Abstract
The amino-alcohol tris-hydroxymethyl-aminomethane (Tris), 2-amino-2-(hydroxymethyl)-1,3-propanediol) has well-known applications in biochemistry and molecular biology. We have synthetized a novel compound from acetylsalicylic acid (ASA) and Tris precursors, with the intent to develop an agent that exhibit bioactivity against inflammation but devoid of hemorrhagic side-effects in the upper gastrointestinal tract. We have characterized the biological effects of ASA-Tris and the derivatives (ASA-bis- and mono-hydroxymethyl-aminomethane (ASA-Bis, ASA-Mono, respectively) using in vivo and in vitro test systems. First, ASA or ASA conjugates (0.55 mmol/kg, each) were administered intragastrically to Sprague-Dawley rats, the changes in the gastric mucosal structure and in the serosal microcirculation were detected by in vivo imaging techniques. The plasma TNF-alpha, tissue xanthine oxidoreductase and myeloperoxidase activities were determined, liver mitochondria were examined with high-resolution respirometry to analyze alterations in the electron transport chain. In separate series, platelet aggregation and carrageenan arthritis-induced inflammatory pain were measured in control, ASA and ASA-Tris-treated groups, and local and remote consequences of ASA-Tris administration in 2-,4-,6-trinitrobenzene-sulfonic acid (TNBS)-induced colitis were also examined.
We detected severe gastric mucosal injury and a significant decrease in serosal red blood cell velocity in the ASA-treated group, and an approx. 2-fold elevation in proinflammatory mediator levels evolved. ASA-Tris did not cause bleeding, microcirculatory dysfunction, mucosal injury or an elevation in proinflammatory markers, did not influence the cyclooxygenase-induced platelet aggregation significantly, but the inflammatory pain was reduced as effectively as in the case of equimolar ASA doses. As compared to ASA, ASA-Tris conjugation provided significant protection against the TNBS-induced colonic injury and cytokine-mediated progression of inflammatory events in experimental colitis without influencing the gastric epithelial structure. Also, ASA significantly reduced the Complex IV-linked respiration of liver mitochondria, which was not observed after ASA-Tris treatment.
We concluded that ASA-Tris conjugation is an effective approach through which the gastrointestinal side-effects of ASA are controlled by decreasing the cytokine-mediated progression of pro-inflammatory events. Besides, as compared to ASA, ASA-Tris conjugation provides significant protection against the colonic injury in experimental colitis without influencing the gastric epithelial structure.
