D-series resolvins (RvD1-6) are Specialized pro-resolving mediators (SPMs) enzymatically synthesized from DHA via 15-LOX in neutrophils, leukocytes, Th2 cells, and microglia. These lipid mediators actively orchestrate resolution of inflammation by inhibiting neutrophil recruitment, promoting efferocytosis, reducing pro-inflammatory cytokines, and protecting multiple organ systems from inflammatory injury.
Imagine a massive construction site after a demolition (acute inflammation). The D-series resolvins are the cleanup foreman who arrives once the wrecking crew has done their job. Instead of just stopping the demolition, this foreman actively coordinates the removal of debris (dead cells via efferocytosis), sends the demolition workers home (stops neutrophil immigration), calls in the repair crew (promotes epithelial healing), and installs protective barriers around vital machinery (organ protection for liver, kidney, lung). The foreman doesn't work alone—he carries specific blueprints (DHA precursor) that need to be processed by the site engineer (15-LOX enzyme) to create actionable work orders (RvD1-6). Without enough raw blueprints from headquarters (dietary omega-3), the foreman can't organize an effective cleanup, and the construction site becomes chronically cluttered with debris and inflammation.
graph TD
A[DHA in membrane] -->|15-LOX| B[17-HDHA intermediate]
B --> C[RvD1]
B --> D[RvD2]
B --> E[RvD3-6]
C -->|GPR32/DRV1| F[Neutrophil]
C -->|GPR18/DRV2| G[Macrophage]
F --> H["↓ Neutrophil immigration"]
F --> I["↓ NF-κB activation"]
G --> J["↑ Efferocytosis"]
G --> K["↑ M2 polarization"]
C --> L[Epithelial cells]
L --> M["↑ Wound healing"]
L --> N["↑ Barrier function"]
C --> O[Microglia]
O --> P["↓ Neuroinflammation"]
O --> Q[Neuroprotection]
Biosynthetic pathway:
- DHA stored in cell membranes → released by Phospholipase A2 during inflammation
- 15-LOX (15-lipoxygenase) in neutrophils, macrophages, or Th2 cells converts DHA → 17S-hydroxy-DHA (17-HDHA)
- 17-HDHA → enzymatic conversion produces RvD1, RvD2, RvD3, RvD4, RvD5, RvD6
- Peak production: 24-48 hours post-inflammatory stimulus (resolution phase timing)
Receptor signaling:
- RvD1 binds ALX-FPR2 (also called FPR2/ALX) and GPR32 (DRV1 receptor)
- RvD2 binds GPR18 (DRV2 receptor)
- Receptor activation → inhibition of NF-κB translocation → ↓ TNF-α, IL-1β, IL-6 production
- Simultaneously activates AKT pathway → cell survival signals
Neutrophil regulation:
- RvDs bind GPR32 on neutrophils → ↓ L-selectin (CD62L) expression → impaired rolling adhesion
- ↓ CXCR3 and CCL2 signaling → reduced transendothelial migration
- Direct inhibition of NF-κB and ERK activation in neutrophils → ↓ oxidative burst
- Typical effective concentration: 1-10 nM in vitro
Macrophage reprogramming:
- RvD1 via GPR32 → ↑ efferocytosis (apoptotic cell clearance) by 40-60% in experimental models
- Promotes M2 macrophages polarization markers: IL-10, TGF-beta, Arginase
- ↑ phagocytic capacity without triggering pro-inflammatory mediator release
Epithelial repair:
Organ protection:
- Liver: RvD1 reduces liver ischemia-reperfusion injury by 50-70% (animal models), ↓ TNF-α, ↓ hepatocyte apoptosis
- Kidney: RvD1 protects against Acute Kidney Injury → ↓ tubular necrosis, ↑ renal blood flow
- Lung: RvD2 reduces ARDS severity → ↓ neutrophil infiltration, ↓ alveolar permeability
Neurological actions:
Metabolic inactivation:
- RvDs undergo SPM metabolic inactivation via dehydrogenation (15-PGDH) and β-oxidation
- Half-life in circulation: 5-15 minutes (rapid clearance ensures temporal control)
- Metabolites are inactive, allowing precise resolution timing
Patient populations requiring RvD support:
Metamodel connections:
- Metamodel 5 (Immune system): RvDs represent the "resolution arm" often deficient in Western populations due to Omega-3 insufficiency
- Selfish Immune System: RvDs prevent the immune system from becoming "selfishly" hyperactive—they enforce boundaries on inflammation
- Evolutionary mismatch: Modern omega-6:omega-3 ratios (15-20:1 vs ancestral 1-4:1) create DHA deficiency → impaired RvD production → chronic unresolved inflammation
- Mismatch Disease: Conditions like Obesity, Type 2 Diabetes, Atherosclerosis all feature resolution deficiency
Clinical biomarkers:
- Direct measurement: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) for plasma RvD levels
- Indirect: Omega-3 index (target >8% for adequate substrate), omega-6:omega-3 ratio (<4:1 optimal)
- DHA levels: plasma phospholipid DHA should be >4% of total fatty acids
