Diabetes aggravates renal ischemia and reperfusion injury in rats by exacerbating oxidative stress, inflammation, and apoptosis
Diabetic patients are more susceptible to renal ischemia/reperfusion (I/R) injury (RI/RI) and have a poor prognosis, but the underlying mechanism remains unclear. The present study aimed to examine whether diabetes could worsen acute kidney injury induced by I/R in rats and clarify its mechanism. Control and streptozotocin-induced diabetic rats were subjected to 45 min renal pedicle occlusion followed by 24 h reperfusion. Tert-butylhydroquinone (TBHQ, 16.7 mg/kg) was administrated intraperitoneally 3 times at intervals of 8 h before ischemia. Serum and kidneys were harvested after reperfusion to evaluate renal function and histological injury. Enzyme-linked immunosorbent assays were used to test pro-inflammatory cytokines. Terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labeling assays were used to detect apoptotic cells, and western blotting was performed to determine the expression of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), and cleaved caspase-3, as well as oxidative stress and inflammation-related proteins, such as nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), Toll-like receptor 4 (TLR4), and nuclear factor-κB (NF-κB). Compared with control animals, diabetic rats undergoing I/R exhibited more severe tubular damage and renal dysfunction. Diabetes exacerbated oxidative stress, the inflammatory response, and apoptosis after renal I/R by enhancing TLR4/NF-κB signaling and blocking the Nrf2/HO-1 pathway. RI/RI in diabetic rats was attenuated by pretreatment with TBHQ (a Nrf2 agonist), which exerted anti-inflammatory and anti-apoptotic properties by inhibiting NF-κB signaling. These findings indicate that hyperglycemia exacerbates RI/RI by intensifying oxidative stress, inflammation, and apoptosis. Antioxidant pretreatment may alleviate RI/RI in diabetic patients.
Berberine ameliorates CCl4‑induced liver injury in rats through regulation of the Nrf2‑Keap1‑ARE and p53 signaling pathways
Berberine (BBR) is an isoquinoline alkaloid, reported to have multiple pharmacological functions. However, its effects against CCl4‑induced oxidative damage remain poorly studied. Therefore, the present study investigated the protective action of BBR, and its antioxidant mechanisms, against CCl4‑induced liver injury in rats. A total of 48 rats were randomly arranged into six groups: Control; model; positive control (PC); BBR low‑dose (BL); BBR middle‑dose (BM); and BBR high‑dose (BH). The BL, BM and BH animals received BBR (5, 10 and 15 mg/kg by weight, respectively) orally for 7 consecutive days. Rats in the PC group were given silymarin (150 mg/kg), and the control and model groups were administered distilled water orally. At the end of the experiment, blood samples and livers were collected. To measure the liver biochemical indices, the reactive oxygen species (ROS) generation and the expression levels of related genes and protein, the following methods were used: An automatic biochemical analyzer; flow cytometry; spectrophotometry; reverse transcription‑quantitative PCR; western blotting; and hematoxylin and eosin staining. The results revealed that BBR significantly decreased the serum levels of alanine transaminase, aspartate transaminase and alkaline phosphatase, and increased those of glutathione and superoxide dismutase, but decreased malondialdehyde activity in hepatic tissue, and significantly decreased the reactive oxygen species level in hepatocytes. In hepatic tissue, the expressions of nuclear factor erythroid 2‑related factor 2 (Nrf2), kelch‑like ECH‑associated protein 1 (Keap-1), NAD(P)H quinone dehydrogenase 1 (NQO-1), heme oxygenase 1 (HO‑1), Bcl‑2 and Bcl‑xL mRNA, and HO‑1 protein were elevated, and the expression of p53 mRNA was decreased, particularly in the BH group (15 mg/kg). In conclusion, BBR exerts a protective action against CCl4‑induced acute liver injury in rats via effectively regulating the expression of Nrf2‑Keap1‑antioxidant responsive element‑related genes and proteins, and inhibiting p53 pathway‑mediated hepatocyte apoptosis.
