4-Hydroxynonenal (HNE) modified proteins in metabolic diseases

Redox imbalance drives magnetic property and function changes in mice

The magnetic properties of substances directly determine their response to an externally applied magnetic field, which are closely associated with magnetoreception, magnetic resonance imaging (MRI), and magnetic bioeffects. However, people's understanding of the magnetic properties of living organisms remains limited. In this study, we utilized NRF2 (nuclear factor erythroid 2-related factor 2) deficient mice to investigate the contribution of redox (oxidation-reduction) homeostasis, in which the key process is the transfer of electron, a direct target of magnetic field and origin of paramagnetism. Our results show that the NRF2-/- mice exhibit significantly altered systemic redox state, accompanied by increased magnetic susceptibility, particularly in the liver and spleen. Further analyses reveal that the levels of paramagnetic reactive oxygen species (ROS) in these tissues are markedly elevated compared to wild-type mice. Moreover, the concentrations of Fe2+ and Fe3+ are significantly elevated in NRF2-/- mice, which are directly correlated with the increased magnetic susceptibility. The disrupted redox balance in NRF2-/- mice not only exacerbates oxidative stress and iron deposition, but also induces impairment to the liver and spleen. The findings highlight the combined effects of ROS and iron metabolism in driving magnetic susceptibility changes, providing valuable theoretical insights for further research into magnetic bioeffects and organ-specific sensitivity to magnetic fields.

NRF2 deficiency leads to inadequate beta cell adaptation during pregnancy and gestational diabetes

The late stages of mammalian pregnancy are accompanied by a mild increase in insulin resistance likely due to enhanced glucose demand of the growing fetus. Therefore, as an adaptive process to maintain euglycemia during pregnancy, maternal β-cell mass expands leading to increased insulin release. Defects in functional β-cell adaptive expansion during pregnancy can lead to gestational diabetes mellitus (GDM). While the exact mechanisms that promote GDM are poorly understood, GDM is associated with inadequate functional β-cell mass expansion and with a systematic increase of oxidative stress. Here, we show that NRF2 levels are upregulated in mouse β-cells at gestational day 15 (GD15). Inducible β-cell-specific Nrf2 deleted (βNrf2KO) mice display reduced β-cell proliferation, increased β-cell oxidative stress and lipid peroxidation, compromised β-cell function, and elevated β-cell death, leading to impaired β-cell mass expansion and dysregulated glucose homeostasis towards the end of pregnancy. Importantly, the gestational hormone 17-β-estradiol (E2) increases NRF2 levels, and downregulation of NRF2 suppresses E2-induced protection of β-cells against oxidative stress, suggesting that E2 exerts its antioxidant effects through activation of NRF2 signaling in β-cells. Collectively, these data highlight the critical role of NRF2 in regulating oxidative stress during the adaptive response of β-cells in pregnancy and identify NRF2 as a potential therapeutic target for GDM treatment.

Aloperine treatment attenuates acute spinal cord injury by reducing oxidative, inflammatory, and apoptotic responses via PI3K/AKT/NF-κB signaling in a rat contusion model

Spinal cord injury (SCI) is a severe condition that can result in nerve damage, impaired motor or sensory function, and ultimately a high mortality rate for injured individuals. High oxidative and inflammatory responses are closely linked to poor prognosis and can influence the recovery of neurological functions. Therefore, overcoming these processes early is a valuable therapy approach for SCI. Aloperine (ALO) is a quinolizidine-type alkaloid with numerous pharmacological activities, including antioxidant, anti-inflammatory, and neuroprotective effects. However, the role of ALO in SCI recovery remains unclear. Herein, we investigated its therapeutic impact on a contusion model of moderate SCI. ALO (100 mg/kg/day) was intraperitoneally administered to adult Sprague-Dawley rats for a week following surgery/SCI. Basso-Beattie-Bresnahan locomotor score was used to assess neural function after post-SCI (day-1/4/7), showing that ALO modestly improved hind-limb locomotor recovery. HE-staining showed that ALO attenuated the increased tissue sparseness and liquefactive necrosis due to the contusion injury. ALO treatments reduced the injury-induced apoptosis (Bax/Bcl-2, cleaved-caspase3), oxidative (4HNE, MDA), and inflammatory (NF-κB, TNF-α) responses, and increased antioxidant enzymes SOD1 and GPx1 levels. The network pharmacology and immunoblot analyses revealed that the molecular targets of ALO and SCI include the PI3K/AKT pathway. Our findings, for the first time, clearly demonstrated that a natural compound, aloperine, has a neuroprotective effect on SCI by reducing apoptosis, inducing the antioxidant defense system, and modulating PI3K/AKT and NF-κB signaling. These results suggest that aloperine administration might improve the total antioxidant status and significantly promote functional recovery following traumatic SCI.

The role of ALDHs in lipid peroxidation-related diseases

Lipid peroxidation presents the oxidative degradation of polyunsaturated fatty acids lincited by reactive species. Excessive accumulation of lipid peroxidation byproducts, including 4-hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA), causes protein dysfunction and various illnesses. Aldehyde dehydrogenases (ALDHs) catalyze the metabolism of both endogenous and exogenous aldehydes. These enzymes participate in detoxification and intermediary metabolism. Contemporary research has affirmed the involvement of both enzymatic and non-enzymatic pathways of ALDHs in modulating the evolution of diseases associated with lipid peroxidation. This review provides an overview of the biological functions and clinical implications concerning the enzymatic and non-enzymatic pathways of ALDHs in diseases related to lipid peroxidation, such as, non-alcoholic fatty liver disease (NAFLD), atherosclerosis, and type 2 diabetes (T2DM). Furthermore, the activators or inhibitors of ALDHs represent a promising therapeutic strategy for lipid peroxidation-related diseases.

Iron chelation by oral deferoxamine treatment decreased brain iron and iron signaling proteins

BACKGROUND

Deferoxamine (DFO) and other iron chelators are clinically used for cancer and stroke. They may also be useful for Alzheimer's disease (AD) to diminish iron from microbleeds. DFO may also stimulate antioxidant membrane repair which is impaired during AD. DFO and other chelators do enter the brain despite some contrary reports.

OBJECTIVE

Low dose, oral DFO was given in lab chow to wildtype (WT) C57BL/6 mice to evaluate potential impact on iron levels, iron-signaling and storage proteins, and amyloid-β protein precursor (AβPP) and processing enzymes. Young WT mice do not have microbleeds or disrupted blood-brain barrier of AD mice.

METHODS

Iron was measured by MRI and chemically after two weeks of dietary DFO. Cerebral cortex was examined for changes in iron metabolism, antioxidant signaling, and AβPP processing by western blot.

RESULTS

DFO decreased brain iron 18% (p < 0.01) estimated by R2 MRI and decreased seven major proteins that mediate iron metabolism by at least 25%. The iron storage proteins ferritin light and heavy chain decreased by at least 30%. AβPP and secretase enzymes also decreased by 30%.

CONCLUSIONS

WT mice respond to DFO with decreased AβPP, amyloid processing enzymes, and antioxidant repair. Potential DFO treatment for early-stage AD by DFO should consider the benefits of lowered AβPP and secretase enzymes.

C-terminal amides mark proteins for degradation via SCF-FBXO31

During normal cellular homeostasis, unfolded and mislocalized proteins are recognized and removed, preventing the build-up of toxic byproducts1. When protein homeostasis is perturbed during ageing, neurodegeneration or cellular stress, proteins can accumulate several forms of chemical damage through reactive metabolites2,3. Such modifications have been proposed to trigger the selective removal of chemically marked proteins3-6; however, identifying modifications that are sufficient to induce protein degradation has remained challenging. Here, using a semi-synthetic chemical biology approach coupled to cellular assays, we found that C-terminal amide-bearing proteins (CTAPs) are rapidly cleared from human cells. A CRISPR screen identified FBXO31 as a reader of C-terminal amides. FBXO31 is a substrate receptor for the SKP1-CUL1-F-box protein (SCF) ubiquitin ligase SCF-FBXO31, which ubiquitylates CTAPs for subsequent proteasomal degradation. A conserved binding pocket enables FBXO31 to bind to almost any C-terminal peptide bearing an amide while retaining exquisite selectivity over non-modified clients. This mechanism facilitates binding and turnover of endogenous CTAPs that are formed after oxidative stress. A dominant human mutation found in neurodevelopmental disorders reverses CTAP recognition, such that non-amidated neosubstrates are now degraded and FBXO31 becomes markedly toxic. We propose that CTAPs may represent the vanguard of a largely unexplored class of modified amino acid degrons that could provide a general strategy for selective yet broad surveillance of chemically damaged proteins.

FAM136A depletion induces mitochondrial stress and reduces mitochondrial membrane potential and ATP production

FAM136A deficiency has been associated with Ménière's disease. However, the underlying mechanism of action of this protein remains unclear. We hypothesized that FAM136A functions in maintaining mitochondria, even in HepG2 cells. To better characterize FAM136A function, we analyzed the cellular response caused by its depletion. FAM136A depletion induced reactive oxygen species (ROS) and reduced both mitochondrial membrane potential and ATP production. However, cleaved caspase-9 levels did not increase significantly. We next investigated why the depletion of FAM136A reduced the mitochondrial membrane potential and ATP production but did not lead to apoptosis. Depletion of FAM136A induced the mitochondrial unfolded protein response (UPRmt) and the expression levels of gluconeogenic phosphoenolpyruvate carboxykinases (PCK1 and PCK2) and ketogenic 3-hydroxy-3-methylglutaryl-CoA synthases (HMGCS1 and HMGCS2) were upregulated. Furthermore, depletion of FAM136A reduced accumulation of holocytochrome c synthase (HCCS), a FAM136A interacting enzyme that combines heme to apocytochrome c to produce holocytochrome c. Notably, the amount of heme in cytochrome c did not change significantly with FAM136A depletion, although the amount of total cytochrome c protein increased significantly. This observation suggests that greater amounts of cytochrome c remain unbound to heme in FAM136A-depleted cells.

