SIRT3-mediated OPA1 deacetylation protects against sepsis-induced acute lung injury by inhibiting alveolar macrophage pro-inflammatory polarization.

AIMS: Mitochondrial dynamics in alveolar macrophages (AMs) are associated with sepsis-induced acute lung injury (ALI). In this study, we aimed to investigate whether changes in mitochondrial dynamics could alter the polarization of AMs in sepsis-induced ALI and to explore the regulatory mechanism of mitochondrial dynamics by focusing on SIRT3-induced optic atrophy protein 1 (OPA1) deacetylation. RESULTS: The AMs of sepsis-induced ALI showed imbalanced mitochondrial dynamics and polarization to the M1 macrophage phenotype. In sepsis, SIRT3 overexpression promotes mitochondrial dynamic equilibrium in AMs. However, 3TYP-specific inhibition of SIRT3 increased the mitochondrial dynamic imbalance and pro-inflammatory polarization of AMs and further aggravated sepsis-induced ALI. OPA1 is directly bound to and deacetylated by SIRT3 in AMs. In AMs of sepsis-induced ALI, SIRT3 protein expression was decreased and OPA1 acetylation was increased. OPA1 acetylation at the lysine 792 amino acid residue (OPA1-K792) promotes self-cleavage and is associated with an imbalance in mitochondrial dynamics. However, decreased acetylation of OPA1-K792 reversed the pro-inflammatory polarization of AMs and protected the barrier function of alveolar epithelial cells in sepsis-induced ALI. INNOVATION: Our study revealed for the first time the regulation of mitochondrial dynamics and AMs polarization by SIRT3-mediated deacetylation of OPA1 in sepsis-induced ALI, which may serve as an intervention target for precision therapy of the disease. CONCLUSIONS: Our data suggest that imbalanced mitochondrial dynamics promote pro-inflammatory polarization of AMs in sepsis-induced ALI, and that deacetylation of OPA1 mediated by SIRT3 improves mitochondrial dynamic equilibrium, thereby ameliorating lung injury.

Melatonin attenuates sepsis-induced acute kidney injury by promoting mitophagy through SIRT3-mediated TFAM deacetylation.

ABBREVIATIONS: AKI: acute kidney injury; ATP: adenosine triphosphate; BUN: blood urea nitrogen; CLP: cecal ligation and puncture; eGFR: estimated glomerular filtration rate; H&E: hematoxylin and eosin staining; LCN2/NGAL: lipocalin 2; LPS: lipopolysaccharide; LTL: lotus tetragonolobus lectin; mKeima: mitochondria-targeted Keima; mtDNA: mitochondrial DNA; PAS: periodic acid - Schiff staining; RTECs: renal tubular epithelial cells; SAKI: sepsis-induced acute kidney injury; Scr: serum creatinine; SIRT3: sirtuin 3; TFAM: transcription factor A, mitochondrial; TMRE: tetramethylrhodamine.

PROMOTING MITOCHONDRIAL DYNAMIC EQUILIBRIUM ATTENUATES SEPSIS-INDUCED ACUTE LUNG INJURY BY INHIBITING PROINFLAMMATORY POLARIZATION OF ALVEOLAR MACROPHAGES.

ABSTRACT: Sepsis-induced acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is characterized by widespread pulmonary inflammation and immune response, in which proinflammatory polarization of alveolar macrophages (AMs) plays an important role. Mitochondria are the key intracellular signaling platforms regulating immune cell responses. Moreover, accumulating evidence suggests that the mitochondrial dynamics of macrophages are imbalanced in sepsis and severe ALI/ARDS. However, the functional significance of mitochondrial dynamics of AMs in septic ALI/ARDS remains largely unknown, and whether it regulates the polarized phenotype of AMs is also unclear. Here, we demonstrated that the mitochondrial dynamics of AMs are imbalanced, manifested by impaired mitochondrial fusion, increased fission and mitochondrial cristae remodeling, both in septic models and ARDS patients. However, suppressing excessive mitochondrial fission with Mdivi-1 or promoting mitochondrial fusion with PM1 to maintain mitochondrial dynamic equilibrium in AMs could inhibit the polarization of AMs into proinflammatory phenotype and attenuate sepsis-induced ALI. These data suggest that mitochondrial dynamic imbalance mediates altered polarization of AMs and exacerbates sepsis-induced ALI. This study provides new insights into the underlying mechanisms of sepsis-induced ALI, suggesting the possibility of identifying future drug targets from the perspective of mitochondrial dynamics in AMs.

