Sirtuin Control of Mitochondrial Dysfunction, Oxidative Stress, and Inflammation in Chagas Disease Models

The Citrus flavanone naringenin prolongs the lifespan in C. elegans and slows signs of brain aging in mice

Aging is one of the main risk factors for neurodegenerative disorders, which represent a global burden on healthcare systems. Therefore, identifying new strategies to slow the progression of brain aging is a compelling challenge. In this article, we first assessed the potential anti-aging effects of the Citrus flavanone naringenin (NAR), an activator of the enzyme sirtuin-1 (SIRT1), in a 3R-compliant and short-lived aging model (i.e., the nematode C. elegans). Then, we investigated the preventive effects of a 6-month treatment with NAR (100 mg/kg, orally) against brain aging and studied its mechanism of action in middle-aged mice. We demonstrated that NAR (100 μM) extends lifespan and improves healthspan in C. elegans. In the brain of middle-aged mice, NAR promotes the activity of metabolic enzymes (citrate synthase, cytochrome C oxidase) and increases the expression of the SIRT1 enzyme. Consistently, NAR up-regulates the expression of downstream antioxidant (Foxo3, Nrf2, Ho-1), anti-senescence (p16), and anti-inflammatory (Il-6, Il-18) markers. Our findings support NAR supplementation to slow the signs of brain aging.

Induction of Oxidative Stress in Sirtuin Gene-Disrupted Ashbya gossypii Mutants Overproducing Riboflavin

AgHST1 and AgHST3 genes encode sirtuins that are NAD+-dependent protein deacetylases. According to previous reports, their disruption leads to the overproduction of riboflavin in Ashbya gossypii. In this study, we investigated the potential causes of riboflavin overproduction in the AgHST1Δ and AgHST3Δ mutant strains of A. gossypii. The generation of reactive oxygen species was increasd in the mutants compared to in WT. Additionally, membrane potential was lower in the mutants than in WT. The NAD+/NADH ratio in AgHST1Δ mutant strain was lower than that in WT; however, the NAD+/NADH ratio in AgHST3Δ was slightly higher than that in WT. AgHST1Δ mutant strain was more sensitive to high temperatures and hydroxyurea treatment than WT or AgHST3Δ. Expression of the AgGLR1 gene, encoding glutathione reductase, was substantially decreased in AgHST1Δ and AgHST3Δ mutant strains. The addition of N-acetyl-L-cysteine, an antioxidant, suppressed the riboflavin production in the mutants, indicating that it was induced by oxidative stress. Therefore, high oxidative stress resulting from the disruption of sirtuin genes induces riboflavin overproduction in AgHST1Δ and AgHST3Δ mutant strains. This study established that oxidative stress is an important trigger for riboflavin overproduction in sirtuin gene-disrupted mutant strains of A. gossypii and helped to elucidate the mechanism of riboflavin production in A. gossypii.

Engineering of VCAM-1-targeted nanostructured lipid carriers for delivery of melatonin against acute lung injury through SIRT1/NLRP3 mediated pyroptosis signaling pathway

Acute lung injury (ALI) is a prevalent and critical condition in clinical practice. Although certain pharmacological interventions have demonstrated benefits in preclinical studies, none have been proven entirely effective thus far. Therefore, the development of more efficient treatment strategies for ALI is imperative. In this study, we prepared nanostructured lipid carriers (NLCs) conjugated with anti-VCAM-1 antibodies to encapsulate melatonin (MLT), resulting in VCAM/MLT NLCs. This approach aimed to enhance the distribution of melatonin in lung vascular endothelial cells. The VCAM/MLT NLCs had an average diameter of 364 nm, high drug loading content, and a sustained drug release profile. Notably, the NLCs conjugated with anti-VCAM-1 antibodies demonstrated more specific cellular delivery mediated by the VCAM-1 receptors, increased cellular internalization, and enhanced accumulation in lung tissues. Treatment with VCAM/MLT NLCs effectively alleviated pulmonary inflammation by activating NLRP3 inflammasome-dependent pyroptosis through up-regulation of Sirtuin 1. Our findings suggest that VCAM/MLT NLCs demonstrate remarkable therapeutic effects on ALI in both in vitro and in vivo settings, making them a promising and efficient treatment strategy for ALI.

