Inhibition of MDM2 attenuates neointimal hyperplasia via suppression of vascular proliferation and inflammation

Bioactive glass 1393 promotes angiogenesis and accelerates wound healing through ROS/P53/MMP9 signaling pathway

Compared to bioactive glass 45S5, bioactive glass 1393 has shown greater potential in activating tissue cells and promoting angiogenesis for bone repair. Nevertheless, the effect of bioactive glass 1393 in the context of wound healing remains extensively unexplored, and its mechanism in wound healing remains unclear. Considering that angiogenesis is a critical stage in wound healing, we hypothesize that bioactive glass 1393 may facilitate wound healing through the stimulation of angiogenesis. To validate this hypothesis and further explore the mechanisms underlying its pro-angiogenic effects, we investigated the impact of bioactive glass 1393 on wound healing angiogenesis through both in vivo and in vitro studies. The research demonstrated that bioactive glass 1393 accelerated wound healing by promoting the formation of granulation, deposition of collagen, and angiogenesis. The results of Western blot analysis and immunofluorescence staining revealed that bioactive glass 1393 up-regulated the expression of angiogenesis-related factors. Additionally, bioactive glass 1393 inhibited the expression of ROS and P53 to promote angiogenesis. Furthermore, bioactive glass 1393 stimulated angiogenesis through the P53 signaling pathway, as evidenced by P53 activation assays. Collectively, these findings indicate that bioactive glass 1393 accelerates wound healing by promoting angiogenesis via the ROS/P53/MMP9 signaling pathway.

Xinshubao tablet rescues cognitive dysfunction in a mouse model of vascular dementia: Involvement of neurogenesis and neuroinflammation

Vascular dementia (VaD) represents a severe cognitive dysfunction syndrome closed linked to cardiovascular function. In the present study, we assessed the potential of Xinshubao tablet (XSB), a traditional Chinese prescription widely used for cardiovascular diseases, to mitigate neuropathological damage in a mouse model of VaD and elucidated the underlying mechanisms. Our findings revealed that oral administration of XSB rescued the cardiac dysfunction resulting from bilateral common carotid artery stenosis (BCAS), improved the cerebral blood flow (CBF) and cognitive function, reduced white matter injury, inhibited excessive microglial and astrocytic activation, stimulated hippocampal neurogenesis, and reduced neural apoptosis in the brains of BCAS mice. Mechanistically, RNA-seq analysis indicated that XSB treatment was significantly associated with neuroinflammation, vasculature development, and synaptic transmission, which were further confirmed by q-PCR assays. Western blot results revealed that XSB treatment hindered the nuclear translocation of nuclear factor-κB (NF-κB), thereby suppressing the NF-κB signaling pathway. These results collectively demonstrated that XSB could ameliorate cognitive dysfunction caused by BCAS through regulating CBF, reducing white matter lesions, suppressing glial activation, promoting neurogenesis, and mitigating neuroinflammation. Notably, the NF-κB signaling pathway emerged as a pivotal player in this mechanism.

Interference of MDM2 attenuates vascular endothelial dysfunction in hypertension partly through blocking Notch1/NLRP3 inflammasome pathway

BACKGROUND

Hypertension is a life-threatening disease mainly featured as vascular endothelial dysfunction. This study aims to explore the regulatory role of murine double minute 2 (MDM2) in hypertension and vascular damage.

METHODS

Mice were infused with angiotensin II (AngII) to establish a hypertension mouse model in vivo and AngII-stimulated HUVECs were constructed to simulate the damage of vascular endothelial cells in hypertension in vitro. The plasmids targeting to MDM2 was injected to mice or transfected to HUVECs. qRT-PCR and western blot were performed to detect corresponding gene expression in mice aorta. Blood pressure was measured. H&E and Masson staining were conducted to evaluate histological changes of aorta. Responses to the acetylcholine (ACh) and sodium nitroprusside (SNP) were assessed in aorta. ZO-1 expression and cell apoptosis were detected by immunofluorescence and TUNEL, respectively. Network formation ability was determined employing a tube formation.

RESULTS

MDM2 was upregulated in hypertensive mice. Knockdown of MDM2 inhibited AngII-induced high BP, histological damage, vascular relaxation to Ach, and promoted the levels of p-eNOS and ZO-1 in the aorta in hypertensive mice. MDM2 knockdown inactivated Notch1 signaling and NLRP3 inflammasome, while the inhibitory effect of MDM2 knockdown on NLRP3 inflammasome activation was partly restored by the activation of Notch1. Furthermore, knockdown of MDM2 relieved AngII-induced endothelial dysfunction in HUVECs, as well as suppressing AngII-promoted cell apoptosis. Whereas, the impacts generated by MDM2 knockdown were partly weakened by the activation of Notch1 signaling or NLRP3 inflammasome.

CONCLUSION

In summary, knockdown of MDM2 can attenuate vascular endothelial dysfunction in hypertension, which may be achieved through inhibiting the activation of Notch1 and NLRP3 inflammasome.

