Cysteine becomes conditionally essential during hypobaric hypoxia and regulates adaptive neuro-physiological responses through CBS/H2S pathway

Brain is well known for its disproportionate oxygen consumption and high energy-budget for optimal functioning. The decrease in oxygen supply to brain, thus, necessitates rapid activation of adaptive pathways – the absence of which manifest into vivid pathological conditions. Amongst these, oxygen sensing in glio-vascular milieu and H₂S-dependent compensatory increase in cerebral blood flow (CBF) is a major adaptive response. We had recently demonstrated that the levels of H₂S were significantly decreased during chronic hypobaric hypoxia (HH)-induced neuro-pathological effects. The mechanistic basis of this phenomenon, however, remained to be deciphered. We, here, describe experimental evidence for marked limitation of cysteine during HH – both in animal model as well as human volunteers ascending to high altitude. We show that the preservation of brain cysteine level, employing cysteine pro-drug (N-acetyl-_L-cysteine, NAC), markedly curtailed effects of HH – not only on endogenous H₂S levels but also, impairment of spatial reference memory in our animal model. We, further, present multiple lines of experimental evidence that the limitation of cysteine was causally governed by physiological propensity of brain to utilize cysteine, in cystathionine beta synthase (CBS)-dependent manner, past its endogenous replenishment potential. Notably, decrease in the levels of brain cysteine manifested despite positive effect (up-regulation) of HH on endogenous cysteine maintenance pathways and thus, qualifying cysteine as a conditionally essential nutrient (CEN) during HH. In brief, our data supports an adaptive, physiological role of CBS-mediated cysteine-utilization pathway – activated to increase endogenous levels of H₂S – for optimal responses of brain to hypobaric hypoxia.     

H2S catalysed by CBS regulates testosterone synthesis through affecting the sulfhydrylation of PDE

Testosterone deficiency resulted in increased mortality in men. Our previous work found that hydrogen sulphide (H₂S) significantly alleviated the spermatogenesis disorder. To investigate whether H₂S could regulate testosterone synthesis and the relative signalling pathways. Disorder model of testosterone synthesis was constructed in vitro and in vivo. The cell viability was detected using CCK-8 method. The concentration of H₂S and testosterone were examined using ELISA kits. The relative mRNA and protein expression of CBS, PDE4A, PDE8A and proteins related to testosterone synthesis were detected by RT-qPCR and western blotting. PAS staining was used to detect the inflammatory status of testis. The sulfhydryl level of PDE4A and PDE8A was determined by Biotin Switch Technique. CBS overexpression inhibited while knockdown promoted LPS + H₂O₂ induced injury in testosterone synthesis of MLTC-1 cells, though regulating the level of H₂S. The LPS + H₂O₂ induced inhibition on cAMP and p-PKA was recovered by CBS overexpression, while addition of the specific inhibitor of PKA had opposite effects. CBS overexpression alleviated the inflammation status in testis and promoted the expression of StAR, P450scc, P450c17 and 3β-HSD. CBS could also exhibit its protective role through promoting sulfhydrylation of PDE4A and PDE8A. H₂S catalysed by CBS could recover testosterone synthesis in vitro and in vivo through inhibiting PDE expression via sulfhydryl modification and activating cAMP/PKA pathway.     

DNA damage induces reactive oxygen species generation through the H2AX-Nox1/Rac1 pathway

The DNA damage response (DDR) cascade and ROS (reactive oxygen species) signaling are both involved in the induction of cell death after DNA damage, but a mechanistic link between these two pathways has not been clearly elucidated. This study demonstrates that ROS induction after treatment of cells with neocarzinostatin (NCS), an ionizing radiation mimetic, is at least partly mediated by increasing histone H2AX. Increased levels of ROS and cell death induced by H2AX overexpression alone or DNA damage leading to H2AX accumulation are reduced by treating cells with the antioxidant N-Acetyl-L-Cysteine (NAC), the NADP(H) oxidase (Nox) inhibitor DPI, expression of Rac1N17, and knockdown of Nox1, but not Nox4, indicating that induction of ROS by H2AX is mediated through Nox1 and Rac1 GTPase. H2AX increases Nox1 activity partly by reducing the interaction between a Nox1 activator NOXA1 and its inhibitor 14-3-3zeta. These results point to a novel role of histone H2AX that regulates Nox1-mediated ROS generation after DNA damage.     

