Quantitative profiling of cochlear synaptosomal proteins in cisplatin-induced synaptic dysfunction

The disruption of ribbon synapses in the cochlea impairs the transmission of auditory signals from the cochlear sensory receptor cells to the auditory cortex. Although cisplatin-induced loss of ribbon synapses is well-documented, and studies have reported nitration of cochlear proteins after cisplatin treatment, yet the underlying mechanism of cochlear synaptopathy is not fully understood. This study tests the hypothesis that cisplatin treatment alters the abundance of cochlear synaptosomal proteins, and selective targeting of nitrative stress prevents the associated synaptic dysfunction. Auditory brainstem responses of mice treated with cisplatin showed a reduction in amplitude and an increase in latency of wave I, indicating cisplatin-induced synaptic dysfunction. The mass spectrometry analysis of cochlear synaptosomal proteins identified 102 proteins that decreased in abundance and 249 that increased in abundance after cisplatin treatment. Pathway analysis suggested that the dysregulated proteins were involved in calcium binding, calcium ion regulation, synapses, and endocytosis pathways. Inhibition of nitrative stress by co-treatment with MnTBAP, a peroxynitrite scavenger, attenuated cisplatin-induced changes in the abundance of 27 proteins. Furthermore, MnTBAP co-treatment prevented the cisplatin-induced decrease in the amplitude and increase in the latency of wave I. Together, these findings suggest a potential role of oxidative/nitrative stress in cisplatin-induced cochlear synaptic dysfunction.

Elevated temperature triggers increase in global DNA methylation, 5-methylcytosine expression levels, apoptosis and NOx levels in the gonads of Atlantic sea urchin

Global warming is one of the greatest threats to living organisms. Among them, marine invertebrates are severely impacted on reproductive fitness by rising seawater surface temperatures due to climate change (e.g., massive heat waves). In this study, we used highly sensitive radioimmunoassay, immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), in situ TUNEL assay, luminescence assay, and colorimetric assay techniques to investigate the impacts of high temperatures on global DNA methylation, cellular apoptosis, and nitrative stress in gonads of Atlantic sea urchin (Arbacia punctulata, a commercially important species). Young adult sea urchins were exposed to 24, 28, and 32 °C for one week in a controlled laboratory setting. High temperatures (28 and 32 °C) markedly increased global DNA methylation (around 1.1-1.5-fold in testes and ~ 1.7-fold in ovaries) and 5-methylcytosine (5-mC) levels in gonads (around 2.7- to ~5.1-fold in ovaries and ~ 3.5- to ~6.2-fold in testes) compared with controls (24 °C). The number of apoptotic nuclei in gonads was much higher in high-temperature groups. The caspase activity also increased significantly (P < 0.05) in gonads in high-temperature groups. Nitrate/nitrites (NOx, a biomarker of reactive nitrogen species) levels were increased around 2.6- to ~5.2-fold in testes and ~ 1.9- to ~3.8-fold in ovaries in high-temperature groups. Collectively, these outcomes indicate that high temperatures drastically induce global DNA methylation, 5-mC expression levels, cellular apoptosis, and NOx levels in the gonads of Atlantic sea urchin.

Oxidative/nitrosative stress increased the risk of recurrent pregnancy loss-Taiwan Recurrent Pregnancy Loss and Environmental Study (TREPLES)

OBJECTIVE

Oxidative stress biomarkers (OSBs) may be strongly associated with disease progression and recurrent pregnancy loss (RPL). However, the research on associations of most OSBs (e.g., 8-nitroguanine [8-NO2Gua] and 4-hydroxy-2-nonenal-mercapturic acid [HNE-MA]) with RPL is limited. Therefore, we aimed to investigate the effect of OSBs exposure on RPL risk by performing a case-control study.

MATERIAL AND METHODS

We use our established dataset, Taiwan Recurrent Pregnancy Loss and Environmental Study (TREPLES), which included 514 Taiwanese reproductive age women (aged 20-50 years; 397 cases and 117 controls) from National Cheng Kung University Hospital. RPL is clinically defined by a history of two or more consecutive miscarriages, where a miscarriage is defined as the termination of pregnancy before 20 weeks of gestation. The urinary levels of several OSBs (e.g., 8-hydroxy-2'-deoxyguanosine [8-OHdG], 8-NO2Gua, 8-isoprostaglandin F2α [8-isoPGF2α], and HNE-MA) and malondialdehyde (MDA) were measured using isotope dilution liquid chromatography-tandem mass spectrometry and thiobarbituric acid reactive substances, respectively.

RESULTS

The median levels of 8-NO2Gua (6.15 vs. 3.76 ng/mL) and HNE-MA (30.12 and 21.54 ng/mL) were significantly higher in the RPL group than in the control group. By categorizing the OSBs data into tertiles, after we adjusted for age and urine creatinine levels discovered that the RPL risk associated with 8-NO2Gua and HNE-MA levels in the third tertile were approximately 2 times higher than those in the first tertile (8-NO2Gua, adjusted OR = 3.27, 95 % CI = 1.66-6.43; HNE-MA, adjusted OR = 1.96, 95 % CI = 1.05-3.64; p < 0.05). These findings suggest that the oxidative stress biomarkers of 8-NO2Gua and HNE-MA are risk factors for RPL.

