Activation of sirtuin1 protects against ischemia/reperfusion-induced acute kidney injury

Water extract of earthworms mitigates kidney injury triggered by oxidative stress via activating intrarenal Sirt1/Nrf2 cascade and ameliorating mitochondrial damage

ETHNOPHARMACOLOGICAL RELEVANCE

Ischemia-reperfusion (IR) injury can result in acute renal failure. Oxidative stress is a major factor in IR-induced cell death in the kidneys. According to traditional Chinese medicine, earthworms (Pheretima aspergillum) can be used to treat various kidney diseases.

AIM OF THE STUDY

The present study was designed to understand the protective effects of the water extract of earthworms (WEE) against oxidative stress on the kidneys and the crucial molecular events associated with its nephroprotective activity.

MATERIALS AND METHODS

Cytotoxicity caused by H2O2 in HEK293, HK2, and primary mouse renal tubular epithelial cells (TECs) was used to investigate the effect of WEE on oxidative stress-induced renal injury in vitro. IR-induced kidney injury was established using rats as an in vivo model. The WEE-mediated protection of the kidneys against oxidative stress was compared with that of glutathione, a common antioxidant used as a positive control.

RESULTS

In HEK293 cells, HK2 cells, and primary mouse TECs, WEE relieved H2O2-induced mitochondrial damage, apoptosis, and ferroptosis. In kidney cells, WEE increased the expression of Sirt1, boosted LKB1 and AMPK phosphorylation, and upregulated nuclear Nrf2. Suppression of Sirt1 and LKB1 knock down abrogated WEE-induced protection against H2O2. WEE ameliorated IR-induced kidney injury and intrarenal inflammation in rats. In rat kidneys, WEE mitigated mitochondrial damage and suppressed IR-induced apoptosis and ferroptosis. Mechanistically, WEE increased Sirt1 expression, enhanced the phosphorylation of LKB1 and AMPK, and increased intranuclear Nrf2 levels in IR kidneys. IR treatment resulted in considerable increase in renal MDA levels and a prominent decrease in antioxidative enzyme activity. These lesions were significantly alleviated by WEE.

CONCLUSIONS

WEE mitigated H2O2-induced cytotoxicity in kidney cells in vitro and improved IR-induced kidney damage in rats. Mechanistically, WEE potentiated the Sirt1/Nrf2 axis and relieved mitochondrial damage in the kidney cells. These events inhibited the apoptosis and ferroptosis induced by oxidative stress. Our findings support the potential application of WEE for the clinical treatment of kidney diseases caused by intrarenal oxidative stress.

Combined effect of naringin and adipose tissue-derived mesenchymal stem cell on cisplatin nephrotoxicity through Sirtuin1/Nrf-2/HO-1 signaling pathway: a promising nephroprotective candidate

Cisplatin nephrotoxicity is a well-known emergency clinical condition caused by oxidative stress and inflammation. Naringin (NAR) is considered an antioxidant agent with renoprotective effects capable of removing reactive oxygen species. Adipose tissue-derived mesenchymal stem cells (AD-MSCs) are reported to have anti-inflammatory and antioxidant properties. The present research examined the renoprotective effect of the combination of NAR and AD-MSCs as opposed to each one alone on cisplatin-induced nephrotoxicity through SIRT-1/Nrf-2/HO-1 pathway. This study included five groups (n = 8 each) of male Sprague-Dawley rats (200 - 220 g): sham, cisplatin: rats receiving cisplatin (6.5 mg/kg, i.p.) on the 4th day; NAR+cisplatin: rats pretreated with NAR (1 week, i.p.) + cisplatin on the 4th day; AD-MSCs: rats receiving AD-MSCs (1 × 106) by injection through the tail vein on the 5th day + cisplatin on the 4th day; and NAR+AD-MSCs+cisplatin. On the 8th day, the animals were anesthetized to obtain tissue and blood samples. Biochemical factors, inflammation, oxidative stress, and gene expression were explored. Cisplatin increased blood urea nitrogen, creatinine, inflammation, and oxidative stress. Moreover, mRNA expression of Sirtuin1, nuclear factor erythroid 2-related factor 2 (Nrf-2), and heme oxygenase-1 (HO-1) remarkably reduced. Furthermore, cisplatin led to a disturbance in kidney structure (glomerular atrophy, cell infiltrations, and tubular dysfunction) as confirmed by histology findings. However, NAR pretreatment, AD-MSC administration, or a combination of both significantly reversed these changes. Overall, when used together, NAR and AD-MSCs had stronger cisplatin-induced effects on kidney dysfunction by inhibiting inflammation, reducing oxidative stress, and increasing the Sirtuin1/Nrf-2/HO-1 pathway.

Low-dose hexavalent chromium induces mitophagy in rat liver via the AMPK-related PINK1/Parkin signaling pathway

Hexavalent chromium (Cr(VI)) is a hazardous metallic compound commonly used in industrial processes. The liver, responsible for metabolism and detoxification, is the main target organ of Cr(VI). Toxicity experiments were performed to investigate the impacts of low-dose exposure to Cr(VI) on rat livers. It was revealed that exposure of 0.05 mg/kg potassium dichromate (K2Cr2O7) and 0.25 mg/kg K2Cr2O7 notably increased malondialdehyde (MDA) levels and the expressions of P-AMPK, P-ULK, PINK1, P-Parkin, and LC3II/LC3I, and significantly reduced SOD activity and P-mTOR and P62 expression levels in liver. Electron microscopy showed that CR(VI) exposure significantly increased mitophagy and the destruction of mitochondrial structure. This study simulates the respiratory exposure mode of CR(VI) workers through intratracheal instillation of CR(VI) in rats. It confirms that autophagy in hepatocytes is induced by low concentrations of CR(VI) and suggest that the liver damage caused by CR(VI) may be associated with the AMPK-related PINK/Parkin signaling pathway.

