The decline of autophagy contributes to proximal tubular dysfunction during sepsis

Autophagy in Acute Lung Injury

Acute lung injury (ALI) is a critical condition marked by rapid-onset respiratory failure due to extensive inflammation and increased pulmonary vascular permeability, often progressing to acute respiratory distress syndrome (ARDS) with high mortality. Autophagy, a cellular degradation process essential for removing damaged organelles and proteins, plays a crucial role in regulating lung injury and repair. This review examines the protective role of autophagy in maintaining cellular function and reducing inflammation and oxidative stress in ALI. It underscores the necessity of precise regulation to fully harness the therapeutic potential of autophagy in this context. We summarize the mechanisms by which autophagy influences lung injury and repair, discuss the interplay between autophagy and apoptosis, and examine potential therapeutic strategies, including autophagy inducers, targeted autophagy signaling pathways, antioxidants, anti-inflammatory drugs, gene editing, and stem cell therapy. Understanding the role of autophagy in ALI could lead to novel interventions for improving patient outcomes and reducing mortality rates associated with this severe condition.

Therapeutic Effect of Herbal-Based Drug on Severe Sepsis in Calves: An Innovative Immunomodulatory and antiinflammatory Strategy in Herd Medicine

Septicemia is a significant threat to newborn calves, often due to inadequate colostrum intake in the first day of life. The study aimed to assess the effects of a newly developed herbal formulation on septicemia induced by Escherichia coli strain O111:H8. Ten Holstein-Friesian calves aged 8-10 days were divided into two groups. Experimental septicemia was induced for all calves (n=10). The treatment group (n=5) received a herbal formulation containing extracts from Rosa canina, Urtica dioica, Tanacetum vulgare, selenium, flavonoids, and carotenes, in addition to antibiotics. The control group (n=5) received a placebo (5% dextrose) along with antibiotics for five days. The animals were monitored for 14 days. Blood samples were analyzed for cytokines, cardiac enzymes, renal function, and total antioxidant capacity before and after treatment. The treatment group had non-significantly higher CD4+ counts compared to the control. The serum level of IL-6 increased after treatment, with a considerable difference between the groups at 72 h (p=0.0014). The herbal formulation positively impacted renal and cardiac function evidenced by decreased cardiac troponin I levels and increased total antioxidant capacity (TAC). Lactate dehydrogenase (LDH) levels changed significantly over time (p<0.05), with a positive correlation between ECG changes and peak LDH levels (p<0.05). The increased cytokines beside ameliorative effects on heart and kidney functions suggest that the herbal drug may possess immunomodulatory and anti-inflammatory properties that aid in managing the inflammatory response during sepsis. These findings support the use of this herbal-based drug as an adjunctive treatment in veterinary practices for managing septicemia in calves.

Macrophage activation syndrome in Sepsis: from pathogenesis to clinical management

BACKGROUND

Sepsis represents a significant global health and hygiene challenge. Excessive activation of macrophages in sepsis can result in certain patients displaying characteristics akin to those observed in Macrophage Activation Syndrome (MAS). MAS represents a grave immune system disorder characterized by persistent and severe inflammation within the body. In the context of sepsis, MAS presents atypically, leading some researchers to refer to it as Macrophage Activation-Like Syndrome (MALS). However, there are currently no effective treatment measures for this situation. The purpose of this article is to explore potential treatment methods for sepsis-associated MALS.

OBJECTIVE

The objective of this review is to synthesize the specific pathophysiological mechanisms and treatment strategies of MAS to investigate potential therapeutic approaches for sepsis-associated MALS.

METHOD

We searched major databases (including PubMed, Web of Science, and Google Scholar etc.) for literature encompassing macrophage activation syndrome and sepsis up to Mar 2024 and combined with studies found in the reference lists of the included studies.

CONCLUSION

We have synthesized the underlying pathophysiological mechanism of MALS in sepsis, and then summarized the diagnostic criteria and the effects of various treatment modalities utilized in patients with MAS or MALS. In both scenarios, heterogeneous treatment responses resulting from identical treatment approaches were observed. The determination of whether the patient is genuinely experiencing MALS significantly impacts the ultimate outcomes of therapeutic efficacy. In order to tackle this concern, additional clinical trials and research endeavors are imperative.

Mitochondrial dysfunction in acute kidney injury

Acute kidney injury (AKI) is a systemic clinical syndrome increasing morbidity and mortality worldwide in recent years. Renal tubular epithelial cells (TECs) death caused by mitochondrial dysfunction is one of the pathogeneses. The imbalance of mitochondrial quality control is the main cause of mitochondrial dysfunction. Mitochondrial quality control plays a crucial role in AKI. Mitochondrial quality control mechanisms are involved in regulating mitochondrial integrity and function, including antioxidant defense, mitochondrial quality control, mitochondrial DNA (mtDNA) repair, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis. Currently, many studies have used mitochondrial dysfunction as a targeted therapeutic strategy for AKI. Therefore, this review aims to present the latest research advancements on mitochondrial dysfunction in AKI, providing a valuable reference and theoretical foundation for clinical prevention and treatment of this condition, ultimately enhancing patient prognosis.

The role of inflammatory response and metabolic reprogramming in sepsis-associated acute kidney injury: mechanistic insights and therapeutic potential

Sepsis represents a severe condition characterized by organ dysfunction resulting from a dysregulated host response to infection. Among the organs affected, the kidneys are particularly vulnerable, with significant functional impairment that markedly elevates mortality rates. Previous researches have highlighted that both inflammatory response dysregulation and metabolic reprogramming are crucial in the onset and progression of sepsis associated acute kidney injury (SA-AKI), making these processes potential targets for innovative therapies. This study aims to elucidate the pathophysiological mechanisms of renal injury in sepsis by perspective of inflammatory response dysregulation, with particular emphasis on pyroptosis, necroptosis, autophagy, and ferroptosis. Furthermore, it will incorporate insights into metabolic reprogramming to provide a detailed analysis of the mechanisms driving SA-AKI and explore potential targeted therapeutic strategies, providing solid theoretical framework for the development of targeted therapies for SA-AKI.

Autophagy and autophagic cell death in sepsis: friend or foe?

In sepsis, inflammation, and nutrient deficiencies endanger cellular homeostasis and survival. Autophagy is primarily a mechanism of cellular survival under fasting conditions. However, autophagy-dependent cell death, known as autophagic cell death, is proinflammatory and can exacerbate sepsis. Autophagy also regulates various types of non-inflammatory and inflammatory cell deaths. Non-inflammatory apoptosis tends to suppress inflammation, however, inflammatory necroptosis, pyroptosis, ferroptosis, and autophagic cell death lead to the release of inflammatory cytokines and damage-associated molecular patterns (DAMPs) and amplify inflammation. The selection of cell death mechanisms is complex and often involves a mixture of various styles. Similarly, protective autophagy and lethal autophagy may be triggered simultaneously in cells. How cells balance the regulatory mechanisms of these processes is an area of interest that is still under investigation. Therapies aimed at modulating autophagy are considered promising. Enhancing autophagy helps clear and recycle damaged organelles and reduce the burden of inflammatory processes while inhibiting excessive autophagy, which could prevent autophagic cell death. In this review, we introduce recent advances in research and the complex regulatory system of autophagy in sepsis.

Metabolic reprogramming in septic acute kidney injury: pathogenesis and therapeutic implications

Acute kidney injury (AKI) is a frequent and severe complication of sepsis and is characterized by significant mortality and morbidity. However, the pathogenesis of septic acute kidney injury (S-AKI) remains elusive. Metabolic reprogramming, which was originally referred to as the Warburg effect in cancer, is strongly related to S-AKI. At the onset of sepsis, both inflammatory cells and renal parenchymal cells, such as macrophages, neutrophils and renal tubular epithelial cells, undergo metabolic shifts toward aerobic glycolysis to amplify proinflammatory responses and fortify cellular resilience to septic stimuli. As the disease progresses, these cells revert to oxidative phosphorylation, thus promoting anti-inflammatory reactions and enhancing functional restoration. Alterations in mitochondrial dynamics and metabolic reprogramming are central to the energetic changes that occur during S-AKI. In this review, we summarize the current understanding of the pathogenesis of metabolic reprogramming in S-AKI, with a focus on each cell type involved. By identifying relevant key regulatory factors, we also explored potential metabolic reprogramming-related therapeutic targets for the management of S-AKI.

Septic acute kidney injury and gut microbiome: Should we change our approach?

