Spirulina and autoimmune hepatitis: hepatocyte NOX2, prednisolone interactions, azathioprine, and liver enzyme monitoring

AIH pathophysiology

T cell and plasma cell infiltration: In AIH, CD4+ Th cells lose tolerance to hepatocyte antigens (CYP2D6 in AIH type 2; soluble liver antigen in AIH type 3) due to Treg dysfunction. Autoreactive T cells and plasma cells infiltrate the portal tracts and liver parenchyma (interface hepatitis on biopsy). Plasma cells produce IgG autoantibodies (anti-smooth muscle/F-actin in AIH type 1; anti-LKM1 in AIH type 2).
Hepatocyte NOX2 and Kupffer cell NF-κB: Inflammatory cytokines (TNF-α, IFN-γ) from infiltrating T cells activate NOX2 in hepatocytes and Kupffer cells. NOX2-derived superoxide amplifies hepatocellular damage beyond direct T cell killing. Kupffer cell NF-κB activation drives further cytokine production. Phycocyanobilin’s NOX2/NF-κB inhibition is mechanistically aligned with reducing this hepatic oxidative amplification.
NK stimulation concern: NK cells are present in the AIH liver infiltrate and are activated by IFN-γ from T cells. NK stimulation from spirulina is an intermediate concern in active AIH. In remission (normalised transaminases on maintenance azathioprine): the NK concern is lower. Discuss with hepatologist before starting spirulina in active or recently diagnosed AIH.

Baseline ALT/AST: Check ALT, AST, and ALP before starting spirulina in any liver condition. Document baseline values.
Spirulina and liver toxicity: Spirulina itself (high-quality, certified, microccystin-free) has hepatoprotective effects in most animal and human studies. However, spirulina contaminated with microcystins (from co-culture with Microcystis species or poor production standards) is hepatotoxic. In AIH with already-damaged hepatocytes, microcystin exposure would be particularly harmful. This is not a concern with certified spirulina from reputable producers with a current Certificate of Analysis showing microcystins <1 µg/g (WHO limit), but is a reason to use only CoA-verified products in AIH. Check ALT/AST 6–8 weeks after starting spirulina to confirm no hepatic reaction.

Prednisolone is first-line induction therapy for AIH (40–60 mg/day initially, tapered over weeks to months). No pharmacokinetic interaction with spirulina. NK stimulation concern at induction doses: intermediate to high. At maintenance dose (≤10 mg/day): lower concern. Discuss with hepatologist; most patients will have spirulina introduced during the stable remission phase rather than acute induction.

Azathioprine is the standard long-term maintenance agent in AIH (50–150 mg/day). It is metabolised by thiopurine methyltransferase (TPMT); TPMT genotyping guides dosing. No pharmacokinetic interaction with spirulina at the TPMT/XO metabolic level. No documented spirulina interaction with azathioprine. In remission on azathioprine alone: NK concern is intermediate; spirulina 1–2 g/day introduction with LFT monitoring at 6–8 weeks is a reasonable approach. Discuss with hepatologist.

MMF is used when azathioprine is not tolerated. No pharmacokinetic interaction with spirulina. Similar NK concern to azathioprine.

Budesonide has lower systemic corticosteroid effects than prednisolone due to first-pass hepatic metabolism. No pharmacokinetic interaction with spirulina. NK concern lower than with systemic prednisolone at equivalent hepatic doses.

AIH–PBC overlap (Paris criteria): features of both AIH and primary biliary cholangitis. NK concern reflects the PBC component (NK cells are primary biliary effectors in PBC). Apply the PBC NK framework: discuss with hepatologist before starting spirulina in overlap syndrome.
AIH–PSC (primary sclerosing cholangitis) overlap: similar consideration; discuss with hepatologist.

Active AIH (elevated transaminases, active immunosuppression at induction doses): defer spirulina until remission; intermediate to high NK concern in active disease
AIH in remission on maintenance azathioprine or low-dose prednisolone: intermediate NK concern; discuss with hepatologist; if approved, start 1–2 g/day
CRITICAL: use only CoA-verified spirulina (microcystins <1 µg/g) in all liver conditions; contaminated spirulina is hepatotoxic
Check ALT/AST at baseline and 6–8 weeks after starting; stop and inform hepatologist if transaminases rise >2× baseline
Overlap AIH–PBC: apply PBC NK framework (NK cells primary biliary effectors)