Reduced skeletal muscle expression of mitochondrial derived peptides humanin and MOTS-C and Nrf2 in chronic kidney disease
Reduced skeletal muscle expression of mitochondrial derived peptides humanin and MOTS-C and Nrf2 in chronic kidney disease Advanced chronic kidney disease (CKD) is characterized by a premature ageing phenotype of multifactorial origin. Mitochondrial dysfunction is prevalent in CKD and has been proposed as a major contributor to poor muscle function. Although mitochondrial derived peptides (MDPs) humanin and mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) are involved in cell survival, suppression of apoptosis and glucose control, the implications of MDP in CKD are unknown. We investigated humanin and MOTS-c protein expression in skeletal muscle and serum levels in CKD 5patients and age-matched controls with normal renal function. Whereas circulating levels of humanin were increased in CKD, the local muscle expression was reduced. In contrast, MOTS-c levels were reduced in both skeletal muscle and serum in CKD. Humanin in serum correlated positively to circulating TNF levels. Reduced MDP levels in skeletal muscle were associated with lower mitochondrial density and evidence of oxidative stress. These results indicate a differential regulation of MDPs in CKD and suggest an alternative site for humanin production than skeletal muscle in the uremic milieu. MDP levels were linked to systemic inflammation and evidence of oxidative stress in the muscle, two hallmark features of premature ageing and uremia.
Antioxidant Defenses: A Context-Specific Vulnerability of Cancer Cells
Reactive oxygen species (ROS) are well known for their capacity to cause DNA damage, augment mutagenesis, and thereby promote oncogenic transformation. Similarly, agents that reduce ROS levels (antioxidants) are frequently thought to have anti-cancer properties given their propensity to minimize DNA damage and mutagenesis. However, numerous clinical studies focused on antioxidants suggest that this is a facile premise and that antioxidant capacity can be important for cancer cells in a similar fashion to normal cells. As a consequence of this realization, numerous laboratories have been motivated to investigate the biological underpinnings explaining how and when antioxidant activity can potentially be beneficial to cancer cells. Relatedly, it has become clear that the reliance of cancer cells on antioxidant activity in certain contexts represents a potential vulnerability that could be exploited for therapeutic gain. Here, we review some of the recent, exciting findings documenting how cancer cells utilized antioxidant activity and under what circumstances this activity could represent an opportunity for selective elimination of cancer cells.
Can Nrf2 Modulate the Development of Intestinal Fibrosis and Cancer in Inflammatory Bowel Disease?
One of the main mechanisms carried out by the cells to counteract several forms of stress is the activation of the nuclear factor erythroid 2-related factor (Nrf2) signaling. Nrf2 signaling controls the expression of many genes through the binding of a specific -acting element known as the antioxidant response element (ARE). Activation of Nrf2/ARE signaling can mitigate several pathologic mechanisms associated with an autoimmune response, digestive and metabolic disorders, as well as respiratory, cardiovascular, and neurodegenerative diseases. Indeed, several studies have demonstrated that Nrf2 pathway plays a key role in inflammation and in cancer development in many organs, including the intestine. Nrf2 appears to be involved in inflammatory bowel disease (IBD), an immune-mediated chronic and disabling disease, with a high risk of developing intestinal fibrotic strictures and cancer. Currently, drugs able to increase cytoprotective Nrf2 function are in clinical trials or already being used in clinical practice to reduce the progression of some degenerative conditions. The role of Nrf2 in cancer development and progression is controversial, and drugs able to inhibit abnormal levels of Nrf2 are also under investigation. The goal of this review is to analyze and discuss Nrf2-dependent signals in the initiation and progression of intestinal fibrosis and cancers occurring in IBD.
