Nitrative Stress Research Articles

GYY4137, an H2S Slow-Releasing Donor, Prevents Nitrative Stress and α-Synuclein Nitration in an MPTP Mouse Model of Parkinson's Disease.

The neuromodulator hydrogen sulfide (H2S) was shown to exert neuroprotection in different models of Parkinson’s disease (PD) via its anti-inflammatory and anti-apoptotic properties. In this study, we evaluated the effect of an H2S slow-releasing compound GYY4137 (GYY) on a mouse PD model induced by acute injection with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). GYY was intraperitoneally (i.p.) injected once daily into male C57BL/6J mice 3 days before and 2 weeks after MPTP (14 mg/kg, four times at 2-h intervals, i.p.) administration. Saline was given as a control. Behavioral tests (rotarod, balance beam, and grid walking) showed that 50 mg/kg GYY significantly ameliorated MPTP-caused motor impairments. At lower doses (12.5 and 25 mg/kg) GYY exhibited a less obvious effect. Consistent with this, immunohistochemistry and western blot analysis demonstrated that 50 mg/kg GYY attenuated the loss of tyrosine hydroxylase (TH) positive neurons in the substantia nigra and the decrease of TH expression in the striatum of MPTP-treated mice. Moreover, at this regimen GYY relieved the nitrative stress, as indicated by the decreases in nitric oxide (NO) generation and neuronal NO synthase (nNOS) upregulation elicited by MPTP in the striatum. The suppression of GYY on nNOS expression was verified in vitro, and the results further revealed that Akt activation may participate in the inhibition by GYY on nNOS upregulation. More important, GYY reduced the nitrated modification of α-synuclein, a PD-related protein, in MPTP-induced mice. Overall, our findings suggest that GYY attenuated dopaminergic neuron degeneration and reduced α-synuclein nitration in the midbrain, thus exerting neuroprotection in MPTP-induced mouse model of PD.

Important Role of Endothelial Caveolin-1 in the Protective Role of Endothelium-dependent Hyperpolarization Against Nitric Oxide-Mediated Nitrative Stress in Microcirculation in Mice.

Nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) play important roles in maintaining cardiovascular homeostasis. We have previously demonstrated that endothelial NO synthase (eNOS) plays diverse roles depending on vessel size, as a NO generating system in conduit arteries and an EDH-mediated system in resistance arteries, for which caveolin-1 (Cav-1) is involved. However, the physiological role of endothelial Cav-1 in microvessels remains to be elucidated. We newly generated endothelium-specific Cav-1-knockout (eCav-1-KO) mice. eCav-1-KO mice showed loss of endothelial Cav-1/eNOS complex and had cardiac hypertrophy despite normal blood pressure. In eCav-1-KO mice, as compared to wild-type controls, the extent of eNOS phosphorylation at inhibitory Thr495 was significantly reduced in mesenteric arteries and the heart. Isometric tension and Langendorff-perfused heart experiments showed that NO-mediated responses were enhanced, whereas EDH-mediated responses were reduced in coronary microcirculation in eCav-1-KO mice. Immunohistochemistry showed increased level of 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP), a marker of nitrative stress, in the heart from eCav-1-KO mice. S-guanylation of cardiac H-Ras in eCav-1-KO mice was also significantly increased compared with wild-type controls. These results suggest that eCav-1 is involved in the protective role of EDH against nitrative stress caused by excessive NO to maintain cardiac microvascular homeostasis.

