A novel mechanism for the protection against acute lung injury by melatonin: mitochondrial quality control of lung epithelial cells is preserved through SIRT3-dependent deacetylation of SOD2

Brazilin alleviates acute lung injury via inhibition of ferroptosis through the SIRT3/GPX4 pathway

Ferroptosis is a novel type of programmed cell death dependent on iron and is characterized by the accumulation of lipid peroxides, which is involved in acute lung injury (ALI). Brazilin, an organic compound known for its potent antioxidant and anti-inflammatory properties, has not been thoroughly studied for its potential impact on lipopolysaccharide (LPS)-induced ALI. Here, we found that pretreatment of brazilin mitigated LPS-induced lung injury and inflammation by inhibiting mitochondrial oxidative stress and ferroptosis, both in vivo and in vitro. Sirtuin 3 (SIRT3) was identified as a downstream target of brazilin, and overexpression of SIRT3 mirrored the protective effects of brazilin against LPS-induced ALI. Additionally, SIRT3 contributed to the upregulation, mitochondrial translocation and deacetylation of glutathione peroxidase 4 (GPX4). Through screening potential acetylation sites on GPX4, we identified lysine 148 (K148) as the residue deacetylated by SIRT3. Mutating the acetylation site of GPX4 within mitochondria (mitoGPX4-K148R) reduced LPS or SIRT3 knockdown-induced GPX4 acetylation, oxidative stress, and ferroptosis, ultimately ameliorating ALI. In conclusion, our study demonstrates the beneficial effects of brazilin in treating LPS-induced ALI. Brazilin enhances SIRT3 expression, which in turn deacetylates and facilitates the mitochondrial translocation of GPX4, thereby reducing mitochondrial oxidative stress and ferroptosis. These findings suggest that the SIRT3/GPX4 pathway may represent a critical mechanism, and brazilin emerges as a promising therapeutic candidate for ALI.

Melatonin Reduces Mito-Inflammation in Ischaemic Hippocampal HT22 Cells and Modulates the cGAS-STING Cytosolic DNA Sensing Pathway and FGF21 Release

Mitochondrial dysfunction is a key event in many pathological conditions, including neurodegenerative processes. When mitochondria are damaged, they release damage-associated molecular patterns (DAMPs) that activate mito-inflammation. The present study assessed mito-inflammation after in vitro oxygen-glucose deprivation as a representation of ischaemia, followed by reoxygenation (OGD/R) of HT22 cells and modulation of the inflammatory response by melatonin. We observed that melatonin prevented mitochondrial structural damage and dysfunction caused by OGD/R. Melatonin reduced oxidative damage and preserved the enzymatic activity for complexes I, III and IV, encoded by mitochondrial DNA, which were reduced by OGD/R. No effect was observed on complex II activity encoded by nuclear DNA. The release of mtDNA into the cytosol was also prevented with a consequent reduction of the cGAS-STING pathway and IFNβ and IL-6 production. Interestingly, melatonin also increased the early release of the fibroblast growth factor-21 (FGF-21), a mitokine secreted in response to mitochondrial stress. These data indicate that melatonin reduces mito-inflammation and modulates FGF-21 release, further highlighting the key role of this molecule in preserving mitochondrial integrity in OGD/R deprivation-type ischaemic brain injury.

SIRT3 Deficiency Promotes Lung Endothelial Pyroptosis Through Impairing Mitophagy to Activate NLRP3 Inflammasome During Sepsis-Induced Acute Lung Injury

Acute lung injury (ALI) is a major cause of death in bacterial sepsis due to endothelial inflammation and endothelial permeability defects. Mitochondrial dysfunction is recognized as a key mediator in the pathogenesis of sepsis-induced ALI. Sirtuin 3 (SIRT3) is a histone protein deacetylase involved in preservation of mitochondrial function, which has been demonstrated in our previous study. Here, we investigated the effects of SIRT3 deficiency on impaired mitophagy to promote lung endothelial cells (ECs) pyroptosis during sepsis-induced ALI. We found that 3-TYP aggravated sepsis-induced ALI with increased lung ECs pyroptosis and enhanced NLRP3 activation. Mitochondrial reactive oxygen species (mtROS) and extracellular mitochondrial DNA (mtDNA) released from damaged mitochondria could be exacerbated in SIRT3 deficiency, which further elicit NLRP3 inflammasome activation in lung ECs during sepsis-induced ALI. Furthermore, Knockdown of SIRT3 contributed to impaired mitophagy via downregulating Parkin, which resulted in mitochondrial dysfunction. Moreover, pharmacological inhibition NLRP3 or restoration of SIRT3 attenuates sepsis-induced ALI and sepsis severity in vivo. Taken together, our results demonstrated SIRT3 deficiency facilitated mtROS production and cytosolic release of mtDNA by impaired Parkin-dependent mitophagy, promoting to lung ECs pyroptosis through the NLRP3 inflammasome activation, which providing potential therapeutic targets for sepsis-induced ALI.