CONCLUSION

Our findings indicate that specific OSBs are associated with an increased RPL risk, suggesting that reducing OSB levels can improve RPL risk. Nevertheless, more studies on preventive medicine are required to understand the exposure sources and adverse outcome pathways of OSBs associated with RPL.

Endothelial MICU1 alleviates diabetic cardiomyopathy by attenuating nitrative stress-mediated cardiac microvascular injury

BACKGROUND

Myocardial microvascular injury is the key event in early diabetic heart disease. The injury of myocardial microvascular endothelial cells (CMECs) is the main cause and trigger of myocardial microvascular disease. Mitochondrial calcium homeostasis plays an important role in maintaining the normal function, survival and death of endothelial cells. Considering that mitochondrial calcium uptake 1 (MICU1) is a key molecule in mitochondrial calcium regulation, this study aimed to investigate the role of MICU1 in CMECs and explore its underlying mechanisms.

METHODS

To examine the role of endothelial MICU1 in diabetic cardiomyopathy (DCM), we used endothelial-specific MICU1ecKO mice to establish a diabetic mouse model and evaluate the cardiac function. In addition, MICU1 overexpression was conducted by injecting adeno-associated virus 9 carrying MICU1 (AAV9-MICU1). Transcriptome sequencing technology was used to explore underlying molecular mechanisms.

RESULTS

Here, we found that MICU1 expression is decreased in CMECs of diabetic mice. Moreover, we demonstrated that endothelial cell MICU1 knockout exacerbated the levels of cardiac hypertrophy and interstitial myocardial fibrosis and led to a further reduction in left ventricular function in diabetic mice. Notably, we found that AAV9-MICU1 specifically upregulated the expression of MICU1 in CMECs of diabetic mice, which inhibited nitrification stress, inflammatory reaction, and apoptosis of the CMECs, ameliorated myocardial hypertrophy and fibrosis, and promoted cardiac function. Further mechanistic analysis suggested that MICU1 deficiency result in excessive mitochondrial calcium uptake and homeostasis imbalance which caused nitrification stress-induced endothelial damage and inflammation that disrupted myocardial microvascular endothelial barrier function and ultimately promoted DCM progression.

CONCLUSIONS

Our findings demonstrate that MICU1 expression was downregulated in the CMECs of diabetic mice. Overexpression of endothelial MICU1 reduced nitrification stress induced apoptosis and inflammation by inhibiting mitochondrial calcium uptake, which improved myocardial microvascular function and inhibited DCM progression. Our findings suggest that endothelial MICU1 is a molecular intervention target for the potential treatment of DCM.

Gastrodin protects endothelial cells against high glucose-induced injury through up-regulation of PPARβ and alleviation of nitrative stress

In diabetes mellitus (DM), high glucose can result in endothelial cell injury, and then lead to diabetic vascular complications. Gastrodin, as the mainly components of Chinese traditional herb Tianma (Gastrodia elata Bl.), has been widely used for cardiovascular diseases. However, the known of the effect of gastrodin on endothelial cell injury is still limited. In this study, we aimed to investigate the effect and possible mechanism of gastrodin on high glucose-injured human umbilical vein endothelial cells (HUVEC). High glucose (30 mmol/L) treatment caused HUVEC injury. After gastrodin (0.1, 1, 10 μmol/L) treatment, compared with the high glucose group, the cell proliferation ability increased in a dose-dependent manner. Meanwhile, gastrodin (10 μmol/L) up-regulated the mRNA and protein expressions of PPARβ and eNOS, decreased the expressions of iNOS, also reduced the protein expression of 3-nitrotyrosine, and lowed the level of ONOO^-, increased NO content. Both the PPARβ antagonist GSK0660 (1 μmol/L) and the eNOS inhibitor L-NAME (10 μmol/L) were able to block the above effects of gastrodin. In conclusion, gastrodin protectes vascular endothelial cells from high glucose injury, which may be, at least partly, mediated by up-regulating the expression of PPARβ and negatively regulating nitrative stress.

PPARβ down-regulation is involved in high glucose-induced endothelial injury via acceleration of nitrative stress

Endothelial injury plays a vital role in vascular lesions from diabetes mellitus (DM). Therapeutic targets against endothelial damage may provide critical venues for the treatment of diabetic vascular diseases. Peroxisome proliferator-activated receptor β (PPARβ) is a crucial regulator in DM and its complications. However, the molecular signal mediating the roles of PPARβ in DM-induced endothelial dysfunction is not fully understood. The impaired endothelium-dependent relaxation and destruction of the endothelium structures appeared in high glucose incubated rat aortic rings. A high glucose level significantly decreased the expression of PPARβ and endothelial nitric oxide synthase (eNOS) at the mRNA and protein levels, and reduced the concentration of nitric oxide (NO), which occurred in parallel with an increase in the expression of inducible nitric oxide synthase (iNOS) and 3-nitrotyrosine. The effect of high glucose was inhibited by GW0742, a PPARβ agonist. Both GSK0660 (PPARβ antagonist) and NG-nitro-l-arginine-methyl ester (NOS inhibitor) could reverse the protective effects of GW0742. These results suggest that the activation of nitrative stress may, at least in part, mediate the down-regulation of PPARβ in high glucose-impaired endothelial function in rat aorta. PPARβ-nitrative stress may hold potential in treating vascular complications from DM.