Macrophage Ferroptotic Resistance Is Required for the Progression of Infantile Hemangioma

BACKGROUND

Ferroptosis is a programmed cell death caused by iron-dependent accumulation and cellular lipid peroxides, which is different from apoptosis and pyroptosis. This study investigated the possible effect of ferroptotic response in the pathogenesis of infantile hemangioma (IH).

METHODS AND RESULTS

The staining level of 4-hydroxynonenal (4-HNE), the marker of ferroptotic cells, was significantly increased in the involutive IH samples compared with the proliferative samples (9 proliferative versus 12 involutive lesions, P=0.0152). By contrast, the expression of glutathione peroxidase 4 (GPX4), a key enzyme regulating ferroptotic resistance, was significantly increased in the involutive IH samples. Meanwhile, the GPX4 was richly expressed in macrophages of IH. The data from in vitro study showed that the mRNA (P=0.0002) and protein (P=0.0385) expression levels of GPX4 were significantly upregulated in macrophages cultured with hemangioma-derived stem cells conditional medium (HemSC-CM). Mechanistically, HemSC-CM promoted the expression of GPX4 in macrophages (P=0.0482) by increasing nuclear factor erythroid 2-related factor 2 translocation to the nucleus (P=0.0026). Additionally, inhibition of GPX4 or inducing ferroptosis in macrophages could inhibit progression of lesion in IH nude mice mode.

CONCLUSIONS

Hemangioma-derived stem cells (HemSCs) could promote macrophage ferroptotic resistance through upregulating expression of GPX4, which is required for the progression of IH.

The attenuated hepatic clearance of propionate increases cardiac oxidative stress in propionic acidemia

Propionic acidemia (PA), arising from PCCA or PCCB variants, manifests as life-threatening cardiomyopathy and arrhythmias, with unclear pathophysiology. In this work, propionyl-CoA metabolism in rodent hearts and human pluripotent stem cell-derived cardiomyocytes was investigated with stable isotope tracing analysis. Surprisingly, gut microbiome-derived propionate rather than the propiogenic amino acids (valine, isoleucine, threonine, and methionine) or odd-chain fatty acids was found to be the primary cardiac propionyl-CoA source. In a Pcca-/-(A138T) mouse model and PA patients, accumulated propionyl-CoA and diminished acyl-CoA synthetase short-chain family member 3 impede hepatic propionate disposal, elevating circulating propionate. Prolonged propionate exposure induced significant oxidative stress in PCCA knockdown HL-1 cells and the hearts of Pcca-/-(A138T) mice. Additionally, Pcca-/-(A138T) mice exhibited mild diastolic dysfunction after the propionate challenge. These findings suggest that elevated circulating propionate may cause oxidative damage and functional impairment in the hearts of patients with PA.

Cerium oxide nanoparticles (nanoceria) pretreatment attenuates cell death in the hippocampus and cognitive dysfunction due to repeated isoflurane anesthesia in newborn rats

General anesthetics exposure, particularly prolonged or repeated exposure, is a crucial cause of neurological injuries. Notably, isoflurane (ISO), used in pediatric anesthesia practice, is toxic to the developing brain. The relatively weak antioxidant system at early ages needs antioxidant support to protect the brain against anesthesia. Cerium oxide nanoparticles (CeO2-NPs, nanoceria) are nano-antioxidants and stand out due to their unique surface chemistry, high stability, and biocompatibility. Although CeO2-NPs have been shown to exhibit neuroprotective and cognitive function-facilitating effects, there are no reports on their protective effects against anesthesia-induced neurotoxicity and cognitive impairments. Herein, Wistar albino rat pups were exposed to ISO (1.5 %, 3-h) at postnatal day (P)7+P9+P11, and the protective properties of CeO2-NP pretreatment (0.5 mg/kg, intraperitoneal route) were investigated for the first time. The control group at P7+9+11 received 50 % O2 (3-h) instead of ISO. Exposure to nanoceria one-hour before ISO protected hippocampal neurons of the developing rat brain against apoptosis [determined by hematoxylin-eosin (HE) staining, immunohistochemistry (IHC) analysis with caspase-3, and immunoblotting with Bax/Bcl2, cleaved caspase-3 and PARP1] oxidative stress, and inflammation [determined by immunoblotting with 4-hydroxynonenal (4HNE), nuclear factor kappa-B (NF-κB), and tumor necrosis factor-alpha (TNF-α)]. CeO2-NP pretreatment also reduced ISO-induced learning (at P28-32) and memory (at P33) deficits evaluated by Morris Water Maze. However, memory deficits and thigmotactic behaviors were detected in the agent-control group; elimination of these harmful effects will be possible with dose studies, thus providing evidence supporting safer use. Overall, our findings support pretreatment with nanoceria application as a simple strategy that might be used for pediatric anesthesia practice to protect infants and children from ISO-induced cell death and learning and memory deficits.

Morphological and Redox/Glycative Alterations in the PCOS Oviducts: Modulating Effects of Carnitines in PCOS Mice

Polycystic ovarian syndrome (PCOS) is a heterogeneous condition characterized by hyperandrogenism (HA), polycystic ovaries, and dysfunctional ovulation, and it is associated with metabolic problems such as insulin resistance (IR) and obesity. After having investigated the morphological and antioxidant/antiglycative alterations on mouse ovaries and uteri, we here focus on PCOS oviducts, a tract of the reproductive system essential for the nourishment and transport of gametes and embryos. The modulating effects of L-carnitine (LC) and acetyl-L-carnitine (ALC) were also assessed. CD1 mice were administered or not with dehydroepiandrosterone (DHEA, 6 mg/100 g body weight) for 20 days, alone or with 0.40 mg of L-carnitine (LC) and 0.20 mg of acetyl-L-carnitine (ALC). Oviducts were then subjected to histology and immunohistochemistry to evaluate their morphology and collagen deposition, and steroidogenesis. Oxidative, mitochondrial, and methylglyoxal (MG)-dependent damage was also investigated. Transmission electron microscopy was used to detect ultrastructural alterations. The PCOS oviducts were affected by hyperfibrosis, hyperplasia, hypertrophy, and altered steroidogenesis, with oxidative alterations associated with MethylGlyoxal-Advanced Glycation End product (MG-AGE) accumulation. A reduced ciliary coverage and numerous dilated intercellular spaces were found in the epithelium. LC-ALC administration mitigated PCOS oviductal alterations. These results provide evidence for the detrimental action of oxidative and glycative stress in PCOS oviducts, confirming a protective role of carnitines on the PCOS phenotype.

The interplay of oxidative stress, apoptotic signaling, and impaired mitochondrial function in the pyrethroid-induced cardiac injury: Alleviative role of curcumin-loaded chitosan nanoparticle

This study assessed the consequence of exposure to a pyrethroid insecticide, fenpropathrin (FPN), on the heart and the probable underlying mechanisms in rats. Moreover, the probable protective effect of curcumin-loaded chitosan nanoparticles (CMN-CNP) was evaluated. Forty male Sprague Dawley rats were distributed into four groups orally given corn oil, CMN-CNP (50 mg/kg b.wt), FPN (15 mg/kg b.wt), or CMN-CNP + FPN for 60 days. The results revealed that FPN exposure increased serum cardiac damage indicators. In addition, a substantial increase in the reactive oxygen species and malondialdehyde content but reduced enzymatic and non-enzymatic antioxidants and altered architecture was recorded in the cardiac tissue of FPN-exposed rats. Additionally, a significant down-regulation of expression of the mitochondrial complexes I-V, mitochondrial dynamics, and antioxidants-related genes but up-regulation of apoptosis-related genes was detected in the FPN-exposed group. Immunofluorescence analyses revealed higher amounts of the harmful protein 4-hydroxynonenal in the heart tissue of FPN-exposed rats. Nevertheless, the earlier disturbances were significantly rescued in the FPN + CMN-CNP treated group. Conclusively, our findings reported the cardiotoxic activity of FPN and the involvement of several mitochondrial imbalances as a probable underlying mechanism. Also, the study findings proved the efficacy of CMN-CNP in combating FPN cardiotoxic effects.

Inflammasome activity regulation by PUFA metabolites

Oxidative stress and the accompanying chronic inflammation constitute an important metabolic problem that may lead to pathology, especially when the body is exposed to physicochemical and biological factors, including UV radiation, pathogens, drugs, as well as endogenous metabolic disorders. The cellular response is associated, among others, with changes in lipid metabolism, mainly due to the oxidation and the action of lipolytic enzymes. Products of oxidative fragmentation/cyclization of polyunsaturated fatty acids (PUFAs) [4-HNE, MDA, 8-isoprostanes, neuroprostanes] and eicosanoids generated as a result of the enzymatic metabolism of PUFAs significantly modify cellular metabolism, including inflammation and the functioning of the immune system by interfering with intracellular molecular signaling. The key regulators of inflammation, the effectiveness of which can be regulated by interacting with the products of lipid metabolism under oxidative stress, are inflammasome complexes. An example is both negative or positive regulation of NLRP3 inflammasome activity by 4-HNE depending on the severity of oxidative stress. 4-HNE modifies NLRP3 activity by both direct interaction with NLRP3 and alteration of NF-κB signaling. Furthermore, prostaglandin E2 is known to be positively correlated with both NLRP3 and NLRC4 activity, while its potential interference with AIM2 or NLRP1 activity is unproven. Therefore, the influence of PUFA metabolites on the activity of well-characterized inflammasome complexes is reviewed.

