SRSF1 promotes vascular smooth muscle cell proliferation through a Δ133p53/EGR1/KLF5 pathway

The PIWI-interacting RNA CRAPIR alleviates myocardial ischemia‒reperfusion injury by reducing p53-mediated apoptosis via binding to SRSF1

Ischemia-reperfusion (I/R) injury refers to the secondary damage that occurs when blood flow is restored to heart tissues and organs following a period of prolonged ischemia. This damage is exacerbated primarily through mechanisms such as oxidative stress, inflammatory responses and apoptosis, all of which can severely impact patient prognosis. PIWI-interacting RNAs (piRNAs) represent a novel class of small noncoding RNAs that play pivotal roles in regulating gene expression and cellular functions. However, the precise role and underlying mechanisms of piRNAs in I/R injury remain poorly understood. In this study, we investigated the role and molecular mechanisms of a cardiac regeneration-associated PIWI-interacting RNA (CRAPIR), previously identified by our team, in I/R injury. An I/R injury model was established in adult male mice. The protein levels of cleaved caspase-3, Bax, Bcl2 and p53 were assessed using Western blotting, and cardiomyocyte apoptosis was detected via TUNEL staining. Our study revealed that, in I/R-damaged heart tissues and hypoxia‒reoxygenation (H/R)-induced cardiomyocyte models, CRAPIR was upregulated 24 h after I/R and H/R but was markedly downregulated at 72 h after I/R injury and 48 h after H/R injury. In the I/R mouse model, agomir-mediated overexpression of CRAPIR alleviated heart dysfunction and reduced cardiomyocyte apoptosis caused by I/R injury. Conversely, CRAPIR knockdown via an antagomir exacerbated I/R-induced cardiac dysfunction and increased the number of apoptotic cardiomyocytes. Mechanistically, CRAPIR interacts with serine/arginine-rich splicing factor 1 (SRSF1), triggering the upregulation of murine double minute 2 (MDM2) expression. The increased MDM2 promoted p53 ubiquitination, leading to reduced p53 levels. Furthermore, silencing SRSF1 or MDM2 attenuated the protective effect of CRAPIR against cardiomyocyte apoptosis following H/R injury. These findings suggest that CRAPIR serves as a critical regulator of I/R injury via the SRSF1/MDM2/p53 signaling pathway.

Loss of Endothelial TRPC1 Induces Aortic Hypercontractility and Hypertension

BACKGROUND

The increasing prevalence of obesity-related cardiovascular diseases demands a better understanding of the contribution of different cell types to vascular function for developing new treatment strategies. Previous studies have established a fundamental role of TRPC1 (transient receptor potential channel canonical family member 1) in blood vessels. However, little is known about its functional roles within different cell types.

METHODS

We generated endothelial-specific TRPC1-deficient and knockin mice and analyzed their changes in vascular function under physiological and pathologically obese state. Wire myography, Ca2+ image, blood pressure measurements, RNA-sequencing analysis, liquid chromatography-mass spectrometry, immunoblotting, ELISA, luciferase reporter assay, and morphometric assessments were performed to unravel phenotype and molecular changes in response to the absence or presence of endothelial TRPC1.

RESULTS

Loss of endothelial TRPC1 reduced endothelial-dependent relaxation and exaggerated endothelial-dependent contraction in mouse aorta. As expected, loss of endothelial TRPC1 amplified blood pressure and decreased acetylcholine-induced intracellular Ca2+ concentration rise in the aorta. In endothelial-specific TRPC1-deficient mouse arteries, the mRNA profile identified upregulation of c-Fos (Fos proto-oncogene, activator protein-1 transcription factor subunit). Blockade of c-Fos rescued the impaired vasomotor tone in the aorta of mice deficient in endothelial TRPC1. Endothelial TRPC1-regulated nitric oxide/endothelin-1 production is involved in vascular c-Fos expression. Moreover, knockin of endothelial TRPC1 ameliorated enhanced endothelial-dependent contraction and hypertension in obese mice which is related to alleviated endothelial endothelin-1/c-Fos production and smooth muscle contraction.

CONCLUSIONS

Our results identify endothelial TRPC1 as a previously unclear regulator of vascular changes and blood pressure in both physiological and pathologically obese state, and it is associated with nitric oxide/endothelin-1/c-Fos signaling.

CircHAT1 regulates the proliferation and phenotype switch of vascular smooth muscle cells in lower extremity arteriosclerosis obliterans through targeting SFRS1

This study aimed to decipher the mechanism of circular ribonucleic acids (circRNAs) in lower extremity arteriosclerosis obliterans (LEASO). First, bioinformatics analysis was performed for screening significantly down-regulated cardiac specific circRNA-circHAT1 in LEASO. The expression of circHAT1 in LEASO clinical samples was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The protein expression of splicing factor arginine/serine-rich 1 (SFRS1), α-smooth muscle actin (α-SMA), Calponin (CNN1), cyclin D1 (CNND1) and smooth muscle myosin heavy chain 11 (SMHC) in vascular smooth muscle cells (VSMCs) was detected by Western blotting. Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU) and Transwell assays were used to evaluate cell proliferation and migration, respectively. RNA immunoprecipitation (RNA-IP) and RNA pulldown verified the interaction between SFRS1 and circHAT1. By reanalyzing the dataset GSE77278, circHAT1 related to VSMC phenotype conversion was screened, and circHAT1 was found to be significantly reduced in peripheral blood mononuclear cells (PBMCs) of LEASO patients compared with healthy controls. Knockdown of circHAT1 significantly promoted the proliferation and migration of VSMC cells and decreased the expression levels of contractile markers. However, overexpression of circHAT1 induced the opposite cell phenotype and promoted the transformation of VSMCs from synthetic to contractile. Besides, overexpression of circHAT1 inhibited platelet-derived growth factor-BB (PDGF-BB)-induced phenotype switch of VSMC cells. Mechanistically, SFRS1 is a direct target of circHAT1 to mediate phenotype switch, proliferation and migration of VSMCs. Overall, circHAT1 regulates SFRS1 to inhibit the cell proliferation, migration and phenotype switch of VSMCs, suggesting that it may be a potential therapeutic target for LEASO.

RNA binding protein with multiple splicing (RBPMS) promotes contractile phenotype splicing in human embryonic stem cell-derived vascular smooth muscle cells

AIMS

Differentiated vascular smooth muscle cells (VSMCs) express a unique network of mRNA isoforms via smooth muscle-specific alternative pre-mRNA splicing (SM-AS) in functionally critical genes, including those comprising the contractile machinery. We previously described RNA Binding Protein with Multiple Splicing (RBPMS) as a potent driver of differentiated SM-AS in the rat PAC1 VSMC cell line. What is unknown is how RBPMS affects VSMC phenotype and behaviour. Here, we aimed to dissect the role of RBPMS in SM-AS in human cells and determine the impact on VSMC phenotypic properties.

METHODS AND RESULTS

We used human embryonic stem cell-derived VSMCs (hESC-VSMCs) as our platform. hESC-VSMCs are inherently immature, and we found that they display only partially differentiated SM-AS patterns while RBPMS protein levels are low. We found that RBPMS over-expression induces SM-AS patterns in hESC-VSMCs akin to the contractile tissue VSMC splicing patterns. We present in silico and experimental findings that support RBPMS' splicing activity as mediated through direct binding and via functional cooperativity with splicing factor RBFOX2 on a significant subset of targets. We also demonstrate that RBPMS can alter the motility and the proliferative properties of hESC-VSMCs to mimic a more differentiated state.

CONCLUSION

Overall, this study emphasizes a critical role for RBPMS in establishing the contractile phenotype splicing programme of human VSMCs.

SRSF1 Is Crucial for Maintaining Satellite Cell Homeostasis During Skeletal Muscle Growth and Regeneration

BACKGROUND

The splicing factor SRSF1 emerges as a mater regulator of cell proliferation, displaying high expression in actively proliferative satellite cells (SCs). In SRSF1 knockout mice (KO) generated via MyoD-Cre, early mortality and muscle atrophy are observed during postnatal muscle growth. Despite these findings, the precise mechanisms through which SRSF1 loss influences SCs' functions and its role in muscle regeneration remain to be elucidated.

METHODS

To unravel the exact mechanisms underlying the impact of SRSF1 deficiency SC functions, we employed single-cell RNA sequencing (scRNA-seq) on a mononuclear cell suspension isolated from the newborn diaphragm of KO and control mice. Concurrently, we subjected diaphragm muscles to RNA-seq analysis to identify dysregulated splicing events associated with SRSF1 deletion. For the analysis of the effect of SRSF1 deletion on muscle regeneration, we generated mice with inducible SC-specific Srsf1 ablation through Pax7-CreER. SRSF1 ablation was induced by intraperitoneal injection of tamoxifen. Using cardiotoxin-induced muscle injury, we examined the consequences of SRSF1 depletion on SC function through HE staining, immunostaining and EdU incorporation assay. C2C12 myoblasts and isolated myoblasts were employed to assess stem cell function and senescence.

