Immunohistochemical appearance of HNE-protein conjugates in human astrocytomas

Relationship between 4-Hydroxynonenal (4-HNE) as Systemic Biomarker of Lipid Peroxidation and Metabolomic Profiling of Patients with Prostate Cancer

An oxidative degradation product of the polyunsaturated fatty acids, 4-hydroxynonenal (4-HNE), is of particular interest in cancer research due to its concentration-dependent pleiotropic activities affecting cellular antioxidants, metabolism, and growth control. Although an increase in oxidative stress and lipid peroxidation was already associated with prostate cancer progression a few decades ago, the knowledge of the involvement of 4-HNE in prostate cancer tumorigenesis is limited. This study investigated the appearance of 4-HNE-protein adducts in prostate cancer tissue by immunohistochemistry using a genuine 4-HNE monoclonal antibody. Plasma samples of the same patients and samples of the healthy controls were also analyzed for the presence of 4-HNE-protein adducts, followed by metabolic profiling using LC-ESI-QTOF-MS and GC-EI-Q-MS. Finally, the analysis of the metabolic pathways affected by 4-HNE was performed. The obtained results revealed the absence of 4-HNE-protein adducts in prostate carcinoma tissue but increased 4-HNE-protein levels in the plasma of these patients. Metabolomics revealed a positive association of different long-chain and medium-chain fatty acids with the presence of prostate cancer. Furthermore, while linoleic acid positively correlated with the levels of 4-HNE-protein adducts in the blood of healthy men, no correlation was obtained for cancer patients indicating altered lipid metabolism in this case. The metabolic pathway of unsaturated fatty acids biosynthesis emerged as significantly affected by 4-HNE. Overall, this is the first study linking 4-HNE adduction to plasma proteins with specific alterations in the plasma metabolome of prostate cancer patients. This study revealed that increased 4-HNE plasma protein adducts could modulate the unsaturated fatty acids biosynthesis pathway. It is yet to be determined if this is a direct result of 4-HNE or whether they are produced by the same underlying mechanisms. Further mechanistic studies are needed to grasp the biological significance of the observed changes in prostate cancer tumorigenesis.

4-Hydroxynonenal Modulates Blood-Brain Barrier Permeability In Vitro through Changes in Lipid Composition and Oxidative Status of Endothelial Cells and Astrocytes

Blood brain barrier (BBB) is a dynamic interface responsible for proper functioning of brain, but also a major obstacle for effective treatment of neurological diseases. Increased levels of free radicals, in high ferrous and high lipid content surrounding, induce lipid peroxidation, leading to production of 4-hydroxynonenal (HNE). HNE modifies all key proteins responsible for proper brain functioning thus playing a major role in the onset of neurological diseases. To investigate HNE effects on BBB permeability, we developed two in vitro BBB models-'physiological' and 'pathological'. The latter mimicked HNE modified extracellular matrix under oxidative stress conditions in brain pathologies. We showed that exogenous HNE induce activation of antioxidative defense systems by increasing catalase activity and glutathione content as well as reducing lipid peroxide levels in endothelial cells and astrocytes of 'physiological' model. While in 'pathological' model, exogenous HNE further increased lipid peroxidation levels of endothelial cells and astrocytes, followed by increase in Nrf2 and glutathione levels in endothelial cells. At lipid composition level, HNE caused increase in ω3 polyunsaturated fatty acid (PUFA) level in endothelial cells, followed by decrease in ω3 PUFA level and increase in monounsaturated fatty acid level in astrocytes. Using these models, we showed for the first time that HNE in 'pathological' model can reduce BBB permeability.

Post-mortem Findings of Inflammatory Cells and the Association of 4-Hydroxynonenal with Systemic Vascular and Oxidative Stress in Lethal COVID-19