Cellular and molecular mechanisms of hepatic ischemia-reperfusion injury: The role of oxidative stress and therapeutic approaches

Ischemia-reperfusion (IR) or reoxygenation injury is the paradoxical exacerbation of cellular impairment following restoration of blood flow after a period of ischemia during surgical procedures or other conditions. Acute interruption of blood supply to the liver and subsequent reperfusion can result in hepatocyte injury, apoptosis, and necrosis. Since the liver requires a continuous supply of oxygen for many biochemical reactions, any obstruction of blood flow can rapidly lead to hepatic hypoxia, which could quickly progress to absolute anoxia. Reoxygenation results in the increased generation of reactive oxygen species and oxidative stress, which lead to the enhanced production of proinflammatory cytokines, chemokines, and other signaling molecules. Consequent acute inflammatory cascades lead to significant impairment of hepatocytes and nonparenchymal cells. Furthermore, the expression of several vascular growth factors results in the heterogeneous closure of numerous hepatic sinusoids, which leads to reduced oxygen supply in certain areas of the liver even after reperfusion. Therefore, it is vital to identify appropriate therapeutic modalities to mitigate hepatic IR injury and subsequent tissue damage. This review covers all the major aspects of cellular and molecular mechanisms underlying the pathogenesis of hepatic ischemia-reperfusion injury, with special emphasis on oxidative stress, associated inflammation and complications, and prospective therapeutic approaches.

Microcirculatory Impairment and Cerebral Injury in Hydrocephalus and the Effects of Cerebrospinal Fluid Diversion

BACKGROUND AND OBJECTIVES

Hydrocephalus is characterized by progressive enlargement of cerebral ventricles, resulting in impaired microvasculature and cerebral hypoperfusion. This study aimed to demonstrate the microvascular changes in hydrocephalic rats and the effects of cerebrospinal fluid (CSF) release on cerebral blood flow (CBF).

METHODS

On postnatal day 21 (P21), male Wistar rats were intracisternally injected with either a kaolin suspension or saline. On P47, Evan's ratio (ER) was measured using MRI. On P49, the arteriolar diameter and vascular density of the pia were quantified using a capillary video microscope. The CBF was measured using laser Doppler flowmetry. The expressions of NeuN and glial fibrillary acidic protein determined by immunochemical staining were correlated with the ER. The CBF and rotarod test performance were recorded before and after CSF release. The expressions of 4-hydroxynonenal (4-HNE) and c-caspase-3 were studied on P56.

RESULTS

Ventriculomegaly was induced to varying degrees, resulting in the stretching and abnormal narrowing of pial arterioles, which regressed with increasing ER. Quantitative analysis revealed significant decreases in the arteriolar diameter and vascular density in the hydrocephalic group compared with those in the control group. In addition, the CBF in the hydrocephalic group decreased to 30%-50% of that in the control group. In hydrocephalus, the neurons appear distorted, and the expression of 4-HNE and reactive astrogliosis increase in the cortex. After CSF was released, improvements in the CBF and rotarod test performance were inversely associated with the ER. In addition, the levels of 4-HNE and c-caspase-3 were further elevated.

CONCLUSION

Rapid ventricular dilatation is associated with severe microvascular distortion, vascular regression, cortical hypoperfusion, and cellular changes that impair the recovery of CBF and motor function after CSF release. Moreover, CSF release may induce reperfusion injury. This pathophysiology should be taken into account when treating hydrocephalus.

Downregulation of 4-HNE and FOXO4 collaboratively promotes NSCLC cell migration and tumor growth

Non-small cell lung cancer (NSCLC) is among the most prevalent cancers and a leading cause of cancer-related mortality globally. Extracellular vesicles (EVs) derived from NSCLC play a pivotal role in lung cancer progression. Our findings reveal a direct correlation between the abundance of EVs and the transfection efficiencies. Co-culturing two different lung cancer cell lines could enhance EVs formation, cell proliferation, migration and tumorigenicity. mRNA chip and metabolic analyses revealed significant alterations in the FOXO signaling pathway and unsaturated fatty acid metabolism within tumor tissues derived from co-cultured cells. Shotgun lipidomics studies and bioinformatics analyses guided our attention towards 4-Hydroxynonenal (4-HNE) and FOXO4. Elevating 4-HNE or FOXO4 levels could reduce the formation of EVs and impede cell growth and migration. While silencing FOXO4 expression lead to an increase in cell cloning rate and enhanced migration. These findings suggest that regulating the production of 4-HNE and FOXO4 might provide an effective therapeutic approach for the treatment of NSCLC.

Arachidonic Acid Mobilization and Peroxidation Promote Microglial Dysfunction in Aβ Pathology

Aberrant increase of arachidonic acid (ARA) has long been implicated in the pathology of Alzheimer's disease (AD), while the underlying causal mechanism remains unclear. In this study, we revealed a link between ARA mobilization and microglial dysfunction in Aβ pathology. Lipidomic analysis of primary microglia from AppNL-GF mice showed a marked increase in free ARA and lysophospholipids (LPLs) along with a decrease in ARA-containing phospholipids, suggesting increased ARA release from phospholipids (PLs). To manipulate ARA-containing PLs in microglia, we genetically deleted lysophosphatidylcholine acyltransferase 3 (Lpcat3), the main enzyme catalyzing the incorporation of ARA into PLs. Loss of microglial Lpcat3 reduced the levels of ARA-containing PLs, free ARA and LPLs, leading to a compensatory increase in monounsaturated fatty acid (MUFA)-containing PLs in both male and female App NL-GF mice. Notably, the reduction of ARA in microglia significantly ameliorated oxidative stress and inflammatory responses while enhancing the phagocytosis of Aβ plaques and promoting the compaction of Aβ deposits. Mechanistically, scRNA seq suggested that LPCAT3 deficiency facilitates phagocytosis by facilitating de novo lipid synthesis while protecting microglia from oxidative damage. Collectively, our study reveals a novel mechanistic link between ARA mobilization and microglial dysfunction in AD. Lowering brain ARA levels through pharmacological or dietary interventions may be a potential therapeutic strategy to slow down AD progression.

Proteome-wide 4-hydroxy-2-nonenal signature of oxidative stress in the marine invasive tunicate Botryllus schlosseri

The colonial ascidian Boytryllus schlosseri is an invasive marine chordate that thrives under conditions of anthropogenic climate change. We show that the B. schlosseri expressed proteome contains unusually high levels of proteins that are adducted with 4-hydroxy-2-nonenal (HNE). HNE represents a prominent posttranslational modification resulting from oxidative stress. Although numerous studies have assessed oxidative stress in marine organisms HNE protein modification has not previously been determined in any marine species. LC/MS proteomics was used to identify 1052 HNE adducted proteins in B. schlosseri field and laboratory populations. Adducted amino acid residues were ascertained for 1849 modified sites, of which 1195 had a maximum amino acid localization score. Most HNE modifications were at less reactive lysines (rather than more reactive cysteines). HNE prevelance on most sites was high. These observations suggest that B. schlosseri experiences and tolerates high intracellular reactive oxygen species levels, resulting in substantial lipid peroxidation. HNE adducted B. schlosseri proteins show enrichment in mitochondrial, proteostasis, and cytoskeletal functions. Based on these results we propose that redox signaling contributes to regulating energy metabolism, the blastogenic cycle, oxidative burst defenses, and cytoskeleton dynamics during B. schlosseri development and physiology. A DIA assay library was constructed to quantify HNE adduction at 72 sites across 60 proteins that represent a holistic network of functionally discernable oxidative stress bioindicators. We conclude that the vast amount of HNE protein adduction in this circumpolar tunicate is indicative of high oxidative stress tolerance contributing to its range expansion into diverse environments.

NEW & NOTEWORTHY

Oxidative stress results from environmental challenges that increase in frequency and severity during the Anthropocene. Oxygen radical attack causes lipid peroxidation leading to HNE production. Proteome-wide HNE adduction is highly prevalent in Botryllus schlosseri , a widely distributed, highly invasive, and economically important biofouling ascidian and the first marine species to be analyzed for proteome HNE modification. HNE adduction of specific proteins physiologically sequesters reactive oxygen species, which enhances fitness and resilience during environmental change.

