LPS-induced effects on angiotensin I-converting enzyme expression and shedding in human pulmonary microvascular endothelial cells

UNVEILING THE PROTECTIVE MECHANISMS OF PUERARIN AGAINST ACUTE LUNG INJURY: A COMPREHENSIVE EXPLORATION OF THE ROLES AND MECHANISMS OF MST1/ERS SIGNALING

ABSTRACT

Objectives: Puerarin, the principal active constituent extracted from Pueraria, is believed to confer protection against sepsis-induced lung injury. The study aimed to elucidate the role and mechanism of Mst1/ERS in puerarin-mediated protection against acute lung injury (ALI). Methods: Monolayer vascular endothelial cell permeability was assessed by gauging the paracellular flow of FITC-dextran 40,000 (FD40). ELISA was employed for the quantification of inflammatory cytokines. Identification of target proteins was conducted through western blotting. Histological alterations and apoptosis were scrutinized using hematoxylin-eosin staining and TUNEL staining, respectively. The ultrastructure of the endoplasmic reticulum was observed via transmission electron microscopy. Results: Puerarin significantly protected mice from LPS-induced ALI, reducing lung interstitial width, neutrophil and lymphocyte infiltration, pulmonary interstitial and alveolar edema, and lung apoptosis. Puerarin treatment also markedly attenuated levels of TNF-α and IL-1β in both alveolar lavage fluid and serum. Furthermore, puerarin significantly attenuated LPS-induced increases in Mst1, GRP78, CHOP, and Caspase12 protein expression and blunted LPS-induced decrease in ZO-1 protein expression in lung tissues. Puerarin obviously reduced endoplasmic reticulum expansion and vesiculation. Similarly, puerarin significantly mitigated the LPS-induced reduction in HUVEC cell viability and ZO-1 expression. Puerarin also attenuated LPS-induced increase in apoptosis, TNF-α and IL-1β, FD40 flux, and Mst1, GRP78, CHOP, and Caspase12 expression in HUVEC cells. Nevertheless, the inhibitory impact of puerarin on vascular endothelial cell injury, lung injury, and endoplasmic reticulum stress (ERS) was diminished by Mst1 overexpression. Conclusion: These findings demonstrated that the Mst1/ERS signaling pathway played a pivotal role in the development of LPS-induced vascular endothelial cell dysfunction and ALI. Puerarin exhibited the ability to attenuate LPS-induced vascular endothelial cell dysfunction and ALI by inhibiting the Mst1/ERS signaling pathway.

Multimodal strategy to counteract vasodilation in septic shock

Early initiation of a multimodal treatment strategy in the management of vasopressors during septic shock has been advocated to reduce delays in restoring adequate organ perfusion and to mitigate side effects associated with the administration of high-dose catecholamines. We provide a review that summarises the pathophysiology of vasodilation, the physiologic response to the vascular response, and the different drugs used in this situation, focusing on the need to combine early different vasopressors. Fluid loading being insufficient for counteracting vasoplegia, norepinephrine is usually the first-line vasopressor used to restore hemodynamics. Norepinephrine sparing is discussed in further detail through the concomitant use of adrenergic, vasopressinergic, and renin-angiotensin systems and the optimisation of endothelial reactivity with methylene blue. A blueprint for the construction of new studies is outlined to address the question of vasopressor selection and timing in septic shock.

Effects of Anacardic Acid Monoene on the Respiratory System of Mice Submitted to Acute Respiratory Distress Syndrome

The acute respiratory distress syndrome caused by viral pathogens is a worldwide public health emergency. It is suggested that patients with this condition should be screened using therapies that address the need to prevent mortality. Anacardic acids found in Anacardium species have biological activities related to the antioxidant capacity of their double bonds in the lateral alkyl chain. The present study seeks to investigate the effects of anacardic acid monoene on acute respiratory distress syndrome caused by lipopolysaccharides. Experiments were carried out on mice divided into three groups: control group, acute respiratory distress-induced group, and anacardic acid monoene pretreated group, subsequently, induced to acute respiratory distress by lipopolysaccharides. Results showed that anacardic acid moeno was able to prevent changes in lung function and preserve its mechanical properties from containing inflammatory cell infiltrate, collapse of alveoli, and decreased airway resistance, suggesting that this compound may be effective in preventing the acute respiratory distress syndrome caused by viral pathogens.

