Nitro-oleic acid ameliorates oxygen and glucose deprivation/re-oxygenation triggered oxidative stress in renal tubular cells via activation of Nrf2 and suppression of NADPH oxidase

Cell-type specific anti-cancerous effects of nitro-oleic acid and its combination with gamma irradiation

Nitro-fatty acids (NFAs) are endogenous lipid mediators capable of post-translational modifications of selected regulatory proteins. Here, we investigated the anti-cancerous effects of nitro-oleic acid (NO2OA) and its combination with gamma irradiation on different cancer cell lines. The effects of NO2OA on cell death, cell cycle distribution, or expression of p21 and cyclin D1 proteins were analyzed in cancer (A-549, HT-29 and FaDu) or normal cell lines (HGF, HFF-1). Dose enhancement ratio at 50 % survival fraction (DERIC50) was calculated for samples pre-treated with NO2OA followed by gamma irradiation. NO2OA suppressed viability and induced apoptotic cell death. These effects were cell line specific but not in general selective for cancer cells. HT-29 cell line exerted higher sensitivity toward NO2OA treatment among cancer cell lines tested: induction of cell cycle arrest in the G2/M phase was associated with an increase in p21 and a decrease in cyclin D1 expression. Pre-treatment of HT-29 cells with NO2OA prior irradiation showed a significantly increased DERIC50, demonstrating radiosensitizing effects. In conclusion, NO2OA exhibited potential for combined chemoradiotherapy. Our results encourage the development of new NFAs with improved features for cancer chemoradiation.

Impaired NRF2 Inhibits Recovery from Ischemic Reperfusion Injury in the Aging Kidney

Deteriorating kidney function is frequently observed in the elderly population, as well as vulnerability to acute kidney failure, such as ischemic/reperfusion injury (IRI), and inadequate recovery from IRI is one of the mechanisms of kidney dysfunction in the elderly. The potential mediators in the progression of kidney dysfunction in the aging kidney have not yet been clearly revealed. In this study, we investigated the role of nuclear factor erythroid 2-related factor 2 (NRF2), which is an essential regulator of cellular redox homeostasis, in restoring kidney function after IRI in the aging kidney. NRF2 expression decreased significantly in the kidneys of old mice, as well as histologic and functional renal recovery after IRI; 45-min renal pedicle clamping was retarded in old compared with young mice. Persistent renal injury during the recovery phase after IRI was aggravated in NRF2 knockout (KO) mice compared to wild-type mice. Oxidative stress occurred in NRF2 KO old mice during the IRI recovery phase along with decreased expression of mitochondrial OXPHOS-related proteins and a reduction in mitochondrial ATP content. In vitro, hypoxia/reoxygenation (H/R) injury was aggravated in senescent human proximal tubuloepithelial cells after NRF2 restriction using NRF2 siRNA, which also increased the level of oxidative stress and deteriorated mitochondrial dysfunction. Treating the mice with an NRF2 activator, CDDO-Me, alleviated the injury. These results suggest that NRF2 may be a therapeutic target for the aging kidney.

REST contributes to AKI-to-CKD transition through inducing ferroptosis in renal tubular epithelial cells

Ischemic-reperfusion injury (IRI) is a major pathogenic factor in acute kidney injury (AKI), which directly leads to the hypoxic injury of renal tubular epithelial cells (RTECs). Although emerging studies suggest repressor element 1-silencing transcription factor (REST) as a master regulator of gene repression under hypoxia, its role in AKI remains elusive. Here, we found that REST was upregulated in AKI patients, mice, and RTECs, which was positively associated with the degree of kidney injury, while renal tubule-specific knockout of Rest significantly alleviated AKI and its progression to chronic kidney disease (CKD). Subsequent mechanistic studies indicated that suppression of ferroptosis was responsible for REST-knockdown-induced amelioration of hypoxia-reoxygenation injury, during which process Cre-expressing adenovirus-mediated REST downregulation attenuated ferroptosis through upregulating glutamate-cysteine ligase modifier subunit (GCLM) in primary RTECs. Further, REST transcriptionally repressed GCLM expression via directly binding to its promoter region. In conclusion, our findings revealed the involvement of REST, a hypoxia regulatory factor, in AKI-to-CKD transition and identified the ferroptosis-inducing effect of REST, which may serve as a promising therapeutic target for ameliorating AKI and its progression to CKD.

