Isao Yokoi

ETS-GS, a new antioxidant, ameliorates renal ischemia-reperfusion injury in a rodent model.

BACKGROUND Ischemia-reperfusion (I/R) contributes to acute kidney injury (AKI). On the other hand, anti-oxidative drugs help to prevent renal injury caused by I/R. The current study examined whether a new antioxidant, ETS-GS, inhibits reactive oxygen species (ROS) generation and thereby prevents renal I/R injury in rodent models. METHODS Rats with experimentally-induced renal I/R injury were treated concurrently with an intravenous injection of either ETS-GS or saline. Anesthesia was induced with sevoflurane. RESULTS Histologic examination revealed marked reduction of interstitial congestion, edema, inflammation, and hemorrhage in kidney tissue harvested 24 h after ETS-GS treatment. Renal I/R-induced secretion of nitric oxide (NO) in serum was inhibited by ETS-GS treatment. Furthermore, malondialdehyde (MDA) levels in the kidney were significantly lower in ETS-GS-treated rats with renal I/R. Moreover, when murine macrophage-like RAW264.7 cells were stimulated with antimycin A in the presence or absence of simultaneous ETS-GS treatment, ETS-GS decreased ROS levels. CONCLUSIONS Thus, ETS-GS lowered ROS levels in cultured cells, reduced serum NO levels, decreased renal MDA levels, and protected rats against I/R-induced kidney injury. Given these in vitro and in vivo findings, ETS-GS is a strong candidate for future exploration of therapeutic potential in various human I/R diseases.

Human Atrial Natriuretic Peptide Attenuates Renal Ischemia-Reperfusion Injury

BACKGROUND Acute kidney injury (AKI) is common in the intensive care unit, and one of its primary causes is renal ischemia-reperfusion (I/R) injury. Human atrial natriuretic peptide (hANP) exerts various pharmacologic effects, including renal protection. In the present study, we evaluated the renal protective effect of hANP in a rat model of renal I/R. MATERIALS AND METHODS Male Wistar rats were divided into three groups that received the following treatments: induction of renal I/R (I/R group); continuous intravenous injection of hANP followed 30 min later by induction of renal I/R (hANP+I/R group); and sham treatment (control group). Rats were sacrificed after 60 min of ischemia and 24 h of reperfusion or sham treatment. To evaluate the renal protective effects if hANP, serum blood urea nitrogen (BUN) and creatinine (Cre) concentrations were determined, kidneys were histologically assessed, and serum biomarkers of oxidative stress were evaluated. In addition, antimycin A (AMA)-stimulated RAW264.7 cells were treated with hANP to assess its antioxidant effects. RESULTS Serum BUN and Cre levels were elevated in the I/R group; however, these increases were significantly inhibited in the hANP + I/R group. Similarly, kidney tissue damage observed in the I/R group was attenuated in the hANP + I/R group. In vitro, AMA-stimulated cells treated with hANP showed reduced reactive oxygen species activity compared to cells treated with AMA alone. CONCLUSIONS Our findings indicate that hANP may be effective in the treatment of various types of I/R injuries.

Monocarboxylates and glucose utilization as energy substrates in rat brain slices under selective glial poisoning – a 31P NMR study

We have investigated effects of various energy substrates including glucose, lactate and pyruvate on the recovery of the high energy phosphate levels after high-K+ stimulation in rat brain slices by using 31P NMR. It was found that lactate, pyruvate and glucose almost equally supported the recovery of phosphocreatine (PCr) levels after high-K+ stimulation (60 mM, 8 min) in artificial cerebrospinal fluid (ACSF). In iodoacetic acid (IAA) and fluorocitrate (FC)-pretreated slices, whereas glucose was unable to be utilized, the recovery of the PCr level after high-K+ stimulation in ACSF containing lactate was completely abolished, the recovery of the PCr in ACSF containing pyruvate was unaffected. These results indicate that neurons themselves can utilize pyruvate as an exogenous energy substrate, but not lactate, without glial support. In intact brain, glucose may be metabolized to pyruvate in glial cells and then transported to neurons as an energy substrate. These suggest an astrocyte-neuron pyruvate shuttle mechanism of the brain energy metabolism in vivo.We also investigated the effect of ischemic-preconditioning in FC-pretreated slices, which showed that the PCr levels recovered substantially in ACSF containing lactate after high-K+ stimulation. This indicates that after the preconditioning, such as ischemia, neurons themselves acquired the ability to utilize lactate as an energy substrate.

