Dexmedetomidine attenuation of renal ischaemia-reperfusion injury requires sirtuin 3 activation

Mechanism of dexmedetomidine protection against cisplatin induced acute kidney injury in rats

OBJECTIVE

This study explored the molecular mechanisms by which dexmedetomidine (Dex) alleviates cisplatin (CP)-induced acute kidney injury (AKI) in rats.

METHODS

CP-induced AKI models were established, and Dex was intraperitoneally injected at different concentrations into rats in the model groups. Subsequently, rats were assigned to the control, CP, CP + Dex 10 μg/kg, and CP + Dex 25 μg/kg groups. After weighing the kidneys of the rats, the kidney arterial resistive index was calculated, and CP-induced AKI was evaluated. In addition, four serum biochemical indices were measured: histopathological damage in rat kidneys was detected; levels of inflammatory factors, interleukin (IL)-1β, IL-18, IL-6, and tumor necrosis factor alpha, in kidney tissue homogenate of rats were assessed through enzyme-linked immunosorbent assay (ELISA); and levels of NLRP-3, caspase-1, cleaved caspase-1, gasdermin D (GSDMD), and GSDMD-N in kidney tissues of rats were determined via western blotting.

RESULTS

Dex treatment reduced nephromegaly and serum clinical marker upregulation caused by CP-induced AKI. In addition, hematoxylin and eosin staining revealed that Dex treatment relieved CP-induced kidney tissue injury in AKI rats. ELISA analyses demonstrated that Dex treatment reduced the upregulated levels of proinflammatory cytokines in the kidney tissue of AKI rats induced by CP, thereby alleviating kidney tissue injury. Western blotting indicated that Dex alleviated CP-induced AKI by inhibiting pyroptosis mediated by NLRP-3 and caspase-1.

CONCLUSION

Dex protected rats from CP-induced AKI, and the mechanism may be related to NLRP-3/Caspase-1-mediated pyroptosis.

Sirtuin 3 in renal diseases and aging: From mechanisms to potential therapies

The longevity protein sirtuins (SIRTs) belong to a family of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases. In mammals, SIRTs comprise seven members (SIRT1-7) which are localized to different subcellular compartments. As the most prominent mitochondrial deacetylases, SIRT3 is known to be regulated by various mechanisms and participate in virtually all aspects of mitochondrial homeostasis and metabolism, exerting significant impact on multiple organs. Notably, the kidneys possess an abundance of mitochondria that provide substantial energy for filtration and reabsorption. A growing body of evidence now supports the involvement of SIRT3 in several renal diseases, including acute kidney injury, chronic kidney disease, and diabetic nephropathy; notably, these diseases are all associated with aging. In this review, we summarize the emerging role of SIRT3 in renal diseases and aging, and highlights the intricate mechanisms by which SIRT3 exerts its effects. In addition, we highlight the potential therapeutic significance of modulating SIRT3 and provide valuable insights into the therapeutic role of SIRT3 in renal diseases to facilitate clinical application.

The protective mechanism of SIRT3 and potential therapy in acute kidney injury

Acute kidney injury (AKI) is a complex clinical syndrome with a poor short-term prognosis, which increases the risk of the development of chronic kidney diseases and end-stage kidney disease. However, the underlying mechanism of AKI remains to be fully elucidated, and effective prevention and therapeutic strategies are still lacking. Given the enormous energy requirements for filtration and absorption, the kidneys are rich in mitochondria, which are unsurprisingly involved in the onset or progression of AKI. Accumulating evidence has recently documented that Sirtuin 3 (SIRT3), one of the most prominent deacetylases highly expressed in the mitochondria, exerts a protective effect on AKI. SIRT3 protects against AKI by regulating energy metabolism, inhibiting oxidative stress, suppressing inflammation, ameliorating apoptosis, inhibiting early-stage fibrosis and maintaining mitochondrial homeostasis. Besides, a number of SIRT3 activators have exhibited renoprotective properties both in animal models and in vitro experiments, but have not yet been applied to clinical practice, indicating a promising therapeutic approach. In this review, we unravel and summarize the recent advances in SIRT3 research and the potential therapy of SIRT3 activators in AKI.

Ferroptosis in organ ischemia-reperfusion injuries: recent advancements and strategies

Ferroptosis is a newly discovered type of regulated cell death participated in multiple diseases. Different from other classical cell death programs such as necrosis and apoptosis, ferroptosis involving iron-catalyzed lipid peroxidation is characterized by Fe2+ accumulation and mitochondria alterations. The phenomenon of oxidative stress following organ ischemia-reperfusion (I/R) has recently garnered attention for its connection to the onset of ferroptosis and subsequent reperfusion injuries. This article provides a comprehensive overview underlying the mechanisms of ferroptosis, with a further focus on the latest research progress regarding interference with ferroptotic pathways in organ I/R injuries, such as intestine, lung, heart, kidney, liver, and brain. Understanding the links between ferroptosis and I/R injury may inform potential therapeutic strategies and targeted agents.

SIRT3 Activation a Promise in Drug Development? New Insights into SIRT3 Biology and Its Implications on the Drug Discovery Process

Sirtuins catalyze deacetylation of lysine residues with a NAD+-dependent mechanism. In mammals, the sirtuin family is composed of seven members, divided into four subclasses that differ in substrate specificity, subcellular localization, regulation, as well as interactions with other proteins, both within and outside the epigenetic field. Recently, much interest has been growing in SIRT3, which is mainly involved in regulating mitochondrial metabolism. Moreover, SIRT3 seems to be protective in diseases such as age-related, neurodegenerative, liver, kidney, heart, and metabolic ones, as well as in cancer. In most cases, activating SIRT3 could be a promising strategy to tackle these health problems. Here, we summarize the main biological functions, substrates, and interactors of SIRT3, as well as several molecules reported in the literature that are able to modulate SIRT3 activity. Among the activators, some derive from natural products, others from library screening, and others from the classical medicinal chemistry approach.

Perioperative acute kidney injury: The renoprotective effect and mechanism of dexmedetomidine

Dexmedetomidine (DEX) is a highly selective and potent α2-adrenoceptor (α2-AR) agonist that is widely used as a clinical anesthetic to induce anxiolytic, sedative, and analgesic effects. In recent years, a growing body of evidence has demonstrated that DEX protects against acute kidney injury (AKI) caused by sepsis, drugs, surgery, and ischemia-reperfusion (I/R) in organs or tissues, indicating its potential role in the prevention and treatment of AKI. In this review, we summarized the evidence of the renoprotective effects of DEX on different models of AKI and explored the mechanism. We found that the renoprotective effects of DEX mainly involved antisympathetic effects, reducing inflammatory reactions and oxidative stress, reducing apoptosis, increasing autophagy, reducing ferroptosis, protecting renal tubular epithelial cells (RTECs), and inhibiting renal fibrosis. Thus, the use of DEX is a promising strategy for the management and treatment of perioperative AKI. The aim of this review is to further clarify the renoprotective mechanism of DEX to provide a theoretical basis for its use in basic research in various AKI models, clinical management, and the treatment of perioperative AKI.