丁苯酞对慢性酒精中毒大鼠海马、杏仁核H2S/CBS通路及学习记忆能力的影响*

目的: 探讨丁苯酞(NBP)对慢性酒精中毒大鼠学习与记忆相关的能力、海马及杏仁核内硫化氢(H₂S)含量、胱硫醚-β-合成酶(CBS)表达和线粒体ATP酶活性的影响。方法: 随机将90只SD雄性大鼠均分为3组:空白对照组(NC)、模型组(M)和治疗组。除对照组外,其余两组均将含6%(v/v)酒精的水溶液作为唯一饮水来源。喂养14d后,治疗组按5mg/Kg比例腹腔注射NBP,每日一次,连续14d,其余两组注射等剂量生理盐水;对照组随后使用Morris水迷宫法,通过观察和记录动物入水后搜索藏在水下平台所需时间、采用策略和它们的游泳轨迹,从而可分析和推断动物的学习、记忆等方面的能力,并检测海马和杏仁核组织中H₂S浓度、CBS表达及线粒体ATP酶活性。结果: 与正常对照组大鼠相比,模型组大鼠第2-4日潜伏期、游泳距离均增加,海马及杏仁核内H₂S含量、CBS平均光密度值均升高,海马以及杏仁核组织中线粒体ATP酶活性均降低,且均有极显著性差异(P＜0.01)。与模型组大鼠相比较,NBP治疗组大鼠学习记忆成绩第2-4日潜伏期、游泳距离减小,海马及杏仁核H₂S含量、CBS平均光密度值均降低,海马以及杏仁核组织中线粒体ATP酶活性均提高,且均有极显著性差异(P＜0.01)。结论: NBP能够减轻酒精对大鼠的学习与记忆能力的影响,可能与NBP影响海马、杏仁核内H₂S浓度和CBS的表达以及线粒体ATP酶活性有关。     

S. choloroleuca, S. mirzayanii and S. santolinifolia protect PC12 cells from H(2)O (2)-induced apoptosis by blocking the intrinsic pathway

Several studies have shown that neuronal cell death due to apoptosis is the major reason for cognitive decline in Alzheimer's disease. In this study, we report the anti-apoptotic effects of three Salvia species from Iran-S. choloroleuca, S. mirzayanii and S. santolinifolia-against H(2)O(2)-induced cytotoxicity in neuron-like PC12 cells. We showed that these antioxidant species could interfere with the intrinsic pathway of apoptosis by attenuating Bax/Bcl-2 ratio, decreasing outer mitochondrial membrane break and decreasing cytochrome c release to cytoplasm. Interestingly, we found that these species were able to replenish reduced glutathione level which affects cellular redox status and cytochrome c activity. Moreover, the decreased level of caspase-3, the executioner caspase, resulted in decrease of PARP-1 cleavage. Anti-apoptotic effects of these species along with their antioxidant effects, may represent a promising approach for treatment of neurodegenerative diseases.     

Metformin protects PC12 cells and hippocampal neurons from H2O 2-induced oxidative damage through activation of AMPK pathway

Metformin, a first line anti type 2 diabetes drug, has recently been shown to extend lifespan in various species, and therefore, became the first antiaging drug in clinical trial. Oxidative stress due to excess reactive oxygen species (ROS) is considered to be an important factor in aging and related disease, such as Alzheimer's disease (AD). However, the antioxidative effects of metformin and its underlying mechanisms in neuronal cells is not known. In the present study, we showed that metformin, in clinically relevant concentrations, protected neuronal PC12 cells from H₂O₂-induced cell death. Metformin significantly ameliorated cell death due to H₂O₂ insult by restoring abnormal changes in nuclear morphology, intracellular ROS, lactate dehydrogenase, and mitochondrial membrane potential induced by H₂O₂. Hoechst staining assay and flow cytometry analysis revealed that metformin significantly reduced the apoptosis in PC12 cells exposed to H₂O₂. Western blot analysis further demonstrated that metformin stimulated the phosphorylation and activation of AMP-activated protein kinase (AMPK) in PC12 cells, while application of AMPK inhibitor compound C, or knockdown of the expression of AMPK by specific small interfering RNA or short hairpin RNA blocked the protective effect of metformin. Similar results were obtained in primary cultured hippocampal neurons. Taken together, these results indicated that metformin is able to protect neuronal cells from oxidative injury, at least in part, via the activation of AMPK. As metformin is comparatively cheaper with much less side effects in clinic, our findings support its potential to be a drug for prevention and treatment of aging and aging-related diseases.     

