A marine fungus‐derived nitrobenzoyl sesquiterpenoid suppresses receptor activator of NF‐κB ligand‐induced osteoclastogenesis and inflammatory bone destruction

Abstract

Background and Purpose: Osteoclasts are unique cells to absorb bone. Targeting osteoclast differentiation is a therapeutic strategy for osteolytic diseases. Natural marine products have already become important sources of new drugs. The naturally occurring nitrobenzoyl sesquiterpenoids first identified from marine fungi in 1998 are bioactive compounds with a special structure, but their pharmacological functions are largely unknown. Here, we investigated six marine fungus-derived nitrobenzoyl sesquiterpenoids on osteoclastogenesis and elucidated the mechanisms. Experimental Approach: Compounds were first tested by RANKL-induced NF-κB luciferase activity and osteoclastic TRAP assay, followed by molecular docking to characterize the structure-activity relationship. The effects and mechanisms of the most potent nitrobenzoyl sesquiterpenoid on RANKL-induced osteoclastogenesis and bone resorption were further evaluated in vitro. Micro-CT and histology analysis were used to assess the prevention of bone destruction by nitrobenzoyl sesquiterpenoids in vivo. Key Results: Nitrobenzoyl sesquiterpenoid 4, with a nitrobenzoyl moiety at C-14 and a hydroxyl group at C-9, was the most active compound on NF-κB activity and osteoclastogenesis. Consequently, nitrobenzoyl sesquiterpenoid 4 exhibited suppression of RANKL-induced osteoclastogenesis and bone resorption from 0.5 μM. It blocked RANKL-induced IκBa phosphorylation, NF-κB p65 and RelB nuclear translocation, NFATc1 activation, reduced DC-STAMP but not c-Fos expression during osteoclastogenesis in vitro. Nitrobenzoyl sesquiterpenoid 4 also ameliorated LPSinduced osteolysis in vivo. Conclusion and Implications: These results highlighted nitrobenzoyl sesquiterpenoid 4 as a novel inhibitor of osteoclast differentiation. This marine-derived sesquiterpenoid is a promising lead compound for the treatment of osteolytic diseases.

A Nitrobenzoyl Sesquiterpenoid Insulicolide A Prevents Osteoclast Formation via Suppressing c-Fos-NFATc1 Signaling Pathway

“…However, our data showed that insulicolide A had no significant reduction on p65 of NF-κB and the phosphorylation of ERK, p38, and JNK of MAPKs, which were incompletely consistent with the effects of NS4 (structural isomer of insulicolide A) on NF-κB. NS4 exhibited inhibitory effects on NF-κB by binding with NF-κB p65 Arg B246 ( Tan et al, 2020 ), the different mechanisms between NS4 and insulicolide A on NF-κB may be due to their different conformations and their affinity with NF-κB. These results suggested that NF-κB and MAPKs might not be a downstream signal by insulicolide A to treat RANKL-induced osteoclast differentiation.…”

“…C-Fos knockout mice showed decreased NFATc1 nuclear translocation and severe bone sclerosis ( Matsuo et al, 2004 ). Here, our findings determined that the nuclear protein level of c-Fos was drastically inhibited by insulicolide A in the BMMs of RANKL stimulation, which was also different with NS4, while NS4 had little effect on c-Fos nuclear expression during RANKL-induced osteoclast formation ( Tan et al, 2020 ). Thus, the decrease in RANKL-induced c-Fos activation and the following attenuated NFATc1 nuclear protein levels, contributes to impaired osteoclastogenesis after insulicolide A treatment.…”

“…Nitrobenzoyl sesquiterpenoids (NSs) represent a novel and rare class of compounds isolated from marine fungi, and only seven are identified until now ( Wu et al, 2012 ; Zhao et al, 2016 ; Tan et al, 2018 ). We have identified one NS compound, 6 β ,9 α -dihydroxy-14- p -nitrobenzoylcinnamolide (NS4), having the potential to suppress osteoclast formation by inhibiting NF-κB/RelB signaling pathway via binding to Arg B246 of NF-κB P65 ( Tan et al, 2020 ). Another NS compound, insulicolide A, isolated from the marine-derived fungus Aspergillus ochraceus , has demostrated antiinflammation and antitumor activity in vitro ( Wang et al, 2014 ; Guo et al, 2018 ).…”

Bioactive Polyketide and Diketopiperazine Derivatives from the Mangrove-Sediment-Derived Fungus Aspergillus sp. SCSIO41407

“…AChE inhibitory activity was evaluated in vitro according to the modified Ellman method [ 25 ]. Briefly, 0.1 U/mL AChE solution was prepared by dissolving in phosphate buffer (pH 8.0).…”

Anti-Osteoclastogenic and Antibacterial Effects of Chlorinated Polyketides from the Beibu Gulf Coral-Derived Fungus Aspergillus unguis GXIMD 02505

“…The differentiation of the osteoclast is modulated by two critical factors, the macrophage colony stimulation factor (M-CSF) and the receptor activator of the nuclear factor kappa-B (NF-κB) ligand (RANKL). RANKL signaling pathways have been recently proposed as key targets for inhibiting osteoclast differentiation and bone resorption [ 4 ]. Hence, many efforts have been recently devoted to the discovery of lead compounds from natural sources that target RANKL-induced osteoclast differentiation for attenuating enhanced bone resorption and bone loss [ 5 ].…”