Overexpression of stanniocalcin-1 inhibits reactive oxygen species and renal ischemia/reperfusion injury in mice

Abstract

Reactive oxygen species, endothelial dysfunction, inflammation, and mitogen-activated protein kinases have important roles in the pathogenesis of ischemia/reperfusion kidney injury. Stanniocalcin-1 (STC1) suppresses superoxide generation in many systems through induction of mitochondrial uncoupling proteins and blocks the cytokine-induced rise in endothelial permeability. Here we tested whether transgenic overexpression of STC1 protects from bilateral ischemia/reperfusion kidney injury. This injury in wild type mice caused a halving of the creatinine clearance; severe tubular vacuolization and cast formation; increased infiltration of macrophages and T cells; higher vascular permeability; greater production of superoxide and hydrogen peroxide; and higher ratio of activated ERK/activated JNK and p38, all compared to sham-treated controls. Mice transgenic for human STC1 expression, however, had resistance to equivalent ischemia/reperfusion injury indicated as no significant change from controls in any of these parameters. Tubular epithelial cells in transgenic mice expressed higher mitochondrial uncoupling protein 2 and lower superoxide generation. Pre-treatment of transgenic mice with paraquat, a generator of reactive oxygen species, before injury restored the susceptibility to ischemia/reperfusion kidney injury, suggesting that STC1 protects by an anti-oxidant mechanism. Thus, STC1 may be a therapeutic target for ischemia/reperfusion kidney injury.

Stanniocalcin-1 Inhibits Renal Ischemia/Reperfusion Injury via an AMP-Activated Protein Kinase-Dependent Pathway

“…Indeed, SIRT3 Tg kidneys express higher baseline levels of UCP2 relative to WT, which correlates with lower baseline superoxide generation ( Figure 13), similar to observations that we made in STC1 Tg kidneys. 16 As observed in WT mice, where pretreatment with CC attenuated I/R-induced UCP2 and SIRT3 expression, pretreatment of STC1 Tg mice with CC decreases the expression of UCP2 and SIRT3 at both baseline and post-I/R (Figure 8). Similarly, in cultured HEK cells, treatment with CC abolishes STC1-induced expression of UCP2 and SIRT3 ( Figure 6B).…”

“…Tg overexpression of STC1 confers resistance to I/R kidney injury through suppression of oxidant stress and inflammation, 16 whereas acute knockdown of STC1 in the kidney leads to severe proximal tubule injury and kidney failure. 30 AMPK regulates cellular metabolism, and recent studies suggest that pretreatment with AMPK activators (5-aminoimidazol-4-carboxamide-1-b-d-ribofuranoside and metformin) may protect from I/R injury.…”

“…Inhibition of AMPK in STC1 Tg Mice Restores Susceptibility to I/R Kidney Injury To show that activation of AMPK mediates the renoprotective effects that we observed in STC1 Tg mice, 16 we pretreated these mice with CC or vehicle before I/R. Pretreatment of STC1 Tg mice with CC diminished AMPK activity ( Figure 7A) and resulted in severe kidney injury after I/R, which was characterized by cellular vacuolization, tubular dilation, and cast formation (predominantly in the cortex) ( Figure 7B), similar to those changes observed in WT kidneys after I/R, increased serum creatinine, decreased CrCl and urine output ( Figure 7C), and increased superoxide and H 2 O 2 generation ( Figure 7D).…”

“…Indeed, we have recently shown that transgenic (Tg) overexpression of STC1 protects from I/R kidney injury in mice through inhibition of ROS and inflammation. 16 Current observations reveal increased activity of AMP-activated protein kinase (AMPK) in STC1 Tg kidneys. AMPK regulates cellular metabolism and is a key component of the cellular adaptive responses to ischemia in the kidney.…”

“…13 Mammalian STC2 is also ubiquitously expressed; cumulative evidence suggests that it also acts in an autocrine/paracrine manner and that its functions are linked to the endoplasmic reticulum. 14 STC1 suppresses superoxide generation through induction of uncoupling proteins (UCPs), 15,16 stabilizes endothelial barrier function, 17 and diminishes macrophage mobility and response to chemoattractants. 18 Thus, STC1 may target core pathways in the pathogenesis of I/R kidney injury.…”