RESULTS

Utilizing scRNA-seq analysis, we observed a noteworthy increase in activated and proliferating myoblasts when SRSF1 was absent. This increase was substantial, with the proportion rising from 28.68% in the control group to 77.06% in the knockout group. However, these myoblasts experienced mitotic abnormalities in the absence of SRSF1, resulting in cell cycle arrest and the onset of cellular senescence. In the knockout mice, the proportion of Pax7+ cells within improper niche positioning increased significantly to 25% compared to 12% in the control cells (n ≥ 10, p < 0.001). Furthermore, there was an observation of persistent cell cycle exit specifically in the Pax7+ cells deficient in SRSF1 (n = 6, p < 0.001). SRSF1 plays a pivotal role in regulating the splicing of Fgfr1op2, favouring the full-length isoform crucial for mitotic spindle organization. Disrupting SRSF1 in C2C12 and primary myoblasts results in multipolar spindle formation (p < 0.001) and dysregulated splicing of Fgfr1op2 and triggers cellular senescence. Consequently, adult SCs lacking SRSF1 initially activate upon injury but face substantial challenge in proliferation (n = 4, p < 0.001), leading to a failure in muscle regeneration.

CONCLUSIONS

SRSF1 plays a critical role in SCs by ensuring proper splicing, maintaining mitotic progression and preventing premature senescence. These findings underscore the significant role of SRSF1 in controlling SC proliferation during skeletal muscle growth and regeneration.

Splicing factor SRSF1 attenuates cardiomyocytes apoptosis via regulating alternative splicing of Bcl2L12

BACKGROUND

Aberrant alternative splicing (AS) events, triggered by the alterations in serine/arginine splicing factor 1 (SRSF1), a member of the SR protein family, have been implicated in various pathological processes. However, the function and mechanism of SRSF1 in cardiovascular diseases remain unclear.

RESULTS

In this study, we found that the expression of SRSF1 was significantly down-regulated in the hearts of mice with acute myocardial infarction (AMI) and H9C2 cells exposed to H2O2. Moreover, in vivo experiments utilizing adeno-associated virus serotype 9-mediated SRSF1 overexpression improved cardiac function and reduced infarct size in AMI mice. Mechanistically, we employed RNA-seq assay to identify AS aberrations associated with altered SRSF1 level in cardiomyocytes, and found that SRSF1 regulates the splice switching of Bcl2L12. Further study showed that silencing SRSF1 inhibits the inclusion of exon7 in Bcl2L12. Importantly, the truncated Bcl2L12 lacked the necessary structural elements and failed to interact with p53, thus compromising its ability to suppress apoptosis.

CONCLUSIONS

Our study unraveled the role of SRSF1 as a splicing factor involved in the regulation of Bcl2L12 splice switching, thereby exerting an anti-apoptotic effect through the p53 pathway, which provides new insights into potential approaches targeting cardiomyocyte apoptosis in cardiovascular diseases.

Role of RNA-binding Proteins in Regulating Cell Adhesion and Progression of the Atherosclerotic Plaque and Plaque Erosion

PURPOSE OF REVIEW

RNA-binding proteins (RBPs) have emerged as crucial regulators of post-transcriptional processes, influencing the fate of RNA. This review delves into the biological functions of RBPs and their role in alternative splicing concerning atherosclerosis (AS), highlighting their participation in essential cellular processes. Our goal is to offer new insights for cardiovascular disease research and treatment.

RECENT FINDING

Dysregulation of RBPs is associated with various human diseases, including autoimmune and neurological disorders. The role of RBPs in the pathogenesis of AS is progressively being elucidated, as they influence plaque formation and disease progression by regulating cell function and gene expression. RBPs play intricate biological roles in regulating pre-mRNA, including editing, splicing, stability and translation. Alternative splicing has been demonstrated to enhance biological complexity and diversity. Our findings indicate that alternative splicing is extensively involved in the pathogenesis of AS. The dysregulated expression of specific RBPs in AS is linked to the production of adhesion molecules and vascular endothelium damage. Further research on RBPs could pave the way for the development of novel therapeutic targets.

Early growth response 1 exacerbates thoracic aortic aneurysm and dissection of mice by inducing the phenotypic switching of vascular smooth muscle cell through the activation of Krüppel-like factor 5

AIM

Vascular smooth muscle cell (VSMC) phenotypic switching has been reported to regulate vascular function and thoracic aortic aneurysm and dissection (TAAD) progression. Early growth response 1 (Egr1) is associated with the differentiation of VSMCs. However, the mechanisms through which Egr1 participates in the regulation of VSMCs and progression of TAAD remain unknown. This study aimed to investigate the role of Egr1 in the phenotypic switching of VSMCs and the development of TAAD.

METHODS

Wild-type C57BL/6 and SMC-specific Egr1-knockout mice were used as experimental subjects and fed β-aminopropionitrile for 4 weeks to construct the TAAD model. Ultrasound and aortic staining were performed to examine the pathological features in thoracic aortic tissues. Transwell, wound healing, CCK8, and immunofluorescence assays detected the migration and proliferation of synthetic VSMCs. Egr1 was directly bound to the promoter of Krüppel-like factor 5 (KLF5) and promoted the expression of KLF5, which was validated by JASPAR database and dual-luciferase reporter assay.

RESULTS

Egr1 expression increased and was partially co-located with VSMCs in aortic tissues of mice with TAAD. SMC-specific Egr1 deficiency alleviated TAAD and inhibited the phenotypic switching of VSMC. Egr1 knockdown prevented the phenotypic switching of VSMCs and subsequently suppressed the migration and proliferation of synthetic VSMCs. The inhibitory effects of Egr1 deficiency on VSMCs were blunted once KLF5 was overexpressed.

CONCLUSION

Egr1 aggravated the development of TAAD by promoting the phenotypic switching of VSMCs via enhancing the transcriptional activation of KLF5. These results suggest that inhibition of SMC-specific Egr1 expression is a promising therapy for TAAD.

p85α deficiency alleviates ischemia-reperfusion injury by promoting cardiomyocyte survival

Myocardial ischemia-reperfusion (I/R) injury is a prevalent cause of myocardial injury, involving a series of interconnected pathophysiological processes. However, there is currently no clinical therapy for effectively mitigating myocardial I/R injury. Here, we show that p85α protein levels increase in response to I/R injury through a comprehensive analysis of cardiac proteomics, and confirm this in the I/R-injured murine heart and failing human myocardium. Genetic inhibition of p85α in mice activates the Akt-GSK3β/Bcl-x(L) signaling pathway and ameliorates I/R-induced cardiac dysfunction, apoptosis, inflammation, and mitochondrial dysfunction. p85α silencing in cardiomyocytes alleviates hypoxia-reoxygenation (H/R) injury through activating the Akt-GSK3β/Bcl-x(L) signaling pathway, while its overexpression exacerbates the damage. Mechanistically, the interaction between MG53 and p85α triggers the ubiquitination and degradation of p85α, consequently enhancing Akt phosphorylation and ultimately having cardioprotective effects. Collectively, our findings reveal that substantial reduction of p85α and subsequently activated Akt signaling have a protective effect against cardiac I/R injury, representing an important therapeutic strategy for mitigating myocardial damage.

Novel Factors Regulating Proliferation, Migration, and Differentiation of Fibroblasts, Keratinocytes, and Vascular Smooth Muscle Cells during Wound Healing

Chronic diabetic foot ulcers (DFUs) are a significant complication of diabetes mellitus, often leading to amputation, increased morbidity, and a substantial financial burden. Even with the advancements in the treatment of DFU, the risk of amputation still exists, and this occurs due to the presence of gangrene and osteomyelitis. Nonhealing in a chronic DFU is due to decreased angiogenesis, granulation tissue formation, and extracellular matrix remodeling in the presence of persistent inflammation. During wound healing, the proliferation and migration of fibroblasts, smooth muscle cells, and keratinocytes play a critical role in extracellular matrix (ECM) remodeling, angiogenesis, and epithelialization. The molecular factors regulating the migration, proliferation, and differentiation of these cells are scarcely discussed in the literature. The literature review identifies the key factors influencing the proliferation, migration, and differentiation of fibroblasts, keratinocytes, and vascular smooth muscle cells (VSMCs), which are critical in wound healing. This is followed by a discussion on the various novel factors regulating the migration, proliferation, and differentiation of these cells but not in the context of wound healing; however, they may play a role. Using a network analysis, we examined the interactions between various factors, and the findings suggest that the novel factors identified may play a significant role in promoting angiogenesis, granulation tissue formation, and extracellular matrix remodeling during wound healing or DFU healing. However, these interactions warrant further investigation to establish their role alone or synergistically.

Inositol 1,4,5-Trisphosphate Receptors Regulate Vascular Smooth Muscle Cell Proliferation and Neointima Formation in Mice

BACKGROUND

Vascular smooth muscle cell (VSMC) proliferation is involved in many types of arterial diseases, including neointima hyperplasia, in which Ca2+ has been recognized as a key player. However, the physiological role of Ca2+ release via inositol 1,4,5-trisphosphate receptors (IP3Rs) from endoplasmic reticulum in regulating VSMC proliferation has not been well determined.

