Abstract
Octreotide exerts a protective effect in hepatic ischemia-reperfusion (HIR) injury. However, whether octreotide preconditioning could also reduce acute kidney injury (AKI) after HIR is unknown. This study was designed to investigate the role of octreotide in AKI after HIR. Male Sprague-Dawley rats were pretreated with octreotide or octreotide combined with 3-methyladenine (autophagy inhibitor, 3MA). Plasma creatinine, inflammation markers (e.g., TNF-α and IL-6 etc.), apoptosis, autophagy and phosphorylation of protein kinase B/mammalian target of rapamycin/p70 ribosomal S6 kinase (Akt/mTOR/p70S6K) in the kidney were measured after 60 minutes of liver ischemia and 24 hours of reperfusion for each rat. Octreotide pretreatment significantly preserved renal function and reduced the severity of renal injury. Moreover, octreotide alleviated inflammation and apoptosis in the kidney after HIR. Additionally, octreotide induced autophagy and autophagy inhibition with 3MA markedly reversed the renoprotective, anti-inflammatory and anti-apoptotic effects of octreotide after HIR. Finally, octreotide abrogated the activation of phosphorylation of Akt, mTOR and p70S6K in the kidney after HIR. Our results indicate that octreotide reduced renal injury after HIR due to its induction of autophagy. The enhancement of autophagy may be potentially linked to the octreotide mediated Akt/mTOR/p70S6K pathway deactivation and reduction of kidney inflammation and apoptosis after HIR.
Highlights
Autophagy is an evolutionally conserved intracellular degradation pathway responsible for maintaining cellular homeostasis[12]
We demonstrated for the first time that octreotide reduces renal inflammation, apoptosis and protects against acute kidney injury (AKI) after hepatic ischemia-reperfusion (HIR)
Octreotide abrogated the activation of the Akt/mTOR/p70S6K signaling pathway in the kidney after HIR. These results support the idea that octreotide reduces AKI after HIR via its induction of autophagy
Summary
Autophagy is an evolutionally conserved intracellular degradation pathway responsible for maintaining cellular homeostasis[12]. Inhibition of autophagy worsens renal tubular injury and renal function, supporting the concept that autophagy is renoprotective[14,15,16] It appears that autophagy is important in AKI and is a potential therapeutic target in the pathogenesis of AKI. The somatostatin receptor type 2 (Sst2), which octreotide targets, was shown to deactivate the PI3K pathway by inhibiting p85 tyrosine phosphorylation and decreasing Akt phosphorylation[19]. Based on these findings, we hypothesized that octreotide-induced autophagy in the renal proximal tubules will lessen renal tubular injury and preserve renal function after HIR by inhibiting the PI3K/Akt/mTOR/p70S6K signaling pathway. We examined the pharmacological function and potential mechanisms of octreotide in AKI after HIR in a rat model
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