Decreased Serum Levels of SIRT1 and SIRT3 Correlate with Severity of Skin and Lung Fibrosis and Peripheral Microvasculopathy in Systemic Sclerosis

Taraxerone exerts antipulmonary fibrosis effect through Smad signaling pathway and antioxidant stress response in a Sirtuin1-dependent manner

Idiopathic pulmonary fibrosis treatments are limited, often with severe side effects, highlighting the need for novel options. Taraxerone has diverse biomedical properties, but its mechanism remains unclear. This study investigates taraxerone's impact and the mechanisms involved in bleomycin-induced pulmonary fibrosis in mice. After establishing a pulmonary fibrosis mouse model, taraxerone was intraperitoneally injected continuously for 14-28 days. The in vivo antifibrotic and antioxidative stress effects of taraxerone were assessed. In vitro, the influence of taraxerone on transforming growth factor-β1-induced myofibroblast transformation and oxidative stress was investigated. Subsequently, quantitative polymerase chain reaction screened the histone deacetylase and Sirtuin family, and taraxerone's effects on SIRT1 were assessed. After SIRT1 siRNA treatment, changes in myofibroblast transformation and antioxidant capacity in response to taraxerone were observed. Acetylation and phosphorylation levels of Smad3 were evaluated. We also examined the binding levels of SIRT1 with Pho-Smad3 and Smad3, as well as the nuclear localization of Smad2/3. EX527 confirmed SIRT1's in vivo action in response to taraxerone. In vitro experiments suggested that taraxerone inhibited myofibroblast differentiation by activating SIRT1 and reducing oxidative stress. We also observed a new interaction between SIRT1 and the Smad complex. Taraxerone activates SIRT1, enabling it to bind directly to Smad3. This leads to reduced Smad complex phosphorylation and limited nuclear translocation. As a result, the transcription of fibrotic factors is reduced. In vivo validation confirms taraxerone's SIRT1-mediated antifibrotic effectiveness. This suggests that targeting SIRT1-mediated inhibition of myofibroblast differentiation could be a key strategy in taraxerone-based therapy for pulmonary fibrosis.

Potential role of SIRT-1 and SIRT-3 as biomarkers for the diagnosis and prognosis of idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a debilitating and progressive lung disease of unknown aetiology, characterized by the relentless deposition of fibrotic tissue. Biomarkers may play a pivotal role as indicators of disease presence, progression, and treatment response. Sirtuins, a family of enzymes with ADP ribosyltransferase or deacetylase activity, have been implicated in several diseases, including pulmonary fibrosis.

METHODS

A cross-sectional, prospective, observational single-center study was conducted to investigate the potential role of serum SIRTs levels as biomarkers in patients with IPF. Demographic, clinical, and functional data and serological samples were collected from 34 patients with IPF followed at the Interstital Lung and Rare Diseases Outpatient Clinic of the Vanvitelli Pneumology Clinic, Monaldi Hospital, Naples, Italy and from 19 age-matched controls.

RESULTS

Serum SIRT-1 levels were significantly reduced in IPF patients compared to controls (median IPF 667 [435-858] pg/mL versus controls 925 [794-1173] pg/mL; p < 0.001 ). In contrast, serum SIRT-3 levels were significantly increased in IPF patients compared to controls (median IPF 338 [230-500] pg/mL versus controls 154 [99.8-246] pg/mL; p < 0.001). There were no statistically significant differences in serum SIRT-6 and SIRT-7 levels between IPF and controls. In addition, we found a significant positive correlation between SIRT-1 and lung function parameters such as FEV1% (ϱ=0.417;p = 0.016), FVC% (ϱ=0.449;p = 0.009) and DLCO% (ϱ=0.393;p = 0.024), while a significant negative correlation was demonstrated between SIR-1 and GAP score, demonstrating a significant reduction in SIRT-1 in advanced Gender-Age-Physiology (GAP) stages 2-3 compared to GAP stage 1 (p = 0.008).

CONCLUSIONS

This prospective, cross-sectional study showed that SIRT-1 was associated with lung function and IPF severity and that both SIRT-1 and SIRT-3 could be considered as potential biomarkers of IPF, whereas SIRT-6 and SIRT-7 were not associated with IPF.