METHODS AND RESULTS

Both in vitro cell culture models and in vivo mouse models were generated to investigate the role of IP3Rs in regulating VSMC proliferation. Expression of all 3 IP3R subtypes was increased in cultured VSMCs upon platelet-derived growth factor-BB and FBS stimulation as well as in the left carotid artery undergoing intimal thickening after vascular occlusion. Genetic ablation of all 3 IP3R subtypes abolished endoplasmic reticulum Ca2+ release in cultured VSMCs, significantly reduced cell proliferation induced by platelet-derived growth factor-BB and FBS stimulation, and also decreased cell migration of VSMCs. Furthermore, smooth muscle-specific deletion of all IP3R subtypes in adult mice dramatically attenuated neointima formation induced by left carotid artery ligation, accompanied by significant decreases in cell proliferation and matrix metalloproteinase-9 expression in injured vessels. Mechanistically, IP3R-mediated Ca2+ release may activate cAMP response element-binding protein, a key player in controlling VSMC proliferation, via Ca2+/calmodulin-dependent protein kinase II and Akt. Loss of IP3Rs suppressed cAMP response element-binding protein phosphorylation at Ser133 in both cultured VSMCs and injured vessels, whereas application of Ca2+ permeable ionophore, ionomycin, can reverse cAMP response element-binding protein phosphorylation in IP3R triple knockout VSMCs.

CONCLUSIONS

Our results demonstrated an essential role of IP3R-mediated Ca2+ release from endoplasmic reticulum in regulating cAMP response element-binding protein activation, VSMC proliferation, and neointima formation in mouse arteries.

Canonical and non-canonical functions of p53 isoforms: potentiating the complexity of tumor development and therapy resistance

Full-length p53 (p53α) plays a pivotal role in maintaining genomic integrity and preventing tumor development. Over the years, p53 was found to exist in various isoforms, which are generated through alternative splicing, alternative initiation of translation, and internal ribosome entry site. p53 isoforms, either C-terminally altered or N-terminally truncated, exhibit distinct biological roles compared to p53α, and have significant implications for tumor development and therapy resistance. Due to a lack of part and/or complete C- or N-terminal domains, ectopic expression of some p53 isoforms failed to induce expression of canonical transcriptional targets of p53α like CDKN1A or MDM2, even though they may bind their promoters. Yet, p53 isoforms like Δ40p53α still activate subsets of targets including MDM2 and BAX. Furthermore, certain p53 isoforms transactivate even novel targets compared to p53α. More recently, non-canonical functions of p53α in DNA repair and of different isoforms in DNA replication unrelated to transcriptional activities were discovered, amplifying the potential of p53 as a master regulator of physiological and tumor suppressor functions in human cells. Both regarding canonical and non-canonical functions, alternative p53 isoforms frequently exert dominant negative effects on p53α and its partners, which is modified by the relative isoform levels. Underlying mechanisms include hetero-oligomerization, changes in subcellular localization, and aggregation. These processes ultimately influence the net activities of p53α and give rise to diverse cellular outcomes. Biological roles of p53 isoforms have implications for tumor development and cancer therapy resistance. Dysregulated expression of isoforms has been observed in various cancer types and is associated with different clinical outcomes. In conclusion, p53 isoforms have expanded our understanding of the complex regulatory network involving p53 in tumors. Unraveling the mechanisms underlying the biological roles of p53 isoforms provides new avenues for studies aiming at a better understanding of tumor development and developing therapeutic interventions to overcome resistance.

SRSF1 Is Required for Mitochondrial Homeostasis and Thermogenic Function in Brown Adipocytes Through its Control of Ndufs3 Splicing

RNA splicing dysregulation and the involvement of specific splicing factors are emerging as common factors in both obesity and metabolic disorders. The study provides compelling evidence that the absence of the splicing factor SRSF1 in mature adipocytes results in whitening of brown adipocyte tissue (BAT) and impaired thermogenesis, along with the inhibition of white adipose tissue browning in mice. Combining single-nucleus RNA sequencing with transmission electron microscopy, it is observed that the transformation of BAT cell types is associated with dysfunctional mitochondria, and SRSF1 deficiency leads to degenerated and fragmented mitochondria within BAT. The results demonstrate that SRSF1 effectively binds to constitutive exon 6 of Ndufs3 pre-mRNA and promotes its inclusion. Conversely, the deficiency of SRSF1 results in impaired splicing of Ndufs3, leading to reduced levels of functional proteins that are essential for mitochondrial complex I assembly and activity. Consequently, this deficiency disrupts mitochondrial integrity, ultimately compromising the thermogenic capacity of BAT. These findings illuminate a novel role for SRSF1 in influencing mitochondrial function and BAT thermogenesis through its regulation of Ndufs3 splicing within BAT.

Investigating the anti-atherosclerotic effects and potential mechanism of Dalbergia odorifera in ApoE-deficient mice using network pharmacology combined with metabolomics

Dalbergia odorifera (DO) is a precious rosewood species in Southern Asia, and its heartwood is used in China as an official plant for invigorating blood circulation and eliminating stasis. This study aims to evaluate the efficacy of DO on atherosclerosis (AS), and further explore its active components and potential mechanisms. The apolipoprotein-E (ApoE)-deficient mice fed a high-fat diet were used as model animals, and the pathological changes in mice with or without DO treatment were compared to evaluate the pharmacodynamics of DO on AS. The mechanisms were preliminarily expounded by combining with metabolomics and network pharmacology. Moreover, the bioactive components and targets were assessed by cell experiments and molecular docking, respectively. Our findings suggested that DO significantly modulated blood lipid levels and alleviated intimal hyperplasia in atherosclerotic-lesioned mice, and the mechanisms may involve the regulation of 18 metabolites that changed during the progression of AS, thus affecting 3 major metabolic pathways and 3 major signaling pathways. Moreover, the interactions between 16 compounds with anti-proliferative effect and hub targets in the 3 signaling pathways were verified using molecular docking. Collectively, our findings preliminarily support the therapeutic effect of DO in atherosclerosis, meanwhile explore the active constituents and potential pharmacological mechanisms, which is conducive to its reasonable exploitation and utilization.

Circular RNA Gtdc1 Protects Against Offspring Osteoarthritis Induced by Prenatal Prednisone Exposure by Regulating SRSF1-Fn1 Signaling

Chondrodysplasia is closely associated with low birth weight and increased susceptibility to osteoarthritis in adulthood. Prenatal prednisone exposure (PPE) can cause low birth weight; however, its effect on offspring cartilage development remains unexplored. Herein, rats are administered clinical doses of prednisone intragastrically on gestational days (GDs) 0-20 and underwent long-distance running during postnatal weeks (PWs) 24-28. Knee cartilage is assayed for quality and related index changes on GD20, PW12, and PW28. In vitro experiments are performed to elucidate the mechanism. PPE decreased cartilage proliferation and matrix synthesis, causing offspring chondrodysplasia. Following long-distance running, the PPE group exhibited more typical osteoarthritis-like changes. Molecular analysis revealed that PPE caused cartilage circRNomics imbalance in which circGtdc1 decreased most significantly and persisted postnatally. Mechanistically, prednisolone reduced circGtdc1 expression and binding with Srsf1 to promote degradation of Srsf1 via K48-linked polyubiquitination. This further inhibited the formation of EDA/B+Fn1 and activation of PI3K/AKT and TGFβ pathways, reducing chondrocyte proliferation and matrix synthesis. Finally, intra-articular injection of offspring with AAV-circGtdc1 ameliorated PPE-induced chondrodysplasia, but this effect is reversed by Srsf1 knockout. Altogether, this study confirms that PPE causes chondrodysplasia and susceptibility to osteoarthritis by altering the circGtdc1-Srsf1-Fn1 axis; in vivo, overexpression of circGtdc1 can represent an effective intervention target for ameliorating PPE-induced chondrodysplasia.

LncRNA HOTAIR accelerates free fatty acid-induced inflammatory response in HepG2 cells by recruiting SRSF1 to stabilize MLXIPL mRNA

LncRNA HOTAIR has been reported to be associated with metabolic diseases of the liver. However, the effect of HOTAIR on non-alcoholic fatty liver disease (NAFLD) inflammation and its potential mechanism have not been reported. Genes and proteins expression were detected by qRT-PCR and Western blot respectively. The level of inflammatory cytokines was assessed by ELISA. HepG2 cell viability was detected by MTT assay. TG level and lipid accumulation were measured by Assay Kit and Oil red O staining, respectively. Direct binding relationship between HOTAIR and Serine/arginine splicing factor 1 (SRSF1), SRSF1 and MLX interacting protein like (MLXIPL) were confirmed by RNA-pull down and RIP assay. HOTAIR was highly expressed in free fatty acids (FFA)-treated HepG2 cells. HOTAIR knockdown alleviated FFA-induced inflammation of HepG2 cells. Then further analysis showed that HOTAIR and SRSF1 had a mutual binding relationship, and HOTAIR maintained MLXIPL mRNA stability via recruiting SRSF1 in HepG2 cells. Moreover, the inhibitory effect of HOTAIR knockdown on FFA-induced inflammation in HepG2 cells was reversed by MLXIPL overexpression. HOTAIR accelerates inflammation of FFA-induced HepG2 cells by recruiting SRSF1 to stabilize MLXIPL mRNA, which will help to find new effective strategies for NAFLD therapy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-023-00614-x.

p55γ degrades RIP3 via MG53 to suppress ischaemia-induced myocardial necroptosis and mediates cardioprotection of preconditioning

AIMS

Regulated necrosis (necroptosis) and apoptosis are important biological features of myocardial infarction, ischaemia-reperfusion (I/R) injury, and heart failure. However, the molecular mechanisms underlying myocardial necroptosis remain elusive. Ischaemic preconditioning (IPC) is the most powerful intrinsic cardioprotection against myocardial I/R injury. In this study, we aimed to determine whether IPC suppresses I/R-induced necroptosis and the underlying molecular mechanisms.