- Resolution capacity test: ex vivo neutrophil migration assay with patient serum (research setting)
Intervention implications:
Red flags for deficiency:
- Prolonged inflammatory episodes (>2 weeks acute inflammation)
- Poor wound healing despite adequate nutrition
- Recurrent infections with excessive tissue damage
- Chronic fatigue with elevated CRP (>3 mg/L) but no identifiable pathology
Clinical pearls:
- RvDs work synergistically with Resolvin E-series (from EPA) and Maresins—provide balanced omega-3 sources
- Production requires active inflammation as stimulus—prophylactic omega-3 primes the system
- Timing matters: RvD peak at 24-48h post-injury, earlier than Lipoxins (4-12h)
- Obesity impairs RvD production even with adequate DHA substrate (lipid mediator class switching defect)
- RvDs are enzymatically synthesized from DHA by 15-LOX in neutrophils, leukocytes, Th2 cells, and microglia
- Six distinct D-series resolvins identified: RvD1 through RvD6, with RvD1 most extensively studied
- Primary receptors: GPR32 (DRV1) for RvD1, GPR18 (DRV2) for RvD2, both G-protein coupled receptors
- RvD1 reduces neutrophil transendothelial migration by 40-80% in experimental models at nanomolar concentrations
- Peak production occurs 24-48 hours after inflammatory stimulus, during active resolution phase
- Effective concentration range: 1-10 nM in vitro for anti-inflammatory and pro-resolution effects
- Organ protection demonstrated in animal models: 50-70% reduction in liver ischemia-reperfusion injury, significant protection against acute kidney injury and ARDS
- Half-life in circulation: 5-15 minutes due to rapid enzymatic inactivation via 15-PGDH and β-oxidation
- DHA requirement: plasma phospholipid DHA >4% of total fatty acids needed for adequate RvD biosynthesis
- Clinical trials using synthetic RvD1 show efficacy in dry eye syndrome (phase 2) and periodontal disease
- Modern Western omega-6:omega-3 ratio (15-20:1) severely impairs RvD production compared to ancestral ratios (1-4:1)
- DHA — essential omega-3 fatty acid precursor; RvD biosynthesis requires adequate membrane DHA stores
- 15-LOX — key enzyme converting DHA to 17-HDHA intermediate for all D-series resolvins
- Specialized pro-resolving mediators (SPMs) — RvDs are one of four major SPM families driving active resolution
- Resolvin E-series — complementary SPMs derived from EPA; work synergistically with RvDs
- Maresins — sister SPM family also from DHA via 12-LOX; synergize with RvDs to reduce neutrophil immigration
- Lipoxins — arachidonic acid-derived SPMs; earlier-acting resolution mediators (4-12h vs 24-48h for RvDs)
- Neutrophils — primary cellular target; RvD1 blocks neutrophil recruitment and activation via GPR32
- Efferocytosis — RvDs enhance macrophage clearance of apoptotic neutrophils by 40-60%
- M2 macrophages — RvDs promote M2 polarization, increasing IL-10 and TGF-beta production
- NF-κB — RvDs inhibit NF-κB nuclear translocation, reducing TNF-α, IL-1β, and IL-6 transcription
- ALX-FPR2 — shared receptor for RvD1 and lipoxins; mediates anti-inflammatory signaling
- Microglia — produce RvDs in CNS; critical for resolving neuroinflammation and neuroprotection
- Neuroinflammation — RvDs reduce microglial activation and excitotoxicity in Alzheimer's, MS, Parkinson's models
- Omega-3 fatty acids — dietary source of DHA substrate; omega-3 index >8% optimal for RvD production
- Chronic inflammation — RvD deficiency contributes to failure of resolution in RA, IBD, asthma
- Wound healing — RvDs accelerate epithelial repair via AKT pathway activation and amphiregulin production
- Liver — RvD1 protects hepatocytes from ischemia-reperfusion injury and reduces fibrosis progression
- Acute Kidney Injury — RvDs reduce tubular necrosis and improve renal blood flow in AKI models
- ARDS — RvD2 reduces neutrophil infiltration and alveolar-capillary permeability in acute respiratory distress
- COX-2 — aspirin-acetylated COX-2 produces AT-RvD1 (aspirin-triggered RvD1) with enhanced activity
- Tight junctions — RvDs increase ZO-1 and occludin expression, restoring intestinal and epithelial barrier function
- Obesity — impairs RvD biosynthesis despite adequate DHA due to lipid mediator class switching defects
- Evolutionary mismatch — modern omega-6:omega-3 imbalance creates substrate competition, reducing RvD production
- Cytokine storm — RvD administration reduces excessive cytokine production in sepsis and COVID-19 models
- AKT pathway — RvDs activate survival and proliferation signaling in epithelial cells and neurons