Glutathione S-Transferase α4 Alleviates Hyperlipidemia-Induced Vascular Neointimal Hyperplasia in Arteriovenous Grafts via Inhibiting Endoplasmic Reticulum Stress

ABSTRACT

Neointimal hyperplasia causes the failure of coronary artery bypass grafting. Our previous studies have found that endothelial dysfunction is 1 candidate for triggering neointimal hyperplasia, but which factors are involved in this process is unclear. Glutathione S-transferase α4 (GSTA4) plays an important role in metabolizing 4-hydroxynonenal (4-HNE), a highly reactive lipid peroxidation product, which causes endothelial dysfunction or death. Here, we investigated the role of GSTA4 in neointima formation after arteriovenous grafts (AVGs) with or without high-fat diet (HFD). Compared with normal diet, HFD caused endothelial dysfunction and increased neointima formation, concomitantly accompanied by downregulated expression of GSTA4 at the mRNA and protein levels. In vitro, overexpression of GSTA4 attenuated 4-HNE-induced endothelial dysfunction and knockdown of GSTA4 aggravated endothelial dysfunction. Furthermore, silencing GSTA4 expression facilitated the activation of 4-HNE-induced endoplasmic reticulum stress and inhibition of endoplasmic reticulum stress pathway alleviated 4-HNE-induced endothelial dysfunction. In addition, compared with wild-type mice, mice with knockout of endothelial-specific GSTA4 (GSTA4 endothelial cell KO) exhibited exacerbated vascular endothelial dysfunction and increased neointima formation caused by HFD. Together, these results demonstrate the critical role of GSTA4 in protecting the function of endothelial cells and in alleviating hyperlipidemia-induced vascular neointimal hyperplasia in arteriovenous grafts.

Protein Haptenation and Its Role in Allergy

Humans are exposed to numerous electrophilic chemicals either as medicines, in the workplace, in nature, or through use of many common cosmetic and household products. Covalent modification of human proteins by such chemicals, or protein haptenation, is a common occurrence in cells and may result in generation of antigenic species, leading to development of hypersensitivity reactions. Ranging in severity of symptoms from local cutaneous reactions and rhinitis to potentially life-threatening anaphylaxis and severe hypersensitivity reactions such as Stephen-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), all these reactions have the same Molecular Initiating Event (MIE), i.e. haptenation. However, not all individuals who are exposed to electrophilic chemicals develop symptoms of hypersensitivity. In the present review, we examine common chemistry behind the haptenation reactions leading to formation of neoantigens. We explore simple reactions involving single molecule additions to a nucleophilic side chain of proteins and complex reactions involving multiple electrophilic centers on a single molecule or involving more than one electrophilic molecule as well as the generation of reactive molecules from the interaction with cellular detoxification mechanisms. Besides generation of antigenic species and enabling activation of the immune system, we explore additional events which result directly from the presence of electrophilic chemicals in cells, including activation of key defense mechanisms and immediate consequences of those reactions, and explore their potential effects. We discuss the factors that work in concert with haptenation leading to the development of hypersensitivity reactions and those that may act to prevent it from developing. We also review the potential harnessing of the specificity of haptenation in the design of potent covalent therapeutic inhibitors.

Dysregulation of cardiac mitochondrial aldehyde dehydrogenase 2: Studies in dogs with chronic heart failure

Mitochondrial (MITO) dysfunction occurs in the failing heart and contributes to worsening of heart failure (HF). Reduced aldehyde dehydrogenase 2 (ALDH2) in left ventricular (LV) myocardium of diabetic hearts has been implicated in MITO dysfunction through accumulation of toxic aldehydes including and elevated levels of 4-hydroxy-2-nonenal (4HNE). This study examined whether dysregulation of MITO ALDH2 (mALDH2) occurs in mitochondria of the failing LV and is associated with increased levels of 4HNE. LV tissue from 7 HF and 7 normal (NL) dogs was obtained. Protein quantification of total mitochondrial ALDH2 (t-mALDH2), phosphorylated mALDH2 (p-mALDH2), total MITO protein kinase c epsilon (t-mPKCε), phosphorylated mPKCε (p-mPKCε) was performed by Western blotting, and total mALDH2 enzymatic activity was measured. Protein adducts of 4HNE-MITO and 4HNE-mALDH2 were also measured in MITO fraction by Western Blotting. Protein level of t-mALDH2 was decreased in HF compared with NL dogs (0.63 ± 0.07 vs 1.17 ± 0.08, p < 0.05) as did mALDH2 enzymatic activity (51.39 ± 3 vs. 107.66 ± 4 nmol NADH/min/mg, p < 0.05). Phosphorylated-mALDH2 and p-mPKCε were unchanged. 4HNE-MITO proteins adduct levels increased in HF compared with NL (2.45 ± 0.08 vs 1.30 ± 0.03 du, p < 0.05) as did adduct levels of 4HNE-mALDH2 (1.60 ± 0.20 vs 0.39 ± 0.08, p < 0.05). In isolated failing cardiomyocytes (CM) exposure to 4HNE decreased mALDH2 activity, increased ROS and 4HNE-ALDH2 adducts, and worsened MITO function. Stimulation of mALDH2 activity with ALDA-1 in isolated HF CMs compared to NL CMs improved ADP-stimulated respiration and maximal ATP synthesis to a greater extant (+47 % and +89 %, respectively). Down-regulation of mALDH2 protein levels and activity occurs in HF and contributes to MITO dysfunction and is likely caused by accumulation of 4HNE-mALDH2 adduct. Increasing mALDH2 activity (via ALDA-1) improved MITO function in failing CMs.

Automated determination of 8-OHdG in cells and tissue via immunofluorescence using a specially created antibody

Despite powerful DNA repair systems, oxidative damage/modification to DNA is an inevitable side effect of metabolism, ionizing radiation, lifestyle habits, inflammatory pathologies such as type-2 diabetes or metabolic syndrome, cancer and natural aging. One of the most common oxidative DNA modifications is 8-OHdG (8‑hydroxy-2'-deoxyguanosine), which is the most widely used marker in research and clinical diagnostics. 8-OHdG is easily and specifically detectable in various samples such as urine, plasma, cells and tissues via a large variety of methods like ELISA, HPLC, chromatographic methods, and immunochemistry. Formed by oxidation of guanine and being representative for the degree of DNA damage, 8-OHdG can be also used as biomarker for risk assessment of various cancers as well as degenerative diseases. Here, we present a highly specific, self-developed 8-OHdG antibody in successful comparison to a commercially one, tested in cells (FF95, HCT116, and HT22) and intestinal tissue, focusing on automatized evaluation via fluorescence/confocal microscopy.

Silver nanoparticles induce formation of multi-protein aggregates that contain cadherin but do not colocalize with nanoparticles

Silver nanoparticles (AgNPs) are increasingly incorporated in diverse products to confer antimicrobial properties. They are released into the environment during manufacture, after disposal, and from the products during use. Because AgNPs bioaccumulate in brain, it is important to understand how they interact with neural cell physiology. We found that the focal adhesion (FA)-associated protein cadherin aggregated in a dose-dependent response to AgNP exposure in differentiating cultured B35 neuroblastoma cells. These aggregates tended to colocalize with F-actin inclusions that form in response to AgNP and also contain β-catenin. However, using hyperspectral microscopy, we demonstrate that these multi-protein aggregates did not colocalize with the AgNPs themselves. Furthermore, expression and organization of the FA protein vinculin did not change in cells exposed to AgNP. Our findings suggest that AgNPs activate an intermediate mechanism which leads to formation of aggregates via specific protein-protein interactions. Finally, we detail the changes in hyperspectral profiles of AgNPs during different stages of cell culture and immunocytochemistry processing. AgNPs in citrate-stabilized solution present mostly blue with some rainbow spectra and these are maintained upon mounting in Prolong Gold. Exposure to tissue culture medium results in a uniform green spectral shift that is not further altered by fixation and protein block steps of immunocytochemistry.

Carbonylation of Runx2 at K176 by 4-Hydroxynonenal Accelerates Vascular Calcification

BACKGROUND

Vascular calcification, which is characterized by calcium deposition in arterial walls and the osteochondrogenic differentiation of vascular smooth muscle cells, is an actively regulated process that involves complex mechanisms. Vascular calcification is associated with increased cardiovascular adverse events. The role of 4-hydroxynonenal (4-HNE), which is the most abundant stable product of lipid peroxidation, in vascular calcification has been poorly investigated.

METHODS

Serum was collected from patients with chronic kidney disease and controls, and the levels of 4-HNE and 8-iso-prostaglandin F2α were measured. Sections of coronary atherosclerotic plaques from donors were immunostained to analyze calcium deposition and 4-HNE. A total of 658 patients with coronary artery disease who received coronary computed tomography angiography were recruited to analyze the relationship between coronary calcification and the rs671 mutation in aldehyde dehydrogenase 2 (ALDH2). ALDH2 knockout (ALDH2-/-) mice, smooth muscle cell-specific ALDH2 knockout mice, ALDH2 transgenic mice, and their controls were used to establish vascular calcification models. Primary mouse aortic smooth muscle cells and human aortic smooth muscle cells were exposed to medium containing β-glycerophosphate and CaCl2 to investigate cell calcification and the underlying molecular mechanisms.

RESULTS

Elevated 4-HNE levels were observed in the serum of patients with chronic kidney disease and model mice and were detected in calcified artery sections by immunostaining. ALDH2 knockout or smooth muscle cell-specific ALDH2 knockout accelerated the development of vascular calcification in model mice, whereas overexpression or activation prevented mouse vascular calcification and the osteochondrogenic differentiation of vascular smooth muscle cells. In patients with coronary artery disease, patients with ALDH2 rs671 gene mutation developed more severe coronary calcification. 4-HNE promoted calcification of both mouse aortic smooth muscle cells and human aortic smooth muscle cells and their osteochondrogenic differentiation in vitro. 4-HNE increased the level of Runx2 (runt-related transcription factor-2), and the effect of 4-HNE on promoting vascular smooth muscle cell calcification was ablated when Runx2 was knocked down. Mutation of Runx2 at lysine 176 reduced its carbonylation and eliminated the 4-HNE-induced upregulation of Runx2.

