phagocytic cells should allow delivery and subsequent release of accumulated drug at sites of infection.

Anti-inflammatory effects of macrolide antibiotics

Macrolides are widely used as antibacterial drugs. Clinical and experimental data, however, indicate that they also modulate inflammatory responses, both contributing to the treatment of infective diseases and opening new opportunities for the therapy of other inflammatory conditions. Considerable evidence, mainly from in vitro studies, suggests that leukocytes and neutrophils in particular, are important targets for modulatory effects of macrolides on host defense responses. This underlies the use of the 14-membered macrolide erythromycin for the therapy of diffuse panbronchiolitis. A variety of other inflammatory mediators and processes are also modulated by macrolides, suggesting that the therapeutic indications for these drugs may be extended significantly in future.

Evaluation of the activity of antimicrobial agents against Legionella pneumophila multiplying in a human monocytic cell line, THP-1, and an alveolar epithelial cell line, A549

The intracellular activity of three antimicrobial agents, erythromycin, clarithromycin, and ciprofloxacin, against Legionella pneumophila was examined in the human monocyte-derived cell line, THP-1, and the human alveolar epithelial cell line, A549. L. pneumophila multiplied by three- to four-log in THP-1 and by two- to three-log in A549 after 48-h incubation. The activity of the two macrolides was markedly greater in A549 than in THP-1, while ciprofloxacin exhibited similar activity in both cell lines. The intracellular concentrations of the two macrolides were markedly higher in A549 than in THP-1, while those of ciprofloxacin were almost equal in both types of cell lines. The intracellular activity of antimicrobial agents and the intracellular growth of L. pneumophila vary with different types of host cells.

Open label trial of oral clarithromycin in active Crohn's disease

BACKGROUND

Crohn's disease seems likely to be due in some way to bacteria. Clarithromycin is a broad spectrum macrolide antibiotic with good penetration into macrophages and may be effective in eradicating the organisms that are presumed to be at the centre of the granulomatous reaction in Crohn's disease.

METHODS

Twenty-five patients with active Crohn's disease were treated with oral clarithromycin 250 mg b.d. in an open label study. Treatment was for an initial 4-week period, continued to 12 weeks in patients who had shown a partial or complete response. The patients had a median age of 30 years (range 17-72), and disease duration of 5 years (range 2 months-28 years); 14 had ileocolonic, four small bowel, seven colonic disease and 10 had previous resections. Twenty patients were receiving a 5-ASA preparation, 15 corticosteroids (prednisolone median dose 10 mg range 2-30 mg) and nine azathioprine. All patients receiving corticosteroids or azathioprine had been on unchanged treatment for at least 12 weeks.

RESULTS

Median pre-treatment Harvey Bradshaw index (HBI) was 9 (range 5-16) and median serum C-reactive protein was 21.5 mg/L (range < 5-117). By 4 weeks the median HBI had decreased to 5 (range 0-18) (P < 0.001) and median CRP to 17 mg/L (range < 5-157) (P=0.16). Sixteen patients (64%) had at least a 3 point fall in HBI and remission (defined as a HBI less than or equal to 4) was achieved in 12 patients (48%). By 12 weeks median HBI was 5 (range 0-18) (P < 0.001) and median CRP was 14.5 mg/L (range < 5-157) (P=0.05). Eleven of the 25 patients studied continued on oral clarithromycin after 12 weeks for a median of 28 weeks (range 20-60). Eight (73%) remained in remission on treatment. When treatment with clarithromycin was stopped three remained in remission and five relapsed after a median of 5 months (range 4-9). Two patients withdrew due to non-serious side-effects. Treatment was well tolerated in the remaining patients.

CONCLUSION

This open label study has shown an impressive response to clarithromycin in a group of patients with active Crohn's disease, many of whom had been resistant to other therapy. A formal randomized controlled trial of clarithromycin in active Crohn's disease is needed.

Clinical pharmacokinetics of clarithromycin

Clarithromycin is a macrolide antibacterial that differs in chemical structure from erythromycin by the methylation of the hydroxyl group at position 6 on the lactone ring. The pharmacokinetic advantages that clarithromycin has over erythromycin include increased oral bioavailability (52 to 55%), increased plasma concentrations (mean maximum concentrations ranged from 1.01 to 1.52 mg/L and 2.41 to 2.85 mg/L after multiple 250 and 500 mg doses, respectively), and a longer elimination half-life (3.3 to 4.9 hours) to allow twice daily administration. In addition, clarithromycin has extensive diffusion into saliva, sputum, lung tissue, epithelial lining fluid, alveolar macrophages, neutrophils, tonsils, nasal mucosa and middle ear fluid. Clarithromycin is primarily metabolised by cytochrome P450 (CYP) 3A isozymes and has an active metabolite, 14-hydroxyclarithromycin. The reported mean values of total body clearance and renal clearance in adults have ranged from 29.2 to 58.1 L/h and 6.7 to 12.8 L/h, respectively. In patients with severe renal impairment, increased plasma concentrations and a prolonged elimination half-life for clarithromycin and its metabolite have been reported. A dosage adjustment for clarithromycin should be considered in patients with a creatinine clearance < 1.8 L/h. The recommended goal for dosage regimens of clarithromycin is to ensure that the time that unbound drug concentrations in the blood remains above the minimum inhibitory concentration is at least 40 to 60% of the dosage interval. However, the concentrations and in vitro activity of 14-hydroxyclarithromycin must be considered for pathogens such as Haemophilus influenzae. In addition, clarithromycin achieves significantly higher drug concentrations in the epithelial lining fluid and alveolar macrophages, the potential sites of extracellular and intracellular respiratory tract pathogens, respectively. Further studies are needed to determine the importance of these concentrations of clarithromycin at the site of infection. Clarithromycin can increase the steady-state concentrations of drugs that are primarily depend upon CYP3A metabolism (e.g., astemidole, cisapride, pimozide, midazolam and triazolam). This can be clinically important for drugs that have a narrow therapeutic index, such as carbamazepine, cyclosporin, digoxin, theophylline and warfarin. Potent inhibitors of CYP3A (e.g., omeprazole and ritonavir) may also alter the metabolism of clarithromycin and its metabolites. Rifampicin (rifampin) and rifabutin are potent enzyme inducers and several small studies have suggested that these agents may significantly decrease serum clarithromycin concentrations. Overall, the pharmacokinetic and pharmacodynamic studies suggest that fewer serious drug interactions occur with clarithromycin compared with older macrolides such as erythromycin and troleandomycin.

