Murine Double Minute-2 Inhibition Attenuates Cardiac Dysfunction and Fibrosis by Modulating NF-κB Pathway After Experimental Myocardial Infarction

Leveraging a neutrophil-derived PCD signature to predict and stratify patients with acute myocardial infarction: from AI prediction to biological interpretation

BACKGROUND

Programmed cell death (PCD) has recently been implicated in modulating the removal of neutrophils recruited in acute myocardial infarction (AMI). Nonetheless, the clinical significance and biological mechanism of neutrophil-related PCD remain unexplored.

METHODS

We employed an integrative machine learning-based computational framework to generate a predictive neutrophil-derived PCD signature (NPCDS) within five independent microarray cohorts from the peripheral blood of AMI patients. Non-negative matrix factorization was leveraged to develop an NPCDS-based AMI subtype. To elucidate the biological mechanism underlying NPCDS, we implemented single-cell transcriptomics on Cd45+ cells isolated from the murine heart of experimental AMI. We finally conducted a Mendelian randomization (MR) study and molecular docking to investigate the therapeutic value of NPCDS on AMI.

RESULTS

We reported the robust and superior performance of NPCDS in AMI prediction, which contributed to an optimal combination of random forest and stepwise regression fitted on nine neutrophil-related PCD genes (MDM2, PTK2B, MYH9, IVNS1ABP, MAPK14, GNS, MYD88, TLR2, CFLAR). Two divergent NPCDS-based subtypes of AMI were revealed, in which subtype 1 was characterized as inflammation-activated with more vibrant neutrophil activities, whereas subtype 2 demonstrated the opposite. Mechanically, we unveiled the expression dynamics of NPCDS to regulate neutrophil transformation from a pro-inflammatory phase to an anti-inflammatory phase in AMI. We uncovered a significant causal association between genetic predisposition towards MDM2 expression and the risk of AMI. We also found that lidoflazine, isotetrandrine, and cepharanthine could stably target MDM2.

CONCLUSION

Altogether, NPCDS offers significant implications for prediction, stratification, and therapeutic management for AMI.

p53 and Myofibroblast Apoptosis in Organ Fibrosis

Organ fibrosis represents a dysregulated, maladaptive wound repair response that results in progressive disruption of normal tissue architecture leading to detrimental deterioration in physiological function, and significant morbidity/mortality. Fibrosis is thought to contribute to nearly 50% of all deaths in the Western world with current treatment modalities effective in slowing disease progression but not effective in restoring organ function or reversing fibrotic changes. When physiological wound repair is complete, myofibroblasts are programmed to undergo cell death and self-clearance, however, in fibrosis there is a characteristic absence of myofibroblast apoptosis. It has been shown that in fibrosis, myofibroblasts adopt an apoptotic-resistant, highly proliferative phenotype leading to persistent myofibroblast activation and perpetuation of the fibrotic disease process. Recently, this pathological adaptation has been linked to dysregulated expression of tumour suppressor gene p53. In this review, we discuss p53 dysregulation and apoptotic failure in myofibroblasts and demonstrate its consistent link to fibrotic disease development in all types of organ fibrosis. An enhanced understanding of the role of p53 dysregulation and myofibroblast apoptosis may aid in future novel therapeutic and/or diagnostic strategies in organ fibrosis.

Hepatic MDM2 Causes Metabolic Associated Fatty Liver Disease by Blocking Triglyceride-VLDL Secretion via ApoB Degradation

Dysfunctional triglyceride-very low-density lipoprotein (TG-VLDL) metabolism is linked to metabolic-associated fatty liver disease (MAFLD); however, the underlying cause remains unclear. The study shows that hepatic E3 ubiquitin ligase murine double minute 2 (MDM2) controls MAFLD by blocking TG-VLDL secretion. A remarkable upregulation of MDM2 is observed in the livers of human and mouse models with different levels of severity of MAFLD. Hepatocyte-specific deletion of MDM2 protects against high-fat high-cholesterol diet-induced hepatic steatosis and inflammation, accompanied by a significant elevation in TG-VLDL secretion. As an E3 ubiquitin ligase, MDM2 targets apolipoprotein B (ApoB) for proteasomal degradation through direct protein-protein interaction, which leads to reduced TG-VLDL secretion in hepatocytes. Pharmacological blockage of the MDM2-ApoB interaction alleviates dietary-induced hepatic steatohepatitis and fibrosis by inducing hepatic ApoB expression and subsequent TG-VLDL secretion. The effect of MDM2 on VLDL metabolism is p53-independent. Collectively, these findings suggest that MDM2 acts as a negative regulator of hepatic ApoB levels and TG-VLDL secretion in MAFLD. Inhibition of the MDM2-ApoB interaction may represent a potential therapeutic approach for MAFLD treatment.