MDM2-Mediated Ubiquitination of RXRβ Contributes to Mitochondrial Damage and Related Inflammation in Atherosclerosis

A novel function of retinoid X receptor beta (RXRβ) in endothelial cells has been reported by us during the formation of atherosclerosis. Here, we extended the study to explore the cellular mechanisms of RXRβ protein stability regulation. In this study, we discovered that murine double minute-2 (MDM2) acts as an E3 ubiquitin ligase to target RXRβ for degradation. The result showed that MDM2 directly interacted with and regulated RXRβ protein stability. MDM2 promoted RXRβ poly-ubiquitination and degradation by proteasomes. Moreover, mutated MDM2 RING domain (C464A) or treatment with an MDM2 inhibitor targeting the RING domain of MDM2 lost the ability of MDM2 to regulate RXRβ protein expression and ubiquitination. Furthermore, treatment with MDM2 inhibitor alleviated oxidized low-density lipoprotein-induced mitochondrial damage, activation of TLR9/NF-κB and NLRP3/caspase-1 pathway and production of pro-inflammatory cytokines in endothelial cells. However, all these beneficial effects were reduced by the transfection of RXRβ siRNA. Moreover, pharmacological inhibition of MDM2 attenuated the development of atherosclerosis and reversed mitochondrial damage and related inflammation in the atherosclerotic process in LDLr^-/- mice, along with the increased RXRβ protein expression in the aorta. Therefore, our study uncovers a previously unknown ubiquitination pathway and suggests MDM2-mediated RXRβ ubiquitination as a new therapeutic target in atherosclerosis.

The p53 pathway in vasculature revisited: A therapeutic target for pathological vascular remodeling?

Pathological vascular remodeling contributes to the development of restenosis following intraluminal interventions, transplant vasculopathy, and pulmonary arterial hypertension. Activation of the tumor suppressor p53 may counteract vascular remodeling by inhibiting aberrant proliferation of vascular smooth muscle cells and repressing vascular inflammation. In particular, the development of different lines of small-molecule p53 activators ignites the hope of treating remodeling-associated vascular diseases by targeting p53 pharmacologically. In this review, we discuss the relationships between p53 and pathological vascular remodeling, and summarize current experimental data suggesting that drugging the p53 pathway may represent a novel strategy to prevent the development of vascular remodeling.

The Role of Ubiquitin E3 Ligase in Atherosclerosis

Atherosclerosis is a chronic inflammatory vascular disease. Atherosclerotic cardiovascular disease is the main cause of death in both developed and developing countries. Many pathophysiological factors, including abnormal cholesterol metabolism, vascular inflammatory response, endothelial dysfunction and vascular smooth muscle cell proliferation and apoptosis, contribute to the development of atherosclerosis and the molecular mechanisms underlying the development of atherosclerosis are not fully understood. Ubiquitination is a multistep post-translational protein modification that participates in many important cellular processes. Emerging evidence suggests that ubiquitination plays important roles in the pathogenesis of atherosclerosis in many ways, including regulation of vascular inflammation, endothelial cell and vascular smooth muscle cell function, lipid metabolism and atherosclerotic plaque stability. This review summarizes important contributions of various E3 ligases to the development of atherosclerosis. Targeting ubiquitin E3 ligases may provide a novel strategy for the prevention of the progression of atherosclerosis.

Targeting the epigenome in in-stent restenosis: from mechanisms to therapy

Coronary artery disease (CAD) is one of the most common causes of death worldwide. The introduction of percutaneous revascularization has revolutionized the therapy of patients with CAD. Despite the advent of drug-eluting stents, restenosis remains the main challenge in treating patients with CAD. In-stent restenosis (ISR) indicates the reduction in lumen diameter after percutaneous coronary intervention, in which the vessel's lumen re-narrowing is attributed to the aberrant proliferation and migration of vascular smooth muscle cells (VSMCs) and dysregulation of endothelial cells (ECs). Increasing evidence has demonstrated that epigenetics is involved in the occurrence and progression of ISR. In this review, we provide the latest and comprehensive analysis of three separate but related epigenetic mechanisms regulating ISR, namely, DNA methylation, histone modification, and non-coding RNAs. Initially, we discuss the mechanism of restenosis. Furthermore, we discuss the biological mechanism underlying the diverse epigenetic modifications modulating gene expression and functions of VSMCs, as well as ECs in ISR. Finally, we discuss potential therapeutic targets of the small molecule inhibitors of cardiovascular epigenetic factors. A more detailed understanding of epigenetic regulation is essential for elucidating this complex biological process, which will assist in developing and improving ISR therapy.