Effects of Proteoglycans on Oxidative/Nitrative Stress

Objective: Enhanced production of reactive oxygen and/or nitrogen species in biological tissues leads to oxidative and nitrative stress, a general pathophysiological phenomenon playing a role in the development of various human diseases including cardiovascular and neurological disorders. Method: Reactive oxygen and/or nitrogen species interact with lipids, DNA and proteins via oxidative or radical- mediated reactions, potentially leading to cell damage or death. Proteoglycans are among the most important structural and functional macromolecules in most tissues. The chemical structure of these molecules consist of a core protein onto which one or more negatively charged glycosaminoglycan (GAG) chain(s) are covalently attached. Interaction of proteoglycans with oxidative/nitrative stress has been demonstrated in various experimental systems. In this review, we discuss the modulatory effects of proteoglycans on tissue oxidative/ nitrative stress and consequent cellular function especially in cardiovascular and neurological disorders. Conclusion: Proteoglycans have been implicated in both deleterious and potentially cytoprotective mechanisms. The protective mechanisms include chelation of positively charged transitional metal ions (e.g. iron and copper), scavenging superoxide anions by extracellular superoxide dismutase, building pericellular net and mediation of signal transduction pathways. Although these results may implicate proteoglycans as potential therapeutic targets, more research should be done to better explore proteoglycans as modulators of reactive oxygen/nitrogen species and to determine their possible therapeutic value in disorders accompanied by oxidative/ nitrative stress. Keywords: Proteoglycan, mucopolysaccharide, GAG, ROS, EC-SOD, perineural net, chelation, superoxide, nitric oxide, peroxynitrite.

Impact of tyrosine nitration at positions Tyr307 and Tyr335 on structural dynamics of Lipoprotein-associated phospholipase A2–A therapeutically important cardiovascular biomarker for atherosclerosis

Protein tyrosine nitration (PTN) is a post translational event which results in the generation of 3-Nitrotyrosine (3-NT). High levels of 3-NT were reported in several human diseases such as Parkinson’s disease, Alzheimer’s disease, amylotrophic lateral sclerosis and coronary artery disease. It was reported that PTN at positions 307 and 335 of Lipoprotein-associated phospholipase A2 (Lp-PLA2) curtails its enzymatic activity but the mechanism of inhibition at the structure level is still incomprehensible. The present study is an in silico endeavor to understand nitrative stress induced structural changes in Lp-PLA2. Molecular docking studies revealed a decreased binding affinity of substrate, Platelet Activating Factor (PAF) with the nitrated forms of Lp-PLA2 (NT-Tyr307 and NT-Tyr335) compared to the wild type, due to differences in the hydrogen bond interaction patterns. Molecular dynamics (MD) simulation studies suggests higher flexibility of nitrated forms compared to wild type, disorientation of the catalytic triad and decreased molecular interactions of NT-Tyr307 and NT-Tyr335 with other residues of the protein. Essential dynamics (ED) further confirmed the enhanced structural flexibility of nitrated forms of Lp-PLA2. Our findings would help understand the molecular mechanism of nitrative stress induced inhibition of Lp-PLA2 which may further assist in designing of therapeutics having protective functions against PTN.

Peroxynitrite-Induced Tyrosine Nitration Contributes to Matrix Metalloprotease-3 Activation: Relevance to Hyperglycemic Ischemic Brain Injury and Tissue Plasminogen Activator.

Matrix metalloprotease-3 (MMP3) activation mediates the tissue plasminogen activator (tPA)-induced hemorrhagic transformation after stroke. Hyperglycemia (HG) further exacerbates this outcome. We have recently shown that HG increases MMP3 activity in the brain after stroke. However, the combined HG-tPA effect on MMP3 activation, and the mechanisms through which MMP3 is activated were not previously reported. Accordingly, this study tested the hypothesis that tPA and HG increases MMP3 activity in the brain after stroke through peroxynitrite induced tyrosine nitration. Normoglycemic and mildly hyperglycemic male Wistar rats were subjected to middle cerebral artery suture occlusion for 90min or thromboembolic occlusion, and up to 24h reperfusion, with and without tPA. MMP3 activity and tyrosine nitration were evaluated in brain homogenates at 24h. Brain microvascular endothelial cells (BMVEC) were subjected to either 3h hypoxia or 6h OGD under either normal or high glucose conditions with or without tPA, with or without peroxynitrite scavenger, FeTPPs. MMP3 activity and MMP3 tyrosine nitration were assessed at 24h. HG and tPA significantly increased activity and tyrosine nitration of MMP3 in the brain. In BMVECs, tPA but not HG increased MMP3 activity. Treating BMVEC with FeTPPs significantly reduced the tPA-induced increase in MMP3 activity and nitration. Augmented oxidative and nitrative stress may be potential mechanisms contributing to MMP3 activation in hyperglycemic stroke, especially with tPA administration. Peroxynitrite may be playing a critical role in mediating MMP3 activation through tyrosine nitration in hyperglycemic stroke.