A recent comparison of clinical and inflammatory parameters, together with biomarkers of oxidative stress, in patients who died from aggressive COVID-19 and survivors suggested that the lipid peroxidation product 4-hydroxynonenal (4-HNE) might be detrimental in lethal SARS-CoV-2 infection. The current study further explores the involvement of inflammatory cells, systemic vascular stress, and 4-HNE in lethal COVID-19 using specific immunohistochemical analyses of the inflammatory cells within the vital organs obtained by autopsy of nine patients who died from aggressive SAR-CoV-2 infection. Besides 4-HNE, myeloperoxidase (MPO) and mitochondrial superoxide dismutase (SOD2) were analyzed alongside standard leukocyte biomarkers (CDs). All the immunohistochemical slides were simultaneously prepared for each analyzed biomarker. The results revealed abundant 4-HNE in the vital organs, but the primary origin of 4-HNE was sepsis-like vascular stress, not an oxidative burst of the inflammatory cells. In particular, inflammatory cells were often negative for 4-HNE, while blood vessels were always very strongly immunopositive, as was edematous tissue even in the absence of inflammatory cells. The most affected organs were the lungs with diffuse alveolar damage and the brain with edema and reactive astrocytes, whereas despite acute tubular necrosis, 4-HNE was not abundant in the kidneys, which had prominent SOD2. Although SOD2 in most cases gave strong immunohistochemical positivity similar to 4-HNE, unlike 4-HNE, it was always limited to the cells, as was MPO. Due to their differential expressions in blood vessels, inflammatory cells, and the kidneys, we think that SOD2 could, together with 4-HNE, be a potential link between a malfunctioning immune system, oxidative stress, and vascular stress in lethal COVID-19.

Breaking barriers: Neurodegenerative repercussions of radiotherapy induced damage on the blood-brain and blood-tumor barrier

Exposure to radiation during the treatment of CNS tumors leads to detrimental damage of the blood brain barrier (BBB) in normal tissue. Effects are characterized by leakage of the vasculature which exposes the brain to a host of neurotoxic agents potentially leading to white matter necrosis, parenchymal calcification, and an increased chance of stroke. Vasculature of the blood tumor barrier (BTB) is irregular leading to poorly perfused and hypoxic tissue throughout the tumor that becomes resistant to radiation. While current clinical applications of cranial radiotherapy use dose fractionation to reduce normal tissue damage, these treatments still cause significant alterations to the cells that make up the neurovascular unit of the BBB and BTB. Damage to the vasculature manifests as reduction in tight junction proteins, alterations to membrane transporters, impaired cell signaling, apoptosis, and cellular senescence. While radiotherapy treatments are detrimental to normal tissue, adapting combined strategies with radiation targeted to damage the BTB could aid in drug delivery. Understanding differences between the BBB and the BTB may provide valuable insight allowing clinicians to improve treatment outcomes. Leveraging this information should allow advances in the development of therapeutic modalities that will protect the normal tissue while simultaneously improving CNS tumor treatments.

The TRPA1 Channel Amplifies the Oxidative Stress Signal in Melanoma

Macrophages (MΦs) and reactive oxygen species (ROS) are implicated in carcinogenesis. The oxidative stress sensor, transient receptor potential ankyrin 1 (TRPA1), activated by ROS, appears to contribute to lung and breast cancer progression. Although TRPA1 expression has been reported in melanoma cell lines, and oxidative stress has been associated with melanocytic transformation, their role in melanoma remains poorly known. Here, we localized MΦs, the final end-product of oxidative stress, 4-hydroxynonenal (4-HNE), and TRPA1 in tissue samples of human common dermal melanocytic nevi, dysplastic nevi, and thin (pT1) and thick (pT4) cutaneous melanomas. The number (amount) of intratumoral and peritumoral M2 MΦs and 4-HNE staining progressively increased with tumor severity, while TRPA1 expression was similar in all samples. Hydrogen peroxide (H₂O₂) evoked a TRPA1-dependent calcium response in two distinct melanoma cell lines (SK-MEL-28 and WM266-4). Furthermore, H₂O₂ induced a TRPA1-dependent H₂O₂ release that was prevented by the TRPA1 antagonist, A967079, or Trpa1 gene silencing (siRNA). ROS release from infiltrating M2 MΦs may target TRPA1-expressing melanoma cells to amplify the oxidative stress signal that affects tumor cell survival and proliferation.