BOP1 Knockdown Attenuates Neointimal Hyperplasia by Activating p53 and Inhibiting Nascent Protein Synthesis

The rate of ribosome biogenesis plays a vital role in cell cycle progression and proliferation and is strongly connected with coronary restenosis and atherosclerosis. Blocking of proliferation 1 (BOP1) has been found as an evolutionarily conserved gene and a pivotal regulator of ribosome biogenesis and cell proliferation. However, little is known about its role in neointimal formation and its relationship with vascular smooth muscle cell (VSMC) proliferation and migration. The present study mainly explores the effect of BOP1 on VSMCs, the progression of neointimal hyperplasia, and the pathogenic mechanism. The expression of BOP1 was found to be significantly elevated during neointimal formation in human coronary samples and the rat balloon injury model. BOP1 knockdown inspires the nucleolus stress, which subsequently activates the p53-dependent stress response pathway, and inhibits the nascent protein synthesis, which subsequently inhibits the proliferation and migration of VSMCs. Knockdown ribosomal protein L11 (RPL11) by transfecting with siRNA or inhibiting p53 by pifithrin-α (PFT-α) partly reserved the biological effects induced by BOP1 knockdown. The present study revealed that BOP1 deletion attenuates VSMC proliferation and migration by activating the p53-dependent nucleolus stress response pathway and inhibits the synthesis of nascent proteins. BOP1 may become a novel biological target for neointimal hyperplasia.

MDM2 contributes to oxidized low-density lipoprotein-induced inflammation through modulation of mitochondrial damage in endothelial cells

BACKGROUND AND AIMS

Murine double minute-2 (MDM2) has been poorly studied in cardiovascular diseases. The aim of the present study was to determine the biological role of MDM2 in inflammation activation and mitochondrial damage in human aortic endothelial cells (HAECs) stimulated with oxidized low-density lipoprotein (ox-LDL).

METHODS

The expression of MDM2 in the aortas of atherosclerotic mice was determined. An adenoviral vector for MDM2 overexpression and siRNA for MDM2 downregulation were constructed and used to transfect HAECs. The functional changes in HAECs stimulated by ox-LDL were observed.

RESULTS

The protein expression of MDM2 was increased in atherosclerotic mice and ox-LDL-treated HAECs. In addition, ox-LDL-induced mRNA expression and secretion of TNF-α, IL-6 and IL-1β were significantly decreased by MDM2 downregulation and increased by MDM2 overexpression, and activation of NF-κB and caspase-1 was involved in the activity of MDM2. The ox-LDL-induced mitochondrial damage, indicated as increase in mitochondrial ROS production, decrease in mitochondrial membrane potential and elevation of mitochondrial DNA release, was significantly reversed by MDM2 downregulation and worsened by MDM2 overexpression. The ox-LDL-induced activation of TLR9/NF-κB and NLRP3/caspase-1 pathway was inhibited by MDM2 downregulation and worsened by MDM2 overexpression. The aggravation caused by MDM2 overexpression was abolished by mito-TEMPO. Treatment with mito-TEMPO significantly reduced the increase in mRNA expression and secretion of TNF-α, IL-6 and IL-1β induced by MDM2 overexpression in ox-LDL treated HAECs.

CONCLUSIONS

These findings suggest that MDM2 contributes to ox-LDL-induced inflammation via regulating mitochondrial damage.

Silencing CCNG1 protects MPC-5 cells from high glucose-induced proliferation-inhibition and apoptosis-promotion via MDM2/p53 signaling pathway

PURPOSE

Diabetic nephropathy (DN) is one of the most serious complications of diabetes mellitus and one of the most important causes of end-stage renal disease, but its pathogenesis has not been elucidated so far, and there is no effective treatment.

METHODS

DN models of rats and MPC-5 cells were established with streptozotocin (STZ) and high glucose (HG) in vivo and in vitro, respectively. Cell markers desmin and nephrin in foot kidney tissue were detected by Western blot. CCNG1 level in vitro was analyzed by Western blot and immunohistochemistry. CCK-8 assay and flow cytometry were conducted to analyze the effect of CCNG1 on HG-treated MPC-5 cells. Apoptosis-related proteins (Bcl-2, Bax and p53), CCNG1, and MDM2 were determined by RT-qPCR and Western blot.

RESULTS

The level of nephrin was decreased, while desmin was increased in STZ-induced DN rats and CCNG1 level was also enhanced by STZ. In vitro experiments indicated that MPC-5 cell viability was inhibited and apoptosis was induced by HG and we also found that CCNG1 expression was up-regulated by HG and negatively correlated with MDM2 level. The effects of HG on MPC-5 cell viability, apoptosis, and cell cycle were reversed by silencing CCNG1, but further deteriorated by overexpression of CCNG1. Furthermore, overexpression of MDM2 inhibited HG-induced MPC-5 cell injury and CCNG1 expression.

CONCLUSIONS

These findings revealed that down-regulation of CCNG1 has protection effects in DN that is mechanistically linked to MDM2-p53 pathways.

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.

