Dimethylarginine Dimethylaminohydrolase II Overexpression Attenuates LPS-Mediated Lung Leak in Acute Lung Injury

Abstract

Acute lung injury (ALI) is a severe hypoxemic respiratory insufficiency associated with lung leak, diffuse alveolar damage, inflammation, and loss of lung function. Decreased dimethylaminohydrolase (DDAH) activity and increases in asymmetric dimethylarginine (ADMA), together with exaggerated oxidative/nitrative stress, contributes to the development of ALI in mice exposed to LPS. Whether restoring DDAH function and suppressing ADMA levels can effectively ameliorate vascular hyperpermeability and lung injury in ALI is unknown, and was the focus of this study. In human lung microvascular endothelial cells, DDAH II overexpression prevented the LPS-dependent increase in ADMA, superoxide, peroxynitrite, and protein nitration. DDAH II also attenuated the endothelial barrier disruption associated with LPS exposure. Similarly, in vivo, we demonstrated that the targeted overexpression of DDAH II in the pulmonary vasculature significantly inhibited the accumulation of ADMA and the subsequent increase in oxidative/nitrative stress in the lungs of mice exposed to LPS. In addition, augmenting pulmonary DDAH II activity before LPS exposure reduced lung vascular leak and lung injury and restored lung function when DDAH activity was increased after injury. Together, these data suggest that enhancing DDAH II activity may prove a useful adjuvant therapy to treat patients with ALI.

Reply

“…So, the effect of OCA on DDAH seems to depend on the etiology of cirrhosis, which is not only a novel finding, but again also might form a potential pitfall when going into clinical trial. Whereas we acknowledge that several researchers have demonstrated a DDAH-1-mediated reduction in ADMA upon FXR agonism, which we could not confirm in this study, for the time being, there is at least an equal amount of publications emphasizing either on the importance of DDAH-2 alone or combined with DDAH-1 with regard to ADMA metabolism, [5][6][7][8][9][10][11] leaving the solution to this puzzle unavailable at this time. To the point of "unprecedented" FXR agonism leading to DDAH-2 expression, we would like to draw the attention of Mookerjee et al to the article of Achan et al, 12 who found that all transretinoic acid, trough nuclear receptor binding, increased nitric oxide synthesis by endothelial cells in vitro through increased DDAH-2 gene expression and promoter activity.…”

The protective role of MLCP-mediated ERM dephosphorylation in endotoxin-induced lung injury in vitro and in vivo

“…To evaluate whether MLCP activity has a barrier-protective and anti-inflammatory role in LPS-induced vascular barrier injury in vivo, we utilized a LPS murine model of ALI in conjunction with a lung-targeted gene delivery method which we have recently developed27. In this approach, commercial (Polyplus) cationic polymer jetPEI (polyethyleneimine) transfection reagent forms a complex with the DNA of interest that specifically targets the lungs with preferential localization to the endothelium27.…”

“…In this approach, commercial (Polyplus) cationic polymer jetPEI (polyethyleneimine) transfection reagent forms a complex with the DNA of interest that specifically targets the lungs with preferential localization to the endothelium27. Utilizing this approach, plasmid encoding C/A MYPT1 1–300 or vector control (empty pcDNA 3.1) complexed with JetPEI was introduced intravenously (i.v.).…”

“…To assess the role of Moesin phosphorylation in vascular barrier regulation in vivo we generated a phospho-null Moesin mutant (Thr558 to Ala18) and utilized an in vivo LPS murine model of ALI in conjunction with jetPEI delivery method, as we have recently described27. Mammalian expression plasmids coding either phospho-null Moesin mutant in pcDNA 3.1 or a control empty pcDNA 3.1 plasmid were injected into mice via a tail vein27. The overexpression of phospho-null Moesin mutant significantly decreased lung permeability inferred from EBD extravasation (Fig.…”

“…Our recently published data have demonstrated barrier-protective effects of HSP-90 inhibitors, DDAH II (dimethylaminohydrolase II) overexpression, microtubule stabilization, extracellular β-NAD (β-nicotinamide adenine dinucleotide) and extracellular purines, ATP and adenosine273541424344. We have previously shown that purine-induced EC barrier strengthening is tightly linked to activation of MLCP and MLCP is involved EC barrier protection against thrombin-induced EC barrier compromise in vitro 161718.…”