INHIBITION OF IRON TOXICITY IN HUMAN HEPATOCYTE CULTURES BY PYOVERDINS PA-A AND PF, THE PEPTIDIC SIDEROPHORES OF PSEUDOMONAS-AERUGINOSA ANDFLUORESCENS

The protective effect of pyoverdins Pa A and Pf, peptidic siderophores secreted respectively by Pseudomonas aeruginosa and fluroescens, was studied in primary cultures of human hepatocytes exposed to iron (50 o r 100 mu M of iron-citrate). AST, ALT and MDA releases were measured a s indexes of cytototoxicity. In order to demonstrate that these chelat ors were able to decrease iron uptake or increase iron release from th e hepatocytes, labelled cells were obtained by maintaining the culture s in the presence of 1 mu M Fe-55 ferric chloride plus 50 mu M iron ci trate, One day after iron treatment, an increase in AST. ALT and MDA r elease was observed with 50 or 100 mu M of iron citrate; rt appeared t hat the concentrations 50 and 100 mu M of iron were highly toxic for h uman hepatocytes. In the presence of 50 or 100 mu M of iron. the addit ion of 50 or 100 mu M of Pa A or Pf nas effective to inhibit the incre ase observed in the enzyme leakage and the MDA production resulting fr om iron exposure. In human hepatocytes cultured for 1 day in the prese nce of 1 mu M Fe-55-50 mu M iron citrate plus 50 or 100 mu M Pa A or P f, a net decrease of iron uptake by the cells was observed, as demonst rated by the low intracellular iron level, When the hepatocytes were c ultured for 1day in the presence of 1 mu M Fe-55-50 mu M iron citrate and then for a further day in the presence of 50 or 100 mu M Pa A or P f without additional iron, the chelators increased the extracellular i ron level, indicating their iron release from the loaded cells; howeve r, the effects of Pa A and Pf on iron release did not differ significa ntly, In conclusion, iron loading achieved by adding iron citrate to t he culture medium is highly toxic for human hepatocytes. Pyoverdins Pa A and Pf are effective in protecting human hepatocytes against the to xic effect of iron by both decreasing the uptake of the metal and incr easing its release from the loaded cells.