Lipid peroxidation in brain tumors

There is a lot of evidence showing that lipid peroxidation plays very important role in development of various diseases, including neurodegenerative diseases and brain tumors. Lipid peroxidation is achieved by two main pathways, by enzymatic or by non-enzymatic oxidation, respectively. In this paper, we focus on non-enzymatic, self-catalyzed chain reaction of poly-unsaturated fatty acid (PUFA) peroxidation generating reactive aldehydes, notably 4-hydroxynonenal (4-HNE), which acts as second messenger of free radicals and as growth regulating factor. It might originate from astrocytes as well as from blood vessels, even within the blood-brain barrier (BBB), which is in case of brain tumors transformed into the blood-brain-tumor barrier (BBTB). The functionality of the BBB is strongly affected by 4-HNE because it forms relatively stable protein adducts thus allowing the persistence and the spread of lipid peroxidation, as revealed by immunohistochemical findings. Because 4-HNE can act as a regulator of vital functions of normal and of malignant cells acting in the cell type- and concentration-dependent manners, the bioactivities of this product of lipid peroxidation be should further studied to reveal if it acts as a co-factor of carcinogenesis or as natural factor of defense against primary brain tumors and metastatic cancer.

The relevance of pathophysiological alterations in redox signaling of 4-hydroxynonenal for pharmacological therapies of major stress-associated diseases

Modern analytical methods combined with the modern concepts of redox signaling revealed 4-hydroxy-2-nonenal (4-HNE) as particular growth regulating factor involved in redox signaling under physiological and pathophysiological circumstances. In this review current knowledge of the relevance of 4-HNE as "the second messenger of reactive oxygen species" (ROS) in redox signaling of representative major stress-associated diseases is briefly summarized. The findings presented allow for 4-HNE to be considered not only as second messenger of ROS, but also as one of fundamental factors of the stress- and age-associated diseases. While standard, even modern concepts of molecular medicine and respective therapies in majority of these diseases target mostly the disease-specific symptoms. 4-HNE, especially its protein adducts, might appear to be the bioactive markers that would allow better monitoring of specific pathophysiological processes reflecting their complexity. Eventually that could help development of advanced integrative medicine approach for patients and the diseases they suffer from on the personalized basis implementing biomedical remedies that would optimize beneficial effects of ROS and 4-HNE to prevent the onset and progression of the illness, perhaps even providing the real cure.

The Appearance of 4-Hydroxy-2-Nonenal (HNE) in Squamous Cell Carcinoma of the Oropharynx

Tumor growth is associated with oxidative stress, which causes lipid peroxidation. The most intensively studied product of lipid peroxidation is 4-hydroxy-2-nonenal (HNE), which is considered as a “second messenger of free radicals” that binds to proteins and acts as a growth-regulating signaling factor. The incidence of squamous cell carcinoma of the oropharynx is associated with smoking, alcohol and infection of human papilloma virus (HPV), with increasing incidence world-wide. The aim of this retrospective study involving 102 patients was to determine the immunohistochemical appearance of HNE-protein adducts as a potential biomarker of lipid peroxidation in squamous cell carcinoma of the oropharynx. The HNE-protein adducts were detected in almost all tumor samples and in the surrounding non-tumorous tissue, while we found that HNE is differentially distributed in squamous cell carcinomas in dependence of clinical stage and histological grading of these tumors. Namely, the level of HNE-immunopositivity was increased in comparison to the normal oropharyngeal epithelium in well- and in moderately-differentiated squamous cell carcinoma, while it was decreasing in poorly differentiated carcinomas and in advanced stages of cancer. However, more malignant and advanced cancer was associated with the increase of HNE in surrounding, normal tissue. This study confirmed the onset of lipid peroxidation, generating HNE-protein adducts that can be used as a valuable bioactive marker of carcinogenesis in squamous cell carcinoma of the oropharynx, as well as indicating involvement of HNE in pathophysiological changes of the non-malignant tissue in the vicinity of cancer.

Cell-Type-Specific Modulation of Hydrogen Peroxide Cytotoxicity and 4-Hydroxynonenal Binding to Human Cellular Proteins In Vitro by Antioxidant Aloe vera Extract

