Rho-kinase inhibitor prevents bleomycin-induced injury in neonatal rats independent of effects on lung inflammation

Inhibition of lysophosphatidic acid receptor 1 relieves PMN recruitment in CNS via LPA1/TSP1/CXCR2 pathway and alleviates disruption on blood-brain barrier following intracerebral haemorrhage in mice

BACKGROUD

The frequencies of morbidity and impairment associated with spontaneous intracerebral haemorrhage (ICH) are comparatively high. Blood-brain barrier (BBB) integrity was compromised due to subsequent brain injury induced by ICH, which is crucial for a poor prognosis. Polymorphonuclear leukocyte (PMN) strongly modulate the disruption of BBB in the central nervous system (CNS). The lysophosphatidic acid receptor 1 (LPA1) mediated thrombospondin-1 (TSP1) regulation in astrocytes, which induce macrophage inflammatory protein 2(MIP2) secretion. MIP2 enhance PMN recruitment through CXC chemokine type 2 (CXCR2) activation. The purpose of this study was to investigate whether the LPA1-mediated inhibition of PMN recruitment and BBB protection after ICH is regulated by TSP1 and CXCR2 networks.

METHODS

ICH induction was performed in CD1 mice using collagenase administration. AM966, a targeted LPA1 antagonist, was orally administered 1 and 12 h following ICH. further identify possible LPA1-mediated BBB protection mechanisms, we intracerebroventricularly (ICV) administered a CXCR2 ligand MIP2, as well as TSP1 CRISPR activation (ACT) with AM966. Consequently, we performed neurobehavioral, brain water content (BWC), Evans blue staining (EBS), immunofluorescence (IF), and western blot (WB) analyses.

RESULTS

After ICH, astrocytes showed signs of LPA1, which peaked after 24 h, while PMN\ displayed evidence of CXCR2. The AM966-mediated LPA1 suppression relieved PMN recruitment, diminished brain oedema, demonstrated extravasation (as evidenced by EBS), protected BBB integrity, and enhanced neurologic activity following ICH. AM966 treatment strongly reduced TSP1, CXCR2, Occludin, and Claudin-5 expressions and PMN recruitment following ICH, and their expressions were restored by MIP2 and TSP1 CRISPR (ACT).

CONCLUSIONS

This study shows that LAP1 suppression reduced PMN recruitment after ICH in mice via TSP1/CXCR2 signalling, which minimized BBB disruption and improved the CNS's neurobehavioral functioning. Hence, LPA1 is a strong candidate for therapy to reduce PMN recruitment and offer protection of BBB integrity after ICH.

A glucocorticoid-receptor agonist ameliorates bleomycin-induced alveolar simplification in newborn rats

BACKGROUND

Glucocorticoids (GCs) are highly effective yet problematic agents against bronchopulmonary dysplasia (BPD). The dimeric trans-activation of GCs induces unfavorable effects, while monomeric trans-repression suppresses inflammation-related genes. Recently, non-steroidal-selective glucocorticoid-receptor agonists and modulators (SEGRAMs) with only the trans-repressive action have been designed.

METHODS

Using a bleomycin (Bleo)-induced alveolar simplification newborn rat model (recapitulating arrested alveolarization during BPD), we evaluated the therapeutic effects of compound-A (CpdA), a SEGRAM. Sprague-Dawley rats were administered Bleo from postnatal day (PD) 0 to 10 and treated with dexamethasone (Dex) or CpdA from PD 0 to 13. The morphological changes and mRNA expression of inflammatory mediators, including interleukin (IL)-1β, C-X-C motif chemokine ligand 1 (CXCL1), and C-C motif chemokine 2 (CCL2) were investigated.

RESULTS

Similar to the effects of Dex, CpdA exerted protective effects on morphological derangements and inhibited macrophage infiltration and production of pro-inflammatory mediators in Bleo-treated animals. The effects of CpdA were probably mediated by GC receptor (GR)-dependent trans-repression, because unlike the Dex-treated group, anti-inflammatory genes specifically induced by GR-dependent trans-activation (such as "glucocorticoid-induced leucine zipper, GILZ") were not upregulated.

CONCLUSIONS

CpdA improved lung inflammation, inhibited the arrest of alveolar maturation, and restored histological and biochemical changes in a Bleo-induced alveolar simplification model.