Remote Ischemic Conditioning Mediates Cardio-protection After Myocardial Ischemia/Reperfusion Injury by Reducing 4-HNE Levels and Regulating Autophagy via the ALDH2/SIRT3/HIF1α Signaling Pathway

Remote ischemic conditioning (RIC) can be effectively applied for cardio-protection. Here, to clarify whether RIC exerts myocardial protection via aldehyde dehydrogenase 2 (ALDH2), we established a myocardial ischemia/reperfusion (I/R) model in C57BL/6 and ALDH2 knockout (ALDH2-KO) mice and treated them with RIC. Echocardiography and single-cell contraction experiments showed that RIC significantly improved myocardial function and alleviated I/R injury in C57BL/6 mice but did not exhibit its cardioprotective effects in ALDH2-KO mice. TUNEL, Evan's blue/triphenyl tetrazolium chloride, and reactive oxygen species (ROS) assays showed that RIC's effect on reducing myocardial cell apoptosis, myocardial infarction area, and ROS levels was insignificant in ALDH2-KO mice. Our results showed that RIC could increase ALDH2 protein levels, activate sirtuin 3 (SIRT3)/hypoxia-inducible factor 1-alpha (HIF1α), inhibit autophagy, and exert myocardial protection. This study revealed that RIC could exert myocardial protection via the ALDH2/SIRT3/HIF1α signaling pathway by reducing 4-HNE secretion.

Sirtuin 3 is required for the dexmedetomidine-mediated alleviation of inflammation and oxidative stress in nephritis

INTRODUCTION

Although sirtuin 3 (SIRT3) is known to be involved in dexmedetomidine (DEX)-mediated alleviation of renal ischemia and reperfusion injury, the influence of the association between DEX and SIRT3 on nephritis development remains unclear. In this study, the role of SIRT3 in DEX-mediated amelioration of inflammation and oxidative stress in nephritis as well as the possible underlying mechanism were explored in vivo and in vitro.

METHODS

An animal model of glomerulonephritis was generated by injecting mice with interferon-alpha (IFNα)-expressing adenoviruses, and periodic acid-Schiff staining was then used to reveal pathogenicity-related changes in the renal tissue. Additionally, human embryonic kidney cells (HEK293) and renal mesangial cells (RMCs) were treated with IFNα to establish cell models of inflammation in vitro.

RESULTS

DEX administration alleviated glomerulonephritis in the animal model and upregulated SIRT3 expression in the renal tissue. SIRT3 knockdown inhibited the renoprotective effects of DEX against nephritis. IFNα induced inflammation, oxidative stress, and apoptosis in the RMCs and HEK293 cells and reduced their growth, as evidenced by the evaluation of cytokine levels (enzyme-linked immunosorbent assay), reactive oxygen species generation, catalase and superoxide dismutase activities, nuclear factor-erythroid factor 2-related factor 2/heme oxygenase-1 signal transduction, apoptotic cell proportion, and cell viability. In addition to promoting SIRT3 expression, DEX inhibited IFNα-induced inflammation, oxidative stress, and apoptosis in these cells and promoted their viability. SIRT3 knockdown partially reversed the beneficial effects of DEX on RMCs and HEK293 cells.

CONCLUSIONS

Our results suggest that DEX exhibits renoprotective activity during nephritis progression, protecting renal cells against inflammatory injury by promoting SIRT3 expression.

AMPK activation coupling SENP1-Sirt3 axis protects against acute kidney injury

Acute kidney injury (AKI) is a critical clinical condition that causes kidney fibrosis, and it currently lacks specific treatment options. In this research, we investigate the role of the SENP1-Sirt3 signaling pathway and its correlation with mitochondrial dysfunction in proximal tubular epithelial cells (PTECs) using folic acid (FA) and ischemia-reperfusion-induced (IRI) AKI models. Our findings reveal that Sirt3 SUMOylation site mutation (Sirt3 KR) or pharmacological stimulation (metformin) protected mice against AKI and subsequent kidney inflammation and fibrosis by decreasing the acetylation level of mitochondrial SOD2, reducing mitochondrial reactive oxygen species (mtROS), and subsequently restoring mitochondrial ATP level, reversing mitochondrial morphology and alleviating cell apoptosis. In addition, AKI in mice was similarly alleviated by reducing mtROS levels using N-acetyl-L-cysteine (NAC) or MitoQ. Metabolomics analysis further demonstrated an increase in antioxidants and metabolic shifts in Sirt3 KR mice during AKI, compared with Sirt3 wild-type (WT) mice. Activation of the AMPK pathway using metformin promoted the SENP1-Sirt3 axis and protected PTECs from apoptosis. Hence, the augmented deSUMOylation of Sirt3 in mitochondria, activated through the metabolism-related AMPK pathway, protects against AKI and subsequently mitigated renal inflammation and fibrosis through Sirt3-SOD2-mtROS, which represents a potential therapeutic target for AKI.

Reno-protective effects of perioperative dexmedetomidine in kidney transplantation: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

There is currently no FDA-approved medical therapy for delayed graft function (DGF). Dexmedetomidine (DEX) has multiple reno-protective effects preventing ischemic reperfusion injury, DGF, and acute kidney injury. Therefore, we aimed to evaluate the reno-protective effects of perioperative DEX during renal transplantation.

METHODS

A systematic review and meta-analysis synthesizing randomized controlled trials (RCTs) from WOS, SCOPUS, EMBASE, PubMed, and CENTRAL until June 8th, 2022. We used the risk ratio (RR) for dichotomous outcomes and the mean difference for continuous outcomes; both presented with the corresponding 95% confidence interval (CI). We registered our protocol in PROSPERO with ID: CRD42022338898.

RESULTS

We included four RCTs with 339 patients. Pooled risk ratio found no difference between DEX and placebo in reducing DGF (RR: 0.58 with 95% CI [0.34, 1.01], p = 0.05) and acute rejection (RR: 0.88 with 95% CI [0.52, 1.49], p = 0.63). However, DEX improved short-term creatinine on day 1 (MD: - 0.76 with 95% CI [- 1.23, - 0.3], p = 0.001) and day 2 (MD: - 0.28 with 95% CI [- 0.5, - 0.07], p = 0.01); and blood urea nitrogen on day 2 (MD: - 10.16 with 95% CI [- 17.21, - 3.10], p = 0.005) and day 3 (MD: - 6.72 with 95% CI [- 12.85, - 0.58], p = 0.03).

CONCLUSION

Although there is no difference between DEX and placebo regarding reducing DGF and acute rejection after kidney transplantation, there may be some evidence that it has reno-protective benefits because we found statistically significant improvement in the short-term serum creatinine and blood urea nitrogen levels. More trials are required to investigate the long-term reno-protective effects of DEX.

The Effects of Dexmedetomidine on Abdominal Aortic Occlusion-Induced Ovarian Injury via Oxidative Stress and Apoptosis

Ischemia/reperfusion (I/R) induced ovarian damage is caused by various diseases such as ovarian torsion, ovarian transplantation, cardiovascular surgery, sepsis, or intra-abdominal surgery. I/R-related oxidative damage can impair ovarian functions, from oocyte maturation to fertilization. This study investigated the effects of dexmedetomidine (DEX), which has been shown to exhibit antiapoptotic, anti-inflammatory, and antioxidant effects, on ovarian I/R injury. We designed four study groups: group 1 (n = 6): control group; group 2 (n = 6): only DEX group; group 3 (n = 6): I/R group; group 4 (n = 6): I/R + DEX group. Then, ovarian samples were taken and examined histologically and immunohistochemically, and tissue malondialdehyde (MDA) and glutathione (GSH) levels were measured. In the I/R group MDA levels, caspase-3, NF-κB/p65, 8-OHdG positivity, and follicular degeneration, edema, and inflammation were increased compared to the control group (p = 0.000). In addition, GSH levels were significantly decreased in the I/R group compared to the control group (p = 0.000). On the other hand, in the I/R + DEX treatment group MDA levels, caspase-3, NF-κB/p65, 8-OHdG positivity, follicular degeneration, edema, and inflammation findings were decreased than in the I/R group (p = 0.000, p = 0.005, p = 0.005, p = 0.001, p = 0.005, respectively). However, GSH levels increased significantly in the I/R + DEX treatment group compared to the I/R group (p = 0.000). DEX protects against ovarian I/R injury through antioxidation and by suppressing inflammation and apoptosis.