Although Aloe vera contains numerous bioactive components, the activity principles of widely used A. vera extracts are uncertain. Therefore, we analyzed the effects of genuine A. vera aqueous extract (AV) on human cells with respect to the effects of hydrogen peroxide (H₂O₂) and 4-hydroxynonenal (HNE). Fully developed A. vera leaves were harvested and analyzed for vitamin C, carotenoids, total soluble phenolic content, and antioxidant capacity. Furthermore, human cervical cancer (HeLa), human microvascular endothelial cells (HMEC), human keratinocytes (HaCat), and human osteosarcoma (HOS) cell cultures were treated with AV extract for one hour after treatment with H₂O₂ or HNE. The cell number and viability were determined using Trypan Blue, and endogenous reactive oxygen species (ROS) production was determined by fluorescence, while intracellular HNE–protein adducts were measured for the first time ever by genuine cell-based HNE–His ELISA. The AV extract expressed strong antioxidant capacities (1.1 mmol of Trolox eq/g fresh weight) and cell-type-specific influence on the cytotoxicity of H₂O₂, as well as on endogenous production of ROS and HNE–protein adducts induced by HNE treatment, while AV itself did not induce production of ROS or HNE–protein adducts at all. This study, for the first time, revealed the importance of HNE for the activity principles of AV. Since HMEC cells were the most sensitive to AV, the effects of AV on microvascular endothelia could be of particular importance for the activity principles of Aloe vera extracts.

Distribution of 4-Hydroxynonenal-Protein Conjugates as a Marker of Lipid Peroxidation and Parameter of Malignancy in Astrocytic and Ependymal Tumors of the Brain

Aims and Background

Lipid peroxidation (LPO) is an autocatalytic process caused by oxidative stress. It results in the production of 4-hydroxynonenal (HNE), which plays a crucial role in hypoxic brain injury, neuronal degeneration and apoptosis. The aim of this study was to evaluate the expression of HNE in 120 astrocytic and 40 ependymal tumors in relation to tumor type, grade of malignancy, angiogenesis, and presence of necrosis and apoptosis.

Methods

Immunohistochemical staining was performed using a monoclonal antibody for the detection of HNE-modified proteins.

Results

HNE-protein adducts were found in all tumors. The incidence of HNE-im-munopositive tumor cells increased with increasing grades of malignancy. Significantly higher HNE expression was found in tumor cells of glioblastomas multiforme than in cells of pilocytic astrocytomas ( P <0.005), and in anaplastic ependymomas than in benign ependymomas ( P <0.01). HNE-immunopositive tumor cells were distributed more diffusely than in perivascular locations ( P <0.05). Pronounced HNE-protein adducts were detected in mitotic, necrotic, and apoptotic cells. HNE was expressed in the endothelium of almost all tumor vessels, but its expression in the walls of the vessels was significantly higher in diffuse and anaplastic astrocytomas than in pilocytic astrocytomas and glioblastomas multiforme ( P <0.05). The number of microvessels containing HNE in their endothelium and walls was significantly associated with the grade of malignancy in both astrocytic ( P <0.001) and ependymal tumors ( P <0.05), although microvessels in pilocytic astrocytomas were significantly more numerous ( P <0.05) than in diffuse astrocytomas.

Conclusions

LPO seems to be a common pathological process in astrocytic and ependymal glial tumors, proportional to the level of malignancy and neovascularization. Therefore, HNE might be involved in the damage of brain cells and the induction of malignancy.

Contribution of the HNE-immunohistochemistry to modern pathological concepts of major human diseases

Excessive production of reactive oxygen species can induce peroxidation of the polyunsaturated fatty acids thus generating reactive aldehydes like 4-hydroxy-2-nonenal (HNE), denoted as "the second messenger of free radicals". Because HNE has high binding affinity for cysteine, histidine and lysine it forms relatively stable and hardly metabolized protein adducts. By changing structure and function of diverse structural and regulatory proteins, HNE achieves not only cytotoxic, but also regulatory functions in various pathophysiological processes. Numerous animal model studies and clinical trials confirmed HNE as one of the crucial factors in development and progression of many disorders, in particular of cancer, (neuro)degenerative, metabolic and inflammatory diseases. Since HNE has multiple biological effects and is in the living system usually bound to proteins and peptides, many research groups work on development of specific immunochemical methods targeting the HNE-histidine adducts as major bioactive marker of lipid peroxidation, following the research pathway initiated by Hermann Esterbauer, who discovered HNE in 60's. Such immunohistochemical studies did not only prove the high biomedical importance of HNE, but have also given new insights into major diseases of the modern man. Immunohistochemical studies have shown reversibility of formation of the HNE-protein adducts, as well as differential onset of the HNE-mediated lipid peroxidation between age- associated atherosclerosis and photoaging, revealing eventually selective anti-cancer effects of HNE produced by non-malignant cells in vicinity of cancer. This review summarizes some of the HNE-histidine immunohistochemistry findings we believe are of broad biomedical interest and could inspire new studies in the field.

