Avoid using spectrophotometric determination of malondialdehyde as a biomarker of oxidative stress

Measurement of cellular MDA content through MTBE-extraction based TBA assay by eliminating cellular interferences

Malondialdehyde (MDA) has long been served as a crucial indicator for assessing cellular oxidative stress levels. In this study, we introduce a new approach to determine cellular MDA levels based on a methyl tert-butyl ether (MTBE) extraction, aimed at eliminating interferences from cellular components during thiobarbituric acid (TBA) derivatization of MDA. By leveraging the effective MTBE extraction, we identified that the determination of the MDA-TBA adduct formed from the MTBE extraction layer can effectively eliminate the interferences from cellular proteins and metabolites. This method demonstrated acceptable linearity and precision in cellular samples and showed significant differences in H2O2 treated cellular oxidative stress models. The MTBE extraction-based MDA-TBA approach provides a reliable, cost-effective, and feasible method to determine cellular MDA levels using batch microplate reader approach for the assessment of cellular oxidative stress.

Bioanalysis of Stress Biomarkers through Sensitive HILIC-MS/MS Method: A Stride toward Accurate Quantification of MDA, ACR, and CTA

Quantifying reactive aldehyde biomarkers, such as malondialdehyde, acrolein, and crotonaldehyde, is the most preferred approach to determine oxidative stress. However, reported analytical methods lack specificity for accurately quantifying these aldehydes as certain methodologies may produce false positive results due to harsh experimental conditions. Thus, in this research work, a novel HILIC-MS/MS method with endogenous histidine derivatization is developed, which proves to have higher specificity and reproducibility in quantifying these aldehydes from the biological matrix. To overcome the reactivity of aldehyde, endogenous histidine is used for its derivatization. The generated adduct is orthogonally characterized by NMR and LC-HRMS. The method employed a hydrophilic HILIC column and multiple reaction monitoring (MRM) to accurately quantify these reactive aldehydes. The developed method is an unequivocal solution for quantifying stress in in vivo and in vitro studies.

Insights into Gastrointestinal Redox Dysregulation in a Rat Model of Alzheimer's Disease and the Assessment of the Protective Potential of D-Galactose

Recent evidence suggests that the gut plays a vital role in the development and progression of Alzheimer's disease (AD) by triggering systemic inflammation and oxidative stress. The well-established rat model of AD, induced by intracerebroventricular administration of streptozotocin (STZ-icv), provides valuable insights into the GI implications of neurodegeneration. Notably, this model leads to pathophysiological changes in the gut, including redox dyshomeostasis, resulting from central neuropathology. Our study aimed to investigate the mechanisms underlying gut redox dyshomeostasis and assess the effects of D-galactose, which is known to benefit gut redox homeostasis and alleviate cognitive deficits in this model. Duodenal rings isolated from STZ-icv animals and control groups were subjected to a prooxidative environment using 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) or H2O2 with or without D-galactose in oxygenated Krebs buffer ex vivo. Redox homeostasis was analyzed through protein microarrays and functional biochemical assays alongside cell survival assessment. Structural equation modeling and univariate and multivariate models were employed to evaluate the differential response of STZ-icv and control samples to the controlled prooxidative challenge. STZ-icv samples showed suppressed expression of catalase and glutathione peroxidase 4 (GPX4) and increased baseline activity of enzymes involved in H2O2 and superoxide homeostasis. The altered redox homeostasis status was associated with an inability to respond to oxidative challenges and D-galactose. Conversely, the presence of D-galactose increased the antioxidant capacity, enhanced catalase and peroxidase activity, and upregulated superoxide dismutases in the control samples. STZ-icv-induced gut dysfunction is characterized by a diminished ability of the redox regulatory system to maintain long-term protection through the transcription of antioxidant response genes as well as compromised activation of enzymes responsible for immediate antioxidant defense. D-galactose can exert beneficial effects on gut redox homeostasis under physiological conditions.

