Krunoslav Nujić

Azithromycin distinctively modulates classical activation of human monocytes in vitro

BACKGROUND AND PURPOSE Azithromycin has been reported to modify activation of macrophages towards the M2 phenotype. Here, we have sought to identify the mechanisms underlying this modulatory effect of azithromycin on human monocytes, classically activated in vitro.

Azithromycin inhibits macrophage interleukin-1β production through inhibition of activator protein-1 in lipopolysaccharide-induced murine pulmonary neutrophilia☆

Macrolide antibiotics, including azithromycin, also possess anti-inflammatory properties. However, the molecular mechanism(s) of activity as well as the target cells for their action have not been unambiguously identified as yet. In this study, the effects of azithromycin on lipopolysaccharide (LPS)-induced pulmonary neutrophilia were investigated in mice. Using immunohistochemistry, mRNA and specific protein assays, we confirmed that azithromycin ameliorates LPS-induced pulmonary neutrophilia by inhibiting interleukin-1β (IL-1β) expression and production selectively in alveolar macrophages as well as in LPS-stimulated J774.2 macrophage-derived cells in vitro. Inhibition by azithromycin of neutrophilia and IL-1β was accompanied by prevention of nuclear expression of activator protein-1 (AP-1) in both alveolar macrophages and J774.2 cells. The macrolide did not alter nuclear factor kappa B (NF-κB) or extracellular signal-regulated kinase 1/2 (ERK1/2) expression, activation or localization in LPS-stimulated lungs or in J774.2 cells. In conclusion, we have shown that inhibition of LPS-induced pulmonary neutrophilia and IL-1β concentrations in lung tissue following azithromycin treatment is mediated through effects on alveolar macrophages. In addition, we have shown for the first time, in an in vivo model, that azithromycin inhibits AP-1 activation in alveolar macrophages, an action confirmed on J774.2 cells in vitro.

Intensity of macrolide anti-inflammatory activity in J774A.1 cells positively correlates with cellular accumulation and phospholipidosis

Some macrolide antibiotics were reported to inhibit interleukin-6 (IL6) and prostaglandin-E2 (PGE(2)) production by bacterial lipopolysaccharide (LPS) stimulated J774A.1 cells. Macrolides are also known to accumulate in cells and some were proven inducers of phospholipidosis. In the present study, with a set of 18 mainly 14- and 15-membered macrolides, we have investigated whether these macrolide induced phenomena in J774A.1 cells are connected. In LPS-stimulated J774A.1 cells, the extent of inhibition of proinflammatory markers (IL6 and PGE(2)) by macrolides significantly correlated with their extent of accumulation in cells, as well as with the induction of phospholipidosis, and cytotoxic effects in prolonged culture (with correlation coefficients (R) ranging from 0.78 to 0.93). The effects observed were related to macrolide binding to phospholipids (CHI IAM), number of positively charged centres, and were inversely proportional to the number of hydrogen bond donors. Similar interdependence of effects was obtained with chloroquine and amiodarone, whereas for dexamethasone and indomethacin these effects were not linked. The observed macrolide induced phenomena in J774A.1 cells were reversible and elimination of the macrolides from the culture media prevented phospholipidosis and the development of cytotoxicity in long-term cultures. Based on comparison with known clinical data, we conclude that LPS-stimulated J774A.1 cells in presented experimental setup are not a representative cellular model for the evaluation of macrolide anti-inflammatory potential in clinical trials. Nevertheless, our study shows that, at least in in vitro models, binding to biological membranes may be the crucial factor of macrolide mechanism of action.

Impairment of lysosomal functions by azithromycin and chloroquine contributes to anti-inflammatory phenotype.

Azithromycin and chloroquine have been shown to exhibit anti-inflammatory activities in a number of cellular systems, but the mechanisms of these activities have still not been clarified unequivocally. Since both drugs are cationic, accumulate in acidic cellular compartments and bind to phospholipids with a consequent increase in lysosomal pH and induce phospholipidosis, we examined the relevance of these common properties to their anti-inflammatory activities. We compared also these effects with effects of concanamycin A, compound which inhibits acidification of lysosomes. All three compounds increased lysosomal pH, accumulation of autophagic vacuoles and ubiquitinated proteins and impaired recycling of TLR4 receptor with consequences in downstream signaling in LPS-stimulated J774A.1 cells. Azithromycin and chloroquine additionally inhibited arachidonic acid release and prostaglandin E2 synthesis. Therefore, impairment of lysosomal functions by azithromycin and chloroquine deregulate TLR4 recycling and signaling and phospholipases activation and lead to anti-inflammatory phenotype in LPS-stimulated J774A.1 cells.