Ferroptosis and its emerging roles in cardiovascular diseases

Ferroptosis is a new form of regulated cell death (RCD) driven by iron-dependent lipid peroxidation, which is morphologically and mechanistically distinct from other forms of RCD including apoptosis, autophagic cell death, pyroptosis and necroptosis. Recently, ferroptosis has been found to participate in the development of various cardiovascular diseases (CVDs) including doxorubicin-induced cardiotoxicity, ischemia/reperfusion-induced cardiomyopathy, heart failure, aortic dissection and stroke. Cardiovascular homeostasis is indulged in delicate equilibrium of assorted cell types composing the heart or vessels, and how ferroptosis contributes to the pathophysiological responses in CVD progression is unclear. Herein, we reviewed recent discoveries on the basis of ferroptosis and its involvement in CVD pathogenesis, together with related therapeutic potentials, aiming to provide insights on fundamental mechanisms of ferroptosis and implications in CVDs and associated disorders.

Profiles of differentially expressed long noncoding RNAs and messenger RNAs in the myocardium of septic mice

Background

Sepsis is the primary cause of mortality in the intensive care unit (ICU), mainly due to sepsis-induced dysfunction of essential organs such as the heart and lungs. This study investigated the myocardium's epigenetic characterization from septic mice to identify potential treatment targets for septic myocardial dysfunction.

Methods

Cecal ligation and puncture (CLP) was used to induce sepsis in male C57BL/6 mice. Hearts were collected 24 h after surgery to determine the expression profiles of long noncoding RNAs (lncRNAs) and messenger RNAs (mRNAs) by microarray. To validate the reliability of microarray results, we randomly chose six differentially expressed lncRNAs for qRT-PCR. Functional mapping of differentially expressed mRNAs was annotated with gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses; lncRNA-mRNA co-expression network was constructed to reveal connections between lncRNAs and mRNAs.

Results

Microarray analysis indicated that 1,568 lncRNAs and 2,166 mRNAs were differentially expressed in the myocardium from septic mice, which was further confirmed by qRT-PCR. KEGG pathway analysis showed that numerous differentially expressed mRNAs were relevant to tumor necrosis factor (TNF) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) signaling pathways. Moreover, according to the lncRNA-mRNA co-expression network constructed by the above six lncRNAs and their interacting mRNAs, the co-expression network profiles had 57 network nodes and 134 connections, including 76 positive interactions and 58 negative interactions.

Conclusions

In mouse hearts, sepsis resulted in differential expression of lncRNAs and mRNAs related to TNF and PI3K-Akt signaling pathways, suggesting that lncRNAs and their interacting mRNAs may participate in the pathogenesis of septic myocardial dysfunction by regulating TNF and PI3K-Akt signaling pathways.

Preoperative myocardial expression of E3 ubiquitin ligases in aortic stenosis patients undergoing valve replacement and their association to postoperative hypertrophy

Currently, aortic valve replacement is the only treatment capable of relieving left ventricle pressure overload in patients with severe aortic stenosis. It aims to improve cardiac function and revert hypertrophy, by triggering myocardial reverse remodeling. Despite immediately relieving afterload, reverse remodeling turns out to be extremely variable. Among other factors, the extent of reverse remodeling may depend on how well ubiquitin-proteasome system tackle hypertrophy. Therefore, we assessed tagged ubiquitin and ubiquitin ligases in the left ventricle collected from patients undergoing valve replacement and tested their association to the degree of reverse remodeling. Patients were classified according to the regression of left ventricle mass (ΔLVM) and assigned to complete (ΔLVM≥15%) or incomplete (ΔLVM≤5%) reverse remodeling groups. No direct inter-group differences were observed. Nevertheless, correlation analysis supports a fundamental role of the ubiquitin-proteasome system during reverse remodeling. Indeed, total protein ubiquitination was associated to hypertrophic indexes such as interventricular septal thickness (r = 0.55, p = 0.03) and posterior wall thickness (r = 0.65, p = 0.009). No significant correlations were observed for Muscle Ring Finger 3. Surprisingly, though, higher levels of atrogin-1 were associated to postoperative interventricular septal thickness (r = 0.71, p = 0.005). In turn, Muscle Ring Finger 1 correlated negatively with this postoperative hypertrophy marker (r = -0.68, p = 0.005), suggesting a cardioprotective role during reverse remodeling. No significant correlations were found with left ventricle mass regression, although a trend for a negative association between the ligase Murine Double Minute 2 and mass regression (r = -0.44, p = 0.10) was found. Animal studies will be necessary to understand whether this ligase is protective or detrimental. Herein, we show, for the first time, an association between the preoperative myocardial levels of ubiquitin ligases and postoperative hypertrophy, highlighting the therapeutic potential of targeting ubiquitin ligases in incomplete reverse remodeling.

