Angiotensin-II-induced apoptosis requires regulation of nucleolin and Bcl-xL by SHP-2 in primary lung endothelial cells

Nucleolin alleviates endotoxemia-induced myocardial dysfunction via inhibiting Drp1-mediated mitochondrial fission

BACKGROUND

Our previous study found that nucleolin expression exerted anti-cardiac injury effects by promoting mitochondrial biogenesis; however, it could not explain the increase in mitochondrial fragmentation during myocardial injury. Mitochondrial fragmentation is associated with mitochondrial fission, but it is unknown whether nucleolin regulates mitochondrial fission. Therefore, this study aims to investigate the mechanism by which nucleolin regulates mitochondrial fission in endotoxemia-induced myocardial dysfunction.

METHODS

Nucleolin myocardial-specific knockout mice were used to construct an endotoxemia-induced myocardial dysfunction model. Mitochondrial membrane potential (MMP), ATP production, Mitotracker Red, Transmission Electron Microscope were measured to assess mitochondrial function. Mitochondria were isolated to observe Drp1 translocation to mitochondria. The expression of pGSK-3β-Tyr216, GSK-3β, pDrp1-Ser637, nucleolin and dynamin-related protein 1 (DNM1L, Drp1) were detected using qRT-PCR and western blot.

RESULTS

Following cecum ligation and puncture (CLP) model, cardiac function was impaired, myocardial mitochondrial function declined, mitochondrial morphology became disorganized and fragmented, nucleolin and Drp1 expression was elevated. Myocardial injury and mitochondrial dysfunction were further exacerbated after nucleolin myocardium-specific knockout. Meanwhile, after cellular-level nucleolin interference, it further led to LPS and TNF-α-induced mitochondrial dysfunction and cardiomyocyte damage. Mechanically, nucleolin interference inhibited Drp1 phosphorylation at Ser637 and promoted Drp1 translocation to mitochondria. Myocardial injury caused by nucleolin knockdown was alleviated by the use of P110, an inhibitor of Drp1 mitochondrial translocation.

CONCLUSION

Endotoxemia-induced myocardial dysfunction is accompanied by increased mitochondrial fragmentation. Nucleolin alleviates endotoxemia-induced myocardial dysfunction by enhancing Drp1 phosphorylation at Ser637, inhibiting Drp1 translocation to the mitochondria and mitochondrial fission.

Apoptosis in post-streptococcal glomerulonephritis and mechanisms for failed of inflammation resolution

Post-streptococcal glomerulonephritis is a condition resulting from infection by group A beta-hemolytic streptococcus. The main mechanism involves the formation of immune complexes formed in the circulation or in situ on the glomerular basement membrane, which activates complement and causes various inflammatory processes. Cellular mechanisms have been reported in the induction of kidney damage represented by the infiltration of innate cells (neutrophils and monocyte/macrophages) and adaptive cells (CD4 + lymphocytes and CD8 + lymphocytes) of the immune system. These cells induce kidney damage through various mechanisms. It has been reported that nephritogenic antigens are capable of inducing inflammatory processes early, even before the formation of immune complexes. Usually, this disease progresses towards clinical and renal normalization; however, in a smaller number of patients, it evolves into chronicity and persistent kidney damage. Hypotheses have been proposed regarding the mechanisms underlying this progression to chronicity including failure to induce apoptosis and failure to phagocytose apoptotic cells, allowing these cells to undergo membrane permeabilization and release pro-inflammatory molecules into the environment, thereby perpetuating renal inflammation. Other mechanisms involved include persistent infection, genetic background of the host's complement system, tubulointerstitial changes, and pre-existing kidney damage due to old age and comorbidities.

The Role of c-Abl Tyrosine Kinase in Brain and Its Pathologies

Differentiated status, low regenerative capacity and complex signaling make neuronal tissues highly susceptible to translating an imbalance in cell homeostasis into cell death. The high rate of neurodegenerative diseases in the elderly population confirms this. The multiple and divergent signaling cascades downstream of the various stress triggers challenge researchers to identify the central components of the stress-induced signaling pathways that cause neurodegeneration. Because of their critical role in cell homeostasis, kinases have emerged as one of the key regulators. Among kinases, non-receptor tyrosine kinase (Abelson kinase) c-Abl appears to be involved in both the normal development of neural tissue and the development of neurodegenerative pathologies when abnormally expressed or activated. However, exactly how c-Abl mediates the progression of neurodegeneration remains largely unexplored. Here, we summarize recent findings on the involvement of c-Abl in normal and abnormal processes in nervous tissue, focusing on neurons, astrocytes and microglial cells, with particular reference to molecular events at the interface between stress signaling, DNA damage, and metabolic regulation. Because inhibition of c-Abl has neuroprotective effects and can prevent neuronal death, we believe that an integrated view of c-Abl signaling in neurodegeneration could lead to significantly improved treatment of the disease.

Acute Lung Injury in aortic dissection : new insights in anesthetic management strategies

Acute aortic dissection (AAD) is a severe cardiovascular disease characterized by rapid progress and a high mortality rate. The incidence of acute aortic dissection is approximately 5 to 30 per 1 million people worldwide. In clinical practice, about 35% of AAD patients are complicated with acute lung injury (ALI). AAD complicated with ALI can seriously affect patients' prognosis and even increase mortality. However, the pathogenesis of AAD combined with ALI remains largely unknown. Given the public health burden of AAD combined with ALI, we reviewed the anesthetic management advances and highlighted potential areas for clinical practice.

Angiotensin receptor-neprilysin inhibitor (thiorphan/irbesartan) improved cardiac function in a rat model of myocardial ischemic reperfusion injury

Mitochondria-mediated apoptosis plays a critical role in myocardial ischemia reperfusion (IR) injury and causes a negative impact on cardiac efficiency and function. The combined angiotensin receptor-neprilysin inhibitor (ARNI) is a promising cardioprotective pharmacological agent that could rescue the heart from IR injury. This study investigated the cardioprotective effect of thiorphan (TH) in combination with three different doses of irbesartan (IRB) on myocardial IR injury and detected the most effective dose combination. Male Wistar rats were used and divided into five groups (10 rats/group): (I) Sham, (II) ischemia-reperfusion I/R, (III) TH/IRB + IR (0.1/5 mg/kg), (IV) TH/IRB + IR (0.1/10 mg/kg), and (V) TH/IRB + IR (0.1/15 mg/kg) groups. Thiorphan and irbesartan were injected intraperitoneally 15 min before IR induction. Mean arterial blood pressure, left ventricular end diastolic pressure (LVEDP), left ventricular maximum rate of pressure (LVdp/dt_max ), and cardiac levels of creatine kinase-MB, malondialdehyde, superoxide dismutase, and endothelin-1 were measured. Cardiac mitochondria complexes activities, histopathological examination of myocardial tissues, immunohistochemistry studies for myocardial apoptosis (Bax and Bcl-2), and electron microscopy examination of left ventricle were performed. TH/IRB combination preserved cardiac functions and mitochondria complex activities and mitigated cardiac damage, oxidative stress, and apoptosis following IR. Also, there was an evident improvement in histopathological changes and electron microscopy examination of left ventricle compared with I/R group. TH/IRB in a dose of 0.1/10 mg/kg showed significant improvement compared with the other treated groups. Thiorphan/irbesartan improved cardiac functions following IR injury. This could be explained by the reported improvement of mitochondria complex activities and reduction of oxidative stress, endothelin-1, and apoptosis.

