The role of macrophage migration inhibitory factor in Alzheimer's disease

Abstract

Previous studies have shown that amyloid beta protein (Abeta ), the essential molecule for the formation of toxic oligomers and, subsequently, Alzheimer plaques, has been associated in vivo with the immune modulator, macrophage migration inhibitory factor (MIF) (17). To further investigate this association in vivo we used the APP transgenic mouse model. Serial brain sections of transgenic APP mice were stained for Abeta plaques and MIF and we observed MIF immunolabeling in microglial cells in association with Abeta plaques in the transgenic mouse brain sections. In addition, functional studies in murine and human neuronal cell lines revealed that Abeta-induced toxicity could be reversed significantly by a small molecule inhibitor of MIF (ISO-1). Finally, to elucidate the role of MIF in Alzheimer's Disease (AD) we measured MIF levels in the brain cytosol and cerebrospinal fluid (CSF) of AD patients and age-matched controls. Our results demonstrate a marked increase of MIF levels within the CSF of AD patients compared with controls. Combined, our results indicate a strong role for MIF in the pathogenesis of AD and furthermore suggest that inhibition of MIF may provide a valuable avenue of investigation for the prevention of disease onset, progression and/or severity.

Figure 1

MIF immunostain in association with amyloid plaques. Serial section of plaque bearing APP 23 mice were stained for amyloid deposits (A) and for MIF proteins (B) using the mentioned antibodies in the appropriate dilution. The overlay (C) of both photographs displays the plaque dependent MIF staining (arrows indicate the MIF positive cells, P: plaque). A similar staining pattern was obtained in a total of eight sections from four different transgenic APP mice.

Figure 2

The MIF specific small molecule inhibitor ISO-1 counter-regulates the neuro-toxic effect of Aβ_1–40 , Aβ_1–42 in neuroblastoma SHSY cells. SHSY cells (30,000 cells per well) were incubated alone or in the presence of 2 μmol/L oligomerized Aβ_1–40 Aβ_1–42, or in the presence of Aβ_1–40 , Aβ_1–42 in the presence of 200 nmol/L MIF specific inhibitor ISO-1. The viability of the cells was determined by MTT assay. The values of the control cells were set as 100% viability.

Figure 3

The MIF specific small molecule inhibitor ISO-1 counter-regulates the neurotoxic effect of Aβ_1–40, at concentrations of 5 μmol/L or 10 μmol/L in murine BV2 microglial cells. At a concentration of 5 μmol/L, Aβ viability of the cells was reduced to 73%, ISO-1 at 50 or 100 μmol/L restored the Aβ dependent toxicity to 85% of the control. This effect was even more prominent when the cells were treated with 10 μmol/L of Aβ . Here, we obtained a toxic Aβ effect of around 60% in comparison to the control cells. That effect was reduced with 50 μmol/L ISO-1 to around 80% and further reduced to around 90% with 100 μmol/L of ISO-1. The graph displays the measurements of the mean from three separate experiments, performed in quadruplicate. The results did not reach statistical significance and can therefore only be interpreted as a trend.

Figure 4

(A) Detection of MIF in CSF of AD patients (n = 7) and age-/gender-matched controls (n = 7). (B) MIF-ELISA with lysed brain tissues collected from AD patients (n = 10) and healthy individuals as control (n = 9). We performed a Mann–Whitney U test for nonparametric distributed values to test group differences in MIF concentrations and found significantly elevated MIF levels (P < 0.001) in AD patients in comparison to healthy controls (A).