In vivo analysis of redox status in organs - from bench to bedside

Cerium-Luteolin Nanocomplexes in Managing Inflammation-Related Diseases by Antioxidant and Immunoregulation

Oxidative stress, characterized by an imbalance between reactive oxygen species (ROS) production and the antioxidant defense system, plays a pivotal role in inflammation-related diseases. Excessive ROS levels can induce cellular damage and impair normal physiological functions, triggering the release of inflammatory mediators and exacerbating the inflammatory response, ultimately leading to irreversible tissue damage. In this study, we synthesized cerium ion-luteolin nanocomplexes (CeLutNCs) by coordinating Ce ions with the natural product luteolin, aiming to develop a therapeutic agent with excellent antioxidant and immunoregulation properties for ROS-related inflammation treatment. In vitro experiments demonstrated that the prepared CeLutNCs effectively scavenged excess ROS, prevented cell apoptosis, down-regulated levels of important inflammatory cytokines, regulated the response of inflammatory macrophages, and suppressed the activation of the nuclear factor-κ-gene binding (NF-κB) pathway. In an acute kidney injury (AKI) animal model, CeLutNCs exhibited significant efficacy in improving kidney function, repairing damaged renal tissue, and reducing oxidative stress, inflammatory response, and cellular apoptosis. Moreover, the therapeutic potential of CeLutNCs in an acute lung injury (ALI) model was confirmed through the assessment of inflammatory responses and histopathological studies. This study emphasizes the effectiveness of these metal-natural product coordination nanocomplexes as a promising therapeutic approach for preventing AKI and other diseases associated with oxidative stress.

A nitroxides-based macromolecular MRI contrast agent with an extraordinary longitudinal relaxivity for tumor imaging via clinical T1WI SE sequence

BACKGROUND

Macromoleculization of nitroxides has been an effective strategy to improve low relaxivities and poor in vivo stability, however, nitroxides-based metal-free magnetic resonance imaging (MRI) macromolecular contrast agents (mCAs) are still under-performed. These mCAs do not possess a high nitroxides content sufficient for a cumulative effect. Amphiphilic nanostructures in these mCAs are not stable enough for highly efficient protection of nitroxides and do not have adequate molecular flexibility for full contact of the paramagnetic center with the peripheral water molecules. In addition, these mCAs still raise the concerns over biocompatibility and biodegradability due to the presence of macromolecules in these mCAs.

RESULTS

Herein, a water-soluble biodegradable nitroxides-based mCA (Linear pDHPMA-mPEG-Ppa-PROXYL) was prepared via covalent conjugation of a nitroxides (2,2,5,5-tetramethyl-1-pyrrolidinyl-N-oxyl, PROXYL) onto an enzyme-sensitive linear di-block poly[N-(1, 3-dihydroxypropyl) methacrylamide] (pDHPMA). A high content of PROXYL up to 0.111 mmol/g in Linear pDHPMA-mPEG-Ppa-PROXYL was achieved and a stable nano-sized self-assembled aggregate in an aqueous environment (ca. 23 nm) was formed. Its longitudinal relaxivity (r1 = 0.93 mM- 1 s- 1) was the highest compared to reported nitroxides-based mCAs. The blood retention time of PROXYL from the prepared mCA in vivo was up to ca. 8 h and great accumulation of the mCA was realized in the tumor site due to its passive targeting ability to tumors. Thus, Linear pDHPMA-mPEG-Ppa-PROXYL could provide a clearly detectable MRI enhancement at the tumor site of mice via the T1WI SE sequence conventionally used in clinical Gd3+-based contrast agents, although it cannot be compared with DTPA-Gd in the longitudinal relaxivity and the continuous enhancement time at the tumor site of mice. Additionally, it was demonstrated to have great biosafety, hemocompatibility and biocompatibility.

CONCLUSIONS

Therefore, Linear pDHPMA-mPEG-Ppa-PROXYL could be a potential candidate as a substitute of metal-based MRI CAs for clinical application.

Free radical imaging of endogenous redox molecules using dynamic nuclear polarisation magnetic resonance imaging

Redox reactions accompanied by the oxidation-reduction of endogenous molecules play important roles in maintaining homeostasis in living organisms. In humans, numerous endogenous molecules that contribute towards maintaining physiological conditions form free radicals via electron transfer. A typical example of this is the mitochondrial electron transport chain, which is involved in energy production. If free radicals derived from endogenous molecules could be visualised and exploited as biological and functional probes, redox reactions mediated by endogenous molecules could be detected non-invasively. We succeeded in visualising the free radicals derived from endogenous molecules using an in vivo dynamic nuclear polarisation (DNP) magnetic resonance imaging (MRI) system. In this review, we describe the visualisation of endogenous redox molecules, such as flavins and ubiquinones, which are mitochondrial electron carriers, as well as vitamin E and vitamin C (ascorbate). In addition, we describe the application of melanin free radicals for the in vivo visualisation of metabola without using probes via in vivo DNP-MRI.