The role of resveratrol in neurogenesis: a systematic review

CONTEXT

Resveratrol (RV) is a natural compound found in grapes, wine, berries, and peanuts and has potential health benefits-namely, neurogenesis improvement. Neurogenesis, which is the process through which new neurons or nerve cells are generated in the brain, occurs in the subventricular zone and hippocampus and is influenced by various factors. RV has been shown to increase neural stem cell proliferation and survival, improving cognitive function in hippocampus-dependent tasks. Thus, to provide a convergent and unbiased conclusion of the available evidence on the correlation between the RV and neurogenesis, a systematic review needs to be undertaken meticulously and with appropriate attention.

OBJECTIVE

This study aimed to systematically review any potential connection between the RV and neurogenesis in animal models.

DATA SOURCES AND EXTRACTION

Based on the particular selection criteria, 8 original animal studies that investigated the relationship between RV and neurogenesis were included. Studies written in English and published in peer-reviewed journals with no restrictions on the starting date of publication on August 17, 2023, were searched in the Google Scholar and PubMed databases. Furthermore, data were extracted and analyzed independently by 2 researchers and then reviewed by a third researcher, and discrepancies were resolved by consensus. This project followed PRISMA reporting standards.

DATA ANALYSIS

In the studies analyzed in this review, there is a definite correlation between RV and neurogenesis, meaning that RV intake, irrespective of the mechanisms thereof, can boost neurogenesis in both the subventricular zone and hippocampus.

CONCLUSION

This finding, albeit with some limitations, provides a plausible indication of RV's beneficial function in neurogenesis. Indeed, RV intake may result in neurogenesis benefits-namely, cognitive function, mood regulation, stress resilience, and neuroprotection, potentially preventing cognitive decline.

SIRT1 and thrombosis

Thrombosis is a major cause of morbidity and mortality worldwide, with a complex and multifactorial pathogenesis. Recent studies have shown that SIRT1, a member of the sirtuin family of NAD + -dependent deacetylases, plays a crucial role in regulating thrombosis, modulating key pathways including endothelial activation, platelet aggregation, and coagulation. Furthermore, SIRT1 displays anti-inflammatory activity both in vitro, in vivo and in clinical studies, particularly via the reduction of oxidative stress. On these bases, several studies have investigated the therapeutic potential of targeting SIRT1 for the prevention of thrombosis. This review provides a comprehensive and critical overview of the main preclinical and clinical studies and of the current understanding of the role of SIRT1 in thrombosis.

BZD9L1 Differentially Regulates Sirtuins in Liver-Derived Cells by Inducing Reactive Oxygen Species

Growing evidence has highlighted that mitochondrial dysfunction contributes to drug-induced toxicities and leads to drug attrition and post-market withdrawals. The acetylation or deacetylation of mitochondrial proteins can affect mitochondrial functions as the cells adapt to various cellular stresses and other metabolic challenges. SIRTs act as critical deacetylases in modulating mitochondrial function in response to drug toxicity, oxidative stress, reactive oxygen species (ROS), and energy metabolism. We previously showed that a recently characterised SIRT inhibitor (BZD9L1) is non-toxic in rodents in a short-term toxicity evaluation. However, the impact of BZD9L1 on mitochondrial function is unknown. This work aims to determine the effects of BZD9L1 on mitochondrial function in human normal liver and kidney-derived cell lines using the Agilent Seahorse Cell Mito Stress Test to complement our short-term toxicity evaluations in vivo. The Mito Stress assay revealed that BZD9L1 could potentially trigger oxidative stress by inducing ROS, which promotes proton leak and reduces coupling efficiency in liver-derived THLE cells. However, the same was not observed in human kidney-derived HEK293 cells. Interestingly, BZD9L1 had no impact on SIRT3 protein expression in both cell lines but affected SOD2 and its acetylated form at 72 h in THLE cells, indicating that BZD9L1 exerted its effect through SIRT3 activity rather than protein expression. In contrast, BZD9L1 reduced SIRT1 protein expression and impacted the p53 protein differently in both cell lines. Although BZD9L1 did not affect the spare respiratory capacity in vitro, these findings call for further validation of mitochondrial function through assessment of other mitochondrial parameters to evaluate the safety of BZD9L1.

