The behavior of ROS-scavenging nanoparticles in blood

Antioxidative Self-Assembling Nanoparticles Attenuate the Development of Steatohepatitis and Inhibit Hepatocarcinogenesis in Mice

Oxidative stress (OS) contributes to nonalcoholic steatohepatitis (NASH) and hepatocarcinogenesis. We investigated whether antioxidative self-assembling nanoparticles (SMAPoTN) could reduce the development of NASH and hepatocellular carcinoma (HCC) in p62/Sqstm1 and Nrf2 double knockout (DKO) mice and studied protective mechanisms. We measured disease development in male DKO mice fed a normal chow (NASH model) or a 60% high-fat diet (HFD; HCC model) with or without SMAPoTN administration for 26 weeks. SMAPoTN inhibited liver fibrosis in both groups and prevented HCC development (0% vs. 33%, p < 0.05) in the HFD group. SMAPoTN reduced OS, inflammatory cytokine signaling, and liver fibrosis. RNA-sequencing revealed that SMAPoTN decreased endoplasmic reticulum stress signaling genes in both groups, HCC driver genes, and cancer pathway genes, especially PI3K-AKT in the HFD groups. In the SMAPoTN treatment HFD group, serum lipopolysaccharide levels and liver lipopolysaccharide-binding protein expression were significantly lower compared with those in the nontreatment group. SMAPoTN improved the α-diversity of gut microbiota, and changed the microbiota composition. Oral SMAPoTN administration attenuated NASH development and suppressed hepatocarcinogenesis in DKO mice by improving endoplasmic reticulum stress in the liver and intestinal microbiota. SMAPoTN may be a new therapeutic option for NASH subjects and those with a high HCC risk.

Self-Assembling Antioxidants for Ischemia-Reperfusion Injuries

Significance: Ischemia-reperfusion (IR) injury is a major component of severe damage in vascular occlusion during stroke, myocardial infarction, surgery, and organ transplantation, and is exacerbated by the excessive generation of reactive oxygen species (ROS), which occurs particularly during reperfusion. With the aging of the population, IR injury is becoming a serious problem in various organs, such as the kidney, brain, and heart, as well as in the mesenteric capillaries. Recent Advances: To prevent reperfusion injuries, natural and synthetic low-molecular-weight (LMW) antioxidants have been well studied. Critical Issues: However, these LMW antioxidants have various problems, including adverse effects due to excessive cellular uptake and their rapid clearance by the kidney, and cannot fully exert their potent antioxidant capacity in vivo. Future Directions: To overcome these problems, we designed and developed redox polymers with antioxidants covalently conjugated with them. These polymers self-assemble into nanoparticles in aqueous media, referred to as redox nanoparticles (RNPs). RNPs suppress their uptake into normal cells, accumulate at inflammation sites, and effectively scavenge ROS in damaged tissues. We had developed two types of RNPs: RNP^N, which disintegrates in response to acidic pH; and RNP^O, which does not collapse, regardless of the environmental pH. Utilizing the pH-sensitive and -insensitive characteristics of RNP^N and RNP^O, respectively, RNPs were found to exhibit remarkable therapeutic effects on various oxidative stress disorders, including IR injuries. Thus, RNPs are promising nanomedicines for use as next-generation antioxidants. This review summarizes the therapeutic impacts of RNPs in the treatment of kidney, cerebral, myocardial, and intestinal IR injuries. Antioxid. Redox Signal. 36, 70-80.

Newly Developed Self-Assembling Antioxidants as Potential Therapeutics for the Cancers

Elevated reactive oxygen species (ROS) have been implicated as significant for cancer survival by functioning as oncogene activators and secondary messengers. Hence, the attenuation of ROS-signaling pathways in cancer by antioxidants seems a suitable therapeutic regime for targeting cancers. Low molecular weight (LMW) antioxidants such as 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO), although they are catalytically effective in vitro, exerts off-target effects in vivo due to their size, thus, limiting their clinical use. Here, we discuss the superior impacts of our TEMPO radical-conjugated self-assembling antioxidant nanoparticle (RNP) compared to the LMW counterpart in terms of pharmacokinetics, therapeutic effect, and adverse effects in various cancer models.