ETS-GS, a New Anti-Oxidative Drug, Protects Against Lipopolysaccharide-Induced Acute Lung and Liver Injury

BACKGROUND Sepsis is a major health threat that remains refractory to treatment. Impairment of normal cellular function due to oxidative stress is implicated in organ injury during systemic inflammatory responses. We investigated whether the new anti-oxidative drug, ETS-GS, could inhibit secretion of cytokines and mono-nitrogen oxides, thus reducing organ damage in a rat model of lipopolysaccharide-induced sepsis. MATERIALS AND METHODS Lipopolysaccharide was administered intravenously to male Wistar rats in order to establish a rat model of systemic inflammation. These rats were challenged with or without intravenous ETS-GS. Mouse macrophage RAW264.7 cells were stimulated with lipopolysaccharide, with or without simultaneous ETS-GS treatment, in order to elucidate the mechanism of action. RESULTS Histologic examination revealed that ETS-GS markedly reduced lipopolysaccharide-induced interstitial edema and leukocytic infiltration in lung tissue, and lipopolysaccharide-induced bleeding and leukocytic infiltration in liver tissue harvested 12 h after treatment. Cytokine (interleukin-6 and tumor necrosis factor-α) secretion was strongly induced by lipopolysaccharide; this induction was similarly inhibited by ETS-GS treatment. Likewise, lipopolysaccharide-induced secretion of mono-nitrogen oxides was inhibited by ETS-GS. In the in vitro studies, ETS-GS administration inhibited IκB phosphorylation. CONCLUSION ETS-GS blocked the lipopolysaccharide-induced inflammatory response and protected against acute lung and liver injury normally associated with endotoxemia in this rat model of systemic inflammation. Further, this protection may be mediated through the inhibition of nuclear factor κ-light-chain-enhancer of activated B cells activation. Our results suggest that ETS-GS is a potential therapeutic agent for sepsis.

Vitamin E derivative ETS-GS reduces liver ischemia-reperfusion injury in rats.

BACKGROUND Ischemic liver injury is often the result of surgical procedures such as liver transplantation and hepatic resection. Liver damage occurs after reperfusion, leading to increased systemic inflammation. Recent studies have reported that vitamin E and glutathione can ameliorate ischemia-reperfusion (I/R) injury. In the present study, we evaluated the ability of a new vitamin E derivative, ETS-GS, to improve liver I/R injury. MATERIALS AND METHODS Male Wistar received a subcutaneous injection of ETS-GS (10 mg/kg) or saline before experimentally-induced liver I/R injury or sham treatment. The rats were sacrificed after the 60-min ischemia and 24-h reperfusion. Histology and serum levels of cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-6, and high-mobility group box 1 (HMGB1) protein] and liver enzymes were determined to evaluate the protective effects of ETS-GS. RESULTS We found that ETS-GS treatment attenuated I/R-induced histologic alterations, reduced levels of liver enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH). In addition, ETS-GS treatment decreased serum cytokine levels. CONCLUSIONS Taken together, our results demonstrate that ETS-GS attenuates I/R injury in a rat model and suggests that ETS-GS may exert anti-inflammatory effects. Accordingly, ETS-GS may have therapeutic potential to treat various clinical conditions involving I/R injury.

The impact of oxidative stress levels on the clinical effectiveness of sivelestat in treating acute lung injury: an electron spin resonance study.

BACKGROUND Sivelestat, a neutrophil elastase inhibitor, has been used to treat acute lung injury (ALI) with varying levels of clinical success. Variable baseline levels of oxidative stress in patients with ALI have been proposed as one explanation for inconsistent results. METHODS Using a bedside electron spin resonance spectrometer, we evaluated electron spin resonance signal intensities of serum ascorbyl free radicals supplemented with dimethyl sulfoxide (AFR/DMSO) in patients with ALI. RESULTS We found a positive correlation between AFR/DMSO and ascorbate levels, suggesting that serum AFR/DMSO measurements may serve as a surrogate for real-time assessments of oxidative stress. Levels of AFR/DMSO in patients with ALI were significantly lower than those found in healthy controls. Stratified analyses revealed that baseline AFR/DMSO levels were significantly lower in patients with ALI who failed to respond to sivelestat compared with those who did respond. CONCLUSIONS Our results suggest that the clinical efficacy of sivelestat is dependent on baseline oxidative stress levels.

Neuroprotective effects of ethyl pyruvate on brain energy metabolism after ischemia depend on glial cells: A 31P-NMR study

Neuroprotective effects of ethyl pyruvate (EP), a stable derivative of pyruvate, on energy metabolism of rat brain exposed to ischemia were investigated by 31P-nuclear magnetic resonance (31P-NMR) spectroscopy.Brain slices (400 m) were incubated in standard artificial cerebrospinal fluid (ACSF) with 2 mM EP (EP+) or ACSF only (EP-) at 25 ◦C. Brain slices were exposed to ischemia by halting the perfusion for 1 h. Levels of high-energy phosphates, phosphocreatine (PCr) and -ATP, relative to pre-ischemic levels were measured by 31P-NMR.Recovery of PCr after reperfusion was significantly greater in EP+ than in EP−. When brain slices were pretreated with 100 M fluorocitrate, an astrocytic poison, such difference in recovery of PCr was not observed. These results indicated that neuroprotective effects of EP depend on the presence of astrocytes. EP might be neuroprotective via functions of astrocytes as a neuro-protectant from oxidative stress and/or a provider of lactate by glycolysis.