Quantitative assessment of mitochondrial morphology relevant for studies on cellular health and environmental toxicity

Mitochondria are essential organelles that play crucial roles in cellular energy metabolism, calcium signaling and apoptosis. Their importance in tissue homeostasis and stress responses, combined to their ability to transition between various structural and functional states, make them excellent organelles for monitoring cellular health. Quantitative assessment of mitochondrial morphology can therefore provide valuable insights into environmentally-induced cell damage. High-content screening (HCS) provides a powerful tool for analyzing organelles and cellular substructures. We developed a fully automated and miniaturized HCS wet-plus-dry pipeline (MITOMATICS) exploiting mitochondrial morphology as a marker for monitoring cellular health or damage. MITOMATICS uses an in-house, proprietary software (MitoRadar) to enable fast, exhaustive and cost-effective analysis of mitochondrial morphology and its inherent diversity in live cells. We applied our pipeline and big data analytics software to assess the mitotoxicity of selected chemicals, using the mitochondrial uncoupler CCCP as an internal control. Six different pesticides (inhibiting complexes I, II and III of the mitochondrial respiratory chain) were tested as individual compounds and five other pesticides present locally in Occitanie (Southern France) were assessed in combination to determine acute mitotoxicity. Our results show that the assayed pesticides exhibit specific signatures when used as single compounds or chemical mixtures and that they function synergistically to impact mitochondrial architecture. Study of environment-induced mitochondrial damage has the potential to open new fields in mechanistic toxicology, currently underexplored by regulatory toxicology and exposome research. Such exploration could inform health policy guidelines and foster pharmacological intervention, water, air and soil pollution control and food safety.

Compartment-specific protein interactions in beryllium lung disease

The study provides insights into proteins that may be relevant in BeS and CBD. It provides a framework to investigate the global changes in lung compartment-specific inflammatory cells to better understand the potential interplay of proteins in CBD. https://bit.ly/3PLNTXC.

NAMPT inhibition relieves intestinal inflammation by regulating macrophage activation in experimental necrotizing enterocolitis

Nicotinamide phosphoribosyl transferase (NAMPT) is associated with various NAD+ -consuming enzymatic reactions. The precise role in intestinal mucosal immunity in necrotizing enterocolitis (NEC) is not well defined. Here, we examined whether NAMPT inhibition by the highly specific inhibitor FK866 could alleviate intestinal inflammation during the pathogenesis of NEC. In the present study, we showed that NAMPT expression was upregulated in the human terminal ileum of human infants with NEC. FK866 administration attenuated M1 macrophage polarization and relieved the symptoms of experimental NEC pups. FK866 inhibited intercellular NAD+ levels, macrophage M1 polarization, and the expression of NAD+ -dependent enzymes, such as poly (ADP ribose) polymerase 1 (PARP1) and Sirt6. Consistently, the capacity of macrophages to phagocytose zymosan particles, as well as antibacterial activity, were impaired by FK866, whereas NMN supplementation to restore NAD+ levels reversed the changes in phagocytosis and antibacterial activity. In conclusion, FK866 reduced intestinal macrophage infiltration and skewed macrophage polarization, which is implicated in intestinal mucosal immunity, thereby promoting the survival of NEC pups.

Sirtuins: Key pieces in the host response to pathogens' puzzle

Global warming is changing the distribution of different pathogens around the globe, and humans are more susceptible to new or re-emerging infections. The human response to microbes is complex and involves different mechanisms of the immune system. Regulation of gene expression of immunity genes and of metabolism of immune cells are essential in this process. Both mechanisms could be regulated by protein lysine acetylation that will control chromatin structure affecting gene expression or key enzyme activity involved in cellular processes. Protein acetylation is crucial for the immunity and involves two families of enzymes: lysine acetyltransferases (KATs), which will promote protein acetylation, and lysine deacetylases (KDACs) that will reduce this modification. Lysine deacetylases are divided into Zinc-dependent or HDACs and NAD⁺ -dependent, or Sirtuins. These enzymes are in the nucleus, cytosol, and mitochondria of mammalian cells affecting different cellular pathways, such as metabolism, gene expression, DNA repair, cell proliferation, and apoptosis, opening the opportunity to explore these proteins as drug targets in different diseases, including cancer and neurodegenerative illness. Although widely explored in chronic diseases, very little is known about the role of Sirtuins during host response against microbes' infection. In this review we aim to explore the most recent literature evidencing a role for these enzymes during host responses to viruses, bacterial and protozoan infections, pointing out how these proteins can be manipulated by these pathogens to progress in the infection. Moreover, we will uncover the potential of host KDACs as therapeutic targets to prevent infections by activating effector immune functions.