CONCLUSIONS

Our results suggest that 4-HNE increases Runx2 stabilization by directly carbonylating its K176 site and promotes vascular calcification. ALDH2 might be a potential target for the treatment of vascular calcification.

Saliva as a Diagnostic Tool for Early Detection of Exercise-Induced Oxidative Damage in Female Athletes

Although blood still remains the most commonly utilized medium to detect increased levels of oxidative damage induced by exercise, saliva diagnostics have gained increasing popularity due to their non-invasive nature and athlete-friendly collection process. Given that the contribution of various phases of the menstrual cycle to the levels of oxidative damage may differ, the aim of this study was to evaluate an agreement between salivary and plasmatic levels of lipid peroxidation products in female swimmers in both the follicular (F) and luteal (L) phases of the menstrual cycle at rest and following exercise. Twelve well-trained female swimmers aged 19.6 ± 1.1 years old were examined. We measured diene conjugates (DCs), triene conjugates (TCs), and Schiff bases (SBs) in lipids immediately after their extraction from both saliva and blood plasma. All female swimmers were studied two times each, in the two different phases of one menstrual cycle, before and after high-intensity interval exercise (HIIE). Salivary and plasmatic levels of DCs, TCs, and SBs significantly increased post-exercise compared to pre-exercise, in both the F and L phases. A high positive correlation was observed between the concentrations of DCs, TCs, and SBs in the saliva and blood plasma of participants in the F and L phases, both at rest and following HIIE. Ordinary least products regression analysis indicates that there was no proportional and differential bias in the data. The Bland-Altman method also declares that there was no differential bias, since the line of equality was within the 95% confidence interval of the mean difference between salivary and plasmatic levels of DCs, TCs, and SBs in female swimmers, in both the F and L phases, before and after HIIE. There was also no proportional bias in the Bland-Altman plots. Thus, this is the first study to report a high agreement between the quantifications of DCs, TCs, and SBs in the saliva and blood plasma of female swimmers in both the F and L phases, at rest and following HIIE.

Computational and physicochemical insight into 4-hydroxy-2-nonenal induced structural and functional perturbations in human low-density lipoprotein

Lipid peroxidation (LPO) is a biological process that frequently occurs under physiological conditions. Undue oxidative stress increases the level of LPO; which may further contribute to the development of cancer. 4-Hydroxy-2-nonenal (HNE), one of the principal by-products of LPO, is present in high concentrations in oxidatively stressed cells. HNE rapidly reacts with various biological components, including DNA and proteins; however, the extent of protein degradation by lipid electrophiles is not well understood. The influence of HNE on protein structures will likely have a considerable therapeutic value. This research elucidates the potential of HNE, one of the most researched phospholipid peroxidation products, in modifying low-density lipoprotein (LDL). In this study, we tracked the structural alterations in LDL by HNE using various physicochemical techniques. To comprehend the stability, binding mechanism and conformational dynamics of the HNE-LDL complex, computational investigations were carried out. LDL was altered in vitro by HNE, and the secondary and tertiary structural alterations were examined using spectroscopic methods, such as UV-visible, fluorescence, circular dichroism and fourier transform infrared spectroscopy. Carbonyl content, thiobarbituric acid-reactive-substance (TBARS) and nitroblue tetrazolium (NBT) reduction assays were used to examine changes in the oxidation status of LDL. Thioflavin T (ThT), 1-anilinonaphthalene-8-sulfonic (ANS) binding assay and electron microscopy were used to investigate aggregates formation. According to our research, LDL modified by HNE results in changes in structural dynamics, oxidative stress and the formation of LDL aggregates. The current investigation must characterize HNE's interactions with LDL and comprehend how it can change their physiological or pathological functions.Communicated by Ramaswamy H. Sarma.

Reactive Carbonyl Species and Protein Lipoxidation in Atherogenesis

Atherosclerosis is a multifactorial disease of medium and large arteries, characterized by the presence of lipid-rich plaques lining the intima over time. It is the main cause of cardiovascular diseases and death worldwide. Redox imbalance and lipid peroxidation could play key roles in atherosclerosis by promoting a bundle of responses, including endothelial activation, inflammation, and foam cell formation. The oxidation of polyunsaturated fatty acids generates various lipid oxidation products such as reactive carbonyl species (RCS), including 4-hydroxy alkenals, malondialdehyde, and acrolein. RCS covalently bind to nucleophilic groups of nucleic acids, phospholipids, and proteins, modifying their structure and activity and leading to their progressive dysfunction. Protein lipoxidation is the non-enzymatic post-translational modification of proteins by RCS. Low-density lipoprotein (LDL) oxidation and apolipoprotein B (apoB) modification by RCS play a major role in foam cell formation. Moreover, oxidized LDLs are a source of RCS, which form adducts on a huge number of proteins, depending on oxidative stress intensity, the nature of targets, and the availability of detoxifying systems. Many systems are affected by lipoxidation, including extracellular matrix components, membranes, cytoplasmic and cytoskeletal proteins, transcription factors, and other components. The mechanisms involved in lipoxidation-induced vascular dysfunction are not fully elucidated. In this review, we focus on protein lipoxidation during atherogenesis.

Age-Dependent Changes in Nrf2/Keap1 and Target Antioxidant Protein Expression Correlate to Lipoxidative Adducts, and Are Modulated by Dietary N-3 LCPUFA in the Hippocampus of Mice

The brain has a high metabolism rate that may generate reactive oxygen and nitrogen species. Consequently, nerve cells require highly efficient antioxidant defenses in order to prevent a condition of deleterious oxidative stress. This is particularly relevant in the hippocampus, a highly complex cerebral area involved in processing superior cognitive functions. Most current evidence points to hippocampal oxidative damage as a causal effect for neurodegenerative disorders, especially Alzheimer's disease. Nuclear factor erythroid-2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/Keap1) is a master key for the transcriptional regulation of antioxidant and detoxifying systems. It is ubiquitously expressed in brain areas, mainly supporting glial cells. In the present study, we have analyzed the relationships between Nrf2 and Keap1 isoforms in hippocampal tissue in response to aging and dietary long-chain polyunsaturated fatty acids (LCPUFA) supplementation. The possible involvement of lipoxidative and nitrosative by-products in the dynamics of the Nrf2/Keap1 complex was examined though determination of protein adducts, namely malondialdehyde (MDA), 4-hydroxynonenal (HNE), and 3-nitro-tyrosine (NTyr) under basal conditions. The results were correlated to the expression of target proteins heme-oxygenase-1 (HO-1) and glutathione peroxidase 4 (GPx4), whose expressions are known to be regulated by Nrf2/Keap1 signaling activation. All variables in this study were obtained simultaneously from the same preparations, allowing multivariate approaches. The results demonstrate a complex modification of the protein expression patterns together with the formation of adducts in response to aging and diet supplementation. Both parameters exhibited a strong interaction. Noticeably, LCPUFA supplementation to aged animals restored the Nrf2/Keap1/target protein patterns to the status observed in young animals, therefore driving a "rejuvenation" of hippocampal antioxidant defense.

The skin sensitization adverse outcome pathway: exploring the role of mechanistic understanding for higher tier risk assessment

For over a decade, the skin sensitization Adverse Outcome Pathway (AOP) has served as a useful framework for development of novel in chemico and in vitro assays for use in skin sensitization hazard and risk assessment. Since its establishment, the AOP framework further fueled the existing efforts in new assay development and stimulated a plethora of activities with particular focus on validation, reproducibility and interpretation of individual assays and combination of assay outputs for use in hazard/risk assessment. In parallel, research efforts have also accelerated in pace, providing new molecular and dynamic insight into key events leading to sensitization. In light of novel hypotheses emerging from over a decade of focused research effort, mechanistic evidence relating to the key events in the skin sensitization AOP may complement the tools currently used in risk assessment. We reviewed the recent advances unraveling the complexity of molecular events in sensitization and signpost the most promising avenues for further exploration and development of useful assays.

Inhibition of the skeletal muscle Lands cycle ameliorates weakness induced by physical inactivity

BACKGROUND

Lipid hydroperoxides (LOOH) have been implicated in skeletal muscle atrophy with age and disuse. Lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme of the Lands cycle, conjugates a polyunsaturated fatty acyl chain to a lysophospholipid to form a polyunsaturated fatty acid containing phospholipid (PUFA-PL) molecule, providing substrates for LOOH propagation. Previous studies suggest that inhibition of the Lands cycle is an effective strategy to suppress LOOH. Mice with skeletal muscle-specific tamoxifen-inducible knockout of LPCAT3 (LPCAT3-MKO) were utilized to determine if muscle-specific attenuation of LOOH may alleviate muscle atrophy and weakness with disuse.

METHODS

LPCAT3-MKO and control mice underwent 7 days of sham or hindlimb unloading (HU model) to study muscle mass and force-generating capacity. LOOH was assessed by quantifying 4-hydroxynonenal (4-HNE)-conjugated peptides. Quantitative PCR and lipid mass spectrometry were used to validate LPCAT3 deletion.