Polysaccharide from Flammulina velutipes residues protects mice from Pb poisoning by activating Akt/GSK3β/Nrf-2/HO-1 signaling pathway and modulating gut microbiota

Lead (Pb) can cause damages to the brain, liver, kidney, endocrine and other systems. Flammulina velutipes residues polysaccharide (FVRP) has been reported to exhibit anti-heavy metal toxicity on yeast, but its regulating mechanism is unclear. Therefore, the protective effect and the underlying mechanism of FVRP on Pb-intoxicated mice were investigated. The results showed that FVRP could reduce liver and kidney function indexes, serum inflammatory factor levels, and increase antioxidant enzyme activity of Pb-poisoned mice. FVRP also exhibited a protective effect on histopathological damages in organs of Pb-intoxicated mice. Furthermore, FVRP attenuated Pb-induced kidney injury by inhibiting apoptosis via activating the Akt/GSK3β/Nrf-2/HO-1 signaling pathway. In addition, based on 16 s rRNA and ITS-2 sequencing data, FVRP regulated the imbalance of gut microbiota to alleviate the damage of Pb-poisoned mice by increasing the abundance of beneficial microbiota (Lachnospiraceae, Lactobacillaceae, Saccharomyces and Mycosphaerella) and decreasing the abundance of harmful microbiota (Muribaculaceae and Pleosporaceae). In conclusion, FVRP inhibited kidney injury in Pb-poisoned mice by inhibiting apoptosis via activating Akt/GSK3β/Nrf-2/HO-1 signaling pathway, and regulating gut fungi and gut bacteria. This study not only revealed the role of gut fungi in Pb-toxicity, but also laid a theoretical foundation for FVRP as a natural drug against Pb-toxicity.

Heme induces intestinal epithelial cell ferroptosis via mitochondrial dysfunction in transfusion-associated necrotizing enterocolitis

Transfusion-associated necrotising enterocolitis (TANEC) is a life-threatening disease with a poor prognosis in preterm infants. This study explored whether and how heme induces ferroptosis in TANEC gut injury. A TANEC mouse model and a cell culture system for heme and Caco-2 cells were established. Ferroptosis was assessed by measuring iron and malondialdehyde (MDA) levels and mitochondrial morphology in intestinal tissues and Caco-2 cells. Mitochondrial dysfunction was evaluated by measuring mitochondrial reactive oxygen species (ROS) production and membrane potential using JC-1. The intestinal injury grade was higher in the anemia-transfusion group than in the control group (p < .0001). Higher intestinal iron concentration (p < .0001), elevated levels of lipid peroxidation MDA (p = .0021), and ferroptotic mitochondrial morphological changes were found in mice of the anemia-transfusion group; specific ferroptosis inhibitor could alleviate anemia-transfusion gut injury, suggesting that ferroptosis play a role in the TANEC gut injury. Next, we explored whether heme released by hemolysis of erythrocytes induces ferroptosis in intestinal epithelial cells in vitro. The viability of Caco-2 cells significantly decreased after heme treatment (p < .0001). Iron accumulation, MDA elevated levels, and mitochondrial dysfunction also existed in the co-culture system, which ferroptosis inhibitors could reduce. In summary, ferroptosis was discovered in TANEC, and heme could induce ferroptosis in intestinal epithelial cells via mitochondrial dysfunction. Heme-inducing ferroptosis may be a possible mechanism and therapeutic target for TANEC.

