Beneficial effects of bardoxolone methyl, an Nrf2 activator, on crush-related acute kidney injury in rats

Piceatannol promotes neuroprotection by inducing mitophagy and mitobiogenesis in the experimental diabetic peripheral neuropathy and hyperglycemia-induced neurotoxicity

Piceatannol (PCN), a SIRT1 activator, regulates multiple oxidative stress mechanism and has anti-inflammatory potential in various inflammatory conditions. However, its role in Diabetic insulted peripheral neuropathy (DN) remains unknown. Oxidative stress and mitochondrial dysfunction are major contributing factors to DN. Myriad studies have proven that sirtuin1 (SIRT1) stimulation convalesce nerve functions by activating mitochondrial functions like mitochondrial biogenesis and mitophagy. Diabetic neuropathy (DN) was provoked by injecting streptozotocin (STZ) at a dose of 55 mg/kg, i.p to male Sprague Dawley (SD) rats. Mechanical, thermal hyperalgesia was evaluated by using water immersion, Vonfrey Aesthesiometer, and Randall Sellito Calipers. Motor, sensory nerve conduction velocity was measured using Power Lab 4sp system whereas The Laser Doppler system was used to evaluate nerve blood flow. To induce hyperglycemia for the in vitro investigations, high glucose (HG) (30 mM) conditions were applied to Neuro2a cells. At doses of 5 and 10 µM, PCN was examined for its role in SIRT1 and Nrf2 activation. HG-induced N2A cells, reactive oxygen exposure, mitochondrial superoxides and mitochondrial membrane potentials were restored by PCN exposure, and their neurite outgrowth was enhanced. Peroxisome proliferator activated receptor-gamma coactivator-1α (PGC-1α) directed mitochondrial biogenesis was induced by increased SIRT1 activation by piceatannol. SIRT1 activation also enhanced Nrf2-mediated antioxidant signalling. Our study results inferred that PCN administration can counteract the decline in mitochondrial function and antioxidant activity in diabetic rats and HG-exposed N2A cells by increasing the SIRT1 and Nrf2 activities.

Bardoxolone methyl ameliorates osteoarthritis by inhibiting osteoclastogenesis and protecting the extracellular matrix against degradation

Inflammation and oxidative damage are closely related to the development of osteoarthritis. Bardoxolone methyl (CDDO-Me), a semisynthetic oleanane triterpenoid, plays a strong anti-inflammatory and antioxidant role. The purpose of our research was to explore fundamental mechanisms of CDDO-Me in orthopaedics development. The results showed that CDDO-Me inhibited nuclear factor-κB ligand (RANKL)-induced osteoclast formation and extracellular matrix (ECM) degradation by activating the Nrf2/HO-1 signaling pathways and inhibiting NF-κB pathway activation and excess ROS production. In vivo, CDDO-Me significantly attenuated articular cartilage proteoglycan loss and the number of TRAP-positive osteoclasts in a destabilized medial meniscus (DMM) mouse model of OA. Taken together, these data demonstrate that CDDO-Me inhibits osteoclastogenesis and ECM degradation, underscoring its potential therapeutic value in treating OA.

Heme Proteins and Kidney Injury: Beyond Rhabdomyolysis

Heme proteins, the stuff of life, represent an ingenious biologic strategy that capitalizes on the biochemical versatility of heme, and yet is one that avoids the inherent risks to cellular vitality posed by unfettered and promiscuously reactive heme. Heme proteins, however, may be a double-edged sword because they can damage the kidney in certain settings. Although such injury is often viewed mainly within the context of rhabdomyolysis and the nephrotoxicity of myoglobin, an increasing literature now attests to the fact that involvement of heme proteins in renal injury ranges well beyond the confines of this single disease (and its analog, hemolysis); indeed, through the release of the defining heme motif, destabilization of intracellular heme proteins may be a common pathway for acute kidney injury, in general, and irrespective of the underlying insult. This brief review outlines current understanding regarding processes underlying such heme protein-induced acute kidney injury (AKI) and chronic kidney disease (CKD). Topics covered include, among others, the basis for renal injury after the exposure of the kidney to and its incorporation of myoglobin and hemoglobin; auto-oxidation of myoglobin and hemoglobin; destabilization of heme proteins and the release of heme; heme/iron/oxidant pathways of renal injury; generation of reactive oxygen species and reactive nitrogen species by NOX, iNOS, and myeloperoxidase; and the role of circulating cell-free hemoglobin in AKI and CKD. Also covered are the characteristics of the kidney that render this organ uniquely vulnerable to injury after myolysis and hemolysis, and pathobiologic effects emanating from free, labile heme. Mechanisms that defend against the toxicity of heme proteins are discussed, and the review concludes by outlining the therapeutic strategies that have arisen from current understanding of mechanisms of renal injury caused by heme proteins and how such mechanisms may be interrupted.

Activation of SIRT1 by silibinin improved mitochondrial health and alleviated the oxidative damage in experimental diabetic neuropathy and high glucose-mediated neurotoxicity

BACKGROUND

Silibinin (SBN), a sirtuin 1 (SIRT1) activator, has been evaluated for its anti-inflammatory activity in many inflammatory diseases. However, its role in diabetes-induced peripheral neuropathy (DPN) remains unknown. The SIRT1 activation convalesces nerve functions by improving mitochondrial biogenesis and mitophagy.

