Specialized pro-resolving mediators (SPMs) biosynthesized from n-3 DPA (22:5 Ο-3 docosapentaenoic acid), representing the T-series resolvin family distinct from D-series (from DHA) and E-series (from EPA). RvTs activate specific G-Protein Receptors including DRV1/GPR32 and DRV2/GPR18, promoting active Resolution of inflammation through neutrophil apoptosis, macrophages Efferocytosis, and reduction of pro-inflammatory cytokine production while enhancing tissue repair signals.
Think of 13-series resolvins as the backup firefighting crew that appears when the main team's water supply is limited. Your city has three fire stations: the D-station (DHA-based), the E-station (EPA-based), and the T-station (n-3 DPA-based). The T-station sits on the route between E and D stations β it's literally the intermediate stop. When your body can't convert enough EPA to DHA (maybe due to genetic FADS2 variants, chronic inflammation, or age-related enzyme decline), the n-3 DPA intermediate accumulates at the T-station. Instead of wasting this resource, the body deploys it directly as RvT firefighters. These crews carry similar equipment to D-series and E-series teams β they still activate the same alarm receptors (GPR32), still coordinate debris cleanup (efferocytosis), and still dampen the inflammatory alarm bells (cytokine reduction). The key insight: this isn't a malfunction β it's evolutionary redundancy. Nature built multiple resolution pathways so that even when your DHA synthesis is impaired (common in modern populations), you still have professional fire crews on duty, just drawn from the intermediate station rather than the final one.
Biosynthetic Pathway:
EPA (20:5 Ο-3) β elongase β n-3 DPA (22:5 Ο-3) β desaturase β DHA (22:6 Ο-3)
When conversion to DHA is rate-limited, n-3 DPA is shunted into resolvin synthesis:
n-3 DPA β 12-LOX or 15-LOX β 13-hydroxy-DPA β resolvin T intermediates β RvT1, RvT2, RvT3, RvT4
graph TD
A["n-3 DPA 22:5"] --> B[12-LOX/15-LOX]
B --> C[13-hydroperoxy-DPA]
C --> D[Epoxide formation]
D --> E[Hydrolysis]
E --> F[RvT1]
E --> G[RvT2]
E --> H[RvT3]
E --> I[RvT4]
F --> J[DRV1/GPR32 activation]
G --> J
H --> J
I --> K[DRV2/GPR18 activation]
J --> L[Neutrophil apoptosis]
J --> M["β NF-ΞΊB signaling"]
J --> N[Macrophage efferocytosis]
K --> L
K --> M
K --> N
L --> O[Resolution]
M --> O
N --> O
Receptor-Mediated Actions:
RvT1-4 β DRV1/GPR32 binding β GΞ±i protein activation β β cAMP β β PKA β β NF-ΞΊB translocation β β IL-1Ξ², β IL-6, β TNF-Ξ± transcription
Simultaneously: RvT β GPR32 β SOCS3 upregulation β JAK-STAT inhibition β cytokine signaling attenuation
RvT4 preferentially β DRV2/GPR18 β similar GΞ±i cascade plus enhanced phosphatidylserine receptor exposure on apoptotic neutrophils
Resolution Actions:
- Neutrophil clearance: RvT1 (10-100 nM) β phosphatidylserine externalization on neutrophils β Efferocytosis signal β macrophage TGF-beta release β anti-inflammatory M2 polarization
- Pain reduction: RvT β TRPV1 channel desensitization β β Substance P release β β inflammatory pain transmission
- Barrier restoration: RvT β epithelial tight junctions assembly via ZO-1 upregulation β β gut permeability
Metabolic Inactivation:
RvT β eicosanoid oxidoreductase β 17-oxo-RvT (inactive) β Ξ²-oxidation β excretion
Half-life: ~30-60 minutes in circulation, allowing pulsatile resolution signaling
When DHA Synthesis is Impaired:
Modern populations show widespread FADS2 polymorphisms (up to 80% in some groups carry low-activity variants), impairing EPAβDHA conversion. In these individuals, 13-series resolvins represent the PRIMARY omega-3 fatty acids-derived resolution pathway. This explains clinical observations where EPA supplementation alone (without DHA) still produces anti-inflammatory benefits β the body converts EPAβn-3 DPAβRvT rather than requiring the full EPAβDHAβRvD pathway.
Metamodel Connections:
- Metabolic System: n-3 DPA accumulation during chronic inflammation reflects Lipid mediator class switching β the body prioritizes immediate resolution capacity (RvT production) over long-term membrane structure (DHA incorporation). This is allostasis in action: sacrificing optimal function for immediate survival.