Considering the Role of Murine Double Minute 2 in the Cardiovascular System?

The E3 ubiquitin ligase Murine double minute 2 (MDM2) is the main negative regulator of the tumor protein p53 (TP53). Extensive studies over more than two decades have confirmed MDM2 oncogenic role through mechanisms both TP53-dependent and TP53-independent oncogenic function. These studies have contributed to designate MDM2 as a therapeutic target of choice for cancer treatment and the number of patents for MDM2 antagonists has increased immensely over the last years. However, the question of the physiological functions of MDM2 has not been fully resolved yet, particularly when expressed and regulated physiologically in healthy tissue. Cardiovascular complications are almost an inescapable side-effect of anti-cancer therapies. While several MDM2 antagonists are entering phase I, II and even III of clinical trials, this review proposes to bring awareness on the physiological role of MDM2 in the cardiovascular system.

Flavonoids as Natural Anti-Inflammatory Agents Targeting Nuclear Factor-Kappa B (NFκB) Signaling in Cardiovascular Diseases: A Mini Review

Cardiovascular diseases (CVDs) such as angina, hypertension, myocardial ischemia, and heart failure are the leading causes of morbidity and mortality worldwide. One of the major transcription factors widely associated with CVDs is nuclear factor-kappa B (NFκB). NFκB activation initiates the canonical and non-conical pathways that promotes activation of transcription factors leading to inflammation, such as leukocyte adhesion molecules, cytokines, and chemokines. Flavonoids are bioactive polyphenolic compounds found abundantly in various fruits, vegetables, beverages (tea, coffee), nuts, and cereal products with cardiovascular protective properties. Flavonoids can be classified into six subgroups based on their chemical structures: flavanones, flavones, flavonols, flavan-3-ols, isoflavones, and anthocyanidins. As NFκB inhibitors, these flavonoids may modulate the expression of pro-inflammatory genes leading to the attenuation of the inflammatory responses underlying various cardiovascular pathology. This review presents an update on the anti-inflammatory actions of flavonoids via inhibition of NFκB mechanism supporting the therapeutic potential of these natural compounds in various CVDs.

Targeting MDM2 for novel molecular therapy: Beyond oncology

The murine double minute 2 (MDM2) oncogene exerts major oncogenic activities in human cancers; it is not only the best-documented negative regulator of the p53 tumor suppressor, but also exerts p53-independent activities. There is an increasing interest in developing MDM2-based targeted therapies. Several classes of MDM2 inhibitors have been evaluated in preclinical models, with a few entering clinical trials, mainly for cancer therapy. However, noncarcinogenic roles for MDM2 have also been identified, demonstrating that MDM2 is involved in many chronic diseases and conditions such as inflammation and autoimmune diseases, dementia and neurodegenerative diseases, heart failure and cardiovascular diseases, nephropathy, diabetes, obesity, and sterility. MDM2 inhibitors have been shown to have promising therapeutic efficacy for treating inflammation and other nonmalignant diseases in preclinical evaluations. Therefore, targeting MDM2 may represent a promising approach for treating and preventing these nonmalignant diseases. In addition, a better understanding of how MDM2 works in nonmalignant diseases may provide new biomarkers for their diagnosis, prognostic prediction, and monitoring of therapeutic outcome. In this review article, we pay special attention to the recent findings related to the roles of MDM2 in the pathogenesis of several nonmalignant diseases, the therapeutic potential of its downregulation or inhibition, and its use as a biomarker.

