Peroxiredoxin6, a Multitask Antioxidant Enzyme Involved in the Pathophysiology of Chronic Noncommunicable Diseases

Enhancing Transcriptomic Insights into Neurological Disorders Through the Comparative Analysis of Shapley Values

Neurological disorders such as Autism Spectrum Disorder (ASD), Schizophrenia (SCH), Bipolar Disorder (BD), and Major Depressive Disorder (MDD) affect millions of people worldwide, yet their molecular mechanisms remain poorly understood. This study describes the application of the Comparative Analysis of Shapley values (CASh) to transcriptomic data from nine datasets associated with these complex disorders, demonstrating its effectiveness in identifying differentially expressed genes (DEGs). CASh, which combines Game Theory with Bootstrap resampling, offers a robust alternative to traditional statistical methods by assessing the contribution of each gene in the broader context of the complete dataset. Unlike conventional approaches, CASh is highly effective at detecting subtle but meaningful molecular patterns that are often missed. These findings highlight the potential of CASh to enhance the precision of transcriptomic analysis, providing a deeper understanding of the molecular mechanisms underlying these disorders and establishing a solid basis to improve diagnostic techniques and developing more targeted therapeutic interventions.

Meta-Analysis and DIA-MS-Based Proteomic Investigation of COPD Patients and Asymptomatic Smokers in the Indian Population

Chronic obstructive pulmonary disease (COPD) is India's second largest cause of death and is largely caused by smoking. Asymptomatic smokers develop COPD due to genetic, environmental, and molecular variables, making early screening crucial. Data-independent acquisition mass spectrometry (DIA-MS) based-proteomics offers an unbiased method to analyze proteomic profiles. This study is the first to use DIA-based proteomics to analyze individual serum samples from three distinct male cohorts: healthy individuals (n = 10), asymptomatic smokers (n = 10), and COPD patients (n = 10). This comprehensive approach identified 667 proteins with a 1% false discovery rate. Differentially expressed proteins included 40 in the normal versus asymptomatic comparison, 88 in the COPD versus normal comparison, and 40 in the COPD versus asymptomatic comparison. Among them, protein-associated genes such as PRDX6, ELANE, PRKCSH, PRTN3, and MNDA could help differentiate COPD from asymptomatic smokers, while ELANE, H3-3A, IGHE, SLC4A1, and SERPINA11 could differentiate COPD from healthy subjects. Pathway enrichment and protein-protein interaction analyses revealed significant alterations in hemostasis, immune system functions, fibrin clot formation, and post-translational protein modifications. Key proteins were validated using a parallel reaction monitoring assay. DIA data are available via ProteomeXchange with identifier PXD055242. Our findings reveal key protein classifiers in COPD patients, asymptomatic smokers, and healthy individuals, helping clinicians understand disease pathobiology and improve disease management and quality of life.

Peroxinredoxin 6 reduction accelerates cigarette smoke extract‑induced senescence by regulating autophagy in BEAS‑2B cells

Cigarette smoke (CS)-induced accelerated senescence and insufficient autophagy has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Peroxiredoxin (PRDX) 6 is a protein with prevalent antioxidant capacity. Previous studies indicate that PRDX6 could activate autophagy and alleviate senescence in other diseases. The present study investigated whether PRDX6-regulated autophagy was involved in the regulation of CS extract (CSE)-induced BEAS-2B cell senescence via the knockdown of PRDX6 expression. Furthermore, the present study evaluated the mRNA levels of PRDX6, autophagy and senescence-associated genes in the small airway epithelium from patients with COPD by analyzing the GSE20257 dataset from the Gene Expression Omnibus database. The results demonstrated that CSE reduced PRDX6 expression levels and transiently induced the activation of autophagy, followed by the accelerated senescence of BEAS-2B cells. Knockdown of PRDX6 induced autophagy degradation and accelerated senescence in CSE-treated BEAS-2B cells. Furthermore, autophagy inhibition by 3-Methyladenine increased P16 and P21 expression levels, while autophagy activation by rapamycin reduced P16 and P21 expression levels in CSE-treated BEAS-2B cells. The GSE20257 dataset revealed that patients with COPD had lower PRDX6, sirtuin (SIRT) 1 and SIRT6 mRNA levels, and higher P62 and P16 mRNA levels compared with non-smokers. P62 mRNA was significantly correlated with P16, P21 and SIRT1, which indicated that insufficient autophagic clearance of damaged proteins could be involved in accelerated cell senescence in COPD. In conclusion, the present study demonstrated a novel protective role for PRDX6 in COPD. Furthermore, a reduction in PRDX6 could accelerate senescence by inducing autophagy impairment in CSE-treated BEAS-2B cells.