Management of tumor growth and angiogenesis in triple-negative breast cancer by using redox nanoparticles

In cancer, angiogenesis is a critical phenomenon of nascent blood vessel development to facilitate the oxygen and nutrient supply prerequisite for tumor progression. Therefore, targeting tumors at the angiogenesis step may be significant to prevent their advanced progression and metastasis. Although angiogenesis inhibitors can limit the further growth of tumors, complete eradication of tumors may not be possible by monotherapy alone. Therefore, a therapeutic regimen targeting both tumor growth and its vasculature is essential. Because reactive oxygen species (ROS) are fundamental to both angiogenesis and tumor growth, the use of antioxidants may be an effective dual approach to inhibit tumors. We previously confirmed that our original antioxidant nitroxide radical-containing nanoparticles (RNPs) such as pH-sensitive RNP^N_, and pH-insensitive RNP^O, effectively attenuates the tumorigenic and metastasis potentials of triple-negative breast cancer. In this study, we further investigated the efficacy of RNPs to limit the tumor progression by inhibiting the ROS-regulated cancer angiogenesis in a triple-negative breast cancer model. Here, we confirmed that RNPs significantly inhibited in vitro angiogenesis, attributed to the downregulation of the ROS-regulated angiogenesis inducer, vascular endothelial growth factor (VEGF) in the breast cancer cell line (MDA-MB231) and human umbilical vein endothelial cells (HUVEC), which was consistent with decreased cellular ROS. TEMPOL, a low-molecular-weight (LMW) control antioxidant, exhibited anti-angiogenic effects accompanied by cytotoxicity to the endothelial cells. In an in vivo xenograft model for breast cancer, RNPs exerted significant anti-tumor effect due to the decreased expression of tumor VEGF, which prevented accumulation of the endothelial cells. It should be noted that such efficacy of RNPs was obtained with negligible off-target effects. On the other hand, TEMPOL, because of its size, exerted anti-angiogenesis effect accompanied with injuries to the kidneys, which corroborated with previous reports. Our findings imply that RNPs are more potential antioxidants than their LMW counterparts, such as TEMPOL, for the management of breast cancers.

Redox injectable gel protects osteoblastic function against oxidative stress and suppresses alveolar bone loss in a rat peri-implantitis model

Dental implant surgery is a routine treatment in clinical dentistry. However, implant surgery is associated with an increased risk of bacterially induced peri-implantitis and the production of reactive oxygen species (ROS), with no established treatment. We recently designed a new redox injectable gel (RIG) containing nitroxide radicals for the treatment of peri-implantitis. Here, we investigated the antioxidative effect of RIG as a preventive therapy for ROS-associated peri-implantitis in a rat model of alveolar bone resorption and in vitro. In each rat, the maxillary first molar tooth was replaced with a screw-type implant, and rats were assigned to one of four groups: an implant alone, an implant with infection, implant with infection and treatment with nRIG (a non-nitroxide radical-containing injectable hydrogel) or RIG. We confirmed the long-term retention of RIG in the peri-implant region and found that RIG significantly protected the alveolar bone volume and decreased lipid peroxidation. In culture, we found that RIG restored osteoblast proliferation and differentiation in the presence of hydrogen peroxide (H₂O₂)-induced oxidative stress. Moreover, using a malondialdehyde assay of lipid peroxidation, we found that RIG suppressed oxidative stress in H₂O₂-treated rat osteoblasts. Overall, RIG is anticipated as a prophylactic treatment for peri-implantitis and may help preserve oral function. Statement of Significance 1. Implant surgery is associated with an increased risk of bacterially induced peri-implantitis and the production of reactive oxygen species (ROS). We designed a novel redox injectable gel (RIG) containing nitroxide radicals for the treatment of peri-implantitis. In this study, we investigated the antioxidative effect of RIG as a preventive therapy for ROS-associated peri-implantitis in a rat model and in vitro. 2. We showed that treatment with RIG reduces oxidative damage in a rat peri-implantitis model, protecting against bone resorption and a loss of bone density. We showed that RIG inhibits H₂O₂-mediated decreases in proliferation, osteoblast differentiation, and mineralization, and also against lipid peroxidation in vitro. Our results indicate that RIG has an antioxidative effect of peri-implantitis.