Cardiomyocyte infection by Trypanosoma cruzi promotes innate immune response and glycolysis activation

Introduction

Chagas cardiomyopathy, a disease caused by Trypanosoma cruzi (T. cruzi) infection, is a major contributor to heart failure in Latin America. There are significant gaps in our understanding of the mechanism for infection of human cardiomyocytes, the pathways activated during the acute phase of the disease, and the molecular changes that lead to the progression of cardiomyopathy.

Methods

To investigate the effects of T. cruzi on human cardiomyocytes during infection, we infected induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) with the parasite and analyzed cellular, molecular, and metabolic responses at 3 hours, 24 hours, and 48 hours post infection (hpi) using transcriptomics (RNAseq), proteomics (LC-MS), and metabolomics (GC-MS and Seahorse) analyses.

Results

Analyses of multiomic data revealed that cardiomyocyte infection caused a rapid increase in genes and proteins related to activation innate and adaptive immune systems and pathways, including alpha and gamma interferons, HIF-1α signaling, and glycolysis. These responses resemble prototypic responses observed in pathogen-activated immune cells. Infection also caused an activation of glycolysis that was dependent on HIF-1α signaling. Using gene editing and pharmacological inhibitors, we found that T. cruzi uptake was mediated in part by the glucose-facilitated transporter GLUT4 and that the attenuation of glycolysis, HIF-1α activation, or GLUT4 expression decreased T. cruzi infection. In contrast, pre-activation of pro-inflammatory immune responses with LPS resulted in increased infection rates.

Conclusion

These findings suggest that T. cruzi exploits a HIF-1α-dependent, cardiomyocyte-intrinsic stress-response activation of glycolysis to promote intracellular infection and replication. These chronic immuno-metabolic responses by cardiomyocytes promote dysfunction, cell death, and the emergence of cardiomyopathy.

Platelets, Macrophages, and Thromboinflammation in Chagas Disease

Chagas disease (CD) is a major health problem in the Americas and an emerging health problem in Europe and other nonendemic countries. Several studies have documented persistence of the protozoan parasite Trypanosoma cruzi, and oxidative and inflammatory stress are major pathogenic factor. Mural and cardiac thrombi, cardiac arrhythmias, and cardiomyopathy are major clinical features of CD. During T. cruzi infection, parasite-released factors induce endothelial dysfunction along with platelet (PLT) and immune-cell activation. PLTs have a fundamental role in maintaining hemostasis and preventing bleeding after vascular injury. Excessive activation of PLTs and coagulation cascade can result in thrombosis and thromboembolic events, which are recognized to occur in seropositive individuals in early stages of CD when clinically symptomatic heart disease is not apparent. Several host and parasite factors have been identified to signal hypercoagulability and increase the risk of ischemic stroke in early phases of CD. Further, PLT interaction with immune cells and their role in host defense against pathogens and inflammatory processes have only recently been recognized and evolving. In the context of parasitic diseases, PLTs function in directly responding to T. cruzi infection, and PLT interactions with immune cells in shaping the proinflammatory or immunoregulatory function of monocytes, macrophages, and neutrophils remains elusive. How T. cruzi infection alters systemic microenvironment conditions to influence PLT and immune-cell interactions is not understood. In this review, we discuss the current literature, and extrapolate the mechanistic situations to explain how PLT and innate immune cell (especially monocytes and macrophages) interactions might be sustaining hypercoagulability and thromboinflammation in chronic CD.

Sirtuin 1 in Host Defense during Infection

Sirtuins (SIRTs) are members of the class III histone deacetylase family and epigenetically control multiple target genes to modulate diverse biological responses in cells. Among the SIRTs, SIRT1 is the most well-studied, with a role in the modulation of immune and inflammatory responses following infection. The functions of SIRT1 include orchestrating immune, inflammatory, metabolic, and autophagic responses, all of which are required in establishing and controlling host defenses during infection. In this review, we summarize recent information on the roles of SIRT1 and its regulatory mechanisms during bacterial, viral, and parasitic infections. We also discuss several SIRT1 modulators, as potential antimicrobial treatments. Understanding the function of SIRT1 in balancing immune homeostasis will contribute to the development of new therapeutics for the treatment of infection and inflammatory disease.

