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

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.

A Potential Target for Diabetic Vascular Damage: High Glucose-Induced Monocyte Extracellular Vesicles Impair Endothelial Cells by Delivering miR-142-5p

Endothelial dysfunction is a key accessory to diabetic cardiovascular complications, and the regulatory role of the extracellular vesicles (EVs) from the innate immune system is growing. We tested whether EVs derived from high glucose-induced monocytes could shuttle microRNAs and impair endothelial cells. EVs from high glucose- and basal glucose-treated THP-1 cells (^HG-THP-1 EVs and ^BG-THP-1 EVs) were isolated and identified. After coculture with THP-1 EVs, human umbilical vein endothelial cells (HUVECs) were tested by proliferation, migration, reactive oxygen species (ROS) detection assays, and western blot for Nrf2/NLRP3 signaling. MiR-142-5p was predicted by miRNAs databases and further verified by RT–qPCR and dual-luciferase reporter gene assays that inhibit Nrf2 expression. The regulation of miR-142-5p in HUVECs was further evaluated. A type 1 diabetes mellitus (T1DM) mouse model was developed for miR-142-5p inhibition. Aorta tissue was harvested for hematoxylin-eosin staining and immunohistochemistry of interleukin-1β (IL-1β). Compared to ^BG-THP-1 EVs, ^HG-THP-1 EVs significantly reduced migration and increased ROS production in HUVECs but did not affect proliferation. ^HG-THP-1 EVs induced suppression of Nrf2 signaling and NLRP3 signaling activation. RT–qPCR results showed that ^HG-THP-1 EVs overexpressed miR-142-5p in HUVECs. The transfection of miR-142-5p mimics into HUVECs exhibited consistent regulatory effects on ^HG-THP-1 EVs, whereas miR-142-5p inhibitors demonstrated protective effects. The miR-142-5p antagomir significantly reduced the IL-1β level in T1DM aortas despite morphological changes. To conclude, miR-142-5p transferred by high glucose-induced monocyte EVs participates in diabetic endothelial damage. The inhibition of miR-142-5p could be a potential adjuvant to diabetic cardiovascular protection.

MG132 Induces Progerin Clearance and Improves Disease Phenotypes in HGPS-like Patients’ Cells

Progeroid syndromes (PS), including Hutchinson-Gilford Progeria Syndrome (HGPS), are premature and accelerated aging diseases, characterized by clinical features mimicking physiological aging. Most classical HGPS patients carry a de novo point mutation within exon 11 of the LMNA gene encoding A-type lamins. This mutation activates a cryptic splice site, leading to the production of a truncated prelamin A, called prelamin A ∆50 or progerin, that accumulates in HGPS cell nuclei and is a hallmark of the disease. Some patients with PS carry other LMNA mutations and are named “HGPS-like” patients. They produce progerin and/or other truncated prelamin A isoforms (∆35 and ∆90). We previously found that MG132, a proteasome inhibitor, induced progerin clearance in classical HGPS through autophagy activation and splicing regulation. Here, we show that MG132 induces aberrant prelamin A clearance and improves cellular phenotypes in HGPS-like patients’ cells other than those previously described in classical HGPS. These results provide preclinical proof of principle for the use of a promising class of molecules toward a potential therapy for children with HGPS-like or classical HGPS.

The Protective Effects of Protease Inhibitor MG-132 on Sepsis-Induced Acute Kidney Injury and Its Mechanisms

MG-132 is an aldehyde peptide proteasome inhibitor, which reduces the inflammatory response and exerts a protective effect on severe acute pancreatitis and associated lung injury of rats. However, the involvement of MG-132 in sepsis-induced acute kidney injury (AKI) and the underlying mechanisms remain unknow. In this study, SD rats were employed to induce sepsis by cecal ligation and puncture (CLP) method and then divided into control, sham, CLP, and CLP + MG-132. Histopathology observation was detected by hematoxylin and eosin staining. The levels of biomarkers representing renal function such as serum creatinine (Scr), blood urea nitrogen (BUN), serum cystatin C (Scys C), and indicators of AKI such as Kim-1, IL-18, α glutathione S-traferase (α-GST) and albumin were measured by ELISA. Western blot and immunohistochemistry were performed to measure Testican-1. In order to assess the role of Testican-1, the expression of β-catenin, c-myc and cyclinD1 were evaluated by western blot. The results indicated that the levels of SCr, BUN, Scys C, KIM-1, IL-18, GST-α and albumin were decreased after MG-132 treatment compared with CLP group. And both pathological injury and W/D ratio were obviously improved in the CLP + MG- 132 group. Furthermore, the level of Testican-1 increased in the CLP group while a decreased presented in the CLP + MG-132 group. The expression of β-catenin, c-myc and cyclinD1 were downregulated in the CLP + MG-132 group compared to the CLP group. Our findings suggested that MG-132 can protect against AKI via inhibiting Testican-1 through the Wnt/β-catenin pathway MG-132 served as a novel biomarker and therapeutic regimen for sepsis-induced AKI.

