Reduced 4-hydroxynonenal degradation in hearts of spontaneously hypertensive rats during normoxia and postischemic reperfusion

Blood trihalomethane and urinary haloacetic acid concentrations in relation to hypertension: An observational study among 1162 healthy men

Disinfection byproducts (DBPs) have demonstrated cardiovascular and reproductive toxicity. However, the associations and mechanisms of DBP exposure in relation to hypertension among healthy young men, which are critical for gaining new insights into the prevention and treatment of male subfertility, remain unclear. In 2017-2018, we recruited 1162 healthy Chinese men. A single blood sample was collected and measured for trihalomethane (THM) concentrations (n = 956). Up to 2930 repeated urinary samples were collected at baseline and during follow-up periods and determined for haloacetic acid concentrations. Oxidative stress (OS) biomarkers were measured in within-subject pooled urinary samples (n = 1003). In total, 403 (34.68 %) participants were diagnosed with stage 1-2 hypertension (≥130/80 mmHg) and 108 (9.29 %) stage 2 hypertension (≥140/90 mmHg). In adjusted models, blood bromodichloromethane (BDCM) concentrations were positively associated with the risk of stage 1-2 and stage 2 hypertension [ORs= 1.48 (95 % CI: 1.15, 1. 91) and 1.65 (95 % CI: 1.08, 2.51), respectively, per 2.7-fold increase in BDCM concentrations]. Additionally, we found positive associations between DBP exposure biomarkers and urinary concentrations of 4-hydroxy-2-nonenal-mercapturic acid and 8-hydroxy-2-deoxyguanosine. However, these OS biomarkers were unrelated to hypertension. Our results suggest that BDCM exposure may be associated with a greater risk of hypertension among healthy young men.

Low-Dose 4-Hydroxy-2-Nonenal (HNE) Reperfusion Therapy Displays Cardioprotective Effects in Mice After Myocardial Infarction That Are Abrogated by Genipin

Background

Revascularization is a successful therapeutic strategy for myocardial infarction. However, restoring coronary blood flow can lead to ischemia-reperfusion (I/R) injury. Low-dose 4-hydroxy-2-nonenal (HNE) therapy appears to play a key role in myocardial tolerance to I/R injury. We hypothesized that the positive effects of HNE on myocardial I/R injury may be UCP3-dependent.

Material/Methods

Adult male wild-type (WT) or UCP3 knockout (UCP3−/−) mice were pre-treated with the UCP inhibitor genipin or saline 1 h before ischemia and underwent 30-min coronary artery ligation followed by 24-h reperfusion. Mice were treated with intravenous HNE (4 mg/kg) or saline 5 min before reperfusion. Echocardiography was conducted to measure left ventricular end-diastolic posterior wall thickness (LVPWd), end-diastolic diameter (LVEDD), and fractional shortening (FS). Infarct size was measured by TTC staining. qRT-PCR and Western blotting were used to assess the expression of UCP3, UCP2, and the apoptosis markers cytochrome C and cleaved caspase-3.

Results

HNE improved survival at 24 h post-MI in wild-type mice (p<0.05) but not in UCP3−/− mice. HNE preserved LVEDD and FS in WT mice (p<0.05) but not in UCP3−/− mice. HNE reduced infarct size in WT mice (p<0.05) but not in UCP3−/− mice. HNE upregulated UCP3 expression (p<0.05) but did not affect UCP2 expression. HNE reduced apoptosis marker expression in WT mice (p<0.05) but not in UCP3−/− mice. HNE’s positive effects were abrogated by genipin in an UCP3-dependent manner.

Conclusions

Low-dose HNE reperfusion therapy attenuates murine myocardial I/R injury in an UCP3-dependent manner. These effects are abrogated by genipin in an UCP3-dependent manner.

Protein carbonylation in kidney medulla of the spontaneously hypertensive rat

Enhanced generation of ROS has been reported in models of hypertension such as the spontaneously hypertensive rat (SHR). Impairment of kidney function has been implicated in development and progression of hypertension, and the renal medulla appears to play an important role in regulating long-term blood pressure. A key biomarker of oxidative stress is the formation of protein carbonyls, which we set out to characterize in the SHR medulla. We identified 11 proteins that were differentially carbonylated in SHR medulla in comparison to normotensive wistars including enolase 1, catalase, carbonic anhydrase II, transferrin and members of the aldo-keto-reductase family. This enhanced protein oxidation was not only accompanied by an increase in intracellular iron deposition, but aldo-keto-reductase activity was also significantly less in SHR medulla than in normotensive Wistars. Oxidative stress appears selectively to target a subset of proteins in SHR kidney and modification of these proteins may in turn contribute to the renopathy associated with hypertension.

