Arginase inhibition protects against hypoxia-induced pulmonary arterial hypertension

Abstract

The present study aimed to determine the role of arginase (Arg) in pulmonary arterial hypertension (PAH). In vitro, human pulmonary artery smooth muscle cells (HPASMCs) were cultured under hypoxic conditions with, or without, the Arg inhibitor, S‑(2‑boronoethyl)‑l‑cysteine (BEC), for 48 h, following which the proliferation of the HPASMCs was determined using MTT and cell counting assays. For the in vivo investigation, 30 male rats were randomly divided into the following three groups (n=10 per group): i) control group, ii) PAH group and iii) BEC group, in which the right ventricle systolic pressure (RVSP) of the rats was assessed. The levels of cyclin D1, cyclin‑dependent kinase (CDK)4 and p27 were measured in vitro and in vivo. The phosphorylation levels of Akt and extracellular‑related kinase (ERK) were also measured in HPASMCs. In vitro, compared with the hypoxia group, Arg inhibition reduced HPASMC proliferation and reduced the expression levels of cyclin D1, CDK4, phosphorylated (p‑)Akt and p‑ERK. By contrast, Arg inhibition increased the expression of p27. In vivo, compared with the control group, the expression levels of cyclin D1 and CDK4 were reduced in the PAH group, however, the expression of p27 and the RVSP increased. In the BEC group, the opposite effects were observed. Therefore, it was suggested that Arg inhibition may reduce the RVSP of PAH rats and reduce HPASMC proliferation by decreasing the expression levels of cyclin D1 and CDK4, increasing the expression of p27, and partly reducing the phosphorylation of Akt and ERK.

Arginase Inhibition Reverses Monocrotaline-Induced Pulmonary Hypertension

“…This finding goes in line with the observations of Nara and co-workers showing a reduction of hypoxia induced PH in response to Arg inhibition using nor-NOHA [ 19 ]. Similar results could be obtained by Jiang and co-workers [ 35 ]. By applying the Arg inhibitor amino-2-borono-6-hexanoic acid, bleomycin induced PH could be prevented in a further study in neonatal rats [ 21 ].…”

“…As for any other PH animal model available, it has several limitations and some concerns should be kept in mind when interpreting the results obtained with this model [ 32 , 33 ]. Against the background of the fact that most studies investigating the role of Arg in PH development as well as effects of enzyme inhibition were performed using models of hypoxia induced PH [ 19 , 20 , 28 , 35 ], it is of certain scientific interest to elucidate these processes in the MCT model as performed in the current study. Protein expression and tissue distribution analysis clearly showed an increased expression of both, Arg I and Arg II in induced PH compared to controls.…”

“…In correspondence with our finding concerning a certain role of Arg I in induced PH, Cowburn and co-workers observed a HIF2α enhancement triggered by chronic hypoxia in a mouse model resulting in an up-regulation of its downstream target Arg I with the consequence of a dysregulated NO homeostasis [ 28 ]. There are only few in vivo studies dealing with the impact of Arg in rat models of PH [ 19 , 21 , 22 , 35 ]. From these, only one study used the MCT model [ 22 ], two studies used hypoxia as pathologic stimulus [ 19 , 35 ] and one study bleomycin [ 21 ].…”

“…There are only few in vivo studies dealing with the impact of Arg in rat models of PH [ 19 , 21 , 22 , 35 ]. From these, only one study used the MCT model [ 22 ], two studies used hypoxia as pathologic stimulus [ 19 , 35 ] and one study bleomycin [ 21 ]. Neither of these studies discriminated between Arg isoforms.…”

Investigation of Mammal Arginase Inhibitory Properties of Natural Ubiquitous Polyphenols by Using an Optimized Colorimetric Microplate Assay

“…S-(2-boronoethyl)-L-cysteine (BEC) is a commercially-available arginase inhibitor, widely-used in in vitro and in vivo studies [28,29]. In order to use it as reference inhibitor in the newly-developed screening assay, we determined its half-maximal inhibitory concentration (IC 50 ) and its maximum percentage of inhibition corresponding to the upper plateau of the sigmoid curve (E max ); these two parameters represent the activity and efficacy of a compound, respectively.…”