METHODS

DPN was induced by streptozotocin (STZ) at a dose of 55 mg/kg, i.p. in the male SD rats whereas neurotoxicity was induced in Neuro2A cells by 30 mM (high glucose) glucose. Neurobehavioural (nerve conduction velocity and nerve blood flow) western blot, immunohistochemistry, and immunocytochemistry were performed to evaluate the protein expression and their cellular localisation.

RESULTS

Two-week SBN treatment improved neurobehavioural symptoms, SIRT1, PGC-1α, and TFAM expression in the sciatic nerve and HG insulted N2A cells. It has also maintained the mitophagy by up-regulating PARL, PINK1, PGAM5, LC3 level and provided antioxidant defence by upregulating Nrf2.

CONCLUSION

SBN has shown neuroprotective potential in DPN through SIRT1 activation and antioxidant mechanism.

Bardoxolone-Methyl Prevents Oxidative Stress-Mediated Apoptosis and Extracellular Matrix Degradation in vitro and Alleviates Osteoarthritis in vivo

PURPOSE

Oxidative stress-induced chondrocyte apoptosis and extracellular matrix (ECM) degradation plays an important role in the progression of osteoarthritis (OA). Bardoxolone methyl (BM), a semisynthetic triterpenoid, exerts strong effect against oxidative stress. The purpose of the present study was to determine the effectiveness of bardoxolone-methyl (BM) in preventing oxidative stress-induced chondrocyte apoptosis and extracellular ECM degradation in vitro and the role of alleviating OA progression in vivo.

METHODS

Oxidative damage was induced by 25 mM tert-butyl hydroperoxide (TBHP) for 24 h in rat chondrocytes. 0.025 and 0.05 µM bardoxolone-methyl (BM) were used in vitro treatment. Ex-vivo cartilage explant model was established to evaluate the effect of BM on oxidative stress-induced ECM degradation. The mouse OA model was induced by surgical destabilization of the medial meniscus.

RESULTS

In vitro, 0.025 and 0.05 µM BM reduced TBHP-induced excessive ROS generation, improved cell viability, increased malondialdehyde level and decreased superoxide dismutase level. 0.025 and 0.05 µM BM prevented TBHP-induced mitochondrial damage and apoptosis in chondrocytes BM activated heme oxygenase-1 (HO-1)/NADPH quinone oxidoreductase 1 (NOQ1) signaling pathway through targeting nuclear factor erythroid derived-2-related factor 2 (Nrf2). Additionally, BM treatment enhanced the expression levels of aggrecan and collagen II and inhibited the expression levels of matrix metalloproteinase 9 (MMP 9), MMP 13, Bax and cleaved-caspase-3. BM increased proteoglycan staining area and IOD value in ex vivo cultured experiment cartilage explants and improved the OARSI score, stands, max contact mean intensity, print area and duty cycle in mouse OA model.

CONCLUSION

BM prevented oxidative stress-induced chondrocyte apoptosis and ECM degradation in vitro and alleviated OA in vivo, suggesting that BM serves as an effective drug for treatment with OA.

RIG-I, a novel DAMPs sensor for myoglobin activates NF-κB/caspase-3 signaling in CS-AKI model

BACKGROUND

Acute kidney injury (AKI) is the main life-threatening complication of crush syndrome (CS), and myoglobin is accepted as the main pathogenic factor. The pattern recognition receptor retinoicacid-inducible gene I (RIG-I) has been reported to exert anti-viral effects function in the innate immune response. However, it is not clear whether RIG-I plays a role in CS-AKI. The present research was carried out to explore the role of RIG-I in CS-AKI.

METHODS

Sprague-Dawley rats were randomly divided into two groups: the sham and CS groups (n = 12). After administration of anesthesia, the double hind limbs of rats in the CS group were put under a pressure of 3 kg for 16 h to mimic crush conditions. The rats in both groups were denied access to food and water. Rats were sacrificed at 12 h or 36 h after pressure was relieved. The successful establishment of the CS-AKI model was confirmed by serum biochemical analysis and renal histological examination. In addition, RNA sequencing was performed on rat kidney tissue to identify molecular pathways involved in CS-AKI. Furthermore, NRK-52E cells were treated with 200 μmol/L ferrous myoglobin to mimic CS-AKI at the cellular level. The cells and cell supernatant samples were collected at 6 h or 24 h. Small interfering RNAs (siRNA) was used to knock down RIG-I expression. The relative expression levels of molecules involved in the RIG-I pathway in rat kidney or cells samples were measured by quantitative Real-time PCR (qPCR), Western blotting analysis, and immunohistochemistry (IHC) staining. Tumor necrosis factor-α (TNF-α) was detected by ELISA. Co-Immunoprecipitation (Co-IP) assays were used to detect the interaction between RIG-I and myoglobin.