Lifetime exposure of ambient PM2.5 elevates intraocular pressure in young mice

Epidemiological studies suggest that ambient particulate matter exposure may be a new risk factor of glaucoma, but it lacks solid experimental evidence to establish a causal relationship. In this study, young mice (4 weeks old) were exposed concentrated ambient PM2.5 (CAP) for 9 months, which is throughout most of the life span of a mouse under heavy pollution. CAP was introduced using a versatile aerosol concentration enrichment system which mimics natural PM2.5 exposure. CAP exposure caused a gradual elevation of intraocular pressure (IOP) and an increase in aqueous humor outflow resistance. In the conventional outflow tissues that regulates IOP, inducible nitric oxide synthase (iNOS) was up-regulated and 3-nitrotyrosine (3-NT) formation increased. At the cellular level, PM2.5 exposure increased the transendothelial electrical resistance of cells that control IOP (AAP cells). This is accompanied by increased reactive oxygen species (ROS), iNOS and 3-NT levels. Peroxynitrite scavenger MnTMPyP successfully treated the IOP elevation and restored it to normal levels by reducing 3-NT formation in outflow tissues. This study provides the novel evidence that in young mice, lifetime whole-body PM2.5 exposure has a direct toxic effect on intraocular tissues, which imposes a significant risk of IOP elevation and may initiate the development of ocular hypertension and glaucoma. This occurs as a result of protein nitration of conventional aqueous humor outflow tissues.

Indoleamine 2, 3-dioxygenase 1 aggravates acetaminophen-induced acute liver failure by triggering excess nitroxidative stress and iron accumulation

Acetaminophen (APAP) is the leading cause of acute liver failure (ALF), which is characterized by GSH depletion, oxidative stress and mitochondrial dysfunction. However, the specific mechanism of APAP-induced ALF remains to be clarified. In this study, we demonstrated that indoleamine 2,3-dioxygenase 1 (IDO1) aggravated APAP-induced ALF associated with excess lipid peroxidation, which was reversed by lipid peroxidation inhibitor (ferrostatin-1). Meanwhile, IDO1 deficiency effectively decreased the accumulation of reactive nitrogen species. Additionally, IDO1 deficiency prevented against APAP-induced liver injury through suppressing the activation of macrophages, thereby reduced their iron uptake and export, eventually reduced iron accumulation in hepatocytes through transferrin and transferrin receptor axis. In summary, our study confirmed that APAP-induced IDO1 aggravated ALF by triggering excess oxidative and nitrative stress and iron accumulation in liver. These results offer new insights for the clinical treatment of ALF or iron-dysregulated liver diseases in the future.

Abundant TNF-LIGHT expression in the airways of patients with asthma with persistent airflow limitation: Association with nitrative and inflammatory profiles

BACKGROUND

The role of the inflammatory secretory protein TNF-LIGHT (LIGHT) in the molecular mechanisms underlying persistent airflow limitation (PAL) in asthma remains unclear. We hypothesized that high airway LIGHT expression may be a feature of asthma with PAL associated with specific expression patterns of inflammatory molecules.

METHODS

This hypothesis was tested in 16 patients with asthma on inhaled corticosteroid treatment. Induced sputum was collected, the expression of LIGHT and 3-nitrotyrosine (NT), which reflects the footprint of reactive nitrogen species content, was measured using immunohistochemical staining, and the inflammatory molecules in the sputum supernatant were analyzed using a magnetic bead array.

RESULTS

LIGHT staining in the cells had a significantly higher intensity in participants with PAL than in participants without PAL (47.9 × 10⁴/ml vs. 5.4 × 10⁴/ml; p < 0.05). The array analysis indicated that IL-8, IL-19, matrix metalloproteinase 2, and osteopontin, were associated with high LIGHT immunoreactivity. The fractionation of 3-NT-positive cells was positively correlated with that of LIGHT-positive cells (r = 0.57, p < 0.05) and the TGF-β1 level (r = 0.61, p < 0.05). LIGHT- and 3-NT-positive cells showed significant positive correlation with the differential cell counts of neutrophils, macrophages, and eosinophils in the induced sputum. Intense immunoreactivities of LIGHT (r = -0.54, p < 0.05) and 3-NT (r = -0.42, p = 0.1) were negatively associated with decreased forced expiratory volume in 1/forced vital capacity ratio.

CONCLUSIONS

The findings suggest that LIGHT is a key component in the association between airway inflammation and airflow limitation in patients with asthma, and its expression may be persistently correlated with the abundance of inflammatory cells and inflammatory and profibrogenic radical/molecules.