Mechanisms Involved in Secondary Cardiac Dysfunction in Animal Models of Trauma and Hemorrhagic Shock

Clinical evidence reveals the existence of a trauma-induced secondary cardiac injury (TISCI) that is associated with poor patient outcomes. The mechanisms leading to TISCI in injured patients are uncertain. Conversely, animal models of trauma hemorrhage have repeatedly demonstrated significant cardiac dysfunction following injury, and highlighted mechanisms through which this might occur. The aim of this review was to provide an overview of the animal studies describing TISCI and its pathophysiology.Basic science models of trauma show evidence of innate immune system activation via Toll-like receptors, the exact protagonists of which remain unclear. Shortly following trauma and hemorrhage, cardiomyocytes upregulate gene regulatory protein and inflammatory molecule expression including nuclear factor kappa beta, tumor necrosis factor alpha, and interleukin-6. This is associated with expression of membrane bound adhesion molecules and chemokines leading to marked myocardial leukocyte infiltration. This cell activation and infiltration is linked to a rise in enzymes that cause oxidative and nitrative stress and subsequent protein misfolding within cardiomyocytes. Such protein damage may lead to reduced contractility and myocyte apoptosis. Other molecules have been identified as cardioprotective following injury. These include p38 mitogen-activated protein kinases and heat shock proteins.The balance between increasing damaging mediators and a reduction in cardio-protective molecules appears to define myocardial function following trauma. Exogenous therapeutics have been trialled in rodents with promising abilities to favorably alter this balance, and subsequently lead to improved cardiac function.

Arctic ground squirrel resist peroxynitrite-mediated cell death in response to oxygen glucose deprivation

Cerebral ischemia-reperfusion (I/R) injury initiates a cascade of events, generating nitric oxide (NO) and superoxide(O2•-) to form peroxynitrite (ONOO-), a potent oxidant. Arctic ground squirrels (AGS; Urocitellus parryii) show high tolerance to I/R injury. However, the underlying mechanism remains elusive. We hypothesize that tolerance to I/R modeled in an acute hippocampal slice preparation in AGS is modulated by reduced oxidative and nitrative stress. Hippocampal slices (400µm) from rat and AGS were subjected to oxygen glucose deprivation (OGD) using a novel microperfusion technique. Slices were exposed to NO, O2.- donors with and without OGD; pretreatment with inhibitors of NO, O2.- and ONOO- followed by OGD. Perfusates collected every 15min were analyzed for LDH release, a marker of cell death. 3-nitrotyrosine (3NT) and 4-hydroxynonenal (4HNE) were measured to assess oxidative and nitrative stress. Results show that NO/O2.- alone is not sufficient to cause ischemic-like cell death, but with OGD enhances cell death more in rat than in AGS. A NOS inhibitor, SOD mimetic and ONOO- inhibitor attenuates OGD injury in rat but has no effect in AGS. Rats also show a higher level of 3NT and 4HNE with OGD than AGS suggesting the greater level of injury in rat is via formation of ONOO-.

Alginate oligosaccharide alleviates myocardial reperfusion injury by inhibiting nitrative and oxidative stress and endoplasmic reticulum stress-mediated apoptosis.