Decreased cardiac mitochondrial NADP+-isocitrate dehydrogenase activity and expression: a marker of oxidative stress in hypertrophy development

Mitochondrial dysfunction subsequent to increased oxidative stress and alterations in energy metabolism is considered to play a role in the development of cardiac hypertrophy and its progression to failure, although the sequence of events remains to be elucidated. This study aimed at characterizing the impact of hypertrophy development on the activity and expression of mitochondrial NADP+-isocitrate dehydrogenase (mNADP+-ICDH), a metabolic enzyme that controls redox and energy status. We expanded on our previous finding of its inactivation through posttranslational modification by the lipid peroxidation product 4-hydroxynonenal (HNE) in 7-wk-old spontaneously hypertensive rat (SHR) hearts before hypertrophy development (Benderdour et al. J Biol Chem 278: 45154-45159, 2003). In this study, we used 7-, 15-, and 30-wk-old SHR and Sprague-Dawley (SD) rats with abdominal aortic coarctation. Compared with age-matched control Wistar-Kyoto (WKY) rats, SHR hearts showed a significant 25% decrease of mNADP+-ICDH activity, which preceded in time 1) the decline in its protein and mRNA expression levels (between 10% and 35%) and 2) the increase in hypertrophy markers. The chronic and persistent loss of mNADP+-ICDH activity in SHR was associated with enhanced tissue accumulation of HNE-mNADP+-ICDH and total HNE-protein adducts at all ages and contrasted with the profile of changes in the activity of other mitochondrial enzymes involved in antioxidant or energy metabolism. Two-way ANOVA of the data also revealed a significant effect of age on most parameters measured in SHR and WKY hearts. The mNADP+-ICDH activity, protein, and mRNA expression were reduced between 25% and 35% in coarctated SD rats and were normalized by treatment of SHR or coarctated SD rats with renin-angiotensin system inhibitors, which prevented or attenuated hypertrophy. Altogether, our data show that cardiac mNADP+-ICDH activity and expression are differentially and sequentially affected in hypertrophy development and, to a lesser extent, with aging. Decreased cardiac mNADP+-ICDH activity, which is attributed at least in part to HNE adduct formation, appears to be a relevant early and persistent marker of mitochondrial oxidative stress-related alterations in hypertrophy development. Potentially, this could also contribute to the aetiology of cardiomyopathy.

Cardiac mitochondrial NADP+-isocitrate dehydrogenase is inactivated through 4-hydroxynonenal adduct formation: an event that precedes hypertrophy development

Mitochondrial NADP+-isocitrate dehydrogenase activity is crucial for cardiomyocyte energy and redox status, but much remains to be learned about its role and regulation. We obtained data in spontaneously hypertensive rat hearts that indicated a partial inactivation of this enzyme before hypertrophy development. We tested the hypothesis that cardiac mitochondrial NADP+-isocitrate dehydrogenase is a target for modification by the lipid peroxidation product 4-hydroxynonenal, an aldehyde that reacts readily with protein sulfhydryl and amino groups. This hypothesis is supported by the following in vitro and in vivo evidence. In isolated rat heart mitochondria, enzyme inactivation occurred within a few minutes upon incubation with 4-hydroxynonenal and was paralleled by 4-hydroxynonenal/NADP+-isocitrate dehydrogenase adduct formation. Enzyme inactivation was prevented by the addition of its substrate isocitrate or a thiol, cysteine or glutathione, suggesting that 4-hydroxynonenal binds to a cysteine residue near the substrate's binding site. Using an immunoprecipitation approach, we demonstrated the formation of 4-hydroxynonenal/NADP+-isocitrate dehydrogenase adducts in the heart and their increased level (210%) in 7-week-old spontaneously hypertensive rats compared with control Wistar Kyoto rats. To the best of our knowledge, this is the first study to demonstrate that mitochondrial NADP+-isocitrate dehydrogenase is a target for inactivation by 4-hydroxynonenal binding. Furthermore, the pathophysiological significance of our finding is supported by in vivo evidence. Taken altogether, our results have implications that extend beyond mitochondrial NADP+-isocitrate dehydrogenase. Indeed, they emphasize the implication of post-translational modifications of mitochondrial metabolic enzymes by 4-hydroxynonenal in the early oxidative stress-related pathophysiological events linked to cardiac hypertrophy development.

Quantitative gas chromatographic-mass spectrometric assay of 4-hydroxynonenal bound to thiol proteins in ischemic/reperfused rat hearts

Increasing evidence indicates that protein-aldehyde adducts involving mostly 4-hydroxynonenal could be causally involved in both pathophysiological and adaptive events following an oxidative stress insult such as ischemia/reperfusion. The goal of this study was to assess if isotope dilution chromatography-mass spectrometry can be used to quantitate changes in the cardiac levels of 4-hydroxynonenal and 1,4-dihydroxynonene, one of its major metabolites, bound to thiol proteins during ischemia/reperfusion. For this purpose, we modified a previously published method to include treatment with Raney Nickel, which specifically cleaves thioether linkages. Our study model was the isolated Langendorff-perfused rat heart subjected to various ischemia/reperfusion protocols. Hearts perfused under normoxia contained small amounts of protein-bound 4-hydroxynonenal and 1,4-dihydroxynonene (1.38 +/- 0.29 and 2.69 +/- 0.17 nmol/g wet weight, respectively). The accumulation of these adducts after global ischemia depended on the severity of the ischemic insult up to a plateau and was not exacerbated by reperfusion. In conclusion, our method allows the quantification of time-dependent changes in 4-hydroxynonenal and 1,4-dihydroxynonene bound to proteins via thioether linkage in ischemic/reperfused heart tissues. The presence of protein-bound 1,4-dihydroxynonene in heart tissues suggests that this organ can detoxify protein-bound 4-hydroxynonenal.

