Anti-neuroinflammatory properties of synthetic cryptolepine in human neuroblastoma cells: Possible involvement of NF-κB and p38 MAPK inhibition

Cryptolepis sanguinolenta and its bioactive alkaloid, cryptolepine have shown anti-inflammatory activity. However, the underlying mechanism of anti-inflammatory action in neuronal cells has not been investigated. In the present study we evaluated an extract of C. sanguinolenta (CSE) and cryptolepine (CAS) on neuroinflammation induced with IL-1 beta in SK-N-SH neuroblastoma cells. We then attempted to elucidate the mechanisms underlying the anti-neuroinflammatory effects of CAS in SK-N-SH cells. Cells were stimulated with 10 U/ml of IL-1 beta in the presence or absence of different concentrations of CSE (25-200 mu g/ml) and CAS (2.5-20 mu M). After 24 h incubation, culture media were collected to measure the production of PGE(2) and the pro-inflammatory cytokines (TNF alpha and IL-6). Protein and gene expressions of cyclooxygenase (COX-2) and microsomal prostaglandin synthase-1 (mPGES-1) were studied by immunoblotting and qPCR, respectively. CSE produced significant (p < 0.05) inhibition of TNF alpha, IL-6 and PGE(2) production in SK-N-SH cells. Studies on CAS showed significant and dose-dependent inhibition of TNF alpha, IL-6 and PGE(2) production in IL-1 beta-stimulated cells without affecting viability. Pre-treatment with CAS (10 and 20 mu M) was also found to inhibit IL-1 beta-induced protein and gene expressions of COX-2 and mPGES-1. Further studies to determine the mechanism of action of CAS showed inhibition of NF-kappa Bp65 nuclear translocation, but not I kappa B phosphorylation. At 10 and 20 mu M, CAS inhibited IL-1 beta-induced phosphorylation of p38 MAPK. Studies on the downstream substrate of p38, MAPK-activated protein kinase 2 (MAPKAPK2) showed that CAS produced significant (p < 0.05) and dose dependent inhibition of MAPKAPK2 phosphorylation in IL-1 beta-stimulated SK-N-SH cells. This study clearly shows that cryptolepine (CAS) inhibits neuroinflammation through mechanisms involving inhibition of COX-2 and mPGES-1. It is suggested that these actions are probably mediated through NF-kappa B and p38 signalling. Crown Copyright (C) 2013 Published by Elsevier Masson SAS. All rights reserved.