Abstract
Nitric oxide synthase (NOS) plays a role in substance use related neurotoxicity and addictive phenotypes. Inhibition of nitric oxide (NO) production can prevent negative phenotypes associated with drugs intake. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NOS. ADMA levels are regulated by dimethylarginine dimethylaminohydrolase type 1 (DDAH1). Numerous evidence suggests that drugs of abuse can increase DDAH1 levels, leading to reduction of ADMA levels, and in turn, causing neurotoxicity associated with NO overproduction. Yet, this data is sparse, and very little mechanistic evidence exists. Here, we review the literature on the impact of substances of abuse and social stress, as a condition implicated in addictive phenotypes, on DDAH1 levels in the brain. This review highlights five things: first, psychostimulants can increase brain DDAH1 levels and DDAH1-ADMA-NOS signaling axis could underlay neurotoxicity and addictive behaviors driven by psychostimulants. Second, opioids can also significantly increase brain DDAH1 levels, yet currently no mechanistic studies exist to determine the consequences of that increase. Three, the nicotine and alcohol studies are inconclusive as results are often complicated with comorbidities associated with cardiovascular impairments, liver toxicity and aging. Four, studies on cannabinoids are insufficient, more data is needed. Finally, social stress affects DDAH1 levels and anti-depressants can reverse this effect, but mechanistic data is lacking. In conclusion, proteomic, metabolomic and functional studies suggest that DDAH1 may play a role in addiction and conditions related to social stress. Further investigation is necessary to elucidate the specific function of DDAH1 in addiction and social stress phenotypes.