Shikonin attenuates kidney tubular epithelial cells apoptosis, oxidative stress, and inflammatory response through nicotinamide adenine dinucleotide phosphate oxidase 4/PTEN pathway in acute kidney injury of sepsis model

Natural compounds were used in the treatment of acute kidney injury (AKI) caused by sepsis. This study investigated the function of shikonin from the roots of Arnebia purpurea in sepsis-induced AKI model. The target genes of shikonin were predicted by traditional Chinese medicine integrative database (TCMID). The markers of kidney injury, oxidative stress, and inflammatory factors were measured by enzyme-linked immunosorbent assay (ELISA). The pathological changes of kidney tubules were assessed by Hematoxylin and Eosin staining. Apoptosis of kidney tubular epithelial cells (KTECs) was detected by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. Protein expression was measured by western blot. Shikonin significantly improved kidney injury induced by cecal ligation and perforation (CLP). Besides, shikonin reduced KTECs apoptosis, malondialdehyde (MDA), reactive oxygen species (ROS), interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) levels, while augmented SOD and IL-10 levels. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase4 (NOX4) was predicted a target gene of shikonin. The expression of NOX4 was significantly inhibited in shikonin-treated group and the levels of phosphatidylinositol 3,4,5-trisphosphate 3-phosphate and dual specificity protein phosphate (PTEN) and p-p65 were decreased, while level of p-Akt was elevated. In vitro experiments, shikonin inhibited cell apoptosis, inflammatory, and ROS in human HK-2 cells and rat TECs. Shikonin downregulated expression of NOX4, PTEN and p-p65, and upregulated p-AKT and Bcl-2 expression in HK2 cells treated with lipopolysaccharide (LPS). Moreover, overexpression of NOX4 enhanced the effect of LPS on the expression level of PTEN, p-p65, p-AKT, and Bcl-2, which was reversed by the addition of shikonin. Taken together, shikonin could improve sepsis-induced AKI in rats, and attenuate the LPS induced KTECs apoptosis, oxidative stress, and inflammatory reaction via modulating NOX4/PTEN/AKT pathway.

Renoprotective effect of vinpocetine against ischemia/reperfusion injury: Modulation of NADPH oxidase/Nrf2, IKKβ/NF-κB p65, and cleaved caspase-3 expressions

Ischemia/reperfusion injury (IRI) during kidney transplantation is a serious clinical problem with a high mortality rate and a lack of therapy. Therefore, there is a need to improve the ability of the kidney to tolerate IRI during transplantation. This study aimed to investigate the possible protective effect of vinpocetine; a derivative of vincamine alkaloid; against renal IRI in rats with the elucidation of the involved mechanisms. Vinpocetine (25 mg/kg; i.p.) was administered for 10 successive days before the induction of ischemia by bilateral clamping of both renal pedicles for 45 min followed by 24 h of reperfusion. Blood and renal tissue samples were then collected for biochemical, molecular, and histopathological investigations. Vinpocetine significantly reduced serum creatinine and blood urea nitrogen levels in rats subjected to IRI. It also reduced mRNA expression of NADPH oxidase and renal content of malondialdehyde, while enhanced Nrf2 protein expression and renal content of reduced glutathione. The suppression of the provoked inflammatory response was evident by the downregulation of IKKβ and NF-κB p65 protein expressions, as well as their downstream inflammatory markers; tumor necrosis factor-α, interleukin-6, and myeloperoxidase. In addition, vinpocetine reduced protein expression of the apoptotic executioner cleaved caspase-3. These nephroprotective effects were confirmed by the improvement in histopathological features. Collectively, the protective effect of vinpocetine against IRI could be attributed to modulation of NADPH oxidase/Nrf2, IKKβ/NF-κB p65, and cleaved caspase-3 expressions. Thus, vinpocetine could improve oxidant/antioxidant balance, suppress triggered inflammatory response, and promote renal cell survival after IRI.

Renal Tubular Epithelial TRPA1 Acts as An Oxidative Stress Sensor to Mediate Ischemia-Reperfusion-Induced Kidney Injury through MAPKs/NF-κB Signaling