Redox nanoparticles: synthesis, properties and perspectives of use for treatment of neurodegenerative diseases

Oxidative stress (OS) and nitrative stress (NS) accompany many diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Antioxidants have been proposed to counteract OS/NS in these diseases. Nevertheless, the effects of antioxidants are limited and new, more efficient antioxidants are searched for. Redox-active nanoparticles (RNPs), containing antioxidants create a new therapeutical perspective. This review examines the recent literature describing synthesis and potential applications of cerium oxide RNPs, boron cluster-containing and silica containing RNPs, Gd₃N_@C₈₀ encapsulated RNPs, and concentrates on nitroxide-containing RNPs. Nitroxides are promising antioxidants, preventing inter alia glycation and nitration, but their application poses several problems. It can be expected that application of RNPs containing covalently bound nitroxides, showing low toxicity and able to penetrate the blood-brain barrier will be more efficient in the treatment of neurodegenerative disease, in particular AD and PD basing on their effects in cellular and animal models of neurodegenerative diseases.

Scavenging of reactive oxygen and nitrogen species with nanomaterials

Reactive oxygen and nitrogen species (RONS) are essential for normal physiological processes and play important roles in cell signaling, immunity, and tissue homeostasis. However, excess radical species are implicated in the development and augmented pathogenesis of various diseases. Several antioxidants may restore the chemical balance, but their use is limited by disappointing results of clinical trials. Nanoparticles are an attractive therapeutic alternative because they can change the biodistribution profile of antioxidants, and possess intrinsic ability to scavenge RONS. Herein, we review the types of RONS, how they are implicated in several diseases, and the types of nanoparticles with inherent antioxidant capability, their mechanisms of action, and their biological applications.

Nitroxide radical-containing nanoparticles attenuate tumorigenic potential of triple negative breast cancer

The critical importance of reactive oxygen species (ROS) as oncogene activators and essential secondary messengers in cancer cell survival have been widely reported. Since oxidative stress has been implicated as being pivotal in various cancers, antioxidant therapy seems an apt strategy to abrogate ROS-mediated cellular processes to attenuate cancers. We therefore synthesized ROS scavenging nitroxide radical-containing nanoparticles (RNPs); pH insensitive RNP^O and pH sensitive RNP^N, to impede the proliferative and metastatic characteristics of the triple negative breast cancer cell line, MDA-MB-231, both in vitro and in vivo. RNPs significantly curtailed the proliferative and clonogenic potential of MDA-MB-231 and MCF-7 cell lines. Inhibition of ROS-mediated migratory and invasive characteristics of MDA-MB-231, via down regulation of NF-κB and MMP-2, was also confirmed. Furthermore, a significant anti-tumor and anti-metastatic potential of RNPs was observed in an MDA-MB-231 mouse xenograft model. Such tumoricidal effects of RNPs were attained with negligible adverse effects, compared to conventional low molecular weight antioxidants, TEMPOL. Thus, the tumoricidal effects of RNPs are suggestive of insights on precedence of nanoparticle-based therapeutics over current low molecular weight antioxidants to curtail ROS-induced tumorigenesis of various cancers.

Nitroxide radical polymers – a versatile material class for high-tech applications

A comprehensive summary of synthetic strategies for the preparation of nitroxide radical polymer materials and a state-of-the-art perspective on their latest and most exciting applications.

TEMPO-Conjugated Gold Nanoparticles for Reactive Oxygen Species Scavenging and Regulation of Stem Cell Differentiation

Controlling the differentiation of human mesenchymal stem cells (hMSCs) shows a great potential in regenerative medicine. Because overproduced reactive oxygen species (ROS) have an obvious inhibitory effect on the differentiation and functions of hMSCs, it is highly desirable to develop an effective strategy for ROS scavenging and stem cell differentiation controlling. In this study, gold nanoparticles (Au NPs) with an average size of 40 nm were conjugated with 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) to endow them with ROS-scavenging capacity while holding the beneficial effect of Au NPs. The TEMPO-conjugated Au NPs (Au-PEG-TEMPO NPs) were used for the culture of hMSCs to investigate their effect on ROS scavenging, proliferation, and osteogenic and adipogenic differentiation of hMSCs. The Au-PEG-TEMPO NPs had a negligible influence on cell viability and proliferation of hMSCs and could effectively reduce the ROS level of hMSCs under H₂O₂-exposed conditions because of their excellent cellular uptake. Similar to the counterparts without surface TEMPO modification (Au-mPEG NPs), the Au-PEG-TEMPO NPs could promote the osteogenic differentiation of hMSCs, whereas they could inhibit the adipogenic differentiation of hMSCs. The results indicated that the TEMPO-conjugated Au NPs had high scavenging capacity for overproduced ROS and maintained the promotive effect of Au NPs on osteogenic differentiation of hMSCs without the inhibitory effect of free TEMPO. This study offers a promising strategy for ROS scavenging to control stem cell differentiation in stem cell transplantation and regenerative medicine.