Incidence of acute kidney injury (AKI) remained relatively stable over the last decade and the adjusted risks for it and mortality are similar across different continents and regions. Also, the mortality of septic-AKI can reach 70% in critically-ill patients. These sole facts can give rise to a question: is there something we do not understand yet? Currently, there are no specific therapies for septic AKI and the treatment aims only to maintain the mean arterial pressure over 65mmHg by ensuring a good fluid resuscitation and by using vasopressors, along with antibiotics. On the other hand, there is an increased concern about the different hemodynamic changes in septic AKI versus other forms and the link between the gut microbiome and the severity of septic AKI. Fortunately, progress has been made in the form of administration of pre- and probiotics, short chain fatty acids (SCFA), especially acetate, and also broad-spectrum antibiotics or selective decontaminants of the digestive tract in a successful attempt to modulate the microbial flora and to decrease both the severity of AKI and mortality. In conclusion, septic-AKI is a severe form of kidney injury, with particular hemodynamic changes and with a strong link between the kidney and the gut microbiome. By modulating the immune response we could not only treat but also prevent severe forms. The most difficult part is to categorize patients and to better understand the key mechanisms of inflammation and cellular adaptation to the injury, as these mechanisms can serve in the future as target therapies.

The Molecular Mechanism and Therapeutic Application of Autophagy for Urological Disease

Autophagy is a lysosomal degradation process known as autophagic flux, involving the engulfment of damaged proteins and organelles by double-membrane autophagosomes. It comprises microautophagy, chaperone-mediated autophagy (CMA), and macroautophagy. Macroautophagy consists of three stages: induction, autophagosome formation, and autolysosome formation. Atg8-family proteins are valuable for tracking autophagic structures and have been widely utilized for monitoring autophagy. The conversion of LC3 to its lipidated form, LC3-II, served as an indicator of autophagy. Autophagy is implicated in human pathophysiology, such as neurodegeneration, cancer, and immune disorders. Moreover, autophagy impacts urological diseases, such as interstitial cystitis /bladder pain syndrome (IC/BPS), ketamine-induced ulcerative cystitis (KIC), chemotherapy-induced cystitis (CIC), radiation cystitis (RC), erectile dysfunction (ED), bladder outlet obstruction (BOO), prostate cancer, bladder cancer, renal cancer, testicular cancer, and penile cancer. Autophagy plays a dual role in the management of urologic diseases, and the identification of potential biomarkers associated with autophagy is a crucial step towards a deeper understanding of its role in these diseases. Methods for monitoring autophagy include TEM, Western blot, immunofluorescence, flow cytometry, and genetic tools. Autophagosome and autolysosome structures are discerned via TEM. Western blot, immunofluorescence, northern blot, and RT-PCR assess protein/mRNA levels. Luciferase assay tracks flux; GFP-LC3 transgenic mice aid study. Knockdown methods (miRNA and RNAi) offer insights. This article extensively examines autophagy's molecular mechanism, pharmacological regulation, and therapeutic application involvement in urological diseases.

3-Hydroxybutyrate ameliorates sepsis-associated acute lung injury by promoting autophagy through the activation of GPR109α in macrophages

BACKGROUND

Sepsis is a systemic inflammatory disease caused by multiple pathogens, with the most commonly affected organ being the lung. 3-Hydroxybutyrate plays a protective role in inflammatory diseases through autophagy promotion; however, the exact mechanism remains unexplored.

METHOD

Our study used the MIMIC-III database to construct a cohort of ICU sepsis patients and figure out the correlation between the level of ketone bodies and clinical prognosis in septic patients. In vivo and in vitro models of sepsis were used to reveal the role and mechanism of 3-hydroxybutyrate in sepsis-associated acute lung injury (sepsis-associated ALI).

RESULT

Herein, we observed a strong correlation between the levels of ketone bodies and clinical prognosis in patients with sepsis identified using the MIMIC- III database. In addition, exogenous 3-hydroxybutyrate supplementation improved the survival rate of CLP-induced sepsis in mice by promoting autophagy. Furthermore, 3-hydroxybutyrate treatment protected against sepsis-induced lung damage. We explored the mechanism underlying these effects. The results indicated that 3-hydroxybutyrate upregulates autophagy levels by promoting the transfer of transcription factor EB (TFEB) to the macrophage nucleus in a G-protein-coupled receptor 109 alpha (GPR109α) dependent manner, upregulating the transcriptional level of ultraviolet radiation resistant associated gene (UVRAG) and increasing the formation of autophagic lysosomes.

CONCLUSION

3-Hydroxybutyrate can serve as a beneficial therapy for sepsis-associated ALI through the upregulation of autophagy. These results may provide a basis for the development of promising therapeutic strategies for sepsis-associated ALI.

Autophagy and mitophagy: physiological implications in kidney inflammation and diseases

Autophagy is a ubiquitous intracellular cytoprotective quality control program that maintains cellular homeostasis by recycling superfluous cytoplasmic components (lipid droplets, protein, or glycogen aggregates) and invading pathogens. Mitophagy is a selective form of autophagy that by recycling damaged mitochondrial material, which can extracellularly act as damage-associated molecular patterns, prevents their release. Autophagy and mitophagy are indispensable for the maintenance of kidney homeostasis and exert crucial functions during both physiological and disease conditions. Impaired autophagy and mitophagy can negatively impact the pathophysiological state and promote its progression. Autophagy helps in maintaining structural integrity of the kidney. Mitophagy-mediated mitochondrial quality control is explicitly critical for regulating cellular homeostasis in the kidney. Both autophagy and mitophagy attenuate inflammatory responses in the kidney. An accumulating body of evidence highlights that persistent kidney injury-induced oxidative stress can contribute to dysregulated autophagic and mitophagic responses and cell death. Autophagy and mitophagy also communicate with programmed cell death pathways (apoptosis and necroptosis) and play important roles in cell survival by preventing nutrient deprivation and regulating oxidative stress. Autophagy and mitophagy are activated in the kidney after acute injury. However, their aberrant hyperactivation can be deleterious and cause tissue damage. The findings on the functions of autophagy and mitophagy in various models of chronic kidney disease are heterogeneous and cell type- and context-specific dependent. In this review, we discuss the roles of autophagy and mitophagy in the kidney in regulating inflammatory responses and during various pathological manifestations.

An Autophagy-Associated MITF-GAS5-miR-23 Loop Attenuates Vascular Oxidative and Inflammatory Damage in Sepsis

BACKGROUND

Sepsis induces GAS5 expression in the vascular endothelium, but the molecular mechanism is unclear, as is the role of GAS5 in sepsis.

METHODS AND RESULTS

We observed that GAS5 expression in the endothelium was significantly upregulated in a sepsis mouse model. ChIP-PCR and EMSA confirmed that the oxidative stress (OS)-activated MiT-TFE transcription factor (MITF, TFE3, and TFEB)-mediated GAS5 transcription. In vitro, GAS5 overexpression attenuated OS and inflammation in endothelial cells (ECs) while maintaining the structural and functional integrity of mitochondria. In vivo, GAS5 reduced tissue ROS levels, maintained vascular barrier function to reduce leakage, and ultimately attenuated sepsis-induced lung injury. Luciferase reporter assays revealed that GAS5 protected MITF from degradation by sponging miR-23, thereby forming a positive feedback loop consisting of MITF, GAS5, and miR-23. Despite the fact that the OS-activated MITF-GAS5-miR-23 loop boosted MITF-mediated p62 transcription, ECs do not need to increase mitophagy to exert mitochondrial quality control since MITF-mediated Nrf2 transcription exists. Compared to mitophagy, MITF-transcribed p62 prefers to facilitate the autophagic degradation of Keap1 through a direct interaction, thereby relieving the inhibition of Nrf2 by Keap1, indicating that MITF can upregulate Nrf2 at both the transcriptional and posttranscriptional levels. Following this, ChIP-PCR demonstrated that Nrf2 can also transcribe MITF, revealing that there is a reciprocal positive regulatory association between MITF and Nrf2.

CONCLUSION

In sepsis, the ROS-activated MITF-GAS5-miR-23 loop integrated the antioxidant and autophagy systems through MITF-mediated transcription of Nrf2 and p62, which dynamically regulate the level and type of autophagy, as well as exert antioxidant and anti-inflammatory effects.

miR-926-3p influences myocardial injury in septic mice through regulation of mTOR signaling pathway by targeting TSC1

BACKGROUND

The purpose of this study is to investigate the influence of miR-926-3p on myocardial injury and its mechanisms.

METHODS

An animal model of sepsis was constructed by CLP, and animals were randomly divided into 4 groups: C group, miR-926-3p inhibitor group, CLP + NC group, and CLP + miR-926-3p inhibitor group.

RESULTS

Compared with those in C group, echocardiographic parameters remarkably declined in CLP + NC group. Compared with CLP + NC group, miR-926-3p inhibitor group indicated elevated echocardiographic parameters in mice, pathological improvement tendency of myocardial tissues and distinct reduction in cardiomyocyte apoptosis. It could be observed by electron microscopy that the number of lysosomes in miR-926-3p inhibitor group was greatly increased relative to CLP + NC group. Immunofluorescence exhibited that the number of green fluorescent puncta was significantly higher in miR-926-3p inhibitor group as compared to that in CLP + NC group. The autophagic flow was verified by observing the relative expression of LC3II at different times. The results of Western blotting manifested that miR-926-3p inhibitor up-regulated mTOR-related protein expressions and down-regulated the protein expression of p-mTOR. LPS was adopted to induce cardiomyocyte injury in vitro, and the results confirmed that, identical to in vivo experiments, miR-926-3p inhibitor was able to up-regulate the protein expressions of mTOR-related protein and down-regulate p-mTOR protein expression in cardiomyocytes. After addition of MHY1485, The expression of mTOR-related proteins changes in each group.

