Endocannabinoid Anandamide Induces High Mobility Group Box 1 (HMGB1) Protein Release in Monocytes and Macrophages

Abstract number: P2382

Biswas¹ KK, Sarker^1,2 KP, Kawahara K, Abeyama¹ K, Hashiguchi¹ T, Yamada³ S, Maruyama¹ I

^{1,2 11}Department of Laboratory and Vascular Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8520, Japan ¹¹Department of Laboratory and Vascular Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8520, Japan ³³Central Institute, Shino-Test Corporation, Kanagawa 229-0011, Japan

Anandamide (arachidonoyl ethanolamide) has been found to activate the brain cannabinoid receptors (CBR) and mimics the pharmacological effects of D-9 tetrahydrocannabinol, the active ingredients of hashish and marijuana, and is termed endocannabinoid. Anandamide production can be enhanced following hemorrhagic and septic shock, and increased serum level during endotoxic shock has been reported, suggesting that blood stream levels of anandamide may go up in certain pathological states. Anandamide exerts diverse biological activities such as vascular relaxation, inhibition of gap junctions formation, tumor proliferation, neurological analgesia, and apoptosis through CB1R and CB2R or VR1 receptors. HMGB1, a DNA binding protein which is recently identified as a pro-inflammatory and lethal cytokine released from cells of the macrophage/monocyte lineage in response to pro-inflammatory stimuli or by necrotic cells. In the present study, we demonstrate that Anandamide induced HMGB1 release in a dose and time dependant fashions in murine macrophage, Raw264.7, and human leukemic promonocytes (U937) cells. Moreover, CP55940, an agonist of CB1 and CB2 receptors also induced the release of HMGB1. CB2 but not CB1 receptor antagonist markedly reduced anandamide-induced HMGB1 release. Anandamide triggered rapid activation of p44/42, p38 MAPKs and its down stream target ATF-2 while protein kinase B (Akt) was down regulated in a time dependant fashion. SB203580, a potent and specific inhibitor of p38 MAPK or p38 siRNA almost completely abrogated the release of HMGB1 in response to anandamide. Moreover, we observed that exposure of HMGB1 to Raw 264.7 cells induced the production of anandamide measured by HPLC suggesting that anandamide may also act as an autocrine manner to produce HMGB1. In conclusion, our data suggest that anandamide may regulate critical pro-inflammatory pathways through inducing HMGB1 release in monocytes/macrophages.