Protective Activity of Melatonin Combinations and Melatonin-Based Hybrid Molecules in Neurodegenerative Diseases

The identification of protective agents for the treatment of neurodegenerative diseases is the mainstay therapeutic goal to modify the disease course and arrest the irreversible disability progression. Pharmacological therapies synergistically targeting multiple pathogenic pathways, including oxidative stress, mitochondrial dysfunction, and inflammation, are prime candidates for neuroprotection. Combination or synergistic therapy with melatonin, whose decline correlates with altered sleep/wake cycle and impaired glymphatic "waste clearance" system in neurodegenerative diseases, has a great therapeutic potential to treat inflammatory neurodegenerative states. Despite the protective outcomes observed in preclinical studies, mild or poor outcomes were observed in clinical settings, suggesting that melatonin combinations promoting synergistic actions at appropriate doses might be more suitable to treat multifactorial neurodegenerative disorders. In this review, we first summarize the key melatonin actions and pathways contributing to cell protection and its therapeutic implication in Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). We remark the major controversies in the field, mostly generated by the lack of a common consensus for the optimal dosing, molecular targets, and toxicity. Then, we review the literature investigating the efficacy of melatonin combinations with approved or investigational neuroprotective agents and of melatonin-containing hybrid molecules, both in vitro and in animal models of AD, PD, and MS, as well as the efficacy of add-on melatonin in clinical settings. We highlight the rationale for such melatonin combinations with a focus on the comparison with single-agent treatment and on the assays in which an additive or a synergistic effect has been achieved. We conclude that a better characterization of the mechanisms underlying such melatonin synergistic actions under neuroinflammation at appropriate doses needs to be tackled to advance successful clinical translation of neuroprotective melatonin combination therapies or melatonin-based hybrid molecules.

Sirtuin 3-activated superoxide dismutase 2 mediates fluoride-induced osteoblastic differentiation in vitro and in vivo by down-regulating reactive oxygen species

Skeletal fluorosis is a chronic metabolic bone disease caused by long-term excessive fluoride intake. Abnormal differentiation of osteoblasts plays an important role in disease progression. Research on the mechanism of fluoride-mediated bone differentiation is necessary for the prevention and treatment of skeletal fluorosis. In the present study, a rat model of fluorosis was established by exposing it to drinking water containing 50 mg/L F-. We found that fluoride promoted Runt-related transcription factor 2 (RUNX2) as well as superoxide dismutase 2 (SOD2) and sirtuin 3 (SIRT3) expression in osteoblasts of rat bone tissue. In vitro, we also found that 4 mg/L sodium fluoride promoted osteogenesis-related indicators as well as SOD2 and SIRT3 expression in MG-63 and Saos-2 cells. In addition, we unexpectedly discovered that fluoride suppressed the levels of reactive oxygen species (ROS) and mitochondrial reactive oxygen species (mtROS) in osteoblasts. When SOD2 or SIRT3 was inhibited in MG-63 cells, fluoride-decreased ROS and mtROS were alleviated, which in turn inhibited fluoride-promoted osteogenic differentiation. In conclusion, our results suggest that SIRT3/SOD2 mediates fluoride-promoted osteoblastic differentiation by down-regulating reactive oxygen species.

The impact of hormones on lung development and function: an overlooked aspect to consider from early childhood

The impact of hormones on the respiratory system constitutes a multifaceted and intricate facet of human biology. We propose a comprehensive review of recent advancements in understanding the interactions between hormones and pulmonary development and function, focusing on pediatric populations. We explore how hormones can influence ventilation, perfusion, and pulmonary function, from regulating airway muscle tone to modulating the inflammatory response. Hormones play an important role in the growth and development of lung tissues, influencing them from early stages through infancy, childhood, adolescence, and into adulthood. Glucocorticoids, thyroid hormones, insulin, ghrelin, leptin, glucagon-like peptide 1 (GLP-1), retinoids, cholecalciferol sex steroids, hormones derived from adipose tissue, factors like insulin, granulocyte-macrophage colony-stimulating factor (GM-CSF) and glucagon are key players in modulating respiratory mechanics and inflammation. While ample evidence underscores the impact of hormones on lung development and function, along with sex-related differences in the prevalence of respiratory disorders, further research is needed to clarify their specific roles in these conditions. Further research into the mechanisms underlying hormonal effects is essential for the development of customizing therapeutic approaches for respiratory diseases. Understanding the impact of hormones on lung function could be valuable for developing personalized monitoring approaches in both medical and surgical pediatric settings, in order to improve outcomes and the quality of care for pediatric patients.

Capsaicin mitigates ventilator-induced lung injury by suppressing ferroptosis and maintaining mitochondrial redox homeostasis through SIRT3-dependent mechanisms

BACKGROUND

Ventilator-induced lung injury (VILI) is one of the severe complications in the clinic concerning mechanical ventilation (MV). Capsaicin (CAP) has anti-inflammatory and inhibitory effects on oxidative stress, which is a significant element causing cellular ferroptosis. Nevertheless, the specific role and potential mechanistic pathways through which CAP modulates ferroptosis in VILI remain elusive.

METHODS

VILI was established in vivo, and the pulmonary epithelial cell injury model induced by circulation stretching (CS) was established in vitro. Both mice and cells were pretreated with CAP. Transmission electron microscopy, ELISA, Western blot, immunofluorescence, RT-PCR, fluorescent probes, and other experimental methods were used to clarify the relationship between iron death and VILI in alveolar epithelial cells, and whether capsaicin alleviates VILI by inhibiting iron death and its specific mechanism.

RESULTS

Ferroptosis was involved in VILI by utilizing in vivo models. CAP inhibited ferroptosis and alleviated VILI's lung damage and inflammation, and this protective effect of CAP was dependent on maintaining mitochondrial redox system through SITR3 signaling. In the CS-caused lung epithelial cell injury models, CAP reduced pathological CS-caused ferroptosis and cell injury. Knockdown SIRT3 reversed the role of CAP on the maintaining mitochondria dysfunction under pathological CS and eliminated its subsequent advantageous impacts for ferroptosis against overstretching cells.

CONCLUSION

The outcomes showed that CAP alleviated ferroptosis in VILI via improving the activity of SITR3 to suppressing mitochondrial oxidative damage and maintaining mitochondrial redox homeostasis, illustrating its possibility as a novel therapeutic goal for VILI.

