Influence of HFE variants and cellular iron on monocyte chemoattractant protein-1.
BACKGROUND
Polymorphisms in the MHC class 1-like gene known as HFE have been proposed as genetic modifiers of neurodegenerative diseases that include neuroinflammation as part of the disease process. Variants of HFE are relatively common in the general population and are most commonly associated with iron overload, but can promote subclinical cellular iron loading even in the absence of clinically identified disease. The effects of the variants as well as the resulting cellular iron dyshomeostasis potentially impact a number of disease-associated pathways. We tested the hypothesis that the two most common HFE variants, H63D and C282Y, would affect cellular secretion of cytokines and trophic factors.


METHODS
We screened a panel of cytokines and trophic factors using a multiplexed immunoassay in human neuroblastoma SH-SY5Y cells expressing different variants of HFE. The influence of cellular iron secretion on the potent chemokine monocyte chemoattractant protein-1 (MCP-1) was assessed using ferric ammonium citrate and the iron chelator, desferroxamine. Additionally, an antioxidant, Trolox, and an anti-inflammatory, minocycline, were tested for their effects on MCP-1 secretion in the presence of HFE variants.


RESULTS
Expression of the HFE variants altered the labile iron pool in SH-SY5Y cells. Of the panel of cytokines and trophic factors analyzed, only the release of MCP-1 was affected by the HFE variants. We further examined the relationship between iron and MCP-1 and found MCP-1 secretion tightly associated with intracellular iron status. A potential direct effect of HFE is considered because, despite having similar levels of intracellular iron, the association between HFE genotype and MCP-1 expression was different for the H63D and C282Y HFE variants. Moreover, HFE genotype was a factor in the effect of minocycline, a multifaceted antibiotic used in treating a number of neurologic conditions associated with inflammation, on MCP-1 secretion.


CONCLUSIONS
Our results demonstrate that HFE polymorphisms influence the synthesis and release of MCP-1. The mechanism of action involves cellular iron status but it appears there could be additional influences such as ER stress. Finally, these data demonstrate a pharmacogenetic effect of HFE polymorphisms on the ability of minocycline to inhibit MCP-1 secretion.
Mitchell
Ryan M
RM
George M Leader Family Laboratory, Department of Neurosurgery, Pennsylvania State University College of Medicine/Milton S Hershey Medical Center, Hershey, PA 17033, USA. rmm311@psu.edu
Lee
Sang Y
SY
Randazzo
William T
WT
Simmons
Zachary
Z
Connor
James R
JR
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D045744:Cell Line, Tumor; D018932:Chemokine CCL2 / Q000378:metabolism*; D002839:Chromans / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D005290:Ferric Compounds / Q000378:metabolism; D015870:Gene Expression; D006360:Heat-Shock Proteins / Q000378:metabolism; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D008911:Minocycline / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D000893:Anti-Inflammatory Agents; D000975:Antioxidants; C111835:CCL2 protein, human; D018932:Chemokine CCL2; D002839:Chromans; D005290:Ferric Compounds; C103673:HFE protein, human; D006360:Heat-Shock Proteins; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I; D007502:Iron Chelating Agents; D008565:Membrane Proteins; D016328:NF-kappa B; D000644:Quaternary Ammonium Compounds; D012333:RNA, Messenger; D007501:Iron; D008911:Minocycline; D003676:Deferoxamine; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; C013531:ferric ammonium citrate