METHODS AND RESULTS

We generated p55γ transgenic and knockout mice and used ligation of left anterior descending coronary artery to produce an in vivo I/R model. The effects of p55γ and its downstream molecules were subsequently identified using mass spectroscopy and co-immunoprecipitation and pulldown assays. We found that p55γ expression was down-regulated in failing human myocardium caused by coronary heart disease as well as in I/R mouse hearts. Cardiac-specific p55γ overexpression ameliorated the I/R-induced necroptosis. In striking contrast, p55γ deficiency (p55γ-/-) and cardiac-specific deletion of p55γ (p55γc-KO) worsened I/R-induced injury. IPC up-regulated p55γ expression in vitro and in vivo. Using reporter and chromatin immunoprecipitation assays, we found that Hif1α transcriptionally regulated p55γ expression and mediated the cardioprotection of IPC. IPC-mediated suppression of necroptosis was attenuated in p55γ-/- and p55γc-KO hearts. Mechanistically, p55γ overexpression decreased the protein levels of RIP3 rather than the mRNA levels, while p55γ deficiency increased the protein abundance of RIP3. IPC attenuated the I/R-induced up-regulation of RIP3, which was abolished in p55γ-deficient mice. Up-regulation of RIP3 attenuated the p55γ- or IPC-induced inhibition of necroptosis in vivo. Importantly, p55γ directly bound and degraded RIP3 in a ubiquitin-dependent manner. We identified MG53 as the E3 ligase that mediated the p55γ-induced degradation of RIP3. In addition, we also found that p55γ activated the RISK pathway during IPC.

CONCLUSIONS

Our findings reveal that activation of the MG53-RIP3 signal pathway by p55γ protects the heart against I/R-induced necroptosis and underlies IPC-induced cardioprotection.

Nanopore long-read RNA sequencing reveals functional alternative splicing variants in human vascular smooth muscle cells

Vascular smooth muscle cells (VSMCs) are the major contributor to vascular repair and remodeling, which showed high level of phenotypic plasticity. Abnormalities in VSMC plasticity can lead to multiple cardiovascular diseases, wherein alternative splicing plays important roles. However, alternative splicing variants in VSMC plasticity are not fully understood. Here we systematically characterized the long-read transcriptome and their dysregulation in  human aortic smooth muscle cells (HASMCs) by employing the Oxford Nanopore Technologies long-read RNA sequencing in HASMCs that are separately treated with platelet-derived growth factor, transforming growth factor, and hsa-miR-221-3P transfection. Our analysis reveals frequent alternative splicing events and thousands of unannotated transcripts generated from alternative splicing. HASMCs treated with different factors exhibit distinct transcriptional reprogramming modulated by alternative splicing. We also found that unannotated transcripts produce different open reading frames compared to the annotated transcripts. Finally, we experimentally validated the unannotated transcript derived from gene CISD1, namely CISD1-u, which plays a role in the phenotypic switch of HASMCs. Our study characterizes the phenotypic modulation of HASMCs from an insight of long-read transcriptome, which would promote the understanding and the manipulation of HASMC plasticity in cardiovascular diseases.

High-density lipoprotein regulates angiogenesis by long non-coding RNA HDRACA

Normal high-density lipoprotein (nHDL) can induce angiogenesis in healthy individuals. However, HDL from patients with coronary artery disease undergoes various modifications, becomes dysfunctional (dHDL), and loses its ability to promote angiogenesis. Here, we identified a long non-coding RNA, HDRACA, that is involved in the regulation of angiogenesis by HDL. In this study, we showed that nHDL downregulates the expression of HDRACA in endothelial cells by activating WW domain-containing E3 ubiquitin protein ligase 2, which catalyzes the ubiquitination and subsequent degradation of its transcription factor, Kruppel-like factor 5, via sphingosine 1-phosphate (S1P) receptor 1. In contrast, dHDL with lower levels of S1P than nHDL were much less effective in decreasing the expression of HDRACA. HDRACA was able to bind to Ras-interacting protein 1 (RAIN) to hinder the interaction between RAIN and vigilin, which led to an increase in the binding between the vigilin protein and proliferating cell nuclear antigen (PCNA) mRNA, resulting in a decrease in the expression of PCNA and inhibition of angiogenesis. The expression of human HDRACA in a hindlimb ischemia mouse model inhibited the recovery of angiogenesis. Taken together, these findings suggest that HDRACA is involved in the HDL regulation of angiogenesis, which nHDL inhibits the expression of HDRACA to induce angiogenesis, and that dHDL is much less effective in inhibiting HDRACA expression, which provides an explanation for the decreased ability of dHDL to stimulate angiogenesis.

Serine and arginine rich splicing factor 1: a potential target for neuroprotection and other diseases

Alternative splicing is the process of producing variably spliced mRNAs by choosing distinct combinations of splice sites within a messenger RNA precursor. This splicing enables mRNA from a single gene to synthesize different proteins, which have different cellular properties and functions and yet arise from the same single gene. A family of splicing factors, Serine-arginine rich proteins, are needed to initiate the assembly and activation of the spliceosome. Serine and arginine rich splicing factor 1, part of the arginine/serine-rich splicing factor protein family, can either activate or inhibit the splicing of mRNAs, depending on the phosphorylation status of the protein and its interaction partners. Considering that serine and arginine rich splicing factor 1 is either an activator or an inhibitor, this protein has been studied widely to identify its various roles in different diseases. Research has found that serine and arginine rich splicing factor 1 is a key target for neuroprotection, showing its promising potential use in therapeutics for neurodegenerative disorders. Furthermore, serine and arginine rich splicing factor 1 might be used to regulate cancer development and autoimmune diseases. In this review, we highlight how serine and arginine rich splicing factor 1 has been studied concerning neuroprotection. In addition, we draw attention to how serine and arginine rich splicing factor 1 is being studied in cancer and immunological disorders, as well as how serine and arginine rich splicing factor 1 acts outside the central or peripheral nervous system.

RNA-binding proteins in vascular inflammation and atherosclerosis

Atherosclerotic cardiovascular disease (ASCVD) remains the major cause of premature death and disability worldwide, even when patients with an established manifestation of atherosclerotic heart disease are optimally treated according to the clinical guidelines. Apart from the epigenetic control of transcription of the genetic information to messenger RNAs (mRNAs), gene expression is tightly controlled at the post-transcriptional level before the initiation of translation. Although mRNAs are traditionally perceived as the messenger molecules that bring genetic information from the nuclear DNA to the cytoplasmic ribosomes for protein synthesis, emerging evidence suggests that processes controlling RNA metabolism, driven by RNA-binding proteins (RBPs), affect cellular function in health and disease. Over the recent years, vascular endothelial cell, smooth muscle cell and immune cell RBPs have emerged as key co- or post-transcriptional regulators of several genes related to vascular inflammation and atherosclerosis. In this review, we provide an overview of cell-specific function of RNA-binding proteins involved in all stages of ASCVD and how this knowledge may be used for the development of novel precision medicine therapeutics.

KLF5 and p53 comprise an incoherent feed-forward loop directing cell-fate decisions following stress

In response to stress, cells make a critical decision to arrest or undergo apoptosis, mediated in large part by the tumor suppressor p53. Yet the mechanisms of these cell fate decisions remain largely unknown, particularly in normal cells. Here, we define an incoherent feed-forward loop in non-transformed human squamous epithelial cells involving p53 and the zinc-finger transcription factor KLF5 that dictates responses to differing levels of cellular stress from UV irradiation or oxidative stress. In normal unstressed human squamous epithelial cells, KLF5 complexes with SIN3A and HDAC2 repress TP53, allowing cells to proliferate. With moderate stress, this complex is disrupted, and TP53 is induced; KLF5 then acts as a molecular switch for p53 function by transactivating AKT1 and AKT3, which direct cells toward survival. By contrast, severe stress results in KLF5 loss, such that AKT1 and AKT3 are not induced, and cells preferentially undergo apoptosis. Thus, in human squamous epithelial cells, KLF5 gates the response to UV or oxidative stress to determine the p53 output of growth arrest or apoptosis.

Dysregulation of alternative splicing contributes to multiple myeloma pathogenesis

BACKGROUND

Dysregulation of alternative splicing (AS) triggers many tumours, understanding the roles of splicing events during tumorigenesis would open new avenues for therapies and prognosis in multiple myeloma (MM).

METHODS

Molecular, genetic, bioinformatic and statistic approaches are used to determine the mechanism of the candidate splicing factor (SF) in myeloma cell lines, myeloma xenograft models and MM patient samples.

RESULTS

GSEA reveals a significant difference in the expression pattern of the alternative splicing pathway genes, notably enriched in MM patients. Upregulation of the splicing factor SRSF1 is observed in the progression of plasma cell dyscrasias and predicts MM patients' poor prognosis. The c-indices of the Cox model indicated that SRSF1 improved the prognostic stratification of MM patients. Moreover, SRSF1 knockdown exerts a broad anti-myeloma activity in vitro and in vivo. The upregulation of SRSF1 is caused by the transcription factor YY1, which also functions as an oncogene in myeloma cells. Through RNA-Seq, we systematically verify that SRSF1 promotes the tumorigenesis of myeloma cells by switching AS events.