Role of Sirtuin 3 in Degenerative Diseases of the Central Nervous System

An NAD⁺-dependent deacetylase called Sirtuin 3 (Sirt3) is involved in the metabolic processes of the mitochondria, including energy generation, the tricarboxylic acid cycle, and oxidative stress. Sirt3 activation can slow down or prevent mitochondrial dysfunction in response to neurodegenerative disorders, demonstrating a strong neuroprotective impact. The mechanism of Sirt3 in neurodegenerative illnesses has been elucidated over time; it is essential for neuron, astrocyte, and microglial function, and its primary regulatory factors include antiapoptosis, oxidative stress, and the maintenance of metabolic homeostasis. Neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS), may benefit from a thorough and in-depth investigation of Sirt3. In this review, we primarily cover Sirt3's role and its regulation in the nerve cells and the connection between Sirt3 and neurodegenerative disorders.

Rapamycin ameliorates brain damage and maintains mitochondrial dynamic balance in diabetic rats subjected to middle cerebral artery occlusion

To investigate the effect of rapamycin on mitochondrial dynamic balance in diabetic rats subjected to cerebral ischemia-reperfusion injury. Male Sprague Dawley (SD) rats (n = 78) were treated with high fat diet combined with streptozotocin injection to construct diabetic model in rats. Transient middle cerebral artery occlusion (MCAO) of 2 hours was induced and the brains were harvested after 1 and 3 days of reperfusion. Rapamycin was injected intraperitoneally for 3 days prior to and immediately after operation, once a day. The neurological function was assessed, infarct volumes were measured and HE staining as well as immunohistochemistry were performed. The protein of hippocampus was extracted and Western blotting were performed to detect the levels of mTOR, mitochondrial dynamin related proteins (DRP1, p-DRP1, OPA1), SIRT3, and Nix/BNIP3L. Diabetic hyperglycemia worsened the neurological function performance (p < 0.01), enlarged infarct size (p < 0.01) and increased ischemic neuronal cell death (p < 0.01). The increased damage was associated with elevations of p-mTOR, p-S6, and p-DRP1; and suppressions of SIRT3 and Nix/BNIP3L. Rapamycin ameliorated diabetes-enhanced ischemic brain damage and reversed the biomarker alterations caused by diabetes. High glucose activated mTOR pathway and caused mitochondrial dynamics toward fission. The protective effect of rapamycin against diabetes-enhanced ischemic brain damage was associated with inhibiting mTOR pathway, redressing mitochondrial dynamic imbalance, and elevating SIRT3 and Nix/BNIP3L expression.

Why Is Longevity Still a Scientific Mystery? Sirtuins-Past, Present and Future

The sirtuin system consists of seven highly conserved regulatory enzymes responsible for metabolism, antioxidant protection, and cell cycle regulation. The great interest in sirtuins is associated with the potential impact on life extension. This article summarizes the latest research on the activity of sirtuins and their role in the aging process. The effects of compounds that modulate the activity of sirtuins were discussed, and in numerous studies, their effectiveness was demonstrated. Attention was paid to the role of a caloric restriction and the risks associated with the influence of careless sirtuin modulation on the organism. It has been shown that low modulators' bioavailability/retention time is a crucial problem for optimal regulation of the studied pathways. Therefore, a detailed understanding of the modulator structure and potential reactivity with sirtuins in silico studies should precede in vitro and in vivo experiments. The latest achievements in nanobiotechnology make it possible to create promising molecules, but many of them remain in the sphere of plans and concepts. It seems that solving the mystery of longevity will have to wait for new scientific discoveries.

Mitochondrial unfolded protein response in ischemia-reperfusion injury

Mitochondrial unfolded protein response (UPRmt) is a mitochondrial stress response that activates the transcriptional program of mitochondrial chaperone proteins and proteases to keep protein homeostasis in mitochondria. Ischemia-reperfusion injury results in multiple severe clinical issues linked to high morbidity and mortality in various disorders. The pathophysiology and pathogenesis of ischemia-reperfusion injury are complex and multifactorial. Emerging evidence showed the roles of UPRmt signaling in ischemia-reperfusion injury. Herein, we discuss the regulatory mechanisms underlying UPRmt signaling in C. elegans and mammals. Furthermore, we review the recent studies into the roles and mechanisms of UPRmt signaling in ischemia-reperfusion injury of the heart, brain, kidney, and liver. Further research of UPRmt signaling will potentially develop novel therapeutic strategies against ischemia-reperfusion injury.

DEXMEDETOMIDINE PREVENTS PDIA3 DECREASE BY ACTIVATING α2-ADRENERGIC RECEPTOR TO ALLEVIATE INTESTINAL I/R IN MICE

ABSTRACT

Background: Dexmedetomidine (DEX) attenuates intestinal I/R injury, but its mechanism of action remains to be further elucidated. Protein disulfide isomerase A3 (PDIA3) has been reported as a therapeutic protein for the prevention and treatment of intestinal I/R injury. This study was to investigate whether PDIA3 is involved in intestinal protection of DEX and explore the underlying mechanisms. Methods: The potential involvement of PDIA3 in DEX attenuation of intestinal I/R injury was tested in PDIA3 Flox/Flox mice and PDIA3 conditional knockout (cKO) in intestinal epithelium mice subjected to 45 min of superior mesenteric artery occlusion followed by 4 h of reperfusion. Furthermore, the α2-adrenergic receptor (α2-AR) antagonist, yohimbine, was administered in wild-type C57BL/6N mice intestinal I/R model to investigate the role of α2-AR in the intestinal protection conferred by DEX. Results: In the present study, we identified intestinal I/R-induced obvious inflammation, endoplasmic reticulum (ER) stress-dependent apoptosis, and oxidative stress, and all the aforementioned changes were improved by the administration of DEX. PDIA3 cKO in the intestinal epithelium have reversed the protective effects of DEX. Moreover, yohimbine also reversed the intestinal protection of DEX and downregulated the messenger RNA and protein levels of PDIA3. Conclusion: DEX prevents PDIA3 decrease by activating α2-AR to inhibit intestinal I/R-induced inflammation, ER stress-dependent apoptosis, and oxidative stress in mice.