CONCLUSION

Inhibition of miR-926-3p enhances autophagy through regulation of the mTOR signaling pathway, thus ameliorating myocardial injury in septic mice.

Epigenetic dysregulation of autophagy in sepsis-induced acute kidney injury: the underlying mechanisms for renoprotection

Sepsis-induced acute kidney injury (SI-AKI), a common critically ill, represents one of the leading causes of global death. Emerging evidence reveals autophagy as a pivotal modulator of SI-AKI. Autophagy affects the cellular processes of renal lesions, including cell death, inflammation, and immune responses. Herein, we conducted a systematic and comprehensive review on the topic of the proposed roles of autophagy in SI-AKI. Forty-one relevant studies were finally included and further summarized and analyzed. This review revealed that a majority of included studies (24/41, 58.5%) showed an elevation of the autophagy level during SI-AKI, while 22% and 19.5% of the included studies reported an inhibition and an elevation at the early stage but a declination of renal autophagy in SI-AKI, respectively. Multiple intracellular signaling molecules and pathways targeting autophagy (e.g. mTOR, non-coding RNA, Sirtuins family, mitophagy, AMPK, ROS, NF-Kb, and Parkin) involved in the process of SI-AKI, exerting multiple biological effects on the kidney. Multiple treatment modalities (e.g. small molecule inhibitors, temsirolimus, rapamycin, polydatin, ascorbate, recombinant human erythropoietin, stem cells, Procyanidin B2, and dexmedetomidine) have been found to improve renal function, which may be attributed to the elevation of the autophagy level in SI-AKI. Though the exact roles of autophagy in SI-AKI have not been well elucidated, it may be implicated in preventing SI-AKI through various molecular pathways. Targeting the autophagy-associated proteins and pathways may hint towards a new prospective in the treatment of critically ill patients with SI-AKI, but more preclinical studies are still warranted to validate this hypothesis.

The Polo-Like Kinase 1-Mammalian Target of Rapamycin Axis Regulates Autophagy to Prevent Intestinal Barrier Dysfunction During Sepsis

The intestines play a crucial role in the development of sepsis. The balance between autophagy and apoptosis in intestinal epithelial cells is dynamic and determines intestinal permeability. The present study focused on the potential role of autophagy in sepsis-induced intestinal barrier dysfunction and explored the mechanisms in vivo and in vitro. Excessive apoptosis in intestinal epithelia and a disrupted intestinal barrier were observed in septic mice. Promoting autophagy with rapamycin reduced intestinal epithelial apoptosis and restored intestinal barrier function, presenting as decreased serum diamine oxidase (DAO) and fluorescein isothiocyanate-dextran 40 (FD40) levels and increased expression of zonula occludens-1 (ZO-1) and Occludin. Polo-like kinase 1 (PLK1) knockdown in mice ameliorated intestinal epithelial apoptosis and the intestinal barrier during sepsis, whereas these effects were reduced with chloroquine and enhanced with rapamycin. PLK1 also promoted cell autophagy and improved lipopolysaccharide-induced apoptosis and high permeability in vitro. Moreover, PLK1 physically interacted with mammalian target of rapamycin (mTOR) and participated in reciprocal regulatory crosstalk in intestinal epithelial cells during sepsis. This study provides novel insight into the role of autophagy in sepsis-induced intestinal barrier dysfunction and indicates that the PLK1-mTOR axis may be a promising therapeutic target for sepsis.

Mitochondria ROS and mitophagy in acute kidney injury

Mitophagy is an essential mitochondrial quality control mechanism that eliminates damaged mitochondria and the production of reactive oxygen species (ROS). The relationship between mitochondria oxidative stress, ROS production and mitophagy are intimately interwoven, and these processes are all involved in various pathological conditions of acute kidney injury (AKI). The elimination of damaged mitochondria through mitophagy in mammals is a complicated process which involves several pathways. Furthermore, the interplay between mitophagy and different types of cell death, such as apoptosis, pyroptosis and ferroptosis in kidney injury is unclear. Here we will review recent advances in our understanding of the relationship between ROS and mitophagy, the different mitophagy pathways, the relationship between mitophagy and cell death, and the relevance of these processes in the pathogenesis of AKI.Abbreviations: AKI: acute kidney injury; AMBRA1: autophagy and beclin 1 regulator 1; ATP: adenosine triphosphate; BAK1: BCL2 antagonist/killer 1; BAX: BCL2 associated X, apoptosis regulator; BCL2: BCL2 apoptosis regulator; BECN1: beclin 1; BH3: BCL2 homology domain 3; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2 interacting protein 3 like; CASP1: caspase 1; CAT: catalase; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CI-AKI: contrast-induced acute kidney injury; CISD1: CDGSH iron sulfur domain 1; CL: cardiolipin; CNP: 2',3'-cyclic nucleotide 3'-phosphodiesterase; DNM1L/DRP1: dynamin 1 like; E3: enzyme 3; ETC: electron transport chain; FA: folic acid; FUNDC1: FUN14 domain containing 1; G3P: glycerol-3-phosphate; G6PD: glucose-6-phosphate dehydrogenase; GPX: glutathione peroxidase; GSH: glutathione; GSK3B: glycogen synthase kinase 3 beta; GSR: glutathione-disulfide reductase; HIF1A: hypoxia inducible factor 1 subunit alpha; HUWE1: HECT, UBA and WWE domain containing 1; IL1B: interleukin 1 beta; IMM: inner mitochondrial membrane; IPC: ischemic preconditioning; IRI: ischemia-reperfusion injury; LIR: LC3-interacting region; LPS: lipopolysaccharide; MA: malate-aspartate; MPT: mitochondrial permeability transition; MUL1: mitochondrial E3 ubiquitin protein ligase 1; mtROS: mitochondrial ROS; NLR: NOD-like receptor; NLRP3: NLR family pyrin domain containing 3; NOX: NADPH oxidase; OGD-R: oxygen-glucose deprivation-reperfusion; OMM: outer mitochondrial membrane; OPA1: OPA1 mitochondrial dynamin like GTPase; OXPHOS: oxidative phosphorylation; PARL: presenilin associated rhomboid like; PINK1: PTEN induced kinase 1; PLSCR3: phospholipid scramblase 3; PMP: peptidase, mitochondrial processing; PRDX: peroxiredoxin; PRKN: parkin RBR E3 ubiquitin protein ligase; RPTC: rat proximal tubular cells; ROS: reactive oxygen species; SLC7A11/xCT: solute carrier family 7 member 11; SOD: superoxide dismutase; SOR: superoxide reductase; SQSTM1/p62: sequestosome 1; TCA: tricarboxylic acid; TIMM: translocase of inner mitochondrial membrane; TOMM: translocase of outer mitochondrial membrane; TXN: thioredoxin; VDAC: voltage dependent anion channel; VCP: valosin containing protein.

Sepsis-induced AKI: From pathogenesis to therapeutic approaches

Sepsis is a heterogenous and highly complex clinical syndrome, which is caused by infectious or noninfectious factors. Acute kidney injury (AKI) is one of the most common and severe complication of sepsis, and it is associated with high mortality and poor outcomes. Recent evidence has identified that autophagy participates in the pathophysiology of sepsis-associated AKI. Despite the use of antibiotics, the mortality rate is still at an extremely high level in patients with sepsis. Besides traditional treatments, many natural products, including phytochemicals and their derivatives, are proved to exert protective effects through multiple mechanisms, such as regulation of autophagy, inhibition of inflammation, fibrosis, and apoptosis, etc. Accumulating evidence has also shown that many pharmacological inhibitors might have potential therapeutic effects in sepsis-induced AKI. Hence, understanding the pathophysiology of sepsis-induced AKI may help to develop novel therapeutics to attenuate the complications of sepsis and lower the mortality rate. This review updates the recent progress of underlying pathophysiological mechanisms of sepsis-associated AKI, focuses specifically on autophagy, and summarizes the potential therapeutic effects of phytochemicals and pharmacological inhibitors.

