Role of the RhoA/ROCK pathway in high-altitude associated neonatal pulmonary hypertension in lambs

Abstract

Exposure to high-altitude chronic hypoxia during pregnancy may cause pulmonary hypertension in neonates, as a result of vasoconstriction and vascular remodeling. We hypothesized that susceptibility to pulmonary hypertension, due to an augmented expression and activity of the RhoA/Rho-kinase (ROCK) pathway in these neonates, can be reduced by daily administration of fasudil, a ROCK inhibitor. We studied 10 highland newborn lambs with conception, gestation, and birth at 3,600 m in Putre, Chile. Five highland controls (HLC) were compared with 5 highland lambs treated with fasudil (HL-FAS; 3 mg·kg(-1)·day(-1) iv for 10 days). Ten lowland controls were studied in Lluta (50 m; LLC). During the 10 days of fasudil daily administration, the drug decreased pulmonary arterial pressure (PAP) and resistance (PVR), basally and during a superimposed episode of acute hypoxia. HL-FAS small pulmonary arteries showed diminished muscular area and a reduced contractile response to the thromboxane analog U46619 compared with HLC. Hypoxia, but not fasudil, changed the protein expression pattern of the RhoA/ROCKII pathway. Moreover, HL-FAS lungs expressed less pMYPT1(T850) and pMYPT1T(696) than HLC, with a potential increase of the myosin light chain phosphatase activity. Finally, hypoxia induced RhoA, ROCKII, and PKG mRNA expression in PASMCs of HLC, but fasudil reduced them (HL-FAS) similarly to LLC. We conclude that fasudil decreases the function of the RhoA/ROCK pathway, reducing the PAP and PVR in chronically hypoxic highland neonatal lambs. The inhibition of ROCKs by fasudil may offer a possible therapeutic tool for the pulmonary hypertension of the neonates.

The newborn sheep translational model for pulmonary arterial hypertension of the neonate at high altitude

“…105 In high-altitude sheep with pulmonary hypertension, the enhancement of nitrergic vasodilator tone does not avoid pulmonary hypertension, 31,104 probably because there is also increased expression and activation of RhoA that allows the maintenance of a strong Ca 2þ sensitivity. 22,106 This response contrasts with the response observed in newborn of species resistant to hypoxic pulmonary hypertension like the llama, where the increased nitrergic together with decreased Ca 2þ sensitization allows effective vasodilation. 32 In addition to Ca 2þ sensitivity, intracellular Ca 2þ concentration is an important mediator of the pulmonary arterial response to hypoxia, and Ca 2þ entry through voltage-dependent or voltage-independent plasma membrane Ca 2þ channels are major regulators.…”

“…104 The RhoA/Rho-kinase (ROCK) pathway also participates in pulmonary vasoconstriction in several species such as rat, mouse, and sheep, contributing to pulmonary vascular remodeling and vasoconstriction by Ca 2þ sensitization. 22 Fasudil and Y-27632, ROCK-specific inhibitors, reduced adult and fetal hypoxic pulmonary contraction. 117,118 Treatment with Fasudil lessens the development of chronic hypoxic PAHN in newborn lambs.…”

“…Some of the most commonly used mammalian models of antenatal and perinatal hypoxia include sheep, 4,[17][18][19][20][21][22][23] rats, 24 mice, 25 piglets, 26 guinea pigs, 5,27,28 and llamas. [29][30][31][32] Sheep have been used as a model for lung development and pulmonary function for several reasons.…”

Pulmonary hypertension: Molecular aspects of current therapeutic intervention and future direction

“…Rho associated serine threonine protein kinases (Rho, Ras, Rab, and Ran families) are recommended as a novel potential therapeutic target for treatment of PH (Lu et al, ). Rho kinase suppresses myosin phosphatase activity by phosphorylating the myosin binding subunit of enzyme and thus, increase VSMC contraction (Lopez et al, ). Rho kinase has supposed to activate various mediators cellular signaling cascade or mediators including monocyte chemoattractant protein‐1 (MCP‐1), plasminogen activator inhibitor‐1, and NADPH oxidase, which finally can cause vascular remodeling (Table ) (Lopez et al, ; Lu et al, ).…”

“…Rho kinase suppresses myosin phosphatase activity by phosphorylating the myosin binding subunit of enzyme and thus, increase VSMC contraction (Lopez et al, ). Rho kinase has supposed to activate various mediators cellular signaling cascade or mediators including monocyte chemoattractant protein‐1 (MCP‐1), plasminogen activator inhibitor‐1, and NADPH oxidase, which finally can cause vascular remodeling (Table ) (Lopez et al, ; Lu et al, ). Inhibition of Rho kinase cause the diminished expression of eNOS and increase inflammatory mediators in PH (Velayati et al, ).…”