IMPACT

SEGRAMs have attracted widespread attention because they are expected to not exhibit unfavorable effects of GCs. Compound A, one of the SEGRAMs, improved lung morphometric changes and decreased lung inflammation in a bleomycin-induced arrested alveolarization, a newborn rat model representing one of the main features of BPD pathology. Compound A did not elicit bleomycin-induced poor weight gain, in contrast to dexamethasone treatment. SEGRAMs, including compound A, may be promising candidates for the therapy of BPD with less adverse effects compared with GCs.

Thrombospondin-1 Plays a Major Pathogenic Role in Experimental and Human Bronchopulmonary Dysplasia

RATIONALE

Extremely preterm infants develop bronchopulmonary dysplasia (BPD), a chronic lung injury that lacks effective treatment. Thrombospondin-1 is an anti-angiogenic protein that activates TGF-β1, a cytokine strongly linked to both experimental and human BPD.

OBJECTIVES

1) To examine effects of inhibiting thrombospondin-1-mediated TGF-β1 activation (LSKL) in neonatal rats with bleomycin-induced lung injury, 2) To examine effects of a thrombospondin-1-mimic (ABT-510) on lung morphology, and 3) To determine whether thrombospondin-1 and related signaling peptides are increased in lungs of human preterm infants at risk for BPD.

METHODS

From postnatal days 1-14, rat pups received daily i.p. bleomycin (1 mg/kg) or vehicle combined with daily s.c. LSKL (20 mg/kg) or vehicle. Separate animals were treated with vehicle or ABT-510 (30 mg/kg/d). Paraffin-embedded lung tissues from 47 autopsies (controls; death <28 days, n=30 and BPD at risk; death ≥28 days, n=17) performed on infants born <29 completed weeks' gestation were semi-quantified for injury markers (collagen, macrophages, 3-nitrotyrosine), thrombospondin-1 and TGF-β1.

MEASUREMENTS AND MAIN RESULTS

Bleomycin or ABT-510 increased lung TGF-β1 activity and macrophage influx, caused pulmonary hypertension and led to alveolar and microvascular hypoplasia. Treatment with LSKL partially prevented abnormal lung morphology secondary to bleomycin. Lungs from human infants at-risk for BPD had increased contents of thrombospondin-1 and TGF-β1 when compared to controls. TGF-β1 content correlated with markers of lung injury.

CONCLUSIONS

Thrombospondin-1 inhibits alveologenesis in neonatal rats, in part via up-regulated activity of TGF-β1. Observations in human lung suggest a similar pathogenic role for thrombospondin-1 in infants at-risk for BPD.

Common Vascular Toxicities of Cancer Therapies

The introduction of targeted agents into modern cancer therapy pursued the goal of molecularly more specific, and thereby more effective and safer, therapies. Paradoxically, however, several toxicities were brought to greater attention, among these not only cardiac but also vascular toxicities. The latter reach far beyond venous thromboembolism and include a broad spectrum of presentations based on the vascular territories and pathomechanisms involved, including abnormal vascular reactivity, acute thrombosis, or accelerated atherosclerosis. This article provides an overview of the most common presentations and their management strategies.

Sodium nitrite augments lung S-nitrosylation and reverses chronic hypoxic pulmonary hypertension in juvenile rats

Deficient nitric oxide (NO) signaling plays a critical role in the pathogenesis of chronic neonatal pulmonary hypertension (PHT). Physiological NO signaling is regulated by S-nitrosothiols (SNOs), which act both as a reservoir for NO and as a reversible modulator of protein function. We have previously reported that therapy with inhaled NO (iNO) increased peroxynitrite-mediated nitration in the juvenile rat lung, although having minimal reversing effects on vascular remodeling. We hypothesized that sodium nitrite (NaNO2) would be superior to iNO in enhancing lung SNOs, thereby contributing to reversal of chronic hypoxic PHT. Rat pups were exposed to air or hypoxia (13% O2) from postnatal days 1 to 21. Dose-response prevention studies were conducted from days 1–21 to determine the optimal dose of NaNO2. Animals then received rescue therapy with daily subcutaneous NaNO2 (20 mg/kg), vehicle, or were continuously exposed to iNO (20 ppm) from days 14–21. Chronic PHT secondary to hypoxia was both prevented and reversed by treatment with NaNO2. Rescue NaNO2 increased lung NO and SNO contents to a greater extent than iNO, without causing nitration. Seven lung SNO proteins upregulated by treatment with NaNO2 were identified by multiplex tandem mass tag spectrometry, one of which was leukotriene A4 hydrolase (LTA4H). Rescue therapy with a LTA4H inhibitor, SC57461A (10 mg·kg−1·day−1 sc), partially reversed chronic hypoxic PHT. We conclude that NaNO2 was superior to iNO in increasing tissue NO and SNO generation and reversing chronic PHT, in part via upregulated SNO-LTA4H.