Protective effect of ghrelin on intestinal I/R injury in rats

This study aimed to investigate whether ghrelin affected the autophagy and inflammatory response of intestinal intraepithelial lymphocytes (IELs) by regulating the NOD2/Beclin-1 pathway in an intestinal ischemia–reperfusion (I/R) injury model. Twenty hours after implementing the intestinal I/R injury rat model, the small intestine and both lungs were collected for histological analysis. The morphological changes in the intestinal mucosa epithelium and lung tissues were evaluated using hematoxylin-eosin staining. The activity of autophagic vacuoles and organ injury were evaluated using electron microscopy. The cytokine levels (IL-10 and TNF-α) in IEL cells and lung tissue were determined using enzyme-linked immunosorbent assay. RT-qPCR and western blot assays were conducted to check the NOD2, Beclin-1, and ATG16 levels. Ghrelin relieved the I/R-induced destruction of the intestinal mucosa epithelium and lung tissues. Moreover, ghrelin enhanced autophagy in the intestinal epithelium and lungs of I/R rats. In addition, the levels of autophagy-associated proteins (Beclin-1, ATG16, and NOD2) were higher in the ghrelin treatment group than in rats with I/R. Ghrelin reduced significantly the IL-10 and TNF-α levels. However, these changes were reversed by the NOD2 antagonist. In conclusion, ghrelin may relieve I/R-induced acute intestinal mucosal damage, autophagy disorder, and inflammatory response in IELs by regulating the NOD2/Beclin-1 pathway.

Programmed Cell Death in Sepsis Associated Acute Kidney Injury

Sepsis-associated acute kidney injury (SA-AKI) is common in patients with severe sepsis, and has a high incidence rate and high mortality rate in ICU patients. Most patients progress to AKI before drug treatment is initiated. Early studies suggest that the main mechanism of SA-AKI is that sepsis leads to vasodilation, hypotension and shock, resulting in insufficient renal blood perfusion, finally leading to renal tubular cell ischemia and necrosis. Research results in recent years have shown that programmed cell death such as apoptosis, necroptosis, pyroptosis and autophagy play important roles. In the early stage of sepsis-related AKI, autophagy bodies form and inhibit various types of programmed cell death. With the progress of disease, programmed cell death begins. Apoptosis promoter represents caspase-8-induced apoptosis and apoptosis effector represents caspase-3-induced apoptosis, however, caspase-11 and caspase-1 regulate gasdermin D-mediated pyroptosis. Caspase-8 and receptor interacting kinase 1 bodies mediate necroptosis. This review focuses on the pathophysiological mechanisms of various programmed cell death in sepsis-related AKI.

Protective effect of H2S on LPS‑induced AKI by promoting autophagy

The present study explored the protective effect of exogenous hydrogen sulfide (H2S) on lipopolysaccharide (LPS)‑induced acute kidney injury (AKI) and the underlying mechanisms. To establish an AKI injury mouse model, LPS (10 mg/kg) was intraperitoneally injected into mice pretreated with 0.8 mg/kg sodium hydrosulfide hydrate (NaHS), an H2S donor. The mouse survival rate and the degree of kidney injury were examined. To construct a cell damage model, HK‑2 cells were pretreated with different concentrations (0.1, 0.3 and 0.5 mM) of NaHS, and then the cells were stimulated with LPS (1 µg/ml). The cell viability, autophagy, apoptosis levels and the release of inflammatory factors were examined in mouse kidney tissue and HK‑2 renal tubular epithelial cells. It was found that pretreatment with NaHS significantly improved the survival rate of septic AKI mice, and reduced the renal damage, release of inflammatory factors and apoptosis. In HK‑2 cells, NaHS protected cells from LPS caused damage via promoting autophagy and inhibiting apoptosis and the release of inflammatory factors. In order to clarify the relationship between autophagy and apoptosis and inflammatory factors, this study used 3‑methyladenine (3‑MA) to inhibit autophagy. The results revealed that 3‑MA eliminated the protective effect of NaHS in HK‑2 cells and AKI mice. Overall, NaHS can protect from LPS‑induced AKI by promoting autophagy and inhibiting apoptosis and the release of inflammatory factors.

Disruption of Kidney-Immune System Crosstalk in Sepsis with Acute Kidney Injury: Lessons Learned from Animal Models and Their Application to Human Health

In addition to being a leading cause of morbidity and mortality worldwide, sepsis is also the most common cause of acute kidney injury (AKI). When sepsis leads to the development of AKI, mortality increases dramatically. Since the cardinal feature of sepsis is a dysregulated host response to infection, a disruption of kidney-immune crosstalk is likely to be contributing to worsening prognosis in sepsis with acute kidney injury. Since immune-mediated injury to the kidney could disrupt its protein manufacturing capacity, an investigation of molecules mediating this crosstalk not only helps us understand the sepsis immune response, but also suggests that their supplementation could have a therapeutic effect. Erythropoietin, vitamin D and uromodulin are known to mediate kidney-immune crosstalk and their disrupted production could impact morbidity and mortality in sepsis with acute kidney injury.

The Interplay between Host Defense, Infection, and Clinical Status in Septic Patients: A Narrative Review

Sepsis is a life-threatening condition that arises when the body's response to an infection injures its own tissues and organs. Despite significant morbidity and mortality throughout the world, its pathogenesis and mechanisms are not clearly understood. In this narrative review, we aimed to summarize the recent developments in our understanding of the hallmarks of sepsis pathogenesis (immune and adaptive immune response, the complement system, the endothelial disfunction, and autophagy) and highlight novel laboratory diagnostic approaches. Clinical management is also discussed with pivotal consideration for antimicrobic therapy management in particular settings, such as intensive care unit, altered renal function, obesity, and burn patients.

Trichostatin A improves the inflammatory response and liver injury in septic mice through the FoxO3a/autophagy signaling pathway

BACKGROUND

Sepsis-induced liver injury is a fatal complication of sepsis. Trichostatin A (TSA) regulates inflammation and autophagy in some human diseases, and forkhead box O3a (FoxO3a) has been shown to regulate autophagy. The present study aims to investigate whether TSA exerts its effects on septic liver injury through the FoxO3a/autophagy signaling pathway.

METHODS

A sepsis mouse model was constructed by the cecal ligation and puncture (CLP) method, and AML12 cells were pretreated with lipopolysaccharide (LPS) (1 μg/mL) to establish a sepsis cell model. Forty mice were divided into four groups, namely control group, TSA group, CLP group, and CLP+TSA group, with 10 mice in each group. Cells were divided into control group, TSA group, LPS group, and LPS+TSA group. Hematoxylin-eosin (H&E) staining and biochemical methods were used to evaluate liver tissue injury. Enzyme-linked immunosorbent assay (ELISA) was applied to detect the expression of proinflammatory cytokines, and Western blotting and immunofluorescence were used to measure autophagy-related protein expression.

RESULTS

Compared with the CLP group (mice), the proinflammatory cytokines (interleukin-β [IL-β] 2,665.27±324.90 pg/mL to 2,080.26±373.66 pg/mL; interleukin-6 [IL-6] 399.01±60.98 pg/mL to 221.90±46.89 pg/mL) and the hepatocyte injury markers (aspartate transaminase [AST] from 198.18±27.07 U/L to 128.42±20.55 U/L; alanine aminotransferase [ALT] from 634.98±74.10 U/L to 478.60±32.56 U/L) were notably decreased after TSA intervention. Moreover, LC3 II and FoxO3a showed an obvious increase and P62 showed an obvious decrease in the CLP+TSA group. Cell experiment results showed the similar trend. After FoxO3a gene was knocked down in AML12 cells, the promotion of autophagy and the improvement of liver enzyme index and inflammation by TSA were weakened.

CONCLUSION

TSA may improve the inflammatory response and liver injury in septic mice through FoxO3a/autophagy.

Innovations and Emerging Therapies to Combat Renal Cell Damage: NAD+ As a Drug Target

Significance: Acute kidney injury (AKI) is a common and life-threatening complication in hospitalized and critically ill patients. It is defined by an abrupt deterioration in renal function, clinically manifested by increased serum creatinine levels, decreased urine output, or both. To execute all its functions, namely excretion of waste products, fluid/electrolyte balance, and hormone synthesis, the kidney requires incredible amounts of energy in the form of adenosine triphosphate. Recent Advances: Adequate mitochondrial functioning and nicotinamide adenine dinucleotide (NAD+) homeostasis are essential to meet these high energetic demands. NAD+ is a ubiquitous essential coenzyme to many cellular functions. NAD+ as an electron acceptor mediates metabolic pathways such as oxidative phosphorylation (OXPHOS) and glycolysis, serves as a cosubstrate of aging molecules (i.e., sirtuins), participates in DNA repair mechanisms, and mediates mitochondrial biogenesis. Critical Issues: In many forms of AKI and chronic kidney disease, renal function deterioration has been associated with mitochondrial dysfunction and NAD+ depletion. Based on this, therapies aiming to restore mitochondrial function and increase NAD+ availability have gained special attention in the last two decades. Future Directions: Experimental and clinical studies have shown that by restoring mitochondrial homeostasis and increasing renal tubulo-epithelial cells, NAD+ availability, AKI incidence, and chronic long-term complications are significantly decreased. This review covers some general epidemiological and pathophysiological concepts; describes the role of mitochondrial homeostasis and NAD+ metabolism; and analyzes the underlying rationale and role of NAD+ aiming therapies as promising preventive and therapeutic strategies for AKI. Antioxid. Redox Signal. 35, 1449-1466.