Oxidative stress and inflammation play important roles in the pathophysiology of acute kidney injury (AKI). Transient receptor potential ankyrin 1 (TRPA1) is a Ca2+-permeable ion channel that is sensitive to reactive oxygen species (ROS). The role of TRPA1 in AKI remains unclear. In this study, we used human and animal studies to assess the role of renal TRPA1 in AKI and to explore the regulatory mechanism of renal TRPA1 in inflammation via in vitro experiments. TRPA1 expression increased in the renal tubular epithelia of patients with AKI. The severity of tubular injury correlated well with tubular TRPA1 or 8-hydroxy-2'-deoxyguanosine expression. In an animal model, renal ischemia-reperfusion injury (IR) increased tubular TRPA1 expression in wild-type (WT) mice. Trpa1^-/- mice displayed less IR-induced tubular injury, oxidative stress, inflammation, and dysfunction in kidneys compared with WT mice. In the in vitro model, TRPA1 expression increased in renal tubular cells under hypoxia-reoxygenation injury (H/R) conditions. We demonstrated that H/R evoked a ROS-dependent TRPA1 activation, which elevated intracellular Ca²⁺ level, increased NADPH oxidase activity, activated MAPK/NF-κB signaling, and increased IL-8. Renal tubular TRPA1 may serve as an oxidative stress sensor and a crucial regulator in the activation of signaling pathways and promote the subsequent transcriptional regulation of IL-8. These actions might be evident in mice with IR or patients with AKI.

Potential Interplay between Nrf2, TRPA1, and TRPV1 in Nutrients for the Control of COVID-19

In this article, we propose that differences in COVID-19 morbidity may be associated with transient receptor potential ankyrin 1 (TRPA1) and/or transient receptor potential vanilloid 1 (TRPV1) activation as well as desensitization. TRPA1 and TRPV1 induce inflammation and play a key role in the physiology of almost all organs. They may augment sensory or vagal nerve discharges to evoke pain and several symptoms of COVID-19, including cough, nasal obstruction, vomiting, diarrhea, and, at least partly, sudden and severe loss of smell and taste. TRPA1 can be activated by reactive oxygen species and may therefore be up-regulated in COVID-19. TRPA1 and TRPV1 channels can be activated by pungent compounds including many nuclear factor (erythroid-derived 2) (Nrf2)-interacting foods leading to channel desensitization. Interactions between Nrf2-associated nutrients and TRPA1/TRPV1 may be partly responsible for the severity of some of the COVID-19 symptoms. The regulation by Nrf2 of TRPA1/TRPV1 is still unclear, but suggested from very limited clinical evidence. In COVID-19, it is proposed that rapid desensitization of TRAP1/TRPV1 by some ingredients in foods could reduce symptom severity and provide new therapeutic strategies.

Nrf-2 as a therapeutic target in acute kidney injury

Multifaceted cellular pathways exhibit a crucial role in the preservation of homeostasis at the molecular, cellular, and organism levels. One of the most important of these protective cascades is Nuclear factor E2-related factor (Nrf-2) that regulates the expression of several genes responsible for cellular detoxification, antioxidant function, anti-inflammation, drug/xenobiotic transportation, and stress-related factors. A growing body of evidence provides information regarding the protective role of Nrf-2 against a number of kidney diseases. Acute kidney injury (AKI) is a substantial clinical problem that causes a huge social burden. In the kidneys, Nrf-2 exerts a dynamic role in improving the injury triggered by inflammation and oxidative stress. Understanding of the exact molecular mechanisms underlying AKI is vital in order to determine the equilibrium between renal adaptation and malfunction and thus reduce disease progression. This review highlights the role of Nrf-2 targeting against AKI and provides evidence that targeting Nrf-2 to prevail oxidative damage and its consequences might exhibit protective effects in kidney diseases.

The role of Nrf2 in acute kidney injury: Novel molecular mechanisms and therapeutic approaches

Acute kidney injury (AKI) is a common clinical syndrome that is related to high morbidity and mortality. Oxidative stress, including the production of reactive oxygen species (ROS), appears to be the main element in the occurrence of AKI and the cause of the progression of chronic kidney disease (CKD) into end-stage renal disease (ESRD). Nuclear factor erythroid 2 related factor 2 (Nrf2) is a significant regulator of redox balance that has been shown to improve kidney disease by eliminating ROS. To date, researchers have found that the use of Nrf2-activated compounds can effectively reduce ROS, thereby preventing or retarding the progression of various types of AKI. In this review, we summarized the molecular mechanisms of Nrf2 and ROS in AKI and described the latest findings on the therapeutic potential of Nrf2 activators in various types of AKI.