A comprehensive review of SHP2 and its role in cancer

Src homology 2-containing protein tyrosine phosphatase 2 (SHP2) is a non-receptor protein tyrosine phosphatase ubiquitously expressed mainly in the cytoplasm of several tissues. SHP2 modulates diverse cell signaling events that control metabolism, cell growth, differentiation, cell migration, transcription and oncogenic transformation. It interacts with diverse molecules in the cell, and regulates key signaling events including RAS/ERK, PI3K/AKT, JAK/STAT and PD-1 pathways downstream of several receptor tyrosine kinases (RTKs) upon stimulation by growth factors and cytokines. SHP2 acts as both a phosphatase and a scaffold, and plays prominently oncogenic functions but can be tumor suppressor in a context-dependent manner. It typically acts as a positive regulator of RTKs signaling with some inhibitory functions reported as well. SHP2 expression and activity is regulated by such factors as allosteric autoinhibition, microRNAs, ubiquitination and SUMOylation. Dysregulation of SHP2 expression or activity causes many developmental diseases, and hematological and solid tumors. Moreover, upregulated SHP2 expression or activity also decreases sensitivity of cancer cells to anticancer drugs. SHP2 is now considered as a compelling anticancer drug target and several classes of SHP2 inhibitors with different mode of action are developed with some already in clinical trial phases. Moreover, novel SHP2 substrates and functions are rapidly growing both in cell and cancer. In view of this, we comprehensively and thoroughly reviewed literatures about SHP2 regulatory mechanisms, substrates and binding partners, biological functions, roles in human cancers, and different classes of small molecule inhibitors target this oncoprotein in cancer.

Scorpion bradykinin potentiating factor mitigates lung damage induced by γ-irradiation in rats: Insights on AngII/ACE/Ang(1-7) axis

The goal of this research is to study the mitigating impact of bradykinin potentiating factor (BPF) found in scorpion Androctonus bicolor venom on irradiation-induced lung damage as a new functional target for angiotensin-converting enzyme inhibitors (ACEIs). Male rats were exposed to 7 Gy of γ-radiation as a single dose, with a biweekly intraperitoneal injection of 1 μg/g BPF. Gamma irradiation not only boosted the ACE activity and angiotensin II (Ang II) level, in lung tissue but also significantly depressed the angiotensin (1-7) (Ang (1-7)) that, lead to lung toxicity through a significant elevation of pulmonary levels of CXC-chemokine receptor 4 (CXCR4), toll-like receptor 4 (TLR4), nitric oxide (NO) and lactate dehydrogenase (LDH) activity with a marked disruption in oxidative stress markers, via a reduction in the level of total thiol (tSH) and superoxide dismutase (SOD) activity associated with an elevation in protein carbonyl (PCO) contents. In addition, apoptotic consequences of gamma irradiation were evidenced by raising the levels of mitogen-activated protein kinase (MAPK), C-Jun N-Terminal Kinases (JNK), and cleaved caspase-3. BPF administration leads to ACE inhibition, consequently sustaining decreased Ang II alongside increased Ang (1-7) production. Those sensitive molecules reduce irradiated lung issues. In conclusion, BPF significantly diminished the biochemical and histopathological consequences of radiation through renin-angiotensin system (RAS) control and ACE suppression in the lung.

Captopril reduces lung inflammation and accelerated senescence in response to thoracic radiation in mice

The lung is sensitive to radiation and exhibits several phases of injury, with an initial phase of radiation-induced pneumonitis followed by delayed and irreversible fibrosis. The angiotensin-converting enzyme inhibitor captopril has been demonstrated to mitigate radiation lung injury and to improve survival in animal models of thoracic irradiation, but the mechanism remains poorly understood. Here we investigated the effect of captopril on early inflammatory events in the lung in female CBA/J mice exposed to thoracic X-ray irradiation of 17-17.9 Gy (0.5-0.745 Gy min-1). For whole-body + thoracic irradiation, mice were exposed to 7.5 Gy (0.6 Gy min-1) total-body 60Co irradiation and 9.5 Gy thoracic irradiation. Captopril was administered orally (110 mg kg-1 day-1) in the drinking water, initiated 4 h through to150 days post-irradiation. Captopril treatment increased survival from thoracic irradiation to 75% at 150 days compared with 0% survival in vehicle-treated animals. Survival was characterized by a significant decrease in radiation-induced pneumonitis and fibrosis. Investigation of early inflammatory events showed that captopril significantly attenuated macrophage accumulation and decreased the synthesis of radiation-induced interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) pro-inflammatory cytokines in the lungs of irradiated mice. Suppression of IL-1β and TNF-α correlated with an increase of the anti-inflammatory cytokine IL-10 in the spleen with captopril treatment. We also found that captopril decreased markers for radiation-induced accelerated senescence in the lung tissue. Our data suggest that suppression of inflammation and senescence markers, combined with an increase of anti-inflammatory factors, are a part of the mechanism for captopril-induced survival in thoracic irradiated mice.

A hypothesis for pathobiology and treatment of COVID-19: The centrality of ACE1/ACE2 imbalance

Angiotensin Converting Enzyme2 is the cell surface binding site for the coronavirus SARS-CoV-2, which causes COVID-19. We propose that an imbalance in the action of ACE1- and ACE2-derived peptides, thereby enhancing angiotensin II (Ang II) signalling is primary driver of COVID-19 pathobiology. ACE1/ACE2 imbalance occurs due to the binding of SARS-CoV-2 to ACE2, reducing ACE2-mediated conversion of Ang II to Ang peptides that counteract pathophysiological effects of ACE1-generated ANG II. This hypothesis suggests several approaches to treat COVID-19 by restoring ACE1/ACE2 balance: (a) AT receptor antagonists; (b) ACE1 inhibitors (ACEIs); (iii) agonists of receptors activated by ACE2-derived peptides (e.g. Ang (1-7), which activates MAS1); (d) recombinant human ACE2 or ACE2 peptides as decoys for the virus. Reducing ACE1/ACE2 imbalance is predicted to blunt COVID-19-associated morbidity and mortality, especially in vulnerable patients. Importantly, approved AT antagonists and ACEIs can be rapidly repurposed to test their efficacy in treating COVID-19. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

A hypothesis for pathobiology and treatment of COVID-19: The centrality of ACE1/ACE2 imbalance

Angiotensin Converting Enzyme2 is the cell surface binding site for the coronavirus SARS-CoV-2, which causes COVID-19. We propose that an imbalance in the action of ACE1- and ACE2-derived peptides, thereby enhancing angiotensin II (Ang II) signalling is primary driver of COVID-19 pathobiology. ACE1/ACE2 imbalance occurs due to the binding of SARS-CoV-2 to ACE2, reducing ACE2-mediated conversion of Ang II to Ang peptides that counteract pathophysiological effects of ACE1-generated ANG II. This hypothesis suggests several approaches to treat COVID-19 by restoring ACE1/ACE2 balance: (a) AT receptor antagonists; (b) ACE1 inhibitors (ACEIs); (iii) agonists of receptors activated by ACE2-derived peptides (e.g. Ang (1-7), which activates MAS1); (d) recombinant human ACE2 or ACE2 peptides as decoys for the virus. Reducing ACE1/ACE2 imbalance is predicted to blunt COVID-19-associated morbidity and mortality, especially in vulnerable patients. Importantly, approved AT antagonists and ACEIs can be rapidly repurposed to test their efficacy in treating COVID-19. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Role of Renin-Angiotensin System in Acute Lung Injury Caused by Viral Infection

The renin-angiotensin system (RAS) is the most important regulatory system of electrolyte homeostasis and blood pressure and acts through angiotensin-converting enzyme (ACE)/angiotensin II (Ang II)/Ang II type 1 (AT1) receptor axis and angiotensin-converting enzyme 2 (ACE2)/angiotensin (1-7)/MAS receptor axis. RAS dysfunction is related to the occurrence and development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) and causes a serious prognosis and even death. ALI/ARDS can be induced by various ways, one of which is viral infections, such as SARS-CoV, SARS-CoV-2, H5N1, H7N9, and EV71. This article reviews the specific mechanism on how RAS dysfunction affects ALI/ARDs caused by viral infections. SARS-CoV and SARS-CoV-2 enter the host cells by binding with ACE2. H5N1 and H7N9 avian influenza viruses reduce the ACE2 level in the body, and EV71 increases Ang II concentration. Treatment with angiotensin-converting enzyme inhibitor and angiotensin AT1 receptor blocker can alleviate ALI/ARDS symptoms. This review provides suggestions for the treatment of lung injury caused by viral infections.