Cisplatin-induced hair cell loss in zebrafish neuromasts is accompanied by protein nitration and Lmo4 degradation

Generation of reactive oxygen species, a critical factor in cisplatin-induced ototoxicity, leads to the formation of peroxynitrite, which in turn results in the nitration of susceptible proteins. Previous studies indicated that LMO4, a transcriptional regulator, is the most abundantly nitrated cochlear protein after cisplatin treatment and that LMO4 nitration facilitates ototoxicity in rodents. However, the role of this mechanism in regulating cisplatin-induced hair cell loss in non-mammalian models is unknown. As the mechanosensory hair cells in the neuromasts of zebrafish share many features with mammalian inner ear and is a good model for studying ototoxicity, we hypothesized that cisplatin treatment induces protein nitration and Lmo4 degradation in zebrafish hair cells, thereby facilitating hair cell loss. Immunostaining with anti-parvalbumin revealed a significant decrease in the number of hair cells in the neuromast of cisplatin treated larvae. In addition, cisplatin treatment induced a significant decrease in the expression of Lmo4 protein and a significant increase in nitrotyrosine levels, in the hair cells. The cisplatin-induced changes in Lmo4 and nitrotyrosine levels strongly correlated with hair cell loss, implying a potential link. Furthermore, a significant increase in the expression of activated Caspase-3 in zebrafish hair cells, post cisplatin treatment, suggested that cisplatin-induced decrease in Lmo4 levels is accompanied by apoptosis. These findings suggest that nitrative stress and Lmo4 degradation are important factors in cisplatin-induced hair cell loss in zebrafish neuromasts and that zebrafish could be used as a model to screen the otoprotective efficacy of compounds that inhibit protein nitration.

Indoleamine 2, 3-dioxygenase 1enhanceshepatocytes ferroptosis in acute immune hepatitis associated with excess nitrative stress

Ferroptosis is a recently recognized form of regulated cell death that is characterized by lipid peroxidation. However, the molecular mechanisms of ferroptosis in acute immune hepatitis (AIH) are largely unknown. In this study, we investigated the classical ferroptotic events in the livers of mice with concanavalin A (ConA) to induce AIH. The dramatically upregulated gene indoleamine 2, 3-dioxygenase 1 (IDO1) was identified with AIH, and its role in generation of ferroptosis and reactive nitrogen species (RNS) was assessed both in vitro and in vivo by genetic deletion or pharmacologic inhibition of IDO1. We observed that ferroptosis contributed to the ConA-induced hepatic damage, which was confirmed by the therapeutical effects of ferroptosis inhibitor (ferrostatin-1). Noteworthy, upregulation of hepatic IDO1 and nitrative stress in ConA-induced hepatic damage were also remarkably inhibited by the ferroptosis abolishment. Additionally, IDO1 deficiency contributed to ferroptosis resistance by activating solute carrier family 7 member 11 (SLC7A11; also known as xCT) expression, accompanied with the reductions of murine liver lesions and RNS. Meanwhile, IDO inhibitor 1-methyl tryptophan alleviated murine liver damage with the reduction of inducible nitric oxide synthase and 3-nitrotyrosine expression. Consistent with the results in vivo, hepatocytes-specific knockdown of IDO1 led to ferroptosis resistance upon exposure to ferroptosis-inducing compound (Erastin) in vitro, whereas IDO1 overexpression aggravated the classical ferroptotic events, and the RNS stress. Overall, these results revealed a novel molecular mechanism of ferroptosis with the key feature of nitrative stress in ConA-induced liver injury, and also identified IDO1-dependent ferroptosis as a potential target for the treatment of AIH.

Trans, trans-2,4-decadienal impairs vascular endothelial function by inducing oxidative/nitrative stress and apoptosis

Aldehydes are implicated in the development of hypertension. Trans, trans-2,4-decadienal (tt-DDE), a dietary α,β-unsaturated aldehyde, is widespread in many food products. However, the role of tt-DDE in the pathophysiology of hypertension remains unknown. This study was designed to investigate whether tt-DDE consumption evokes hypertension and to explore the mechanisms underlying such a role. Sprague-Dawley rats were administered different concentrations of tt-DDE. After 28 days, blood pressure and endothelial function of mesenteric arteries were measured. Results showed that tt-DDE treatment significantly increased blood pressure and impaired endothelial function based on endothelium-dependent vasorelaxation and p-VASP levels. Mechanistically, tt-DDE induced oxidative/nitrative stress in the arteries of rats as evidenced by overproductions of superoxide and peroxynitrite, accompanied with increased expressions of iNOS and gp91^phox. To further investigate the effects of tt-DDE on endothelial cells and underlying mechanisms, human umbilical vein endothelial cells (HUVECs) were treated with different concentrations of tt-DDE. tt-DDE induced oxidative/nitrative stress in HUVECs. Moreover, tt-DDE induced endothelial cells apoptosis through JNK-mediated signaling pathway. These results show, for the first time, that oral intake of tt-DDE elevates blood pressure and induces endothelial dysfunction in rats through oxidative/nitrative stress and JNK-mediated apoptosis signaling, indicating that excess ingestion of tt-DDE is a potential risk factor for endothelial dysfunction and hypertension.