The new ketolide HMR3647 accumulates in the azurophil granules of human polymorphonuclear cells

HMR3647 is a semisynthetic representative of a new group of drugs, the ketolides, derived from erythromycin A. Since macrolides have been shown to accumulate in human polymorphonuclear cells (PMNs), we have investigated the ability of the molecule HMR3647 to enter human PMNs as well as other cell types, such as peripheral blood mononuclear cells and cell lines of hematopoietic and nonhematopoietic origin. In these experiments, HMR3647 was compared to erythromycin A, azithromycin, clarithromycin, and roxithromycin. Our results show that HMR3647 is specifically trapped in PMNs, where it is concentrated up to 300 times. In addition, it is poorly released by these cells, 80% of the compound remaining cell associated after 2 h in fresh medium. By contrast, it is poorly internalized and quickly released by the other cell types studied. This differs from the results obtained with the macrolide molecules, which behaved similarly in the different cells studied. In addition, subcellular fractionation of PMNs allowed us to identify the intracellular compartment where HMR3647 was trapped. In PMNs, more than 75% of the molecule was recovered in the azurophil granule fraction. Similarly, in NB4 cells differentiated into PMN-like cells, almost 60% of the molecules accumulated in the azurophil granule fraction. In addition, when HMR3647 was added to disrupted PMNs, 63% accumulated in the azurophil granules. Therefore, this study shows that the ketolide HMR3647 specifically accumulates in PMN azurophil granules, thus favoring its delivery to bacteria phagocytosed in these cells.

Efficacy of novel antimicrobials against clinical isolates of opportunistic amebas

We examined the effects of the macrolide antimicrobial agent azithromycin and phenothiazine compounds against clinical isolates of Acanthamoeba spp. and Balamuthia mandrillaris, opportunistic pathogens of human beings and other animals. Acanthamoeba growth was inhibited in vitro at 1, 5, and 10 micrograms/ml of azithromycin, but not the macrolides, erythromycin, and clarithromycin. In experiments attempting to simulate in vivo conditions, azithromycin protected monolayers of rat glioma cells from destruction by Acanthamoeba at a concentration of 0.1 microgram/ml, and delayed destruction at concentrations of 0.001 and 0.01 microgram/ml. We concluded that the minimal inhibitory concentration of azithromycin was 0.1 microgram/ml. Our results, however, suggested that the drug was amebastatic but not amebicidal, since ameba growth eventually resumed after drug removal. The phenothiazines (chlorpromazine, chlorprothixene, and triflupromazine) inhibited Acanthamoeba growth by 70-90% at 5 and 10 micrograms/ml, but some of these compounds were toxic for rat glioma cells at 10 micrograms/ml. Azithromycin was not very effective against B. mandrillaris in an in vitro setting, but was amebastatic in tissue culture monolayers at concentrations of 0.1 microgram/ml and higher. Balamuthia amebas showed in vitro sensitivity to phenothiazines. Ameba growth was inhibited 30-45% at 5 micrograms/ml in vitro, but completely at 5 micrograms/ml in the rat glioma model. In spite of their potential as antiamebic drugs in Balamuthia infections, toxicity of phenothiazines limits their use in clinical settings.

Inhibition of intracellular growth of Staphylococcus aureus by exposure of infected human monocytes to clarithromycin and azithromycin

The direct effect of clarithromycin and azithromycin on human polymorphonuclear leukocyte (PMN) functions and their intracellular activity against Staphylococcus aureus, phagocytosed by human monocytes, were studied. The presence of both antibiotics, in the range of concentrations from 0.25 to 20 micrograms/ml, did not affect chemotaxis, opsonized-zymosan phagocytosis, respiratory burst measured by nitroblue tetrazolium reduction and phorbol myristate acetate-induced superoxide production, or the microbicidal activity of human PMNs against Candida albicans. Both macrolides were bactericidal against staphylococci in the monocyte system, while bacteriostatic activity was found in cell free system. At concentrations equal to the minimum inhibitory concentrations (MICs) (0.75 and 0.1 respectively for azithromycin and clarithromycin) more than 99% of intraphagocytic S. aureus were killed after 24 h incubation. Increasing the concentrations of each drug above the MICs (5 and 10 MICs) did not alter the killing rate of intracellular bacteria. Moreover, no differences between the intracellular bioactivity of these antibiotics were demonstrated, despite their different uptake kinetics.