Advance in Iron Metabolism, Oxidative Stress and Cellular Dysfunction in Experimental and Human Kidney Diseases

Kidney diseases pose a significant global health issue, frequently resulting in the gradual decline of renal function and eventually leading to end-stage renal failure. Abnormal iron metabolism and oxidative stress-mediated cellular dysfunction facilitates the advancement of kidney diseases. Iron homeostasis is strictly regulated in the body, and disturbance in this regulatory system results in abnormal iron accumulation or deficiency, both of which are associated with the pathogenesis of kidney diseases. Iron overload promotes the production of reactive oxygen species (ROS) through the Fenton reaction, resulting in oxidative damage to cellular molecules and impaired cellular function. Increased oxidative stress can also influence iron metabolism through upregulation of iron regulatory proteins and altering the expression and activity of key iron transport and storage proteins. This creates a harmful cycle in which abnormal iron metabolism and oxidative stress perpetuate each other, ultimately contributing to the advancement of kidney diseases. The crosstalk of iron metabolism and oxidative stress involves multiple signaling pathways, such as hypoxia-inducible factor (HIF) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways. This review delves into the functions and mechanisms of iron metabolism and oxidative stress, along with the intricate relationship between these two factors in the context of kidney diseases. Understanding the underlying mechanisms should help to identify potential therapeutic targets and develop novel and effective therapeutic strategies to combat the burden of kidney diseases.

Effects of poly (ADP-ribose) polymerase inhibitor treatment on the repair process of ischemic acute kidney injury

Excessive activation of poly (ADP-ribose) polymerase (PARP) contributes to ischemic acute kidney injury (AKI). PARP inhibition has been shown to be beneficial in renal ischemia-reperfusion injury (IRI) in the early phase, but its role in the repair process remains unclear. The effects of JPI-289, a novel PARP inhibitor, during the healing phase after renal IRI were investigated. IRI was performed on 9-week-old male C57BL/6 mice. Saline or JPI-289 100 mg/kg was intraperitoneally administered once at 24 h or additionally at 48 h after IRI. Hypoxic HK-2 cells were treated with JPI-289. Renal function and fibrosis extent were comparable between groups. JPI-289 treatment caused more prominent tubular atrophy and proinflammatory intrarenal leukocyte phenotypes and cytokines/chemokines changes at 12 weeks after unilateral IRI. JPI-289 treatment enhanced gene expressions associated with collagen formation, toll-like receptors, and the immune system in proximal tubules and endothelial cells after IRI. JPI-289 treatment at 3 or 6 h after hypoxia facilitated proliferation of hypoxic HK-2 cells, whereas further treatment after 24 h suppressed proliferation. Delayed inhibition of PARP after renal IRI did not facilitate the repair process during the early healing phase but rather may aggravate renal tubular atrophy during the late healing phase in ischemic AKI.

Molecular Mechanisms of Oxidative Stress in Acute Kidney Injury: Targeting the Loci by Resveratrol

Reactive oxygen species are a group of cellular molecules that stand as double-edged swords, their good and bad being discriminated by a precise balance. Several metabolic reactions in the biological system generate these molecules that interact with cellular atoms to regulate functions ranging from cell homeostasis to cell death. A prooxidative state of the cell concomitant with decreased clearance of such molecules leads to oxidative stress, which contributes as a prime pathophysiological mechanism in various diseases including renal disorders, such as acute kidney injury. However, targeting the generation of oxidative stress in renal disorders by an antioxidant, resveratrol, is gaining considerable therapeutic importance and is known to improve the condition in preclinical studies. This review aims to discuss molecular mechanisms of oxidative stress in acute kidney injury and its amelioration by resveratrol. The major sources of data were PubMed and Google Scholar, with studies from the last five years primarily included, with significant earlier data also considered. Mitochondrial dysfunction, various enzymatic reactions, and protein misfolding are the major sources of reactive oxygen species in acute kidney injury, and interrupting these loci of generation or intersection with other cellular components by resveratrol can mitigate the severity of the condition.

SerpinA3K Deficiency Reduces Oxidative Stress in Acute Kidney Injury

We previously showed that SerpinA3K is present in urine from rats and humans with acute kidney injury (AKI) and chronic kidney disease (CKD). However, the specific role of SerpinA3K during renal pathophysiology is unknown. To begin to understand the role of SerpinA3K on AKI, SerpinA3K-deficient (KOSA3) mice were studied 24 h after inducing ischemia/reperfusion (I/R) and compared to wild type (WT) mice. Four groups were studied: WT+S, WT+IR, KOSA3+S, and KOSA3+IR. As expected, I/R increased serum creatinine and BUN, with a GFR reduction in both genotypes; however, renal dysfunction was ameliorated in the KOSA3+IR group. Interestingly, the increase in UH₂O₂ induced by I/R was not equally seen in the KOSA3+IR group, an effect that was associated with the preservation of antioxidant enzymes' mRNA levels. Additionally, FOXO3 expression was initially greater in the KOSA3 than in the WT group. Moreover, the increase in BAX protein level and the decrease in Hif1a and Vegfa induced by I/R were not observed in the KOSA3+IR group, suggesting that these animals have better cellular responses to hypoxic injury. Our findings suggest that SerpinA3K is involved in the renal oxidant response, HIF1α/VEGF pathway, and cell apoptosis.

