Maresin conjugates in tissue regeneration 1 (MCTR1) is a specialized pro-resolving mediator (SPM) synthesized from docosahexaenoic acid in macrophages at the site of inflammation. DHA is oxidized to maresin 1 , which is then converted to MCTR1 by glutathione S-transferase Mu 4 or leukotriene C4 synthase. MCTR1 accelerates tissue regeneration in planaria (1 and 100 nM). Pretreatment with MCTR1 (50 ng mouse, i.p.) prior to E. coli administration reduces neutrophil infiltration, shortens the inflammatory resolution period, and increases phagocytosis of E. coli by macrophages. When administered at a dose of 100 ng 12h post E. coli infection in a mouse model of peritonitis, MCTR1 reduces the amount of eicosanoids in the exudate.