Downregulation of the transcriptional co-activator PCAF inhibits the proliferation and migration of vascular smooth muscle cells and attenuates NF-κB-mediated inflammatory responses

P300/CBP-associated factor (PCAF) regulates vascular inflammation. This study was to explore the effect of PCAF on the proliferation and migrationof vascular smooth muscle cells (VSMCs) and neointimal hyperplasia in balloon-injured rat carotid artery. Downregulation of PCAF remarkably suppressed VSMCs proliferation and migration induced by lipopolysaccharide, and also significantly inhibit the nuclear translocation of nuclear factor-kappaB p65. Meanwhile, downregulation of PCAF inhibited the mRNA expression of tumor necrosis factor-α and interleukin-6, and also the levels in culture supernatants. Moreover, downregulation of PCAF profoundly reduced the intima area and the ratio of intima area to media area in balloon-injured rat carotid artery. In addition, the expression of PCNA and NF-κB p65 in intima were decreased by downregulation of PCAF. These results highlight that PCAF may be a potential target for prevention and treatment of neointimal hyperplasia and restenosis after angioplasty.

Semaphorin-3A protects against neointimal hyperplasia after vascular injury

BACKGROUND

Neointimal hyperplasia is a prominent pathological event during in-stent restenosis. Phenotype switching of vascular smooth muscle cells (VSMCs) from a differentiated/contractile to a dedifferentiated/synthetic phenotype, accompanied by migration and proliferation of VSMCs play an important role in neointimal hyperplasia. However, the molecular mechanisms underlying phenotype switching of VSMCs have yet to be fully understood.

METHODS

The mouse carotid artery ligation model was established to evaluate Sema3A expression and its role during neointimal hyperplasia in vivo. Bioinformatics analysis, chromatin immunoprecipitation (ChIP) assays and promoter-luciferase reporter assays were used to examine regulatory mechanism of Sema3A expression. SiRNA transfection and lentivirus infection were performed to regulate Sema3A expression. EdU assays, Wound-healing scratch experiments and Transwell migration assays were used to assess VSMC proliferation and migration.

FINDINGS

In this study, we found that semaphorin-3A (Sema3A) was significantly downregulated in VSMCs during neointimal hyperplasia after vascular injury in mice and in human atherosclerotic plaques. Meanwhile, Sema3A was transcriptionally downregulated by PDGF-BB via p53 in VSMCs. Furthermore, we found that overexpression of Sema3A inhibited VSMC proliferation and migration, as well as increasing differentiated gene expression. Mechanistically, Sema3A increased the NRP1-plexin-A1 complex and decreased the NRP1-PDGFRβ complex, thus inhibiting phosphorylation of PDGFRβ. Moreover, we found that overexpression of Sema3A suppressed neointimal hyperplasia after vascular injury in vivo.

INTERPRETATION

These results suggest that local delivery of Sema3A may act as a novel therapeutic option to prevent in-stent restenosis.

Semaphorin-3E attenuates neointimal formation via suppressing VSMCs migration and proliferation

Aims

The migration and proliferation of vascular smooth muscle cells (VSMCs) are crucial events in the neointimal formation, a hallmark of atherosclerosis and restenosis. Semaphorin3E (Sema3E) has been found to be a critical regulator of cell migration and proliferation in many scenarios. However, its role on VSMCs migration and proliferation is unclear. This study aimed to investigate the effect of Sema3E on VSMCs migration, proliferation and neointimal formation, and explore possible mechanisms.

Methods and results

We found that the expression of Sema3E was progressively decreased during neointimal formation in a carotid ligation model. H&E-staining showed lentivirus-mediated overexpression of Sema3E in carotid ligation area attenuated neointimal formation. Immunofluorescence staining showed that the receptor (PlexinD1) of Sema3E was expressed in vascular walls. In cultured mouse VSMCs, Sema3E inhibited VSMCs migration and proliferation via plexinD1 receptor. The inhibitory effect was mediated, at least in part, by inactivating Rap1-AKT signalling pathways in VSMCs. Moreover, we found that PDGFBB down-regulated the expression of Sema3E in VSMCs and Sema3E notably inhibited the expression of PDGFB in endothelial cells. In addition, the number of Sema3E-positive VSMCs was diminished in plaques of atherosclerotic patients. Results from a public GEO microarray database showed a negative correlation between Sema3E and PDGFB transcriptional levels in the human plaques examined.

Conclusion

Our study demonstrates that Sema3E/plexinD1 inhibits proliferation and migration of VSMCs via inactivation of Rap1-AKT signalling pathways. The mutual inhibition between PDGF-BB and Sema3E after vascular injury plays a critical role in the process of neointimal formation.