Alginate oligosaccharide (AOS) has recently demonstrated the ability to protect against acute doxorubicin cardiotoxicity and neurodegenerative disorders by inhibiting oxidative stress and endoplasmic reticulum (ER) stress-mediated apoptosis, which are both involved in myocardial ischemia/reperfusion (I/R) injury. In the present study, we investigated whether pretreatment with AOS protects against myocardial I/R injury in mice and explored potential cardioprotective mechanisms. AOS pretreatment significantly decreased the infarct size, reduced the cardiac troponin-I concentration, and ameliorated the cardiac dysfunction. Accompanied with the reduced cardiac injury, AOS pretreatment clearly decreased I/R-induced myocardial apoptosis. With regard to mechanism, AOS pretreatment markedly attenuated nitrative/oxidative stress, as evidenced by decreases in 3-nitrotyrosine content and superoxide generation, and downregulated inducible nitric oxide synthase, NADPH oxidase2, and 4-hydroxynonenal. Moreover, AOS pretreatment decreased myocardial apoptosis by inhibiting the ER stress-mediated apoptosis pathway, which is reflected by the downregulation of C/EBP homologous protein, glucose-regulated protein 78, caspase-12, and Bcl-2-associated X protein, and by the upregulation of the anti-apoptotic protein B-cell lymphoma-2. Collectively, these findings demonstrate that AOS renders the heart resistant to I/R injury, at least in part, by inhibiting nitrative/oxidative stress and ER stress-mediated apoptosis.

Ginsenoside Rk1 ameliorates paracetamol-induced hepatotoxicity in mice through inhibition of inflammation, oxidative stress, nitrative stress and apoptosis

BackgroundFrequent overdose of paracetamol (APAP) has become the major cause of acute liver injury. The present study was designed to evaluate the potential protective effects of ginsenoside Rk1 on APAP-induced hepatotoxicity and investigate the underlying mechanisms for the first time. MethodsMice were treated with Rk1 (10 mg/kg or 20 mg/kg) by oral gavage once per d for 7 d. On the 7th d, all mice treated with 250 mg/kg APAP exhibited severe liver injury after 24 h, and hepatotoxicity was assessed. ResultsOur results showed that pretreatment with Rk1 significantly decreased the levels of serum alanine aminotransferase, aspartate aminotransferase, tumor necrosis factor, and interleukin-1β compared with the APAP group. Meanwhile, hepatic antioxidants, including superoxide dismutase and glutathione, were elevated compared with the APAP group. In contrast, a significant decrease in levels of the lipid peroxidation product malondialdehyde was observed in the ginsenoside Rk1-treated group compared with the APAP group. These effects were associated with a significant increase of cytochrome P450 E1 and 4-hydroxynonenal levels in liver tissues. Moreover, ginsenoside Rk1 supplementation suppressed activation of apoptotic pathways by increasing Bcl-2 and decreasing Bax protein expression levels, which was shown using western blotting analysis. Histopathological observation also revealed that ginsenoside Rk1 pretreatment significantly reversed APAP-induced necrosis and inflammatory infiltration in liver tissues. Biological indicators of nitrative stress, such as 3-nitrotyrosine, were also inhibited after pretreatment with Rk1 compared with the APAP group. ConclusionThe results clearly suggest that the underlying molecular mechanisms in the hepatoprotection of ginsenoside Rk1 in APAP-induced hepatotoxicity may be due to its antioxidation, antiapoptosis, anti-inflammation, and antinitrative effects.

Amyloidogenic medin induces endothelial dysfunction and vascular inflammation through the receptor for advanced glycation endproducts.

Medin is a common amyloidogenic protein in humans that accumulates in arteries with advanced age and has been implicated in vascular degeneration. Medin's effect on endothelial function remains unknown. The aims are to assess medin's effects on human arteriole endothelial function and identify potential mechanisms underlying medin-induced vascular injury. Ex vivo human adipose and leptomeningeal arterioles were exposed (1 h) to medin (0.1, 1, or 5µM) without or with FPS-ZM1 [100µM, receptor for advanced glycation endproducts (RAGE)-specific inhibitor] and endothelium-dependent function (acetylcholine dilator response) and endothelium-independent function (dilator response to nitric oxide donor diethylenetriamine NONOate) were compared with baseline control. Human umbilical vein endothelial cells were exposed to medin without or with FPS-ZM1 and oxidative and nitrative stress, cell viability, and pro-inflammatory signaling measures were obtained. Medin caused impaired endothelial function (vs. baseline response: -45.2 ± 5.1 and -35.8 ± 7.9% in adipose and leptomeningeal arterioles, respectively, each P < 0.05). Dilator response to NONOate was not significantly changed. Medin decreased arteriole and endothelial cell nitric oxide production, increased superoxide production, reduced endothelial cell viability, proliferation, and migration. Medin increased gene and protein expression of interleukin-6 and interleukin-8 via activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB). Medin-induced endothelial dysfunction and oxidative stress were reversed by antioxidant polyethylene glycol superoxide dismutase and by RAGE inhibitor FPS-ZM1. Medin causes human microvascular endothelial dysfunction through oxidative and nitrative stress and promotes pro-inflammatory signaling in endothelial cells. These effects appear to be mediated via RAGE. The findings represent a potential novel mechanism of vascular injury.

