Dietary flaxseed protects against lung ischemia reperfusion injury via inhibition of apoptosis and inflammation in a murine model

Dexmedetomidine Alleviates Lung Oxidative Stress Injury Induced by Ischemia-Reperfusion in Diabetic Rats via the Nrf2-Sulfiredoxin1 Pathway

Oxidative stress injury (OSI) is an important pathological process in lung ischemia-reperfusion injury (LIRI), and diabetes mellitus (DM) can exacerbate this injury. Dexmedetomidine protects against LIRI by reducing OSI. However, the effect of dexmedetomidine on LIRI under diabetic conditions remains unclear. Therefore, this study is aimed at exploring the effects and mechanisms of dexmedetomidine on OSI induced by LIRI in diabetic rats. Rats were randomly divided into control+sham (CS), DM+sham (DS), control+ischemia-reperfusion (CIR), DM+ischemia-reperfusion (DIR), and DM+ischemia-reperfusion+dexmedetomidine (DIRD) groups ( $n=6$ ). In the CS and DS groups, the nondiabetic and diabetic rats underwent thoracotomy only without LIRI. In the CIR, DIR, and DIRD groups, LIRI was induced through left hilum occlusion for 60 min, followed by reperfusion for 120 min in nondiabetic and diabetic rats, and rats in the DIRD group were administered dexmedetomidine (3, 5, and 10 μg/kg). Compared with those in the CS group, the OSI, lung compliance, apoptosis, and oxygenation indices deteriorated in the DS group ( $P<0.05$ ), and these indices were further aggravated in the CIR and DIR groups ( $P<0.05$ ), being the worst in the DIR group ( $P<0.05$ ). Compared to those of the DIR group, the OSI, lung compliance ( $15.8\pm 2.4$ vs. $11.6\pm 1.7\text{ml}/\text{kg}$ ), apoptosis ( $22.5\pm 2.6$ vs. $51.8\pm 5.7$ ), oxygenation ( $381\pm 58$ vs. $308\pm 78\text{mmHg}$ ), and caspase-3 and caspase-9 protein expression indices were attenuated, and Nrf2 and sulfiredoxin1 protein expression was increased in the DIRD group ( $P<0.05$ ). And the lung injury, oxygenation, OSI, and Nrf2 and sulfiredoxin1 protein expression changed in a concentration-dependent manner. In conclusion, dexmedetomidine alleviated lung OSI and improved lung function in a diabetic rat LIRI model through the Nrf2-sulfiredoxin1 pathway.

Effect of ischemic preconditioning on radiation damage to the submandibular gland in rats

To investigate the effects of radiation on rat submandibular glands and the possible protective effects of ischemic preconditioning, the submandibular glands of Wistar rats were subjected to in situ radiation after ischemic preconditioning. The glands were exposed to X-radiation at a single dose of 20 Gy. Ischemic preconditioning was achieved by three min of ischemia and three min of reperfusion, repeated three times before irradiation. Salivary secretion, histological changes, alterations in tight junctions, and the levels of oxidative stress, pro-inflammatory cytokines, and water secretion proteins mediated by the muscarinic acetylcholine M3 subtype receptor were determined at 1 and 12 weeks post-irradiation. In glands subjected to irradiation only, the secretion, superoxide dismutase activity, tight junction width, acinar cell number, and M3 receptor and aquaporin-5 levels were lower at 1 and 12 weeks than seen in the ischemically preconditioned irradiated glands. In contrast, tumor necrosis factor-α, malondialdehyde, myeloperoxidase activity, and the expression of the tight junction protein claudin-4 were significantly higher in the irradiated only glands. Our study revealed that radiation caused a series of injury-stress responses, especially damage to the water secretion pathway mediated by the M3 receptor that ultimately led to hyposecretion, which might play an important role in the dysfunction of the irradiated only glands. Ischemic preconditioning reduced the radiation-induced injury to submandibular glands and ameliorated salivary hyposecretion.

LGM2605 Reduces Space Radiation-Induced NLRP3 Inflammasome Activation and Damage in In Vitro Lung Vascular Networks

Updated measurements of charged particle fluxes during the transit from Earth to Mars as well as on site measurements by Curiosity of Martian surface radiation fluxes identified potential health hazards associated with radiation exposure for human space missions. Designing mitigation strategies of radiation risks to astronauts is critical. We investigated radiation-induced endothelial cell damage and its mitigation by LGM2605, a radioprotector with antioxidant and free radical scavenging properties. We used an in vitro model of lung vascular networks (flow-adapted endothelial cells; FAECs), exposed to gamma rays, low/higher linear energy transfer (LET) protons (3⁻4 or 8⁻10 keV/µm, respectively), and mixed field radiation sources (gamma and protons), given at mission-relevant doses (0.25 gray (Gy)⁻1 Gy). We evaluated endothelial inflammatory phenotype, NLRP3 inflammasome activation, and oxidative cell injury. LGM2605 (100 µM) was added 30 min post radiation exposure and gene expression changes evaluated 24 h later. Radiation induced a robust increase in mRNA levels of antioxidant enzymes post 0.25 Gy and 0.5 Gy gamma radiation, which was significantly decreased by LGM2605. Intercellular cell adhesion molecule-1 (ICAM-1) and NOD-like receptor protein 3 (NLRP3) induction by individual or mixed-field exposures were also significantly blunted by LGM2605. We conclude that LGM2605 is a likely candidate to reduce tissue damage from space-relevant radiation exposure.