Activation of angiotensin II type-2 receptor protects against cigarette smoke-induced COPD

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally. Cumulative evidence has implicated renin-angiotensin system (RAS) in the pathogenesis of COPD. This study aimed to investigate potential protective effects of angiotensin II type-2 receptor (AT2R) activation in cigarette smoke (CS)-induced COPD models. Compound 21 (C21), a selective and potent non-peptide small molecule AT2R agonist, was evaluated for anti-inflammatory, anti-oxidative and anti-remodeling activities in a two-week (acute) and an eight-week (chronic) CS-induced COPD models. C21 inhibited CS-induced increases in macrophage and neutrophil counts, pro-inflammatory cytokines and oxidative damage markers in bronchoalveolar lavage (BAL) fluid, and TGF-β1 in lung tissues, from COPD models. C21 restored phosphatase activities and reduced phospho-p38 MAPK, phospho-ERK and p65 subunit of NF-κB levels in CS-exposed lung tissues. C21 also suppressed CS-induced increases in α-Sma, Mmp9, Mmp12 and hydroxyproline levels in lung tissues, and neutrophil elastase activity in BAL fluid. C21 modulated RAS in CS-exposed lungs by downregulating Ang II but upregulating Ang-(1–7) and Mas receptor levels. C21 prevented CS-induced emphysema and improved lung functions in chronic COPD model. We report here for the first time the protective effects of AT2R agonist C21 against CS-induced COPD, and provide strong evidence for further development of AT2R agonist for the treatment of COPD.

Integrated analysis of patient samples identifies biomarkers for venetoclax efficacy and combination strategies in acute myeloid leukemia

Deregulation of the BCL2 gene family plays an important role in the pathogenesis of acute myeloid leukemia (AML). The BCL2 inhibitor, venetoclax, has received FDA approval for the treatment of AML. However, upfront and acquired drug resistance ensues due, in part, to the clinical and genetic heterogeneity of AML, highlighting the importance of identifying biomarkers to stratify patients onto the most effective therapies. By integrating clinical characteristics, exome and RNA sequencing, and inhibitor data from primary AML patient samples, we determined that myelomonocytic leukemia, upregulation of BCL2A1 and CLEC7A, as well as mutations of PTPN11 and KRAS conferred resistance to venetoclax and multiple venetoclax combinations. Venetoclax in combination with an MCL1 inhibitor AZD5991 induced synthetic lethality and circumvented venetoclax resistance.

Systems pharmacology reveals the mechanism of activity of Ge-Gen-Qin-Lian decoction against LPS-induced acute lung injury: A novel strategy for exploring active components and effective mechanism of TCM formulae

Acute lung injury (ALI), a severe and life-threatening inflammation of the lung, with high morbidity and mortality, underscoring the urgent need for novel treatments. Ge-Gen-Qin-Lian decoction (GQD), a classic Chinese herbal formula, has been widely used to treat intestine-related diseases in the clinic for centuries. In recent years, a growing number of studies have found that GQD has a favorable anti-inflammatory effect. With the further study on the viscera microbiota, the link between the lungs and the gut-the gut-lung axis has been established. Based on the theory of the gut-lung axis, we used systems pharmacology to explore the effects and mechanisms of GQD treatment in ALI. Hypothesizing that GQD inhibits ALI progression, we used the experimental model of lipopolysaccharide (LPS)-induced ALI in Balb/c mice to evaluate the therapeutic potential of GQD. Our results showed that GQD exerted protective effects against LPS-induced ALI by reducing pulmonary edema and microvascular permeability. Meanwhile, GQD can downregulate the expression of LPS-induced TNF-α, IL-1β, and IL-6 in lung tissue, bronchoalveolar lavage fluid (BLAF), and serum. To further understand the molecular mechanism of GQD in the treatment of ALI, we used the network pharmacology to predict the disease targets of the active components of GQD. Lung tissue and serum samples of the mice were separately analyzed by transcriptomics and metabolomics. KEGG pathway analysis of network pharmacology and transcriptomics indicated that PI3K/Akt signaling pathway was significantly enriched, suggesting that it may be the main regulatory pathway for GQD treatment of ALI. By immunohistochemical analysis and apoptosis detection, it was verified that GQD can inhibit ALI apoptosis through PI3K/Akt signaling pathway. Then, we used the PI3K inhibitor LY294002 to block the PI3K/Akt signaling pathway, and reversely verified that the PI3K/Akt signaling pathway is the main pathway of GQD anti-ALI. In addition, differential metabolites in mice serum samples indicate that GQD can inhibit the inflammatory process of ALI by reversing the imbalance of energy metabolism. Our study showed that, GQD did have a better therapeutic effect on ALI, and initially elucidated its molecular mechanism. Thus, GQD could be exploited to develop novel therapeutics for ALI. Moreover, our study also provides a novel strategy to explore active components and effective mechanism of TCM formula combined with TCM theory to treat ALI.

E-Selectin-Binding Peptide-Modified Bovine Serum Albumin Nanoparticles for the Treatment of Acute Lung Injury

Currently, there is no specific treatment for acute lung injury (ALI). E-selectin-binding peptide (Esbp), a high-affinity peptide that delivers drugs targeting inflammatory vascular endothelial cells, can bind to E-selectin and act as a targeting ligand for selective drug delivery. In this study, we coupled the thiol groups of Esbp to the amino groups on the surface of bovine serum albumin (BSA) using succinimidyl iodoacetic acid to make Esbp-modified BSA nanoparticles (BSANPs) at the average ratio of 19.3 μg Esbp to 1 mg BSA. The Esbp-modified BSANPs were spherical in shape and had a particle size of 266.7 ± 2.7 nm, polydispersity index of 0.165 ± 0.02, zeta potential of - 33.64 ± 1.23 mV, encapsulation efficiency of 84.3 ± 2.3%, and drug loading of 6.7 ± 0.32%. The cumulative release rate of dexamethasone-loaded Esbp-modified BSANPs was 51.2% within 12 h, significantly lower than that of 88.2% of free drugs. Moreover, Esbp-modified BSANPs could be uptaken in vitro by activated human umbilical vein endothelial cells and in vivo by the lungs of the established ALI mouse model. These results indicated that our Esbp-modified BSANPs delivery system has characteristics of good targeting ability and biocompatibility and is able to inhibit inflammation. Overall, our Esbp-modified BSANPs delivery system has therapeutic potentials as a new targeting drug system for the treatment of ALI in the future.

Angiotensin II induces apoptosis of human right and left ventricular endocardial endothelial cells by activating the AT2 receptor 1

Endocardial endothelial cells (EECs) form a monolayer lining the ventricular cavities. Studies from our laboratory and the literature have shown differences between EECs isolated from the right and left ventricles (EECRs and EECLs, respectively). Angiotensin II (Ang II) was shown to induce apoptosis of different cell types mainly via AT₁ receptor activation. In this study, we verified whether Ang II induces apoptosis of human EECRs and EECLs (hEECRs and hEECLs, respectively) and via which type of receptor. Using the annexin V labeling and in situ TUNEL assays, our results showed that Ang II induced apoptosis of both hEECRs and hEECLs in a concentration-dependent manner. Our results using specific AT₁ and AT₂ receptor antagonists showed that the Ang-II-induced apoptosis in both hEECRs and hEECLs is mediated mainly via the AT₂ receptor. However, AT₁ receptor blockade partially prevented Ang-II-induced apoptosis, particularly in hEECRs. Hence, our results suggest that mainly AT₂ receptors mediate Ang-II-induced apoptosis of hEECRs and hEECLs. The damage of EECs would affect their function as a physical barrier between the blood and cardiomyocytes, thus affecting cardiomyocyte functions.