Anti-inflammatory mechanism of action of azithromycin in LPS-stimulated J774A.1 cells

Azithromycin is a macrolide antibiotic with well-described anti-inflammatory properties which can be attributed, at least partially, to its action on macrophages. We have previously shown, with 18 different macrolide molecules, that IL-6 and PGE₂ inhibition correlates with macrolide accumulation, as well as with their binding to phospholipids in J774A.1 cells. The present study was performed in order to substantiate the hypothesis that biological membranes are a target for macrolide anti-inflammatory activity. By analyzing the effect of azithromycin on overall eicosanoid production, we found that in LPS-stimulated J774A.1 cells, azithromycin, like indomethacin, inhibited the synthesis of all eicosanoids produced downstream of COX. Upstream of COX, azithromycin inhibited arachidonic acid release in the same way as a cPLA₂ inhibitor, while indomethacin had no effect. Further comparison revealed that in LPS-stimulated J774A.1 cells, the cPLA₂ inhibitor showed the same profile of inhibition as azithromycin in inhibiting PGE₂, IL-6, IL-12p40 and arachidonic acid release. Therefore, we propose that the anti-inflammatory activity of azithromycin in this model may be due to interactions with cPLA₂, causing inadequate translocation of the enzyme or disturbing physical interactions with its substrates.

Fluorescently labeled macrolides as a tool for monitoring cellular and tissue distribution of azithromycin

Exceptional therapeutic effects of macrolides in treating various infections and inflammatory conditions can be significantly contributed to their unique pharmacokinetic properties. Macrolides accumulate in cells and tissues, with concentrations usually 10 to more than 100 times higher of those measured in plasma. Intracellular distribution of macrolides has so far been examined using extensive subcellular fractionation techniques, radiolabeled compounds and conventional pharmacokinetic methods. In this study we evaluated four fluorescently labeled macrolides on their applicability to monitor azithromycin distribution in vitro and in vivo. 9-Deoxo-9a-{3-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]propyl}-9a-aza-9a-homoerythromycin A (9a-NBD-azithromycin) was selected as a compound with most similar cellular pharmacokinetics to azithromycin. 9a-NBD-azithromycin demonstrated antimicrobial properties comparable to azithromycin, displayed the same biological activity profile in LPS-stimulated J774A.1 murine macrophage cells and, even though it accumulated in cells almost 50% more than azithromycin, it showed same rate of retention. Identical to azithromycin, 9a-NBD-azithromycin was localized in lysosomes of J774A.1 cells. Two hours after 9a-NBD-azithromycin was administered intraperitonally to mice, a strong fluorescent signal was located in kidneys and liver and slightly weaker in the spleen. In kidneys, the signal was concentrated in tubuli, and glomeruli were negative. Patchy florescence in hepatocytes supports lysosomal cellular localization. Weaker staining of white pulp compared to red pulp of spleen is in agreement with lower accumulation of azithromycin in lymphocytes compared to other cell types present. We conclude that 9a-NBD-azithromycin can be used as a fluorescent analog of azithromycin to visualize its distribution in in vitro systems, and is also suitable for in vivo studies.

Valosin containing protein (VCP) interacts with macrolide antibiotics without mediating their anti-inflammatory activities

In addition to antibacterial activity, some macrolide antibiotics, such as azithromycin and clarithromycin, also exhibit anti-inflammatory properties in vitro and in vivo, although the targets and mechanism(s) of action remain unknown. The aim of the present study was to identify protein targets of azithromycin and clarithromycin which could potentially explain their anti-inflammatory effects. Using chemical proteomics approach, based on compound-immobilized affinity chromatography, valosin containing protein (VCP) was identified as a potential target of the macrolides. Validation studies confirmed the interaction of macrolides and VCP and gave some structural characteristics of this interaction. Cell based assays however, including the use of gene silencing and the study of VCP specific cellular functions in J774.A1 (murine macrophage) and IB3-1 (human cystic fibrotic epithelial) cell lines, failed to confirm an association between the binding of the macrolides to VCP and anti-inflammatory effects. These findings suggest the absence of an abundant high affinity protein target and the potential involvement of other biological molecules in the anti-inflammatory activity of macrolides.

