Deletion of angiotensin II type 1 receptor gene or scavenge of superoxide prevents chronic alcohol-induced aortic damage and remodelling

Essential role of Nrf2 in sulforaphane-induced protection against angiotensin II-induced aortic injury

AIMS

Cardiovascular disease (CVD) is the leading cause of death worldwide. Inflammation and oxidative stress are the primary factors underlying angiotensin II (Ang II)-induced aortic damage. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important antioxidative stress factor. Sulforaphane (SFN), which is naturally found in cruciferous vegetables, is an Nrf2 agonist that is safe for oral administration. Here, we aimed to explore the potential of SFN in protecting against Ang II-induced aortic damage by upregulating Nrf2 expression via the extracellular signal-regulated kinase (ERK)/glycogen synthase kinase-3 beta (GSK-3β)/Fyn pathway.

MAIN METHODS AND KEY FINDINGS

Wild-type (WT) C57BL/6J and Nrf2-knockout (Nrf2-KO) mice were injected with Ang II to induce aortic inflammation, oxidative stress, and cardiac remodeling (increased fibrosis and wall thickness). SFN treatment prevented aortic damage via Nrf2 activation in the WT mice. However, the protective effect of SFN on Ang II-induced aortic damage and upregulation of genes downstream of Nrf2 were not observed in Nrf2-KO mice. SFN induced the upregulation of aortic Nrf2 and inhibited the accumulation of ERK, GSK-3β, and Fyn in the nuclei.

SIGNIFICANCE

These results revealed that Nrf2 plays a central role in protecting against Ang II-induced aortic injury. Furthermore, SFN prevented Ang II-induced aortic damage by activating Nrf2 through the ERK/GSK-3β/Fyn pathway.

Quercetin Attenuates Ethanol-Induced Iron Uptake and Myocardial Injury by Regulating the Angiotensin II-L-Type Calcium Channel

SCOPE

Increased iron deposition in the myocardium in alcoholics may lead to increased risk of cardiac dysfunction. Quercetin has been demonstrated to quench production of intracellular free iron-induced -OH, but the effect of quercetin in ethanol-induced cardiac damage remains unclear. This study aims to explore whether quercetin attenuates ethanol-induced iron uptake and myocardial injury by regulating angiotensin II-L-type voltage-dependent Ca2+ channel (Ang II-LTCC).

METHODS AND RESULTS

Adult male C57BL/6J mice are isocalorically pair-fed either a regular or ethanol-containing Lieber De Carli liquid diets supplemented with either quercetin (100 mg kg^-1  bw) or desferrioxamine mesylate (DFO, 100 mg kg^-1 bw) for 15 weeks. Quercetin alleviated ethanol-induced histopathological changes, creatine kinase isoenzyme release, Ang II secretion, ROS generation, total cardiac iron, and labile iron level. Ethanol exposure or quercetin intervention fails to regulate traditional iron transporters except LTCC. LTCC is upregulated by ethanol and inhibited by quercetin. In H9C2 cell, LTCC is increased by ethanol (100 mm) and/or Ang II (1 μm) concomitant with iron disorders and oxidative stress. This effect is partially normalized by quercetin (50 μm), nifedipine (LTCC inhibitor, 15 μm), or losartan (Ang II receptor antagonist, 100 μm).

CONCLUSION

Alcohol-induced cardiac injury is associated with excessive NTBI uptake mediated by Ang II-LTCC activation which may be mediated by quercetin against ethanol cardiotoxicity.

Inhibition of angiotensin II and calpain attenuates pleural fibrosis

Pleural fibrosis is associated with various inflammatory processes such as tuberculous pleurisy and bacterial empyema. There is currently no ideal therapeutic to attenuate pleural fibrosis. Some pro-fibrogenic mediators induce fibrosis through inflammatory processes, suggesting that blockage of these mediators might prevent pleural fibrosis. The MeT-5A human pleural mesothelial cell line (PMC) was used in this study as an in vitro model of fibrosis; and intra-pleural injection of bleomycin with carbon particles was used as an in vivo mouse model of pleural fibrosis. Calpain knockout mice, calpain inhibitor (calpeptin), and angiotensin (Ang) II type 1 receptor (AT₁R) antagonist (losartan) were evaluated in prevention of experimental pleural fibrosis. We found that bleomycin and carbon particles induced calpain activation in cultured PMCs. This in vitro response was associated with increased collagen-I synthesis, and was blocked by calpain inhibitor or AT₁R antagonist. Calpain genetic or treatment with calpeptin or losartan prevented pleural fibrosis in a mouse model induced by bleomycin and carbon particles. Our findings indicate that Ang II signaling and calpain activation induce collagen-I synthesis and contribute to fibrotic alterations in pleural fibrosis. Inhibition of Ang II and calpain might therefore be a novel strategy in treatment of pleural fibrosis.