Dexmedetomidine Confers Protection Against Neuronal Oxygen Glucose Deprivation-Reperfusion by Regulating SIRT3 Mediated Autophagy

Dexmedetomidine (Dex) plays protective effects on brain ischemia-reperfusion (I/R) injury, but its mechanism remains unclear. In this study, we aimed to investigate whether Dex protects neurons against I/R injury by activating SIRT3 mediated autophagy. The oxygen glucose deprivation-reperfusion (OGD/R) model was constructed in HT22 cells. Different doses of Dex (50 ng/mL, 100 ng/mL and 500 ng/mL) were treated to observe the changes of autophagy and SIRT3 expression. Further, the mimic of SIRT3 and SIRT3 inhibitor were used to analyze the effects of Dex on the SIRT3 expression in HT22 cells. Additionally, the autophagy inhibitor and AMPK inhibitor were used to analyze the effects of Dex on SIRT3 mediated autophagy. The cells viability, oxidative stress and ATP were observed using assay kits. The mitochondrial membrane potential (MMP) and death were analyzed by flow cytometry. The degree of autophagy was observed by acridine orange staining. Western blotting was used to analyze the expression of autophagy related proteins and AMPK/mTOR pathway related proteins. After Dex treatment, the OGD/R induced cell injury was significantly improved through decreasing the levels of LDH and H₂O₂, increasing levels of ATP and MMP. Furthermore, Dex increased the degree of autophagy and expression of SIRT3 in OGD/R injured cells. Through overexpression of SIRT3, the OGD/R induced cell injury was also clearly improved. But the SIRT3 inhibitor or autophagy inhibitor covered the roles of Dex. Additionally, AMPK inhibitor played an opposite role compared with the effects of Dex treatment. From this study, the protection mechanism of Dex on neurons I/R injury might related to the activation of SIRT3 mediated autophagy.

The Role of Dexmedetomidine in Tumor-Progressive Factors in the Perioperative Period and Cancer Recurrence: A Narrative Review

Dexmedetomidine, a specific α2 adrenergic receptor agonist, is highly frequently used in the perioperatively for its favorable pharmacology, such as mitigating postoperative cognitive dysfunction. Increasing attention has been recently focused on the effect of whether dexmedetomidine influences cancer recurrence, which urges the discussion of the role of dexmedetomidine in tumor-progressive factors. The pharmacologic characteristics of dexmedetomidine, the tumor-progressive factors in the perioperative period, and the relationships between dexmedetomidine and tumor-progressive factors were described in this review. Available evidence suggests that dexmedetomidine could reduce the degree of immune function suppression, such as keeping the number of CD3+ cells, NK cells, CD4+/CD8+ ratio, and Th1/Th2 ratio stable and decreasing the level of proinflammatory cytokine (interleukin 6 and tumor necrosis factor-alpha) during cancer operations. However, dexmedetomidine exhibits different roles in cell biological behavior depending on cancer cell types. The conclusions on whether dexmedetomidine would influence cancer recurrence could not be currently drawn for the lack of strong clinical evidence. Therefore, this is still a new area that needs further exploration.

Dexmedetomidine Attenuates Ferroptosis-Mediated Renal Ischemia/Reperfusion Injury and Inflammation by Inhibiting ACSL4 via α2-AR

Ischemia-reperfusion (I/R) injury is a serious clinical pathology associated with acute kidney injury (AKI). Ferroptosis is non-apoptotic cell death that is known to contribute to renal I/R injury. Dexmedetomidine (Dex) has been shown to exert anti-inflammatory and organ protective effects. This study aimed to investigate the detailed molecular mechanism of Dex protects kidneys against I/R injury through inhibiting ferroptosis. We established the I/R-induced renal injury model in mice, and OGD/R induced HEK293T cells damage in vitro. RNA-seq analysis was performed for identifying the potential therapeutic targets. RNA-seq analysis for differentially expressed genes (DEGs) reported Acyl-CoA synthetase long-chain family member 4 (ACSL4) related to ferroptosis and inflammation in I/R mice renal, which was validated in rodent renal. Liproxstatin-1, the specific small-molecule inhibitor of ferroptosis, significantly attenuated ferroptosis-mediated renal I/R injury with decreased LPO, MDA, and LDH levels, and increased GSH level. Inhibiting the activity of ACSL4 by the Rosiglitazone (ROSI) resulted in the decreased ferroptosis and inflammation, as well as reduced renal tissue damage, with decreasing LPO, MDA and LDH level, increasing GSH level, reducing COX2 and increasing GPx4 protein expression, and suppressing the TNF-α mRNA and IL-6 mRNA levels. Dex as a α2-adrenergic receptor (α2-AR) agonist performed renal protective effects against I/R-induced injury. Our results also revealed that Dex administration mitigated tissue damage, inhibited ferroptosis, and downregulated inflammation response following renal I/R injury, which were associated with the suppression of ACSL4. In addition, ACSL4 overexpression abolishes Dex-mediated protective effects on OGD/R induced ferroptosis and inflammation in HEK293T cells, and promotion of ACSL4 expression by α2-AR inhibitor significantly reversed the effects on the protective role of Dex. This present study indicated that the Dex attenuates ferroptosis-mediated renal I/R injury and inflammation by inhibiting ACSL4 via α2-AR.

Sirtuin 3 and mitochondrial permeability transition pore (mPTP): A systematic review

Mitochondrial permeability transition pore (mPTP) is a channel that opens at the inner mitochondrial membrane under conditions of stress. Sirtuin 3 (Sirt3) is a mitochondrial deacetylase known to play a major role in stress resistance and a regulatory role in cell death. This systematic review aims to elucidate the role of Sirt3 in mPTP inhibition. Electronic databases, including PubMed, EMBASE, Web of Science and Cochrane Library were searched up to May 2020. Original studies that investigated the relationship between Sirt3 and mPTP were included. Two reviewers independently extracted data on study characteristics, methods and outcomes. A total of 194 articles were found. Twenty-nine articles, which met criteria were included in the systematic review. Twenty-three studies provided evidence of the inhibitory effect of Sirt3 on the mPTP aperture. This review summarizes up-to-date evidence of the protective and inhibitory role of Sirt3 through deacetylating Cyclophilin D (CypD) on the mPTP aperture. Furthermore, we discuss the implications of this effect in disease.

Renoprotective Effect of Intraoperative Dexmedetomidine in Renal Transplantation

BACKGROUND

Renal dysfunction after kidney transplantation may be influenced by many reasons. This study was designed to evaluate whether the administration of dexmedetomidine (Dex) could ameliorate renal function and prognosis after kidney transplantation.

METHODS

A total of 65 patients were divided into Dex group (n = 33) and Con group (Con, n = 32). Dex group intravenously received an initial loading dose of 0.6 μg/kg Dex for 15 min before anaesthesia induction, followed by a rate of 0.4 μg/kg/h until 30 min after kidney reperfusion. By contrast, Con group received saline. The concentration of urinary kidney injury molecule-1 (KIM-1), serum creatinine (Cr), blood urea, urine output, β2 microglobulin (β2-MG), Cystatin C (CysC), and estimated glomerular filtration rate (eGFR) was recorded and compared between two groups during the course of the hospitalization or follow-up. Mean arterial pressure (MAP) and heart rate (HR), vasoactive drugs, and anaesthetics were recorded during the operation. Pain degree was evaluated using a visual analogue scale (VAS) after operation. Delayed graft function (DGF), graft loss, length of hospital stay, and mortality were compared between groups.

RESULTS

The concentration of KIM-1 in Dex group was lower than Con group at 2 h (P = 0.018), 24 h (P = 0.013), 48 h (P < 0.01), and 72 h (P < 0.01) after reperfusion. MAP of Dex group after tracheal intubation (P = 0.012) and incision (P = 0.018) and HR after intubation (P = 0.021) were lower than that of Con group. The dosage of sufentanil during operation in Dex group was less than Con group (P = 0.039). Patients that used atropine in Dex group were more than Con group (P = 0.027). Patients who received Dex presented with lower VAS scores at 6 h (P = 0.01) and 12 h (P = 0.002) after operation. Concentration of serum Cr and blood urea had no significant differences between groups before operation and on postoperative day 1 to 6. Urine output was recorded for 6 days after operation and had no differences between groups. Also, no differences were identified between two groups in urea, Cr, β2-MG, CysC, and eGFR in the first 3 months after operation. Incidence of DGF after operation was detected no difference between groups, while length of hospital stay in Dex group was less than Con group (P = 0.012).