CONCLUSION

Our results emphasise the importance of AS for promoting tumorigenesis of MM. The candidate SF might be considered as a valuable therapeutic target and a potential prognostic biomarker for MM.

Participation of Krüppel-like Factors in Atherogenesis

Atherosclerosis is an important problem in modern medicine, the keys to understanding many aspects of which are still not available to clinicians. Atherosclerosis develops as a result of a complex chain of events in which many cells of the vascular wall and peripheral blood flow are involved. Endothelial cells, which line the vascular wall in a monolayer, play an important role in vascular biology. A growing body of evidence strengthens the understanding of the multifaceted functions of endothelial cells, which not only organize the barrier between blood flow and tissues but also act as regulators of hemodynamics and play an important role in regulating the function of other cells in the vascular wall. Krüppel-like factors (KLFs) perform several biological functions in various cells of the vascular wall. The large family of KLFs in humans includes 18 members, among which KLF2 and KLF4 are at the crossroads between endothelial cell mechanobiology and immunometabolism, which play important roles in both the normal vascular wall and atherosclerosis.

The role of truncated p53 isoforms in the DNA damage response

The tumour suppressor p53 is activated following genotoxic stress and regulates the expression of target genes involved in the DNA damage response (DDR). The discovery that p53 isoforms alter the transcription of p53 target genes or p53 protein interactions unveiled an alternative DDR. This review will focus on the role p53 isoforms play in response to DNA damage. The expression of the C-terminally truncated p53 isoforms may be modulated via DNA damage-induced alternative splicing, whereas alternative translation plays an important role in modulating the expression of N-terminally truncated isoforms. The DDR induced by p53 isoforms may enhance the canonical p53 DDR or block cell death mechanisms in a DNA damage- and cell-specific manner, which could contribute to chemoresistance in a cancer context. Thus, a better understanding of the involvement of p53 isoforms in the cell fate decisions could uncover potential therapeutic targets in cancer and other diseases.

Splicing factor SRSF1 deficiency in the liver triggers NASH-like pathology and cell death

Regulation of RNA processing contributes profoundly to tissue development and physiology. Here, we report that serine-arginine-rich splicing factor 1 (SRSF1) is essential for hepatocyte function and survival. Although SRSF1 is mainly known for its many roles in mRNA metabolism, it is also crucial for maintaining genome stability. We show that acute liver damage in the setting of targeted SRSF1 deletion in mice is associated with the excessive formation of deleterious RNA-DNA hybrids (R-loops), which induce DNA damage. Combining hepatocyte-specific transcriptome, proteome, and RNA binding analyses, we demonstrate that widespread genotoxic stress following SRSF1 depletion results in global inhibition of mRNA transcription and protein synthesis, leading to impaired metabolism and trafficking of lipids. Lipid accumulation in SRSF1-deficient hepatocytes is followed by necroptotic cell death, inflammation, and fibrosis, resulting in NASH-like liver pathology. Importantly, SRSF1-depleted human liver cancer cells recapitulate this pathogenesis, illustrating a conserved and fundamental role for SRSF1 in preserving genome integrity and tissue homeostasis. Thus, our study uncovers how the accumulation of detrimental R-loops impedes hepatocellular gene expression, triggering metabolic derangements and liver damage.

IL-13 alleviates idiopathic pulmonary hypertension by inhibiting the proliferation of pulmonary artery smooth muscle cells and regulating macrophage infiltration

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is characterized by medial hypertrophy due to pulmonary artery smooth muscle cell (PASMC) hyperplasia. In the present study, we conducted bioinformatic analyses and cellular experiments to assess the involvement of the interleukin-13 (IL-13) in IPAH.

METHODS

The differentially expressed genes (DEGs) in IPAH and DEGs in IPAH caused by IL-13 treatment were screened using the GEO database. PPI networks were used to analyze the hub genes. Hypoxia-induced PASMCs were treated with IL-13 for in vitro assays. CCK8 and EdU staining were used to observe proliferation of PASMCs, and RT-qPCR was applied to detect the expression of hub genes. The conserved binding sites of microRNAs (miRNAs) in the 3'UTR of hub genes were investigated, and the regulatory relationships of the relevant miRNAs on their targets were verified by RT-qPCR and dual-luciferase assays. The GO and KEGG analyses were performed to study the downstream pathways. The effect of hub genes on immune cell infiltration in IPAH was investigated.

RESULTS

IL-13 altered gene expression in IPAH. IL-13 inhibited the proliferation and the expression of hub genes in PASMCs. The 3'UTR sites between HNRNPA2B1, HNRNPH1, SRSF1, HNRNPU and HNRNPA3 in the hub genes and candidate regulatory miRNAs were well conserved in humans. IL-13-mediated hub genes regulated multiple pathways and influenced immune cell infiltration. Hypoxia-induced PASMCs promoted the M2 polarization of macrophages, whereas IL-13-treated PASMCs skewed the macrophages toward M1 polarization.

CONCLUSIONS

IL-13-mediated alterations in hub genes inhibit PASMC proliferation and promote M1 macrophage infiltration in IPAH.

Induction of GLI1 by miR-27b-3p/FBXW7/KLF5 pathway contributes to pulmonary arterial hypertension

Glioma-associated oncogene homolog 1 (GLI1), a zinc-finger transcription factor, is upregulated in tumors and promotes cancer cell proliferation and migration. However, whether GLI1 involves in pulmonary artery smooth muscle cells (PASMCs) proliferation and migration and the detailed molecular mechanisms underlying GLI1 in pulmonary arterial hypertension (PAH) are not yet clear. Primary cultured rat PASMCs and monocrotaline (MCT)-induced PAH rats model were applied to address these issues in the present study. We found that the expression of GLI1 was significantly increased in endothelin-1 (ET-1) treated PASMCs, accompanied with the activation of microRNA (miR)-27b-3p/F-box and WD repeat domain containing 7 (FBXW7)/kruppel-like factor 5 (KLF5)/GLI1 pathway through endothelin-1 receptor type A (ETAR). Elevated miR-27b-3p suppressed FBXW7 expression, which led to KLF5 accumulation by decreasing its ubiquitinated degradation, KLF5 further induced GLI1 upregulation leading to PASMCs proliferation and migration. In addition, in MCT-induced PAH rats, targeting ETAR/miR-27b-3p/FBXW7/KLF5/GLI1 pathway effectively prevented the pulmonary vascular remodeling and the development of PAH in rats. Our study indicates that interfering ETAR/miR-27b-3p/FBXW7/KLF5/GLI1 signaling axis might have a potential value in the prevention and treatment of PAH.

In leukemia, knock-down of the death inducer-obliterator gene would inhibit the proliferation of endothelial cells by inhibiting the expression of CDK6 and CCND1

BACKGROUND

Endothelial cells (ECs) are a critical component of the hematopoietic niche, and the cross-talk between ECs and leukemia was reported recently. This study aimed to determine the genes involved in the proliferation inhibition of endothelial cells in leukemia.

METHODS

Human umbilical vein endothelial cells (HUVEC) were cultured alone or co-cultured with K562 cell lines. GeneChip assays were performed to identify the differentially expressed genes. The Celigo, MTT assay, and flow cytometric analysis were used to determine the effect of RNAi DIDO on cell growth and apoptosis. The differently expressed genes were verified by qRT-PCR (quantitative real-time PCR) and western-blot.

RESULTS

In K562-HUVEC co-cultured cell lines, 323 down-regulated probes were identified and the extracellular signal-regulated kinase 5 (ERK5) signaling pathway was significantly inhibited. Among the down-regulated genes, the death inducer-obliterator gene (DIDO) is a part of the centrosome protein and may be involved in cell mitosis. As shown in the public data, leukemia patients with lower expression of DIDO showed a better overall survival (OS). The HUVEC cells were infected with shDIDO lentivirus, and reduced expression, inhibited proliferation, and increased apoptosis was observed in shDIDO cells. In addition, the expression of Cyclin-Dependent Kinase 6 (CDK6) and Cyclin D1 (CCND1) genes was inhibited in shDIDO cells. Finally, the public ChIP-seq data were used to analyze the regulators that bind with DIDO, and the H3K4me3 and PolII (RNA polymerase II) signals were found near the Exon1 and exon2 sites of DIDO.

CONCLUSION

The knock-down of DIDO will inhibit the proliferation of endothelial cells in the leukemia environment. The expression of DIDO may be regulated by H3K4me3 and the inhibition of DIDO may lead to the down-regulation of CDK6 and CCND1. However, how DIDO interacts with CDK6 and CCND1 requires further study.

