Attenuation of Innate Immunity by Andrographolide Derivatives Through NF-κB Signaling Pathway

Abstract

Andrographolide derivatives or analogs exhibit potent anti-inflammatory effects in several disease models through NF-κB activity. In this study, we synthesized different andrographolide derivatives and investigated their effects on the toll-like receptor (TLR)-induced production of pro-inflammatory cytokines. Among these compounds, 3b, 5a, and 5b inhibited both TNF-α/NF-κB and TLR4/NF-κB signaling pathways. Treatment with compounds 3b, 5a, and 5b and their structural analogs, 3a and 6b, suppressed the expression of pro-inflammatory cytokines upon the activation of TLR3 and TLR4 ligands. Compounds 3b and 5a, but not 3a, 5b, or 6b, inhibited the nuclear translocation of the NF-κB p65 subunit. Treatment with compounds 3b, 5a, 3a, 5b, and 6b attenuated the phosphorylation of p65 and IκBα. Compounds 6b suppressed the expression of the NF-κB p65 subunit. However, these compounds, except for 5b, did not affect the TLR9-induced NF-κB-independent production of the pro-inflammatory cytokines, TNF-α, and IFN-β. Compound 3b potentially protected mice from LPS-induced acute pulmonary inflammation through the inhibition of p65 phosphorylation and the decrease of serum pro-inflammatory cytokines and chemokine. Our study revealed a functional structure–activity relationship between andrographolide derivatives and innate immunity. We identified compound 3b as a potent immune suppressive agent with the potential to protect acute pulmonary infection.

Discovery and preliminary SAR of 14-aryloxy-andrographolide derivatives as antibacterial agents with immunosuppressant activity

“…The preparation and characterization of 2, 3a, 3b, 4 and 5a1, 5b1, 6a1 and 6b1 were modied from our previous papers 25,26 4.2.1. Preparation of compounds 5a and 5b General method for synthesis of 5a and 5b.…”

“…The title derivatives were synthesized according to our previously reported synthesis; 25,26 the synthesis is outlined in Scheme 1 (ArO groups are depicted in Table 1). Accordingly, 14a-3,19-acetonylidene-protected andrographolide (3a) was prepared by the reaction of andrographolide (1) with 2,2-dimethoxypropane catalyzed by PPTS, followed by a Mitsunobu reaction with acetic acid, which inverted 14a-OH of 3a into 14b-OAc of 4.…”

“…The protocols were adopted and modied from our previous report. 25 All compounds were dissolved in DMSO at 10 mM as a stock solution. The nal concentration of DMSO was 0.1% in the culture medium.…”

“…Our previous report 25 revealed that some analogs of andrographolide play a role in the attenuation of innate immunity; these were identied as potential immunomodulatory inhibitors of TLR signaling with distinct regulation of NF-kB family members. Furthermore, one compound effectively reduced LPSinduced pulmonary injury in a mouse in vivo study; biochemical results showed that the nucleus translocation of phosphorylated p65 and serum pro-inammatory cytokines decreased.…”

“…25) to examine the activities of the antibacterial active andrographolide analogs in the regulation of signaling pathways that govern inammatory response (Table 2). It was noted that these derivatives did not show obvious cytotoxicity to AD-293 cells; DCB-3503 was used as a positive compound 36 ( Table 2).…”