RESULTS

Seven days of HU was sufficient to induce muscle atrophy and weakness concomitant to a ~2-fold increase in 4-HNE (P = 0.0069). Deletion of LPCAT3 reversed HU-induced increase in muscle 4-HNE (P = 0.0256). No difference was found in body mass, body composition, or caloric intake between genotypes. The soleus (SOL) and plantaris (PLANT) muscles of the LPCAT3-MKO mice experienced ~15% and ~40% less atrophy than controls, respectively. (P = 0.0011 and P = 0.0265). Type I and IIa SOL myofibers experienced a ~40% decrease in cross sectional area (CSA), which was attenuated to only 15% in the LPCAT3-MKO mice (P = 0.0170 and P = 0.0411, respectively). Strikingly, SOL muscles were fully protected and extensor digitorum longus (EDL) muscles experienced a ~35% protection from HU-induced reduction in force-generating capacity in the LPCAT3-MKO mice compared with controls (P < 0.0001 for both muscles).

CONCLUSIONS

Our findings demonstrate that attenuation of skeletal muscle lipid hydroperoxides is sufficient to restore its function, in particular a protection from reduction in muscle specific force. Our findings suggest muscle lipid peroxidation contributes to atrophy and weakness induced by disuse in mice.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Focus on Mitochondrial Respiratory Chain: Potential Therapeutic Target for Chronic Renal Failure

The function of the respiratory chain is closely associated with kidney function, and the dysfunction of the respiratory chain is a primary pathophysiological change in chronic kidney failure. The incidence of chronic kidney failure caused by defects in respiratory-chain-related genes has frequently been overlooked. Correcting abnormal metabolic reprogramming, rescuing the "toxic respiratory chain", and targeting the clearance of mitochondrial reactive oxygen species are potential therapies for treating chronic kidney failure. These treatments have shown promising results in slowing fibrosis and inflammation progression and improving kidney function in various animal models of chronic kidney failure and patients with chronic kidney disease (CKD). The mitochondrial respiratory chain is a key target worthy of attention in the treatment of chronic kidney failure. This review integrated research related to the mitochondrial respiratory chain and chronic kidney failure, primarily elucidating the pathological status of the mitochondrial respiratory chain in chronic kidney failure and potential therapeutic drugs. It provided new ideas for the treatment of kidney failure and promoted the development of drugs targeting the mitochondrial respiratory chain.

Cardiometabolic Changes in Sirtuin1-Heterozygous Mice on High-Fat Diet and Melatonin Supplementation

A hypercaloric fatty diet predisposes an individual to metabolic syndrome and cardiovascular complications. Sirtuin1 (SIRT1) belongs to the class III histone deacetylase family and sustains anabolism, mitochondrial biogenesis, and fat distribution. Epididymal white adipose tissue (eWAT) is involved in inflammation, whilst interscapular brown adipose tissue (iBAT) drives metabolism in obese rodents. Melatonin, a pineal indoleamine, acting as a SIRT1 modulator, may alleviate cardiometabolic damage. In the present study, we morphologically characterized the heart, eWAT, and iBAT in male heterozygous SIRT1+/- mice (HET mice) on a high-fat diet (60%E lard) versus a standard rodent diet (8.5% E fat) and drinking melatonin (10 mg/kg) for 16 weeks. Wild-type (WT) male C57Bl6/J mice were similarly fed for comparison. Cardiomyocyte fibrosis and endoplasmic reticulum (ER) stress response worsened in HET mice on a high-fat diet vs. other groups. Lipid peroxidation, ER, and mitochondrial stress were assessed by 4 hydroxy-2-nonenal (4HNE), glucose-regulated protein78 (GRP78), CCAA/enhancer-binding protein homologous protein (CHOP), heat shock protein 60 (HSP60), and mitofusin2 immunostainings. Ultrastructural analysis indicated the prevalence of atypical inter-myofibrillar mitochondria with short, misaligned cristae in HET mice on a lard diet despite melatonin supplementation. Abnormal eWAT adipocytes, crown-like inflammatory structures, tumor necrosis factor alpha (TNFα), and iBAT whitening characterized HET mice on a hypercaloric fatty diet and were maintained after melatonin supply. All these data suggest that melatonin's mechanism of action is strictly linked to full SIRT1 expression, which is required for the exhibition of effective antioxidant and anti-inflammatory properties.

Lipid peroxidation: Reactive carbonyl species, protein/DNA adducts, and signaling switches in oxidative stress and cancer

Under the exposure of lipids to reactive oxygen species (ROS), lipid peroxidation proceeds non-enzymatically and generates an extremely heterogeneous mixture of reactive carbonyl species (RCS). Among them, HNE, HHE, MDA, methylglyoxal, glyoxal, and acrolein are the most studied and/or abundant ones. Over the last decades, significant progress has been achieved in understanding mechanisms of RCS generation, protein/DNA adduct formation, and their identification and quantification in biological samples. In our review, we critically discuss the advancements in understanding the roles of RCS-induced protein/DNA modifications in signaling switches to provide adaptive cell response under physiological and oxidative stress conditions. At non-toxic concentrations, RCS modify susceptible Cys residue in c-Src to activate MAPK signaling and Cys, Lys, and His residues in PTEN to cause its reversible inactivation, thereby stimulating PI3K/PKB(Akt) pathway. RCS toxic concentrations cause irreversible Cys modifications in Keap1 and IKKβ followed by stabilization of Nrf2 and activation of NF-κB, respectively, for their nuclear translocation and antioxidant gene expression. Dysregulation of these mechanisms causes diseases including cancer. Alterations in RCS, RCS detoxifying enzymes, RCS-modified protein/DNA adducts, and signaling pathways have been implicated in various cancer types.

Neuroprotective Effects of Aldehyde-Reducing Composition in an LPS-Induced Neuroinflammation Model of Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disease in which neuroinflammation and oxidative stress interact to contribute to pathogenesis. This study investigates the in vivo neuroprotective effects of a patented yeast extract lysate in a lipopolysaccharide (LPS)-induced neuroinflammation model. The yeast extract lysate, named aldehyde-reducing composition (ARC), exhibited potent antioxidant and anti-aldehyde activities in vitro. Oral administration of ARC at 10 or 20 units/kg/day for 3 days prior to intraperitoneal injection of LPS (10 mg/kg) effectively preserved dopaminergic neurons in the substantia nigra (SN) and striatum by preventing LPS-induced cell death. ARC also normalized the activation of microglia and astrocytes in the SN, providing further evidence for its neuroprotective properties. In the liver, ARC downregulated the LPS-induced increase in inflammatory cytokines and reversed the LPS-induced decrease in antioxidant-related genes. These findings indicate that ARC exerts potent antioxidant, anti-aldehyde, and anti-inflammatory effects in vivo, suggesting its potential as a disease-modifying agent for the prevention and treatment of neuroinflammation-related diseases, including Parkinson's disease.

Zika virus remodelled ER membranes contain proviral factors involved in redox and methylation pathways

Zika virus (ZIKV) has emerged as a global health issue, yet neither antiviral therapy nor a vaccine are available. ZIKV is an enveloped RNA virus, replicating in the cytoplasm in close association with ER membranes. Here, we isolate ER membranes from ZIKV-infected cells and determine their proteome. Forty-six host cell factors are enriched in ZIKV remodeled membranes, several of these having a role in redox and methylation pathways. Four proteins are characterized in detail: thioredoxin reductase 1 (TXNRD1) contributing to folding of disulfide bond containing proteins and modulating ZIKV secretion; aldo-keto reductase family 1 member C3 (AKR1C3), regulating capsid protein abundance and thus, ZIKV assembly; biliverdin reductase B (BLVRB) involved in ZIKV induced lipid peroxidation and increasing stability of viral transmembrane proteins; adenosylhomocysteinase (AHCY) indirectly promoting m6A methylation of ZIKV RNA by decreasing the level of S- adenosyl homocysteine and thus, immune evasion. These results highlight the involvement of redox and methylation enzymes in the ZIKV life cycle and their accumulation at virally remodeled ER membranes.

Oxidative modification of carbonic anhydrase by peroxynitrite trigger immune response in mice and rheumatic disease patients

BACKGROUND

Carbonic anhydrases (CA) are metalloenzymes with wide tissue distribution, involved in many important physiological processes, and in some rheumatic diseases, autoantibodies are formed against these enzymes. Recent studies have suggested that oxidative stress triggers anti-CA antibody formation. In this study, we aimed to investigate the effects of modification with oxidative/nitrosative stress end products on CA antigenicity in mice and the relationship between the modified CA autoantibodies and oxidant-antioxidant status in patients with rheumatoid arthritis (RA) and Sjögren's syndrome (SjS).

METHODS

CA I and CA II isoenzymes were isolated from human erythrocytes and modified with 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), and peroxynitrite (PN). Balb-c mice were immunized with these agents to determine the effects of modification on CA antigenicity. The autoantibody titers of modified CA isoenzymes were detected in patients. In addition MDA, 4-HNE, 3-nitrotyrosine (3-NT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities were measured to assess the oxidant-antioxidant status in patients.

RESULTS

Modifications of carbonic anhydrase with oxidative stress end products, HNE, MDA and PN, lead to alterations in the immune response to these enzymes in mice. It was found that HNE and MDA decreased the antigenicity while PN increased. In addition, PN-modified CA autoantibody levels were found to be significantly different in both RA and SjS patients compared to their controls (p<0.05).

CONCLUSIONS

PN modifications can also trigger an immune response against CA isoenzymes in mice, and PN-modified CA I and CA II autoantibody titers were found at a significantly high level in both RA and SjS patients.

