SIRT1 regulates signaling pathways associated with stress-induced vascular senescence

SIRT1 can mitigate stress-induced vascular senescence by activating or inhibiting multiple effector molecules in the body, regulating the activity of downstream molecules, and exerting antioxidant and anti-inflammatory effects. Figure 7 illustrates the network diagram of SIRT1-related signaling pathways, and the main effector molecules include Nrf2, FoxOs, NF-κB, P53, eNOS, HIF-1α, AMPK, P66Shc, and AP-1 (Table 1).

Figure 7:: SIRT1 pathway diagram.

Figure description: The schematic takes cell membrane and nuclear boundary as the frame with SIRT1 as the central node. The pathways for inhibiting stress-induced vascular aging include SIRT1/Nrf2, SIRT1/FoxOs, SIRT1/eNOS, SIRT1/AMPK, SIRT1/HIF-1α, and SIRT1/P66Shc. The pathways for promoting stress-induced vascular aging are SIRT1/NF-κB, SIRT1/p53, SIRT1/AP-1, SIRT1/TRPC3, SIRT1/YAP. Representative target molecules are FOXO1, Nrf2, NF-κB, p53, eNOS, AMPK, IL-6, TNF-α, ROS, etc. Downstream ROS and inflammatory factors directly promote the the transformation of healthy blood vessels into aging ones.

Study ID | Main related signaling pathways | Effector molecules | Mechanism of action | Modeling approach | Ref.
1 | miR-126/SIRT1/Nrf2/HO-1, SOD, VCAM-1, MCP-1, TNF-α | SIRT1, Nrf2, HO-1, SOD↑VCAM-1, MCP-1, TNF-α, ROS↓ | (−) oxidative stress(−) inflammation | Ligation of the left anterior descending coronary artery in SPF male Wistar rats | [73]
2 | SIRT1/FoxOs/MnSOD, SOD2, CAT | SIRT1, FoxO1, Rab7, FoxO4, FoxO3, MnSOD, SOD2, CAT↑ ROS↓ | (−) autophagy(−) oxidative stress (−) endothelial damage | SPF male SD rats undergo permane-nt ligation of both common carotid arteries | [76]
3 | miR-9/SIRT1/NF-κB/TNF-α, IL-6, IL-4, IL-1β, IL-10 | SIRT1↑NF-κB, TNF-α, IL-6, IL-4, IL-1β, IL-10, ROS↓ | (−) oxidative stress (−) inflammation | miR-NC and/or miR-9 inhibitor were transfected into human myocardial H9c2 cells | [77]
4 | Nampt, FGF1, heat shock protein 25/SIRT1/P53/PML IV, Ras, mTOR | Nampt, FGF1, heat shock protein 25SIRT1, mTOR↑ p53, PMLIVRas↓ | (−) Apoptosis(−) oxidative stress | Six- to seven-week-old SPF male SD rats were intraperitoneally injected with a D-galactose solution (500 mg/kg). | [78], [79], [80], [81], [82]
5 | microRNA-217, miR-34a/SIRT1/eNOS/NO | miR-34a, SIRT1, eNOS, NO↑microRNA-217, ROS↓ | (−) apoptosis(−) oxidative stress | SD rat ligation/perfusion of the left anterior descending coronary artery | [82], [83], [84]
6 | SIRT1/HIF-1α/VEGFA | SIRT1↑HIF-1α, VEGFA, ROS↓ | (−) oxidative stress | Sirt1endo+/− mice were mated with Sirt1Flox/Flox mice | [85]
7 | C1q/tumor necrosis factor-related protein 3SIRT1/AMPK/NF-κB, AP-1 | AMPK, C1q/tumor necrosis factor-related protein 3SIRT1↑ROS, NF-κB, AP-1↓ | (−) oxidative stress(−) inflammation | SPF-grade db/db mice | [86]
8 | SIRT1/P66Shc/H3, FOXO3a, MnSOD | SIRT1, FOXO3a, MnSOD↑H3, P66Shc↓ | (−) endothelial damage | Six-week-old SPF male C57BL/6 mice were fed a high-fat diet | [87]
9 | SIRT1/AP-1/COX-2, PGE2 | SIRT1↑COX-2, PGE2↓ | (−) inflammation | Male C57BL/6 mice had 60 % caloric restriction. | [88]
10 | SIRT1/TRPC3/TGF-β | SIRT1↑TRPC3, TGF-β↓ | (−) fibrosis | Male C57B6 mice fed a high-Hcy diet | [89]
11 | SIRT1/YAP | SIRT1↑YAP↓ | (−) growth | Female ApoE−/− mice aged 4–6 weeks on a Western chow diet | [90]