Flavonoid 4,4'-dimethoxychalcone induced ferroptosis in cancer cells by synergistically activating Keap1/Nrf2/HMOX1 pathway and inhibiting FECH

Flavonoids are widely distributed in plants as secondary metabolites and have various biological benefits such as anti-tumor, anti-oxidant, anti-inflammatory and anti-aging. We previously reported that 4,4'-dimethoxychalcone (DMC) suppressed cancer cell proliferation by aggravating oxidative stress and inducing G2/M cell cycle arrest. In the present study, we explored the underlying mechanisms by which DMC inhibited cancer cell growth. Given that ferrochelatase (FECH) is a potential target of DMC identified by thermal proteome profiling (TPP) method, herein, we confirmed that DMC inhibited the enzymatic activity of FECH. Furthermore, we proved that DMC induced Keap1 degradation via ubiquitin-proteasome system, which led to the nuclear translocation of Nrf2 and upregulated Nrf2 targeted gene HMOX1. FECH inhibition and HMOX1 upregulation resulted in iron overload and triggered ferroptosis in cancer cells. Collectively, we revealed that DMC induced ferroptosis by synergistically activating Keap1/Nrf2/HMOX1 pathway and inhibiting FECH. Our findings indicate that FECH contributes to the non-canonical ferroptosis induction, shed light on the mechanisms of DMC inhibiting cancer cell growth, and set an example for studying biological functions of flavonoids.

Association between oxidized nucleobases and mitochondrial DNA damage with long-term mortality in patients with sepsis

BACKGROUND

Sepsis not only leads to short-term mortality during hospitalization, but is also associated with increased mortality during long-term follow-up after hospital discharge. Metabolic stress during sepsis may cause oxidative damage to both nuclear and mitochondrial DNA (mtDNA) and RNA, which could affect long-term health and life span. Therefore, the aim of this study was to assess the association of sepsis with oxidized nucleobases and (mt)DNA damage and long-term all-cause mortality in septic patients.

METHODS

91 patients with sepsis who visited the emergency department (ED) of the University Medical Center Groningen between August 2012 and June 2013 were included. Urine and plasma were collected during the ED visit. Septic patients were matched with 91 healthy controls. Death rate was obtained until June 2020.The degree of oxidation of DNA, RNA and free nucleobases were assessed in urine by mass-spectrometry. Lipid peroxidation was assessed in plasma using a TBAR assay. Additionally, plasma levels of mtDNA and damage to mtDNA were determined by qPCR.

RESULTS

Sepsis patients denoted higher levels of oxidated DNA, RNA, free nucleobases and lipid peroxidation than controls (all p < 0.01). Further, sepsis patients displayed an increase in plasma mtDNA with an increase in mtDNA damage compared to matched controls (p < 0.01). Kaplan meier survival analyses revealed that high degrees of RNA- and nucleobase oxidation were associated with higher long-term all-cause mortality after sepsis (p < 0.01 and p = 0.01 respectively). Of these two, high RNA oxidation was associated with long-term all-cause mortality, independent of adjustment for age, medical history and sepsis severity (HR 1.29 [(1.17-1.41, 95% CI] p < 0.01).

CONCLUSIONS

Sepsis is accompanied with oxidation of nuclear and mitochondrial DNA and RNA, where RNA oxidation is an independent predictor of long-term all-cause mortality. In addition, sepsis causes mtDNA damage and an increase in cell free mtDNA in plasma.

Serum Inflammatory Factors and Oxidative Stress Factors Are Associated With Increased Risk of Frailty and Cognitive Frailty in Patients With Cerebral Small Vessel Disease

Objective: To study the correlation between serum inflammatory factors, oxidative stress factors and frailty, and cognitive frailty in patients with cerebral small vessel disease (CSVD).

Methods: A total of 281 patients with CSVD were selected from Tianjin Huanhu Hospital and Inner Mongolia People's Hospital from March 2019 to March 2021. CSVD was diagnosed by MRI. The FRAIL scale was used to evaluate the frailty of patients. Patients with CSVD with frailty and MMSE score <27 were considered to have cognitive frailty. Patients with non-cognitive frailty were included in the control group. The Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE) were used to evaluate the cognitive function of patients with CSVD. The serum interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), matrix metalloproteinase 3 (MMP-3), superoxide dismutase (SOD), and malondialdehyde (MDA) of patients with CSVD were detected. The correlation between blood inflammatory factors and oxidative stress factors with the frailty and cognitive frailty patients of CSVD were analyzed. Univariate and multivariate logistic regression were used to analyze the correlation between cognitive frailty and CSVD.

