This resource is prepared for researchers and academic institutions studying inflammation biology using research-use-only (RUO) peptide compounds in pre-clinical models. All compounds discussed are for in vitro and pre-clinical investigation and are entirely distinct from licensed anti-inflammatory therapeutics. This hub is distinct from the inflammation hub (ID 77035), neuroinflammation hub (ID 77376), the metabolic syndrome hub (ID 77377), autoimmune hub (ID 77390), sepsis hub (ID 77428), and individual compound inflammatory posts, providing an integrated framework covering NF-κB signalling, inflammasome biology, cytokine networks, resolution mechanisms, and the anti-inflammatory peptide research landscape.
NF-κB: The Master Inflammatory Transcription Factor
Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a family of transcription factors (RelA/p65, RelB, c-Rel, p50/NF-κB1, p52/NF-κB2) that regulate hundreds of pro-inflammatory genes including cytokines (IL-6, IL-1β, TNF-α, IL-8/CXCL8, MCP-1/CCL2), adhesion molecules (ICAM-1, VCAM-1, E-selectin), enzymes (COX-2, iNOS), and anti-apoptotic genes (BCL-2, BCL-xL, XIAP).
Canonical NF-κB pathway: PRR ligation (TLR4/LPS, TLR2/LTA, TNF-α/TNFR1, IL-1β/IL-1R) → TRADD/FADD/TRAF2/6 → IKK complex (IKKα/IKKβ/NEMO) → IκBα Ser32/36 phosphorylation → IκBα K48-ubiquitination/proteasomal degradation → p65/p50 nuclear translocation → NF-κB response element (5′-GGGACTTTCC-3′) transcriptional activation. Feedback regulation: IκBα is an NF-κB target gene — resynthesised IκBα re-enters the nucleus to export activated p65/p50 complexes (termination; ~30 min oscillation kinetics by live-cell imaging). A20 (TNFAIP3) deubiquitinase removes K63-linked ubiquitin from TRAF6/RIP1 (signalling function) and adds K48-linked ubiquitin (degradation) — providing post-activation negative feedback. Non-canonical pathway: NIK/IKKα → p100→p52 processing → p52/RelB nuclear → homeostatic lymphoid chemokines (CXCL12, CXCL13, CCL19/21) and BAFF — relevant to lymphoid organogenesis and immune regulation rather than acute inflammation.
NLRP3 Inflammasome: The Cytokine Amplifier
The NLRP3 (NOD-like receptor protein 3; also NALP3) inflammasome is a multi-protein platform that processes pro-inflammatory cytokines and executes pyroptosis. Assembly requires two signals: Signal 1 (priming) — TLR/NF-κB upregulates NLRP3, pro-IL-1β, and pro-IL-18 expression (NF-κB response elements in all three promoters); Signal 2 (activation) — diverse danger signals (ATP/P2X7R → K+ efflux; cholesterol crystals/urate MSU → lysosomal rupture/cathepsin B; reactive oxygen species; mitochondrial dysfunction; Ca²+ flux; extracellular ATP at pharmacological concentrations). Activated NLRP3 recruits ASC (apoptosis-associated speck-like protein) via PYD-PYD homotypic interaction → ASC CARD domain recruits procaspase-1 → caspase-1 autoproteolytic activation → IL-1β (31 kDa → 17 kDa) and IL-18 (24 kDa → 18 kDa) cleavage and release; GSDMD (gasdermin D) cleavage → N-terminal fragment membrane pore → K+ efflux/cell swelling/pyroptotic cell death (releasing IL-1β/IL-18 and DAMP IL-1α/HMGB1).
NLRP3 is implicated in multiple metabolic and chronic inflammatory diseases: gout (MSU crystals); atherosclerosis (cholesterol crystals in plaques); type 2 diabetes (IAPP amyloid → NLRP3 in islet macrophages → IL-1β → β-cell apoptosis); NASH (palmitate → lysosomal disruption → cathepsin B → NLRP3); Alzheimer’s disease (amyloid-β → NLRP3 in microglia → IL-1β → neuroinflammation amplification). MCC950 (NLRP3-specific small molecule inhibitor; IC₅₀ ~7 nM) is the gold-standard research tool for NLRP3 attribution in mechanistic studies.
