Metabolic Syndrome Mediates ROS-miR-193b-NFYA-Dependent Down Regulation of sGC and Contributes to Exercise-Induced Pulmonary Hypertension in HFpEF

Background: Many patients with heart failure with preserved ejection fraction (HFpEF) have metabolic syndrome and develop exercise-induced pulmonary hypertension (EIPH). Increases in pulmonary vascular resistance in patients with HFpEF portend a poor prognosis; this phenotype is referred to as combined pre-and post-capillary PH (CpcPH). Therapeutic trials for EIPH and CpcPH have been disappointing, suggesting the need for strategies that target upstream mechanisms of disease. This work reports novel rat EIPH models and mechanisms of pulmonary vascular dysfunction centered around the transcriptional repression of the soluble guanylate cyclase (sGC) enzyme in pulmonary artery smooth muscle cells (PAVSMCs). Methods: We used obese ZSF-1 leptin-receptor knock-out rats (HFpEF model), obese ZSF-1 rats treated with SU5416 to stimulate resting PH (Obese+sugen, CpcPH model), and Lean ZSF-1 rats (controls). Right and left ventricular hemodynamics were evaluated via implanted-catheters during treadmill exercise. PA function was evaluated using MRI and myography. Overexpression of NFYA, a transcriptional-enhancer of sGCβ1, was performed by PA delivery of adeno-associated-virus 6 (AAV6). Treatment groups received SGLT2 inhibitor Empagliflozin in drinking water. PAVSMCs from rats and humans were cultured with Palmitic acid, Glucose, and Insulin (PGI) to induce metabolic-stress. Results: Obese rats showed normal resting right ventricular systolic pressures (RVSP) which significantly increased during exercise, modeling EIPH. Obese+sugen rats showed anatomical PA remodeling and developed elevated RVSP at rest, which was exacerbated with exercise, modeling CpcPH. Myography and MRI during dobutamine-challenge revealed PA functional impairment of both obese groups. PAs of obese rats produced reactive oxygen species (ROS) and decreased sGCβ1 expression. Mechanistically, cultured PAVSMCs from obese rats, humans with diabetes or treated with PGI, showed increased mitochondrial-ROS, which enhanced miR-193b-dependent RNA-degradation of NFYA, resulting in decreased sGCβ1-cGMP signaling. Forced NYFA expression by AAV6 delivery increased sGCβ1 levels and improved exercise-PH in Obese+sugen rats. Treatment of Obese+sugen rats with Empagliflozin improved metabolic syndrome, reduced mitochondrial ROS and miR-193b levels, restored NFYA/sGC activity, and prevented EIPH. Conclusions: In HFpEF and CpcPH models, metabolic syndrome contributes to pulmonary vascular dysfunction and EIPH through enhanced ROS and miR-193b expression, which down-regulates NFYA-dependent sGCβ1 expression. AAV-mediated NFYA overexpression and SGLT2 inhibition restores NFYA-sGCβ1-cGMP signaling and ameliorates EIPH.

Ghrelin Protects Lipopolysaccharide-Induced Acute Lung Injury Rats against Pulmonary Vascular Dysfunction by Inhibiting Inflammation

Objective. To determine the effect and mechanism of the anti-inflammatory agent ghrelin on pulmonary vascular dysfunction (PVD) in lipopolysaccharide- (LPS-) induced acute lung injury (ALI) rat models. Methods. Thirty-two adult male Sprague Dawley rats (n = 16/group) were randomly divided into ghrelin and saline groups, wherein ghrelin (10 nmol/kg) or saline was subcutaneously administered. After 30 min, eight rats from each group were randomly selected, and LPS (5 mg/kg) or saline was administered by intratracheal instillation to induce ALI. Four hours after establishing the ALI rat model, the mean pulmonary arterial pressure (mPAP), mean right ventricular systolic pressure (RVSP), levels of proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the bronchoalveolar lavage fluid (BALF), BALF cell count, wet-to-dry (W/D) lung weight ratios, and myeloperoxidase (MPO) activity in lung tissue for all four groups (ghrelin, ghrelin + ALI, saline, and saline + ALI) were measured. Immunohistochemical staining to detect alpha-smooth muscle actin (α-SMA) and proliferating cell nuclear antigen (PCNA) expression was performed to assess the intrapulmonary arterial wall thickness and the proliferation of smooth muscle cells, respectively. Results. The ghrelin-pretreated ALI rats showed lower mPAP, RVSP, PCNA expression, MPO activity, W/D lung weight ratio, TNF-α and IL-6 levels, and BALF cell count than the saline-pretreated ALI rats, but ghrelin had no effect on the intrapulmonary arterial wall thickness of ALI rats. Conclusion. Our results confirmed the association between inflammation and PVD in ALI and suggested that the suppression of inflammation by ghrelin pretreatment could protect LPS-induced ALI rats against PVD.

Vitamin D deficiency downregulates TASK-1 channels and induces pulmonary vascular dysfunction

Vitamin D (VitD) receptor regulates the expression of several genes involved in signaling pathways affected in pulmonary hypertension (PH). VitD deficiency is highly prevalent in PH, and low levels are associated with poor prognosis. We investigated if VitD deficiency may predispose to or exacerbate PH. Male Wistar rats were fed with a standard or a VitD-free diet for 5 wk. Next, rats were further divided into controls or PH, which was induced by a single dose of Su-5416 (20 mg/kg) and exposure to hypoxia (10% O2) for 2 wk. VitD deficiency had no effect on pulmonary pressure in normoxic rats, indicating that, by itself, it does not trigger PH. However, it induced several moderate but significant changes characteristic of PH in the pulmonary arteries, such as increased muscularization, endothelial dysfunction, increased survivin, and reduced bone morphogenetic protein ( Bmp) 4, Bmp6, DNA damage-inducible transcript 4, and K+ two - pore domain channel subfamily K member 3 ( Kcnk3) expression. Myocytes isolated from pulmonary arteries from VitD-deficient rats had a reduced whole voltage-dependent potassium current density and acid-sensitive (TASK-like) potassium currents. In rats with PH induced by Su-5416 plus hypoxia, VitD-free diet induced a modest increase in pulmonary pressure, worsened endothelial function, increased the hyperreactivity to serotonin, arterial muscularization, decreased total and TASK-1 potassium currents, and further depolarized the pulmonary artery smooth muscle cell membrane. In human pulmonary artery smooth muscle cells from controls and patients with PH, the active form of VitD calcitriol significantly increased KCNK3 mRNA expression. Altogether, these data strongly suggest that the deficit in VitD induces pulmonary vascular dysfunction.

Review 2: Primary graft dysfunction after lung transplant—pathophysiology, clinical considerations and therapeutic targets

Primary graft dysfunction (PGD) is one of the most common complications in the early postoperative period and is the most common cause of death in the first postoperative month. The underlying pathophysiology is thought to be the ischaemia–reperfusion injury that occurs during the storage and reperfusion of the lung engraftment; this triggers a cascade of pathological changes, which result in pulmonary vascular dysfunction and loss of the normal alveolar architecture. There are a number of surgical and anaesthetic factors which may be related to the development of PGD. To date, although treatment options for PGD are limited, there are several promising experimental therapeutic targets. In this review, we will discuss the pathophysiology, clinical management and potential therapeutic targets of PGD.