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 (PGE2) 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 PGE2) 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.