Autophagy in acute kidney injury and maladaptive kidney repair

Acute kidney injury (AKI) is a major renal disease characterized by a sudden decrease in kidney function. After AKI, the kidney has the ability to repair, but if the initial injury is severe the repair may be incomplete or maladaptive and result in chronic kidney problems. Autophagy is a highly conserved pathway to deliver intracellular contents to lysosomes for degradation. Autophagy plays an important role in maintaining renal function and is involved in the pathogenesis of renal diseases. Autophagy is activated in various forms of AKI and acts as a defense mechanism against kidney cell injury and death. After AKI, autophagy is maintained at a relatively high level in kidney tubule cells during maladaptive kidney repair but the role of autophagy in maladaptive kidney repair has been controversial. Nonetheless, recent studies have demonstrated that autophagy may contribute to maladaptive kidney repair after AKI by inducing tubular degeneration and promoting a profibrotic phenotype in renal tubule cells. In this review, we analyze the role and regulation of autophagy in kidney injury and repair and discuss the therapeutic strategies by targeting autophagy.

Effects of resveratrol on renal ischemia-reperfusion injury: A systematic review and meta-analysis

Renal ischemia-reperfusion (I/R) injury may lead to acute kidney injury, which is characterized by high morbidity and mortality rates. Resveratrol (RSV) can be extracted from Chinese herbs, and multiple animal experiments have demonstrated its potential for renal protection. This systematic review evaluates the protective effect of RSV against renal I/R injury in animal models. The PubMed, Embase, Web of Science, and Science Direct databases were searched for animal experiments related to RSV in renal I/R injury from their establishment to June 2022. In total, 19 studies were included with 249 animals (129 treated with RSV and 120 as controls). The pooled analysis revealed that RSV administration significantly decreased serum creatinine (SCr) levels (16 studies, n = 243, WMD = -58.13, 95% CI = -79.26 to -37.00, p < 0.00001) and blood urea nitrogen (BUN) levels (12 studies, n = 163, WMD = -34.37, 95% CI = -46.70 to -22.03, p < 0.00001) in the renal I/R injury model. The level of malondialdehyde (MDA), an oxidative stress index, was alleviated [7 studies, n = 106, standardized mean difference (SMD) = -6.05, 95% CI = -8.90 to -3.21, p < 0.0001] and antioxidant enzymes such as glutathione (GSH) (7 studies, n = 115, SMD = 9.25, 95% CI = 5.51-13.00, p < 0.00001) and catalase (CAT) (4 studies, n = 59, SMD = 8.69, 95% CI = 4.35-13.03, p < 0.0001) were increased after treatment of RSV. The subgroup analysis suggested that 5-10 mg/kg of RSV optimally protects against renal I/R injury as both the BUN and SCr levels were significantly decreased at this dosage. The protective effects of RSV against renal I/R injury might be attributed to multiple mechanisms, such as inhibiting oxidative stress, apoptosis, inflammation, fibrillation, and promoting autophagy. For a deeper understanding of the protective effects of RSV, experimental studies on animal models and large randomized controlled trials in humans are needed.

Targeted Mitochondrial Drugs for Treatment of Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is a complex hemodynamic pathology that is a leading cause of death worldwide and occurs in many body organs. Numerous studies have shown that mitochondria play an important role in the occurrence mechanism of ischemia-reperfusion injury and that mitochondrial structural abnormalities and dysfunction lead to the disruption of the homeostasis of the whole mitochondria. At this time, mitochondria are not just sub-organelles to produce ATP but also important targets for regulating ischemia-reperfusion injury; therefore, drugs targeting mitochondria can serve as a new strategy to treat ischemia-reperfusion injury. Based on this view, in this review, we discuss potential therapeutic agents for both mitochondrial structural abnormalities and mitochondrial dysfunction, highlighting the application and prospects of targeted mitochondrial drugs in the treatment of ischemia-reperfusion injury, and try to provide new ideas for the clinical treatment of the ischemia-reperfusion injury.

MiR-6918-5p prevents renal tubular cell apoptosis by targeting MBD2 in ischemia/reperfusion-induced AKI

AIMS

Although previous studies reported that miRNAs are involved in the progression of acute kidney injury (AKI), their exact function and mechanism in ischemic AKI remains largely unknown. This study aims to define the role of miR-6918-5p in ischemia-reperfusion AKI. Materials and methods The renal arteries of C57BL/6J mice were clamped to establish a model of ischemia-reperfusion renal injury. BUMPT cells were added with Antimycin A and calcium ionophore to establish a model of ATP depletion in vitro. Cell apoptosis was detected by CCK8, flow cytometry and western blot, while HE staining and TUNEL staining were used to assess the degree of kidney damage.