Effect of Esmolol on Clinical Outcomes in Critically Ill Patients: Data from the MIMIC-IV Database.

BACKGROUND AND AIMS: Esmolol is a common short-acting drug to control ventricular rate. This study aimed to evaluate the association between use of esmolol and mortality in critically ill patients. METHODS: This is a retrospective cohort study from MIMIC-IV database containing adult patients with a heart rate of over 100 beats/min during the intensive care unit (ICU) stay. Multivariable Cox proportional hazard models and logistic regression were used to explore the association between esmolol and mortality and adjust confounders. A 1:1 nearest neighbor propensity score matching (PSM) was performed to minimize potential cofounding bias. The comparison for secondary outcomes was performed at different points of time using an independent t-test. RESULTS: A total of 30,332 patients were reviewed and identified as critically ill. There was no significant difference in 28-day mortality between two groups before (HR = 0.90, 95% CI = 0.73-1.12, p = 0.343) and after PSM (HR = 0.84, 95% CI = 0.65-1.08, p = 0.167). Similar results were shown in 90-day mortality before (HR = 0.93, 95% CI = 0.75-1.14, p = 0.484) and after PSM (HR = 0.85, 95% CI = 0.67-1.09, p = 0.193). However, esmolol treatment was associated with higher requirement of vasopressor use before (HR = 2.89, 95% CI = 2.18-3.82, p < 0.001) and after PSM (HR = 2.66, 95% CI = 2.06-3.45, p < 0.001). Esmolol treatment statistically reduced diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (all p < 0.001) and increased fluid balance at 24 hours (p < 0.05) but did not significantly lower SBP (p = 0.721). Patients in esmolol group showed no significant difference in lactate levels and daily urine output when compared with those in non-esmolol group when adjusted for confounders (all p > 0.05). CONCLUSION: Esmolol treatment was associated with reduced heart rate and lowered DBP and MAP, which may increase vasopressor use and fluid balance at the timepoint of 24 hours in critically ill patients during ICU stay. However, after adjusting for confounders, esmolol treatment was not associated with 28-day and 90-day mortality.

PDHA1 hyperacetylation-mediated lactate overproduction promotes sepsis-induced acute kidney injury via Fis1 lactylation.

The increase of lactate is an independent risk factor for patients with sepsis-induced acute kidney injury (SAKI). However, whether elevated lactate directly promotes SAKI and its mechanism remain unclear. Here we revealed that downregulation of the deacetylase Sirtuin 3 (SIRT3) mediated the hyperacetylation and inactivation of pyruvate dehydrogenase E1 component subunit alpha (PDHA1), resulting in lactate overproduction in renal tubular epithelial cells. We then found that the incidence of SAKI and renal replacement therapy (RRT) in septic patients with blood lactate ≥ 4 mmol/L was increased significantly, compared with those in septic patients with blood lactate < 2 mmol/L. Further in vitro and in vivo experiments showed that additional lactate administration could directly promote SAKI. Mechanistically, lactate mediated the lactylation of mitochondrial fission 1 protein (Fis1) lysine 20 (Fis1 K20la). The increase in Fis1 K20la promoted excessive mitochondrial fission and subsequently induced ATP depletion, mitochondrial reactive oxygen species (mtROS) overproduction, and mitochondrial apoptosis. In contrast, PDHA1 activation with sodium dichloroacetate (DCA) or SIRT3 overexpression decreased lactate levels and Fis1 K20la, thereby alleviating SAKI. In conclusion, our results show that PDHA1 hyperacetylation and inactivation enhance lactate overproduction, which mediates Fis1 lactylation and exacerbates SAKI. Reducing lactate levels and Fis1 lactylation attenuate SAKI.

Neat1 promotes acute kidney injury to chronic kidney disease by facilitating tubular epithelial cells apoptosis via sequestering miR-129-5p.