Metabolic Reprogramming and Host Tolerance: A Novel Concept to Understand Sepsis-Associated AKI

Acute kidney injury (AKI) is a frequent complication of sepsis that increases mortality and the risk of progression to chronic kidney disease. However, the mechanisms leading to sepsis-associated AKI are still poorly understood. The recognition that sepsis induces organ dysfunction in the absence of overt necrosis or apoptosis has led to the consideration that tubular epithelial cells (TEC) may deploy defense mechanisms to survive the insult. This concept dovetails well with the notion that the defense against infection does not only depend on the capacity of the immune system to limit the microbial load (known as resistance), but also on the capacity of cells and tissues to limit tissue injury (known as tolerance). In this review, we discuss the importance of TEC metabolic reprogramming as a defense strategy during sepsis, and how this cellular response is likely to operate through a tolerance mechanism. We discuss the fundamental role of specific regulatory nodes and of mitochondria in orchestrating this response, and how this opens avenues for the exploration of targeted therapeutic strategies to prevent or treat sepsis-associated AKI.

The attenuation of Th1 and Th17 responses via autophagy protects against methicillin-resistant Staphylococcus aureus-induced sepsis

Whether autophagy affects methicillin-resistant Staphylococcus aureus (MRSA)-induced sepsis and the associated mechanisms are largely unknown. This study investigated the role of autophagy in MRSA-induced sepsis. The levels of microtubule-associated protein light chain 3 (LC3)-II/I, Beclin-1 and p62 after USA300 infection were examined by Western blotting and immunohistochemical staining. Bacterial burden analysis, hematoxylin-eosin staining, and Kaplan-Meier analysis were performed to evaluate the effect of autophagy on MRSA-induced sepsis. IFN-γ and IL-17 were analyzed by ELISA, and CD4+ T cell differentiation was assessed by flow cytometry. Our results showed that LC3-II/I and Beclin-1 were increased, while p62 was decreased after infection. Survival rates were decreased in the LC3B-/- and Beclin-1+/- groups, accompanied by worsened organ injuries and increased IFN-γ and IL-17 levels, whereas rapamycin alleviated organ damage, decreased IFN-γ and IL-17 levels, and improved the survival rate. However, there was no significant difference in bacterial burden. Flow cytometric analysis showed that rapamycin treatment decreased the frequencies of Th1 and Th17 cells, whereas these cells were upregulated in the LC3B-/- and Beclin-1+/- groups. Therefore, autophagy plays a protective role in MRSA-induced sepsis, which may be partly associated with the alleviation of organ injuries via the downregulation of Th1 and Th17 responses. These results provide a nonantibiotic treatment strategy for sepsis.

RIP3 impedes transcription factor EB to suppress autophagic degradation in septic acute kidney injury

Autophagy is an important renal-protective mechanism in septic acute kidney injury (AKI). Receptor interacting protein kinase 3 (RIP3) has been implicated in the renal tubular injury and renal dysfunction during septic AKI. Here we investigated the role and mechanism of RIP3 on autophagy in septic AKI. We showed an activation of RIP3, accompanied by an accumulation of the autophagosome marker LC3II and the autophagic substrate p62, in the kidneys of lipopolysaccharide (LPS)-induced septic AKI mice and LPS-treated cultured renal proximal tubular epithelial cells (PTECs). The lysosome inhibitor did not further increase the levels of LCII or p62 in LPS-treated PTECs. Moreover, inhibition of RIP3 attenuated the aberrant accumulation of LC3II and p62 under LPS treatment in vivo and in vitro. By utilizing mCherry-GFP-LC3 autophagy reporter mice in vivo and PTECs overexpression mRFP-GFP-LC3 in vitro, we observed that inhibition of RIP3 restored the formation of autolysosomes and eliminated the accumulated autophagosomes under LPS treatment. These results indicated that RIP3 impaired autophagic degradation, contributing to the accumulation of autophagosomes. Mechanistically, the nuclear translocation of transcription factor EB (TFEB), a master regulator of the lysosome and autophagy pathway, was inhibited in LPS-induced mice and LPS-treated PTECs. Inhibition of RIP3 restored the nuclear translocation of TFEB in vivo and in vitro. Co-immunoprecipitation further showed an interaction of RIP3 and TFEB in LPS-treated PTECs. Also, the expression of LAMP1 and cathepsin B, two potential target genes of TFEB involved in lysosome function, were decreased under LPS treatment in vivo and in vitro, and this decrease was rescued by inhibiting RIP3. Finally, overexpression of TFEB restored the autophagic degradation in LPS-treated PTECs. Together, the present study has identified a pivotal role of RIP3 in suppressing autophagic degradation through impeding the TFEB-lysosome pathway in septic AKI, providing potential therapeutic targets for the prevention and treatment of septic AKI.

Mitochondrial Metabolism in Acute Kidney Injury

The kidney is a highly metabolic organ that requires substantial adenosine triphosphate for the active transport required to maintain water and solute reabsorption. Aberrations in energy availability and energy utilization can lead to cellular dysfunction and death. Mitochondria are essential for efficient energy production. The pathogenesis of acute kidney injury is complex and varies with different types of injury. However, multiple distinct acute kidney injury syndromes share a common dysregulation of energy metabolism. Pathways of energy metabolism and mitochondrial dysfunction are emerging as critical drivers of acute kidney injury and represent new potential targets for treatment. This review shows the basic metabolic pathways that all cells depend on for life; describes how the kidney optimizes those pathways to meet its anatomic, physiologic, and metabolic needs; summarizes the importance of metabolic and mitochondrial dysfunction in acute kidney injury; and analyzes the mitochondrial processes that become dysregulated in acute kidney injury including mitochondrial dynamics, mitophagy, mitochondrial biogenesis, and changes in mitochondrial energy metabolism.

The application of omic technologies to research in sepsis-associated acute kidney injury

Acute kidney injury (AKI) is common in critically ill children and adults, and sepsis-associated AKI (SA-AKI) is the most frequent cause of AKI in the ICU. To date, no mechanistically targeted therapeutic interventions have been identified. High-throughput "omic" technologies (e.g., genomics, proteomics, metabolomics, etc.) offer a new angle of approach to achieve this end. In this review, we provide an update on the current understanding of SA-AKI pathophysiology. Omic technologies themselves are briefly discussed to facilitate interpretation of studies using them. We next summarize the body of SA-AKI research to date that has employed omic technologies. Importantly, omic studies are helping to elucidate a pathophysiology of SA-AKI centered around cellular stress responses, metabolic changes, and dysregulation of energy production that underlie its clinical features. Finally, we propose opportunities for future research using clinically relevant animal models, integrating multiple omic technologies and ultimately progressing to translational human studies focusing therapeutic strategies on targeted disease mechanisms.

Capsaicin protects cardiomyocytes against lipopolysaccharide-induced damage via 14-3-3γ-mediated autophagy augmentation

Background: The myocardium is susceptible to lipopolysaccharide (LPS)-induced damage in sepsis, and cardiac dysfunction is a leading cause of mortality in patients with sepsis. The changes in cardiomyocyte autophagy in sepsis and the effects and mechanism of action of capsaicin (Cap) remain unclear.

Methods and Results: The potential pathway of 14-3-3γ-dependent autophagy and the effects and mechanisms of Cap were studied in LPS-induced injury to primary cultured neonatal rat cardiomyocytes. The results showed that cardiomyocyte viability decreased, lactate dehydrogenase and creatine kinase activities increased, 14-3-3γ expression was downregulated, and autophagy was inhibited after LPS challenge. Cap pretreatment augmented autophagy by upregulating 14-3-3γ expression and activating AMP-activated protein kinase (AMPK) and unc-51 like autophagy-activating kinase 1 (ULK1), suppressing mammalian target of rapamycin (mTOR), alleviating cardiac dysfunction and improving the inflammation response, whereas pAD/14-3-3γ-shRNA nullified the above effects. Cap pretreatment also decreased the levels of IL-1β, TNF-α, IL-6, and IL-10; suppressed intracellular oxidative stress; reduced the intracellular/mitochondrial reactive oxygen species (ROS); balanced GSH/GSSG; increased GSH-Px, catalase, and SOD activities; and decreased MDA contents. It also increased ATP content, activated complex Ⅰ and complex Ⅲ, stabilized the mitochondrial membrane potential, and decreased the mitochondrial permeability transition pore opening, thereby improving mitochondrial function.

Conclusion: Pretreatment with Cap can regulate autophagy by upregulating 14-3-3γ expression, inhibiting oxidative stress and inflammation, maintaining mitochondrial function, and protecting cardiomyocytes against LPS-induced injury.