Novel natural product therapeutics targeting both inflammation and cancer

Inflammation is recently recognized as one of the hallmarks of human cancer. Chronic inflammatory response plays a critical role in cancer development, progression, metastasis, and resistance to chemotherapy. Conversely, the oncogenic aberrations also generate an inflammatory microenvironment, enabling the development and progression of cancer. The molecular mechanisms of action that are responsible for inflammatory cancer and cancer-associated inflammation are not fully understood due to the complex crosstalk between oncogenic and pro-inflammatory genes. However, molecular mediators that regulate both inflammation and cancer, such as NF-κB and STAT have been considered as promising targets for preventing and treating these diseases. Recent works have further demonstrated an important role of oncogenes (e.g., NFAT1, MDM2) and tumor suppressor genes (e.g., p53) in cancer-related inflammation. Natural products that target these molecular mediators have shown anticancer and anti-inflammatory activities in preclinical and clinical studies. Sesquiterpenoids (STs), a class of novel plant-derived secondary metabolites have attracted great interest in recent years because of their diversity in chemical structures and pharmacological activities. At present, we and other investigators have found that dimeric sesquiterpenoids (DSTs) may exert enhanced activity and binding affinity to molecular targets due to the increased number of alkylating centers and improved conformational flexibility and lipophilicity. Here, we focus our discussion on the activities and mechanisms of action of STs and DSTs in treating inflammation and cancer as well as their structure-activity relationships.

P53 Promotes Retinoid Acid-induced Smooth Muscle Cell Differentiation by Targeting Myocardin

TP53 is a widely studied tumor suppressor gene that controls various cellular functions, including cell differentiation. However, little is known about its functional roles in smooth muscle cells (SMCs) differentiation from embryonic stem cells (ESCs). SMC differentiation is at the heart of our understanding of vascular development, normal blood pressure homeostasis, and the pathogenesis of vascular diseases such as atherosclerosis, hypertension, restenosis, as well as aneurysm. Using retinoid acid (RA)-induced SMC differentiation models, we observed that p53 expression is increased during in vitro differentiation of mouse ESCs into SMCs. Meanwhile, suppression of p53 by shRNA reduced RA-induced SMC differentiation. Mechanistically, we have identified for the first time that Myocardin, a transcription factor that induces muscle cell differentiation and muscle-specific gene expression, is the direct target of p53 by bioinformatic analysis, luciferase reporter assay, and chromatin immunoprecipitation approaches. Moreover, in vivo SMC-selective p53 transgenic overexpression inhibited injury-induced neointimal formation. Taken together, our data demonstrate that p53 and its target gene, Myocardin, play regulatory roles in SMC differentiation. This study may lead to the identification of novel target molecules that may, in turn, lead to novel drug discoveries for the treatment of vascular diseases.

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

Inflammation has been implicated in myocardial infarction (MI). MDM2 associates with nuclear factor-κB (NF-κB)-mediated inflammation. However, the role of MDM2 in MI remains unclear. This study aimed to evaluate the impacts of MDM2 inhibition on cardiac dysfunction and fibrosis after experimental MI and the underlying mechanisms. Three-month-old male C57BL/6 mice were subjected to left anterior descending (LAD) coronary artery ligation for induction of myocardial infarction (MI). Immediately after MI induction, mice were treated with Nutlin-3a (100 mg/kg) or vehicle twice daily for 4 weeks. Survival, heart function and fibrosis were assessed. Signaling molecules were detected by Western blotting. Mouse myofibroblasts under oxygen and glucose deprivation were used for in vitro experiments. MDM2 protein expression was significantly elevated in the mouse heart after MI. Compared with vehicle-treated animals, Nutlin-3a treatment reduced the mouse mortality. Nutlin-3a treatment improved heart function and decreased the infarct scar and fibrosis compared with vehicle. Furthermore, MDM2 inhibition restored IκB and inhibited NF-κB activation, leading to suppressed production of proinflammatory cytokines in the heart after MI. The consistent results were obtained in vitro. MDM2 inhibition reduced cardiac dysfunction and fibrosis after MI. These effects of MDM2 inhibition is mediated through modulating NF-κB activation, resulting in inhibition of inflammatory response.

RhoA promotes epidermal stem cell proliferation via PKN1-cyclin D1 signaling

OBJECTIVE

Epidermal stem cells (ESCs) play a critical role in wound healing, but the mechanism underlying ESC proliferation is not well defined. Here, we explore the effects of RhoA on ESC proliferation and the possible underlying mechanism.

METHODS

Human ESCs were enriched by rapid adhesion to collagen IV. RhoA(+/+)(G14V), RhoA(-/-)(T19N) and pGFP control plasmids were transfected into human ESCs. The effect of RhoA on cell proliferation was detected by cell proliferation and DNA synthesis assays. Induction of PKN1 activity by RhoA was determined by immunoblot analysis, and the effects of PKN1 on RhoA in terms of inducing cell proliferation and cyclin D1 expression were detected using specific siRNA targeting PKN1. The effects of U-46619 (a RhoA agonist) and C3 transferase (a RhoA antagonist) on ESC proliferation were observed in vivo.

RESULTS

RhoA had a positive effect on ESC proliferation, and PKN1 activity was up-regulated by the active RhoA mutant (G14V) and suppressed by RhoA T19N. Moreover, the ability of RhoA to promote ESC proliferation and DNA synthesis was interrupted by PKN1 siRNA. Additionally, cyclin D1 protein and mRNA expression levels were up-regulated by RhoA G14V, and these effects were inhibited by siRNA-mediated knock-down of PKN1. RhoA also promoted ESC proliferation via PKN in vivo.