Protective role of NRF2 in macrovascular complications of diabetes

Macrovascular complications develop in over a half of the diabetic individuals, resulting in high morbidity and mortality. This poses a severe threat to public health and a heavy burden to social economy. It is therefore important to develop effective approaches to prevent or slow down the pathogenesis and progression of macrovascular complications of diabetes (MCD). Oxidative stress is a major contributor to MCD. Nuclear factor (erythroid‐derived 2)‐like 2 (NRF2) governs cellular antioxidant defence system by activating the transcription of various antioxidant genes, combating diabetes‐induced oxidative stress. Accumulating experimental evidence has demonstrated that NRF2 activation protects against MCD. Structural inhibition of Kelch‐like ECH‐associated protein 1 (KEAP1) is a canonical way to activate NRF2. More recently, novel approaches, such as activation of the Nfe2l2 gene transcription, decreasing KEAP1 protein level by microRNA‐induced degradation of Keap1 mRNA, prevention of proteasomal degradation of NRF2 protein and modulation of other upstream regulators of NRF2, have emerged in prevention of MCD. This review provides a brief introduction of the pathophysiology of MCD and the role of oxidative stress in the pathogenesis of MCD. By reviewing previous work on the activation of NRF2 in MCD, we summarize strategies to activate NRF2, providing clues for future intervention of MCD. Controversies over NRF2 activation and future perspectives are also provided in this review.

An overview of treatment strategies for Hutchinson-Gilford Progeria syndrome

Hutchinson-Gilford progeria syndrome (HGPS) is a sporadic, autosomal dominant disorder characterized by premature and accelerated aging symptoms leading to death at the mean age of 14.6 years usually due to cardiovascular complications. HGPS is caused by a de novo point mutation in the LMNA gene encoding the intermediate filament proteins lamins A and C which are structural components of the nuclear lamina. This mutation leads to the production of a truncated toxic form of lamin A, issued from aberrant splicing and called progerin. Progerin accumulates in HGPS cells' nuclei and is a hallmark of the disease. Small amounts of progerin are also produced during normal aging. HGPS cells and animal preclinical models have provided insights into the molecular and cellular pathways that underlie the disease and have also highlighted possible mechanisms involved in normal aging. This review reports recent medical advances and treatment approaches for patients affected with HGPS.

The Protective Effects of Protease Inhibitor MG-132 on Sepsis-Induced Acute Lung Rats and Its Possible Mechanisms

Background

The aim of the present study was to investigate the protective effects of protease inhibitor MG-132 on sepsis-induced acute lung injury rats.

Material/Methods

Sprague Dawley rats were employed to induce sepsis by cecal ligation and puncture (CLP) method. Rats were divided into 4 groups: control, sham, model (CLP), and MG-132. Histopathology observation was detected by hematoxylin and eosin staining. The ratio of wet lung to dry lung (W/D) was calculated. In addition, the levels of inflammatory factors in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA). Also, superoxide dismutase (SOD) and malondialdehyde (MDA) levels were evaluated. Western blotting was performed to measure the expression of hypoxia-inducible factor-1 α (HIF-1α). In order to assess the role of HIF-1α, YC-1, the inhibitor of HIF-1α, was used to treat the rats. The expression of phosphor-mTOR (p-mTOR), p-4EBP1, and p-EIF4E were evaluated by western blotting.

Results

Obvious pathological injury and increasing ratio of W/D in the model group were observed. Both pathological injury and W/D were improved in the MG-132 group, and the greatest improvement could be seen in the YC-1+MG-132 group. Furthermore, the MDA levels in the MG-132 group was decreased, accompanied by an increase in SOD levels. The level of HIF-1α was increased in the model group while a decreased was detected in the MG-132 group. The levels of inflammatory factors were high in the model group, whereas the opposite result was found in the MG-132 group, and the lowest in were in the YC-1+MG-132 group. Furthermore, the expression levels of p-mTOR, p-4EBP1, and p-EIF4E proteins were downregulated in the MG-132 group compared to the model group, and the lowest was in the YC-1+MG-132 group.