Sepsis-Associated Acute Kidney Injury

Sepsis-associated acute kidney injury (S-AKI) is a common and life-threatening complication in hospitalized and critically ill patients. It is characterized by rapid deterioration of renal function associated with sepsis. The pathophysiology of S-AKI remains incompletely understood, so most therapies remain reactive and nonspecific. Possible pathogenic mechanisms to explain S-AKI include microcirculatory dysfunction, a dysregulated inflammatory response, and cellular metabolic reprogramming. In addition, several biomarkers have been developed in an attempt to improve diagnostic sensitivity and specificity of S-AKI. This article discusses the current understanding of S-AKI, recent advances in pathophysiology and biomarker development, and current preventive and therapeutic approaches.

Single-cell RNA sequencing reveals the sustained immune cell dysfunction in the pathogenesis of sepsis secondary to bacterial pneumonia

Sepsis is a leading cause of mortality in intensive care unit worldwide, it's accompanied by immune cell dysfunction induced by multiple factors. However, little is known about the specific alterations in immune cells in the dynamic pathogenesis of sepsis secondary to bacterial pneumonia. Here, we used single cell RNA sequencing (scRNA-seq) to profile peripheral blood mononuclear cells (PBMCs) in a healthy control and two patients with sepsis secondary to bacterial pneumonia, including acute, stable and recovery stage. We analyzed the quantity and function of immune cells. During disease course, interferon gamma response was upregulated; T/NK cell subtypes presented activation and exhaustion properties, which might be driven by monocytes through IL-1β signaling pathways; The proportion of plasma cells was increased, which might be driven by NK cells through IFN signaling pathways; Additionally, interferon gamma response was upregulated to a greater degree in sepsis secondary to pneumonia induced by SARS-COV-2 compared with that induced by influenza virus and bacteria.

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.

Effects of circular RNA Ttc3/miR-148a/Rcan2 axis on inflammation and oxidative stress in rats with acute kidney injury induced by sepsis

Aim Increasing evidence demonstrated circular RNAs (circRNAs) are involved in the development of various diseases, including sepsis-induced AKI. Although CIRC-Ttc3 has been proved to regulate cardiac function after myocardial infarction, its role in sepsis-induced AKI remains unclear.

MATERIALS AND METHODS

The AKI rat model was firstly induced by sepsis through cecal ligation puncture (CLP). Serum levels of creatinine, BUN, NGAL, TNF-α, IL-6, SOD, MDA and IL-1β were measured through appropriate kits. The pathological alteration and renal microvascular permeability in renal tissues were determined by HE staining and Evans Blue assays. Cell apoptosis was detected by TUNEL assay. The expression levels of CIRC-Ttc3, miR-148a, TNF-α, IL-1β and iNOS in rats' renal samples were tested by qRT-PCR or/and western blot. The binding ability between CIRC-Ttc3 and miR-148a was evaluated through luciferase reporter, RIP and RNA pull-down assays.

KEY FINDINGS

Kidney injury was found in CLP-treated rats. CIRC-Ttc3 expression was down-regulated, and upregulation of CIRC-Ttc3 improved inflammatory responses and oxidative stress in AKI rats. Mechanismly, CIRC-Ttc3 was confirmed to bind to and negatively regulate miR-148a. Further rescue assays revealed that overexpression of miR-148a rescued the improvement of CIRC-Ttc3 on sepsis-induced AKI. Then, it was illustrated that CIRC-Ttc3 regulated Rcan2 expression by binding to miR-148a. Finally, knockdown of Rcan2 reversed the effects of miR-148a inhibition on sepsis-induced AKI.

SIGNIFICANCE

CIRC-Ttc3 relieved inflammation and oxidative stress through regulating the miR-148a/Rcan2 axis in rats with AKI induced by sepsis. Therefore, CIRC-Ttc3 may be a potential therapeutic target for sepsis-induced AKI.

Profiles of differentially expressed long noncoding RNAs and messenger RNAs in the myocardium of septic mice

Background

Sepsis is the primary cause of mortality in the intensive care unit (ICU), mainly due to sepsis-induced dysfunction of essential organs such as the heart and lungs. This study investigated the myocardium's epigenetic characterization from septic mice to identify potential treatment targets for septic myocardial dysfunction.

Methods

Cecal ligation and puncture (CLP) was used to induce sepsis in male C57BL/6 mice. Hearts were collected 24 h after surgery to determine the expression profiles of long noncoding RNAs (lncRNAs) and messenger RNAs (mRNAs) by microarray. To validate the reliability of microarray results, we randomly chose six differentially expressed lncRNAs for qRT-PCR. Functional mapping of differentially expressed mRNAs was annotated with gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses; lncRNA-mRNA co-expression network was constructed to reveal connections between lncRNAs and mRNAs.

Results

Microarray analysis indicated that 1,568 lncRNAs and 2,166 mRNAs were differentially expressed in the myocardium from septic mice, which was further confirmed by qRT-PCR. KEGG pathway analysis showed that numerous differentially expressed mRNAs were relevant to tumor necrosis factor (TNF) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) signaling pathways. Moreover, according to the lncRNA-mRNA co-expression network constructed by the above six lncRNAs and their interacting mRNAs, the co-expression network profiles had 57 network nodes and 134 connections, including 76 positive interactions and 58 negative interactions.

Conclusions

In mouse hearts, sepsis resulted in differential expression of lncRNAs and mRNAs related to TNF and PI3K-Akt signaling pathways, suggesting that lncRNAs and their interacting mRNAs may participate in the pathogenesis of septic myocardial dysfunction by regulating TNF and PI3K-Akt signaling pathways.

Apolipoprotein L1 (APOL1) Coding Variants Are Associated With Creatinine Rise After Cardiac Surgery

OBJECTIVE

Acute kidney injury (AKI) is a complication of cardiac surgery that is considerably more common in African Americans (1.5-fold). Although homozygous status for apolipoprotein L1 (APOL1) risk alleles is associated with chronic kidney disease in individuals of African ancestry, whether these coding variants confer AKI risk is unknown. The present study examined whether APOL1 homozygous risk allele status was associated with AKI in African Americans after cardiac surgery.

DESIGN

Retrospective analysis of a cohort.

SETTING

Single-center university hospital.

PARTICIPANTS

African American patients from the CATHeterization GENetics study cohort who underwent cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

Genotyping of APOL1 alleles.

MEASUREMENTS AND MAIN RESULTS

Data from 125 African American patients included 12 APOL1 risk (ie, homozygous for risk alleles) patients and 113 APOL1 control (ie, wildtype or heterozygous for risk alleles) patients. The primary outcome to reflect AKI was peak serum creatinine rise after surgery relative to the preoperative creatinine (%ΔCr). The secondary outcome was Kidney Disease: Improving Global Outcomes (KDIGO) AKI criteria. In the primary analysis, peak creatinine rise was higher in risk compared with control patients in both univariate (%ΔCr 69.1 v 29.6%; p = 0.005) and multivariate regression (%ΔCr 88.5 v 43.7%; p = 0.006) analyses. For the secondary outcome, a trend toward KDIGO AKI development was noted in APOL1 risk patients, but this was not statistically significant.

CONCLUSIONS

African American cardiac surgery patients homozygous for APOL1 chronic kidney disease risk variants averaged a more than 2-fold higher postoperative creatinine rise even after adjustment for other risk factors, suggesting these alleles also are independent risk factors for AKI.

Autophagy in kidney homeostasis and disease

Autophagy is a conserved lysosomal pathway for the degradation of cytoplasmic components. Basal autophagy in kidney cells is essential for the maintenance of kidney homeostasis, structure and function. Under stress conditions, autophagy is altered as part of the adaptive response of kidney cells, in a process that is tightly regulated by signalling pathways that can modulate the cellular autophagic flux - mammalian target of rapamycin, AMP-activated protein kinase and sirtuins are key regulators of autophagy. Dysregulated autophagy contributes to the pathogenesis of acute kidney injury, to incomplete kidney repair after acute kidney injury and to chronic kidney disease of varied aetiologies, including diabetic kidney disease, focal segmental glomerulosclerosis and polycystic kidney disease. Autophagy also has a role in kidney ageing. However, questions remain about whether autophagy has a protective or a pathological role in kidney fibrosis, and about the precise mechanisms and signalling pathways underlying the autophagy response in different types of kidney cells and across the spectrum of kidney diseases. Further research is needed to gain insights into the regulation of autophagy in the kidneys and to enable the discovery of pathway-specific and kidney-selective therapies for kidney diseases and anti-ageing strategies.