Mitochondrial dysfunction in diabetic kidney disease

Although diabetic kidney disease (DKD) is the most common cause of end-stage kidney disease worldwide, the pathogenic mechanisms are poorly understood. There is increasing evidence that mitochondrial dysfunction contributes to the development and progression of DKD. Because the kidney is the organ with the second highest oxygen consumption in our body, it is distinctly sensitive to mitochondrial dysfunction. Mitochondrial dysfunction contributes to the progression of chronic kidney disease irrespective of underlying cause. More importantly, high plasma glucose directly damages renal tubular cells, resulting in a wide range of metabolic and cellular dysfunction. Overproduction of reactive oxygen species (ROS), activation of apoptotic pathway, and defective mitophagy are interlinked mechanisms that play pivotal roles in the progression of DKD. Although renal tubular cells have the highest mitochondrial content, podocytes, mesangial cells, and glomerular endothelial cells may all be affected by diabetes-induced mitochondrial injury. Urinary mitochondrial DNA (mtDNA) is readily detectable and may serve as a marker of mitochondrial damage in DKD. Unfortunately, pharmacologic modulation of mitochondrial dysfunction for the treatment of DKD is still in its infancy. Nonetheless, understanding the pathobiology of mitochondrial dysfunction in DKD would facilitate the development of novel therapeutic strategies.

Neuroprotective effect of Dictyopteris divaricata extract-capped gold nanoparticles against oxygen and glucose deprivation/reoxygenation

Combination therapy remains a promising approach to ameliorate cerebral ischemia injury. Nevertheless, the primary mechanism of the neuroprotective properties of Dictyopteris divaricata extract-capped gold nanoparticles (DD-GNPs) is not completely understood. DD-GNPs displayed maximum absorption at 525 nm and a diameter of 62.6 ± 1.2 nm, with a zeta potential value of -26.1 ± 0.6 mV. High resolution-transmission electron microscopy confirmed the spherical shape and average diameter (28.01 ± 2.03 nm). Crystalline structure and gold nanoparticle synthesis of DD-GNPs were determined by X-ray powder diffraction, and the presence of elemental gold was confirmed by energy-dispersive X-ray spectroscopy and Fourier transform-infrared spectroscopy. We examined the neuroprotective properties of DD-GNPs and explored their potential mechanisms in human SH-SY5Y neuroblastoma cells treated with oxygen and glucose deprivation/reoxygenation (OGD/R). We found that DD-GNPs inhibited OGD/R-induced release of lactate dehydrogenase (LDH), loss of cell viability, and production of reactive oxygen species. This neuroprotection was accompanied by regulation of apoptosis-related proteins, as indicated by decreased levels of cleaved-caspase-3, cleaved-PARP, cleaved-caspase-9, p53, p21, and Bax, as well as an increased level of Bcl-2. Notably, the neuroprotective effects of DD-GNPs were partially abolished by HO-1, NQO1, Nrf2, and AMPK knockdown. Our results established that DD-GNPs effectively attenuated OGD/R-stimulated neuronal injury, as evidenced by reduced neuronal injury. Even though the accumulating evidence has indicated the low toxicity and minimal side effects of GNPs, experimental clinical trials of DD-GNPs are still limited because of the lack of knowledge regarding the effects of DD-GNPs as neuroprotective agents against neurodegenerative diseases.

Profile of Phosphatidylserine Modifications under Nitroxidative Stress Conditions Using a Liquid Chromatography-Mass Spectrometry Based Approach