Neospora caninum infection induced mitochondrial dysfunction in caprine endometrial epithelial cells via downregulating SIRT1

Background

Infection of Neospora caninum, an important obligate intracellular protozoan parasite, causes reproductive dysfunctions (e.g. abortions) in ruminants (e.g. cattle, sheep and goats), leading to serious economic losses of livestock worldwide, but the pathogenic mechanisms of N. caninum are poorly understood. Mitochondrial dysfunction has been reported to be closely associated with pathogenesis of many infectious diseases. However, the effect of N. caninum infection on the mitochondrial function of hosts remains unclear.

Methods

The effects of N. caninum infection on mitochondrial dysfunction in caprine endometrial epithelial cells (EECs), including intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) contents, mitochondrial DNA (mtDNA) copy numbers and ultrastructure of mitochondria, were studied by using JC-1, DCFH-DA, ATP assay kits, quantitative real-time polymerase chain reaction (RT-qPCR) and transmission electron microscopy, respectively, and the regulatory roles of sirtuin 1 (SIRT1) on mitochondrial dysfunction, autophagy and N. caninum propagation in caprine EECs were investigated by using two drugs, namely resveratrol (an activator of SIRT1) and Ex 527 (an inhibitor of SIRT1).

Results

The current study found that N. caninum infection induced mitochondrial dysfunction of caprine EECs, including accumulation of intracellular ROS, significant reductions of MMP, ATP contents, mtDNA copy numbers and damaged ultrastructure of mitochondria. Downregulated expression of SIRT1 was also detected in caprine EECs infected with N. caninum. Treatments using resveratrol and Ex 527 to caprine EECs showed that dysregulation of SIRT1 significantly reversed mitochondrial dysfunction of cells caused by N. caninum infection. Furthermore, using resveratrol and Ex 527, SIRT1 expression was found to be negatively associated with autophagy induced by N. caninum infection in caprine EECs, and the intracellular propagation of N. caninum tachyzoites in caprine EECs was negatively affected by SIRT1 expression.

Conclusions

These results indicated that N. caninum infection induced mitochondrial dysfunction by downregulating SIRT1, and downregulation of SIRT1 promoted cell autophagy and intracellular proliferation of N. caninum tachyzoites in caprine EECs. The findings suggested a potential role of SIRT1 as a target to develop control strategies against N. caninum infection.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05406-4.

Nicotinamide riboside relieves the severity of experimental necrotizing enterocolitis by regulating endothelial function via eNOS deacetylation

BACKGROUND

Nicotinamide adenine dinucleotide (NAD+) is involved in regulating oxidative stress. Although NAD+ is associated with various health issues, its role in the intestinal microcirculation in necrotizing enterocolitis (NEC) remains to be confirmed. In the current study, we explored whether nicotinamide riboside (NR), a natural NAD + precursor, ameliorates the severity of NEC through endothelial nitric oxide synthase(eNOS) signaling.

METHODS

A mouse experimental NEC model was induced by formula gavage and hypoxia in full-term mouse pups. Intestinal endothelial cells (MIMECs) were isolated and subjected to stress using tumor necrosis factor (TNF)-α. NR was administered to assess the intestinal microcirculation and lipid peroxidation levels and to explore the involved signaling pathways.

RESULTS

NAD + levels were reduced after induction of NEC stress, which was associated with intestinal injury. NR administration promoted NAD + levels, attenuated oxidative stress and relieved the symptoms of experimental NEC, which were relevant to increased intestinal microcirculatory perfusion through the sirtuin (SIRT) 1 pathway in experimental NEC mice. However, this improvement was not found in eNOS-knockout mice. Consistently, MIMECs exposed to TNFα showed decreased SIRT1 activity associated with increased eNOS acetylation, which could bring about endothelial dysfunction due to limited nitric oxide production. NR administration increased the NAD + content and repressed the production of reactive oxygen species (ROS) in MIMECs under TNFα stress. NR also promoted SIRT1 activity and accordingly suppressed the eNOS acetylation levels under TNFα stress.

CONCLUSION

The current data indicate that NR administration improves the survival of experimental NEC mice via SIRT1-associated eNOS acetylation/deacetylation modulation, which is implicated in endothelial dysfunction. Although NR is commonly found in the human diet, it may also be a promising strategy for NEC treatment because of its pathogenic association with NEC.