- Immune System: RvT production provides evolutionary backup when primary resolution pathways (Resolvins D-series) are compromised. This redundancy prevents complete resolution failure even under suboptimal Omega-3 status.
- Selfish Systems: The selfish immune system will preferentially shunt available omega-3 fatty acids toward immediate resolution (RvT/RvE production) rather than allowing incorporation into neuronal membranes or retinal tissue β explaining why brain DHA depletion often precedes measurable immune dysfunction.
Clinical Thresholds:
- RvT1 plasma levels: typically 50-200 pg/mL in healthy resolution
- During acute inflammatory resolution: RvT1 peaks 200-800 pg/mL at 24-48h post-injury
- Chronic low-grade inflammation: RvT1 <50 pg/mL suggests failed resolution signaling
- Omega-3 index: when <4%, RvT production capacity is severely limited
Intervention Implications:
- EPA-focused protocols: In patients with confirmed FADS2 polymorphisms, emphasize EPA supplementation (2-3g/day) knowing it will primarily generate RvE and RvT rather than converting to DHA
- Combined supplementation: For optimal coverage, provide both EPA (for RvE/RvT) AND preformed DHA (for RvD) rather than relying on endogenous conversion
- Resolution support: When RvT levels are low despite adequate EPA intake, investigate 12-LOX/15-LOX cofactor status (vitamin B6, iron, selenium)
- Chronic pain: RvT-mediated TRPV1 desensitization makes this pathway particularly relevant for chronic pain syndromes with inflammatory components (fibromyalgia, CRPS, IBS with visceral pain)
- Biosynthesized from n-3 DPA (22:5 Ο-3), the intermediate between EPA (20:5) and DHA (22:6)
- Four main forms identified: RvT1, RvT2, RvT3, RvT4, each with distinct receptor preferences
- Activate DRV1/GPR32 (RvT1-3) and DRV2/GPR18 (RvT4) with EC50 values 10-100 nM
- Promote neutrophil apoptosis within 2-4 hours at physiological concentrations (50-200 nM)
- Enhance macrophages Efferocytosis by 40-60% compared to baseline in vitro
- Reduce IL-6, IL-1Ξ², and TNF-Ξ± secretion by 50-80% in LPS-stimulated cells
- Plasma half-life: 30-60 minutes, requiring pulsatile production for sustained effects
- Provide resolution capacity when FADS2 genetic variants (present in 40-80% of populations) limit DHA synthesis
- RvT1 reduces inflammatory pain by 30-50% in rodent models via TRPV1 desensitization
- May explain why populations with low DHA status (vegetarians, elderly) still show anti-inflammatory benefits from EPA supplementation
- Resolvins β T-series represents third major resolvin family alongside D- and E-series
- Specialized pro-resolving mediators (SPMs) β member of SPM superfamily alongside Lipoxins, Maresins, Protectins
- n-3 DPA β direct biosynthetic precursor, accumulates when DHA synthesis is impaired
- EPA β upstream precursor that elongates to form n-3 DPA
- DHA β final product of EPAβDPAβDHA pathway; when conversion blocked, DPA shunts to RvT
- 12-LOX β primary biosynthetic enzyme converting n-3 DPA to 13-hydroperoxy intermediates
- 15-LOX β alternative biosynthetic pathway for RvT production, tissue-dependent
- DRV1/GPR32 β primary receptor for RvT1-3, mediates anti-inflammatory signaling
- neutrophils β RvT promotes apoptosis and phosphatidylserine exposure for clearance
- Efferocytosis β RvT enhances macrophage clearance of apoptotic neutrophils by 40-60%
- macrophages β RvT drives M2 polarization and efferocytic programming
- Resolution of inflammation β RvT actively terminates inflammatory responses and restores tissue homeostasis
- omega-3 fatty acids β derived from omega-3 metabolic pathway between EPA and DHA
- Lipid mediator class switching β RvT production exemplifies switching from DHA-based to DPA-based resolution when substrate limited
- cytokines β reduces IL-6, IL-1Ξ², TNF-Ξ± production via NF-ΞΊB inhibition
- chronic inflammation β RvT deficiency (<50 pg/mL) contributes to failed resolution and persistent inflammation
- tissue repair β promotes regenerative signaling through TGF-beta and Amphiregulin release
- inflammatory pain β reduces nociceptor sensitization via TRPV1 desensitization
- gut permeability β restores epithelial barrier function via tight junctions assembly
- FADS2 β genetic variants in this desaturase gene determine whether EPA converts to DHA or accumulates as n-3 DPA for RvT synthesis
- NF-ΞΊB β RvT inhibits nuclear translocation, blocking pro-inflammatory gene transcription
- SOCS3 β upregulated by RvT signaling, providing cytokine resistance