Nitrated lipids have been detected in vitro and in vivo, usually associated with a protective effect. While nitrated fatty acids have been widely studied, few studies reported the nitration and nitroxidation of the phospholipid classes phosphatidylcholine, and phosphatidylethanolamine. However, no information regarding nitrated and nitroxidized phosphatidylserine can be found in the literature. This work aims to identify and characterize the nitrated and nitroxidized derivatives of 1-palmitoyl-2-oleoyl-sn-3-glycero-phosphoserine (POPS), obtained after incubation with nitronium tetrafluoroborate, by liquid chromatography (LC) coupled to mass spectrometry (MS) and tandem MS (MS/MS). Several nitrated and nitroxidized products were identified, namely, nitro, nitroso, nitronitroso, and dinitro derivatives, as well as some nitroxidized species such as nitrosohydroxy, nitrohydroxy, and nitrohydroperoxy. The fragmentation pathways identified were structure-dependent and included the loss of HNO and HNO₂ for nitroso and nitro derivatives, respectively. Combined losses of PS polar head group plus HNO or HNO₂ and carboxylate anions of modified fatty acyl chain were also observed. The nitrated POPS also showed antiradical potential, demonstrated by the ability to scavenge the ABTS^●+ and DPPH^● radicals. Overall, this in vitro model of nitration based on LC-MS/MS provided additional insights into the nitrated and nitroxidized derivatives of PS and their fragmentation fingerprinting. This information is a valuable tool for targeted analysis of these modified PS in complex biological samples, to further explore the new clues on the antioxidant potential of nitrated POPS.

Urinary mitochondrial DNA level as a biomarker of tissue injury in non-diabetic chronic kidney diseases

Background

Urinary mitochondrial DNA (mtDNA) fragment level has been proposed as a biomarker of chronic kidney disease (CKD). In this study, we determine the relation between urinary mtDNA level and rate of renal function deterioration in non-diabetic CKD.

Methods

We recruited 102 non-diabetic CKD patients (43 with kidney biopsy that showed non-specific nephrosclerosis). Urinary mtDNA level was measured and compared to baseline clinical and pathological parameters. The patients were followed 48.3 ± 31.8 months for renal events (need of dialysis or over 30% reduction in estimated glomerular filtration rate [eGFR]).

Results

The median urinary mtDNA level was 1519.42 (inter-quartile range 511.81–3073.03) million copy/mmol creatinine. There were significant correlations between urinary mtDNA level and baseline eGFR (r = 0.429, p < 0.001), proteinuria (r = 0.368, p < 0.001), severity of glomerulosclerosis (r = − 0.537, p < 0.001), and tubulointerstitial fibrosis (r = − 0.374, p = 0.014). The overall rate of eGFR decline was − 2.18 ± 5.94 ml/min/1.73m² per year. There was no significant correlation between the rate of eGFR decline and urinary mtDNA level. By univariate analysis, urinary mtDNA level predicts dialysis-free survival, but the result became insignificant after adjusting for clinical and histological confounding factors.

Conclusion

Urinary mtDNA levels have no significant association with the rate of renal function decline in non-diabetic CKD, although the levels correlate with baseline renal function, proteinuria, and the severity of histological damage. Urinary mtDNA level may be a surrogate marker of permanent renal damage in non-diabetic CKD.

Tempol Protects Against Acute Renal Injury by Regulating PI3K/Akt/mTOR and GSK3β Signaling Cascades and Afferent Arteriolar Activity

BACKGROUND/AIMS

Free radical scavenger tempol is a protective antioxidant against ischemic injury. Tubular epithelial apoptosis is one of the main changes in the renal ischemia/reperfusion (I/R) injury. Meanwhile some proteins related with apoptosis and inflammation are also involved in renal I/R injury. We tested the hypothesis that tempol protects against renal I/R injury by activating protein kinase B/mammalian target of rapamycin (PKB, Akt/mTOR) and glycogen synthase kinase 3β (GSK3β) pathways as well as the coordinating apoptosis and inflammation related proteins.

METHODS

The right renal pedicle of C57Bl/6 mouse was clamped for 30 minutes and the left kidney was removed in the study. The renal injury was assessed with serum parameters by an automatic chemistry analyzer. Renal expressions of Akt/mTOR and GSK3β pathways were measured by western blot in I/R mice treated with saline or tempol (50mg/kg) and compared with sham-operated mice.

RESULTS

The levels of blood urea nitrogen (BUN), creatinine and superoxide anion (O2.-) increased, and superoxide dismutase (SOD) and catalase (CAT) decreased significantly after renal I/R injury. However, tempol treatment prevented the changes. Besides, I/R injury reduced renal expression of p-Akt, p-GSK3β, p-mTOR, Bcl2 and increased NF-κB, p-JNK and p53 in kidney, tempol significantly normalized these changes. In addition, renal I/R injury reduced the response of afferent arteriole to Angiotensin II (Ang II), while tempol treatment improved the activity of afferent arteriole.

