Impaired pulmonary blood flow distribution in congestive heart failure assessed using synchrotron radiation microangiography

Association between endothelial function and micro-vascular remodeling measured by synchrotron radiation pulmonary micro-angiography in pulmonary arterial hypertension

OBJECTIVES

Pulmonary arterial hypertension (PAH) is a progressive disease which causes increased vascular resistance. In this study, our purpose was to quantify the micro-vascular remodeling in monocrotaline-induced PAH rats using synchrotron radiation pulmonary micro-angiography (SRPA), a method we have previously established in an in vivo rat model. To determine the relationship between endothelial function and vascular remodeling, the local expression of endothelin-1 (ET-1), endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) was evaluated using immunohistochemical staining.

METHODS

Monocrotaline-induced PAH rats were created by subcutaneous injection of monocrotaline. After 2 weeks, SRPA was performed at the Photon Factory of the High Energy Accelerator Research Organization. The internal diameters of pulmonary arterioles were measured using SRPA images. Semi-quantified analyses of ET-1, eNOS and VEGF expression in pulmonary arterioles were performed by immunohistochemical staining.

RESULTS

Micro-vascular density and the internal diameters of pulmonary arterioles were significantly decreased in PAH. ET-1 expression was significantly increased in PAH compared with the control (1.53 ± 0.45 vs. 0.80 ± 0.14) and eNOS expression was significantly decreased in PAH compared with the control (1.12 ± 0.59 vs. 1.91 ± 0.66), although VEGF expression did not differ between the groups.

CONCLUSIONS

SRPA can be effectively used for visualizing the decreased pulmonary micro-vasculature associated with PAH. Increased ET-1 expression and decreased eNOS expression may contribute to the proliferation and vasospasm of pulmonary arterioles induced by endothelial dysfunction due to PAH. This SRPA technology may help to identify a correlation between endothelial function and micro-vasculature remodeling in PAH.

Analysis of Clinically Relevant Factors for Pulmonary Hypertension in Maintenance Hemodialysis Patients

BACKGROUND Pulmonary hypertension (PH) is common in patients with maintenance hemodialysis (MHD) and is associated with high mortality. This study analyzed clinically relevant factors for pulmonary hypertension in MHD patients and the effect of serum pentraxin3 (PTX3) in the pathogenesis of PH to provide the basis for early diagnosis and treatment of MHD patients with PH. MATERIAL AND METHODS This study included 60 MHD patients (group A) and 30 healthy controls (group B). Group A was further divided into PH and non-PH groups. Clinical characteristics, auxiliary examination results and serum PTX3 level of the PH and non-PH groups were compared. Binary logistic regression was used to assess the risk factors for PH in MHD patients. ROC curve was applied to evaluate the diagnostic value of PTX3 in PH. RESULTS The incidence rate of PH in MHD patients was 50%, and most presented as mild to moderate. Compared with the non-PH group, patients in PH group presented significantly longer atrial diameter, right ventricular diameter and main pulmonary artery diameter (P<0.05), as well as higher PTX3 and NT-proBNP level. Atrial diameter and PTX3 level were the risk factors for PH in MHD patients. AUC of PTX3 was 0.721 (95%CI: 0.590-0.851, P=0.003). CONCLUSIONS The prevalence of PH was higher in MHD patients and mostly presented as mild to moderate. Such patients often developed heart structural changes and cardiac ultrasound was highly recommended. Serum PTX3 level was significantly elevated and could be used as a marker of PH in MHD patients.

Pulmonary vascular tone is dependent on the central modulation of sympathetic nerve activity following chronic intermittent hypoxia

Chronic intermittent hypoxia (IH) provokes a centrally mediated increase in sympathetic nerve activity (SNA). Although this sympathetic hyperexcitation has been linked to systemic hypertension, its effect on the pulmonary vasculature is unclear. This study aimed to assess IH-mediated sympathetic excitation in modulating pulmonary vasculature tone, particularly acute hypoxia vasoconstrictor response (HPV), and the central β-adrenergic signaling pathway for facilitating the increase in SNA. Sprague-Dawley rats were exposed to IH (cycle of 4% O2 for 90 s/air for 90 s) for 8 h/day for 6 weeks. Subsequently, rats were anesthetized and either pulmonary SNA was recorded (electrophysiology), or the pulmonary vasculature was visualized using microangiography. Pulmonary sympathetic and vascular responses to acute hypoxia were assessed before and after central β1-adrenergic receptor blockade (Metoprolol, 200 nmol i.c.v.). Chronic IH increased baseline SNA (110% increase), and exacerbated the sympathetic response to acute hypoxia. Moreover, the magnitude of HPV in IH rats was blunted compared to control rats (e.g., 10 and 20% vasoconstriction, respectively). In only the IH rats, β1-receptor blockade with metoprolol attenuated the hypoxia-induced increase in pSNA and exacerbated the magnitude of acute HPV, so that both sympathetic and HPV responses were similar to that of control rats. Interestingly, the expression of β1-receptors within the brainstem was similar between both control and IH rats. These results suggest that the centrally mediated increase in SNA following IH acts to blunt the local vasoconstrictor effect of acute hypoxia, which reflects an inherent difference between vasodilator and vasoconstrictor actions of SNA in pulmonary and systemic circulations.