Protective effects of intermedin/adrenomedullin-2 in a cellular model of human pulmonary arterial hypertension

Establishment of a canine model of pulmonary arterial hypertension induced by dehydromonocrotaline and ultrasonographic study of right ventricular remodeling

OBJECTIVE

Pulmonary arterial hypertension (PAH) means high blood pressure in the lungs. We aimed to observe the right ventricular size, wall thickness and characteristic functional changes and their associations with PAH in an established model of beagle dogs, and to explore convenient, reliable and sensitive ultrasound indicators for assessing right ventricular remodeling.

METHODS

Twenty healthy beagle dogs (8-10 kg) were randomly divided into control group (N-dimethylformamide, n = 10) and dehydromonocrotaline (DHMCT) group (DHMCT, n = 10). N-dimethylformamide or DHMCT was injected through a catheter into the right atrium, and then right heart catheterization, routine echocardiography and two-dimensional speckle tracking imaging (2D-STI) were performed before modeling (0 weeks) and 8, 14 weeks after modeling. Hemodynamic parameters and right ventricular function-related ultrasound data were acquired. At the end of the experiment, the animals were killed and the lung tissues were taken for HE staining. Left and right ventricular walls were separated and weighed respectively, and right ventricular hypertrophy index (RVHI) was measured. The associations of the routine ultrasound data and 2D-STI data at each time point with hemodynamic parameters and RVHI were analyzed.

RESULTS

At 0, 8 and 14 weeks, gradual decreases in the right ventricular global longitudinal strain (RVLS) were found in DHMCT group. RVH occurred in DHMCT group, and DHMCT group had a significantly higher RVHI than that of control group (49.83 ± 4.83% vs. 39.80 ± 1.40%, P < .001) and larger pulmonary artery media thickness. RVLS had significant positive correlations with RVSP (r = 0.74, P < .001), mRVP (r = 0.72, P < .001), PASP (r = 0.75, P < .001), mPAP (r = 0.72, P < .001) and PVR (r = 0.68, P < .001). There was a significant positive correlation between RVLS and RVHI (r = 0.74, P < .001).

CONCLUSION

The right ventricular function in PAH can be effectively assessed by echocardiography, and RVLS measured by 2D-STI sensitively reflects right ventricular remodeling following PAH.

Intermedin Reduces Oxidative Stress and Apoptosis in Ventilator-Induced Lung Injury via JAK2/STAT3

Mechanical ventilation is an effective treatment for acute respiratory distress syndrome (ARDS), which can improve the prognosis of ARDS to a certain extent. However, it may further aggravate lung tissue injury, which is defined as ventilator-induced lung injury (VILI). Intermedin (IMD) belongs to the calcitonin gene-related peptide (CPRP) superfamily. Our previous studies have found that IMD reduces the expression proinflammatory cytokines, down-regulates nuclear translocation and improves the integrity of endothelial barrier in ARDS. However, the effect of IMD on VILI has not been clarified. Oxidative stress imbalance and apoptosis are the main pathophysiological characteristics of VILI. In the current study, we used C57B6/J mice and human pulmonary microvascular endothelial cells (HPMECs) to establish a VILI model to analyze the effects of IMD on VILI and explore its potential mechanism. We found that IMD alleviated lung injury and inflammatory response in VILI, mainly in reducing ROS levels, upregulating SOD content, downregulating MDA content, reducing the expression of Bax and caspase-3, and increasing the expression of Bcl-2. In addition, we also found that IMD played its anti-oxidative stress and anti-apoptotic effects via JAK2/STAT3 signaling. Our study may provide some help for the prevention and treatment of VILI.

Pulsatility protects the endothelial glycocalyx during extracorporeal membrane oxygenation

BACKGROUND

Pulsatile flow protects vital organ function and improves microcirculatory perfusion during extracorporeal membrane oxygenation (ECMO). Studies revealed that pulsatile shear stress plays a vital role in microcirculatory function and integrity. The objective of this study was to investigate how pulsatility affects wall shear stress and endothelial glycocalyx components during ECMO.

METHODS

Using the i-Cor system, sixteen canine ECMO models were randomly allocated into the pulsatile or the non-pulsatile group (eight canines for each). Hemodynamic parameters, peak wall shear stress (PWSS), serum concentration of syndecan-1, and heparan sulfate were measured at different time points during ECMO. Pulsatile shear stress experiments were also performed in endothelial cells exposed to different magnitudes of pulsatility (five plates for each condition), with cell viability, the expressions of syndecan-1, and endothelial-to-mesenchymal transformation (EndMT) markers analyzed.

RESULTS

The pulsatile flow generated more surplus hemodynamic energy and preserved higher PWSS during ECMO. Serum concentrations of both syndecan-1 and heparan sulfate were negatively correlated with PWSS, and significantly lower levels were observed in the pulsatile group. Besides, non-pulsatility triggered EndMT and endothelial cells exposed to low pulsatility had the lowest possibility of EndMT.

CONCLUSION

The maintenance of the PWSS by pulsatility during ECMO possesses beneficial effects on glycocalyx integrity. Moreover, pulsatility prevents EndMT in endothelial cells, and low pulsatility exhibits the best protective effects. The augmentation of pulsatility may be a plausible future direction to improve the clinical outcome in ECMO.

Intermedin alleviates the inflammatory response and stabilizes the endothelial barrier in LPS-induced ARDS through the PI3K/Akt/eNOS signaling pathway

Inflammatory storms and endothelial barrier dysfunction are the central pathophysiological features of acute respiratory distress syndrome (ARDS). Intermedin (IMD), a member of the calcitonin gene-related peptide (CGRP) family, has been reported to alleviate inflammation and protect endothelial cell (EC) integrity. However, the effects of IMD on ARDS have not been clearly elucidated. In the present study, clinical ARDS data were used to explore the relationship between serum IMD levels and disease severity and prognosis, and we then established a model to predict the possibility of hospital survival. Mouse models of ARDS and LPS-challenged endothelial cells were used to analyze the protective effect and underlying mechanism of IMD. We found that in patients with ARDS, increased serum IMD levels were associated with reduced disease severity and increased rates of hospital survival. IMD alleviated the LPS-induced inflammatory response by decreasing proinflammatory cytokines, NF-κB p65 expression and NF-κB p65 nuclear translocation. In addition, IMD stabilized the endothelial barrier by repairing adherens junctions (AJs), cytoskeleton and capillary leakage. IMD exerted protective effects against ARDS on pulmonary endothelial cells, at least partly, through PI3K/Akt/eNOS signaling, while IMD's anti-inflammation effect was mediated through an eNOS-independent mechanism. Our study may provide new therapeutic insight for ARDS treatment.