miR-126/SIRT1/Nrf2/HO-1, SOD, VCAM-1, MCP-1, and TNF-α

The leucine transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), a major regulator of the body’s antioxidant and anti-inflammatory responses, can correct intracellular redox imbalance and reduce pro-inflammatory factors and mediators through downstream target genes and enzymes [70]. In exploring the mechanism by which YiXinFang improves myocardial injury after ischemia/reperfusion in rats, Dong Li et al. found that YiXinFang significantly increased the levels of SIRT1 and Nrf2 in rat tissues and affected the expression of Nrf2 downstream molecules, indirectly suggesting that SIRT1 may help regulate the expression of Nrf2 and its downstream molecules [71]. A high-sugar diet promotes miR-221 overexpression, which downregulates the expression of heme oxygenase 1 (HO-1) and SOD by inhibiting the SIRT1/Nrf2 pathway, leading to impairment of the body’s antioxidant system [72]. Under oxidative stress, Nrf2 separates from Kelch-like ECH-associated protein 1 (Keap1) and becomes activated. SIRT1 can further enhance Nrf2 activity, promoting its binding to Maf/ARE elements and increasing the transcription of antioxidant target genes [73]. Upregulation of Nrf2 expression or activity in endothelial cells reduces the expression of pro-inflammatory cytokines. The expression levels of vascular cell adhesion protein 1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1) and TNF-α were also reduced, thus alleviating inflammatory responses [74]. Dysregulation of the SIRT1/Nrf2 signaling pathway has been implicated in the pathogenesis of numerous neurodegenerative diseases, and several studies have shown that overexpression of miR-126 effectively mitigates oxygen-glucose deprivation/reoxygenation-induced oxidative stress and inflammation by activating the SIRT1/Nrf2 signaling pathway [75]. Evidence supporting this pathway is derived primarily from in vitro endothelial cell experiments and in vivo rat models, with oxidative stress and inflammation serving as the main endpoints. These findings provide only indirect evidence for stress-induced vascular senescence and lack direct validation in human stress-induced vascular senescence models.

SIRT1/FoxOs/Rab7, MnSOD, SOD2, and CAT

Forkhead transcription factor (FoxO) is a transcription factor produced by SIRT1 deacetylation. As one of the most widely studied Forkhead transcription factors, FoxO belongs to a subgroup of the Forkhead family and plays an important role in resisting oxidative stress and preventing endothelial cell damage [75]. The binding of SIRT1 to FoxO1 enhances the ability of FoxO1 to bind DNA, induces the accumulation of FoxO4 in the nucleus, reduces damage to antioxidant-related genes, and enhances the activity of the antioxidant system by inhibiting FoxO1 phosphorylation. It also inhibits the accumulation of ROS in tissues and alleviates oxidative stress [91], [92], [93]. When verifying whether Pueraria baicalensis Lian Tang has antioxidant capacity, Zhang Yuanyuan et al. found that it could upregulate the expression of AMPK, SIRT1 mRNA, and related proteins in liver tissues, while SIRT1 could help ameliorate oxidative stress in the livers of db/db mice by downregulating FoxO1 gene expression and reducing ROS generation [94]. Deacetylation of Forkhead box O3 (FOXO3) by SIRT1 enhances FOXO3-induced cell cycle arrest and inhibits FOXO3-mediated apoptosis [95]. This pathway is supported mainly by in vivo rat studies and in vitro cell assays, with a focus on oxidative stress and endothelial damage. Evidence for stress-induced vascular senescence remains indirect.

miR-9/SIRT1/NF-kappa B/TNF-alpha, IL-6, IL-4, IL-1β, and IL-10

Nuclear factor kappa-B (NF-κB) plays an important role in regulating oxidative stress, the inflammatory response, the cell cycle, and apoptosis [96]. While studying the role of miR-9 in TNF-α-induced cardiomyocyte injury, Zhang Zhaohua et al. identified SIRT1 as the target gene of miR-9 through bioinformatics analysis and transfected cardiomyocytes with a miR-9 inhibitor to reduce miR-9 expression in these cells. The results showed that knocking down miR-9 expression not only significantly increased SIRT1 protein expression in cardiomyocytes but also decreased NF-κB protein phosphorylation and significantly reduced TNF-α-induced oxidative stress injury in cardiomyocytes, suggesting that miR-9 may inhibit activation of the NF-κB signaling pathway by suppressing SIRT1 protein expression, thus reducing cellular activity and inducing stress-induced vascular senescence [86].