RESULTS

RNA sequencing of CS-AKI rat kidney tissue revealed that the different expression of RIG-I signaling pathway. qPCR, Western blotting, and IHC assays showed that RIG-I, nuclear factor kappa-B (NF-κB) P65, p-P65, and the apoptotic marker caspase-3 and cleaved caspase-3 were up-regulated in the CS group (P < 0.05). However, the levels of interferon regulatory factor 3 (IRF3), p-IRF3 and the antiviral factor interferon-beta (IFN-β) showed no significant changes between the sham and CS groups. Co-IP assays showed the interaction between RIG-I and myoglobin in the kidneys of the CS group. Depletion of RIG-I could alleviate the myoglobin induced expression of apoptosis-associated molecules via the NF-κB/caspase-3 axis.

CONCLUSION

RIG-I is a novel damage-associated molecular patterns (DAMPs) sensor for myoglobin and participates in the NF-κB/caspase-3 signaling pathway in CS-AKI. In the development of CS-AKI, specific intervention in the RIG-I pathway might be a potential therapeutic strategy for CS-AKI.

Emerging medical therapies in crush syndrome - progress report from basic sciences and potential future avenues

Crush injury is a disease that is commonly found in victims of earthquakes, debris flows, mine disasters, explosions, terrorist attacks, local wars, and other accidents. The complications that arise due to the crush injury inflicted on victims give rise to crush syndrome (CS). If not treated in time, the mortality rate of CS is very high. The most important measure that can be taken to reduce mortality in such situations is to immediately start treatment. However, the traditional treatment methods such as fluid resuscitation, diuresis, and hemodialysis are not feasible enough to be carried out at the disaster scene. So there is a need for developing new treatments that are efficient and convenient. Because it is difficult to diagnose in the disaster area and reach the treatment equipment and treat on time. It has become a new research needs to be directed into identifying new medical treatment targets and methods using the etiology and pathophysiological mechanisms of CS. In recent years, a large number of new anti-oxidant and anti-inflammatory drug therapies have been shown to be highly efficacious in CS rat/mouse models. Some of them are expected to become specific drugs for the emergency treatment of a large number of patients who may develop CS in the aftermath of earthquakes, wars, and other disasters in the future. Hence, we have reviewed the latest research on the medical therapy of CS as a source for anyone wishing to pursue research in this direction.

TUNEL Assay: A Powerful Tool for Kidney Injury Evaluation

Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay is a long-established assay used to detect cell death-associated DNA fragmentation (3'-OH DNA termini) by endonucleases. Because these enzymes are particularly active in the kidney, TUNEL is widely used to identify and quantify DNA fragmentation and cell death in cultured kidney cells and animal and human kidneys resulting from toxic or hypoxic injury. The early characterization of TUNEL as an apoptotic assay has led to numerous misinterpretations of the mechanisms of kidney cell injury. Nevertheless, TUNEL is becoming increasingly popular for kidney injury assessment because it can be used universally in cultured and tissue cells and for all mechanisms of cell death. Furthermore, it is sensitive, accurate, quantitative, easily linked to particular cells or tissue compartments, and can be combined with immunohistochemistry to allow reliable identification of cell types or likely mechanisms of cell death. Traditionally, TUNEL analysis has been limited to the presence or absence of a TUNEL signal. However, additional information on the mechanism of cell death can be obtained from the analysis of TUNEL patterns.

β1-Blocker improves survival and ventricular remodelling in rats with lethal crush injury

BACKGROUND

Crush injury/crush syndrome (CI/CS) is the second most common cause of death during earthquakes. Most studies of CI/CS have mainly focused on kidney injury after decompression. Few studies have focused on myocardial injury caused by crush injury and its potential mechanisms.

METHODS

We first verified cardiomyocyte injury during compression in rats with a crush injury. The survival rate, electrocardiographic results, histological results, catecholamine changes and cardiac β1-AR expression were evaluated. Next, we explored the effects of pretreatment with a selective β1-blocker (bisoprolol) with or without fluid resuscitation on rats with a crush injury. In addition to evaluating the survival rates, biochemical and histological analyses and echocardiographic measurements were also performed.

RESULTS

Reduced heart rates, elevated ST segments, and tall-peaked T waves were observed in the rats with a crush injury. The changes in the myocardial enzymes and pathological results demonstrated that myocardial damage occurred during compression in rats with a crush injury. The levels of the catecholamine norepinephrine in both the serum and myocardial tissue were elevated during compression. Pretreatment with a selective β1-blocker combined with fluid resuscitation significantly improved the survival rates of the rats with lethal crush injury. The myocardial enzymes and pathological results showed that the combined therapy decreased myocardial damage. The echocardiography measurements showed that the rats that received the combined therapy exhibited decreased left ventricular mass (LVM), left ventricular volume at end-systole (LVVs) and left ventricular internal diameter (LVID) compared with the rats with a crush injury.

CONCLUSIONS

Our findings demonstrated the presence of myocardial injury in the early stage of compression in rats with a crush injury. Pretreatment with a β1-blocker (bisoprolol) with fluid resuscitation significantly reduced mortality, decreased myocardial tissue damage, and improved ventricular remodelling in rats with a lethal crush injury.