CONCLUSION

This study shows that the effect of RhoA on ESC proliferation is mediated by activation of the PKN1-cyclin D1 pathway in vitro, suggesting that RhoA may serve as a new therapeutic target for wound healing.

Murine Double Minute-2 Inhibition Ameliorates Established Crescentic Glomerulonephritis

Rapidly progressive glomerulonephritis is characterized by glomerular necroinflammation and crescent formation. Its treatment includes unspecific and toxic agents; therefore, the identification of novel therapeutic targets is required. The E3-ubiquitin ligase murine double minute (MDM)-2 is a nonredundant element of NF-κB signaling and the negative regulator of tumor suppressor gene TP53-mediated cell cycle arrest and cell death. We hypothesized that the MDM2 would drive crescentic glomerulonephritis by NF-κB-dependent glomerular inflammation and by p53-dependent parietal epithelial cell hyperproliferation. Indeed, the pre-emptive MDM2 blockade by nutlin-3a ameliorated all aspects of crescentic glomerulonephritis. MDM2 inhibition had identical protective effects in Trp53-deficient mice, with the exception of crescent formation, which was not influenced by nutlin-3a treatment. In vitro experiments confirmed the contribution of MDM2 for induction of NF-κB-dependent cytokines in murine glomerular endothelial cells and for p53-dependent parietal epithelial cell proliferation. To evaluate MDM2 blockade as a potential therapeutic intervention in rapidly progressive glomerulonephritis, we treated mice with established glomerulonephritis with nutlin-3a. Delayed onset of nutlin-3a treatment was equally protective as the pre-emptive treatment in abrogating crescentic glomerulonephritis. Together, the pathogenic effects of MDM2 are twofold, that is, p53-independent NF-κB activation increasing intraglomerular inflammation and p53-dependent parietal epithelial cell hyperplasia and crescent formation. We therefore propose MDM2 blockade as a potential novel therapeutic strategy in rapidly progressive glomerulonephritis.

Tryptanthrin reduces mast cell proliferation promoted by TSLP through modulation of MDM2 and p53

BACKGROUND

Atopic dermatitis (AD) results from complex interactions between mast cells and inflammatory mediators. An inflammatory mediator, thymic stromal lymphopoietin (TSLP) is known to promote mast cell proliferation through up-regulation of mouse double minute 2 (MDM2, a negative regulator of p53) and aggravate AD. In this study, we investigated whether tryptanthrin (TR, an anti-inflammatory agent) would regulate TSLP-induced mast cell proliferation and TSLP-induced a pro-inflammatory cytokine, tumor necrosis factor (TNF)-α production from mast cells.

METHODS

Human mast cell line (HMC-1) cells were treated with TR and stimulated with TSLP. Proliferation was measured with a bromodeoxyuridine incorporation assay. And pro- and anti-apoptotic factors were analyzed with quantitative real-time PCR, Western blot analysis, and ELISA. The mRNA expression and production of TNF-α were analyzed with quantitative real-time PCR and ELISA.

RESULTS

TR significantly inhibited the proliferation of HMC-1 cells promoted by TSLP. TR inhibited MDM2 expression, whereas TR increased the expression of p53, poly ADP-ribose polymerase, and caspase-3 in the TSLP-stimulated HMC-1 cells. TR significantly inhibited Ki67 mRNA expression as well as mRNA expression and production of interleukin (IL)-13 in the TSLP-stimulated HMC-1 cells. Moreover, TR significantly suppressed mRNA expression and production of TNF-α in the TSLP-stimulated HMC-1 cells. Finally, the mRNA expression of IL-7 receptor α chain and TSLP receptor was inhibited by TR in the TSLP-stimulated HMC-1 cells.

CONCLUSION

Our results suggest that TR determined with new concept has intensive potential for the treatment of mast cell-mediated allergic diseases, such as AD.

Inhibition of MDM2 expression by rosmarinic acid in TSLP-stimulated mast cell

Rosmarinic acid (RA) has an anti-inflammatory property while thymic stromal lymphopoietin (TSLP) has an important role in mast cell-mediated inflammatory responses. Thus, the aim of this study was to determine the regulatory effect of RA in TSLP-stimulated human mast cell line, HMC-1 cells, and short ragweed pollen-induced allergic conjunctivitis mouse model. As a result, we found that RA significantly decreased the TSLP-induced mast cell proliferation and murine double minute (MDM) 2 expression. RA significantly decreased the levels of interleukin (IL)-13 and phosphorylated the signal transducer and activation of transcription 6 in the TSLP-stimulated HMC-1 cells. RA induced the increment of p53 levels, caspase-3 activation, and poly-ADP-ribose polymerase cleavage and the reduction of the procaspase-3 and Bcl2. RA significantly reduced the production of tumor necrosis factor-α, IL-1β, and IL-6 on the TSLP-stimulated HMC-1 cells. In addition, RA significantly reduced the levels of IgE, IL-4, and TSLP in the short ragweed pollen-induced allergic conjunctivitis mouse model. In conclusion, the results of the study suggest that RA has a significant anti-inflammatory effect on TSLP-induced inflammatory reactions. These effects of RA are likely to be mediated through inhibiting the MDM2 increased by TSLP.