Cancer growth regulation by 4-hydroxynonenal

While reactive oxygen species (ROS) gain their carcinogenic effects by DNA mutations, if generated in the vicinity of genome, lipid peroxidation products, notably 4-hydroxynonenal (HNE), have much more complex modes of activities. Namely, while ROS are short living and have short efficiency distance range (in nm or µm) HNE has strong binding affinity for proteins, thus forming relatively stable adducts. Hence, HNE can diffuse from the site or origin changing structure and function of respective proteins. Consequently HNE can influence proliferation, differentiation and apoptosis of cancer cells on one hand, while on the other it can affect genome functionality, too. Although HNE is considered to be important factor of carcinogenesis due to its ability to covalently bind to DNA, it might also be cytotoxic for cancer cells, as well as it can modulate their growth. In addition to direct cytotoxicity, HNE is also involved in activity mechanisms by which several cytostatic drugs and radiotherapy exhibit their anticancer effects. Complementary to that, the metabolic pathway for HNE detoxification through RLIP76, which is enhanced in cancer, may be a target for anti-cancer treatments. In addition, some cancer cells can undergo apoptosis or necrosis, if exposed to supraphysiological HNE levels in the cancer microenvironment, especially if challenged additionally by pro-oxidative cytostatics and/or inflammation. These findings could explain previously observed disappearance of HNE from invading cancer cells, which is associated with the increase of HNE in non-malignant cells close to invading cancer utilizing cardiolipin as the source of cancer-inhibiting HNE.

Short overview on metabolomics approach to study pathophysiology of oxidative stress in cancer

Association of oxidative stress with carcinogenesis is well known, but not understood well, as is pathophysiology of oxidative stress generated during different types of anti-cancer treatments. Moreover, recent findings indicate that cancer associated lipid peroxidation might eventually help defending adjacent nonmalignant cells from cancer invasion. Therefore, untargeted metabolomics studies designed for advanced translational and clinical studies are needed to understand the existing paradoxes in oncology, including those related to controversial usage of antioxidants aiming to prevent or treat cancer. In this short review we have tried to put emphasis on the importance of pathophysiology of oxidative stress and lipid peroxidation in cancer development in relation to metabolic adaptation of particular types of cancer allowing us to conclude that adaptation to oxidative stress is one of the main driving forces of cancer pathophysiology. With the help of metabolomics many novel findings are being achieved thus encouraging further scientific breakthroughs. Combined with targeted qualitative and quantitative methods, especially immunochemistry, further research might reveal bio-signatures of individual patients and respective malignant diseases, leading to individualized treatment approach, according to the concepts of modern integrative medicine.

Positron emission tomography-computed tomography and 4-hydroxynonenal-histidine immunohistochemistry reveal differential onset of lipid peroxidation in primary lung cancer and in pulmonary metastasis of remote malignancies

The Aim of the study was to reveal if PET-CT analysis of primary and of secondary lung cancer could be related to the onset of lipid peroxidation in cancer and in surrounding non-malignant lung tissue.

METHODS

Nineteen patients with primary lung cancer and seventeen patients with pulmonary metastasis were involved in the study. Their lungs were analyzed by PET-CT scanning before radical surgical removal of the cancer. Specific immunohistochemistry for the major bioactive marker of lipid peroxidation, 4-hydroxynonenal (HNE), was done for the malignant and surrounding non-malignant lung tissue using genuine monoclonal antibody specific for the HNE-histidine adducts.

RESULTS

Both the intensity of the PET-CT analysis and the HNE-immunohistochemistry were in correlation with the size of the tumors analyzed, while primary lung carcinomas were larger than the metastatic tumors. The intensity of the HNE-immunohistochemistry in the surrounding lung tissue was more pronounced in the metastatic than in the primary tumors, but it was negatively correlated with the cancer volume determined by PET-CT. The appearance of HNE was more pronounced in non-malignant surrounding tissue than in cancer or stromal cells, both in case of primary and metastatic tumors.

CONCLUSIONS

Both PET-CT and HNE-immunohistochemistry reflect the size of the malignant tissue. However, lipid peroxidation of non-malignant lung tissue in the vicinity of cancer is more pronounced in metastatic than in primary malignancies and might represent the mechanism of defense against cancer, as was recently revealed also in case of human liver cancer.