Acute kidney injury (AKI) is increasingly identified as a crucial risk factor for progression to CKD. However, the factors governing AKI to CKD progression remain largely unknown. By high-throughput RNA sequencing, we found that Neat1_2, a transcript variant of Neat1, was upregulated in 40-min ischemia/reperfusion injury (IRI), which resulted in the development of renal fibrotic lesions. The upregulation of Neat1_2 in hypoxia-treated TECs was attributed to p53 transcriptional regulation. Gain- and loss-of-function studies, both in vitro and in vivo, demonstrated that Neat1_2 promoted apoptosis of injured TECs induced by IRI and caused tubulointerstitial inflammation and fibrosis. Mechanistically, Neat1_2 shares miRNA response elements with FADD, CASP-8, and CASP-3. Neat1_2 competitively binds to miR-129-5p and prevents miR-129-5p from decreasing the levels of FADD, CASP-8, and CASP-3, and ultimately facilitates TEC apoptosis. Increased expression of Neat1_2 associated with kidney injury and TEC apoptosis was recapitulated in human AKI, highlighting its clinical relevance. These findings suggest that preventing TEC apoptosis by hindering Neat1_2 expression may be a potential therapeutic strategy for AKI to CKD progression.

p53 Deacetylation Alleviates Sepsis-Induced Acute Kidney Injury by Promoting Autophagy.

Recent studies have shown that autophagy upregulation can attenuate sepsis-induced acute kidney injury (SAKI). The tumor suppressor p53 has emerged as an autophagy regulator in various forms of acute kidney injury (AKI). Our previous studies showed that p53 acetylation exacerbated hemorrhagic shock-induced AKI and lipopolysaccharide (LPS)-induced endothelial barrier dysfunction. However, the role of p53-regulated autophagy in SAKI has not been examined and requires clarification. In this study, we observed the dynamic changes of autophagy in renal tubular epithelial cells (RTECs) and verified the protective effects of autophagy activation on SAKI. We also examined the changes in the protein expression, intracellular distribution (nuclear and cytoplasmic), and acetylation/deacetylation levels of p53 during SAKI following cecal ligation and puncture (CLP) or LPS treatment in mice and in a LPS-challenged human RTEC cell line (HK-2 cells). After sepsis stimulation, the autophagy levels of RTECs increased temporarily, followed by a sharp decrease. Autophagy inhibition was accompanied by an increased renal tubular injury score. By contrast, autophagy agonists could reduce renal tubular damage following sepsis. Surprisingly, the expression of p53 protein in both the renal cortex and HK-2 cells did not significantly change following sepsis stimulation. However, the translocation of p53 from the nucleus to the cytoplasm increased, and the acetylation of p53 was enhanced. In the mechanistic study, we found that the induction of p53 deacetylation, due to either the resveratrol/quercetin -induced activation of the deacetylase Sirtuin 1 (Sirt1) or the mutation of the acetylated lysine site in p53, promoted RTEC autophagy and alleviated SAKI. In addition, we found that acetylated p53 was easier to bind with Beclin1 and accelerated its ubiquitination-mediated degradation. Our study underscores the importance of deacetylated p53-mediated RTEC autophagy in future SAKI treatments.

SIRT1 attenuates sepsis-induced acute kidney injury via Beclin1 deacetylation-mediated autophagy activation.

Our previous studies showed that silent mating-type information regulation 2 homologue-1 (SIRT1, a deacetylase) upregulation could attenuate sepsis-induced acute kidney injury (SAKI). Upregulated SIRT1 can deacetylate certain autophagy-related proteins (Beclin1, Atg5, Atg7 and LC3) in vitro. However, it remains unclear whether the beneficial effect of SIRT1 is related to autophagy induction and the underlying mechanism of this effect is also unknown. In the present study, caecal ligation and puncture (CLP)-induced mice, and an LPS-challenged HK-2 cell line were established to mimic a SAKI animal model and a SAKI cell model, respectively. Our results demonstrated that SIRT1 activation promoted autophagy and attenuated SAKI. SIRT1 deacetylated only Beclin1 but not the other autophagy-related proteins in SAKI. SIRT1-induced autophagy and its protective effect against SAKI were mediated by the deacetylation of Beclin1 at K430 and K437. Moreover, two SIRT1 activators, resveratrol and polydatin, attenuated SAKI in CLP-induced septic mice. Our study was the first to demonstrate the important role of SIRT1-induced Beclin1 deacetylation in autophagy and its protective effect against SAKI. These findings suggest that pharmacologic induction of autophagy via SIRT1-mediated Beclin1 deacetylation may be a promising therapeutic approach for future SAKI treatment.

Polydatin protects against lipopolysaccharide-induced endothelial barrier disruption via SIRT3 activation.