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Trans, trans-2,4-decadienal (tt-DDE) is a dietary α,β-unsaturated aldehyde.

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tt-DDE raised blood pressure and impaired endothelial function in rats.

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Oxidative/nitrative stress was induced by tt-DDE in both rats and HUVECs.

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HUVEC apoptosis in response to tt-DDE exposure was mediated by JNK signaling.

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tt-DDE may be a risk factor for hypertension and associated cardiovascular disease.

Differential regulation of Nrf2 is linked to elevated inflammation and nitrative stress in monocytes of children with autism

Autism spectrum disorder (ASD) is a very complex neurodevelopmental disorder characterized by deficits in social and communication skills. Innate immune cells like monocytes are believed to play a cardinal role in neuroimmune inflammation and nitrative stress. On the other hand, Nrf2, a basic leucine zipper transcription factor plays a significant role in protecting the immune cells against inflammation and oxidants. However, its role in monocytes of ASD children and typically developing control (TDC) children has not been elucidated in relation with inflammation and nitrative stress. Therefore, this study was undertaken to evaluate Nrf2 expression/activity along with parameters of inflammation (NFkB, IL-6, IL-1β) and nitrative stress (iNOS, nitrotyrosine) in monocytes of ASD/TDC children. Further, sulforaphane (SFN) was utilized as an Nrf2 activator to assess its effect on above said inflammatory and nitrative stress parameters. Our study shows that monocytes of ASD subjects have decreased Nrf2 expression/activity along with increased inflammation and nitrative stress. Further, monocytes from ASD have deficiency in induction of Nrf2 activity upon stimulation with LPS. However, activation of Nrf2 in vitro by SFN reverses LPS-induced effects on inflammation in monocytes by reduction in NFkB signaling. Further, treatment with SFN also reverses LPS-induced effects on nitrative stress (iNOS, nitrotyrosine) in monocytes of ASD subjects. This study propounds the idea that SFN protects against nitrative stress and inflammation by downregulating oxidative stress and inflammation through blockade of NFkB signaling in autistic children. This may be the reason behind reported ameliorative effects of SFN in ASD subjects.

Inhibition of protein nitration prevents cisplatin-induced inactivation of STAT3 and promotes anti-apoptotic signaling in organ of Corti cells

JAK/STAT pathway is one among the several oxidative stress-responsive signaling pathways that play a critical role in facilitating cisplatin-induced ototoxicity. Cisplatin treatment decreases the levels of cochlear LMO4, which acts as a scaffold for IL6-GP130 protein complex. Cisplatin-induced nitration and degradation of LMO4 could destabilize this protein complex, which in turn could compromise the downstream STAT3-mediated cellular defense mechanism. Here, we investigated the link between cisplatin-induced nitrative stress and STAT3-mediated apoptosis by using organ of Corti cell cultures. SRI110, a peroxynitrite decomposition catalyst that prevented cisplatin-induced decrease in LMO4 levels and ototoxicity, was used to inhibit nitrative stress. Immunoblotting and immunostaining indicated that cisplatin treatment decreased the expression levels, phosphorylation, and nuclear localization of STAT3 in UB/OC1 cells. Inhibition of nitration by SRI110 co-treatment prevented cisplatin-induced inactivation of STAT3 and promoted its nuclear localization. SRI110 co-treatment reversed the cisplatin-induced changes in the expression levels of Bcl2l1, Ccnd1, Jak2, Jak3, and Src and significantly attenuated the changes in the expression levels of Cdkn1a, Egfr, Fas, Il6st, Jak1, Stat3, and Tyk2. Collectively, these results suggest that the inhibition of cisplatin-induced nitration prevents the inactivation of STAT3, which in turn enables the transcription of anti-apoptotic genes and thereby helps to mitigate cisplatin-induced toxicity.

A high-sensitivity electrochemiluminescence-based ELISA for the measurement of the oxidative stress biomarker, 3-nitrotyrosine, in human blood serum and cells

The generation of 3-nitrotyrosine, within proteins, is a post-translational modification resulting from oxidative or nitrative stress. It has been suggested that this modification could be used as a biomarker for inflammatory diseases. Despite the superiority of mass spectrometry-based determinations of nitrotyrosine, in a high-throughput clinical setting the measurement of nitrotyrosine by an enzyme-linked immunosorbent assay (ELISA) is likely to be more cost-effective. ELISAs offer an alternative means to detect nitrotyrosine, but many commercially available ELISAs are insufficiently sensitive to detect nitrotyrosine in healthy human serum. Here, we report the development, validation and clinical application of a novel electrochemiluminescence-based ELISA for nitrotyrosine which provides superior sensitivity (e.g. a 50-fold increase in sensitivity compared with one of the tested commercial colorimetric ELISAs). This nitrotyrosine ELISA has the following characteristics: a lower limit of quantitation of 0.04 nM nitrated albumin equivalents; intra- and inter-assay coefficients of variation of 6.5% and 11.3%, respectively; a mean recovery of 106 ± 3% and a mean linearity of 0.998 ± 0.001. Far higher nitration levels were measured in normal human blood cell populations when compared to plasma. Mass spectrometry was used to validate the new ELISA method. The analysis of the same set of chemically modified albumin samples using the ELISA method and mass spectrometry showed good agreement for the relative levels of nitration present in each sample. The assay was applied to serum samples from patients undergoing elective surgery which induces the human inflammatory response. Matched samples were collected before and one day after surgery. An increase in nitration was detected following surgery (median (IQR): 0.59 (0.00-1.34) and 0.97 (0.00-1.70) nitrotyrosine (fmol of nitrated albumin equivalents/mg protein) for pre- and post-surgery respectively. The reported assay is suitable for nitrotyrosine determination in patient serum samples, and may also be applicable as a means to determine oxidative stress in primary and cultured cell populations.