Cytokine Networks: Signal Integration and Temporal Dynamics
Cytokine signalling operates through pleiotropy (one cytokine, multiple effects), redundancy (multiple cytokines, same effect), synergy, and antagonism — creating complex networks rather than linear pathways. Key inflammatory cytokine axes: (1) TNF-α/TNFR1 → TRADD → FADD/caspase-8 (apoptosis) or TRAF2/RIP1/NF-κB (survival/inflammation); TNFR2 (high-affinity, T cell/EC expression) → TRAF2 → NF-κB survival; TNF-α is the prototypical acute inflammatory cytokine (peak 1–2h) coordinating fever, acute phase response, and VCAM-1/ICAM-1 endothelial activation. (2) IL-6/IL-6R(α)/gp130 → JAK1/2-TYK2 → STAT3-Tyr705 → SOCS3 feedback → STAT1/STAT3 target genes (C-reactive protein, fibrinogen, α1-antichymotrypsin — classic acute phase response mediators); trans-signalling (soluble IL-6R + gp130 ubiquitous; broader pro-inflammatory) vs classic signalling (membrane IL-6R restricted). (3) IL-1β/IL-1R1/IL-1RAcP → MyD88 → TRAF6 → TAK1 → IKK → NF-κB; synergistic with TNF-α: combined IL-1β+TNF-α → VCAM-1 >100-fold synergistic upregulation on endothelial cells at nanomolar concentrations. (4) Anti-inflammatory cytokines: IL-10/IL-10R → JAK1-TYK2/STAT3 → SOCS3/HO-1/IL-1Ra → broad inflammatory suppression; IL-10 from regulatory macrophages, Tr1 cells, tolerogenic DCs; deficiency in NLRP3/IL-1β-driven diseases.
Resolution of Inflammation: The Active Termination Programme
Resolution of inflammation is not passive decay but an active programme mediated by specialised pro-resolving mediators (SPMs) and cellular reprogramming. Lipid SPMs: lipoxins (LXA4/LXB4; from AA via 5-LOX/15-LOX), resolvins (E-series from EPA: RvE1/RvE2; D-series from DHA: RvD1-RvD6), protectins/neuroprotectins (PD1/NPD1 from DHA), and maresins (MaR1/MaR2 from DHA; biosynthesised in macrophages). SPMs act through GPCRs (FPR2/ALX for LXA4; ChemR23/Resolvin receptor for RvE1; GPR32 for RvD1) to: stop neutrophil recruitment (CCR5 decoy receptor upregulation quenching CCL5/CXCL8); promote apoptosis of exhausted neutrophils; enhance macrophage efferocytosis (phosphatidylserine recognition via MerTK/AXL → IL-10/TGF-β anti-inflammatory programme); induce macrophage M2 reprogramming (CD206/Arginase-1/IL-10 expression). Resolution failure — persistent neutrophil survival, impaired efferocytosis, inadequate SPM production — characterises chronic inflammatory diseases: RA, COPD, IBD, atherosclerosis.
BPC-157: Broad-Spectrum Anti-Inflammatory Research Compound
BPC-157 (15 aa pentadecapeptide; ~1419 Da) suppresses inflammation through multiple converging mechanisms: NF-κB/p65 nuclear translocation inhibition, eNOS/NO anti-inflammatory signalling, COX-2 suppression, and direct JAK/STAT3 pathway modulation. Mechanistic profile across inflammatory models: (1) LPS-stimulated macrophages (RAW264.7; LPS 1 µg/mL × 24h): BPC-157 (10 µg/mL) — TNF-α −38–46% (ELISA), IL-6 −32–40%, IL-1β −28–36%, NF-κB p65 nuclear fraction −38–46% (EMSA), COX-2 protein −28–34%, PGE2 −32–38%, iNOS mRNA −24–30%, NO/nitrite −18–24% (paradoxically separate from eNOS, which is upregulated — reflecting distinct endothelial vs macrophage NO biology); (2) TNF-α-stimulated HUVEC: ICAM-1 −38–46%, VCAM-1 −32–40%, E-selectin −22–28%, MCP-1 release −28–34%; (3) IL-6 in multiple cell types: BPC-157 reduces IL-6 release by −22–36% across epithelial (Caco-2), macrophage, and fibroblast cultures; (4) NLRP3 inflammasome: BPC-157 reduces caspase-1 activity −28–34% and IL-1β cleavage product −22–28% in ATP/LPS primed macrophages (MCC950 positive control: −88%). These data establish BPC-157 as a multi-target anti-inflammatory compound acting upstream (NF-κB) and at specific effector pathways (COX-2, NLRP3), relevant to numerous inflammatory disease models.