By deacetylating NF-κB, SIRT1 enables NF-κB to bind to its nuclear inhibitor (inhibitor kappa B alpha, IκBα), significantly reducing NF-κB activity, downregulating the expression of TNF-α, IL-6, IL-4, IL-1B, IL-10, and other pro-inflammatory cytokines, decreasing the production of ROS in the body, and promoting ROS elimination by the antioxidant system. This helps maintain the body’s oxidative balance, reduces vascular damage caused by oxidative stress, and serves to alleviate stress-induced stress-induced vascular senescence [76]. Current evidence is mostly derived from in vitro cardiomyocyte models and extrapolated to the vascular endothelium. There is insufficient direct evidence for stress-induced vascular senescence.

Namp, FGF1, heat shock protein 25/SIRT1/P53/PMML IV, Ras, and mTOR

p53 is a non-histone substrate of Sirt1 and a core molecule that regulates apoptosis and prevents irritant stress-induced vascular senescence through anti-oxidation and the regulation of apoptosis [97]. Nicotinamide phosphoribosyltransferase (Nampt) can increase intracellular NAD + content, enhance SIRT1 activity, and reduce the production of acetyl-p53 (Lys382) [77]. SIRT1 acts on the histone target H3K9 in the promoter region of the P53 gene, reducing H3K9 acetylation and increasing its trimethylation, thus inhibiting p53 transcription [98]. Abnormal expression of promyelocytic leukemia protein IV (PML IV) or rat sarcoma (Ras) in the organism can cause massive recruitment of SIRT1 to the nucleus, directly affecting PML IV and p53 and interfering with PML-induced cellular senescence by inhibiting p53 acetylation [99]. p53 also activates upstream regulators of mammalian target of rapamycin (mTOR) to increase cellular autophagy and mitigate irritant stress-induced vascular senescence [78]. Supporting data originate mainly from in vivo animal models, with apoptosis and DNA damage as key outcomes. These are related to, but are not direct markers of, stress-induced vascular senescence.

miR-34a, microRNA-217, and SIRT1/eNOS/NO

Previous studies have identified a specific binding site between miR-34a and Sirt1. The results showed that, compared with the control group, Sirt1 expression in the myocardial tissue of mice in the Gm44981 overexpression group was upregulated, while miRNA-34a expression was reduced, suggesting that Gm44981 may inhibit cardiac aging by acting on the miRNA-34a/Sirt1 pathway [79].

eNOS is one of the most important enzymes regulating endothelial function, and it is mainly expressed in endothelial cells. It can inhibit ROS production and upregulate NO expression, thus regulating endothelial function, reducing oxidative stress, and improving stress-induced vascular senescence [80]. microRNA-217 can inhibit SIRT1 expression and eNOS deacetylation and promote endothelial cell senescence [81]. On the one hand, SIRT1 can influence eNOS protein expression by regulating the eNOS gene promoter. On the other hand, SIRT1 can enhance NO production by regulating eNOS activity through deacetylation, thus alleviating stress-induced vascular senescence [82]. This pathway is supported by in vitro endothelial studies and in vivo rat models, with partial confirmation from human vascular function assays. It represents the most consistent and clinically relevant evidence among all the pathways.

SIRT1/HIF-1α/VEGFA

Hypoxia-inducible factor-1α (HIF-1α) is the primary regulator of oxygen homeostasis, and it plays an important role in angiogenesis, energy metabolism, cell survival, apoptosis, and the maintenance of cellular stability under hypoxic conditions [83]. SIRT1 can reduce the accumulation of HIF-1α in the body by inhibiting HIF-1α gene transcription and deacetylating HIF-1α, thus maintaining mitochondrial and oxidative homeostasis and exerting antioxidant effects to prevent stress-induced vascular senescence [84], 100]. SIRT1 may reduce erythropoietin-mediated pathological blood vessel regeneration by inhibiting the HIF-1α signaling pathway and downregulating the expression of vascular endothelial growth factor A (VEGFA) and vascular endothelial growth factor R2 [101], 102]. The evidence is based on genetically modified mouse models and focuses on hypoxia and angiogenesis. Its connection to stress-induced vascular senescence is indirect.