KEY FINDINGS

We suppressed mmu_miR-6918-5p by ischemic injury in vitro and in vivo. We found that ischemia-reperfusion (I/R)-induced renal tubular cell apoptosis and the expression of cleaved caspase3 were enhanced by the inhibitor of mmu_miR-6918-5p; this effect was attenuated by an mmu_miR-6918-5p mimic. Mechanistically, mmu_miR-6918-5p binds to the 3' UTR region of MBD2 and represses its expression. The mmu_miR-6918-5p mimic alleviated the ischemic AKI by targeting MBD2. Conversely, the inhibitor of mmu_miR-6918-5p enhanced the ischemic AKI; this was diminished by MBD2-KO.

SIGNIFICANCE

Mmu_miR-6918-5p protected against the development of ischemic AKI by targeting MBD2.

Sirtuins: Research advances on the therapeutic role in acute kidney injury

BACKGROUND

Acute kidney injury (AKI), a common multidisciplinary diagnostic clinical critical illness, eventually causes end-stage renal disease (ESRD). Although many clinical measures have been taken to prevent or treat AKI, high morbidity and death rates were recorded. Therefore, in-depth pathogenesis study and search for new therapeutic targets are in demand. Interestingly, the suirtuins family showed a significant protective effect in AKI. Sirtuins (SIRT1-7) is a family of seven proteins with NAD⁺-dependent type III histone deacetylase activity. Sirtuins family members were involved by AKI, and regulation of sirtuins activities significantly improved AKI-induced renal injury. Therefore, the therapeutic role and molecular mechanisms of the sirtuins family in AKI has important research implications for clinical applications or basic research.

PURPOSE

This review summarizes recent advances in the roles and functions of the sirtuins family, discusses their therapeutic effects on AKI and related molecular mechanisms, and the mechanisms of action of small molecule specific activators or inhibitors sirtuins in the prevention and treatment of AKI were discussed.

METHODS

The data in this review were retrieved from various scientific databases (PubMed, Google scholar, Science Direct, and Web of Science), till December 2021. The keywords were used as follows: "Sirtuins", "Acute kidney injury", "AKI", "Sirtuins modulators" and "Histone deacetylation". The retrieved data followed PRISMA criteria (preferred reporting items for systematic review).

RESULTS

Growing evidence indicates that members of the sirtuins family regulate the development and progression of different renal diseases, including AKI, through anti-inflammation, antioxidation, anti-apoptotic, and maintenance of mitochondrial homeostasis. The molecular mechanism of Sirtuins family on AKI mainly regulated NF-κB, JNK/ERK, and AMPK/mTOR signaling pathways, upregulated the expression of PGC-1α, HO-1, NRF2, Bcl-2, OPA1, and AMPK, and downregulated the expression of NRLP3, IL-1β, TNF-α, IL-6, ROS, MFF, Drp1, Bax, ERK, and mTOR. In addition, the active ingredients of herbs (resveratrol, thujaplicins, huperzine, and curcumin) could activate the activity of SIRT1 or SIRT3, thereby improving AKI. Meanwhile, the synthetic Sirtuins inhibitor (AK-1) inhibited SIRT2 activity, thus alleviating AKI. In the future, more specific modulators will remain needed to enhance the clinical therapeutic role of the Sirtuins family in AKI.

CONCLUSION

The sirtuins family is a promising type III histone deacetylase for AKI treatment. This review will provide insight into sirtuins family's therapeutic role in AKI and promote the clinical use of sirtuins modulators in AKI.

6-Paradol alleviates Diclofenac-induced acute kidney injury via autophagy enhancement-mediated by AMPK/AKT/mTOR and NLRP3 inflammasome pathways

Diclofenac (DIC)-induced acute kidney injury (AKI) causes high morbidity and mortality. With the absence of satisfactory treatment, we investigated the protective effects of 6-Paradol (PDL) against DIC-induced AKI, with focus on renal autophagy and NLRP3 inflammasome pathways . PDL has anti-inflammatory, antioxidant and AMPK-activation properties. PDL was administered to DIC-challenged rats. Nephrotoxicity, oxidative stress, inflammatory, and autophagy markers and histopathological examinations were evaluated. Compared to DIC, PDL restored serum nephrotoxicity, renal oxidative stress and pro-inflammatory markers. PDL almost restored renal architecture, upregulated renal Nrf2 pathway via enhancing Nrf2 mRNA expression and HO-1 levels. PDL suppressed renal NF-κB mRNA expression, and NLRP3 inflammasome pathway expression. Moreover, PDL enhanced renal autophagy through upregulating LC3B, AMPK and SIRT-1, and suppressed mTOR, p-AKT mRNA expressions and phosphorylated-p62 levels. Our study confirmed that autophagy suppression mediates DIC-induced AKI via AMPK/mTOR/AKT and NLRP3-inflammasome pathways. Also, PDL's nephroprotective effects could provide a promising therapeutic approach against DIC-induced AKI.