Conclusions

Our study suggested that MG-132 was able to protect against acute lung injury via inhibition of HIF-1α mediated mTOR/4EBP1/EIF4E pathway.

Sodium butyrate attenuates diabetes-induced aortic endothelial dysfunction via P300-mediated transcriptional activation of Nrf2

Oxidative stress and inflammation are major contributors to diabetes-induced endothelial dysfunction which is the critical first step to the development of diabetic macrovascular complications. Nuclear factor erythroid 2-related factor 2 (NRF2) plays a key role in combating diabetes-induced oxidative stress and inflammation. Sodium butyrate (NaB) is an inhibitor of histone deacetylase (HDAC) and an activator of NRF2. However, NaB's effect on diabetes-induced aortic injury was unknown. It was also not known whether or to what extent NRF2 is required for both self-defense and NaB's protection in the diabetic aorta. Additionally, the mechanism by which NaB activates NRF2 was unclear. Therefore, C57BL/6 Nrf2 knockout (KO) and wild type (WT) mice were induced to diabetes by streptozotocin, and were treated in the presence or absence of NaB, for 20 weeks. The KO diabetic mice developed more severe aortic endothelial oxidative stress, inflammation and dysfunction, as compared with the WT diabetic mice. NaB significantly attenuated these effects in the WT, but not the KO, mice. In high glucose-treated aortic endothelial cells, NaB elevated Nrf2 mRNA and protein without facilitating NRF2 nuclear translocation, an effect distinct from that of sulforaphane. NaB inhibited HDAC activity, and increased occupancy of the transcription factor aryl hydrocarbon receptor and the co-activator P300 at the Nrf2 gene promoter. Further, the P300 inhibitor C646 completely abolished NaB's efficacies. Thus, NRF2 is required for both self-defense and NaB's protection against diabetes-induced aortic endothelial dysfunction. Other findings suggest that P300 mediates the transcriptional activation of Nrf2 by NaB.

MG132-induced progerin clearance is mediated by autophagy activation and splicing regulation

Hutchinson–Gilford progeria syndrome (HGPS) is a lethal premature and accelerated aging disease caused by a de novo point mutation in LMNA encoding A‐type lamins. Progerin, a truncated and toxic prelamin A issued from aberrant splicing, accumulates in HGPS cells' nuclei and is a hallmark of the disease. Small amounts of progerin are also produced during normal aging. We show that progerin is sequestered into abnormally shaped promyelocytic nuclear bodies, identified as novel biomarkers in late passage HGPS cell lines. We found that the proteasome inhibitor MG132 induces progerin degradation through macroautophagy and strongly reduces progerin production through downregulation of SRSF‐1 and SRSF‐5 accumulation, controlling prelamin A mRNA aberrant splicing. MG132 treatment improves cellular HGPS phenotypes. MG132 injection in skeletal muscle of Lmna^G609G/G609G mice locally reduces SRSF‐1 expression and progerin levels. Altogether, we demonstrate progerin reduction based on MG132 dual action and shed light on a promising class of molecules toward a potential therapy for children with HGPS.

Transplantation of Bone Marrow Mesenchymal Stem Cells Prevents Radiation-Induced Artery Injury by Suppressing Oxidative Stress and Inflammation

The present study aims to explore the protective effect of human bone marrow mesenchymal stem cells (hBMSCs) on radiation-induced aortic injury (RIAI). hBMSCs were isolated and cultured from human bone marrow. Male C57/BL mice were irradiated with a dose of 18-Gy 6MV X-ray and randomly treated with either vehicle or hBMSCs through tail vein injection with a dose of 10³ or 10⁴ cells/g of body weight (low or high dose of hBMSCs) within 24 h. Aortic inflammation, oxidative stress, and vascular remodeling were assessed by immunohistochemical staining at 3, 7, 14, 28, and 84 days after irradiation. The results revealed irradiation caused aortic cell apoptosis and fibrotic remodeling indicated by aortic thickening, collagen accumulation, and increased expression of profibrotic cytokines (CTGF and TGF-β). Further investigation showed that irradiation resulted in elevated expression of inflammation-related molecules (TNF-α and ICAM-1) and oxidative stress indicators (4-HNE and 3-NT). Both of the low and high doses of hBMSCs alleviated the above irradiation-induced pathological changes and elevated the antioxidant enzyme expression of HO-1 and catalase in the aorta. The high dose even showed a better protective effect. In conclusion, hBMSCs provide significant protection against RIAI possibly through inhibition of aortic oxidative stress and inflammation. Therefore, hBMSCs can be used as a potential therapy to treat RIAI.