Impaired CBS-H2S signaling axis contributes to MPTP-induced neurodegeneration in a mouse model of Parkinson's disease

Hydrogen sulfide (H₂S), a novel neuromodulator, is linked to the pathogenesis of several neurodegenerative disorders. Exogenous application of H₂S exerts neuroprotection via anti-inflammation and anti-oxidative stress in animal and cellular models of Parkinson's disease (PD). However, the role of endogenous H₂S and the contribution of its various synthases in PD remain unclear. In the present study, we found a decline of plasma and striatal sulfide level in 1-methy-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced PD mouse model. Interestingly, among the three H₂S generating enzymes, only cystathionine β-synthase (CBS) expression was largely reduced in the striatum of MPTP-treated mice. The in vitro study confirmed a significant decrease of CBS expression in 1-methyl-4-phenylpyridinium (MPP⁺)-stimulated astrocytes and microglia, but not in neurons or SH-SY5Y dopaminergic cells. Striatal CBS overexpression, elicited by stereotaxic delivery with Cbs gene using recombinant adeno-associated-virus (rAAV-Cbs), successfully enhanced the sulfide level in the striatum and partially rescued the MPTP-induced dopaminergic neurotoxicity in the midbrain. Specifically, striatal CBS overexpression alleviated the motor deficits and dopaminergic neuron losses in the nigro-striatal pathway, with a concomitant inhibition of glial activation in MPTP-treated mice. Furthermore, compared to rAAV-Vector, rAAV-Cbs injection reduced the aberrant accumulation of nitric oxide and 3-nitrotyrosine (an indicator of protein nitration) in the striatum of MPTP-treated mice. Notably, it also attenuated the increase of nitrated α-synuclein level in MPTP mice. The in vitro study demonstrated that lentivirus-mediated CBS overexpression elevated the sulfide generation in glial cells. Moreover, glial CBS overexpression offered protection to midbrain dopaminergic neurons through repressing nitric oxide overproduction in both glial and neuronal cells induced by MPP⁺. Taken together, our data suggest that impaired CBS-H₂S axis may contribute to the pathogenesis of PD, and that modulation of this axis may become a novel therapeutic approach for PD.

Nitration-mediated deficiency of cystathionine β-synthase activity accelerates the progression of hyperhomocysteinemia

Deficiency of cystathionine β-synthase (CBS) activity is the most common cause of increased homocysteine (Hcy). However, until now the underlying mechanisms why CBS activity decreased still remain unresolved. The goal of this study was to explore the contribution of nitrative stress to deficiency of CBS activity, and further identify the possible nitration sites of CBS protein. Results showed that in elderly people, there was an increased nitrative stress level, which was relative to elevated Hcy level. In natural aging rats and diet-induced hyperhomocysteinemia (HHcy) rats, the levels of Hcy and nitrative stress were both elevated, and interestingly, pretreatment with peroxynitrite (ONOO^-) scavenger FeTMPyP ameliorated the elevation of Hcy as well as nitrative stress. Further experiments showed the reduction of CBS bioactivity and elevation of CBS nitration in two rats models were both reversed by FeTMPyP pretreatment. In vitro, replacement of tyrosine (Tyr, Y) residue (Tyr¹⁶³, Tyr²²³, Tyr³⁸¹, Tyr⁵¹⁸) in CBS with alanine (Ala, A) abolished the Hcy-mediated CBS inactivation. These results highlighted that deficiency of CBS activity was correlated with the nitration of CBS at Tyr¹⁶³, Tyr²²³, Tyr³⁸¹ and Tyr⁵¹⁸, which may play a mutual role in the progression of HHcy. This discovery may shed a novel light on the pathogenesis of HHcy and provide a possible gene therapy target to HHcy.

