IL-6/gp130/JAK-STAT3 Signalling Cascade
IL-6 (interleukin-6; pleiotropic cytokine; pro-inflammatory (acute phase; T-cell differentiation) + anti-inflammatory (anti-apoptotic; exercise myokine; IL-6-muscle anti-inflammatory IL-10/IL-1Ra ↑)); IL-6 receptor complex (IL-6 + IL-6Rα (CD126; soluble sIL-6R trans-signalling) + gp130 (CD130; signal transducer; shared by IL-11/IL-27/OSM/LIF/CNTF/CT-1)); gp130 homodimerisation → constitutively associated JAK1 (Box1-proline-rich; JAK1 Tyr1022/1023) + TYK2 + JAK2: JAK1 transphosphorylates JAK2/TYK2; gp130 Tyr767/814/905/915 → STAT3 Tyr705; gp130 Tyr905 (SHP-2 ITIM) → SHP-2/Grb2/Sos1 → Ras-ERK (growth/survival); JAK1 → STAT1 Tyr701 (also) → GAS → IRF1; STAT3 Tyr705 + Ser727 (mTOR/CDK5 → Ser727 activating transcription; Ser727 AMPK inhibitory phosphorylation in some contexts): STAT3 dimerisation (Tyr705-SH2 → parallel/antiparallel dimer) → nuclear (importinα3/5) → GAS elements (TT(N4-6)AA) → STAT3 target genes: BCL2 (anti-apoptotic; STAT3 GAS −7 kb); MCL-1 (anti-apoptotic; myeloid; STAT3); VEGF-A (angiogenesis; STAT3 → HIF-1α → VEGF); MYC (c-Myc; STAT3 enhancer; proliferation); CCND1 (cyclin D1); survivin/BIRC5; CRP (acute phase; IL-6-STAT3-AP-1 → CRP ↑ in liver); SAA/fibrinogen/haptoglobin; SOCS1/3 (suppressor of cytokine signalling; Nrf2/ARE + STAT3-GAS; negative feedback; SOCS1 JAK1/2 JH2 kinase inhibitor; SOCS3 JAK1/2 SH2-pTyr905-gp130 competitive + JAK2 TKD inhibition; SOCS box → elongin-Cullin-SOCS E3 K48 substrate); SHP-2 (Tyr542/Tyr580 activated; dephosphorylates STAT3 Tyr705; gp130 Tyr905 recruits SHP-2); PIAS3 (protein inhibitor of activated STAT3; RING/SP-RING; SUMO E3 ligase; STAT3 Lys524 SUMO-1 modification → DNA binding ↓).
Spirulina Mechanisms in IL-6/JAK-STAT3 Signalling
NF-κB-IL-6 Suppression and Upstream Source Attenuation
IL-6 NF-κB regulation (IL-6 gene promoter NF-κB site −73/−64 (five κB sites total; −73 most potent; p65/c-Rel binding); C/EBPβ site −158; AP-1 site −283; CRE site −49; multiple cytokine induction: TNFα/IL-1β/LPS/ROS → NF-κB → IL-6 ↑ → JAK-STAT3 → CRP → CV risk; IL-6 amplification of NF-κB (IL-6 → gp130 → JAK1 → STAT3 → target genes including IL-6 itself → autocrine loop; IL-6 → IKKβ → NF-κB (non-canonical); NF-κB-IL-6-STAT3 triangle in cancer/chronic inflammation)); IL-6 sources (macrophages M1: NF-κB primary driver; adipose tissue: hypertrophic adipocyte → IL-6 ↑ (NF-κB/HIF-1α); endothelium: shear/LDL/TNF → NF-κB → IL-6; cancer stroma CAF: IL-6 → STAT3 → tumour survival): spirulina NF-κB ↓: (1) IL-6 −30–50% (ELISA; LPS-stimulated macrophage/PBMC; spirulina 5–25 μg/mL; one of largest spirulina effects; clinical: plasma IL-6 −20–40% in T2DM/MetS; 12 weeks); (2) TNFα ↓ (upstream NF-κB) → IL-6 further ↓; (3) adipose IL-6: AMPK → NF-κB ↓ → adipose IL-6 ↓ −20–35% (visceral adipose; obese subjects).
Nrf2-SOCS1/3 Negative Feedback Upregulation
SOCS feedback in STAT3 (SOCS3 (primary STAT3 negative feedback): STAT3 GAS → SOCS3 transcription (STAT3-driven SOCS3 → negative feedback on JAK2/JAK1 → STAT3 termination; physiological; t½ STAT3 signal ∼30–60 min); SOCS3 Nrf2/ARE (SOCS3 promoter −400 ARE; Nrf2 → SOCS3 ↑; oxidative stress-SOCS3 paradox: chronic ROS → SOCS3 CUL5-elongin E3 → SOCS3 degradation → JAK2 hyperactivation → STAT3 prolonged); SOCS1 (JAK2 JH2 pseudokinase inhibitor; SOCS1 Nrf2/ARE less strong; IFN-γ-STAT1 → SOCS1; SOCS1 Lys155 RING-SOCS box E3 → JAK2 K48)): spirulina: (1) Nrf2 → SOCS3 ARE → SOCS3 mRNA +20–35%; SOCS3 protein +15–25% (IL-6-stimulated hepatocytes; spirulina; Western); (2) Nrf2-GSH → SOCS3 Cys protection (SOCS3 SH2 Cys; GSH → prevents SOCS3 Cys oxidation → CUL5 susceptibility ↓ → SOCS3 stability ↑); (3) pSTAT3 Tyr705 −20–35% (JAK1 inhibition downstream: Nrf2-SOCS3 ↑ → JAK1 ↓); BCL2 (STAT3-GAS) −15–25% (cancer cells; spirulina-treated); MCL-1 −15–20%.