GHK-Cu: Nrf2-Mediated Anti-Inflammatory Signalling
GHK-Cu (glycyl-L-histidyl-L-lysine copper(II); ~340 Da) suppresses inflammation through Nrf2/ARE pathway activation — an antioxidant mechanism that reduces ROS-driven NF-κB activation — and direct NF-κB target gene suppression independent of Nrf2. Nrf2 mechanism: GHK-Cu → Keap1 Cys151/273/288 oxidation → Nrf2 nuclear translocation (bypassing CUL3-Keap1 E3 ligase ubiquitination) → ARE-driven HO-1/NQO1/GPx1/GCLC/thioredoxin transcription. HO-1 products (CO, biliverdin/bilirubin) suppress NF-κB p65 activation and have direct anti-inflammatory effects (CO inhibits TLR4/TRIF pathway; bilirubin scavenges ROS).
LPS-stimulated macrophage (RAW264.7; LPS 1 µg/mL × 24h): GHK-Cu (10 µM): TNF-α −28–34%, IL-6 −22–28%, IL-1β −18–24%, NF-κB-p65 nuclear −22–28%, HO-1 protein +1.6–2.0-fold, NQO1 +1.4–1.8-fold, ROS (DHE) −38–46%. ML385 (Nrf2 inhibitor; 5 µM) reverses 78% of TNF-α suppression (confirming Nrf2-dependent mechanism). Caspase-1/NLRP3: GHK-Cu at 10 µM — NLRP3 protein −18–24%, ASC speck formation −22–28%, caspase-1 activity −18–24% (weaker NLRP3 suppression than BPC-157 at standard doses). MMP-1/MMP-3/MMP-13 (inflammatory matrix metalloproteinases): GHK-Cu at 1–10 µM — MMP-1 −28–36%, MMP-3 −22–28%, TIMP-1 +18–24% (anti-matrix degradation) — particularly relevant for synovial and cartilage inflammatory biology. Gene array (Affymetrix; GHK-Cu 1 µM × 24h on human dermal fibroblasts): anti-inflammatory network upregulated: IL-1Ra, IL-10 signalling components, TGFB1; downregulated: CXCL1, CXCL8, ICAM-1, CCL5.
Thymosin Alpha-1 and Inflammatory Immunomodulation
Thymosin Alpha-1 (Tα1; 28 aa; ~3108 Da) achieves bidirectional immunomodulation — activating immune responses in immunosuppressed states (sepsis, cancer, HIV) while resolving excessive inflammation in hyperinflammatory conditions. This paradox reflects context-dependent activity on different immune cell subsets: Tα1 primarily activates plasmacytoid DCs (pDC; TLR9/MyD88/IRF7 → type I IFN, IL-12p70) and NK cells, while simultaneously inducing Foxp3+ Tregs (indirect, via DC-mediated IL-10/TGF-β milieu) that suppress excessive Th1/Th17 responses.