Amelioration of Renal Injury by Resveratrol in a Rat Renal Transplantation Model via Activation of the SIRT1/NF-κB Signaling Pathway

Purpose. The improvement of the long-term survival of patients receiving kidney transplantation remains challenging. Ischemia reperfusion injury (IRI) reduces long-term renal graft survival in the early posttransplantation phase. However, few studies have investigated the effects of IRI on the pathogenesis of chronic renal graft failure. Silent information regulator 1 (SIRT1) regulates antioxidative stress and inflammatory response and protects against IRI. This study is aimed at investigating the role of resveratrol (RSV), an SIRT1 activator, in preventing renal injury in a rat renal transplantation model. Methods. A classical F334-to-LEW orthotopic renal transplantation rat model was established. The experiment group was treated with RSV from three days prior to kidney transplantation and the treatment lasted until the day of harvest. Uninephrectomized F344 and Lewis rats were used as controls. After 12 weeks, the effects of RSV were evaluated according to renal function, histopathology, immunohistochemistry, and western blotting. The activities of oxidative stress-related markers and proinflammatory cytokines were also assessed. Results. RSV treatment significantly ameliorated renal function and histopathological lesions in kidney-transplanted rats and increased the levels of GSH, SOD, and CAT and decreased the levels of MDA and iNOS. Furthermore, RSV also inhibited the expression of proinflammatory cytokines/chemokines such as TNF-α, CD68, and IL-6 in kidney-transplanted rats. In addition, the transplant group displayed significantly lower level of SIRT1 and higher level of Ac-NF-κBp65. RSV increased the expression of SIRT1 and decreased the expression of Ac-NF-κBp65. Conclusion. SIRT1 plays an important role in the pathogenesis of chronic renal allograft dysfunction. It is a potential therapeutic agent for ameliorating inflammation and oxidative stress-induced renal injury following kidney transplantation by activating the SIRT1/NF-κB signaling pathway.

Potential of Polyphenols to Restore SIRT1 and NAD+ Metabolism in Renal Disease

SIRT1 is an NAD⁺-dependent class III histone deacetylase that is abundantly expressed in the kidney, where it modulates gene expression, apoptosis, energy homeostasis, autophagy, acute stress responses, and mitochondrial biogenesis. Alterations in SIRT1 activity and NAD⁺ metabolism are frequently observed in acute and chronic kidney diseases of diverse origins, including obesity and diabetes. Nevertheless, in vitro and in vivo studies and clinical trials with humans show that the SIRT1-activating compounds derived from natural sources, such as polyphenols found in fruits, vegetables, and plants, including resveratrol, quercetin, and isoflavones, can prevent disease and be part of treatments for a wide variety of diseases. Here, we summarize the roles of SIRT1 and NAD⁺ metabolism in renal pathophysiology and provide an overview of polyphenols that have the potential to restore SIRT1 and NAD⁺ metabolism in renal diseases.

Fucoxanthin Attenuates Oxidative Damage by Activating the Sirt1/Nrf2/HO-1 Signaling Pathway to Protect the Kidney from Ischemia-Reperfusion Injury

Oxidative stress is a key component of renal ischemia/reperfusion (I/R) injury. Fucoxanthin (Fx), a marine carotenoid with enhanced antioxidant capacity, acts as a ROS inhibitor in diseases such as ischemic stroke and acute lung injury. We hypothesized that fucoxanthin could attenuate renal I/R-induced oxidative damage. C57BL/6 mice ( $n=30$ ) were randomly assigned to sham, IR, $\text{IR}+\text{DMSO}$ , and $\text{IR}+\text{Fx}$ (25, 50, and 100 mg/kg) groups. The renal I/R injury was induced by clamping the left kidney nephron tip in mice. Fucoxanthin was injected intraperitoneally 24 hours before surgery. Compared with the IR group, pretreatment with fucoxanthin significantly improved renal dysfunction and tissue structural damage and inhibited ROS levels and apoptosis. Consistent results were observed in HK-2 cells. Besides, we found that renal I/R resulted in decreased expression of Sirt1, Nrf2, and HO-1, while fucoxanthin upregulated the expression of Sirt1, Nrf2, and HO-1. The protective effects of fucoxanthin were significantly reversed by EX527 (a selective inhibitor of Sirt1) or si-Sirt1. In conclusion, our study investigated the protective effect of fucoxanthin against renal I/R injury, and the underlying mechanism may be related to the activation of the Sirt1/Nrf2/HO-1 signaling pathway by fucoxanthin to attenuate oxidative stress-induced apoptosis.

Combating Ischemia-Reperfusion Injury with Micronutrients and Natural Compounds during Solid Organ Transplantation: Data of Clinical Trials and Lessons of Preclinical Findings

Although extended donor criteria grafts bear a higher risk of complications such as graft dysfunction, the exceeding demand requires to extent the pool of potential donors. The risk of complications is highly associated with ischemia-reperfusion injury, a condition characterized by high loads of oxidative stress exceeding antioxidative defense mechanisms. The antioxidative properties, along with other beneficial effects like anti-inflammatory, antiapoptotic or antiarrhythmic effects of several micronutrients and natural compounds, have recently emerged increasing research interest resulting in various preclinical and clinical studies. Preclinical studies reported about ameliorated oxidative stress and inflammatory status, resulting in improved graft survival. Although the majority of clinical studies confirmed these results, reporting about improved recovery and superior organ function, others failed to do so. Yet, only a limited number of micronutrients and natural compounds have been investigated in a (large) clinical trial. Despite some ambiguous clinical results and modest clinical data availability, the vast majority of convincing animal and in vitro data, along with low cost and easy availability, encourage the conductance of future clinical trials. These should implement insights gained from animal data.

