Endothelial NOS-derived nitric oxide prevents injury resulting from reoxygenation in the hypoxic lung

Ac2-26 Alleviates Brain Injury after Cardiac Arrest and Cardiopulmonary Resuscitation in Rats via the eNOS Pathway

Background

Brain injury is the leading cause of death following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Ac2-26 and endothelial nitric oxide synthase (eNOS) have been shown to reduce neuroinflammation. This study is aimed at determining the mechanism by which Ac2-26 protects against inflammation during brain injury following CA and CPR.

Methods

Sixty-four rats were randomized into sham, saline, Ac2-26, and Ac2-26+L-NIO (endothelial nitric oxide synthase (eNOS) inhibitor) groups. Rats received Ac2-26, Ac2-26+L-NIO, or saline after CPR. Neurologic function was assessed at baseline, 24, and 72 hours after CPR. At 72 hours after resuscitation, serum and brain tissues were collected.

Results

Blood-brain barrier (BBB) permeability increased, and the number of surviving neurons and neurological function decreased in the saline group compared to the sham group. Anti-inflammatory and proinflammatory factors, neuron-specific enolase (NSE) levels, and the expression of eNOS, phosphorylated (p)-eNOS, inducible nitric oxide synthase (iNOS), and oxidative stress-related factors in the three CA groups significantly increased (P < 0.05). BBB permeability decreased, and the number of surviving neurons and neurological function increased in the Ac2-26 group compared to the saline group (P < 0.05). Ac2-26 increased anti-inflammatory and reduced proinflammatory markers, raised NSE levels, increased the expression of eNOS and p-eNOS, and reduced the expression of iNOS and oxidative stress-related factors compared to the saline group (P < 0.05). The effect of Ac2-26 on brain injury was reversed by L-NIO (P < 0.05).

Conclusions

Ac2-26 reduced brain injury after CPR by inhibiting oxidative stress and neuroinflammation and protecting the BBB. The therapeutic effect of Ac2-26 on brain injury was largely dependent on the eNOS pathway.

Ac2-26 ameliorates lung ischemia-reperfusion injury via the eNOS pathway

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) is a major complication after lung transplantation. Annexin A1 (AnxA1) ameliorates inflammation in various injured organs. This study aimed to determine the effects and mechanism of AnxA1 on LIRI after lung transplantation.

METHODS

Thirty-two rats were randomized into sham, saline, Ac2-26 and Ac2-26/L groups. Rats in the saline, Ac2-26 and Ac2-26/L groups underwent left lung transplantation and received saline, Ac2-26, and Ac2-26/L-NIO, respectively. After 24 h of reperfusion, serum and transplanted lung tissues were examined.

RESULTS

The partial pressure of oxygen (PaO₂) was increased in the Ac2-26 group compared to that in the saline group but was decreased by L-NIO treatment. In the Ac2-26 group, the wet-to-dry (W/D) weight ratios, total protein concentrations, proinflammatory factors and inducible nitric oxide synthase levels were notably decreased, but the concentrations of anti-inflammatory factors and endothelial nitric oxide synthase levels were significantly increased. Ac2-26 attenuated histological injury and cell apoptosis, and this improvement was reversed by L-NIO.

CONCLUSIONS

Ac2-26 reduced LIRI and improved alveoli-capillary permeability by inhibiting oxygen stress, inflammation and apoptosis. The protective effect of Ac2-26 on LIRI largely depended on the endothelial nitric oxide synthase pathway.

Temporal Patterns of Gene Expression Profiles in the Neonatal Mouse Lung after Hypoxia-Reoxygenation

BACKGROUND

One out of four children with neonatal asphyxia has lung involvement. Still, there has been little research on injury mechanisms of hypoxia-reoxygenation in the neonatal lung.

OBJECTIVES

To make a temporal profile of the gene expression changes of 44 a priori selected genes after hypoxia-reoxygenation in the newborn mouse lung, and to compare the changes after hyperoxic and normoxic reoxygenation.

METHODS

Postnatal day 7 mice were randomized to 2-hour hypoxia (8% O2) and 30-min reoxygenation in either 60% O2 or air. After 0-72 h of observation, gene expression changes and protein concentrations in whole lung homogenates were examined.

RESULTS

Immediately after completed reoxygenation, 7 genes of mediators of inflammation were downregulated, and there was an antiapoptotic gene expression pattern. Three DNA glycosylases were downregulated, while genes involved in cell cycle renewal indicated both increased and decreased cell cycle arrest. Sod1 (T2.5h median H60: 1.01, H21: 0.88, p = 0.005; T5h median H60: 1.04, H21: 0.85, p = 0.038) and Il1b (T0h median H60: 0.86, H21: 1.08, p = 0.021) were significantly differentially expressed when comparing hyperoxic and normoxic reoxygenation.

CONCLUSION

In this newborn mouse lung hypoxia-reoxygenation model, we found downregulation of genes of mediators of inflammation, an antiapoptotic gene expression pattern, and downregulation of DNA glycosylases. Sod1 and Il1b were significantly differentially expressed when comparing reoxygenation using 60% O2 with air.