Endothelial Damage in Acute Respiratory Distress Syndrome

The pulmonary endothelium is a metabolically active continuous monolayer of squamous endothelial cells that internally lines blood vessels and mediates key processes involved in lung homoeostasis. Many of these processes are disrupted in acute respiratory distress syndrome (ARDS), which is marked among others by diffuse endothelial injury, intense activation of the coagulation system and increased capillary permeability. Most commonly occurring in the setting of sepsis, ARDS is a devastating illness, associated with increased morbidity and mortality and no effective pharmacological treatment. Endothelial cell damage has an important role in the pathogenesis of ARDS and several biomarkers of endothelial damage have been tested in determining prognosis. By further understanding the endothelial pathobiology, development of endothelial-specific therapeutics might arise. In this review, we will discuss the underlying pathology of endothelial dysfunction leading to ARDS and emerging therapies. Furthermore, we will present a brief overview demonstrating that endotheliopathy is an important feature of hospitalised patients with coronavirus disease-19 (COVID-19).

Immunomodulatory properties of captopril, an ACE inhibitor, on LPS-induced lung inflammation and fibrosis as well as oxidative stress

BACKGROUND

The role of angiotensin converting enzyme inhibitors on the inflammation process has been demonstrated previously. In the present study, the effects of captopril on lung injury induced by lipopolysaccharide (LPS) were investigated.

METHODS

Control, LPS, 12.5, 25 and 50 mg/kg captopril-treated before LPS administration and captopril 50 mg/kg before saline administration groups of rats were studied. Total and percentage of differential WBC, the levels of MDA, total thiol groups, the activities of SOD and CAT, the levels of IFN-γ, PGE2, TGF-β1 and IL-4 in the BALF were evaluated.

RESULTS

MDA concentration in LPS groups treated with all captopril concentrations, total WBC in LPS + Cap50, percent of neutrophils in LPS + Cap25 and LPS + Cap50, levels of IFN-γ, PGE2, TGF-β1 in LPS + Cap50 and IFN-γ/IL-4 ratio in LPS + Cap25 and LPS + Cap50 were significantly decreased but total thiol groups and activity of SOD in LPS + Cap25 and LPS + Cap50, percent of lymphocyte, CAT activity and concentration of IL-4 only in LPS + Cap50 group were increased in comparison to the LPS group (p < 0.05 to p < 0.001).

CONCLUSION

Captopril dose dependently improved oxidant-antioxidant biomarkers, the imbalance between pro-inflammatory and anti-inflammatory cytokines and showed specific immunomodulatory effect on Th1/Th2 balance in the BALF of lung injury induced by LPS.

Age-Dependent Changes in the Pulmonary Renin-Angiotensin System Are Associated With Severity of Lung Injury in a Model of Acute Lung Injury in Rats

OBJECTIVES

A growing body of evidence suggests that age affects the main pathophysiologic mechanisms of the acute respiratory distress syndrome. This may imply the need for developing age-tailored therapies for acute respiratory distress syndrome. However, underlying molecular mechanisms governing age-related susceptibility first need to be unraveled. In a rat model of acute lung injury, we investigated whether age affects the balance between the two key enzymes of the pulmonary renin-angiotensin system, angiotensin-converting enzyme, and angiotensin-converting enzyme 2. We hypothesized that aging shifts the balance toward the lung injury-promoting angiotensin-converting enzyme, which may form an explanation for the differences in severity of lung injury between different age groups.

DESIGN

Prospective, randomized controlled animal study.

SETTING

University medical research laboratory.

SUBJECTS

Infant (15 ± 2 d), juvenile (37 ± 2 d), adult (4 ± 0.2 mo), and elderly (19.5 ± 0.5 mo) male RCCHan Wistar rats.

INTERVENTIONS

Lung injury was induced by intratracheal administration of lipopolysaccharide (5 mg/kg) and 4 hours of mechanical ventilation (15 mL/kg).

MEASUREMENTS AND MAIN RESULTS

In lipopolysaccharide-exposed and mechanical ventilated rats, angiotensin-converting enzyme activity in bronchoalveolar lavage fluid increased 3.2-fold in elderly when compared with infants. No changes in bronchoalveolar lavage fluid angiotensin-converting enzyme 2 activity were found. In addition, membrane-bound angiotensin-converting enzyme activity decreased. Together with the presence of angiotensin-converting enzyme-sheddase ADAM9 (a disintegrin and metalloproteinase domain-containing protein 9) and an age-dependent increase in tumor necrosis factor-α, an activator of ADAM9, these results indicate increased shedding of angiotensin-converting enzyme in the alveolar compartment, thereby shifting the balance toward the injurious pathway. This imbalance was associated with an increased inflammatory mediator response and more lung injury (wet-to-dry ratio and histology) in elderly rats.

