title: MAP kinase kinase kinase-2 (MEKK2) regulates hypertrophic remodeling of the right ventricle in hypoxia-induced pulmonary hypertension.
abstract: Pulmonary hypertension (PH) results in pressure overload of the right ventricle (RV) of the heart, initiating pathological RV remodeling and ultimately leading to right heart failure. Substantial research indicates that signaling through the MAPK superfamily mediates pathological cardiac remodeling. These considerations led us to test the hypothesis that the regulatory protein MAPKKK-2 (MEKK2) contributes to RV hypertrophy in hypoxia-induced PH. Transgenic mice with global knockout of MEKK2 (MEKK2(-/-) mice) and age-matched wild-type (WT) mice were exposed to chronic hypobaric hypoxia (10% O(2), 6 wk) and compared with animals under normoxia. Exposure to chronic hypoxia induced PH in WT and MEKK2(-/-) mice. In response to PH, WT mice showed RV hypertrophy, demonstrated as increased ratio of RV weight to body weight, increased RV wall thickness at diastole, and increased cardiac myocyte size compared with normoxic control animals. In contrast, each of these measures of RV hypertrophy seen in WT mice after chronic hypoxia was attenuated in MEKK2(-/-) mice. Furthermore, chronic hypoxia elicited altered programs of hypertrophic and inflammatory gene expression consistent with pathological RV remodeling in WT mice; MEKK2 deletion selectively inhibited inflammatory gene expression compared with WT mice. The actions of MEKK2 were mediated in part through regulation of the abundance and phosphorylation of its effector, ERK5. In conclusion, signaling by MEKK2 contributes to RV hypertrophy and altered myocardial inflammatory gene expression in response to hypoxia-induced PH. Therapies targeting MEKK2 may protect the myocardium from hypertrophy and pathological remodeling in human PH.
authors.affiliation: Department of Pediatrics, University of Colorado-Denver, Aurora, CO 80045, USA. Dale.Brown@ucdenver.edu
authors.forename: R Dale
authors.initials: RD
authors.lastname: Brown
authors.forename: S Kelly
authors.initials: SK
authors.lastname: Ambler
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Sullivan
authors.forename: Lauren N
authors.initials: LN
authors.lastname: Henry
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Crossno
authors.forename: Carlin S
authors.initials: CS
authors.lastname: Long
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Garrington
authors.forename: Kurt R
authors.initials: KR
authors.lastname: Stenmark
mesh_terms: D000818:Animals; D002908:Chronic Disease; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000201:enzymology* / Q000503:physiopathology; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging / Q000201:enzymology / Q000209:etiology* / Q000235:genetics / Q000503:physiopathology; D017380:Hypertrophy, Right Ventricular / Q000000981:diagnostic imaging / Q000201:enzymology / Q000209:etiology* / Q000235:genetics / Q000503:physiopathology / Q000517:prevention & control; D000860:Hypoxia / Q000150:complications* / Q000201:enzymology / Q000235:genetics; D018836:Inflammation Mediators / Q000378:metabolism; D048730:MAP Kinase Kinase Kinase 2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D048054:Mitogen-Activated Protein Kinase 7 / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000473:pathology; D010766:Phosphorylation; D013997:Time Factors; D014463:Ultrasonography; D020257:Ventricular Remodeling
chemical_list: D018836:Inflammation Mediators; D048054:Mitogen-Activated Protein Kinase 7; D048730:MAP Kinase Kinase Kinase 2; C482619:Map3k2 protein, mouse