Inflammatory signal transduction pathways induced by prilocaine toxicity in cultured ARPE-19 cells

Prilocaine (PRL) is a common local anesthetic. Despite the successful use of regional anesthesia for intraocular surgery, there are associated side effects that may affect the retina in case of accidental intravitreal injection. This study examined the signal transduction pathways activated by PRL toxicity and determined the protective role of nitric oxide synthase-2 (NOS2) inhibition in cultured human-derived retinal pigment epithelial cells (ARPE-19). Toxicity analysis was performed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay to detect the toxic dose of PRL and protective effectiveness of asperglaucide (ASP), an NOS2 inhibitor. Nuclear factor kappa B p65 (NF-κB p65), phosphorylated NF-κB p65, phospho-protein kinase B (AKT), NOS2, nitrotyrosine, and cleaved caspase-3 protein levels were evaluated by immunofluorescence staining and/or western blot analysis. Interleukin-6 (IL-6) and nitrated protein levels were quantified using an immunoassay, whereas caspase-3 activity and nitrite/nitrate levels were measured using a fluorometric method. A significant increase in NF-κB p65, and phosphorylated NF-κB p65 and AKT levels due to PRL toxicity was observed. Similarly, IL-6, NOS2, nitrite/nitrate, and nitrotyrosine levels were significantly higher in PRL-treated cells than in control cells. Application of ASP to PRL-treated cells reduced NF-κB p65, and phosphorylated NF-κB p65 and AKT to basal levels. IL-6, NOS2, nitrite/nitrate, and nitrotyrosine levels also considerably decreased following ASP treatment in cells experiencing PRL-induced toxicity. Moreover, the caspase-3-dependent apoptotic pathway was not activated. Our results indicate that ASP could ameliorate PRL-induced activation of NF-κB p65 that led to inflammation in cultured ARPE-19 cells.

Changes of auditory event-related potentials in ovariectomized rats injected with d-galactose: Protective role of rosmarinic acid

Rosmarinic acid (RA), which has multiple bioactive properties, might be a useful agent for protecting central nervous system against age related alterations. In this context, the purpose of the present study was to investigate possible protective effects of RA on mismatch negativity (MMN) component of auditory event-related potentials (AERPs) as an indicator of auditory discrimination and echoic memory in the ovariectomized (OVX) rats injected with d-galactose combined with neurochemical and histological analyses. Ninety female Wistar rats were randomly divided into six groups: sham control (S); RA-treated (R); OVX (O); OVX+RA-treated (OR); OVX+d-galactose-treated (OD); OVX+d-galactose+RA-treated (ODR). Eight weeks later, MMN responses were recorded using the oddball condition. An amplitude reduction of some components of AERPs was observed due to ovariectomy with or without d-galactose administiration and these reduction patterns were diverse for different electrode locations. MMN amplitudes were significantly lower over temporal and right frontal locations in the O and OD groups versus the S and R groups, which was accompanied by increased thiobarbituric acid reactive substances (TBARS) and hydroxy-2-nonenal (4-HNE) levels. RA treatment significantly increased AERP/MMN amplitudes and lowered the TBARS/4-HNE levels in the OR and ODR groups versus the O and OD groups, respectively. Our findings support the potential benefit of RA in the prevention of auditory distortion related to the estrogen deficiency and d-galactose administration at least partly by antioxidant actions.

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.

Effects of pre- and postnatal exposure to extremely low-frequency electric fields on mismatch negativity component of the auditory event-related potentials: Relation to oxidative stress

In our previous study, the developmental effects of extremely low-frequency electric fields (ELF-EF) on visual and somatosensory evoked potentials in adult rats were studied. There is no study so far examining the effects of 50 Hz electric field (EF) on mismatch negativity (MMN) recordings after exposure of rats during development. Therefore, our present study aimed to investigate MMN and oxidative brain damage in rats exposed to EF (12 kV/m, 1 h/day). Rats were divided into four groups, namely control (C), prenatal (Pr), postnatal (Po), and prenatal+postnatal (PP). Pregnant rats of Pr and PP groups were exposed to EF during pregnancy. Following birth, rats of PP and Po groups were exposed to EF for three months. After exposure to EF, MMN was recorded by electrodes positioned stereotaxically to the surface of the dura, and then brain tissues were removed for histological and biochemical analyses. The MMN amplitude was higher to deviant tones than to standard tones. It was decreased in all experimental groups compared with the C group. 4-Hydroxy-2-nonenal (4-HNE) levels were significantly increased in the Po group with respect to the C group, whereas they were significantly decreased in the PP group compared with Pr and Po groups. Protein carbonyl levels were significantly decreased in the PP group compared with C, Pr, and Po groups. EF decreased MMN amplitudes were possibly induced by lipid peroxidation.