Marginal BH4 Deficiencies, iNOS, and Self-perpetuating Oxidative Stress in Post-acute Sequelae of Covid-19

The treatment of post-acute sequelae of Covid-19 (PASC) has been informed primarily by symptomatic parallels with other chronic inflammatory syndromes. This manuscript takes a more systemic approach by examining how a marginal deficiency of tetrahydrobiopterin (BH4) resulting from mutations of the GCH1 (GTP cyclohydrolase 1) gene may result in the uncoupling of inducible Nitric Oxide Synthase (iNOS) early in the initial response of the innate immune system to SARS-CoV-2. The resulting production of superoxide instead of nitric oxide leads to a self-perpetuating cycle of oxidative stress with the potential to impair numerous metabolic processes and damage multiple organ systems. This marginal deficiency of BH4 may be exhibited by 30% or more of the patient population that have heterozygous or homozygous mutations of GCH1. As the cycle of oxidative stress continues, there is less BH4 available for other metabolic needs such as 1) resisting increased ferroptosis with its damage to organs, and 2) regulating the deactivation of the hyperinflammatory state. Finally, possible steps are proposed for clinical treatment of the hypothesized oxidative stress involved with PASC.

The Oxidative Stress and Chronic Inflammatory Process in Chagas Disease: Role of Exosomes and Contributing Genetic Factors

Chagas disease is a neglected tropical disease caused by the flagellated protozoa Trypanosoma cruzi that affects several million people mainly in Latin American countries. Chagas disease has two phases, which are acute and chronic, both separated by an indeterminate time period in which the infected individual is relatively asymptomatic. The acute phase extends for 40-60 days with atypical and mild symptoms; however, about 30% of the infected patients will develop a symptomatic chronic phase, which is characterized by either cardiac, digestive, neurological, or endocrine problems. Cardiomyopathy is the most important and severe result of Chagas disease, which leads to left ventricular systolic dysfunction, heart failure, and sudden cardiac death. Most deaths are due to heart failure (70%) and sudden death (30%) resulting from cardiomyopathy. During the chronic phase, T. cruzi-infected macrophages respond with the production of proinflammatory cytokines and production of superoxide and nitric oxide by the NADPH oxidase 2 (NOX2) and inducible nitric oxide synthase (iNOS) enzymes, respectively. During the chronic phase, myocardial changes are produced as a result of chronic inflammation, oxidative stress, fibrosis, and cell death. The cellular inflammatory response is mainly the result of activation of the NF-κB-dependent pathway, which activates gene expression of inflammatory cytokines, leading to progressive tissue damage. The persisting production of reactive oxygen species (ROS) is the result of mitochondrial dysfunction in the cardiomyocytes. In this review, we will discuss inflammation and oxidative damage which is produced in the heart during the chronic phase of Chagas disease and recent evidence on the role of macrophages and the production of proinflammatory cytokines during the acute phase and the origin of macrophages/monocytes during the chronic phase of Chagas disease. We will also discuss the contributing factors and mechanisms leading to the chronic inflammation of the cardiac tissue during the chronic phase of the disease as well as the innate and adaptive host immune response. The contribution of genetic factors to the progression of the chronic inflammatory cardiomyopathy of chronic Chagas disease is also discussed. The secreted extracellular vesicles (exosomes) produced for both T. cruzi and infected host cells can play key roles in the host immune response, and those roles are described. Lastly, we describe potential treatments to attenuate the chronic inflammation of the cardiac tissue, designed to improve heart function in chagasic patients.

Modulation of Sirt1-mTORC1 Pathway in Microglia Attenuates Retinal Ganglion Cell Loss After Optic Nerve Injury

Purpose

Optic nerve injury (ONI) causes neuroinflammation and neurodegeneration leading to visual deficits. The response of microglia has emerged as an impactful component of etiology in neurodegeneration. This study aimed to investigate the effect of SIRT1-mTORC1 signaling pathway in microglia regulation after ONI.