Sildenafil attenuates hepatocellular injury after liver ischemia reperfusion in rats: a preliminary study

We evaluated the role of sildenafil in a rat liver ischemia-reperfusion model. Forty male rats were randomly allocated in four groups. The sham group underwent midline laparotomy only. In the sildenafil group, sildenafil was administered intraperitoneally 60 minutes before sham laparotomy. In the ischemia-reperfusion (I/R) group, rats were subjected to 45 minutes of hepatic ischemia followed by 120 minutes of reperfusion, while in the sild+I/R group rats were subjected to a similar pattern of I/R after the administration of sildenafil, 60 minutes before ischemia. Two hours after reperfusion, serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured and histopathological examination of the lobes subjected to ischemia as well as TUNEL staining for apoptotic bodies was performed. Additionally, myeloperoxidase (MPO) activity and the expression of intercellular adhesion molecule-1 (ICAM-1) were analyzed. Serum markers of hepatocellular injury were significantly lower in the sild+I/R group, which also exhibited lower severity of histopathological lesions and fewer apoptotic bodies, as compared to the I/R group. The I/R group showed significantly higher MPO activity and higher expression of ICAM-1, as compared to the sild+I/R group. Use of sildenafil as a preconditioning agent in a rat model of liver I/R exerted a protective effect.

Lung oxidative damage by hypoxia

One of the most important functions of lungs is to maintain an adequate oxygenation in the organism. This organ can be affected by hypoxia facing both physiological and pathological situations. Exposure to this condition favors the increase of reactive oxygen species from mitochondria, as from NADPH oxidase, xanthine oxidase/reductase, and nitric oxide synthase enzymes, as well as establishing an inflammatory process. In lungs, hypoxia also modifies the levels of antioxidant substances causing pulmonary oxidative damage. Imbalance of redox state in lungs induced by hypoxia has been suggested as a participant in the changes observed in lung function in the hypoxic context, such as hypoxic vasoconstriction and pulmonary edema, in addition to vascular remodeling and chronic pulmonary hypertension. In this work, experimental evidence that shows the implied mechanisms in pulmonary redox state by hypoxia is reviewed. Herein, studies of cultures of different lung cells and complete isolated lung and tests conducted in vivo in the different forms of hypoxia, conducted in both animal models and humans, are described.

Upregulation of cardiac NO/NOS system during short-term hypoxia and the subsequent reoxygenation period

Hypoxia/reoxygenation (H/R) reportedly influences nitric oxide (NO) production and NO synthase (NOS) expression in the heart. Nonetheless, a number of works have shown controversial results regarding the changes that the cardiac NO/NOS system undergoes under such situations. Therefore, this study aims to clarify the behaviour of this system in the hypoxic heart by investigating seven different reoxygenation times. Wistar rats were submitted to H/R (hypoxia for 30 min; reoxygenation of 0, 2, 12, 24, 48, 72 h, and 5 days) in a novel approach to address the events provoked by assaults under such circumstances. Endothelial and inducible NOS (eNOS and iNOS) mRNA and protein expression, as well as enzymatic activity and enzyme location were determined. NO levels were indirectly quantified as nitrate/nitrite, and other S-nitroso compounds (NOx), which would act as NO-storage molecules. The results showed a significant increase in eNOS mRNA, protein and activity, as well as in NOx levels immediately after hypoxia, while iNOS protein and activity were induced throughout the reoxygenation period. These findings indicate that, not only short-term hypoxia, but also the subsequent reoxygenation period upregulate cardiac NO/NOS system until at least 5 days after the hypoxic stimulus, implying major involvement of this system in the changes occurring in the heart in response to H/R.

Nitric oxide averts hypoxia-induced damage during reoxygenation in rat heart

Nitric oxide (NO), synthesized by the hemoproteins NO synthases (NOS), is known to play important roles in physiological and pathological conditions in the heart, including hypoxia/reoxygenation (H/R). This work investigates the role that endogenous NO plays in the cardiac H/R-induced injury. A follow-up study was conducted in Wistar rats subjected to 30 min of hypoxia, with or without prior treatment using the nonselective NOS inhibitor L-NAME (1.5 mM). The rats were studied at 0 h, 12 h, and 5 days of reoxygenation, analysing parameters of cell, and tissue damage (lipid peroxidation, apoptosis, and protein nitration), as well as in situ NOS activity and NO production (NOx). The results showed that after L-NAME administration, in situ NOS activity was almost completely eliminated in all the experimental groups, and consequently, NOx levels fell. Contrarily, the lipid peroxidation level and the percentage of apoptotic cells rose throughout the reoxygenation period. These results reveal that NOS inhibition exacerbates the peroxidative and apoptotic damage observed before the treatment with L-NAME in the hypoxic heart, pointing to a cardioprotective role of NOS-derived NO against H/R-induced injury. These findings could open the possibility of future studies to design new therapies for H/R-dysfunctions based on NO-pharmacology.