Diphenyleneiodonium exhibits protective effects against both nociception and gastrointestinal inflammation in vivo

Reactive oxygen species (ROS) and nitrogen-derived oxidants, such as nitric oxide (NO), are produced by immune cells through the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and nitric oxide synthases (NOS), respectively. These pro-oxidants disrupt physiological homeostasis, contributing to hyperalgesia, the excessive release of inflammatory markers and oxidative stress during ulcerative colitis (UC). Consequently, diphenyleneiodonium chloride (DPI), an inhibitor of NOXs and NOS, could be effective in alleviating visceral pain and UC. This study examines the antioxidant and analgesic properties of DPI, as well as its ability to modulate oxidative stress and pro-inflammatory responses in UC. The antioxidant properties of DPI and its ability to bind free iron were determined using ABTS and DPPH tests, as well as a ferrous iron chelating capacity assay. DPI's analgesic activity was investigated using a 0.6% acetic acid (AA) mouse model of hyperalgesia, and its preventive effects against UC were determined using a 3% AA rat model of UC. Our results demonstrate that DPI limits free radicals, chelates ferrous iron and reduces writhing number (Wn) by p < 0.001, confirming its analgesic activity. Furthermore, intraperitoneal administration of DPI (100 ng/kg) protected rats from UC by repairing large-scale colonic damage, lowering oxidative stress by decreasing NO levels and restoring antioxidant enzymatic activities in colonic tissue. DPI also lowers plasmatic C-reactive protein (C-RP), NO content, lactate dehydrogenase (LDH) and γ-glutamyl transferase (γ-GT) activity during colitis. Therefore, targeting NOXs and NOS with DPI could be a promising strategy for treating inflammatory diseases such as colitis.