Inhibition of neutral sphingomyelinase decreases elevated levels of nitrative and oxidative stress markers in liver ischemia-reperfusion injury

Oxidative stress and excessive nitric oxide production via induction of inducible nitric oxide synthase (NOS)-2 have been shown in the pathogenesis of liver ischemia-reperfusion (IR) injury. Neutral sphingomyelinase (N-SMase)/ceramide pathway can regulate NOS2 expression therefore this study determined the role of selective N-SMase inhibition on nitrative and oxidative stress markers following liver IR injury. Selective N-SMase inhibitor was administered via intraperitoneal injections. Liver IR injury was created by clamping blood vessels supplying the median and left lateral hepatic lobes for 60 min, followed by 60 min reperfusion. Nitrative and oxidative stress markers were determined by evaluating NOS2 expression, protein nitration, nitrite/nitrate levels, 4-hydroxynonenal (HNE) formation, protein carbonyl levels and xanthine oxidase/xanthine dehydrogenase (XO/XDH) activity. Levels of sphingmyelin and ceramide in liver tissue were determined by an optimized multiple reaction monitoring method using ultra-fast liquid chromatography coupled with tandem mass spectrometry (MS/MS). Spingomyelin levels were significantly increased in all IR groups compared to controls. Treatment with a specific N-SMase inhibitor significantly decreased all measured ceramides in IR injury. NOS2 expression, nitrite/nitrate levels and protein nitration were significantly greater in IR injury and decreased with N-SMase inhibition. Treatment with a selective N-SMase inhibitor significantly decreased HNE formation, protein carbonyl levels and the hepatic conversion of XO. Data confirm the role of nitrative and oxidative injury in IR and highlight the protective effect of selective N-SMase inhibition. Future studies evaluating agents blocking N-SMase activity can facilitate the development of treatment strategies to alleviate oxidative injury in liver I/R injury.

Biomarkers of stress-mediated metabolic deregulation in diabetes mellitus

This review illustrates the relationship of oxidative and nitrative stress to diabetes mellitus and its complications. This is of considerable interest because diabetes mellitus is a lifetime systemic metabolic disease that may have childhood or adult onset and affects not only a triad of pancreatic islet cell insulin, pituitary insulin-like growth hormone, and liver steatosis, it has a long-term association with adiposity, atherosclerosis, coronary vascular disease, kidney disease of the nature afferent arteriolar sclerosis and nodular glomerulosclerosis, cerebrovascular disease, and amyloid deposition in the pancreas and kidney. Only at the end of the 20th century do we gain insight into oxidative and nitrative stress and their consequences. Of special interest here is the fact that reactive oxygen and nitrogen radicals are with us generated throughout the life cycle, and the roles for glutathione and Fe³⁺ are key elements in the metabolic picture, which brings into the picture dietary factors. More research is required to demonstrate the clinical relivance of naturally-occuring whole-food antioxidants in ameliorating human diabetic complications in vivo.

Endothelial endoplasmic reticulum and nitrative stress in endothelial dysfunction in the atherogenic rabbit model

Oxidative stress causes endothelial dysfunction which ultimately leads to atherogenesis, yet anti-oxidant therapy has failed to reduce human clinical outcomes. We hypothesise that endoplasmic reticulum stress and oxidative stress are both present in the endothelial layer of aorta with atherosclerosis. Rabbits were fed for 4 weeks a diet supplemented with 1% methionine +0.5% cholesterol (MC). Control animals received a normal diet. The endothelial function of the abdominal aorta was examined using organ bath techniques. Semi-quantitative immunohistochemistry was used to determine endothelial nitrotyrosine (for nitrative/oxidative stress) and glucose regulated protein 78 (GRP 78) and CHOP to determine endoplasmic reticulum stress. Endothelium dependent relaxation in response to acetylcholine significantly decreased in MC. Stress markers were significantly elevated in endothelia in MC compared to control. The total endothelial area examined for GRP78 increased by 8.4±0.25% in MC vs control (p=0.026) and C/EBP homologous protein (CHOP) increased by 21.9±0.05% in MC vs control (p=0.014). Nitrotyrosine increased by 13.3±0.03% in MC vs control (p=0.012).

CONCLUSIONS

Both endoplasmic reticulum stress and nitrative stress are present during endothelial dysfunction. Treatment directed at both stresses might be beneficial in the prevention of atherosclerosis.

Oxidative and nitrative stress in neurodegeneration

Aerobes require oxygen for metabolism and normal free radical formation. As a result, maintaining the redox homeostasis is essential for brain cell survival due to their high metabolic energy requirement to sustain electrochemical gradients, neurotransmitter release, and membrane lipid stability. Further, brain antioxidant levels are limited compared to other organs and less able to compensate for reactive oxygen and nitrogen species (ROS/RNS) generation which contribute oxidative/nitrative stress (OS/NS). Antioxidant treatments such as vitamin E, minocycline, and resveratrol mediate neuroprotection by prolonging the incidence of or reversing OS and NS conditions. Redox imbalance occurs when the antioxidant capacity is overwhelmed, consequently leading to activation of alternate pathways that remain quiescent under normal conditions. If OS/NS fails to lead to adaptation, tissue damage and injury ensue, resulting in cell death and/or disease. The progression of OS/NS-mediated neurodegeneration along with contributions from microglial activation, dopamine metabolism, and diabetes comprise a detailed interconnected pathway. This review proposes a significant role for OS/NS and more specifically, lipid peroxidation (LPO) and other lipid modifications, by triggering microglial activation to elicit a neuroinflammatory state potentiated by diabetes or abnormal dopamine metabolism. Subsequently, sustained stress in the neuroinflammatory state overwhelms cellular defenses and prompts neurotoxicity resulting in the onset or amplification of brain damage.