Kimchi attenuates fatty streak formation in the aorta of low-density lipoprotein receptor knockout mice via inhibition of endoplasmic reticulum stress and apoptosis

BACKGROUND/OBJECTIVES

Endoplasmic reticulum (ER) stress is positively associated with atherosclerosis via elevating macrophage cell death and plaque formation, in which oxidative stress plays a pivotal role. Antioxidative, lipid-lowering, and anti-atherogenic effects of kimchi, a Korean fermented vegetable, have been established, wherein capsaicin, ascorbic acid, quercetin, 3-(4'-hydroxyl-3',5'-dimethoxyphenyl)propionic acid, and lactic acids were identified. In this study, mechanisms of action of kimchi methanol extracts (KME) on fatty streak formation via suppression of ER stress and apoptosis in aorta were examined in low-density lipoprotein receptor knockout mice.

MATERIALS AND METHODS

Mice fed a high cholesterol diet with an oral administration of KME (KME group, 200 mg·kg-bw⁻¹·day⁻¹) or distilled water (control group) for 8 weeks (n = 20 for group). Plasma lipid and oxidative stress levels were evaluated. Protein expression was measured by western blot assay. Fatty streak lesion size and the degree of apoptosis were examined in the aorta.

RESULTS

Compared to the control group, in the KME group, plasma lipids levels were decreased and oxidative stress was alleviated (P < 0.05). Protein expression levels of nuclear factor (erythroid-derived 2)-like 2-mediated antioxidants in aorta were increased whereas those for ER stress markers, glucose regulated protein 78, phospho-protein kinase RNA-like ER kinase, phospho-eukaryotic initiation factor 2 subunit α, X-box binding protein 1, and C/EBP homologous protein were decreased in the KME group (P < 0.05). Moreover, apoptosis was suppressed via downregulation of phospho-c-Jun N-terminal kinase, bcl-2-associated X protein, caspases-9, and -3 with a concomitant upregulation of anti-apoptotic protein, B-cell lymphoma 2 (P < 0.05). Fatty streak lesion size was reduced and the degree of apoptosis was less severe in the KME group (P < 0.05).

CONCLUSIONS

In conclusion, antioxidant activity of KME might prevent fatty streak formation through, in part, inhibition of ER stress and apoptosis in aortic sinus where macrophages are harbored.

Valsartan blocked alcohol-induced, Toll-like receptor 2 signaling-mediated inflammation in human vascular endothelial cells

BACKGROUND

Alcohol consumption induces inflammatory damage in vessels, and the underlying mechanism is unclear. Valsartan, as one of the angiotensin receptor blockers (ARBs), plays a role in the inhibition of inflammatory reactions in vascular dysfunction. This study is to investigate the role of Toll-like receptor 2 (TLR2) in alcohol-induced inflammatory damage in vascular endothelial cells in vitro and to explore the protective effect of valsartan on alcohol-induced and TLR2-mediated inflammatory damage.

METHODS

The human umbilical vein cell line (EA.hy926) were exposed to alcohol at 0 to 80 mM for 0 to 48 hours with or without valsartan pretreatment. The expression of TLR2 signaling, including TLR2, tumor necrosis factor receptor associated factor 6 (TRAF-6) and nuclear factor kappa B (NF-κB) p65 were detected by Western blot. The levels of proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), were determined by ELISA. To confirm the role of TLR2, we functionally up-regulated or down-regulated TLR2 by using TLR2 agonist or TLR2 small interfering RNA (siRNA), respectively. To further investigate the mechanism of alcohol on renin-angiotensin system, we detected the expression of angiotensin II receptor type 1 (AGTR1) in protein levels.

RESULTS

The expression of TLR2, TRAF-6, NF-κB p65, and the proinflammatory cytokines, TNF-α and IL-6, were significantly increased after alcohol exposure in EA.hy926 endothelial cells. This was enhanced by TLR2 agonist, and was inhibited by TLR2 siRNA transfection. The pretreatment of valsartan resulted in an inhibition of TLR2 signaling and proinflammatory cytokines. The expression of AGTR1 was up-regulated after alcohol exposure, and was blocked by valsartan pretreatment.

CONCLUSIONS

TLR2 signaling-mediated alcohol induced inflammatory response in human vascular epithelial cells in vitro, which was inhibited by valsartan.