Matricellular protein thrombospondin-1 in pulmonary hypertension: multiple pathways to disease

Matricellular proteins are secreted molecules that have affinities for both extracellular matrix and cell surface receptors. Through interaction with structural proteins and the cells that maintain the matrix these proteins can alter matrix strength. Matricellular proteins exert control on cell activity primarily through engagement of membrane receptors that mediate outside-in signaling. An example of this group is thrombospondin-1 (TSP1), first identified as a component of the secreted product of activated platelets. As a result, TSP1 was initially studied in relation to coagulation, growth factor signaling and angiogenesis. More recently, TSP1 has been found to alter the effects of the gaseous transmitter nitric oxide (NO). This latter capacity has provided motivation to study TSP1 in diseases associated with loss of NO signaling as observed in cardiovascular disease and pulmonary hypertension (PH). PH is characterized by progressive changes in the pulmonary vasculature leading to increased resistance to blood flow and subsequent right heart failure. Studies have linked TSP1 to pre-clinical animal models of PH and more recently to clinical PH. This review will provide analysis of the vascular and non-vascular effects of TSP1 that contribute to PH, the experimental and translational studies that support a role for TSP1 in disease promotion and frame the relevance of these findings to therapeutic strategies.

Redistribution of Extracellular Superoxide Dismutase Causes Neonatal Pulmonary Vascular Remodeling and PH but Protects Against Experimental Bronchopulmonary Dysplasia

BACKGROUND

A naturally occurring single nucleotide polymorphism (SNP), (R₂₁₃G), in extracellular superoxide dismutase (SOD3), decreases SOD3 matrix binding affinity. Humans and mature mice expressing the R₂₁₃G SNP exhibit increased cardiovascular disease but decreased lung disease. The impact of this SNP on the neonatal lung at baseline or with injury is unknown.

METHODS

Wild type and homozygous R₂₁₃G mice were injected with intraperitoneal bleomycin or phosphate buffered saline (PBS) three times weekly for three weeks and tissue harvested at 22 days of life. Vascular and alveolar development were evaluated by morphometric analysis and immunostaining of lung sections. Pulmonary hypertension (PH) was assessed by right ventricular hypertrophy (RVH). Lung protein expression for superoxide dismutase (SOD) isoforms, catalase, vascular endothelial growth factor receptor 2 (VEGFR2), endothelial nitric oxide synthase (eNOS) and guanosine triphosphate cyclohydrolase-1 (GTPCH-1) was evaluated by western blot. SOD activity and SOD3 expression were measured in serum.

RESULTS

In R₂₁₃G mice, SOD3 lung protein expression decreased, serum SOD3 protein expression and SOD serum activity increased compared to wild type (WT) mice. Under control conditions, R₂₁₃G mice developed pulmonary vascular remodeling (decreased vessel density and increased medial wall thickness) and PH; alveolar development was similar between strains. After bleomycin injury, in contrast to WT, R₂₁₃G mice were protected from impaired alveolar development and their vascular abnormalities and PH did not worsen. Bleomycin decreased VEGFR2 and GTPCH-1 only in WT mice.

CONCLUSION

R₂₁₃G neonatal mice demonstrate impaired vascular development and PH at baseline without alveolar simplification, yet are protected from bleomycin induced lung injury and worsening of pulmonary vascular remodeling and PH. These results show that vessel bound SOD3 is essential in normal pulmonary vascular development, and increased serum SOD3 expression and SOD activity prevent lung injury in experimental bronchopulmonary dysplasia (BPD) and PH.