CONCLUSION

Dex can decrease kidney injury marker level, attenuate perioperative stress, relieve the dosage of sufentanil and postoperative pain, and reduce length of hospital stay. However, Dex is not associated with changes in prognosis in the first 3 months after transplantation.

Research on Mechanism of miR-106a Nanoparticles Carrying Dexmedetomidine in Regulating Recovery and Metabolism of Nerve Cells in Hypoxia-Reoxygenation Injury

We studied the mechanism of miR-106a nanoparticles carrying dexmedetomidine (DEX) in regulating the recovery and metabolism of nerve cells in hypoxia-reoxygenation injury. Hippocampus neuron model in hypoxia-reoxygenation injury was prepared in vitro. Study groups were randomly divided into control set, ischemic reperfusion (IR) set, dexmedetomidine (DEX) set, miR-106a-nanoparticles (NPs) set and set of dexmedetomidine (DEX) and miR-106a-NPs. We studied miR-106a expression, proliferative and apoptotic activity, secretion of IL-6 and tumor necrosis factor (TNF)-α, quantity of Phosphocreatine (PCr), adenosine triphosphate (ATP) and total adenine nucleotide, and also content of reactive oxygen species (ROS) and superoxide dismutases (SOD). Expressions of of Bax, Bcl-2 and NF-κB were also detected. Results showed that the expression of miR-106a in hippocampus neuron was reduced, while proliferation was reduced and apoptotic activity was increased. The secretions of IL-6 and TNF-α were increased, while the quantities of Phosphocreatine (PCr), adenosine triphosphate (ATP) and total adenine nucleotide were reduced. Bax expression was also increased and Bcl-2 expression was reduced. Moreover, ROS content was increased and SOD activity was reduced, while the NF-κB presentation was increased. The above-mentioned changes could be reversed in IR set, DEX set and miR-106a-NPs set. The action was more notable in the DEX and miR-106a-NPs sets. Finally, the proliferation in hippocampus neuron in hypoxia-reoxygenation injury could be prompted and apoptosis could be restrained by DEX and miR-106a-NPs. The secretion of inflammatory factors could be restrained through restraining the inflammatory pathway and oxidative stress. The energy metabolism could therefore be improved effectively and recovery of nerve cells in HBI could be improved.

SIRT3 mediates mitofusin 2 ubiquitination and degradation to suppress ischemia reperfusion-induced acute kidney injury

Ischemia reperfusion-induced acute kidney injury (IR-induced AKI) is a life-threatening disease with many complications. Mitofusin 2 (Mfn2) ubiquitination is related to AKI. But the underlying molecular mechanisms remain unknown. This study aimed to probe the mechanism of Mfn2 ubiquitination in IR-induced AKI development. In IR-induced AKI mouse models, orbital blood and urine were collected for assessing kidney function. The kidney injury, ultrastructure of mitochondria, and histopathology in mice were evaluated after injection of G5, an ubiquitination inhibitor. Oxygen glucose deprivation/reoxygenation (OGD/R) models were established in HK-2 cells, and the mitochondria were extracted. Cell viability, apoptosis, oxidative stress, inflammatory reaction, mitochondrial membrane potential, and ATP production were measured. Mfn2 ubiquitination in mouse and cell models was evaluated. si-SIRT3 and pcDNA3.1-SIRT3 were transfected into cell models. Consequently, kidney function in mice was impaired by IR-induced AKI. Mfn2 ubiquitination and degradation promoted IR-induced AKI. OGD/R induced renal tubular epithelial cell injury and disrupted mitochondrial dynamics and functions through promoting Mfn2 ubiquitination. SIRT3 knockdown led to Mfn2 ubiquitination by binding to UBC; while its overexpression alleviated tubular epithelial cell injury. Briefly, SIRT3 mediates Mfn2 ubiquitination to relieve IR-induced AKI. This investigation may offer new insights for the treatment of IR-induced AKI injury.

The Protective Effect of Dexmedetomidine Against Ischemia-Reperfusion Injury after Hepatectomy: A Meta-Analysis of Randomized Controlled Trials

Background: Hepatic inflow occlusion proceeded to reduce blood loss during hepatectomy induces ischemia-reperfusion (IR) injury in the remnant liver. Dexmedetomidine, a selective α₂-adrenoceptor agonist used as an anesthetic adjuvant, has been shown to attenuate IR injury in preclinical and clinical studies. However, a meta-analysis is needed to systematically evaluate the protective effect of perioperative dexmedetomidine use on IR injury induced by hepatectomy.

Methods: A prospectively registered meta-analysis following Cochrane and PRISMA guidelines concerning perioperative dexmedetomidine use on IR injury after hepatectomy was performed via searching Cochrane Library, PubMed, EMBASE, ClinicalTrials.gov, Web of Science, CNKI, WanFang, and Sinomed for eligible randomized controlled trials up to 2021.3.31. The main outcome is postoperative liver function. Risk of bias was assessed by the Cochrane Risk of Bias tool. Review Manager 5.3 and Stata12.0 were applied to perform data analyses.

Results: Eight RCTs enrolling 468 participants were included. Compared with 0.9% sodium chloride, dexmedetomidine decreased serum concentration of ALT (WMD = −66.54, 95% CI: −92.10–−40.98), AST (WMD= −82.96, 95% CI: −106.74–−59.17), TBIL (WMD = −4.51, 95% CI: −7.32–−1.71), MDA (WMD = −3.09, 95% CI: −5.17–−1.01), TNF-α (WMD = −36.54, 95% CI: −61.33–−11.95) and IL-6 (WMD = −165.05, 95% CI: −225.76–−104.34), increased SOD activity (WMD = 24.70, 95% CI: 18.09–31.30) within postoperative one day. There was no significant difference in intraoperative or postoperative recovery parameters between groups.

Conclusions: Perioperative administration of dexmedetomidine can exert a protective effect on liver IR injury after hepatectomy. Additional studies are needed to further evaluate postoperative recovery outcomes of dexmedetomidine with different dosing regimens.

Post-translational Acetylation Control of Cardiac Energy Metabolism

Perturbations in myocardial energy substrate metabolism are key contributors to the pathogenesis of heart diseases. However, the underlying causes of these metabolic alterations remain poorly understood. Recently, post-translational acetylation-mediated modification of metabolic enzymes has emerged as one of the important regulatory mechanisms for these metabolic changes. Nevertheless, despite the growing reports of a large number of acetylated cardiac mitochondrial proteins involved in energy metabolism, the functional consequences of these acetylation changes and how they correlate to metabolic alterations and myocardial dysfunction are not clearly defined. This review summarizes the evidence for a role of cardiac mitochondrial protein acetylation in altering the function of major metabolic enzymes and myocardial energy metabolism in various cardiovascular disease conditions.