Baicalein acts as a nephroprotectant that ameliorates colistin-induced nephrotoxicity by activating the antioxidant defence mechanism of the kidneys and down-regulating the inflammatory response.

Nephrotoxicity is the major adverse effect patients experience during colistin therapy. The development of effective nephroprotective agents that can be co-administered during polymyxin therapy remains a priority area in antimicrobial chemotherapy. To investigate the nephroprotective effect of baicalein, a component of the root of Scutellaria baicalensis, against colistin-induced nephrotoxicity using a mouse model. C57BL/6 mice were randomly divided into the following groups: control, baicalein 100 mg/kg/day (administered orally), colistin (18 mg/kg/day administered intraperitoneally) and colistin (18 mg/kg/day) plus baicalein (25, 50 and 100 mg/kg/day). After 7 day treatments, histopathological damage, the markers of renal functions, oxidative stress and inflammation were examined. The expressions of Nrf2, HO-1 and NF-κB mRNAs were also further examined using quantitative RT-PCR examination. Baicalein co-administration markedly attenuated colistin-induced oxidative and nitrative stress, apoptosis, the infiltration of inflammatory cells, and caused decreases in IL-1β and TNF-α levels (all P < 0.05 or 0.01) in the kidney tissues. Baicalein co-administration up-regulated expression of Nrf2 and HO-1 mRNAs and down-regulated the expression of NF-κB mRNA, compared with those in the colistin alone group. To the best of our knowledge, this is the first study demonstrating the protective effect of baicalein on colistin-induced nephrotoxicity and apoptosis by activating the antioxidant defence mechanism in kidneys and down-regulating the inflammatory response. Our study highlights that oral baicalein could potentially ameliorate nephrotoxicity in patients undergoing polymyxin therapy.

P 19 Alpha-1 microglobulin as a potential therapeutic candidate for the treatment of high blood pressure and oxidative stress in the STOX1 preeclampsia-model

Introduction Preeclampsia (PE) is a serious pregnancy-related disease with hypertension and proteinuria manifesting after 20 weeks of gestation. The worldwide prevalence is 3–8%, making it the most common cause of maternal and fetal mortality. PE lacks an effective therapy, and the only cure is delivery. We have previously shown that exogenously administered alpha-1-microglobulin (A1M) alleviates PE-like symptoms and the effects of oxidative stress in a dual-placenta perfusion model as well as in pregnant animal PE-models. Objectives A1M was evaluated as a therapeutic agent in the STOX1 PE-model. Materials and methods The STOX1 transgene mouse PE-model is one of the most complete PE-models available, since it reflects both stages of the disease and exhibit symptoms that mimic human PE. STOX1 is a transcription factor associated with PE that modulates proliferation and migration of trophoblasts. Wild type females are mated to STOX1-transgenic males, resulting in transgene-expressing fetuses and thereby restricting the expression to the utero-placental unit and typical PE symptoms in the female. Results One group of pregnant females received A1M injections i.p. every second day from day 6 of pregnancy until day 17, while another group received buffer. A1M significantly reduced the hypertension during gestation, especially at mid-gestation. It significantly reduced the level of hypoxia as well as the level of nitrative stress in the placenta. Also, A1M treatment reduced cellular damage in placenta and kidney tissue, such as disruption of plasma membranes, ER structures and mitochondria. However, A1M treatment had no significant effect on increased plasma levels of anti-angiogenic factors or the increased heart weight observed in the STOX1 PE-model. A1M was well tolerated with no side effects at the given dose. Conclusion A1M was able to alleviate PE symptoms observed in the STOX1 PE-model.