Focal adhesion kinase, RhoA, and p38 mitogen-activated protein kinase modulates apoptosis mediated by angiotensin II AT2 receptors

Apoptosis plays an important role in cellular processes such as development, differentiation, and homeostasis. Although the participation of angiotensin II (Ang II) AT₂ receptors (AT ₂ R) in cellular apoptosis is well accepted, the signaling pathway involved in this process is not well established. We evaluated the participation of signaling proteins focal adhesion kinase (FAK), RhoA, and p38 mitogen-activated protein kinase (p38MAPK) in apoptosis induced by Ang II via AT ₂ R overexpressed in HeLa cells. Following a short stimulation time (120 to 240 minutes) with Ang II, HeLa-AT ₂ cells showed nuclear condensation, stress fibers disassembly and membrane blebbing. FAK, classically involved in cytoskeleton reorganization, has been postulated as an early marker of cellular apoptosis. Thus, we evaluated FAK cleavage, detected at early stimulation times (15 to 30 minutes). Apoptosis was confirmed by increased caspase-3 cleavage and enzymatic activity of caspase-3/7. Participation of RhoA was evaluated. HeLa-AT ₂ cells overexpressing RhoA wild-type (WT) or their mutants, RhoA V14 (constitutively active form) or RhoA N19 (dominant-negative form) were used to explore RhoA participation. HeLa-AT ₂ cells expressing the constitutively active variant RhoA V14 showed enhanced apoptotic features at earlier times as compared with cells expressing the WT variant. RhoA N19 expression prevented nuclear condensation/caspase activation. Inhibition of p38MAPK caused an increase in nuclear condensation and caspase-3/7 activation, suggesting a protective role of p38MAPK. Our results clearly demonstrated that stimulation of AT ₂ R induce apoptosis with participation of FAK and RhoA while p38MAPK seems to play a prosurvival role.

The tyrosine phosphatase SHP2 controls TGFβ-induced STAT3 signaling to regulate fibroblast activation and fibrosis

Uncontrolled activation of TGFβ signaling is a common denominator of fibrotic tissue remodeling. Here we characterize the tyrosine phosphatase SHP2 as a molecular checkpoint for TGFβ-induced JAK2/STAT3 signaling and as a potential target for the treatment of fibrosis. TGFβ stimulates the phosphatase activity of SHP2, although this effect is in part counterbalanced by inhibitory effects on SHP2 expression. Stimulation with TGFβ promotes recruitment of SHP2 to JAK2 in fibroblasts with subsequent dephosphorylation of JAK2 at Y570 and activation of STAT3. The effects of SHP2 on STAT3 activation translate into major regulatory effects of SHP2 on fibroblast activation and tissue fibrosis. Genetic or pharmacologic inactivation of SHP2 promotes accumulation of JAK2 phosphorylated at Y570, reduces JAK2/STAT3 signaling, inhibits TGFβ-induced fibroblast activation and ameliorates dermal and pulmonary fibrosis. Given the availability of potent SHP2 inhibitors, SHP2 might thus be a potential target for the treatment of fibrosis.

GPCRs in pulmonary arterial hypertension: tipping the balance

Pulmonary arterial hypertension (PAH) is a progressive, fatal disease characterised by increased pulmonary vascular resistance and excessive proliferation of pulmonary artery smooth muscle cells (PASMC). GPCRs, which are attractive pharmacological targets, are important regulators of pulmonary vascular tone and PASMC phenotype. PAH is associated with the altered expression and function of a number of GPCRs in the pulmonary circulation, which leads to the vasoconstriction and proliferation of PASMC and thereby contributes to the imbalance of pulmonary vascular tone associated with PAH; drugs targeting GPCRs are currently used clinically to treat PAH and extensive preclinical work supports the utility of a number of additional GPCRs. Here we review how GPCR expression and function changes with PAH and discuss why GPCRs continue to be relevant drug targets for the disease.

Post-Transcriptional Regulation of Anti-Apoptotic BCL2 Family Members

Anti-apoptotic B cell lymphoma 2 (BCL2) family members (BCL2, MCL1, BCLxL, BCLW, and BFL1) are key players in the regulation of intrinsic apoptosis. Dysregulation of these proteins not only impairs normal development, but also contributes to tumor progression and resistance to various anti-cancer therapies. Therefore, cells maintain strict control over the expression of anti-apoptotic BCL2 family members using multiple mechanisms. Over the past two decades, the importance of post-transcriptional regulation of mRNA in controlling gene expression and its impact on normal homeostasis and disease have begun to be appreciated. In this review, we discuss the RNA binding proteins (RBPs) and microRNAs (miRNAs) that mediate post-transcriptional regulation of the anti-apoptotic BCL2 family members. We describe their roles and impact on alternative splicing, mRNA turnover, and mRNA subcellular localization. We also point out the importance of future studies in characterizing the crosstalk between RBPs and miRNAs in regulating anti-apoptotic BCL2 family member expression and ultimately apoptosis.

Vascular mechanotransduction data in a rodent model of diabetes: Pressure-induced regulation of SHP2 and associated signaling in the rat inferior vena cava

The effect of diabetes on vascular mechano-transductive response is of great concern. Given the higher rate of vein graft failures associated with diabetes, understanding the multiple cellular and molecular events associated with vascular remodeling is of vital importance. This article represents data related to a study published in Cardiovascular Diabetology [1] (Rice et al., 2006) and Open Journal of Endocrine and Metabolic Diseases [2] (Rice et al., 2015) evaluating the effect of pressurization on rat inferior venae cavae (IVC). Provided within this articles is information related to the method and processing of raw data related to our prior publish work and Data in Brief articles [3], [4] (Rice et al., 2017), as well as the evaluation of alternation in SHP-2 signaling and associated proteins in response to mechanical force. IVC from lean and obese animals were exposed to a 30 min perfusion of 120 mm Hg pressure and evaluated for changes in expression of SHP2, BCL-3, BCL-XL, HSP 27, HSP 70, and PI3K p85, along with the phosphorylation of SHP-2 (Tyr 542).

Endothelial cell apoptosis in angiogenesis and vessel regression

Blood vessel regression is an essential process for ensuring blood vessel networks function at optimal efficiency and for matching blood supply to the metabolic needs of tissues as they change over time. Angiogenesis is the major mechanism by which new blood vessels are produced, but the vessel growth associated with angiogenesis must be complemented by remodeling and maturation events including the removal of redundant vessel segments and cells to fashion the newly forming vasculature into an efficient, hierarchical network. This review will summarize recent findings on the role that endothelial cell apoptosis plays in vascular remodeling during angiogenesis and in vessel regression more generally.

Deletion of AT2 Receptor Prevents SHP-1-Induced VEGF Inhibition and Improves Blood Flow Reperfusion in Diabetic Ischemic Hindlimb

OBJECTIVE

Ischemia caused by narrowing of femoral artery is a major cause of peripheral arterial disease and morbidity affecting patients with diabetes mellitus. We have previously reported that the inhibition of the angiogenic response to VEGF (vascular endothelial growth factor) in diabetic mice was associated with the increased expression of SHP-1 (SH2 domain-containing phosphatase 1), a protein that can be activated by the AT2 (angiotensin II type 2) receptor. Deletion of AT2 receptor has been shown to promote angiogenesis within the ischemic muscle. However, the relative impact of AT2 receptor in diabetic condition remains unknown.

APPROACH AND RESULTS

Nondiabetic and diabetic AT2 null (Atgr2^-/Y) mice underwent femoral artery ligation after 2 months of diabetes mellitus. Blood perfusion was measured every week ≤4 weeks post-surgery. Expression of the VEGF, SHP-1, and renin-angiotensin pathways was evaluated. Blood flow in the ischemic muscle of diabetic Atgr2^-/Y mice recovered faster and ≤80% after 4 weeks compared with 51% recovery in diabetic control littermates. Diabetic Atgr2^-/Y had reduced apoptotic endothelial cells and elevated small vessel formation compared with diabetic Atgr2^+/Y mice, as well as increased SHP-1 expression and reduced VEGF receptor activity. In endothelial cells, high glucose levels and AT2 agonist treatment did not change SHP-1, VEGF, and VEGF receptor expression. However, the activity of SHP-1 and its association with the VEGF receptors were increased, causing inhibition of the VEGF action in endothelial cell proliferation and migration.