Atractylon treatment prevents sleep-disordered breathing-induced cognitive dysfunction by suppression of chronic intermittent hypoxia-induced M1 microglial activation

Chronic intermittent hypoxia (CIH) induced by sleep-disordered breathing (SDB) is a key factor involved in cognitive dysfunction (CD). Increasing evidence has shown that atractylon (ATR) has anti-inflammatory effects. However, it remains unclear if ATR has a protective effect against SDB-induced nerve cell injury and CD. So, in the present study, CIH-exposed mice and CIH-induced BV2 cells were used to mimic SDB. The results showed that ATR treatment decreased CIH-induced CD and the expression of inflammatory factors in the hippocampal region by suppression of M1 microglial activation and promotion of M2 microglial activation. Also, ATR treatment promoted sirtuin 3 (SIRT3) expression. Down-regulation of SIRT3 decreased the protective effect of ATR against CIH-induced microglial cell injury. Furthermore, in vitro detection found that SIRT3 silencing suppressed ATR-induced M2 microglial activation after exposure to CIH conditions. Taken together, these results indicate that ATR treatment prevents SDB-induced CD by inhibiting CIH-induced M1 microglial activation, which is mediated by SIRT3 activation.

Effects of dexmedetomidine on the function of distal organs and oxidative stress after lower limb ischaemia-reperfusion in elderly patients undergoing unilateral knee arthroplasty

Aims

This study aims to evaluate the effects of dexmedetomidine on organ function, inflammation response, and oxidative stress in elderly patients following iatrogenic lower limb ischaemia–reperfusion (IR) during unilateral total knee arthroplasty.

Methods

Following unilateral total knee arthroplasty, 54 elderly patients were randomized to receive either intraoperative intravenous injection of dexmedetomidine (n = 27) or equivalent volume of 0.9% saline (n = 27). Blood samples were harvested at 5 minutes before lower limb tourniquet release (baseline); and 1, 6 and 24 hours after tourniquet release. Surrogate markers of cardiac, pulmonary, hepatic and renal function, oxidative stress, inflammatory response, along with parasympathetic and sympathetic activity were recorded and analysed.

Results

The levels of blood xanthine oxidase, creatine kinase, lactic acid and respiratory index increased in patients following tourniquet‐induced lower limb IR injury. Dexmedetomidine administration decreased the respiratory index (P = .014, P = .01, and P = .043) and the norepinephrine level (P < .001) at 1, 6 and 24 hours; and decreased the xanthine oxidase level (P = .049, P < .001) at 6 and 24 hours after tourniquet release compared with the Control group. Other measurements, including creatine kinase isoenzyme, lactate dehydrogenase, creatinine, urea nitrogen, glutamic–oxalacetic transaminase, glutamic–pyruvic transaminase, malondialdehyde, interleukin‐1, interleukin‐6 and tumour necrosis factor‐α, were not statistically significantly different between the 2 groups.

Conclusions

Intraoperative dexmedetomidine administration in elderly patients dampens the deterioration in respiratory function and suppresses the oxidative stress response in elderly patients following iatrogenic lower limb IR injury.

Dexmedetomidine protects cardiac microvascular endothelial cells from the damage of ogd/r through regulation of the pparδ-mediated autophagy

BACKGROUND

Dexmedetomidine (Dex) exerts an effective therapeutic role in numerous diseases associated with ischemia/reperfusion (I/R) injury via its anti-apoptosis properties. Therefore, this study explores the cardioprotective effects of Dex in cardiac microvascular endothelial cells (CMECs) in response to oxygen-glucose deprivation and re-oxygenation (OGD/R) injury and its potential mechanism.

MATERIAL AND METHODS

CMECs were pretreatment with different concentration of Dex, then exposed to OGD/R. Cell viability was measured with CCK-8 assay. Apoptosis was evaluated by flow cytometry, and apoptosis-related protein was determined by Western blot. Autophagy was assessed by transmission electron microscopy and autophagy-related proteins. Besides, the role peroxisome proliferator-activated receptors (PPARδ) in Dex-mediated anti-apoptosis property was validated with agonist and antagonist.

RESULTS

OGD/R significantly decreased cell viability, increased reactive oxygen species, caused disorder of autophagy, and increased apoptosis in CMECs. Dex enhanced the viability of the OGD/R-treated CMECs and effectively decreased reactive oxygen species production. Autophagy in CMECs was activated by Dex, as evidenced by the increase in the ratio of LC3B-II/I, expression level of Beclin1 and number of autophagosomes in the OGD/R-induced CMECs. The mechanistic investigation indicated that PPARδ antagonist GW501516 aggravated cell damage following OGD/R, while PPARδ agonist GW6471 partly abolished the Dex-mediated protective effects.

CONCLUSIONS

Dex activated the PPARδ-AMPK-PGC-1α pathway-mediated autophagy in CMECs, therefore to inhibit excessive apoptosis induced by OGD/R. Dex may potentially be a therapeutic intervention for myocardial I/R injury.

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.

Impact of Dexmedetomidine Infusion on Postoperative Acute Kidney Injury in Elderly Patients Undergoing Major Joint Replacement: A Retrospective Cohort Study

Purpose

Postoperative acute kidney injury (AKI) is a frequent complication in elderly patients that increases morbidity and mortality. Approximately 1.7 million people die from AKI worldwide every year. Dexmedetomidine (Dex) is often used as an adjunct to multimodal analgesia. Our study investigated whether Dex could safely decrease the incidence of AKI in elderly patients undergoing major joint replacement.

Methods

A single-center retrospective study was conducted in patients aged >65 years undergoing major joint replacement. Propensity score–matching analysis was used, and a total of 1,006 patients were matched successfully. The primary outcome was the incidence of postoperative AKI. Secondary outcomes included perioperative adverse complications, opioid consumption, time to extubation, and length of hospital stay.

Results

Among the 1,006 patients included, postoperative AKI occurred in 9.3% (n=94). The Dex group (perioperative Dex infusion) had lower incidence of postoperative AKI than the control group (7.2% vs 11.5%, P=0.017). Compared with the control group, the Dex group had less opioid consumption (P<0.05), reduced time to extubation (P=0.004), and shorter length of hospital stay (P=0.001). The Dex group also showed higher incidence of bradycardia (20.1% vs 15.1%, P=0.038). There were no differences in intraoperative hypotension (19.5% vs 17.5%), postoperative nausea and vomiting (4.2% vs 5.4%), time in PACU (45.0±6.4 vs 45.5±6.2 minutes), or rate of ICU admission (9.7% vs 11.1%) between the Dex group and control group (All P>0.05).

Conclusion

This retrospective study showed Dex infusion in elderly patients undergoing major joint replacement was associated with lower incidence of postoperative AKI, less opioid consumption, and shorter extubation time and hospital stay. However, the Dex group had higher incidence of bradycardia. We found no statistical differences in other perioperative adverse complications between the groups.

Protein acetylation and deacetylation: An important regulatory modification in gene transcription (Review)

Cells primarily rely on proteins to perform the majority of their physiological functions, and the function of proteins is regulated by post-translational modifications (PTMs). The acetylation of proteins is a dynamic and highly specific PTM, which has an important influence on the functions of proteins, such as gene transcription and signal transduction. The acetylation of proteins is primarily dependent on lysine acetyltransferases and lysine deacetylases. In recent years, due to the widespread use of mass spectrometry and the emergence of new technologies, such as protein chips, studies on protein acetylation have been further developed. Compared with histone acetylation, acetylation of non-histone proteins has gradually become the focus of research due to its important regulatory mechanisms and wide range of applications. The discovery of specific protein acetylation sites using bioinformatic tools can greatly aid the understanding of the underlying mechanisms of protein acetylation involved in related physiological and pathological processes.

