Immunomodulatory Effects of Multi-Strain Probiotic Capsules for Psoriatic Arthritis: A Pilot Double-Blind Randomized Controlled Trial.

Psoriatic arthritis (PsA) is characterized by joint inflammation and is frequently associated with psoriasis. Gut dysbiosis has been implicated in PsA pathogenesis, raising interest in probiotics as potential immunomodulatory agents. In a pilot, double-blind, randomized, placebo-controlled trial, 14 adults aged 18-60 years with mild-to-moderate psoriatic arthritis (PsA; Disease Activity in Psoriatic Arthritis [DAPSA] < 28) were randomized to receive either probiotic capsules or placebo daily for 12 weeks. The probiotic group received a multi-strain cocktail with a total concentration of 1 × 109 CFU (including Lactobacillus rhamnosus, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus helveticus, Lactobacillus acidophilus, Bifidobacterium bifidum, Lactobacillus bulgaricus, Lactobacillus gasseri, Bifidobacterium lactis, Bifidobacterium longum, and Streptococcus thermophilus). The placebo group received lactose-based inert capsules for the same period. Immune cell populations (CD4+ IFN-γ T cells, B cells, Th2 cells) and cytokine levels (IFN-γ, IL-10, TGF-β, IL-4) were assessed. Compared with the placebo, probiotic supplementation resulted in a significant reduction in CD4+ IFN-γ T cells (6% ± 0.82 vs. 3.6% ± 0.8; p < 0.001), B cells (14.6% ± 1.05 vs. 8.9% ± 1.7; p < 0.0001), and IFN-γ concentrations (37.5 ± 2.4 pg/mL vs. 29.3 ± 2.6 pg/mL, p = 0.016). In addition, a significant increase was observed in IL-10 (9.4 ± 2.8 pg/mL vs. 99.89 ± 28.1 pg/mL, p = 0.0032), TGF-β (18.1 ± 2.7 pg/mL vs. 30.48 ± 7.7 pg/mL, p = 0.0073), and IL-4 (17.6 ± 6.7 pg/mL vs. 58.3 ± 29.2 pg/mL, p = 0.0117). Changes in Th2 cell levels were not statistically significant (p = 0.54). A multi-strain probiotic demonstrated promising immunomodulatory effects in PsA by reducing pro-inflammatory markers and enhancing regulatory cytokines that can be used as a complementary or alternative treatment for PsA patients. Trial Registration: IRCT20221213056802N1.