Allicin ameliorates renal ischemia/reperfusion injury via inhibition of oxidative stress and inflammation in rats

Allicin has been reported to play a biological role in human pathophysiological processes via interaction with numerous signaling pathways and gene expression alteration. The purpose of the present study was to evaluate the protective effects of allicin against renal ischemia/reperfusion injury (RIRI) in rats. In the present study, the RIRI model with 45-min ischemia and 22-h reperfusion in rats was generated and allicin was used as the intervention. Changes in renal tissue pathomorphology, renal function, oxidative stress, inflammatory response and apoptosis were evaluated in the RIRI model in rats. Compared with those in the RIRI group, renal function, renal pathological injury, and anti-inflammatory and antioxidant properties were markedly improved in the RIRI+allicin group. Thus, our research suggested that allicin exerted its protective effect against ischemia/reperfusion-induced renal injury by regulating apoptosis, oxidative stress and inflammatory response in rats.

Sirtuin 1 activated by SRT1460 protects against myocardial ischemia/reperfusion injury

BACKGROUND

Ischemia reperfusion usually results in certain degree of damage to the myocardium, which is called myocardial ischemia/reperfusion (I/R) injury.

OBJECTIVE

Previous studies have found that Sirt1 plays a critical role in I/R injury by protecting cardiac function. SRT1460 is the activator for Sirt1 that participates in the regulation of various diseases. However, whether SRT1460 has any effects on myocardial I/R injury needs further study.

METHODS

The I/R rat model and H/R H9C2 model were established to simulate myocardial I/R injury. The infarct area of the rat heart was examined through TTC staining. The EF and FS of rats were detected through echocardiography. The levels of CK-MB, LDH, MDA, SOD and CK in cardiac tissues, serum or H9C2 cells were measured using commercial kits. Cell viability was assessed through MTT assay. Apoptosis was determined through flow cytometry analysis. Sirt1 expression was measured through western blot.

RESULTS

Our work found that SRT1460 reduced the infarct area of the heart induced by myocardial I/R injury. In addition, SRT1460 was confirmed to ameliorate cardiac dysfunction induced by myocardial I/R injury. Further exploration discovered that SRT1460 weakened oxidative stress induced by myocardial I/R injury. Findings from in vitro assays demonstrated that SRT1460 relieved injury of H/R-treated H9C2 cells. Finally, rescue assays proved that Sirt1 knockdown reversed the protective effects of SRT1460 on the injury of H/R-treated H9C2 cells.

CONCLUSION

Sirt1 activated by SRT1460 protected against myocardial I/R injury. This discovery may offer new sights on the treatment of myocardial I/R injury.

Prospective Pharmacological Potential of Resveratrol in Delaying Kidney Aging

Aging is an unavoidable part of life. The more aged we become, the more susceptible we become to various complications and damages to the vital organs, including the kidneys. The existing drugs for kidney diseases are mostly of synthetic origins; thus, natural compounds with minimal side-effects have attracted growing interest from the scientific community and pharmaceutical companies. A literature search was carried out to collect published research information on the effects of resveratrol on kidney aging. Recently, resveratrol has emerged as a potential anti-aging agent. This versatile polyphenol exerts its anti-aging effects by intervening in various pathologies and multi-signaling systems, including sirtuin type 1, AMP-activated protein kinase, and nuclear factor-κB. Researchers are trying to figure out the detailed mechanisms and possible resveratrol-mediated interventions in divergent pathways at the molecular level. This review highlights (i) the causative factors implicated in kidney aging and the therapeutic aspects of resveratrol, and (ii) the effectiveness of resveratrol in delaying the aging process of the kidney while minimizing all possible side effects.

miR-132-3p promotes the cisplatin-induced apoptosis and inflammatory response of renal tubular epithelial cells by targeting SIRT1 via the NF-κB pathway

Cisplatin is a highly effective and broad-spectrum anticancer drug for the clinical treatment of solid tumors. However, it causes acute kidney injury (AKI) in patients with cancer. Consequently, its clinical application is limited. The occurrence, development, and prognosis of AKI are closely associated with microRNA (miRNA), which needs validation as a biomarker, especially for the early stages of cisplatin-induced AKI. An example of miRNA is miR-132-3p, which plays important roles in inflammatory responses, cell proliferation, and apoptosis in a variety of diseases. However, variations in its expression, potential mechanisms, and downstream targets in cisplatin-induced AKI remain unclear. This study aimed to investigate the functions of miR-132-3p in cisplatin-induced AKI. Sequencing and qRT-PCR revealed that miR-132-3p was significantly upregulated in cisplatin-induced AKI models of mouse and human proximal renal tubular epithelial (HK-2) cells. Apoptosis and inflammatory responses were significantly suppressed by the inhibition of the miR-132-3p expression in cisplatin-stimulated HK-2 cells, and this suppression was blocked by miR-132-3p mimics. Bioinformatics and dual luciferase reporter gene assay identified the 3'- UTR of SIRT1 mRNA as a direct target of miR-132-3p. RNA-FISH and immunofluorescence co-localization demonstrated that miR-132-3p and SIRT1 directly combined and interacted in the cytoplasm of HK-2 cells. Mechanistically, the SIRT1 expression was suppressed and the NF-κB signaling pathway was activated by the upregulation of miR-132-3p in cisplatin-induced AKI. By contrast, the SIRT1 expression was upregulated after the inhibition of miR-132-3p. The ratios of p-p65/p65 and p-IκBα/IκBα were significantly reduced, and the expression levels of inflammatory biomarkers and apoptotic proteins induced by cisplatin were obviously attenuated. Our results suggested that miR-132-3p exacerbated cisplatin-induced AKI by negatively regulating SIRT1 and activating the NF-κB signaling pathway. Therefore, targeting miR-132-3p might be a potential adjuvant therapy for ameliorating AKI in cisplatin-treated patients.

