Dimethylarginine dimethylaminohydrolase 1 deficiency aggravates monocrotaline-induced pulmonary oxidative stress, pulmonary arterial hypertension and right heart failure in rats
Introduction
Pulmonary arterial hypertension (PAH) is a disease characterized by progressively increased pulmonary arterial pressure due to aberrant pulmonary artery remodeling and vasoconstriction, which ultimately results in right ventricular (RV) hypertrophy and consequent uncompensated RV failure [1]. RV hypertrophy and failure in response to the increased pulmonary pressure overload are crucial determinants of prognosis in patients with PAH [2,3]. Although the detailed mechanisms of PAH and RV failure development are not totally clear, studies have consistently demonstrated that methods to enhance nitric oxide (NO)/cGMP signaling are effective in treating PAH [1].
Asymmetric dimethylarginine (ADMA) is an endogenous NO synthases (NOS) inhibitor that competes with l-arginine and, as a result, attenuates NOS activity and NO production [4]. In mammals, there are at least three main NOS isozymes, neuronal (nNOS), inducible (iNOS), and endothelial (eNOS) [5]. Increased ADMA is associated with various cardiovascular diseases such as pulmonary hypertension, atherosclerosis, hypertension, and chronic renal diseases etc. [6,7]. Dimethylarginine dimethylaminohydrolase-1 (DDAH1) degrades ADMA [8,9], and in fact appears to be the critical enzyme for ADMA degradation [10]. Thus, global DDAH1 KO not only results in increases of tissue and plasma ADMA, but also results in abolished ADMA degradation capacity in mice [10]. Chronic hypoxia-induced PAH is associated with reduced lung DDAH1 protein expression, increased ADMA concentration and decreased NO production in rats [11]. However, it is unclear whether DDAH1 dysfunction or chronic ADAM accumulation is sufficient to cause spontaneous PAH and RV hypertrophy under control conditions or exacerbate PAH development and RV hypertrophy after stressed conditions such as after MCT injection, a commonly used method to generate PAH in rats.
Here, by using a novel DDAH1 knockout (DDAH1−/−) rat strain generated in our laboratory, we studied the effect of DDAH1 dysfunction on monocrotaline-induced PAH, lung vascular remodeling and RV hypertrophy in rats. Our findings indicate that DDAH1 plays an important role in attenuating monocrotaline-induced PAH development and RV hypertrophy.
Section snippets
Methods
Detailed methods are available in the online-only Data Supplement.
DDAH1 knockout in rats results in abolished DDAH1 expression in all tissues tested
As presented in Fig. 1, the experimental approach resulted in deletion of exon1 of DDAH1 in DDAH1−/− rats (Fig. S1A–B). DDAH1−/− totally abolished DDAH1 protein expression in heart, lung, liver, kidney, spleen, skeletal muscle and brain tissues (Fig. S1C). DDAH2 protein expression was unchanged in DDAH1−/− rats. The DDAH1−/− rats showed no detectable gross defect in development and growth, a finding that is consistent with the prior observations in global DDAH1−/− mouse strain [10].
DDAH1−/− has no detectable effect on PAH and RV hypertrophy in rats under control conditions
We found
Discussion
The present study has several important findings. First, we demonstrated for the first time that DDAH1−/− rats had an increase of systemic and tissue ADMA contents, relative to wild type rats, but had no detectable effect on the growth and development. Second, we found that DDAH1−/− had no effect on LV or RV hypertrophy and dysfunction, and PAH development under control conditions. Third, we demonstrated that DDAH1−/− significantly exacerbated MCT-induced PAH, lung vascular remodeling, and RV
Conclusion
In summary, we have demonstrated that DDAH1 deficiency could increase ADMA levels in plasma and tissue and impair the capacity of the RV in response to PAH, indicating that modulation of DDAH1 activity may be a promising therapeutic approach for treatment of PAH-induced RV failure.
Acknowledgements
None.
Sources of funding
This study was supported by research grants 81470512 and 81570355 from National Natural Science Foundation of China, and a grant in aid from American Heart Association.
Declaration of competing interest
None.
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