P53: The endothelium defender

The beneficial effects of the active components from Maclura tricuspidata fruits in the treatment of diabetes mellitus

Five active compounds, daidzein, luteolin, alpinumisoflavone (AI), 6,8-diprenylgenistein (DG), and warangalone (WA), were identified from the fruits of Maclura tricuspidata via LC-Q/TOF-MS. WA and DG were shown to reverse the high glucose (HG)-induced injury in human umbilical vein endothelial cells (HUVECs), indicating their potential protective effects in alleviating diabetic symptoms. Network pharmacology was conducted to reveal the potential mechanisms of action of the compounds, and Hsp90α (degree: 47), Src (degree: 49), Akt (degree: 69) and p53 (degree: 60) were shown as the core targets related to antidiabetic properties. Further experimental verification suggested that the compounds could enhance phosphorylation of Src and Akt, increase p53 expression act as Hsp90 inhibitors, and protect against HG induced endothelial dysfunction. Our findings will provide a comprehensive understanding of the active substances of M. tricuspidata, which will be helpful for their utilisation.

Activating transcription factor 6 protects against endothelial barrier dysfunction

BACKGROUND

Endothelial hyperpermeability is associated with sepsis and acute respiratory distress syndrome (ARDS). The identification of molecular pathways involved in barrier dysfunction; may reveal promising therapeutic targets to combat ARDS. Unfolded protein response (UPR) is a highly conserved molecular pathway, which ameliorates endoplasmic reticulum stress. The present work focuses on the effects of ATF6, which is a UPR sensor, in lipopolysaccharides (LPS)-induced endothelial hyperpermeability.

METHODS

The in vitro effects of AA147 and Ceapin-A7 in LPS-induced endothelial barrier dysfunction were investigated in bovine pulmonary artery endothelial cells (BPAEC). Small interfering (si) RNA was utilized to "silence" ATF6, and electric cell-substrate impedance sensing (ECIS) measured transendothelial resistance. Fluorescein isothiocyanate (FITC)-dextran assay was utilized to assess paracellular permeability. Protein expression levels were evaluated with Western blotting, and cell viability with MTT assay.

RESULTS

We demonstrated that AA147 prevents LPS-induced barrier disruption by counteracting Cofilin and myosin light chain 2 (MLC2) activation, as well as VE-Cadherin phosphorylation. Moreover, this ATF6 inducer opposed LPS-triggered decrease in transendothelial resistance (TEER), as well as LPS-induced paracellular hyperpermeability. On the other hand, ATF6 suppression due to Ceapin-A7 or small interfering RNA exerted the opposite effects, and potentiated LPS-induced endothelial barrier disruption. Moderate concentrations of both ATF6 modulators did not affect cell viability.

CONCLUSIONS

ATF6 activation protects against endothelial barrier function, suggesting that this UPR sensor may serve as a therapeutic target for sepsis and ARDS.

Unfolded protein response in endothelial injury

Endothelial barrier dysfunction is associated with sepsis and lung injury, both direct and indirect. We discuss the involvement of unfolded protein response in the protective effects of heat shock protein 90 inhibitors and growth hormone releasing hormone antagonists in the vascular barrier, to reveal new possibilities in acute respiratory distress syndrome treatment.

Induction of the NEK family of kinases in the lungs of mice subjected to cecal ligation and puncture model of sepsis

Endothelial barrier dysfunction (EBD) is the hallmark of Acute Respiratory Distress Syndrome (ARDS), a potentially lethal respiratory disorder associated with the COVID-19 - related deaths. Herein, we employed a cecal ligation and puncture (CLP) murine model of sepsis, to evaluate the effects of sepsis-induced EBD in the expression of the never in mitosis A (NIMA)-related kinases (NEKs). Members of that family of kinases regulate the activity and expression of the tumor suppressor P53, previously shown to modulate the actin cytoskeleton remodeling. Our results introduce the induction of NEK2, NEK3, NEK4, NEK7, and NEK9 in a CLP model of sepsis. Hence, we suggest that NEKs are involved in inflammatory processes and are holding the potential to serve as novel therapeutic targets for pathologies related to EBD, including ARDS and sepsis. Further studies will delineate the underlying molecular events and their interrelations with P53.