Myeloid-derived Suppressor Cells Are Necessary for Development of Pulmonary Hypertension

Pulmonary hypertension (PH) complicates the care of patients with chronic lung disease, such as idiopathic pulmonary fibrosis (IPF), resulting in a significant increase in morbidity and mortality. Disease pathogenesis is orchestrated by unidentified myeloid-derived cells. We used murine models of PH and pulmonary fibrosis to study the role of circulating myeloid cells in disease pathogenesis and prevention. We administered clodronate liposomes to bleomycin-treated wild-type mice to induce pulmonary fibrosis and PH with a resulting increase in circulating bone marrow-derived cells. We discovered that a population of C-X-C motif chemokine receptor (CXCR) 2⁺ myeloid-derived suppressor cells (MDSCs), granulocytic subset (G-MDSC), is associated with severe PH in mice. Pulmonary pressures worsened despite improvement in bleomycin-induced pulmonary fibrosis. PH was attenuated by CXCR2 inhibition, with antagonist SB 225002, through decreasing G-MDSC recruitment to the lung. Molecular and cellular analysis of clinical patient samples confirmed a role for elevated MDSCs in IPF and IPF with PH. These data show that MDSCs play a key role in PH pathogenesis and that G-MDSC trafficking to the lung, through chemokine receptor CXCR2, increases development of PH in multiple murine models. Furthermore, we demonstrate pathology similar to the preclinical models in IPF with lung and blood samples from patients with PH, suggesting a potential role for CXCR2 inhibitor use in this patient population. These findings are significant, as there are currently no approved disease-specific therapies for patients with PH complicating IPF.

mTOR-Notch3 signaling mediates pulmonary hypertension in hypoxia-exposed neonatal rats independent of changes in autophagy

BACKGROUND/AIM

Mammalian target of rapamycin (mTOR) is a pivotal regulator of cell proliferation, survival, and autophagy. Autophagy is increased in adult experimental chronic pulmonary hypertension (PHT), but its contributory role to pulmonary vascular disease remains uncertain and has yet to be explored in the neonatal animal. Notch is a major pro-proliferative pathway activated by mTOR. A direct relationship between autophagy and Notch signaling has not been previously explored. Our aim was to examine changes in mTOR-, Notch-, and autophagy-related pathways and the therapeutic effects of autophagy modulators in experimental chronic neonatal PHT secondary to chronic hypoxia.

METHODS

Rat pups were exposed to normoxia or hypoxia (13% O₂ ) from postnatal days 1-21, while receiving treatment with temsirolimus (mTOR inhibitor), DAPT (Notch inhibitor), or chloroquine (inhibitor of autophagic flux).

RESULTS

Exposure to hypoxia up-regulated autophagy and Notch3 signaling markers in lung, pulmonary artery (PA), and PA-derived smooth muscle cells (SMCs). Temsirolimus prevented chronic PHT and attenuated PA and SMC signaling secondary to hypoxia. These effects were replicated by DAPT. mTOR or Notch inhibition also down-regulated smooth muscle content of platelet-derived growth factor β-receptor, a known contributor to vascular remodeling. In contrast, chloroquine had no modifying effects on markers of chronic PHT. Knockdown of Beclin-1 in SMCs had no effect on hypoxia-stimulated Notch3 signaling.

CONCLUSIONS

mTOR-Notch3 signaling plays a critical role in experimental chronic neonatal PHT. Inhibition of autophagy did not suppress Notch signaling and had no effect on markers of chronic PHT.

Pulmonary Hypertension Associated with Idiopathic Pulmonary Fibrosis: Current and Future Perspectives

Pulmonary hypertension (PH) is commonly present in patients with chronic lung diseases such as Chronic Obstructive Pulmonary Disease (COPD) or Idiopathic Pulmonary Fibrosis (IPF) where it is classified as Group III PH by the World Health Organization (WHO). PH has been identified to be present in as much as 40% of patients with COPD or IPF and it is considered as one of the principal predictors of mortality in patients with COPD or IPF. However, despite the prevalence and fatal consequences of PH in the setting of chronic lung diseases, there are limited therapies available for patients with Group III PH, with lung transplantation remaining as the most viable option. This highlights our need to enhance our understanding of the molecular mechanisms that lead to the development of Group III PH. In this review we have chosen to focus on the current understating of PH in IPF, we will revisit the main mediators that have been shown to play a role in the development of the disease. We will also discuss the experimental models available to study PH associated with lung fibrosis and address the role of the right ventricle in IPF. Finally we will summarize the current available treatment options for Group III PH outside of lung transplantation.

