Contrast-induced nephropathy (CIN), caused by a combination of the direct tubular toxicity of contrast media, a reduction in medullary blood flow, and the generation of reactive oxygen species, is a serious clinical problem. A need exists for effective strategies for its prevention. Thioredoxin-1 (Trx) is a low-molecular-weight endogenous redox-active protein with a short half-life in the blood due to renal excretion. We produced a long-acting form of Trx as a recombinant human albumin-Trx fusion protein (HSA-Trx) and examined its effectiveness in preventing renal injury in a rat model of ioversol-induced CIN. Compared with saline, a mixture of HSA and Trx, or Trx alone, intravenous HSA-Trx pretreatment significantly attenuated elevations in serum creatinine, blood urea nitrogen, and urinary N-acetyl-β-D-glucosaminidase along with the decrease in creatinine clearance. HSA-Trx also caused a substantial reduction in the histological features of renal tubular injuries and in the number of apoptosis-positive tubular cells. Changes in the markers 8-hydroxy deoxyguanosine and malondialdehyde indicated that HSA-Trx significantly suppressed renal oxidative stress. In HK-2 cells, HSA-Trx decreased the level of reactive oxygen species induced by hydrogen peroxide, and subsequently improved cell viability. Thus, our results suggest that due to its long-acting properties, HSA-Trx has the potential to effectively prevent CIN.

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Rhabdomyolysis-associated acute kidney injury (AKI) is a serious life-threatening condition. As such, more effective strategies are needed for its prevention. Thioredoxin-1 (Trx), a redox-active and macrophage migration inhibitory factor (MIF) modulating protein, has a short retention time in the blood. We examined the renoprotective effect of long acting Trx that was genetically fused with human serum albumin (HSA-Trx) against glycerol-induced AKI. An intravenous HSA-Trx pre-treatment attenuated the glycerol-induced decline in renal function, compared to a PBS, HSA or Trx alone. HSA-Trx caused a reduction in the tubular injuries and in the number of apoptosis-positive tubular cells. Renal superoxide, 8-hydroxy deoxyguanosine, nitrotyrosine and the plasma Cys34-cysteinylated albumin were clearly suppressed by the HSA-Trx treatment. Prior to decreasing TNF-α and IL-6, HSA-Trx suppressed an increase of plasma MIF level. In LLC-PK1 cells, HSA-Trx decreased the level of reactive oxygen species and lactate dehydrogenase release induced by myoglobin. HSA-Trx treatment resulted in a threefold increase in the survival of lethal glycerol-treated mice. The post-administration of HSA-Trx at 1 and 3 hr after glycerol injection exerted a significant renoprotective effect. These results suggest HSA-Trx has potential for use in the treatment of rhabdomyolysis-associated AKI via its extended effects of modulating oxidative stress and MIF.

Idiopathic pulmonary fibrosis (IPF) is thought to involve inflammatory cells and reactive oxygen species (ROS), such as superoxide anion radical (O 2 ·2). There is currently no effective treatment of IPF. We previously developed a human serum albumin (HSA)-thioredoxin 1 (Trx) fusion protein (HSA-Trx) designed to overcome the unfavorable pharmacokinetic and short pharmacological properties of Trx, an antioxidative and anti-inflammatory protein.In this study, we examined the therapeutic effect of HSA-Trx on an IPF animal model of bleomycin (BLM)-induced pulmonary fibrosis. A pharmacokinetic study of HSA-Trx or Trx in BLM mice showed that the plasma retention and lung distribution of Trxc was markedly improved by fusion with HSA. A weekly intravenous administration of HSA-Trx, but not Trx, ameliorated BLM-induced fibrosis, as evidenced by a histopathological analysis and pulmonary hydroxyproline levels. HSA-Trx suppressed active-transforming growth factor (TGF)-b levels in the lung and inhibited the increase of inflammatory cells in bronchoalveolar lavage fluid, pulmonary inflammatory cytokines, and oxidative stress markers. An in vitro EPR experiment using phosphate-buffered saline-stimulated neutrophils confirmed the O 2 ·2 scavenging ability of HSA-Trx. Furthermore, post-treatment of HSA-Trx had a suppressive effect against BLM-induced fibrosis. These results suggest that HSA-Trx has potential as a novel therapeutic agent for IPF, because of its long-acting antioxidative and anti-inflammatory modulation effects.

Overdoses of acetaminophen (APAP) are a major cause of acute liver failure. N-Acetylcysteine (NAC) is the standard therapy for patients with such an overdose because oxidative stress plays an important role in the pathogenesis of APAP-induced hepatitis. However, NAC is not sufficiently efficacious. We previously developed a recombinant human serum albumin (HSA)-thioredoxin 1 (Trx) fusion protein (HSA-Trx), designed to overcome the unfavorable pharmacokinetic and short pharmacological properties of Trx, an endogenous protein with antioxidative and anti-inflammatory properties. In this study, we investigated the therapeutic impact of HSA-Trx in mice with APAP-induced hepatitis. The systemic administration of HSA-Trx significantly improved the survival rate of mice treated with a lethal dose of APAP compared with saline. HSA-Trx strongly attenuated plasma transaminases in APAP-induced hepatitis mice compared with HSA or Trx, components of the fusion protein. HSA-Trx also markedly caused a diminution in the histopathological features of hepatic injuries and the number of apoptosis-positive hepatic cells. In addition, an evaluation of oxidative stress markers and plasma cytokine and chemokine levels clearly showed that HSA-Trx significantly improved the breakdown of hepatic redox conditions and inflammation caused by the APAP treatment. HSA-Trx also significantly decreased oxidative and nitrosative/nitrative stress induced by SIN-1 in vitro. Finally, HSA-Trx, but not the NAC treatment at 4 h after APAP injection, significantly inhibited the elevation in plasma transaminase levels. In conclusion, the findings suggest that HSA-Trx has considerable potential for use as a novel therapeutic agent for APAP-induced hepatitis, due to its long-lasting antioxidative and anti-inflammatory effects.