CONCLUSIONS

Increasing age is associated with an imbalance of the pulmonary renin-angiotensin system, which correlates with aggravated inflammation and more lung injury. These changes might form the ground for new therapeutic strategies in terms of dosing and effectiveness of renin-angiotensin system-modulating agents for treatment of acute respiratory distress syndrome.

Key Molecular Mechanisms of Chaiqinchengqi Decoction in Alleviating the Pulmonary Albumin Leakage Caused by Endotoxemia in Severe Acute Pancreatitis Rats

To reveal the key molecular mechanisms of Chaiqinchengqi decoction (CQCQD) in alleviating the pulmonary albumin leakage caused by endotoxemia in severe acute pancreatitis (SAP) rats. Rats models of SAP endotoxemia-induced acute lung injury were established, the studies in vivo provided the important evidences that the therapy of CQCQD significantly ameliorated the increases in plasma levels of lipopolysaccharide (LPS), sCd14, and Lbp, the elevation of serum amylase level, the enhancements of systemic and pulmonary albumin leakage, and the depravation of airways indicators, thus improving respiratory dysfunction and also pancreatic and pulmonary histopathological changes. According to the analyses of rats pulmonary tissue microarray and protein-protein interaction network, c-Fos, c-Src, and p85α were predicted as the target proteins for CQCQD in alleviating pulmonary albumin leakage. To confirm these predictions, human umbilical vein endothelial cells were employed in in vitro studies, which provide the evidences that (1) LPS-induced paracellular leakage and proinflammatory cytokines release were suppressed by pretreatment with inhibitors of c-Src (PP1) or PI3K (LY294002) or by transfection with siRNAs of c-Fos; (2) fortunately, CQCQD imitated the actions of these selective inhibitions agents to inhibit LPS-induced high expressions of p-Src, p-p85α, and c-Fos, therefore attenuating paracellular leakage and proinflammatory cytokines release.

Local corticosterone production and angiotensin-I converting enzyme shedding in a mouse model of intestinal inflammation

AIM: To investigate local corticosterone production and angiotensin-I converting enzyme (ACE) protein expression and their interaction in healthy and inflamed intestine.

METHODS: Acute intestinal inflammation was induced to six weeks old male Balb/c mice by administration of either 3% or 5% dextran sodium sulfate (DSS) in drinking water for 7 d (n = 12 in each group). Healthy controls (n = 12) were given tap water. Corticosterone production and ACE protein shedding were measured from ex vivo incubates of the small and large intestine using EIA and ELISA, respectively. Morphological changes of the intestinal wall were assessed in hematoxylin-eosin stained tissue preparations of jejunum and distal colon. Effects of angiotensin II, captopril and metyrapone on corticosterone production was assessed by incubating pieces of small intestine of healthy mice in the presence of 0.1, 1 or 10 μmol/L angiotensin II, 1, 10 or 100 μmol/L captopril or 1, 10 or 100 μmol/L metyrapone solutions and measuring corticosterone released to the incubation buffer after 90 min (n = 5 in each group).

RESULTS: Both concentrations of DSS induced inflammation and morphological changes in large intestines but not in small intestines. Changes were observed as distortions of the crypt structure, mucosal erosion, immune cell infiltration to the mucosa and submucosal edema. Ex vivo corticosterone production (2.9 ± 1.0 ng/mL vs 2.0 ± 0.8 ng/mL, P = 0.034) and ACE shedding (269.2 ± 97.1 ng/mL vs 175.7 ± 52.2 ng/mL, P = 0.016) were increased in small intestines in 3% DSS group compared to the controls. In large intestine, corticosterone production was increased compared to the controls in both 3% DSS (229 ± 81 pg/mL vs 158 ± 30 pg/mL, P = 0.017) and 5% DSS groups (366 ± 163 pg/mL vs 158 ± 30 pg/mL, P = 0.002). Large intestine ACE shedding was increased in 5% DSS group (41.5 ± 9.0 ng/mL vs 20.9 ± 5.2 ng/mL, P = 0.034). Angiotensin II treatment augmented corticosterone production in small intestine at concentration of 10 μmol/L (0.97 ± 0.21 ng/mg protein vs 0.40 ± 0.09 ng/mg protein, P = 0.036).

CONCLUSION: Intestinal ACE shedding is increased by DSS-induced intestinal inflammation and parallels local corticosterone production. ACE product angiotensin II stimulates corticosterone formation in healthy intestine.