Fenton-like reaction of the iron(II)-histidine complex generates hydroxyl radicals: implications for oxidative stress and Alzheimer's disease

Comparative analysis and mechanistic insights into polysorbate 80 stability differences in biopharmaceutical buffer systems

Polysorbate 80 (PS80) is a non-ionic surfactant extensively utilized in biopharmaceutical formulations for stabilizing proteins. However, PS80 degradation has become a widespread concern throughout the industry over the past decade. In this work, the impact of most frequently employed pH/buffer systems on the stability of PS80 was assessed. PS80 degraded fastest in histidine buffer, followed by acetate and succinate buffers, whereas it remained stable in citrate, phosphate and tris buffers. When there was PS80 degradation, the extent of degradation was found to be pH-dependent. The predominant degradation pathway was oxidation mainly triggered by metal ions. The varying stability of PS80 across different pH/buffer systems was attributed to the role of buffer agents, which can either promote or inhibit the oxidation process through their interactions with metal ions. Specifically, buffers except histidine exhibited metal ion chelation similar to ethylenediaminetetraacetic acid (EDTA), which can suppress the oxidation of PS80, although the effectiveness of chelation varies to different extents. Furthermore, the binding capacity appeared stronger at higher pH in acetate and succinate buffers. Conversely, histidine was reported to form pro-oxidant complexes with metal ions to accelerate PS80 degradation, especially at higher pH levels. Our work for the first time offers a comprehensive understanding of PS80 oxidation in biopharmaceutical buffer systems. This provides a strong foundation for buffer and excipient selection in parenteral formulations.

Oxidative Stress-Mediated Programmed Cell Death: a Potential Therapy Target for Atherosclerosis

Nowadays, as a type of orderly and active death determined by genes, programmed cell death (PCD), including apoptosis, pyroptosis, ferroptosis, and necroptosis, has attracted much attention owing to its participation in numerous chronic cardiovascular diseases, especially atherosclerosis (AS), a canonical chronic inflammatory disease featured by lipid metabolism disturbance. Abundant researches have reported that PCD under distinct internal conditions fulfills different roles of atherosclerotic pathological processes, including lipid core expansion, leukocyte adhesion, and infiltration. Noteworthy, emerging evidence recently has also suggested that oxidative stress (OS), an imbalance of antioxidants and oxygen free radicals, has the potential to mediate PCD occurrence via multiple ways, including oxidization and deubiquitination. Interestingly, more recently, several studies have proposed that the mediating mechanisms could effect on the atherosclerotic initiation and progression significantly from variable aspects, so it is of great clinical importance to clarify how OS-mediated PCD and AS interact. Herein, with the aim of summarizing potential and sufficient atherosclerotic therapy targets, we seek to provide extensive analysis of the specific regulatory mechanisms of PCD mediated by OS and their multifaceted effects on the entire pathological atherosclerotic progression.

Water extract of moschus alleviates erastin-induced ferroptosis by regulating the Keap1/Nrf2 pathway in HT22 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Moschus, first described in the Shennong's Classic of the Materia medicine, is a scarce and precious animal medicine. Modern pharmacological researches have suggested that Moschus has neuroprotective actions, and its mechanism is related to anti-inflammatory, antioxidant, and anti-apoptosis effects. Ferroptosis is one of the major pathologies of Alzheimer's disease (AD) and is widely implicated in the pathogenesis and progression of AD. Although previous studies have suggested that Moschus possesses neuroprotective effect, whether Moschus could mitigate neuronal damages by inhibiting the onset of ferroptosis is unknown in model cells of AD.

AIM OF THE STUDY

The aim of study was to explore the water extract of Moschus (WEM) on ferroptosis caused by erastin and the potential mechanism.

MATERIALS AND METHODS

Erastin was used to stimulate HT22 cells to form ferroptosis model to evaluate the anti-ferroptosis effect of WEM by cell counting kit-8 and lactic dehydrogenase (LDH) tests. The malondialdehyde (MDA) and glutathione (GSH) kits are used for detection of MDA and GSH levels, and 2',7'-dichlorofluorescein diacetate and C11 BODIPY 581/591 fluorescence probe are used for evaluation of reactive oxygen species (ROS) and lipid peroxide (LOOH) levels. And Western blot was used to test nuclear factor erythroid 2-related factor 2 (Nrf2), Kelch-like ECH-associated protein 1 (Keap1), heme oxygenase-1 (HO-1), and ferroptosis associated proteins including glutathione peroxidase 4 (GPX4), cystine/glutamate antiporter subunit (SLC7A11), ferritin heavy chain 1 (FTH1), ferroportin1 (FPN1), transferrin receptor (TFRC). In addition, the Nrf2 inhibitor ML385 was applied to verify whether WEM prevents erastin-induced ferroptosis by activating the Keap1/Nrf2 pathway.