The Role of Nrf2 in Cardiovascular Function and Disease

Free radicals, reactive oxygen/nitrogen species (ROS/RNS), hydrogen sulphide, and hydrogen peroxide play an important role in both intracellular and intercellular signaling; however, their production and quenching need to be closely regulated to prevent cellular damage. An imbalance, due to exogenous sources of free radicals and chronic upregulation of endogenous production, contributes to many pathological conditions including cardiovascular disease and also more general processes involved in aging. Nuclear factor erythroid 2-like 2 (NFE2L2; commonly known as Nrf2) is a transcription factor that plays a major role in the dynamic regulation of a network of antioxidant and cytoprotective genes, through binding to and activating expression of promoters containing the antioxidant response element (ARE). Nrf2 activity is regulated by many mechanisms, suggesting that tight control is necessary for normal cell function and both hypoactivation and hyperactivation of Nrf2 are indicated in playing a role in different aspects of cardiovascular disease. Targeted activation of Nrf2 or downstream genes may prove to be a useful avenue in developing therapeutics to reduce the impact of cardiovascular disease. We will review the current status of Nrf2 and related signaling in cardiovascular disease and its relevance to current and potential treatment strategies.

Diabetes and ageing-induced vascular inflammation

Diabetes and the ageing process independently increase the risk for cardiovascular disease (CVD). Since incidence of diabetes increases as people get older, the diabetic older adults represent the largest population of diabetic subjects. This group of patients would potentially be threatened by the development of CVD related to both ageing and diabetes. The relationship between CVD, ageing and diabetes is explained by the negative impact of these conditions on vascular function. Functional and clinical evidence supports the role of vascular inflammation induced by the ageing process and by diabetes in vascular impairment and CVD. Inflammatory mechanisms in both aged and diabetic vasculature include pro-inflammatory cytokines, vascular hyperactivation of nuclear factor-кB, increased expression of cyclooxygenase and inducible nitric oxide synthase, imbalanced expression of pro/anti-inflammatory microRNAs, and dysfunctional stress-response systems (sirtuins, Nrf2). In contrast, there are scarce data regarding the interaction of these mechanisms when ageing and diabetes co-exist and its impact on vascular function. Older diabetic animals and humans display higher vascular impairment and CVD risk than those either aged or diabetic, suggesting that chronic low-grade inflammation in ageing creates a vascular environment favouring the mechanisms of vascular damage driven by diabetes. Further research is needed to determine the specific inflammatory mechanisms responsible for exacerbated vascular impairment in older diabetic subjects in order to design effective therapeutic interventions to minimize the impact of vascular inflammation. This would help to prevent or delay CVD and the specific clinical manifestations (cognitive decline, frailty and disability) promoted by diabetes-induced vascular impairment in the elderly.

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.

Diabetic cardiomyopathy and its prevention by nrf2: current status

Diabetic cardiomyopathy (DCM), as one of the major cardiac complications in diabetic patients, is known to related with oxidative stress that is due to a severe imbalance between reactive oxygen species (ROS) and/or reactive nitrogen species (RNS) generation and their clearance by antioxidant defense systems. Transcription factor nuclear factor NF-E2-related factor 2 (Nrf2) plays an important role in maintaining the oxidative homeostasis by regulating multiple downstream antioxidants. Diabetes may up-regulate several antioxidants in the heart as a compensative mechanism at early stage, but at late stage, diabetes not only generates extra ROS and/or RNS but also impairs antioxidant capacity in the heart, including Nrf2. In an early study, we have established that Nrf2 protect the cardiac cells and heart from high level of glucose in vitro and hyperglycemia in vivo, and in the following study demonstrated the significant down-regulation of cardiac Nrf2 expression in diabetic animals and patients. Using Nrf2-KO mice or Nrf2 inducers, blooming evidence has indicated the important protection by Nrf2 from cardiac pathogenesis in the diabetes. Therefore, this brief review summarizes the status of studies on Nrf2's role in preventing DCM and even other complications, the need for new and safe Nrf2 inducer screening and the precaution for the undesirable side of Nrf2 under certain conditions.