Methods

Cx3Cr1-Cre^ERT2/Raptor^F/F and Cx3Cr1-Cre^ERT2/Sirt1^F/F mice were used to delete Raptor and Sirt1 in microglia, respectively. Optic nerve crush (ONC) model was established to mimic ONI. PLX5622, a highly specific inhibitor of the colony-stimulating factor 1 receptor (CSF1R), is used to eliminate microglia in optic nerve. Ionized calcium binding adaptor molecule 1 (Iba1) immunostaining was used to detect microglial activation. Retinal ganglion cells (RGCs) were quantified by Nissl staining and retinal whole-mount immunostaining with RNA-binding protein with multiple splicing (RBPMS). Axonal damage was valued by transmission electron microscopy (TEM).

Results

Microglial activation emerged on day 3 post ONC and was earlier than RGCs loss which occurred at day 5 after injury. Depleting microglia with PLX5622 could attenuate the loss of RGCs and axon damage after ONC. Gain- and loss-of-function studies revealed that SIRT1 determined the activation of microglia in optic nerve. In addition, microglia-specific deletion of Raptor resulted in decreased microglial activation. Interestingly, activating mTORC1 with CCT007093 could reverse the function of SIRT1 in regulating the process of microglial activation mediated RGCs loss.

Conclusion

Our study reveals a potential novel mechanism of SIRT1-mTORC1 pathway in microglia regulation, and indicates a therapeutic potential for the protection of RGCs in ONI.

The Protective Activity of Penehyclidine Hydrochloride against Renal Ischemia/Reperfusion-Mediated NLRP3 Inflammasome Activation is Induced by SIRT1

Background: The activation of alveolar macrophages (AMs) modulated via leucine-rich repeat (NLR) pyrin domain containing 3 (NLRP3) inflammasome activation is key to the progression of renal ischemia/reperfusion (rI/R)-mediated acute lung injury (ALI). Sirtuin-1 (SIRT1) can attenuate NLRP3 inflammasome activation during I/R stress and may be an important mechanism underlying ALI pathogenesis. Penehyclidine hydrochloride (PHC), an anticholinergic drug, exerts protective effects against rI/R-mediated ALI. This study aimed to decipher the effects of PHC on SIRT1 activation and the underlying mechanism of the protective activity of PHC against rI/R-mediated ALI.Materials and methods: We used an ALI rat model and the rat AMs cell line NR8383 to assess the degree of lung injury in vivo and in vitro.Results: The results show that PHC attenuates rI/R-mediated lung injury indices, myeloperoxidase, and apoptosis in vivo. It decreases the rI/R-mediated release of prostaglandin E2 and nitric oxide, mitochondrial reactive oxygen species production, and the activity of NADPH oxidase-4 in vitro. PHC ameliorates the rI/R-induced activation of the thioredoxin-interacting protein, caspase 1 (P10 unit), and NLRP3 inflammasome, along with reduced activation of interleukin-1β and interleukin-18 in vitro. We show that PHC alleviates the rI/R-induced reduction of SIRT1 and the depletion of SIRT1 eliminates the ameliorating activity of PHC on the NLRP3 inflammasome activation in vitro. Conclusions: In summary, the findings suggest that PHC ameliorates the rI/R-mediated ALI through the SIRT1-mediated NLRP3 inflammasome activation.

Hsp22 Deficiency Induces Age-Dependent Cardiac Dilation and Dysfunction by Impairing Autophagy, Metabolism, and Oxidative Response

Heat shock protein 22 (Hsp22) is a small heat shock protein predominantly expressed in skeletal and cardiac muscle. Previous studies indicate that Hsp22 plays a vital role in protecting the heart against cardiac stress. However, the essential role of Hsp22 in the heart under physiological conditions remains largely unknown. In this study, we used an Hsp22 knockout (KO) mouse model to determine whether loss of Hsp22 impairs cardiac growth and function with increasing age under physiological conditions. Cardiac structural and functional alterations at baseline were measured using echocardiography and invasive catheterization in Hsp22 KO mice during aging transition compared to their age-matched wild-type (WT) littermates. Our results showed that Hsp22 deletion induced progressive cardiac dilation along with declined function during the aging transition. Mechanistically, the loss of Hsp22 impaired BCL-2-associated athanogene 3 (BAG3) expression and its associated cardiac autophagy, undermined cardiac energy metabolism homeostasis and increased oxidative damage. This study showed that Hsp22 played an essential role in the non-stressed heart during the early stage of aging, which may bring new insight into understanding the pathogenesis of age-related dilated cardiomyopathy.