RESULTS

After WEM treatment, erastin-induced HT22 cell survival was significantly elevated, the accumulation of intracellular MDA, ROS, and LOOH were significantly reduced, the level of GSH and expressions of ferroptosis inhibitors GPX4 and SLC7A11 were significantly increased, and iron metabolism-related proteins TFRC, FPN1, and FTH1 were regulated. These effects of WEM are implemented by activating the Keap1/Nrf2 pathway.

CONCLUSIONS

This study demonstrated that WEM could perform neuroprotective effects by alleviating ferroptosis, verified that WEM treatment of AD can be mediated by the Keap1/Nrf2 pathway, and provided theoretical support for the application of WEM in the treatment of AD.

Ratiometric electrochemical determination of hydroxyl radical based on graphite paper modified with metal-organic frameworks and impregnated with salicylic acid

Hydroxyl radical (•OH) detection is pivotal in medicine, biochemistry and environmental chemistry. Yet, electrochemical method-specific detection is challenging because of hydroxyl radicals' high reactivity and short half-life. In this study, we aimed to modify the electrode surface with a specific recognition probe for •OH. To achieve this, we conducted a one-step hydrothermal process to fabricate a CoZnMOF bimetallic organic framework directly onto conductive graphite paper (Gp). Subsequently, we introduced salicylic acid (SA) and methylene blue (MB), which easily penetrated the pores of CoZnMOF. By selectively capturing •OH by SA and leveraging the electrochemical signal generated by the reaction product, we successfully developed an electrochemical sensor Gp/CoZnMOF/SA + MB. The prepared sensor exhibited a good linear relationship with •OH concentrations ranging from 1.25 to 1200 nM, with a detection limit of 0.2 nM. Additionally, the sensor demonstrated excellent reproducibility and accuracy due to the incorporation of an internal reference. It exhibited remarkable selectivity for •OH detection, unaffected by other electrochemically active substances. The establishment of this sensor provides a way to construct MOF-modified sensors for the selective detection of other reactive oxygen species (ROS), offering a valuable experimental basis for ROS-related disease research and environmental safety investigations.

Hydroxyl radical generations form the physiologically relevant Fenton-like reactions

Iron(II) species can participate in the Fenton and Fenton-like reactions to generate the hydroxyl radical that can oxidatively damage biomolecules and induce oxidative stress in biological systems. Many diseases, including neurodegeneration, cardiovascular disease and cancer, are associated with oxidative stress. However, it is proposed recently that hydroxyl radical would not be generated from the Fenton reaction under physiological conditions and thus would not cause oxidative stress in biological systems. This proposal may cause confusion for understanding oxidative stress and can also have impact on therapeutic strategies for the diseases associated with oxidative stress. In this Mini-review, the up-to-date convincing evidences of hydroxyl radical generation from the physiologically relevant Fenton-like reactions of the iron(II) complexes with physiological ligands in human blood plasma, including histidine, citrate and phosphate, are succinctly reviewed. The oxidative damages caused by hydroxyl radical to biomolecules and cells are briefly summarized. These findings strongly challenge the above proposal.

Biochemical and Molecular Pathways in Neurodegenerative Diseases: An Integrated View

Neurodegenerative diseases (NDDs) like Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) are defined by a myriad of complex aetiologies. Understanding the common biochemical molecular pathologies among NDDs gives an opportunity to decipher the overlapping and numerous cross-talk mechanisms of neurodegeneration. Numerous interrelated pathways lead to the progression of neurodegeneration. We present evidence from the past pieces of literature for the most usual global convergent hallmarks like ageing, oxidative stress, excitotoxicity-induced calcium butterfly effect, defective proteostasis including chaperones, autophagy, mitophagy, and proteosome networks, and neuroinflammation. Herein, we applied a holistic approach to identify and represent the shared mechanism across NDDs. Further, we believe that this approach could be helpful in identifying key modulators across NDDs, with a particular focus on AD, PD, and ALS. Moreover, these concepts could be applied to the development and diagnosis of novel strategies for diverse NDDs.

Flammulina velutipes-derived carbon dots for fluorescence detection and imaging of hydroxyl radical

Monitoring hydroxyl radical (•OH) fluctuation is of great importance to study some relative pathological processes and to predict early diagnosis of diseases. Efficient •OH-responsive fluorescent sensors based on carbon dots (CDs) have been reported, but most researches have focused on the new strategies for the synthesis and doping of the CDs. Herein, a kind of biomass CDs (F-CDs) with Flammulina velutipes (F. velutipes) as the carbon source was prepared by a one-step hydrothermal method without any additional modification. The prepared F-CDs have remarkable sensitivity and selectivity and there is a good linear relationship from 0 to 12 μM with a low detection limit of 95 nM for quantitative •OH assay. With excitation-independent emission, favourable biocompatibility and low toxicity, the F-CDs can penetrate cell membranes as •OH-responsive fluorescent sensors to detect intracellular •OH in A549 cells stimulated by phorbol 12-myristate 13-acetate (PMA) and successfully monitor the •OH concentration levels by the corresponding fluorescence change. Given the combined benefits of the green and eco-friendly approach, the F-CDs show promise as novel theranostics tools for early detection and treatment of related diseases.