Cytoplasmic DAXX drives SQSTM1/p62 phase condensation to activate Nrf2-mediated stress response
Autophagy cargo recognition and clearance are essential for intracellular protein quality control. SQSTM1/p62 sequesters intracellular aberrant proteins and mediates cargo delivery for their selective autophagic degradation. The formation of p62 non-membrane-bound liquid compartments is critical for its function as a cargo receptor. The regulation of p62 phase separation/condensation has yet been poorly characterised. Using an unbiased yeast two-hybrid screening and complementary approaches, we found that DAXX physically interacts with p62. Cytoplasmic DAXX promotes p62 puncta formation. We further elucidate that DAXX drives p62 liquid phase condensation by inducing p62 oligomerisation. This effect promotes p62 recruitment of Keap1 and subsequent Nrf2-mediated stress response. The present study suggests a mechanism of p62 phase condensation by a protein interaction, and indicates that DAXX regulates redox homoeostasis, providing a mechanistic insight into the prosurvival function of DAXX.
Resolvin D1 attenuates ventilator-induced lung injury by reducing HMGB1 release in a HO-1-dependent pathway
Mechanical ventilation (MV) is a major support for patients with severe clinical disease, surgery and anesthesia. However, complications of mechanical ventilation especially ventilator-induced lung injury(VILI) can make the course and prognosis worse. Resolvin D1(RvD1) is a class of endogenous polyunsaturated fatty acid derivative, which has protective effects on various pulmonary inflammatory diseases. However, the mechanism of RvD1 in the process of VILI has not been fully elucidated. Our study found that RvD1 does have a protective effect on VILI including inhibiting inflammatory responses, reducing tissue damage and improving pulmonary function. The protective effect of RvD1 is positively related to its dose. Our research suggested RvD1 plays a role that increases the expression of heme oxygenase‑1 (HO-1) and decreases the expression of the high mobility group chromosomal protein B1 (HMGB-1) in VILI. HO-1 can exert the protective effect of organism through multiple mechanisms such as anti-inflammatory, anti-oxidation, anti-apoptosis, etc. HMGB1 is a potent inflammatory response factor in the body, which can aggravate the inflammatory response of the body. Our study demonstrated that RvD1 can ameliorate lung inflammation and reduce pathological changes in lung tissue in a model of lung injury induced by mechanical ventilation. The protective role of RvD1 is closely linked to the increased expression of HO-1 and the decreased expression of HMGB1. Moreover, we found that RvD1 can increase the expression of Nrf2 and inhibit the expression of NF-κB. We found the specific inhibitor of HO-1, ZnPP, can significantly inhibit the protective role of RvD1 in VILI. When HO-1 is inhibited, pathological damage and inflammatory reaction in the lungs are considerably aggravated, and pulmonary function is significantly weakened. In addition, the expression of HMGB1 is drastically increased. This indicates that the HO-1-HMGB1 pathway plays an important role in the protective effect of RvD1 on mechanical ventilation lung injury.
Rosmarinic Acid, the Main Effective Constituent of Orthosiphon stamineus, Inhibits Intestinal Epithelial Apoptosis Via Regulation of the Nrf2 Pathway in Mice
Many studies have shown that Orthosiphon stamineus extract (OE) has antioxidant activity, and we previously reported that OE protects the intestine against injury from a high-fat diet. However, the molecular mechanism underlying this protective effect of OE was unclear. Here, OE was separated according to polarity and molecular weight, and the antioxidant activity of each component was compared. The components with the highest antioxidant activity were analyzed by HPLC, which confirmed that rosmarinic acid (RA) was the main effective constituent in OE. OE and RA were then tested in a mouse high-fat diet-induced intestinal injury model. The antioxidant indices and morphological characteristics of the mouse jejunum were measured, and activation of the nuclear factor E2-related factor 2 (Nrf2) pathway and apoptosis of jejunal epithelial cells were analyzed. Of all the constituents in OE, RA contributed the most. Both RA and OE activated the Nrf2 pathway and increased downstream antioxidant enzyme activity. RA and OE protected the mouse intestine against high-fat diet-induced oxidative stress by preventing intestinal epithelial cell apoptosis via both extracellular and intracellular pathways. Thus, RA, the main effective constituent in OE, inhibits intestinal epithelial apoptosis by regulating the Nrf2 pathway in mice.