In a previous study, we demonstrated the role of polydatin (PD) in protecting against multiple organ dysfunction in sepsis. The aim of this study is to investigate whether PD protects against lipopolysaccharide (LPS)-induced endothelial barrier disruption through SIRT3 activation and to disclose the underlying mechanisms. Wild-type mice were injected with LPS and Evans Blue assay was performed to evaluate vascular permeability. Primary human umbilical vein endothelial cells (HUVECs) were stimulated with LPS. Endothelial permeability was evaluated by transendothelial electrical resistance (TER) and FITC-dextran leakage. SIRT3 activity was determined by a Deacetylase Fluorometric kit, and protein expression level of SIRT3 was detected by western blotting. Mitochondrial function was evaluated by determination of ROS level, mitochondrial membrane potential and mPTP opening. In endotoxemic mice, PD pretreatment attenuated vascular leakage in multiple organs while SIRT3 inhibition with 3-TYP reversed the effects of PD. PD treatment in late sepsis also exhibited barrier protective effects. In HUVECs, PD alleviated LPS-induced F-actin rearrangement, cadherin-catenin complex dissociation and endothelial hyperpermeability, whereas 3-TYP or SIRT3 siRNA attenuated the protective effects of PD. PD enhanced SIRT3 deacetylase activity, and attenuated LPS-induced decrease in SIRT3 expression as well. Furthermore, gain-of-function and loss-of-function strategies also confirmed the role of SIRT3 in enhancing endothelial barrier integrity. It was further ascertained that PD enhanced SIRT3-mediated deacetylation of SOD2 and cyclophilin D (CypD), thus suppressing mitochondrial dysfunction and subsequent endothelial barrier dysfunction. In addition, it was revealed that RAGE was involved in LPS-regulated SIRT3 signaling. Our results suggest that polydatin protects against LPS-induced endothelial barrier disruption dependent on SIRT3 and can be applied as a potential therapy for sepsis.

Propofol-induced miR-219-5p inhibits growth and invasion of hepatocellular carcinoma through suppression of GPC3-mediated Wnt/ß-catenin signalling activation.

Propofol is one of the most extensively used intravenous anaesthetic agents, which has been found to improve the surgical intervention outcome of several types of cancer, including hepatocellular carcinoma (HCC). Additionally, in vitro and in vivo experiments have also indicated that propofol affects the biological behaviour of HCC. However, the underlying mechanisms of the surgical resection of HCC with propofol have not been fully understood. In the present study, we aimed to investigate the underlying mechanism of propofol inhibition of the growth and invasion of HCC cells. Our results showed that treatment with propofol suppressed the proliferation, invasion and migration of HCC in vitro. The subcutaneous xenograft tumour and orthotopic xenograft tumour experiments in nude mice showed that propofol significantly decreased tumour volumes, growth rates and the liver orthotopic xenograft tumour in vivo. Furthermore, the underlying mechanism investigations of the suppressive effects of propofol on HCC cells revealed that propofol treatment upregulated the expression levels of the candidate tumour suppressor miR-219-5p. Silencing of propofol-induced miR-219-5p using anti-miR-219-5p abrogated the inhibitory effects on the proliferation, migration and invasion of HCC cells exerted by propofol treatment. Additionally, we demonstrated that propofol reversed the epithelial-mesenchymal transition of Huh7 and SMMC7721 cells via miR-219-5p induction. The molecular mechanism behind these findings is that propofol-induced miR-219-5p inhibits HCC cell progression by targeting glypican-3 and subsequently results in the inhibition of Wnt/ß-catenin signalling. Taken together, our study provides new insights into the advantages of the surgical intervention of HCC with propofol anaesthetization.

Emerging role of SIRT3 in mitochondrial dysfunction and cardiovascular diseases.

As a nicotinamide adenine dinucleotide (NAD)+-dependent protein deacetylase, SIRT3 is highly expressed in tissues with high metabolic turnover and mitochondrial content. It has been demonstrated that SIRT3 plays a critical role in maintaining normal mitochondrial biological function through reversible protein lysine deacetylation. SIRT3 has a variety of substrates that are involved in mitochondrial biological processes such as energy metabolism, reactive oxygen species production and clearance, electron transport chain flux, mitochondrial membrane potential maintenance, and mitochondrial dynamics. In the suppression of SIRT3, functional deficiencies of mitochondria contribute to the development of various cardiovascular disorders. Activation of SIRT3 may represent a promising therapeutic strategy for the improvement of mitochondrial function and the treatment of relevant cardiovascular disorders. In the current review, we discuss the emerging roles of SIRT3 in mitochondrial derangements and subsequent cardiovascular malfunctions, including cardiac hypertrophy and heart failure, ischemia-reperfusion injury, and endothelial dysfunction in hypertension and atherosclerosis.