Circular RNA circEsyt2 regulates vascular smooth muscle cell remodeling via splicing regulation

Circular RNAs (circRNAs) have been recently recognized as playing a role in the pathogenesis of vascular remodeling-related diseases by modulating the functions of miRNAs. However, the interplay between circRNAs and proteins during vascular remodeling remains poorly understood. Here, we investigated a previously identified circRNA, circEsyt2, whose expression is known to be upregulated during vascular remodeling. Loss- and gain-of‑function mutation analyses in vascular smooth muscle cells (VSMCs) revealed that circEsyt2 enhanced cell proliferation and migration and inhibited apoptosis and differentiation. Furthermore, the silencing of circEsyt2 in vivo reduced neointima formation, while circEsyt2 overexpression enhanced neointimal hyperplasia in the injured carotid artery, confirming its role in vascular remodeling. Using unbiased protein-RNA screening and molecular validation, circEsyt2 was found to directly interact with polyC-binding protein 1 (PCBP1), an RNA splicing factor, and regulate PCBP1 intracellular localization. Additionally, circEsyt2 silencing substantially enhanced p53β splicing via the PCBP1-U2AF65 interaction, leading to the altered expression of p53 target genes (cyclin D1, p21, PUMA, and NOXA) and the decreased proliferation of VSMCs. Thus, we identified a potentially novel circRNA that regulated vascular remodeling, via altered RNA splicing, in atherosclerotic mouse models.

Adaptive homeostasis and the p53 isoform network

All living organisms have developed processes to sense and address environmental changes to maintain a stable internal state (homeostasis). When activated, the p53 tumour suppressor maintains cell and organ integrity and functions in response to homeostasis disruptors (stresses) such as infection, metabolic alterations and cellular damage. Thus, p53 plays a fundamental physiological role in maintaining organismal homeostasis. The TP53 gene encodes a network of proteins (p53 isoforms) with similar and distinct biochemical functions. The p53 network carries out multiple biological activities enabling cooperation between individual cells required for long‐term survival of multicellular organisms (animals) in response to an ever‐changing environment caused by mutation, infection, metabolic alteration or damage. In this review, we suggest that the p53 network has evolved as an adaptive response to pathogen infections and other environmental selection pressures.

Serum from Patients with Severe Alcoholic Liver Cirrhosis Inhibits Proliferation and Migration of Human Coronary Artery Smooth Muscle Cells

Liver cirrhosis has been associated with an increased risk of coronary artery disease and clinical complications following percutaneous coronary revascularization. The present study is based on the hypothesis that cirrhosis may influence intimal hyperplasia following PCI. Sera from 10 patients with alcoholic liver cirrhosis and 10 age-matched healthy controls were used to stimulate cultured human coronary artery smooth muscle cells (HCASMC) for 48 h. HCASMC proliferation, migration, gene expression and apoptosis were investigated. Serum concentrations of growth factors and markers of liver function were also determined in patients and healthy controls. Treatment of HCASMC with patient sera reduced cell proliferation and migration (p < 0.05 vs. healthy controls), whereas apoptosis was unaffected (p = 0.160). Expression of genes associated with a synthetic vascular smooth muscle cell phenotype was decreased in cells stimulated with serum from cirrhotic patients (RBP1, p = 0.001; SPP1, p = 0.003; KLF4, p = 0.004). Platelet-derived growth factor-BB serum concentrations were lower in patients (p = 0.001 vs. controls). The results suggest the presence of circulating factors in patients with alcoholic liver cirrhosis affecting coronary smooth muscle cell growth. These findings may have implications for clinical outcomes following percutaneous coronary revascularization in these patients.

Long Noncoding RNA MIAT Controls Advanced Atherosclerotic Lesion Formation and Plaque Destabilization

Supplemental Digital Content is available in the text.

Long noncoding RNAs (lncRNAs) are important regulators of biological processes involved in vascular tissue homeostasis and disease development. The present study assessed the functional contribution of the lncRNA myocardial infarction-associated transcript (MIAT) to atherosclerosis and carotid artery disease.

The Expanding Role of Alternative Splicing in Vascular Smooth Muscle Cell Plasticity

Vascular smooth muscle cells (VSMCs) display extraordinary phenotypic plasticity. This allows them to differentiate or dedifferentiate, depending on environmental cues. The ability to ‘switch’ between a quiescent contractile phenotype to a highly proliferative synthetic state renders VSMCs as primary mediators of vascular repair and remodelling. When their plasticity is pathological, it can lead to cardiovascular diseases such as atherosclerosis and restenosis. Coinciding with significant technological and conceptual innovations in RNA biology, there has been a growing focus on the role of alternative splicing in VSMC gene expression regulation. Herein, we review how alternative splicing and its regulatory factors are involved in generating protein diversity and altering gene expression levels in VSMC plasticity. Moreover, we explore how recent advancements in the development of splicing-modulating therapies may be applied to VSMC-related pathologies.

Valsartan Prevented Neointimal Hyperplasia and Inhibited SRSF1 Expression and the TLR4-iNOS-ERK-AT1 Receptor Pathway in the Balloon-injured Rat Aorta

Valsartan has the potential to attenuate neointimal hyperplasia and to suppress the inflammatory response. This study aimed to evaluate the role of valsartan in neointimal hyperplasia and the toll-like receptor 4 (TLR4)-nitric oxide synthase (NOS) pathway in the balloon-injured rat aorta.Forty-eight Wistar rats were randomly allocated to three groups: sham control (control), balloon-injured group (surgery), and balloon-injured+valsartan-treated group (valsartan). Rats were killed at 14 and 28 days after balloon-injury, and then the aortic tissues were collected for morphometric analysis as well as for measurements of the mRNA or protein expression of angiotensin II, angiotensin II type 1 (AT1) receptor, angiotensin II type 2 (AT2) receptor, TLR4, endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), serine/arginine-rich splicing factor 1(SRSF1) and extracellular signal regulated kinase (ERK). Valsartan at a dose of 20 mg/kg/day markedly decreased neointimal hyperplasia in the aorta of balloon-injured rats, and significantly reduced the mRNA or protein expression of TLR4, AT1 receptor, SRSF1 and phosphorylated-ERK (p-ERK) as well as the aortic levels of iNOS (all p < 0.05). Moreover, valsartan increased the eNOS level and AT2 receptor mRNA and protein expression levels (all p < 0.05). Valsartan prevented neointimal hyperplasia and inhibited SRSF1 expression and the TLR4-iNOS-ERK-AT1 receptor pathway in the balloon-injured rat aorta.

Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) accelerates vascular remodelling via p53 and JAK2-STAT3 regulation in vascular smooth muscle cells

BACKGROUND AND PURPOSE

Abnormal vascular smooth muscle cell (VSMC) proliferation and migration lead to neointima formation, which eventually results in cardiovascular hyperplastic diseases. The molecular mechanisms underlying these cellular processes have not been fully understood. Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) has been identified as an anti-apoptotic molecule, but little is known about its target genes and related pathways in VSMC dysfunction or its clinical implication in neointima formation following vascular injury.

EXPERIMENTAL APPROACH

Determination, using loss/gain-of-function approaches by gene delivery, of whether CIAPIN1 modulates VSMC proliferation, migration and neointima formation and the underlying mechanisms was carried out. Balloon injury or ligation and local delivery of lentivirus were performed on rat or mouse carotid arteries. Rat aortic smooth muscle cells, the primary cell, was used as the model to evaluate the effect of CIAPIN1 on proliferation and migration.

KEY RESULTS

CIAPIN1 was overexpressed in the neointimal region of rat arteries. CIAPIN1 deficiency markedly inhibited injury-induced or ligation-induced intimal hyperplasia and suppressed PDGF-BB-induced VSMC proliferation, migration and cell cycle progression, while overexpression promoted proliferation, migration and neointima formation. CIAPIN1 negatively regulated Tp53 transcription, which promoted cell cycle progression and migration via cyclin E1-CDK2/pRb/PCNA and the MMP2 pathway. CIAPIN1 also increased JAK2 expression, enhancing JAK2 and STAT3 phosphorylation by vascular injury, which forced phenotypic switching from contractile to synthetic state in injured arteries.

CONCLUSIONS AND IMPLICATIONS

These findings provide new insights into the mechanism by which CIAPIN1 regulates vascular remodelling and suggest a novel therapeutic target for treating vascular proliferative diseases.

LncRNA GASAL1 Interacts with SRSF1 to Regulate Trophoblast Cell Proliferation, Invasion, and Apoptosis Via the mTOR Signaling Pathway

Long noncoding RNAs (lncRNAs) are crucial regulatory molecules involved in diverse biological processes and human diseases, including preeclampsia (PE). The lncRNA growth arrest associated lncRNA 1 (GASAL1) has been implicated in multiple malignant solid tumors and other diseases, while it is poorly known as the potential molecular mechanism of GASAL1 in PE. In this study, GASAL1 was significantly downregulated in the placentas' of tissues from primipara with PE and trophoblast cell lines. Then, the upregulation of GASAL1 dramatically decreased proliferation and invasion and enhanced apoptosis in HTR-8/SVneo and JAR cells. Bioinformatics tool predicated that there is a potential interaction between GASAL1 and serine/arginine splicing factor 1 (SRSF1). RNA pull-down assays showed that GASAL1 directly binds with SRSF1 that could promote cell proliferation and invasion and suppress cell apoptosis. Further research showed that promoting effects of trophoblasts proliferation and invasion caused by co-transfecting GASAL1 and SRSF1 into HTR-8/SVneo and JAR cells were impaired by SRSF1 knockdown. Moreover, inhibition of the mammalian target of rapamycin (mTOR) activity by rapamycin influenced the effects of GASAL1 on cell proliferation, invasion, and apoptosis. Taken together, these findings suggest that lncRNA GASAL1 interacts with SRSF1 to regulate the proliferative, invasive, and apoptotic abilities of trophoblast cells via the mTOR signaling pathway.

