NOS2 and atrial fibrillation: We examined the gene expression of IL-1β, IL-6, IL-8, cyclooxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS), and human prostaglandin E synthase 2 (PTGES2) in human IVD cells (mixture of NP and AF cells with different NP/AF ratios depending on the biopsy) infected with C. acnes to assess the extent of inflammation.