Relationship between ferroptosis and mitophagy in acute lung injury: a mini-review

Acute lung injury (ALI) is one of the most deadly and prevalent diseases in the intensive care unit. Ferroptosis and mitophagy are pathological mechanisms of ALI. Ferroptosis aggravates ALI, whereas mitophagy regulates ALI. Ferroptosis and mitophagy are both closely related to reactive oxygen species (ROS). Mitophagy can regulate ferroptosis, but the specific relationship between ferroptosis and mitophagy is still unclear. This study summarizes previous research findings on ferroptosis and mitophagy, revealing their involvement in ALI. Examining the functions of mTOR and NLPR3 helps clarify the connection between ferroptosis and mitophagy in ALI, with the goal of establishing a theoretical foundation for potential therapeutic approaches in the future management of ALI.

BRD3308 suppresses macrophage oxidative stress and pyroptosis via upregulating acetylation of H3K27 in sepsis-induced acute lung injury

Background

Sepsis-induced acute lung injury (ALI) leads to severe hypoxemia and respiratory failure, contributing to poor prognosis in septic patients. Endotoxin dissemination triggers oxidative stress and the release of inflammatory cytokines in macrophages, initiating diffuse alveolar damage. The role of epigenetic histone modifications in organ injury is increasingly recognized. The present study aimed to investigate the use of a histone modification inhibitor to alleviate sepsis-induced ALI, revealing a new strategy for improving sepsis patient survival.

Methods

In vivo models of ALI were established through the intraperitoneal injection of lipopolysaccharide and cecal ligation and puncture surgery. Furthermore, the disease process was simulated in vitro by stimulating Tamm-Horsfall protein-1 (THP-1) cells with lipopolysaccharide. Hematoxylin and eosin staining, blood gas analysis and pulmonary function tests were utilized to assess the extent of lung tissue damage. Western blot analysis, real-time polymerase chain reaction, enzyme-linked immunosorbent assay and immunofluorescence were used to measure the levels and distribution of the indicated indicators within cells and tissues. Reactive oxygen species and autophagic flux alterations were detected using specific probes.

Results

BRD3308, which is a inhibitor of histone deacetylase 3, improved lung tissue damage, inflammatory infiltration and edema in ALI by inhibiting Nod-like receptor protein3-mediated pyroptosis in macrophages. By upregulating autophagy, BRD3308 improved the disruption of redox balance in macrophages and reduced the accumulation of reactive oxygen species. Mechanistically, BRD3308 inhibited histone deacetylase 3 activity by binding to it and altering its conformation. Following histone deacetylase 3 inhibition, acetylation of H3K27 was significantly increased. Moreover, the increase in H3K27Ac led to the upregulation of autophagy-related gene 5, a key component of autophagosomes, thereby activating autophagy.

Conclusions

BRD3308 inhibits oxidative stress and pyroptosis in macrophages by modulating histone acetylation, thereby preventing sepsis-induced ALI. The present study provides a potential strategy and theoretical basis for the clinical treatment of sepsis-induced ALI.

KLF13 Attenuates Lipopolysaccharide-Induced Alveolar Epithelial Cell Damage by Regulating Mitochondrial Quality Control via Binding PGC-1α

Sepsis is a clinically life-threatening syndrome, and acute lung injury is the earliest and most serious complication. We aimed to assess the role of kruppel-like factor 13 (KLF13) in lipopolysaccharide (LPS)-induced human alveolar type II epithelial cell damage and to reveal the possible mechanism related to peroxisome proliferator-activated receptor-γ co-activator 1-α (PGC-1α). In LPS-treated A549 cells with or without KLF13 overexpression or PGC-1α knockdown, cell viability was measured by a cell counting kit-8 assay. Enzyme-linked immunosorbent assay kits detected the levels of inflammatory factors, and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining measured cell apoptosis. Besides, mitochondrial reactive oxygen species (MitoSOX) and mitochondrial membrane potential were detected using MitoSOX red- and JC-1 staining. Expression of proteins related to mitochondrial quality control (MQC) was evaluated by western blot. Co-immunoprecipitation (Co-IP) assay was used to analyze the interaction between KLF13 and PGC-1α. Results indicated that KLF13 was highly expressed in LPS-treated A549 cells. KLF13 upregulation elevated the viability and reduced the levels of inflammatory factors in A549 cells exposed to LPS. Moreover, KLF13 gain-of-function inhibited LPS-induced apoptosis of A549 cells, accompanied by upregulated BCL2 expression and downregulated Bax and cleaved caspase3 expression. Furthermore, MQC was improved by KLF13 overexpression, as evidenced by decreased MitoSOX, JC-1 monomers and increased JC-1 aggregates, coupled with the changes of proteins related to MQC. In addition, Co-IP assay confirmed the interaction between KLF13 and PGC-1α. PGC-1α deficiency restored the impacts of KLF13 upregulation on the inflammation, apoptosis, and MQC in LPS-treated A549 cells. In conclusion, KLF13 attenuated LPS-induced alveolar epithelial cell inflammation and apoptosis by regulating MQC via binding PGC-1α.