CONCLUSIONS

Our results suggest that the deletion of AT2 receptor reduced SHP-1 activity and restored VEGF actions, leading to an increased blood flow reperfusion after ischemia in diabetes mellitus.

Bindarit reduces the incidence of acute aortic dissection complicated lung injury via modulating NF-κB pathway

The pathogenesis of acute aortic dissection (AAD) complicated acute lung injury (ALI) is not currently well defined. At present, no effective animal model has been established for AAD complicated ALI, which hinders research and development of an appropriate treatment regimen for the concurrent conditions. The aim of the present study was to evaluate the therapeutic effects of bindarit (Bnd), an indazolic derivative, on the production of monocyte chemoattractant protein (MCP)-1 in angiotensin II (AngII)-induced complicated ALI in rats. An AAD complicated ALI rat model was established using aminopropionitrile (BAPN) and AngII. The pathological features of AAD complicated ALI were assessed via biochemical and histopathological evaluations. AngII-stimulated human pulmonary microvascular endothelial cells (hPMVECs) were used to assess the effects of Bnd on MCP-1 expression. Western blot analysis was performed to analyze the expression of proteins that may be associated with the process. AAD complicated ALI was established following BAPN and AngII interference, and a massive accumulation of macrophages was observed in the lung tissues of the study rats. Bnd was able to significantly attenuate the incidence of AAD complicated ALI (P<0.05), and significantly inhibit the accumulation of macrophages (P<0.05). The overexpression of MCP-1 induced by AngII in hPMVECs was significantly inhibited by Bnd (P<0.05), which may be associated with downregulation of the classical nuclear factor-κB pathway. Bnd was able to attenuate the incidence of AAD complicated ALI, and inhibit the accumulation of macrophages in vivo. These findings provide a basis for future applications of Bnd as part of a therapeutic treatment schedule for aortic dissection complicated lung injury.

Erythropoietin Regulation by Angiotensin II

The renin-angiotensin system (RAS) is a key regulator of blood pressure and blood volume homeostasis. The RAS is primarily comprised of the precursor protein angiotensinogen and the two proteases, renin and angiotensin-converting enzyme (ACE). Angiotensin I (Ang I) is derived from angiotensinogen by renin, but appears to have no biological activity. In contrast, angiotensin II (Ang II) that has a variety of biological functions in the cells is converted from Ang I through removal of two-C-terminal residues by ACE. The physiological effects of Ang II are due to Ang II signaling through specific receptor binding, resulting in muscle contraction leading to increased blood pressure and volume. To modulate RAS, three classes of drugs have been developed: (1) renin inhibitors to prevent angiotensinogen conversion to Ang I, (2) ACE inhibitors, to prevent Ang I processing to Ang II and (3) angiotensin receptor blockers, to inhibit Ang II signaling through its receptor. Studies using the RAS inhibitors and Ang II demonstrated that RAS signaling mediates actions of Ang II in the regulation of proliferation and differentiation of specific hematopoietic cell types, especially in the red blood cell lineage. Accumulating evidence indicates that RAS regulates EPO, an essential mediator of red cell production, for human anemia and erythropoiesis in vivo and in vitro. The regulation of EPO expression by Ang II may be responsible for maintaining red blood cell homeostasis. This review highlights the biological roles of RAS for blood cell and EPO homeostasis through Ang II signaling. The molecular mechanism for Ang II-induced EPO production of the cell or tissue type-specific expression is discussed.

Angiotensin II degrades myeloid cell leukemia 1 in human umbilical vein endothelial cells

Angiotensin II (Ang II) plays a central role in cardiovascular diseases by causing endothelial apoptosis and dysfunction. Myeloid cell leukemia 1 (Mcl-1) is an antiapoptotic member of the Bcl-2 family of apoptosis-regulating proteins. It has been reported that Mcl-1 plays a pivotal role in protecting cells against apoptosis. Presently, the effects of Ang II on the expression of Mcl-1 remain unknown. In this study, we report, for the first time, that the antiapoptotic protein Mcl-1 is degraded by the proteasome during Ang II-induced apoptosis in HUVECs. Notably, our results demonstrate that prior phosphorylation by GSK-3β is required for proteasomal degradation of Mcl-1. Notably, the reduced level of Mcl-1 was abolished by a specific GSK-3β inhibitor, suggesting that the phosphorylation of Mcl-1 by GSK-3β is required for proteasomal degradation of Mcl-1. Overexpression of Mcl-1 rescued apoptosis induced by Ang II, however, knockdown of Mcl-1 exacerbated Ang II-induced apoptosis, thereby indicating that the protein level of Mcl-1 determines the response of endothelial cells to this drug. © 2017 IUBMB Life, 69(5):321-327, 2017.

Mitochondrial-dependent mechanisms are involved in angiotensin II-induced apoptosis in dopaminergic neurons

Introduction:

We recently demonstrated that angiotensin II (Ang II) was involved in the etiology of Parkinson’s disease (PD) via induction of apoptosis of dopaminergic neurons, but the mechanisms are not completely elucidated. Here, we asked whether mitochondrial-dependent mechanisms contributed to the Ang II-induced dopaminergic neuronal apoptosis.

Materials and methods:

CATH.a cells were incubated with Ang II in combination with mitochondrial permeability transition pore (mPTP) inhibitors or angiotensin receptor antagonists, and apoptosis rate, caspase-3 activity, cytochrome c levels, and mPTP opening were assessed.

Results:

We showed that Ang II triggered apoptosis via a mitochondrial-dependent pathway, as elevated cytochrome c levels were observed in the cytosol. By employing cyclosporin A and sanglifehrin A, two specific mPTP inhibitors, we revealed that cytochrome c release from mitochondria into cytoplasm was ascribed to mPTP opening. Meanwhile, the aforementioned effects could be abrogated by an AT₁ receptor antagonist losartan rather than an AT₂ receptor antagonist PD123319.

Conclusion:

This study demonstrates that Ang II triggers mitochondrial-dependent apoptosis via facilitating mPTP opening through an AT₁ receptor-mediated fashion in dopaminergic neurons. These findings give insight into the effect of Ang II in the etiology of PD, and reinforce the application of AT₁ receptor antagonists for PD treatment.

The hepatocyte growth factor isoform NK2 activates motogenesis and survival but not proliferation due to lack of Akt activation

Hepatocyte growth factor (HGF) is a pleiotrophic factor involved in cellular proliferation, migration and morphogenesis. HGF is required for normal tissue and organ development during embryogenesis, but in the adult HGF has been demonstrated to drive normal tissue repair and inhibit fibrotic remodeling. HGF has two naturally occurring human isoforms as a result of alternative splicing, NK1 and NK2. While NK1 has been defined as an agonist for HGF receptor, Met, NK2 is defined as a partial Met antagonist. Furthermore, under conditions of fibrotic remodeling, NK2 is still expressed while full length HGF is suppressed. Furthermore, the mechanism by which NK2 partially signals through Met is not completely understood. Here, we investigated the mitogenic, motogenic, and anti-apoptotic activities of NK2 compared with full length HGF in primary human bronchial epithelial cells (BEpC) and bovine pulmonary artery endothelial cells (PAEC). In human BEpC, NK2 partial activated Met, inducing Met phosphorylation at Y1234/1235 in the tyrosine-kinase domain but not at Y1349 site in the multifunctional docking domain. Partial phosphorylation of Met by NK2 resulted in activation of MAPK and STAT3, but not AKT. This correlated with motogenesis and survival in a MAPK-dependent manner, but not cell proliferation. Overexpression of a constitutively active AKT complemented NK2 signaling, allowing NK2 to induce cell proliferation. These data indicate that NK2 and HGF drive motogenic and anti-apoptotic signaling but only HGF drives cell proliferation by activating AKT-pathway signaling. These results have implications for the biological consequences of differential regulation of the two isoforms under pro-fibrotic conditions.