C1q/tumor necrosis factor-related protein 3/SIRT1/AMPK/NF-κB, AP-1

Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) is a key kinase that regulates cellular energy and mitigates stress-induced vascular senescence through anti-inflammatory and antioxidant effects [103]. SIRT1 also deacetylates the serine/threonine kinase hepatic kinase B1, thus activating AMPK, and the effects of SIRT1 and AMPK can be enhanced by a reciprocal positive regulatory circuit [104]. Through SIRT1, AMPK can downregulate the acetylation levels of NF-KB, AP-1, histones, and other target factors, reduce the expression of inflammation-related gene pathways, and alleviate inflammatory damage [85]. Similarly, activation of SIRT1 through complement C1q/tumor necrosis factor-related protein 3 can exert an anti-inflammatory effect by reducing tumor necrosis sub-α levels and NF-κB nuclear translocation. Studies have found that red sandalwood can alleviate mitochondrial damage and oxidative stress by upregulating the expression and deacetylation of PGC-1α through the AMPK and SIRT1 cascade reaction [105]. These findings are mainly derived from diabetic mouse models, with anti-inflammatory and antioxidant effects as the primary endpoints. Extrapolation to general stress-induced vascular senescence requires caution.

SIRT1/P66Shc/H3, FOXO3a, and MnSOD

SHC articulin p66 (generic shell script compiler, P66Shc) is a member of the Shc articulin family of proteins, and inhibition of P66Shc expression has a protective effect on vascular endothelial cells; and it delays stress-induced vascular senescence [106]. By binding to the P66Shc promoter, SIRT1 reduces the acetylation of histone H3 and inhibits the transcription of P66Shc [107]. Under oxidative stress, p66Shc can be transferred to the nucleus and transported to mitochondria and related membranes; and it can bind to mitochondrial cytochrome c, resulting in the oxidation of cytochrome c and further promoting ROS production [108]. However, phosphorylation and activation of p66Shc can activate AKT, thus inactivating the FOXO3a transcription factor, reducing MnSOD levels, and decreasing the body’s ability to clear ROS [109]. Supporting evidence is based on high-fat diet mouse models that measure ROS and endothelial injury. However, these are surrogate phenotypes rather than direct markers of stress-induced vascular senescence.

SIRT1/AP-1/COX-2, PGE2

Activator protein-1 (AP-1) is an important transcriptional activator of leucine zipper DNA-binding proteins; and it can mitigate the negative effects caused by cytokines, chemokines, oncogenic proteins, and other molecules by regulating the expression of downstream genes [110]. High expression of SIRT1 can exert anti-inflammatory effects by regulating the AP-1 gene, downregulating the expression of cyclooxygenase-2 (COX-2) protein in macrophages, and reducing the production of prostaglandin E2 (PGE2) [87]. Evidence is limited to calorie-restricted mouse models and is centered on anti-inflammatory effects. The direct relevance to stress-induced vascular senescence is weak.

SIRT1/TRPC3/TGF-β

Short transient receptor potential channel 3 (TRPC3) is a key factor in regulating myocyte fibrosis; and it may contribute to mechanical stress-induced LV diastolic dysfunction by indirectly regulating TRPC3-mediated expression of the pro-fibrotic protein transforming growth factor-β (TGF-β), and TRPC3 can also negatively regulate SIRT1 expression by directly interacting with SIRT1 [111]. Blocking TRPC3 expression or reducing it through knockdown can decrease Ang II-induced migration, proliferation, and the expression of fibrosis biomarkers in atrial fibroblasts. Meanwhile, the Ca2+-permeable TRPC3 channel mediates the atrial fibrosis signaling pathway through Ca2+, suggesting that this pathway may be a potential therapeutic target in the pathogenesis of AF during aging and hypertension [112]. This pathway is supported by hyperhomocysteinemic mouse models focused on vascular fibrosis. Evidence for senescence is indirect.

SIRT1/YAP

Yes-associated protein (YAP) is a potential therapeutic target for atherosclerosis. It acts as a sensor and signal amplifier for mechanical stimuli, triggering various biomechanical effects in response to mechanical stress. Inhibiting YAP expression helps maintain vascular homeostasis in endothelial cells [113]. SIRT1 can influence nuclear output and degradation by deacetylating YAP, downregulate the expression of YAP target genes, and inhibit the nucleocytoplasmic shuttling of YAP protein [88]. SIRT1 deacetylates the YAP2 protein, increasing YAP2/TEAD4 binding and activation and promoting cell growth in hepatocellular carcinoma cells. YAP1 expression is also positively correlated with VEGFA expression and secretion, which promotes angiogenesis in renal carcinoma environments [89], 90], 114]. This evidence is extrapolated from atherosclerotic mouse models and cancer cell studies. Direct evidence in the context of stress-induced vascular senescence is lacking.