MDM2 promotes rheumatoid arthritis via activation of MAPK and NF-κB

Murine double minute-2 (MDM2) has pleiotropic roles in immune activation and regulation. However, the role of MDM2 in rheumatoid arthritis (RA) remains unknown. We undertook this study to investigate the role of MDM2 in rheumatoid arthritis (RA). Fibroblast-like synoviocytes (FLS) were isolated from 25 patients with active RA and 25 patients with osteoarthritis (OA). FLS were stimulated in the presence or absence of IL-1β in vitro. Mice with collagen-induced arthritis (CIA) were treated with Nutlin-3a (100mg/kg) or vehicle twice daily for 2weeks. MDM2 expression was determined by Western blot. MDM2 was down-regulated by specific gene silencing. The concentrations of pro-inflammatory cytokines and matrix metalloproteinases (MMPs) were analyzed using enzyme-linked immunosorbent assay (ELISA). The pathways of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) were investigated by Western blot. Arthritis scoring and histological analysis were conducted. MDM2 expression was significantly higher in RA-FLS than in OA-FLS. MDM2 protein expression was positively correlated with disease activity of RA. MDM2 promoted the production of TNF-α, IL-6, MMP1 and MMP13 through MAPK and NF-κB pathways in RA-FLS. Nutlin-3a treatment decreased the arthritis severity and joint damage in CIA. Nutlin-3a also inhibited the activation of MAPK and NF-κB in arthritic joints. In conclusion, MDM2 inhibition exhibits anti-inflammatory activity and MDM2 might be a new therapeutic target for RA.

The DNA damage response and immune signaling alliance: Is it good or bad? Nature decides when and where

The characteristic feature of healthy living organisms is the preservation of homeostasis. Compelling evidence highlight that the DNA damage response and repair (DDR/R) and immune response (ImmR) signaling networks work together favoring the harmonized function of (multi)cellular organisms. DNA and RNA viruses activate the DDR/R machinery in the host cells both directly and indirectly. Activation of DDR/R in turn favors the immunogenicity of the incipient cell. Hence, stimulation of DDR/R by exogenous or endogenous insults triggers innate and adaptive ImmR. The immunogenic properties of ionizing radiation, a prototypic DDR/R inducer, serve as suitable examples of how DDR/R stimulation alerts host immunity. Thus, critical cellular danger signals stimulate defense at the systemic level and vice versa. Disruption of DDR/R-ImmR cross talk compromises (multi)cellular integrity, leading to cell-cycle-related and immune defects. The emerging DDR/R-ImmR concept opens up a new avenue of therapeutic options, recalling the Hippocrates quote "everything in excess is opposed by nature."

The MDM2 inhibitor Nutlin-3 attenuates streptozotocin-induced diabetes mellitus and increases serum level of IL-12p40

Besides its well-established oncosuppressor activity, a key function of p53 in regulating metabolic pathways has been recently identified. Nevertheless, the role of p53 with respect to diabetes mellitus (DM) appears highly controversial. To address this issue, we have used the cis-imidazoline compound Nutlin-3, an inhibitor of MDM2/p53 interaction, which represents a potent and selective non-genotoxic activator of the p53 pathway both in in vivo and in vitro experimental settings. Experimental DM was induced by intraperitoneal injections of low concentrations of streptozotocin (STZ) in C57BL/6N mice (n = 20). A group of control vehicle-injected mice (n = 10) and of STZ-treated mice (n = 10) was co-injected with Nutlin-3. Mice co-injected with STZ + Nutlin-3 exhibited attenuated features of DM with respect to animals treated with STZ alone. Indeed, STZ + Nutlin-3-treated mice were characterized by significantly (p < 0.05) lower levels of hyperglycemia, reduced weight loss, and increased spleen weight. In addition, STZ alone promoted a marked decrease in the levels of several circulating cytokines, including interleukin-12 (IL-12)p40. On the other hand, co-injection of STZ + Nutlin-3 significantly (p < 0.01) counteracted IL-12p40 down-modulation. In vitro experiments performed on the RAW264.7 macrophagic cell line model, used as cellular source of IL-12p40, demonstrated that Nutlin-3 treatment increased IL-12p40 release, strongly suggesting a direct effect of Nutlin-3 on the immune system. Overall, these data demonstrate that systemic administration of Nutlin-3 ameliorates the severity of STZ-induced DM and increases the levels of circulating IL-12p40.

p53-independent roles of MDM2 in NF-κB signaling: implications for cancer therapy, wound healing, and autoimmune diseases