Melatonin: A potential protective multifaceted force for sepsis-induced cardiomyopathy

Sepsis is a life-threatening condition manifested by organ dysfunction caused by a dysregulated host response to infection. Lung, brain, liver, kidney, and heart are among the affected organs. Sepsis-induced cardiomyopathy is a common cause of death among septic patients. Sepsis-induced cardiomyopathy is characterized by an acute and reversible significant decline in biventricular both systolic and diastolic function. This is accompanied by left ventricular dilatation. The pathogenesis underlying sepsis-induced cardiomyopathy is multifactorial. Hence, targeting an individual pathway may not be effective in halting the extensive dysregulated immune response. Despite major advances in sepsis management strategies, no effective pharmacological strategies have been shown to treat or even reverse sepsis-induced cardiomyopathy. Melatonin, namely, N-acetyl-5-methoxytryptamine, is synthesized in the pineal gland of mammals and can also be produced in many cells and tissues. Melatonin has cardioprotective, neuroprotective, and anti-tumor activity. Several literature reviews have explored the role of melatonin in preventing sepsis-induced organ failure. Melatonin was found to act on different pathways that are involved in the pathogenesis of sepsis-induced cardiomyopathy. Through its antimicrobial, anti-inflammatory, and antioxidant activity, it offers a potential role in sepsis-induced cardiomyopathy. Its antioxidant activity is through free radical scavenging against reactive oxygen and nitrogen species and modulating the expression and activity of antioxidant enzymes. Melatonin anti-inflammatory activities control the overactive immune system and mitigate cytokine storm. Also, it mitigates mitochondrial dysfunction, a major mechanism involved in sepsis-induced cardiomyopathy, and thus controls apoptosis. Therefore, this review discusses melatonin as a promising drug for the management of sepsis-induced cardiomyopathy.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

Echinatin attenuates acute lung injury and inflammatory responses via TAK1-MAPK/NF-κB and Keap1-Nrf2-HO-1 signaling pathways in macrophages

Echinatin is an active ingredient in licorice, a traditional Chinese medicine used in the treatment of inflammatory disorders. However, the protective effect and underlying mechanism of echinatin against acute lung injury (ALI) is still unclear. Herein, we aimed to explore echinatin-mediated anti-inflammatory effects on lipopolysaccharide (LPS)-stimulated ALI and its molecular mechanisms in macrophages. In vitro, echinatin markedly decreased the levels of nitric oxide (NO) and prostaglandin E2 (PGE2) in LPS-stimulated murine MH-S alveolar macrophages and RAW264.7 macrophages by suppressing inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) expression. Furthermore, echinatin reduced LPS-induced mRNA expression and release of interleukin-1β (IL-1β) and IL-6 in RAW264.7 cells. Western blotting and CETSA showed that echinatin repressed LPS-induced activation of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) pathways through targeting transforming growth factor-beta-activated kinase 1 (TAK1). Furthermore, echinatin directly interacted with Kelch-like ECH-associated protein 1 (Keap1) and activated the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway to enhance heme oxygenase-1 (HO-1) expression. In vivo, echinatin ameliorated LPS-induced lung inflammatory injury, and reduced production of IL-1β and IL-6. These findings demonstrated that echinatin exerted anti-inflammatory effects in vitro and in vivo, via blocking the TAK1-MAPK/NF-κB pathway and activating the Keap1-Nrf2-HO-1 pathway.

Peficitinib alleviated acute lung injury by blocking glycolysis through JAK3/STAT3 pathway

Peficitinib is a selective Janus kinase (JAK3) inhibitor recently developed and approved for the treatment of rheumatoid arthritis in Japan. Glycolysis in macrophages could induce NOD-like receptor (NLR) family and pyrin domain-containing protein 3 (NLRP3) inflammasome activation, thus resulting in pyroptosis and acute lung injury (ALI). The aim of our study was to investigate whether Peficitinib could alleviate lipopolysaccharide (LPS)-induced ALI by inhibiting NLRP3 inflammasome activation. Wild type C57BL/6J mice were intraperitoneally injected with Peficitinib (5 or 10 mg·kg-1·day-1) for 7 consecutive days before LPS injection. The results showed that Peficitinib pretreatment significantly relieved LPS-induced pulmonary edema, inflammation, and apoptosis. NLRP3 inflammasome and glycolysis in murine lung tissues challenged with LPS were also blocked by Peficitinib. Furthermore, we found that the activation of JAK3/signal transducer and activator of transcription 3 (STAT3) was also suppressed by Peficitinib in mice with ALI. However, in Jak3 knockout mice, Peficitinib did not show obvious protective effects after LPS injection. In vitro experiments further showed that Jak3 overexpression completely abolished Peficitinib-elicited inhibitory effects on pyroptosis and glycolysis in LPS-induced RAW264.7 macrophages. Finally, we unveiled that LPS-induced activation of JAK3/STAT3 was mediated by toll-like receptor 4 (TLR4) in RAW264.7 macrophages. Collectively, our study proved that Peficitinib could protect against ALI by blocking JAK3-mediated glycolysis and pyroptosis in macrophages, which may serve as a promising candidate against ALI in the future.

Mangiferin alleviates diabetic pulmonary fibrosis in mice via inhibiting endothelial-mesenchymal transition through AMPK/FoxO3/SIRT3 axis

Diabetes mellitus results in numerous complications. Diabetic pulmonary fibrosis (DPF), a late pulmonary complication of diabetes, has not attracted as much attention as diabetic nephropathy and cardiomyopathy. Mangiferin (MF) is a natural small molecular compound that exhibits a variety of pharmacological effects including anti-inflammatory, anti-cancer, anti-diabetes, and anti-fibrosis effects. In this study, we investigated whether long-term diabetes shock induces DPF, and explored whether MF had a protective effect against DPF. We first examined the lung tissues and sections of 20 diabetic patients obtained from discarded lung surgical resection specimens and found that pulmonary fibrosis mainly accumulated around the pulmonary vessels, accompanied by significantly enhanced endothelial-mesenchymal transition (EndMT). We established a mouse model of DPF by STZ injections. Ten days after the final STZ injection, the mice were administered MF (20, 60 mg/kg, i.g.) every 3 days for 4 weeks, and kept feeding until 16 weeks and euthanized. We showed that pulmonary fibrotic lesions were developed in the diabetic mice, which began around the pulmonary vessels, while MF administration did not affect long-term blood glucose levels, but dose-dependently alleviated diabetes-induced pulmonary fibrosis. In human umbilical vein endothelial cells (HUVECs), exposure to high glucose (33.3 mM) induced EndMT, which was dose-dependently inhibited by treatment with MF (10, 50 μM). Furthermore, MF treatment promoted SIRT3 expression in high glucose-exposed HUVECs by directly binding to AMPK to enhance the activity of FoxO3, which finally reversed diabetes-induced EndMT. We conclude that MF attenuates DPF by inhibiting EndMT through the AMPK/FoxO3/SIRT3 axis. MF could be a potential candidate for the early prevention and treatment of DPF.

