Prion Protein Protects against Renal Ischemia/Reperfusion Injury.

The cellular prion protein (PrPC), a protein most noted for its link to prion diseases, has been found to play a protective role in ischemic brain injury. To investigate the role of PrPC in the kidney, an organ highly prone to ischemia/reperfusion (IR) injury, we examined wild-type (WT) and PrPC knockout (KO) mice that were subjected to 30-min of renal ischemia followed by 1, 2, or 3 days of reperfusion. Renal dysfunction and structural damage was more severe in KO than in WT mice. While PrP was undetectable in KO kidneys, Western blotting revealed an increase in PrP in IR-injured WT kidneys compared to sham-treated kidneys. Compared to WT, KO kidneys exhibited increases in oxidative stress markers heme oxygenase-1, nitrotyrosine, and Nε-(carboxymethyl)lysine, and decreases in mitochondrial complexes I and III. Notably, phosphorylated extracellular signal-regulated kinase (pERK) staining was predominantly observed in tubular cells from KO mice following 2 days of reperfusion, a time at which significant differences in renal dysfunction, histological changes, oxidative stress, and mitochondrial complexes between WT and KO mice were observed. Our study provides the first evidence that PrPC may play a protective role in renal IR injury, likely through its effects on mitochondria and ERK signaling pathways

Detection of pERK of sham and IR-injured WT and KO kidneys.

<p>(A) Detection of pERK of renal homogenates from sham and IR-injured WT and KO mice by Western blotting. The equal amounts of total proteins from renal tissue homogenates were loaded based on BCA protein assay and the amounts of samples loaded were monitored by determining GAPDH. The Western blots are representative of three experiments. (B) Bar graph of pERK intensity based on quantitative analysis of pERK band from the kidney of sham and IR-injured mice by densitometric analysis. The intensity of the protein band was normalized with GAPDH band intensity in each corresponding land. *<i>p</i> < 0.05; ***<i>p</i> < 0.005. (C) pERK immunohistochemistry of sham and IR-injured WT and KO mice. Immunohistochemistry (IHC) staining images are representative renal tissue sections from three mice of each group (bar = 50 μm; original magnification, x 400).</p

Loss of body weight of IR-injured mice.

<p>*<i>p</i> <0.05</p><p>**<i>p</i> < 0.01</p><p>***<i>p</i> < 0.005</p><p>****<i>p</i> < 0.001 compared with mice on day 1</p><p>^Δ<i>p</i> < 0.05 compared with knockout mice on day 2, or 3; IR, Ischemia/reperfusion injury.</p><p>Loss of body weight of IR-injured mice.</p

Detection of HO-1, nitrotyrosine and CML of sham and IR-injured WT and KO kidneys.

<p>(A) Detection of HO-1 from the frozen renal tissues of IR-injured WT and KO mice (three each) by Western blotting. The equal amounts of total proteins from renal homogenates were loaded based on BCA protein assay and the amounts of samples loaded were monitored by determining GAPDH. The Western blots are representative of three experiments. (B) Bar graph of HO-1 intensity based on quantitative analysis of the HO-1 band by densitometric analysis. The intensity of the protein band was normalized with GAPDH band intensity in each corresponding land. *<i>p</i> < 0.05; **<i>p</i> < 0.01. (C) HO-1 immunohistochemistry of sham and IR-injured WT and KO mice. IHC staining images are representative renal tissue sections from three mice of each group (bar = 200 μm; original magnification, x 400). (D) Nitrotyrosine immunohistochemistry of sham and IR-injured WT and KO mice. IHC staining images are representative renal tissue sections from three mice of each group (bar = 200 μm; original magnification, x 400). (E) CML immunohistochemistry of sham and IR-injured WT and KO mice. IHC staining images are representative renal tissue sections from three mice of each group (original magnification, x 200).</p