Unfolded Protein Response: A Regulator of the Endothelial Barrier

Recent evidence suggest that the endothelial barrier function is enhanced by the mild activation of the unfolded protein response (UPR), which aims to suppress abnormal increases of endoplasmic reticulum stress. Heat shock protein 90 inhibitors and growth hormone releasing hormone antagonists exert the capacity to activate this multifaceted cellular mechanism (UPR). Thus, investigations on the signalling network involved in those events, may deliver exciting opportunities in diseases related to endothelial barrier dysfunction. The diverse spectrum of those pathologies include sepsis and Acute Respiratory Distress Syndrome (ARDS).

P53 Regulates the Redox Status of Lung Endothelial Cells

The anti-inflammatory activities of P53 in the vasculature have been associated with the enhancement of the endothelial barrier function. In the present study, we employed human and bovine lung endothelial cells, to investigate whether P53 expression levels affect the redox status of pulmonary cells. Moreover, we tested the possibility that those events affect the endothelial integrity of the lung microvascular monolayers. Our observations suggest that P53 suppression by LPS, pifithrin, or small interfering RNA increased the expression of the redox marker malondialdehyde. In contrast, P53 induction by Nutlin or the Hsp90 inhibitor AUY922 exerted the opposite effects, namely, suppressed that lipid oxidation marker. The direct measurement of the reactive oxygen species by 2,7-Dichlorodihydrofluorescein diacetate confirmed the antioxidant activity of P53 in the vasculature. Furthermore, the increased reactive oxygen species production due to P53 suppression was associated with lung hyperpermeability responses. In conclusion, P53 supports endothelial barrier function, at least in part, via the modulation of the reactive oxygen species.

P53 deficiency potentiates LPS-Induced acute lung injury in vivo

Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) represent a significant cause of morbidity and mortality in critically ill hospitalized patients. Emerging evidence suggest that the expression levels of P53 in the lungs are associated with the supportive effects of heat shock protein 90 inhibitors and growth hormone releasing hormone antagonists in the endothelium. In the current study, we employed an in vivo model of intratracheal administration of lipopolysaccharides (LPS)-induced ALI to investigate the role of P53 in counteracting LPS-induced lung inflammatory responses. In wild type mice, LPS induced the expression of IL-1α, IL-1β, and TNFα in the lungs, increased bronchoalveolar lavage fluid protein concentration, and activated cofilin. Remarkably; those responses were more potent in P53 knockout mice, suggesting the crucial role of P53 in orchestrating rigorous endothelial defenses against inflammatory stimuli. The present study supports previous endeavors on the protective role of P53 against lung inflammatory disease, and enrich our knowledge on the development of medical countermeasures against ARDS.

P53 in acute respiratory distress syndrome

P53 is a tumor suppressor protein, associated with strong anti-inflammatory activities. Recent evidence suggest that this transcription factor counteracts lung inflammatory diseases, including the lethal acute respiratory distress syndrome. Herein we provide a brief discussion on the relevant topic.

A glimpse at growth hormone-releasing hormone cosmos

Growth hormone-releasing hormone is a hypothalamic neuropeptide, which regulates the secretion of growth hormone by the anterior pituitary gland. Recent evidence suggest that it exerts growth factor activities in a diverse variety of in vivo and in vitro experimental malignancies, which are counteracted by growth hormone-releasing hormone antagonists. Those peptides support lung endothelial barrier integrity by suppressing major inflammatory pathways and by inducing the endothelial defender P53. The present effort provides information regarding the effects of growth hormone-releasing hormone in the regulation of P53 and the unfolded protein response. Furthermore, it suggests the possible application of growth hormone-releasing hormone antagonists towards the management of acute lung injury, including the lethal acute respiratory distress syndrome.

P53 in the impaired lungs

Our laboratory is focused on investigating the supportive role of P53 towards the maintenance of lung homeostasis. Acute lung injury, acute respiratory distress syndrome, chronic obstructive pulmonary disease, pulmonary fibrosis, bronchial asthma, pulmonary arterial hypertension, pneumonia and tuberculosis are respiratory pathologies, associated with dysfunctions of this endothelium defender (P53). Herein we review the evolving role of P53 towards the aforementioned inflammatory disorders, to potentially reveal new therapeutic possibilities in pulmonary disease.

Unfolded Protein Response in Lung Health and Disease

The unfolded protein response (UPR) is a complex element, destined to protect the cells against a diverse variety of extracellular and intracellular challenges. UPR activation devises highly efficient responses to counteract cellular threats. If those activities fail, it will dictate cellular execution. The current work focuses on the role of UPR in pulmonary function, by immersing into the highly interrelated network that operates toward the endothelial barrier function. A highly sophisticated UPR manipulation shall reveal new therapeutic possibilities against inflammatory lung disease, such as acute lung injury and acute respiratory distress syndrome.