Protection of procyanidin B2 on mitochondrial dynamics in sepsis associated acute kidney injury via promoting Nrf2 nuclear translocation

In septic acute kidney injury (SAKI), the positive feedback between damaged mitochondria and accumulation of reactive oxygen species results in cell and tissue damage through multiple mechanisms. Removing the damaged mitochondria or neutralizing the reactive oxygen species has been considered beneficial to alleviating cell damage. The antioxidant Procyanidin B2 has been reported to inhibits reactive oxygen species and thereby reduces cell injury. However, it is unclear whether this effect is associated with clearance of damaged mitochondria. Here, we evaluated the efficacy of procyanidin B2 on SAKI, and focused on its effects on mitochondrial dynamics and removing damaged mitochondria via mitophagy. The results showed that the renal function, renal tubular cell vacuolization and oxidative stress were decreased in SAKI mice treated with procyanidin B2, moreover, skewed mitochondrial fusion/fission, mitochondrial mediated apoptosis and impaired mitophagy were improved in SAKI mice treated with procyanidin B2. In mechanism, the improvement of procyanidin B2 on mitochondrial dynamics were associated with increased nuclear translocation of the transcription factor, Nrf2. In summary, our findings highlighted that the protective efficacy of procyanidin B2 in reducing cellular damage in SAKI, and mechanisms improving mitochondrial dynamics and quality control at least in part by promoting Nrf2 translocation into the nucleus.

A metabolic handbook for the COVID-19 pandemic

For infectious-disease outbreaks, clinical solutions typically focus on efficient pathogen destruction. However, the COVID-19 pandemic provides a reminder that infectious diseases are complex, multisystem conditions, and a holistic understanding will be necessary to maximize survival. For COVID-19 and all other infectious diseases, metabolic processes are intimately connected to the mechanisms of disease pathogenesis and the resulting pathology and pathophysiology, as well as the host defence response to the infection. Here, I examine the relationship between metabolism and COVID-19. I discuss why preexisting metabolic abnormalities, such as type 2 diabetes and hypertension, may be important risk factors for severe and critical cases of infection, highlighting parallels between the pathophysiology of these metabolic abnormalities and the disease course of COVID-19. I also discuss how metabolism at the cellular, tissue and organ levels might be harnessed to promote defence against the infection, with a focus on disease-tolerance mechanisms, and speculate on the long-term metabolic consequences for survivors of COVID-19.

Fyn Kinase: A Potential Therapeutic Target in Acute Kidney Injury

Acute kidney injury (AKI) is a common disease with a complex pathophysiology which significantly contributes to the development of chronic kidney disease and end stage kidney failure. Preventing AKI can consequently reduce mortality, morbidity, and healthcare burden. However, there are no effective drugs in use for either prevention or treatment of AKI. Developing therapeutic agents with pleiotropic effects covering multiple pathophysiological pathways are likely to be more effective in attenuating AKI. Fyn, a non-receptor tyrosine kinase, has been acknowledged to integrate multiple injurious stimuli in the kidney. Limited studies have shown increased Fyn transcription level and activation under experimental AKI. Activated Fyn kinase propagates various downstream signaling pathways associated to the progression of AKI, such as oxidative stress, inflammation, endoplasmic reticulum stress, as well as autophagy dysfunction. The versatility of Fyn kinase in mediating various pathophysiological pathways suggests that its inhibition can be a potential strategy in attenuating AKI.

Beclin 1/Bcl-2 complex-dependent autophagy activity modulates renal susceptibility to ischemia-reperfusion injury and mediates renoprotection by Klotho

Klotho- and beclin 1-driven autophagy extends life. We examined the role of beclin 1 in modifying acute kidney injury (AKI) and whether beclin 1 mediates Klotho's known renoprotective action in AKI. AKI was induced by ischemia-reperfusion injury in mice with different levels of autophagy activity by genetic manipulation: wild-type (WT) mice with normal beclin 1 expression and function, mice with normal beclin 1 levels but high activity through knockin of gain-of-function mutant beclin 1 (Becn1F121A), mice with low beclin 1 levels and activity caused by heterozygous global deletion of beclin 1 (Becn1+/-), or mice with extremely low beclin 1 activity from knockin of the mutant constitutively active beclin 1 inhibitor Bcl-2 (Bcl2AAA). Klotho was increased by transgenic overexpression (Tg-Kl) or recombinant Klotho protein administration. After ischemia-reperfusion injury, Becn1F121A mice (high autophagy) had milder AKI and Becn1+/- and Bcl2AAA mice (low autophagy) had more severe AKI than WT mice. Tg-Kl mice had milder AKI, but its renoprotection was partially attenuated in Becn1+/-;Tg-Kl mice and was significantly reduced, although not completely abolished, in Bcl2AAA;Tg-Kl mice. Recombinant Klotho protein conferred more renoprotection from AKI in WT mice than in Becn1+/- or Bcl2AAA mice. Klotho reduced beclin 1/Bcl-2 protein complexes and increased autophagy activity, but this effect was less prominent in mice or cells with Bcl2AAA. Transfected Bcl2AAA or Becn1F123A decreased or increased autophagy activity and rendered cells more susceptible or more resistant to oxidative cytotoxicity, respectively. In conclusion, beclin 1 confers renoprotection by activating autophagy. Klotho protects the kidney partially via disruption of beclin 1/Bcl-2 interactions and enhancement of autophagy activity.

Autophagy in kidney disease: Advances and therapeutic potential

Autophagy is a highly conserved intracellular catabolic process for the degradation of cytoplasmic components that has recently gained increasing attention for its importance in kidney diseases. It is indispensable for the maintenance of kidney homeostasis both in physiological and pathological conditions. Investigations utilizing various kidney cell-specific conditional autophagy-related gene knockouts have facilitated the advancement in understanding of the role of autophagy in the kidney. Recent findings are raising the possibility that defective autophagy exerts a critical role in different pathological conditions of the kidney. An emerging body of evidence reveals that autophagy exhibits cytoprotective functions in both glomerular and tubular compartments of the kidney, suggesting the upregulation of autophagy as an attractive therapeutic strategy. However, there is also accumulating evidence that autophagy could be deleterious, which presents a formidable challenge in developing therapeutic strategies targeting autophagy. Here, we review the recent advances in research on the role of autophagy during different pathological conditions, including acute kidney injury (AKI), focusing on sepsis, ischemia-reperfusion injury, cisplatin, and heavy metal-induced AKI. We also discuss the role of autophagy in chronic kidney disease (CKD) focusing on the pathogenesis of tubulointerstitial fibrosis, podocytopathies including focal segmental glomerulosclerosis, diabetic nephropathy, IgA nephropathy, membranous nephropathy, HIV-associated nephropathy, and polycystic kidney disease.

Lithium targeting of AMPK protects against cisplatin-induced acute kidney injury by enhancing autophagy in renal proximal tubular epithelial cells

Autophagy has been demonstrated to be vital for kidney homeostasis and is centrally implicated in the pathogenesis of cisplatin-induced acute kidney injury (AKI). Lithium is a potent autophagy inducer in a number of cell types. However, it remains uncertain whether its autophagic activity is associated with a beneficial effect on renal tubular cells in AKI. This study aimed to examine the effect of lithium on renal autophagy in cisplatin-induced AKI. Mice or renal proximal tubular epithelial cells in culture were exposed to cisplatin-induced acute injury in the presence or absence of lithium treatment. AKI or tubular cell injury was evaluated, and cell signaling associated with autophagy was examined. Lithium pretreatment prominently ameliorated acute renal tubular damage in mice exposed to cisplatin insult, associated with enhanced autophagy in renal tubules, as assessed by measuring microtubule-associated protein 1A/1B-light chain 3 (LC3)BII/I expression and autophagosome formation. Consistently, in cisplatin-injured renal tubular cells in vitro, lithium enhanced autophagic activities, improved cell viability, and attenuated cell death. Mechanistically, lithium triggered AMPK-α phosphorylation and activation, which in turn positively correlated with the induced expression of autophagy-related molecules, like mammalian target of rapamycin and LC3BII/I. AMPK-α activation is likely required for lithium-induced tubular cell autophagy and protection in cisplatin-induced AKI because blockade of AMPK-α phosphorylation by compound C markedly abrogated lithium-induced autophagosome formation and mitigated the protective effect of lithium on AKI. Our findings suggest that lithium represents a promising therapeutic strategy for protecting renal tubular cells against cisplatin-induced AKI by enhancing autophagy via AMPK-α activation.-Bao, H., Zhang, Q., Liu, X., Song, Y., Li, X., Wang, Z., Li, C., Peng, A., Gong, R. Lithium targeting of AMPK protects against cisplatin-induced acute kidney injury by enhancing autophagy in renal proximal tubular epithelial cells.

Sepsis roadmap: What we know, what we learned, and where we are going

Sepsis is a life-threatening condition originating as a result of systemic blood infection causing, one or more organ damage due to the dysregulation of the immune response. In 2017, the world health organization (WHO) declared sepsis as a disease of global health priority, needing special attention due to its high prevalence and mortality around the world. Most of the therapeutics targeting sepsis have failed in the clinics. The present review highlights the history of the sepsis, its immunopathogenesis, and lessons learned after the failure of previously used immune-based therapies. The subsequent section, where to go describes in details the importance of the complement system (CS), autophagy, inflammasomes, and microbiota along with their targeting to manage sepsis. These systems are interconnected to each other, thus targeting one may affect the other. We are in an urgent need for a multi-targeting therapeutic approach for sepsis.

