Assessment of Protection Offered By the NRF2 Pathway Against Hyperoxia-Induced Acute Lung Injury in NRF2 Knockout Rats.

ABSTRACT: Nuclear factor erythroid 2-related factor (Nrf2) is a redox-sensitive transcription factor that responds to oxidative stress by activating expressions of key antioxidant and cytoprotective enzymes via the Nrf2-antioxidant response element (ARE) signaling pathway. Our objective was to characterize hyperoxia-induced acute lung injury (HALI) in Nrf2 knock-out (KO) rats to elucidate the role of this pathway in HALI. Adult Nrf2 wildtype (WT), and KO rats were exposed to room air (normoxia) or >95% O2 (hyperoxia) for 48 h, after which selected injury and functional endpoints were measured in vivo and ex vivo. Results demonstrate that the Nrf2-ARE signaling pathway provides some protection against HALI, as reflected by greater hyperoxia-induced histological injury and higher pulmonary endothelial filtration coefficient in KO versus WT rats. We observed larger hyperoxia-induced increases in lung expression of glutathione (GSH) synthetase, 3-nitrotyrosine (index of oxidative stress), and interleukin-1ß, and in vivo lung uptake of the GSH-sensitive SPECT biomarker 99mTc-HMPAO in WT compared to KO rats. Hyperoxia also induced increases in lung expression of myeloperoxidase in both WT and KO rats, but with no difference between WT and KO. Hyperoxia had no effect on expression of Bcl-2 (anti-apoptotic protein) or peroxiredoxin-1. These results suggest that the protection offered by the Nrf2-ARE pathway against HALI is in part via its regulation of the GSH redox pathway. To the best of our knowledge, this is the first study to assess the role of the Nrf2-ARE signaling pathway in protection against HALI using a rat Nrf2 knockout model.

Depolarized mitochondrial membrane potential and protection with duroquinone in isolated perfused lungs from rats exposed to hyperoxia.

Dissipation of mitochondrial membrane potential (Δψm) is a hallmark of mitochondrial dysfunction. Our objective was to use a previously developed experimental-computational approach to estimate tissue Δψm in intact lungs of rats exposed to hyperoxia and to evaluate the ability of duroquinone (DQ) to reverse any hyperoxia-induced depolarization of lung Δψm. Rats were exposed to hyperoxia (>95% O2) or normoxia (room air) for 48 h, after which lungs were excised and connected to a ventilation-perfusion system. The experimental protocol consisted of measuring the concentration of the fluorescent dye rhodamine 6 G (R6G) during three single-pass phases: loading, washing, and uncoupling, in which the lungs were perfused with and without R6G and with the mitochondrial uncoupler FCCP, respectively. For normoxic lungs, the protocol was repeated with 1) rotenone (complex I inhibitor), 2) rotenone and either DQ or its vehicle (DMSO), and 3) rotenone, glutathione (GSH), and either DQ or DMSO added to the perfusate. Hyperoxic lungs were studied with and without DQ and GSH added to the perfusate. Computational modeling was used to estimate lung Δψm from R6G data. Rat exposure to hyperoxia resulted in partial depolarization (-33 mV) of lung Δψm and complex I inhibition depolarized lung Δψm by -83 mV. Results also demonstrate the efficacy of DQ to fully reverse both rotenone- and hyperoxia-induced lung Δψm depolarization. This study demonstrates hyperoxia-induced Δψm depolarization in intact lungs and the utility of this approach for assessing the impact of potential therapies such as exogenous quinones that target mitochondria in intact lungs.NEW & NOTEWORTHY This study is the first to measure hyperoxia-induced Δψm depolarization in isolated perfused lungs. Hyperoxia resulted in a partial depolarization of Δψm, which was fully reversed with duroquinone, demonstrating the utility of this approach for assessing the impact of potential therapies that target mitochondria such as exogenous quinones.

Population variations in atherogenic dyslipidemia: A report from the HeartSCORE and IndiaSCORE Studies.

BACKGROUND: Asian Indians and blacks have a higher risk for cardiovascular disease (CVD) events compared to whites. Atherogenic dyslipidemia, comprised of small-dense low-density lipoprotein (LDL), low high-density lipoprotein (HDL) levels, and high triglyceride (TG) levels, constitutes an important risk factor for CVD often seen in the presence of obesity. The contribution of atherogenic dyslipidemia to CVD risk across diverse racial populations is not well established. OBJECTIVE: Our primary aim was to investigate the relationship between race and atherogenic dyslipidemia among whites, blacks, and Asian Indians. A secondary aim was to evaluate the association between obesity and atherogenic dyslipidemia across populations. METHODS: From community-based sampling, 720 whites and 373 blacks underwent evaluation of CVD risk factors, including fasting lipoproteins. An identical protocol was administered to 205 Asian Indians from Chennai, India. Lipid profiles, including those comprising atherogenic dyslipidemia, were compared among populations. RESULTS: The prevalence of small-dense LDL (pattern B) and of TG/HDL ratio >3 was greatest among Asian Indians and smallest among blacks. Compared to whites, the adjusted odds for Indians having a LDL pattern B was 2.06 (P < .001) and TG/HDL ratio >3 was 9.42 (P < .001). The adjusted odds of having LDL pattern B (odds ratio 0.39, P < 0.001) or TG/HDL ratio >3 (odds ratio 0.41, P < .001) was lower in blacks compared to whites. Among Indians, obesity had a weak association with atherogenic dyslipidemia, in contrast to the strong association among whites. CONCLUSIONS: Significant population variations in atherogenic dyslipidemia exist. This may be an important component to explain population differences in cardiovascular risk.