Pachypodol, a Methoxyflavonoid Isolated from Bentham Exerts Antioxidant and Cytoprotective Effects in HepG2 Cells: Possible Role of ERK-Dependent Nrf2 Activation
Oxidative stress has been implicated in the pathogenesis of many diseases including chronic liver diseases. Nrf2 is a master transcriptional factor regulating the induction of cellular antioxidant defense systems. Here, the Nrf2-activating effect of the crude methanol extract of dried leaves of Bentham was demonstrated by measuring the antioxidant response element (ARE)-driven luciferase activity and pachypodol, 4',5-dihydroxy-3,3',7-trimethoxyflavone, was isolated by bioactivity-guided fractionation and further separation using chromatographic techniques. To our knowledge, this is the first study to evaluate the antioxidant and cytoprotective effects of pachypodol in HepG2 cells as well as the underlying molecular mechanisms. Indeed, pachypodol protected HepG2 cells from cell death caused by -butylhydroperoxide-induced oxidative stress and also attenuated ROS production. The ability of pachypodol to activate Nrf2/ARE pathway was further confirmed by observing Nrf2 expression in nuclear fraction, mRNA levels of Nrf2 target antioxidants, and cellular glutathione content in HepG2 cells. Extracellular signal-regulated kinase (ERK) is one of the important kinases involved in Nrf2 activation. Pachypodol increased ERK phosphorylation and ERK inhibition by PD98059 totally abrogated the increase in ARE luciferase activity, nuclear Nrf2 accumulation and mRNA levels of antioxidant enzymes by pachypodol. In conclusion, pachypodol isolated from can protect hepatocytes from oxidative injury, possibly mediated by enhancing endogenous antioxidant defense system through ERK-dependent Nrf2 activation.
Melatonin Treatment Ameliorates Hyperhomocysteinemia-Induced Impairment of Erectile Function in a Rat Model
Hyperhomocysteinemia (HHcy) has been reported to be strongly correlated with the occurrence of erectile dysfunction (ED), but the mechanisms are not fully understood. Moreover, whether melatonin could be a potential treatment of HHcy-induced ED needs to be elucidated.
Histone chaperone FACT complex mediates oxidative stress response to promote liver cancer progression
Facilitates Chromatin Transcription (FACT) complex is a histone chaperone participating in DNA repair-related and transcription-related chromatin dynamics. In this study, we investigated its oncogenic functions, underlying mechanisms and therapeutic implications in human hepatocellular carcinoma (HCC).
The anti-nephritic activity of a polysaccharide from okra (Abelmoschus esculentus (L.) Moench) via modulation of AMPK-Sirt1-PGC-1α signaling axis mediated anti-oxidative in type 2 diabetes model mice
Diabetic nephropathy (DN) with high morbidity and mortality is one of the most severe diabetes complications and affects nearly one-third of people with diabetes. Our present experiment was designed to assess the potential therapeutic of a polysaccharide purified from okra (OP) on DN in high-fat diet-fed and streptozotocin (STZ)-induced diabetic mice. We found that an 8-week treatment with OP could significantly decrease the 24-h urine protein (24-h UP), serum creatinine (Scr), serum urea nitrogen (SUN) and glycosylated hemoglobin (HbA1c) levels, which are regard as the biomarkers of renal injury. The results of immunohistochemical analysis and histopathological examination showed that the diabetic-induced microstructural changes and fibrosis in kidney can be alleviated by the administration of OP (400 mg/kg). Our immunofluorescences results demonstrated that OP (400 mg/kg) could greatly reduce the level of reactive oxygen species (ROS) in kidney. In addition, we also studied the level of SOD, GSH, CAT, HO-1, Nrf2, p-AMPK, PGC-1α, Sirt1, Bcl-2, cleaved caspase-3 and Bax in renal tissue by assay kit and western blot. Our results suggested that OP ameliorated DN in diabetic mice, which is possibly related to suppressing apoptosis and oxidative stress through activating AMPK-Sirt1-PGC-1α signaling axis.
Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) contributes to the neuroprotective effects of histone deacetylase inhibitors in retinal ischemia-reperfusion injury
Histone deacetylase inhibitors (HDACis) have displayed neuroprotective effects in animal models of retinal ischemia/reperfusion (I/R) injury. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a redox-sensitive transcription factor responds to oxidative damage. We investigated the role of Nrf2 in retinal I/R injury, and further explored the mechanisms underlying Nrf2-mediated neuroprotection exerted by HDACi. High intraocular pressure was used to establish retinal I/R model in wild type (WT) and Nrf2 knockout (KO) mice. Nrf2 KO mice displayed more severe retinal damage after I/R. Trichostatin A (TSA) was administered to both WT and Nrf2 KO mice with retinal I/R damage. TSA significantly diminished the retinal ganglion cell degeneration in WT mice but offered no notable protection in Nrf2 KO mice. TSA markedly promoted Nrf2 nuclear translocation and its acetylation. In addition, TSA upregulated Nrf2 downstream proteins, such as Ho-1 and Nqo1, in retinal tissues. In the retinal neuronal cell line 661W, TSA reduced the expression of proinflammatory cytokines, Il-1β, Il-6, Tnf-α and Mmp-9, and it upregulated Bdnf under oxidative stress. However, this trend was not continued after silencing Nrf2. Chromatin immunoprecipitation assay demonstrated that Nrf2 at the Ho-1 promoter significantly increased transcriptional activity after oxidative stress induction. Nrf2, which is dispensable in HDACi-mediated neuroprotection, plays a major neuroprotective role in retinal I/R injury.
[Effects of hydrogen on lung injury in wild-type and Nrf2 gene knockout mice: relationship with Nrf2/HO-1/HMGB1 pathway]
To investigate the key role of nuclear factor E2-related factor 2 (Nrf2) in the treatment of lung injury in sepsis mice by regulating Nrf2/heme oxygenase-1 (HO-1)/high mobility group protein B1 (HMGB1) pathway.
17-β estradiol exerts anti-inflammatory effects through activation of Nrf2 in mouse embryonic fibroblasts
Several reports indicate crosstalk between the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and estrogen, which has a protective effect in colorectal cancer (CRC). The aim of this study was to investigate the role of Nrf2 signaling in the anti-inflammatory effect of estrogen using Nrf2 knockout (Nrf2 KO) mouse embryonic fibroblasts (MEFs), a powerful system to test the function of target genes due to their easy accessibility, and rapid growth rates. After inducing inflammation by tumor necrosis factor alpha (TNF-α), the effects of 17β-estradiol (E2) on the expression of proinflammatory mediators [i.e., NF-κB and inducible nitric oxide synthase (iNOS)] and estrogen receptors were evaluated by Western blot. In wild type (WT) MEFs, E2 treatment ameliorated TNF-α-induced nuclear translocation of NF-κB and expression of its target protein iNOS. Estrogen receptor beta (ERβ) expression was decreased by TNF-α-induced inflammation and restored by E2 treatment. When treated to WT MEFs, E2 induced nuclear translocation of Nrf2. The inhibitory effect of E2 on TNF-α-induced enhancement of iNOS was markedly dampened in Nrf2 KO MEFs. Notably, ERβ expression was significantly diminished in Nrf2 KO MEFs compared to that in WT cells. Promoter Database (EPD) revealed two putative anti-oxidant response elements (AREs) within the mouse ERβ promoter. Furthermore, in WT MEFs, E2 treatment repressed TNF-α-induced expression of iNOS protein and recovered by 4-(2-phenyl-5,7-bis(trifluoromethyl)pyrazolo(1,5-a)pyrimidin-3-yl)phenol (PHTPP), a selective ERβ antagonist, treatment, but not in Nrf2 KO MEFs. In conclusion, Nrf2 plays a pivotal role in the anti-inflammatory of estrogen by direct regulating the expression of ERβ.