Molecular pathophysiology of acute kidney injury: The role of sirtuins and their interactions with other macromolecular players

Acute kidney injury (AKI), a rapid drop in kidney function, displays high mortality and morbidity, and its repeated or severe status can shift into chronic kidney disease or even end-stage renal disease. How and which events cause AKI still is controversial. In addition, no specific therapies have emerged that can attenuate AKI or expedite recovery. Some central mechanisms including tubular epithelial cells injury, endothelial injury, renal cell apoptosis, and necrosis signaling cascades, and inflammation have been reported in the pathophysiology of AKI. However, the timing of the activation of each pathway, their interactions, and the hierarchy of these pathways remain unknown. The main molecular mechanisms that might be complicated in this process are the mitochondrial impairment and alteration/shifting of cellular metabolites (e.g., acetyl-CoA and NAD⁺ /NADH) acting as cofactors to alter the activities of many enzymes, for instance, sirtuins. Moreover, alteration of mitochondrial structure over the fusion and fission mechanisms can regulate cellular signaling pathways by modifying the rate of reactive oxygen species generation and metabolic activities. The aim of this review is to better understand the underlying pathophysiological and molecular mechanisms of AKI. In addition, we predicted the main other molecular players in interaction with sirtuins as energy/stresses monitoring proteins for the development of future approaches in the treatment or prevention of ischemic AKI.

Mitochondrial Sirtuin 3: New emerging biological function and therapeutic target

Sirtuin 3 (SIRT3) is one of the most prominent deacetylases that can regulate acetylation levels in mitochondria, which are essential for eukaryotic life and inextricably linked to the metabolism of multiple organs. Hitherto, SIRT3 has been substantiated to be involved in almost all aspects of mitochondrial metabolism and homeostasis, protecting mitochondria from a variety of damage. Accumulating evidence has recently documented that SIRT3 is associated with many types of human diseases, including age-related diseases, cancer, heart disease and metabolic diseases, indicating that SIRT3 can be a potential therapeutic target. Here we focus on summarizing the intricate mechanisms of SIRT3 in human diseases, and recent notable advances in the field of small-molecule activators or inhibitors targeting SIRT3 as well as their potential therapeutic applications for future drug discovery.

Effect of dexmedetomidine on acute kidney injury after aortic surgery: a single-centre, placebo-controlled, randomised controlled trial

BACKGROUND

Acute kidney injury (AKI) is a frequent and serious complication after aortic surgery requiring cardiopulmonary bypass (CPB). Dexmedetomidine, a selective α-2 adrenoreceptor agonist, may reduce AKI because of its sympatholytic and anti-inflammatory effects against ischaemia-reperfusion injury. We investigated the effect of dexmedetomidine administration on AKI after aortic surgery requiring CPB in a placebo-controlled randomised controlled trial.

METHODS

A total of 108 patients were randomly assigned to an infusion of dexmedetomidine or saline at a rate of 0.4 μg kg-1 h-1 for 24 h starting after anaesthetic induction. The primary outcome was the incidence of AKI, as defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. The secondary outcomes included delirium and major morbidity. Safety outcomes were drug-related adverse events (bradycardia, hypotension).

RESULTS

AKI occurred in 7/54 (13%) subjects randomised to dexmedetomidine, compared with 17/54 (31%) subjects randomised to saline infusion (odds ratio=0.32; 95% confidence interval [CI], 0.12-0.86; P=0.026). Secondary outcomes, including stroke, mortality, and delirium, were similar between subjects randomised to dexmedetomidine (16/54 [30%] or saline control (22 [41%]; odds ratio=0.61 [95% CI, 0.28-1.36]). The incidence of bradycardia and hypotension was similar between groups (14/54 (26%) vs. 17/54 (32%) (odds ratio:0.76 (95%CI:0.33-1.76) and 29/54 (54%) vs. 36/54 (67%) (odds ratio:0.58 (95%CI:0.27-1.26), respectively). The length of hospital stay was shorter in the dexmedetomidine group (12 [10-17] days) vs saline control (15 [11-21] days; P=0.039).

CONCLUSIONS

Pre-emptive dexmedetomidine administration for 24 h starting after induction of anaesthesia reduced the incidence of AKI after aortic surgery requiring CPB, without any untoward side-effects related to its sedative or sympatholytic effects.

CLINICAL TRIAL REGISTRATION

NCT02607163 (www.

CLINICALTRIALS

gov).

The sympathetic nervous system in acute kidney injury

Acute kidney injury (AKI) is frequently accompanied by activation of the sympathetic nervous system (SNS). This may result from pre-exisiting chronic diseases associated with sympathetic activation prior to AKI or it may be induced by stressors that ultimately lead to AKI such as endotoxins and arterial hypotension in circulatory shock. Conversely, sympathetic activation may also result from acute renal injury. Focusing on studies in experimental renal ischaemia and reperfusion (IR), this review summarizes the current knowledge on how the SNS is activated in IR-induced AKI and on the consequences of sympathetic activation for the development of acute renal damage. Experimental studies show beneficial effects of sympathoinhibitory interventions on renal structure and function in response to IR. However, few clinical trials obtained in scenarios that correspond to experimental IR, namely major elective surgery, showed that peri-operative treatment with centrally acting sympatholytics reduced the incidence of AKI. Apparently, discrepant findings on how sympathetic activation influences renal responses to acute IR-induced injury are discussed and future areas of research in this field are identified.

Dexmedetomidine alleviates cisplatin‑induced acute kidney injury by attenuating endoplasmic reticulum stress‑induced apoptosis via the α2AR/PI3K/AKT pathway

Cisplatin (CP) is an effective antineoplastic agent; however, CP-induced acute kidney injury (AKI) seriously affects the prognosis of patients with cancer. Endoplasmic reticulum (ER) stress (ERS)-induced apoptosis serves a pivotal role in the pathogenesis of CP-induced AKI. Dexmedetomidine (Dex), a potent α₂ adrenergic agonist, has been reported to exert protective effects against AKI. However, the protective effects of Dex against CP-induced AKI and the potential molecular mechanisms remain unknown. In the present study, male Sprague-Dawley rats were divided into four groups (n=10/group), as follows: Control group; CP group, rats received an intraperitoneal (i.p.) injection of 5 mg/kg CP; Dex + CP group, rats received an i.p. injection of 25 µg/kg Dex immediately after CP treatment; and Dex + CP + atipamezole (Atip) group, rats received an i.p. injection of 250 µg/kg Atip, an α₂ adrenoreceptor (α₂AR) antagonist, and then received the same treatment as the Dex + CP group. Rats were anesthetized and sacrificed 96 h after CP injection. Subsequently, serum blood urea nitrogen (BUN) and serum creatinine (Scr) were analyzed, and kidney samples were collected for analyses. Pathological changes were examined using hematoxylin and eosin staining, and protein expression levels were assessed using western blotting and immunohistochemical staining. In addition, apoptosis was examined using a terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. The present results suggested that Dex protected against CP-induced AKI by attenuating histological changes in the kidney, serum BUN and Scr production. Furthermore, the expression levels of 78-kDa glucose-regulated protein, C/EBP homologous protein and caspase-12, and the apoptotic rate in the kidney were decreased following Dex treatment. In addition, the expression levels of phosphorylated (p)-PI3K and p-AKT in the Dex + CP group were significantly increased. Conversely, the renoprotective effects of Dex were attenuated following the addition of Atip. In conclusion, Dex may alleviate CP-induced AKI by attenuating ERS-induced apoptosis, at least in part, via the α₂AR/PI3K/AKT signaling pathway.

