TNF and Arthritis: Proline-rich receptor-like protein kinase (PERK) and eukaryotic initiation factor 2-α (eIF2a) are also ER stress-associated molecules, which are involved in regulating many biochemical processes, such as cardiac hypertrophy,11 osteoporosis,12 arthritis,13 and inhibition of tumor necrosis factor alpha (TNF-α)-triggered nuclear factor κB (NF-κB) activation.14