Deletion of TXNIP Mitigates High-Fat Diet-Impaired Angiogenesis and Prevents Inflammation in a Mouse Model of Critical Limb Ischemia.

Background: Previous work demonstrated that high-fat diet (HFD) triggered thioredoxin-interacting protein (TXNIP) and that silencing TXNIP prevents diabetes-impaired vascular recovery. Here, we examine the impact of genetic deletion of TXNIP on HFD-impaired vascular recovery using hind limb ischemia model. Methods: Wild type mice (WT, C57Bl/6) and TXNIP knockout mice (TKO) were fed either normal chow diet (WT-ND and TKO-ND) or 60% high-fat diet (WT-HFD and TKO-HFD). After four weeks of HFD, unilateral hind limb ischemia was performed and blood flow was measured using Laser doppler scanner at baseline and then weekly for an additional three weeks. Vascular density, nitrative stress, infiltration of CD68+ macrophages, and expression of inflammasome, vascular endothelial growth factor (VEGF), VEGF receptor-2 were examined by slot blot, Western blot and immunohistochemistry. Results: By week 8, HFD caused similar increases in weight, cholesterol and triglycerides in both WT and TKO. At week 4 and week 8, HFD significantly impaired glucose tolerance in WT and to a lesser extent in TKO. HFD significantly impaired blood flow and vascular density (CD31 labeled) in skeletal muscle of WT mice compared to ND but not in TKO. HFD and ischemia significantly induced tyrosine nitration, and systemic IL-1β and infiltration of CD68+ cells in skeletal muscle from WT but not from TKO. HFD significantly increased cleaved-caspase-1 and IL-1 β compared to ND. Under both ND, ischemia tended to increase VEGF expression and increased VEGFR2 activation in WT only but not TKO. Conclusion: Similar to prior observation in diabetes, HFD-induced obesity can compromise vascular recovery in response to ischemic insult. The mechanism involves increased TXNIP-NLRP3 (nucleotide-binding oligomerization domain-like receptor protein 3) inflammasome activation, nitrative stress and impaired VEGFR2 activation. Deletion of TXNIP restored blood flow, reduced nitrative stress and blunted inflammasome-mediated inflammation; however, it did not impact VEGF/VEGFR2 in HFD. Targeting TXNIP-NLRP3 inflammasome can provide potential therapeutic target in obesity-induced vascular complication.

MiR-106a Associated with Diabetic Peripheral Neuropathy Through the Regulation of 12/15-LOX-meidiated Oxidative/Nitrative Stress.

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes with a complex pathogenesis. Study has reported that oxidative stress and nitrative stress are all involved in the DPN. However, the mechanism between them is still unclear. In the present study, we investigated whether miR-106a regulated 12/15-Lipoxygenase (12/15-LOX) of oxidative/nitrative stress (OS/NS) in DPN. Dorsal root ganglion (DRG) was isolated from 10 healthy mice and 10 DPN mice. DPN mouse model was established by the injection of streptozotocin (STZ), and high glucose was used for inducing the in vitro model of DPN. In DPN mice, the levels of fasting blood-glucose (FBG) level, Methane Dicarboxylic Aldehyde (MDA) and the Inducible Nitric Oxide Synthase (iNOS) were increased, while the levels of motor nerve conduction velocity (MNCV), sensory nerve conduction velocity (SNCV) and superoxide dismutase (SOD) were decreased. MiR-106a level in DRG cells of DPN was decreased. The 12/15-LOX expression and cell apoptosis were increased. DRG cells subjected to high glucose resulted in the same effects as above. MiR-106a was observed to target 12/15-LOX and regulated its expression. MiR-106a overexpression reversed the effect that was induced by high glucose, however, overexpression of 12/15-LOX reversed the effect that was induced by miR-106a overexpression. MiR-106 may be associated with 12/15-LOX mediated OS/NS in DPN and may be considered as a potential therapeutic target.