Inducible and endothelial nitric synthetase expression and nitrotyrosine accumulation in iris vasculature of patients with primary open-angle glaucoma: a pilot study

Background

The “double-faced” effect of nitric oxide (NO) is thought to play an important role in triggering and progression of glaucoma.

Material/Methods

Iris samples were obtained during iridectomy in 35 patients (mean age of 65.4±5.3 years) with diagnosed primary open-angle glaucoma (POAG). The controls were collected postmortem from 10 donors with a mean age of 62.2±1.9 years. Visual field defects were evaluated by perimetry. The Hodapp-Parrish-Anderson classification was used to divide patients into 3 visual field defect groups. The intraocular pressure was measured 3 times before surgery using applanation tonometry. The phenotype activity of nitric oxide synthase (NOS) isoenzymes (endothelial – eNOS and inducible – iNOS) and expression of nitrotyrosine in iris vasculature was assessed.

Results

Significant differences were found between glaucoma patients and the controls in eNOS and iNOS activity (Mann-Whitney test, U=35.5, Z=−2.037, p=0.04 and U=21, Z=2.69, p=0.007, respectively). In addition, the results showed an upregulation of nitrotyrosine in the capillary endothelial cells in the study group, which was associated with the duration of diagnosed glaucoma (R-Spearman of 0.33, p=0.0047) and visual field mean defect MD (R-Spearman of 0.29, p=0.019). Moreover, the activity of nitrotyrosine was significantly correlated with iNOS immunoreactivity (R-Spearman of 0.5, p=0.0001). However, the iNOS activity significantly varied among Hodapp-Parrish-Anderson groups (p=0.03).

Conclusions

Our observations confirmed the association between glaucomatous disturbances and upregulation of iNOS, together with increased nitrotyrosine storage.

Measurement of intracellular biomolecular oxidation in liver ischemia-reperfusion injury via immuno-spin trapping

Hepatic ischemia-reperfusion (I/R) can lead to liver failure in association with remote organ damage, both of which have significant rates of morbidity and mortality. In this study, novel spin trapping and histopathological techniques have been used to investigate in vivo free radical formation in a rat model of warm liver I/R injury. 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) was administered to rats via intraperitoneal injection at a single dose of 1.5g of pure DMPO/kg body wt 2h before the initiation of liver ischemia. Blood vessels supplying the median and left lateral hepatic lobes were occluded with an arterial clamp for 60min, followed by 60min reperfusion. The effects of DMPO on I/R injury were evaluated by assessing the hepatic ultrastructure via transmission electron microscopy and by histopathological scoring. Immunoelectron microscopy was performed to determine the cellular localization of DMPO nitrone adducts. Levels of nitrone adducts were also measured to determine in situ scavenging of protein and DNA radicals. Total histopathological scoring of cellular damage was significantly decreased in hepatic I/R injury after DMPO treatment. DMPO treatment significantly decreased the hepatic conversion of xanthine oxidase and 4-hydroxynonenal formation in I/R injury compared to the untreated I/R group. The distribution of gold-nanoparticle-labeled DMPO nitrone adducts was observed in mitochondria, cytoplasm, and nucleus of hepatocytes. The formation of protein- and DNA-nitrone adducts was increased in DMPO-treated I/R livers compared to DMPO controls, indicating increased in situ protein and DNA radical formation and scavenging by DMPO. These results suggest that DMPO reduces I/R damage via protection against oxidative injury.