Pretreatment with dexmedetomidine alleviates lung injury in a rat model of intestinal ischemia reperfusion

The aim of the present study was to investigate the antioxidant mechanisms of dexmedetomidine against lung injury during intestinal ischemia reperfusion (IIR) in rats. The model of IIR-induced acute lung injury was established by occluding the superior mesenteric artery (SMA) for 1 h and reperfusing for 2 h using Sprague-Dawley rats. Pathological examination was used to assess the extent of the lung injury. Oxidative stress was evaluated by measuring malondialdehyde, myeloperoxidase and superoxide dismutase in the lung and plasma. The proinflammatory cytokines tumor necrosis factor-α and interleukin-6 were determined via an enzyme-linked immunosorbent assay. The mRNA and protein expression of nuclear factor-erythroid 2 related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) were determined using a reverse transcription-quantitative polymerase chain reaction and western blotting. Pretreatment with dexmedetomidine significantly inhibited the oxidative stress response and proinflammatory factor release caused by IIR compared with the normal saline group (MDA and SOD in lung and plasma, P<0.05; MPO, IL-1β and TNF-α in lung and plasma, P<0.05). Dexmedetomidine improved pulmonary pathological changes in IIR rats compared with the normal saline group. Investigations into the molecular mechanism revealed that dexmedetomidine increased the expression levels of Nrf2 and HO-1 via activating α2 adrenergic receptors compared with the normal saline group. The antagonism of α2 adrenergic receptors may reverse the protective effect of dexmedetomidine on lung injury during IIR, including decreasing the expression levels of Nrf2 and HO-1, elevating the oxidative stress response and increasing the proinflammatory factor release. In conclusion, pretreatment with dexmedetomidine demonstrated protective effects against lung injury during IIR via α2 adrenergic receptors. The Nrf2/HO-1 signaling pathway may serve a function in the protective effect of dexmedetomidine.

Protective effect of dabrafenib on renal ischemia-reperfusion injury in vivo and in vitro

AIMS

Ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI), which can lead to poor outcome and increased risk of mortality. Dabrafenib (DAB) is an approved cancer treatment. Little is known about the effect of DAB in prevention or treatment of renal IRI.

METHODS

For in vivo experiments, C57BL/6 mice were divided into four groups: sham (no IRI, no DAB), IRI, DAB, and DAB + IRI. IRI was induced by clamping of bilateral renal pedicles for 30 min. For in vitro experiments, HK-2 cells were used to establish the hypoxia/reoxygenation (H/R) injury model, with four groups: control (no H/R, no DAB), H/R, DAB, and DAB + H/R. Renal function and renal histological changes were recorded. Expression of NGAL and KIM-1 proteins and mRNAs were determined by western blotting and qRT-PCR; secretion of inflammatory cytokines (IL-6 and TNF- α) was determined by qRT-PCR; Cell death was determined using the TUNEL assay, measurement of cleaved caspase-3, and flow cytometry. Necroptosis-related proteins were determined by western blotting.

RESULTS

In mice, DAB pretreatment improved renal function and also reduced histological injury, inflammation, cell death, and expression of necroptosis-associated proteins. In HK-2 cells, DAB significantly decreased the levels of NGAL and KIM-1, inflammatory cytokines, cell death, and necroptosis-related proteins.

CONCLUSION

Our in vitro and in vivo experiments indicated that DAB appears to alleviate renal IRI by suppressing cell death and inhibiting inflammatory responses. DAB has potential use for the clinical prevention and treatment of AKI-induced IRI.

Dexmedetomidine exerts a protective effect on ischemia-reperfusion injury after hepatectomy: A prospective, randomized, controlled study

STUDY OBJECTIVE

Dexmedetomidine, a highly selective α₂-receptor agonist, has been widely used for protection against ischemia-reperfusion (IR) injury. We hypothesized that dexmedetomidine might exert a protective effect on IR injury after hepatectomy.

DESIGN

A prospective, randomized, single-blind study was conducted in 58 patients undergoing hepatectomy who were randomly assigned to two study groups. The dexmedetomidine group (D group) received a loading dose of 0.5 μg/kg for 10 min, and maintained it with 0.5 μg/kg/h until resection of the liver lobes. The control group (C group), received 0.9% sodium chloride administered in the same volume and infusion rate as D group. Eleven patients had hepatic inflow occlusion in D group as did 14 patients in C group.

MEASUREMENTS

The primary outcome was the serum concentration of α-glutathione S-transferase (α-GST), which reflects hepatic ischemic injury. Secondary outcomes included laboratory variables reflecting inflammatory responses, liver and kidney function, and blood coagulation, as well as hemodynamic changes, recovery variables, and complications related to anesthesia and surgery.

RESULTS

The concentration of α-GST at 0.5 h after resection was significantly lower in the dexmedetomidine group than the control group (9.1 ± 3.4 ng/mL vs 15.8 ± 6.5 ng/mL; p < .01), and was also significantly lower in the dexmedetomidine group in subgroup analyses of patients with and without hepatic inflow occlusion. While the concentrations of α-GST at 0.5 h after resection in patients with or without occlusion in D group were comparable, in C group the α-GST concentration without occlusion was significantly higher than that with occlusion. There was an interaction between dexmedetomidine and no occlusion (p < .01), and its concentration in D group without occlusion was the lowest of all subgroups. In addition, there were significant differences in interleukin (IL)-6 and tumor necrosis (TNF)-α concentrations at 24 h after hepatectomy between the two groups, and mean arterial pressure, heart rate, and the bispectral index were also significantly lower in D group than in C group (p < .05). There were significant differences between the two groups in ALT and AST at 2 h and 24 h after the resection of the liver lobe. However, there were no significant differences in renal function, recovery variables, blood coagulation. No severe complications related surgeries and anesthesia were found in both groups.

CONCLUSION

Dexmedetomidine exerts a protective effect on ischemia-reperfusion injury after hepatectomy.

Preventive Effects of Dexmedetomidine on Renal Dysfunction and Hemodynamic Stability in Malignant Obstructive Jaundice Patients During Peri-Operative Period

Background

This study aimed to investigate effects of intra-operative administration with dexmedetomidine (Dex) on hemodynamics and renal function in patients with malignant obstructive jaundice.

Material/Methods

Our randomized, double-blinded, placebo-controlled study was conducted among 40 patients with malignant obstructive jaundice between August 2009 and March 2011 in The Affiliated Hospital of Inner Mongolia Medical University. The 40 patients were randomly divided into 2 groups: the Dex group (receiving Dex 0.5 μg/kg 10-minutes before induction and then a 0.5 μg/kg/hour maintenance infusion until end of operation 30 minutes) and the Control group (receiving normal saline of same amount and at same rate). The adverse events, including incidence of cardiovascular complications and nausea and vomiting, and length of hospital stay were determined. The level of cystatin C (CysC), retinol-binding protein (RBP), creatinine (Scr), and blood urea nitrogen (BUN) were also evaluated.

Results

Dexmedetomidine administration significantly decreased heart rate (HR) and stroke volume variation (SVV) and significantly increased capital venous pressure (CVP) and mean arterial pressure (MAP) values compared to that in the Control group (P<0.05). Dexmedetomidine administration significantly upregulated urine volume and significantly downregulated atropine levels compared to the Control group (P<0.05). Dexmedetomidine administration significantly improved renal functions, by modulating CysC, RBP, Scr and BUN levels compared to the Control group (P<0.05). Dexmedetomidine administration demonstrated no additional side-effects. Dexmedetomidine administration significantly shortened length of hospitalization in the Dex group compared to the Control group (P<0.05).

Conclusions

Dexmedetomidine plays preventive effects on renal dysfunction and hemodynamic stability in malignant obstructive jaundice patients during peri-operative period.