Intermittent hypoxia during recovery from neonatal hyperoxic lung injury causes long-term impairment of alveolar development: A new rat model of BPD

Bronchopulmonary dysplasia (BPD) is a chronic lung injury characterized by impaired alveologenesis that may persist into adulthood. Rat models of BPD using varying degrees of hyperoxia to produce injury either cause early mortality or spontaneously recover following removal of the inciting stimulus, thus limiting clinical relevance. We sought to refine an established rat model induced by exposure to 60% O₂ from birth by following hyperoxia with intermittent hypoxia (IH). Rats exposed from birth to air or 60% O₂ until day 14 were recovered in air with or without IH (FI_O2 = 0.10 for 10 min every 6 h) until day 28 Animals exposed to 60% O₂ and recovered in air had no evidence of abnormal lung morphology on day 28 or at 10-12 wk. In contrast, 60% O₂-exposed animals recovered in IH had persistently increased mean chord length, more dysmorphic septal crests, and fewer peripheral arteries. Recovery in IH also increased pulmonary vascular resistance, Fulton index, and arterial wall thickness. IH-mediated abnormalities in lung structure (but not pulmonary hypertension) persisted when reexamined at 10-12 wk, accompanied by increased pulmonary vascular reactivity and decreased exercise tolerance. Increased mean chord length secondary to IH was prevented by treatment with a peroxynitrite decomposition catalyst [5,10,15,20-Tetrakis(4-sulfonatophenyl)-21H,23H-porphyrin iron (III) chloride, 30 mg/kg/day, days 14-28], an effect accompanied by fewer inflammatory cells. We conclude that IH during recovery from hyperoxia-induced injury prevents recovery of alveologenesis and leads to changes in lung and pulmonary vascular function lasting into adulthood, thus more closely mimicking contemporary BPD.

Endothelin-1-Rho kinase interactions impair lung structure and cause pulmonary hypertension after bleomycin exposure in neonatal rat pups

Bronchopulmonary dysplasia (BPD) is the chronic lung disease associated with premature birth, characterized by impaired vascular and alveolar growth. In neonatal rats bleomycin decreases lung growth and causes pulmonary hypertension (PH), which is poorly responsive to nitric oxide. In the developing lung, through Rho kinase (ROCK) activation, ET-1 impairs endothelial cell function; however, whether ET-1-ROCK interactions contribute to impaired vascular and alveolar growth in experimental BPD is unknown. Neonatal rats were treated daily with intraperitoneal bleomycin with and without selective ETA (BQ123/BQ610) and ETB (BQ788) receptor blockers, nonselective ET receptor blocker (ETRB) (bosentan), or fasudil (ROCK inhibitor). At day 14, lungs were harvested for morphometrics, and measurements of Fulton's index (RV/LV+S), medial wall thickness (MWT), and vessel density. Lung ET-1 protein and ROCK activity (phospho-MYPT-1:total MYPT-1 ratio) were also measured by Western blot analysis. Bleomycin increased lung ET-1 protein expression by 65%, RV/LV+S by 60%, mean linear intercept (MLI) by 212%, and MWT by 140% and decreased radial alveolar count (RAC) and vessel density by 40 and 44%, respectively (P < 0.01 for each comparison). After bleomycin treatment, fasudil and bosentan partially restored RAC and vessel density and decreased MLI, RV/LV+S, and MWT to normal values. Bleomycin increased ROCK activity by 120%, which was restored to normal values by bosentan but not selective ETRB. We conclude that ET-1-ROCK interactions contribute to decreased alveolar and vascular growth and PH in experimental BPD. We speculate that nonselective ETRB and ROCK inhibitors may be effective in the treatment of infants with BPD and PH.