Inhibition of JNK by compound C66 prevents pathological changes of the aorta in STZ-induced diabetes

Cardiovascular diseases as leading causes of the mortality world-wide are related to diabetes. The present study was to explore the protective effect of curcumin analogue C66 on diabetes-induced pathogenic changes of aortas. Diabetes was induced in male C57BL/6 mice with a single intraperitoneal injection of streptozotocin. Diabetic mice and age-matched non-diabetic mice were randomly treated with either vehicle (Control and Diabetes), C66 (C66 and Diabetes/C66) or c-Jun N-terminal kinase (JNK) inhibitor (sp600125, JNKi and Diabetes/JNKi). All three treatments were given by gavage at 5 mg/kg every other day for 3 months. Aortic inflammation, oxidative stress, fibrosis, cell apoptosis and proliferation, Nrf2 expression and transcription were assessed by immunohistochemical staining for the protein level and real-time PCR method for mRNA level. Diabetes increased aortic wall thickness and structural derangement as well as JNK phosphorylation, all of which were attenuated by C66 treatment as JNKi did. Inhibition of JNK phosphorylation by C66 and JNKi also significantly prevented diabetes-induced increases in inflammation, oxidative and nitrative stress, apoptosis, cell proliferation and fibrosis. Furthermore, inhibition of JNK phosphorylation by C66 and JNKi significantly increased aortic Nrf2 expression and transcription function (e.g. increased expression of Nrf2-downstream genes) in normal and diabetic conditions. These results suggest that diabetes-induced pathological changes in the aorta can be protected by C66 via inhibition of JNK function, accompanied by the up-regulation of Nrf2 expression and function.

Sulforaphane attenuation of type 2 diabetes-induced aortic damage was associated with the upregulation of Nrf2 expression and function

Type 2 diabetes mellitus (T2DM) significantly increases risk for vascular complications. Diabetes-induced aorta pathological changes are predominantly attributed to oxidative stress. Nuclear factor E2-related factor-2 (Nrf2) is a transcription factor orchestrating antioxidant and cytoprotective responses to oxidative stress. Sulforaphane protects against oxidative damage by increasing Nrf2 expression and its downstream target genes. Here we explored the protective effect of sulforaphane on T2DM-induced aortic pathogenic changes in C57BL/6J mice which were fed with high-fat diet for 3 months, followed by a treatment with streptozotocin at 100 mg/kg body weight. Diabetic and nondiabetic mice were randomly divided into groups with and without 4-month sulforaphane treatment. Aorta of T2DM mice exhibited significant increases in the wall thickness and structural derangement, along with significant increases in fibrosis (connective tissue growth factor and transforming growth factor), inflammation (tumor necrosis factor-α and vascular cell adhesion molecule 1), oxidative/nitrative stress (3-nitrotyrosine and 4-hydroxy-2-nonenal), apoptosis, and cell proliferation. However, these pathological changes were significantly attenuated by sulforaphane treatment that was associated with a significant upregulation of Nrf2 expression and function. These results suggest that sulforaphane is able to upregulate aortic Nrf2 expression and function and to protect the aorta from T2DM-induced pathological changes.

Combating oxidative stress in diabetic complications with Nrf2 activators: how much is too much?

Diabetes is increasing at an alarming rate and, despite anti-hypertensive and insulin therapies, diabetic patients are still at risk of developing complications such as chronic kidney disease, cardiovascular disease, and retinopathy. There is therefore an urgent need for more effective therapies to prevent the development and progression of diabetic complications. Oxidative stress is a major player in the aetiology of diabetic complications. However, results from clinical trials thus far using general antioxidants have been disappointing. Mechanism-based antioxidants have gained considerable attention due to their more targeted approach at reducing oxidative stress and associated complications in diabetes. The transcription factor, NFE2-related factor 2 (Nrf2), is a master regulator of redox homeostasis and the cellular detoxification response. Instead of relying on a single antioxidant, activation of Nrf2 results in the concerted upregulation of several antioxidant enzymes and cytoprotective genes, making it an attractive therapeutic target for diabetic complications. Several Nrf2 activators have been discovered and have proven effective at activating Nrf2 signalling through different mechanisms in both in vitro and in vivo models of diabetes. This review will address some of the most promising and well-known Nrf2 activators and their roles in preventing the development and progression of diabetic complications. Challenges facing the advancement of this drug class into the clinic will be discussed, as will be the future of Nrf2 activation as a therapeutic strategy in preventing the development of diabetic complications.