Relationship between diabetic retinopathy "metabolic memory" and oxidative stress

Metabolic means if the hyperglycemia can't be controlled at early stage of diabetes, chronic complications such as diabetic retinopathy (DR) will continue to develop even if the blood glucose level maintains normal level at later stage. Oxidative stress plays an important role in the metabolic memory of DR, which interacts with the nitrative stress, advanced glycation end products, genetic modification and endoplasmic reticulum stress in the pathogenesis of DR. Further elucidation of the relationship between oxidative stress andmetabolic memory of DR can open the way for the discovery of novel therapeutic targets to prevent DR progression. Key words: Diabetic retinopathy/physiopathology; Oxidative stress; Endoplasmic reticulum stress; Review

РОЛЬ NO-СИНТАЗИ І АРГІНАЗИ У МЕХАНІЗМАХ ОКИСНО-НІТРАТИВНОГО СТРЕСУ В ШКІРІ ЩУРІВ ЗА УМОВ НАДЛИШКОВОГО НАДХОДЖЕННЯ В ОРГАНІЗМ НІТРАТУ НАТРІЮ

РОЛЬ NO-СИНТАЗИ І АРГІНАЗИ У МЕХАНІЗМАХ ОКИСНО-НІТРАТИВНОГО СТРЕСУ В ШКІРІ ЩУРІВ ЗА УМОВ НАДЛИШКОВОГО НАДХОДЖЕННЯ В ОРГАНІЗМ НІТРАТУ НАТРІЮ

Insulin enhances the peroxidase activity of heme by forming heme-insulin complex: Relevance to type 2 diabetes mellitus

Evidences have implicated the involvement of heme in the type 2 diabetes mellitus (T2Dm) pathogenesis, but possible mediators linking between heme and diabetes are still poorly understood. Here, we explored a potential mechanism that linked heme, insulin and diabetes. Our results demonstrated the formation of heme-insulin complex by two classical methods, i.e. UV–vis and capillary electrophoresis-frontal analysis (CE-FA). UV–vis results implied heme binding insulin via bis-histidine sites, and CE-FA further revealed that, when insulin uses two sites binding with heme, this interaction occurs at high affinity (Kd=3.13×10−6M). Molecule docking supported that histidine-B5 of insulin binds with heme-Fe. In addition to that, tyrosine-B26, phenylalanine-B1 and valine-B2 are also contributed to binding heme. The binding amplified the peroxidase activity of heme itself. Under oxidative and nitrative stress, it affects pathogenesis of diabetes from two aspects: promoting insulin cross-linking that leads to permanent loss of insulin functionality on one hand, and enhancing protein tyrosine nitration that may result in inactivation of proteins associated with diabetes on the other hand. This study suggested that the enhanced peroxidase activity of heme through binding with insulin might be a previously unrecognized contributor to the pathogenesis of T2Dm in some heme-associated disorders.

Saponins (Ginsenosides) from the Leaves of Panax quinquefolius Ameliorated Acetaminophen-Induced Hepatotoxicity in Mice.