Cannabinoids protect astrocytes from ceramide-induced apoptosis through the phosphatidylinositol 3-kinase/protein kinase B pathway

Cannabinoids, the active components of marijuana and their endogenous counterparts, exert many of their actions on the central nervous system by binding to the CB(1) cannabinoid receptor. Different studies have shown that cannabinoids can protect neural cells from different insults. However, those studies have been performed in neurons, whereas no attention has been focused on glial cells. Here we used the pro-apoptotic lipid ceramide to induce apoptosis in astrocytes, and we studied the protective effect exerted by cannabinoids. Results show the following: (i) cannabinoids rescue primary astrocytes from C(2)-ceramide-induced apoptosis in a dose- and time-dependent manner; (ii) triggering of this anti-apoptotic signal depends on the phosphatidylinositol 3-kinase/protein kinase B pathway; (iii) ERK and its downstream target p90 ribosomal S6 kinase might be also involved in the protective effect of cannabinoids; and (iv) cannabinoids protect astrocytes from the cytotoxic effects of focal C(2)-ceramide administration in vivo. In summary, results show that cannabinoids protect astrocytes from ceramide-induced apoptosis via stimulation of the phosphatidylinositol 3-kinase/protein kinase B pathway. These findings constitute the first evidence for an "astroprotective" role of cannabinoids.     

H2O2 induces oxidative stress damage through the BMP-6/SMAD/hepcidin axis

Age-related macular degeneration (AMD) is one of the leading causes of blindness in elderly individuals worldwide. Oxidative stress injury to retinal pigment epithelial (RPE) cells plays a major role in the pathogenesis of AMD. The purpose of this study was to observe the correlation between Hepcidin and neovascular age-related macular degeneration (nAMD) and to further observe whether oxidative stress can inhibit Hepcidin expression through relevant signaling pathways to produce oxidative damage. We compared the concentrations of Hepcidin in the aqueous humor of nAMD patients and a control group and found that the concentration of Hepcidin was lower in nAMD patients. Through PCR and western blotting, we observed that H₂O₂ can significantly inhibit the expression of Bone morphogenetic protein-6 (BMP-6) and Hepcidin and increase the intracellular iron concentration in RPE cells, while BMP-6 can reverse the inhibition of Hepcidin and the increase in iron concentration caused by H₂O₂. In addition, alterations in smad1 and smad5 expression were examined, and pretreatment with BMP-6 was demonstrated to reduce H₂O₂-induced activation of smad1 and smad5. The effects of BMP-6 were attenuated by smad1 and smad5 siRNA, further verifying that oxidative stress inhibits the expression of Hepcidin by inhibiting activation of the BMP/SMAD signaling pathway. To some extent, this study verified that oxidative stress injury plays a role in nAMD by affecting the level of hepcidin, which lays a foundation for exploring new methods to treat nAMD.     

Activation of the CaR-CSE/H2S pathway confers cardioprotection against ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a multifactorial process triggered when an organ is subjected to transiently reduced blood supply. The result is a cascade of pathological complications and organ damage due to the production of reactive oxygen species following reperfusion. The present study aims to evaluate the role of activated calcium-sensing receptor (CaR)-cystathionine γ-lyase (CSE)/hydrogen sulfide (H2S) pathway in I/R injury. Firstly, an I/R rat model with CSE knockout was constructed. Transthoracic echocardiography, TTC and HE staining were performed to determine the cardiac function of rats following I/R Injury, followed by TUNEL staining observation on apoptosis. Besides, with the attempt to better elucidate how CaR-CSE/H2S affects I/R, in-vitro culture of human coronary artery endothelial cells (HCAECs) was conducted with gadolinium chloride (GdCl3, a CaR agonist), H₂O₂, siRNA against CSE (siCSE), or W7 (a CaM inhibitor). The interaction between CSE and CaM was subsequently detected. Plasma oxidative stress indexes, H2S and CSE, and apoptosis-related proteins were all analyzed following cell apoptosis. We found that H2S elevation led to the improvement whereas CSE knockdown decreased cardiac function in rats with I/R injury. Moreover, oxidative stress injury in I/R rats with CSE knockout was aggravated, while the increased expression of H2S and CSE in the aortic tissues resulted in alleviated the oxidative stress injury. Moreover, increased H2S and CSE levels were found to inhibit cell apoptotic ability in the aortic tissues after I/R injury, thus attenuating oxidative stress injury, accompanied by inhibited expression of apoptosis-related proteins. In HCAECs following oxidative stress treatment, siCSE and CaM inhibitor were observed to reverse the protection of CaR agonist. Coimmunoprecipitation assay revealed the interaction between CSE and CaM. Taken together, all above-mentioned data provides evidence that activation of the CaR-CSE/H2S pathway may confer a potent protective effect in cardiac I/R injury.     