Peroxiredoxin 6 Modulates Insulin Secretion and Beta Cell Death via a Mitochondrial Dynamic Network

In pancreatic beta cells, mitochondrial metabolism controls glucose-stimulated insulin secretion (GSIS) by ATP production, redox signaling, and calcium (Ca²⁺) handling. Previously, we demonstrated that knockout mice for peroxiredoxin 6 (Prdx6^-/- ), an antioxidant enzyme with both peroxidase and phospholipase A2 activity, develop a mild form of diabetes mellitus with a reduction in GSIS and in peripheral insulin sensitivity. However, whether the defect of GSIS present in these mice is directly modulated by Prdx6 is unknown. Therefore, the main goal of the present study was to evaluate if depletion of Prdx6 affects directly GSIS and pancreatic beta β-cell function. Murine pancreatic β-cell line (βTC6) knockdown for Prdx6 (Prdx6^KD) was employed, and insulin secretion, ATP, and intracellular Ca²⁺ content were assessed in response to glucose stimulation. Mitochondrial morphology and function were also evaluated through electron microscopy, and by testing mitochondrial membrane potential, oxygen consumption, and mitochondrial mass. Prdx6^KD cells showed a significant reduction in GSIS as confirmed by decrease in both ATP release and Ca²⁺ influx. GSIS alteration was also demonstrated by a marked impairment of mitochondrial morphology and function. These latest are mainly linked to mitofusin downregulation, which are, in turn, strictly related to mitochondrial homeostasis (by regulating autophagy) and cell fate (by modulating apoptosis). Following a pro-inflammatory stimulus (typical of diabetic subjects), and in agreement with the deregulation of mitofusin steady-state levels, we also observed an enhancement in apoptotic death in Prdx6^KD compared to control cells. We analyzed molecular mechanisms leading to apoptosis, and we further demonstrated that Prdx6 suppression activates both intrinsic and extrinsic apoptotic pathways, ultimately leading to caspase 3 and PARP-1 activation. In conclusion, Prdx6 is the first antioxidant enzyme, in pancreatic β-cells, that by controlling mitochondrial homeostasis plays a pivotal role in GSIS modulation.

The Roles of Peroxiredoxin 6 in Brain Diseases

Peroxiredoxin 6 (PRDX6), the only mammalian 1-Cys member of the peroxiredoxins (PRDXs) family, has multiple functions of glutathione peroxidase (Gpx) activity, acidic calcium-independent phospholipase (aiPLA2) activity, and lysophosphatidylcholine acyl transferase (LPCAT) activity. It has been documented to be involved in redox homeostasis, phospholipid turnover, glycolipid metabolism, and cellular signaling. Here, we reviewed the characteristics of the available Prdx6 genetic mouse models and the research progresses made with regard to PRDX6 in neuropsychiatric disorders, including neurodegenerative diseases, brain aging, stroke, neurotrauma, gliomas, major depressive disorder, drug addiction, post-traumatic stress disorder, and schizophrenia. The present review highlights the important roles of PRDX6 in neuropsychiatric disorders and may provide novel insights for the development of effective pharmacological treatments and genetic therapies.

Identification of a Blood-Based Protein Biomarker Panel for Lung Cancer Detection

Lung cancer is the deadliest cancer worldwide, mainly due to its advanced stage at the time of diagnosis. A non-invasive method for its early detection remains mandatory to improve patients’ survival. Plasma levels of 351 proteins were quantified by Liquid Chromatography-Parallel Reaction Monitoring (LC-PRM)-based mass spectrometry in 128 lung cancer patients and 93 healthy donors. Bootstrap sampling and least absolute shrinkage and selection operator (LASSO) penalization were used to find the best protein combination for outcome prediction. The PanelomiX platform was used to select the optimal biomarker thresholds. The panel was validated in 48 patients and 49 healthy volunteers. A 6-protein panel clearly distinguished lung cancer from healthy individuals. The panel displayed excellent performance: area under the receiver operating characteristic curve (AUC) = 0.999, positive predictive value (PPV) = 0.992, negative predictive value (NPV) = 0.989, specificity = 0.989 and sensitivity = 0.992. The panel detected lung cancer independently of the disease stage. The 6-protein panel and other sub-combinations displayed excellent results in the validation dataset. In conclusion, we identified a blood-based 6-protein panel as a diagnostic tool in lung cancer. Used as a routine test for high- and average-risk individuals, it may complement currently adopted techniques in lung cancer screening.