CONCLUSION

Tempol attenuates renal I/R injury. The protective mechanisms seem to relate with activation of PI3K/Akt/mTOR and GSK3β pathways, inhibition of cellular damage markers and inflammation factors, as well as improvement of afferent arteriolar activity.

Nitrolipids in kidney physiology and disease

The kidneys are vital organs responsible for maintaining body fluid homeostasis within proper physiologic ranges. Kidney disease is an epidemic clinical problem causing significant morbidity and mortality, and current treatments are limited to renin-angiotensin system blockade or renal replacement therapy for the majority of affected individuals. There is a critical, unmet need for novel pharmacological agents to improve the outcome of patients with kidney disease. Nitro-oleic acid (NO2-OA) is an endogenously generated electrophilic compound with the capacity to modify thiols in proteins, altering their function. The most important targets appear to be the Keap1/Nrf2 and NF-κB pathways, which have widespread effects on antioxidant, detoxifying, and inflammatory responses in cells and tissues. Through these and potentially additional protective actions, NO2-OA may be capable of preserving or enhancing kidney function in acute and chronic kidney diseases.

NF-E2-Related Factor 2 Suppresses Intestinal Fibrosis by Inhibiting Reactive Oxygen Species-Dependent TGF-β1/SMADs Pathway

BACKGROUND AND AIMS

This study aimed to evaluate the antifibrotic effects of NF-E2-Related Factor 2 (Nrf2) on intestinal fibrosis. Intestinal fibrosis is a common complication of Crohn's disease; however, its mechanism of intestinal fibrosis is largely unclear.

METHODS

BALB/c mice received 2,4,6-trinitrobenzene sulfonic acid weekly via intrarectal injections to induce chronic fibrotic colitis. They also diet containing received 1% (w/w) tert-butylhydroquinone (tBHQ), which is an agonist of Nrf2. Human intestinal fibroblasts (CCD-18Co cells) were pretreated with tBHQ or si-Nrf2 followed by stimulation with transforming growth factor-β1 (TGF-β1), which transformed the cells into myofibroblasts. The main fibrosis markers such as α-smooth muscle actin, collagen I, tissue inhibitor of metalloproteinase-1, and TGF-β1/SMADs signaling pathway were detected by quantitative real-time RT-PCR, immunohistochemical analysis, and Western blot analysis. Levels of cellular reactive oxygen species (ROS) were detected by dichlorodihydrofluorescein diacetate.

RESULTS

tBHQ suppressed the intestinal fibrosis through the TGF-β1/SMADs signaling pathway in TNBS-induced colitis and CCD-18Co cells. Moreover, Nrf2 knockdown enhanced the TGF-β1-induced differentiation of CCD-18Co cells. ROS significantly increased in TGF-β1-stimulated CCD-18Co cells. Pretreatment with H₂O₂, the primary component of ROS, was demonstrated to block the effect of tBHQ on reducing the expression of TGF-β1. Moreover, scavenging ROS by N-acetyl cysteine could inhibit the increasing expression of TGF-β1 promoted by Nrf2 knockdown.

CONCLUSIONS

The results suggested that Nrf2 suppressed intestinal fibrosis by inhibiting ROS/TGF-β1/SMADs pathway in vivo and in vitro.

MnTBAP therapy attenuates the downregulation of sodium transporters in obstructive kidney disease