Mitochondrial control of apoptosis through modulation of cardiolipin oxidation in hepatocellular carcinoma: A novel link between oxidative stress and cancer

Altered redox status in cancer cells has been linked to lipid peroxidation induced by reactive oxygen species (ROS) and subsequent formation of reactive lipid electrophiles, especially 4-hydroxy-nonenal (4-HNE). Emerging evidence suggests that cancer cells manipulate redox status to acquire anti-apoptotic phenotype but the underlying mechanisms are poorly understood. Cardiolipin (CL), a mitochondria-specific inner membrane phospholipid, is critical for maintaining mitochondrial function. Paradoxically, liver tissues contain tetralinoleoyl cardiolipin (TLCL) as the major CL in mitochondria yet emerging evidence suggests that ROS generated in mitochondria may lead to CL peroxidation and activation of intrinsic apoptosis. It remains unclear how CL oxidation leads to apoptosis and its relevance to the pathogenesis of hepatocellular carcinoma (HCC). We employed a mass spectrometry-based lipidomic approach to profile lipids in human tissues of HCC and found that CL was gradually decreased in tumor comparing to peripheral non-cancerous tissues, accompanied by a concomitant decrease of oxidized CL and its oxidation product, 4-HNE. Incubation of liver cancer cells with TLCL significantly restored apoptotic sensitivity accompanied by an increase of CL and its oxidation products when treated with staurosporine (STS) or Sorafenib (the standard treatment for late stage HCC patients). Our studies uncovered a novel mechanism by which cancer cells adopt to evade apoptosis, highlighting the importance of mitochondrial control of apoptosis through modulation of CL oxidation and subsequent 4-HNE formation in HCC. Thus manipulation of mitochondrial CL oxidation and lipid electrophile formation may have potential therapeutic value for diseases linked to oxidative stress and mitochondrial dysfunctions.

Lipid mediators involved in the oxidative stress and antioxidant defence of human lung cancer cells

Background

The oxidative modifications of bioactive macromolecules have important roles in carcinogenesis. Of particular interest are lipid peroxidation products, which are involved in the activation of Nrf2 and endocannabinoids that affect cancer progression.

Methods

In lung cancer tissues (squamous cell lung carcinoma - SCC and adenocarcinoma - AC), the glutathione peroxidase and catalase activity and glutathione level, together with the expression of Nrf2 and its activators/inhibitors were estimated. The oxidative modifications of DNA (8-hydroxy-2′-deoxyguanosine and N7-methylguanine), endocannabinoids (anandamide and 2- arachidonylglyceriol), their receptors (CB1/2, TRV1, GPR55), phospholipid fatty acids (arachidonic, linoleic and docosahexaenoic), and reactive aldehydes (4-hydroxynonenal, 4-oxononenal and malondialdehyde) were determined.

Results

Tumour tissues showed lower antioxidant capacity than healthy tissues, which was accompanied by lower levels of fatty acids and higher levels of reactive aldehydes. Disturbances in antioxidant capacity and enhanced DNA oxidative modifications were observed in 88% of AC patients and 81% of SCC patients. The 4-hydroxynonenal-Histidine adducts were detected in the necrotic and stromal cells in all tumours. These findings were associated with the enhanced Nrf2 activity, especially in AC. The strong difference between the cancer subtypes was evident in the levels of endocannabinoids, with an increase in 89% of SCC and a decrease in 85% of AC patients being observed. Additionally, the increase in the expression of CB1/2 receptors was observed only in 82% of AC, while the expression of VR1 and GPR55 was enhanced in 79% of SCC and 82% of AC patients.

Conclusions

This study shows significant differences in the redox status, Nrf2 pathway and endocannabinoid system between SCC and AC tissues. Understanding the relation between the various lipid mediators and antioxidants in different lung cancer subtypes may be beginning for further research on the effective anticancer therapy.

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AC tissues show lower antioxidant capacity than SCC.

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Nrf2/ARE pathway is activated stronger in AC than in SCC.

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AC exhibits more lipid oxidative modifications than SCC.

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HNE-protein adducts are detected in the necrotic and stromal cells in SCC and AC.

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SCC exhibits increase in endocannabinoids level while in AC reverse effect is observed.