Procyanidins protect Caco-2 cells from bile acid- and oxidant-induced damage

Procyanidins can exert cytoprotective, anti-inflammatory, and anticarcinogenic actions in the gastrointestinal tract. Previous evidence has shown that procyanidins can interact with synthetic membranes and protect them from oxidation and disruption. Thus, in this study we investigated the capacity of a hexameric procyanidin fraction (Hex) isolated from cocoa to protect Caco-2 cells from deoxycholic (DOC)-induced cytotoxicity, cell oxidant increase, and loss of monolayer integrity. Hex interacted with the cell membranes without affecting their integrity, as evidenced by a Hex-mediated increase in the transepithelial electrical resistance, and inhibition of DOC-induced cytotoxicity. DOC induced an increase in cell oxidants, alterations in the paracellular transport, and redistribution of the protein ZO-1 from cell-cell contacts into the cytoplasm. Hex partially inhibited all these events at concentrations ranging from 2.5 to 20 microM. Similarly, Hex (5-10 microM) inhibited the increase in cell oxidants, and the loss of integrity of polarized Caco-2 cell monolayers induced by a lipophilic oxidant (2,2'-azobis (2,4-dimethylvaleronitrile). Results show that the assayed procyanidin fraction can interact with cell membranes and protect Caco-2 cells from DOC-induced cytotoxicity, oxidant generation, and loss of monolayer integrity. At the gastrointestinal tract, large procyanidins may exert beneficial effects in pathologies such us inflammatory diseases, alterations in intestinal barrier permeability, and cancer.     

大豆异黄酮通过刺激BEX2/BNIP3/NIX通路激活线粒体自噬保护SH-SY5Y神经元

阿特拉津是一种广泛使用的除草剂,可诱导黑质多巴胺能神经元变性,损害线粒体功能,导致帕金森病样综合征。尽管环境暴露的风险很高,但很少有研究预防阿特拉津神经毒性的药物和方法。黄酮类化合物具有良好的生物活性,如抗炎、抗氧化和细胞保护作用。异黄酮是大豆中含量最丰富的天然黄酮类化合物,具有多种有益的生物活性,包括线粒体保护作用。     

Myocardial mechanical dysfunction and calcium overload following rewarming from experimental hypothermia in vivo

Rewarming patients from accidental hypothermia are regularly complicated with cardiovascular instability ranging from minor depression of cardiac output to fatal circulatory collapse also termed “rewarming shock”. Since altered Ca²⁺ handling may play a role in hypothermia-induced heart failure, we studied changes in Ca²⁺ homeostasis in in situ hearts following hypothermia and rewarming. A rat model designed for studies of the intact heart in a non-arrested state during hypothermia and rewarming was used. Rats were core cooled to 15 °C, maintained at 15 °C for 4 h and thereafter rewarmed. As time-matched controls, one group of animals was kept at 37 °C for 5 h. Total intracellular myocardial Ca²⁺ content ([Ca²⁺]_i) was measured using ⁴⁵Ca²⁺. Following rewarming we found a significant reduction of stroke volume and cardiac output compared to prehypothermic control values as well as to time-matched controls. Likewise, we found that hypothermia and rewarming resulted in a more than six-fold increase in [Ca²⁺]_i to 3.01 ± 0.43 μmol/g dry weight compared to 0.44 ± 0.05 μmol/g dry weight in normothemia control. These findings indicate that hypothermia-induced alterations in the Ca²⁺-handling result in Ca²⁺ overload during hypothermia, which may contribute to myocardial failure during and after rewarming.     

Red blood cells protect endothelial cells against H2O2-mediated but not hyperoxia-induced damage

We studied the effect of intact red blood cells on the exogenous H2O2-mediated damage as well as on the hyperoxia-induced injury of cultured endothelial cells. Red blood cells protected endothelial cells against H2O2-mediated injury efficiently, but had no effect on the hyperoxia-induced damage. Failure of red blood cells to protect endothelial cells against hyperoxia-induced injury was not due to hemolysis. Furthermore, hyperoxia-exposed red blood cells were still capable of protecting endothelial cells against H2O2-mediated damage.