Title: Measuring nitrate reductase activity from human and rodent tongues.
Authors: Ahmed, Khandaker A; Nichols, Alexandria L; Honavar, Jaideep; Dransfield, Mark T; Matalon, Sadis; Patel, Rakesh P
Published In Nitric Oxide, (2017 Jun 01)
Abstract: Reduction of salivary nitrate to nitrite by oral microbes expressing nitrate-reductase has emerged as a crucial pathway in systemic NO homeostasis in humans and other mammals. Selective depletion of oral microbes prevents dietary nitrate-dependent lowering of blood pressure, inhibition of platelet aggregation and ischemic injury. To date, most studies interrogate enterosalivary nitrate reduction by following changes in saliva or plasma nitrite and NO-signaling (functional) end points. Little is known about whether, and if so how, nitrate-reductase enzymatic activity per se (i.e. independent of nitrate levels) is a variable and may account for any individual to individual variation. Here, we describe a minimally invasive protocol that allows for NR activity determination from human, rat and mouse tongue scrapes/swabs. We validate this method using selective application of antiseptic agents to the distal tongue surface which decreased NR activity by >80% and show that bacterial number is a significant variable in measured NR activities between males and females. Also, we show that NR activity is >80% lower in smokers (humans) and after bromine gas exposure (mice), suggesting that exposure to inhaled reactive substances inhibit NR activity identifying a potentially new mechanism by which environmental toxicants promote dysfunction in NO-bioavailability. The described method will facilitate studies testing whether NR specific activity is a variable in different pathophysiologic settings, and in turn how this activity modulates enterosalivary nitrate-reduction.
PubMed ID: 28390999
MeSH Terms: Adult; Animals; Bromine/toxicity; Chlorhexidine/pharmacology; Colony Count, Microbial; Female; Humans; Inhalation Exposure; Male; Mice; Mice, Inbred C57BL; Middle Aged; Nitrate Reductase/analysis*; Nitrate Reductase/drug effects; Nitrate Reductase/metabolism*; Nitric Oxide/metabolism; Rats; Rats, Sprague-Dawley; Tobacco Smoke Pollution; Tongue/drug effects; Tongue/enzymology*; Tongue/microbiology; Young Adult