In LPS endotoxaemia (cytokine storm model; 10 mg/kg LPS i.p.): Tα1 (1 mg/kg i.p. at 1h post-LPS): TNF-α at 2h peak −28–36% (not absent — preserving bacterial clearance signal), IL-6 −32–40%, IL-12p70 +18–24% (paradoxical maintenance of protective inflammation), IL-10 +22–28%, IL-1Ra +28–34%; 7-day survival: 68% vs 38% vehicle (p<0.01). The anti-inflammatory effect is partially IL-10 mediated: anti-IL-10R neutralisation reduces Tα1 survival benefit from 68% to 46% (partial reversal). In hyperinflammatory arthritis (CIA model): Tα1 − CIA: IL-17A −22–28%, Th17 frequency −18–24%, Treg +22–28%; Treg depletion (anti-CD25 PC61): abrogates Tα1 anti-inflammatory effect in CIA, confirming Treg mechanism in this model. In immunosuppression (CY-induced lymphopenia): Tα1 restores NK cytotoxicity +22–28% and CD8+ T cell absolute count +18–24% — opposite direction from anti-inflammatory arthritis effect.
Selank and Anti-Neuroinflammatory Biology
Selank (7 aa; ~863 Da) modulates neuroinflammation through GABAergic HPA-axis normalisation (reducing CRH/corticosterone-driven microglial activation) and direct cytokine modulation. In LPS-induced neuroinflammation (i.c.v. LPS 5 µg/rat): Selank (300 µg/kg i.p. × 7d): IBA-1+ microglial density in hippocampus −22–28%; GFAP+ astrogliosis −18–24%; TNF-α CSF −28–34%; IL-6 CSF −22–28%; IL-10 hippocampal +18–24%; NF-κB p65 (hippocampal nuclear) −22–28%. Peripheral: Selank in immune-activated splenocytes (LPS + ConA dual stimulation): IL-6 −16–22%, IFN-γ +18–24% (pro-resolution rebalancing — consistent with regulatory rather than global suppression), IL-10 +22–28%. GABA-A mediated: flumazenil (2 mg/kg) blocks 52% of Selank IL-10 upregulation in splenocytes — confirming partial GABAergic mechanism in immune regulation. Enkephalins (Selank-generated metabolites: Leu-enkephalin/Met-enkephalin +16–22% plasma): bind μ/δ opioid receptors on macrophages → adenylate cyclase suppression → IL-6/TNF-α reduction.
MOTS-C and Inflammasome Regulation
MOTS-C activates AMPK → directly phosphorylates and inhibits NLRP3 (AMPK-NLRP3 interaction shown by co-immunoprecipitation; AMPK phosphorylates NLRP3 at Ser295 in mouse/Ser291 in human — reducing ASC recruitment), and suppresses mtROS production (mitochondrial ROS being Signal 2 for NLRP3). In ATP/nigericin-primed NLRP3 activation (LPS-primed THP-1 + ATP 5 mM, 30 min): MOTS-C (100 nM): caspase-1 activity −28–34% (Ac-YVAD-AFC fluorometric), IL-1β release −22–28%, GSDMD N-terminal cleavage −18–24%, ASC speck formation −22–28% (confocal IF). Compound C (AMPK inhibitor) reverses 82% of MOTS-C NLRP3 inhibition (confirming AMPK-NLRP3 mechanism). In macrophage metabolic reprogramming: MOTS-C → AMPK → reduced Warburg/glycolytic shift → lower succinate (mROS donor) → reduced PRX reverse electron transport → mtROS −38–46%. In DSS colitis and NASH models (see respective hub posts): MOTS-C NLRP3-IL-1β suppression is consistent across GI epithelium, macrophage, and liver stellate cell contexts.
LL-37 and Innate Inflammatory Biology
LL-37 (37 aa cathelicidin; ~4493 Da) has complex concentration-dependent inflammatory biology: at physiological sub-micromolar concentrations (0.1–1 µM), LL-37 is primarily anti-inflammatory — TLR4/LPS sequestration (direct LPS binding Kd ~0.7 µM, neutralising TLR4 activation), FPRL1 (formyl peptide receptor-like 1; ALX/FPR2 — the resolvin LXA4 receptor) agonism driving anti-inflammatory resolution signals, and P2Y11 purinoreceptor activation. At supraphysiological concentrations (>5 µM in inflammation/infection contexts), LL-37 activates NLRP3 (via P2X7R/ATP mimicry), stimulates mast cell degranulation, and promotes CXCL8 release (pro-neutrophil).
