Impact of AMP-Activated Protein Kinase α1 Deficiency on Tissue Injury following Unilateral Ureteral Obstruction.
BACKGROUND
AMP-activated protein kinase (Ampk) is a sensor of the cellular energy status and a powerful regulator of metabolism. Activation of Ampk was previously shown to participate in monocyte-to-fibroblast transition and matrix protein production in renal tissue. Thus, the present study explored whether the catalytic Ampkα1 isoform participates in the regulation of the renal fibrotic response following unilateral ureteral obstruction (UUO).


METHODS
UUO was induced in gene-targeted mice lacking functional Ampkα1 (Ampkα1-/-) and in corresponding wild-type mice (Ampkα1+/+). In the obstructed kidney and, for comparison, in the non-obstructed control kidney, quantitative RT-PCR, Western blotting and immunostaining were employed to determine transcript levels and protein abundance, respectively.


RESULTS
In Ampkα1+/+ mice, UUO significantly up-regulated the protein abundance of the Ampkα1 isoform, but significantly down-regulated the Ampkα2 isoform in renal tissue. Phosphorylated Ampkα protein levels were significantly increased in obstructed kidney tissue of Ampkα1+/+ mice but not of Ampkα1-/- mice. Renal expression of α-smooth muscle actin was increased following UUO, an effect again less pronounced in Ampkα1-/- mice than in Ampkα1+/+ mice. Histological analysis did not reveal a profound effect of Ampkα1 deficiency on collagen 1 protein deposition. UUO significantly increased phosphorylated and total Tgf-ß-activated kinase 1 (Tak1) protein, as well as transcript levels of Tak1-downstream targets c-Fos, Il6, Pai1 and Snai1 in Ampkα1+/+ mice, effects again significantly ameliorated in Ampkα1-/- mice. Moreover, Ampkα1 deficiency inhibited the UUO-induced mRNA expression of Cd206, a marker of M2 macrophages and of Cxcl16, a pro-fibrotic chemokine associated with myeloid fibroblast formation. The effects of Ampkα1 deficiency during UUO were, however, paralleled by increased tubular injury and apoptosis.


CONCLUSIONS
Renal obstruction induces an isoform shift from Ampkα2 towards Ampkα1, which contributes to the signaling involved in cell survival and fibrosis.
Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076, Tübingen, Germany.
Sobuj
S
Mia
Department of Cellular and Molecular Pathology, German Cancer Research Center, Im Neuenheimer Feld, 280, 69120, Heidelberg, Germany.
Giuseppina
G
Federico
Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076, Tübingen, Germany.
Martina
M
Feger
Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076, Tübingen, Germany.
Tatsiana
T
Pakladok
Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076, Tübingen, Germany.
Adrian
A
Meissner
Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076, Tübingen, Germany.
Jakob
J
Voelkl
Department of Cellular and Molecular Pathology, German Cancer Research Center, Im Neuenheimer Feld, 280, 69120, Heidelberg, Germany.
Hermann-Josef
HJ
Groene
Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076, Tübingen, Germany.
Ioana
I
Alesutan
Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076, Tübingen, Germany.
Florian
F
Lang
D055372:AMP-Activated Protein Kinases / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D005355:Fibrosis / Q000209:etiology / Q000473:pathology*; D007124:Immunoenzyme Techniques; D007674:Kidney Diseases / Q000209:etiology / Q000473:pathology*; D051379:Mice; D018345:Mice, Knockout; D058628:Myofibroblasts / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014517:Ureteral Obstruction / Q000150:complications* / Q000473:pathology
D012333:RNA, Messenger; C548179:Prkaa1 protein, mouse; D055372:AMP-Activated Protein Kinases