Tetrahydrobiopterin protects against guanabenz-mediated inhibition of neuronal nitric-oxide synthase in vitro and in vivo.
نویسندگان
چکیده
It is established that guanabenz inhibits neuronal nitric-oxide (NO) synthase (nNOS) and causes the enhanced proteasomal degradation of nNOS in vivo. Although the time- and NADPH-dependent inhibition of nNOS has been reported in studies where guanabenz was incubated with crude cytosolic preparations of nNOS, the exact mechanism for inhibition is not known. Moreover, even less is known about how the inhibition of nNOS triggers its proteasomal degradation. In the current study, we show, with the use of purified nNOS, that guanabenz treatment leads to the oxidation of tetrahydrobiopterin and formation of a pterin-depleted nNOS, which is not able to form NO. With the use of 14C-labeled guanabenz, we were unable to detect any guanabenz metabolites or guanabenz-nNOS adducts, indicating that reactive intermediates of guanabenz probably do not play a role in the inhibition. Superoxide dismutase, however, prevents the guanabenz-mediated oxidation of tetrahydrobiopterin and inhibition of nNOS, suggesting the role of superoxide as an intermediate. Studies in rats show that administration of tetrahydrobiopterin prevents the inhibition and loss of penile nNOS due to guanabenz, indicating that the loss of tetrahydrobiopterin plays a major role in the effects of guanabenz in vivo. Our findings are consistent with the destabilization and enhanced degradation of nNOS found after tetrahydrobiopterin depletion. These studies suggest that drug-mediated destabilization and subsequent enhanced degradation of protein targets will likely be an important toxicological consideration.
منابع مشابه
Dmd #9951 Tetrahydrobiopterin Protects against Guanabenz-mediated Inhibition of Neuronal No Synthase in Vitro and in Vivo
متن کامل
Guanabenz-mediated inactivation and enhanced proteolytic degradation of neuronal nitric-oxide synthase.
Guanabenz, a metabolism-based irreversible inactivator of neuronal nitric-oxide synthase (nNOS) in vitro, causes the loss of immunodetectable nNOS in vivo. This process is selective in that the slowly reversible inhibitor N(G)-nitro-L-arginine did not decrease the levels of nNOS in vivo. To better understand the mechanism for the loss of nNOS protein in vivo, we have investigated the effects of...
متن کاملRole of matrix metalloproteinase II on analgesic effect of nitric oxide inhibition in rat
Abstract Introduction: Matrix metalloproteinase 2 is one of the inflammatory mediators that is involved in nociceptive processing and its production is regulated by many inflammatory factors such as nitric oxide. We studied the role of MMP-2 on the analgesic effects of nNOS inhibitor. Methods: Considering that nitric oxide has many roles in pain processing, we studied the CSF levels of MMP-2 ...
متن کاملAGE proteins as a causative factor in Alzheimer's Disease
The reaction between reducing sugars and protein free amines, known as the Maillar reaction results in the formation of advanced glycation endproducts (AGEs). AGE modification changes the structure of proteins to amyloid cross-beta structure. These protein structures can activate receptors known as RAGE on glial cells (microglia and astrocytes), and induce the expression of inducible nitric oxi...
متن کاملAGE proteins as a causative factor in Alzheimer's Disease
The reaction between reducing sugars and protein free amines, known as the Maillar reaction results in the formation of advanced glycation endproducts (AGEs). AGE modification changes the structure of proteins to amyloid cross-beta structure. These protein structures can activate receptors known as RAGE on glial cells (microglia and astrocytes), and induce the expression of inducible nitric oxi...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Drug metabolism and disposition: the biological fate of chemicals
دوره 34 9 شماره
صفحات -
تاریخ انتشار 2006