Overview on major lipid peroxidation bioactive factor 4-hydroxynonenal as pluripotent growth-regulating factor

The reactive aldehyde 4-hydroxynonenal (HNE) is major bioactive marker of lipid peroxidation generated under oxidative stress from polyunsaturated fatty acids. Biomedical significance of HNE was first revealed in pathogenesis of various degenerative and malignant diseases. Thus, HNE was considered for decades only as cytotoxic molecule, "second toxic messenger of free radicals" responsible for numerous undesirable consequences of oxidative stress. However, the increase of knowledge on physiology of redox signaling revealed also desirable, physiological roles of HNE, especially in the field of cellular signaling pathways regulating proliferation, differentiation, and apoptosis. These pluripotent effects of HNE can be explained by its concentration-dependent interactions with the cytokine networks and complex cellular antioxidant systems also showing cell and tissue specificities. Therefore, this paper gives a comprehensive, yet short overview on HNE as pluripotent growth-regulating factor.

Divergent behaviour of oxidative stress markers 8-hydroxydeoxyguanosine (8-OHdG) and 4-hydroxy-2-nonenal (HNE) in breast carcinogenesis

AIMS

To clarify the role of oxidative stress during breast carcinogenesis by studying the expression of 8-hydroxydeoxyguanosine (8-OHdG) (a marker of oxidative DNA damage) and 4-hydroxy-2-nonenal (HNE) (a marker of lipid peroxidation) during the different phases of breast carcinogenesis.

METHODS AND RESULTS

The study material consisted of a total of 219 patients: 31 with usual ductal hyperplasia (UDH), 25 with atypical ductal hyperplasia (ADH), 30 with ductal carcinoma in situ (DCIS) and 133 with invasive carcinoma. The expression of 8-OHdG and HNE were evaluated immunohistochemically. Both 8-OHdG (77.4%) and HNE (45.8%) expression was already seen in UDH lesions. Interestingly, the trend of these two immunostainings during breast carcinogenesis was diverse. 8-OHdG expression diminished significantly in invasive breast carcinomas compared to non-invasive lesions (P < 0.005 when set against non-invasive cohorts). Also within the same lesions, 8-OHdG expression was the most intensive in benign cells. Conversely, HNE immunostaining was strongest in invasive breast carcinomas (UDH versus invasive cohort, P = 0.015).

CONCLUSIONS

4-hydroxy-2-nonenal as a marker of lipid peroxidation increases during breast carcinogenesis, reflecting the role of oxidative stress in the pathogenesis of breast cancer. However, 8-OHdG shows diminished levels in carcinomas, possibly resulting from the induction of DNA repair in these invasive lesions.

Advances in methods for the determination of biologically relevant lipid peroxidation products

Lipid peroxidation is recognized to be an important contributor to many chronic diseases, especially those of an inflammatory pathology. In addition to their value as markers of oxidative damage, lipid peroxidation products have also been shown to have a wide variety of biological and cell signalling effects. In view of this, accurate and sensitive methods for the measurement of lipid peroxidation products are essential. Although some assays have been described for many years, improvements in protocols are continually being reported and, with recent advances in instrumentation and technology, highly specialized and informative techniques are increasingly used. This article gives an overview of the most currently used methods and then addresses the recent advances in some specific approaches. The focus is on analysis of oxysterols, F(2)-isoprostanes and oxidized phospholipids by gas chromatography or liquid chromatography mass spectrometry techniques and immunoassays for the detection of 4-hydroxynonenal.

HNE Michael adducts to histidine and histidine-containing peptides as biomarkers of lipid-derived carbonyl stress in urines: LC-MS/MS profiling in Zucker obese rats