MDM2 controls NRF2 antioxidant activity in prevention of diabetic kidney disease

Oxidative stress and P53 contribute to the pathogenesis of diabetic kidney disease (DKD). Nuclear factor erythroid 2-related factor 2 (NRF2) is a master regulator of cellular antioxidant defense system, is negatively regulated by P53 and prevents DKD. Recent findings revealed an important role of mouse double minute 2 (MDM2) in protection against DKD. However, the mechanism remained unclear. We hypothesized that MDM2 enhances NRF2 antioxidant signaling in DKD given that MDM2 is a key negative regulator of P53. The MDM2 inhibitor nutlin3a elevated renal P53, inhibited NRF2 signaling and induced oxidative stress, inflammation, fibrosis, DKD-like renal pathology and albuminuria in the wild-type (WT) non-diabetic mice. These effects exhibited more prominently in nutlin3a-treated WT diabetic mice. Interestingly, nutlin3a failed to induce greater renal injuries in the Nrf2 knockout (KO) mice under both the diabetic and non-diabetic conditions, indicating that NRF2 predominantly mediates MDM2's action. On the contrary, P53 inhibition by pifithrin-α activated renal NRF2 signaling and the expression of Mdm2, and attenuated DKD in the WT diabetic mice, but not in the Nrf2 KO diabetic mice. In high glucose-treated mouse mesangial cells, P53 gene silencing completely abolished nutlin3a's inhibitory effect on NRF2 signaling. The present study demonstrates for the first time that MDM2 controls renal NRF2 antioxidant activity in DKD via inhibition of P53, providing MDM2 activation and P53 inhibition as novel strategies in the management of DKD.

DNA induction of MDM2 promotes proliferation of human renal mesangial cells and alters peripheral B cells subsets in pediatric systemic lupus erythematosus

The study is aimed to investigate the role of MDM2 in the pathogenesis of lupus nephritis (LN) in pediatric SLE (pSLE). We confirmed that MDM2 expression was increased in peripheral blood mononuclear cells (PBMCs) as well as renal specimen of SLE compared with that of controls by western blot and immunofluorescence staining. Percentage of apoptotic and necrotic CD4⁺T, CD8⁺T and B cells were detected by flow cytometry respectively and levels of plasma cell free DNA (cfDNA) were quantified in SLE and healthy controls (HC). We also proved that elevated apoptotic and necrotic CD4⁺T cells were the main cause for increased plasma levels of cfDNA in pSLE. Additionally, upon DNA transfection MDM2 increased while P53 and P21 decreased in human renal mesangial cells (HRMC), with concomitant increase in proliferation rate and proportion of cells in S phase, as demonstrated by cell proliferation assay and cell cycle analysis. However, MDM2 inhibition reversed the trend. Furthermore, percentage of switched memory B cells decreased and proportion of double negative B cells increased upon blockage of MDM2 in PBMC. In summary, our study provided the first evidence that DNA induction of MDM2 promotes proliferation of HRMC and alters peripheral B cells subsets in pSLE. Thus our study has not only elucidated the pathogenesis of MDM2 in pediatric LN but also provided a novel target for drug development. In conclusion, our data suggested that apoptosis, cfDNA and MDM2 could form a pathological axis in SLE, especially in pSLE.

LRP6 targeting suppresses gastric tumorigenesis via P14ARF-Mdm2-P53-dependent cellular senescence

NLRP6, a member of the Nod-like receptor family, protects against chemically induced intestinal injury and colitis-associated colon cancer. However, the cellular mechanisms involved in this NLRP6-mediated protection remain unclear. Here, we show that NLRP6 was down-regulated in approximately 75% of primary gastric cancer cases and exhibited significant associations with advanced clinical-stage lymph node metastasis and poor overall survival. Functional studies established that ectopic overexpression or down-regulation of NLRP6 inhibited cancer cell proliferation by inducing cell cycle arrest at the G1 phase via P21 and Cyclin D1 both in vitro and in vivo. Activation of the P14^ARF-P53 pathway played a crucial role in the observed cellular senescence. We further demonstrated that ectopic overexpression of NLRP6 combined with inactivation of NF-κB(p65) and Mdm2 activates P14^ARF-P53 to promote the senescence of gastric cancer cells. These findings indicate that NLRP6 functions as a negative regulator of gastric cancer and offer a potential new option for preventing gastric cancer.