Acidic Preconditioning Protects Against Ischemia-Reperfusion Lung Injury Via Inhibiting the Expression of Matrix Metalloproteinase 9

BACKGROUND

Acidic preconditioning (APC) has been demonstrated to protect against ischemia-reperfusion (IR)-induced lung injury, which could occur during lung transplantation or cardiopulmonary bypass. However, the pathophysiological mechanisms underlying IR lung injury and APC protection are not completely understood. The key factors responsible for the protective effects of APC are not clear. In this study, bioinformatics was used to predict the potential key factor in IR lung injury and explore the important mediator of the APC protective effect in IR lung injury.

METHODS

First, we screened GSE6730, which is related to both lung injury and IR in Gene Expression Omnibus, and STRING was used later to select the genes in GSE6730 needed in the future. Animal models were established and classified to validate the effect of matrix metalloproteinase 9 (MMP-9) on lung injury after IR by adding a selective inhibitor (4-phenoxyphenylsulfonyl) methylthiirane, MMP-9 inhibitor. Next, for better understanding of APC inhibition of the expression of MMP-9 in lung injury, assessment of lung tissues, Western blot analysis, and RNA extraction and reverse transcription quantitative polymerase chain reaction were conducted.

RESULTS

MMP-9 was identified to be overexpressed after IR according to the analysis on GSE67370. MMP-9 was an unknown gene in relation to acute lung injury and found to be associated with interleukin (IL)-1B, IL-6, and IL-8. The expressions of these inflammatory factors, including MMP-9, were all elevated in IR. Furthermore, lung injury was ameliorated, and the level of MMP-9 was lower when an MMP-9 inhibitor, (4-phenoxyphenylsulfonyl) methylthiirane, was added. Compared with group IR, APC reversed the ischemia-induced lung injury, and the level of MMP-9 was lower, and the concentrations of IL-1β, IL-6, and IL-8 were decreased.

CONCLUSIONS

Our findings reveal a novel mechanism indicating that IR induces higher expression of MMP-9 in lung injury by increasing the expression of inflammation-related factors. APC might protect against IR lung injury by inhibiting the expression of MMP-9.

Lung Ischaemia-Reperfusion Injury: The Role of Reactive Oxygen Species

Lung ischaemia-reperfusion injury (LIRI) occurs in many lung diseases and during surgical procedures such as lung transplantation. The re-establishment of blood flow and oxygen delivery into the previously ischaemic lung exacerbates the ischaemic injury and leads to increased microvascular permeability and pulmonary vascular resistance as well as to vigorous activation of the immune response. These events initiate the irreversible damage of the lung with subsequent oedema formation that can result in systemic hypoxaemia and multi-organ failure. Alterations in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been suggested as crucial mediators of such responses during ischaemia-reperfusion in the lung. Among numerous potential sources of ROS/RNS within cells, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, nitric oxide synthases and mitochondria have been investigated during LIRI. Against this background, we aim to review here the extensive literature about the ROS-mediated cellular signalling during LIRI, as well as the effectiveness of antioxidants as treatment option for LIRI.

Asbestos Induces Oxidative Stress and Activation of Nrf2 Signaling in Murine Macrophages: Chemopreventive Role of the Synthetic Lignan Secoisolariciresinol Diglucoside (LGM2605)

The interaction of asbestos fibers with macrophages generates harmful reactive oxygen species (ROS) and subsequent oxidative cell damage that are key processes linked to malignancy. Secoisolariciresinol diglucoside (SDG) is a non-toxic, flaxseed-derived pluripotent compound that has antioxidant properties and may thus function as a chemopreventive agent for asbestos-induced mesothelioma. We thus evaluated synthetic SDG (LGM2605) in asbestos-exposed, elicited murine peritoneal macrophages as an in vitro model of tissue phagocytic response to the presence of asbestos in the pleural space. Murine peritoneal macrophages (MFs) were exposed to crocidolite asbestos fibers (20 µg/cm²) and evaluated at various times post exposure for cytotoxicity, ROS generation, malondialdehyde (MDA), and levels of 8-iso Prostaglandin F2α (8-isoP). We then evaluated the ability of LGM2605 to mitigate asbestos-induced oxidative stress by administering LGM2605 (50 µM) 4-h prior to asbestos exposure. We observed a significant (p < 0.0001), time-dependent increase in asbestos-induced cytotoxicity, ROS generation, and the release of MDA and 8-iso Prostaglandin F2α, markers of lipid peroxidation, which increased linearly over time. LGM2605 treatment significantly (p < 0.0001) reduced asbestos-induced cytotoxicity and ROS generation, while decreasing levels of MDA and 8-isoP by 71%–88% and 41%–73%, respectively. Importantly, exposure to asbestos fibers induced cell protective defenses, such as cellular Nrf2 activation and the expression of phase II antioxidant enzymes, HO-1 and Nqo1 that were further enhanced by LGM2605 treatment. LGM2605 boosted antioxidant defenses, as well as reduced asbestos-induced ROS generation and markers of oxidative stress in murine peritoneal macrophages, supporting its possible use as a chemoprevention agent in the development of asbestos-induced malignant mesothelioma.