Aralia armata (Wall.) Seem Improves Intimal Hyperplasia after Vascular Injury by Downregulating the Wnt3α/Dvl-1/β-Catenin Pathway

The aim of the study is to examine the mechanism of Aralia armata (Wall.) Seem (AAS) in improving intimal hyperplasia after vascular injury in rats. Rats with femoral artery injury were randomly divided into three groups: the model group, AAS low-dose group (40 mg/kg), and AAS high-dose group (80 mg/kg). The sham operation group was used as a control group. HE staining was used to observe the changes in femoral artery vessels. Immunohistochemistry was adopted to detect α-SMA, PCNA, GSK-3β, and β-catenin proteins in femoral artery tissue. The CCK-8 test and wound healing assay were employed to analyze the effect of AAS on proliferation and migration of vascular smooth muscle cells (VSMCs) cultured in vitro. Western blotting (WB) and polymerase chain reaction (PCR) assays were used to evaluate the molecular mechanism. AAS reduced the stenosis of blood vessels and the protein expressions of α-SMA, PCNA, GSK-3β, and β-catenin compared to the model group. In addition, AAS (0-15 μg/mL) effectively inhibited the proliferation and migration of VSMCs. Moreover, the results of WB and PCR showed that AAS could inhibit the activation of β-catenin induced by 15% FBS and significantly decrease the expression levels of Wnt3α, Dvl-1, GSK-3β, β-catenin, and cyclin D1 in the upstream and downstream of the pathway. AAS could effectively inhibit the proliferation and migration of neointima after vascular injury in rats by regulating the Wnt/β-catenin signaling pathway.

Ablation of lncRNA Miat attenuates pathological hypertrophy and heart failure

Rationale: The conserved long non-coding RNA (lncRNA) myocardial infarction associate transcript (Miat) was identified for its multiple single-nucleotide polymorphisms that are strongly associated with susceptibility to MI, but its role in cardiovascular biology remains elusive. Here we investigated whether Miat regulates cardiac response to pathological hypertrophic stimuli. Methods: Both an angiotensin II (Ang II) infusion model and a transverse aortic constriction (TAC) model were used in adult WT and Miat-null knockout (Miat-KO) mice to induce pathological cardiac hypertrophy. Heart structure and function were evaluated by echocardiography and histological assessments. Gene expression in the heart was evaluated by RNA sequencing (RNA-seq), quantitative real-time RT-PCR (qRT-PCR), and Western blotting. Primary WT and Miat-KO mouse cardiomyocytes were isolated and used in Ca²⁺ transient and contractility measurements. Results: Continuous Ang II infusion for 4 weeks induced concentric hypertrophy in WT mice, but to a lesser extent in Miat-KO mice. Surgical TAC for 6 weeks resulted in decreased systolic function and heart failure in WT mice but not in Miat-KO mice. In both models, Miat-KO mice displayed reduced heart-weight to tibia-length ratio, cardiomyocyte cross-sectional area, cardiomyocyte apoptosis, and cardiac interstitial fibrosis and a better-preserved capillary density, as compared to WT mice. In addition, Ang II treatment led to significantly reduced mRNA and protein expression of the Ca²⁺ cycling genes Sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a (SERCA2a) and ryanodine receptor 2 (RyR2) and a dramatic increase in global RNA splicing events in the left ventricle (LV) of WT mice, and these changes were largely blunted in Miat-KO mice. Consistently, cardiomyocytes isolated from Miat-KO mice demonstrated more efficient Ca²⁺ cycling and greater contractility. Conclusions: Ablation of Miat attenuates pathological hypertrophy and heart failure, in part, by enhancing cardiomyocyte contractility.

p53/p73 Protein Network in Colorectal Cancer and Other Human Malignancies

Simple Summary

The p53 family of proteins comprises p53, p63, and p73, which share high structural and functional similarity. The two distinct promoters of each locus, the alternative splicing, and the alternative translation initiation sites enable the generation of numerous isoforms with different protein-interacting domains and distinct activities. The co-expressed p53/p73 isoforms have significant but distinct roles in carcinogenesis. Their activity is frequently impaired in human tumors including colorectal carcinoma due to dysregulated expression and a dominant-negative effect accomplished by some isoforms and p53 mutants. The interactions between isoforms are particularly important to understand the onset of tumor formation, progression, and therapeutic response. The understanding of the p53/p73 network can contribute to the development of new targeted therapies.

Abstract

The p53 tumor suppressor protein is crucial for cell growth control and the maintenance of genomic stability. Later discovered, p63 and p73 share structural and functional similarity with p53. To understand the p53 pathways more profoundly, all family members should be considered. Each family member possesses two promoters and alternative translation initiation sites, and they undergo alternative splicing, generating multiple isoforms. The resulting isoforms have important roles in carcinogenesis, while their expression is dysregulated in several human tumors including colorectal carcinoma, which makes them potential targets in cancer treatment. Their activities arise, at least in part, from the ability to form tetramers that bind to specific DNA sequences and activate the transcription of target genes. In this review, we summarize the current understanding of the biological activities and regulation of the p53/p73 isoforms, highlighting their role in colorectal tumorigenesis. The analysis of the expression patterns of the p53/p73 isoforms in human cancers provides an important step in the improvement of cancer therapy. Furthermore, the interactions among the p53 family members which could modulate normal functions of the canonical p53 in tumor tissue are described. Lastly, we emphasize the importance of clinical studies to assess the significance of combining the deregulation of different members of the p53 family to define the outcome of the disease.

Matrix stiffening induces a pathogenic QKI-miR-7-SRSF1 signaling axis in pulmonary arterial endothelial cells

Pulmonary arterial hypertension (PAH) refers to a set of heterogeneous vascular diseases defined by elevation of pulmonary arterial pressure (PAP) and pulmonary vascular resistance (PVR), leading to right ventricular (RV) remodeling and often death. Early increases in pulmonary artery stiffness in PAH drive pathogenic alterations of pulmonary arterial endothelial cells (PAECs), leading to vascular remodeling. Dysregulation of microRNAs can drive PAEC dysfunction. However, the role of vascular stiffness in regulating pathogenic microRNAs in PAH is incompletely understood. Here, we demonstrated that extracellular matrix (ECM) stiffening downregulated miR-7 levels in PAECs. The RNA-binding protein quaking (QKI) has been implicated in the biogenesis of miR-7. Correspondingly, we found that ECM stiffness upregulated QKI, and QKI knockdown led to increased miR-7. Downstream of the QKI-miR-7 axis, the serine and arginine-rich splicing factor 1 (SRSF1) was identified as a direct target of miR-7. Correspondingly, SRSF1 was reciprocally upregulated in PAECs exposed to stiff ECM and was negatively correlated with miR-7. Decreased miR-7 and increased QKI and SRSF1 were observed in lungs from patients with PAH and PAH rats exposed to SU5416/hypoxia. Lastly, miR-7 upregulation inhibited human PAEC migration, whereas forced SRSF1 expression reversed this phenotype, proving that miR-7 depended upon SRSF1 to control migration. In aggregate, these results define the QKI-miR-7-SRSF1 axis as a mechanosensitive mechanism linking pulmonary arterial vascular stiffness to pathogenic endothelial function. These findings emphasize implications relevant to PAH and suggest the potential benefit of developing therapies that target this miRNA-dependent axis in PAH.

Regulation of autophagy by controlling Erk1/2 and mTOR for platelet-derived growth factor-BB-mediated vascular smooth muscle cell phenotype shift

AIMS

Vascular smooth muscle cell (VSMC) phenotype shift is involved in the pathophysiology of vascular injury or platelet-derived growth factor (PDGF)-induced abnormal proliferation and migration of VSMCs. We aimed to investigate the underlying mechanism involved in PDGF-mediated signaling pathways and autophagy regulation followed by VSMC phenotype shift.

MAIN METHODS

The proliferation, migration and apoptosis of cultured rat aortic VSMCs were measured, and cells undergoing phenotype shift and autophagy were examined. Specific inhibitors for target proteins in signaling pathways were applied to clarify their roles in regulating cell functions.

KEY FINDINGS

PDGF-BB stimulation initiated autophagy activation and synthetic phenotype transition by decreasing α-smooth muscle-actin (SMA), calponin and myosin heavy chain (MHC) and increasing osteopontin (OPN) expression. However, U0126, a potent extracellular signal-regulated kinase 1/2 (Erk1/2) inhibitor, decreased PDGF-BB-induced LC3 expression, while rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), increased it. Furthermore, U0126 decreased the expresseion of autophagy-related genes (Atgs) such as beclin-1, Atg7, Atg5, and Atg12-Atg5 complex, indicating that Erk1/2 is a regulator of PDGF-BB-induced VSMC autophagy. Regardless of autophagy inhibition by U0126 or activation by rapamycin, the PDGF-BB-induced decrease in SMA, calponin and MHC and increase in OPN expression were inhibited. Furthermore, PDGF-BB-stimulated VSMC proliferation, migration and proliferating cell nuclear antigen (PCNA) expression were inhibited by U0126 and rapamycin.