Angiotensin II induces apoptosis of human pulmonary microvascular endothelial cells in acute aortic dissection complicated with lung injury patients through modulating the expression of monocyte chemoattractant protein-1

Patients with acute aortic dissection (AAD) usually showed acute lung injury (ALI). However, its pathogenesis is still not well defined. Apoptosis of pulmonary microvascular endothelial cells (PMVECs) is closely related to the alveolus-capillary barrier injury and the increased vascular permeability. In this study, we aim to investigate the human PMVECs (hPMVECs) apoptosis induced by angiotensin II (AngII) and monocyte chemoattractant protein-1 (MCP-1) and their potential interaction in the pathogenesis of AAD complicated with ALI. Fifty-eight newly diagnosed AAD, 12 matched healthy individuals were included. Pulmonary tissues of AAD complicated with lung injury were obtained from 2 cadavers to determine the levels of AngII type 1 receptor (AT1-R) and MCP-1. Serum AngII was measured using commercial ELISA kit. H&E staining and immunohistostaining were performed to determine the expression of AT1-R and MCP-1. For the in vitro experiment, hPMVECs were divided into control, AngII group, AngII+Bindarit group and Bindarit group, respectively. Flow cytometry was performed to analyze the apoptosis in each group. Reverse transcription-polymerase chain reaction was performed to determine the mRNA expression of MCP-1. Western blot analysis was performed to evaluate the expression of MCP-1 and apoptosis related protein. Apoptosis of hPMVECs was observed in the lung tissues in the cadavers with AAD complicated with ALI. Besides, the expression of AT1-R and MCP-1 was remarkably elevated. Compared with normal individuals and the non-lung injury AAD patients, the expression of serum AngII was remarkably elevated in AAD patients complicated with ALI. In vitro experiments showed AngII contributed to the apoptosis and elevation of MCP1 in hPMVECs. Besides, it involved in the down-regulation of Bcl-2 protein, and up-regulation of Bax and Caspase-3. Such phenomenon was completely reversed after administration of MCP-1 inhibitor (Bindarit). The production of MCP-1 and cellular apoptosis induced by AngII in hPMVECs are closely related to the pathogenesis of AAD complicated with ALI. The association between MCP-1 and AngII is crucial in the apoptosis of hPMVECs.

MSCs modified with ACE2 restore endothelial function following LPS challenge by inhibiting the activation of RAS

Angiotensin (Ang) II plays an important role in the process of endothelial dysfunction in acute lung injury (ALI) and is degraded by angiotensin-converting enzyme2 (ACE2). However, treatments that target ACE2 to injured endothelium and promote endothelial repair of ALI are lacking. Mesenchymal stem cells (MSCs) are capable of homing to the injured site and delivering a protective gene. Our study aimed to evaluate the effects of genetically modified MSCs, which overexpress the ACE2 protein in a sustained manner via a lentiviral vector, on Ang II production in endothelium and in vitro repair of lipopolysaccharide (LPS)-induced endothelial injury. We found that the efficiency of lentiviral vector transduction of MSCs was as high as 97.8% and was well maintained over 30 passages. MSCs modified with ACE2 showed a sustained high expression of ACE2 mRNA and protein. The modified MSCs secreted soluble ACE2 protein into the culture medium, which reduced the concentration of Ang II and increased the production of Ang 1-7. MSCs modified with ACE2 were more effective at restoring endothelial function than were unmodified MSCs, as shown by the enhanced survival of endothelial cells; the downregulated production of inflammatory mediators, including ICAM-1, VCAM-1, TNF-α, and IL-6; reduced paracellular permeability; and increased expression of VE-cadherin. These data demonstrate that MSCs modified to overexpress the ACE2 gene can produce biologically active ACE2 protein over a sustained period of time and have an enhanced ability to promote endothelial repair after LPS challenge. These results encourage further testing of the beneficial effects of ACE2-modified MSCs in an ALI animal model.

Nucleolin down-regulation is involved in ADP-induced cell cycle arrest in S phase and cell apoptosis in vascular endothelial cells

High concentration of extracellular ADP has been reported to induce cell apoptosis, but the molecular mechanisms remain not fully elucidated. In this study, we found by serendipity that ADP treatment of human umbilical vein endothelial cells (HUVEC) and human aortic endothelial cells (HAEC) down-regulated the protein level of nucleolin in a dose- and time-dependent manner. ADP treatment did not decrease the transcript level of nucloelin, suggesting that ADP might induce nucleolin protein degradation. HUVEC and HAEC expressed ADP receptor P2Y13 receptor, but did not express P2Y1 or P2Y12 receptors. However, P2Y1, 12, 13 receptor antagonists MRS2179, PSB0739, MRS2211 did not inhibit ADP-induced down-regulation of nucleolin. Moreover, MRS2211 itself down-regulated nucleolin protein level. In addition, 2-MeSADP, an agonist for P2Y1, 12 and 13 receptors, did not down-regulate nucleolin protein. These results suggested that ADP-induced nucleolin down-regulation was not due to the activation of P2Y1, 12, or 13 receptors. We also found that ADP treatment induced cell cycle arrest in S phase, cell apoptosis and cell proliferation inhibition via nucleolin down-regulation. The over-expression of nucleolin by gene transfer partly reversed ADP-induced cell cycle arrest, cell apoptosis and cell proliferation inhibition. Furthermore, ADP sensitized HUVEC to cisplatin-induced cell death by the down-regulation of Bcl-2 expression. Taken together, we found, for the first time to our knowledge, a novel mechanism by which ADP regulates cell proliferation by induction of cell cycle arrest and cell apoptosis via targeting nucelolin.

Syk interacts with and phosphorylates nucleolin to stabilize Bcl-x(L) mRNA and promote cell survival

The Syk protein tyrosine kinase, a well-characterized regulator of immune cell function, plays an increasingly recognized role in tumorigenesis as a promoter of cell survival in both hematological and nonhematological malignancies. We show here that the expression of Syk in MCF7 or MDA-MB-231 breast cancer cells or in DG75 B-lymphoma cells protects cells from apoptosis induced by oxidative or genotoxic stress by stabilizing the mRNA for Bcl-x(L), an antiapoptotic protein. Syk binds robustly to nucleolin and phosphorylates it on tyrosine, enhancing its ability to bind the Bcl-x(L) mRNA. Consequently, reducing the level of nucleolin by RNA interference attenuates the ability of Syk to protect cells from stress-induced cell death.

Beyond TGFβ--novel ways to target airway and parenchymal fibrosis

Within the lungs, fibrosis can affect both the parenchyma and the airways. Fibrosis is a hallmark pathological change in the parenchyma in patients with idiopathic pulmonary fibrosis (IPF), whilst in asthma or chronic obstructive pulmonary disease (COPD) fibrosis is a component of the remodelling of the airways. In the past decade, significant advances have been made in understanding the disease behaviour and pathogenesis of parenchymal and airway fibrosis and as a result a variety of novel therapeutic targets for slowing or preventing progression of these fibrotic changes have been identified. This review highlights a number of these targets and discusses the potential for treating parenchymal or airway fibrosis through these mediators/pathways in the future.