A new liquid chromatography-tandem mass spectrometric (LC-MS/MS) approach, based on the precursor ion scanning technique using a triple-stage quadrupole, has been developed to detect free and protein-bound histidine (His) residues modified by reactive carbonyl species (RCS) generated by lipid peroxidation. This approach has been applied to urines from Zucker obese rats, a nondiabetic animal model characterized by obesity and hyperlipidemia, where RCS formation plays a key role in the development of renal and cardiac dysfunction. The immonium ion of His at m/z 110 was used as a specific product ion of His-containing peptides to generate precursor ion spectra, followed by MS2 acquisitions of each precursor ion of interest for structural characterization. By this approach, three novel adducts, which are excreted in free form only, have been identified, two of them originating from the conjugation of 4-hydroxy-trans-2-nonenal (HNE) to His, followed by reduction/oxidation of the aldehyde: His-1,4-dihydroxynonane (His-DHN), His-4-hydroxynonanoic acid (His-HNA), and carnosine-HNE, this last recognized in previous in vitro studies as a new potential biomarker of carbonyl stress. No free His-HNE was found in urines, which was detected only in protein hydrolysates. The same LC-MS/MS method, working in multiple reaction monitoring (MRM) mode, has been developed, validated, and applied to quantitatively profile in Zucker urines both conventional (1,4-dihydroxynonane mercapturic acid, DHN-MA) and the newly identified adducts, except His-HNA. The analytes were separated on a C12 reversed-phase column by gradient elution from 100% A (water containing 5 mM nonafluoropentanoic acid) to 80% B (acetonitrile) in 24 min at a flow rate of 0.2 mL/min and analyzed for quantification in MRM mode by applying the following precursor-to-product ion transitions m/z 322.2 --> 164.1 + 130.1 (DHN-MA), m/z 314.7 --> 268.2 + 110.1 (His-DHN), m/z 312.2 --> 110.1 + 156.0 (His-HNE), m/z 383.1 --> 266.2 + 110.1 (CAR-HNE), m/z 319.2 --> 301.6 + 156.5 (H-Tyr-His-OH, internal standard). Precision and accuracy data, as well as the lower limits of quantification in urine, were highly satisfactory (from 0.01 nmol/mL for CAR-HNE, His-DHN, His-HNE, to 0.075 nmol/mL for DHN-MA). The method, applied to evaluate for the first time the advanced lipoxidation end products profile in urine from obese Zucker rats, an animal model for the metabolic syndrome, has proved to be suitable and sensitive enough for testing in vivo the carbonyl quenching ability of newly developed RCS sequestering agents.

Aldehydic lipid peroxidation products in human brain astrocytomas

Among mediators of oxidative stress, highly reactive secondary aldehydic lipid peroxidation products can initiate the processes of spontaneous mutagenesis and carcinogenesis and can also act as a growth-regulating factors and signaling molecules. We explored whether these aldehydes and histone H3 mRNA levels could serve as biomarkers of malignancy and predictive factor in human brain astrocytomas. Histone H3 mRNA, a biomarker of cellular proliferation, was analyzed by QRT-PCR (TaqMan). Aldehydic lipid peroxidation products were determined as their dinitrophenylhydrazone derivatives in specimens obtained from 26 adult patients with brain astrocytomas. RP-HPLC with diode array detector and MSMS spectrometer were used for the analysis. H3 mRNA, 2-hydroxyhexanal, and 4-hydroxynonenal levels were higher in high-grade astrocytomas compared to low-grade astrocytomas and showed negative correlation with survival. Higher levels of 2-hydroxyhexanal and 4-hydroxynonenal, and lower levels of n-hexanal were associated with poorer patient prognosis. Our data suggest that tissue concentrations of aldehydic lipid peroxidation products can assist grading and predicting the clinical outcome in patients with astrocytic brain tumors. Possibly, this parameter will enhance optimal selection of patients for individualized treatment protocols, tailored to unique biochemical and molecular profile of the tumor.

Enzyme-linked immunosorbent assay for 4-hydroxynonenal-histidine conjugates

Highly reactive aldehyde 4-hydroxynonenal (HNE) is the final product of lipid peroxidation, known as a second messenger of free radicals and a signaling molecule. It forms protein conjugates involved in pathology of various diseases. To determine cellular HNE-protein conjugates we developed indirect ELISA based on well-known, monoclonal antibody against HNE-histidine (HNE-His) adducts. The method was calibrated using HNE-albumin conjugates as standards (R(2) = 0.999) and validated on human osteosarcoma cell cultures (HOS). The ELISA showed good sensitivity (8.1 pmol HNE-His/mg of protein), precision ( +/- 8% intra-assay and +/- 12% inter-assay) and spiking recovery ( +/- 9%). The assay revealed 60-fold increase of cellular HNE-His adducts upon copper-induced lipid peroxidation of HOS. The ELISA matched HNE-immunocytochemistry of HNE-treated HOS cells and quantified the increase of cellular HNE-His conjugates in parallel to the decrease of free HNE in culture medium. The ELISA was developed as ELISA Stress for severe lipid peroxidation and ELISA Fine for studies on HNE physiology.