2,8-dithia-dibenzo〔e,h〕azulenes and their 8-oxa analogs: synthesis and anti-inflammatory activity

Synthesis of 2, 8-dithia-dibenzo[e, h]azulenes (III, X = S) and their 8-oxa analogs (III, X = O), 1 two novel classes of fused heterocyclic compounds, is described. Starting 11H-dibenzo[b, f]thiepin-10-one, 11H-dibenzo[b, f]oxepin- 10-one and its 2-chloro derivative (1a-c) were oxidized to 1, 2-diketones (2a-c) which subsequently reacted with 2, 2’ -dimethyl thiodiglycolate to form fused thiophene ring by Hinsberg cyclization reaction. Substituents at positions C(1) and C(3) were then further transformed in order to obtain aminoalkoxy derivatives 8-11. Structures of regioisomers 6c and 6d were elucidated using two-dimensional NMR techniques. All compounds with tetracyclic skeleton were tested in vitro for their anti-inflammatory activity.

Immunomodulatory effects of azithromycin on the establishment of lipopolysaccharide tolerance in mice.

Recent reports suggest that azithromycin can shift macrophage polarization towards the alternatively activated M2 phenotype. In order to investigate its immunomodulatory activity in vivo, the influence of azithromycin on survival and cytokine production was assessed in the LPS tolerance model which is characterized by an M2 skewed response. For induction of tolerance, mice received an intraplantar injection of 30 μg LPS, 24 h prior to intravenous challenge with 350 μg LPS. Azithromycin (100 mg/kg) was administered orally, 2 h before LPS application. Influence of treatment on survival and cytokine concentration in serum was monitored. Azithromycin alone, instead of LPS, could not induce an LPS tolerant state. However, when administered before LPS priming it significantly increased survival, which was enhanced by concomitant azithromycin before LPS challenge. Azithromycin had no effect on survival when administered only prior to the LPS challenge. Tolerance induction by LPS priming was associated, upon LPS challenge, with decreased serum concentrations of pro-inflammatory cytokines, TNFα, IL-12p40 and CCL5, and increased serum concentrations of the anti-inflammatory cytokines, IL-10 and IL-1ra. Azithromycin treatment, prior to LPS priming, further reduced serum TNFα and CCL5, yielding the greatest inhibition when the macrolide was also given prior to LPS challenge. Serum concentrations of the anti-inflammatory cytokines, IL-10 and IL-1ra, were unchanged following azithromycin treatment. In summary, we have confirmed the immunomodulatory activity of azithromycin, as reflected in its ability to augment tolerance induction to LPS, promoting increased survival and reduced pro-inflammatory cytokine production, without affecting overt inflammation to LPS or anti-inflammatory cytokine production.

Tebrophen—An Old Polyphenol Drug with Anticancer Potential

In vitro high-throughput screening was carried out in order to detect new activities for old drugs and to select compounds for the drug development process comprising new indications. Tebrophen, a known antiviral drug, was found to inhibit activities on inflammation and cancer related targets. In primary screening this semisynthetic halogenated polyphenol was identified to inhibit the activities of kinases ZAP-70 and Lck (IC50 0.34 µM and 16 µM, respectively), as well as hydrolase DPPIV (at 80 µM 41% inhibition). Next, it showed no cytotoxic effects on standard cell lines within 24 h. However, tebrophen slowed propagation of breast cancer (MDA-MB-231), osteosarcoma (U2OS) and cervical carcinoma (HeLa), through at least 35 population doublings in a dose-dependent manner. It completely stopped the division of the prostate cancer (PC3) cell line at 50 µM concentration and the cells entered massive cell death in less than 20 days. On the other hand, tebrophen did not influence the growth of normal fibroblasts. According to the measured oxidative burst and estimated in silico parameters its direct antioxidative ability is limited. The obtained results indicate that tebrophen can be considered a promising lead molecule for generating more soluble derivatives with specific anticancer efficacy.