Histone lysine-specific demethylase 1 induced renal fibrosis via decreasing sirtuin 3 expression and activating TGF-β1/Smad3 pathway in diabetic nephropathy

Objective Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. Histone lysine-specific demethylase 1 (LSD1) is a flavin-containing amino oxidase that can repress or activate transcription. The aim of this study is to explore the mechanism of LSD1 aggravating DN-induced renal fibrosis. Methods The STZ-induced DN rat model was established for in vivo study. The rats were divided into four groups: Sham, STZ, STZ + Ad-shNC and Ad-shLSD1. The Hematoxylin–eosin (HE) staining was used to evaluate the renal injury. The Immunofluorescence assay was used to determine the LSD1, Fibronectin and α-SMA expression. The related protein expression was detected by western blot. Results Knockdown of LSD1 alleviated STZ-induced renal injury. Moreover, knockdown of LSD1 decreased the expression of serum biochemical markers, containing urine output (24 h), urinary protein (24 h), serum creatinine, BUN and UACR. Furthermore, we proved that knockdown of LSD1 alleviated renal fibrosis in STZ-induced DN rats. In vitro, knockdown of LSD1 suppressed NRK-49F cells activation and overexpression of LSD1 induced renal fibrosis. In addition, knockdown of LSD1 could deactivate TGF-β1/Smad3 pathway and promote sirtuin 3 (SIRT3) expression in vivo and in vitro. The rescue experiments confirmed that LSD1 induced renal fibrosis via decreasing SIRT3 expression and activating TGF-β1/Smad3 pathway. Conclusion LSD1 deficiency leads to alleviate STZ-induced renal injury and overexpression of LSD1 induces renal fibrosis via decreasing SIRT3 expression and activating TGF-β1/Smad3 pathway, which provides a reasonable strategy for developing novel drugs targeting LDS1 to block renal fibrosis.

Sirtuin-3 Protects Cochlear Hair Cells Against Noise-Induced Damage via the Superoxide Dismutase 2/Reactive Oxygen Species Signaling Pathway

Mitochondrial oxidative stress is involved in hair cell damage caused by noise-induced hearing loss (NIHL). Sirtuin-3 (SIRT3) plays an important role in hair cell survival by regulating mitochondrial function; however, the role of SIRT3 in NIHL is unknown. In this study, we used 3-TYP to inhibit SIRT3 and found that this inhibition aggravated oxidative damage in the hair cells of mice with NIHL. Moreover, 3-TYP reduced the enzymatic activity and deacetylation levels of superoxide dismutase 2 (SOD2). Subsequently, we administered adeno-associated virus-SIRT3 to the posterior semicircular canals and found that SIRT3 overexpression significantly attenuated hair cell injury and that this protective effect of SIRT3 could be blocked by 2-methoxyestradiol, a SOD2 inhibitor. These findings suggest that insufficient SIRT3/SOD2 signaling leads to mitochondrial oxidative damage resulting in hair cell injury in NIHL. Thus, ameliorating noise-induced mitochondrial redox imbalance by intervening in the SIRT3/SOD2 signaling pathway may be a new therapeutic target for hair cell injury.

Sirtuin 3 Inhibition Targets AML Stem Cells through Perturbation of Fatty Acid Oxidation

