Role of PON in anoxia-reoxygenation injury: a Drosophila melanogaster transgenic model

Ecological adaptations of Amazonian fishes acquired during evolution under environmental variations in dissolved oxygen: A review of responses to hypoxia in fishes, featuring the hypoxia-tolerant Astronotus spp

The Amazon Basin presents a dynamic regime of dissolved oxygen (DO) oscillations, which varies among habitats within the basin, including spatially, daily, and seasonally. Fish species inhabiting these environments have developed many physiological adaptations to deal with the frequent and periodic events of low (hypoxia), or no (anoxia) DO in the water. Cichlid fishes, especially the genus Astronotus (A. ocellatus and A. crassipinnis), are hypoxic-tolerant species that can survive in very low DO levels for long periods, while adults often inhabit places where DO is close to zero. The present review will focus on some metabolic adjustments that Amazonian fish use in response to hypoxic conditions, which include many strategies from behavioral, morphological, physiological, and biochemical strategies. These strategies include ASR (aerial surface respiration), lip expansion, branchial tissue remodeling, increases in glycolytic metabolism with the increase of blood glucose levels, and increases in anaerobic metabolism with increases of plasma lactate levels. Other groups over evolutionary time developed obligate aerial respiration with changes in pharyngeal and swim bladder vascularization as well as the development of a true lung. However, most species are water-breathing species, such as A. ocellatus and A. crassipinnis, which are detailed in this study because they are used as hypoxia-tolerant model fish. Herein, we draw together the literature data of the physiological mechanisms by which these species decrease aerobic metabolism and increase anaerobic metabolism to survive hypoxia. This is the first attempt to synthesize the physiological mechanisms of the hypoxia-tolerant Astronotus species.

Prazosin protects myocardial cells against anoxia-reoxygenation injury via the extracellular signal‑regulated kinase signaling pathway

Ischemic heart disease (including coronary arterial atherosclerosis, or vascular cavity stenosis or occlusion) remains the leading cause of disease-associated mortality worldwide. Prazosin, a receptor blocker of postsynaptic adrenaline, is essential in expanding peripheral arteries, which decreases peripheral vascular resistance, and regulates anti-hypertensive action. However, the mechanisms underlying the effects of prazosin have not been fully elucidated. The aim of the present study was to investigate the protective effects of prazosin on myocardial cells against anoxia-reoxygenation injury in a mouse model. The regulatory effects of prazosin on blood lipid levels and blood pressure were investigated in experimental mice. Furthermore, inflammation responses and oxidative stress in myocardial cells were analyzed in mice treated with prazosin. Apoptotic myocardial cells were investigated in experimental mice treated with prazosin. In addition, apoptotic gene expression levels were evaluated in myocardial cells. Extracellular signal-regulated kinase (ERK) expression and phosphorylation was investigated in myocardial cells in mice with anoxia-reoxygenation injury following prazosin treatment. The activity and expression levels of nuclear factor of activated T cells (NF-AT), activator protein 1 (AP-1) and necrosis factor (NF)-κB were observed in myocardial cells. Furthermore, histological analyses were performed to investigate the benefits of prazosin treatment on anoxia-reoxygenation injury. The results of the present study identified that prazosin decreased the expression levels of inflammatory factors, interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-10 and IL-1 in the serum of mice exhibiting hypoxia/reoxygenation injury. Oxidative stress was observed to be improved and the apoptosis rate was decreased in myocardial cells in anoxia-reoxygenation injury model mice treated with prazosin. ERK expression and phosphorylation was upregulated, and expression levels of NF-AT, AP-1 and NF-κB were downregulated in the myocardial cells of mice treated with prazosin. Blood lipid levels and blood pressure of the anoxia-reoxygenation injury model mice were markedly improved following treatment with prazosin. Histological analysis indicated that the area, circumference fragmentation and segmentation of myocardial cells were significantly improved following prazosin treatment. Thus, these results indicate that prazosin treatment decreases inflammation responses, oxidative stress, and apoptosis of myocardial cells via regulation of the ERK signaling pathway. The findings indicate that prazosin may present as a potential therapeutic agent for the treatment of hypoxia/reoxygenation injury.