Evaluation of potential aging biomarkers in healthy individuals: telomerase, AGEs, GDF11/15, sirtuin 1, NAD+, NLRP3, DNA/RNA damage, and klotho

Aging is a natural process of gradual decrease in physical and mental capacity. Biological age (accumulation of changes and damage) and chronological age (years lived) may differ. Biological age reflects the risk of various types of disease and death from any cause. We selected potential biomarkers of aging - telomerase, AGEs, GDF11 and 15 (growth differentiation factor 11/15), sirtuin 1, NAD+ (nicotinamide adenine dinucleotide), inflammasome NLRP3, DNA/RNA damage, and klotho to investigate changes in their levels depending on age and sex. We included 169 healthy volunteers and divided them into groups according to age (under 35; 35-50; over 50) and sex (male, female; male and female under 35; 35-50, over 50). Markers were analyzed using commercial ELISA kits. We found differences in values depending on age and gender. GDF15 increased with age (under 30 and 35-50 p < 0.002; 35-50 and over 50; p < 0.001; under 35 and over 50; p < 0.001) as well as GDF11 (35-50 and over 50; p < 0.03; under 35 and over 50; p < 0.02), AGEs (under 30 and 35-50; p < 0.005), NLRP3 (under 35 over 50; p < 0.03), sirtuin 1 (35-50 and over 50; p < 0.0001; under 35 and over 50; p < 0.004). AGEs and GDF11 differed between males and females. Correlations were identified between individual markers, markers and age, and markers and sex. Markers that reflect the progression of biological aging vary with age (GDF15, GDF11, AGEs, NLRP3, sirtuin) and sex (AGEs, GDF11). Their levels could be used in clinical practice, determining biological age, risk of age-related diseases and death of all-causes, and initiating or contraindicating a therapy in the elderly based on the patient's health status.

Biomarkers in the Pathogenesis, Diagnosis, and Treatment of Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by vascular damage, vasoinstability, and decreased perfusion with ischemia, inflammation, and exuberant fibrosis of the skin and internal organs. Biomarkers are analytic indicators of the biological and disease processes within an individual that can be accurately and reproducibly measured. The field of biomarkers in SSc is complex as recent studies have implicated at least 240 pathways and dysregulated proteins in SSc pathogenesis. Anti-nuclear antibodies (ANA) are classical biomarkers with well-described clinical classifications and are present in more than 90% of SSc patients and include anti-centromere, anti-Th/To, anti-RNA polymerase III, and anti-topoisomerase I antibodies. Transforming growth factor-β (TGF-β) is central to the fibrotic process of SSc and is intimately intertwined with other biomarkers. Tyrosine kinases, interferon-1 signaling, IL-6 signaling, endogenous thrombin, peroxisome proliferator-activated receptors (PPARs), lysophosphatidic acid receptors, and amino acid metabolites are new biomarkers with the potential for developing new therapeutic agents. Other biomarkers implicated in SSc-ILD include signal transducer and activator of transcription 4 (STAT4), CD226 (DNAX accessory molecule 1), interferon regulatory factor 5 (IRF5), interleukin-1 receptor-associated kinase-1 (IRAK1), connective tissue growth factor (CTGF), pyrin domain containing 1 (NLRP1), T-cell surface glycoprotein zeta chain (CD3ζ) or CD247, the NLR family, SP-D (surfactant protein), KL-6, leucine-rich α2-glycoprotein-1 (LRG1), CCL19, genetic factors including DRB1 alleles, the interleukins (IL-1, IL-4, IL-6, IL-8, IL-10 IL-13, IL-16, IL-17, IL-18, IL-22, IL-32, and IL-35), the chemokines CCL (2,3,5,13,20,21,23), CXC (8,9,10,11,16), CX3CL1 (fractalkine), and GDF15. Adiponectin (an indicator of PPAR activation) and maresin 1 are reduced in SSc patients. A new trend has been the use of biomarker panels with combined complex multifactor analysis, machine learning, and artificial intelligence to determine disease activity and response to therapy. The present review is an update of the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.

Biomarkers in Systemic Sclerosis: An Overview

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by significant fibrosis of the skin and internal organs, with the main involvement of the lungs, kidneys, heart, esophagus, and intestines. SSc is also characterized by macro- and microvascular damage with reduced peripheral blood perfusion. Several studies have reported more than 240 pathways and numerous dysregulation proteins, giving insight into how the field of biomarkers in SSc is still extremely complex and evolving. Antinuclear antibodies (ANA) are present in more than 90% of SSc patients, and anti-centromere and anti-topoisomerase I antibodies are considered classic biomarkers with precise clinical features. Recent studies have reported that trans-forming growth factor β (TGF-β) plays a central role in the fibrotic process. In addition, interferon regulatory factor 5 (IRF5), interleukin receptor-associated kinase-1 (IRAK-1), connective tissue growth factor (CTGF), transducer and activator of transcription signal 4 (STAT4), pyrin-containing domain 1 (NLRP1), as well as genetic factors, including DRB1 alleles, are implicated in SSc damage. Several interleukins (e.g., IL-1, IL-6, IL-10, IL-17, IL-22, and IL-35) and chemokines (e.g., CCL 2, 5, 23, and CXC 9, 10, 16) are elevated in SSc. While adiponectin and maresin 1 are reduced in patients with SSc, biomarkers are important in research but will be increasingly so in the diagnosis and therapeutic approach to SSc. This review aims to present and highlight the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.