Acute myeloid leukemia (AML) in adults has a 5-year survival of approximately 30% and a high rate of disease recurrence in part due to our inability to eliminate the disease-initiating leukemic stem cells (LSCs) (Shlush et al. Nature, 2017). Previous studies have shown that LSCs uniquely rely on oxidative phosphorylation (OXPHOS) for survival (Lagadinou et al. Cell Stem Cell, 2013). Thus, novel therapies that are designed to target LSC metabolism have the potential to improve patient outcomes. Work from our group and others has demonstrated that a critical metabolite for OXPHOS regulation in LSCs is the coenzyme NAD + (Jones et al. Cell Stem Cell, 2020; Mitchell et al. Blood Advances 2019). One family of NAD + dependent proteins important in cancer biology, and AML specifically (Yan et al. Blood Cancer Discovery, 2021), are sirtuins. To determine if any sirtuins are important in LSC function we knocked down each sirtuin family member (sirtuin 1-7) with siRNA in four primary AML specimens and measured viability and colony forming ability. Knockdown of sirtuin 3 (SIRT3) decreased viability and colony forming potential of all AML specimens tested. SIRT3 is a mitochondrial de-acetylase with a multi-faceted role in metabolic regulation and oncogenesis (Finley, et al. Trends in Molecular Medicine, 2016). SIRT3 interacts with pathways upstream of OXPHOS including the tricarboxylic acid (TCA) and fatty acid oxidation (FAO). Importantly, a SIRT3 inhibitor (YC8-02) has been developed and has been shown to be effective pre-clinically for the treatment of B-cell lymphoma (Li et al. Cancer Cell, 2019). To further understand the significance of SIRT3 in LSCs, we assessed viability and colony forming potential upon YC8-02 treatment. LSCs were enriched from primary specimens based upon relative reactive oxygen species (ROS) level as previously described (Lagadinou et al. Cell Stem Cell, 2013). LSCs and blasts enriched from ten primary AML, and four AML cell lines (MOLM13, TEX, OCI-AML2, OCI-AML3) were cultured for 48 hours with or without YC8-02 before assessing viability and colony forming ability. YC8-02 treatment resulted in a significant decrease in colony forming potential of AML cells compared to control (data not shown). Similarly, LSCs, blasts, and cell lines showed a significant decrease in viability upon YC8-02 treatment (Fig 1A and data not shown). Cord blood and mobilized peripheral blood samples conversely did not show a change in colony forming potential following SIRT3 knockdown or YC8-02 treatment, respectively (data not shown). To assess YC8-02's effect on LSC function, three AML samples were treated with 10µM of drug for 24 hours and transplanted into NSG-S mice. YC8-02 treatment resulted in a significant decrease in AML engraftment, indicating a decrease in LSC function (Fig 1B). To determine the mechanism by which SIRT3 inhibition causes cell death, LSCs enriched from three primary specimens were treated with YC8-02; metabolite and lipid levels were determined by mass spectrometry. This analysis revealed a significant accumulation of fatty acids post YC8-02 treatment. To further characterize these changes, MOLM13 cells were treated with 13C 16-palmitic acid following 4 hours of incubation with 10µM YC8-02. Cells were collected 4 and 16 hours after introduction of palmitic acid and metabolic tracing was assessed by mass spectrometry. We found an accumulation of long and very long chain fatty acids and a decrease in TCA cycle intermediates (Fig 1C). FAO normally supplies TCA with intermediate acetyl-CoA; thus, these data indicate a decrease in FAO upon YC8-02 treatment. Accordingly, we measured changes in OXPHOS in response to treatment with YC8-02, in primary LSCs (Fig 1D) and AML cell lines (data not shown) and found a significant decrease in basal oxygen consumption. Further, ATP levels were significantly decreased upon YC8-02 treatment in LSCs (Fig 1E). In conclusion, we show that SIRT3 plays a pivotal role in FAO and LSC function. When SIRT3 is inhibited, FAO activity decreases resulting in the accumulation of long and very long chain fatty acids. This change in FAO activity reduces the availability of products for the TCA cycle, limiting necessary intermediates for OXPHOS, decreasing ATP production, and ultimately causing cell death. Therefore, our data suggests that SIRT3 is a potential therapeutic target for LSCs and should be considered in future pre-clinical and clinical investigations. Figure 1 Figure 1. Disclosures Melnick: Constellation: Consultancy; Epizyme: Consultancy; Daiichi Sankyo: Research Funding; Sanofi: Research Funding; Janssen Pharmaceuticals: Research Funding; KDAC Pharma: Membership on an entity's Board of Directors or advisory committees. Minden: Astellas: Consultancy. D'Alessandro: Omix Thecnologies: Other: Co-founder; Rubius Therapeutics: Consultancy; Forma Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Necroptosis Inhibition by Hydrogen Sulfide Alleviated Hypoxia-Induced Cardiac Fibroblasts Proliferation via Sirtuin 3

Myocardial ischemia or hypoxia can induce myocardial fibroblast proliferation and myocardial fibrosis. Hydrogen sulfide (H2S) is a gasotransmitter with multiple physiological functions. In our present study, primary cardiac fibroblasts were incubated with H2S donor sodium hydrosulfide (NaHS, 50 μM) for 4 h followed by hypoxia stimulation (containing 5% CO2 and 1% O2) for 4 h. Then, the preventive effects on cardiac fibroblast proliferation and the possible mechanisms were investigated. Our results showed that NaHS reduced the cardiac fibroblast number, decreased the hydroxyproline content; inhibited the EdU positive ratio; and down-regulated the expressions of α-smooth muscle actin (α-SMA), the antigen identified by monoclonal antibody Ki67 (Ki67), proliferating cell nuclear antigen (PCNA), collagen I, and collagen III, suggesting that hypoxia-induced cardiac fibroblasts proliferation was suppressed by NaHS. NaHS improved the mitochondrial membrane potential and attenuated oxidative stress, and inhibited dynamin-related protein 1 (DRP1), but enhanced optic atrophy protein 1 (OPA1) expression. NaHS down-regulated receptor interacting protein kinase 1 (RIPK1) and RIPK3 expression, suggesting that necroptosis was alleviated. NaHS increased the sirtuin 3 (SIRT3) expressions in hypoxia-induced cardiac fibroblasts. Moreover, after SIRT3 siRNA transfection, the inhibitory effects on cardiac fibroblast proliferation, oxidative stress, and necroptosis were weakened. In summary, necroptosis inhibition by exogenous H2S alleviated hypoxia-induced cardiac fibroblast proliferation via SIRT3.

Sirtuin 3 (SIRT3) Pathways in Age-Related Cardiovascular and Neurodegenerative Diseases

Age-associated cardiovascular and neurodegenerative diseases lead to high morbidity and mortality around the world. Sirtuins are vital enzymes for metabolic adaptation and provide protective effects against a wide spectrum of pathologies. Among sirtuins, mitochondrial sirtuin 3 (SIRT3) is an essential player in preserving the habitual metabolic profile. SIRT3 activity declines as a result of aging-induced changes in cellular metabolism, leading to increased susceptibility to endothelial dysfunction, hypertension, heart failure and neurodegenerative diseases. Stimulating SIRT3 activity via lifestyle, pharmacological or genetic interventions could protect against a plethora of pathologies and could improve health and lifespan. Thus, understanding how SIRT3 operates and how its protective effects could be amplified, will aid in treating age-associated diseases and ultimately, in enhancing the quality of life in elders.