Propofol protects against angiotensin II-induced mouse hippocampal HT22 cells apoptosis via inhibition of p66Shc mitochondrial translocation

Hippocampal neuronal oxidative stress and apoptosis have been reported to be involved in cognitive impairment, and angiotensin II could induce hippocampal oxidative stress and apoptosis. Propofol is a widely used intravenous anesthetic agent in clinical practice, and it demonstrates significant neuroprotective activities. In this study, we investigated the mechanism how propofol protected mouse hippocampal HT22 cells against angiotensin II-induced oxidative stress and apoptosis. Cell viability was evaluated with CCK8 kit. Protein expressions of active caspase 3, cytochrome c, p66(Shc), p-p66(shc)-Ser(36), protein kinase C βII (PKCβII), Pin-1 and phosphatase A2 (PP2A) were measured by Western blot. Superoxide anion (O2(.-)) accumulation was measured with the reduction of ferricytochrome c. Compared with the control group, angiotensin II up-regulated expression of PKCβII, Pin-1 and PP2A, induced p66(Shc)-Ser(36) phosphorylation, and facilitated p66(Shc) mitochondrial translocation, resulting in O2(.-) accumulation, mitochondrial cytochrome c release, caspase 3 activation, and the inhibition of cell viability. Importantly, we found propofol inhibited angiotensin II-induced PKCβII and PP2A expression and improved p66(Shc) mitochondrial translocation, O2(.-) accumulation, mitochondrial cytochrome c release, caspase 3 activation, inhibition of cell viability. On the other hand, propofol had no effects on angiotensin II-induced Pin-1 expression and p66(Shc)-Ser(36) phosphorylation. Moreover, the protective effects of propofol on angiotensin II-induced HT22 apoptosis were similar with calyculin A, an inhibitor of PP2A and CGP53353, an inhibitor of PKCβII. However, the protective effect of propofol could be reversed by FTY720, an activator of PP2A, rather than PMA, an activator of PKCβII. Our data indicated that propofol down-regulated PP2A expression, inhibiting dephosphorylation of p66(Shc)-Ser(36) and p66(Shc) mitochondrial translocation, decreasing O2(.-) accumulation, reducing mitochondrial cytochrome c release, inhibiting caspase 3 activation. By these mechanisms, it protects mouse hippocampal HT22 cells against angiotensin II-induced apoptosis.

The role of Bcl-2 family proteins in pulmonary fibrosis

Pulmonary fibrosis is characterized by epithelial injury, abnormal tissue repair, fibroproliferation and loss of pulmonary function as a result of a complex interaction of multiple cellular and molecular processes. There is accumulating evidence in support of a role for apoptosis in the pathogenesis of interstitial lung diseases. The Bcl-2 (B-cell lymphoma-2) family of proteins, which consists of antiapoptotic and pro-apoptotic members, is a critical regulator for apoptosis and development of pulmonary fibrosis. The association between Bcl-2 family members and various pathways and mediators has been also described in the pulmonary fibrosis. This article reviews the recent advances regarding the roles of Bcl-2 family as the apoptosis-regulatory factors in pulmonary fibrosis from human tissue studies, animal models, ex vivo and in vitro studies. Further understanding of apoptosis signaling regulation through Bcl-2 family proteins in the lung tissue may lead to better design of new therapeutic interventions for pulmonary fibrosis.

Mechanism of erythropoietin regulation by angiotensin II

Erythropoietin (EPO) is the primary regulator of red blood cell development. Although hypoxic regulation of EPO has been extensively studied, the mechanism(s) for basal regulation of EPO are not well understood. In vivo studies in healthy human volunteers and animal models indicated that angiotensin II (Ang II) and angiotensin converting enzyme inhibitors regulated blood EPO levels. In the current study, we found that Ang II induced EPO expression in situ in murine kidney slices and in 786-O kidney cells in culture as determined by reverse transcription polymerase chain reaction. We further investigated the signaling mechanism of Ang II regulation of EPO in 786-O cells. Pharmacological inhibitors of Ang II type 1 receptor (AT1R) and extracellular signal-regulated kinase 1/2 (ERK1/2) suppressed Ang II transcriptional activation of EPO. Inhibitors of AT2R or Src homology 2 domain-containing tyrosine phosphatase had no effect. Coimmunoprecipiation experiments demonstrated that p21Ras was constitutively bound to the AT1R; this association was increased by Ang II but was reduced by the AT1R inhibitor telmisartan. Transmembrane domain (TM) 2 of AT1R is important for G protein-dependent ERK1/2 activation, and mutant D74E in TM2 blocked Ang II activation of ERK1/2. Ang II signaling induced the nuclear translocation of the Egr-1 transcription factor, and overexpression of dominant-negative Egr-1 blocked EPO promoter activation by Ang II. These data identify a novel pathway for basal regulation of EPO via AT1R-mediated Egr-1 activation by p21Ras-mitogen-activated protein kinase/ERK kinase-ERK1/2. Our current data suggest that Ang II, in addition to regulating blood volume and pressure, may be a master regulator of erythropoiesis.

Maternal high-salt intake during pregnancy reprogrammed renin-angiotensin system-mediated cardiomyocyte apoptosis in the adult offspring heart

AIMS

Excess salt intake during pregnancy may alter fetal organ structures and functions leading to increased risks in the development of cardiovascular diseases in later life. The present study determined whether and how the prenatal high-salt (HS) diets affect renin-angiotensin system (RAS) that may mediate cardiac cell death.

METHODS AND RESULTS

Angiotensin II receptors, AT1 and AT2, protein expression was increased in the myocardium of the offspring exposed to prenatal HS; apoptotic cells appeared in the myocardium of the adult offspring. Mitochondrion was isolated in cell experiments, and the data showed cardiomyocyte apoptosis requiring cytochrome C release. Pretreating H9C2 cells with AT2 agonist CGP42112A induced cell apoptosis in DNA fragments and activated caspase 3. CGP42112A increased mitochondrion cytochrome C release and apoptosis in the cells.

CONCLUSION

Both in vitro and in vivo study demonstrated that cardiomyocyte apoptosis was related to AT2 activation. Prenatal HS diets may reprogram RAS that mediates apoptosis in the offspring myocardium, and AT2 may contribute to cardiomyocyte apoptosis via the cytochrome C release pathway.

Role of angiotensin II type 2 receptor during regression of cardiac hypertrophy in spontaneously hypertensive rats

We previously reported that the AT1 receptor antagonist valsartan and the angiotensin converting enzyme (ACE) inhibitor enalapril decrease DNA synthesis and stimulate apoptosis in interstitial fibroblasts and epicardial mesothelial cells during regression of ventricular hypertrophy in spontaneously hypertensive rats (SHR). To examine the role of the AT2 receptor in this model, we studied hearts from SHR treated with valsartan or enalapril either alone or combined with the AT2 antagonist PD123319 for 1 or 2 weeks. Apoptosis was evaluated by quantification of DNA fragmentation or by TUNEL labeling. At 1 week, valsartan significantly increased ventricular DNA fragmentation, increased apoptosis in epicardial mesothelial cells, and decreased DNA synthesis. At 2 weeks, ventricular DNA content and cardiomyocyte cross-sectional area were significantly reduced. These valsartan-induced changes were attenuated by PD123319 co-administration. However, valsartan-induced increases in apoptosis of left ventricular interstitial non-cardiomyocytes was unaffected by the AT2 blocker. Enalapril-induced changes were similar to those observed with valsartan but were not affected by co-treatment with PD123319. These results demonstrate that AT1 and AT2 receptors act in a coordinated yet cell-specific manner to regulate cell growth and apoptosis in the left ventricle of SHR during AT1 receptor blockade but not ACE inhibition.

A review of current and novel therapies for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressively fibrotic interstitial lung disease that is associated with a median survival of 2-3 years from initial diagnosis. To date, there is no treatment approved for IPF in the United States, and only one pharmacological agent has been approved outside of the United States. Nevertheless, research over the past 10 years has provided us with a wealth of information on its histopathology, diagnostic work-up, and a greater understanding of its pathophysiology. Specifically, IPF is no longer thought to be a predominantly pro-inflammatory disorder. Rather, the fibrosis in IPF is increasingly understood to be the result of a fibroproliferative and aberrant wound healing cascade. The development of therapeutic targets has shifted in accord with this paradigm change. This review highlights the current understanding of IPF, and the recent as well as novel therapeutics being explored in clinical trials for the treatment of this devastating disease.