Prdx6 Plays a Main Role in the Crosstalk Between Aging and Metabolic Sarcopenia

With the increase in average life expectancy, several individuals are affected by age-associated non-communicable chronic diseases (NCDs). The presence of NCDs, such as type 2 diabetes mellitus (T2DM), leads to the reduction in skeletal muscle mass, a pathological condition defined as sarcopenia. A key factor linking sarcopenia with cellular senescence and diabetes mellitus (DM) is oxidative stress. We previously reported as the absence of Peroxiredoxin 6 (Prdx6), an antioxidant enzyme implicated in maintaining intracellular redox homeostasis, induces an early-stage of T2DM. In the present study we sought to understand the role of Prdx6 in the crosstalk between aging and diabetic sarcopenia, by using Prdx6 knockout (Prdx6^-/-) mice. Absence of Prdx6 reduced telomeres length and Sirtuin1 (SIRT1) nuclear localization. An increase in Sa-β-Gal activity and p53-p21 pro-aging pathway were also evident. An impairment in IGF-1 (Insulin-like Groth Factor-1)/Akt-1/mTOR pathway leading to a relative increase in Forkhead Box O1 (FOXO1) nuclear localization and in a decrease of muscle differentiation as per lower levels of myoblast determination protein 1 (MyoD) was observed. Muscle atrophy was also present in Prdx6^-/- mice by the increase in Muscle RING finger 1 (MuRF1) levels and proteins ubiquitination associated to a reduction in muscle strength. The present study, innovatively, highlights a fundamental role of Prdx6, in the crosstalk between aging, sarcopenia, and DM.

Addition of Orange Peel in Orange Jam: Evaluation of Sensory, Physicochemical, and Nutritional Characteristics

Orange is highly nutritious and a source of phytochemical compounds. However, its by-products are usually discarded. In this study, we evaluated the effect of orange peel (OP) addition in orange jam on sensory, physicochemical, and nutritional characteristics. Four jam formulations were elaborated with different OP levels: OP0 (standard), OP4, OP8, and OP12 (Orange Peel 0, 4, 8 and 12%, respectively). All samples were evaluated for sensory acceptability, and physicochemical and nutritional composition. The addition of 12% orange peel in jam reduced (p < 0.05) the acceptability for all evaluated attributes, as well as overall acceptance and purchase intention. However, OP utilization increased (p < 0.05) the levels of water activity, soluble solids, titratable acidity, and sugars. Soluble solids/titratable acidity ratio, luminosity (L*), and yellow content (b*) decreased in all added OP jams, while red content (a*) increased. No change in the pH and moisture values of the product were observed after OP addition. Ash, protein, lipid, dietary fiber, ascorbic acid, carotenoids, phenolic compounds, and antioxidant capacity values increased after OP addition, while carbohydrate and energy content decreased. A texture test showed that adhesiveness decreased, while gumminess, chewiness, and elasticity increased after OP addition. We concluded that the addition of up to 8% orange peel in jam maintains sensory acceptability similar to that of the standard product. OP addition is a viable alternative to improve some of the product's physicochemical and nutritional characteristics.

Peroxiredoxin 6 Is a Key Antioxidant Enzyme in Modulating the Link between Glycemic and Lipogenic Metabolism

Insulin action and often glucose-stimulated insulin secretion are reduced in obesity. In addition, the excessive intake of lipids increases oxidative stress leading to overt type 2 diabetes mellitus (T2DM). Among the antioxidative defense systems, peroxiredoxin 6 (PRDX6) is able to reduce H₂O₂ and short chain and phospholipid hydroperoxides. Increasing evidences suggest that PRDX6 is involved in the pathogenesis of atherosclerosis and T2DM, but its role in the etiopathology of obesity and its complications is still not known. Therefore, in the present study, we sought to investigate this association by using PRDX6 knockout mice (PRDX6^−/−). Metabolic parameters, like carbon dioxide (VCO₂) production, oxygen consumption (VO₂), and the respiratory exchange ratio (RER), were determined using metabolic cages. Intraperitoneal insulin and glucose tolerance tests were performed to evaluate insulin sensitivity and glucose tolerance, respectively. Liver and pancreas histochemical analyses were also evaluated. The expression of enzymes involved in lipid and glucose metabolism was analyzed by real-time PCR. Following 24 weeks of high-fat-diet (HFD), PRDX6^−/− mice showed weight gain and higher food and drink intake compared to controls. VO₂ consumption and VCO₂ production decreased in PRDX6^−/− mice, while the RER was lower than 0.7 indicating a prevalent lipid metabolism. PRDX6^−/− mice fed with HFD showed a further deterioration on insulin sensitivity and glucose-stimulated insulin secretion. Furthermore, in PRDX6^−/− mice, insulin did not suppress adipose tissue lipolysis with consequent hepatic lipid overload and higher serum levels of ALT, cholesterol, and triglycerides. Interestingly, in PRDX6^−/− mice, liver and adipose tissue were associated with proinflammatory gene upregulation. Finally, PRDX6^−/− mice showed a higher rate of nonalcoholic steatohepatitis (NASH) compared to control. Our results suggest that PRDX6 may have a functional and protective role in the development of obesity-related metabolic disorders such as liver diseases and T2DM and may be considered a potential therapeutic target against these illnesses.

