TNF and Alzheimer disease: Igalan, a sesquiterpene lactone from Inula helenium (L.), suppressed the JAK/STAT3 signaling pathway and induced KC differentiation, thereby improving inflammatory cytokine (tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) or IL-4)-induced AD-like HaCaT cells [67].