Fibroblast growth factor 21 deletion aggravates diabetes-induced pathogenic changes in the aorta in type 1 diabetic mice

Fibroblast growth factor 21 (FGF21) is an important regulator in glucose and lipid metabolism, and has been considered as a potential therapy for diabetes. The effect of FGF21 on the development and progression of diabetes-induced pathogenic changes in the aorta has not currently been addressed. To characterize these effects, type 1 diabetes was induced in both FGF21 knockout (FGF21KO) and C57BL/6 J wild type (WT) mice via multiple-dose streptozotocin injection. FGF21KO diabetic mice showed both earlier and more severe aortic remodeling indicated by aortic thickening, collagen accumulation and fibrotic mediator connective tissue growth factor expression. This was accompanied by significant aortic cell apoptosis than in WT diabetic mice. Further investigation found that FGF21 deletion exacerbated aortic inflammation and oxidative stress reflected by elevated expression of tumor necrosis factor α and transforming growth factor β, and the accumulation of 3-nitrotyrocine and 4-Hydroxynonenal. FGF21 administration can reverse the pathologic changes in FGF21KO diabetic mice. These findings demonstrate that FGF21 deletion aggravates aortic remodeling and cell death probably via exacerbation of aortic inflammation and oxidative stress. This marks FGF21 as a potential therapy for the treatment of aortic damage due to diabetes.

Alcohol abuse: critical pathophysiological processes and contribution to disease burden

Alcohol abuse; the most common and costly form of drug abuse, is a major contributing factor to many disease categories. The alcohol-attributable disease burden is closely related to the average volume of alcohol consumption, with dose-dependent relationships between amount and duration of alcohol consumption and the incidence of diabetes mellitus, hypertension, cardiovascular disease, stroke, and pneumonia. The frequent occurrence of alcohol use disorders in the adult population and the significant and widespread detrimental organ system effects highlight the importance of recognizing and further investigating the pathophysiological mechanisms underlying alcohol-induced tissue and organ injury.

Therapeutic effect of MG132 on the aortic oxidative damage and inflammatory response in OVE26 type 1 diabetic mice

The present study tested whether MG132 increases vascular nuclear factor E2-related factor-2 (Nrf2) expression and transcription to provide a therapeutic effect on diabetes-induced pathogenic changes in the aorta. To this end, three-month-old OVE26 diabetic and age-matched control mice were intraperitoneally injected with MG-132, 10 μg/kg daily for 3 months. OVE26 transgenic type 1 diabetic mice develop hyperglycemia at 2-3 weeks of age and exhibit albuminuria at 3 months of age with mild increases in TNF-α expression and 3-NT accumulation in the aorta. Diabetes-induced significant increases in the wall thickness and structural derangement of aorta were found in OVE26 mice with significant increases in aortic oxidative and nitrosative damage, inflammation, and remodeling at 6 months of diabetes, but not at 3 months of diabetes. However, these pathological changes seen at the 6 months of diabetes were abolished in OVE26 mice treated with MG-132 for 3 months that were also associated with a significant increase in Nrf2 expression in the aorta as well as transcription of downstream genes. These results suggest that chronic treatment with low-dose MG132 can afford an effective therapy for diabetes-induced pathogenic changes in the aorta, which is associated with the increased Nrf2 expression and transcription.

Potential role for Nrf2 activation in the therapeutic effect of MG132 on diabetic nephropathy in OVE26 diabetic mice

Oxidative stress is a major cause of diabetic nephropathy. Upregulation of the key antioxidative transcription factor, nuclear factor-erythroid 2-related factor 2 (Nrf2), was found to prevent the development of diabetic nephropathy. The present study was designed to explore the therapeutic effect of Nrf2 induced by proteasomal inhibitor MG132 at a low dose (10 μg/kg) on diabetic nephropathy. Transgenic type 1 diabetic (OVE26) mice displayed renal dysfunction with albuminuria by 3 mo of age, at which time MG132 treatment was started. After 3-mo treatment with MG132, renal function, morphology, and biochemical changes were examined with real-time PCR, Western blotting, and immunohistochemical examination. Compared with age-matched, nontreated diabetic mice, MG132-treated diabetic mice showed significant improvements in terms of renal structural and functional alterations. These therapeutic effects were associated with increased Nrf2 expression and transcriptional upregulation of Nrf2-regulated antioxidants. Mechanistic study using human renal tubular HK11 cells confirmed the role of Nrf2, as silencing the Nrf2 gene with its specific siRNA abolished MG132 prevention of high-glucose-induced profibrotic response. Furthermore, diabetes was found to significantly increase proteasomal activity in the kidney, an effect that was significantly attenuated by 3 mo of treatment with MG132. These results suggest that MG132 upregulates Nrf2 function via inhibition of diabetes-increased proteasomal activity, which can provide the basis for the therapeutic effect of MG132 on the kidney against diabetes-induced oxidative damage, inflammation, fibrosis, and eventual dysfunction.