E-, D-, and T-series resolvins (Rvs)
Resolvin (Rv) is a pro-resolving mediator that is derived from omega-3 fatty acids, primarily eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and clupanodonic acid (Duvall and Levy 2016; Serhan et al. 2014). Rvs are divided into several subclasses based on the unique aspects of their structure and/or the straight-chain PUFAs from which they are formed. Resolvin Ds (RvDs) are metabolites of 22-carbon PUFA, DHA. Resolvin Es (RvE) are metabolites of 20 carbons PUFA, EPA; Resolvin Dn-6DPA (RvDn-6DPA) is a DPA isomer, a metabolite of osbond acids; Resolvin Dn-3DPA (RvDn-3DPA) is a DPA isomer, a metabolite of clupanodonic acid; Resolvin Ts (RvT) is a metabolite of clupanodonic acid with 17R-hydroxyl residues, unlike RvDsn-3DPA (all have 17S-hydroxyl residues). AT-RvDs, RvD isomers are synthesized by the aspirin-modified COX-2 enzyme to form 17 (R)-hydroxyl rather than the 17 (S)-hydroxyl residue of RvE. Cytochrome P450 enzymes that have not yet been characterized may also form this 17 (R)-hydroxy intermediate and contribute to the production of AT-RvE. All mentioned Rvs except RvDsn-6DPA are metabolites of omega-3 fatty acids (Serhan et al. 2014; Duvall and Levy 2016).

E-series resolvins
RvE is a di- or tri-hydroxyl metabolite of EPA. To date, four RvEs (RvE1, 18S-RvE1, RvE2, and RvE3) have been discovered. COX-2, acetylated by aspirin in hypoxic endothelial cells, introduces oxygen groups into 18R-hydro (peroxy)-eicosapentaenoic acid (18R-HEPE). Activated PMN uses 5-LOX to convert 18R-HEPE to 5S (6)-epoxy-18R-HEPE, which is further hydrolyzed to RvE1 (Serhan et al. 2000).
RvE2 is produced by reduction of 18R HEPE products by 5-LOX to 5S-hydroperoxy, 18-hydroxy-EPE in whole blood (Oh et al. 2012). Unlike RvE1, RvE2 and RvE3 are biosynthesized from 18-HEPE via the 12/15-LOX pathway in eosinophils (Isobe et al. 2012b). Endogenous RvE1 has been shown to accumulate for between 48 and 72 hours, which is a delayed time point of inflammation (Hong et al. 2008). RvE2 appeared at the time point corresponding to initial PMN infiltration in rat peritoneal exudate stimulated by zymosan A and decreased within 24 hours (Isobe et al. 2012a). 18S-RvE1 is produced by 5-LOX and LTA4 hydrolase using 18S-HEPE as a substrate (Oh et al. 2011).

D-series resolvins
RvD is a polyhydroxy metabolite of DHA. To date, six RvDs with different positions of cis-trans isomers, as well as the number, position and chirality of the hydroxyl residues have been discovered. D-series Rvs (RvD1-RvD6) are biosynthesized from DHA by the LOX in PMN and macrophages (Serhan et al. 2002). Hydrolysis of peroxide intermediates derived from two LOXs in DHA produces RvD1 and RvD2. On the other hand, the reduction of the peroxide intermediates produces RvD5 (Serhan et al. 2002). In hypoxic endothelial cells in the presence of aspirin, COX-2 converts DHA to 13-hydroxy-DHA or 17R-hydroxy-DHA and activated PMN converts these products to AT-RvD1, AT-RvD2, and other AT-RvD-series. RvD3 and RvD4 are produced through hydrolysis of 4S-hydroperoxy-17S-hydroxy-docosahexaenoic acid, whereas RvD6 is derived from peroxidase of the same precursor.
In a peritonitis model, the in vivo RvD3 levels after zymosan A challenge increases significantly up to 48 hours after inflammation initiation, while RvD1, RvD2, and RvD5 peak at the early stages of the inflammation termination phase (6–24 hours) (Dalli et al. 2013b). RvD3 appears to be produced by a subpopulation of macrophages with high 15-LOX activity (Dalli et al. 2013b). In vivo production of RvD4 in an Staphylococcus aureus injected the dorsal pouch infection model continues for more than 72 hours after sustained release, suggesting that RvD is produced continuously and is under different control from other Rvs (Winkler et al. 2016). RvD6 kinetics have not been reported yet.

Resolvin Ts (RvTs)
In human platelets, COX-2 pre-treated with aspirin or atorvastatin metabolizes omega-3s, DPA and clupanodonic acid (DPAn-3), to 13S-hydroperoxy forms. Aspirin and atorvastatin change the activity of COX-2 from cyclooxygenase to hydroperoxide-forming enzyme. The intermediates formed are transported to the nearby human neutrophils and perhaps by the activity of the ALOX5 enzyme they are metabolized into four polyhydroxy metabolites: RvT1 (7,13R, 20-trihydroxy-DPAn-3); RvT2 (7, 8,13R-trihydroxy-DPAn-3); RvT3 (7,12,13R-trihydroxy-8Z, 10E, 14E, 16Z, 19Z-DPAn-3); RvT4 (7,13R-dihydroxy-DPAn-3). These four RvTs are formed by human neutrophils and vascular endothelial cells and are also found in rodents and human infected tissues (Dalli et al. 2013a, 2015). Recently, the total synthesis of RvT1, RvT2, and its 13R-epimer RvT2, and RvT4 were successfully achieved (Rodriguez and Spur 2020a, b). Therefore, it is expected that there will be many physiological and pharmacological research on RvTs in the future.