Regulation of nitric oxide synthesis by dimethylarginine dimethylaminohydrolase

Abstract

1Dimethylarginine dimethylaminohydrolase (DDAH), an enzyme that metabolizes the endogenous nitric oxide synthase inhibitors N0-monomethyl-L-arginine and NG,NG-dimethy-L-arginine to citrulline, was identified by Western blotting in rat and human tissue homogenates.2 S-2-amino-4(3-methylguanidino)butanoic acid (4124W) inhibited the metabolism of ["4C]-N0-monomethyl-L-arginine to ["4C]-citrulline by rat liver homogenates (IC50 416 + 66 giM; n = 9), human cultured endothelial cells (IC50 250 + 34 gLM; n = 9) and isolated purified dimethylarginine dimethylaminohydrolase. 3 Addition of 4124W to culture medium increased the accumulation of endogenously-generated N',N0-dimethy-L-arginine in the supernatant of human cultured endothelial cells from 3.1 + 0.3 to 5+0.7 ,M (n= 15; P<0.005). 4 4124W (1 uM-1 mM) had no direct effect on endothelial nitric oxide synthase activity but caused endothelium-dependent contraction of rat aortic rings (1 mM 4124W increased tone by 81.5 + 9.6% of that caused by phenylephrine 100 nM). This effect was reversed by L-arginine (100 giM). 4124W reversed endothelium-dependent relaxation of human saphenous vein (19.2 + 6.7% reversal of bradykinin-induced relaxation at 1 mM 4124W). 5 These data suggest that inhibition of dimethylarginine dimethylaminohydrolase increases the intracellular concentration of N',N0-dimethyl-L-arginine sufficiently to inhibit nitric oxide synthesis.Inhibiting the activity of DDAH may provide an alternative mechanism for inhibition of nitric oxide synthases and changes in the activity of DDAH could contribute to pathophysiological alterations in NO generation.

Asymmetrical dimethylarginine: A novel risk factor for coronary artery disease

“…MacAllister et al showed that inhibition of DDAH blocked ADMA degradation and caused vasoconstriction in isolated vascular rings. 34 A recent report also demonstrated that reduction of DDAH activity might account for increased production of ADMA by endothelium cell treated with oxidized LDL or cytokines. 35 The DDAH activity in patients with CAD deserves further investigation.…”

A role for asymmetric dimethylarginine in the pathophysiology of portal hypertension in rats with biliary cirrhosis

“…12 Under certain conditions, inhibition of DDAH is known to lead to high local concentrations of ADMA, further feeding the issue of whether plasma levels adequately reflect biologically active ADMA-or, indeed, whether they represent a marker of high intracellular levels. 12,37,38 In conclusion, we have demonstrated that the pathogenesis of impaired intrahepatic NO production in cirrhosis depends on the etiology of cirrhosis. Whereas in TAA-induced cirrhosis decreased intrahepatic NO bioavailability results from reduced eNOS enzyme levels and activity, in rats with biliary cirrhosis eNOS enzyme levels were unaltered.…”

Dimethylarginine dimethylaminohydrolase I enhances tumour growth and angiogenesis

“…Aliquots of 500 ml were incubated with [ 14 C] L-NMMA (0.4 mCi ml 71 ) for 1 h at 378C. The formation of [ 14 C] citrulline was determined as previously described (MacAllister et al, 1996). The enzymatic activity was corrected for the protein concentration.…”

“…Free ADMA is found in plasma and urine of healthy individuals and is synthesised by the post-translational methylation of protein arginine residues and liberated upon their hydrolysis (Kakimoto and Akazawa, 1970;Fickling et al, 1993). The intracellular concentration of ADMA reaches levels sufficient to inhibit NO synthesis (Macallister et al, 1994) and can be modulated by changes in the activity of the enzyme dimethylarginine dimethylaminohydrolase (DDAH) (Ogawa et al, 1989;Macallister et al, 1996).…”