Introduction: Osteoarthritis is the most common joint disease in humans. Footprints inflammation in osteoarthritis is not a new discovery. The degenerative change in inflammatory joints is associated with overproduction of inflammatory cytokines. In the process, the monocyte and macrophage cells enter the synovium and play a role in the production of the cytokines. The aim of this study was to investigate the effect of the essential oil of Nigella sativa L in reducing expression of pre-inflammatory cytokines in human macrophage and monocyte cells in comparison with steroid anti- inflammatory drugs in a model similar to osteoarthritis.
 
Materials & methods: Culturing THP-1 cells, providing Nigella sativa L essential oil, determining the degree of toxicity through SDH, LDH and MTT methods, treatment of the cells with LPS, placebos and essential oil, isolation of RNA and then, producing cDNA were performed. The expression of TNF-α and IL-18 was determined by RT-PCR method and analyzed through ANOVA, F static, and REST methods.
 
Findings: The essential oil of Nigella sativa L reduced the expression of TNF-α and IL-18 and has a significant difference (p<0.05) with the control group.
 
Discussion & conclusions: The results showed that the Nigella sativa L essential oil reduces the expression TNF-α and IL-18 in THP-1 cells stimulated with LPS and can be used in treating inflammatory diseases due to its anti- inflammatory properties.