UMIN000003878.

High mortality of acute kidney injury (AKI) is associated with acute lung injury (ALI), which is a typical complication of AKI. Although it is suggested that dysregulation of lung salt and water channels following AKI plays a pivotal role in ALI, the mechanism of its dysregulation has not been elucidated. Here, we examined the involvement of a typical oxidative stress-inducing uremic toxin, indoxyl sulfate (IS), in the dysregulation of the pulmonary predominant water channel, aquaporin 5 (AQP-5), in bilateral nephrectomy (BNx)-induced AKI model rats. BNx evoked AKI with the increases in serum creatinine (SCr), blood urea nitrogen (BUN) and serum IS levels and exhibited thickening of interstitial tissue in the lung. Administration of AST-120, clinically-used oral spherical adsorptive carbon beads, resulted in a significant decrease in serum IS level and thickening of interstitial tissue, which was accompanied with the decreases in IS accumulation in various tissues, especially lung. Interestingly, a significant decrease in AQP-5 expression of lung was observed in BNx rats. Moreover, the BNx-induced decrease in pulmonary AQP-5 protein expression was markedly restored by oral administration of AST-120. These results suggest that BNx-induced AKI causes dysregulation of pulmonary AQP-5 expression, in which IS could play a toxico-physiological role as a mediator involved in renopulmonary crosstalk.

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Background:The present study explored the nephropreventive effect of shikonin, a naturally occurring herbal medicine, possessing proteasome inhibitory and antioxidant effects via activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) against lipopolysaccharide (LPS)induced septic acute kidney injury (AKI) using a murine model. Methods:Septic AKI was induced in C57BL mice by intraperitoneal administration of LPS (20 mg/kg). Shikonin (5 mg/kg) was administered intraperitoneally to mice 1 hr before the LPS treatment. Development of renal injury, Nrf2 activation and antioxidative responses (heme oxygenase-1; HO-1 and NAD(P)H: quinone oxidoreductase; NQO1) in the kidney of LPS-treated mice with or without shikonin were compared.Results: Serum levels of Interleukin (IL)-6 and tumor necrosis factor (TNF)-α were markedly elevated in LPStreated mice. However, shikonin administration resulted in a significant decrease in the normally elevated levels of these cytokines. Survival rates of LPS-treated mice and LPS-and shikonin-treated mice were 36 and 82%, respectively. Serum creatinine and blood urea nitrogen (BUN) markedly increased in LPS-treated mice, whereas shikonin improved these renal function markers. Histochemical examination revealed that glomerular and tubular injuries of LPS-treated mice were reduced by shikonin. Serum hydroperoxide and renal malondialdehyde levels were markedly increased by LPS treatment, whereas shikonin significantly suppressed these oxidative stress markers. Shikonin administration induced a marked expression of Nrf2 in the renal nuclear fraction, which was associated with significant increases in mRNA expression of HO-1 and NQO1. Conclusion:These results suggest that shikonin could be a potential nephropreventive agent against septic AKI, at least in part, through the transient activation of renal Nrf2 followed by induction of its downstream antioxidant molecules.