Anti-inflammatory Effect of Shikonin on Cultured Astrocytes Derived from Rat Brain

Astrocytes have an important role in many neurodegenerative diseases. Active astrocytes release inflammatory factors such as NO and ILs. Shikonin, a naphthoquinone pigment of Lithospermum erythrorhizon roots has anti-inflammatory and antitumoral effects. The present study aims to investigate the anti-inflammatory and toxic effects of Shikonin on cultured astrocytes. Two-day-old rat infants'' brains were homogenized after removal of the meninges, and cultured in DMEMF12+10% FBS medium. Ten days later, astrocytes were harvested and re-cultivated for more purifications to 95%, using immunocytochemistry method, and then treated by different concentrations of shikonin (0.1, 0.5, 1, 2.5, 5, 10, 20, 30, 50 and 100μM) for one hour, which was followed by LPS exposure. Viability was measured by MTT assay and NO concentrations were assessed by Griess method, to reveal the inflammation process, after 24 and 48 hours. Shikonin concentrations of 1, 2.5, 5, 10, 20 and 30μM had no anti-inflammatory and cell death effects but at 0.1 and 0.5μM showed a significant anti-inflammatory effect and ability to reduce NO production by astrocytes (p<0.001) and at 100 and 50μM showed a significant cell death effect and NO production reduction (p<0.001). Reduction of NO production might be due to inhibition of release and expression of inflammatory and cell signaling factors such as ILs and iNOS under the shikonin anti-inflammatory effects at concentration around 0.1 and 0.5μM. However, inhibition of NO production by shikonin at 50 and 100μM is probably due to cell death induction.