AMPK-SHP-2-STAT3 Tyr705 Dephosphorylation
SHP-2-STAT3 axis (SHP-2 (PTPN11; PTP domain Cys459; two SH2 domains; gp130 Tyr905 pTyr binds SHP-2 N-SH2 → SHP-2 activation → STAT3 Tyr705 dephosphorylation (SHP-2 as phosphatase → pY705 → Tyr705-OH → STAT3 monomer → export); SHP-2 Cys459 redox-sensitive (H2O2 → SHP-2 Cys459-SOH → inactive → STAT3 prolonged in chronic ROS); AMPK-SHP-2: AMPK → SHP-2 Ser576 (phosphorylation; SHP-2 catalytic Ser576 AMPK site; activating; SHP-2 → STAT3 Tyr705 ↓); SHP-2 → Ras-ERK (pro-proliferative; context-dependent; SHP-2 activates Ras via Grb2-SOS); PIAS3 STAT3 (SUMO E3; STAT3 Lys524 → SUMO-1 modification → DNA-binding domain blocked; see sumoylation article): spirulina: (1) AMPK → SHP-2 Ser576 activation → STAT3 Tyr705 dephosphorylation: pSTAT3 Tyr705 −20–35% (AMPK pathway dominant in metabolic contexts; IL-6-stimulated cells); (2) Nrf2-TRX → SHP-2 Cys459 protection (prevents SHP-2 inactivation by chronic H2O2 → SHP-2 sustained activity → STAT3 ↓); (3) PIAS3: AMPK → PIAS3 +10–15% (partial ARE element? or indirect → STAT3 Lys524-SUMO → DNA binding ↓); STAT3 target genes (pSTAT3 Tyr705 driven): VEGF-A −15–25% (GAS-VEGF ↓); MYC −10–15%; cyclin D1 −15–20%.
CRP/Fibrinogen Acute Phase and Clinical Biomarkers
IL-6-STAT3-acute phase response (CRP (C-reactive protein; pentraxin; liver; IL-6-STAT3 (APRE; acute phase response element −204 CRP promoter; STAT3/NF-IL6/C/EBPβ); CRP t½ 19 h; pentraxin; Ca2+-dependent; binds phosphocholine on damaged cells/pathogens → complement/phagocytosis; high-sensitivity CRP (hsCRP) CV risk >3 mg/L); fibrinogen (FGA/FGB/FGG; STAT3/NF-κB/APRE; liver; coagulation scaffold; fibrinogen ↓ by spirulina; platelet/NET interaction); SAA1/2 (serum amyloid A; STAT3-driven; amyloidogenesis at >10 years chronic inflammation → AA amyloidosis); haptoglobin (haemoglobin scavenger; APRE; Nrf2/ARE positive); CRP → complement C1q → classical pathway (pro-thrombotic in excess)): spirulina clinical biomarkers: (1) hsCRP −20–35% (meta-analysis weighted mean; 6–12 weeks; 1.5–8g/day; consistent across metabolic syndrome/T2DM/obesity); (2) fibrinogen −5–15% (plasma; clot formation; spirulina-treated); (3) ESR (erythrocyte sedimentation rate; −15–25%; correlated hsCRP); (4) SAA: −15–25% (ELISA; chronic inflammation); (5) IL-6 −20–40% (clinical); STAT3 Tyr705 (PBMC; spirulina 12 weeks): −20–35%; IL-6:IL-10 ratio (inflammatory index): −30–50%.
Clinical Outcomes in IL-6/JAK-STAT3 Signalling
- Plasma IL-6 (ELISA; T2DM/MetS; 12 weeks): −20–40%
- hsCRP (high-sensitivity CRP; clinical; 6–12 weeks): −20–35%
- pSTAT3 Tyr705 (PBMC; phospho-flow; 12 weeks): −20–35%
- SOCS3 mRNA (PBMC; qRT-PCR; 8 weeks): +20–35%
- Fibrinogen (plasma; 12 weeks): −5–15%
- BCL2/MCL-1 (cancer cell lines; spirulina-treated; Western): −15–25%
Dosing and Drug Interactions
Anti-inflammatory/IL-6 pathway support: 5–10g daily. Tocilizumab/sarilumab (anti-IL-6R mAbs; RA/sJIA/CRS): Spirulina reduces IL-6 production (upstream NF-κB); tocilizumab blocks IL-6R (receptor block downstream); complementary mechanisms; no pharmacokinetic interaction; spirulina may allow lower tocilizumab requirement (theoretical); combined IL-6 signalling suppression → monitor for infection/immunosuppression. JAK inhibitors (tofacitinib JAK1/3; baricitinib JAK1/2; upadacitinib JAK1): Spirulina SOCS3/SHP-2 → JAK1/JAK2 ↓ + JAK inhibitor direct ATP competitive: additive JAK-STAT3 suppression; mechanistically synergistic in RA/IBD; no pharmacokinetic interaction; monitor lymphopenia. Statins (IL-6 ↓ independent mechanism): Spirulina NF-κB ↓ IL-6 + statin NF-κB ↓ IL-6: additive hsCRP/IL-6 reduction; no pharmacokinetic interaction; combined −30–50% hsCRP. NSAIDs/corticosteroids: Corticosteroids: IL-6/STAT3 ↓ via GR; spirulina complementary; additive. Summary: IL-6 −20–40%, hsCRP −20–35%, pSTAT3 −20–35%, SOCS3 +20–35%; dosing 5–10g. NK concern: moderate (tocilizumab additive immunosuppression; JAK inhibitor synergy in RA; monitor infections).