Ruxolitinib reverses alopecia areata via a triple mechanism: JAK-STAT inhibition, localized oxidative stress attenuation and selective apoptosis modulation.

Alopecia areata (AA) is an autoimmune hair loss disorder driven by the IFN-γ-JAK-STAT signaling and cytotoxic T-cell attack. Although JAK inhibitors like ruxolitinib show clinical efficacy, their integrated mechanism remains unclear. This study elucidated ruxolitinib's therapeutic actions in a C3H/HeJ mouse model of AA induced by adoptive transfer of activated lymph node cells. Mice were treated daily with ruxolitinib or vehicle for 98 days, with weekly clinical scoring of hair loss. Comprehensive analyses quantified systemic and skin cytokines (IFN-γ, TNF-α, IL-5, IL-6, IL-10, and CXCL1/KC), oxidative stress markers (malondialdehyde [MDA] and superoxide dismutase), apoptosis (cleaved caspase-3), autophagy (LC3-II), immune infiltration (CD3(+), CD4(+), CD8(+) T cells), and JAK-STAT activation (phosphorylated-STAT1/3). Ruxolitinib significantly improved hair regrowth from day 85 onward, suppressed key inflammatory cytokines in serum and skin, reduced T-cell infiltration and STAT phosphorylation, attenuated local oxidative stress (lower MDA), and decreased keratinocyte apoptosis, without affecting autophagy or systemic oxidative markers. These results demonstrate that ruxolitinib reverses AA through a coordinated triple mechanism: upstream inhibition of the JAK-STAT pathway, downstream alleviation of local oxidative stress and apoptosis, and disruption of the self-amplifying inflammatory cycle. The findings provide a mechanistic foundation for JAK inhibitor's clinical efficacy and support the development of targeted topical therapies.