PICK1 Deficiency Exacerbates Sepsis-Associated Acute Kidney Injury

We performed in vitro and in vivo experiments to explore the role of protein kinase C-binding protein 1 (PICK1), an intracellular transporter involved in oxidative stress-related neuronal diseases, in sepsis-related acute kidney injury (AKI). Firstly, PCR, western blotting, and immunohistochemistry were used to observe the expression of PICK1 after lipopolysaccharide- (LPS-) induced AKI. Secondly, by inhibiting PICK1 in vivo and silencing PICK1 in vitro, we further explored the effect of PICK1 on AKI. Finally, the relationship between PICK1 and oxidative stress and the related mechanisms were explored. We found that the expression of PICK1 was increased in LPS-induced AKI models both in vitro and in vivo. PICK1 silencing significantly aggravated LPS-induced apoptosis, accompanied by ROS production in renal tubular epithelial cells. FSC231, a PICK1-specific inhibitor, aggravated LPS-induced kidney injury. Besides, NAC (N-acetylcysteine), a potent ROS scavenger, significantly inhibited the PICK1-silencing-induced apoptosis. In conclusion, PICK1 might protect renal tubular epithelial cells from LPS-induced apoptosis by reducing excessive ROS, making PICK1 a promising preventive target in LPS-induced AKI.

Total Glucosides of Paeony Inhibited Autophagy and Improved Acute Kidney Injury Induced by Ischemia-Reperfusion via the lncRNA TUG1/miR-29a/PTEN Axis

Objective

Total glucosides of paeony (TGP) has been proven to affect anti-inflammatory, immunomodulatory and hypoxia tolerance. This study investigates the effect of TGP on autophagy in acute kidney injury (AKI) induced by ischemia-reperfusion (I/R).

Methods

Rat model of AKI induced by I/R was established. Rats were administered with TGP at different doses by oral gavage. The contents of BUN, creatinine, NGAL, Kim-1 and IL-18 were detected. The levels of inflammatory factors (TNF-α, IL-1β and IL-6) and autophagy were measured. The expressions of lncRNA TUG1, miR-29a and PTEN were detected and their binding relationships were verified. I/R rat model with overexpressed TUG1 was established to explore the effect of TGP on kidney injury and autophagy. The hypoxia/reoxygenation (HR) model of HK-2 cells and the HR model of HK-2 cells overexpressing TUG1 and low-expressing PTEN were established.

Results

TGP decreased the contents of BUN, creatinine, NGAL, Kim-1 and IL-18, and reduced the levels of inflammatory factors. LncRNA TUG1 and PTEN were downregulated, and miR-29a was upregulated in kidney tissues. The binding relationships between lncRNA TUG1 and miR-29a, and miR-29a and PTEN were confirmed. TGP suppressed PTEN expression via the lncRNA TUG1/miR-29a axis. Overexpressing lncRNA TUG1 attenuated the protective effect of TGP on AKI and autophagy in HK-2 cells. TGP improved cell viability and inhibited the autophagy in HR model of HK-2 cells via lncRNA TUG1/miR-29a/PTEN axis.

Conclusion

TGP inhibited autophagy and improved AKI induced by I/R via the lncRNA TUG1/miR-29a/PTEN axis.

Activators of SIRT1 in the kidney and protective effects of SIRT1 during acute kidney injury (AKI) (effect of SIRT1 activators on acute kidney injury)

Acute kidney injury (AKI) is a complex disorder and a clinical condition characterized by acute reduction in renal function. If AKI is not treated, it can lead to chronic kidney disease, which is associated with a high risk of death. SIRT1 (silent information regulator 1) is an NAD-dependent deacetylase. This enzyme is responsible for the processes of DNA repair or recombination, chromosomal stability, and gene transcription. This enzyme also plays a protective role in many diseases, including AKI. In this study, we review the mechanisms that mediate the protective effects of SIRT1 on AKI, including SIRT1 activators.

Sirtuin 1 promotes autophagy and proliferation of endometrial cancer cells by reducing acetylation level of LC3

Endometrial cancer (EC) constitutes a common female genital tract tumor with a rising incidence rate. Sirtuin 1 (SIRT1) is a member of histone deacetylase, which extensively participates in the progression of aging, cell death, and tumorigenesis. This study explored the effect of SIRT1-mediated LC3 acetylation on autophagy and proliferation of EC cells. SIRT1 expression in EC tissues and adjacent tissues, EC cell lines and normal human epithelial cells was detected. SIRT1 expression was elevated in EC cell lines and tissues. Knockdown of SIRT1 inhibited proliferation, migration, and invasion of EC cells. Then, EC cells were starved in serum-free medium, and levels of autophagy-related proteins were detected. Starvation induced autophagy of EC cells. The starvation-treated EC cells showed an increased SIRT1 expression, a decreased LC3 acetylation level and an increased autophagy level. The proliferation and autophagy of EC cells under different treatments were evaluated. In EC cells transfected with overexpressing SIRT1, LC3 acetylation was inhibited and cell proliferation was promoted. Moreover, overexpressing SIRT1 facilitated growth and autophagy of transplanted tumors in nude mice. In conclusion, SIRT1 promoted autophagy and proliferation of EC cells by reducing acetylation level of LC3.