Endothelial relaxation mechanisms and nitrative stress are partly restored by Vitamin D3 therapy in a rat model of polycystic ovary syndrome

AIMS

In polycystic ovary syndrome (PCOS), metabolic and cardiovascular dysfunction is related to hyperandrogenic status and insulin resistance, however, Vitamin D3 has a beneficial effect partly due to its anti-oxidant capacity. Nitrative stress is a major factor in the development of cardiovascular dysfunction and insulin resistance in various diseases. Our aim was to determine the effects of vitamin D3 in a rat model of PCOS, particularly the pathogenic role of nitrative stress.

MAIN METHODS

Female Wistar rats weighing 100-140g were administered vehicle (C), dihydrotestosterone (DHT) or dihydrotestosterone plus vitamin D3 (DHT+D) (n=10 per group). On the 10th week, acetylcholine (Ach) induced relaxation ability of the isolated thoracic aorta rings was determined. In order to examine the possible role of endothelial nitric oxide synthase (eNOS) and cyclooxygenase-2 (COX-2) pathways in the impaired endothelial function, immunohistochemical labeling of aortas with anti-eNOS and anti-COX-2 antibodies was performed. Leukocyte smears, aorta and ovary tissue sections were also immunostained with anti-nitrotyrosine antibody to determine nitrative stress.

KEY FINDINGS

Relaxation ability of aorta was reduced in group DHT, and vitamin D3 partly restored Ach induced relaxation. eNOS labeling was significantly lower in DHT rats compared to the other two groups, however COX-2 staining showed an increment. Nitrative stress showed a significant increase in response to dihydrotestosterone, while vitamin D3 treatment, in case of the ovaries, was able to reverse this effect.

SIGNIFICANCE

Nitrative stress may play a role in the pathogenesis of PCOS and in the development of the therapeutic effect of vitamin D3.

Protective Effect of Calendula officinalis L. Flowers Against Monosodium Glutamate Induced Oxidative Stress and Excitotoxic Brain Damage in Rats

Monosodium glutamate (MSG) is a popular flavour enhancer used in food industries; however, excess MSG is neurotoxic. Oxidative stress is well documented in MSG induced neurotoxicity. The compounds having antioxidant and anti-inflammatory properties reportedly possess beneficial effects against various neurotoxic insults. Calendula officinalis Linn. flower extract (COE) is known for its potent antioxidant and anti-inflammatory activities. Hence, this present study has been designed to evaluate the neuroprotective effect of COE on MSG-induced neurotoxicity in rats. Adult Wistar rats were administered systemically for 7 days with MSG and after one h of MSG injection, rats were treated with COE (100 and 200 mg/kg) orally. At the end the treatment period, animals were assessed for locomotor activity and were sacrificed; brains were isolated for estimation of LPO, GSH, CAT, TT, GST, Nitrite and histopathological studies. MSG caused a significant alteration in animal behavior, oxidative defense (raised levels of LPO, nitrite concentration, depletion of antioxidant levels) and hippocampal neuronal histology. Treatment with COE significantly attenuated behavioral alterations, oxidative stress, and hippocampal damage in MSG-treated animals. Hence, this study demonstrates that COE protects against MSG-induced neurotoxicity in rats. The antioxidant and anti-inflammatory properties of COE may be responsible for its observed neuroprotective action.

Reduced denitration activity in peripheral lung of chronic obstructive pulmonary disease

BACKGROUND

Accumulation of nitrated protein is seen in peripheral lung and cells from patients with chronic obstructive pulmonary disease (COPD). Nitrated protein causes abnormal protein function, but the nitration was believed to be an irreversible process. However, there are accumulating evidences that this process is reversible by an active denitration pathway. The aim of this study is to detect denitration activity in protein extracts from peripheral lung tissue of COPD and to compare with those in healthy subjects.

MATERIALS AND METHODS

Peripheral lung tissue from 4 healthy, 4 smokers without COPD, 4 GOLD stage 1 and 4 GOLD stage 2 were used for denitration assay. Denitration activity was determined as reduction of nitro-tyrosine level of nitrated histone protein after incubation with protein extracts from peripheral lung, which was determined by western blotting. In addition, RNA is extracted from peripheral lung of 8 healthy, 7 smoking control, 8 stage 1 and 2 COPD and 10 stage 3 and 4 COPD and nitrate reductase mRNA expression was determined by real time RT-PCR.

RESULTS

Peripheral lung protein extracts from healthy subjects reduced nitro-tyrosine level of nitrated histone. Thus, we were able to show denitration activity in peripheral lungs. The denitration activity was slightly reduced in smoking controls, and significantly reduced in COPD patients. We also showed that the expression of the human homologue of nitrate reductase (chytochrome β2 reductase), a potential candidate of denitrase, was significanty reduced in COPD lung.

CONCLUSION

This study suggests that accumulation of nitrated protein in lung tissue of COPD may, at least in part, be induced by a reduction in denitration activity or nitrate reductase.