TNF and atrial fibrillation: As shown in Fig. 4, mRNA expression levels of pro-inflammatory cytokines, TNF-α and IL-6, were significantly upregulated by IL-1β treatment in both NP cells (+6.5-fold and +82.5-fold vs control, respectively; P < 0.05) and AF cells (+7.6-fold and +102.1-fold vs control, respectively; P < 0.05).