Luteolin inhibits hyperglycemia-induced proinflammatory cytokine production and its epigenetic mechanism in human monocytes.

Hyperglycemia is a key feature in diabetes. Hyperglycemia has been implicated as a major contributor to several complications of diabetes. High glucose levels induce the release of proinflammatory cytokines. Luteolin is a flavone isolated from celery, green pepper, perilla leaf, and chamomile tea. Luteolin has been reported to possess antimutagenic, antitumorigenic, antioxidant, and anti-inflammatory properties. In this study, we investigated the effects of luteolin on proinflammatory cytokine secretion and its underlying epigenetic regulation in high-glucose-induced human monocytes. Human monocytic (THP-1) cells were cultured under controlled (14.5 mM mannitol), normoglycemic (NG, 5.5 mM glucose), or hyperglycemic (HG, 20 mM glucose) conditions, in the absence or presence of luteolin. Luteolin (3-10 μM) was added for 48 h. While hyperglycemic conditions significantly induced histone acetylation, NF-κB activation, and proinflammatory cytokine (IL-6 and TNF-α) release from THP-1 cells, luteolin suppressed NF-κB activity and cytokine release. Luteolin also significantly reduced CREB-binding protein/p300 (CBP/p300) gene expression, as well as the levels of acetylation and histone acetyltransferase (HAT) activity of the CBP/p300 protein, which is a known NF-κB coactivator. These results suggest that luteolin inhibits HG-induced cytokine production in monocytes, through epigenetic changes involving NF-κB. We therefore suggest that luteolin may be a potential candidate for the treatment and prevention of diabetes and its complications.