Autophagy in Kidney Disease

Autophagy is a cellular homeostatic program for the turnover of cellular organelles and proteins, in which double-membraned vesicles (autophagosomes) sequester cytoplasmic cargos, which are subsequently delivered to the lysosome for degradation. Emerging evidence implicates autophagy as an important modulator of human disease. Macroautophagy and selective autophagy (e.g., mitophagy, aggrephagy) can influence cellular processes, including cell death, inflammation, and immune responses, and thereby exert both adaptive and maladaptive roles in disease pathogenesis. Autophagy has been implicated in acute kidney injury, which can arise in response to nephrotoxins, sepsis, and ischemia/reperfusion, and in chronic kidney diseases. The latter includes comorbidities of diabetes and recent evidence for chronic obstructive pulmonary disease-associated kidney injury. Roles of autophagy in polycystic kidney disease and kidney cancer have also been described. Targeting the autophagy pathway may have therapeutic benefit in the treatment of kidney disorders.

Regulation of hippocampal neuronal apoptosis and autophagy in mice with sepsis-associated encephalopathy by immunity-related GTPase M1

Aims

Sepsis‐associated encephalopathy (SAE) is a common complication of severe sepsis. Our goal was to investigate the role of immunity‐related GTPase M1 (IRGM1) in SAE and its underlying mechanism.

Methods

A mouse sepsis model was established by cecal ligation and perforation. SAE was diagnosed by behavior, electroencephalography, and somatosensory evoked potentials. Wild‐type mice with SAE were treated with SB203580 to block the p38 mitogen‐activated protein kinase (MAPK) signaling pathway. We assessed hippocampal histological changes and the expression of IRGM1, interferon‐γ (IFN‐γ), and p38 MAPK signaling pathway‐related proteins.

Results

Immunity‐related GTPase M1 and IFN‐γ levels increased in the hippocampus, with apoptosis, autophagy, and the p38 MAPK signaling pathway activated in neurons. Administration of SB203580 to mice with SAE reduced apoptosis and autophagy. Relative to wild‐type mice with SAE, the general condition of Irgm1^‐/‐ mice with SAE was worsened, the p38 MAPK signaling pathway was inhibited, and neuronal apoptosis and autophagy were reduced. The absence of IRGM1 exacerbated SAE, with higher p38 MAPK signaling pathway activity and increased apoptosis and autophagy.

Conclusions

During SAE, IRGM1 can at least partially regulate apoptosis and autophagy in hippocampal neurons through the p38 MAPK signaling pathway.

Involvement of phosphatase and tensin homolog-induced putative kinase 1-Parkin-mediated mitophagy in septic acute kidney injury

BACKGROUND

Studies have reported mitophagy activation in renal tubular epithelial cells (RTECs) in acute kidney injury (AKI). Phosphatase and tensin homolog-induced putative kinase 1 (PINK1) and E3 ubiquitin-protein ligase Parkin are involved in mitophagy regulation; however, little is known about the role of PINK1-Parkin mitophagy in septic AKI. Here we investigated whether the PINK1-Parkin mitophagy pathway is involved in septic AKI and its effects on cell apoptosis in vitro and on renal functions in vivo.

METHODS

Mitophagy-related gene expression was determined using Western blot assay in human RTEC cell line HK-2 stimulated with bacterial lipopolysaccharide (LPS) and in RTECs from septic AKI rats induced by cecal ligation and perforation (CLP). Autophagy-related ultrastructural features in rat RTECs were observed using electron microscopy. Gain- and loss-of-function approaches were performed to investigate the role of the PINK1-Parkin pathway in HK-2 cell mitophagy. Autophagy activators and inhibitors were used to assess the effects of mitophagy modulation on cell apoptosis in vitro and on renal functions in vivo.

RESULTS

LPS stimulation could significantly induce LC3-II and BECN-1 protein expression (LC3-II: 1.72 ± 0.05 vs. 1.00 ± 0.05, P < 0.05; BECN-1: 5.33 ± 0.57 vs. 1.00 ± 0.14, P < 0.05) at 4 h in vitro. Similarly, LC3-II, and BECN-1 protein levels were significantly increased and peaked at 2 h after CLP (LC3-II: 3.33 ± 0.12 vs. 1.03 ± 0.15, P < 0.05; BECN-1: 1.57 ± 0.26 vs. 1.02 ± 0.11, P < 0.05) in vivo compared with those after sham operation. Mitochondrial deformation and mitolysosome-mediated mitochondria clearance were observed in RTECs from septic rats. PINK1 knockdown significantly attenuated LC3-II protein expression (1.35 ± 0.21 vs. 2.38 ± 0.22, P < 0.05), whereas PINK1 overexpression markedly enhanced LC3-II protein expression (2.07 ± 0.21 vs. 1.29 ± 0.19, P < 0.05) compared with LPS-stimulated HK-2 cells. LPS-induced proapoptotic protein expression remained unchanged in autophagy activator-treated HK-2 cells and was significantly attenuated in PINK1-overexpressing cells, but was remarkably upregulated in autophagy inhibitor-treated and in PINK1-depleted cells. Consistent results were observed in flow cytometric apoptosis assay and in renal function indicators in rats.

CONCLUSION

PINK1-Parkin-mediated mitophagy might play a protective role in septic AKI, serving as a potential therapeutic target for septic AKI.

Protective role of thymoquinone in sepsis-induced liver injury in BALB/c mice

Sepsis increases the risk of developing liver injury. Previous studies have demonstrated that thymoquinone (TQ) exhibits hepatoprotective properties in vivo as well as in vitro. The present study aimed to investigate the underlying mechanisms of the protective effects of TQ against liver injury in septic BALB/c mice. Male BALB/c mice (age, 8 weeks) were randomly divided into four groups, namely, the control, TQ (50 mg/kg/day) treatment, cecal ligation and puncture (CLP), and TQ + CLP groups. CLP was performed following gavage of TQ for 2 weeks. At 48 h post-CLP, the histopathological alterations in the liver tissue (LT) and plasma levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were assessed. The present study evaluated microtubule-associated protein light chain 3 (LC3), sequestosome-1 (p62) and beclin 1 protein expression by western blotting and immunostaining, as well as interleukin (IL)-6, IL-1β, IL-10, monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) mRNA expression by RT-qPCR. The results of the present study indicated that administration of TQ to mice reduced the histological alterations caused by CLP in LT. TQ inhibited the plasma levels of ALT, AST and ALP in the CLP group. TQ significantly inhibited the elevation of p62, IL-1β, IL-6, MCP-1 and TNF-α levels as well as increased the LC3, beclin 1 and IL-10 levels in LT. PI3K expression in the TQ + CLP group was significantly decreased compared with that in the CLP group. TQ treatment effectively modulated the expression levels of p62, LC3, beclin 1, PI3K and proinflammatory cytokines, and may be an important agent for the treatment of sepsis-induced liver injury.

Autophagy Enhancing Contributes to the Organ Protective Effect of Alpha-Lipoic Acid in Septic Rats

Alpha-lipoic acid (ALA) reportedly has protective effects against sepsis, which is a leading cause of mortality worldwide and is associated with multiple organ dysfunction. The present study aimed to investigate further the possible action mechanisms of ALA. Male Sprague-Dawley rats were subjected to cecal ligation and puncture (CLP) in order to establish a sepsis model. The rats received an oral gavage of 200 mg/kg ALA or saline immediately after surgery. The heart rate (HR), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and maximum rising and lowering rates of left ventricular pressure (±dp/dt) were examined for assessing the cardiac function. Blood urea nitrogen (BUN) and serum creatinine levels were assessed for evaluating renal function. Neutrophil gelatinase-associated lipocalin (NAGL) was examined for reflecting acute renal injury. Histopathological alterations of the small intestine were examined by hematoxylin-eosin staining. The ultrastructure of the small intestine and kidney was observed under electron microscopy. The levels of autophagy- and inflammation-associated proteins were determined via western blot analysis. The binding of nuclear factor-kappa B (NF-κB) to DNA was tested via an electrophoretic mobility shift assay. Cell apoptosis was examined using TUNEL staining. ALA treatment improved the survival rate, restored the loss of body weight and pro-inflammatory cytokines production in the serum of CLP-induced septic rats. ALA improved the cardiac and renal functions, downregulated the expression levels of interleukin-1β, tumor necrosis factor-α, and inducible nitric oxide synthase in the myocardium and small intestine of septic rats. ALA treatment also inactivated the NF-κB signaling pathway in the small intestine. An examination of autophagy showed that ALA increased the LC3II/I ratio, upregulated Atg5, Atg7, and beclin-1 and downregulated p62 protein levels in the myocardium, kidney, and small intestine of septic rats, and further promoted autophagosome accumulation in the kidney and small intestine. In addition, ALA could also reduce cell apoptosis in myocardium, kidney and small intestine tissues. These effects can be completely or party inhibited by 3-MA. Our findings suggest that autophagy enhancing may contribute to the organ protective effect of ALA in septic rats.