Nigella sativa Oil Reduces LPS-Induced Microglial Inflammation: An Evaluation on M1/M2 Balance

Objectives. The immune system plays a critical defence role against infections, injuries, and carcinogenic stimuli. As the macrophages of the brain resides in the innate immune system, microglia and their polarisation (M-1/M-2) play regulatory roles in inflammation in CNS, such as Parkinson's, Alzheimer's, dementia complex, and multiple sclerosis. Nigella sativa belongs to the Ranunculaceae family and has different anti-inflammatory and antioxidant effects. We conducted this study to evaluate the anti-inflammatory and protective properties of N. sativa oil (NSO) on the microglial cells and their polarisation (M-1/M-2) in the presence of LPS as a model of neuroinflammation. Methods. The protective effects of NSO (10-40 mu g/ml) were studied on the LPS-induced microglial cells, and the levels of tumour necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6, prostaglandin E-2 (PGE(2)), and IL-10 were evaluated using both ELISA and gene expression methods. The levels of cyclooxygenase-2 (COX-2), inducible NOS (iNOS), and arginase-1 (Arg1) were also evaluated using the real-time PCR method. In addition, nitrite oxide (NO) and urea were measured using biochemical methods. Results. NSO decreased LPS-induced toxicity at all doses (P < 0.001). NSO (10-40 mu g/ml) also significantly reduced the levels of TNF-alpha, PGE2, IL-1 beta, and IL-6 in the presence of LPS (P < 0.01 to 0.001). Pretreatment with NSO attenuated the levels of iNOS but increased Arg1 (P < 0.001). The ratio of iNOS/Arg1 was also decreased in the presence of NSO (P < 0.001) than that of the LPS group (P < 0.001). Conclusion. NSO attenuated LPS-induced inflammation and increased microglia's anti-inflammatory status. These results may prove that NSO is potentially an immunomodulator for various neurodegenerative diseases by M1 phenotype dominancy, such as Alzheimer's and Parkinson's diseases.

Automated summary

This study evaluated the anti-inflammatory and protective properties of N. sativa oil on microglial cells and their polarization. The results showed that N. sativa oil reduced inflammation and increased the anti-inflammatory status of microglia.