Elevated microsomal prostaglandin-E synthase-1 in Alzheimer's disease

Abstract

Background: The proinflammatory prostaglandin E(2) (PGE(2)) fluctuates over time in the cerebrospinal fluid of patients with Alzheimer's disease (AD), but the cerebral distribution and expression patterns of microsomal prostaglandin-E synthase (mPGES)-1 have not been compared with those of normal human brains.

Methods: Middle frontal gyrus tissue from AD and age-matched control brains was analyzed by Western blot, immunofluorescence, and immunohistochemistry with mPGES-1-specific antibodies.

Results: Western blotting revealed that mPGES-1 expression was significantly elevated in AD tissue. Furthermore, immunofluorescence of mPGES-1 was observed in neurons, microglia, and endothelial cells of control and AD tissue. Although mPGES-1 was consistently present in astrocytes of control tissue, it was present in only some astrocytes of AD tissue. Immunohistochemical staining suggested that mPGES-1 was elevated in pyramidal neurons of AD tissue when compared with controls.

Conclusions: The results suggest that mPGES-1 is normally expressed constitutively in human neurons, microglia, astrocytes, and endothelial cells but is up-regulated in AD.

Fig 1

Differential expression of mPGES-1 in human brain MFG. (A) Western blot analysis showed that mPGES-1 protein was expressed in the MFG of AD (n = 10) and age-matched control (n = 9) brains. (B) After normalization to actin, the mean expression of mPGES-1 in the AD brains was shown to be significantly greater than that of the control brains; **P < .001.

Fig 2

Immunohistochemical study of mPGES-1 in AD. (A) Negative control normal brain; (B) a normal brain positively immunostained with anti–mPGES-2. (C) Negative control sporadic AD brain tissue; (D) mPGES-1–stained sporadic AD brain tissue. (E) Negative control familial AD brain tissue; (F) positively immunostained familial AD brain tissue. Neurons displayed visible detectable immunostaining. Original magnification, 40×.

Fig 3

Microsomal PGES-1 (green) colocalization with various cell types (red) in normal brain. Yellow areas show overlap of mPGES-1 with the cell type, indicating colocalization. mPGES-1 colocalized with neurons labeled by SMI-32 antibody (A–C), with microglia labeled by CD11b antibody (D–F), with astrocytes labeled by GFAP antibody (G–I), and with endothelial cells labeled by vWB antibody (J–L). mPGES-1 did not colocalize with smooth muscle cells labeled by SMC antibody (M–O). Aβ₁₋₄₂, which was stained with 6E10 antibody, colocalized with mPGES-1 in microglial-shaped cells (P–R). The plaque itself (red area seen in R) did not remarkably colocalize with mPGES-1. Green scale bar = 50 μm; red/white scale bar = 100 μm.

Fig 4

Microsomal PGES-1 (green) colocalization with various cell types (red) in AD brain. Staining was similar to that of control brain. mPGES-1 colocalized with neurons labeled by SMI-32 antibody (A–C), microglia labeled by CD11b antibody (D–F), and endothelial cells labeled by vWB antibody (G–I). mPGES-1 colocalized with astrocytes (labeled by anti-GFAP) in some areas (Jc, Kc) but not in others (Lc). mPGES-1 did not colocalize with smooth muscle cells labeled by SMC antibody (M–O). Aβ₁₋₄₂, which was stained with 6E10 antibody, colocalized with mPGES-1 in microglial-shaped cells (P–R). The plaque itself (red area seen in R) did not colocalize with mPGES-1. Scale bar = 100 μm.