AB0030 BETA BOSWELLIC ACID BLOCKS INNATE IMMUNE RESPONSES IN MULTIPLE OA JOINT CELLS

Background:

Osteoarthritis (OA) incidence has skyrocketed in the last decade and yet a definitive treatment has still to be found. This worldwide disease is depriving our society from their life quality and has become a grave economic burden. Research on anti-inflammatory tools has been done on traditional Asian medicine. Boswellic acid is a plant-derived molecule from the Boswellia species that has shown to prevent cartilage loss in an OA mouse model[1]. However, the specific mechanism of action is still unclear. The activation of innate immune receptors, such Toll-like receptor 4 (TLR4) has been involved in chondrocyte-mediated inflammatory responses and OA development. Although, boswellic acid has shown an inhibitory effect on TLR4-mediated inflammatory responses little is known about its role on TLR4-mediated chondrocyte inflammatory and catabolic responses.

Objectives:

Determine the ability of beta boswellic acid (BBA) to block TLR4-mediated innate immune responses in chondrocytes and synoviocytes.

Methods:

In silico

The binding affinity of beta boswellic acid (BBA) to TLR4 complex signalling was determined by optimized docking algorithm in the BIO-HPC Research Group facilities.

In vitro

Cellular proteome and secretome profiling (LC-MALDI/TOFF) was used to study inflammatory pathways induced by the agonist of TLR4 (LPS [100ng/ml]) and IL1R (IL1β [0.1ng/ml]). The effect of BBA on TLR4-mediated innate immune responses was determined by RT-PCR, Western Blot and ELISA in primary human OA chondrocytes (hOC), murine ATDC5 chondrocytes, human synoviocytes (SW982) and primary human osteoblasts (hOB). Cell viability was tested using the methyl-thiazolyl-tetrazolium (MTT) reagent. Nitric oxide production in cell culture media was assessed by Griess reaction. Green Malachite Assay was used to semi-quantify the whole phosphoproteome.

Ethics

This study was approved by the CEIC (CAEIG 2014/310).

Results:

Cellular proteome and secretome profiling validated the activation of TLR4 and IL1R signalling by LPS and IL1β ligands and revealed an enrichment in innate immune responses (NF-Kβ, NLRP3, MMPs, Interleukins, etc).

Non-toxic doses of BBA [0.5-1000nM] prevented the activation of TLR4 in multiple articular joint cells and inhibited TLR4 & IL1R-dependant innate immune responses at the mRNA and protein level such as inflammatory factors IL6, NOS2, COX2, LCN2, MMP1, -3, -9, -13 and ADAMTS4, among others. Furthermore, NF-Kβ/IKBα and NLRP3/PYCARD/IL1β axis were also severely inhibited after BBA treatment. Moreover, these results were validated by in silico docking analysis that showed BBA interacted with TLR4/NF-Kβ.

Conclusion:

We prove that BBA inhibit TLR4 & IL1R -dependent innate immune responses in multiple human joint cells (Figure 1). We show that NF-Kβ & NLRP3 signalling, both associated to OA, are blocked (mRNA and protein) after BBA treatment (Figure 1).

Our data support previous studies showing the prevention of cartilage loss in an OA animal models by BBA might come from its ability to inhibit TLR4 signalling. In the clinical practice of rheumatologists, Boswellia Serrata could be a useful nutraceutical to manage OA inflammation due to its content in BBA.

Figure 1.

References:

[1]Wang, Q.; Pan, X.; Wong, H.H.; Wagner, C.A.; Lahey, L.J.; Robinson, W.H.; Sokolove, J. Oral and topical boswellic acid attenuates mouse osteoarthritis. Osteoarthr. Cartil.2014, 22, 128–132, doi:10.1016/j.joca.2013.10.012.

Acknowledgements:

Eloi Franco-Trepat and Ana Lois-Iglesias contributed equally to this work.

This research has been funded by the non-profit FER (Fundación Española de Reumatologia /Spanish Foundation of Rheumatology) through the project “Búsqueda de nuevos fármacos bloqueantes de la inflamación asociada a TLR4 en condrocitos humanos artrósicos”.

Disclosure of Interests:

None declared

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