SIGNIFICANCE

These findings suggest that PDGF-BB-induced autophagy is strongly regulated by Erk1/2, an mTOR-independent pathway, and any approach for targeting autophagy modulation is a potential therapeutic strategy for addressing abnormal VSMC proliferation and migration.

The splicing factor SRSF1 stabilizes the mRNA of TSLP to enhance acute lung injury

Acute lung injury (ALI) is a severe disease with a high rate of morbidity and mortality, characterized by excessive and uncontrolled inflammatory response in lung. Recent studies demonstrated that serine arginine-rich splicing factor 1 (SRSF1) is involved in inflammation. However, whether SRSF1 modulates ALI remains to be determined. In this study, we established an ALI mouse model that induced by lipopolysaccharide (LPS), with or without the treatment of SRSF1 antibody. Our result showed that SRSF1 expression was elevated in LPS-induced ALI. Importantly, treatment with SRSF1 antibody notably ameliorated ALI in mice, as determined by reduction in lung W/D ratios, histopathological changes, lung inflammation and TSLP expression. Besides, exposure of human alveolar epithelial A549 cells to LPS enhanced the expression of both SRSF1 and TSLP, while knockdown or overexpression of SRSF1 significantly lowered or upregulated the expression of TSLP induced by LPS. Interestingly, the expression of SRSF1 and TSLP showed a positive correlation in normal human lung tissues. Mechanistically, we found that SRSF1 directly bound with the mRNA of TSLP and may exert its function by stabilizing the mRNA of TSLP in LPS-induced ALI. Therefore, our results indicated that SRSF1 may be an important contributor in lung inflammation of LPS-induced ALI and SRSF1 signaling blocking may serve as a potential treatment of ALI.

Current knowledge of Krüppel-like factor 5 and vascular remodeling: providing insights for therapeutic strategies

Vascular remodeling is a pathological basis of various disorders. Therefore, it is necessary to understand the occurrence, prevention, and treatment of vascular remodeling. Krüppel-like factor 5 (KLF5) has been identified as a significant factor in cardiovascular diseases during the last two decades. This review provides a mechanism network of function and regulation of KLF5 in vascular remodeling based on newly published data and gives a summary of its potential therapeutic applications. KLF5 modulates numerous biological processes, which play essential parts in the development of vascular remodeling, such as cell proliferation, phenotype switch, extracellular matrix deposition, inflammation, and angiogenesis by altering downstream genes and signaling pathways. Considering its essential functions, KLF5 could be developed as a potent therapeutic target in vascular disorders.

An Overview of Vascular Dysfunction and Determinants: The Case of Children of African Ancestry

The balance between dilatory and constrictive factors is important as it keeps blood vessels in a homeostatic state. However, altered physiological processes as a result of obesity, hypertension, oxidative stress, and other cardiovascular risk factors may lead to vascular damage, causing an imbalance of vasoactive factors. Over time, the sustained imbalance of these vasoactive factors may lead to vascular dysfunction, which can be assessed by non-invasive methods, such as flow-mediated dilation, pulse wave velocity, flow-mediated slowing, retinal vessel analysis, peripheral vascular reactivity, and carotid intima-media thickness assessment. Although there is increasing prevalence of cardiovascular risk factors (obesity and hypertension) in children in sub-Saharan Africa, little is known about how this may affect vascular function. This review focuses on vasoactive factors implicated in vascular (dys)function, highlighting the determinants and consequences of vascular dysfunction. It further describes the non-invasive methods used for vascular (dys)function assessments and, last, describes the impact of cardiovascular risk factors on vascular dysfunction in children of African ancestry.

Curcumol inhibits KLF5-dependent angiogenesis by blocking the ROS/ERK signaling in liver sinusoidal endothelial cells

AIMS

Liver fibrosis is a difficult problem in the medical field. We previously reported that curcumol, a bioactive substance, may inhibit the pathological angiogenesis of liver sinusoidal endothelial cells (LSECs) and play a good anti-hepatic fibrosis effect. However, the mechanism of curcumol inhibiting angiogenesis in LSEC needs to be further clarified. Here, we focus on how curcumol inhibits LSEC angiogenesis in liver fibrosis.

MATERIALS AND METHODS

Primary rat LSECs were cultured in vitro, and various molecular experiments including real-time PCR, western blot, immunofluorescence, tube formation assay and transwell migration assay were used to clarify the potential mechanism of curcumol. Carbon tetrachloride (CCl4) was applied to create a mouse liver fibrosis model. Blood and livers were taken to elucidate the efficacy of curcumol in vivo.

KEY FINDINGS

We found that curcumol could effectively inhibit LSEC angiogenesis in vitro. Interestingly, this process may depend on curcumol's inhibition of the expression of transcription factor KLF5. Mice experiment also showed that curcumol could alleviate chronic liver injury by reducing KLF5 expression. In addition, we suggested that curcumol could reduce the production of mitochondrial ROS and improve mitochondrial morphology in LSEC. More importantly, we proved that curcumol could suppress KLF5-mediated LSEC angiogenesis by inhibiting ROS/ERK signaling.

SIGNIFICANCE

We suggested that transcription factor KLF5 could be considered as a new target molecule of curcumol in improving liver fibrosis, and pointed out that curcumol targeted ROS/ERK-mediated KLF5 expression could inhibit LSEC angiogenesis. This provided a new theoretical basis for curcumol to ameliorate liver fibrosis.

Alternative splicing in endothelial cells: novel therapeutic opportunities in cancer angiogenesis

Alternative splicing (AS) is a pervasive molecular process generating multiple protein isoforms, from a single gene. It plays fundamental roles during development, differentiation and maintenance of tissue homeostasis, while aberrant AS is considered a hallmark of multiple diseases, including cancer. Cancer-restricted AS isoforms represent either predictive biomarkers for diagnosis/prognosis or targets for anti-cancer therapies. Here, we discuss the contribution of AS regulation in cancer angiogenesis, a complex process supporting disease development and progression. We consider AS programs acting in a specific and non-redundant manner to influence morphological and functional changes involved in cancer angiogenesis. In particular, we describe relevant AS variants or splicing regulators controlling either secreted or membrane-bound angiogenic factors, which may represent attractive targets for therapeutic interventions in human cancer.

Identification of a novel and potent small molecule inhibitor of SRPK1: mechanism of dual inhibition of SRPK1 for the inhibition of cancer progression

Protein kinases are the family of attractive enzyme targets for drug design with relevance to cancer biology. Serine arginine protein kinase 1 (SRPK1) is responsible for the phosphorylation of serine/arginine (SR)-rich proteins. Alternative Splicing Factor/Splicing Factor 2 (ASF/SF2) involved in mRNA editing. ASF/SF2 is over expressed in many cancers and plays crucial roles in the cell survival. Phosphorylation of ASF/SF2 is decisive for its functions in cancer. In search of potential anticancer therapeutic agents for attenuating phosphorylation of ASF/SF2, we have explored specific and potential inhibitors of SRPK1 from natural and drug like compounds databases using in-silico methods. Compound ZINC02154892 (C02) was found to be the most potent inhibitor for SRPK1. In-vitro molecular and cell biology studies have shown C02 as a potent and specific inhibitor of phosphorylation of ASF/SF2 and cell survival in leukemic cell line. Structural analysis of SRPK1 with compound C02 revealed a unique pattern of binding targeting ATP binding site along with inhibiting recruitment of ASF/SF2 by SRPK1. The possibilities of compound C02 to be used as a lead compound paving way for the development of potent and specific inhibitors of SRPK1 for designing of novel potential anticancer inhibitor is inferred from the current studies.

Vascular Smooth Muscle FTO Promotes Aortic Dissecting Aneurysms via m6A Modification of Klf5

Background: Aortic dissecting aneurysm (ADA) represents an aortic remodeling disease with a high mortality rate. Fat mass and obesity-associated protein (FTO) exerts RNA demethylation function to regulate gene expression related to stem cell differentiation, DNA damage repair, and tumorigenesis, but the role of FTO in ADA is still unclear.

Methods: The expression and location of FTO in 43 ADA tissues and 11 normal tissues were determined by RT-qPCR, WB, immunohistochemistry, and immunofluorescence staining. Detecting proliferation and migration of VSMCs. M6A methylated RNA immuno-precipitation qRT-PCR and dual luciferase reporter assay were performed for determining m6A level and interaction between m6A modulation and Klf5 mRNA, respectively.

Results: FTO are highly expressed in VSMCs. FTO was positively correlated with BMI, triglyceride, and D-dimer (all P < 0.05). Functionally, both AngII-induced FTO expression and over expression of FTO promote cell proliferation and migration, whereas knockdown of FTO inhibits these functions. Mechanically, we identified Krüppel-like factor 5 (Klf5) as a target of FTO mediating m6A modification. Overexpression of FTO reduced m6A modification on Klf5 mRNA and promoted Klf5 mRNA expression. Furthermore, the p-GSK3β and Klf5 levels increased after FTO overexpression. Finally, knockdown of FTO suppresses the p-GSK3β levels and Klf5 expression regardless of AngII treatment.

Conclusions: Our study revealed that FTO expression significantly contributes to the phenotype conversion of VSMCs and the ADA by the demethylation function (m6A), thereby providing a novel therapeutic target.