Vascular Toxicities of Cancer Therapies: The Old and the New--An Evolving Avenue

Since the late 1990s, there has been a steady decline in cancer-related mortality, in part related to the introduction of so-called targeted therapies. Intended to interfere with a specific molecular pathway, these therapies have, paradoxically, led to a number of effects off their intended cancer tissue or molecular targets. The latest examples are tyrosine kinase inhibitors targeting the Philadelphia Chromosome mutation product, which have been associated with progressive atherosclerosis and acute vascular events. In addition, agents designed to interfere with the vascular growth factor signaling pathway have vascular side effects ranging from hypertension to arterial events and cardiomyocyte toxicity. Interestingly, the risk of cardiotoxicity with drugs such as trastuzumab is predicted by preexisting cardiovascular risk factors and disease, posing the question of a vascular component to the pathophysiology. The effect on the coronary circulation has been the leading explanation for the cardiotoxicity of 5-fluorouracil and may be the underlying the mechanism of presentation of apical ballooning syndrome with various chemotherapeutic agents. Classical chemotherapeutic agents such as cisplatin, often used in combination with bleomycin and vinca alkaloids, can lead to vascular events including acute coronary thrombosis and may be associated with an increased long-term cardiovascular risk. This review is intended to provide an update on the evolving spectrum of vascular toxicities with cancer therapeutics, particularly as they pertain to clinical practice, and to the conceptualization of cardiovascular diseases, as well. Vascular toxicity with cancer therapy: the old and the new, an evolving avenue.

Animal Models, Learning Lessons to Prevent and Treat Neonatal Chronic Lung Disease

Bronchopulmonary dysplasia (BPD) is a unique injury syndrome caused by prolonged injury and repair imposed on an immature and developing lung. The decreased septation and decreased microvascular development phenotype of BPD can be reproduced in newborn rodents with increased chronic oxygen exposure and in premature primates and sheep with oxygen and/or mechanical ventilation. The inflammation caused by oxidants, inflammatory agonists, and/or stretch injury from mechanical ventilation seems to promote the anatomic abnormalities. Multiple interventions targeted to specific inflammatory cells or pathways or targeted to decreasing ventilation-mediated injury can substantially prevent the anatomic changes associated with BPD in term rodents and in preterm sheep or primate models. Most of the anti-inflammatory therapies with benefit in animal models have not been tested clinically. None of the interventions that have been tested clinically are as effective as anticipated from the animal models. These inconsistencies in responses likely are explained by the antenatal differences in lung exposures of the developing animals relative to very preterm humans. The animals generally have normal lungs while the lungs of preterm infants are exposed variably to intrauterine inflammation, growth abnormalities, antenatal corticosteroids, and poorly understood effects from the causes of preterm delivery. The animal models have been essential for the definition of the mediators that can cause a BPD phenotype. These models will be necessary to develop and test future-targeted interventions to prevent and treat BPD.

Peroxisome proliferator activated receptor-γ-Rho-kinase interactions contribute to vascular remodeling after chronic intrauterine pulmonary hypertension

Peroxisome proliferator-activated receptor-γ (PPARγ) and Rho-kinase (ROCK) regulate smooth muscle cell (SMC) proliferation and contribute to vascular remodeling in adult pulmonary hypertension. Whether these pathways interact to contribute to the development of vascular remodeling in persistent pulmonary hypertension of the newborn (PPHN) remains unknown. We hypothesized that ROCK-PPARγ interactions increase SMC proliferation resulting in vascular remodeling in experimental PPHN. Pulmonary artery SMCs (PASMCs) were harvested from fetal sheep after partial ligation of the ductus arteriosus in utero (PPHN) and controls. Cell counts were performed daily for 5 days with or without PPARγ agonists and ROCK inhibition. PPARγ and ROCK protein expression/activity were measured by Western blot in normal and PPHN PASMCs. We assessed PPARγ-ROCK interactions by studying the effect of ROCK activation on PPARγ activity and PPARγ inhibition (siRNA) on ROCK activity and PASMC proliferation. At baseline, PPHN PASMC cell number was increased by 38% above controls on day 5. ROCK protein expression/activity were increased by 25 and 34% and PPARγ protein/activity decreased by 40 and 50% in PPHN PASMC. ROCK inhibition and PPARγ activation restored PPHN PASMC growth to normal values. ROCK inhibition increased PPARγ activity by 50% in PPHN PASMC, restoring PPARγ activity to normal. In normal PASMCs, ROCK activation decreased PPARγ activity and PPARγ inhibition increased ROCK activity and cell proliferation, resulting in a PPHN hyperproliferative PASMC phenotype. PPARγ-ROCK interactions regulate SMC proliferation and contribute to increased PPHN PASMC proliferation and vascular remodeling in PPHN. Restoring normal PPARγ-ROCK signaling may prevent vascular remodeling and improve outcomes in PPHN.