These data indicate that the aged Nrf2-deficient female mice develop lupus-like autoimmune nephritis and suggest that nrf2 is one of the genes determining susceptibility to autoimmune disease. Analysis of nephritis in the Nrf2-deficient female mouse may clarify the mechanisms leading to the development of lupus disease.

The transcription factor Nrf2 regulates the expression of antioxidant genes. Hyperglycemia‐induced oxidative stress is involved in the pathogenesis of diabetes and its complications. However, little is known about the protective role of Nrf2 in diabetes. To gain insight into the protective role of Nrf2 in diabetes we treated Nrf2 knockout (Nrf2 KO) mice with streptozotocin (STZ). The STZ Nrf2 KO mice did not develop renal hyperfiltration, which was observed in the STZ‐treated wild‐type (STZ WT) mice, but renal function gradually deteriorated over the 10‐week observation period. Urinary excretion of nitric oxide metabolites and the occurrence of 8‐nitroguanosine, which was detected in glomerular lesions, were increased in STZ Nrf2 KO mice during the early stages after treatment. In vivo electron paramagnetic resonance analysis revealed an accelerated rate of decay of the 3‐carbamoyl‐2,2,5,5‐tetramethylpyrrolidine‐1‐oxyl spin probe signal in STZ Nrf2 KO mice. The addition of superoxide dismutase prolonged the half‐life of the signal, which suggested that increased oxygen radical formation occurred in the STZ Nrf2 KO mice. These results suggested that hyperglycemia increased oxidative and nitrosative stress and accelerated renal injury in the Nrf2 KO mice and that Nrf2 serves as a defense factor against some diabetic complications.

The ultimate objective of nanoparticle-based therapy is to functionalize nanomedicines in a micro-disease environment without any side effects. Here, we reveal that our pH-responsive nitroxide radical-containing nanoparticles (RNP(pH)) disintegrate within the renal acidic lesion and act as scavengers of reactive oxygen species (ROS), leading to a relief of acute kidney injury (AKI). RNP(pH) was prepared using amphiphilic block copolymers possessing 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) moieties via amine linkage as a side chain of the hydrophobic segment. The self-assembled RNP(pH) disintegrated at pH below 7.0 because of a protonation of the amino groups in the hydrophobic core of the nanoparticles, thereby resulting in an improvement in ROS scavenging activity. Using a renal ischemia-reperfusion AKI model in mice, the therapeutic effect of RNP(pH) on ROS damage was evaluated. Unlike the RNP without pH-triggered disintegration (RNP(Non-pH)), the RNP(pH) showed extremely high ROS scavenging activity and renal protective effects. It is interesting to note that the side effect of nitroxide radicals was markedly suppressed due to the compartmentalization of nitroxide radicals in the core of RNP(pH) in untargeted area. The morphology changes in RNP(pH) were confirmed by analyzing electron spin resonance spectra, and these findings provide the evidence of the real therapeutic effect of the environment-sensitive specific disintegration of nanoparticles in vivo.

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For the imaging of low pH circumstances in vivo, a pH-sensitive radical-containing-nanoparticle (RNP), which has an intense electron paramagnetic resonance (EPR) signal, was designed and developed using a self-assembling amphiphilic block copolymer (PEG-b-PCTEMPO) composed of a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic poly(chloromethylstyrene) (PCMS) segment in which the chloromethyl groups were converted to 2,2,6,6-tetramethylpiperidinyloxys (TEMPOs) via the amination of PEG-b-PCMS block copolymer with 4-amino-TEMPO. This RNP formed core-shell-type micelles in the physiological environment, and the cumulant average diameter of the RNP was about 50 nm. The cytotoxicity and acute toxicity studies for the RNP revealed that the median inhibitory concentration (IC(50)) of TEMPO radicals in RNP core and median lethal dose (LD(50)) of RNP were >8 mmol N(TEMPO)/L and >600 mg/kg (>960 mumol N(TEMPO)/kg), respectively, indicating fairly low toxicity. The blood circulation of the RNP was evaluated using ICR mice. Contrary to the rapid clearance of low-molecular-weight TEMPO derivatives such as 4-hydroxy-TEMPO (TEMPOL) from the bloodstream, the EPR signal of the RNP remained for a fairly long period of time. Actually, the signal was observed in the blood for more than 2 h, as monitored by EPR spectroscopy. The compartmentalization of the TEMPO radicals in the RNP core improved the stability in the bloodstream. Since an amino group was introduced in each repeating unit of the PCTEMPO segment, the disintegration of the RNP was caused by the protonation of the amino groups in response to the acidic pH environment (pH < 6.0), as confirmed by the dynamic light scattering (DLS) measurements. In addition, a drastic change in the EPR spectra from broad to sharp triplet was observed, accompanying the disintegration. This change was based upon the mobility of the TEMPO moieties covalently conjugated in the hydrophobic segment, which was confirmed by the rotational correlation time of the TEMPO moieties on the PCTEMPO segment. Note that the peak intensity of the EPR signal increased at around the phase transition point (ca. pH = 6.0). When pH-sensitive RNP solutions at pH values 5.6 and 7.4 were visualized using an L-band EPR imaging system, the phantom images showed a remarkable on-off regulation in response to the acidic pH environment. These results demonstrate that pH-sensitive RNPs are expected to serve as nanoprobes for the in vivo EPR imaging of low pH circumstances.

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Ulcerative colitis (UC) is a chronic inflammatory bowel disease that may become intractable when treated with conventional medications such as aminosalicylates, corticosteroids, and azathioprine. The herbal medicine Qing Dai has traditionally been used in Chinese medicine to treat UC patients, but there is a lack of published data on the efficacy of Qing Dai in UC treatment. We report several cases of patients with intractable UC who take Qing Dai in a retrospective observational study. Furthermore, we explore the mechanisms of action of Qing Dai. Nine patients with active UC who received conventional medications but wished to receive Qing Dai as an alternative medication were included in our analysis. The UC severity level was determined based on the clinical activity index (CAI). Additionally, 5 of the 9 patients were endoscopically evaluated according to the Matts grading system. Each patient received 2 g/d of Qing Dai orally and continued taking other medications for UC as prescribed. Electron spin resonance was applied to explore the mechanisms of action of Qing Dai. After 4 mo of treatment with Qing Dai, the CAI score decreased from 8.3 ± 2.4 to 2.4 ± 3.4 (mean ± SD; P < 0.001). Similarly, the endoscopic Matts grade decreased from 3.4 ± 0.5 to 2.2 ± 0.8 (P = 0.02). Six of 7 patients who were on prednisolone upon enrollment in the study were able to discontinue this corticosteroid. Electron spin resonance revealed that Qing Dai possesses strong hydroxyl radical scavenging activity. Qing Dai showed significant clinical and endoscopic efficacy in patients who failed to respond to conventional medications. Scavenging of hydroxyl radicals appears to be a potential mechanism through which Qing Dai acts, but the significance of the scavenging ability of Qing Dai with respect to the anti-inflammatory effect in UC patients warrants further investigation.

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