Neuritogenic Effect of Epolactaene Derivatives on Human Neuroblastoma Cells Which Lack High-Affinity Nerve Growth Factor Receptors

Abstract

Neurotrophic factors such as nerve growth factor (NGF) are involved in survival, growth, and differentiation in normal and neoplastic nerve cells. 1,2 At least three receptors bearing tyrosine kinase activity for neurotrophic factors have beeen cloned; 3-5 TRK-A encodes a high-affinity receptor for NGF and also binds neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5). 6-8 TRK-B encodes a receptor for brain-derived neurotrophic factor (BDNF) and also binds NT-3 and NT-4/5, and TRK-C encodes a receptor for NT-3. 9-11 Despite high sequence homology among the receptors, the developmental and physiological functions of each neurotrophic factor appear to be different, suggesting that each factor has a unique role.In addition, it has been reported that most benign neuroblastomas express high levels of TRK-A, while malignant neuroblastomas, especially those with N-myc amplification, express little or no detectable TRK-A mRNA. 12-16 NGF is expected to induce the differentiation of benign neuroblastomas to neurons, but NGF has no effect on malignant neuroblastomas lacking NGF receptors. Therefore, compounds which induce the differentiation of neuroblastomas might be good candidates for pharmaceutical agents for various neurodegenerative diseases.We have screened microbial products to discover neuritogenic compounds which induced neurite outgrowth in the human neuroblastoma cell line SH-SY5Y that lacks significant TRK family mRNAs. 17,18 During the screening, we isolated a novel, non-protein neurotrophic compound, epolactaene (Figure 1), produced by Penicillium sp. 1689-P, having an epoxide-containing γ-lactam ring in the molecule. 19 However, only small quantities of epolactaene could be isolated from the fungus; furthermore, the compound was unstable under light because of a labile triene group in the side chain and an epoxide fused to a γ-lactam ring. In the present paper, we prepared a number of epolactaene derivatives, 3-substituted 3-pyrrolin-2-ones possessing a double bond in the γ-lactam ring, to find compounds with more effective neuritogenic activity. In addition, we described the structure-activity relationship of 3-substituted 3-pyrrolin-2-ones on the neuritogenic effect in SH-SY5Y cells. MT-5, 3-acetyl-4,5-dimethyl-5-octadecyloxy-3-pyrrolin-2-one, the most effective derivative for neuritogenic activity in SH-SY5Y cells, also arrested cell cycle progression at G0/G1 like epolactaene.Chemistry. We focused on the γ-lactam ring of epolactaene in developing derivatives that have more simple structure and potent activity. The intermediates were synthesized essentially according to the procedure of Howard et al., 20 in which R, -diketones, including aliphatic diketones, react smoothly in aqueous solution pH 7-10 at room temperature with a variety of acetamides possessing a strong electron-withdrawing group in the R-position to give 3-substituted 5-hydroxy-3-pyrrolin-2-ones. For example, as shown in Scheme 1, R, -diketone (1) reacted with acetoacetamide (2) to give 3 and the following treatment with alcohols under aci...

Synthetic and Structure-Activity Relationship Studies on Bioactive Natural Products

“…1,[8][9][10] They found that epolactaene bound to human Hsp60 and inhibited its chaperone activity. 9,10) Ikekita et al found that 1 induced apoptosis in a human leukemia B cell line, BALL-1.…”

“…Treatment of 6 with aqueous HF in CH 3 CN led to desilylation and cyclization to form -angelica lactone (7). Epoxidation of 7 by a modification of Font's procedure 20) gave enantiomerically pure -angelica lactone epoxide (8) in 60% yield and 98% ee (by HPLC). After treatment of 8 with K 2 CO 3 in MeOH, the resulting alcohol was protected as TBS ether 9.…”

Requirement of protein kinase (Krs/MST) activation for MT-21-induced apoptosis

“…MT-21 was synthesized as previously described (Kakeya et al, 1997), solubilized in methanol and used for experiments. Z-Asp-CH 2 -DCB (Z-Asp) was purchased from Peptide Institute, Inc. (Osaka, Japan) and used as an inhibitor with a broad speci®city to various caspases.…”

Activation of MST/Krs and c-Jun N-terminal Kinases by Different Signaling Pathways during Cytotrienin A-induced Apoptosis

“…It is possible that most apoptotic signals including the Fas-mediated signal and the cytotrienin-induced signal activate several pathways for apoptosis in a target cell. Unlike these apoptosis inducers, MT-21 (3-acetyl-4,5-dimethyl-5-octyloxy-3-pyrrolin-2-one), our synthetic apoptosis inducer, activates the signal from caspase-3, MST/Krs to JNK in a rather simple manner (16,17). In the present study, we have investigated the caspase-mediated proteolytic activation of MST/Krs proteins in cytotrienin A-sensitive and -resistant human tumor cell lines.…”