Aspirin protects human trophoblast HTR-8/SVneo cells from H2O2-Induced oxidative stress via NADPH/ROS pathway

INTRODUCTION

Pre-eclampsia (PE) is a pregnancy complication that can lead to maternal, fetal, and neonatal deaths in clinical practice. Accumulation of trophoblastic reactive oxygen species (ROS), which could result in oxidative stress and cell apoptosis, is considered to play an important role in PE pathology. It has been reported that aspirin has a positive effect on PE treatment in high-risk pregnant women.

METHODS

In vitro, extravillous trophoblast cell line (HTR-8/SVneo) were treated with hydrogen peroxide (H2O2, 150 μM) after the presence of aspirin (90 and 120 μM) with or without GKT137831 (a Nox4 inhibitor, 20 μM). A series of experiments including CCK-8 assays, flow cytometry, biochemical testing, and Western Blotting etc. verified the protective effects and potential mechanisms of aspirin against oxidative stress-induced damage in PE.

RESULTS

Our results demonstrated that H2O2 induces oxidative stress and apoptosis in HTR8/SVneo cells. However, aspirin pretreatment rescue cell viability and reduce LDH activity of HTR-8/SVneo cells. Aspirin can suppress the ROS overproduction and MDA level while increase SOD content and CAT activity. In addition, aspirin pretreatment significantly alleviated cell apoptosis and suppressed the expression of Nox4 and its subunits (p22phox and p47phox) at protein and mRNA levels. The above results were more obvious after the combination of aspirin with GKT137831.

DISCUSSION

This study demonstrated that aspirin protects human trophoblasts against H2O2-induced oxidative stress and cell apoptosis via suppressing NADPH/ROS pathway. These findings provide novel insights for the application of aspirin as a protective and curative agent against PE.

Danggui Buxue decoction alleviates cyclophosphamide-induced myelosuppression by regulating β-hydroxybutyric acid metabolism and suppressing oxidative stress

CONTEXT

Danggui Buxue Decoction (DBD) is an effective complementary medicine in alleviating myelosuppression after chemotherapy (MAC). However, its mechanism of action is elusive.

OBJECTIVE

To illustrate that regulating β-hydroxybutyric acid (β-OHB) metabolism and suppressing oxidative stress could be a potential mechanism of action for DBD in alleviating MAC.

MATERIALS AND METHODS

After HPLC quantification and dose testing (3, 6 and 10 g/kg, gavage) of DBD, Sprague-Dawley rats were divided into control, cyclophosphamide (CTX) (30 mg/kg CTX for 5 days, intraperitoneal administration) and CTX + DBD groups (6 g/kg DBD for 14 days, gavage). Blood cell counts, thigh bone histological examination, β-OHB levels, oxidative stress indices and HDAC1 activity were tested. The biological function of β-OHB was verified in vitro (hBMSC cells were incubated in culture mediums that contained 40 μM CTX and β-OHB in 0, 1, 2.5, 5, 10 mM) and in vivo (MAC rat model, 3 g/kg β-OHB for 14 days, gavage).

RESULTS

Rats in the CTX + DBD group showed upregulated blood cell counts (118-243%), β-OHB levels (495 nmol/mL in blood, 122 nmol/mg in marrow supernatant) and downregulated HDAC1 activity (59%), and oxidative stress indices (60-85%). In vitro, 5 mM β-OHB improved hBMSC cell migration (123%) and proliferation (131%). In vivo, rats treated with 3 g/kg β-OHB showed upregulated blood cell counts (121-182%) and downregulated HDAC1 activity (64%) and oxidative stress indices (65-83%).

DISCUSSION AND CONCLUSIONS

DBD, a traditional Chinese medicine, alleviates MAC by intervening in β-OHB metabolism and oxidative stress.

Comparison of Pollutant Effects on Cutaneous Inflammasomes Activation

The skin is the outermost layer of the body and, therefore, is exposed to a variety of stressors, such as environmental pollutants, known to cause oxinflammatory reactions involved in the exacerbation of several skin conditions. Today, inflammasomes are recognized as important modulators of the cutaneous inflammatory status in response to air pollutants and ultraviolet (UV) light exposure. In this study, human skin explants were exposed to the best-recognized air pollutants, such as microplastics (MP), cigarette smoke (CS), diesel engine exhaust (DEE), ozone (O3), and UV, for 1 or 4 days, to explore how each pollutant can differently modulate markers of cutaneous oxinflammation. Exposure to environmental pollutants caused an altered oxidative stress response, accompanied by increased DNA damage and signs of premature skin aging. The effect of specific pollutants being able to exert different inflammasomes pathways (NLRP1, NLRP3, NLRP6, and NLRC4) was also investigated in terms of scaffold formation and cell pyroptosis. Among all environmental pollutants, O3, MP, and UV represented the main pollutants affecting cutaneous redox homeostasis; of note, the NLRP1 and NLRP6 inflammasomes were the main ones modulated by these outdoor stressors, suggesting their role as possible molecular targets in preventing skin disorders and the inflammaging events associated with environmental pollutant exposure.

Hepatic safety profile of pancreatic cancer‑bearing mice fed a ketogenic diet in combination with gemcitabine

Ketogenic diets (KDs) are actively being evaluated for their potential anticancer effects. Although KDs are generally considered safe, their safety profile when combined with chemotherapy remains unknown. It is known that a KD enhances the anticancer effect of gemcitabine (2',2'-difluoro-2'-deoxycytidine) in LSL-KrasLSL-G12D/+Trp53R172H/+Pdx-1-Cre (KPC) tumor-bearing mice. In the present study, whether a KD in combination with gemcitabine affected the liver safety profile in KPC mice was evaluated. For this purpose, male and female pancreatic tumor-bearing KPC mice were allocated to a control diet (CD; % kcal: 20% fat, 65% carbohydrate, 15% protein) + gemcitabine [control plus gemcitabine group (CG)] or a KD (% kcal: 84% fat, 15% protein, 1% carbohydrate) + gemcitabine [ketogenic plus gemcitabine group (KG)] for two months. After two months of treatment, no significant differences in body weight were observed between CGs and KGs. Moreover, the KD did not significantly alter the serum protein expression levels of liver enzymes, including aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase. In addition, the KD did not alter markers of liver-lipid accumulation as well as serum cholesterol and triglyceride levels, compared with the CG-treated group. Upon histologic examination, steatosis was rare, with no notable differences between treatment groups. When examining liver fatty acid composition, KD treatment significantly increased the content of saturated fatty acids and significantly decreased levels of cis-monounsaturated fatty acids compared with the CG. Finally, the KD did not affect liver markers of inflammation and oxidative stress, nor the protein expression levels of enzymes involved in ketone bodies, such as 3-hydroxy-3-methylglutaryl-CoA lyase and hidroximetilglutaril-CoA sintasa, and glucose metabolism, such as hexokinase 2, pyruvate dehydrogenase and phosphofructokinase. In summary, a KD in combination with gemcitabine appears to be safe, with no apparent hepatotoxicity and these data support the further evaluation of a KD as an adjuvant dietary treatment for pancreatic cancer.

Overexpression of Interleukin-8 Promotes the Progression of Fatty Liver to Nonalcoholic Steatohepatitis in Mice

Nonalcoholic steatohepatitis (NASH) is an advanced stage of fatty liver disease characterized by liver damage, inflammation, and fibrosis. Although neutrophil infiltration is consistently observed in the livers of patients with NASH, the precise role of neutrophil-recruiting chemokines and infiltrating neutrophils in NASH pathogenesis remains poorly understood. Here, we aimed to elucidate the role of neutrophil infiltration in the transition from fatty liver to NASH by examining hepatic overexpression of interleukin-8 (IL8), a major chemokine responsible for neutrophil recruitment in humans. Mice fed a high-fat diet (HFD) for 3 months developed fatty liver without concurrent liver damage, inflammation, and fibrosis. Subsequent infection with an adenovirus overexpressing human IL8 for an additional 2 weeks increased IL8 levels, neutrophil infiltration, and liver injury in mice. Mechanistically, IL8-induced liver injury was associated with the upregulation of components of the NADPH oxidase 2 complex, which participate in neutrophil oxidative burst. IL8-driven neutrophil infiltration promoted macrophage aggregate formation and upregulated the expression of chemokines and inflammatory cytokines. Notably, IL8 overexpression amplified factors associated with fibrosis, including collagen deposition and hepatic stellate cell activation, in HFD-fed mice. Collectively, hepatic overexpression of human IL8 promotes neutrophil infiltration and fatty liver progression to NASH in HFD-fed mice.

Efficient scavenging of reactive carbonyl species in chloroplasts is required for light acclimation and fitness of plants

Reactive carbonyl species (RCS) derived from lipid peroxides can act as critical damage or signaling mediators downstream of reactive oxygen species by modifying target proteins. However, their biological effects and underlying mechanisms remain largely unknown in plants. Here, we have uncovered the mechanism by which the RCS 4-hydroxy-(E)-2-nonenal (HNE) participates in photosystem II (PSII) repair cycle of chloroplasts, a crucial process for maintaining PSII activity under high and changing light conditions. High Light Sensitive 1 (HLT1) is a potential NADPH-dependent reductase in chloroplasts. Deficiency of HLT1 had no impact on the growth of Arabidopsis plants under normal light conditions but increased sensitivity to high light, which resulted from a defective PSII repair cycle. In hlt1 plants, the accumulation of HNE-modified D1 subunit of PSII was observed, which did not affect D1 degradation but hampered the dimerization of repaired PSII monomers and reassembly of PSII supercomplexes on grana stacks. HLT1 is conserved in all photosynthetic organisms and has functions in overall growth and plant fitness in both Arabidopsis and rice under naturally challenging field conditions. Our work provides the mechanistic basis underlying RCS scavenging in light acclimation and suggests a potential strategy to improve plant productivity by manipulating RCS signaling in chloroplasts.