Manganese porphyrin reduces retinal injury induced by ocular hypertension in rats

This study aimed to clarify the possible therapeutic benefit of preferential nitric oxide synthase (NOS) inhibition and catalytic antioxidant Mn (III) meso-tetrakis (N-n-hexylpyridinium-2-yl) porphyrin (MnTnHex-2-PyP(5+)) treatment in a rat model of elevated intraocular pressure (EIOP). Rats were randomly divided into different experimental groups which received either intraperitoneal MnTnHex-2-PyP(5+) (0.1 mg/kg/day), intragastric NOS inhibitor (S-methylthiourea: SMT; 5 mg/kg/day) or both agents for a period of 6 weeks. Ocular hypertension was induced by unilaterally cauterizing three episcleral vessels and the unoperated eye served as control. Neuroprotective effects of given treatments were determined via electrophysiological measurements of visual evoked potentials (VEP) while retina and vitreous levels of MnTnHex-2-PyP(5+) were measured via LC-MS/MS. Latencies of all VEP components (P(1), N(1), P(2), N(2), P(3)) were significantly prolonged (p < 0.05) in EIOP and returned to control levels following all three treatment protocols. Ocular hypertension significantly increased retinal protein nitration (p < 0.001) which returned to baseline levels in all treated groups. NOS-2 expression and nitrate/nitrite levels were significantly greater in non-treated rats with EIOP. Retinal TUNEL staining showed apoptosis in all ocular hypertensive rats. The presented data confirm the role of oxidative injury in EIOP and highlight the protective effect of MnTnHex-2-PyP(5+) treatment and NOS inhibition in ocular hypertension.

Functional consequences of actin nitration: in vitro and in disease states

To link the phenomena of inflammatory-induced increases in protein nitrotyrosine (NO(2)Tyr) derivatives to protein dysfunction and consequent pathological conditions, the evaluation of discrete NO(2)Tyr modifications on specific proteins must be undertaken. Mass spectrometric (MS) proteomics-based strategies allow for the identification of all individual proteins that are nitrated by separating tissue homogenates using 2D gel electrophoresis, detecting the nitrated proteins using an anti-NO(2)Tyr antibody, and then identifying the peptides generated during an in-gel proteolytic digest using matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) MS. Actin, one of the most abundant proteins in eukaryotic cells, constitutes 5% or more of cell protein and serves with other cytoskeletal proteins as a critical target for nitration-induced functional impairment. Herein, examples of actin nitration detected under physiological conditions in various models of human disease or in clinically derived tissues are given and the impact that this post-translational protein modification can have on cell and organ function is discussed.

Effect of astaxanthin on hepatocellular injury following ischemia/reperfusion

This study investigated the effect of astaxanthin (ASX; 3,3-dihydroxybeta, beta-carotene-4,4-dione), a water-dispersible synthetic carotenoid, on liver ischemia-reperfusion (IR) injury. Astaxanthin (5 mg/kg/day) or olive oil was administered to rats via intragastric intubation for 14 consecutive days before the induction of hepatic IR. On the 15th day, blood vessels supplying the median and left lateral hepatic lobes were occluded with an arterial clamp for 60 min, followed by 60 min reperfusion. At the end of the experimental period, blood samples were obtained from the right ventricule to determine plasma alanine aminotransferase (ALT) and xanthine oxidase (XO) activities and animals were sacrificed to obtain samples of nonischemic and postischemic liver tissue. The effects of ASX on IR injury were evaluated by assessing hepatic ultrastructure via transmission electron microscopy and by histopathological scoring. Hepatic conversion of xanthine dehygrogenase (XDH) to XO, total GSH and protein carbonyl levels were also measured as markers of oxidative stress. Expression of NOS2 was determined by immunohistochemistry and Western blot analysis while nitrate/nitrite levels were measured via spectral analysis. Total histopathological scoring of cellular damage was significantly decreased in hepatic IR injury following ASX treatment. Electron microscopy of postischemic tissue demonstrated parenchymal cell damage, swelling of mitochondria, disarrangement of rough endoplasmatic reticulum which was also partially reduced by ASX treatment. Astaxanthine treatment significantly decreased hepatic conversion of XDH to XO and tissue protein carbonyl levels following IR injury. The current results suggest that the mechanisms of action by which ASX reduces IR damage may include antioxidant protection against oxidative injury.