Acetaminophen (APAP) overdose is one of the most common inducements of drug-induced liver injury (DILI) in the world. The main purpose of this paper was to investigate the liver protection activity of saponins (ginsenosides) from the leaves of Panax quinquefolius (PQS) against APAP-induced hepatotoxicity, and the involved mechanisms were demonstrated for the first time. Mice were pretreated with PQS (150 and 300 mg/kg) by oral gavage for 7 days before being treated with 250 mg/kg APAP. Severe liver injury was exerted at 24 h post-APAP, and hepatotoxicity was assessed. Our results showed that pretreatment with PQS significantly decreased the serum alanine aminotransferase (ALT), aspartate transaminase (AST), tumor necrosis factor (TNF-α), and interleukin-1β (IL-1β) levels in a dose-dependent manner as compared to the APAP administration. Meanwhile, compared with that in the APAP group, PQS decreased hepatic malondialdehyde (MDA) contents and 4-hydroxynonenal (4-HNE) expression and restored reduced glutathione (GSH) content and superoxide dismutase (SOD) activity in livers of mice. PQS inhibited the overexpression of pro-inflammatory factors cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in the liver tissues. Furthermore, Western blotting analysis revealed that PQS pretreatment inhibited the activation of apoptotic signaling pathways via increase of Bcl-2 and decrease of Bax and caspase-3 protein expression levels. Liver histopathological observation provided further evidence that PQS pretreatment significantly inhibited APAP-induced hepatocyte necrosis, inflammatory cell infiltration, and congestion. Biological indicators of nitrative stress such as 3-nitrotyrosine (3-NT) were inhibited after PQS pretreatment, compared to the APAP group. The present study clearly demonstrates that PQS exerts a protective effect against APAP-induced hepatic injury because of its antioxidant, anti-apoptotic, and anti-inflammatory activities. The findings from the present investigation show that PQS might be a promising candidate treatment agent against drug-induced ALI.

Ameliorative Effects and Possible Molecular Mechanism of Action of Black Ginseng (Panax ginseng) on Acetaminophen-Mediated Liver Injury.

Background: Frequent overdosing of acetaminophen (APAP) has become the major cause of acute liver injury (ALI). The present study aimed to evaluate the potential hepatoprotective effects of black ginseng (BG) on APAP-induced mice liver injuries and the underlying mechanisms of action were further investigated for the first time. Methods: Mice were treated with BG (300, 600 mg/kg) by oral gavage once a day for seven days. On the 7th day, all mice were treated with 250 mg/kg APAP which caused severe liver injury after 24 h and hepatotoxicity was assessed. Results: Our results showed that pretreatment with BG significantly decreased the levels of serum alanine aminotransferase (ALT) and aspartate transaminase (AST) compared with the APAP group. Meanwhile, hepatic antioxidant including glutathione (GSH) was elevated compared with the APAP group. In contrast, a significant decrease of the levels of the lipid peroxidation product malondialdehyde (MDA) was observed in the BG-treated groups compared with the APAP group. These effects were associated with significant increases of cytochrome P450 E1 (CYP2E1) and 4-hydroxynonenal (4-HNE) levels in liver tissues. Moreover, BG supplementation suppressed activation of apoptotic pathways through increasing Bcl-2 and decreasing Bax protein expression levels according to western blotting analysis. Histopathological examination revealed that BG pretreatment significantly inhibited APAP-induced necrosis and inflammatory infiltration in liver tissues. Biological indicators of nitrative stress like 3-nitrotyrosine (3-NT) were also inhibited after pretreatment with BG, compared with the APAP group. Conclusions: The results clearly suggest that the underlying molecular mechanisms of action of BG-mediated alleviation of APAP-induced hepatotoxicity may involve its anti-oxidant, anti-apoptotic, anti-inflammatory and anti-nitrative effects.

Pathogenic mechanisms following ischemic stroke.

Stroke is the second most common cause of death and the leading cause of disability worldwide. Brain injury following stroke results from a complex series of pathophysiological events including excitotoxicity, oxidative and nitrative stress, inflammation, and apoptosis. Moreover, there is a mechanistic link between brain ischemia, innate and adaptive immune cells, intracranial atherosclerosis, and also the gut microbiota in modifying the cerebral responses to ischemic insult. There are very few treatments for stroke injuries, partly owing to an incomplete understanding of the diverse cellular and molecular changes that occur following ischemic stroke and that are responsible for neuronal death. Experimental discoveries have begun to define the cellular and molecular mechanisms involved in stroke injury, leading to the development of numerous agents that target various injury pathways. In the present article, we review the underlying pathophysiology of ischemic stroke and reveal the intertwined pathways that are promising therapeutic targets.