The kynurenine pathway of tryptophan metabolism: a neglected therapeutic target of COVID-19 pathophysiology and immunotherapy

SARS-CoV-2 (COVID-19) exerts profound changes in the kynurenine (Kyn) pathway (KP) of tryptophan (Trp) metabolism that may underpin its pathophysiology. The KP is the main source of the vital cellular effector NAD+ and intermediate metabolites that modulate immune and neuronal functions. Trp metabolism is the top pathway influenced by COVID-19. Sixteen studies established virus-induced activation of the KP mediated mainly by induction of indoleamine 2,3-dioxygenase (IDO1) in most affected tissues and of IDO2 in lung by the increased release of proinflammatory cytokines but could additionally involve increased flux of plasma free Trp and induction of Trp 2,3-dioxygenase (TDO) by cortisol. The major Kyn metabolite targeted by COVID-19 is kynurenic acid (KA), the Kyn metabolite with the greatest affinity for the aryl hydrocarbon receptor (AhR), which is also activated by COVID-19. AhR activation initiates two important series of events: a vicious circle involving IDO1 induction, KA accumulation and further AhR activation, and activation of poly (ADP-ribose) polymerase (PARP) leading to NAD+ depletion and cell death. The virus further deprives the host of NAD+ by inhibiting its main biosynthetic pathway from quinolinic acid, while simultaneously acquiring NAD+ by promoting its synthesis from nicotinamide in the salvage pathway. Additionally, the protective effects of sirtuin 1 are minimised by the PARP activation. KP dysfunction may also underpin the mood and neurological disorders acutely and during 'long COVID'. More studies of potential effects of vaccination therapy on the KP are required and exploration of therapeutic strategies involving modulation of the KP changes are proposed.

Sirtuin family in autoimmune diseases

In recent years, epigenetic modifications have been widely researched. As humans age, environmental and genetic factors may drive inflammation and immune responses by influencing the epigenome, which can lead to abnormal autoimmune responses in the body. Currently, an increasing number of studies have emphasized the important role of epigenetic modification in the progression of autoimmune diseases. Sirtuins (SIRTs) are class III nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases and SIRT-mediated deacetylation is an important epigenetic alteration. The SIRT family comprises seven protein members (namely, SIRT1-7). While the catalytic core domain contains amino acid residues that have remained stable throughout the entire evolutionary process, the N- and C-terminal regions are structurally divergent and contribute to differences in subcellular localization, enzymatic activity and substrate specificity. SIRT1 and SIRT2 are localized in the nucleus and cytoplasm. SIRT3, SIRT4, and SIRT5 are mitochondrial, and SIRT6 and SIRT7 are predominantly found in the nucleus. SIRTs are key regulators of various physiological processes such as cellular differentiation, apoptosis, metabolism, ageing, immune response, oxidative stress, and mitochondrial function. We discuss the association between SIRTs and common autoimmune diseases to facilitate the development of more effective therapeutic strategies.

The role of sirtuins in dermal fibroblast function

The sirtuins are a family of seven proteins that perform a variety of dermatological functions and help maintain both the structure and function of the skin. More specifically, the sirtuins have been shown to be altered in multiple dermal cell types including dermal fibroblasts. The functions of dermal fibroblasts are extensive, and include playing a significant role in wound healing as well as helping to maintain the integrity of the skin. As dermal fibroblasts age, they can undergo a state of permanent cell cycle arrest, known as cellular senescence. This senescent process can occur as a result of various stressors, including oxidative stress, ultraviolet radiation -induced stress, and replicative stress. In recent years, there has been a growing interest in both enhancing the cutaneous fibroblast’s ability to facilitate wound healing and altering fibroblast cellular senescence. Thus, in this review, we examine the relationship between sirtuin signaling and dermal fibroblasts to understand how this family of proteins may modulate skin conditions ranging from the wound healing process to photocarcinogenesis associated with fibroblast senescence. Additionally, we offer supporting data from experiments examining the relationship between fibroblast senescence and sirtuin levels in an oxidative stress model indicating that senescent dermal fibroblasts exhibit diminished sirtuin levels. Furthermore, we survey the research on the role of sirtuins in specific dermatological disease states that where dermal fibroblast function has been implicated. Finally, we conclude with outlining potential clinical applications of sirtuins in dermatology. In sum, we find that the literature on the involvement of sirtuins in dermal fibroblasts is limited, with research still in its early stages. Nevertheless, intriguing preliminary findings merit additional investigation into the clinical implications of sirtuins in dermatology.