An Efficient and Reliable Assay for Investigating the Effects of Hypoxia/Anoxia on Drosophila

Stroke is a leading cause of death worldwide. Up to one thousand potential drugs or interventions have been developed to treat stroke, out of which ~160 have gone on to clinical trials. However, none of them has been successful. New insights into the molecular and cellular mechanisms of ischemia-induced injury are needed for discovering new therapeutic targets. Recently, Drosophila has been used to uncover new hypoxia-related genes. In this study, we describe an efficient and reliable assay with a sophisticated apparatus for studying the effects of oxygen deprivation on flies. Using this assay, wild-type flies were exposed to an anoxic environment for varying lengths of time, then the cumulative death rate and mobility recovery were systematically analyzed. We found that anoxia for over one hour caused lethality. The cumulative death rate on day 5 after anoxia was linearly and positively correlated with the duration of anoxia, and reached 50% when the duration was 2.5 h-3 h. We also found that the mobility recovery in normoxia was slow, as the climbing ability remained largely unchanged 4 h-6 h after 2.5-h of anoxia. We suggest that 2.5 h-3 h of anoxia and 4 h-6 h of recovery before mobility analysis are appropriate for future use of the anoxia assay.

Molecular impact of omega 3 fatty acids on lipopolysaccharide-mediated liver damage

BACKGROUND

Growing evidence suggests that omega 3 fatty acid containing lipid emulsions have a beneficial effect on parenteral nutrition associated liver disease (PNALD). However, the cellular and molecular mechanisms responsible for this effect are unclear. In this study, we investigated whether Omegaven™ fish oil emulsion could inhibit lipopolysaccharidase (LPS) mediated liver damage.

METHODS

We examined the effects of Omegaven™ and LPS alone and synergistically on hepatic paraoxonase 1 (PON1), a potent antioxidant protein, ERK1/2 activity, and TLR4 regulation.

RESULTS

LPS did not alter PON1 release from HepG2 cells but did significantly decrease PON1 protein synthesis (44%, P<0.05). Omegaven™ alone had no direct effect on PON1 release. However, it did significantly reverse LPS-mediated decrease in PON1 protein levels (control: 100%; LPS alone: 56+/4%; LPS+Omegaven™: 87+/6%, P<0.05). Furthermore, molecular analysis indicated that Omegaven™ blocked LPS-mediated increase in ERK1/2 activity (35% increase), an important LPS signal transduction pathway. TLR4, the receptor for LPS, was down-regulated in the presence of Omegaven™.

CONCLUSION

Omegaven™ may be beneficial in patients with PNAC because of its ability to reverse LPS-mediated inhibition of antioxidant promoting PON1 expression, and this activity may be in part mediated by the ERK1/2 pathway.

New chemiluminescent substrates of paraoxonase 1 with improved specificity: synthesis and properties

Paraoxonase 1 (PON1) is an important hydrolase, and the enzyme activity decreases in patients with liver disease, diabetes, coronary heart disease, etc. Phenyl acetate and organophosphates are usually employed as substrates for serum PON1 activity assay. However, phenyl acetate for arylesterase activity assay exhibits disadvantage of high background. According to properties of PON1, four new chemiluminescent acridinium esters were designed, prepared through three steps, and characterized with (1)H NMR and mass spectrometry (MS) data, and their properties as PON1 substrates were investigated. The hydrolyses of the four compounds catalyzed by recombinant human PON1 (rhPON1) (or serum) followed first-order kinetics within 22 min. The PON1 activator (NaCl, 0.10 mol L(-1)) could boost the rhPON1-mediated and serum-mediated hydrolyses of the acridinium esters to 2.01 ~ 2.26 folds, but 1.0 mol L(-1) NaCl decreased the serum arylesterase activity. RhPON1 showed selectivity over other serum esterases such as lipase, acetylcholinesterase, and esterase D more than 300 folds. By using ethylene diamine tetraacetic acid (EDTA) inhibitor, the specificities of the four substrates toward serum PON1 were determined as 78.3 ~ 92.9%, which is improved than that of the model compound 9-(4-chloro-phenoxycarbonyl)-10-methylacridinium ester triflate. Due to low toxicity, high specificity, and sensitivity of the substrates, they are useful for serum PON1 activity assay.

Association between PON1 L55M polymorphism and ischemic stroke: a systematic review and meta-analysis

OBJECTIVE

The present study aims to evaluate the relation between PON1 L55M polymorphism and ischemic stroke by a meta-analysis method.

METHODS

English and Chinese databases were retrieved to find qualified studies; a random or fixed effects model was used to merge the odds ratio (OR); Q test was used to assess the heterogeneity among studies, and Egger's test and funnel plot were used for the assessment of publication bias.

RESULTS

14 studies were included in the meta-analysis; in total populations, there was no association between PON1 gene L55M polymorphism and ischemic stroke in additive, dominant, and recessive model, respectively. Furthermore, we did not found associations between L55M and ischemic stroke in Asian or Caucasian population.

CONCLUSION

Available evidences suggested that L55M polymorphism had no effect on the risk of ischemic stroke. However, this conclusion needs further validation by larger sample and well-designed studies.