Combination Treatment of Murine Colon Cancer with Doxorubicin and Redox Nanoparticles

Conventional chemotherapeutic drugs such as doxorubicin (DOX) are associated with severe adverse effects such as cardiac, hepatic, and gastrointestinal (GI) toxicities. Excessive production of reactive oxygen species (ROS) was reported to be one of the main mechanisms underlying these severe adverse effects. Recently, we have developed 2 types of novel redox nanoparticles (RNPs) including pH-sensitive redox nanoparticle (RNP(N)) and pH-insensitive redox nanoparticle (RNP(O)), which effectively scavenge overproduced ROS in inflamed and cancerous tissues. In this study, we investigated the effects of these RNPs on DOX-induced adverse effects during cancer chemotherapy. The DOX-induced body weight loss was significantly attenuated in the mice treated with RNPs, particularly pH-insensitive RNP(O). We also found that cardiac ROS levels in the DOX-treated mice were dramatically decreased by treatment with RNPs, resulting in the reversal of cardiac damage, as confirmed by both plasma cardiac biomarkers and histological analysis. It was interesting to notice that, during cotreatment with DOX and RNPs, the DOX uptake was significantly enhanced in the cancer cells, but not in healthy aortic endothelial cells in vitro. Treatment with RNPs also improved anticancer efficacy of DOX in the colitis-associated colon cancer model mice in vivo. On the basis of these results, a combination of the novel antioxidative nanotherapeutics (RNPs) with conventional anticancer drugs seems to be a robust strategy for well-tolerated anticancer therapy.

Redox nanoparticles as a novel treatment approach for inflammation and fibrosis associated with nonalcoholic steatohepatitis

AIM

Oxidative stress (OS) is largely thought to be a central mechanism responsible for liver damage, inflammation and fibrosis in nonalcoholic steatohepatitis (NASH). Our aim was to investigate whether suppression of OS in the liver via redox nanoparticles (RNPs) reduces liver damage in a mouse model of NASH.

MATERIALS & METHODS

RNPs were prepared by self-assembly of redox polymers possessing antioxidant nitroxide radicals and were orally administered by daily gavage for 4 weeks.

RESULTS

The redox polymer was delivered to the liver after disintegration of nanoparticle in the stomach. RNP treatment in NASH mice via gavage led to a reduction of liver OS, improvement of fibrosis, and significant reduction of inflammation.

CONCLUSION

These findings uncover RNP as a novel potential NASH therapy.

Recovery of Cognitive Dysfunction via Orally Administered Redox-Polymer Nanotherapeutics in SAMP8 Mice

Excessively generated reactive oxygen species are associated with age-related neurodegenerative diseases. We investigated whether scavenging of reactive oxygen species in the brain by orally administered redox nanoparticles, prepared by self-assembly of redox polymers possessing antioxidant nitroxide radicals, facilitates the recovery of cognition in 17-week-old senescence-accelerated prone (SAMP8) mice. The redox polymer was delivered to the brain after oral administration of redox nanoparticles via a disintegration of the nanoparticles in the stomach and absorption of the redox polymer at small intestine to the blood. After treatment for one month, levels of oxidative stress in the brain of SAMP8 mice were remarkably reduced by treatment with redox nanoparticles, compared to that observed with low-molecular-weight nitroxide radicals, resulting in the amelioration of cognitive impairment with increased numbers of surviving neurons. Additionally, treatment by redox nanoparticles did not show any detectable toxicity. These findings indicate the potential of redox polymer nanotherapeutics for treatment of the neurodegenerative diseases.

Development of silica-containing redox nanoparticles for medical applications

Silica-containing redox nanoparticles act as adsorbents for peritoneal dialysis and orally administrable drug carriers for the treatment of gastrointestinal inflammation.