Oxidized proteins as a marker of oxidative stress during coronary heart surgery

The measurement of the degree of oxidative stress in patients often causes problems because of the lack of useful parameters. Therefore, we used an ELISA technique to evaluate serum protein carbonyls as a parameter of oxidative stress in patients during coronary heart surgery. Protein carbonyls were detected in serum samples of 14 patients undergoing coronary surgery and cardiopulmonary artery bypass grafting. A clear 2- to 3-fold increase in protein carbonyls in serum samples taken from human venous coronary sinus could be detected in the reperfusion period of the heart. We compared these data with markers of oxidative stress previously used, such as the glutathione status and the lipid peroxidation product malondialdehyde (MDA). Strong correlations of the protein carbonyl formation with MDA (r2 = 0.86) and oxidized glutathione (r2 = 0.81) were found in the early reperfusion stage. Increased levels of oxidized glutathione and MDA were detected only in the early reperfusion period. In contrast, the serum protein carbonyl content remained elevated for several hours, indicating a considerably slower serum clearance of oxidized proteins compared with that of lipid peroxidation products and the normalization of the glutathione status. We therefore concluded that the measurement of serum carbonyls by this ELISA technique is suitable to detect oxidative stress in serum samples of patients. The relative stability of the parameter makes the protein carbonyl detection even more valuable for clinical purposes.

4-Hydroxynonenal as a biological signal: molecular basis and pathophysiological implications

Reactive oxygen intermediates (ROI) and other pro-oxidant agents are known to elicit, in vivo and in vitro, oxidative decomposition of omega-3 and omega-6 polyunsaturated fatty acids of membrane phospholipids (i.e, lipid peroxidation). This leads to the formation of a complex mixture of aldehydic end-products, including malonyldialdehyde (MDA), 4-hydroxy-2,3-nonenal (HNE), and other 4-hydroxy-2,3-alkenals (HAKs) of different chain length. These aldehydic molecules have been considered originally as ultimate mediators of toxic effects elicited by oxidative stress occurring in biological material. Experimental and clinical evidence coming from different laboratories now suggests that HNE and HAKs can also act as bioactive molecules in either physiological and pathological conditions. These aldehydic compounds can affect and modulate, at very low and nontoxic concentrations, several cell functions, including signal transduction, gene expression, cell proliferation, and, more generally, the response of the target cell(s). In this review article, we would like to offer an up-to-date review on this particular aspect of oxidative stress--dependent modulation of cellular functions-as well as to offer comments on the related pathophysiological implications, with special reference to human conditions of disease.

High metabolic rates of 4-hydroxynonenal in brain capillary endothelial cells during hypoxia/reoxygenation

We measured the accumulation of 4-hydroxynonenal (HNE), a major lipid peroxidation product during hypoxia/reoxygenation of brain capillary endothelial cells (BCEC). The concentration of HNE after 2 h of hypoxia was 0.23 nmol/mg protein and rose up to 0.28 nmol/mg protein after 30 min of reoxygenation. That reflects a 1.5-fold increase, whereas aortic endothelial cells (AEC) increased the HNE level 5-fold, compared to the control. Therefore, the ability of BCEC to degrade exogenously added HNE was tested. The HNE consumption in BCEC achieved a rate of about 600 nmol.min-1.mg protein-1, about two times higher than in AEC. The higher ability of BCEC to degrade HNE is probably the reason of the 2-fold higher IC50 value against the aldehyde. Therefore, we concluded that the high ability of BCEC to degrade HNE is a substantial part of the secondary antioxidative defense of the brain.

4-hydroxynonenal is degraded to mercapturic acid conjugate in rat kidney

The cytotoxic lipid peroxidation product 4-hydroxynonenal (HNE) was infused into rat kidney. During the first 2 min a rapid degradation of a 100 microM HNE solution was demonstrated. After 5 min the consumption rate of 4-HNE reached a steady state of about 75 nmoles/ml. The total HNE consumption rate was about 200 nmoles/g w.w./min. The excretion rate into urine was about 0.1% of total HNE consumption. It could be demonstrated that the HNE-mercapturic acid formation takes place in the kidney. The formation of the HNE-mercapturic acid contributes up to 6% to total HNE consumption. Within 10 min of perfusion 2% of the HNE-mercapturic acid were excreted into urine. The residual 98% flow back into the blood circulation.