Shenshuaikang Enema, a Chinese Herbal Remedy, Inhibited Hypoxia and Reoxygenation-Induced Apoptosis in Renal Tubular Epithelial Cells by Inhibiting Oxidative Damage-Dependent JNK/Caspase-3 Signaling Pathways Using Network Pharmacology

Background

Acute kidney injury (AKI) is a common clinically critical illness with serious consequences for the patients. Shenshuaikang enema (SE) is a Chinese herbal compound that is used to treat AKI in clinical practice. However, its mechanism of action remains unclear.

Aim

The aim of this study was to investigate the therapeutic effect of SE and explore the molecular mechanisms using network pharmacology and in vitro experiments.

Materials and Methods

The herb-component-target network was constructed based on network pharmacology. The predicted targets and pathways were validated using in vitro experiments. A renal tubular epithelial cell line (HK-2 cells) was exposed to hypoxia and reoxygenation (H/R) using air-tight conditions for five hours and treated with different concentrations of SE (25%, 50%, and 75%) to assess cell viability and apoptosis and determine the optimal experimental dose. Subsequently, H/R-injured HK-2 cells were pretreated with the optimal SE dose and then randomly divided into three groups, the SE, SE-SP600125 (inhibitor of JNK), and SE-NAC (antioxidant) groups. The cell vitality, apoptosis, and death were evaluated using the cell counting kit 8 (CCK8) and carboxyfluorescein succinimidyl ester/propidium iodide (CFSF/PI) staining. The apoptosis-related protein JNK and Caspase-3 were assessed by Western blot. Expression of JNK and Caspase-3 genes was analyzed using real-time quantitative polymerase chain reaction (RT-qPCR).

Results

123 active components and 226 targets were identified from four herbs that composed the herb-compound-target network based on transcriptomics and network pharmacology analyses. The KEGG pathway analyses revealed that the mitochondrial apoptosis pathway was involved in the therapeutic AKI effects of SE. Cell vitality of H/R-induced HK-2 cells was obviously increased when treating them with SE, and the apoptosis was significantly inhibited, especially in the SE (50%) group at 4 and 12 h after modeling. Pretreatment with antioxidant NAC obviously prevented cell death compared to the SE (50%) group, while no obvious reduction of apoptosis was observed in the SP600125 group. JNK expression level was significantly increased in the SE (50%) group compared to the SP600125 (P < 0.01) and the NAC group (P < 0.05). Caspase-3 was downregulated in the SE (50%) group compared to the SP600125 (P < 0.01) and NAC group (P < 0.05). Caspase-3 activation in the SP600125 group was higher than that in the NAC group (P < 0.05). Moreover, the oxidative damage-dependent JNK/Caspase-3 pathway was identified in the H/R-injured HK-2 cells by inhibiting the JNK activation and oxidative damage.

Conclusions

Our findings suggested that the H/R-triggered apoptosis in HK-2 cells was abrogated by SE by upregulating the oxidative damage-dependent JNK to trigger suppression of Caspase-3.

Dexmedetomidine Ameliorates Hippocampus Injury and Cognitive Dysfunction Induced by Hepatic Ischemia/Reperfusion by Activating SIRT3-Mediated Mitophagy and Inhibiting Activation of the NLRP3 Inflammasome in Young Rats

Hepatic ischemia-reperfusion (HIR) has been proven to trigger oxidative stress and pyroptosis in the hippocampus. Sirtuin 3 (SIRT3) is an essential mitochondrial protein deacetylase regulating oxidative stress and mitophagy. Dexmedetomidine (Dex) has been demonstrated to confer neuroprotection in different brain injury models. However, whether the protective effects of Dex following HIR are orchestrated by activation of SIRT3-mediated mitophagy and inhibition of NOD-like receptor protein 3 (NLRP3) inflammasome activation remains unknown. Herein, two-week-old rats were treated with Dex or a selective SIRT3 inhibitor (3-TYP)/autophagy inhibitor (3-MA) and then subjected to HIR. The results revealed that Dex treatment effectively attenuated neuroinflammation and cognitive deficits via upregulating SIRT3 expression and activity. Furthermore, Dex treatment inhibited the activation of NLRP3 inflammasome, while 3-TYP and 3-MA eliminated the protective effects of Dex, suggesting that SIRT3-mediated mitophagy executes the protective effects of Dex. Moreover, 3-TYP treatment downregulated the expression level of SIRT3 downstream proteins: forkhead-box-protein 3α (FOXO3α), superoxide dismutase 2 (SOD2), peroxiredoxin 3 (PRDX3), and cyclophilin D (CYP-D), which were barely influenced by 3-MA treatment. Notably, both 3-TYP and 3-MA were able to offset the antioxidative and antiapoptosis effects of Dex, indicating that SIRT3-mediated mitophagy may be the last step and the major pathway executing the neuroprotective effects of Dex. In conclusion, Dex inhibits HIR-induced NLRP3 inflammasome activation mainly by triggering SIRT3-mediated mitophagy.