Ureteral obstruction is associated with reduced expressions of renal sodium transporters, which contributes to impaired urinary concentrating capacity. In this study, we employed a synthetic mitochondrial superoxide dismutase 2 (SOD2) mimic MnTBAP to investigate the role of mitochondrial oxidative stress in modulating the sodium transporters in obstructive kidney disease. Following unilateral ureteral obstruction (UUO) for 7 days, a global reduction of sodium transporters including NHE3, NCC, NKCC2, and ENaCα was observed as determined by qRT-PCR, Western Blotting or immunohistochemistry. Among these sodium transporters, the downregulation of NHE3, NCC, and NKCC2 was partially reversed by MnTBAP treatment. In contrast, the reduction of ENaCα was not affected by MnTBAP. The β and γ subunits of ENaC were not significantly altered by ureteral obstruction or MnTBAP therapy. To further confirm the anti-oxidant effect of MnTBAP, we examined the levels of TBARs in the urine collected from the obstructed ureters of UUO mice and bladder of sham mice. As expected, the increment of urinary TBARs in UUO mice was entirely abolished by MnTBAP therapy, indicating an amelioration of oxidative stress. Meantime, we found that three types of SOD were all reduced in obstructed kidneys determined by qRT-PCR, which was unaffected by MnTBAP. Collectively, these results demonstrated an important role of mitochondrial oxidative stress in mediating the downregulation of sodium transporters in obstructive kidney disease.

Dexmedetomidine protects against oxygen-glucose deprivation/reoxygenation injury-induced apoptosis via the p38 MAPK/ERK signalling pathway

Objective

To investigate the protective effects of dexmedetomidine (DEX) in oxygen-glucose deprivation/reoxygenation (OGD/R) injury, which is involved in a number of ischaemic diseases.

Methods

An in vitro OGD/R injury model was generated using mouse Neuro 2A neuroblastoma (N2A) cells. Different concentrations of DEX were administrated to OGD/R cells. CV-65 was used to inhibit p38 microtubule associated protein kinase/extracellular signal-regulated kinases (MAPK/ERK) signalling. Cell proliferation, cell cycle, apoptosis, and the levels of proteins related to p38 MAPK/ERK signalling and apoptosis were evaluated using Cell Counting Kit-8, flow cytometry, TdT-UTP nick end labelling and Western blot analysis, respectively.

Results

DEX treatment of OGD/R cells promoted cell survival and attenuated OGD/R-induced cell apoptosis. It also activated the p38 MAPK/ERK signalling pathway, increased the levels of Bcl-2, and decreased the levels of Bax and cleaved caspase-3. Treatment with the p38 MAPK/ERK inhibitor CV-65 inhibited the activation of p38 MAPK/ERK and abrogated the DEX-induced effects on cell survival and apoptosis.

Conclusions

DEX protects N2A cells from OGD/R-induced apoptosis via the activation of the p38 MAPK/ERK signalling pathway. DEX might be an effective agent for the treatment of ischaemic diseases.

Antioxidative and Antiapoptotic Effects of Delta-Opioid Peptide [D-Ala2, D-Leu5] Enkephalin on Spinal Cord Ischemia-Reperfusion Injury in Rabbits

Background: In our previous study, we found that regional administration of delta-opioid peptide [D-Ala², D-Leu⁵] enkephalin (DADLE) could provide dose-dependent protection on spinal cord ischemia-reperfusion (I/R) injury in rabbits. However, the relative protective molecular mechanisms underlying this neuroprotection remain unclear. The purpose of this study was to investigate whether DADLE provided the protection in spinal cord I/R injury through its antioxidant property by decreasing malondialdehyde (MDA) and nitric oxide (NO) levels and increasing glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) levels and through its antiapoptotic capacity by inhibiting caspase-3 and p53 expression. Methods: The rabbits were divided into three groups. The animals in Group NS and Group DADLE were administered with normal saline (NS) or DADLE via aorta during 30 min of ischemia respectively, while the one in Group Sham received no intervention. During the period of reperfusion, the rabbit's blood samples were collected for enzyme-linked immunoabsorbent assay (ELISA) examinations of MDA, NO, GSH-Px and SOD. At 48 h after reperfusion, the lumbar spinal cords were harvested for immunohistochemical, real-time polymerase chain reaction (PCR) and western blot studies to detect the caspase-3 and p53 expressions. Results: The activities of serum MDA and NO showed significant reductions in the DADLE group as compared with the control group. By contrast, the levels of serum GSH-Px and SOD were significantly higher in the DADLE group than those in the NS group. In addition, caspase-3 and p53 expression were significantly increased in the NS group, while DADLE mitigated these changes. Conclusions: The protective effects of DADLE at the dosage of 0.05 mg/kg may be related to its antioxidant and antiapoptosis properties in the rabbit model of spinal cord I/R injury.