Peroxiredoxin 6 Down-Regulation Induces Metabolic Remodeling and Cell Cycle Arrest in HepG2 Cells

Peroxiredoxin 6 (Prdx6) is the only member of 1-Cys subfamily of peroxiredoxins in human cells. It is the only Prdx acting on phospholipid hydroperoxides possessing two additional sites with phospholipase A2 (PLA2) and lysophosphatidylcholine-acyl transferase (LPCAT) activities. There are contrasting reports on the roles and mechanisms of multifunctional Prdx6 in several pathologies and on its sensitivity to, and influence on, the redox environment. We have down-regulated Prdx6 with specific siRNA in hepatoblastoma HepG2 cells to study its role in cell proliferation, redox homeostasis, and metabolic programming. Cell proliferation and cell number decreased while cell volume increased; import of glucose and nucleotide biosynthesis also diminished while polyamines, phospholipids, and most glycolipids increased. A proteomic quantitative analysis suggested changes in membrane arrangement and vesicle trafficking as well as redox changes in enzymes of carbon and glutathione metabolism, pentose-phosphate pathway, citrate cycle, fatty acid metabolism, biosynthesis of aminoacids, and Glycolysis/Gluconeogenesis. Specific redox changes in Hexokinase-2 (HK2), Prdx6, intracellular chloride ion channel-1 (CLIC1), PEP-carboxykinase-2 (PCK2), and 3-phosphoglycerate dehydrogenase (PHGDH) are compatible with the metabolic remodeling toward a predominant gluconeogenic flow from aminoacids with diversion at 3-phospohglycerate toward serine and other biosynthetic pathways thereon and with cell cycle arrest at G1/S transition.

Mouse Models of Genetically Altered Peroxiredoxin 6

Peroxiredoxin 6 (Prdx6) has been shown to have three enzymatic activities: peroxidase, phospholipase A₂ (PLA₂) and acyl transferase. The peroxidase activity is unusual, as it is capable of reducing phospholipid hydroperoxides (as well as hydrogen peroxide and short chain organic peroxides). Knockout and overexpressing mice have been produced that demonstrate the effect that eliminating or overproducing Prdx6 has on the animals' physiology. In addition, mutations in various amino acids of Prdx6 have been identified that interfere with different enzymatic functions as well as protein transport. These mutations were originally characterized biochemically; subsequently, several knock-in mouse strains have been produced, each containing one mutation. These mice include the S32T knock-in that affects protein transport, the C47S knock-in that inactivates the peroxidase enzymatic activity, the D140A knock-in that inactivates the PLA₂ enzymatic activity and the H26A knock-in that inactivates the peroxidase and blocks binding to phospholipids. This review summarizes the properties of these mice based upon studies conducted with the knockout, overexpressing and knock-in mice and the effect of the genetic changes on the biochemistry and physiology of these mice. The availability of these mice is also briefly discussed.

Radioprotective Role of Peroxiredoxin 6

Peroxiredoxin 6 (Prdx6) is a member of an evolutionary ancient family of peroxidase enzymes with diverse functions in the cell. Prdx6 is an important enzymatic antioxidant. It reduces a wide range of peroxide substrates in the cell, thus playing a leading role in the maintenance of the redox homeostasis in mammalian cells. Beside peroxidase activity, Prdx6 has been shown to possess an activity of phospholipase A2, an enzyme playing an important role in membrane phospholipid metabolism. Moreover, Prdx6 takes part in intercellular and intracellular signal transduction due to its peroxidase and phospholipase activity, thus facilitating the initiation of regenerative processes in the cell, suppression of apoptosis, and activation of cell proliferation. Being an effective and important antioxidant enzyme, Prdx6 plays an essential role in neutralizing oxidative stress caused by various factors, including action of ionizing radiation. Endogenous Prdx6 has been shown to possess a significant radioprotective potential in cellular and animal models. Moreover, intravenous infusion of recombinant Prdx6 to animals before irradiation at lethal or sublethal doses has shown its high radioprotective effect. Exogenous Prdx6 effectively alleviates the severeness of radiation lesions, providing normalization of the functional state of radiosensitive organs and tissues, and leads to a significant elevation of the survival rate of animals. Prdx6 can be considered as a potent and promising radioprotective agent for reducing the pathological effect of ionizing radiation on mammalian organisms. The radioprotective properties and mechanisms of radioprotective action of Prdx6 are discussed in the current review.