1 F - 00248 - 2010 R 1 2 3 Parenteral Iron Formulations Differentially Affect 4 5 Mcp - 1 , Ho - 1 , and Ngal Gene Expression 6 7 and Renal Responses to Injury

32 Despite their pro-oxidant effects, ferric iron compounds are routinely administered to patients 33 with renal disease to correct Fe deficiency. This study assessed relative degrees to which three 34 clinically employed Fe formulations (Fe sucrose, FeS; Fe gluconate; FeG; ferumoxytol; FMX) 35 impact renal redoxsensitive signaling, cytotoxicity, and responses to superimposed stress 36 (endotoxin; glycerol induced ARF). Cultured human proximal tubule (HK-2) cells, isolated 37 proximal tubule segments (PTS), or mice were exposed to variable, but equal, amounts of FeS, 38 FeG, or FMX. Oxidant stimulated signaling was assessed by heme oxygenase 1 (HO-1) or 39 MCP-1 mRNA induction. Cell injury was gauged by MTT assay (HK-2 cells), %LDH release 40 (PTS), or renal cortical NGAL protein / mRNA levels. Endotoxin sensitivity and ARF severity 41 were assessed by TNF-α and BUN concentrations, respectively. FeS and FeG induced lethal 42 cell injury (in HK-2 cells, PTS), increased HO-1 and MCP-1 mRNAs (HK-2 cells; in vivo), and 43 markedly raised plasma (~10x), and renal cortical (~3x) NGAL protein levels. Both renal and 44 extra-renal (e.g., hepatic) NGAL production likely contributed to these results, based on 45 assessments of tissue and HK-2 cell NGAL mRNA. FeS pre-treatment exacerbated 46 endotoxemia. However, it conferred marked protection against the glycerol model of ARF 47 (halving azotemia). FMX appeared to be “bioneutral”, as it exerted none of the above noted 48 FeS / FeG effects. We conclude that: 1) parenteral iron formulations that stimulate redox 49 signaling can evoke cyto/nephrotoxicity; 2) secondary adaptive responses to this injury (e.g., 50 HO-1 / NGAL induction) can initiate a renal tubular cytoresistant state; this suggests a potential 51 new clinical application for IV Fe therapy; and 3) FMX is “bioneutral”, regarding these 52 responses. The clinical implication(s) of the latter, vis a vis the treatment of Fe deficiency in 53 renal disease patients, remains to be defined. 54 55 56 57