The role and therapeutic potential of SIRTs in sepsis

Sepsis is a life-threatening organ dysfunction caused by the host's dysfunctional response to infection. Abnormal activation of the immune system and disturbance of energy metabolism play a key role in the development of sepsis. In recent years, the Sirtuins (SIRTs) family has been found to play an important role in the pathogenesis of sepsis. SIRTs, as a class of histone deacetylases (HDACs), are widely involved in cellular inflammation regulation, energy metabolism and oxidative stress. The effects of SIRTs on immune cells are mainly reflected in the regulation of inflammatory pathways. This regulation helps balance the inflammatory response and may lessen cell damage and organ dysfunction in sepsis. In terms of energy metabolism, SIRTs can play a role in immunophenotypic transformation by regulating cell metabolism, improve mitochondrial function, increase energy production, and maintain cell energy balance. SIRTs also regulate the production of reactive oxygen species (ROS), protecting cells from oxidative stress damage by activating antioxidant defense pathways and maintaining a balance between oxidants and reducing agents. Current studies have shown that several potential drugs, such as Resveratrol and melatonin, can enhance the activity of SIRT. It can help to reduce inflammatory response, improve energy metabolism and reduce oxidative stress, showing potential clinical application prospects for the treatment of sepsis. This review focuses on the regulation of SIRT on inflammatory response, energy metabolism and oxidative stress of immune cells, as well as its important influence on multiple organ dysfunction in sepsis, and discusses and summarizes the effects of related drugs and compounds on reducing multiple organ damage in sepsis through the pathway involving SIRTs. SIRTs may become a new target for the treatment of sepsis and its resulting organ dysfunction, providing new ideas and possibilities for the treatment of this life-threatening disease.

CPT1A as a potential therapeutic target for lipopolysaccharide-induced acute lung injury in mice

Acute lung injury (ALI) remains a high mortality rate with dramatic lung inflammation and alveolar epithelial cell death. Although fatty acid β-oxidation (FAO) impairment has been implicated in the pathogenesis of ALI, whether Carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme for FAO, plays roles in lipopolysaccharide (LPS)-induced ALI remains unclear. Accordingly, we focused on exploring the effect of CPT1A in the context of ALI and the underlying mechanisms. We found that overexpression of CPT1A (AAV-CPT1A) effectively alleviated lung injury by reduction of lung wet-to-dry ratio, inflammatory cell infiltration, and protein levels in the BALF of ALI mice. Meanwhile, AAV-CPT1A significantly lessened histopathological changes and several cytokines' secretions. In contrast, blocking CPT1A with etomoxir augmented inflammatory responses and lung injury in ALI mice. Furthermore, we found that overexpression of CPT1A with lentivirus reduced the apoptosis rates of alveolar epithelial cells and the expression of apoptosis-related proteins induced by LPS in MLE12 cells, while etomoxir increased the apoptosis of MLE12 cells. Overexpression of CPT1A prevented the drop in bioenergetics, palmitate oxidation, and ATP levels. In conclusion, the results rendered CPT1A worthy of further development into a pharmaceutical drug for the treatment of ALI.

Restoring the infected powerhouse: Mitochondrial quality control in sepsis

Sepsis is a dysregulated host response to an infection, characterized by organ failure. The pathophysiology is complex and incompletely understood, but mitochondria appear to play a key role in the cascade of events that culminate in multiple organ failure and potentially death. In shaping immune responses, mitochondria fulfil dual roles: they not only supply energy and metabolic intermediates crucial for immune cell activation and function but also influence inflammatory and cell death pathways. Importantly, mitochondrial dysfunction has a dual impact, compromising both immune system efficiency and the metabolic stability of end organs. Dysfunctional mitochondria contribute to the development of a hyperinflammatory state and loss of cellular homeostasis, resulting in poor clinical outcomes. Already in early sepsis, signs of mitochondrial dysfunction are apparent and consequently, strategies to optimize mitochondrial function in sepsis should not only prevent the occurrence of mitochondrial dysfunction, but also cover the repair of the sustained mitochondrial damage. Here, we discuss mitochondrial quality control (mtQC) in the pathogenesis of sepsis and exemplify how mtQC could serve as therapeutic target to overcome mitochondrial dysfunction. Hence, replacing or repairing dysfunctional mitochondria may contribute to the recovery of organ function in sepsis. Mitochondrial biogenesis is a process that results in the formation of new mitochondria and is critical for maintaining a pool of healthy mitochondria. However, exacerbated biogenesis during early sepsis can result in accumulation of structurally aberrant mitochondria that fail to restore bioenergetics, produce excess reactive oxygen species (ROS) and exacerbate the disease course. Conversely, enhancing mitophagy can protect against organ damage by limiting the release of mitochondrial-derived damage-associated molecules (DAMPs). Furthermore, promoting mitophagy may facilitate the growth of healthy mitochondria by blocking the replication of damaged mitochondria and allow for post sepsis organ recovery through enabling mitophagy-coupled biogenesis. The remaining healthy mitochondria may provide an undamaged scaffold to reproduce functional mitochondria. However, the kinetics of mtQC in sepsis, specifically mitophagy, and the optimal timing for intervention remain poorly understood. This review emphasizes the importance of integrating mitophagy induction with mtQC mechanisms to prevent undesired effects associated with solely the induction of mitochondrial biogenesis.