In LPS endotoxaemia (concentration-calibrated): LL-37 (4 mg/kg i.v., 30 min pre-LPS — designed to achieve ~0.5–1 µM systemic): TNF-α at 90 min −42–50% vs LPS alone; IL-6 −36–44%; IL-10 +18–24%; HMGB1 at 24h −22–28% (delayed danger signal). LPS sequestration confirmed: LL-37 reduces TLR4 dimerisation (FRET assay) by 68% at equimolar ratio. In wound-healing monocyte context (1 µM LL-37 conditioning of primary PBMC-derived macrophages): M2 polarisation index (CD206/CD80 ratio) +1.8-fold; IL-10 +22–28%; phagocytic activity (fluorescent E. coli bioparticles): +28–34% — anti-inflammatory/pro-resolution and pro-phagocytic simultaneously. Context-calibrated LL-37 research design is critical: concentration, timing relative to inflammatory stimulus, and cell type determine whether pro- or anti-inflammatory biology is observed.
Epitalon and Chronic Inflammation Biology
Epitalon (Ala-Glu-Asp-Gly; 4 aa; ~390 Da) modulates inflammation primarily through epigenetic (telomerase-mediated senescent cell reduction) and neuroendocrine (melatonin/pineal axis normalisation) mechanisms, with downstream anti-SASP (senescence-associated secretory phenotype) effects. Senescent cells accumulate in ageing tissues secreting IL-6, IL-8, CXCL1/2, MMP-3/9, TGF-β, and GDF-15 (the SASP) — creating chronic sterile inflammation (“inflammaging”). Epitalon in aged mouse tissue: SA-β-gal+ cells in liver −18–24%, kidney −14–20%; SASP cytokines: IL-6 liver/plasma −18–24%, IL-8 −16–22%, GDF-15 −14–18% (measured at 24 months vs 12 months baseline). Pineal melatonin restored by Epitalon (24-month mice: melatonin 28 vs 12 pg/mL vehicle at 02:00; amplitude restoration; Epitalon dose 0.1 µg/kg × 12 months i.p.): melatonin → MT1/MT2 on macrophages → cAMP → PKA → NF-κB suppression → anti-inflammatory. CRP (inflammatory marker) −14–20% in aged Epitalon-treated mice (ELISA at 24 months).
Inflammation Research Protocol Framework
Inflammatory biology research requires precise model selection, inflammatory stimulus calibration, and multi-endpoint integration. Acute inflammation models: LPS endotoxaemia (systemic; i.p. 1–20 mg/kg; cytokine peak 1–2h for TNF-α/IL-6; 8–24h for IL-10 and late HMGB1); localised: carrageenan paw oedema (neutrophil-driven; 4h peak; caliper measurement + MPO + histology); zymosan peritonitis (PMN→monocyte/macrophage temporal sequence ideal for resolution biology). Chronic/sterile models: CIA/AIA (autoimmune joint); ApoE−/− HFD (atherosclerotic); DSS/TNBS (GI); NLRP3-specific: MSU crystal peritonitis; cholesterol crystal macrophage. Key endpoints: cytokine multiplex (ELISA or Luminex: TNF-α, IL-1β, IL-6, IL-10, IL-12p70, IFN-γ, MCP-1); NF-κB activity (EMSA, p65 nuclear fraction by western, NF-κB luciferase reporter); NLRP3 (caspase-1 activity Ac-YVAD-AFC; IL-1β p17 cleavage western; ASC speck by confocal; GSDMD western; LDH release for pyroptosis); Nrf2 (HO-1/NQO1 western; ARE-luciferase; nuclear Nrf2 ChIP); resolution endpoints (efferocytosis assay; SPM profiling by LC-MS/MS; PMN clearance kinetics; M1/M2 macrophage phenotyping by flow or IHC). Mechanistic controls: IKKβ inhibitor (PS-1145) for NF-κB; MCC950 for NLRP3; ML385 for Nrf2; AMPK inhibitor (Compound C) for MOTS-C AMPK dependency.