Beneficial effects of inhaled NO on apoptotic pneumocytes in pulmonary thromboembolism model

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) may occur in the region of the affected lung after reperfusion therapy. Inhaled NO may be useful in treating acute and chronic pulmonary thromboembolism (PTE) due to the biological effect property of NO.

METHODS

A PTE canine model was established through selectively embolizing blood clots to an intended right lower lobar pulmonary artery. PaO2/FiO2, the mPAP and PVR were investigated at the time points of 2, 4, 6 hours after inhaled NO. Masson's trichrome stain, apoptotic pneumocytes and lung sample ultrastructure were also investigated among different groups.

RESULTS

The PaO2/FiO2 in the Inhaled NO group increased significantly when compared with the Reperfusion group at time points of 4 and 6 hours after reperfusion, mPAP decreased significantly at point of 2 hours and the PVR decreased significantly at point of 6 hours after reperfusion. The amounts of apoptotic type II pneumocytes in the lower lobar lung have negative correlation trend with the arterial blood PaO2/FiO2 in Reperfusion group and Inhaled NO group. Inhaled nitric oxide given at 20 ppm for 6 hours can significantly alleviate the LIRI in the model.

CONCLUSIONS

Dramatic physiological improvements are seen during the therapeutic use of inhaled NO in pulmonary thromboembolism canine model. Inhaled NO may be useful in treating LIRI in acute or chronic PTE by alleviating apoptotic type II pneumocytes. This potential application warrants further investigation.

Favorable effects of flaxseed supplemented diet on liver and kidney functions in hypertensive Wistar rats

Hypertension is a major risk factor for cardiovascular diseases and is detrimental to several organs including the liver and kidneys. The flaxseed-derived polyunsaturated fatty acids including the omega-3 and omega-6 essential fatty acids have been shown to blunt the effects of hypertension. It is however, unclear whether the flaxseed, which is rich in these essential fatty acids, could improve the liver and kidney dysfunctions observed in the hypertensive condition. To test this, functional markers of the liver and kidneys, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN), uric acid (UA), creatinine, and renin were examined in hypertensive male Wistar rats fed a flaxseed diet. Normotensive rats maintained on a standard diet were rendered hypertensive with a daily administration of cyclosporin A (CYS) (25 mg/kg) for 4 weeks. Subsequently, hypertensive rats were either fed a standard diet alone or a flaxseed-supplemented standard diet (FLX; 10% W/W) for 8 weeks. Compared to normotensive rats, standard diet-fed hypertensive rats had significantly elevated blood pressure, altered lipid profile, and increased plasma levels of tissue markers measured immediately following the CYS treatment and thereafter at 4 and 8 week intervals. On the other hand, rats fed the FLX-supplemented diet had significantly lower blood pressure, an improved lipid profile and decreased tissue marker levels measured after 4 and 8 week durations. The data demonstrate for the first time the favourable effects of FLX in improving liver and kidney functions in the hypertensive condition. These effects are likely to be mediated by the alpha-linolenic acid (ALA) and linoleic acid (LA) contents of flaxseed oil due to its demonstrated ability to lower the blood pressure.

Gene expression profiling of flaxseed in mouse lung tissues-modulation of toxicologically relevant genes

BACKGROUND

Flaxseed (FS), a nutritional supplement consisting mainly of omega-3 fatty acids and lignan phenolics has potent anti-inflammatory, anti-fibrotic and antioxidant properties. The usefulness of flaxseed as an alternative and complimentary treatment option has been known since ancient times. We have shown that dietary FS supplementation ameliorates oxidative stress and inflammation in experimental models of acute and chronic lung injury in mice resulting from diverse toxicants. The development of lung tissue damage in response to direct or indirect oxidant stress is a complex process, associated with changes in expression levels of a number of genes. We therefore postulated that flaxseed might modulate gene expression of vital signaling pathways, thus interfering with the development of tissue injury.

METHODS

We evaluated gene expression in lungs of flaxseed-fed (10%FS) mice under unchallenged, control conditions. We reasoned that array technology would provide a powerful tool for studying the mechanisms behind this response and aid the evaluation of dietary flaxseed intervention with a focus on toxicologically relevant molecular gene targets. Gene expression levels in lung tissues were analyzed using a large-scale array whereby 28,800 genes were evaluated.

RESULTS

3,713 genes (12.8%) were significantly (p < 0.05) differentially expressed, of which 2,088 had a >1.5-fold change. Genes affected by FS include those in protective pathways such as Phase I and Phase II.

CONCLUSIONS

The array studies have provided information on how FS modulates gene expression in lung and how they might be related to protective mechanisms. In addition, our study has confirmed that flaxseed is a nutritional supplement with potentially useful therapeutic applications in complementary and alternative (CAM) medicine especially in relation to treatment of lung disease.