Melatonin and ferroptosis: Mechanisms and therapeutic implications

Ferroptosis, a regulated form of cell death, is characterized by iron-dependent lipid peroxidation leading to oxidative damage to cell membranes. Cell sensitivity to ferroptosis is influenced by factors such as iron overload, lipid metabolism, and the regulation of the antioxidant system. Melatonin, with its demonstrated capacity to chelate iron, modulate iron metabolism proteins, regulate lipid peroxidation, and regulate antioxidant systems, has promise as a potential therapeutic agent in mediating ferroptosis. The availability of approved drugs targeting ferroptosis is limited; therefore, melatonin is a candidate for broad application due to its safety and efficacy in attenuating ferroptosis in noncancerous diseases. Melatonin has been demonstrated to attenuate ferroptosis in cellular and animal models of noncancerous diseases, showcasing effectiveness in organs such as the heart, brain, lung, liver, kidney, and bone. This review outlines the molecular mechanisms of ferroptosis, investigates melatonin's potential effects on ferroptosis, and discusses melatonin's therapeutic potential as a promising intervention against diseases associated with ferroptosis. Through this discourse, we aim to lay a strong foundation for developing melatonin as a therapeutic strategy to modulate ferroptosis in a variety of disease contexts.

Mitophagy involved the biological processes of hormones

Mitochondria fulfill vital functions in energy production, maintaining ion balance, and facilitating material metabolism. Mitochondria are sacrificed to protect cells or induce apoptosis when the body is under stress. The regulatory pathways of mitophagy include both ubiquitin-dependent and non-dependent pathways. The involvement of mitophagy has been demonstrated in the onset and progression of numerous diseases, highlighting its significant role. Endocrine hormones are chemical substances secreted by endocrine organs or endocrine cells, which participate in the regulation of physiological functions and internal environmental homeostasis of the body. Imbalances in endocrine hormones contribute to the development of various diseases. However, the precise impact of mitophagy on the physiological and pathological processes involving endocrine hormones remains unclear. This article aims to comprehensively overview recent advancements in understanding the mechanisms through which mitophagy regulates endocrine hormones.

Bezafibrate attenuates acute lung injury by preserving mitochondrial dynamics equilibrium in pulmonary epithelial cells

Acute lung injury (ALI) serves as a common life-threatening clinical syndrome with high mortality rates, which is characterized by disturbed mitochondrial dynamics in pulmonary epithelial barrier. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is one of the critical nuclear receptors, exerting important roles in preserving mitochondrial dynamics equilibrium. Previous studies have suggested that bezafibrate (BEZ), a PPAR-γ agonist, could improve obesity and insulin resistance. In the present study, we explored whether bezafibrate could attenuate lipopolysaccharide (LPS)-induced ALI in vivo and in vitro. Using C57BL/6 mice exposed to LPS, we observed that BEZ pretreatment (100 mg/kg) for 7 days decreased lung pathologic injury, reduced oxidative stress, suppressed inflammation and apoptosis, accompanied by shifting the dynamic course of mitochondria from fission into fusion. Meanwhile, we observed that BEZ could reverse the inhibition of PPAR-γ in lung tissues from LPS-treated mice. In vitro experiments also disclosed that BEZ could improve cell viability in primary pulmonary epithelial cells in a concentration-dependent manner. And BEZ (80 μM) treatment could not only inhibit oxidative stress but also preserve mitochondrial dynamics equilibrium in primary pulmonary epithelial cells. However, PPAR-γ knockdown partially abolished BEZ-mediated antioxidation and completely offset its regulatory effects on mitochondrial dynamics in primary pulmonary epithelial cells. In PPAR-γ-deficient mice, BEZ lost its pulmonary protection including anti-inflammatory and antioxidative effects in mice with ALI. Taken together, BEZ could attenuate ALI by preserving mitochondrial dynamics equilibrium in pulmonary epithelial cells in a PPAR-γ-dependent manner.

Pretreatment with Kahweol Attenuates Sepsis-Induced Acute Lung Injury via Improving Mitochondrial Homeostasis in a CaMKKII/AMPK-Dependent Pathway

SCOPE

It is well-established that dysregulated mitochondrial homeostasis in macrophages leads to inflammation, oxidative stress, and tissue damage, which are essential in the pathogenesis of sepsis-induced acute lung injury (ALI). Kahweol, a natural diterpene extracted from coffee beans, reportedly possesses anti-inflammatory and mitochondrial protective properties. Herein, the study investigates whether Kahweol can alleviate sepsis-induced ALI and explore the underlying mechanisms.

METHODS AND RESULTS

C57BL/6J mice are intraperitoneally injected with lipopolysaccharide (LPS) for 12 h to induce ALI. Pretreatment with kahweol by gavage for 5 days significantly alleviates lung pathological injury, inflammation, and oxidative stress, accompanied by shifting the dynamic process of mitochondria from fission to fusion, enhancing mitophagy, and activating AMPK. To investigate the underlying molecular mechanisms, differentiated THP-1 cells are cultured in a medium containing Kahweol for 12 h prior to LPS exposure, yielding consistent findings with the in vivo results. Moreover, AMPK inhibitors abrogate the above effects, indicating Kahweol acts in an AMPK-dependent manner. Furthermore, the study explores how Kahweol activates AMPK and finds that this process is mediated by CamKK II.