Results: Among the patients with CSVD selected in this study, female patients and older patients had a higher proportion of frailty (p < 0.001). In the Frail group, MoCA score and MMSE score were significantly lower than in the Pre-Frail and Robust groups, Hamilton Depression Scale (HAMD) and Hamilton Anxiety Scale (HAMA) scores were significantly higher than the Pre-Frail and Robust groups, and the differences were statistically significant (p < 0.05). Serum CRP, IL-6, TNF-α, MMP-3, and MDA levels in the Frail group were higher, but SOD levels were lower. The levels of serum CRP, IL-6, TNF-α, MMP-3, and MDA in patients with CSVD in the Cognitive Frailty group were significantly higher than those of the Control group, while the levels of SOD were significantly lower than those of the Control group, and the differences were significant (p < 0.001). The results of univariate and multivariate logistic regression analysis showed that CRP, TNF-α, MMP-3, and MDA levels were associated with cognitive frailty in patients with CSVD (p < 0.05).

Conclusion: The increase of serum CRP, TNF-α, MMP-3, and MDA levels are significantly related to the increased risk of frailty and cognitive frailty in patients with CSVD.

Variations of Serum Oxidative Stress Biomarkers under First-Line Antituberculosis Treatment: A Pilot Study

Tuberculosis (TB) is one of the highest infectious burdens worldwide, and pathogenesis is yet incompletely elucidated. Bacilli dissemination is due to poor antioxidant defense mechanisms and intensified oxidative stress. There are few recent studies that analyzed and compared free radicals or antioxidant status before and after anti-TB treatment. Hence, the present study underlines the need to identify oxidative stress as it could be a useful tool in TB monitorisation. Thirty newly diagnosed patients with pulmonary TB were included after signing an informed consent. Blood was collected before receiving first-line anti-tubercular therapy (T0) and after 60 days (T2). Spectrophotometric methods were used to quantify oxidative parameters (TBARS—thiobarbituric acid reactive species); enzymatic antioxidants such as SOD (superoxide dismutase), CAT (catalase), GPx (glutathione peroxidase), and TAC (total antioxidant capacity); and non-enzymatic antioxidants such as GSH (reduced glutathione). A moderate positive correlation was found between GSH and TAC (r = 0.63, p-value = 0.046) and GSH and SOD (r = 0.64, p-value = 0.041) at T2. Increased values of GSH, CAT, and SOD were noted at T2 in comparison with T0, while GPx, TAC, and TBARS decreased at T2. A better monitorisation in TB could be based on oxidative stress and antioxidant status. Nevertheless, restoring redox host balance could reduce TB progression.

LC-MS Quantification of Malondialdehyde-Dansylhydrazine Derivatives in Urine and Serum Samples

We developed a robust analytical method for quantification of malondialdehyde (MDA) in urine and serum samples using dansylhydrazine (DH) as a derivatizing reagent. The derivatization procedure was partially carried out using an autosampler injection program to minimize errors associated with the low-volume addition of reagents and was optimized to yield a stable hydrazone derivative of MDA and its labeled d2-MDA analogue. The target MDA-DH derivatives were separated on an Agilent Zorbax Eclipse Plus Phenyl-Hexyl (3.0 × 100 mm, 3.5 μm) column. The mass-to-charge ratios of the target derivatives [(M+H)+ of 302 and 304 for MDA-DH and d2-MDA-DH, respectively] were analyzed in single ion monitoring mode using a single quadrupole mass spectrometer operated under positive electrospray ionization. The method limits of quantification were 5.63 nM (or 0.405 ng/mL) for urine analysis and 5.68 nM (or 0.409 ng/mL) for serum analysis. The quantification range for urine analysis was 5.63-500 nM (0.405-36.0 ng/mL) while the quantification range for serum analysis was 5.68-341 nM (0.409-24.6 ng/mL). The method showed good relative recoveries (98-103%), good accuracies (92-98%), and acceptable precisions (relative standard deviations 1.8-7.3% for inter-day precision; 1.8-6.1% for intra-day precision) as observed from the repeat analysis of quality control samples prepared at different concentrations. The method was used to measure MDA in individual urine samples (n = 287) and de-identified archived serum samples (n = 22) to assess the overall performance of the method. The results demonstrated that our method is capable of measuring urinary and serum levels of MDA, allowing its future application in epidemiologic investigations.