Current Trends in Vascular Biomarkers for Systemic Sclerosis: A Narrative Review

Systemic sclerosis (SSc, scleroderma) is a multifaceted rare connective tissue disease whose pathogenesis is dominated by immune dysregulation, small vessel vasculopathy, impaired angiogenesis, and both cutaneous and visceral fibrosis. Microvascular impairment represents the initial event of the disease, preceding fibrosis by months or years and accounting for the main disabling and/or life-threatening clinical manifestations, including telangiectasias, pitting scars, periungual microvascular abnormalities (e.g., giant capillaries, hemorrhages, avascular areas, ramified/bushy capillaries) clinically detectable by nailfold videocapillaroscopy, ischemic digital ulcers, pulmonary arterial hypertension, and scleroderma renal crisis. Despite a variety of available treatment options, treatment of SSc-related vascular disease remains problematic, even considering SSc etherogenity and the quite narrow therapeutic window. In this context, plenty of studies have highlighted the great usefulness in clinical practice of vascular biomarkers allowing clinicians to assess the evolution of the pathological process affecting the vessels, as well as to predict the prognosis and the response to therapy. The current narrative review provides an up-to-date overview of the main candidate vascular biomarkers that have been proposed for SSc, focusing on their main reported associations with characteristic clinical vascular features of the disease.

Resveratrol alleviates postpartum depression-like behavior by activating autophagy via SIRT1 and inhibiting AKT/mTOR pathway

BACKGROUND

Postpartum depression (PPD) causes maternal mortality, and has a high disability rate. In recent years, studies have suggested the Sirt1 gene to be involved in the pathogenesis of depression. Resveratrol (RSV), an activator of Sirt1, has been investigated in depressive behavior. However, its effect on PPD remains to be thoroughly elucidated.

METHODS

We employed a mice model with bilateral oophorectomy combined with hormone-simulated pregnancy to assess postpartum depression-like behavior. The behavioral tests were performed 2 days after the withdrawal of estradiol benzoate. RSV was administered subcutaneously to the PPD model mice. Several behavioral tests were executed, including the open field test, forced swimming test, and tail suspension test. Western blot analyses and immunofluorescence staining were used to evaluate protein expression levels of SIRT1, autophagy markers, and the AKT/mTOR.

RESULTS

Postpartum depressive-like behavior was triggered following the withdrawal of estradiol benzoate after hormone-stimulated-pregnancy. RSV improved postpartum depressive-like behavior of mice via its upregulation of the SIRT1 and autophagy markers, such as Beclin1, ATG5 and LC3B. Also, the downregulation of the p62 protein expression was observed. More importantly, we also detected the inhibition of phosphorylated AKT and mTOR in the hippocampus of postpartum depressive-like mice.

CONCLUSION

RSV could alleviate postpartum depression-like behavior in mice by stimulating the SIRT1, induce autophagy and inhibit the AKT/ mTOR signaling pathway.

The Molecular Mechanisms of Systemic Sclerosis-Associated Lung Fibrosis

Systemic sclerosis (SSc), also known as scleroderma, is an autoimmune disorder that affects the connective tissues and has the highest mortality rate among the rheumatic diseases. One of the hallmarks of SSc is fibrosis, which may develop systemically, affecting the skin and virtually any visceral organ in the body. Fibrosis of the lungs leads to interstitial lung disease (ILD), which is currently the leading cause of death in SSc. The identification of effective treatments to stop or reverse lung fibrosis has been the main challenge in reducing SSc mortality and improving patient outcomes and quality of life. Thus, understanding the molecular mechanisms, altered pathways, and their potential interactions in SSc lung fibrosis is key to developing potential therapies. In this review, we discuss the diverse molecular mechanisms involved in SSc-related lung fibrosis to provide insights into the altered homeostasis state inherent to this fatal disease complication.

Sirtuins and Hypoxia in EMT Control

Epithelial–mesenchymal transition (EMT), a physiological process during embryogenesis, can become pathological in the presence of different driving forces. Reduced oxygen tension or hypoxia is one of these forces, triggering a large number of molecular pathways with aberrant EMT induction, resulting in cancer and fibrosis onset. Both hypoxia-induced factors, HIF-1α and HIF-2α, act as master transcription factors implicated in EMT. On the other hand, hypoxia-dependent HIF-independent EMT has also been described. Recently, a new class of seven proteins with deacylase activity, called sirtuins, have been implicated in the control of both hypoxia responses, HIF-1α and HIF-2α activation, as well as EMT induction. Intriguingly, different sirtuins have different effects on hypoxia and EMT, acting as either activators or inhibitors, depending on the tissue and cell type. Interestingly, sirtuins and HIF can be activated or inhibited with natural or synthetic molecules. Moreover, recent studies have shown that these natural or synthetic molecules can be better conveyed using nanoparticles, representing a valid strategy for EMT modulation. The following review, by detailing the aspects listed above, summarizes the interplay between hypoxia, sirtuins, and EMT, as well as the possible strategies to modulate them by using a nanoparticle-based approach.