CONCLUSION

Pretreatment with Kahweol attenuates sepsis-induced acute lung injury via improving mitochondrial homeostasis in a CaMKKII/AMPK-dependent pathway and may be a potential candidate to prevent sepsis-induced ALI.

Limonin, a novel AMPK activator, protects against LPS-induced acute lung injury

AMP-activated protein kinase (AMPK) activation plays crucial roles in the treatment of many oxidative stress- and inflammation-induced diseases, including acute lung injury (ALI). Limonin is a naturally occurring tetracyclic triterpenoid extracted from the plants of Rutaceae and Meliaceae. Limonin also serves as an AMPK activator with anti-inflammatory and anti-oxidation effects. However, the potential beneficial effects of limonin on ALI and the possible mechanisms have never been disclosed till now. Here, the effects of limonin on lipopolysaccharide (LPS)-induced ALI in C57 BL/6 mice, plus bone marrow-derived macrophages (BMDM) stimulated with LPS to induce in vitro ALI model were investigated. Limonin significantly improved pulmonary function and alleviated lung pathological injury in LPS-induced mice. Meanwhile, limonin also markedly decreased inflammation and oxidative stress in lung tissues from LPS-treated mice. In vitro experiments also unveiled that limonin could decrease inflammation and oxidative stress in LPS-induced BMDM in a concentration-dependent manner. Mechanically, limonin could promote the activation of AMPKα and upregulate the expression of nuclear factor erythroid 2-related factor 2 (NRF2) in lung tissues and BMDM. Pharmacological inhibition of AMPKα by Compound C or AMPKα knockout could abolish the pulmonary protection from limonin during ALI. In conclusion, limonin mediates the activation of AMPKα/NRF2 pathway, providing an attractive therapeutic target for ALI in the future.

PM2.5 contributed to pulmonary epithelial senescence and ferroptosis by regulating USP3-SIRT3-P53 axis

Pulmonary epithelial cells act as the first line of defense against various air pollutant particles. Previous studies have reported that particulate matter 2.5 (PM2.5) could trigger pulmonary inflammation and fibrosis by inducing pulmonary epithelial senescence and ferroptosis. Sirtuin 3 (SIRT3) is one of critical the mitochondrial NAD+-dependent deacetylases, exerting antioxidant and anti-aging effects in multiple diseases. The present study aimed to explore the role of SIRT3 in PM2.5-induced lung injury as well as possible mechanisms. The role of SIRT3 in PM2.5-induced lung injury was investigated by SIRT3 genetic depletion, adenovirus-mediated overexpression in type II alveolar epithelial (AT2) cells, and pharmacological activation by melatonin. The protein level and activity of SIRT3 in lung tissues and AT2 cells were significantly downregulated after PM2.5 stimulation. SIRT3 deficiency in AT2 cells aggravated inflammatory response and collagen deposition in PM2.5-treated lung tissues. RNA-sequence and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the differentially expressed genes (DEGs) between SIRT3 flox and SIRT3 CKO mice were mainly enriched in ferroptosis and cellular longevity. Western blot further showed that SIRT3 deficiency in AT2 cells significantly upregulated the proteins associated with ferroptosis and cell senescence in PM2.5-treated lung tissues. In vitro experiments also showed that SIRT3 overexpression could decrease the levels of ferroptosis and cell senescence in PM2.5-treated AT2 cells. In addition, we found that PM2.5 could increase the acetylation of P53 via triggering DNA damage in AT2 cells. And SIRT3 could deacetylate P53 at lysines 320 (K320), thus reducing its transcriptional activity. PM2.5 decreased the protein level of SIRT3 by inducing proteasome pathway through downregulating USP3. Finally, we found that SIRT3 agonist, melatonin treatment could alleviate PM2.5-induced senescence and ferroptosis in mice. In conclusion, targeting USP3-SIRT3-P53 axis may be a novel therapeutic strategy against PM2.5-induced pulmonary inflammation and fibrosis by decreasing pulmonary epithelial senescence and ferroptosis.

MiR-15b-5p and PCSK9 inhibition reduces lipopolysaccharide-induced endothelial dysfunction by targeting SIRT4

BACKGROUND

Endothelial dysfunction and deregulated microRNAs (miRNAs) participate in the development of sepsis and are associated with septic organ failure and death. Here, we explored the role of miR-15b-5p on inflammatory pathways in lipopolysaccharide (LPS)-treated human endothelial cells, HUVEC and TeloHAEC.

METHODS

The miR-15b-5p levels were evaluated in LPS-stimulated HUVEC and TeloHAEC cells by quantitative real-time PCR (qRT-PCR). Functional experiments using cell counting kit-8 (CCK-8), transfection with antagomir, and enzyme-linked immunosorbent assays (ELISA) were conducted, along with investigation of pyroptosis, apoptosis, autophagy, and mitochondrial reactive oxygen species (ROS) by cytofluorometric analysis and verified by fluorescence microscopy. Sirtuin 4 (SIRT4) levels were detected by ELISA and immunoblotting, while proprotein convertase subtilisin-kexin type 9 (PCSK9) expression was determined by flow cytometry (FACS) and immunofluorescence analyses. Dual-luciferase reporter evaluation was performed to confirm the miR-15b-5p-SIRT4 interaction.