MicroRNA let-7c inhibits Bcl-xl expression and regulates ox-LDL-induced endothelial apoptosis

Endothelial cells (ECs) apoptosis induced by oxidized low-density lipoprotein (ox-LDL) is thought to play a critical role in atherosclerosis. MicroRNAs (miRNAs) are a class of noncoding RNAs that posttranscriptionally regulate the expression of genes involved in diverse cell functions, including differentiation, growth, proliferation, and apoptosis. MiRNA let-7 family is known to be involved in the regulation of cell apoptosis. However, the function of let-7 in ox-LDL induced ECs apoptosis and atherosclerosis is still unknown. Here, we show that let-7c expression was markedly up-regulated in ox-LDL induced apoptotic human umbilical cord vein endothelial cells (HUVECs). Let-7c over-expression enhanced apoptosis in ECs whereas inhibition of let-7c could partly alleviate apoptotic cell death mediated by ox-LDL. Searching for how let-7c affected apoptosis, we discovered that antiapoptotic protein Bcl-xl was a direct target of let-7c in ECs. Our data suggest that let-7c contributes to endothelial apoptosis through suppression of Bcl-xl.

Impact of cell type and epitope tagging on heterologous expression of G protein-coupled receptor: a systematic study on angiotensin type II receptor

Despite heterologous expression of epitope-tagged GPCR is widely adopted for functional characterization, there is lacking of systematic analysis of the impact of expression host and epitope tag on GPCR expression. Angiotensin type II (AT2) receptor displays agonist-dependent and -independent activities, coupling to a spectrum of signaling molecules. However, consensus has not been reached on the subcellular distributions, signaling cascades and receptor-mediated actions. To examine the contributions of host cell and epitope tag on receptor expression and activity, epitope-tagged AT2 receptor variants were transiently or stably expressed in HEK293, CHO-K1 and PC12 cells. The epitope-tagged AT2 receptor variants were detected both on the cell membrane and in the perinuclear region. In transiently transfected HEK293 cells, Myc-AT2 existed predominantly as monomer. Additionally, a ladder of ubiquitinated AT2 receptor proteins was detected. By contrast, stably expressed epitope-tagged AT2 receptor variants existed as both monomer and high molecular weight complexes, and the latter was enriched in cell surface. Glycosylation promoted cell surface expression of Myc-AT2 but had no effect on AT2-GFP in HEK293 cells. In cells that stably expressed Myc-AT2, serum starvation induced apoptosis in CHO-K1 cells but not in HEK293 or PC12 cells. Instead, HEK293 and PC12 cells stably expressing Myc-AT2 exhibited partial cell cycle arrest with cells accumulating at G1 and S phases, respectively. Taken together, these results suggest that expression levels, subcellular distributions and ligand-independent constitutive activities of AT2 receptor were cell type-dependent while posttranslational processing of nascent AT2 receptor protein was modulated by epitope tag and mode of expression.

Protein Arginine Methyltransferases (PRMTs): promising targets for the treatment of pulmonary disorders

Protein arginine methylation is a novel posttranslational modification that plays a pivotal role in a variety of intracellular events, such as signal transduction, protein-protein interaction and transcriptional regulation, either by the direct regulation of protein function or by metabolic products originating from protein arginine methylation that influence nitric oxide (NO)-dependent processes. A growing body of evidence suggests that both mechanisms are implicated in cardiovascular and pulmonary diseases. This review will present and discuss recent research on PRMTs and the methylation of non-histone proteins and its consequences for the pathogenesis of various lung disorders, including lung cancer, pulmonary fibrosis, pulmonary hypertension, chronic obstructive pulmonary disease and asthma. This article will also highlight novel directions for possible future investigations to evaluate the functional contribution of arginine methylation in lung homeostasis and disease.

Receptors and ionic transporters in nuclear membranes: new targets for therapeutical pharmacological interventions

Work from our group and other laboratories showed that the nucleus could be considered as a cell within a cell. This is based on growing evidence of the presence and role of nuclear membrane G-protein coupled receptors and ionic transporters in the nuclear membranes of many cell types, including vascular endothelial cells, endocardial endothelial cells, vascular smooth muscle cells, cardiomyocytes, and hepatocytes. The nuclear membrane receptors were found to modulate the functioning of ionic transporters at the nuclear level, and thus contribute to regulation of nuclear ionic homeostasis. Nuclear membranes of the mentioned types of cells possess the same ionic transporters; however, the type of receptors is cell-type dependent. Regulation of cytosolic and nuclear ionic homeostasis was found to be dependent upon a tight crosstalk between receptors and ionic transporters of the plasma membranes and those of the nuclear membrane. This crosstalk seems to be the basis for excitation–contraction coupling, excitation–secretion coupling, and excitation – gene expression coupling. Further advancement in this field will certainly shed light on the role of nuclear membrane receptors and transporters in health and disease. This will in turn enable the successful design of a new class of drugs that specifically target such highly vital nuclear receptors and ionic transporters.

Angiotensin II induces apoptosis in intestinal epithelial cells through the AT2 receptor, GATA-6 and the Bax pathway

Angiotensin II (Ang II) has been shown to play an important role in cell apoptosis. However, the mechanisms of Ang-II-induced apoptosis in intestinal epithelial cells are not fully understood. GATA-6 is a zinc finger transcription factor expressed in the colorectal epithelium, which directs cell proliferation, differentiation and apoptosis. In the present study we investigated the underlying mechanism of which GATA-6 affects Ang-II induced apoptosis in intestinal epithelial cells. The in vitro intestinal epithelial cell apoptosis model was established by co-culturing Caco-2 cells with Ang II. Pretreatment with Angiotensin type 2 (AT2) receptor antagonist, PD123319, significantly reduced the expression of Bax and prevented the Caco-2 cells apoptosis induced by Ang II. In addition, Ang II up-regulated the expression of GATA-6. Interestingly, GATA-6 short hairpin RNA prevented Ang II-induced intestinal epithelial cells apoptosis and reduced the expression of Bax, but not Bcl-2. Taken together, the present study suggests that Angiotensin II promotes apoptosis in intestinal epithelial cells through GATA-6 and the Bax pathway in an AT2 receptor-dependent manner.

Angiotensin II regulates activation of Bim via Rb/E2F1 during apoptosis: involvement of interaction between AMPKβ1/2 and Cdk4

Apoptotic cell death is essential for mammalian development and tissue homeostasis. Dysregulation of apoptosis has been identified in pathologies including in pulmonary fibrotic remodeling. We previously reported that a key proapoptotic factor in fibrosis, angiotensin II (Ang II), mediates apoptosis in primary pulmonary artery endothelial cells (PAEC) via the AT(2) receptor and requires activation of AMP-regulated protein kinase (AMPK). We now demonstrate that Ang II induces E2F1 transcription factor binding to and activation of the promoter for the Bcl-2 homology 3 (BH3)-only protein Bim. In PAEC, Ang II treatment induced cyclin-dependent kinase 4 (Cdk4)-mediated hyperphosphorylation of retinoblastoma protein (Rb) and its disassociation from E2F1, a key step in facilitating E2F1-directed transcriptional activity. Indeed, ectopic expression of a dominant negative Cdk4 mutant inhibited Ang II-mediated hyperphosphorylation of Rb and Bim promoter activation. Our data also show that the β-subunit of AMPK was constitutively associated with Cdk4 in PAEC and that Ang II treatment induced AMPKβ phosphorylation and subsequent disassociation of this complex. Both Ang II-induced Rb hyperphosphorylation and Cdk4-AMPK disassociation were blocked by the AMPK inhibitor compound C. Together these findings illuminate a novel proapoptotic signaling pathway in endothelial cells, whereby Ang II triggers E2F1-mediated transcriptional upregulation of Bim via activation of AMPKβ1/2 and Cdk4.