Colchicine (Cochinxine) - Mechanism of Action in Rheumatoid Arthritis

Note: "Cochinxine" appears to be a phonetic spelling of colchicine (kol-chi-seen), an alkaloid derived from Colchicum autumnale (autumn crocus). While colchicine is primarily used in gout, pseudogout (CPP deposition disease), familial Mediterranean fever, and pericarditis, its anti-inflammatory mechanisms are relevant to synovial inflammation in RA.

1. Primary Mechanism: Tubulin Binding and Microtubule Disruption

"Colchicine binds tightly to unpolymerized tubulin and forms a tubulin-colchicine complex that regulates microtubule and cytoskeleton function. Binding of the tubulin-colchicine complex at the ends of microtubules physically acts on elongation of the microtubule polymer."

• Rheumatology, 2-Volume Set (2022, Elsevier), Mechanism of Action section

• Disruption of the cytoskeletal network within leukocytes
• Impairment of cell proliferation
• Altered signal transduction and gene expression
• Inhibition of chemotaxis (directed cell migration)
• Suppression of neutrophil secretion of granule contents

2. Neutrophil-Specific Effects (Key in Synovial Inflammation)

"Nanomolar colchicine concentrations, achievable in plasma with low daily prophylactic doses of colchicine, suppress E-selectin redistribution in the endothelial cell plasma membrane, thereby inhibiting neutrophil adhesion."

• Rheumatology, 2-Volume Set (2022)

3. NLRP3 Inflammasome Inhibition (IL-1β Pathway)

• Microtubule integrity is required for NLRP3 inflammasome assembly and activation
• By disrupting microtubules, colchicine blocks NLRP3 inflammasome activation
• This prevents caspase-1 cleavage and the maturation and secretion of:
  • IL-1β (a major driver of synovial pannus formation in RA)
  • IL-18

"Colchicine modulates multiple pathways implicated in MSU crystal-induced inflammation by preventing microtubule assembly and thereby disrupting NLRP3 inflammasome activation, inflammatory cell chemotaxis, generation of leukotrienes and cytokines, and phagocytosis."

• Firestein & Kelley's Textbook of Rheumatology

4. AMPK Activation in Macrophages

"In macrophages, activates the nutritional biosensor AMP activated protein kinase, which transduces multiple anti-inflammatory effects of colchicine in macrophages."

• Rheumatology, 2-Volume Set (2022)

5. Downstream Cytokine and Eicosanoid Suppression

• Leukotriene generation (LTB4, a potent neutrophil chemoattractant)
• Pro-inflammatory cytokines (IL-1β, IL-6, TNF-α)
• Phagocytosis (reducing crystal/immune complex-induced lysosomal activation)

Summary Diagram of Mechanisms

Colchicine
    |
    ↓
Binds unpolymerized TUBULIN
    |
    ↓
Tubulin-Colchicine complex → blocks microtubule polymerization
    |
    ├──→ Neutrophil chemotaxis inhibited
    ├──→ Neutrophil degranulation inhibited
    ├──→ E-selectin redistribution suppressed → neutrophil adhesion blocked
    ├──→ NLRP3 Inflammasome disrupted → ↓ IL-1β, IL-18
    ├──→ AMPK activation in macrophages → anti-inflammatory signaling
    └──→ ↓ Leukotrienes, ↓ Cytokines (IL-6, TNF-α)
                ↓
        Reduced synovial inflammation in RA

Important Pharmacological Notes

Colchicine in RA Context

• Managing acute flares in RA patients, especially when NSAIDs are contraindicated
• Treating concomitant crystal arthritis (gout or pseudogout) in RA patients
• In RA patients with secondary AA amyloidosis (colchicine reduces amyloid A precursor production by limiting inflammation)