Unfolded protein response in cardiovascular disease

The unfolded protein response (UPR) is a highly conserved molecular machinery, which protects the cells against a diverse variety of stimuli. Activation of this element has been associated with both human health and disease. The purpose of the current manuscript is to provide the most updated information on the involvement of UPR towards the improvement; or deterioration of cardiovascular functions. Since UPR is consisted of three distinct elements, namely the activating transcription factor 6, the protein kinase RNA-like endoplasmic reticulum kinase; and the inositol-requiring enzyme-1α, a highly orchestrated manipulation of those molecular branches may provide new therapeutic possibilities against the severe outcomes of cardiovascular disease.

P53 in lung vascular barrier dysfunction

Endothelial barrier dysfunction is the hallmark of inflammatory lung disease, including Acute Lung Injury and Acute Respiratory Distress Syndrome. The purpose of the present editorial is to emphasize on recent advances in the corresponding field, as it relates to P53. This tumor suppressor protein has been shown to enhance the vascular barrier integrity via distinct molecular pathways. Further, it mediates the beneficial effects of heat shock protein 90 inhibitors and growth hormone releasing hormone antagonists in the lung microvasculature.

Effects of Heat Shock Protein 90 Inhibition In the Lungs

Inhibition of Hsp90 is associated with anti-inflammatory effects. We employed human lung microvascular endothelial cells to investigate the effects of the Hsp90 inhibitors 17-AAG, AUY-922 and 17-DMAG in the unfolded protein response (UPR) and viability of lung cells. Our observations indicate that moderate doses of those compounds trigger the activation of the UPR without inducing lethal effects in vitro. Indeed, AUY-922 triggered UPR activation in the lungs of C57BL/6 mice. UPR has been previously involved in the enhancement of the lung endothelial barrier function. Thus, the present study suggests that the barrier protective effects of Hsp90 inhibition in the lung microvasculature are highly probable to be associated with the activation of the UPR. Hence, the development of novel compounds which stochastically capacitate the repairing elements of UPR, may deliver new therapeutic possibilities against the severities of the acute respiratory distress syndrome.

The highly interrelated GHRH, p53, and Hsp90 universe

p53 universe is composed of a complex regulatory network, destined to counteract multifarious challenges threatening cell survival. Imbalance in those responses may result in human disease associated with inevitable consequences. The present work delivers our view of the corresponding phenomena, by involving the endothelium defender in meticulously orchestrated events against inflammatory stimuli. Immersing into the great depths of p53 cosmos may lead to promising therapies against devastating disorders, including acute respiratory distress syndrome.

P53 versus inflammation: an update

Etiologies of human pathophysiology have been associated with states of severe inflammation. The endothelium defender P53 supports cellular functions, by orchestrating anti-inflammatory responses. The purpose of the present article is to provide an update on the mechanisms enforcing the protective actions of P53 in human homeostasis, and to discuss current efforts on the development of new therapies against inflammatory abnormalities.

Hsp90 inhibitors induce the unfolded protein response in bovine and mice lung cells

The unfolded protein response element protects against endoplasmic reticulum stress and delivers protection towards potentially harmful challenges. The components of this multi-branch molecular machinery, namely the protein kinase RNA-like ER kinase, the activating transcription factor 6, and the inositol-requiring enzyme-1α; expand the endoplasmic reticulum capacity to support cellular function under stress conditions. In the present study, we employed bovine pulmonary aortic endothelial cells and mice to investigate the possibility that the Hsp90 inhibitors Tanespimycin (17-AAG) and Luminespib (AUY-922) exert the capacity to trigger the unfolded protein response. The induction of the unfolded protein response regulators immunoglobulin heavy-chain-binding protein, endoplasmic reticulum oxidoreductin-1alpha; and protein disulfide isomerase was also examined. It appears that both inhibitors capacitate the induction of the unfolded protein response element in vitro, since lung cells exposed to 1, 2 and 10 μM of 17-AAG or AUY-922 for 4, 6, 8, 16 and 48 h demonstrated increased levels of those proteins. Similar events occurred in the lungs of mice treated with AUY-922. Thus, our study demonstrates that Hsp90 inhibition triggers the activities of the unfolded protein response, and suggests that this molecular machinery contributes in the protective action of Hsp90 inhibitors in the lung microvasculature.