Murine double minute-2 (MDM2) is an intracellular molecule with multiple biologic functions. It serves as a negative regulator of p53 and thereby limits cell cycle arrest and apoptosis. Because MDM2 blockade suppresses tumor cell growth in vitro and in vivo, respective MDM2 inhibition is currently evaluated as anti-cancer therapy in clinical trials. However, the anti-proliferative effects of MDM2 inhibition also impair regenerative cell growth upon tissue injury. This was so far documented for tubular repair upon postischemic acute kidney injury and might apply to wound healing responses in general. Furthermore, MDM2 has numerous p53-independent effects. As a new entry, MDM2 was identified to act as a co-transcription factor for nuclear factor-kappa-light-enhancer of activated B cells (NF-κB) at cytokine promoters. This explains the potent anti-inflammatory effects of MDM2 inhibitors in vitro and in vivo. For example, the NF-κB-antagonistic and p53-agonistic activities of MDM2 inhibitors elicit potent therapeutic effects on experimental lymphoproliferative autoimmune disorders such as systemic lupus erythematosus. In this review, we discuss the classic p53-dependent, the recently discovered p53-independent, and the NF-κB-agonistic biologic functions of MDM2. We describe its complex regulatory role on p53 and NF-κB signaling and name areas of research that may help to foresee previously unexpected effects or potential alternative indications of therapeutic MDM2 blockade.

Deletion of phd2 in myeloid lineage attenuates hypertensive cardiovascular remodeling

BACKGROUND

Hypertension induces cardiovascular hypertrophy and fibrosis. Infiltrated macrophages are critically involved in this process. We recently reported that inhibition of prolyl hydroxylase domain protein 2 (PHD2), which hydroxylates the proline residues of hypoxia-inducible factor-α (HIF-α) and thereby induces HIF-α degradation, suppressed inflammatory responses in macrophages. We examined whether myeloid-specific Phd2 deletion affects hypertension-induced cardiovascular remodeling.

METHODS AND RESULTS

Myeloid-specific PHD2-deficient mice (MyPHD2KO) were generated by crossing Phd2-floxed mice with LysM-Cre transgenic mice, resulting in the accumulation of HIF-1α and HIF-2α in macrophage. Eight- to ten-week-old mice were given N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, and Angiotensin II (Ang II) infusion. L-NAME/Ang II comparably increased systolic blood pressure in control and MyPHD2KO mice. However, MyPHD2KO mice showed less aortic medial and adventitial thickening, and macrophage infiltration. Cardiac interstitial fibrosis and myocyte hypertrophy were also significantly ameliorated in MyPHD2KO mice. Transforming growth factor-β and collagen expression were decreased in the aorta and heart from MyPHD2KO mice. Echocardiographic analysis showed that left ventricular hypertrophy and reduced ejection fraction induced by L-NAME/Ang II treatment in control mice were not observed in MyPHD2KO mice. Administration of digoxin that inhibits HIF-α synthesis to L-NAME/Ang II-treated MyPHD2KO mice reversed these beneficial features.

CONCLUSIONS

Phd2 deletion in myeloid lineage attenuates hypertensive cardiovascular hypertrophy and fibrosis, which may be mediated by decreased inflammation- and fibrosis-associated gene expression in macrophages. PHD2 in myeloid lineage plays a critical role in hypertensive cardiovascular remodeling.

Activation of lung p53 by Nutlin-3a prevents and reverses experimental pulmonary hypertension

BACKGROUND

Induction of cellular senescence through activation of the p53 tumor suppressor protein is a new option for treating proliferative disorders. Nutlins prevent the ubiquitin ligase MDM2 (murine double minute 2), a negative p53 regulator, from interacting with p53. We hypothesized that cell senescence induced by Nutlin-3a exerted therapeutic effects in pulmonary hypertension (PH) by limiting the proliferation of pulmonary artery smooth muscle cells (PA-SMCs).

METHODS AND RESULTS

Nutlin-3a treatment of cultured human PA-SMCs resulted in cell growth arrest with the induction of senescence but not apoptosis; increased phosphorylated p53 protein levels; and expression of p53 target genes including p21, Bax, BTG2, and MDM2. Daily intraperitoneal Nutlin-3a treatment for 3 weeks dose-dependently reduced PH, right ventricular hypertrophy, and distal pulmonary artery muscularization in mice exposed to chronic hypoxia or SU5416/hypoxia. Nutlin-3a treatment also partially reversed PH in chronically hypoxic or transgenic mice overexpressing the serotonin-transporter in SMCs (SM22-5HTT+ mice). In these mouse models of PH, Nutlin-3a markedly increased senescent p21-stained PA-SMCs; lung p53, p21, and MDM2 protein levels; and p21, Bax, PUMA, BTG2, and MDM2 mRNA levels; but induced only minor changes in control mice without PH. Marked MDM2 immunostaining was seen in both mouse and human remodeled pulmonary vessels, supporting the use of Nutlins as a PH-targeted therapy. PH prevention or reversal by Nutlin-3a required lung p53 stabilization and increased p21 expression, as indicated by the absence of Nutlin-3a effects in hypoxia-exposed p53(-/-) and p21(-/-) mice.

CONCLUSIONS

Nutlin-3a may hold promise as a prosenescence treatment targeting PA-SMCs in PH.