Lipid peroxidation in osteoarthritis: focusing on 4-hydroxynonenal, malondialdehyde, and ferroptosis

Osteoarthritis (OA) is a multifactorial and increasingly prevalent degenerative disease that affects the whole joint. The pathogenesis of OA is poorly understood and there is a lack of therapeutic interventions to reverse the pathological process of this disease. Accumulating studies have shown that the overproduction of reactive oxygen species (ROS) and ROS-induced lipid peroxidation are involved in the pathogenesis of OA. 4-Hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA) have received considerable attention for their role in cartilage degeneration and subchondral bone remodeling during OA development. Ferroptosis is a form of cell death characterized by a lack of control of membrane lipid peroxidation and recent studies have suggested that chondrocyte ferroptosis contributes to OA progression. In this review, we aim to discuss lipid peroxidation-derived 4-HNE and MDA in the progression of OA. In addition, the therapeutic potential for OA by controlling the accumulation of lipid peroxidation and inhibiting chondrocyte ferroptosis are discussed.

Inhibition of skeletal muscle Lands cycle ameliorates weakness induced by physical inactivity

Background

Lipid hydroperoxides (LOOH) have been implicated in skeletal muscle atrophy with age and disuse. Lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme of Lands cycle, conjugates a polyunsaturated fatty acyl chain to a lysophospholipid (PUFA-PL) molecule, providing substrates for LOOH propagation. Previous studies suggest that inhibition of Lands cycle is an effective strategy to suppress LOOH. Mice with skeletal muscle-specific tamoxifen-inducible knockout of LPCAT3 (LPCAT3-MKO) were utilized to determine if muscle-specific attenuation of LOOH may alleviate muscle atrophy and weakness with disuse.

Methods

LPCAT3-MKO and control mice underwent 7 days of sham or hindlimb unloading (HU model) to study muscle mass and force-generating capacity. LOOH was assessed by quantifying 4-hydroxynonenal (4-HNE)-conjugated peptides. Quantitative PCR and lipid mass spectrometry were used to validate LPCAT3 deletion.

Results

7 days of HU was sufficient to induce muscle atrophy and weakness concomitant to an increase in 4-HNE. Deletion of LPCAT3 reversed HU-induced increase in muscle 4HNE. No difference was found in body mass, body composition, or caloric intake between genotypes. The soleus (SOL) and plantaris (PLANT) muscles of the LPCAT3-MKO mice were partially protected from atrophy compared to controls, concomitant to attenuated decrease in cross-sectional areas in type I and IIa fibers. Strikingly, SOL and extensor digitorum longus (EDL) were robustly protected from HU-induced reduction in force-generating capacity in the LPCAT3-MKO mice compared to controls.

Conclusion

Our findings demonstrate that attenuation of muscle LOOH is sufficient to restore skeletal muscle function, in particular a protection from reduction in muscle specific force. Thus, muscle LOOH contributes to atrophy and weakness induced by HU in mice.

Aldehyde Dehydrogenase and Aldo-Keto Reductase Enzymes: Basic Concepts and Emerging Roles in Diabetic Retinopathy

Diabetic retinopathy (DR) is a complication of diabetes mellitus that can lead to vision loss and blindness. It is driven by various biochemical processes and molecular mechanisms, including lipid peroxidation and disrupted aldehyde metabolism, which contributes to retinal tissue damage and the progression of the disease. The elimination and processing of aldehydes in the retina rely on the crucial role played by aldehyde dehydrogenase (ALDH) and aldo-keto reductase (AKR) enzymes. This review article investigates the impact of oxidative stress, lipid-derived aldehydes, and advanced lipoxidation end products (ALEs) on the advancement of DR. It also provides an overview of the ALDH and AKR enzymes expressed in the retina, emphasizing their growing importance in DR. Understanding the relationship between aldehyde metabolism and DR could guide innovative therapeutic strategies to protect the retina and preserve vision in diabetic patients. This review, therefore, also explores various approaches, such as gene therapy and pharmacological compounds that have the potential to augment the expression and activity of ALDH and AKR enzymes, underscoring their potential as effective treatment options for DR.

Oxidative Stress-Induced Cellular Senescence: Is Labile Iron the Connecting Link?

Cellular senescence, a cell state characterized by a generally irreversible cell cycle arrest, is implicated in various physiological processes and a wide range of age-related pathologies. Oxidative stress, a condition caused by an imbalance between the production and the elimination of reactive oxygen species (ROS) in cells and tissues, is a common driver of cellular senescence. ROS encompass free radicals and other molecules formed as byproducts of oxygen metabolism, which exhibit varying chemical reactivity. A prerequisite for the generation of strong oxidizing ROS that can damage macromolecules and impair cellular function is the availability of labile (redox-active) iron, which catalyzes the formation of highly reactive free radicals. Targeting labile iron has been proven an effective strategy to counteract the adverse effects of ROS, but evidence concerning cellular senescence is sparse. In the present review article, we discuss aspects of oxidative stress-induced cellular senescence, with special attention to the potential implication of labile iron.

Isoform-specific modification of apolipoprotein E by 4-hydroxynonenal: protective role of apolipoprotein E3 against oxidative species

High levels of 4-hydroxynonenal (HNE), arising from lipid peroxidation, and HNE-modified proteins have been identified in postmortem brains of ageing and Alzheimer's disease (AD) patients. The goal of this study is to understand the effect of HNE modification on the structure and function of recombinant apolipoprotein E3 (apoE3) and apolipoprotein E4 (apoE4), which play a critical role in brain cholesterol homeostasis. The two isoforms differ in a single amino acid at position 112: Cys in apoE3 and Arg in apoE4. Immunoblot with HNE-specific antibody indicates HNE modification of apoE3 and apoE4 with a major band at ~ 36 kDa, while LC-MS/MS revealed Michael addition at His140 (60-70% abundance) and His299 (3-5% abundance) in apoE3 and apoE4, and Cys112 adduct in apoE3 (75% abundance). Circular dichroism spectroscopy revealed no major differences in the overall secondary structure or helical content between unmodified and HNE-modified apoE. HNE modification did not affect their ability to promote cholesterol efflux from J774.1 macrophages. However, it led to a 3-fold decrease in their ability to bind lipids and 25-50% decrease in the ability of cerebral cortex endothelial cells to uptake lipoproteins bearing HNE-modified HNE-apoE3 or HNE-apoE4 as noted by fluorescence microscopy and flow cytometry. Taken together, the data indicate that HNE modification impairs lipid binding and cellular uptake of both isoforms, and that apoE3, bearing a Cys, offers a protective role by sequestering lipid peroxidation products that would otherwise cause indiscriminate damage to biomolecules. ApoE4, lacking Cys, is unable to protect against oxidative damage that is commensurate with ageing.

Lipid Peroxidation Products Influence Calpain-1 Functionality In Vitro by Covalent Binding

The objective of the current study was to evaluate the effects of lipid peroxidation products, malondialdehyde (MDA), hexenal, and 4-hydroxynonenal (HNE), on calpain-1 function, and liquid chromatography and tandem mass spectrometry (LC-MS/MS) identification of adducts on calpain-1. Calpain-1 activity slightly increased after incubation with 100 μM MDA but not with 500 and 1000 μM MDA. However, calpain-1 activity was lowered by hexenal and HNE at 100, 500, and 1000 μM. No difference in calpain-1 autolysis was observed between the control and 1000 μM MDA. However, 1000 μM hexenal and HNE treatments slowed the calpain-1 autolysis. Adducts of MDA were detected on glutamine, arginine, lysine, histidine, and asparagine residues via Schiff base formation, while HNE adducts were detected on histidine, lysine, glutamine, and asparagine residues via Michael addition. These results are the first to demonstrate that lipid peroxidation products can impact calpain-1 activity in a concentration-dependent manner and may impact the development of meat tenderness postmortem.

Metabolic Functions of Biliverdin IXβ Reductase in Redox-Regulated Hematopoietic Cell Fate

Cytoprotective heme oxygenases derivatize heme to generate carbon monoxide, ferrous iron, and isomeric biliverdins, followed by rapid NAD(P)H-dependent biliverdin reduction to the antioxidant bilirubin. Recent studies have implicated biliverdin IXβ reductase (BLVRB) in a redox-regulated mechanism of hematopoietic lineage fate restricted to megakaryocyte and erythroid development, a function distinct and non-overlapping from the BLVRA (biliverdin IXα reductase) homologue. In this review, we focus on recent progress in BLVRB biochemistry and genetics, highlighting human, murine, and cell-based studies that position BLVRB-regulated redox function (or ROS accumulation) as a developmentally tuned trigger that governs megakaryocyte/erythroid lineage fate arising from hematopoietic stem cells. BLVRB crystallographic and thermodynamic studies have elucidated critical determinants of substrate utilization, redox coupling and cytoprotection, and have established that inhibitors and substrates bind within the single-Rossmann fold. These advances provide unique opportunities for the development of BLVRB-selective redox inhibitors as novel cellular targets that retain potential for therapeutic applicability in hematopoietic (and other) disorders.