GHRH antagonists support lung endothelial barrier function

Growth Hormone-Releasing Hormone (GHRH) regulates the release of growth hormone from the anterior pituitary gland. GHRH also acts as a growth and inflammatory factor in a variety of experimental models in oncology. In the current study, we used bovine pulmonary arterial cells in order to investigate the effects of GHRH and its antagonistic and agonistic analogs in key intracellular pathways that regulate endothelial permeability. GHRH antagonists suppressed the activation of MLC2, ERK1/2, JAK2/STAT3 pathway and increased the intracellular P53 and pAMPK levels. In contrast, both GHRH and GHRH agonist MR409 exerted the opposite effects. Furthermore, GHRH antagonists supported the integrity of endothelial barrier, while GHRH and GHRH agonists had the contrary effects, as reflected in measurements of transendothelial resistance. Our observations support the evidence for the anti - inflammatory role of GHRH antagonists in the vasculature. Moreover, our results suggest that GHRH antagonists should be considered as promising therapeutic agents for treating severe respiratory abnormalities, such as the lethal Acute Respiratory Distress Syndrome (ARDS).

Unfolded protein response regulates P53 expression in the pulmonary endothelium

Lung endothelial barrier dysfunction leads to severe pathologies, including the lethal Acute Respiratory Distress Syndrome. P53 has been associated with anti-inflammatory activities. The current study employs a variety of unfolded protein response (UPR) activators and inhibitors to investigate the regulation of P53 by UPR in lung cells. The bovine cells that were exposed to the UPR inductors brefeldin A, dithiothreitol, and thapsigargin; demonstrated elevated expression levels of P53 compared to the vehicle-treated cells. On the contrary, the UPR inhibitors N-acetyl cysteine, kifunensine, and ATP-competitive IRE1α kinase-inhibiting RNase attenuator; produced the opposite effects. The outcomes of the present study reveal a positive regulation between UPR and P53. Since it has been shown that a mild induction of the unfolded protein response opposes inflammation, we suggest that P53 is involved in those protective activities in the lung.

P53-induced reduction of lipid peroxidation supports brain microvascular endothelium integrity

Dysregulation of the blood brain barrier due to oxidative stress causes neurological disorders, such as Alzheimer's and Parkinson's disease. We employed brain microvascular endothelial cells; to investigate the effects of P53 towards the lipid oxidation of the BBB. P53 reduction by LPS, siRNA for P53 and Pifithrin increased the expression levels of malondialdehyde, a marker of oxidative stress and lipid peroxidation. Furthermore, P53 suppression impaired the permeability of the BBB monolayers. In contrast, P53 induction by Nutlin and Hsp90 inhibitor AUY922 enhanced the BBB function. In conclusion, P53 supports BBB integrity, at least in part, by reducing lipid peroxidation.

Unfolded Protein Response supports endothelial barrier function

Ongoing efforts are oriented towards the development of novel therapeutic agents to repress lung hyperpermeability responses due to inflammation. The endothelial barrier dysfunction triggered by such events, may eventually lead to severe cardiovascular complications, such as the Acute Respiratory Distress Syndrome. Hsp90 inhibitors are anticancer compounds, associated with strong anti-inflammatory responses in the endothelium. Our latest observations in experimental models of Acute Lung Injury suggest that P53 orchestrates, at least in part, such activities. Remarkably, both Hsp90 inhibition and P53 induction are associated with the activation of the Unfolded Protein Response element. The purpose of the current manuscript, is to introduce the hypotheses that UPR induction protects the vasculature against inflammation.

P53 supports endothelial barrier function via APE1/Ref1 suppression

The tumor suppressor protein P53 is strongly involved in orchestrating cellular defenses in the diverse variety of human tissues. Anomalies to lung endothelium permeability are streaming severe consequences towards human health, often associated with fatal outcomes. Ongoing investigations suggest that P53 exerts a prominent strategic role in crucial signaling cascades, in charge of both the maintenance and defense of pulmonary endothelium against toxic intruders. The current study employs human and bovine lung microvascular cells, as well as pharmacologic and genetic P53 modulators to demonstrate the negative regulation of APE1/Ref1 by P53. Moreover, it includes real time measurements of endothelial permeability, to reveal the disruptive role of APE1/Ref1 towards endothelial integrity. Those findings supports our efforts to elucidate the highly sophisticated regulatory network that enact endothelial adaptations under the plethora of challenging environmental factors.