RESULTS

The results showed a correlation among miR-15b-5p, PCSK9, and SIRT4 levels in septic HUVEC and TeloHAEC. Inhibition of miR-15b-5p upregulated SIRT4 content, alleviated sepsis-related inflammatory pathways, attenuated mitochondrial stress, and prevented apoptosis, pyroptosis, and autophagic mechanisms. Finally, a PCSK9 inhibitor (i-PCSK9) was used to analyze the involvement of PCSK9 in septic endothelial injury. i-PCSK9 treatment increased SIRT4 protein levels, opposed the septic inflammatory cascade leading to pyroptosis and autophagy, and strengthened the protective role of miR-15b-5p inhibition. Increased luciferase signal validated the miR-15b-5p-SIRT4 binding.

CONCLUSIONS

Our in vitro findings suggested the miR-15b-5p-SIRT4 axis as a suitable target for LPS-induced inflammatory pathways occurring in sepsis, and provide additional knowledge on the beneficial effect of i-PCSK9 in preventing vascular damage by targeting SIRT4.

HDAC3 deficiency protects against acute lung injury by maintaining epithelial barrier integrity through preserving mitochondrial quality control

Sepsis is one common cause of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), which is closely associated with high mortality in intensive care units (ICU). Histone deacetylase 3 (HDAC3) serves as an important epigenetic modifying enzyme which could affect chromatin structure and transcriptional regulation. Here, we explored the effects of HDAC3 in type II alveolar epithelial cells (AT2) on lipopolysaccharide (LPS)-induced ALI and shed light on potential molecular mechanisms. We generated ALI mouse model with HDAC3 conditional knockout mice (Sftpc-cre; Hdac3^f/f) in AT2 and the roles of HDAC3 in ALI and epithelial barrier integrity were investigated in LPS-treated AT2. The levels of HDAC3 were significantly upregulated in lung tissues from mice with sepsis and in LPS-treated AT2. HDAC3 deficiency in AT2 not only decreased inflammation, apoptosis, and oxidative stress, but also maintained epithelial barrier integrity. Meanwhile, HDAC3 deficiency in LPS-treated AT2 preserved mitochondrial quality control (MQC), evidenced by the shift of mitochondria from fission into fusion, decreased mitophagy, and improved fatty acid oxidation (FAO). Mechanically, HDAC3 promoted the transcription of Rho-associated protein kinase 1 (ROCK1) in AT2. In the context of LPS stimulation, the upregulated ROCK1 elicited by HDAC3 could be phosphorylated by Rho-associated (RhoA), thus disturbing MQC and triggering ALI. Furthermore, we found that forkhead box O1 (FOXO1) was one of transcription factors of ROCK1. HDAC3 directly decreased the acetylation of FOXO1 and promoted its nuclear translocation in LPS-treated AT2. Finally, HDAC3 inhibitor RGFP966 alleviated epithelial damage and improved MQC in LPS-treated AT2. Altogether, HDAC3 deficiency in AT2 alleviated sepsis-induced ALI by preserving mitochondrial quality control via FOXO1-ROCK1 axis, which provided a potential strategy for the treatment of sepsis and ALI.

Redefining Autoimmune Disorders' Pathoetiology: Implications for Mood and Psychotic Disorders' Association with Neurodegenerative and Classical Autoimmune Disorders

Although previously restricted to a limited number of medical conditions, there is a growing appreciation that 'autoimmune' (or immune-mediated) processes are important aspects of a wide array of diverse medical conditions, including cancers, neurodegenerative diseases and psychiatric disorders. All of these classes of medical conditions are associated with alterations in mitochondrial function across an array of diverse cell types. Accumulating data indicate the presence of the mitochondrial melatonergic pathway in possibly all body cells, with important consequences for pathways crucial in driving CD8⁺ T cell and B-cell 'autoimmune'-linked processes. Melatonin suppression coupled with the upregulation of oxidative stress suppress PTEN-induced kinase 1 (PINK1)/parkin-driven mitophagy, raising the levels of the major histocompatibility complex (MHC)-1, which underpins the chemoattraction of CD8⁺ T cells and the activation of antibody-producing B-cells. Many factors and processes closely associated with autoimmunity, including gut microbiome/permeability, circadian rhythms, aging, the aryl hydrocarbon receptor, brain-derived neurotrophic factor (BDNF) and its receptor tyrosine receptor kinase B (TrkB) all interact with the mitochondrial melatonergic pathway. A number of future research directions and novel treatment implications are indicated for this wide collection of poorly conceptualized and treated medical presentations. It is proposed that the etiology of many 'autoimmune'/'immune-mediated' disorders should be conceptualized as significantly determined by mitochondrial dysregulation, with alterations in the mitochondrial melatonergic pathway being an important aspect of these pathoetiologies.

Development of indolealkylamine derivatives as potential multi-target agents for COVID-19 treatment

COVID-19 is a complex disease with short-term and long-term respiratory, inflammatory and neurological symptoms that are triggered by the infection with SARS-CoV-2. As many drugs targeting single targets showed only limited effectiveness against COVID-19, here, we aimed to explore a multi-target strategy. We synthesized a focused compound library based on C2-substituted indolealkylamines (tryptamines and 5-hydroxytryptamines) with activity for three potential COVID-19-related proteins, namely melatonin receptors, calmodulin and human angiotensin converting enzyme 2 (hACE2). Two molecules from the library, 5e and h, exhibit affinities in the high nanomolar range for melatonin receptors, inhibit the calmodulin-dependent calmodulin kinase II activity and the interaction of the SARS-CoV-2 Spike protein with hACE2 at micromolar concentrations. Both compounds inhibit SARS-CoV-2 entry into host cells and 5h decreases SARS-CoV-2 replication and M^Pro enzyme activity in addition. In conclusion, we provide a proof-of-concept for the successful design of multi-target compounds based on the tryptamine scaffold. Optimization of these preliminary hit compounds could potentially provide drug candidates to treat COVID-19 and other coronavirus diseases.